UV (ultraviolet) tackifying film with dual curing mechanisms and preparation method of UV tackifying film

Abstract

The invention discloses a UV tackifying film with a dual curing mechanism and a preparation method thereof.The UV tackifying film comprises a base material layer and a pressure-sensitive adhesive layer arranged on at least one face of the base material layer, and the pressure-sensitive adhesive layer comprises 5-40 parts of hydroxyl-terminated polyfunctional polyurethane resin, 100 parts of acrylate oligomer with double bonds, 0.1-2 parts of acrylate monomer and 0.1-0.6 part of photoinitiator m; and 0.4 to 3.2 parts of an isocyanate curing agent, wherein the hydroxyl-terminated polyfunctional polyurethane resin is prepared by carrying out a reaction on polypropylene oxide triol and diisocyanate. The preparation method comprises the following steps: fully mixing the hydroxyl-terminated polyfunctional polyurethane resin with the double-bond acrylate oligomer, the acrylate monomer, the photoinitiator and the isocyanate curing agent, then coating the corona surface of the base material layer with the mixture, and drying and curing to obtain the UV tackified film. The UV tackifying film has the advantages of excellent reprocessability, reliable final adhesion and better storage stability.

Description

Technical Field

[0001] This invention belongs to the field of UV adhesion-enhancing film technology, and in particular to an adhesive film used for surface protection and structural reinforcement in the manufacturing, assembly and transportation of electronic devices, optical components or precision components, and also has excellent reprocessability. Specifically, it relates to a UV adhesion-enhancing film with a dual curing mechanism and its preparation method. Background Technology

[0002] In the manufacturing process of precision products such as electronic devices, it is often necessary to temporarily apply protective or reinforcing films to the product surface to prevent scratches, damage, or to provide necessary rigidity. These films need to meet two seemingly contradictory requirements: on the one hand, they should have low adhesion in the initial stage of bonding to facilitate easy peeling and re-bonding in case of poor bonding such as air bubbles or misalignment (i.e., good reprocessability), and should not leave any residue on the adhered surface after peeling; on the other hand, after final positioning, they need to form a strong bond with the adhered object to provide reliable long-term protection or reinforcement. For example, Chinese patent application CN111876092A discloses a reinforcing film whose adhesion strength increases from low to high through photocuring. However, this solution relies on a single photocurable adhesive layer, and its initial performance is entirely determined by the uncured photosensitive resin, requiring extremely high standards for formulation design and storage stability. Furthermore, once the light exposure is missed, its performance transformation becomes uncontrollable. Moreover, the adhesive strength of the film before photocuring is relatively high, resulting in poor reprocessability. Therefore, there is an urgent need to develop a new type of adhesive film that can balance storage stability, easy reprocessing in the early stages, and high reliability in the later stages. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a UV thickening film with a dual curing mechanism and its preparation method, which addresses the shortcomings of the prior art.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A UV tackifying film with a dual curing mechanism includes a substrate layer and a pressure-sensitive adhesive layer disposed on at least one side of the substrate layer, the pressure-sensitive adhesive layer comprising the following components in parts by weight: 5 to 40 parts of hydroxyl-terminated multifunctional polyurethane resin 100 parts of acrylate oligomers with double bonds 0.1 to 2 parts of acrylate monomer, Photoinitiator m: 0.1 to 0.6 parts Isocyanate curing agent: 0.4 parts to 3.2 parts The hydroxyl-terminated multifunctional polyurethane resin has a functionality ≥2. The hydroxyl-terminated multifunctional polyurethane resin is prepared by reacting polypropylene triol with a molecular weight of 1000-5000 with diisocyanate. The molar ratio of polypropylene triol to diisocyanate is 1:0.51-0.58. The molecular weight of the double-bonded acrylate oligomer is 230,000-280,000.

[0005] Preferably, in the above-mentioned UV tackifying film with a dual curing mechanism, the molecular weight of the polyoxypropylene triol is 3000 or 5000; and the diisocyanate is hexamethylene diisocyanate (HDI) or isoflurane diisocyanate (IPDI).

