WO2024029513A1 - Electroconductive adhesive and electromagnetic shield film - Google Patents

Abstract

Provided is an electroconductive adhesive which has both a high creep resistance at high temperatures and high adhesivity. This electroconductive adhesive is a sheet-type electroconductive adhesive comprising: electroconductive particles; a resin composition; a first main surface; and a second main surface opposing the first main surface. The conductive adhesive is characterized in that: the storage elastic modulus thereof at 65°C is 1.6×104Pa or more; and the arithmetic roughness Ra of the first main surface is 4 μm or less.

Description

Conductive adhesive and electromagnetic shielding film

The present invention relates to a conductive adhesive and an electromagnetic shielding film.

Conventionally, conductive adhesives have been widely used in printed wiring boards. For example, an electromagnetic shielding film (hereinafter sometimes simply referred to as a "shielding film") that is used by adhering to a printed wiring board consists of a shielding layer such as metal foil and a conductive adhesive provided on the surface of the shielding layer. It has a sheet. The conductive adhesive sheet is formed, for example, by applying a conductive adhesive in sheet form to the surface of the shield layer, and it adheres the shield layer to the surface of the printed wiring board, and also connects the ground pattern of the printed wiring board and the shield layer. It has the function of conducting.

As such a conductive adhesive, Patent Document 1 discloses a conductive adhesive sheet having a storage modulus peak top temperature of 120° C. or less and an average arithmetic surface roughness Ra of the application surface of 0.1 μm or more. Disclosed.

In the conductive adhesive sheet described in Patent Document 1, a metal layer serving as a shield layer is laminated and placed on a printed wiring board. At this time, the laminate of the conductive adhesive sheet and the shield layer is temporarily attached to the printed wiring board by laminating or the like, and then heated and pressurized at high temperature to harden the conductive adhesive sheet. This fixes the laminate of the conductive adhesive sheet and the shield layer to the printed wiring board.
When temporary bonding is performed in this way, if the adhesive strength is weak during temporary bonding, the laminate of the conductive adhesive sheet and shield layer may become misaligned with respect to the printed wiring board before the main curing process. , it may fall off the printed wiring board.
In the conductive adhesive sheet described in Patent Document 1, the above problem is prevented by setting the peak top temperature of the storage elastic modulus and the average arithmetic surface roughness of the attachment surface to predetermined values.

International Publication No. 2020-085316

Patent Document 1 discloses a conductive adhesive sheet using a thermosetting resin as a binder component.
In recent years, there has been a trend for conductive adhesive sheets that can be bonded to printed wiring boards under relatively mild conditions rather than under high temperature and high pressure conditions. That is, there is a tendency to require a adhesive resin as a binder component.

When a thermosetting resin is used as a binder, the thermosetting resin is cured by heat, so it has a characteristic of high creep resistance.
However, when an adhesive resin is used as a binder component, there is a problem that creep resistance is low because the adhesive resin does not harden like a thermosetting resin.
Electromagnetic shielding films containing adhesive resin are sometimes used for movable parts and bent parts on FFCs and printed wiring boards. Tensile stress is likely to be applied to the electromagnetic shielding film placed in such a location. Furthermore, when the electromagnetic shielding film is placed close to a heat source, it becomes susceptible to heat. When an electromagnetic shielding film is placed in such a location, creep resistance becomes a particular problem.
In addition, when using adhesive resin as a binder component, one possible method to improve creep resistance is to use a material that is difficult to deform, but there is a problem that using a material that is difficult to deform reduces adhesive strength. be.
That is, there is a trade-off relationship between improving creep resistance and improving adhesiveness, and it has been difficult to achieve both.

The present invention was made to solve the above problems, and an object of the present invention is to provide a conductive adhesive that has both high creep resistance and high adhesiveness at high temperatures. It is to provide.

The present inventors have found that by setting the storage modulus of the conductive adhesive to a predetermined value and setting the adhesive surface of the conductive adhesive to a predetermined state, the creep resistance of the conductive adhesive is increased, and It was discovered that the adhesiveness also increased, and the present invention was completed.

That is, the conductive adhesive of the present invention is a sheet-shaped conductive adhesive that includes conductive particles and a resin composition, and has a first main surface and a second main surface opposite to the first main surface. The electrically conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and an arithmetic mean roughness Ra of the first principal surface is 4 μm or less.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and a maximum height Rz of the first principal surface is 16 μm or less. .

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the maximum peak height Rp of the first principal surface is 9.5 μm or less. shall be.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and a maximum valley depth Rv of the first principal surface is 9 μm or less. do.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the average height Rc of the first principal surface is 11 μm or less. .

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the maximum cross-sectional height Rt of the first principal surface is 16 μm or less. do.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the root mean square height Rq of the first principal surface is 5 μm or less. shall be.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the ten-point average roughness RzJIS of the first principal surface is 14 μm or less. shall be.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the level difference Rk of the core portion of the first principal surface is 7 μm or less. shall be.

A conductive adhesive according to another aspect of the present invention is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The adhesive is characterized in that the storage elastic modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the average length Rdc of the elements on the first principal surface is 7 μm or less. shall be.

The electrically conductive adhesive of the present invention has in common that the storage modulus at 65° C. is 1.6×10 ⁴ Pa or more.
Therefore, when the storage modulus of the conductive adhesive at 65° C. is within the above range, the conductive adhesive becomes difficult to deform and has high creep resistance at high temperatures.

In the conductive adhesive of the present invention, the surface quality parameters (Ra, Rz, Rp, Rv, Rc, Rt, Rq, RzJIS, Rk, Rdc) of the first main surface are within predetermined ranges.
The fact that these parameters are within the above ranges means that the first principal surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive pressure-sensitive adhesive of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

The conductive adhesive of the present invention may have isotropic conductivity or anisotropic conductivity depending on its use.

The electromagnetic shielding film of the present invention is characterized by comprising the conductive adhesive of the present invention and a shield layer laminated so as to be in contact with the second main surface of the conductive adhesive.

As described above, the conductive adhesive of the present invention has high creep resistance and high adhesiveness at high temperatures. Therefore, the shield layer can be reliably bonded to the adherend.

