Crosslinked polyester resin composition, adhesive film, laminate, and printed wiring board

Abstract

The purpose of the present disclosure is to provide a crosslinked polyester resin composition having good transparency even when held under high-temperature and high-humidity conditions. The present disclosure relates to a crosslinked polyester resin composition containing a crosslinked polyester resin (C) and a transesterification catalyst (D). The crosslinked polyester resin (C) has a structure in which a polyester resin (A) having a carboxy group in a side chain is crosslinked with an aromatic epoxy compound (B) containing no nitrogen atom in the molecule.

Description

Crosslinked polyester resin composition, adhesive film, laminate, and printed wiring board

[0001] The present disclosure relates to a crosslinked polyester resin composition, an adhesive film containing the crosslinked polyester resin composition, a laminate including the adhesive film and a base material, and a printed wiring board containing the laminate, particularly to a transparent flexible printed circuit (FPC).

[0002] Among electronic circuit boards, flexible printed wiring boards (hereinafter also referred to as "FPC") and the like, transparent FPCs use highly transparent polyimide films, polyester films, and PEN films, and are used as transparent wirings that do not block the field of view in applications such as flexible displays. In recent years, adhesive films obtained by forming an adhesive into a film have come to be used for printed wiring boards. Adhesive films used for transparent FPC applications require excellent transparency in addition to suppressing a decrease in connection reliability caused by thermal stress arising from the use of various materials with different coefficients of thermal expansion, and improving embedding properties for unevenness of wiring boards. Patent Document 1 proposes an adhesive film in which an aliphatic or alicyclic epoxy resin is blended with acrylic rubber.

[0003] Japanese Patent Application Laid-Open No. 2011-159693

[0004] However, when a conventional adhesive film as disclosed in Patent Document 1 is used for an electronic circuit board (particularly a transparent FPC), discoloration may occur and transparency may be impaired due to long-term use under high temperature and high humidity conditions.

[0005] A main object of the present disclosure is to provide a crosslinked polyester resin composition that has suppressed discoloration and good transparency even when held under high temperature and high humidity conditions. Another object of the present disclosure is to provide an adhesive film containing the above-mentioned crosslinked polyester resin composition, a laminate including the above-mentioned adhesive film and a base material, and a printed wiring board including the above-mentioned laminate.

[0006] The present inventors have diligently studied to solve the above problems and have found that the resin compositions shown below can achieve the above objectives, and have completed this disclosure. That is, embodiments of this disclosure are, for example, any of the following [1] to

[11] . [1] A crosslinked polyester resin composition containing a crosslinked polyester resin (C) and a transesterification catalyst (D), wherein the crosslinked polyester resin (C) has a structure in which a polyester resin (A) having carboxyl groups in its side chains is crosslinked with an aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule. [2] The crosslinked polyester resin composition according to [1], wherein the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule contains three or more epoxy groups in its molecule. [3] The crosslinked polyester resin composition according to [1] or [2], wherein the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule has a structure in which a glycidyloxy group is directly bonded to an aromatic ring. [4] The crosslinked polyester resin composition according to any of [1] to [3], wherein the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule has 2 to 15 aromatic rings in its molecule. [5] The crosslinked polyester resin composition according to any one of [1] to [4], wherein the epoxy equivalent of the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule is 120 to 500 g / eq. [6] The crosslinked polyester resin composition according to any one of [1] to [5], wherein in the crosslinked polyester resin (C), the content of epoxy groups of the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule before crosslinking is 50 to 150 mole parts per 100 mole parts of carboxyl groups of the polyester resin (A) having carboxyl groups in its side chains before crosslinking. [7] The crosslinked polyester resin composition according to any one of [1] to [6], wherein the amount of the transesterification catalyst (D) in the crosslinked polyester resin composition is 1 to 70 mole parts per 100 mole parts of carboxyl groups of the polyester resin (A) having carboxyl groups in its side chains before crosslinking. [8] The crosslinked polyester resin composition according to any one of [1] to [7], wherein the acid value of the polyester resin (A) having carboxyl groups in its side chains is 5 to 40 mg KOH / g.[9] An adhesive film comprising the crosslinked polyester resin composition according to any one of [1] to [8].

[10] A laminate comprising the adhesive film according to [9] and a base material.

[11] A printed wiring board comprising the laminate according to

[10] .

[0007] According to the present disclosure, it is possible to provide a crosslinked polyester resin composition that suppresses discoloration and has good transparency even when held under high temperature and high humidity. Further, according to the present disclosure, there can be provided an adhesive film containing the crosslinked polyester resin composition, a laminate including the adhesive film and a base material, and a printed wiring board including the laminate.

[0008] FIG. 1 shows the appearance of the laminate of Example 1 after holding under high temperature and high humidity. FIG. 2 shows the appearance of the laminate of Example 2 after holding under high temperature and high humidity. FIG. 3 shows the appearance of the laminate of Comparative Example 1 after holding under high temperature and high humidity. FIG. 4 shows the appearance of the copper-clad laminate of a reference example.

[0009] <Crosslinked Polyester Resin Composition> The crosslinked polyester resin composition according to the present disclosure (hereinafter, also simply referred to as "resin composition") contains a crosslinked polyester resin (C) and a transesterification catalyst (D), wherein the crosslinked polyester resin (C) has a structure in which a polyester resin (A) having a carboxy group in a side chain is crosslinked with an aromatic epoxy compound (B) containing no nitrogen atom in the molecule. According to the resin composition of the present disclosure, discoloration is suppressed even when held for a long period of time (for example, 3 weeks) under high temperature and high humidity (for example, in an environment of 85° C. and 85% RH), whereby an adhesive film having good transparency (transparent appearance) can be formed, and preferably an adhesive film excellent in heat resistance can also be formed. Further, the resin composition according to the present disclosure may optionally contain other components within a range that does not impair the effects of the present disclosure. In the present specification, unless otherwise specified, one type or a combination of two or more types of the compounds exemplified as each component can be used.

[0010] <Cross-linked polyester resin (C)> Cross-linked polyester resin (C) has a structure in which a polyester resin (A) having carboxyl groups in its side chains is cross-linked with an aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule. Specifically, it has a structure in which the carboxyl groups in the side chains of the polyester resin (A) having carboxyl groups in its side chains are cross-linked with an aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule.

[0011] The crosslinked polyester resin (C) can undergo a transesterification reaction under high temperature conditions (e.g., 120°C or higher) in the presence of a transesterification catalyst (D), by reacting the hydroxyl groups within the molecule of the crosslinked polyester resin (C) (for example, hydroxyl groups in the crosslinked structure derived from an aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule) with the ester bonds in the crosslinked polyester resin (C) that are located nearby. As a result, a resin composition containing the crosslinked polyester resin (C) exhibits softening behavior and can show good adhesion when heat-pressed to an adherend.

[0012] <Transesterification Catalyst (D)> Transesterification catalyst (D) is a catalyst that promotes the transesterification reaction, which is a reaction between ester bonds in a crosslinked polyester resin (C) (for example, ester bonds derived from a polyester resin (A) having carboxyl groups in its side chains) and hydroxyl groups (for example, hydroxyl groups within the molecule of the crosslinked polyester resin (C), and in particular, hydroxyl groups in the crosslinked structure derived from an aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule). By containing transesterification catalyst (D) in the resin composition, the crosslinked polyester resin (C) becomes capable of bond exchange at high temperatures (for example, 120°C or higher). Because the crosslinked polyester resin (C) has dynamic covalent crosslinks that enable bond exchange at high temperatures, the resin composition has high strength at room temperature, and above the ester bond exchange activation temperature, it exhibits good adhesion to substrates, films, and wiring, as well as stress relaxation, which can suppress problems such as cracks and circuit distortion caused by differences in thermal expansion between adherends.

[0013] Examples of transesterification catalysts (D) include zinc acetate, zinc acetate anhydride, zinc acetate dihydrate, zinc(II) acetylacetonate, aluminum(III) acetylacetonate, triphenylphosphine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene, 1,8-diazabicyclo[5.4.0]undecene-7, and tetrabutyl titanate. Among these, zinc acetate anhydride, zinc acetate dihydrate, and zinc(II) acetylacetonate are preferred, with zinc acetate anhydride being more preferred.

