Resin composition, cured product, polyimide film, multilayer wiring board, copper foil with resin, coil structure, and magnetic device

Abstract

The present disclosure provides a resin composition comprising (X) a polyimide and (Y) a flame retardant, wherein the (Y) component includes (Y1) a phosphorus-based flame retardant; and the blending amount of the (Y) component is more than 10 mass% and less than 50 mass% with respect to 100 mass% of the solid content of the resin composition.

Description

Resin Composition, Cured Product, Polyimide Film, Multilayer Wiring Board, Copper Foil with Resin, Coil Structure, and Magnetic Device

[0001] The present invention relates to a resin composition, a cured product, a polyimide film, a multilayer wiring board, a copper foil with resin, a coil structure, and a magnetic device.

[0002] As a thin transformer which is one type of magnetic device, for example, Patent Document 1 describes a thin transformer including a printed coil, a core made of a magnetic material, and a terminal-equipped base on which the printed coil and the core are mounted. This thin transformer is characterized in that the surface of the printed coil where the conductor is exposed is covered with a heat-resistant resin.

[0003] Japanese Patent Application Laid-Open No. 9-326316

[0004] However, in recent years, magnetic devices have been required to withstand higher voltages and larger currents. When a conventional prepreg (glass cloth substrate / epoxy resin) is used as the heat-resistant resin layer, there has been a problem of high dielectric constant. On the other hand, low dielectric constant can be achieved by producing a resin film obtained by removing the glass cloth substrate from a conventional prepreg. However, such a resin film has insufficient properties such as flame retardancy and insulation reliability. Moreover, countermeasures for individual properties often result in conflicting properties, making it difficult to satisfy all the required various properties. For example, phosphorus-based flame retardants are effective for improving flame retardancy by generating carbide (char) during combustion. On the other hand, when carbonized conductive paths (tracks) are formed on the surface of an insulating material, the insulating material loses its insulating property. The resistance (durability) against tracking is also referred to as tracking resistance. Furthermore, materials that are easily carbonized tend to undergo charring or deformation during laser cutting or processing, resulting in reduced processability.

[0005] An object of the present invention is to provide a resin composition excellent in flame retardancy, tracking resistance and laser processability, as well as a cured product, a polyimide film, a multilayer wiring board, a copper foil with resin, a coil structure, and a magnetic device.

[0006] The present invention provides the following resin compositions, cured products, polyimide films, multilayer wiring boards, resin-coated copper foils, coil structures, and magnetic devices. [1] A resin composition comprising (X) polyimide and (Y) a flame retardant, wherein component (Y) contains (Y1) a phosphorus-based flame retardant, and the amount of component (Y) is greater than 10% by mass and less than 50% by mass with respect to 100% by mass of the solid content of the resin composition. [2] The resin composition according to [1], wherein the amount of component (Y1) is greater than or equal to 10% by mass and less than 50% by mass with respect to 100% by mass of the solid content of the resin composition. [3] The resin composition according to [1] or [2], wherein component (X) comprises (X1) a polyimide having at least one end modified with a maleimide group. [4] A cured product obtained by curing the resin composition according to any one of [1] to [3]. [5] A polyimide film comprising a cured resin composition according to any one of [1] to [3]. [6] A polyimide film according to [5], which is for laser processing. [7] A multilayer wiring board comprising an insulating layer formed using the polyimide film according to [6]. [8] A resin-coated copper foil comprising the polyimide film according to [6] and a copper foil laminated on the polyimide film. [9] A coil structure comprising an insulating layer formed using the polyimide film according to [6].

[10] A magnetic device comprising an insulating layer formed using the polyimide film according to [6].

[0007] According to one aspect of the present invention, a resin composition with excellent flame retardancy, tracking resistance, and laser processability can be provided, as well as a cured product, a polyimide film, a multilayer wiring board, a resin-coated copper foil, a coil structure, and a magnetic device.

[0008] [Resin Composition] The resin composition according to this embodiment is a resin composition containing (X) polyimide and (Y) a flame retardant. The (Y) component contains (Y1) a phosphorus-based flame retardant. The amount of the (Y) component is greater than 10% by mass and less than 50% by mass, based on 100% by mass of the solid content of the resin composition.

