Release film for FPC and preparation method thereof

Abstract

The release film for the FPC comprises a PET base film, a high-temperature-resistant layer and a release layer, the PET base film is coated with the high-temperature-resistant layer, and the high-temperature-resistant layer is coated with the release layer; the high-temperature-resistant layer coating liquid is prepared from the following components in parts by weight: 2 to 8 parts of macromolecular resin, 10 to 85 parts of first organic solvent, 0.1 to 0.8 part of organic silicon resin, 0.4 to 1.6 parts of flatting agent and 0.04 to 0.64 part of adhesion promoter. The high-temperature-resistant layer is coated between the PET base film layer and the release layer, so that the problem that the existing PET release film cannot resist high temperature can be effectively solved.

Description

Technical Field

[0001] The invention relates to a release film for FPC and a preparation method thereof, belonging to the technical field of release films. Background Art

[0002] FPC, also known as flexible circuit board or flexible printed circuit board, is made of polyimide or polyester film as the base material. It has the advantages of high wiring density, light weight, thin thickness, bendability and high flexibility. It is mainly used in electronic terminal products.

[0003] In the preparation of FPC, in order to prevent the metal circuit from being oxidized and corroded by air, water vapor and other substances, which will affect its electrical performance, it is usually necessary to cover one side of the printed circuit with a protective film. The protective film is bonded to the surface of the printed circuit by thermal pressing. The pressing temperature during the FPC pressing process is about 180°C. If pressing is performed directly, the covering protective film will easily adhere to the surface of the heating plate.

[0004] Therefore, the surface of the protective film needs to be covered with a release film, and the release film should have high temperature resistance to avoid adhesion between the protective film and the surface of the heating plate, but the existing PET release film is difficult to meet this requirement. Summary of the invention

[0005] In order to overcome the drawbacks of the prior art, the present invention provides a release film for FPC and a preparation method thereof, wherein a high temperature resistant layer is coated between the PET base film layer and the release layer, which can effectively solve the problem that the existing PET release film cannot withstand high temperatures.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A release film for FPC, the release film comprising a PET base film, a high temperature resistant layer and a release layer, the high temperature resistant layer is coated on the PET base film, and the release layer is coated on the high temperature resistant layer; the high temperature resistant layer coating liquid comprises the following components in parts by weight:

[0008] 2 to 8 parts of polymer resin

[0009] 10 to 85 parts of the first organic solvent

[0010] 0.1 to 0.8 parts of silicone resin

[0011] Leveling agent 0.4 to 1.6 parts

[0012] Adhesion promoter 0.04 to 0.64 parts.

[0013] The above-mentioned FPC release film, the polymer resin is any one of polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE) or polyvinyl fluoride (PVF).

[0014] In the above-mentioned release film for FPC, the silicone resin is any one of epoxy-modified silicone resin, acrylic-modified silicone resin or alkyd-modified silicone resin.

[0015] In the above-mentioned release film for FPC, the adhesion promoter is a silane-based adhesion promoter or a high molecular weight copolymer-based adhesion promoter containing acidic or basic groups.

[0016] In the above-mentioned release film for FPC, the first organic solvent is N,N-dimethylformamide; and the leveling agent is a fluorine-based leveling agent.

[0017] The release film for FPC, the release layer coating liquid comprises the following components in parts by weight:

[0018] 30 to 50 parts of silicone oil release agent

[0019] 300 to 500 parts of the second organic solvent

[0020] Crosslinking agent 0.21 to 0.7 parts

[0021] Anchoring agent 0.12 to 0.3 parts

[0022] Catalyst 0.48 to 1.2 parts.

[0023] In the above-mentioned release film for FPC, the silicone oil release agent is a solvent-based release agent with a viscosity of 7000 to 30000 cps.

[0024] In the above-mentioned FPC release film, the second organic solvent is one of toluene, butanone, ethyl acetate, cyclohexanone, n-heptane, and isopropanol, or a combination of multiple ones in any weight ratio; the cross-linking agent is a hydrogen-containing cross-linking agent; the anchoring agent is a silane anchoring agent; and the catalyst is a platinum catalyst.