[0014] The ratio of the transesterification catalyst (D) in the resin composition is preferably 1 to 70 moles, more preferably 3 to 60 moles, even more preferably 5 to 50 moles, even more preferably 8 to 40 moles, and even more preferably 10 to 30 moles, per 100 moles of carboxyl groups in the side chains of the polyester resin (A) having carboxyl groups in its side chains before crosslinking. If the ratio of the transesterification catalyst (D) in the resin composition is within the above range, the softening of the resin composition during heating can be promoted, and the adhesion can be improved.

[0015] <Polyester resin (A) having carboxyl groups in the side chains> Polyester resin (A) having carboxyl groups in the side chains (hereinafter also simply referred to as "polyester resin (A)") has at least one carboxyl group (-COOH) in the side chain of the polyester resin (hereinafter also referred to as "branched structure"). Polyester resin (A) also has an ester bond in its molecule. The structure of polyester resin (A) may be a structure in which a carboxyl group is present in a substituent branched from the main chain of the polyester resin (for example, an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, etc.) (i.e., a structure having substituents with carboxyl groups as side chains), or a structure in which a carboxyl group is directly present in the main chain of the polyester resin (i.e., a structure having carboxyl groups as side chains), and preferably a structure in which a carboxyl group is directly present in the main chain of the polyester resin.

[0016] The number-average molecular weight (Mn) of the polyester resin (A) is preferably 5,000 to 50,000, more preferably 8,000 to 30,000, even more preferably 10,000 to 25,000, and even more preferably 12,000 to 20,000. If the number-average molecular weight (Mn) of the polyester resin (A) is within the above range, it becomes easier to control the acid value of the polyester resin (A).

[0017] The acid value of the polyester resin (A) is preferably 5 to 40 mg KOH / g, more preferably 8 to 30 mg KOH / g, even more preferably 10 to 25 mg KOH / g, and even more preferably 12 to 20 mg KOH / g. If the acid value of the polyester resin (A) is within the above range, the crosslinking density in the crosslinked polyester resin (C) can be appropriately controlled, so that ester bond exchange occurs easily without the movement of the molecules themselves being suppressed, and stress relaxation and softening are sufficient, resulting in a resin composition with good adhesion.

[0018] The glass transition temperature (Tg) of the polyester resin (A) is preferably -10 to 110°C, more preferably 0 to 100°C, even more preferably 5 to 80°C, even more preferably 8 to 60°C, and even more preferably 10 to 45°C.

[0019] The polyester resin (A) preferably contains ester bonds and carboxyl groups at multiple points within the molecule. The number of carboxyl groups per polymer chain of the polyester resin (A) is preferably 2 to 60, more preferably 3 to 50, and even more preferably 4 to 30 per molecule of polyester resin (A) before crosslinking. If the number of carboxyl groups per polymer chain of the polyester resin (A) is within the above range, a resin composition with good heat resistance and adhesion can be obtained. The number of carboxyl groups per polymer chain of the polyester resin (A) is related to proton nuclear magnetic resonance ( １ This can be determined by methods such as H NMR.

[0020] It is preferable that the resin components (polyester components) derived from polyester resin (A) be included as the main components in the resin composition. Specifically, the main components in the resin composition refer to the component with the highest content in the solid content of the resin composition (i.e., the component with the highest content among the resin components derived from polyester resin (A), resin components derived from epoxy compounds, and other components). The content of the resin components derived from polyester resin (A) in the resin composition according to this disclosure is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the solid content of the resin composition. Furthermore, the content of the resin components derived from polyester resin (A) in the resin composition is preferably 99.0% by mass or less, more preferably 98.0% by mass or less, and even more preferably 97.5% by mass or less, based on 100% by mass of the solid content of the resin composition. Specifically, the content of resin components derived from polyester resin (A) in the resin composition is preferably 50 to 99.0% by mass, more preferably 60 to 98.0% by mass, and even more preferably 70 to 97.5% by mass, based on 100% by mass of the solid content of the resin composition. This range is preferable because it results in good heat resistance.

[0021] Polyester resin (A) has side chains (branched structure) within its molecule. Because polyester resin (A) has this branched structure, the polymerization components that serve as raw materials for the resin may also have a branched structure.

[0022] Polyester resin (A) can be produced by the reaction of a polycarboxylic acid component and a polyhydric alcohol component, and may be obtained by adding a monomer having a carboxyl group to a polyester having a reaction site obtained by the reaction of a polycarboxylic acid component and a polyhydric alcohol component, but it is preferable that a polymer polyol (a) obtained by the reaction of a polycarboxylic acid component and a polyhydric alcohol component is reacted (copolymerized) with a polycarboxylic acid component with three or more functionalities to impart a carboxyl group.

[0023] <High Polymer Polyol (a)> High polymer polyol (a) may be a polymer of a polycarboxylic acid component and a polyhydric alcohol component (high polymer polyester polyol). Furthermore, high polymer polyol (a) may contain a polyhydric alcohol component with three or more functions or a polycarboxylic acid component with three or more functions.

[0024] (Polycarboxylic acid component) As the polycarboxylic acid component used in polymer polyol (a), an aromatic dicarboxylic acid component and / or a polycarboxylic acid component other than an aromatic dicarboxylic acid component may be used, and it is preferable to use at least an aromatic dicarboxylic acid component.

[0025] As the polycarboxylic acid component used in polymer polyol (a), it is preferable to use an aromatic dicarboxylic acid component from the viewpoint of increasing the cohesive strength of the resin and improving its strength. Examples of aromatic dicarboxylic acid components include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and diphenic acid. In addition, aromatic dicarboxylic acids having a sulfonic acid group, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5-(4-sulfophenoxy)isophthalic acid, and aromatic dicarboxylic acids having a sulfonic acid base, such as metal salts and ammonium salts thereof, may also be used. These may be used individually or in mixtures of two or more. Among these, terephthalic acid, isophthalic acid, and mixtures thereof are preferred.

[0026] Examples of polycarboxylic acid components other than aromatic dicarboxylic acid components include alicyclic dicarboxylic acids such as acid anhydrides of 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,2-cyclohexanedicarboxylic acid, and their acid anhydrides; aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid, and their acid anhydrides; unsaturated bond-containing dicarboxylic acids such as fumaric acid and maleic acid, and their acid anhydrides; thiomalic acid having a thiol group in its molecular structure; and biomass-derived 2,5-franzicarboxylic acid (FDCA). These may be used individually or in combination of two or more.

[0027] (Polyhydric alcohol component) A glycol component is preferred as the polyhydric alcohol component used in the polymer polyol (a). Examples of glycol components include aliphatic glycols, alicyclic glycols, aromatic glycols, or ether bond-containing glycols.

[0028] Examples of aliphatic glycols include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol (DMH), neopentyl glycol hydroxypivalate, dimethylolheptane, and 2,2,4-trimethyl-1,3-pentanediol.

[0029] Examples of alicyclic glycols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, tricyclodecanediol, tricyclodecanedimethylol, spiroglycol, hydrogenated bisphenol A, ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A, and dimergol.

[0030] Examples of aromatic glycols include paraxylene glycol, metaxylene glycol, orthoxylene glycol, p-hydroxyphenethyl alcohol, 1,4-phenylene glycol, ethylene oxide adducts of 1,4-phenylene glycol, bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A, and glycols obtained by adding 1 to several moles of ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols. In addition, glycol-modified aromatic dicarboxylic acids may be used, and specific examples include bis-2-hydroxyethyl terephthalate (BHET), an ethylene glycol-modified terephthalic acid, propylene glycol-modified terephthalic acid, ethylene glycol-modified isophthalic acid, propylene glycol-modified isophthalic acid, ethylene glycol-modified orthophthalic acid, and propylene glycol-modified orthophthalic acid. Other examples of glycol-modified aromatic dicarboxylic acids include glycol-modified aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, biphenyldicarboxylic acid, diphenic acid, and 5-hydroxyisophthalic acid; and glycol-modified aromatic dicarboxylic acids having a sulfonic acid group or sulfonic acid base, such as sulfoterephthalic acid, 5-sulfisophthalic acid, 4-sulfoterephthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5-(4-sulfophenoxy)isophthalic acid, sulfoterephthalic acid, and their metal salts and ammonium salts.

[0031] Examples of ether bond-containing glycols include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol ethylene oxide adduct, and neopentyl glycol propylene oxide adduct.

[0032] These may be used individually or in combination of two or more. Among these, aliphatic glycols are preferred, and more preferably ethylene glycol, 2-methyl-1,3-butanediol, 2,2-dimethyl-1,3-propanediol, and 1,6-hexanediol.

