Curable composition, cured product, overcoat film for flexible wiring board, flexible wiring board, and method for producing flexible wiring board

Abstract

To provide a curable composition, a cured product, an overcoat film for a flexible wiring board and a flexible wiring board which have excellent disconnection suppression property, low warpage property, flexibility and defoaming properties and contain no fluorine atom and a method for producing a flexible wiring board.SOLUTION: There are provided: a curable composition, a cured product, an overcoat film for a flexible wiring board and a flexible wiring board which contain (component a) a polyurethane containing an organic residue derived from a polyisocyanate having a carboxyl group and an aromatic ring concentration of 0.1 to 6.5 mmol / g, (component b) a solvent, (component c) a compound having two or more epoxy groups in one molecule and (component d) a defoaming agent containing an olefin, and do not contain fluorine atom; and a method for producing a flexible wiring board.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curable composition, a cured product, an overcoat film for a flexible wiring board, a flexible wiring board, and a method for producing a flexible wiring board. [Background technology]

[0002] Conventionally, surface protection films for flexible wiring circuits have been produced by punching a polyimide film, called a coverlay film, into a mold that matches the pattern, and then attaching it with an adhesive, or by applying a flexible UV-curable or heat-curable overcoat agent by screen printing, the latter of which has been particularly useful in terms of workability. These curable overcoat agents are primarily epoxy resin-based, acrylic resin-based, or composite resin compositions of these. These often contain, as their main component, a resin that has been modified, for example, by the introduction of a butadiene skeleton, a siloxane skeleton, a polycarbonate diol skeleton, or a long-chain aliphatic skeleton.

[0003] However, in recent years, flexible substrates have become lighter and thinner as electronic devices have become lighter and smaller, and as a result, there has been a strong demand for improvements in the physical properties of the overcoating resin compositions.

[0004] As a related technology, for example, Patent Document 1 discloses a curable composition that can be used for a protective film of a flexible wiring board, and that contains polyurethane, a solvent, and a compound having two or more epoxy groups in one molecule.

[0005] Patent Document 2 discloses a curable polyurethane resin composition containing a curable polyurethane resin (A) and an antifoaming agent (B) as essential components, in which an ethylene-α-olefin co-oligomer is used as the antifoaming agent (B). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6912385 [Patent Document 2] Japanese Patent Application Publication No. 05-247161 Summary of the Invention [Problem to be solved by the invention]

[0007] However, there is room for further improvement in the curable compositions used in the protective films. For example, further improvements are desired in physical properties such as wire breakage suppression, low warpage, flexibility, and defoaming properties of the curable compositions when they are cured to be used in protective films for wiring on flexible wiring boards and the like. In addition, from the viewpoint of safety, it is desirable to minimize the use of fluorine-containing compounds such as PFAS (organofluorine compounds). From this viewpoint, it is desirable to develop curable compositions that do not contain fluorine atoms but can exhibit excellent physical properties.

[0008] In view of the above circumstances, an object of the present invention is to provide a curable composition, a cured product, an overcoat film for a flexible wiring board, a flexible wiring board, and a method for producing a flexible wiring board, which have excellent wire breakage prevention properties, low warpage properties, flexibility, and defoaming properties and do not contain fluorine atoms. [Means for solving the problem]

[0009] As a result of extensive research aimed at solving the above problems, the present inventors have discovered a method for producing a polyurethane comprising: (component a) a polyurethane having a carboxyl group and an aromatic ring concentration of 0.1 to 6.5 mmol / g, the polyurethane containing an organic residue derived from a polyisocyanate; (component b) a solvent; 、 The present inventors have found that a curable composition containing (component c) a compound having two or more epoxy groups in one molecule and (component d) an olefin-containing defoaming agent can be formed, which does not contain fluorine atoms, and have thus completed the present invention.

[0010] That is, the present invention is as follows.

[0011] <1> The curable composition contains (component a) a polyurethane containing an organic residue derived from a polyisocyanate, which has a carboxyl group and an aromatic ring concentration of 0.1 to 6.5 mmol / g; (component b) a solvent; (component c) a compound having two or more epoxy groups in one molecule; and (component d) a first antifoaming agent containing an olefin, and does not contain fluorine atoms. <2> Component a is represented by formula (1)

[0012] [ka]

[0013] It is a polyurethane having a structural unit represented by <1> The curable composition according to claim 1, <3> Component a is represented by formula (2)

[0014] [ka]

[0015] (where R 1 each independently represents a phenylene group or a phenylene group having a substituent. It is a polyurethane having a structural unit represented by <1> or <2> The curable composition according to claim 1, <4> Component a is represented by formula (3)

[0016] [ka]

[0017] (where n R 1 each independently represents a phenylene group or a phenylene group having a substituent, and (n+1) R 2 each independently represents an alkylene group having 3 to 9 carbon atoms, and n is a natural number of 50 or less. It is a polyurethane having a structural unit represented by <1> or <2> The curable composition according to claim 1, <5> In component a, the organic residue derived from a cycloaliphatic polyisocyanate accounts for 70 mol% or more of the total amount of organic residues derived from the polyisocyanate. <1> or <2> The curable composition according to claim 1, <6> Component a is 60 to 99.9 mass% based on the total amount of components a and c; <1> or <2> The curable composition according to claim 1, <7> Component b is 25 to 75 mass% based on the total amount of components a, b, and c. <1> or <2> The curable composition according to claim 1, <8> The number average molecular weight of component a is 3,000 to 50,000, and the acid value of component a is 10 to 70 mgKOH / g. <1> or <2> The curable composition according to claim 1, <9> (Component e) further comprises a second defoaming agent containing an acrylic resin and / or a methacrylic resin; <1> or <2> The curable composition according to claim 1, <10> The total amount of component d and component e is 0.01 to 3 mass%. <9> The curable composition according to claim 1, <11> the total amount of components d and e is 0.01 to 5 mass% when the total amount of components obtained by excluding the content of component b from the total amount of the curable composition is taken as 100 mass%; <9> The curable composition according to claim 1, <12> Component e is 1 to 150 mass% relative to component d; <9> The curable composition according to claim 1, <13> (Component f) further containing at least one type of fine particles selected from the group consisting of inorganic fine particles and organic fine particles, <1> or <2> The curable composition according to claim 1, <14> Component f contains silica fine particles. <13> The curable composition according to claim 1, <15> Component f contains hydrotalcite microparticles; <13> The curable composition according to claim 1, <16> <1> or <2> 1. A cured product of the curable composition according to claim 1. <17> <16> 1. An overcoat film for flexible wiring boards, comprising the cured product according to claim 1. <18> A flexible wiring board is a flexible substrate having wiring formed on it. The surface on which the wiring is formed is partially or entirely <17> 1. A flexible wiring board covered with the overcoat film for flexible wiring boards according to claim 1. <19> (Step A) A flexible wiring board having wiring formed on a flexible substrate is provided with a method of forming a flexible wiring board on a part or all of the surface on which the wiring is formed. <1> or <2> a step of printing the curable composition according to claim 1 to form a printed film on the wiring; (Step B) A step of evaporating a part or all of the solvent in the printed film by placing the printed film obtained in Step A in an atmosphere of 40°C to 100°C; (Step C) A method for producing a flexible wiring board covered with an overcoat film, which includes a step of curing the printed film obtained in step A or the printed film obtained in step B by heating at 100°C to 170°C to form an overcoat film. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a curable composition, a cured product, an overcoat film for a flexible wiring board, a flexible wiring board, and a method for producing a flexible wiring board, which have excellent wire breakage prevention properties, low warpage properties, flexibility, and defoaming properties and do not contain fluorine atoms. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be carried out by appropriately modifying it within the scope of its gist.

[0020] <Curable composition>

[0021] The curable composition according to the present embodiment is a curable composition containing (component a) a polyurethane having a carboxyl group and an organic residue derived from a polyisocyanate, with an aromatic ring concentration of 0.1 to 6.5 mmol / g, (component b) a solvent, (component c) a compound having two or more epoxy groups per molecule, and (component d) a first antifoaming agent containing an olefin, and does not contain fluorine atoms. Each component will be described below.

[0022] (ingredient a)

[0023] Component a is a polyurethane having a carboxyl group and an aromatic ring concentration of 0.1 to 6.5 mmol / g, and contains an organic residue derived from a polyisocyanate. Polyurethane is defined as a substance having multiple urethane bonds.

[0024] Examples of the aromatic ring structure of component a include a benzene ring structure, a biphenyl structure, a naphthalene structure, and a fluorene structure.

[0025] The aromatic ring concentration of component a is 0.1 to 6.5 mmol / g, with the lower limit being preferably 0.5 mmol / g or more, more preferably 1.6 mmol / g or more, even more preferably 2.0 mmol / g or more, and still more preferably 2.5 mmol / g or more, and the upper limit being preferably 6.3 mmol / g or less, more preferably 6.0 mmol / g or less, and even more preferably 5.8 mmol / g or less.

[0026] An example of a preferred combination of upper and lower limits is 0.1 to 6.5 mmol (i.e., 0.1 to 6.5 mmol / g) of component a1g, preferably 0.1 to 6.3 mmol (i.e., 0.1 to 6.3 mmol / g) of component a1g, more preferably 0.5 to 6.3 mmol (i.e., 0.5 to 6.3 mmol / g) of component a1g, even more preferably 1.6 to 6.0 mmol (i.e., 1.6 to 6.0 mmol / g), and even more preferably 2.0 to 6.0 mmol (i.e., 2.0 to 6.0 mmol / g) of component a1g. When the aromatic ring concentration of component a is within the above-mentioned range, it becomes easy to balance the solvent resistance of the overcoat film of this embodiment described below with the breakage suppression and warpage of the flexible wiring board of this embodiment described below (however, the functions and effects of this embodiment are not limited to these).

[0027] The aromatic ring concentration can be calculated from the feed ratio, 1 H-NMR, 13 After determining the structure by C-NMR and IR, 1 Compare the number of protons derived from the aromatic ring and the number of protons derived from the unit in H-NMR ( 1 It can also be analyzed by comparing the integral curves of H-NMR.

[0028] In this specification, the number of aromatic rings is counted as 1 for each aromatic ring, and fused rings are also counted as 1. For example, as shown below, a benzene ring such as in formula (51) has 1 aromatic ring. A biphenyl structure such as in formula (52) and a 9H-fluorene structure such as in formula (53) have two benzene rings, and therefore the number of aromatic rings is counted as 2. A naphthalene structure such as in formula (54) has 2 aromatic rings. Similarly, an anthracene structure (formula (55)) and a phenanthrene structure (formula (56)) have 3 aromatic rings. A triphenylene structure (formula (57)) and a binaphthyl structure (formula (58)) have 4 aromatic rings.

[0029] The number of circles in formulas (51') to (58') represents the number of aromatic rings in formulas (51) to (58), respectively.

