Stretchable device

Abstract

Provided is a stretchable device comprising a stretchable base material and a protective layer provided on the stretchable base material. The stretchable base material is provided with a first main surface and a second main surface that face each other in the thickness direction of the stretchable base material, and a side surface that connects the first main surface and the second main surface. The protective layer covers the first main surface and at least one of the second main surface and the side surface.

Description

stretchable devices

[0001] The present disclosure relates to stretchable devices.

[0002] Stretchable devices including a stretchable substrate have been known for some time. These stretchable devices can be used in, for example, living organisms or devices that require stretchability.

[0003] Patent No. 5,448,736 U.S. Patent Application Publication No. 2018 / 132350

[0004] Generally, a stretchable device includes a stretchable substrate made of resin. During use of the stretchable device, the stretchable substrate may be stretched and contracted. If the stretchable substrate has a structural defect, stress may be concentrated at the defect site during the stretching and contracting movement of the stretchable substrate. This may cause the stretchable substrate to break or tear from the defect site.

[0005] The present disclosure has been made in view of the above-mentioned problems. That is, a main object of the present disclosure is to provide a stretchable device in which breakage of a stretchable substrate is suitably suppressed.

[0006] The inventors of the present application have come up with the invention of a stretchable device that achieves the above-mentioned main object.

[0007] A stretchable device according to one embodiment of the present disclosure comprises a stretchable substrate and a protective layer provided on the stretchable substrate, wherein the stretchable substrate comprises a first main surface and a second main surface facing each other in a thickness direction of the stretchable substrate, and a side surface connecting the first main surface and the second main surface, and the protective layer covers at least one of the second main surface and the side surface and the first main surface.

[0008] According to the stretchable device according to an embodiment of the present disclosure, breakage of the stretchable substrate is suitably suppressed.

[0009] FIG. 1A is a cross-sectional view schematically showing the appearance of a stretchable device according to a first embodiment of the present disclosure. FIG. 1B is a cross-sectional view schematically showing a stretchable device according to a first embodiment of the present disclosure. FIG. 1C is a cross-sectional view schematically showing a stretchable device according to a first embodiment of the present disclosure. FIG. 1D is a cross-sectional view schematically showing a stretchable device according to a first embodiment of the present disclosure. FIG. 2 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 3 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 4 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 5 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 6 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 7 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 8 is a cross-sectional view schematically showing a stretchable device according to a modified version of the first embodiment of the present disclosure. FIG. 9A is a cross-sectional view schematically showing a stretchable device according to a second embodiment of the present disclosure. FIG. 9B is a schematic cross-sectional view showing a stretchable device according to a modified example of the second embodiment of the present disclosure. FIG. 9C is a schematic cross-sectional view showing a stretchable device according to a modified example of the second embodiment of the present disclosure. FIG. 10A is a schematic perspective cross-sectional view showing a stretchable device according to a third embodiment of the present disclosure. FIG. 10B is a schematic perspective cross-sectional view showing a stretchable device according to a modified example of the third embodiment of the present disclosure. FIG. 11A is a schematic cross-sectional view showing an A-A cross section of the stretchable device shown in FIG. 10A. FIG. 11B is a schematic cross-sectional view showing a B-B cross section of the stretchable device shown in FIG. 10B. FIG. 12 is a schematic plan view showing a stretchable device according to a fourth embodiment of the present disclosure. FIG. 13 is a schematic exploded cross-sectional view showing a C-C cross section of the stretchable device shown in FIG. 12. FIG. 14 is a schematic cross-sectional view showing a C-C cross section of the stretchable device shown in FIG. 12. FIG. 15 is a schematic cross-sectional view showing a stretchable device according to a modified example of the fourth embodiment of the present disclosure. Fig. 16 is a schematic cross-sectional view showing a stretchable device according to a modified example of the fourth embodiment of the present disclosure. Fig. 17 is a schematic plan view showing a stretchable device according to a modified example of the fourth embodiment of the present disclosure.

[0010] The following describes specific embodiments of the present disclosure. The applicant provides the following description and examples to enable those skilled in the art to fully understand the present disclosure, and it should be noted that these are not intended to limit the subject matter described in the claims. In other words, the present disclosure is not particularly limited to the preferred embodiments described below, and can be implemented with appropriate modifications within the scope of its purpose. For convenience, the present disclosure may be divided into embodiments and examples, etc., in consideration of ease of explanation or understanding of the main points. However, partial substitution and / or combination of the configurations shown in different embodiments, etc. is possible. In describing such embodiments, redundant explanations of substantially identical matters may be omitted, and only differences may be described. In particular, similar actions and effects resulting from similar configurations may not be mentioned in each embodiment.

[0011] In this specification, the terms "thickness direction of the stretchable device," "thickness direction of the stretchable substrate," "stacking direction of the stretchable substrate," and "stacking direction" may be used interchangeably. This direction corresponds to direction Y in the drawings.

[0012] As used herein, the term "cross-sectional view" or "cross-sectional shape" refers to the shape of the stretchable device as viewed from a direction substantially perpendicular to the thickness direction (in other words, the shape of the stretchable device cut along a plane parallel to the thickness direction). When the stretchable device has a layered structure including multiple stretchable substrate layers, the term "cross-sectional view" or "cross-sectional shape" refers to the shape of the stretchable device as viewed from a direction substantially perpendicular to the stacking direction of the stretchable substrates (in other words, the shape of the stretchable device cut along a plane parallel to the stacking direction). Furthermore, the term "planar view" used herein refers to a sketch of the object as viewed from above or below along the thickness direction (or stacking direction) of the stretchable device.

[0013] Furthermore, in this specification, "above" an element includes not only the case of contacting the top surface of the element, but also the case of not contacting the top surface of the element. In other words, "above" an element does not only mean above the element, i.e., a position above the element via another object or a position above with a gap, but also a position directly above the element. Furthermore, "above" does not necessarily mean above in the vertical direction. "Above" merely indicates the relative positional relationship of an element.

[0014] The various numerical ranges referred to herein are intended to include the lower and upper numerical limits themselves unless otherwise specified, and the term "about" means that there may be a variation or difference of a few percent, for example, ±10%.

[0015] As used herein, "vertical" and "substantially vertical" do not necessarily mean completely "vertical," but include aspects that are slightly deviated from the completely vertical (for example, a range of ±10° from the completely vertical, e.g., a range of ±5°).

[0016] Furthermore, in this specification, "substantially parallel" does not necessarily mean completely "parallel," but includes a state where the parallelism is slightly deviated from the parallelism (for example, within a range of ±10° from completely parallelism, e.g., within a range of ±5°).

[0017] [Basic configuration of stretchable device] The structure of a stretchable device will be described with reference to Fig. 1A. Fig. 1A is a cross-sectional view illustrating an example of a stretchable device according to an embodiment of the present disclosure. Note that cross-sectional views in this specification are cross-sections parallel to the thickness direction Y of the stretchable device 1.

[0018] The stretchable device 1 includes at least a stretchable substrate 10. Here, the "main surface" of the stretchable substrate refers to a surface extending in a direction different from the thickness direction Y of the stretchable substrate, for example, a surface extending in a direction X that is approximately perpendicular to the thickness direction Y of the stretchable substrate. The "main surface" corresponds to a surface that is clearly larger in area than the other surfaces (side surfaces facing the width direction X) of the sheet-like stretchable substrate 10. The stretchable substrate 10 has main surfaces 12A and 12B that face each other. The sheet-like or film-like stretchable substrate 10 may extend along the stretch direction of the stretchable device 1. In such a structure, the "main surface" of the stretchable substrate 10 can also be interpreted as a surface extending along the stretch direction of the stretchable substrate 10. In an embodiment including a stretchable wiring, which will be described later, it can also be interpreted as a surface extending along the extension direction of the stretchable wiring (see FIG. 9A ). Note that, although the drawings show a stretchable device extending in a specific direction for clarity, the shape of the stretchable device is not particularly limited. The planar shape of the stretchable device is not particularly limited, and can be, for example, a quadrilateral (e.g., square, rectangle, etc.), a polygon such as a triangle, a circle, an ellipse, a semicircle, a crescent, or an irregular shape.

[0019] The main components included in the stretchable device of the present disclosure will now be described, primarily with reference to FIG. 1A.

[0020] (Stretchable Substrate 10) The stretchable substrate 10 (hereinafter also referred to simply as "substrate") may be a sheet-like or film-like stretchable substrate, and may be composed of, for example, a stretchable resin material. Here, in this specification, "stretchability" simply means the property of being able to stretch and contract, and may also be referred to as stretchability, stretchability, etc. More specifically, it means the property of being able to stretch from a non-stretched state, which is the normal state in which no tensile stress is applied, by applying tensile stress, and being able to contract when released from the stretched state. Examples of resin materials used for the stretchable substrate 10 include elastomer resins such as silicone-based resins, acrylic-based resins, olefin-based resins, urethane-based resins, and styrene-based resins, and the like. These may be used alone or in combination of two or more. For example, thermoplastic polyurethane may be used as the stretchable material 10.

[0021] The thickness of the stretchable substrate 10 is not particularly limited, but when emphasis is placed on the stretchability of the device, it is preferably 1 mm or less, more preferably 100 μm or less, and even more preferably 50 μm or less. When emphasis is placed on the mechanical strength of the device, the thickness of the stretchable substrate is preferably 10 μm or more. When a laminate is formed from multiple stretchable substrates, each of the multiple stacked stretchable substrates may have the same thickness or may have different thicknesses.

[0022] (Stretchable Wiring 40) In one embodiment, the stretchable device may include a stretchable wiring 40 (see FIGS. 9A to 9C). The stretchable wiring 40 (hereinafter also simply referred to as "wiring") contains conductive particles and a resin. Examples of the stretchable wiring 40 include a mixture of conductive particles such as metal powder of Ag (silver), Cu (copper), or Ni (nickel) and an elastomer resin such as a silicone resin. The average particle size of the conductive particles is not particularly limited, but is preferably 0.01 μm or more and 10 μm or less. The conductive particles are preferably spherical. The wiring may be formed not only from a stretchable wiring but also from a horseshoe-shaped metal foil (e.g., copper foil). The wiring may be formed using a subtractive method or by attaching a foil having a predetermined wiring shape.

