Laminate and sensor

Abstract

To provide a laminate which has a low initial resistance value and can suppress increase in a resistance value in telescopic motion.SOLUTION: A laminate has a conductive layer (B) containing a binder resin and conductive particles on at least one surface side of a base material sheet (A), wherein in the conductive layer (B), a content of the conductive particles with respect to 100 pts.mass of the content of the binder resin is 250-1,000 pts.mass, a dispersion value of the particle size of the conductive particles by an image analysis method is 0 μm2 to 80,000 μm2, and a ratio (R50 / R0) of a resistance value (R0) of the conductive layer at elongation of 0% to a resistance value (R50) of the conductive layer when the laminate is uniaxially drawn and reaches elongation of 50% is 8.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a stretchable laminate with a conductive layer. [Background technology]

[0002] A stretchable laminated sheet, which has a structure in which a conductive layer is laminated onto a sheet made of a stretchable material, can be bent freely and adapted to various free-form surfaces, and is therefore expected to realize soft and flexible electronic devices that can follow any shape, for example, by attaching them to clothing or the body. For example, it is expected to be used in a wide range of fields, such as wearables, sensors, displays, and robots.

[0003] Regarding such stretchable laminated sheets, for example, Patent Document 1 discloses a rubber material having a stretchable base material whose main component is rubber and which has a conductive portion formed by bringing conductive particles into contact with each other.

[0004] Patent Document 2 discloses a conductive member having (A) wiring formed by drying a conductive paste of polyurethane dispersion and conductive particles, and (B) a flexible substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-173226 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-54192 Summary of the Invention [Problem to be solved by the invention]

[0006] A conventional challenge for stretchable laminates with conductive layers has been to keep the initial resistance low while simultaneously preventing an increase in resistance even after repeated stretching. Therefore, an object of the present invention is to provide a new laminate that has a low initial resistance value and can suppress an increase in resistance value even when stretched and contracted repeatedly. [Means for solving the problem]

[0007] For this purpose, the present invention provides a laminate comprising a substrate sheet (A) and a conductive layer (B) containing a binder resin and conductive particles on at least one side thereof, In the conductive layer (B), the content of the conductive particles is 250 to 1000 parts by mass relative to 100 parts by mass of the binder resin, The dispersion value of the particle size of the conductive particles by image analysis method is 0 μm 2 ~80,000μm 2 and The resistance value (R0) of the conductive layer at 0% elongation and the resistance value (R 50 ) and the ratio (R 50 / R0) is 8.0 or less. [Effects of the Invention]

[0008] The laminate proposed by the present invention has a low initial resistance value and can suppress an increase in resistance value even when stretched and contracted repeatedly. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 10 is a plan view showing the application shape of the conductive paste, i.e., the dumbbell shape, when measuring the resistance values ​​for the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described based on embodiments, although the present invention is not limited to the embodiments described below.

[0011] <This laminate> A laminate according to one embodiment of the present invention (referred to as "the present laminate") is a laminate comprising a conductive layer (B) on at least one side of a substrate sheet (A).

[0012] The present laminate only needs to have a conductive layer (B) on at least one side of the base sheet (A). For example, if necessary, another layer may be interposed between the base sheet (A) and the conductive layer (B), or another layer may be laminated on the side of the base sheet (A) opposite the conductive layer (B), or another layer may be laminated on the surface of the conductive layer (B).

[0013] (Resistance change during tensile test) The resistance value of the conductive layer of this laminate when it is 0% elongated (R0) and the resistance value of the conductive layer when it is uniaxially stretched and reaches 50% elongation (R 50 ) and the ratio (R 50 / R0) is preferably 8.0 or less, more preferably 7.5 or less, and even more preferably 7.0 or less. When the base sheet is stretchable and has a conductive layer as described below, the ratio (R 50 / R0) tends to be small, and it was found that the conductivity can be maintained even when the laminate is stretched.

[0014] (Resistance change during expansion and contraction test) It is preferable that the ratio (maximum resistance when stretched / initial resistance) of the maximum electrical resistance of the conductive layer when stretched 40,000 times between 0 and 10% elongation (referred to as "maximum resistance when stretched") divided by the resistance of the conductive layer before stretching (referred to as "initial resistance") of this laminate is 10 or less, preferably 9.0 or less, and even more preferably 8.0 or less. Note that "when stretched 40,000 times between 0 and 10% elongation" means when stretched 40,000 times at 23°C (room temperature) at a stretching rate of 3.33 mm / sec, alternating between 0% elongation and 10% elongation. When the base sheet is stretchable and has a conductive layer as described below, the ratio (maximum resistance value when stretched / initial resistance value) tends to be small, and it has been found that the conductivity can be maintained even when the laminate is stretched and contracted many times.

[0015] <Base sheet (A)> The base sheet (A) is preferably stretchable. Specifically, the tensile elongation at break of the base sheet (A) measured in accordance with JIS K7161:2014 is preferably 25% or more, more preferably 50% or more, and even more preferably 100% or more.

[0016] Examples of materials for the base sheet (A) that can have stretchability include elastomers such as polyethylene terephthalate, vinyl chloride, polyethylene, polyimide, stretchable polyurethane, and other resins. Among these, a sheet containing epoxy resin as the main resin component (referred to as an "elastic epoxy resin sheet") is particularly preferred from the viewpoints of adhesion to the conductive layer and heat resistance. The "main component resin" means the resin with the highest mass proportion among the resin components constituting the base sheet, and can be, for example, 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 100 mass% of the resin components constituting the base sheet.

[0017] (Stretchable epoxy resin sheet) The elastic epoxy resin sheet is a sheet containing epoxy resin as a main component resin, and has a tensile storage modulus of 1.0×10 at 100°C to 200°C. 4 ~6.0×10 7 Pa and / or a tensile breaking elongation measured in accordance with JIS K7161:2014 of 25% or more.