The electromagnetic shielding film of the present invention preferably further includes a protective layer formed on the shielding layer.
By forming the protective layer, the shield layer and the conductive adhesive can be protected.

According to the present invention, it is possible to provide a conductive adhesive that has both high creep resistance and high adhesiveness at high temperatures.

FIG. 1 is a cross-sectional view schematically showing an example of a conductive adhesive according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of the electromagnetic shielding film according to the first embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of a shield printed wiring board including an electromagnetic shielding film according to the first embodiment of the present invention.

Hereinafter, the conductive adhesive of the present invention will be specifically explained. However, the present invention is not limited to the following embodiments, and can be modified and applied as appropriate without changing the gist of the present invention.

(First embodiment)
The conductive adhesive according to the first embodiment of the present invention is made of conductive particles and a resin composition, and has a first main surface and a second main surface opposite to the first main surface. The conductive adhesive must have a storage modulus of 1.6×10 ⁴ Pa or more at 65°C and an arithmetic mean roughness Ra of the first principal surface of 4 μm or less. This is a configuration requirement.
As long as these constituent requirements are satisfied, the present invention can be modified and applied as appropriate within the scope of producing the effects of the invention.

FIG. 1 is a cross-sectional view schematically showing an example of a conductive adhesive according to a first embodiment of the present invention.
The conductive adhesive 10 shown in FIG. 1 consists of conductive particles and a resin composition.
Further, the conductive adhesive 10 is in the form of a sheet, and has a first main surface 11 and a second main surface 12 opposite to the first main surface 11.

The conductive adhesive 10 has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.
Note that the storage elastic modulus is preferably 1.6×10 ⁴ to 1.0×10 ⁵ Pa or less, more preferably 1.6×10 ⁴ Pa to 9.0×10 ⁴ Pa. .
When the storage modulus at 65° C. is 1.6×10 ⁴ Pa or more, the conductive adhesive becomes difficult to deform and has high creep resistance at high temperatures.

Note that the "storage modulus at 65°C" can be measured with a dynamic viscoelasticity measuring device (rheometer).

The storage modulus of the conductive adhesive 10 at 65° C. can be controlled by adjusting the type and content of the resin composition contained in the conductive adhesive 10 or by adding additives.

In the conductive adhesive 10, the arithmetic mean roughness Ra of the first main surface 11 is 4 μm or less.
Note that the arithmetic mean roughness Ra is preferably 3.97 μm or less, more preferably 3.65 μm or less.
In the conductive adhesive 10, since the arithmetic mean roughness Ra of the first main surface 11 is 4 μm or less, it can be said that the first main surface 11 is nearly flat.
Therefore, when an adherend is brought into contact with the first main surface 11, the first main surface 11 and the adherend are likely to come into close contact with each other. Therefore, the adhesive force on the first main surface 11 of the conductive adhesive 10 becomes high.

Further, the maximum height Rz of the first main surface 11 is preferably 16 μm or less, more preferably 15.5 μm or less, and even more preferably 15 μm or less.
Further, the maximum peak height Rp of the first main surface 11 is preferably 9.5 μm or less, more preferably 8.6 μm or less, and even more preferably 7.5 μm or less.
Further, the maximum valley depth Rv of the first main surface 11 is preferably 9 μm or less, more preferably 8.8 μm or less, and even more preferably 7 μm or less.
Further, the average height Rc of the first main surface 11 is preferably 11 μm or less, more preferably 10.6 μm or less, and even more preferably 10.3 μm or less.
Further, the maximum cross-sectional height Rt of the first main surface 11 is preferably 16 μm or less, more preferably 15.5 μm or less, and even more preferably 15 μm or less.
Further, the root mean square height Rq of the first principal surface 11 is preferably 5 μm or less, more preferably 4.5 μm or less, and even more preferably 4.1 μm or less.
Further, the ten-point average roughness RzJIS of the first main surface 11 is preferably 14 μm or less, more preferably 13.5 μm or less, and even more preferably 13.3 μm or less.
Further, the level difference Rk of the core portion of the first main surface 11 is preferably 7 μm or less, more preferably 6.8 μm or less, and even more preferably 6.5 μm or less.
Further, the average length Rdc of the elements of the first main surface 11 is preferably 7 μm or less, more preferably 6.6 μm or less, and even more preferably 6.3 μm or less.
The fact that the surface quality parameters of the first main surface 11 are within the above range means that the first main surface 11 is nearly flat.
Therefore, when an adherend is brought into contact with the first main surface 11 having the above-mentioned surface quality parameters, the first main surface 11 and the adherend are likely to come into close contact with each other. Therefore, the adhesive force on the first main surface 11 of the conductive adhesive 10 becomes high.

Generally, when a conductive adhesive has a high storage modulus, its creep resistance increases, but its tackiness tends to decrease.
However, in the conductive adhesive 10, the arithmetic mean roughness Ra of the first principal surface 11 is 4 μm or less, so even if the storage modulus at 65° C. is 1.6×10 ⁴ Pa or more, sufficient adhesiveness is not achieved. shows.
That is, it can be said that the conductive adhesive 10 has high creep resistance at high temperatures and high adhesiveness, which are both compatible.

