JP6435540B2 - Electromagnetic wave shielding film, flexible printed wiring board with electromagnetic wave shielding film, and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electromagnetic wave shielding film, a flexible printed wiring board provided with the electromagnetic wave shielding film, and a method for producing them.

  In order to shield electromagnetic wave noise generated from the flexible printed wiring board and external electromagnetic noise, an electromagnetic wave shielding film may be provided on the surface of the flexible printed wiring board (for example, see Patent Document 1).

FIG. 7: is sectional drawing which shows an example of the manufacturing process of the conventional flexible printed wiring board with an electromagnetic wave shielding film.
The flexible printed wiring board 101 with the electromagnetic wave shielding film includes a flexible printed wiring board 130, an insulating film 140, and an electromagnetic wave shielding film 110 from which the release film 118 is peeled off.
The flexible printed wiring board 130 has a printed circuit 134 provided on one side of a base film 132.
The insulating film 140 is provided on the surface of the flexible printed wiring board 130 on the side where the printed circuit 134 is provided.
The electromagnetic wave shielding film 110 includes an insulating protective layer 112, a metal thin film layer 114 covering the first surface of the insulating protective layer 112, a conductive adhesive layer 116 covering the surface of the metal thin film layer 114, and an insulating protection. A release film 118 (carrier film) covering the second surface of the layer 112.
The conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is bonded to the surface of the insulating film 140 and cured. In addition, the conductive adhesive layer 116 is electrically connected to the printed circuit 134 through the through hole 142 formed in the insulating film 140.

For example, as shown in FIG. 7, the flexible printed wiring board 101 with the electromagnetic wave shielding film is manufactured through the following steps.
(I) A step of providing an insulating film 140 in which a through hole 142 is formed at a position corresponding to the ground of the printed circuit 134 on the surface of the flexible printed wiring board 130 on which the printed circuit 134 is provided.
(Ii) The electromagnetic wave shielding film 110 is stacked on the surface of the insulating film 140 so that the conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is in contact with each other, and these are hot-pressed to make the surface of the insulating film 140 conductive. Bonding the adhesive layer 116 and electrically connecting the conductive adhesive layer 116 to the ground of the printed circuit 134 through the through hole 142;
(Iii) The process of obtaining the flexible printed wiring board 101 with an electromagnetic wave shield film by peeling and removing the release film 118 which finished the role as a carrier film from the insulating protective layer 112 after hot pressing.

Japanese Patent No. 4201548

  However, in the portion of the through hole 142 of the flexible printed wiring board 101 with the electromagnetic wave shielding film, peeling is likely to occur between the metal thin film layer 114 and the conductive adhesive layer 116. When peeling occurs between the metal thin film layer 114 and the conductive adhesive layer 116 and the gap 144 is formed, the metal thin film layer 114 and the printed circuit 134 cannot be electrically connected. The reason why peeling occurs between the metal thin film layer 114 and the conductive adhesive layer 116 is considered as follows.

  At a part of the interface between the metal thin film layer 114 and the conductive adhesive layer 116, the metal thin film layer 114 and the conductive particles in the conductive adhesive layer 116 are merely in contact with each other. Adhesiveness between the layer 114 and the conductive adhesive layer 116 is insufficient. Then, when the insulating protective layer 112 that has been bent and deformed along the shape of the through hole 142 tries to recover to the original flat shape by elastic deformation, the metal thin film follows the insulating protective layer 112 that is elastically deformed. Layer 114 also attempts to recover to its original flat shape. As a result, peeling occurs between the metal thin film layer 114 and the conductive adhesive layer 116.

  The present invention is an electromagnetic wave shielding film having high adhesion between the metal thin film layer and the conductive adhesive layer, a flexible printed wiring board with an electromagnetic wave shielding film in which the metal thin film layer and the printed circuit are electrically and reliably connected, And methods for their manufacture.

