Carboxyl group-containing modified imide resin, resin composition, laminate, and flexible printed wiring board

Abstract

Provided is a carboxyl group-containing modified imide resin which is useful as an adhesive for an electronic member or a material for forming a coating film such as a surface protective layer and an insulating protective film and which has excellent solution stability, elastic modulus and heat resistance. The carboxyl group-containing modified imide resin includes a structure having a constituent unit derived from a polyol (a), a constituent unit derived from a polyamine (b), and a constituent unit derived from a tetracarboxylic dianhydride (c) and represented by general formula (X) (in general formula (X), n represents a number of 0-20, R1 represents an organic group obtained by removing an acid anhydride group from the tetracarboxylic dianhydride, R2 represents an organic group obtained by removing an amino group from the polyamine (b), and R3 represents an organic group obtained by removing a hydroxyl group from the polyol (a)), wherein the polyamine (b) contains an aromatic diamine (b1), and the imide bond concentration is 0.5-2.0 mmol / g.

Description

Carboxygroup-containing modified imide resin, resin composition, laminate, and flexible printed circuit board 【0001】 The present invention relates to a carboxyl group-containing modified imide resin, a resin composition, a laminate, and a flexible printed circuit board. 【0002】 Generally, polyimide resins are widely used as materials for forming adhesive layers, surface protective layers, and insulating protective layers of electronic components because they are highly elastic, as well as have excellent heat resistance, flexibility, and insulation properties. In particular, regarding heat resistance, there is a demand for long-term heat resistance, such as not degrading even when exposed to high temperatures of 150°C or higher for extended periods. 【0003】 Furthermore, polyimide resins are poorly soluble in solvents, often requiring high-boiling point solvents for dissolution. Additionally, forming coatings may require high-temperature treatment above 200°C, posing challenges in terms of processability. When forming insulating protective coatings for electronic components by applying and drying resin solutions, it is desirable to be able to dry and cure at lower temperatures and in shorter times. For polyimide resins, there has been a need for improved solubility in solvents with boiling points below 200°C and improved solution stability. 【0004】 To address the above-mentioned challenges, attempts have been made to improve solution stability by incorporating a highly flexible skeleton into polyimide resins. For example, a urethaneimide resin having carboxyl groups has been proposed, obtained by reacting an isocyanate-terminated polyurethane, consisting of a polycarbonate polyol and an isocyanate, with an acid anhydride and a chain extender (Patent Document 1). Also, a polyimide resin having carboxyl groups in the side chains has been proposed, obtained by reacting an acid anhydride-terminated imide oligomer, obtained by reacting a tetracarboxylic dianhydride and an isocyanate, with a polyol (Patent Documents 2 and 3). Furthermore, an esterimide resin synthesized from a polyol, a dimer amine, and a tetracarboxylic dianhydride has been proposed (Patent Document 4). In addition, an adhesive composition containing a polyimide resin obtained using a dimer amine, a monoamine, and a tetracarboxylic dianhydride, along with a curing agent, has been proposed (Patent Document 5). 【0005】Japanese Patent Publication No. 2011-094037, Japanese Patent Publication No. 6882263, Japanese Patent Publication No. 5304954, Japanese Patent Publication No. 7436352, Japanese Patent Publication No. 2023-097359 【0006】 However, while the urethane-imide resin proposed in Patent Document 1 has good flexibility, its heat resistance is not necessarily good because it has a high proportion of constituent units derived from polyols and a low imide bond concentration. Furthermore, while the polyimide resins proposed in Patent Documents 2 and 3 have good flexibility, they have constituent units derived from isocyanates with relatively small molecular weights, resulting in short distances between imide bonds and strong cohesive forces. Therefore, there was room for improvement in terms of solution stability. 【0007】 The polyimide resins proposed in Patent Documents 4 and 5 contain many highly flexible structural units derived from dimer amine, resulting in good solution stability and flexibility, but their elastic modulus is not necessarily good. Furthermore, because dimer amine contains many branched structures, it is prone to oxidative degradation, leaving room for improvement in terms of long-term heat resistance. In addition, the polyimide resin proposed in Patent Document 5 has crosslinking points concentrated at the ends of the resin, making it difficult to sufficiently increase the crosslinking density of the cured product, leaving room for improvement in terms of thermal dimensional stability. 【0008】 This invention has been made in view of the problems of the prior art, and its objective is to provide a carboxyl group-containing modified imide resin with excellent solution stability, elastic modulus, and heat resistance, which is useful as an adhesive for electronic components and as a material for forming coatings such as surface protective layers and insulating protective films. Another objective of this invention is to provide a resin composition capable of forming a cured product with excellent elastic modulus, thermal dimensional stability, long-term heat resistance, and flexibility. Furthermore, an objective of this invention is to provide a laminate with excellent solder heat resistance having a cured layer formed using the above resin composition, and a flexible printed circuit board containing this laminate as a component. 【0009】In other words, the present invention provides the following carboxyl group-containing modified imide resin: [1] A carboxyl group-containing modified imide resin comprising a structure represented by the following general formula (X), having a constituent unit derived from a polyol (a), a constituent unit derived from a polyamine (b), and a constituent unit derived from a tetracarboxylic dianhydride (c), wherein the polyamine (b) comprises an aromatic diamine (b1), and the imide bond concentration is 0.5 to 2.0 mmol / g. 【0010】 (In the above general formula (X), n represents a number from 0 to 20, R １ R represents an organic group obtained by removing the acid anhydride group from a tetracarboxylic dianhydride, ２ R represents the organic group obtained by removing the amino group from polyamine (b), ３ (This indicates an organic group obtained by removing a hydroxyl group from polyol (a)). 【0011】 [2] The carboxyl group-containing modified imide resin according to [1], wherein the polyol (a) comprises at least one selected from the group consisting of polycarbonate diols and polyester diols. [3] The carboxyl group-containing modified imide resin according to [2], wherein the polyol (a) further comprises a polyol (a1) that is liquid at 25°C, and the content of constituent units derived from the polyol (a1) is 20 to 60% by mass. [4] The carboxyl group-containing modified imide resin according to any one of [1] to [3], wherein the aromatic diamine (b1) is a compound having an aromatic ether bond, and the molecular weight of the portion of the aromatic diamine (b1) other than the amino group is 240 to 500. [5] The carboxyl group-containing modified imide resin according to any one of [1] to [4], wherein the number average molecular weight is 10,000 to 50,000 and the acid value is 5 to 40 mgKOH / g. 【0012】 Furthermore, the present invention provides the following resin compositions: [6] A resin composition comprising a carboxyl group-containing modified imide resin according to any one of [1] to [5] above, and an epoxy resin having two or more epoxy groups in one molecule. [7] The resin composition according to [6] above, further comprising an organic solvent having a boiling point of 200°C or less for dissolving the carboxyl group-containing modified imide resin. 