JP2019026745A - Thermosetting composition for forming elastic resin layer, elastic resin layer and flexible wiring board - Google Patents

Abstract

To provide a curable composition that can form an elastic resin layer that has sufficient elasticity, adhesion and insulation reliability, and low tackiness, and is, therefore, easy to handle, and an elastic resin layer and a flexible wiring board comprising the same.SOLUTION: A thermosetting composition for forming an elastic resin layer contains (A) styrenic elastomer partially modified with maleic anhydride, (B) cyclohexane tricarboxylic acid anhydride, and (C) thermosetting resin.SELECTED DRAWING: None

Description

  The present invention relates to a thermosetting composition for forming a stretchable resin layer, a stretchable resin layer, and a flexible wiring board.

  In recent years, with respect to wearable devices, biosensors, and connection connector members, there has been an increasing demand for flexible wiring boards having elasticity in addition to conventional flexibility. For example, in addition to downsizing, wearable devices need to be flexible and stretchable in order to be easily attached to a curved surface of the body and to suppress poor connection due to attachment / detachment. In general, a member requiring flexibility and stretchability can be formed of liquid silicone or the like.

  However, silicone has problems such as low adhesion to other materials.

  On the other hand, Patent Document 1 discloses a moisture-proof insulating paint containing a copolymer rubber having a styrene block, a tackifier, a silane coupling agent, and a solvent. Moreover, patent document 2 is disclosing the thermosetting resin composition characterized by including the hardening | curing agent component containing the component which has an epoxy group, and a cyclohexane tricarboxylic acid anhydride.

JP 2005-162986 A International Publication No. 2011/19003

  Incidentally, there is also a demand for a stretchable resin layer that is sufficiently adhered to a stretchable flexible wiring board constituting a wearable device or the like and that has insulation reliability. In addition, a low-tack stretchable resin layer is also required for easy handling. However, it has been clarified that the moisture-proof insulating paint of Patent Document 1 has room for improvement in tackiness, and the thermosetting resin composition of Patent Document 2 has room for improvement in stretchability and the like.

  Accordingly, an object of one aspect of the present invention is to provide a curable composition capable of forming a stretchable resin layer that has sufficient stretchability, adhesion, and insulation reliability and is easy to handle because of low tack, and An object is to provide a stretchable resin layer and a flexible wiring board using the same.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the inventions described in the following [1] to [6].
[1] A thermosetting composition for forming a stretchable resin layer, comprising (A) a styrenic elastomer partially modified with maleic anhydride, (B) cyclohexanetricarboxylic anhydride, and (C) a thermosetting resin. object.
[2] The thermosetting composition for forming a stretchable resin layer according to [1], wherein (A) the styrenic elastomer partially modified with maleic anhydride is a hydrogenated elastomer.
[3] (B) Heat for forming a stretchable resin layer according to [1] or [2], wherein the cyclohexanetricarboxylic acid anhydride is cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride Curable composition.
[4] The thermosetting composition for forming a stretchable resin layer according to any one of [1] to [3], wherein (C) the thermosetting resin is an epoxy resin.
[5] A stretchable resin layer, which is a cured product of the thermosetting composition for forming a stretchable resin layer according to any one of [1] to [4].
[6] A flexible wiring board comprising the stretchable resin layer according to [5].

  The curable composition according to one aspect of the present invention has sufficient stretchability, adhesion, and insulation reliability, and can form a stretchable resin layer that is easy to handle because of low tack. Since the stretchable resin layer according to one aspect of the present invention uses the above-described curable composition, the stretchable resin layer has sufficient stretchability, adhesion, insulation reliability, and low tack, and is easy to handle. Therefore, it can be suitably used as a protective material for wiring of a flexible wiring board, a wearable device, a biosensor, and a connector member.

It is a stress-strain curve which shows the example of a measurement of an expansion-contraction recovery rate.

  Hereinafter, although an embodiment of the present disclosure will be specifically described, the present disclosure is not limited thereto. In the following embodiment, it is needless to say that its constituent elements (including element steps and the like) are not necessarily essential unless otherwise specified or apparently essential in principle. . This also applies to numerical values and ranges, and should not be construed to unduly limit the present disclosure.

