Stretchable wiring board

Abstract

A stretchable wiring board 1A is provided with: a stretchable substrate 10A having a first principal surface 10Aa and a second principal surface 10Ab facing one another in a thickness direction T; a wiring member 20A that is provided to at least the first principal surface 10Aa side of the stretchable substrate 10A, and comprises at least one stretchable wiring that extends in planar directions that include a length direction L orthogonal to the thickness direction T as well as a width direction W orthogonal to the thickness direction T and to the length direction L; a protective member 40A for covering the first principal surface 10Aa and / or the second principal surface 10Ab of the stretchable substrate 10A; and a film member 50A provided to the protective member 40A on a stretchable substrate 10A side and / or an opposite side from the stretchable substrate 10A. When stretched in the length direction L, the film member 50A experiences an irreversible change in appearance.

Description

stretchable wiring board

[0001] The present invention relates to a stretchable wiring board.

[0002] Patent Document 1 discloses a cord-like thermal fuse having a linear fuse disposed within an insulating sheathed tube, characterized in that the linear fuse is bent into a shape that allows it to stretch in its longitudinal direction.

[0003] Japanese Patent Application Publication No. 10-188756

[0004] In recent years, the condition of the human body has been managed by acquiring and analyzing biological information (vital signs) using a stretchable wiring board. When a stretchable wiring board is used in a state where it is attached to the human body, for example, the wiring used in the stretchable wiring board is required to have stretchability that allows it to follow the movement of the human body. In other words, the wiring used in the stretchable wiring board is required to be a stretchable wiring having stretchability.

[0005] However, even if the wiring used in a stretchable wiring board is a stretchable wiring, if the stretchable wiring board is stretched more than expected, the resistance of the stretchable wiring board is likely to increase as the stretchable wiring board stretches. If the resistance of the stretchable wiring increases in this way, when an excessive current flows through the stretchable wiring, the stretchable wiring may generate heat and become prone to breakage. Furthermore, if the stretchable wiring board is used while the resistance of the stretchable wiring is still high, there is a risk that errors will occur in the acquired biometric information, or that excessive current flowing through the stretchable wiring may generate heat, causing adverse effects such as burns to the human body.

[0006] In response to this, it is conceivable to incorporate a stretchable fuse such as the cord-like thermal fuse described in Patent Document 1 into a stretchable wiring board, so that when an overcurrent flows through the stretchable wiring in a state in which the stretchable wiring board is stretched more than expected, the fuse will blow, electrically destroying the stretchable wiring board. However, it is technically difficult to incorporate a cord-like thermal fuse having a hollow structure, as described in Figure 1 of Patent Document 1, into a stretchable wiring board. Even if it were possible to incorporate the cord-like thermal fuse described in Patent Document 1 into a stretchable wiring board, the stretchable wiring board would reach a high temperature when the cord-like thermal fuse blows, which could have adverse effects on the human body.

[0007] For these reasons, when a stretchable wiring board is used in a state where it is attached to the human body, a mechanism is required that can safely detect excessive stretching of the stretchable wiring board.

[0008] The present invention has been made to solve the above problems, and has an object to provide a stretchable wiring board that can safely detect an excessively stretched state.

[0009] The stretchable wiring board of the present invention comprises a stretchable substrate having a first main surface and a second main surface that face each other in a thickness direction; a wiring member provided on at least the first main surface side of the stretchable substrate and consisting of at least one stretchable wiring extending in a plane direction that includes a length direction perpendicular to the thickness direction and a width direction perpendicular to the thickness direction and the length direction; a protective member that covers at least one of the first main surface and the second main surface of the stretchable substrate; and a film member provided on at least one of the stretchable substrate side and the side opposite to the stretchable substrate with respect to the protective member, wherein the appearance of the film member changes irreversibly when stretched in the length direction.

[0010] According to the present invention, it is possible to provide a stretchable wiring board that can safely detect an excessively stretched state.

[0011] Fig. 1 is a schematic perspective view showing an example of a stretchable wiring board according to a first embodiment of the present invention. Fig. 2 is a schematic plan view showing the state of the film member in Fig. 1 before it is stretched in the length direction. Fig. 3 is a schematic plan view showing the state of the film member in Fig. 1 after it has been stretched in the length direction. Fig. 4 is a schematic perspective view showing an example of a stretchable wiring board according to a second embodiment of the present invention. Fig. 5 is a schematic plan view showing the state of the film member in Fig. 4 before it is stretched in the length direction. Fig. 6 is a schematic plan view showing the state of the film member in Fig. 4 after it has been stretched in the length direction.

[0012] The stretchable wiring board of the present invention will be described below. Note that the present invention is not limited to the following configurations, and may be modified as appropriate within the scope of the present invention. In addition, a combination of multiple individual preferred configurations described below also constitutes the present invention.

[0013] The following embodiments are merely examples, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. From embodiment 2 onwards, descriptions of matters common to embodiment 1 will be omitted, and differences will be mainly described. In particular, similar effects resulting from similar configurations will not be mentioned one after the other for each embodiment.

[0014] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, scale, etc. may differ from those of the actual product.

