Resin composition for cover film and cover film

Abstract

The invention provides a resin composition for a cover film and the cover film. The resin composition for the cover film comprises the following components in parts by weight: 40-50 parts of phenoxy resin, 5-10 parts of polyvinyl butyral resin, 15-20 parts of epoxy resin, 5-10 parts of methacrylate-butadiene-styrene core-shell rubber and 5-20 parts of a curing agent, wherein the curing agent comprises an isocyanate curing agent and an amine curing agent. The covering film comprises a base film, an adhesive layer and a protective layer which are sequentially arranged in a stacked mode. The adhesive layer is prepared from the resin composition for the cover film. By designing the specific composition of the resin composition, the resin composition with high glass transition temperature, excellent processability and high reliability is obtained, the prepared cover film has good heat resistance, and the problems of curling of the cover film and adhesive falling during paper tearing are solved.

Description

Technical Field

[0001] This invention belongs to the field of polymer film technology, and specifically relates to a resin composition for a cover film and a cover film. Background Technology

[0002] Cover film is a film-like insulating material made by coating one side of an insulating base film such as polyimide film or polyester film with adhesive. It covers the surface of the circuitry and is an important component of flexible printed circuit boards (PCBs), serving to resist soldering, protect the circuitry, and improve the PCB's flexibility. As thinner and higher-density designs become the mainstream development trend for flexible printed circuit boards, these boards are becoming increasingly thinner with smaller line widths and spacings. This leads to a sharp increase in heat generation during operation, causing operating temperatures to exceed room temperature and deteriorating operating conditions. Currently, the commonly used adhesives for cover films are mainly acrylic adhesives and rubber-epoxy adhesives. Both of these adhesives have glass transition temperatures near room temperature, which cannot meet the requirements of applications demanding high heat resistance and high reliability.

[0003] Research on high glass transition temperature (Tg) adhesives for cover films has become a current industry hotspot. CN109233724A discloses a high glass transition temperature adhesive and its application in cover films. The high glass transition temperature adhesive comprises the following raw materials: phenolic resin, epoxy resin, toughening agent, flame retardant, curing agent, silane coupling agent, and solvent. This technical solution discloses that: traditional adhesives with low molecular weight epoxy resin as the main resin have strong fluidity during hot pressing, resulting in a large amount of adhesive overflow. Rubber toughening agents are needed to suppress adhesive overflow during hot pressing, but the addition of rubber toughening agents lowers the glass transition temperature. However, the high glass transition temperature adhesive described in this technical solution uses high molecular weight, low fluidity phenolic resin as the main resin, eliminating the need for rubber toughening agents to suppress overflow, thus ensuring the glass transition temperature of the adhesive. Furthermore, the adhesive contains a special epoxy resin, further improving the glass transition temperature of the adhesive.

[0004] CN114685989A provides a resin composition and an adhesive film and a cover film containing the resin composition. The resin composition comprises, by weight, the following components: 40-80 parts polyamide-imide resin, 10-40 parts epoxy resin, 5-30 parts phenolic resin, and 5-20 parts phosphorus-containing flame retardant. This technical solution, through the selection and synergistic compounding of components, significantly improves the glass transition temperature and heat resistance of the resin composition, while also exhibiting excellent adhesion and flame retardancy. The adhesive film and cover film containing the resin composition both achieve a glass transition temperature above 160°C, demonstrating outstanding heat resistance, stability, and reliability. They also exhibit high peel strength, good adhesion, and flame retardancy, fully meeting the processing and application requirements of flexible circuit boards, and are particularly suitable for preparing high-temperature resistant, high-reliability flexible copper-clad laminates and flexible printed circuit boards.

[0005] Although the cover films disclosed in the above two technical solutions have advantages such as high Tg (glass transition temperature) and good heat resistance, they also have processing problems such as brittle adhesive that is easy to tear and paper that falls off, and the cover film curling after the adhesive layer dries.

