JP7358670B1 - connection body - Google Patents

Abstract

An object of the present invention is to provide a connecting body that can suppress deterioration of interlayer adhesion over time. [Solution] A connection body having a first metal base material, a conductive adhesive layer, and a second metal base material in this order, wherein the conductive adhesive layer is attached to an adhesive and a surface of a resin core. conductive particles having a conductive layer, and the adhesive comprises a cured product of an acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g and a glycidylamine-based epoxy compound. [Selection diagram] Figure 1

Description

The present invention relates to a connecting body.

2. Description of the Related Art Connecting bodies in which two conductive members are electrically connected via an adhesive layer are sometimes used as materials for electrical and electronic devices.
Examples of the adhesive used for the connection body include an isotropically conductive adhesive and an anisotropically conductive adhesive.

A typical example of an isotropic conductive adhesive is an adhesive using carbon black as a conductive agent. The isotropic conductive adhesive needs to contain a large amount of a conductive agent in order to make an electrical connection. For this reason, a connection body using an isotropically conductive adhesive has a problem in that interlayer adhesion tends to decrease. Furthermore, a connection body using an isotropically conductive adhesive has a problem in that the resistance value cannot be sufficiently reduced.

As a connection body using an anisotropic conductive adhesive, one using conductive particles having a conductive layer on the surface of a resin core has been proposed (for example, Patent Document 1).

Japanese Patent Application Publication No. 2017-182709

Since the connecting body of Patent Document 1 does not need to contain a large amount of conductive particles in the adhesive, it can be expected to improve interlayer adhesion. However, in the connection body of Patent Document 1, the interlayer adhesion may deteriorate over time.

An object of the present invention is to provide a connecting body in which deterioration in interlayer adhesion over time is suppressed.

As a result of intensive research, the present inventors found that the cause of the deterioration of the interlayer adhesion of the connection body over time is the influence of chemicals such as electrolyte. As a result of further research, the present inventors were able to solve the above problem.

The present invention provides the following [1] to [9].
[1] A connection body having a first metal base material, a conductive adhesive layer, and a second metal base material in this order, wherein the conductive adhesive layer includes an adhesive and a conductive layer on the surface of a resin core. conductive particles having a layer, and the adhesive comprises a cured product of an acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g and a glycidylamine-based epoxy compound.
[2] The connector according to [1], wherein the glycidylamine-based epoxy compound has an epoxy equivalent of 70 g/eq or more and 140 g/eq or less.
[3] The connector according to [1] or [2], which contains 0.1 parts by mass or more and 27.5 parts by mass or less of the glycidylamine-based epoxy compound based on 100 parts by mass of the acid-modified polyolefin resin.
[4] The connector according to any one of [1] to [3], wherein the acid-modified polyolefin resin has an acid value of 0.1 mgKOH/g or more and less than 15.0 mgKOH/g.
[5] The connected body according to any one of [1] to [4], wherein the melting point of the cured product is 60°C or more and 115°C or less.
[6] The connecting body according to any one of [1] to [5], which contains the conductive particles in an amount of 0.1 parts by mass or more and 2.0 parts by mass or less, based on 100 parts by mass of the adhesive.
[7] When the average thickness of the conductive adhesive layer is defined as Tn [μm] and the average diameter of the conductive particles in the thickness direction is defined as Dn [μm], a relationship in which Dn/Tn is 1.00 or more. The connecting body according to any one of [1] to [6], which satisfies the following.
[8] The connected body according to [7], wherein Dn/Tn satisfies the relationship of 1.01 or more and 1.50 or less.
[9] The connecting body according to any one of [1] to [8], which is for a lithium ion battery.

The connecting body of the present invention can suppress the deterioration of the interlayer adhesion of the connecting body over time.

FIG. 1 is a sectional view showing an embodiment of a connecting body of the present invention. It is a sectional view showing other embodiments of the connecting body of the present invention. It is a figure explaining the manufacturing process of the connection body of this invention.

Embodiments of the connecting body of the present invention will be described below.

[Connection body]
The connecting body of the present invention includes:
having a first metal base material, a conductive adhesive layer and a second metal base material in this order,
The conductive adhesive layer includes an adhesive and conductive particles having a conductive layer on the surface of a resin core,
The adhesive includes a cured product of an acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g and a glycidylamine-based epoxy compound.

In this specification, "conductive particles having a conductive layer on the surface of a resin core" and "acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g" are referred to as "conductive particles" and "acid-modified polyolefin resin". It is sometimes abbreviated as "polyolefin resin".

1 and 2 are cross-sectional views showing embodiments of the connecting body of the present invention.
The connecting body 100 in FIGS. 1 and 2 has a conductive adhesive layer 30 and a second metal base material 20 on a first metal base material 10 in this order. 1 and 2, conductive adhesive layer 30 includes adhesive 31 and conductive particles 30. In FIGS. In FIGS. 1 and 2, a first metal base material 10 and a second metal base material 20 are electrically connected via conductive particles 30.
In the connection body shown in FIG. 1, the conductive adhesive layer 30 and the second metal base material 20 are in full contact with each other. On the other hand, in the connection body of FIG. 2, the conductive adhesive layer 30 and the second metal base material 20 are not partially in contact with each other.
In FIGS. 1 and 2, the conductive particles 30 have a particle diameter in the thickness direction that is smaller than a particle diameter in the width direction. This state indicates that the particle diameter in the thickness direction is reduced due to the pressure during lamination.

<Metal base material>
Examples of the metal constituting the first metal base material and the second metal base material include one or more metals selected from copper, stainless steel, brass, silver, aluminum, nickel, and the like.
The metals constituting the first metal base material and the second metal base material may be of the same type or may be of different types.
In order to improve adhesion, the first metal base material and the second metal base material may be roughened on the surface of the metal base material or treated to remove residual oil on the surface of the metal base material. .

The thickness of the first metal base material and the second metal base material is preferably 1 μm or more and 200 μm or less, more preferably 3 μm or more and 100 μm or less, and even more preferably 6 μm or more and 50 μm or less.
By setting the thickness to 1 μm or more, the strength of the connecting body can be easily improved. Furthermore, by setting the thickness to 1 μm or more, a predetermined strength can be imparted to the first metal base material and the second metal base material, and the base material will not be damaged when tension is applied to the base material. can be easily suppressed.
By setting the thickness to 200 μm or less, the first metal base material and the second metal base material can be easily rolled up, so that the connected body can be easily manufactured by roll-to-roll.

<Conductive adhesive layer>
The conductive adhesive layer includes an adhesive and conductive particles having a conductive layer on the surface of a resin core.

