WO2020137347A1

WO2020137347A1 - Method for producing polyurethane, method for producing curable composition, method for producing cured product, method for producing overcoat film and method for producing flexible wiring board

Info

Publication number: WO2020137347A1
Application number: PCT/JP2019/046663
Authority: WO
Inventors: 圭孝石橋; 和弥木村
Original assignee: 昭和電工株式会社
Priority date: 2018-12-25
Filing date: 2019-11-28
Publication date: 2020-07-02
Also published as: TW202028275A

Abstract

Provided is a method for producing a polyurethane, by which it is possible to impart a curable composition with low stringiness and excellent defoaming properties. A polyurethane is produced by reacting a polyisocyanate compound I, a first polyol compound H1, a second polyol compound H2 and a third polyol compound H3. The first polyol compound H1 has a higher aromatic ring concentration than the second polyol compound H2. The first polyol compound H1 and the second polyol compound H2 have a higher reaction rate constant for a urethane bond-forming reaction than the third polyol compound H3. The entire amount of the polyisocyanate compound I, the entire amount of the first polyol compound H1, the entire amount of the second polyol compound H2 and some of the entire amount of the third polyol compound H3 are mixed, a polymerization reaction is carried out to obtain an intermediate polymer, the remainder of the third polyol compound H3 is then added to the intermediate polymer, and a further polymerization reaction is carried out.

Description

Polyurethane production method, curable composition production method, cured product production method, overcoat film production method, and flexible wiring board production method

The present invention relates to a method for producing polyurethane, a method for producing a curable composition, a method for producing a cured product, a method for producing an overcoat film, and a method for producing a flexible wiring board.

The flexible wiring board is covered with an overcoat film for surface protection. This overcoat film is formed by applying a curable composition to the surface of the flexible substrate on which the wiring is formed by a printing method or the like and curing it. This curable composition is required to have low stringiness and excellent defoaming property in order to increase printing speed and improve productivity. The stringing property and the defoaming property will be described below.

After the curable composition is applied in a film form on the surface of the flexible substrate using the printing plate, when the printing plate is separated from the surface of the flexible substrate, a fiber is present between the printing plate and the film-shaped curable composition. In some cases, a stringing phenomenon occurs in which the curable composition in the shape of a line remains. When the stringing phenomenon occurs, the peripheral parts of the printing plate and the flexible substrate are contaminated, and the flexible substrate coated with the curable composition cannot be transferred to the next step. The flexible substrate coated with the composition needs to be allowed to stand. As described above, when the stringing phenomenon occurs, workability and productivity in the printing process are deteriorated, so that the curable composition has been required to be hard to cause the stringing phenomenon (low stringing property).

Also, bubbles of the curable composition may remain on the surface of the film-shaped curable composition applied to the flexible substrate. If bubbles remain, the appearance of the flexible wiring board deteriorates, so it is necessary to leave the flexible substrate coated with the curable composition still until the bubbles disappear. As described above, when bubbles remain, workability and productivity in the printing process are deteriorated, and therefore the curable composition has been required to be easy to eliminate bubbles (excellent defoaming property).

A large number of curable compositions for forming an overcoat film of a flexible wiring board have been proposed in the past. For example, Patent Document 1 contains a polyurethane obtained by reacting a diisocyanate compound with a plurality of diol compounds. A curable composition is disclosed. When the curable composition disclosed in Patent Document 1 is used, it is possible to obtain an overcoat film for a flexible wiring board, which is excellent in low warpage, flexibility, long-term insulation reliability, and wiring disconnection suppression.

International Publication No. 2017/110591

However, the curable composition disclosed in Patent Document 1 does not have sufficiently satisfactory properties with respect to stringiness and defoaming properties, and improvements in properties have been demanded.
The present invention provides a method for producing a polyurethane capable of imparting low stringiness and excellent defoaming property to a curable composition, and a curable composition having low stringiness and excellent defoaming property. The challenge is to provide a method. Another object of the present invention is to provide a method for producing a cured product excellent in workability and productivity, a method for producing an overcoat film, and a method for producing a flexible wiring board.

One aspect of the present invention is as described in [1] to [16] below.
[1] Polyisocyanate compound I having two or more isocyanato groups in one molecule, a first polyol compound H1 having two or more hydroxy groups in one molecule, and two or more hydroxy in one molecule A method for producing a polyurethane by reacting a second polyol compound H2 having a group with a third polyol compound H3 having two or more hydroxy groups in one molecule,
The aromatic ring concentration of the first polyol compound H1 is higher than the aromatic ring concentration of the second polyol compound H2,
The reaction rate constant of the reaction for forming a urethane bond from the isocyanato group of the polyisocyanate compound I and the hydroxy group of the first polyol compound H1 is K1, and the isocyanato group of the polyisocyanate compound I and the second polyol compound H2. K2 is the reaction rate constant of the reaction of forming a urethane bond from the hydroxy group of the above, and the reaction rate constant of the reaction of forming a urethane bond from the isocyanato group of the polyisocyanate compound I and the hydroxy group of the third polyol compound H3 is When K3 is satisfied, both the expression K1/K3>50 and the expression K2/K3>50 are satisfied,
One of the total amount of the polyisocyanate compound I used in the production of the polyurethane, the total amount of the first polyol compound H1, the total amount of the second polyol compound H2, and the total amount of the third polyol compound H3. Part, and mixing, a polymerization reaction for forming a urethane bond from an isocyanato group and a hydroxy group, a first polymerization step for obtaining an intermediate polymer,
The weight average molecular weight of the intermediate polymer is not less than twice the sum of the molecular weights of the polyisocyanate compound I, the first polyol compound H1, the second polyol compound H2, and the third polyol compound H3. Then, the remaining part of the total amount of the third polyol compound H3 used in the production of the polyurethane is added to the intermediate polymer to carry out a polymerization reaction for forming a urethane bond from an isocyanato group and a hydroxy group. A second polymerization step further performed,
A method for producing a polyurethane comprising:

[2] The total number of isocyanato groups in the total amount of the polyisocyanate compound I used for producing the polyurethane is F _I , the total number of hydroxy groups in the total amount of the first polyol compound H1 is F _H1 , and the second Of the total amount of hydroxy groups contained in the total amount of the polyol compound _H2 , F _H2 , among the total amount of the third polyol compound H3, the total number of hydroxy groups contained in the part is Fa _H3 , and among the total amount of the third polyol compound H3 When the total number of hydroxy groups contained in the balance to be additionally charged is Fb _H3 ,
0.4≦(F _H1 +F _H2 )/F _I ≦0.6
0.01≦Fa _H3 /F _I ≦0.2
0.25≦Fb _H3 /F _I ≦0.5
0.8≦(F _H1 +F _H2 +Fa _H3 +Fb _H3 )/F _I ≦1.2
The method for producing a polyurethane according to [1], wherein the first polymerization step and the second polymerization step are performed so as to satisfy all of the following four formulas.

[3] The aromatic ring concentration of the first polyol compound H1 is 5.0 mmol/g or more and 15.0 mmol/g or less, and the aromatic ring concentration of the second polyol compound H2 is 0.5 mmol/g or more and 5.0 mmol/g The method for producing a polyurethane according to [1] or [2], wherein the concentration is not more than g and the aromatic ring concentration of the first polyol compound H1 is higher than the aromatic ring concentration of the second polyol compound H2.

[4] The method for producing a polyurethane according to any one of [1] to [3], wherein the first polyol compound H1 is a diol having a fluorene structure.
[5] The method for producing a polyurethane according to [4], wherein the diol having a fluorene structure is 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene represented by the following formula (1).

[6] The second polyol compound H2 is a polyester diol represented by the following formula (2), and R ¹ in the following formula (2) is independently a divalent group having 6 to 14 carbon atoms. And R ² each independently represent a divalent hydrocarbon group having 3 to 9 carbon atoms, and n is an integer of 1 to 50, which is any one of [1] to [5]. The method for producing a polyurethane according to the item 1.

[7] The third polyol compound H3 is a carboxy group-containing diol represented by the following formula (3), and R ³ in the following formula (3) is a methyl group or an ethyl group [1] to [1] [6] The method for producing the polyurethane according to any one of [6].

[8] The method for producing a polyurethane according to any one of [1] to [7], wherein the number average molecular weight of the polyurethane is 3,000 or more and 100,000 or less.
[9] The method for producing a polyurethane according to any one of [1] to [8], wherein the acid value of the polyurethane is 10 mgKOH/g or more and 70 mgKOH/g or less.

[10] A polyurethane (a) produced by the method for producing a polyurethane according to any one of [1] to [9], a solvent (b), and an epoxy having two or more epoxy groups in one molecule. A method for producing a curable composition, which comprises mixing the compound (c) and the composition.
[11] The ratio of the content of the solvent (b) to the total amount of the curable composition is 25% by mass or more and 75% by mass or less, and the ratio to the total amount of the polyurethane (a) and the epoxy compound (c) is The method for producing a curable composition according to [10], wherein the content ratio of the polyurethane (a) is 40% by mass or more and 99% by mass or less.

[12] A polyurethane (a) produced by the method for producing a polyurethane according to any one of [1] to [9], a solvent (b), and an epoxy having two or more epoxy groups in one molecule. A method for producing a curable composition, which comprises mixing a compound (c) and fine particles (d) to form a composition.
[13] The ratio of the content of the solvent (b) to the total amount of the curable composition is 25% by mass or more and 75% by mass or less, and the content of the fine particles (d) relative to the total amount of the curable composition is The ratio is 0.1% by mass or more and 60% by mass or less, and the ratio of the content of the polyurethane (a) to the total amount of the polyurethane (a) and the epoxy compound (c) is 40% by mass or more and 99% by mass or less. The method for producing a curable composition according to [12].

[14] A method for producing a cured product, which comprises curing the curable composition produced by the method for producing a curable composition according to any one of [10] to [13].
[15] The curable composition produced by the method for producing a curable composition according to any one of [10] to [13] is used to form the wiring on the surface of a flexible substrate on which the wiring is formed. A method for producing an overcoat film, wherein the curable composition in the form of a film is cured to form a cured product in the form of a film after the film-shaped curable composition is disposed on a portion where the film is formed.
[16] The wiring is formed on the surface of the flexible substrate on which the wiring is formed, by using the curable composition manufactured by the method for manufacturing the curable composition according to any one of [10] to [13]. A method for manufacturing a flexible wiring board, in which the curable composition in the form of a film is cured to form an overcoat film after being arranged in a film form on the portion where the film is formed.

According to the present invention, it is possible to manufacture a polyurethane capable of imparting low stringiness and excellent defoaming property to a curable composition. Further, according to the present invention, a curable composition having low stringiness and excellent defoaming property can be produced. Furthermore, according to the present invention, a cured product, an overcoat film, and a flexible wiring board can be manufactured with excellent workability and productivity.

It is a GPC chart figure which shows the molecular weight distribution of polyurethane.

An embodiment of the present invention will be described below. The present embodiment shows an example of the present invention, and the present invention is not limited to this embodiment. In addition, various changes or improvements can be added to the present embodiment, and a mode in which such changes or improvements are added can be included in the present invention.

The present inventors have conducted extensive studies to solve the above problems, and as a result, as a polyol compound which is a monomer of polyurethane, reactivity with an isocyanato group of a polyisocyanate compound (that is, an isocyanate group and a polyol compound of a polyisocyanate compound). By using multiple types of polyol compounds with different reaction rate constants of the reaction to form a urethane bond from the hydroxy group of the above, and by specifying the timing of the polyol compound with the lowest reactivity among them, the molecular weight is determined. The present invention found that a polyurethane having a narrow distribution can be produced, and that by containing the polyurethane, a curable composition having low stringiness during coating and excellent defoaming property can be obtained, and the present invention Has been completed.

I. Polyurethane and Manufacturing Method Thereof The polyurethane of the present embodiment and the manufacturing method thereof will be described in detail below.
(1) Polyurethane Monomer The monomers used for producing polyurethane will be described. In this embodiment, a polyisocyanate compound and a polyol compound are used as a polyurethane monomer, and a polyurethane is produced by reacting an isocyanato group of the polyisocyanate compound with a hydroxy group of the polyol compound.

As the polyisocyanate compound, polyisocyanate compound I having two or more isocyanato groups in one molecule is used. As the polyol compound, a first polyol compound H1 having two or more hydroxy groups in one molecule, a second polyol compound H2 having two or more hydroxy groups in one molecule, and one molecule Is used as the third polyol compound H3 having two or more hydroxy groups.

The first polyol compound H1, the second polyol compound H2, and the third polyol compound H3 are compounds having different aromatic ring concentrations and reactivity with the isocyanato group of the polyisocyanate compound I.
First, the aromatic ring concentrations of the first polyol compound H1 and the second polyol compound H2 are different, and the aromatic ring concentration of the first polyol compound H1 is higher than the aromatic ring concentration of the second polyol compound H2.

