JP7766080B2 - Wiring sheet - Google Patents

Description

The present invention relates to a wiring sheet.

A sheet-like conductive member (hereinafter also referred to as a "conductive sheet") having a pseudo-sheet structure in which multiple conductive linear elements are arranged at intervals may be useful as a component for a variety of items, such as a heating element for a heating device, a heat-generating textile material, or a protective film for a display (shatter-resistant film).
As an example of a sheet used as a heating element, Patent Document 1 describes a conductive sheet having a pseudo-sheet structure in which a plurality of linear elements extending in one direction are arranged at intervals. A pair of electrodes is provided on both ends of the linear elements, thereby obtaining a wiring sheet that can be used as a heating element.

International Publication No. 2017/086395

Electrodes used in wiring sheets are typically made of metal foil or silver paste. However, from the perspective of flexibility in the electrode portion of the wiring sheet, the use of metal wire instead of metal foil or silver paste has been considered. However, when metal wire is used as the electrode, the resistance value of the electrode becomes relatively high. As a result, the difference with the resistance value of the linear body, which is the heat-generating portion, becomes small, and the resistance value of the electrode, which should normally be negligible, becomes significant. In such cases, the resistance value of the electrode can be reduced by increasing the number of metal wires. From this perspective, a large number of metal wires is preferable. However, it has been found that when an electrode is made of multiple metal wires, the amount of heat generated by each metal wire differs when heated, resulting in large temperature variations within the electrode.

The object of the present invention is to provide a wiring sheet that can suppress temperature unevenness within the electrode.

According to one aspect of the present invention, there is provided a wiring sheet including a pseudo sheet structure in which a plurality of conductive linear objects are arranged at intervals, and a pair of electrodes in direct contact with the conductive linear objects, wherein each of the pair of electrodes includes two or more metal wires, and when the number of metal wires in one of the pair of electrodes is N and the resistance value of the n-th metal wire counting from the outside of the electrode in a planar view of the wiring sheet is _Rn , the wiring sheet provides a wiring sheet in which each of the pair of electrodes satisfies all of the conditions shown in the following formula (F1) and the following formula (F2):
R _n ≦R _n+1 ...(F1)
R ₁ <R _N ...(F2)

In a wiring sheet according to one embodiment of the present invention, it is preferable that the metal wire is gold-plated.

In a wiring sheet according to one embodiment of the present invention, it is preferable that adjacent metal wires are not in contact with each other.

In a wiring sheet according to one embodiment of the present invention, it is preferable that the spacing between adjacent metal wires constituting the electrode is 0.5 mm or more and 5 mm or less.

In a wiring sheet according to one embodiment of the present invention, it is preferable that the distance between the outermost metal wire and the innermost metal wire constituting the electrode is 3 mm or more and 30 mm or less.

In a wiring sheet according to one embodiment of the present invention, when the resistance value of the pseudo sheet structure is r and the resistance value of the electrode is R, it is preferable that the condition shown in the following formula (F3) is satisfied.
r/R<20...(F3)

In a wiring sheet according to one embodiment of the present invention, it is preferable that the metal wires constituting the pair of electrodes are symmetrical about an axis when viewed in a plane of the wiring sheet.

According to one aspect of the present invention, a wiring sheet can be provided that can suppress temperature unevenness within the electrode.

1 is a schematic diagram showing a wiring sheet according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing the II-II cross section of FIG. FIG. 4 is a schematic diagram showing a wiring sheet according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view showing the IV-IV cross section of FIG. 3.

[First embodiment]
The present invention will be described below with reference to the drawings, taking an embodiment as an example. The present invention is not limited to the content of the embodiment. In the drawings, some parts are illustrated enlarged or reduced in size for ease of explanation.

(wiring sheet)
As shown in Figures 1 and 2, the wiring sheet 100 according to this embodiment includes a substrate 1, a pseudo sheet structure 2, a resin layer 3, and a pair of electrodes 4. Specifically, the wiring sheet 100 includes the resin layer 3 laminated on the substrate 1, and the pseudo sheet structure 2 laminated on the resin layer 3. The pseudo sheet structure 2 includes a plurality of conductive linear members 21 arranged at intervals. Each of the pair of electrodes 4 includes two or more metal wires 41. Each of the pair of electrodes 4 is provided with a power supply portion 5.

In this embodiment, when the number of metal wires 41 of one electrode 4 is N and the resistance value of the n-th metal wire 41 counting from the outside of the electrode 4 in a planar view of the wiring sheet 100 is _Rn , it is necessary to satisfy all of the conditions shown in formula (F1) and formula (F2) described below.
Here, the "nth metal wire 41 counted from the outside of the electrode 4" refers to the metal wire 41 electrically connected to the conductive linear body 21, and refers to the nth metal wire 41 when counted from the end side of the conductive linear body 21.

In this embodiment, it is necessary to satisfy the condition shown in the following formula (F1).
R _n ≦R _n+1 ...(F1)

If the condition shown in formula (F1) is not satisfied, the temperature unevenness in the electrode cannot be suppressed.
In the formula (F1), n is an integer equal to or greater than 1. The upper limit of n is the number N of the metal wires 41.
The number N of metal wires 41 is preferably 3 or more, more preferably 4 or more, and even more preferably 5 or more. The greater the number of metal wires 41, the more likely temperature unevenness is to occur within the electrode. However, even when there are a large number of metal wires 41, the wiring sheet 100 according to this embodiment can suppress temperature unevenness within the electrode. The upper limit of the number N of metal wires 41 is not particularly limited, but may be, for example, 10.