【0013】 Furthermore, the present invention provides the following laminates and flexible printed circuit boards: [8] A laminate having a cured layer obtained by curing the resin composition described in [6] or [7] above. [9] A flexible printed circuit board comprising the laminate described in [8] above as a component. 【0014】 The present invention provides a carboxyl group-containing modified imide resin with excellent solution stability, elastic modulus, and heat resistance, which is useful as an adhesive for electronic components and as a material for forming coatings such as surface protective layers and insulating protective films. Furthermore, the present invention provides a resin composition capable of forming a cured product with excellent elastic modulus, thermal dimensional stability, long-term heat resistance, and flexibility. Moreover, the present invention provides a laminate having a cured layer formed using the above resin composition and having excellent solder heat resistance, and a flexible printed circuit board containing this laminate as a component. 【0015】 <Carboxyloid-containing Modified Imide Resin> The embodiments of the present invention will be described below, but the present invention is not limited to the embodiments described below. One embodiment of the carboxyloid-containing modified imide resin of the present invention (hereinafter also simply referred to as "modified imide resin") is a resin containing a structure represented by the following general formula (X), having a constituent unit derived from polyol (a), a constituent unit derived from polyamine (b), and a constituent unit derived from tetracarboxylic dianhydride (c). Polyamine (b) includes aromatic diamine (b1). The imide bond concentration of the carboxyloid-containing modified imide resin of this embodiment is 0.5 to 2.0 mmol / g. The modified imide resin of this embodiment may be a resin substantially composed only of the structure represented by the following general formula (X), or it may be a resin further containing structures other than the structure represented by the following general formula (X). The details of the carboxyloid-containing modified imide resin (modified imide resin) of this embodiment will be described below. 【0016】 (In the above general formula (X), n represents a number from 0 to 20, R １ R represents an organic group obtained by removing the acid anhydride group from a tetracarboxylic dianhydride, ２R represents the organic group obtained by removing the amino group from polyamine (b), ３ (This indicates an organic group obtained by removing a hydroxyl group from polyol (a)). 【0017】 (Polyol (a)) Polyol (a) is a compound (diol) having two hydroxyl groups in its molecule. It is preferable to use polycarbonate diol and polyester diol as polyol (a). By using polycarbonate diol as polyol (a), it is possible to form a cured product such as a cured layer with even better heat resistance. Furthermore, by using polyester diol as polyol (a), it is possible to form a cured product such as a cured layer with even better flexibility. 【0018】 The polyol (a) preferably contains at least one selected from the group consisting of polycarbonate diols and polyester diols. Furthermore, the polyol (a) preferably further contains polyol (a1) that is liquid at 25°C. By using polyol (a1) that is liquid at 25°C, the viscosity of the resin solution can be reduced and the solution stability of the modified imide resin solution can be further improved. It is preferable that the polyol (a) contains 30% by mass or more of polyol (a1) that is liquid at 25°C. On the other hand, if the polyol (a) contains more than 70% by mass of polyol that is solid at 25°C, compared to the case where only polyol that is liquid at 25°C is included, the heat resistance and elastic modulus are improved, and the tackiness (stickiness) when formed into a film is reduced, and handling tends to be improved. 【0019】 In the modified imide resin, the content of constituent units derived from polyol (a1) that is liquid at 25°C is preferably 20 to 60% by mass, more preferably 25 to 55% by mass, and particularly preferably 30 to 50% by mass. If the content of constituent units derived from polyol (a1) that is liquid at 25°C is less than 20% by mass, the effect of improving flexibility may be insufficient. On the other hand, if the content of constituent units derived from polyol (a1) that is liquid at 25°C is more than 60% by mass, the heat resistance and elastic modulus may decrease slightly. 【0020】As polycarbonate diols, for example, reaction products of dialkyl carbonates such as dimethyl carbonate and diol compounds having two hydroxyl groups in the molecule can be used. Commercially available polycarbonate diols can also be used. Examples of diol compounds include linear or side-chain diols having 2 to 10 carbon atoms. 【0021】 Examples of diol compounds include aliphatic diols and alicyclic diols. Examples of aliphatic diols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, and 2-methyl-1,8-octanediol. Examples of alicyclic diols include 1,4-cyclohexanedimethanol. From the viewpoint of improving the flexibility of the modified imide resin, aliphatic diols are preferred, and 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and 3-methyl-1,5-pentanediol are more preferred. 【0022】 Examples of polyester diols include those obtained by condensation polymerization of at least one of aliphatic dicarboxylic acids and aromatic dicarboxylic acids with low molecular weight glycols. Examples of aliphatic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, glutaric acid, and azelaic acid. Examples of aromatic dicarboxylic acids include isophthalic acid and terephthalic acid. Examples of low molecular weight glycols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 3-methylpentanediol, 1,6-hexamethylene glycol, neopentyl glycol, and 1,4-bishydroxymethylcyclohexane. 【0023】 As the polyol (a), other polymer polyols other than the above-mentioned polycarbonate diol and polyester diol can also be used. Examples of other polymer polyols include polyether polyol, polylactone polyol, and dimer diol. Furthermore, a short-chain polyol having a molecular weight of 300 or less can also be used in combination. By appropriately using the short-chain polyol, the acid value of the modified imide resin can be adjusted. 【0024】 The number average molecular weight (Mn) of the polyol (a) is preferably from 350 to 3,500, more preferably from 400 to 3,000. When the number average molecular weight (Mn) of the polyol (a) is less than 300, the acid value of the modified imide resin may become high, and the modified imide resin, cured product, etc. may be prone to warping. On the other hand, when the number average molecular weight (Mn) of the polyol (a) exceeds 3,500, it may be difficult to increase the acid value of the modified imide resin, and the heat resistance of the cured product, etc. may decrease. 【0025】 (Polyamine (b)) The polyamine (b) contains an aromatic diamine (b1). It is preferable that the polyamine (b) is substantially only the aromatic diamine (b1). By using the polyamine (b), an imide bond can be introduced into the resin. And by introducing an imide bond derived from the aromatic diamine (b1), the tensile elastic modulus, thermal dimensional stability, and long-term heat resistance of the obtained modified imide resin can be enhanced. 【0026】Examples of the aromatic diamine (b1) include 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl methane, 3,3'-diaminodiphenyl methane, 3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3'-dimethyl-4,4'-biphenyldiamine, benzidine, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl propane, 2,4-diaminotoluene, bis(4-amino-3-carboxyphenyl)methane, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, bis[4-(4-aminophenoxy)phenyl]sulfone, bis-p-(1,1-dimethyl-5-aminopentyl)benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, 4,4'-methylenebis(2,6-xylidine), and α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, etc. 