TWI875697B - Conductive substrate, wiring substrate, stretchable element, and method for manufacturing wiring substrate - Google Patents

Abstract

A conductive substrate comprises a stretchable resin layer and a conductive foil disposed on the stretchable resin layer. The stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester-based curing agent.

Description

Conductive substrate, wiring substrate, stretchable element, and method for manufacturing wiring substrate

One aspect of the present invention relates to a highly stretchable wiring substrate and a method for manufacturing the same. Another aspect of the present invention relates to a conductive substrate that can be used to form the wiring substrate. Another aspect of the present invention relates to a stretchable element using the wiring substrate.

In recent years, in the fields of wearable devices and health care-related devices, for example, flexibility and stretchability are required to be able to be used along the curved surface or joints of the body, and to prevent poor connection even when being put on and taken off. In order to construct such devices, a wiring substrate or base material with high stretchability is required.

Patent document 1 describes a method for sealing semiconductor devices such as memory chips using a stretchable resin composition. Patent document 1 mainly studies the application of stretchable resin compositions in sealing applications. [Prior art document] [Patent document]

[Patent Document 1] International Publication No. 2016/080346

[The problem that the invention wants to solve]

As described in Patent Document 1, by making the sealing material elastic, it is possible to realize a component having elasticity which is difficult to realize with conventional sealing materials. On the other hand, the base substrate does not have elasticity, so it is difficult to have a higher elasticity. Therefore, a wiring substrate having a higher elasticity is required.

In addition, from the viewpoint of improving heat resistance, the use of a crosslinking component having a reactive functional group as a material for a base substrate for manufacturing a wiring board has been studied. However, if a crosslinking component having a reactive functional group is used, there is a problem that the dielectric loss tangent of the obtained base substrate is likely to increase, and the transmission loss of the wiring provided on the base substrate is likely to increase.

Under such circumstances, one aspect of the present invention is to provide a conductive substrate having high stretchability and low dielectric loss tangent, a wiring substrate using the conductive substrate, a stretchable element, and a method for manufacturing the wiring substrate. [Means for Solving the Problem]

In order to achieve the above-mentioned object, one aspect of the present invention provides a conductive substrate comprising: a stretchable resin layer; and a conductive foil disposed on the stretchable resin layer, wherein the stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester-based curing agent.

Another aspect of the present invention provides a conductive substrate comprising: a stretchable resin layer; and a conductive coating disposed on the stretchable resin layer. The stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester-based curing agent.

According to the conductive substrate, high stretchability can be obtained by using a stretchable resin layer containing (A) a rubber component as its base substrate. In addition, it is believed that the reason why the dielectric loss tangent increases when a crosslinking component having a reactive functional group is used as a material for making a stretchable resin layer is that the crosslinking component generates a hydroxyl group during the curing reaction. The hydroxyl group is a small and highly polarizable functional group, so the material having a hydroxyl group will increase the dielectric loss tangent as a whole. On the other hand, the inventors and others found that by combining a crosslinking component (B) having an epoxy group as a crosslinking component and an ester-based curing agent (C) as a curing agent, the generation of hydroxyl groups during the curing reaction of the crosslinking component can be significantly suppressed. The reason is that the curing reaction between the epoxy group of the crosslinking component and the ester-based curing agent does not involve the generation of hydroxyl groups, and it is difficult to generate hydroxyl groups after curing. Furthermore, these cured products do not have an adverse effect on elasticity. Therefore, according to the conductive substrate having the above structure, a low dielectric loss tangent is achieved by using a crosslinking component that can maintain high elasticity and improve heat resistance.

Another aspect of the present invention provides a wiring substrate, which includes the conductor substrate of the present invention, wherein the conductor foil or the conductor coating forms a wiring pattern. The wiring substrate is a substrate in which the conductor foil or the conductor coating forms a wiring pattern in the conductor substrate of the present invention, and the wiring substrate includes a stretchable resin layer having the specific structure, so that it has high stretchability. In addition, by using a crosslinking component, it has high heat resistance and can have a low dielectric loss tangent, so that the transmission loss of the wiring pattern can be sufficiently reduced.

Another aspect of the present invention provides a stretchable component, comprising: the wiring substrate of the present invention; and an electronic device mounted on the wiring substrate. The stretchable component comprises the wiring substrate of the present invention, and comprises a stretchable resin layer having the specific structure, so that it has high stretchability, and by using a cross-linking component, it has high heat resistance and can have a low dielectric loss tangent, so that the transmission loss of the wiring pattern can be sufficiently reduced.

Another aspect of the present invention provides a conductive substrate of the present invention, which is used to form a wiring substrate. The wiring substrate includes a conductive substrate having a stretchable resin layer and a conductive foil or a conductive coating disposed on the stretchable resin layer, wherein the conductive foil or the conductive coating forms a wiring pattern.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: preparing a laminate having a stretchable resin layer and a conductive foil laminated on the stretchable resin layer; forming an etching resist on the conductive foil; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the conductive foil; removing the conductive foil of the portion not covered by the etching resist pattern; and removing the etching resist pattern.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: a step of forming a coating anti-etching agent on a stretchable resin layer; a step of exposing the coating anti-etching agent and developing the exposed coating anti-etching agent to form an anti-etching agent pattern covering a portion of the stretchable resin layer; a step of forming a conductive coating film by electroless plating on the surface of the portion of the stretchable resin layer not covered by the anti-etching agent pattern; and a step of removing the anti-etching agent pattern.

Another aspect of the present invention provides a method for manufacturing the wiring board of the present invention, comprising: forming a conductive coating on a stretchable resin layer by electroless plating; forming a coating anti-corrosion agent on the conductive coating; exposing the coating anti-corrosion agent and developing the exposed coating anti-corrosion agent to form a coating layer covering the stretchable resin layer. a step of forming an anti-etching pattern on a portion of the conductive coating film; a step of further forming a conductive coating film by electroplating on the portion of the conductive coating film not covered by the anti-etching pattern; a step of removing the anti-etching pattern; and a step of removing the portion of the conductive coating film formed by electroless plating that is not covered by the conductive coating film formed by electroplating.

Another aspect of the present invention provides a method for manufacturing the wiring substrate of the present invention, comprising: a step of forming an etching resist on a conductor coating formed on a stretchable resin layer; a step of exposing the etching resist and developing the exposed etching resist to form an anti-etching pattern covering a portion of the stretchable resin layer; a step of removing the conductor coating portion not covered by the anti-etching pattern; and a step of removing the anti-etching pattern.

By using the manufacturing method, the wiring substrate of the present invention in which a wiring pattern is formed by a conductor foil or a conductor film can be efficiently manufactured. [Effect of the invention]

According to one aspect of the present invention, a conductive substrate having high stretchability and low dielectric loss tangent, a wiring substrate using the conductive substrate, a stretchable element, and a method for manufacturing the wiring substrate can be provided.