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] [ka]

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] The method for producing component a is not particularly limited, but it can be synthesized, for example, by reacting a polyisocyanate compound, a carboxyl group-containing diol, a polyol other than the carboxyl group-containing diol, and optionally a monohydroxyl compound and a monoisocyanate compound, using a solvent in the presence or absence of a known urethane-forming catalyst such as dibutyltin dilaurate. This reaction is preferably carried out without a catalyst, since this improves the physical properties of the overcoat film of this embodiment, such as wire breakage prevention, flexibility, and low warpage, which will be described later.

[0047] There are no particular restrictions on the structure of component a, as long as it is a polyurethane containing an organic residue derived from a polyisocyanate that has a carboxyl group and an aromatic ring concentration of 0.1 to 6.5 mmol / g. However, it is preferable for component a to have at least one of a structural unit of formula (1) and a structural unit of formula (2), and it is more preferable for component a to have both.

[0048] [ka]

[0049] [ka]

[0050] (where R 1 each independently represents a phenylene group or a phenylene group having a substituent.

[0051] Furthermore, it is preferable that component a is a polyurethane having a structural unit represented by formula (3). More specifically, it is more preferable that some or all of the structural units of formula (2) are present in the polyurethane as part of the structural units represented by formula (3).

[0052] [ka]

[0053] (where n R 1 each independently represents a phenylene group or a phenylene group having a substituent, and (n+1) R 2 each independently represents an alkylene group having 3 to 9 carbon atoms, and n is a natural number of 50 or less.

[0054] In addition, R in formula (2) and formula (3) 1each independently represents a phenylene group or a phenylene group having a substituent, preferably a phenylene group. Examples of the substituent include an alkyl group having 1 to 5 carbon atoms and a halogen atom. However, from the viewpoint of being fluorine-free, particularly halogen-free, the substituent is preferably not a fluorine atom, and more preferably not a halogen atom.

[0055] R 2 each independently represents an alkylene group having 3 to 9 carbon atoms, and R 2 Preferably, the group has 3 to 8 carbon atoms, and more preferably 4 to 8 carbon atoms.

[0056] An example of a compound having the structural unit of formula (1) is 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene shown in formula (4).

[0057] [ka]

[0058] Examples of compounds having the structural unit of formula (3) include polyester polyols formed by combining at least one selected from the group of dicarboxylic acids below and at least one selected from the group of diols below.

[0059] Examples of dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 3-methyl-benzene-1,2-dicarboxylic acid, 4-methyl-benzene-1,2-dicarboxylic acid, 4-methyl-benzene-1,3-dicarboxylic acid, 5-methyl-benzene-1,3-dicarboxylic acid, and 2-methyl-benzene-1,4-dicarboxylic acid. Only one of these can be used, or two or more can be used.

[0060] Examples of diols include 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, 2,4-diethyl-1,5-pentanediol, and 2-ethyl-2-butyl-1,3-propanediol. These may be used alone or in combination of two or more.

[0061] Preferred dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 3-methyl-benzene-1,2-dicarboxylic acid, and 4-methyl-benzene-1,2-dicarboxylic acid, and more preferably phthalic acid.

[0062] As the diol, preferred examples include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol, and more preferred are 1,6-hexanediol and 3-methyl-1,5-pentanediol.

[0063] As the polyester polyol having the structural unit of formula (3), one having a number average molecular weight of 800 to 5,000 is preferably used, more preferably 800 to 4,000, and even more preferably 900 to 3,500.

[0064] The polyester polyol having the structural unit of formula (3) may be one kind of polyester polyol. of They may be used alone or in combination of two or more.

[0065] The carboxyl group-containing diol used as a raw material for component a is not particularly limited as long as it is a compound having one or more carboxyl groups and two alcoholic hydroxyl groups in the molecule. Specific examples of carboxyl group-containing diols include dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and N,N-bis(hydroxyethyl)glycine. Among these, dimethylolpropionic acid and 2,2-dimethylolbutanoic acid are preferred in terms of solubility in the reaction solvent for synthesizing component a. These carboxyl group-containing diols may be used alone or in combination of two or more.

[0066] When a low-molecular-weight polyol is used as a polyol other than the polyester polyol having the structural unit of formula (3) and the carboxyl group-containing diol, for example, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, etc. can be used alone or in combination of two or more, and it is preferable to use 1,6-hexanediol or 3-methyl-1,5-pentanediol.

[0067] The polyisocyanate compound used in the synthesis of component a is not particularly limited as long as it is a compound having two or more isocyanate groups. Specific examples of the polyisocyanate compound include alicyclic polyisocyanates such as 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, methylenebis(4-cyclohexylisocyanate), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, norbornane diisocyanate, and biuret compounds of isophorone diisocyanate; 2,4-trilethyl isocyanate; Polyisocyanates having aromatic rings, such as diphenylmethane diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate; biuret derivatives of hexamethylene diisocyanate, lysine triisocyanate, lysine diisocyanate, hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate. M ethylene diisocyanate etc. Examples of the polyisocyanate include chain aliphatic polyisocyanates, and polyisocyanates having a heterocycle such as isocyanurates of isophorone diisocyanate and isocyanurates of hexamethylene diisocyanate. These may be used alone or in combination of two or more.

[0068] Among these, in order to maintain high heat resistance and electrical insulation performance of the cured product according to the present embodiment described below, it is preferable that the cyclic aliphatic polyisocyanate is contained in an amount of 70 mol% or more relative to the total amount of isocyanates (i.e., in component a, the organic residues derived from the cyclic aliphatic polyisocyanate are 70 mol% or more relative to the total amount of organic residues derived from polyisocyanates), more preferably 80 mol% or more, and even more preferably 90 mol% or more.

[0069] Among these cycloaliphatic polyisocyanates, preferred are isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, and norbornane diisocyanate, more preferred are methylene bis(4-cyclohexyl isocyanate), isophorone diisocyanate, and norbornane diisocyanate, and even more preferred is methylene bis(4-cyclohexyl isocyanate).

[0070] The monohydroxyl compound used as a raw material for component a, if necessary, is not particularly limited as long as it has one alcoholic hydroxyl group in the molecule and does not have any other substituents that are more reactive with isocyanato groups than the alcoholic hydroxyl group. Specific examples of the monohydroxyl compound include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol monopropyl ether, and methyl ethyl ketoxime.

[0071] These monohydroxyl compounds may be used alone or in combination of two or more.

[0072] As a raw material for component a, the monoisocyanate compound used as needed may be cyclohexyl isocyanate, octadecyl isocyanate, phenyl isocyanate, toluoyl isocyanate, etc. In consideration of the discoloration resistance of the curable composition according to this embodiment when heated, cyclohexyl isocyanate and octadecyl isocyanate are preferred.

[0073] In order to maintain high electrical insulating performance and high heat resistance of the cured product according to this embodiment described below, it is preferable that the aromatic ring is contained in the polyol side of the raw material, and it is more preferable that the aromatic ring is contained only in the polyol side of the raw material and that the polyisocyanate side of the raw material does not contain an aromatic ring (i.e., polyisocyanate having an aromatic ring is not used as a raw material). In the method for producing component a, the blending amounts of each component are as follows.

[0074] When a compound having a structural unit of formula (1) is used, the amount of the compound having a structural unit of formula (1) used relative to the total amount of raw materials for component a is preferably 3 to 20 mass %, more preferably 5 to 15 mass %. When the amount of the compound having a structural unit of formula (1) used relative to the total amount of raw materials for component a is 3 to 20 mass %, a balance can be achieved between the low warpage properties and the effect of suppressing wire breakage in a flexible wiring board covered with the overcoat film of this embodiment described below.

[0075] When a polyester polyol having a structural unit of formula (3) is used, the amount of the polyester polyol having a structural unit of formula (3) used relative to the total amount of the raw materials for component a is preferably 30 to 70 mass%, more preferably 35 to 70 mass%, and even more preferably 40 to 70 mass%. When the amount of the polyester polyol having a structural unit of formula (3) used relative to the total amount of the raw materials for component a is 30 to 70 mass%, the modulus of elasticity of the overcoat film described below is not too low, and the cured film is not too brittle, so a well-balanced overcoat film can be obtained.

[0076] The solids concentration during production of component a is preferably 10 to 90 mass%, more preferably 15 to 70 mass%, and even more preferably 20 to 60 mass%. When a solution with a solids concentration of 20 to 60 mass% is used to produce the curable composition according to the present embodiment described below, the solution viscosity of component a solution is preferably, for example, 5000 to 1,000,000 mPa s under the measurement conditions described in the Examples, from the viewpoint of uniform dispersion.

[0077] There are no particular restrictions on the order in which raw materials are charged into a reactor when producing component a. For example, the compound of formula (4), polyester polyol having a structural unit of formula (3), carboxyl group-containing diol, and, if necessary, the compound of formula (4), the structure of formula (3), unit The polyol having the formula (I) and the polyol other than the carboxyl group-containing diol are first charged into a reactor and dissolved in a solvent. Then, a polyisocyanate compound is added dropwise, usually at 20°C to 140°C, more preferably at 60°C to 120°C, and then the above components are reacted at 50°C to 160°C, more preferably at 60°C to 150°C.

[0078] The molar ratio of the raw materials is adjusted depending on the molecular weight and acid value of the desired component a. The molecular weight of the desired component a can also be adjusted by using a monohydroxyl compound. That is, once the desired number average molecular weight is reached (or approaches the desired number average molecular weight), a monohydroxyl compound can be added to block the terminal isocyanato groups and prevent further increase in the number average molecular weight.

[0079] When a monohydroxyl compound is used, the compound of formula (4), a polyester polyol having a structural unit of formula (3), and the compound of formula (4), a structure of formula (3) unit There is no problem whether the number of isocyanato groups in the polyisocyanate compound is less than, equal to, or greater than the total number of hydroxyl groups in the raw materials of component a, which includes the polyol components other than the polyol having the formula (I).

[0080] Furthermore, when an excess amount of the monohydroxyl compound is used, unreacted monohydroxyl compound remains. In this case, the excess monohydroxyl compound may be used as it is as part of the solvent, or may be removed by distillation or the like.

[0081] Furthermore, in order to use a monoisocyanate compound as a raw material for component a, the number of isocyanate groups in all the raw materials for component a minus the number of isocyanate groups in the monoisocyanate compound (i.e., the total number of isocyanate groups in the polyisocyanate compounds used as raw materials for component a) must be less than the total number of alcoholic hydroxyl groups in all the raw materials for component a, so that the terminals of the polyurethane being produced before the monoisocyanate compound is used in the reaction are hydroxyl groups. When the reaction between the alcoholic hydroxyl groups in all the raw materials for component a and the isocyanate groups in the polyisocyanate compound used in component a is nearly complete, the monoisocyanate compound is added dropwise to a solution of the carboxyl group-containing polyurethane being produced at 30°C to 150°C, more preferably 70°C to 140°C, to react the hydroxyl groups remaining at the terminals of the polyurethane being produced with the monoisocyanate compound, and then the reaction is maintained at the same temperature to complete the reaction.