"glue"
The connecting body of the present invention is required to contain, as an adhesive, a cured product of an acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g and a glycidylamine-based epoxy compound. By including the cured product as an adhesive, resistance to chemicals such as electrolyte can be improved, so that it is possible to suppress the interlayer adhesion of the connected body from decreasing over time. In particular, it is preferable because it can provide good resistance to high-temperature chemicals. Examples of the electrolytic solution include electrolytic solutions for lithium ion batteries. Examples of electrolytic solutions for lithium ion batteries include those containing an electrolyte such as lithium hexafluorophosphate and a solvent such as ethylene carbonate. The electrolyte in lithium-ion batteries tends to reach high temperatures. Therefore, the connecting body of the present invention is particularly useful as a connecting body for lithium ion batteries.

-Acid-modified polyolefin resin-
The acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g has a role as a main ingredient of an adhesive.
When the acid value of the acid-modified polyolefin resin exceeds 20.0 mgKOH/g, the coating liquid for a conductive adhesive layer tends to gel, making it difficult to form a conductive adhesive layer. Further, when the acid value of the acid-modified polyolefin resin exceeds 20.0 mgKOH/g, the number of crosslinking points in the cured product between the acid-modified polyolefin resin and the glycidylamine-based epoxy compound tends to increase. When the number of crosslinking points increases, it becomes difficult for the cured product to follow changes in volume due to temperature changes, and thus the interlayer adhesion of the connected body may deteriorate over time.

In order to easily suppress the deterioration of the interlayer adhesion of the connecting body over time, the acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g is 80% by mass or more based on the total amount of the base resin. The content is preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass.

The acid value of the acid-modified polyolefin resin is preferably less than 15.0 mgKOH/g, more preferably less than 10.0 mgKOH/g, and even more preferably less than 5.0 mgKOH/g.
If the acid value of the acid-modified polyolefin resin is too low, the crosslinking density of the cured product may be insufficient. If the crosslinking density of the cured product is insufficient, the chemical resistance decreases, and it may not be possible to suppress the deterioration of the interlayer adhesion of the connected body over time. Therefore, the acid value of the acid-modified polyolefin resin is preferably 0.1 mgKOH/g or more, more preferably 0.5 mgKOH/g or more, and even more preferably 0.9 mgKOH/g or more.

As the acid-modified polyolefin resin, at least one polyolefin resin selected from polyethylene, polypropylene, propylene-α-olefin copolymer, etc. is grafted with at least one α,β-unsaturated carboxylic acid and its acid anhydride. The following can be mentioned. Acid-modified polyolefin resin can be produced, for example, by radical graft reaction.

Propylene-α-olefin copolymer is a copolymer of α-olefin with propylene as the main component. As the α-olefin, for example, at least one selected from ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used. Among α-olefins, ethylene and 1-butene are preferred. The ratio of the propylene component to the α-olefin component of the propylene-α-olefin copolymer is not limited, but the proportion of the propylene component is preferably 50 mol% or more, more preferably 70 mol% or more.

Examples of the α,β-unsaturated carboxylic acid and its acid anhydride include maleic acid, itaconic acid, citraconic acid, and acid anhydrides thereof. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred.

Specific examples of acid-modified polyolefin resins include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, and maleic anhydride-modified propylene-ethylene-butene copolymer. etc.

The weight average molecular weight of the acid-modified polyolefin resin is preferably 20,000 or more and 200,000 or less, more preferably 40,000 or more and 150,000 or less, and even more preferably 60,000 or more and 100,000 or less.
By setting the weight average molecular weight to 20,000 or more, it is possible to easily suppress a decrease in adhesive strength after immersion in an electrolytic solution. By setting the weight average molecular weight to 200,000 or less, the melting point is prevented from increasing and suitability for lamination is improved, and furthermore, by preventing the viscosity from increasing, it is possible to easily improve the suitability for coating.
In this specification, the weight average molecular weight means a polystyrene equivalent value measured by gel permeation chromatography.

-Glycidylamine-based epoxy compound-
The glycidylamine-based epoxy compound has a role as a curing agent that hardens the main resin. Although there are many types of curing agents, by using a glycidylamine-based epoxy compound as the curing agent, it is possible to suppress the deterioration of the interlayer adhesion of the connecting body over time. In addition, glycidylamine-based epoxy compounds are preferable because they can proceed with the curing reaction at low temperatures and can therefore suppress oxidation of the metal base material.
Examples of curing agents other than glycidylamine-based epoxy compounds include glycidyl ether-based epoxy compounds and isocyanate-based compounds. When a glycidyl ether type epoxy compound is used, the chemical resistance becomes insufficient and it is not possible to suppress the deterioration of the interlayer adhesion of the connecting body over time. When an isocyanate compound is used, carbon dioxide is produced as a by-product. Since the metal base material has low gas permeability, carbon dioxide causes defects such as blistering.
In this specification, a glycidyl ether-based epoxy compound means a compound that has a glycidyl ether group in its molecule and does not have a nitrogen atom in its molecule.

The glycidylamine-based epoxy compound is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and 100% by mass based on the total amount of the curing agent. Most preferably.

Examples of glycidylamine-based epoxy compounds include compounds having glycidylamine as a molecular constituent unit. The number of glycidyl groups in one molecule of the glycidylamine-based epoxy compound may be 1 or more, but is preferably 2 or more in order to more easily suppress the deterioration of the interlayer adhesion of the connecting body over time. .
If the number of glycidyl groups in one molecule of the glycidylamine-based epoxy compound is too large, the initial interlayer adhesion of the connected body may be weakened. Therefore, the number of glycidyl groups in one molecule of the glycidylamine-based epoxy compound is preferably 6 or less, more preferably 4 or less.

As the glycidylamine-based epoxy compound, a compound represented by the following general formula (1) is preferable.

In the general formula (1), R is an aromatic hydrocarbon group which may have a substituent, or a saturated or unsaturated alicyclic hydrocarbon group which may have a substituent.
When m is 1, examples of the aromatic hydrocarbon group which may have a substituent include aryl groups such as phenyl group and naphthyl group. When m is 1, examples of the saturated or unsaturated alicyclic hydrocarbon group which may have a substituent include cycloalkyl groups such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. When m is 1, R is preferably a cycloalkyl group, more preferably a cyclohexyl group.
When m is 2, examples of the aromatic hydrocarbon group which may have a substituent include arylene groups such as a phenylene group and a naphthylene group. When m is 2, examples of the saturated or unsaturated alicyclic hydrocarbon group which may have a substituent include cycloalkylene groups such as a cyclopentylene group, a cyclohexylene group, and a cycloheptylene group. When m is 2, R is preferably a cycloalkylene group, more preferably a cyclohexylene group.
Examples of the substituent for R include, but are not limited to, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, an amino group, a glycidyl group, a glycidylamino group, or a glycidyl ether group. It will be done.

