Pure adhesive film and preparation method thereof

Abstract

The invention relates to the technical field of pure adhesive films, in particular to a pure adhesive film and a preparation method thereof. The adhesive is composed of the following components: 75-95 parts of polymer resin, 25-45 parts of tackifying resin, 2-6 parts of a dynamic cross-linking agent, 5-12 parts of a functional filler, 5-15 parts of a high refractive index component, 1.5-3.5 parts of an anti-aging agent and 90-130 parts of a solvent, and the polymer resin is composed of an acrylate copolymer and a hydrogenated styrene-isoprene-styrene block copolymer according to a mass ratio of 6: (0-5). The preparation method of the pure adhesive film comprises the following steps: S1, premixing; s2, performing supercritical fluid dispersion; s3, mixing and defoaming; s4, coating and UV curing are carried out; and S5, film covering and rolling. The preparation method is stable in process, easy to control and suitable for large-scale industrial production. The prepared product is high in heat conductivity coefficient, good in peel strength and good in high-temperature and high-humidity resistance.

Description

Technical Field

[0001] This invention relates to the field of pure adhesive film technology, and in particular to a pure adhesive film and its preparation method. Background Technology

[0002] Pure adhesive film, also known as substrate-free double-sided tape, is a high-performance adhesive product that is directly formed into a film through specific formulations and processes without relying on substrates such as fabrics or films. It has the following advantages:

[0003] (1) Ultra-thin structure: thickness range of 2-200μm (e.g. 5μm for precision electronics), solving the needs of space-constrained scenarios;

[0004] (2) High adhesion strength: peel strength reaches 1.5-2.2 N / mm (IPC standard), and can withstand 260℃ soldering temperature;

[0005] (3) Environmental adaptability: Resistant to chemical corrosion and UV aging, some models meet the RoHS halogen-free standard;

[0006] (4) Interface compatibility: Excellent fit to irregular surfaces (such as metal grooves and curved screens).

[0007] Due to its excellent performance, it is widely used in electronic components (such as display modules and touch panels), optical components (such as lens assembly), automotive interior parts bonding, and precision structural parts fixing, to meet the requirements of thinness, high bonding reliability, and good cushioning and sealing.

[0008] Currently, most pure adhesive films on the market are based on acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, or rubber-based pressure-sensitive adhesive systems. However, these systems all have their own inherent drawbacks:

[0009] (1) Acrylic ester system: It has good overall performance, but its bonding strength and cohesive strength are easily reduced in high temperature and high humidity environment (e.g., 85℃ / 85%RH), and it is easy to experience edge curling, peeling and other phenomena; at the same time, its resistance to chemical solvents (such as alcohols and esters) is relatively poor, and it may be corroded in subsequent processing.

[0010] (2) Organosilicon system: It has excellent high and low temperature resistance and chemical stability, but its bonding strength is usually low and it is easy to adsorb dust and other particles in the environment, affecting the appearance and bonding effect. More importantly, it is expensive and has poor bonding compatibility with some plastics (such as PC and ABS).

[0011] (3) Rubber-type system: high initial tack, but poor aging resistance (especially thermo-oxidative aging and ultraviolet aging), insufficient cohesive strength, and easy to creep under continuous stress, resulting in displacement of the adhered objects.

[0012] CN116285718B discloses a method for manufacturing a low dielectric loss pure adhesive film, comprising the following steps: Step 1, synthesizing a low dielectric loss thermoplastic polyimide resin precursor-polyamic acid solution; Step 2, preparing the adhesive: sequentially adding the polyamic acid solution synthesized in Step 1, epoxy resin YX8100BH30, epoxy resin NC-3000-H, curing agent (CUA-4), latent curing agent (boron trifluoride-2-methylimidazole), flame retardant (SPB-100), solvent (cyclohexanone), and solvent (butanone) to a PE bottle, then stirring and allowing to stand to defoam; Step 3, taking the adhesive prepared in Step 2 and coating it onto a PET release film. The produced pure adhesive film has a low dielectric loss value, with a test value of approximately 0.003 at 10GHz; good heat resistance: solder heat resistance of 300℃ / 30s; peel strength ≥1.0kgf / cm; and excellent chemical resistance.

