A resin composition and a covering film prepared therefrom

Abstract

The present invention provides a resin composition and a cover film prepared therefrom. The resin composition comprises the following components in parts by weight: 35 - 45 parts of an epoxy resin, 20 - 30 parts of a carboxyl-terminated nitrile rubber, 3 - 5 parts of a phenoxy resin, 2 - 4 parts of a polyvinyl butyral resin, and 2.8 - 4.2 parts of an amine curing agent. The present invention can solve the problem of glue overflow of the cover film. When laminating, the overflowed glue edge is neat, there is no small-molecule glue overflow, and it can take into account the heat resistance and adhesiveness of the resin composition.

Description

Technical Field

[0001] The present invention belongs to the technical field of flexible copper clad laminates, and relates to a resin composition and a cover film prepared therefrom. Background Art

[0002] As the surface protection layer of flexible printed circuit boards (FPCBs), cover films protect the circuits from contamination by dust, moisture, and chemicals, as well as other forms of damage, acting as insulation and solder mask, and at the same time having certain flexibility and reinforcement effects. They can reduce the influence of stress on conductors during the bending process and improve the bending resistance of flexible printed circuit boards. The most widely used cover film for FPCBs is the polyimide film type cover film, which is formed by coating a resin composition (epoxy adhesive) on one side of a polyimide film (PI film), drying, and partially crosslinking. The epoxy adhesive cover film has good comprehensive properties and high cost performance. The ideal morphology of the overflow edge should be flat, but in the application process, quality problems such as serrated overflow, secondary overflow, spray glue, and skipping glue of small molecules often occur.

[0003] When small molecule overflow occurs in the cover film, the overflowed adhesive will leave glue residues on the pads and circuits, reducing the effective area of the conductor. Therefore, in this field, improving the overflow quality of the cover film has become an important research topic in the industry.

[0004] Therefore, it is desirable to develop materials that can improve the overflow quality of the cover film. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a resin composition and a cover film prepared therefrom. The resin composition of the present invention can solve the problem of overflow of the cover film, and the overflow edge is neat during lamination, without small molecule overflow.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a resin composition, which comprises the following components in parts by weight:

[0008] 35 - 45 parts of epoxy resin, 20 - 30 parts of carboxyl-terminated nitrile rubber, 3 - 5 parts of phenoxy resin, 2 - 4 parts of polyvinyl butyral resin, and 2.8 - 4.2 parts of amine curing agent.

[0009] In the epoxy resin system of the present invention, phenoxy resin, polyvinyl butyral resin, and carboxyl-terminated nitrile rubber are combined to jointly improve the toughening and glue resistance properties. With carboxyl-terminated nitrile rubber as the main toughening and glue resistance component, and phenoxy resin and polyvinyl butyral resin introduced as auxiliary toughening and glue resistance components, the cover film prepared from this resin composition has excellent overflow characteristics. The overflow edge of the cover film during lamination is neat, without small molecule overflow, and can take into account the heat resistance and adhesiveness of the resin composition.

[0010] In the present invention, the molecular weights and melt viscosities of the phenoxy resin and polyvinyl butyral resin are both very high, and the molecular weights and melt viscosities of the two are designed in a gradient manner. When added to the resin composition, the melt viscosity of the resin composition at different melting stages is increased, which can synergistically supplement the gel blocking voids left by the phase separation of the carboxyl-terminated nitrile rubber and epoxy resin due to the formation of a "sea-island" structure during the curing process, effectively preventing the appearance of small molecule overflow glue on the cover film.

[0011] In the resin composition of the present invention, the content of the epoxy resin can be 35 parts, 38 parts, 40 parts, 42 parts or 45 parts, the content of the carboxyl-terminated nitrile rubber can be 20 parts, 23 parts, 25 parts, 28 parts or 30 parts, the content of the phenoxy resin can be 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, the content of the polyvinyl butyral resin can be 2 parts, 2.5 parts, 3 parts, 3.5 parts or 4 parts, and the content of the amine curing agent can be 2.8 parts, 3 parts, 3.2 parts, 3.5 parts, 3.8 parts or 4.2 parts.