In the general formula (1), X1 and X2 are each independently a linear alkylene group which may have a substituent having 1 or more carbon atoms and 5 or less carbon atoms, preferably 4 or less carbon atoms, and more preferably It is 3 or less, more preferably 2 or less.
Examples of the substituent include, but are not particularly limited to, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and an amino group.

In general formula (1), m is 1 or 2, and n is 1 or 2. Preferably, either m or n is 2, more preferably both m and n are 2.

Specific examples of glycidylamine-based epoxy compounds include 1,3-bis(diglycidylaminomethyl)cyclohexane, tetraglycidyldiaminodiphenylmethane, triglycidylpara-aminophenol, tetraglycidylbisaminomethylcyclohexanone, N,N,N',N' -tetraglycidyl-m-xylene diamine and the like. Among these, 1,3-bis(diglycidylaminomethyl)cyclohexane is preferred.

The glycidylamine-based epoxy compound preferably has an epoxy equivalent of 70 g/eq or more and 140 g/eq or less, more preferably 80 g/eq or more and 125 g/eq or less, and 85 g/eq or more and 110 g/eq or less. is more preferable, and more preferably 90 g/eq or more and 100 g/eq or less.
By setting the epoxy equivalent to 125 g/eq or less, it is possible to more easily suppress the deterioration of the interlayer adhesion of the connecting body over time. By setting the epoxy equivalent to 80 g/eq or more, it is possible to easily suppress weakening of the initial interlayer adhesion of the connecting body.

The blending amount of the glycidylamine-based epoxy compound is preferably 0.1 parts by mass or more and 27.5 parts by mass or less, and 0.5 parts by mass or more and 20.0 parts by mass, based on 100 parts by mass of the acid-modified polyolefin resin. It is more preferably at least 0.7 parts by mass and at most 10.0 parts by mass, even more preferably at least 1.0 parts by mass and at most 8.0 parts by mass.
By setting the blending amount of the glycidylamine-based epoxy compound to 0.1 part by mass or more, it is possible to more easily suppress the deterioration of the interlayer adhesion of the connecting body over time. By controlling the blending amount of the glycidylamine-based epoxy compound to 27.5 parts by mass or less, it is possible to easily suppress weakening of the initial interlayer adhesion of the connecting body.

The cured product of acid-modified polyolefin resin and glycidylamine-based epoxy compound preferably has a melting point of 60°C or more and 115°C or less, more preferably 65°C or more and 110°C or less, and 70°C or more and 95°C or less. It is even more preferable that there be.
By setting the melting point to 60° C. or higher, it is possible to easily suppress a decrease in interlayer adhesion of the connecting body due to heat. In particular, by setting the melting point to 60° C. or higher, it is possible to easily suppress a decrease in interlayer adhesion when the connecting body is immersed in a high-temperature electrolytic solution.
By setting the melting point to 115° C. or less, the first metal base material and the second metal base material can be easily bonded together. In addition, by setting the melting point to 115°C or lower, the lamination temperature when bonding the first metal base material and the second metal base material can be set low, making it easier to suppress oxidation of the metal base material. can.
As used herein, melting point can be measured by differential scanning calorimetry (DSC). Specifically, the melting point can be measured by the method described in Examples. Further, in this specification, when a melting peak is observed at a plurality of temperatures, the temperature of the melting peak on the lower temperature side is regarded as the melting point.

The melting point of the cured product can be adjusted, for example, by adjusting the weight average molecular weight of the acid-modified polyolefin resin and the amount of the curing agent. For example, increasing the weight average molecular weight tends to increase the melting point, while decreasing the weight average molecular weight tends to decrease the melting point. Furthermore, increasing the blending amount of the curing agent tends to increase the melting point, and decreasing the blending amount of the curing agent tends to lower the melting point. Furthermore, the longer the aging time, the higher the melting point, and the shorter the aging time, the lower the melting point. Furthermore, increasing the aging temperature tends to increase the melting point, and decreasing the aging temperature tends to decrease the melting point.

《Conductive particles》
In the present invention, particles having a conductive layer on the surface of a resin core are used as the conductive particles. Since the conductive particles have a conductive layer on their surfaces, they can electrically connect the first metal base material and the second metal base material. Furthermore, since the conductive particles have resin cores, the particle diameter in the thickness direction becomes smaller due to the pressure during lamination. By reducing the particle size of the conductive particles in the thickness direction, the contact area between the conductive adhesive layer and the second metal base material increases, making it easier to improve interlayer adhesion.
Particles having a conductive layer on the surface of a resin core can be obtained by, for example, plating or vapor depositing a metal on the resin core.

The conductive particles preferably have protrusions on their surfaces. Even if an oxide film is formed on the surfaces of the first metal base material and the second metal base material, conductive particles having protrusions on the surface easily break through the oxide film due to the protrusions. It is possible to easily electrically connect the metal base material and the second metal base material.
Particles having protrusions on the surface can be obtained, for example, by arranging a plurality of core substances that form protrusions on the surface of a resin core, and then plating or vapor depositing metal.
As a method for attaching the core substance to the surface of the resin core particle, for example, a method of adding the core substance to a dispersion liquid of the resin core and accumulating the core substance on the surface of the resin core particle by van der Waals force or the like. etc.

Examples of the resin constituting the resin core include benzoguanamine resin, acrylic resin, styrene resin, silicone resin, and polybutadiene resin. Furthermore, examples of the resin constituting the resin core include copolymers that are a combination of two or more of the monomers constituting the resins described above.

The compression recovery rate of the resin core is preferably 55% or less, more preferably 47% or less, more preferably 40% or less, more preferably 30% or less, and 18% or less. It is more preferable that By setting the compression recovery rate to 55% or less, the particle diameter of the conductive particles in the thickness direction tends to become smaller due to the pressure during lamination. Therefore, the contact area between the conductive adhesive layer and the second metal base material increases, making it easier to improve the interlayer adhesion of the connection body.
The compression recovery rate of the resin core is preferably 5% or more, more preferably 6% or more, and even more preferably 7% or more. By setting the compression recovery rate to 5% or more, it is possible to prevent the particle diameter of the conductive particles in the thickness direction from becoming extremely small due to the pressure during lamination. Therefore, it is possible to easily electrically connect the first metal base material and the second metal base material.
The compression recovery rate of the resin core can be adjusted by, for example, the components of the resin constituting the resin core and the degree of crosslinking of the resin constituting the resin core. Specifically, as the degree of crosslinking of the resin increases, the compression recovery rate tends to increase, and as the degree of crosslinking of the resin decreases, the compression recovery rate tends to decrease.