[0013] There is an urgent need in this field to develop a new type of pure adhesive film that can possess excellent properties such as high initial adhesion and excellent high temperature resistance without sacrificing any key performance characteristics. Summary of the Invention

[0014] This invention provides a pure adhesive film composed of the following components by mass: 75-95 parts polymer resin, 25-45 parts tackifying resin, 2-6 parts dynamic crosslinking agent, 5-12 parts functional filler, 5-15 parts high refractive index component, 1.5-3.5 parts anti-aging agent, and 90-130 parts solvent. The polymer resin is composed of acrylate copolymer and hydrogenated styrene-isoprene-styrene block copolymer in a mass ratio of 6:(0-5).

[0015] Furthermore, the acrylate copolymer is a methyl methacrylate-butyl acrylate copolymer, wherein the ratio of methyl methacrylate to butyl acrylate monomers is (1~2):1, and the hydrogenation degree of the hydrogenated styrene-isoprene-styrene block copolymer is greater than 98%. The acrylate copolymer possesses tackiness and holding power, excellent weather resistance, and wettability on various substrates, ensuring that the film remains soft and tacky even at low temperatures. The hydrogenated styrene-isoprene-styrene block copolymer provides extremely high cohesive strength, creep resistance, and elastic recovery ability; its hydrogenated saturated structure endows it with excellent resistance to heat oxidation and UV aging. When the two are blended in a specific ratio, the acrylate ensures excellent adhesion, while the physical cross-linking network of the hydrogenated styrene-isoprene-styrene block copolymer acts like a "steel bar," greatly enhancing the cohesive strength and peel resistance of the colloid, avoiding the softening defect of a single acrylate system at high temperatures. The two have good compatibility and will not undergo phase separation, achieving a "combination of rigidity and flexibility."

[0016] Furthermore, the tackifying resin is composed of hydrogenated terpene resin and hydrogenated petroleum resin, with a mass ratio of 1:(1~2.5). The hydrogenated terpene resin exhibits excellent initial tack and good compatibility with acrylates, has a light color, and is resistant to aging. The hydrogenated petroleum resin has a higher softening point and better hardening effect, effectively improving the cohesive strength and temperature resistance of the adhesive film. The combination of these two components allows the hydrogenated terpene resin to quickly wet the bonded surfaces, providing instantaneous adhesion, while the hydrogenated petroleum resin maintains colloidal stability at high temperatures, preventing adhesive overflow. Their saturated structure together ensures the excellent aging resistance of the entire tackifying system, preventing it from becoming brittle or sticky due to oxidation.

[0017] Furthermore, the dynamic crosslinking agent is a mixture of adipic acid dihydrazide and aluminum triacetylacetonate, with a mass ratio of adipic acid dihydrazide to aluminum triacetylacetonate of 2:1. During the heating and curing process, adipic acid dihydrazide undergoes dehydration condensation with the carboxyl groups on the acrylate chain, achieving chemical crosslinking and significantly improving heat resistance and solvent resistance. Aluminum triacetylacetonate binds to the polar groups in the acrylate and hydrogenated styrene-isoprene-styrene block copolymers, exhibiting good compatibility and ensuring the thermal stability of the crosslinked network.

[0018] Furthermore, the functional filler is composed of sheet-like silica and hydroxylated boron nitride nanosheets, with a mass ratio of 2:1. The hydroxylated boron nitride nanosheets are prepared by adding boron nitride nanosheets and silane coupling agent KH-550 to N-methylpyrrolidone, performing surface hydroxylation via ultrasound, and then filtering and drying to obtain hydroxylated boron nitride nanosheets. The mass ratio of boron nitride nanosheets, silane coupling agent KH-550, and N-methylpyrrolidone is 1:0.2:6. Sheet-like silica effectively blocks the penetration paths of water vapor and oxygen, greatly improving the film's resistance to damp heat aging. Boron nitride nanosheets, as a two-dimensional thermally conductive filler, efficiently conduct heat along the surface direction, preventing localized overheating. The hydroxylated boron nitride nanosheets, due to the introduction of hydroxyl groups, have better compatibility with other components in the formulation, resulting in superior technical performance.