[0018] Here, "the tensile storage modulus at 100°C to 200°C is 1.0 × 10 4 ~6.0×10 7"Pa" means that the tensile storage modulus is 1.0 x 10 Pa over the entire temperature range of 100°C to 200°C. 4 Above 6.0×10 7 This means that the value is maintained at or below Pa. Other numerical ranges are treated similarly. The tensile storage modulus and tensile elongation at break of the stretchable epoxy resin sheet can be measured specifically by the method described in the examples.

[0019] The tensile storage modulus of the elastic epoxy resin sheet at 100°C to 200°C is 1.0×10 4 Pa ~ 6.0 × 10 7 Pa, and more preferably 6.0×10 4 Pa or more or 1.0 x 10 7 Pa or less, among which 4.0 × 10 5 Pa or above or 9.0 x 10 6 It is more preferable that the pressure is 100 Pa or less. The tensile elongation at break of the stretchable epoxy resin sheet measured in accordance with JIS K7161:2014 is preferably 25% or more, more preferably 50% or more, and even more preferably 100% or more. The upper limit is preferably 500% or less.

[0020] An example of such an elastic epoxy resin sheet is an epoxy resin sheet whose main component is an epoxy resin having an aliphatic soft segment introduced into the molecular skeleton. An example of such an epoxy resin sheet is a sheet-like molded article made of a cured product of an epoxy resin composition (hereinafter referred to as "epoxy resin composition (a)") containing, as a main component resin, an epoxy resin (hereinafter referred to as "epoxy resin (α)") having a block structure of rigid and flexible components. "Curing" here means intentionally curing the epoxy resin (α) in the epoxy resin composition (a) by heat and / or light, etc. Note that "intentionally" here also includes cases where, for example, an uncured stretchable epoxy resin sheet is stored for a long period of time, resulting in gradual curing due to the influence of heat and light over time.

[0021] [Epoxy resin composition (a)] The epoxy resin composition (a) preferably contains an epoxy resin having a block structure of a rigid component and a flexible component (hereinafter referred to as "epoxy resin (α)"). The rigid component preferably contains a ring structure having aromaticity, for example, a fused aromatic ring structure such as a benzene ring, a naphthalene ring, an anthracene ring, or a pyrene ring, a structure containing multiple aromatic ring structures such as a biphenol ring, a cardo structure, or a fluorene ring, or a heterocyclic structure such as a pyrrole ring or a thiophene ring. The soft component preferably comprises an aliphatic hydrocarbon, such as an alkylene group having 1 to 8 carbon atoms, an ethylene glycol group, a propylene glycol group, or a butylene glycol group. By including such an epoxy resin (α), it is possible to impart flexibility to the cured product. The epoxy resin composition (a) does not necessarily have to have an epoxy group or an epoxy group-derived structure in both the rigid component and the soft component. That is, it is sufficient that at least one of the rigid component and the soft component has an epoxy group or an epoxy group-derived structure. From the viewpoint of imparting flexibility while retaining the inherent properties of epoxy resins, such as heat resistance and mechanical strength, it is preferable that only one of the rigid component and the soft component has an epoxy group or an epoxy group-derived structure.

[0022] The epoxy resin composition (a) contains at least an epoxy resin (α) and a curing agent, and may contain other epoxy compounds other than the epoxy resin (α), a curing accelerator, other components, and the like, as needed. The epoxy resin composition (a) may contain only one type of epoxy resin (α), or may contain two or more types. Furthermore, any curing agent generally known as an epoxy resin curing agent can be used as the curing agent contained in the epoxy resin composition (a). The epoxy resin composition (a) may contain only one type of curing agent, or may contain two or more types.

[0023] [Epoxy resin (α)]The epoxy resin (α) is not particularly limited, and specific examples thereof include a copolymer of bisphenol F and 1,6-hexanediol diglycidyl ether, a copolymer of 1,6-hexanediol and bisphenol F diglycidyl ether, a copolymer of bisphenol F and 1,4-butanediol diglycidyl ether, a copolymer of 1,4-butanediol and bisphenol F diglycidyl ether, a copolymer of bisphenol A and 1,6-hexanediol diglycidyl ether, a copolymer of 1,6-hexanediol and bisphenol A diglycidyl ether, copolymers of bisphenol A and 1,4-butanediol diglycidyl ether, copolymers of 1,4-butanediol and bisphenol A diglycidyl ether, copolymers of tetramethylbiphenol and 1,6-hexanediol diglycidyl ether, copolymers of 1,6-hexanediol and tetramethylbiphenol diglycidyl ether, copolymers of tetramethylbiphenol and 1,4-butanediol diglycidyl ether, copolymers of 1,4-butanediol and tetramethylbiphenol diglycidyl ether Polymer, copolymer of biphenol and 1,6-hexanediol diglycidyl ether, copolymer of 1,6-hexanediol and biphenol diglycidyl ether, copolymer of biphenol and 1,4-butanediol diglycidyl ether, copolymer of 1,4-butanediol and biphenol diglycidyl ether, copolymer of 1,4-naphthalenediol and 1,6-hexanediol diglycidyl ether, copolymer of 1,6-hexanediol and 1,4-naphthalenediol diglycidyl ether, copolymer of 1,4-naphthalenediol and 1, Examples include a copolymer of 1,4-butanediol and 1,4-naphthalenediol diglycidyl ether, a copolymer of 1,6-naphthalenediol and 1,6-hexanediol diglycidyl ether, a copolymer of 1,6-hexanediol and 1,6-naphthalenediol diglycidyl ether, a copolymer of 1,6-naphthalenediol and 1,4-butanediol diglycidyl ether, and a copolymer of 1,4-butanediol and 1,6-naphthalenediol diglycidyl ether. These may be used alone or in any combination and ratio of two or more. Among these, from the viewpoint of flexibility, the epoxy resin (α) is preferably a copolymer of bisphenol F and 1,6-hexanediol diglycidyl ether.