[0033] (Polycarboxylic acid components with three or more functions) Examples of polycarboxylic acid components with three or more functions used in polymer polyol (a) include trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic anhydride (PMDA), oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic acid dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA), 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA), and other compounds. These may be used individually or in combination of two or more. Among these, trimellitic anhydride is preferred.

[0034] (Polyhydric alcohol components with three or more functions) Examples of polyhydric alcohol components with three or more functions used in high molecular weight polyol (a) include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. These may be used individually or in combination of two or more.

[0035] The polymer polyol (a) may also contain other components such as oxycarboxylic acid compounds having a hydroxyl group and a carboxyl group in their molecular structure, including 5-hydroxyisophthalic acid, p-hydroxybenzoic acid, p-hydroxyphenylpropionic acid, p-hydroxyphenylacetic acid, 6-hydroxy-2-naphthoic acid, and 4,4-bis(p-hydroxyphenyl)valeric acid.

[0036] The number-average molecular weight (Mn) of the polymer polyol (a) is preferably 1,000 to 30,000, more preferably 2,000 to 25,000, and even more preferably 3,000 to 20,000.

[0037] The polymer polyol (a) may contain two or more polymer polyols with different number-average molecular weights (Mn). When polymer polyol (a) contains two or more polymer polyols with different number-average molecular weights (Mn), it may contain a long-chain polymer polyol (a1) component with a number-average molecular weight (Mn) of 7000 or more, and a short-chain polymer polyol (a2) component with a number-average molecular weight (Mn) of 1000 or more and less than 7000. By including two or more polymer polyols with different number-average molecular weights (Mn), the heat resistance of the resin composition can be improved. For example, the long-chain molecules of the block derived from the long-chain polymer polyol (a1) contribute to the heat resistance, while introducing a block derived from the short-chain polymer polyol (a2) allows for the introduction of a sufficient amount of carboxylic acid to impart heat resistance. The upper limit of the number-average molecular weight (Mn) of the long-chain polymer polyol (a1) is not particularly limited, but for example, it may be 20000 or less.

[0038] When polymer polyol (a) contains a long-chain polymer polyol (a1) component and a short-chain polymer polyol (a2) component, the polymerization ratio of the long-chain polymer polyol (a1) and short-chain polymer polyol (a2) in polymer polyol (a) is preferably 5 to 50 parts by mass of short-chain polymer polyol (a2) per 100 parts by mass of the total of the long-chain polymer polyol (a1) and short-chain polymer polyol (a2). By having the polymerization ratio of the long-chain polymer polyol (a1) and short-chain polymer polyol (a2) within the above range, the heat resistance of the resin composition can be improved. The amount of the short-chain polymer polyol (a2) component is more preferably 10 to 40 parts by mass, and even more preferably 20 to 30 parts by mass, per 100 parts by mass of the total of the long-chain polymer polyol (a1) and short-chain polymer polyol (a2) components.

[0039] When polymer polyol (a) contains a long-chain polymer polyol (a1) component and a short-chain polymer polyol (a2) component, the polymerization amount of the long-chain polymer polyol (a1) is preferably 50 to 90% by mass, when polymer polyol (a) is considered to be 100% by mass. By having the polymerization amount of the long-chain polymer polyol (a1) in polymer polyol (a) within the above range, the heat resistance and adhesion of the resin composition are improved by balancing it with the polymerization amounts of the short-chain polymer polyol (a2) and the trifunctional or more polyvalent carboxylic acid components described later. The polymerization amount of the long-chain polymer polyol (a1) is more preferably 60 to 85% by mass, and even more preferably 70 to 80% by mass, when polymer polyol (a) is considered to be 100% by mass.

[0040] (Polycarboxylic acid components with three or more functions) The polycarboxylic acid components with three or more functions that react (polymerize) with the high molecular weight polyol (a) are not particularly limited as long as they are compounds having three or more carboxyl groups in their molecule. The carboxyl groups may also form acid anhydride groups within the molecule, in which case one acid anhydride group is counted as two carboxyl groups.

[0041] Examples of polycarboxylic acid components with three or more functions include trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic anhydride (PMDA), oxydiphthalic acid dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic acid dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA). These may be used individually or in combination of two or more. Among these, pyromellitic anhydride is preferred.

[0042] The ratio of the trifunctional or higher polycarboxylic acid component to be reacted (polymerized) with the polymer polyol (a) may be 0.1 to 3 moles of the trifunctional or higher polycarboxylic acid component per 100 moles of polyester resin (A), more preferably 0.3 to 2 moles, and even more preferably 0.5 to 1.5 moles.

[0043] In polyester resin (A), the polymerization ratio of the high-molecular-weight polyol (a) to the trifunctional or higher polycarboxylic acid component is preferably 0.5 to 10 parts by mass, more preferably 1 to 8 parts by mass, and even more preferably 2 to 5 parts by mass, of the trifunctional or higher polycarboxylic acid component per 100 parts by mass of high-molecular-weight polyol (a). When the polymerization ratio of the trifunctional or higher polycarboxylic acid component is above the lower limit, the amount of crosslinking is sufficient, and the heat resistance of the resin composition is improved. When the polymerization ratio of the trifunctional or higher polycarboxylic acid component is below the upper limit, the crosslinking density does not become too high, ester bond exchange occurs easily, softening is sufficient, and adhesion is improved.

[0044] The acid value of the polymer polyol (a) is preferably, for example, 0.1 to 20 mg KOH / g, more preferably 0.2 to 15 mg KOH / g, and even more preferably 0.3 to 10 mg KOH / g.

[0045] When the polymer polyol (a) includes a long-chain polymer polyol (a1) and a short-chain polymer polyol (a2), the acid value of the long-chain polymer polyol (a1) is preferably, for example, 1 to 20 mg KOH / g, more preferably 2 to 15 mg KOH / g, and even more preferably 3 to 10 mg KOH / g. The acid value of the short-chain polymer polyol (a2) is preferably, for example, 0.1 to 10 mg KOH / g, more preferably 0.2 to 8 mg KOH / g, and even more preferably 0.3 to 5 mg KOH / g.

[0046] The glass transition temperature of the polymer polyol (a) is preferably -10 to 100°C, more preferably 0 to 80°C, and even more preferably 5 to 60°C.

[0047] When the polymer polyol (a) includes a long-chain polymer polyol (a1) and a short-chain polymer polyol (a2), the glass transition temperature of the long-chain polymer polyol (a1) is preferably -10 to 60°C, more preferably -5 to 30°C, and even more preferably 0 to 15°C. The glass transition temperature of the short-chain polymer polyol (a2) is preferably 5 to 100°C, more preferably 20 to 90°C, and even more preferably 30 to 80°C.

[0048] (Reaction Catalyst) When producing polyester resin (A), a reaction catalyst may be used to the extent that it does not impair the effects described above. Examples of reaction catalysts include imidazole compounds such as 2-methylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, or 1-cyanoethyl-2-ethyl-4-methylimidazole; triethylamine, triethylenediamine, N'-methyl-N-(2-dimethylaminoethyl)piperazine, N,N-diisopropylethylamine, N,N-dimethylaminopyridine, 1,8-diazabicyclo[5,4,0]-undecene-7, 1,5-diazabicyclo[4,3,0]-nonene-5,6-dibutylamino Examples include tertiary amines such as -1,8-diazabicyclo[5,4,0]-undecene-7 and compounds obtained by amine salting these tertiary amines with phenol, octic acid, or quaternized tetraphenyl borate salt; and quaternary ammonium salts such as tetramethylammonium bromide, tetraethylammonium bromide, tetra-n-butylammonium bromide, tetramethylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, tetramethylammonium hydroxide, trimethylbenzylammonium hydroxide, and tetra-n-butylammonium hydroxide. These may be used individually or in combination of two or more. Among these, tertiary amines and compounds obtained by amine salting these tertiary amines with phenol, octic acid, or quaternized tetraphenyl borate salt are preferred, and triethylamine is more preferred.

[0049] (Chain extender) The polyester resin (A) may optionally contain a chain extender as a copolymer component, as long as it does not impair the effects described above. The acid value can be efficiently imparted by using a chain extender. As the chain extender, for example, a low molecular weight diol with a molecular weight of 1000 or less may be used. However, the low molecular weight diol with a molecular weight of 1000 or less does not contain aliphatic glycols. Examples of low molecular weight diols with a molecular weight of 1000 or less include dimethylolbutanoic acid.