[0082] The number-average molecular weight of component a obtained as described above is preferably 3,000 to 50,000, more preferably 5,000 to 50,000, and even more preferably 5,000 to 30,000. A number-average molecular weight within this range can further improve the resistance to wire breakage, flexibility, and low warpage of the cured film. Furthermore, flexibility, elongation, and strength are not impaired, and the solubility of component a in a solvent (i.e., component b) is good. Even when dissolved, the viscosity does not become too high, and further improved physical properties can be expected. This makes the curable composition according to this embodiment suitable for use in producing a flexible wiring board coated with the overcoat film for flexible wiring boards of this embodiment, which will be described later.

[0083] The "number average molecular weight" referred to here is the polystyrene equivalent number average molecular weight measured by gel permeation chromatography (hereinafter referred to as GPC). In this specification, unless otherwise specified, the GPC measurement conditions are as follows: Device name: JASCO Corporation HPLC unit HSS-2000 Column: Shodex column LF-804 Mobile phase: tetrahydrofuran Flow rate: 1.0mL / min Detector: JASCO RI-2031Plus Temperature: 40.0℃ Sample volume: Sample loop 100 μL Sample concentration: adjusted to around 0.1% by mass.

[0084] The acid value of component a is preferably 10 to 70 mgKOH / g, more preferably 15 to 50 mgKOH / g. When the acid value is 10 to 70 mgKOH / g, the reactivity with other components contained in the curable composition according to this embodiment, such as the compound having two or more epoxy groups per molecule (i.e., component c), described below, is not reduced, and the heat resistance of the cured product according to this embodiment, described below, is not reduced, and the product does not become too hard or brittle. Furthermore, it is easy to balance the solvent resistance of the overcoat film, described below, and the warpage of the flexible wiring board according to this embodiment, described below. In this specification, the acid value of component a is the acid value measured by potentiometric titration according to JIS K0070.

[0085] The content of component a is preferably 60 to 99.9 mass% (a / (a+c)) relative to the total amount of components a and c. The lower limit of this content (a / (a+c)) is more preferably 70 mass% or more, even more preferably 80 mass% or more, still more preferably 90 mass% or more, and even more preferably 93 mass% or more. The upper limit of this content (a / (a+c)) is more preferably 99.5 mass% or less, even more preferably 99.3 mass% or less, and still more preferably 99.0 mass% or less.

[0086] (component b)

[0087] The solvent (component b), which is one of the essential components of the curable composition according to this embodiment, is not particularly limited as long as it can dissolve component a, but preferably has a boiling point of 150°C or higher and 250°C or lower at atmospheric pressure. In order to balance the solubility of component a and the volatility of the solvent, it is possible and preferable to use two or more solvents each having a boiling point of 150°C or higher and 250°C or lower at atmospheric pressure. More preferably, a solvent having a boiling point of 170°C or higher and lower than 200°C at atmospheric pressure is used in combination with a solvent having a boiling point of 200°C or higher and 220°C or lower at atmospheric pressure.

[0088] Examples of solvents having a boiling point of 170°C or higher and lower than 200°C under atmospheric pressure include diethylene glycol diethyl ether (boiling point 189°C), diethylene glycol ethyl methyl ether (boiling point 176°C), dipropylene glycol dimethyl ether (boiling point 171°C), 3-methoxybutyl acetate (boiling point 171°C), and ethylene glycol monobutyl ether acetate (boiling point 192°C).

[0089] Furthermore, examples of solvents having a boiling point of 200°C or higher and 220°C or lower under atmospheric pressure include diethylene glycol butyl methyl ether (boiling point 212°C), tripropylene glycol dimethyl ether (boiling point 215°C), triethylene glycol dimethyl ether (boiling point 216°C), ethylene glycol dibutyl ether (boiling point 203°C), diethylene glycol monoethyl ether acetate (boiling point 217°C), diethylene glycol monoethyl ether acetate (boiling point 217°C), and γ-butyrolactone (boiling point 204°C).

[0090] Because of its high volatility, it can impart low-temperature curing properties, and the production reaction of component a can be carried out efficiently in a homogeneous system. Therefore, it is preferable to combine at least one solvent selected from the group consisting of diethylene glycol diethyl ether (boiling point 189°C), diethylene glycol ethyl methyl ether (boiling point 176°C), and dipropylene glycol dimethyl ether (boiling point 171°C) as a solvent having a boiling point of 170°C or more and less than 200°C at atmospheric pressure with at least one solvent selected from the group consisting of diethylene glycol monoethyl ether acetate (boiling point 217°C) and γ-butyrolactone (boiling point 204°C) as a solvent having a boiling point of 200°C or more and 220°C or less at atmospheric pressure. More preferably, diethylene glycol diethyl ether (boiling point: 189°C) is combined as a solvent having a boiling point of 170°C or higher and lower than 200°C at atmospheric pressure, with diethylene glycol monoethyl ether acetate (boiling point: 217°C) and γ-butyrolactone (boiling point: 204°C) being combined as solvents having a boiling point of 200°C or higher and 220°C or lower at atmospheric pressure.

[0091] These preferred solvent combinations are excellent as solvents for screen printing inks due to their low hygroscopicity, high boiling points and low volatility.

[0092] In order to fully exert the above-mentioned effects, the ratio by mass of the solvent having a boiling point of 170°C or more and less than 200°C under atmospheric pressure to the solvent having a boiling point of 200°C or more and 220°C or less under atmospheric pressure is preferably in the range of 5:95 to 80:20, more preferably in the range of 10:90 to 60:40.

[0093] Furthermore, as part of these preferred solvents, the solvent used in synthesis when producing the above-mentioned component a can be used as is as part of the solvent for the curable composition according to this embodiment, which is preferable from the viewpoint of process.

[0094] Furthermore, to the extent that the solubility of component a is not impaired, solvents other than those having a boiling point of 170°C or more and less than 200°C under atmospheric pressure and those having a boiling point of 200°C or more and 220°C or less under atmospheric pressure can also be used in combination. Reactive monomers and reactive diluents can also be used as solvents.

[0095] The content of component b in the curable composition according to this embodiment is preferably 25 to 75 mass %, more preferably 35 to 70 mass %, and even more preferably 35 to 65 mass %, based on the total amount of components a, b, c, and f (described later) that are components of the curable composition according to this embodiment (however, when component f is not contained in the curable composition according to this embodiment, the total amount of components a, b, and c). 、 See below Component c and When the amount of component f is in the range of 25 to 75 mass% relative to the total amount of component f (however, when component f is not contained in the curable composition according to the present embodiment, the total amount of components a, b, and c), the viscosity of the curable composition is favorable for printing by screen printing, and the curable composition does not spread significantly due to bleeding after screen printing. As a result, the actual printing area of ​​the curable composition does not become too large compared to the area where the curable composition is to be applied (i.e., the shape of the printing plate), which is preferable.

[0096] (ingredient c)

[0097] Component c, which is an essential component of the curable composition according to this embodiment, is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule, and functions as a curing agent in the curable composition according to this embodiment.

[0098] Examples of compounds having two or more epoxy groups in one molecule include phenol novolac epoxy resins, orthocresol novolac epoxy resins, and other novolac resins obtained by condensing or co-condensing phenols such as phenol, cresol, xylenol, resorcinol, and catechol, and / or naphthols such as α-naphthol, β-naphthol, and dihydroxynaphthalene with compounds having aldehyde groups such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde under an acidic catalyst. Novolac-type epoxy resins epoxidized with bisphenol A, bisphenol F, bisphenol S, alkyl-substituted or unsubstituted biphenols, diglycidyl ethers of stilbene-based phenols (bisphenol A-type epoxy compounds, bisphenol F-type epoxy compounds, bisphenol S-type epoxy compounds, biphenyl-type epoxy compounds, stilbene-type epoxy compounds); glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; glycidyl ester-type epoxy resins of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; glycidyl-type or methylglycidyl-type epoxy resins such as aniline, bis(4-aminophenyl)methane, and isocyanuric acid, in which the active hydrogen bonded to the nitrogen atom is substituted with a glycidyl group; glycidyl-type or methylglycidyl-type epoxy resins such as compounds in which the active hydrogen bonded to the nitrogen atom of aminophenols such as p-aminophenol and the active hydrogen of phenolic hydroxyl groups are substituted with a glycidyl group; vinylcyclohexene diepoxide, 3,4-epoxide, and the like, obtained by epoxidizing an olefin bond in the molecule, are also available. Alicyclic epoxy resins such as 2-(3,4-epoxy)cyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane; glycidyl ethers of para-xylylene and / or meta-xylylene-modified phenolic resins; glycidyl ethers of terpene-modified phenolic resins; glycidyl ethers of dicyclopentadiene-modified phenolic resins; glycidyl ethers of cyclopentadiene-modified phenolic resins; glycidyl ethers of polycyclic aromatic ring-modified phenolic resins;Glycidyl ethers of naphthalene ring-containing phenolic resins; halogenated phenol novolac epoxy resins; hydroquinone epoxy resins; trimethylolpropane epoxy resins; linear aliphatic epoxy resins obtained by oxidizing olefin bonds with peracids such as peracetic acid; diphenylmethane epoxy resins; epoxidized aralkyl phenolic resins such as phenol aralkyl resins and naphthol aralkyl resins; sulfur-containing epoxy resins; tricyclo[5.2.1.0; 2,6 diglycidyl ether of ]decanedimethanol; and epoxy resins having an adamantane structure such as 1,3-bis(1-adamantyl)-4,6-bis(glycidyloyl)benzene, 1-[2',4'-bis(glycidyloyl)phenyl]adamantane, 1,3-bis(4'-glycidyloylphenyl)adamantane, and 1,3-bis[2',4'-bis(glycidyloyl)phenyl]adamantane. However, from the viewpoint of being fluorine-free, and particularly halogen-free, component c preferably does not contain fluorine atoms, and more preferably does not contain halogen atoms.

[0099] Among these, compounds having two or more epoxy groups in one molecule and an aromatic ring structure and / or an alicyclic structure are preferred.

[0100] From the viewpoint of further improving the physical properties of the cured product of this embodiment described below, among compounds having two or more epoxy groups in one molecule and an aromatic ring structure and / or an alicyclic structure, glycidyl ether of dicyclopentadiene-modified phenolic resin (i.e., tricyclo[5.2.1.0] 2,6 ]decane structure and an aromatic ring structure and a compound having two or more epoxy groups), epoxy resins having an adamantane structure such as 1,3-bis(1-adamantyl)-4,6-bis(glycidyloyl)benzene, 1-[2',4'-bis(glycidyloyl)phenyl]adamantane, 1,3-bis(4'-glycidyloylphenyl)adamantane, and 1,3-bis[2',4'-bis(glycidyloyl)phenyl]adamantane (i.e., tricyclo[3.3.1.1 3,7Compounds having a tricyclodecane structure and an aromatic ring structure and having two or more epoxy groups, such as a compound having a tricyclodecane structure and an aromatic ring structure and having two or more epoxy groups, are preferred because they can provide a cured product with low water absorption, and more preferred are compounds of the following formula (5).

[0101] [ka]

[0102] (In the formula, l represents a natural number.)