[0009] (Component (X)) Any known polyimide can be used as the (X) polyimide used in this embodiment. Examples of component (X) include polyimides obtained by imidizing polyamic acid. Furthermore, it is preferable that the (X) polyimide used in this embodiment contains (X1) a polyimide in which at least one end is modified with a maleimide group. With such a (X1) component, it is possible to adjust the molecular weight by modifying the ends with maleimide groups while introducing an imide skeleton with a low dielectric constant. However, the (X) polyimide used in this embodiment may also contain polyimides other than component (X1) (hereinafter also referred to as component (X2)). The polyamic acid used in this embodiment is preferably a polyaddition reaction product of (A) an acid dianhydride and (B) a diamine. It is preferable that this polyamic acid contains (B1) dimeramine in a molar ratio of 0.2 or more relative to the total diamine component. That is, the polyimide formed using the polyamic acid used in this embodiment has an ester skeleton and a dimer skeleton, and low water absorption can be achieved from the ester skeleton. Furthermore, the dimer skeleton provides low dielectric properties, and the inclusion of a certain amount of dimer amine as a diamine component allows for even lower dielectric constant and dielectric loss tangent, thereby achieving the desired low dielectric properties. In addition, it is possible to form a polyimide with excellent thermal decomposition resistance.

[0010] (Component (A)) The polyamic acid used in this embodiment uses (A) an acid dianhydride as one of its raw materials. Any known acid dianhydride can be used as appropriate. Examples of acid dianhydride components include 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BTDA), pyromellitic acid dianhydride (PMDA), 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride (6FDA), and ester-type acid dianhydrides having an ester bond in the molecule. In this embodiment, it is preferable that the acid dianhydride component has structural units derived from an ester-type acid dianhydride having an ester bond in the molecule. By having structural units derived from an ester-type acid dianhydride, the polyamic acid can be imparted with low water absorption to the resulting polyimide. The acid dianhydride has two acid anhydride groups in one molecule, and is preferably a tetracarboxylic acid dianhydride, and more preferably an aromatic tetracarboxylic acid dianhydride. The molecule may contain one or more ester bonds, preferably one to three, and more preferably one or two. The acidic dianhydride may be used alone or in combination of two or more types.

[0011] Such acidic dianhydrides preferably have the structure shown in the following formula (1). In formula (1), Ar represents a substituted or unsubstituted arylene group, and a substituted arylene group means that the hydrogen atoms of an unsubstituted arylene group are substituted with any substituent. The number of carbon atoms in the substituted or unsubstituted arylene group (excluding the number of carbon atoms of the substituent) is preferably 6 or more and 20 or less, and more preferably 6 or more and 12 or less.

[0012]

[0013] In formula (1), examples of unsubstituted arylene groups in Ar include o-phenylene, m-phenylene, p-phenylene, 2,6-naphthylene, and 4,4'-biphenylylene. Among these, p-phenylene, 2,6-naphthylene, or 4,4'-biphenylylene are preferred.

[0014] Examples of substituents on the substituted arylene group include C1-C8 alkyl groups, halogen atoms (fluorine, chlorine, bromine, or iodine atoms), and halogenated alkyl groups in which the hydrogen atoms of the alkyl group are substituted with the halogen atoms. Among these substituents, C1-C8 alkyl groups are preferred, and methyl groups are more preferred. The number of substituents may be one or two or more. If there are two or more substituents, they may be the same or different. Specific examples of substituted arylene groups include the 2,2',3,3',5,5'-hexamethyl-4,4'-biphenylylene group.

[0015] Preferred examples of the acid dianhydride represented by formula (1) include the compound represented by the following formula (1-1) and the compound represented by the following formula (1-2) (TMPBP-TME), with the compound represented by the following formula (1-2) being more preferred.