The aromatic ring concentration of the first polyol compound H1 is preferably 5.0 mmol/g or more and 15.0 mmol/g or less, and more preferably 8.0 mmol/g or more and 12.0 mmol/g or less. The aromatic ring concentration of the second polyol compound H2 is preferably 0.5 mmol/g or more and 5.0 mmol/g or less, more preferably 1.0 mmol/g or more and 4.0 mmol/g or less. When the aromatic ring concentrations of the first polyol compound H1 and the second polyol compound H2 are within the above numerical range, the balance between the solvent resistance of the overcoat film described later and the warp of the flexible wiring board described later is good. It is easy to become.

The aromatic ring concentration means the number (moles) of aromatic rings contained in 1 g of the compound. For example, if a polyol compound having a molecular weight of 438.5 has four aromatic rings (for example, phenyl groups) per molecule, 1 g of this polyol compound is 2.28 mmol, so the aromatic ring concentration is 9.12 mmol/g. (4×2.28 mmol/1 g).
The kind of aromatic ring is not particularly limited as long as it is a cyclic functional group having 3 or more ring members and having aromaticity, and examples thereof include a monocyclic aromatic hydrocarbon group such as a phenyl group, a biphenyl group, and a fluorene group. And polycyclic aromatic hydrocarbon groups such as, naphthalene groups, condensed cyclic aromatic hydrocarbon groups such as indenyl groups, and heteroaromatic hydrocarbon groups such as pyridyl groups.

However, in the case of a functional group having a plurality of cyclic structure moieties such as a polycyclic aromatic hydrocarbon group or a condensed cyclic aromatic hydrocarbon group, the number of aromatic rings is not one and To do. For example, since a fluorene group has two benzene rings, which are cyclic structure sites, in the case of a polyol compound having one fluorene group, the number of aromatic rings in the polyol compound is two per molecule. To do.

Further, in the first polyol compound H1, the second polyol compound H2, and the third polyol compound H3, the reactivity with the isocyanato group of the polyisocyanate compound I (that is, the isocyanate group of the polyisocyanate compound I and the polyol compound The reaction rate constant of the reaction of forming a urethane bond from the hydroxy groups of H1, H2 and H3 is different.

More specifically, the reaction rate constant of the reaction for forming a urethane bond from the isocyanato group of the polyisocyanate compound I and the hydroxy group of the first polyol compound H1 is K1, the isocyanato group of the polyisocyanate compound I and the second polyol compound H2 are K2 is the reaction rate constant of the reaction of forming a urethane bond from the hydroxy group of OH and K3 is the reaction rate constant of the reaction of forming the urethane bond from the isocyanato group of the polyisocyanate compound I and the hydroxy group of the third polyol compound H3. Then, both the equations K1/K3>50 and the equations K2/K3>50 are satisfied.

By using the polyol compounds H1, H2 and H3 satisfying the above two formulas and subjecting the third polyol compound H3 having the smallest reaction rate constant to the polymerization reaction at the timing described below, a polyurethane having a narrow molecular weight distribution can be easily obtained. .. The reaction rate constants K1 and K2 may be the same or different. Also, the above two equations are preferably K1/K3>100 and K2/K3>100.

Here, the method of measuring the reaction rate constants K1, K2, and K3 will be described. Usually, polyurethane is synthesized by a polymerization reaction by reacting a polyisocyanate compound having two or more isocyanato groups in one molecule with a polyol compound having two or more hydroxy groups in one molecule. However, since the products of the polymerization reaction are diverse, the analysis for measuring the reaction rate constant becomes complicated.

Therefore, in order to avoid the complexity of the analysis due to the diversification of the products of the polymerization reaction, the polyisocyanate compound is replaced with a monoisocyanate compound having one isocyanato group in one molecule, and a monoisocyanate compound and a polyol compound H1, The reaction rate constant is measured by analyzing the reaction with H2 and H3. When a monoisocyanate compound is used, the polymerization reaction does not proceed and a low molecular weight compound is obtained, which facilitates the analysis.

The types of monoisocyanate compounds used when measuring the reaction rate constants K1, K2, and K3 are as follows. That is, when the polyisocyanate compound I used in the polymerization reaction is a primary isocyanate compound, a primary monoisocyanate compound is used, and when the polyisocyanate compound I is a secondary isocyanate compound, a secondary monoisocyanate compound is used. When the polyisocyanate compound I is a tertiary isocyanate compound, the reaction rate can be qualitatively evaluated by using the tertiary monoisocyanate compound. Dodecyl isocyanate is used as the primary monoisocyanate compound, cyclohexyl isocyanate is used as the secondary monoisocyanate compound, and tert-butyl isocyanate is used as the tertiary monoisocyanate compound.

When the polyisocyanate compound I used in the polymerization reaction has at least two kinds of primary isocyanate, secondary isocyanate and tertiary isocyanate, a monoisocyanate having lower reactivity is selected. That is, when the polyisocyanate compound I used in the polymerization reaction has a primary isocyanate and a secondary isocyanate, a secondary monoisocyanate compound is used, and when the polyisocyanate compound I has a primary isocyanate or a secondary isocyanate and a tertiary isocyanate, it is 3 A grade monoisocyanate compound is used.

In the reaction between the monoisocyanate compound and the polyol compound, the following formula is established, and therefore the reaction rate constants K1, K2, and K3 can be calculated using the formula below. In the following formula, C ₀ is the initial concentration of the polyol compound, C is the concentration of the polyol compound, t is the reaction elapsed time, and K is the reaction rate constant.
1/C-1/C ₀ =K·t
The concentration of the polyol compound is sequentially measured during the reaction between the monoisocyanate compound and the polyol compound, and the measured value is plotted on a graph with the reaction elapsed time t as the X axis and 1/C as the Y axis. Then, the slope of the straight line drawn in the graph becomes the reaction rate constant K.

The method for measuring the concentration of the polyol compound in the reaction is not particularly limited, but ¹ H-NMR, ¹³ C-NMR, IR and other spectroscopic techniques can be used. For example, a portion of a reaction solution of a reaction between a monoisocyanate compound and a polyol compound is sampled, and the reaction is stopped by diluting with a solvent for NMR measurement, and then subjected to NMR analysis to measure the concentration of the polyol compound. can do.

[First polyol compound H1]
The type of the first polyol compound H1 is not particularly limited as long as the conditions such as the aromatic ring concentration and the reaction rate constant described above are satisfied, but a diol having a fluorene structure is preferable, and it is represented by the above formula (1). The represented 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene is more preferred.

[Second polyol compound H2]
The type of the second polyol compound H2 is not particularly limited as long as it satisfies the conditions such as the aromatic ring concentration and the reaction rate constant described above, but the polyester diol represented by the above formula (2) is preferable. R ¹ in the above formula (2) each independently represents a divalent organic group having 6 to 14 carbon atoms, and R ² each independently represents a divalent hydrocarbon group having 3 to 9 carbon atoms. Represents a group, and n is an integer of 1 or more and 50 or less.

The polyester diol represented by the above formula (2) can be synthesized by esterification of a dicarboxylic acid and a diol.
Examples of the dicarboxylic acid include orthophthalic acid, isophthalic acid, terephthalic acid, 3-methyl-benzene-1,2-dicarboxylic acid, 4-methyl-benzene-1,2-dicarboxylic acid, 4-methyl-benzene-1, Examples thereof include 3-dicarboxylic acid, 5-methyl-benzene-1,3-dicarboxylic acid and 2-methyl-benzene-1,4-dicarboxylic acid. As the dicarboxylic acid, one of these may be used alone, or two or more thereof may be used in combination.

Examples of the diol include 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 3-methyl-1,5. -Pentanediol, 1,8-octanediol, 1,9-nonanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol and the like. it can. As the diol, one of these may be used alone, or two or more thereof may be used in combination.

Preferred dicarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, 3-methyl-benzene-1,2-dicarboxylic acid, 4-methyl-benzene-1,2-dicarboxylic acid, and particularly preferred is phthalic acid. is there.
The preferred diols are 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 3-methyl-1,5-pentanediol, and Preferred are 1,6-hexanediol and 3-methyl-1,5-pentanediol.

The number average molecular weight of the polyester diol represented by the above formula (2) is preferably 800 or more and 5000 or less, more preferably 800 or more and 4000 or less, and further preferably 900 or more and 3500 or less.
The polyester diol represented by the above formula (2) may be used alone or in combination of two or more.

Note that a low molecular weight polyol can be used as the second polyol compound H2. For example, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neo Pentyl glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, etc. can be used.

[Third Polyol Compound H3]
The type of the third polyol compound H3 is not particularly limited as long as it satisfies the conditions such as the reaction rate constants described above, but has at least one carboxy group and two hydroxy groups in the molecule. Carboxyl group-containing diols are preferred.
The kind of the carboxy group-containing diol is not particularly limited, and examples thereof include dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and N,N-bis(hydroxyethyl)glycine. As the carboxy group-containing diol, one of these may be used alone, or two or more may be used in combination.

Among these carboxy group-containing diols, the carboxy group-containing diol represented by the above formula (3) is more preferable from the viewpoint of solubility in a reaction solvent during the production of polyurethane. R ³ in the above formula (3) represents a methyl group or an ethyl group. That is, as the carboxy group-containing diol, 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid are particularly preferable.

Note that a low molecular weight polyol can be used as the third polyol compound H3. For example, 1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, neo Pentyl glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, etc. can be used.

[Polyisocyanate Compound I]
The type of the polyisocyanate compound I is not particularly limited, and examples thereof include a cycloaliphatic polyisocyanate, an aromatic ring-containing polyisocyanate, a chain aliphatic polyisocyanate, and a heterocyclic polyisocyanate.
Examples of the cycloaliphatic polyisocyanate include 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, methylene bis(4-cyclohexyl isocyanate), 1,3-bis(isocyanatomethyl)cyclohexane, 1,4 -Bisettes of bis(isocyanatomethyl)cyclohexane, norbornene diisocyanate and isophorone diisocyanate.

Examples of the polyisocyanate having an aromatic ring include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1,3-xylylene diisocyanate and 1,4-xylylene diisocyanate. Isocyanate may be mentioned.
Examples of the chain aliphatic polyisocyanate include biuret of hexamethylene diisocyanate, lysine triisocyanate, lysine diisocyanate, hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 2,2,4-trimethylhexane methylene diisocyanate. Are listed.

Examples of the polyisocyanate having a heterocycle include an isocyanurate body of isophorone diisocyanate and an isocyanurate body of hexamethylene diisocyanate.
These polyisocyanates may be used alone or in combination of two or more.

In order to maintain high electrical insulation performance and heat resistance of the cured product of the curable composition described later, at least one of the polyol compounds H1, H2, and H3, which is a monomer of polyurethane, has an aromatic ring. Is preferred, and the polyisocyanate compound I preferably has no aromatic ring.

(2) Polymerization Method of Polyurethane A method of polymerizing the above monomers to produce polyurethane will be described. The method for producing a polyurethane according to this embodiment includes a first polymerization step for obtaining an intermediate polymer (prepolymer) and a second polymerization step for obtaining a final polymer.
In the first polymerization step, the total amount of polyisocyanate compound I, the total amount of first polyol compound H1, the total amount of second polyol compound H2, and a part of the total amount of third polyol compound H3 are mixed. Then, a polymerization reaction for forming a urethane bond from the isocyanato group and the hydroxy group is performed to obtain an intermediate polymer.
In the second polymerization step, the remaining part of the total amount of the third polyol compound H3 used for the production of polyurethane is additionally added to the intermediate polymer to further carry out a polymerization reaction for forming a urethane bond from an isocyanato group and a hydroxy group. This is the step of obtaining the final polymer.

The above-mentioned "total amount" means the total amount of each monomer to be used to obtain the final polymer. That is, the polyisocyanate compound I, the first polyol compound H1, and the second polyol compound H2 are subjected to the polymerization reaction in the first polymerization step, but the third polyol compound H3 is subjected to the first polymerization step. Then, only a part is subjected to the polymerization reaction, and the rest is subjected to the polymerization reaction in the second polymerization step to complete the polymerization reaction.

The timing of adding the remaining part of the total amount of the third polyol compound H3 used for the production of polyurethane to the intermediate polymer (that is, the timing of starting the second polymerization step) is as follows. Although the polymerization proceeds in the first polymerization step and the weight average molecular weight of the intermediate polymer increases, the weight average molecular weight of the intermediate polymer is the polyisocyanate compound I, the first polyol compound H1, and the second polyol compound. When the total of the molecular weights of H2 and the third polyol compound H3 is twice or more, the balance of the total amount of the third polyol compound H3 is additionally charged to start the second polymerization step.