The present invention has the following aspects.
(1) and the insulating protective layer, and the metal thin film layer, and a primer layer, and a conductive adhesive layer in this order, said primer layer, Ri layer der derived from primer comprising a synthetic rubber carboxylated, the thickness of the primer layer is a 0.05 to 1 [mu] m, a part of the primer is that is penetrated absorbed in the metal thin film layer, an electromagnetic wave shielding film.
( 2 ) The electromagnetic wave shielding film according to (1 ), wherein the conductive adhesive layer is an anisotropic conductive adhesive layer.
( 3 ) The electromagnetic wave shielding film of (1) or (2) , further comprising a first release film provided on the surface of the insulating protective layer.
( 4 ) The electromagnetic wave shielding film according to ( 3 ), further comprising a second release film provided on the surface of the conductive adhesive layer.
( 5 ) A method for producing an electromagnetic wave shielding film according to ( 4 ), comprising the following steps (a) to (e).
(A) A step of forming an insulating protective layer on one surface of the first release film.
(B) A step of forming a metal thin film layer on the surface of the insulating protective layer.
(C) By applying the primer having a viscosity of 1 to 100 mPa · s on the surface of the metal thin film layer to form a primer layer, a first release film, an insulating protective layer, a metal thin film layer, The process of obtaining the 1st laminated body provided with the primer layer in order.
(D) The process of obtaining the 2nd laminated body provided with the 2nd release film and the conductive adhesive layer in order by forming a conductive adhesive layer in the single side | surface of a 2nd release film.
(E) A step of bonding the first laminated body and the second laminated body so that the primer layer and the conductive adhesive layer are in contact with each other.
( 6 ) A flexible printed wiring board provided with a printed circuit on at least one side of the base film, an insulating film provided on the surface of the flexible printed wiring board provided with the printed circuit, and a surface of the insulating film (1) or (2) electromagnetic wave shielding film to which the conductive adhesive layer is bonded to the printed circuit through the through-hole formed in the insulating film. An electrically connected flexible printed wiring board with an electromagnetic shielding film.
( 7 ) The manufacturing method of the flexible printed wiring board with an electromagnetic wave shielding film which has the following process (f)-(h).
(F) An insulating film in which a through hole is formed at a position corresponding to the printed circuit is provided on the surface of the flexible printed wiring board having the printed circuit on at least one side of the base film on the side where the printed circuit is provided; The process of obtaining the flexible printed wiring board with a film.
(G) After the step (f), the flexible printed wiring board with an insulating film and the electromagnetic wave shielding film of any one of (1) to ( 3 ) are placed on the surface of the insulating film with the conductive adhesive layer. The conductive adhesive layer is adhered to the surface of the insulating film by stacking them so that they are in contact with each other, and the conductive adhesive layer is attached to the printed circuit through the through hole. Electrical connection process.
(H) A step of peeling off the first release film after the step (g) when the electromagnetic wave shielding film includes a first release film.

The electromagnetic wave shielding film of the present invention has high adhesion between the metal thin film layer and the conductive adhesive layer.
According to the method for producing an electromagnetic wave shielding film of the present invention, an electromagnetic wave shielding film having high adhesion between the metal thin film layer and the conductive adhesive layer can be produced.
In the flexible printed wiring board with an electromagnetic wave shielding film of the present invention, the metal thin film layer and the printed circuit are electrically connected reliably.
According to the method for producing a flexible printed wiring board with an electromagnetic wave shielding film of the present invention, a flexible printed wiring board with an electromagnetic wave shielding film in which the metal thin film layer and the printed circuit are electrically connected reliably can be produced.

It is sectional drawing which shows an example of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows an example of process (a)-(c) in the manufacturing method of the electromagnetic wave shield film of this invention. It is sectional drawing which shows an example of the process (d) in the manufacturing method of the electromagnetic wave shield film of this invention. It is sectional drawing which shows an example of the process (e) in the manufacturing method of the electromagnetic wave shield film of this invention. It is sectional drawing which shows an example of the flexible printed wiring board with an electromagnetic wave shielding film of this invention. It is sectional drawing which shows an example of process (f)-(h) in the manufacturing method of the flexible printed wiring board with an electromagnetic wave shielding film of this invention. It is sectional drawing which shows an example of the manufacturing process of the conventional flexible printed wiring board with an electromagnetic wave shielding film.

