Stretchable circuit substrate and stretchable device

Abstract

This stretchable circuit substrate (100) comprises: a stretchable substrate (10); a non-stretchable part (20) connected to a region of the outer peripheral part of a first surface (10aa) of the stretchable substrate (10); a first electrical wiring (30A) arranged on the first surface (10aa) of the stretchable substrate (10); and a second electrical wiring (30B) arranged on the non-stretchable part, wherein the first electrical wiring (30A) and the second electrical wiring (30B) are connected, and the stretchable substrate (10) and the non-stretchable part (20) are connected by a conductive adhesive (40) containing a stretchable resin.

Description

TECHNICAL FIELD

[0001] The present invention relates to a stretchable circuit substrate and a stretchable device.

[0002] Priority is claimed to Japanese Application No. 2022-212027, filed on December 28, 2022, the contents of which are incorporated herein by reference. BACKGROUND ART

[0003] In recent years, along with the development of flexible sensors, wearable devices capable of managing physical condition have attracted attention. Wearable devices are expected to have a wide range of applications in the fields of sports science and healthcare, where they are designed to measure and monitor specific body parts, such as those attached directly to the skin or those incorporated into clothing. Since human skin is repeatedly stretched and contracted daily, it is desirable for a stretchable device to be stretchable depending on the object on which it is worn if strain-free wearability of the wearable device is desired.Furthermore, it is desirable for the wearable device to exhibit a certain level or higher of strength against stresses generated during its bending and rolling during handling or human movement. Devices with such a property are referred to in this specification as stretchable devices, although their use is not limited to wearable devices.

[0004] Patent Document 1 describes a wiring board comprising: a substrate including a first substrate having stretchability and a second substrate located outside a side surface of the first substrate and having a larger modulus of elasticity than that of the first substrate; and a conductor including wiring located on one side of the first surface of the first substrate. Further, electronic components connected to the conductor and arranged on the first surface side of the first substrate are described.

[0005] Stretchable devices are expected to incorporate electrodes, wiring, devices, electronic components, thin-film sensors, and the like into stretchable elements, and they must maintain their quality even in a usage environment where stretching and contraction occur repeatedly. However, it is difficult to realize such stretchable devices with polyimide films used in conventional thin-film resin boards. For this reason, resins compatible with stretchability, such as urethane resins, silicone resins, acrylic resins, epoxy resins, polycarbonates, polystyrene, and polyolefins, are expected to be used as the main constituent materials for elements and electrodes in stretchable devices.Among them, it is believed that a stretchable film which is a cured product of a composition containing a (meth)acrylate compound having a siloxane bond, a (meth)acrylate compound other than the (meth)acrylate compound having a urethane bond, and an organic solvent having a boiling point in the range of 115°C to 200°C at atmospheric pressure, and in which the (meth)acrylate compound having a siloxane bond is unevenly distributed on the surface of the film, would have excellent stretchability and strength comparable to those of polyurethanes, and the surface of the film would have excellent water-repellent properties comparable to those of silicones (see Patent Document 2). Citation listPatent document Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2021-57507 Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2017-206626 SUMMARY OF THE INVENTIONTechnical Problem

[0006] In the wiring board of Patent Document 1, the conductor including the wiring is formed on the first substrate having extensibility, and when the electronic components are arranged on the wiring board as described in Patent Document 1, the electronic components connected to the conductor are also arranged on the first substrate. In a configuration in which an adhesive seal that can be adhered is provided on the back of this wiring board, the electronic components mounted on the first substrate having extensibility are likely to be damaged when peeled off, and there is a particularly high risk of damage to the electronic components when the attachment and peeling are repeated.

[0007] In the case of the resin sheet (resin film) mainly made of a cured product of a resin composition as described in Patent Document 2, if the curing reaction is not uniform, there is a problem that variations in the composition and degree of curing may occur in the resin sheet, resulting in the film not having the desired properties of stretchability, strength, and resistance to aging deterioration. Furthermore, to realize stretchable devices, wiring with high conductivity and stretchability, as well as a small change in conductivity upon stretching and contraction, is desired.

[0008] The present invention provides a stretchable circuit substrate and a stretchable device in which the risk of damage to mounted electronic components and the like is reduced when attachment and detachment are repeated.

[0009] Furthermore, the present invention provides a stretchable circuit substrate and a stretchable device equipped with electrical wiring that is highly conductive and highly stretchable, and that exhibits minimal change in conductivity when repeated attachment and detachment. Solution to the Problem

[0010] The present invention provides the following means to solve the problems described above.

[0011] Aspect 1 of the present invention is a stretchable circuit substrate comprising: a stretchable substrate; a non-stretchable part connected to at least a portion of the outer peripheral part of a first surface of the stretchable substrate or a side surface part of the stretchable substrate; a first electrical wiring having stretchability arranged on the first surface of the stretchable substrate; and a second electrical wiring arranged on the non-stretchable part, wherein at least a portion of the first electrical wiring and the second electrical wiring are connected.

[0012] In aspect 2 of the present invention, in the stretchable circuit substrate according to aspect 1, the stretchable substrate and the non-stretchable part are bonded by a conductive adhesive containing a stretchable resin.

[0013] In aspect 3 of the present invention, in the stretchable circuit substrate according to aspect 1 or 2, a portion of the non-stretchable part has an upwardly projecting protrusion part.

[0014] In aspect 4 of the present invention, in the stretchable circuit substrate according to any one of aspects 1 to 3, the non-stretchable part is arranged on the outer peripheral part of the stretchable substrate.

[0015] In aspect 5 of the present invention, in the stretchable circuit substrate according to any one of aspects 1 to 3, the non-stretchable part is connected to the side surface part of the stretchable substrate, and the lower surface of the non-stretchable part and the lower surface of the stretchable substrate are arranged flush with each other.

[0016] In aspect 6 of the present invention, in the stretchable circuit substrate according to any one of aspects 1 to 5, a gasket for attachment to an adhesive surface is provided on the surface on the back of the first surface of the stretchable circuit substrate.

[0017] Aspect 7 of the present invention is a stretchable device comprising: an electronic component disposed on the non-stretchable part included in the stretchable circuit substrate according to any one of aspects 1 to 6.

[0018] Aspect 8 of the present invention is a stretchable device comprising: a module disposed on the non-stretchable part included in the stretchable circuit substrate according to any one of aspects 1 to 6.

[0019] Aspect 9 of the present invention is a stretchable device comprising: a battery disposed on the non-stretchable part included in the stretchable circuit substrate according to any one of aspects 1 to 6. Advantageous effects of the invention

[0020] According to the present invention, it is possible to provide a stretchable circuit substrate in which the risk of damage to a mounted electronic component and the like is reduced when attachment and detachment are repeated. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a plan view conceptually showing a stretchable circuit substrate according to the present embodiment, and is a plan view showing a stretchable circuit substrate according to a first mode. Fig.1B is a plan view conceptually showing a stretchable circuit substrate according to the present embodiment, and is a plan view showing a stretchable circuit substrate according to a second mode. Fig. 1C is a plan view conceptually showing a stretchable circuit substrate according to the present embodiment, and is a plan view showing a stretchable circuit substrate according to a third mode. Fig. 2 is a cross-sectional view of the stretchable circuit substrate used in Fig. 1 is shown. Fig. Figure 3A is a conceptual view showing how a stretchable substrate having no non-stretchable part is peeled off from an adhesive surface to which it is attached. Fig. Figure 3B is a conceptual view showing how the stretchable substrate is formed after the Fig. 3A is further peeled off from the adhesive surface. Fig.3C is a view for conceptually explaining the operation effect of a stretchable substrate having a non-stretchable part (the stretchable circuit substrate according to the present embodiment), and is a conceptual view showing a state in which the stretchable circuit substrate is attached to an adhesive surface. Fig. 3D is a conceptual view that shows how after the Fig. 3C, the stretchable circuit substrate begins to be peeled off from the adhesive surface. Fig. 4 is a cross-sectional view conceptually showing a stretchable circuit substrate according to another embodiment. Fig. 5A is a plan view conceptually showing a stretchable circuit substrate according to yet another embodiment. Fig. 5B is a cross-sectional view conceptually showing a stretchable circuit substrate according to yet another embodiment. DESCRIPTION OF THE EMBODIMENTS

[0021] Hereinafter, the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, an element that becomes a feature is sometimes enlarged for convenience in order to easily understand the feature, and the dimensional ratios of the individual constituent elements and the like are sometimes different from the actual ones. The materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not limited thereto and can be implemented by appropriately modifying it within the range in which the effect of the present invention is set forth. [Stretchable circuit substrate]

[0022] A stretchable circuit substrate according to the present embodiment comprises: a stretchable substrate; a non-stretchable part connected to at least one of the outer peripheral part and the side surface part of the stretchable substrate; a first electrical wiring having stretchability and disposed on the stretchable substrate; and a second electrical wiring disposed on the non-stretchable part, in which at least a part of the first electrical wiring and the second electrical wiring are connected. The stretchable substrate and the non-stretchable part are preferably bonded by a conductive adhesive containing a stretchable resin.

