TWI908129B - Curable composition, cured object, overcoat film for flexible wiring board, flexible wiring board, and production method of flexible wiring board - Google Patents

Abstract

Provided are a curable composition, a cured object, a overcoat film for a flexible wiring board, a flexible wiring board, and a production method of a flexible wiring board, which are excellent in wiring disconnection preventing properties, low-warpage properties, flexibility, and defoaming properties and do not contain fluorine atoms. The present invention provides a curable composition, a cured object, a overcoat film for a flexible wiring board, a flexible wiring board, and a production method of a flexible wiring board, which contain: (component a) a polyurethane having carboxyl groups and an aromatic-ring concentration of 0.1-6.5 mmol/g and containing an organic residue derived from a polyisocyanate, (component b) a solvent, (component c) a compound having two or more epoxy groups in one molecule, and (component d) an olefin-containing defoaming agent, and do not contain fluorine atoms.

Description

Curing composition, curing agent, coating for flexible wiring board, flexible wiring board, and method for manufacturing flexible wiring board.

This invention relates to a curing composition, a curing agent, an outer coating for a flexible wiring board, a flexible wiring board, and a method for manufacturing a flexible wiring board.

Traditionally, surface protective films for flexible wiring circuits have come in several types: those where a die-cut polyimide film, known as a cover film, is made to conform to a pattern and then adhered using an adhesive; and those where a flexible UV-curing or thermosetting coating is applied using screen printing, with the latter being particularly useful from a workability standpoint. As for these curing-type coatings, resin compositions primarily composed of epoxy resins, acrylic resins, or composites thereof are known. These often use resins modified, particularly by incorporating butadiene, silicate, polycarbonate glycol, or long-chain aliphatic backbones, as the main component.

However, in recent years, with the miniaturization and lightness of electronic devices, flexible substrates have also become thinner and lighter. Along with this, there is a strong desire to improve the physical properties of the resin composition used for coating.

As a related technology, for example, in Patent 1, regarding the composition of a protective film that can be used in flexible wiring boards, a curable composition is disclosed, which contains: polyurethane, solvent, and a compound having two or more epoxy groups in one molecule.

Patent document 2 discloses a curable polyurethane composition containing a curable polyurethane resin (A) and a defoamer (B) as essential components, wherein an ethylene-α-olefin copolymer oligomer is used as the defoamer (B).

[Previous Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent No. 6912385 [Patent Document 2] Japanese Patent Application Publication No. Hei 05-247161

[The problem the invention aims to solve]

However, there is room for further improvement regarding the curing components used in the aforementioned protective films. For example, when using curing agents as protective films for wiring in flexible wiring boards, it is desirable to further improve their properties such as breakage inhibition, low warping, flexibility, and defoaming properties. Furthermore, from a safety perspective, it is desirable to minimize the use of fluorinated compounds such as PFAS (per- and polyfluoroalkyl substances). From this perspective, it is desirable to develop a curing component that is free of fluorine atoms and exhibits superior properties.

In view of the above, the purpose of this invention is to provide a curable composition, a curable material, an outer coating for flexible wiring boards, a flexible wiring board, and a method for manufacturing a flexible wiring board that are free of fluorine atoms and possess excellent properties of wire breakage suppression, low warping, flexibility, and defoaming. [Means of Solving the Problem]

To solve the above problems, the inventors conducted repeated research and discovered a curable composition that does not contain fluorine atoms, comprising: component (a) a polyurethane containing organic residues derived from polyisocyanate, having a carboxyl group and an aromatic ring concentration of 0.1 mmol/g (millomoll/gram) to 6.5 mmol/g; (b) a solvent; (c) a compound having two or more epoxy groups in one molecule; and (d) an olefinic defoamer, thereby completing the present invention.

That is, the present invention is as described below.

<1> A curable composition, free of fluorine atoms, comprising: component (a) a polyurethane containing an organic residue derived from a polyisocyanate, having a carboxyl group and an aromatic ring concentration of 0.1 mmol/g 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 defoamer containing an olefin.

<2> The curable composition as described in <1>, wherein component a is a polyurethane having the structural unit represented by formula (1).

<3> The curable composition as described in <1> or <2>, wherein component a is a polyurethane having the structural unit represented by formula (2). (Here, R ¹ independently represents either a phenyl group or a phenyl group with a substituent.)

<4> The curable composition as described in <1> or <2>, wherein component a is a polyurethane having the structural unit represented by formula (3). (Here, each of the n R ^1s independently represents an enylphenyl or an enylphenyl with a substituent, and each of the (n+1) R ^2s independently represents an enylalkyl group having 3 to 9 carbon atoms, where n is a natural number less than 50.)

<5> The curing composition as described in <1> or <2>, wherein in component a, the organic residues derived from cyclic aliphatic polyisocyanates are 70 mol% or more relative to the total amount of the aforementioned organic residues derived from polyisocyanates.

<6> The hardening composition as described in <1> or <2>, wherein component a is 60% to 99.9% by mass relative to the total amount of component a and component c.

<7> The hardening composition as described in <1> or <2>, wherein component b is 25% to 75% by mass relative to the total amount of components a, b, and c.

<8> The curing composition as described in <1> or <2>, wherein the average molecular weight of component a is 3,000 to 50,000, and the acid value of component a is 10 mgKOH/g to 70 mgKOH/g.

<9> The curing composition as described in <1> or <2> further comprises: (component e) a second defoamer containing acrylic resin and/or methacrylic resin.

<10> As described in <9>, in a curing composition, the total amount of component d and component e is from 0.01% to 3% by mass relative to the total amount of the curing composition.

<11> As described in <9>, in a curing composition, where the total amount of components after removing the content of component b from the total amount of the aforementioned curing composition is set to 100% by mass, the total amount of components d and e is 0.01% by mass to 5% by mass.

<12> The hardening composition as described in <9>, wherein component e is 1% to 150% by mass relative to component d.

<13> The hardening composition as described in <1> or <2> further comprises: (component f) at least one microparticle selected from the group consisting of inorganic and organic microparticles.

<14> The hardening composition as described in <13>, wherein component f comprises silicon dioxide microparticles.

<15> The hardening composition as described in <13>, wherein component f comprises hydrotalcite microparticles.

<16> A hardening agent, which is a hardening agent of the hardening composition described in <1> or <2>.

<17> An outer coating for a flexible wiring board, comprising the hardener described in <16>.

<18> A flexible wiring board, which is formed by forming wiring on a flexible substrate, wherein a portion or all of the surface on which the wiring is formed is covered by an outer coating of the flexible wiring board as described in <17>.

<19> A method for manufacturing a flexible wiring board, comprising: (Step A) printing a curable composition as described in <1> or <2> onto a portion or all of the surface of the flexible wiring board formed by forming wiring on a flexible substrate, thereby forming a printed film on the wiring; (Step B) placing the printed film obtained in Step A in an environment of 40°C to 100°C, thereby causing a portion or total amount of the solvent in the printed film to evaporate; and (Step C) at 100°C... The process involves heating the printed film obtained in step A or step B at 170°C to harden it and form an outer coating. [Effects of the Invention]

This invention provides a curable composition, a curable material, an outer coating for a flexible wiring board, a flexible wiring board, and a method for manufacturing a flexible wiring board, all of which have excellent wire breakage suppression, low warping, flexibility, and defoaming properties and are free of fluorine atoms.

The following provides a detailed description of the embodiments used to implement the present invention (hereinafter referred to as "the embodiments"). The embodiments described below are illustrative of the present invention and are not intended to limit the present invention to the following content. The present invention may be implemented by appropriate modifications within the scope of its spirit and spirit.

<Hardened components>

The curing composition involved in this embodiment is a curing composition that does not contain fluorine atoms, comprising: component (a) a polyurethane containing an organic residue derived from polyisocyanate, having a carboxyl group and an aromatic ring concentration of 0.1 mmol/g to 6.5 mmol/g; (b) a solvent; (c) a compound having two or more epoxy groups in one molecule; and (d) a first defoamer containing an olefin. The components are described below.

(ingredient a)

Component a is a polyurethane with a carboxyl group and an aromatic ring concentration of 0.1 mmol/g to 6.5 mmol/g, and contains organic residues derived from polyisocyanates. Polyurethane is defined as a substance containing a plurality of urethane bonds.

The aromatic ring structures of component a can be listed as: benzene ring structure, biphenyl structure, naphthalene structure, fusiform structure, etc.

The aromatic ring concentration of component a is from 0.1 mmol/g to 6.5 mmol/g, with the lower limit preferably above 0.5 mmol/g, more preferably above 1.6 mmol/g, further preferably above 2.0 mmol/g, and even more preferably above 2.5 mmol/g. The upper limit is preferably below 6.3 mmol/g, more preferably below 6.0 mmol/g, and even more preferably below 5.8 mmol/g.

Furthermore, if an example of a preferred combination of upper and lower limits is shown, then the aromatic concentration relative to 1 gram of component a is 0.1 mmol to 6.5 mmol (i.e., 0.1 mmol/g to 6.5 mmol/g), preferably 0.1 mmol to 6.3 mmol (i.e., 0.1 mmol/g to 6.3 mmol/g), more preferably 0.5 mmol to 6.3 mmol (i.e., 0.5 mmol/g to 6.3 mmol/g), and even more preferably 1.6 mmol to 6.0 mmol (i.e., 1.6 mmol/g to 6.0 mmol/g). The aromatic concentration of component a is preferably 2.0 mmol/g to 6.0 mmol/g (i.e., 2.0 mmol/g to 6.0 mmol/g) relative to 1 gram of component a. When the aromatic concentration of component a is within the above range, it is easy to achieve a balance between the solvent resistance of the coating film of the present embodiment described later and the flexibility of the wiring board, the wire breakage inhibition, or warping, etc. (wherein, the function and effect of the present embodiment are not limited to these).

Furthermore, the concentration of aromatic rings can be calculated based on the packing ratio, but it can also be analyzed by comparing the number ^of protons originating from ^the aromatic rings with the number of protons originating from the unit in ^1H -NMR after the structure has been determined using ^1H -NMR, ^13C -NMR and IR (infrared spectroscopy) ^.

Furthermore, as the number of aromatic rings in this specification, aromatic rings are counted as 1, and condensed rings are also counted as 1. For example, as described below, in the benzene ring of formula (51), the number of aromatic rings is counted as 1. In the biphenyl structure of formula (52) and the 9H-furo structure of formula (53), since there are two benzene rings, the number of aromatic rings is counted as 2. In the naphthalene structure of formula (54), the number of aromatic rings is counted as 2. Similarly, in the anthracene structure (formula (55)) or the phenanthrene structure (formula (56)), the number of aromatic rings is counted as 3. In the triphenylene structure (formula (57)) or the binaphthyl structure (formula (58)), the number of aromatic rings is counted as 4.

Furthermore, the number of ○ in equations (51') to (58') respectively represents the number of aromatic rings in equations (51) to (58).

