WO2021005914A1

WO2021005914A1 - Cured object, overcoat film, and flexible wiring board

Info

Publication number: WO2021005914A1
Application number: PCT/JP2020/021412
Authority: WO
Inventors: 圭孝石橋; こゆき召田; 未央山下; 和弥木村
Original assignee: 日本ポリテック株式会社
Priority date: 2019-07-08
Filing date: 2020-05-29
Publication date: 2021-01-14
Also published as: TW202106741A; TWI800737B; CN114080408B; CN114080408A; KR20220032573A; JPWO2021005914A1

Abstract

Provided is a cured object highly effective in preventing flexible wiring boards from warping and in inhibiting the flexible wiring boards from suffering wiring breakage. When examined by a pulse nuclear magnetic resonance method at a frequency of 20 MHz, the cured object formed from a curable resin composition gives a magnetization-intensity free induction decay signal f(t), which is for determining the spin-spin relaxation time T2 of a proton, and when the free induction decay signal f(t) is approximated by the following numerical expression, then the value of [A(1)×T2(1)+A(2)×T2(2)] calculated from the A(1), A(2), T2(1), and T2(2) contained in the numerical expression is 0.015 ms or less and the value of T2(3) is 0.50 ms or greater.

Description

Hardened material, overcoat film, and flexible wiring board

The present invention relates to a cured product, an overcoat film, and a flexible wiring board.

The flexible wiring board is coated with an overcoat film to protect the surface. This overcoat film is formed by applying a curable resin composition to the surface of a flexible substrate on which wiring is formed by a printing method or the like and curing it. As the circuit formed on the flexible wiring board is processed into fine wiring and the module is made lighter and smaller, the curable resin composition for forming the overcoat film causes the flexible substrate to warp as compared with the conventional one. Difficult performance is required. If the flexible substrate is warped, the alignment accuracy of the mounting position of the IC chip is adversely affected in the mounting process of mounting the IC chip on the flexible wiring board, so that the yield in the manufacturing process may be lowered.

Many curable resin compositions for forming an overcoat film of a flexible wiring plate used in electronic devices and the like have been conventionally proposed. For example, in Patent Document 1, a diisocyanate compound is reacted with a plurality of types of diol compounds. The curable resin composition containing the obtained polyurethane is disclosed. By using the curable resin composition disclosed in Patent Document 1, 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 wire breakage suppression property.

International Publication No. 2017/110591

However, with the development of the semi-additive method, it is expected that the distance (pitch) between the wires of the flexible wiring board will be further narrowed (for example, 20 μm or less). Therefore, the low warpage of the flexible wiring board and the flexible wiring board Further improvement in wire breakage suppression was desired.

The present invention has low warpage (hereinafter, the performance that makes it difficult for the flexible wiring board to warp and the performance that the flexible wiring board has a small warp may be referred to as "low warpage") and the ability to suppress disconnection of wiring (hereinafter,). A cured product, an overcoat film, and a flexible material having excellent performance of suppressing disconnection of wiring on a flexible wiring board and performance of preventing disconnection of wiring on a flexible wiring board are sometimes referred to as "wiring disconnection suppressing property"). An object is to provide a wiring board.

One aspect of the present invention is as follows [1] to [17].
[1] A free-induced decay signal of magnetization strength for determining the spin-spin relaxation time T2 of a proton, which is a cured product of a curable resin composition and is measured at a measurement frequency of 20 MHz by a pulse nuclear magnetic resonance method. When f (t) is approximated by the following formula, it is calculated from A (1), A (2), T2 (1), and T2 (2) in the formula [A (1) × T2 ( 1) + A (2) × T2 (2)] is 0.015 ms or less, and T2 (3) is 0.50 ms or more.

Here, the (offset) of the fourth term of the above-mentioned mathematical expression consisting of four terms is an offset term. Further, A (1), A (2), and A (3) in the above formula are constants, respectively, and A (1) + A (2) + A (3) = 1. T2 (1), T2 (2), and T2 (3) in the above formula are spin-spin relaxation times T2, respectively, and T2 (1) <T2 (2) <T2 (3). Further, W (1), W (2), and W (3) in the above formula are Weibull coefficients, which are numbers 1 or more and 2 or less. Further, t in the above formula is time, and exp is an exponential function with the Napier number e as the base.

[2] The curable resin composition comprises a polyurethane (a) having a functional group reactive with an epoxy group, a solvent (b), and an epoxy compound having two or more epoxy groups in one molecule. c) and the cured product according to [1] containing.
[3] The polyurethane (a) has a first urethane structural unit having at least one of a polyester structure and a polycarbonate structure, and at least one urethane structural unit of a second urethane structural unit having a carboxy group [[3] 2] The cured product according to.

[4] The cured product according to [3], wherein the polyurethane (a) further has a third urethane structural unit having a fluorene structure.
[5] The cured product according to any one of [2] to [4], wherein the polyurethane (a) has a trans-type 1,4-cyclohexanedimethylene group.

[6] The cured product according to any one of [2] to [5], wherein the polyurethane (a) has a number average molecular weight of 10,000 or more and 50,000 or less.
[7] The cured product according to any one of [2] to [6], wherein the polyurethane (a) has an acid value of 10 mgKOH / g or more and 70 mgKOH / g or less.
[8] The cured product according to any one of [2] to [7], wherein the polyurethane (a) has an aromatic ring concentration of 0.1 mmol / g or more and 5.0 mmol / g or less.

[9] The ratio of the content of the solvent (b) to the total amount of the curable resin composition is 25% by mass or more and 75% by mass or less, and the ratio of the content of the polyurethane (a) to the total amount of the epoxy compound (c). The cured product according to any one of [2] to [8], wherein the content ratio of the polyurethane (a) is 40% by mass or more and 99% by mass or less.

[10] The curing according to any one of [2] to [9], wherein the curable resin composition further contains at least one fine particle (d) selected from the group consisting of inorganic fine particles and organic fine particles. Stuff.
[11] The cured product according to [10], wherein the fine particles (d) contain silica fine particles.
[12] The cured product according to [10], wherein the fine particles (d) contain hydrotalcite fine particles.

[13] The ratio of the content of the solvent (b) to the total amount of the curable resin composition is 25% by mass or more and 75% by mass or less, the polyurethane (a), the solvent (b), and the epoxy compound (c). The ratio of the content of the fine particles (d) to the total amount of the fine particles (d) is 0.1% by mass or more and 60% by mass or less, and the ratio of the content of the fine particles (d) to the total amount of the polyurethane (a) and the epoxy compound (c). The cured product according to any one of [10] to [12], wherein the content ratio of the polyurethane (a) is 40% by mass or more and 99% by mass or less.

[14] A method for producing a cured product according to any one of [1] to [13], wherein the curable resin composition is cured by heat or active energy rays.
[15] An overcoat film containing the cured product according to any one of [1] to [13].
[16] A flexible wiring board in which a portion of the surface of a flexible substrate on which wiring is formed is covered with the overcoat film according to [15].
[17] The flexible wiring board according to [16], wherein the wiring is tin-plated copper wiring.

The cured product, overcoat film, and flexible wiring board according to the present invention are excellent in low warpage and wire breakage suppression.

An embodiment of the present invention will be described below. It should be noted that the present embodiment shows an example of the present invention, and the present invention is not limited to the present embodiment. In addition, various changes or improvements can be added to the present embodiment, and the modified or improved forms may be included in the present invention.

In order to solve the above problems, the present inventors have conducted intensive studies on a cured product obtained by curing a curable resin composition. As a result, the spin-spin relaxation time T2 of protons measured by a pulsed nuclear magnetic resonance method has been studied. We have found that the cured product whose free induction decay signal f (t) shows a specific result is excellent in low warpage property and wire disconnection suppression property, and has completed the present invention.

That is, the cured product of the present embodiment is a cured product of the curable resin composition, and is used for determining the spin-spin relaxation time T2 of the proton measured at a measurement frequency of 20 MHz by the pulse nuclear magnetic resonance method. When the free induction decay signal f (t) of the magnetization intensity is approximated by the following formula, it is calculated from A (1), A (2), T2 (1), and T2 (2) in the formula [ The value of A (1) × T2 (1) + A (2) × T2 (2)] is 0.015 ms or less, and T2 (3) is 0.50 ms or more. The value of [A (1) × T2 (1) + A (2) × T2 (2)] is preferably 0.002 ms or more and 0.013 ms or less. T2 (3) is preferably 0.70 ms or more and 2.00 ms or less.

The above approximation is an approximation of the free induction decay signal f (t) of the magnetization strength of the cured product by synthesizing curves showing three different spin-spin relaxation times T2, and can be interpreted as follows. That is, the first, second, and third terms of the above formula are terms indicating the properties of the three components having relatively different molecular motility, and T2 (1) <T2 (2) <T2. Since it is (3), it is represented in order from the one having the lowest molecular motion. That is, the first term is a term indicating the properties of the hard portion having low molecular mobility, the third term is a term indicating the properties of the soft portion having high molecular mobility, and the second term is the term indicating the properties of the hard portion. It is a term indicating the property of the intermediate portion having molecular mobility between the soft portion and the soft portion.

That is, the term in which the decay of the free induction decay signal f (t) is relatively fastest is the first term, the term in which the decay is relatively slowest is the third term, and the term in the middle speed is the second term. Therefore, the characteristics of the cured product are expressed by the above approximate expression by synthesizing these three components. In other words, it can be said that the characteristics of the cured product are expressed by the approximate expression decomposed into the above three terms.

Further, A (1), A (2), and A (3) in the above formula are constants indicating the component ratios of the hard portion, the intermediate portion, and the soft portion in the cured product. T2 (1), T2 (2), and T2 (3) in the above formula are spin-spin relaxation times T2 of the hard portion, the intermediate portion, and the soft portion. Further, W (1), W (2), and W (3) in the above formula are Weibull coefficients of the hard portion, the intermediate portion, and the soft portion.

With the above configuration, the cured product of the present embodiment has good flexibility, so that it has excellent low warpage and wire disconnection suppressing property. Further, the overcoat film of the present embodiment containing the cured product of the present embodiment is excellent in low warpage property and wire disconnection suppressing property. Further, the flexible wiring board of the present embodiment in which the portion of the surface of the flexible substrate on which the wiring is formed is covered with the overcoat film of the present embodiment has low warpage and suppresses disconnection of the wiring. Excellent in sex.

In this embodiment, from the approximation of the free induction decay signal f (t) of the magnetization intensity measured by the pulse nuclear magnetic resonance method, it is [A (1) × T2 (1) + A (2) × T2 (2)]. Obtain T2 (3). [A (1) × T2 (1) + A (2) × T2 (2)] is the hard portion having low molecular mobility and the intermediate portion having molecular mobility between the hard portion and the soft portion of the cured product. Since the properties are exhibited, if the value of [A (1) × T2 (1) + A (2) × T2 (2)] is small, it means that the hard portion in the cured product has a harder structure. Further, if the value of T2 (3) indicating the properties of the soft portion having high molecular mobility is large, it means that the soft portion in the cured product has a softer structure.

Conventionally, the evaluation of the cured product (overcoat film) has been performed by measuring the bending resistance, warpage, mechanical properties, etc. of the cured product. By changing the type of resin contained in the curable resin composition, it is possible to improve bending resistance and reduce warpage, but it is an empirical factor because it is a matrix search. It was not easy to design the function intentionally.

In the present invention, the hard and soft parts in the cured product, which are indicators of the mechanical properties of the cured product, that is, the hard and soft components constituting the molecular chain of the resin contained in the curable resin composition. The relative amount and the degree of hardness and softness thereof are quantitatively evaluated using the spin-spin relaxation time T2 obtained by the pulse nuclear magnetic resonance method.