[0050] The polymerization amount of the chain extender in the polyester resin (A) is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 4 parts by mass, and even more preferably 1 to 3 parts by mass, per 100 parts by mass of the polymer polyol (a). If the polymerization amount of the chain extender is too high, phenomena such as difficulty in increasing the molecular weight and clouding of the varnish due to reactions between the chain extenders may occur.

[0051] <Aromatic epoxy compound (B) that does not contain nitrogen atoms in the molecule> The aromatic epoxy compound (B) that does not contain nitrogen atoms in the molecule (hereinafter also simply referred to as "epoxy compound (B)") has an aromatic ring and is a compound that has an epoxy group in its molecule, and preferably has two or more epoxy groups in its molecule. Furthermore, the epoxy compound (B) does not contain nitrogen atoms in its molecule. The epoxy compound (B) is not particularly limited as long as it reacts with the carboxyl group of the polyester resin (A) to crosslink. The epoxy compound (B) preferably has the epoxy group as a glycidyl group, more preferably as a glycidyloxy group, and even more preferably has a structure in which the glycidyloxy group is directly bonded to the aromatic ring. When it has a structure in which the glycidyloxy group is bonded to the aromatic ring, the number of glycidyloxy groups bonded to one aromatic ring is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1. When it has a structure in which a substituent having an epoxy group (e.g., a glycidyloxy group) is bonded to the aromatic ring, the substituent that does not have an epoxy group may also be bonded to the aromatic ring. The substituents that do not have an epoxy group are preferably hydrocarbon groups having 1 to 12 carbon atoms, more preferably aliphatic hydrocarbon groups having 1 to 8 carbon atoms, more preferably aromatic hydrocarbon groups having 6 to 12 carbon atoms, even more preferably aliphatic hydrocarbon groups having 1 to 8 carbon atoms, even more preferably saturated aliphatic hydrocarbon groups having 1 to 6 carbon atoms, and even more preferably alkyl groups having 1 to 3 carbon atoms. The number of substituents that do not have an epoxy group attached to one aromatic ring is preferably 1 to 3, more preferably 1 to 2, and even more preferably 1. The epoxy compound (B) preferably has 1 to 20 aromatic rings in its molecule, more preferably 2 to 15, and even more preferably 3 to 10.When the molecule contains two or more aromatic rings, the aromatic rings may be directly bonded to each other, or they may be bonded together via linking groups such as alkylene groups having 1 to 4 carbon atoms, oxyalkylene groups having 1 to 5 carbon atoms, or ether groups. Preferably, the aromatic rings are bonded together via a methylene group, and the methylene group may have substituents such as hydrocarbon groups having 1 to 12 carbon atoms (preferably 1 to 6, more preferably 1 to 3), but it is preferable that it does not have substituents. By using epoxy compound (B), three-dimensional crosslinking is facilitated, and the crosslinking density can be appropriately controlled in the presence of the transesterification catalyst (D), so a resin composition with better heat resistance and adhesion can be obtained. Furthermore, because epoxy compound (B) does not contain nitrogen atoms in its molecule and has a structure containing aromatic rings, discoloration is suppressed even when maintained under high temperature and high humidity, so a resin composition with good transparency can be obtained.

[0052] The number of epoxy groups in the molecule of epoxy compound (B) is preferably 2 or more, more preferably 3 or more, and even more preferably 3 to 20.

[0053] Examples of epoxy compounds (B) include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, phenol novolac type epoxy compounds, cresol novolac type epoxy compounds, bisphenol A novolac type epoxy compounds, bisphenol F novolac type epoxy compounds, stilbene type epoxy compounds, fluorene skeleton-containing epoxy compounds, triphenolmethane type epoxy compounds, biphenyl type epoxy compounds, xylylene type epoxy compounds, biphenyl aralkyl type epoxy compounds, and naphthalene type epoxy compounds. These may be used individually or in combination of two or more. Among these, bisphenol A type epoxy compounds and cresol novolac type epoxy compounds are preferred as epoxy compounds (B), with cresol novolac type epoxy compounds being more preferred. As the bisphenol A type epoxy compound, commercially available products such as the trade names "jER825", "jER827", "jER828", and "jER834" (all manufactured by Mitsubishi Chemical Corporation) may be used, and as the cresol novolac type epoxy compound, commercially available products such as the trade names "YDCN-704", "YDCN-700-3", "YDCN-700-7", and "YDCN-700-10" (all manufactured by Tetsu Chemical & Material Co., Ltd.) may be used.

[0054] The number-average molecular weight (Mn) of the epoxy compound (B) is preferably 100 to 4000, and more preferably 300 to 2000, from the viewpoint of the crosslinking density of the crosslinked polyester resin (C).

[0055] The weight-average molecular weight (Mw) of the epoxy compound (B) is preferably 100 to 5000, and more preferably 300 to 3000, from the viewpoint of the crosslinking density of the crosslinked polyester resin (C).

[0056] The epoxy equivalent (mass per equivalent of epoxy group) of epoxy compound (B) is preferably 100 to 1000 g / eq, more preferably 120 to 500 g / eq, even more preferably 140 to 300 g / eq, and still more preferably 160 to 250 g / eq.

[0057] The crosslinked polyester resin (C) may be a resin using an epoxy compound other than the epoxy compound (B) described above (hereinafter also referred to as "other epoxy compound (Bb)"). The other epoxy compound (Bb) is a compound that contains a nitrogen atom in its molecule and has an epoxy group in its molecule, or a compound that has an epoxy group in its molecule without having an aromatic ring, and is preferably a compound that has two or more epoxy groups in its molecule. The other epoxy compound (Bb) is not particularly limited as long as it reacts with the carboxyl group of the polyester resin (A) to crosslink. The number of epoxy groups in the molecule of the other epoxy compound (Bb) is preferably 2 to 4, and more preferably 2 to 3.

[0058] Other epoxy compounds (Bb) include diol diglycidyl ethers without aromatic rings, epoxyamine compounds having two or more epoxy groups and two or more tertiary amino groups in the molecule, and compounds containing two or more epoxy groups and one tertiary amino group in the molecule. Examples of diol diglycidyl ethers without aromatic rings include aliphatic diol diglycidyl ethers such as ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. Examples of epoxyamine compounds having two or more epoxy groups and two or more tertiary amino groups in the molecule include compounds having two diglycidylamino groups and a benzene ring, such as N,N,N',N'-tetraglycidyl-m-xylylenediamine and 4,4'-methylenebis(N,N-diglycidylaniline). Examples of compounds containing two or more epoxy groups and one tertiary amino group in their molecule include triglycidyl-para-aminophenol, which has one diglycidyl-amino group, a glycidyl-oxy group, and a benzene ring, and N,N-diglycidylaniline, which has one diglycidyl-amino group and a benzene ring. These may be used individually or in combination of two or more.

[0059] The number-average molecular weight (Mn) of the other epoxy compound (Bb) is preferably 100 to 500, and more preferably 250 to 400, from the viewpoint of the crosslinking density of the crosslinked polyester resin (C).

[0060] When the total amount of epoxy compounds used in the crosslinked polyester resin (C) is 100 moles, the content of epoxy compound (B) is preferably 50 to 100 moles, more preferably 80 to 100 moles, even more preferably 90 to 100 moles, and particularly preferably 100 moles.

[0061] The mixing ratio of polyester resin (A) and epoxy compound (B) can be determined based on the functional group molar ratio of carboxyl groups (particularly those on the side chains) of polyester resin (A) to epoxy groups of epoxy compound (B). In the preparation of crosslinked polyester resin (C), the content of epoxy groups of epoxy compound (B) per 100 moles of carboxyl groups of polyester resin (A) is preferably 50 to 150 moles, more preferably 80 to 140 moles, and even more preferably 90 to 130 moles. By determining the mixing ratio of polyester resin (A) and epoxy compound (B) based on the above functional group molar ratio range, a resin composition with good transparency can be obtained by suppressing discoloration even when maintained under high temperature and high humidity. The amount of carboxyl groups of polyester resin (A) may be calculated from the raw material blending amount during the preparation of polyester resin (A), or it may be determined by measurement using NMR or the like.

[0062] The reaction temperature between the polyester resin (A) and the epoxy compound (B) is preferably 80 to 200°C, more preferably 100 to 180°C, and even more preferably 120 to 160°C. The reaction time between the polyester resin (A) and the epoxy compound (B) depends on the reaction temperature, but is preferably 30 minutes to 20 hours, more preferably 1 to 15 hours, and even more preferably 2 to 10 hours.