There are no particular limitations on the manufacturing method of component a. For example, it can be synthesized by reacting a polyisocyanate compound, a carboxyl-containing diol, a polyol other than a carboxyl-containing diol, a monohydroxy compound, or a monoisocyanate compound as needed, with or without a known carboxyl esterification catalyst such as dibutyltin dilaurate, using a solvent. The reaction is better performed without a catalyst because it improves the linear breakage inhibition, flexibility, and low warpage properties of the coating of the present embodiment described later.

As long as component a is a polyurethane containing organic residues derived from polyisocyanate and has a carboxyl group and an aromatic ring concentration of 0.1 mmol/g to 6.5 mmol/g, there are no particular restrictions on its structure. It is preferred to have at least one of the structural units of formula (1) and formula (2), and more preferably to have both. (Here, R ¹ independently represents either a phenyl group or a phenyl group with a substituent.)

Furthermore, component a is preferably a polyurethane having the structural unit represented by formula (3). More specifically, it is even more preferable that part or all of the structural unit of formula (2) exists in the polyurethane as part of the structural unit represented by formula (3). (Here, each of the n R ^1s independently represents an enylphenyl or an enylphenyl with a substituent, and each of the (n+1) R ^2s independently represents an enylalkyl group having 3 to 9 carbon atoms, where n is a natural number less than 50.)

Furthermore, ^R1 in formulas (2) and (3) independently represents an alkylene group or an alkylene group with a substituent, preferably an alkylene group. As a substituent, alkyl groups having 1 to 5 carbon atoms, halogen atoms, etc. can be listed. Among them, from the viewpoint of being fluorine-free, and especially halogen-free, the substituent is preferably not a fluorine atom, and more preferably not a halogen atom.

^R2 independently represents an alkyl group having 3 to 9 carbon atoms, with ^R2 preferably having 3 to 8 carbon atoms, and more preferably having 4 to 8 carbon atoms.

As a compound having a structural unit of formula (1), for example, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fu, represented by formula (4) can be listed.

As a compound having a structural unit of formula (3), examples include: polyester polyols comprising at least one of the following dicarboxylic acids and at least one of the following diols.

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 may be used, or two or more may be used.

In addition, diols, for example, 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, 2-ethyl-2-butyl-1,3-propanediol, etc., and only one of these may be used, or two or more may be used.

As a dicarboxylic acid, preferred examples include phthalic acid, isophthalic acid, terephthalic acid, 3-methyl-benzene-1,2-dicarboxylic acid, and 4-methyl-benzene-1,2-dicarboxylic acid, with phthalic acid being more preferred.

In addition, preferred diols include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol, with 1,6-hexanediol and 3-methyl-1,5-pentanediol being more preferred.

As a polyester polyol having the structural unit of formula (3), it is preferable to use one with a number average molecular weight of 800 to 5000, more preferably 800 to 4000, and even more preferably 900 to 3500.

In addition, as a polyester polyol having the structural unit of formula (3), one polyester polyol can be used, or two or more can be combined.

There are no particular restrictions on the carboxyl-containing diols used as raw materials for component a, as long as they are compounds having one or more carboxyl groups and two hydroxyl groups in their molecules. Specific examples of carboxyl-containing diols include dihydroxymethylpropionic acid, 2,2-dihydroxymethylbutyric acid, and N,N-bis(hydroxyethyl)glycine. Among these, dihydroxymethylpropionic acid and 2,2-dihydroxymethylbutyric acid are preferred from the viewpoint of the solubility of component a in the synthesis reaction solvent. One of these carboxyl-containing diols may be used alone, or two or more may be used in combination.

Polyester polyols having the structural unit of formula (3) and polyols other than carboxyl diols, when using low molecular weight polyols, for example, one or more of the following can be used: 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol, neopentanediol, diethylene glycol, dipropylene glycol, glycerol, trihydroxymethylpropane, etc., with 1,6-hexanediol or 3-methyl-1,5-pentanediol being preferred.

There are no particular restrictions on the polyisocyanate compound used in the synthesis of component a, as long as it has two or more isocyanate groups. Specific examples of polyisocyanate compounds include: cyclic aliphatic polyisocyanates such as 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl)isocyanate, 1,3-bis(isocyanomethyl)cyclohexane, 1,4-bis(isocyanomethyl)cyclohexane, norbornene diisocyanate, and biuret forms of isophorone diisocyanate; 2,4-methylenephenyl diisocyanate, 2,6-methylenephenyl diisocyanate, and diphenylmethane-4,4'-di... Polyisocyanates with aromatic rings, such as isocyanates, 1,3-endoyldiisocyanates, and 1,4-endoyldiisocyanates; chain-like aliphatic polyisocyanates such as biuret forms of hexamethylene diisocyanates, lysine triisocyanates, lysine diisocyanates, hexamethylene diisocyanates, 2,4,4-trimethylhexamethylene diisocyanates, and 2,2,4-trimethylhexamethylene diisocyanates; and heterocyclic polyisocyanates such as isocyanurate forms of isophorone diisocyanates and isocyanurate forms of hexamethylene diisocyanates. These can be used alone or in combination with two or more.

In order to maintain high heat resistance or electrical insulation properties of the cured product of the present embodiment as described later, it is preferable to include 70 mol% or more of cyclic aliphatic polyisocyanate relative to the total amount of isocyanate (i.e., in component a, the organic residues derived from cyclic aliphatic polyisocyanate are 70 mol% or more relative to the total amount of organic residues derived from polyisocyanate), more preferably 80 mol% or more of cyclic aliphatic polyisocyanate, and even more preferably 90 mol% or more of cyclic aliphatic polyisocyanate.

Among these cyclic aliphatic polyisocyanates, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), 1,3-bis(isocyanomethyl)cyclohexane, 1,4-bis(isocyanomethyl)cyclohexane and norbornane diisocyanate are preferred, more preferably methylene bis(4-cyclohexyl isocyanate), isophorone diisocyanate and norbornane diisocyanate, and even more preferably methylene bis(4-cyclohexyl isocyanate).

Regarding the raw materials for component a, there are no particular restrictions as to whether a monohydroxyl compound is used as needed, provided that it has an alcoholic hydroxyl group in its molecule and does not have any substituents that are more reactive with the isocyanate group than the alcoholic hydroxyl group. Specific examples of monohydroxyl compounds include: methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, dibutanol, tert-butanol, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol monopropyl ether, methyl ethyl ketone oxime, etc.

These monohydroxy compounds may be used alone or in combination of two or more.

As a raw material for component a, the monoisocyanate compound used may include cyclohexyl isocyanate, octadecyl isocyanate, phenyl isocyanate, and toluene isocyanate, etc., as needed. Considering the color change resistance of the curing component involved in this embodiment when heated, cyclohexyl isocyanate and octadecyl isocyanate are preferred.

In order to maintain high electrical insulation properties and high heat resistance of the cured product involved in the present embodiment as described later, it is preferable that the polyol of the raw material contains an aromatic ring, and more preferably that only the polyol of the raw material contains an aromatic ring, while the polyisocyanate of the raw material does not contain an aromatic ring (that is, polyisocyanate with an aromatic ring is not used in the raw material). In the method for manufacturing component a, the proportions of each component are as follows.

When using a compound having a structural unit of formula (1), the amount of the compound having a structural unit of formula (1) used relative to the total amount of raw materials of component a is preferably 3% to 20% by mass, more preferably 5% to 15% by mass. When the amount of the compound having a structural unit of formula (1) used relative to the total amount of raw materials of component a is 3% to 20% by mass, a balance can be achieved between the low warping and the wire breakage suppression effect of the flexible wiring board covered by the outer coating of the present embodiment described later.

When using a polyester polyol having a structural unit of formula (3), the amount of polyester polyol having a structural unit of formula (3) used relative to the total amount of raw materials of component a is preferably 30% to 70% by mass, more preferably 35% to 70% by mass, and even more preferably 40% to 70% by mass. When the amount of polyester polyol having a structural unit of formula (3) used relative to the total amount of raw materials of component a is 30% to 70% by mass, the elastic modulus of the outer coating described later will not become too low, and the hardened film will not become too brittle, thus achieving a balanced outer coating.

The preferred solid content concentration for manufacturing component a is 10% to 90% by mass, more preferably 15% to 70% by mass, and even more preferably 20% to 60% by mass. Furthermore, when using a solution with a solid content concentration of 20% to 60% by mass to manufacture the hardenable composition described later in this embodiment, from the viewpoint of uniform dispersion, under the measurement conditions described in the embodiment, the solution viscosity of component a solution is preferably, for example, 5000 mPa·s to 1,000,000 mPa·s.

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

The molar ratio of the raw materials is adjusted based on the molecular weight and acid value of the target component a. The molecular weight of the target component a can also be adjusted by using a monohydroxyl compound. That is, after reaching (or approaching) the target number average molecular weight, a monohydroxyl compound can be added to block the terminal isocyanate groups and suppress further increases in the number average molecular weight.

When using monohydroxyl compounds, the following approach is acceptable: the number of isocyanate groups in the raw materials of component a can be less, equal to, or more than the total number of hydroxyl groups in the raw materials of component a, which is the sum of the polyol components other than the polyol components of the polyols of formula (3) and formula (4) with the polyols of formula (3).

In cases of excessive use of monohydroxy compounds, unreacted monohydroxy compounds may remain. In such cases, the excess monohydroxy compounds can be used directly as part of the solvent, or they can be removed by distillation or other methods.

In addition, in order to use monoisocyanate compounds as raw materials for component a, the number of isocyanate groups obtained by removing the number of isocyanate groups of monoisocyanate compounds from the number of isocyanate groups of all raw material components of component a (i.e., the total number of isocyanate groups of polyisocyanate compounds used in the raw materials of component a) needs to be less than the total number of isocyanate groups of all raw material components of component a, so that the end of the polyurethane in the manufacturing process before the monoisocyanate compound is used in the reaction becomes hydroxyl. The point at which the reaction between the alcoholic hydroxyl groups of all raw material components of component a and the isocyanate groups of the polyisocyanate compound used in component a is approximately completed. In order to allow the residual hydroxyl groups at the ends of the polyurethane in production to react with the monoisocyanate compound, the monoisocyanate compound is added dropwise to the solution of the carboxyl-containing polyurethane in production at 30°C to 150°C, preferably 70°C to 140°C, and then maintained at the same temperature until the reaction is complete.

The number-average molecular weight of component a obtained in the above manner is preferably 3,000 to 50,000, more preferably 5,000 to 50,000, and even more preferably 5,000 to 30,000. If the number-average molecular weight is within the above range, the fracture resistance, flexibility, and low warpage of the hardened film can be further improved. Furthermore, it can be expected that without compromising flexibility, elongation, and strength, component a will also have good solubility in the solvent (i.e., component b), and even if dissolved, the viscosity will not become excessively high, thereby further improving the physical properties. Therefore, it is suitable to use the curable composition involved in this embodiment to manufacture a flexible wiring board covered by the outer coating of the flexible wiring board of this embodiment, as described later.