In this embodiment, it is necessary to satisfy the condition shown in the following formula (F2).
R ₁ <R _N ...(F2)

If the condition shown in formula (F2) is not satisfied, the temperature unevenness in the electrode cannot be suppressed.
From the viewpoint of further suppressing temperature unevenness within the electrode, the value of R _N /R ₁ is preferably 1.5 or more, more preferably 2 or more, and even more preferably 3 or more.

The inventors of the present invention believe that the reason why temperature unevenness in the electrode can be suppressed when all the conditions shown in formula (F1) and formula (F2) are satisfied is as follows.
That is, when electrode 4 is made of two or more metal wires 41 made of materials with the same resistance value, current tends to flow more easily through the metal wire 41 located on the inside in a plan view of wiring sheet 100, making this metal wire 41 more likely to generate heat. As a result, the inventors surmise that when current is passed through wiring sheet 100 to generate heat, temperature unevenness occurs within the electrode.
In contrast, when the conditions shown in formula (F1) and formula (F2) are satisfied, the resistance value of the metal wires 41 becomes higher the closer they are to the inside in a plan view of the wiring sheet 100. Furthermore, the closer they are to the inside, the less current flows through the metal wires 41. As a result, heat generated by the metal wires 41 on the inside can be dispersed to the metal wires 41 on the outside. The inventors speculate that this makes it possible to suppress temperature unevenness within the electrode.

In this embodiment, when the resistance value of the pseudo sheet structure 2 is r and the resistance value of the electrode 4 is R, it is preferable to satisfy the condition shown in the following formula (F3).
r/R<20...(F3)

When the value of r/R is 20 or more, the resistance value of pseudo sheet structure 2, which is the heat-generating portion, is sufficiently larger than the resistance value of electrode 4. Therefore, in wiring sheet 100, the resistance value of electrode 4 can be almost ignored, and problems of temperature unevenness within the electrode tend not to occur.
On the other hand, as the value of r/R decreases, the problem of temperature unevenness within the electrode becomes more likely to occur, and therefore the significance of using wiring sheet 100 according to this embodiment increases.
The resistance values of the electrode 4 and the pseudo sheet structure 2 can be measured using a tester. First, the resistance value of the electrode 4 is measured, and then the resistance value of the pseudo sheet structure 2 to which the electrode 4 is attached is measured. Then, the resistance value of each of the electrode 4 and the pseudo sheet structure 2 is calculated by subtracting the measured value of the electrode 4 from the resistance value of the pseudo sheet structure 2 to which the electrode 4 is attached. Also, if necessary, the electrode 4 can be removed from the wiring sheet 100 and the resistance value can be measured.

The resistance values of the pseudo sheet structure 2 and the conductive linear body 21, as well as the resistance values of the electrode 4 and the metal wire 41, can be set using any known method, and can be adjusted, for example, by changing the material, cross-sectional area, length, etc.

(Base material)
The substrate 1 can directly or indirectly support the pseudo sheet structure 2. Examples of the substrate 1 include synthetic resin films, paper, metal foils, nonwoven fabrics, cloth, and glass films. The substrate 1 is preferably an elastic substrate. If the substrate 1 is an elastic substrate, the elasticity of the wiring sheet 100 can be ensured even when the pseudo sheet structure 2 is provided on the substrate 1.
As the stretchable substrate, a synthetic resin film, a nonwoven fabric, a cloth, or the like can be used.
Examples of synthetic resin films include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polyethylene naphthalate films, polybutylene terephthalate films, polyurethane films, ethylene-vinyl acetate copolymer films, ionomer resin films, ethylene-(meth)acrylic acid copolymer films, ethylene-(meth)acrylic acid ester copolymer films, polystyrene films, polycarbonate films, and polyimide films. Other stretchable substrates include crosslinked films and laminated films of these.
Examples of nonwoven fabrics include spunbond nonwoven fabrics, needle-punched nonwoven fabrics, melt-blown nonwoven fabrics, and spunlace nonwoven fabrics. Examples of cloth include woven fabrics and knitted fabrics. The paper, nonwoven fabric, and cloth used as the stretchable substrate are not limited to these.
The thickness of the stretchable substrate is not particularly limited. The thickness of the stretchable substrate is preferably 10 μm or more and 10 mm or less, more preferably 15 μm or more and 3 mm or less, and even more preferably 50 μm or more and 1.5 mm or less.

(pseudo seat structure)
The pseudo sheet structure 2 has a structure in which a plurality of conductive linear bodies 21 are arranged at intervals from one another. That is, the pseudo sheet structure 2 is a structure in which a plurality of conductive linear bodies 21 are arranged at intervals from one another to form a flat or curved surface. The conductive linear bodies 21 extend in one direction and have a straight or wavy shape in a planar view of the wiring sheet 100. The pseudo sheet structure 2 has a structure in which a plurality of conductive linear bodies 21 are arranged in a direction perpendicular to the axial direction of the conductive linear bodies 21.
Preferably, the conductive linear members 21 have a wave shape in a plan view of the wiring sheet 100. Examples of the wave shape include a sine wave, a rectangular wave, a triangular wave, and a sawtooth wave. If the pseudo sheet structure 2 has such a structure, breakage of the conductive linear members 21 can be suppressed when the wiring sheet 100 is stretched in the axial direction of the conductive linear members 21.