[0016]

[0017] (Component (B)) The polyamic acid used in this embodiment uses (B) diamine as one of its raw materials. Any known diamine can be used as appropriate. The diamine component has structural units derived from a diamine, and one of the diamine components has structural units derived from (B1) dimer amine. Here, dimer amine is a cyclic or acyclic dimer acid obtained as a dimer of an unsaturated fatty acid in which two terminal carboxylic acid groups (-COOH) are primary aminomethyl groups (-CH ２ -NH ２ ) or amino group (-NH ２ This refers to an aliphatic diamine substituted with (B1). By having a polyamic acid with structural units derived from dimer amine, low dielectric properties can be imparted to the resulting polyimide. (B1) Dimer amine may be used alone or in combination of two or more types.

[0018] Dimer acids are dibasic acids obtained by the intermolecular polymerization reaction of unsaturated fatty acids. Aliphatic diamines derived from dimer acids are obtained by polymerizing unsaturated fatty acids such as oleic acid, linoleic acid, or linolenic acid to form dimer acids, which are then reduced and aminated. Such dimer amines are preferably diamine compounds obtained by substituting the terminal carboxylic acid group of a dibasic acid compound having 18 to 54 carbon atoms, preferably 22 to 44 carbon atoms, with a primary aminomethyl group or an amino group.

[0019] Commercially available dimeramines include "Versamin® 551" and "Versamin® 552" from Cognics Japan, and "PRIAMINE® 1073," "PRIAMINE® 1074," and "PRIAMINE® 1075" from Croda Japan.

[0020] Furthermore, in the polyamic acid according to this embodiment, it is preferable that (B1) dimeramine is contained in a molar ratio of 0.2 or more relative to the total diamine components. By including dimeramine in a molar ratio above a certain level relative to the total diamine, the resulting polyimide can be given a lower dielectric constant and a lower dielectric loss tangent. The molar ratio of (B1) dimeramine to the total diamine components is more preferably 0.3 or more, even more preferably 0.5 or more, and particularly preferably 0.7 to 0.95.

[0021] The polyamic acid according to this embodiment preferably contains a (B2) aromatic diamine as another diamine component. Examples of (B2) aromatic diamines include p-phenylenediamine (PDA), m-phenylenediamine, 4,4'-oxydianiline (4,4'-DPE), 3,3'-bistrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis(anilino)ethane, and diaminodiphenylsulfane. Examples include phono, diaminobenzanilide, diaminobenzoate, diaminodiphenyl sulfide, 2,2-bis(p-aminophenyl)propane, 2,2-bis(p-aminophenyl)hexafluoropropane, 1,5-diaminonaphthalene, diaminotoluene, diaminobenzotrifluoride, 1,4-bis(p-aminophenoxy)benzene, 4,4'-bis(p-aminophenoxy)biphenyl, diaminoanthraquinone, and 4,4'-bis(3-aminophenoxyphenyl)diphenylsulfone. Among these aromatic diamines, PDA, 4,4'-DPE, or TFMB are preferred, with 4,4'-DPE being more preferred. (B2) Aromatic diamines may be used alone or in combination of two or more.

[0022] The molar ratio of diamine to acidic dianhydride [(B) / (A)] is not particularly limited, but is preferably 0.5 to 2.5, more preferably 0.7 to 2, even more preferably 0.8 to 1.6, and particularly preferably 0.9 to 1.1.

[0023] (Polyimide modified with maleimide group at the end) The polyimide according to this embodiment preferably contains (X1) a polyimide in which at least one end is modified with a maleimide group. Specifically, in a repeating unit of polyimide having a structure derived from (A) an acid dianhydride and a structure derived from (B) a diamine, the end is modified via the nitrogen atom (N) of the maleimide group, and preferably, at least one end of the structural portion derived from the diamine is modified with a maleimide group. In such a polyimide structure, only one end may be modified with a maleimide group, or both ends may be modified with a maleimide group. In component (X1), since the reactive group of the maleimide group is introduced at the end, it is possible to increase the molecular weight in further reactions.

[0024] From the viewpoint of fluidity and film-forming properties, the molecular weight (weight-average molecular weight) of the polyimide is preferably 50,000 or less, more preferably 40,000 or less, and even more preferably 35,000 or less. Furthermore, from the viewpoint of imparting low dielectric properties to the polyimide, the lower limit of the molecular weight of the polyimide is preferably 5,000 or more. The molecular weight of the polyimide can be determined, for example, from the value converted to standard polystyrene by gel filtration chromatography (GPC) measurement.