【0027】 The aromatic diamine (b1) is preferably a compound having an aromatic ether bond. And the molecular weight of the portion other than the amino group of the aromatic diamine (b1) is 240 to 500. When an aromatic diamine having no aromatic ether bond and having a molecular weight of less than 240 for the portion other than the amino group is used, the imide bond distance in the obtained modified imide resin becomes short, and due to the cohesive force between the imide bonds, the solution stability may be likely to decrease. Also, since the ratio of the polyol increases, the heat resistance may be likely to decrease. On the other hand, when an aromatic diamine having a molecular weight of more than 500 for the portion other than the amino group is used, since the ratio of the aromatic diamine in the obtained modified imide resin increases, the flexibility may be likely to decrease. 【0028】Aromatic diamines (b1) having an aromatic ether bond and a molecular weight of 240 to 500 for the non-amino group portion include 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and bis[4-(4-aminophenoxy)phenyl]sulfone. Using these aromatic diamines (b1) with appropriately separated aniline structures at both ends effectively suppresses turbidity or precipitate formation during synthesis. 【0029】 The modified imide resin may, if necessary, further contain constituent units derived from polyamines other than aromatic diamines (b1) (other polyamines (diamines)). Examples of other polyamines include dimer amines, and the cyclic aliphatic diamines and linear aliphatic diamines described later. 【0030】 Examples of cyclic aliphatic diamines include di(p-aminocyclohexyl)methane, 1,4-diaminocyclohexane, 1,3-bisaminomethylcyclohexane, isophoronediamine, and norbornanediamine. Furthermore, examples of linear aliphatic diamines include hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,17-diaminoeicosadecane, 1,10-diamino-1,10-dimethyldecane, and 1,12-diaminooctadecane. 【0031】(Tetracarboxylic acid dianhydride (c)) Examples of tetracarboxylic acid dianhydride (c) (hereinafter also simply referred to as "acid anhydride (c)") include trimellitic anhydride ester of ethylene glycol, 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 3,4'-oxydiphthalic acid anhydride, and 4,4'-oxydiphthalic acid Examples include anhydrides, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, ethylene glycol bis(anhydrotrimellitate), p-phenylene bis(trimellitate anhydride), cyclobutanetetracarboxylic dianhydride, methylcyclobutanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, ethanetetracarboxylic dianhydride, and 3,3',4,4'-bicyclohexyltetracarboxylic dianhydride. 【0032】 From the viewpoint of heat resistance and other factors, the acid anhydride (c) is preferably an ester of trimellitic anhydride and ethylene glycol, 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and 4,4'-oxydiphthalic anhydride. 【0033】(Polyisocyanate) The modified imide resin of the present embodiment may further have a structural unit having a urethane bond derived from polyisocyanate. That is, the modified imide resin of the present embodiment preferably contains a structure represented by the following general formula (Y), and may be substantially composed only of the structure represented by the following general formula (Y). By having a structural unit having a urethane bond (urethane-modifying), the compatibility with an epoxy resin can be improved. Further, by urethane-extending with polyisocyanate, it becomes easy to adjust the molecular weight to an arbitrary value. The polyisocyanate is preferably a diisocyanate having two isocyanate groups in its molecule. Examples of the diisocyanate include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. 【0034】 (In the general formula (Y), n represents a number from 0 to 20, m represents a number from 1 to 5, and R １ represents an organic group obtained by removing an acid anhydride group from a tetracarboxylic dianhydride, R ２ represents an organic group obtained by removing an amino group from a polyamine (b), R ３ represents an organic group obtained by removing a hydroxyl group from a polyol (a), R ４ represents an organic group obtained by removing an isocyanate group from a polyisocyanate) 【0035】 Examples of the aromatic diisocyanate include tolylene diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, diphenylmethane diisocyanate, durylene diisocyanate, xylylene diisocyanate, 1,5-naphthalene diisocyanate, benzidine diisocyanate, o-nitrobenzidine diisocyanate, and 4,4'-diisocyanate dibenzyl. 【0036】Examples of aliphatic diisocyanates include methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,10-decamethylene diisocyanate. 【0037】 Examples of alicyclic diisocyanates include 1,4-cyclohexylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate. 【0038】 From the viewpoint of reactivity and other factors, polyisocyanates such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI), 1,5-pentamethylene diisocyanate (PDI), and hydrogenated diphenylmethane diisocyanate (HMDI) are preferred. 【0039】 (Carboxyloidy-containing modified imide resin) The modified imide resin of this embodiment has constituent units derived from polyamine (b) containing aromatic diamine (b1), and therefore has excellent elastic modulus and solution stability, and can form cured products with excellent elastic modulus, flexibility, and long-term heat resistance. Furthermore, since the modified imide resin of this embodiment has carboxyloid groups in the side chains of the polymer chain, which serve as reaction sites with epoxy groups, the crosslinking density of the cured product obtained by curing with epoxy resin is higher compared to imide resins that have crosslinking sites such as carboxyloid groups or acid anhydride groups at the ends of the polymer chain, and can form cured products such as cured layers with better thermal dimensional stability. 【0040】In the modified imide resin, the imide bond concentration (imide bond concentration derived from polyamine(b)) is 0.5 to 2.0 mmol / g, preferably 0.7 to 1.8 mmol / g, and more preferably 0.8 to 1.7 mmol / g. If the imide bond concentration is less than 0.5 mmol / g, the heat resistance and elastic modulus may decrease. On the other hand, if the imide bond concentration is greater than 2.0 mmol / g, the solution stability may decrease. 【0041】 In this specification, "imide bond concentration" refers to the amount of imide bonds (moles) per gram of modified imide resin. Furthermore, in this specification, "imide bond" refers to a bond derived from the reaction between an acid anhydride and polyamine (b), and does not include a bond derived from the reaction between an acid anhydride and isocyanate. The imide bond concentration of the modified imide resin can be controlled, for example, by adjusting the amount (mol) of polyamine (b) and the amount (g) of solids in the preparation containing polyol (a) and tetracarboxylic dianhydride (c). The theoretical imide bond concentration of the modified imide resin can be calculated using the following formula (A): Theoretical imide bond concentration of modified imide resin = A １ ×N １ ×1,000 / C １ ... (A) A １ : Amount of polyamine (b) (mol) N １ : Number of amino groups in polyamine (b) C １ : Amount of solids added (g) 【0042】 When the modified imide resin contains a structure represented by general formula (Y), the urethane bond concentration in the modified imide resin is preferably 1.0 mmol / g or less, and more preferably 0.5 mmol / g or less. If the urethane bond concentration in the modified imide resin exceeds 1.0 mmol / g, the heat resistance may tend to decrease. 【0043】"Urethane bond concentration" refers to the amount of urethane bonds (mol) per gram of modified imide resin. The urethane bond concentration of modified imide resin can be controlled, for example, by adjusting the amount of polyisocyanate (mol) and the amount of solid content (g) containing polyol (a) and tetracarboxylic dianhydride (c). The theoretical urethane bond concentration of modified imide resin can be calculated using the following formula (B): Theoretical urethane bond concentration of modified imide resin = A ２ ×N ２ ×1,000 / C ２ ... (B) A ２ : Amount of polyisocyanate (mol) N ２ : Number of isocyanate groups in polyisocyanate C ２ : Amount of solids added (g) 【0044】 The number-average molecular weight (Mn) of the modified imide resin is preferably 10,000 to 50,000, and more preferably 12,000 to 45,000. If the number-average molecular weight of the modified imide resin is less than 10,000, the film-forming ability may decrease slightly, and the heat resistance of the cured product, such as the formed cured layer, may decrease. On the other hand, if the number-average molecular weight of the modified imide resin is greater than 50,000, the solubility in organic solvents may decrease. 