TWI870018B - A polyimide film with a carrier layer and a preparation method thereof - Google Patents

Abstract

The present invention provides a polyimide film with a carrier layer, comprising a carrier layer and a polyimide layer formed on the carrier layer. Based on the total weight of the polyimide layer, the polyimide layer includes a polyimide in an amount of 50 wt% to 95 wt%. The carrier layer on the side contacting the polyimide layer has a surface roughness Rz of 0.001 to 10 μm; and the polyimide layer on the side contacting the air has a surface roughness Rz of 0.5 to 20 μm. The polyimide layer has a glossiness from 0 to 60 GU. The present invention further provides a preparation method of the polyimide film with the carrier layer.

Description

Polyimide film with carrier layer and preparation method thereof

The present invention relates to a polyimide film having a carrier layer, and more particularly to a polyimide film for electronic products and a method for preparing the same.

Polyimide (PI) is a type of polymer with imide repeating units, which has the advantages of wide applicable temperature, chemical corrosion resistance, high strength, etc. As a special engineering material, polyimide is now widely used in aviation, aerospace, microelectronics, nano, liquid crystal, separator, laser and other fields.

Conventional polyimide is prepared by casting, which has excellent mechanical properties and good bending resistance, but average thermal conductivity. The surface free energy is increased by corona technology. However, the corona effect will cause the surface free energy of the PI surface to drop to <36 dynes (mN/m) as the storage time increases and the process is subjected to high temperature and high humidity. This will cause the glue layer and PI layer to separate when used by downstream manufacturers, or the inability to print text or reinforcement to fall off.

In view of this, there is still a need to develop and improve the preparation method of polyimide membranes to meet the various requirements of the industry.

In order to solve the above technical problems, the present invention provides a polyimide film with a carrier layer, which has properties equivalent to those of a product prepared by a biaxial stretching method, and due to the presence of the carrier layer, the polyimide film provided by the present invention has excellent dimensional stability, which is beneficial to downstream processes in ultra-thin film scenarios. The polyimide layer in the polyimide film provided by the present invention has high surface roughness, low gloss, high heat resistance, excellent adhesion, high and stable surface free energy, and good thermal conductivity. In addition, by adjusting the surface energy and roughness design of the carrier layer, the present invention does not need to use a release agent on the carrier layer, making the downstream terminal production line easy to operate, and at the same time, there will be no pollution caused by release agent transfer. Furthermore, the design of the present invention is ultra-thin and has excellent heat dissipation, becoming a major indicator in applications such as wireless charging, high-frequency and high-speed, and automotive applications.

Specifically, the present invention provides a polyimide film having a carrier layer, comprising a carrier layer and a polyimide layer formed on the carrier layer; wherein, based on the total weight of the polyimide layer, the polyimide layer comprises 50wt% to 95wt% of a polyimide resin; wherein, the carrier layer has a surface roughness Rz value of 0.001 to 10μm on the side contacting the polyimide layer, and the polyimide layer has a surface roughness Rz value of 0.5 to 20μm on the side contacting the air; and wherein, the polyimide film has a gloss of 0 to 60 GU at a measurement angle of 60°.

In a specific embodiment of the present invention, the polyimide layer includes an epoxy resin, and the content of the epoxy resin is greater than 0 and 25 wt% based on the total weight of the polyimide layer.

In a specific embodiment of the present invention, the polyimide layer includes an inorganic filler, and the content of the inorganic filler is greater than 0 and 50 wt% based on the total weight of the polyimide layer.

In a specific embodiment of the present invention, the polyimide layer includes a catalyst, and the content of the catalyst is greater than 0 and 10 wt% based on the total weight of the polyimide layer.

In a specific embodiment of the present invention, the polyimide layer includes polyimide resin, polyamide imide resin or a combination thereof.

In a specific embodiment of the present invention, the polyimide resin is obtained by polymerizing monomers containing diamine and anhydride, and the polyamide imide resin is obtained by polymerizing monomers containing optionally diamine, anhydride and isocyanate compounds.