[0023] In this specification, the term "non-stretchable part" refers to a part made of an insulating material with an elastic modulus of 0.6 kPa or more. As long as the elastic modulus is 0.6 kPa or more, the material is not particularly limited, and known insulating materials can be used. Representative insulating materials that can be used include resin materials, and examples of such materials include resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polyimide (PI), polyamide, polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), polypropylene, polysiloxane, polyacrylic acid, epoxy, glass epoxy, and silicon wafer. These resins can be used alone or in combination of two or more of them. Details are described below.

[0024] For example, PMMA with approximately 2.5 GPa, PI with approximately 3 GPa, or a PET film with approximately 4 GPa can be used as the material for the non-stretchable part. These Young's modulus values ​​are approximate, as the Young's modulus depends on the method used to prepare the material.

[0025] On the other hand, in the present specification, the "stretchable substrate" is made of an insulating material having an elastic modulus 1 / 2 or less of that of the insulating material constituting the "non-stretchable part," preferably an insulating material having an elastic modulus 1 / 5 or less, more preferably an insulating material having an elastic modulus of 1 / 10 or less, even more preferably an insulating material having an elastic modulus of 1 / 20 or less, even more preferably an insulating material having an elastic modulus of 1 / 50 or less, and even more preferably an insulating material having an elastic modulus of 1 / 100 or less. A typical insulating material that can be used is a resin material, and examples of such materials include resins such as epoxy resins, urethane resins, and methacrylic acid resins. These resins can be used alone or in combination of two or more of them.Details are described below.

[0026] Fig. 1 shows plan views showing conceptually stretchable circuit substrates according to the present embodiment.

[0027] A stretchable circuit substrate 101 (100) which is Fig.1A, comprises: a stretchable substrate 10; a non-stretchable part 21 (20) connected to a portion of the outer peripheral part of a first surface 10aa of the stretchable substrate 10; a first electrical wiring 31A (30A) arranged on the first surface 10aa of the stretchable substrate 10; and a second electrical wiring 31B (30B) arranged on the non-stretchable part, wherein the first electrical wiring 31A (30A) and the second electrical wiring 31B (30B) are connected, and the stretchable substrate 10 and the non-stretchable part 21 (20) are connected by a conductive adhesive 40 containing a stretchable resin (hereinafter sometimes referred to as a “stretchable resin-containing conductive adhesive”).

[0028] In the Fig.In the stretchable circuit substrate 101 (100) shown in Fig. 1A, the non-stretchable part 21 (20) is arranged near one of the four corners of the outer peripheral part of the rectangular stretchable substrate 10 in a plan view in the Z direction.

[0029] Furthermore, the Fig. 1A, the first electrical wiring 31A (30A) arranged on the stretchable substrate 10 and the second electrical wiring 31B (30B) arranged on the non-stretchable part are connected via the conductive adhesive 40 containing stretchable resin.

[0030] Furthermore, in the Fig.1A, the conductive adhesive 40 containing stretchable resin is arranged on one of the four sides of the rectangular non-stretchable part 21 (20) in a plan view in the Z direction, but this arrangement is merely an example and is not particularly limited as long as it functions to connect the stretchable substrate 10 and the non-stretchable part 21 (20).

[0031] A stretchable circuit substrate 102 (100) which is Fig.1B, comprises: a stretchable substrate 10; a non-stretchable part 22A (20) and a non-stretchable part 22B (20) connected to a portion of the outer peripheral part of the stretchable substrate 10; first electrical wirings 32A (30A) arranged on the stretchable substrate 10; and second electrical wirings 32B (30B) arranged on the non-stretchable parts, wherein the first electrical wirings 32A (30A) are respectively connected to the second electrical wirings 32B (30B), and the stretchable substrate 10 is connected to the non-stretchable parts 21 (20) by conductive adhesives 40 containing a stretchable adhesive.

[0032] In the Fig. In the stretchable circuit substrate 102 (100) shown in Fig. 1B, the non-stretchable part 22A (20) and the non-stretchable part 22B (20) are spaced apart from each other and arranged near one of the four sides of the outer peripheral part of the rectangular stretchable substrate 10.

[0033] Furthermore, the Fig. 1B, the first electrical wirings 32A (30A) arranged on the stretchable substrate 10 are respectively connected to the second electrical wirings 32B (30B) arranged on the non-stretchable parts via the conductive adhesives 40 containing stretchable resin.

[0034] Furthermore, in the stretchable circuit substrate 102 (100) shown in Fig. 1B, the conductive adhesives 40 containing stretchable resin are arranged along the inner side of one of the four sides of the rectangular non-stretchable part 22A (20) and the non-stretchable part 22B (20) in a plan view in the Z direction, but this arrangement is merely an example and is not particularly limited as long as it functions to bond the stretchable substrate 10 to the non-stretchable part 22A (20) and the non-stretchable part 22B (20).

[0035] A stretchable circuit substrate 103 (100) which is Fig. 1C, comprises: a stretchable substrate 10; a non-stretchable part 23 (20) connected to a portion of the outer peripheral part of the stretchable substrate 10; a first electrical wiring 33A (30A) arranged on the stretchable substrate 10; and a second electrical wiring 33B (30B) arranged on the non-stretchable part, wherein the first electrical wiring 33A (30A) and the second electrical wiring 33B (30B) are connected, and the stretchable substrate 10 and the non-stretchable part 23 (20) are connected by a conductive adhesive 40 containing a stretchable adhesive.

[0036] In the Fig. In the stretchable circuit substrate 103 (100) shown in Fig. 1C, the non-stretchable part 23 (20) is arranged near one of the four corners of the outer peripheral part of the rectangular stretchable substrate 10 in a plan view in the Z direction.

[0037] Furthermore, the Fig. 1C, the first electrical wiring 33A (30A) arranged on the stretchable substrate 10 and the second electrical wiring 33B (30B) arranged on the non-stretchable part are connected via the conductive adhesive 40 containing stretchable resin.

[0038] Furthermore, in the Fig. 1C, the conductive adhesive 40 containing stretchable resin is arranged along the entire circumference of the circular non-stretchable part 23 (20) in a plan view in the Z direction, but this arrangement is merely an example and is not particularly limited as long as it functions to connect the stretchable substrate 10 and the non-stretchable part 23 (20).

[0039] In the in the Fig.In the stretchable circuit substrates 100 (101, 102, 103) shown in FIGS. 1A to 1C, the non-stretchable parts 20 (21, 22A, 22B, 23) are arranged near a portion of the outer peripheral parts of the respective rectangular stretchable substrates in a plan view in the Z direction, specifically near one of the four sides or one of the four corners thereof. The non-stretchable parts may also be spaced apart from each other and arranged near two, three, or four of the four sides, or some may be connected to each other, or they may be spaced apart from each other and arranged near two, three, or four of the four corners. Furthermore, some of the non-stretchable parts 20 (21, 22A, 22B, 23) may be arranged near some of the four sides and some may be arranged near some of the four corners.Furthermore, the non-stretchable parts 20 (21, 22A, 22B, 23) can be arranged in any manner as long as they are located on a portion of the outer peripheral portion of the rectangular stretchable substrate in a plan view in the Z direction. When the stretchable circuit substrates 100 are used by attaching them to an adhesive surface (e.g., skin or clothing), the non-stretchable parts 20 can be arranged over the entire outer peripheral portion of the stretchable substrate 10 or over the entire circumference.

[0040] The width of the outer peripheral part of the stretchable substrate 10 in which the non-stretchable part 20 is arranged may be, for example, about 5 mm to 20 mm, but is not limited to this width.

[0041] Fig. 2 is a cross-sectional view of the stretchable circuit substrate 100 shown in Fig. 1A to 1C. The Fig.The cross-sectional view of the stretchable circuit substrate 100 shown in Fig. 2 is taken along a cross section along the first electrical wiring 30A and the second electrical wiring 30B.

[0042] As in Fig. 2, the non-stretchable part 20 is arranged on the outer peripheral part of the stretchable substrate 10.

[0043] Fig. 3A to 3D are views for conceptually illustrating the operating effect of the stretchable circuit substrate according to the present embodiment.

[0044] Fig. 3A and Fig. 3B are views showing how an end portion of a stretchable substrate 10 is pulled and peeled off from an adhesive surface (e.g., skin or clothing) OB to which the stretchable substrate 10 is attached. Reference symbol PD indicates the peeling direction.

[0045] Fig. 3C and Fig.3D are views showing how a non-stretchable part 20 disposed on the outer peripheral part of a stretchable substrate 10 is pulled and peeled from an adhesive surface (e.g., skin or clothing) OB to which the stretchable circuit substrate 100 (configured with a non-stretchable part on the outer peripheral part of the stretchable substrate) according to the present embodiment is attached. Reference symbol PD indicates the peeling direction.

[0046] In Fig. 3A and Fig. 3B, when the stretchable substrate is attached to the adhesive surface, if the adhesive strength is high, initially a strong peel strength (peel force) is required during peeling. This is because the soft, stretchable substrate stretches during peeling. On the other hand, if the stretchable substrate is in the Fig. 3C and Fig.3D has a part that does not stretch (non-stretchable part) on its outer peripheral part, the non-stretchable part does not stretch when pulled and peeled off, and therefore can be peeled off with a lower peel strength (peel force) than in the Fig. 3A and Fig. 3B.

