High-performance leather membrane suitable for FFC and preparation method of high-performance leather membrane

Abstract

The invention discloses a high-performance membrane suitable for an FFC and a preparation method thereof, and relates to the field of membrane preparation. The leather film comprises a base material film layer, a photo-thermal compound adhesive layer and a release film layer, and the photo-thermal compound adhesive layer comprises 20-40 parts of light curing system matrix resin, 20-40 parts of thermocuring system matrix resin, 10-30 parts of a curing agent and 5-20 parts of an auxiliary additive. According to the invention, a solvent-free coating environment-friendly process is realized by adopting a photo-thermal dual-curing compound system, and the adhesive layer is shaped on a base material through ultraviolet curing and rapid pre-crosslinking, so that microbubbles brought by a small-molecule solvent can be avoided, and the hidden danger of electric field distortion can be eliminated; zero-defect construction in the adhesive layer is realized, and the insulation performance is ensured to be completely presented; molecular chain movement constraint of a thermocuring component is realized by regulating and controlling the content of a photocuring prepolymer gel network, the room-temperature reaction rate of epoxy resin is pressed to a relatively low level, the cold chain storage limitation of a traditional adhesive is broken through, and double-roller hot pressing at relatively low temperature is realized.

Description

Technical Field

[0001] This invention relates to the field of film preparation technology, and in particular to a high-performance film suitable for FFC and its preparation method. Background Technology

[0002] With the rapid increase in the penetration rate of new energy vehicles, the requirements for signal acquisition accuracy and insulation reliability of power battery modules are becoming increasingly stringent. Flexible flat cable (FFC), as a core component of signal acquisition modules, requires its sheath to simultaneously meet the requirements of high insulation, resistance to electrolyte corrosion, and long-term dimensional stability. The current mainstream solution of coating PET substrates with solvent-based epoxy adhesives has significant ecological and technological drawbacks: on the one hand, the benzene / ketone solvents released during production (VOC > 250g / L) violate EU REACH regulations, requiring the investment of a high-cost exhaust gas treatment system (accounting for 30% of manufacturing costs); on the other hand, solvent evaporation residues can easily lead to the aggregation of micron-sized bubbles (5μm-20μm), causing local electric field distortion in the insulation layer and a sharp drop in withstand voltage of 40%, posing a potential hazard to the safe operation of the module.

[0003] Traditional technological approaches face more severe process bottlenecks: the active components of solvent-based adhesives continue to react at room temperature, forcing the materials to be stored and transported under a complete cold chain, and curing often requires temperatures above 150°C, which increases the risk of hydrolytic oxidation. Although solvent-free epoxy systems have been attempted as alternatives, they still suffer from drawbacks such as short shelf life at room temperature and high hot-pressing temperatures. The industry urgently needs to develop new film materials that combine long shelf life, low-temperature processability, and zero VOC emissions to meet the demands of large-scale power battery manufacturing.

[0004] Currently, photothermal dual-curing solutions are widely used in the adhesive industry, typically fixing components through photocuring and then finalizing them through thermal curing. However, this process technology has not yet been adopted for the preparation of film materials in FFC components in the automotive field. Based on the principle of photothermal dual curing, a completely solvent-free and anhydrous formulation system can be designed, optimizing the appropriate degree of photocuring and gel content. This allows for control over the viscoelasticity, initial tack strength, and storage time of the adhesive layer, resulting in a more environmentally friendly process technology and FFC films with superior processing and performance. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a high-performance film suitable for FFC and its preparation method.