[0025] In the method for preparing the release film for FPC, the thickness of the PET base film is 25 to 100 μm; the thickness of the high temperature resistant layer is 1 to 10 μm; and the thickness of the release layer is 0.01 to 0.1 μm.

[0026] A method for preparing a release film for FPC, the method comprising the following steps:

[0027] a. Preparation of high temperature resistant layer coating liquid:

[0028] Dissolving a proportion of a polymer resin in a first organic solvent and stirring the mixture sufficiently to obtain a polymer resin solution;

[0029] Adding a proportion of organic silicone resin, a leveling agent and an adhesion promoter to the prepared polymer resin solution in sequence, and stirring thoroughly to obtain a high temperature resistant layer coating solution;

[0030] b. Apply high temperature resistant coating liquid:

[0031] Apply the high temperature resistant layer coating liquid on one side of the PET base film and solidify it at 90-130°C to form a high temperature resistant layer;

[0032] c. Preparation of release layer coating liquid:

[0033] Dissolving a proportion of a solvent-based release agent in a second organic solvent, adding a cross-linking agent, an anchoring agent and a catalyst in sequence, and stirring sufficiently to obtain a release agent coating liquid;

[0034] d. Forming release film for FPC:

[0035] The release agent coating liquid is applied on the high temperature resistant layer and cured at 120-150°C to form a release film for FPC.

[0036] The beneficial effects of the present invention are:

[0037] 1. The present invention coats a high temperature resistant layer on one side of the PET base film, which can effectively improve the problem that the PET base film is not resistant to high temperatures. Since the modified silicone resin has excellent high temperature resistance, the modified silicone resin is added to the polymer resin to further enhance the temperature resistance of the high temperature resistant layer.

[0038] 2. At the same time, an adhesion promoter is added to the polymer resin to improve the adhesion between the high temperature resistant layer and the PET base film, making it difficult for the two to fall off.

[0039] 3. The viscosity of the silicone oil release agent in the release layer of the present invention also affects the performance of the release film for FPC. If the viscosity is too high, the fluidity of the release layer coating liquid is poor, and the thickness of the release layer will increase after coating, resulting in a high amount of dry silicon and a low residual adhesion rate. If the viscosity is too low, the temperature resistance is affected. The present invention limits the viscosity of the silicone oil release agent to ensure the release force and residual adhesion rate of the release film while ensuring good temperature resistance.

[0040] In summary, the technical solution of the present application can effectively solve the problem that the existing PET release film cannot withstand high temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Schematic diagram of the layer structure of the release film for FPC of the present invention.

[0042] In the figure: 1. PET base film; 2. High temperature resistant layer; 3. Release layer. DETAILED DESCRIPTION

[0043] The technical solution of the invention is clearly and completely described. Obviously, the described embodiments are part of the embodiments of the invention, not all of them. Based on the described embodiments of the invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the invention.

[0044] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0045] The release film of the present invention comprises a PET base film, a high temperature resistant layer and a release layer, wherein the high temperature resistant layer is coated on the PET base film, and the release layer is coated on the high temperature resistant layer; the high temperature resistant layer coating liquid comprises the following components in parts by weight:

[0046] 2 to 8 parts of polymer resin

[0047] 10 to 85 parts of the first organic solvent

[0048] 0.1 to 0.8 parts of silicone resin

[0049] Leveling agent 0.4 to 1.6 parts

[0050] Adhesion promoter 0.04 to 0.64 parts.

