Wiring sheet

Abstract

To provide a flexible wiring sheet capable of electrically connecting printed flexible wiring lines or a printed flexible wiring line and a flexible metal wiring line by a simple method and exhibiting high sealing performance.SOLUTION: A wiring sheet includes a sheet-like substrate (1), a first conductive wiring line (2) disposed on the sheet-like substrate, a film protective layer (3) that protects the first conductive wiring line, and a second conductive wiring line (4) connected to the first conductive wiring line (2), and the first conductive wiring line (2) and the second conductive wiring line (4) are connected with a conductive adhesive sheet (6) containing silver or carbon, and the connection portion is sealed by a sealing adhesive sheet (7).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wiring sheet in which flexible printed wiring is bonded by a bonding method that is simple and has long-term reliability. [Background technology]

[0002] In the field of electronic devices, methods for joining rigid wiring boards include rigid-flexible boards that incorporate a flexible board into an inner layer (Patent Document 1), connections via connectors, and methods for joining wiring boards with anisotropic conductive materials (Patent Document 2). However, the method of Patent Document 1 requires complex processes such as pattern formation by etching and thermocompression bonding via prepregs for multilayering. Joining via anisotropic conductive materials, as in Patent Document 2, is expensive and does not provide sufficient connection strength for applications that are subject to repeated physical stress, such as biosensors. To address these issues, a method of joining electrodes with solder and filling the gap with a thermosetting resin (Patent Document 3) has been proposed. However, soldering is insufficient in areas of flexible substrates that are constantly subjected to physical stress, and materials such as PET substrates, which are suitable for circuit formation by printing, cannot withstand the high temperatures that occur during soldering.

[0003] In recent years, flexible hybrid materials that combine flexible wiring with rigid substrates such as IC modules have become necessary for wearable devices that are attached to the body to acquire biosignals, and sensing devices used outdoors. How to join wiring materials printed on substrates that are not heat-resistant, such as PET, to wiring from rigid components is a major challenge, and the reality is that a joining technology that combines practical joining reliability with light weight and ease of use has not yet been achieved. Conductive adhesives (Patent Document 4) are used as a method for joining printed wiring, but in the case of cross-linking adhesive joining, stress occurs at the interface with the printed wiring during hardening, which can cause poor bonding during long-term environmental tests at high temperatures and humidity or repeated bending. Furthermore, when using liquid adhesives for simple outdoor joining work, it is difficult to determine the amount of adhesive, making it difficult to achieve a stable conductive bond. Furthermore, room-temperature curing requires a long time (approximately 24 hours), which necessitates interrupting the next process, posing a major problem for simple construction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2012-114482 [Patent Document 2] Patent Publication No. 2012-174589 [Patent Document 3] Patent Publication No. 2014-183087 [Patent Document 4] Patent Publication No. 2020-64889 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a flexible wiring sheet that easily and conductively bonds between printed flexible wirings or between printed flexible wirings and flexible metal wirings, while at the same time exhibiting high bending resistance and sealing stability that can withstand high-temperature, high-humidity environments. [Means for solving the problem]

[0006] As a result of extensive research into solving the above-mentioned problems, the inventors have completed a wiring sheet that provides a simple and stable conductive bond by electrically connecting flexible circuits with a conductive adhesive sheet and sealing the surrounding area with an adhesive sheet.

[0007] The present invention joins printed flexible printed wiring or printed flexible wiring and flexible metal wiring with a conductive adhesive sheet, while simultaneously sealing the periphery with an adhesive sheet composition, thereby easily making the joint resistant to physical stress even during on-site work and simultaneously achieving high sealing properties even in high-temperature, high-humidity environments, thereby ensuring the long-term reliability of the wiring.

[0008] That is, the present invention relates to a wiring sheet having a sheet-like substrate (1), a first conductive wiring (2) printed on the sheet-like substrate, a film protective layer (3) that protects the first conductive wiring, and a second conductive wiring (4) connected to the first conductive wiring (2), characterized in that the first conductive wiring (2) and the second conductive wiring (4) are connected with a conductive adhesive sheet (6) containing silver or carbon, and the connected portion is sealed with a sealing adhesive sheet (7).

[0009] The present invention also relates to the wiring sheet, wherein the conductive adhesive sheet (6) is a sheet-type adhesive material having a film thickness of 10 to 50 μm.

[0010] The present invention also relates to the wiring sheet, wherein the conductive adhesive sheet (6) contains conductive particles (A) and a resin (B), the conductive particles (A) contain silver or carbon, the conductive particles (A) contain conductive particles (a1) that satisfy the following formula (1), and the volume ratio of the conductive particles (a1) to the resin (B) is 1:99 to 15:85: Formula (1) Z≦Y≦3Z (In formula (1), Y represents the particle diameter of the conductive particles (a1), and Z represents the film thickness of the conductive adhesive sheet. represents.)

[0011] The present invention also relates to the wiring sheet, wherein the adhesive strength of the conductive adhesive sheet (6) is 3N / 25mm or more between the first printed conductive wiring sheet (2) and the second conductive wiring (6).

[0012] The present invention also relates to the wiring sheet, wherein the conductive adhesive sheet (6) contains at least one resin selected from the group consisting of styrene-based resins, acrylic resins, urethane resins, and polyamide resins.

[0013] The present invention also relates to the wiring sheet, wherein the styrene-based resin of the conductive adhesive sheet (6) contains at least one selected from the group consisting of styrene-isoprene copolymer, hydrogenated styrene-isoprene copolymer, styrene-butadiene copolymer, and hydrogenated styrene-butadiene copolymer.

[0014] The present invention also relates to the wiring sheet, wherein the sealing adhesive sheet (7) contains at least one resin selected from the group consisting of styrene-based resins, acrylic resins, urethane resins, and polyamide resins.

[0015] The present invention also relates to the wiring sheet, wherein the sheet-like substrate (1) is made of PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PVC (polyvinyl chloride). [Effects of the Invention]

[0016] The present invention makes it possible to easily bond printed flexible conductive wirings together, or between printed flexible conductive wirings and flexible metal wirings, and achieves a bonded wiring that is strong and reliable for a long period of time, without breaking the conductive joint even when moved during use. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows an example of the structure of the laminate of the present invention. [Figure 2] indicates a method for preparing a sample sheet for the "conductivity test" in the examples. [Figure 3] indicates a method for preparing a sample sheet for "Flexibility Test 1" in the Examples. [Figure 4] indicates the stretch test method in "Flexibility Test 1" in the Examples. [Figure 5] indicates the method of preparing the sample sheets in "Durability Test 2" in the Examples and "Long-term Reliability Test" in Example 4. [Figure 6] indicates the stretch test method in "Flexibility Test 2" in the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0018] The wiring sheet of the present invention comprises a sheet-like substrate (1) printed with first conductive wiring (2) and a film protective layer (3) protecting the first conductive wiring, the first conductive wiring (2) having a first opening exposing the conductive wiring (2), the conductive adhesive sheet (6) disposed in the opening (1), the sealing adhesive sheet disposed around the first opening, the first conductive wiring (2) and the second conductive wiring (4) connected by the conductive adhesive sheet (6), and the first film protective layer (3) and the second conductive wiring around the connection area bonded by the sealing adhesive sheet (7). The conductive adhesive sheet (6) does not require a long waiting time (usually 24 hours) after application and bonding to develop the specified bond strength, as with liquid conductive adhesives, and can ensure stable bonding through simple and short bonding times (Fig. 1).