[0019] Furthermore, the anti-aging agent is composed of antioxidant 2246 and UV329, and the mass ratio of antioxidant 2246 to UV329 is 1:1.

[0020] Furthermore, the high refractive index component is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene or bis(4-methacryloylthiophenyl)sulfide. The introduction of this high refractive index component allows it to participate in copolymerization to form a high refractive index network under UV irradiation, making it particularly suitable for bonding optical devices and reducing interfacial reflection loss. After copolymerization with the polymer resin, the refractive index of the film is increased while maintaining high transparency, meeting the requirements of optical encapsulation. When the high refractive index component is bis(4-methacryloylthiophenyl)sulfide, this component contains sulfur atoms and aromatic rings, giving it a high refractive index and superior performance.

[0021] Furthermore, the solvent is a mixture of toluene and acetone, with a mass ratio of toluene to acetone of 7:3.

[0022] The present invention also provides a method for preparing the above-mentioned pure adhesive film, comprising the following steps:

[0023] S1. Premixing: Add the polymer resin, tackifying resin, high refractive index component and 50% solvent into a mixer, and stir at 300-500 rpm for 2 hours at 40-50°C under inert gas protection until completely dissolved to obtain a premixed adhesive solution.

[0024] S2. Supercritical fluid dispersion: Dynamic crosslinking agent, functional filler, anti-aging agent and 50% solvent are mixed and put into a supercritical fluid device. CO2 is introduced and dispersed for 30 minutes at a pressure of 12~18MPa and a temperature of 45~50℃, and then the pressure is released to obtain slurry.

[0025] S3. Mixing and Degassing: Add the slurry obtained in step S2 to the premixed adhesive obtained in step S1, and stir in a mixer at 200 rpm for 1 hour to ensure thorough mixing. Then, transfer the mixed adhesive to a degassing tank and degas under a vacuum of -0.095 MPa for 30 minutes to obtain the final adhesive.

[0026] S4. Coating and UV curing: The degassed adhesive is coated onto the corona-treated PET release film, and then sent into a segmented drying tunnel for drying and curing. The first segment of the segmented drying tunnel is dried at 80°C for 3 minutes, the second segment is dried at 110°C for 5 minutes, and the third segment is dried at 130°C for 3 minutes.

[0027] S5. Lamination and winding: After curing, another layer of PET release film is laminated onto the other side of the adhesive film, and then cut and wound to obtain the finished pure adhesive film.

[0028] The preparation method uses supercritical fluid technology to treat the filler, which solves the problem of easy agglomeration of nanofillers, greatly improves the dispersion uniformity, and makes the prepared membrane more uniform.

[0029] Furthermore, the third stage in step S4 requires drying and curing under UV light.

[0030] This invention prepares a pure adhesive film by cleverly compounding an acrylate copolymer and a hydrogenated styrene-isoprene-styrene block copolymer, combined with dynamic crosslinking technology, high refractive index components, and a multifunctional filler system. The prepared pure adhesive film achieves a breakthrough balance between adhesive strength, high temperature and humidity resistance, UV aging resistance, cohesive strength, and flexibility. It also exhibits good light transmittance, high thermal conductivity, good peel strength, and good high temperature and humidity resistance. The preparation method is stable, easy to control, and suitable for large-scale industrial production. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Example 1

[0033] A pure adhesive film is composed of the following components by weight: 80 kg of polymer resin, 30 kg of tackifying resin, 3 kg of dynamic crosslinking agent, 6 kg of functional filler, 10 kg of high refractive index component, 2 kg of anti-aging agent, and 100 kg of solvent.

