JP6998172B2 - Elastic circuit board - Google Patents

Description

The present disclosure relates to a stretchable circuit board having a stretchable substrate and wiring.

In recent years, stretchable electronics (also referred to as stretchable electronics) have been attracting attention, and stretchable circuit boards have been actively developed. As one of the methods for obtaining a stretchable circuit board, Patent Document 1 describes a wrinkle-shaped metal thin film by arranging a metal thin film on a pre-stretched stretchable base material and then releasing tension. Has been proposed.

Japanese Unexamined Patent Publication No. 2017-103459

In the method of pre-stretching the stretchable base material as described above, when the tension is released, the shrinkage difference between the surface on which the metal thin film of the stretchable base material is arranged and the surface on the opposite side thereof. There is a problem that the resulting elastic circuit board is warped. If the stretchable circuit board is warped, it may be difficult to apply it to an object, or it may be difficult to perform post-processes such as adhesive processing and packaging.

The present disclosure has been made in view of the above problems, and an object of the present disclosure is to provide a stretchable circuit board capable of controlling the degree of warpage.

In order to achieve the above object, the present disclosure discloses an elastic base material, wiring and functional members on one side of the base material, and a surface of the base material opposite to the one side. The wiring provides an elastic circuit board having a stress adjusting layer on the side and having an uneven cross-sectional shape.

The present disclosure has the effect of being able to provide a stretchable circuit board capable of controlling the degree of warpage.

It is a schematic plan view and sectional drawing which shows an example of the stretchable circuit board of this disclosure. It is a process drawing which shows an example of the manufacturing method of the elastic circuit board of this disclosure. It is a schematic sectional drawing which shows an example of the conventional elastic circuit board. It is the schematic sectional drawing which shows the other example of the stretchable circuit board of this disclosure. It is a schematic plan view which shows the other example of the elastic circuit board of this disclosure. It is a schematic diagram which shows an example of the uneven shape of wiring in the elastic circuit board of this disclosure. It is the schematic sectional drawing which shows the other example of the stretchable circuit board of this disclosure. It is the schematic sectional drawing which shows the other example of the stretchable circuit board of this disclosure. It is the schematic sectional drawing which shows the other example of the elastic circuit board of this disclosure. It is a schematic diagram for demonstrating the method of measuring the warp of the elastic circuit board of this disclosure. It is a process drawing which shows the other example of the manufacturing method of the stretchable circuit board of this disclosure.

Hereinafter, the elastic circuit board of the present disclosure will be described in detail.

The stretchable circuit board of the present disclosure includes a base material having elasticity, wiring and functional members on one surface side of the base material, and stress on the surface side opposite to the one surface of the base material. It has an adjusting layer, and the wiring has a concavo-convex cross-sectional shape.

Here, the "stretchability" means a property that can be expanded and contracted, that is, a property that can be expanded from a normal non-extended state and can be restored when released from this expanded state. Elasticity is also called stretchable.

"Wiring and functional members on one side of the substrate" means that the wiring and functional members may be arranged directly on one surface of the substrate, and the wiring and functional members are on one side of the substrate. It means that it may be indirectly arranged on the surface via another member.
Further, the “stress adjusting layer on the surface side opposite to one surface of the base material” may mean that the stress adjusting layer may be directly arranged on the surface opposite to one surface of the base material, and the stress may be applied. It means that the adjusting layer may be indirectly arranged on the surface opposite to one surface of the base material via the other member.

The elastic circuit board of the present disclosure will be described with reference to the drawings. 1 (a) and 1 (b) are schematic plan views and cross-sectional views showing an example of the stretchable circuit board of the present disclosure, and FIG. 1 (b) is a sectional view taken along line AA of FIG. 1 (a). be. The stretchable circuit board 1 exemplified in FIGS. 1 (a) and 1 (b) has a stretchable base material 2, and has a wiring 5 and a functional member 6 on one surface of the base material 2. The stress adjusting layer 8 is provided on the surface of the base material 2 opposite to one surface. The stretchable circuit board 1 may have a support base material 4 between the base material 2, the wiring 5, and the functional member 6, and further, a first adhesion between the base material 2 and the support base material 4. It may have a layer 3. That is, the wiring base material 10 having the wiring 5 and the functional member 6 on one surface of the support base material 4 may be arranged on one surface of the base material 2 via the first adhesive layer 3. Further, the stretchable circuit board 1 may have a second adhesive layer 7 between the base material 2 and the stress adjusting layer 8. That is, the stress adjusting layer 8 may be arranged on the surface opposite to one surface of the base material 2 via the second adhesive layer 7. The wiring 5 has a concavo-convex cross-sectional shape. Further, the first adhesive layer 3, the supporting base material 4, the second adhesive layer 7, and the stress adjusting layer 8 can also have a concavo-convex cross-sectional shape. The wiring 5 has a concavo-convex cross-sectional shape and has a structure that is repeatedly folded in the thickness direction, so that the wiring 5 can be expanded and contracted.
The cross-sectional shape means a cross-sectional shape in the thickness direction.