In this specification, compression recovery rate can be measured as follows.
Spread the resin core onto the sample stage. For each dispersed resin core, a load (reversed load value) is applied in the direction of the center of the resin core using a micro compression tester until the resin core is compressed and deformed by 30%. Thereafter, the load is unloaded to the origin load value (0.40 mN). The load-compression displacement during this time can be measured, and the compression recovery rate can be determined from the following formula. The loading rate is 0.33 mN/sec. As a micro compression tester, for example, "Fisherscope H-100" manufactured by Fisher Co., Ltd. is used.
Compression recovery rate (%) = [(L1-L2)/L1] x 100
L1: Compression displacement from the origin load value to the reverse load value when applying a load L2: Unloading displacement from the reverse load value to the origin load value when releasing the load

The Mohs hardness of the core material is preferably 5 or more, more preferably 7 or more, and even more preferably 9 or more.
Examples of the core material include nickel (Mohs hardness: 5), zirconia (Mohs hardness: 8 to 9), alumina (Mohs hardness: 9), tungsten carbide (Mohs hardness: 9), and diamond (Mohs hardness: 10). The core substances may be used alone or in combination of two or more types.

The average particle diameter of the core substance is preferably 50 nm or more and 250 nm or less, more preferably 100 nm or more and 200 nm or less. Further, the number of protrusions formed on the surface of the resin core is preferably 1 or more and 500 or less, more preferably 30 or more and 200 or less.

Preferably, the conductive layer is made of metal. Examples of the metal constituting the conductive layer include gold, palladium, nickel, copper, silver, tin, and aluminum. The metal constituting the conductive layer may be an alloy.

The thickness of the conductive layer is preferably 50 nm or more and 250 nm or less, more preferably 80 nm or more and 150 nm or less, from the viewpoint of balance between conductivity and economical efficiency.

The content of the conductive particles is preferably 0.1 parts by mass or more and 2.0 parts by mass or less, and 0.15 parts by mass or more and 1.8 parts by mass or less, based on 100 parts by mass of the adhesive. It is more preferable that the amount is 0.2 parts by mass or more and 1.7 parts by mass or less.
By setting the content of the conductive particles to 0.1 part by mass or more, the resistance value of the connecting body can be easily lowered. By setting the content of the conductive particles to 2.0 parts by mass or less, agglomeration of the conductive particles can be easily suppressed, and therefore the resistance value of the connecting body can be easily lowered.

《Thickness》
When the average thickness of the conductive adhesive layer is defined as Tn [μm] and the average diameter of the conductive particles in the thickness direction is defined as Dn [μm], it is preferable that Dn/Tn satisfies the relationship of 1.00 or more. .
By setting Dn/Tn to 1.00 or more, it is possible to easily electrically connect the first metal base material and the second metal base material.
Dn/Tn is more preferably 1.01 or more, and even more preferably 1.03 or more. In addition, Dn/Tn is preferably 1.50 or less, more preferably 1.40 or less, and even more preferably 1.30 or less, in order to facilitate good interlayer adhesion of the connection body. preferable.

The difference between Dn and Tn (Dn-Tn) is preferably 0.01 μm or more, more preferably 0.03 μm or more, and even more preferably 0.05 μm or more.
The difference between Dn and Tn (Dn-Tn) is preferably 1.0 μm or less, more preferably 0.8 μm or less, and even more preferably 0.7 μm or less.

In this specification, Tn indicating the average thickness of the conductive adhesive layer is the average value of the thickness of the conductive adhesive layer at 30 randomly selected locations. The thicknesses at the 30 points described above can be measured, for example, from a cross-sectional photograph of the conductive adhesive layer taken with a SEM or the like.

In this specification, Dn, which indicates the average particle diameter of the conductive particles, can be measured, for example, by the following procedures A1 and A2.
A1: Take a cross-sectional photograph of the conductive adhesive layer using a SEM or the like.
A2: Measure the diameter in the thickness direction of the conductive particles shown in the cross-sectional photograph. The average diameter in the thickness direction of a total of 30 conductive particles is defined as Dn.

Tn, which indicates the average thickness of the conductive adhesive layer, is preferably 1.0 μm or more and 10.0 μm or less, more preferably 2.0 μm or more and 8.0 μm or less, and even more preferably 3.0 μm or more and 6.0 μm or less. By setting Tn to 1.0 μm or more, it is possible to easily improve the interlayer adhesion of the connecting body, and it is possible to make it possible to make contact between the first metal base material and the second metal base material without intervening conductive particles. It can be easily suppressed. By setting Tn to 10.0 μm or less, the coating stability of the conductive adhesive layer can be easily improved.

Dn, which indicates the average diameter of the conductive particles in the thickness direction, is preferably 1.5 μm or more and 12.0 μm or less, more preferably 2.5 μm or more and 9.0 μm or less, and even more preferably 3.5 μm or more and 7.0 μm or less.

The CV value, which indicates the variation in particle size distribution of the conductive particles, is preferably 10% or less, more preferably 5% or less. By using a material with a small CV value, it is possible to suppress convex defects caused by fillers with large particle diameters in the appearance of lamination. CV value is an abbreviation for "coefficient of variation."

<Area ratio>
The area of the connecting body when viewed from above is S, the area of the first metal base when viewed from above is S1, and the area of the second metal base when viewed from above. When is S2, it is preferable that the following formulas (1) and (2) are satisfied. By satisfying the following formulas (1) and (2), alignment can be made unnecessary. Moreover, by satisfying the following formulas (1) and (2), it is possible to easily electrically connect the first metal base material and the second metal base material.
0.99≦S1/S≦1.01 (1)
0.99≦S2/S≦1.01 (2)

When the area of the conductive adhesive layer when the connecting body is viewed in plan is S3, it is preferable that S1 and S2 and S3 described above satisfy the following formulas (3) and (4). By satisfying the following formulas (3) and (4), alignment can be made unnecessary. Moreover, by satisfying the following formulas (3) and (4), it is possible to easily electrically connect the first metal base material and the second metal base material.
1.00≦S1/S3≦1.02 (3)
1.00≦S2/S3≦1.02 (4)

<Resistance value>
The resistance value of the connecting body is preferably 10.0 mΩ or less, more preferably 8.0 mΩ or less, and even more preferably 6.0 mΩ or less. Although the lower limit of the resistance value of the connecting body is not particularly limited, it is preferably 1.0 mΩ or more, and more preferably 2.0 mΩ or more.
The resistance value of the connection body can be measured by a four-terminal method by installing one terminal on the first metal base material and installing the other terminal on the second metal base material.