In a specific embodiment of the present invention, the diamine is selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, At least one of the group consisting of 2,2-bis[4-(4-aminophenoxy)phenyl]sulfonamide, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)benzophenone, 1,3-bis(4-aminophenoxy)benzene and 1,4-bis(4-aminophenoxy)benzene.

In a specific embodiment of the present invention, the acid anhydride is at least one selected from the group consisting of hexafluorodianhydride (6FDA), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2-ethylenebis[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, trimellitic anhydride (TMA) and cis-abiotic anhydride.

In a specific embodiment of the present invention, the isocyanate compound is at least one selected from the group consisting of diphenylmethane diisocyanate (MDI), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and lysine diisocyanate.

In a specific embodiment of the present invention, the molar ratio of diamine to anhydride in the polyimide resin is 1:0.90 to 1:1.10, and the molar ratio of diamine to anhydride in the polyamideimide resin is 1:2.05 to 1:2.20.

In a specific embodiment of the present invention, the molar ratio of diamine to isocyanate compound in the polyamide imide resin is 1:1.05 to 1:1.50.

In a specific embodiment of the present invention, the epoxy resin is at least one selected from the group consisting of glycidylamine epoxy resin, glycidyl ester epoxy resin, epoxide alkylene compound, alicyclic epoxy resin, polyphenol glycidyl ether epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin and mixed epoxy resin.

In a specific embodiment of the present invention, the inorganic filler is selected from at least one of the group consisting of calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder and clay.

In a specific embodiment of the present invention, the catalyst is at least one selected from the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl-2-phenylimidazole.

In a specific embodiment of the present invention, the particle size of the inorganic filler is 0.5 μm to 10 μm.

In a specific embodiment of the present invention, the carrier layer includes at least one polymer selected from the group consisting of polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide.

In a specific embodiment of the present invention, the inorganic filler further comprises at least one flame retardant selected from the group consisting of halogen-containing compounds, phosphorus compounds, nitrogen compounds and boron compounds.

The present invention further provides a method for preparing a polyimide film having a carrier layer, comprising: coating a polyimide layer on the surface of the carrier layer; and curing the carrier layer coated with the polyimide layer at 50 to 180° C. to form the polyimide film.

In another specific embodiment of the preparation method of the present invention, the polyimide layer is dried before curing.

As can be seen from the above, the polyimide film with a carrier layer and the preparation method thereof provided by the present invention utilize the surface energy of the carrier layer and the polyimide layer and the matching surface roughness between each other, and there is no need to use a release agent on the carrier layer. The high surface energy of the polyimide layer makes it easy to use in the lamination and coating process, and there is no need to use a separate surface treatment process such as corona. In addition, the preparation method provided by the present invention is easy to take into account various characteristics through a multi-layer coating composition, and can match the processing requirements of the downstream process.

Compared with the film produced by the casting process, the polyimide film and its preparation method provided by the present invention are cheaper, and the finished product does not need to be prepared separately in the downstream process to avoid problems such as tearing, and is easier to operate and process. In addition, since there is no residual stress after stretching in the casting process, it has better dimensional stability. Furthermore, the present invention is coated with a carrier layer, and the product width has greater elasticity, and the film materials such as PET and PEN used as the carrier film are produced in a large width, which can be produced with multiple widths and still have high utilization rate, and can be produced continuously in large quantities, so the production cost can be reduced.

The present invention is easy to produce various thicknesses and can produce thinned polyimide films to replace the high-priced thin polyimide products on the market (<10μm, usually about 3 to 8μm).

100: Polyimide film

101: Polyimide layer

1011: Inorganic filler

102: Carrier layer

110: Covering film

103: Next layer

104: Release layer

Figure 1 is a schematic diagram of the structure of a specific implementation of the polyimide film with a carrier layer of the present invention.

Figure 2 is a schematic diagram of the structure of a covering film prepared by a specific implementation of the polyimide film with a carrier layer of the present invention.