[0006] In the aforementioned UV tackifying film with a dual curing mechanism, preferably, the hydroxyl-terminated multifunctional polyurethane resin is a polyether polyurethane resin with a solid content of 55% to 65%; and the isocyanate curing agent is hexamethylene diisocyanate trimer.

[0007] Preferably, in the aforementioned UV-curing film with a dual curing mechanism, the acrylate oligomer containing double bonds is a mixture of the following components in parts by weight, polymerized via a photoinitiated reaction. 30 to 60 parts of butyl acrylate 15 to 40 parts of isooctyl acrylate Acrylamide 5 to 20 parts 3 to 10 parts acrylic acid Photoinitiator n: 0.01 parts to 0.04 parts.

[0008] Preferably, in the above-mentioned UV tackifying film with a dual curing mechanism, the photoinitiator n is one or a mixture of two of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) and ethyl 2,4,6-trimethylbenzoyl phosphate (TPO-L).

[0009] Preferably, in the above-mentioned UV tackifying film with a dual curing mechanism, the acrylate monomer is one or a mixture of two of 1,4-butanediol diacrylate and 1,6-hexanediol diacrylate.

[0010] Preferably, in the above-mentioned UV tackifying film with a dual curing mechanism, the photoinitiator m is one or a mixture of several of the following: (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoyl phosphate (TPO-L), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819), 1-hydroxycyclohexyl-phenyl ketone (184), 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propanone (2959), and 2-hydroxy-2-methyl-1-phenylpropanone (1173).

[0011] Preferably, in the above-mentioned UV tackifying film with a dual curing mechanism, the photoinitiator m is a mixture of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819), wherein the mass ratio of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) to bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819) is 3:0.8 to 1.2.

[0012] As a general technical concept, the present invention also provides a method for preparing the above-mentioned UV tackifying film with a dual curing mechanism, comprising the following steps: (1) Preparation of multifunctional polyurethane resins with terminal hydroxyl groups; (2) Preparation of acrylate oligomers with double bonds; (3) Mix the hydroxyl-terminated polyurethane resin, double-bonded acrylate oligomer, acrylic monomer, photoinitiator m, and isocyanate curing agent, and adjust the solid content with solvent to obtain pressure-sensitive adhesive. (4) Apply the pressure-sensitive adhesive to at least one side of the substrate layer, dry it, protect the adhesive surface with a release film, and cure it in the dark to obtain a UV tackifying film with a dual curing mechanism.

[0013] The UV tackifying film with dual curing mechanism described above, preferably, in step (1), the preparation steps of the hydroxyl-terminated multifunctional polyurethane resin include: heating polyoxypropylene triol to 105℃~120℃ under stirring, vacuum dehydrating for 1.5h~2.5h, removing the vacuum, cooling to below 80℃, adding diisocyanate, and after the temperature stabilizes, raising the temperature to 80℃~90℃ and reacting for 5h~7h, and then adding solvent to adjust the solid content to obtain the hydroxyl-terminated multifunctional polyurethane resin.

[0014] Preferably, in step (2), the preparation steps of the acrylate oligomer with double bonds include: stirring butyl acrylate, isooctyl acrylate, acrylamide, acrylic acid and photoinitiator at a constant temperature of 0℃ to 3℃, and after mixing, waiting for the material temperature to drop below 5℃, and then initiating the polymerization reaction by a light source to obtain the acrylate oligomer with double bonds.

[0015] In the above-mentioned UV tackifying film with dual curing mechanism, preferably, in step (4), the curing temperature is 40℃~60℃ and the curing time is 36h~72h.

[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) The UV tackifying film of the present invention has a dual curing mechanism. It consists of a thermosetting system composed of a multifunctional polyurethane resin with terminal hydroxyl groups and an isocyanate curing agent. During the preparation and curing of the UV tackifying film, a crosslinking reaction occurs, giving the pressure-sensitive adhesive layer initial cohesive strength. At the same time, the present invention consists of a UV curing system composed of double-bonded acrylate oligomers, acrylate monomers (used to adjust the degree of crosslinking) and a photoinitiator. Under ultraviolet irradiation, a polymerization reaction occurs, which together with the already formed polyurethane network forms an interpenetrating network structure. In the early stage of bonding, the UV tackifying film relies on the polyurethane network formed by the thermosetting reaction to provide sufficient cohesive strength, binding the acrylate oligomers in the crosslinked network of polyurethane. Due to the low cohesive strength of the acrylate oligomers, the characteristics of low adhesion and no residue are achieved. When final fixation is required, the curing reaction of the acrylate oligomers is triggered by ultraviolet (UV) irradiation, which rapidly increases the molecular weight and greatly enhances the cohesive force, breaking through the constraint of the polyurethane crosslinked network, thereby obtaining high adhesion and achieving a reliable reinforcing effect.