[0015] The stretchable wiring board of the present invention comprises a stretchable substrate having a first main surface and a second main surface that face each other in a thickness direction; a wiring member provided on at least the first main surface side of the stretchable substrate and consisting of at least one stretchable wiring extending in a plane direction that includes a length direction perpendicular to the thickness direction and a width direction perpendicular to the thickness direction and the length direction; a protective member that covers at least one of the first main surface and the second main surface of the stretchable substrate; and a film member provided on at least one of the stretchable substrate side and the side opposite to the stretchable substrate with respect to the protective member, wherein the appearance of the film member changes irreversibly when stretched in the length direction.

[0016] [Embodiment 1] In the stretchable wiring board of embodiment 1 of the present invention, the film member changes from a transparent state to an opaque state when stretched in the length direction.

[0017] FIG. 1 is a perspective schematic view showing an example of a stretchable wiring board according to a first embodiment of the present invention.

[0018] The stretchable wiring board 1A shown in FIG. 1 has a stretchable base material 10A, a wiring member 20A, a protective member 40A, and a film member 50A.

[0019] In this specification, the length direction, thickness direction, and width direction are defined as directions L, T, and W, respectively, as shown in Fig. 1 etc. The length direction L, thickness direction T, and width direction W are perpendicular to one another. Furthermore, a direction perpendicular to the thickness direction T and including the length direction L and width direction W is defined as a surface direction.

[0020] In this specification, unless otherwise specified, various dimensions in the length direction, thickness direction, and width direction are shown for the stretchable wiring board in an unstretched state. Various dimensions in the length direction, thickness direction, and width direction are each measured by viewing the stretchable wiring board in a plan view or cross section using an optical microscope.

[0021] The stretchable substrate 10A has a first main surface 10Aa and a second main surface 10Ab that face each other in the thickness direction T.

[0022] The stretchable substrate 10A has a narrow portion 11A having a minimum cross-sectional area when viewed in a cross section perpendicular to the length direction L.

[0023] In the example shown in Fig. 1, the dimension of the stretchable substrate 10A in the thickness direction T is constant regardless of the position along the length direction L. In other words, in the example shown in Fig. 1, the narrow portion 11A corresponds to the part of the stretchable substrate 10A where the dimension in the width direction W is the smallest. Note that when the dimension of the stretchable substrate 10A in the width direction W is constant regardless of the position along the length direction L, the narrow portion 11A corresponds to, for example, the part of the stretchable substrate 10A where the dimension in the thickness direction T is the smallest.

[0024] The stretchable substrate 10A preferably contains at least one resin selected from the group consisting of styrene-based resins, olefin-based resins, and silicone-based resins. Examples of styrene-based resins include styrene-butadiene-styrene copolymer resins (SBS).

[0025] The dimension of the stretchable substrate 10A in the thickness direction T is preferably 100 μm or less, and more preferably 50 μm or less. When the dimension of the stretchable substrate 10A in the thickness direction T is within the above range, the stretchable wiring board 1A can easily follow the movements of the human body when used in a state where it is attached to the human body.

[0026] The dimension of the stretchable substrate 10A in the thickness direction T is preferably 10 μm or more.

[0027] The breaking elongation rate of the stretchable substrate 10A in the length direction L is preferably 50% or more. When the breaking elongation rate of the stretchable substrate 10A in the length direction L is within the above range, the stretchable wiring board 1A can easily follow the movements of the human body when used in a state where it is attached to the human body.

[0028] From the viewpoint of making it easier for the stretchable wiring board 1A to follow the movements of the human body, the higher the breaking elongation rate in the length direction L of the stretchable substrate 10A is, the more preferable it is within a range of 50% or more.

[0029] The Young's modulus of the stretchable substrate 10A is preferably 100 MPa or less, and more preferably 30 MPa or less. When the Young's modulus of the stretchable substrate 10A is within the above range, when the stretchable wiring board 1A is used in a state where it is attached to the human body, the stretchable wiring board 1A is less likely to inhibit the expansion and contraction of the surface of the human body, and therefore the stretchable wiring board 1A is less likely to cause discomfort.

[0030] The Young's modulus of the stretchable substrate 10A is preferably 3 MPa or more.

[0031] In the example shown in FIG. 1, the shape of the stretchable substrate 10A when viewed in the thickness direction T is such that the dimension in the width direction W is larger at one end than at other portions.

[0032] The shape of the stretchable substrate 10A when viewed in the thickness direction T may be a shape in which the dimension in the width direction W is constant regardless of the position along the length direction L.

[0033] Furthermore, the shape of the stretchable substrate 10A when viewed in the thickness direction T may be a shape in which one end is looped, for example, a shape in which a straight portion and a loop portion are connected in the length direction L. In this case, the stretchable substrate 10A may have a narrow portion at the position where the straight portion and the loop portion are connected.

[0034] The wiring member 20A is provided on at least the first main surface 10Aa side of the stretchable substrate 10A.

[0035] In the example shown in FIG. 1, the wiring member 20A is provided on the first main surface 10Aa side of the stretchable substrate 10A.