[0025] From the viewpoint of low dielectric properties, fluidity, and film-forming properties, the upper limit of the melt viscosity of polyimide is preferably 3000 mPa·s or less, and more preferably 1800 mPa·s or less. Furthermore, from the viewpoint of imparting low dielectric properties to the polyimide, the lower limit of the melt viscosity of polyimide is preferably 1000 mPa·s or more. The melt viscosity of polyimide can be measured, for example, using an analytical instrument such as a rheometer.

[0026] (Synthesis of Polyimide) Component (X1) of the polyimide according to this embodiment can be produced, for example, by the following steps: (i) A polyamic acid, which is a precursor of polyimide, is synthesized by polyaddition reaction of the above-mentioned acid dianhydride with at least two diamines. (ii) The obtained polyamic acid is imidized to synthesize a polyimide with amine-modified terminals. (iii) The polyimide with amine-modified terminals is reacted with maleic anhydride to add maleic anhydride to the terminal amine. (iv) The polyimide with maleic anhydride added is further imidized to produce a polyimide modified with maleimide groups at the terminals.

[0027] (Synthesis of Polyamic Acids) Polyamic acids can be synthesized by known general methods. For example, polyamic acid (polyamic acid solution) can be obtained by reacting an acidic dianhydride with a diamine in an organic solvent. The organic solvent used for polymerization of polyamic acid is not particularly limited as long as it can dissolve the acidic dianhydride and diamine as monomer components and also dissolve the polyamic acid produced by the polyaddition reaction. Examples of such organic solvents include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, and hexamethylphosphate triamide; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform and methylene chloride; aromatic hydrocarbon-based solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. These organic solvents may be used individually or in combination of two or more. From the viewpoint of enhancing the solubility and reactivity of polyamic acids, the organic solvent is preferably selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, with amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, and N-methyl-2-pyrrolidone being more preferred.

[0028] The molecular weight of the polyamic acid and the subsequently synthesized polyimide can be adjusted by adjusting the molar ratio of the total number of moles of the acidic dianhydride component to the total number of moles of the diamine component. The molecular weight (weight-average molecular weight) of the polyamic acid is not particularly limited, but it is preferably between 5,000 and 50,000 from the viewpoint of solubility in organic solvents. The weight-average molecular weight of the polyamic acid can be determined, for example, from the value converted to standard polystyrene by gel filtration chromatography (GPC) measurement.

[0029] The synthesis of polyamic acids by the polyaddition reaction of dianhydrides and diamines is preferably carried out in an inert atmosphere such as argon or nitrogen. In an inert atmosphere, the polyaddition reaction proceeds by dissolving the dianhydride and diamine in an organic solvent and mixing them. The order of addition of the dianhydride and diamine is not particularly limited. For example, the diamine may be dissolved in an organic solvent or dispersed in a slurry to form a diamine solution, and the dianhydride may be added to the diamine solution. The dianhydride and diamine may be added directly to the organic solvent in a solid state, or they may be added separately dissolved in an organic solvent or dispersed in a slurry.

[0030] The temperature conditions for the polyaddition reaction are not particularly limited, but from the viewpoint of suppressing the decrease in molecular weight of the polyamic acid due to depolymerization, the reaction temperature is preferably 100°C or lower. Furthermore, from the viewpoint of allowing the polyaddition reaction to proceed appropriately, the reaction temperature is more preferably 20°C to 80°C. The reaction time can be arbitrarily set within the range of 1 hour to 72 hours, and if necessary, it may be left overnight at room temperature.

[0031] When preparing polyamic acid, the viscosity of the polyamic acid solution is preferably 100 mPa·s or higher from the viewpoint of imparting good film-forming properties to the resulting polyimide. Furthermore, the solid content (concentration) of polyamic acid in the polyamic acid solution is preferably 10% by mass or higher, more preferably 15% by mass or higher, and even more preferably 20% by mass or higher. In particular, if the concentration of polyamic acid is 30% by mass or higher, the productivity of forming polyimide coating films using polyamic acid can be increased. Furthermore, the upper limit of the concentration of polyamic acid is preferably 40% by mass or lower, and even more preferably 30% by mass or lower, from the viewpoint of sufficiently dissolving the polyamic acid in the organic solvent.

