Stretchable 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 or display device using the same, and a method for producing the stretchable multilayer circuit board. [Background technology]

[0002] Various developments have been made so far regarding multilayer circuit boards. For example, the technology described in Patent Document 1 is known as an example of this type of technology. Patent Document 1 describes a multilayer circuit board in which multiple resin films made of thermoplastic resin, on which conductor patterns made of metal foil are formed, are bonded to each other by applying heat and pressure (Claim 1, Figure 2(b) of Patent Document 1, etc.). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Publication 2008-198859 Summary of the Invention [Problem to be solved by the invention]

[0004] However, as a result of investigations by the present inventors, it has been found that there is room for improvement in the electrical stretching properties of the multilayer circuit board described in Patent Document 1. [Means for solving the problem]

[0005] After further investigation, the inventors found that by configuring each component of the multilayer wiring structure, such as the substrate, wiring, and insulating layer, to contain a thermosetting elastomer, it is possible to improve the stretchable electrical properties, while also realizing a stretchable multilayer circuit board that allows for high integration by arranging an intersecting structure in which the upper wiring and the lower wiring intersect, thereby completing the present invention.

[0006] According to the present invention, A substrate; a plurality of lower wirings provided on the substrate; a lower insulating layer provided on the lower wiring; a plurality of upper wirings provided on the lower insulating layer; An upper insulating layer provided on the upper wiring, the substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer each contain a thermosetting elastomer; In the multilayer wiring structure, a crossing structure in which the first lower wiring and the first upper wiring cross each other when viewed in a direction perpendicular to one surface of the substrate; a connection structure that allows the first lower wiring and the first upper wiring to be electrically connected to each other; A stretchable multilayer circuit board is provided, comprising:

[0007] Further, according to the present invention, There is provided a stretchable display, a wearable device, or a biosensor, which includes the above-described stretchable multilayer circuit board.

[0008] Further, according to the present invention, A display device comprising a display unit, a control unit, a power supply unit and / or a communication unit, There is provided a display device, wherein the display unit comprises the stretchable display described above.

[0009] Further, according to the present invention, forming a substrate; forming a plurality of underlying interconnects on the substrate; forming a lower insulating layer on the lower wiring; forming a plurality of upper wirings on the lower insulating layer; A method for producing a stretchable multilayer circuit board having a multilayer wiring structure, comprising: forming an upper insulating layer on the upper wiring; the substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer are each formed using a thermosetting elastomer; forming the lower wiring and the upper wiring so that, when viewed in a direction perpendicular to one surface of the substrate, at least the first upper wiring intersects with the first lower wiring and yet are electrically connectable to each other; A method for making a stretchable multilayer circuit board is provided. [Effects of the Invention]

[0010] According to the present invention, there are provided a stretchable multilayer circuit board having excellent stretchable electrical properties, a stretchable display, a wearable device, or a biosensor or display device using the same, and a method for producing the stretchable multilayer circuit board. [Brief explanation of the drawings]

[0011] [Figure 1] 1(a) is a top view schematically illustrating the configuration of a stretchable multilayer circuit board according to the present embodiment, and (b) is an enlarged view of region A in FIG. [Figure 2] (a) to (c) are cross-sectional views of a1 to a3 of region A in FIG. 1(a), (d) is a cross-sectional view of b1 of region B in FIG. 1(a), and (e) is a cross-sectional view of c1 of region C in FIG. 1(a). [Figure 3] 1A to 1C are diagrams schematically illustrating an example of a manufacturing process for a stretchable multilayer circuit board according to an embodiment of the present invention. [Figure 4] 1 is a functional block diagram showing an example of the configuration of a display device including a stretchable display according to an embodiment of the present invention. [Figure 5] FIG. 1 is a top view schematically illustrating the configuration of a stretchable multilayer circuit board in an example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted as appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

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

[0014] The stretchable multilayer circuit board of this embodiment is a multilayer flexible stretchable board having 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 the substrate, the lower wirings, the lower insulating layer, the upper wirings, and the upper insulating layer are each configured to contain a thermosetting elastomer. This stretchable multilayer circuit board has, in its multilayer wiring structure, an intersection structure in which the first lower wiring and the first upper wiring intersect with each other when viewed perpendicularly to 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.

[0015] According to the findings of the present inventors, by using an elastomer for each component of a multilayer wiring structure, such as a substrate, upper wiring, lower wiring, upper insulating layer, and lower insulating layer, it is possible to improve the stretchable electrical properties of a stretchable multilayer circuit board. Furthermore, by arranging a cross structure in which at least a first upper wiring and a first lower wiring cross each other, it is possible to achieve high integration of the stretchable multilayer circuit board. Furthermore, since multiple electronic components can be mounted in each of the connection structures between multiple upper wirings and multiple lower wirings, such as between the first lower wiring and the first upper wiring, functional integration becomes easier.

[0016] However, the thermoplastic resin described in Patent Document 1 may be thermally shrunk by heat treatment during wiring formation, which may reduce connection reliability in multilayer circuit boards. This problem becomes more pronounced in structures where wiring is integrated.

[0017] In contrast, in the stretchable multilayer circuit board of this embodiment, by using a thermosetting elastomer, particularly silicone rubber, as the elastomer, heat resistance is improved and thermal shrinkage of the board size due to the thermal history experienced during the manufacturing process can be suppressed, thereby realizing a multilayer wiring structure with excellent connection reliability. Furthermore, in the stretchable multilayer circuit board of this embodiment, constituent members such as the board, circuit, and insulating layer are made of elastic bodies, so they are less susceptible to plastic deformation than thermoplastic materials.

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

[0019] The stretchable multilayer circuit board of this embodiment can be equipped with various electronic components, like a printed wiring board. Examples of electronic components include light-emitting elements such as LED chips, biometers that detect bioelectrical potentials such as brain waves and muscle potentials, and biological activities such as blood pressure and pulse rate, 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, and communication modules.

[0020] According to this embodiment, it is possible to provide a stretchable multilayer circuit board capable of two-dimensional (surface) sensing on one surface side of the board.

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

[0022] The stretchable multilayer circuit board of this embodiment will be described in detail below.

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

[0024] The stretchable multilayer circuit board 100 of this embodiment comprises 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, for example, that when stretched in the extension direction of the stretchable wiring, the extension rates of components such as the substrate 110, lower wiring 120, and upper wiring 150 can be extended to, for example, 10% or more, preferably 20% or more, more preferably 50% or more, and even more preferably 100% relative to the unstretched length. When the stretchable multilayer circuit board 100 is stretched in the extension direction of the lower wiring 120 and / or upper wiring 150, the lower wiring 120 or upper wiring 150 can maintain a state in which it is not broken within the above-mentioned extension rate range. Here, the extending direction can be defined as the direction from one end to the other end of the portion of the lower wiring 120 or the upper wiring 150 that has the longest length in the in-plane direction.

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

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

[0028] Intersection means that between two wirings arranged with an insulating layer in the stacking direction, the extension direction of the lower wiring and the extension direction of the upper wiring are not the same direction, and there is a region where different wiring areas overlap when viewed from above. In one example of this embodiment, in top view, at least a partial region of the lower wiring 120 and the upper wiring 150 may intersect in an orthogonal direction, that is, at an intersecting angle of 90 degrees.

[0029] Furthermore, when viewed in a direction perpendicular to one surface of the substrate 110 (when viewed from above), the stretchable multilayer circuit board 100 may have a plurality of crossing structures in which a plurality of lower wirings and a plurality of upper wirings cross each other in the multilayer wiring structure 200. These multiple crossing structures may be arranged in a lattice pattern. This makes it possible to further increase the degree of functional integration.

[0030] In this way, when the stretchable multilayer circuit board 100 has multiple intersection structures, the intersection angles of each intersection structure when viewed from above may be the same or different, but from the standpoint of integration, they may all be configured to be the same, or from the standpoint of durability, they may all be configured to be approximately 90 degrees.

[0031] In this specification, unless otherwise specified, the term "approximately" means that a range is included taking into consideration manufacturing tolerances, variations, and the like.

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

[0033] The structure and components of connection structure 220 are not particularly limited, and it has a structure that allows first lower wiring 120 and first upper wiring 150 to be electrically connected via electronic component 170 or the like.

[0034] In one example of the connection structure 220, the lower wiring 120 has a lower connection portion 122 that connects to an external device such as an electronic component 170, and the upper wiring 150 has an upper connection portion 152 that connects to an external device such as an electronic component 170.

[0035] 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. The lower connection portion 122 functions as an electrode pad, and can improve connection stability with the electronic component 170 in the stacking direction.

[0036] 2(a) and 2(b), the lower connection portion 122 may have a protruding connection portion. In a cross-sectional view of the multilayer wiring structure 200 cut in the stacking direction, the protruding connection portion has a structure that protrudes upward from the lower wiring 120 from the substrate 110 toward the lower wiring 120. At least the first lower wiring 120 may have a lower connection portion 122 that is composed of a protruding connection portion. This can improve the ease of connection between the lower connection portion 122 and the upper connection portion 152.