A polyurethane having a narrow molecular weight distribution can be obtained by first subjecting all of the polyol compounds H1 and H2 having a large reaction rate constant to the polymerization reaction and then subjecting the polyol compound H3 having the smallest reaction rate constant to the polymerization reaction later. When the curable composition is produced using polyurethane having a narrow molecular weight distribution, the obtained curable composition has low stringiness when applied to a flexible substrate and is excellent in defoaming property.

Next, the compounding ratio of each monomer in the polyurethane production method of the present embodiment will be described. The total amount of isocyanato groups contained in the total amount of polyisocyanate compound I used for the production of polyurethane is F _I , the total number of hydroxy groups contained in the total amount of first polyol compound H1 is F _H1 , and the total amount of second polyol compound H2 is The total number of hydroxy groups is F _H2 , the total number of hydroxy groups in the first polymerization step of the total amount of the third polyol compound _H3 is Fa _H3 , and the total amount of the third polyol compound H3 is Let Fb _H3 be the total number of hydroxy groups in the remainder that is additionally charged in the second polymerization step.

At this time, in the method for producing the polyurethane of the present embodiment, the first polymerization step and the second polymerization step can be performed by mixing the respective monomers so as to satisfy all of the following four formulas.
0.4≦(F _H1 +F _H2 )/F _I ≦0.6
0.01≦Fa _H3 /F _I ≦0.2
0.25≦Fb _H3 /F _I ≦0.5
0.8≦(F _H1 +F _H2 +Fa _H3 +Fb _H3 )/F _I ≦1.2

In the method for producing the polyurethane of the present embodiment, it is preferable that the respective monomers are blended so as to satisfy all of the following four formulas, and the first polymerization step and the second polymerization step are performed.
0.4≦(F _H1 +F _H2 )/F _I ≦0.6
0.01≦Fa _H3 /F _I ≦0.2
0.3≦Fb _H3 /F _I ≦0.5
0.8≦(F _H1 +F _H2 +Fa _H3 +Fb _H3 )/F _I ≦1.2
Thereby, polyurethane having a narrow molecular weight distribution can be obtained. When a polyurethane having a desired molecular weight distribution is obtained, the polymerization reaction may be stopped and the polyurethane may be taken out from the polymerization product (for example, polyurethane solution).

The above four equations are more preferably as follows.
0.45≦(F _H1 +F _H2 )/F _I ≦0.55
0.05≦Fa _H3 /F _I ≦0.15
0.31≦Fb _H3 /F _I ≦0.40
0.90≦(F _H1 +F _H2 +Fa _H3 +Fb _H3 )/F _I ≦1.10.

Further, it is more preferable that the above four expressions are as follows.
0.48≦(F _H1 +F _H2 )/F _I ≦0.52
0.08≦Fa _H3 /F _I ≦0.12
0.32≦Fb _H3 /F _I ≦0.35
0.95≦(F _H1 +F _H2 +Fa _H3 +Fb _H3 )/F _I ≦1.05

The polymerization method used in the method for producing the polyurethane of the present embodiment is not particularly limited, but for example, in the presence or absence of a urethane-forming catalyst such as dibutyltin dilaurylate, the polyisocyanate compound I, the first A method of reacting the polyol compound H1, the second polyol compound H2, and the third polyol compound H3 in a solvent may be used. However, it is preferable to carry out the polymerization reaction without a catalyst because the long-term insulation reliability of the overcoat film described later is improved.
The polymerization reaction for synthesizing polyurethane may be carried out in a solvent. When carried out in a solvent, the solid content concentration is preferably 10% by mass or more and 90% by mass or less, and 15% by mass or more and 70% by mass or less. More preferably, 20 mass% or more and 60 mass% or less are still more preferable.

The type of solvent used as the polymerization solvent is not particularly limited as long as it can dissolve the polyurethane of the present embodiment, for example, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dibutyl ether, Ether-based solvents such as diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, ethylene Glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, methyl methoxypropionate, Examples thereof include ester solvents such as ethyl methoxypropionate, methyl ethoxypropionate, ethyl ethoxypropionate and γ-butyrolactone, hydrocarbon solvents such as decahydronaphthalene, and ketone solvents such as cyclohexanone. These solvents may be used alone or in combination of two or more.

Further, when a curable composition described below is produced using a polyurethane solution having a solid content concentration of 20% by mass or more and 60% by mass or less, the solution viscosity of the polyurethane solution is measured under the measurement conditions described below in the section of Examples. In the above, for example, it is preferably 5,000 mPa·s or more and 1 million mPa·s or less from the viewpoint of uniform dispersion.
If necessary, a polyurethane may be produced by subjecting a monoisocyanate compound having one isocyanato group in one molecule or a monohydroxy compound having one hydroxy group in one molecule to a reaction.

The type of monoisocyanate compound that can be used is not particularly limited, but cyclohexyl isocyanate, octadecyl isocyanate, phenyl isocyanate, toluyl isocyanate, etc. can be used. Considering the discoloration resistance of the curable composition containing the polyurethane of the present embodiment when heated, cyclohexyl isocyanate and octadecyl isocyanate are preferable.

The type of monohydroxy compound that can be used is not particularly limited as long as it is a compound that does not have a substituent that has a higher reactivity with an isocyanato group than a hydroxy group, and may be methanol, ethanol, n-propanol, Isopropanol, n-butanol, isobutanol, sec-butanol, t-butanol, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol monopropyl ether, methyl ethyl ketoxime, etc. are used. be able to. These monohydroxy compounds may be used alone or in combination of two or more.

There is no particular restriction on the order of charging the monomers into the reaction vessel when carrying out the polymerization reaction for synthesizing polyurethane, but for example, the following order may be used. That is, the polyol compounds H1, H2, and H3 are first charged into a reaction vessel and dissolved in a solvent. The temperature of the solution of the polyol compounds H1, H2, H3 is usually 20° C. to 160° C., preferably 60° C. to 140° C., and then the polyisocyanate compound I is added little by little to the reaction vessel at 50° C. to 180° C. Preferably, the above monomers are reacted at 60° C. to 170° C. to carry out polymerization.

The molar ratio of the charged monomers is adjusted according to the molecular weight and acid value of the desired polyurethane.
By using a monohydroxy compound or a monoisocyanate compound, the molecular weight of the target polyurethane can be adjusted. For example, when the molecular weight of the polyurethane reaches the target number average molecular weight (or when it approaches the target number average molecular weight), a monohydroxy compound is added to seal the isocyanate terminal group at the molecular end of the polymerization product, Suppress further increase in number average molecular weight.

When a monohydroxy compound is used, the total amount of hydroxy groups possessed by the total amount of polyol compounds H1, H2, H3 used in the production of polyurethane is higher than the total amount of hydroxy groups possessed by the polyisocyanate compound I used in the production of polyurethane. The total number may be smaller, the same or larger.
When an excessive amount of monohydroxy compound is used, unreacted monohydroxy compound remains, but in this case, the excess monohydroxy compound may be used as it is as a part of the solvent. Alternatively, it may be removed by an operation such as distillation.

In order to use a monoisocyanate compound as a raw material for polyurethane, the total amount of polyol compounds H1, H2, and H3 used in the production of polyurethane is adjusted so that the molecular end of the polymerization product at the time of adding the monoisocyanate compound becomes a hydroxy group. It is necessary to reduce the total number of isocyanato groups contained in the total amount of the polyisocyanate compound I used for producing the polyurethane, compared to the total number of hydroxy groups contained in.

When the reaction between the polyol compounds H1, H2, and H3 and the polyisocyanate compound I is almost completed, the hydroxy group remaining at the molecular end of the polymerization product is reacted with the isocyanato group of the monoisocyanate compound. To this end, the temperature of the polyurethane solution during the production of the polyurethane is adjusted to 30° C. to 150° C., preferably 70° C. to 140° C., the monoisocyanate compound is added little by little to the polyurethane solution, and the temperature is maintained at the above temperature to complete the reaction. Let

(3) Polyurethane Since the polyurethane of the present embodiment is a polyurethane obtained by reacting the polyol compounds H1, H2, H3 and the polyisocyanate compound I, the first polyol compound H1 reacts with the polyisocyanate compound I. And a second urethane structural unit formed by the reaction of the second polyol compound H2 with the polyisocyanate compound I, and a reaction of the third polyol compound H3 with the polyisocyanate compound I. And a third urethane structural unit.

The number average molecular weight of the polyurethane of the present embodiment is not particularly limited, but is preferably 3000 or more and 100000 or less, more preferably 5000 or more and 50000 or less, and further preferably 5000 or more and 30000 or less. ..
When the number average molecular weight is within the above range, the solvent solubility of polyurethane is good, and since the viscosity of the polyurethane solution is unlikely to be high, the curable composition described below is used to produce an overcoat film or a flexible wiring board described below. It is suitable for use in. Furthermore, the elongation, flexibility, and strength of the cured product or overcoat film described later tend to be good.

The "number average molecular weight" here is a polystyrene equivalent number average molecular weight measured by gel permeation chromatography (hereinafter referred to as "GPC"). In addition, in this specification, the measurement conditions of GPC are as follows unless otherwise specified.
Device name: HPLC unit HSS-2000 manufactured by JASCO Corporation
Column: Shodex column LF-804 manufactured by Showa Denko KK
Mobile phase: Tetrahydrofuran Flow rate: 1.0 mL/min
Detector: RI-2031Plus manufactured by JASCO Corporation
Temperature: 40.0°C
Sample volume: Sample loop 100 μL
Sample concentration: approx. 0.1% by mass

The acid value of the polyurethane of the present embodiment is not particularly limited, but is preferably 10 mgKOH/g or more and 70 mgKOH/g or less, and more preferably 15 mgKOH/g or more and 50 mgKOH/g or less.
When the acid value is within the above range, the polyurethane has sufficient reactivity with the epoxy group. Therefore, in the curable composition described below, reactivity with other components such as an epoxy compound having two or more epoxy groups in one molecule is unlikely to be insufficient, and thus the heat resistance of the cured product of the curable composition Of the curable composition does not become too hard and brittle. Further, it becomes easy to balance the solvent resistance of the overcoat film described later and the warp of the flexible wiring board described later.
In addition, in this specification, the acid value of polyurethane is the value of the acid value measured by the potentiometric titration method defined in JIS K0070.

II. Curable composition and its manufacturing method A curable composition can be obtained using the polyurethane of this embodiment manufactured as mentioned above. The curable composition is a composition obtained by mixing the polyurethane (a) of the present embodiment, a solvent (b), and an epoxy compound (c) having two or more epoxy groups in one molecule. Can be manufactured by.

(1) Solvent (b)
The type of the solvent (b) which is one of the essential components of the curable composition of the present embodiment is not particularly limited, but it is preferable that the polyurethane (a) of the present embodiment can be dissolved, Further, it is more preferable that it has a boiling point of 150°C or higher and 250°C or lower under atmospheric pressure. In order to balance the solubility of the polyurethane (a) of the present embodiment, the volatility of the solvent, and the like, it is more preferable to use two or more kinds of solvents having a boiling point of 150° C. or higher and 250° C. or lower under atmospheric pressure in combination. It is particularly preferable to use a solvent having a boiling point of 170° C. or more and less than 200° C. under atmospheric pressure and a solvent having a boiling point of 200° C. or more and 220° C. or less under atmospheric pressure in combination.

Examples of the solvent having a boiling point of 150° C. or higher and 250° C. or lower under atmospheric pressure include the following.
Examples of the solvent having a boiling point of 170° C. or more and less than 200° C. under atmospheric pressure include diethylene glycol diethyl ether (boiling point 189° C.), diethylene glycol ethyl methyl ether (boiling point 176° C.), dipropylene glycol dimethyl ether (boiling point 171° C.), 3 -Methoxybutyl acetate (boiling point 171°C), ethylene glycol monobutyl ether acetate (boiling point 192°C), ethylene glycol mono-n-butyl ether (boiling point 171°C), dimethyl sulfoxide (boiling point 189°C) and the like can be mentioned.

As a solvent having a boiling point of 200° C. or more and 220° C. or less under atmospheric pressure, 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 Examples include dibutyl ether (boiling point 203° C.), diethylene glycol monoethyl ether acetate (boiling point 217° C.), γ-butyrolactone (boiling point 204° C.), acetophenone (boiling point 202° C.), N-methylpyrrolidone (boiling point 202° C.) and the like. ..
Examples of the solvent having a boiling point of 150° C. or higher under atmospheric pressure include methylcyclohexanone (boiling point 163° C.), N,N-dimethylformamide (boiling point 153° C.), ethylene glycol monoethyl ether acetate (boiling point 156° C.) and the like. You can

It has a boiling point of 170° C. or more and less than 200° C. under atmospheric pressure because it has low volatility due to its high volatility and can efficiently carry out the production reaction of the polyurethane of this embodiment in a homogeneous system. It is preferable to use a solvent in combination with a solvent having a boiling point of 200° C. or higher and 220° C. or lower under atmospheric pressure. And, as a solvent having a boiling point of 170° C. or more and less than 200° C. under atmospheric pressure, from among 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.) It is preferable to use at least one selected and use γ-butyrolactone (boiling point 204° C.) as a solvent having a boiling point of 200° C. or more and 220° C. or less under atmospheric pressure.

