Resin wiring board and stretchable device

Abstract

This resin wiring board (10) comprises: a metal wiring pattern (21); and a stretchable resin base material (11) disposed so as to cover at least one surface of the metal wiring pattern (21). The stretchable resin base material (11) does not have a gap having a maximum diameter of 0.5 μm or more in the vicinity of an adhesion interface with the metal wiring pattern.

Description

Resin wiring boards and stretchable devices

[0001] This disclosure relates to resin wiring substrates and stretchable devices. This application claims priority under Japanese Patent Application No. 2025-019338, filed in Japan on February 7, 2025, the contents of which are incorporated herein by reference.

[0002] Wearable devices are attracting attention in a wide range of fields, including sports science and healthcare. Wearable devices are preferably designed for comfortable, stress-free wear. Therefore, it is desirable that they be stretchable to accommodate the object they are worn on. In this specification, devices possessing such characteristics are referred to as stretchable devices, not limited to their use as wearable devices.

[0003] Conventionally, rigid and hard plastics such as polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), cellulose triacetate (TAC), and cellulose acetate propionate (CAP) have been known as materials used for printed circuit boards. Printed circuit boards made from these materials do not return to their original shape when bent, and the metal wiring may peel off or break due to stress from the board.

[0004] Patent Document 1 describes an epoxy resin sheet that exhibits recovery after stretching, with a hysteresis loss of 40% or less after maintaining a 50% elongation in tensile mode for 2 seconds, as measured according to JIS K 7312:1996. Patent Document 1 also describes stretchable and flexible members equipped with epoxy resin sheets.

[0005] Patent Document 2 describes a bendable wiring substrate comprising a film made of polyurethane that can be synthesized by reacting a long-chain polyol with a polyisocyanate, wherein the temperature at which the storage modulus becomes 1 MPa by dynamic viscoelastic measurement is 155°C or higher, the storage modulus at 25°C is 20 to 200 MPa, the tensile strength is 20 to 80 MPa, and the elongation at break is 500 to 900%, and circuit wiring formed in contact with the surface of the film.

[0006] Patent Document 3 describes a stretchable conductive substrate comprising a sheet-like stretchable base material and a stretchable conductive pattern formed on one side of the stretchable base material, which is used by folding it.

[0007] Japanese Patent Publication No. 2023-32668, International Publication No. 2020 / 090634, Japanese Patent Publication No. 2017-22173

[0008] For stretchable devices, it is preferable that the stretchable wiring board has no gaps between the wiring pattern and the resin substrate, even after repeated bending, and maintains high adhesion.

[0009] This disclosure has been made in view of the above-mentioned problems, and aims to provide a resin wiring substrate in which there is no or extremely reduced void between the wiring pattern and the resin substrate, and a stretchable device equipped therewith.

[0010] To solve the above problems, the following means are provided.

[0011] One aspect of the present disclosure is a resin wiring substrate comprising a metal wiring pattern and a stretchable resin substrate disposed to cover at least one surface of the metal wiring pattern, wherein the stretchable resin substrate does not have voids with a maximum diameter of 0.5 μm or more near the adhesive interface with the metal wiring pattern.

[0012] Aspect 2 of the present disclosure is a resin wiring substrate according to aspect 1, wherein the thickness of the overlapping portion formed by the overlapping of the metal wiring pattern and the stretchable resin substrate is greater than the thickness of the non-overlapping portion consisting only of the stretchable resin substrate.

[0013] Aspect 3 of this disclosure is a resin wiring board according to aspect 1 or aspect 2, wherein the elongation at break of the resin material constituting the stretchable resin substrate is 200% or more.

[0014] Aspect 4 of the present disclosure is a resin wiring board in any one of aspects 1 to 3, wherein the standard deviation σ of the thickness of the non-overlapping portion is 2.5 or less.

[0015] Embodiment 5 of this disclosure is a stretchable device comprising a resin wiring substrate from any one of Embodiments 1 to 4.

[0016] According to the resin wiring substrate of this disclosure, there is no or extremely reduced void between the wiring pattern and the resin substrate, making it possible to provide a resin wiring substrate with high adhesion.

[0017] This is a schematic cross-sectional view showing an example of a resin wiring substrate of the present disclosure. This is a schematic cross-sectional view showing another example of a resin wiring substrate of the present disclosure. This is an electron microscope (SEM) image of a cross-section of a resin wiring substrate. This is a schematic plan view showing an example of a stretchable device of the present disclosure. This is a cross-sectional view of the stretchable device shown in Figure 2A, cut along the line B-B'. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. This is a schematic cross-sectional view showing the steps of a method for manufacturing a resin wiring substrate. These are the infrared absorption (IR) spectra of resin substrate 8 and resin substrate 18.

[0018] The resin wiring board and stretchable device of this embodiment will be described in detail below, with appropriate reference to the drawings. The drawings used in the following description may be enlarged for convenience to clearly illustrate the features of this disclosure. Therefore, the dimensional ratios of each component may differ from those of the actual components. The materials, dimensions, etc., exemplified in the following description are examples only, and this disclosure is not limited to them. It is possible to modify and implement these examples as appropriate without altering the essence of the invention.

[0019] [Resin Wiring Substrate] Figure 1A is a schematic cross-sectional view showing an example of a resin wiring substrate of this embodiment. The resin wiring substrate 10 shown in Figure 1A has a metal wiring pattern 21 and a stretchable resin substrate 11 that is arranged to cover one surface 21a of the metal wiring pattern 21, and the stretchable resin substrate 11 does not have a void with a maximum diameter of 0.5 μm or more near the adhesive interface 11ac with the metal wiring pattern 21.

[0020] In a method for manufacturing a resin wiring substrate, if the process includes forming a metal wiring pattern on a stretchable resin substrate by plating, the stretchable resin substrate usually undergoes the plating and photolithography processes. In this case, there is a risk that the stretchable resin substrate may be damaged by the plating and photolithography processes. The inventors have found that the above damage can be avoided by forming a metal wiring pattern on a separate film, covering the metal wiring pattern with a stretchable resin, and then peeling off the stretchable resin substrate on which the metal wiring pattern is embedded to manufacture a resin wiring substrate (hereinafter, this method may be referred to as the "plating transfer method"). Furthermore, in this plating transfer method, the inventors have found that if a spray coating method is used to cover the metal wiring pattern with the stretchable resin, voids are less likely to form near the adhesive interface between the stretchable resin substrate and the metal wiring pattern. If there are no voids near the adhesive interface between the stretchable resin substrate and the metal wiring pattern, or if only minute voids (here, meaning voids with a maximum diameter of less than 0.5 μm) exist, the adhesion between the stretchable resin substrate and the metal wiring pattern is improved.

[0021] In the spray coating method, a mist (a mixture of resin and solvent) of the resin solution is sprayed onto the substrate from above using a spray nozzle that moves at a constant speed and interval. This method allows for uniform resin application and the formation of a resin layer with minimal thickness variation. In the spray coating method, the resin layer is thickened by spraying multiple times, with each spray applying a thickness of several micrometers or sub-micrometers. Typically, one or more drying steps are performed to partially dry the resin layer while forming the desired thickness. The resin layer can be formed by drying and solidification without a curing reaction. Alternatively, the resin layer may be formed by a curing reaction.

