Elastic multilayer circuit board, elastic display using the same, wearable device or biological sensor, display device and method of manufacturing elastic multilayer circuit board

Abstract

To provide an elastic multilayer circuit board which is excellent in the elastic electrical property.SOLUTION: An elastic multilayer circuit board of the present invention comprises a multilayer wiring structure including: a board; a plurality of pieces of lower wiring provided on the board; a lower insulating layer provided on the lower wiring; a plurality of pieces of upper wiring provided on the lower insulating layer; and an upper insulating layer provided on the upper wiring. Each of the board, lower wiring, lower insulating layer, upper wiring and upper insulating layer includes a thermosetting elastomer. The multilayer wiring structure includes an intersection structure in which the first lower wiring and the first upper wiring intersect each other when viewed in the vertical direction with respect to the one surface of the board, and a connection structure in which the first lower wiring and the first upper wiring can be electrically connected to each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stretchable multilayer circuit board, a stretchable display, a wearable device, or a biosensor, a display device, and a method for manufacturing a stretchable multilayer circuit board.

Background Art

[0002] Various developments have been made on multilayer circuit boards so far. As this type of technology, for example, the technology described in Patent Document 1 is known. Patent Document 1 describes a multilayer circuit board in which a plurality of resin films made of a thermoplastic resin on which a conductor pattern made of a metal foil is formed are bonded to each other by heating and pressing (Claim 1 of Patent Document 1, FIG. 2(b), etc.).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, as a result of the study by the present inventor, it has been found that there is room for improvement in terms of stretchable electrical characteristics in the multilayer circuit board described in Patent Document 1.

Means for Solving the Problems

[0005] As a result of further study by the present inventor, in the multilayer wiring structure, by configuring each component such as a substrate, wiring, and insulating layer to include a thermosetting elastomer, while improving the stretchable electrical characteristics, by arranging an intersection structure where the upper wiring and the lower wiring intersect, it has been found that a stretchable multilayer circuit board capable of high integration can be realized, and the present invention has been completed.

[0006] According to the present invention, a substrate, and a plurality of lower wirings provided on the substrate; a lower insulating layer provided on the lower wirings; a plurality of upper wirings provided on the lower insulating layer; an upper insulating layer provided on the upper wirings, the stretchable multilayer circuit board comprising a multilayer wiring structure, wherein the substrate, the lower wirings, the lower insulating layer, the upper wirings, and the upper insulating layer each contain a thermosetting elastomer; in the multilayer wiring structure, when viewed in a direction perpendicular to one surface of the substrate, an intersection structure in which a first one of the lower wirings and a first one of the upper wirings intersect each other; a connection structure in which a first one of the lower wirings and a first one of the upper wirings can be electrically connected to each other; there is provided a stretchable multilayer circuit board including the above.

[0007] Also, according to the present invention, there is provided a stretchable display, a wearable device, or a biosensor having the above stretchable multilayer circuit board.

[0008] Also, according to the present invention, a display device including a display unit, a control unit, a power supply unit, and / or a communication unit, wherein the display unit includes the above stretchable display, there is provided a display device.

[0009] Also, according to the present invention, a method for manufacturing a stretchable multilayer circuit board having a multilayer wiring structure, the method including: a step of forming a substrate; a step of forming a plurality of lower wirings on the substrate; a step of forming a lower insulating layer on the lower wirings; a step of forming a plurality of upper wirings on the lower insulating layer; The substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer are each formed using a thermosetting elastomer, and when viewed in a direction perpendicular to one surface of the substrate, the lower wiring and the upper wiring are formed such that at least the first upper wiring intersects the first lower wiring while being electrically connectable to each other. A method for manufacturing a stretchable multilayer circuit board is provided.

Advantages of the Invention

[0010] According to the present invention, there are provided a stretchable multilayer circuit board excellent in stretchable electrical characteristics, a stretchable display, a wearable device, or a biosensor, a display device using the same, and a method for manufacturing a stretchable multilayer circuit board.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are assigned to the same components, and the description will be omitted as appropriate. Also, the figures are schematic and do not match the actual dimensional ratios.

[0013] The stretchable multilayer circuit board of this embodiment will be outlined.

[0014] The stretchable multilayer circuit board of this embodiment has a multilayer wiring structure including a substrate, a plurality of lower wirings provided on the substrate, a lower insulating layer provided on the lower wirings, a plurality of upper wirings provided on the lower insulating layer, and an upper insulating layer provided on the upper wirings, and is a multilayer flexible stretchable substrate configured such that the substrate, the lower wirings, the lower insulating layer, the upper wirings, and the upper insulating layer each contain a thermosetting elastomer. In this stretchable multilayer circuit board, in the multilayer wiring structure, when viewed in a direction perpendicular to one surface of the substrate, it has an intersection structure in which a first lower wiring and a first upper wiring intersect each other, and a connection structure in which the first lower wiring and the first upper wiring can be electrically connected to each other.

[0015] According to the findings of the present inventor, by configuring each component member in the multilayer wiring structure such as the substrate, the upper wiring, the lower wiring, the upper insulating layer, and the lower insulating layer using an elastomer, the stretchable electrical characteristics of the stretchable multilayer circuit board can be improved. Further, by arranging an intersection structure in which at least the first upper wiring and the first lower wiring intersect each other, high integration of the stretchable multilayer circuit board becomes possible. Also, in each of the connection structures between a plurality of upper wirings and a plurality of lower wirings, such as between the first lower wiring and the first upper wiring, a plurality of electronic components can be mounted, so that functional integration becomes easy.

[0016] Here, the thermoplastic resin described in Patent Document 1 may thermally contract due to heat treatment during wiring formation, and there is a risk of a decrease in connection reliability in the multilayer circuit board. Such a problem becomes more prominent in a structure in which wirings are integrated.

[0017] In contrast, in the stretchable multilayer circuit board of the present embodiment, by using a thermosetting elastomer, particularly silicone rubber, as the elastomer, the heat resistance can be enhanced, and shrinkage of the substrate size due to the heat history received during the manufacturing process can be suppressed. Therefore, a multilayer wiring structure with excellent connection reliability can be realized. Further, in the stretchable multilayer circuit board of the present embodiment, since constituent members such as the substrate, circuit, and insulating layer are made of an elastic body, it is less likely to undergo plastic deformation compared to thermoplastic materials.

[0018] According to the present embodiment, since wiring members such as upper wiring and lower wiring can be formed by a printing method, a stretchable multilayer circuit board with excellent wiring design freedom can be provided.

[0019] The stretchable multilayer circuit board of the present embodiment can mount various electronic components like a printed wiring board. Examples of the electronic components include light-emitting elements such as LED chips, biological measuring instruments that detect biological potentials such as brain waves and myoelectric potentials and biological activities such as blood pressure and pulse, general measuring instruments that detect environmental information such as pressure, temperature, position, humidity, light, sound, and acceleration, portable power sources such as capacitors, acoustic modules, communication modules, and the like.

[0020] According to the present embodiment, a stretchable multilayer circuit board capable of two-dimensional (surface) sensing can be provided on one surface side of the substrate.

[0021] According to the present embodiment, various electronic devices such as stretchable displays, wearable devices, or biosensors can be provided using the stretchable multilayer circuit board. Even when deformation such as bending or stretching is required during the use of the electronic device, high connection reliability can be achieved by using the stretchable multilayer circuit board.

[0022] Hereinafter, the stretchable multilayer circuit board of the present embodiment will be described in detail.

[0023] FIG. 1(a) is a top view schematically showing an example of the stretchable multilayer circuit board 100 of the present embodiment. FIG. 1(b) is an enlarged view of the A region in FIG. 1(a). FIGS. 2(a) to 2(c) are cross-sectional views at three dotted-line locations a1 to a3 in the A region in FIG. 1(a). FIG. 2(d) is a cross-sectional view at the dotted-line location b1 in the B region in FIG. 1(a). FIG. 2(e) is a cross-sectional view at the dotted-line location c1 in the C region in FIG. 1(a).

[0024] The stretchable multilayer circuit board 100 of the present embodiment includes a stretchable substrate (substrate 110), a plurality of stretchable lower wirings (first lower wiring 120, second lower wiring 126), a stretchable lower insulating layer (lower insulating layer 130), a plurality of stretchable upper wirings (first upper wiring 150, second upper wiring 156), and a stretchable upper insulating layer (upper insulating layer 160).

[0025] In this specification, having stretchability means that, for example, when stretched in the extending direction of the stretchable wiring, the elongation rates of the constituent members such as the substrate 110, the lower wiring 120, and the upper wiring 150 can be stretched, for example, by 10% or more, preferably 20% or more, more preferably 50% or more, and still more preferably up to 100% with respect to the length when not stretched. When the stretchable multilayer circuit board 100 is stretched in the extending direction of the lower wiring 120 and / or the upper wiring 150, the lower wiring 120 or the upper wiring 150 can be maintained in a state where it does not break within the above elongation rate range. Here, the extending direction can be defined as the direction from one end to the other end of the portion having the longest length in the in-plane direction among the lower wiring 120 or the upper wiring 150.

[0026] In one of the cross-sections in the stacking direction of the stretchable multilayer circuit board 100 (hereinafter, sometimes simply referred to as "in cross-sectional view"), as shown in FIG. 2(b), the multilayer wiring structure 200 includes the substrate 110, the lower wiring 120 provided on the substrate 110, the lower insulating layer 130 provided on the lower wiring 120, the upper wiring 150 provided on the lower insulating layer 130, and the upper insulating layer 160 provided on the upper wiring 150.

[0027] As shown in FIGS. 1(b) and 2(a), when viewed in a direction perpendicular to one surface of the substrate 110 in the multilayer wiring structure 200 (hereinafter, sometimes simply referred to as "top view"), the stretchable multilayer circuit board 100 includes an intersection structure 210 in which a first lower wiring 120 and a first upper wiring 150 intersect each other.

[0028] "Intersection" means a state in which, between two wirings arranged via an insulating layer in the stacking direction, there is a region where the extending direction of the lower-side wiring and the extending direction of the upper-side wiring are not the same direction, and different wiring regions overlap each other in the top view. In an example of the present embodiment, in the top view, at least a part of the regions of the lower wiring 120 and the upper wiring 150 may intersect in a perpendicular direction, that is, the intersection angle is 90 degrees.

[0029] Further, when the stretchable multilayer circuit board 100 is viewed in a direction perpendicular to one surface of the substrate 110 (when viewed in the top view), in the multilayer wiring structure 200, the stretchable multilayer circuit board 100 may include a plurality of intersection structures in which a plurality of lower wirings and a plurality of upper wirings intersect each other. These plurality of intersection structures may be arranged in a lattice pattern. Thereby, it becomes possible to further enhance the function integration.

[0030] Thus, when the stretchable multilayer circuit board 100 has a plurality of intersection structures, the intersection angles in the top view of each intersection structure may be the same or different, but from the viewpoint of integration, they may be configured to be all the same, and from the viewpoint of durability, they may be configured to be all approximately 90 degrees.

[0031] In this specification, the term "substantially" represents that, unless otherwise explicitly stated, it includes a range considering manufacturing tolerances, variations, etc.

[0032] Further, as shown in FIG. 2(a), the stretchable multilayer circuit board 100 includes a connection structure 220 in which the first lower wiring 120 and the first upper wiring 150 can be electrically connected to each other.

[0033] The connection structure 220 is not particularly limited in terms of its structure and constituent members, and has a structure in which the first lower wiring 120 and the first upper wiring 150 can be electrically connected via an electronic component 170 or the like.

[0034] In an example of the connection structure 220, the lower wiring 120 has a lower connection portion 122 that connects to the outside of the electronic component 170 or the like, and the upper wiring 150 has an upper connection portion 152 that connects to the outside of the electronic component 170 or the like.

[0035] As shown in FIG. 1(b), the lower connection portion 122 may be configured to be wider than the line width of the lower wiring 120 in a top view. This lower connection portion 122 functions as an electrode pad and can enhance the connection stability in the stacking direction with the electronic component 170.