[0019] <Conductive adhesive sheet (6)> The conductive adhesive sheet used in the present invention is used to bond the first printed conductive wiring (2) and the second conductive wiring (4). The conductive adhesive sheet can be obtained by forming a conductive adhesive composition into a sheet, and the conductive adhesive composition is produced by dispersing conductive particles (hereinafter sometimes referred to as conductive filler) in the adhesive composition. Before being formed into a sheet, the conductive adhesive composition is produced into a sheet through a hot-melt type conductive adhesive composition that does not use a solvent or a solvent-based adhesive composition that uses a solvent.

[0020] The conductive adhesive sheet can be produced by preparing a conductive adhesive composition and then performing a sheeting process. The method for producing the conductive adhesive composition used in this case varies depending on the sheeting process. The sheeting process includes a hot melt method and a printing method. In the hot melt method, a conductive adhesive composition is prepared by dispersing a conductive filler in an adhesive composition without using a solvent, and this conductive adhesive composition is then thermally melted and thermally coated to produce a conductive adhesive sheet. In the printing method, a conductive adhesive composition is dissolved in a solvent, and a conductive filler is mixed and dispersed in the solvent-based adhesive composition, followed by printing and a subsequent solvent drying process to produce a conductive adhesive sheet.

[0021] The conductive filler may be a metal or carbon, preferably silver or carbon. For silver, examples include silver, silver-plated metal, and inorganic or organic particles. For carbon, examples include carbon-based materials such as carbon black, graphite, graphene, carbon nanotubes, fullerenes, graphene oxide, and acetylene black, but are not limited to these. Also preferred are graphite, carbon black, carbon nanotubes, graphene, and graphene oxide, and more preferred are graphite, carbon black, carbon nanotubes, graphene, and graphene oxide. These may be used alone or in combination of two or more. Metals with low resistance, such as silver or silver-plated copper, or inorganic or organic particles, are preferably used.

[0022] The shape of the silver powder or carbon powder that is the conductive filler may be, but is not limited to, flake (scale-like), spherical, needle-like, fibrous, or dendritic. However, spherical or dendritic shapes are preferred, as they allow the conductive particles to be easily oriented in the thickness direction of the coating film. If you want to reduce the amount of conductive filler added to strengthen the adhesive strength, it is preferable to sieve and remove particles of 10 μm or less in the particle size distribution of the conductive powder that do not contribute to the conductivity between the wires to be joined.

[0023] The amount of conductive particles added is preferably 1 to 15% by volume of the resin, because if it is 15% or less, an adhesive strength of 3N or more can be ensured.

[0024] The conductive particles preferably contain conductive particles (a1) that satisfy the following formula (1), and the volume ratio of the conductive particles (a1) to the resin (B) is preferably 1:99 to 15:85. Formula (1) Z≦Y≦3Z (In formula (1), Y represents the particle diameter of the conductive particles (a1), and Z represents the film thickness of the conductive adhesive sheet.) A good conductive bond at the bonded portion can be obtained by including conductive particles having a particle diameter greater than the thickness of the conductive adhesive sheet but less than three times the thickness, at a volume ratio of 1% or more of the total solid content, preferably 3% or more, and even more preferably 5% or more. If the conductive particle diameter exceeds three times the thickness, uneven distribution of the conductive powder can occur during the production of the conductive adhesive sheet, making it impossible to achieve uniform conductivity and resulting in an unstable product.

[0025] The conductive pressure-sensitive adhesive composition may contain a thermoplastic resin as a resin. The thermoplastic resin may include at least one selected from the group consisting of polyurethane-based, acrylonitrile-based, diene-based, acrylic-based, butadiene-based, polyamide-based, polyvinyl butyral-based, olefin-based, isoprene-based, butadiene-based, chloroprene-based, acrylonitrile-based, polyester-based, polyvinyl chloride-based, styrene-based, ethylene-vinyl acetate-based, fluorine-based, silicone-based, and copolymers thereof. However, the thermoplastic resin is not limited to these resins. From the viewpoints of durability, weather resistance, heat resistance, and adhesive strength, the thermoplastic resin preferably includes a styrene-based thermoplastic resin. The thermoplastic resin may be used alone or in combination of two or more types. Furthermore, the thermoplastic resin may be a copolymer formed by linking different monomers. In order to develop holding power, it is also effective to slightly crosslink the thermoplastic resin in the process of forming it into a sheet, to the extent that the adhesiveness is not impaired.

[0026] Styrenic thermoplastic resins, more specifically styrene elastomers, generally have polystyrene blocks and rubber mid-blocks. The polystyrene portions form physical crosslinks (domains) and act as crosslinking points, while the middle rubber blocks provide the product with rubber elasticity. The middle soft segments include polybutadiene (B), polyisoprene (I), and polyolefin elastomers (ethylene-propylene, EP), and depending on the arrangement of the hard segments with polystyrene (S), they are divided into linear and radial types. Among the above-mentioned preferred styrene-based elastomers, the present invention may more specifically include at least one selected from the group consisting of styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEPS), styrene-butylene-styrene block copolymer (SBS), hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-isoprene-styrene block copolymer (SBIS) or hydrogenated styrene-butadiene-isoprene-styrene block copolymer (SEEPS), hydrogenated styrene block copolymer (HSBC), and reinforced rubber segment (ERS), but is not limited to these resins.

[0027] The conductive adhesive composition of the present invention may further contain a tackifier resin, a softener, an antioxidant and other additives as required.

[0028] A tackifying resin is a resin component that improves the adhesiveness of a thermoplastic resin that has poor adhesiveness when blended with the resin.

[0029] Examples of tackifying resins include hydrogenated terpene resins, terpene resins, hydrogenated rosin resins, rosin resins, hydrogenated hydrocarbon resins, epoxy resins, hydrogenated epoxy resins, ketone resins, hydrogenated ketone resins, polyamide resins, hydrogenated polyamide resins, elastomer resins, hydrogenated elastomer resins, phenolic resins, hydrogenated phenolic resins, petroleum resins, hydrogenated petroleum resins, styrene resins, and hydrogenated styrene resins. These tackifying resins can be used alone or in combination. Among these, hydrogenated hydrocarbon resins are preferred from the standpoint of durability. Hydrogenation eliminates conjugated double bonds in the molecular structure, making adhesives containing tackifying resins less susceptible to degradation due to light or heat during long-term adhesion to adherends, allowing them to maintain adhesive strength for more than 10 years.

[0030] The blending ratio of the thermoplastic resin to the tackifier resin is preferably 30 to 100% by weight of the thermoplastic resin and 0 to 70% by weight of the tackifier resin, and more preferably 30 to 50% by weight of the thermoplastic resin and 50 to 70% by weight of the tackifier resin.