[0063] The reaction between the polyester resin (A) and the epoxy compound (B) may be carried out without a solvent or in the presence of an organic solvent. When an organic solvent is used, the organic solvent is not particularly limited as long as it does not react with the polyester resin (A) and the epoxy compound (B). Examples include aromatic organic solvents such as toluene and xylene, aliphatic organic solvents such as heptane and octane, ketone solvents such as methyl ethyl ketone, ether solvents such as tetrahydrofuran and diethyl ether, and amide solvents such as dimethylformamide, N-methylpyrrolidone, and N,N-dimethylformamide. Aromatic organic solvents, ketone solvents, and amide solvents are preferred, more preferably aromatic organic solvents, and even more preferably toluene. These solvents may be used alone or in combination of two or more.

[0064] The ratio (composition ratio) of the components derived from the polyester resin (A) to the components derived from the epoxy compound (B) in the crosslinked polyester resin (C) can be determined based on the mixing ratio during the reaction between the polyester resin (A) and the epoxy compound (B). From the viewpoint of obtaining a resin composition that exhibits good transparency and suppresses discoloration even when held under high temperature and high humidity, it is preferable that the content of epoxy groups in the pre-crosslinked epoxy compound (B) relative to 100 moles of carboxyl groups in the pre-crosslinked polyester resin (A) in the crosslinked polyester resin (C) is 50 to 150 moles, more preferably 80 to 140 moles, even more preferably 90 to 135 moles, and even more preferably 95 to 130 moles. By keeping the content of epoxy groups in the pre-crosslinked epoxy compound (B) relative to carboxyl groups in the pre-crosslinked polyester resin (A) within the above range, it is also preferable to improve the heat resistance of the resin composition.

[0065] <Flame Retardant (E)> The resin composition may contain a flame retardant (hereinafter also referred to as "flame retardant (E)"). By including a flame retardant (E), flame retardancy can be imparted to the resin composition. The flame retardant (E) is not particularly limited as long as it exhibits flame retardancy, but it is preferable that it does not dissolve in organic solvents.

[0066] As the flame retardant (E), for example, a flame retardant filler may be used, and examples of flame retardant fillers include inorganic flame retardant fillers and organic flame retardant fillers. Inorganic flame retardant fillers and organic flame retardant fillers may be used individually or in combination.

[0067] Examples of inorganic flame-retardant fillers include metal oxides such as magnesium oxide, molybdenum oxide, zirconium oxide, tin oxide, tin oxide hydrate, and antimony oxide; metal hydroxide compounds such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide, and barium hydroxide; metal carbonate compounds such as basic magnesium carbonate, zinc carbonate, magnesium-calcium carbonate (a mixture of magnesium carbonate and calcium carbonate), calcium carbonate, and barium carbonate; metal borate compounds such as zinc borate, zinc metaborate, and barium metaborate; inorganic metal compounds such as dolomite, hydrotalcite, and borax; and inorganic phosphorus compounds such as red phosphorus. These may be used individually or in mixtures of two or more.

[0068] Examples of organic flame retardant fillers include phosphorus compounds such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium phosphate, ammonium polyphosphate, carbamate phosphate, carbamate polyphosphate, aluminum tris-diethylphosphinate, aluminum tris-methylethylphosphinate, aluminum tris-diphenylphosphinate, zinc bis-diethylphosphinate, zinc bis-methylethylphosphinate, zinc bis-diphenylphosphinate, titanyl bis-diethylphosphinate, titanium tetrakis-diethylphosphinate, titanyl bis-methylethylphosphinate, titanium tetrakis-methylethylphosphinate, titanyl bis-diphenylphosphinate, and titanium tetrakis-diphenylphosphinate; nitrogen compounds such as triazine compounds (e.g., melamine, melam, melamine cyanurate, etc.), cyanuric acid compounds, isocyanuric acid compounds, triazole compounds, tetrazole compounds, diazo compounds, and urea; and silicon compounds such as silicone compounds and silane compounds. These may be used individually, or two or more may be used in combination.

[0069] Among these, metal hydroxide compounds or phosphorus compounds are preferred, and phosphorus compounds are more preferred. Among phosphorus compounds, aluminum phosphinates such as aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, and aluminum trisdiphenylphosphinate are more preferred.

[0070] Phosphorus compounds are commercially available, for example, from Clariant Japan Co., Ltd. as "EXOLIT® OP-935".

[0071] The average particle size of the flame retardant (E) may be, for example, 1 to 50 μm, preferably 2 to 30 μm, and more preferably 3 to 10 μm. The maximum particle size of the flame retardant (E) may be, for example, 100 μm or less, preferably 90 μm or less, and more preferably 80 μm or less. The particle size (median diameter) of the flame retardant (E) can be measured on a volume basis using a laser diffraction / scattering particle size distribution analyzer.

[0072] When the resin composition contains a flame retardant (E), the amount ratio of the flame retardant (E) in the resin composition is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and even more preferably 10 to 40 parts by mass, per 100 parts by mass of polyester resin (A). By setting the amount ratio of the flame retardant (E) in the resin composition within the above range, the flame retardancy of the resin composition can be improved.

[0073] <Other Components> The resin composition may contain components other than the crosslinked polyester resin (C), the transesterification catalyst (D), and the flame retardant (E) as needed, to the extent that they do not impair the effects of the invention. Examples of other components include silica. If other components are included, their content is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, and even more preferably 0.05 to 1% by mass, based on the total amount of solids in the resin composition.

[0074] The resin composition can be obtained by mixing a crosslinked polyester resin (C), a transesterification catalyst (D), and optionally a flame retardant (E) and other components. Alternatively, the resin composition can be obtained by mixing a polyester resin (A), an epoxy compound (B), a transesterification catalyst (D), and optionally a flame retardant (E) and other components, heating the mixture, and carrying out a crosslinking reaction via an epoxy ring-opening reaction. The heating temperature is preferably 80 to 200°C, more preferably 100 to 180°C, and even more preferably 120 to 160°C. The heating time depends on the heating temperature, but for example, it is preferably 30 minutes to 20 hours, more preferably 1 to 15 hours, and even more preferably 2 to 10 hours.

[0075] The mixing of the crosslinked polyester resin (C) and the transesterification catalyst (D), as well as the mixing and heating of the polyester resin (A), epoxy compound (B), and transesterification catalyst (D), may be carried out without a solvent or in the presence of an organic solvent. When an organic solvent is used, the organic solvent is not particularly limited as long as it does not react with the mixed components. Examples include aromatic organic solvents such as toluene and xylene, aliphatic organic solvents such as heptane and octane, ketone solvents such as methyl ethyl ketone, ether solvents such as tetrahydrofuran and diethyl ether, and amide solvents such as dimethylformamide, N-methylpyrrolidone, and N,N-dimethylformamide. Aromatic organic solvents, ketone solvents, and amide solvents are preferred, and aromatic organic solvents and amide solvents are more preferred. These solvents may be used alone or in combination of two or more.

[0076] The resin composition preferably has a storage modulus at 200°C of 1.50 to 10 MPa, more preferably 1.80 to 8 MPa, even more preferably 2.00 to 6 MPa, even more preferably 2.20 to 5 MPa, and even more preferably 2.60 to 4 MPa. If the storage modulus at 200°C is above the lower limit, a resin composition with good heat resistance and good durability can be obtained, as the resin composition is less susceptible to damage from external impacts, etc. If the storage modulus at 200°C is below the upper limit, a resin composition with better adhesion can be obtained.

[0077] The resin composition preferably has a storage modulus at 250°C of 1.00 to 12 MPa, more preferably 1.30 to 10 MPa, even more preferably 1.50 to 8 MPa, even more preferably 1.70 to 6 MPa, and even more preferably 2.20 to 5 MPa. If the storage modulus at 250°C is above the lower limit, a resin composition with good solder heat resistance can be obtained. If the storage modulus at 250°C is below the upper limit, a resin composition with better adhesion can be obtained.

[0078] The storage modulus of the resin composition at 200°C and 250°C can be calculated by measuring the dynamic viscoelasticity of the resin composition using a dynamic viscoelasticity measuring device, with a measurement frequency of 1 Hz, in a temperature range of room temperature to 300°C, under air, and at a heating rate of 4°C / min.

[0079] <Adhesive Film> The present disclosure also includes adhesive films containing the above resin composition. The adhesive film only needs to have a film formed from the above resin composition (hereinafter also referred to as the "adhesive layer"), and may be a single-layer film obtained by processing the above resin composition into a film, or it may be a two-layer or more film (laminated) having an adhesive layer made of the above resin composition and other layers such as a substrate layer or a release layer. The adhesive film may have two or more adhesive layers made of the above resin composition.