In addition, in the conductive adhesive 10, the arithmetic mean roughness Ra of the second main surface 12 is preferably 4 μm or less, more preferably 3.97 μm or less, and even more preferably 3.65 μm or less. .
Further, the maximum height Rz of the second main surface 12 is preferably 16 μm or less, more preferably 15.5 μm or less, and even more preferably 15 μm or less.
Further, the maximum peak height Rp of the second main surface 12 is preferably 9.5 μm or less, more preferably 8.6 μm or less, and even more preferably 7.5 μm or less.
Further, the maximum valley depth Rv of the second main surface 12 is preferably 9 μm or less, more preferably 8.8 μm or less, and even more preferably 7 μm or less.
Further, the average height Rc of the second main surface 12 is preferably 11 μm or less, more preferably 10.6 μm or less, and even more preferably 10.3 μm or less.
Further, the maximum cross-sectional height Rt of the second main surface 12 is preferably 16 μm or less, more preferably 15.5 μm or less, and even more preferably 15 μm or less.
Further, the root mean square height Rq of the second principal surface 12 is preferably 5 μm or less, more preferably 4.5 μm or less, and even more preferably 4.1 μm or less.
Further, the ten-point average roughness RzJIS of the second main surface 12 is preferably 14 μm or less, more preferably 13.5 μm or less, and even more preferably 13.3 μm or less.
Further, the level difference Rk of the core portion of the second main surface 12 is preferably 7 μm or less, more preferably 6.8 μm or less, and even more preferably 6.5 μm or less.
Further, the average length Rdc of the elements of the second main surface 12 is preferably 7 μm or less, more preferably 6.6 μm or less, and even more preferably 6.3 μm or less.
When the parameters of the surface properties of the second main surface 12 are within the above range, the adhesive force of the second main surface 12 becomes high.

In addition, in this specification, among the parameters of the surface properties of the conductive adhesive, Ra, Rz, Rp, Rv, Rc, Rt, Rq, RzJIS and Rdc are parameters defined in JIS B 0601:2013, Rk is a parameter defined in JIS B0671-2:2002, and can be measured using analysis software attached to a surface shape measuring device such as a confocal microscope (OPTELICS HYBRID, manufactured by Lasertec).

As will be described in detail later, in the conductive adhesive 10, the surface properties such as the arithmetic mean roughness Ra of the first main surface 11 are controlled by adjusting the content, size, shape, etc. of the conductive particles. be able to.

The conductive adhesive 10 may have isotropic conductivity or anisotropic conductivity depending on its use.
As will be described in detail later, by adjusting the size, content, etc. of the conductive particles contained in the conductive adhesive 10, the conductive adhesive 10 can be made into a conductive adhesive having isotropic conductivity. It can be made into a conductive adhesive having anisotropic conductivity.

The thickness of the conductive adhesive 10 is preferably determined appropriately depending on the application, but from the viewpoint of creep resistance and adhesiveness, it is preferably 3 to 100 μm, more preferably 5 to 50 μm. .

Hereinafter, each structure of the conductive adhesive of the present invention will be explained in detail.

(conductive particles)
The conductive particles are not particularly limited, and examples thereof include metal particles, metal-coated resin particles, carbon filler, and the like.

Examples of the metal constituting the coating portion of the metal particles and metal-coated resin particles include gold, silver, copper, nickel, and zinc. The above metals may be used alone or in combination of two or more.

Specific examples of the metal particles include copper particles, silver particles, nickel particles, silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, gold-coated nickel particles, and silver-coated alloy particles.
Examples of the silver-coated alloy particles include silver-coated copper alloy particles in which alloy particles containing copper (for example, copper alloy particles made of an alloy of copper, nickel, and zinc) are coated with silver.
Metal particles can be produced by an electrolysis method, an atomization method, a reduction method, or the like.

Among the metal particles, silver particles, silver-coated copper particles, and silver-coated copper alloy particles are preferable. Silver-coated copper particles and silver-coated copper alloy particles are particularly preferred from the viewpoints of excellent conductivity, suppressing oxidation and aggregation of metal particles, and lowering the cost of metal particles.

A portion of the conductive particles are exposed on the first main surface 11 of the conductive adhesive 10. Therefore, the content, size, shape, etc. of the conductive particles affect the arithmetic mean roughness Ra of the first main surface 11.
By adjusting the content, size, shape, etc. of the conductive particles, the arithmetic mean roughness Ra of the first main surface 11 can be set to 4 μm or less.

From the viewpoint of making the arithmetic mean roughness Ra of the first main surface of the conductive adhesive 4 μm or less, the content of the conductive particles is preferably 5 to 85% by weight, and 5 to 70% by weight, for example. It is more preferable that

Furthermore, from the viewpoint of setting the arithmetic mean roughness Ra of the first principal surface of the conductive adhesive to 4 μm or less, the median diameter (D ₅₀ ) of the conductive particles is preferably 3 to 100 μm, and preferably 5 to 50 μm. It is more preferable that

Note that in this specification, the median diameter (D ₅₀ ) of conductive particles means the particle diameter at 50% of the integrated value in the particle size distribution determined by laser diffraction/scattering method.

The shape of the conductive particles is not particularly limited, and may be spherical (true sphere, ellipsoid, etc.), flake (scaly, flat, etc.), dendritic (dendritic), fibrous, filamentary, amorphous ( polyhedron). Among these, from the viewpoint of improving the conductivity of the conductive adhesive and flattening the first main surface of the conductive adhesive, spherical, flake, dendrite, and filament shapes are preferable.

Note that the content, size, and shape of the conductive particles also affect whether the conductive adhesive has isotropic conductivity or anisotropic conductivity.
For example, when imparting isotropic conductivity to a conductive adhesive, a method may be used in which the content of conductive particles is adjusted to 50 to 85% by weight. Further, when imparting anisotropic conductivity to the conductive adhesive, a method may be mentioned in which the content of conductive particles is set to 5% by weight or more and less than 49% by weight.

The content, size, and shape of the conductive particles are preferably determined as appropriate depending on the use of the conductive adhesive and desired performance.

(Resin composition)
The resin composition is not particularly limited as long as it has adhesive properties, but at least one resin selected from the group consisting of natural rubber, acrylic resin, polyurethane resin, silicone resin, and polyester resin. Preferably, it contains a resin.
Among these, acrylic resins and silicone resins are more preferred.

The acrylic resin preferably has a glass transition temperature (Tg) of 0°C or lower, more preferably -5°C or lower, and even more preferably -10°C or lower.
If the glass transition temperature of the acrylic resin exceeds 0° C., the adhesive strength will be low when attached to an adherend under low pressure and temperature conditions.
Note that the glass transition temperature of the acrylic resin is determined by differential scanning calorimetry.