In addition, diethylene glycol diethyl ether (boiling point 189° C.) is used as a solvent having a boiling point of 170° C. or more and less than 200° C. under atmospheric pressure, and γ-butyrolactone (solvent having a boiling point of 200° C. or more and 220° C. or less under atmospheric pressure is used. It is further preferred to use a boiling point of 204° C.).
When the combination of these preferable solvents is used, the curable composition of the present embodiment can be suitably used as an ink for screen printing because it has low hygroscopicity, high boiling point, and low volatility.

In order to sufficiently develop the above effects, the use ratio of the solvent having a boiling point of 170° C. or more and less than 200° C. under atmospheric pressure and the solvent having a boiling point of 200° C. or more under 220° C. under atmospheric pressure is a mass ratio. Then, it is preferably within the range of 5:95 to 80:20, and more preferably within the range of 10:90 to 60:40.

Further, as a part or all of the solvent (b) contained in the curable composition of the present embodiment, it is possible to directly use the solvent for synthesis used when producing the polyurethane (a) of the present embodiment. Which is preferable in terms of process since the curable composition of the present embodiment can be easily produced.
Further, as long as the solubility of the polyurethane (a) of the present embodiment is not impaired, a solvent other than a solvent having a boiling point of 170°C or higher and lower than 200°C under atmospheric pressure or 200°C or higher and 220°C under atmospheric pressure. A solvent other than the solvents having the following boiling points can be used together. Reactive monomers and reactive diluents can also be used as the solvent (b).

The content of the solvent (b) in the curable composition of the present embodiment is preferably 25% by mass or more and 75% by mass or less, more preferably 35% by mass, with respect to the total amount of the curable composition of the present embodiment. % To 70% by mass, more preferably 35% to 65% by mass. Here, the total amount of the curable composition of the present embodiment is the total amount of the polyurethane (a), the solvent (b), and the epoxy compound (c) having two or more epoxy groups in one molecule. .. However, when the curable composition of the present embodiment contains other components such as fine particles (d) described below, the total amount of the curable composition of the present embodiment means polyurethane (a) and solvent. The total amount of (b), the epoxy compound (c) having two or more epoxy groups in one molecule, and other components.

When the content of the solvent (b) is in the range of 25% by mass or more and 75% by mass or less with respect to the total amount of the curable composition of the present embodiment, the viscosity of the curable composition is printed by the screen printing method. However, the viscosity of the curable composition after screen printing is not so large due to bleeding. As a result, it is less likely that the printed area of the curable composition actually printed is larger than the area where the curable composition is desired to be applied (that is, the shape of the printing plate), which is preferable.

(2) Epoxy compound (c) having two or more epoxy groups in one molecule
The epoxy compound (c) which is one of the essential components of the curable composition of the present embodiment functions as a curing agent in the curable composition, and is a compound having two or more epoxy groups in one molecule. If so, it is not particularly limited.
Examples of the epoxy compound (c) having two or more epoxy groups in one molecule include a novolac type epoxy resin obtained by epoxidizing a novolac resin. Specific examples of the novolac type epoxy resin include a phenol novolac type epoxy resin. Resin, ortho-cresol novolac type epoxy resin, etc. may be mentioned.

The novolak resin means phenols such as phenol, cresol, xylenol, resorcin, and catechol and/or naphthols such as α-naphthol, β-naphthol, and dihydroxynaphthalene, and formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, salicylaldehyde. And a compound having an aldehyde group such as, for example, are condensed or co-condensed under an acidic catalyst.

Furthermore, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include diglycidyl ethers of phenols and glycidyl ethers of alcohols. Examples of the above-mentioned phenols include bisphenol A, bisphenol F, bisphenol S, alkyl-substituted or unsubstituted biphenol, and stilbene-based phenols. That is, diglycidyl ethers of these phenols are bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, biphenyl type epoxy compounds, and stilbene type epoxy compounds. Examples of the alcohol include butanediol, polyethylene glycol, polypropylene glycol and the like.

Furthermore, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include glycidyl ester type epoxy resins of carboxylic acids such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid, aniline, and bis(4 -Aminophenyl) glycidyl-type or methylglycidyl-type epoxy resin, which is a compound obtained by substituting the active hydrogen bonded to the nitrogen atom of methane, isocyanuric acid, etc., with a glycidyl group, and nitrogen contained in aminophenols such as p-aminophenol Examples thereof include a glycidyl-type or methylglycidyl-type epoxy resin, which is a compound in which active hydrogen bonded to an atom and active hydrogen contained in a phenolic hydroxy group are each substituted with a glycidyl group.

Furthermore, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include vinylcyclohexene diepoxide, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 2-(3 Alicyclic epoxy resins such as ,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane. These alicyclic epoxy resins are obtained by epoxidizing an olefin bond of an alicyclic hydrocarbon compound having an olefin bond in the molecule.

Further, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include, for example, glycidyl ether of paraxylylene and/or metaxylylene modified phenol resin, glycidyl ether of terpene modified phenol resin, and dicyclopentadiene modified phenol resin. And glycidyl ether of cyclopentadiene-modified phenol resin, glycidyl ether of polycyclic aromatic ring-modified phenol resin, and glycidyl ether of naphthalene ring-containing phenol resin.

Furthermore, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include halogenated phenol novolac type epoxy resin, hydroquinone type epoxy resin, trimethylolpropane type epoxy resin, and linear aliphatic epoxy resin. (Obtained by oxidizing an olefin bond of a linear aliphatic hydrocarbon compound having an olefin bond in the molecule with a peracid such as peracetic acid), and a diphenylmethane type epoxy resin.

Furthermore, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include epoxidized aralkyl type phenolic resins such as phenol aralkyl resin and naphthol aralkyl resin, sulfur atom-containing epoxy resin, and tricyclo Examples include [5.2.1.0 ^2,6 ]decane dimethanol diglycidyl ether and epoxy resins having an adamantane structure. Examples of the epoxy resin having an adamantane structure include 1,3-bis(1-adamantyl)-4,6-bis(glycidyloyl)benzene, 1-[2′,4′-bis(glycidyloyl)phenyl]adamantane, 1 , 3-bis(4′-glycidyloylphenyl)adamantane, 1,3-bis[2′,4′-bis(glycidyloyl)phenyl]adamantane, and the like.
These epoxy compounds (c) may be used alone or in combination of two or more.

Among these epoxy compounds (c), an epoxy compound having two or more epoxy groups in one molecule and having an aromatic ring structure and/or an alicyclic structure is preferable.
When the long-term insulation performance of the cured product of the present embodiment described below is emphasized, a cured product having a low water absorption rate is obtained, and therefore, it has two or more epoxy groups in one molecule and has an aromatic ring structure and/or Alternatively, among epoxy compounds having an alicyclic structure, a compound having a tricyclodecane structure and an aromatic ring structure and having two or more epoxy groups is preferable.

Specific examples of the compound having a tricyclodecane structure and an aromatic ring structure and having two or more epoxy groups include a glycidyl ether of a dicyclopentadiene-modified phenol resin (that is, tricyclo[5.2.1.0 ^{2, 6} ] a compound having a decane structure and an aromatic ring structure and having two or more epoxy groups), 1,3-bis(1-adamantyl)-4,6-bis(glycidyloyl)benzene, 1-[2′ ,4'-bis(glycidyloyl)phenyl]adamantane, 1,3-bis(4'-glycidyloylphenyl)adamantane, and 1,3-bis[2',4'-bis(glycidyloyl)phenyl]adamantane An epoxy resin having an adamantane structure (that is, a compound having a tricyclo[3.3.1.1 ^3,7 ]decane structure and an aromatic ring structure and having two or more epoxy groups), or the following formula (4) The compounds represented may be mentioned. Among these, the compound represented by the following formula (4) is particularly preferable. Note that k in the following formula (4) is an integer of 1 or more. K in the following formula (4) is preferably an integer of 10 or less.

On the other hand, when importance is attached to reactivity with polyurethane, an amino group and an aromatic ring structure among epoxy compounds having two or more epoxy groups in one molecule and having an aromatic ring structure and/or an alicyclic structure And a compound having two or more epoxy groups are preferred.
Specific examples of the compound having an amino group and an aromatic ring structure and having two or more epoxy groups include aniline and bis(4-aminophenyl)methane in which active hydrogen bonded to a nitrogen atom is substituted with a glycidyl group. A glycidyl-type or methylglycidyl-type epoxy resin that is a compound, or a glycidyl-type or methylglycidyl that is a compound in which the active hydrogens bound to the nitrogen atom of aminophenols and the active hydrogens of a phenolic hydroxy group are each substituted with a glycidyl group Examples include epoxy resins of the type and compounds represented by the following formula (5). Among these, the compound represented by the following formula (5) is particularly preferable.

In the curable composition of the present embodiment, the preferable content of the epoxy compound (c) with respect to the content of the polyurethane (a) is that of the functional group (for example, carboxy group) capable of reacting with the epoxy group, which polyurethane (a) has. Since it depends on the amount, it cannot be said unequivocally.
However, the ratio of the number of functional groups capable of reacting with the epoxy group of the polyurethane (a) to the number of epoxy groups of the epoxy compound (c) ([the number of functional groups capable of reacting with the epoxy group]/[ The number of 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 within the range of 1/3 to 2/1, when the curable composition of the present embodiment is cured, there is no large amount of unreacted epoxy compound remaining, and the epoxy compound does not remain. There are not so many functional groups capable of reacting with the group, and the functional group capable of reacting with the epoxy group and the epoxy group in the epoxy compound can react in a well-balanced manner.

Further, the ratio of the content of the epoxy compound (c) to the total amount of the polyurethane (a) and the epoxy compound (c) in the curable composition of the present embodiment is 1% by mass or more and 60% by mass or less. It is more preferably 2% by mass or more and 50% by mass or less, further preferably 3% by mass or more and 40% by mass or less. That is, the ratio of the content of the polyurethane (a) to the total amount of the polyurethane (a) and the epoxy compound (c) in the curable composition of the present embodiment is preferably 40% by mass or more and 99% by mass or less. Is more preferably 50% by mass or more and 98% by mass or less, further preferably 60% by mass or more and 97% by mass or less.

When the ratio of the content of the epoxy compound (c) to the total amount of the polyurethane (a) and the epoxy compound (c) is 1% by mass or more and 60% by mass or less, the solvent resistance of the overcoat film described later is excellent and Thus, it is possible to balance the low warpage property of the flexible wiring board, which will be described later, covered with the overcoat film and the wire disconnection suppression property.

(3) Fine particles (d)
At least one kind of fine particles (d) selected from the group consisting of inorganic fine particles and organic fine particles may be added to the curable composition of the present embodiment.
Examples of the inorganic fine particles include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), zirconia (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ). , Barium titanate (BaO.TiO ₂ ), barium carbonate (BaCO ₃ ), lead titanate (PbO.TiO ₂ ), lead zirconate titanate (PZT), zirconate titanate, lead lanthanum (PLZT), gallium oxide (Ga ₂ O _3), spinel _{_{(MgO · Al 2 O 3)}} , mullite _{_{_{(3Al 2 O 3 · 2SiO 2}}} ), cordierite _{_{(2MgO · 2Al 2 O 3 ·}} 5SiO 2), talc (3MgO · 4SiO ₂ · H ₂ O), aluminum titanate _{_{_{(TiO 2 -Al 2 O 3)}}} , yttria-containing zirconia _{_{_{(Y 2 O 3 -ZrO 2)}}} , barium silicate (BaO · 8SiO _2), boron nitride (BN), calcium carbonate (CaCO ₃ ), calcium sulfate (CaSO ₄ ), zinc oxide (ZnO), magnesium titanate (MgO·TiO ₂ ), barium sulfate (BaSO ₄ ), organic bentonite, carbon (C), hydrotalcite, and the like. May be used alone or in combination of two or more.

The organic fine particles are preferably fine particles of a heat resistant resin having an amide bond, an imide bond, an ester bond or an ether bond. Examples of these resins include a polyimide resin or a precursor thereof, a polyamideimide resin or a precursor thereof, or a polyamide resin from the viewpoint of heat resistance and mechanical properties.
Among these fine particles, silica fine particles and hydrotalcite fine particles are preferable, and the curable composition of the present embodiment preferably contains at least one selected from silica fine particles and hydrotalcite fine particles.