[0047] In the stretchable circuit substrate according to the present embodiment, the non-stretchable part may be configured to be connected to the side surface part of the stretchable substrate.

[0048] One in Fig.The stretchable circuit substrate 200 shown in FIG. 4 comprises: a stretchable substrate 10A; a non-stretchable part 20 connected to a portion of a side surface part 10Ab of the stretchable substrate 10A; a first electrical wiring 30A disposed on the stretchable substrate 10A; and a second electrical wiring 30B disposed on the non-stretchable part, wherein the first electrical wiring 30A and the second electrical wiring 30B are connected, and the stretchable substrate 10A and the non-stretchable part 20 are connected by a conductive adhesive 40 containing a stretchable resin. Furthermore, this is a case where a lower surface 20a of the non-stretchable part 20 and a lower surface 10Aa of the stretchable substrate 10A are substantially flush with each other.

[0049] In Fig.4, the elements designated by the same reference numerals as those previously described in the drawings indicate elements having the same functions.

[0050] A non-stretchable part 120, which is Fig. 5A and Fig. 5B, has a projection portion 120a that projects upwards. Fig. 5B is a cross-sectional view of a stretchable circuit substrate 104 (100) taken along a cross section along the first electrical wiring 30A and the second electrical wiring 30B in the plan view of the stretchable circuit substrate of Fig. 5A.

[0051] By grasping and pulling the protrusion portion 120a protruding upward from a portion of the non-stretchable portion 120, the stretchable circuit substrate 104 can be more easily peeled off from an adhesive surface (e.g., skin or clothing).

[0052] The non-stretchable part 20 of the Fig.The stretchable circuit substrate 200 shown in Fig. 4 may be configured to have an upwardly projecting protrusion portion. <Dehnbares Substrat>

[0053] As described above, the stretchable substrate 10 is an insulating material having an elastic modulus 1 / 10 or less than that of the insulating material constituting a non-stretchable part, preferably an insulating material having an elastic modulus 1 / 50 or less, and more preferably an insulating material having an elastic modulus 1 / 100 or less.

[0054] As the material for the stretchable substrate 10, a stretchable resin is preferably used. The stretchable resin is not particularly limited, and any known stretchable resin can be used as the stretchable resin. Examples include epoxy resins, urethane resins, polyurethane-urea resins, methacrylic acid resins, polyacrylic resins, silicone resins, diene resins, polyester resins, polyether resins, polyamide resins, and polystyrene resins.

[0055] A sheet-shaped stretchable resin substrate made of a stretchable resin (hereinafter sometimes referred to as a "resin sheet") can be used as the stretchable substrate 10. Furthermore, a plurality of resin sheets can be laminated to prepare a stretchable resin substrate that can be used as the stretchable substrate 10.

[0056] Hereinafter, a case in which the stretchable substrate 10 is made of a stretchable resin material will be mainly described.

[0057] The resin used in the stretchable substrate 10 is preferably soluble in one or more solvents selected from N,N-dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate (BCA), diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, acetone, ethanol, methanol, ethyl lactate, butyl lactate, toluene, isopropyl alcohol, isobutyl alcohol, ethyl acetate, and butyl acetate.

[0058] The stretchable substrate 10 can be formed by applying and solidifying a resin composition containing a solvent and the resin used in the stretchable substrate 10 described above.

[0059] Among the resins described above, a urethane resin that can be molded by simply applying and drying a resin composition without a curing reaction is preferred. This is because, for resins requiring a curing reaction, if the curing reaction does not proceed uniformly, variations in composition and curing degree may occur in resin films, resulting in resins that do not have the desired properties in terms of stretchability, strength, and resistance to aging deterioration.

[0060] Furthermore, when using a urethane resin, the resin component should preferably contain a siloxane bond. This is because the resin composition in this case exhibits moderate water-repellent properties, which inhibits the hydrolysis of urethane bonds.

[0061] The properties of the stretchable substrate 10 will be described below, giving a specific example of a resin composition for producing the stretchable substrate 10 from a stretchable resin material.

[0062] As a specific example, there can be mentioned a resin composition containing a resin component (sometimes referred to as “resin component (II)” in the present specification) having a urethane bond and a group represented by the following general formulas (11), (21) or (31).

[0063] (In the formula, Z 1 an alkyl group, and one or more hydrogen atoms in the alkyl group may be substituted with a cyano group, a carboxy group, or a methoxycarbonyl group, and two or more of the substituents may be the same or different from each other. Z 2 is an alkyl group. Z 3 is an aryl group. R 4is a hydrogen atom or a halogen atom. A bond marked with a * is formed at a bonding target in the group represented by the above general formulas (11), (21), or (31).

[0064] The resin component (II) contained in this resin composition is highly flexible due to a urethane bond.

[0065] Furthermore, the resin component (II) is obtained by a polymerization reaction using a resin having a urethane bond and a polymerizable unsaturated bond and a RAFT agent to conduct reversible addition-fragmentation chain transfer polymerization (abbreviated as "RAFT polymerization" in the present specification), from which the group represented by the above general formulas (11), (21), or (31) is derived. By conducting the polymerization reaction in this manner, gelation of the resin during polymerization is avoided in the formation of a crosslinked structure, and resin components having the desired degree of polymerization and crosslinking state are obtained.In other words, the resin component (II) having the group represented by the above general formulas (11), (21) or (31) has little variation in the degree of polymerization and the crosslinking state.

[0066] Furthermore, the resin component (II) may have a siloxane bond, in which case the resin composition exhibits moderate water-repellent properties that inhibit the hydrolysis of the urethane bonds in the resin component (II). Such a resin component (II) is obtained by a further polymerization reaction using a resin having a siloxane bond and a polymerizable unsaturated bond.

[0067] The process for preparing the resin component (II) in which RAFT polymerization is carried out is described separately in detail.

[0068] The resin having a urethane bond and a polymerizable unsaturated bond used in the preparation of the resin component (II) is an oligomer and may be referred to as “resin (a)”.

[0069] Furthermore, the resin having a siloxane bond and a polymerizable unsaturated bond used in the preparation of the resin component (II) is an oligomer and may be referred to as “resin (b)” in the present embodiment.

[0070] The resin component (II) is a polymer formed by polymerizing resins (a) at their polymerizable unsaturated bonds. When resin (b) is used, the resin component (II) is a polymer formed by polymerizing resin (a) and resin (b) at their polymerizable unsaturated bonds.

[0071] When the resin (b) is used, the resin component (II) preferably has both urethane and siloxane bonds in one molecule.

[0072] The resin (a) is not particularly limited as long as it has a urethane bond and a polymerizable unsaturated bond.

[0073] Examples of the resin (a) include those having a (meth)acryloyl group as a group having a urethane bond and a polymerizable unsaturated bond, and more specific examples thereof include urethane (meth)acrylate.

[0074] In this specification, "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate." The same applies to terms similar to (meth)acrylate. For example, "(meth)acryloyl group" is a term that encompasses both "acryloyl group" and "methacryloyl group."

[0075] The resin (b) is not particularly limited as long as it has a siloxane bond and a polymerizable unsaturated bond.

[0076] Examples of the resin (b) include various known silicone resins having a (meth)acryloyl group as a group having a polymerizable unsaturated bond, and more specific examples thereof include a modified polydialkylsiloxane in which a (meth)acryloyl group is bonded to a single end or both ends of a polydialkylsiloxane such as polydimethylsiloxane.

[0077] Due to its composition, the resin component (II) exhibits high solubility in solvents. Therefore, the resin composition containing the resin component (II) also exhibits high solubility in solvents.

[0078] Such a resin composition with high solubility can easily form a resin composition layer by printing on an object to be applied, for example, using various printing methods. This resin composition layer can then be solidified by drying without curing to produce a layer (resin layer, resin film) similar to the resin films. Such a method is suitable for the production of electrodes or wiring using the resin composition containing conductive components.

[0079] Such a resin composition with high solubility is used to form a stretchable resin film, and a stretchable device formed from this resin film has the great advantage of suppressing damage during its stretching and contracting.

[0080] Factors that can cause damage to normal stretchable devices during stretching and contracting include, from the materials perspective, (i) interfacial delamination and structural defects such as voids caused by contraction due to heat or curing reactions, (ii) uneven hardness caused by uneven composition, and (iii) deterioration of materials over time due to light exposure, oxidation, and the like.

[0081] Therefore, structural defects such as voids, interfacial delamination, uneven composition, and deterioration of materials over time can be suppressed, preventing damage to the stretchable devices during stretching and contracting.

[0082] Although molding by thermal melting and crosslinking by thermosetting or photocuring reactions are commonly used to process stretchable substrates, there is concern that the reliability of the stretchable devices will decrease if even micromachining is considered, for reasons (i) to (iii). In contrast, favorable results are expected to be achieved, for example, if a resin is available that can be molded only by applying and drying a resin composition in response to a lamination process.