Further, the adhesive layer that the elastic circuit board has between the base material and the wiring and the functional member is referred to as a first adhesive layer. Further, the adhesive layer that the elastic circuit board has between the base material and the stress adjusting layer is referred to as a second adhesive layer.

FIG. 2 is a process diagram showing an example of the method for manufacturing the elastic circuit board of the present disclosure. First, as shown in FIG. 2A, a wiring base material 10 having a wiring 5 and a functional member 6 on one surface of the support base material 4 is prepared. Next, as shown in FIGS. 2 (b) to 2 (c), the stretchable base material 2 is stretched. This step is also referred to as pre-stretching a stretchable substrate. Next, as shown in FIG. 2D, in a state where the base material 2 is stretched, the support base material 4 side of the wiring base material 10 is placed on one surface of the base material 2 via the first adhesive layer 3. The stress adjusting layer 8 is bonded to the surface of the base material 2 opposite to one surface of the base material 2 via the second adhesive layer 7. Subsequently, as shown in FIG. 2 (e), the tension of the base material 2 is released. At this time, as the elastic base material 2 shrinks, the wiring 5, the support base material 4, the first adhesive layer 3, the stress adjusting layer 8 and the second adhesive layer 7 also shrink, and these members Irregularities such as wavy lines occur. As a result, the stretchable circuit board 1 is obtained.

Here, when the stress adjusting layer is not arranged in the method of manufacturing the stretchable circuit board, the surface on the side of the wiring and the functional member of the stretchable base material and the surface on the opposite side when the tension is released. A shrinkage difference occurs between the two, and as shown in FIG. 3, for example, the obtained elastic circuit board 100 is warped. If the stretchable circuit board is warped, it may be difficult to apply it to an object, or it may be difficult to perform post-processes such as adhesive processing and packaging.
For example, when the wiring of the elastic circuit board and the surface on the functional member side are attached to the object via the adhesive layer, the elastic circuit board 100 is the wiring 5 and the functional member 6 as illustrated in FIG. If it is along the convex side, it is difficult to attach the wiring of the elastic substrate and the surface on the functional member side to the object, and it is easy to peel off from the end portion of the elastic circuit board.
Further, for example, when an adhesive layer is arranged on one surface of an elastic circuit board for attachment to an object, it is difficult to arrange the adhesive layer if the elastic circuit board is warped.

In the present disclosure, since the stretchable circuit board has a stress adjusting layer on the surface opposite to the wiring and the functional member of the stretchable base material, tension is released in the manufacturing process of the stretchable circuit board. It is possible to control the degree of warpage of the stretchable circuit board by adjusting the shrinkage difference between the surface on the side of the wiring and the functional member of the stretchable base material and the surface on the opposite side. When controlling the degree of warpage of the stretchable circuit board, it is also possible to reduce the warp of the stretchable circuit board as compared with the case where the stretchable circuit board does not have a stress adjusting layer. The warp can be increased or the warp direction of the stretchable circuit board can be reversed. For example, the stretchable circuit board 1 shown in FIG. 4 is convexly warped toward the stress adjusting layer 8, and is elastic as compared with the stretchable circuit board 100 having no stress adjusting layer as shown in FIG. The direction of warpage of the circuit board 1 is reversed.
Therefore, it is possible to control the degree of warpage of the stretchable circuit board according to the curved surface or the flat surface of the object, and to facilitate the application of the stretchable circuit board to the object. Further, when one side of the elastic circuit board is attached to the object via the adhesive layer, it can be made difficult to peel off.
In addition, it is possible to suppress warpage of the stretchable circuit board and facilitate post-processes such as adhesive processing and packaging. For example, stretchable circuit boards are expected to be used in wearable devices, especially in the medical and healthcare fields, specifically, human skin and clothing with one side of the stretchable circuit board via an adhesive layer. It may be affixed to. Therefore, an elastic circuit board that suppresses warpage and facilitates post-processes such as adhesive processing is useful.

The stretchable circuit board of the present disclosure has a stretchable base material, wiring, a functional member, and a stress adjusting layer. Hereinafter, each configuration of the elastic circuit board of the present disclosure will be described.

1. 1. Stress adjustment layer The stress adjustment layer may be any as long as it can control the degree of warpage of the stretchable circuit board and can withstand expansion and contraction. Above all, as described above, the surface on the side of the wiring and the functional member of the elastic base material and the surface on the opposite side when the tension is released in the manufacturing process of the elastic circuit board by the stress adjusting layer. It is preferable that the stress adjusting layer has a larger tensile elastic modulus than the elastic substrate because the shrinkage difference of the stretchable circuit board can be adjusted and the degree of warpage of the stretchable circuit board can be controlled.

Further, the material used for the stress adjusting layer may have elasticity or may not have elasticity.

