Polyimide, resin composition, resin film, laminate, cover film, resin-coated copper foil, metal-clad laminate and circuit board

Abstract

This invention provides a polyimide using a dimerized diamine as a raw material, capable of forming a resin film with both low dielectric loss tangent and excellent adhesion. The polyimide contains, relative to all diamine residues, diamine residues derived from a dimerized diamine composition in the range of 40 mol% to 95 mol%, wherein the dimerized diamine composition is primarily composed of a dimerized diamine formed by replacing the two terminal carboxylic acid groups of a dimer acid with primary aminomethyl or amino groups, and contains, in the range of 5 mol% to 25 mol%, diamine residues derived from a diamine compound comprising a biphenyl backbone or a naphthalene backbone, wherein the biphenyl backbone or the naphthalene backbone has at least one substituent containing an intercarbon double bond selected from the group consisting of vinyl, acrylate, methacrylate, and allyl groups.

Description

Technical Field

[0001] This invention relates to polyimide, resin composition, resin film, laminate, cover film, resin-coated copper foil, metal-clad laminate, and circuit board, which are effective as adhesives in circuit boards such as printed wiring boards. Background Technology

[0002] In recent years, with the miniaturization, weight reduction, and space-saving development of electronic devices, the demand for flexible printed circuit boards (FPCs) that are thin, lightweight, flexible, and have excellent durability even after repeated bending has increased. FPCs can achieve three-dimensional and high-density installation even in limited spaces, thus their applications are expanding to wiring, cables, connectors, and other components for moving parts of electronic devices such as hard disk drives (HDDs), digital video discs (DVDs), and mobile phones.

[0003] Polyimide, which constitutes the insulating resin layer of circuit boards such as FPCs, is widely used due to its excellent heat resistance, chemical resistance, flexibility, mechanical properties, and electrical properties. Furthermore, various additives are formulated to improve the functionality of polyimide. For example, by combining specific phosphorus compounds into polyimide, an adhesive composition with excellent adhesion, heat resistance, flame retardancy, processability, and high insulation reliability has been proposed (Patent Document 1).

[0004] In addition to the continuous development of high-density applications, the performance of devices is also constantly improving, thus requiring solutions for higher frequency transmission signals. In information processing or communication, efforts have been made to increase transmission frequencies to transmit and process large amounts of information, requiring printed circuit board materials to reduce transmission losses through thinning of the insulating layer and improvement of its dielectric properties. Going forward, there is an increasing demand for reducing transmission losses and addressing higher frequency requirements for the insulating layer (including the adhesive layer) constituting the FPC. Regarding the improvement of the dielectric properties of printed circuit board materials, a resin composition comprising a multifunctional vinyl aromatic polymer and a thermosetting compound, but without a free radical polymerization initiator, has been proposed (Patent Document 2).

[0005] Furthermore, it is proposed to apply cross-linked polyimide resin to the adhesive layer of a cover film. This cross-linked polyimide resin is obtained by reacting a thermoplastic polyimide derived from a diamine compound derived from a dimer acid (dimeric fatty acid) with an amino compound having at least two primary amino groups as functional groups (Patent Document 3). In an embodiment of Patent Document 3, it is also disclosed to incorporate flake-like talc into a thermoplastic polyimide composition based on a dimer acid. Here, the dimer acid is, for example, a dimerized fatty acid obtained by using natural fatty acids such as soybean oil fatty acids, tall oil fatty acids, and rapeseed oil fatty acids, as well as oleic acid, linoleic acid, linolenic acid, sinapic acid, etc., refined from them, through a Diels-Alder reaction. It is known that polyacid compounds derived from dimer acids can be obtained as fatty acids from the source or as a composition of trimerized or higher fatty acids (Patent Document 4).

[0006] [Existing Technical Documents]

[0007] [Patent Literature]

[0008] [Patent Document 1] Japanese Patent No. 6733845

[0009] [Patent Document 2] International Publication No. WO2020 / 175537

[0010] [Patent Document 3] Japanese Patent No. 5777944

[0011] [Patent Document 4] Japanese Patent Application Publication No. 2017-137375 Summary of the Invention

[0012] [The problem the invention aims to solve]

[0013] Polyimide, made from dimerized diamine, is an effective resin material for use as an adhesive due to its solubility in solvents, excellent adhesion, and good handling. However, in order to cope with the future development of high frequency, in addition to meeting the above-mentioned characteristics, it is also required to further reduce the dielectric loss tangent.

[0014] Therefore, the object of the present invention is to provide a polyimide that uses dimerized diamine as a raw material, which can form a resin film that has both low dielectric loss tangent and excellent adhesion.

[0015] [Technical means to solve the problem]

[0016] The polyimide of the present invention is a polyimide containing a tetracarboxylic acid residue derived from a tetracarboxylic anhydride component and a diamine residue derived from a diamine component.

[0017] The polyimide of the present invention contains diamine residues derived from a dimer diamine composition in a range of 40 mol% to 95 mol% relative to all diamine residues, wherein the dimer diamine composition is a dimer diamine formed by replacing the two terminal carboxylic acid groups of a dimer acid with primary aminomethyl or amino groups as the main component.

[0018] In addition, the polyimide of the present invention contains, relative to all diamine residues, diamine residues derived from a diamine compound in the range of 5 mol% to 25 mol%, the diamine compound comprising a biphenyl skeleton or a naphthalene skeleton, and the biphenyl skeleton or the naphthalene skeleton having at least one substituent containing an intercarbon double bond selected from the group consisting of vinyl, acrylate, methacrylate and allyl.

[0019] The resin composition of the present invention contains the following components (A) and (B);

[0020] (A) The polyimide, and

[0021] (B) Crosslinking agent,

[0022] And relative to 100 parts by weight of component (A), the content of component (B) is in the range of 5 parts by weight or more and 30 parts by weight or less.

[0023] The resin composition of the present invention may further contain the following component (C);

[0024] (C) Elastomer resin.

[0025] The content of component (C) may be in the range of 5 parts by weight or more and 100 parts by weight or less, relative to 100 parts by weight of component (A).

[0026] The resin composition of the present invention may further contain the following component (D);

[0027] (D) Polymerization initiator,

[0028] The content of component (D) may be in the range of more than 0.5 parts by weight and less than 2.0 parts by weight relative to 100 parts by weight of component (A).

[0029] The resin film of the present invention contains the polyimide.

[0030] The resin membrane of the present invention may have a dielectric loss tangent (Tanδ) of less than 0.002 at 10 GHz, measured by a split post dielectric resonator (SPDR) after 24 hours of conditioning under constant temperature and humidity conditions (normal) of 23°C and 50%RH.

[0031] The laminate of the present invention is a laminate having a substrate and an adhesive layer laminated on at least one side of the substrate, the adhesive layer comprising the resin film.

[0032] The cover film of the present invention is a cover film having a cover film material layer and an adhesive layer laminated on the cover film material layer, wherein the adhesive layer comprises the resin film.

[0033] The resin-coated copper foil of the present invention is a resin-coated copper foil formed by laminating an adhesive layer with a copper foil, wherein the adhesive layer comprises the resin film.

[0034] The metal-clad laminate of the present invention is a metal-clad laminate having an insulating resin layer and a metal layer laminated on at least one side of the insulating resin layer, wherein at least one layer of the insulating resin layer comprises the resin film.

[0035] The circuit board of the present invention is formed by wiring the metal layer of the metal-clad laminate.

[0036] [The effects of the invention]

[0037] The polyimide of the present invention contains diamine residues derived from a dimerized diamine composition and diamine residues derived from a diamine compound having substituents containing intercarbon double bonds. Therefore, it can form a resin film that, in addition to excellent high-frequency characteristics, also possesses practically sufficient adhesion (especially peel strength), solder heat resistance, and flame retardancy. Thus, the resin composition and resin film of the present invention are particularly preferably used as circuit board materials for FPCs and the like in electronic devices requiring high-speed signal transmission. Furthermore, by improving the dielectric properties of the resin film, it can be applied to receivers using direct conversion methods. Moreover, as a highly reliable low-dielectric adhesive, it can be applied to electronic devices of all structures. Detailed Implementation

[0038] The embodiments of the present invention will be described below.

[0039] [Polyimide]

[0040] The polyimide of one embodiment of the present invention is an adhesive polyimide. Hereinafter, the polyimide of this embodiment will sometimes be referred to as an "adhesive polyimide". The adhesive polyimide contains tetracarboxylic acid residues derived from the tetracarboxylic dianhydride component and diamine residues derived from the diamine component. When the tetracarboxylic dianhydride and the diamine compound, which are raw materials, are reacted in approximately equimolar amounts, the types and molar ratios of the tetracarboxylic acid residues and diamine residues contained in the polyimide can be made to approximately correspond to the types and molar ratios of the raw materials.

[0041] Furthermore, when referred to as "polyimide" in this invention, it refers not only to polyimide, but also to resins containing polymers having an imide group in their molecular structure, such as polyamide imide, polyether imide, polyester imide, polysiloxane imide, and polybenzimidazole imide.

[0042] The tetracarboxylic acid residues and diamine residues that constitute adhesive polyimide will be described below together with their raw materials.