[0031] A softener is used as needed to impart adhesiveness. Examples of softeners include petrolatum, mineral oil, vegetable oils, and animal fats. Examples of mineral oils include liquid paraffin, paraffin, paraffin-based mineral oils in which the number of carbon atoms in the paraffin chain accounts for 50% or more of the total number of carbon atoms, naphthenic mineral oils in which the number of carbon atoms in the naphthenic ring accounts for 30 to 40% by weight of the total number of carbon atoms, and aromatic mineral oils in which the number of aromatic carbon atoms accounts for 30% or more by weight of the total number of carbon atoms. Examples of vegetable oils include olive oil, carnauba wax, rice germ oil, corn oil, camellia oil, castor oil, jojoba seed oil, mink oil, and eucalyptus leaf oil. Examples of animal oils include beeswax, squalane, and honey. Other examples include myristic acid, oleic acid, isopropyl myristic acid, zinc myristic acid, octyldodecyl myristate, glycerin triisooctanoate, octyldodecanol, Other examples of softening agents include xyldecanol, diisopropyl adipate, diethyl sebacate, stearic acid, isostearic acid, crotamiton, medium-chain triglyceride, ethylene glycol salicylate, cetyl ethylhexanoate, glycol distearate, cetearyl alcohol, cetanol, cetyl palmitate, ethylhexyl palmitate, isopropyl palmitate, behenyl alcohol, etc. These softening agents can be used alone or in combination.

[0032] The antioxidant is used to prevent oxidation from progressing due to heating during the production of the adhesive composition or over time during use as a conductive adhesive. Examples of the antioxidant include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene)bis[3-(5-t-butyl-4-hydroxy-m-tolyl]propionate, tris(2,4-di-t-butylphenyl)phosphite, and bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite. The phenol-based antioxidant is preferably pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and the phosphorus-based antioxidant is preferably tris(2,4-di-t-butylphenyl)phosphite.

[0033] The conductive adhesive composition may contain various additives as appropriate, provided that the effects of the present invention are not impaired. For example, organic or inorganic fillers may be added to reduce cure shrinkage, reduce thermal expansion, improve dimensional stability, improve elastic modulus, adjust viscosity, improve strength, and improve toughness. Such fillers may be composed of materials such as polymers, ceramics, metal oxides, metal salts, and dyes and pigments. Furthermore, the shape of the fillers is not particularly limited and may be, for example, particulate or fibrous. In addition, in order to improve leveling properties with the substrate, adjust coating properties, and improve adhesion, silane coupling agents, titanate coupling agents, flame retardants, storage stabilizers, antioxidants, metal deactivators, ultraviolet absorbers, thixotropy-imparting agents, leveling agents, antifoaming agents, dispersion stabilizers, fluidity-imparting agents, antifoaming agents, coloring materials, etc. Also, a solvent may be added to improve fluidity.

[0034] <Hot melt conductive adhesive sheet> The conductive adhesive composition used in the hot melt type conductive adhesive sheet can be produced by blending a thermoplastic elastomer resin and a tackifier resin as the main components, and optionally a softener, a tackifier, an antioxidant, and other components, and then uniformly dispersing a conductive filler. The blend is heated and mixed using a hot triple roll mixer, a Banbury mixer, a kneader, a melting pot equipped with a stirrer, or a single-screw or twin-screw extruder, etc., to produce the hot melt type conductive adhesive composition.

[0035] Hot melt conductive adhesive sheets can be produced by heating and melting a solid hot melt conductive adhesive at room temperature using a hot melt gun and applying it directly to the substrate of the wiring sheet, but they can also be produced by coating or printing it in the form of a film on a release film or substrate film using the method described below, and then sandwiching it between release films to produce a conductive adhesive sheet. The coating and printing method of the hot melt type conductive adhesive composition is not particularly limited. Examples of the coating method include slot spray coating, omega coating, spiral coating, controlled seam coating, slot spray coating, dot coating, hot melt applicator coating, hot melt coater coating, blade coating, dip coating, gravure coating, curtain spray coating, bead coating, hot melt A roll coater spin coating method can be used. The thickness of the hot-melt conductive adhesive composition is preferably 10 to 50 μm. If it is too thick, it is difficult to adjust the film thickness and the conductivity will be unstable, and if it is too thin, the adhesive strength will not be sufficient.

[0036] <Solvent-based conductive adhesive sheet> The solvent-based conductive adhesive composition used in the solvent-based conductive adhesive sheet is obtained by dissolving the adhesive composition in a solvent and stirring and mixing the resulting mixture to obtain a uniform solvent-based adhesive composition. There are no particular restrictions on the solvent used, as long as it dissolves the thermoplastic resin and the adhesive composition. Thermoplastic elastomers that cannot be melt-mixed with tackifiers and other components even when heated to 200°C are deemed to be unsuitable for sheeting.

[0037] The solvent-based conductive adhesive composition can be obtained by mixing and stirring a conductive filler and an adhesive composition, and then uniformly mixing and dispersing the conductive filler with the adhesive composition using a three-roll or sand mill disperser.

[0038] The solvent-based conductive adhesive sheet of the present invention can be produced by applying a solvent-based conductive adhesive composition to a wiring sheet substrate or a release sheet by screen printing or the like, removing the solvent at a specified temperature, and then laminating the coating surface with a release sheet. The coating or printing method for the solvent-based conductive adhesive is not particularly limited. Examples of coating methods include inkjet printing, spray printing, roll coating printing, doctor roll printing, doctor blade printing, curtain coating printing, slit coating printing, screen printing, reverse printing, push coating printing, and slit coater printing. The drying conditions are not particularly limited, and examples include hot air drying, infrared drying, and reduced pressure drying. Drying conditions vary depending on the film thickness and the selected organic solvent, but typically involve heating with hot air at about 60 to 130°C. The thickness of the conductive adhesive composition is preferably 10 to 50 μm. If the thickness is too thin, sufficient adhesive strength cannot be obtained, and if the thickness is too thick, the solvent will remain, causing a decrease in the properties of the coating film.

[0039] <Sealing adhesive sheet (7)> The sealing adhesive sheet used in the present invention is adhesively bonded to the periphery of the conductive adhesive sheet (6) that conductively bonds the first printed conductive wiring (2) and the second conductive wiring (4) in a manner that protects the conductive adhesive sheet (6). The sealing adhesive sheet is produced by forming a pressure-sensitive adhesive composition into a sheet.

[0040] A sealing adhesive sheet is produced by preparing an adhesive composition and then performing a sheeting process. The method for producing the adhesive composition varies depending on the sheeting process. The sheeting process includes a hot melt method and a printing method. In the hot melt method, an adhesive composition is prepared without a solvent, and a sealing adhesive sheet is produced by thermally melting and applying the adhesive composition. In the printing method, a pressure-sensitive adhesive composition is dissolved in a solvent, and a sealing adhesive sheet is produced by printing as a solvent-based adhesive composition and then performing a solvent drying process.

[0041] The thermoplastic resin of the pressure-sensitive adhesive composition may include one or more resins selected from the group consisting of polyurethane-based, acrylonitrile-based, diene-based, acrylic-based, butadiene-based, polyamide-based, polyvinyl butyral-based, olefin-based, isoprene-based, butadiene-based, chloroprene-based, acrylonitrile-based, polyester-based, polyvinyl chloride-based, styrene-based, ethylene-vinyl acetate-based, fluorine-based, silicone-based, and copolymers thereof. However, the thermoplastic resin is not limited to these resins. From the viewpoints of durability, weather resistance, heat resistance, and adhesive strength, it is more preferable that the thermoplastic resin include a styrene-based thermoplastic resin. The thermoplastic resin may be used alone or in combination of two or more types. Furthermore, the thermoplastic resin may be a copolymer formed by linking different monomers. In order to develop holding power, it is also effective to slightly crosslink this thermoplastic resin in the process of forming it into a sheet, within a range that does not impair adhesiveness.