[0024] [Hardening agent] The curing agent used in the epoxy resin composition (a) refers to a substance that contributes to the crosslinking reaction between the crosslinking groups of the epoxy resin (α). Such curing agents are not particularly limited, and any of those generally known as epoxy resin curing agents can be used. Examples include phenol-based curing agents, amine-based curing agents such as aliphatic amines, polyetheramines, alicyclic amines, and aromatic amines, acid anhydride-based curing agents, amide-based curing agents, tertiary amines, imidazole and its derivatives, organic phosphines, phosphonium salts, tetraphenylboron salts, organic acid dihydrazides, boron halide amine complexes, polymercaptan-based curing agents, isocyanate-based curing agents, and blocked isocyanate-based curing agents. From the viewpoints of high transparency and little coloration, curing agents having an alicyclic structure are preferred.

[0025] The curing agent having an alicyclic structure is not particularly limited as long as it has an alicyclic structure and contributes to the crosslinking reaction and / or chain extension reaction between epoxy groups of the epoxy resin, and examples thereof include alicyclic polyamines and alicyclic acid anhydrides. More specific examples include 1,4-diazabicyclo-2,2,2-octane, 1,8-diazabicyclo-5,4,0-undec-7-ene, N,N'-dimethylpiperazine, N-aminoethylpiperazine, menthene diamine, isophorone diamine, hexamethylenetetramine, methylenebiscyclohexanamine, 1,3-bisaminomethylcyclohexane, norbornene diamine, 1,2-diaminocyclohexane, and modified alicyclic polyamines obtained by epoxy-modifying, ethylene oxide-modifying, dimer acid-modifying, Mannich-modifying, Michael addition-modifying, thiourea condensing-modifying, or ketiminizing these alicyclic polyamines; hexahydrophthalic anhydride; and methylhexahydrophthalic anhydride. Of these, alicyclic polyamines are preferred, and among these, isophoronediamine, hexamethylenetetramine, methylenebiscyclohexanamine, 1,3-bisaminomethylcyclohexane, norbornenediamine, 1,2-diaminocyclohexane, and modified products thereof are particularly preferred.

[0026] Commercially available curing agents having an alicyclic structure can also be used, such as "jER Cure 113" and "jER Cure ST-14" manufactured by Mitsubishi Chemical Corporation, and "Rikacid MH-700" manufactured by New Japan Chemical Co., Ltd.

[0027] The content of the curing agent in the epoxy resin composition (a) (when a curing agent other than the curing agent having an alicyclic structure is used, the total content of the curing agent having an alicyclic structure and the other curing agent) is preferably 0.1 to 100 parts by mass per 100 parts by mass of the epoxy resin (α) (when an epoxy compound other than the epoxy resin (α) described below is contained, the total content of the epoxy resin (α) and the other epoxy resin)), more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 40 parts by mass or less.

[0028] [Other epoxy compounds] When the epoxy resin composition (a) contains an epoxy compound other than the epoxy resin (α), examples of the other epoxy compound include one or more of various epoxy resins such as glycidyl ether type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, biphenyl type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, linear aliphatic epoxy resins, alicyclic epoxy resins, and heterocyclic epoxy resins.

[0029] When the epoxy resin composition (a) contains the epoxy resin (α) and other epoxy compounds, the proportion of the other epoxy compounds in the total epoxy components as solids in the epoxy resin composition is preferably 5% by mass or more, more preferably 10% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less. When the proportion of the other epoxy compounds is equal to or greater than the above lower limit, the physical property-improving effect of blending the other epoxy compounds can be fully obtained. On the other hand, when the proportion of the other epoxy compounds is equal to or less than the above upper limit, the softness and flexibility-improving effect of the epoxy resin (α) can be fully obtained.

[0030] In the present invention, the term "solid content" refers to components excluding the solvent, and includes not only solid epoxy resins or epoxy compounds, but also semi-solid and viscous liquid substances. The term "total epoxy components" refers to the total of the epoxy resin (α) and the other epoxy compounds described above.

[0031] [solvent] The epoxy resin composition (a) may be diluted by blending a solvent to adjust the viscosity of the epoxy resin composition appropriately when handling it for forming a coating film, etc. The solvent in the epoxy resin composition (a) is used to ensure the ease of handling and workability when molding the epoxy resin composition, and there is no particular limitation on the amount used. In the present invention, the terms "solvent" and "solvents" are used to distinguish between them depending on the form of use, but the same or different types may be used independently.

[0032] Examples of solvents that may be contained in the epoxy resin composition (a) include acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, N,N-dimethylformamide, N,N-dimethylacetamide, methanol, and ethanol. Two or more of these solvents may be used as mixed solvents, as appropriate.

[0033] [Other ingredients] The epoxy resin composition (a) may contain other components in addition to the components listed above. The other components can be used in appropriate combination depending on the desired physical properties of the epoxy resin composition. For example, to improve various properties such as reducing the cure shrinkage rate and the thermal expansion rate of the resulting cured product, inorganic fillers can be blended into the epoxy resin composition (a) to expand its applications in the electrical and electronic fields, particularly as a liquid semiconductor encapsulant. Organic fillers such as rubber particles and acrylic particles may also be included to impart toughness.

[0034] Usable inorganic fillers include powdered reinforcing agents and fillers, for example, metal oxides such as aluminum oxide and magnesium oxide, metal carbonates such as calcium carbonate and magnesium carbonate, diatomaceous earth powder, basic magnesium silicate, calcined clay, finely powdered silica, fused silica, silicon compounds such as zeolite, metal hydroxides such as aluminum hydroxide, and others, such as kaolin, mica, quartz powder, graphite, carbon black, carbon nanotubes, molybdenum disulfide, boron nitride, and aluminum nitride. When an inorganic filler is added, it is necessary to ensure that the tensile storage modulus of the epoxy resin sheet layer and its laminate falls within the above range. The amount of these inorganic fillers added is preferably 900 parts by mass or less per 100 parts by mass of the epoxy resin (the total of the epoxy resin (α) and other epoxy compounds used as needed, the same applies hereinafter) and the curing agent. On the other hand, the lower limit is not particularly limited, but is preferably 1.0 part by mass or more.