[0103] Furthermore, when emphasis is placed on reactivity with component a, among compounds having two or more epoxy groups in one molecule and having an aromatic ring structure and / or an alicyclic structure, preferred are compounds having an amino group and an aromatic ring structure and having two or more epoxy groups, such as glycidyl- or methylglycidyl-type epoxy resins, such as compounds in which the active hydrogen bonded to the nitrogen atom of aniline or bis(4-aminophenyl)methane is substituted with a glycidyl group, and glycidyl- or methylglycidyl-type epoxy resins, such as compounds in which the active hydrogen bonded to the nitrogen atom of aminophenols, such as p-aminophenol, and the active hydrogen of a phenolic hydroxyl group are substituted with a glycidyl group, and more preferred are compounds of the following formula (6):

[0104] [ka]

[0105] Component c may be used alone or in combination of two or more.

[0106] The amount of component c to be blended relative to 100 parts by mass of component a, which is an essential component of the curable composition according to this embodiment, cannot be generalized because it differs depending on the amount of functional groups in component a that are reactive with carboxyl-containing epoxy groups.

[0107] However, the ratio of the number of functional groups reactive with epoxy groups containing carboxyl groups contained in component a to the number of epoxy groups in component c (a compound having two or more epoxy groups per molecule) (functional groups reactive with epoxy groups / epoxy groups) is preferably in the range of 1 / 3 to 2 / 1, and more preferably in the range of 1 / 2.5 to 1.5 / 1. When this ratio is in the range of 1 / 3 to 2 / 1, when the curable composition according to this embodiment is cured, neither a large amount of component c remains unreacted nor a large number of functional groups reactive with epoxy groups containing carboxyl groups remain, allowing for a well-balanced reaction between the functional groups reactive with epoxy groups containing carboxyl groups and the epoxy groups in component c (a compound having two or more epoxy groups per molecule).

[0108] The amount of component c in the curable composition according to this embodiment is preferably 1 to 60 mass %, more preferably 2 to 50 mass %, and even more preferably 3 to 40 mass %, based on the total amount of components a and c in the curable composition. When the amount of component c in the curable composition according to this embodiment is in the range of 1 to 60 mass %, based on the total amount of components a and c in the curable composition, a balance can be achieved between the solvent resistance of the overcoat film of this embodiment, which will be described later, and the low warpage and wire breakage prevention effect of a flexible wiring board characterized by being coated with the overcoat film.

[0109] (ingredient d)

[0110] Component d is a first defoaming agent containing an olefin. In this specification, the term "olefin" includes alkenes, alkene polymers, and chemically modified compounds thereof, and the term "olefin-based" includes olefins themselves and mixtures containing olefins. The term "alkene polymer" includes homopolymers and copolymers. Specific examples of component d include defoaming agents containing olefin polymers (e.g., olefin oligomers, olefin polymers, etc.). Component d can be a so-called olefin-based defoaming agent, and commercially available products can also be used. Specific examples include BYK-1791 (manufactured by BYK Japan), FLOWRENE AC-2000HF (manufactured by Kyoeisha Chemical Co., Ltd.), FLOWRENE AC-2200HF (manufactured by Kyoeisha Chemical Co., Ltd.), DISPARLON P-465 (manufactured by Kusumoto Chemical Co., Ltd.), and DISPARLON P-466 (manufactured by Kusumoto Chemical Co., Ltd.).

[0111] When the curable composition according to this embodiment is used as a resist ink composition for insulating and protecting wiring (i.e., an overcoat agent for wiring boards), it is possible and preferable to use an antifoaming agent for the purposes of eliminating bubbles during printing (defoaming), suppressing the generation of bubbles (foam suppression), and removing bubbles from the liquid (defoaming).

[0112] In the curable composition according to the present embodiment, by blending at least component d as an antifoaming agent with the composition of components a, b, and c described above, it is possible to unexpectedly obtain a cured product with superior physical properties compared to antifoaming agents containing fluorine-based compounds or the like, and also to maintain antifoaming effects such as antifoaming, foam suppression, and defoaming.

[0113] (ingredient e)

[0114] The curable composition according to this embodiment may and preferably contains the following component e. In the curable composition according to this embodiment, by using component e as an antifoaming agent in addition to component d in the composition of the above-mentioned components a, b, and c, it is expected that the above-mentioned effects will be further improved.

[0115] Component e is a second defoaming agent containing an acrylic resin and / or a methacrylic resin. Here, the acrylic resin refers to a resin having an acrylic skeleton, and the methacrylic resin refers to a resin having a methacrylic skeleton. Component e can be a so-called acrylic defoaming agent or a methacrylic defoaming agent, and commercially available products can also be used. Specific examples of such antifoaming agents include acrylic polymer antifoaming agents such as Dappo SN-348 (manufactured by San Nopco Ltd.), Dappo SN-354 (manufactured by San Nopco Ltd.), Dappo SN-368 (manufactured by San Nopco Ltd.), Disparlon 230HF (manufactured by Kusumoto Chemical Co., Ltd.), BYK-361 (manufactured by BYK Japan KK), BYK-381 (manufactured by BYK Japan KK), BYK-394 (manufactured by BYK Japan KK), Polyflow 36 (manufactured by Kyoeisha Chemical Co., Ltd.), Polyflow 75 (manufactured by Kyoeisha Chemical Co., Ltd.), and Polyflow 77 (manufactured by Kyoeisha Chemical Co., Ltd.). The curable composition according to this embodiment can achieve practical levels of effectiveness as an antifoaming agent using only component e. Additionally, the curable composition according to this embodiment can achieve even higher levels of effectiveness by using component e and component d in combination as antifoaming agents. Furthermore, the curable composition according to this embodiment can achieve a sufficiently excellent effect even when only the component e and the component d are used as the defoaming agent.

[0116] (Other antifoaming agents)

[0117] The curable composition according to this embodiment can sufficiently achieve the desired effect even without containing any antifoaming agent other than the above-described components d and e. However, if necessary, it may contain an antifoaming agent other than components d and e (a third antifoaming agent). Specific examples of such a third antifoaming agent include silicone-based antifoaming agents such as BYK-333 (manufactured by BYK Japan KK), BYK-342 (manufactured by BYK Japan KK), SN DEFOAMER 470 (manufactured by San Nopco Ltd.), TSA750S (manufactured by Momentive Performance Materials), and Silicone Oil SH-203 (manufactured by DuPont-Toray Specialty Materials Co., Ltd.), and acetylene diol-based antifoaming agents such as Surfynol DF-110D (manufactured by Nissin Chemical Industry Co., Ltd.) and Surfynol DF-37 (manufactured by Nissin Chemical Industry Co., Ltd.). However, from the viewpoint of obtaining a fluorine-free curable composition that does not contain fluorine atoms, it is preferable that the curable composition according to this embodiment does not contain a fluorine-containing silicone-based antifoaming agent. Furthermore, from the viewpoint of being silicone-free, the curable composition according to this embodiment preferably does not contain an antifoaming agent containing a silicone-based ingredient such as silicone (a silicone-based antifoaming agent).

[0118] Regarding the content of the antifoaming agent, the total amount (d+e) of components d and e in the curable composition according to this embodiment is preferably 0.01 to 3 mass%. The lower limit of this content is more preferably 0.1 mass% or more, even more preferably 0.3 mass% or more, still more preferably 0.5 mass% or more, and even more preferably 0.6 mass% or more. The upper limit of this content is more preferably 2.5 mass% or less, even more preferably 2.0 mass% or less, still more preferably 1.5 mass% or less, and even more preferably 1.3 mass% or less.

[0119] Regarding the content of the antifoaming agent, when the total amount of the curable composition according to this embodiment, excluding the content of component b, is taken as 100 mass%, the total amount of components d and e is preferably 0.01 to 5 mass%. The lower limit is more preferably 0.5 mass% or more, even more preferably 1 mass% or more, still more preferably 1.5 mass% or more, even more preferably 1.7 mass% or more, and even more preferably 2 mass% or more. The upper limit is more preferably 4 mass% or less, even more preferably 3.5 mass% or less, and even more preferably 3 mass% or less.

[0120] The content of the antifoaming agent is preferably 0.01 to 5 parts by mass, more preferably 0.05 to 4 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the total amount of components a, b, c, and f.

[0121] The ratio of component e to component d (e / d) is preferably 1 to 150% by mass. The lower limit is more preferably 3% by mass or more, even more preferably 5% by mass or more, and even more preferably 7% by mass or more. The upper limit is more preferably 120% by mass or less, even more preferably 100% by mass or less, even more preferably 60% by mass or less, even more preferably 30% by mass or less, even more preferably 17% by mass or less, even more preferably 15% by mass or less, and even more preferably 13% by mass or less. By blending components d and e in the above mass ratio, the balance between wire breakage prevention, low warpage, flexibility, and defoaming properties can be improved to a higher level.

[0122] (Component f)

[0123] The curable composition according to this embodiment can and preferably contains the following component f.

[0124] Component f is at least one kind of fine particles selected from the group consisting of inorganic fine particles and organic fine particles.

[0125] Examples of inorganic fine particles include silica (SiO2), alumina (Al2O3), titania (TiO2), tantalum oxide (Ta2O5), zirconia (ZrO2), silicon nitride (Si3N4), barium titanate (BaO·TiO2), barium carbonate (BaCO3), lead titanate (PbO·TiO2), lead zirconate titanate (PZT), lead lanthanum zirconate titanate (PLZT), gallium oxide (Ga2O3), spinel (MgO·Al2O3), mullite (3Al2O3·2SiO2), and cordierite. Examples include zirconia (Y2O3-ZrO2), barium silicate (BaO-8SiO2), boron nitride (BN), calcium carbonate (CaCO3), calcium sulfate (CaSO4), zinc oxide (ZnO), magnesium titanate (MgO-TiO2), barium sulfate (BaSO4), organic bentonite, carbon (C), and hydrotalcite.

[0126] The organic fine particles are preferably fine particles of a heat-resistant resin having an amide bond, an imide bond, an ester bond, or an ether bond. From the viewpoint of heat resistance and mechanical properties, these resins are preferably polyimide resins or precursors thereof, polyamideimide resins or precursors thereof, or polyamide resins.

[0127] As the component f, the above-mentioned components may be used alone or in combination of two or more.

[0128] Among these, it is preferable that component f contains at least one selected from silica fine particles and hydrotalcite fine particles. That is, it is preferable that component f contains silica fine particles. It is also preferable that component f contains hydrotalcite fine particles. Component f may contain both silica fine particles and hydrotalcite.

[0129] The silica microparticles used in the curable composition according to this embodiment are defined to include microparticles that are physically coated in powder form or chemically surface-treated with an organic compound.The silica microparticles used in the curable composition according to this embodiment are not particularly limited as long as they are dispersed in the curable composition according to this embodiment to form a paste, and examples thereof include Aerosil, etc., provided by Nippon Aerosil Co., Ltd.These silica microparticles, such as Aerosil, are sometimes used to impart printability during screen printing, and in this case, they are used for the purpose of imparting thixotropy.