[Production method]
The connecting body of the present invention can be manufactured, for example, by the following steps 1 and 2.

Step 1: A coating liquid for a conductive adhesive layer containing an adhesive composition and conductive particles having a conductive layer on the surface of a resin core is applied onto the first metal base material, dried, and conductive. Step of forming a adhesive layer. The adhesive composition is a composition containing an acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g and a glycidylamine-based epoxy compound.
Step 2: Laminating a second metal base material on the conductive adhesive layer to have the first metal base material, the conductive adhesive layer, and the second metal base material in this order. Process of obtaining a connected body.

<Step 1>
Step 1 is to apply a coating liquid for a conductive adhesive layer containing an adhesive and conductive particles having a conductive layer on the surface of a resin core onto a first metal base material, and dry it to form a conductive adhesive. This is a step of forming a chemical layer.

In step 1, when the average thickness of the conductive adhesive layer is defined as T1 [μm] and the average particle diameter of the conductive particles is defined as D1 [μm], it is possible to satisfy the relationship T1<D1. preferable.

FIG. 3(a) is a cross-sectional view showing an embodiment of the state after step 1.
The laminate 50 in FIG. 3(a) has a conductive adhesive layer 30 on the first metal base 10. In FIG. 3A, the conductive adhesive layer 30 includes an adhesive 31 and conductive particles 32 having a conductive layer on the surface of a resin core.

In step 1, it is preferable to satisfy the relationship T1<D1.
By satisfying the relationship T1<D1, the first metal base material and the second metal base material can be electrically connected through a simple lamination process without the need for high temperature and high pressure processing during manufacturing. I can do it.

The ratio between D1 and T1 (D1/T1) is preferably 1.03 or more, more preferably 1.05 or more, and even more preferably 1.10 or more. By setting the ratio to 1.03 or more, it is possible to easily electrically connect the first metal base material and the second metal base material.
The ratio between D1 and T1 (D1/T1) is preferably 1.50 or less, more preferably 1.30 or less, and even more preferably 1.20 or less. By setting the ratio to 1.50 or less, the interlayer adhesion of the connecting body can be easily improved.

The difference between D1 and T1 (D1-T1) is preferably 0.1 μm or more, more preferably 0.3 μm or more, and even more preferably 0.4 μm or more.
The difference between D1 and T1 (D1-T1) is preferably 2.0 μm or less, more preferably 1.0 μm or less, and even more preferably 0.7 μm or less.

T1, which indicates the average thickness of the conductive adhesive layer, is preferably 1.0 μm or more and 10.0 μm or less, more preferably 2.0 μm or more and 8.0 μm or less, and even more preferably 3.0 μm or more and 6.0 μm or less. By setting T1 to 1.0 μm or more, it is possible to easily improve the interlayer adhesion of the connection body, and it is also possible to prevent the first metal base material and the second metal base material from coming into contact without intervening conductive particles. It can be easily suppressed. By setting T1 to 10.0 μm or less, the coating stability of the conductive adhesive layer can be easily improved.

D1, which indicates the average particle diameter of the conductive particles, is preferably 1.5 μm or more and 12.0 μm or less, more preferably 2.5 μm or more and 9.0 μm or less, and even more preferably 3.5 μm or more and 7.0 μm or less.
As described above, the conductive particles are slightly crushed in the thickness direction by the pressure during lamination. For this reason, it is preferable that D1 be slightly larger than Dn. The difference between D1 and Dn is 0.05 μm or more and about 0.70 μm.

In this specification, T1 indicating the average thickness of the conductive adhesive layer is the average value of the thickness of the conductive adhesive layer at 30 randomly selected locations. It is assumed that the thickness measurements at the 30 points described above are carried out after the completion of step 1 and before the start of step 2. The thicknesses at the 30 points described above can be measured, for example, from a cross-sectional photograph of the conductive adhesive layer taken with a SEM or the like.

In this specification, D1 indicating the average particle diameter of the conductive particles can be measured, for example, by the following procedures B1 and B2. B1 and B2 below are to be performed after Step 1 is completed and before Step 2 is started.
B1: Take a cross-sectional photograph of the conductive adhesive layer using SEM or the like.
B2: Measure the maximum diameter of the conductive particles shown in the cross-sectional photograph. The average maximum diameter of a total of 30 conductive particles is defined as D1.

It is preferable that the coating liquid for the conductive adhesive layer contains a solvent. Examples of solvents include ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), aliphatic hydrocarbons (hexane, etc.), alicyclic hydrocarbons (cyclohexane, etc.), aromatic hydrocarbons (toluene, xylene, etc.) ), esters (methyl acetate, ethyl acetate, butyl acetate, etc.), alcohols (isopropanol, butanol, cyclohexanol, etc.), cellosolves (methyl cellosolve, ethyl cellosolve, etc.), glycol ethers (propylene glycol monomethyl ether acetate, etc.) ), and other organic solvents. Further, as the solvent, a mixed solvent of the above-mentioned organic solvent and water can also be used. The solvent may be a single type of solvent or a mixed solvent of two or more types.

Examples of the coating means include general-purpose coating means such as gravure coating, bar coating, roll coating, reverse roll coating, comma coating, and die coating.
The drying conditions may be adjusted depending on the characteristics of the metal base material, the material constituting the coating liquid for the conductive adhesive layer, the amount of the coating liquid applied, and the like. For example, it is preferable that the drying temperature be 80° C. or more and 120° C. or less, and the drying time be 30 seconds or more and 90 seconds or less. In the above temperature range, expansion and oxidation of the metal base material can be easily suppressed, and the quality of the connected body can be easily improved.
The curing reaction between the acid-modified polyolefin resin and the glycidylamine-based epoxy compound also proceeds during the drying in step 1. In order to further advance the curing reaction, it is preferable to perform step 3 after step 2.

<Step 2>
Step 2 is to laminate a second metal base material on the conductive adhesive layer to have the first metal base material, the conductive adhesive layer, and the second metal base material in this order. , is the process of obtaining a connected body.