[0043] (acid anhydride)

[0044] Adaptive polyimides can use tetracarboxylic dianhydrides, which are generally used in polyimides, without particular restriction. Examples of tetracarboxylic dianhydride residues derived from such tetracarboxylic dianhydrides include 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,3',3,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, or 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride (DSDA), 4,4'-oxyphthalic anhydride (ODPA), 4,4'-(hexafluoroisopropylidene)phthalic anhydride (6FDA), and 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPAD). A) Phenylidene bis(triphenylene oxide monoester anhydride) (TAHQ), ethylene glycol bis(triphenylene oxide) anhydride (TMEG), pyromellitic dianhydride, 2,3',3,4'-biphenyltetracarboxylic acid dianhydride, 2,3',3,4'-diphenyl ether tetracarboxylic acid dianhydride, bis(2,3-dicarboxyphenyl) ether dianhydride, 3,3”,4,4”-p-triphenyltetracarboxylic acid dianhydride, 2,3,3”,4”-p-triphenyltetracarboxylic acid dianhydride or 2,2”,3,3”-p-triphenyltetracarboxylic acid dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride or 2,2-bis(3,4-dicarboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride or bis(3,4-dicarboxyphenyl) Methane dianhydride, bis(2,3-dicarboxyphenyl)sulfone dianhydride or bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride or 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2,7,8-phenanthrene-tetracarboxylic acid dianhydride, 1,2,6,7-phenanthrene-tetracarboxylic acid dianhydride or 1,2,9,10-phenanthrene-tetracarboxylic acid dianhydride, 2,3,6,7-anthracite-tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)tetrafluoropropane dianhydride, 1,2,5,6-naphthalene-tetracarboxylic acid dianhydride, 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride, 2,3,6,7-naphthalene-tetracarboxylic acid dianhydride, 4,8-dimethyl-1,2,3,5,6,7-hexahydronaphthalene- 1,2,5,6-Tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride or 2,7-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-(or 1,4,5,8-)tetrachloronaphthalene-1,4,5,8-(or 2,3,6,7-)tetracarboxylic dianhydride, 2,3,8,9-perylene-tetracarboxylic dianhydride, 3,4,9,10-perylene-tetracarboxylic dianhydride, 4,5,10,11-perylene-tetracarboxylic dianhydride or 5,6,11,12-perylene-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic dianhydride, 4,4'-bis(2,Tetracarboxylic acid residues derived from aromatic tetracarboxylic acid dianhydrides such as 3-dicarboxyphenoxy)diphenylmethane dianhydride, or tetracarboxylic acid residues derived from aliphatic tetracarboxylic acid dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, 1,2,4,5-cycloheptanetetracarboxylic acid dianhydride, and 1,2,5,6-cyclooctanetetracarboxylic acid dianhydride.

[0045] Among these, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), and 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) are preferred, as they have a greater effect on reducing the dielectric loss tangent. More preferably, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and 4,4'-(hexafluoroisopropylidene) phthalic anhydride (6FDA) are preferred.

[0046] (Diamine)

[0047] Adaptive polyimides can use, without particular limitation, diamine compounds commonly used in polyimides as raw materials. The diamine composition contains diamine residues derived from a dimer diamine composition in a range of 40 mol% to 95 mol% and preferably 70 mol% to 90 mol% relative to all diamine residues. The dimer diamine composition is primarily composed of a dimer diamine in which two terminal carboxylic acid residues of a dimer acid are substituted with primary aminomethyl or amino groups. By containing diamine residues derived from the dimer diamine composition within the range described above, the solubility of the polyimide can be improved, and the relative permittivity and dielectric loss tangent can be reduced.

[0048] When the content of diamine residues derived from the dimerized diamine composition is less than 40 mol% relative to all diamine residues, the relative dielectric constant and dielectric loss tangent tend to increase due to the relatively increased polar groups contained in the polyimide. Furthermore, by including diamine residues derived from the dimerized diamine composition in the aforementioned amount, the hot-pressing properties caused by the lower glass transition temperature (lower Tg) of the polyimide can be improved, and the internal stress caused by the lower elastic modulus can be mitigated. On the other hand, when the content of diamine residues derived from the dimerized diamine composition exceeds 95 mol% relative to all diamine residues, the mobility of the polyimide molecular chains is excessively increased, and the dielectric loss tangent may sometimes increase.

[0049] The dimer diamine composition is a refined product containing the following component (a) as the main component, and the amounts of components (b) and (c) are controlled.

[0050] (a) Dimeric diamine;

[0051] The dimer diamine, as component (a), refers to a diamine formed by replacing the two terminal carboxylic acid groups (-COOH) of a dimer acid with primary aminomethyl (-CH2-NH2) or amino (-NH2). Dimer acids are known dicarboxylic acids obtained through intermolecular polymerization of unsaturated fatty acids. Their industrial manufacturing process is largely standardized in the industry, and they are obtained by dimerizing unsaturated fatty acids with 11 to 22 carbon atoms using clay catalysts or the like. The dimer acids obtained industrially are mainly 36-carbon dicarboxylic acids obtained by dimerizing 18-carbon unsaturated fatty acids such as oleic acid, linoleic acid, or linolenic acid. Depending on the degree of purification, they contain arbitrary amounts of monomeric acids (18 carbon atoms), trimer acids (54 carbon atoms), and other polymeric fatty acids with 20 to 54 carbon atoms. In addition, double bonds remain after the dimerization reaction, but in this invention, it is assumed that the dimer acid also contains acids that undergo hydrogenation to reduce the degree of unsaturation. Dimeric diamines, which are components of (a), can be defined as diamine compounds obtained by replacing the terminal carboxylic acid group of a dicarboxylic acid compound having 18 to 54 carbon atoms, preferably 22 to 44, with a primary aminomethyl or amino group.

[0052] As a characteristic of dimerized diamines, they can impart properties derived from the dimer acid backbone. Specifically, dimerized diamines are aliphatic molecules with a molecular weight of approximately 560–620, thus increasing the molar volume of the molecule and relatively reducing the polar groups in the polyimide. This characteristic of dimer acid-type diamines is believed to help suppress the decrease in the heat resistance of polyimides, while simultaneously reducing the relative dielectric constant and dielectric loss tangent, thereby improving dielectric properties. Furthermore, due to the presence of two freely moving hydrophobic chains with 7–9 carbon atoms and two chain-like aliphatic amino groups with a length close to 18 carbon atoms, not only can polyimides be endowed with flexibility, but they can also be configured with asymmetric or non-planar chemical structures, thus enabling the lower dielectric constant of polyimides.

[0053] The dimer diamine composition preferably uses a composition in which the content of dimer diamine as component (a) is increased to 96% by weight or more, preferably 97% by weight or more, and more preferably 98% by weight or more, through purification methods such as molecular distillation. By setting the content of dimer diamine as component (a) to 96% by weight or more, the expansion of the molecular weight distribution of the polyimide can be suppressed. Furthermore, if technically feasible, it is most preferably that the entire (100% by weight) of the dimer diamine composition comprises dimer diamine as component (a).

[0054] (b) Monoamine compounds obtained by replacing the terminal carboxylic acid group of a monocarboxylic acid compound in the range of 10 to 40 carbon atoms with a primary aminomethyl or amino group;

[0055] Monocarboxylic acid compounds with a carbon number range of 10 to 40 are mixtures of monocarboxylic unsaturated fatty acids with a carbon number range of 10 to 20 derived from dimer acid raw materials, and monocarboxylic acid compounds with a carbon number range of 21 to 40, which are byproducts of dimer acid production. Monoamine compounds are compounds obtained by replacing the terminal carboxylic acid group of the aforementioned monocarboxylic acid compounds with a primary aminomethyl or amino group.

[0056] The monoamine compound, as component (b), is a component that inhibits the increase in molecular weight of the polyimide. During the polymerization of the polyamic acid or the polyimide, the monofunctional amino group of the monoamine compound reacts with the terminal anhydride group of the polyamic acid or the polyimide, thereby sealing the terminal anhydride group and inhibiting the increase in molecular weight of the polyamic acid or the polyimide.

[0057] (c) An amine compound obtained by replacing the terminal carboxylic acid group of a polyacid compound having a hydrocarbon group in the range of 41 to 80 carbon atoms with a primary aminomethyl or amino group (except for the dimer diamine);

[0058] Polybasic acid compounds containing hydrocarbon groups and having a carbon number of 41 to 80 are polybasic acid compounds whose main component is a tribasic acid compound having a carbon number of 41 to 80, which is a byproduct of the production of dimer acids. Additionally, polymeric fatty acids other than dimer acids having a carbon number of 41 to 80 may be included. Amine compounds are compounds obtained by replacing the terminal carboxylic acid group of the aforementioned polybasic acid compound with a primary aminomethyl or amino group.

[0059] Amine compounds, as component (c), contribute to the increase in the molecular weight of polyimides. The molecular weight of polyimides increases dramatically by reacting a trifunctional or higher amino group, primarily composed of a triamine derived from a trimer acid, with the terminal anhydride group of the polyamic acid or polyimide. Additionally, amine compounds derived from polymeric fatty acids other than dimer acids with 41 to 80 carbon atoms also contribute to the increase in the molecular weight of polyimides, thus causing gelation of the polyamic acid or polyimide.

[0060] When quantifying each component using gel permeation chromatography (GPC), to easily identify the peak start, peak top, and peak end of each component in the dimer diamine composition, a sample treated with acetic anhydride and pyridine was used, and cyclohexanone was used as an internal standard. Using the sample prepared as described, each component was quantified using the area percentage of the GPC chromatogram. The peak start and peak end of each component were used as the minimum values ​​of the respective peak curves, and the area percentage of the chromatogram was calculated based on these values.

[0061] Furthermore, the total percentage of components (b) and (c) in the dimer diamine composition, based on the area percentage of the chromatogram obtained by GPC determination, should preferably be 4% or less, and more preferably less than 4%. By setting the total percentage of components (b) and (c) to 4% or less, the expansion of the molecular weight distribution of the polyimide can be suppressed.

[0062] Furthermore, the area percentage of the chromatogram of component (b) is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. By setting it to this range, the decrease in the molecular weight of the polyimide can be suppressed, thereby expanding the range of the molar ratio of the tetracarboxylic dianhydride component and the diamine component. In addition, component (b) may not be included in the dimer diamine composition.

[0063] Furthermore, the area percentage of the chromatogram of component (c) is preferably 2% or less, more preferably 1.8% or less, and even more preferably 1.5% or less. By setting it within this range, the rapid increase in the molecular weight of the polyimide can be suppressed, thereby suppressing the rise of the dielectric loss tangent of the resin film over a wide frequency range. In addition, component (c) may not be included in the dimer diamine composition.

[0064] In addition, when the ratio of the area percentages of the chromatograms of components (b) and (c) is 1 or more, the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component / diamine component) is preferably set to 0.97 or more and less than 1.0. By setting this molar ratio, it is easier to control the molecular weight of the polyimide.

[0065] Furthermore, if the ratio of the area percentages of the chromatograms of components (b) and (c) is less than 1, the molar ratio of the tetracarboxylic dianhydride component and the diamine component (tetracarboxylic dianhydride component / diamine component) is preferably set to 0.97 or more and 1.1 or less. By setting this molar ratio, it is easier to control the molecular weight of the polyimide.