The non-stretchable material used for the stress adjusting layer may be a thin film and may be a material that can withstand stretching and contraction, and examples thereof include resin. Specific examples thereof include polyethylene naphthalate, polyethylene terephthalate, polycarbonate, polyimide and the like. When the stress adjusting layer contains a resin, the material of the stress adjusting layer may be the same as or different from the material of the supporting base material of the wiring base material. When the warp of the stretchable circuit board is suppressed to make it flat, the material of the stress adjusting layer is preferably the same material as the supporting base material of the wiring base material. When the material of the stress adjusting layer does not have elasticity, a resin base material can be used as the stress adjusting layer.

The elasticity of the stretchable material used for the stress adjusting layer can be the same as the stretchability of the stretchable base material described later.
As the stretchable material used for the stress adjusting layer, for example, an elastomer can be mentioned. As the elastomer, general thermoplastic elastomers and thermosetting elastomers can be used, and specifically, styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, amide-based elastomers, silicone rubbers, urethane rubbers, and fluororubbers. , Polybutadiene, polyisobutylene, polystyrene butadiene, polychloroprene and the like.

The stress regulating layer is usually non-adhesive. This is because if the stress adjusting layer has adhesiveness, the post-process becomes difficult. Further, the stretchable circuit board may have an adhesive layer for being attached to an object, and the stress adjusting layer is distinguished from such an adhesive layer.
Here, having no adhesiveness means that the adhesive strength of the stress adjusting layer is 0.01 N / 25 mm or less, preferably 0.005 N / 25 mm or less, and more preferably 0.001 N / 25 mm or less. be.

The adhesive strength of the stress adjusting layer can be measured by the following method. First, a test piece having a width of 25 mm is collected from an elastic circuit board, and a glass plate having a width of 25 mm is attached to the surface of the test piece on the stress adjusting layer side. Next, using a tensile tester, the adhesive force (N / 25 mm) to the glass plate shall be measured under the conditions of tensile speed: 1200 mm / min, peeling angle: 180 °, temperature: 20 ° C., and humidity: 50%. Can be done. If the release layer is arranged on the surface of the elastic circuit board to be measured, the release layer is peeled off before measurement.

The stress adjusting layer may or may not have a concavo-convex cross-sectional shape. When the material of the stress adjusting layer does not have elasticity, the stress adjusting layer 8 usually has a concavo-convex cross-sectional shape as illustrated in FIG. The cross-sectional shape of the concavo-convex shape can be the same as the cross-sectional shape of the concavo-convex shape described in the section of wiring described later.

The thickness of the stress adjusting layer may be a thickness that can withstand expansion and contraction, and is appropriately selected depending on the degree of warpage of the target elastic circuit board, the material of the stress adjusting layer, and the like.
For example, when the material of the stress adjusting layer does not have elasticity, the thickness of the stress adjusting layer can be 1 μm or more. Further, in this case, the thickness of the stress adjusting layer can be 25 μm or less, preferably 10 μm or less, and more preferably 5 μm or less.
When the material of the stress adjusting layer has elasticity, the thickness of the stress adjusting layer can be 1 μm or more, preferably 10 μm or more, and more preferably 20 μm or more. Further, in this case, the thickness of the stress adjusting layer can be 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less.

The degree of warpage of the stretchable circuit board can be adjusted by adjusting the material, thickness, and the like of the stress adjusting layer.
For example, by increasing the thickness of the stress adjusting layer, it is possible to reduce the amount of displacement of the surface of the base material on the stress adjusting layer side due to the stress when the base material is stretched. Further, for example, by using a material having a relatively large tensile elastic modulus for the stress adjusting layer, it is possible to reduce the amount of displacement of the surface of the base material on the stress adjusting layer side due to the stress when the base material is stretched. This makes it possible to suppress the warp of the stretchable circuit board.
Further, for example, by using the same member for the stress adjusting layer and the supporting base material of the wiring base material, it is possible to suppress the warp of the stretchable circuit board.

In the present disclosure, the degree of warpage of the stretchable circuit board can be controlled by the stress adjusting layer, but it is particularly preferable to suppress the warp of the stretchable circuit board.

The stress adjusting layer may be arranged on the surface opposite to one surface of the base material, may be arranged on the entire surface, or may be partially arranged.

The method of arranging the stress adjusting layer on the surface opposite to one surface of the base material is appropriately selected depending on the material and the like. Details will be described in the section of the method for manufacturing the stretchable circuit board described later.

2. 2. Wiring Wiring has a concavo-convex cross-sectional shape. The uneven shape is not particularly limited as long as the wiring can be expanded and contracted, and examples thereof include a wavy shape. Further, the uneven shape may be a regular shape or an irregular shape.

Further, as for the uneven shape, the ridgeline of the convex portion may be, for example, a straight line, a curved line, or a wavy shape in a plan view. Further, in a plan view, the spacing between the ridges of the convex portions may be regular or irregular. 5 (a) to 5 (c) are plan views showing an example of wiring. In FIG. 5A, the convex ridges 21 are linear, and the intervals between the convex ridges 21 are regular. In FIG. 5B, the convex ridges 21 are wavy, and the intervals between the convex ridges 21 are regular. In FIG. 5C, the convex ridges 21 are curved, and the intervals between the convex ridges 21 are irregular. In FIGS. 5A to 5C, the solid line indicates the ridgeline 21 of the convex portion, and the broken line indicates the ridgeline 22 of the concave portion.