In this specification, the terms “layer” and “film” refer to a structure formed in part in addition to a structure formed over the entire surface when observed as a plan view. Is included. The term “process” is not limited to an independent process, and is included in this term if the intended effect of the process is achieved even when it cannot be clearly distinguished from other processes.
Moreover, the numerical value range shown using "to" in this specification shows the range which includes the numerical value described before and behind "to" as a minimum value and a maximum value, respectively.
Furthermore, when referring to the amount of each component in the composition in the present specification, when there are a plurality of substances corresponding to each component in the composition, the plurality of the components present in the composition unless otherwise specified. Means the total amount of substances.

  In the present specification, the term “stretchability” means a property that, after being strained by a tensile load, can be restored to its original shape or a shape close thereto by releasing from the load. For example, it can be said that a material that can be restored to its original shape or a shape close thereto after generating 50% strain by a tensile load has elasticity. More specifically, it can be said that a resin layer having a stretch recovery rate described later of 80% or more is a stretchable resin layer.

[Thermosetting composition for forming elastic resin layer]
A thermosetting composition for forming a stretchable resin layer according to an embodiment (hereinafter, also simply referred to as “curable composition”) is (A) a styrenic elastomer partially modified with maleic anhydride, ( B) contains cyclohexanetricarboxylic acid anhydride and (C) thermosetting resin. This curable composition can be cured by heating to form a stretched cured product or cured film.

<(A) Styrenic elastomer partially modified with maleic anhydride>
The styrene elastomer partially modified with maleic anhydride is a diene elastomer containing an unsaturated double bond selected from polystyrene as a hard segment portion, polybutadiene, polyisoprene, etc. as a soft segment portion, An elastomer having a maleic anhydride moiety partially added to the chain. Maleic anhydride can be partially introduced into the side chain by a radical reaction. In addition, the unsaturated double bond in the soft segment portion may be subjected to hydrogenation treatment (hydrogenation) as described later.

  (A) As a styrenic elastomer partially modified with maleic anhydride, for example, “Tufprene 912” manufactured by Asahi Kasei Corporation is available.

  The hydrogenated styrene elastomer is obtained by adding hydrogen to the unsaturated double bond portion of the soft segment portion of the styrene elastomer, and an effect such as improvement in weather resistance can be expected.

  Styrenic elastomers partially modified with hydrogenated maleic anhydride include “FG1901” and “FG1924” from Clayton Polymer Japan Co., Ltd. “Tuftec M1911”, “Tuftech M1913” and “Tuftec M1913” from Asahi Kasei Corporation. M1943 ".

  The weight average molecular weight of the component (A) is preferably 20,000 to 200,000, more preferably 30,000 to 150,000, and more preferably 50,000 to 50,000 from the viewpoint of coating properties. More preferably, it is 125,000.

  In addition, a weight average molecular weight (Mw) can be calculated | required from the standard polystyrene conversion value by a gel permeation chromatography (GPC).

  The content of component (A) is preferably 40 to 98% by mass, more preferably 50 to 97% by mass, and still more preferably 60% with respect to the total amount of component (A), component (B) and component (C). It is -95 mass%. When the content of the component (A) is 40% by mass or more, flexibility is further improved, and when it is 98% by mass or less, adhesion and heat resistance tend to be improved.

<(B) Cyclohexanetricarboxylic acid anhydride>
(B) Cyclohexanetricarboxylic acid anhydride functions as a curing agent for (C) thermosetting resin. Examples of the cyclohexanetricarboxylic acid anhydride include cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride and cyclohexane-1,2,3-tricarboxylic acid-1,2-anhydride. These compounds may be used alone or in combination.

  Although content of (B) component can be set suitably, it is preferable that it is 1-50 mass parts with respect to 100 mass parts of (A) component, and it is more preferable that it is 2-30 mass parts. Preferably, the amount is 3 to 20 parts by mass. When the content of the component (B) is 1 part by mass or more, adhesion, heat resistance, and insulation reliability tend to be further improved, and when it is 50 parts by mass or less, compatibility with the component (A) is improved. There is a tendency to improve and improve transparency.