[0051] The present invention coats a high temperature resistant layer on a PET base film, and a modified silicone resin is added to the coating liquid of the high temperature resistant layer, specifically any one of epoxy modified silicone resin SMH-30, SMH-60, acrylic modified silicone resin SM-1046, SM-1046D and alkyd modified silicone resin SM-1057. Whether it is epoxy modified, acrylic modified or alkyd modified silicone resin, its main chain still retains a silicon oxygen bond (Si-O), and the silicon oxygen bond bond energy is relatively high, about 422.5 kJ / mol, which is much higher than the carbon carbon bond (CC) bond energy of about 345.6 kJ / mol. This makes it difficult for the silicon oxygen bond of the main chain to break under high temperature conditions, and can maintain the integrity of the molecular structure, providing a basic thermal stability guarantee for the high temperature resistant layer. Epoxy modified silicone resins SMH-30 and SMH-60, the introduction of epoxy groups can increase the degree of crosslinking between molecules, making the molecular structure more rigid. At high temperatures, this rigid structure can reduce the thermal motion of molecules, limit the stretching and deformation of molecular chains, and thus enhance high temperature resistance. For acrylic modified silicone resin SM-1046 and SM-1046D, the introduction of acrylic groups increases the polarity of the molecules, which enhances the intermolecular interactions. At high temperatures, strong intermolecular forces can hinder the separation and thermal degradation of molecules, and improve temperature resistance. For alkyd modified silicone resin SM-1057, the alkyd groups can give the molecules a certain flexibility, and also improve the heat resistance to a certain extent. During high temperature processes, this flexibility can alleviate the internal stress caused by factors such as thermal expansion, and with its own heat resistance, enhance the overall high temperature resistance. When the modified silicone resin is not added, the high temperature resistant layer composed of fluororesin may begin to thermally degrade at a relatively low temperature. After the modified silicone resin is added, due to its own high thermal stability, the thermal degradation starting temperature of the entire system will be increased. At high temperatures, when the modified silicone resin is degraded at high temperatures, some inorganic products such as silicon dioxide will be produced. These inorganic products can form a relatively dense protective layer on the surface of the material, which can effectively block further erosion of the high-temperature resistant layer by oxygen, heat, etc. After the two are combined, while maintaining the original advantages of fluororesin, the high-temperature resistance of the modified silicone resin is utilized to achieve an improvement in the overall temperature resistance of the high-temperature resistant layer, meeting the need for the high-temperature resistant layer coated on the PET base film to adapt to high-temperature environments.

[0052] An adhesion promoter is also added to the high temperature resistant layer coating liquid, specifically any one of the silane adhesion promoters BYK-4500, BYK-4509 and the high molecular weight copolymer adhesion promoters BYK-4510, BYK-3941P and BYK-3942P containing acidic and basic groups. The siloxane groups in the molecular structure of the silane adhesion promoters BYK-4500 and BYK-4509 can react with a small amount of unreacted hydroxyl and other active groups in the fluororesin, or with active groups such as hydroxyl groups in the modified silicone resin to form a cross-linked network structure, thereby enhancing the cohesion of the fluororesin coating and the adhesion to the PET base film. One end of the silane-based adhesion promoter has good bonding with the PET base film, and the organic functional group (such as alkyl, aromatic, etc.) at the other end has a certain compatibility with the fluororesin, and can play the role of a "bridge" between the PET base film and the fluororesin coating, improving the interface compatibility between the two, reducing interface defects, and improving adhesion. High molecular weight copolymer adhesion promoters containing acidic and basic groups, BYK-4510, BYK-3941P and BYK-3942P, these high molecular weight copolymers have longer molecular chains, which can be entangled with each other in the fluororesin to form physical crosslinking points. This physical entanglement can increase the cohesion of the coating, making the coating more tightly attached to the PET base film and improving the adhesion between the high temperature resistant layer and the PET base film.

[0053] The polymer resin in the coating liquid of the high temperature resistant layer is selected from any one of polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE), and polyvinyl fluoride (PVF). Such polymer resins have the characteristics of high temperature resistance, oxidation resistance, and good weather resistance.

[0054] The first organic solvent is N,N-dimethylformamide, which has a very strong polarity and can fully dissolve the fluorine-containing polymer resin.

[0055] The leveling agent is a fluorine-based leveling agent, specifically any one of MEGAFACE F440, F470, F553, F554, F556, and F557. The fluorine-based leveling agent is added to improve the flatness of the high temperature resistant layer to reduce surface defects.

[0056] The release layer coating solution of the present invention comprises the following components in parts by weight:

[0057] 30 to 50 parts of silicone oil release agent

[0058] 300 to 500 parts of the second organic solvent

[0059] Crosslinking agent 0.21 to 0.7 parts

[0060] Anchoring agent 0.12 to 0.3 parts

[0061] Catalyst 0.48 to 1.2 parts.