Then, by making the hard part in the cured product harder and the soft part softer, the cured product and the overcoat film are provided with excellent low warpage property and wire disconnection suppressing property. Quantitative evaluation of the hard and soft parts in the cured product makes it possible to intentionally design the function in addition to the conventional empirical method.

For the cured product of the present embodiment, the method of measuring the free induction decay signal f (t) of the magnetization intensity for determining the spin-spin relaxation time T2 of the proton by the pulse nuclear magnetic resonance method is not particularly limited. However, it can be measured by the following method, for example. That is, the curable resin composition is coated on a base material or the like to form a film, and is cured by heating to, for example, 120 to 150 ° C. to obtain a film-like cured product having a thickness of, for example, 20 μm. Then, a free induction decay signal f (t) of the magnetization intensity for determining the spin-spin relaxation time T2 of the proton is obtained by a pulse nuclear magnetic resonance method at a measurement frequency of 20 MHz, for example, a solid echo method.

Here, an example of a specific method for measuring the free induction decay signal f (t) of the magnetization intensity for determining the spin-spin relaxation time T2 of the proton by the pulse nuclear magnetic resonance method is shown below.
As the sample, a sample cut into strips having a length of 3 cm and a width of several mm is used. This sample is packed in a glass sample tube having a diameter of 10 mm so that the total mass is about 500 mg, and the glass sample tube is installed in the pulse nuclear magnetic resonance apparatus so that the sample is located in the coil portion of the pulse nuclear magnetic resonance apparatus. Then, using a pulse nuclear magnetic resonance apparatus, the measurement nucleus is a hydrogen nucleus, and the measurement is performed under the measurement conditions of a measurement temperature of 40 ° C., a frequency of 20 MHz, and a 90 ° pulse width of 0.1 s. Measurements are performed on three samples, and a free induction decay signal f (t) is obtained from the measurement results.

First, in order to determine RECYCLE Delay = T1 × 5s in the parameter of spin-spin relaxation time T2, the spin-lattice relaxation time T1 is obtained by the Innovation Recovery method. An example of the measurement conditions for the spin-lattice relaxation time T1 is shown below.

Equipment: Bruker's Biospin the minispec mq20
Measurement frequency: 20MHz
Temperature: 40 ° C
Pulse program: T1 Innovation Recovery method (reversal recovery method)
First Pulse Separation: 5ms
Final Pulse Separation: 1000ms
Recycle delay: 1s
Gain: 95 dB
Data Points: 20
Delay Sumpling Window: 0.050ms
Sample window: 0.020ms
Scan: 16 times Acquisition scale: 0.3ms

Curve fitting (Mono-exponential) is performed on the signal spectrum thus obtained, and the spin-lattice relaxation time T1 is calculated. Then, RECYCLE Delay = T1 × 5s is set based on the calculated spin-lattice relaxation time T1, and the free induction decay signal f (t) of the magnetization intensity for determining the spin-spin relaxation time T2 is measured. An example of the measurement conditions for the spin-spin relaxation time T2 is shown below.

Equipment: Bruker's Biospin the minispec mq20
Measurement frequency: 20MHz
Temperature: 40 ° C
Pulse program: T2 solid echo method Recycle delay: 1s
Gain: 77 dB
Data Points: 100
Scan: 16 times Acquisition scale: 0.3ms

Curve fitting (7. Gauss-Decay Extended) is performed on the free induction decay signal f (t) thus obtained, and the spin-spin relaxation time T2 is calculated. At the time of curve fitting of spin-spin relaxation time T2, an approximate function can be obtained by arbitrarily changing the ratio of the exponential function / Gaushan function or the Abragamian function.

The spin-spin relaxation time T2 can be obtained by using the fitting calculation formula as the above formula. The fitting is performed for a decay time t in the range of 0 ms to 0.3 ms. At this time, the Weibull coefficient is set to W (1) = 2.0, W (2) = 1.0, W (3) = 1.0, and A (1) and A (2) of the above formula are set. , A (3), T2 (1), T2 (2), T2 (3), and offset are calculated.

The cured product, the overcoat film, and the flexible wiring board of the present embodiment will be described in more detail below. First, a curable resin composition that produces a cured product of the present embodiment by curing will be described.
I. Curable Resin Composition The curable resin composition of the present embodiment is used for manufacturing a flexible wiring board in which a portion of the surface of a flexible substrate on which wiring is formed is coated with an overcoat film. This is a cured product that forms an overcoat film.

The composition of the curable resin composition of the present embodiment is particularly limited as long as it contains a component that can be cured by heat or active energy rays (for example, ultraviolet rays, electron beams, X-rays) to produce a cured product. However, it is preferable to contain a curable resin.
For example, the curable resin composition of the present embodiment preferably contains polyurethane (a), a solvent (b), and an epoxy compound (c) having two or more epoxy groups in one molecule. .. The polyurethane (a), solvent (b), and epoxy compound (c) described above will be described in detail below.

(I-1) Polyurethane (a)
The type of polyurethane (a) is not particularly limited as long as it has a functional group having reactivity with the epoxy group of the epoxy compound (c) and is cured by reacting with the epoxy compound (c). Absent. Examples of the functional group having reactivity with the epoxy group of the epoxy compound (c) include a carbamate group (-NHCOO-), a carboxy group, an isocyanato group, a hydroxy group, an amide group and a cyclic acid anhydride group. .. The polyurethane (a) may contain one of these functional groups, or may contain two or more of these functional groups. The cyclic acid anhydride group refers to an acid anhydride group formed by dehydration of two carboxy groups in the molecule when the acid anhydride group forms a part of the ring structure.

Among the functional groups exemplified above, a carboxy group, an isocyanato group, an amide group, and a cyclic acid anhydride group are preferable in consideration of the reactivity of the epoxy compound (c) with the epoxy group. Further, considering the balance between the storage stability of the polyurethane (a) and the reactivity of the epoxy compound (c) with the epoxy group, a carboxy group and a cyclic acid anhydride group are more preferable, and a carboxy group is further preferable. The carbamate group is preferable in consideration of the ease of introducing the functional group into the polyurethane (a). Polyurethane (a) may be provided with these functional groups at the end of the molecule, or may be provided so as to branch off from the molecular chain.

The polyurethane (a) may have a first urethane structural unit having at least one of a polyester structure and a polycarbonate structure, and at least one urethane structural unit of a second urethane structural unit having a carboxy group in the molecule. preferable.
Further, it is preferable that the polyurethane (a) further has a third urethane structural unit having a fluorene structure in addition to at least one of the first urethane structural unit and the second urethane structural unit.

Further, the polyurethane (a) preferably has a trans-type 1,4-cyclohexanedimethylene group.
If the polyurethane (a) has the above-mentioned urethane structural unit or a trans-type 1,4-cyclohexanedimethylene group, it imparts excellent low warpage property and wiring disconnection suppressing property to the overcoat film and the flexible wiring board. can do.

The method for synthesizing the polyurethane (a) is not particularly limited, but for example, a polyol compound having two or more hydroxy groups in one molecule in the presence or absence of a urethanization catalyst such as dibutyltin dilaurylate. Examples thereof include a method of polymerizing (for example, a diol compound) and a polyisocyanate compound having two or more isocyanato groups in one molecule (for example, a diisocyanate compound) in a solvent or the like. As the polyol compound and the polyisocyanate compound, one type may be used alone, or a plurality of types may be used in combination.

If desired, at least one of a monohydroxy compound having one hydroxy group in one molecule and a monoisocyanate compound having one isocyanato group in one molecule is allowed to coexist, and the above polymerization reaction is carried out. May be done.
Further, it is preferable to carry out the above polymerization reaction without a catalyst or in the presence of a small amount of catalyst because the long-term insulation reliability of the overcoat film described later is improved.

The type of the polyisocyanate compound is not particularly limited, and examples thereof include cyclic aliphatic polyisocyanates, polyisocyanates having an aromatic ring, chain aliphatic polyisocyanates, and polyisocyanates having a heterocycle.
Examples of the cyclic aliphatic polyisocyanate include 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, isophoronediisocyanate, methylenebis (4-cyclohexylisocyanate), 1,3-bis (isocyanatomethyl) cyclohexane, and 1,4. Examples thereof include biuret forms of -bis (isocyanatomethyl) cyclohexane (particularly trans-1,4-bis (isocyanatomethyl) cyclohexane), norbornene diisocyanate, norbornan 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 can be mentioned.

Examples of the chain aliphatic polyisocyanate include a biuret form of hexamethylene diisocyanate, lysine triisocyanate, lysine diisocyanate, hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and 2,2,4-trimethylhexanemethylene diisocyanate. Can be mentioned.

Examples of the polyisocyanate having a heterocycle include an isocyanurate form of isophorone diisocyanate and an isocyanurate form of hexamethylene diisocyanate.
One of these polyisocyanates may be used alone, or two or more thereof may be used in combination.

The type of the diol compound is not particularly limited, but preferred diol compounds include, for example, polyester diols, polycarbonate diols, and diols having a carboxy group in the molecule (hereinafter, may be referred to as "carboxy group-containing diol"). , A diol having a fluorene structure, and a diol having a phenyl group or a biphenyl group.

Polyester diols can be synthesized by esterification of dicarboxylic acids with diols. One type of polyester diol may be used alone, or two or more types may be used in combination.
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, 2-methyl-benzene-1,4-dicarboxylic acid and the like. 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 can be mentioned. it can. As the diol, one of these may be used alone, or two or more thereof may be used in combination.
By using such a diol, the value of T2 (3) can be made larger.

Among the above dicarboxylic acids, phthalic acid, isophthalic acid, terephthalic acid, 3-methyl-benzene-1,2-dicarboxylic acid, 4-methyl-benzene-1,2-dicarboxylic acid are particularly preferable. Is a phthalic acid.
Among the above diols, preferred ones are 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 3-methyl-1,5-pentanediol. It is particularly preferable that it is 1,6-hexanediol or 3-methyl-1,5-pentanediol.

The number average molecular weight of the polyester diol 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.
A low molecular weight polyol can also be used as the polyol compound. 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 and the like can be used.

Polycarbonate diol can be synthesized by a polycondensation reaction of phosgene and diol. One type of polycarbonate diol may be used alone, or two or more types may be used in combination.
The diol suitable as a raw material for the polycarbonate diol is the same as that for the polyester diol, and thus the description thereof will be omitted. Moreover, since the preferable number average molecular weight of the polycarbonate diol is the same as that of the polyester diol, the description thereof will be omitted.

The type of carboxy group-containing diol is not particularly limited, but for example, dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, N, N-bis (hydroxyethyl) glycine, N, N-bis (hydroxy). Ethyl) glycine and the like can be mentioned. As the carboxy group-containing diol, one of these may be used alone, or two or more thereof may be used in combination.

Among these carboxy group-containing diols, 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid are particularly preferable from the viewpoint of solubility in a reaction solvent during polyurethane production.
The type of diol having a fluorene structure is not particularly limited, but preferred ones include, for example, 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene.

The type of diol having a phenyl group or a biphenyl group is not particularly limited, but preferred ones are, for example, 1,1-dimethyl-bis [4- (2-hydroxyethoxy) phenyl] methane and bis-4. Examples thereof include- (2-hydroxyethoxy) biphenyl and 1,1-bis [4- (2-hydroxyethoxy) phenyl] cyclohexane.