  The curable composition of this embodiment can contain single or multiple hardening agent components, such as an acid anhydride and carboxylic acid, other than (B) component. The kind is not specifically limited, It can mix | blend in the range which does not impair the characteristic of a curable composition and its hardened | cured material.

  Examples of the acid anhydride that can be included as the curing agent component include tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic acid anhydride, and trialkyltetrahydrophthalic anhydride. Acid, methylcyclohexene tetracarboxylic dianhydride, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic dianhydride, ethylene glycol bisanhydro trimellitate, glycerin bis (anhydro trimellitate) ) Monoacetate, dodecenyl succinic anhydride, aliphatic dibasic acid polyanhydride, chlorendic anhydride, hydrogenated compounds of the above acid anhydrides, and the like.

  Examples of the carboxylic acid that can be included as the curing agent component include cyclohexane-1,2,4-tricarboxylic acid, cyclohexane-1,2,3-tricarboxylic acid, cyclohexane-1,3,5-tricarboxylic acid, cyclohexane- Examples include 1,2-dicarboxylic acid, 3-methylcyclohexane-1,2-dicarboxylic acid, 4-methylcyclohexane-1,2-dicarboxylic acid and the like.

The carboxylic acid that can be included as the curing agent component may be a polycarboxylic acid hemiacetal ester derivative or a blocked carboxylic acid blocked with an alkyl vinyl ether represented by the following general formula (1). By containing a block carboxylic acid as a curing agent component, the content of cyclohexanetricarboxylic acid anhydride can be reduced, and as a result, thickening of the composition before thermosetting can be suppressed, and the pot life can be prolonged. it can. Among these, the block carboxyl blocked with an alkyl vinyl ether represented by the following general formula (1) from the viewpoint of suppressing the thickening of the composition before thermosetting and further improving the adhesion and heat resistance of the cured film. Acid is preferred.

In the general formula (1), R ¹ represents an n-valent organic group, R ² represents a monovalent organic group, and n represents an integer of 1 or more. Here, n is preferably an integer of 2 or more, and more preferably an integer of 3 or more.

  Examples of the block carboxylic acid represented by the general formula (1) include, for example, Nocure HK-6, Nofcure TN-1, Nocure TN-2, Santasid G, Santasid H, Santasid I, Santasid K (above, NOF ( Etc.).

In order to improve the compatibility with the component (A), in the block carboxylic acid represented by the general formula (1), R ¹ preferably has an aliphatic chain or an alicyclic group. Examples of such block carboxylic acids include Nocure HK-6, Santasid G, Santasid H, Santasid I, Santasid K, and the like.

  Furthermore, in the block carboxylic acid represented by the general formula (1), 2 to 6 is preferable and 3 to 4 is more preferable in order to obtain better curability. Examples of such block carboxylic acids include Nocure HK-6, Santacid K, and the like.

  The block carboxylic acid represented by the general formula (1) can be used alone or in combination of two or more.

  Although content of the block carboxylic acid represented by the said General formula (1) can be set suitably, it is preferable that it is 1-50 mass parts with respect to 100 mass parts of (A) component, 2 More preferably, it is -30 mass parts, and it is still more preferable that it is 3-20 mass parts.

<(C) Thermosetting resin>
(C) As a thermosetting resin, an epoxy resin, a urethane resin, a silicone resin, a polyester resin, those modified resins etc. are mentioned, for example. Among these, an epoxy resin is preferable, and an alicyclic epoxy resin having good compatibility with the component (A), an epoxy resin having a fatty chain, and an epoxy resin having a polybutadiene chain are more preferable.