[0042] The pressure-sensitive adhesive composition of the present invention comprises a thermoplastic resin, a tackifier resin, a softener, an antioxidant, and other optional components that are used as needed.

[0043] Styrenic thermoplastic resins, more specifically styrene elastomers, generally have a polystyrene block and a rubber intermediate block, with the polystyrene portion forming physical crosslinks (domains) and serving as crosslinking points, and the intermediate rubber block providing rubber elasticity to the product. The intermediate soft segment includes polybutadiene (B), polyisoprene (I) and polyolefin. The styrene elastomers include ethylene-propylene (EP) elastomers, which are divided into linear and radial types depending on the arrangement of the hard segment polystyrene (S). Among the above-mentioned preferred styrene elastomers, the present invention more specifically includes at least one selected from the group consisting of styrene-isoprene-styrene block copolymer (SIS), hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEPS), styrene-butylene-styrene block copolymer (SBS), hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-isoprene-styrene block copolymer (SBIS) or hydrogenated styrene-butadiene-isoprene-styrene block copolymer (SEEPS), hydrogenated styrene block copolymer (HSBC), and reinforced rubber segment (ERS). However, the resins are not limited to these.

[0044] A tackifying resin is a resin component that improves the adhesiveness of a thermoplastic resin that has poor adhesiveness when blended with the resin.

[0045] Examples of tackifying resins include hydrogenated terpene resins, terpene resins, hydrogenated rosin resins, rosin resins, hydrogenated hydrocarbon resins, epoxy resins, hydrogenated epoxy resins, ketone resins, hydrogenated ketone resins, polyamide resins, hydrogenated polyamide resins, elastomer resins, hydrogenated elastomer resins, phenol resins, hydrogenated phenol resins, petroleum resins, hydrogenated petroleum resins, styrene resins, and hydrogenated styrene resins. These tackifying resins can be used alone or in combination of two or more. Among these, hydrogenated hydrocarbon resins are preferred from the viewpoint of durability. Hydrogenation eliminates the conjugated double bonds in the molecular structure, making it difficult for adhesives containing tackifying resins to deteriorate due to light or heat when bonded to adherends over long periods of time, allowing adhesive strength to be maintained for 10 years or more.

[0046] The present invention contains 30 to 100% by weight of the thermoplastic resin and 0 to 70% by weight of a tackifier resin, preferably 30 to 50% by weight of the thermoplastic resin and 50 to 70% by weight of the tackifier resin.

[0047] A softener is used as needed to impart adhesiveness. Examples of softeners include petrolatum, mineral oil, vegetable oils, and animal fats and oils. Examples of mineral oils include liquid paraffin, paraffin, paraffin-based mineral oils in which the number of carbon atoms in the paraffin chain accounts for 50% or more of the total number of carbon atoms, naphthenic mineral oils in which the number of carbon atoms in the naphthenic ring accounts for 30 to 40% by weight of the total number of carbon atoms, and aromatic mineral oils in which the number of aromatic carbon atoms accounts for 30% or more by weight of the total number of carbon atoms. Examples of vegetable oils and oils include olive oil, carnauba wax, rice germ oil, corn oil, camellia oil, castor oil, jojoba seed oil, mink oil, and eucalyptus leaf oil. Examples of animal oils and oils include beeswax, squalane, and honey. Other examples of softeners include myristic acid, oleic acid, isopropyl myristicate, zinc myristicate, octyldodecyl myristate, glycerin triisooctanoate, octyldodecanol, hexyldecanol, diisopropyl adipate, diethyl sebacate, stearic acid, isostearic acid, crotamiton, medium-chain triglyceride, ethylene glycol salicylate, cetyl ethylhexanoate, glycol distearate, cetearyl alcohol, cetanol, cetyl palmitate, ethylhexyl palmitate, isopropyl palmitate, and behenyl alcohol. These softeners may be used alone or in combination.

[0048] The antioxidant is used to prevent oxidation from progressing due to heating during the production of the adhesive composition or over time during use as a conductive adhesive. Examples of the antioxidant include pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, diethyl[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]phosphonate, 4,6-bis(octylthiomethyl)-o-cresol, ethylene bis(oxyethylene)bis[3-(5-t-butyl-4-hydroxy-m-tolyl]propionate, tris(2,4-di-t-butylphenyl)phosphite, and bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite. The phenol-based antioxidant is preferably pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and the phosphorus-based antioxidant is preferably tris(2,4-di-t-butylphenyl)phosphite.

[0049] The pressure-sensitive adhesive composition of the present invention can also be appropriately blended with various additives as long as the effects of the present invention are not impaired. For example, organic or inorganic fillers can be blended to reduce cure shrinkage, reduce thermal expansion, improve dimensional stability, improve elastic modulus, adjust viscosity, improve strength, and improve toughness. Such fillers may be composed of materials such as polymers, ceramics, metals, metal oxides, metal salts, and dyes and pigments. Their shape is not particularly limited and may be, for example, particulate or fibrous. Furthermore, silane coupling agents, titanate coupling agents, flame retardants, storage stabilizers, antioxidants, metal deactivators, UV absorbers, thixotropy-imparting agents, leveling agents, antifoaming agents, dispersion stabilizers, fluidity-imparting agents, antifoaming agents, and colorants can also be added to improve fluidity and adjust the leveling and coating properties with the substrate. A solvent may also be added to improve fluidity.

[0050] <Hot melt sealing adhesive sheet> The adhesive composition used for the hot-melt sealing adhesive sheet contains the above-mentioned thermoplastic elastomer resin and tackifier resin as main components, and further contains, as necessary, a softener, a tackifier, an antioxidant and other components, and then the hot-melt sealing adhesive is produced using a hot triple roll, a Banbury mixer, a kneader, a melting pot equipped with a stirrer, or a single-screw or twin-screw extruder.

[0051] A hot-melt sealing adhesive sheet can be produced by heating and melting a solid hot-melt sealing adhesive at room temperature using a hot-melt gun and applying it directly to the substrate of a wiring sheet. Alternatively, the hot-melt sealing adhesive can be coated or printed as a film on a release film or substrate film by the method described below, and then sandwiched between release films to produce a sealing adhesive sheet. The coating or printing method for the hot-melt sealing adhesive composition is not particularly limited. Examples of coating methods include slot spray coating, omega coating, spiral coating, control seam coating, slot spray coating, dot coating, hot-melt applicator coating, hot-melt coater coating, blade coating, dip coating, gravure coating, curtain spray coating, bead coating, and hot-melt roll coater spin coating. The thickness of the hot-melt conductive adhesive composition is preferably 10 to 100 μm.

[0052] <Solvent-based sealing adhesive sheet> The solvent-based adhesive used in the solvent-based sealing adhesive sheet is prepared by dissolving the adhesive composition in a solvent and stirring and mixing the resulting mixture to obtain a uniform solvent-based adhesive composition. The solvent used is not particularly limited as long as it dissolves the thermoplastic resin and the adhesive composition. Thermoplastic elastomers that cannot be melt-mixed with tackifiers and other components even when heated to 200°C are deemed to be unsuitable for sheeting.