[0036] The wiring member 20A may be provided on the second main surface 10Ab side of the stretchable substrate 10A in addition to the first main surface 10Aa side of the stretchable substrate 10A.

[0037] 1, the wiring member 20A is provided on the first main surface 10Aa of the stretchable substrate 10A. That is, in the example shown in Fig. 1, the stretchable substrate 10A and the wiring member 20A are in contact with each other.

[0038] It should be noted that another member may be interposed between the stretchable substrate 10A and the wiring member 20A.

[0039] The wiring member 20A is composed of at least one elastic wire extending in a planar direction including the length direction L and the width direction W.

[0040] In the example shown in FIG. 1, the wiring member 20A is composed of two elastic wires 21Aa and 21Ab that extend in the planar direction.

[0041] The wiring member 20A may be made up of only one stretchable wire, or may be made up of three or more stretchable wires.

[0042] The dimension of the stretchable wiring in the thickness direction T, and the dimension of the stretchable wiring 21Aa and the stretchable wiring 21Ab in the thickness direction T in the example shown in Fig. 1 are preferably 100 µm or less, and more preferably 50 µm or less. When the dimension of the stretchable wiring in the thickness direction T is within the above range, the stretchable wiring board 1A can more easily follow the movements of the human body when used in a state where it is attached to the human body.

[0043] The dimension of the elastic wire in the thickness direction T, that of the elastic wire 21Aa and the elastic wire 21Ab in the example shown in FIG. 1, in the thickness direction T is preferably 1 μm or more, more preferably 10 μm or more.

[0044] The elastic wires, the elastic wires 21Aa and 21Ab in the example shown in FIG. 1, contain, for example, conductive particles and resin.

[0045] Examples of materials constituting the conductive particles contained in the elastic wiring include metals such as silver, copper, nickel, etc. Among these, silver is preferred from the viewpoint of realizing low resistance of the elastic wiring.

[0046] The average particle size of the conductive particles contained in the elastic wiring is preferably 0.01 μm or more and 10 μm or less.

[0047] The average particle size of the conductive particles contained in the stretchable wiring is determined as follows. First, the stretchable wiring substrate is polished or the like so that a cross section in which the target stretchable wiring is exposed appears. Next, an image of the cross section is taken using a scanning electron microscope (SEM) or the like. Then, the equivalent circle diameter of the conductive particles contained in the stretchable wiring is measured by performing image analysis on the taken cross section image, and the obtained equivalent circle diameter is taken as the particle size of the conductive particles. Thereafter, a number-based cumulative particle size distribution is calculated from the particle sizes of the conductive particles obtained, and the particle size at which the cumulative probability in the number-based cumulative particle size distribution is 50% (median diameter D ５０ ) is defined as the average particle size of the conductive particles.

[0048] The conductive particles contained in the stretchable wire are preferably spherical in shape. In order to reduce the change in resistance of the stretchable wire due to stretching, the conductive particles contained in the stretchable wire may have a shape other than spherical, such as a flat shape or an irregular shape having protrusions.

[0049] When the wiring member 20A is composed of multiple stretchable wirings, it is preferable that the conductive particles contained in each stretchable wiring are the same as each other at least in terms of the type of constituent material, but they may be different from each other or may be partially different.

[0050] The resin contained in the stretchable wiring is preferably at least one elastomer resin selected from the group consisting of epoxy resins, urethane resins, acrylic resins, and silicone resins. In this case, the stretchability of the stretchable wiring is more easily ensured. Note that the resin contained in the stretchable wiring may be a resin other than those listed above, as long as it can impart stretchability.

[0051] When the wiring member 20A is composed of multiple stretchable wires, it is preferable that the resin contained in each stretchable wire is the same as each other at least in terms of type, but they may be different from each other or may be partially different.

[0052] The stretchable wiring, the stretchable wiring 21Aa and the stretchable wiring 21Ab in the example shown in FIG. 1, are formed, for example, as follows. First, a conductive paste containing conductive particles and a resin is applied to at least the first main surface 10Aa of the stretchable substrate 10A. Examples of methods for applying the conductive paste include screen printing, inkjet printing, and dispensing. Then, the applied conductive paste is heat-treated to form the stretchable wiring.

[0053] 1, the stretchable wiring 21Aa and the stretchable wiring 21Ab are each electrically connected to the electronic component 30. That is, the stretchable wiring 21Aa and the stretchable wiring 21Ab form an electrical path to the outside, in the example shown in FIG. 1, an electrical path to the external electronic component 30.

[0054] The electronic component 30 is mounted on each of the elastic wires 21Aa and 21Ab via a joining member such as solder.

[0055] Examples of the electronic component 30 include a diode, an integrated circuit (IC), a capacitor, a resistor, an inductor, an amplifier (an operational amplifier, a transistor, etc.), and the like.

[0056] The protective member 40A covers at least one of the first main surface 10Aa and the second main surface 10Ab of the stretchable substrate 10A.

[0057] In the example shown in FIG. 1, the protective member 40A covers both the first main surface 10Aa and the second main surface 10Ab of the stretchable substrate 10A.