[0066] The dimer diamine composition can be made from commercially available products, and is preferably refined to reduce components other than the dimer diamine as component (a). For example, component (a) is preferably set to 96% or more in area. There are no particular limitations on the refining method, but known methods such as distillation or precipitation refining are preferred. Examples of commercially available dimer diamine compositions include PRIAMINE 1073 (trade name), PRIAMINE 1074 (trade name), and PRIAMINE 1075 (trade name) manufactured by Croda Japan.

[0067] In addition, the adhesive polyimide contains, relative to all diamine residues, in the range of 5 mol% to 25 mol% and preferably 10 mol% to 20 mol% of a diamine compound (hereinafter sometimes referred to as "diamine compound containing a reactive double bond"), which comprises a biphenyl skeleton or a naphthalene skeleton, and these biphenyl skeletons or naphthalene skeletons have at least one substituent containing an intercarbon double bond selected from the group consisting of vinyl, acrylate, methacrylate and allyl.

[0068] By including diamine residues derived from diamine compounds containing self-contained reactive double bonds within the specified range, it is possible to achieve a low dielectric loss tangent in adhesive polyimides, and also improve solder heat resistance and flame retardancy. Furthermore, by including highly reactive double bonds, cross-linking formation is possible, and flame-retardant compounds can be easily introduced into the polyimide backbone, thus further improving solder heat resistance and flame retardancy. When the diamine residues derived from diamine compounds containing self-contained reactive double bonds are less than 5 mol%, the improvement in dielectric properties, solder heat resistance, and flame retardancy is sometimes not observed. When the percentage exceeds 25 mol%, the diamine compounds containing reactive double bonds readily polymerize with each other, making cross-linking formation difficult.

[0069] As a diamine compound containing reactive double bonds, for example, the diamine compound represented by the following general formula (1) or general formula (2) can be preferably used. The diamine compounds represented by general formula (1) and general formula (2) can increase the concentration of aromatic rings in polyimide through their basic skeleton, suppress the mobility of polyimide molecules, and thus contribute to low dielectric loss tangent.

[0070] [Chemistry 1]

[0071]

[0072] In general formulas (1) and (2), X independently represents vinyl, acrylate, methacrylate, or allyl, and m and n independently represent integers from 0 to 3. Except for the case where m and n are both 0.

[0073] Preferred examples of diamine compounds containing reactive double bonds include 2,2'-divinyl-4,4'-diaminobiphenyl (VAB) and 4,8-divinylnaphthalene-2,6-diamine.

[0074] Other than those mentioned above, aromatic diamine compounds can be listed as diamine compounds that can be used in polyimides. Specific examples of these include: 1,4-diaminobenzene (p-PDA; p-phenylenediamine), 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), 2,2'-n-propyl-4,4'-diaminobiphenyl (m-NPB), 4-aminophenyl-4'-aminobenzoate (APAB), 2,2-bis-[4-(3-aminophenoxy)phenyl]propane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)]biphenyl, bis[1-(3-aminophenoxy)]biphenyl, bis[4-(3-aminophenoxy)phenyl]phenyl Methane, bis[4-(3-aminophenoxy)phenyl] ether, bis[4-(3-aminophenoxy)]benzophenone, 9,9-bis[4-(3-aminophenoxy)phenyl]fluorene, 2,2-bis-[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis-[4-(3-aminophenoxy)phenyl]hexafluoropropane, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-ditoluidine, 4,4'-methylenedi-2,6-diethylaniline, 3,3'-diaminodiphenylethane, 3,3'-Diaminobiphenyl, 3,3'-Dimethoxybenzidine, 3,3”-Diamino-p-triphenyl, 4,4'-[1,4-phenylenebis(1-methylethylene)]bisaniline, 4,4'-[1,3-phenylenebis(1-methylethylene)]bisaniline, bis(p-aminocyclohexyl)methane, bis(p-β-amino-tert-butylphenyl) ether, bis(p-β-methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis Diamine compounds including (β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole, piperazine, 2'-methoxy-4,4'-diaminobenzoylaniline, 4,4'-diaminobenzoylaniline, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 6-amino-2-(4-aminophenoxy)benzoxazole, and 1,3-bis(3-aminophenoxy)benzene.

[0075] Polyimide can be manufactured by reacting the tetracarboxylic anhydride component with a diamine component in a solvent to generate polyamic acid, followed by heating to close the ring. For example, the tetracarboxylic anhydride component and the diamine component are dissolved in an organic solvent at approximately equimolar amounts, and a polymerization reaction is carried out by stirring at a temperature in the range of 0°C to 100°C for 30 minutes to 24 hours, thereby obtaining polyamic acid as a precursor of polyimide. During the reaction, the reactants are dissolved in an organic solvent at a concentration in the range of 5% to 50% by weight, preferably 10% to 40% by weight. Examples of organic solvents used in polymerization reactions include: N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, methylcyclohexane, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, methanol, ethanol, benzyl alcohol, and cresol. These solvents can also be used in combination with two or more, and can also be used in combination with aromatic hydrocarbons such as xylene and toluene. Furthermore, there is no particular limitation on the amount of this organic solvent used, but it is preferable to adjust the concentration of the polyamic acid solution obtained by the polymerization reaction to about 5% to 50% by weight.

[0076] The synthesized polyamic acid is generally advantageous for use as a reaction solvent solution, and can be concentrated, diluted, or replaced with other organic solvents as needed. Furthermore, polyamic acid is generally advantageous due to its excellent solvent solubility. The viscosity of the polyamic acid solution is preferably in the range of 500 cps to 100,000 cps. If it deviates from this range, uneven thickness, streaks, and other defects are likely to occur in the film when coating operations are performed using a coating machine or similar equipment.

[0077] There are no particular limitations on the method for imidizing polyamic acid to form polyimide. For example, heat treatment such as heating in the solvent at a temperature range of 80°C to 400°C for 1 hour to 24 hours is preferred. Furthermore, regarding temperature, heating can be performed at a fixed temperature or the temperature can be changed midway through the process.

[0078] In adhesive polyimides, dielectric properties, coefficient of thermal expansion, tensile elastic modulus, and glass transition temperature can be controlled by selecting the types of tetracarboxylic anhydride and diamine components, or by using the molar ratio of two or more tetracarboxylic anhydride or diamine components. Furthermore, in adhesive polyimides having multiple polyimide structural units, they can exist in a block form or randomly, preferably randomly.

[0079] The concentration of imide groups in the adhesive polyimide is preferably 22% by weight or less, more preferably 20% by weight or less. Here, "imide group concentration" refers to the value obtained by dividing the molecular weight of the imide group (-(CO)2-N-) in the polyimide by the molecular weight of the overall structure of the polyimide. If the imide group concentration exceeds 22% by weight, the molecular weight of the resin itself decreases, and the low hygroscopicity deteriorates due to the increase of polar groups, while the Tg and tensile elastic modulus increase.

[0080] The most preferred structure for the adhesive polyimide is a fully imidized structure. A portion of the polyimide may be an amyl acid. The imidization rate can be measured using a Fourier transform infrared spectrophotometer (commercially available: Nippon Spectrophotometer, trade name: FT / IR620) and the attenuated total reflection (ATR) method, with a 10¹⁵ cm⁻¹ diameter as the reference value. -1 Using the nearby benzene ring absorber as a reference, from 1780 cm⁻¹ -1 The absorbance is calculated based on the C=O stretching of the imide group.

[0081] [Resin Composition]

[0082] The resin composition of one embodiment of the present invention contains the following components (A) and (B);

[0083] (A) Adhesive polyimide,

[0084] and

[0085] (B) Crosslinking agent.

[0086] <(A) Ingredient: Adhesive polyimide>

[0087] In the resin composition of this embodiment, the adhesive polyimide, which is component (A), is as described.

[0088] <(B) Component: Crosslinking Agent>

[0089] By using a crosslinking agent containing component (B), crosslinking of adhesive polyimide can be achieved, which can improve the solder heat resistance and flame retardancy of the resin film obtained from the resin composition, and suppress exudation and achieve low dielectric loss tangent.

[0090] Regarding the crosslinking agent that can be incorporated into the resin composition as component (B), any compound having a functional group within its molecule capable of reacting with a highly reactive substituent containing an intercarbon double bond in the adhesive polyimide (component (A)) to form a crosslinking agent is acceptable. Examples of such functional groups include vinyl, acrylate, methacrylate, allyl, and acryloyl groups. Furthermore, examples of compounds having such functional groups include 1,5-hexadiene, triallylamine, and dipentaerythritol hexaacrylate. Additionally, regarding the crosslinking agent as component (B), as shown in the examples described later, it can be a compound containing atoms such as phosphorus within its molecule. In this case, it is expected to further improve the flame retardancy of the resin film after crosslinking.

[0091] The content of component (B) in the resin composition is preferably in the range of 5 parts by weight or more and 30 parts by weight or less, more preferably in the range of 10 parts by weight or more and 25 parts by weight or less, relative to 100 parts by weight of component (A). If the content of component (B) is less than 5 parts by weight, cross-linking formation cannot be sufficiently achieved, making it difficult to improve the heat resistance, low dielectric loss tangent, and flame retardancy of the solder. If the content of component (B) exceeds 30 parts by weight, unreacted cross-linking agents become the cause of exudation, or the adhesion during resin film formation decreases, and the components (B) react with each other, sometimes reducing workability.

[0092] The crosslinking formation of component (A) and component (B) is carried out by reacting the substituents with intercarbon double bonds in the adhesive polyimide as component (A) with the functional groups contained in the crosslinking agent as component (B).

[0093] For example, the following methods can be used: (i) a method of adding a crosslinking agent as component (B) and heating immediately after the synthesis (imidization) of the adhesive polyimide; (ii) a method of heating after processing the resin composition containing components (A) and (B) into a predetermined shape (e.g., after coating onto any substrate or forming a film).

[0094] There are no particular limitations on the reaction conditions used for crosslinking formation; for example, heating in the range of 100°C to 220°C, preferably in the range of 120°C to 200°C, is preferable. The reaction time is preferably about 30 minutes to 24 hours. In addition, to accelerate the start of the reaction, the polymerization initiator described later as component (D) may be used as needed.

