Polyimide, polyimide film, multilayer wiring board, resin-coated copper foil, coil structure, magnetic device, and insulated wire.

Abstract

The objective is to provide a polyimide capable of forming a polyimide film that exhibits low dielectric properties and low fluidity, as well as good film-forming properties, and also excellent embedding and adhesion properties, and to provide polyimide films, multilayer wiring substrates, resin-coated copper foils, coil structures, and magnetic devices made using the same. [Solution] A polyimide having (A) a structure derived from an ester-type dianhydride and (B) a structure derived from at least two diamines, wherein the (B) diamine contains (B1) dimeramine in a molar ratio of 0.3 or more when the total number of moles of diamines is 1.0, and furthermore, at least one terminal is modified with a maleimide group.

Description

Technical Field

[0006]

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

Background Art

[0002] In recent years, the development of printed wiring boards for next-generation high-frequency wireless with high speed and large capacity has been carried out, and high-speed signal transmission is enabled by adopting a circuit board having a multilayer wiring structure. In the multilayer wiring structure, a prepreg having characteristics such as high insulation, adhesion, and embedding property between wirings due to a combination of a glass fiber cloth and an epoxy resin is used as an adhesive for each electronic circuit board.

[0003] However, epoxy resin usually has high dielectric properties such as a dielectric constant, resulting in a large capacitance. Therefore, in use for high-speed communication (high frequency), the wiring near the insulating film generates heat, which may cause failures in the printed wiring board.

[0004] In order to cope with such high frequencies, the demand for polyimide showing high insulation and low dielectric properties is increasing. For example, Patent Document 1 discloses that a polyimide produced using an aromatic diamine having a specific structure and a tetracarboxylic dianhydride shows a low dielectric constant and excellent heat resistance.

[0005] In addition, a method of reducing the imide group concentration, reducing the polarity of the whole molecule, and lowering the dielectric constant of polyimide by introducing a fluorene skeleton into the diamine component is also known. For example, Patent Document 2 discloses that a polyimide using trimellitic anhydride chloride as an acid anhydride and 9,9-bis(4-aminophenyl)fluorene as a diamine shows high heat resistance and a low relative dielectric constant.

[0006] On the other hand, while polyimides have excellent dielectric properties, their high melt viscosity makes them difficult to flow, and their elasticity results in poor embedding and adhesion. Therefore, there is a need for the development of polyimides that not only exhibit low dielectric properties but also low fluidity, and that can form polyimide films with excellent embedding and adhesion properties. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 10-152559 [Patent Document 2] Japanese Patent Publication No. 2005-298625 [Overview of the project] [Problems that the invention aims to solve]

[0008] In view of the above circumstances, the object of the present invention is to provide a polyimide that can form a polyimide film exhibiting low dielectric properties and low fluidity, as well as good film-forming properties, and furthermore, excellent embedding and adhesion properties, and a polyimide film, multilayer wiring board, resin-coated copper foil, coil structure, magnetic device, and insulated wire made using the same. [Means for solving the problem]

[0009] An aspect of the present invention is a polyimide having (A) a structure derived from an ester-type acidic dianhydride and (B) a structure derived from at least two diamines, wherein the (B) diamine contains (B1) dimeramine in a molar ratio of 0.3 or more when the total number of moles of diamines is 1.0, and furthermore, at least one terminal is modified with a maleimide group.

[0010] In one embodiment of the present invention, the (A1) ester-type dianhydride has a structure represented by the following formula (1). [ka] (In formula (1), Ar represents a substituted or unsubstituted arylene group.)

[0011] Another aspect of the present invention is a polyimide film containing the above-mentioned polyimide.

[0012] Another aspect of the present invention is a multilayer wiring board comprising an insulating layer formed using the above-mentioned polyimide film.

[0013] Another aspect of the present invention is a resin-coated copper foil comprising the polyimide film and a copper foil laminated on the polyimide film.

[0014] Another aspect of the present invention is a coil structure comprising an insulating layer formed using the above-mentioned polyimide film.

[0015] Another aspect of the present invention is a magnetic device comprising an insulating layer formed using the above-mentioned polyimide film.