The volume resistivity of the conductive linear members 21 is preferably 1.0×10 ⁻⁹ Ω·m or more and 1.0×10 ⁻³ Ω·m or less, and more preferably 1.0×10 ⁻⁸ Ω·m or more and 1.0×10 ⁻⁴ Ω·m or less. When the volume resistivity of the conductive linear members 21 is in the above range, the surface resistance of the pseudo sheet structure 2 is likely to be reduced.
The volume resistivity of the conductive linear body 21 was measured as follows: Silver paste was applied to both ends of the conductive linear body 21, and the resistance was measured at a length of 40 mm from each end to determine the resistance value of the conductive linear body 21. The volume resistivity of the conductive linear body 21 was then calculated by multiplying the resistance value by the cross-sectional area (unit: ^m2 ) of the conductive linear body 21 and dividing the obtained value by the measured length (0.04 m).

The cross-sectional shape of the conductive linear body 21 is not particularly limited and may be polygonal, flat, elliptical, circular, or the like. However, from the viewpoint of compatibility with the resin layer 3, an elliptical or circular shape is preferable.
When the cross section of the conductive linear member 21 is circular, the thickness (diameter) D (see FIG. 2 ) of the conductive linear member 21 is preferably 5 μm or more and 75 μm or less. From the viewpoints of suppressing an increase in sheet resistance and improving heat generation efficiency and dielectric breakdown resistance when the wiring sheet 100 is used as a heating element, the diameter D of the conductive linear member 21 is more preferably 8 μm or more and 60 μm or less, and even more preferably 12 μm or more and 40 μm or less.
When the cross section of the conductive linear body 21 is elliptical, it is preferable that the major axis is in the same range as the diameter D described above.

The diameter D of the conductive linear body 21 is determined by observing the conductive linear body 21 of the pseudo-sheet structure 2 using a digital microscope, measuring the diameter of the conductive linear body 21 at five randomly selected locations, and taking the average value.

The interval L (see FIG. 2) between the conductive linear members 21 is preferably 0.3 mm or more and 50 mm or less, more preferably 0.5 mm or more and 30 mm or less, and even more preferably 0.8 mm or more and 20 mm or less.
If the spacing between the conductive linear elements 21 is within the above range, the conductive linear elements are relatively densely packed, thereby improving the functionality of the wiring sheet 100, such as maintaining a low resistance of the pseudo-sheet structure and uniformly distributing the temperature rise when the wiring sheet 100 is used as a heating element.

The distance L between the conductive linear members 21 is measured by observing the conductive linear members 21 of the pseudo sheet structure 2 using a digital microscope and measuring the distance between two adjacent conductive linear members 21 .
The interval between two adjacent conductive linear bodies 21 is the length along the direction in which the conductive linear bodies 21 are arranged, and is the length between opposing portions of the two conductive linear bodies 21 (see FIG. 2 ). When the conductive linear bodies 21 are arranged at uneven intervals, the interval L is the average value of the intervals between all adjacent conductive linear bodies 21.

The conductive linear body 21 is not particularly limited, but is preferably a linear body including a metal wire (hereinafter also referred to as a "metal wire linear body"). Metal wire has high thermal conductivity, high electrical conductivity, easy handling, and versatility, so when a metal wire linear body is used as the conductive linear body 21, the resistance value of the pseudo sheet structure 2 is reduced while the light transmittance is easily improved. Furthermore, when the wiring sheet 100 (pseudo sheet structure 2) is used as a heating element, rapid heat generation is easily achieved. Furthermore, as described above, it is easy to obtain linear bodies with a small diameter.
In addition to a metal wire linear body, examples of the conductive linear body 21 include a linear body containing carbon nanotubes and a linear body in which a thread is provided with a conductive coating.

The metal wire linear body may be a linear body made of a single metal wire, or may be a linear body made of a plurality of twisted metal wires.
Examples of metal wires include wires containing metals such as copper, aluminum, tungsten, iron, molybdenum, nickel, titanium, silver, and gold, or alloys containing two or more metals (e.g., steels such as stainless steel and carbon steel, brass, phosphor bronze, zirconium-copper alloys, beryllium copper, iron-nickel, nichrome, nickel-titanium, Kanthal, Hastelloy, and rhenium-tungsten). Furthermore, the metal wire may be plated with gold, tin, zinc, silver, nickel, chromium, a nickel-chromium alloy, or solder, or may be surface-coated with a carbon material or polymer, as described below. Wires containing one or more metals selected from tungsten, molybdenum, and alloys containing these metals are particularly preferred from the viewpoint of forming a conductive linear body 21 that is thin, has high strength, and has a low volume resistivity.
The metal wire may be a metal wire coated with a carbon material. When the metal wire is coated with a carbon material, the metallic luster is reduced, making it easier to make the metal wire less noticeable. Furthermore, when the metal wire is coated with a carbon material, metal corrosion is also suppressed.
Examples of carbon materials that can be used to coat metal wires include amorphous carbon (e.g., carbon black, activated carbon, hard carbon, soft carbon, mesoporous carbon, and carbon fiber), graphite, fullerene, graphene, and carbon nanotubes.