[0080] Adhesive films can be obtained, for example, by applying a resin composition to a release substrate according to a conventional method and drying it, thereby laminating an adhesive layer made of the resin composition onto the surface of the release substrate. Furthermore, if a second release substrate is attached to the adhesive layer after drying, it becomes possible to wind the film without transfer to the back of the release substrate, resulting in excellent operability, as well as excellent storage properties and ease of use due to the protection of the adhesive layer. In addition, if the adhesive layer is attached to another substrate after application and drying to the release substrate, the adhesive layer itself can be transferred to another substrate.

[0081] Examples of release substrates include those obtained by applying a coating layer of a sealant such as clay, polyethylene, or polypropylene to the surface (one or both sides) of paper such as fine paper, kraft paper, roll paper, or glassine paper, and then applying a silicone-based, fluorine-based, or alkyd-based release agent on top of the coating layer. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, as well as those obtained by applying the above-mentioned release agent on top of films such as polyethylene terephthalate and polyethylene naphthalate. Due to reasons such as the release force between the release substrate and the adhesive layer, and the adverse effect of silicone on electrical properties, it is preferable to obtain a release substrate obtained by sealing the surface (especially both sides) of fine paper with polypropylene and then applying an alkyd-based release agent on top of it, or by applying an alkyd-based release agent on top of a polyethylene terephthalate film.

[0082] The method for applying the resin composition to the release substrate is not particularly limited, but examples include a comma coater and a reverse roll coater. If necessary, an adhesive layer may be provided directly or by transfer to the rolled copper foil or polyimide film, which are materials constituting the printed circuit board.

[0083] The thickness of the adhesive layer can be adjusted as needed, but is preferably 5 to 200 μm. Sufficient adhesive strength can be obtained by making the adhesive layer 5 μm or thicker.

[0084] <Laminates> The present disclosure also includes laminates comprising the adhesive film and a substrate. Examples of laminates include those in which an adhesive film is laminated onto a substrate (substrate / adhesive film laminate), or those in which a substrate is further bonded (substrate / adhesive film / substrate laminate). In a laminate comprising an adhesive film and a substrate, the adhesive film is preferably an adhesive layer made of a resin composition obtained by applying the resin composition to a substrate and drying it, or an adhesive layer made of a resin composition obtained by bonding the adhesive layer of an adhesive film made using the resin composition to a substrate and laminating it.

[0085] Examples of substrates include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, paper, and composite materials. Resin substrates are preferred, and film-like resins (hereinafter also referred to as the "substrate film layer") are preferred. By using a resin substrate, the adhesive strength and durability with the adhesive layer constituting the adhesive film can be improved.

[0086] Examples of resin substrate materials include polyester resin, polyamide resin, polyimide resin, polyamide-imide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluororesin.

[0087] As the material for the metal substrate, any conventionally known conductive material usable for circuit boards may be used. Examples of conductive materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, plated products, and metals treated with other metals such as zinc or chromium compounds. Among these, SUS, copper, and aluminum are preferred from the viewpoint of adhesion strength to the adhesive layer of the adhesive film and durability. As the metal substrate, it is preferable to use foil of the conductive material described above, and more preferably copper foil. As the copper foil, any product manufactured by rolling or electrolysis can be used. The conductive material foil may be subjected to physical surface treatment such as roughening or chemical surface treatment such as acid cleaning for the purpose of ensuring adhesion strength to the adhesive layer. The thickness of the conductive material foil is not particularly limited, but for example, it is preferably 1 to 50 μm, more preferably 3 to 30 μm, and even more preferably 10 to 20 μm. If the thickness of the conductive material foil is too thin, it may be difficult to obtain sufficient electrical performance of the circuit, and if the thickness of the conductive material foil is too thick, the processing efficiency during circuit fabrication may decrease.

[0088] Examples of paper types include fine paper, kraft paper, roll paper, and glassine paper.

[0089] Examples of composite materials include glass epoxy.

[0090] It is preferable that the resin composition, adhesive film, and laminate according to the present disclosure exhibit little color change and have good transparency even when stored under high temperature and high humidity conditions. For example, in a laminate (such as a laminate including an adhesive film and a copper foil), the color difference (ΔE) between the base material (such as a copper foil) before lamination and the laminate after being left standing under high temperature and high humidity is preferably 45 or less, more preferably 40 or less, and still more preferably 30 or less. The lower limit of the color difference (ΔE) is not particularly limited, and may be 0. If the color difference (ΔE) when stored under high temperature and high humidity falls within the above range, a resin composition suitable for applications such as transparent FPC where transparency is required can be obtained.

[0091] The above color difference (ΔE) is a value measured using a color difference meter, and is based on L ＊ a ＊ b ＊ In the color space, from the lightness L ＊ value, chromaticity a ＊ value, and chromaticity b ＊ value of the base material before lamination and the laminate after storage under high temperature and high humidity, it can be calculated by the following formula. ΔE = {(L ＊ 1-L ＊ 2) ２ +(a ＊ 1-a ＊ 2) ２ +(b ＊ 1-b ＊ 2) ２} ０．５ (In the formula, L ＊ 1, a ＊ 1, b ＊ 1 represent the L ＊ , a ＊ , b ＊ of the base material before lamination, respectively, and L ＊ 2, a ＊ 2, b ＊ 2 represent the L ＊ , a ＊ , b ＊ of the laminate after storage under high temperature and high humidity, respectively.)

[0092] In the resin composition, adhesive film, and laminate according to the present disclosure, the lightness L before and after storage under high temperature and high humidity ＊It is also preferable that the change is small. For example, in a laminate (such as a laminate containing an adhesive film and copper foil), the difference in brightness (ΔL) between the substrate before lamination and the laminate after being left to stand under high temperature and high humidity is desirable. ＊ The absolute value of the brightness difference (ΔL) is preferably 35 or less, more preferably 30 or less, and even more preferably 20 or less. ＊ The lower limit of the absolute value of ) is not particularly limited, but may be 0. ＊ ) is a value measured using a colorimeter, L ＊ a ＊ b ＊ Lightness L of the substrate before lamination in the color space ＊ Value L ＊ 1. Brightness L of the laminate after being maintained under high temperature and high humidity. ＊ Value L ＊ When set to 2, it can be calculated using the following formula: △L ＊ = (L ＊ 1-L ＊ 2)

[0093] <Printed Wiring Boards> The present disclosure also includes printed wiring boards that include the above-mentioned laminate. A printed wiring board includes as a component a laminate formed from a foil of a conductive material and a resin substrate that forms a conductive circuit.

[0094] Printed wiring boards are manufactured, for example, using metal-clad laminates by conventionally known methods such as the subtractive method. Depending on the circumstances, so-called flexible circuit boards (FPCs), flat cables, and circuit boards for automated tape bonding (TAB), in which conductive circuits formed by conductive material foil are partially or completely covered with cover films or screen printing inks, are collectively referred to as types of printed wiring boards.

[0095] The printed circuit board can have any lamination configuration that can be used as a printed circuit board. For example, it can be a printed circuit board composed of four layers: a base film layer, a conductive material layer, an adhesive layer, and a cover film layer. Alternatively, it can be a printed circuit board composed of five layers: a base film layer, an adhesive layer, a conductive material layer, an adhesive layer, and a cover film layer. Furthermore, if necessary, it can be configured by laminating two or three or more of the above printed circuit boards.

[0096] Printed circuit boards can be manufactured, for example, by a process that includes heating an adhesive film containing a resin composition and a substrate to a temperature above the softening start temperature of the resin composition and bonding them together. That is, for example, by stacking the materials of each layer as described above, and then heating them to a temperature above the softening start temperature of the resin composition and bonding them together, the properties of the polyester resin (A) allow the components to be laminated without curing treatment, and a printed circuit board can be obtained.

[0097] Examples of printed circuit boards include products in which a desired circuit pattern is formed by laminating a conductive material layer onto a base film layer (hereinafter also referred to as "base film-side two-layer product") or products in which a desired circuit pattern is formed by laminating a resin composition layer onto a base film layer and then laminating a conductive material layer on top of that (hereinafter also referred to as "base film-side three-layer product"). Hereinafter, "base film-side two-layer product" and "base film-side three-layer product" may be collectively referred to as "base film-side product". By laminating the base film-side products obtained in this way, a four-layer or five-layer printed circuit board can be obtained. Conventional known methods can be used to form the circuit pattern, for example, the additive method and the subtractive method, with the subtractive method being preferred.