[0016] Another aspect of the present invention is an insulated wire comprising an insulating layer formed using the above-mentioned polyimide and a wire covered with the insulating layer. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a polyimide that can form a polyimide film exhibiting low dielectric properties and low fluidity, as well as good film-forming properties, and furthermore, excellent embedding and adhesion properties, and a polyimide film, multilayer wiring board, resin-coated copper foil, coil structure, magnetic device, and insulated wire made using the same. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments of the present invention will be described in detail. The polyimide of the present invention has a structure derived from (A) an ester-type acid dianhydride and a structure derived from (B) at least two diamines, and furthermore, at least one terminal is modified with a maleimide group. Also, (B) the diamine contains (B1) a dimer diamine in a molar ratio of 0.3 or more when the total number of moles of all diamines is 1.0. By including a certain amount of dimer diamine as the diamine component, the dielectric constant and dielectric tangent can be made lower, and the desired low dielectric characteristics can be realized. Further, while introducing a low dielectric imide skeleton, the terminal is modified with a maleimide group and the molecular weight is adjusted, whereby a polyimide showing improved embedding property can be synthesized. Furthermore, by reducing the molecular weight, the melt viscosity can be decreased, and the fluidity and adhesion can be improved.

[0019] (A1) Ester-type acid dianhydride The polyimide of the present invention has, as an acid dianhydride component, a structure derived from an ester-type acid dianhydride having an ester bond in the molecule. 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 number of ester bonds in the molecule may be one or more, preferably 1 to 3, and more preferably 1 or 2. The ester-type acid dianhydride may be used alone or in combination of two or more.

[0020] Such an ester-type acid dianhydride preferably has a structure represented by the following formula (1). In formula (1), Ar represents a substituted or unsubstituted arylene group, and the substituted arylene group means that a hydrogen atom of the unsubstituted arylene group is substituted by an arbitrary substituent. The number of carbon atoms of the substituted or unsubstituted arylene group (however, the carbon number of the substituent is not included) is preferably 6 to 20, and more preferably 6 to 12.

[0021] [Chemical formula]

[0022] Examples of the unsubstituted arylene group in Ar include, for example, o-phenylene group, m-phenylene group, p-phenylene group, 2,6-naphthylene group, 4,4'-biphenylylene group, etc. Among these, p-phenylene group, 2,6-naphthylene, 4,4'-biphenylylene group are preferred.

[0023] Examples of any substituent in the substituted arylene group include an alkyl group having 1 to 8 carbon atoms, a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a halogenated alkyl group in which a hydrogen atom of the alkyl group is substituted with the halogen atom, etc. Among these substituents, an alkyl group having 1 to 8 carbon atoms is preferred, and a methyl group is more preferred. The number of any substituent may be 1 or 2 or more. When there are 2 or more substituents, those substituents may be the same or different. Specific examples of the substituted arylene group include 2,2',3,3',5,5'-hexamethyl-4,4'-biphenylylene group, etc.

[0024] Preferred examples of the ester-type acid dianhydride represented by formula (1) include the compound (TAHQ) represented by the following formula (1-1), and the compound (TMPBP-TME) represented by the following formula (1-2), and the compound represented by the following formula (1-2) is more preferred.

[0025]

Chemical formula

[0026] (B) Diamine The polyimide of the present invention has a structure derived from at least two diamines as diamine components, one of which is derived from a (B1) dimer amine. Here, dimer amine refers to an aliphatic diamine in which two terminal carboxylic acid groups (-COOH) of a cyclic or acyclic dimer acid obtained as a dimer of an unsaturated fatty acid are substituted with a primary aminomethyl group (-CH2-NH2) or an amino group (-NH2). By having a structure derived from a dimer amine in the polyimide, low dielectric properties can be imparted to the resulting polyimide. Dimer amines may be used alone or in combination of two or more.

[0027] 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, and 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.

[0028] Commercially available dimeramine products include "Versamin® 551" and "Versamin® 552" from Cognics Japan, and "PRIAMINE® 1073," "PRIAMINE® 1074," and "PRIAMINE® 1075" from Croda Japan.