[0058] The protective member 40A may cover only the first main surface 10Aa of the stretchable substrate 10A, or may cover only the second main surface 10Ab of the stretchable substrate 10A.

[0059] 1, the protective member 40A is composed of a first protective portion 40Aa and a second protective portion 40Ab. In the example shown in Fig. 1, the first protective portion 40Aa covers the first main surface 10Aa of the stretchable substrate 10A, and the second protective portion 40Ab covers the second main surface 10Ab of the stretchable substrate 10A.

[0060] 1 , the protective member 40A, more specifically, the first protective portion 40Aa, covers the first main surface 10Aa of the stretchable substrate 10A, while also covering the wiring member 20A and the electronic component 30. By the protective member 40A covering the wiring member 20A and the electronic component 30, the following effects are obtained: - The wiring member 20A and the electronic component 30 are protected from the outside. - The moisture resistance of the wiring member 20A and the electronic component 30 is improved. - Chemical substances used in the wiring member 20A and the electronic component 30 are prevented from coming into contact with the human body. - Electric leakage from the wiring member 20A and the electronic component 30 to the human body is prevented.

[0061] Examples of materials that can be used to form the protective member 40A, and the first and second protective portions 40Aa and 40Ab in the example shown in FIG. 1, include elastomer resins such as polyvinyl chloride, polyethylene, polystyrene, polycarbonate, polyvinylidene fluoride, polyimide, liquid crystal polymer, polytetrafluoroethylene, phenolic resin, epoxy resin, urethane resin, acrylic resin, silicone resin, and styrene-butadiene resin.

[0062] The protective member 40A is formed, for example, by pressing a film containing the above-mentioned material onto at least one of the first main surface 10Aa and the second main surface 10Ab of the stretchable substrate 10A. Alternatively, the protective member 40A is formed, for example, by applying a slurry containing the above-mentioned material to at least one of the first main surface 10Aa and the second main surface 10Ab of the stretchable substrate 10A, and then subjecting the applied slurry to a heat treatment or UV treatment. Examples of methods for applying the slurry include screen printing, inkjet printing, and dispensing.

[0063] The film member 50A is provided on at least one of the stretchable substrate 10A side and the opposite side to the stretchable substrate 10A with respect to the protection member 40A.

[0064] In the example shown in FIG. 1, the film member 50A is provided on the opposite side of the protective member 40A to the stretchable substrate 10A.

[0065] 1, the film member 50A is provided on the side of the first protective part 40Aa opposite the stretchable substrate 10A. In the example shown in Fig. 1, by providing the film member 50A on the side of the first protective part 40Aa opposite the stretchable substrate 10A, the area where the film member 50A is provided, i.e., the area where the first protective part 40Aa and the film member 50A overlap, is mechanically reinforced.

[0066] The film member 50A may be provided on the opposite side of the second protective portion 40Ab from the stretchable substrate 10A.

[0067] The film member 50A may be provided on both the side of the first protective part 40Aa opposite the stretchable substrate 10A and the side of the second protective part 40Ab opposite the stretchable substrate 10A.

[0068] 1, the film member 50A is provided on the main surface of the first protective part 40Aa opposite to the stretchable substrate 10A. That is, in the example shown in FIG. 1, the protective member 40A and the film member 50A are in contact with each other.

[0069] It should be noted that another member may be interposed between the protective member 40A and the film member 50A.

[0070] The film member 50A may be provided on the stretchable substrate 10A side of the protective member 40A. More specifically, the film member 50A may be provided only on the stretchable substrate 10A side of the first protective part 40Aa, or only on the stretchable substrate 10A side of the second protective part 40Ab, or may be provided on both the stretchable substrate 10A side of the first protective part 40Aa and the stretchable substrate 10A side of the second protective part 40Ab.

[0071] The film member 50A may be provided on both the side of the protective member 40A facing the stretchable substrate 10A and the side of the protective member 40A opposite to the stretchable substrate 10A.

[0072] As described above, in the example shown in FIG. 1 , each of the elastic wires 21Aa and 21Ab is electrically connected to the electronic component 30 .

[0073] For example, when a light-emitting diode, which is a type of diode, is used as the electronic component 30, the stretchable wiring 21Aa and the stretchable wiring 21Ab function as drive wiring through which a large current flows for driving the light-emitting diode. In this case, if the stretchable wiring board 1A is stretched excessively in the length direction L, the resistance of the stretchable wiring 21Aa and the stretchable wiring 21Ab will become too high as the stretchable wiring 21Aa and the stretchable wiring 21Ab stretch, and this may make it difficult for a large current for driving the light-emitting diode to flow to the light-emitting diode via the stretchable wiring 21Aa and the stretchable wiring 21Ab, or may make the stretchable wiring 21Aa and the stretchable wiring 21Ab more susceptible to breakage when a large current flows, or may make the stretchable wiring 21Aa and the stretchable wiring 21Ab more susceptible to heat generation when a large current flows. In this way, if the elastic wiring board 1A is stretched excessively in the longitudinal direction L, the light-emitting diode serving as the electronic component 30 may not light up, or the elastic wiring 21Aa and the elastic wiring 21Ab may generate excessive heat.