Carbon nanotube-containing linear bodies can be obtained, for example, by drawing carbon nanotubes into a sheet from the end of a carbon nanotube forest (a growth structure in which multiple carbon nanotubes are grown on a substrate so that they are aligned perpendicular to the substrate; sometimes referred to as an "array"). The drawn carbon nanotube sheets are then bundled and twisted. In this production method, ribbon-shaped carbon nanotube linear bodies are obtained if no twist is applied during twisting, while thread-shaped carbon nanotubes are obtained if twist is applied. Ribbon-shaped carbon nanotube linear bodies are linear bodies in which the carbon nanotubes do not have a twisted structure. Carbon nanotube linear bodies can also be obtained by spinning a carbon nanotube dispersion. Carbon nanotube linear bodies can be produced by spinning, for example, using the method disclosed in U.S. Patent Application Publication No. 2013/0251619 (JP Patent Publication No. 2012-126635). From the viewpoint of obtaining uniformity in the diameter of the carbon nanotube linear bodies, it is desirable to use thread-like carbon nanotube linear bodies, and from the viewpoint of obtaining high-purity carbon nanotube linear bodies, it is preferable to obtain thread-like carbon nanotube linear bodies by twisting a carbon nanotube sheet. The carbon nanotube linear body may be a linear body formed by weaving two or more carbon nanotube linear bodies together. Furthermore, the carbon nanotube linear body may be a linear body formed by combining carbon nanotubes with another conductive material (hereinafter also referred to as a "composite linear body").

Examples of the composite linear body include: (1) a composite linear body in which, in a process of obtaining a carbon nanotube linear body by drawing carbon nanotubes into a sheet form from the end of a carbon nanotube forest, bundling the drawn carbon nanotube sheets, and then twisting the carbon nanotube bundles, a metal element or a metal alloy is supported on the surface of the carbon nanotube forest, sheet, or bundle, or twisted linear body by vapor deposition, ion plating, sputtering, wet plating, or the like; (2) a composite linear body in which bundles of carbon nanotubes are twisted together with linear bodies of a metal element or a metal alloy, or a composite linear body; and (3) a composite linear body in which linear bodies of a metal element or a metal alloy, or a composite linear body, are braided with carbon nanotube linear bodies or composite linear bodies. In the composite linear body of (2), a metal may be supported on the carbon nanotubes when twisting the bundles of carbon nanotubes, as in the composite linear body of (1). Furthermore, the composite linear body of (3) is a composite linear body in which two linear bodies are braided together, but as long as it contains at least one linear body of a simple metal or a metal alloy, or a composite linear body, it may be a composite linear body in which three or more carbon nanotube linear bodies, or linear bodies of a simple metal or a metal alloy, or a composite linear body are braided together.
Examples of the metal for the composite linear body include simple metals such as gold, silver, copper, iron, aluminum, nickel, chromium, tin, and zinc, and alloys containing at least one of these simple metals (such as copper-nickel-phosphorus alloys and copper-iron-phosphorus-zinc alloys).

The conductive linear body 21 may be a linear body in which a conductive coating is applied to the thread. Examples of the thread include threads spun from resins such as nylon and polyester. Examples of the conductive coating include coatings of metals, conductive polymers, carbon materials, etc. The conductive coating can be formed by plating or vapor deposition, etc. A linear body in which a conductive coating is applied to the thread can improve the conductivity of the linear body while maintaining the flexibility of the thread. In other words, it becomes easier to reduce the resistance of the pseudo sheet structure 2.

(Resin layer)
The resin layer 3 is a layer containing resin. This resin layer 3 can directly or indirectly support the pseudo sheet structure 2. Furthermore, the resin layer 3 is preferably a layer containing an adhesive. When the pseudo sheet structure 2 is formed on the resin layer 3, the adhesive makes it easy to attach the conductive linear members 21 to the resin layer 3. Furthermore, the resin layer 3 is preferably stretchable. In such a case, the stretchability of the wiring sheet 100 can be ensured.

The resin layer 3 may be a layer made of a dryable or curable resin. This provides the resin layer 3 with sufficient hardness to protect the pseudo-sheet structure 2, allowing the resin layer 3 to also function as a protective film. Furthermore, after curing or drying, the resin layer 3 has impact resistance, and deformation of the resin layer 3 due to impact can be suppressed.

The resin layer 3 is preferably energy ray-curable, such as ultraviolet light, visible energy rays, infrared rays, or electron beams, as this allows for easy curing in a short period of time. Note that "energy ray curing" also includes thermal curing through heating using energy rays.

The adhesive for resin layer 3 may be a thermosetting adhesive that hardens when heated, a heat-seal type that bonds when heated, or an adhesive that becomes adhesive when moistened. However, for ease of application, it is preferable that resin layer 3 be energy ray-curable. Examples of energy ray-curable resins include compounds that have at least one polymerizable double bond in the molecule, and acrylate compounds with a (meth)acryloyl group are preferred.

Examples of the acrylate-based compounds include (meth)acrylates containing a chain aliphatic skeleton (trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate). acrylates, etc.), alicyclic skeleton-containing (meth)acrylates (dicyclopentanyl di(meth)acrylate, dicyclopentadiene di(meth)acrylate, etc.), polyalkylene glycol (meth)acrylates (polyethylene glycol di(meth)acrylate, etc.), oligoester (meth)acrylates, urethane (meth)acrylate oligomers, epoxy-modified (meth)acrylates, polyether (meth)acrylates other than the above-mentioned polyalkylene glycol (meth)acrylates, and itaconic acid oligomers.