The acid value of the acrylic resin is not particularly limited, but is preferably 5 mgKOH/g or less, more preferably 1 to 5 mgKOH/g, and even more preferably 1 to 3 mgKOH/g.
When the acid value of the acrylic resin is 5 mgKOH/g or less, the curing of the acrylic resin by the curing agent will not proceed excessively, so it can be easily adhered to the adherend, and the adhesive strength to the adherend is improved. do.

The weight average molecular weight of the acrylic resin is not particularly limited, but is preferably from 100,000 to 1,000,000, more preferably from 200,000 to 600,000. When the weight average molecular weight is within the above range, the adhesive strength to an adherend is improved.
The weight average molecular weight of the acrylic resin can be measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

In the present specification, "acrylic resin" refers to a polymer composed of a (meth)acrylate compound as a monomer component, that is, a polymer (or copolymer) having a structural unit derived from a (meth)acrylate compound. ).
In addition, in this specification, "(meth)acrylate" means acrylate and/or methacrylate. The term "(meth)acrylate compound" refers to a compound having an acryloyl group and/or a methacryloyl group. The same applies to "(meth)acrylic".
The acrylic resin may consist of only one type of (meth)acrylate compound, or may consist of two or more types.

Examples of the above (meth)acrylate compounds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, and (meth)acrylate. Isobutyl acid, s-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, isoamyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate , (meth)acrylic acid alkyl esters having a linear or branched alkyl group such as isononyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate; (meth)acrylic acid; carboxyethyl Carboxyl group-containing (meth)acrylic esters such as acrylate; 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 6 - Hydroxyl group-containing (meth)acrylic esters such as hydroxyhexyl (meth)acrylate, diethylene glycol mono(meth)acrylate, and dipropylene glycol mono(meth)acrylate; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate Ester; (meth)acrylic acid amide derivatives such as N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide; dimethylamino (Meth)acrylic acid dialkylaminoalkyl esters such as ethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dipropylaminopropyl (meth)acrylate, etc. can be mentioned.

In addition, the above (meth)acrylate compounds include neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, ) Polyfunctional (meth)acrylates such as acrylates are also included. Further examples include 2-hydroxy-3-acryloyloxypropyl (meth)acrylate, phenylglycidyl ether (meth)acrylate hexamethylene diisocyanate urethane prepolymer, and bisphenol A diglycidyl ether acrylic acid adduct.

The acrylic resin may have a structural unit derived from a monomer component other than the (meth)acrylate compound. Such monomer components are not particularly limited, but include, for example, carboxyl group-containing polymerizable unsaturated compounds such as crotonic acid, itaconic acid, fumaric acid, and maleic acid, or their anhydrides; styrene, vinyltoluene, α- Styrenic compounds such as methylstyrene; Vinyl esters such as vinyl acetate and vinyl propionate; Vinyl halides such as vinyl chloride; Vinyl ethers such as methyl vinyl ether; Cyano group-containing vinyl compounds such as (meth)acrylonitrile; ethylene, propylene α-olefins such as

The content of the resin composition in the conductive adhesive 10 is not particularly limited, but is preferably 15 to 95% by weight, and 30 to 95% by weight, based on 100% by weight of the total solid content in the resin composition. It is more preferably 95% by weight, and even more preferably 30 to 85% by weight.
If the content is less than 15% by weight, the adhesive strength to the adherend will decrease.
When the content exceeds 95% by weight, the proportion of conductive particles becomes relatively small, resulting in a decrease in electrical stability.

(Other ingredients)
In addition to the conductive particles and the resin composition, the conductive adhesive 10 may optionally contain a curing agent, a flame retardant, a plasticizer, an antifoaming agent, a viscosity modifier, an antioxidant, a diluent, an antisettling agent, It may also contain fillers, colorants, leveling agents, coupling agents, tackifiers, and the like.

The curing agent is not particularly limited, but when the resin composition is an acrylic resin, an isocyanate curing agent can be used.
The isocyanate curing agent is a compound having two or more isocyanate groups in the molecule, and promotes curing of the acrylic resin. Only one type of isocyanate curing agent may be used, or two or more types may be used.

Examples of the isocyanate curing agent include lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate; cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, Alicyclic polyisocyanates such as hydrogenated toluene diisocyanate and hydrogenated xylylene diisocyanate; aromatic polyisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, etc. Can be mentioned.

The content of the isocyanate curing agent is preferably 0.05 to 5.0 parts by weight, more preferably 0.1 to 4.0 parts by weight, and 1.0 parts by weight based on 100 parts by weight of the acrylic resin. More preferably, the amount is 3.5 parts by weight.
When the content of the isocyanate curing agent is 0.05 parts by weight or more, the acrylic resin can be appropriately cured, and the storage modulus at 65° C. of the conductive adhesive 10 is 1.6×10 It becomes easier to increase the pressure to ⁴ Pa or higher.
When the content of the isocyanate curing agent is 5.0 parts by weight or less, the curing agent suppresses excessive curing of the acrylic resin and improves adhesive strength.

Next, an electromagnetic shielding film including the conductive adhesive of the present invention will be explained.
Note that the electromagnetic shielding film including the conductive adhesive of the present invention is one embodiment of the present invention.
FIG. 2 is a cross-sectional view schematically showing an example of the electromagnetic shielding film according to the first embodiment of the present invention.

The electromagnetic wave shielding film 40 shown in FIG. A layer 30 is provided.
Note that in the electromagnetic shielding film 40, the first main surface 11 of the conductive adhesive 10 is the surface that comes into contact with the adherend.

As described above, the conductive adhesive 10 has high creep resistance and high adhesiveness at high temperatures. Therefore, the shield layer 20 can be reliably bonded to the adherend.

Further, by forming the protective layer 30, the shield layer 20 and the conductive adhesive 10 can be protected.

Next, the shield layer 20 and protective layer 30 of the electromagnetic shielding film 40 will be explained.

(shield layer)
The structure of the shield layer 20 is not particularly limited as long as it can shield electromagnetic waves by reflecting or absorbing them, but it is preferably a metal layer, for example.

Examples of the metal constituting such a metal layer include gold, silver, copper, aluminum, nickel, tin, palladium, chromium, titanium, zinc, and alloys thereof. Among these, a copper layer and a silver layer are preferred from the viewpoint of superior electromagnetic shielding effect, and copper is more preferred from the viewpoint of economy.