Figure 3 shows the surface morphology of a specific implementation of the polyimide film with a carrier layer of the present invention under a laser concentric focus microscope.

Figure 4 shows the surface morphology of another specific embodiment of the polyimide film with a carrier layer of the present invention under a laser concentric focus microscope.

The following is a specific and concrete example to illustrate the implementation of the present invention. People familiar with this art can easily understand the advantages and effects of the present invention from the content disclosed in this manual.

It should be noted that the structures, proportions, sizes, etc. depicted in the drawings attached to this manual are only used to match the contents disclosed in the manual for people familiar with this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the effects and purposes that can be achieved by the present invention. At the same time, terms such as "first", "second", "upper", "lower" and "one" cited in this specification are only for convenience of description and are not used to limit the scope of the present invention. Changes or adjustments in their relative relationships, without substantively changing the technical content, shall also be regarded as the scope of the present invention. Furthermore, all ranges and values herein are inclusive and combinable. Any value or point that falls within the range described in this article, such as any integer, can be used as a minimum or maximum value to derive a lower range, etc.

As shown in FIG. 1 , a specific embodiment of the polyimide film 100 having a carrier layer 102 of the present invention includes a carrier layer 102 and a polyimide layer 101 formed on the carrier layer 102, and the polyimide layer 101 includes a polyimide resin and an inorganic filler 1011. Based on the total weight of the polyimide layer 101, the polyimide layer 101 includes 50wt% to 95wt% of the polyimide resin, for example, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt% or 95wt%.

In one embodiment, the carrier layer has a surface roughness Rz value of 0.001 to 10 μm on the side contacting the polyimide layer, for example, 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 or 10. μm, preferably 0.1 to 5 μm; the polyimide layer has a surface roughness Rz value of 0.5 to 20 μm on the side in contact with air, for example, 0.5, 0.6, 0.61, 0.7, 0.8, 0.9, 1, 2, 2.01, 3, 3.89, 4, 5, 5.21, 6, 6.52, 7, 8, 9, 9.53, 10, 10.95, 11, 11.67, 12, 13, 14, 15, 16, 17, 18, 19 or 20 μm, preferably 3 to 12 μm.

In a specific embodiment, the polyimide film has a gloss of 0 to 60 GU at a measurement angle of 60°, for example, 0, 0.4, 0.5, 0.7, 1, 1.1, 1.3, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 42, 58 or 60 GU, preferably 0 to 40 GU, more preferably 0 to 20 GU.

In one embodiment, the polyimide layer has a surface energy of 50 to 90 mN/m, for example, 50, 55, 56, 60, 65, 70, 74, 75, 76, 78, 80, 82, 85 or 90 mN/m.

In a specific embodiment, the polyimide layer has a surface energy of 50 to 90 mN/m and a surface roughness Rz value of 0.5 to 20 μm on the side in contact with air.

In a specific embodiment, the thickness of the carrier layer may be 25 to 250 μm, for example, 25, 30, 35, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240 or 250 μm.

In a specific embodiment, the thickness of the polyimide layer may be 1 to 150 μm, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140 or 150 μm.

In another specific embodiment, as shown in FIG. 1 , the polyimide film 100 may include a plurality of polyimide layers 101.

In one embodiment, the polyimide layer includes an epoxy resin, and the content of the epoxy resin is greater than 0 and 25 wt % based on the total weight of the polyimide layer. In another specific embodiment, the epoxy resin is selected from at least one of the group consisting of glycidylamine epoxy resin, glycidyl ester epoxy resin, epoxide alkylene compound, alicyclic epoxy resin, polyphenol glycidyl ether epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin and mixed epoxy resin.

In one embodiment, the polyimide layer includes an inorganic filler, and the content of the inorganic filler is greater than 0 and 50 wt %, for example, 1 wt %, 5 wt %, 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt %, 35 wt %, 40 wt %, 45 wt % or 50 wt % based on the total weight of the polyimide layer. In another embodiment, the inorganic filler is at least one selected from the group consisting of calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder and clay. In another specific embodiment, the inorganic filler has a particle size of 0.5 μm to 10 μm, for example, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10 μm. In another specific embodiment, the inorganic filler further comprises at least one flame retardant selected from the group consisting of halogen-containing compounds, phosphorus compounds, nitrogen compounds and boron compounds.