[0017] (1.1) Excellent reprocessability: Thanks to the initial cohesive strength provided by thermosetting polyurethane, the UV tackifying film of the present invention exhibits low tack (5-20g / 25mm) before UV irradiation, can be easily and completely peeled off from the substrate without leaving any adhesive residue, and is easy to rework.

[0018] (1.2) Reliable final bonding: After UV irradiation, the acrylate system is cured and interpenetrates with the polyurethane network, which significantly improves the adhesion (≥1000g / 25mm) and greatly increases the cohesive strength, effectively strengthening and protecting the bonded materials.

[0019] (1.3) High process flexibility: The thermosetting and UV curing processes are independent and do not interfere with each other. The thermosetting is completed during the film production stage, ensuring the storage stability of the product; while the UV curing time can be selected arbitrarily according to actual production needs, which greatly improves the flexibility of the production process.

[0020] (1.4) Stable performance over a wide temperature range: The storage modulus of this pressure-sensitive adhesive layer at low temperature (-20℃) is approximately 6.0 × 10⁻⁶. 6 (Pa) relative to the storage modulus of conventional adhesives (approximately 1.0 × 10⁻⁶ Pa) 8 The low Pa ensures adhesion in cold environments and prevents the adhered object from easily detaching when subjected to high-frequency vibrations. Under high temperature and high humidity (85℃ / 85%RH) conditions, it can still maintain no displacement for 48 hours, demonstrating excellent weather resistance and reliability.

[0021] (2) The method for preparing the UV tackifying film with a dual curing mechanism of the present invention involves thoroughly mixing a multifunctional polyurethane resin with terminal hydroxyl groups with an acrylate oligomer containing double bonds, an acrylate monomer, a photoinitiator, and an isocyanate curing agent, then coating it onto the corona-treated surface of a substrate layer, drying and curing it to obtain a UV tackifying film. The UV tackifying film prepared by the method of the present invention has an initial tack of 5-20 g / 25 mm, and after UV irradiation, the tack can reach more than 1000 g / 25 mm, exhibiting excellent reprocessability and reliable final adhesion. Furthermore, it can overcome the limitations of a single curing system in terms of storage stability through an independent and controllable dual curing mechanism. The preparation method of the present invention is more advantageous than the existing technology that uses an acrylic copolymer containing both double bonds and hydroxyl groups to form a crosslinked UV tackifying film. In the existing method, the acrylic copolymer reacts with the isocyanate to form a thermal crosslinked network, and then the double bonds participate in UV curing, further increasing the crosslinking density. Excessive crosslinking density leads to low tack, resulting in limited improvement in tack after UV curing, making it difficult to obtain satisfactory initial processability and high reliability in the later stage. Furthermore, the same component participates in both thermosetting and photosetting, causing the two reactions to interfere with each other and making it impossible to form an ideal interpenetrating network. This invention avoids this drawback from a mechanistic perspective. Detailed Implementation

[0022] The present invention will be further described below in conjunction with the specification and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0023] Example 1 The present invention discloses a UV tackifying film with a dual curing mechanism, comprising a substrate layer and a pressure-sensitive adhesive layer disposed on at least one side of the substrate layer, wherein the pressure-sensitive adhesive layer comprises the following components in parts by weight: 5 parts of hydroxyl-terminated multifunctional polyurethane resin, 100 parts of acrylate oligomers with double bonds 0.1 parts of acrylate monomer, Photoinitiator m 0.1 parts, 0.4 parts isocyanate curing agent, In this embodiment, the functionality of the hydroxyl-terminated multifunctional polyurethane resin is ≥2. The hydroxyl-terminated multifunctional polyurethane resin is prepared by reacting polypropylene triol with a molecular weight of 3000 with diisocyanate. The molar ratio of polypropylene triol to diisocyanate is 1:0.55, and the diisocyanate is hexamethylene diisocyanate (HDI).