Several embodiments of the present invention are described in detail below. However, the present invention is not limited to the following embodiments.

According to one embodiment, a conductive substrate comprises a stretchable resin layer and a conductive layer disposed on one or both sides of the stretchable resin layer. The stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a cross-linking component having an epoxy group, and (C) an ester-based curing agent. An embodiment of a wiring substrate comprises a stretchable resin layer comprising the cured product of the resin composition, and a conductive layer disposed on one or both sides of the stretchable resin layer and forming a wiring pattern. The conductive layer may be a conductive foil or a conductive coating.

<Conductor substrate> [Conductor foil] The elastic modulus of the conductor foil may be 40 GPa to 300 GPa. When the elastic modulus of the conductor foil is 40 GPa to 300 GPa, the conductor foil tends to be less likely to break due to the elongation of the wiring substrate. From the same point of view, the elastic modulus of the conductor foil may be 50 GPa or more, or 60 GPa or more, or 280 GPa or less, or 250 GPa or less. The elastic modulus of the conductor foil here may be a value measured by a resonance method.

The conductor foil may be a metal foil. Examples of the metal foil include copper foil, titanium foil, stainless steel foil, nickel foil, permalloy foil, 42 alloy foil, Kovar foil, Nichrome foil, palladium foil, phosphor bronze foil, brass foil, zinc copper foil, aluminum foil, tin foil, lead foil, zinc foil, solder foil, iron foil, tantalum foil, niobium foil, molybdenum foil, zirconium foil, gold foil, silver foil, palladium foil, Monel foil, Inconel foil, Hastelloy foil, and the like. From the viewpoint of suitable elastic modulus, etc., the conductive foil may be selected from copper foil, gold foil, nickel foil, and iron foil. From the viewpoint of wiring formability, the conductive foil may be copper foil. Copper foil can be easily formed into a wiring pattern by photolithography without damaging the properties of the elastic resin layer.

The copper foil is not particularly limited, and for example, electrolytic copper foil and rolled copper foil used in copper-clad laminates and flexible wiring boards can be used. Examples of commercially available electrolytic copper foils include F0-WS-18 (manufactured by Furukawa Electric Co., Ltd., trade name), NC-WS-20 (manufactured by Furukawa Electric Co., Ltd., trade name), YGP-12 (manufactured by Nippon Electrolysis Co., Ltd., trade name), GTS-18 (manufactured by Furukawa Electric Co., Ltd., trade name), and F2-WS-12 (manufactured by Furukawa Electric Co., Ltd., trade name). Examples of rolled copper foil include TPC foil (trade name, manufactured by JX Metal Co., Ltd.), HA foil (trade name, manufactured by JX Metal Co., Ltd.), HA-V2 foil (trade name, manufactured by JX Metal Co., Ltd.), and C1100R (trade name, manufactured by Sumitomo Mitsui Metal Mining & Copper Co., Ltd.). From the perspective of adhesion to the elastic resin layer, a copper foil subjected to a roughening treatment can be used. From the perspective of folding resistance, a rolled copper foil can be used.

The metal foil may have a roughened surface formed by roughening treatment. In this case, the metal foil is usually placed on the stretchable resin layer in a direction in which the roughened surface is in contact with the stretchable resin layer. From the perspective of the adhesion between the stretchable resin layer and the metal foil, the surface roughness Ra of the roughened surface may be 0.1 μm to 3 μm, or 0.2 μm to 2.0 μm. In order to easily form fine wiring, the surface roughness Ra of the roughened surface may be 0.3 μm to 1.5 μm.

The surface roughness Ra can be measured, for example, using the surface shape measuring device Wyko NT9100 (manufactured by Veeco) under the following conditions. Measurement conditions Internal lens: 1x External lens: 50x Measurement range: 0.120×0.095 mm Measurement depth: 10 μm Measurement method: Vertical scanning interferometry (VSI method)

The thickness of the conductor foil is not particularly limited and may be 1 μm to 50 μm. When the thickness of the conductor foil is 1 μm or more, a wiring pattern can be formed more easily. When the thickness of the conductor foil is 50 μm or less, etching and processing are particularly easy.

The conductive foil is provided on one side or both sides of the elastic resin layer. By providing the conductive foil on both sides of the elastic resin layer, warping caused by heating for curing etc. can be suppressed.

The method of providing the conductive foil is not particularly limited, and examples thereof include: a method of directly applying a resin composition for forming a stretchable resin layer to a metal foil; and a method of applying a resin composition for forming a stretchable resin layer to a carrier film to form a resin layer (stretchable resin layer before curing), and laminating the formed resin layer on the conductive foil.

[Conductor coating] Conductor coating can be formed by a conventional coating method used in an additive method or a semi-additive method. For example, after a coating catalyst is treated to attach palladium, a stretchable resin layer is immersed in an electroless plating solution to deposit an electroless plating layer (conductor layer) with a thickness of 0.3 μm to 1.5 μm on the entire surface of the primer. Electroplating (electrical plating) can be further performed as needed to adjust the thickness to the desired thickness. As the electroless plating solution used in the electroless plating, any electroless plating solution can be used without any particular limitation. Regarding electroplating, a conventional method can also be adopted without any particular limitation. From the perspective of cost and resistance value, the conductive film (electroless film, electroplated film) can be a copper film.

Furthermore, the unnecessary parts can be etched away to form a circuit layer. The etching solution used in the etching can be appropriately selected according to the type of the coating. For example, when the conductor is copper plating, as the etching solution used in the etching, for example, a mixed solution of concentrated sulfuric acid or hydrogen peroxide, or a ferric chloride solution can be used.

In order to improve the adhesion with the conductive coating, the stretchable resin layer may be preliminarily formed with unevenness. As a method for forming unevenness, for example, a method of transferring to the roughened surface of copper foil can be cited. As copper foil, for example, YGP-12 (manufactured by Nippon Electrolysis Co., Ltd., trade name), GTS-18 (manufactured by Furukawa Electric Co., Ltd., trade name), or F2-WS-12 (manufactured by Furukawa Electric Co., Ltd., trade name) can be used.

As a method for transferring the roughened surface of the copper foil, there are, for example, a method of directly applying a resin composition for forming a stretchable resin layer to the roughened surface of the copper foil, and a method of applying a resin composition for forming a stretchable resin layer to a carrier film and then forming a resin layer (stretchable resin layer before curing) on the copper foil. By forming a conductive coating on both sides of the stretchable resin layer, warping caused by heating for curing, etc. can be suppressed.

The stretchable resin layer may be subjected to surface treatment for the purpose of achieving high adhesion with the conductive coating. Examples of surface treatment include roughening treatment (de-smear treatment), ultraviolet (UV) treatment, and plasma treatment, which are generally used in the manufacturing process of wiring boards.

As the desmear treatment, a method used in a general wiring board manufacturing step can be used, for example, a sodium permanganate aqueous solution can be used.