In one embodiment, the polyimide layer includes a catalyst, and the content of the catalyst is greater than 0 and 10 wt% based on the total weight of the polyimide layer. In another embodiment, the catalyst is selected from at least one of the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl-2-phenylimidazole.

In one specific embodiment, the carrier layer includes at least one polymer selected from the group consisting of polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide. In another specific embodiment, the polypropylene in the carrier layer is biaxially oriented polypropylene.

In a specific embodiment, the polyimide layer includes polyimide resin, polyamide imide resin or a combination thereof.

In one embodiment, the polyimide resin is obtained by polymerizing monomers comprising a diamine and an acid anhydride; and the polyamide imide resin is obtained by polymerizing monomers comprising optionally a diamine, an acid anhydride and an isocyanate compound. In another embodiment, the diamine is selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide , 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)benzophenone, 1,3-bis(4'-aminophenoxy)benzene and 1,4-bis(4'-aminophenoxy)benzene, at least one of the group consisting of The acid anhydride is selected from hexafluorodianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2-ethylenebis[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, At least one of the group consisting of trimellitic anhydride and cis-acoustic anhydride; and the isocyanate compound is at least one of the group consisting of diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and lysine diisocyanate.

In a specific embodiment, the molar ratio of diamine to anhydride in the polyamide imide resin is 1:2.05 to 1:2.20. For example, 1:2.05, 1:2.06, 1:2.07, 1:2.08, 1:2.09, 1:2.10, 1:2.11, 1:2.12, 1:2.13, 1:2.14, 1:2.15, 1:2.16, 1:2.17, 1:2.18, 1:2.19 or 1:2.20.

In a specific embodiment, the molar ratio of diamine to anhydride in the polyimide resin is 1:0.90 to 1:1.10. For example, 1:0.90, 1:0.91, 1:0.92, 1:0.93, 1:0.94, 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1.00, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09 or 1:1.10.

In a specific embodiment, the molar ratio of the diamine and the isocyanate compound in the polyamide imide resin is 1:1.05 to 1:1.50. For example, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45 or 1:1.50.

In a specific embodiment, as shown in FIG. 1 , the method for preparing the polyimide film 100 having the carrier layer 102 of the present invention includes coating the polyimide layer 101 on the surface of the carrier layer 102; curing the carrier layer 102 coated with the polyimide layer 101 at 50 to 180° C. to form the polyimide film 100.

In one embodiment, the polyimide layer further comprises a tertiary amine as a catalyst before curing, and the content of the tertiary amine is greater than 0 and 3 wt%, such as 0.01, 0.5, 1, 1.5, 2, 2.5 or 3 wt%, based on the total weight of the polyimide layer. In another embodiment, the tertiary amine is at least one selected from the group consisting of triethylamine, isoquinoline, pyridine, N-ethylpiperidine and benzimidazole.

In a specific embodiment, the polyimide layer comprises at least one solvent selected from the group consisting of N-methylpyrrolidone, γ-butyrolactone, cyclohexanone, acetone, butanone, N,N-dimethylformamide, N,N-dimethylacetamide, pyridine, cyclohexane, dichloromethane, tetrahydrofuran, ethyl acetate, acetonitrile, 1,2-dichloroethane, trichloroethylene, triethylamine, 4-methyl-2-pentanone, toluene or xylene before curing.

In a specific embodiment, the polyimide layer 101 is dried before curing.

In another specific embodiment, as shown in FIG1 , after curing the polyimide layer 101, the steps of coating and curing are repeated to obtain a polyimide film 100 including a plurality of polyimide layers 101.