[0037] The upper connection portion 152 may be composed of a branch connection portion branching off from the upper wiring 150. For example, as shown in FIG. 1(b), the branch connection portion is 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. This branch connection portion is formed in the vicinity of the lower connection portion 122. This allows the integration of the stretchable multilayer circuit board 100 to be increased.

[0038] In the connection structure 220, a portion of the lower wiring 120 and the lower insulating layer 130 may be configured in an exposed state 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) is formed penetrating at least the lower insulating layer 130 and the upper insulating layer 160, and an upper opening (opening 142) may also be formed penetrating at least the upper insulating layer 160. The opening 140 and the opening 142 may each be an independent hole, or may be configured as a single hole in which two or more open spaces are connected to each other.

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

[0041] The electronic component 170 is mounted on the stretchable multilayer circuit board 100 by various connection means, for example, in a state where it is electrically connected to the lower connection portion 122 and the upper connection portion 152, as shown in Figure 2(a).

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

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

[0044] 1(a), the lower wiring 120 may have a lower connection portion 124 at its end, and the upper wiring 150 may have an upper connection portion 154 at its end. These lower connection portion 124 and upper connection portion 154 function as electrodes that can be connected to an external device such as an external power source.

[0045] The lower wiring 120 and the upper connection portion 154 are configured so that at least a portion thereof is not covered by a member constituting the multilayer wiring structure 200, such as an insulating layer, and is in an exposed state. As an example, the lower wiring 120 and the upper connection portion 154 may be configured as a protruding connection portion that protrudes up to the outermost upper insulating layer 160, as shown in Figures 2(d) and 2(e). This allows for a structure that is easy to connect.

[0046] 2(a), the stretchable multilayer circuit board 100 may be configured so that the substrate 110 does not have wiring on the other side opposite to the side on which the lower wiring 120 and the upper wiring 150 are provided. In other words, the stretchable multilayer circuit board 100 may be a one-sided circuit board. This makes it possible to increase the degree of integration of the wiring circuit while ensuring the flexibility and stretchability of the stretchable multilayer circuit board 100.

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

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

[0049] The plurality of stretchable lower wirings and the plurality of stretchable upper wirings may have one or more wirings having wiring portions that are parallel to each other when viewed from above.

[0050] At least a part or the whole of the first lower wiring 120 and the second lower wiring 126 is disposed 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 to contact one surface of the substrate 110.

[0051] Furthermore, at least a part or the whole of the first upper wiring 150 and the second upper wiring 156 is disposed 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 contact 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 portion thereof in contact with one surface of substrate 110 and may be formed in the same layer as first lower wiring 120 and second lower wiring 126.

[0052] The multilayer wiring structure 200 may further include one or more other wiring layers on the upper insulating layer 160. That is, the number of wiring layers in the multilayer wiring structure 200 is not limited to two layers as shown in FIG. 2(a), but may be three or more layers, four or more layers, as necessary. In this case, at least one insulating layer is formed between the most 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, the number of crossing structures may be the product of the number of upper wirings and the number of lower wirings. Examples of multiple 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, etc.

[0054] The position of the connection surface of the upper connection portion 152 may be located in any of the layers of the lower insulating layer 130, the upper wiring 150, and the upper insulating layer 160, or may be substantially flush with 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, i.e., may be configured as a printed layer. The upper wiring 150 and the upper connection portion 152 may also be formed by a printing method using a conductive paste, i.e., may be configured as a printed layer. This allows the wiring and the connection portion to be formed almost seamlessly, making it possible to almost eliminate the boundary between them.

[0056] At least one of the lower insulating layer 130 and the upper insulating layer 160 may be configured as a plurality of insulating layers spaced apart from each other in the same layer, or may be configured as a single insulating layer.

[0057] In a cross-sectional view, 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 below the upper insulating layer 160.

[0058] The opening may be composed of at least one of a through hole that penetrates the insulating layer, a separation portion where multiple insulating layers are separated from each other, and an uncovered portion where the insulating layer does not cover the substrate 110 when viewed from above.

[0059] 2 may be formed as voids, or may be filled with a material that constitutes an insulating layer. By using a void structure, stress generated when the stretchable multilayer circuit board 100 expands and contracts is less likely to be transmitted to the connection portion of the electronic component 170, thereby improving connection reliability during expansion and contraction. On the other hand, by using a filled structure, it is possible to prevent foreign matter such as dust from entering the openings and to prevent the connection portion from being exposed to the external environment, thereby improving long-term connection reliability.

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

[0061] The electronic component 170 may be partially or entirely embedded in an opening formed in the insulating layer, such as the opening 140 and the opening 142. This can improve the connection stability of the electronic component 170. When the periphery of the electronic component 170 is sealed, the entire electronic component 170 may be provided outside the opening.

[0062] The thickness ratio, expressed as wiring thickness / insulating layer thickness, is, for example, 0.05 to 20.0, preferably 0.08 to 15.0, and more preferably 0.1 to 10.0. By keeping it within such a range, electrical conductivity and insulating properties can be improved. The thickness ratio, expressed as 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, and more preferably 0.08 to 0.7. By keeping it within this range, flexibility and insulating properties can be improved.

[0063] The thickness ratio may be satisfied by at least one of the lower wiring 120 and the upper wiring 150, preferably by both wirings, and may be satisfied by at least one of the lower insulating layer 130 and the upper insulating layer 160, preferably by both insulating layers.

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

[0065] Next, the materials and properties 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 be configured to include the same and / or different thermosetting elastomers, preferably the same thermosetting elastomers. More specifically, the lower wiring 120 and the upper wiring 150 may each be made 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 made of the same and / or different insulating elastomers.

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

[0068] The insulating elastomer may contain a non-conductive filler instead of a conductive filler. This improves the mechanical properties of the conductive elastomer. Known materials can be used as the non-conductive filler, but inorganic fillers, for example, may also be used. Examples of inorganic fillers that may be used include silica particles, silicone rubber particles, and talc.

[0069] The conductive elastomer may contain, for example, a thermosetting elastomer such as silicone rubber, urethane rubber, fluororubber, nitrile rubber, acrylic rubber, styrene rubber, chloroprene rubber, or ethylene propylene rubber, and a conductive filler. 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. This improves the elasticity and electrical properties of the conductive elastomer.

[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, metal-based fillers, preferably silver powder, may be used as the conductive filler. The conductive elastomer may contain a non-conductive filler in addition to the conductive filler, thereby improving the stretch durability.

[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. This improves adhesion between them, thereby increasing the stretch durability of the stretchable multilayer circuit board 100.

[0072] In this specification, "including the same thermosetting elastomer," "including the same insulating elastomer," and "including the same conductive elastomer" respectively mean that at least one or more of the same type of elastomer is included 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. This improves adhesion between the layers. It also increases the dielectric strength of the insulating layer sandwiched between the upper and lower wiring.

[0074] At least one, and preferably all, of the substrate 110, the lower insulating layer 130, and the upper insulating layer 160 may be configured to contain an inorganic filler, which can appropriately improve the mechanical properties of these layers.

[0075] Alternatively, the lower wiring 120 and the upper wiring 150 may each be configured to contain the same silicone rubber and conductive filler, thereby improving both the elasticity and the conductivity.

[0076] At least one of, and preferably all of, the lower wiring 120 and the upper wiring 150 may be configured to contain an inorganic filler, which can improve electrical conductivity as well as mechanical properties.

[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 type of silicone rubber. This improves adhesion between the layers and also improves durability during expansion and contraction.

[0078] Here, the components of the silicone rubber-based hardening 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 type of vinyl group-containing linear organopolysiloxane, and may further contain one or more selected from the group consisting of the same type of crosslinking agent, the same type of non-conductive filler, the same type of silane coupling agent, and the same type of catalyst.

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

[0081] The same type of vinyl group-containing linear organopolysiloxanes are sufficient as long as they contain the same vinyl groups as functional groups and have a linear structure, but may differ in the amount of vinyl groups in the molecule, the molecular weight distribution, or the amount of vinyl groups added.

[0082] The same type of crosslinking agent may have at least a common structure such as a linear structure or a branched structure, and may have different molecular weight distributions in the molecule, different functional groups, or different amounts of functional groups added.

[0083] Non-conductive fillers of the same type may have at least a common constituent material, but may differ in particle size, specific surface area, surface treatment agent, or amount of the surface treatment agent added.

[0084] Silane coupling agents of the same type are only required to have at least a common functional group, and may differ in other functional groups in the molecule or in the amount added.

[0085] The same type of catalysts are those that have at least common constituent materials, and may contain different compositions or may have different amounts of the components added.

[0086] The silicone rubber-based curable composition constituting the same silicone rubber may further contain one or more different types of vinyl group-containing linear organopolysiloxanes, crosslinking agents, non-conductive fillers, silane coupling agents, and catalysts.

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

[0088] The 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, which become crosslinking points during curing.

[0090] The vinyl group content of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but preferably has two or more vinyl groups in the molecule and is 15 mol% or less, which optimizes the amount of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1) and ensures the formation of networks with the components described below.