[0098] The printed circuit board may be a reinforcing material side product manufactured by coating a resin composition onto a soft, windable reinforcing material such as a polyimide film. If the reinforcing material is hard and cannot be wound, such as a metal plate such as SUS or aluminum, or a plate made of glass fiber hardened with epoxy resin, it is preferable to manufacture it by transferring a resin composition that has been pre-coated onto a release substrate. Furthermore, if necessary, a crosslinking reaction can be performed in the coated resin composition. The resulting reinforcing material side product may be used directly for bonding to the back surface of the printed circuit board, or it may be used for bonding to the base film side product after bonding a release substrate (release film) to it and storing it.

[0099] This application claims the benefit of priority based on Japanese Patent Application No. 2025-045646, filed on 19 March 2025. The entire specification of Japanese Patent Application No. 2025-045646, filed on 19 March 2025, is incorporated herein by reference.

[0100] The contents of this disclosure will be explained in more detail below with reference to examples, but the contents of this disclosure are not limited by the examples below, and it is of course possible to implement modifications to the extent that are in line with the spirit described above and below, and all such modifications are included in the technical scope of this disclosure.

[0101] First, long-chain polymer polyols (a1-1) and short-chain polymer polyols (a2-1) were produced. Then, the long-chain polymer polyol (a1-1), the short-chain polymer polyol (a2-1), and a polycarboxylic acid component with three or more functionalities were polymerized to produce a polyester resin (A-1) having carboxyl groups in its side chains.

[0102] Preparation of Long-Chain Polymer Polyol (a1-1): In a reaction vessel equipped with a stirrer, thermometer, and distillation condenser, 30 moles of terephthalic acid, 69 moles of isophthalic acid, and 1 mole of trimellitic anhydride were added as polycarboxylic acid components, along with 15 moles of 2-methyl-1,3-butanediol and 85 moles of 1,6-hexanediol as polyhydric alcohol components, and 0.2 moles of tetrabutyl titanate. The temperature was gradually increased to 250°C, and the esterification reaction was carried out while removing the distilled water from the system. After the esterification reaction was completed, initial polymerization was carried out while gradually reducing the pressure to 10 mmHg, and the temperature was increased to 250°C. Further late polymerization was carried out at a pressure of 1 mmHg or less until the desired torque was reached. After that, the pressure was returned to atmospheric pressure with nitrogen, and 1 mole of trimellitic anhydride was added as a trifunctional or more polycarboxylic acid component. The reaction was carried out at 220°C for 30 minutes to obtain long-chain polymer polyol (a1-1). The composition of the obtained long-chain polymer polyol (a1-1) is shown in Table 1.

[0103] Preparation of Short-Chain Polymer Polyol (a2-1): In a reaction vessel equipped with a stirrer, thermometer, and distillation condenser, 50 moles of terephthalic acid and 50 moles of isophthalic acid were added as polycarboxylic acid components, 55 moles of ethylene glycol and 45 moles of 2,2-dimethyl-1,3-propanediol as polyhydric alcohol components, and 0.2 moles of tetrabutyl titanate were added. The temperature was gradually increased to 250°C, and the esterification reaction was carried out while removing the distilled water from the system. After the esterification reaction was completed, initial polymerization was carried out while gradually reducing the pressure to 10 mmHg and raising the temperature to 250°C. Further late polymerization was carried out at a pressure of 1 mmHg or less until a predetermined torque was reached, thereby obtaining short-chain polymer polyol (a2-1). The composition of the obtained short-chain polymer polyol (a2-1) is shown in Table 1.

[0104] The obtained long-chain polymer polyol (a1-1) and short-chain polymer polyol (a2-1) were measured for number-average molecular weight (Mn), acid value, and glass transition temperature using the following procedure. These physical properties are shown in Table 1.

[0105] (i) Number-average molecular weight (Mn) The obtained long-chain polymer polyol (a1-1) or short-chain polymer polyol (a2-1) was dissolved or diluted in tetrahydrofuran to a concentration of approximately 0.5% by mass, and filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm to be used as the sample for measurement. The number-average molecular weight was measured by gel permeation chromatography using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate was 1 mL / min and the column temperature was 30°C. Monodisperse polystyrene was used as the molecular weight standard. The number-average molecular weight was calculated by excluding the portion corresponding to a molecular weight of less than 1000.

[0106] (ii) Acid Value 0.2 g of the obtained long-chain polymer polyol (a1-1) or short-chain polymer polyol (a2-1) was dissolved in 20 ml of chloroform and titrated with 0.1 N potassium hydroxide (KOH) ethanol solution using phenolphthalein as an indicator. From the titration volume, the number of mg of KOH consumed in neutralization was converted to the amount per gram of long-chain polymer polyol (a1-1) or short-chain polymer polyol (a2-1) to calculate the acid value (mg KOH / g).

[0107] (iii) Glass transition temperature 5 mg of the obtained long-chain polymer polyol (a1-1) or short-chain polymer polyol (a2-1) was placed in an aluminum pan, sealed by pressing down on the lid, and used as the sample for measurement. The sample was measured using a differential scanning calorimetry analyzer "DSC220" manufactured by Seiko Electronics Industries, Ltd., after being held at 250°C for 5 minutes, rapidly cooled with liquid nitrogen, and then heated from -100°C to 300°C at a heating rate of 20°C / min. The inflection point of the obtained curve was defined as the glass transition temperature.

[0108]

[0109] Preparation of polyester resin (A-1) having carboxyl groups in the side chains: In a reaction vessel equipped with a stirrer, thermometer, and reflux tube, 80 parts by mass of long-chain polymer polyol (a1-1), 20 parts by mass of short-chain polymer polyol (a2-1), 2.6 parts by mass of pyromellitic anhydride as a trifunctional or higher polycarboxylic acid component, and 100 parts by mass of toluene were charged, and the mixture was dissolved in toluene while gradually raising the temperature to 80°C. After dissolution was complete, 0.05 parts by mass of triethylamine was added as a reaction catalyst, and the temperature was gradually raised to 105°C and the reaction was carried out for 24 hours. After confirming the completion of the reaction by infrared spectroscopy (IR), 54 parts by mass of toluene was added to dilute the mixture, and a solution of polyester resin (A-1) having carboxyl groups in the side chains with a solid content of 40% by mass was obtained. The composition of the obtained polyester resin (A-1) having carboxyl groups in the side chains is shown in Table 2.

[0110] For the obtained polyester resin (A-1) having carboxyl groups in its side chains, the number-average molecular weight (Mn), acid value, and glass transition temperature were measured according to the procedures described in (i) to (iii) above. These physical properties are shown in Table 2. Furthermore, for the obtained polyester resin (A-1) having carboxyl groups in its side chains, the number of carboxyl groups per polymer chain was determined by proton nuclear magnetic resonance ( １ The results were determined by 1H NMR. A Bruker Analytik DPX400 spectrum meter (400 MHz) was used as the measurement device, with deuterium DMSO as the measurement solvent and a measurement temperature of 25°C. The results are shown in Table 2.

[0111]

[0112] Next, a mixture (resin composition before crosslinking) was prepared using the obtained polyester resin having a carboxyl group in its side chain (A-1), an aromatic epoxy compound (B) that does not contain a nitrogen atom in its molecule (B), a transesterification catalyst (D), and a flame retardant (E) according to the formulations shown in Examples 1 and 2. Furthermore, a mixture (resin composition before crosslinking) was prepared using the obtained polyester resin having a carboxyl group in its side chain (A-1), the following epoxy compound (B-3), a transesterification catalyst (D), and a flame retardant (E) according to the formulation shown in Comparative Example 1. As the aromatic epoxy compound (B) that does not contain a nitrogen atom in its molecule, any of the following epoxy compounds (B-1) to (B-2) were used; as the transesterification catalyst (D), the following transesterification catalyst (D-1) was used; and as the flame retardant, the following flame retardant (E-1) was used.

