A UV debondable acrylic pressure sensitive adhesive tape based on the synergistic structure of suspended double bond and photolyzable side chain and its preparation method and application

Abstract

This invention discloses a UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains, its preparation method, and its application. First, a crosslinking agent containing photolytically degradable units, ONB, is synthesized and then copolymerized with acrylate monomers to obtain a main adhesive containing active groups. Then, dangling double bonds are introduced by reacting epoxy-based acrylates (such as GMA) with the carboxyl groups in the main adhesive. Finally, photoinitiators, curing agents, and other additives are added for coating and curing. UV irradiation can simultaneously trigger the photolytic degradation of the o-NB side chains and the photocrosslinking of the dangling double bonds. The synergistic effect of these two factors causes a sharp decrease in the peel strength of the tape after UV irradiation (e.g., from >18 N / 25 mm to <0.08 N / 25 mm), achieving rapid and thorough tape reduction and preventing peel residue. Simultaneously, the structure is stable, with no risk of small molecule migration.

Description

Technical Field

[0001] This invention belongs to the field of functional polymer adhesives technology, specifically relating to a UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains, its preparation method, and its application. Background Technology

[0002] UV-reducing pressure-sensitive adhesive is a smart adhesive material that can significantly reduce its adhesion force through ultraviolet light irradiation, thereby achieving controlled peeling. It is widely used in semiconductor wafer dicing, temporary fixation of precision components, and protective films. Existing technologies mainly revolve around two mechanisms: The first type is the physically blended semi-interpenetrating network (Semi-IPN) system. This involves physically mixing a linear acrylate pressure-sensitive adhesive (base adhesive) with multifunctional acrylate monomers / oligomers (such as dipentaerythritol hexaacrylate). After UV irradiation, the latter crosslinks, forming a semi-interpenetrating network with the base adhesive. This results in significant volume shrinkage and modulus increase, leading to a reduction in interfacial contact area and thus achieving anti-tack properties. However, this system carries the risk of small molecule migration from the photosensitive resin, and anti-tack relies primarily on physical shrinkage. For substrates with high surface energy and rough surfaces, the effectiveness of anti-tack and the ability to prevent adhesive residue are limited.

[0003] The second type is chemically modified fully cross-linked network systems. For example, photocrosslinkable C=C double bonds are introduced into the side chains of acrylic polymers through chemical means (such as using isocyanate functional monomers or glycidyl methacrylate GMA). UV irradiation induces cross-linking of the side chain double bonds, forming a dense network, which reduces viscosity by increasing modulus and decreasing viscoelasticity. Although this method avoids small molecule migration, the viscosity reduction mode is singular, mainly relying on cross-linking to increase modulus. There is still room for improvement in the reduction of peel force and the ability to prevent residue buildup, and it cannot achieve a synergistic or sequential triggering of "cross-linking" and "degradation".

[0004] Furthermore, o-Nitrobenzyl ester, as a classic photoinstability group, can undergo cleavage under UV irradiation, leading to polymer backbone degradation and loss of cohesion, thus providing a possibility for achieving "photodegradation" for viscosity reduction. However, existing technologies mostly study it as a single mechanism or as a simple physical addition, failing to conduct in-depth synergistic design with chemical crosslinking mechanisms.

[0005] Therefore, developing a novel pressure-sensitive adhesive system that combines high initial bond strength, rapid and thorough tack reduction after UV triggering, and prevention of residue at its source is a pressing technical problem in this field. This invention aims to integrate two mechanisms—photoinduced backbone degradation and photoinduced side chain crosslinking—into the same polymer backbone through innovative molecular structure design, achieving synergistic performance enhancement and precise control. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains, as well as its preparation method and application, which overcomes the problems existing in the current UV-resistant pressure-sensitive adhesive technology, such as incomplete adhesion reduction, easy residue, single response mode, or risk of small molecule migration.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains, comprising a substrate film and a UV-resistant adhesive layer coated thereon, wherein the UV-resistant adhesive layer comprises the following components by weight: 100 parts of main adhesive, 0.5-5 parts of photoinitiator, 0.5-3 parts of curing agent, and 0-40 parts of solvent.