[0083] For the stretchable substrate 10, the resin composition of the specific example can be solidified by drying to obtain a sheet-shaped stretchable resin substrate (hereinafter sometimes referred to as a "resin sheet"). A plurality of resin sheets can be laminated to prepare a stretchable substrate.

[0084] The resin film exhibits favorable stretchability because it contains resin component (II) as its main ingredient. When resin (b) is used, the resin film also exhibits moderate water-repellent properties, which suppress deterioration caused by hydrolysis over time. The resin film with such properties is particularly suitable for the production of various types of stretchable devices, including wearable devices.

[0085] The resin film can be formed simply by solidifying the resin composition through drying as described above, without any curing reaction. Therefore, it does not have the disadvantages associated with conducting a curing reaction.

[0086] For example, in a photocuring reaction, it is significantly difficult to uniformly cure materials that do not transmit ultraviolet light. For example, when the edge of an assembled device or electronic component is irradiated with ultraviolet light, the degree of curing may vary in some areas of a photocuring resin film due to variations in ultraviolet light transmittance, and the resin film is easily damaged in areas with low crosslinking density. Furthermore, non-crosslinked areas are easily deteriorated by oxidation.

[0087] On the other hand, a thermal curing reaction easily leads to contraction differences in the resin film due to heat distribution during curing. When such contraction differences occur, the various components of devices, seals, and the like are easily delaminated at these interfaces. Furthermore, if areas with different degrees of cure arise in the resin film due to heat distribution, the film is easily deteriorated due to repeated stretching and contraction.

[0088] Furthermore, both photocuring and thermal curing reactions make it difficult for the reactions to proceed uniformly within the resin film. In such cases, variations in composition and degree of curing occur within the resin film, and the cured resin film lacks the desired extensibility and strength. Furthermore, since a curing agent is incorporated, it is also easily subject to deterioration over time due to heat or light.

[0089] In contrast, the resin film obtained by solidifying the resin composition of the specific example by drying has no such defects.

[0090] The resin film can be produced without curing reaction, for example, by applying the resin composition to a desired part and solidifying it by drying.

[0091] The resin composition can be applied, for example, by known methods using various coaters, wire rods or the like, or by various printing methods including inkjet printing methods.

[0092] The drying temperature of the resin composition during the production of the resin film is preferably 25°C to 150°C, and more preferably 25°C to 120°C. When the drying temperature is 25°C or higher, it is possible to produce a resin film more efficiently. When the drying temperature is 150°C or lower, the drying temperature is suppressed from becoming excessively high, deformation of a release film and damage to the resin film are less likely, and deterioration of the resin film is suppressed.

[0093] The drying time of the resin composition during resin film production can be adjusted according to the drying temperature, but is preferably 10 minutes to 120 minutes, and more preferably 30 minutes to 90 minutes. When the drying time is within these ranges, resin films with advantageous properties can be efficiently produced.

[0094] The complete solidification of the resin composition by drying (formation of the resin film) can be confirmed, for example, by the fact that no significant mass change of the resin composition subjected to drying is observed.

[0095] The elongation of the stretchable resin substrate can be adjusted according to the elongation required for the stretchable circuit substrate. For example, the elongation can be adjusted by increasing the amount of stretchable resin to increase the elongation. Furthermore, the elongation can be adjusted by increasing the mol% of high-elongation bonds in the resin. For example, the elongation of the stretchable resin substrate can be increased by increasing the proportion of urethane bonds in the resin.

[0096] The thickness of the stretchable resin substrate is not particularly limited, but can be, for example, 10 µm to 5,000 µm. <Nicht dehnbarer Teil>

[0097] The inextensible part 20 is made of an insulating material having an elastic modulus of 0.6 kPa or more. Furthermore, with respect to the material of the stretchable substrate 10, the inextensible part 20 is made of an insulating material having an elastic modulus at least twice that of the stretchable substrate 10, preferably an insulating material having an elastic modulus at least five times as high, more preferably an insulating material having an elastic modulus at least ten times as high, even more preferably an insulating material having an elastic modulus at least twenty times as high, even more preferably an insulating material having an elastic modulus at least fifty times as high, and even more preferably an insulating material having an elastic modulus at least one hundred times as high.

[0098] The non-stretchable part 20 is not particularly limited as long as it has a Young's modulus of 0.6 kPa or more, and known insulating materials can be used. Typical insulating materials that can be used are resins, and examples of such materials include resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), and polyimide (PI). These resins can be used alone or in combination with two or more of them. <Erste elektrische Verdrahtung mit Dehnbarkeit>

[0099] The first stretchable electrical wiring 30A can be formed using a stretchable resin (stretchable resin) containing a metal powder. Hereinafter, the first stretchable electrical wiring is sometimes referred to as "stretchable electrical wiring."

[0100] When an expandable resin containing a metal powder is used as the first electrical wiring 30A with expandability, a known expandable resin can be used. Examples include urethane resins, acrylic resins, epoxy resins, urea resins, polyurethane-urea resins, methacrylic acid resins, polyacrylic resins, silicone resins, diene resins, polyester resins, polyether resins, polyamide resins, polystyrene resins, and polyimide resins. These can be used alone or in combination of two or more of them.

[0101] The resins described above are preferably soluble in one or more types of solvents selected from diethylene glycol monobutyl ether acetate (BCA), butyl carbitol (BC), ethyl cyanoacrylate (ECA), α-terpineol, diethylene glycol monobutyl ether and diethylene glycol monoethyl ether acetate.

[0102] It is preferable that the stretchable electrical wiring 30A has high conductivity and high stretchability, and that its change in conductivity upon stretching and contracting is minimal.

[0103] A stretchable electrical wiring 30A of a first aspect can be formed by applying and solidifying a resin composition containing a resin used, a metal powder, and a solvent.

[0104] Among the resins described above, it is preferable to use a dry-curing resin that can be molded and solidified without a curing reaction simply by applying and drying the resin composition. Examples of dry-curing resins include urethane resins. In this case, the stretchable electrical wiring 30A according to the first aspect can be referred to as a dry-curing stretchable electrical wiring.

[0105] This is because, for resins that require a curing reaction, if the curing reaction does not proceed uniformly, variations in composition and degree of cure may occur in the stretchable electrical wiring, resulting in resins that do not have the desired properties in terms of stretchability, strength, and resistance to aging deterioration.

[0106] Furthermore, when a urethane resin is used, the resin component should preferably also contain a siloxane bond. This is because the resin composition in this case exhibits moderate water-repellent properties, which inhibits the hydrolysis of urethane bonds.

[0107] The proportion of the resin in the stretchable electrical wiring 30A of the first aspect is 8 wt% to 20 wt%.

[0108] The stretchable electrical wiring 30A of the first aspect is a stretchable electrical wiring with a small change in conductivity during stretching and contracting, but the resin content is 8 wt% or more to ensure high stretchability (high elongation at break) as a prerequisite therefor. On the other hand, the stretchable electrical wiring 30A of the first aspect is a stretchable electrical wiring with high conductivity before and during stretching and contracting, but the resin content is set to 20 wt% or less to ensure high conductivity (low resistivity).

[0109] The resin content in the stretchable electrical wiring 30A is preferably 10 wt% or more. The resin content in the stretchable electrical wiring 30A is preferably 18 wt% or less.

[0110] When a urethane resin is contained in the resin in the stretchable electrical wiring 30A of the first aspect, the proportion of urethane bonds in the resin is preferably 15 wt% or more, and more preferably 17 wt% or more.

[0111] The proportion of urethane bonds in the resin can be determined, for example, by calculating the peak area corresponding to the urethane bonds in the C 13 -nuclear magnetic resonance (NMR) spectrum.

[0112] Furthermore, the elongation at break may be low in test examples with a high proportion of urethane bonds in the resin, which will be described below. The reason for this is currently unclear, but based on the test examples, the proportion of urethane bonds in the resin is preferably 30 wt% or less, more preferably 25 wt% or less, and even more preferably 22 mol% or less. (metal powder)

[0113] Metal powders are not particularly limited, and those known as metal powders can be used. Examples include silver powder (Ag), carbon powder (C), copper powder (Cu), palladium powder (Pd), gold powder (Au), and platinum powder (Pt). Among them, silver powder or an alloy powder composed mainly of silver is preferable because of its low resistance. Here, an alloy powder composed mainly of silver means that more than 50% by weight of the powder is silver, and the proportion of silver is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more.

[0114] Suitable manufactured or commercially available products can be used as metal powder.

[0115] Examples of methods for producing silver powder include adding an aqueous solution containing a reducing agent to an aqueous reaction system containing silver ions to reduce and precipitate silver particles. Furthermore, a silver powder, such as a silver-coated copper powder, which has a silver surface and an interior formed of a metal other than silver, can be used.

[0116] A metal powder includes a flake-shaped powder. The term "flake-shaped powder" in this specification refers to a powder (metal powder) with a thickness of 1 / 10 or less of the maximum particle diameter. The maximum particle diameter of the flake-shaped powder is defined as follows: Each powder particle has different end-to-end lengths depending on the direction in plan view, and the longest of these lengths is taken as the maximum particle diameter. The maximum particle diameter can be determined by optical microscopy, scanning electron microscopy (e.g., 5000x field of view), or the like.