[0006] The following technical problems exist with existing technologies: 1. Environmental defects: Traditional solvent-based adhesives contain benzene / ketone organic solvents, requiring a costly exhaust gas treatment system during production, increasing manufacturing costs by more than 30%. 2. Insulation performance defects: Solvent evaporation residues form micron-sized bubble clusters (average diameter 5μm-20μm), causing local electric field distortion in the film, attenuating insulation withstand voltage, and affecting the safety requirements of FFC modules. 3. Storage stability defects: The active components of the adhesive continue to react at room temperature, forcing the material to be stored and transported under a complete cold chain. Furthermore, the operating window after thawing is short, increasing logistics costs and production scheduling difficulties. 4. Process energy consumption defects: Existing epoxy adhesives typically require high temperatures above 150℃ for activation and curing. High-temperature environments exacerbate metal oxidation and limit the application to ultra-thin substrates. Therefore, this invention provides a high-performance film suitable for FFC and its preparation method. The film used in this invention comprises a three-layer structure: the first layer is a substrate film, the second layer is a photothermal composite adhesive layer, and the third layer is a release layer. The photothermal composite adhesive layer of this invention includes both photocurable and thermocurable matrix resins, utilizing the photothermal curing principle to solve the aforementioned technical problems. Although the photothermal curing principle is existing technology, different application scenarios in practical applications result in different requirements for materials and performance. Therefore, the inventors comprehensively evaluated the production, molding, and usage characteristics of materials based on the pain points of actual application scenarios, considering their advantages and disadvantages from multiple dimensions, designing a more competitive formulation and process technology route, and identifying key core technical parameters to control product performance and achieve industrialization. Specifically, this invention first photocures the base resin of the photocurable system, then pre-crosslinks it to form a gel network structure, allowing the adhesive layer to be shaped on the substrate film for easy winding, packaging, and storage. Then, during the hot-pressing stage of FFC production, thermocuring is performed. In this stage, further crosslinking of the molecular chains occurs within the pre-defined network gaps. Through double crosslinking and zero volatility, zero-defect construction of the adhesive layer is achieved, ensuring complete insulation performance. The base resin of the thermocurable system is embedded in the gel network structure, giving it a suitable gel content range. Within this range, initial film tack strength is achieved while restricting the movement of thermocurable resin molecules, reaching a balance between low pressing temperature and long room temperature storage time, effectively solving the aforementioned technical problems.

[0007] The technical solution of the present invention is as follows: A first aspect of the present invention provides a high-performance film suitable for FFC, the film comprising a substrate film layer, a photothermal composite adhesive layer disposed on the substrate film layer, and a release film layer disposed on the photothermal composite adhesive layer; The photothermal composite adhesive layer comprises, by weight, 20 to 40 parts of the photocurable system matrix resin, 20 to 40 parts of the thermocurable system matrix resin, 10 to 30 parts of the curing agent, and 5 to 20 parts of the auxiliary additives.

[0008] Optionally, the matrix resin of the photocurable system includes an acrylate series, including at least one of basic acrylates and modified acrylates, wherein the modified acrylates include at least one of epoxy acrylates, polyurethane acrylates, and polyester acrylates; The thermosetting system matrix resin includes epoxy resin series, including at least one of basic epoxy resin and modified epoxy resin, wherein the modified epoxy resin includes at least one of polyurethane modified epoxy resin, silicone modified epoxy resin, polyester modified epoxy resin, acrylate modified epoxy resin, and rubber modified epoxy resin.

[0009] Optionally, the acrylate has a functionality of 2 to 8, and the epoxy resin has an epoxy value of 0.45 mol / 100g to 0.55 mol / 100g.

[0010] Optionally, the thickness of the photothermal composite adhesive layer is 30µm to 60µm, and the gelation rate of the photothermal composite adhesive layer is 15% to 40%.

[0011] Optionally, the initial tack strength of the film is 1 N / cm to 2 N / cm, and the roll bonding temperature of the film is less than 100°C.

[0012] Optionally, the curing agent is at least one of methylhexahydrophthalic anhydride, 2-ethyl-4-methylimidazolium, and polyamide 650; Each portion of the aforementioned auxiliary additives comprises, by weight, 5.0 to 15.0 parts of diluent, 0.1 to 0.5 parts of leveling agent, 1.0 to 5.0 parts of photoinitiator, 0.1 to 1.0 parts of photosensitizer, and 0.5 to 2.0 parts of antioxidant; The diluent is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and dipropylene glycol methyl ether. The leveling agent is at least one of polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and acrylate copolymer. The photoinitiator is at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; The photosensitizer is at least one of 2-isopropylthioxanthone, ethyl 4-dimethylaminobenzoate, and N-phenylglycine. The antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and 2,6-di-tert-butyl-4-methylphenol (BHT).

[0013] Optionally, the substrate film is a thin film prepared from at least one of PET, PI, PPS, and PC, and the thickness of the substrate film is 20µm to 100µm. The release film layer is at least one of PET, PP, and fiber paper, and the thickness of the release film layer is 30um~100um.