[0130] The hydrotalcite fine particles used in the curable composition according to this embodiment are Mg6A l 2(OH) 16 Hydrotalcite is a type of naturally occurring clay mineral, typically CO3·4H2O, and is a layered inorganic compound. (1-x) Al x (OH)2(CO3) x / 2 Hydrotalcite is a Mg / Al-based layered compound, and chloride ions (Cl) are released by ion exchange with the carbonate groups between the layers. - ) and / or sulfate ions (SO4 - ) anions can be immobilized. This function can be used to immobilize chloride ions (Cl - ) and sulfate ions (SO4 - ) and can be used to improve insulation reliability.

[0131] Examples of commercially available hydrotalcite products include STABIACE HT-1, STABIACE HT-7, and STABIACE HT-P manufactured by Sakai Chemical Industry Co., Ltd., and DHT-4A, DHT-4A-2, and DHT-4C manufactured by Kyowa Chemical Industry Co., Ltd.

[0132] The average particle size of these inorganic fine particles and / or organic fine particles is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm.

[0133] The amount of component f is preferably 0.1 to 60 mass%, more preferably 0.3 to 55 mass%, and even more preferably 0.5 to 40 mass%, relative to the total amount of components a, b, c, and f. When the amount of component f is in the range of 0.1 to 60 mass%, relative to the total amount of components a, b, c, and f, the viscosity of the curable composition is favorable for printing by screen printing and the curable composition does not spread too much due to bleeding after screen printing. As a result, the actual printing area of ​​the curable composition does not become too large compared to the desired area to apply the curable composition (i.e., the shape of the printing plate), which is preferable.

[0134] (curing accelerator)

[0135] The curable composition according to this embodiment may further contain a curing accelerator, and preferably does so. The curing accelerator is not particularly limited as long as it is a compound that accelerates the reaction between the epoxy group of component c and the carboxyl group of component a. Examples of the curing accelerator include melamine, acetoguanamine, benzoguanamine, 2,4-diamino-6-methacryloyloxyethyl- s-triazine, 2,4-methacryloyloxyethyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine-isocyanuric acid adduct and other triazine compounds, imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2 ... Ethyl-4-methylimidazole, 1-aminoethyl-2-ethyl-4-methylimidazole, 1-aminoethyl-2-methylimidazole, 1-(cyanoethylaminoethyl)-2-methylimidazole, N-[2-(2-methyl-1-imidazolyl)ethyl]urea, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-methylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazole Undecylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, N,N'-bis(2-methyl-1-imidazolylethyl)urea, N,N'-bis(2-methyl-1-imidazolylethyl)adipamide , 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-methylimidazole-isocyanuric acid adduct, 2-phenylimidazole-isocyanuric acid adduct, 2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazine-isocyanuric acid adduct, 2-methyl-4-formylimidazole, 2-ethyl-4-methyl-5-formylimidazole, 2-phenyl-4-methylformylimidazole, 1-benzyl-2-phenylimidazole, 1,Imidazole compounds such as 2-dimethylimidazole, 1-(2-hydroxyethyl)imidazole, vinylimidazole, 1-methylimidazole, 1-allylimidazole, 2-ethylimidazole, 2-butylimidazole, 2-butyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-benzyl-2-phenylimidazole hydrobromide, and 1-dodecyl-2-methyl-3-benzylimidazolium chloride; cycloamidine compounds and derivatives thereof such as diazabicycloalkenes such as 1,5-diazabicyclo(4.3.0)nonene-5 and its salts, and 1,8-diazabicyclo(5.4.0)undecene-7 and its salts; triethylenediamine, benzyldimethylamine, triethanolamine, tertiary amino group-containing compounds such as diolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; organic phosphine compounds such as triphenylphosphine, diphenyl(p-tolyl)phosphine, tris(alkylphenyl)phosphine, tris(alkoxyphenyl)phosphine, tris(alkylalkoxyphenyl)phosphine, tris(dialkylphenyl)phosphine, tris(trialkylphenyl)phosphine, tris(tetraalkylphenyl)phosphine, tris(dialkoxyphenyl)phosphine, tris(trialkoxyphenyl)phosphine, tris(tetraalkoxyphenyl)phosphine, trialkylphosphine, dialkylarylphosphine, and alkyldiarylphosphine; dicyandiaceous phosphine; M Examples include:

[0136] These curing accelerators may be used alone or in combination of two or more.

[0137] Among these curing accelerators, in consideration of both the curing acceleration effect and the electrical insulating performance of the cured product of the present embodiment described below, preferred curing accelerators are melamine, imidazole-based compounds, cycloamidine compounds and derivatives thereof, phosphine-based compounds, and amine-based compounds, and more preferred are melamine, 1,5-diazabicyclo(4.3.0)nonene-5 and salts thereof, and 1,8-diazabicyclo(5.4.0)undecene-7 and salts thereof.

[0138] The amount of these curing accelerators blended is not particularly limited as long as the curing acceleration effect can be achieved. However, from the viewpoint of the curability of the curable composition according to this embodiment and the electrical insulation properties and water resistance of the cured product of this embodiment described below, the curing accelerator is blended in an amount of 0.05 to 5 parts by mass, and more preferably 0.1 to 3.0 parts by mass, per 100 parts by mass of the total amount of components a and c. When the blending amount is in the range of 0.05 to 5 parts by mass, the curable composition according to this embodiment can be cured in a short time, and the cured product obtained by curing the composition of this embodiment described below has good electrical insulation properties and water resistance.

[0139] (Other ingredients)

[0140] When the curable composition according to this embodiment is cured, a cured product with good electrical insulating properties is obtained, and therefore the composition can be used, for example, as a resist ink for insulating and protecting wiring.

[0141] Furthermore, if necessary, surfactants such as a leveling agent, and known colorants such as phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, carbon black, and naphthalene black may be added to the curable composition according to this embodiment.

[0142] Furthermore, when it is necessary to suppress oxidative deterioration of component a and discoloration during heating, it is possible and preferable to add an antioxidant such as a phenol-based antioxidant, a phosphite-based antioxidant, or a thioether-based antioxidant.

[0143] If necessary, a flame retardant and a lubricant may also be added.

[0144] The curable composition according to the present embodiment can be obtained by uniformly kneading and mixing some or all of the components using a roll mill, a bead mill, etc. When some of the components have been mixed, the remaining components can be mixed when actually using the composition.

[0145] (Viscosity of the curable composition according to this embodiment)

[0146] The curable composition according to this embodiment has excellent handleability while maintaining excellent physical properties such as the aforementioned resistance to wire breakage, low warpage, flexibility, and defoaming. From this perspective, the viscosity of the curable composition according to this embodiment at 25°C is preferably 10,000 to 100,000 mPa·s. The lower limit of the viscosity is more preferably 20,000 mPa·s or more, even more preferably 23,000 mPa·s or more, and even more preferably 25,000 mPa·s or more. The upper limit of the viscosity is more preferably 60,000 mPa·s or less, even more preferably 50,000 mPa·s or less, and even more preferably 45,000 mPa·s or less. In this specification, the viscosity of the curable composition according to the present embodiment at 25°C is the viscosity measured using a cone / plate viscometer (manufactured by Brookfield, model: DV-II+Pro, spindle model number: CPE-52) at a rotation speed of 10 rpm, 7 minutes after the start of rotation.

[0147] (Thixotropy index of the curable composition according to this embodiment)

[0148] Furthermore, when the curable composition according to the present embodiment is used as a resist ink composition for insulating and protecting wiring (i.e., an overcoat agent for wiring boards), etc., it is desirable to set the thixotropy index of the composition within a certain range in order to improve the printability of the curable composition according to the present embodiment.

[0149] The "thixotropy index" used in this specification is defined as the ratio of the viscosity at 25°C and a rotation speed of 1 rpm to the viscosity at 25°C and a rotation speed of 10 rpm (viscosity at 1 rpm / viscosity at 10 rpm), measured using a cone / plate viscometer (manufactured by Brookfield, model: DV-III+Pro, spindle model number: CPE-52).

[0150] When the curable composition according to the present embodiment is used as an overcoat agent for a wiring board, in order to improve the printability of the curable composition according to the present embodiment, the thixotropy index of the composition is preferably 1.1 or more, more preferably in the range of 1.1 to 3.0, and even more preferably in the range of 1.1 to 2.5. When the curable composition according to the present embodiment is used as an overcoat agent for a wiring board, if the thixotropy index of the curable composition is 1.1 to 3.0, after printing, the curable composition can be formed into a constant film thickness, the printed pattern can be maintained, and the defoaming properties of the printed film of the composition are also good.

[0151] <Cured product and overcoat film for flexible wiring boards>

[0152] The curable composition described above can be cured and suitably used as a cured product. That is, the cured product according to this embodiment is a cured product obtained by curing the curable composition described above.

[0153] Such a cured product can be suitably used as an overcoat film for a flexible wiring board, etc. That is, the overcoat film for a flexible wiring board according to this embodiment is an overcoat film for a flexible wiring board that includes the above-described cured product.

[0154] The cured product of this embodiment and the overcoat film of this embodiment can be obtained, for example, by heating the curable composition of this embodiment to allow the curing reaction to proceed. There are no particular limitations on the method for obtaining the cured product of this embodiment as a cured film, but for example, the cured film or overcoat film can be obtained by going through the following steps. (First step) A step of printing the curable composition according to this embodiment onto a substrate or the like to obtain a printed film. (Second step) A step of thermally curing the printed film obtained in the first step, or the printed film obtained in the first step by placing the printed film in an atmosphere of 40°C to 100°C to evaporate some or all of the solvent in the printed film, from which some or all of the solvent has been removed, in an atmosphere of 100°C to 170°C to obtain a cured film or an overcoat film.

[0155] The printing method of the curable composition according to the present embodiment in the first step is not particularly limited, and for example, the curable composition described above can be applied to a substrate or the like by a screen printing method, a roll coater method, a spray method, a curtain coater method, or the like to obtain a printed film.

[0156] The operation of evaporating the solvent in the second step is an operation that is performed as needed, and the operation of thermal curing may be performed immediately after the operation of the first step, so that the curing reaction and removal of the solvent are performed simultaneously. When the operation of evaporating the solvent in the second step is performed before thermal curing, the temperature is usually 40°C to 100°C, preferably 60°C to 100°C, and more preferably 70°C to 90°C, taking into consideration the evaporation rate of the solvent and a rapid transition to the thermal curing step. The time for evaporating the solvent in the second step is not particularly limited, but is preferably 10 to 120 minutes, and more preferably 20 to 100 minutes.

[0157] The temperature for the heat curing carried out in the second step is preferably in the range of 100° C. to 170° C., more preferably 105° C. to 160° C., and even more preferably 110° C. to 150° C. The time for the heat curing carried out in the second step is not particularly limited, but is preferably in the range of 20 minutes to 240 minutes, and more preferably in the range of 30 minutes to 120 minutes.

[0158] <Flexible wiring board and method for manufacturing the flexible wiring board>

[0159] The flexible wiring board of this embodiment and a method for manufacturing the flexible wiring board of this embodiment will be described. The curable composition of this embodiment can be used, for example, as a resist ink for insulating and protecting wiring, and the cured product of this embodiment can be used as an insulating and protecting film. In particular, by covering all or part of the wiring of a flexible wiring board such as a chip-on film, it can be used as a resist for insulating and protecting wiring.