In order to make the value of [A (1) × T2 (1) + A (2) × T2 (2)] smaller, polyurethane (a) using a diol having a high aromatic ring concentration as a monomer was used. It is preferable to use it, and in order to increase the value of T2 (3), it is preferable to use a polyurethane (a) in which a diol having a high aliphatic concentration is used as a monomer.

The number average molecular weight of the polyurethane (a) is not particularly limited, but is preferably 7,000 or more and 50,000 or less, preferably 7500, in consideration of the ease of adjusting the viscosity of the curable resin composition of the present embodiment described later. It is more preferably 40,000 or more, and further preferably 8,000 or more and 30,000 or less.

When the number average molecular weight is within the above range, the solvent solubility of the polyurethane (a) is good and the viscosity of the polyurethane solution is unlikely to increase. Therefore, the curable resin composition described later can be described later in an overcoat film or flexible. It is suitable for use in the manufacture of wiring boards. Further, the elongation, flexibility, and strength of the cured product and the overcoat film, which will be described later, tend to be good.
The "number average molecular weight" referred to here is a polystyrene-equivalent number average molecular weight measured by gel permeation chromatography (hereinafter referred to as "GPC"). In this specification, unless otherwise specified, the measurement conditions of GPC are as follows.

Device name: HPLC unit HSS-2000 manufactured by JASCO Corporation
Column: Showa Denko Corporation Shodex column LF-804 x 3 (series)
Mobile phase: tetrahydrofuran Flow velocity: 1.0 mL / min
Detector: RI-2031Plus manufactured by JASCO Corporation
Temperature: 40.0 ° C
Sample amount: Sample loop 100 μL
Sample concentration: Approximately 0.1% by mass

The acid value of the polyurethane (a) is not particularly limited, but is preferably 10 mgKOH / g or more and 70 mgKOH / g or less, more preferably 15 mgKOH / g or more and 50 mgKOH / g or less, and 20 mgKOH / g or more. It is more preferably 35 mgKOH / g or less.

When the acid value is within the above range, the polyurethane (a) has sufficient reactivity with the epoxy group. Therefore, in the curable resin composition described later, the reactivity with other components such as the epoxy compound (c) having two or more epoxy groups in one molecule is unlikely to be insufficient, so that the curable resin composition The heat resistance of the cured product is unlikely to decrease, and the cured product of the curable resin composition does not become too hard and brittle. In addition, it becomes easy to balance the solvent resistance of the overcoat film described later with the warp of the flexible wiring board described later.
In this specification, the acid value of polyurethane is the value of the acid value measured by the potentiometric titration method specified in JIS K0070.

The aromatic ring concentration of the polyurethane (a) is not particularly limited, but is preferably 0.1 mmol / g or more and 5.0 mmol / g or less, and 0.5 mmol / g or more and 4.5 mmol / g or less. More preferably, it is 1.0 mmol / g or more and 4.0 mmol / g or less.
When the aromatic ring concentration is within the above range, it becomes easy to balance the solvent resistance of the overcoat film described later and the warp of the flexible wiring board described later. Further, the value of [A (1) × T2 (1) + A (2) × T2 (2)] can be made smaller.

The aromatic ring concentration means the number (number of moles) of aromatic rings contained in 1 g of the compound. For example, if a polyurethane having a molecular weight of 438.5 as a repeating unit (structural unit) has four aromatic rings (for example, phenyl groups) per repeating unit, the number of repeating units in 1 g of this polyurethane is 2. Since it is .28 mmol, the aromatic ring concentration is 9.12 mmol / g (4 × 2.28 mmol / 1 g).

The type of aromatic ring is not particularly limited as long as it is a cyclic functional group having aromaticity with 3 or more ring members, and for example, a monocyclic aromatic hydrocarbon group such as a phenyl group, a biphenyl group, or a fluorene group. Examples thereof include a polycyclic aromatic hydrocarbon group such as, a condensed ring aromatic hydrocarbon group such as a naphthalene group and an indenyl group, and a heteroaromatic hydrocarbon group such as a pyridyl group.

However, in the case of a functional group having a plurality of cyclic structural parts such as a polycyclic aromatic hydrocarbon group and a fused cyclic aromatic hydrocarbon group, the number of aromatic rings is not one but the number of cyclic structural parts. To do. For example, since a fluorene group has two benzene rings which are cyclic structure sites, in the case of a polyurethane having one fluorene group per repeating unit, the number of aromatic rings possessed by the polyurethane is 1 repeating unit. Two per piece.

Similarly, in the case of a biphenyl group or naphthalene group, the number of aromatic rings is 2, in the case of an anthracene group or phenanthrene group, the number of aromatic rings is 3, and in the case of a triphenylene group or binaphthyl group, the number of aromatic rings is 4. And.
The aromatic ring concentration can be calculated from the charging ratio of the monomers, but can be obtained by ¹ H-NMR analysis after determining the structure of the polyurethane by spectroscopic methods such as ¹ H-NMR, ¹³ C-NMR, and IR. It can also be calculated by comparing the number of protons derived from the aromatic ring with the number of protons derived from one repeating unit using the integration curve.

The polymerization reaction for synthesizing polyurethane (a) may be carried out in a solvent, but the type of solvent used as the polymerization solvent when carried out in a solvent is particularly as long as it is a solvent capable of dissolving polyurethane (a). Not limited. Examples of the solvent used for synthesizing the polyurethane (a) include diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, and tri. Ether-based solvents such as ethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, and tripropylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and 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, ethyl methoxypropionate, methyl ethoxypropionate, ethyl ethoxypropionate, γ -Examples include ester solvents such as butyrolactone, hydrocarbon solvents such as decahydronaphthalin, and ketone solvents such as cyclohexanone. One of these solvents may be used alone, or two or more of these solvents may be used in combination.

Among these solvents, γ-butyrolactone, diethylene glycol diethyl ether, diethylene glycol monoethyl ether acetate, considering the ease of adjusting the molecular weight of polyurethane and the printability of the curable resin composition described later during screen printing, Diethylene glycol monomethyl ether acetate is preferable, and γ-butyrolactone, diethylene glycol monoethyl ether acetate, and diethylene glycol diethyl ether are more preferable, and a single solvent of γ-butyrolactone, a mixed solvent of γ-butyrolactone and diethylene glycol monoethyl ether acetate, and γ-butyrolactone. A two-kind mixed solvent of diethylene glycol diethyl ether and a three-kind mixed solvent of γ-butyrolactone, diethylene glycol monoethyl ether acetate, and diethylene glycol diethyl ether are more preferable.

The solid content concentration of the solution of polyurethane (a) is not particularly limited, but is preferably 10% by mass or more and 90% by mass or less, more preferably 15% by mass or more and 70% by mass or less, and 20% by mass or more and 60% by mass or less. The following is more preferable. When a polyurethane solution having a solid content concentration of 20% by mass or more and 60% by mass or less is used to produce a curable resin composition described later, the viscosity of the solution of polyurethane (a) is described in the section of Examples. Under the measurement conditions described later, for example, it is preferably 5,000 mPa · s or more and one million mPa · s or less from the viewpoint of uniform dispersion.

The order in which the raw materials such as monomers are charged into the reaction vessel when the polymerization reaction for synthesizing the polyurethane (a) is performed is not particularly limited, but may be charged in the following order, for example. That is, after the diol compound is dissolved in the solvent in the reaction vessel, the diisocyanate compound is added little by little to the reaction vessel at 30 ° C. or higher and 140 ° C. or lower, preferably 60 ° C. or higher and 120 ° C. or lower, and 50 ° C. or higher and 160 ° C. or lower. , Preferably at 60 ° C. or higher and 150 ° C. or lower, each of the above monomers is reacted to carry out polymerization.

The molar ratio of the monomer charged is adjusted according to the molecular weight and acid value of the target polyurethane (a). A monohydroxy compound may be used as a raw material for the polyurethane (a) in order to adjust the molecular weight of the polyurethane (a). In that case, when the molecular weight of the polyurethane being polymerized reaches the target number average molecular weight (or approaches the target number average molecular weight) by the above method, the isocyanato group at the molecular end of the polyurethane being polymerized is sealed. A monohydroxy compound is added for the purpose of stopping and suppressing a further increase in the number average molecular weight.

When a monohydroxy compound is used, it is the total number of hydroxy groups obtained by subtracting the total number of hydroxy groups of the monohydroxy compound from the total number of hydroxy groups of all the raw materials of polyurethane (a) (that is, the raw material of polyurethane (a)). The total number of isocyanato groups contained in all the raw materials of polyurethane (a) may be smaller or the same as the total number of hydroxy groups contained in a compound having two or more hydroxy groups in one molecule. , Or more.

When an excess amount of the monohydroxy compound is used, an unreacted monohydroxy compound remains. 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.
The reason why the monohydroxy compound is used as the raw material of the polyurethane (a) is to suppress the increase in the molecular weight of the polyurethane (a) (that is, to stop the polymerization reaction), and to add the monohydroxy compound in the reaction solution at 30 ° C. or higher and 150 ° C. or higher. Add in small portions at ° C. or lower, preferably 70 ° C. or higher and 140 ° C. or lower, and then hold at the above temperature to complete the reaction.

Further, a monoisocyanate compound may be used as a raw material for the polyurethane (a) in order to adjust the molecular weight of the polyurethane (a). In that case, the total number of hydroxy groups of the polyurethane (a) is larger than the total number of hydroxy groups of all the raw materials of the polyurethane (a) so that the molecular end of the polyurethane (a) at the time of adding the monoisocyanate compound becomes a hydroxy group. The total number of isocyanato groups obtained by subtracting the total number of isocyanato groups contained in the monoisocyanate compound from the total number of isocyanato groups contained in the raw material (that is, the compound having two or more isocyanato groups in one molecule which is the raw material of the polyurethane (a)) has. It is necessary to reduce the total number of isocyanato groups).

When the reaction between the hydroxy group contained in all the raw materials of the polyurethane (a) and the isocyanato group of the diisocyanate compound is almost completed, the hydroxy group remaining at the molecular terminal of the polyurethane (a) being manufactured and the isocyanato of the monoisocyanate compound are produced. React with the group. For that purpose, the temperature of the polyurethane solution during polyurethane production is set to 30 ° C. or higher and 150 ° C. or lower, preferably 70 ° C. or higher and 140 ° C. or lower, and then the monoisocyanate compound is added little by little to the polyurethane solution and then maintained at the above temperature. To complete the reaction.

When producing polyurethane (a), the blending amount of each component of the raw material is preferably as follows. The ratio of the total number of hydroxy groups contained in the diol compound, which is the raw material of polyurethane (a), to the total number of isocyanato groups contained in the diisocyanate compound, which is the raw material of polyurethane (a), is: hydroxy group: isocyanato group = 1: 0.9. It is preferably ~ 0.9: 1, and more preferably hydroxy group: isocyanato group = 1: 0.92 to 0.92: 1.

(I-2) Solvent (b)
The type of the solvent (b), which is one of the essential components of the curable resin composition of the present embodiment, is not particularly limited as long as the polyurethane (a) can be dissolved, but for example, diethylene glycol dimethyl ether, etc. Diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dibutyl ether, 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, etc. Ether-based solvent can be mentioned.

Examples of the solvent (b) include 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, and dipropylene glycol monoethyl ether acetate. Examples thereof include ester solvents such as diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, methyl methoxypropionate, ethyl methoxypropionate, methyl ethoxypropionate, ethyl ethoxypropionate, and γ-butyrolactone.
Further, examples of the solvent (b) include hydrocarbon solvents such as decahydronaphthalene and ketone solvents such as cyclohexanone.
One of these solvents may be used alone, or two or more of these solvents may be used in combination.