In the uneven shape, the spacing between the convex portions may be regular or irregular. The distance between the protrusions can be, for example, 10 μm or more, preferably 50 μm or more, and more preferably 100 μm or more. The distance between the convex portions can be, for example, 1000 μm or less, preferably 750 μm or less, and more preferably 500 μm or less. Since the distance between the protrusions is within the above range, the wiring can be expanded and contracted. The distance between the convex portions is the distance d between adjacent convex portions as shown in FIG.

Further, in the uneven shape, the height difference between the convex portion and the concave portion may be regular or irregular. The height difference between the convex portion and the concave portion can be, for example, 1 μm or more, preferably 50 μm or more, and more preferably 100 μm or more. Further, the height difference between the convex portion and the concave portion can be, for example, 500 μm or less, preferably 400 μm or less, and more preferably 300 μm or less. Since the height difference between the convex portion and the concave portion is within the above range, the wiring can be expanded and contracted. The height difference between the convex portion and the concave portion is the height h from the top of the convex portion to the bottom of the concave portion as shown in FIG.

As the wiring material, it is possible to obtain elastic wiring by a method of manufacturing an elastic circuit board in which an elastic base material is previously stretched, and any material that can withstand expansion and contraction may be used, as long as it is itself. May have elasticity and may not have elasticity.

Examples of the non-stretchable material used for wiring include metals such as gold, silver, copper, aluminum, platinum, and chromium, and alloys containing these metals. When the material of the wiring does not have elasticity, a metal film can be used as the wiring.

The elasticity of the elastic material used for wiring can be the same as the elasticity of the elastic base material described later.
Examples of the stretchable material used for wiring include a conductive composition containing conductive particles and an elastomer. The conductive particles may be any particles that can be used for wiring, and examples thereof include particles of gold, silver, copper, nickel, palladium, platinum, carbon and the like. Of these, silver particles are preferably used. Further, as the elastomer, general thermoplastic elastomers and thermosetting elastomers can be used, for example, styrene-based elastomers, acrylic-based elastomers, olefin-based elastomers, urethane-based elastomers, silicone rubbers, urethane rubbers, fluororubbers, and the like. Examples thereof include nitrile rubber, polybutadiene, and polychloroprene.

Further, the shape of the wiring in a plan view is not particularly limited, but it is particularly preferable that the wiring is linear as illustrated in FIG. 1 (a). This is because the design of the elastic circuit board becomes easy.

The thickness of the wiring may be any thickness that can withstand expansion and contraction, and is appropriately selected depending on the material of the wiring and the like.
For example, when the material of the wiring does not have elasticity, the thickness of the wiring can be 25 nm or more, preferably 50 nm or more, and more preferably 100 nm or more. Further, in this case, the thickness of the wiring can be 10 μm or less, preferably 5 μm or less, and more preferably 1 μm or less.
When the material of the wiring has elasticity, the thickness of the wiring can be 5 μm or more, preferably 10 μm or more, and more preferably 20 μm or more. Further, in this case, the thickness of the wiring can be 60 μm or less, preferably 50 μm or less, and more preferably 40 μm or less.

The wiring forming method is appropriately selected depending on the material and the like. When the wiring material does not have elasticity, for example, a method of forming a metal film on a supporting substrate by a vapor deposition method, a sputtering method, or the like, and then patterning the metal film by a photolithography method can be mentioned. Further, when the material of the wiring has elasticity, for example, a method of printing a conductive composition containing the above-mentioned conductive particles and an elastomer in a pattern on a supporting base material by a general printing method can be mentioned.

3. 3. Functional member The functional member is appropriately selected depending on the application of the stretchable circuit board, and examples thereof include ICs, LEDs, sensors, resistors, capacitors, inductors, piezoelectric elements, batteries, and the like. .. Among them, the sensor is preferably used.

Examples of the sensor include a temperature sensor, a pressure sensor, an optical sensor, a photoelectric sensor, a proximity sensor, a shear force sensor, a magnetic sensor and the like. Above all, the sensor is preferably a biological sensor capable of measuring biological information such as heartbeat, pulse, electrocardiogram, blood pressure, body temperature, blood oxygen concentration, myoelectricity, and brain wave.

The functional member is connected to the wiring. As for the connection structure of the functional member and the wiring, a general one can be applied.
Further, in order to reinforce the functional member and the connecting portion connecting the wiring, the periphery of the functional member can be covered with a resin such as a potting agent. This makes it possible to improve the mechanical reliability of the functional member and the connection portion of the wiring.

The functional member may have a concavo-convex cross-sectional shape as long as it can withstand expansion and contraction. The uneven shape can be the same as the above wiring. For example, when the functional member is a TFT, an OLED, or the like, it can have an uneven cross-sectional shape.