[0032] (Synthesis of Polyimides with Amine-Modified Ends) The method for converting the polyamic acid synthesized as described above into polyimide is not particularly limited, but polyimide can be produced by dehydrating and cyclizing (imidizing) the obtained polyamic acid. Known methods such as thermal imidization, which involves dehydrating and cyclizing by heating, and chemical imidization, which involves chemical cyclization using a known dehydration and cyclization catalyst, can be employed for dehydration and cyclization (imidization).

[0033] In the case of thermal imidation, the heating temperature is preferably 120°C to 350°C, and more preferably 150°C to 250°C. In the case of chemical imidation, for example, pyridine, triethylamine, or acetic anhydride can be used as the dehydration and ring-closing catalyst. In this case, the reaction temperature can be selected to any temperature between 20°C and 180°C, but it is preferably 150°C or lower. Imidation may be carried out in air, under reduced pressure, or in an inert gas such as nitrogen, but in order to obtain a highly transparent polyimide film, it is preferable to carry it out under reduced pressure or in an inert gas such as nitrogen.

[0034] (Addition of maleic anhydride) The polyimide with the amine-modified terminals described above is subjected to an addition reaction with maleic anhydride to add the ring-opened maleic anhydride to the terminal amine. The heating temperature for the addition reaction is preferably 50°C to 120°C, and more preferably 70°C to 100°C. The heating time for the addition reaction is preferably 1 hour to 24 hours, and more preferably 3 hours to 12 hours.

[0035] (Terminal Maleimidization) By further imidizing a polyimide to which ring-opened maleic anhydride has been added, a polyimide modified with a maleimide group at its terminus can be synthesized. Imidization can be carried out using known methods such as the thermal imidization and chemical imidization described above, and chemical imidization is preferred. In this way, a polyimide having a maleimide group at its terminus can be produced.

[0036] (Component (Y)) The (Y) flame retardant used in this embodiment must contain a (Y1) phosphorus-based flame retardant. Any known phosphorus-based flame retardant can be used as component (Y1) as appropriate.(Y1) The components include halogenated phosphate esters such as tris(chloroethyl) phosphate, tris(2,3-dichloropropyl) phosphate, tris(2-chloropropyl) phosphate, tris(2,3-bromopropyl) phosphate, tris(bromochloropropyl) phosphate, 2,3-dibromopropyl-2,3-chloropropyl phosphate, tris(tribromophenyl) phosphate, tris(dibromophenyl) phosphate, and tris(tribromoneopentyl) phosphate. Non-halogenated aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, and tributoxyethyl phosphate; triphenyl phosphate, cresyl diphenyl phosphate, dicresyl phenyl phosphate, tricresyl phosphate, trixylenyl phosphate, xylenyl diphenyl phosphate, tris(isopropylphenyl) phosphate, isopropylphenyl diphenyl phosphate, diisopropylphenyl Examples include non-halogenated aromatic phosphate esters such as triphenyl phosphate, tris(trimethylphenyl) phosphate, tris(t-butylphenyl) phosphate, hydroxyphenyldiphenyl phosphate, and octyldiphenyl phosphate; metal salts of phosphinic acids such as aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanium bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, and titanium tetrakisdiphenylphosphinate; and phosphin oxide compounds such as diphenylvinylphosphin oxide, triphenylphosphin oxide, trialkylphosphin oxide, and tris(hydroxyalkyl)phosphin oxide.

[0037] The amount of component (Y1) is preferably 10% by mass or more and less than 50% by mass, based on 100% by mass of the solid content of the resin composition. If the amount of component (Y1) is less than 10% by mass, the resulting polyimide film tends to have insufficient flame retardancy. On the other hand, if the amount of component (Y1) is 50% by mass or more, the resulting polyimide film tends to have insufficient laser processability. From a similar viewpoint, the amount of component (Y1) is preferably 14% by mass or more and 40% by mass or less, more preferably 16% by mass or more and 30% by mass or less, and particularly preferably 18% by mass or more and 25% by mass or less, based on 100% by mass of the solid content of the resin composition.