[0062] The silicone oil release agent is a solvent-based release agent, specifically any one of Shin-Etsu 847T, Elkem 7413, KCC SG1410A, LTC 759, Shin-Etsu X-62-2892, and Wacker D955. The viscosity of the solvent-based release agent is 7000 to 30000 cps. The viscosity of the silicone oil release agent is limited to solve the problem that the viscosity of the silicone oil release agent is too high, the fluidity of the release layer coating liquid is poor, and the thickness of the release layer will increase after coating, resulting in a high dry silicon content and a low residual adhesion rate; the viscosity of the silicone oil release agent is too low, affecting the temperature resistance.

[0063] The second organic solvent is one of toluene, butanone, ethyl acetate, cyclohexanone, n-heptane, and isopropanol, or a combination of multiple solvents in any weight ratio.

[0064] The crosslinking agent is a hydrogen-containing crosslinking agent, specifically any one of Elkem 91A, KCC SC0025B, KCC SC0016B, Dow Corning 7028, and Wacker V60. The hydrogen-containing crosslinking agent can crosslink with the silicon-oxygen chains in the silicone oil release agent to form a three-dimensional network structure.

[0065] The anchoring agent is a silane anchoring agent, specifically any one of KCC SC0052S, KCC SC0050S, Elkem ADD208, Dow Corning 9250, and Wacker HF87. The silane anchoring agent can effectively improve the adhesion between the release layer and the high temperature resistant layer and reduce the silicon loss phenomenon.

[0066] The catalyst is a platinum catalyst, specifically any one of Elkem 93B, KCC PCT-50, Shin-Etsu PL-50T, Dow Corning 4000, and Wacker C05. The platinum catalyst can promote the reaction between the hydrogen-containing crosslinking agent and the functional groups in the silicone oil release agent to form a more stable three-dimensional structure, and can shorten the reaction time and improve the efficiency of crosslinking.

[0067] The present invention provides a method for preparing a release film for FPC, comprising the following steps:

[0068] 1. Preparation of high temperature resistant layer coating liquid:

[0069] Dissolving a proportion of polymer resin in an organic solvent and stirring thoroughly to obtain a polymer resin solution;

[0070] Add the organic silicon resin, leveling agent and adhesion promoter in the proportioned amounts to the polymer resin solution prepared above in sequence, and stir thoroughly to obtain a high temperature resistant layer coating solution.

[0071] 2. Apply high temperature resistant coating liquid:

[0072] The high temperature resistant layer coating liquid is applied to one side of the PET base film and cured at 90-130°C to form a high temperature resistant layer.

[0073] 3. Preparation of release layer coating liquid:

[0074] A solvent-based release agent in a certain proportion is dissolved in an organic solvent, and a cross-linking agent, an anchoring agent and a catalyst are added in sequence, and the mixture is stirred sufficiently to obtain a release agent coating liquid.

[0075] 4. Forming release film for FPC:

[0076] The release agent coating liquid is applied on the high temperature resistant layer and cured at 120-150°C to form a release film for FPC.

[0077] The present invention will be further described below in conjunction with the embodiments.

[0078] Example 1

[0079] S1. Dissolve 2 g of polytetrafluoroethylene (PTFE) in 10 g of N,N-dimethylformamide and stir thoroughly to obtain a polytetrafluoroethylene (PTFE) solution.

[0080] S2. Add 0.1 g of epoxy-modified silicone resin (SMH-30), 0.4 g of leveling agent (MEGAFACE F440), and 0.04 g of silane adhesion promoter (BYK-4500) to the polytetrafluoroethylene (PTFE) solution prepared above, stir thoroughly, and obtain a high temperature resistant layer coating solution.

[0081] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film, and curing at 90° C. to form a high temperature resistant layer.

[0082] S4. Dissolve 30 g of Shin-Etsu 847T in 300 g of toluene, add 0.21 g of a crosslinking agent (Eken 91A), 0.12 g of an anchoring agent (KCC SC0052S), and 0.48 g of a platinum catalyst (Eken 93B) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0083] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3, and curing at 120°C to form a release film for FPC.