[0034] The polymer resin is composed of 50 kg of acrylate copolymer and 30 kg of hydrogenated styrene-isoprene-styrene block copolymer. The acrylate copolymer is methyl methacrylate-butyl acrylate copolymer, wherein the ratio of methyl methacrylate monomers to butyl acrylate monomers is 1:1, and the degree of hydrogenation of the hydrogenated styrene-isoprene-styrene block copolymer is 98%.

[0035] The tackifying resin consists of 15 kg of hydrogenated terpene resin and 15 kg of hydrogenated petroleum resin.

[0036] The dynamic crosslinking agent consists of 2 kg of adipic dihydrazide and 1 kg of aluminum triacetylacetonate.

[0037] The functional filler consists of 4 kg of sheet-like silica and 2 kg of hydroxylated boron nitride nanosheets. The preparation method of the hydroxylated boron nitride nanosheets is as follows: boron nitride nanosheets and silane coupling agent KH-550 are added to N-methylpyrrolidone, and surface hydroxylation is performed by ultrasound. After filtration and drying, hydroxylated boron nitride nanosheets are obtained. The mass ratio of boron nitride nanosheets, silane coupling agent KH-550 and N-methylpyrrolidone is 1:0.2:6.

[0038] The anti-aging agent consists of 1 kg of antioxidant 2246 and 1 kg of UV329.

[0039] The high refractive index component is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.

[0040] The solvent consists of 70 kg toluene and 30 kg acetone.

[0041] The method for preparing the pure adhesive film includes the following steps:

[0042] S1. Premixing: Add the polymer resin, tackifying resin, high refractive index component and 50% solvent into a mixer, and stir at 400 rpm for 2 hours at 40~42℃ under inert gas protection until completely dissolved to obtain a premixed adhesive solution.

[0043] S2. Supercritical fluid dispersion: Dynamic crosslinking agent, functional filler, anti-aging agent and 50% solvent are mixed and put into a supercritical fluid device. CO2 is introduced and dispersed at a pressure of 13MPa and a temperature of 45~47℃ for 30 minutes, and then the pressure is released to obtain slurry.

[0044] S3. Mixing and Degassing: Add the slurry obtained in step S2 to the premixed adhesive obtained in step S1, and stir in a mixer at 200 rpm for 1 hour to ensure thorough mixing. Then, transfer the mixed adhesive to a degassing tank and degas under a vacuum of -0.095 MPa for 30 minutes to obtain the final adhesive.

[0045] S4. Coating and UV curing: The degassed adhesive is coated onto the corona-treated PET release film, and then sent into a segmented drying tunnel for drying and curing. The first segment of the segmented drying tunnel is dried at 80°C for 3 minutes, the second segment is dried at 110°C for 5 minutes, and the third segment is dried at 130°C for 3 minutes.

[0046] S5. Lamination and winding: After curing, another layer of PET release film is laminated onto the other side of the adhesive film, and then cut and wound to obtain the finished pure adhesive film.

[0047] Example 2

[0048] A pure adhesive film is composed of the following components by weight: 80 kg of polymer resin, 30 kg of tackifying resin, 3 kg of dynamic crosslinking agent, 6 kg of functional filler, 10 kg of high refractive index component, 2 kg of anti-aging agent, and 100 kg of solvent.

[0049] The polymer resin is composed of 50 kg of acrylate copolymer and 30 kg of hydrogenated styrene-isoprene-styrene block copolymer. The acrylate copolymer is methyl methacrylate-butyl acrylate copolymer, wherein the ratio of methyl methacrylate monomers to butyl acrylate monomers is 1:1, and the degree of hydrogenation of the hydrogenated styrene-isoprene-styrene block copolymer is 98%.

[0050] The tackifying resin consists of 15 kg of hydrogenated terpene resin and 15 kg of hydrogenated petroleum resin.