[0036] As shown in FIGS. 2(a) and 2(b), the lower connection portion 122 may have a protruding connection portion. The protruding connection portion has a structure that protrudes upward from the substrate 110 toward the lower wiring 120 in a cross-sectional view when cut in the stacking direction of the multilayer wiring structure 200. At least the first lower wiring 120 may have the lower connection portion 122 formed by the protruding connection portion. Thereby, the ease of connection between the lower connection portion 122 and the upper connection portion 152 can be improved.

[0037] The upper connection portion 152 may be composed of a branched connection portion branched from the upper wiring 150. The branched connection portion is, for example, a wiring that protrudes from the side surface of the upper wiring 150 in the same layer as the upper wiring 150 and extends in a direction different from the extending direction of the upper wiring 150, as shown in FIG. 1(b). This branched connection portion is formed in the vicinity of the lower connection portion 122. Thereby, the integration of the stretchable multilayer circuit board 100 can be enhanced.

[0038] In the connection structure 220, a part of the lower wiring 120 and the lower insulating layer 130 may be configured to be exposed without being covered by the lower insulating layer 130 and the upper insulating layer 160.

[0039] In the connection structure 220, as shown in Fig. 2(a), a lower opening (opening 140) penetrating at least the lower insulating layer 130 and the upper insulating layer 160 is formed, and an upper opening (opening 142) penetrating at least the upper insulating layer 160 may be formed. Each of the opening 140 and the opening 142 may be an independent hole, or may be composed of one hole in which two or more opening spaces are connected to each other.

[0040] When having such an opening, the first lower wiring 120 has a lower connection part 122 configured to be exposed within the opening 140, and the first upper wiring 150 may have an upper connection part 152 configured to be exposed within the opening 142.

[0041] As shown in Fig. 2(a), the electronic component 170 is mounted on the stretchable multilayer circuit board 100 in a state of being electrically connected to, for example, the lower connection part 122 and the upper connection part 152 by various connection means.

[0042] The electronic component 170 may be configured to be electrically connected to the first lower wiring 120 and the first upper wiring 150 by using at least one of, for example, a conductive paste and a soldering material. The same material as that used for forming the wiring may be used for the conductive paste.

[0043] In the multilayer wiring structure 200, the stretchable multilayer circuit board 100 may include a sealing part (not shown) for sealing the electronic component 170. The sealing part may be configured to cover at least a part of the upper surface and the side surface of the electronic component 170, or may be configured to cover at least a part of the connection part between the electronic component 170 and each wiring. Thereby, the connection stability of the electronic component 170 can be enhanced. As the sealing material, for example, a thermosetting elastomer may be used.

[0044] As shown in Fig. 1(a), the lower wiring 120 may have a lower connection part 124 at its end, and the upper wiring 150 may have an upper connection part 154 at its end. These lower connection part 124 and upper connection part 154 function as electrodes connectable to the outside such as an external power source.

[0045] At least a part of the lower wiring 120 and the upper connection part 154 are configured to be in an exposed state without being covered by a member constituting the multilayer wiring structure 200, for example, an insulating layer. An example of the lower wiring 120 and the upper connection part 154 may constitute a protruding connection part protruding to the outermost upper insulating layer 160 as shown in Figs. 2(d) and 2(e). Thereby, a structure easy to connect can be realized.

[0046] As shown in Fig. 2(a), the stretchable multilayer circuit board 100 may be configured such that the substrate 110 has no wiring on the other surface opposite to the surface where the lower wiring 120 and the upper wiring 150 are provided. That is, the stretchable multilayer circuit board 100 may be a one-sided circuit board. Thereby, while ensuring the flexible stretchability of the stretchable multilayer circuit board 100, the integration degree of the wiring circuit can be increased.

[0047] Next, a modified example of the stretchable multilayer circuit board 100 will be described.

[0048] As shown in Fig. 1(a), the plurality of stretchable lower wirings may be composed of at least two or more wirings, such as the first lower wiring 120 and the second lower wiring 126, and may have three or more, four or more, eight or more wirings. Similarly, as shown in Fig. 1(a), the plurality of stretchable upper wirings may be composed of at least two or more wirings, such as the first upper wiring 150 and the second upper wiring 156, and may have three or more, four or more, eight or more wirings. Note that the upper limit of the number of wirings of the plurality of stretchable lower wirings and the plurality of stretchable upper wirings can be set as required and is not particularly limited.

[0049] The plurality of stretchable lower wirings and the plurality of stretchable upper wirings may have one or two or more wirings having wiring portions parallel to each other in a top view.

[0050] The first lower wiring 120 and the second lower wiring 126 are at least partially or entirely arranged in the same lower wiring layer. At least a part or the whole of the first lower wiring 120 and the second lower wiring 126 may be formed so as to be in contact with one surface of the substrate 110.

[0051] Also, the first upper wiring 150 and the second upper wiring 156 are at least partially or entirely arranged in the same upper wiring layer. At least a part or the whole of the first upper wiring 150 and the second upper wiring 156 may be formed so as to be in contact with one surface of the lower insulating layer 130 located between the lower wiring and the upper wiring. Such first upper wiring 150 and second upper wiring 156 may have a part thereof in contact with one surface of the substrate 110 and be formed in the same layer as the first lower wiring 120 and the second lower wiring 126.

[0052] The multilayer wiring structure 200 may further have one or two or more other wiring layers on the upper insulating layer 160. That is, the number of wiring layers of the multilayer wiring structure 200 is not limited to the two layers shown in Fig. 2(a), and may be three or more layers, four or more layers as required. In this case, at least one or more insulating layers are formed between the re-adjacent wiring layers in the stacking direction.

[0053] The stretchable multilayer circuit board 100 may have at least one or more crossing structures 210, for example, it may have as many as the integrated value of the number of wirings of the upper wiring and the number of wirings of the lower wiring. Examples of the plurality of crossing structures include a first crossing structure 210 between the lower wiring 120 and the upper wiring 150, a second crossing structure 212 between the lower wiring 120 and the upper wiring 156, and the like.

[0054] The position of the connection surface of the upper connection portion 152 may be arranged in any of the layers of the lower insulating layer 130, the upper wiring 150, and the upper insulating layer 160, or may form substantially the same surface as the connection surface of the upper connection portion 152.

[0055] The lower wiring 120 and the lower connection portion 122 may be formed by a printing method using a conductive paste, that is, may be composed of a printed layer. Also, the upper wiring 150 and the upper connection portion 152 may also be formed by a printing method using a conductive paste, that is, may be composed of a printed layer. Thereby, the space between the wiring and the connection portion can be formed almost seamlessly, and it becomes possible to substantially eliminate their boundaries.

[0056] At least one of the lower insulating layer 130 and the upper insulating layer 160 may be composed of a plurality of insulating layers separated in the same layer, or may be composed of one insulating layer.

[0057] The multilayer wiring structure 200 may have at least one of a region where the upper insulating layer 160 exists on the lower insulating layer 130, a region where the upper insulating layer 160 does not exist on the lower insulating layer 130, and a region where the lower insulating layer 130 does not exist under the upper insulating layer 160 in a cross-sectional view.

[0058] The above-mentioned opening may be composed of at least one of a through hole penetrating the insulating layer, a separation portion where a plurality of insulating layers are separated from each other, and a non-covered portion where the substrate 110 is not covered by the insulating layer in a top view.

[0059] The openings 140 and 142 in FIG. 2 may be composed of voids, or may be filled with a material constituting the insulating layer or the like. By adopting a void structure, it becomes difficult for the stress generated during the expansion and contraction of the stretchable multilayer circuit board 100 to be transmitted to the connection portion of the electronic component 170, and the connection reliability during expansion and contraction can be improved. On the other hand, by adopting a filling structure, the intrusion of foreign substances such as dust into the opening can be suppressed, and the exposure of the connection portion to the external environment can be suppressed, so the long-term connection reliability can be improved.

[0060] An example of the void structure is a structure in which there is a separation between an insulating layer such as the upper insulating layer 160 so as not to contact the insulating layer around the connection portion between the electronic component 170, the lower connection portion 122, and the upper connection portion 152.

[0061] Part or all of the electronic component 170 may be embedded in openings formed in the insulating layer, such as the opening 140 and the opening 142. Thereby, the connection stability of the electronic component 170 can be enhanced. In addition, when sealing the periphery of the electronic component 170, the whole of the electronic component 170 may be provided outside the opening.

[0062] The thickness ratio represented by the thickness of the wiring / the thickness of the insulating layer is, for example, 0.05 to 20.0, preferably 0.08 to 15.0, more preferably 0.1 to 10.0. By setting it within such a range, conductivity and insulation can be improved. The thickness ratio represented by the thickness of the insulating layer / the thickness of the substrate is, for example, 0.01 to 2.0, preferably 0.05 to 1.0, more preferably 0.08 to 0.7. By setting it within such a range, flexibility and insulation can be improved.

[0063] The thickness ratio only needs to be satisfied by at least one of the lower wiring 120 and the upper wiring 150, and it is preferable that both wirings are satisfied. It only needs to be satisfied by at least one of the lower insulating layer 130 and the upper insulating layer 160, and it is preferable that both insulating layers are satisfied.

[0064] The upper limit of the thickness of the substrate 110 can be set according to the application. For example, it may be 10 mm or less, preferably 1 mm or less, but from the viewpoint of wearable device applications, it is more preferably 400 μm or less. By setting it to 400 μm or less, the stretchable multilayer circuit board 100 of the thin film can be realized. The lower limit of the thickness of the substrate 110 is, from the viewpoint of mechanical strength, for example, 10 μm or more, preferably 50 μm or more, more preferably 100 μm or more.

[0065] Next, the materials and characteristics of the stretchable multilayer circuit board 100 will be described.

[0066] In this embodiment, the substrate 110, the lower wiring 120, the lower insulating layer 130, the upper wiring 150, and the upper insulating layer 160 may each include the same and / or different thermosetting elastomers, and preferably may be configured to include the same thermosetting elastomer. More specifically, the lower wiring 120 and the upper wiring 150 may each be composed of the same and / or different conductive elastomers, and the substrate 110, the lower insulating layer 130, and the upper insulating layer 160 may each be composed of the same and / or different insulating elastomers.

[0067] The insulating elastomer can include, for example, thermosetting elastomers such as silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber, etc. Among these, the insulating elastomer may include one or more selected from the group consisting of silicone rubber, urethane rubber, and fluororubber, and preferably may be composed of silicone rubber. Silicone rubber is chemically stable and has excellent mechanical strength among elastomers.

[0068] The insulating elastomer may not contain a conductive filler and may contain a non-conductive filler. Thereby, the mechanical properties of the conductive elastomer can be enhanced. As the non-conductive filler, known materials can be used. For example, an inorganic filler may be used. As the inorganic filler, silica particles, silicone rubber particles, talc, etc. may be used.

[0069] Conductive elastomers can include, for example, thermosetting elastomers such as silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, ethylene propylene rubber, etc. and conductive fillers. Among these, the conductive elastomer may contain one or more selected from the group consisting of silicone rubber, urethane rubber, and fluororubber, and preferably may be configured to contain silicone rubber and a conductive filler. Thereby, the stretchability and electrical characteristics of the conductive elastomer can be enhanced.

[0070] Examples of the conductive filler include powdery or fibrous metal-based fillers, carbon-based fillers, metal oxide fillers, metal-plated fillers, etc. Among these, as the conductive filler, a metal-based filler, preferably silver powder, may be used. Also, the conductive elastomer may contain a non-conductive filler together with the conductive filler. Thereby, the stretch durability can be enhanced.

[0071] As an example of this embodiment, the substrate 110, the lower wiring 120, the lower insulating layer 130, the upper wiring 150, and the upper insulating layer 160 may each contain the same thermosetting elastomer. Thereby, the adhesion to each other can be improved, and the stretch durability of the stretchable multilayer circuit board 100 can be enhanced.

[0072] In this specification, "containing the same thermosetting elastomer", "containing the same insulating elastomer", and "containing the same conductive elastomer" each mean containing at least one or more of the same type of elastomer among the types of thermosetting elastomers exemplified above.

[0073] More specifically, the substrate 110, the lower insulating layer 130, and the upper insulating layer 160 may each be configured to contain the same silicone rubber. Thereby, the adhesion between the layers can be improved. Also, in the insulating layer sandwiched between the upper and lower wirings, the breakdown voltage can be increased.