[0029] In the polyimide, the (B) diamine contains (B1) dimeramine in a molar ratio of 0.3 or more when the total number of moles of diamine is set to 1.0. By including dimeramine in a specific molar ratio or higher relative to the total number of diamine, the resulting polyimide can be given a lower dielectric constant and a lower dielectric loss tangent. The molar ratio of (B1) dimeramine when the total number of moles of diamine is set to 1.0 is preferably 0.5 or more, more preferably 0.60 or more, and even more preferably 0.9 or more.

[0030] The polyimide of the present invention may also contain (B2) aromatic diamines as other diamine components. Examples of aromatic diamines include p-phenylenediamine (PDA), m-phenylenediamine, 4,4'-oxydianiline (ODA), 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, diaminodiphenylsulfone, Examples include 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, ODA, and TFMB are preferred, with ODA being more preferred. Aromatic diamines may be used individually or in combination of two or more.

[0031] The molar ratio of diamine to ester-type acidic dianhydride [(B) / (A)] is not particularly limited, but is preferably 0.3 to 2.0, more preferably 0.5 to 1.9, even more preferably 0.75 to 1.8, and particularly preferably 0.75 to 1.7.

[0032] (C) Terminally modified maleimide group The polyimide of the present invention has at least one terminus modified with a maleimide group. Specifically, in a repeating unit of polyimide having (A) a structure derived from an ester-type acid dianhydride and (B) a structure derived from at least two diamines, the terminus is modified via the nitrogen atom (N) of the maleimide group, preferably at least one terminus of the structural portion derived from the diamine is modified with a maleimide group. In such a polyimide structure, only one terminus may be modified with a maleimide group, or both terms may be modified with a maleimide group. In the polyimide of the present invention, since the reactive group of the maleimide group is introduced at the terminus, it is possible to increase the molecular weight in further reactions.

[0033] From the viewpoint of fluidity and film-forming properties, the molecular weight (weight-average molecular weight) of 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 is preferably 5,000 or more. The molecular weight of polyimide can be determined, for example, from the standard polystyrene equivalent value obtained by gel filtration chromatography (GPC).

[0034] 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 is preferably 1000 mPa·s or more, and more preferably 1000 mPa·s or more. The melt viscosity of polyimide can be measured, for example, using an analytical instrument such as a rheometer.

[0035] <Synthesis of polyimides> The polyimide of the present invention can be produced through the following steps. (i) Polyamic acid, a precursor of polyimide, is synthesized by polyaddition reaction of the ester-type dianhydride described above with at least two diamines. (ii) The obtained polyamic acid is imidized to synthesize a polyimide with amine-modified terminals. (iii) A polyimide with amine-modified terminals is reacted with maleic anhydride to add maleic anhydride to the terminal amine. (iv) A polyimide modified with maleimide groups at its terminus is produced by further imidizing the polyimide to which maleic anhydride has been added.

[0036] (Synthesis of polyamic acids) Polyamic acids can be synthesized by known general methods. For example, polyamic acids (polyamic acid solutions) can be obtained by reacting ester-type dianhydrides with diamines in an organic solvent. The organic solvent used for polymerization of polyamic acids is not particularly limited, as long as it can dissolve the ester-type dianhydrides and diamines 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 acid, the organic solvent is preferably selected from the group consisting of amide solvents, aromatic hydrocarbon solvents, ketone solvents, ester solvents, and ether solvents. Amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylacetamide, and N-methyl-2-pyrrolidone, and aromatic hydrocarbon solvents such as toluene are preferred.

[0037] The molecular weight of the polyamic acid and the subsequently synthesized polyimide can be adjusted by adjusting the molar ratio of the total moles of the ester-type dianhydride component to the total 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.

[0038] The synthesis of polyamic acids by the polyaddition reaction of ester-type 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 ester-type dianhydride and diamine in an organic solvent and mixing them. The order of addition of the ester-type 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 ester-type dianhydride may be added to the diamine solution. The ester-type 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.

[0039] The temperature conditions for the polyaddition reaction are not particularly limited, but from the viewpoint of suppressing the decrease in molecular weight of polyamic acid due to depolymerization, the reaction temperature is preferably 100°C or lower, and from the viewpoint of allowing the polyaddition reaction to proceed appropriately, the reaction temperature is more preferably 20 to 80°C. The reaction time can be arbitrarily set in the range of 1 to 72 hours, and if necessary, it may be left overnight at room temperature.