[0051] The dynamic crosslinking agent consists of 2 kg of adipic dihydrazide and 1 kg of aluminum triacetylacetonate.

[0052] The functional filler consists of 4 kg of sheet-like silica and 2 kg of hydroxylated boron nitride nanosheets. The preparation method of the hydroxylated boron nitride nanosheets is as follows: boron nitride nanosheets and silane coupling agent KH-550 are added to N-methylpyrrolidone, and surface hydroxylation is performed by ultrasound. After filtration and drying, hydroxylated boron nitride nanosheets are obtained. The mass ratio of boron nitride nanosheets, silane coupling agent KH-550 and N-methylpyrrolidone is 1:0.2:6.

[0053] The anti-aging agent consists of 1 kg of antioxidant 2246 and 1 kg of UV329.

[0054] The high refractive index component is bis(4-methacryloylthiophenyl) sulfide.

[0055] The solvent consists of 70 kg toluene and 30 kg acetone.

[0056] The method for preparing the pure adhesive film includes the following steps:

[0057] S1. Premixing: Add the polymer resin, tackifying resin, high refractive index component and 50% solvent into a mixer, and stir at 400 rpm for 2 hours at 40~42℃ under inert gas protection until completely dissolved to obtain a premixed adhesive solution.

[0058] S2. Supercritical fluid dispersion: Dynamic crosslinking agent, functional filler, anti-aging agent and 50% solvent are mixed and put into a supercritical fluid device. CO2 is introduced and dispersed at a pressure of 13MPa and a temperature of 45~47℃ for 30 minutes, and then the pressure is released to obtain slurry.

[0059] S3. Mixing and Degassing: Add the slurry obtained in step S2 to the premixed adhesive obtained in step S1, and stir in a mixer at 200 rpm for 1 hour to ensure thorough mixing. Then, transfer the mixed adhesive to a degassing tank and degas under a vacuum of -0.095 MPa for 30 minutes to obtain the final adhesive.

[0060] S4. Coating and UV curing: The degassed adhesive is coated onto the corona-treated PET release film, and then sent into a segmented drying tunnel for drying and curing. The first segment of the segmented drying tunnel is dried at 80°C for 3 minutes, the second segment is dried at 110°C for 5 minutes, and the third segment is dried at 130°C for 3 minutes.

[0061] S5. Lamination and winding: After curing, another layer of PET release film is laminated onto the other side of the adhesive film, and then cut and wound to obtain the finished pure adhesive film.

[0062] Example 3

[0063] A pure adhesive film is composed of the following components by weight: 80 kg of polymer resin, 30 kg of tackifying resin, 3 kg of dynamic crosslinking agent, 6 kg of functional filler, 10 kg of high refractive index component, 2 kg of anti-aging agent, and 100 kg of solvent.

[0064] The polymer resin is composed of 80 kg of acrylate copolymer.

[0065] The tackifying resin consists of 15 kg of hydrogenated terpene resin and 15 kg of hydrogenated petroleum resin.

[0066] The dynamic crosslinking agent consists of 2 kg of adipic dihydrazide and 1 kg of aluminum triacetylacetonate.

[0067] The functional filler consists of 4 kg of sheet-like silica and 2 kg of hydroxylated boron nitride nanosheets. The preparation method of the hydroxylated boron nitride nanosheets is as follows: boron nitride nanosheets and silane coupling agent KH-550 are added to N-methylpyrrolidone, and surface hydroxylation is performed by ultrasound. After filtration and drying, hydroxylated boron nitride nanosheets are obtained. The mass ratio of boron nitride nanosheets, silane coupling agent KH-550 and N-methylpyrrolidone is 1:0.2:6.

[0068] The anti-aging agent consists of 1 kg of antioxidant 2246 and 1 kg of UV329.

[0069] The high refractive index component is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.

[0070] The solvent consists of 70 kg toluene and 30 kg acetone.