[0012] Preferably, the epoxy resin is selected from one or a mixture of at least two of bisphenol A epoxy resin, dicyclopentadiene phenol epoxy resin, phenol novolac epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin, biphenyl epoxy resin, naphthalene epoxy resin, phosphorus-containing epoxy resin, nitrogen-containing epoxy resin, and tetrafunctional epoxy resin. If the amount of the epoxy resin is too much, the flexibility of the resin composition will decrease and the overflow glue amount of the cover film will increase; if the amount of the epoxy resin is too little, the curing crosslinking density and heat resistance of the resin composition will decrease.

[0013] Preferably, the carboxyl-terminated nitrile rubber is formed by terpolymerization of butadiene, acrylonitrile and an organic acid (such as acrylic acid, methacrylic acid, etc.), and the acrylonitrile content is 18-50% by mass (such as 18% by mass, 20% by mass, 25% by mass, 30% by mass, 40% by mass or 50% by mass). The carboxyl-terminated nitrile rubber can use commercially available products, including but not limited to: Nipol 1072CGX and Nipol 1072CGJ (Zeon Corporation), NANCAR 1072CG (Southern Dynatech Co., Ltd.), XER-32 (JSR Corporation), KRYNAC X740 and KRYNAC X750 (ARLANXEO Corporation). If the amount of the carboxyl-terminated nitrile rubber is too little, the toughening and gel blocking effects are not obvious; if the amount of the carboxyl-terminated nitrile rubber is too much, the glue layer of the cover film will be sticky, and the peel strength and heat resistance will decrease.

[0014] In the present invention, the phenoxy resin has a relatively high melting temperature and melting viscosity, which can retard the flow of the resin composition under high temperature and high pressure. If the amount of the phenoxy resin is too large, the crosslinking density of the resin composition is relatively low, and the heat resistance decreases; if the amount is too small, the synergistic effect of resist blocking is not obvious, and the overflow edge of the cover film is not neat enough. The phenoxy resin can be a commercially available product, and exemplary ones include but are not limited to: 1276 of Mitsubishi Chemical Corporation, EPONOL Resin53-BH-35 of Momenti ye Company, or PKHH of Inchem Company.

[0015] Preferably, the number average molecular weight of the polyvinyl butyral resin is 100,000 - 130,000 (such as 100,000, 110,000, 120,000 or 130,000, etc.). The larger the molecular weight of the polyvinyl butyral resin, the higher the glass transition temperature and melting viscosity, and the better the flexibility, film-forming property and resist blocking effect. If the amount of the polyvinyl butyral resin is too small, the synergistic effect of resist blocking is not obvious; if the amount is too large, the heat resistance of the resin composition will decrease. The polyvinyl butyral resin can be a commercially available product, and exemplary ones include but are not limited to KS-5Z and KS-6Z of Sekisui Chemical Co., Ltd.

[0016] Preferably, the amine curing agent is selected from one or a combination of two or more of dicyandiamide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, diaminodiphenyl methane, diaminodiphenyl ether or aliphatic amine.

[0017] Preferably, the amine curing agent is a combination of 4,4'-diaminodiphenyl sulfone and dicyandiamide. Preferably, the amount of 4,4'-diaminodiphenyl sulfone in the combination is 2.5 - 4.0 parts by weight, and the amount of dicyandiamide is 0.1 - 0.3 parts by weight. As a preferred technical solution of the present invention, by combining the high-temperature resistant curing agent 4,4'-diaminodiphenyl sulfone and the latent curing agent dicyandiamide to form a composite curing agent, the resin composition and the cover film prepared therefrom can have high heat resistance and peel strength.

[0018] In the present invention, if the amount of the amine curing agent is too large, the crosslinking density of the resin composition is high and the flexibility decreases; if the amount of the curing agent is too small, the crosslinking density of the resin composition is insufficient and the heat resistance decreases.

[0019] Preferably, the resin composition further contains 18 - 28 parts of a filler, such as 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 25 parts or 28 parts. If the amount of the filler is too small, the flame retardancy of the resin composition will be affected; if the amount of the filler is too large, the heat resistance and flexibility of the resin composition will be affected.

[0020] Preferably, the filler is an inorganic filler or an organic filler.

[0021] Preferably, the inorganic filler is at least one of aluminum hydroxide, magnesium hydroxide, boehmite, talcum powder, silicon dioxide, kaolin or alumina.

[0022] Preferably, the organic filler is at least one of aluminum diethylphosphinate, melamine or cyanuric acid.