[0040] 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 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.

[0041] To impart processing properties and various functionalities to polyamic acid, various organic or inorganic low-molecular-weight or high-molecular-weight compounds may be blended into the polyamic acid solution. For example, the polyamic acid composition may contain dyes, surfactants, leveling agents, plasticizers, fine particles, sensitizers, silane coupling agents, etc. The fine particles may be either organic or inorganic, and may have a porous or hollow structure.

[0042] (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 dehydration and cyclization by heating, and chemical imidization, which involves chemical cyclization using a known dehydration and cyclization catalyst, can be employed for dehydration and cyclization (imidization).

[0043] In the case of thermal imidation, the heating temperature is preferably 120 to 350°C, and more preferably 150 to 250°C. The heating time is preferably 0.5 to 3 hours, and more preferably 1 to 2 hours. In the case of chemical imidation, for example, pyridine, triethylamine, γ-valerolactone, acetic anhydride, etc. can be used as the dehydration and ring-closing catalyst. In this case, the reaction temperature can be selected from any temperature between 20 and 100°C, preferably 50°C or lower, and the reaction time is preferably 1 to 3 hours. Among these imidation methods, chemical imidation is preferred. Furthermore, 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.

[0044] (Addition of maleic anhydride) The addition reaction between the amine-modified polyimide and maleic anhydride adds the ring-opened maleic anhydride to the terminal amine. The heating temperature for the addition reaction is preferably 50 to 120°C, and more preferably 70 to 100°C. The heating time for the addition reaction is preferably 1 to 24 hours, and more preferably 3 to 12 hours.

[0045] (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 thermal imidization or chemical imidization, as described above, with chemical imidization being preferred. In this way, a polyimide having a maleimide group at its terminus can be produced.

[0046] <Polyimide film> The polyimide film of the present invention contains the polyimide obtained as described above. By applying a solution (composition) containing the polyimide of the present invention onto a substrate, drying the resulting coating film, and further curing it, a polyimide film can be formed on the substrate having polyimide formed by the activation of terminal maleimide groups. The substrate is not particularly limited, but examples include polyethylene terephthalate film (PET film) and polyethylene naphthalate film. The surface of the substrate may be treated with a release agent.

[0047] The thickness of the polyimide film is not particularly limited, but is preferably 25 μm to 60 μm, and more preferably 30 μm to 50 μm. The thickness of the substrate is not particularly limited, but is preferably 15 μm to 75 μm, and more preferably 25 μm to 50 μm.

[0048] Examples of coating apparatus for applying a polyimide-containing solution onto a substrate include bar coaters, curtain coaters, spray coaters, roll coaters, and screen printing machines. When drying the coated film formed on the substrate, the drying temperature is preferably 50°C to 120°C, and more preferably 80°C to 110°C. The drying time is preferably 180 seconds to 720 seconds, and more preferably 300 seconds to 600 seconds. Furthermore, when thermally curing the coated film after drying, the curing temperature is preferably 150°C to 250°C, and more preferably 180°C to 220°C. The curing time is preferably 180 seconds to 1500 seconds, and more preferably 300 seconds to 1200 seconds.

[0049] <Copper foil with resin coating> The resin-coated copper foil of the present invention is obtained by laminating the above-mentioned polyimide film onto copper foil. With such resin-coated copper foil, the polyimide film can be used as an insulating layer to build up wiring on a wiring board. The copper foil may be laminated on one side of the resin film, or it may be laminated on both sides of the resin film with polyimide.

[0050] <Multilayer wiring board> The multilayer wiring board of the present invention comprises an insulating layer formed using the polyimide film described above. As an example of manufacturing such a multilayer wiring board, for example, a double-sided copper foil substrate is made by sandwiching the polyimide layer surface of resin-coated copper foil from both sides using the polyimide film described above as a core substrate. Then, a wiring pattern is formed on the copper foil by etching to produce a single-layer wiring board. Furthermore, by appropriately layering the polyimide film and resin-coated copper foil on top of that, a multilayer wiring board can be made in which insulating layers and wiring pattern layers are alternately provided.