[0035] Furthermore, it is also possible to compound fibrous reinforcing agents or fillers. Examples include glass fibers, ceramic fibers, carbon fibers, alumina fibers, silicon carbide fibers, boron fibers, aramid fibers, cellulose nanofibers, and cellulose nanocrystals. Cloths or nonwoven fabrics of organic fibers or inorganic fibers can also be used. Furthermore, these inorganic fillers, fibers, cloths, and nonwoven fabrics can also be surface-treated with a silane coupling agent, a titanate-based coupling agent, an aluminate-based coupling agent, or a primer.

[0036] Furthermore, the epoxy resin composition (a) may contain, as necessary, coupling agents, plasticizers, diluents, flexibility-imparting agents, dispersants, wetting agents, colorants, pigments, UV absorbers, light stabilizers such as hindered amine light stabilizers, antioxidants, defoamers, mold release agents, flow control agents, etc. The amount of these added is preferably 20 parts by mass or less per 100 parts by mass of the epoxy resin and curing agent combined. On the other hand, the lower limit is not particularly limited, but is preferably 0.1 parts by mass or more.

[0037] Furthermore, to improve the resin properties of the final coating film, various curable monomers, oligomers, and synthetic resins may be blended into the epoxy resin composition (a) as needed. Examples include cyanate ester resins, acrylic resins, silicone resins, polyester resins, and combinations of two or more of these resins. The blending ratio of these resins is preferably within a range that does not impair the inherent properties of the epoxy resin composition (a), i.e., 50 parts by mass or less per 100 parts by mass of the epoxy resin and curing agent combined. While the lower limit is not particularly limited, 1.0 part by mass or more is preferred.

[0038] The stretchable epoxy resin sheet is preferably made of a cured product obtained by curing an epoxy resin composition (a) containing an epoxy resin and an alicyclic polyamine.

[0039] Thickness The thickness of the stretchable epoxy resin sheet is preferably 10 μm to 500 μm, more preferably 20 μm or more and 200 μm or less, even more preferably 30 μm or more and 150 μm or less, even more preferably 50 μm or more and 140 μm or less. The thickness (average thickness) of the stretchable epoxy resin sheet can be measured with a micrometer and calculated as the arithmetic average.

[0040] [Manufacturing method] The stretchable epoxy resin sheet can be produced by curing the epoxy resin composition (a) in a sheet shape of a predetermined thickness, or by forming a semi-cured product obtained from the epoxy resin composition (a) into a sheet shape of a predetermined thickness and further curing it.

[0041] The method for curing the epoxy resin composition (a) varies depending on the components and amounts of the components in the epoxy resin composition (a) and the shape of the compounded product (e.g., the thickness of a sheet), but typically includes a method of heating at 23 to 200°C for 5 minutes to 24 hours. This heating is preferably carried out as a two-stage process, consisting of a primary heating at 23 to 160°C for 5 minutes to 24 hours, a secondary heating at 80 to 200°C, which is 40 to 177°C higher than the primary heating temperature, for 5 minutes to 24 hours, and a third heating at 100 to 200°C, which is higher than the secondary heating temperature, for 5 minutes to 24 hours, in order to reduce poor curing.

[0042] When producing a cured product as a semi-cured product, the curing reaction of the epoxy resin composition (a) may be allowed to proceed to an extent that the shape can be maintained by heating, etc. When the epoxy resin composition (a) contains a solvent, most of the solvent is removed by techniques such as heating, reduced pressure, and air drying, but 5% by mass or less of the solvent may remain in the semi-cured product.

[0043] The present laminate may be one in which the elastic epoxy resin sheet is in a semi-cured state, which may facilitate the formation of a wound body and improve secondary processability.

[0044] [Surface texture] The surface of the stretchable epoxy resin sheet is preferably roughened from the viewpoint of more suitably maintaining the adhesiveness of the conductive layer (B) when stretched. That is, the surface roughness of the stretchable epoxy resin sheet is preferably 300 nm to 2500 nm in terms of arithmetic mean roughness Sa as defined in JIS B0601:2001, more preferably 400 nm or more or 2000 nm or less, and even more preferably 500 nm or more or 1500 nm or less. Furthermore, the maximum height Sz defined in JIS B0601:2001 is preferably 10,000 nm to 50,000 nm, more preferably 20,000 nm or more or 40,000 nm or less, and even more preferably 25,000 nm or more or 35,000 nm or less. The method for roughening the surface of the elastic epoxy resin sheet is not particularly limited, and various methods can be used, such as transfer treatments such as embossing roll transfer, embossing belt transfer, and embossing film transfer, sandblasting, shot blasting, etching, engraving, and surface crystallization.

[0045] (Thickness) From the viewpoint of handleability, the thickness of the base sheet (A) is preferably 50 μm or more, more preferably 75 μm or more, and even more preferably 100 μm or more, while from the viewpoint of flexibility, the thickness is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 600 μm or less.

[0046] <Conductive layer (B)> The conductive layer (B) is a layer containing a binder resin and conductive particles, and is preferably stretchable.

[0047] The conductive layer (B) may have any shape in plan view, such as various wiring patterns and mesh patterns.

[0048] However, the length in the stretching direction of the linear portions constituting the pattern of the conductive layer (B) is preferably 100 μm or more, more preferably 500 μm or more, and even more preferably 1000 μm or more, from the viewpoint of preventing breakage during stretching and further suppressing an increase in resistance value. Furthermore, the length of the linear portions constituting the pattern of the conductive layer (B) in the direction perpendicular to the direction of expansion and contraction is preferably 100 μm or more, more preferably 500 μm or more, and even more preferably 1000 μm or more, from the viewpoint of preventing breakage during expansion and contraction and further suppressing an increase in resistance value.