4. Stretchable base material The base material has elasticity. As for the elasticity of the base material, after stretching to 150% (1.5 times the initial length) based on the normal state (non-stretched state), the restoration rate when released from this stretched state is 80% or more. It is preferably present, more preferably 85% or more, and even more preferably 90% or more. The upper limit of the restoration rate is 100%.
The restoration rate can be calculated by preparing a test piece having a width of 25 mm, stretching the test piece by 150% and holding it for 1 hour, releasing the stretch and leaving it for 1 hour to restore it, and then using the following formula. can.
Restoration rate (%) = (length immediately after elongation-length after restoration) ÷ (length immediately after elongation-length before tension) x 100
The length immediately after stretching means the length in a state of being stretched by 150%.

The material of the base material may be any material having elasticity, and examples thereof include elastomers, which are appropriately selected depending on the use of the elastic circuit board and the like. As the elastomer, general thermoplastic elastomers and thermosetting elastomers can be used, and specifically, styrene-based elastomers, olefin-based elastomers, urethane-based elastomers, amide-based elastomers, silicone rubbers, urethane rubbers, and fluororubbers. , Polybutadiene, polyisobutylene, polystyrene butadiene, polychloroprene and the like.

The thickness of the base material is not particularly limited, but is preferably 25 μm or more, more preferably 50 μm or more, for example, from the viewpoint of not hindering the movement of the object to which the stretchable circuit board is applied and from the viewpoint of handleability. It is preferably 100 μm or more, more preferably 2 mm or less, still more preferably 1 mm or less, still more preferably 500 μm or less.

5. Adhesive layer The elastic circuit board of the present disclosure may have an adhesive layer on the surface of the stress adjusting layer opposite to the substrate, or on the surface of the wiring and functional members opposite to the substrate. good. The adhesive layer is provided for attaching the stretchable circuit board to the object.

The adhesive layer 9 may be arranged on the surface of the stress adjusting layer 8 opposite to the base material 2, as shown in FIG. 7, for example, and as shown in FIG. 8, the wiring 5 and the functional member 6 may be arranged. It may be arranged on the surface opposite to the base material 2.

Since the adhesive layer is usually arranged after forming wiring or the like having a concavo-convex cross-sectional shape, it does not have a concavo-convex cross-sectional shape.

The adhesive layer is not particularly limited, and a general adhesive can be used, and is appropriately selected depending on the application of the stretchable circuit board and the like. For example, an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, and the like can be mentioned.

The thickness of the adhesive layer may be any thickness as long as it can be expanded and contracted and the elastic circuit board can be attached to the object, and is appropriately selected depending on the application of the elastic circuit board and the like. The thickness of the adhesive layer can be, for example, in the range of 10 μm or more and 100 μm or less.

Further, the release layer may be arranged on the surface of the adhesive layer opposite to the base material. As the release layer, a general one can be used.

As a method of arranging the adhesive layer, for example, a method of applying an adhesive to the surface of the stress adjusting layer opposite to the base material, or a method of applying an adhesive to the surface of the wiring and the functional member opposite to the base material, or peeling off. An adhesive film having an adhesive layer on one surface of the layer is prepared, and the surface of the adhesive film on the adhesive layer side is used as a surface opposite to the base material of the stress adjusting layer or a base material of wiring and functional members. Can be attached to the opposite surface.

6. Supporting Substrate and First Adhesive Layer The elastic circuit boards of the present disclosure typically have a supporting substrate between the substrate and the wiring and functional members, on one surface of the supporting substrate. It has a wiring substrate with wiring and functional members. Further, the stretchable circuit board of the present disclosure usually has a first adhesive layer between the base material and the supporting base material. That is, the stretchable circuit board has a first adhesive layer and a supporting base material in this order from the base material side between the base material and the supporting base material. The elastic circuit board has a wiring base material having wiring and functional members on one surface of the support base material, and the first adhesive layer is arranged on the support base material side of the wiring base material. The wiring base material can be easily attached to the base material.

The supporting base material may be any material that can withstand expansion and contraction, and examples thereof include a resin base material. Specific examples of the material constituting the resin base material include polyesters such as polyethylene naphthalate and polyethylene terephthalate, polyimides, polyamides, polycarbonates, polyolefins, cycloolefin polymers and the like.

The supporting base material usually has a concavo-convex cross-sectional shape. The uneven shape can be the same as the above wiring.

The thickness of the supporting base material may be any thickness as long as it can be expanded and contracted by having a concavo-convex cross-sectional shape, and can be, for example, 1 μm or more, and can be 10 μm or less.

The first adhesive layer is not particularly limited, and a general adhesive or adhesive used for a circuit board can be used.

The first adhesive layer usually has an uneven cross-sectional shape. The uneven shape can be the same as the above wiring.

The thickness of the first adhesive layer may be any thickness as long as it can be expanded and contracted and the surface of the wiring substrate on the support substrate side can be attached to the substrate, for example, within the range of 10 μm or more and 100 μm or less. be able to.

Further, the first adhesive layer may be a molecular adhesive layer. In addition, "molecular adhesion" means that a compound serving as a molecular adhesive is applied between two adherends, and these two adherends are adhered and bonded by a chemical bond. In the present disclosure, the elastic base material and the supporting base material can be adhered and bonded by a chemical bond with a molecular adhesive.