[0038] The (Y) flame retardant used in this embodiment may also contain (Y2) aluminum hydroxide. As the (Y2) component, any known flame retardant can be used as appropriate. When using the (Y2) component, the amount blended is preferably 5 parts by mass or more and 30 parts by mass or less, and more preferably 7 parts by mass or more and 25 parts by mass or less, based on 100% by mass of the solid content of the resin composition.

[0039] The amount of component (Y) must be more than 10% by mass and less than 50% by mass, based on 100% by mass of the solid content of the resin composition. If the amount of component (Y) is 10% by mass or less, the flame retardancy of the resulting polyimide film will be insufficient. On the other hand, if the amount of component (Y) is 50% by mass or more, the laser processability and tracking resistance of the resulting polyimide film will be insufficient. From a similar viewpoint, the amount of component (Y) is preferably 14% by mass or more and 40% by mass or less, more preferably 16% by mass or more and 30% by mass or less, and particularly preferably 18% by mass or more and 25% by mass or less, based on 100% by mass of the solid content of the resin composition.

[0040] In the resin composition according to this embodiment, in addition to components (X) and (Y), extender pigments, curing accelerators, colorants, surfactants, leveling agents, plasticizers, sensitizers, silane coupling agents, and non-reactive diluents may be added as needed.

[0041] The method for producing the resin composition according to the present embodiment is not limited to a specific method. For example, after blending each of the above components in a predetermined ratio, the resin composition can be produced by kneading or mixing at room temperature using a kneading means such as a three-roll mill, a ball mill, or a sand mill, or a stirring means such as a super mixer or a planetary mixer. Further, preliminary kneading or preliminary mixing may be performed as necessary before the kneading or mixing.

[0042] [Cured product and polyimide film] The cured product according to the present embodiment is obtained by curing the resin composition according to the present embodiment described above. Further, the polyimide film according to the present embodiment is formed of a cured product of the resin composition according to the present embodiment described above. Furthermore, the resin composition according to the present embodiment described above is excellent in flame retardancy, tracking resistance, and laser processability. Therefore, the polyimide film according to the present embodiment can be particularly suitably used for laser processing.

[0043] The method for producing the polyimide film according to the present embodiment is not particularly limited, and for example, the polyimide film can be obtained by applying the above-mentioned resin composition in a film form on a substrate and curing the applied resin composition. Examples of the substrate include plastic films made of resins such as polyethylene, polypropylene, urethane, polyester, polyethylene terephthalate (PET), and polycarbonate, glass plates, stainless steel plates, copper plates including thin copper foils, and aluminum plates. A release treatment may be applied to the surface of the substrate. Examples of the coating apparatus include bar coaters, curtain coaters, spray coaters, roll coaters, and screen printing machines. When drying the coating film, the drying temperature is preferably 50°C or higher and 120°C or lower, and more preferably 80°C or higher and 110°C or lower. Further, the drying time is preferably 3 minutes or more and 20 minutes or less, and more preferably 5 minutes or more and 15 minutes or less. When curing the coating film after drying, the curing temperature is preferably 150°C or higher and 300°C or lower, and more preferably 180°C or higher and 280°C or lower. Further, the curing time is preferably 15 minutes or more and 150 minutes or less, and more preferably 25 minutes or more and 100 minutes or less.

[0044] The thickness of the polyimide film is not particularly limited, and can be appropriately selected depending on the application. The thickness of the polyimide film can be easily controlled by appropriately adjusting the solid content concentration of each component in the polyamic acid composition, the coating thickness, the viscosity, and the like. The thickness of the polyimide film is preferably 10 µm or more and 200 µm or less, more preferably 20 µm or more and 120 µm or less, and particularly preferably 30 µm or more and 100 µm or less.

[0045] [Use of Polyimide Film] The polyimide film according to the present embodiment can be suitably used for multilayer wiring boards, copper clad laminates, coil structures, magnetic devices, and the like. Furthermore, the polyimide film according to the present embodiment is suitably used as a film for various members such as color filters, flexible displays, semiconductor components, and optical members. Since the polyimide film exhibits insulating properties, it is suitably applied as an insulating substrate for printed wiring boards. In addition, since the polyimide film is a thin and flexible film with insulating properties, it is also effectively applicable as a base film for flexible circuit boards called flexible printed circuits (FPC).