Among these solvents, γ-butyrolactone, diethylene glycol diethyl ether, diethylene glycol monoethyl ether acetate and diethylene glycol monomethyl ether acetate are preferable, and γ-butyrolactone and diethylene glycol are preferable in consideration of the balance between printability during screen printing and solvent volatility. More preferably, monoethyl ether acetate and diethylene glycol diethyl ether are a single solvent of γ-butyrolactone, a mixed solvent of γ-butyrolactone and diethylene glycol monoethyl ether acetate, a mixed solvent of γ-butyrolactone and diethylene glycol diethyl ether, and γ-. A three-kind mixed solvent of butyrolactone, diethylene glycol monoethyl ether acetate, and diethylene glycol diethyl ether is more preferable.

A combination of these preferable solvents is suitable because it is excellent as a solvent for screen printing ink.
Further, as a part or all of the solvent (b) contained in the curable resin composition of the present embodiment, the synthetic solvent used in producing the polyurethane (a) can be used as it is. This is preferable in terms of process because the curable resin composition of the present embodiment can be easily produced.

The content of the solvent (b) in the curable resin composition of the present embodiment is preferably 25% by mass or more and 75% by mass or less, preferably 35% by mass, based on the total amount of the curable resin composition of the present embodiment. More preferably, it is% or more and 65% by mass or less. Here, the total amount of the curable resin 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. is there. However, when the curable resin composition of the present embodiment contains other components such as fine particles (d) described later, the total amount of the curable resin composition of the present embodiment is the polyurethane (a). , The total amount of the solvent (b), the epoxy compound (c) having two or more epoxy groups in one molecule, and other components such as fine particles (d).

When the content of the solvent (b) is within the range of 25% by mass or more and 75% by mass or less with respect to the total amount of the curable resin composition of the present embodiment, the viscosity of the curable resin composition is determined by the screen printing method. The viscosity is good for printing, and the spread of the curable resin composition due to bleeding after screen printing is not so large. As a result, the phenomenon that the printed area of the curable resin composition actually printed is larger than the portion where the curable resin composition is to be coated (that is, the shape of the printing plate) is less likely to occur, which is preferable.

(I-3) Epoxy compound having two or more epoxy groups in one molecule (c)
The epoxy compound (c), which is one of the essential components of the curable resin composition of the present embodiment, reacts with functional groups such as carboxy group and hydroxy group contained in polyurethane (a) and is cured in the curable resin composition. It functions as an agent. Since the functional groups such as the carboxy group and the hydroxy group of the polyurethane (a) have reactivity with the epoxy group, they react with the epoxy group of the epoxy compound (c).

The type of the epoxy compound (c) is not particularly limited as long as it is a compound having two or more epoxy groups in one molecule, and examples thereof include a novolak type epoxy resin obtained by epoxidizing a novolak resin. Specific examples of the novolak type epoxy resin include phenol novolac type epoxy resin and orthocresol novolac type epoxy resin.

The novolak resin includes 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, and salicylaldehyde. It is a resin obtained by condensing or co-condensing a compound having an aldehyde group such as the above under an acidic catalyst.

Further, 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. Here, examples of the above-mentioned phenols include bisphenol A, bisphenol F, bisphenol S, alkyl-substituted or unsubstituted biphenols, and stillben-based phenols. That is, the diglycidyl ethers of these phenols are bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, biphenyl type epoxy compound, and stillben type epoxy compound. Examples of the alcohol include butanediol, polyethylene glycol, polypropylene glycol and the like.

Further, 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, and aniline and bis (4). -Aminophenyl) Nitrogen contained in glycidyl-type or methylglycidyl-type epoxy resins, which are compounds in which active hydrogen bonded to nitrogen atoms of methane, isocyanuric acid, etc. is replaced with glycidyl groups, and aminophenols such as p-aminophenol. Examples thereof include glycidyl-type or methylglycidyl-type epoxy resins, which are compounds in which active hydrogen bonded to an atom and active hydrogen of a phenolic hydroxy group are substituted with glycidyl groups, respectively.

Further, 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). , 4-Epoxy) Cyclohexyl-5,5-Spiro (3,4-Epoxy) Cyclohexane-m-dioxane and other alicyclic epoxy resins can be mentioned. These alicyclic epoxy resins are obtained by epoxidizing the olefin bonds 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 glycidyl ether of paraxylylene and / or metaxylylene-modified phenol resin, glycidyl ether of terpene-modified phenol resin, and dicyclopentadiene-modified phenol resin. Glycidyl ether, cyclopentadiene-modified phenol resin glycidyl ether, polycyclic aromatic ring-modified phenol resin glycidyl ether, and naphthalene ring-containing phenol resin glycidyl ether.

Further, examples of the epoxy compound (c) having two or more epoxy groups in one molecule include a halogenated phenol novolac type epoxy resin, a hydroquinone type epoxy resin, a trimethylol propane type epoxy resin, and a linear aliphatic epoxy resin. (A product 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 can be mentioned.

Further, as the epoxy compound (c) having two or more epoxy groups in one molecule, for example, an epoxidized product of an aralkyl type phenol resin such as a phenol aralkyl resin or a naphthol aralkyl resin, a sulfur atom-containing epoxy resin, or a tricyclo [5.2.1.0 ^2,6 ] Examples thereof include diglycidyl ether of decandimethanol and an epoxy resin having an adamantan structure. Examples of epoxy resins having an adamantane structure include 1,3-bis (1-adamantyl) -4,6-bis (glycidyloyl) benzene, 1- [2', 4'-bis (glycidiroyl) phenyl] adamantane, 1 , 3-Bis (4'-glycidyl phenyl) adamantane, 1,3-bis [2', 4'-bis (glycidyl phenyl) phenyl] adamantane and the like.
One of these epoxy compounds (c) may be used alone, or two or more thereof may be used in combination.

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 later is emphasized, a cured product having a low water absorption rate can be obtained. Therefore, one molecule has two or more epoxy groups and has an aromatic ring structure and /. Alternatively, among the epoxy compounds having an alicyclic structure, a compound having two or more epoxy groups in one molecule and having a tricyclodecane structure and an aromatic ring structure is preferable.

Specific examples of the compound having two or more epoxy groups in one molecule and having a tricyclodecane structure and an aromatic ring structure include glycidyl ether of a dicyclopentadiene-modified phenol resin (that is, two or more in one molecule). Compounds having an epoxy group of and having a tricyclo [5.2.1.0 ^2,6 ] decane structure and aromatic ring structure), 1,3-bis (1-adamantyl) -4,6-bis (glycidyloyl) ) Benzene, 1- [2', 4'-bis (glycidylyl) phenyl] adamantane, 1,3-bis (4'-glycidylphenyl) adamantane, and 1,3-bis [2', 4'-bis (Glysidiloyl) phenyl] An epoxy resin having an adamantane structure such as adamantane (that is, having two or more epoxy groups in one molecule and having a tricyclo [3.3.1.1 ^3,7 ] decan structure and aromatic ring structure A compound having (1) and a compound represented by the following chemical formula (1) can be mentioned. Among these, the compound represented by the following chemical formula (1) is particularly preferable. In addition, k in the following chemical formula (1) is an integer of 1 or more, preferably an integer of 1 or more and 10 or less.

On the other hand, when the reactivity with polyurethane is emphasized, among the epoxy compounds having two or more epoxy groups in one molecule and having an aromatic ring structure and / or an alicyclic structure, two in one molecule. A compound having the above epoxy group and having an amino group and an aromatic ring structure is preferable.
As a specific example of a compound having two or more epoxy groups in one molecule and having an amino group and an aromatic ring structure, glycidyl is an active hydrogen bonded to a nitrogen atom of aniline and bis (4-aminophenyl) methane. Glycidyl-type or methylglycidyl-type epoxy resin, which is a compound substituted with a group, and glycidyl, which is a compound in which active hydrogen bonded to a nitrogen atom of aminophenols and active hydrogen of a phenolic hydroxy group are each substituted with a glycidyl group. Examples thereof include type or methylglycidyl type epoxy resins and compounds represented by the following chemical formula (2). Among these, the compound represented by the following chemical formula (2) is particularly preferable.

In the curable resin composition of the present embodiment, the preferable content of the epoxy compound (c) with respect to the content of the polyurethane (a) is a functional group (for example, a carboxy group) of the polyurethane (a) that can react with the epoxy group. It cannot be said unconditionally because it depends on the amount of.
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) ([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 in the range of 1/3 to 2/1, when the curable resin composition of the present embodiment is cured, a large amount of unreacted epoxy compound does not remain. Not so many functional groups that can react with the epoxy group remain, and the functional group that can react with the epoxy group and the epoxy group in the epoxy compound can react in a well-balanced manner.

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 resin composition of the present embodiment is preferably 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, and 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 resin composition of the present embodiment is 40% by mass or more and 99% by mass or less. It is more preferably 50% by mass or more and 98% by mass or less, and 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 overcoat film described later is coated, which will be described later. It is possible to balance the low warpage of the flexible wiring board and the ability to suppress disconnection of the wiring.

(I-4) 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 resin composition of the present embodiment.
Examples of the inorganic fine particles include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titanium (TIO ₂ ), titanium oxide (Ta ₂ O ₅ ), zirconia (ZrO ₂ ), and silicon nitride (Si ₃ N ₄ ). , Barium titanate (BaO · TiO ₂ ), barium carbonate (BaCO ₃ ), lead titanate (PbO · TiO ₂ ), lead zirconate titanate (PZT), lead 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, etc. May be used alone or in combination of two or more.

As the organic fine particles, fine particles of a heat-resistant resin having an amide bond, an imide bond, an ester bond or an ether bond are preferable. Examples of these resins include polyimide resins or precursors thereof, polyamideimide resins or precursors thereof, or polyamide resins 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 resin 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 resin composition of the present embodiment are in the form of powder, 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 resin composition of the present embodiment are not particularly limited as long as they are dispersed in the curable resin composition to form a paste, but for example, Nippon Aerosil Co., Ltd. Aerosil (trade name) provided by the company can be mentioned. Silica fine particles typified by Aerosil (trade name) are sometimes used to impart printability during screen printing to a curable resin composition, and in that case, they are used for the purpose of imparting thixophilicity. Ru.

Hydrotalcite particles used in the curable resin composition of the present embodiment is a kind of clay minerals naturally occurring typified by _{_{_{Mg 6 Al 2 (OH) 16}}} CO 3 · 4H 2 O and the like, layered It is an inorganic compound of. Hydrotalcite can also be obtained synthetically. For example, Mg _1-x Al _x (OH) ₂ (CO ₃ ) _{x / 2} · mH ₂ O and the like can be obtained synthetically. That is, the hydrotalcite is Mg / Al-based layered compound, by ion exchange with carbonate groups in the interlayer, chloride ion - fixing an anion and / or sulfate ions (SO ₄ ^{^2-)} (Cl) Can be converted. Using this feature, chloride ions that cause migration of copper and tin (Cl ^-) and trapping the sulfate ion (SO ₄ ^2-), it is possible to improve the long-term insulation reliability of the cured product.

Examples of commercially available hydrotalcite products include STABIACE HT-1, STABIACE HT-7, and STABIACE HT-P of Sakai Chemical Industry Co., Ltd., and DHT-4A, DHT-4A2, and DHT-4C of Kyowa Chemical Industry Co., Ltd. Can be mentioned.
The mass average particle diameter of these inorganic fine particles and organic fine particles is preferably 0.01 to 10 μm, and more preferably 0.1 to 5 μm.

The content of the fine particles (d) in the curable resin composition of the present embodiment is 0.1 with respect to the total amount of the polyurethane (a), the solvent (b), the epoxy compound (c) and the fine particles (d). It is preferably mass% or more and 60 mass% or less, more preferably 0.5 mass% or more and 40 mass% or less, and further preferably 1 mass% or more and 20 mass% or less.