The "number average molecular weight" mentioned here refers to the number average molecular weight of polystyrene determined by gel permeation chromatography (GPC). Furthermore, unless otherwise specified in this instruction manual, the GPC determination conditions are as follows: Apparatus: HPLC unit HSS-2000 manufactured by Nippon Spectroscopy Corporation Column: Shodex LF-804 column Mobile phase: Tetrahydrofuran Flow rate: 1.0 mL/min Detector: RI-2031Plus manufactured by Nippon Spectroscopy Corporation Temperature: 40.0°C Sample volume: 100 μL (sample loop) Sample concentration: Adjusted to approximately 0.1% by mass.

The acid value of component a is preferably between 10 mgKOH/g and 70 mgKOH/g, more preferably between 15 mgKOH/g and 50 mgKOH/g. When the acid value is between 10 mgKOH/g and 70 mgKOH/g, the reactivity with other components in the curing composition involved in this embodiment, such as compounds having two or more epoxy groups per molecule (i.e., component c), will not deteriorate. The heat resistance of the cured product of this embodiment will not decrease, and it will not become excessively hard or brittle. Furthermore, a balance can be easily achieved between the solvent resistance of the coating film and the flexibility of the circuit board and the warping of the flexible circuit board described in this embodiment. Moreover, in this specification, the acid value of component a is the value determined by potentiometric titration according to JIS K0070.

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

(Component b)

As one of the essential components of the hardening composition involved in this embodiment, the solvent (component b) is not particularly limited as long as it is a solvent capable of dissolving component a, but preferably a solvent having a boiling point of 150°C or higher and 250°C or lower at atmospheric pressure. With the intention of achieving a balance between the solubility of component a and the volatility of the solvent, it is possible and preferable to use two or more solvents 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 less than 200°C at atmospheric pressure and a solvent having a boiling point of 200°C or higher and 220°C or lower at atmospheric pressure are used together.

Examples of solvents that have a boiling point of 170°C or higher and less than 200°C at 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).

In addition, solvents with boiling points above 200°C and below 220°C at 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), γ-butyrolactone (boiling point 204°C), etc.

Because its high volatility endows it with low-temperature curing properties and allows for efficient and good production of component a in a homogeneous system, the preferred combination is the following: as a solvent having a boiling point of 170°C or higher and less than 200°C at atmospheric pressure, at least one of 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); and as a solvent having a boiling point of 200°C or higher and less than 220°C at atmospheric pressure, at least one of the group consisting of diethylene glycol monoethyl ether acetate (boiling point 217°C) and γ-butyrolactone (boiling point 204°C). The preferred combination is diethylene glycol diethyl ether (boiling point 189°C), which is a solvent with a boiling point of 170°C or higher and less than 200°C at atmospheric pressure, and diethylene glycol monoethyl ether acetate (boiling point 217°C) and γ-butyrolactone (boiling point 204°C), which are solvents with a boiling point of 200°C or higher and less than 220°C at atmospheric pressure.

If such a combination of solvents is used, it will have low hygroscopicity, high boiling point, and low volatility, making it an excellent solvent for screen printing inks.

To fully realize the above effects, the ratio of solvents with a boiling point of 170°C or higher and less than 200°C at atmospheric pressure to solvents with a boiling point of 200°C or higher and less than 220°C at atmospheric pressure is preferably in the range of 5:95 to 80:20 by mass, and more preferably in the range of 10:90 to 60:40.

In addition, as part of these preferred solvents, it is possible and preferable for the process to directly use the solvent used in the synthesis of the aforementioned component a as part of the solvent for the hardening composition involved in this embodiment.

Furthermore, within the range that does not impair the solubility of component a, it can be used in combination with solvents other than those with a boiling point of 170°C or higher and less than 200°C at atmospheric pressure and those with a boiling point of 200°C or higher and less than 220°C at atmospheric pressure. Reactive monomers or reactive diluents can also be used as solvents.

The total amount of components a, b, c and f (described later) that constitute the curable composition involved in this embodiment (except when component f is not present in the curable composition involved in this embodiment, the total amount of components a, b and c) is preferred to be 25% to 75% by mass, more preferably 35% to 70% by mass, and even more preferably 35% to 65% by mass. The total amount of components a, b, c (described later), and f (except when component f is not present in the curing composition involved in this embodiment) of the curing composition is as follows: if the content of component b is in the range of 25% to 75% by mass, the viscosity of the curing composition is good for printing using screen printing. Furthermore, the diffusion caused by the seepage of the curing composition after screen printing does not become quite large. As a result, the actual printing area of the curing composition is not too large compared to the area where the curing composition is to be coated (i.e., the shape of the printing plate).

(Component C)

Component c, which is an essential component of the curing composition involved in 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 curing composition involved in this embodiment.

Compounds having two or more epoxy groups in one molecule include, for example, phenolic varnish-type epoxy resins obtained by condensing or co-condensing phenolic resins such as phenol, cresol, xylenol, resorcinol, and catechol, and/or naphthols such as α-naphthol, β-naphthol, and dihydroxynaphthol with aldehyde-containing compounds such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, and salicylaldehyde under acidic catalysts. Phenolic varnish-type epoxy resins and o-cresol varnish-type epoxy resins are representative examples. Bisphenol A, bisphenol F, bisphenol S, and biphenols with alkyl substitution or non-substituted alkyl groups are also included. 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); diglycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; diglycidyl ester type epoxy resins of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; diglycidyl or methyl diglycidyl type epoxy resins of compounds formed by replacing the active hydrogen atom bonded to the nitrogen atom with a diglycidyl group, such as aniline, bis(4-aminophenyl)methane, and isocyanuric acid; p-amine Glyceryl or methyl glyceryl epoxy resins, including compounds formed by replacing the active hydrogen atom bonded to the nitrogen atom of aminophenols such as hydroxyl phenols and the active hydrogen atom of phenolic hydroxyl groups with glyceryl groups; vinylcyclohexene diester, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane, etc., alicyclic epoxy resins obtained by epoxidizing intramolecular olefin bonds; glyceryl ethers of p-xylene and/or m-xylene-modified phenolic resins; and glyceryl ethers of terpene-modified phenolic resins. Glyceryl ether; dicyclopentadiene-modified phenolic resin glyceryl ether; cyclopentadiene-modified phenolic resin glyceryl ether; polycyclic aromatic ring-modified phenolic resin glyceryl ether; naphthalene-containing phenolic resin glyceryl ether; halogenated phenolic varnish-type epoxy resin; hydroquinone-type epoxy resin; trihydroxyl Methylpropane-type epoxy resins; linear aliphatic epoxy resins obtained by oxidizing olefin bonds using peracetic acid or other peracids; diphenylmethane-type epoxy resins; epoxides of aralkyl-type phenolic resins such as phenol aralkyl resins and naphthol aralkyl resins; sulfur-containing epoxy resins; tricyclic [5.2.1.0] Diglycidyl ether of ^2,6 ]decanediethanol; 1,3-bis(1-dacryl)-4,6-bis(glycidyl)benzene, 1-[2',4'-bis(glycidyl)phenyl]dacrylane, 1,3-bis(4'-glycidyl)phenyl]dacrylane, and 1,3-bis[2',4'-bis(glycidyl)phenyl]dacrylane, etc., epoxy resins with a dacrylane structure. Among these, from the viewpoint of being fluorine-free, and especially halogen-free, component c is preferably free of fluorine atoms, and more preferably free of halogen atoms.

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

From the viewpoint of further improving the physical properties of the cured product of the present embodiment described below, among compounds having two or more epoxy groups in one molecule and having an aromatic ring structure and/or an alicyclic structure, the following compounds are preferred because they can provide a cured product with low water absorption: dicyclopentadiene-modified phenolic resin glycidyl ether (i.e., having a tricyclic [5.2.1.0 ^2,6]) . Compounds with a decane structure and an aromatic ring structure having two or more epoxy groups, 1,3-bis(1-dacryl)-4,6-bis(glycidyl)benzene, 1-[2',4'-bis(glycidyl)phenyl]dacrylane, 1,3-bis(4'-glycidylphenyl)dacrylane, and 1,3-bis[2',4'-bis(glycidyl)phenyl]dacrylane, etc., having a dacrylane structure (i.e., compounds with a tricyclic [3.3.1.1 ^3,7 ] Compounds having a tricyclic decane structure and an aromatic ring structure and having two or more epoxy groups, and preferably compounds of the following formula (5). (In the formula, l represents a natural number)

Furthermore, given the importance of 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, the following compounds having an amino group and an aromatic ring structure and having two or more epoxy groups are preferred: glycidyl or methyl glycidyl epoxy resins such as compounds in which active hydrogen bonds to nitrogen atoms of aniline, bis(4-aminophenyl)methane, etc. are replaced by glycidyl groups; glycidyl or methyl glycidyl epoxy resins such as compounds in which active hydrogen bonds to nitrogen atoms of aminophenols such as p-aminophenol and active hydrogen bonds to phenolic hydroxyl groups are replaced by glycidyl groups; and more preferably, compounds of the following formula (6) are preferred.

Component C can be used alone or in combination with two or more.

The amount of component c varies depending on the amount of functional groups in component a that contain carboxyl groups and can react with epoxy groups, as it is an essential component of the curable composition involved in this embodiment, relative to 100 parts by mass of component a. Therefore, it cannot be generalized.

However, the ratio of the number of functional groups containing carboxyl groups that can react with epoxy groups in component a to the number of epoxy groups in component c (a compound having two or more epoxy groups in one molecule) (functional groups that can react 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 the ratio is in the range of 1/3 to 2/1, when the curable component involved in this embodiment is cured, there is no situation where there is a large amount of unreacted component c remaining, and the functional groups containing carboxyl groups that can react with epoxy groups are also not left in large quantities. The functional groups containing carboxyl groups that can react with epoxy groups and the epoxy groups in component c (a compound having two or more epoxy groups in one molecule) can react in a good balance.

Furthermore, relative to the total amount of components a and c in the curing composition, the amount of component c in the curing composition involved in this embodiment is preferably from 1% to 60% by mass, more preferably from 2% to 50% by mass, and even more preferably from 3% to 40% by mass. If the amount of component c in the curing composition involved in this embodiment is in the range of 1% to 60% by mass relative to the total amount of components a and c in the curing composition, then the outer coating of this embodiment described later can achieve a balance between solvent resistance, low warpage of the flexible wiring board characterized by being covered by the outer coating, and the effect of preventing wire breakage.

(Component d)

Component d is a first defoamer containing olefins. Furthermore, in this specification, the term "olefin" includes olefins, olefin polymers, and compounds formed by chemical modification of these; the term "olefinic system" includes olefins themselves and mixtures containing olefins. Additionally, the term "olefin polymer" includes homopolymers and copolymers. Specific examples of component d include defoamers containing olefin polymers (e.g., olefin oligomers, olefin polymers, etc.). Component d can be a so-called olefinic defoamer or a commercially available product. Specific examples include: BYK-1791 (manufactured by BYK-Chemie Japan Co., Ltd.), FLOWLEN AC-2000HF (manufactured by Kyoei Chemical Co., Ltd.), FLOWLEN AC-2200HF (manufactured by Kyoei Chemical Co., Ltd.), DISPARLON P-465 (manufactured by Kusumoto Chemical Co., Ltd.), and DISPARLON P-466 (manufactured by Kusumoto Chemical Co., Ltd.).