[0074] In contrast, in the stretchable wiring board 1A, the appearance of the film member 50A changes irreversibly when stretched in the length direction L. In the stretchable wiring board 1A, by utilizing the fact that the appearance of the film member 50A changes irreversibly when stretched in the length direction L, it is possible to detect an excessively stretched state of the stretchable wiring board 1A, such as the stretchable wiring board 1A being excessively stretched in the length direction L, before a defect such as breakage of the stretchable wiring 21Aa and the stretchable wiring 21Ab occurs due to the stretchable wiring 21Aa and the stretchable wiring 21Ab being excessively stretched in the length direction L.

[0075] In the stretchable wiring board 1A, by determining in advance the elongation rate of the film member 50A and the timing at which the appearance of the film member 50A changes, and then providing the film member 50A as described above, it is possible to adjust the timing at which the appearance of the film member 50A changes when the stretchable wiring board 1A is stretched in the longitudinal direction L, i.e., the timing at which an excessive stretched state of the stretchable wiring board 1A is detected.

[0076] In the stretchable wiring board 1A, the appearance of the film member 50A changes irreversibly when the board is stretched in the length direction L, and this makes it possible to leave a trace that the stretchable wiring board 1A has been excessively stretched in the length direction L. In other words, from the stretchable wiring board 1A in which the appearance of the film member 50A has changed, it is possible to confirm that the stretchable wiring board 1A has been excessively stretched in the length direction L in the past.

[0077] Furthermore, when the stretchable wiring board 1A is used, the user can be urged to stop using the stretchable wiring board 1A at the point in time when the appearance of the film member 50A changes, that is, before the stretchable wiring 21Aa and the stretchable wiring 21Ab are excessively stretched in the length direction L. In other words, when the stretchable wiring board 1A is used, the user can be urged to stop using the stretchable wiring board 1A before the stretchable wiring 21Aa and the stretchable wiring 21Ab generate excessive heat due to the stretchable wiring 21Aa and the stretchable wiring 21Ab being excessively stretched in the length direction L. Therefore, when the stretchable wiring board 1A is used, not only is the stretchable wiring 21Aa and the stretchable wiring 21Ab prevented from generating excessive heat, but the excessive heat generated by the stretchable wiring 21Aa and the stretchable wiring 21Ab is prevented from being exposed to the user's body, resulting in increased safety.

[0078] As described above, the stretchable wiring board 1A can realize a stretchable wiring board that can safely detect an excessively stretched state.

[0079] In this specification, the phrase "the appearance of a film member changes irreversibly when stretched in the longitudinal direction" means that the appearance of the film member changes when stretched in the longitudinal direction, and that the appearance does not return to its original state even if the film member is contracted after being stretched in the longitudinal direction. The appearance of the film member includes the color, shape, etc. of the film member.

[0080] Fig. 2 is a schematic plan view showing the film member in Fig. 1 in a state before being stretched in the length direction. Fig. 3 is a schematic plan view showing the film member in Fig. 1 in a state after being stretched in the length direction.

[0081] The film member 50A shown in Figure 2, which is in a transparent state before being stretched in the length direction L, is in a transparent state. In contrast, the film member 50A shown in Figure 3, which is in an opaque state after being stretched in the length direction L, is in an opaque state. In this way, the film member 50A changes from a transparent state to an opaque state when stretched in the length direction L. On the other hand, after the film member 50A has changed from a transparent state to an opaque state by being stretched in the length direction L, it does not change from an opaque state to a transparent state even if it is shrunk back to the state before being stretched in the length direction L.

[0082] In this specification, the change of a film member from a transparent state to an opaque state means that when white light containing wavelengths of 450 nm or more and 780 nm or less is transmitted through the film member, the transmittance, as defined by the following formula (1), changes from 95% or more to 90% or less: Transmittance (%) = 100 × transmitted light intensity / light source intensity (1)

[0083] An example of how the film member 50A changes from a transparent state to an opaque state when stretched in the length direction L will be described below.

[0084] The film member 50A may be made of a resin that changes from an amorphous state to a crystalline state when the film member 50A is stretched in the length direction L. In this case, the molecular structure of the resin that constitutes the film member 50A is amorphous (also called amorphous plastic) before the film member 50A is stretched in the length direction L, and therefore the film member 50A is in a transparent state that transmits light before being stretched in the length direction L. In contrast, the molecular structure of the resin that constitutes the film member 50A changes to a crystalline state (also called crystalline plastic) when the film member 50A is stretched in the length direction L, and therefore the film member 50A is in an opaque state that diffuses light after being stretched in the length direction L.

[0085] In this specification, the change of a resin from an amorphous state to a crystalline state means that in the solidified state of the resin, the string-like polymers change from an irregularly entangled state to an regularly arranged state, preferably the degree of orientation of the resin changes from a state of 1% or less to a state of 20% or more. The degree of orientation of the resin is calculated, for example, from the crystalline peak of the resin measured by X-ray diffraction or the like.