【0045】 In this specification, the "number-average molecular weight (Mn)" of a resin refers to the polystyrene-converted value measured by gel permeation chromatography (GPC). GPC can be measured, for example, using the following apparatus and conditions. 【0046】 (1) Equipment: Product name "HLC-8020" (manufactured by Tosoh Corporation) (2) Column: Product names "TSKgel G2000HXL", "G3000HXL", "G4000GXL" (manufactured by Tosoh Corporation) (3) Solvent: THF (4) Flow rate: 1.0 mL / min (5) Sample concentration: 2 g / L (6) Injection volume: 100 μL (7) Temperature: 40°C (8) Detector: Model number "RI-8020" (manufactured by Tosoh Corporation) (9) Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation) 【0047】The acid value of the modified imide resin is preferably 5 to 40 mg KOH / g, more preferably 10 to 35 mg KOH / g, and particularly preferably 20 to 30 mg KOH / g. When the acid value of the modified imide resin is 5 mg KOH / g or higher, the crosslinking density of the cured product (crosslinked product) formed by reaction with a curing agent such as epoxy resin increases, further improving the heat resistance and thermal dimensional stability of the cured product. Furthermore, when the acid value of the modified imide resin is 40 mg KOH / g or lower, it is possible to suppress an excessive increase in the crosslinking density of the cured product (crosslinked product) formed by reaction with a curing agent such as epoxy resin. This suppresses a decrease in flexibility (flexibility). 【0048】 The acid value (measured value) of modified imide resin can be measured using a solution prepared by dissolving the modified imide resin in an organic solvent such as methyl ethyl ketone (MEK) as a sample, in accordance with the method compliant with JIS K1557-5:2007. 【0049】 (Method for producing carboxyl group-containing modified imide resin) Modified imide resin can be produced, for example, by a production method comprising the following steps (1) and (2). Steps (1) and (2) may be performed simultaneously. Step (2) may further include introducing urethane bonds by reacting a polyisocyanate with the hydroxyl groups present at the ends of the obtained modified imide resin. Step (1): A step of reacting a tetracarboxylic dianhydride (c) with a polyamine (b) to obtain an imide oligomer having an acid anhydride end. Step (2): A step of reacting the imide oligomer having an acid anhydride end obtained in step (1) with a polyol (a) to obtain a carboxyl group-containing modified imide resin. 【0050】An example of a specific procedure for producing the modified imide resin of this embodiment is shown below. First, polyamine (b), tetracarboxylic dianhydride (c), and an organic solvent are mixed and reacted at 130 to 160°C for about 1 to 7 hours while stirring to obtain an imide oligomer having acid anhydride groups at its ends. Next, polyol (a) is added so that the molar ratio of acid anhydride groups to hydroxyl groups (= acid anhydride groups / hydroxyl groups) is approximately 0.5 to 1.0 (0.7 to 1.0 is preferable if urethane modification is not performed; 0.5 to 0.7 is preferable if urethane modification is performed), and the mixture is reacted at 50 to 150°C for about 1 to 12 hours. After that, the mixture is diluted with an organic solvent as needed and cooled to obtain the desired carboxyl group-containing modified imide resin in resin solution form. Note that the molar ratio of acid anhydride groups to hydroxyl groups (= acid anhydride groups / hydroxyl groups) affects the acid value of the obtained carboxyl group-containing modified imide resin. For example, if the acid anhydride group / hydroxyl group (molar ratio) is less than 0.5 or greater than 1.0, the molecular weight of the resulting carboxyl group-containing modified imide resin may not be sufficiently increased, and its flexibility may decrease. 【0051】 As the organic solvent, it is preferable to use an organic solvent that does not substantially react with any of the polyols (a), polyamines (b), and tetracarboxylic dianhydrides (c). In particular, it is preferable to use an organic solvent with a boiling point of 200°C or lower. By reacting and diluting with an organic solvent with a boiling point of 200°C or lower, the resulting resin solution can be used directly as a paint or composition, and can be dried or cured at low temperatures and in a short time. 【0052】Examples of organic solvents with a boiling point of 200°C or lower include toluene, cyclohexane, methylcyclohexane, ethylene glycol diethyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, methyl methoxypropionate, ethyl methoxypropionate, ethyl acetate, n-butyl acetate, isoamyl acetate, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, dimethyl carbonate, tetrahydrofuran, and dioxane. Among these, toluene, methyl ethyl ketone, dimethyl carbonate, cyclopentanone, and cyclohexanone are preferred from the viewpoint of solubility and ease of drying of the modified imide resin, and toluene, methyl ethyl ketone, cyclohexanone, and dimethyl carbonate are more preferred. 【0053】 <Resin Composition> One embodiment of the resin composition of the present invention contains the carboxyl group-containing modified imide resin described above and an epoxy resin having two or more epoxy groups in one molecule. That is, by reacting the modified imide resin described above with an epoxy resin which is a curing agent and curing it, a cured product such as a cured layer with excellent elastic modulus, thermal dimensional stability, long-term heat resistance, and flexibility can be formed. 【0054】 The epoxy resin used as a curing agent has two or more epoxy groups in one molecule. Examples of such epoxy resins include bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, bisphenol F type epoxy resin, brominated bisphenol A type epoxy resin, phenol novolac type epoxy resin, o-cresol novolac type epoxy resin, flexible epoxy resin, epoxidized polybutadiene, amine type epoxy resin, heterocyclic epoxy resin, alicyclic epoxy resin, bisphenol S type epoxy resin, dicyclopentadiene type epoxy resin, triglycidyl isocyanurate, bixylenol type epoxy resin, and compounds having glycidyl groups. 【0055】 The epoxy equivalent of the epoxy resin is preferably 100 to 10,000 g / eq, and more preferably 100 to 600 g / eq, from the viewpoint of the mechanical strength, flexibility, and heat resistance of the cured product formed. 【0056】 The number-average molecular weight (Mn) of the epoxy resin is preferably 100 to 100,000, and more preferably 300 to 70,000, from the viewpoint of compatibility with the modified imide resin to be reacted with. 【0057】 By adjusting the molar ratio of epoxy groups in the epoxy resin to carboxyl groups in the modified imide resin, a cured product with desired properties can be obtained. For example, it is preferable to react the epoxy resin and the modified imide resin in amounts such that the molar ratio of epoxy groups to carboxyl groups is 10 / 1 to 1 / 2. If the molar ratio is outside this range, the crosslinking properties tend to decrease, and the thermal dimensional stability of the resulting cured product may be slightly reduced. 【0058】 In the resin composition, the epoxy resin content is preferably 5 to 200 parts by mass, and more preferably 10 to 100 parts by mass, per 100 parts by mass of modified imide resin (solids). A epoxy resin content of 5 parts by mass or more per 100 parts by mass of modified imide resin results in better crosslinking properties. Furthermore, a epoxy resin content of 200 parts by mass or less per 100 parts by mass of modified imide resin makes it less likely for crosslinking properties to decrease, and further improves the heat resistance of the resulting cured product. 