When the curable composition involved in this embodiment is used as an insulating ink composition for wiring (i.e., a coating for wiring boards), an antifoaming agent may be used for purposes such as eliminating bubbles during printing (defoaming), suppressing the generation of bubbles (foam suppression), and removing bubbles from liquids (defoaming), and it is preferable to use an antifoaming agent.

In the hardening composition involved in this embodiment, at least component d is incorporated as a defoamer in the composition of components a, b and c. As a result, the hardened composition has superior physical properties compared with defoamers containing fluorine compounds, and can also maintain defoaming, foam suppression and defoaming effects.

(Component e)

The curing composition involved in this embodiment may include component e, and preferably includes component e. In the curing composition involved in this embodiment, the composition of components a, b, and c is combined with components d and e as defoamers, thereby expecting to further improve the above-mentioned effects.

Ingredient e is a second defoamer containing acrylic resins and/or methacrylic resins. Acrylic resins refer to resins with an acrylic skeleton, and methacrylic resins refer to resins with a methacrylic skeleton. Ingredient e can be any acrylic defoamer or methacrylic defoamer, or a commercially available product. Specific examples include: DAPPO SN-348 (manufactured by SAN NOPCO Co., Ltd.), DAPPO SN-354 (manufactured by SAN NOPCO Co., Ltd.), DAPPO SN-368 (manufactured by SAN NOPCO Co., Ltd.), DISPARLON 230HF (manufactured by Kusumoto Chemical Co., Ltd.), BYK-361 (manufactured by BYK-Chemie Japan Co., Ltd.), BYK-381 (manufactured by BYK-Chemie Japan Co., Ltd.), BYK-394 (manufactured by BYK-Chemie Japan Co., Ltd.), POLYFLOW 36 (manufactured by Kyoeisha Chemical Co., Ltd.), POLYFLOW 75 (manufactured by Kyoeisha Chemical Co., Ltd.), POLYFLOW 77 (manufactured by Kyoeisha Chemical Co., Ltd.), and other acrylic polymer defoamers. Furthermore, in the curing composition of this embodiment, component e alone can achieve a practical level of effectiveness as a defoamer. Moreover, the curing composition of this embodiment can also utilize components e and d together as defoamers to further enhance the effect to an even higher level. Even more significantly, the curing composition of this embodiment achieves sufficiently excellent results even when using only components e and d as defoamers.

(Other defoamers)

The hardening composition involved in this embodiment can achieve the desired effect even without defoamers other than components d and e mentioned above. However, if necessary, it may contain defoamers other than components d and e (third defoamer). Specific examples of this type of third defoamer include: BYK-333 (manufactured by BYK-Chemie Japan Co., Ltd.), BYK-342 (manufactured by BYK-Chemie Japan Co., Ltd.), SN DEFOAMER 470 (manufactured by SAN NOPCO Co., Ltd.), TSA750S (manufactured by Momentive Performance Materials Co., Ltd.), silicone oil SH-203 (manufactured by DuPont Toray Specialty Materials Co., Ltd.), and acetylene glycol defoamers such as SURFYNOL DF-110D (manufactured by Nissin Chemical Industry Co., Ltd.) and SURFYNOL DF-37 (manufactured by Nissin Chemical Industry Co., Ltd.). From the perspective of producing a fluorine-free curable composition that does not contain fluorine atoms, the curable composition involved in this embodiment is preferably free of fluorine-containing silicone-based defoamers. Furthermore, from the perspective of being silicone-free, the curable composition involved in this embodiment is preferably free of defoamers containing silicone or other silicone-based compounds (silicone-based defoamers).

Regarding the content of the defoamer, the total amount (d+e) of component d and component e in the hardened component involved in this embodiment is preferably 0.01% to 3% by mass. The lower limit of this content is more preferably 0.1% by mass or more, further preferably 0.3% by mass or more, further preferably 0.5% by mass or more, and even more preferably 0.6% by mass or more. In addition, the upper limit of this content is more preferably 2.5% by mass or less, further preferably 2.0% by mass or less, further preferably 1.5% by mass or less, and even more preferably 1.3% by mass or less.

Furthermore, regarding the content of the defoamer, when the total amount of the components remaining after removing the content of component b from the total amount of the hardening components involved in this embodiment is set to 100% by mass, the total amount of components d and e is preferably 0.01% to 5% by mass. This lower limit is more preferably 0.5% by mass or more, further preferably 1% by mass or more, even more preferably 1.5% by mass or more, even more preferably 1.7% by mass or more, and even more preferably 2% by mass or more. Furthermore, this upper limit is more preferably 4% by mass or less, even more preferably 3.5% by mass or less, and even more preferably 3% by mass or less.

The content of defoamer is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 4 parts by weight, and even more preferably 0.1 to 3 parts by weight, relative to the total amount of 100 parts by weight of ingredients a, b, c and f.

The ratio of component e (e/d) to component d is preferably 1% to 150% by mass. The lower limit is more preferably 3% by mass or more, further 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, further 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 setting the mixing ratio of component d to component e to the above-mentioned mass ratio, the balance between line breakage inhibition, low warpage, flexibility, and defoaming properties can be improved to a higher level.

(ingredient f)

The hardening composition involved in this embodiment may include the following component f, and preferably includes the following component f.

Component f is at least one microparticle selected from a group consisting of inorganic and organic microparticles.

Examples of inorganic microparticles include: silicon dioxide ( _SiO₂ ), aluminum oxide ( _Al₂O₃ ), titanium dioxide _{( TiO₂} ), tantalum oxide ( _Ta₂O₅ ), zirconium oxide ( _ZrO₂ ), silicon nitride ( _{Si₃N₄ )} , barium tantalum (BaO· _TiO₂ ), _barium carbonate ( _BaCO₃ ), lead tantalum (PbO·TiO₂), lead zirconium tantalum (PZT ₎ , lanthanum zirconium tantalum (PLZT), gallium oxide ( _Ga₂O₃ ), spinel (MgO· _Al₂O₃ ), mullite ( _3Al₂O₃ · _2SiO₂ ), and cordierite ₍ 2MgO· _{2Al₂O₃ · 5SiO₂ ) .} Talc (3MgO· _4SiO2 · _H2O ), aluminum titanium oxide ( _TiO2 - _Al2O3 ), zirconia oxide containing yttrium oxide ( _{Y2O3 -ZrO2 )} , barium silicate (BaO· _8SiO2 ), boron nitride ( _BN ), calcium carbonate ( _CaCO3 ), calcium sulfate ( _CaSO4 ), zinc oxide (ZnO), magnesium titanium oxide (MgO· _TiO2 ), barium sulfate ( _BaSO4 ), organic bentonite, carbon (C), hydrotalcite, etc.

As organic microparticles, microparticles of heat-resistant resins having amide bonds, amide bonds, ester bonds, or ether bonds are preferred. From the viewpoint of heat resistance and mechanical properties, polyimide resins or their precursors, polyamide-amide resins or their precursors, or polyimide resins are preferred examples of such resins.

Component f may be used alone or in combination with two or more of the above-mentioned components.

In these components, component f preferably comprises at least one selected from silica microparticles and hydrotalcite microparticles. That is, component f preferably comprises silica microparticles. In addition, component f preferably comprises hydrotalcite microparticles. Component f may also comprise both silica microparticles and hydrotalcite.

The silica microparticles used in the curable composition of this embodiment are defined as including microparticles that are powdered and physically coated or chemically surface-treated with organic compounds. There are no particular limitations on the silica microparticles used in the curable composition of this embodiment, as long as they are dispersed in the curable composition to form a paste; for example, Aerosil supplied by Aerosil Co., Ltd. of Japan can be cited. These silica microparticles, represented by Aerosil, are sometimes also used to impart printability during screen printing, in which case they are used for the purpose of imparting thixotropic properties.

The hydrotalcite microparticles used in _the hardening composition involved in this embodiment are a type of naturally occurring clay mineral, represented by _Mg6Al2 (OH) _16CO3 · _{4H2O ,} and are layered inorganic compounds. Alternatively, hydrotalcite can also be obtained, for example, by synthesizing Mg _{(1-x) Alx} (OH) ₂ ( _CO3 ) _x/2 · _mH2O . That is, hydrotalcite is a Mg/Al-based layered compound that can immobilize chloride ions ( ^Cl- ) and/or sulfate ions ( _SO4- ) anions through ion exchange ^with carbonate groups located in the interlayer. This feature can be used to capture chloride ions ( ^Cl- ) or sulfate ions ( _SO4- ) that cause copper or tin to migrate, thereby improving insulation reliability, ^and can be used for this purpose.

Commercially available hydrotalcite products include, for example, STABIACE HT-1, STABIACE HT-7, and STABIACE HT-P from Sakai Kagaku Co., Ltd., or DHT-4A, DHT-4A-2, and DHT-4C from Kyowa Chemical Industry Co., Ltd.

The average particle size of these inorganic and/or organic microparticles is preferably from 0.01 micrometers to 10 micrometers, and more preferably from 0.1 micrometers to 5 micrometers.

Furthermore, relative to the total amount of components a, b, c, and f, the amount of component f is preferably 0.1% to 60% by mass, more preferably 0.3% to 55% by mass, and even more preferably 0.5% to 40% by mass. If the amount of component f is in the range of 0.1% to 60% by mass relative to the total amount of components a, b, c, and f, the viscosity of the curing composition is good for printing using screen printing, and the diffusion caused by the seepage of the curing composition after screen printing does not become quite large. Therefore, as a result, the actual printing area of the curing composition will not become too large compared to the area where the curing composition is to be coated (i.e., the shape of the printing plate), which is appropriate.