[0117] When a metal powder is flake-shaped, it has upper and lower surfaces that spread in the surface direction, and therefore the proportion of surface contact between the metal powders is increased, resulting in high conductivity (low resistivity).

[0118] Furthermore, appropriately manufactured or commercially available products can be used as flake-shaped metal powders.

[0119] Flake-shaped metal powders, for example, can be produced by preparing a thin film of a desired metal and then finely grinding the thin film. Since flake-shaped metal powders are obtained by finely grinding thin films using the manufacturing method, the individual crushed metal pieces are also flattened. The thickness in relation to the particle diameter (i.e., the degree of flattening) can be adjusted by adjusting the thickness of the thin films and the degree of fine grinding.

[0120] The proportion of the flaky powder in the metal powder is preferably 2.5 wt% or more, more preferably 5 wt% or more, and even more preferably 7.5 wt% or more. Furthermore, the proportion of the flaky powder in the metal powder is preferably 50 wt% or less, more preferably 40 wt% or less, even more preferably 30 wt% or less, and even more preferably 25 wt% or less.

[0121] From the perspective of high conductivity (low resistivity), a higher proportion of flaky powder in the metal powder is preferable. However, if the proportion is too high, the extensibility decreases and the elongation at break decreases. The degree of freedom of movement of the metal powder is necessary for smooth expansion and contraction of the 30A stretchable electrical wiring, but if the proportion of flaky powder exceeds 50 wt%, this is believed to be due to the fact that the flaky shape itself has high resistance to movement.

[0122] The average maximum particle diameter of the flake powder is preferably 3 µm to 10 µm.

[0123] This is because when the average maximum particle diameter is 3 µm or more, sufficiently high conductivity (low resistivity) can be achieved due to the effect of surface contact between metal powders, and when the average maximum particle diameter is 10 µm or less, sufficient ductility decreases and the elongation at break is reduced. (elongation at break)

[0124] The breaking elongation of the stretchable electrical wiring 30A is 130% or more. The breaking elongation is preferably 150% or more, more preferably 200% or more, even more preferably 250% or more, and even more preferably 300% or more.

[0125] The breaking elongation of the stretchable electrical wiring 30A can be increased by increasing the resin content of the stretchable electrical wiring 30A, but increasing the resin content results in an increase in resistivity. Therefore, the breaking elongation is adjusted accordingly by adjusting the resin content according to the breaking elongation and resistivity required for a stretchable device using the stretchable electrical wiring 30A.

[0126] In this specification, the term "break elongation" is defined as {(length at break - length before drawing) / length before drawing} × 100. Although the break elongation can be measured in any of the specified directions, the term "break elongation of 150% or more" in this specification is defined as the break elongation in a direction where the break elongation is greatest. When there is no anisotropy in the break elongation, the break elongation is uniform in all directions, and when the anisotropy in the break elongation is small, the break elongation has values ​​close to each other in all directions. (Method for measuring elongation at break)

[0127] First, an example of a procedure for preparing a sample is described below.

[0128] A glass plate with a clean surface is prepared. A PET film is then placed on the glass plate, and the upper surface is taped. An applicator (e.g., Type YA, 75 mm, 152 µm, manufactured by Yoshimitsu Seiki) is then prepared and adjusted. Stretchable electrical wiring paste is stirred in a container without air supply. The stretchable electrical wiring paste is then applied to the PET film. The stretchable electrical wiring paste is then spread by sliding the applicator. After applying the stretchable electrical wiring paste, the PET film and the glass plate are bonded. After standing for 3 to 5 minutes, the glass plate is placed in a dryer preheated to 90°C to 100°C and dried for 1 hour.By the process described above, a sheet-shaped sample of the stretchable electrical wiring 30A with a thickness of 30 µm to 70 µm is obtained. The combined thickness of the PET film and the sheet-shaped sample of the stretchable electrical wiring 30A is approximately 150 µm.

[0129] The elongation at break can be measured as follows. From each sheet-shaped sample of the 30A stretchable electrical wiring, six strip-shaped test specimens of 10 mm width and 30 mm length are cut. For each test specimen, the elongation at break is calculated according to the method shown below, and an average value is taken as the elongation at break. A metal substrate is clamped between the gripping parts at the top and bottom of the gauge, and each test specimen is fixed with double-sided tape so that the measuring point is 10 mm wide and 10 mm long. The test specimen is then pulled with a tensile tester (example, product name: Autograph AGS-5kNX, manufactured by Shimadzu Corporation) at a speed of 10 mm / min. The length of each test specimen at break is then measured, and the length before pulling, 10 mm, is subtracted from this length to calculate the elongation at break of each test specimen.An average value of this is taken as the elongation at break, and the elongation at break is calculated according to the definition described above. (Specific resistance before stretching and contracting)

[0130] The specific resistance before stretching and contracting (Normal specific resistance) of the stretchable electrical wiring 30A is 2× 10 -2 [Ω mm] or less. The specific resistance is preferably 7× 10 -3 [Ω mm] or less, more preferably 6× 10 -3 [Ω mm] or less and more preferably 4× 10 -3 [Ω mm] or less.

[0131] The resistivity before stretching and contracting of the stretchable electrical wiring 30A can be reduced by increasing the proportion of metal powder in the stretchable electrical wiring 30A. However, reducing the resin proportion in accordance with the increase in the proportion of metal powder results in a reduction in the elongation at break. Therefore, the resistivity before stretching and contracting is appropriately adjusted by adjusting the proportion of metal powder according to the elongation at break and the resistivity required for a stretchable device in which the stretchable electrical wiring 30A is used. (Method for measuring resistance and resistivity)

[0132] First, a foil-shaped sample of the stretchable electrical wiring 30A is prepared according to the method described above.

[0133] The resistivity before stretching and contracting can be measured as follows. Similar to the elongation at break measurement, six strip-shaped test samples of 10 mm wide and 30 mm long are cut from each film-shaped sample of 30A stretchable electrical wiring. A metal substrate is clamped between gripping parts at the top and bottom of the measuring device, and each test sample is fixed with double-sided tape so that the measuring point is 10 mm wide and 10 mm long. The resistance value of each test sample is measured under these conditions. An average value of this is taken as the resistance value R0 before stretching and contracting. The resistance value for each stretch is measured each time during stretching while the sample is stretched by moving the metal substrate by 1 mm each, and an average value of the six samples is taken as the resistance value R during stretching.

[0134] Next, the thickness of each sheet-shaped sample of the stretchable electrical wiring 30A is measured as follows. Each sheet-shaped sample of the stretchable electrical wiring 30A is punched out into a circular shape. Then, the sample is placed on a flat table, and a rectangular PET film, one side of which is larger than the diameter of the circular sample, is placed on the sample. The thickness of four corners of a rectangular PET film is measured using, for example, a Digimicro ZC-101 (manufactured by Nikon Corporation), and the average value is taken as the thickness of the PET film. Next, the combined thickness of the sample and the PET film is measured at five points (top, bottom, left, right, and center), and the thickness of the PET film is subtracted from the average thickness to calculate the thickness t of the sample.

[0135] Then, the specific resistance ρ0 (=R0 × (cross-sectional area / length)) is calculated from the resistance value R0 before stretching and contracting described above and the thickness t, width and length of the foil-shaped sample of the stretchable electrical wiring 30A.

[0136] Furthermore, the resistivity at each strain is similarly calculated from the resistance value at each strain and the thickness t, width and length of the sheet-shaped sample of the stretchable electrical wiring 30A using the resistivity formula ρ (=R × (cross-sectional area / length)).

[0137] In the stretchable electrical wiring 30A according to the first aspect, the ratio (ρ 50 / ρ0) of a resistance (ρ 50) at 50% elongation to a resistance (ρ0) before stretching and contracting is preferably 7 or less, more preferably 6 or less, and even more preferably 5 or less. Furthermore, the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation is preferably 8 or less, more preferably 7 or less, even more preferably 6 or less, and even more preferably 5 or less.

[0138] The ratio (ρ 50 / ρ0) of a specific resistance (ρ 50 ) at 50% elongation to a specific resistance (ρ0)before stretching and contracting and the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100 % elongation to a specific resistance (ρ 50 ) at 50% elongation are both preferably 7 or less, more preferably 6 or less, and even more preferably 5 or less.

[0139] In the stretchable electrical wiring 30A according to the first aspect, the rate of change of the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation with respect to the ratio (ρ 50 / ρ0) of a specific resistance (ρ 50 ) at 50% elongation to a specific resistance (ρ0) before stretching and contracting preferably 140% or less, more preferably 80% or less, even more preferably 70% or less, even more preferably 60% or less, and even more preferably 50% or less.

[0140] In the stretchable electrical wiring 30A according to the first aspect, it is preferable that the ratio (ρ 50 / ρ0) of a specific resistance (ρ 50 ) at 50% elongation to a specific resistance (ρ0)before stretching and contracting and the ratio (ρ 100 / ρ 50) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% strain are both 7 or less and that the rate of change of the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation with respect to the ratio (ρ 50 / ρ0) of a specific resistance (ρ 50 ) at 50% strain to a specific resistance (ρ0) before stretching and contracting is 140% or less.