[0006] Therefore, how to develop a resin composition with good processability, heat resistance, reliability, and high glass transition temperature, and then prepare a high-performance cover film, has become an urgent technical problem to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a resin composition for cover film and a cover film. In this invention, by designing the specific composition of the resin composition, a resin composition with a high glass transition temperature, excellent processability, and high reliability is obtained. The cover film prepared thereby exhibits good heat resistance and solves the problems of cover film curling and adhesive detachment during tearing.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a resin composition for a cover film, the resin composition for a cover film comprising the following components in parts by weight:

[0010] 40-50 parts of phenolic resin;

[0011] 5-10 parts of polyvinyl butyral resin;

[0012] 15-20 parts epoxy resin;

[0013] 5-10 parts of methacrylate-butadiene-styrene core-shell rubber;

[0014] 5-20 parts of curing agent;

[0015] The curing agent includes isocyanate curing agents and amine curing agents.

[0016] In this invention, by designing the specific composition of the resin composition, a resin composition with a high glass transition temperature, excellent processability, and high reliability is obtained. The resulting cover film has good heat resistance and solves the problems of cover film curling and paper tearing.

[0017] The resin composition provided by this invention uses phenolic resin and polyvinyl butyral resin as the main resins, which endows the entire resin composition with a high glass transition temperature (Tg) and excellent film-forming properties. Polyvinyl butyral resin contains a large number of hydroxyl groups and has strong polarity, resulting in poor compatibility with phenolic resin. In the formulation, isocyanate is used as a curing agent, which can chemically bond the hydroxyl groups in polyvinyl butyral resin and phenolic resin, thereby not only improving the compatibility between the two, but also improving the adhesive resistance and heat resistance. Epoxy resin has good reactivity, which can improve the crosslinking density and heat resistance of the resin composition. Core-shell rubber can reduce the problem of cover film curling caused by volume shrinkage after the resin composition dries and the problem of paper tearing and adhesive peeling caused by brittle adhesive layer.

[0018] In this invention, the core-shell rubber has a flexible rubber core and a rigid outer shell. The flexible core has a curling and relaxation effect at high temperatures. In addition, the polymethyl methacrylate outer shell has good compatibility with the resin matrix, which allows it to form a discontinuous dot-like dispersion in the resin matrix and will not form a continuous phase. As a result, the entire covering film will not curl due to volume shrinkage after the solvent dries and evaporates.

[0019] In this invention, by controlling the amount of each component within a specific range, a resin composition with excellent performance is prepared through the synergistic effect of the components.

[0020] In this invention, by controlling the amount of core-shell rubber in the resin composition within a specific range, a resin composition with excellent performance is prepared, solving the problems of cover film curling and adhesive detachment during paper tearing. If the amount of core-shell rubber is too small, it can easily lead to cover film curling, adhesive detachment during paper tearing, and low peel strength; if the amount of core-shell rubber is too large, it can easily lead to a decrease in the glass transition temperature of the adhesive layer and a decrease in heat resistance.

[0021] In the resin composition provided by the present invention, the weight parts of phenolic resin can be 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, or 50 parts, etc.

[0022] The weight parts of polyvinyl butyral resin can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, or 10 parts, etc.

[0023] The weight parts of epoxy resin can be 15 parts, 15.5 parts, 16 parts, 16.5 parts, 17 parts, 17.5 parts, 18 parts, 18.5 parts, 19 parts, 19.5 parts, or 20 parts, etc.

[0024] The weight percentages of the core-shell rubber can be 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, or 10 parts, etc.

[0025] The weight percentage of the curing agent can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 parts, etc.

[0026] The "parts" and "parts by weight" used in this invention are calculated based on solid content and do not include solvents, dispersants, etc.

[0027] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0028] As a preferred embodiment of the present invention, the weight-average molecular weight of the phenolic resin is 50,000 to 90,000, for example, it can be 50,000, 52,000, 54,000, 56,000, 58,000, 60,000, 65,000, 76,000, 81,000 or 90,000.

[0029] As a preferred embodiment of the present invention, the glass transition temperature of the polyvinyl butyral resin is 70℃~100℃, for example, it can be 70℃, 72℃, 75℃, 77℃, 80℃, 81℃, 84℃, 86℃, 88℃, 90℃, 93℃, 96℃ or 100℃, etc.