[0049] The thickness of the conductive layer (B), for example, when the thickness of the conductive layer (B) exhibits various wiring patterns, is preferably smaller than the thickness of the base sheet (A) from the viewpoint of ease of processing, and is more preferably 1% to 60% of the thickness of the base sheet (A), more preferably 2% or more or 50% or less, and even more preferably 3% or more or 40% or less. Furthermore, the thickness of the conductive layer (B) is preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more, from the viewpoint of preventing breakage when stretched and further suppressing an increase in resistance value.

[0050] (binder resin) The binder resin is preferably a resin having elasticity, and more preferably has heat resistance. Examples of the binder resin include acrylic resin, olefin resin, polyurethane resin, polyester resin, polyamide resin, polyurea resin, and fluororesin. Furthermore, elastomers are also suitable as binder resins because of their stretchability, and examples of such elastomers include thermosetting elastomers such as silicone rubber, urethane rubber, and fluororubber.

[0051] Among these, when the base sheet (A) is an elastic epoxy resin sheet, thermoplastic polyurethanes are preferred, and among these, polyester polyurethanes are particularly preferred. Polyester polyurethane has the advantage of being superior in stretchability and heat resistance compared to, for example, aliphatic polyurethane or aromatic siloxane.

[0052] The thermoplastic polyurethane resin is a resin obtained by polymerizing an isocyanate compound and a hydroxyl group component, such as a polyester polyol or a polyether polyol. Examples of the isocyanate compound include diisocyanates such as trimethylene diisocyanate (TDI), hexamethylene diisocyanate (HDI), methylenebis(4,1-phenylene) diisocyanate (MDI), 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI), and xylylene diisocyanate (XDI), as well as trimethylolpropane adducts of these diisocyanates, isocyanurates which are trimers of these diisocyanates, biuret conjugates of these diisocyanates, and polyisocyanates having two or more isocyanate groups in the molecule, such as polymeric diisocyanates. Examples of the hydroxyl group component include the hydroxyl group component constituting the polyester resin (G4) described below, as well as polyester polyols, polyether polyols, and polyurethane polyols which are reaction products of these polyols with polyisocyanates.

[0053] (Conductive particles) Examples of conductive particles include metal particles such as silver particles, copper particles, and iron particles, as well as carbon black, carbon fiber, and carbon-based fine particles. Particles made of any material, such as particles having the conductive particles as core materials and having part or all of their surfaces coated with a different conductive material, such as gold, silver, copper, nickel, or tin, may also be used. However, these are not intended to be limiting, and any conductive material can be used. These materials can be used alone or in combination of two or more.

[0054] The shape of the conductive particles is not particularly limited, and examples thereof include spherical, oval-spherical, needle-like (oval-spherical), flake-like (scale-like), irregular shape, etc. Among these, spherical or oval-spherical shapes are preferred from the viewpoint of being able to maintain the shape even after repeated expansion and contraction and maintaining constant conductivity.

[0055] The conductive particles preferably have an average particle size of 10 to 1000 μm, more preferably 100 μm or more or 500 μm or less, and even more preferably 200 μm or more or 300 μm or less, as determined by image analysis. If the average particle size of the conductive particles is equal to or greater than the lower limit, the conductive particles in the conductive layer are less likely to aggregate and the dispersion state is improved, which is preferable. On the other hand, if the average particle size is equal to or less than the upper limit, the surface area of ​​the conductive particles increases and the particles are more likely to come into contact with each other, which is preferable.

[0056] The conductive particles have a particle size distribution of 80,000 μm as determined by image analysis. 2 Preferably, it is: If the dispersion value of particle size is large, that is, if there are significantly large particles, stress is likely to concentrate at the interfaces of the large particles, which may easily become the starting points of cracks or the like. From this point of view, the dispersion value of the conductive particles is 80000 μm 2 Preferably it is less than 70,000 μm 2 Below, among them, 60,000 μm 2 More preferably, it is: On the other hand, the lower limit of the dispersion value of the conductive particles is not particularly limited, and is 0 μm 2 It is sufficient if it is more than 1000 μm, and practically it is preferable to use 1000 μm. 2 That's all.

[0057] In the conductive layer (B), the content of the conductive particles is preferably 250 to 1000 parts by mass per 100 parts by mass of the binder resin. If the content of the conductive particles is too low, it may be difficult to obtain the desired conductivity and to keep the initial resistance low. On the other hand, if the content of the conductive particles is too high, in other words, if the content of the binder is too low, the conductive layer (B) may not be able to follow expansion and contraction, and it may be difficult to suppress an increase in resistance when the layer expands and contracts. From this viewpoint, the content of the conductive particles per 100 parts by mass of the binder resin is preferably 250 to 1000 parts by mass, more preferably 350 parts by mass or more or 750 parts by mass or less, even more preferably 380 parts by mass or more or 700 parts by mass or less, and even more preferably 400 parts by mass or more or 650 parts by mass or less.

[0058] <Manufacturing method> The laminate can be produced, for example, by applying a conductive paste containing a binder resin and conductive particles to a substrate sheet (A) and solidifying the conductive paste. That is, the conductive layer (B) is typically a solidified patterned conductive paste. However, the method for producing the present laminate is not limited to this method.

[0059] (Conductive paste) The conductive paste preferably contains a binder resin, conductive particles, a solvent, and, if necessary, other additives.