[0023] 9A to 9C, for the sake of clarity, only wires extending in a specific direction are shown, but the stretchable wires 40 may extend in any direction on the main surface and / or inside the stretchable substrate 10. Preferably, the stretchable wires 40 may extend along the extension direction of the main surface of the stretchable substrate 10. Furthermore, when viewed from the thickness direction Y of the stretchable substrate 10, the stretchable wires 40 do not necessarily have to be arranged in a straight line, and may be arranged in a curved line, for example. Furthermore, when viewed from the thickness direction Y, the stretchable wires 40 do not necessarily have to extend in one direction. The number of stretchable wires 40 is not particularly limited, and one or more wires may be arranged. Furthermore, multiple stretchable wires may extend at different heights in a cross-sectional view. Wires extending at different heights may be electrically connected to each other. In short, the wires may be electrically connected to each other between layers. That is, the wires may also be connected to each other in the thickness direction. The wirings may be connected to each other via vias, for example.

[0024] First Embodiment Based on the details of the main components of the stretchable device described above, the following describes the characteristic parts of the stretchable device according to the first embodiment of the present disclosure.

[0025] 1A to 1D are cross-sectional views schematically illustrating a stretchable device according to an embodiment of the present disclosure. As illustrated, the stretchable device of the present disclosure further includes a protective layer 20 covering the stretchable substrate 10. Specifically, the stretchable device of the present disclosure includes the protective layer 20, and the protective layer 20 may be provided on at least one of the two opposing major surfaces 12A and 12B of the stretchable substrate 10 (e.g., the first major surface 12A). Furthermore, the protective layer 20 may also be positioned on at least one of the second major surface 12B and the side surface 14 opposite the first major surface 12A. In other words, as shown in FIG. 1A, the protective layer 20 may cover the first major surface 12A of the stretchable substrate 10 and further extend to the side surface 14. Alternatively, as shown in FIGS. 1B to 1D, the protective layer 20 may be provided to cover both the first major surface 12A and the second major surface 12B of the stretchable substrate 10.

[0026] 1A , the protective layer 20 may extend from one of the first major surface 12A and the second major surface 12B of the stretchable substrate to the side surface 14 located between the first major surface 12A and the second major surface 12B. That is, the protective layer 20 may extend from the main surface (e.g., 12A) of the stretchable substrate to the side surface 14. In such a configuration, the protective layer 20 can cover the ridge connecting the main surface 12A and the side surface 14 of the stretchable substrate.

[0027] The protective layer 20 may extend so as to mainly cover the main surface 12A or 12B of the stretchable substrate 10. In other words, the main portion of the protective layer 20 may cover the main surface 12A or 12B of the stretchable substrate 10, and the sub-portion of the protective layer 20 excluding the main portion may cover the side surface 14 of the stretchable substrate 10. It is preferable that the protective layer 20 covers a wide area of ​​the stretchable substrate 10. For example, when viewed in the thickness direction Y, the protective layer 20 may cover at least 60% of the planar area of ​​the main surface of the stretchable substrate 10.

[0028] The inventors of the present application discovered that structural defects (scratches, holes, etc.) that could be fracture initiation points in the stretchable substrate 10 are likely to occur at the edge portions of the stretchable substrate 10, and that when defects exist at the edge portions, stress is more likely to concentrate at the defect portions, making fracture propagation from the defect portions more likely, compared to when defects exist in portions other than the edge portions. According to the stretchable device 1 of the present disclosure, the protective layer 20 can be continuously provided from the main surface 12A of the stretchable substrate to the side surface 14. This allows the edge portions of the stretchable substrate 10, which are likely to be fracture initiation points, to be covered by the protective layer 20. Therefore, even when a defect exists at the edge portion of the stretchable substrate 10, the protective layer 20 integrally covers the defect and the stretchable substrate 10 surrounding the defect, thereby dispersing stress at the defect. This may more effectively suppress fracture propagation from the defect in the stretchable substrate 10.

[0029] 1A , the presence of the protective layer 20 makes it possible to prevent contact between the stretchable substrate 10 and foreign matter. This makes it possible to suitably prevent defects from occurring in the stretchable substrate 10 due to contact with foreign matter. In other words, by including the protective layer 20, the stretchable device of the present disclosure can suitably prevent the occurrence of defects in the stretchable substrate 10 that could be the starting point for fracture.

[0030] Furthermore, the inventors of the present application have discovered that the oil resistance of the stretchable substrate 10 may decrease when the stretchable device is stretched. Specifically, when the stretchable substrate 10 is stretched, the molecular structure of the stretchable substrate 10 changes, making it easier for foreign matter such as oil and fat components including sebum and machine oil to penetrate into the molecular structure. When foreign matter penetrates into the molecular structure, the stretchability locally decreases at the penetration point, and as a result, structural defects such as holes may occur at the penetration point. According to the present disclosure, by covering the stretchable substrate 10 with a protective layer 20, which is a separate member, it is possible to suppress local adhesion of foreign matter to the stretchable substrate 10. Therefore, the occurrence of defects in the stretchable substrate 10 due to adhesion of foreign matter can be suitably suppressed.

[0031] 1A , the protective layer 20 extends from the main surface 12A of the stretchable substrate to the side surface 14. This makes it possible to more suitably retain the protective layer 20 on the stretchable substrate 10 compared to a structure in which the protective layer 20 is provided only on the main surface 12A. In particular, by having the protective layer cover not only the main surface 12A but also a large area of ​​the stretchable substrate 10 from the main surface 12A to the side surface 14, the protective layer 20 can more suitably follow the expansion and contraction of the entire stretchable device. Therefore, peeling of the protective layer 20 from the stretchable substrate 10 can be suitably suppressed when the stretchable device expands and contracts.

[0032] Furthermore, in the stretchable device of the present disclosure, as shown in FIGS. 1B to 1D , a protective layer 20 may be provided on both of the two main surfaces 12A and 12B of the stretchable substrate 10 that face each other in the thickness direction Y. This structure can be interpreted as including a first protective layer 20A positioned on the first main surface 12A of the stretchable substrate 10 and a second protective layer 20B positioned on the second main surface 20B opposite the first main surface 12A. The first protective layer 20A and the second protective layer 20B do not necessarily cover the entire first main surface 12A and the second main surface 12B, respectively. The first main surface 12A and / or the second main surface 12B may have regions that are not partially covered by the protective layer 20. At least one of the first protective layer 20A and the second protective layer 20B may be positioned so as to overlap the stretchable substrate 10 when viewed in the thickness direction Y. In other words, at least one of the first protective layer 20A and the second protective layer 20B may be disposed in the region overlapping with the stretchable substrate 10 when viewed in the thickness direction Y.

[0033] In this structure, the first protective layer 20A and the second protective layer 20B do not necessarily have to face each other over the entire area when viewed from the thickness direction Y. When viewed from the thickness direction Y, one of the first protective layer 20A and the second protective layer 20B may be positioned in the area overlapping the stretchable substrate 10, and there may be an area where the first protective layer 20A and the second protective layer 20B do not overlap each other. With this structure, the presence of the first protective layer 20A and the second protective layer 20B can suppress stress concentration on the stretchable substrate 10. Furthermore, the stretchable substrate 10 can have areas that are suppressed from both main surfaces by the protective layers 20A and 20B provided on each of the two main surfaces 12A and 12B that face each other in the thickness direction Y. This makes it possible to effectively suppress damage to the stretchable substrate 10.

[0034] For example, as shown in Fig. 1B, the first protective layer 20A may cover the entire first major surface 12A, while the second protective layer 20B may cover only a portion of the second major surface 12B. Alternatively, as shown in Fig. 1C, the first protective layer 20A and the second protective layer 20B may be offset from each other in a cross-sectional view. In this way, when viewed from the thickness direction Y, there may be an area where either the first protective layer 20A or the second protective layer 20B overlaps with the stretchable substrate 10, and an area where both the first protective layer 20A and the second protective layer 20B overlap with the stretchable substrate 10.

[0035] 1D , the stretchable device may include two protective layers 20A and 20B that face each other in the thickness direction Y, sandwiching the stretchable substrate 10 therebetween. The first protective layer 20A and the second protective layer 20B may be disposed facing each other with the stretchable substrate interposed therebetween. The protective layers 20A and 20B may be provided on both main surfaces (12A, 12B) of the stretchable substrate 10 so as to sandwich the stretchable substrate 10 from both sides.

[0036] By covering each of the two main surfaces 12A, 12B of the stretchable substrate 10 with two protective layers 20A, 20B, it is possible to more appropriately distribute stress applied to the stretchable substrate 10 among the two protective layers 20A, 20B. For example, even if a portion of one of the first protective layer 20A and the second protective layer 20B separates from the main surface of the stretchable substrate 10 during stretching of the stretchable device, causing the protective layer to lift, the provision of the other protective layer disposed opposite the first protective layer can suppress local stress concentration in the stretchable substrate 10. Therefore, it can also be understood that the two protective layers 20A and 20B complementarily protect the stretchable substrate 10 from both sides in the thickness direction Y.

[0037] At least one of the first protective layer 20A and the second protective layer 20B may extend along the first main surface 12A or the second main surface 12B so as to reach at least the edge of the stretchable substrate 10. For example, when viewed in the thickness direction Y, the first protective layer 20A may have the same width as the stretchable substrate 10. Similarly, the second protective layer 20B may have the same width as the stretchable substrate 10. In such a configuration, the end surface 22 of the first protective layer 20A and / or the end surface 22 of the second protective layer 20B may be flush with the side surface 14 of the stretchable substrate 10 in a cross-sectional view. Therefore, the end surface 22 of the first protective layer 20A, the end surface 22 of the second protective layer 20B, and the side surface 14 of the stretchable substrate 10 may form the outer surface of the stretchable device.

[0038] As described above, according to the present disclosure, by providing a protective layer 20 on the stretchable substrate 10 from the main surface 12A to the side surface 14 and / or on both of the two opposing main surfaces 12A, 12B, a stretchable device can be provided that can suitably suppress breakage of the stretchable substrate 10.