[0014] A second aspect of the present invention provides a method for preparing the membrane, comprising the following steps: The base resin of the photocurable system, the base resin of the thermocurable system, the curing agent and auxiliary additives are mixed evenly to obtain the adhesive. The adhesive is applied to the substrate film layer, and the substrate film layer coated with adhesive is cured by UV irradiation. The cured substrate film is laminated with the release film and then wound up to obtain the skin film.

[0015] Optionally, the coating viscosity of the adhesive is ≤10000 mPa·s, and the coating thickness of the adhesive is 20µm~60µm.

[0016] Optionally, the parameters for UV curing include: wavelength of 365nm and energy of 500mJ / cm².

[0017] This invention has at least one of the following beneficial effects: 1. This invention employs a photothermal dual-curing compound system to achieve a solvent-free, environmentally friendly coating process. Rapid pre-crosslinking via UV curing allows the adhesive layer to be shaped on a PET substrate, facilitating winding, packaging, and storage. Finally, it is combined with conductor wires via dual-roll hot pressing to produce FFC. This method avoids microbubbles caused by small-molecule solvents, eliminating the risk of electric field distortion; it achieves zero-defect construction within the adhesive layer, ensuring complete insulation performance; simultaneously, by controlling the gel network content of the photocurable prepolymer, it restricts the molecular chain movement of the thermosetting components, suppressing the room-temperature reaction rate of epoxy resin to a lower level, overcoming the limitations of traditional adhesive cold chain storage, and imparting excellent thermal processing properties to the adhesive layer, enabling dual-roll hot pressing at lower temperatures.

[0018] 2. Compared with existing technologies, this invention completely eliminates the volatilization of organic solvents (zero VOC emissions) through the design of a solvent-free / anhydrous resin system, solving the problem of waste gas pollution from traditional processes at the source of materials and meeting the most stringent environmental regulations in the world.

[0019] 3. The present invention uses a dense network skeleton formed by photocuring pre-crosslinking and no small molecule solvents to effectively avoid the generation of microbubbles and eliminate the hidden danger of electric field distortion; in the thermocuring stage, the molecular chains are precisely crosslinked within the preset network gaps to achieve zero-defect construction inside the adhesive layer and ensure the complete presentation of insulation performance.

[0020] 4. The photocurable prepolymer network of the present invention restricts the molecular chain movement of thermocurable components, thereby suppressing the room temperature reaction rate of epoxy resin to a low level, breaking through the limitations of traditional cold chain storage of adhesives, and achieving a technological leap in room temperature storage.

[0021] 5. The photocuring stage of this invention imparts a certain strength to the adhesive layer, giving the film excellent roll forming properties. The viscoelastic balance characteristics exhibited by the semi-interpenetrating network structure during hot pressing allow it to achieve complete interface wetting under low temperature and pressure. Detailed Implementation

[0022] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] An embodiment of the present invention provides a high-performance film suitable for FFC, the film comprising a substrate film layer, a photothermal composite adhesive layer disposed on the substrate film layer, and a release film layer disposed on the photothermal composite adhesive layer; The photothermal composite adhesive layer comprises, by weight, 20 to 40 parts of the photocurable system matrix resin, 20 to 40 parts of the thermocurable system matrix resin, 10 to 30 parts of the curing agent, and 5 to 20 parts of the auxiliary additives.

[0024] The film of the present invention comprises three layers: a substrate film layer, a photothermal composite adhesive layer, and a release film layer. The photothermal composite adhesive layer of the present invention includes both a photocurable matrix resin and a thermocurable matrix resin. By selecting raw materials with appropriate proportions, the present invention uses a curing agent to photocur the photocurable matrix resin, which forms a gel network structure. The thermocurable matrix resin is embedded in the gel network structure, so that the gel network structure has a suitable gel content range. Within this gel content range, a balance can be achieved between the initial tack strength, pressing temperature, and room temperature storage time of the film.

[0025] In some embodiments, the matrix resin of the photocurable system includes an acrylate series, including at least one of a base acrylate and a modified acrylate, wherein the modified acrylate includes at least one of an epoxy acrylate, a polyurethane acrylate, or a polyester acrylate; preferably a base acrylate.

[0026] In some embodiments, the thermosetting system matrix resin includes an epoxy resin series, including at least one of a base epoxy resin and a modified epoxy resin. The modified epoxy resin includes at least one of polyurethane modified epoxy resin, silicone modified epoxy resin, polyester modified epoxy resin, acrylic modified epoxy resin, and rubber modified epoxy resin, preferably a base epoxy resin.