[0008] Furthermore, the main adhesive is an acrylate copolymer solution containing photolytic side chains and dangling double bonds; The acrylate copolymer containing photolytic side chains and dangling double bonds has a main chain composed of acrylate monomer units, and the side chains simultaneously contain o-nitrobenzyl ester photolytic units and methacryloxy dangling double bond units connected by chemical bonds.

[0009] Furthermore, the photoinitiator is a pyrolysis-type free radical photoinitiator, selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenylmethyl.

[0010] Furthermore, the curing agent is an isocyanate-based curing agent; the solvent is ethyl acetate.

[0011] This invention proposes a method for preparing a UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains, comprising the following steps: 1) Synthesis of the main adhesive: First, the photoresponsive crosslinking agent ONB is synthesized; then ONB is copolymerized with acrylate monomers to obtain a polymer solution containing active groups; then GMA is used for modification to introduce dangling double bonds to obtain the copolymer solution. 2) Preparation of UV-resistant adhesive composition: Add photoinitiator, curing agent and solvent to the reaction system of step S1 according to the ratio, and mix thoroughly under light-protected conditions to obtain UV-resistant adhesive composition; 3) Coating and curing: The UV anti-tack adhesive composition obtained in step 2) is coated onto the substrate film, heated and dried to evaporate the solvent and trigger the curing agent reaction to form a UV anti-tack adhesive layer. After laminating with a release film, it is cured to obtain a pressure-sensitive adhesive tape.

[0012] Furthermore, the specific process of step 1) is as follows: 1.1) Under an inert atmosphere and at 0-5℃, o-nitrobenzyl alcohol was dissolved in an organic base and solvent, and acryloyl chloride was slowly added dropwise. After the reaction was completed, ONB was obtained through post-treatment. 1.2) Mix acrylic acid, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate and the photoresponsive crosslinking agent ONB prepared in step 1.1) in proportion, add solvent and free radical initiator, and carry out solution polymerization at 65-75℃. After the reaction is completed, raise the temperature to 80-85℃ to consume the residual initiator to obtain a main adhesive solution containing hydroxyl, carboxyl and o-nitrobenzyl ester side chains. 1.3) Cool the main adhesive solution obtained in step 1.2) to 50-65℃, add GMA and catalyst, and keep it at the temperature for 3-6 hours to allow the epoxy group of GMA to undergo a ring-opening esterification reaction with the carboxyl group in the main adhesive, thereby introducing methacryloyloxy group into the polymer in the form of a suspended side chain.

[0013] Furthermore, the photoresponsive crosslinking agent ONB has an o-NO2-C6H4-CH2-O-CO-CR=CH2 structure, wherein R is H or CH3; The amount of photoresponsive crosslinking agent ONB in ​​the monomer mixture accounts for 0.5%-5% of the total weight of the monomers, the amount of acrylic acid in the monomer mixture accounts for 0.5%-8% of the total weight of the monomers, and the amount of hydroxyethyl acrylate accounts for 2%-10% of the total weight of the monomers. The amount of GMA used is 0.8-2.0 times the molar amount of carboxyl groups in the acrylate polymer containing hydroxyl, carboxyl, and o-NB side chains.

[0014] Further, in step 1.1), the organic base is triethylamine and the solvent is ethyl acetate; in step 1.2), the free radical initiator is AIBN, wherein the total amount of free radical initiator is 0.03%-0.3% of the total weight of the monomer, and the solvent is ethyl acetate; in step 1.3), the catalyst is triphenylphosphine, and the amount of catalyst is 0.5-2% of the mass of GMA.

[0015] Furthermore, in step 3), the heating and drying temperature is 80-130℃, and the time is 1-5 minutes.

[0016] This invention proposes the application of UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains prepared by the method described above in the fields of semiconductor wafer cutting protection, temporary fixation of precision components, or peelable protective film.

[0017] The mechanism of this invention is as follows: The core of this invention lies in a "dual-response unit integrated design": on the side chains of the acrylate polymer backbone, photodegradable o-nitrobenzyl ester (o-NB) units and photocrosslinkable dangling unsaturated double bond (C=C) units are simultaneously introduced via chemical bonds. UV irradiation can simultaneously or sequentially trigger the degradation of adjacent units in the backbone and the crosslinking of dangling double bonds in the side chains. Through the synergistic effect of "cohesive disintegration" and "modulus enhancement / interfacial shrinkage," efficient and thorough viscosity reduction is achieved.