[0039] The stretchable substrate 10 and the protective layer 20 may be adhered to each other. More specifically, the main surface 12A of the stretchable substrate 10 and the protective layer 20A provided on the main surface 12A may be adhered to each other. This allows the stretchable substrate 10 and the protective layer 20 to stretch together when the stretchable device stretches, making it possible to prevent the protective layer 20 from peeling off from the stretchable substrate 10. For example, the stretchable substrate 10 and the protective layer 20 may be directly bonded by thermocompression bonding or the like. Alternatively, an adhesive layer may be provided between the stretchable substrate 10 and the protective layer 20.

[0040] The material of the protective layer may be a stretchable resin material. For example, a thermoplastic elastomer resin may be used for the protective layer. Examples of the protective layer include elastomer resins such as silicone resins, acrylic resins, olefin resins, urethane resins, and styrene resins. These resins may be used alone or in combination.

[0041] An example of the silicone elastomer resin material is a film containing polydimethylsiloxane (PDMA).

[0042] Examples of acrylic elastomer resins include copolymers containing (meth)acrylic monomers, acrylic acid esters, polymethyl methacrylate (PMMA), and / or butyl acrylate, and further containing other monomers. Although merely illustrative, examples of such other monomers include vinyl acetate, vinylpyrrolidone, acrylamide monomers, styrene monomers, and vinyl ether monomers.

[0043] Examples of olefinic elastomer resins include copolymers containing propylene, ethylene, ethylene-propylene rubber, butene, and / or octene.

[0044] Examples of urethane elastomer resins include thermoplastic polyurethane elastomers made from copolymers of diisocyanate, short-chain diol, and / or polyester polyol, polyether polyol, and / or polycarbonate polyol.

[0045] Examples of styrene-butadiene elastomer resins include block copolymers such as styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-butadiene-butylene-styrene copolymer, and styrene-isobutylene-styrene copolymer.

[0046] It is more preferable that the protective layer 20 has the same or similar elasticity as the stretchable substrate 10 on which the protective layer 20 is provided. "Same or similar elasticity" means, for example, that the stretching behavior when an external force is applied is the same or similar. Specifically, it means that the amount of change in length (stretching amount) when the same tensile force is applied is the same or similar to that when the tensile force is released. By making the elasticity of the protective layer 20 the same or similar to that of the stretchable substrate 10, the stretchable substrate 10 and the protective layer 20 can stretch more integrally when the stretchable device is stretched. This makes it possible to suppress peeling between the stretchable substrate 10 and the protective layer 20.

[0047] The combination of materials for the stretchable substrate 10 and the protective layer 20 can be evaluated by the values ​​calculated using the following formulas (1) and (2).

[0048]

[0049] (In the formula, M ｃｏｖｅｒ : Young's modulus of the protective layer (MPa), t ｃｏｖｅｒ : Thickness of protective layer (μm), M ｓｕｂ : Young's modulus of the elastic substrate (MPa), t ｓｕｂ : Thickness of stretchable substrate (μm)

[0050] Equation (1) relates to the relative strength of the protective layer 20 with respect to the stretchable substrate 10. For the stretchable substrate 10, the value obtained by equation (1) may be 0.2 or more, preferably 0.35 or more, or more preferably 0.4 or more. When such a protective layer 20 is combined, the protective layer 20 can have sufficient strength relative to the stretchable substrate 10. By providing such a protective layer 20, it is possible to more effectively prevent the stretchable substrate 10 from breaking.

[0051] Furthermore, formula (2) relates to the degree of hardness of the entire stretchable device, which is a combination of the stretchable substrate 10 and the protective layer 20. A combination of the stretchable substrate 10 and the protective layer 20 such that the value obtained by formula (2) is 1800 or less, 2000 or less, or 2200 or less can provide a stretchable device with suitable stretchability. The lower limit is not particularly limited, but may be, for example, 100 or more, 300 or more, or 500 or more.

[0052] In this specification, the thickness t of the protective layer 20 ｓｕｂ refers to the thickness of the protective layer located on the main surface of the stretchable substrate. In other words, the thickness of the portion covering the side surface of the stretchable substrate is irrelevant to this calculation formula. In addition, when the protective layer 20 has a protective layer covering the first and second main surfaces, the thickness of the protective layer is the sum of the thickness of the protective layer covering the first main surface and the thickness of the protective layer covering the second main surface. In addition, the Young's modulus M of the stretchable substrate ｃｏｖｅｒ and the Young's modulus M of the protective layer ｓｕｂ can be measured in accordance with JIS K 7161-1:2014. The measurement environment may be controlled at a temperature of 23±2°C and a relative humidity of 50±10%. Young's modulus can be determined, for example, by a tensile test using an RSA-G2 manufactured by Ta Instruments.

[0053] As shown in FIGS. 1B to 1D , in an embodiment in which the first and second main surfaces 12A and 12B of the stretchable substrate 10 are provided with protective layers 20A and 20B, respectively, it is more preferable that the first protective layer 20A positioned on the first main surface 12A side and the second protective layer 20B positioned on the second main surface 12B side are made of the same material. In other words, the two main surfaces 12A and 12B of the stretchable substrate 10 that face each other in the thickness direction Y may be provided with the same protective layer. That is, the stretchable substrate 10 may be sandwiched between two protective layers 20A and 20B made of the same material. By using the same material for the first protective layer 20A and the second protective layer 20B, the two protective layers 20A and 20B have the same stretchability, allowing them to stretch more integrally as the stretchable device stretches. This suppresses uneven stress distribution during stretching due to differences in stretchability, allowing the stretchable device to stretch more uniformly. As a result, breakage of the stretchable substrate 10 due to uneven stress can be more effectively prevented. Meanwhile, the first protective layer 20A and the layer 20B positioned on the second main surface 12B side do not necessarily have to be made of the same material. For example, the first protective layer 20A and the second protective layer 20B may be made of different materials with similar stretchability. From the same perspective, it is preferable that the thicknesses of the protective layers 20A and 20B are approximately the same.

[0054] (Modifications of First Embodiment) Various modifications can be adopted as the stretchable device according to the first embodiment. Figures 2 to 8 are cross-sectional views schematically showing stretchable devices according to modifications of the first embodiment.

[0055] In the stretchable device 1C shown in FIG. 2 , the protective layer 20 extends along one of the main surfaces 12A and the side surface 14 of the stretchable substrate 10. The protective layer 20 may extend so as to cover the side surface 14 of the stretchable substrate 10. In such a structure, the protective layer 20 may continuously cover the main surface 12A and the side surface 14 of the stretchable substrate 10. More preferably, the protective layer 20 may extend over the entire surface of the side surface 14 of the stretchable substrate 10. With such a structure, the stretchable substrate 10 is covered by the protective layer 20 from the main surface 12A to the side surface 14, and the stretchable substrate 10 can be more suitably protected.

[0056] In the stretchable device 1D shown in Fig. 3, a first protective layer 20A and a second protective layer 20B are provided on the first main surface 12A and the second main surface 12B of the stretchable substrate 10, respectively. At least one of the first protective layer 20A and the second protective layer 20B may extend to the side surface 14 of the stretchable substrate 10. With this structure, not only can the first protective layer 20A and the second protective layer 20B protect both main surfaces of the stretchable substrate 10, but also, by providing the protective layer 20 that extends to the side surface 14 of the stretchable substrate 10, the protective layer 20 can be suitably held on the stretchable substrate 10.

[0057] In the stretchable device 1E shown in FIG. 4 , either the first protective layer 20A or the second protective layer 20B has a width dimension larger than the width dimension of the main surface A of the stretchable substrate 10 on which the protective layer is provided. Alternatively, as in the stretchable device 1F shown in FIG. 5 , both the first protective layer 20A and the second protective layer 20B may have a width dimension larger than the width dimension of the stretchable substrate 10. In such a structure, the protective layers 20A / 20B may extend so as to protrude outward from the edge portions of the stretchable substrate 10. This allows the protective layers 20A / 20B to more effectively cover the edge portions of the stretchable substrate 10 that may be the starting point for breakage. Therefore, such a structure can provide a stretchable device that can effectively suppress breakage of the stretchable substrate 10.

[0058] For example, the width dimensions of the first protective layer 20A and the second protective layer 20B may each be greater than 100%, or may be 103% or more, 105% or more, or 110% or more of the width dimension of the stretchable substrate 10. When the width dimensions of the first protective layer 20A and the second protective layer 20B are within the above-mentioned ranges, breakage of the stretchable substrate 10 can be suitably suppressed. Meanwhile, although there are no particular limitations on the upper limits of the width dimensions of the first protective layer 20A and the second protective layer 20B, when prioritizing miniaturization of the stretchable device, the width dimensions can be 130% or less, 120% or less, or 115% or less of the width dimension of the stretchable substrate 10.

[0059] As shown in FIG. 4 , when the width dimension of the protective layer 20 is greater than the width dimension of the stretchable substrate 10, the protective layer 20 may extend outward from the stretchable substrate 10 by a dimension D when viewed from the thickness direction Y. In such a structure, the end face of the protective layer 20 is located outward from the side surface 14 of the stretchable substrate 10 along the width direction X. The dimension D can also be interpreted as the amount of protrusion of the protective layer 20 when viewed from the thickness direction Y. For example, the dimension D is greater than 0 mm, preferably 1 mm or more, and more preferably 2 mm or more. When the dimension D is the above-described value, the protective layer 20 largely covers the stretchable substrate 10, thereby more effectively suppressing breakage of the stretchable substrate 10. While there is no particular upper limit for the dimension D, when emphasis is placed on miniaturization of the stretchable device, the dimension D may be 10 mm or less. Note that the dimension D does not necessarily have to be constant.

[0060] The first protective layer 20A and the second protective layer 20B may have the same width or different widths. Similarly, the dimension D of the first protective layer 20A and the second protective layer 20B extending outward from the stretchable substrate may be the same or different. That is, the arrangement and width of the protective layer 20 are not particularly limited. For example, the protective layer 20 may be arranged so that different dimensions protrude from both ends, or may be arranged so that it protrudes from only one side. For example, when viewed from the thickness direction Y, either the first protective layer 20A or the second protective layer 20B may not protrude from the stretchable substrate 10, while the second protective layer 20B may protrude from the stretchable substrate 10. As shown in Figures 4 and 5, it is preferable to configure the protective layer 20 so that it protrudes by the same dimension D at both ends in the left-right direction (X direction, width direction). By using the above configuration, the overall amount of stretch can be made more uniform.