[Stretchable resin layer] The stretchable resin layer may have a stretchability such that the recovery rate after being stretched to a strain of 20% is 80% or more. The recovery rate is obtained in a tensile test of a test sample using the stretchable resin layer. The strain (displacement) applied in the first tensile test is set as X, and the difference between the position when the load is applied when the tensile test is performed again after returning to the initial position and X is set as Y, and R is calculated by the formula: R (%) = (Y/X) × 100%, and this R is defined as the recovery rate. The recovery rate can be measured by setting X to 20%. Figure 1 is a stress-strain curve showing an example of the measurement of the recovery rate. From the perspective of tolerance to repeated use, the recovery rate may be greater than 80%, greater than 85%, or greater than 90%. The upper limit of the recovery rate is defined as 100%.

The elastic modulus (tensile elastic modulus) of the elastic resin layer may be 0.1 MPa to 1000 MPa. If the elastic modulus is 0.1 MPa to 1000 MPa, the handling and flexibility as a base material tend to be particularly excellent. From this point of view, the elastic modulus may be 0.3 MPa to 100 MPa, or 0.5 MPa to 50 MPa.

The elongation at break of the stretchable resin layer may be 100% or more. If the elongation at break is 100% or more, sufficient stretchability tends to be easily obtained. From this point of view, the elongation at break may be 150% or more, 200% or more, 300% or more, or 500% or more. There is no particular upper limit on the elongation at break, and it is usually about 1000% or less.

The dielectric loss tangent (Df) of the elastic resin layer can be 0.004 or less. If the dielectric loss tangent is 0.004 or less, there is a tendency to sufficiently reduce the transmission loss of the wiring pattern provided on the elastic resin layer. From this point of view, the dielectric loss tangent can be 0.0035 or less, 0.003 or less, or 0.0025 or less. There is no particular lower limit for the dielectric loss tangent, and it is usually about 0.0005 or more.

The dielectric constant (Dk) of the elastic resin layer may be 4.0 or less. If the dielectric constant is 4.0 or less, there is a tendency to sufficiently reduce the transmission loss of the wiring pattern provided on the elastic resin layer. From this point of view, the dielectric constant may be 3.5 or less, 3.0 or less, or 2.5 or less.

The elastic resin layer may be a layer having no absorption peak attributable to the stretching vibration of the hydroxyl group in its infrared absorption spectrum. Thereby, the dielectric loss tangent of the elastic resin layer is sufficiently reduced, and there is a tendency to sufficiently reduce the transmission loss of the wiring pattern provided on the elastic resin layer.

The elastic resin layer includes a cured product of a resin composition (curable resin composition), wherein the resin composition includes (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester-based curing agent. That is, the elastic resin layer includes a crosslinked polymer of the crosslinking component (B) having an epoxy group. The elasticity is easily imparted to the elastic resin layer mainly by the rubber component (A).

The rubber component (A) may include, for example, at least one rubber selected from the group consisting of acrylic rubber, isoprene rubber, butyl rubber, styrene butadiene rubber, butadiene rubber, acrylonitrile butadiene rubber, silicone rubber, urethane rubber, chloroprene rubber, ethylene propylene rubber, fluororubber, vulcanized rubber, epichlorohydrin rubber, and chlorobutyl rubber. From the viewpoint of protecting the wiring from damage due to moisture absorption, etc., a rubber component with low air permeability may be used. From this viewpoint, the rubber component (A) may include at least one selected from the group consisting of styrene butadiene rubber, butadiene rubber, and butyl rubber. By using styrene butadiene rubber, the resistance of the elastic resin layer to various chemical solutions used in the coating step can be improved, and wiring boards can be manufactured with high yield.

Examples of commercially available acrylic rubbers include "Nipol AR Series" manufactured by ZEON Co., Ltd. of Japan and "KURARITY Series" manufactured by Kuraray Co., Ltd.

Examples of commercially available isoprene rubber include "Nipol IR Series" manufactured by ZEON Co., Ltd. of Japan.

Examples of commercially available butyl rubber include "BUTYL series" manufactured by JSR Corporation.

Examples of commercially available styrene butadiene rubber include "Dynaron SEBS series" and "Dynaron HSBR series" from JSR Corporation, "Kraton D polymer series" from Kraton Polymers Japan Co., Ltd., and "AR series" from Aronkasei Co., Ltd.

Examples of commercially available butadiene rubber include "Nipol BR series" manufactured by ZEON Co., Ltd. of Japan.

Examples of commercially available acrylonitrile butadiene rubber include "JSR NBR series" manufactured by JSR Corporation.

Examples of commercially available silicone rubber include "KMP series" manufactured by Shin-Etsu Silicone Co., Ltd.

Examples of commercially available products of ethylene propylene rubber include "JSR EP series" manufactured by JSR Corporation.

Examples of commercially available fluororubber products include the "DAIEL series" of Daikin Co., Ltd.

Examples of commercially available epichlorohydrin rubbers include the "Hydrin series" produced by ZEON Co., Ltd. of Japan.

The (A) rubber component can also be produced by synthesis. For example, acrylic rubber can be obtained by reacting (meth)acrylic acid, (meth)acrylate, aromatic vinyl compound, cyanide vinyl compound, etc.

The rubber component (A) may also contain a rubber having a crosslinking group. By using a rubber having a crosslinking group, the heat resistance of the elastic resin layer tends to be improved. The crosslinking group can be any reactive group that can cause a reaction to crosslink the molecular chains of the rubber component (A). Examples thereof include reactive groups, anhydride groups, amino groups, hydroxyl groups, epoxy groups, and carboxyl groups that are contained in the crosslinking component (B) described later.

(A) The rubber component may also include a rubber having at least one crosslinking group of an acid anhydride group and a carboxyl group. As an example of a rubber having an acid anhydride group, a rubber partially modified with maleic anhydride can be cited. A rubber partially modified with maleic anhydride is a polymer containing a constituent unit derived from maleic anhydride. As a commercial product of a rubber partially modified with maleic anhydride, for example, there is a styrene elastomer "Tufprene 912" manufactured by Asahi Kasei Corporation.

The rubber partially modified with maleic anhydride may be a hydrogenated styrene elastomer partially modified with maleic anhydride. The hydrogenated styrene elastomer can also be expected to have effects such as improved weather resistance. The hydrogenated styrene elastomer is an elastomer obtained by adding hydrogen to the unsaturated double bonds of a styrene elastomer having a soft chain segment containing unsaturated double bonds. Examples of commercially available hydrogenated styrene elastomers partially modified with maleic anhydride include "FG1901" and "FG1924" from Kraton Polymers Japan Co., Ltd., and "TufTech M1911", "TufTech M1913", and "TufTech M1943" from Asahi Kasei Corporation.

From the viewpoint of coating properties, the weight average molecular weight of the rubber component (A) may be 20,000 to 200,000, 30,000 to 150,000, or 50,000 to 125,000. The weight average molecular weight (Mw) herein refers to a standard polystyrene conversion value determined by gel permeation chromatography (GPC).