The material and thickness of the metal layer may be appropriately determined depending on the required electromagnetic shielding effect and repeated bending/sliding resistance.
For example, from the viewpoint of obtaining a sufficient electromagnetic shielding effect, the thickness of the metal layer is preferably 0.1 μm or more.
Further, from the viewpoint of productivity, flexibility, etc., it is preferable that the thickness is 12 μm or less.

Note that the metal layer can be formed by an electrolytic plating method, an electroless plating method, a sputtering method, an electron beam evaporation method, a vacuum evaporation method, a CVD method, a metal organic method, or the like. Moreover, the metal layer can also be formed from metal foil, metal nanoparticles, scaly metal particles, or the like.

(protective layer)
It is preferable that the protective layer 30 is made of a resin material, has insulation properties, and satisfies predetermined mechanical strength, chemical resistance, and heat resistance.

The resin material constituting the protective layer 30 is not particularly limited as long as it has sufficient insulation, but examples include thermoplastic resin compositions, thermosetting resin compositions, and active energy ray-curable compositions. Can be used.

Thermoplastic resin compositions include, but are not particularly limited to, styrene resin compositions, vinyl acetate resin compositions, polyester resin compositions, polyethylene resin compositions, polypropylene resin compositions, imide resin compositions, Also, acrylic resin compositions and the like can be used. The thermosetting resin composition is not particularly limited, but phenolic resin compositions, epoxy resin compositions, urethane resin compositions, melamine resin compositions, alkyd resin compositions, etc. can be used. can. The active energy ray-curable composition is not particularly limited, but for example, a polymerizable compound having at least two (meth)acryloyloxy groups in the molecule can be used. These compositions may be used alone or in combination of two or more.

The protective layer 30 contains a curing accelerator, a tackifier, an antioxidant, a pigment, a dye, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity adjuster, as necessary. and an antiblocking agent may also be included.

In addition, in the electromagnetic shielding film of the present invention, the protective layer has an arbitrary structure, and the protective layer does not need to be formed.

The electromagnetic shielding film of the present invention is attached to an adherend by the adhesive force of the conductive adhesive of the electromagnetic shielding film.
Even after the electromagnetic shielding film of the present invention is attached to an adherend, the conductive adhesive does not harden and remains flexible. Therefore, even if the electromagnetic shielding film of the present invention is applied to a movable part and the movable part moves, the electromagnetic shielding film of the present invention will not be easily damaged and will not easily peel off from the movable part.
Therefore, the electromagnetic shielding film of the present invention is suitable as an electromagnetic shielding film to be attached to a movable part.

Next, a method for manufacturing the electromagnetic shielding film of the present invention will be explained.
When manufacturing the electromagnetic shielding film of the present invention, first, conductive particles and a resin composition are mixed to prepare a conductive adhesive composition.
At this time, a solvent and other additives may be added to the conductive adhesive composition.

Examples of the solvent include xylene, toluene, tert-butyl alcohol, ethyl acetate, and methyl ethyl ketone.

Next, a conductive adhesive composition is applied onto the first base material such as a separator film, and if necessary, the solvent is removed and/or partially cured by heating or the like to form a conductive adhesive. The above heating is preferably performed at, for example, 25 to 100° C. for about 1 to 72 hours.

Note that a known coating method can be used to apply the conductive adhesive composition. For example, coaters such as a gravure roll coater, reverse roll coater, kiss roll coater, lip coater dip roll coater, bar coater, knife coater, spray coater, comma coater, direct coater, and slot die coater can be used.

The main surface of the conductive adhesive on the side that is in contact with the base material is the first main surface, and the main surface of the conductive adhesive on the side that is not in contact with the base material is the second main surface.

Next, a composition for forming a protective layer is applied or laminated onto the second base material, and a shield layer is further formed on the protective layer.
Conventionally known methods can be used for applying and laminating the composition for forming the protective layer and for forming the shield layer.

Thereafter, the electromagnetic shielding film of the present invention can be manufactured by laminating the adhesive composition formed on the first base material and the shielding layer of the second base material.

When attaching the electromagnetic shielding film manufactured in this way to an adherend, first, the first base material is peeled off, and the adherend is brought into contact with the first main surface of the conductive adhesive. At this time, pressure is applied to the electromagnetic shielding film so that the electromagnetic shielding film does not peel off from the adherend. After that, the second base material is peeled off.
Thereby, the electromagnetic shielding film of the present invention can be attached to an adherend.

Next, a shield printed wiring board including the electromagnetic shielding film of the present invention will be explained.

FIG. 3 is a cross-sectional view schematically showing an example of a shield printed wiring board including an electromagnetic shielding film according to the first embodiment of the present invention.

A shield printed wiring board 60 shown in FIG. 3 includes a printed wiring board 50 and an electromagnetic shielding film 40.
The printed wiring board 50 includes a base film 51, a printed circuit 52 placed on the base film 51, and a coverlay 53 placed so as to cover the printed circuit 52.
In the printed wiring board 50, the printed circuit 52 includes a ground circuit 52a, and the coverlay 53 has an opening 53a that exposes the ground circuit 52a.

In the shield printed wiring board 60, the electromagnetic shielding film 40 is arranged on the printed wiring board 50 so that the coverlay 53 and the conductive adhesive 10 are in contact with each other.

In the shield printed wiring board 60, the conductive adhesive 10 fills the opening 53a of the coverlay 53 and is in contact with the ground circuit 52a. With such a configuration, the shielding characteristics of the electromagnetic shielding film 40 can be improved.

In the printed wiring board 50, both the base film 51 and the coverlay 53 are preferably made of engineering plastic. Examples include resins such as polypropylene, crosslinked polyethylene, polyester, polybenzimidazole, polyimide, polyimide amide, polyetherimide, and polyphenylene sulfide (PPS).

In the printed wiring board 50, the printed circuit 52 can be made of a common circuit material such as copper.