[0027] In some embodiments, the functionality of the base acrylate is 2 to 8, and the epoxy value of the base epoxy resin is 0.45 mol / 100g to 0.55 mol / 100g. Preferably, the functionality of the base acrylate is 3 to 8, and the epoxy value of the base epoxy resin is 0.47 mol / 100g to 0.53 mol / 100g. More preferably, the functionality of the base acrylate is 4 to 8, and the epoxy value of the base epoxy resin is 0.48 mol / 100g to 0.52 mol / 100g.

[0028] In some embodiments, the thickness of the photothermal composite adhesive layer is 20 μm to 60 μm, and the gelation rate of the photothermal composite adhesive layer is 15% to 40%. Preferably, the thickness of the photothermal composite adhesive layer is 25 μm to 50 μm, and the gelation rate of the photothermal composite adhesive layer is 15% to 35%. More preferably, the thickness of the photothermal composite adhesive layer is 30 μm to 40 μm, and the gelation rate of the photothermal composite adhesive layer is 15% to 30%.

[0029] In some embodiments, the initial tack strength of the film is 1 N / cm to 2 N / cm, and the roll bonding temperature of the film is less than 100°C; preferably, the initial tack strength of the film is 1.1 N / cm to 1.9 N / cm, and the roll bonding temperature of the film is less than 80°C; more preferably, the initial tack strength of the film is 1.2 N / cm to 1.8 N / cm, and the roll bonding temperature of the film is 30°C to 60°C.

[0030] In some embodiments, the curing agent is at least one of methylhexahydrophthalic anhydride, 2-ethyl-4-methylimidazolium, and polyamide 650.

[0031] In some embodiments, each part of the auxiliary additive comprises, by weight, 5.0 to 15.0 parts of diluent, 0.1 to 0.5 parts of leveling agent, 1.0 to 5.0 parts of photoinitiator, 0.1 to 1.0 parts of photosensitizer, and 0.5 to 2.0 parts of antioxidant; The diluent is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and dipropylene glycol methyl ether. The leveling agent is at least one of polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and acrylate copolymer. The photoinitiator is at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexylphenyl ketone, and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; The photosensitizer is at least one of 2-isopropylthioxanthone, ethyl 4-dimethylaminobenzoate, and N-phenylglycine. The antioxidant is at least one of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (1010) and 2,6-di-tert-butyl-4-methylphenol (BHT).

[0032] In some embodiments, the substrate film is a thin film prepared from at least one material selected from PET, PI, PPS, and PC. The thickness of the substrate film is 20 μm to 100 μm; preferably 20 μm to 80 μm; more preferably 20 μm to 60 μm.

[0033] In some embodiments, the release film layer is at least one of PET, PP, and fiber paper, and the thickness of the release film layer is 30um to 100um.

[0034] Another embodiment of the present invention provides a method for preparing the film, comprising the following steps: The base resin of the photocurable system, the base resin of the thermocurable system, the curing agent and auxiliary additives are mixed evenly to obtain the adhesive. The adhesive is applied to the substrate film layer, and the substrate film layer coated with adhesive is cured by UV irradiation. The cured substrate film is laminated with the release film and then wound up to obtain the skin film.

[0035] The preparation method of the present invention is simple and practical. The film prepared by the method can balance the initial adhesion strength, pressing temperature and room temperature storage time.

[0036] In some embodiments, the coating viscosity of the adhesive is ≤10000 mPa·s (which can be finely controlled by a small amount of thinner and coating temperature), and the coating thickness is 20µm~60µm. Preferably, the coating viscosity of the adhesive is ≤8000 mPa·s, and the coating thickness is 25µm~50µm. Preferably, the coating viscosity of the adhesive is ≤6000 mPa·s, and the coating thickness is 30µm~40µm.

[0037] In some embodiments, the parameters for UV curing include: wavelength of 365 nm and energy of 500 mJ / cm².

[0038] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following specific embodiments.

[0039] The curing agent used in the following examples and comparative examples is methyl hexahydrophthalic anhydride, the diluent is 1,6-hexanediol diacrylate, the leveling agent is polyether-modified polydimethylsiloxane, the photoinitiator is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, the photosensitizer is 2-isopropylthioxanthrone, and the antioxidant is 1010.