[0091] In this specification, the vinyl group content refers to the mole percent of vinyl group-containing siloxane units when all units constituting the vinyl group-containing linear organopolysiloxane (A1) are taken as 100 mole percent, where it is considered that there is one vinyl group per vinyl group-containing siloxane unit.

[0092] The degree of polymerization of the vinyl group-containing linear organopolysiloxane (A1) is not particularly limited, but is preferably within a range of, for example, about 1,000 to 10,000, and more preferably about 2,000 to 5,000. The degree of polymerization can be determined, for example, as the polystyrene-equivalent number-average degree of polymerization (or number-average molecular weight) measured by GPC (gel permeation chromatography) using chloroform as a developing solvent. In this specification, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[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 a vinyl group-containing linear organopolysiloxane (A1) having a degree of polymerization and 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 preferred.

[0096] [ka]

[0097] In formula (1), R 1 is a hydrocarbon group selected from substituted or unsubstituted alkyl groups, alkenyl groups, aryl groups, or combinations thereof having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl groups, ethyl groups, and propyl groups, with methyl groups being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl groups, allyl groups, and butenyl groups, with vinyl groups being preferred. Examples of aryl groups having 1 to 10 carbon atoms include phenyl groups.

[0098] Also, R 2 is a substituted or unsubstituted alkyl group, alkenyl group, aryl group, or a hydrocarbon group combining these groups, each having 1 to 10 carbon atoms. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of alkenyl groups having 1 to 10 carbon atoms include vinyl, allyl, and butenyl groups. Examples of aryl groups having 1 to 10 carbon atoms include phenyl groups.

[0099] Also, R 3 is a substituted or unsubstituted alkyl group or aryl group having 1 to 8 carbon atoms, or a hydrocarbon group consisting of a combination thereof. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of aryl groups having 1 to 8 carbon atoms include phenyl groups.

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

[0101] In addition, in formula (1), multiple R 1 are independent of each other and may be different or the same. 2 , and R 3 The same is true for .

[0102] Furthermore, m and n are the numbers of repeating units constituting the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1), where 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] Specific examples of the vinyl group-containing linear organopolysiloxane (A1) represented by formula (1) include those represented by the following formula (1-1).

[0104] [ka]

[0105] In 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 two or more vinyl groups in the molecule and having a vinyl group content of 0.4 mol% or less. The vinyl group content of the first vinyl group-containing linear organopolysiloxane (A1-1) may be 0.1 mol% or less.

[0107] The vinyl group-containing linear organopolysiloxane (A1) may also 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] By combining a first vinyl-containing linear organopolysiloxane (A1-1) with a second vinyl-containing linear organopolysiloxane (A1-2) having a high vinyl group content as the raw rubber used to make the silicone rubber, the vinyl groups can be unevenly distributed, allowing for more effective formation of a crosslink density distribution within the crosslinked network of the silicone rubber, thereby more effectively increasing the tear strength of the silicone rubber.

[0109] Specifically, as the vinyl group-containing linear organopolysiloxane (A1), it is preferable to use, for example, a first vinyl group-containing linear organopolysiloxane (A1-1) having two or more units in which R1 is a vinyl group and / or units in which R2 is a vinyl group in the molecule, and containing 0.4 mol % or less of these units, and a 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 units in which R2 is a vinyl group, in the above formula (1-1).

[0110] The first vinyl group-containing linear organopolysiloxane (A1-1) preferably has a vinyl group content of 0.01 to 0.2 mol %, and 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, but 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] The first and second vinyl group-containing linear organopolysiloxanes (A1-1) and (A1-2) may each be used alone or in combination of two or more.

[0113] The vinyl group-containing organopolysiloxane (A) may also contain a vinyl group-containing branched organopolysiloxane (A2) having a branched structure.

[0114] <<Organohydrogenpolysiloxane (B)>> The silicone rubber-based curable composition of this 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 may contain either 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), and is a polymer that undergoes a hydrosilylation reaction with the vinyl groups of the vinyl group-containing organopolysiloxane (A) and with vinyl groups of the components blended into the silicone rubber-based curable composition, thereby crosslinking these components.

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

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

[0118] Furthermore, it is generally preferred that the linear organohydrogenpolysiloxane (B1) does not contain a vinyl group, which can reliably prevent the crosslinking reaction from proceeding within the molecule of the linear organohydrogenpolysiloxane (B1).

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

[0120] [ka]

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

[0123] In addition, in formula (2), multiple R 4 are independent of each other and may be different or the same. 5 The same applies to multiple R 4 and R5 At least two of these are hydride groups.

[0124] Also, R 6 is a substituted or unsubstituted alkyl group or aryl group having 1 to 8 carbon atoms, or a hydrocarbon group combining these. Examples of alkyl groups having 1 to 8 carbon atoms include methyl groups, ethyl groups, and propyl groups, with methyl groups being preferred. Examples of aryl groups having 1 to 8 carbon atoms include phenyl groups. 6 are independent of each other and may be different from each other or may be the same.

[0125] In addition, R in formula (2) 4 ,R 5 ,R 6 Examples of the substituent include a methyl group and a vinyl group, and a methyl group is preferred from the viewpoint of preventing intramolecular crosslinking reactions.

[0126] Furthermore, m and n are the numbers of repeating units constituting the linear organohydrogenpolysiloxane (B1) represented by formula (2), where 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] The linear organohydrogenpolysiloxane (B1) may be used alone or in combination of two or more.

[0128] Because the branched organohydrogenpolysiloxane (B2) has a branched structure, it forms regions with high crosslink density, and is a component that significantly contributes to the formation of a sparsely crosslinked structure in the silicone rubber system. Like the linear organohydrogenpolysiloxane (B1), it has a structure in which hydrogen is directly bonded to silicon (≡Si-H), and undergoes a hydrosilylation reaction with the vinyl groups of the vinyl-group-containing organopolysiloxane (A) and with the vinyl groups of other components incorporated into the silicone rubber-based curable composition, forming a polymer that crosslinks these components.

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

[0130] Furthermore, it is generally preferred that the branched organohydrogenpolysiloxane (B2) does not contain vinyl groups, which can reliably prevent crosslinking reactions from occurring within the molecules of the branched organohydrogenpolysiloxane (B2).

[0131] The branched organohydrogenpolysiloxane (B2) is preferably one represented by the following average composition formula (c).

[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 ranging from 1 to 3, and m is H a (R 7 ) 3-a SiO 1 / 2 The number of units, n, is SiO 4 / 2 (the number of units)

[0133] In formula (c), R 7 is a monovalent organic group, preferably a substituted or unsubstituted alkyl group or aryl group having 1 to 10 carbon atoms, or a hydrocarbon group consisting of a combination thereof. Examples of alkyl groups having 1 to 10 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of aryl groups having 1 to 10 carbon atoms include phenyl groups.

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

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

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

[0137] Because the branched organohydrogenpolysiloxane (B2) has a branched structure, it leaves a residue amount of 5% or more when heated, for example, in a nitrogen atmosphere to 1000°C at a heating rate of 10°C / min. In contrast, because the linear organohydrogenpolysiloxane (B1) is linear, it leaves almost no residue amount after heating under the above conditions.

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

[0139] [ka]

[0140] In formula (3), R 7 R is a substituted or unsubstituted alkyl group or aryl group having 1 to 8 carbon atoms, or a hydrocarbon group combining these, or a hydrogen atom. Examples of alkyl groups having 1 to 8 carbon atoms include methyl, ethyl, and propyl groups, with methyl being preferred. Examples of aryl groups having 1 to 8 carbon atoms include phenyl groups. 7 Examples of the substituent include a methyl group.

[0141] In addition, in formula (3), multiple R 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≡" indicates that Si has a branched structure that spreads three-dimensionally.

[0143] The branched organohydrogenpolysiloxane (B2) may be used alone or in combination of two or more.

[0144] Furthermore, the amount of hydrogen atoms (hydride groups) directly bonded to Si in the linear organohydrogenpolysiloxane (B1) and the branched organohydrogenpolysiloxane (B2) 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, more preferably 1 to 3.5 moles, per mole of vinyl groups in the vinyl group-containing linear organopolysiloxane (A1). This ensures the reliable formation of a crosslinked network 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 this embodiment may contain silica particles (C) as a non-conductive filler, if necessary.

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

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

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

[0149] <<Silane coupling agent (D)>> The silicone rubber-based curable composition of this embodiment may contain a silane coupling agent (D). The silane coupling agent (D) may have a hydrolyzable group, which is hydrolyzed by water to form a hydroxyl group, which undergoes a dehydration condensation reaction with the hydroxyl groups on the surface of the silica particles (C), thereby modifying the surface of the silica particles (C).

[0150] The silane coupling agent (D) may also contain a silane coupling agent having a hydrophobic group. This provides the silica particles (C) with hydrophobic groups on their surfaces, reducing the cohesive strength of the silica particles (C) in the silicone rubber-based curable composition and, ultimately, in the silicone rubber (reducing aggregation due to hydrogen bonding via silanol groups). This is believed to result in improved dispersibility of the silica particles in the silicone rubber-based curable composition. This increases the interface between the silica particles and the rubber matrix, enhancing the reinforcing effect of the silica particles. Furthermore, it is believed that the sliding properties of the silica particles within the matrix are improved during deformation of the rubber matrix. The improved dispersibility and sliding properties of the silica particles (C) contribute to improved mechanical strength (e.g., tensile strength, tear strength, etc.) of the silicone rubber.