[0074] The substrate 110, the lower insulating layer 130, and the upper insulating layer 160 may be configured such that at least one of them, preferably all of them, contains an inorganic filler. Thereby, it becomes possible to moderately enhance their mechanical properties.

[0075] Also, the lower wiring 120 and the upper wiring 150 may each be configured to contain the same silicone rubber and conductive filler. Thereby, conductivity can be enhanced together with stretchability.

[0076] At least one of the lower wiring 120 and the upper wiring 150, preferably all of them, may be configured to contain an inorganic filler. Thereby, it becomes possible to improve the mechanical properties together with conductivity.

[0077] The substrate 110, the lower wiring 120, the lower insulating layer 130, the upper wiring 150, and the upper insulating layer 160 may each be configured to contain the same kind of silicone rubber. Thereby, the adhesion between the layers can be enhanced. Also, the durability during stretching and shrinking can be improved.

[0078] Here, the components in the silicone rubber-based curable composition will be described in detail.

[0079] Here, containing the same silicone rubber means that the silicone rubber-based curable composition contains at least the same kind of vinyl group-containing linear organopolysiloxane, and further may contain one or more selected from the group consisting of the same kind of crosslinking agent, the same kind of non-conductive filler, the same kind of silane coupling agent, and the same kind of catalyst.

[0080] The insulating silicone rubber may be composed of the cured product of a silicone rubber-based curable composition containing a vinyl group-containing organopolysiloxane. Also, the conductive silicone rubber may be composed of a conductive filler and the cured product of a silicone rubber-based curable composition containing a vinyl group-containing organopolysiloxane.

[0081] The same kind of vinyl group-containing linear organopolysiloxane means that it only needs to contain the same vinyl group as the functional group at least, and it only needs to have a linear structure. The amount of vinyl groups in the molecule, the molecular weight distribution, or the addition amount thereof may be different.

[0082] The same kind of crosslinking agent means that it only needs to have at least a common structure such as a linear structure or a branched structure. The molecular weight distribution in the molecule or different functional groups may be included, and the addition amount thereof may be different.

[0083] The same kind of non-conductive filler means that it only needs to have at least a common constituent material. The particle size, specific surface area, surface treatment agent, or the addition amount thereof may be different.

[0084] The same kind of silane coupling agent means that it only needs to have at least a common functional group. Other functional groups or the addition amount in the molecule may be different.

[0085] The same kind of catalyst means that it only needs to have at least a common constituent material. Different compositions may be included in the catalyst, and the addition amount thereof may be different.

[0086] The silicone rubber-based curable composition constituting the same silicone rubber may further contain one or more selected from the group consisting of different kinds of vinyl group-containing linear organopolysiloxane, crosslinking agent, non-conductive filler, silane coupling agent, and catalyst.

[0087] The silicone rubber-based curable composition of the present embodiment can contain a vinyl group-containing organopolysiloxane (A). The vinyl group-containing organopolysiloxane (A) is a polymer that is the main component of the silicone rubber-based curable composition of the present embodiment.

[0088] The above vinyl group-containing organopolysiloxane (A) can contain a vinyl group-containing linear organopolysiloxane (A1) having a linear structure.

[0089] The vinyl group-containing linear organopolysiloxane (A1) has a linear structure and contains vinyl groups, and such vinyl groups serve as crosslinking points during curing.

[0090] The content of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited. For example, it preferably has two or more vinyl groups in the molecule and is 15 mol% or less. Thereby, the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1) is optimized, and the formation of a network with each of the components described below can be surely carried out.

[0091] In this specification, the vinyl group content means the mol% of vinyl group-containing siloxane units when the total units constituting the vinyl group-containing linear organopolysiloxane (A1) are 100 mol%. However, one vinyl group is considered for one vinyl group-containing siloxane unit.

[0092] Also, the degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited. For example, it is preferably in the range of about 1000 to 10000, more preferably about 2000 to 5000. The degree of polymerization can be determined, for example, as the number average degree of polymerization (or number average molecular weight) in terms of polystyrene in GPC (gel permeation chromatography) using chloroform as the developing solvent. In this specification, "~" represents including the upper limit value and the lower limit value unless otherwise specified.

[0093] Furthermore, the specific gravity of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably in the range of about 0.9 to 1.1.

[0094] By using the vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and a specific gravity within the above ranges, it is possible to improve the heat resistance, flame retardancy, chemical stability, etc. of the resulting silicone rubber.

[0095] As the vinyl group-containing linear organopolysiloxane (A1), those having a structure represented by the following formula (1) are particularly preferable.

[0096]

Chemical formula

[0097] In formula (1), R 1 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, or a hydrocarbon group combining these. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, etc. Among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group, etc. Among them, a vinyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group, etc.

[0098] Also, R 2 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group having 1 to 10 carbon atoms, or a hydrocarbon group combining these. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, etc. Among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0099] Also, R 3 is a substituted or unsubstituted alkyl group, aryl group having 1 to 8 carbon atoms, or a hydrocarbon group combining these. Examples of the alkyl group having 1 to 8 carbon atoms include a methyl group, an ethyl group, a propyl group, etc. Among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include a phenyl group.

[0100] Furthermore, examples of the substituents of R 1 and R 2 in formula (1) include a methyl group, a vinyl group, etc. R 3Examples of the substituent include a methyl group and the like.

[0101] In the formula (1), a plurality of Rs 1 are independent of each other and may be different from each other or the same. Further, the same applies to R 2 , and R 3 .

[0102] Furthermore, m and n are the number of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by the formula (1). m is an integer of 0 to 2000, and n is an integer of 1000 to 10000. m is preferably 0 to 1000, and n is preferably 2000 to 5000.

[0103] In addition, specific structures of the vinyl group-containing linear organopolysiloxane (A1) represented by the formula (1) include, for example, those represented by the following formula (1-1).

[0104]

Chemical formula

[0105] In the formula (1-1), R 1 and R 2 are each independently a methyl group or a vinyl group, and at least one of them is a vinyl group.

[0106] The vinyl group-containing linear organopolysiloxane (A1) may contain a first vinyl group-containing linear organopolysiloxane (A1-1) having a vinyl group content of 2 or more vinyl groups in the molecule and 0.4 mol% or less. The vinyl group amount of the first vinyl group-containing linear organopolysiloxane (A1-1) may be 0.1 mol% or less.

[0107] In addition, the vinyl group-containing linear organopolysiloxane (A1) may contain a first vinyl group-containing linear organopolysiloxane (A1-1) and a second vinyl group-containing linear organopolysiloxane (A1-2) having a vinyl group content of 0.5 to 15 mol%.

[0108] As the raw rubber, which is a raw material for silicone rubber, by combining the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2) having a high vinyl group content, the vinyl groups can be unevenly distributed, and in the crosslinked network of the silicone rubber, the density of the crosslinking density can be more effectively formed. As a result, the tear strength of the silicone rubber can be more effectively increased.

[0109] Specifically, as the vinyl group-containing linear organopolysiloxane (A1), for example, in the above formula (1-1), the first vinyl group-containing linear organopolysiloxane (A1-1) having two or more units in the molecule in which R1 is a vinyl group and / or R2 is a vinyl group and containing 0.4 mol% or less, and the second vinyl group-containing linear organopolysiloxane (A1-2) containing 0.5 to 15 mol% of units in which R1 is a vinyl group and / or R2 is a vinyl group are preferably used.

[0110] In addition, the first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of 0.01 to 0.2 mol%. Further, the second vinyl group-containing linear organopolysiloxane (A1-2) preferably has a vinyl group content of 0.8 to 12 mol%.

[0111] Furthermore, when the first vinyl group-containing linear organopolysiloxane (A1-1) and the second vinyl group-containing linear organopolysiloxane (A1-2) are combined and blended, the ratio of (A1-1) to (A1-2) is not particularly limited. For example, the weight ratio of (A1-1):(A1-2) is preferably 50:50 to 95:5, and more preferably 80:20 to 90:10.

[0112] In addition, only one kind of each of the first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may be used, or two or more kinds may be used in combination.

[0113] Further, the vinyl group-containing organopolysiloxane (A) may contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

[0114] <<Organohydrogenpolysiloxane (B)>> The silicone rubber-based curable composition of the present embodiment can contain an organohydrogenpolysiloxane (B). The organohydrogenpolysiloxane (B) is classified into a linear organohydrogenpolysiloxane (B1) having a linear structure and a branched organohydrogenpolysiloxane (B2) having a branched structure, and can contain any one or both of these.

[0115] The linear organohydrogenpolysiloxane (B1) has a linear structure and a structure in which hydrogen is directly bonded to Si (≡Si-H). It undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and the vinyl groups of the components contained in the silicone rubber-based curable composition, and is a polymer that crosslinks these components.

[0116] The molecular weight of the linear organohydrogenpolysiloxane (B1) is not particularly limited. For example, the weight average molecular weight is preferably 20,000 or less, more preferably 1,000 or more and 10,000 or less.

[0117] Incidentally, the weight average molecular weight of the linear organohydrogenpolysiloxane (B1) can be measured, for example, by polystyrene conversion in GPC (gel permeation chromatography) using chloroform as the developing solvent.

[0118] In addition, the linear organohydrogenpolysiloxane (B1) preferably usually has no vinyl group. Thereby, it is possible to accurately prevent the crosslinking reaction from proceeding within the molecule of the linear organohydrogenpolysiloxane (B1).

[0119] As the linear organohydrogenpolysiloxane (B1) as described above, for example, those having a structure represented by the following formula (2) are preferably used.

[0120] [Chemical formula]

[0121] In formula (2), R 4 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, hydrocarbon group combining these, or hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, etc. Among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group, etc. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0122] Also, R 5 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, hydrocarbon group combining these, or hydride group having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group. Among them, a methyl group is preferable. Examples of the alkenyl group having 1 to 10 carbon atoms include a vinyl group, an allyl group, a butenyl group, etc. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0123] In addition, in formula (2), a plurality of R 4 are independent of each other, and may be different from each other or the same. The same applies to R 5 . However, a plurality of R 4 and R5 Among them, at least two or more are hydride groups.

[0124] Also, R 6 is a substituted or unsubstituted alkyl group, aryl group, or hydrocarbon group combining these with carbon numbers of 1 to 8. Examples of the alkyl group with carbon numbers of 1 to 8 include a methyl group, an ethyl group, a propyl group, etc. Among them, the methyl group is preferable. Examples of the aryl group with carbon numbers of 1 to 8 include a phenyl group. A plurality of R 6 are independent of each other, and may be different from each other or the same.

[0125] In addition, as the substituents of R 4 , R 5 , R 6 in formula (2), for example, a methyl group, a vinyl group, etc. are mentioned, and from the viewpoint of preventing the crosslinking reaction in the molecule, the methyl group is preferable.

[0126] Furthermore, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), m is an integer of 2 to 150, and n is an integer of 2 to 150. Preferably, m is an integer of 2 to 100, and n is an integer of 2 to 100.

[0127] In addition, the linear organohydrogenpolysiloxane (B1) may be used alone by only one kind, or may be used in combination of two or more kinds.

[0128] Since the branched organohydrogenpolysiloxane (B2) has a branched structure, it forms a region with a high crosslinking density and is a component that greatly contributes to the formation of the dense structure of the crosslinking density in the silicone rubber system. Also, similar to the above linear organohydrogenpolysiloxane (B1), it has a structure in which hydrogen is directly bonded to Si (≡Si-H), and in addition to the vinyl group of the vinyl group-containing organopolysiloxane (A), it undergoes a hydrosilylation reaction with the vinyl groups of the components blended in the silicone rubber-based curable composition and is a polymer that crosslinks these components.

[0129] Also, the specific gravity of the branched organohydrogenpolysiloxane (B2) is in the range of 0.9 to 0.95.

[0130] Furthermore, the branched organohydrogenpolysiloxane (B2) preferably does not usually have a vinyl group. Thereby, it is possible to accurately prevent the crosslinking reaction from proceeding in the molecule of the branched organohydrogenpolysiloxane (B2).