[0030] Preferably, the number average molecular weight of the polyvinyl butyral resin is 90,000 to 120,000, for example, it can be 90,000, 92,000, 94,000, 97,000, 100,000, 102,000, 105,000, 108,000, 110,000, 113,000, 115,000, 118,000 or 120,000.

[0031] As a preferred embodiment of the present invention, the epoxy resin includes a multifunctional epoxy resin.

[0032] Preferably, the epoxy equivalent of the epoxy resin is 100-300 g / eq, for example, it can be 100 g / eq, 120 g / eq, 140 g / eq, 160 g / eq, 180 g / eq, 200 g / eq, 220 g / eq, 240 g / eq, 260 g / eq, 280 g / eq or 300 g / eq, etc.

[0033] In this invention, multifunctional epoxy resin refers to a resin in which each molecule contains an average of two or more crosslinkable epoxy groups.

[0034] Preferably, the multifunctional epoxy resin is selected from any one or a combination of at least two of phenolic epoxy resin, bisphenol A epoxy resin, o-cresol epoxy resin, or dicyclopentadiene epoxy resin.

[0035] As a preferred embodiment of the present invention, the core layer of the core-shell rubber is a copolymer of butadiene and styrene.

[0036] Preferably, the shell material of the core-shell rubber is polymethyl methacrylate.

[0037] Preferably, the core-shell rubber is a solid powder with butadiene-styrene copolymer as the core and polymethyl methacrylate as the shell.

[0038] Preferably, the average particle size of the core-shell rubber is 100nm to 500nm, for example, it can be 100nm, 120nm, 140nm, 160nm, 180nm or 500nm.

[0039] Preferably, the core-shell rubber is selected from any one or a combination of two of CLEARSTRENGTH XT-100 core-shell rubber (purchased from Arkema) and CLEARSTRENGTH XT-151 core-shell rubber (purchased from Arkema).

[0040] As a preferred embodiment of the present invention, the isocyanate curing agent is 3-5 parts, for example, it can be 3 parts by weight, 3.5 parts by weight, 4 parts by weight, 4.5 parts by weight or 5 parts by weight.

[0041] Preferably, the isocyanate curing agent is selected from any one or a combination of at least two of hexamethylene diisocyanate trimer, toluene diisocyanate trimer, 4,4'-diphenylmethyl diisocyanate trimer or isophorone diisocyanate trimer.

[0042] If the amount of the isocyanate curing agent is too small, the compatibility between the phenolic resin and the polyvinyl butyral resin will be insufficient, resulting in a brittle adhesive layer with poor heat resistance and low peel strength. If the amount of the isocyanate curing agent is too large, it will easily lead to excessive cross-linking of the phenolic resin and the polyvinyl butyral resin, forming a gel.

[0043] Preferably, the amine curing agent is 2-15 parts by weight, for example, it can be 2 parts by weight, 3 parts by weight, 4 parts by weight, 5 parts by weight, 6 parts by weight, 8 parts by weight, 9 parts by weight, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight or 15 parts by weight.

[0044] Preferably, the amine curing agent is selected from any one or a combination of at least two of dicyandiamide, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, or diphenylmethane diamine.

[0045] As a preferred embodiment of the present invention, the resin composition for the covering film further includes 10 to 20 parts of flame retardant, for example, 10 parts by weight, 11 parts by weight, 12 parts by weight, 13 parts by weight, 14 parts by weight, 15 parts by weight, 16 parts by weight, 17 parts by weight, 18 parts by weight, 19 parts by weight, or 20 parts by weight.

[0046] Preferably, the flame retardant includes a phosphorus-containing flame retardant.

[0047] It should be noted that the present invention does not impose any specific limitations on the selection of phosphorus-containing flame retardants, and commonly used phosphorus-containing flame retardants in the art are applicable.

[0048] As a preferred embodiment of the present invention, the resin composition for the covering film further includes a solvent.

[0049] Preferably, the solvent is selected from any one or a combination of at least two of acetone, butanone, toluene, ethanol, isopropanol, cyclohexanone, ethylene glycol methyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate, or ethyl acetate.

[0050] Preferably, the solid content of the resin composition for the covering film is 30wt% to 60wt%, for example, it can be 30wt%, 33wt%, 36wt%, 38wt%, 40wt%, 42wt%, 44wt%, 46wt%, 49wt%, 52wt%, 54wt%, 56wt%, 58wt%, or 60wt%, etc.