In the resin composition, based on the total amount of the (A) rubber component, the (B) crosslinking component and the (C) ester hardener, the content of the (A) rubber component is preferably 60% by mass to 95% by mass, more preferably 65% by mass to 90% by mass, and even more preferably 70% by mass to 85% by mass. If the content of the (A) rubber component is 60% by mass or more, there is a tendency that more sufficient stretchability is easily obtained, and the rubber component and the crosslinking component are fully mixed. If the content of the (A) rubber component is 95% by mass or less, there is a tendency that the stretchable resin layer has particularly excellent properties in terms of adhesion, insulation reliability and heat resistance. The content of the rubber component (A) in the elastic resin layer may be within the above range based on the mass of the elastic resin layer.

(B) The crosslinking component having an epoxy group is a component that crosslinks during the curing reaction to form a crosslinked polymer. (B) The crosslinking component having an epoxy group is not particularly limited as long as it has an epoxy group in the molecule, and may be, for example, a common epoxy resin. The epoxy resin may be monofunctional, difunctional, or polyfunctional, and is not particularly limited, but in order to obtain sufficient curability, a difunctional or polyfunctional epoxy resin may be used.

Examples of epoxy resins include bisphenol A type, bisphenol F type, phenol novolac type, naphthalene type, dicyclopentadiene type, cresol novolac type, etc. Epoxy resins modified with a fat chain can impart flexibility. Examples of commercially available aliphatic chain-modified epoxy resins include EXA-4816 manufactured by DIC Corporation. From the viewpoints of hardening, low viscosity, and heat resistance, phenol novolac type, cresol novolac type, naphthalene type, or dicyclopentadiene type epoxy resins can be selected. The epoxy resins can be used alone or in combination of two or more.

By combining a rubber having a maleic anhydride group or a carboxyl group with a compound having an epoxy group (epoxy resin), particularly excellent effects can be obtained in terms of heat resistance and low moisture permeability of the stretchable resin layer, adhesion between the stretchable resin layer and the conductive layer, and low viscosity of the stretchable resin layer. If the heat resistance of the stretchable resin layer is improved, it is possible to suppress deterioration of the stretchable resin layer in a heating step such as nitrogen reflux. If the stretchable resin layer has a low viscosity, a conductive substrate or a wiring substrate can be handled with good workability.

The resin composition may contain other crosslinking components other than the crosslinking component (B) having an epoxy group within a range that does not significantly impair the effect of the present invention. From the viewpoint of more sufficiently reducing the dielectric loss tangent of the elastic resin layer, the content of the other crosslinking components is preferably less than 10 parts by mass relative to 100 parts by mass of the crosslinking component (B) having an epoxy group.

(C) Ester-based hardeners are compounds that themselves participate in the hardening reaction and can improve the heat resistance of the elastic resin layer and reduce the dielectric loss tangent.

There are no particular limitations on the ester-based curing agent, but from the viewpoint of more fully obtaining the effect of improving heat resistance and reducing dielectric loss tangent, compounds having one or more highly reactive ester groups in one molecule, such as phenol esters, thiophenol esters, N-hydroxylamine esters, and esters of heterocyclic hydroxyl compounds, are preferably used. More specifically, as ester-based curing agents, for example, "Epiclon HPC8000-65T", "Epiclon HPC8000-L-65MT", and "Epiclon HPC8150-60T" (all trade names manufactured by DIC Corporation) can be cited. These can be used alone or in combination of two or more.

It is believed that the ester-based curing agent reacts with the crosslinking component (B) as shown in the following formula (I) during the curing reaction. It is believed that no hydroxyl group is generated in the reaction between the ester-based curing agent (C) and the crosslinking component (B), and even if a side reaction occurs, a hydroxyl group is unlikely to be generated, resulting in a low dielectric loss tangent.

[Chemistry 1] In the formula, R ¹ , R ² and R ³ each independently represent a monovalent organic group, and may be a monovalent organic group having an aromatic ring in order to more fully achieve the effects of the present invention.

The resin composition may contain other curing agents other than the (C) ester curing agent within a range that does not significantly impair the effects of the present invention. From the viewpoint of more sufficiently reducing the dielectric loss tangent of the elastic resin layer, the content of the other curing agent is preferably less than 10 parts by mass relative to 100 parts by mass of the (C) ester curing agent.

In the resin composition, the total content of the (B) crosslinking component and the (C) ester hardener is preferably 5% by mass to 40% by mass, more preferably 10% by mass to 35% by mass, and even more preferably 15% by mass to 30% by mass, based on the total amount of the (A) rubber component, the (B) crosslinking component, and the (C) ester hardener. When the total content of the (B) crosslinking component and the (C) ester hardener is 5% by mass or more, there is a tendency that more sufficient hardening is easily obtained and the elastic resin layer has particularly excellent properties in terms of adhesion, insulation reliability, and heat resistance. When the total content of the (B) crosslinking component and the (C) ester-based hardener is 40% by mass or less, more sufficient stretchability tends to be easily obtained, and the rubber component and the crosslinking component tend to be sufficiently mixed.

In the resin composition, the content ratio of the crosslinking component (B) to the ester-based curing agent (C) is preferably in the range of 4:5 to 5:4 in terms of the equivalent ratio of the epoxy group in the epoxy resin (B) to the ester bond in the ester-based curing agent (C). When the content ratio is in the above range, more sufficient curing is easily obtained and the elastic resin layer tends to have particularly excellent properties in terms of adhesion, insulation reliability and heat resistance.

The resin composition may further contain (D) a hardening accelerator. (D) The hardening accelerator is a compound that functions as a catalyst for the hardening reaction. (D) The hardening accelerator may be selected from tertiary amines, imidazoles, metal salts of organic acids, phosphorus compounds, Lewis acids, amine complex salts, and phosphines. Among them, imidazoles may be used from the viewpoint of the storage stability and hardening properties of the varnish of the resin composition. In the case where the (A) rubber component includes a rubber partially modified with maleic anhydride, an imidazole compatible with the rubber may also be selected.

In the resin composition, the content of the (D) hardening accelerator may be 0.1 to 10 parts by mass relative to 100 parts by mass of the total amount of the (A) rubber component, the (B) crosslinking component, and the (C) ester hardener. If the content of the (D) hardening accelerator is 0.1 parts by mass or more, there is a tendency to easily obtain more sufficient hardening. If the content of the (D) hardening accelerator is 10 parts by mass or less, there is a tendency to easily obtain more sufficient heat resistance. From the above viewpoints, the content of the (D) hardening accelerator may be 0.3 to 7 parts by mass, or 0.5 to 5 parts by mass.

In addition to the above-mentioned components, the resin composition may further include antioxidants, yellowing inhibitors, ultraviolet absorbers, visible light absorbers, colorants, plasticizers, stabilizers, fillers, flame retardants, leveling agents, etc. as needed within the range that does not significantly impair the effects of the present invention.