[0151] Furthermore, the silane coupling agent (D) may contain a silane coupling agent having a vinyl group. This introduces a vinyl group onto the surface of the silica particles (C). Therefore, during curing of the silicone rubber-based curable composition, i.e., when the vinyl groups of the vinyl group-containing organopolysiloxane (A) and the hydride groups of the organohydrogenpolysiloxane (B) undergo a hydrosilylation reaction to form a network (crosslinked structure), the vinyl groups of the silica particles (C) also participate in the hydrosilylation reaction with the hydride groups of the organohydrogenpolysiloxane (B), thereby incorporating the silica particles (C) into the network. This allows for a silicone rubber with a low hardness and a high modulus to be formed.

[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 a functional group having a hydrophobic group, a hydrophilic group, or a vinyl group, and when n is 1, it is a hydrophobic group, and when n is 2 or 3, at least one of the groups 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 formed by combining these groups, such as a methyl group, an ethyl group, a propyl group, or a phenyl group, with a methyl group being particularly preferred.

[0156] Examples of the hydrophilic group include a hydroxyl group, a sulfonic acid group, a carboxyl group, and a carbonyl group, and among these, a hydroxyl group is particularly preferred. Although a hydrophilic group may be contained as a functional group, it is preferable that the hydrophilic group is not contained from the viewpoint of imparting hydrophobicity to the silane coupling agent (D).

[0157] Further, examples of the hydrolyzable group include alkoxy groups such as methoxy and ethoxy groups, chloro groups, and silazane groups. Among these, silazane groups are preferred because of their high reactivity with the silica particles (C). Note that, those having a silazane group as the hydrolyzable group have structural characteristics such that (Y n -Si-) structures.

[0158] Specific examples of the silane coupling agent (D) represented by the above formula (4) include those having a hydrophobic group as a functional group, such as alkoxysilanes like methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, and decyltrimethoxysilane; chlorosilanes like methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, and phenyltrichlorosilane; and hexamethyldisilazane. Examples of the vinyl group-containing silane include alkoxysilanes such as methacryloxypropyltriethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropylmethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, and vinylmethyldimethoxysilane; chlorosilanes such as vinyltrichlorosilane and vinylmethyldichlorosilane; and divinyltetramethyldisilazane. Among these, taking into consideration the above, hexamethyldisilazane is particularly preferred as the silane having a hydrophobic group, and divinyltetramethyldisilazane is particularly preferred as the silane 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, based on 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, based on 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 the above lower limit or more, the silicone rubber has adequate adhesion to the substrate, and when silica particles (C) are used, this contributes to improving the mechanical strength of the silicone rubber as a whole. Furthermore, by setting the content of the silane coupling agent (D) to the above upper limit or less, the silicone rubber has adequate mechanical properties.

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

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

[0162] The platinum or platinum compound (E) may be used alone or in combination of two or more.

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

[0164] Water (F) functions as a dispersion medium to disperse the components contained in the silicone rubber-based curable composition, and also contributes to the reaction between the silica particles (C) and the silane coupling agent (D). This allows the silica particles (C) and the silane coupling agent (D) to be more reliably bonded to each other in the silicone rubber, allowing the composition to exhibit uniform properties overall.

[0165] Furthermore, when water (F) is contained, its content can be appropriately set, but 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, per 100 parts by weight of the silane coupling agent (D), which allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

[0166] (Other ingredients) Furthermore, the silicone rubber-based curable composition of this embodiment may further contain other components in addition to the above components (A) to (F), such as inorganic fillers other than the 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, and mica, as well as additives such as reaction inhibitors, dispersants, pigments, dyes, antistatic agents, antioxidants, flame retardants, and thermal conductivity improvers.

[0167] The content ratio of each component in the silicone rubber-based hardening composition is not particularly limited, but may be set, for example, as follows:

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

[0169] The silane coupling agent (D) is preferably contained in an amount of 5 to 100 parts by weight, more preferably 5 to 40 parts by weight, per 100 parts by weight of the vinyl group-containing organopolysiloxane (A), which ensures improved dispersibility of the silica particles (C) in the silicone rubber-based curable composition.

[0170] The content of organohydrogenpolysiloxane (B) is preferably 0.5 to 20 parts by weight, more preferably 0.8 to 15 parts by weight, per 100 parts by weight of the total of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D). By keeping the content of (B) within this range, a more effective curing reaction may be achieved.

[0171] The content of platinum or platinum compound (E) refers to the catalytic amount and can be set as appropriate. Specifically, it is an amount such that the platinum group metal in this component is 0.01 to 1000 ppm by weight, preferably 0.1 to 500 ppm, relative to the total amount of vinyl group-containing organopolysiloxane (A), silica particles (C), and silane coupling agent (D). By ensuring that the content of platinum or platinum compound (E) is at or above the lower limit, the resulting silicone rubber composition can be sufficiently cured. By ensuring that the content of platinum or platinum compound (E) is at or below the upper limit, the curing rate of the resulting silicone rubber composition can be improved.

[0172] Furthermore, when water (F) is contained, its content can be appropriately set, but 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, per 100 parts by weight of the silane coupling agent (D), which allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

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

[0174] First, the components of the silicone rubber-based hardening composition are mixed uniformly using any kneading device to prepare the silicone rubber-based hardening 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 using any kneading device to obtain a kneaded product containing these components (A), (C), and (D).

[0176] The kneaded mixture is preferably obtained by first kneading the vinyl group-containing organopolysiloxane (A) with the silane coupling agent (D) and then kneading (mixing) the silica particles (C), which further improves the dispersibility of the silica particles (C) in the vinyl group-containing organopolysiloxane (A).

[0177] Furthermore, when obtaining this kneaded mixture, water (F) may be added to the kneaded mixture of the components (A), (C), and (D) as needed, which allows the reaction between the silane coupling agent (D) and the silica particles (C) to proceed more reliably.

[0178] Furthermore, the kneading of components (A), (C), and (D) is preferably carried out through a first step in which the components are heated at a first temperature and a second step in which the components are heated at a second temperature. This allows the surfaces of the silica particles (C) to be surface-treated with the coupling agent (D) in the first step, and allows by-products formed by the reaction between the silica particles (C) and the coupling agent (D) to be reliably removed from the kneaded mixture in the second step. If necessary, component (A) may then be added to the resulting kneaded mixture, followed by further kneading. This improves the compatibility of the components in the kneaded mixture.

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

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

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

[0182] By setting the conditions for the first and second steps as described above, the above-mentioned effects can be more significantly obtained.

[0183] [2] Next, predetermined amounts of organohydrogenpolysiloxane (B) and platinum or a platinum compound (E) are weighed out, and then, using any kneading device, components (B) and (E) are kneaded into the mixture prepared in step [1] above, thereby obtaining a silicone rubber-based curable composition. The obtained silicone rubber-based curable composition may be a paste containing a solvent.

[0184] When kneading components (B) and (E), it is preferable to first knead the mixture prepared in step [1] with the organohydrogenpolysiloxane (B), and then knead the mixture prepared in step [1] with platinum or a platinum compound (E), and then knead the respective mixtures together. This ensures that components (A) to (E) are dispersed in the silicone rubber-based curable composition without promoting the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B).

[0185] The temperature at which the components (B) and (E) are kneaded is, for example, preferably about 10 to 70°C, more preferably about 25 to 30°C, as the roll temperature.

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

[0187] In steps [1] and [2], by maintaining the temperature within the above range, it is possible to more effectively prevent or inhibit the progress of the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B). Furthermore, by maintaining the kneading time within the above range in steps [1] and [2], it is possible to more reliably disperse the components (A) to (E) in the silicone rubber-based curable composition.

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

[0189] Furthermore, in step [2], a reaction inhibitor such as 1-ethynylcyclohexanol may be added to the kneaded mixture, which makes it possible to more effectively prevent or inhibit the reaction between the vinyl group-containing organopolysiloxane (A) and the organohydrogenpolysiloxane (B) even when the temperature of the kneaded mixture is set at a relatively high temperature.

[0190] [3] Next, the silicone rubber-based hardening composition is hardened to form a silicone rubber.

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

[0192] By going through the above steps, a silicone rubber consisting of a cured product of the silicone rubber-based curable resin composition is obtained.

[0193] [3] Next, the silicone rubber-based curable composition obtained in step [2] is dissolved in a solvent to obtain an insulating paste. [3] Next, the silicone rubber-based curable composition obtained in step [2] is dissolved in a solvent, and a conductive filler is added to the solution to obtain a conductive paste.

[0194] (solvent) The conductive paste and the insulating paste contain a solvent. As the solvent, various known solvents can be used, including, for example, high-boiling point solvents, which may be used alone or in combination of two or more.