[0051] In this invention, the solid content of the resin composition is equal to (the sum of the weight parts of all components of the resin composition - the amount of solvent used) ÷ the sum of the weight parts of all components of the resin composition × 100%.

[0052] In this invention, there are no special restrictions on the preparation method of the resin composition, and the preparation methods commonly used in the art are applicable. However, it is preferred that the preparation of the resin composition be carried out in two steps to avoid the isocyanate curing agent and the amine curing agent consuming each other, thereby causing a decrease in the system compatibility and heat resistance.

[0053] As a preferred embodiment of the present invention, the method for preparing the resin composition for the covering film includes the following steps:

[0054] (1) Phenoxy resin, polyvinyl butyral resin, methacrylate-butadiene-styrene core-shell rubber, isocyanate curing agent and solvent are mixed to obtain adhesive solution;

[0055] (2) Cool the adhesive obtained in step (1) to 20-25°C, then add epoxy resin and amine curing agent, mix, and obtain the resin composition for the cover film.

[0056] It should be noted that if the resin composition contains a flame retardant, the flame retardant is added and mixed in step (1).

[0057] As a preferred technical solution of the present invention, the temperature of the adhesive liquid in step (1) is 40-80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, etc.

[0058] Preferably, the mixing time in step (1) is 1-24h, for example, it can be 1h, 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h.

[0059] Preferably, the mixing method in step (1) includes high shear, ball milling or sand milling.

[0060] Preferably, the mixing time in step (2) is 1-8 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0061] The preparation method of the resin composition for the covering film specifically includes the following steps:

[0062] (1) Mix phenolic resin, polyvinyl butyral resin, methacrylate-butadiene-styrene core-shell rubber, isocyanate curing agent and solvent, and disperse and stir using high shear, ball milling or sand milling, etc., while controlling the temperature of the adhesive solution to 40-80℃, and mix for 1-24 hours to ensure that the isocyanate curing agent reacts fully with phenolic resin and polyvinyl butyral resin, while the core-shell rubber is effectively dispersed.

[0063] (2) Cool the mixture from step (1) to 20-25°C, then add epoxy resin and amine curing agent, stir and disperse for 1-8 hours to obtain the resin composition for the covering film.

[0064] In a second aspect, the present invention provides a cover film, the cover film comprising a base film, an adhesive layer and a protective layer stacked sequentially;

[0065] The adhesive layer is prepared from a resin composition for a cover film as described in the first aspect.

[0066] As a preferred embodiment of the present invention, the thickness of the adhesive layer is 5μm to 100μm, for example, it can be 5μm, 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, etc.

[0067] As a preferred embodiment of the present invention, the base film includes a polyimide film (PI film).

[0068] Preferably, the protective layer comprises either a release film or a release paper.

[0069] In this invention, there are no special limitations on the preparation method of the covering film; commonly used preparation methods in the art are applicable, including but not limited to:

[0070] A resin composition for covering film is coated onto either side of the base film and dried to obtain an adhesive layer.

[0071] The protective layer is laminated onto the side of the adhesive layer away from the base film to obtain the cover film.

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] In this invention, by designing the specific composition of the resin composition and through the synergistic effect of the components in the resin composition, and further by using a specific amount of methacrylate-butadiene-styrene core-shell rubber, a resin composition with high glass transition temperature, excellent processability, and high reliability is obtained. The resulting cover film has good heat resistance and solves the problems of cover film curling and adhesive peeling. The peel strength of the resulting cover film is 0.95-1.37 N / mm, the glass transition temperature is 105.3-121.6℃, and the heat resistance temperature is 330-360℃. Detailed Implementation

[0074] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0075] The sources of some components in the examples and comparative examples are shown in Table 1 below:

[0076] Table 1

[0077]

[0078] Examples 1 to 4, Comparative Examples 1 to 7

[0079] Examples 1 to 4 and Comparative Examples 1 to 7 each provide a resin composition and a covering film. The specific composition of the resin composition is detailed in Table 2 (the amounts of each component in Table 2 are parts by weight).