The weight average molecular weight (Mw) of the energy ray-curable resin is preferably 100 to 30,000, and more preferably 300 to 10,000.

The adhesive composition may contain one or more types of energy ray-curable resins, and if two or more types are used, the combination and ratio of these may be selected as desired. Furthermore, the adhesive composition may be combined with a thermoplastic resin, as described below, and the combination and ratio may be selected as desired.

The resin layer 3 may be an adhesive layer formed from a pressure-sensitive adhesive (pressure-sensitive adhesive). The adhesive of the adhesive layer is not particularly limited. Examples of adhesives include acrylic adhesives, urethane adhesives, rubber adhesives, polyester adhesives, silicone adhesives, and polyvinyl ether adhesives. Among these, the adhesive is preferably at least one selected from the group consisting of acrylic adhesives, urethane adhesives, and rubber adhesives, and more preferably an acrylic adhesive.

Examples of acrylic adhesives include polymers containing structural units derived from alkyl (meth)acrylates with straight-chain or branched alkyl groups (i.e., polymers obtained by polymerizing at least alkyl (meth)acrylates), and acrylic polymers containing structural units derived from (meth)acrylates with a cyclic structure (i.e., polymers obtained by polymerizing at least (meth)acrylates with a cyclic structure). Here, "(meth)acrylate" is used to refer to both "acrylate" and "methacrylate," and the same applies to other similar terms.

The acrylic copolymer may be crosslinked with a crosslinking agent. Examples of crosslinking agents include known epoxy crosslinking agents, isocyanate crosslinking agents, aziridine crosslinking agents, and metal chelate crosslinking agents. When crosslinking an acrylic copolymer, functional groups derived from the monomer components of the acrylic polymer, such as hydroxyl groups or carboxyl groups, which react with these crosslinking agents, can be introduced into the acrylic copolymer.

When resin layer 3 is formed from an adhesive, resin layer 3 may contain the above-mentioned energy ray-curable resin in addition to the adhesive. Furthermore, when an acrylic adhesive is used as the adhesive, the energy ray-curable component may be a compound having both a functional group reactive with a functional group derived from a monomer component in an acrylic copolymer and an energy ray-polymerizable functional group in one molecule. The reaction between the functional group of this compound and the functional group derived from a monomer component in the acrylic copolymer makes the side chain of the acrylic copolymer polymerizable by energy ray irradiation. Even when the adhesive is not an acrylic adhesive, a component whose side chain is energy ray-polymerizable may also be used as a polymer component other than an acrylic polymer.

The thermosetting resin used in the resin layer 3 is not particularly limited, and specific examples include epoxy resins, phenolic resins, melamine resins, urea resins, polyester resins, urethane resins, acrylic resins, benzoxazine resins, phenoxy resins, amine compounds, and acid anhydride compounds. These can be used alone or in combination. Among these, epoxy resins, phenolic resins, melamine resins, urea resins, amine compounds, and acid anhydride compounds are preferred because they are suitable for curing using an imidazole curing catalyst. In particular, epoxy resins, phenolic resins, mixtures thereof, or mixtures of epoxy resins with at least one selected from the group consisting of phenolic resins, melamine resins, urea resins, amine compounds, and acid anhydride compounds are preferred because they exhibit excellent curing properties.

The moisture-curing resin used in the resin layer 3 is not particularly limited, but examples include urethane resins, which are resins that generate isocyanate groups when exposed to moisture, and modified silicone resins.

When using an energy ray-curable resin or a thermosetting resin, it is preferable to use a photopolymerization initiator or a thermal polymerization initiator. By using a photopolymerization initiator or a thermal polymerization initiator, a crosslinked structure is formed, making it possible to more firmly protect the pseudo-sheet structure 2.

Photopolymerization initiators include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, 2-chloroanthraquinone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide.

Thermal polymerization initiators include hydrogen peroxide, peroxodisulfates (ammonium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, etc.), azo compounds (2,2'-azobis(2-amidinopropane) dihydrochloride, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), etc.), and organic peroxides (benzoyl peroxide, lauroyl peroxide, peracetic acid, persuccinic acid, di-t-butyl peroxide, t-butyl hydroperoxide, cumene hydroperoxide, etc.).

These polymerization initiators may be used alone or in combination of two or more.
When forming a crosslinked structure using these polymerization initiators, the amount used is preferably 0.1 parts by mass or more and 100 parts by mass or less, more preferably 1 part by mass or more and 100 parts by mass or less, and particularly preferably 1 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the energy ray-curable resin or the thermosetting resin.

The resin layer 3 may not be curable, but may be a layer made of, for example, a thermoplastic resin composition. The thermoplastic resin layer can be softened by adding a solvent to the thermoplastic resin composition. This makes it easier to attach the conductive linear members 21 to the resin layer 3 when forming the pseudo-sheet structure 2 on the resin layer 3. Meanwhile, the thermoplastic resin layer can be dried and solidified by volatilizing the solvent in the thermoplastic resin composition.

Examples of the thermoplastic resin include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl acetate, polyurethane, polyether, polyethersulfone, polyimide, and acrylic resin.
Examples of the solvent include alcohol-based solvents, ketone-based solvents, ester-based solvents, ether-based solvents, hydrocarbon-based solvents, alkyl halide-based solvents, and water.