In particular, the resin composition may contain at least one anti-degradation agent selected from the group consisting of an antioxidant, a heat stabilizer, a light stabilizer, and an anti-hydrolysis agent. The antioxidant inhibits degradation caused by oxidation. In addition, the antioxidant imparts sufficient heat resistance at high temperatures to the elastic resin layer. The heat stabilizer imparts stability at high temperatures to the elastic resin layer. Examples of light stabilizers include: ultraviolet absorbers that prevent degradation caused by ultraviolet rays, light blocking agents that block light, and matting agents that have a matting function that stabilizes the organic material by receiving light energy absorbed by the organic material. The anti-hydrolysis agent inhibits degradation caused by moisture. The anti-degradation agent may be at least one selected from the group consisting of an antioxidant, a heat stabilizer, and an ultraviolet absorber. As the anti-degradation agent, only one of the components listed above may be used, or two or more may be used in combination. In order to obtain a better effect, two or more anti-degradation agents may be used in combination.

The antioxidant may be, for example, one or more selected from the group consisting of phenolic antioxidants, amine antioxidants, sulfur antioxidants, and phosphite antioxidants. In order to obtain a better effect, two or more antioxidants may be used in combination. A phenolic antioxidant and a sulfur antioxidant may also be used in combination.

Phenolic antioxidants may be compounds having a substituent with large stereohindrance such as tert-butyl (t-butyl) and trimethylsilyl at the adjacent position of the phenolic hydroxyl group. Phenolic antioxidants are also called hindered phenolic antioxidants.

The phenolic antioxidant may be, for example, one or more compounds selected from the group consisting of 2-tert-butyl-4-methoxyphenol, 3-tert-butyl-4-methoxyphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,2'-methylene-bis(4-methyl-6-tert-butylphenol), 4,4'-thiobis-(3-methyl-6-tert-butylphenol), 4,4'-butylenebis(3-methyl-6-tert-butylphenol), 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. The phenolic antioxidant may be a high molecular weight phenolic antioxidant represented by 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene and tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane.

The phosphite antioxidant may be selected from, for example, triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, 4,4'-butylene-bis(3-methyl-6-tert-butylphenyl)-di(tridecyl)phosphite, cycloneopentanetetrayl-bis(nonylphenyl)phosphite, cycloneopentanetetrayl-bis(dinonylphenyl)phosphite, cycloneopentanetetrayl-tris(nonylphenyl)phosphite, cycloneopentanetetrayl-tris(di- The present invention can be selected from the group consisting of at least one compound selected from the group consisting of 1,2-di-(2,4-di-tert-butylphenyl) phosphite, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, 2,2-methylenebis(4,6-di-tert-butylphenyl)-2-ethylhexyl phosphite, diisodecylpentaerythritol diphosphite and tris(2,4-di-tert-butylphenyl) phosphite, and tris(2,4-di-tert-butylphenyl) phosphite.

Examples of other antioxidants include hydroxyamine antioxidants represented by N-methyl-2-dimethyl amino acetohydroxamic acid and sulfur-based oxidants represented by dilauryl 3,3'-thiodipropionate.

The content of the antioxidant can also be 0.1% to 20% by mass based on the mass of the resin composition (total solid content). If the content of the antioxidant is 0.1% by mass or more, sufficient heat resistance of the elastic resin layer can be easily obtained. If the content of the antioxidant is 20% by mass or less, bleeding and blooming can be suppressed.

From the viewpoint of preventing sublimation during heating, the molecular weight of the antioxidant may be 400 or more, 600 or more, or 750 or more. When two or more antioxidants are included, the average value of the molecular weights thereof may be within the above range.

Examples of the thermal stabilizer (thermal degradation inhibitor) include metal soaps or inorganic acid salts such as a combination of zinc salts and barium salts of higher fatty acids, organic tin compounds such as organic tin maleates and organic tin thiolates, and fullerenes (such as hydroxylated fullerenes).

Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers represented by 2,4-dihydroxybenzophenone, benzotriazole ultraviolet absorbers represented by 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and cyanoacrylate ultraviolet absorbers represented by 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate.

Examples of the anti-hydrolysis agent include carbodiimide derivatives, epoxy compounds, isocyanate compounds, acid anhydrides, oxazoline compounds, and melamine compounds.

As other anti-degradation agents, for example, hindered amine light stabilizers, ascorbic acid, propyl gallate, catechin, oxalic acid, malonic acid, and phosphites can be cited.

The stretchable resin layer can be produced, for example, by the following method, which comprises: dissolving or dispersing (A) a rubber component, (B) a crosslinking component, and (C) an ester-based hardener, and other components as required, in an organic solvent to obtain a resin varnish; and forming a film of the resin varnish on a conductive foil or a carrier film by the method described below.

The organic solvent used here is not particularly limited, and examples thereof include aromatic hydrocarbons such as toluene, xylene, mesitylene, cumene, and p-cymene; cyclic ethers such as tetrahydrofuran and 1,4-dioxane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and 4-hydroxy-4-methyl-2-pentanone; esters such as methyl acetate, ethyl acetate, butyl acetate, methyl lactate, ethyl lactate, and γ-butyrolactone; carbonates such as ethyl carbonate and propyl carbonate; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone, etc. From the viewpoint of solubility and boiling point, toluene or N,N-dimethylacetamide can also be used. These organic solvents may be used alone or in combination of two or more. The solid content (components other than the organic solvent) concentration in the resin varnish may be 20 mass % to 80 mass %.

The carrier film is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; polycarbonate, polyamide, polyimide, polyamide imide, polyetherimide, polyether sulfide, polyether sulfide, polyether ketone, polyphenylene ether, polyphenylene sulfide, polyarylate, polysulfide, liquid crystal polymer, and the like. Among them, from the viewpoint of flexibility and toughness, films of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polypropylene, polycarbonate, polyamide, polyimide, polyamide imide, polyphenylene ether, polyphenylene sulfide, polyarylate, or polysulfone can also be used as the carrier film.

The thickness of the carrier film is not particularly limited and may be 3 μm to 250 μm. If the thickness of the carrier film is 3 μm or more, the film strength is sufficient, and if the thickness of the carrier film is 250 μm or less, sufficient flexibility can be obtained. From the above viewpoints, the thickness may be 5 μm to 200 μm, or 7 μm to 150 μm. From the viewpoint of improving the releasability from the stretchable resin layer, a film subjected to a release treatment of the carrier film using a silicone compound, a fluorine-containing compound, etc. may also be used as needed.

If necessary, a protective film may be attached to the stretchable resin layer to form a laminated film having a three-layer structure including a conductive foil or a carrier film, a stretchable resin layer, and a protective film.