[0131] Also, as the branched organohydrogenpolysiloxane (B2), those represented by the following average composition formula (c) are preferable.

[0132] Average composition formula (c) (H a (R 7 ) 3-a SiO 1 / 2 ) m (SiO 4 / 2 ) n (In formula (c), R 7 is a monovalent organic group, a is an integer in the range of 1 to 3, m is the number of H a (R 7 ) 3-a SiO 1 / 2 units, and n is the number of SiO 4 / 2 units)

[0133] In formula (c), R 7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group, aryl group, or hydrocarbon group combining these having 1 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, a propyl group, etc., and among them, a methyl group is preferable. Examples of the aryl group having 1 to 10 carbon atoms include a phenyl group.

[0134] In formula (c), a is the number of hydride groups (hydrogen atoms directly bonded to Si), an integer in the range of 1 to 3, preferably 1.

[0135] Also, in formula (c), m is H a(R 7 ) 3-a SiO 1 / 2 The number of units, n, is the number of SiO 4 / 2 units.

[0136] Branched organohydrogenpolysiloxane (B2) has a branched structure. Linear organohydrogenpolysiloxane (B1) and branched organohydrogenpolysiloxane (B2) differ in that their structures are linear or branched, and the number of alkyl groups R bonded to Si when the number of Si is 1 (R / Si) is in the range of 1.8 to 2.1 for linear organohydrogenpolysiloxane (B1) and 0.8 to 1.7 for branched organohydrogenpolysiloxane (B2).

[0137] Note that since branched organohydrogenpolysiloxane (B2) has a branched structure, for example, the amount of residue when heated at a heating rate of 10 °C / min up to 1000 °C in a nitrogen atmosphere is 5% or more. In contrast, since linear organohydrogenpolysiloxane (B1) is linear, the amount of residue after heating under the above conditions is almost zero.

[0138] Moreover, specific examples of branched organohydrogenpolysiloxane (B2) include those having a structure represented by the following formula (3).

[0139] [Chemical formula]

[0140] In formula (3), R 7 is a substituted or unsubstituted alkyl group, aryl group, or hydrocarbon group combining these, each having 1 to 8 carbon atoms, or a hydrogen atom. Examples of the alkyl group having 1 to 8 carbon atoms include, for example, a methyl group, an ethyl group, a propyl group, etc., and among them, a methyl group is preferable. Examples of the aryl group having 1 to 8 carbon atoms include, for example, a phenyl group. Examples of the substituent of R 7 include, for example, a methyl group, etc.

[0141] In formula (3), a plurality of Rs 7 are independent of each other and may be different from each other or may be the same.

[0142] In addition, in formula (3), “-O-Si≡” represents that Si has a branched structure extending three-dimensionally.

[0143] Note that as the branched organohydrogenpolysiloxane (B2), only one kind may be used alone, or two or more kinds may be used in combination.

[0144] In addition, in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2), the amount of hydrogen atoms (hydride groups) directly bonded to Si is not particularly limited. However, in the silicone rubber-based curable composition, the total amount of hydride groups in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) is preferably 0.5 to 5 moles, and more preferably 1 to 3.5 moles, per 1 mole of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1). Thereby, a crosslinked network can be surely formed between the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) and the vinyl group-containing linear organopolysiloxane (A1).

[0145] <<Silica particles (C)>> The silicone rubber-based curable composition of the present embodiment can contain silica particles (C) as a non-conductive filler, if necessary.

[0146] The silica particles (C) are not particularly limited. For example, fumed silica, calcined silica, precipitated silica, etc. are used. These may be used alone or in combination of two or more kinds.

[0147] The silica particles (C) have, for example, a specific surface area by the BET method of, for example, 50 to 400 m2 Preferably, it is / g, and 100 to 400 m 2 / g is more preferable. Further, the average primary particle diameter of the silica particles (C) is preferably, for example, 1 to 100 nm, and more preferably about 5 to 20 nm.

[0148] By using silica particles (C) within the range of such specific surface area and average particle diameter, it is possible to improve the hardness and mechanical strength of the formed silicone rubber, particularly the tensile strength.

[0149] <<Silane coupling agent (D)>> The silicone rubber-based curable composition of this embodiment can contain a silane coupling agent (D). The silane coupling agent (D) can have a hydrolyzable group. The hydrolyzable group is hydrolyzed by water to become a hydroxyl group, and this hydroxyl group can perform surface modification of the silica particles (C) by undergoing a dehydration condensation reaction with the hydroxyl groups on the surface of the silica particles (C).

[0150] Further, this silane coupling agent (D) can contain a silane coupling agent having a hydrophobic group. As a result, this hydrophobic group is imparted to the surface of the silica particles (C), so that in the silicone rubber-based curable composition and thus in the silicone rubber, the cohesive force of the silica particles (C) is reduced (less aggregation due to hydrogen bonding by silanol groups), and as a result, it is presumed that the dispersibility of the silica particles in the silicone rubber-based curable composition is improved. Thereby, the interface between the silica particles and the rubber matrix increases, and the reinforcing effect of the silica particles increases. Furthermore, when the matrix of the rubber is deformed, it is presumed that the slipperiness of the silica particles within the matrix is improved. And due to the improvement of the dispersibility and slipperiness of the silica particles (C), the mechanical strength of the silicone rubber by the silica particles (C) (for example, tensile strength, tear strength, etc.) is improved.

[0151] Furthermore, the silane coupling agent (D) can include a silane coupling agent having a vinyl group. As a result, a vinyl group is introduced onto the surface of the silica particles (C). Therefore, when the silicone rubber-based curable composition cures, that is, when the vinyl group of the vinyl group-containing organopolysiloxane (A) and the hydride group of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction to form a network (crosslinked structure) thereby, the vinyl group of the silica particles (C) also participates in the hydrosilylation reaction with the hydride group of the organohydrogenpolysiloxane (B), so that the silica particles (C) are also incorporated into the network. As a result, it is possible to achieve a reduction in the hardness and an increase in the modulus of the formed silicone rubber.

[0152] As the silane coupling agent (D), a silane coupling agent having a hydrophobic group and a silane coupling agent having a vinyl group can be used in combination.

[0153] Examples of the silane coupling agent (D) include those represented by the following formula (4).

[0154] Y n -Si-(X) 4-n ···(4) In the above formula (4), n represents an integer of 1 to 3. Y represents any functional group having a hydrophobic group, a hydrophilic group, or a vinyl group. When n is 1, it is a hydrophobic group, and when n is 2 or 3, at least one of them is a hydrophobic group. X represents a hydrolyzable group.

[0155] The hydrophobic group is an alkyl group having 1 to 6 carbon atoms, an aryl group, or a hydrocarbon group combining these, and examples include a methyl group, an ethyl group, a propyl group, a phenyl group, etc. Among them, in particular, a methyl group is preferable.

[0156] The hydrophilic group includes, for example, a hydroxyl group, a sulfonic acid group, a carboxyl group, a carbonyl group, etc. Among them, a hydroxyl group is particularly preferable. The hydrophilic group may be included as a functional group, but it is preferably not included from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

[0157] Furthermore, the hydrolyzable group includes an alkoxy group such as a methoxy group or an ethoxy group, a chloro group, a silazane group, etc. Among them, a silazane group is preferable because of its high reactivity with the silica particles (C). Note that those having a silazane group as the hydrolyzable group will have two structures of (Y n -Si-) in the above formula (4) due to the structural characteristics.

[0158] Specific examples of the silane coupling agent (D) represented by the above formula (4) include, for example, as those having a hydrophobic group as a functional group, alkoxysilanes such as methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, decyltrimethoxysilane; chlorosilanes such as methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane; hexamethyldisilazane. As those having a vinyl group as a functional group, alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane, vinylmethyldichlorosilane; divinyldimethyltetrasilazane. However, considering the above description, among them, hexamethyldisilazane is particularly preferable as those having a hydrophobic group, and divinyldimethyltetrasilazane is particularly preferable as those having a vinyl group.

[0159] In this embodiment, the lower limit of the content of the silane coupling agent (D) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more with respect to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). The upper limit of the content of the silane coupling agent (D) is preferably 100% by mass or less, more preferably 80% by mass or less, and even more preferably 40% by mass or less with respect to 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). By setting the content of the silane coupling agent (D) to be not less than the above lower limit value, the silicone rubber has appropriate adhesion to the substrate, and when the silica particles (C) are used, it can contribute to the improvement of the mechanical strength of the whole silicone rubber. Also, by setting the content of the silane coupling agent (D) to be not more than the above upper limit value, the silicone rubber can have appropriate mechanical properties.

[0160] <<Platinum or platinum compound (E)>> The silicone rubber-based curable composition of this embodiment may contain platinum or a platinum compound (E). Platinum or a platinum compound (E) is a catalyst component that acts as a catalyst during curing. The addition amount of platinum or a platinum compound (E) is a catalytic amount.

[0161] As the platinum or platinum compound (E), known ones can be used, for example, platinum black, platinum supported on silica, carbon black, etc., chloroplatinic acid or an alcohol solution of chloroplatinic acid, a complex salt of chloroplatinic acid and an olefin, a complex salt of chloroplatinic acid and a vinylsiloxane, etc.

[0162] Note that only one kind of platinum or platinum compound (E) may be used alone, or two or more kinds may be used in combination.

[0163] <<Water (F)>> In addition, the silicone rubber-based curable composition of the present embodiment may contain water (F) in addition to the above components (A) to (E).

[0164] Water (F) functions as a dispersion medium for dispersing each component contained in the silicone rubber-based curable composition, and is a component that contributes to the reaction between the silica particles (C) and the silane coupling agent (D). Therefore, in the silicone rubber, the silica particles (C) and the silane coupling agent (D) can be more surely connected to each other, and uniform properties can be exhibited as a whole.

[0165] Furthermore, when water (F) is contained, its content can be appropriately set. Specifically, for example, it is preferably in the range of 10 to 100 parts by weight, and more preferably in the range of 30 to 70 parts by weight with respect to 100 parts by weight of the silane coupling agent (D). Thereby, the reaction between the silane coupling agent (D) and the silica particles (C) can proceed more surely.

[0166] (Other components) Furthermore, the silicone rubber-based curable composition of the present embodiment may further contain other components in addition to the above components (A) to (F). Examples of such other components include inorganic fillers other than silica particles (C) such as diatomaceous earth, iron oxide, zinc oxide, titanium oxide, barium oxide, magnesium oxide, cerium oxide, calcium carbonate, magnesium carbonate, zinc carbonate, glass wool, mica, reaction inhibitors, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, thermal conductivity improvers, and other additives.

[0167] In the silicone rubber-based curable composition, the content ratio of each component is not particularly limited, but is set as follows, for example.

[0168] In this embodiment, the upper limit of the content of the silica particles (C) may be, for example, 60 parts by weight or less, preferably 50 parts by weight or less, more preferably 40 parts by weight or less, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A). Thereby, the balance of mechanical strengths such as hardness and tensile strength can be achieved. The lower limit of the content of the silica particles (C) is not particularly limited, but may be, for example, 10 parts by weight or more, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A).

[0169] The silane coupling agent (D) is preferably contained in a proportion of 5 parts by weight or more and 100 parts by weight or less, more preferably 5 parts by weight or more and 40 parts by weight or less, based on 100 parts by weight of the vinyl group-containing organopolysiloxane (A). Thereby, the dispersibility of the silica particles (C) in the silicone rubber-based curable composition can be surely improved.

[0170] Specifically, the content of the organohydrogenpolysiloxane (B) is preferably in a proportion of 0.5 parts by weight or more and 20 parts by weight or less, more preferably 0.8 parts by weight or more and 15 parts by weight or less, based on 100 parts by weight of the total amount of the vinyl group-containing organopolysiloxane (A), the silica particles (C), and the silane coupling agent (D). When the content of (B) is within the above range, there is a possibility that a more effective curing reaction can occur.

[0171] The content of platinum or platinum compound (E) means a catalytic amount and can be set as appropriate. Specifically, based on the total amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D), the platinum group metal in this component is in an amount of 0.01 to 1000 ppm by weight, preferably in an amount of 0.1 to 500 ppm by weight. By setting the content of platinum or platinum compound (E) to be not less than the above lower limit value, the resulting silicone rubber composition can be sufficiently cured. By setting the content of platinum or platinum compound (E) to be not more than the above upper limit value, the curing rate of the resulting silicone rubber composition can be improved.