[0084] The performance test results are shown in Table 1.

[0085] Example 2

[0086] S1. Dissolve 3 g of polytrifluorochloroethylene (PCTFE) in 18 g of N,N-dimethylformamide and stir thoroughly to obtain a polytrifluorochloroethylene (PCTFE) solution.

[0087] S2. 0.18 g of modified silicone resin (SMH-60), 0.6 g of leveling agent (MEGAFACE F470), and 0.12 g of adhesion promoter (BYK-4509) were added to the polychlorotrifluoroethylene (PCTFE) solution prepared above in sequence, and the mixture was stirred thoroughly to obtain a high temperature resistant layer coating solution.

[0088] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film and curing at 100° C. to form a high temperature resistant layer.

[0089] S4. Dissolve 32g of Aiken 7413 in 320g of a mixed solvent of toluene, butanone and ethyl acetate, add 0.256g of a crosslinking agent (KCC SC0025B), 0.144g of an anchoring agent (KCC SC0050S) and 0.576g of a platinum catalyst (KCC PCT-50) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0090] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3, and curing at 125°C to form a release film for FPC.

[0091] The performance test results are shown in Table 1.

[0092] Example 3

[0093] S1. Dissolve 4 g of polyvinylidene fluoride (PVDF) in 28 g of N,N-dimethylformamide and stir thoroughly to obtain a polyvinylidene fluoride (PVDF) solution.

[0094] S2. 0.28 g of modified silicone resin (SM-1046), 0.8 g of leveling agent (MEGAFACE F553), and 0.2 g of adhesion promoter (BYK-4510) were added to the polyvinylidene fluoride (PVDF) solution prepared above in sequence, and the mixture was stirred thoroughly to obtain a high temperature resistant layer coating solution.

[0095] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film and curing at 110° C. to form a high temperature resistant layer.

[0096] S4. Dissolve 35g of KCC SG1410A in 350g of a mixed solvent of toluene, butanone and n-heptane, add 0.35g of a crosslinking agent (KCC SC0016B), 0.168g of an anchoring agent (Aiken ADD208) and 0.7g of a platinum catalyst (Shin-Etsu PL-50T) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0097] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3, and curing at 130°C to form a release film for FPC.

[0098] The performance test results are shown in Table 1.

[0099] Example 4

[0100] S1. Dissolve 5 g of ethylene-chlorotrifluoroethylene copolymer (ECTFE) in 40 g of N,N-dimethylformamide and stir thoroughly to obtain an ethylene-chlorotrifluoroethylene copolymer (ECTFE) solution.

[0101] S2. Add 0.4 g of modified silicone resin (SM-1046D), 1 g of leveling agent (MEGAFACE F554), and 0.3 g of adhesion promoter (BYK-3941P) to the above-prepared ethylene-chlorotrifluoroethylene copolymer (ECTFE) solution in sequence and stir thoroughly to obtain a high temperature resistant layer coating solution.

[0102] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film at 120°C to form a high temperature resistant layer.

[0103] S4. Dissolve 40 g of LTC 759 in 400 g of a mixed solvent of toluene, cyclohexanone and n-heptane, add 0.44 g of a crosslinking agent (Dow Corning 7028), 0.2 g of an anchoring agent (Dow Corning 9250) and 0.84 g of a platinum catalyst (Dow Corning 4000) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0104] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3 to form a release film for FPC at 135°C.

[0105] The performance test results are shown in Table 1.

[0106] Example 5

[0107] S1. Dissolve 7 g of ethylene-tetrafluoroethylene copolymer (ETFE) in 63 g of N,N-dimethylformamide and stir thoroughly to obtain an ethylene-tetrafluoroethylene copolymer (ETFE) solution.

[0108] S2. 0.63 g of modified silicone resin (SM-1057), 1.4 g of leveling agent (MEGAFACE F556), and 0.49 g of adhesion promoter (BYK-3942P) were added to the ethylene-tetrafluoroethylene copolymer (ETFE) solution prepared above, and the mixture was stirred thoroughly to obtain a high temperature resistant layer coating solution.

[0109] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film at 125°C to form a high temperature resistant layer.