[0024] In this embodiment, the molecular weight of the acrylate oligomer with double bonds is 280,000.

[0025] In this embodiment, the acrylate monomer is 1,4-butanediol diacrylate (BBDA).

[0026] In this embodiment, the photoinitiator m is a combination of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide (TPO) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819) in a mass ratio of 3:1.

[0027] In this embodiment, the isocyanate curing agent is hexamethylene diisocyanate trimer.

[0028] This invention discloses a method for preparing a UV tackifying film with a dual curing mechanism, comprising the preparation of an adhesive and the application of the adhesive onto a substrate to form the tackifying film. The specific steps are as follows: (1) Synthesis of polyurethane resin with hydroxyl-terminated polyoxypropylene triol (Lanxing Dongda EP-330N(G)) with a molecular weight of 3000 was placed in a 5L reaction flask and heated to 110℃ under stirring. It was then dehydrated under vacuum for 2h. After removing the vacuum, the temperature was lowered to below 80℃. 73.9g of hexamethylene diisocyanate (HDI) was added. After the temperature stabilized, the temperature was slowly raised to 85℃ and reacted at this temperature for 6h. Then, 1650g of ethyl acetate was added for dilution to obtain a polyurethane resin with hydroxyl-terminated polyoxypropylene triol with a solid content of 60%, which was denoted as component a.

[0029] (2) Synthesis of acrylate oligomers with double bonds: 30 parts of butyl acrylate (BA), 15 parts of isooctyl acrylate (EHA), 5 parts of acrylamide (AM), 10 parts of acrylic acid (AA), and 0.01 parts of TPO were put into a constant temperature stirred tank at 0℃~3℃ and stirred for 30 min. When the material temperature dropped to below 5℃, the material was injected into the pipeline reactor at a constant speed of 0.3 m / min. The reaction was initiated by LED light source to prepare acrylate oligomers with double bonds with a molecular weight of 280,000, which were denoted as component b1.

[0030] (3) Dissolve TPO and 819 in butanone at a mass ratio of 3:1 to prepare a photoinitiator solution with a solid content of 50%, denoted as component c.

[0031] According to the mass proportions in Table 1, the hydroxyl-terminated polyurethane resin (component a) obtained in step (1) and the double-bonded acrylate oligomer (component b1) obtained in step (2) are thoroughly mixed with 1,4-butanediol diacrylate (BBDA), photoinitiator solution (component c), and hexamethylene diisocyanate trimer (HDI trimer), and diluted with methyl ethyl ketone to a solid content of 40% to obtain a pressure-sensitive adhesive with UV tackifying effect.

[0032] The preferred solvent is methyl ethyl ketone (MEK), but other solvents can also be used. The amount used is to dilute the solid content of the system to 40%, which is beneficial for coating.

[0033] (4) The pressure-sensitive adhesive obtained in step (3) is coated onto the corona surface of the PET film using a coating machine, dried in an oven, and the adhesive surface is protected with a release film. It is then cured at 50°C in the dark for 72 hours to obtain the UV-curing film with a dual curing mechanism of the present invention.

[0034] Example 2 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 1, except that the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0035] The present invention provides a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 1. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1.

[0036] Example 3 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 1. The main difference is that the molecular weight of the acrylate oligomer with double bonds is 260,000, and the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0037] This invention discloses a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 1. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1. Furthermore, the amounts of each component used in step (2) are different, resulting in different molecular weights of the acrylate oligomers with double bonds. The details are as follows: 40 parts of butyl acrylate (BA), 23 parts of isooctyl acrylate (EHA), 10 parts of acrylamide (AM), 8 parts of acrylic acid (AA), and 0.02 parts of TPO were added to a constant-temperature stirred tank at 0℃~3℃ and stirred thoroughly for 30 minutes. After the material temperature dropped below 5℃, the material was injected into a pipeline reactor at a constant speed of 0.3m / min. The reaction was initiated by an LED light source to prepare an acrylate oligomer with a molecular weight of 260,000 and double bonds, denoted as component b2.