【0059】 The resin composition can be prepared by mixing an epoxy resin and the aforementioned modified imide resin in a desired ratio. During preparation, the mixture may be mixed in the presence of the aforementioned organic solvent, or the epoxy resin may be added to a solution of the modified imide resin and then mixed. That is, the resin composition of this embodiment may further contain an organic solvent. By using an organic solvent, it can be used as a paint composition. When used as a paint composition, it can be used as an adhesive that can dry and cure at low temperatures and has excellent properties such as heat resistance and adhesion. Such a paint composition is useful, for example, as an adhesive for electronic components or as a paint composition for forming insulating protective films. Furthermore, the paint composition can be used in applications such as solder resists, electromagnetic shielding films, and paints, as well as as an adhesive for flexible printed circuit boards (substrates), conductive adhesives, and structural material adhesives. 【0060】 The organic solvent is preferably one that can dissolve both epoxy resin and modified imide resin. When considering its use as a paint composition, it is preferable to use an organic solvent with a boiling point of 200°C or lower, and more preferably a non-nitrogen-based organic solvent with a boiling point of 200°C or lower. By using an organic solvent with a boiling point of 200°C or lower, drying and curing can be carried out under lower temperature conditions. 【0061】 As the organic solvent, the same organic solvents that can be used when producing modified imide resins can be used. Specifically, toluene, cyclohexane, methylcyclohexane, ethylene glycol diethyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, methyl methoxypropionate, ethyl methoxypropionate, ethyl acetate, n-butyl acetate, isoamyl acetate, acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, and dimethyl carbonate can be used. Among these, toluene, methyl ethyl ketone, cyclohexanone, and dimethyl carbonate are preferred from the viewpoint of solubility of epoxy resins and modified imide resins, and drying efficiency when used as a paint composition. 【0062】 The resin composition may optionally contain other components besides the modified imide resin, epoxy resin, and organic solvent mentioned above. Examples of other components include curing accelerators, isocyanate crosslinking agents, thermoplastic polymers, tackifying resins, pigments, antioxidants, UV absorbers, surfactants, and fillers. 【0063】 The resin composition of this embodiment can be cured, for example, by applying it to a desired substrate and then holding it at a temperature of preferably 40 to 200°C, and more preferably 130 to 180°C. 【0064】<Laminate and Flexible Printed Wiring Board> One embodiment of the laminate of the present invention has a cured layer obtained by curing the resin composition described above. Another embodiment of the flexible printed wiring board of the present invention includes this laminate as a component. 【0065】 The aforementioned resin composition containing an organic solvent can be used as a paint composition. For example, the paint composition can be applied to a release film by methods such as screen printing, spraying, roll coating, electrostatic coating, and curtain coating to form a coating film with a thickness of 5 to 80 μm. Then, the organic solvent is removed by holding the film at 0 to 180°C for 3 to 10 minutes, and the coating film is dried. This yields an adhesive film, which is a dried film. The drying of the coating film may be done in air or in an inert atmosphere. Furthermore, to adjust the fluidity during heat bonding, the film may be heat-treated after drying to react a portion of the modified imide resin with the curing agent. This state before heat bonding is generally called the B stage. 【0066】 The laminate of this embodiment is suitable as a component of a flexible printed circuit board (substrate) (FPC). Among the constituent layers of the FPC, examples of layers formed by the aforementioned resin composition (paint composition (adhesive)) and laminate include CL (coverlay) film, adhesive film, and three-layer copper-clad laminate. 【0067】 Since CL films and adhesive films are generally wound, stored, cut, and die-cut in their B-stage state, they need to be flexible in that state. Furthermore, after heat-pressing the B-stage film with the adherend, a cured layer is formed by heat-curing treatment. 【0068】The CL film is composed of, for example, an "insulating plastic film / adhesive layer" or an "insulating plastic film / adhesive layer / protective film". The insulating plastic film is a film with a thickness of 1 to 200 μm, formed from plastics such as polyimide, polyimide urethane, polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aramid, polycarbonate, and polyarylate. Multiple sheets of these films may be laminated together. 【0069】 The protective film is preferably a film that can be peeled off without impairing the properties of the adhesive. Examples of protective films include films made of plastics such as polyethylene, polypropylene, polyolefin, polyester, polymethylpentene, polyvinyl chloride, polyvinylidene fluoride, and polyphenylene sulfide; films obtained by coating these films with silicone, fluoride, and other release agents; paper laminated with these films; and paper impregnated or coated with a release resin. 【0070】 The adhesive film has a structure in which a protective film is provided on at least one surface of an adhesive layer formed from a resin composition (paint composition), and is composed, for example, of "protective film / adhesive layer" or "protective film / adhesive layer / protective film". In some cases, an insulating plastic film layer is provided within the adhesive layer. The adhesive film can also be used in multilayer printed circuit boards. 【0071】 A three-layer copper-clad laminate has a structure in which copper foil is bonded to at least one surface of an insulating plastic film via an adhesive layer formed of a resin composition (coating composition). As the copper foil, for example, rolled copper foil or electrolytic copper foil conventionally used in flexible printed circuit boards can be used. The resin composition (coating composition) becomes the solder resist layer, surface protection layer, interlayer insulating layer, or adhesive layer of the FPC. 【0072】The resin composition (paint composition) of this embodiment is useful as a material for constructing semiconductor elements, overcoat inks for various electronic components, solder resist inks, and interlayer insulating films, and can also be used as a paint, coating agent, and adhesive. Solder resist ink is an ink used to form a solder resist layer. The solder resist layer is a layer that forms a film over the entire surface of a circuit conductor except for the part to be soldered, and functions as a protective film that prevents solder from adhering to unnecessary parts when wiring electronic components on a printed circuit board, and also prevents the circuit from being directly exposed to air. 【0073】 The surface protection layer is a layer applied to the surface of circuit components to mechanically and chemically protect the electronic components from processing and usage environments. The interlayer insulation layer (film) is a layer (film) that prevents current from flowing between layers in the package substrate where fine wiring is formed. The adhesive layer is a layer mainly used to bond metal layers and film layers, and is used when laminating them. 【0074】 The present invention will be described in detail below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are based on mass unless otherwise specified. 【0075】 <Preparation of materials> The following materials were prepared. 