[0195] The lower limit of the boiling point of the high-boiling solvent is, for example, 100°C or higher, preferably 130°C or higher, and more preferably 150°C or higher. This can improve printing stability in screen printing and the like. On the other hand, the upper limit of the boiling point of the high-boiling solvent is not particularly limited, but may be, for example, 300°C or lower, 290°C or lower, or 280°C or lower. This can suppress excessive thermal history during wiring formation, thereby preventing damage to the substrate and maintaining a good shape of the wiring formed from the conductive paste.

[0196] The solvent can be appropriately selected from the viewpoint of the solubility and boiling point of the silicone rubber-based curable resin composition, and may include, for example, an aliphatic hydrocarbon having 5 to 20 carbon atoms, preferably an aliphatic hydrocarbon having 8 to 18 carbon atoms, and more preferably an aliphatic hydrocarbon having 10 to 15 carbon atoms.

[0197] 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; diethyl ether, diisopropyl ether, dibutyl ether, cyclopentyl methyl ether, cyclopentyl ethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, and diethylene glycol. Examples of such solvents include ethers 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; and esters such as diethyl carbonate. These may be used alone or in combination of two or more. The solvent used here may be appropriately selected from among solvents that can uniformly dissolve or disperse the components in the conductive paste.

[0198] The above solvents are the polarity term of the Hansen solubility parameters (δ p ) is, for example, 10 MPa 1 / 2 or less, preferably 7 MPa 1 / 2 or less, more preferably 5.5 MPa 1 / 2 The silicone rubber-based curable resin composition may contain a first solvent having the following polarity term (δ) of the first solvent. This makes it possible to improve the dispersibility and solubility of the silicone rubber-based curable resin composition in the paste. p The lower limit of the pressure is not particularly limited, but may be, for example, 0 Pa. 1 / 2 More than that is fine.

[0199] The hydrogen bond term (δ h ) is, for example, 20 MPa 1 / 2 or less, preferably 10 MPa 1 / 2 More preferably, it is 7 MPa or less. 1 / 2 This allows the silicone rubber-based curable resin composition to have good dispersibility and solubility in the paste. h The lower limit of the pressure is not particularly limited, but may be, for example, 0 Pa. 1 / 2 More than that is fine.

[0200] Hansen solubility parameter (HSP) is an index that indicates the solubility of a substance, i.e., how much a substance dissolves in another substance. HSP expresses solubility as a three-dimensional vector. This three-dimensional vector is typically expressed as a dispersion term (δ d ), polarity term (δ p ), hydrogen bond term (δ h ) and those with similar vectors can be judged to have high solubility. The similarity of vectors can be judged by the distance of the Hansen solubility parameter (HSP distance).

[0201] The Hansen Solubility Parameters (HSP values) used in this specification can be calculated using software called HSPiP (Hansen Solubility Parameters in Practice). The computer software HSPiP, developed by Hansen and Abbott, includes a function for calculating HSP distances and a database listing the Hansen parameters for various resins and solvents or non-solvents. The solubility of each resin in pure solvents and mixed solvents of good and poor solvents is investigated, and the results are entered into the HSPiP software to calculate D: dispersion term, P: polar term, H: hydrogen bond term, and R0: radius of the solubility sphere.

[0202] As the solvent of this embodiment, for example, one can be selected that has a small difference in HSP distance, polarity term, or hydrogen bond term between the elastomer or the structural units that make up the elastomer and the solvent.

[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 25°C is, for example, 1 Pa·s or more, preferably 5 Pa·s or more, and more preferably 10 Pa·s or more. This can improve film-forming properties. Also, shape retention can be improved even when forming a thick film. On the other hand, the upper limit of the viscosity of the conductive paste and / or insulating paste at room temperature 25°C is, for example, 100 Pa·s or less, preferably 90 Pa·s or less, and more preferably 80 Pa·s or less. This can improve the printability of the paste.

[0204] At room temperature of 25°C, the viscosity measured at a shear rate of 1 [1 / s] is η1, the viscosity measured at a shear rate of 5 [1 / s] is η5, and the thixotropy index is the viscosity ratio (η1 / η5). In this case, the lower limit of the thixotropic 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. This allows the shape of the wiring obtained by the printing method to be stably maintained. On the other hand, the upper limit of the thixotropic 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. This allows the paste to be more easily printed.

[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, based on 100% by mass of the insulating paste. 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, based on 100% by mass of the insulating paste.

[0206] (Conductive filler) As the conductive filler, a known conductive material may be used, but metal powder (G) may also be used. The metal constituting the metal powder (G) is not particularly limited, but may include, for example, at least one of copper, silver, gold, nickel, tin, lead, zinc, bismuth, antimony, or metal powders alloyed with these, or two or more of these. Of these, the metal powder (G) preferably contains silver or copper, that is, silver powder or copper powder, because of their high conductivity and easy availability. These metal powders (G) may also be coated with other metals.

[0207] In this embodiment, the shape of the metal powder (G) is not limited, and conventionally used shapes such as dendritic, spherical, scale-like, etc. Among these, scale-like metal powder (G) may be used.

[0208] The particle size of the metal powder (G) is not limited, but for example, the average particle size D 50 The particle size of the metal powder (G) is, for example, an average particle size D 50 It 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 the value of the thickness of the silicone rubber in this range, the silicone rubber can exhibit an appropriate electrical conductivity. The particle size of the metal powder (G) can be defined as the average particle size of 200 arbitrarily selected metal powder particles, for example, by observing the conductive paste or silicone rubber molded using the conductive paste with a transmission electron microscope or the like and performing image analysis.

[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, based on 100% by mass of the conductive paste. 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, based on 100% by mass of the conductive paste. By setting the content of the conductive filler to the above lower limit or more, the silicone rubber can have appropriate conductive properties. By setting the content of the conductive filler to the above upper limit or less, 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, based on 100% by mass of the conductive paste. 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, based on 100% by mass of the conductive paste. By adjusting the content of the silicone rubber-based curable composition to be equal to or greater than the lower limit, the silicone rubber can have an appropriate degree of flexibility, while by adjusting the content of the silicone rubber-based curable composition to be equal to or less than the upper limit, the mechanical strength of the silicone rubber can be improved.

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

[0212] The content of the conductive filler in the conductive cured product obtained by curing the conductive paste that constitutes wiring such as the lower wiring and the upper wiring is preferably 65% by mass or more, more preferably 70% by mass or more, and even more preferably 75% by mass or more, based on 100% by mass of the conductive cured product. Furthermore, 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, based on 100% by mass of the conductive cured product. By setting the content of the conductive filler to the above lower limit or more, the silicone rubber can have appropriate conductive properties, and by setting the content of the conductive filler to the above upper limit or less, the silicone rubber can have appropriate flexibility.

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

[0214] The method for manufacturing a stretchable multilayer circuit board of this embodiment is a method for manufacturing a flexible circuit board having a multilayer wiring structure, and includes the steps of forming a substrate, 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. In a method for manufacturing an elastic multilayer circuit board, the substrate, lower wiring, lower insulating layer, upper wiring, and upper insulating layer are each formed using a thermosetting elastomer, and the lower wiring and upper wiring are formed so that, when viewed perpendicularly to one surface of the substrate, at least the first upper wiring intersects with the first lower wiring, yet are electrically connectable to each other.

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

[0216] Here, an example of a manufacturing process for the stretchable multilayer circuit board 100 will be described with reference to FIG. 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 to the support 12. Various methods can be used for application, for example, a printing method such as a squeegee method using a squeegee 14. The insulating paste 13 in the form of a coating is then dried to form an insulating layer 32 (a substrate 110 made of an insulating elastomer) on the support 12. The drying conditions can be set appropriately depending on the type and amount of solvent in the insulating paste 13, but for example, the drying temperature can be set to 150°C to 180°C, and the drying time can be set to 1 minute to 30 minutes, etc.

[0218] The insulating layer 32 constituting the substrate 110 may be formed by a molding method such as calendar molding or compression molding using the above-mentioned silicone rubber-based hardening composition.

[0219] 3(b), a mask 16 having a predetermined opening pattern is placed on the insulating layer 32. Then, as shown in FIGS. 3(b) and 3(c), a conductive paste 15 is applied onto the insulating layer 32 through the mask 16. The coating method can be the same as the coating method for the insulating paste 13, and 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, a conductive coating film (conductive layer 52) having a predetermined pattern may be laminated on the dried insulating layer 32, and then these may be cured together. The curing process can be appropriately set depending on the silicone rubber-based curable composition, but for example, the curing temperature may be 160°C to 220°C, and the curing time may be 1 hour to 3 hours. After or before the curing process, the mask 16 can be removed as shown in FIG. 3(d). This allows a cured product of the conductive layer 52 (lower wiring 120 made of a conductive elastomer) having a predetermined pattern to be formed on the substrate made of the cured product of the insulating layer 32.