The protective film is not particularly limited, and examples thereof include films of polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; and films of polyolefins such as polyethylene and polypropylene. Among them, films of polyesters such as polyethylene terephthalate; and films of polyolefins such as polyethylene and polypropylene can be used as the protective film from the viewpoint of softness and toughness. From the viewpoint of improving the releasability from the stretchable resin layer, the protective film can be subjected to a mold release treatment using silicone compounds, fluorine-containing compounds, and the like.

The thickness of the protective film can be appropriately changed according to the desired flexibility, and may be 10 μm to 250 μm. If the thickness is 10 μm or more, the film strength tends to be sufficient, and if it is 250 μm or less, sufficient flexibility tends to be obtained. From the above viewpoints, the thickness may be 15 μm to 200 μm, or 20 μm to 150 μm.

[Manufacturing method of wiring board] A wiring board having a conductor foil in one embodiment can be manufactured, for example, by the following method, the method comprising: preparing a laminate (conductor board) having a stretchable resin layer and a conductor foil laminated on the stretchable resin layer; forming an etching resist on the conductor foil; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the conductor foil; removing the portion of the conductor foil not covered by the etching resist pattern; and removing the etching resist pattern.

As a method for obtaining a laminated board (conductive substrate) having a stretchable resin layer and a conductive foil, any method can be used, including a method of applying a varnish of a resin composition for forming a stretchable resin layer to a conductive foil, and a method of forming a stretchable resin layer by laminating a conductive foil on a carrier film using a vacuum press, a laminating press, etc. The stretchable resin layer can be formed by heating the resin composition and causing a crosslinking reaction (hardening reaction) of a crosslinking component.

As a method of laminating the stretchable resin layer on the carrier film on the conductive foil, any method may be used, and a roll laminating press, a vacuum laminating press, a vacuum press, etc. may be used. From the viewpoint of production efficiency, molding may be performed using a roll laminating press or a vacuum laminating press.

The thickness of the elastic resin layer after drying is not particularly limited, but is generally 5 μm to 1000 μm. Within the above range, sufficient strength of the elastic resin layer can be easily obtained, and the amount of residual solvent in the elastic resin layer can be reduced because the elastic resin layer is dried sufficiently.

A conductor foil may be further laminated on the surface of the elastic resin layer opposite to the conductor foil, thereby manufacturing a laminate having conductor foil formed on both sides of the elastic resin layer. By providing the conductor layer on both sides of the elastic resin layer, warping of the laminate during curing can be suppressed.

As a method for forming a wiring pattern on a conductor foil of a laminate (a laminate for forming a wiring board), a method using etching or the like can be generally used. For example, when a copper foil is used as the conductor foil, as an etching solution, for example, a mixed solution of concentrated sulfuric acid and hydrogen peroxide, a ferric chloride solution, or the like can be used.

Examples of etch resists used in etching include Photec H-7025 (manufactured by Hitachi Chemical Co., Ltd., trade name), Photec H-7030 (manufactured by Hitachi Chemical Co., Ltd., trade name), and X-87 (manufactured by Taiyo Holdings Co., Ltd., trade name). After the wiring pattern is formed, the etch resist is usually removed.

An embodiment of a method for manufacturing a wiring board having a conductive coating film includes: forming a conductive coating film on a stretchable resin layer by electroless plating; forming a coating resist on the conductive coating film; exposing the coating resist and developing the exposed coating resist to form a coating layer covering the stretchable resin layer; The method comprises the steps of forming an anti-etching pattern on a portion of the conductive coating film not covered by the anti-etching pattern; further forming a conductive coating film by electroplating on the portion of the conductive coating film not covered by the anti-etching pattern; removing the anti-etching pattern; and removing the portion of the conductive coating film formed by electroless plating that is not covered by the conductive coating film formed by electroplating.

Another embodiment of the method for manufacturing a wiring board includes: forming an etching resist on a conductive coating formed on a stretchable resin layer; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the stretchable resin layer; removing the conductive coating portion not covered by the etching resist pattern; and removing the etching resist pattern.

Examples of coating resists used as a mask for coating include Photech RY3325 (manufactured by Hitachi Chemical Co., Ltd., trade name), Photech RY-5319 (manufactured by Hitachi Chemical Co., Ltd., trade name), and MA-830 (manufactured by Taiyo Holdings Co., Ltd., trade name). The details of electroless plating and electroplating are as described above.

By mounting various electronic devices on a wiring substrate, a stretchable element can be obtained. [Example]

The present invention is further specifically described with reference to the following embodiments, but the present invention is not limited to these embodiments.

(Example 1) <Preparation of resin varnish for forming a stretchable resin layer> On the one hand, 80 parts by weight (amount of non-volatile components) of maleic anhydride-modified styrene-ethylene-butadiene rubber (trade name "FG1924GT" manufactured by KRATON Co., Ltd.) diluted with toluene and adjusted to 25% by weight of non-volatile components as component (A), and 80 parts by weight (amount of non-volatile components) of dicyclopentadiene-type epoxy resin (trade name "EPICL" manufactured by DIC Co., Ltd.) diluted with toluene and adjusted to 25% by weight of non-volatile components as component (B) were added. 11.1 parts by mass (the amount of non-volatile components) of 1-benzyl-2-methylimidazole ("1B2MZ" manufactured by Shikoku Chemicals Co., Ltd.) were stirred and mixed to obtain a resin varnish.

<Preparation of laminated film> A release-treated polyethylene terephthalate (PET) film (product name "Purex A31" manufactured by Teijin DuPont Films Co., Ltd., thickness 25 μm) was prepared as a carrier film. The resin varnish was applied to the release-treated surface of the PET film using a doctor blade coater (product name "SNC-350" manufactured by Yasui Seiki Co., Ltd.). The coated film was heated at 100°C for 20 minutes in a dryer (product name "MSO-80TPS" manufactured by Futaba Scientific Co., Ltd.) to dry, forming a resin layer (stretchable resin layer before curing) with a thickness of 100 μm. On the formed resin layer, a release-treated PET film as a protective film, which is the same as the carrier film, is attached with the release-treated surface being oriented toward the resin layer side to obtain a laminated film.

<Production of Conductive Substrate> The protective film of the laminated film was peeled off, and an electrolytic copper foil (trade name "F2-WS-12" manufactured by Furukawa Electric Co., Ltd.) with a roughened surface Ra of 1.5 μm was superimposed on the exposed resin layer with the roughened surface facing the resin layer side. In this state, the electrolytic copper foil layer was pressed onto the resin layer using a vacuum press (trade name "V130" manufactured by Nikko Materials Co., Ltd.) at a pressure of 0.5 MPa, a temperature of 90°C, and a pressing time of 60 seconds. Thereafter, the substrate was heated at 180°C for 60 minutes in a dryer (product name "MSO-80TPS" manufactured by Futaba Scientific Co., Ltd.), thereby obtaining a conductive substrate having a hardened elastic resin layer as a resin layer and an electrolytic copper foil as a conductive layer.