[0110] S4. Dissolve 45 g of Shin-Etsu X-62-2892 in 400 g of a mixed solvent of toluene, isopropanol and n-heptane, add 0.54 g of a cross-linking agent (Wacker V60), 0.248 g of an anchoring agent (Wacker HF87) and 0.99 g of a platinum catalyst (Wacker C05) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0111] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3 to form a release film for FPC at 140°C.

[0112] The performance test results are shown in Table 1.

[0113] Example 6

[0114] S1. Dissolve 8 g of polyvinyl fluoride (PVF) in 85 g of N,N-dimethylformamide and stir thoroughly to obtain a polyvinyl fluoride (PVF) solution.

[0115] S2. 0.8 g of modified silicone resin (SMH-30), 1.6 g of leveling agent (MEGAFACE F557), and 0.64 g of adhesion promoter (BYK-3942P) were added to the polyvinyl fluoride (PVF) solution prepared above in sequence, and the mixture was stirred thoroughly to obtain a high temperature resistant layer coating solution.

[0116] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film at 130°C to form a high temperature resistant layer.

[0117] S4. Dissolve 50 g of Wacker D955 in 500 g of a mixed solvent of toluene, butanone and ethyl acetate, add 0.7 g of a crosslinking agent (Wacker V60), 0.3 g of an anchoring agent (Wacker HF87) and 1.2 g of a platinum catalyst (Wacker C05) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0118] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3 to form a release film for FPC at 150°C.

[0119] The performance test results are shown in Table 1.

[0120] Comparative Example 1 of Example 1

[0121] S1. Dissolve 2 g of polytetrafluoroethylene (PTFE) in 10 g of N,N-dimethylformamide and stir thoroughly to obtain a polytetrafluoroethylene (PTFE) solution.

[0122] S2. 0.1 g of epoxy-modified silicone resin (SMH-30) and 0.4 g of leveling agent (MEGAFACE F440) were added to the polytetrafluoroethylene (PTFE) solution prepared above, and the mixture was stirred thoroughly to obtain a high temperature resistant layer coating solution.

[0123] S3, coating the high temperature resistant layer coating liquid obtained in step S2 on one side of the PET base film, and curing at 90° C. to form a high temperature resistant layer.

[0124] S4. Dissolve 30 g of Shin-Etsu 847T in 300 g of toluene, add 0.21 g of a crosslinking agent (Eken 91A), 0.12 g of an anchoring agent (KCC SC0052S), and 0.48 g of a platinum catalyst (Eken 93B) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0125] S5, coating the release agent coating liquid obtained in step S4 on the high temperature resistant layer obtained in step S3, and curing at 120°C to form a release film for FPC.

[0126] The performance test results are shown in Table 1.

[0127] Comparative Example 2 of Example 1

[0128] S1. Dissolve 30 g of Shin-Etsu 847T in 300 g of toluene, add 0.21 g of crosslinking agent (Akem 91A), 0.12 g of anchoring agent (KCC SC0052S), and 0.48 g of platinum catalyst (Akem 93B) in sequence, and stir thoroughly to obtain a release agent coating liquid.

[0129] S2, coating the release agent coating liquid obtained in step S1 on one side of the PET base film to form a PET release film at 120°C.

[0130] The performance test results are shown in Table 1.

[0131] The performance test methods in Table 1 are as follows:

[0132] 1. Release force: the test standard is GB / T25256-2010, the test tape is Tesa7475 tape, and the peeling speed is 300mm / min;

[0133] 2. Residual adhesion rate: the test standard is GB / T25256-2010, the test tape is Nitto 31B tape; the peeling speed is 300mm / min;

[0134] 3. Adhesion: The test standard is GB / T9286-88, 5B means there is no peeling on the edge of the 100-grid test, and the cut edge is completely smooth;

[0135] 4. Temperature resistance: Cut the FPC release film into A4 size, put it into a 200℃ oven for 15 minutes, take it out and observe whether the sample is wrinkled;

[0136] 5. Peelability: Cut the FPC release film into samples with a width of 25mm and a length of 200mm, stick them on the SUS304 steel plate, put them in a 200℃ oven for 15s, take them out and observe whether the samples are easy to peel off.