[0141] A stretchable electrical wiring according to a second aspect comprises: a resin; and a metal powder in which an elongation at break is 130% or more, a ratio (ρ 50 / ρ0) of a specific resistance (ρ 50) at 50% elongation to a specific resistance (ρ0) before stretching and contracting is 7 or less, the metal powder comprises a flake-shaped powder, and a proportion of the resin is 8 wt% to 20 wt%. Descriptions of configurations common to the stretchable electrical wiring according to the first aspect will not be repeated.

[0142] Furthermore, the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation preferably 8 or less.

[0143] Furthermore, the resin content in the stretchable electrical wiring is preferably 10 wt% or more. The resin content in the stretchable electrical wiring is preferably 18 wt% or less.

[0144] The smaller the change in resistivity when stretching the stretchable electrical wiring, the more preferable it is.

[0145] The ratio (ρ 50 / ρ0) of the specific resistance at 50% elongation to the specific resistance before stretching and contracting is preferably 6 or less, and more preferably 5 or less. Furthermore, the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation is preferably 7 or less, more preferably 6 or less, and even more preferably 5 or less.

[0146] In the stretchable electrical wiring according to the second aspect, the rate of change of the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50) at 50% elongation with respect to the ratio (ρ 50 / ρ0) of a specific resistance (ρ 50 ) at 50% elongation to a specific resistance (ρ0)before stretching and contracting preferably 140% or less.

[0147] A stretchable electrical wiring according to a third aspect comprises: a resin; and a metal powder in which an elongation at break is 130% or more, a rate of change of a ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation with respect to a ratio (ρ 50 / ρ0) of a specific resistance (ρ 50) at 50% elongation to a specific resistance (ρ0) before stretching and contracting is 140% or less, the metal powder comprises a flake-shaped powder, and a resin content of 8 wt% to 20 wt%. Descriptions of configurations common to the stretchable electrical wiring according to the first aspect will not be repeated.

[0148] Furthermore, the resin content in the stretchable electrical wiring is preferably 10 wt% or more. The resin content in the stretchable electrical wiring is preferably 18 wt% or less.

[0149] Although the resistivity of stretchable electrical wiring decreases with stretching, the lower the rate of decrease, the more preferable it is. The rate of change (ratio (ρ 100 / ρ 50 ) / ratio (ρ 50 / ρ0)) is preferably 80% or less, more preferably 70% or less, even more preferably 60% or less, and even more preferably 50% or less. (Method for preparing stretchable electrical wiring)

[0150] The stretchable electrical wirings of the first to third aspects can be manufactured through the following main steps: a (1) stretchable electrical wiring paste preparation step; a (2) stretchable electrical wiring paste application step; and a (3) drying and solidifying step.

[0151] In other words, in the (1) stretchable electrical wiring paste preparation step, a metal powder is incorporated into a resin composition containing the above-described resin and solvent to prepare a stretchable electrical wiring paste. Subsequently, in the (2) stretchable electrical wiring paste application step, the stretchable electrical wiring paste is applied to a base material (e.g., a PET film). After that, in the (3) drying and solidification step, a stretchable electrical wiring 30A can be prepared by removing the solvent and drying and solidifying the stretchable wiring paste.

[0152] As a specific example of a resin composition (a resin and a solvent) for producing the stretchable electrical wiring 30A similar to the stretchable substrate 10, there may be mentioned a resin composition containing a resin component (II) having a urethane bond and a group represented by the above-described general formulas (11), (21) or (31).

[0153] Due to its composition, the resin component (II) exhibits high solubility in solvents. Therefore, the resin composition containing the resin component (II) also exhibits high solubility in solvents.

[0154] Such a resin composition, which has high solubility, can easily form a resin composition layer by printing it onto an object to be coated, for example, using various printing methods. This resin composition layer is then solidified by drying without curing, thereby producing a stretchable electrical wiring. Such a method is suitable for manufacturing electrodes or wiring using the resin composition containing conductive components.

[0155] Such a resin composition with high solubility is used to form a stretchable electrical wiring with stretchability, and a stretchable device formed from the stretchable electrical wiring has the great advantage of suppressing damage during its stretching and contracting.

[0156] Factors that can cause damage to normal stretchable devices during stretching and contracting include, from the materials perspective, (i) interfacial delamination and structural defects such as voids caused by contraction due to heat or curing reactions, (ii) uneven hardness caused by uneven composition, and (iii) deterioration of materials over time due to light exposure, oxidation, and the like.

[0157] Therefore, structural defects such as voids, interfacial delamination, uneven composition, and deterioration of materials over time can be suppressed, preventing damage to the stretchable devices during stretching and contracting.

[0158] Although molding by thermal melting and crosslinking by thermosetting or photocuring reactions are commonly used to process stretchable substrates, there is concern that the reliability of the stretchable devices will decrease if even micromachining is considered, for reasons (i) to (iii). In contrast, favorable results are expected to be achieved if, for example, there is a resin that can be molded only by applying and drying a resin composition in response to a lamination process.

[0159] The stretchable electrical wiring can be obtained by preparing a stretchable electrical wiring paste by incorporating a metal powder into the resin composition of the specific example described above, applying the stretchable electrical wiring paste to a substrate, and then solidifying it by drying.

[0160] The stretchable electrical wiring exhibits favorable stretchability because it contains the resin component (II) as its main ingredient. When the resin (b) is used, the stretchable electrical wiring also exhibits moderate water-repellent properties, which suppresses deterioration caused by hydrolysis over time. Stretchable electrical wiring with such properties is particularly suitable for the construction of various types of stretchable devices, including wearable devices.

[0161] The stretchable electrical wiring can be formed simply by solidifying the resin composition through drying, as described above, without a curing reaction. Therefore, it does not have the disadvantages associated with conducting a curing reaction.

[0162] For example, in a photocuring reaction, it is significantly difficult to uniformly cure materials that do not transmit ultraviolet light. For example, when the edge of an assembled device or electronic component is irradiated with ultraviolet light, the degree of curing may vary in some areas of photocured electrical wiring due to variations in ultraviolet light transmittance, and the stretchable electrical wiring is easily damaged in areas with low crosslinking density. Furthermore, non-crosslinked areas are easily deteriorated by oxidation.

[0163] On the other hand, a thermal curing reaction easily leads to contraction differences in the stretchable electrical wiring due to heat distribution during curing. When such contraction differences occur, the various components of devices, seals, and the like are easily delaminated at these interfaces. Furthermore, if areas with different degrees of curing arise in the stretchable electrical wiring due to heat distribution, the stretchable electrical wiring is easily deteriorated due to repeated stretching and contraction.

[0164] Furthermore, both photocuring and thermal curing reactions in the stretchable electrical wiring make it difficult to ensure uniform reactions. In such cases, variations in the composition and degree of curing occur in the stretchable electrical wiring, and the cured stretchable electrical wiring lacks the desired extensibility and strength. Furthermore, since a curing agent is incorporated, deterioration over time due to heat or light is also easily caused.

[0165] In contrast, the stretchable electrical wiring obtained by solidifying the stretchable electrical wiring paste containing the resin composition of the specific example described above by drying has no such defects.

[0166] The stretchable electrical wiring can be manufactured without a curing reaction, for example, by applying the stretchable electrical wiring paste to a desired location and solidifying it by drying.

[0167] The stretchable electrical wiring paste can be applied, for example, by known methods using various coaters, wire rods or the like, or by various printing methods including inkjet printing methods.

[0168] During the production of the stretchable electrical wiring, the drying temperature of the stretchable electrical wiring paste is preferably 25°C to 150°C, and more preferably 25°C to 120°C. When the drying temperature is 25°C or higher, it is possible to produce the stretchable electrical wiring more efficiently. When the drying temperature is 150°C or lower, the drying temperature is suppressed from becoming excessively high, deformation of a release liner and damage to the stretchable electrical wiring are less likely, and deterioration of the stretchable electrical wiring is suppressed.

[0169] The drying time of the stretchable electrical wiring paste during the production of the stretchable electrical wiring can be adjusted according to the drying temperature, but is preferably 10 minutes to 120 minutes, and more preferably 30 minutes to 90 minutes. When the drying time is within these ranges, stretchable electrical wiring with advantageous properties can be efficiently produced.

[0170] The complete solidification of the stretchable electrical wiring paste by drying (formation of the stretchable electrical wiring) can be confirmed, for example, by the fact that no significant mass change of the resin composition subjected to drying is observed.

[0171] The thickness of the stretchable electrical wiring is not particularly limited, but can be, for example, 10 µm to 5,000 µm. <Zweite elektrische Verdrahtung>

[0172] Similar to the first electrical wiring 30A, the second electrical wiring 30B can also be made of an electrical wiring material with stretchability. In this case, it is preferable to use the same conductive material as the stretchable material of the second electrical wiring 30B. For example, a stretchable resin material containing a flaky metal powder can be used as the material for the first electrical wiring 30A and the second electrical wiring 30B. <Leitfähiger Klebstoff>

[0173] In the conductive adhesive 40 containing an expandable resin, an expandable resin containing a metal powder (expandable resin) can be used. Furthermore, known solder materials can also be used.