As the molecular adhesive used for the molecular adhesive layer, a known molecular adhesive can be used, and is appropriately selected depending on the application of the stretchable circuit board and the like. For example, a silane coupling agent, a thiol-based compound, and the like can be mentioned.

The thickness of the molecular adhesive layer is, for example, about several nm.
As a method of arranging the molecular adhesive layer, for example, a method of surface-modifying one surface of the elastic base material and the surface of the support base material opposite to the wiring and the functional member with a molecular adhesive is used. Can be mentioned.

7. Second Adhesive Layer The elastic circuit board of the present disclosure may have a second adhesive layer between the base material and the stress adjusting layer. The second adhesive layer allows the stress adjusting layer to be easily attached to the substrate.

When the material of the stress adjusting layer does not have elasticity, it is preferable that the second adhesive layer is arranged between the base material and the stress adjusting layer. Further, when the material of the stress adjusting layer has elasticity, a second adhesive layer may be arranged between the base material and the stress adjusting layer, and the second adhesive layer is not arranged. You may.

The second adhesive layer usually has an uneven cross-sectional shape. The uneven shape can be the same as the above wiring.

The material and thickness of the second adhesive layer can be the same as those of the first adhesive layer.

Further, the second adhesive layer may be a molecular adhesive layer. In the present disclosure, the base material and the stress adjusting layer can be adhesively bonded by a chemical bond with a molecular adhesive.
The molecular adhesive layer can be the same as that of the first adhesive layer.

8. Elastic circuit board The elastic circuit board may be flat or may have a warp. Further, when the stretchable circuit board has a warp, for example, it may be warped convexly toward the wiring 5 and the functional member 6 as shown in FIG. 9, and may be convexly warped toward the stress adjusting layer 8 side as shown in FIG. It may be warped. Above all, the stretchable circuit board preferably has a small warp, and more preferably flat. This is because the post-process becomes easy.

Specifically, the warp of the stretchable circuit board is observed from a cross section by installing the stretchable circuit board 1 on a flat place in a form in which the end portion of the stretchable circuit board 1 is warped, as illustrated in FIG. It can be evaluated by measuring the amount of warp D of the stretchable circuit board 1 at the time of. As illustrated in FIG. 10, the elastic circuit board 1 is installed on a flat place in a form in which the end portion of the elastic circuit board 1 is warped, and the concave surface of the elastic circuit board 1 is observed from a cross section. Let the maximum depth of be the warp amount D of the stretchable circuit board 1. Further, when the warp of the stretchable circuit board is relatively large, the warp of the stretchable circuit board can be confirmed by observing from the cross section of the stretchable circuit board.

The amount of warpage of the stretchable circuit board is, for example, preferably 10 mm or less, more preferably 5 mm or less, and further preferably 2 mm or less. When the amount of warpage is within the above range, the warpage of the stretchable circuit board can be reduced, and a flat shape can be realized.
Here, the flatness of the stretchable circuit board means that the amount of warpage is 2 mm or less.

9. Manufacturing Method of Stretchable Circuit Board The stretchable circuit board of the present disclosure can be manufactured by a method of pre-stretching a stretchable circuit board. The method for manufacturing the stretchable circuit board of the present disclosure can be divided into two modes depending on the material of the stress adjusting layer. Hereinafter, each aspect will be described.

(1) First Embodiment The first aspect of the method for manufacturing an elastic circuit board of the present disclosure is a case where the material of the stress adjusting layer does not have elasticity. The method for manufacturing the stretchable circuit board of this embodiment includes a stretching step of stretching a stretchable base material, wiring for arranging wiring and functional members on one surface of the base material in a stretched state, and wiring. A functional member placement process, a stress adjustment layer placement process in which a stress adjustment layer is placed on a surface opposite to one surface of the base material in an elongated state, a wiring and functional member placement process, and stress. After the adjusting layer arranging step, it has a tension releasing step of releasing the tension of the base material.

2 (a) to 2 (e) are process diagrams showing an example of a method for manufacturing an elastic circuit board according to this embodiment. Since FIGS. 2 (a) to 2 (e) have already been described, the description thereof will be omitted here.

(A) Stretching Step When stretching the base material, for example, it may be stretched in the uniaxial direction or may be stretched in the biaxial direction.

The base material preferably extends to 120% (1.2 times the initial length) or more, and more preferably 130% (1.3 times the initial length) or more based on the normal state. It is preferable to extend to 150% (1.5 times the initial length) or more. Stretchable wiring can be obtained by stretching the base material within the above range.

Also, the substrate is usually mechanically elongated. The stretching conditions are appropriately selected according to the material and thickness of the base material.

(B) Wiring and Functional Member Placement Process As a method of arranging the wiring and the functional member on one surface of the base material, usually, a wiring base material having the wiring and the functional member on one surface of the support base material is used. A method is used in which the surface of the wiring substrate on the support substrate side is bonded to one surface of the substrate via the first adhesive layer.