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

Further, when the curable resin composition of the present embodiment contains fine particles (d), the content of the solvent (b) in the curable resin composition of the present embodiment is determined by the curable resin composition of the present embodiment. It is preferably 25% by mass or more and 75% by mass or less, preferably 30% by mass, based on the total amount of the substance, that is, the total amount of the polyurethane (a), the solvent (b), the epoxy compound (c) and the fine particles (d). It is more preferably 75% by mass or less, and further preferably 35% by mass or more and 70% by mass or less.

When the content of the solvent (b) is within the range of 25% by mass or more and 75% by mass or less with respect to the total amount of the curable resin composition of the present embodiment, the viscosity of the curable resin composition is determined by the screen printing method. The viscosity is good for printing, and the spread of the curable resin composition due to bleeding after screen printing is not so large. As a result, in addition to the fact that the printed area of the curable resin composition actually printed is less likely to be larger than the portion to which the curable resin composition is to be coated (that is, the shape of the printing plate), in addition to the fact that it is unlikely to occur. The printability of screen printing (good plate release, etc.) is improved.

Further, even when the curable resin composition of the present embodiment contains fine particles (d), the epoxy compound (with respect to the total amount of the polyurethane (a) and the epoxy compound (c) in the curable resin composition of the present embodiment ( The ratio of the content of c) is preferably 1% by mass or more and 60% by mass or less, more preferably 2% by mass or more and 50% by mass or less, and 3% by mass or more and 40% by mass or less. More preferred. 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 resin composition of the present embodiment is 40% by mass or more and 99% by mass or less. It is more preferably 50% by mass or more and 98% by mass or less, and further preferably 60% by mass or more and 97% by mass or less.

Even when the curable resin composition of the present embodiment contains fine particles (d), 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. When it is 60% by mass or less, it is possible to balance the low warpage property of the flexible wiring board described later, which is coated with the overcoat film described later, and the disconnection suppressing property of the wiring.

(I-5) Curing Accelerator (e)
A curing accelerator (e) may be added to the curable resin 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 functional group such as the carboxy group of the polyurethane (a) and the epoxy group of the epoxy compound (c), but the functional group is not particularly limited. When the group is a carboxy group, for example, the following compounds can be mentioned.

That is, examples of curing accelerators 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-undecyl imidazole, 2-heptadecyl imidazole, 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 trimerite, 1-cyanoethyl-2-phenylimidazolium trimerite, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimerite, 1-cyanoethyl-2-undecylimidazole Rium trimerite, 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, vinyl imidazole, 1-methylimidazole, 1-allyl imidazole, 2-ethylimidazole, 2-Buchi Luimidazole, 2-butyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 1-benzyl-2-phenylimidazole hydrogen bromide, 1-dodecyl-2 Examples thereof 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 curing accelerators include triphenylphosphine, diphenyl (p-tryl) phosphine, tris (alkylphenyl) phosphine, tris (alkoxyphenyl) phosphine, tris (alkyl alkoxyphenyl) phosphine, tris (dialkylphenyl). Trisphine, 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 amine compounds such as triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris (dimethylaminomethyl) phenol, and dicyandiazide.
One of these curing accelerators may be used alone, or two or more thereof may be used in combination.

Among these curing accelerators, melamine, imidazole compound, cycloamidine compound and its derivative, phosphine compound, and amine compound are considered in consideration of both the curing promoting action and the electrical insulation performance of the cured product of the present embodiment described later. Is preferable, and melamine, 1,5-diazabicyclo (4.3.0) nonen-5 and a salt thereof, 1,8-diazabicyclo (5.4.0) undecene-7 and a salt thereof are more preferable.

The content of the curing accelerator (e) in the curable resin composition of the present embodiment is not particularly limited as long as the curing promoting effect is exhibited, but the curing of the curable resin composition of the present embodiment is not particularly limited. From the viewpoint of properties, the cured product of the present embodiment described later, the electrical insulation characteristics of the overcoat film, and water resistance, the curing accelerator (e) is used with the total amount of the polyurethane (a) and the epoxy compound (c) being 100 parts by mass. It is preferably blended in the range of 0.05 parts by mass or more and 5 parts by mass or less, and more preferably in the range of 0.1 parts by mass or more and 3 parts by mass or less.
When the content of the curing accelerator (e) in the curable resin composition of the present embodiment is within the above range, the curable resin composition of the present embodiment can be cured in a short time, and will be described later. The cured product of this embodiment and the overcoat film have good electrical insulation characteristics and water resistance.

(I-6) Other Additives In addition to the fine particles (d) and the curing accelerator (e), various additives may be added to the curable resin composition of the present embodiment. The additives that can be blended in the curable resin composition of the present embodiment will be described below.

When the curable resin composition of the present embodiment is cured, a cured product having good electrical insulation characteristics can be obtained. Therefore, the curable resin composition of the present embodiment is used, for example, as a resist ink for insulating protection of wiring. It can be used as a composition such as. When the curable resin composition of the present embodiment is used as a composition for resist ink for insulating and protecting wiring (that is, an overcoating agent for flexible wiring boards), the generation of bubbles during printing is prevented or suppressed. The antifoaming agent (f) may be added for the purpose of

The type of defoaming agent is such that the generation of bubbles can be prevented or suppressed when the curable resin composition of the present embodiment is printed and applied on the surface of the flexible substrate at the time of manufacturing the flexible wiring board. For example, the following antifoaming agent is mentioned as an example, although it is not particularly limited.
That is, examples of defoamers include BYK-077 (manufactured by Big Chemie Japan Co., Ltd.), SN Deformer 470 (manufactured by Sannopco Co., Ltd.), TSA750S (manufactured by Momentive Performance Materials Co., Ltd.), and silicone oil SH-203 (manufactured by Momentive Performance Materials). Silicone defoamers 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 polymerization system defoamers such as Disparon 230HF (manufactured by Kusumoto Kasei Co., Ltd.), Surfinol DF-110D (manufactured by Nisshin Chemical Industry Co., Ltd.), Surfinol DF-37 (manufactured by Nisshin Chemical Industry Co., Ltd.), etc. Examples thereof include an acetylene diol-based defoaming agent and a fluorine-containing silicone-based defoaming agent such as FA-630.

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

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

If it is necessary to suppress the oxidative deterioration of polyurethane (a) and discoloration during heating, use an antioxidant such as a phenol-based antioxidant, a phosphite-based antioxidant, or a thioether-based antioxidant. It is preferably added to the curable resin composition of the embodiment.
Further, a flame retardant or a lubricant can be added to the curable resin composition of the present embodiment, if necessary.

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

<Viscosity of curable resin composition>
The viscosity of the curable resin composition of the present embodiment at 25 ° C. is preferably 10,000 mPa · s or more and 100,000 mPa · s or less, and more preferably 20,000 mPa · s or more and 60,000 mPa · s or less.

In the present specification, the viscosity of the curable resin composition of the present embodiment at 25 ° C. is determined by using a cone / plate viscometer (manufactured by Brookfield, model DV-II + Pro, spindle model number CPE-52). The viscosity is measured 7 minutes after the start of rotation under the condition of a rotation speed of 10 rpm.

<Thixotropy index of curable resin composition>
When the curable resin composition of the present embodiment is used as a composition for resist ink for insulation protection of wiring (that is, an overcoat agent for a flexible wiring board), printing of the curable resin composition of the present embodiment In order to improve the properties, it is preferable that the thixotropy index of the curable resin composition of the present embodiment is within a certain range.

When the curable resin composition of the present embodiment is used as an overcoat agent for a flexible wiring board, in order to improve the printability (for example, printability in screen printing) of the curable resin composition of the present embodiment, The chixotropy index of the curable resin composition of the embodiment is preferably 1.1 or more, more preferably 1.1 or more and 3.0 or less, and 1.1 or more and 2.5 or less. It is more preferably within the range.

When the curable resin composition of the present embodiment is used as an overcoat agent for a flexible wiring board, if the chixotropy index of the curable resin composition of the present embodiment is within the range of 1.1 or more and 3.0 or less. Since the printed curable resin composition of the present embodiment does not easily flow and can be maintained in the form of a film having a constant thickness, it is easy to maintain the printed pattern.

As a method of setting the thixotropy index of the curable resin composition to 1.1 or more, a method of adjusting the thixotropy index by using the above-mentioned inorganic fine particles or organic fine particles, or a method of adjusting the thixotropy index by using a polymer additive. However, a method of adjusting the thixotropy index using inorganic fine particles or organic fine particles is preferable.

In the present specification, the thixotropy index of the curable resin composition of the present embodiment is the ratio of the viscosity measured at a rotation speed of 1 rpm at 25 ° C. to the viscosity measured at a rotation speed of 10 rpm at 25 ° C. ([Rotation speed]. [Viscosity at 1 rpm] / [Viscosity at rotation speed of 10 rpm]). These viscosities can be measured using a cone / plate viscometer (Brookfield, model DV-II + Pro, spindle model number CPE-52).

II. Cured product The cured product of the present embodiment is a cured product obtained by curing the curable resin composition of the present embodiment. The method for curing the curable resin composition of the present embodiment is not particularly limited, and it can be cured by heat or active energy rays (for example, ultraviolet rays, electron beams, X-rays). Therefore, a polymerization initiator such as a thermal radical generator or a photoradical generator may be added to the curable resin composition of the present embodiment.

The cured product of this embodiment can be used as an insulating protective film (overcoat film). In particular, the cured product of this embodiment can be used as an insulating protective film for wiring by covering all or part of the wiring of a flexible wiring board such as a chip-on film (COF).

If the overcoat film containing the cured product of the present embodiment is formed on the surface of the flexible substrate, it is possible to form a flexible wiring board having both excellent low warpage property and wire disconnection suppressing property. Further, since the cured product of the present embodiment has low stringiness and excellent defoaming property of the curable resin composition of the present embodiment, it can be produced with excellent workability and productivity. Further, the cured product of the present embodiment has good low warpage, flexibility, and moisture resistance, and also has excellent long-term insulation reliability. Further, the cured product of the present embodiment has good adhesion to a base material such as a flexible substrate. Further, the cured product of the present embodiment is less likely to cause a tack phenomenon on the surface.

III. Overcoat film and flexible wiring board and method for manufacturing the overcoat film of the present embodiment is a film containing a cured product of the present embodiment, and is manufactured by curing the curable resin composition of the present embodiment. Can be done. More specifically, the overcoat film of the present embodiment is formed by applying the curable resin composition of the present embodiment to all or a part of the surface of the flexible substrate on which the wiring is formed. It can be produced by curing the film-like curable resin composition by heating or the like to obtain a film-like cured product. The overcoat film of this embodiment is suitable as an overcoat film for a flexible wiring board.

In the flexible wiring board of the present embodiment, all or a part of the surface of the flexible substrate on which the wiring is formed is covered with an overcoat film.
The flexible wiring board of the present embodiment can be manufactured from the curable resin composition of the present embodiment and a flexible substrate. More specifically, the flexible wiring board of the present embodiment is formed by applying the curable resin composition of the present embodiment to all or a part of the surface of the flexible substrate on which the wiring is formed. It can be produced by curing the film-like curable resin composition to form an overcoat film. The wiring covered with the overcoat film is preferably tin-plated copper wiring in consideration of antioxidant and economical aspects of the wiring.