In a specific embodiment, the polyimide film with a carrier layer of the present invention can be used for the preparation of a covering film. As shown in FIG. 2 , the specific stacking structure of the covering film 110 includes a polyimide film 100, which is composed of a carrier layer 102 and a polyimide layer 101 containing an inorganic filler 1011; a bonding layer 103, which is disposed on the polyimide layer 101, so that the polyimide layer 101 is located between the bonding layer 103 and the carrier layer 102; and a release layer 104, which is disposed on the bonding layer 103, so that the bonding layer 103 is located between the release layer 104 and the polyimide layer 101.

In a specific embodiment, the adhesive layer includes at least one resin selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, polyparaxylene resin, dimaleimide resin, styrene-ethylene-butylene-styrene block copolymer, polyimide resin and polyamide imide.

In a specific embodiment, the release layer is a release film or release paper including polypropylene, polyethylene terephthalate or a combination thereof. For example, the polypropylene may be biaxially oriented polypropylene, but is not limited thereto.

[Example]

Preparation Example 1: Synthesis of polyamide imide

The examples in Tables 1 and 2 below are configured according to the following materials and conditions, and the dosage can be increased or decreased proportionally according to the needs: 37.8g TMA (trimellitic anhydride) and 52.2g MDI (isocyanate) are added to 210g NMP (N-methylpyrrolidone) and reacted at 140°C for 2 hours to obtain the polyamide imide resin used in the polyimide layer of Preparation Example 1 of the present invention.

Alternatively, the polyamide imide resin used in the polyimide layer of the present invention can be prepared by the following materials and conditions, and the amount can be proportionally increased or decreased according to the needs: first, 41.1g of BAPP (2,2-bis[4-(4-aminophenoxy)phenyl]) is dissolved in 330g of NMP, and then 40.3g of TMA is added to react at 80°C for 1 hour. Then, 50ml of toluene is added and the temperature is raised to 170°C for dehydration, and then the temperature is raised to 190°C to evaporate the toluene. After returning to room temperature, 30g of MDI and 1.3g of Et ₃ N (triethylamine) are added, and the reaction is carried out at 120°C for 3 hours to obtain the polyamide imide resin used in the polyimide layer of the present invention.

The polyimide resin used in the polyimide layer of the present invention can also be prepared by the following materials and conditions, and the amount can be proportionally increased or reduced according to the needs: 32.02g TFMB (2,2'-bis(trifluoromethyl)diaminobiphenyl), 21.99g 6FDA (hexafluorodianhydride) and 12.41g B1317 (bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride) are added to 349g NMP at 80°C, and then 0.80g N-ethylpiperidine is added after the temperature is raised to 150°C, and then the temperature is raised to 190°C for reaction for 4 hours to obtain the polyimide resin used in the polyimide layer of the present invention.

The above-mentioned preparation examples of synthetic polyamide imide are only illustrative examples. Those skilled in the art can formulate and prepare the formula and method of synthetic polyamide imide according to the requirements and existing polyimide resins or polyamide imide resins, and are not limited to the synthetic formula and method disclosed in this article.

Preparation Example 2: Preparation of a polyimide film with a carrier layer

The polyamide-imide resin prepared in Preparation Example 1 was respectively mixed with epoxy resin, inorganic filler and catalyst in different proportions to prepare the polyimide layer compositions of Examples 1 to 7 and Comparative Example 1 as shown in Table 1, and the polyimide layer varnish was coated on the carrier layer (50 μm), and low-temperature curing at 50° C. to 180° C. was adopted to form a polyimide layer (12.5 μm), and a laminated coating-type insulating layer film with a carrier layer as shown in FIG. 1 was obtained, so as to carry out the test analysis of the subsequent Examples and Comparative Examples. The inorganic fillers of the examples and comparative examples are SiO ₂ (D90=8μm), carbon black (D90=7μm) and/or TiO ₂ (D90=7μm). 20wt% of cyclopentadiene phenolic epoxy resin (DCPD) was added to Example 1 and Comparative Example 1, and 8wt% of DCPD was added to Examples 2 to 7. 0.30wt% of 2-ethyl-4-methylimidazole was added as a catalyst to Example 1 and Comparative Example 1, and 0.13wt% of 2-ethyl-4-methylimidazole was added as a catalyst to Examples 2 to 7.