The following definitions of terms apply throughout this specification and the claims.
For the average particle diameter of the conductive particles, 30 conductive particles are randomly selected from the electron microscopic image of the conductive particles, and the minimum diameter and the maximum diameter are measured for each conductive particle. Is a value obtained by arithmetically averaging the measured particle diameters of 30 conductive particles.
The specific surface area of the conductive particles is a value calculated by immersing degassed particles in liquid nitrogen and measuring the amount of adsorbed nitrogen.
The thickness of film (release film, insulating film, etc.), coating film (insulating protective layer, conductive adhesive layer, etc.), metal thin film layer, etc. is observed using a transmission electron microscope. It is the value obtained by measuring the thickness at five locations and averaging.
The storage elastic modulus is calculated as one of the viscoelastic characteristics using a dynamic viscoelasticity measuring device that is calculated from the stress applied to the measurement object and the detected strain and outputs it as a function of temperature or time.
The surface resistance is measured by using two thin film metal electrodes (length 10 mm, width 5 mm, distance 10 mm between electrodes) formed by depositing gold on quartz glass, placing an object to be measured on the electrodes, and measuring the surface resistance. This is a resistance between electrodes measured by pressing a 10 mm × 20 mm region of the object to be measured with a load of 0.049 N from above the object with a measurement current of 1 mA or less.

<Electromagnetic wave shielding film>
FIG. 1 is a cross-sectional view showing an example of the electromagnetic wave shielding film of the present invention.
The electromagnetic wave shielding film 10 includes an insulating protective layer 12, a metal thin film layer 14 covering the first surface of the insulating protective layer 12, a primer layer 15 covering the surface of the metal thin film layer 14, and a surface of the primer layer 15. The conductive adhesive layer 16 to cover, the 1st release film 18 which covers the 2nd surface of the insulating protective layer 12, and the 2nd release film 20 which covers the surface of the conductive adhesive layer 16 are provided. .

(Insulating protective layer)
The insulating protective layer 12 becomes a base (base) for forming the metal thin film layer 14, and after the electromagnetic wave shielding film 10 is attached to the surface of the insulating film provided on the surface of the flexible printed wiring board, the insulating protective layer 12 is a metal. The thin film layer 14 is protected.
The surface resistance of the insulating protective layer 12 is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the insulating protective layer 12 is preferably 1 × 10 ¹⁹ Ω or less from a practical point of view.

  As the insulating protective layer 12, a coating film formed by applying and curing a paint containing a thermosetting resin and a curing agent, a coating film formed by applying a paint containing a thermoplastic resin, thermoplasticity Examples thereof include a layer made of a film obtained by melt-molding a resin. From the viewpoint of heat resistance during soldering or the like, a coating film formed by applying and curing a paint containing a thermosetting resin and a curing agent is preferable.

  Examples of thermosetting resins include amide resins, epoxy resins, phenol resins, amino resins, alkyd resins, urethane resins, synthetic rubbers, UV curable acrylate resins, etc. From the viewpoint of excellent heat resistance, amide resins and epoxy resins are preferable.

The storage elastic modulus at 160 ° C. of the insulating protective layer 12 is preferably 5 × 10 ⁶ to 1 × 10 ⁸ Pa, more preferably 8 × 10 ⁶ to 2 × 10 ⁷ Pa. Usually, since a cured product of a thermosetting resin is hard, a coating film made thereof is poor in flexibility, and in particular, when the thickness is reduced, it is very brittle and does not have enough strength to exist as a self-supporting film. The insulating protective layer 12 preferably has sufficient strength at the temperature at which the first release film 18 is peeled (the temperature at which the conductive adhesive is cured, usually 150 to 200 ° C.). . When the storage elastic modulus at 160 ° C. of the insulating protective layer 12 is 5 × 10 ⁶ Pa or more, the insulating protective layer 12 is not softened. If the storage elastic modulus at 160 ° C. of the insulating protective layer 12 is 1 × 10 ⁸ Pa or less, flexibility and strength are sufficient. As a result, when the first release film 18 is peeled off, the electromagnetic shielding film 10 as well as the insulating protective layer 12 is hardly broken.

The insulating protective layer 12 may be colored in order to impart designability to the flexible printed wiring board with an electromagnetic wave shielding film.
The insulating protective layer 12 may be composed of two or more layers having different properties such as storage elastic modulus, materials, and the like.