[0053] The solvent-type sealing adhesive may contain inorganic fillers, organic thixotropic agents, antifoaming agents, etc. to provide printability.

[0054] As the inorganic filler, silicic acid, talc, precipitated barium sulfate, etc. are used as they exhibit appropriate rheological properties in the printing process, but there is no limitation to these, and any inorganic filler that can form a stable and uniform coating film by screen printing or the like can be used.

[0055] For the solvent-based pressure-sensitive adhesive composition, the components are mixed and stirred, and then the blended components are uniformly mixed and dispersed as a pressure-sensitive adhesive composition using a three-roll or sand mill disperser.

[0056] The solvent-based sealing adhesive sheet of the present invention can be produced as a sealing adhesive sheet by applying the solvent-based sealing adhesive onto the substrate of a wiring sheet or onto a release sheet by screen printing or the like, removing the solvent at a specified temperature, and then laminating the coating surface with a release sheet. The method for applying or printing the solvent-based sealing adhesive is not particularly limited. Examples of the application method include inkjet printing, spray printing, roll coating printing, doctor roll printing, doctor blade printing, curtain coating printing, slit coating printing, screen printing, reverse printing, push coating printing, and slit coater printing. The drying conditions are particularly There are no limitations on the drying method, and examples include hot air drying, infrared drying, and reduced pressure methods. Drying conditions vary depending on the film thickness and the selected organic solvent, but hot air heating at about 60 to 130°C is usually used. The thickness of the sealing adhesive composition is preferably 10 to 100 μm. If it is too thin, adhesive strength cannot be obtained, and if it is too thick, solvent will remain, causing a decrease in the coating film properties.

[0057] <Sheet-shaped substrate (1)> The wiring sheet of the present invention is suitable for wearable sensing wiring for acquiring biosignals, which requires a flexible wiring substrate. It can also be used for measuring electrocardiograms for periods ranging from several days to one month. Furthermore, for applications where the sheet can be easily worn and discarded after a few measurements, it is necessary to design various components inexpensively.

[0058] The substrate is selected from resin sheets. Examples include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate resins, polyarylate resins, acrylic resins, polyphenylene sulfide resins, polystyrene resins, vinyl resins, vinyl chloride resins, polyimide resins, epoxy resins, and polyolefin resins such as polyethylene, polypropylene, and polynorbornene. In some cases, high-temperature processing that deforms the substrate due to heat is required. Therefore, heat-resistant substrates such as polyimide (PI) sheets, polynaphthalene sheets, propylene sheets, and silicone resin sheets, or substrates with improved heat resistance due to filler filling, can also be used. However, for low-cost applications, PET, PEN, and PVC are preferred. In such cases, low-temperature bonding at temperatures below 130°C is required.

[0059] <Conductive wiring (2)> The first conductive wiring (2) used in the present invention is prepared by printing a conductive circuit on the sheet-like substrate (1) using conductive ink made of metal or carbon.

[0060] (Conductive ink) The conductive material for the conductive ink is not particularly limited as long as it is a material that is conductive, but examples include carbon materials such as graphite, carbon black, conductive carbon fibers (carbon nanotubes, carbon nanofibers, carbon fibers), and fullerenes, as well as metal powders such as gold, silver, copper, aluminum, nickel, and tin, which can be used alone or in combination of two or more types.

[0061] The binder resin for dispersing the conductivity-imparting agent in the conductive ink may include one or more resins selected from the group consisting of polyurethane, polyamide, acrylonitrile, acrylic, butadiene, polyvinyl butyral, polyolefin, polyester, polystyrene, EVA, fluorine-based (e.g., polyvinylidene fluoride), and silicone-based resins. However, the binder resin is not limited to these resins. One type of binder resin may be used alone, or two or more types may be used in combination. In particular, it is preferable that the binder resin include at least one resin selected from urethane resin, polyester resin, polyamide resin, acrylic resin, fluorine-based resin, epoxy resin, and styrene-based elastomer. The binder resin can also be a curable resin that undergoes a curing (crosslinking) reaction after the binder resin is applied to a substrate. That is, the binder resin can be selected to be self-curing or combined with a crosslinking agent, and the conductive composition can be printed or coated on a substrate and then cured (crosslinked).

[0062] (Conductive ink manufacturing method) Conductive ink can be manufactured by premixing the above-mentioned conductive material with a binder resin, and optionally other ingredients such as inorganic fillers, flow adjusters, solvents, and antifoaming agents, followed by a dispersion process. There are no particular restrictions on the dispersion method, but specifically, the components are mixed uniformly using a three-roll mill, sand mill, etc., and powder ingredients such as the conductive material and inorganic filler are pulverized to a certain particle size or less, which gives the ink printability in the printing process described below and drying properties, while also allowing it to exhibit performance as conductive wiring after printing.

[0063] (Conductive ink printing method) The method for applying the conductive composition onto the sheet-like substrate is not particularly limited, and any known method can be used.

[0064] Specific examples of the coating method include die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, and electrostatic painting. Drying methods that can be used include, but are not limited to, standing to dry, blowing dryers, hot air dryers, infrared heaters, and far-infrared heaters. After coating, the coating may be rolled using a lithographic press or a calender roll.

[0065] <Film protective layer (3)> The wiring sheet, in which the first conductive wiring (2) is printed on the aforementioned sheet-like substrate, is covered with an insulating film, which serves as a protective layer for the first conductive wiring and prevents the conductive wiring from coming into direct contact with the outside air. The substrate for the film protective layer is a resin sheet. Examples of resin sheets include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonate resins, polyarylate resins, acrylic resins, polyphenylene sulfide resins, polystyrene resins, vinyl resins, vinyl chloride resins, polyimide resins, epoxy resins, and polyolefin resins such as polyethylene, polypropylene, and polynorbornene. In addition, because high-temperature processing processes that cause thermal deformation of the substrate may be required, highly heat-resistant substrates such as polyimide (PI) sheets, polynaphthalene sheets, propylene sheets, and silicone resin sheets, or substrates with improved heat resistance due to filler filling, can also be used. However, for low-cost applications, PET, PEN, and PVC are preferred. In such cases, low-temperature bonding at temperatures below 130°C is required.

[0066] The film protective layer has an adhesive or pressure-sensitive adhesive layer formed on one side and is laminated onto the sheet-like substrate (1) on which the first conductive wiring (2) is formed. The adhesive may be an acrylic or urethane adhesive. The adhesive may be an olefin-, rubber-, or polyamide-based hot melt adhesive for extrusion lamination, or a polyester-, acrylic-, or epoxy-based adhesive for dry lamination.

[0067] <Conductive wiring (4)> The second conductive wiring (4) used in the present invention may be used in combination with the above-mentioned conductive wiring sheet (1), or may be a metal wiring sheet in which a circuit of copper or aluminum is formed on a sheet-like substrate such as PET or PI by metal etching, a metal wiring sheet in which a metal foil with one side adhesive is adhesively bonded to a sheet-like substrate, or a wiring cord in which a metal wire such as copper or aluminum is coated with insulating resin.