[0022] In this specification, "near the adhesive interface" means the area from the adhesive surface 21a of the metal wiring pattern to 5 μm. In Figures 1A and 1B, the adhesive interface is indicated only on the upper surface of the metal wiring pattern 21, but it also includes the side surfaces of the metal wiring pattern 21.

[0023] Figure 2 shows an electron microscope (SEM) image of a cross-section of a resin wiring board fabricated using a spray coating method. In this sample, the thickness of the copper wiring pattern was 25.0 μm, and the thickness of the stretchable resin substrate was 74.0 μm. The resin of the stretchable resin substrate was urethane resin. The line width of the copper wiring pattern was 400 μm.

[0024] In the SEM image shown in Figure 2, the overlapping portion S is formed when the metal wiring pattern 21 and the stretchable resin substrate 11 overlap. １ (See Figure 1A) The thickness (the sum of the thickness of the metal wiring pattern 21 and the thickness of the stretchable resin substrate 11) of the non-overlapping portion S consisting only of the stretchable resin substrate 11 is ２ It can be seen that it is thicker than the thickness shown in Figure 1A.

[0025] Furthermore, in the SEM image shown in Figure 2, the superimposed area S １ The thickness of the stretchable resin substrate in the non-overlapping portion S is ２It can be seen that the thickness is about the same as that of the metal wiring pattern. Thus, by forming an elastic resin layer (substrate) using the spray coating method, it is possible to form a thick elastic resin layer (substrate) on the metal wiring pattern. This is because it can be grown little by little in thicknesses of a few micrometers or even sub-micrometers. In contrast, with conventional methods such as the casting method, the resin layer on the metal wiring pattern is leveled, making it difficult to form a thick layer. By using the spray coating method, the thickness of the resin layer on the metal wiring pattern can be formed to be about the same as the thickness of the resin layer in areas without a metal wiring pattern (see Figure 2). A thicker elastic resin layer (substrate) on the metal wiring pattern has the effect of being less likely to peel off.

[0026] Furthermore, in the SEM image shown in Figure 2, the non-overlapping area S ２ (See Figure 1A) The thickness was 74.0 μm, and the standard deviation of thickness (variation in thickness measurements) σ was 1.9. In this case, "standard deviation (variation in thickness measurements) σ" refers to the standard deviation of thickness calculated using nine thickness measurements taken at arbitrary 1 mm intervals in a cross-sectional SEM image obtained at any point in the non-overlapping area. It is more preferable that the standard deviation of thickness σ in the non-overlapping area is 2.0 or less. Also, a smaller standard deviation of thickness σ in the non-overlapping area is preferable, but the lower limit can be set to 1.0, 1.3, or 1.5. Thus, by forming an expandable resin layer (substrate) using the spray coating method, it is possible to grow it little by little in thicknesses of a few μm or sub-μm, thus suppressing variations in thickness. In contrast, with conventional methods such as the casting method, it is difficult to suppress variations in thickness because the material is hardened all at once by a curing reaction.

[0027] Furthermore, the SEM image shown in Figure 2 reveals that the stretchable resin substrate does not have voids near the adhesive interface with the metal wiring pattern (see reference numeral 11ac in Figures 1A and 1B). In the spray coating method, a mist (fine mist of resin solution) of a resin solution mixed with a solvent is sprayed onto the substrate little by little to build up the resin layer. As the solvent is sprayed onto the substrate while it is being evaporated, voids are less likely to form. In contrast, in conventional methods such as the casting method, the resin solution has high viscosity, so voids are easily formed when the solvent tries to evaporate during drying, and the viscosity of the resin solution makes it difficult for the formed voids to escape.

[0028] In contrast, when a stretchable resin layer (substrate) was formed using screen printing, although this varied depending on the solvent selected, voids of 0.6 μm or more existed near the adhesive interface with the metal wiring pattern in the stretchable resin layer. Furthermore, with the dip method (immersion in resin solution and drying), although this varied depending on the solvent and drying method, voids of 1.5 μm or more existed near the adhesive interface with the metal wiring pattern in the stretchable resin layer.

[0029] In fact, cross-sectional SEM images were obtained for samples made from the same material and size as the sample shown in Figure 2, but using screen printing and dipping methods (immersing in resin solution and drying) instead of spray coating, for which only the stretchable resin layer (substrate) was prepared. The standard deviation of thickness in the non-overlapping areas and the number of voids of 0.5 μm or more near the interface (per 400 μm length (corresponding to the line width of the copper wiring pattern in the above sample)) were measured. As described above, when the stretchable resin layer (substrate) was formed using the spray coating method, the standard deviation of thickness was 1.9, and the number of voids of 0.5 μm or more near the interface was 0 / 400 μm. In contrast, for the sample in which the stretchable resin layer (substrate) was formed using screen printing, the standard deviation of thickness was 2.7, and the number of voids of 0.5 μm or more near the interface was 12 / 400 μm. Furthermore, in samples in which a stretchable resin layer (substrate) was formed using the dip method, the standard deviation of the thickness was 3.9, and the number of voids of 0.5 μm or more near the interface was 38 per 400 μm.

[0030] As shown in FIG. 1B, the resin wiring substrate 10A may be configured to include a stretchable resin layer 31 disposed so as to cover one surface 21b of the metal wiring pattern 21, in addition to the stretchable resin base material 11 disposed so as to cover one surface 21a of the metal wiring pattern 21.

[0031] FIGS. 3A and 3B show an example of a stretchable device including the resin wiring substrate of the present disclosure. FIG. 3A is a plan schematic view, and FIG. 3B is a cross-sectional schematic view taken along the line B-B' shown in FIG. 3A. Note that FIG. 1B corresponds to a cross-sectional schematic view taken along the line A-A' shown in FIG. 3A.

[0032] The stretchable device 100 of the present embodiment shown in FIGS. 3A and 3B includes a resin wiring substrate 10A (see FIG. 1B) having stretchability. The resin wiring substrate 10A includes a stretchable resin base material 11 having stretchability, a metal wiring pattern 21 formed on the stretchable resin base material 11, and a stretchable resin layer 31 having stretchability disposed so as to sandwich the metal wiring pattern 21. As shown in FIGS. 3A and 3B, two electronic components 41 are disposed on a surface 11Aa of the stretchable resin base material 11 disposed substantially at the center in the length direction of the resin wiring substrate 10.

[0033] (Stretchable Resin Base Material) The stretchable resin base material ********** 11 preferably has an elongation at break of 200% or more. The stretchable resin base material 11 is in a sheet form, and the Young's modulus is 30 N / mm ２ or less. The Young's modulus of the stretchable resin base material 11 is preferably 20 N / mm ２ or less, and more preferably 10 N / mm ２ or less. This is because it becomes a resin wiring substrate 1 that can form a stretchable device having a more comfortable wearing property. The Young's modulus of the stretchable resin base material 11 is preferably 0.2 N / mm ２ or more, and more preferably 0.4 N / mm ２ or more. This is because it easily becomes a resin wiring substrate 1 having good stretch durability in which the stretchability is less likely to deteriorate even when repeatedly stretched and contracted.