  1-10 micrometers is preferable and, as for the thickness of the insulating protective layer 12, 1-5 micrometers is more preferable. When the thickness of the insulating protective layer 12 is 1 μm or more, the heat resistance is good. If the thickness of the insulating protective layer 12 is 10 μm or less, the electromagnetic wave shielding film 10 can be thinned.

(Metal thin film layer)
The metal thin film layer 14 is a layer made of a metal thin film. Since the metal thin film layer 14 is formed so as to spread in the plane direction, it has conductivity in the plane direction and functions as an electromagnetic wave shielding layer or the like.

  Examples of the metal thin film layer 14 include physical vapor deposition (vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.), metal thin films, metal foils, and the like formed by CVD, plating, etc. A metal thin film (deposited film) by physical vapor deposition is preferable because it has excellent surface conductivity even when the thickness is small and can be easily formed by a dry process.

  Examples of the material for the metal thin film constituting the metal thin film layer 14 include aluminum, silver, copper, gold, and conductive ceramics. From the viewpoint of electrical conductivity, copper is preferable, and from the viewpoint of chemical stability, conductive ceramics are preferable.

  The thickness of the metal thin film layer 14 is preferably 0.01 to 1 μm, and more preferably 0.05 to 1 μm. When the thickness of the metal thin film layer 14 is 0.01 μm or more, the surface conductivity is further improved. When the thickness of the metal thin film layer 14 is 0.05 μm or more, the electromagnetic noise shielding effect is further improved. If the thickness of the metal thin film layer 14 is 1 μm or less, the electromagnetic wave shielding film 10 can be thinned. In addition, the productivity and flexibility of the electromagnetic wave shielding film 10 are improved.

  The surface resistance of the metal thin film layer 14 is preferably 0.001 to 1Ω, and more preferably 0.001 to 0.1Ω. When the surface resistance of the metal thin film layer 14 is 0.001Ω or more, the metal thin film layer 14 can be made sufficiently thin. If the surface resistance of the metal thin film layer 14 is 1Ω or less, it can sufficiently function as an electromagnetic wave shielding layer.

(Primer layer)
The primer layer 15 is a layer made of a material having adhesion to both the metal thin film layer 14 and the conductive adhesive layer 16.

  Examples of the primer layer 15 include a layer derived from a primer including a synthetic rubber containing a carboxy group. At least a part of the carboxyl group of the carboxy group-containing synthetic rubber is electronically, chemically or mechanically bonded to the material of the metal thin film layer 14 and / or the material of the conductive adhesive layer 16.

  Since the metal thin film layer 14 has poor adhesion, in order to improve the contact property of the conductive adhesive layer 16 with the conductive particles 22 and obtain stable conductivity, the primer has an adhesive property with the metal thin film layer 14. It is preferred to include a good carboxy group-containing synthetic rubber.

  Examples of the carboxy group-containing synthetic rubber include those obtained by carboxylating the terminal of an acrylonitrile-butadiene copolymer rubber in which acrylonitrile and butadiene are copolymerized. Specifically, there are Hiker CTBN, Hiker CTBNX, Hiker 1072, manufactured by Goodrich, Nipol 1072J, Nipol 1072, Nipol DN612, Nipol DN631, Nipol DN601, etc., manufactured by Nippon Zeon.

  Moreover, as a synthetic rubber containing carboxy group, unsaturated monomer containing carboxy group such as (meth) acrylic acid, 4-carboxybutyl (meth) acrylate, maleic acid, and ethyl acrylate, butyl acrylate, methoxy acrylate, etc. Examples thereof include acrylic rubber which is a (meth) acrylic acid ester or a copolymer of (meth) acrylic acid ester containing a glycidyl group, a hydroxyl group and an amino group. Specifically, there are Vamac-G, Vamac-GLS, Vamac-HVG manufactured by DuPont, Act Flow CB-3060, Act Flow CB-3098, Act Flow CBB-3098 manufactured by Soken Chemical.

  The carboxy group-containing synthetic rubber may be used alone or in combination of two or more. As for the content rate of a carboxy group, 2-8 mass% is preferable in a synthetic rubber (100 mass%) containing a carboxy group.