The resin layer 3 may contain an inorganic filler. By including an inorganic filler, the hardness of the resin layer 3 after curing can be further improved. The thermal conductivity of the resin layer 3 can also be improved.

Examples of inorganic fillers include inorganic powders (such as silica, alumina, talc, calcium carbonate, titanium white, red iron oxide, silicon carbide, metal, and boron nitride powders), beads made by spheroidizing inorganic powders, single-crystal fibers, and glass fibers. Among these, silica filler and alumina filler are preferred as inorganic fillers. One type of inorganic filler may be used alone, or two or more types may be used in combination.

The resin layer 3 may contain other components, such as well-known additives such as organic solvents, flame retardants, tackifiers, UV absorbers, antioxidants, preservatives, antifungal agents, plasticizers, antifoaming agents, and wettability adjusters.

The thickness of the resin layer 3 is determined appropriately depending on the application of the wiring sheet 100. For example, from the standpoint of adhesiveness, the thickness of the resin layer 3 is preferably 3 μm or more and 150 μm or less, and more preferably 5 μm or more and 100 μm or less.

(electrode)
The electrodes 4 are used to supply current to the conductive linear body 21. The electrodes 4 are in direct contact with the conductive linear body 21. The electrodes 4 are disposed so as to be electrically connected to both ends of the conductive linear body 21.
The electrode 4 includes two or more metal wires 41. As shown in FIG. 1 , the number of metal wires 41 may be four. In addition, the number of metal wires 41 used in one electrode 4 of a pair of electrodes 4 may be different from the number of metal wires 41 used in the other electrode 4. However, from the viewpoint of suppressing temperature unevenness, it is preferable that the number of metal wires 41 used in one electrode 4 is the same as the number of metal wires 41 used in the other electrode 4. From the same viewpoint, it is preferable that the metal wires 41 constituting the pair of electrodes 4 are line-symmetrical when viewed in a plan view of the wiring sheet 100.
Furthermore, metal wire 41 preferably has a wave shape in a plan view of wiring sheet 100. Examples of the wave shape include a sine wave, a rectangular wave, a triangular wave, and a sawtooth wave. If electrode 4 has such a structure, breakage of electrode 4 can be suppressed when wiring sheet 100 is stretched in the axial direction of electrode 4.

The metal wire 41 may be made of copper, aluminum, tungsten, iron, molybdenum, nickel, titanium, silver, gold, or an alloy containing two or more metals (e.g., stainless steel, carbon steel, brass, phosphor bronze, zirconium-copper alloy, beryllium copper, iron-nickel, nichrome, nickel-titanium, Kanthal, Hastelloy, and rhenium-tungsten). The metal wire 41 may also be plated with gold, tin, zinc, silver, nickel, chromium, nickel-chromium alloy, solder, or the like. However, gold plating is preferred for the metal wire 41. In this case, contact resistance between the metal wire 41 and the conductive linear body 21 is reduced, thereby suppressing heat generation in the electrode 4.

The cross-sectional shape of the metal wire 41 is not particularly limited and may be polygonal, flat, elliptical, circular, or the like, but is preferably elliptical or circular.
When the cross section of the metal wire 41 is circular, the thickness (diameter) of the metal wire 41 is preferably 5 μm or more and 1000 μm or less, more preferably 20 μm or more and 500 μm or less, and even more preferably 50 μm or more and 300 μm or less.
When the cross section of the metal wire 41 is elliptical, it is preferable that the major axis is in the same range as the diameter described above.

Adjacent metal wires 41 may be in contact with each other, but preferably are not in contact with each other. Here, "adjacent metal wires 41 are in contact with each other" means that adjacent metal wires 41 are in direct contact with each other. "Adjacent metal wires 41 are not in contact with each other" means that adjacent metal wires 41 are not in direct contact with each other, and in this case, adjacent metal wires 41 may be electrically connected to each other. For example, if all adjacent metal wires 41 are in contact with each other, it is the same as a single piece of metal foil, and the problem of temperature unevenness within the electrode tends to be less likely to occur.
In contrast, if adjacent metal wires 41 are not in contact with each other, the problem of temperature unevenness within the electrode is more likely to occur, and therefore the significance of using wiring sheet 100 according to this embodiment is enhanced.

The distance between adjacent metal wires 41 is preferably 0.5 mm or more and 5 mm or less, and more preferably 1 mm or more and 4 mm or less. If the distance between adjacent metal wires 41 is above the lower limit, electrical conduction between adjacent metal wires 41 can be reliably prevented. If the distance between adjacent metal wires 41 is below the upper limit, this is preferable because it makes it easier to adjust the number of metal wires 41.

Of the metal wires 41 that make up the electrode 4, the distance between the outermost metal wire 41 and the innermost metal wire 41 is preferably 3 mm or more and 30 mm or less, and more preferably 5 mm or more and 20 mm or less. If this distance is within the above range, it is easy to adjust the number of metal wires 41, etc.