[0034] The stretchable resin substrate 11 comprises a resin component made of a base material resin and a filler as needed. It is preferable that the stretchable resin substrate 11 contains a filler. The Young's modulus is 30 N / mm². ２ The stretchable resin substrate 11 described below tends to lose its elasticity when repeatedly stretched and contracted. However, if the stretchable resin substrate 11 contains a filler, it tends to have good stretch durability, meaning that its elasticity does not deteriorate easily even when repeatedly stretched and contracted.

[0035] "Resin for base material" Examples of resin components for the base material contained in the stretchable resin base material 11 include epoxy resins, urethane resins, urea resins, polyurethane urea resins, (meth)acrylic acid resins, polyacrylic resins, silicone resins, diene resins, polyester resins, polyether resins, polyamide resins, and polystyrene resins.

[0036] In this specification, "(meth)acrylic acid" is a concept that encompasses both "acrylic acid" and "methacrylic acid." Similarly, "(meth)acrylate" is a concept that encompasses both "acrylate" and "methacrylate." The same applies to terms similar to (meth)acrylate; for example, "(meth)acryloyl group" is a concept that encompasses both "acryloyl group" and "methacryloyl group."

[0037] The resin for the base material preferably has one or more structural units selected from the following as monomer-derived structural units: structural units derived from compounds having urethane bonds and polymerizable unsaturated bonds (hereinafter sometimes referred to as "urethane-derived structural units"), structural units derived from compounds having a fluorene skeleton (hereinafter sometimes referred to as "fluorene-derived structural units"), structural units derived from compounds having siloxane bonds and polymerizable unsaturated bonds (hereinafter sometimes referred to as "siloxane-derived structural units"), structural units derived from alkyl (meth)acrylate esters (hereinafter sometimes referred to as "(meth)acrylic acid-derived structural units"), and structural units derived from reversible addition-fragmentation chain transfer agents (hereinafter sometimes abbreviated as "RAFT agents" in this specification) (hereinafter sometimes referred to as "RAFT agent-derived structural units").

[0038] The resin for the base material preferably contains, as monomer-derived structural units, one or both of urethane-derived structural units and fluorene-derived structural units, one or both of siloxane-derived structural units and (meth)acrylic acid-derived structural units, and RAFT agent-derived structural units. The reason for this is that the Young's modulus is 30 N / mm². ２ The following is true, and it is easy to obtain a stretchable resin substrate 11 with good stretch durability that does not deteriorate easily even when repeatedly stretched and contracted.

[0039] The proportions of urethane-derived structural units, fluorene-derived structural units, siloxane-derived structural units, (meth)acrylic acid-derived structural units, and RAFT agent-derived structural units among the monomer-derived structural units of the base resin are not particularly limited and can be appropriately determined according to the application of the stretchable resin base material 11 and the required strength, elongation at break, stretch durability, and other properties.

[0040] The more urethane bonds there are in the base resin, the lower the Young's modulus and the easier it is to obtain a resin wiring board 1 with excellent flexibility. For this reason, it is preferable that the base resin contains urethane-derived structural units. When the base resin contains urethane-derived structural units as structural units derived from monomers, the proportion of urethane-derived structural units among the monomer-derived structural units in the base resin is preferably 1% to 80% by mass, and more preferably 5% to 50% by mass. This is because if the proportion of urethane-derived structural units is 1% by mass or more, the effects of including urethane-derived structural units can be fully obtained. Furthermore, if the proportion of urethane-derived structural units is 80% by mass or less, it is possible to sufficiently include structural units other than urethane-derived structural units, making it easier to obtain a stretchable resin base material 11 with good stretch durability that does not deteriorate easily even when repeatedly stretched and contracted.

[0041] The greater the number of fluorene-derived structural units in the base resin, the more likely it is to result in a stretchable resin base material 11 with excellent flexibility and good durability. When the base resin contains fluorene-derived structural units as monomer-derived structural units, the proportion of fluorene-derived structural units among the monomer-derived structural units in the base resin is preferably 30% to 99% by mass, and more preferably 35% to 90% by mass. This is because if the proportion of fluorene-derived structural units is 30% by mass or more, the effects of including fluorene-derived structural units can be fully obtained. Furthermore, if the proportion of fluorene-derived structural units is 99% by mass or less, it is possible to sufficiently include structural units other than fluorene-derived structural units, making it easier to obtain a stretchable resin base material 11 with a lower Young's modulus.

[0042] When the base resin has siloxane-derived structural units, the stretchable resin base material 11 will have appropriate water repellency. As a result, the stretchable resin base material 11 will have excellent durability with suppressed deterioration over time caused by moisture. Furthermore, when the base resin has siloxane-derived structural units, the stretchable resin base material 11 will have good tackiness (adhesion), and the stretchable resin base material 11 and the stretchable resin layer 31 will be less prone to delamination (interlayer separation) in the resin wiring board 10.

[0043] When the resin for the base material contains siloxane-derived structural units as structural units derived from monomers, the ratio of siloxane-derived structural units to 100 parts by mass of the first oligomer, which is obtained by polymerizing one or more monomers selected from urethane-derived structural units, fluorene-derived structural units, and (meth)acrylic acid-derived structural units by a known method, is preferably 0.5 to 10 parts by mass, and more preferably 1 to 5 parts by mass. When the ratio of siloxane-derived structural units is 0.5 parts by mass or more, the effects of including siloxane-derived structural units can be fully obtained. Furthermore, when the ratio of siloxane-derived structural units is 10 parts by mass or less, structural units other than siloxane-derived structural units can be sufficiently included, making it easier to obtain an expandable resin base material 11 with properties appropriate to the application.

[0044] When the base resin contains both urethane-derived structural units and siloxane-derived structural units, it is preferable because the urethane bonds in the stretchable resin base material 11 are less susceptible to hydrolysis, resulting in a stretchable resin base material 11 with suppressed deterioration over time due to hydrolysis. When the base resin contains both urethane-derived structural units and siloxane-derived structural units, the greater the number of siloxane bonds in the stretchable resin base material 11, the less susceptible the urethane bonds in the stretchable resin base material 11 are to hydrolysis, resulting in a resin wiring board 10 with excellent durability. When the base resin contains both urethane-derived structural units and siloxane-derived structural units, the ratio of the number of urethane bonds to the number of siloxane bonds in the base resin is not particularly limited and can be appropriately determined according to the application of the resin wiring board 10, the required stretch durability, and the characteristics such as elongation at break.

[0045] When the base resin contains (meth)acrylic acid-derived structural units, the greater the number of (meth)acrylic acid-derived structural units, the higher the Young's modulus and the more durable the stretchable resin base material 11 becomes, with good stretchability that does not deteriorate easily even after repeated stretching. When the base resin contains (meth)acrylic acid-derived structural units as structural units derived from monomers, the proportion of (meth)acrylic acid-derived structural units among the monomer-derived structural units in the base resin is preferably 21% to 44% by mass. This is because if the proportion of (meth)acrylic acid-derived structural units is 21% by mass or more, the effect of improving stretchability due to the inclusion of (meth)acrylic acid-derived structural units is sufficiently obtained. Furthermore, if the proportion of (meth)acrylic acid-derived structural units is 44% or less, the Young's modulus becomes 30 N / mm² due to the inclusion of structural units other than (meth)acrylic acid-derived structural units. ２ This is because the following stretchable resin base material 11 is easily obtained.