[0071] The method for preparing the pure adhesive film includes the following steps:

[0072] S1. Premixing: Add the polymer resin, tackifying resin, high refractive index component and 50% solvent into a mixer, and stir at 400 rpm for 2 hours at 40~42℃ under inert gas protection until completely dissolved to obtain a premixed adhesive solution.

[0073] S2. Supercritical fluid dispersion: Dynamic crosslinking agent, functional filler, anti-aging agent and 50% solvent are mixed and put into a supercritical fluid device. CO2 is introduced and dispersed at a pressure of 13MPa and a temperature of 45~47℃ for 30 minutes, and then the pressure is released to obtain slurry.

[0074] S3. Mixing and Degassing: Add the slurry obtained in step S2 to the premixed adhesive obtained in step S1, and stir in a mixer at 200 rpm for 1 hour to ensure thorough mixing. Then, transfer the mixed adhesive to a degassing tank and degas under a vacuum of -0.095 MPa for 30 minutes to obtain the final adhesive.

[0075] S4. Coating and UV curing: The degassed adhesive is coated onto the corona-treated PET release film, and then sent into a segmented drying tunnel for drying and curing. The first segment of the segmented drying tunnel is dried at 80°C for 3 minutes, the second segment is dried at 110°C for 5 minutes, and the third segment is dried at 130°C for 3 minutes.

[0076] S5. Lamination and winding: After curing, another layer of PET release film is laminated onto the other side of the adhesive film, and then cut and wound to obtain the finished pure adhesive film.

[0077] Example 4

[0078] A pure adhesive film is composed of the following components by weight: 80 kg of polymer resin, 30 kg of tackifying resin, 3 kg of dynamic crosslinking agent, 6 kg of functional filler, 10 kg of high refractive index component, 2 kg of anti-aging agent, and 100 kg of solvent.

[0079] The polymer resin is composed of 50 kg of acrylate copolymer and 30 kg of hydrogenated styrene-isoprene-styrene block copolymer. The acrylate copolymer is methyl methacrylate-butyl acrylate copolymer, wherein the ratio of methyl methacrylate monomers to butyl acrylate monomers is 1:1, and the degree of hydrogenation of the hydrogenated styrene-isoprene-styrene block copolymer is 98%.

[0080] The tackifying resin consists of 15 kg of hydrogenated terpene resin and 15 kg of hydrogenated petroleum resin.

[0081] The dynamic crosslinking agent consists of 2 kg of adipic dihydrazide and 1 kg of aluminum triacetylacetonate.

[0082] The functional filler consists of 4 kg of sheet-like silica and 2 kg of hydroxylated boron nitride nanosheets. The preparation method of the hydroxylated boron nitride nanosheets is as follows: boron nitride nanosheets and silane coupling agent KH-550 are added to N-methylpyrrolidone, and surface hydroxylation is performed by ultrasound. After filtration and drying, hydroxylated boron nitride nanosheets are obtained. The mass ratio of boron nitride nanosheets, silane coupling agent KH-550 and N-methylpyrrolidone is 1:0.2:6.

[0083] The anti-aging agent consists of 1 kg of antioxidant 2246 and 1 kg of UV329.

[0084] The high refractive index component is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.

[0085] The solvent consists of 70 kg toluene and 30 kg acetone.

[0086] The method for preparing the pure adhesive film includes the following steps:

[0087] S1. Premixing: Add the polymer resin, tackifying resin, high refractive index component and 50% solvent into a mixer, and stir at 400 rpm for 2 hours at 40~42℃ under inert gas protection until completely dissolved to obtain a premixed adhesive solution.

[0088] S2. Supercritical fluid dispersion: Dynamic crosslinking agent, functional filler, anti-aging agent and 50% solvent are mixed and put into a supercritical fluid device. CO2 is introduced and dispersed at a pressure of 13MPa and a temperature of 45~47℃ for 30 minutes, and then the pressure is released to obtain slurry.