(Power supply unit)
The power supply portion 5 is a portion that applies a voltage to the wiring sheet 100. If the electrode 4 is exposed and can be electrically connected, any portion of the electrode 4 can be used as the power supply portion 5. However, since the electrode 4 includes two or more metal wires 41, the power supply portion 5 must be electrically connected to all of the metal wires 41. Furthermore, if the electrode 4 is covered with an insulating material to prevent short circuits, etc., the portion where part of the insulating material has been removed can be used as the power supply portion 5.
1, a power supply unit 5 may be provided separately to facilitate connection of a power source (not shown) to the electrode 4. In this case, the material of the power supply unit 5 may be the same as the material of the electrode 4.

(Method for manufacturing wiring sheet)
There are no particular limitations on the method for manufacturing interconnect sheet 100 according to this embodiment. Interconnect sheet 100 can be manufactured, for example, by the following steps.
First, a composition for forming the resin layer 3 is applied to the substrate 1 to form a coating film. The coating film is then dried to form the resin layer 3. Next, conductive linear bodies 21 are arranged and positioned on the resin layer 3 to form the pseudo-sheet structure 2. For example, with the resin layer 3 with the substrate 1 disposed on the outer circumferential surface of a drum member, the drum member is rotated while the conductive linear bodies 21 are spirally wound around the resin layer 3. The spirally wound bundle of conductive linear bodies 21 is then cut along the axial direction of the drum member. This forms the pseudo-sheet structure 2 and places it on the resin layer 3. The resin layer 3 with the substrate 1 on which the pseudo-sheet structure 2 is formed is then removed from the drum member to obtain a sheet-like conductive member. According to this method, for example, while rotating the drum member, the spacing L between adjacent conductive linear bodies 21 in the pseudo-sheet structure 2 can be easily adjusted by moving the unwinding portion of the conductive linear bodies 21 in a direction parallel to the axis of the drum member.
Next, a pair of two or more metal wires 41 that constitute the electrode 4 is prepared, and two or more metal wires 41 are attached to each side of the pair of both ends of the conductive linear body 21 in the pseudo-sheet structure 2 of the sheet-like conductive member, and then a power supply section 5 is provided to produce the wiring sheet 100.

(Operation and effect of the first embodiment)
According to this embodiment, the following effects can be achieved.
(1) According to this embodiment, by satisfying the conditions shown in Formula (F1) and Formula (F2), the resistance value of the metal wires 41 becomes higher as the wires 41 are closer to the inside in a plan view of the wiring sheet 100. Furthermore, the closer the wires 41 are to the inside, the less current flows through them. As a result, heat generated in the metal wires 41 located on the inside can be dispersed to the metal wires 41 located on the outside. In this way, temperature unevenness within the electrode can be suppressed.

[Second embodiment]
Next, a second embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the content of this embodiment. Note that in the drawings, some parts are illustrated enlarged or reduced in size for ease of explanation.
The second embodiment differs from the first embodiment in that the resistance value of the metal wire 41 is adjusted by changing the cross-sectional area of the metal wire 41 .
In the following description, differences from the first embodiment will be mainly described, and overlapping descriptions will be omitted or simplified. The same components as those in the first embodiment will be assigned the same reference numerals, and descriptions thereof will be omitted or simplified.

3 and 4 , the wiring sheet 100A according to this embodiment includes a substrate 1, a pseudo sheet structure 2, a resin layer 3, and a pair of electrodes 4. The electrodes 4 include four metal wires 41. Each electrode 4 is provided with a power supply portion 5.
The four metal wires 41 each have a different cross-sectional area. The metal wires 41 are all made of the same material. The cross-sectional areas of the metal wires 41 decrease from the outside to the inside of the electrode 4. As a result, when the resistance value of the first metal wire 41 counting from the outside of the electrode 4 is _Rn , the relationship expressed by the following formula is satisfied.
R ₁ <R ₂ <R ₃ <R ₄
That is, all the conditions shown in the formula (F1) and the formula (F2) are satisfied.

(Operation and effect of the second embodiment)
According to this embodiment, in addition to the effect (1) of the first embodiment, the following effect (2) can be achieved.
(2) In this embodiment, the resistance value of the metal wire 41 that constitutes the electrode 4 can be changed without changing the material of the metal wire 41 .

[Modification of the embodiment]
The present invention is not limited to the above-described embodiment, and includes modifications and improvements within the scope of achieving the object of the present invention.
For example, in the above-described embodiment, interconnect sheet 100 includes substrate 1, but is not limited to this. For example, interconnect sheet 100 does not have to include substrate 1. In such a case, interconnect sheet 100 can be used by being attached to an adherend by resin layer 3.
In the above-described embodiment, wiring sheet 100 includes resin layer 3, but this is not limiting. For example, wiring sheet 100 may not include resin layer 3. In such a case, pseudo sheet structure 2 may be formed by using a knitted fabric as substrate 1 and weaving conductive linear members 21 into substrate 1.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to these examples in any way.