[0095] <(C) Component: Elastomer Resin>

[0096] The resin composition may further contain an elastomeric resin as component (C). By formulating the elastomeric resin as component (C), the toughness of the resin film can be improved, maintaining sufficient peel strength and a low dielectric loss tangent. The elastomeric resin as component (C) is preferably a copolymer of styrene or its derivatives and a conjugated diene compound, and includes its hydride. Here, styrene or its derivatives are not particularly limited, and examples include: styrene, methylstyrene, butylstyrene, divinylbenzene, vinyltoluene, etc. Furthermore, the conjugated diene compound is not particularly limited, and examples include: butadiene, isoprene, 1,3-pentadiene, etc.

[0097] Furthermore, the elastomer resin is preferably hydrogenated. Hydrogenation further improves thermal stability, reduces the likelihood of decomposition or polymerization, enhances aliphatic properties, and improves compatibility with adhesive polyimides.

[0098] The copolymer structure of the elastomeric resin as component (C) can be either a block structure or a random structure. Preferred specific examples of elastomeric resins include: styrene-butadiene-styrene block copolymer (SBS), styrene-butadiene-butylene-styrene block copolymer (SBBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), and styrene-ethylene-ethylene / propylene-styrene block copolymer (SEEPS), but are not limited to these specific examples.

[0099] The acid value of the elastomeric resin used as component (C) is 10 mg KOH / g or less, preferably 1 mg KOH / g or less, and more preferably 0 mg KOH / g. By incorporating an elastomeric resin with an acid value of 10 mg KOH / g or less into the resin composition, the dielectric loss tangent during resin film formation can be reduced, and good peel strength can be maintained. In contrast, if the acid value exceeds 10 mg KOH / g, the dielectric properties deteriorate due to the increase in polar groups, and the compatibility with component (A) deteriorates, resulting in reduced adhesion during resin film formation. Therefore, the lower the acid value, the better, and unmodified resin (i.e., resin with an acid value of 0 mg KOH / g) is most suitable as component (C) of the present invention. In the present invention, excellent adhesion is exhibited when the adhesive polyimide contains residues derived from dimer diamine, so even when using an unmodified (i.e., aliphatic) elastomeric resin, a decrease in adhesion strength can be avoided.

[0100] The elastomeric resin used as component (C) is preferably found to contain styrene units [-CH2CH(C6H5)-] in a ratio of 10% by weight or more and 65% by weight or less, more preferably in a ratio of 20% by weight or more and 65% by weight or less, and most preferably in a ratio of 30% by weight or more and 60% by weight or less. When the styrene unit content in the elastomeric resin is less than 10% by weight, the elastic modulus of the resin decreases, resulting in deterioration of its operability as a film. If the content increases to more than 65% by weight, the resin becomes rigid and difficult to use as an adhesive. In addition, the rubber component in the elastomeric resin decreases, thus leading to deterioration of its dielectric properties.

[0101] Furthermore, by having a styrene unit content within the specified range, the proportion of aromatic rings in the resin film increases. Therefore, when forming through holes (through holes) and blind holes by laser processing during the manufacturing of circuit boards using resin films, the absorption in the ultraviolet region can be improved, further enhancing laser processability.

[0102] The weight-average molecular weight of the elastomeric resin as component (C) is preferably in the range of 50,000 to 300,000, and more preferably in the range of 80,000 to 270,000. If the weight-average molecular weight of component (C) is lower than the range, the improvement effect on peel strength and dielectric properties may be lower; conversely, if it is higher than the range, the viscosity of the resin composition becomes higher, and the production of the resin film may become difficult.

[0103] Regarding the elastomer resin as component (C), commercially available products can be appropriately selected as long as the acid value is below 10 mg KOH / g. Examples of such commercially available elastomer resins preferably include, for example, A1535HU (trade name), G1652MU (trade name), G1726VS (trade name), G1645VS (trade name), FG1901GT (trade name), G1650MU (trade name), G1654HU (trade name), G1730VO (trade name), and MD1653MO (trade name) manufactured by Kraton.

[0104] The content of component (C) relative to 100 parts by weight of component (A) in the resin composition is in the range of 5 parts by weight or more and 100 parts by weight or less, preferably in the range of 10 parts by weight or more and 90 parts by weight or less, and more preferably in the range of 20 parts by weight or more and 80 parts by weight or less. When the content of component (C) is less than 5 parts by weight relative to 100 parts by weight of component (A), the peel strength may not be sufficiently exhibited. On the other hand, when the weight ratio of component (C) exceeds 100 parts by weight, the adhesion when forming the resin film decreases, and the viscosity increases due to the excessively high concentration of solid components in the resin composition, which may sometimes reduce workability.

[0105] <(D) Component: Polymerization Initiator>

[0106] The resin composition may also contain a polymerization initiator as component (D). Regarding the polymerization initiator as component (D), substances commonly used as free radical polymerization initiators can be used without particular limitation. Preferred polymerization initiators include, for example, dihalogen compounds, azo compounds, and organic peroxides. Among these, organic peroxides are preferred. Regarding the polymerization initiator as component (D), commercially available products can be appropriately selected. Examples of such commercially available polymerization initiators include, for example, Perbutyl (registered trademark) P (manufactured by Nippon Yushi Co., Ltd.) and Perbutyl (registered trademark) C (manufactured by Nippon Yushi Co., Ltd.).

[0107] The content of component (D) is preferably in the range of 0.5 parts by weight or more and 2.0 parts by weight or less, relative to 100 parts by weight of component (A) in the resin composition. When the content of component (D) is less than 0.5 parts by weight relative to 100 parts by weight of component (A), the effect of adding a polymerization initiator may not be sufficiently manifested. On the other hand, when the weight ratio of component (D) exceeds 2.0 parts by weight, the dielectric loss tangent may deteriorate, and the shelf life or workability of the resin composition may decrease.

[0108] Furthermore, as a curing method for adhesive polyimides, it is also possible to formulate compounds with unsaturated bonds, such as epoxy resins, epoxy resin curing agents, maleimides, activated ester resins, or resins with a styrene backbone, for curing.

[0109] Furthermore, the resin composition of this embodiment may contain solvents such as organic solvents. Since adhesive polyimides are solvent-soluble, the resin composition of this embodiment can be prepared into a polyimide solution (varnish) containing solvent. As an organic solvent, a mixed solvent is preferably used, for example, which is a mixture of one or more selected from N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 2-butanone, dimethyl sulfoxide (DMSO), hexamethylphosphoramide, N-methylcaprolactam, dimethyl sulfate, cyclohexanone, dioxane, tetrahydrofuran, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, cresol, etc., mixed with the aromatic hydrocarbon solvent in any ratio.

[0110] There are no particular restrictions on the content of the solvent, but it is preferable to adjust it to a concentration of about 5% to 30% by weight before use.

[0111] In the resin composition of this embodiment, inorganic fillers, organic fillers, plasticizers, curing accelerators, coupling agents, pigments, flame retardants, etc., can be appropriately formulated as any component, within the range that does not impair the effect of the invention. Examples of inorganic fillers include: silicon dioxide, aluminum oxide, beryllium oxide, niobium oxide, titanium oxide, magnesium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, magnesium fluoride, potassium silicofluoride, and metal salts of phosphonates. One or more of these can be used. Additionally, other resin components such as epoxy resin, fluororesin, and olefin resin can also be formulated as any component.

[0112] [Viscosity]

[0113] Regarding the viscosity of the resin composition, a viscosity range that improves operability when applying the resin composition and facilitates the formation of a coating film of uniform thickness is preferably set within the range of 3000 cps to 100000 cps, and more preferably within the range of 5000 cps to 50000 cps. If the viscosity deviates from this range, defects such as uneven thickness and streaks are likely to occur in the film when applying the coating using a coating machine or the like.

[0114] [Preparation of Resin Composition]

[0115] The resin composition can be prepared, for example, by adjusting component (B) into a resin solution of adhesive polyimide (component A) made using any solvent, and then adjusting and mixing components (C), (D), etc., as needed. In this case, to ensure uniform mixing, mixing can be performed while components (B), (C), and (D) are dissolved in the solvent, or a solvent exhibiting high solubility relative to components (B), (C), and (D) can be added.

[0116] The resin composition of this embodiment is a material that exhibits excellent flexibility and thermoplasticity when used to form an adhesive layer. Therefore, it has desirable properties for applications such as FPCs, rigid / flexible circuit boards, etc., as a material for adhesive layers or as an adhesive for covering films that protect wiring portions.

[0117] [Resin film]

[0118] The resin film of this embodiment is a single-layer or multi-layer resin film containing a polyimide layer, wherein the polyimide layer is formed by film formation of adhesive polyimide or the solid component (residue after removing the solvent) of the resin composition as the main component. In addition to excellent high-frequency characteristics, the resin film of this embodiment also possesses practically sufficient adhesion (especially peel strength), solder heat resistance, and flame retardancy.

[0119] The resin film in this embodiment is not particularly limited as long as it is an insulating resin film containing the thermoplastic resin layer. It can be a film (sheet) containing only insulating resin, or an insulating resin film laminated on a substrate such as a copper foil, glass plate, polyimide film, polyamide film, polyester film, etc.

[0120] (Relative permittivity)

[0121] In this embodiment, to ensure impedance matching when used in circuit boards such as FPCs, and to reduce signal loss, the relative permittivity (ε) of the resin film, measured using a split column dielectric resonator (SPDR) at 10 GHz after 24 hours of conditioning under constant temperature and humidity conditions (normal) of 23°C and 50% RH, is preferably 3.3 or less, more preferably 3.1 or less. If the relative permittivity exceeds 3.3, for example, when used in circuit boards such as FPCs, it is easy to cause adverse conditions such as signal loss in the high-frequency signal transmission path.

[0122] (Dielectric loss tangent)

[0123] Furthermore, in order to reduce electrical signal loss when the resin film of this embodiment is used in circuit boards such as FPCs, after being conditioned for 24 hours under constant temperature and humidity conditions (normal) of 23°C and 50% RH, the dielectric loss tangent (Tanδ) at 10 GHz, measured using a split column dielectric resonator (SPDR), is preferably less than 0.002, and more preferably less than 0.0017. If the dielectric loss tangent is 0.0020 or more, for example, when used in circuit boards such as FPCs, it is easy to cause adverse conditions such as electrical signal loss in the transmission path of high-frequency signals.