[0023] Preferably, the average particle size D50 of the filler is 0.5 - 5 μm (0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm). If the particle size of the filler is too large, the coating appearance is poor; if the particle size is too small, the dispersion effect is poor.

[0024] Preferably, the resin composition further contains 0.05 - 0.15 parts of an antioxidant, such as 0.06 parts, 0.08 parts, 0.10 parts, 0.12 parts, 0.14 parts or 0.15 parts. Preferably, the antioxidant is a hindered phenol antioxidant or a hindered amine antioxidant. The antioxidant can delay the oxidation of the resin composition during high-temperature curing and subsequent processing applications. The antioxidant can be hindered phenol antioxidants such as CHINOX 1010, CHINOX 1076, CHINOX 1098, CHIN0Z 1325 (all from Double Bond Chemical Industry Co., Ltd.), and hindered amine antioxidants such as DNP (from Kaiyuan Fine Chemicals), etc.

[0025] On the other hand, the present invention provides a resin solution, which is obtained by dissolving or dispersing the resin composition as described above in an organic solvent.

[0026] Preferably, the organic solvent is selected from one or a combination of at least two of acetone, methyl ethyl ketone, cyclohexanone, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl acetate, butyl acetate, etc.

[0027] The organic solvent is used to dissolve the curing agent, disperse the filler and adjust the viscosity of the resin composition solution. For the prepared resin composition solution, the solid content is preferably 35% - 45%, such as 35%, 38%, 40%, 42% or 45%. With appropriate solution viscosity, good processability can be provided, and no appearance defects will occur during the coating process.

[0028] On the other hand, the present invention provides a cover film, which includes a polymer-based film, an adhesive layer on the polymer-based film, and a release paper layer on the adhesive layer, and the adhesive layer is formed from the resin composition as described above.

[0029] Preferably, the polymer-based film is a polyimide film.

[0030] Preferably, the thickness of the polymer-based film is 7.5 - 50 μm, such as 7.5 μm, 9 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0031] Preferably, the thickness of the adhesive layer is 5 - 50 μm, such as 5 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0032] Preferably, the thickness of the release paper layer is 110 - 130 μm, such as 110 μm, 112 μm, 115 μm, 118 μm, 120 μm, 122 μm, 125 μm, 128 μm or 130 μm.

[0033] In the present invention, the covering film can be prepared by the following preparation method:

[0034] First, use a bead mill in combination with a high-shear stirring and dispersing device to mix the various components in the combination of the present invention together to prepare a resin composition. Then use a coater to coat the resin composition on one surface of a polyimide film, and dry it in an oven, heat it at 140 °C for 5 minutes to remove the organic solvent and partially crosslink and cure the resin composition to form a semi-cured resin composition layer on the polyimide film. Next, roll-compound it with the release paper at a lamination temperature of 80 °C, and wind it up to obtain the covering film.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] In the epoxy resin system of the present invention, a combination of phenoxy resin, polyvinyl butyral resin and carboxyl-terminated nitrile rubber is used to jointly improve the toughening and anti-gumming properties, synergistically solve the problem of gumming overflow of the covering film, the gumming edge during lamination is neat, there is no small molecule gumming overflow, and the heat resistance and adhesiveness of the resin composition can be taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is an optical topography diagram of the smooth gumming edge of the covering film;

[0038] Figure 2 It is an optical topography diagram of the serrated gumming of the covering film;

[0039] Figure 3 It is an optical topography diagram of the sprayed glue of the covering film. DETAILED DESCRIPTION OF THE INVENTION

[0040] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0041] Example 1

[0042] A resin composition comprising: 40 parts by weight of bisphenol A epoxy resin (GESN901, Hongchang Electronic Materials Co., Ltd.), 25 parts by weight of carboxyl-terminated nitrile rubber (NANCAR 1072CG, Southern Chemical Industries Co., Ltd.), 4 parts by weight of phenoxy resin (1256, Mitsubishi Chemical Corporation), 3 parts by weight of polyvinyl butyral resin (KS-5Z, Sekisui Chemical Co., Ltd., molecular weight 130,000), 3.5 parts by weight of 4,4'-diaminodiphenyl sulfone (from Atul India), 0.2 parts by weight of dicyandiamide (from Ningxia Darong Chemical Industry and Metallurgy Co., Ltd.), 13 parts by weight of aluminum hydroxide (H-42M, Showa Denko KK, D50 particle size 1.1 μm), 14 parts by weight of aluminum diethyl phosphinate (OP-935, Clariant, D50 particle size 3.5 μm), and 0.1 parts by weight of antioxidant 1010 (CHINOX 1010, Double Bond Chemical Industry Co., Ltd.).