[0160] This embodiment is a flexible wiring board in which wiring is formed on a flexible substrate, and the surface on which the wiring is formed is partially or entirely covered with the cured product of this embodiment (for example, the above-mentioned overcoat film for flexible wiring boards, etc.). Note that, in consideration of preventing oxidation of the wiring and economical aspects, the wiring covered with the cured product of this embodiment is preferably tin-plated copper wiring.

[0161] The manufacturing method according to this embodiment is a method for manufacturing a flexible wiring board covered with a protective film, characterized in that the curable composition according to this embodiment is printed on at least a part of a wiring pattern portion of a flexible wiring board to form a printed film on the pattern, and the printed film is cured by heating at 100° C. to 170° C. to form a protective film. For example, the protective film for a flexible wiring board can be formed through the following steps A to C. (Step A) A step of printing the curable composition according to the present embodiment onto at least a part of a wiring pattern portion of a flexible wiring board, thereby forming a printed film on the pattern. (Step B) A step of evaporating part or all of the solvent in the printed film by placing the printed film obtained in Step A in an atmosphere of 40°C to 100°C. (Step C) A step of curing the printed film obtained in step A or the printed film obtained in step B by heating at 100°C to 170°C to form a protective film for the flexible wiring board.

[0162] In this embodiment, more preferably, (Step A) A step of printing the curable composition according to the present embodiment onto a part or the entire surface of a flexible wiring board having wiring formed on a flexible substrate, on which wiring is formed, to form a printed film on the wiring; (Step B) A step of evaporating a part or all of the solvent in the printed film by placing the printed film obtained in Step A in an atmosphere of 40°C to 100°C; (Step C) A step of curing the printed film obtained in Step A or the printed film obtained in Step B by heating at 100°C to 170°C to form an overcoat film. The method for producing a flexible wiring board covered with an overcoat film includes the steps of:

[0163] The operation of evaporating the solvent in step B is an operation that is performed as needed, and the operation of thermal curing may be performed immediately after the operation of step A, so that the curing reaction and removal of the solvent are carried out simultaneously. When the operation of evaporating the solvent before thermal curing in step B is performed, the temperature is usually 40°C to 100°C, preferably 60°C to 100°C, and more preferably 70°C to 90°C, taking into consideration the evaporation rate of the solvent and a rapid transition to the thermal curing step. The time for evaporating the solvent in step B is not particularly limited, but is preferably 10 to 120 minutes, and more preferably 20 to 100 minutes.

[0164] The conditions for the thermal curing carried out in step C are in the range of 100°C to 170°C from the viewpoints of preventing diffusion of the plating layer and obtaining low warpage, flexibility, and pliability suitable for a protective film. The thermal curing temperature is preferably 105°C to 160°C, and more preferably 110°C to 150°C. The time for the thermal curing carried out in step C is not particularly limited, but is preferably 10 minutes to 150 minutes, and more preferably 15 minutes to 120 minutes.

[0165] As described above, when the curable composition according to this embodiment is cured to form a cured product, it exhibits excellent resistance to wire breakage, low warpage, flexibility, etc. Therefore, when the curable composition according to this embodiment is applied to a flexible substrate such as a flexible wiring board or a polyimide film and then a cured product (protective film) is produced by a curing reaction, the warpage of the flexible wiring board or flexible substrate with the protective film is small, facilitating alignment in the subsequent IC chip mounting process. Therefore, the curable composition according to this embodiment can be suitably used to form an overcoat film for a flexible wiring board.

[0166] Furthermore, the curable composition according to this embodiment is expected to provide good handleability, and when cured, it is expected to provide good adhesion to the substrate, flexibility, moisture resistance, and the like, as well as good long-term electrical insulation reliability.

[0167] Furthermore, the cured product of the present embodiment is expected to have at least excellent breakage prevention properties and also have good flexibility that contributes to this, and is therefore suitable for providing flexible wiring boards with an electrically insulating protective film that are less susceptible to cracking (for example, flexible printed wiring boards such as COF). [Example]

[0168] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0169] <Acid value measurement> The solvent in the polyurethane solution used in this embodiment was distilled off under reduced pressure while heating to obtain component a. The acid value of component a obtained by the above method was measured in accordance with the potentiometric titration method of JIS K0070. The apparatus used for potentiometric titration is described below. Device name: Kyoto Electronics Manufacturing Co., Ltd. Automatic potentiometric titrator AT-510 Electrode: Kyoto Electronics Manufacturing Co., Ltd. composite glass electrode C-173

[0170] <Measurement of number average molecular weight of component a> The number average molecular weight is a polystyrene equivalent number average molecular weight measured by GPC, and the GPC measurement conditions are as follows. Device name: JASCO Corporation HPLC unit HSS-2000 Column: Shodex column LF-804 Mobile phase: tetrahydrofuran Flow rate: 1.0mL / min Detector: JASCO RI-2031Plus Temperature: 40.0℃ Sample volume: Sample loop 100 μL Sample concentration: adjusted to around 0.1% by mass

[0171] <Measurement of viscosity of solution containing component a>

[0172] The viscosity of the polyurethane solution was measured by the following method. Using approximately 0.8 g of polyurethane solution, the viscosity was measured 7 minutes after the start of measurement using a cone / plate viscometer (Brookfield, model: DV-II+Pro, spindle model number: CPE-52) at a temperature of 25.0°C and a rotation speed of 5 rpm.

[0173] <Measurement of Viscosity of Curable Composition>

[0174] Viscosity of the curable composition of Measurement was carried out by the following method. Using approximately 0.6 g of the curable composition, the viscosity was measured 7 minutes after the start of measurement using a cone / plate viscometer (manufactured by Brookfield, model: DV-II+Pro, spindle model number: CPE-52) at a temperature of 25.0°C and a rotation speed of 10 rpm.

[0175] <Synthesis of polyester polyol>

[0176] (Reference synthesis example 1) A reaction vessel equipped with a stirrer, thermometer, and distillation condenser was charged with 983.5 g (6.74 mol) of phthalic anhydride and 879.2 g (7.44 mol) of 1,6-hexanediol. The internal temperature of the reaction vessel was raised to 140 °C using an oil bath, and stirring was continued for 4 hours. Subsequently, while continuing stirring, 1.74 g of mono-n-butyltin oxide was added, and the internal temperature of the reaction vessel was gradually raised. A vacuum pump was connected, and the pressure inside the reaction vessel was gradually reduced, and water was removed from the reaction vessel by vacuum distillation. Finally, the internal temperature was raised to 220 °C, and the pressure was reduced to 133.32 Pa. After 15 hours, the reaction was terminated when it was confirmed that water had not completely distilled off. The hydroxyl value of the resulting polyester polyol (hereinafter referred to as polyester diol (α)) was measured and found to be 53.1 mg-KOH / g.

[0177] <Synthesis of polyurethane>

[0178] (Synthesis Example 1)

[0179] A reaction vessel equipped with a stirrer, a thermometer, and a condenser was charged with 10.7 g (24.4 mmol, aromatic ring 97.6 mmol) of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., trade name: BPEF), 61.52 g of P-2030 (manufactured by Kuraray Co., Ltd., polyester polyol composed of isophthalic acid / 3-methyl-1,5-pentanediol), 6.48 g of 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a carboxyl group-containing diol, and 137.7 g of γ-butyrolactone as a solvent, and the mixture was heated to 100°C to dissolve all of the raw materials.

[0180] The temperature of the reaction solution was lowered to 90°C, and 28.31 g of methylenebis(4-cyclohexylisocyanate) (manufactured by Sumika Bayer Urethane Co., Ltd., trade name: Desmodur-W) as a polyisocyanate compound was added dropwise over 30 minutes using a dropping funnel. The reaction was carried out at 145°C to 150°C for 8 hours, and after confirming by IR that absorption due to the C=O stretching vibration of the isocyanate group was almost no longer observed, 1.5 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) and 24.3 g of diethylene glycol diethyl ether (manufactured by Nippon Nyukazai Co., Ltd.) were added dropwise, and the reaction was carried out for a further 3 hours at 80°C to obtain a solution containing polyurethane having carboxyl groups and an aromatic ring concentration of 3.1 mmol / g (hereinafter referred to as "Polyurethane Solution A1").

[0181] The viscosity of the resulting polyurethane solution A1 was 120,000 mPa·s. The polyurethane contained in the polyurethane solution A1 had a carboxyl group and an aromatic ring concentration of 3.1 mmol / g (hereinafter referred to as "polyurethane AU1") and had a number average molecular weight of 20,000 and an acid value of 25.0 mg-KOH / g.

[0182] The solid content concentration in the polyurethane solution A1 was 40.0% by mass.

[0183] (Synthesis Example 2)

[0184] A reaction vessel equipped with a stirrer, a thermometer, and a condenser was charged with 21.0 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (trade name: BPEF, manufactured by Osaka Gas Chemicals Co., Ltd.), 66.7 g of the above polyester diol (α) (a polyester polyol composed of phthalic acid / 1,6-hexanediol), 3.00 g of 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a carboxyl group-containing diol, and 83.24 g of γ-butyrolactone as a solvent, and the mixture was heated to 100°C to dissolve all of the raw materials.

[0185] The temperature of the reaction solution was lowered to 90 ° C., and a solution of 26.50 g of diphenylmethane-4,4'-diisocyanate (manufactured by Tosoh Corporation, trade name: Millionate MT) as a polyisocyanate compound dissolved in 60.0 g of γ-butyrolactone was added dropwise over 20 minutes using a dropping funnel. The reaction was carried out at 125 ° C. to 130 ° C. for 8 hours, and after confirming by IR that absorption due to the C = O stretching vibration of the isocyanate group was almost no longer observed, 1.5 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.), 6.19 g of γ-butyrolactone, and 26.37 g of diethylene glycol diethyl ether (manufactured by Nippon Nyukazai Co., Ltd.) were added dropwise, and the reaction was carried out for another 3 hours at 80 ° C. to obtain a solution containing polyurethane having carboxyl groups and an aromatic ring concentration of 5.6 mmol / g (hereinafter referred to as "Polyurethane Solution A2").

[0186] The viscosity of the resulting polyurethane solution A2 was 120,000 mPa·s. The number average molecular weight of the polyurethane (hereinafter referred to as "polyurethane AU2") containing carboxyl groups and having an aromatic ring concentration of 5.6 mmol / g in polyurethane solution A2 was 20,000, and the acid value of polyurethane AU2 was 10.6 mg-KOH / g.

[0187] The solid content concentration in the polyurethane solution A2 was 40.0% by mass.

[0188] (Synthesis Example 3)

[0189] A reaction vessel equipped with a stirrer, a thermometer, and a condenser was charged with 5.0 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., trade name: BPEF), 73.00 g of polycarbonate diol (a polyester polyol composed of 3-methyl-1,5-pentanediol / 1,6-hexanediol, trade name: Kuraray Polyol C-2090, hydroxyl value: 1955), 6.75 g of 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a carboxyl group-containing diol, and 136.34 g of γ-butyrolactone as a solvent, and the mixture was heated to 100°C to dissolve all of the raw materials.