  Examples of the alicyclic epoxy resin include 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxylate [trade names: Celoxide 2021P, Celoxide 2081, Celoxide 8000 (manufactured by Daicel Corporation). ERL 4221, ERL 4221D, ERL 4221E (manufactured by Cinacia)], bis (3,4-epoxycyclohexylmethyl) adipate [trade name: ERL 4299 (manufactured by Cinacia)], hydrogenated bisphenol A type epoxy resin [trade name: Epicoat YX8000, Epicoat YX8034, Epicoat YL8040 (manufactured by Mitsubishi Chemical Corp.)] 1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol Product name: EHPE3150 (manufactured by Daicel Corporation)], butanetetracarboxylic acid tetra (3,4-epoxycyclohexylmethyl) modified ε-caprolactone [trade name: Epolide GT-401 (manufactured by Daicel Corporation)], alicyclic And an epoxy group-containing silicone oligomer [trade name: X-40-2670 (manufactured by Shin-Etsu Chemical Co., Ltd.)].

  Examples of the epoxy resin having a fatty chain include 1,4-butanediol diglycidyl ether [trade name: EX-214L (manufactured by Nagase ChemteX Corp.)], 1,6-hexanediol diglycidyl ether [EX- 212L (manufactured by Nagase ChemteX Corporation)] and the like.

  Examples of the epoxy resin having a polybutadiene chain include trade names JP-100, JP-200 (above, Nippon Soda Co., Ltd.), Ricon657 (manufactured by Clay Valley Co., Ltd.), Epolide PB3600, Epolide PB4700 (above, Daicel Corporation). ) And the like.

  When the (C) thermosetting resin is an epoxy resin, the epoxy equivalent is preferably 0.2 to 5.0 equivalents, more preferably 0.5 to 1 equivalent of the carboxy group of the component (B). It is -3.0 equivalent, More preferably, it is 0.8-2.0 equivalent. When the epoxy equivalent is 0.2 equivalent or more, better curability is obtained, and the adhesion and heat resistance tend to be further improved. When the epoxy equivalent is 2.0 equivalents or less, the tack tends to be smaller.

In the curable composition of this embodiment, if necessary, silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), barium carbonate (BaCO ₃ ), talc (3MgO · 4SiO _2).・ Inorganic fine particles such as H ₂ O), zinc oxide (ZnO), barium sulfate (BaSO ₄ ), organic bentonite, hydrotalcite, tertiary amine, imidazole, phosphorus compound, quaternary ammonium salt, organic metal Contains known and commonly used additives such as salt-based curing catalysts, silicone-based, fluorine-based, polymer-based antifoaming agents and / or leveling agents, thiazole-based, triazole-based silane coupling agents, etc. In addition, antioxidants, yellowing inhibitors, ultraviolet absorbers, visible light absorbers, colorants, plasticizers, stabilizers, and the like can also be blended.

  The curable composition of this embodiment may be diluted with a suitable organic solvent and used as a resin varnish. The organic solvent used here is not particularly limited as long as it can dissolve the curable composition. For example, toluene, xylene, mesitylene, cumene, p-cymene, 1,2,3,4-tetrahydronaphthalene. Aromatic hydrocarbons such as tetrahydrofuran, cyclic ethers such as 1,4-dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone; methyl acetate, ethyl acetate, Esters such as butyl acetate, methyl lactate, ethyl lactate and γ-butyrolactone; carbonates such as ethylene carbonate and propylene carbonate; amides such as N, N-dimethylformamide, N, N-dimethylacetamide and N-methylpyrrolidone; methylcyclohexane ,ethyl Cycloalkanes such as cyclohexane and the like. These organic solvents can be used alone or in combination of two or more.

  The curable composition of the present embodiment includes a step of printing the curable composition on the wiring pattern of the flexible wiring board, and a step of thermally curing the printed curable composition to form a cured film as a protective film. Can be suitably used for forming a protective film for a wiring pattern of a flexible wiring board.

  The conditions for thermosetting are preferably 80 ° C. to 180 ° C., more preferably 90 ° C. to 160 ° C. from the viewpoint of preventing the copper wiring from being oxidized and obtaining warpage and flexibility suitable as a protective film. The heating time is 30 to 120 minutes, preferably 50 to 90 minutes, from the viewpoint of preventing oxidation of the copper wiring and obtaining warpage and flexibility suitable as a protective film.