[0046] When the base resin contains structural units derived from the RAFT agent, variations in the degree of polymerization and crosslinking state are suppressed, resulting in a base resin that is easily dispersed or dissolved in a solvent. When the base resin contains structural units derived from the RAFT agent as monomer-derived structural units, it is preferable that the amount is 0.2 to 5 parts by mass per 100 parts by mass of the total monomers contained in the base resin. This is because if the amount of RAFT agent-derived structural units is 0.2 parts by mass or more per 100 parts by mass of the total monomers contained in the base resin, the effects of containing RAFT agent-derived structural units can be fully obtained. Furthermore, if the amount of RAFT agent-derived structural units is 5 parts by mass or less per 100 parts by mass of the total monomers contained in the base resin, it is possible to sufficiently contain structural units other than RAFT agent-derived structural units, making it easier to obtain an expandable resin base material 11 with properties appropriate to the application.

[0047] The base resin can be produced, for example, by the method shown below. First, one or more monomers selected from a compound having urethane bonds and polymerizable unsaturated bonds, a compound having a fluorene skeleton, and alkyl (meth)acrylate esters are polymerized by a known method to produce a first oligomer. Next, a compound having siloxane bonds and polymerizable unsaturated bonds is polymerized by a known method to produce a second oligomer. Subsequently, the first oligomer, the second oligomer, a polymerization initiator, and a RAFT agent are used to produce a base resin by reversible addition-fraction chain transfer polymerization (RAFT polymerization) under known conditions. This production method is preferable because it makes it easy to obtain a base resin having a skeleton made of a polymer of the first oligomer and short-chain branching containing structural units derived from a compound having siloxane bonds and polymerizable unsaturated bonds.

[0048] The resin for the base material may be produced by a method of reversible addition-fraction chain transfer polymerization (RAFT polymerization) under known conditions using a compound having urethane bonds and polymerizable unsaturated bonds, a compound having a fluorene skeleton, an alkyl (meth)acrylate ester, a compound having siloxane bonds and polymerizable unsaturated bonds, a polymerization initiator, and a RAFT agent.

[0049] Examples of compounds having urethane bonds and polymerizable unsaturated bonds that can be used as monomers when manufacturing resins for base materials include known compounds (urethane (meth)acrylates) that have urethane bonds and a (meth)acryloyl group as a polymerizable unsaturated bond group. Only one type of compound having urethane bonds and polymerizable unsaturated bonds may be used, or two or more types may be used.

[0050] The compound having a urethane bond and a polymerizable unsaturated bond used in the manufacture of the resin for the base material may be an oligomer having a urethane bond and a polymerizable unsaturated bond. Specific examples of oligomers having a urethane bond and a polymerizable unsaturated bond include acrylic urethane, polyether urethane, carbonate urethane, polyester urethane, and aromatic urethane. As the oligomer having a urethane bond and a polymerizable unsaturated bond, it is preferable to use acrylic urethane because it results in a highly flexible and stretchable resin base material 11. It is even more preferable to use an oligomer having a structural unit having a urethane bond and a (meth)acryloyl group, and a structural unit having a urethane bond and not having a (meth)acryloyl group. In particular, it is preferable to use the compound represented by the following formula (1).

[0051]

[0052] As an oligomer having urethane bonds and polymerizable unsaturated bonds, it is also preferable to use an acrylic urethane represented by the following formula (12) because it results in a highly flexible and stretchable resin substrate 11.

[0053] (n in equation (12)) １ R indicates the degree of polymerization, ranging from 1 to 40. １１ R is a methylene chain having 1 to 10 carbon atoms, which may be substituted with alkyl groups having 1 to 4 carbon atoms. １２ (This is a divalent group derived from polyols.)

[0054] In equation (12), n １ R indicates the degree of polymerization, which is 1 to 40, and preferably 10 to 20. In formula (12), R １１ R is a methylene chain having 1 to 10 carbon atoms, and may be substituted with an alkyl group having 1 to 4 carbon atoms. １１ It is preferable that the R is a methylene chain having 1 to 8 carbon atoms, which may be substituted with an alkyl group having 1 to 3 carbon atoms. １１ Specifically, for example, -(CH ２ ) ２ -, - (CH ２ ​) ３ -, - (CH ２ ) ４ -, - (CH ２ ) ６ -ien-CH ２ CH (CH ２ CH ３ )-(CH ２ ) ４ - are some examples. Multiple R's included in equation (12) １１ They may all be different, or some or all of them may be the same, but it is preferable that they all be the same because it is easier to manufacture. In formula (12), R １２ Examples of divalent groups derived from polyols represented by include -(CH ２ )-,-(CH ２ ) ２ -, - (CH ２ ) ３ -, - (CH ２ ) ４ -ien-CH ２ CH (CH ３ )CH ２ -ien-CH ２ CH (CH ２ CH ３ )-(CH ２ ) ４ - are some examples. R １２ R １１ It may be the same as, or it may be different.

[0055] An oligomer having a urethane bond and a polymerizable unsaturated bond is an acrylic urethane represented by formula (12) with acryloyl groups (CH ２ =CH ２ Of the C(=O)- groups, one or both are methacryloyl groups (CH ２ =CH(CH ２ It is also preferable to use one that is C(=O)-).

[0056] When using acrylic urethane as the oligomer having urethane bonds and polymerizable unsaturated bonds, it is preferable to use one with a weight-average molecular weight (Mw) of 5,000 to 180,000, and more preferably one with a weight-average molecular weight (Mw) of 5,000 to 150,000. Furthermore, when using acrylic urethane as the oligomer having urethane bonds and polymerizable unsaturated bonds, it is preferable to use one with a number-average molecular weight (Mn) of 3,000 to 150,000, and more preferably one with a number-average molecular weight (Mn) of 3,000 to 120,000, because it can be easily manufactured. This is because a weight-average molecular weight (Mw) of 5,000 or more and / or a number-average molecular weight (Mn) of 3,000 or more makes it easier to obtain a more flexible and stretchable resin base material 11. In addition, if the weight-average molecular weight (Mw) is 180,000 or less and / or the number-average molecular weight (Mn) is 150,000 or less, it is possible to prevent the resin component from gelling during polymerization for manufacturing the base material resin.

[0057] As oligomers having urethane bonds and polymerizable unsaturated bonds, for example, a polyether-based urethane represented by the following formula (13) and / or a polyester-based urethane represented by the following formula (14) may be used.

[0058] (n in equation (13)) ２ indicates the degree of polymerization, ranging from 1 to 50. m indicates the degree of polymerization, ranging from 5 to 20. R １３ R is a divalent organic group having 1 to 10 carbon atoms and possessing polymerizable unsaturated bonds. １４ and R １５ R is a monovalent terminal group, and may be the same or different.) (R in formula (14) １６ and R １７ R is a monovalent terminal group, and may be the same or different. １８ It is a divalent organic group having 1 to 10 carbon atoms and possessing polymerizable unsaturated bonds. １９ These are divalent organic groups having 1 to 10 carbon atoms and possessing polymerizable unsaturated bonds; they may be the same or different.