(Hardening accelerator)

The curing composition involved in this embodiment may further include a curing accelerator, and preferably further includes a curing accelerator. As a curing accelerator, there are no particular limitations as long as it is a compound that promotes the reaction between the epoxy group of component c and the carboxyl group of component a. Examples of curing accelerators include: melamine, acetoguanidine, benzoguanidine, 2,4-diamino-6-methacryloxyethyl-triazine, 2,4-methacryloxyethyl-triazine, 2,4-diamino-6-vinyl-triazine, 2,4-diamino-6-vinyl-triazine, isocyanuric acid adducts, and other triazine compounds; imidazole, 2-methylimidazolium, 2-ethyl-4-methylimidazolium... azole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-aminoethyl-2-ethyl-4-methylimidazole, 1-aminoethyl-2-methylimidazole, 1-(cyanoethylaminoethyl)-2-methylimidazole, N-[2-(2-)-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-phenyl ... [-methyl-1-imidazolyl)ethyl]urea, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-methylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]- Ethyl-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-triazine, 1-dodecyl-2-methyl-3-benzylimidazolyl chloride, N,N'-bis(2-methyl-1-imidazolylethyl)urea, N,N'-bis(2-methyl-1-imidazolylethyl)urea (2,4-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-methylimidazolium-isocyanuric acid adduct, 2-phenylimidazolium-isocyanuric acid adduct, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-triazine-isocyanuric acid adduct, 2-methyl-4-methylimidazolium, 2-ethyl-4-methyl-5-methylimidazolium) 2-Phenylacetyl-4-methylmethylimidazolium, 1-benzyl-2-phenylimidazolium, 1,2-dimethylimidazolium, 1-(2-hydroxyethyl)imidazolium, vinylimidazolium, 1-methylimidazolium, 1-allylimidazolium, 2-ethylimidazolium, 2-butylimidazolium, 2-butyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-benzyl-2-phenylimidazolium bromide, 1-decyl... Dialkyl-2-methyl-3-benzylimidazolium chloride and other imidazole compounds; 1,5-diazabicyclo(4.3.0)nonene-5 and its salts, 1,8-diazabicyclo(5.4.0)undecene-7 and its salts and other diazabicycloalkenes and their derivatives; triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol and other compounds containing tertiary amino groups. Organic phosphine compounds such as triphenylphosphine, diphenyl(p-tolyl)phosphine, tri(alkylphenyl)phosphine, tri(alkoxyphenyl)phosphine, tri(alkyl-alkoxyphenyl)phosphine, tri(dialkylphenyl)phosphine, tri(trialkylphenyl)phosphine, tri(tetraalkylphenyl)phosphine, tri(dialkoxyphenyl)phosphine, tri(trialkoxyphenyl)phosphine, tri(tetraalkoxyphenyl)phosphine, trialkylphosphine, dialkylarylphosphine, alkyldiarylphosphine, etc.; dicyandiamine, etc.

These hardening accelerators can be used alone or in combination of two or more.

Among these curing accelerators, considering both the curing accelerator effect and the electrical insulation properties of the cured product of the present embodiment described later, the preferred curing accelerators are melamine, imidazole compounds, cycloamidine compounds and their derivatives, phosphine compounds and amine compounds, more preferably melamine, 1,5-diazabicyclo(4.3.0)nonene-5 and its salt, 1,8-diazabicyclo(5.4.0)undecene-7 and its salt.

There are no particular limitations on the amount of these curing accelerators as long as the curing accelerator effect is achieved. However, from the viewpoint of the curability of the curable composition involved in this embodiment and the electrical insulation properties or water resistance of the cured product of this embodiment (described later), it is preferable to formulate the curing accelerator in the range of 0.05 to 5 parts by mass relative to the total amount of 100 parts by mass of components a and c, and more preferably in the range of 0.1 to 3.0 parts by mass. If the formulation amount is in the range of 0.05 to 5 parts by mass, the curable composition involved in this embodiment can be cured in a short time, and the electrical insulation properties or water resistance of the cured product obtained by curing the composition of this embodiment (described later) are good.

(Other ingredients)

The curable composition involved in this embodiment can be cured to obtain a cured material with good electrical insulation properties, and therefore can be used, for example, as an insulating ink for wiring.

Furthermore, in the curing components involved in this embodiment, surfactants such as leveling agents, and conventional colorants such as phthalocyanine blue, phthalocyanine green, iodine green, diazo yellow, crystal violet, carbon black, and naphthalene black may be added as needed.

In addition, when it is necessary to inhibit the oxidative degradation of component a and the discoloration during heating, antioxidants such as phenolic antioxidants, phosphite antioxidants, and thioether antioxidants can be added, and it is preferable to add antioxidants such as phenolic antioxidants, phosphite antioxidants, and thioether antioxidants.

In addition, flame retardants or lubricants may be added as needed.

The hardening composition involved in this embodiment can be obtained by uniformly mixing one or all of the formulation components using a roller mill, bead mill, or the like. In the case where one part of the formulation components has been mixed, the remaining components can be mixed in during actual use.

(Viscosity of the hardening component involved in this embodiment)

The hardening composition involved in this embodiment is a composition with excellent processing properties, and can maintain the aforementioned properties such as line breakage inhibition, low warpage, flexibility, and defoaming at an excellent level. From this perspective, the viscosity of the hardening composition involved in this embodiment at 25°C is preferably set to be between 10,000 mPa·s and 100,000 mPa·s. Furthermore, the lower limit of the viscosity is more preferably 20,000 mPa·s or more, further preferably 23,000 mPa·s or more, and even more preferably 25,000 mPa·s or more. Additionally, the upper limit of the viscosity is more preferably 60,000 mPa·s or less, further preferably 50,000 mPa·s or less, and even more preferably 45,000 mPa·s or less. Furthermore, in this specification, the viscosity of the hardening composition involved in this embodiment at 25°C was measured using a tapered/plate viscometer (manufactured by Brookfield, model: DV-II+Pro, rotor model: CPE-52) at a speed of 10 rpm, after 7 minutes from the start of rotation.

(Thixotropic index of the hardening components involved in this embodiment)

Furthermore, when the curable composition involved in this embodiment is used as an insulating ink composition for wiring (i.e., a coating for wiring boards), in order to ensure good printability of the curable composition involved in this embodiment, it is desirable to set the thixotropic index of the composition within a certain range.

Furthermore, the "thixotropic index" described in this manual is defined as the ratio of the viscosity at 1 rpm at 25°C to the viscosity at 10 rpm at 25°C, as measured using a cone/plate viscometer (manufactured by Brookfield, model: DV-III+Pro, rotor model: CPE-52) (viscosity at 1 rpm / viscosity at 10 rpm).

When the curable composition of this embodiment is used as a top coat for wiring boards, in order to ensure good printability of the curable composition, the thixotropic index of the composition is preferably 1.1 or higher, 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 of this embodiment is used as a top coat for wiring boards, if the thixotropic index of the curable composition is 1.1 to 3.0, after printing the curable composition, the composition can form a certain film thickness, maintain the printed pattern, and the defoaming properties of the printed film of the composition also become good.

<Coatings for Hardened and Flexible Wiring Boards>

The aforementioned curable composition can be hardened and used appropriately in the form of a hardened product. That is, the hardened product involved in this embodiment is a hardened product obtained by hardening the aforementioned curable composition.

Furthermore, the hardened material can be suitable for use as an outer coating for flexible wiring boards, etc. That is, the outer coating for flexible wiring boards involved in this embodiment is an outer coating for flexible wiring boards containing the aforementioned hardened material.

The cured material and the outer coating of this embodiment can be obtained, for example, by heating the curable component involved in this embodiment and causing it to undergo a curing reaction. There are no particular limitations on the method used to obtain the cured material of this embodiment in the form of a cured film; for example, the cured film or outer coating can be obtained by the following steps. (Step 1) A step of obtaining a printed film by printing the curable component involved in this embodiment onto a substrate, etc. (Step 2) A step of obtaining a cured film or an outer coating by thermally curing the printed film obtained in Step 1, or by placing the printed film obtained in Step 1 in an environment of 40°C to 100°C to evaporate part or all of the solvent in the printed film, resulting in a printed film after removing part or all of the solvent, at an environment of 100°C to 170°C.

There are no particular limitations on the printing method of the curable component involved in the first step of this embodiment. For example, the curable component can be coated onto a substrate or the like by screen printing, roller coating, spraying, or curtain coating to obtain a printed film.

The solvent evaporation step in the second step is optional and can be performed immediately after the first step, with the hardening reaction and solvent removal occurring simultaneously. In the second step, when solvent evaporation is carried out before heat hardening, considering the evaporation rate of the solvent and the rapid transition to the heat hardening step, the temperature is typically 40°C to 100°C, preferably 60°C to 100°C, and more preferably 70°C to 90°C. There is no particular limitation on the solvent evaporation time in the second step, but it is preferably 10 minutes to 120 minutes, and more preferably 20 minutes to 100 minutes.

The heat curing temperature 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 heat curing time 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.

<Flexible wiring board and its manufacturing method>

The flexible wiring board of this embodiment and its manufacturing method are described. The curable component involved in this embodiment can be used, for example, as an insulating ink for wiring, and the cured material of this embodiment can be used as an insulating protective film. In particular, for example, it can be used as an insulating resist for wiring by coating all or part of the wiring of a flexible wiring board such as a flip-chip film.

In this embodiment of the flexible wiring board, a portion or all of the surface of the flexible wiring board on which the wiring is formed is covered by a cured material of this embodiment (e.g., the aforementioned outer coating film for flexible wiring boards). Furthermore, considering the oxidation resistance and economic aspects of the wiring, the wiring covered by the cured material of this embodiment is preferably tin-copper wiring.

The manufacturing method described in this embodiment is a method for manufacturing a flexible wiring board covered with a protective film. Its characteristic feature is that: a curable component of the present embodiment is printed onto at least a portion of the wiring pattern of the flexible wiring board, thereby forming a printed film on the pattern; and the printed film is heat-cured at 100°C to 170°C, thereby forming a protective film. For example, the protective film of the flexible wiring board can be formed by the following steps A to C. (Step A) The step of printing the curable component of the present embodiment onto at least a portion of the wiring pattern of the flexible wiring board, thereby forming a printed film on the pattern. (Step B) Place the printed film obtained in Step A at an environment of 40°C to 100°C to allow some or all of the solvent in the printed film to evaporate. (Step C) Heat the printed film obtained in Step A or Step B at 100°C to 170°C to harden it and form a protective film for the flexible wiring board.

This embodiment is preferably a method for manufacturing a flexible wiring board coated with an outer coating, comprising: (Step A) printing the curable composition involved in this embodiment onto a portion or all of the surface of the flexible wiring board on which the wiring is formed, thereby forming a printed film on the wiring; (Step B) placing the printed film obtained in Step A in an environment of 40°C to 100°C, thereby causing a portion or the total amount of the solvent in the printed film to evaporate; and (Step C) heating the printed film obtained in Step A or the printed film obtained in Step B at 100°C to 170°C, thereby curing it to form an outer coating.

The solvent evaporation operation in step B is optional and can be performed immediately after step A, with the hardening reaction and solvent removal occurring simultaneously. In step B, when solvent evaporation is performed before heat hardening, considering the evaporation rate and rapid migration to the heat hardening step, the temperature is typically 40°C to 100°C, preferably 60°C to 100°C, and even more preferably 70°C to 90°C. The solvent evaporation time in step B is not particularly limited, but is preferably 10 minutes to 120 minutes, and even more preferably 20 minutes to 100 minutes.

From the viewpoints of preventing the diffusion of the coating and obtaining suitable low warpage, flexibility, and softness as a protective film, the heat curing conditions performed in step C are in the range of 100°C to 170°C. The heat curing temperature is preferably 105°C to 160°C, more preferably 110°C to 150°C. There is no particular limitation on the heat curing time in step C, but it is preferably 10 minutes to 150 minutes, more preferably 15 minutes to 120 minutes.

As explained above, the curable composition of this embodiment exhibits excellent wire breakage suppression, low warpage, and flexibility when used to create a cured product. Therefore, when the curable composition of this embodiment is coated onto a flexible substrate such as a flexible wiring board or polyimide film, and a cured product (protective film) is subsequently created through a curing reaction, the flexible wiring board or flexible substrate with the protective film exhibits less warpage. This allows for easier alignment during the IC (integrated circuit) chip mounting process. Therefore, the curable composition of this embodiment is suitable for forming an outer coating for flexible wiring boards.