[0172] Furthermore, when water (F) is contained, its content can be set as appropriate. Specifically, for example, it is preferably in the range of 10 to 100 parts by weight, more preferably in the range of 30 to 70 parts by weight, based on 100 parts by weight of the silane coupling agent (D). Thereby, the reaction between the silane coupling agent (D) and the silica particles (C) can proceed more reliably.

[0173] <Method for producing silicone rubber> Next, the method for producing the silicone rubber of the present embodiment will be described. As the method for producing the silicone rubber of the present embodiment, a silicone rubber-based curable composition is prepared, and the silicone rubber can be obtained by curing this silicone rubber-based curable composition. Details will be described below.

[0174] First, each component of the silicone rubber-based curable composition is uniformly mixed by an arbitrary kneading device to prepare a silicone rubber-based curable composition.

[0175] [1] For example, a predetermined amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D) are weighed, and then kneaded by an arbitrary kneading device to obtain a kneaded product containing these components (A), (C), and (D).

[0176] Incidentally, it is preferable to obtain this kneaded product by previously kneading a vinyl group-containing organopolysiloxane (A) and a silane coupling agent (D), and then kneading (mixing) silica particles (C). Thereby, the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A) is further improved.

[0177] Also, when obtaining this kneaded product, water (F) may be added to the kneaded product of each component (A), (C), and (D) as necessary. Thereby, the reaction between the silane coupling agent (D) and the silica particles (C) can proceed more reliably.

[0178] Furthermore, it is preferable that the kneading of each component (A), (C), and (D) goes through a first step of heating at a first temperature and a second step of heating at a second temperature. Thereby, in the first step, the surface of the silica particles (C) can be surface-treated with the coupling agent (D), and in the second step, the by-products generated by the reaction between the silica particles (C) and the coupling agent (D) can be surely removed from the kneaded product. Thereafter, if necessary, component (A) may be added to the obtained kneaded product and further kneaded. Thereby, the compatibility of the components of the kneaded product can be improved.

[0179] The first temperature is preferably about 40 to 120°C, for example, and more preferably about 60 to 90°C. The second temperature is preferably about 130 to 210°C, for example, and more preferably about 160 to 180°C.

[0180] Also, the atmosphere in the first step is preferably an inert atmosphere such as under a nitrogen atmosphere, and the atmosphere in the second step is preferably under a reduced pressure atmosphere.

[0181] Furthermore, the time for the first step is preferably about 0.3 to 1.5 hours, more preferably about 0.5 to 1.2 hours. The time for the second step is preferably about 0.7 to 3.0 hours, more preferably about 1.0 to 2.0 hours.

[0182] By setting the first step and the second step under the above conditions, the above effects can be obtained more significantly.

[0183] [2] Next, a predetermined amount of organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) are weighed, and then, using an arbitrary kneading device, each component (B) and (E) is kneaded into the kneaded product prepared in the above step [1] to obtain a silicone rubber-based curable composition. The obtained silicone rubber-based curable composition may be a paste containing a solvent.

[0184] When kneading each of these components (B) and (E), it is preferable to first knead the kneaded product prepared in the above step [1] with organohydrogenpolysiloxane (B), and the kneaded product prepared in the above step [1] with platinum or a platinum compound (E), and then knead the respective kneaded products. Thereby, each component (A) to (E) can be surely dispersed in the silicone rubber-based curable composition without allowing the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) to proceed.

[0185] The temperature during kneading of each component (B) and (E) is preferably about 10 to 70°C, more preferably about 25 to 30°C, as the roll setting temperature.

[0186] Furthermore, the kneading time is preferably about 5 minutes to 1 hour, more preferably about 10 to 40 minutes.

[0187] In the above step [1] and the above step [2], by setting the temperature within the above range, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) can be more accurately prevented or suppressed. Further, in the above step [1] and the above step [2], by setting the kneading time within the above range, the components (A) to (E) can be more reliably dispersed in the silicone rubber-based curable composition.

[0188] The kneading apparatus used in each of the steps [1] and [2] is not particularly limited. For example, a kneader, two-roll mill, Banbury mixer (continuous kneader), pressure kneader, etc. can be used.

[0189] Also, in this step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded product. Thereby, even if the temperature of the kneaded product is set to a relatively high temperature, the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) can be more accurately prevented or suppressed.

[0190] [3] Next, a silicone rubber is formed by curing the silicone rubber-based curable composition.

[0191] In this embodiment, the curing step of the silicone rubber-based curable resin composition is performed, for example, by heating at 100 to 250 °C for 1 to 30 minutes (primary curing) and then post-baking at 200 °C for 1 to 4 hours (secondary curing).

[0192] Through the above steps, a silicone rubber composed of a cured product of the silicone rubber-based curable resin composition is obtained.

[0193] Incidentally, [3] Next, an insulating paste can be obtained by dissolving the silicone rubber-based curable composition obtained in step [2] in a solvent. Next, [3] thirdly, a conductive paste can be obtained by dissolving the silicone rubber-based curable composition obtained in step [2] in a solvent and adding a conductive filler.

[0194] (Solvent) Conductive pastes and insulating pastes contain a solvent. As the solvent, various known solvents can be used. For example, it can contain a high-boiling solvent. These can be used alone or in combination of two or more.

[0195] The lower limit of the boiling point of the above high-boiling solvent is, for example, 100 °C or higher, preferably 130 °C or higher, more preferably 150 °C or higher. Thereby, the printing stability such as screen printing can be improved. On the other hand, the upper limit of the boiling point of the above high-boiling solvent is not particularly limited. For example, it may be 300 °C or lower, 290 °C or lower, or 280 °C or lower. Thereby, an excessive heat history during wiring formation can be suppressed, so that damage to the substrate and the shape of the wiring formed of the conductive paste can be maintained well.

[0196] Also, as the solvent, it can be appropriately selected from the viewpoints of solubility and boiling point of the silicone rubber-based curable resin composition. For example, it can contain an aliphatic hydrocarbon having 5 to 20 carbon atoms, preferably an aliphatic hydrocarbon having 8 to 18 carbon atoms, more preferably an aliphatic hydrocarbon having 10 to 15 carbon atoms.

[0197] In addition, examples of the solvent include aliphatic hydrocarbons such as pentane, hexane, cyclohexane, heptane, methylcyclohexane, ethylcyclohexane, octane, decane, dodecane, and tetradecane; aromatic hydrocarbons such as benzene, toluene, ethylbenzene, xylene, mesitylene, trifluoromethylbenzene, and benzotrifluoride; ethers such as diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol monobutyl ether, dipropylene glycol dimethyl ether, dipropylene glycol methyl-n-propyl ether, 1,4-dioxane, 1,3-dioxane, and tetrahydrofuran; haloalkanes such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, and 1,1,2-trichloroethane; carboxylic acid amides such as N,N-dimethylformamide and N,N-dimethylacetamide; sulfoxides such as dimethyl sulfoxide and diethyl sulfoxide; esters such as diethyl carbonate, etc. These can be used alone or in combination of two or more. The solvent used herein may be appropriately selected from solvents capable of uniformly dissolving or dispersing the components in the above conductive paste.

[0198] The above solvent may contain a first solvent in which the upper limit value of the polar term (δ p ) of the Hansen solubility parameter is, for example, 10 MPa 1 / 2 or less, preferably 7 MPa 1 / 2 or less, and more preferably 5.5 MPa 1 / 2 or less. Thereby, the dispersibility and solubility of the silicone rubber-based curable resin composition in the paste can be made good. The lower limit value of the above polar term (δ p ) of this first solvent is not particularly limited, but may be, for example, 0 Pa 1 / 2 or more.

[0199] The upper limit of the hydrogen bonding term (δ h ) of the Hansen solubility parameter in the above first solvent is, for example, 20 MPa 1 / 2 or less, preferably 10 MPa 1 / 2 or less, more preferably 7 MPa 1 / 2 or less. Thereby, in the paste, the dispersibility and solubility of the silicone rubber-based curable resin composition can be made good. The lower limit of the hydrogen bonding term (δ h ) of this first solvent is not particularly limited, but may be, for example, 0 Pa 1 / 2 or more.

[0200] The Hansen solubility parameter (HSP) is an index representing the solubility of how well one substance dissolves in another substance. HSP represents solubility as a three-dimensional vector. This three-dimensional vector can typically be represented by a dispersion term (δ d ), a polar term (δ p ), and a hydrogen bonding term (δ h ). And substances with similar vectors can be judged to have high solubility. It is possible to judge the similarity of the vectors by the distance of the Hansen solubility parameter (HSP distance).

[0201] The Hansen solubility parameter (HSP value) used in this specification can be calculated using software called HSPiP (Hansen Solubility Parameters in Practice). Here, the computer software HSPiP developed by Hansen and Abbott includes a function for calculating the HSP distance and a database describing the Hansen parameters of various resins and solvents or non-solvents. Examine the solubility of each resin in pure solvents and mixed solvents of good solvents and poor solvents, input the results into the HSPiP software, and calculate D: dispersion term, P: polar term, H: hydrogen bonding term, and R0: dissolution sphere radius.

[0202] As the solvent of the present embodiment, for example, those with a small difference in HSP distance, polar term, or hydrogen bond term between the elastomer or the structural unit constituting the elastomer and the solvent can be selected.

[0203] The lower limit of the viscosity of the conductive paste and / or insulating paste when measured at a shear rate of 20 [1 / s] at room temperature of 25°C is, for example, 1 Pa·s or more, preferably 5 Pa·s or more, and more preferably 10 Pa·s or more. Thereby, the film-forming property can be improved. Also, the shape retention property can be enhanced even during thick film formation. On the other hand, the upper limit of the viscosity of the conductive paste and / or insulating paste at room temperature of 25°C is, for example, 100 Pa·s or less, preferably 90 Pa·s or less, and more preferably 80 Pa·s or less. Thereby, the printability of the paste can be improved.

[0204] At room temperature of 25°C, let the viscosity measured at a shear rate of 1 [1 / s] be η1, the viscosity measured at a shear rate of 5 [1 / s] be η5, and the thixotropy index be the viscosity ratio (η1 / η5). At this time, the lower limit of the thixotropy index of the conductive paste and / or insulating paste is, for example, 1.0 or more, preferably 1.1 or more, and more preferably 1.2 or more. Thereby, the shape of the wiring obtained by the printing method can be stably retained. On the other hand, the upper limit of the thixotropy index of the conductive paste and / or insulating paste is, for example, 3.0 or less, preferably 2.5 or less, and more preferably 2.0 or less. Thereby, the ease of printing the paste can be improved.

[0205] The content of the silicone rubber-based curable composition in the insulating paste is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more in 100% by mass of the insulating paste. Also, the content of the silicone rubber-based curable composition in the insulating paste is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less in 100% by mass of the insulating paste.

[0206] (Conductive filler) As the conductive filler, a known conductive material may be used, or metal powder (G) may be used. The metal constituting the metal powder (G) is not particularly limited. For example, it can include at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, or metal powders alloyed thereof, or can include two or more of these. Among these, as the metal powder (G), it is preferable to contain silver or copper, that is, to contain silver powder or copper powder, because of high conductivity and high availability. In addition, these metal powders (G) coated with other metals can also be used.

[0207] In this embodiment, the shape of the metal powder (G) is not limited, but conventionally used ones such as dendritic, spherical, and flaky can be used. Among these, flaky metal powder (G) may be used.

[0208] Also, the particle size of the metal powder (G) is not limited. For example, the average particle size D 50 is preferably 0.001 μm or more, more preferably 0.01 μm or more, and even more preferably 0.1 μm or more. The particle size of the metal powder (G) is, for example, the average particle size D 50 is preferably 1,000 μm or less, more preferably 100 μm or less, and even more preferably 20 μm or less. Average particle size D 50By setting it within such a range, it is possible to exhibit appropriate conductivity as a silicone rubber. The particle size of the metal powder (G) can be defined, for example, as the average value of 200 arbitrarily selected metal powders through observation with a transmission electron microscope or the like and image analysis for a conductive paste or a silicone rubber molded using the conductive paste.