[0046] Next, the present invention will be described in further detail with reference to Examples and Comparative Examples, but the present invention is not limited in any way by these examples. The materials used in the Examples and Comparative Examples are shown below. ((Component X1)) Polyimide A: varnish containing polyimide obtained in Preparation Example 1 Polyimide B: varnish containing polyimide obtained in Preparation Example 2 ((Component X2)) Polyimide C: varnish containing polyamic acid obtained in Preparation Example 3 ((Component Y1)) Phosphorus-based flame retardant: phosphinic acid metal salt, trade name "OP-935F", manufactured by Clariant ((Component Y2)) Aluminum hydroxide A: trade name "BF013STV", manufactured by Nippon Light Metal Co., Ltd. Aluminum hydroxide B: trade name "ECOMAG Z-10", manufactured by Tateho Chemical Industry Co., Ltd.

[0047] [Preparation Example 1] 144.2 g of dimeramine ("PRIAMINE® 1075", manufactured by Croda Japan Co., Ltd.), 5.4 g of aromatic diamine (4,4-oxydianiline), 264.8 g of N-methylpyrrolidone (NMP), and 415.8 g of toluene were placed in a separable flask and heated to 70°C to dissolve the diamine. Next, 124.0 g of ester-type acidic dianhydride ("TMPBP-TME", manufactured by Honshu Chemical Co., Ltd.) was added, and the mixture was stirred at 70°C for 3 hours. Then, 0.9 g of γ-valerolactone and 1.4 g of pyridine were added, and the mixture was stirred at 150°C for 3 hours. Next, after cooling to 70°C, 20.0 g of maleic anhydride was added, and the mixture was stirred at 70°C for 3 hours. Subsequently, the mixture was stirred at 150°C for 10 to 24 hours to prepare a varnish containing a polyimide having maleimide groups at its termini. The molar ratio of diamine to acidic dianhydride in this polyimide [(B) / (A)] is 1.5. The molar ratio of (B1) dimeramine to the total diamine components is 0.9.

[0048] [Preparation Example 2] 120.2 g of dimeramine ("PRIAMINE® 1075", manufactured by Croda Japan Co., Ltd.), 5.0 g of aromatic diamine (4,4-oxydianiline), 228.4 g of N-methylpyrrolidone (NMP), and 454.7 g of toluene were placed in a separable flask and heated to 70°C to dissolve the diamine. Next, 77.5 g of ester-type acidic dianhydride ("TMPBP-TME", manufactured by Honshu Chemical Co., Ltd.) was added, and the mixture was stirred at 70°C for 3 hours. Then, 0.5 g of γ-valerolactone and 0.9 g of pyridine were added, and the mixture was stirred at 150°C for 3 hours. Next, after cooling to 70°C, 25.8 g of maleic anhydride was added, and the mixture was stirred at 70°C for 3 hours. Subsequently, the mixture was stirred at 150°C for 10 to 24 hours to prepare a varnish containing a polyimide having maleimide groups at its termini. The molar ratio of diamine to acidic dianhydride in this polyimide [(B) / (A)] is 2. The molar ratio of (B1) dimeramine to the total diamine components is 0.9.

[0049] [Preparation Example 3] 120.2 g of dimer amine ("PRIAMINE® 1075", manufactured by Croda Japan Co., Ltd.), 15.0 g of aromatic diamine (4,4-oxydianiline), and 750.8 g of NMP were placed in a separable flask and heated to 50°C to dissolve the diamine. Next, 186.1 g of ester-type acidic dianhydride ("TMPBP-TME", manufactured by Honshu Chemical Co., Ltd.) was added, and the mixture was stirred at 50°C for 3.5 hours, and then stirred at room temperature for 24 hours to prepare a varnish containing polyamic acid. The molar ratio of diamine to acidic dianhydride [(B) / (A)] in the polyimide obtained from this polyamic acid is 1. The molar ratio of (B1) dimer amine to the total diamine components is 0.75.