Furthermore, the curable composition involved in this embodiment can be expected to have good treatability. Furthermore, when manufacturing the cured material, good adhesion to the substrate, flexibility, and moisture resistance can be expected, and good long-term electrical insulation reliability can also be expected.

Furthermore, the cured product of this embodiment possesses at least excellent wire breakage suppression properties and is also expected to have good flexibility, which contributes to this characteristic. Therefore, it is suitable to provide a flexible wiring board with an electrically insulating protective film that is less prone to cracking (e.g., flexible printed circuit boards such as COF (Chip On Film)). [Example]

The invention will be further illustrated below with examples, but the invention is not limited to the following examples.

<Determination of Acid Value> The solvent in the polyurethane solution used in this embodiment was removed by depressurization under heating to obtain component a. Using component a obtained by the above method, the acid value was determined according to the potentiometric titration method of JIS K0070. The apparatus used in the potentiometric titration method is described below. Apparatus Name: Kyoto Electronics Industry Co., Ltd. Automatic Potential Difference Titration Apparatus AT-510 Electrode: Kyoto Electronics Industry Co., Ltd. Composite Glass Electrode C-173

<Determination of the Number Average Molecular Weight of Component A> The number average molecular weight is the molecular weight converted from that of polystyrene determined by GPC. The GPC determination conditions are as follows: Apparatus: HPLC unit HSS-2000 manufactured by Nippon Spectroscopy Corporation Column: Shodex LF-804 column Mobile phase: Tetrahydrofuran Flow rate: 1.0 mL/min Detector: RI-2031Plus manufactured by Nippon Spectroscopy Corporation Temperature: 40.0°C Sample volume: 100 μL sample loop Sample concentration: Adjusted to approximately 0.1% by mass

<Determination of the viscosity of a solution containing component a>

The viscosity of a polyurethane solution was determined using the following method. Approximately 0.8 grams of polyurethane solution was used, and a tapered/plate viscometer (Brookfield Instruments, Model: DV-II+Pro, Rotor Model: CPE-52) was employed at 25.0°C and 5 rpm to measure the viscosity after 7 minutes from the start of the measurement.

<Determination of viscosity of hardening components>

The viscosity of the curing composition was determined using the following method. Approximately 0.6 grams of the curing composition was used, and the viscosity was measured 7 minutes after measurement using a tapered/plate viscometer (Brookfield Instruments, Model: DV-II+Pro, Rotor Model: CPE-52) at 25.0°C and 10 rpm.

Synthesis of Polyester Polyols

(Refer to Synthesis Example 1) In a reaction vessel including a stirring device, a thermometer, and a condenser equipped with a distillation device, 983.5 g (6.74 moles) of phthalic anhydride and 879.2 g (7.44 moles) of 1,6-hexanediol were added. 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 to stir, 1.74 g of mono-n-butyltin oxide was added to slowly raise the internal temperature of the reaction vessel. A vacuum pump was connected, and the pressure inside the reaction vessel was gradually reduced. Water was removed from the reaction vessel by depressurized distillation. Finally, the internal temperature was raised to 220°C, and the pressure was reduced to 133.32 Pa. After 15 hours, to confirm that no more water could be removed by distillation, the reaction was terminated. The hydroxyl value of the obtained polyester polyol (hereinafter referred to as polyester diol (α)) was determined to be 53.1 mg-KOH/g.

<Synthesis of Polyurethane>

(Implementation Example 1)

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

The temperature of the reaction solution was lowered to 90°C, and 28.31 grams of methylene bis(4-cyclohexyl isocyanate) (manufactured by Sumitomo 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. After confirming that the absorption of the C=O stretching vibration originating from the isocyanate group was almost undetectable by IR, 1.5 g of ethanol (manufactured by Wako Junya Pharmaceutical Co., Ltd.) and 24.3 g of diethylene glycol diethyl ether (manufactured by Nippon Emulsifier Co., Ltd.) were added dropwise. The reaction was further carried out at 80°C for 3 hours to obtain a solution containing polyurethane with a carboxyl group and an aromatic ring concentration of 3.1 mmol/g (hereinafter referred to as "polyurethane solution A1").

The viscosity of the obtained polyurethane solution A1 is 120,000 mPa·s. In addition, the average molecular weight of the polyurethane (hereinafter referred to as "polyurethane AU1") containing carboxyl groups and aromatic ring concentration of 3.1 mmol/g contained in polyurethane solution A1 is 20,000, and the acid value of polyurethane AU1 is 25.0 mg-KOH/g.

In addition, the solid content concentration in polyurethane solution A1 is 40.0% by mass.

(Implementation Example 2)

In a reaction vessel including a stirring device, a thermometer, and a condenser, 21.0 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]furan (manufactured by Gas Chemicals Co., Ltd., Osaka, trade name: BPEF), 66.7 g of the above-mentioned polyester diol (α) (a polyester polyol containing phthalic acid/1,6-hexanediol), 3.00 g of 2,2-dihydroxymethylpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a carboxyl-containing diol, and 83.24 g of γ-butyrolactone as a solvent were added, and the mixture was heated to 100°C to dissolve all the raw materials.

The temperature of the reaction solution was lowered to 90°C, and the following solution was added dropwise over 20 minutes using a dropping funnel: a solution of 26.50 g of diphenylmethane-4,4'-diisocyanate (manufactured by Tosoh Corporation, trade name: Millionate MT) dissolved in 60.0 g of γ-butyrolactone. The reaction was carried out at 125°C to 130°C for 8 hours. After confirming that the absorption of C=O stretching vibrations originating from isocyanate groups was almost undetectable by IR, 1.5 g of ethanol (manufactured by Wako Junya Pharmaceutical Co., Ltd.), 6.19 g of γ-butyrolactone and 26.37 g of diethylene glycol diethyl ether (manufactured by Nippon Emulsifier Co., Ltd.) were added dropwise. The reaction was further carried out at 80°C for 3 hours to obtain a solution containing polyurethane with a carboxyl group and an aromatic ring concentration of 5.6 mmol/g (hereinafter referred to as "polyurethane solution A2").

The viscosity of the obtained polyurethane solution A2 is 120,000 mPa·s. In addition, the average molecular weight of the polyurethane (hereinafter referred to as "polyurethane AU2") containing carboxyl groups and aromatic ring concentration of 5.6 mmol/g contained in polyurethane solution A2 is 20,000, and the acid value of polyurethane AU2 is 10.6 mg-KOH/g.

In addition, the solid content concentration in polyurethane solution A2 is 40.0% by mass.

(Implementation Example 3)

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

The temperature of the reaction solution was lowered to 90°C, and 26.80 grams of methylene bis(4-cyclohexyl isocyanate) (manufactured by Sumitomo 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 10 hours. After confirming that the absorption of C=O stretching vibrations originating from isocyanate groups was almost undetectable by IR, 1.5 g of ethanol (manufactured by Wako Pure Pharmaceutical Co., Ltd.), 5.89 g of γ-butyrolactone and 25.10 g of diethylene glycol diethyl ether (manufactured by Nippon Emulsifier Co., Ltd.) were added dropwise. The reaction was further carried out at 80°C for 3 hours to obtain a solution containing polyurethane with carboxyl groups and an aromatic ring concentration of 0.4 mmol/g (hereinafter referred to as "polyurethane solution A3").

The viscosity of the obtained polyurethane solution A3 is 120,000 mPa·s. In addition, the average molecular weight of the polyurethane (hereinafter referred to as "polyurethane AU3") containing carboxyl groups and aromatic ring concentration of 0.4 mmol/g contained in polyurethane solution A3 is 20,000, and the acid value of polyurethane AU3 is 25.0 mg-KOH/g.

In addition, the solid content concentration in polyurethane solution A3 is 40.0% by mass.

(Comparative synthesis example 1)

248.0 grams of C-1090 (manufactured by Kuraray Co., Ltd., a polycarbonate diol using 1,6-hexanediol and 3-methyl-1,5-pentanediol as raw materials, hydroxyl price 122.22) as a polycarbonate polyol was added to a reaction vessel including a stirring device, thermometer, and condenser. 47.5 g of 2,2-dihydroxymethylbutyric acid (manufactured by Nippon Chemical Co., Ltd.) as a carboxyl-containing diol, 2.7 g of trihydroxymethylethane (manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a (poly)carbonate polyol and a polyol other than a carboxyl-containing diol, 467.5 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) as a solvent, and 82.5 g of diethylene glycol diethyl ether (manufactured by Nippon Emulsifier Co., Ltd.) were heated to 100°C to dissolve all the raw materials.

The temperature of the reaction solution was lowered to 90°C, and 150.4 grams of methylene bis(4-cyclohexyl isocyanate) (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name: Desmodur-W) as a diisocyanate compound was added dropwise over 30 minutes using a dropping funnel.

The reaction was carried out at 120°C for 8 hours, and absorption from the C=O stretching vibration of the isocyanate group was almost undetectable by IR. Subsequently, 1.5 g of ethanol (manufactured by Wako Pure Pharmaceutical Co., Ltd.) was added dropwise to the reaction solution, and the reaction was further carried out at 80°C for 3 hours to obtain a polyurethane solution with carboxyl and carbonate bonds (hereinafter referred to as "polyurethane solution B1").

The viscosity of the obtained polyurethane solution B1 is 145,000 mPa·s. The 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 is 14,000, and the acid value of polyurethane BU1 is 40.0 mg-KOH/g. In addition, the solid content of polyurethane solution B1 is 45.0% by mass.

(Comparative synthesis example 2)

611.0 g of bis[4-(2-hydroxyethoxy)phenyl]methane, 297.3 g of dimethyl isophthalate, and 0.5 g of dioctyl tin oxide were charged into a 1-liter three-necked flask equipped with a distillation apparatus. The mixture was heated at 180°C under a nitrogen atmosphere, and the generated methanol was distilled off. When approximately 50 g of methanol had distilled off, the reaction system was depressurized to 1.3 kPa to accelerate the methanol distillation rate. After the theoretical amount of methanol had distilled off, the mixture was further heated for 1 hour at 185°C–0.13 kPa. The reactor was then cooled to obtain 810 g of polyester polyol (hereinafter referred to as polyester diol (β)). The hydroxyl value of the obtained polyester diol (β) was determined, and the result was 55.4 mg-KOH/g.

In a reaction vessel including a stirring device, a thermometer, and a condenser, 11.0 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]furan (manufactured by Gas Chemicals Co., Ltd., Osaka, trade name: BPEF), 61.52 g of polyester glycol (β), 6.32 g of 2,2-dihydroxymethylpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) as a carboxyl-containing diol, and 135.6 g of γ-butyrolactone as a solvent were added, and the mixture was heated to 100°C to dissolve all the raw materials.