[0061] In the stretchable device 1G shown in FIG. 6 , the first protective layer 20A and the second protective layer 20B may cover the first main surface 12A and the second main surface 12B of the stretchable substrate 10, respectively, and may extend to the side surface 14 side, thereby entirely covering the stretchable substrate 10. Specifically, both the first protective layer 20A and the second protective layer 20B may extend to the side surface 14 side of the stretchable substrate 10, thereby surrounding the stretchable substrate 10. Alternatively, as in the stretchable device 1H shown in FIG. 7 , either the first protective layer 20A or the second protective layer 20B may cover the side surface 14 side of the stretchable substrate 10, thereby entirely surrounding the stretchable substrate. In this way, the stretchable substrate 10 is entirely protected by the protective layer 20. This makes it possible to more effectively suppress breakage of the stretchable substrate 10.

[0062] As shown in Figures 6 and 7, the first protective layer 20A and the second protective layer 20B surrounding the stretchable device may be adhered to each other. For example, the first protective layer 20A and the second protective layer 20B may be adhered to each other on the side surface 14 of the stretchable substrate 10. By adhering the protective layers to each other, it is possible to suitably prevent foreign matter from entering the stretchable substrate 10 from between the first protective layer 20A and the second protective layer 20B. Furthermore, by adhering the protective layers to each other, it is possible to suitably hold the first protective layer 20A and the second protective layer 20B surrounding the stretchable substrate 10.

[0063] Furthermore, the adhesive portion 24 between the first protective layer 20A and the second protective layer 20B may be positioned on the side surface 14 side of the stretchable substrate 10. As described above, the stretchable device can stretch mainly along the extension direction of the main surfaces 12A and 12B. By positioning the adhesive portion 24 between the protective layers on the side surface 14 side rather than on the main surfaces 12A and / or 12B side, stress that may act on the adhesive portion 24 when the stretchable device stretches can be further alleviated. This releases the adhesive between the protective layers when the stretchable device stretches, making it possible to prevent the protective layers 20A and / or 20B from peeling off from the stretchable substrate 10.

[0064] The first protective layer 20A and the second protective layer 20B surrounding the stretchable substrate 10 may be an integrated body. That is, the stretchable substrate 10 may be integrally surrounded by a protective layer that extends continuously along the outer periphery of the stretchable substrate 10. With this structure, there is no adhesive portion between the protective layers, and therefore peeling of the protective layers due to the release of the adhesive can be avoided.

[0065] Furthermore, the side surface 14 of the stretchable substrate 10 and the protective layer 20 do not necessarily need to be in close contact. For example, as in the stretchable device 1I shown in FIG. 8 , a gap 30 may exist between the side surface 14 of the stretchable substrate 10 and the protective layer 20A and / or 20B. The gap 30 corresponds to the space surrounded by the side surface 14 of the stretchable substrate and the protective layer 20A and / or 20B. The gap 30 may exist in at least a portion of the side surface 14. In other words, the stretchable substrate 10 may be in close contact with the protective layer 20A or 20B in a portion of the side surface 14, and may be separated from the protective layer 20A and 20B in other portions of the side surface 14. This can also be interpreted as a structure in which the side surface 14 has portions that are not in contact with the protective layer 20A and 20B and portions that are in contact with the protective layer 20A or 20B. Alternatively, the gap 30 may exist throughout the entire side surface 14. In such a structure, the protective layer 20A and / or 20B located on the side surface 14 side may be spaced apart from the side surface 14.

[0066] In this way, by providing the gap 30 between the side surface 14 of the stretchable substrate 10 and the protective layer 20A and / or 20B, the influence of the protective layers 20A and 20B on the stretchability of the stretchable substrate 10 is reduced. This can improve the degree of freedom of stretch of the stretchable substrate 10 surrounded by the protective layer 20A and / or 20B. Therefore, with this structure, a stretchable device can be provided that includes a stretchable substrate 10 with good stretchability while suitably suppressing breakage of the stretchable substrate 10.

[0067] [Second embodiment] Next, a description will be given of a stretchable device according to a second embodiment. The stretchable device according to the second embodiment differs from the stretchable device according to the first embodiment in that it includes a laminate in which a plurality of stretchable substrates 10 are stacked.

[0068] 9A to 9C are schematic cross-sectional views of stretchable devices 1J to 1L according to the second embodiment. The stretchable substrates 10 may be stacked on top of each other in the thickness direction Y. More specifically, the stretchable device 1J may have a multilayer structure in which a plurality of stretchable substrates 10 are stacked with their main surfaces facing each other. In other words, a plurality of stretchable substrates 10 may be stacked in the thickness direction Y of the stretchable substrates 10 to form a stacked body 50. The number of stacked stretchable substrates 10 is not particularly limited. Furthermore, as shown in FIGS. 9A to 9C, the stretchable device may further include a stretchable wiring 40 disposed on the stretchable substrate 10.

[0069] 9A to 9C, in the stretchable device according to the second embodiment, the protective layer 20 is provided on the laminate 50. In short, in a stretchable device having a laminate structure, the above-described protective layer 20 (20A, 20B) is positioned on the outer surface of the laminate.

[0070] Similar to the protective layer 20 provided on the stretchable substrate 10 in the first embodiment, in the stretchable device according to the second embodiment, a protective layer 20 is provided on the laminate 50. That is, any of the structures of the protective layer 20 on the stretchable substrate 10 in the first embodiment described above may be applicable to the laminate 50. The protective layer 20 may be provided on the stretchable substrate 10 that has a surface that constitutes the outer surface of the laminate 50, among the multiple stretchable substrates 10 included in the laminate 50.

[0071] The protective layer 20 is positioned on at least one of the main surfaces 52A and 52B of the stretchable substrate 10 that constitute the outer surface of the laminate 50. The main surface of the stretchable substrate 10 that constitutes the outer surface of the laminate 50 can also be interpreted as the main surface of the laminate 50. Therefore, the protective layer 20 is positioned on at least one of the main surfaces 52A and 52B of the laminate 50. The protective layer 20 may also be provided on the side surface 54 of the laminate 50. The protective layer 20 is provided on the first main surface 52A of the laminate and either the second main surface 52B facing the first main surface 52A or the side surface 54. In other words, the protective layer 20 is provided on the surface of the multiple stretchable substrates 10 that constitute the laminate 50 that constitutes the first main surface 52A of the laminate and either the second main surface 52B facing the first main surface 52A or the side surface 54.

[0072] 9A , the protective layer 20 may be provided on the main surface 52A of the laminate 50 and extend to the side surface 54 of the laminate. In other words, the protective layer 20 may extend continuously from the main surface 52A of the laminate 50 to the side surface 54. This can also be interpreted as the protective layer 20 extending from the main surface of the stretchable substrate 10 that constitutes the main surface 52A of the laminate 50 to the side surface of the stretchable substrate 10 that constitutes the side surface 54 of the laminate 50.

[0073] 9B , the protective layers 20A and 20B may be provided on both of two opposing main surfaces 52A and 52B of the laminate 50 in the stacking direction Y. That is, the stretchable device 1K may include a first protective layer 20A provided on the main surface of the stretchable substrate 10 that constitutes the first main surface 52A of the laminate 50, and a second protective layer 20B provided on the main surface of the stretchable substrate 10 that constitutes the second main surface 52B of the laminate 50. The first protective layer 20A and the second protective layer 20B may also be interpreted as being arranged to sandwich the laminate 50.

[0074] 9C , the first protective layer 20A and the second protective layer 20B may surround the laminate 50. That is, the first protective layer 20A and the second protective layer 20B may extend continuously along the outer surface of the laminate 50, and may entirely cover the laminate 50. The first protective layer 20A and the second protective layer 20B that cover the laminate 50 may be adhered to each other.

[0075] In a stretchable device having a laminated structure, if a structural defect exists on the surface of the stretchable substrate 10 that constitutes the outer surface of the laminate 50, stress will concentrate at the defect during stretching, which may result in breakage and tearing of the stretchable substrate 10 originating from the defect. As described above, by providing the protective layer 20 (20A, 20B) on the laminate 50, the stretchable substrate 10 that constitutes the laminate 50 is suitably protected. Furthermore, even if a defect exists in the stretchable substrate 10 that constitutes the laminate 50, stress is dispersed in the protective layer 20 that covers the stretchable substrate 10, which can suitably prevent breakage of the stretchable substrate 10 originating from the defect. Thus, according to the present disclosure, a stretchable device that can prevent breakage of the stretchable substrate 10 can be provided even in an embodiment having a laminated structure.

[0076] [Third embodiment] Next, a description will be given of a stretchable device according to a third embodiment. The stretchable device according to the third embodiment differs from the stretchable device according to the first embodiment in that the protective layer has an opening.

[0077] FIG. 10A is a perspective cross-sectional view schematically illustrating a stretchable device 1M according to a third embodiment. FIG. 11A is a cross-sectional view schematically illustrating the A-A cross section of FIG. 10A . As illustrated, a protective layer 20A positioned on a stretchable substrate 10 may include an opening 25. When viewed from the thickness direction Y, the opening 25 may be provided at a position overlapping a region of locally high hardness in the stretchable device. Specifically, in a mode in which the stretchable device includes a first region I having a relatively high hardness and a second region II other than the first region I having a relatively low hardness, the protective layer 20A may include an opening 25 at a position overlapping the first region I when viewed from the thickness direction Y. In other words, the protective layer 20A may be open in a region overlapping the first region I having a locally high hardness. This can also be interpreted as a structure in which the protective layer 20A is provided at least in the second region II having a relatively low hardness.

[0078] The opening 25 may be a through-hole. For example, the opening 25 may be formed by punching a portion of the protective layer 20A. The first surface 12A of the stretchable substrate 10 provided with the protective layer 20A may be partially exposed at the opening 25.

[0079] A stretchable substrate 10 including the protective layer 20 may be less likely to break than one not including the protective layer 20, but may have reduced stretchability. Therefore, according to the structure including the openings 25 as described above, by selectively not providing the protective layer 20 in the first region I, which has high hardness and relatively low stretchability, the difference between the stretchability in the first region I and the stretchability in the second region II other than the first region I is reduced. Therefore, the local decrease in stretchability in the first region I is mitigated, and the stretchable device can have more uniform stretchability as a whole. This reduces the bias in stress during stretching caused by local changes in stretchability, thereby suppressing the occurrence of breakage in the stretchable member.