(Example 2 to Example 6 and Comparative Example 1 to Comparative Example 2) A resin varnish, a laminate film and a conductive substrate were prepared in the same manner as in Example 1 except that the composition of the resin varnish was changed to the composition shown in Table 1. In Table 1, "HP5000" is a novolac epoxy resin (a product name "EPICLON HP5000" manufactured by DIC Corporation), "HPC8000-L-65MT" is an ester hardener (a product name "EPICLON HPC8000-L-65MT" manufactured by DIC Corporation, a low molecular weight grade of HPC8000-L-65MT), and "HPC8150-60T" is an ester hardener (a product name "EPICLON HPC8150-60T" manufactured by DIC Corporation, a compound having a naphthalene skeleton). In addition, the blending amount of each component in Table 1 is the blending amount of the non-volatile component, and the unit is "parts by mass".

[Determination of tensile modulus and elongation at break] The laminated films obtained in the examples and comparative examples were heated at 180°C for 60 minutes to harden the resin layer and form an elastic resin layer. The carrier film and the protective film were removed, and the elastic resin layer was cut into strips of 40 mm in length and 10 mm in width to obtain a test piece. The test piece was subjected to a tensile test using an autograph (trade name "EZ-S" manufactured by Shimadzu Corporation) to obtain a stress-strain curve. The tensile modulus and elongation at break were calculated based on the obtained stress-strain curve. The tensile test was conducted at a chuck distance of 20 mm and a tensile speed of 50 mm/min. The tensile modulus of elasticity was determined from the slope of the stress-strain curve in the range of 0.5 N to 1.0 N. The strain at the time when the specimen broke was recorded as the elongation at break. The results are shown in Table 1.

[Determination of recovery rate] Similar to the measurement of the tensile modulus and elongation at break, a test piece of a 40 mm long and 10 mm wide strip of elastic resin layer was prepared. Using an automatic plotter (trade name "EZ-S" manufactured by Shimadzu Corporation), the test piece was stretched at a tensile speed of 100 mm/min until the strain reached 20%, and then the stress was released and the test piece returned to the initial position, and then the tensile test was performed again. The recovery rate R is calculated by setting the strain (displacement) applied in the first tensile test as X and the difference between the position at the start of the load application in the next tensile test and X as Y, using the following formula. In this test, X is 20%. The results are shown in Table 1. R (%) = Y/X × 100

[Determination of dielectric constant (Dk) and dielectric loss tangent (Df)] Similar to the measurement of tensile modulus and elongation at break, a test piece of a 80 mm × 80 mm elastic resin layer was prepared. Using the test piece, Dk and Df were calculated by the cavity resonator method. The measurement instruments used were vector network analyzer E8364B (manufactured by Keysight Technologies), CP531 (manufactured by Kanto Electronics Application Development Co., Ltd.), and CPMA-V2 (program), respectively, and the measurement was performed at an ambient temperature of 25°C and a frequency of 10 kHz. The results are shown in Table 1.

[Evaluation of heat resistance] The laminated films obtained in Examples 1 to 6 and Comparative Examples 1 to 2 were heated at 180°C for 60 minutes to harden the resin layer and form a stretchable resin layer. After removing the carrier film and the protective film, the stretchable resin layer was subjected to a heat resistance test using a nitrogen reflow system (trade name "TNV-EN" manufactured by Tamura Manufacturing Co., Ltd.), wherein the heat treatment step using the temperature distribution of Figure 3 of IPC/JEDEC J-STD-020 was repeated 10 times. After the heat resistance test, the tensile modulus, elongation at break, and recovery rate of the stretchable resin layer were measured using the same method as described above. The results are shown in Tables 2 and 3 together with the measurement results before the heat resistance test.

[Measurement of infrared absorption spectrum (IR)] Regarding the resin layer of the laminated film of Comparative Example 1 (stretchable resin layer before curing) and the stretchable resin layer cured by heating at 180°C for 60 minutes, and the stretchable resin layer of the laminated film of Example 1 and Comparative Example 3 cured by heating at 180°C for 60 minutes, after removing the carrier film and the protective film, the infrared absorption spectrum was measured by the transmission method using a Fourier transform infrared spectrophotometer (trade name "FTS3000MX" manufactured by Bio-Rad Corporation). FIG4 shows the infrared absorption spectra of the elastic resin layer before and after curing of Comparative Example 1, and FIG5 shows the infrared absorption spectra of the elastic resin layer after curing of Example 1, Example 3, and Comparative Example 1.

As shown in Fig. 4, in the elastic resin layer of Comparative Example 1, an absorption peak at about 3400 cm ^-1 attributable to the stretching vibration of the hydroxyl group, which did not exist before the curing, was confirmed to appear after the curing, and a hydroxyl group was generated by the curing reaction. In addition, as shown in Fig. 5, in the elastic resin layers of Examples 1 and 3, it was confirmed that the absorption peak attributable to the stretching vibration of the hydroxyl group was almost absent, and the generation of the hydroxyl group was suppressed.

[Manufacturing and evaluation of wiring substrate] A wiring substrate 1 for testing as shown in FIG2 was manufactured, and the wiring substrate 1 for testing had a stretchable resin layer 3 and a conductor foil (electrolytic copper foil) having a corrugated pattern formed on the stretchable resin layer 3 as a conductor layer 5. First, an etching resist (trade name "Photec RY-5325" manufactured by Hitachi Chemical Co., Ltd.) was attached to the conductor layer of the conductor substrate obtained in the embodiment and the comparative example having concavities and convexities formed on the surface of the stretchable resin layer using a roller press, and a photo mask (photo tool) having a corrugated pattern formed thereon was closely attached. The etching resist was exposed to an energy of 50 mJ/ ^cm2 using an EXM-1201 exposure machine manufactured by ORC Manufacturing Co., Ltd. Then, spray development was performed for 240 seconds with a 1 mass% sodium carbonate aqueous solution at 30°C to dissolve the unexposed portion of the etching resist and form an etching resist pattern with a wavy opening. Then, the copper foil not covered by the etching resist pattern was removed using an etching liquid. Thereafter, the etching resist was removed using a stripping liquid to obtain a wiring substrate 1 having a conductor layer 5 on a stretchable resin layer 3 with a wavy wiring pattern having a wiring width of 50 μm and meandering in a predetermined direction X.

The obtained wiring substrate was stretched and deformed in the X direction until the strain reached 10%, and the elastic resin layer and the wavy wiring pattern were observed when the wiring substrate returned to the original state. As a result, the wiring substrate of either the embodiment or the comparative example did not break the elastic resin layer and the wiring pattern when stretched.

[Table 1]

[Table 2]

[Table 3]

According to the results shown in Table 1, it can be understood that the conductive substrates of Examples 1 to 6 have excellent elasticity and low dielectric loss tangent compared with the conductive substrates of Comparative Examples 1 to 2. In addition, according to the results shown in Tables 2 and 3, it can be understood that the conductive substrates of Examples 1 to 6 can maintain good elasticity and elastic modulus even after the heat resistance test. [Industrial Applicability]

The conductive substrate of the present invention and the wiring substrate obtained therefrom are expected to be used as substrates for wearable devices, for example.