[0089] S3. Mixing and Degassing: Add the slurry obtained in step S2 to the premixed adhesive obtained in step S1, and stir in a mixer at 200 rpm for 1 hour to ensure thorough mixing. Then, transfer the mixed adhesive to a degassing tank and degas under a vacuum of -0.095 MPa for 30 minutes to obtain the final adhesive.

[0090] S4. Coating and UV Curing: The degassed adhesive is coated onto the corona-treated PET release film, and then sent into a segmented drying tunnel for drying and curing. The first segment of the segmented drying tunnel is dried at 80°C for 3 minutes, the second segment is dried at 110°C for 5 minutes, and the third segment is dried at 130°C for 3 minutes. The third segment needs to be dried and cured by UV lamp irradiation. The specific conditions are: wavelength 365nm, irradiation time 3 minutes, and intensity 900mJ / cm².

[0091] S5. Lamination and winding: After curing, another layer of PET release film is laminated onto the other side of the adhesive film, and then cut and wound to obtain the finished pure adhesive film.

[0092] Comparative Example 1

[0093] The only difference is that the hydrogenated petroleum resin component in Example 1 is replaced with hydrogenated terpene resin; otherwise, it is the same as in Example 1 and will not be repeated here.

[0094] Comparative Example 2

[0095] The only difference is that the adipic dihydrazide component in Example 1 is replaced with aluminum triacetylacetonate; otherwise, it is the same as in Example 1 and will not be repeated.

[0096] Comparative Example 3

[0097] The only difference is that the hydroxylated boron nitride nanosheet component in Example 1 is replaced with sheet-like silicon dioxide; otherwise, it is the same as in Example 1 and will not be repeated.

[0098] Comparative Example 4

[0099] The only difference is that the fluid dispersion in step S2 of Example 1 is replaced with ordinary stirring dispersion. Everything else is the same as in Example 1, and will not be repeated here.

[0100] The performance test results of the pure adhesive films prepared in the embodiments and comparative examples of the present invention are shown in Table 1.

[0101] Table 1

[0102] Transmittance, 500nm, % Thermal conductivity, W / (m·K) Peel strength 90˚ copper pull, kgf / cm Peel strength retention rate after high temperature and high humidity aging, % Example 1 91.5 0.48 3.2 88 Example 2 92.1 0.47 3.3 89 Example 3 91.4 0.47 2.9 84 Example 4 91.8 0.51 3.4 91 Comparative Example 1 91.4 0.48 2.4 79 Comparative Example 2 91.2 0.46 3.1 82 Comparative Example 3 91.3 0.42 2.9 79 Comparative Example 4 89.9 0.39 2.8 76

[0103] Note: The high temperature and high humidity conditions are: 85℃ / 85%RH.

[0104] As can be seen from the data in Table 1 above, the pure adhesive film prepared by this invention has good light transmittance, high thermal conductivity, good peel strength, and good resistance to high temperature and humidity. Data from Examples 1, 2, 3, and 4 show that when the high refractive index component is bis(4-methacryloylthiophenyl) sulfide, the product has better light transmittance. The synergistic effect is only achieved when the polymer resin is composed of acrylate copolymer and hydrogenated styrene-isoprene-styrene block copolymer, resulting in good peel strength and resistance to high temperature and humidity. The third step in step S4 of the preparation method requires drying and curing under UV light, leading to a comprehensive improvement in the performance of the prepared product. Comparative Example 1 data shows that the absence of hydrogenated petroleum resin in the tackifying resin leads to the disappearance of the synergistic effect, resulting in a decrease in the product's peel strength and resistance to high temperature and humidity. Comparative Example 2 data shows that the absence of adipate dihydrazide in the dynamic crosslinking agent leads to a decrease in the product's high temperature resistance. Comparative Example 3 data shows that the removal of the hydroxylated boron nitride nanosheet component significantly reduces the product's thermal conductivity, eliminates the synergistic effect, and causes varying degrees of decrease in peel strength and resistance to high temperature and humidity. Comparative Example 3 data also shows that compared to ordinary stirring dispersion, supercritical fluid dispersion results in a comprehensive improvement in the performance of the prepared product due to better component dispersibility.