【0076】(Polyol (a)) ・PH-50: Product name "Ethanacol PH-50", manufactured by UBE, polyhexamethylene / pentamethylene copolymer carbonate diol, number average molecular weight 508, liquid at 25°C ・PH-100: Product name "Ethanacol PH-100", manufactured by UBE, polyhexamethylene / pentamethylene copolymer carbonate diol, number average molecular weight 984, liquid at 25°C ・PH-200: Product name "Ethanacol PH-200", manufactured by UBE, polyhexamethylene / pentamethylene copolymer carbonate diol, number average molecular weight 1,968, liquid at 25°C ・PH-300: Product name "Ethanacol PH-300: Manufactured by UBE, polyhexamethylene / pentamethylene copolymer carbonate diol, number average molecular weight 2,914, liquid at 25°C. UH-100: Product name "Ethanacol UH-100", Manufactured by UBE, polyhexamethylene carbonate diol, number average molecular weight 1,000, solid at 25°C. UH-200: Product name "Ethanacol". UH-200: Manufactured by UBE, polyhexamethylene carbonate diol, number average molecular weight 1,958, solid at 25°C; P-1050: Product name "Kuraray Polyol P1050", manufactured by Kuraray, 3-methyl-1,5-pentanediol / sebacate polyester diol, number average molecular weight 989, liquid at 25°C; P-2050: Product name "Kuraray Polyol P2050", manufactured by Kuraray, 3-methyl-1,5-pentanediol / sebacate polyester diol, number average molecular weight 1,941, liquid at 25°C; 1,6-HD: 1,6-hexanediol, solid at 25°C 【0077】 (Aromatic diamines (b1)) ・BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane, molecular weight 410 (molecular weight of non-amino group portion 378) ・TPE-R: 1,3-bis(4-aminophenoxy)benzene, molecular weight 292 (molecular weight of non-amino group portion 260) ・ODA: 4,4'-diaminodiphenyl ether, molecular weight 200 (molecular weight of non-amino group portion 168) 【0078】(Aliphatic diamines) ・P1074: Trade name "Priamine 1074", manufactured by CRODA, dimer amine, number average molecular weight 529 ・1,3-BAC: 1,3-bisaminomethylcyclohexane, number average molecular weight 142.25 【0079】 (Acid anhydride (c)) ・BPADA: 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic anhydride ・BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride 【0080】 (Polyisocyanates) • TDI: Trilene-2,4-diisocyanate • MDI: Diphenylmethane diisocyanate 【0081】 (Hardening agent) Epoxy resin A: Product name "jER828", manufactured by Mitsubishi Chemical Corporation, bisphenol A type epoxy resin, epoxy equivalent weight 184 g / eq, number average molecular weight 368 【0082】 <Production of Modified Imide Resin> (Example 1) 45.0 parts (0.11 mol) of BAPP, 83.5 parts (0.16 mol) of BPADA, and 57.2 parts of cyclohexanone were placed in a separable flask equipped with a stirrer. The mixture was reacted at 150°C for 3 hours to obtain an imide oligomer having acid anhydride groups at its ends. After dilution with the addition of 95.4 parts of cyclohexanone, 100.0 parts (0.05 mol) of PH-200 and 0.4 parts (0.003 mol) of 1,6-HD were added, and the mixture was reacted at 120°C for 5 hours. Infrared absorption spectroscopy revealed that the free acid anhydride groups were responsible for the 1,850 cm⁻¹ absorption spectroscopy. －１ After confirming that the absorption had disappeared, 190.7 parts of cyclohexanone were added to dilute the solution, and it was cooled to room temperature to obtain a solution of modified imide resin A with a solid content of 40%. The number-average molecular weight (Mn) of modified imide resin A was 15,000, and the acid value (measured value) was 25 mg KOH / g. 【0083】(Example 9) 55.0 parts (0.13 mol) of BAPP, 99.3 parts (0.19 mol) of BPADA, and 64.2 parts of cyclohexanone were placed in a separable flask equipped with a stirrer. The mixture was reacted at 150°C for 3 hours to obtain an imide oligomer having acid anhydride groups at its ends. After dilution with the addition of 106.9 parts of cyclohexanone, 100.0 parts (0.1 mol) of PH-100 was added and the mixture was reacted at 120°C for 5 hours. Infrared absorption spectroscopy revealed that the free acid anhydride groups were responsible for the 1,850 cm⁻¹ absorption spectroscopy. －１ After confirming that the absorption had disappeared, 7.1 parts (0.04 mol) of TDI was added and the mixture was reacted at 90°C for 2 hours. Infrared absorption spectroscopy revealed that the absorption at 2,270 cm⁻¹ originated from the free isocyanate group. －１ After confirming that the absorption had disappeared, 213.8 parts of cyclohexanone were added to dilute the solution, and it was cooled to room temperature to obtain a solution of modified imide resin I with urethane bonds and a solid content of 40%. The number-average molecular weight (Mn) of modified imide resin I was 25,000, and the acid value (measured value) was 25 mg KOH / g. 【0084】 (Comparative Example 1) 63.0 parts (0.12 mol) of P1074, 90.9 parts (0.17 mol) of BPADA, and 62.6 parts of cyclohexanone were placed in a separable flask equipped with a stirrer. The mixture was reacted at 150°C for 3 hours to obtain an imide oligomer having an acid anhydride group at its end. After dilution with the addition of 104.4 parts of cyclohexanone, 100.0 parts (0.05 mol) of PH-200 and 1.0 part (0.01 mol) of 1,6-HD were added, and the mixture was reacted at 120°C for 5 hours. Infrared absorption spectroscopy revealed that the free acid anhydride group was present at 1,850 cm⁻¹. －１ After confirming that the absorption had disappeared, 208.8 parts of cyclohexanone were added to dilute the solution, and it was cooled to room temperature to obtain a 40% solids solution of modified imide resin AA. The number-average molecular weight (Mn) of modified imide resin AA was 15,000, and the acid value (measured value) was 25 mgKOH / g. 【0085】(Comparative Example 6) 100.0 parts (0.19 mol) of BPADA, 34.4 parts (0.14 mol) of MDI, and 53.3 parts of cyclohexanone were placed in a separable flask equipped with a stirrer. 0.1 parts of diazabicycloundecene (DBU) was added as a catalyst, and the mixture was reacted at 150°C for 8 hours to obtain an imide resin. After diluting with 164.6 parts of cyclohexanone, 112.5 parts (0.06 mol) of PH-200 was added, and the mixture was reacted at 120°C for 3 hours. However, the mixture became insoluble during the reaction, and no resin could be obtained. 【0086】 (Comparative Example 7) 100 parts (0.24 mol) of BAPP, 140.1 parts (0.27 mol) of BPADA, and 154.2 parts of cyclohexanone were placed in a separable flask equipped with a stirrer and reacted at 150°C for 8 hours. 192.8 parts of cyclohexanone were added to dilute the mixture, and the mixture was cooled to room temperature to obtain a solution of modified imide resin GG with a solid content of 40%. This modified imide resin GG is a modified imide resin having acid anhydride groups at its ends. The number-average molecular weight (Mn) of the modified imide resin GG was 15,000, and the acid anhydride value (theoretical value) was 12.5 mgKOH / g. 【0087】 (Examples 2-8, 11-14) Solutions of modified imide resins B-H and K-N were obtained in the same manner as in Example 1, except that the formulations were as shown in Tables 1-1 and 1-2 (all with a solid content concentration of 40%). The physical properties of the modified imide resins are shown in Tables 1-1 and 1-2. 【0088】 (Example 10) A solution of modified imide resin J was obtained in the same manner as in Example 9, except that the formulation was as shown in Table 1-2. The physical properties of the modified imide resin are shown in Table 1-2. 【0089】 (Comparative Examples 2-5) Solutions of modified imide resins BB-EE were obtained in the same manner as in Comparative Example 1, except that the formulations were as shown in Table 1-3. The physical properties of the modified imide resins are shown in Table 1-3. In Comparative Example 2 (modified imide resin BB), it became insoluble during the reaction. In Comparative Examples 3 and 5 (modified imide resins CC and EE), turbidity or precipitates were formed during the reaction. 【0090】<Evaluation of Modified Imide Resins> The solution stability, elastic modulus, and heat resistance of the modified imide resins were evaluated below. The results are shown in Tables 1-1 to 1-3. Note that the elastic modulus and heat resistance were evaluated only for modified imide resins BB and FF, which became insoluble during synthesis, and modified imide resins CC and EE, which produced turbidity or precipitates. 【0091】 (Solution Stability) The stability of the solution during and after synthesis was evaluated according to the following criteria. ○: No turbidity or precipitates formed in the obtained solution after storage at 25°C for one week. ×: Turbidity or precipitates formed during synthesis. 【0092】 (Modulus of Elasticity) A modified imide resin solution was applied to release paper to a thickness of 40 μm after drying, and then dried at 150°C for 10 minutes to form a coating film (dried film). The formed coating film was cut to a size of 60 mm in length and 15 mm in width to obtain test specimens. Tensile tests were performed on the obtained test specimens using an Autograph (product name "AGS-J", manufactured by Shimadzu Corporation) in accordance with JIS K-7127:1999 under room temperature (25°C) conditions. The tensile modulus of elasticity of the test specimens was then measured, and the modulus of elasticity was evaluated according to the evaluation criteria shown below. ◎: Tensile modulus of elasticity of 800 N / mm ２ That concludes the report. ○: Tensile modulus of elasticity is 200 N / mm ２ More than 800N / mm ２ It was less than . △: Tensile modulus of elasticity is 100 N / mm ２ 200N / mm or more ２ It was less than . ×: Tensile modulus of elasticity was 100 N / mm ２ It was less than [amount missing]. 