[0040] In the following examples and comparative examples, each part of auxiliary additive contains, by weight, 7 parts of diluent, 0.5 parts of leveling agent, 1 part of photoinitiator, 0.5 parts of photosensitizer and 1 part of antioxidant.

[0041] Example 1 A high-performance film suitable for FFC and its preparation method, comprising the following steps: 1) Select a PI substrate with a thickness of 25um as the substrate film layer; 2) Mix 20 parts by weight of acrylic resin (functionality 4), 40 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 30 parts by weight of curing agent, and 10 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and shaped by UV irradiation (365nm, 500mJ / cm²).

[0042] 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0043] The gel content, initial tack strength, pressing temperature, and room temperature storage time of the pre-formed film were measured using the following methods: (1) Gel content: The gel content is usually tested by centrifugation. The steps are as follows: Take the prepared cured adhesive layer, add an appropriate amount of solvent (such as ethyl acetate), and stir it thoroughly to make it evenly dispersed. Place the mixed solution in a centrifuge and centrifuge to separate it. Take out the upper liquid and precipitate, dry the precipitate in a thermostat, and divide the weight of the precipitate by the total weight to obtain the gel content.

[0044] (2) Initial adhesion strength: After peeling off the release film on the upper layer of the film, the adhesive layer is tested for adhesion (GB / T 2792-2014), peeling at 180℃.

[0045] (3) Pressing temperature: After peeling off the release film on the upper layer of the film, it is pressed together with the copper wire through a roller press. During the bonding process, the bonding effect is observed online under a microscopic microscope. There is no delamination between the adhesive layers and between the adhesive layer and the copper wire. The adhesive completely covers the copper wire without gaps.

[0046] (4) Room temperature storage time: The standard for measuring room temperature storage time is the time when the bonding effect of the adhesive layer after being pressed at high temperature (150℃ in this test) can no longer meet the normal requirements (such as adhesive layer delamination, low initial bonding strength, defects in copper wire coating, etc.).

[0047] The gelation rate of the adhesive layer after light curing was measured to be 18.6%.

[0048] The film prepared in this embodiment can be rolled and bonded at 30°C, with an initial bond strength of 1.8 N / cm. Therefore, it has a good covering and initial bonding effect on the conductor wire. Furthermore, the rolled and bonded film can be stored at room temperature for 10 days.

[0049] Example 2 A high-performance film suitable for FFC and its preparation method, comprising the following steps: 1) Select a PI substrate with a thickness of 25µm; 2) Mix 30 parts by weight of acrylic resin (functionality 4), 32 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 24 parts by weight of curing agent, and 14 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and set by UV irradiation (365nm, 500mJ / cm²); 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0050] The gelation rate of the adhesive layer after light curing was measured to be 27.3%.

[0051] The film prepared in this embodiment can be rolled and bonded at 45°C, with an initial bond strength of 1.6 N / cm. Therefore, it has a good covering and initial bonding effect on the conductor wire. Furthermore, the rolled and bonded film can be stored at room temperature for 15 days.

[0052] Example 3 A high-performance film suitable for FFC and its preparation method, comprising the following steps: 1) Select a PI substrate with a thickness of 25µm; 2) Mix 40 parts by weight of acrylic resin (functionality 4), 24 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 18 parts by weight of curing agent, and 18 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and set by UV irradiation (365nm, 500mJ / cm²); 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0053] The gelation rate of the adhesive layer after light curing was measured to be 36.5%.

[0054] The film prepared in this embodiment can be rolled and bonded at 60°C, with an initial bond strength of 1.3 N / cm. Therefore, it has a good covering and initial bonding effect on the conductor wire. Furthermore, the rolled and bonded film can be stored at room temperature for 20 days.

[0055] Example 4 A high-performance film suitable for FFC and its preparation method, comprising the following steps: 1) Select a PI substrate with a thickness of 25µm; 2) Mix 30 parts by weight of acrylic resin (functionality 6), 32 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 24 parts by weight of curing agent, and 14 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and set by UV irradiation (365nm, 500mJ / cm²); 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0056] The gelation rate of the adhesive layer after light curing was measured to be 28.8%.

[0057] The film prepared in this embodiment can be rolled and laminated at 45°C, with an initial adhesion strength of 1.5 N / cm, and has good coverage and initial adhesion effect on the conductor wire; furthermore, the rolled and laminated film can be stored at room temperature for 16 days.