[0137] Table 1 Performance data of various embodiments and comparative examples

[0138]

[0139] It can be seen from the test data of the embodiments and comparative examples that the release force, residual adhesion rate, adhesion of the high temperature resistant layer, temperature resistance and peelability of the release film for FPC prepared by the technical solution of the present invention are all stable, which means that coating the high temperature resistant layer on the PET base film can effectively solve the problem that the existing PET release film is not resistant to high temperatures. In comparative example 1, no adhesion promoter is added to the high temperature resistant layer, and the adhesion of the high temperature resistant layer tested is NG. In comparative example 2, the release layer is directly coated on the PET base film without a high temperature resistant layer, and both the temperature resistance and peelability tests are unqualified.

[0140] The above is only an embodiment of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A release film for FPC, characterized in that: The release film comprises a PET base film, a high temperature resistant layer and a release layer, wherein the high temperature resistant layer is coated on the PET base film, and the release layer is coated on the high temperature resistant layer; the high temperature resistant layer coating liquid comprises the following components in parts by weight: 2~8 parts of polymer resin 10 to 85 parts of the first organic solvent Silicone resin 0.1~0.8 parts Leveling agent 0.4~1.6 parts Adhesion promoter 0.04~0.64 parts.

2. The release film for FPC according to claim 1, characterized in that: The polymer resin is any one of polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-tetrafluoroethylene copolymer (ETFE) or polyvinyl fluoride (PVF).

3. The release film for FPC according to claim 1, characterized in that: The silicone resin is any one of epoxy-modified silicone resin, acrylic-modified silicone resin or alkyd-modified silicone resin.

4. The release film for FPC according to claim 1, characterized in that: The adhesion promoter is a silane-based adhesion promoter or a high molecular weight copolymer-based adhesion promoter containing acidic or basic groups.

5. The release film for FPC according to claim 1, characterized in that: The first organic solvent is N,N-dimethylformamide; and the leveling agent is a fluorine-based leveling agent.

6. The release film for FPC according to claim 1, characterized in that: The release layer coating liquid comprises the following components in parts by weight: 30~50 parts of silicone oil release agent 300 to 500 parts of the second organic solvent Cross-linking agent 0.21~0.7 parts Anchoring agent 0.12~0.3 parts Catalyst 0.48~1.2 parts.

7. The release film for FPC according to claim 6, characterized in that: The silicone oil release agent is a solvent-based release agent with a viscosity of 7000-30000 cps.

8. The release film for FPC according to claim 6, characterized in that: The second organic solvent is one of toluene, butanone, ethyl acetate, cyclohexanone, n-heptane, and isopropanol, or a combination of multiples in any weight ratio; the cross-linking agent is a hydrogen-containing cross-linking agent; the anchoring agent is a silane anchoring agent; and the catalyst is a platinum catalyst.

9. The method for preparing a release film for FPC according to claim 1, characterized in that: The thickness of the PET base film is 25-100 μm; the thickness of the high temperature resistant layer is 1-10 μm; and the thickness of the release layer is 0.01-0.1 μm.

10. A method for preparing a release film for FPC according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: a. Preparation of high temperature resistant layer coating liquid: Dissolving a proportion of a polymer resin in a first organic solvent and stirring the mixture sufficiently to obtain a polymer resin solution; Adding a proportion of organic silicone resin, a leveling agent and an adhesion promoter to the prepared polymer resin solution in sequence, and stirring thoroughly to obtain a high temperature resistant layer coating solution; b. Apply high temperature resistant coating liquid: Apply the high temperature resistant layer coating liquid on one side of the PET base film and solidify it at 90-130°C to form a high temperature resistant layer; c. Preparation of release layer coating liquid: Dissolving a proportion of a solvent-based release agent in a second organic solvent, adding a cross-linking agent, an anchoring agent and a catalyst in sequence, and stirring sufficiently to obtain a release agent coating liquid; d. Forming release film for FPC: The release agent coating liquid is applied on the high temperature resistant layer and cured at 120~150℃ to form a release film for FPC.

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