[0050] [Example 1] 85 parts by mass of polyimide A (in terms of resin solids) and 15 parts by mass of a phosphorus-based flame retardant were placed in a container, pre-mixed with a stirrer, and then mixed and dispersed at room temperature using a three-roll roller to obtain a resin composition.

[0051] [Examples 2-9] Resin compositions were obtained in the same manner as in Example 1, except that each material was blended according to the composition shown in Table 1.

[0052] [Comparative Examples 1-6] Resin compositions were obtained in the same manner as in Example 1, except that each material was blended according to the composition shown in Table 1.

[0053] [Evaluation of Resin Compositions] The resin compositions were evaluated (tracking resistance, flame retardancy, laser processability) using the following methods. The results are shown in Table 1. (1) Tracking Resistance First, test specimens were prepared as follows. Specifically, the resin composition was applied to a substrate (PET film, thickness: 38 μm, with release treatment) using a bar coater, and heat treatment was performed at 100°C for 10 minutes, followed by 190°C for 30 to 90 minutes to prepare test specimens of a predetermined size. However, for Example 9, a polyamic acid composition was used to prepare the test specimens (which hardened during heat treatment to become polyimide films). The comparative tracking index (CTI) was measured for the obtained test specimens using a method compliant with IEC 60112. The tracking resistance was then evaluated according to the following criteria. AA: CTI is 600V or higher. A: CTI is 400V or higher and less than 600V. C: CTI is less than 400V. (2) Except for the size of the flame retardant test specimen, test specimens of the specified size were prepared in the same manner as the tracking resistance test specimen in (1). The obtained test specimens were tested in accordance with the method described in UL-94, and the flame retardancy was evaluated according to the following criteria: AA: Not completely burned within 10 seconds. (Equivalent to UL94V-0) A: Not completely burned within 7 seconds. C: Completely burned within 7 seconds. (3) Except for the size of the laser processability test specimen, test specimens of the specified size were prepared in the same manner as the tracking resistance test specimen in (1). The obtained test specimens were processed with a 445 nm blue diode laser with a maximum output of 3.5 W. Linear cuts were made at a laser speed of 500 mm / min and output of 20% (0.7 W), 40% (1.4 W), and 60% (2.1 W), and the condition of the cut surface was observed. Then, for each of the three outputs, the charring and deformation of the cross-section were observed, and the laser processability was evaluated according to the following criteria. (Charring of the cross-section) AA: No charring on the cut surface (width less than 200 μm). A: Charring present on the cut surface (width 200 μm or more, less than 300 μm). C: Charring present on the cut surface (width 300 μm or more). (Deformation of the cross-section) AA: No deformation near the cut surface. A: Slight deformation near the cut surface. C: Deformation near the cut surface.

[0054]

[0055] As is clear from the results shown in Table 1, the polyimide films obtained from the resin composition of the present invention (Examples 1 to 9) were confirmed to have good results in all aspects: tracking resistance, flame retardancy, and laser processability. Therefore, it was confirmed that the resin composition of the present invention can yield polyimide films with excellent flame retardancy, tracking resistance, and laser processability.

Claims

1. A resin composition comprising (X) polyimide and (Y) a flame retardant, wherein component (Y) contains (Y1) a phosphorus-based flame retardant, and the amount of component (Y) is greater than 10% by mass and less than 50% by mass, based on 100% by mass of the solid content of the resin composition.

2. The resin composition according to claim 1, wherein the amount of component (Y1) blended is 10% by mass or more and less than 50% by mass, based on 100% by mass of the solid content of the resin composition.

3. The resin composition according to claim 1, wherein the (X) component contains (X1) a polyimide in which at least one end is modified with a maleimide group.

4. A cured product obtained by curing the resin composition according to any one of claims 1 to 3.

5. A polyimide film comprising a cured product of the resin composition according to any one of claims 1 to 3.

6. A polyimide film according to claim 5, wherein the polyimide film is for laser processing.

7. A multilayer wiring board comprising an insulating layer formed using the polyimide film described in claim 6.

8. A resin-coated copper foil comprising a polyimide film according to claim 6 and a copper foil laminated on the polyimide film.

9. A coil structure comprising an insulating layer formed using the polyimide film described in claim 6.

10. A magnetic device comprising an insulating layer formed using the polyimide film described in claim 6.

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