An example of the method for manufacturing the overcoat film and the flexible wiring board of the present embodiment will be described below. The overcoat film and the flexible wiring board of the present embodiment can be formed, for example, through the following steps 1, 2, and 3.
(Step 1) A printing step of forming a printing film on the wiring pattern portion by printing the curable resin composition of the present embodiment on at least a part of the wiring pattern portion of the flexible substrate.
(Step 2) A solvent removing step of evaporating part or all of the solvent in the printing film by placing the printing film obtained in step 1 in an atmosphere of 40 to 100 ° C.
(Step 3) A curing step of forming an overcoat film by curing the printing film obtained in step 1 or the printing film obtained in step 2 by heating at 100 to 170 ° C.

The printing method of the curable resin composition in step 1 is not particularly limited. For example, the curable resin composition of the present embodiment can be applied to a flexible substrate by a screen printing method, a roll coater method, a spray method, a curtain coater method, or the like. A printed film can be obtained by coating.
Step 2 is an operation performed as needed, and step 3 may be performed immediately after step 1, and the curing reaction and solvent removal may be performed simultaneously in step 3. When step 2, the temperature is preferably 40 ° C. or higher and 100 ° C. or lower, and 60 ° C. or higher and 100 ° C. or lower, in consideration of the evaporation rate of the solvent and the rapid transition to the thermosetting operation. Is more preferable, and it is further preferable that the temperature is 70 ° C. or higher and 90 ° C. or lower. The time for evaporating the solvent in step 3 and step 2 is not particularly limited, but 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 step 3 is preferably 105 ° C. or higher and 160 ° C. or lower from the viewpoint of preventing diffusion of the plating layer and imparting low warpage and flexibility suitable as a protective film to the overcoat film. , 110 ° C. or higher and 150 ° C. or lower is more preferable. The thermosetting time performed in the step 3 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.

By the above method, it is possible to obtain a flexible wiring board in which all or a part of the surface of the flexible substrate on which the wiring is formed is covered with an overcoat film. Since the overcoat film thus obtained is excellent in flexibility and flexibility, the flexible wiring board of the present embodiment is also excellent in flexibility and flexibility, and the flexible wiring board is shaken. Even so, it is difficult for wiring to break (excellent in suppressing wiring breaks). Therefore, the flexible wiring board of the present embodiment is less likely to cause cracks, and is suitable for a flexible printed wiring board used in a technique such as chip-on-film (COF).

Further, since the curable resin composition of the present embodiment is less likely to shrink during curing, the flexible wiring board of the present embodiment has a small warp. 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. Further, since the overcoat film has excellent long-term insulation reliability, the flexible wiring board of the present embodiment also has excellent long-term insulation reliability.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
<Synthesis of polyester diol (reference synthesis example)>
983.5 g (6.74 mol) of phthalic anhydride and 879.2 g (7.44 mol) of 1,6-hexanediol 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. and stirring was continued for 4 hours. Then, while continuing stirring, 1.74 g of mono-n-butyltin oxide was added.

Then, while gradually raising the internal temperature of the reaction vessel, the pressure inside the reaction vessel was gradually reduced by a vacuum pump, and water was removed from the reaction vessel by vacuum distillation. Finally, the internal temperature was raised to 220 ° C. and the pressure was reduced to 133.32 Pa. After 15 hours, it was confirmed that the water did not completely distill off, and the reaction was terminated.
When the hydroxyl value of the obtained polyester diol was measured, the hydroxyl value was 53.1 mgKOH / g.

<Synthesis of polyurethane>
(Example 1 of Synthesis)
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, polyester diol (Polylite (registered trademark) OD-X-2900 manufactured by DIC Co., Ltd., hydroxyl value 53.4 mgKOH / g, 1,6-hexanediol and anhydrous phthal) 122.1 g of polyester diol made from acid, 12.9 g of 2,2-dimethylol propanoic acid (manufactured by Nippon Kasei Co., Ltd.), which is a carboxy group-containing diol, and diols other than polyester diol and carboxy group-containing diol. 21.4 g of a certain 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (manufactured by Osaka Gas Chemical Co., Ltd., trade name BPEF) and γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) 203. 5 g was charged and heated to 100 ° C. to dissolve all the raw materials.

After lowering the temperature of the reaction solution to 90 ° C, 20.9 g of the diisocyanate compound trans-1,4-bis (isocyanatomethyl) cyclohexane (Fortimo (registered trademark) manufactured by Mitsui Chemicals, Inc.) and dicyclohexylmethane-4 , 4'-Diisocyanate (manufactured by Mitsui Chemicals, Inc.) was added dropwise over 30 minutes using a dropping funnel.

After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (Manufactured) 1.7 g was added dropwise to the reaction solution, and the reaction was further carried out 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. After cooling the polyurethane solution A1 to room temperature, 44.7 g of γ-butyrolactone and 43.8 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A1 was 133000 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”) is 8000, the weight average molecular weight (Mw) is 74000, and the z average molecular weight (Mz). ) Is 658600, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 8.9. The acid value of polyurethane AU1 was 25.0 mgKOH / g. The aromatic ring concentration was 3.21 mmol / g. The solid content concentration in the polyurethane solution A1 was 40.5% by mass.

(Example 2 of Synthesis)
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, polyester diol (Polylite (registered trademark) OD-X-2900 manufactured by DIC Co., Ltd., hydroxyl value 53.4 mgKOH / g, 1,6-hexanediol and anhydrous phthal). 112.0 g of polyester diol made from acid, 11.8 g of 2,2-dimethylol propanoic acid (manufactured by Nippon Kasei Co., Ltd.), which is a carboxy group-containing diol, and diols other than polyester diol and carboxy group-containing diol. 9.79 g of a certain 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (manufactured by Osaka Gas Chemical Co., Ltd., trade name BPEF) and a fluorene group-containing diol represented by the following chemical formula (3) (Osaka) 19.62 g of Gas Chemical Co., Ltd., trade name BPEF-9EO) and 203.1 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) as a solvent were charged and heated to 100 ° C. to dissolve all the raw materials.

After lowering the temperature of the reaction solution to 90 ° C., 51.8 g of methylenebis (4-cyclohexylisocyanate) (Death Module-W (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), which is a diisocyanate compound, was added to 30 by a dropping funnel. Dropped over a minute.
After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (Manufactured) 1.7 g was added dropwise to the reaction solution, and the reaction was further carried out at 80 ° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as "polyurethane solution A2") was obtained. After cooling the polyurethane solution A2 to room temperature, 45.1 g of γ-butyrolactone and 43.8 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A2 was 131000 mPa · s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group contained in the polyurethane solution A2 (hereinafter referred to as "polyurethane AU2") is 10,000, the weight average molecular weight (Mw) is 61,000, and the z average molecular weight (Mz). ) Is 359,900, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 5.9. The acid value of polyurethane AU2 was 23.9 mgKOH / g. The aromatic ring concentration was 2.51 mmol / g. The solid content concentration in the polyurethane solution A2 was 42.5% by mass.

(Example 3 of Synthesis)
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, polyester diol (Polylite (registered trademark) OD-X-2900 manufactured by DIC Co., Ltd., hydroxyl value 53.4 mgKOH / g, 1,6-hexanediol and anhydrous phthal) 112.9 g of polyester diol made from acid, 12.8 g of 2,2-dimethylol propanoic acid (manufactured by Nippon Kasei Co., Ltd.), which is a carboxy group-containing diol, and diols other than polyester diol and carboxy group-containing diol. 20.4 g of a certain 1,1-dimethyl-bis [4- (2-hydroxyethoxy) phenyl] methane (Biz-A-2EO manufactured by Meiwa Kasei Co., Ltd.) and γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) as a solvent. ) 204.7 g was charged and heated to 100 ° C. to dissolve all the raw materials.

After lowering the temperature of the reaction solution to 90 ° C., 58.6 g of methylenebis (4-cyclohexylisocyanate) (Death Module-W (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), which is a diisocyanate compound, was added to 30 by a dropping funnel. Dropped over a minute.
After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (Manufactured) 2.0 g was added dropwise to the reaction solution, and the reaction was further carried out at 80 ° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as "polyurethane solution A3") was obtained. After cooling the polyurethane solution A3 to room temperature, 45.5 g of γ-butyrolactone and 43.8 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A3 was 150,000 mPa · s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group (hereinafter referred to as "polyurethane AU3") contained in the polyurethane solution A3 is 12000, the weight average molecular weight (Mw) is 57,000, and the z average molecular weight (Mz). ) Is 221730, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 3.89. The acid value of polyurethane AU3 was 24.8 mgKOH / g. The aromatic ring concentration was 2.73 mmol / g. The solid content concentration in the polyurethane solution A3 was 44.5% by mass.

(Example 4 of Synthesis)
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, polyester diol (Polylite (registered trademark) OD-X-2900 manufactured by DIC Co., Ltd., hydroxyl value 53.4 mgKOH / g, 1,6-hexanediol and anhydrous phthal) 110.6 g of polyester diol made from acid, 12.9 g of 2,2-dimethylol propanoic acid (manufactured by Nippon Kasei Co., Ltd.), which is a carboxy group-containing diol, and diols other than polyester diol and carboxy group-containing diol. 20.0 g of a certain bis-4- (2-hydroxyethoxy) biphenyl (BP-2EO manufactured by Meiwa Kasei Co., Ltd.) and 204.6 g of a solvent γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) were charged at 100 ° C. All raw materials were dissolved by heating to.

After lowering the temperature of the reaction solution to 90 ° C., 61.1 g of methylenebis (4-cyclohexylisocyanate) (Death Module-W (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), which is a diisocyanate compound, was added to 30 by a dropping funnel. Dropped over a minute.
After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (Manufactured) 2.1 g was added dropwise to the reaction solution, and the reaction was further carried out at 80 ° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as "polyurethane solution A4") was obtained. After cooling the polyurethane solution A4 to room temperature, 45.6 g of γ-butyrolactone and 43.8 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A4 was 166000 mPa · s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group (hereinafter referred to as "polyurethane AU4") contained in the polyurethane solution A4 is 12600, the weight average molecular weight (Mw) is 59000, and the z average molecular weight (Mz). ) Is 248,390, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 4.21. The acid value of polyurethane AU4 was 25.1 mgKOH / g. The aromatic ring concentration was 2.77 mmol / g. The solid content concentration in the polyurethane solution A4 was 41.2% by mass.

(Example 5)
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, polyester diol (Polylite (registered trademark) OD-X-2900 manufactured by DIC Co., Ltd., hydroxyl value 53.4 mgKOH / g, 1,6-hexanediol and anhydrous phthal) 114.4 g of polyester diol made from acid, 12.9 g of 2,2-dimethylol propanoic acid (manufactured by Nippon Kasei Co., Ltd.), which is a carboxy group-containing diol, and diols other than polyester diol and carboxy group-containing diol. 20.5 g of a certain 1,1-bis [4- (2-hydroxyethoxy) phenyl] cyclohexane (Biz-Z-2EO manufactured by Meiwa Kasei Co., Ltd.) and γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) 204 as a solvent. 8.8 g was charged and heated to 100 ° C. to dissolve all the raw materials.

After lowering the temperature of the reaction solution to 90 ° C., 57.0 g of methylenebis (4-cyclohexylisocyanate) (Death Module-W (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), which is a diisocyanate compound, was added to 30 by a dropping funnel. Dropped over a minute.
After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (Manufactured) 2.0 g was added dropwise to the reaction solution, and the reaction was further carried out at 80 ° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as "polyurethane solution A5") was obtained. After cooling the polyurethane solution A5 to room temperature, 45.4 g of γ-butyrolactone and 43.8 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A5 was 106000 mPa · s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group contained in the polyurethane solution A5 (hereinafter referred to as "polyurethane AU5") is 8300, the weight average molecular weight (Mw) is 95,000, and the z average molecular weight (Mz). ) Is 263150, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 2.77. The acid value of polyurethane AU5 was 24.7 mgKOH / g. The aromatic ring concentration was 2.69 mmol / g. The solid content concentration in the polyurethane solution A5 was 38.7% by mass.