[Example 1]
An acrylic adhesive ("PK" manufactured by Lintec Corporation) was applied to a thickness of 20 μm on a 50 μm-thick PET film to prepare a pressure-sensitive adhesive sheet. Gold-plated tungsten wire (25 μm diameter, "Au(0.1)-TWG" manufactured by Tokusai Corporation) was prepared as the conductive linear body. Next, the pressure-sensitive adhesive sheet was wrapped around a drum member with a rubber outer periphery, with the surface of the pressure-sensitive adhesive layer facing outward and ensuring no wrinkles, and both ends of the adhesive sheet in the circumferential direction were fixed with double-sided tape. The conductive linear body wound around the bobbin was attached to the surface of the pressure-sensitive adhesive layer of the adhesive sheet located near the end of the drum member, and the wire was then unwound and wound around the drum member. The drum member was gradually moved in a direction parallel to the drum axis so that the conductive linear body was wound around the drum member in a spiral at equal intervals. Thirty conductive linear bodies were provided at equal intervals of 10 mm.
Next, the following four metal wires were prepared as one electrode of a pair of electrodes 4. Next, the four metal wires were placed on both ends of the conductive linear body with a spacing of 2.5 mm between them, in a direction perpendicular to the direction of extension of the conductive linear body, so that the distance between the electrodes was 200 mm. The other electrode was also attached in the same manner to form a pair of electrodes. A 50 μm-thick PET film was then attached to the adhesive surface of the electrode-attached film on which the conductive linear body was placed, to produce a sheet-like heater. Note that the two power supply points used for energization were located on the opposite electrode sides of the sheet-like heater.
(four metal wires)
Type of metal wire: Gold-plated copper wire (Tokusai "C1100-H AuP")
Diameter of the first metal wire counting from the outside: 200 μm
Diameter of the second metal wire counting from the outside: 150 μm
Diameter of the third metal wire counting from the outside: 130 μm
Diameter of the fourth metal wire counting from the outside: 100 μm

[Comparative Example 1]
A sheet-type heater was produced in the same manner as in Example 1, except that the four metal wires were changed as follows.
(four metal wires)
Type of metal wire: Gold-plated copper wire (Tokusai "C1100-H AuP")
Diameter of the first metal wire counting from the outside: 150 μm
Diameter of the second metal wire counting from the outside: 150 μm
Diameter of the third metal wire counting from the outside: 150 μm
Diameter of the fourth metal wire counting from the outside: 150 μm

[Comparative Example 2]
A sheet-type heater was produced in the same manner as in Example 1, except that the four metal wires were changed as follows.
(four metal wires)
Type of metal wire: Gold-plated copper wire (Tokusai "C1100-H AuP")
Diameter of the first metal wire counting from the outside: 100 μm
Diameter of the second metal wire counting from the outside: 130 μm
Diameter of the third metal wire counting from the outside: 150 μm
Diameter of the fourth metal wire counting from the outside: 200 μm

[Resistance value of the nth metal wire counting from the outside of the electrode]
The metal wires used in the examples and comparative examples were cut to a length of 30 cm. The resistance was measured by the four-terminal method using a resistance meter ("RM3545-02" manufactured by Hioki E.E. Corporation), and the resistance per unit length (30 cm) was estimated. The results are shown in Table 1.

[Evaluation of electrode temperature difference]
After a current of 3.5 A was passed through the sheet heater to generate heat, the temperature distribution of the electrodes (four metal wires) was measured using a thermographic camera (FLIR C2 manufactured by FLIR) from a position 150 mm from the surface of the sheet heater. The emissivity was set to 0.95 during this measurement. The difference between the maximum and minimum temperatures at the electrode was taken as the temperature difference (unit: °C). The smaller this temperature difference, the more suppressed temperature unevenness within the electrode is. The results are shown in Table 1.

From the results shown in Table 1, it was confirmed that when the resistance value _Rn of the nth metal wire counting from the outside of the electrode satisfies the conditions shown in formula (F1) and formula (F2) (Example 1), temperature unevenness within the electrode can be suppressed compared to when either of the conditions shown in formula (F1) and formula (F2) is not satisfied (Comparative Examples 1 and 2).

1...substrate, 2...pseudo sheet structure, 21...conductive linear body, 3...resin layer, 4...electrode, 41...metal wire, 5...power supply section, 100, 100A...wiring sheet.

Claims (7)

A wiring sheet comprising a pseudo-sheet structure in which a plurality of conductive linear bodies are arranged at intervals, and a pair of electrodes in direct contact with the conductive linear bodies,
Each of the pair of electrodes includes two or more metal wires;
When the number of metal wires of one electrode of the pair of electrodes is N and the resistance value of the n-th metal wire counting from the outside of the electrode in a plan view of the wiring sheet is _Rn , each of the pair of electrodes satisfies all of the conditions shown in the following formula (F1) and the following formula (F2):
Wiring sheet.
R _n ≦R _n+1 ...(F1)
R ₁ <R _N ...(F2) The wiring sheet according to claim 1 ,
The metal wire is gold plated.
Wiring sheet. The wiring sheet according to claim 1 or 2,
Adjacent metal wires are not in contact with each other.
Wiring sheet. The wiring sheet according to any one of claims 1 to 3,
Among the metal wires constituting the electrode, the interval between adjacent metal wires is 0.5 mm or more and 5 mm or less.
Wiring sheet. The wiring sheet according to any one of claims 1 to 4,
Among the metal wires constituting the electrode, the distance between the outermost metal wire and the innermost metal wire is 3 mm or more and 30 mm or less.
Wiring sheet. The wiring sheet according to any one of claims 1 to 5,
When the resistance value of the pseudo sheet structure is r and the resistance value of the electrode is R, the condition shown in the following formula (F3) is satisfied:
Wiring sheet.
r/R<20...(F3) The wiring sheet according to any one of claims 1 to 6,
The metal wires constituting the pair of electrodes are line-symmetrical in a plan view of the wiring sheet.
Wiring sheet.