[0209] The content of the conductive filler in the conductive paste is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more in 100% by mass of the conductive paste. Also, the content of the conductive filler in the conductive paste is preferably 85% by mass or less, more preferably 75% by mass or less, and even more preferably 65% by mass or less in 100% by mass of the conductive paste. By setting the content of the conductive filler to be not less than the above lower limit value, the silicone rubber can have appropriate conductive properties. Also, by setting the content of the conductive filler to be not more than the above upper limit value, the silicone rubber can have appropriate flexibility.

[0210] The content of the silicone rubber-based curable composition in the conductive paste is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more in 100% by mass of the conductive paste. Also, the content of the silicone rubber-based curable composition in the conductive paste is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less in 100% by mass of the conductive paste. By setting the content of the silicone rubber-based curable composition to be not less than the above lower limit value, the silicone rubber can have appropriate flexibility. Also, by setting the content of the silicone rubber-based curable composition to be not more than the above upper limit value, it is possible to improve the mechanical strength of the silicone rubber.

[0211] The lower limit of the content of the silica particles (C) in the conductive paste is, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more in 100% by mass of the total amount of the silica particles (C) and the conductive filler. Thereby, the mechanical strength of the silicone rubber can be improved. On the other hand, the upper limit of the content of the silica particles (C) in the conductive paste is, for example, 20% by mass or less, preferably 15% by mass or less, and more preferably 10% by mass or less in 100% by mass of the total amount of the silica particles (C) and the conductive filler. Thereby, the balance between the stretchable electrical properties and the mechanical strength in the silicone rubber can be achieved.

[0212] In the conductive cured product obtained by curing the conductive paste that constitutes wirings such as the lower wiring and the upper wiring, the content of the conductive filler is preferably 65% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more in 100% by mass of the conductive cured product. Further, the content of the conductive filler in the conductive cured product is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less in 100% by mass of the conductive cured product. By setting the content of the conductive filler to be equal to or higher than the above lower limit value, the silicone rubber can have appropriate conductive properties. Also, by setting the content of the conductive filler to be equal to or lower than the above upper limit value, the silicone rubber can have appropriate flexibility.

[0213] Next, the manufacturing process of the stretchable multilayer circuit board 100 of the present embodiment will be described.

[0214] The manufacturing method of the stretchable multilayer circuit board of the present embodiment is a manufacturing method of a flexible circuit board having a multilayer wiring structure, and includes a step of forming a substrate, a step of forming a plurality of lower wirings on the substrate, a step of forming a lower insulating layer on the lower wirings, a step of forming a plurality of upper wirings on the lower insulating layer, and a step of forming an upper insulating layer on the upper wirings. In a method for manufacturing a stretchable multilayer circuit board, a substrate, a lower wiring, a lower insulating layer, an upper wiring, and an upper insulating layer are each formed using a thermosetting elastomer. When viewed in a direction perpendicular to one surface of the substrate, the lower wiring and the upper wiring are formed such that at least the first upper wiring intersects the first lower wiring while being electrically connectable to each other.

[0215] In a method for manufacturing a stretchable multilayer circuit board, the plurality of lower wirings and the plurality of upper wirings may each be formed by applying and drying the same or different conductive pastes.

[0216] Here, an example of the manufacturing process of the stretchable multilayer circuit board 100 will be described with reference to FIG. 3. FIG. 3 is a cross-sectional view showing an outline of the manufacturing process of the stretchable multilayer circuit board 100.

[0217] First, as shown in FIG. 3(a), a support 120 is placed on a workbench 11, and an insulating paste 13 is applied onto the support 12. As the application method, various methods can be used. For example, a printing method such as a squeegee method using a squeegee 14 can be used. Subsequently, the coated insulating paste 13 is dried to form an insulating layer 32 (substrate 110 composed of an insulating elastomer) on the support 12. The drying conditions can be appropriately set according to the type and amount of the solvent in the insulating paste 13. For example, the drying temperature can be 150°C to 180°C, and the drying time can be 1 minute to 30 minutes, etc.

[0218] Note that the insulating layer 32 constituting the substrate 110 may be formed by a molding method such as calender molding or compression molding using the above silicone rubber-based curable composition.

[0219] Subsequently, as shown in FIG. 3(b), a mask 16 having a predetermined opening pattern shape is placed on the insulating layer 32. Then, as shown in FIGS. 3(b) and (c), a conductive paste 15 is applied onto the insulating layer 32 through the mask 16. The coating method can use the same method as the coating method of the insulating paste 13. For example, squeegee printing using a squeegee 14 may be used. Here, when the insulating paste 13 and the conductive paste 15 each contain a silicone rubber-based curable composition, after laminating a conductive coating film (conductive layer 52) having a predetermined pattern shape on the dried insulating layer 32, these may be cured together. The curing treatment can be appropriately set according to the silicone rubber-based curable composition. For example, the curing temperature can be 160°C to 220°C, and the curing time can be 1 hour to 3 hours. Before or after the curing treatment, as shown in Fig. 3(d), the mask 16 can be removed. Thereby, on the substrate composed of the cured product of the insulating layer 32, a cured product of the conductive layer 52 (lower wiring 120 composed of a conductive elastomer) having a predetermined pattern shape can be formed.

[0220] Subsequently, as shown in Fig. 3(e), an insulating paste 17 is further coated on the insulating layer 32 and the patterned conductive layer 52, and an insulating layer 72 (lower insulating layer 130 composed of an insulating elastomer) can be formed as shown in Fig. 3(f). Thereafter, the steps from Fig. 3(b) to Fig. 3(e) may be appropriately repeated. Thereby, an upper wiring 150 composed of a conductive elastomer, an upper insulating layer 160 composed of an insulating elastomer, etc. can be formed, and the circuit can be multilayered. Also, by adjusting the mask pattern and its arrangement position, an intersection structure of the lower wiring 120 and the upper wiring 150 can be formed. Note that the repeating process may be performed after separating the support 120 from the insulating layer 32. As described above, the stretchable multilayer circuit board 100 shown in Fig. 1(a) can be obtained.

[0221] Thus, in the stretchable multilayer circuit board 100, at least one, preferably all, of the substrate 110, the lower insulating layer 130, and the upper insulating layer 160 may be composed of an insulating printed layer printed using an insulating paste. Thereby, it is possible to improve the adhesion to the wiring.

[0222] In the stretchable multilayer circuit board 100, the lower wiring 120 and the upper wiring 150 may each be composed of a conductive printed layer printed using a conductive paste. Thereby, the pattern shape of the conductive printed layer can be freely selected.

[0223] The lower limit of the content of the conductive filler in at least one of the lower wiring 120 and the upper wiring 150 is, for example, 70% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more in 100% by mass of the wiring. Thereby, the stretchable electrical characteristics of the stretchable multilayer circuit board can be enhanced. On the other hand, the upper limit of the content of the conductive filler in at least one of the lower wiring 120 and the upper wiring 150 is, for example, 90% by mass or less, preferably 88% by mass or less, more preferably 85% by mass or less in 100% by mass of the wiring. Thereby, a decrease in rubber characteristics such as stretchability of the stretchable multilayer circuit board can be suppressed.

[0224] Hereinafter, the characteristics of the stretchable multilayer circuit board 100 will be described.

[0225] In the present embodiment, at least one of the substrate 110, the lower wiring 120, the lower insulating layer 130, the upper wiring 150, and the upper insulating layer 160 may be composed of an elastomer having at least one of the following characteristics. One of the preferred embodiments is that the substrate 110 is composed of an elastomer having at least one of the following tear strength, elongation at break, and durometer hardness A.

[0226] The lower limit of the tear strength of the elastomer is, for example, 25 N / mm or more, preferably 28 N / mm or more, more preferably 30 N / mm or more, still more preferably 33 N / mm or more, and even more preferably 35 N / mm or more. Thereby, the durability during repeated use of the elastomer can be improved. Also, the mechanical strength of the elastomer can be improved. On the other hand, the upper limit of the tear strength of the elastomer is not particularly limited, but may be, for example, 80 N / mm or less, or 70 N / mm or less. Thereby, the balance of various characteristics of the elastomer can be achieved.

[0227] The lower limit of the tensile strength of the elastomer is, for example, 5.0 MPa or more, preferably 10.0 MPa or more, and more preferably 12.0 MPa or more. Thereby, the mechanical strength of the elastomer can be improved. In addition, an elastomer excellent in durability that can withstand repeated deformation can be realized. On the other hand, the upper limit of the tensile strength of the elastomer is not particularly limited, but may be, for example, 25 MPa or less, or 20 MPa or less. Thereby, the balance of various properties of the elastomer can be achieved.

[0228] The lower limit of the elongation at break of the elastomer is, for example, 100% or more, preferably 200% or more, more preferably 300% or more, and still more preferably 400% or more. Thereby, the high stretchability and durability of the elastomer can be improved. On the other hand, the upper limit of the elongation at break of the elastomer is not particularly limited, but may be, for example, 2000% or less, or 1500% or less. Thereby, the balance of various properties of the elastomer can be achieved.

[0229] The upper limit of the durometer hardness A of the elastomer is not particularly limited, but may be, for example, 90 or less, preferably 75 or less, and more preferably 70 or less. Thereby, the balance of the cured physical properties of the silicone rubber can be achieved. Thereby, in the elastomer, the ease of deformation that facilitates deformation such as bending and stretching can be enhanced. On the other hand, the lower limit of the durometer hardness A of the elastomer is not particularly limited, but is, for example, 30 or more, preferably 35 or more, and more preferably 40 or more. Thereby, the mechanical strength of the elastomer can be enhanced.

[0230] In the present embodiment, as a method for measuring the characteristics of each member of the stretchable multilayer circuit board and the characteristics of the elastomer used for each member, for example, the following method can be adopted. For measuring the characteristics of each member, as a test piece, for example, each member such as a substrate may be used as it is.

[0231] (Measurement conditions for tear strength) Using an elastomer, a crescent-shaped test piece is prepared, and for the obtained crescent-shaped test piece, the tear strength is measured at 25°C in accordance with JIS K6252 (2001).

[0232] (Measurement conditions for tensile strength) Using an elastomer, a dumbbell-shaped No. 3 test piece is prepared, and for the obtained dumbbell-shaped No. 3 test piece, the tensile strength is measured at 25°C in accordance with JIS K6251 (2004).

[0233] (Measurement conditions for elongation at break) Using an elastomer, a dumbbell-shaped No. 3 test piece is prepared, and for the obtained dumbbell-shaped No. 3 test piece, the elongation at break is measured at 25°C in accordance with JIS K6251 (2004).

[0234] (Measurement procedure for durometer hardness A) Using an elastomer, a sheet-shaped test piece is prepared, and in accordance with JIS K6253 (1997), the durometer hardness A of the obtained sheet-shaped test piece at 25°C is measured.

[0235] The volume resistivity of at least one of the first lower wiring 120 and the first upper wiring 150 at 25°C when not stretched is, for example, 1×10 -5 Ω·cm or more and 1×10 -1 Ω·cm or less, preferably 5×10 -5 Ω·cm or more and 5×10 -2 Ω·cm or less, more preferably 1×10 -4 Ω·cm or more and 1×10 -2 Ω·cm or less. By setting it within such a range, a stretchable multilayer circuit board 100 with excellent electrical characteristics can be obtained when not stretched and even when stretched.

[0236] At least one of the electrical resistance values of the first lower wiring 120 and the first upper wiring 150 at 25°C and when not stretched is, for example, 0.01 Ω / cm or more and 1000 Ω / cm or less, preferably 0.05 Ω / cm or more and 500 Ω / cm or less, more preferably 0.1 Ω / cm or more and 200 Ω / cm or less.

[0237] When the electrical resistance value at 25°C and when not stretched is within the above range, at least one of the electrical resistance values of the first lower wiring 120 and the first upper wiring 150 at 25°C and when stretched by 50% is 0.1 Ω / cm or more and 1200 Ω / cm or less, preferably 0.2 Ω / cm or more and 700 Ω / cm or less, more preferably 0.3 Ω / cm or more and 300 Ω / cm or less. By setting it within such a range, a stretchable multilayer circuit board 100 with excellent electrical characteristics can be obtained both when not stretched and when stretched.