[0018] A UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains, comprising the following raw materials: Acrylic ester copolymers containing photolytic side chains (main adhesive): are copolymerized from acrylate monomers and photoresponsive crosslinking agent ONB. The ONB is prepared by esterification of o-nitrobenzyl alcohol and acryloyl chloride, and its general structural formula is o-NO2-C6H4-CH2-O-CO-CR=CH2 (where R is H or CH3). This polymer contains both hydroxyl (-OH) and carboxyl (-COOH) functional groups.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) Synergistic dual viscosity reduction mechanism: Under a single UV irradiation, photolysis of the o-nitrobenzyl ester side chain and photocrosslinking of the dangling double bond can be triggered simultaneously. The former leads to degradation of adjacent points on the polymer backbone, resulting in a decrease in molecular weight and collapse of cohesion; the latter forms a crosslinked network, increases modulus and is accompanied by volume shrinkage, and disrupts the interface. The two mechanisms work synergistically to achieve faster and more thorough viscosity reduction than a single mechanism (e.g., peel force can be reduced from >20 N / 25 mm to <0.1 N / 25 mm).

[0020] 2) Stable structure: The photoresponse units (o-NB and suspended C=C) are all connected to the polymer backbone through stable chemical bonds, without small molecule migration problems, and the adhesive has good storage stability.

[0021] 3) High performance designability: By adjusting the amount of ONB (controlling the photolysis point density), the amount of GMA (controlling the dangling double bond density), and the molecular weight and glass transition temperature (Tg) of the main adhesive, the initial bonding performance and the degree of tack reduction after UV treatment can be controlled in a wide range and with precision, adapting to different application scenarios. Attached Figure Description

[0022] Figure 1 This is a comparison diagram of the peel force of the pressure-sensitive adhesive before and after UV testing in Example 2 of the present invention. Detailed Implementation

[0023] The present invention will be further illustrated below with examples and comparative examples, but the present invention is not limited thereto.

[0024] Unless otherwise specified, all ingredients are commercially available products, and all quantities are by weight.

[0025] Examples 1-10 1.1) Synthesis of photoresponsive crosslinking agent ONB Under nitrogen protection and in an ice bath at 0-5℃, 23.0 g (0.15 mol) of o-nitrobenzyl alcohol, 16.7 g (0.165 mol) of triethylamine, and 150 mL of anhydrous tetrahydrofuran were added to a 500 mL four-necked flask equipped with a stirrer and a dropping funnel. After stirring to dissolve, 13.6 g (0.15 mol) of acryloyl chloride was slowly added dropwise, controlling the dropping rate to keep the internal temperature below 10℃. After the addition was complete, the reaction was continued at room temperature for 12 hours. The reaction solution was washed successively with 1M HCl solution, saturated NaHCO3 solution, and deionized water. The organic phase was dried over anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation to obtain a pale yellow oily product, ONB, in approximately 85% yield.

[0026] 1.2) Synthesis of acrylate copolymers (main binder) containing photolytic side chains Following the formulations shown in Table 1 (Examples 1-10), acrylic acid (AA), butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), hydroxyethyl acrylate (HEA), ONB, and ethyl acetate (part of the total solvent) were added to a four-necked flask. After purging with nitrogen for 30 minutes, the temperature was raised to 70°C, and a solution of ethyl acetate initiator AIBN was added dropwise (the total amount of AIBN was 0.2% of the total weight of the monomers). After the dropwise addition was completed (approximately 3 hours), the reaction was maintained at 70°C for 6 hours (with initiator added every 2 hours). Subsequently, the temperature was lowered to 65°C and stirred for 4 hours. Then, the mixture was stored in an oven at 65°C in a sealed container for 120 hours to consume the residual initiator. After cooling to room temperature, a main adhesive solution with a solid content of approximately 40% was obtained.

[0027] 1.3) Introducing a suspended double key The above-mentioned main adhesive solution was heated to 60°C, and GMA and the catalyst triphenylphosphine (1% of the mass of GMA) were added according to the proportions shown in Table 1. Under nitrogen protection, the reaction was carried out at 60°C for 5 hours to obtain the modified main adhesive solution.

[0028] 2) Formulate UV-resistant adhesive composition Add photoinitiator TPO, curing agent L75 (Desmodur) and supplemented ethyl acetate to the modified base adhesive solution obtained in step 1.3) according to the proportions shown in Table 1. Stir and mix for 2 hours under light-protected conditions to obtain a uniform UV-resistant adhesive composition.