[0060] In this case, as the solvent, a known organic solvent capable of dissolving the binder resin can be used. For example, dihydroterpinyl acetate, isobornyl acetate, isobornyl propionate, isobornyl butyrate, isobornyl isobutyrate, ethylene glycol monobutyl ether acetate, dipropylene glycol methyl ether acetate, 3-methoxy-3-methylbutyl acetate, 1-methoxypropyl-2-acetate and other acetate solvents, ethyl acetate, propyl acetate, isobutyl acetate, butyl acetate and other acetate ester solvents, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexane, 4-hydroxy-4-methyl-2-pentane, isophorone and other ketone solvents, terpineol, dihydroterpineol and other terpene solvents, tridecane, nonane, cyclohexane and other aliphatic hydrocarbon solvents, ethylene glycol ethers, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether and other glycol ether solvents can be mentioned. These may be used alone or in combination of two or more. Among these, acetate-based solvents are particularly preferred from the viewpoint of being able to reduce the drying temperature and drying time. By using acetate-based solvents, a conductive layer (B) having elasticity and conductivity can be formed under drying conditions of a drying temperature of 20 to 130°C and a drying time of 10 to 90 minutes, which are favorable in terms of reducing thermal damage to the substrate sheet and the conductive layer.

[0061] The conductive paste may be applied by any method, such as a printing method or a coating method. Examples of printing methods include screen printing, offset printing, inkjet printing, flexographic printing, gravure printing, stamping, dispensing, squeegee printing, silk screen printing, spraying, and brush painting.

[0062] After applying the conductive paste to the base sheet (A), the conductive paste can be solidified by heating to volatilize the solvent. By volatilizing the solvent in this way, the conductive particles are bound by the binder, and an elastic conductive layer is formed. In this case, the heating temperature can be, for example, 20°C or higher and 150°C, and from the viewpoint of saving energy through low-temperature drying and suppressing thermal damage to the base sheet (A), it is more preferable that the heating temperature be 130°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower. The heating time can be, for example, from 0.1 hours to 50 hours, and from the viewpoint of shortening the process time and suppressing thermal damage to the base sheet (A), it is more preferably 10 minutes or more or 120 minutes or less, more preferably 100 minutes or less, more preferably 90 minutes or less, even more preferably 60 minutes or less, even more preferably 40 minutes or less, and even more preferably 30 minutes or less. The drying atmosphere may be a non-oxidizing atmosphere such as an inert gas (for example, nitrogen gas) atmosphere, air, a vacuum atmosphere, an oxygen or mixed gas atmosphere, or an air stream.

[0063] <Uses of this laminate> Because the laminate has stretchability, this characteristic can be utilized to find applications in a wide range of fields, such as wearable devices, sensors, displays, robots, and electronic devices.

[0064] <Explanation of terms> In the present invention, the term "film" also includes the term "sheet", and the term "sheet" also includes the term "film".

[0065] In the present invention, when it is stated that "X to Y" (X and Y are any numbers), unless otherwise specified, it means "X or more and Y or less", and also means "preferably larger than X" or "preferably smaller than Y". Furthermore, when it is stated that the amount is "X or more" (X is any number), it also means that the amount is "preferably greater than X" unless otherwise specified, and when it is stated that the amount is "Y or less" (Y is any number), it also means that the amount is "preferably smaller than Y" unless otherwise specified. [Example]

[0066] The present invention is further illustrated by the following examples, which are not intended to limit the invention in any way.

[0067] <Material> The materials used in the following examples and comparative examples will be described.

[0068] (Stretchable epoxy resin sheet) An epoxy resin composition was prepared by blending 100 parts by weight of the following epoxy resin (α) with 8.5 parts by weight of a curing agent (alicyclic polyamine, "jER Cure ST-14" manufactured by Mitsubishi Chemical Corporation). This epoxy resin composition was sandwiched between two peelable, surface-roughened carrier sheets described below and heat-treated at 40°C for 16 hours, followed by a further heat treatment at 80°C for 6 hours, to obtain a laminate comprising an elastic epoxy resin sheet. The thickness of the elastic epoxy resin sheet after heat treatment was measured and found to be 100 μm.

[0069] This elastic epoxy resin sheet was measured by the dynamic viscoelasticity measurement method in accordance with JIS K7244 using a viscoelasticity spectrometer ("DVA-200" manufactured by IT Measurement & Control Co., Ltd.) under the conditions of a frequency of 1 Hz, strain of 0.1%, temperature range of 50 to 250°C, heating rate of 3°C / min, and double-support tensile mode. The tensile storage modulus at 100 to 200°C was 1.0 × 10 6 ~1.0×10 7 In particular, the tensile storage modulus at 100°C was 2.4 × 10 6 The tensile storage modulus at 150°C is 2.6×10 6 The tensile storage modulus at 200°C is 2.4×10 6 It was Pa. The elastic epoxy resin sheet had an arithmetic mean roughness Sa of 907 nm and a maximum height Sz of 31,948 nm, as defined in JIS B0601:2001. Furthermore, the tensile elongation at break of the stretchable epoxy resin sheet measured in accordance with JIS K7161:2014 was 324%.

[0070] [Epoxy resin (α)] A 1-L glass flask equipped with a stirrer, dropping funnel, and thermometer was charged with 141.8 parts by mass of 1,6-hexanediol preheated to 45°C and 0.51 parts by mass of boron trifluoride ethyl ether, and the mixture was heated to 80°C. 244.3 parts by mass of epichlorohydrin was added dropwise over a period of time so as not to exceed 85°C. The mixture was aged for 1 hour while maintaining the temperature at 80-85°C, and then cooled to 45°C. 528.0 parts by mass of a 22% by mass aqueous sodium hydroxide solution was added, and the mixture was vigorously stirred at 45°C for 4 hours. The mixture was cooled to room temperature, the aqueous phase was separated, and the mixture was heated under reduced pressure to remove unreacted epichlorohydrin and water, yielding 283.6 parts by mass of crude 1,6-hexanediol diglycidyl ether. This crude 1,6-hexanediol diglycidyl ether was purified by distillation using an Oldershaw distillation column (15 plates), and the fraction at a pressure of 1300 Pa and 170 to 190°C was taken as the main fraction, thereby obtaining 127.6 parts by mass of 1,6-hexanediol diglycidyl ether having a diglycidyl purity of 97% by mass as determined by gas chromatography, a total chlorine content of 0.15% by mass, and an epoxy equivalent of 116 g / eq. 100 parts by mass of the 1,6-hexanediol diglycidyl ether, 69.3 parts by mass of bisphenol F (phenolic hydroxyl group equivalent: 100 g / eq), and 0.13 parts by mass of ethyltriphenylphosphonium iodide (30% by mass solution in methyl cellosolve) were placed in a pressure-resistant reaction vessel, and a polymerization reaction was carried out at 165 to 170°C for 5 hours under a nitrogen gas atmosphere, thereby obtaining a copolymer of bisphenol F and 1,6-hexanediol glycidyl ether having an epoxy equivalent of 1,000 g / eq and a number average molecular weight of 3,000.