【0093】(Heat Resistance) A modified imide resin solution was applied to release paper to a thickness of 40 μm after drying, and then dried at 150°C for 10 minutes to form a coating film (dried film). Next, using TG-DTA (product name "TG8120", manufactured by Rigaku Corporation), the temperature was increased from room temperature at 10°C / min under an atmosphere of 100 mL / min of dry air to obtain a TG-DTA curve. Then, focusing on the temperature at which the mass decreased by 10% (10% decomposition temperature), the heat resistance was evaluated according to the evaluation criteria shown below. ○: 10% decomposition temperature was 340°C or higher. △: 10% decomposition temperature was 330°C or higher and less than 340°C. ×: 10% decomposition temperature was less than 330°C. 【0094】 【0095】 【0096】 【0097】 <Preparation of Resin Compositions> (Examples 15-28, Comparative Examples 8-10) Solutions of the main component (modified imide resins A-N, AA, DD, GG) (solid content concentration 40%) and a curing agent were mixed to obtain resin compositions 1-17 in the compositions shown in Table 2. 【0098】 <Evaluation of Resin Composition> (Elastic Modulus) The resin composition was applied to release paper to a thickness of 40 μm after drying, and then dried at 120°C for 10 minutes to form a coating film (dried film). The formed coating film was heated at 150°C for 3 hours to heat-cur it and form a cured film. The formed cured film was cut to a size of 60 mm in length and 15 mm in width to obtain test specimens. Tensile tests were performed on the obtained test specimens using an Autograph (product name "AGS-J", manufactured by Shimadzu Corporation) in accordance with JIS K-7127:1999 under room temperature (25°C) conditions. The tensile modulus of the test specimens was then measured, and the elastic modulus of the cured film was evaluated according to the evaluation criteria shown below. The results are shown in Table 2. ◎: Tensile modulus of 800 N / mm ２ That was all. ○: Tensile modulus of elasticity is 300 N / mm ２ More than 800N / mm ２ It was less than . △: Tensile modulus of elasticity is 100 N / mm ２ 300N / mm or more ２It was less than . ×: Tensile modulus of elasticity was 100 N / mm ２ It was less than [amount missing]. 【0099】 (Thermal Dimensional Stability) The resin composition was applied to release paper to a thickness of 40 μm after drying, and then dried at 120°C for 10 minutes to form a coating film (dried film). The formed coating film was heated at 150°C for 3 hours to heat-cur it and obtain a test specimen (cured film). The coefficient of linear expansion (CTE, 25-300°C) of the obtained test specimens was measured under the conditions shown below, and the heat resistance of the cured film was evaluated according to the evaluation criteria shown below. The results are shown in Table 2. (1) Equipment: Product name "Thermomechanical analyzer TMA-7100E" (manufactured by Hitachi High-Tech Science Co., Ltd.) (2) Probe: Metal tensile probe (3) Load: 10 mN (4) Heating rate: 5 °C / min (5) Measurement temperature range: 20 to 300 °C (6) Sample length: 10 mm ◎: CTE was less than 200 ppm / °C ○: CTE was 200 ppm / °C or more and less than 320 ppm / °C. △: CTE was 320 ppm / °C or more and less than 400 ppm / °C. ×: CTE was 400 ppm / °C or more. 【0100】 (Long-term heat resistance) The resin composition was applied to release paper to a thickness of 40 μm after drying, and then dried at 120°C for 10 minutes to form a coating film (dried film). The formed coating film was heated at 150°C for 3 hours to heat-cur it and form a cured film. The formed cured film was cut to a size of 10 cm in length x 10 cm in width to obtain a cured film. A long-term heat resistance test was conducted on the obtained cured film by storing it in a hot air oven at 150°C in an air atmosphere for 500 hours. The cured film before and after the test were cut to a size of 60 mm in length x 15 mm in width to obtain test pieces. Tensile tests were performed on the obtained test pieces using an Autograph (product name "AGS-J", manufactured by Shimadzu Corporation) in accordance with JIS K-7127:1999 under room temperature (25°C) conditions. The fracture strength of the test specimens was measured, and the rate of change in fracture strength was calculated according to the following formula (C). The long-term heat resistance of the cured film was then evaluated according to the evaluation criteria shown below. The results are shown in Table 2. Rate of change in fracture strength (%) = (S ２ / S １ )×100...(C) S１ : Breaking strength of cured film before long-term heat resistance test S ２ : Breaking strength of cured film after long-term heat resistance test ◎: Breaking strength change rate was 90% or more and less than 110%. ○: Breaking strength change rate was 110% or more and less than 130%. △: Breaking strength change rate was 130% or more and less than 150%. ×: Breaking strength change rate was 150% or more. 【0101】 (Flexibility) The resin composition was applied to release paper to a thickness of 40 μm after drying, and then dried at 120°C for 10 minutes to form a coating film (dried film). The formed coating film was heated at 150°C for 3 hours to heat-cur it and form a cured film. The formed cured film was cut to a size of 1.5 cm in length and 10 cm in width to obtain test pieces. The obtained test pieces were subjected to a flexibility test using an MIT testing machine under the conditions shown below, and the number of folds at which the cured film broke was recorded. The flexibility of the cured film was then evaluated according to the evaluation criteria shown below. The results are shown in Table 2. (1) Equipment: Product name "MIT type bending resistance tester" (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) (2) Load: 0.98 N (3) Angle: ±135° (4) Number of folds: 175 times / min (5) Radius of curvature: 0.38 mm ○: The number of folds was 12,000 or more. △: The number of folds was 5,000 or more but less than 12,000. ×: The number of folds was less than 5,000. 【0102】 【0103】<Manufacturing of Laminates> Resin compositions 1 to 17 obtained in Examples 15 to 28 and Comparative Examples 8 to 10 were each applied to a release film so that the thickness after drying was 20 μm, and heated at 150°C for 10 minutes to dry and form a coating film (dried film). The formed coating film was heat-pressed onto a polyimide film (PI) film (product name "Kapton 200H", manufactured by Toray DuPont) at 100°C using a laminating machine. A copper-clad laminate (product name "ESPANEX MC12-25-00HRM", manufactured by Nippon Steel Chemical & Material Co., Ltd.) was laminated onto the coating film so that the copper surface was in contact with it, and heat-pressed onto it at 150°C and 3 MPa for 1 hour using a hot press machine. After that, it was heat-cured at 150°C for 2 hours to obtain a laminate (PI film / adhesive layer (cured resin composition) / copper-clad laminate (copper surface)). 【0104】 <Evaluation of Laminate> (Solder Heat Resistance) The obtained laminate was cut into 20 mm x 20 mm pieces to prepare test specimens. The prepared test specimens were suspended in a 288°C solder bath with the PI film side facing upwards and held for a predetermined time. The test specimens after holding were observed, and the solder heat resistance of the laminate was evaluated according to the evaluation criteria shown below. The results are shown in Table 3. Generally, if no change occurs in a 288°C solder bath for 30 seconds, the solder heat resistance is judged to be satisfactory. ○: No blistering occurred at 288°C for 30 seconds. △: No blistering occurred at 288°C for 20 seconds, but blistering occurred at 288°C for 30 seconds. ×: Blistering occurred at 288°C for 20 seconds. 【0105】 【0106】 The carboxyl group-containing modified imide resin of the present invention is useful, for example, as a material for flexible printed circuit boards.