The temperature of the reaction solution was lowered to 90°C, and 27.00 grams of diphenylmethane-4,4'-diisocyanate (manufactured by Sumitomo Bayer Urethane Co., Ltd., trade name: MDI) as a polyisocyanate compound 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 that the absorption of the C=O stretching vibration originating from the isocyanate group was almost undetectable by IR, 1.5 g of ethanol (manufactured by Wako Junya Pharmaceutical Co., Ltd.) and 23.9 g of diethylene glycol diethyl ether (manufactured by Nippon Emulsifier Co., Ltd.) were added dropwise. The reaction was further carried out at 80°C for 3 hours to obtain a solution containing polyurethane with a carboxyl group and an aromatic ring concentration of 6.9 mmol/g (hereinafter referred to as "polyurethane solution B2").

The viscosity of the obtained polyurethane solution B2 is 125,000 mPa·s. In addition, the average molecular weight of the polyurethane (hereinafter referred to as "polyurethane BU2") containing carboxyl groups and aromatic ring concentration of 6.9 mmol/g contained in polyurethane solution B2 is 20,000, and the acid value of polyurethane BU2 is 25.0 mg-KOH/g.

In addition, the solid content concentration in polyurethane solution B2 is 40.0% by mass.

Furthermore, the properties of polyurethane AU1 to polyurethane AU3 and polyurethane BU1 to polyurethane BU2 are described in Table 1.

[Table 1] polyurethane AU1 AU2 AU3 BU1 BU2 Number average molecular weight 20000 20000 20000 14000 20000 acid value mg-KOH/g 25.0 10.6 25.0 40.0 25.0 Aromatic concentration m-mol/g 3.1 5.6 0.4 0 6.9

<Manufacturing of the Main Ingredient>

(Example 1 of implementation)

160.0 parts by weight of polyurethane solution A1, 6.3 parts by weight of silica powder (manufactured by Aerosil Co., Ltd., Japan, trade name: Aerosil R-974), 0.72 parts by weight of melamine (manufactured by Nissan Chemical Industries, Ltd.) as a curing accelerator, and 8.4 parts by weight of diethylene glycol diethyl ether were mixed using a three-roll mill (manufactured by Inoue Seisakusho Co., Ltd., model: S-4 3/4×11) to mix the silica powder and curing accelerator into polyurethane solution A1. Then, 2.0 parts by weight of defoamer (olefinic defoamer containing polyolefins, manufactured by BYK-Chemie Japan Co., Ltd., trade name: BYK-1791) was added, and the mixture was mixed using a scraper. This compound is used as the main compound C1.

(Implementation Example 2)

160.0 parts by weight of polyurethane solution A1, 6.3 parts by weight of silica powder (manufactured by Aerosil Co., Ltd., Japan, trade name: Aerosil R-974), 1.0 parts by weight of hydrotalcite (manufactured by Kyowa Chemical Co., Ltd., trade name: DHT-4A), 0.72 parts by weight of melamine (manufactured by Nissan Chemical Co., 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 (manufactured by Inoue Seisakusho Co., Ltd., model: S-4 3/4×11). Next, add 2.0 parts by weight of defoamer (an olefinic defoamer containing polyolefins, manufactured by BYK-Chemie Japan Co., Ltd., trade name: BYK-1791), and mix using a spatula. Use this mixture as the main agent, formulation C2.

(Implementation examples 3 to 7)

The formulation was prepared according to the formulation composition shown in Table 2, using the same method as in Example 1. The formulations prepared in Examples 3 to 7 were respectively used as main agent formulations C3 to C7. Furthermore, the values in the table represent "parts by mass". In addition, "Disparlon 230HF" is an acrylic defoamer containing acrylic resin, and "TSA750S" is a silicone defoamer containing silicone resin.

(Compare with example 1)

140.0 parts by weight of polyurethane solution B1, 5.5 parts by weight of silica powder (manufactured by Aerosil Co., Ltd., Japan, trade name: Aerosil R-974), 0.72 parts by weight of melamine (manufactured by 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 (manufactured by Inoue Seisakusho Co., Ltd., model: S-4 3/4×11). Subsequently, 2.0 parts by weight of defoamer (olefinic defoamer containing polyolefins, manufactured by BYK-Chemie Japan Co., Ltd., trade name: BYK-1791) were added, and the mixture was mixed using a scraper. Use this compound as the main compound D1.

(Compare with Example 2)

The formulation was prepared according to the formulation shown in Table 2, using the same method as in Formulation Example 1. The formulation prepared in Comparative Formulation Example 2 is used as the main formulation D2. Furthermore, the values in the table represent "parts by mass".

(Compare and adjust Example 3)

The formulation was prepared according to the formulation shown in Table 2 using the same method as in Formulation Example 1. The formulation prepared in Comparative Formulation Example 3 was used as the main formulation D3. Furthermore, the values in the table represent "parts by mass".

[Table 2] Example 1 of implementation of allocation Implementation of Allocation Example 2 Implementation of Allocation Example 3 Implementation of Allocation Example 4 Implementation of allocation example 5 Implementation of Allocation Example 6 Implementation of allocation example 7 Comparative Allocation Example 1 Comparative Allocation Example 2 Comparative Distribution Example 3 Main formulation C1 Main ingredient C2 Main ingredient C3 Main ingredient C4 Main ingredient C5 Main ingredient C6 Main ingredient C7 Main formulation D1 Main formulation D2 Main formulation D3 Polyurethane solution A1 160.0 160.0 160.0 160.0 160.0 160 Polyurethane solution A2 160.0 Polyurethane solution A3 160.0 Polyurethane solution B1 140.0 Polyurethane solution B2 140.0 Aerosil R-974 silicon dioxide powder 6.3 6.3 6.3 9.45 6.3 6.3 6.3 5.5 6.3 6.3 Hydrotalcite DHT-4A 1.0 Diethylene glycol diethyl ether 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 melamine, a hardening accelerator 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 Defoamer BYK-1791 2.0 2.0 2.0 2.0 2.0 0.4 0.4 2.0 2.0 Defoamer Disparlon 230HF 0.2 0.4 0.2 Silicone defoamer TSA750S 2.0

<Preparation of Hardener Solution>

(Example 1 of preparing hardener solution)

Add 16.85 parts by weight of epoxy resin (manufactured by Mitsubishi Chemical Corporation, grade name: jER (registered trademark) 604, epoxy equivalent 120 g/eqv (grams/equivalent)) having the structure of the following formula (6) and 18.25 parts by weight of diethylene glycol diethyl ether to a container including a mixer, thermometer and condenser, and start stirring.

While stirring, heat the container to 40°C using an oil bath. After reaching 40°C, continue stirring for 30 minutes. Then, confirm that jER (registered trademark) 604 is completely dissolved, cool to room temperature, and obtain a solution containing 48% by mass of jER (registered trademark) 604. This solution will be used as curing agent solution E1.

(Example 2 of hardener solution preparation)

Add 16.85 parts by weight of epoxy resin (manufactured by Mitsubishi Chemical Corporation, grade name: jER (registered trademark) 630, epoxy equivalent 98 g/eqv) with N,N-diglycidyl-4-(glycidyloxy)aniline as the main component and 18.25 parts by weight of diethylene glycol diethyl ether to a container including a mixer, thermometer and condenser, and start stirring.

While stirring, heat the container to 40°C using an oil bath. After reaching 40°C, continue stirring for 30 minutes. Then, confirm that jER (registered trademark) 630 is completely dissolved, cool to room temperature, and obtain a solution containing 48% by mass of jER (registered trademark) 630. This solution will be used as hardener solution E2.

<Mixture of solutions containing main formulation and hardener>

(Example 1 of formulation of hardening components)

88.7 parts by weight of the main agent formulation C1 and 3.5 parts by weight of the curing agent solution E1 were placed in a plastic container. Further, to ensure the viscosity was consistent with the curing compositions of the other formulations and comparative formulations described later, 3.0 parts by weight of diethylene glycol diethyl ether and 1.5 parts by weight of diethylene glycol monoethyl ether acetate were added as solvents. The mixture was stirred with a spatula at room temperature for 5 minutes to obtain the curing composition (hereinafter referred to as "curing composition F1").

(Formulation Examples 2 to 8 of Hardening Components)

The formulation was prepared according to the formulation shown in Table 3 using the same method as in Formulation Example 1 of the curing composition. The formulations prepared in Formulation Examples 2 to 8 of the curing compositions were respectively designated as curing compositions F2 to F8.

(Comparative formulation example 1 of hardening components)

78.6 parts by weight of the main agent formulation D1 and 5.6 parts by weight of the hardener solution E1 were placed into a plastic container. Further, to ensure the viscosity was consistent with the hardening components of other formulations and comparative formulations, 4.8 parts by weight of diethylene glycol diethyl ether and 1.3 parts by weight of diethylene glycol monoethyl ether acetate were added as solvents. The mixture was stirred for 5 minutes at room temperature using a spatula to obtain the hardening component (hereinafter referred to as "hardening component G1").

(Comparative formulation example 2 of hardening components)

By using the same method as in the “Comparative Formulation Example 1 of Hardening Components” above, a hardening component (hereinafter referred to as “hardening component G2”) was prepared according to the formulation shown in Table 3.

(Comparative formulation example 3 of hardening components)

By using the same method as in “Comparative Formulation Example 1 of Hardening Components” above, a hardening component (hereinafter referred to as “hardening component G3”) was prepared according to the formulation shown in Table 3.

The formulations of each main component of curing components F1 to F8 and G1 to G3, and their blending with the polyurethane solution are described in Table 3. Furthermore, the formulations of each component of curing components F1 to F8 and G1 to G3 are summarized and described in Table 4.

• In Table 4, "a/(a+c)" represents the content (mass %) of component a relative to the total amount of components a and 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 components d and e in the curing composition. • In Table 4, "(d+e)/(total amount of composition - b)" represents the total amount of components d and e when the total amount of components after removing the content of component b from the total amount of the curing composition is set to 100 parts by mass. • In Table 4, "e/d" represents the content ratio (mass %) of component e relative to component d.