[0071] [Carrier Sheet] The carrier sheet used was an OPP / PET film (a two-layer film made by bonding together a 50 μm thick unmodified polypropylene (oriented polypropylene: OPP) film and a 50 μm thick biaxially oriented polyethylene terephthalate (PET) film), with the release surface roughened by adding fine particles.

[0072] (Conductive paste A) A conductive paste containing 11 parts by mass of polyester polyurethane, 59 parts by mass of silver particles, and 30 parts by mass of an acetate-based solvent was prepared. The parts by mass of silver per 100 parts by mass of binder resin in the conductive layer after the conductive paste was applied and dried was calculated on the assumption that the parts by mass of the solvent component in the conductive layer after drying was 0.

[0073] (Conductive paste B) A conductive paste containing 28 parts by mass of aliphatic polyurethane, 66 parts by mass of silver particles, and 6 parts by mass of an alcohol-based solvent was prepared. The parts by mass of silver per 100 parts by mass of binder resin in the conductive layer after the conductive paste was applied and dried was calculated in the same manner as for conductive paste A.

[0074] (Conductive paste C) A conductive paste containing 14 parts by mass of aromatic siloxane, 84 parts by mass of silver particles, and 3 parts by mass of an alcohol-based solvent was prepared. The parts by mass of silver per 100 parts by mass of binder resin in the conductive layer after the conductive paste was applied and dried was calculated in the same manner as for conductive paste A.

[0075] Example 1 The carrier sheet of the laminate with the elastic epoxy resin sheet was peeled off, and the conductive paste A was applied onto the 100 μm thick elastic epoxy resin sheet by screen printing in the form of a dumbbell as shown in Figure 1, i.e., a dumbbell shape with a gauge length of 10 mm and a width of 5 mm (total length 36 mm, maximum width 11 mm). After application, heat treatment was carried out in an oven at 80°C for 30 minutes in an air atmosphere to volatilize the solvent component of the conductive paste, thereby forming a stretchable conductive layer and obtaining a laminate A (sample). The thickness of the conductive layer in the laminate A was 30 μm.

[0076] <Comparative Example 1> A laminate B (sample) was obtained in the same manner as in Example 1, except that conductive paste B was applied instead of conductive paste A, the drying temperature was 100° C., and the drying time was 60 minutes. The thickness of the conductive layer in the laminate B was 30 μm.

[0077] <Comparative Example 2> A laminate C (sample) was obtained in the same manner as in Example 1, except that conductive paste C was applied instead of conductive paste A, the drying temperature was 130° C., and the drying time was 15 minutes. The thickness of the conductive layer in the laminate C was 30 μm.

[0078] <Evaluation and measurement methods> (1) Tensile storage modulus The elastic epoxy resin sheet was measured using a viscoelasticity spectrometer ("DVA-200" manufactured by IT Measurement & Control Co., Ltd.) under the dynamic viscoelasticity measurement method in accordance with JIS K7244, with a frequency of 1 Hz, strain of 0.1%, temperature range of 50 to 250°C, heating rate of 3°C / min, and double-support tensile mode, and the tensile storage modulus was determined at 100°C, 150°C, and 200°C.

[0079] (2) Surface roughness The arithmetic mean roughness Sa and maximum height Sz of the surface of the elastic epoxy resin sheet were measured in accordance with JIS B0601:2001. The surface roughness Sa and Sz were measured using a white light interference microscope "Contour GTX" (manufactured by Bruker). The laminate with the elastic epoxy resin sheet was cut into a 10 cm square, and then the carrier sheet was peeled off. The surface of the peeled side of the elastic epoxy resin sheet was measured under the following conditions, and the surface roughness Sa and Sz were calculated from the analysis results of the image. Filter: White Objective: 5× FOVLens: 1.0× Backscan length: 5 Scan length: 25

[0080] (3) Tensile elongation at break The elastic epoxy resin sheet was measured in accordance with JIS K7161:2014 under conditions of 23°C and 50% humidity in a one-sided tension mode, and the elongation at which the film broke (tensile breaking elongation) was measured at a tension speed of 200 mm / min.

[0081] (4) Measurement of the particle size of conductive particles in the conductive layer The surface of the conductive layer of the laminate (sample) obtained in the examples and comparative examples was subjected to image analysis using a scanning electron microscope (SEM), and the average particle size ("average particle size [μm]" in the table) and dispersion value ("dispersion [μm]" in the table) of the silver particles in the conductive layer were determined. 2 ]”). Specifically, the conductive layers of the laminates (samples) obtained in the examples and comparative examples were photographed with backscattered electron images magnified 10,000 times and analyzed using the image analysis software "ImageJ." The analysis procedure is shown below. The image was cut out so that 1 pixel was 9.8425 μm, and the image was binarized so that the silver particle parts were black and the other parts were white. The black parts of the binarized image were corrected using the median, and the value was set to 1.0. Next, a thinning process was performed, and each particle was approximated to an ellipse. Five hundred particles were randomly selected from each elliptical approximation, and the major axis length (major axis diameter) of each was calculated. A particle size histogram was created using the major axis diameter, and the average particle size and dispersion value were calculated from this histogram. The silver particles in the conductive layer of the laminate (sample) obtained in Example 1 were spherical or oval-spherical in shape.