  The substrate of the flexible wiring board is not particularly limited. For example, polyesters such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; polycarbonate, polyamide, polyimide, polyamideimide, polyetherimide, poly Examples include ether sulfide, polyether sulfone, polyether ketone, polyphenylene ether, polyphenylene sulfide, polyarylate, polysulfone, and liquid crystal polymer. Among these, from the viewpoint of flexibility and toughness, it may be polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polypropylene, polycarbonate, polyamide, polyimide, polyamideimide, polyphenylene ether, polyphenylene sulfide, polyarylate or polysulfone. preferable.

  The curable composition of the present embodiment can be suitably applied as a film forming material for various electric products and electronic components by an application method such as screen printing, dispenser, spin coating and the like. In particular, application by screen printing is preferable.

  The curable composition of this embodiment can be used not only suitably as a protective film for wiring on a flexible substrate, but also in a wide range such as wearable devices, biosensors, sealing connector connectors, protective films, and the like.

[Hardened product (elastic resin layer)]
The cured product (stretchable resin layer) formed from the curable composition according to the above-described embodiment is prepared by adjusting the above-described curable composition to a viscosity suitable for the coating method with the organic solvent, and on the substrate. After applying by a method such as a screen printing method, it can be obtained, for example, by heating to a temperature of 80 ° C. to 180 ° C. and curing. The elastic modulus of the cured product (stretchable resin layer) is preferably from 0.1 MPa to 1000 MPa. If it is 0.1 MPa or more and 1000 MPa or less, the handleability and flexibility as a film can be obtained. From this viewpoint, the pressure is more preferably 0.3 MPa or more and 100 MPa or less, and particularly preferably 0.5 MPa or more and 50 MPa or less.

  Moreover, it is preferable that the breaking elongation rate by the tensile test of the hardened | cured material (elastic resin layer) formed from a curable composition is 100% or more. If it is 100% or more, sufficient stretchability can be obtained. In this respect, it is more preferably 300% or more, and particularly preferably 500% or more.

The tack of the cured product (stretchable resin layer) formed from the curable composition is preferably 2.0 g / mm ² or less. From the viewpoint of handleability, it is more preferably 1.5 g / mm ² or less, and particularly preferably 1.2 g / mm ² or less. If it is 2.0 g / mm < ² > or less, sticking of hardened | cured material can be reduced.
In addition, the above-mentioned tack is about a 100-micrometer-thick film obtained by hardening | curing a curable composition, using a tacking tester "TAC-II" made from Resuka Co., Ltd., and a probe (material: SUS304) with a diameter of 5.1 mm. ), A value measured under the conditions of an indentation load of 100 gf, an indentation speed of 120 mm / min, an indentation time of 1 second, a pulling speed of 600 mm / min, and a measurement temperature of 25 ° C.

A cured product (stretchable resin layer) formed from the curable composition can have high stretchability. Stretchability can be evaluated using stretch recovery properties as an index, measured by the following procedure including two tensile tests.
1) A strip-shaped cured product having a length of 70 mm and a width of 5 mm is prepared as a test piece.
2) With the test piece held by a chuck having a distance between chucks of 50 mm, the test piece is pulled to a displacement (strain) X in the first tensile test.
3) Return the chuck to the initial position.
4) Perform the second tensile test, and record the difference Y between the displacement amount (strain) at the position where the load starts to be applied (the position at which the load rises) and X.
5) The expansion / contraction recovery rate is calculated by the formula: expansion / contraction recovery rate R = (Y / X) × 100.
The tensile test is performed in an environment of 25 ° C. X can be set to a displacement of 25 mm (strain 50%). As a tester, for example, a microforce tester (Illinois Tool Works Inc, “Instron 5948”) can be used. FIG. 1 is an example of a stress-strain curve obtained from a tensile test for obtaining stretch recovery properties.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