[0086] When the film member 50A is made of a resin that changes from an amorphous state to a crystalline state when the film member 50A is stretched in the length direction L, the constituent material of the film member 50A is preferably polyethylene.

[0087] The film member 50A may contain microcapsules containing a pigment that can be broken when the film member 50A is stretched in the length direction L. In this case, when the film member 50A is stretched in the length direction L, the microcapsules contained in the film member 50A are broken and the pigment seeps out, causing the color of the film member 50A to change overall and become opaque.

[0088] As described above, when the film member 50A is stretched in the length direction L, it changes from a transparent state to an opaque state, and thereby the color, which is an example of the appearance, changes irreversibly.

[0089] As described above, the narrow portion 11A corresponds to the portion of the stretchable substrate 10A that has the smallest cross-sectional area when viewed in a cross section perpendicular to the longitudinal direction L. Therefore, when the stretchable wiring board 1A is stretched in the longitudinal direction L, stress tends to concentrate in the narrow portion 11A of the stretchable substrate 10A, and as a result, the narrow portion 11A is more likely to stretch than other portions.

[0090] In contrast, in the stretchable wiring board 1A, the film member 50A is provided in a position that overlaps the narrow portion 11A when viewed from the thickness direction T. That is, in the stretchable wiring board 1A, the film member 50A, whose appearance changes irreversibly when stretched in the length direction L, is provided in the narrow portion 11A that stretches the most when the stretchable base material 10A is stretched in the length direction L. Therefore, with the stretchable wiring board 1A in which the film member 50A is provided in the narrow portion 11A, the appearance of the film member 50A is more likely to change earlier when stretched in the length direction L, compared to a stretchable wiring board in which the film member 50A is not provided in the narrow portion 11A, and therefore an excessively stretched state can be detected earlier.

[0091] In the example shown in FIG. 1, the film member 50A is provided only at a position overlapping the narrow portion 11A when viewed in the thickness direction T.

[0092] In addition to being positioned so as to overlap the narrow portion 11A when viewed from the thickness direction T, the film member 50A may also be positioned so as not to overlap the narrow portion 11A when viewed from the thickness direction T.

[0093] The tensile strength of the film member 50A in the length direction L is preferably lower than the tensile strength of the wiring member 20A in the length direction L. In this case, when the stretchable wiring board 1A is stretched in the length direction L, the film member 50A will break before the wiring member 20A breaks due to excessive stretching of the wiring member 20A in the length direction L. As a result, when the film member 50A is stretched in the length direction L, not only the color, as an example of its appearance, but also the shape will change irreversibly, making it easier to detect an excessively stretched state of the stretchable wiring board 1A.

[0094] The tensile strength of the protective member 40A in the length direction L, and the tensile strength of each of the first protective portion 40Aa and the second protective portion 40Ab in the length direction L in the example shown in Fig. 1 are preferably higher than the tensile strength of the wiring member 20A in the length direction L. In this case, when the stretchable wiring board 1A is stretched in the length direction L, the protective member 40A does not break before the wiring member 20A. In other words, when the stretchable wiring board 1A is stretched in the length direction L, the protective member 40A does not break at the time when the wiring member 20A breaks due to excessive stretching of the wiring member 20A in the length direction L. Therefore, when the stretchable wiring board 1A is used, the user can be urged to stop using the stretchable wiring board 1A at the point in time when the film member 50A detects that the wiring member 20A has been excessively stretched in the length direction L, that is, before problems occur such as chemical substances used in the wiring member 20A and the electronic components 30 coming into contact with the human body or electric leakage from the wiring member 20A and the electronic components 30 to the human body due to breakage of the protective member 40A. As a result, safety is improved when using the stretchable wiring board 1A having the protective member 40A.

[0095] The breaking elongation rate in the length direction L of the protective member 40A, and the breaking elongation rate in the length direction L of each of the first protective portion 40Aa and the second protective portion 40Ab in the example shown in FIG. 1, is preferably 200% or more.

[0096] The breaking elongation rate in the length direction L of the protective member 40A, and the breaking elongation rate in the length direction L of each of the first protective portion 40Aa and the second protective portion 40Ab in the example shown in FIG. 1, is preferably 800% or less.

[0097] The stretchable wiring board 1A may further include an electrode connected to at least one of the stretchable wiring 21Aa and the stretchable wiring 21Ab. The stretchable wiring board 1A can function as a sensor by being attached to the human body via such an electrode. In this case, the stretchable wiring board 1A can detect, for example, an excessive stretching state before at least one of the stretchable wiring 21Aa and the stretchable wiring 21Ab connected to the electrode is excessively stretched in the length direction L and breaks, i.e., before a sensor abnormality occurs. This allows the user to be prompted to stop using the stretchable wiring board 1A before a sensor abnormality occurs, thereby preventing problems such as obtaining erroneous biometric information or being diagnosed based on erroneous biometric information.

[0098] The electrodes are preferably gel electrodes. The use of gel electrodes makes it easier to attach the stretchable wiring board 1A to the human body. The gel electrodes are made of a conductive gel material containing, for example, water, alcohol, a moisturizer, an electrolyte, etc. Examples of such gel materials include hydrogels.