[0082] (5) Resistance value during tensile test Test pieces having a width of 12 mm and a length of 35 mm were cut out from the laminates (samples) obtained in the examples and comparative examples to prepare test pieces for measuring resistance values. The resistance value during the tensile test and the initial resistance value of the test piece were measured using a Tektronix multimeter "DMM4050" using a two-wire resistance measurement method. The sampling frequency was set to 10 Hz and the measurement was carried out at a room temperature of 23°C. The test piece for measuring the resistance value was uniaxially stretched, and the resistance value was measured by the above-mentioned method, and the change in the resistance value when stretched was measured. The test piece was stretched from 0% to 100% elongation using an electric slider "EAS4NY-D010-AZAAD-3" manufactured by Oriental Motor Co., Ltd. The stretching speed was 1.00 mm / sec. At this time, the resistance value R when the test piece was stretched by 50% was 50 The resistance value of the test piece before stretching, which had an elongation of 0%, was taken as the initial resistance value (R0).

[0083] (6) Resistance value during expansion and contraction test Test pieces having a width of 12 mm and a length of 35 mm were cut out from the laminates (samples) obtained in the examples and comparative examples to prepare test pieces for measuring resistance values. The resistance values ​​of the test specimens during expansion and contraction and the initial resistance values ​​were measured using a Tektronix multimeter "DMM4050" using a two-wire resistance measurement method. The sampling frequency was set to 0.1 Hz and the measurements were carried out at a room temperature of 23°C. Using an electric slider "EAS4NY-D010-AZAAD-3" manufactured by Oriental Motor Co., Ltd., the sample was stretched and contracted by alternating between 0% and 10% elongation. The number of stretches was set to 40,000. The stretching speed during this time was set to 3.33 mm / sec. During this stretching test, the resistance of the test piece was continuously measured, and the maximum value was designated as the "maximum resistance during stretching." Meanwhile, the resistance of the test piece before the stretching test was designated as the "initial resistance." The value obtained by dividing the "maximum resistance during stretching" by the "initial resistance" was also calculated.

[0084] [Table 1]

[0085] <Results / Discussion> The conductive paste used in Example 1 had an appropriate ratio of silver particles to binder, and the silver particles had a narrow particle size distribution, so that when the base sheet, the elastic epoxy resin film, expanded and contracted, the conductive layer also expanded and contracted accordingly. As a result, Laminate A had a low initial resistance value, and was able to suppress an increase in resistance value even after repeated expansion and contraction. On the other hand, since the conductive paste of Comparative Example 1 contained a small proportion of silver particles relative to the binder, the laminate B had high initial resistance and resistance during expansion and contraction. Furthermore, the conductive paste of Comparative Example 2 had a wide particle size distribution of silver particles, with significantly large aggregates of silver particles scattered throughout, and Laminate C had high resistance during expansion and contraction. This is thought to be because stress was concentrated near the aggregate interfaces as the substrate expanded and contracted, and the vicinity of the aggregate interfaces became the starting point for cracks.

[0086] From the results of these examples and comparative examples, as well as the results of tests conducted so far by the present invention, it was found that if the content ratio of conductive particles to binder is within an appropriate range and the particle size distribution of the conductive particles is also within an appropriate range, the initial resistance can be reduced, and cracks caused by expansion and contraction and the resulting breakage are unlikely to occur, so the resistance value does not increase even during the expansion and contraction test process.

Claims

1. A laminate comprising a substrate sheet (A) and a conductive layer (B) containing a binder resin and conductive particles on at least one side of the substrate sheet (A), The base sheet (A) has a tensile elongation at break measured in accordance with JIS K7161:2014 of 25% or more, the binder resin is a polyester-based polyurethane, the content of the conductive particles in the conductive layer (B) is 250 to 1000 parts by mass relative to 100 parts by mass of the binder resin, The dispersion value of the particle diameter of the conductive particles in the conductive layer (B) determined by image analysis is 0 μm. 2 ~80,000 μm 2 and the conductive particles in the conductive layer (B) have an average particle size of 10 to 1000 μm as determined by image analysis; The resistance value of the conductive layer when the elongation is 0% (R ０ ) and the resistance value (R ５０ ) and the ratio (R ５０ / R ０ ) is 8.0 or less.

2. A laminate comprising a substrate sheet (A) and a conductive layer (B) containing a binder resin and conductive particles on at least one side of the substrate sheet (A), the binder resin is a polyester-based polyurethane, the base sheet (A) is a sheet containing an epoxy resin as a main component resin, and has a tensile elongation at break measured in accordance with JIS K7161:2014 of 25% or more; the content of the conductive particles in the conductive layer (B) is 250 to 1000 parts by mass relative to 100 parts by mass of the binder resin, The dispersion value of the particle diameter of the conductive particles in the conductive layer (B) determined by image analysis is 0 μm. 2 ~80,000 μm 2 and The resistance value of the conductive layer when the elongation is 0% (R ０ ) and the resistance value (R ５０ ) and the ratio (R ５０ / R ０ ) is 8.0 or less.

3. A laminate as described in claim 1 or 2, wherein the base sheet (A) comprises a cured product of an epoxy resin composition (a) containing an epoxy resin as a main component resin, and the epoxy resin composition (a) comprises an epoxy resin (α) having a block structure having a rigid component and a flexible component, and the rigid component comprises a ring structure having aromaticity, and the flexible component comprises an aliphatic hydrocarbon group.

4. A laminate as described in Claim 3, wherein the epoxy resin (α) is a copolymer of bisphenol F and 1,6-hexanediol diglycidyl ether.

5. 5. The laminate according to claim 1, wherein the conductive layer (B) is a patterned conductive paste that has been solidified.

6. The laminate according to any one of claims 1 to 5, wherein the thickness of the conductive layer (B) is smaller than the thickness of the base sheet (A).

7. A sensor comprising the laminate according to any one of claims 1 to 6.

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