[0059] In equation (13), n ２ represents the degree of polymerization, which is 1 to 50, and preferably 10 to 40. In formula (13), m represents the degree of polymerization, which is 5 to 20, and preferably 10 to 20.

[0060] In equation (13), R １３ R is a divalent organic group having 1 to 10 carbon atoms and possessing polymerizable unsaturated bonds. １３ The group having a polymerizable unsaturated bond preferably has a group containing an ethylenically unsaturated bond, such as an acryloyl group (CH ２ =CH ２ C(=O)-) and / or methacryloyl group (CH ２ =CH(CH ２ It is preferable that it is a divalent organic group having 1 to 10 carbon atoms and containing )C(=O)-). １３ The structure, along with the acryloyl group and / or methacryloyl group, is derived from an epoxy group, and one or more methylene groups (-CH ２ It is preferable that the structure or group includes one of the following: a methylene chain having -), a carbonyl group (>C=O), or a carbonate group (-O-(C=O)-O-).

[0061] In equation (13), R １４ and R １５ R is a monovalent terminal group, and may be the same or different. １４ and R １５ Each of these is preferably a terminal group selected from the group consisting of a hydrogen atom, a hydroxyl group, a carboxyl group, an aldehyde group, and an amide group. １４ It is preferable that R is -OH or -COOH. １５ R １３ R １５ If the structure connected to is not a methylene group, -CH ２ OH or -CH ２ It is preferable that it be COOH.

[0062] In equation (14), R １６ and R １７is a monovalent terminal group, which may be the same or different from each other. R １６ and R １７ are each preferably any terminal group selected from the group consisting of a hydrogen atom, a hydroxyl group, a carboxyl group, an aldehyde group, and an amide group. R １６ and R １７ are each preferably any one selected from -OH, -COOH, -CH ２ OH, -CH ２ COOH, -C(=O)CH ３ .

[0063] In formula (14), R １８ is a divalent organic group having 1 to 10 carbon atoms and having a polymerizable unsaturated bond. R １８ is preferably a group having an ethylenically unsaturated bond as a group having a polymerizable unsaturated bond, and an acryloyl group (CH ２ =CH ２ C(=O)-) and / or a methacryloyl group (CH ２ =CH(CH ２ ))C(=O)-), and is preferably a divalent organic group having 1 to 10 carbon atoms. R １８ is preferably a structure derived from an epoxy group, a methylene chain having one or more methylene groups (-CH ２ -), a carbonyl group (>C=O), or a carbonate group (-O-(C=O)-O-) together with an acryloyl group and / or a methacryloyl group.

[0064] The oligomer having a urethane bond and a polymerizable unsaturated bond may be any of a random copolymer, a block copolymer, and an alternating copolymer, and since it can be easily produced, it is preferably a random copolymer.

[0065] Compounds having a fluorene skeleton (9,9-bisphenylfluorene skeleton) used as monomers when manufacturing base resins can include fluorene compounds that have a fluorene skeleton and reactive groups such as hydroxyl groups and amino groups. Specific examples of compounds having a fluorene skeleton include bisphenol fluorene (BPF), biscresol fluorene (BCF), bisaminophenyl fluorene (BAFL), and bisphenoxyethanol fluorene (BPEF). Only one type of compound having a fluorene skeleton may be used, or two or more types may be used.

[0066] Examples of alkyl (meth)acrylate esters used as monomers when manufacturing resins for base materials include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, and decyl (meth)acrylate. Only one type of alkyl (meth)acrylate ester may be used, or two or more types may be used. Since alkyl meth)acrylate has good dispersibility with compounds having urethane bonds and polymerizable unsaturated bonds used as monomers in the production of resins for base materials, methyl (meth)acrylate is preferred.

[0067] Examples of compounds having siloxane bonds and polymerizable unsaturated bonds that can be used as monomers when manufacturing resins for base materials include various known silicone resins having a (meth)acryloyl group as the group having a polymerizable unsaturated bond. Only one type of compound having siloxane bonds and polymerizable unsaturated bonds may be used, or two or more types may be used.

[0068] Compounds having siloxane bonds and polymerizable unsaturated bonds may be oligomers obtained by polymerizing compounds having siloxane bonds and polymerizable unsaturated bonds. Examples of such oligomers include those having structural units derived from modified polydialkylsiloxanes in which (meth)acryloyl groups are bonded to one or both ends of a polydialkylsiloxane such as polydimethylsiloxane. Preferably, the above oligomer has structural units derived from modified polydialkylsiloxanes in which a (meth)acryloyl group is bonded to one end of a polydialkylsiloxane. This is because it is possible to produce an expandable resin substrate 11 made of a substrate resin having short-chain branching containing siloxane-derived structural units, and the effects of containing siloxane-derived structural units are fully obtained. As an oligomer obtained by polymerizing a compound having a siloxane bond and a polymerizable unsaturated bond, it is particularly preferable to use the compound represented by the following formula (2) (Sylabrene® FM-0721; trade name, manufactured by JNC Corporation) which has structural units derived from modified polydimethylsiloxane.

[0069] (In formula (2), n represents the degree of polymerization and ranges from 10 to 150. Me is -CH ３ Therefore, n-Bu is -CH ２ CH ２ CH ２ CH ３ (That is the case.)

[0070] As the RAFT agent, it is preferable to use one or more groups represented by the following general formulas (11), (21), or (31).

[0071] (In formula (11), Z １ Z is an alkyl group, and one or more hydrogen atoms in the alkyl group may be substituted with a cyano group, a carboxyl group, a methoxycarbonyl group, or an aryl group, and the two or more substituents may be the same or different from each other. In formula (21), Z ２ is an alkyl group, Z ３ R is an aryl group. In formula (31), R ４is a hydrogen atom or a halogen atom. The asterisk (*) in formulas (11), (21), or (31) indicates the bond that the group represented by formula (11), (21), or (31) forms with its host.

[0072] When manufacturing resins for base materials, one or more known polymerization initiators can be used, such as persulfates, hydrogen peroxide, azo compounds, and organic peroxides. It is preferable to use an azo compound such as dimethyl-2,2'-azobis(2-methylpropionate).

[0073] In the above method for producing the base resin, the first oligomer and the second oligomer are polymerized using a RAFT agent, so that a cross-linked structure is formed during polymerization, thereby preventing the resin component from gelling. Furthermore, in the above method, since the first oligomer and the second oligomer are polymerized using RAFT, a base resin with the desired degree of polymerization and cross-linked state can be easily produced.

[0074] Furthermore, if the base resin does not have siloxane-derived structural units, the base resin can be produced, for example, by the method shown below. That is, it can be produced by reversible addition-fraction chain transfer polymerization (RAFT polymerization) under known conditions using a polymerization initiator and a RAFT agent, with one or more monomers selected from compounds having urethane bonds and polymerizable unsaturated bonds, compounds having a fluorene skeleton, and alkyl (meth)acrylate esters. In this case, since one or more monomers are polymerized using a RAFT agent, the formation of a crosslinked structure during polymerization can prevent the resin components from gelling. In addition, in the above production method, since one or more monomers are polymerized using a RAFT agent, a base resin with the desired degree of polymerization and crosslinked state can be easily produced.