[0099] [Embodiment 2] In a stretchable wiring board of embodiment 2 of the present invention, the film member has a notch that can be broken when stretched in the length direction. Except for this, the stretchable wiring board of embodiment 2 of the present invention is similar to the stretchable wiring board of embodiment 1 of the present invention.

[0100] FIG. 4 is a perspective schematic diagram showing an example of a stretchable wiring board according to a second embodiment of the present invention.

[0101] The stretchable wiring board 1B shown in Fig. 4 has a stretchable base material 10A, a wiring member 20A, a protective member 40A, and a film member 50B. In other words, the stretchable wiring board 1B differs from the stretchable wiring board 1A in that it has a film member 50B instead of the film member 50A.

[0102] Fig. 5 is a schematic plan view showing the film member in Fig. 4 before it is stretched in the length direction. Fig. 6 is a schematic plan view showing the film member in Fig. 4 after it has been stretched in the length direction.

[0103] The film member 50B has a notch 51 that can be broken when stretched in the length direction L. In the film member 50B shown in FIG. 5 , which shows the state before being stretched in the length direction L, the notch 51 is not broken. In contrast, in the film member 50B shown in FIG. 6 , which shows the state after being stretched in the length direction L, the notch 51 is broken at the breaking point 52. In this way, the shape of the film member 50B changes when stretched in the length direction L. On the other hand, even if the film member 50B is shrunk to the state before being stretched in the length direction L after its shape has changed due to being stretched in the length direction L, the notch 51 remains broken at the breaking point 52, and the shape does not return to its original state.

[0104] As described above, when the film member 50B is stretched in the length direction L, the shape, which is an example of the appearance, is irreversibly changed.

[0105] Therefore, according to the stretchable wiring board 1B, by utilizing the fact that the appearance of the film member 50B changes irreversibly when stretched in the length direction L, it is possible to realize a stretchable wiring board that can safely detect an excessively stretched state, similar to the stretchable wiring board 1A.

[0106] In the following, an example of a state in which the shape of the film member 50B is likely to change when it is stretched in the length direction L will be described.

[0107] In the film member 50B, the cuts 51 are preferably provided along the width direction W.

[0108] In the stretchable wiring board 1B, by arranging the notch 51 along the width direction W as described above after understanding in advance the relationship between the dimension D2 of the notch 51 in the width direction W and the breaking elongation rate in the length direction L of the film member 50B until the notch 51 breaks, it is possible to adjust the timing at which the appearance of the film member 50B changes (the notch 51 breaks) when the stretchable wiring board 1B is stretched in the length direction L, that is, the timing at which the excessive stretching state of the stretchable wiring board 1B is detected.

[0109] In the stretchable wiring board 1B, the breaking elongation rate in the length direction L of the film member 50B until the incisions 51 break can be adjusted not only by the dimension D2 of the incisions 51 in the width direction W, but also by the distance D1 between the incisions 51 in the length direction L and the distance D3 between the incisions 51 in the width direction W. For example, by shortening the distance D1 between the incisions 51 in the length direction L and lengthening the dimension D2 of the incisions 51 in the width direction W, it is possible to increase the breaking elongation rate in the length direction L of the film member 50B until the incisions 51 break.

[0110] In the film member 50B, the cuts 51 may be provided along a surface direction other than the width direction W (for example, the length direction L).

[0111] The film member 50B preferably has a plurality of incisions 51. In this case, the plurality of incisions 51 are preferably arranged in the same straight line along the width direction W. The plurality of incisions 51 are also preferably arranged in the length direction L such that rows of incisions 51 arranged in the same straight line along the width direction W are spaced apart from one another.

[0112] In the stretchable wiring board 1B, by determining in advance the relationship between the number, arrangement, etc. of the notches 51 and the breaking elongation rate in the length direction L of the film member 50B until the notches 51 break, and then setting the number, arrangement, etc. of the notches 51 as described above, it is possible to adjust the timing at which the appearance of the film member 50B changes (the notches 51 break) when the stretchable wiring board 1B is stretched in the length direction L, that is, the timing at which the excessive stretching state of the stretchable wiring board 1B is detected.

[0113] It should be noted that only one cut 51 may be provided in the film member 50B.

[0114] The film member 50B is preferably made of a non-stretchable resin, which makes the incisions 51 more likely to break sooner when the film member 50B is stretched in the length direction L, and therefore makes the appearance of the film member 50B more likely to change sooner.

[0115] In this specification, a resin being non-elastic means that when the resin in question is molded into a resin film having a length of 18 mm, a width of 5 mm and a thickness of 38 μm, the tensile modulus of elasticity in the length direction of the resin film is 1 GPa or more.

[0116] When the film member 50B is made of a non-elastic resin, the constituent material of the film member 50B is preferably at least one of polyethylene terephthalate and polyimide. That is, the constituent material of the film member 50B is preferably polyethylene terephthalate, or preferably polyimide, or more preferably a mixture of polyethylene terephthalate and polyimide.

[0117] In each of the above embodiments, a mode in which the stretchable wiring board is stretched in the length direction when the stretchable wiring board is used has been described. However, the stretchable wiring board may be stretched in a surface direction other than the length direction (for example, the width direction) in addition to the length direction.