The primer preferably further contains an adhesion promoter from the viewpoint of improving adhesiveness. Examples of the adhesion promoter include silane coupling agents, titanate coupling agents, nonionic surfactants, polar resin oligomers, and the like.
The primer preferably further contains a silane coupling agent from the viewpoint that the primer layer 15 is easily formed and that the adhesiveness is excellent in both the metal thin film layer 14 and the conductive adhesive layer 16.

  Examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-acryloxy. Propyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, tris- (trimethoxysilylpropyl) isocyanate Nurate, 3-ureidopropyltrialkoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanate Sulphonate propyl triethoxysilane, and the like.

  The primer may contain a curing agent for curing the primer, if necessary. Until the conductive adhesive layer 16 is hot-pressed so that the electrical connection between the metal thin film layer 14 and the conductive particles 22 in the conductive adhesive layer 16 is not hindered, the primer is not cured. It should have sufficient heat flow characteristics. Therefore, the primer needs to be cured at a speed equal to or lower than the curing speed of the conductive adhesive layer 16. Therefore, a latent curing agent is preferable as the curing agent.

  The thickness of the primer layer 15 is 0.05 to 1 μm, preferably 0.05 to 0.5 μm, and more preferably 0.1 to 0.3 μm. When the thickness of the primer layer 15 is 0.05 μm or more, the adhesion between the metal thin film layer 14 and the conductive adhesive layer 16 is good. If the thickness of the primer layer 15 is 1 μm or less, a decrease in conductivity between the metal thin film layer 14 and the conductive adhesive layer 16 can be suppressed.

(Conductive adhesive layer)
The conductive adhesive layer 16 has conductivity at least in the thickness direction and has adhesiveness.
As the conductive adhesive layer 16, an anisotropic conductive adhesive layer having conductivity in the thickness direction and having no conductivity in the surface direction, and having conductivity in the thickness direction and the surface direction, etc. And an electrically conductive adhesive layer. As the conductive adhesive layer 16, the conductive adhesive layer 16 can be thinned, the amount of the conductive particles 22 can be reduced, and as a result, the electromagnetic wave shielding film 10 can be thinned, and the flexibility of the electromagnetic wave shielding film 10 is improved. From the point of view, an anisotropic conductive adhesive layer is preferable. The conductive adhesive layer 16 is preferably an isotropic conductive adhesive layer from the viewpoint that it can sufficiently function as an electromagnetic wave shielding layer.

The conductive adhesive layer 16 is preferably a thermosetting conductive adhesive layer from the viewpoint that heat resistance can be exhibited after curing.
The thermosetting conductive adhesive layer 16 includes, for example, a thermosetting adhesive and conductive particles 22. The conductive adhesive layer 16 may be in an uncured state or may be in a B-staged state.

Examples of the thermosetting adhesive include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, and UV curable acrylate resin. An epoxy resin is preferable from the viewpoint of excellent heat resistance. The epoxy resin may contain a rubber component for imparting flexibility (carboxy-modified nitrile rubber, acrylic rubber, etc.), a tackifier, and the like.
The thermosetting adhesive may contain a cellulose resin and microfibril (such as glass fiber) in order to increase the strength of the conductive adhesive layer 16 and improve the punching characteristics.

  Examples of the conductive particles 22 include graphite powder, calcined carbon particles, metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.) particles, plated calcined carbon particles, and the like. From the viewpoint of the fluidity of the conductive adhesive layer 16, hard carbon particles that are hard and spherical are preferable.

  When the conductive adhesive layer 16 is an anisotropic conductive adhesive layer, the average particle diameter of the conductive particles 22 is preferably 2 to 26 μm, and more preferably 4 to 16 μm. If the average particle diameter of the conductive particles 22 is 2 μm or more, the thickness of the conductive adhesive layer 16 can be secured by making the thickness of the conductive adhesive thicker than 2 μm, and sufficient adhesive strength can be obtained. Can do. If the average particle diameter of the conductive particles 22 is 26 μm or less, the fluidity of the conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be secured, and the inside of the through hole of the insulating film is conductive. Can be fully filled with adhesive.