[0075] "Filler" Fillers that may be included in the stretchable resin substrate 11 as needed include, for example, carbon black, silica, calcium carbonate, talc, clay, etc. Only one type of filler may be used, or two or more types may be used. The type and shape of the filler, such as particle size, are not particularly limited and can be appropriately determined according to the application of the stretchable resin substrate 11 and the required strength, elongation at break, stretch durability, and other characteristics.

[0076] When the stretchable resin base material 11 contains a filler, the filler content in the stretchable resin base material 11 is preferably 5 to 30 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the base material resin. If the filler content in the stretchable resin base material 11 is 5 parts by mass or more per 100 parts by mass of the base material resin, the effect of improving stretchability due to the inclusion of the filler can be sufficiently obtained. Furthermore, if the filler content in the stretchable resin base material 11 is 30 parts by mass or less per 100 parts by mass of the base material resin, it is possible to prevent the filler content from being too high and impairing the flexibility of the stretchable resin base material 11.

[0077] The stretchable resin substrate 11 is preferably obtained by solidifying a resin composition containing a base resin, a filler as needed, and a solvent. The solvent contained in the resin composition can be any solvent that can disperse or dissolve the base resin. Specifically, as the solvent, you can use N,N-dimethylacetamide (DMAc), methyl ethyl ketone (MEK), N,N-dimethylformamide (DMF), diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, butyl carbitol (BC), butyl carbitol acetate (BCA), ethyl cyanoacrylate (ECA), α-terpineol, acetone, ethanol, methanol, ethyl lactate, butyl lactate, toluene, isopropyl alcohol, isobutyl alcohol, ethyl acetate, butyl acetate, etc. As the solvent, you may use only one of the above solvents or two or more. As a solvent, methyl ethyl ketone (MEK) and / or butyl carbitol acetate (BCA) are preferred because they facilitate the dispersion or dissolution of the base resin.

[0078] The stretchable resin substrate 11 preferably has a breaking elongation of 50% or more, and more preferably 100% or more. When the stretchable resin substrate 11 has a breaking elongation of 50% or more, it becomes a resin wiring board 10 that can be suitably used in various stretchable devices such as wearable devices. The breaking elongation of the stretchable resin substrate 11 can be changed by appropriately selecting the material and amount used for the stretchable resin substrate 11. Furthermore, the breaking elongation of the stretchable resin substrate 11 is preferably 3000% or less. This is because it is easier to obtain a stretchable resin substrate 11 with good stretch durability that does not deteriorate easily even when repeatedly stretched and contracted.

[0079] In this specification, "elongation at break" is defined as {(length at break - length before stretching) / length before stretching} × 100 (%). Elongation at break can be measured for each predetermined direction. In this specification, for example, "elongation at break of the stretchable resin substrate 11 is 50% or more" means that the elongation at break in the direction with the maximum elongation at break is 50% or more. If there is no anisotropy in the elongation at break, the elongation at break will be the same in all directions. Also, if the anisotropy of the elongation at break is small, the elongation at break will be close in all directions.

[0080] (Metal Wiring Pattern) The metal wiring pattern 21 is linear in shape with a uniform width in plan view. The planar shape of the metal wiring pattern 21 is not particularly limited and can be appropriately determined according to the application of the resin wiring substrate 10. Preferably, the planar shape of the metal wiring pattern 21 is such that it is difficult for the wires to break and peel off even if the stretchable resin substrate 11 is deformed. For example, as shown in Figure 3A, it can be a curved shape in which a series of arcs with a predetermined radius of curvature are connected. The number of metal wiring patterns 21 can also be appropriately determined according to the application of the resin wiring substrate 10. The line width of the metal wiring pattern 21 can be, for example, 0.003 to 2.00 mm.

[0081] (Stretchable resin layer) The stretchable resin layer 31 can be made of the same type of resin as the stretchable resin base material 11, but it can also be made of other known materials, and it is preferable that it contains a stretchable resin. Examples of stretchable resins include polyimide resin, polyamide resin, epoxy resin, polycarbonate, silicone resin, polyacrylic resin, fluororesin, etc.

[0082] The stretchable resin contained in the stretchable resin layer 31 can be the same as the resin used to form the stretchable resin substrate 11. The stretchable resin contained in the stretchable resin layer 31 and the resin used to form the stretchable resin substrate 11 may be the same or different. It is preferable that the stretchable resin contained in the stretchable resin layer 31 and the resin used to form the stretchable resin substrate 11 are the same, as this tends to result in a stretchable resin layer 31 with good adhesion to the stretchable resin substrate 11.

[0083] (Electronic components 41) In the stretchable device of this embodiment, two electronic components 41 are arranged on the first surface 11a of the stretchable resin substrate 11 of the resin wiring board 10. The number and type of electronic components 41 are not particularly limited and are appropriately determined according to the application of the stretchable device.

[0084] As the electronic component 41, any known electronic component can be used. Examples of electronic components 41 include various sensors, capacitors, inductors, high-frequency filters, transformers, resistors, varistors, diodes, various ICs, various actuators, antennas, and batteries. When the electronic component 41 is a battery, examples include solar cells, lithium-ion batteries, and electric double-layer capacitors. As for solar cells, from the viewpoint of electrode arrangement, double-sided electrode solar cells and back-side electrode solar cells can be mentioned. Furthermore, from the viewpoint of materials, examples include silicon-based solar cells, inorganic material solar cells such as compound semiconductor solar cells, and organic solar cells.

[0085] [Method for Manufacturing Resin Wiring Boards] Figures 4A to 4H are process diagrams illustrating an example of the method for manufacturing the resin wiring board shown in Figure 1A. Figures 4A to 4H are schematic cross-sectional views showing enlarged regions corresponding to a part of the cross-section in a direction perpendicular to the longitudinal direction of the resin wiring board shown in Figure 1A.

[0086] First, as shown in Figure 4A, a plate-shaped manufacturing substrate 5 is prepared. As the manufacturing substrate 5, known materials such as resin substrates made of polyethylene terephthalate (PET) or polytetrafluoroethylene (PTFE) can be used. Next, as shown in Figure 4B, a plating seed layer 6 made of a copper thin film or the like is applied to the manufacturing substrate 5 by sputtering, CVD, or the like.

[0087] Next, a photosensitive resist layer 7 is formed on the plated seed layer 6 using a known method. Then, the photosensitive resist layer 7 is patterned using photolithography to a shape corresponding to the planar shape of the linear wiring 22, exposing a portion of the plated seed layer 6 as shown in Figure 4C. Next, as shown in Figure 4D, wiring 25 made of copper or the like is formed on the exposed plated seed layer 6 by a plating method.

[0088] Next, as shown in Figure 4E, the photosensitive resist layer 7 is peeled off by a known method to expose the plating seed layer 6. Then, as shown in Figure 4F, the exposed plating seed layer 6 is removed by a known method such as etching.