[0038] Example 4 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 3, except that the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0039] The present invention provides a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 3. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1.

[0040] Example 5 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 1. The main difference is that the molecular weight of the acrylate oligomer with double bonds is 230,000, and the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0041] This invention discloses a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 1. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1. Furthermore, the amounts of each component used in step (2) are different, resulting in different molecular weights of the acrylate oligomers with double bonds. The details are as follows: 50 parts of butyl acrylate (BA), 40 parts of isooctyl acrylate (EHA), 15 parts of acrylamide (AM), 3 parts of acrylic acid (AA), and 0.04 parts of TPO were added to a constant-temperature stirred tank at 0℃~3℃ and stirred thoroughly for 30 minutes. After the material temperature dropped below 5℃, the material was injected into a pipeline reactor at a constant speed of 0.3m / min. The reaction was initiated by an LED light source to prepare an acrylate oligomer with a molecular weight of 230,000 and double bonds, denoted as component b3.

[0042] Example 6 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 5, except that the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0043] The present invention provides a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 5. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1.

[0044] Example 7 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 1. The main difference is that the molecular weight of the acrylate oligomer with double bonds is 240,000, and the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0045] This invention discloses a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 1. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1. Furthermore, the amounts of each component used in step (2) are different, resulting in different molecular weights of the acrylate oligomers with double bonds. The details are as follows: 60 parts of butyl acrylate (BA), 30 parts of isooctyl acrylate (EHA), 20 parts of acrylamide (AM), 6 parts of acrylic acid (AA), and 0.03 parts of TPO were added to a constant-temperature stirred tank at 0℃~3℃ and stirred thoroughly for 30 minutes. After the material temperature dropped below 5℃, the material was injected into a pipeline reactor at a constant speed of 0.4m / min. The reaction was initiated by an LED light source to prepare an acrylate oligomer with a molecular weight of 240,000 and double bonds, denoted as component b4.

[0046] Example 8 The present invention provides a UV tackifying film with a dual curing mechanism, which is basically the same as that in Example 7, except that the amount of each component of the pressure-sensitive adhesive layer is different, as detailed in Table 1.

[0047] The present invention provides a method for preparing a UV tackifying film with a dual curing mechanism. The preparation steps are basically the same as those in Example 7. The main difference is that the mass fractions of each component used in step (3) are different, as detailed in Table 1.

[0048] The UV tackifying films with dual curing mechanisms prepared in Examples 1 to 8 were subjected to performance tests as follows, and the test results are shown in Table 1: UV Pre-Adhesion: The 180° peel force of the UV tackifying film on a stainless steel sheet was measured at 25°C according to ASTM D3330 standard.

[0049] UV adhesion: After the stainless steel sheet was bonded according to ASTM D3330 standard, it was cured by UV lamp with a wavelength of 365nm and an energy of 4000±1000mJ / cm². The 180° peel force of the UV tackifying film on the stainless steel sheet was then measured at 25℃.

[0050] Dynamic mechanical analysis (test method according to ASTM D2196): The storage modulus at -20℃, 25℃ and 85℃ of the UV-cured UV-adhesive films prepared in each example after UV irradiation was measured respectively.

[0051] High temperature and high humidity retention: According to ASTM D3654 standard, the UV tackifying film sample was attached to a steel plate, a 1000g weight was suspended, and the sample was placed in an environment of 85℃ / 85%RH to measure the displacement.