[0124] (Glass transition temperature)

[0125] The glass transition temperature (Tg) of the resin film in this embodiment is preferably 250°C or lower, more preferably in the range of 40°C or higher and 200°C or lower. With a Tg of 250°C or lower, hot pressing can be performed at low temperatures, thus mitigating internal stress generated during lamination and suppressing dimensional changes after circuit fabrication. If the Tg of the resin film exceeds 250°C, the temperature subsequently rises, raising concerns that this may impair the dimensional stability of the circuit after fabrication.

[0126] (thickness)

[0127] In this embodiment, the thickness of the resin film is preferably in the range of 5 μm or more and 125 μm or less, and more preferably in the range of 8 μm or more and 100 μm or less. If the thickness of the resin film is less than 5 μm, there is a concern that defects such as wrinkles may occur during the handling of the resin film during manufacturing, etc. On the other hand, if the thickness of the resin film exceeds 125 μm, there is a concern that the productivity of the resin film may be reduced.

[0128] (Tension elastic modulus)

[0129] From the viewpoints of reducing wrinkle formation, preventing air bubbles from being incorporated during lamination, and improving operability, the tensile elastic modulus of the resin film in this embodiment is preferably in the range of 0.1 GPa to 3.0 GPa, and more preferably in the range of 0.2 GPa to 2.0 GPa.

[0130] (Maximum elongation)

[0131] From the viewpoint of flexibility and crack prevention when used as an insulating resin layer in FPC, the maximum elongation of the resin film in this embodiment is preferably in the range of 30% to 250%, and more preferably in the range of 100% to 200%.

[0132] The resin film of this embodiment has a low dielectric loss tangent and excellent adhesion, so it is effectively used as an adhesive layer in cover films, a circuit board, a multilayer circuit board, an adhesive layer in resin-coated copper foil, a substrate bonding sheet, a pure adhesive bonding sheet, etc.

[0133] (Solder heat resistance)

[0134] The resin film of this embodiment preferably has a solder heat resistance (drying) of 280°C or higher, as measured under the test methods and conditions described in the later embodiments, and more preferably a solder heat resistance (moisture absorption) of 260°C or higher. If expansion occurs at the temperature during solder reflow, it can cause wiring misalignment or poor conductivity. Therefore, by ensuring that the solder heat resistance (drying and moisture absorption) is above the aforementioned temperature, the yield during the assembly process can be improved, and the reliability of electronic components can be enhanced. Until now, without pretreatment such as pre-drying, it has been impossible to obtain an adhesive film with high solder heat resistance and low dielectric loss tangent. Therefore, a requirement exists for high solder heat resistance without pretreatment, and the resin film of this embodiment meets these requirements.

[0135] (Peel strength)

[0136] The resin film in this embodiment preferably has a peel strength of 1.0 kN / m or higher, measured under the test methods and conditions described in the embodiments described later. With a peel strength of 1.0 kN / m or higher, practically sufficient adhesion is achieved between the wiring layer and the resin layer after circuit fabrication.

[0137] [Layered Body]

[0138] One embodiment of the present invention provides a laminate comprising a substrate and an adhesive layer laminated on at least one side of the substrate, the adhesive layer comprising the resin film. Furthermore, the laminate may comprise any layer other than those described above. Examples of substrates in the laminate include inorganic materials such as copper foil and glass plates; or resin materials such as polyimide films, polyamide films, and polyester films.

[0139] Preferred forms of laminates include cover films and resin-coated copper foils.

[0140] [Covering film]

[0141] A cover film, as a type of laminate, has a cover film material layer as a substrate and an adhesive layer laminated on one side of the cover film material layer, the adhesive layer comprising the resin film. Furthermore, the cover film may comprise any other layer besides the one described above.

[0142] The material of the covering membrane layer is not particularly limited; for example, polyimide-based films such as polyimide resin, polyetherimide resin, and polyamideimide resin, or polyamide-based films and polyester-based films can be used. Among these, polyimide-based films with excellent heat resistance are preferred. In addition, in order to effectively exhibit light-blocking, concealment, and design flexibility, the covering membrane material may also contain black pigments. Furthermore, any components such as matte pigments that suppress surface gloss can be included within the range that does not impair the improvement effect on dielectric properties.

[0143] The thickness of the covering membrane material layer is not particularly limited, but is preferably in the range of 5 μm or more and 100 μm or less.

[0144] Furthermore, the thickness of the adhesive layer is not particularly limited, but is preferably in the range of 10 μm or more and 75 μm or less.

[0145] The covering film of this embodiment can be manufactured using the methods illustrated below.

[0146] First, as a first method, after coating one side of the covering film material layer with a varnish-like resin composition containing a solvent, the adhesive layer is formed by drying at a temperature of 80°C to 180°C, for example, thereby forming a covering film having a covering film material layer and an adhesive layer.

[0147] Alternatively, as a second method, a varnish-like resin composition containing a solvent is coated onto any substrate, dried at a temperature of 80°C to 180°C, and then peeled off to form a resin film for an adhesive layer. The resin film is then heat-pressed onto a covering film material layer at a temperature of 60°C to 220°C, for example, to form a covering film.

[0148] [Resin-coated copper foil]

[0149] Another form of resin-coated copper foil is formed by laminating an adhesive layer on at least one side of a copper foil as a substrate, the adhesive layer comprising the resin film. Furthermore, the resin-coated copper foil of this embodiment may comprise any layer other than those described above.

[0150] The thickness of the adhesive layer in the resin-coated copper foil is preferably in the range of 2 μm to 125 μm, and more preferably in the range of 2 μm to 100 μm. If the thickness of the adhesive layer is less than the lower limit, problems such as insufficient adhesion may occur. On the other hand, if the thickness of the adhesive layer exceeds the upper limit, adverse conditions such as reduced dimensional stability may occur. Furthermore, from the viewpoint of achieving a low dielectric constant and a low dielectric loss tangent, it is preferable to set the thickness of the adhesive layer to 3 μm or more.

[0151] The copper foil in the resin-coated copper foil is preferably made of a material with copper or a copper alloy as the main component. The thickness of the copper foil is preferably 35 μm or less, more preferably in the range of 5 μm to 25 μm. From the viewpoint of production stability and operability, the lower limit of the copper foil thickness is preferably set to 5 μm. Furthermore, the copper foil can be rolled copper foil or electrolytic copper foil. Alternatively, commercially available copper foil can be used.

[0152] Resin-coated copper foil can be prepared, for example, by sputtering metal onto a resin film to form a seed layer, followed by copper plating to form a copper layer, or by laminating a resin film and copper foil using methods such as hot pressing. Furthermore, to form an adhesive layer on the copper foil, resin-coated copper foil can also be prepared by casting a coating solution of the resin composition, drying it to form a coating film, and then performing the required heat treatment.

[0153] [Metal-clad laminate]

[0154] (First Form)

[0155] One embodiment of the metal-clad laminate of the present invention includes an insulating resin layer and a metal layer laminated on at least one side of the insulating resin layer, wherein at least one layer of the insulating resin layer comprises the resin film. Furthermore, the metal-clad laminate of this embodiment may include any layer other than those described above.

[0156] (Second Form)

[0157] Another embodiment of the metal-clad laminate of the present invention is, for example, a so-called three-layer metal-clad laminate comprising an insulating resin layer, an adhesive layer laminated on at least one side of the insulating resin layer, and a metal layer laminated on the insulating resin layer through the adhesive layer, wherein the adhesive layer comprises the resin film. Furthermore, the three-layer metal-clad laminate may comprise any layer other than those described above. The adhesive layer of the three-layer metal-clad laminate may be disposed on one or both sides of the insulating resin layer, and the metal layer may be disposed on one or both sides of the insulating resin layer through the adhesive layer. That is, the three-layer metal-clad laminate may be a single-sided metal-clad laminate or a double-sided metal-clad laminate. A single-sided FPC or a double-sided FPC can be manufactured by etching the metal layer of the three-layer metal-clad laminate and performing wiring circuit processing.

[0158] As the insulating resin layer in a three-layer metal-clad laminate, there are no particular limitations as long as it includes a resin with electrical insulating properties. Examples include polyimide, epoxy resin, phenolic resin, polyethylene, polypropylene, polytetrafluoroethylene, silicone, and ethylene tetrafluoroethylene (ETFE), etc., with polyimide being preferred. The polyimide layer constituting the insulating resin layer can be a single layer or multiple layers, and it is preferable to include a non-thermoplastic polyimide layer.

[0159] The thickness of the insulating resin layer in a three-layer metal-clad laminate is preferably in the range of 1 μm to 125 μm, and more preferably in the range of 5 μm to 100 μm. If the thickness of the insulating resin layer is less than the lower limit, problems such as insufficient electrical insulation may occur. On the other hand, if the thickness of the insulating resin layer exceeds the upper limit, defects such as warping of the metal-clad laminate may occur.

[0160] The thickness of the adhesive layer in the three-layer metal-clad laminate is preferably in the range of 0.1 μm to 125 μm, and more preferably in the range of 0.3 μm to 100 μm. In the three-layer metal-clad laminate of this embodiment, if the thickness of the adhesive layer is less than the lower limit value, problems such as insufficient adhesion may occur. On the other hand, if the thickness of the adhesive layer exceeds the upper limit value, adverse conditions such as reduced dimensional stability may occur. Furthermore, from the viewpoint of reducing the dielectric constant and the dielectric loss tangent of the overall insulating layer of the laminate of insulating resin layer and adhesive layer, the thickness of the adhesive layer is preferably set to 3 μm or more.

[0161] Furthermore, the ratio of the thickness of the insulating resin layer to the thickness of the adhesive layer (thickness of the insulating resin layer / thickness of the adhesive layer) is preferably in the range of 0.1 to 3.0, and more preferably in the range of 0.15 to 2.0. By setting this ratio, warping of the three-layer metal-clad laminate can be suppressed. In addition, the insulating resin layer may contain fillers as needed. Examples of fillers include: silica, alumina, magnesium oxide, beryllium oxide, boron nitride, aluminum nitride, silicon nitride, aluminum fluoride, calcium fluoride, and metal salts of organophosphonic acids. One or more of these can be used.