(Example 6 of Synthesis)
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, polyester diol (Polylite (registered trademark) HS-2H-209P manufactured by DIC Co., Ltd., hydroxyl value 28.8 mgKOH / g, 1,6-hexanediol and anhydrous phthal). 121.5 g of polyester diol made from acid, 12.9 g of 2,2-dimethylol propanoic acid (manufactured by Nippon Kasei Co., Ltd.), which is a carboxy group-containing diol, and diols other than polyester diol and carboxy group-containing diol. 22.3 g of a certain 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene (manufactured by Osaka Gas Chemical Co., Ltd., trade name BPEF) and γ-butyrolactone (manufactured by Mitsubishi Chemical Co., Ltd.) 203. 2 g was charged and heated to 100 ° C. to dissolve all the raw materials.

After lowering the temperature of the reaction solution to 90 ° C., 48.6 g of methylenebis (4-cyclohexylisocyanate) (Death Module-W (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), which is a diisocyanate compound, was added to 30 by a dropping funnel. Dropped over a minute.
After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (Manufactured) 1.7 g was added dropwise to the reaction solution, and the reaction was further carried out at 80 ° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as "polyurethane solution A6") was obtained. After cooling the polyurethane solution A6 to room temperature, 45.0 g of γ-butyrolactone and 43.8 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A6 was 123000 mPa · s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group contained in the polyurethane solution A6 (hereinafter referred to as "polyurethane AU6") is 10500, the weight average molecular weight (Mw) is 89000, and the z average molecular weight (Mz). ) Is 335530, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 3.77. The acid value of polyurethane AU6 was 25.1 mgKOH / g. The aromatic ring concentration was 1.64 mmol / g. The solid content concentration in the polyurethane solution A6 was 41.2% by mass.

(Example 7)
[Synthesis of polyester diol]
1,6-Hexanediol (manufactured by Kuraray Co., Ltd.) 98.7 g, 9, 9- in a reaction vessel equipped with a stirrer, a thermometer, and a Leibich-type condenser capable of distilling water of by-products generated by the reaction. Add 109.6 g of bis [4- (2-hydroxyethoxy) phenyl] fluorene (manufactured by Osaka Gas Chemical Co., Ltd., trade name BPEF) and 154.1 g of hexahydrophthalic anhydride (manufactured by Mitsubishi Gas Chemicals Co., Ltd.) in an oil bath. The internal temperature of the reaction vessel was raised to 210 ° C. using Fluorene to dissolve all the raw materials.

After continuing the reaction at 210 ° C. for 4 days while removing the by-produced water, the temperature was lowered to 120 ° C. when the amount of distilled water reached 18 g, and the reaction was stopped. As a result, a polyester diol PE1 having a fluorene skeleton was obtained.
When the hydroxyl value of the obtained polyester diol PE1 was measured, the hydroxyl value was 60.0 mgKOH / g. Therefore, the number average molecular weight of the polyester diol PE1 is 3360.

[Synthesis of polyurethane]
In a reaction vessel equipped with a stirrer, a thermometer and a condenser, 93.1 g of the above polyester diol PE1 (hydroxyl value 60.0 mgKOH / g) and 2,2-dimethylol propanoic acid (Nippon Kasei), which is a carboxy group-containing diol, are placed. 7.5 g of (manufactured by Mitsubishi Chemical Corporation) and 125.0 g of γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation) as a solvent were charged and heated to 100 ° C. to dissolve all the raw materials.
After lowering the temperature of the reaction solution to 90 ° C., 23.3 g of methylenebis (4-cyclohexylisocyanate) (Death Module-W (trade name) manufactured by Sumika Bayer Urethane Co., Ltd.), which is a diisocyanate compound, was added to 30 by a dropping funnel. Dropped over a minute.

After the reaction at 120 ° C. for 8 hours, it was confirmed by infrared spectroscopy (IR) that the absorption due to the C = O expansion and contraction vibration of the isocyanato group was hardly observed. Methylethyloxime (Ube Kosan Co., Ltd.) (M.) 1.1 g was added dropwise to the reaction solution, and the reaction was further carried out at 80 ° C. for 3 hours. As a result, a solution containing a polyurethane having a carboxy group (hereinafter referred to as "polyurethane solution A7") was obtained. After cooling the polyurethane solution A7 to room temperature, 27.9 g of γ-butyrolactone and 27.0 g of diethylene glycol diethyl ether were added to adjust the viscosity.

The viscosity of the obtained polyurethane solution A7 was 77,000 mPa · s. Further, the number average molecular weight (Mn) of the polyurethane having a carboxy group contained in the polyurethane solution A7 (hereinafter referred to as "polyurethane AU7") is 12000, the weight average molecular weight (Mw) is 78,000, and the z average molecular weight (Mz). ) Is 399,360, and the parameter Mz / Mw representing the spread of the molecular weight distribution was calculated to be 5.12. The acid value of polyurethane AU7 was 25.0 mgKOH / g. The aromatic ring concentration was 1.88 mmol / g. The solid content concentration in the polyurethane solution A7 was 43.2% by mass.
The data for polyurethanes AU1 to AU7 are summarized in Table 1.

(Measurement of acid value)
A 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 under heating to obtain polyurethane, and the acid value was measured according to the potentiometric titration method specified in JIS K0070. For the measurement of the acid value by the potentiometric titration method, for example, a potentiometric titration device AT-510 manufactured by Kyoto Denshi Kogyo Co., Ltd. and a composite glass electrode C-173 can be used.

(Measurement of number average molecular weight, weight average molecular weight, z average molecular weight of polyurethane)
The number average molecular weight, weight average molecular weight, and z average molecular weight of the synthesized polyurethane are polystyrene-equivalent number average molecular weight (Mn), weight average molecular weight (Mw), and z average molecular weight (Mz) measured by GPC. The measurement conditions of GPC are as described above.

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

<Manufacturing of main ingredient formulation>
160.0 parts by mass of polyurethane solution A1 with γ-butyrolactone added to adjust the solid content concentration to 40% by mass, and 6.3 parts by mass of silica fine particles (manufactured by Nippon Aerosil Co., Ltd., trade name Aerosil R-974). , 0.72 parts by mass of melamine (manufactured by Nissan Chemical Industries, Ltd.) and 8.4 parts by mass of diethylene glycol diethyl ether, which are curing accelerators, in a three-roll mill (manufactured by Inoue Seisakusho Co., Ltd., model S-4 3 / 4 × 11) was used for mixing. To this, 2.0 parts by mass of an antifoaming agent (manufactured by Momentive Performance Materials, trade name TSA750S) was added and mixed using a spatula to obtain a main agent formulation C1.
The same operations as for the main agent formulation C1 were carried out except that the type of the polyurethane solution was changed from the polyurethane solution A1 to any of the polyurethane solutions A2 to A7 to obtain the main agent formulations C2 to C7, respectively.

<Manufacturing of curing agent solution>
(Production Example 1 of Hardener 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 chemical formula (2) (manufactured by Mitsubishi Chemical Corporation, grade name: JER604, epoxy equivalent 120 g / eqv) and diethylene glycol diethyl. After adding 18.25 parts by mass of ether and raising the internal temperature of the container to 40 ° C. while stirring, stirring was continued for 30 minutes. After confirming that the epoxy compound was completely dissolved, the mixture 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 E1.

(Production Example 2 of Hardener Solution)
In a container equipped with a stirrer, thermometer and condenser, 21.66 parts by mass of cyclohexanedimethanol epoxy resin (manufactured by Showa Denko Co., Ltd., grade name: Showfree (registered trademark) CDMDG, epoxy equivalent 126 g / eqv) and diethylene glycol diethyl After adding 18.25 parts by mass of ether and raising the internal temperature of the container to 40 ° C. while stirring, stirring was continued for 30 minutes. After confirming that the epoxy resin was completely dissolved, the mixture was cooled to room temperature to obtain an epoxy resin solution having a concentration of 48% by mass. This epoxy resin solution is referred to as a curing agent solution E2.

(Production Example 3 of Hardener Solution)
Cyclohexanedimethanol epoxy resin (manufactured by Showa Denko Co., Ltd., grade name: show-free (registered trademark) PETG, epoxy equivalent 90 g / eqv) 15.47 parts by mass and diethylene glycol diethyl in a container equipped with a stirrer, a thermometer and a condenser. After adding 18.25 parts by mass of ether and raising the internal temperature of the container to 40 ° C. while stirring, stirring was continued for 30 minutes. After confirming that the epoxy resin was completely dissolved, the mixture was cooled to room temperature to obtain an epoxy resin solution having a concentration of 48% by mass. This epoxy resin solution is referred to as a curing agent solution E3.

<Manufacturing of curable resin composition>
90 parts by mass of the main agent formulation C1 and 4.0 parts by mass of the curing agent solution E1 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 were added as solvents. .. The curable resin composition F1 was obtained by stirring with a spatula at room temperature for 5 minutes.

Curable resin compositions F2 to F7 were obtained in the same manner as in the case of the curable resin composition F1 except that any of the main agent formulations C2 to C7 was used instead of the main agent formulation C1 (Table 2). See). Further, the curable resin compositions F8 and F9 were obtained in the same manner as in the case of the curable resin composition F1 except that the curing agent solution E2 or the curing agent solution E3 was used instead of the curing agent solution E1. See Table 2).

Furthermore, 700 parts by mass of FREX SOLDER MASK NPR (registered trademark) -3400 A (corresponding to the main agent formulation) manufactured by Nippon Polytech Co., Ltd. and the curing agent HARDENER NPR (registered trademark) -3400 B (registered trademark) manufactured by Nippon Polytech Co., Ltd. 120 parts by mass (corresponding to the curing agent solution) was mixed to obtain a curable resin composition G1.
Further, 100 parts by mass of SN-9000FA (corresponding to the main agent formulation) manufactured by Hitachi Kasei Co., Ltd. and 10 parts by mass of the curing agent SN-9000FB (corresponding to the curing agent solution) manufactured by Hitachi Kasei Co., Ltd. Mixing gave a curable resin composition G2.
The NPR-3400 A, B and SN-9000F A, B are commercially available as curable compositions for forming an overcoat film of a flexible wiring board.

<Evaluation of overcoat film and flexible wiring board>
Flexible wiring boards having an overcoat film (Examples 1 to 9 and Comparative Examples 1 and 2) were produced using the curable resin compositions F1 to F9 and G1 and G2, and were flexible and had a wire disconnection inhibitory property. , Warpage, and long-term insulation reliability were evaluated.

(Evaluation of flexibility)
Flexible copper-clad laminate (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex, copper thickness 8 μm, polyimide thickness 38 μm) on copper with a width of 75 mm and a length of 110 mm, and the thickness after curing. The curable resin composition was applied by screen printing so that the thickness was 15 μm. The flexible copper-clad laminate on which the curable resin composition was printed was held 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 resin composition.

After peeling off the PET film lining the flexible copper-clad laminate, it was cut out with a cutter knife to prepare a strip-shaped test piece with a width of 10 mm. The test piece was bent about 180 degrees so that the surface on which the film of the cured product was formed was on the outside, and compressed at a pressure of 0.5 ± 0.2 MPa for 3 seconds using a compressor. Then, with the bent portion of the test piece bent, the film of the cured product was observed at a magnification of 30 times using a microscope to confirm the presence or absence of cracks. The results are shown in Table 2.