[0052] Table 1 - Component dosage (parts by mass) and product performance test results for UV-adhesive films prepared in Examples 1-8

[0053] As shown in Table 1, the UV-cured tackifying films prepared in Examples 1 to 8 all exhibit pre-UV adhesion ≤20 (g / 25mm), meeting the low-tack requirement. They can be easily and completely peeled off from the substrate without leaving any residue, demonstrating excellent reprocessability. The post-UV adhesion of the UV-cured tackifying films prepared in Examples 1 to 8 is ≥1000g / 25mm, indicating high post-curing reliability. After UV curing, the storage modulus of the UV-cured tackifying films prepared in Examples 1 to 8 at -20°C is 2.3 × 10⁻⁶. 6 Pa ~ 8.2 × 10 6 Pa is significantly lower than the storage modulus of conventional adhesives (approximately 1.0 × 10⁻⁶ Pa). 8 The UV-cured adhesive film prepared in Examples 1 to 8 has a storage modulus of 4.4 × 10⁻⁶ Pa after UV curing at 25°C. This ensures adhesion in cold environments and prevents the film from easily detaching when the substrate is dropped and subjected to high-frequency vibration. 4 Pa ~ 7.1 × 10 4 Pa, storage modulus at 85℃ is 1.4×10 Pa. 4 Pa ~ 3.8 × 10 4 Pa indicates that the pressure-sensitive adhesive in the UV-cured film prepared by this invention not only maintains high peel strength but is also relatively soft after UV curing. Under high temperature and high humidity conditions (85℃ / 85%RH), it can still maintain no displacement for 48 hours, demonstrating excellent weather resistance and reliability.

[0054] Comparative Example 1 A UV tackifying film with a dual curing mechanism is basically the same as that in Example 5, except that the molar ratio of polypropylene triol to diisocyanate used to prepare the hydroxyl-terminated polyfunctional polyurethane resin is reduced to 1:0.50.

[0055] A method for preparing a UV tackifying film with a dual curing mechanism is provided. The preparation steps are basically the same as those in Example 5, except that the amount of HDI used in step (1) is different, decreasing from 73.9g in Example 5 to 67.5g. In order to maintain the solid content of the product, the amount of ethyl acetate is reduced to 1645g, as follows: 2.4 kg of 3000 molecular weight polyoxypropylene triol (Bluestar Dongda EP-330N(G)) was placed in a 5 L reaction flask and heated to 110 °C with stirring. It was then dehydrated under vacuum for 2 h. After removing the vacuum, the temperature was lowered to below 80 °C, and 67.5 g of HDI was added. After the temperature stabilized, the temperature was slowly raised to 85 °C and reacted at this temperature for 6 h. Then, 1645 g of ethyl acetate was added for dilution to obtain a polyfunctional polyurethane resin with 60% solid content and terminal hydroxyl groups, denoted as component a1.

[0056] The other steps and parameters are the same as in Example 5, as detailed in Table 2.

[0057] Comparative Example 2 A UV tackifying film with a dual curing mechanism is basically the same as that in Example 6, except that the molar ratio of polypropylene triol to diisocyanate used to prepare the hydroxyl-terminated polyfunctional polyurethane resin is reduced to 1:0.50.

[0058] A method for preparing a UV tackifying film with a dual curing mechanism is provided. The preparation steps are basically the same as those in Example 6, except that the amount of HDI used in step (1) is different, decreasing from 73.9g in Example 6 to 67.5g. In order to maintain the solid content of the product, the amount of ethyl acetate is reduced to 1645g, as follows: 2.4 kg of 3000 molecular weight polyoxypropylene triol (Bluestar Dongda EP-330N(G)) was placed in a 5 L reaction flask and heated to 110 °C with stirring. It was then dehydrated under vacuum for 2 h. After removing the vacuum, the temperature was lowered to below 80 °C, and 67.5 g of HDI was added. After the temperature stabilized, the temperature was slowly raised to 85 °C and reacted at this temperature for 6 h. Then, 1645 g of ethyl acetate was added for dilution to obtain a polyfunctional polyurethane resin with 60% solid content and terminal hydroxyl groups, denoted as component a1.

[0059] The other steps and parameters are the same as in Example 6, as detailed in Table 2.

[0060] Comparative Example 3 A UV tackifying film with a dual curing mechanism is basically the same as that in Example 5, except that the molar ratio of polypropylene triol to diisocyanate used to prepare the hydroxyl-terminated polyfunctional polyurethane resin is increased to 1:0.63.