[0080] The first region I may be a region where the hardness is relatively increased and the stretchability is reduced, for example, due to the three-dimensional intersection of multiple stretchable wirings or an increase in the thickness of the stretchable wirings and / or the stretchable substrate. Alternatively, the first region I may be a region where the hardness is relatively increased due to the provision of a component such as a sensor. Such a first region I may also be referred to as, for example, a "high hardness region," a "low stretchability region," a "component placement region," or the like. On the other hand, the second region II other than the first region I may be referred to as a "low hardness region," a "high stretchability region," or a "non-component placement region." Note that the opening 25 may be provided in a portion other than the first region I, and the stretchable device may not have the first region I.

[0081] 10B and 11B , a component 60 may be positioned in the opening 25 of the protective layer 20A. In other words, the component 60 provided in the stretchable device may be disposed in the opening 25 of the protective layer 20A. That is, the protective layer 20A may have a structure that opens at the location where the component 60 is disposed. With such a structure, a suitable stretchable device can be provided in which the protective layer can suppress breakage of the stretchable substrate 10 while also mitigating localized reductions in stretchability at the location where the component 60 is disposed.

[0082] [Fourth embodiment] Next, a description will be given of a stretchable device according to a fourth embodiment. The stretchable device according to the fourth embodiment differs from the stretchable device according to the first embodiment in that it includes a structure connected to the end of the stretchable substrate 10.

[0083] Fig. 12 is a schematic plan view showing a portion of a stretchable device according to a fourth embodiment of the present disclosure. Fig. 13 is an exploded cross-sectional view schematically showing a CC cross section of the stretchable device shown in Fig. 12. Fig. 14 is a schematic cross-sectional view of the CC cross section of the stretchable device shown in Fig. 12.

[0084] As shown in FIG. 12 , the stretchable device may further include a structure 70 located on the second main surface 12B side of the stretchable substrate 10 including the protective layer 20. When viewed from the thickness direction Y, the structure 70 may be overlapped with an end of the stretchable substrate 10 at an end of the structure 70. In short, the structure 70 and the stretchable substrate 10 may be end-connected such that their ends overlap when viewed from the thickness direction Y. In such a structure, the protective layer 20 located on the first main surface 12A of the stretchable substrate 10 may be positioned so as to overlap with an end of the structure 70 when viewed from the thickness direction Y. This allows the stretchable substrate 10 to be suitably protected at the connection portion between the structure 70 and the stretchable substrate 10, and can prevent the stretchable substrate 10 from breaking at the connection portion.

[0085] The structure 70 may have a structure main surface 70A facing the second main surface 12B of the stretchable substrate 10. The protective layer 20 located on the first main surface 12A of the stretchable substrate 10 may extend from the first main surface 12A of the stretchable substrate 10 to the structure main surface 70A (see FIGS. 15 and 17). For example, the protective layer 20 may extend to the structure main surface 70A in the width direction of the stretchable substrate 10 as viewed in the thickness direction Y, so as to extend outside the stretchable substrate 10 (see FIG. 17). Additionally or alternatively, the protective layer 20 may extend to the structure main surface 70A in the extension direction of the stretchable substrate 10 (i.e., the end side) as viewed in the thickness direction Y, so as to extend outside the stretchable substrate 10 (see FIG. 15). In such a structure, the end 23A of the protective layer 20 may be in contact with the structure main surface 70A. That is, the protective layer 20 may be in contact with both the stretchable substrate 10 and the main surface 70A of the structure. This allows the protective layer 20 to be more firmly held by contact between the stretchable substrate 10 and the structure 70, thereby preventing peeling of the protective layer 20. Furthermore, such a protective layer 20 can also contribute to maintaining the connection structure between the stretchable substrate 10 and the structure 70.

[0086] Furthermore, as viewed from the thickness direction Y, the protective layer 20 extends to the outside of the stretchable substrate 10, so that the protective layer 20 also covers the side surfaces 14 of the stretchable substrate 10. Specifically, the protective layer 20 may cover the side surfaces 14 located in the width direction of the stretchable substrate 10 and / or the side surfaces (which may also be referred to as end surfaces) located on the end sides of the stretchable substrate 10. This allows the stretchable substrate 10 at the connection portions to be more suitably covered, thereby enhancing the breakage suppression effect of the protective layer 20.

[0087] 13 and 14 , the structure 70 may be connected to a laminate 50 including a plurality of stretchable substrates 10A, 10B stacked on top of each other and a stretchable wiring 40 disposed between the plurality of stretchable substrates 10A, 10B. The structure 70 may include a connection wiring 75 electrically connected to the stretchable wiring 40, a support substrate 73 that supports the connection wiring 75, and a covering layer 71 that partially covers the connection wiring 75 disposed on the support substrate 73. While the laminate 50 may be made of a stretchable material, the structure 70 may be made of a stretchable material similar to the laminate 50, or may be made of a non-stretchable material. For example, the structure 70 may be a flexible printed circuit board using a flexible substrate.

[0088] For example, the support substrate 73 may be a flat, sheet-like, or film-like elastic or non-elastic member. While not particularly limited, the second substrate 22 may be made of a thermoplastic elastomer material similar to the elastic substrate described above, or may be made of a flexible resin material. Examples of flexible resin materials include at least one selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether ether ketone (PEEK), polyimide (PI), and liquid crystal polymer.

[0089] The connection wiring 75 may be an elastic wiring similar to the wiring arranged in the laminate 50, or may be a wiring made of a non-elastic conductive material. For example, the connection wiring 75 may be a metal foil patterned on the support substrate 73. An example of the metal foil is copper foil. As with the elastic wiring, the extension direction, shape, and number of the connection wiring 75 are not particularly limited.

[0090] In a state in which the laminate 50 and the structure 70 are connected, the connection wiring 75 may be electrically connected to the stretchable wiring 40. The laminate 50 and the structure 70 may be coupled such that the stretchable wiring and the connection wiring 75 are electrically connected. As shown in Figures 13 and 14, the laminate 50 and the structure 70 may be coupled such that the stretchable wiring and the connection wiring 75 overlap each other when viewed from the thickness direction Y. More specifically, the main surfaces of the stretchable wiring and the connection wiring 75 may be superimposed so as to partially oppose each other, and the stretchable wiring 40 and the connection wiring 75 may be electrically connected. In such a structure, the stretchable substrate 10 of the laminate 50 and the support substrate 73 of the structure 70 may partially oppose each other via the connection portion between the stretchable wiring 40 and the connection wiring 75.

[0091] The stretchable wiring 40 and the connection wiring 75 may be electrically connected by being overlapped so as to be in direct contact. Alternatively, as long as the stretchable wiring 40 and the connection wiring 75 are electrically connectable, the stretchable wiring 40 and the connection wiring 75 do not need to be in direct contact. For example, a conductive member such as an ACF (Anisotropic Conducting Film) and / or a conductive adhesive may be present between the stretchable wiring 40 and the connection wiring 75. The stretchable wiring 40 and the connection wiring 75 may be electrically connected via a conductive member.

[0092] The structure 70 may further include a covering layer 71 that covers the connection wiring 75 arranged on the support substrate 73. The connection wiring 75 arranged on the support substrate 73 may be covered with the covering layer 71. The connection wiring 75 may be covered with the covering layer 71 except for the connection portion with the stretchable wiring 40. The covering layer 71 may be an insulating resin member in the form of a flat plate, a sheet, or a film. The covering layer 71 may be made of, for example, a stretchable resin material such as a thermoplastic elastomer material, or a flexible resin material, similar to the stretchable substrate 10.

[0093] The laminate 50 may include a first stretchable substrate 10A positioned as the outermost layer of the laminate 50, and a second stretchable substrate 10B positioned as the outermost layer of the laminate 50 on the opposite side of the first stretchable substrate 10A in the thickness direction Y. The structure 70 may partially overlap the stretchable wiring 40 arranged on the second main surface 12B side of the first stretchable substrate 10A. The protective layer 20 may cover the first main surface 12A of the first stretchable substrate 10A among the multiple stretchable substrates 10 constituting the laminate 50. Furthermore, the end of the first stretchable substrate 10A and the end of the protective layer 20 may be arranged to overlap the end of the coating layer 71 included in the structure 70 in the thickness direction Y. With this configuration, the stretchable substrate 10 is suitably protected by the protective layer 20 at the connection portion between the laminate 50 and the structure 70, and breakage of the stretchable substrate 10 can be suppressed.

[0094] 15 and 16 are cross-sectional views schematically showing a stretchable device according to a modified example of the fourth embodiment. Also, FIG. 17 is a schematic plan view of a stretchable device according to another modified example. As shown in the figures, the protective layer 20 may extend onto the covering layer 71 so as to extend outside the first stretchable substrate 10A when viewed from the thickness direction Y. For example, as shown in FIG. 14 , the protective layer 20 may extend onto the covering layer 71 beyond the end (end surface 14) of the first stretchable substrate 10A so as to have a dimension larger than that of the first stretchable substrate 10A in the extension direction Z of the stretchable substrate.

[0095] Additionally or alternatively, as shown in FIG. 17 , the protective layer 20 may extend beyond the side surface 14 of the first stretchable substrate 10A onto the main surface 70A of the structure (e.g., onto the covering layer 71) so as to have a dimension larger than that of the first stretchable substrate 10A in the width direction X of the stretchable substrate. In one embodiment, the protective layer 20 may be in contact with the covering layer 71. That is, the protective layer 20 may be in contact with both the first stretchable substrate 10A and the covering layer 71. With this structure, the protective layer 20 can integrally cover not only the first main surface 12A of the first stretchable substrate 10A that constitutes the outer surface of the laminate 50, but also the side surface and / or end surface continuing from the first main surface 12A. This provides better protection for the first stretchable substrate 10A and can improve the peel resistance of the protective layer 20.

[0096] 13 and 14 , a protective layer 20 may also be provided on the second main surface 12B of the second stretchable substrate 10B, which constitutes the outermost layer of the laminate 50, on the side opposite the first stretchable substrate 10A. In such a structure, the laminate 50 may be provided with a protective layer 20 on each of the outer surfaces that face each other in the thickness direction Y. The protective layer 20 may be in contact with the supporting substrate 73 of the structure 70. This allows the laminate 50, which includes a plurality of stretchable substrates, to be suitably protected by the protective layer 20, thereby enhancing the effect of suppressing breakage of the stretchable substrates.