[0238] Let the electrical resistance value of the wiring at 25°C and when stretched by 20% be X1, and the electrical resistance value of the wiring at 25°C and when stretched by 50% be X2. When the electrical resistance value at 25°C and when not stretched is within the above range, at least one of the first lower wiring 120 and the first upper wiring 150 is configured to satisfy, for example, 1.2 ≤ X2 / X1 ≤ 8.0, preferably 1.3 ≤ X2 / X1 ≤ 7.0, more preferably 1.4 ≤ X2 / X1 ≤ 6.0. By setting it within such a range, a stretchable multilayer circuit board 100 with excellent electrical characteristics can be obtained even when stretched.

[0239] Let the electrical resistance value of the wiring at 25°C and when not stretched be Z1, and the electrical resistance value of the wiring in the non-stretched state after performing the 50% stretching operation at 25°C 100 times be Z2. At least one of the first lower wiring 120 and the first upper wiring 150 is configured to satisfy, for example, 1.1 ≤ Z2 / Z1 ≤ 3.0, preferably 1.2 ≤ Z2 / Z1 ≤ 2.9, more preferably 1.3 ≤ Z2 / Z1 ≤ 2.8. By setting it within such a range, a stretchable multilayer circuit board 100 with excellent electrical characteristics can be obtained even during repeated stretching.

[0240] The electronic device of this embodiment includes the above-described stretchable multilayer circuit board. Examples of the electronic device include a stretchable display, a wearable device, a biosensor, or the like.

[0241] Hereinafter, an example of applying the stretchable multilayer circuit board to a stretchable display will be described with reference to FIG. 4. FIG. 4 is a functional block diagram showing an example of the configuration of a display device including a stretchable display.

[0242] An example of the display device 300 includes a display unit 310 and a control unit 320. This display device 300 may further include at least one or more other functional units such as a power supply unit 350 and a communication unit 340.

[0243] The display unit 310 includes a stretchable display (display unit 310) and performs display by the stretchable display. The stretchable display is composed of the above-described stretchable multilayer circuit board on which display elements and the like are mounted. Such a display device 300 can be attached to objects according to various applications such as clothes and the body.

[0244] The control unit 320 controls the display content of the display unit 310. The display unit 310 can control the display content based on, for example, information input from the input unit 330.

[0245] The input unit 330 may be provided directly on the display device 300, or may be provided on an external terminal such as a smartphone. Information input from the input unit 330 is transmitted to the control unit 320 via the communication unit 340 provided in the display device 300. The input unit 330 may be composed of, for example, a button or a touch panel. When a display is provided on an external terminal, the same content as the display content of the display unit 310 may be displayed on that display via the communication unit 340. The communication unit 340 includes various communication means such as Bluetooth (registered trademark) and Wi-Fi.

[0246] The display device 300 may further include a storage unit 360. The control unit 320 may cause the display unit 310 to display the display content stored in the storage unit 360. Further, the control unit 320 can generate, change, or delete information constituting the display content stored in the storage unit 360.

[0247] The power supply unit 350 may be composed of a mobile battery and may include an electrode connectable to an external power supply.

[0248] In the display device 300, in addition to the display area on the substrate 110 of the stretchable multilayer circuit board constituting the display unit 310 where display elements are mounted, a non-display area may be provided around the display area. On the substrate 110 of the non-display area, at least one or two or more of the respective units such as the control unit 320, the power supply unit 350, the input unit 330, the communication unit 340, and the storage unit 360 may be provided. Thereby, the display elements can be connected to the respective units and between the respective units by stretchable wiring.

[0249] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the range capable of achieving the object of the present invention are included in the present invention.

Example

[0250] Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0251] (Vinyl group-containing organopolysiloxane (A)) (A1-1): First vinyl group-containing linear organopolysiloxane: Vinyl group-containing dimethylpolysiloxane synthesized according to the following synthesis scheme 1 (structure represented by the above formula (1-1)) (A1-2): Second vinyl group-containing linear organopolysiloxane: Vinyl group-containing dimethylpolysiloxane synthesized according to the following synthesis scheme 2 (structure represented by the above formula (1-1) where R 1 and R2 a structure in which it is a vinyl group)

[0252] (organohydrogenpolysiloxane (B)) (B-1): organohydrogenpolysiloxane: manufactured by Momentive, "TC-25D"

[0253] (silica particles (C)) (C): silica fine particles (particle size 7 nm, specific surface area 300 m 2 / g), manufactured by Nippon Aerosil Co., Ltd., "AEROSIL 300"

[0254] (silane coupling agent (D)) (D-1): hexamethyldisilazane (HMDZ), manufactured by Gelest, "HEXAMETHYLDISILAZANE (SIH6110.1)" (D-2) divinyltetramethyldisilazane, manufactured by Gelest, "1,3-DIVINYLTETRAMETHYLDISILAZANE (SID4612.0)"

[0255] (platinum or platinum compound (E)) (E-1): platinum compound (manufactured by Momentive, trade name "TC-25A")

[0256] (water (F)) (F): pure water

[0257] (metal powder (G)) (G1): silver powder, manufactured by Tokuri Chemical Research Institute, trade name "TC-101", median diameter d 50 : 8.0 μm, aspect ratio 16.4, average major axis 4.6 μm

[0258] (Synthesis of vinyl group-containing organopolysiloxane (A)) [Synthesis Scheme 1: Synthesis of the first vinyl group-containing linear organopolysiloxane (A1-1)] According to the following formula (5), the first vinyl group-containing linear organopolysiloxane (A1-1) was synthesized. That is, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium silicate were placed in a 300 mL separable flask equipped with a cooling tube and a stirring blade, and the Ar gas was replaced. Then, the temperature was raised, and the mixture was stirred at 120 °C for 30 minutes. At this time, an increase in viscosity was confirmed. Thereafter, the temperature was raised to 155 °C, and stirring was continued for 3 hours. Then, after 3 hours, 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added, and the mixture was further stirred at 155 °C for 4 hours. Furthermore, after 4 hours, the mixture was diluted with 250 mL of toluene and then washed three times with water. The washed organic layer was reprecipitated and purified by washing several times with 1.5 L of methanol to separate the oligomer and the polymer. The obtained polymer was dried under reduced pressure at 60 °C overnight to obtain a first vinyl group-containing linear organopolysiloxane (A1-1) (Mn = 2.2×10 5 , Mw = 4.8×10 5 ). Also, the vinyl group content calculated by 1H-NMR spectrum measurement was 0.04 mol%.

[0259] [Chemical formula]

[0260] [Synthesis Scheme 2: Synthesis of the second vinyl group-containing linear organopolysiloxane (A1-2)] In the synthesis step of the above (A1-1), except that 0.86 g (2.5 mmol) of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane was used in addition to 74.7 g (252 mmol) of octamethylcyclotetrasiloxane, the second vinyl group-containing linear organopolysiloxane (A1-2) was synthesized as shown in the following formula (6) in the same manner as the synthesis step of (A1-1). Also, the vinyl group content calculated by 1H-NMR spectrum measurement was 0.92 mol%.

[0261] [Chemical formula]

[0262] (Preparation of silicone rubber-based curable composition) Silicone rubber-based curable compositions 1 to 5 were prepared according to the following procedure. First, a mixture of 90% vinyl group-containing organopolysiloxane (A), silane coupling agent (D), and water (F) was kneaded in advance at the ratios shown in Table 1 below. Then, silica particles (C) were added to the mixture and further kneaded to obtain a kneaded product (silicone rubber compound). Here, the kneading after adding the silica particles (C) is carried out through a first step of kneading for 1 hour at 60 to 90 °C under a nitrogen atmosphere for the coupling reaction, and a second step of kneading for 2 hours at 160 to 180 °C under a reduced pressure atmosphere for removing by-products (ammonia). Then, it was cooled, and the remaining 10% vinyl group-containing organopolysiloxane (A) was added in two portions and kneaded for 20 minutes. Subsequently, organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) were added to 100 parts by weight of the obtained kneaded product (silicone rubber compound) at the ratios shown in Table 2 below, and kneaded with a roll to obtain silicone rubber-based curable compositions 1 to 5.

[0263] [Table 1]

[0264] (Preparation of insulating paste) The obtained 32 parts by weight of silicone rubber-based curable composition 4 was immersed in 68 parts by weight of tetradecane (solvent), and then stirred with a planetary mixer to obtain a conductive paste.

[0265] (Preparation of conductive paste) The obtained 13.7 parts by weight of silicone rubber-based curable composition 5 was immersed in 31.8 parts by weight of tetradecane (solvent), and then stirred with a planetary mixer. After adding 54.5 parts by weight of metal powder (G1), it was kneaded with a three-roll mill to obtain a conductive paste.

[0266] <Example 1> (Fabrication of Stretchable Circuit Substrate) The stretchable multilayer circuit substrate 100 shown in FIG. 5 was fabricated according to the following procedure. First, the obtained silicone rubber-based curable composition 1 was pressed at 170° C. and 10 MPa for 10 minutes to be formed into a sheet shape and was primarily cured. Subsequently, it was secondarily cured at 200° C. for 4 hours to obtain a substrate 110 (a cured product of the silicone rubber-based curable composition) having a length × width × thickness of 12 cm × 12 cm × the substrate thickness shown in Table 3. Using the obtained conductive paste, eight lower wiring patterns were drawn on the substrate 110 through a mask having a predetermined pattern and dried at 140° C. for 20 minutes. Each of the lower wirings 120 numbered 1 to 8 had a structure in which a vertical wiring and a horizontal wiring having the lengths shown in Table 2 were connected by changing the direction by 90 degrees in this order, and the width of each wiring was 1.0 mm and the thickness was the wiring thickness shown in Table 3. Using the obtained insulating paste, an insulating layer was formed on the substrate 110 and on the lower wiring 120 through a mask having a predetermined pattern and dried at 140° C. for 20 minutes, thereby forming a lower insulating layer 130 having the insulating layer thickness shown in Table 3. However, openings were formed in the lower insulating layer 130 so that the lower connection portions 122 and 124 in the eight lower wirings 120 were exposed. Using the obtained conductive paste, eight upper wiring patterns each having a wiring intersecting the eight lower wirings 120 at 90 degrees in a top view were drawn on the lower insulating layer 130 through a mask having a predetermined pattern and dried at 140° C. for 20 minutes. Each of the upper wirings 150 numbered 9 to 16 had a structure in which a vertical wiring (long), a horizontal wiring, and a vertical wiring (short) having the lengths shown in Table 2 were connected by changing the direction by 90 degrees in this order, and the width of each wiring was 1.0 mm and the thickness was the wiring thickness shown in Table 3. In addition, eight upper connection portions 152 each having a wiring width of 1.0 mm and a thickness of the wiring thickness shown in Table 3 were formed near the lower connection portions 122 in each of the vertical wirings (short) of the eight upper wirings 150. Using the obtained insulating paste, an insulating layer was formed on the substrate 110, on the lower insulating layer 130, and on the upper wiring 150 through a mask having a predetermined pattern, and dried at 140 °C for 20 minutes to form an upper insulating layer 160 having the insulating layer thickness shown in Table 3. However, openings were formed in the upper insulating layer 160 so that the lower connection portions 122 and 124 in the eight lower wirings 120 and the upper connection portions 152 and 154 in the eight upper wirings 150 were exposed. The multilayer structure having the above substrate 110, lower wiring 120, lower insulating layer 130, upper wiring 150, and upper insulating layer 160 was cured at 180 °C for 2 hours to obtain a stretchable multilayer circuit board 100 of Example 1 shown in FIG. 5.

[0267] <Examples 2 and 3> The silicone rubber-based curable composition 1 constituting the substrate was changed to the silicone rubber-based curable composition 2 or 3 shown in Table 1, and stretchable multilayer circuit boards 100 of Examples 2 and 3 were produced in the same manner as in Example 1, except that the substrate thickness, insulating layer thickness, and wiring thickness shown in Table 3 were adopted. In the cross-section in the stacking direction of the stretchable multilayer circuit board 100, the substrate thickness, insulating layer thickness, and wiring thickness were measured using a microscope.