The silica fine particles used in the curable composition of the present embodiment are powdery, and may be silica fine particles having a coating on the surface or silica fine particles chemically surface-treated with an organic compound.
The silica fine particles used in the curable composition of the present embodiment is not particularly limited as long as it is dispersed in the curable composition to form a paste, for example, from Nippon Aerosil Co., Ltd. The offered Aerosil (brand name) etc. can be mentioned. Silica fine particles represented by Aerosil (trade name) are sometimes used to impart printability to the curable composition during screen printing, and in that case, they are used for the purpose of imparting thixotropy. ..

The hydrotalcite fine particles used in the curable composition of the present embodiment is a kind of naturally occurring clay mineral represented by Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O, and has a layered structure. It is an inorganic compound. Further, hydrotalcite can be obtained by synthesis, and for example, Mg _1-x Al _x (OH) ₂ (CO ₃ ) _x/2 ·mH ₂ O can be obtained by synthesis. That is, hydrotalcite is a Mg/Al-based layered compound, and anions such as chloride ions (Cl ⁻ ) and/or sulfate ions (SO ₄ ⁻ ) are immobilized by ion exchange with carbonic acid groups between layers. it can. By using this function, chloride ions (Cl ⁻ ) and sulfate ions (SO ₄ ⁻ ) that cause migration of copper and tin can be captured, and the insulation reliability of the cured product can be improved.

Examples of commercial products of hydrotalcite include Sakai Chemical Co., Ltd.'s STABACE HT-1, STAVIACE HT-7, STABACE HT-P, and Kyowa Chemical Co., Ltd.'s DHT-4A, DHT-4A2, DHT-4C, etc. Are listed.
The mass average particle diameter of these inorganic fine particles and organic fine particles is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm.

The content of the fine particles (d) in the curable composition of the present embodiment is the total amount of the curable composition containing the polyurethane (a), the solvent (b), the epoxy compound (c), and the fine particles (d). On the other hand, it is preferably 0.1% by mass or more and 60% by mass or less, more preferably 0.3% by mass or more and 55% by mass or less, and 0.5% by mass or more and 40% by mass or less. More preferable.

When the content of the fine particles (d) in the curable composition of the present embodiment is within the above range, the curable composition has a good viscosity for printing by the screen printing method, and The spread of the curable composition after printing due to bleeding does not become so large. As a result, it is less likely that the printed area of the curable composition actually printed is larger than the area where the curable composition is desired to be applied (that is, the shape of the printing plate), which is preferable.

(4) Curing accelerator A curing accelerator may be added to the curable composition of the present embodiment. The type of the curing accelerator is not particularly limited as long as it is a compound that promotes the reaction between the carboxy group of the polyurethane (a) and the epoxy group of the epoxy compound (c), and examples thereof include the following compounds. To be

That is, examples of the curing accelerator include melamine, acetoguanamine, benzoguanamine, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, 2,4-methacryloyloxyethyl-s-triazine and 2,4-diamino. Examples thereof include triazine compounds such as -6-vinyl-s-triazine and 2,4-diamino-6-vinyl-s-triazine/isocyanuric acid adduct.

Examples of curing accelerators include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methyl. Imidazole, 2-phenyl-4-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-aminoethyl-2-ethyl-4-methylimidazole, 1-amino Ethyl-2-methylimidazole, 1-(cyanoethylaminoethyl)-2-methylimidazole, N-[2-(2-methyl-1-imidazolyl)ethyl]urea, 1-cyanoethyl-2-undecylimidazole, 1- Cyanoethyl-2-methylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazo Lithium trimellitate, 2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazine, 2,4-diamino-6-[2′-undecylimidazolyl-(1 ')]-Ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 1-dodecyl-2-methyl- 3-benzylimidazolium chloride, N,N'-bis(2-methyl-1-imidazolylethyl)urea, N,N'-bis(2-methyl-1-imidazolylethyl)adipamide, 2-phenyl-4-methyl -5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-methylimidazole-isocyanuric acid adduct, 2-phenylimidazole-isocyanuric acid adduct, 2,4-diamino-6-[2' -Methylimidazolyl-(1')]-ethyl-s-triazine/isocyanuric acid adduct, 2-methyl-4-formylimidazole, 2-ethyl-4-methyl-5-formylimidazole, 2-phenyl-4 -Methylformylimidazole, 1-benzyl-2-phenylimidazole, 1,2-dimethylimidazole, 1-(2-hydroxyethyl)imidazole, vinylimidazole, 1-methylimidazole, 1-allylimidazole, 2-ethylimidazole, 2-buchi Ruimidazole, 2-butyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-benzyl-2-phenylimidazole hydrobromide, 1-dodecyl-2 Examples include imidazole compounds such as -methyl-3-benzylimidazolium chloride.

Further, examples of the curing accelerator include cycloamidine compounds such as diazabicycloalkene and salts thereof and derivatives thereof. Examples of the diazabicycloalkene include 1,5-diazabicyclo(4.3.0)nonene-5 and 1,8-diazabicyclo(5.4.0)undecene-7.

Further, examples of the curing accelerator include triphenylphosphine, diphenyl(p-tolyl)phosphine, tris(alkylphenyl)phosphine, tris(alkoxyphenyl)phosphine, tris(alkylalkoxyphenyl)phosphine, tris(dialkylphenyl). Phosphine, tris(trialkylphenyl)phosphine, tris(tetraalkylphenyl)phosphine, tris(dialkoxyphenyl)phosphine, tris(trialkoxyphenyl)phosphine, tris(tetraalkoxyphenyl)phosphine, trialkylphosphine, dialkylarylphosphine, Examples include organic phosphine compounds such as alkyldiarylphosphine.

Further, examples of the curing accelerator include triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol, and other tertiary amino group-containing compounds, and dicyandiazide.
These curing accelerators may be used alone or in combination of two or more.

Among these curing accelerators, melamine, an imidazole compound, a cycloamidine compound and a derivative thereof, a phosphine compound, and a tertiary compound are considered in consideration of both the curing acceleration action and the electrical insulation performance of the cured product of the present embodiment described later. Amino group-containing compounds are preferable, and melamine, 1,5-diazabicyclo(4.3.0)nonene-5 and salts thereof, 1,8-diazabicyclo(5.4.0)undecene-7 and salts thereof are more preferable.

The content of the curing accelerator in the curable composition of the present embodiment is not particularly limited as long as the curing acceleration effect is exhibited, but the curability of the curable composition of the present embodiment and the book described below. From the viewpoint of electrical insulation properties and water resistance of the cured product of the embodiment, the total amount of the polyurethane (a) and the epoxy compound (c) is 100 parts by mass, and the curing accelerator is in a range of 0.05 parts by mass or more and 5 parts by mass or less. It is preferable to mix within the range of 0.1 to 3 parts by mass.
If the content of the curing accelerator in the curable composition of the present embodiment is within the above range, the curable composition of the present embodiment can be cured in a short time, and the curing of the present embodiment described later. Good electrical insulation properties and water resistance.

(5) Other additives Various additives may be added to the curable composition of the present embodiment in addition to the fine particles (d) and the curing accelerator. The additives that can be added to the curable composition of this embodiment will be described below.
When the curable composition of the present embodiment is cured, a cured product having good electric insulation properties can be obtained. Therefore, the curable composition of the present embodiment can be used, for example, as a resist ink application for insulation protection of wiring. It can be used as a composition. When the curable composition of the present embodiment is used as a composition for use as a resist ink for insulation protection of wiring (that is, an overcoat agent for flexible wiring boards), it prevents or suppresses the occurrence of bubbles during printing. An antifoaming agent may be added for the purpose.

The type of the defoaming agent is such that, when the curable composition of the present embodiment is printed and applied on the surface of the flexible substrate during the production of the flexible wiring board, the generation of bubbles can be prevented or suppressed. Although not particularly limited, for example, the following defoaming agents are listed.
That is, as an example of the defoaming agent, BYK-077 (manufactured by Big Chemie Japan Co., Ltd.), SN Deformer 470 (manufactured by San Nopco Co., Ltd.), TSA750S (manufactured by Momentive Performance Materials Co., Ltd.), silicone oil SH-203 ( Silicone-based defoaming agents such as Toray Dow Corning Co., Ltd., Dappo SN-348 (San Nopco Co., Ltd.), Dappo SN-354 (San Nopco Co., Ltd.), Dappo SN-368 (San Nopco Co., Ltd.), Acrylic polymer defoaming agents such as Disparlon 230HF (Kusumoto Kasei Co., Ltd.), Surfynol DF-110D (Nisshin Chemical Industry Co., Ltd.), Surfynol DF-37 (Nisshin Chemical Industry Co., Ltd.), etc. Examples thereof include acetylene diol-based defoaming agents and fluorine-containing silicone-based defoaming agents such as FA-630.

The content of the defoaming agent in the curable composition of the present embodiment is not particularly limited, but the total amount of polyurethane (a), solvent (b), epoxy compound (c), and fine particles (d). Is preferably 100 parts by mass, and the antifoaming agent is preferably blended in the range of 0.01 parts by mass or more and 5 parts by mass or less, and more preferably in the range of 0.05 parts by mass or more and 4 parts by mass or less. Further, it is more preferable to mix within a range of 0.1 part by mass or more and 3 parts by mass or less.

Further, the curable composition of the present embodiment, if necessary, a surfactant such as a leveling agent, phthalocyanine blue, phthalocyanine green, iodin green, disazo yellow, crystal violet, carbon black, naphthalene black. A colorant such as can be added.

When it is necessary to suppress oxidative deterioration of the polyurethane (a) and discoloration during heating, antioxidants such as phenol-based antioxidants, phosphite-based antioxidants and thioether-based antioxidants should be used. It is preferably added to the curable composition of the embodiment.
Furthermore, a flame retardant or a lubricant may be added to the curable composition of the present embodiment, if necessary.

In the curable composition of the present embodiment, some or all of the components to be blended (that is, polyurethane (a), solvent (b), epoxy compound (c), fine particles (d), etc.) are roll mills, bead mills, etc. It can be obtained by uniformly kneading and mixing. When some of the components to be mixed are mixed, the remaining components can be mixed when the curable composition of the present embodiment is actually used.

<Viscosity of curable composition>
The viscosity of the curable composition of the present embodiment at 25° C. is preferably 10,000 mPa·s or more and 100000 mPa·s or less, more preferably 20,000 mPa·s or more and 60,000 mPa·s or less.
In addition, in the present specification, the viscosity of the curable composition of the present embodiment at 25° C. is measured by using a cone/plate type viscometer (manufactured by Brookfield, model DV-II+Pro, spindle model CPE-52). The viscosity was measured 7 minutes after the start of rotation under the condition of a rotation speed of 10 rpm.

<Thixotropic index of curable composition>
When the curable composition of the present embodiment is used as a composition for resist ink application for wiring insulation protection (that is, an overcoating agent for flexible wiring boards), the printability of the curable composition of the present embodiment is improved. In order to make it good, it is preferable to set the thixotropy index of the curable composition of the present embodiment within a certain range.

When using the curable composition of the present embodiment as an overcoating agent for a flexible wiring board, in order to improve the printability of the curable composition of the present embodiment, the thixotropy index of the curable composition of the present embodiment. Is preferably 1.1 or more, more preferably 1.1 or more and 3.0 or less, and further preferably 1.1 or more and 2.5 or less.

When the curable composition of this embodiment is used as an overcoating agent for flexible wiring boards, if the thixotropy index of the curable composition of this embodiment is in the range of 1.1 or more and 3.0 or less, printing Since it is possible to maintain the curable composition of the present embodiment in the form of a film having a constant thickness, it is easy to maintain a printing pattern, and at the same time, a printed film of the curable composition of the present embodiment is formed. The defoaming property is also good.

In addition, in the present specification, the thixotropy index of the curable composition of the present embodiment is a ratio of the viscosity measured at a rotation speed of 1 rpm at 25° C. and the viscosity measured at a rotation speed of 10 rpm at 25° C. ([rotation speed 1 rpm In the case of []/[viscosity in the case of a rotation speed of 10 rpm]]. These viscosities can be measured using a cone/plate viscometer (Model DV-III+Pro, spindle model CPE-52, manufactured by Brookfield).

As described above, the curable composition of the present embodiment has good handleability and low threading property when the curable composition is applied to a substrate such as a flexible substrate by a printing method or the like. In addition, it has excellent defoaming properties. In addition, the curable composition of the present embodiment is unlikely to cause shrinkage during curing.