(Evaluation of wiring disconnection suppression)
Flexible copper-covered laminated board (manufactured by Sumitomo Metal Mining Co., Ltd., grade name: Esperflex US, copper thickness 8 μm, polyimide thickness 38 μm) is etched and JPCA- is a standard of the Japan Electronic Circuit Industry Association (JPCA). A substrate having a fine comb-shaped pattern as described in ET01 (copper wiring width / copper wiring spacing = 15 μm / 15 μm) was used, and the substrate having a fine comb-shaped pattern was tin-plated to produce a flexible wiring board.

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

Testing machine: MIT tester BE202 manufactured by Tester Sangyo Co., Ltd.
Bending speed: 10 times / minute Load: 200 g
Bending angle: ± 90 °
Radius of the tip of the grip: 0.5 mm
A MIT test was conducted under the above test conditions, and the presence or absence of cracks in the wiring was visually observed every 10 bends, and the wire breakage inhibitory property was evaluated by the number of bends in which the cracks occurred. The results are shown in Table 2.

(Evaluation of warpage)
Screen printing was performed using a # 180 mesh polyester printing plate, and a curable resin composition was applied onto a polyimide base material (Kapton (registered trademark) 100EN manufactured by Toray DuPont, thickness 25 μm).

The substrate coated with the curable resin composition thus obtained is placed in a hot air circulation dryer having a temperature of 80 ° C. for 30 minutes, and then placed in a hot air circulation dryer having a temperature of 120 ° C. for 60 minutes. , The coating film of the curable resin composition formed on the substrate was cured.
The base material having the cured product film was cut with a circle cutter to obtain a circular base material having a cured product film and having a diameter of 50 mm (hereinafter referred to as “substrate”). The obtained substrate exhibits a deformation in which the vicinity of the center warps in a convex or concave shape.

After the substrate is left at 23 ° C. for 1 hour, the substrate is placed on a flat plate in a downwardly convex state. That is, the convex portion near the center of the warped substrate is placed on the flat plate with the convex portion facing downward so that the convex portion of the warped substrate is in contact with the horizontal plane of the flat plate. Then, the distance of the portion of the peripheral edge of the warped substrate farthest from the horizontal plane of the flat plate and the distance of the closest portion were measured, the average value was obtained, and the warpage property was evaluated by this average value. The results are shown in Table 2.
The numerical values shown in Table 2 indicate the direction of warpage, and when the substrate is allowed to stand in a downwardly convex state, if the film of the cured product is on the upper side with respect to the polyimide base material, it is "+", and on the lower side. If it becomes, it is set to "-". Then, the case where the size of the warp was more than -3.0 mm + less than 3.0 mm was regarded as acceptable.

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

Next, the curable resin composition was applied onto the flexible wiring board by a screen printing method. The thickness of the film of the printed curable resin composition was set so that the thickness of the film of the curable resin composition on the polyimide surface after drying was 15 μm.
The flexible wiring plate thus obtained was placed in a hot air circulation dryer having a temperature of 80 ° C. for 30 minutes, and then placed in a hot air circulation dryer having a temperature of 120 ° C. for 120 minutes to cure the flexible wiring plate formed on the flexible wiring plate. The film of the sex resin 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 constant temperature / humidity test was conducted under the conditions of a temperature of 120 ° C. and a humidity of 85% RH.
The resistance values of the flexible wiring boards were measured at the initial stage of the temperature and humidity steady test, 100 hours after the start, 250 hours, and 400 hours after the start. The results are shown in Table 2.

(Measurement of spin-spin relaxation time T2 by pulse nuclear magnetic resonance)
On a PET film (manufactured by Toray Co., Ltd., grade name: Lumirror, thickness 125 μm) that has undergone mold release treatment, the size is 75 mm in width and 110 mm in length, and the film thickness after curing is 30 μm. The curable resin composition was applied by bar coat printing. The PET film on which the curable resin composition is printed is held at room temperature for 10 minutes, then placed in a hot air circulation dryer at a temperature of 120 ° C. for 60 minutes, and then placed in a hot air circulation dryer at a temperature of 150 ° C. for 120 minutes. As a result, the film of the curable resin composition formed on the PET film was cured to obtain a film of the cured product.

After peeling off the PET film, a film of the cured product was cut out with a cutter knife to prepare a strip-shaped sample having a length of 3 cm and a width of 5 mm. Then, this sample is packed in a glass sample tube having a diameter of 10 mm so that the total mass is about 500 mg, and the glass sample tube is installed in the pulse nuclear magnetic resonance device so that the sample is located in the coil portion of the pulse nuclear magnetic resonance device. did. Measurements were performed on the three samples under the following conditions, curve fitting (Mono-exponential) was performed on the free induction decay signal f (t) obtained by the measurement, and the spin-lattice relaxation time T1 was calculated. The results are shown in Table 2.

Equipment: Bruker's Biospin the minispec mq20
Measurement nuclide: Hydrogen nucleus Measurement temperature: 40 ° C
Measurement frequency: 20MHz
Pulse program: T1 Innovation Recovery method (reversal recovery method)
First Pulse Separation: 5ms
Final Pulse Separation: 1000ms
Recycle delay: 1s
Gain: 95 dB
Data Points: 20
Delay Sumpling Window: 0.050ms
Sample window: 0.020ms
Scan: 16 times Acquisition scale: 0.3ms

The calculated spin-lattice relaxation time T1 is a value sufficiently smaller than 1s, and if RECYCLE Delay = T1 × 5s is set to 1s in the measurement of the spin-spin relaxation time, it is a sufficient relaxation time. It can be said that. Therefore, the cycle delay is set to 1s, and the spin-spin relaxation time (T2) by the pulse nuclear magnetic resonance method is set for three samples in almost the same manner as in the case of the spin-lattice relaxation time T1. Measurements were made.

Equipment: Bruker's Biospin the minispec mq20
Measurement nuclide: Hydrogen nucleus Measurement frequency: 20MHz
Temperature: 40 ° C
Pulse program: T2 Solid Echo method Recycle delay: 1s
Gain: 77 dB
Data Points: 100
Scan: 16 times Acquisition scale: 0.3ms

For the free induction decay signal f (t) obtained in the above measurement, curve fitting (7. Gauss-Decay Extended) was performed using the above formula as a fitting calculation formula. At that time, the Weibull coefficient was set to W (1) = 2.0, W (2) = 1.0, and W (3) = 1.0. Further, curve fitting was performed in a region where the decay time t was up to 0.3 ms.

A (1), A (2), T2 (1), T2 (2), and T2 (3) were obtained by curve fitting. Further, from the obtained A (1), A (2), T2 (1), and T2 (2), the value of [A (1) × T2 (1) + A (2) × T2 (2)] is obtained. Calculated. These results are shown in Table 2.

From the results shown in Table 2, the value of [A (1) × T2 (1) + A (2) × T2 (2)] is 0.015 ms or less, and T2 (3) is 0.50 ms or more. It can be seen that the flexible wiring boards of Examples 1 to 9 are excellent in low warpage, flexibility, wiring disconnection suppressing property, and long-term insulation reliability.

Therefore, the film containing the cured product of the curable resin compositions F1 to F9 is useful as an insulating protective film for a flexible wiring board. In particular, the flexible wiring board having an overcoat film containing the cured products of the curable resin compositions F1 to F9 has excellent low warpage, so that the processability is improved in the printing process and the curing process. For example, in the mounting process of mounting the IC chip on the flexible wiring board, the alignment accuracy of the mounting position of the IC chip is improved, so that the yield in the manufacturing process is increased.
On the other hand, a comparative example in which the value of [A (1) × T2 (1) + A (2) × T2 (2)] exceeds 0.015 ms and T2 (3) is less than 0.50 ms. The flexible wiring boards 1 and 2 were insufficient in low warpage property and wire disconnection suppression property.

Claims

A free-induced decay signal f (t) of magnetization strength for determining the spin-spin relaxation time T2 of a proton, which is a cured product of a curable resin composition and is measured by a pulse nuclear magnetic resonance method at a measurement frequency of 20 MHz. ) Is approximated by the following formula, and is calculated from A (1), A (2), T2 (1), and T2 (2) in the formula [A (1) × T2 (1) + A. (2) × T2 (2)] is 0.015 ms or less, and T2 (3) is 0.50 ms or more.

Here, the fourth term (offset) of the above-mentioned mathematical expression including four terms is an offset term. Further, A (1), A (2), and A (3) in the above formula are constants, respectively, and A (1) + A (2) + A (3) = 1. T2 (1), T2 (2), and T2 (3) in the above formula are spin-spin relaxation times T2, respectively, and T2 (1) <T2 (2) <T2 (3). Further, W (1), W (2), and W (3) in the above formula are Weibull coefficients, which are numbers 1 or more and 2 or less. Further, t in the above formula is time, and exp is an exponential function with the Napier number e as the base.
The curable resin composition comprises a polyurethane (a) having a functional group reactive with an epoxy group, a solvent (b), and an epoxy compound (c) having two or more epoxy groups in one molecule. The cured product according to claim 1, which contains.
The second aspect of claim 2, wherein the polyurethane (a) has a first urethane structural unit having at least one of a polyester structure and a polycarbonate structure, and at least one urethane structural unit of a second urethane structural unit having a carboxy group. The cured product described.
The cured product according to claim 3, wherein the polyurethane (a) further has a third urethane structural unit having a fluorene structure.
The cured product according to any one of claims 2 to 4, wherein the polyurethane (a) has a trans-type 1,4-cyclohexanedimethylene group.
The cured product according to any one of claims 2 to 5, wherein the polyurethane (a) has a number average molecular weight of 10,000 or more and 50,000 or less.
The cured product according to any one of claims 2 to 6, wherein the acid value of the polyurethane (a) is 10 mgKOH / g or more and 70 mgKOH / g or less.
The cured product according to any one of claims 2 to 7, wherein the aromatic ring concentration of the polyurethane (a) is 0.1 mmol / g or more and 5.0 mmol / g or less.
The ratio of the content of the solvent (b) to the total amount of the curable resin composition is 25% by mass or more and 75% by mass or less, and the polyurethane (the polyurethane (a) and the epoxy compound (c) are the total amount. The cured product according to any one of claims 2 to 8, wherein the content ratio of a) is 40% by mass or more and 99% by mass or less.
The cured product according to any one of claims 2 to 9, wherein the curable resin composition further contains at least one fine particle (d) selected from the group consisting of inorganic fine particles and organic fine particles.
The cured product according to claim 10, wherein the fine particles (d) contain silica fine particles.
The cured product according to claim 10, wherein the fine particles (d) contain hydrotalcite fine particles.
The ratio of the content of the solvent (b) to the total amount of the curable resin composition is 25% by mass or more and 75% by mass or less, the polyurethane (a), the solvent (b), the epoxy compound (c), and the fine particles. The ratio of the content of the fine particles (d) to the total amount with (d) is 0.1% by mass or more and 60% by mass or less, and the polyurethane (a) with respect to the total amount of the polyurethane (a) and the epoxy compound (c). The cured product according to any one of claims 10 to 12, wherein the content ratio of a) is 40% by mass or more and 99% by mass or less.
A method for producing a cured product according to any one of claims 1 to 13, wherein the curable resin composition is cured by heat or active energy rays.
An overcoat film containing the cured product according to any one of claims 1 to 13.
A flexible wiring board in which the portion of the surface of the flexible substrate on which the wiring is formed is covered with the overcoat film according to claim 15.
The flexible wiring board according to claim 16, wherein the wiring is tin-plated copper wiring.