FIG. 3(b) is a cross-sectional view showing an embodiment of the state after step 2.
The connection body 100 in FIG. 3(b) has a conductive adhesive layer 30 and a second metal base material 20 on the first metal base material 10 in this order. In FIG. 3(b), the first metal base material 10 and the second metal base material 20 are electrically connected via conductive particles 30.

Comparing FIG. 3(a) and FIG. 3(b), the conductive particles 30 in FIG. 3(b) are crushed in the thickness direction, so that the particle diameter in the thickness direction is reduced. As the conductive particles are crushed in the thickness direction, the adhesive present above the conductive particles (the adhesive 31 present above the conductive particles 32 in FIG. 3(a)) is removed during lamination. The pressure makes it easier to spread in the width direction. Therefore, the contact area between the conductive adhesive layer and the second metal base material can be easily increased, and the interlayer adhesion of the connected body can be easily improved.

At both left and right ends in FIG. 3(b), the conductive adhesive layer 30 and the second metal base material 20 are not in contact. Such areas are caused by air bubbles mixed in during lamination. As will be described later, bubbles can be easily reduced by adjusting the temperature during lamination.

In step 2, the lamination temperature is preferably 55°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher.
By setting the lamination temperature to 55° C. or higher, inclusion of air bubbles during lamination can be suppressed and the resistance value can be easily lowered. If air bubbles are mixed in during lamination, it becomes difficult for the adhesive to suppress the conductive particles from restoring to their original shape, so the resistance value of the connection body may increase over time. Therefore, by setting the lamination temperature within the above range, the initial resistance value can be lowered, and the increase in resistance value of the connecting body over time can be easily suppressed.
The upper limit of the lamination temperature is not particularly limited, but is preferably 110°C or lower, more preferably 100°C or lower, and still more preferably 90°C or lower.

The laminating pressure in Step 2 is preferably 0.1 MPa or more and 1.0 MPa or less, more preferably 0.2 MPa or more and 0.7 MPa or less, and even more preferably 0.3 MPa or more and 0.5 MPa or less.
By setting the pressure to 0.1 MPa or more, the conductive particles can be easily crushed in the thickness direction. In addition, by setting the pressure to 0.1 MPa or more, the adhesive present above the conductive particles (the adhesive 31 present above the conductive particles 32 in FIG. 1) is removed in the width direction by the pressure during lamination. It can spread easily.
By setting the pressure to 1.0 MPa or less, there is no need to apply high pressure, which simplifies and stabilizes the manufacturing of the connecting body. It can be manufactured easily.

The laminating speed in step 2 is preferably 0.2 m/min or more and 30 m/min or less, more preferably 0.4 m/min or more and 2.0 m/min or less, and 1.0 m/min or more and 15.0 m/min or less. More preferred.

<Roll toe roll>
The above-described method for manufacturing a connecting body includes performing the step 1 by continuously feeding out the first metal base material from a roll-shaped object of the first metal base material, and at the same time performing the step 1 on the second metal base material. It is preferable to carry out the step 2 by continuously feeding out the second metal base material from a roll-shaped material.
By employing the above means, the connecting bodies can be manufactured continuously, and manufacturing efficiency can be dramatically improved.
Note that after step 1, the laminate in which the conductive adhesive layer is formed on the first metal base material may be wound up once. Then, step 2 is carried out by continuously feeding out the laminate from the rolled-up roll-shaped laminate and by continuously feeding out the second metal base material from the roll-shaped object of the second metal base material. You may go. In this way, even if the step of winding up the laminate is included between Step 1 and Step 2, the manufacturing rate can be dramatically increased because the manufacturing is performed using a roll-to-roll method.

<Step 3>
The method for manufacturing a connecting body may further include the following step 3.
Step 3: A step of aging the connected body.

By performing the aging treatment in step 3, curing of the acid-modified polyolefin resin and the glycidylamine-based epoxy compound can proceed. Therefore, the connected body subjected to Step 3 can easily suppress the deterioration of the interlayer adhesion of the connected body over time. Furthermore, in the connected body that has undergone Step 3, the adhesive can more easily suppress the conductive particles from restoring to their original shape, so it is easier to suppress changes in the resistance value of the connected body over time.

In step 3, the temperature and time of the aging treatment are preferably within the following ranges.

The temperature of the aging treatment is preferably 55°C or lower, more preferably 50°C or lower, and even more preferably 47°C or lower. By setting the temperature of the aging treatment to 55° C. or lower, oxidation of the metal base material can be easily suppressed. Furthermore, by setting the temperature of the aging treatment to 55° C. or lower, it is possible to easily suppress the conductive particles from restoring to their original shape during the aging treatment.
The lower limit of the temperature of the aging treatment is preferably 25°C or higher, more preferably 30°C or higher, and even more preferably 40°C or higher, in order to promote curing of the acid-modified polyolefin resin and the glycidylamine-based epoxy compound.
The aging treatment time is not particularly limited, but is preferably 1 day or more and 9 days or less, more preferably 3 days or more and 7 days or less.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples.

1. Measurement 1-1. Resistance Value The resistance values of the connected bodies produced in Examples and Comparative Examples were measured. One pair of terminals was installed on the first metal base material, and the other pair of terminals was installed on the second metal base material, and the resistance value was measured by a four-terminal method. As a measuring device, a product name of "Resistance Meter RM3544" manufactured by Hioki Electric Co., Ltd. was used. The results are shown in Table 1.

1-2. Time-dependent change in interlayer adhesion (1) Measurement of initial interlayer adhesion Two samples were prepared by cutting the connected bodies prepared in Examples and Comparative Examples into pieces of 15 mm in width and 10 cm in length. Peel off the second metal base material of 10 mm from the tip of one sample, grasp the peeled second metal base material with a chuck, and use Shimadzu Corporation's product name "AUTOGRAPH AGS-50D" to peel it off at a peel angle of 180°. Peeling was performed at a peeling rate of 200 mm/min, and the peeling force 1 was measured.
Peel off the first metal base material of 10 mm from the tip of the other sample, grasp the peeled first metal base material with a chuck, and adjust the peeling angle using Shimadzu Corporation's product name "AUTOGRAPH AGS-50D". Peeling was performed at a 180° peeling rate of 200 mm/min, and peeling force 2 was measured.
The weaker of peeling force 1 and peeling force 2 was defined as "initial interlayer adhesion strength".