[0162] [Circuit board]

[0163] The circuit board of the present invention is formed by wiring the metal layers of the metal-clad laminate of any of the embodiments. By using conventional methods to pattern one or more metal layers of the metal-clad laminate to form a wiring layer (conductor circuit layer), circuit boards such as FPCs can be manufactured. Furthermore, the circuit board may include a cover film covering the wiring layer.

[0164] [Example]

[0165] The following embodiments illustrate the features of the present invention in more detail. However, the scope of the present invention is not limited to these embodiments. Furthermore, in the following embodiments, unless otherwise specified, various measurements and evaluations are performed based on the following principles.

[0166] [Determination of the weight-average molecular weight (Mw) of polyimide]

[0167] Weight-average molecular weight was determined using a gel permeation chromatography system (manufactured by Tosoh Corporation, trade name: HLC-8220GPC). Polystyrene was used as the standard, and tetrahydrofuran (THF) was used as the developing solvent.

[0168] [Hydroxy equivalent]

[0169] The determination was performed according to Japanese Industrial Standards (JIS) K 0070. Specifically, a potentiometric titration apparatus was used, with 1,4-dioxane as the solvent, acetylation was performed using 1.5 mol / L acetyl chloride, excess acetyl chloride was decomposed using water, and titration was performed using 0.5 mol / L potassium hydroxide.

[0170] [Phosphorus content]

[0171] Sulfuric acid, hydrochloric acid, and perchloric acid were added to the sample, and the mixture was heated and wet-ashed to determine all phosphorus atoms as orthophosphoric acid. Vanadate and molybdate were reacted in a sulfuric acid solution, and the absorbance of the resulting vanadium-molybdate complex was measured at 420 nm. The phosphorus atom content was determined as a percentage using a calibration curve prepared in advance with potassium dihydrogen phosphate.

[0172] [Field desorption mass spectrometry (FD-MS)]

[0173] Molecular weight was determined using a JMS-T100GCV manufactured by Nippon Electronics.

[0174] [Determination of Storage Elasticity Coefficient]

[0175] The measurements were performed using a dynamic viscoelasticity measuring apparatus (dynamic mechanical analyzer (DMA): manufactured by TA Instruments, trade name: RSA-G2).

[0176] The storage elasticity coefficient at 30℃ is 1.0 × 10⁻⁶. 9 The storage elasticity coefficient at 280℃ and above Pa is 3.0 × 10⁻⁶. 8 Polyimides with a strength of Pa or higher are defined as "non-thermoplastic polyimides". Additionally, the storage elastic modulus at 30°C is 1.0 × 10⁻⁶. 8 Storage elasticity coefficient above Pa and at 280℃ is less than 3.0 × 10⁻⁶. 7 The polyimide of Pa is set as "thermoplastic polyimide".

[0177] [Evaluation of dielectric properties]

[0178] Using a vector network analyzer (manufactured by Agilent Technologies, trade name: Vector Network Analyzer E8363C) and an SPDR resonator, the relative permittivity (ε) and dielectric loss tangent (Tanδ) of the polyimide film (cured polyimide film) were measured at a frequency of 10 GHz after being placed at a temperature of 23°C and a humidity of 50%RH for 24 hours.

[0179] [Glass transition temperature (Tg)]

[0180] Adhesive sheets, pressed under conditions of 160℃, 3.5MPa, and 60 minutes, were cut into 5mm × 20mm test pieces. Dynamic viscoelasticity was measured using a dynamic viscoelasticity measuring device (DMA: manufactured by TA Instruments, trade name: RSA-G2) from 30℃ to 200℃ at a heating rate of 4℃ / min and a frequency of 11Hz. The temperature at which the change in elastic modulus (tanδ) was the largest was set as the glass transition temperature.

[0181] [Tensive modulus of elasticity and maximum elongation]

[0182] Using a tension tester (Tensilon manufactured by Orientec), a tensile test was conducted on a resin film test piece (width: 12.7 mm, length: 127 mm) at a speed of 50 mm / min to determine the tensile elastic modulus and maximum elongation at 25°C.

[0183] [Solder Heat Resistance Test (Drying)]

[0184] A single copper foil of a double-sided copper-clad laminate (manufactured by NIPPON STEEL Chemical & Material Co., Ltd., trade name: Espanex MB12-25-12UEG) was etched away. The other copper foil side was then laminated with an adhesive sheet in a copper foil-clad configuration, and pressed under conditions of 160°C, 3.5 MPa, and 60 minutes. The copper foil-coated test piece was dried at 135°C for 60 minutes, then immersed in a solder bath at evaluation temperatures ranging from 260°C to 300°C in increments of 10°C for 10 seconds. The adhesion was observed to check for defects such as foaming, expansion, and peeling. As a criterion, no defects were detected at 280°C and marked as ○ (good), while defects were detected and marked as × (bad).

[0185] [Solder Heat Resistance Test (Moisture Absorption)]

[0186] The copper foil on one side of a double-sided copper-clad laminate (manufactured by NIPPON STEEL Chemical & Material Co., Ltd., trade name: Espanex MB12-25-12UEG) was etched away. The other copper foil side was then laminated with an adhesive sheet, held together by the copper foil. The laminate was pressed under the conditions of 160°C, 3.5 MPa, and 60 minutes. After the copper foil-coated test pieces were placed at 40°C and 90% RH for 72 hours, they were immersed in solder baths at evaluation temperatures ranging from 240°C to 300°C in increments of 10°C for 10 seconds each. The adhesion was observed to check for defects such as foaming, expansion, and peeling. As a criterion, no defects were detected at 260°C and marked as ○ (good), while defects were detected and marked as × (bad).

[0187] [Determination of peel strength]

[0188] A double-sided copper-clad laminate (manufactured by NIPPON STEEL Chemical & Material Co., Ltd., trade name: Espanex MB12-25-12UEG) was cut into pieces with a width of 50 mm and a length of 100 mm. The adhesive sheet used as the test object was placed on the copper foil side of the sample after etching to remove the copper foil on one side. Then, a polyimide film (manufactured by Toray-DuPont Co., Ltd., trade name: Kapton 50EN-S) was laminated on the adhesive sheet. The laminate was prepared by pressing under the conditions of temperature: 160°C, pressure: 3.5 MPa and time: 60 minutes. The laminate was cut into 5mm wide pieces to make test pieces. Using a tensile testing machine (manufactured by Toyo Seiki Co., Ltd., trade name: Strograph VE), the test pieces were stretched in a 180° direction at a speed of 50mm / min. The peel strength between the adhesive sheet and the copper foil at this time was measured and set as the peel strength.

[0189] [Evaluation methods for membrane retention]

[0190] Cut the adhesive sheet into test pieces 20mm wide and 20mm long. Bend the piece along the diagonal to form a crease, then open it and observe the condition of the film. At this point, a test piece without cracking after opening the crease is designated as "good," while a piece showing some cracking is designated as "unacceptable."

[0191] [Evaluation methods for flame retardancy]

[0192] Flame retardancy was evaluated using the following method. Polyimide films (manufactured by Toray-DuPont, trade name: Kapton 50EN-S) were laminated on both sides of a resin film with two layers of 50 μm thickness. The film was pressed at 160°C, 3.5 MPa, and for 60 minutes. Samples were cut into 200 mm ± 5 mm × 50 mm ± 1 mm pieces, rolled into tubes approximately 12.7 mm in diameter and 200 mm ± 5 mm in length, and test pieces were prepared according to UL 94VTM standards. A flammability test was performed if the time to extinguish the flame was less than 11 seconds. A "○" (Good) was awarded if the time exceeded 11 seconds. A "×" (Poor) was awarded if the time to extinguish the flame was less than 11 seconds.

[0193] [Methods for determining amine value]

[0194] Weigh approximately 2 g of the dimerized diamine composition into a 200 mL–250 mL Erlenmeyer flask. Using phenolphthalein as an indicator, before the solution turns a light pink, add dropwise 0.1 mol / L ethanolic potassium hydroxide solution and dissolve it in approximately 100 mL of neutralized butanol. Add 3–7 drops of phenolphthalein solution and titrate with 0.1 mol / L ethanolic potassium hydroxide solution while stirring before the sample solution turns a light pink. Add 5 drops of bromophenol blue solution and titrate with 0.2 mol / L hydrochloric acid / isopropanol solution while stirring before the sample solution turns yellow.

[0195] The amine value is calculated using the following formula (1).

[0196] Amine value = {(V2×C2)-(V1×C1)}×M KOH / m···(1)

[0197] Here, the amine value is expressed in mg-KOH / g, M KOH The molecular weight of potassium hydroxide is 56.1. Additionally, V and C represent the volume and concentration of the solution used for titration, respectively. The subscripts 1 and 2 indicate a 0.1 mol / L ethanolic potassium hydroxide solution and a 0.2 mol / L hydrochloric acid / isopropanol solution, respectively. Furthermore, m is the sample weight in grams.

[0198] [Calculation of GPC and the percentage of area in the chromatogram]

[0199] (a) Dimeric diamine

[0200] (b) Monoamine compounds obtained by replacing the terminal carboxylic acid group of a monocarboxylic acid compound having 10 to 40 carbon atoms with a primary aminomethyl or amino group.

[0201] (c) An amine compound obtained by replacing the terminal carboxylic acid group of a polybasic acid compound having a hydrocarbon group in the range of 41 to 80 carbon atoms with a primary aminomethyl or amino group (except for the dimer diamine).

[0202] Regarding GPC, a 100 mg solution was prepared by pretreating 20 mg of a dimerized diamine composition with 200 μL of acetic anhydride, 200 μL of pyridine, and 2 mL of THF, and then diluted with 10 mL of THF (containing 1000 ppm cyclohexanone). The prepared sample was analyzed using a Tosoh (TOSOH) HLC-8220 GPC at the following conditions: TSK-gel G2000HXL and G1000HXL columns, flow rate of 1 mL / min, column (oven) temperature of 40 °C, and injection volume of 50 μL. Cyclohexanone was used as a standard to correct for elution time.