Test method

Gloss test: Prepare a sample larger than 3cm×8cm, measure the sample in the longitudinal direction (Machine Direction, MD) using a gloss meter (Miley, GZD-60°), and read the 60° value as the measured value.

Surface roughness: The surface roughness Rz value is measured using a laser conjugate focusing microscope (Keyence, VK-X3000) in accordance with ISO-25178. The air surface tested refers to the surface of the polyimide layer farthest from the carrier layer.

Surface free energy (dyne pen) test: According to DIN ISO 8296, after tearing off the carrier layer, hold dyne pens (Arcotest) with different surface energies from small to large, and apply an ink strip of about 100mm long on the contact between the polyimide layer and the carrier layer. Observe whether more than 90% of the edges of the ink strip shrink and form ink drops within 2 seconds. If not, replace the dyne pen with a higher surface energy level. Apply the ink strip again and make the same observation until ink drops appear (i.e. the surface shrinks). The surface energy of the previous level of the dyne pen that produces ink drops corresponds to the surface energy of the PI (the minimum dyne pen is 36mN/m. If it exceeds the lower limit, no further testing will be performed).

Next, strength: According to IPC-TM-650 2.4.19C (5/98) specification, use a tensile testing machine (SHIMADZU, EHF-E) for testing.

Solderability and thermal stress test: According to IPC-TM-650 2.6.8 specification, use a lead-free soldering furnace (Debang) for testing.

Test Example 1: Characteristic Analysis

From the data presented in Table 1, it can be seen that compared with Comparative Examples 2 and 3 using commercially available polyimide films, Examples 1 to 7 of the present invention use a polyimide layer with a specific composition, which significantly helps to improve the surface roughness of the polyimide layer contacting the air surface, increase the surface energy, and at the same time reduce the gloss of the polyimide layer, so that it exhibits extinction characteristics. Comparative Examples 2 and 3 are commercially available black polyimide films (PI GD050A) and yellow polyimide films (PI GF050), respectively.

Table 1

In addition, Figures 3 and 4 respectively show the surface morphologies of Examples 2 and 7 of the present invention photographed by a laser conjugate focusing microscope. It can be seen from Figures 3 and 4 that the degree of surface roughness of the polyimide layer is indeed affected by the composition of the polyimide layer, such as the type and proportion of the added inorganic filler.

Preparation Example 3: Preparation of covering film

The polyimide films of Examples 1 to 7 and Comparative Example 1, as well as the commercially available polyimide films of Comparative Examples 2 and 3, were matched with epoxy resin adhesives (glossy, AU-25KA) and release layers of the same thickness (25 μm) to form a stacked covering film as shown in Figure 2 for subsequent testing and analysis.

Test Example 2: Adhesion strength, solderability and thermal stress tests

As can be seen from Table 2, the polyimide layer with a higher degree of roughening has a relatively smaller total thickness for the actual thickness of the overall finished product, and has a significantly improved bonding strength compared to the polyimide layer with a smaller amount of inorganic powder added. Although comparative example 1 does not add inorganic powder, it also has high bonding strength due to the polarity effect between the two interfaces. Overall, the polyimide layer prepared according to the present invention exhibits bonding strength superior to that of commercially available polyimide films. In addition, both the embodiment and the comparative example passed the solderability and thermal stress tests.

Table 2

The above embodiments are used to illustrate the principle and effect of the present invention, but not to limit the present invention. Anyone familiar with this technology can modify the above embodiments without violating the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be as listed in the scope of the patent application described below.