Claims

1. A pure adhesive film, characterized in that, The substance is composed of the following components by mass: 75-95 parts polymer resin, 25-45 parts tackifying resin, 2-6 parts dynamic crosslinking agent, 5-12 parts functional filler, 5-15 parts high refractive index component, 1.5-3.5 parts anti-aging agent, and 90-130 parts solvent. The polymer resin is composed of acrylate copolymer and hydrogenated styrene-isoprene-styrene block copolymer in a mass ratio of 6:(0-5).

2. The pure adhesive film according to claim 1, characterized in that, The acrylate copolymer is a methyl methacrylate-butyl acrylate copolymer, wherein the ratio of methyl methacrylate to butyl acrylate monomers is (1~2):1, and the hydrogenation degree of the hydrogenated styrene-isoprene-styrene block copolymer is greater than 98%.

3. The pure adhesive film according to claim 1, characterized in that, The tackifying resin is composed of hydrogenated terpene resin and hydrogenated petroleum resin, wherein the mass ratio of the hydrogenated terpene resin to the hydrogenated petroleum resin is 1:(1-2.5).

4. The pure adhesive film according to claim 1, characterized in that, The dynamic crosslinking agent is a mixture of adipic acid dihydrazide and aluminum triacetylacetonate, with a mass ratio of adipic acid dihydrazide to aluminum triacetylacetonate of 2:

1.

5. The pure adhesive film according to claim 1, characterized in that, The functional filler is composed of sheet-like silica and hydroxylated boron nitride nanosheets, with a mass ratio of 2:1 between the sheet-like silica and the hydroxylated boron nitride nanosheets.

6. The pure adhesive film according to claim 1, characterized in that, The anti-aging agent is composed of antioxidant 2246 and UV329, and the mass ratio of antioxidant 2246 to UV329 is 1:

1.

7. The pure adhesive film according to claim 1, characterized in that, The high refractive index component is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene or bis(4-methacryloylthiophenyl) sulfide.

8. The pure adhesive film according to claim 1, characterized in that, The solvent is a mixture of toluene and acetone, with a mass ratio of toluene to acetone of 7:

3.

9. A method for preparing a pure adhesive film according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Premixing: Add the polymer resin, tackifying resin, high refractive index component and 50% solvent into a mixer, and stir at 300-500 rpm for 2 hours at 40-50°C under inert gas protection until completely dissolved to obtain a premixed adhesive solution. S2. Supercritical fluid dispersion: Dynamic crosslinking agent, functional filler, anti-aging agent and 50% solvent are mixed and put into a supercritical fluid device. CO2 is introduced and dispersed for 30 minutes at a pressure of 12-18MPa and a temperature of 45-50℃, and then the pressure is released to obtain slurry. S3. Mixing and Degassing: Add the slurry obtained in step S2 to the premixed adhesive obtained in step S1, and stir in a mixer at 200 rpm for 1 hour to ensure thorough mixing. Then, transfer the mixed adhesive to a degassing tank and degas under a vacuum of -0.095 MPa for 30 minutes to obtain the final adhesive. S4. Coating and UV curing: The degassed adhesive is coated onto the corona-treated PET release film, and then sent into a segmented drying tunnel for drying and curing. The first segment of the segmented drying tunnel is dried at 80°C for 3 minutes, the second segment is dried at 110°C for 5 minutes, and the third segment is dried at 130°C for 3 minutes. S5. Lamination and winding: After curing, another layer of PET release film is laminated onto the other side of the adhesive film, and then cut and wound to obtain the finished pure adhesive film.

10. The method for preparing the pure adhesive film according to claim 9, characterized in that, The third segment needs to be dried and cured under UV light, with the specific conditions being: wavelength 365nm, irradiation time 3min, and intensity 900mJ / cm².