[0029] 3) Coating and curing The composition was coated onto a 50 μm thick PET substrate film that had undergone corona treatment, with the dry adhesive thickness controlled at 25 μm. After drying in a 100°C oven for 2 minutes, a 38 μm thick PET release film was laminated, and the film was cured at 50°C for 48 hours to obtain a UV-resistant pressure-sensitive adhesive tape sample.

[0030] Comparative Examples 1-4 Comparative Example 1: No ONB was added, and the other steps were the same as in Example 2.

[0031] Comparative Example 2: No GMA was added, and the other steps were the same as in Example 2.

[0032] Comparative Example 3: Neither ONB nor GMA was added, and the other steps were the same as in Example 2, i.e., a common thermosetting acrylic pressure-sensitive adhesive was prepared.

[0033] Comparative Example 4: Based on Comparative Example 3, a UV-resistant tape was prepared by physically mixing multifunctional oligomers (dipentaerythritol hexaacrylate DPHA monomer). Performance Tests and Results

[0034] The pressure-sensitive adhesive tape samples prepared in Examples 1-10 and Comparative Examples 1-4 were bonded to a standard mirror-finish stainless steel plate, and their initial 180° peel strength (before UV) was tested according to GB / T 2792 standard. Then, the adhesive surface was irradiated with a 365nm LED UV light source with a power of 250 mW / cm² at a dose of 300 mJ / cm², and its peel strength was tested again (after UV). The peel force unit is N / 25mm. The peel interface condition was observed simultaneously, and the residual adhesive was evaluated. The results are detailed in Table 2.

[0035] Table 1: Composition and Formulation (parts by weight) of Examples and Comparative Examples

[0036] Table 2: Performance Test Results

[0037] 1. All examples (1-10) exhibited excellent UV-cured adhesive strength reduction properties, with peel force reduction rates all exceeding 93%, and most exceeding 99%. The peel interface after UV treatment primarily showed cohesive breakdown or pulverization, demonstrating that the dual synergistic mechanism described in this invention effectively breaks down cohesion, thereby achieving a near-zero residue peel effect. The selection of appropriate monomer ratios, ONB content, and dangling double bond density are all factors controlling the adhesive strength reduction effect. Comparative Example 3, however, did not add either ONB or GMA, thus preparing a conventional thermosetting acrylic pressure-sensitive adhesive and did not exhibit any adhesive strength reduction effect.

[0038] 2. Comparing Example 2, Comparative Example 1, and Comparative Example 2, it can be seen that the sample possessing both structures (Example 2) has a significantly lower post-UV peel strength (0.08 N / 25 mm) than the samples containing only dangling double bonds (Comparative Example 1, 1.85 N / 25 mm) or only photolytic side chains (Comparative Example 2, 0.50 N / 25 mm). This demonstrates a significant synergistic effect between "dangling double bond crosslinking" and "photolytic side chain degradation," rather than a simple additive effect.

[0039] 3. Compared to Example 2 (ONB content 2.0 parts), Example 3 (ONB content 3.0 parts) showed lower peel strength after UV curing, indicating that increasing the density of photolysis points helps to more thoroughly break cohesive forces. Example 6 (GMA content 6.0 parts) showed a decrease in initial peel strength, indicating that excessive dangling double bonds may introduce excessive rigidity during the thermosetting stage.

[0040] 4. Although the physical Semi-IPN system of Comparative Example 4 also has a low peel force after UV treatment, a small amount of adhesive layer remains, and its initial peel force is too high (24.4 N / 25 mm), which may not be suitable for some precision fixing scenarios that require moderate initial adhesion. In addition, its mechanism relies on interfacial shrinkage, and multifunctional monomer molecules may remain when dealing with complex interfaces. Overall, it is not as good as the synergistic mechanism of the present invention.

Claims

1. A UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains, the UV-resistant acrylic pressure-sensitive tape comprising a substrate film and a UV-resistant adhesive layer coated thereon, characterized in that... By weight, the UV-resistant adhesive layer comprises the following components: 100 parts of main adhesive, 0.5-5 parts of photoinitiator, 0.5-3 parts of curing agent, and 0-40 parts of solvent.