100: Polyimide film

101: Polyimide layer

1011: Inorganic filler

102: Carrier layer

Claims (17)

A polyimide film with a carrier layer comprises a carrier layer and a polyimide layer formed on the carrier layer; wherein, based on the total weight of the polyimide layer, the polyimide layer comprises: 50wt% to 95wt% of a polyimide resin, more than 0 and 25wt% of an epoxy resin, more than 15 and 50wt% of an inorganic filler, and The catalyst is greater than 0 and 10 wt%; wherein the carrier layer has a surface roughness Rz value of 0.001 to 10 μm on the side contacting the polyimide layer, and the polyimide layer has a surface roughness Rz value of 3.89 to 20 μm on the side contacting the air; and wherein the polyimide film has a gloss of 0 to 60 GU at a measurement angle of 60°. The polyimide film as described in claim 1, wherein the polyimide layer comprises polyimide resin, polyamide imide resin or a combination thereof. The polyimide film as described in claim 2, wherein the polyimide resin is obtained by polymerizing monomers containing diamine and acid anhydride, and the polyamide imide resin is obtained by polymerizing monomers containing optionally diamine, acid anhydride and isocyanate compounds. The polyimide membrane as described in claim 3, wherein the diamine is selected from 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2'-bis(trifluoromethyl)diaminobiphenyl, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl ether, bis[4-(3-aminophenoxy)phenyl]sulfonamide, bis[4-(4-aminophenoxy)phenyl]sulfonamide, At least one of the group consisting of 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(4-aminophenoxy)phenyl]methane, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)benzophenone, 1,3-bis(4'-aminophenoxy)benzene and 1,4-bis(4'-aminophenoxy)benzene. The polyimide film as described in claim 3, wherein the acid anhydride is at least one selected from the group consisting of hexafluorodianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 1,2-ethylenebis[1,3-dihydro-1,3-dioxoisobenzofuran-5-carboxylate], 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, trimellitic anhydride and cis-abietic anhydride. The polyimide film as described in claim 3, wherein the isocyanate compound is at least one selected from the group consisting of diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and lysine diisocyanate. The polyimide film as described in claim 3, wherein the molar ratio of diamine to anhydride in the polyimide resin is 1:0.90 to 1:1.10; and wherein the molar ratio of diamine to anhydride in the polyimide resin is 1:2.05 to 1:2.20. The polyimide film as described in claim 3, wherein the molar ratio of the diamine and the isocyanate compound in the polyimide imide resin is 1:1.05 to 1:1.50. The polyimide film as described in claim 1, wherein the epoxy resin is at least one selected from the group consisting of glycidylamine epoxy resin, glycidyl ester epoxy resin, epoxide alkylene compound, aliphatic epoxy resin, polyphenol glycidyl ether epoxy resin, bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic glycidyl ether epoxy resin, heterocyclic epoxy resin and mixed epoxy resin. The polyimide film as described in claim 1, wherein the inorganic filler is at least one selected from the group consisting of calcium sulfate, carbon black, silicon dioxide, titanium dioxide, zinc sulfide, zirconium oxide, calcium carbonate, silicon carbide, boron nitride, aluminum oxide, talc, aluminum nitride, glass powder, quartz powder and clay. The polyimide membrane as described in claim 1, wherein the catalyst is at least one selected from the group consisting of 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole and 1-benzyl-2-phenylimidazole. The polyimide film as described in claim 1, wherein the inorganic filler has a particle size of 0.5 μm to 10 μm. The polyimide film as described in claim 1, wherein the carrier layer comprises at least one polymer selected from the group consisting of polypropylene, polyethylene terephthalate, polyimide, polyphenylene sulfide, polyethylene naphthalate, polyurethane and polyamide. The polyimide film as described in claim 1, wherein the inorganic filler further comprises at least one flame retardant selected from the group consisting of halogen-containing compounds, phosphorus compounds, nitrogen compounds and boron compounds. The polyimide film as described in claim 1, wherein the polyimide layer has a surface energy of 50 to 90 mN/m. A method for preparing a polyimide film as described in any one of claims 1 to 15, comprising: coating a polyimide layer on the surface of a carrier layer; and curing the carrier layer coated with the polyimide layer at a temperature of 50 to 180°C to form the polyimide film. The preparation method as described in claim 16 further includes drying the polyimide layer before curing.

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