1. Wiring board 3. Elastic resin layer 5. Conductor layer (conductor foil or conductor coating) X. Strain (displacement) applied in the first tensile test Y. The difference between the position at the start of the load application and X when the tensile test is repeated

FIG1 is a stress-strain curve showing an example of measuring the recovery rate. FIG2 is a plan view showing an embodiment of a wiring board. FIG3 is a curve diagram showing the temperature profile of a heat resistance test. FIG4 is a diagram showing the infrared absorption spectrum of the elastic resin layer before and after curing of Comparative Example 1. FIG5 is a diagram showing the infrared absorption spectrum of the elastic resin layer after curing of Example 1, Example 3, and Comparative Example 1.

1‧‧‧Wiring board

3‧‧‧Stretchable resin layer

5. Conductive layer (conductive foil or conductive film)

X‧‧‧The strain (displacement) applied in the first tensile test

Claims (21)

A conductive substrate comprises: a stretchable resin layer; and a conductive foil disposed on the stretchable resin layer, wherein the stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester-based curing agent, wherein the recovery rate of the stretchable resin layer after being stretched and deformed to a strain of 20% is 80% or more, and based on the total amount of the (A) rubber component, the (B) crosslinking component, and the (C) ester-based curing agent, the content of the (A) rubber component is 60% by mass to 95% by mass. A conductive substrate comprises: a stretchable resin layer; and a conductive foil disposed on the stretchable resin layer, wherein the stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester curing agent, wherein the content of the (A) rubber component is 60% by mass to 95% by mass based on the total amount of the (A) rubber component, the (B) crosslinking component, and the (C) ester curing agent. A conductive substrate as described in item 1 or 2 of the patent application, wherein the elastic modulus of the conductive foil is 40 GPa to 300 GPa. A conductive substrate comprises: a stretchable resin layer; and a conductive coating disposed on the stretchable resin layer, wherein the stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester-based curing agent, wherein the recovery rate of the stretchable resin layer after being stretched and deformed to a strain of 20% is greater than 80%, and based on the total amount of the (A) rubber component, the (B) crosslinking component, and the (C) ester-based curing agent, the content of the (A) rubber component is 60% by mass to 95% by mass. A conductive substrate comprises: a stretchable resin layer; and a conductive coating disposed on the stretchable resin layer, wherein the stretchable resin layer comprises a cured product of a resin composition, wherein the resin composition comprises (A) a rubber component, (B) a crosslinking component having an epoxy group, and (C) an ester curing agent, wherein the content of the (A) rubber component is 60% by mass to 95% by mass based on the total amount of the (A) rubber component, the (B) crosslinking component, and the (C) ester curing agent. A conductive substrate as described in any one of items 1, 2, 4, and 5 of the patent application, wherein the (A) rubber component comprises at least one rubber selected from the group consisting of acrylic rubber, isoprene rubber, butyl rubber, styrene butadiene rubber, butadiene rubber, acrylonitrile butadiene rubber, silicone rubber, urethane rubber, chloroprene rubber, ethylene propylene rubber, fluororubber, vulcanized rubber, epichlorohydrin rubber, and chlorobutyl rubber. A conductive substrate as described in any one of item 1, item 2, item 4, and item 5 of the patent application scope, wherein the (A) rubber component contains a rubber having a crosslinking group. The conductive substrate as described in item 7 of the patent application, wherein the cross-linking group is at least one of an anhydride group and a carboxyl group. A conductive substrate as described in any one of item 1, item 2, item 4, and item 5 of the patent application, wherein the resin composition further contains (D) a curing accelerator. The conductive substrate described in item 1, item 2, item 4, and item 5 of the patent application scope, wherein the resin composition further contains an antioxidant. The conductive substrate as described in item 1, item 2, item 4, and item 5 of the patent application scope, wherein the (A) rubber component includes a rubber partially modified by maleic anhydride. As described in item 1, item 2, item 4, and item 5 of the patent application scope, the (A) rubber component includes a hydrogenated styrene elastomer partially modified with maleic anhydride. A wiring substrate, comprising a conductor substrate as described in item 1 or item 2 of the patent application scope, wherein the conductor foil forms a wiring pattern. A wiring substrate, comprising a conductor substrate as described in item 4 or 5 of the patent application, wherein the conductor coating forms a wiring pattern. A retractable element, comprising: a wiring substrate as described in item 13 or 14 of the patent application; and an electronic device mounted on the wiring substrate. The conductive substrate as described in item 1 or 2 of the patent application scope is used to form a wiring substrate, wherein the wiring substrate comprises a conductive substrate having a stretchable resin layer and a conductive foil disposed on the stretchable resin layer, wherein the conductive foil forms a wiring pattern. The conductive substrate as described in item 4 or 5 of the patent application scope is used to form a wiring substrate, wherein the wiring substrate comprises a conductive substrate having a stretchable resin layer and a conductive coating disposed on the stretchable resin layer, wherein the conductive coating forms a wiring pattern. A method for manufacturing a wiring board, the wiring board being the wiring board as described in item 13 of the patent application, the method comprising: preparing a laminate having a stretchable resin layer and a conductive foil laminated on the stretchable resin layer; forming an etching resist on the conductive foil; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the conductive foil; removing the conductive foil not covered by the etching resist pattern; and removing the etching resist pattern. A method for manufacturing a wiring board, wherein the method comprises: forming a coating anti-corrosion agent on a stretchable resin layer; exposing the coating anti-corrosion agent and developing the exposed coating anti-corrosion agent to form an anti-corrosion agent pattern covering a portion of the stretchable resin layer; forming a conductive coating film by electroless plating on the surface of the portion of the stretchable resin layer not covered by the anti-corrosion agent pattern; and removing the anti-corrosion agent pattern. A method for manufacturing a wiring substrate, wherein the method comprises: forming a conductive coating film on a stretchable resin layer by electroless plating; forming a coating resist on the conductive coating film; exposing the coating resist and developing the exposed coating resist to form a conductive coating covering the stretchable resin layer; The step of forming an anti-etching pattern on a portion of the shrinkable resin layer; the step of further forming a conductive coating by electroplating on the portion of the conductive coating not covered by the anti-etching pattern; the step of removing the anti-etching pattern; and the step of removing the portion of the conductive coating not covered by the conductive coating formed by electroplating in the conductive coating formed by electroless plating. A method for manufacturing a wiring board, wherein the method comprises: forming an etching resist on a conductor coating formed on a stretchable resin layer; exposing the etching resist and developing the exposed etching resist to form an etching resist pattern covering a portion of the stretchable resin layer; removing the conductor coating not covered by the etching resist pattern; and removing the etching resist pattern.