[0118] The present specification discloses the following:

[0119] <1> A stretchable wiring board comprising: a stretchable substrate having a first main surface and a second main surface opposing each other in a thickness direction; a wiring member provided on at least the first main surface side of the stretchable substrate and consisting of at least one stretchable wiring extending in a plane direction including a length direction perpendicular to the thickness direction and a width direction perpendicular to the thickness direction and the length direction; a protective member covering at least one of the first main surface and the second main surface of the stretchable substrate; and a film member provided on at least one of the stretchable substrate side and the side opposite to the stretchable substrate with respect to the protective member, wherein the appearance of the film member changes irreversibly when stretched in the length direction.

[0120] <2> The stretchable wiring board according to <1>, wherein the film member changes from a transparent state to an opaque state when stretched in the length direction.

[0121] <3> The stretchable wiring board according to <2>, wherein the film member is made of a resin that changes from an amorphous state to a crystalline state when the film member is stretched in the length direction.

[0122] <4> The stretchable wiring board according to <3>, wherein the constituent material of the film member is polyethylene.

[0123] <5> The stretchable wiring board according to any one of <1> to <4>, wherein the film member has a notch that can be broken when stretched in the length direction.

[0124] <6> The stretchable wiring board according to <5>, wherein the cuts are provided along the width direction.

[0125] <7> The stretchable wiring board according to <5> or <6>, wherein the film member is made of a non-stretchable resin.

[0126] <8> The stretchable wiring board according to <7>, wherein the constituent material of the film member is at least one of polyethylene terephthalate and polyimide.

[0127] <9> The stretchable substrate has a narrow portion having a minimum cross-sectional area when viewed in a cross section perpendicular to the length direction, and the film member is provided in a position overlapping the narrow portion when viewed in the thickness direction. The stretchable wiring board according to any one of <1> to <8>.

[0128] <10> The stretchable wiring board according to any one of <1> to <9>, wherein the film member is provided on the opposite side of the protective member to the stretchable substrate.

[0129] 1A, 1B Stretchable wiring board 10A Stretchable base material 10Aa First main surface 10Ab Second main surface 11A Narrowed portion 20A Wiring member 21Aa, 21Ab Stretchable wiring 30 Electronic component 40A Protective member 40Aa First protective portion 40Ab Second protective portion 50A, 50B Film member 51 Incision 52 Fracture location D1 Distance between incisions in the length direction D2 Dimension of incision in the width direction D3 Distance between incisions in the width direction L Length direction T Thickness direction W Width direction

Claims

1. An elastic substrate having a first main surface and a second main surface opposed to each other in a thickness direction; A wiring member comprising at least one elastic wiring provided on at least the first main surface side of the elastic base material and extending in a surface direction including a length direction perpendicular to the thickness direction and a width direction perpendicular to the thickness direction and the length direction; A protective member covering at least one of the first main surface and the second main surface of the stretchable substrate; A film member provided on at least one of the elastic substrate side and the opposite side to the elastic substrate with respect to the protective member, The film member is provided with a notch that can be broken when stretched in the length direction, The film member has an appearance that irreversibly changes when stretched in the length direction.

2. An elastic substrate having a first principal surface and a second principal surface opposed to each other in a thickness direction; A wiring member comprising at least one elastic wiring provided on at least the first main surface side of the elastic base material and extending in a surface direction including a length direction perpendicular to the thickness direction and a width direction perpendicular to the thickness direction and the length direction; A protective member covering at least one of the first main surface and the second main surface of the stretchable substrate; A film member provided on at least one of the elastic substrate side and the opposite side to the elastic substrate with respect to the protective member, The stretchable substrate has a narrow portion having a minimum cross-sectional area when viewed in a cross section perpendicular to the longitudinal direction, the film member is provided at a position overlapping the narrow portion when viewed from the thickness direction, The film member has an appearance that irreversibly changes when stretched in the length direction.

3. The stretchable wiring board according to claim 1 or 2, wherein the film member changes from a transparent state to an opaque state when stretched in the length direction.

4. The stretchable wiring board according to claim 3 , wherein the film member is made of a resin that changes from an amorphous state to a crystalline state when the film member is stretched in the length direction.

5. The stretchable wiring board according to claim 4 , wherein a constituent material of the film member is polyethylene.

6. The stretchable wiring board according to claim 1 , wherein the cuts are provided along the width direction.

7. The stretchable wiring board according to claim 1 or 6, wherein the film member is made of a non-stretchable resin.

8. The stretchable wiring board according to claim 7 , wherein a constituent material of the film member is at least one of polyethylene terephthalate and polyimide.

9. The stretchable substrate has a narrow portion having a minimum cross-sectional area when viewed in a cross section perpendicular to the longitudinal direction, The stretchable wiring board according to claim 1 , wherein the film member is provided at a position overlapping the narrow portion when viewed in the thickness direction.

10. The stretchable wiring board according to claim 1 or 2, wherein the film member is provided on the protective member opposite to the stretchable base material.