[0190] The temperature of the reaction solution was lowered to 90°C, and 26.80 g of methylenebis(4-cyclohexylisocyanate) (manufactured by Sumika Bayer Urethane Co., Ltd., product name: Desmodur-W) as a polyisocyanate compound was added dropwise over 30 minutes using a dropping funnel. The reaction was carried out at 145°C to 150°C for 10 hours, and after confirming by IR that absorption due to the C=O stretching vibration of the isocyanate group was almost completely eliminated, 1.5 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.), 5.89 g of γ-butyrolactone, and 25.10 g of diethylene glycol diethyl ether (manufactured by Nippon Nyukazai Co., Ltd.) were added dropwise, and the reaction was carried out for a further 3 hours at 80°C to obtain a solution containing a polyurethane having carboxyl groups and an aromatic ring concentration of 0.4 mmol / g (hereinafter referred to as "Polyurethane Solution A3").

[0191] The viscosity of the resulting polyurethane solution A3 was 120,000 mPa·s. The polyurethane contained in polyurethane solution A3, which had a carboxyl group and an aromatic ring concentration of 0.4 mmol / g (hereinafter referred to as "polyurethane AU3"), had a number average molecular weight of 20,000 and an acid value of 25.0 mg-KOH / g.

[0192] The solid content concentration in the polyurethane solution A3 was 40.0% by mass.

[0193] (Comparative Synthesis Example 1)

[0194] A reaction vessel equipped with a stirrer, a thermometer, and a condenser was charged with 248.0 g of C-1090 (manufactured by Kuraray Co., Ltd., a (poly)carbonate diol made from 1,6-hexanediol and 3-methyl-1,5-pentanediol, having a hydroxyl value of 122.22 mg-KOH / g) as a (poly)carbonate polyol, 47.5 g of 2,2-dimethylolbutanoic acid (manufactured by Nippon Kasei Co., Ltd.) as a carboxyl group-containing diol, 2.7 g of trimethylolethane (manufactured by Mitsubishi Gas Chemical Company, Inc.) as a polyol other than the (poly)carbonate polyol and the carboxyl group-containing diol, and 467.5 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) and 82.5 g of diethylene glycol diethyl ether (manufactured by Nippon Nyukazai Co., Ltd.) as solvents, and the mixture was heated to 100°C to dissolve all of the raw materials.

[0195] The temperature of the reaction liquid was lowered to 90°C, and 150.4 g of methylenebis(4-cyclohexylisocyanate) (manufactured by Sumika Bayer Urethane Co., Ltd., trade name: Desmodur-W) as a diisocyanate compound was added dropwise using a dropping funnel over 30 minutes.

[0196] The reaction was carried out at 120°C for 8 hours, and it was confirmed by IR that the absorption due to the C=O stretching vibration of the isocyanato group was almost no longer observed. Thereafter, 1.5 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) was added dropwise to the reaction solution, and the reaction was carried out at 80°C for an additional 3 hours to obtain a polyurethane solution having carboxyl groups and carbonate bonds (hereinafter referred to as "Polyurethane Solution B1").

[0197] The viscosity of the obtained polyurethane solution B1 was 145,000 mPa·s. The number average molecular weight of the polyurethane (hereinafter referred to as "polyurethane BU1") containing an aromatic ring concentration of 0 mmol / g in the obtained polyurethane solution B1 was 14,000, and the acid value of polyurethane BU1 was 40.0 mg-KOH / g. The solid content concentration in polyurethane solution B1 was 45.0 mass%.

[0198] (Comparative Synthesis Example 2)

[0199] A 1-liter three-neck flask equipped with a distillation apparatus was charged with 611.0 g of bis[4-(2-hydroxyethoxy)phenyl]methane, 297.3 g of dimethyl isophthalate, and 0.5 g of dioctyltin oxide. The mixture was heated to 180°C under a nitrogen stream, and the resulting methanol was distilled off. When approximately 50 g of methanol had distilled off, the pressure in the reaction system was reduced to 1.3 kPa to accelerate the rate of methanol distillation. After the theoretical amount of methanol had distilled off, the mixture was heated for an additional hour and then held at 185°C and 0.13 kPa for another hour. The reactor was then cooled, yielding 810 g of polyester polyol (hereinafter referred to as polyester diol (β)). The hydroxyl value of the resulting polyester diol (β) was measured, and found to be 55.4 mg-KOH / g.

[0200] A reaction vessel equipped with a stirrer, a thermometer, and a condenser was charged with 11.0 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (trade name: BPEF, manufactured by Osaka Gas Chemicals Co., Ltd.), 61.52 g of polyester diol (β), 6.32 g of 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a carboxyl group-containing diol, and 135.6 g of γ-butyrolactone as a solvent, and the mixture was heated to 100°C to dissolve all of the raw materials.

[0201] The temperature of the reaction solution was lowered to 90°C, and 27.00 g of diphenylmethane-4,4'-diisocyanate (manufactured by Sumika Bayer Urethane Co., Ltd., trade name: MDI) was added in several portions over 30 minutes using a dropping funnel. The reaction was carried out at 145°C to 150°C for 15 hours. After confirming by IR that absorption due to the C=O stretching vibration of the isocyanate group had almost disappeared, 1.5 g of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) and 23.9 g of diethylene glycol diethyl ether (manufactured by Nippon Nyukazai Co., Ltd.) were added dropwise, and the reaction was carried out for an additional 3 hours at 80°C to obtain a solution containing polyurethane having carboxyl groups and an aromatic ring concentration of 6.9 mmol / g (hereinafter referred to as "Polyurethane Solution B2").

[0202] The viscosity of the resulting polyurethane solution B2 was 125,000 mPa·s. The polyurethane contained in polyurethane solution B2 had a carboxyl group and an aromatic ring concentration of 6.9 mmol / g (hereinafter referred to as "polyurethane BU2") and had a number average molecular weight of 20,000 and an acid value of 25.0 mg-KOH / g.

[0203] The solid content concentration in the polyurethane solution B2 was 40.0% by mass.

[0204] The properties of polyurethanes AU1 to AU3 and polyurethanes BU1 and BU2 are shown in Table 1.

[0205] [Table 1]

[0206] <Production of main compound>

[0207] (Example of Mixture 1)

[0208] 160.0 parts by weight of polyurethane solution A1, 6.3 parts by weight of silica powder (Nippon Aerosil Co., Ltd., product name: Aerosil R-974), 0.72 parts by weight of melamine (Nissan Chemical Industries, Ltd.) as a curing accelerator, and 8.4 parts by weight of diethylene glycol diethyl ether were mixed. The silica powder and curing accelerator were mixed into polyurethane solution A1 using a three-roll mill (Inoue Seisakusho Co., Ltd., model: S-4 3 / 4 x 11). Then, 2.0 parts by weight of a defoamer (olefin-based defoamer containing polyolefin, BYK-1791, product name: BYK-Chemie Japan Co., Ltd.) were added and mixed using a spatula. This formulation was designated base formulation C1.

[0209] (Example of Mixture 2)

[0210] 160.0 parts by weight of polyurethane solution A1, 6.3 parts by weight of silica powder (Nippon Aerosil Co., Ltd., product name: Aerosil R-974), 1.0 part by weight of hydrotalcite (Kyowa Chemical Industry Co., Ltd., product name: DHT-4A), 0.72 parts by weight of melamine (Nissan Chemical Industries, Ltd.) as a curing accelerator, and 8.4 parts by weight of diethylene glycol diethyl ether were mixed. The silica powder and curing accelerator were mixed into polyurethane solution A1 using a three-roll mill (Inoue Seisakusho Co., Ltd., model: S-4 3 / 4 x 11). Then, 2.0 parts by weight of a defoamer (olefin-based defoamer containing polyolefin, BYK-Chemie Japan Co., Ltd., product name: BYK-1791) were added and mixed using a spatula. This formulation was designated base formulation C2.

[0211] (Examples 3-7)

[0212] The formulations were compounded according to the formulations shown in Table 2 using the same method as in Formulation Example 1. The formulations prepared in Formulation Examples 3 to 7 were designated Main Compounds C3 to C7, respectively. The values ​​in the table represent parts by mass. Disparlon 230HF is an acrylic defoamer containing an acrylic resin, and TSA750S is a silicone defoamer containing a silicone resin.

[0213] (Comparative formulation example 1)

[0214] 140.0 parts by weight of polyurethane solution B1, 5.5 parts by weight of silica powder (Nippon Aerosil Co., Ltd., product name: Aerosil R-974), 0.72 parts by weight of melamine (Nissan Chemical Industries, Ltd.) as a curing accelerator, and 8.4 parts by weight of diethylene glycol diethyl ether were mixed. The silica powder and curing accelerator were mixed into polyurethane solution B1 using a three-roll mill (Inoue Seisakusho Co., Ltd., model: S-4 3 / 4 x 11). Then, 2.0 parts by weight of a defoamer (olefin-based defoamer containing polyolefin, BYK-1791, product name: BYK-Chemie Japan Co., Ltd.) were added and mixed using a spatula. This formulation was designated base formulation D1.

[0215] (Comparative formulation example 2)

[0216] The formulation was prepared in the same manner as in Formulation Example 1, according to the formulation shown in Table 2. The formulation prepared in Comparative Formulation Example 2 was designated as Main Formulation D2. The values ​​in the table represent "parts by mass."

[0217] (Comparative formulation example 3)

[0218] The formulation was prepared in the same manner as in Formulation Example 1, according to the formulation shown in Table 2. The formulation prepared in Comparative Formulation Example 3 was designated as Main Formulation D3. The values ​​in the table represent parts by mass.

[0219] [Table 2]

[0220] <Preparation of hardener solution>

[0221] (Example 1 of hardener solution formulation)

[0222] To a vessel equipped with a stirrer, a thermometer, and a condenser were added 16.85 parts by mass of an epoxy resin having the structure of the following formula (6) (manufactured by Mitsubishi Chemical Corporation, grade name: jER (registered trademark) 604, epoxy equivalent 120 g / eqv) and 18.25 parts by mass of diethylene glycol diethyl ether, and stirring was commenced.

[0223] While continuing stirring, the temperature inside the container was raised to 40°C using an oil bath. After the internal temperature was raised to 40°C, stirring was continued for 30 minutes. After confirming that the jER (registered trademark) 604 had completely dissolved, the container was cooled to room temperature to obtain a solution containing jER (registered trademark) 604 at a concentration of 48% by mass. This solution is designated as curing agent solution E1.

[0224] [ka]

[0225] (Example 2 of hardener solution)

[0226] To a vessel equipped with a stirrer, a thermometer, and a condenser were added 16.85 parts by mass of an epoxy resin containing N,N-diglycidyl-4-(glycidyloxy)aniline as a main component (manufactured by Mitsubishi Chemical Corporation, grade name: jER (registered trademark) 630, epoxy equivalent: 98 g / eqv) and 18.25 parts by mass of diethylene glycol diethyl ether, and stirring was commenced.