[0097] Furthermore, as shown in FIG. 16 , the end of the protective layer 20 covering the second main surface 12B of the second stretchable substrate 10B may be positioned between the second stretchable substrate 10B and the support substrate 73. When viewed from the thickness direction Y, in the connection region where the laminate 50 and the structure 70 overlap, the end of the protective layer 20 covering the second stretchable substrate 10B may be positioned between the second stretchable substrate 10B and the support substrate 73. With this structure, the end of the protective layer 20 is sandwiched between the laminate 50 and the structure 70, thereby improving the peel resistance of the protective layer 20. Alternatively, the protective layer 20 may extend from the second main surface of the second stretchable substrate 10B to the main surface of the support substrate 73 that constitutes the outer surface of the structure 70. In other words, the protective layer 20 may be positioned so as to cover the connection portion between the laminate 50 and the structure 70 from the outside. According to this configuration, the protective layer 20 can prevent foreign matter such as moisture from entering through the connection portion between the laminate 50 and the structure 70 .

[0098] As shown in FIG. 13 , the end of the laminate 50 connected to the structure 70 may have a stepped structure in which the thickness decreases stepwise toward the end. That is, the laminate 50 may have a plurality of laminate step portions 55 in which the thickness decreases stepwise at the end. The laminate step portions 55 may be formed by stacking the components constituting the laminate 50 so as to form a stepped step at the end. For example, the plurality of stretchable substrates 10 constituting the laminate 50 and the stretchable wiring 20 disposed between the stretchable substrates 10 may be stacked to form a plurality of laminate step portions 55 in which the thickness decreases stepwise at the end. Specifically, as shown in FIG. 13 , a portion including only the stretchable substrate 10 when viewed from the thickness direction Y and a portion including the stretchable substrate 10 and the stretchable wiring 40 may be positioned adjacent to each other in the extension direction Z of the stretchable substrate, thereby forming a step portion 55 in which the thickness of the laminate 50 is varied.

[0099] Similarly, the end of the structure 70 connected to the laminate 50 may also have a stepped structure in which the thickness decreases stepwise toward the end. The structure 70 may have a plurality of structure step portions 77 in which the thickness decreases stepwise at the end connected to the laminate 50. The structure step portions 77 may be formed by stacking the members constituting the structure 70 so as to form a stepped step at the end. For example, the support substrate 73, connection wiring 75, and coating layer 71 constituting the structure 70 may be stacked so as to form a plurality of structure step portions 77 in which the thickness decreases stepwise at the end.

[0100] As shown in Figures 13 and 14, the laminate 50 and the structure 70 may be combined such that each of the multiple laminate step portions 55 and each of the multiple structure step portions 77 face each other in the thickness direction Y. Each of the laminate step portion 55 and the structure step portion 77 has a step side surface 55B, 77B extending along the thickness direction Y and a step main surface 55A, 77A extending along the extension direction Z of the stretchable substrate. The side surfaces 55B, 77B are surfaces that extend in a direction rising from the extension direction Z of the stretchable substrate to form a step, and may also be referred to as a rising surface, etc. The laminate 50 and the structure 70 may be combined such that a member constituting the main surface 55A of the laminate step portion 55 and a member constituting the main surface 77A of the structure step portion 77 face each other in the thickness direction Y. 14 , the laminate 50 and the structure 70 may be combined so that, in the thickness direction Y, the first stretchable substrate 10A faces the covering layer 71, the stretchable wiring 40 faces the connecting wiring 75, and the second stretchable substrate 10B faces the supporting substrate 73. Furthermore, the side surface 55B of the laminate step 55 and the side surface 77B of the structure step 77 may be combined so as to face each other in the extension direction Z of the stretchable substrate. In short, this structure can also be interpreted as the laminate step 55 and the structure step 77 facing each other in the extension direction Z of the stretchable substrate.

[0101] In a cross-sectional view, the heights T1a, T1b of the multiple laminate step portions 55 are preferably 50% to 150% and more preferably 75% to 125% of the heights T2a, T2b of the structure step portions 77 facing the laminate step portions 55 in the extension direction Z of the stretchable substrate (see FIG. 14 ). Here, the heights of the laminate step portions 55 and the structure step portions 77 refer to heights based on the step portions adjacent to the respective step portions. Specifically, the heights of the laminate step portions 55 and the structure step portions 77 correspond to the difference in position in the thickness direction Y between an imaginary plane extending from the main surface of the respective step portions and the main surface of the step adjacent to the respective step portion (i.e., the step portion having a reduced thickness from the respective step portions and adjacent to the respective step portions). By having the heights of the opposing laminate step portions 55 and the structure step portions 77 within the above-mentioned ranges, the laminate 50 and the structure 70 can be suitably bonded to each other at their opposing main surfaces in the thickness direction Y. This allows for a more stable connection between the laminate 50 and the structure 70. By stabilizing the connection, a stretchable device can be obtained that is suitable in terms of improving the mechanical strength at the connection portion between the laminate 50 and the structure 70 and maintaining the insulation around the wiring. Furthermore, since the stretchable wiring 40 and the connection wiring 75 can be stably connected electrically, this can also be useful in terms of reducing electrical resistance. Furthermore, with this structure, the overall thickness of the stretchable device is made more uniform at the connection portion between the laminate 50 and the structure 70, thereby suppressing stress concentration caused by a sudden change in stretchability due to differences in thickness, and making it possible to suppress breakage of the stretchable substrate.

[0102] The above-described structure can also have advantageous effects when connecting the laminate 50 and the structure 70. Specifically, when the laminate 50 and the structure 70 are superimposed and joined by thermocompression bonding, the height of each of the opposing steps is within a predetermined range, making it possible to uniformly apply heat and pressure across the entire opposing main surfaces. This allows the laminate 50 and the structure 70 to be more firmly joined across the entire opposing main surfaces, resulting in a stretchable device with excellent connection stability.

[0103] 13 , the ratio of the thicknesses T3a to T3c of the laminate in each of the plurality of laminate step portions 55 is preferably within a predetermined range in cross-sectional view. Specifically, the thickness of the laminate 50 in each of the plurality of laminate step portions 55 is preferably 250% or less, and more preferably 200% or less, of the thickness T3a of the laminate 50 in the laminate step portion 55 located at the endmost side of the laminate 50. Here, the thickness of the laminate 50 in each of the plurality of laminate step portions 55 corresponds to the overall thickness of the laminate 50 at the center of the main surface 55A of each laminate step portion 55 in cross-sectional view, and is clearly distinguishable from the height of the step portion. By having the thickness of the laminate 50 in each of the laminate step portions 55 within the above-mentioned range, it is possible to avoid an excessive difference in thickness between the thinnest laminate step portion 55 and the thickest laminate step portion 55, thereby mitigating changes in stretchability due to the difference in thickness. This reduces stress concentration due to changes in stretchability, and can prevent the stretchable substrate from breaking.

[0104] The above-described structure can also have advantageous effects when connecting the laminate 50 and the structure 70. Specifically, when the laminate 50 and the structure 70 are overlapped and bonded by thermocompression, the thickness ratio of the laminate 50 at each of the laminate step portions 55 is within a predetermined range, thereby reducing unevenness in the heat and pressure applied to each of the laminate step portions 55. In other words, when thermocompression bonding the laminate 50 and the structure 70, it is possible to apply heat and pressure more uniformly to each of the laminate step portions 55. This allows the laminate 50 to be more firmly bonded to the structure 70 at each of the laminate step portions 55, resulting in a stretchable device with excellent connection stability between the laminate 50 and the structure 70.

[0105] (Method for Producing a Stretchable Device) An exemplary method for producing a stretchable device according to an embodiment of the present disclosure will now be described.

[0106] First, prepare the stretchable substrate 10. In an embodiment in which the stretchable wiring 40 (see FIG. 9A ) is disposed on the stretchable substrate 10, the stretchable wiring 40 may be formed on the main surface of the stretchable substrate layer 10 after the stretchable substrate layer 10 is prepared.

[0107] The stretchable wiring 40 may be formed by printing a conductive paste (for example, a conductive paste containing a mixture of silver and resin) onto the stretchable substrate 10 using screen printing, inkjet printing, or the like. This allows a desired circuit pattern to be obtained. Alternatively, a copper foil may be attached, a resist coating may be applied, and wiring may be formed into a desired shape by further exposure and etching processes.

[0108] After forming a circuit pattern of the stretchable wiring 40 on the stretchable substrate 10, the conductive paste for the stretchable wiring is dried and cured, thereby forming the stretchable wiring 40 on the stretchable substrate 10. Note that printing may be performed not only on one main surface of the stretchable substrate 10, but also on both main surfaces. It is also possible to mount components such as sensors as needed.

[0109] Next, another stretchable substrate 10 may be stacked in the thickness direction Y so as to cover the stretchable wiring 40 arranged on the stretchable substrate 10, to form a laminate 50. Thereafter, a protective layer 20 is further stacked on the main surface of the laminate 50. Next, the stacked stretchable substrates 10 and protective layer 20 may be bonded to each other by, for example, pressing the stacked stretchable substrates 10 and protective layer 20 under a predetermined temperature condition. In this manner, a stretchable device equipped with a protective layer 20 according to an embodiment of the present disclosure can be obtained.

[0110] Although the embodiments of the present disclosure have been described above, they are merely typical examples. Those skilled in the art will readily understand that the present disclosure is not limited thereto, and that various modifications are possible within the scope of the present disclosure.

[0111] For example, the stretchable device may include a stretchable wiring disposed on the main surface 12A of the stretchable substrate. In such a structure, the protective layer 20A may integrally cover the main surface 12A together with the stretchable wiring. In other words, the stretchable wiring disposed on the main surface 12A may be covered by the protective layer 20A. According to such a structure, the protective layer 20A can suitably suppress breakage not only of the stretchable substrate 10 but also of the stretchable wiring disposed on the stretchable substrate 10.