[0174] The material of the stretchable resin-containing conductive adhesive 40 may be an electrical wiring material with stretchability. For example, a stretchable resin material containing a metal powder (e.g., a flake metal powder) may be used. In this case, by changing the content ratio between the stretchable resin and the metal powder, for example, by increasing the content ratio of the metal powder, the conductivity of the stretchable resin-containing conductive adhesive 40 can be made higher than that of the first electrical wiring 30A. Conversely, by increasing the content ratio of the stretchable resin, the stretchability of the stretchable resin-containing conductive adhesive 40 can be made higher than that of the first electrical wiring 30A. [Stretchable device]

[0175] A stretchable device according to an embodiment has a configuration in which an electronic component is arranged on a non-stretchable part comprising the stretchable circuit substrate described above.

[0176] Here, the term "electronic component" is not particularly restricted, as long as it can be installed on a non-stretchable part, and known electronic components can be used. Examples include various sensors, capacitors, inductors, high-frequency filters, transformers, resistors, varistors, diodes, various ICs, and various actuators.

[0177] Furthermore, a stretchable device according to another embodiment has a configuration in which a module is arranged on a non-stretchable part comprising the stretchable circuit substrate described above.

[0178] Here, the term "module" is not particularly limited as long as it can be installed on a non-stretchable part, and known modules can be used. Examples include a sensor module comprising various sensors, a wireless communication unit, and a battery, as well as DC / DC converters.

[0179] Furthermore, a stretchable device according to yet another embodiment has a configuration in which a battery is arranged on a non-stretchable part comprising the stretchable circuit substrate described above.

[0180] Here, the term "battery" is not particularly restricted, as long as it can be installed on a non-stretchable part, and known batteries can be used. Examples include various solar cells, lithium-ion batteries, and electric double-layer capacitors.

[0181] Examples of solar cells from the perspective of electrode arrangement include double-sided electrode solar cells and back-side electrode solar cells. Furthermore, examples of solar cells from the perspective of materials include solar cells based on inorganic materials such as silicon-based solar cells and compound semiconductor-based solar cells, as well as organic solar cells. Examples

[0182] The present invention will be described in more detail below. However, the present invention is not limited to the examples shown below. Experimental examples are shown below in which the properties of the first electrical wiring with stretchability included in the stretchable circuit substrate according to the present invention were investigated using specific materials.

[0183] The raw materials used to prepare an expandable electrical wiring paste are shown below. • Resin (a) (a)-1: Urethane acrylate oligomer (product name: UN-5500, manufactured by Negami Chemical Industrial Co., Ltd.) • Resin (b) (b)-1: Methacrylate-modified polydimethylsiloxane modified with a methacryloyl group at a single end (product name: Silaplane (registered trademark) FM-0721, manufactured by JNC Corporation) • Polymerization initiator (c) (c)-1: Dimethyl 2,2'-azobis(2-methylpropionate), azo polymerization initiator (product name: V601, manufactured by FUJIFILM Wako Pure Chemical Corporation) • RAFT funds (1)-1: RAFT agent represented by formula (1)-1 below (manufactured by FUJIFILM Wako Pure Chemical Corporation) (3)-1: RAFT agent represented by the following formula (3)-1 (manufactured by FUJIFILM Wako Pure Chemical Corporation) • Other polymerizable components MMA: Methyl methacrylate • Solvents BCA: Butyl Carbitol Acetate • Metal powder Silver powder (proportion of flake powder: 12.5 [wt.%], average maximum particle diameter: 3 µm) [Experiment Example 1]

[0184] To prepare a stretchable electrical wiring paste, a resin (a)-1, a polymerization initiator (c)-1, a RAFT agent (1)-1, a silver powder, and BCA were weighed in a flask and mixed using a stirrer at normal temperature.

[0185] The formulation amounts of resin (b), polymerization initiator (c), and RAFT agent were determined such that the proportion of urethane bonds in the resins in the resulting stretchable electrical wiring was 20 wt% based on 100 parts by mass of resin (a). Furthermore, the formulation amount of silver powder was determined such that the proportion of the resins in the resulting stretchable electrical wiring was 5 wt%. In other words, the formulation amount of silver powder was determined such that the ratio of the resins to the silver powder was 8 wt%:92 wt%.

[0186] Subsequently, foil-shaped samples of stretchable electrical wiring were prepared according to the procedure described above and the elongation at break, a specific resistance (ρ0) before stretching and contracting, a specific resistance (ρ 50 ) at 50% elongation and a specific resistance (ρ 100) at 100% elongation. The results obtained are shown in Table 1. [Table 1] resin metal powder Elongation at break [%] specific resistance (Rdc) before stretching and contracting [Ω cm] r 50 / p0 r 100 / r 50 Rate of change of(ρ 50 / ρ0) in relation to(ρ 50 / ρ0) (%) Proportion of resin in the wiring material [wt.%] Proportion of urethane bond in resin [%] Proportion of flake-shaped powder [wt.%] Comparison example 1 6 20 12,5 5,3 8,60*10^ (-3) - - - Example 1 8 20 12,5 130,0 2,81*10^ (-3) 5,3 8,0 51% Example 2 10 20 12,5 165,3 4,28*10^ (-3) 4,0 4,5 13% Example 3 15 20 12,5 322,1 4,64*10^ (-3) 5,3 5,4 0% Example 4 18 20 12,5 370,8 3,00*10^ (-3) 2,9 5,2 82% Example 5 20 20 12,5 414,9 1,53*10^ (-2) 1,7 4,0 133% Comparison example 2 22 20 12,5 482 2,89*10^ (-1) 0,012 4,4 36030% Comparison example 3 15 0 12,5 6,0 3,59*10^ (-1) - - - Comparison example 4 15 10 12,5 7,0 1,13*10^ (-2) - - - Comparison example 5 15 15 12,5 37,4 6,48*10^ (-3) - - - Example 6 15 17,5 12,5 172,3 7,34*10^ (-3) 3,3 4,1 25% Example 3 15 20 12,5 322,1 4,64*10^ (-3) 5,3 5,4 0% Example 7 15 22 12,5 297,1 6,61*10^ (-3) 5,0 5,35 7% Example 8 15 25 12,5 245,5 4,75*10^ (-3) 2,8 4,9 75% Example 9 15 30 12,5 130,4 3,29*10^ (-3) 5,0 - - Comparison example 6 15 30 0 47,2 4,71*10^ (-1) - - - Comparison example 7 15 30 12,5 8,9 1,93*10^ (-3) - - - Example 10 15 20 2,5 322,1 4,72*10^ (-3) 3,3 4,2 27% Example 11 15 20 7,5 275,9 4,77*10^ (-3) 2,8 3,9 42% Example 3 15 20 12,5 322,1 4,64*10^ (-3) 5,3 5,4 0% Example 12 15 20 30 300 4,76*10^ (-3) 4,0 6,9 73% Example 13 15 20 40 230,5 5,62*10^ (-3) 2,2 5,10 131% Example 14 15 20 50 169,3 2,66*10^ (-3) 51 - - (Test examples 2 to 5 and comparative examples 1 and 2)

[0187] For Experimental Examples 2 to 5 and Comparative Examples 1 and 2, sheet-shaped stretchable electrical wiring samples were prepared in the same manner as in Experimental Example 1, except that the formulation amount of silver powder was adjusted so that the resin content in each resulting stretchable electrical wiring was 10 wt%, 15 wt%, 18 wt%, 20 wt%, 6 wt%, and 22 wt%. The same properties were measured on the resulting samples. The results are shown in Table 1. (Test examples 6 to 9 and comparative examples 3 to 5)

[0188] For all of Experimental Examples 6 to 9 and Comparative Examples 3 to 5, sheet-shaped stretchable electrical wiring samples were prepared in the same manner as in Experimental Example 1, except that the formulation amount was adjusted so that the proportion of resins in each resulting stretchable electrical wiring was 15 wt% and the proportion of urethane bonds in the resins in each resulting stretchable electrical wiring was 17.5 wt%, 20 wt%, 22 wt%, 25 wt%, 30 wt%, 0 wt%, 10 wt%, and 15 wt%. The same properties were measured on the resulting samples. The results are shown in Table 1. (Comparison examples 6 and 7)

[0189] Comparative Examples 6 and 7 are those in which each stretchable electrical wiring paste was applied and then subjected to a curing reaction instead of drying and solidifying. In Comparative Example 6, a stretchable electrical wiring paste was prepared in the same manner as in Comparative Example 5, except that the silver powder was not in a flake form. In Comparative Example 7, the same stretchable electrical wiring paste as in Experimental Example 9 was used. The same properties were measured on the resulting samples. The results are shown in Table 1. (Experiment examples 10 to 16)

[0190] For all of Experimental Examples 10 to 16, sheet-shaped samples of stretchable electrical wiring were prepared in the same manner as in Experimental Example 1, except that the proportion of resins in each resulting stretchable electrical wiring was 15 wt%, the proportion of urethane bonds in the resins in each resulting stretchable electrical wiring was 20 mol%, and a silver powder in which the proportion of each flake-shaped powder was 2.5 wt%, 7.5 wt%, 12.5 wt%, 30 wt%, 40 wt%, and 50 wt%.