[0068] <Bonding of conductive adhesives and sealing adhesive sheets> In a first printed conductive wiring (2) prepared by laminating a first conductive wiring printed on a sheet-like substrate (1) and a film protective layer (3) that protects the first conductive wiring, a conductive adhesive sheet (6) is placed in an opening that exposes the conductive wiring. Next, a sealing adhesive sheet (7) is placed around the periphery of the first opening, and the wiring portion of the second conductive wiring (4) is pressed and, if necessary, thermocompressed, whereby the first printed conductive wiring and the second conductive wiring are conductively bonded, and at the same time, the periphery is sealed and bonded by the sealing adhesive sheet.

[0069] If the conductive adhesive sheet and conductive wiring can achieve an adhesive strength of 3N or more by pressure bonding alone, thermocompression bonding is not required. There are no particular restrictions on the bonding between the sealing adhesive sheet and the substrate, but if an adhesive strength of 10N can be achieved by pressure bonding alone at room temperature, thermocompression bonding is not required. If the sealing adhesive sheet is weakly adhesive and the adhesive strength by pressure bonding is less than 10N, it can be produced by bonding the sealing material and the adherend using a hot iron or induction heating device.

[0070] The present invention can also be used with film substrates that are not heat-resistant, such as PET (polyethylene terephthalate) and PVC (polyvinyl chloride). The heat resistance temperature of these films is 130°C or less, and the film shrinks at temperatures higher than that. For this reason, the printing temperature of printed wiring and the direct heating temperature of the conductive adhesive sheet should be 130°C or less, preferably 100°C or less. [Example]

[0071] The present invention will be described in more detail below with reference to examples, but these examples are merely one embodiment of the present invention and the present invention is not limited to these examples. In the tables, "parts" and "%" represent "parts by weight" and "% by weight", respectively.

[0072] <Conductive adhesive sheet manufacturing example> [Production Examples 1 to 5: Conductive Adhesive Sheets 1 to 5] Toyochem's hot melt adhesive Toyomelt P804G was dissolved in Solvesso 100 solvent to create a 50% varnish, designated Resin Varnish 1. Six parts of Fukuda Metal Powder Co., Ltd.'s silver-plated conductive powder FCC115 (as conductive powder 1) were added to 10 parts of Resin Varnish 1, and after gentle stirring, the mixture was dispersed for three minutes using a planetary stirrer to create a conductive adhesive composition. This composition was applied to a release PET film using various applicators and dried at 130°C for 30 minutes to create Conductive Adhesive Sheets 1 to 5 with the film thicknesses listed in Table 1.

[0073] [Manufacturing Examples 6 to 9] Conductive adhesive sheets with different thicknesses were prepared in the same manner as in Production Example 1, except that the amount of conductive powder 1 added was changed to 7.5 parts. Sheets 6 to 9 were created.

[0074] [Manufacturing Examples 10 to 14: Conductive Adhesive Sheets 10 to 14] Conductive powder 1 was filtered through a 650 stainless steel mesh with a mesh size of 20 μm, and the residual components were collected. This powder was designated as conductive powder 2. The powder was prepared in the same manner as for conductive adhesive sheet 1, and then coated and dried to prepare conductive adhesive sheets 10 to 14 with different film thicknesses.

[0075] [Manufacturing Examples 15 to 19: Conductive Adhesive Sheets 15 to 19] Conductive powder 1 was filtered through a 400 stainless steel mesh with a mesh size of 30 μm, and the residual components were collected. Guidance This powder was designated as Electrical Powder 3. A conductive adhesive composition was prepared from this powder in the same manner as in the case of the conductive adhesive sheet 1, and then coated and dried to prepare Conductive Adhesive Sheets 15 to 19 with different film thicknesses.

[0076] [Manufacturing Examples 20-21: Conductive Adhesive Sheets 20-21] Toyochem's hot melt adhesive Toyomelt P804G was dissolved in Solvesso 100 solvent to create a 50% varnish, designated Resin Varnish 1. Six parts of Dowa Electronics' silver-plated conductive powder AOP-RCE-43 (as Conductive Powder 4) were added to 10 parts of Resin Varnish 1, and after light stirring, the mixture was dispersed for three minutes using a planetary stirrer to create a conductive adhesive composition. This composition was applied to release PET film using various applicators and dried at 130°C for 30 minutes to create Conductive Adhesive Sheets 20-21 with different film thicknesses.

[0077] [Manufacturing Examples 22 to 23: Conductive Adhesive Sheets 22 to 23] Conductive powder 4 was filtered through a 650 stainless steel mesh with 20 μm openings, and the residual components were collected to obtain conductive powder 5. A conductive adhesive composition was prepared from the powder in the same manner as for conductive adhesive sheet 1, and then coated and dried in the same manner as for conductive adhesive sheet 1 to obtain conductive adhesive sheets 22 to 23 with different film thicknesses.

[0078] The manufactured conductive adhesive sheets are shown in Table 1. The volume % of conductive powder in the table is shown as a resin specific gravity of 1.2 and a conductor specific gravity of 10.5 relative to the weight added amount. Additionally, the volume % of conductive powder greater than the coating thickness but less than three times the coating thickness is shown as the volume % of conductive powder greater than the thickness of the manufactured sheet relative to the total conductive powder volume, based on the particle size distribution of each type of conductive powder.

[0079] [Table 1]

[0080] Manufacturing example of sealing adhesive sheet [Manufacturing Example 24] A stainless steel beaker equipped with a stirrer was charged with 40 parts of SEBS G1726 manufactured by Kraton Corporation as a thermoplastic resin, 50 parts of Alcon P-100 manufactured by Arakawa Chemical Industries as a tackifier, 10 parts of Diana Process Oil N90 manufactured by Idemitsu Kosan Co., Ltd. as a softener, and optionally an antioxidant, and heated to a temperature of 150°C to melt. The mixture was then stirred to obtain a uniform molten solution. The uniformly dispersed hot melt adhesive composition 1 was sandwiched between release films and heated to 100°C and 100 kgf / cm using a Tester Sangyo tabletop test press. 2 The mixture was then heat-pressed at 0°C for 30 seconds to process it into a sheet having a thickness of 50 to 100 μm, which was used as a sealing adhesive sheet 1.

[0081] [Manufacturing Example 25] A sealing material sheet was prepared in the same manner as above, except that the plastic resin was changed to ERS G1642 manufactured by Kraton Corporation, and a sealing adhesive sheet 2 was prepared.

[0082] [Table 2]

[0083] [Example] Conductivity Test [Create a sample sheet] Two printed conductive traces (2) measuring 10 mm wide, 10 mm apart, and 100 mm long were printed on a 50 μm thick, 50 x 150 mm PET film (Luminar X10S, manufactured by Toray Industries) sheet substrate, and dried at 130°C for 30 minutes. A conductive adhesive sheet cut to a width of 40 mm and a length of 20 mm from Production Example 1 was attached across the two printed traces, and a printed trace sheet (4) with the same conductor size was attached on top of it, pressure-bonded with finger pressure, and left to stand at room temperature for at least one hour to create sample sheet 1 (Figure 2).

[0084] Sample sheets 2 to 23 were prepared in the same manner as sample sheet 1 using the conductive adhesive sheets of Production Examples 2 to 23.