[0227] While continuing stirring, the temperature inside the container was raised to 40°C using an oil bath. After the internal temperature was raised to 40°C, stirring was continued for 30 minutes. After confirming that the jER (registered trademark) 630 had completely dissolved, the container was cooled to room temperature to obtain a solution containing jER (registered trademark) 630 at a concentration of 48% by mass. This solution was designated as curing agent solution E2.

[0228] <Mixing the base compound and the solution containing the hardener>

[0229] (Formulation example 1 of curable composition)

[0230] 88.7 parts by mass of base compound C1 and 3.5 parts by mass of curing agent solution E1 were placed in a plastic container. Furthermore, to match the viscosity with the curable compositions of the other formulation examples and comparative formulation examples described below, 3.0 parts by mass of diethylene glycol diethyl ether and 1.5 parts by mass of diethylene glycol monoethyl ether acetate were added as solvents. Mixing was carried out by stirring with a spatula at room temperature for 5 minutes, yielding a curable composition (hereinafter referred to as "curable composition F1").

[0231] (Formulation Examples 2 to 8 of Curable Compositions)

[0232] They were blended according to the blending compositions shown in Table 3 in the same manner as in Formulation Example 1 of the curable composition. The blends prepared in Formulation Examples 2 to 8 of the curable composition were designated as Curable Compositions F2 to F8, respectively.

[0233] (Comparative Formulation Example 1 of Curable Composition)

[0234] 78.6 parts by mass of base compound D1 and 5.6 parts by mass of curing agent solution E1 were placed in a plastic container. Furthermore, to match the viscosity with the curable compositions of the other formulation examples and comparative formulation examples, 4.8 parts by mass of diethylene glycol diethyl ether and 1.3 parts by mass of diethylene glycol monoethyl ether acetate were added as solvents. Mixing was carried out with a spatula by stirring at room temperature for 5 minutes to obtain a curable composition (hereinafter referred to as "curable composition G1").

[0235] (Comparative Formulation Example 2 of Curable Composition)

[0236] A curable composition (hereinafter referred to as "curable composition G2") was prepared according to the formulation shown in Table 3 in the same manner as in the above-mentioned "Comparative Formulation Example 1 of Curable Composition."

[0237] (Comparative Formulation Example 3 of Curable Composition) A curable composition (hereinafter referred to as "curable composition G3") was prepared according to the formulation shown in Table 3 in the same manner as in the above-mentioned "Comparative Formulation Example 1 of Curable Composition."

[0238] The blending compositions of the polyurethane solution with the main component blends of curable compositions F1 to F8 and curable compositions G1 to G3 are shown in Table 3. In addition, the blending compositions of each component of curable compositions F1 to F8 and curable compositions G1 to G3 are summarized in Table 4.

[0239] In Table 4, "a / (a+c)" represents the content (mass%) of component a relative to the total amount of component a and component c. In Table 4, "b / (a+b+c)" represents the content (mass%) of component b relative to the total amount of components a, b, and c. In Table 4, "(d+e)" represents the total amount (mass %) of component d and component e in the curable composition. In Table 4, "(d + e) / (total amount of composition - b)" represents the total amount of component d and component e when the total amount of components obtained by excluding the content of component b from the total amount of the curable composition is taken as 100 parts by mass. "e / d" in Table 4 represents the content ratio (mass%) of component e to component d.

[0240] [Table 3]

[0241] [Table 4]

[0242] (Examples 1 to 8, Comparative Examples 1 to 3)

[0243] Curable compositions F1 to F8 and curable compositions G1 to G3 were evaluated for breakage prevention, warpage, flexibility, and defoaming time by the methods described below. The results are shown in Table 5.

[0244] <Evaluation of wiring board wiring breakage prevention (MIT test)>

[0245] A flexible wiring board was prepared by etching a flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex US, copper thickness: 8 μm, polyimide thickness: 38 μm), and the substrate had a fine comb-shaped pattern as described in JPCA-ET01 (copper wiring width / copper wiring spacing = 15 μm / 15 μm), and was then tin-plated. Curable composition F1 was applied to the flexible wiring board by screen printing so that the thickness of the printed film from the wiring surface was 5 μm (after drying). The printed film-formed wiring board was placed in a hot air circulation dryer at 80 ° C for 30 minutes, and then in a hot air circulation dryer at 120 ° C for 120 minutes to cure the printed film.

[0246] Using this test piece, tests were carried out under the following conditions in accordance with the method described in JIS C-5016. (Test conditions) Testing machine: MIT Tester BE202 manufactured by Tester Sangyo Co., Ltd. Bending speed: 10 times / min Load: 200g Bending angle: ±90° Grip tip radius: 0.5 mm Under the above test conditions, the number of times of bending was increased by 10 times each, and the presence or absence of cracks in the wiring was visually observed, and the number of times of bending when cracks appeared was recorded. The results are shown in Table 5. The same evaluations were also carried out using curable compositions F2 to F8 and curable compositions G1 to G3. The results are also shown in Table 5.

[0247] <Evaluation of warpage>

[0248] Curable composition F1 was applied to a substrate by screen printing using a #180 mesh polyester plate, and the substrate was placed in a hot air circulation dryer at 80°C for 30 minutes.The substrate was then placed in a hot air circulation dryer at 120°C for 60 minutes to cure the applied curable composition F1.A 25 μm thick polyimide film (Kapton (registered trademark) 100EN, manufactured by DuPont-Toray Co., Ltd.) was used as the substrate.

[0249] The curable composition was applied and cured using a hot air circulation dryer. The resulting cured film was then cut into 50 mm diameter pieces using a circle cutter. The circular cut pieces exhibited a convex or concave warp near the center. After one hour, the substrates with the cured film formed thereon were left in a convex position, i.e., with the center of the cured film on the substrate in contact with a horizontal surface. The maximum and minimum heights of warp from the horizontal surface were measured and averaged. The sign indicates the direction of warp. When left in a convex position, a "+" indicates that the cured film was on the upper side of the copper substrate or polyimide film, and a "-" indicates that the cured film was on the lower side. A warp of less than +3.0 mm was considered acceptable. The results are shown in Table 5.

[0250] The same evaluations were also carried out using curable compositions F2 to F8 and curable compositions G1 to G3. The results are also shown in Table 5.

[0251] <Flexibility evaluation>

[0252] Curable composition F1 was applied by screen printing to the copper of a flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex, copper thickness: 8 μm, polyimide thickness: 38 μm) to a width of 75 mm, a length of 110 mm, and a cured film thickness of 15 μm. The specimen was then held at room temperature for 10 minutes and cured in a hot air circulating dryer at 120 °C for 60 minutes. The PET film backing of the prepared test specimen was peeled off, and the specimen was cut into 10 mm wide strips with a utility knife. The specimen was then bent approximately 180 degrees with the cured film facing outward and compressed at 0.5 ± 0.2 MPa for 3 seconds using a compressor. The bent portion was observed under a 30x microscope to check for the presence or absence of cracks.

[0253] When the flexibility of curable compositions F1 to F8 was evaluated, all of them were found to have "no cracks." On the other hand, when the flexibility of curable compositions G1 to G3 was evaluated, G1 and G3 were found to have "no cracks," but G2 was found to have "cracks."

[0254] <Defoaming time>

[0255] Curable composition F1 was applied by screen printing to the copper of a flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex, copper thickness: 8 μm, polyimide thickness: 38 μm) so as to have a width of 75 mm, a length of 110 mm, and a film thickness after curing of 15 μm. At this time, bubbles on the coating surface were visually observed, and the time until the bubbles disappeared was measured, taking the time after the completion of screen printing as 0 seconds, and was taken as the defoaming time.

[0256] The same evaluations were also carried out using curable compositions F2 to F8 and curable compositions G1 to G3. The results are also shown in Table 5.

[0257] [Table 5]

[0258] From the above results, it was confirmed at least that the curable composition of this example is excellent in at least the properties of preventing wire breakage, reducing warpage, flexibility, and defoaming, and that the cured product is useful as an insulating protective film for flexible wiring boards, etc.

Claims

1. (Component a) a polyurethane containing an organic residue derived from a polyisocyanate, which has a carboxyl group and an aromatic ring concentration of 0.1 to 6.5 mmol / g; (Component b) a solvent, (Component c) a compound having two or more epoxy groups in one molecule, (Component d) an olefin-containing first antifoam agent, and (Component e) a second defoaming agent containing an acrylic resin and / or a methacrylic resin, The component a is a polyurethane having a structural unit represented by formula (2), The component a is 80 to 99.9% by mass based on the total amount of the component a and the component c, the component b is 25 to 75% by mass based on the total amount of the components a, b, and c, the total amount of the component d and the component e is 0.1 to 3 mass %, The component e is 5 to 150% by mass relative to the component d, Contains no fluorine atoms or silicone-based defoamers. Curable composition. 【Chemistry 1】 (where R １ each independently represents a phenylene group or a phenylene group having a substituent.

2. Component a is represented by formula (1) 【Chemistry 2】 2. The curable composition according to claim 1, which is a polyurethane having structural units represented by the formula:

3. Component a is represented by formula (3) 【Transformation 3】 (where n R １ each independently represents a phenylene group or a phenylene group having a substituent, and (n+1) R ２ each independently represents an alkylene group having 3 to 9 carbon atoms, and n is a natural number of 50 or less. The curable composition according to claim 1 or 2, which is a polyurethane having a structural unit represented by the formula:

4. 3. The curable composition according to claim 1, wherein in component a, the organic residue derived from the cycloaliphatic polyisocyanate accounts for 70 mol % or more of the total amount of organic residues derived from the polyisocyanate.

5. 3. The curable composition according to claim 1, wherein the number average molecular weight of component a is 3,000 to 50,000, and the acid value of component a is 10 to 70 mgKOH / g.

6. 3. The curable composition according to claim 1, wherein the total amount of components d and e is 0.01 to 5 mass% when the total amount of components obtained by excluding the content of component b from the total amount of the curable composition is taken as 100 mass%.

7. The curable composition according to claim 1 or 2, further comprising (component f) at least one kind of fine particles selected from the group consisting of inorganic fine particles and organic fine particles.

8. The curable composition of claim 7 , wherein component f comprises silica microparticles.

9. The curable composition of claim 7 , wherein component f comprises hydrotalcite fine particles.

10. A cured product of the curable composition according to claim 1 or 2.

11. An overcoat film for flexible wiring boards, comprising the cured product according to claim 10.

12. A flexible wiring board having wiring formed on a flexible substrate, the surface on which the wiring is formed being partially or entirely covered with the overcoat film for flexible wiring boards according to claim 11.

13. (Step A) a step of printing the curable composition according to claim 1 or 2 on a part or all of the surface of a flexible wiring board having wiring formed on a flexible substrate, on which wiring is formed, to form a printed film on the wiring; (Step B) A step of evaporating a part or all of the solvent in the printed film by placing the printed film obtained in Step A in an atmosphere of 40°C to 100°C; (Step C) A step of curing the printed film obtained in Step A or the printed film obtained in Step B by heating at 100°C to 170°C to form an overcoat film. A method for producing a flexible wiring board covered with an overcoat film, comprising:

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