[0220] Next, as shown in FIG. 3(e), an insulating paste 17 is further applied onto the insulating layer 32 and the patterned conductive layer 52, thereby forming an insulating layer 72 (a lower insulating layer 130 made of an insulating elastomer) as shown in FIG. 3(f). 3(b) to 3(e) may be repeated as appropriate. This allows the formation of upper wiring 150 made of a conductive elastomer, an upper insulating layer 160 made of an insulating elastomer, and the like, making it possible to form a multi-layer circuit. Furthermore, by adjusting the mask pattern and its placement position, it is possible to form a crossing structure of the lower wiring 120 and the upper wiring 150. The repeating step may be performed after separating the support 120 from the insulating layer 32. In this way, the stretchable multilayer circuit board 100 shown in FIG. 1(a) can be obtained.

[0221] In this way, in the stretchable multilayer circuit board 100, at least one of the substrate 110, the lower insulating layer 130, and the upper insulating layer 160, and preferably all of them, may be made of an insulating printed layer printed using an insulating paste, which can improve adhesion with the wiring.

[0222] In the stretchable multilayer circuit board 100, the lower wiring 120 and the upper wiring 150 may each be made of a conductive printed layer printed using a conductive paste, which allows for flexible selection of the pattern shape of the conductive printed layer.

[0223] The lower limit of the conductive filler content 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, and more preferably 80% by mass or more, based on 100% by mass of the wiring. This improves the stretchable electrical properties of the stretchable multilayer circuit board. On the other hand, the upper limit of the conductive filler content 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, and more preferably 85% by mass or less, based on 100% by mass of the wiring. This prevents a decrease in the rubber properties, such as the stretchability, of the stretchable multilayer circuit board.

[0224] The properties of the stretchable multilayer circuit board 100 will be described below.

[0225] In this 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 made of an elastomer having at least one of the following properties: In one preferred embodiment, the substrate 110 is made of an elastomer having at least one of the following tear strength, breaking elongation, 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, even more preferably 33 N / mm or more, and even more preferably 35 N / mm or more. This can improve the durability of the elastomer during repeated use. It can also improve the mechanical strength of the elastomer. 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, which allows the various properties of the elastomer to be balanced.

[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. This improves the mechanical strength of the elastomer. Furthermore, it is possible to realize an elastomer with excellent durability that can withstand repeated deformation. 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, which allows the various properties of the elastomer to be balanced.

[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 even more preferably 400% or more, which can improve the high stretchability and durability of the elastomer. 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, which allows the various properties of the elastomer to be balanced.

[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. This allows the cured physical properties of the silicone rubber to be balanced. This increases the deformability of the elastomer, making it easier to deform, such as by bending or stretching. On the other hand, the lower limit of the durometer hardness A of the elastomer is not particularly limited, but is, for example, at least 30, preferably at least 35, and more preferably at least 40. This increases the mechanical strength of the elastomer.

[0230] In this embodiment, the following method can be used to measure the properties of each component of the stretchable multilayer circuit board and the properties of the elastomer used in each component. To measure the properties of each component, each component, such as a substrate, can be used as a test piece.

[0231] (Tear strength measurement conditions) A crescent-shaped test piece is prepared using the elastomer, and the tear strength of the obtained crescent-shaped test piece is measured at 25°C in accordance with JIS K6252 (2001).

[0232] (Tensile strength measurement conditions) A dumbbell-shaped No. 3 test piece is prepared using the elastomer, and the tensile strength of the obtained dumbbell-shaped No. 3 test piece is measured at 25°C in accordance with JIS K6251 (2004).

[0233] (Measurement conditions for breaking elongation) A dumbbell-shaped No. 3 test piece is prepared using the elastomer, and the resulting dumbbell-shaped No. 3 test piece is measured for breaking elongation at 25°C in accordance with JIS K6251 (2004).

[0234] (Durometer hardness A measurement procedure) A sheet-like test piece is prepared using the elastomer, and the durometer hardness A of the obtained sheet-like test piece at 25°C is measured in accordance with JIS K6253 (1997).

[0235] At least one of the first lower wiring 120 and the first upper wiring 150 has a volume resistivity of, for example, 1×10 at 25° C. when unstretched. -5 Ω cm or more 1×10 -1 Ω·cm or less, preferably 5×10 -5 Ω cm or more 5×10 -2 Ω·cm or less, preferably 1×10 -4 Ω cm or more 1×10 -2 By setting the resistance within this range, it is possible to obtain a stretchable multilayer circuit board 100 that has excellent electrical properties both when unstretched and when stretched.

[0236] At 25°C, at least one of the electrical resistance values of the first lower wiring 120 and the first upper wiring 150 when unstretched 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, and more preferably 0.1 Ω / cm or more and 200 Ω / cm or less.

[0237] When the electrical resistance at 25°C when unstretched is within the above range, at least one of the electrical resistances of the first lower wiring 120 and the first upper wiring 150 when stretched by 50% at 25°C 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, and more preferably 0.3 Ω / cm or more and 300 Ω / cm or less. By keeping the electrical resistance within such a range, a stretchable multilayer circuit board 100 with excellent electrical properties can be obtained when unstretched and even when stretched.

[0238] The electrical resistance value of the wiring at 25°C and 20% elongation is defined as X1, and the electrical resistance value of the wiring at 25°C and 50% elongation is defined as X2. When the electrical resistance at 25°C when unstretched 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, and more preferably 1.4≦X2 / X1≦6.0. By ensuring that the resistance is within such a range, a stretchable multilayer circuit board 100 with excellent electrical properties can be obtained even when stretched.

[0239] The electrical resistance of the wiring at 25°C when unstretched is defined as Z1, and the electrical resistance of the wiring in an unstretched state after 100 cycles of 50% stretching at 25°C is defined as 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, and more preferably 1.3≦Z2 / Z1≦2.8. By satisfying this range, a stretchable multilayer circuit board 100 with excellent electrical properties can be obtained even when repeatedly stretched.

[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, and a biosensor.

[0241] An example of applying a stretchable multilayer circuit board to a stretchable display will be described below with reference to FIG. 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. The display device 300 may further include at least one other functional unit such as a power supply unit 350 or a communication unit 340.

[0243] The display unit 310 includes a stretchable display (display unit 310) and displays information using the stretchable display. The stretchable display is configured from the above-described stretchable multilayer circuit board on which a display element and the like are mounted. Such a display device 300 can be attached to clothing, the body, or other objects depending on various uses.

[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 information input from the input unit 330, for example.

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

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

[0247] The power supply unit 350 may be configured as a mobile battery, or may include electrodes that can be connected to an external power source.

[0248] In the display device 300, in addition to a display area where a display element is mounted, a non-display area around the display area may be provided on the substrate 110 of the stretchable multilayer circuit board that constitutes the display unit 310. At least one or more of the following units may be provided on the substrate 110 in the non-display area: a control unit 320, a power supply unit 350, an input unit 330, a communication unit 340, and a memory unit 360. This allows the display element to be connected to each unit or between each unit via stretchable wiring.