[0058] Comparative Example 1 1) Select a PI substrate with a thickness of 25µm; 2) Mix 20 parts by weight of acrylic resin (functionality 2), 40 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 30 parts by weight of curing agent, and 10 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and set by UV irradiation (365nm, 500mJ / cm²); 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0059] The gelation rate of the adhesive layer after light curing was measured to be 13.2%.

[0060] The initial tack strength of the film prepared in this comparative example is 0.6 N / cm, which is relatively low. At the same time, it has good fluidity and is prone to glue overflow during the pressing process. The storage time is also short, and the film can only be stored at room temperature for 8 days.

[0061] Comparative Example 2 1) Select a PI substrate with a thickness of 25µm; 2) Mix 10 parts by weight of acrylic resin (functionality 4), 46 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 34 parts by weight of curing agent, and 10 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and set by UV irradiation (365nm, 500mJ / cm²); 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0062] The gelation rate of the adhesive layer after light curing was measured to be 8.3%.

[0063] The initial tack strength of the film prepared in this comparative example is 0.4 N / cm, which is relatively low. At the same time, it has good fluidity and is prone to glue overflow during the pressing process. The storage time is also short, and the film can only be stored at room temperature for 4 days.

[0064] Comparative Example 3 1) Select a PI substrate with a thickness of 25µm; 2) Mix 60 parts by weight of acrylic resin (functionality 6), 12 parts by weight of epoxy resin (epoxy value 0.50mol / 100g), 8 parts by weight of curing agent, and 20 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is pre-cured and set by UV irradiation (365nm, 500mJ / cm²); 5) After laminating with a release film of 50um thickness and PET material, the film is wound up to obtain a skin film.

[0065] The gelation rate of the adhesive layer after light curing was measured to be 56.5%.

[0066] The film prepared in this comparative example has an initial tack strength of less than 0.1 N / cm, a pressing temperature of 180℃, and can be stored at room temperature for 30 days. Although it can be stored at room temperature for a long time, its extremely low initial tack and high pressing temperature make it unsuitable.

[0067] Comparative Example 4 1) Select a PI substrate with a thickness of 25µm; 2) Mix 50 parts by weight of ethyl acetate solvent, 26 parts by weight of epoxy resin (epoxy value 0.50 mol / 100 g), 19 parts by weight of curing agent, and 5 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is baked, dried, and shaped for pre-curing and shaping; 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0068] The gelation rate of the adhesive layer after light curing was measured to be 0.

[0069] The film prepared in this comparative example has an initial tack strength of less than 0.1 N / cm, a pressing temperature of 150℃, and can be stored at room temperature for 2 days. Because it only undergoes thermosetting, it belongs to a traditional film material system, which suffers from problems such as low initial tack, high pressing temperature, and short storage time.

[0070] Comparative Example 5 1) Select a PI substrate with a thickness of 25µm; 2) Mix 50 parts by weight of ethyl acetate solvent, 20 parts by weight of acrylate (functionality 4), 30 parts by weight of curing agent, and 10 parts by weight of auxiliary additives evenly to obtain the adhesive. 3) Apply the adhesive evenly to the PI substrate, with a wet film thickness of 40µm; 4) The coated base film is baked, dried and shaped, and pre-cured.

[0071] 5) After laminating with a 50µm thick PET release film, the film is wound up to obtain a skin film.

[0072] The gelation rate of the adhesive layer after light curing was measured to be 19.3%.

[0073] The initial tack strength of the film prepared in this comparative example is <0.1 N / cm, the pressing temperature is room temperature ℃, and it can be stored at room temperature for >20 days.

[0074] The performance of the samples prepared in the above embodiments and comparative examples was compared and analyzed, and the results are shown in Table 1.

[0075] Table 1 Comparison of Effects The results above show that controlling the gel content is crucial to product performance, requiring a balance between initial tack strength, pressing temperature, and room temperature storage time. The results indicate that after photocuring, the acrylate forms a gel network structure with epoxy resin embedded within it. Within a suitable gel range (Examples 1-4), as the gel content increases, the initial tack strength decreases, the pressing temperature gradually increases, and the room temperature storage time lengthens. This is mainly due to the restriction of molecular chain movement by the gel content. When the gel content is too low (<15%), such as the low functionality of the acrylic resin in Comparative Example 1 or the low amount of acrylic resin added in Comparative Example 2, the molecular weight of the adhesive layer is low, resulting in insufficient strength and low initial tack strength. Simultaneously, the good flowability makes it prone to overflow during pressing, and the storage time is also short. In Comparative Example 3, the excessively high gel content inhibits the movement of epoxy resin molecules. Although the storage time is long, it results in extremely low initial tack and a high pressing temperature, making it unsuitable. Comparative Example 4, lacking acrylic resin and only thermosetting, belongs to a traditional film material system, exhibiting problems such as low initial tack, high pressing temperature, and short storage time. Comparative Example 5, lacking epoxy resin, could not be further cured, resulting in low strength after bonding. Although it could be stored for a long time, it was unusable.