The first adhesive layer may be placed on the surface of the wiring base material on the supporting base material side after the base material is stretched, or may be placed on one surface of the base material before the base material is stretched. good. Further, when the first adhesive layer is arranged on one surface of the base material, the first adhesive layer may be arranged on one surface of the base material before the stretching step.

Examples of the method for arranging the first adhesive layer include a method of applying an adhesive or an adhesive, and a method of preparing an adhesive film having an adhesive layer on one surface of the release layer and adhering the adhesive film. Be done.

(C) Stress adjustment layer placement step As a method of arranging the stress adjustment layer on the surface opposite to one surface of the base material, usually, the stress adjustment layer is placed on one side of the base material via the second adhesive layer. A method of bonding to the surface opposite to the surface of is used.

The second adhesive layer may be placed on the surface of the stress adjusting layer after the base material is stretched, or may be placed on one surface of the base material before the base material is stretched. Further, when the second adhesive layer is arranged on one surface of the base material, the second adhesive layer may be arranged on one surface of the base material before the stretching step.

Examples of the method for arranging the second adhesive layer include a method of applying an adhesive or an adhesive, and a method of preparing an adhesive film having an adhesive layer on one surface of the release layer and adhering the adhesive film. Be done.

Any of the wiring and functional member arranging steps and the stress adjusting layer arranging step may be performed first.

(D) Tension release step When the base material is mechanically stretched in the stretching step, the tension is released.

(E) Other Steps In the method of manufacturing the stretchable circuit board of this embodiment, after the tension release step, the surface of the stress adjusting layer is opposite to the substrate of the stress adjusting layer, or the surface of the wiring and the functional member is opposite to the substrate. There may be an adhesive layer arranging step of arranging the adhesive layer on the surface of the surface.

(2) Second Embodiment The second aspect of the method for manufacturing the stretchable circuit board of the present disclosure is a case where the material of the stress adjusting layer has elasticity. The method for manufacturing the stretchable circuit board of this embodiment includes a laminate manufacturing step of manufacturing a laminate having a stress adjusting layer on a surface opposite to one surface of the elastic substrate, and an extension of the laminate. It has a stretching step, a wiring and functional member arranging step of arranging wiring and functional members on one surface of the base material in a stretched state, and a tension releasing step of releasing the tension of the laminated body.

11 (a) to 11 (f) are process diagrams showing an example of the method for manufacturing the stretchable circuit board of this embodiment. First, as shown in FIG. 11A, a wiring base material 10 having a wiring 5 and a functional member 6 on one surface of the support base material 4 is prepared. Next, as shown in FIG. 11B, a laminate having the stress adjusting layer 8 on the surface opposite to one surface of the base material 2 is produced. Next, as shown in FIGS. 11 (c) to 11 (d), the laminate of the base material 2 and the stress adjusting layer 8 is stretched. Next, as shown in FIG. 11 (e), in a state where the laminated body of the base material 2 and the stress adjusting layer 8 is stretched, a wiring group is provided on one surface of the base material 2 via the first adhesive layer 3. The surfaces of the material 10 on the support base material 4 side are bonded together. Subsequently, as shown in FIG. 11 (f), the tension of the laminated body of the base material 2 and the stress adjusting layer 8 is released. At this time, as the base material 2 and the stress adjusting layer 8 shrink, the wiring 5, the supporting base material 4, and the first adhesive layer 3 also shrink, and irregularities such as wavy lines are generated in these members. As a result, the stretchable circuit board 1 is obtained.

(A) Laminate manufacturing step As a method for manufacturing a laminated body having a stress adjusting layer on a surface opposite to one surface of the base material, for example, a method of simultaneously molding a base material and a stress adjusting layer, a base material and Examples thereof include a method of thermally laminating the stress adjusting layer and a method of adhering the stress adjusting layer to the surface opposite to one surface of the base material via the second adhesive layer.

(B) Stretching step The stretching step can be the same as the stretching step of the first aspect.

(C) Wiring and functional member arranging process The wiring and functional member arranging process can be the same as the wiring and functional member arranging process of the first aspect.

(D) Tension release step The tension release step can be the same as the tension release step of the first aspect.

(E) Other Steps In the method of manufacturing the stretchable circuit board of this embodiment, after the tension release step, the surface of the stress adjusting layer is opposite to the substrate of the stress adjusting layer, or the surface of the wiring and the functional member is opposite to the substrate. There may be an adhesive layer arranging step of arranging the adhesive layer on the surface of the surface.

10. Applications Since the stretchable circuit board has elasticity, it can be applied to a curved surface and can follow deformation. Because of these advantages, the stretchable circuit board can be used in, for example, wearable devices, medical devices, robots, and the like. Specific examples thereof include various sensors such as a temperature sensor, a pressure sensor, an optical sensor, a photoelectric sensor, a proximity sensor, a shear force sensor, and a magnetic sensor. Further, the elastic circuit board is useful for a biological sensor that detects biological information such as heartbeat, pulse, electrocardiogram, blood pressure, body temperature, blood oxygen concentration, myoelectricity, and brain wave.
The stretchable circuit board may be used by being attached to human skin, for example, or may be attached to a wearable device or a robot.