[0080] The preparation methods of the resin compositions provided in Examples 1 to 3 and Comparative Examples 1 to 7 are as follows:

[0081] (1) Phenoxy resin, polyvinyl butyral resin, core-shell rubber (or block copolymer or styrene-butadiene rubber), isocyanate curing agent, flame retardant and solvent are mixed and stirred with high shear dispersion. The temperature of the adhesive solution is controlled at 60°C and mixed for 12 hours. This allows the isocyanate curing agent to fully react with phenoloxy resin and polyvinyl butyral resin, while the core-shell rubber is effectively dispersed.

[0082] (2) Cool the mixture from step (1) to room temperature (25°C), then add epoxy resin and amine curing agent, stir and disperse for 4 hours to obtain the resin composition.

[0083] The method for preparing the resin composition provided in Example 4 is as follows:

[0084] The resin composition was obtained by mixing the components of the resin composition at 60°C under high shear for 12 hours.

[0085] Examples 1 to 4 and Comparative Examples 1 to 7 each provide a cover film, wherein the cover film comprises a base film, an adhesive layer and a protective layer stacked together;

[0086] The base membrane is a PI membrane;

[0087] The adhesive layer is prepared from the resin composition and has a thickness of 30 μm;

[0088] The protective layer is release paper.

[0089] The method for preparing the covering film is as follows:

[0090] The resin composition was coated on either side of the PI film, and the solvent (toluene) was removed by heating at 150°C for 7 minutes in an online drying oven to obtain the adhesive layer.

[0091] The release paper is laminated onto the side of the adhesive layer away from the PI film to obtain the cover film.

[0092] Table 2

[0093]

[0094] The performance of the covering films provided in the above embodiments and comparative examples was tested, and the specific test methods are as follows:

[0095] (1) Peel strength: The cover film was pressed onto the smooth surface of 18μm rolled copper foil and cured at 180℃ for 1 hour, and then tested according to IPC-TM-650 2.4.9 method.

[0096] (2) Glass transition temperature: After the adhesive layer is cured at 180°C for 1 hour, the glass transition temperature is tested by differential scanning calorimetry (DSC) in nitrogen atmosphere at a heating rate of 10°C / min.

[0097] (3) Heat resistance temperature: The ultimate resistance temperature for immersion soldering is tested. The cover film is pressed with the smooth surface of 18μm rolled copper foil and cured at 180℃ for 1 hour. Then, it is placed in a solder bath at different temperatures for 20 seconds and then taken out for observation to check whether there is delamination and blistering. The test temperature starts from 280℃ and gradually increases in 10℃ increments. The temperature before delamination and blistering occurs is the ultimate resistance temperature for immersion soldering.

[0098] (4) Curlability: After tearing the paper off the covering film, observe whether the coated PI film curls.

[0099] (5) Tearing off the paper and removing the adhesive: After tearing off the cover film, observe whether the adhesive layer remains on the surface of the release paper.

[0100] The performance test results are shown in Table 3 below.

[0101] Table 3

[0102]

[0103]

[0104] As can be seen from the above, Examples 1-4 of the present invention, through the design of the specific composition of the resin composition and the synergistic effect of the components in the resin composition, and further through the use of a specific amount of methacrylate-butadiene-styrene core-shell rubber, obtained a resin composition with high glass transition temperature, excellent processability, and high reliability. The resulting cover film has good heat resistance and solves the problems of cover film curling and adhesive peeling. The peel strength of the cover film prepared in this way is 0.95-1.37 N / mm, the glass transition temperature is 105.3-121.6℃, and the heat resistance temperature is 330-360℃.

[0105] Compared with Example 1, Example 4 uses a one-step mixing method, which involves adding all materials at once. This causes the isocyanate curing agent and the amine curing agent to consume each other, which may lead to a slight decrease in compatibility and heat resistance.

[0106] Compared with Example 1, the amount of core-shell rubber used in Comparative Examples 1-2 was lower and higher, respectively, resulting in a deterioration in the overall performance of the cover film.

[0107] Compared with Example 1, Comparative Examples 3-5 used non-inventive methacrylate-butadiene-styrene core-shell rubber or block copolymer or styrene-butadiene rubber, wherein the heat resistance of Comparative Example 3 was worse, and the cover films of Comparative Examples 4 and 5 showed curling and paper tearing.