[0085] In the sample sheets 1 to 23, the conductivity between the first printed conductive trace (2) and the second printed conductive trace (4) was measured as a vertical conduction test. As a result of the measurement, a resistance value of 20Ω or less was marked as ◯, a resistance value of 20Ω or more but 100Ω or less was marked as △, and a resistance value that was unstable or no continuity was observed was marked as ×. In addition, the conductivity between two printed conductive wires (2) was measured as a lateral conduction test. In this case, no conduction was marked with ◯, and conduction was marked with ×.

[0086] 2. Peel strength test [Create a sample sheet] Carbon ink was printed to a width of 25 mm on a sheet substrate of 50 μm thick PET film (Luminar X10S manufactured by Toray), dried, and cut to a size of 25 mm × 150 mm to prepare a peel test sheet. A 25 mm × 100 mm conductive adhesive sheet of Production Example 1 was attached to this peel test sheet, and another peel test sheet was attached to it to prepare adhesive sample sheet 1.

[0087] For Production Examples 2 to 23, adhesive sample sheets 2 to 23 were prepared in the same manner as adhesive sample sheet 1.

[0088] The 90° peel strength of each of the adhesive sample sheets 1 to 23 was measured using a tensile tester AGS-X manufactured by Shimadzu Corporation. Peel strength of 3N / 25mm or more was evaluated as ◯, 1 to 3N as △, and 1N or less as ×.

[0089] The results are shown in Table 3.

[0090] [Table 3]

[0091] The results in Table 3 show that peel strength decreases when the volume percentage of conductive particles in the solid content is 15% or more. Furthermore, when conductive particles with a particle size greater than the coating thickness are present in a solid content volume ratio of 1 to 15%, vertical conductivity is achieved between the bonded conductors, while there is no horizontal conductivity between adjacent wiring, maintaining insulation, making this material effective for joining horizontal wiring all at once during construction. When the volume percentage of conductive particles greater than the coating thickness is less than 1%, stable vertical conductivity is not achieved.

[0092] 3. Flexural test 1 [Create a print sample sheet] A 10mm wide, 100mm long carbon wiring was printed on a 125μm thick, 25mm x 100mm PET film (Toray Luminar X10S) and dried at 130°C for 30 minutes. A 125μm thick PET film (Toray Luminar X10S) protective layer with an acrylic adhesive was laminated on top, leaving a 10mm gap on both sides from the edge, to create a printed carbon wiring sample sheet for bending tests. This wiring sheet, when used as the first printed conductive wiring sheet, was designated Printed Sample Sheet 1 (Figure 3(a)), and when used as the second conductive wiring sheet, was designated Printed Sample Sheet 2 (Figure 3(b)).

[0093] [Creating a copper sample sheet] A 100mm long, 10mm wide copper foil tape manufactured by Teraoka Seisakusho was attached to a sheet substrate of 125mm thick, 25mm x 100mm PET film (Luminar X10S manufactured by Toray Industries, Ltd.), and a film protective layer of 125μm PET film (Luminar X10S manufactured by Toray Industries, Ltd.) processed with an acrylic adhesive was laminated on top, leaving a space of 5mm on both sides from the edge, to create copper sample sheet 1 (Figure 3(c)) as a second conductive wiring sheet.

[0094] [Conductive adhesive sheet] The conductive adhesive sheet having a thickness of 10 μm produced in Production Example 1 was designated as conductive adhesive sheet 1. The conductive adhesive sheet having a thickness of 32 μm produced in Production Example 12 was used as conductive adhesive sheet 2. The conductive adhesive sheet having a thickness of 50 μm produced in Production Example 19 was used as conductive adhesive sheet 3.

[0095] [Conductive adhesive] Conductive adhesive 1 was prepared by mixing equal amounts of Agent A and Agent B of Conductive Epoxy CW2460 manufactured by Chemtronics. 20 parts of Nanomelt XF301S manufactured by Fukuda Metal Powder Co., Ltd. was added to 10 parts of epoxy resin JER827 manufactured by Mitsubishi Chemical Corporation and stirred, and then dispersed using a three-roll mill to form the main component of conductive adhesive 2. 20 parts of Nanomelt XF301S was added to 10 parts of Mitsubishi Chemical's epoxy curing agent YN100 and stirred lightly, and then dispersed using a three-roll mill to form a curing agent for conductive adhesive 2. Conductive adhesive 2 was prepared by mixing the base agent and curing agent in a ratio of 100:45.

[0096] [Creating test samples] The conductive adhesive sheet 1 of Example 1 was cut to a size of 10 mm × 10 mm and attached to a 10 mm × 10 mm area where the carbon wiring of the first conductive wiring printed sample sheet 1 (FIG. 3) (a) was exposed. The conductive portion of the copper sample sheet 1 (FIG. 3) (c), which is the second conductive wiring, was attached to that area and joined by finger pressure to prepare a test sample for bending test 1 of Example 24.

[0097] Test samples of Examples 25 and 26 were prepared in the same manner except that the conductive adhesive sheets were changed to 2 and 3.

[0098] Test samples of Examples 27 to 29 were prepared in the same manner as in Examples 24 to 26, except that the second conductive wiring of Example 1 was replaced with printed sample sheet 2 (FIG. 3)(b).

[0099] For the purpose of the comparative test, conductive adhesive 1 was applied to a 10 mm x 10 mm area where the carbon wiring of the printed sample sheet 1 (Figure 3) (a), which is the first conductive wiring, was exposed, and a copper sample sheet 1 (Figure 3) (c), which is the second conductive wiring, was attached, and the resultant was cured at room temperature for 24 hours to obtain a test sample for bending test 1 of Comparative Example 1.

[0100] A test sample for bending test 1 of Comparative Example 2 was prepared in the same manner as in Comparative Example 1, except that conductive adhesive 1 was changed to conductive adhesive 2.

[0101] Samples for bending test 1 in comparative examples 3 and 4 were prepared in the same manner, except that the copper sample sheet 1 (Figure 3) (c) of the second conductive wiring in comparative examples 1 and 2 was replaced with printed sample sheet 2 (Figure 3) (b).

[0102] The sample sheets of Examples 24 to 29 and Comparative Examples 1 to 4 were subjected to a bending test using a multi-function small desktop durability tester DLDM111LH manufactured by Yuasa System Co., Ltd.

[0103] Specifically, the resistance values ​​at both ends of the wiring sheet and between the ends of the first conductive wiring and the second conductive wiring were measured, and then the measurement sample was bent into a U-shape and set in a durability testing machine manufactured by Yuasa System Equipment, and an expansion / contraction test was carried out at intervals of 70 mm to 20 mm and 30 rpm. After the test, the presence or absence of fracture in the joint was evaluated based on the resistance value between the wiring (Figure 4). ◎: Resistance fluctuation is less than ±10% after 1000 stretches ○: Resistance fluctuation is less than ±10% when stretching 100 to less than 1000 times ×: Breakage or resistance value of ±10% or more after less than 100 stretches

[0104] The results are shown in Table 4.

[0105] [Table 4]

[0106] From the results in Table 4, as shown in the comparative example, when a conductive adhesive is used for wiring joints using printed wiring, cohesive failure of the wiring occurs and bending resistance cannot be imparted, but by using a conductive adhesive sheet, high bending resistance is achieved.