[0061] A method for preparing a UV tackifying film with a dual curing mechanism is provided. The preparation steps are basically the same as those in Example 5, except that the amount of HDI used in step (1) is different, increasing from 73.9g in Example 5 to 84.2g. In order to maintain the solid content of the product, the amount of ethyl acetate is increased to 1656g, as detailed below: 2.4 kg of 3000 molecular weight polyoxypropylene triol (Bluestar Dongda EP-330N(G)) was placed in a 5 L reaction flask and heated to 110 °C with stirring. It was then dehydrated under vacuum for 2 h. After removing the vacuum, the temperature was lowered to below 80 °C, and 84.2 g of HDI was added. After the temperature stabilized, the temperature was slowly raised to 85 °C and reacted at this temperature for 6 h. Then, 1656 g of ethyl acetate was added for dilution to obtain a 60% solid polyfunctional polyurethane resin containing terminal hydroxyl groups, denoted as component a2.

[0062] The other steps and parameters are the same as in Example 5, as detailed in Table 2.

[0063] Comparative Example 4 A UV tackifying film with a dual curing mechanism is basically the same as that in Example 5, except that the molar ratio of polypropylene triol to diisocyanate used to prepare the hydroxyl-terminated polyfunctional polyurethane resin is increased to 1:0.63.

[0064] A method for preparing a UV tackifying film with a dual curing mechanism is provided. The preparation steps are basically the same as those in Example 6, except that the amount of HDI used in step (1) is different, increasing from 73.9g in Example 6 to 84.2g. In order to maintain the solid content of the product, the amount of ethyl acetate is increased to 1656g, as detailed below: 2.4 kg of 3000 molecular weight polyoxypropylene triol (Bluestar Dongda EP-330N(G)) was placed in a 5 L reaction flask and heated to 110 °C with stirring. It was then dehydrated under vacuum for 2 h. After removing the vacuum, the temperature was lowered to below 80 °C, and 84.2 g of HDI was added. After the temperature stabilized, the temperature was slowly raised to 85 °C and reacted at this temperature for 6 h. Then, 1656 g of ethyl acetate was added for dilution to obtain a 60% solid polyfunctional polyurethane resin containing terminal hydroxyl groups, denoted as component a2.

[0065] The other steps and parameters are the same as in Example 6, as detailed in Table 2.

[0066] Table 2 - Component dosage (parts by mass) and product performance test results for UV-adhesive films prepared in Comparative Examples 1-4

[0067] A comparison of Comparative Examples 1-2 in Table 2 with Examples 5-6 in Table 1 shows that when the amount of HDI added is low when preparing hydroxyl-terminated multifunctional polyurethane resin, the adhesion before and after UV treatment increases simultaneously, while the storage modulus decreases. The increased adhesion before UV treatment is detrimental to initial reprocessability. A comparison of Comparative Examples 3-4 in Table 2 with Examples 5-6 in Table 1 shows that when the amount of HDI added is high when preparing hydroxyl-terminated multifunctional polyurethane resin, the crosslinking density is higher. The three-dimensional network structure formed after the hydroxyl-terminated multifunctional polyurethane resin and HDI trimer react and cures is more compact, resulting in stronger binding of the double-bonded acrylate oligomers. This manifests as a decrease in adhesion before and after UV treatment, significantly reducing later reliability, and an increase in storage modulus, which is detrimental to the shock absorption and protection of precision devices. Therefore, in order to simultaneously achieve the three major advantages of storage stability, easy initial reprocessing, and high reliability in the later stage, the amount of isocyanate curing agent added during the preparation of hydroxyl-terminated multifunctional polyurethane resin needs to be controlled within a suitable range. This invention controls the molar ratio of polyoxypropylene triol to diisocyanate to be 1:0.51 to 0.58, which can ensure that the UV tackifying film has excellent effects.

[0068] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A UV tackifying film with a dual curing mechanism, comprising a substrate layer and a pressure-sensitive adhesive layer disposed on at least one side of the substrate layer, characterized in that: The pressure-sensitive adhesive layer comprises the following components in parts by weight: 5 to 40 parts of hydroxyl-terminated multifunctional polyurethane resin 100 parts of acrylate oligomers with double bonds 0.1 to 2 parts of acrylate monomer, Photoinitiator m: 0.1 to 0.6 parts Isocyanate curing agent: 0.4 parts to 3.2 parts The hydroxyl-terminated multifunctional polyurethane resin has a functionality ≥2. The hydroxyl-terminated multifunctional polyurethane resin is prepared by reacting polypropylene triol with a molecular weight of 1000-5000 with diisocyanate. The molar ratio of polypropylene triol to diisocyanate is 1:0.51-0.