The base film 51 and the printed circuit 52 may be bonded together using an adhesive, or may be bonded together without using an adhesive, similar to a so-called non-adhesive type copper clad laminate. Further, the coverlay 53 may be formed by bonding a plurality of flexible insulating films together with an adhesive, and is formed by a series of methods such as coating with photosensitive insulating resin, drying, exposure, development, and heat treatment. It may be formed.

As a method for attaching the electromagnetic shielding film 40 to the printed wiring board 50, a conventionally known method can be employed.
In particular, since the electromagnetic shielding film 40 includes the conductive adhesive 10, it can be attached at relatively low temperatures and pressures such as 23 to 65° C. and 0.1 to 1.0 MPa.

(Second embodiment)
In the conductive adhesive according to the second embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" The configuration requirements are the same as those of the conductive adhesive according to the first embodiment of the present invention, except that the configuration requirement is changed to "the maximum height Rz of the first principal surface is 16 μm or less".
That is, the conductive adhesive according to the second embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. A conductive adhesive having a shape, characterized in that the storage modulus of the conductive adhesive at 65° C. is 1.6 × 10 Pa or more, and the maximum height Rz of the first principal surface is 16 μm or less. shall be.

In addition, in the conductive adhesive according to the second embodiment of the present invention, the maximum height Rz of the first main surface is preferably 15.5 μm or less, more preferably 15 μm or less.
The fact that the maximum height Rz of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the second embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the second embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the second embodiment of the present invention other than these parameters are the same as preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Third embodiment)
In the conductive adhesive according to the third embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" The configuration requirements are the same as those of the conductive adhesive according to the first embodiment of the present invention, except that the configuration requirement is changed to "the maximum peak height Rp of the first principal surface is 9.5 μm or less".
That is, the conductive adhesive according to the third embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The conductive adhesive has a storage elastic modulus of 1.6×10 ⁴ Pa or more at 65° C., and a maximum peak height Rp of the first main surface is 9.5 μm or less. characterized by something.

In addition, in the conductive adhesive according to the third embodiment of the present invention, the maximum peak height Rp of the first main surface is preferably 8.6 μm or less, more preferably 7.5 μm or less.
The fact that the maximum peak height Rp of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the third embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the third embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the third embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Fourth embodiment)
In the conductive adhesive according to the fourth embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" These are the same constituent requirements as the conductive adhesive according to the first embodiment of the present invention, except for the constituent requirement that "the maximum valley depth Rv of the first principal surface is 9 μm or less".
That is, the conductive adhesive according to the fourth embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. a conductive adhesive having a storage elastic modulus of 1.6× ^{10 4} Pa or more at 65° C. and a maximum valley depth Rv of the first principal surface of 9 μm or less. It is characterized by

In addition, in the conductive adhesive according to the fourth embodiment of the present invention, the maximum valley depth Rv of the first main surface is preferably 8.8 μm or less, more preferably 7 μm or less.
The fact that the maximum valley depth Rv of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the fourth embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the fourth embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the fourth embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Fifth embodiment)
In the conductive adhesive according to the fifth embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" These are the same constituent requirements as the conductive adhesive according to the first embodiment of the present invention, except for the constituent requirement that "the average height Rc of the first principal surface is 11 μm or less".
That is, the conductive adhesive according to the fifth embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The electrically conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and the average height Rc of the first principal surface is 11 μm or less. It is characterized by

In addition, in the conductive adhesive according to the fifth embodiment of the present invention, the average height Rc of the first main surface is preferably 10.6 μm or less, more preferably 10.3 μm or less.
The fact that the average height Rc of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the fifth embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the fifth embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the fifth embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Sixth embodiment)
In the conductive adhesive according to the sixth embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" These are the same constituent requirements as the conductive adhesive according to the first embodiment of the present invention, except for the constituent requirement that "the maximum cross-sectional height Rt of the first principal surface is 16 μm or less".
That is, the conductive adhesive according to the sixth embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. a conductive adhesive having a storage elastic modulus of 1.6× ^{10 4} Pa or more at 65° C. and a maximum cross-sectional height Rt of the first principal surface of 16 μm or less. It is characterized by

In addition, in the conductive adhesive according to the sixth embodiment of the present invention, the maximum cross-sectional height Rt of the first main surface is preferably 15.5 μm or less, more preferably 15 μm or less.
The fact that the maximum cross-sectional height Rt of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the sixth embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the sixth embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the sixth embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Seventh embodiment)
In the conductive adhesive according to the seventh embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" These are the same constituent requirements as the conductive adhesive according to the first embodiment of the present invention, except for the constituent requirement that "the root mean square height Rq of the first principal surface is 5 μm or less".
That is, the conductive adhesive according to the seventh embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The electrically conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and the root mean square height Rq of the first principal surface is 5 μm or less. characterized by something.

In addition, in the conductive adhesive according to the seventh embodiment of the present invention, the root mean square height Rq of the first principal surface is preferably 4.5 μm or less, more preferably 4.1 μm or less. .
The fact that the root mean square height Rq of the first principal surface is within the above range means that the first principal surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the seventh embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the seventh embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the seventh embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Eighth embodiment)
In the conductive adhesive according to the eighth embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" These are the same constituent requirements as the conductive adhesive according to the first embodiment of the present invention, except that the constituent requirement is that "the ten-point average roughness RzJIS of the first principal surface is 14 μm or less".
That is, the conductive adhesive according to the eighth embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. a conductive adhesive having a storage elastic modulus of 1.6×10 ⁴ Pa or more at 65° C., and a ten-point average roughness RzJIS of the first principal surface of 14 μm or less; characterized by something.

In addition, in the conductive adhesive according to the eighth embodiment of the present invention, the ten-point average roughness RzJIS of the first main surface is preferably 13.5 μm or less, more preferably 13.3 μm or less. .
The fact that the ten-point average roughness RzJIS of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the eighth embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the eighth embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the eighth embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(Ninth embodiment)
In the conductive adhesive according to the ninth embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" The configuration requirements are the same as those of the conductive adhesive according to the first embodiment of the present invention, except that the configuration requirement is changed to "the level difference Rk of the core portion of the first principal surface is 7 μm or less".
That is, the conductive adhesive according to the ninth embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The conductive adhesive has a storage elastic modulus of 1.6× ^{10 4} Pa or more at 65° C., and a level difference Rk of the core portion of the first principal surface is 7 μm or less. characterized by something.