The present disclosure is not limited to the above embodiment. The above embodiment is an example, and any object having substantially the same structure as the technical idea described in the claims of the present disclosure and having the same effect and effect is the present invention. Included in the technical scope of the disclosure.

Examples and comparative examples are shown below, and the present disclosure will be described in more detail.

[Example]
1) Formation of a laminated body of elastic base material and adhesive layer A pressure-sensitive adhesive sheet (manufactured by 3M, model number: 8146) is used as the adhesive layer, and two-component addition condensation polydimethylsiloxane (hereinafter referred to as PDMS) is used on the pressure-sensitive adhesive sheet. ) Is applied to a thickness of 700 μm, and an adhesive sheet (manufactured by 3M, model number: 8146) is laminated on the surface of the uncured PDMS to cure the PDMS, and the adhesive layer / elastic base material / adhesive layer is formed. A laminate was prepared.

2) Formation of wiring substrate A polyethylene naphthalate (hereinafter referred to as PEN) film having a thickness of 2.5 μm is used as a support substrate, and Ag paste is screen-printed on the PEN film to form an electrode pair having a width of 500 μm (hereinafter referred to as PEN). Wiring) was formed. Next, an LED chip having a size of 1.0 × 0.5 mm was connected between the electrodes with a conductive adhesive (manufactured by Kaken Tech Co., Ltd., model number: CL-3160). Further, a silicone-based potting agent (manufactured by ThreeBond Co., Ltd., model number: TB1220G) was applied around the LED chip and cured.

3) Preparation of elastic circuit board In a state where the above-mentioned adhesive layer / elastic base material / adhesive layer laminate is stretched by 150% on one axis, the above-mentioned wiring base material is applied to one of the adhesive layer surfaces of the laminate. The supporting substrate surfaces were bonded together. Next, a PEN film having a thickness of 2.5 μm was bonded to the other adhesive layer surface of the laminated body as a stress adjusting layer. Next, when the laminated body of the adhesive layer / elastic base material / adhesive layer was shrunk by releasing the elongation, an uneven shape was formed on the surface in a region other than the region where the LED and the silicone-based potting agent were arranged. It occurred and contracted. As a result, an elastic circuit board having an uneven cross-sectional shape of the wiring, the supporting base material, the adhesive layer and the stress adjusting layer was obtained.
In the obtained stretchable circuit board, the amount of warpage was 2 mm or less in the direction orthogonal to the uniaxial extension direction.

[Comparison example]
1) Formation of a laminated body of elastic base material / adhesive layer An adhesive sheet (manufactured by 3M, model number: 8146) is used as an adhesive layer, and PDMS of two-component addition condensation is applied onto the adhesive sheet so as to have a thickness of 700 μm. And cured to form a laminate of elastic substrate / adhesive layer.

2) Formation of Wiring Base Material The wiring base material was formed in the same manner as in Example 1.

3) Preparation of stretchable circuit board With the stretchable base material / adhesive layer laminated body stretched by 150% on one axis, the support base material surface of the wiring base material is placed on the adhesive layer surface of the laminated body. I pasted them together. Next, when the laminate of the elastic base material / adhesive layer was shrunk by releasing the elongation, an uneven shape was generated on the surface and shrunk in a region other than the region where the LED and the silicone-based potting agent were arranged. did.
The obtained stretchable circuit board had a warp amount of 10 mm or more in a direction orthogonal to the uniaxial extension direction and was curled. It is considered that this is because the shrinkage amount of the elastic base material was different between the surface on which the wiring base material of the laminated body was bonded and the surface on the opposite side.

1 ... Elastic circuit board 2 ... Elastic base material 3 ... First adhesive layer 4 ... Supporting base material 5 ... Wiring 6 ... Functional member 7 ... Second adhesive layer 8 ... Stress adjustment layer 9 ... Adhesive layer 10 ... Wiring base material

Claims (6)

With elastic base material,
Wiring and functional members on one side of the base material,
The wiring has a stress adjusting layer on the surface side opposite to the one surface of the base material, and the wiring has a concavo-convex cross-sectional shape .
The stress adjusting layer is an elastic circuit board containing at least one of a resin and an elastomer . The stretchable circuit board according to claim 1, wherein the stress adjusting layer has a concavo-convex cross-sectional shape. The stretchable circuit board according to claim 1 or 2, wherein the stress adjusting layer does not have adhesiveness. Claims 1 to 3 have an adhesive layer on the surface of the stress adjusting layer opposite to the substrate or the surface of the wiring and the functional member opposite to the substrate. The elastic circuit board according to any one of the claims. The expansion and contraction according to any one of claims 1 to 4, wherein an adhesive layer and a supporting base material are provided between the base material, the wiring, and the functional member in order from the base material side. Sex circuit board. The stretchable circuit board according to any one of claims 1 to 5, which is flat.

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