(2) Measurement of interlayer adhesion after carrying out a durability test for 300 hours Regarding the connected bodies of each example and comparative example, two samples similar to the above (1) were produced. After filling the pouch with the following durability test liquid, a sample was further placed in the pouch. After the pouch was immersed in a 60°C oil bath for 300 hours, the sample was taken out from the pouch. Thereafter, the peeling force of the two samples was measured in the same manner as in (1) above. The measured peeling forces were designated as peeling forces 3 and 4. The weaker of peeling force 3 and peeling force 4 was defined as "interlayer adhesion strength after 300 hours."
<Durability test liquid>
X1: Lithium hexafluorophosphate and a solvent were mixed so that the concentration of lithium hexafluorophosphate was 1 mol/L to prepare an electrolytic solution for a lithium ion battery. The solvent used was a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a mass ratio of 1:1.
X2: 600 mg of water was added to 1 kg of the electrolyte obtained in X1. The reason for adding water is to generate hydrofluoric acid from lithium hexafluorophosphate.

(3) Calculation of change in interlayer adhesion over time For the connected bodies of each example and comparative example, interlayer adhesion after 300 hours/initial interlayer adhesion was calculated. The results are shown in Table 1. In Comparative Example 4, the interface of the sample peeled off in the durability test liquid, and the interlayer adhesion strength after 300 hours could not be measured. Therefore, the evaluation of Comparative Example 4 in Table 1 was written as "-".

1-3. Measurement of Melting Point The melting point of the cured product of the acid-modified polyolefin resin and the epoxy compound used in Examples and Comparative Examples was measured. The measurement method was as follows.
<Method of measuring melting point>
The melting peak temperature was measured using a differential scanning calorimeter (trade name: EXSTRA DSC6200, manufactured by Hitachi High-Tech Science) under conditions of a measurement temperature of 0 to 160°C and a heating rate of 20°C/min. The melting peak of the 1st heating was taken as the melting point of the cured product.

2. Preparation of conductive particles having a conductive layer on the surface of a resin core According to the description in Example 3 of JP-A-2020-97739, a layer with a thickness of 0.5% was applied to the surface of a resin core (compression recovery rate: 9.8%). Conductive particles on which a conductive layer (nickel layer) of about 1 μm was formed were obtained (average particle size: 3.1 μm).

3. Production of acid-modified polyolefin resin (1) Acid-modified polyolefin resin 1
In a 1L autoclave, 100 parts by mass of propylene-butene copolymer ("Tafmer (registered trademark) XM7080" manufactured by Mitsui Chemicals), 150 parts by mass of toluene, 1 part by mass of maleic anhydride, and 5 parts by mass of di-tert-butyl peroxide was added, the temperature was raised to 140°C, and the mixture was further stirred for 3 hours. Thereafter, the resulting reaction solution was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate the resin. Thereafter, the liquid containing the resin was centrifuged to separate and purify the acid-modified propylene-butene copolymer graft-polymerized with maleic anhydride, the (poly)maleic anhydride, and the low molecular weight substance. Thereafter, acid-modified polyolefin resin 1 (maleic anhydride-modified propylene-butene copolymer, acid value 1 mgKOH/g, weight average molecular weight 100,000) was obtained by drying at 70° C. for 5 hours under reduced pressure.

(2) Acid-modified polyolefin resin 2
Acid-modified polyolefin resin 2 ( A maleic anhydride-modified propylene-butene copolymer (acid value: 12 mgKOH/g, weight average molecular weight: 100,000) was obtained.

(3) Acid-modified polyolefin resin 3
Changing the propylene-butene copolymer (“Tafmer (registered trademark) XM7080” manufactured by Mitsui Chemicals) to a propylene-butene copolymer (“Tafmer (registered trademark) Acid-modified polyolefin resin 3 (maleic anhydride-modified propylene -butene copolymer, acid value 12 mgKOH/g, weight average molecular weight 100,000) was obtained.

4. Production of connection body [Example 1]
The connection body of Example 1 was produced by the following steps 1 to 3. In the connection body of Example 1, T1 was 2.9 μm, D1 was 3.1 μm, Tn was 2.9 μm, and Dn was 2.93 μm.

Step 1: On the first metal base material (aluminum foil with a thickness of 50 μm), the following coating liquid 1 for conductive adhesive layer was applied by gravure coating. Next, it was dried at 100° C. for 1 minute to form a conductive adhesive layer with an average thickness of 2.9 μm. Step 1 was carried out continuously by continuously feeding out the first metal base material from a roll of the first metal base material.

<Coating liquid 1 for conductive adhesive layer>
- 0.27 parts by mass of conductive particles prepared in "2" above - 100 parts by mass of main agent (acid-modified polyolefin resin 1 above)
・Curing agent 5 parts by mass (glycidylamine epoxy compound)
(1,3-bis(diglycidylaminomethyl)cyclohexane)
・Appropriate amount of diluting solvent

Step 2: Laminate the second metal base material (copper foil with a thickness of 8 μm) on the conductive adhesive layer to combine the first metal base material, the conductive adhesive layer, and the second metal base material. A connected body having these components in this order was obtained. The lamination conditions were as follows.
Step 2 was carried out continuously by continuously feeding out the second metal base material from a roll of the second metal base material. Step 1 and Step 2 were performed continuously on one line.
<Lamination conditions>
・Temperature of laminating roll: 80℃
・Lamination pressure: 0.4MPa
・Lamination speed: 5m/min

Step 3: The connected body obtained in Step 2 was wound up and aged at 45° C. for 5 days.

[Example 2]
A connection body of Example 2 was produced in the same manner as in Example 1, except that Coating Liquid 1 for conductive adhesive layer was changed to Coating Liquid 2 for conductive adhesive layer below.
<Coating liquid 2 for conductive adhesive layer>
・0.28 parts by mass of conductive particles prepared in “2” above ・100 parts by mass of main agent (acid-modified polyolefin resin 2 above)
・Curing agent 1.12 parts by mass (glycidylamine-based epoxy compound)
(1,3-bis(diglycidylaminomethyl)cyclohexane)
・Appropriate amount of diluting solvent

[Example 3]
A connection body of Example 3 was produced in the same manner as in Example 1, except that Coating Liquid 1 for conductive adhesive layer was changed to Coating Liquid 3 for conductive adhesive layer below.
<Coating liquid 3 for conductive adhesive layer>
・0.75 parts by mass of the conductive particles prepared in “2” above ・100 parts by mass of the main agent (acid-modified polyolefin resin 3 above)
・Curing agent 2.45 parts by mass (glycidylamine-based epoxy compound)
(1,3-bis(diglycidylaminomethyl)cyclohexane)
・Appropriate amount of diluting solvent