[0107] 4. Flexural test 2 Based on the results of the bending test 1, the bending resistance of the conductive adhesive material provided with a sealing layer made of a sealing adhesive sheet around the conductive adhesive material was confirmed in a bending test 2. [Create a print sample sheet] A 10mm x 100mm conductive trace was printed with conductive carbon ink on a 125μm thick, 25mm x 100mm PET film (Toray Luminar X10S) sheet substrate and dried at 130°C for 30 minutes. A 10mm x 10mm opening was made in the 125μm PET film (Toray Luminar X10S) with acrylic adhesive, 10mm from the edge. The opening was then aligned to expose the carbon conductive traces on the PET film. A film protective layer was laminated on the opposite side of the sheet, exposing the carbon traces for resistance measurement. This trace sheet, used as the first conductive trace sheet, was designated Print Sample Sheet 3, and used as the second conductive trace sheet, designated Print Sample Sheet 4 (Figure 5).

[0108] [Creating test samples] The conductive adhesive sheet 1 produced in Production Example 1 was cut to a size of 10 mm × 10 mm and attached to the 10 mm × 10 mm location where the carbon wiring was exposed on the printed sample sheet 3. A 30 mm × 30 mm SEBS G1726-based adhesive sealing sheet 1 from Production Example 24 with a 10 mm × 10 mm opening at the surrounding conductive joint was attached, and the printed sample sheet 4 was placed on top of it so that the openings overlapped and joined by finger pressure to prepare a sample sheet for bending test 2 in Example 30.

[0109] Sample sheets for bending test 2 of Examples 31 and 32 were prepared in the same manner except that conductive adhesive sheet 1 was replaced with conductive adhesive sheets 2 and 3.

[0110] Sample sheets for bending test 2 of Examples 39 to 41 were prepared in the same manner as above, except that the adhesive sealing sheets of Examples 30 to 32 were changed to ERS G1642-based adhesive sealing sheet 2 of Production Example 25.

[0111] For the purpose of the comparative test, conductive adhesive 1 was applied to a 10 mm x 10 mm area where the carbon wiring of the printed sample sheet was exposed, and adhesive sealing sheet 1 was attached to a 30 mm x 30 mm area with a 10 mm x 10 mm opening around the surrounding conductive joint. A printed sample sheet 4, which was a second conductive wiring, was then attached, and the sealing adhesive sheet was joined with finger pressure. After that, the conductive adhesive 1 was cured at room temperature for 24 hours to produce a sample for bending test 2 of Comparative Example 5.

[0112] A sample for bending test 2 of Comparative Example 6 was prepared in the same manner as in Comparative Example 5, except that conductive adhesive 1 was changed to conductive adhesive 2.

[0113] Samples for bending test 2 in Comparative Examples 7 and 8 were prepared in the same manner as in Comparative Examples 5 and 6, except that adhesive sealing sheet 1 was changed to adhesive sealing sheet 2.

[0114] Bending test 2 In Examples 30 to 35 and Comparative Examples 5 to 8, a bending test was carried out using a multi-function small desktop durability tester DLDM111LH manufactured by Yuasa System Co., Ltd.

[0115] Specifically, the resistance values ​​at both ends of the wiring sheet and between the ends of the first conductive wiring and the second conductive wiring were measured, and then the measurement sample was bent into a U-shape and set in a durability testing machine manufactured by Yuasa System Equipment, and an expansion / contraction test was carried out at intervals of 70 mm to 20 mm and 30 rpm. After the test, the presence or absence of fracture at the joint was evaluated based on the resistance value between the wiring (Figure 6). 〇: Resistance fluctuation is less than ±10% after 10,000 stretches △: Resistance fluctuation is less than ±10% after 1,000 to 10,000 stretches ×: Breakage or resistance value of ±10% or more after less than 1000 stretches

[0116] The results are shown in Table 5.

[0117] [Table 5]

[0118] From the results in Table 5, it can be seen that even when reinforced with a sealing adhesive sheet, the wiring joined with a conductive adhesive sheet gave better results in the bending test than when joined with a conductive adhesive.

[0119] 5. Long-term reliability test A long-term reliability test was carried out on the samples of Examples 30 to 35 and Comparative Examples 5 to 8 in the bending test 2 according to the following procedure (FIG. 5).

[0120] The resistance between the conductive wiring at both ends of the test sample, printed sample sheet 3 and printed sample sheet 4, was measured as the initial resistance, and the test sample was left in an environment of 60°C and 90% RH for 1000 hours in an ESPEC CORP MODEL PL-1KPH environmental tester, after which the resistance at both ends was measured again. The resistance was then measured again after 2000 hours and 3000 hours. The test results were obtained in the following manner. ○: No change in the appearance of the encapsulant or the conductive material covered with the encapsulant, and no change in resistance value ±10% or less of initial resistance ×: Changes in appearance such as flow of the sealing material, corrosion of the conductive material coated with the sealing material, etc. are observed, or the resistance value fluctuation exceeds ±10% of the initial resistance.

[0121] The results are shown in Table 6.

[0122] [Table 6]

[0123] The results in Table 6 show that bonding using a conductive adhesive sheet shows stable resistance to high temperatures and constant humidity. In the case of adhesive bonding, it is stable up to 1000 hours, but once it exceeds 1000 hours, the resistance value fluctuates and stability cannot be ensured.

Claims

1. A wiring sheet having a sheet-like substrate (1), a first printed conductive wiring (2) arranged on the sheet-like substrate, a film protective layer (3) that protects the first printed conductive wiring, and a second conductive wiring (4) connected to the first printed conductive wiring (2), wherein the first printed conductive wiring (2) and the second conductive wiring (4) are connected by a conductive adhesive sheet (6) containing metal or carbon, and the connected portion is sealed with a sealing adhesive sheet (7); A wiring sheet characterized in that the adhesive strength of the conductive adhesive sheet (6) is 3 N / 25 mm or more between the first printed conductive wiring sheet (2) and the second conductive wiring (6).

2. 2. The wiring sheet according to claim 1, wherein the conductive adhesive sheet (6) has a film thickness of 10 to 50 μm.

3. 3. The wiring sheet according to claim 1 or 2, wherein the conductive adhesive sheet (6) contains conductive particles (A) and a resin (B), the conductive particles (A) contain silver or carbon, the conductive particles (A) contain conductive particles (a1) that satisfy the following formula (1), and the volume ratio of the conductive particles (a1) to the resin (B) is 1:99 to 15:

85. Formula (1) Z≦Y≦3Z (In formula (1), Y represents the particle diameter of the conductive particles (a1), and Z represents the film thickness of the conductive adhesive sheet.)

4. The wiring sheet according to any one of claims 1 to 3, wherein the conductive adhesive sheet (6) contains at least one resin selected from the group consisting of styrene-based resins, acrylic resins, urethane resins, and polyamide resins.

5. The wiring sheet according to claim 4, wherein the conductive adhesive sheet (6) contains at least one selected from the group consisting of styrene-isoprene copolymer, hydrogenated styrene-isoprene copolymer, styrene-butadiene copolymer, and hydrogenated styrene-butadiene copolymer.

6. The wiring sheet according to any one of claims 1 to 5, wherein the sealing adhesive sheet (7) contains at least one resin selected from the group consisting of styrene-based resins, acrylic resins, urethane resins, and polyamide resins.

7. The wiring sheet according to any one of claims 1 to 6, wherein the sheet-like substrate (1) comprises PET (polyethylene terephthalate), PEN (polyethylene naphthalate), or PVC (polyvinyl chloride).

Images