[0108] Compared to Example 1, Comparative Example 6 does not contain isocyanate curing agent, which will lead to compatibility problems between phenolic resin and polyvinyl butyral resin, resulting in a deterioration in the overall performance of the cover film.

[0109] Compared with Example 1, Comparative Example 7 does not contain amine curing agents, resulting in incomplete crosslinking of epoxy resin, which leads to low crosslinking density, poor compatibility, and decreased peel strength and heat resistance of the cover film.

[0110] The applicant declares that the detailed process flow of this invention is illustrated by the above embodiments, but this invention is not limited to the above detailed process flow, that is, it does not mean that this invention must rely on the above detailed process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product of this invention, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A resin composition for a cover film, characterized by comprising: The resin composition for the cover film comprises components in the following weight proportions: The curing agent comprises an isocyanate curing agent and an amine curing agent.

2. The resin composition for a cover film according to claim 1, characterized by The phenolic oxygen resin has a weight average molecular weight of 50,000-90,000; Preferably, the polyvinyl butyral resin has a glass transition temperature of 70-100℃. Preferably, the polyvinyl butyral resin has a number average molecular weight of 90,000-120,000.

3. The resin composition for a cover film according to claim 1 or 2, characterized by The epoxy resin comprises a multifunctional epoxy resin; Preferably, the multifunctional epoxy resin is selected from any one or a combination of at least two of a phenol novolac epoxy resin, a bisphenol A novolac epoxy resin, an o-cresol novolac epoxy resin or a dicyclopentadiene novolac epoxy resin.

4. The resin composition for a coverlay film according to any one of claims 1 to 3, characterized by, The core layer of the core-shell rubber is a copolymer of butadiene-styrene; Preferably, the shell layer of the core-shell rubber is polymethyl methacrylate; Preferably, the average particle size of the core-shell rubber is 100-500nm.

5. The resin composition for a coverlay film according to any one of claims 1 to 4, characterized by, The isocyanate curing agent is 3-5 parts; Preferably, the isocyanate curing agent is selected from any one or a combination of at least two of a hexamethylene diisocyanate trimer, a toluene diisocyanate trimer, a 4,4'-diphenylmethane diisocyanate trimer or an isophorone diisocyanate trimer; Preferably, the amine curing agent is 2-15 parts; Preferably, the amine curing agent is selected from any one or a combination of at least two of dicyandiamide, 4,4'-diamino diphenyl sulfone, 3,3'-diamino diphenyl sulfone or diphenylmethane diamine.

6. The resin composition for a coverlay film according to any one of claims 1 to 5, characterized by The resin composition for the cover film further comprises a flame retardant in an amount of 10-20 parts; Preferably, the flame retardant comprises a phosphorus-containing flame retardant; Preferably, the resin composition for the cover film further comprises a solvent; Preferably, the solvent is selected from any one or a combination of at least two of acetone, butanone, toluene, ethanol, isopropyl alcohol, cyclohexanone, ethylene glycol methyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate or ethyl acetate; Preferably, the resin composition for the cover film has a solid content of 30wt%-60wt%.

7. A method for producing the resin composition for a covering film according to any one of claims 1 to 6, characterized by, The preparation method comprises the following steps: (1) mixing a phenolic oxygen resin, a polyvinyl butyral resin, a methyl methacrylate-butadiene-styrene core-shell rubber, an isocyanate curing agent and a solvent to obtain a glue solution; (2) cooling the glue solution obtained in step (1) to 20-25℃, then adding an epoxy resin and an amine curing agent and mixing to obtain the resin composition for the cover film.

8. The production method according to claim 7, characterized by, The temperature of the glue solution in step (1) is 40-80℃; Preferably, the mixing time in step (1) is 1-24h; Preferably, the mixing time in step (2) is 1-8h.

9. A cover film characterized by, The cover film comprises a base film, a glue layer and a protective layer which are sequentially stacked; The glue layer is prepared from the resin composition for the cover film according to any one of claims 1-6.

10. The cover film according to claim 9, characterized in that, The thickness of the glue layer is 5μm-100μm.

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