[0249] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. Below, examples of reference forms are given. 1. A substrate; a plurality of lower wirings provided on the substrate; a lower insulating layer provided on the lower wiring; a plurality of upper wirings provided on the lower insulating layer; An upper insulating layer provided on the upper wiring, the substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer each contain a thermosetting elastomer; In the multilayer wiring structure, a crossing structure in which the first lower wiring and the first upper wiring cross each other when viewed in a direction perpendicular to one surface of the substrate; a connection structure that allows the first lower wiring and the first upper wiring to be electrically connected to each other; A stretchable multilayer circuit board comprising: 2. The stretchable multilayer circuit board according to 1., The substrate, the lower insulating layer, and the upper insulating layer each comprise silicone rubber. 3. The stretchable multilayer circuit board according to 1. or 2., The lower wiring and the upper wiring each comprise silicone rubber and a conductive filler. 4. The stretchable multilayer circuit board according to any one of 1. to 3., The substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer are made of the same type of silicone rubber. 5. The stretchable multilayer circuit board according to 3., The stretchable multilayer circuit board, wherein the conductive filler comprises silver powder. 6. The stretchable multilayer circuit board according to any one of 1. to 5., At least one of the substrate, the lower insulating layer, and the upper insulating layer comprises an inorganic filler. 7. The stretchable multilayer circuit board according to any one of 1. to 6., At least one of the lower wiring and the upper wiring comprises an inorganic filler. 8. The stretchable multilayer circuit board according to 6. or 7., The stretchable multilayer circuit board, wherein the inorganic filler comprises silica. 9. The stretchable multilayer circuit board according to any one of 1. to 8., 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. The stretchable multilayer circuit board according to any one of 1. to 9., The 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. 11. The stretchable multilayer circuit board according to any one of 1. to 10., A stretchable multilayer circuit board, wherein the tear strength of the board at 25°C measured in accordance with JIS K6252 (2001) is 25 N / mm or more. 12. The stretchable multilayer circuit board according to any one of 1. to 11., A stretchable multilayer circuit board, wherein the breaking elongation of the board at 25°C measured in accordance with JIS K6251 (2004) is 100% or more. 13. The stretchable multilayer circuit board according to any one of 1. to 12., A stretchable multilayer circuit board, wherein the board has a durometer hardness A at 25°C, as defined in accordance with JIS K6253 (1997), of 30 or more and 90 or less. 14. The stretchable multilayer circuit board according to any one of 1. to 13., A stretchable multilayer circuit board, wherein the ratio of the thickness of the lower insulating layer to the thickness of the board is 0.01 or more and 2.0 or less. 15. The stretchable multilayer circuit board according to any one of 1. to 14., A stretchable multilayer circuit board, wherein the thickness of the lower wiring / the thickness of the lower insulating layer is 0.05 or more and 20.0 or less. 16. The stretchable multilayer circuit board according to any one of 1. to 15., The volume resistivity of the first lower wiring and the first upper wiring at 25°C when unstretched is 1×10 -5 Ω cm or more 1×10 -1 Stretchable multilayer circuit board with a resistance of less than Ω·cm. 17. The stretchable multilayer circuit board according to any one of 1. to 16., A stretchable multilayer circuit board, wherein when the electrical resistance of the first lower wiring and the first upper wiring at 25°C when unstretched is within the range of 0.01 Ω / cm or more and 1000 Ω / cm or less, and when the electrical resistance of the first lower wiring and the first upper wiring at 20% stretch is X1 and the electrical resistance of the first lower wiring and the first upper wiring at 50% stretch is X2, X2 / X1 is 1.2 or more and 8.0 or less. 18. The stretchable multilayer circuit board according to any one of 1. to 17., An elastic multilayer circuit board, wherein when the electrical resistance of the first lower wiring and the first upper wiring at 25°C when unstretched is in the range of 0.01 Ω / cm or more and 1000 Ω / cm or less, the electrical resistance of the first lower wiring and the first upper wiring at 50% stretch is 0.1 Ω / cm or more and 1200 Ω / cm or less. 19. The stretchable multilayer circuit board according to any one of 1. to 18., When Z1 is the electrical resistance of the first lower wiring at 25°C when unstretched, and Z2 is the electrical resistance of the first lower wiring in an unstretched state after 100 50% stretching operations, A stretchable multilayer circuit board having Z2 / Z1 of 1.1 or more and 3.0 or less. 20. The stretchable multilayer circuit board according to any one of 1. to 19., In the connection structure, the first lower wiring and the first upper wiring are electrically connected via an electronic component. 21. The stretchable multilayer circuit board according to 20., The electronic component is configured to electrically connect to the first lower wiring and the first upper wiring using at least one of a conductive paste and a solder material. 22. The stretchable multilayer circuit board according to 20. or 21., The stretchable multilayer circuit board comprises a sealing portion that seals the electronic component in the multilayer wiring structure. 23. The stretchable multilayer circuit board according to any one of 1. to 22., In the connection structure, a lower opening is formed penetrating at least the lower insulating layer and the upper insulating layer, and an upper opening is formed penetrating at least the upper insulating layer, a first lower wiring having a lower connection portion configured to be exposed in the lower opening; A stretchable multilayer circuit board, wherein a first of the upper traces has an upper connection portion configured to be exposed within the upper opening. 24. The stretchable multilayer circuit board according to any one of 1. to 23. In a cross-sectional view when cut in the stacking direction of the multilayer wiring structure, the first lower wiring in the connection structure has a protruding connection portion that protrudes from the substrate toward the lower wiring. A stretchable multilayer circuit board. 25. The stretchable multilayer circuit board according to any one of 1. to 24., The substrate is a stretchable multilayer circuit board having no wiring on the other side opposite to the side on which the upper wiring and the lower wiring are provided. 26. The stretchable multilayer circuit board according to any one of 1. to 25., When viewed in a direction perpendicular to one surface of the substrate, the multilayer wiring structure includes a plurality of crossing structures in which a plurality of the lower wirings and a plurality of the upper wirings cross each other, The stretchable multilayer circuit board, wherein the plurality of crossing structures are arranged in a grid pattern. 27. A stretchable display, a wearable device, or a biosensor, comprising the stretchable multilayer circuit board according to any one of 1. to 26. 28. A display device comprising a display unit, a control unit, a power supply unit, and / or a communication unit, A display device, wherein the display unit comprises the stretchable display described in 27. 29. Forming a substrate; forming a plurality of underlying interconnects on the substrate; forming a lower insulating layer on the lower wiring; forming a plurality of upper wirings on the lower insulating layer; A method for producing a stretchable multilayer circuit board having a multilayer wiring structure, comprising: forming an upper insulating layer on the upper wiring; the substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer are each formed using a thermosetting elastomer; forming the lower wiring and the upper wiring so that, when viewed in a direction perpendicular to one surface of the substrate, at least the first upper wiring intersects with the first lower wiring and yet are electrically connectable to each other; A method for producing a stretchable multilayer circuit board. 30. A method for producing a stretchable multilayer circuit board according to 29, comprising: The method for manufacturing a stretchable multilayer circuit board, wherein the plurality of lower wirings and the plurality of upper wirings are formed by applying and drying the same or different conductive pastes. [Example]

[0250] The present invention will be described in detail below 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: a vinyl group-containing dimethylpolysiloxane (structure represented by the above formula (1-1)) synthesized according to the following synthesis scheme 1. (A1-2): Second vinyl group-containing linear organopolysiloxane: A vinyl group-containing dimethylpolysiloxane (having the structure represented by the above formula (1-1) and R 1 and R 2 is a vinyl group)

[0252] (Organohydrogenpolysiloxane (B)) (B-1): Organohydrogenpolysiloxane: Momentive Corporation, "TC-25D"

[0253] (Silica particles (C)) (C): Silica microparticles (particle size 7 nm, specific surface area 300 m 2 / g), Nippon Aerosil Co., Ltd., "AEROSIL300"

[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 compounds (E)) (E-1): Platinum compound (manufactured by Momentive, product name "TC-25A")

[0256] (Water(F)) (F):Pure water

[0257] (Metal powder (G)) (G1): Silver powder, manufactured by Tokuriki Chemical Laboratory Co., Ltd., product name "TC-101", median diameter d 50 :8.0μm, aspect ratio 16.4, average major axis 4.6μm

[0258] (Synthesis of vinyl group-containing organopolysiloxane (A)) [Synthesis Scheme 1: Synthesis of First Vinyl Group-Containing Linear Organopolysiloxane (A1-1)] A first vinyl group-containing linear organopolysiloxane (A1-1) was synthesized according to the following formula (5). Specifically, 74.7 g (252 mmol) of octamethylcyclotetrasiloxane and 0.1 g of potassium siliconate were placed in a 300 mL separable flask equipped with a condenser and stirring blade and purged with Ar gas, and the mixture was heated to 120° C. and stirred for 30 minutes. An increase in viscosity was confirmed during this time. The temperature was then raised to 155°C and stirring was continued for 3 hours, after which 0.1 g (0.6 mmol) of 1,3-divinyltetramethyldisiloxane was added and the mixture was further stirred at 155°C for 4 hours. After another 4 hours, the mixture was diluted with 250 mL of toluene and washed three times with water. The washed organic layer was reprecipitated and purified by washing with 1.5 L of methanol several times, and the oligomer and polymer were separated. The resulting 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 The vinyl group content calculated by H-NMR spectroscopy was 0.04 mol %.

[0259] [ka]

[0260] [Synthesis Scheme 2: Synthesis of Second Vinyl-Containing Linear Organopolysiloxane (A1-2)] A second vinyl-containing linear organopolysiloxane (A1-2) was synthesized as shown in formula (6) below, by the same procedure as in the synthesis of (A1-1) above, 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. Furthermore, the vinyl group content calculated by H-NMR spectroscopy was 0.92 mol%.

[0261] [ka]

[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 pre-kneaded in the proportions shown in Table 1 below, and 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) was carried out through two steps: a first step of kneading for 1 hour under a nitrogen atmosphere at 60 to 90°C for the coupling reaction, and a second step of kneading for 2 hours under a reduced pressure atmosphere at 160 to 180°C for the removal of the by-product (ammonia).The mixture was then cooled, and the remaining 10% of the vinyl group-containing organopolysiloxane (A) was added in two portions, followed by kneading for 20 minutes. Next, organohydrogenpolysiloxane (B), platinum or a platinum compound (E) were added to 100 parts by weight of the obtained kneaded product (silicone rubber compound) in the proportions 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) 32 parts by weight of the obtained silicone rubber-based hardening composition 4 was immersed in 68 parts by weight of tetradecane (solvent), and then stirred with a planetary centrifugal mixer to obtain a conductive paste.