[0112] It should be noted that one embodiment of the present disclosure as described above includes the following preferred aspects. <1> A stretchable device comprising: a stretchable substrate; and a protective layer provided on the stretchable substrate; the stretchable substrate comprising a first main surface and a second main surface opposing each other in a thickness direction of the stretchable substrate; and a side surface connecting the first main surface and the second main surface; and the protective layer covering the first main surface and at least one of the second main surface and the side surface. <2> The stretchable device according to <1>, wherein the protective layer covers the first main surface and is positioned so as to extend from the first main surface to the side surface. <3> The stretchable device according to <1> or <2>, wherein the protective layer covers each of the first main surface and the second main surface. <4> The stretchable device according to any one of <1> to <3>, wherein the protective layer has a width dimension equal to or greater than a width dimension of the main surface of the stretchable substrate when viewed in the thickness direction. <5> The stretchable device according to any one of <1> to <4>, wherein the protective layer extends over the entire surface of the main surface. <6> The stretchable device according to any one of <1> to <5>, wherein the protective layer comprises a main portion that is a major portion of the protective layer and a sub-portion other than the main portion, the main portion being on the main surface and the sub-portion being on the side surface. <7> The stretchable device according to any one of <1> to <6>, wherein the protective layer protrudes outward from the main surface of the stretchable substrate when viewed in the thickness direction. <8> The stretchable device according to any one of <1> to <7>, wherein the protective layer comprises a first protective layer covering the first main surface and a second protective layer covering the second main surface. <9> The stretchable device according to <8>, wherein the stretchable substrate overlaps at least one of the first protective layer and the second protective layer when viewed in the thickness direction. <10> The stretchable device according to <8> or <9>, wherein the first protective layer and the second protective layer are made of the same material. <11> The stretchable device according to any one of <8> to <10>, wherein at least one of the first protective layer and the second protective layer extends to a side surface connecting the first main surface and the second main surface. <12> The stretchable device according to <11>, wherein the first protective layer and the second protective layer are adhered to each other.<13> The stretchable device according to <12>, wherein the adhesive portion between the first protective layer and the second protective layer is positioned on the side surface of the stretchable substrate. <14> The stretchable device according to any one of <8> to <13>, wherein the stretchable substrate is surrounded by the first protective layer and the second protective layer. <15> The stretchable device according to any one of claims <1> to <14>, wherein the protective layer is continuous over the entire outer surface of the stretchable device. <16> The stretchable device according to any one of <1> to <15>, wherein the protective layer is positioned at the outermost side of the stretchable device. <17> The stretchable device according to any one of <1> to <16>, wherein the stretchable substrate and the protective layer satisfy the following formulas (1) and (2): (In the formula, M ｃｏｖｅｒ : Young's modulus of the protective layer (MPa), t ｃｏｖｅｒ : Thickness of protective layer (μm), M ｓｕｂ : Young's modulus of the elastic substrate (MPa), t ｓｕｂ: Thickness (μm) of the stretchable substrate.) <18> The stretchable device according to any one of <1> to <17>, comprising a laminate including a plurality of stretchable substrates stacked on top of each other, wherein the protective layer is positioned on at least one of the first main surface of the stretchable substrate constituting the outer surface of the laminate, and the second main surface of the stretchable substrate constituting the outer surface of the laminate opposite the first main surface, and the outer surface of the laminate. <19> The stretchable device according to <18>, wherein the protective layer surrounds the laminate. <20> The stretchable device according to any one of <1> to <19>, comprising a first region having a relatively high hardness and a second region other than the first region and having a relatively low hardness, wherein the protective layer extends to cover at least the second region when viewed in the thickness direction. <21> The stretchable device according to <20>, wherein the protective layer has an opening in a region overlapping with the first region when viewed in the thickness direction. <22> The stretchable device according to <20> or <21>, wherein an electronic component is disposed in the first region. <23> The stretchable device according to any one of <1> to <22>, further comprising a structure arranged to overlap an end of the stretchable substrate and face the second main surface of the stretchable substrate when viewed in the thickness direction, wherein the protective layer is arranged to overlap the end of the structure when viewed in the thickness direction. <24> The stretchable device according to <23>, wherein the structure has a structure main surface facing the second main surface of the stretchable substrate, and the protective layer extends from the first main surface of the stretchable substrate so as to reach onto the structure main surface and is in contact with the structure main surface.<25> The stretchable device according to any one of <1> to <22>, further comprising: a laminate including a plurality of the stretchable substrates stacked on each other and stretchable wiring disposed between the plurality of stretchable substrates; and a structure including: connection wiring arranged to overlap an end of the laminate in a thickness direction and electrically connected to the stretchable wiring, a supporting substrate supporting the connection wiring, and a covering layer partially covering the connection wiring, wherein, in the thickness direction, a first stretchable substrate located in the outermost layer of the laminate among the plurality of stretchable substrates, and the protective layer covering a first main surface of the first stretchable substrate, are arranged to overlap an end of the covering layer. <26> The stretchable device according to <25>, wherein the structure has a structure main surface facing the laminate, and the protective layer extends from the first main surface of the stretchable substrate to reach onto the covering layer and is in contact with the covering layer. <27> The stretchable device according to <25> or <26>, further comprising the protective layer disposed on a second main surface of a second stretchable substrate located in the outermost layer opposite to the first stretchable substrate. <28> The stretchable device according to <27>, wherein an end of the second stretchable substrate and an end of the protective layer positioned on the second main surface of the second stretchable substrate are positioned between the stretchable wiring and the supporting substrate of the structure. <29> The stretchable device according to any one of <25> to <28>, wherein the plurality of stretchable substrates and the stretchable wiring are stacked at the end of the laminate so as to form a plurality of laminate step portions whose thickness decreases stepwise toward the end, the structure comprises a plurality of structure step portions whose thickness decreases stepwise toward the structure end at structure end portions overlapping with the end of the laminate, the laminate and the structure are combined so that side surfaces of the laminate step portions and side surfaces of the structure step portions face each other in the thickness direction, and the height of the laminate step portions is 50% or more and 150% or less of the height of the structure step portion facing the laminate step portions in a cross-sectional view. <30> The stretchable device according to <29>, wherein the thickness of the laminate at the plurality of laminate step portions is 250% or less of the thickness of the laminate at the laminate step portion located at the end furthest side of the laminate.

[0113] The above effects are merely exemplary, and the present disclosure is not limited to the above, and additional effects may also be provided.

[0114] A demonstration test was conducted in accordance with the present disclosure.

[0115] (Demonstration Test 1) For stretchable substrates made of various materials, stretchable devices were fabricated that included a first protective layer located on the first main surface side of the stretchable substrate and / or a second protective layer located on the second main surface side, and the breakage resistance of the stretchable devices was evaluated.

[0116] Examples 1 to 4: A sheet-like stretchable substrate measuring 30 mm x 50 mm and 0.03 to 0.2 mm thick was prepared. The stretchable substrate was made of an olefin-based elastomer resin (Mitsubishi Chemical Corporation, Zelas series), a urethane-based elastomer resin (Nikkan Industries Co., Ltd., STRC40), a silicone-based elastomer resin (Wacker Asahi Kasei Silicone Co., Ltd., SILPURAN® FILM), or a styrene-based elastomer resin (Aronkasei Co., Ltd., Arostomer). The stretchable devices of Examples 1 to 4 were fabricated using a polyester urethane-based resin (Nihon Matai Co., Ltd., Elfan PH) as the protective layer. The protective layer was cut to a size of 60 mm x 60 mm and had a thickness of 0.1 mm. When both a first protective layer and a second protective layer were provided, the first protective layer and the second protective layer were cut to have the same size. The protective layer was disposed so as to extend outward by a predetermined distance from both side edges of the stretchable substrate in the width direction.

[0117] The stretchable substrate and the protective layer were stacked in the thickness direction Y and then thermocompression bonded by applying a pressure of 1 MPa for 1 minute at a temperature of 100° C. to 140° C. The stretchable devices obtained had the structure shown in FIG. 1A for the stretchable device of Example 1, and the structures shown in FIG. 6 for the stretchable devices of Examples 2 to 4.

[0118] Example 5 In Example 5, a stretchable device similar to Example 1 was produced, except that the protective layer had the same width as the stretchable substrate. That is, in the stretchable device of Example 5, the amount of protrusion of the protective layer from the stretchable substrate was 0 mm, and the side surfaces of the protective layer and the side surfaces of the stretchable substrate were flush with each other.

[0119] (Comparative Examples 1 to 5) As Comparative Examples 1 to 4, stretchable devices without protective layers were produced. The size of the stretchable devices was the same as that of Examples 1 to 4. Furthermore, as Comparative Example 5, a stretchable device was produced that included a first protective layer and a second protective layer whose width dimension was 4 mm smaller than that of the stretchable substrate. The protective layers were arranged so as to be located 2 mm inward from each of the two side edges of the stretchable substrate in the width direction.

[0120] The fabricated stretchable devices were subjected to a fracture resistance evaluation test. Specifically, the stretchable devices were held in a state where tensile tension was applied along the length so that the stretchability was 100%, and the time until fracture was measured. Specifically, the time until the stretchable devices completely fractured and split was measured. This measurement was performed on n = 20 devices, and the 1% failure time (B1) was calculated from the Weibull plot and recorded as the fracture occurrence time. The test was performed for 48 hours, and if no fracture was observed after 48 hours, it was determined that no fracture occurred. Here, 100% stretchability refers to a state in which the length from one end to the other end of the stretchable substrate in the longitudinal direction in a state where no tensile tension is applied (normal state) is 2L. A time until fracture (fracture occurrence time) of 48 hours or more was evaluated as A (best), a time until 24 hours or more was evaluated as B (good), and a time until less than 24 hours was evaluated as C (poor), and a time until 24 hours or more was evaluated as passing.

[0121] The evaluation results of the examples and comparative examples are shown in Table 1.

[0122]

[0123] According to the above results, the stretchable device of Example 1 had a breakage time that was approximately 2.4 times longer than the stretchable device of Comparative Example 4 that had a stretchable substrate made of the same material. On the other hand, the stretchable device of Comparative Example 5, which had a protective layer with a width dimension shorter than the stretchable substrate, broke in approximately the same time as the stretchable device without the protective layer, and no effect of the protective layer was observed. From the above, it was demonstrated that the stretchable device of the present disclosure, which has a protective layer extending to the sides of the stretchable substrate, can effectively suppress breakage of the stretchable substrate. Furthermore, for the stretchable devices of Examples 2 to 4, in which protective layers were disposed on both main surfaces of the stretchable substrate, the breakage time was 48 hours or more, and the presence of the protective layer further improved breakage resistance. Therefore, according to the present disclosure, breakage can be effectively suppressed in stretchable substrates made of various materials.