Claims

1. A carboxyl group-containing modified imide resin comprising a structure represented by the following general formula (X), having a constituent unit derived from a polyol (a), a constituent unit derived from a polyamine (b), and a constituent unit derived from a tetracarboxylic dianhydride (c), wherein the polyamine (b) contains an aromatic diamine (b1), and the imide bond concentration is 0.5 to 2.0 mmol / g. (In the above general formula (X), n represents a number from 0 to 20, R １ R represents an organic group obtained by removing the acid anhydride group from a tetracarboxylic dianhydride, ２ R represents the organic group obtained by removing the amino group from polyamine (b), ３ (This indicates an organic group obtained by removing a hydroxyl group from polyol (a)).

2. The carboxyl group-containing modified imide resin according to claim 1, wherein the polyol (a) comprises at least one selected from the group consisting of polycarbonate diols and polyester diols.

3. The carboxyl group-containing modified imide resin according to claim 2, wherein the polyol (a) further contains a polyol (a1) that is liquid at 25°C, and the content of constituent units derived from the polyol (a1) is 20 to 60% by mass.

4. The carboxyl group-containing modified imide resin according to any one of claims 1 to 3, wherein the aromatic diamine (b1) is a compound having an aromatic ether bond, and the molecular weight of the portion of the aromatic diamine (b1) other than the amino group is 240 to 500.

5. A carboxyl group-containing modified imide resin according to any one of claims 1 to 4, wherein the number average molecular weight is 10,000 to 50,000 and the acid value is 5 to 40 mgKOH / g.

6. A resin composition comprising a carboxyl group-containing modified imide resin according to any one of claims 1 to 5, and an epoxy resin having two or more epoxy groups in one molecule.

7. The resin composition according to claim 6, further comprising an organic solvent having a boiling point of 200°C or less, for dissolving the carboxyl group-containing modified imide resin.

8. A laminate having a cured layer obtained by curing the resin composition according to claim 6 or 7.

9. A flexible printed circuit board comprising the laminate described in claim 8 as a component.

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