Example 1
[Preparation of Resin Varnish (Curable Composition) WA1]
As component (A), 22 parts by mass of a hydrogenated styrene-butadiene copolymer partially modified with maleic anhydride (“Tuftec M1943” manufactured by Asahi Kasei Co., Ltd.), and as component (B) cyclohexane-1, 2, 5 parts by mass of 4-tricarboxylic acid-1,2-anhydride (“H-TMAn” manufactured by Mitsubishi Gas Chemical Co., Inc.), 1,2-bis (hydroxymethyl) -1-butanol as 1, (C) component 2-Epoxy-4- (2-oxiranyl) cyclohexane adduct [trade name: EHPE3150 (manufactured by Daicel Corporation)] 5 parts by mass, 68 parts by mass of 1,2,3,4-tetrahydronaphthalene were added, and 500 ml flask was added. And stirring at 60 ° C. to obtain a resin varnish WA1.

[Preparation of resin film FC1]
Surface release-treated PET film (“Purex A31” manufactured by Teijin DuPont Films Co., Ltd., thickness 50 μm) was used as the base film, and a knife coater (“SNC-” manufactured by Yasui Seiki Co., Ltd.) was formed on this release-treated surface. 350 ”), the resin varnish WA1 was applied so that the film thickness after drying and curing was 100 μm. Next, the resin film FC1 was obtained by drying and thermosetting at 150 ° C. for 60 minutes in a dryer (“MSO-80TPS” manufactured by Futaba Kagaku Co., Ltd.).

(Examples 2-3 and Comparative Examples 1-5)
Resin varnishes WA2 to WA8 were prepared and resin films FC2 to FC8 were prepared in the same manner as in Example 1 except that the components and their blending ratios were changed as shown in Table 1.

<Evaluation>
[Measurement of tack]
The resin film was cut into a size of 100 mm in length and 15 mm in width, and the protective film was removed to prepare a measurement sample. For the tack measurement, using a tacking tester “TAC-II” manufactured by Reska Co., Ltd., with a probe (material: SUS304) having a diameter of 5.1 mm, an indentation load of 1 Pa (100 gf / m ² ), an indentation speed of 120 mm / min, The measurement was performed under the conditions of an indentation time of 1 second, a lifting speed of 600 mm / min, and a measurement temperature of 25 ° C.

[Measurement of elastic modulus and elongation]
The resin film was cut into a length of 40 mm and a width of 10 mm, and the base film and the protective film were removed to prepare a measurement sample. The elastic modulus and elongation of this measurement sample were measured using an autograph (Shimadzu Corporation “EZ-S”), a stress-strain curve, and the elastic modulus and elongation were determined from the graph. The distance between chucks at the time of measurement was 20 mm, and the pulling speed was 50 mm / min. Here, the elastic modulus was a value at a load of 0.5 to 1.0 N, and the elongation was a value when the film was broken (breaking elongation).

[Measurement of recovery rate]
The resin film was cut into a length of 70 mm and a width of 5 mm, and the base film and the protective film were removed to prepare a measurement sample. The recovery rate of this sample was measured using a micro force tester (Illinois Tool Works Inc “Instron 5948”).
Here, the recovery rate is X when the displacement amount (strain) applied in the first tensile test is X, and then Y is the position at which the load starts when the tensile test is performed again after returning to the initial position. R = R indicated by Y / X. In this measurement, the initial length (distance between chucks) was 50 mm, and X was 25 mm (strain 50%).

[Adhesion with polyimide]
The above resin varnish is applied on a polyimide film having a thickness of 50 μm (“Kapton 100H” manufactured by Toray DuPont Co., Ltd.) using a film applicator (All Good Co., Ltd.) so that the film thickness after curing becomes 30 μm. And cured at 150 ° C. for 60 minutes. After that, make a cut so that there is a grid of 100 squares, and strongly press the cello tape (registered trademark) on the grid, peel off the end of the tape at a 45 ° angle, evaluated.
A: 100/100 (no peeling = good adhesion)
B: 95/100 to 99/100
C: <95/100

[Adhesion with copper foil]
The resin varnish was applied on an unroughened surface of a 50 μm thick electrolytic copper foil using a film applicator (All Good Co., Ltd.) so that the film thickness after curing was 30 μm, and 150 ° C. for 60 minutes. And cured. After that, make a cut so that there is a grid of 100 squares, and strongly press the cello tape (registered trademark) on the grid, peel off the end of the tape at a 45 ° angle, evaluated.
A: 100/100 (no peeling = good adhesion)
B: 95/100 to 99/100
C: <95/100