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

[0266] Example 1 (Fabrication of stretchable circuit boards) The stretchable multilayer circuit board 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 form it into a sheet, and then subjected to primary curing. Subsequently, secondary curing was performed at 200°C for 4 hours to obtain a substrate 110 (cured product of the silicone rubber-based curable composition) having a length x width x thickness of 12 cm x 12 cm with 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 then dried at 140° C. for 20 minutes. The lower wirings 120 Nos. 1 to 8 each had a structure in which vertical and horizontal wiring having the lengths shown in Table 2 were connected in this order with their orientations changed by 90 degrees, and each wiring had a width of 1.0 mm and a thickness shown in Table 3. Using the obtained insulating paste, an insulating layer was formed on the substrate 110 and the lower wirings 120 through a mask having a predetermined pattern, and dried at 140°C for 20 minutes to form the 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 of the eight lower wirings 120 were exposed. Using the obtained conductive paste, eight upper wiring patterns having wirings that intersect with the eight lower wirings 120 at 90 degrees in top view were drawn on the lower insulating layer 130 through a mask having a predetermined pattern, and then dried at 140° C. for 20 minutes. The upper wirings 150 Nos. 9 to 16 each had a structure in which a vertical wiring (long), a horizontal wiring, and a vertical wiring (short), each having the lengths shown in Table 2, were connected in that order with their orientations changed by 90 degrees, and each wiring had a width of 1.0 mm and a thickness shown in Table 3. Furthermore, eight upper connection portions 152 each having a wiring width of 1.0 mm and a wiring thickness as shown in Table 3 were formed near the lower connection portion 122 of each of the eight vertical wirings (short) of the upper wirings 150. Using the obtained insulating paste, an insulating layer was formed on the substrate 110, the lower insulating layer 130, and the upper wiring 150 through a mask having a predetermined pattern, and dried at 140°C for 20 minutes to form the 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 of the eight lower wirings 120 were exposed, and the upper connection portions 152 and 154 of 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 the stretchable multilayer circuit board 100 of Example 1 shown in Figure 5.

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

[0268] (Electronic Device Manufacturing) 5, an LED chip (electronic component 170) was placed at each of 64 locations where the lower connection portions 122 of the lower wirings 120 No. 1 to 9 and the upper connection portions 152 of the upper wirings 150 No. 10 to 16 straddled each other, and these were adhered with the conductive paste, dried and cured for 20 minutes at 140° C. Thereafter, the LED chip was sealed with the insulating paste, dried and cured for 20 minutes at 140° C., and an electronic device was obtained.

[0269] [Table 2]

[0270] [Table 3]

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

[0272] (hardness) The silicone rubber-based curable composition of each of Examples 1 to 3 was pressed at 170°C and 10 MPa for 10 minutes to form a sheet, and then subjected to primary curing. Subsequently, secondary curing was performed at 200°C for 4 hours, and sheet-like substrates (cured products of the silicone rubber-based curable composition) having the substrate thicknesses shown in Table 3 were used as test specimens. The above test pieces were stacked to a thickness of 6 mm, and the durometer hardness A of the resulting sheet-like test piece at 25° C. was measured in accordance with JIS K6253 (1997).

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

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

[0275] The test specimens were used to measure the elongation at break in accordance with JIS K6251 (2004). The elongation at break was calculated by [movement distance between chucks (mm)] ÷ [initial distance between chucks (35 mm)] × 100. The unit is %.

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

[0277] (Electrical characteristics) It was confirmed that all 64 LED chips emitted light simultaneously when a voltage of 5V was applied to the obtained electronic device via each lower wiring 120 and each upper wiring 150. If 5% or more of the total number of LEDs had poor connections (non-emitting), it was evaluated as ×, and if less than 5%, it was evaluated as ○. The results are shown in Table 1.

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

[0279] (Stretching electrical properties) The stretchable multilayer circuit board 100 in the obtained electronic device was repeatedly stretched 20% in the vertical direction of FIG. 5 10 times. A voltage was applied to the electronic device after the stretching operation, similar to the electrical characteristics described above, and it was confirmed that all 64 LED chips emitted light simultaneously. Poorly connected (non-emitting) LEDs in 5% or more of the total number were evaluated as ×, and those in less than 5% were evaluated as ○. The results are shown in Table 1.

[0280] (Stretching durability) When the cross section of the stretchable multilayer circuit board 100 cut in the thickness direction after the stretching operation was observed, it was confirmed that no peeling occurred at the adhesion interfaces between the substrate 110, lower wiring 120, lower insulating layer 130, upper wiring 150, and upper insulating layer 160.

[0281] Examples 1 to 3 showed results that a stretchable multilayer circuit board having excellent stretchable electrical properties 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 124 Lower connection 126 Lower wiring 130 Lower insulating layer 140 Opening 142 Opening 150 Upper wiring 152 Upper connection 154 Upper connection 156 Upper wiring 160 Upper insulating layer 170 Electronic Components 200 Multilayer wiring structure 210 Cross 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 wiring; a plurality of upper wirings provided on the lower insulating layer; An upper insulating layer provided on the upper wiring, the substrate, the lower insulating layer, and the upper insulating layer each comprise a thermosetting elastomer; the lower wiring and the upper wiring (excluding an embodiment in which the lower wiring and the upper wiring have a bellows-shaped portion in which peaks and valleys in a normal direction to the surface of the substrate appear repeatedly along an in-plane direction of the surface of the substrate) are each made of a thermosetting elastomer and a conductive elastomer containing a conductive filler; In the multilayer wiring structure, a crossing structure in which the first lower wiring and the first upper wiring cross each other when viewed in a direction perpendicular to one surface of the substrate; a connection structure that allows the first lower wiring and the first upper wiring to be electrically connected to each other; A stretchable multilayer circuit board comprising:

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

3. The stretchable multilayer circuit board according to claim 1 or 2, The lower wiring and the upper wiring each comprise silicone rubber.

4. The stretchable multilayer circuit board according to any one of claims 1 to 3, The substrate, the lower wiring, the lower insulating layer, the upper wiring, and the upper insulating layer are made of the same type of silicone rubber.

5. The stretchable multilayer circuit board according to any one of claims 1 to 4, The stretchable multilayer circuit board, wherein the conductive filler comprises silver powder.

6. The stretchable multilayer circuit board according to any one of claims 1 to 5, At least one of the substrate, the lower insulating layer, and the upper insulating layer comprises an inorganic filler.

7. The stretchable multilayer circuit board according to any one of claims 1 to 6, At least one of the lower wiring and the upper wiring comprises an inorganic filler.

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

9. The stretchable multilayer circuit board according to any one of claims 1 to 8, 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. The stretchable multilayer circuit board according to any one of claims 1 to 9, The 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.

11. The stretchable multilayer circuit board according to any one of claims 1 to 10, A stretchable multilayer circuit board, wherein the tear strength of the board at 25°C measured in accordance with JIS K6252 (2001) is 25 N / mm or more.

12. The stretchable multilayer circuit board according to any one of claims 1 to 11, A stretchable multilayer circuit board, wherein the board has a breaking elongation of 100% or more at 25°C as measured in accordance with JIS K6251 (2004).

13. The stretchable multilayer circuit board according to any one of claims 1 to 12, A stretchable multilayer circuit board, wherein the board has a durometer hardness A at 25°C, as defined in accordance with JIS K6253 (1997), of 30 or more and 90 or less.

14. The stretchable multilayer circuit board according to any one of claims 1 to 13, An elastic multilayer circuit board, wherein when the electrical resistance of the first lower wiring and the first upper wiring at 25°C when unstretched is in the range of 0.01 Ω / cm or more and 1000 Ω / cm or less, the electrical resistance of the first lower wiring and the first upper wiring at 50% stretch is 0.1 Ω / cm or more and 1200 Ω / cm or less.

15. The stretchable multilayer circuit board according to any one of claims 1 to 14, When Z1 is the electrical resistance value of the first lower wiring at 25°C when unstretched, and Z2 is the electrical resistance value of the first lower wiring in an unstretched state after 100 50% stretching operations, A stretchable multilayer circuit board, wherein Z2 / Z1 is 1.1 or more and 3.0 or less.

16. The stretchable multilayer circuit board according to any one of claims 1 to 15, In the connection structure, the first lower wiring and the first upper wiring are electrically connected via an electronic component.

17. 17. The stretchable multilayer circuit board of claim 16, The electronic component is configured to electrically connect to the first lower wiring and the first upper wiring using at least one of a conductive paste and a solder material.

18. 18. The stretchable multilayer circuit board according to claim 16 or 17, The stretchable multilayer circuit board comprises a sealing portion that seals the electronic component in the multilayer wiring structure.

19. The stretchable multilayer circuit board according to any one of claims 1 to 18, In the connection structure, a lower opening is formed penetrating at least the lower insulating layer and the upper insulating layer, and an upper opening is formed penetrating at least the upper insulating layer, a first lower wiring having a lower connection portion configured to be exposed in the lower opening; A stretchable multilayer circuit board, wherein a first of the upper traces has an upper connection portion configured to be exposed within the upper opening.

20. The stretchable multilayer circuit board according to any one of claims 1 to 19, In a cross-sectional view when cut in the stacking direction of the multilayer wiring structure, the first lower wiring in the connection structure has a protruding connection portion that protrudes from the substrate toward the lower wiring. A stretchable multilayer circuit board.

21. The stretchable multilayer circuit board according to any one of claims 1 to 20, The substrate is a stretchable multilayer circuit board having no wiring on the other side opposite to the side on which the upper wiring and the lower wiring are provided.

22. The stretchable multilayer circuit board according to any one of claims 1 to 21, When viewed in a direction perpendicular to one surface of the substrate, the multilayer wiring structure includes a plurality of crossing structures in which a plurality of the lower wirings and a plurality of the upper wirings cross each other, The stretchable multilayer circuit board, wherein the plurality of crossing structures are arranged in a grid pattern.

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