III. Hardened|cured material and its manufacturing method The hardened|cured material of this embodiment is hardened|cured material obtained by hardening the curable composition of this embodiment. The method for curing the curable composition of the present embodiment is not particularly limited, and the curable composition can be cured by heat or active energy rays (for example, ultraviolet rays, electron beams, X rays). Therefore, a polymerization initiator such as a heat radical generator or a photo radical generator may be added to the curable composition of the present embodiment.

The cured product of the present embodiment can be manufactured with excellent workability and productivity because the curable composition of the present embodiment has low stringiness and excellent defoaming property. Further, the cured product of the present embodiment has good flexibility and moisture resistance, and also has excellent long-term insulation reliability. Furthermore, the cured product of this embodiment has good adhesion to a substrate such as a flexible substrate. Furthermore, the cured product of the present embodiment is unlikely to cause a tack phenomenon on the surface.

IV. Overcoat Film and Method for Producing the Same The overcoat film of the present embodiment contains the cured product of the present embodiment, and can be produced by curing the curable composition of the present embodiment. More specifically, the overcoat film of the present embodiment is a film obtained by arranging the curable composition of the present embodiment in a film shape on the portion of the surface of the flexible substrate on which the wiring is formed, where the wiring is formed. It can be produced by curing the curable composition in the form of a film by heating to give a cured product in the form of a film.

The specific method for producing the overcoat film of the present embodiment is not particularly limited, but one example is shown below. That is, the method for producing an overcoat film according to the present embodiment includes a printing step of printing the curable composition of the present embodiment on the surface of a flexible substrate to obtain a printed film, and a printing film obtained in the printing step at 100° C. And a curing step of obtaining an overcoat film by heat curing in an atmosphere at 170° C. or lower. A solvent removing step may be provided between the printing step and the curing step. The solvent removal process is a printing process in which the solvent is removed by evaporating a part or all of the solvent in the printing film by placing the printing film obtained in the printing process in an atmosphere of 40° C. or higher and 100° C. or lower. This is the step of obtaining a film.
The method for printing the curable composition in the printing step is not particularly limited, and for example, the curable composition of the present embodiment is applied to a flexible substrate by a screen printing method, a roll coater method, a spray method, a curtain coater method, or the like. The printed film can be obtained.

The solvent removal step is an operation that is performed as necessary, and the curing step may be performed immediately after the printing step, and the curing reaction and solvent removal may be performed simultaneously in the curing step. When the solvent removal step is performed, the temperature is preferably 40° C. or higher and 100° C. or lower, and is 60° C. or higher and 100° C. or lower, in consideration of the evaporation rate of the solvent and a rapid shift to the heat curing operation. It is more preferable that the temperature is 70° C. or higher and 90° C. or lower. The time for evaporating the solvent in the curing step and the solvent removing step is not particularly limited, but it is preferably 10 minutes or more and 120 minutes or less, and more preferably 20 minutes or more and 100 minutes or less.

The thermosetting temperature in the curing step is preferably 100° C. or higher and 170° C. or lower, more preferably 105° C. or higher and 160° C. or lower, and further preferably 110° C. or higher and 150° C. or lower. The time of heat curing performed in the curing step is not particularly limited, but is preferably 20 minutes or more and 4 hours or less, and more preferably 30 minutes or more and 2 hours or less.

The overcoat film of the present embodiment thus obtained can be produced with excellent workability and productivity because the curable composition of the present embodiment has low stringiness and excellent defoaming property. It is possible. Further, the overcoat film of this embodiment is excellent in flexibility, flexibility, adhesion to a flexible substrate, and long-term insulation reliability. Furthermore, the overcoat film of the present embodiment is unlikely to cause a tack phenomenon on the surface. As a result, the flexible wiring board on which the overcoat film is formed has excellent performance described later.

V. Flexible Wiring Board and Manufacturing Method Thereof The curable composition of the present embodiment can be used, for example, as a resist ink for insulation protection of wiring, and the cured product of the present embodiment can be used as an insulation protection film. In particular, by coating all or part of the wiring of a flexible wiring board such as a chip-on-film, the cured product of this embodiment can be used as an insulating protective film for wiring.

The flexible wiring board of this embodiment can be manufactured from the curable composition of this embodiment and a flexible substrate. More specifically, the flexible wiring board of the present embodiment is a film after the curable composition of the present embodiment is arranged in a film shape on the portion of the surface of the flexible substrate on which the wiring is formed, in which the wiring is formed. It can be produced by curing the curable composition in the form of a strip to form an overcoat film. The wiring covered with the overcoat film is preferably tin-plated copper wiring in consideration of oxidation prevention and economical aspects of the wiring.

The specific method for manufacturing the flexible wiring board of the present embodiment is not particularly limited, but an example is shown below. That is, in the method for manufacturing a flexible wiring board of the present embodiment, the curable composition of the present embodiment is printed on the surface of the flexible substrate to obtain a printed film, and the printed film obtained in the printing step is heated to 100° C. And a curing step of obtaining a protective film (overcoat film) of the flexible wiring board by heat curing in an atmosphere of 170° C. or less. A solvent removing step may be provided between the printing step and the curing step. The solvent removal process is a printing process in which the solvent is removed by evaporating a part or all of the solvent in the printing film by placing the printing film obtained in the printing process in an atmosphere of 40° C. or higher and 100° C. or lower. This is the step of obtaining a film.
The method for printing the curable composition in the printing step is not particularly limited, and for example, the curable composition of the present embodiment is applied to a flexible substrate by a screen printing method, a roll coater method, a spray method, a curtain coater method, or the like. The printed film can be obtained.

The solvent removal step is an operation that is performed as necessary, and the curing step may be performed immediately after the printing step, and the curing reaction and solvent removal may be performed simultaneously in the curing step. When the solvent removal step is performed, the temperature is preferably 40° C. or higher and 150° C. or lower, and is 60° C. or higher and 100° C. or lower, in consideration of the evaporation rate of the solvent and a rapid shift to the operation of heat curing. It is more preferable that the temperature is 70° C. or higher and 90° C. or lower. The time for evaporating the solvent in the curing step and the solvent removing step is not particularly limited, but it is preferably 10 minutes or more and 120 minutes or less, and more preferably 20 minutes or more and 100 minutes or less.

The temperature of thermosetting in the curing step is preferably 100° C. or higher and 170° C. or lower, and 105° C. or higher and 160° C. or lower, from the viewpoint of preventing diffusion of the plated layer and obtaining low warpage and flexibility suitable as a protective film. Is more preferable, and it is further preferable that the temperature is 110° C. or higher and 150° C. or lower. The time of heat curing performed in the curing step is not particularly limited, but is preferably 10 minutes or more and 150 minutes or less, and more preferably 15 minutes or more and 120 minutes or less.
In addition, when performing a solvent removal process and a hardening process simultaneously, it can perform, for example at 120 to 150 degreeC.

The flexible wiring board of this embodiment thus obtained can be manufactured with excellent workability and productivity because the curable composition of this embodiment has low stringiness and excellent defoaming properties. It is possible. Moreover, since the flexibility and flexibility of the overcoat film are excellent, the flexible wiring board of the present embodiment is also excellent in flexibility and flexibility, and even if the flexible wiring board is shaken, the wiring is disconnected. Is less likely to occur (excellent in suppressing wire disconnection). Therefore, the flexible wiring board of the present embodiment hardly causes cracks, and is suitable for a flexible printed wiring board used for a technology such as chip-on-film (COF).

Furthermore, since the curable composition of the present embodiment is less likely to shrink during curing, the flexible wiring board of the present embodiment has less warpage. Therefore, in the process of mounting the IC chip on the flexible wiring board of the present embodiment, it is easy to align the mounting position of the IC chip. Furthermore, the flexible wiring board of this embodiment has excellent adhesion between the overcoat film and the flexible substrate. Furthermore, since the long-term insulation reliability of the overcoat film is excellent, the flexible wiring board of this embodiment is also excellent in long-term insulation reliability. Furthermore, in the flexible wiring board of the present embodiment, the tack phenomenon is unlikely to occur on the surface of the overcoat film.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
<Synthesis of polyester diol>
(Reference synthesis example 1)
983.5 g (6.74 mol) of phthalic anhydride and 879.2 g (7.44 mol) of phthalic anhydride were put into a reaction vessel equipped with a stirrer, a thermometer and a condenser with a distillation device, and an oil bath was added. The internal temperature of the reaction vessel was raised to 140° C. by using and stirring was continued for 4 hours. Then, with continued stirring, 1.74 g of mono-n-butyltin oxide was added.

Then, while gradually raising the internal temperature of the reaction container, the pressure inside the reaction container was gradually reduced by a vacuum pump, and water was removed to the outside of the reaction container by vacuum distillation. Finally, the internal temperature was raised to 220° C. and the pressure was reduced to 133.32 Pa. After 15 hours, it was confirmed that water was not completely distilled off, and the reaction was terminated.
When the hydroxyl value of the obtained polyester diol (hereinafter referred to as “polyester diol (α)”) was measured, the hydroxyl value was 53.1 mgKOH/g.

(Measurement of reaction rate constant)
The reaction rate constant of the reaction for forming a urethane bond from the isocyanato group of the isocyanate compound and the hydroxy group of the polyol compound was measured. However, the reaction rate constant of the model compound was measured instead of the reaction rate constant of the polymerization reaction. That is, the reaction rate constant of the reaction between cyclohexyl isocyanate (manufactured by Tokyo Kasei Co., Ltd.), which is a monoisocyanate compound, and various polyol compounds is measured, and the urethane bond is determined from the isocyanato group of the polyisocyanate compound and the hydroxy group of the polyol compound. Was used as the reaction rate constant of the polymerization reaction for forming.

The solvent used in the reaction between cyclohexyl isocyanate and the polyol compound was γ-butyrolactone, which was the same as the solvent used for polyurethane synthesis, and the reaction substrate concentration was the same as that used during polyurethane synthesis. Then, the reaction solution during the reaction was sequentially analyzed to calculate the reaction conversion rate, and the reaction rate constant was calculated therefrom. The analysis method of the reaction solution is shown below.

A part of the reaction solution (about 0.05 mL) was sampled using a Pasteur pipette under an inert atmosphere such as nitrogen, and diluted with deuterated chloroform (Aldrich) as an NMR measurement solvent to stop the reaction. Then, using a nuclear magnetic resonance spectrometer (JNM-AL400 manufactured by JEOL Ltd., frequency 400 MHz), ¹ H-NMR analysis of the diluted reaction solution was performed.

^{In 1} H-NMR analysis, methine hydrogen contained in the carbon linked to the isocyanato group of cyclohexyl isocyanate is detected, and the reaction conversion is performed by the integrated intensity ratio of the signal derived from the raw material proton and the signal derived from the product proton. The rate was calculated. Then, using the following formula, the reaction rate constant was calculated from the reaction conversion rate for each elapsed time.
1/C-1/C ₀ =K·t

That is, the concentration of the polyol compound for each elapsed time is calculated from the reaction conversion rate for each elapsed time, and the calculated value for the concentration of the polyol compound is plotted on a graph with the reaction elapsed time t as the X axis and 1/C as the Y axis. To do. Then, the slope of the straight line drawn in the graph becomes the reaction rate constant K.
In the above formula, C ₀ is the initial concentration of the polyol compound, C is the concentration of the polyol compound, t is the reaction elapsed time, and K is the reaction rate constant.

As a result of calculation by the above method, the reaction rate constants of various polyol compounds were as follows.
The reaction rate constant K1 of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (manufactured by Osaka Gas Chemicals Co., Ltd., trade name BPEF) is 250 at a reaction temperature of 115° C. and is 145° C. at a reaction temperature of 145° C. It is 1000. The aromatic ring concentration is 9.12 mmol/g.

The reaction rate constant K2 of polyester diol P-2030 (polyester polyol consisting of isophthalic acid and 3-methyl-1,5-pentanediol) manufactured by Kuraray Co., Ltd. is 500 at a reaction temperature of 115° C. and at a reaction temperature of 145° C. 2000. The aromatic ring concentration is 3.52 mmol/g.
The reaction rate constant K2 of polyester diol P-2050 (polyester polyol composed of sebacic acid and 3-methyl-1,5-pentanediol) manufactured by Kuraray Co., Ltd. is 550 at a reaction temperature of 115° C. and at a reaction temperature of 145° C. 2200. The aromatic ring concentration is 0 mmol/g.

The reaction rate constant K2 of polycarbonate diol (trade name: Duranol T5652) manufactured by Asahi Kasei Co., Ltd. is 550 at a reaction temperature of 115° C. and 3100 at a reaction temperature of 145° C. The aromatic ring concentration is 0 mmol/g.
The reaction rate constant K2 of the polyester diol (α) of Reference Synthesis Example 1 is 480 at a reaction temperature of 115° C. and 2200 at a reaction temperature of 145° C. The aromatic ring concentration is 2.00 mmol/g.