[Insulation reliability]
Flexible copper composed of a polyimide film having a thickness of 38 μm, a copper foil having a thickness of 8 μm (sputtered copper), and a copper wiring (wiring pattern) having a thickness of 0.2 to 0.3 μm formed on the copper foil. A stretched laminate (copper wiring width / copper wiring width = 50 μm / 50 μm) was prepared. The resin varnish was applied to the flexible copper-clad laminate using a film applicator (All Good Co., Ltd.) so that the film thickness after curing was 50 μm, and cured at 150 ° C. for 60 minutes. Measurement was started by applying a bias voltage of 5 V to the substrate on which the protective film was formed using an ion migration tester (Espec Corp. “AMI-150-S-5”) in an atmosphere of 130 ° C. and 85% relative humidity. The resistance value was evaluated based on the following criteria after 100 hours.
A: 1.0 × 10 ⁸ Ω or more B: 1.0 × 10 ⁵ Ω or more and less than 1.0 × 10 ⁸ Ω C: Less than 1.0 × 10 ⁵ Ω

(A) Styrenic elastomer partially modified with maleic anhydride 1) Tuftec M1943 (hydrogenated styrene butadiene copolymer partially modified with maleic anhydride, manufactured by Asahi Kasei Corporation, weight average molecular weight: 50 , 000)
(A ′) Other elastomer 2) Kraton G1643 (hydrogenated styrene butadiene copolymer, manufactured by Kraton Polymer Japan, Inc., weight average molecular weight: about 110,000)
3) Clarity LA2250 (methyl methacrylate-acrylbutyl copolymer, manufactured by Kuraray Co., Ltd., weight average molecular weight: about 80,000)
(B) Cyclohexanetricarboxylic acid anhydride 4) H-TMAn (cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride, manufactured by Mitsubishi Gas Chemical Co., Inc., molecular weight: 191)
(B ′) Block carboxylic acid 5) Santacid K (monoalkyl vinyl ether block trifunctional block carboxylic acid, acid equivalent 270, manufactured by NOF Corporation)
(C) Thermosetting resin 6) EHPE3150 (1,2-epoxy-4- (2-oxiranyl) cyclohexane adduct of 2,2-bis (hydroxymethyl) -1-butanol, epoxy equivalent 180, Daicel Corporation Made)

As is clear from Table 1, the curable compositions of Examples 1 to 3 have low tack, good flexibility, excellent adhesion to polyimide and copper foil, and excellent insulation reliability.
On the other hand, although the curable composition of Comparative Examples 1-5 is excellent in flexibility, it turns out that adhesiveness and insulation reliability with a low tack, a polyimide, and copper foil are inferior.

  Since the cured product (stretchable resin layer) formed from the curable composition of the present invention exhibits excellent stretchability and adhesion, it is suitable for the protection of wiring of flexible substrates, wearable devices, biosensors, and connector connectors. It can be suitably used as a sealing material.

Claims (6)

  A thermosetting composition for forming a stretchable resin layer, comprising (A) a styrenic elastomer partially modified with maleic anhydride, (B) cyclohexanetricarboxylic acid anhydride, and (C) a thermosetting resin.   (A) The thermosetting composition for forming a stretchable resin layer according to claim 1, wherein the styrenic elastomer partially modified with maleic anhydride is a hydrogenated elastomer.   (B) The thermosetting composition for stretchable resin layer formation according to claim 1 or 2, wherein the cyclohexanetricarboxylic acid anhydride is cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride.   (C) The thermosetting composition for stretchable resin layer formation according to any one of claims 1 to 3, wherein the thermosetting resin is an epoxy resin.   The elastic resin layer which is a hardened | cured material of the thermosetting composition for elastic resin layer formation as described in any one of Claims 1-4.   A flexible wiring board comprising the stretchable resin layer according to claim 5.

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