[0051] Polyimide is subjected to a heat-curing treatment to form a cured resin layer consisting of a cured polyimide product. Examples of heat-curing treatments include heat-pressing treatment and heat treatment. The heat-curing treatment may be a single-stage treatment or a two-stage or more-stage treatment. The temperature of the heat-curing treatment is preferably 150°C to 250°C, and more preferably 180°C to 200°C. The pressure of the heat-curing treatment is preferably 0.5 MPa to 5.0 MPa, and more preferably 1.1 MPa to 5.0 MPa. The duration of the heat-curing treatment is preferably 0.5 hours to 3 hours, and more preferably 1 hour to 2 hours.

[0052] <Coil structure> The coil structure of the present invention comprises an insulating layer formed using the polyimide film described above. Such a coil structure can be manufactured by the same method as the multilayer wiring substrate described above. That is, the coil structure can be manufactured by using a wiring substrate having coil-shaped wiring as the material for the multilayer wiring substrate.

[0053] <Magnetic devices> The magnetic device of the present invention comprises an insulating layer formed using the polyimide film described above. Such a magnetic device can be manufactured by the same method as the multilayer wiring substrate described above. By using a wiring substrate having coil-shaped wiring as a single-layer wiring substrate, a coil structure can be manufactured. Then, by providing a known magnetic material such as ferrite on this coil structure, a magnetic device can be manufactured.

[0054] <Insulated wire> The insulated wire of the present invention comprises an insulating layer formed using the polyimide described above, and a wire covered with the insulating layer. Such an insulated wire can be manufactured by applying a composition containing the polyimide of the present invention onto the wire, drying it in the same manner as described above to form a coating film, and then heat-curing it. For example, highly conductive materials such as copper or aluminum can be used as the wire material. The wire may also be plated. [Examples]

[0055] Next, embodiments of the present invention will be described, but the present invention is not limited to these examples unless it exceeds the spirit of the invention. In the following table, the values ​​of each component are in parts by mass unless otherwise specified.

[0056] <Example 1> 144.2g of dimeramine ("PRIAMINE® 1075," manufactured by Croda Japan), 5.4g of aromatic diamine (4,4-oxydianiline), 264.8g of N-methylpyrrolidone (NMP), and 415.8g of toluene were placed in a separable flask and heated to 70°C to dissolve the diamine. Next, 124.0g 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, 0.9g of γ-valerolactone and 1.4g of pyridine were added, and the mixture was stirred at 150°C for 3 hours. After cooling to 70°C, 20g 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 polyimide composition having maleimide groups at the ends.

[0057] <Example 2> 118.7 g of dimeramine ("PRIAMINE® 1075," manufactured by Croda Japan), 24.7 g of aromatic diamine (4,4-oxydianiline), 297.4 g of NMP, and 392.6 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. After cooling to 70°C, 30 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 polyimide composition having maleimide groups at the ends.

[0058] <Comparative Example 1> 120.2 g of dimeramine ("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 polyamic acid composition.

[0059] (Preparation of test specimens) Each of the compositions prepared as described above was coated onto a substrate, heat-treated, and then the substrate was peeled off to prepare a test specimen which was a cured polyimide. Substrate: PET film (38 μm thick, with release treatment) Coating method: Bar coater DRY film thickness (20 μm to 100 μm) Heat treatment: Dry in a hot air circulating drying oven at 100°C for 10 minutes, then heat-cur at 190°C for 20 minutes.

[0060] <Rating> (1) Film formability The film-forming properties of the cured material obtained from the test specimens were evaluated for isolation from the substrate according to the following criteria.

[0061] ○: Can be isolated without cracks, chips, etc. △: Some cracking occurs during isolation. ×: Cracks occurred

[0062] (2) Dielectric constant Using an impedance analyzer ("4291B", manufactured by Hewlett Packard), the cured specimen (thickness: 25 μm, length: 20 mm, width: 20 mm) prepared as described above was used as a sample, and measurements were taken at a measurement temperature of 25°C and a frequency of 1 MHz to determine the dielectric constant at a frequency of 1 MHz.