[0043] First, dissolve the rubber, resin, and curing agent with methyl ethyl ketone and ethylene glycol monomethyl ether respectively, then mix with the remaining components, and adjust the solid content of the resin composition solution to 40% with methyl ethyl ketone to prepare a resin composition glue solution.

[0044] Examples 2-4, Comparative Examples 1-10

[0045] A resin composition, the components and their contents are shown in Table 1 and Table 2. The dosage units of each component in Tables 1-2 are all parts by weight (i.e., the solid parts by weight without solvent).

[0046] Coat the resin composition glue solutions of Examples 1-4 and Comparative Examples 1-10 onto a polyimide film (TL-012, Taimei Technology Co., Ltd.) with a thickness of 12.5 μm respectively using a coater, control the thickness of the resin composition layer to be 15 μm, then put it into an oven at 160 °C and bake for 5 minutes to form a partially crosslinked and cured resin composition layer on the polyimide film, and then roll and laminate it with 120 μm release paper at a lamination temperature of 75 °C to obtain a cover film.

[0047] Test the properties of the cover films of Examples 1-4 and Comparative Examples 1-10, and the results are shown in Table 1 and Table 2.

[0048] Table 1

[0049]

[0050] Table 2

[0051]

[0052] The test methods for the properties of the cover film are as follows:

[0053] (1) Glue overflow amount and glue overflow morphology: The glue overflow amount is tested according to the method of IPC-TM-650 2.3.17.1; observe the glue overflow morphology of the cover film, and the judgment criteria for the glue overflow morphology are as Figures 1-3 shown, where Figure 1 is that the glue overflow edge is flat, Figure 2 is serrated glue overflow, Figure 3 is spray glue.

[0054] (2) Peel strength: Test according to the method of IPC-TM-650 2.4.9. First, press the cover film and a 18μm rolled copper foil (BHYX-92F-T, Nippon Mining & Metals Co., Ltd.) on the smooth surface, and then test the peel strength after baking at 160°C for 1 hour.

[0055] (3) Immersion soldering resistance: Test according to the method of IPC-TM-650 2.4.13. Immerse the specimen completely in the tin bath for 20 seconds, and record the highest test temperature at which the specimen does not delaminate or blister.

[0056] It can be seen from the data in Table 1 that the cover film prepared from the resin composition of the present invention has good heat resistance and adhesiveness. The glue overflow edge of the cover film is flat, the peel strength is above 0.83 N / mm, and the immersion soldering temperature is above 325°C; among them, compared with Example 4, Example 1 uses a composite curing agent, and its heat resistance and peel strength are better.

[0057] In Comparative Example 1 and Comparative Example 2, only polyvinyl butyral resin or phenoxy resin is used alone. In Comparative Example 3, neither polyvinyl butyral resin nor phenoxy resin is used, and the glue overflow edges of the cover films all show serrated glue overflow to varying degrees. Among them, the glue overflow edge of the cover film in Comparative Example 3 shows more serrated glue overflow.

[0058] In Comparative Example 4, the amount of carboxyl-terminated nitrile rubber is too small. Even though polyvinyl butyral resin and phenoxy resin are added, the glue blocking effect is poor, and the glue overflow edge of the cover film shows more serrated glue overflow; in Comparative Example 5, the amount of carboxyl-terminated nitrile rubber is too large, and the peel strength and heat resistance of the cover film decrease.

[0059] In Comparative Example 6, the amount of phenoxy resin is too small, and the glue overflow edge of the cover film shows less serrated glue overflow; in Comparative Example 7, the amount of phenoxy resin is too large. Although the glue overflow edge of the cover film is flat, its heat resistance and peel strength decrease.

[0060] In Comparative Example 8, the amount of polyvinyl butyral resin is too small, and the glue overflow edge of the cover film shows less serrated glue overflow; in Comparative Example 9, the amount of polyvinyl butyral resin is too large. Although the glue overflow edge of the cover film is flat, its heat resistance decreases.