[0203] At this point, adjustments were made to change the retention time of the cyclohexanone main peak from 27 minutes to 31 minutes, and to make the time from the start to the end of the cyclohexanone main peak 2 minutes. Furthermore, the time of the main peak excluding the cyclohexanone peak was changed from 18 minutes to 19 minutes, and the time from the start to the end of the main peak excluding the cyclohexanone peak was changed from 2 minutes to 4 minutes and 30 seconds. These were then used as components (a) to (c), and the following tests were performed.

[0204] (a) The components represented by the main peak;

[0205] (b) The component represented by the GPC peak detected at a later time, based on the minimum value on the time side of the main peak with a later retention time;

[0206] (c) The component represented by the GPC peak detected at an earlier time, based on the minimum value of the retention time of the main peak at an earlier time.

[0207] The abbreviations used in this embodiment refer to the following compounds.

[0208] BTDA: 3,3',4,4'-benzophenone tetracarboxylic dianhydride

[0209] VAB: 2,2'-divinyl-4,4'-diaminobiphenyl

[0210] DDA: A substance obtained by distillation and refining PRIAMINE 1075, manufactured by Croda Japan Co., Ltd. (component a: 99.2%, component b: 0%, component c: 0.8%, amine value: 210 mg KOH / g).

[0211] N-12: Dodecanedioic acid dihydrazide

[0212] NMP: N-methyl-2-pyrrolidone

[0213] 6FDA: 4,4'-(hexafluoroisopropylidene)phthalic anhydride

[0214] BPDA: 3,3',4,4'-Biphenyltetracarboxylic acid dianhydride

[0215] Elastomer Resin 1: Manufactured by KRATON, trade name: A1535HU (hydrogenated polystyrene elastomer resin, styrene unit content 58% by weight, specific gravity: 0.96, acid-free)

[0216] Furthermore, in the DDA, the "%" for components a, b, and c refers to the area percentage of the chromatogram in the GPC assay. Additionally, the molecular weight of the DDA is calculated using the following formula (1).

[0217] Molecular weight = 56.1 × 2 × 1000 / amine value…(1)

[0218] (Synthesis example 1)

[0219] <Preparation of phosphorus-containing phenols (phosphorus compound A)>

[0220] 1500g of phosphorus oxychloride, 471g of phenol, and 1.2g of magnesium chloride as a catalyst were added to a 2-liter four-necked flask containing a stirrer, a thermometer, and a hydrochloric acid recovery device (the condenser connected to the water scrubber).

[0221] While stirring the obtained mixed solution, the temperature was slowly increased to 90°C over approximately 3 hours to carry out the reaction. The generated hydrogen chloride (hydrochloric acid gas) was recovered using a water scrubber. Then, the pressure inside the flask was slowly reduced to 12 kPa at 120°C to remove unreacted phosphorus trichloride, phenol, and the byproduct hydrogen chloride, thereby obtaining 1055 g of monophenyl phosphorodichloride (MPC).

[0222] A 2-liter four-necked flask, including a stirrer, thermometer, dropping funnel, and condenser, was filled with 822 g of 2,3,5-trimethylhydroquinone, 6.3 g of aluminum chloride as a catalyst, and 1000 g of 1,2-dichlorobenzene as a solvent. Additionally, 570 g of the aforementioned MPC was filled into the dropping funnel.

[0223] While stirring the mixed solution in the four-necked flask, the temperature was heated to 110°C. While maintaining this temperature (110°C), MPC was added dropwise through a dropping funnel over a period of 2 hours. After the addition was complete, the temperature was slowly raised to 160°C and stirred for 4 hours to obtain the reaction product. Then, the mixture was cooled to 105°C, and the pressure inside the flask was slowly reduced to 6.3 kPa to remove the byproduct hydrogen chloride.

[0224] The reaction product was washed with dilute hydrochloric acid and water, then neutralized and washed again with an aqueous sodium carbonate solution, followed by washing with water. The mixture was then heated to 150°C, reduced to 1 kPa, and water and 1,2-dichlorobenzene were recovered. Subsequently, steam distillation was performed at 110°C under reduced pressure (1 kPa) to remove low-boiling components. The mixture was cooled to room temperature, yielding 1195 g of a dark brown solid containing phosphorus-containing phenolic compound (phosphorus compound A). The obtained mixture of phosphorus compound A contained 6.5% phosphorus and had a hydroxyl equivalent of 272 g / eq.

[0225] (Synthesis example 2)

[0226] <Preparation of Phosphorus-Containing Vinyl Benzyl Ether Compounds (Phosphorus Compound B)>

[0227] 200.0 g of phosphorus compound A and 133.2 g of diethylene glycol dimethyl ether were added to a separable glass flask including a stirrer, thermometer, and cooling tube. The mixture was heated to 75°C under nitrogen and allowed to dissolve. 134.0 g of CMS-P (trade name, manufactured by AGC Seimi Chemical) was added, and after homogenization, 10.0 g of tetrabutylammonium bromide and 222.4 g of 50% potassium carbonate aqueous solution were added. The reaction was allowed to proceed for 10 hours.

[0228] Subsequently, the reaction solution was concentrated and dissolved in 674.4 g of toluene, then neutralized with a 10% sodium dihydrogen phosphate aqueous solution and washed with water. The solution was then dehydrated and filtered, and the solvent was further concentrated to obtain 340.0 g of a toluene solution containing a phosphorus-containing vinyl benzyl ether compound (phosphorus compound B). FD-MS analysis of the obtained phosphorus compound B confirmed the peak at molecular weight 674, thus identifying the compound with the following structure as the major component. Furthermore, the phosphorus content was 4.7%.

[0229] [Chemistry 2]

[0230]

[0231] (Synthesis example 3)

[0232] <Preparation of Phosphorus-Containing Methacryloyl Compounds (Phosphorus Compound C)>

[0233] 200.0 g of phosphorus compound A, 133.2 g of tetrahydrofuran, and 104.0 g of triethylamine were added to a separable glass flask containing a stirrer, thermometer, cooling tube, and dropping funnel. After dissolution, the mixture was cooled to below 5°C using an ice bath. Under nitrogen atmosphere, 89.6 g of methacrylamide chloride was added dropwise over 1 hour, and the reaction was continued for 2 hours.

[0234] Subsequently, the reaction solution was concentrated and dissolved in 608.0 g of toluene, and then washed in the following order: hydrochloric acid, sodium carbonate aqueous solution, and water. After washing with water, the solution was dehydrated and filtered, and the solvent was then concentrated to obtain 212.64 g of a toluene solution containing a phosphorus-containing methacryloyl compound (phosphorus compound C). FD-MS analysis of the obtained phosphorus compound C confirmed a peak at a molecular weight of 578, thus confirming that the compound with the following structure is the major component. Furthermore, the phosphorus content was 5.6%.

[0235] [Chemistry 3]

[0236]

[0237] [Example 1]

[0238] In a 1000 ml separable flask, 58.71 g of BTDA (0.1819 mol), 87.01 g of DDA (0.1629 mol), 4.28 g of VAB (0.0181 mol), 210 g of NMP, and 140 g of xylene were added and mixed thoroughly at 40 °C for 1 hour to prepare a polyamic acid solution. The polyamic acid solution was heated to 190 °C and stirred for 10 hours. Then, 125 g of xylene was added to prepare imidized polyimide solution 1 (solid composition: 32.7 wt%, weight average molecular weight: 56,611, thermoplastic polyimide), which was designated as polyimide varnish 1a.

[0239] [Example 2]

[0240] In 100g of the polyimide solution 1 prepared in Example 1, 5.6g of phosphorus-containing vinyl benzyl ether compound B, 6.5g of elastomer resin 1 and 0.3g of perbutyl P (trade name, manufactured by Nippon Yushi Co., Ltd.) were added, and xylene and NMP were added to make the solid content 30% by weight. The mixture was diluted and stirred to prepare polyimide varnish 2a.

[0241] [Example 3]

[0242] In a 1000 ml separable flask, 59.97 g of BTDA (0.1857 mol), 83.51 g of DDA (0.1563 mol), 6.52 g of VAB (0.0276 mol), 210 g of NMP, and 140 g of xylene were added and mixed thoroughly at 40 °C for 1 hour to prepare a polyamic acid solution. The polyamic acid solution was heated to 190 °C and stirred for 10 hours. Then, 125 g of xylene was added to prepare imidized polyimide solution 2 (solid composition: 31 wt%, weight average molecular weight: 52,515, thermoplastic polyimide), which was designated as polyimide varnish 3a.

[0243] [Example 4]

[0244] In 100g of the polyimide solution 2 prepared in Example 3, 5.6g of phosphorus compound B, 6.5g of elastomer resin 1 and 0.3g of perbutyl P were added, and xylene and NMP were added to make the solid content 30% by weight. The mixture was diluted and stirred to prepare polyimide varnish 4a.

[0245] [Example 5]

[0246] The amount of phosphorus compound B was set to 7.5 g, and the polyimide varnish 5a was prepared in the same manner as in Example 4.

[0247] [Example 6]

[0248] Polyimide varnish 6a was prepared in the same manner as in Example 4, except that 7.5g of phosphorus compound C was used in place of 5.6g of phosphorus compound B.

[0249] [Example 7]

[0250] In a 1000 ml separable flask, 71.81 g of 6FDA (0.1613 mol), 72.53 g of DDA (0.1358 mol), 5.66 g of VAB (0.0240 mol), 210 g of NMP, and 140 g of xylene were added and mixed thoroughly at 40 °C for 1 hour to prepare a polyamic acid solution. The polyamic acid solution was heated to 190 °C and stirred for 10 hours. Then, 125 g of xylene was added to prepare imidized polyimide solution 3 (solid content: 32.6 wt%, weight average molecular weight: 54,197, thermoplastic polyimide), which was designated as polyimide varnish 7a.

[0251] [Example 8]

[0252] In a 1000 ml separable flask, 56.73 g of BPDA (0.1924 mol), 86.52 g of DDA (0.1619 mol), 6.75 g of VAB (0.0286 mol), 210 g of NMP, and 140 g of xylene were added and mixed thoroughly at 40 °C for 1 hour to prepare a polyamic acid solution. The polyamic acid solution was heated to 190 °C and stirred for 10 hours. Then, 125 g of xylene was added to prepare imidized polyimide solution 4 (solid composition: 32.5 wt%, weight average molecular weight: 55,345, thermoplastic polyimide), which was designated as polyimide varnish 8a.