58. The molecular weight of the acrylate oligomer with double bonds is 230,000 to 280,000.

2. The UV-curing film with a dual curing mechanism according to claim 1, characterized in that, The molecular weight of the polyoxypropylene triol is 3000 or 5000; the diisocyanate is hexamethylene diisocyanate or isoflurane diisocyanate.

3. The UV-curing film with a dual curing mechanism according to claim 1, characterized in that, The hydroxyl-terminated multifunctional polyurethane resin is a polyether polyurethane resin with a solid content of 55% to 65%; the isocyanate curing agent is hexamethylene diisocyanate trimer.

4. The UV-curing film with a dual curing mechanism according to claim 1, characterized in that, The acrylate oligomer containing double bonds is produced by mixing the following components in parts by weight and polymerizing them via a photoinitiated reaction. 30 to 60 parts of butyl acrylate 15 to 40 parts of isooctyl acrylate Acrylamide 5 to 20 parts 3 to 10 parts acrylic acid Photoinitiator n: 0.01 parts to 0.04 parts.

5. The UV-curing film with a dual curing mechanism according to claim 4, characterized in that, The photoinitiator n is one or a mixture of two of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide and ethyl 2,4,6-trimethylbenzoyl phosphate.

6. The UV-curing film with a dual curing mechanism according to claim 1, characterized in that, The acrylate monomer is one or a mixture of two of 1,4-butanediol diacrylate and 1,6-hexanediol diacrylate.

7. The UV-curing adhesive film with a dual curing mechanism according to any one of claims 1 to 6, characterized in that, The photoinitiator m is one or a mixture of several of the following: (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phosphate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 1-hydroxycyclohexyl-phenyl ketone, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propanone, and 2-hydroxy-2-methyl-1-phenylpropanone.

8. The UV tackifying film with a dual curing mechanism according to claim 7, characterized in that, The photoinitiator m is a mixture of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, wherein the mass ratio of (2,4,6-trimethylbenzoyl)diphenylphosphine oxide to bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 3:0.8 to 1.

2.

9. A method for preparing a UV-curing film with a dual curing mechanism as described in any one of claims 1 to 8, characterized in that, Includes the following steps: (1) Preparation of multifunctional polyurethane resins with terminal hydroxyl groups; (2) Preparation of acrylate oligomers with double bonds; (3) Mix the polyfunctional polyurethane resin with terminal hydroxyl groups, acrylate oligomer with double bonds, acrylic monomer, photoinitiator m, and isocyanate curing agent, and adjust the solid content with solvent to obtain pressure-sensitive adhesive. (4) Apply the pressure-sensitive adhesive to at least one side of the substrate layer, dry it, protect the adhesive surface with a release film, and cure it in the dark to obtain a UV tackifying film with a dual curing mechanism.

10. The method for preparing the UV-curing film with a dual curing mechanism according to claim 9, characterized in that, In step (1), the preparation steps of the hydroxyl-terminated multifunctional polyurethane resin include: heating polyoxypropylene triol to 105℃~120℃ under stirring, vacuum dehydrating for 1.5h~2.5h, removing the vacuum, cooling to below 80℃, adding diisocyanate, and after the temperature stabilizes, raising the temperature to 80℃~90℃ and reacting for 5h~7h, and then adding solvent to adjust the solid content to obtain the hydroxyl-terminated multifunctional polyurethane resin. In step (2), the preparation steps of the acrylate oligomer with double bonds include: stirring butyl acrylate, isooctyl acrylate, acrylamide, acrylic acid and photoinitiator at a constant temperature of 0℃ to 3℃, and after mixing, waiting for the material temperature to drop below 5℃, and then initiating the polymerization reaction by a light source to obtain the acrylate oligomer with double bonds. In step (4), the aging temperature is 40℃~60℃ and the aging time is 36h~72h.

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