In addition, in the conductive adhesive according to the ninth embodiment of the present invention, the level difference Rk of the core portion of the first main surface is preferably 6.8 μm or less, more preferably 6.5 μm or less. .
The fact that the level difference Rk of the core portion of the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the ninth embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the ninth embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the ninth embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

(10th embodiment)
In the conductive adhesive according to the tenth embodiment of the present invention, the constituent requirement of the conductive adhesive according to the first embodiment of the present invention is that "the arithmetic mean roughness Ra of the first principal surface is 4 μm or less" These are the same constituent requirements as the conductive adhesive according to the first embodiment of the present invention, except that the constituent requirement is "the average length Rdc of the elements on the first principal surface is 7 μm or less".
That is, the conductive adhesive according to the tenth embodiment of the present invention is a sheet comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface. The electrically conductive adhesive has a storage modulus of 1.6× ^{10 4} Pa or more at 65° C., and the average length Rdc of the elements on the first principal surface is 7 μm or less. characterized by something.

In addition, in the conductive adhesive according to the tenth embodiment of the present invention, the average length Rdc of the elements on the first main surface is preferably 6.6 μm or less, more preferably 6.3 μm or less. .
The fact that the average length Rdc of the elements on the first main surface is within the above range means that the first main surface is nearly flat.
Therefore, when a flat adherend is brought into contact with the first main surface of the conductive adhesive according to the tenth embodiment of the present invention, the first main surface and the adherend are likely to come into close contact with each other. Therefore, the adhesive force of the conductive adhesive becomes high.

Further, in the conductive adhesive according to the tenth embodiment of the present invention, the arithmetic mean roughness Ra of the first main surface is preferably 4 μm or less, more preferably 3.97 μm or less, and 3.65 μm or less. It is more preferable that it is the following.

Preferred aspects of the conductive adhesive according to the tenth embodiment of the present invention other than these parameters are the same as the preferred aspects of the conductive adhesive according to the first embodiment of the present invention.

The following items are disclosed in this specification.

The present disclosure (1) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and an arithmetic mean roughness Ra of the first principal surface of 4 μm or less. be.

The present disclosure (2) is a sheet-shaped conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and a maximum height Rz of the first principal surface is 16 μm or less. .

The present disclosure (3) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, A conductive adhesive characterized in that the storage elastic modulus at 65° C. of the conductive adhesive is 1.6×10 ⁴ Pa or more, and the maximum peak height Rp of the first principal surface is 9.5 μm or less. It is.

The present disclosure (4) is a sheet-shaped conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and a maximum valley depth Rv of the first principal surface is 9 μm or less. be.

The present disclosure (5) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C., and an average height Rc of the first principal surface is 11 μm or less. .

The present disclosure (6) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage modulus of 1.6× ^{10 4} Pa or more at 65° C., and a maximum cross-sectional height Rt of the first principal surface is 16 μm or less. be.

The present disclosure (7) is a sheet-shaped conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, A conductive adhesive characterized in that the storage elastic modulus at 65° C. of the conductive adhesive is 1.6×10 ⁴ Pa or more, and the root mean square height Rq of the first principal surface is 5 μm or less. It is.

The present disclosure (8) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, A conductive adhesive characterized in that the storage modulus at 65° C. of the conductive adhesive is 1.6×10 ⁴ Pa or more, and the ten-point average roughness RzJIS of the first principal surface is 14 μm or less. It is.

The present disclosure (9) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage elastic modulus of 1.6× ^{10 4} Pa or more at 65° C., and a level difference Rk of the core portion of the first principal surface is 7 μm or less. It is.

The present disclosure (10) is a sheet-like conductive adhesive comprising conductive particles and a resin composition, and having a first main surface and a second main surface opposite to the first main surface, The conductive adhesive has a storage modulus of 1.6× ^{10 4} Pa or more at 65° C., and an average length Rdc of the elements on the first principal surface is 7 μm or less. It is.

The present disclosure (11) is the conductive adhesive according to any one of the present disclosure (1) to (10), wherein the conductive adhesive has isotropic conductivity or anisotropic conductivity.

The present disclosure (12) includes the conductive adhesive according to any one of the present disclosures (1) to (11), and a shield layer laminated so as to be in contact with the second main surface of the conductive adhesive. This is an electromagnetic shielding film that features:

The present disclosure (13) is the electromagnetic wave shielding film according to the present disclosure (12), further comprising a protective layer formed on the shield layer.

(Example 1)
As a resin composition for a conductive adhesive, 84.5 parts by weight of an acrylic adhesive, 15 parts by weight of filamentary nickel particles as conductive particles, and 0.5 parts by weight of toluene diisocyanate as a curing agent were mixed. A conductive adhesive composition according to Example 1 was prepared.

Next, a separate film made of polyethylene terephthalate whose surface has been treated with a release agent is prepared as a first base material, and a conductive adhesive is applied to the surface of the first base material using an applicator to a thickness of 13 μm. The composition was applied.

Next, a separate film made of polyethylene terephthalate whose surface has been treated with a release agent is prepared as a second base material, and a protective layer is applied to the surface of the second base material to a thickness of 5 μm using an applicator. A protective layer was formed by coating a polyester resin, which is a resin composition for
Thereafter, a 10 μm thick copper foil was placed on the protective layer.

Next, the conductive adhesive composition placed on the first base material and the copper foil placed on the second base material were pasted together so that they were in contact with each other.
Thereafter, aging was performed at 40° C. for 3 days to produce the electromagnetic shielding film according to Example 1. Note that due to aging, the resin composition and curing agent in the conductive pressure-sensitive adhesive composition react to form a conductive pressure-sensitive adhesive.