[Example 4]
A connection body of Example 4 was produced in the same manner as in Example 1, except that Coating Liquid 1 for conductive adhesive layer was changed to Coating Liquid 4 for conductive adhesive layer below.
<Coating liquid 4 for conductive adhesive layer>
- 0.27 parts by mass of conductive particles prepared in "2" above - 100 parts by mass of main agent (acid-modified polyolefin resin 1 above)
・Curing agent 25 parts by mass (glycidylamine-based epoxy compound)
(1,3-bis(diglycidylaminomethyl)cyclohexane)
・Appropriate amount of diluting solvent

[Example 5]
A connection body of Example 5 was produced in the same manner as in Example 1, except that Coating Liquid 1 for conductive adhesive layer was changed to Coating Liquid 5 for conductive adhesive layer below.
<Coating liquid 5 for conductive adhesive layer>
- 0.27 parts by mass of conductive particles prepared in "2" above - 100 parts by mass of main agent (acid-modified polyolefin resin 1 above)
・Curing agent 30 parts by mass (glycidylamine-based epoxy compound)
(1,3-bis(diglycidylaminomethyl)cyclohexane)
・Appropriate amount of diluting solvent

[Comparative example 1]
A connected body of Comparative Example 1 was produced in the same manner as in Example 1, except that Coating Liquid 1 for Conductive Adhesive Layer was changed to Coating Liquid 6 for Conductive Adhesive Layer below.
<Coating liquid 6 for conductive adhesive layer>
・0.14 parts by mass of conductive particles prepared in “2” above ・100 parts by mass of main agent (acid-modified polyolefin resin 2 above)
・Curing agent 2.16 parts by mass (glycidyl ether epoxy compound)
(Nagase ChemteX, product name: Denacol EX-321L, solid content 100%)
・Appropriate amount of diluting solvent

[Comparative example 2]
The procedure was the same as in Example 1, except that the conductive adhesive layer coating liquid 1 was changed to the above-mentioned conductive adhesive layer coating liquid 6, and the aging treatment in step 3 was changed to 120 ° C. for 2 hours. Thus, a connection body of Comparative Example 2 was produced.

[Comparative example 3]
The procedure was the same as in Example 1, except that the conductive adhesive layer coating liquid 1 was changed to the conductive adhesive layer coating liquid 7 below, and the aging treatment in step 3 was changed to 120°C for 2 hours. Thus, a connection body of Comparative Example 3 was produced.
<Coating liquid 7 for conductive adhesive layer>
・0.14 parts by mass of conductive particles prepared in “2” above ・100 parts by mass of main agent (acid-modified polyolefin resin 2 above)
・Curing agent 2.16 parts by mass (glycidyl ether epoxy compound)
(Nagase ChemteX, product name: Denacol EX-321L, solid content 100%)
・Curing catalyst 0.9 parts by mass (Shikoku Kasei Co., Ltd., Curesol 2E4MZ, solid content 1%)
・Appropriate amount of diluting solvent

[Comparative example 4]
A connected body of Comparative Example 4 was produced in the same manner as in Example 1, except that Coating Liquid 1 for Conductive Adhesive Layer was changed to Coating Liquid 8 for Conductive Adhesive Layer below.
<Coating liquid 8 for conductive adhesive layer>
・0.24 parts by mass of conductive particles prepared in “2” above ・100 parts by mass of main agent (polyester resin)
(Toyo Morton Co., Ltd., product name: AD76P1, solid content 51% by mass)
・Curing agent 10 parts by mass (isocyanate compound)
(Toyo Morton Co., Ltd., product name: CAT10L, solid content 53% by mass)
・Appropriate amount of diluting solvent

[Comparative example 5]
A connected body of Comparative Example 5 was produced in the same manner as in Example 1, except that Coating Liquid 1 for conductive adhesive layer was changed to Coating Liquid 9 for conductive adhesive layer below.
<Coating liquid 9 for conductive adhesive layer>
- 0.27 parts by mass of conductive particles prepared in "2" above - 100 parts by mass of main agent (acid-modified polyolefin resin 1 above)
・Appropriate amount of diluting solvent

From the results in Table 1, it can be confirmed that the connection bodies of Examples can suppress the deterioration of interlayer adhesion over time. Note that in Examples 1 to 4, the interlayer adhesion strength increased after 300 hours. The reasons for this were that "the adhesive layer was not sufficiently softened during lamination in step 2" and "due to long immersion in a 60°C oil bath, it was not softened sufficiently in step 2." This is thought to be due to the fact that the adhesive layer softened and the adhesion between the metal base material and the adhesive layer improved.
Although not listed in Table 1, all of the connected bodies of Examples had an initial interlayer adhesion force, an interlayer adhesion force after 100 hours, and an interlayer adhesion force after 300 hours of 0.20 N/mm or more. It had sufficient interlayer adhesion.
Although not listed in Table 1, S1/S, S2/S, S1/S3, and S2/S3 in the main body of the specification are all 1.00 for the connectors of Examples and Comparative Examples.

10:: First metal base material 20:: Second metal base material 30: Conductive adhesive layer 31: Adhesive 32: Conductive particles having a conductive layer on the surface of the resin core 50: Laminated body 100: Connection body

Claims (9)

A connection body having a first metal base material, a conductive adhesive layer, and a second metal base material in this order,
The conductive adhesive layer includes an adhesive and conductive particles having a conductive layer on the surface of a resin core,
A connection body comprising, as the adhesive, a cured product of an acid-modified polyolefin resin having an acid value of less than 20.0 mgKOH/g and a glycidylamine-based epoxy compound. The connector according to claim 1, wherein the glycidylamine-based epoxy compound has an epoxy equivalent of 70 g/eq or more and 140 g/eq or less. The connecting body according to claim 1, comprising 0.1 parts by mass or more and 27.5 parts by mass or less of the glycidylamine-based epoxy compound based on 100 parts by mass of the acid-modified polyolefin resin. The connector according to claim 1, wherein the acid-modified polyolefin resin has an acid value of 0.1 mgKOH/g or more and less than 15.0 mgKOH/g. The connecting body according to claim 1, wherein the cured product has a melting point of 60°C or more and 115°C or less. The connecting body according to claim 1, wherein the conductive particles are contained in a range of 0.1 parts by mass to 2.0 parts by mass based on 100 parts by mass of the adhesive. When the average thickness of the conductive adhesive layer is defined as Tn [μm] and the average diameter in the thickness direction of the conductive particles is defined as Dn [μm], Dn/Tn satisfies the relationship of 1.00 or more. The connecting body according to claim 1. The connecting body according to claim 7, wherein Dn/Tn satisfies a relationship of 1.01 or more and 1.50 or less. The connecting body according to any one of claims 1 to 8, which is for use in a lithium ion battery.