  When the conductive adhesive layer 16 is an isotropic conductive adhesive layer, the average particle diameter of the conductive particles 22 is preferably 0.1 to 10 μm, and more preferably 0.2 to 1 μm. If the average particle diameter of the conductive particles 22 is 0.1 μm or more, the number of contact points of the conductive particles 22 increases, and the conductivity in the three-dimensional direction can be stably increased. If the average particle diameter of the conductive particles 22 is 10 μm or less, the fluidity of the conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be secured, and the inside of the through hole of the insulating film is conductive. Can be fully filled with adhesive.

2-50 m < ² > / g is preferable and, as for the specific surface area of the electroconductive particle 22, 2-20 m < ² > / g is more preferable. If the specific surface area of the conductive particles 22 is 2 m ² / g or more, the conductive particles 22 are easily available. If the specific surface area of the conductive particles 22 is 50 m ² / g or less, the oil absorption amount of the conductive particles 22 does not become too large, and as a result, the viscosity of the conductive adhesive does not become too high and the coatability is further improved. It becomes. Further, the fluidity of the conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be further ensured.

  When the conductive adhesive layer 16 is an anisotropic conductive adhesive layer, the proportion of the conductive particles 22 is preferably 1 to 30% by volume in 100% by volume of the conductive adhesive layer 16, and 2 to 10 volumes. % Is more preferable. If the ratio of the electroconductive particle 22 is 1 volume% or more, the electroconductivity of the electroconductive adhesive layer 16 will become favorable. When the proportion of the conductive particles 22 is 30% by volume or less, the adhesiveness and fluidity (followability to the shape of the through hole of the insulating film) of the conductive adhesive layer 16 are improved. Moreover, the flexibility of the electromagnetic wave shielding film 10 is improved.

  When the conductive adhesive layer 16 is an isotropic conductive adhesive layer, the ratio of the conductive particles 22 is preferably 50 to 80% by volume, and 60 to 70% by volume, out of 100% by volume of the conductive adhesive layer 16. % Is more preferable. If the ratio of the electroconductive particle 22 is 50 volume% or more, the electroconductivity of the electroconductive adhesive layer 16 will become favorable. When the ratio of the conductive particles 22 is 80% by volume or less, the adhesiveness and fluidity (followability to the shape of the through hole of the insulating film) of the conductive adhesive layer 16 are improved. Moreover, the flexibility of the electromagnetic wave shielding film 10 is improved.

  When the conductive adhesive layer 16 is an anisotropic conductive adhesive layer, the thickness of the conductive adhesive layer 16 is preferably 3 to 25 μm, and more preferably 5 to 15 μm. If the thickness of the conductive adhesive layer 16 is 3 μm or more, the fluidity of the conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be secured, and the inside of the through hole of the insulating film can be electrically conductive. Can be sufficiently filled with adhesive. If the thickness of the conductive adhesive layer 16 is 25 μm or less, the electromagnetic wave shielding film 10 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 10 is improved.

  When the conductive adhesive layer 16 is an isotropic conductive adhesive layer, the thickness of the conductive adhesive layer 16 is preferably 5 to 20 μm, and more preferably 7 to 17 μm. When the thickness of the conductive adhesive layer 16 is 5 μm or more, the conductive adhesive layer 16 has good conductivity and can function sufficiently as an electromagnetic wave shielding layer. Further, the fluidity of the conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be ensured, and the through hole of the insulating film can be sufficiently filled with the conductive adhesive, so that the folding resistance is improved. The conductive adhesive layer 16 will not tear even if it is repeatedly bent. If the thickness of the conductive adhesive layer 16 is 20 μm or less, the electromagnetic wave shielding film 10 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 10 is improved.

When the conductive adhesive layer 16 is an anisotropic conductive adhesive layer, the surface resistance of the conductive adhesive layer 16 is preferably 1 × 10 ⁴ to 1 × 10 ¹⁶ Ω, and 1 × 10 ⁶ to 1 × 10 ^14. Ω is more preferable. If the surface resistance of the conductive adhesive layer 16 is 1 × 10 ⁴ Ω or more, the content of the conductive particles 22 can be kept low. If the surface resistance of the conductive adhesive layer 16 is 1 × 10 ¹⁶ Ω or less, there is no problem in anisotropy practically.