[0191] The same properties were measured on the resulting samples. The results are shown in Table 1.

[0192] The findings from the results in Table 1 are shown. Values ​​not included in Table 1 are those that could not be measured or were not measured.

[0193] Experimental Examples 1 to 6 and Comparative Examples 1 and 2 were compared. When the proportion of urethane bonds in the resins and the proportion of flake powder were set to the proportions shown in Table 1, the following results were obtained.

[0194] When the resin content in the stretchable electrical wiring was 8 wt% or more (resin:silver powder=8:92), the elongation at break was 130% or more, and the higher the resin content, the higher the elongation at break. On the other hand, when the resin content was 20 wt% or more, the resistivity before stretching and contracting was 1 × 10 -2 [Ω cm] or more. In order to achieve both a higher elongation at break (150% or more) and a lower resistivity before stretching and contracting (5×10 -3[Ω cm] or less), the proportion of resins in stretchable electrical wiring is preferably 10 wt% to 18 wt%.

[0195] Furthermore, at a resin content of 20 wt.% (resin: silver powder=20:80) (Experiment Example 5), the specific resistance before stretching and contracting was 1.53×10 -2 [Ω cm], which is somewhat high. However, if its high elongation at break is taken into account, the ratio (ρ 50 / ρ0) of the specific resistance (ρ 50 ) at 50% strain to the specific resistance (ρ0) before stretching and contracting is 1.7, which represents a low rate of change, and the ratio (ρ 100 / ρ 50 ) of a specific resistance (ρ 100 ) at 100% elongation to a specific resistance (ρ 50 ) at 50% elongation is 4.0, which is a sufficiently low rate of change. To achieve both high elongation at break (150% or more) and low ratios (ρ 50 / ρ0) and (ρ 100 / ρ 50 ), the proportion of resins in stretchable electrical wiring is preferably 10 wt% to 20 wt%.

[0196] Furthermore, the proportion of resins in the stretchable electrical wiring is preferably 10 wt% to 15 wt% in order to achieve both the high elongation at break (150% or more) and a low rate of change of the ratio (ρ 100 / ρ 50 ) to the ratio (ρ 50 / ρ0).

[0197] In addition, to meet all the requirements of high elongation at break (150% or more), low specific resistance before stretching and contracting, low ratios (ρ 50 / ρ0) and (ρ 100 / ρ 50 ), and the low rate of change of the ratio (ρ 100 / ρ 50 ) to the ratio (ρ 50 / ρ0), the proportion of resins in stretchable electrical wiring is preferably 10 wt% to 15 wt%.

[0198] Next, Experimental Examples 3, 6 to 9 and Comparative Examples 3 and 4 are compared. When the proportion of resins in the stretchable electrical wiring and the proportion of a flake-shaped powder were set to the proportions shown in Table 1, the following results were obtained.

[0199] When the proportion of urethane bonds in the resins was 15 wt% or less, the elongation at break was 40% or less. However, when the proportion of urethane bonds was 25 wt% (Test Example 8), the elongation at break was 245.5%, while when the proportion was 30 wt% (Test Example 9), the elongation at break was 130.4%. Regarding a high elongation at break (150% or more), the proportion of urethane bonds in resins is preferably 17.5 wt% to 25 wt%. Furthermore, in order to achieve both a higher elongation at break (150% or more) and a lower specific resistance before stretching and contracting (7×10 -3[Ω cm] or less), the proportion of urethane bonds in resins is preferably 20 wt% to 25 wt%.

[0200] Furthermore, to achieve high elongation at break (150% or more) and low ratios (ρ 50 / ρ0) and (ρ 100 / ρ 50 ), the proportion of urethane bonds in resins is preferably 17.5 wt% to 25 wt%.

[0201] Furthermore, in order to achieve both a high elongation at break (150% or more) and a low rate of change of the ratio (ρ 100 / ρ 50 ) to the ratio (ρ 50 / ρ0), the proportion of urethane bonds in resins is preferably 17.5 wt% to 22 wt%.

[0202] In addition, to meet all the conditions of high elongation at break (150% or more), low specific resistance before stretching and contracting, low ratios (ρ 50 / ρ0) and (ρ 100 / ρ 50) and the low rate of change of the ratio (ρ 100 / ρ 50 ) to the ratio (ρ 50 / ρ0), the proportion of urethane bonds in resins is preferably 17.5 wt% to 22 wt%.

[0203] In Comparative Examples 6 and 7, each stretchable electrical wiring paste was applied and then subjected to a curing reaction instead of drying and solidifying. However, the resistivity before stretching and contracting in Comparative Example 6, in which the silver powder did not have a flake shape, was about 5×10 -1 [Ω cm], which was considerably high, and the elongation at break in Comparative Example 7, in which the composition of the electrical wiring paste itself was the same as that of Experimental Example 9, was 10% or less. Therefore, Comparative Examples 6 and 7 were found to be unsuitable for application to stretchable devices.

[0204] Next, Test Examples 3, 10, and 14 are compared. When the proportion of resins in the stretchable electrical wiring and the proportion of urethane bonds in the resins were set to the proportions shown in Table 1, the following results were obtained.

[0205] At a proportion of 40 wt% or 50 wt% of a flake-shaped powder in a silver powder, the elongation at break was negatively affected and gradually decreased. In addition, at 40 wt% (Experiment 13), the rate of change of the ratio (ρ 100 / ρ 50 ) to (ρ 50 / ρ0) to 130% or more, and at 50 wt.% (Experiment Example 14) the ratio (ρ 50 / ρ0) 51 times larger.

[0206] When the proportion of a flake-shaped powder in a silver powder is in a range of 2.5 wt% to 50 wt%, it is possible to obtain both a higher elongation at break (150% or more) and a lower resistivity before stretching and contracting (7×10 -3 [Ω cm] or less).

[0207] In order to achieve both high elongation at break (150% or more) and low ratios (ρ 50 / ρ0) and (ρ 100 / ρ 50 ), the proportion of a flake-shaped powder in a silver powder is preferably 2.5 wt% to 40 wt%.

[0208] Furthermore, in order to achieve both a high elongation at break (150% or more) and a low rate of change of the ratio (ρ 100 / ρ 50 ) to the ratio (ρ 50 / ρ0), the proportion of a flake-shaped powder in a silver powder is preferably 2.5 wt% to 12.5 wt%.

[0209] In addition, to meet all the conditions of high elongation at break (150% or more), low specific resistance before stretching and contracting, low ratios (ρ 50 / ρ0) and (ρ 100 / ρ 50 ), and the low rate of change of the ratio (ρ 100 / ρ 50 ) to the ratio (ρ 50 / ρ0), the proportion of a flake-shaped powder in a silver powder is preferably 2.5 wt% to 12.5 wt%.

[0210] High flexibility is achieved by the content of urethane bonds in resins. Furthermore, when resins contain either urethane bonds or siloxane bonds, both high extensibility and low resistivity can be achieved through an effect of improving the dispersion and aggregation of silver powder. Furthermore, when both urethane bonds and siloxane bonds are included, a greater improvement effect is achieved. REFERENCE SYMBOL LIST 10 Stretchable substrate 20 Non-stretchable part 30A First electrical wiring 30B Second electrical wiring 40 Conductive adhesive 100, 200 Stretchable circuit substrate QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-212027

[0002] JP 2021-57507

[0005] JP 2017-206626

[0005]

Claims

[1] A stretchable circuit substrate comprising: a stretchable substrate; a non-stretchable part connected to at least a portion of the outer peripheral part of a first surface of the stretchable substrate or a side surface part of the stretchable substrate; a first electrical wiring having stretchability disposed on the first surface of the stretchable substrate; and a second electrical wiring arranged on the non-stretchable part, wherein at least a part of the first electrical wiring and the second electrical wiring are connected. [2] The stretchable circuit substrate according to claim 1, wherein the stretchable substrate and the non-stretchable part are bonded by a conductive adhesive containing a stretchable resin. [3] The stretchable circuit substrate according to claim 1 or 2, wherein a portion of the non-stretchable part has an upwardly projecting protrusion part. [4] The stretchable circuit substrate according to claim 1 or 2, wherein the non-stretchable part is arranged on the outer peripheral part of the stretchable substrate. [5] The stretchable circuit substrate according to claim 1 or 2, wherein the non-stretchable part is connected to the side surface part of the stretchable substrate, and the lower surface of the non-stretchable part and the lower surface of the stretchable substrate are flush with each other. [6] The stretchable circuit substrate according to claim 1 or 2, wherein a gasket for attachment to an adhesive surface is provided on the surface on the back of the first surface of the stretchable circuit substrate. [7] A stretchable device comprising: an electronic component disposed on the non-stretchable part included in the stretchable circuit substrate according to claim 1 or 2. [8] A stretchable device comprising: a module disposed on the non-stretchable part included in the stretchable circuit substrate according to claim 1 or 2. [9] A stretchable device comprising: a battery disposed on the non-stretchable part included in the stretchable circuit substrate according to claim 1 or 2.

Images