[0089] (Formation of the stretchable resin substrate 11) The stretchable resin substrate 11 is formed by a spray coating method. First, the resin and solvent are mixed, and the mixed solution is filtered to create a spray coating solution. The solvent used is a good solvent for the resin and may be prepared by mixing two or more solvents with different boiling points, for example. This makes it possible to control the solvent that volatilizes due to the atomization pressure during spray coating and the solvent that remains on the substrate. By adjusting the contact angle of the resin with water to a value of 85-105°, good adhesion with the wiring 25 made of copper or the like can be achieved. If necessary, a filler can be included in the spray coating solution.

[0090] Next, as shown in Figure 4G, the resin composition is applied to the manufacturing substrate 5 having the wiring 25 by spraying it approximately 200 to 300 times using the obtained spray coating solution, thereby forming a resin composition layer 12 having a shape corresponding to the planar shape of the stretchable resin substrate 11 (coating step).

[0091] Next, the resin composition layer 12 is dried and solidified (drying and solidification step). This yields a sheet-like stretchable resin substrate 11. In the drying and solidification step, the drying temperature for drying the resin composition layer 12 is preferably, for example, 25°C to 150°C, and more preferably 25°C to 120°C. If the drying temperature is 25°C or higher, the resin composition layer 12 can be dried more efficiently, and the sheet-like stretchable resin substrate 11 can be produced efficiently. If the drying temperature is 150°C or lower, deterioration of the sheet-like stretchable resin substrate 11 due to excessively high drying temperature can be suppressed.

[0092] In the drying and solidification process, the completion of solidification (completion of a sheet-like stretchable resin substrate 11) by drying the resin composition layer 12 can be confirmed, for example, by the fact that no clear change in the mass of the resin composition layer 12 being dried is observed.

[0093] Next, in this embodiment, the sheet-like stretchable resin substrate 11 and the wiring 25 are peeled off from the manufacturing substrate 5 in an integrated state (plating). The exposed surface of the wiring 25 is appropriately processed to obtain a resin wiring substrate 10 (see Figure 1A) in which the metal wiring pattern 21 is embedded.

[0094] (Formation of stretchable resin layer 31) By forming a stretchable resin layer 31 on the exposed side of the wiring 25 using a resin composition containing the above-mentioned base material resin and solvent, a resin wiring substrate 10A (see Figure 1B) in which the metal wiring pattern 21 is embedded can be obtained.

[0095] In this case, first, the resin composition containing the above-mentioned base resin and solvent is applied to the first surface 11Aa of the stretchable resin base material 11 in a shape corresponding to the planar shape of the stretchable resin layer 31, forming a resin composition layer of a predetermined thickness (coating step). Next, the resin composition layer is dried and solidified (drying and solidification step). This forms a stretchable resin layer 31 that covers the stretchable wiring 24. In the drying and solidification step, the drying temperature for drying the resin composition layer is preferably, for example, 25°C to 150°C, and more preferably 25°C to 120°C. If the drying temperature is 25°C or higher, the resin composition layer can be dried more efficiently, and the stretchable resin layer 31 can be manufactured efficiently. If the drying temperature is 150°C or lower, it is possible to suppress deterioration of the stretchable resin base material 11 and the stretchable resin layer 31 having the stretchable wiring 24 due to excessively high drying temperatures.

[0096] In the drying and solidification process, the completion of solidification (completion of the stretchable resin layer 31) by drying the resin composition layer can be confirmed, for example, by the fact that no clear change is observed in the mass of the resin composition layer being dried (the total mass of the stretchable resin substrate 11, linear wiring 22, stretchable wiring 24, and resin composition layer).

[0097] [Method for manufacturing a stretchable device] When forming the resin wiring board 10 or resin wiring board 10A described above, an exposed surface 11Aa of the stretchable resin substrate 11 is provided for mounting electronic components.

[0098] (Mounting of electronic components 41) Next, in this embodiment, the electronic components 41 are placed at predetermined positions on the first surface 11Aa of the stretchable resin substrate 11 or stretchable resin substrate 11A having a stretchable resin layer 31 and a metal wiring pattern 21, using a known method such as a surface mount machine (mounter). By performing the above steps, the stretchable device of this embodiment is obtained.

[0099] [Other Examples] Although embodiments of the present invention have been described in detail above, the configurations and combinations thereof in each embodiment are merely examples, and additions, omissions, substitutions, and other modifications of the configurations are possible without departing from the spirit of the present invention.

[0100] The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the following examples. [Resin Composition 1 to Resin Composition 26] A mixed monomer was prepared by mixing the urethane, fluorene, and methacrylic acid shown in Table 1 in the proportions shown in Table 1. A siloxane shown in Table 1 was then mixed in the proportions shown in Table 1 (parts by mass per 100 parts by mass of the mixed monomer). Dimethyl-2,2'-azobis(2-methylpropionate) (V601; trade name, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added as a polymerization initiator at a rate of 1.0 part by mass per 100 parts by mass of the total monomers, and a RAFT agent (S,S dibenzyltrithiocarbonate; manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added at a rate of 1.5 parts by mass per 100 parts by mass of the total monomers. Reversible addition-cleavage chain transfer polymerization (RAFT polymerization) was performed by heating in methyl ethyl ketone (MEK) to obtain a resin.

[0101] The obtained resin was mixed with the fillers shown in Table 1 in the proportions shown in Table 1 (parts by mass per 100 parts by mass of resin), and dispersed in MEK as a solvent to prepare resin compositions 1 to 26 having a resin content of 70% to 100% by mass.

[0102]

[0103] The urethane, fluorene, methacrylic acid, siloxane, and fillers A, B, C, and D shown in Table 1 are as follows: [Urethane (resin compositions 1-9, 11-24)] A random copolymer represented by formula (1) (weight-average molecular weight (Mw) 61000, number-average molecular weight (Mn) 30800). [Urethane (resin compositions 25, 26)] A random copolymer represented by formula (12) (n in formula (12) １ It is 20. １１ is, -(CH ２ ) ６ - is R １２ is, -(CH ２ ) - The weight-average molecular weight (Mw) is 5200, and the number-average molecular weight (Mn) is 4110.

[0104] [Fluorene] GA-2800 (trade name; manufactured by Osaka Gas Chemical Co., Ltd.). [Methacrylic acid] Methyl methacrylate (manufactured by Kuraray Co., Ltd.). [Siloxane] A compound represented by formula (2) having structural units derived from modified polydimethylsiloxane (Sirabrain® FM-0721; trade name; manufactured by JNC Co., Ltd.). [A] Silica, average particle size 2.1 μm to 2.6 μm (manufactured by Tosoh Silica Co., Ltd.). [B] Silica, average particle size 1.5 μm to 1.9 μm (manufactured by Tosoh Silica Co., Ltd.). [C] Calcium carbonate, average particle size: 0.7 μm (manufactured by Shiraishi Calcium Co., Ltd.). [D] Silica, average particle size: 2.5 μm to 3.5 μm (manufactured by Tosoh Silica Co., Ltd.).

[0105] Using the resin compositions 1 to 26 obtained in this manner, stretchable resin substrates 1 to 26 were formed by the following method. Resin compositions 1 to 26 were each applied to a manufacturing substrate made of PET film using a coater, and dried and solidified at 80°C to obtain sheet-like stretchable resin substrates 1 to 26 with a thickness of 0.05 mm.