2. The UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 1, characterized in that... The main adhesive is an acrylate copolymer solution containing photolytic side chains and dangling double bonds; The acrylate copolymer containing photolytic side chains and dangling double bonds has a main chain composed of acrylate monomer units, and the side chains simultaneously contain o-nitrobenzyl ester photolytic units and methacryloxy dangling double bond units connected by chemical bonds.

3. The UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 1, characterized in that... The photoinitiator is a cleavage-type free radical photoinitiator, selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenylmethyl.

4. The UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 1, characterized in that... The curing agent is an isocyanate-based curing agent; the solvent is ethyl acetate.

5. A method for preparing a UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains as described in any one of claims 1-4, characterized in that... Includes the following steps: 1) Synthesis of the main adhesive: First, the photoresponsive crosslinking agent ONB is synthesized; then ONB is copolymerized with acrylate monomers to obtain a polymer solution containing active groups; then GMA is used for modification to introduce dangling double bonds to obtain the copolymer solution. 2) Preparation of UV-resistant adhesive composition: Add photoinitiator, curing agent and solvent to the reaction system of step S1 according to the ratio, and mix thoroughly under light-protected conditions to obtain UV-resistant adhesive composition; 3) Coating and curing: The UV anti-tack adhesive composition obtained in step 2) is coated onto the substrate film, heated and dried to evaporate the solvent and trigger the curing agent reaction to form a UV anti-tack adhesive layer. After laminating with a release film, it is cured to obtain a pressure-sensitive adhesive tape.

6. The method for preparing UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 5, characterized in that... Step 1) The specific process is as follows: 1.1) Under an inert atmosphere and at 0-5℃, o-nitrobenzyl alcohol was dissolved in an organic base and solvent, and acryloyl chloride was slowly added dropwise. After the reaction was completed, ONB was obtained through post-treatment. 1.2) Mix acrylic acid, butyl acrylate, isooctyl acrylate, hydroxyethyl acrylate and the photoresponsive crosslinking agent ONB prepared in step 1.1) in proportion, add solvent and free radical initiator, and carry out solution polymerization at 65-75℃. After the reaction is completed, raise the temperature to 80-85℃ to consume the residual initiator to obtain a main adhesive solution containing hydroxyl, carboxyl and o-nitrobenzyl ester side chains. 1.3) Cool the main adhesive solution obtained in step 1.2) to 50-65℃, add GMA and catalyst, and keep it at the temperature for 3-6 hours to allow the epoxy group of GMA to undergo a ring-opening esterification reaction with the carboxyl group in the main adhesive, thereby introducing methacryloyloxy group into the polymer in the form of a suspended side chain.

7. The method for preparing UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 6, characterized in that... The photoresponsive crosslinking agent ONB has an o-NO2-C6H4-CH2-O-CO-CR=CH2 structure, wherein R is H or CH3; The amount of photoresponsive crosslinking agent ONB in ​​the monomer mixture accounts for 0.5%-5% of the total weight of the monomers, the amount of acrylic acid in the monomer mixture accounts for 0.5%-8% of the total weight of the monomers, and the amount of hydroxyethyl acrylate accounts for 2%-10% of the total weight of the monomers. The amount of GMA used is 0.8-2.0 times the molar amount of carboxyl groups in the acrylate polymer containing hydroxyl, carboxyl, and o-NB side chains.

8. The method for preparing UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 6, characterized in that... In step 1.1), the organic base is triethylamine and the solvent is ethyl acetate; in step 1.2), the free radical initiator is AIBN, wherein the total amount of free radical initiator is 0.03%-0.3% of the total weight of the monomer, and the solvent is ethyl acetate; in step 1.3), the catalyst is triphenylphosphine, and the amount of catalyst is 0.5-2% of the mass of GMA.

9. The method for preparing UV-resistant acrylic pressure-sensitive tape based on the synergistic structure of dangling double bonds and photolytically degradable side chains according to claim 5, characterized in that... In step 3), the heating and drying temperature is 80-130℃, and the time is 1-5 minutes.

10. The application of a UV-resistant acrylic pressure-sensitive tape based on a synergistic structure of dangling double bonds and photolytically degradable side chains, prepared by the method described in any one of claims 5-9, in the fields of semiconductor wafer cutting protection, temporary fixation of precision components, or peelable protective film.

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