[0061] Comparative Example 10 shows that when using a polyvinyl butyral resin with a lower molecular weight (number average molecular weight of 92,000), fewer serrated overflows appeared on the overflow edges of the covering film.

[0062] The applicant declares that the present invention uses the above embodiments to illustrate the resin composition of the present invention and the covering film prepared therefrom, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the raw materials selected for the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A resin composition, characterized in that, The resin composition comprises the following components in parts by weight: 35 - 45 parts of epoxy resin, 20 - 30 parts of carboxyl - terminated nitrile rubber, 3 - 5 parts of phenoxy resin, 2 - 4 parts of polyvinyl butyral resin, 2.8 - 4.2 parts of amine curing agent; The number - average molecular weight of the polyvinyl butyral resin is 100,000 - 130,000.

2. The resin composition according to claim 1, characterized in that, The epoxy resin is selected from one or a mixture of at least two of bisphenol A epoxy resin, dicyclopentadiene phenol epoxy resin, phenol novolac epoxy resin, o - cresol novolac epoxy resin, bisphenol A novolac epoxy resin, biphenyl - type epoxy resin, naphthalene - type epoxy resin, phosphorus - containing epoxy resin, nitrogen - containing epoxy resin, and tetra - functional epoxy resin.

3. The resin composition according to claim 1, characterized in that, The carboxyl - terminated nitrile rubber is formed by the terpolymerization of butadiene, acrylonitrile and organic acid, wherein the acrylonitrile content is 18 - 50% by mass.

4. The resin composition according to claim 1, wherein The amine curing agent is selected from one or a combination of two or more of dicyandiamide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, diaminodiphenyl methane, and diaminodiphenyl ether.

5. The resin composition according to claim 1, characterized in that, The amine curing agent is selected from one or a combination of two or more of 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, diaminodiphenyl methane, diaminodiphenyl ether, and aliphatic amine.

6. The resin composition according to claim 4, wherein The amine curing agent is a combination of 4,4'-diaminodiphenyl sulfone and dicyandiamide.

7. The resin composition according to claim 6, characterized in that, In the combination, the dosage of 4,4'-diaminodiphenyl sulfone is 2.5 - 4.0 parts by weight, and the dosage of dicyandiamide is 0.1 - 0.3 parts by weight.

8. The resin composition according to claim 1, wherein, The resin composition further contains 18 - 28 parts of filler.

9. The resin composition according to claim 8, wherein, The filler is an inorganic filler or an organic filler.

10. The resin composition according to claim 9, characterized in that, The inorganic filler is at least one of aluminum hydroxide, magnesium hydroxide, boehmite, talcum powder, silicon dioxide, kaolin, or alumina.

11. The resin composition according to claim 9, wherein, The organic filler is at least one of aluminum diethyl phosphinate, melamine, or cyanuric acid.

12. The resin composition according to claim 8, wherein The average particle size D50 of the filler is 0.5 - 5 μm.

13. The resin composition according to claim 1, wherein The resin composition further contains 0.05 - 0.15 parts of antioxidant.

14. The resin composition according to claim 13, wherein The antioxidant is a hindered phenol antioxidant or a hindered amine antioxidant.

15. A resin glue solution, characterized in that, It is obtained by dissolving or dispersing the resin composition according to any one of claims 1 - 14 in an organic solvent.

16. The resin adhesive solution according to claim 15, wherein, The organic solvent is selected from one or a combination of at least two of acetone, methyl ethyl ketone, cyclohexanone, ethylene glycol monomethyl ether, propylene glycol methyl ether, propylene glycol methyl ether acetate, ethyl acetate, and butyl acetate.

17. The resin adhesive solution according to claim 15, wherein, The solid content of the resin glue solution is 35% - 45%.

18. A covering film, characterized in that, The cover film comprises a polymer - based film, an adhesive layer on the polymer - based film, and a release paper layer on the adhesive layer, and the adhesive layer is formed by the resin composition according to any one of claims 1 - 14.

19. The cover film according to claim 18, wherein The polymer - based film is a polyimide film.

20. The cover film according to claim 18, characterized in that, The thickness of the polymer - based film is 7.5 - 50 μm.

21. The cover film according to claim 18, wherein The thickness of the adhesive layer is 5 - 50 μm.

22. The cover film according to claim 18, wherein The thickness of the release paper layer is 110 - 130 μm.

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