[0268] (Fabrication of Electronic Device) In the obtained stretchable multilayer circuit board 100 of FIG. 5, LED chips (electronic components 170) were placed at 64 locations where the lower connection portions 122 in the lower wirings 120 numbered 1 to 9 and the upper connection portions 152 in the upper wirings 150 numbered 10 to 16 straddle each other, and these were adhered with the above conductive paste, dried and cured at 140 °C for 20 minutes. Thereafter, the LED chips were sealed with the above insulating paste, dried and cured at 140 °C for 20 minutes to obtain an electronic device.

[0269]

Table 2

[0270]

Table 3

[0271] The following items were evaluated for the obtained stretchable multilayer circuit board and electronic device.

[0272] (Hardness) The silicone rubber-based curable compositions of Examples 1 to 3 were pressed at 170 °C and 10 MPa for 10 minutes to form a sheet shape and were primarily cured. Subsequently, they were secondarily cured at 200 °C for 4 hours, and a sheet-shaped substrate (a cured product of the silicone rubber-based curable composition) having the substrate thickness shown in Table 3 was used as a test piece. The above test pieces were laminated to a thickness of 6 mm, and the durometer hardness A of the obtained sheet-shaped test pieces at 25 °C was measured in accordance with JIS K6253 (1997).

[0273] (Tear strength) Using the above test pieces, the tear strength at 25 °C was measured in accordance with JIS K6252 (2001). The unit is N / mm.

[0274] (Tensile strength) Using the above test pieces, the tensile strength at 25 °C was measured in accordance with JIS K6251 (2004). The unit is MPa.

[0275] Using the above test pieces, the elongation at break was measured in accordance with JIS K6251 (2004). The elongation at break was calculated as [distance of movement between chucks (mm)] ÷ [initial distance between chucks (35 mm)] × 100. The unit is %.

[0276] (Connection reliability) The above test pieces (sheet-shaped substrates) obtained using the silicone rubber-based curable compositions of Examples 1 to 3 were further heat-treated at 180 °C for 2 h. The dimensional change of the test pieces before and after this heat treatment was approximately 0%.

[0277] (Electrical characteristics) A 5V voltage was applied to the obtained electronic device via each of the lower wirings 120 and upper wirings 150, and it was confirmed that 64 LED chips emitted light simultaneously. When there were LED chips with connection failures (non-emission) of 5% or more of the total number, it was evaluated as ×, and when it was less than 5%, it was evaluated as ○, and the results were described in Table 1.

[0278] In the cured product (wiring pattern) of the conductive paste used for the lower wiring 120 and upper wiring 150, the volume resistivity at 25 °C and when not stretched was 3.2×10 -4 Ω·cm, and the electrical resistance at 25 °C and when not stretched was 1.4 Ω / cm.

[0279] (Stretchable electrical characteristics) Regarding the stretchable multilayer circuit board 100 in the obtained electronic device, stretching by 20% in the vertical direction of FIG. 5 was repeated 10 times. In the electronic device after the stretching operation, a voltage was applied in the same manner as the above electrical characteristics, and it was confirmed that 64 LED chips emitted light simultaneously. When there were LED chips with connection failures (non-emission) of 5% or more of the total number, it was evaluated as ×, and when it was less than 5%, it was evaluated as ○, and the results were described in Table 1.

[0280] (Stretchable durability) As a result of observing the cross-sectional view cut in the thickness direction of the stretchable multilayer circuit board 100 after the stretching operation, it was confirmed that peeling did not occur at the adhesion interfaces of the substrate 110, lower wiring 120, lower insulating layer 130, upper wiring 150, and upper insulating layer 160, respectively.

[0281] Examples 1 to 3 showed the result that a stretchable multilayer circuit board excellent in stretchable electrical characteristics and the like was obtained while having a structure in which a plurality of electronic components (LEDs) were highly integrated.

Explanation of symbols

[0282] 11 Workbench 12 Support 13 Insulating paste 14 Squeegee 15 Conductive paste 16 Mask 17 Insulating paste 32 Insulating layer 52 Conductive layer 72 Insulating layer 100 Stretchable multilayer circuit board 110 Substrate 120 Lower wiring 120 Support 122 Lower connection part 124 Lower connection part 126 Lower wiring 130 Lower insulating layer 140 Opening 142 Opening 150 Upper wiring 152 Upper connection part 154 Upper connection part 156 Upper wiring 160 Upper insulating layer 170 Electronic component 200 Multilayer wiring structure 210 Crossing structure 220 Connection structure

Claims

1. A substrate, a plurality of lower wirings provided on the substrate, a lower insulating layer provided on the lower wirings, a plurality of upper wirings provided on the lower insulating layer, an upper insulating layer provided on the upper wirings, and a multilayer wiring structure having the same, a stretchable multilayer circuit board, wherein the substrate, the lower wirings, the lower insulating layer, the upper wirings, and the upper insulating layer each contain a thermosetting elastomer, in the multilayer wiring structure, when viewed in a direction perpendicular to one surface of the substrate, a crossing structure in which the first lower wiring and the first upper wiring cross each other, and a connection structure in which the first lower wiring and the first upper wiring can be electrically connected to each other, a stretchable multilayer circuit board comprising the same.

2. A stretchable multilayer circuit board according to claim 1, wherein the substrate, the lower insulating layer, and the upper insulating layer each contain silicone rubber.

3. A stretchable multilayer circuit board according to claim 1 or 2, wherein the lower wirings and the upper wirings each contain silicone rubber and a conductive filler.

4. A stretchable multilayer circuit board according to any one of claims 1 to 3, wherein the substrate, the lower wirings, the lower insulating layer, the upper wirings, and the upper insulating layer each contain the same kind of silicone rubber.

5. A stretchable multilayer circuit board according to claim 3, wherein the conductive filler contains silver powder.

6. A stretchable multilayer circuit board according to any one of claims 1 to 5, wherein at least one of the substrate, the lower insulating layer, and the upper insulating layer contains an inorganic filler.

7. A stretchable multilayer circuit board according to any one of claims 1 to 6, wherein at least one of the lower wirings and the upper wirings contains an inorganic filler.

8. A stretchable multilayer circuit board according to claim 6 or 7, wherein the inorganic filler contains silica.

9. A stretchable multilayer circuit board according to any one of claims 1 to 8, wherein at least one of the substrate, the lower insulating layer, and the upper insulating layer is composed of an insulating printed layer printed using an insulating paste.

10. A stretchable multilayer circuit board according to any one of claims 1 to 9, A stretchable multilayer circuit board, wherein the lower wiring and the upper wiring are each composed of a conductive printed layer printed using a conductive paste. **Claim 11** The stretchable multilayer circuit board according to any one of Claims 1 to 10, wherein the tear strength of the board at 25°C, measured in accordance with JIS K6252 (2001), is 25 N / mm or more. **Claim 12** The stretchable multilayer circuit board according to any one of Claims 1 to 11, wherein the elongation at break of the board at 25°C, measured in accordance with JIS K6251 (2004), is 100% or more. **Claim 13** The stretchable multilayer circuit board according to any one of Claims 1 to 12, wherein the durometer hardness A of the board at 25°C, defined in accordance with JIS K6253 (1997), is 30 or more and 90 or less. **Claim 14** The stretchable multilayer circuit board according to any one of Claims 1 to 13, wherein the thickness of the lower insulating layer / the thickness of the board is 0.01 or more and 2.0 or less. **Claim 15** The stretchable multilayer circuit board according to any one of Claims 1 to 14, wherein the thickness of the lower wiring / the thickness of the lower insulating layer is 0.05 or more and 20.0 or less. **Claim 16** The stretchable multilayer circuit board according to any one of Claims 1 to 15, The volume resistivity of the first lower wiring and the first upper wiring at 25°C and when not stretched is 1×10 －５ Ω·cm or more and 1×10 －１ Ω·cm or less, a stretchable multilayer circuit board. **Claim 17** The stretchable multilayer circuit board according to any one of Claims 1 to 16, when the electrical resistance values of the first lower wiring and the first upper wiring at 25°C and when not stretched are in the range of 0.01 Ω / cm or more and 1000 Ω / cm or less, and the electrical resistance value of the first lower wiring and the first upper wiring at 20% elongation is X1, and the electrical resistance value of the first lower wiring and the first upper wiring at 50% elongation is X2, then X2 / X1 is 1.2 or more and 8.0 or less. **Claim 18** The stretchable multilayer circuit board according to any one of Claims 1 to 17, when the electrical resistance values of the first lower wiring and the first upper wiring at 25°C and when not stretched are in the range of 0.01 Ω / cm or more and 1000 Ω / cm or less, the electrical resistance value of the first lower wiring and the first upper wiring at 50% elongation is 0.1 Ω / cm or more and 1200 Ω / cm or less. **Claim 19** A stretchable multilayer circuit board according to any one of claims 1 to 18, when Z1 is the electrical resistance value of the first lower wiring at 25°C and in the unextended state, and Z2 is the electrical resistance value of the first lower wiring in the unextended state after performing a 50% stretching operation 100 times, a stretchable multilayer circuit board in which Z2 / Z1 is 1.1 or more and 3.0 or less.

20. A stretchable multilayer circuit board according to any one of claims 1 to 19, in the connection structure, a stretchable multilayer circuit board configured such that the first lower wiring and the first upper wiring are electrically connected via an electronic component.

21. A stretchable multilayer circuit board according to claim 20, wherein the electronic component is configured to be electrically connected to the first lower wiring and the first upper wiring using at least one of a conductive paste and a solder material.

22. A stretchable multilayer circuit board according to claim 20 or 21, a stretchable multilayer circuit board including a sealing portion for sealing the electronic component in the multilayer wiring structure.

23. A stretchable multilayer circuit board according to any one of claims 1 to 22, in the connection structure, a lower opening penetrating at least the lower insulating layer and the upper insulating layer is formed, and an upper opening penetrating at least the upper insulating layer is formed, the first lower wiring has a lower connection portion configured to be exposed within the lower opening, a stretchable multilayer circuit board in which the first upper wiring has an upper connection portion configured to be exposed within the upper opening.

24. A stretchable multilayer circuit board according to any one of claims 1 to 23, in a cross-sectional view when cut in the stacking direction of the multilayer wiring structure, in the connection structure, the first lower wiring has a protruding connection portion protruding from the substrate toward the lower wiring.

25. A stretchable multilayer circuit board according to any one of claims 1 to 24, wherein the substrate has no wiring on the other surface opposite to the surface where the upper wiring and the lower wiring are provided.

26. A stretchable multilayer circuit board according to any one of claims 1 to 25, when viewed in a direction perpendicular to one surface of the substrate, In the multi-layer wiring structure, a plurality of the lower wirings and a plurality of the upper wirings cross each other, and the multi-layer wiring structure includes a plurality of crossing structures. A stretchable multi-layer circuit board in which the plurality of crossing structures are arranged in a lattice pattern. **Claim 27** A stretchable display, wearable device, or biosensor having the stretchable multi-layer circuit board according to any one of Claims 1 to 26. **Claim 28** A display device including a display unit, a control unit, a power supply unit, and / or a communication unit, wherein the display unit includes the stretchable display according to Claim 27. **Claim 29** A method for manufacturing a stretchable multi-layer circuit board having a multi-layer wiring structure, the method including: forming a plurality of lower wirings on the substrate; forming a lower insulating layer on the lower wirings; forming a plurality of upper wirings on the lower insulating layer; and forming an upper insulating layer on the upper wirings, wherein the substrate, the lower wirings, the lower insulating layer, the upper wirings, and the upper insulating layer are each formed using a thermosetting elastomer, and the lower wirings and the upper wirings are formed such that, when viewed in a direction perpendicular to one surface of the substrate, at least a first upper wiring crosses a first lower wiring while being electrically connectable to each other. A method for manufacturing a stretchable multi-layer circuit board. **Claim 30** A method for manufacturing a stretchable multi-layer circuit board according to Claim 29, wherein the plurality of lower wirings and the plurality of upper wirings are each formed by applying and drying the same or different conductive pastes.

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