The reaction rate constant K2 of the polyester diol (β) of Reference Synthesis Example 2 is 460 at a reaction temperature of 115° C. and 1800 at a reaction temperature of 145° C. The aromatic ring concentration is 2.00 mmol/g.
The reaction rate constant K3 of 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) is 1.6 at a reaction temperature of 115° C. and 7.2 at a reaction temperature of 145° C. The aromatic ring concentration is 0 mmol/g.
It can be seen that 2,2-dimethylolpropionic acid having a carboxy group and a diol structure has a smaller reaction rate constant and a lower reaction rate than the other five diols.

<Synthesis of polyurethane>
(Practical Synthesis Example 1: Method of Synthesizing Polyurethane by Controlling Narrow Molecular Weight Distribution)
In a reaction vessel equipped with a stirrer, a thermometer, and a condenser, the first polyol compound H1 was 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (Osaka Gas Chemical Co., Ltd., trade name BPEF ) 10.7 g, polyester diol P-2030 (manufactured by Kuraray Co., Ltd.) which is the second polyol compound H2, and 2,2-dimethylolpropionic acid (Tokyo Kasei Kogyo Co., Ltd.) which is the third polyol compound H3 1.62 g (produced by KK) and 137.7 g of γ-butyrolactone as a solvent were charged and heated to 100° C. to dissolve all the raw materials.

After the temperature of the reaction solution was lowered to 90° C., 28.31 g of polyisocyanate compound I, methylenebis(4-cyclohexylisocyanate) (manufactured by Sumika Bayer Urethane Co., Ltd., trade name Desmodur-W) was added with a dropping funnel at 30 It was dripped over a period of minutes. After the reaction was carried out at 145° C. to 150° C. for 1 hour, 4.86 g of 2,2-dimethylolpropionic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was additionally charged. The weight average molecular weight of the polyurethane (that is, the intermediate polymer) at the time of additionally adding 2,2-dimethylolpropionic acid was 7,500.

The total amount of isocyanato groups F _I in the total amount of polyisocyanate compound I used in the production of polyurethane, the total number of hydroxy groups F _H1 in the total amount of first polyol compound H1, and the total amount of second polyol compound H2 have The total number F _{H2 of} hydroxy groups, the total number Fa _{H3 of} hydroxy groups possessed from the initial amount of the total amount of the third polyol compound _H3 , and the additional amount of the total amount of the third polyol compound H3. The ratio of the total number Fb _H3 of hydroxy groups possessed by each is as follows.

F _H1 /F _I =0.22
F _H2 /F _I =0.29
Fa _H3 /F _I =0.11
(F _H1 +F _H2 )/F _I =0.51
(F _H1 +F _H2 +Fa _H3 )/F _I =0.62
Fb _H3 /F _I =0.33
(F _H1 +F _H2 +Fa _H3 +Fb _H3 )/F _I =0.95

After the reaction was continued at 145°C to 150°C, it was confirmed by infrared spectroscopy (IR) that the absorption derived from the C=O stretching vibration of the isocyanato group was almost not observed, and methyl ethyl oxime (Ube Industries, Ltd. 1.5 g (manufactured by the company) was added dropwise to the reaction solution, and the reaction was further performed at 80° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as “polyurethane solution A1”) was obtained.

The viscosity of the obtained polyurethane solution A1 was 100,000 mPa·s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group contained in the polyurethane solution A1 (hereinafter referred to as “polyurethane AU1”) was 12,000 and the weight average molecular weight (Mw) was 73,000. The acid value of polyurethane AU1 was 25.0 mgKOH/g. The solid content concentration of the polyurethane solution A1 was 43.4% by mass.

(Comparative Synthesis Example 1: Method of synthesizing polyurethane without controlling molecular weight distribution)
In a reaction vessel equipped with a stirrer, a thermometer, and a condenser, the first polyol compound H1 was 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene (Osaka Gas Chemical Co., Ltd., trade name BPEF ) 10.7 g, polyester diol P-2030 (manufactured by Kuraray Co., Ltd.) which is the second polyol compound H2, and 2,2-dimethylolpropionic acid (Tokyo Kasei Kogyo Co., Ltd.) which is the third polyol compound H3 6.48 g (produced by Co., Ltd.) and 137.7 g of γ-butyrolactone as a solvent were charged and heated to 100° C. to dissolve all the raw materials.

After the temperature of the reaction solution was lowered to 90° C., 28.31 g of polyisocyanate compound I, methylenebis(4-cyclohexylisocyanate) (manufactured by Sumika Bayer Urethane Co., Ltd., trade name Desmodur-W) was added with a dropping funnel at 30 It was dripped over a period of minutes.
The total amount of isocyanato groups F _I in the total amount of polyisocyanate compound I used in the production of polyurethane, the total number of hydroxy groups F _H1 in the total amount of first polyol compound H1, and the total amount of second polyol compound H2 have The ratio of the total number F _{H2 of} hydroxy groups and the total number F _H3 of hydroxy groups contained in the total amount of the third polyol compound H3 is as follows.

F _H1 /F _I =0.22
F _H2 /F _I =0.29
F _H3 /F _I =0.44
(F _H1 +F _H2 )/F _I =0.51
(F _H1 +F _H2 +F _H3 )/F _I =0.95

After carrying out the reaction at 120° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that absorption due to C═O stretching vibration of the isocyanato group was almost not observed, and then ethanol (Wako Pure Chemical Industries, Ltd.) 1.5 g) was added dropwise to the reaction solution, and the mixture was further reacted at 80° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as “polyurethane solution B1”) was obtained.

The viscosity of the obtained polyurethane solution B1 was 120,000 mPa·s. The number average molecular weight (Mn) of the polyurethane having a carboxy group contained in the polyurethane solution B1 (hereinafter referred to as “polyurethane BU1”) was 14,000 and the weight average molecular weight (Mw) was 104,000. The acid value of polyurethane BU1 was 25.0 mgKOH/g. The solid content concentration of the polyurethane solution B1 was 39.6% by mass.

The GPC charts of polyurethane AU1 and polyurethane BU1 are shown in FIG. Polyurethane AU1 has a lower molecular weight dispersity in the high molecular weight region with a shorter retention time than that of polyurethane BU1, and therefore it can be seen that polymer chains exhibiting a narrow molecular weight distribution are obtained.
As described above, the molecular weight distribution of the generated polyurethane can be controlled by performing the polymerization reaction of the low-reactivity third polyol compound H3 at once or in a plurality of times. When polyurethane having a narrow molecular weight distribution is used, it is possible to obtain a curable composition having a low stringiness when applied to a substrate such as a flexible substrate and having good defoaming property.

(Practical Synthesis Examples 2 to 7 and Comparative Synthesis Examples 2 to 7)
The type of the second polyol compound H2 as a raw material was variously changed as shown in Tables 1 and 2, and the reaction was carried out under the same conditions as those in Example Synthesis 1 or Comparative Synthesis Example 1 to obtain a polyurethane solution (polyurethanes AU2 to AU7). , Polyurethanes BU2 to BU7) were obtained. The results are shown in Tables 1 and 2.

(Measurement of acid value)
The method for measuring the acid value of the synthesized polyurethane will be described. The solvent in the polyurethane solution was distilled off under reduced pressure with heating to obtain polyurethane, and the acid value was measured according to the potentiometric titration method specified in JIS K0070. For measuring the acid value by the potentiometric titration method, for example, an automatic potentiometric titrator AT-510 manufactured by Kyoto Electronics Manufacturing Co., Ltd. and a composite glass electrode C-173 can be used.

(Measurement of number average molecular weight and weight average molecular weight of polyurethane)
The number average molecular weight and weight average molecular weight of polyurethane are the polystyrene equivalent number average molecular weight and weight average molecular weight measured by GPC, and the GPC measurement conditions are as follows.
Device name: HPLC unit HSS-2000 manufactured by JASCO Corporation
Column: Shodex column LF-804
Mobile phase: Tetrahydrofuran Flow rate: 1.0 mL/min
Detector: RI-2031Plus manufactured by JASCO Corporation
Temperature: 40.0°C
Sample volume: Sample loop 100 μL
Sample concentration: approx. 0.1% by mass

(Measurement of viscosity of polyurethane solution)
The viscosity of the polyurethane solution was measured using a cone/plate type viscometer (Model DV-II+Pro, spindle model CPE-52, manufactured by Brookfield) at a temperature of 25.0° C. and a rotation speed of 5 rpm. The measured value is the viscosity measured 7 minutes after the start of rotation of the spindle. Further, in measuring the viscosity, about 0.8 g of a polyurethane solution was used.

<Manufacture of base compound>
160.0 parts by mass of a polyurethane solution A1 having a solid content concentration adjusted to 40% by mass by adding γ-butyrolactone, and 6.3 parts by mass of silica powder (manufactured by Nippon Aerosil Co., Ltd., trade name Aerosil R-974). 0.72 parts by mass of melamine (manufactured by Nissan Chemical Industries, Ltd.), which is an accelerator, and 8.4 parts by mass of diethylene glycol diethyl ether were added to a three-roll mill (manufactured by Inoue Co., Ltd., model S-4 3/4×11). ) Was used for mixing. 2.0 parts by mass of an antifoaming agent (manufactured by Momentive Performance Materials Co., Ltd., trade name TSA750S) was added thereto and mixed using a spatula to obtain a base compound C1 (see Table 3). ).
Polyurethane solutions A2 to A7 and B1 to B7 and the above-mentioned other components were mixed in the same manner as the base compound C1 according to the composition shown in Table 3 to prepare the base compounds C2 to C7 and D1 to D7, respectively. Obtained. In addition, the numerical value in Table 3 represents a "mass part."

<Production of curing agent solution>
In a container equipped with a stirrer, a thermometer and a condenser, 16.85 parts by mass of an epoxy compound represented by the above formula (5) (manufactured by Mitsubishi Chemical Corporation, grade name JER604, epoxy equivalent 120 g/eqv) and diethylene glycol diethyl ether. After adding 18.25 parts by mass and raising the inner temperature of the container to 40° C. with stirring, stirring was continued for 30 minutes. After confirming that the epoxy compound was completely dissolved, it was cooled to room temperature to obtain an epoxy compound solution having a concentration of 48% by mass. This epoxy compound solution is referred to as a curing agent solution E.

<Production of curable composition>
90.0 parts by mass of the base compound C1 and 4.0 parts by mass of the curing agent solution E were placed in a plastic container, and 5.0 parts by mass of diethylene glycol diethyl ether and 1.5 parts by mass of diethylene glycol ethyl ether acetate as a solvent were placed therein. Was added. The mixture was stirred at room temperature for 5 minutes using a spatula to obtain a curable composition F1. The viscosity of the curable composition F1 at 25° C. was 37,000 mPa·s.

The viscosity of the curable composition is measured by using a cone/plate type viscometer (Model DV-II+Pro, spindle model CPE-52, manufactured by Brookfield) at a temperature of 25.0° C. and a rotation speed of 10 rpm. did. The measured value is the viscosity measured 7 minutes after the start of rotation of the spindle. Further, in measuring the viscosity, about 0.6 g of the curable composition was used.
Curable compositions F2 to F14 were obtained in the same manner as in the case of the curable composition F1 except that any of the main agent formulations C2 to C7 and D1 to D7 was used in place of the main agent formulation C1. See Table 4). The viscosities of the curable compositions F2 to F14 at 25° C. are as shown in Table 4.

<Evaluation of defoaming property of curable composition>
Next, the defoaming properties of the curable compositions F1 to F14 during printing were evaluated. The evaluation method will be described below.
A screen printing plate was placed on a polyimide base material (Kapton (registered trademark) manufactured by Toray-Dupont Co., Ltd.), 15 g of the curable composition was placed on the screen printing plate, and the stage moving time was 0.5 seconds. I made a temporary print. Thereafter, the screen printing plate was transferred onto another polyimide substrate, 15 g of the curable composition was further placed on the screen printing plate, and main printing was performed under the condition that the stage moving time was 0.5 seconds. At this time, the time until the bubbles generated in the curable composition printed on the polyimide substrate disappeared (foaming time) was visually measured.

After the measurement of the defoaming time was completed, the screen printing plate was transferred onto another polyimide substrate and printing was performed in the same manner to measure the defoaming time. By repeating this operation, the defoaming time was measured 9 times in total, and the average value of these was taken as the defoaming time of the curable composition, and the defoaming property of the curable composition was evaluated by the length of the defoaming time. did. The results are shown in Table 4.
The screen printing plate used was a stainless mesh plate having a wire diameter of 60 μm and a mesh number of 150/inch (SUS#150-wire diameter 60).