[0076] In summary, by employing a photocurable matrix resin and a thermocurable matrix resin, and by controlling the appropriate ratio of the two and the functionality of the photocurable matrix resin within a suitable range, the present invention achieves a gel content of 15% to 40% in the prepared photothermal composite adhesive layer, which balances the initial tack strength, pressing temperature, and room temperature storage time.

[0077] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high performance film for FFC, characterized by, The film comprises a base film layer, a light-heat compounded adhesive layer arranged on the base film layer, and a release film layer arranged on the light-heat compounded adhesive layer. The light-heat compounded adhesive layer comprises, in terms of weight fraction, 20-40 parts of a photocuring system matrix resin, 20-40 parts of a thermal curing system matrix resin, 10-30 parts of a curing agent, and 5-20 parts of an auxiliary additive.

2. The film according to claim 1, characterized in that The photocuring system matrix resin is at least one of acrylate, epoxy acrylate, polyurethane acrylate, and polyester acrylate. The thermal curing system matrix resin is at least one of epoxy resin, polyurethane modified epoxy resin, silicone modified epoxy resin, polyester modified epoxy resin, acrylate modified epoxy resin, and rubber modified epoxy resin.

3. The film of claim 2, wherein The functionality of the acrylate is 2-8, and the epoxy value of the epoxy resin is 0.45-0.55 mol / 100 g.

4. The film of claim 1, wherein The thickness of the light-heat compounded adhesive layer is 30-60 um, and the gel rate of the light-heat compounded adhesive layer is 15-40%.

5. The film of claim 1, wherein The initial adhesion strength of the film is 1-2 N / cm, and the roll bonding temperature of the film is less than 100℃.

6. The film according to claim 1, characterized in that The curing agent is at least one of methyl hexahydrophthalic anhydride, 2-ethyl-4-methyl imidazole, and polyamide 650. Each part of the auxiliary additive comprises, in terms of weight fraction, 5.0-15.0 parts of a diluent, 0.1-0.5 parts of a leveling agent, 1.0-5.0 parts of a photoinitiator, 0.1-1.0 parts of a photosensitizer, and 0.5-2.0 parts of an antioxidant. The diluent is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and dipropylene glycol methyl ether. The leveling agent is at least one of polyether modified polydimethylsiloxane, polyester modified polydimethylsiloxane, and acrylate copolymer. The photoinitiator is at least one of 2-hydroxy-2-methyl-1-phenyl-1-propanone, 1-hydroxycyclohexyl phenyl ketone, and 2,4,6-trimethylbenzoyl-diphenyl phosphine oxide. The photosensitizer is at least one of 2-isopropyl thioxanthone, 4-dimethylamino benzoic acid ethyl ester, and N-phenyl glycine. The antioxidant is at least one of tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester and 2,6-di-tert-butyl-4-methyl phenol.

7. The film according to claim 1, characterized in that The base film layer is a film prepared from at least one of PET, PI, PPS, and PC, and the thickness of the base film layer is 20-100 um. The release film layer is at least one of PET, PP, and fiber paper, and the thickness of the release film layer is 30-100 um.

8. The method of claim 1 to 7, characterized in that, The method comprises the following steps: The photocuring system matrix resin, the thermal curing system matrix resin, the curing agent, and the auxiliary additive are uniformly mixed to obtain a glue. The glue is coated on the base material film layer, and the base material film layer coated with the glue is cured by UV irradiation; The cured base material film layer is wound after being compounded with a release film layer to obtain the skin film.

9. The production method according to claim 8, characterized by, The coating viscosity of the glue is less than or equal to 10,000 mPa·s, and the coating thickness of the glue is 20-60 um.

10. The preparation method according to claim 8, characterized in that, The parameters of the UV irradiation curing include a wavelength of 365 nm and an energy of 500 mJ / cm².

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