[0063] (3) Melt viscosity Using a rheometer ("HAKKE MARS III", Thermo Scientific), the melt viscosity of polyimide pellets was measured under conditions of a measurement temperature of 30-200°C and a heating rate of 2°C / min.

[0064] (4) Implantability The polyimide solution prepared as described above was applied to a PET substrate and dried at 100°C for 10 minutes. The dried polyimide film was vacuum-laminated over another polyimide film (thickness: 25 μm, "Kapton®", manufactured by Toray DuPont) to create a sheet with a polyimide film / polyimide film ("Kapton®") / polyimide film laminated structure. Multiple layers of polyimide film were laminated so that each layer was 50-80 μm thick. Printed circuit boards with copper wiring ("FR-4 substrate", thickness: 400 μm, conductor thickness: 35 μm) were placed on both sides of this sheet and vacuum-pressed under the conditions of (i) 150°C, 20 minutes, 0.5 MPa and (ii) 190°C, 60 minutes, 3.3 MPa. The embedding ability was evaluated by observing the cross-section between the copper wirings of this substrate according to the following criteria.

[0065] ○: Polyimide can be filled horizontally along the wiring. ×: Due to the wiring, polyimide is not filled horizontally.

[0066] (5) Adhesion (peel strength) The polyimide solution prepared as described above was coated onto a PET substrate to a film thickness of 25-35 μm and dried at 100°C for 10 minutes. The dried polyimide film was vacuum-laminated onto copper foil at 100°C to create a sheet with a copper foil / polyimide film / copper foil laminated structure (copper foil thickness: 12 μm). Subsequently, the test specimens were vacuum-pressed at (i) 140°C, 10 minutes, 0.5 MPa and (ii) 190°C, 90 minutes, 2.5 MPa. The sheets thus prepared were subjected to a 90° peel at a speed of 50 mm / min using an Autograph (Shimadzu Corporation) to evaluate their adhesion.

[0067] [Table 1]

[0068] As shown in Table 1, in Examples 1 and 2, polyimides were used that had (A) a structure derived from an ester-type dianhydride and (B) a structure derived from at least two diamines, wherein (B) the diamine contained (B1) dimeramine in a molar ratio of 0.3 or more when the total number of moles of diamines was set to 1.0, and furthermore, at least one terminal was modified with a maleimide group. The resulting polyimides exhibited low dielectric properties and low fluidity, and polyimide films with excellent embedding and adhesion properties were produced. In addition, they could be isolated from the substrate without cracking or chipping, and film formation was also good.

[0069] On the other hand, in Comparative Example 1, which used a polyimide whose terminals were not modified with maleimide groups, the embedding ability was evaluated as "×", and the peel strength was lower and the adhesion was inferior to that of Examples 1 and 2. Furthermore, it was not possible to obtain a polyimide that exhibited high melt viscosity and low fluidity. [Industrial applicability]

[0070] The polyimide of the present invention exhibits low dielectric properties and low fluidity, as well as good film-forming properties. Furthermore, since polyimide films with excellent embedding and adhesion can be produced using such polyimide, it has high value as a substrate material for high-frequency circuits.

Claims

1. A polyimide having (A) a structure derived from an ester-type dianhydride and (B) a structure derived from at least two diamines, The (B) diamine contains (B1) dimeramine in a molar ratio of 0.3 or more when the total number of moles of diamine is set to 1.

0. Furthermore, the polyimide is characterized in that at least one terminal is modified with a maleimide group.

2. The adhesive resin composition according to claim 1, wherein the (A1) ester-type dianhydride has a structure represented by the following formula (1). 【Chemistry 1】 (In formula (1), Ar represents a substituted or unsubstituted arylene group.)

3. A polyimide film comprising the polyimide described in claim 1 or 2.

4. A multilayer wiring board comprising an insulating layer formed using the polyimide film described in claim 3.

5. A resin-coated copper foil comprising a polyimide film according to claim 3 and a copper foil laminated on the polyimide film.

6. A coil structure comprising an insulating layer formed using the polyimide film described in claim 3.

7. A magnetic device comprising an insulating layer formed using the polyimide film described in claim 3.

8. An insulated electric wire comprising an insulating layer formed using the polyimide described in claim 1 or 2, and an electric wire covered with the insulating layer.

Images