(Example 2) - (Example 9) and (Comparative example 1) - (Comparative example 2)
Electromagnetic shielding films according to Examples 2 to 9 and Comparative Examples 1 to 2 were manufactured in the same manner as in Example 1, except that the materials used were changed to the types and blending ratios shown in Tables 1 and 2. .
Note that in Tables 1 and 2, the numerical values for the composition of the conductive adhesive mean "parts by weight."
Further, the types of materials listed in Tables 1 and 2 are as follows.
The median diameter (D ₅₀ ) of Conductive Particles 1 to 3 below was measured using a particle size distribution analyzer (manufactured by Micro Track Bell Co., Ltd., MT3300EXII).
Resin composition 1 for protective layer: Polyester resin/PET/PSA (black)
Resin composition 2 for protective layer: Polyester resin/PET/PSA (transparent)
Resin composition for conductive adhesive: Acrylic adhesive Conductive particles 1: Filament-shaped nickel particles (median diameter (D ₅₀ ): 20 μm)
Conductive particles 2: dendrite-like silver-coated copper particles (median diameter (D ₅₀ ): 12 μm)
Conductive particles 3: Silver-coated copper particles produced by atomization method (median diameter (D ₅₀ ): 5 μm)
Curing agent: toluene diisocyanate

(Measurement of storage modulus)
The storage modulus at 65° C. of the conductive adhesives according to each example and each comparative example was measured using “Modular Compact Rheometer (MCR) 302” manufactured by Anton Paar. The results are shown in Tables 1 and 2.

(Measurement of surface properties of conductive adhesive)
In the electromagnetic shielding film according to each example and each comparative example, the first base material was peeled off to expose the first main surface of the conductive adhesive, and the film was exposed to a confocal microscope (manufactured by Lasertec, OPTELICS HYBRID, objective lens 20x). ) to measure five arbitrary locations on the first main surface, then use data analysis software (LMeye7) to measure Ra, Rz, Rp, Rv, Rc, Rt, Rq, RzJIS, Rdc and Rk were measured. The results are shown in Tables 1 and 2.

(Creep resistance test)
The electromagnetic shielding films according to the Examples and Comparative Examples cut into 1 cm long and 7 cm wide pieces were pressed onto an aluminum plate (A5052) using a roller under a pressure of 2 kgf, and left to stand for 24 hours. In addition, if the electromagnetic shielding film was damaged during pressure bonding, it was reinforced with a backing film.
Next, the electromagnetic wave shielding films according to each example and each comparative example were installed in a thermal shock tester (TSA-43EL-A) manufactured by ESPEC Corporation so that a load of 1 kgf was applied, and after being allowed to stand at 0°C for 30 minutes, This process was repeated for 24 cycles in which the sample was allowed to stand for 30 minutes at ℃, and a heat cycle test was conducted to evaluate the creep resistance.
The evaluation criteria are as follows. The results are shown in Tables 1 and 2.
○: After 24 cycles, the electromagnetic shielding film was stuck to the aluminum plate.
×: After 24 cycles, the electromagnetic shielding film was peeled off from the aluminum plate and fell off.

(Peeling test)
A peel test was conducted using the adhesive tape/adhesive sheet test method specified in ASTM D3330. Specifically, the electromagnetic shielding film according to each example and each comparative example cut into 125 mm in length and 25 mm in width was attached to a test plate made of stainless steel material, and the electromagnetic shield film was cut in a 180° direction from the test plate using a tensile tester. The adhesion was evaluated by measuring the tensile force when peeled off. The results are shown in Tables 1 and 2. Note that if the tensile force when peeled off is 1 N/25 mm or more, it can be said that the adhesive force is sufficiently strong.

As shown in Tables 1 and 2, the storage modulus of the conductive adhesive at 65° C. is 1.6×10 ⁴ Pa or more, and the parameters of the surface properties of the conductive adhesive are within the scope of the present invention. It was found that the electromagnetic shielding films according to each example had high creep resistance and high adhesiveness.
On the other hand, the electromagnetic shielding film according to Comparative Example 1 in which the conductive adhesive had a storage modulus of less than 1.6×10 ⁴ Pa at 65° C. was found to have low creep resistance.
Furthermore, it was found that the electromagnetic shielding film according to Comparative Example 2, in which the parameters of the surface properties of the conductive adhesive were not included in the scope of the present invention, also had low creep resistance.

10 Conductive adhesive 11 First main surface 12 Second main surface 20 Shield layer 30 Protective layer 40 Electromagnetic shielding film 50 Printed wiring board 51 Base film 52 Printed circuit 52a Ground circuit 53 Coverlay 53a Opening 60 Shield printed wiring board

Claims (13)

1. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the first principal surface has an arithmetic mean roughness Ra of 4 μm or less.
2. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the first principal surface has a maximum height Rz of 16 μm or less.
3. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the first main surface has a maximum peak height Rp of 9.5 μm or less.
4. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the first principal surface has a maximum valley depth Rv of 9 μm or less.
5. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the average height Rc of the first principal surface is 11 μm or less.
6. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the first principal surface has a maximum cross-sectional height Rt of 16 μm or less.
7. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the root mean square height Rq of the first principal surface is 5 μm or less.
8. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that the first principal surface has a ten-point average roughness RzJIS of 14 μm or less.
9. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
   The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
   A conductive adhesive characterized in that a level difference Rk of the core portion of the first principal surface is 7 μm or less.
10. A sheet-shaped conductive adhesive comprising conductive particles and a resin composition and having a first main surface and a second main surface opposite to the first main surface,
    The conductive adhesive has a storage modulus of 1.6×10 ⁴ Pa or more at 65° C.,
    A conductive adhesive characterized in that the average length Rdc of the elements on the first main surface is 7 μm or less.
11. The conductive adhesive according to any one of claims 1 to 10, wherein the conductive adhesive has isotropic conductivity or anisotropic conductivity.
12. The conductive adhesive according to any one of claims 1 to 11,
    An electromagnetic shielding film comprising: a shielding layer laminated so as to be in contact with the second main surface of the conductive adhesive.
13. The electromagnetic shielding film according to claim 12, further comprising a protective layer formed on the shielding layer.
    
    

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