[Table 3] unit Hardening component F1 Hardening component F2 Hardening component F3 Hardening component F4 Hardening component F5 Hardening component F6 Hardening component F7 Hardening component F8 Hardening component G1 Hardening component G2 Hardening component G3 Main formulation C1 mass 88.7 Main ingredient C2 89.2 Main ingredient C3 88.7 Main ingredient C4 90.3 Main ingredient C5 88.7 Main ingredient C6 88.7 Main ingredient C7 88.7 Polyurethane solution A1 100 Main formulation D1 78.6 Main formulation D2 88.7 Main formulation D3 88.7 Hardener solution E1 3.5 3.5 4.5 3.5 3.5 3.5 3.5 5.6 3.5 3.5 Hardener solution E2 1.2 Diethylene glycol diethyl ether 3.0 3.0 2.5 2.5 5.5 3.0 3.0 3.0 4.8 3.0 3.0 Diethylene glycol monoethyl ether acetate 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.3 1.5 1.5 1,5-Diazabiscyclic (4.3.0)nonene-5 0.25 Defoamer BYK-1791 1.0

[Table 4] Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Implementation Example 5 Implementation Example 6 Implementation Example 7 Implementation Example 8 Comparative example 1 Comparative example 2 Comparative example 3 unit Hardening component F1 Hardening component F2 Hardening component F3 Hardening component F4 Hardening component F5 Hardening component F6 Hardening component F7 Hardening component F8 Hardening component G1 Hardening component G2 Hardening component G3 Ingredients (a) Polyurethane AU1 mass 32.1 32.1 40.1 32.1 32.1 32.1 32.1 Polyurethane AU2 32.2 Polyurethane AU3 32.1 Polyurethanes other than component (a) Polyurethane BU1 31.6 Polyurethane BU2 32.1 Component (b) γ-Butyrolactone 40.7 40.7 50.9 40.6 40.7 40.7 40.7 40.7 32.9 40.7 40.7 Diethylene glycol diethyl ether 16.2 16.2 13.1 14.5 18.7 16.2 16.2 16.2 17.7 16.2 16.2 Diethylene glycol monoethyl ether acetate 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.3 1.5 Ingredient (c) jER604 1.69 1.69 2.14 1.69 1.69 1.69 1.69 2.7 1.69 1.69 jER630 0.58 Component (d) BYK-1791 1.0 1.0 1.0 1.0 1.0 1.0 0.2 0.2 1.0 1.0 Component (e) Disparlon 230HF 0.1 0.2 0.1 Defoamers other than ingredient (d) and ingredient (e) TSA750S 1.0 Ingredients(f) Aerosil R-974 3.15 3.15 2.31 3.15 4.73 3.15 3.15 3.15 2.76 3.15 3.15 Hydrotalcite DHT-4A 0.5 Hardened catalyst melamine 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 0.36 1,5-Diazabiscyclic (4.3.0)nonene-5 0.25 a / (a + c) Quality % 95.00 95.00 94.93 98.23 95.00 95.00 95.00 95.00 - - - b / (a + b + c) 63.35 63.35 60.24 63.33 64.32 63.35 63.35 63.35 - - - (d+e) 1.03 1.02 0.91 1.07 0.99 1.14 0.42 0.31 - - - (d+e)/(total quantity of components - b) 2.61 2.58 2.18 2.68 2.57 2.86 1.06 0.80 - - - e/d 0.00 0.00 0.00 0.00 0.00 10.00 100.00 50.00 - - -

(Examples 1 to 8, Comparative Examples 1 to 3)

Using curing components F1 to F8 and curing components G1 to G3, the resistance to thread breakage, warping, flexibility, and defoaming time were evaluated by the methods described below. The results are recorded in Table 5.

<Evaluation of the interruption suppression capability of wiring in a patch panel (MIT test)>

A flexible wiring board is obtained by applying a hardening composition F1 to a flexible wiring board by means of a 5-micron thick (after drying) printed film from the wiring surface: a substrate (copper wiring width/copper wiring spacing = 15 microns/15 microns) with a fine comb pattern shape as described in JPCA-ET01, which is manufactured by etching a flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Sperflex US, copper thickness: 8 microns, polyimide thickness: 38 microns) and performing tin plating on it. The obtained printed film is formed into a wiring board and placed in an 80°C hot air circulating dryer for 30 minutes, and then placed in a 120°C hot air circulating dryer for 120 minutes to harden the printed film.

Using this test piece, the test was conducted under the following conditions according to the method described in JIS C-5016. (Test Conditions) Testing Machine: Tester (MIT) BE202 Tester, manufactured by Tester Industrial Co., Ltd. Bending Speed: 10 times/minute Load: 200 grams Bending Angle: ±90° Relative Diameter of the Clamp Front End: 0.5 mm Under the above test conditions, the number of bends was increased every 10 bends. The presence or absence of wire cracks was visually observed, and the number of bends at which cracks appeared was recorded. The results are recorded in Table 5. In addition, the same evaluation was performed using hardening components F2 to F8 and hardening components G1 to G3. These results are also set forth in Table 5.

<Evaluation of Warpness>

The curable component F1 was applied to a substrate using a #180 mesh polyester screen and screen printing. The substrate was then placed in a hot air circulating dryer at 80°C for 30 minutes. Subsequently, the substrate was placed in a hot air circulating dryer at 120°C for 60 minutes to cure the applied curable component F1. A 25-micron thick polyimide film (Kapton 100EN, manufactured by Toray-DuPont) was used as the substrate.

A circular cutter was used to cut a hardened film, obtained by coating a curable component and curing it using a hot air circulating dryer, into 50 mm φ pieces. The center of each circularly cut piece exhibits a convex or concave warping deformation. The pieces with the hardened film formed on the substrate, cut by the circular cutter, were left to stand for one hour in a downward convex position, i.e., with the center of the piece in contact with the horizontal plane. The maximum and minimum warping heights, measured from the horizontal plane, were measured, and their average value was calculated. The symbols indicate the direction of warping. When placed in a downward convex position, a "+" is used if the hardened film is on the upper side relative to the copper substrate or polyimide film, and a "-" is used if the hardened film is on the lower side. Furthermore, if the warping is less than +3.0 mm, it is considered acceptable. The results are recorded in Table 5.

In addition, the same evaluation was performed using curing components F2 to F8 and curing components G1 to G3. These results are also recorded in Table 5.

<Evaluation of flexibility>

The curing component F1 was applied to the copper of a flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Sperflex, copper thickness: 8 micrometers, polyimide thickness: 38 micrometers) by screen printing in a size of 75 mm wide and 110 mm long, with a cured film thickness of 15 micrometers. The film was kept at room temperature for 10 minutes and then placed in a hot air circulating dryer at 120°C for 60 minutes to cure it. The PET (polyethylene terephthalate) film lining the prepared test piece was peeled off and cut into a strip 10 mm wide using a cutting tool. The strip was then bent approximately 180 degrees with the hardened film side facing outwards, and compressed for 3 seconds using a compressor at 0.5 ± 0.2 MPa. The bent section was then observed under a 30x microscope to check for the presence of cracks.

The flexibility of hardening components F1 to F8 was evaluated, and the result for all of them was "no cracks were generated". On the other hand, the flexibility of hardening components G1 to G3 was evaluated, and the results for G1 and G3 were "no cracks were generated", while G2 was "cracks were generated".

<Defoaming time>

On a flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Sperflex, copper thickness: 8 micrometers, polyimide thickness: 38 micrometers), a hardened component F1 was applied by screen printing in a size of 75 mm wide and 110 mm long, with a hardened film thickness of 15 micrometers. At this time, the bubbles on the coating surface were visually observed. The time from the completion of screen printing was set to 0 seconds, and the time until the bubbles disappeared was calculated and set as the defoaming time.

In addition, the same evaluation was performed using curing components F2 to F8 and curing components G1 to G3. These results are also recorded in Table 5.

[Table 5] Implementation Example 1 Implementation Example 2 Implementation Example 3 Implementation Example 4 Implementation Example 5 Implementation Example 6 Implementation Example 7 Implementation Example 8 Comparative example 1 Comparative example 2 Comparative example 3 unit Hardening component F1 Hardening component F2 Hardening component F3 Hardening component F4 Hardening component F5 Hardening component F6 Hardening component F7 Hardening component F8 Hardening component G1 Hardening component G2 Hardening component G3 Thickness of the hardened film micrometer 5 5 5 5 5 5 5 5 5 5 5 Disconnection inhibition (MIT experiment) Second-rate 270 260 240 270 240 260 280 290 130 300 220 Upturned (Pass/Fail) millimeters 2.0 (Qualified) 2.2 (Qualified) 1.3 (Qualified) 2.8 (Qualified) 1.3 (Qualified) 1.3 (Qualified) 1.3 (Qualified) 1.3 (Qualified) 1.2 (Qualified) 7.5 (Unacceptable) 2.0 (Qualified) Defoaming time Second 5 5 5 5 5 2 2 2 5 5 15

Based on the above results, it is at least confirmed that the hardened composition of this embodiment is excellent in terms of wire breakage inhibition, low warping, flexibility and defoaming properties, and that the hardened composition is useful as an insulating protective film for flexible wiring boards.

without

without

Claims (16)

A curable composition comprising: (component a) a polyurethane containing an organic residue derived from a polyisocyanate, having a carboxyl group and an aromatic ring concentration of 0.1 mmol/g to 6.5 mmol/g; (component b) a solvent; (component c) a compound having two or more epoxy groups in one molecule; (component d) a first defoamer containing an olefin; and (component e) a second defoamer containing an acrylic resin and/or a methacrylate resin, wherein component a is a polyurethane having a structural unit represented by formula (2). In which R ¹ independently represents an enylphenyl or an enylphenyl with a substituent; in which component e is 1% to 150% by mass relative to component d; and in which the curing composition is free of fluorine atoms and silicone defoamers. The curable composition as described in claim 1, wherein component a is a polyurethane having the structural unit represented by formula (1), . The curable composition as described in claim 1 or 2, wherein component a is a polyurethane having the structural unit represented by formula (3), In this denoted , n R ^1s each independently represent an enylphenyl group or an enylphenyl group with a substituent, (n+1) R ^2s each independently represent an enylalkyl group having 3 to 9 carbon atoms, and n is a natural number less than 50. The curable composition as described in claim 1 or 2, wherein in component a, the organic residues derived from cyclic aliphatic polyisocyanates are 70 mol% or more relative to the total amount of organic residues derived from the polyisocyanate. The hardening composition as described in claim 1 or 2, wherein component a is 60% to 99.9% by mass relative to the total amount of component a and component c. The hardening composition as described in claim 1 or 2, wherein component b is 25% to 75% by mass relative to the total amount of components a, b and c. The curing composition as described in claim 1 or 2, wherein the number average molecular weight of component a is from 3,000 to 50,000, and the acid value of component a is from 10 mgKOH/g to 70 mgKOH/g. The curing composition as described in claim 1 or 2, wherein the total amount of component d and component e is 0.01% to 3% by mass relative to the total amount of the curing composition. The curing composition as described in claim 1 or 2, wherein when the total amount of the components after removing the content of component b from the total amount of the curing composition is set to 100% by mass, the total amount of components d and e is 0.01% by mass to 5% by mass. The hardening composition as described in claim 1 or 2 further comprises: (component f) at least one microparticle selected from the group consisting of inorganic microparticles and organic microparticles. The hardening composition as described in claim 10, wherein component f comprises silicon dioxide microparticles. The hardening composition as described in claim 10, wherein component f comprises hydrotalcite microparticles. A hardening material, which is a hardening composition as described in claim 1 or 2. An outer coating for a flexible wiring board, comprising a hardener as described in claim 13. A flexible wiring board is formed by forming wiring on a flexible substrate, wherein a portion or all of the surface on which the wiring is formed is covered by an outer coating of the flexible wiring board as described in claim 14. A method for manufacturing a flexible wiring board, comprising: (Step A) printing a curable composition as described in claim 1 or 2 onto a portion or all of the surface of the flexible wiring board formed by forming wiring on a flexible substrate, thereby forming a printed film on the wiring; (Step B) placing the printed film obtained in Step A in an environment of 40°C to 100°C, thereby causing a portion or total amount of the solvent in the printed film to evaporate; and (Step C) heating the printed film obtained in Step A or the printed film obtained in Step B at 100°C to 170°C, thereby curing it to form an outer coating.