[0124] (Demonstration Test 2) Next, in the stretchable device of the present disclosure, the combination of the material and thickness of the stretchable substrate and the protective layer was evaluated. Specifically, in a stretchable device having the same structure as in Example 2, a plurality of stretchable devices were fabricated in which the material and thickness of the stretchable substrate and the material and thickness of the protective layer were changed, and the time to fracture was measured for each stretchable device. Furthermore, from the Young's modulus and thickness of the stretchable substrate and the protective layer in each stretchable device, the difference in relative hardness between the stretchable substrate and the protective layer given by the following formula (1) and the overall hardness of the stretchable device given by formula (2) were evaluated.

[0125]

[0126] (In the formula, M ｃｏｖｅｒ : Young's modulus of the protective layer (MPa), t ｃｏｖｅｒ : Thickness of protective layer (μm), M ｓｕｂ : Young's modulus of the elastic substrate (MPa), t ｓｕｂ : Thickness of stretchable substrate (μm)

[0127] The smaller the value given by formula (1), the softer the protective layer is relative to the stretchable substrate. Furthermore, the larger the value given by formula (2), the higher the overall hardness of the stretchable device. The first and second protective layers were made of the same material and had the same size.

[0128] The Young's modulus of the stretchable substrate and the protective layer was measured in accordance with JIS K7161-1:2014 using a dynamic viscoelasticity measuring device (manufactured by TA Instruments, model number RSA-G2). Specifically, each material was stretched at a temperature of 23°C ± 2°C and a humidity of 50 ± 10% RH to measure the Young's modulus. The thickness was measured using a micrometer.

[0129] The evaluation results of the examples are shown in Table 2.

[0130]

[0131] According to the above results, in all of the stretchable devices of Examples 6 to 14, the breakage occurrence time was 24 hours or more, indicating that the protective layer effectively suppressed breakage of the stretchable substrate. Furthermore, the stretchable device of Example 6, in which the value of Equation (1), which indicates the degree of hardness of the protective layer relative to the stretchable substrate, was less than 0.3, showed results showing a shorter breakage occurrence time compared to the stretchable devices of Examples 7 to 14, in which the value of Equation (1) was 0.3 or more. From this, it was found that the greater the hardness of the protective layer relative to the stretchable substrate (i.e., the hardness expressed as the product of the Young's modulus and thickness of the material), the greater the effect of extending the breakage occurrence time of the stretchable substrate. The effect of the protective layer was more pronounced when the value of Equation (1) was 0.3 or more. This is thought to be because the protective layer does not necessarily need to have the same hardness as the substrate, but only needs to have the effect of dispersing stress.

[0132] Furthermore, a stretchable device (for example, the stretchable device of Example 14) having a higher value of formula (2), which indicates the degree of hardness of the entire stretchable device including the stretchable substrate and the protective layer, achieved a breakage time of 48 hours or more, but the stretchability of the entire stretchable device decreased. On the other hand, the stretchable devices of Examples 6 to 13, which had smaller values ​​of formula (2), exhibited good stretchability and were shown to be able to suitably suppress breakage of the stretchable substrate.

[0133] 1: Stretchable device 10: Stretchable substrate 12: Main surface 12A: First main surface 12B: Second main surface 14: Side surface 20: Protective layer 20A: First protective layer 20B: Second protective layer 22: End surface of protective layer 24: Adhesion portion 25: Opening 30: Void 40: Stretchable wiring 50: Laminate 52: Main surface of laminate 52A: First main surface of laminate 52B: Second main surface of laminate 54: Side surface of laminate 55: Laminate step 60: Electronic component 70: Structure 71: Covering layer 73: Connection wiring 75: Support substrate 77: Structure step

Claims

1. A stretchable device comprising: a stretchable substrate; and a protective layer provided on the stretchable substrate; wherein the stretchable substrate has a first main surface and a second main surface that face each other in a thickness direction of the stretchable substrate; and a side surface connecting the first main surface and the second main surface; and the protective layer covers at least one of the second main surface and the side surface, and the first main surface.

2. The stretchable device according to claim 1, wherein the protective layer is positioned so as to cover the first main surface and extend from the first main surface to the side surface.

3. The stretchable device according to claim 1 or 2, wherein the protective layer covers each of the first major surface and the second major surface.

4. The stretchable device according to any one of claims 1 to 3, wherein the protective layer has a width dimension equal to or greater than the width dimension of the main surface of the stretchable substrate when viewed in the thickness direction.

5. The stretchable device according to any one of claims 1 to 4, wherein the protective layer extends over the entirety of the main surface.

6. The stretchable device according to any one of claims 1 to 5, wherein the protective layer comprises a main portion that is a major portion of the protective layer and a sub-portion other than the main portion, the main portion being on the main surface, and the sub-portion being on the side surface.

7. The stretchable device according to any one of claims 1 to 6, wherein the protective layer protrudes outward from the main surface of the stretchable substrate when viewed in the thickness direction.

8. The stretchable device of any one of claims 1 to 7, wherein the protective layer comprises a first protective layer covering the first major surface and a second protective layer covering the second major surface.

9. The stretchable device according to claim 8, wherein the stretchable substrate overlaps at least one of the first protective layer and the second protective layer when viewed in the thickness direction.

10. The stretchable device according to claim 8 or 9, wherein the first protective layer and the second protective layer are made of the same material.

11. The stretchable device according to any one of claims 8 to 10, wherein at least one of the first protective layer and the second protective layer extends to a side surface connecting the first main surface and the second main surface.

12. The stretchable device of claim 11, wherein the first protective layer and the second protective layer are adhered to one another.

13. The stretchable device according to claim 12, wherein the adhesive portion between the first protective layer and the second protective layer is positioned on the side surface of the stretchable substrate.

14. The stretchable device of any one of claims 8 to 13, wherein the stretchable substrate is surrounded by the first protective layer and the second protective layer.

15. The stretchable device of any one of claims 1-14, wherein the protective layer is continuous across the entire exterior surface of the stretchable device.

16. The stretchable device of any one of claims 1 to 15, wherein the protective layer is located on the outermost side of the stretchable device.

17. The stretchable device according to any one of claims 1 to 16, wherein the stretchable substrate and the protective layer satisfy the following formulas (1) and (2): (In the formula, M ｃｏｖｅｒ : Young's modulus of the protective layer (MPa), t ｃｏｖｅｒ : Thickness of protective layer (μm), M ｓｕｂ : Young's modulus of the elastic substrate (MPa), t ｓｕｂ : Thickness of elastic substrate (μm) 18. The stretchable device according to any one of claims 1 to 17, comprising a laminate including a plurality of stretchable substrates stacked on one another, wherein the protective layer is positioned on at least one of the first main surface of the stretchable substrate constituting the outer surface of the laminate, the second main surface of the stretchable substrate constituting the outer surface of the laminate opposite the first main surface, and the outer surface of the laminate.

19. The stretchable device of claim 18, wherein the protective layer surrounds the laminate.

20. The stretchable device according to any one of claims 1 to 19, comprising a first region having a relatively high hardness and a second region other than the first region having a relatively low hardness, wherein the protective layer extends to cover at least the second region when viewed in the thickness direction.

21. The stretchable device according to claim 20, wherein the protective layer has an opening in a region overlapping the first region when viewed in the thickness direction.

22. The stretchable device according to claim 20 or 21, wherein an electronic component is disposed in the first region.

23. The stretchable device according to any one of claims 1 to 22, further comprising a structure arranged so as to overlap an end of the stretchable substrate and face the second main surface of the stretchable substrate, as viewed in the thickness direction, and wherein the protective layer is arranged so as to overlap an end of the structure, as viewed in the thickness direction.

24. The stretchable device of claim 23, wherein the structure comprises a structure major surface that faces the second major surface of the stretchable substrate, and the protective layer extends from the first major surface of the stretchable substrate onto the structure major surface and is in contact with the structure major surface.

25. The stretchable device according to any one of claims 1 to 22, further comprising: a laminate including a plurality of the stretchable substrates stacked on top of each other and stretchable wiring arranged between the plurality of stretchable substrates; and a structure including: connection wiring arranged to overlap an end of the laminate in the thickness direction and electrically connected to the stretchable wiring, a support substrate supporting the connection wiring, and a covering layer that partially covers the connection wiring, wherein, in the thickness direction, a first stretchable substrate located at the outermost layer of the laminate among the plurality of stretchable substrates and the protective layer covering a first main surface of the first stretchable substrate are arranged to overlap an end of the covering layer.

26. The stretchable device of claim 25, wherein the structure comprises a structure major surface facing the laminate, and the protective layer extends from the first major surface of the stretchable substrate onto the covering layer and is in contact with the covering layer.

27. The stretchable device of claim 25 or 26, further comprising the protective layer disposed on a second major surface of a second stretchable substrate located on the outermost layer opposite the first stretchable substrate.

28. The stretchable device of claim 27, wherein an end of the second stretchable substrate and an end of the protective layer positioned on the second major surface of the second stretchable substrate are positioned between the stretchable wiring and the support substrate of the structure.

29. The stretchable device according to any one of claims 25 to 28, wherein the plurality of stretchable substrates and the stretchable wiring are stacked at the end of the laminate so as to constitute a plurality of laminate step portions whose thickness decreases stepwise toward the end, and the structure comprises a plurality of structure step portions whose thickness decreases stepwise toward the structure end at an end of the structure that overlaps with the end of the laminate, the laminate and the structure are combined so that a side surface of the laminate step portion and a side surface of the structure step portion face each other in the thickness direction, and the height of the laminate step portion is 50% or more and 150% or less of the height of the structure step portion facing the laminate step portion in a cross-sectional view.

30. The stretchable device of claim 29, wherein, in a cross-sectional view, the thickness of the laminate at the plurality of laminate step portions is 250% or less of the thickness of the laminate at the laminate step portion located at the end-most side of the laminate.

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