[0113] Epoxy compound (B-1): "jER828" manufactured by Mitsubishi Chemical Corporation (bisphenol A type epoxy resin, 2 epoxy groups in the molecule, epoxy equivalent: 184-194 g / eq) Epoxy compound (B-2): "YDCN-700-10" manufactured by Nippon Steel Chemical & Material Co., Ltd. (cresol novolac type epoxy resin, 3 or more epoxy groups in the molecule, epoxy equivalent: 198-210 g / eq) Epoxy compound (B-3): "jER630" manufactured by Mitsubishi Chemical Corporation (3 epoxy groups in the molecule, 1 tertiary amino group in the molecule, epoxy equivalent: 90-106 g / eq) Transesterification catalyst (D-1): Anhydrous zinc acetate (Zn(CH) ３ COO) ２ (Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flame retardant (E-1): Clariant Japan Co., Ltd. "Exolit® OP-935"

[0114] (Example 1) Solution 1 was prepared by dissolving 100 parts by mass of a polyester resin (A-1) having carboxyl groups in its side chains and 10.7 parts by mass of a flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, and Solution 2 was prepared by dissolving 1.1 parts by mass of a transesterification catalyst (D-1) in N,N-dimethylformamide. Mixture 1 was prepared by mixing Solution 1, Solution 2, and 5.55 parts by mass of epoxy compound (B-1) with 100 parts by mass of the polyester resin (A-1). In Mixture 1, the amount of transesterification catalyst (D-1) per 100 mole parts of carboxyl groups of the polyester resin (A-1) having carboxyl groups in its side chains was 20 mole parts, and the amount of epoxy groups of epoxy compound (B-1) per 100 mole parts of carboxyl groups of the polyester resin (A-1) having carboxyl groups in its side chains was 100 mole parts. The content of polyester resin (A) in 100% by mass of the solid content of Mixture 1 was 85.2% by mass.

[0115] (Example 2) Solution 1 was prepared by dissolving 100 parts by mass of a polyester resin (A-1) having carboxyl groups in its side chains and 11.3 parts by mass of a flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, and Solution 2 was prepared by dissolving 1.1 parts by mass of a transesterification catalyst (D-1) in N,N-dimethylformamide. Mixture 2 was prepared by mixing Solution 1, Solution 2, and 100 parts by mass of the polyester resin (A-1) with 8.1 parts by mass of an epoxy compound (B-2). In Mixture 2, the amount of transesterification catalyst (D-1) per 100 mole parts of carboxyl groups of the polyester resin (A-1) having carboxyl groups in its side chains was 20 moles, and the amount of epoxy groups of the epoxy compound (B-2) per 100 mole parts of carboxyl groups of the polyester resin (A-1) having carboxyl groups in its side chains was 130 moles. The content of polyester resin (A) in 100% by mass of the solid content of Mixture 2 was 83.0% by mass.

[0116] (Comparative Example 1) Solution 1 was prepared by dissolving 100 parts by mass of a polyester resin (A-1) having carboxyl groups in its side chains and 10.5 parts by mass of a flame retardant (E-1) in a mixed solvent of methyl ethyl ketone and toluene, and Solution 2 was prepared by dissolving 1.1 parts by mass of a transesterification catalyst (D-1) in N,N-dimethylformamide. Mixture 3 was prepared by mixing Solution 1, Solution 2, and 100 parts by mass of the polyester resin (A-1) with 2.8 parts by mass of an epoxy compound (B-3). In mixture 3, the amount of transesterification catalyst (D-1) per 100 mole parts of carboxyl groups of the polyester resin (A-1) having carboxyl groups in its side chains was 20 mole parts, and the amount of epoxy groups of the epoxy compound (B-3) per 100 mole parts of carboxyl groups of the polyester resin (A-1) having carboxyl groups in its side chains was 100 mole parts. The content of polyester resin (A) in 100% by mass of the solid content of mixture 3 was 87.4% by mass.

[0117] The compositions of mixtures 1 to 3 are shown in Table 3 below.

[0118]

[0119] Next, the obtained mixture was applied to a substrate, dried, and cured to produce a laminate consisting of an adhesive film (adhesive layer) and a substrate. Specifically, the obtained mixture was applied to a 12.5 μm thick polyimide film (Apical®, manufactured by Kaneka Corporation) so that the thickness after drying was 25 μm, heated at 80°C for 1 minute, then heated at 140°C for 2 minutes to dry, and then heated at 150°C for 3 hours to cure, thereby obtaining a laminate consisting of an adhesive film containing a resin composition and a substrate.

[0120] (Heat Resistance Evaluation) The dynamic viscoelasticity of adhesive films (adhesive layers) was measured in the temperature range of 25°C to 300°C using the "DVA-200" dynamic viscoelasticity measuring device manufactured by IT Measurement Control Co., Ltd. Measurements were performed in air at a temperature change rate of 4°C / min, with a measurement frequency of 1 Hz. The storage modulus of the adhesive films at 200°C and 250°C is shown in Table 4. The higher the storage modulus at 200°C and 250°C, the better the shape retention at high temperatures and the higher the heat resistance.

[0121] Next, a 49 μm thick copper-clad laminate (manufactured by Nippon Steel Chemical & Material Co., Ltd., ESPANEX series, Cu / polyimide / Cu = 12 μm / 25 μm / 12 μm) was bonded to the adhesive film (adhesive layer) side of the resulting laminate, and the temperature was set to 170°C and 20.4 kgf / cm². ２ Test specimens were prepared by pressing and bonding them together under a pressure of 2 MPa for 280 seconds. The obtained test specimens were placed in a constant temperature and humidity chamber at 85°C and 85% RH and left to stand for 3 weeks.

[0122] (Transparency evaluation) A test piece removed from the constant temperature and humidity chamber was cut into a 2 cm x 2 cm piece, and a color difference meter ZE7700 (manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the L-axis from the polyimide film side of the test piece. ＊ a ＊ , and b ＊ Measurement was performed (L ＊ The brightness is a ＊ and b ＊ (The value indicates chromaticity). The color difference (ΔE) before and after holding under high temperature and high humidity conditions is L for a copper-clad laminate without an adhesive film (reference example). ＊ a ＊ , b ＊ Based on this, the following formula was used to calculate the color difference (ΔE). Table 4 shows the color difference (ΔE), and Figures 1 to 4 show the appearance of the laminates of the examples and comparative examples, as well as the copper-clad laminate of the reference example, after being held under high temperature and high humidity. The smaller the value of ΔE, the more suppressed the discoloration and the better the transparency. ΔE = {(L ＊ 1-L ＊ 2) ２ + (a ＊ 1-a ＊ 2) ２ + (b ＊ 1-b ＊ 2) ２} ０．５ (In the formula, L ＊ 1, a ＊ 1, b ＊ 1 is L of the copper-clad laminate (reference example) ＊ a ＊ , b ＊ L ＊ 2, a ＊ 2, b ＊ 2 is the L of the laminate after being held under high temperature and high humidity conditions. ＊ a ＊, b ＊ (This indicates...)

[0123]

Claims

1. A crosslinked polyester resin composition comprising a crosslinked polyester resin (C) and a transesterification catalyst (D), wherein the crosslinked polyester resin (C) has a structure in which a polyester resin (A) having carboxyl groups in its side chains is crosslinked with an aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule.

2. The crosslinked polyester resin composition according to claim 1, wherein the aromatic epoxy compound (B) that does not contain a nitrogen atom in its molecule contains three or more epoxy groups in its molecule.

3. The crosslinked polyester resin composition according to claim 1, wherein the aromatic epoxy compound (B) that does not contain a nitrogen atom in its molecule has a structure in which a glycidyloxy group is directly bonded to an aromatic ring.

4. The crosslinked polyester resin composition according to claim 1, wherein the aromatic epoxy compound (B) that does not contain a nitrogen atom in its molecule has 2 to 15 aromatic rings in its molecule.

5. The crosslinked polyester resin composition according to claim 1, wherein the epoxy equivalent of the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule is 120 to 500 g / eq.

6. The crosslinked polyester resin composition according to claim 1, wherein in the crosslinked polyester resin (C), the content of epoxy groups of the aromatic epoxy compound (B) that does not contain nitrogen atoms in its molecule before crosslinking is 50 to 150 moles, relative to 100 moles of carboxyl groups of the polyester resin (A) having carboxyl groups in its side chains before crosslinking.

7. The crosslinked polyester resin composition according to claim 1, wherein the amount of the transesterification catalyst (D) in the crosslinked polyester resin composition is 1 to 70 moles per 100 moles of carboxyl groups in the polyester resin (A) having carboxyl groups in its side chains before crosslinking.

8. The crosslinked polyester resin composition according to claim 1, wherein the acid value of the polyester resin (A) having a carboxyl group in the side chain is 5 to 40 mgKOH / g.

9. An adhesive film containing the crosslinked polyester resin composition described in claim 1.

10. A laminate comprising the adhesive film described in claim 9 and a substrate.

11. A printed circuit board containing the laminate described in claim 10.

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