[0253] [Example 9]

[0254] Polyimide varnish 9a was prepared in the same manner as in Example 4, except that elastomer resin 1 was not incorporated.

[0255] Comparative Example 1

[0256] In a 1000 ml separable flask, 55.51 g of BTDA (0.1721 mol), 94.49 g of DDA (0.1735 mol), 210 g of NMP, and 140 g of xylene were added and mixed thoroughly at 40 °C for 1 hour to prepare a polyamic acid solution. The polyamic acid solution was heated to 190 °C and stirred for 10 hours. Then, 125 g of xylene was added to prepare imidized polyimide solution 5 (solid composition: 31 wt%, weight average molecular weight: 80,900, thermoplastic polyimide), which was designated as polyimide varnish 10a.

[0257] Comparative Example 2

[0258] 1.12 g of N-12 was added to 100 g of the polyimide solution 5 prepared in Comparative Example 1, and xylene and NMP were added to dilute the solution to a solid content of 31% by weight and stirred to prepare polyimide varnish 11a.

[0259] Table 1 shows the formulations of Examples 1 to 9 and Comparative Examples 1 to 2.

[0260] [Table 1]

[0261]

[0262] [Example 10]

[0263] The polyimide varnish 1a prepared in Example 1 was coated on one side of a polyethylene terephthalate (PET) film that had undergone demolding treatment. After drying at 100°C for 5 minutes, it was dried at 120°C for 10 minutes and then peeled off to prepare a resin sheet 1b (thickness: 25 μm).

[0264] The evaluation results of the following tablets are as follows.

[0265] Relative permittivity: 2.7, dielectric loss tangent: 0.0017, flame retardancy: ○

[0266] [Example 11]

[0267] Resin sheet 2b was prepared using polyimide varnish 2a in the same manner as in Example 10.

[0268] The evaluation results of the following tablets are as follows.

[0269] Relative permittivity: 2.6, Dielectric loss tangent: 0.0015, Tensile modulus: 0.5 GPa, Maximum elongation: 171%, Tg: 44℃, Film retention: Good, Solder heat resistance test (dry): ○, Solder heat resistance test (moisture absorption): ○, Peel strength: 1.2 kN / m, Flame retardancy: ○

[0270] [Example 12]

[0271] Resin sheet 3b was prepared using polyimide varnish 3a in the same manner as in Example 10.

[0272] The evaluation results of the following tablets are as follows.

[0273] Relative permittivity: 2.6, dielectric loss tangent: 0.0016, flame retardancy: ○

[0274] [Example 13]

[0275] Resin sheet 4b was prepared using polyimide varnish 4a in the same manner as in Example 10.

[0276] The evaluation results of the following tablets are as follows.

[0277] Relative permittivity: 2.6, Dielectric loss tangent: 0.0014, Tensile modulus: 0.7 GPa, Maximum elongation: 199%, Tg: 49℃, Film retention: Good, Solder heat resistance test (dry): ○, Solder heat resistance test (moisture absorption): ○, Peel strength: 1.2 kN / m, Flame retardancy: ○

[0278] [Example 14]

[0279] Resin sheet 5b was prepared using polyimide varnish 5a in the same manner as in Example 10.

[0280] The evaluation results of the 5b tablets are as follows.

[0281] Relative permittivity: 2.6, Dielectric loss tangent: 0.0014, Tensile modulus: 0.7 GPa, Maximum elongation: 162%, Tg: 46℃, Film retention: Good, Solder heat resistance test (dry): ○, Solder heat resistance test (moisture absorption): ○, Peel strength: 1.1 kN / m, Flame retardancy: ○

[0282] [Example 15]

[0283] Resin sheet 6b was prepared using polyimide varnish 6a in the same manner as in Example 10.

[0284] The evaluation results of the following tablets are as follows.

[0285] Relative permittivity: 2.7, Dielectric loss tangent: 0.0017, Tensile modulus: 0.8 GPa, Maximum elongation: 183%, Tg: 49℃, Film retention: Good, Solder heat resistance test (dry): ○, Solder heat resistance test (moisture absorption): ○, Peel strength: 1.1 kN / m, Flame retardancy: ○

[0286] [Example 16]

[0287] Resin sheet 7b was prepared using polyimide varnish 7a in the same manner as in Example 10.

[0288] The evaluation results of the following tablets are as follows.

[0289] Relative permittivity: 2.5, dielectric loss tangent: 0.0014, flame retardancy: ○

[0290] [Example 17]

[0291] Resin sheet 8b was prepared using polyimide varnish 8a in the same manner as in Example 10.

[0292] The evaluation results of the following tablets are as follows.

[0293] Relative permittivity: 2.7, dielectric loss tangent: 0.0015, flame retardancy: ○

[0294] [Example 18]

[0295] Resin sheet 9b was prepared using polyimide varnish 9a in the same manner as in Example 10.

[0296] The evaluation results of the following tablets are as follows.

[0297] Relative permittivity: 2.7, Dielectric loss tangent: 0.0016, Tensile modulus: 0.9 GPa, Maximum elongation: 130%, Tg: 47℃, Film retention: Good, Solder heat resistance test (dry): ○, Solder heat resistance test (moisture absorption): ○, Peel strength: 0.5 kN / m, Flame retardancy: ○

[0298] Comparative Example 4

[0299] Resin sheet 10b was prepared using polyimide varnish 10a in the same manner as in Example 10.

[0300] The evaluation results of the various components of tablet 10b are as follows.

[0301] Relative permittivity: 2.6, dielectric loss tangent: 0.0021, flame retardancy: ×

[0302] Comparative Example 5

[0303] Resin sheet 11b was prepared using polyimide varnish 11a in the same manner as in Example 10.

[0304] The evaluation results of the following tablets are as follows.

[0305] Relative permittivity: 2.6, Dielectric loss tangent: 0.0021, Tensile modulus: 0.5 GPa, Maximum elongation: 119%, Tg: 44℃, Film retention: Good, Solder heat resistance test (dry): ×, Solder heat resistance test (moisture absorption): ×, Peel strength: 1.0 kN / m, Flame retardancy: ×

[0306] The results are summarized in Table 2.

[0307] [Table 2]

[0308]

[0309] As confirmed by Table 2, compared with resin sheets 10b and 11b of Comparative Examples 4 and 5, the resin sheets 1b to 9b of Examples 10 to 18, which had modified resins, had a dielectric loss tangent of 0.0017 or less, resulting in high peel strength, good solder heat resistance, and flame retardancy. Based on these results, it is confirmed that the adhesive sheet of the resin film of this embodiment can be expected to reduce transmission losses in high-frequency bands, such as around 10 GHz to 20 GHz, and while maintaining flexibility or film retention, it exhibits excellent peel strength, solder heat resistance, and flame retardancy.

[0310] As shown in the above embodiments, a clear improvement in dielectric properties can be observed in polyimides using aliphatic diamines and vinyl-containing diamines as raw materials. Consequently, improvements in peel strength, solder heat resistance, and flame retardancy can also be observed in resin compositions using these polyimides.

[0311] Based on the above results, it is confirmed that the resin film of this embodiment, as a material for circuit boards such as high-frequency FPCs, can be preferably used in various high-frequency signal transmission devices, such as receivers using direct conversion methods.

[0312] The embodiments of the present invention have been described in detail above for illustrative purposes, but the present invention is not limited to the described embodiments and can be modified in various ways.

Claims

1. A polyimide, characterized by, It contains tetracarboxylic acid residues derived from the tetracarboxylic anhydride component and diamine residues derived from the diamine component. The composition contains, relative to all diamine residues, diamine residues derived from a dimer diamine composition in the range of 40 mol% to 95 mol%, wherein the dimer diamine composition is a dimer diamine whose main component is a dimer diamine in which the two terminal carboxylic acid groups of a dimer acid are replaced with primary aminomethyl or amino groups. The compound contains, relative to all diamine residues, diamine residues derived from a diamine compound comprising a biphenyl or naphthalene skeleton, wherein the biphenyl or naphthalene skeleton has at least one substituent containing an intercarbon double bond selected from the group consisting of vinyl, acrylate, methacrylate, and allyl groups. The layer formed by film formation was conditioned for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH. The dielectric loss tangent Tanδ at 10 GHz, measured by a dielectric resonator in a separation column, was less than 0.

002.

2. A resin composition characterized by comprising: It contains the following components (A) and (B): (A) the polyimide as described in claim 1, and (B) Crosslinking agent, And relative to 100 parts by weight of component (A), the content of component (B) is in the range of 5 parts by weight or more and 30 parts by weight or less.

3. The resin composition according to claim 2, characterized in that, It also contains the following component (C): (C) Elastomer resin. And relative to 100 parts by weight of component (A), the content of component (C) is in the range of 5 parts by weight or more and 100 parts by weight or less.

4. The resin composition according to claim 2 or 3, characterized in that, It also contains the following component (D): (D) Polymerization initiator, And relative to 100 parts by weight of component (A), the content of component (D) is in the range of 0.5 parts by weight or more and 2.0 parts by weight or less.

5. A resin film, characterized in that, Contains the polyimide as described in claim 1.

6. The resin membrane according to claim 5, wherein after being conditioned for 24 hours under constant temperature and humidity conditions of 23°C and 50%RH, the dielectric loss tangent Tanδ at 10 GHz, measured by a separation column dielectric resonator, is less than 0.

002.

7. A laminate comprising a substrate and an adhesive layer laminated on at least one side of the substrate, characterized in that, The adhesive layer comprises the resin film as described in claim 5 or 6.

8. A covering film comprising a covering film material layer and an adhesive layer laminated on the covering film material layer, characterized in that, The adhesive layer comprises the resin film as described in claim 5 or 6.

9. A resin-coated copper foil, formed by laminating an adhesive layer onto a copper foil, characterized in that, The adhesive layer comprises the resin film as described in claim 5 or 6.

10. A metal-clad laminate, characterized in that, It has an insulating resin layer and a metal layer laminated on at least one side of the insulating resin layer. At least one layer of the insulating resin layer comprises the resin film as described in claim 5 or 6.

11. A circuit board, which is formed by wiring the metal layer of the metal-clad laminate as described in claim 10.

Images