<Evaluation of stringiness of curable composition>
Next, the stringiness of the curable compositions F1 to F14 during printing was evaluated. The evaluation method will be described below.
When printing the evaluation of the above defoaming property, when moving the stage to separate the screen printing plate from the polyimide substrate, between the curable composition and the screen printing plate printed on the polyimide substrate, fibrous It was observed whether or not the stringing phenomenon in which the curable composition of No. 1 remained occurred. The main printing is performed 9 times, and the threading property was evaluated by the number of times of printing until the threading phenomenon occurred. The results are shown in Table 4.

<Evaluation of overcoat film and flexible wiring board>
By using the curable compositions F1 to F14, flexible wiring boards (Examples 1 to 7 and Comparative Examples 1 to 7) having an overcoat film are produced, and flexibility, disconnection controllability, warpability, and long-term insulation are obtained. The reliability was evaluated.

(Evaluation of flexibility)
Flexible copper clad laminate (Sumitomo Metal Mining Co., Ltd., grade name: Esperflex, copper thickness 8 μm, polyimide thickness 38 μm) on copper, width 75 mm, length 110 mm, and film thickness after curing Of 15 μm was applied to the curable composition by screen printing. The flexible copper-clad laminate having the curable composition printed thereon was kept at room temperature for 10 minutes and then placed in a hot air circulation dryer at a temperature of 120° C. for 60 minutes to cure the curable composition.

After peeling off the PET film lining the flexible copper-clad laminate, it was cut with a cutter knife to prepare a strip-shaped test piece with a width of 10 mm. The test piece was bent about 180° so that the surface on which the film of the cured product was formed was on the outside, and was compressed for 3 seconds at a pressure of 0.5±0.2 MPa using a compressor. Then, in a state in which the bent portion of the test piece was bent, the film of the cured product was observed by enlarging it 30 times using a microscope, and the presence or absence of cracks was confirmed. The results are shown in Table 5.

(Evaluation of breaking control)
A flexible copper-clad laminate (made by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex US, copper thickness 8 μm, polyimide thickness 38 μm) is etched, and the Japan Electronic Circuits Association (JPCA) standard JPCA- A substrate having a fine comb-shaped pattern described in ET01 (copper wiring width/copper wiring interval=15 μm/15 μm) was used, and the substrate having the fine comb-shaped pattern was tin-plated to manufacture a flexible wiring board.

Next, the curable composition was applied onto this flexible wiring board by screen printing. The thickness of the printed film of the curable composition was such that the thickness of the film of the curable composition on the polyimide surface after drying was 10 μm.
The flexible wiring board thus obtained was placed in a hot air circulation dryer at a temperature of 80° C. for 30 minutes, and then placed in a hot air circulation dryer at a temperature of 120° C. for 120 minutes to cure the flexible wiring board. The film of the volatile composition was cured. Then, using this test piece, an MIT test was performed by the method described in JIS C5016 to evaluate the wire breakage suppressing property of the flexible wiring board. The test conditions of the MIT test are as follows.

Testing machine: MIT tester BE202 manufactured by Tester Sangyo Co., Ltd.
Bending speed: 10 times/min Load: 200g
Bending angle: ±90°
Radius of gripper tip: 0.5 mm
The MIT test was conducted under the above-mentioned test conditions, and the presence or absence of cracks in the wiring was visually observed after every 10 bendings, and the breakage suppressing property was evaluated by the number of times the crack was bent. The results are shown in Table 5.

(Evaluation of warpage)
Screen-printing was performed using a #180 mesh polyester printing plate, and the curable composition was applied onto a polyimide base material (Kapton (registered trademark) 100EN manufactured by Toray-Dupont Co., Ltd., thickness 25 μm).
The thus obtained base material coated with the curable composition was put in a hot air circulation dryer having a temperature of 80° C. for 30 minutes, and then put in a hot air circulation dryer having a temperature of 120° C. for 60 minutes. The coating film of the curable composition formed on the substrate was cured.
The substrate having the cured film was cut with a circle cutter to obtain a substrate having a circular cured film with a diameter of 50 mm. A circular base material having a cured film exhibits a convex or concave warp near the center.

After leaving the circular base material with the cured film at 23°C for 1 hour, place the base material on the flat plate in a convex state. That is, the convex portion near the center of the warped base material is placed downward on the flat plate so that the convex portion of the warped base material contacts the horizontal surface of the flat plate. Then, the distance of the portion farthest from the horizontal plane of the flat plate and the distance of the closest portion in the peripheral portion of the warped substrate were measured, the average value thereof was obtained, and the warpage property was evaluated by this average value. The results are shown in Table 5.

The symbols of the numerical values shown in Table 5 represent the warp direction, and when the base material is left standing in a convex state downward, “+” is given when the cured film is on the upper side of the polyimide base material, and it is the lower side. In the case, "-" was used. And, when the magnitude of the warp is more than −3.0 mm and less than +3.0 mm, the “warp property is good”.

(Evaluation of long-term insulation reliability)
A flexible copper-clad laminate (made by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex US, copper thickness 8 μm, polyimide thickness 38 μm) is etched, and the Japan Electronic Circuits Association (JPCA) standard JPCA- A substrate having a fine comb-shaped pattern described in ET01 (copper wiring width/copper wiring interval=15 μm/15 μm) was used, and the substrate having the fine comb-shaped pattern was tin-plated to manufacture a flexible wiring board.

Next, the curable composition was applied onto this flexible wiring board by screen printing. The thickness of the printed film of the curable composition was such that the thickness of the film of the curable composition on the polyimide surface after drying was 15 μm.
The flexible wiring board thus obtained was placed in a hot air circulation dryer at a temperature of 80° C. for 30 minutes, and then placed in a hot air circulation dryer at a temperature of 120° C. for 120 minutes to cure the flexible wiring board. The film of the volatile composition was cured.

Then, a bias voltage of 60 V was applied to this test piece using a MIGRATION TESTER MODEL MIG-8600 manufactured by IMV, and a steady temperature/humidity test was performed under the conditions of a temperature of 120° C. and a humidity of 85% RH.
The resistance value of the flexible wiring board was measured at the initial stage of the temperature and humidity steady state test, and at 100 hours, 250 hours, and 400 hours after the start. The results are shown in Table 5.

From the results of Table 5, the flexible wiring boards (Examples 1 to 7) having the overcoat film made of the cured products of the curable compositions F1 to F7 were found to be the overcoat film made of the cured products of the curable compositions F8 to F14. It can be seen that the flexible wiring boards (Comparative Examples 1 to 7) having the above-mentioned properties have excellent flexibility, breakage controllability, warpage, and long-term insulation reliability. Therefore, the film formed of the cured product of the curable compositions F1 to F7 is useful as an insulating protective film for a flexible wiring board.

Claims

Polyisocyanate compound I having two or more isocyanato groups in one molecule, a first polyol compound H1 having two or more hydroxy groups in one molecule, and two or more hydroxy groups in one molecule A method for producing a polyurethane by reacting a second polyol compound H2 with a third polyol compound H3 having two or more hydroxy groups in one molecule,
The aromatic ring concentration of the first polyol compound H1 is higher than the aromatic ring concentration of the second polyol compound H2,
The reaction rate constant of the reaction for forming a urethane bond from the isocyanato group of the polyisocyanate compound I and the hydroxy group of the first polyol compound H1 is K1, and the isocyanato group of the polyisocyanate compound I and the second polyol compound H2. K2 is the reaction rate constant of the reaction of forming a urethane bond from the hydroxy group of the above, and the reaction rate constant of the reaction of forming a urethane bond from the isocyanato group of the polyisocyanate compound I and the hydroxy group of the third polyol compound H3 is When K3 is satisfied, both the expression K1/K3>50 and the expression K2/K3>50 are satisfied,
One of the total amount of the polyisocyanate compound I used in the production of the polyurethane, the total amount of the first polyol compound H1, the total amount of the second polyol compound H2, and the total amount of the third polyol compound H3. Part, and mixing, a polymerization reaction for forming a urethane bond from an isocyanato group and a hydroxy group, a first polymerization step for obtaining an intermediate polymer,
The weight average molecular weight of the intermediate polymer is not less than twice the sum of the molecular weights of the polyisocyanate compound I, the first polyol compound H1, the second polyol compound H2, and the third polyol compound H3. Then, the remaining part of the total amount of the third polyol compound H3 used in the production of the polyurethane is added to the intermediate polymer to carry out a polymerization reaction for forming a urethane bond from an isocyanato group and a hydroxy group. A second polymerization step further performed,
A method for producing a polyurethane comprising:
The total number of isocyanato groups in the total amount of the polyisocyanate compound I used in the production of the polyurethane is F I , the total number of hydroxy groups in the total amount of the first polyol compound H1 is F H1 , and the second polyol compound H2 is The total number of hydroxy groups in the total amount of F H2 , the total number of hydroxy groups in the part of the total amount of the third polyol compound H3 in Fa H3 , and the total amount of the third polyol compound H3 in total. When the total number of hydroxy groups contained in the rest is Fb H3 ,
0.4≦(F H1 +F H2 )/F I ≦0.6
0.01≦Fa H3 /F I ≦0.2
0.25≦Fb H3 /F I ≦0.5
0.8≦(F H1 +F H2 +Fa H3 +Fb H3 )/F I ≦1.2
The method for producing a polyurethane according to claim 1, wherein the first polymerization step and the second polymerization step are performed so as to satisfy all of the following four expressions.
When the aromatic ring concentration of the first polyol compound H1 is 5.0 mmol/g or more and 15.0 mmol/g or less and the aromatic ring concentration of the second polyol compound H2 is 0.5 mmol/g or more and 5.0 mmol/g or less. The method for producing a polyurethane according to claim 1 or 2, wherein the aromatic ring concentration of the first polyol compound H1 is higher than the aromatic ring concentration of the second polyol compound H2.
The method for producing a polyurethane according to any one of claims 1 to 3, wherein the first polyol compound H1 is a diol having a fluorene structure.
The method for producing a polyurethane according to claim 4, wherein the diol having a fluorene structure is 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene represented by the following formula (1).
The second polyol compound H2 is a polyester diol represented by the following formula (2), and R 1 in the following formula (2) is independently a divalent organic group having 6 to 14 carbon atoms. And R 2 each independently represents a divalent hydrocarbon group having 3 or more and 9 or less carbon atoms, and n is an integer of 1 or more and 50 or less. Method for producing polyurethane.
7. The third polyol compound H3 is a carboxy group-containing diol represented by the following formula (3), and R 3 in the following formula (3) represents a methyl group or an ethyl group. The method for producing a polyurethane according to the item 1.
The method for producing a polyurethane according to any one of claims 1 to 7, wherein the number average molecular weight of the polyurethane is 3,000 or more and 100,000 or less.
The method for producing a polyurethane according to any one of claims 1 to 8, wherein the acid value of the polyurethane is 10 mgKOH/g or more and 70 mgKOH/g or less.
A polyurethane (a) produced by the method for producing a polyurethane according to any one of claims 1 to 9, a solvent (b), and an epoxy compound (c) having two or more epoxy groups in one molecule. A method for producing a curable composition, comprising:
The ratio of the content of the solvent (b) to the total amount of the curable composition is 25% by mass or more and 75% by mass or less, and the polyurethane (a) relative to the total amount of the polyurethane (a) and the epoxy compound (c). The method for producing a curable composition according to claim 10, wherein the content ratio of () is 40% by mass or more and 99% by mass or less.
A polyurethane (a) produced by the method for producing a polyurethane according to any one of claims 1 to 9, a solvent (b), and an epoxy compound (c) having two or more epoxy groups in one molecule. And a fine particle (d) are mixed to obtain a composition, which is a curable composition.
The ratio of the content of the solvent (b) to the total amount of the curable composition is 25% by mass or more and 75% by mass or less, and the ratio of the content of the fine particles (d) to the total amount of the curable composition is 0. 1 mass% or more and 60 mass% or less, and the ratio of the content of the polyurethane (a) to the total amount of the polyurethane (a) and the epoxy compound (c) is 40 mass% or more and 99 mass% or less. Item 13. A method for producing a curable composition according to item 12.
A method for producing a cured product, which comprises curing the curable composition produced by the method for producing a curable composition according to any one of claims 10 to 13 to obtain a cured product.
The curable composition produced by the method for producing a curable composition according to any one of claims 10 to 13 is applied to a portion of the surface of a flexible substrate on which the wiring is formed, on which the wiring is formed. A method for producing an overcoat film, which comprises arranging in a film shape and then curing the film-like curable composition to obtain a film-like cured product.
The curable composition produced by the method for producing a curable composition according to any one of claims 10 to 13 is applied to a portion of the surface of a flexible substrate on which the wiring is formed, on which the wiring is formed. A method for manufacturing a flexible wiring board, which comprises forming a film-like curable composition and then curing the film-like curable composition to form an overcoat film.