[0106] The stretchable resin substrates 1 to 26 obtained in this manner were peeled off from the manufacturing substrate, and their Young's modulus, elongation at break, strength, and stretch durability were investigated using the method described below. The results are shown in Table 2. In the method described below, the Young's modulus, elongation at break, strength, and stretch durability of the stretchable resin substrates were measured at a measurement point with a width of 10 mm and a length of 10 mm. However, the measurement results for the Young's modulus, elongation at break, strength, and stretch durability of the stretchable resin substrates were similar regardless of the dimensions of the measurement point. Therefore, the dimensions of the measurement point for the above items on the stretchable resin substrate may be, for example, 5 mm wide and 5 mm long, or 3 mm wide and 3 mm long.

[0107] [Measurement of Young's Modulus] Five strip-shaped measurement samples, each 10 mm wide and 35 mm long, were cut from the stretchable resin substrate. A metal substrate was placed between the grips above and below the measuring instrument, and the measurement samples were fixed to the metal substrate with double-sided tape so that the measurement area was 10 mm wide and 10 mm long. Then, the tensile stress and strain of the measurement samples were measured using a tensile testing machine (product name: Autograph AGS-5kNX, manufactured by Shimadzu Corporation). A stress-strain diagram was created using the results, and the Young's modulus of the measurement samples was calculated from the slope of the proportional limit. The average of the Young's moduli of the five measurement samples was then taken as the Young's modulus of each stretchable resin substrate.

[0108] [Strength Measurement] Five strip-shaped measurement samples, each 10 mm wide and 35 mm long, were cut from a stretchable resin substrate. For each measurement sample, the maximum tensile strength was calculated using the method described below, and the average value was taken as the strength. A metal substrate was placed between the grips above and below the measuring instrument, and the measurement sample was fixed to the metal substrate with double-sided tape so that the measurement area was 10 mm wide and 10 mm long. Then, the measurement sample was pulled at a tensile speed of 10 mm / min using a tensile testing machine (product name: Autograph AGS-5kNX, manufactured by Shimadzu Corporation). The maximum tensile strength of the measurement sample was then measured.

[0109] [Measurement of Elongation at Break] Six strip-shaped measurement samples, each 10 mm wide and 30 mm long, were cut from the stretchable resin substrate. For each measurement sample, the elongation at break was calculated using the method described below.

[0110] A metal substrate was clamped between the grips above and below the measuring instrument, and the measurement sample was fixed to the metal substrate with double-sided tape so that the measurement area was 10 mm wide and 10 mm long. Then, the measurement sample was pulled at a tensile speed of 10 mm / min using a tensile testing machine (product name: Autograph AGS-5kNX, manufactured by Shimadzu Corporation). The length of the measurement sample at the time of fracture was measured, and the length before pulling (10 mm) was subtracted from this length to calculate the elongation at fracture (length at fracture - length before pulling) for each measurement sample. The average value was taken as the elongation at fracture, and the fracture elongation rate was calculated using the following formula: Fracture elongation rate (%) = {Elongation at fracture / Length before pulling} × 100

[0111] [Stretch Durability] A strip-shaped measurement sample measuring 10 mm wide and 30 mm long was cut from the stretchable resin substrate in the same manner as the measurement of the elongation at break, and the stretch durability was calculated using the method shown below.

[0112] A metal substrate was placed between the grips above and below the measuring instrument, and the measurement sample was fixed to the metal substrate with double-sided tape so that the measurement area was 10 mm wide and 10 mm long. Then, the measurement sample was pulled at a tensile speed of 10 mm / min using a tensile testing machine (product name: Autograph AGS-5kNX, manufactured by Shimadzu Corporation), and the change in tensile strength when the length was stretched by 2 mm (20% of the length of the measurement area) was measured. Subsequently, the change in tensile strength when the measurement sample was returned to its original length at a tensile speed of 10 mm / min was measured. From these measurement results, the peak strength (maximum value) of the first tensile strength when the measurement sample was stretched and when it was returned to its original length was determined.

[0113] Subsequently, the peak intensity of the stretching strength for the second to 100th stretching tests was determined in the same manner as the peak intensity of the first stretching test. Then, the ratio of the peak intensity of the stretching strength for the first stretching test to the peak intensity of the stretching strength for the 100th stretching test (peak intensity of the stretching strength for the 100th stretching test / peak intensity of the stretching strength for the first stretching test) was calculated to evaluate the stretching durability.

[0114]

[0115] As shown in Tables 1 and 2, by using resin compositions 1-18 and 20-26, a Young's modulus of 30 N / mm² is obtained.２ It was confirmed that the following low-strength stretchable resin substrates 1-18 and 20-26 could be obtained. Furthermore, as shown in stretchable resin substrates 17 and 19, when [urethane] [siloxane] [methacrylic acid] was used as the monomer, it was found that reducing the proportion of [urethane] and increasing the proportion of "methacrylic acid" tended to increase the Young's modulus and improve stretch durability. In addition, as shown in stretchable resin substrates 16 and 20-24, when [urethane] [siloxane] was used as the monomer, it was confirmed that the stretch durability was improved by including a filler.

[0116] The stretchable resin substrates 8 and 18 described above were analyzed using photothermal conversion infrared spectroscopy (O-PTIR) with an infrared spectrometer (product name: mIRage, manufactured by Japan Thermal Consulting Co., Ltd.). The results are shown in Figure 4.

[0117] Figure 5 shows the infrared absorption (IR) spectra of the stretchable resin substrate 8 and the stretchable resin substrate 18. In Figure 5, the dotted line shows the results for the stretchable resin substrate 18, and the solid line shows the results for the stretchable resin substrate 18.

[0118] The IR spectrum shown in Figure 5 has a wavelength of 1114 cm⁻¹. －１ ±35cm －１ , wavelength 1500cm －１ ±35cm －１ , wavelength 1600cm －１ ±35cm －１ The peak originates from fluorene. Also, the IR spectrum wavelength is 1150 cm. －１ ±35cm －１ The peak originates from methacrylic acid. Also, the IR spectrum wavelength is 1260 cm. －１ ±35cm －１ , wavelength 1741cm －１ ±25cm －１ The peak originates from C=O.

[0119] 10... Resin wiring board, 11... Stretchable resin substrate, 21... Metal wiring pattern, 100... Stretchable device

Claims

1. A resin wiring substrate comprising a metal wiring pattern and a stretchable resin substrate disposed to cover at least one surface of the metal wiring pattern, wherein the stretchable resin substrate does not have voids with a maximum diameter of 0.5 μm or more near the adhesive interface with the metal wiring pattern.

2. The resin wiring substrate according to claim 1, wherein the thickness of the overlapping portion formed by the overlapping of the metal wiring pattern and the stretchable resin substrate is greater than the thickness of the non-overlapping portion consisting only of the stretchable resin substrate.

3. The resin wiring substrate according to claim 2, wherein the elongation at break of the resin material constituting the stretchable resin substrate is 200% or more.

4. The resin wiring board according to claim 2, wherein the standard deviation σ of the thickness of the non-overlapping portion is 2.5 or less.

5. A stretchable device comprising a resin wiring substrate according to any one of claims 1 to 4.

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