  When the conductive adhesive layer 16 is an isotropic conductive adhesive layer, the surface resistance of the conductive adhesive layer 16 is preferably 0.05 to 2.0Ω, and more preferably 0.1 to 1.0Ω. If the surface resistance of the conductive adhesive layer 16 is 0.05Ω or more, the content of the conductive particles 22 can be kept low, the viscosity of the conductive adhesive does not become too high, and the coatability is further improved. Further, the fluidity of the conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be further ensured. If the surface resistance of the conductive adhesive layer 16 is 2.0Ω or less, the entire surface of the conductive adhesive layer 16 has uniform conductivity.

(First release film)
The first release film 18 is a carrier film for forming the insulating protective layer 12 and the metal thin film layer 14, and improves the handling properties of the electromagnetic wave shielding film 10. The first release film 18 is peeled from the insulating protective layer 12 after the electromagnetic wave shielding film 10 is attached to a flexible printed wiring board or the like.

  As the resin material of the first release film 18, polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polychlorinated Examples thereof include vinyl, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, and the like, and polyethylene terephthalate is preferable from the viewpoint of heat resistance (dimensional stability) and cost when manufacturing the electromagnetic wave shielding film 10.

The storage elastic modulus at 160 ° C. of the first release film 18 is preferably 0.8 × 10 ⁸ to 4 × 10 ⁸ Pa, and more preferably 0.8 × 10 ^{8 to} 3 × 10 ⁸ Pa. When the storage elastic modulus at 160 ° C. of the first release film 18 is 0.8 × 10 ⁸ Pa or more, the handling property of the electromagnetic wave shielding film 10 is good. If the storage elastic modulus at 160 ° C. of the first release film 18 is 4 × 10 ⁸ Pa or less, the flexibility of the first release film 18 will be good.

  The thickness of the first release film 18 is preferably 5 to 500 μm, more preferably 10 to 150 μm, and further preferably 25 to 100 μm. If the thickness of the 1st release film 18 is 5 micrometers or more, the handleability of the electromagnetic wave shielding film 10 will become favorable. Further, the first release film 18 functions sufficiently as a cushioning material, and the conductive adhesive layer 16 of the electromagnetic wave shielding film 10 is adhered to the surface of the insulating film provided on the surface of the flexible printed wiring board by hot pressing. In doing so, the conductive adhesive layer 16 easily follows the uneven shape on the surface of the insulating film. If the thickness of the first release film 18 is 500 μm or less, heat is easily transmitted to the conductive adhesive layer 16 when the conductive adhesive layer 16 of the electromagnetic wave shielding film 10 is hot-pressed on the surface of the insulating film. .

(Release agent layer)
A release treatment with a release agent is performed on the surface of the release film main body 18a on the insulating protective layer 12 side to form a release agent layer 18b. When the first release film 18 has the release agent layer 18b, the first release film 18 is peeled off from the insulating protective layer 12 in the step (h) described later. 18 easily peels off, and the insulating protective layer 12 and the conductive adhesive layer 16 after curing are less likely to break.
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 18b is preferably 0.05 to 2.0 μm, and more preferably 0.1 to 1.5 μm. If the thickness of the release agent layer 18b is within the above range, the first release film 18 is more easily peeled in the step (h) described later.

(Second release film)
The second release film 20 protects the conductive adhesive layer 16 and improves the handling properties of the electromagnetic wave shielding film 10. The second release film 20 is peeled from the conductive adhesive layer 16 before the electromagnetic wave shielding film 10 is attached to a flexible printed wiring board or the like.

Examples of the resin material of the second release film 20 include the same resin material as that of the first release film 18.
The thickness of the second release film 20 is preferably 5 to 500 μm, more preferably 10 to 150 μm, and further preferably 25 to 100 μm.

(Release agent layer)
A release treatment with a release agent is performed on the surface of the release film body 20a on the side of the conductive adhesive layer 16 to form a release agent layer 20b. When the second release film 20 has the release agent layer 20b, the second release film 20 is peeled off from the conductive adhesive layer 16 in the step (h) to be described later. The film 20 is easily peeled off, and the conductive adhesive layer 16 is not easily broken.
As the release agent, a known release agent may be used.

  The thickness of the release agent layer 20b is preferably 0.05 to 2.0 μm, and more preferably 0.1 to 1.5 μm. When the thickness of the release agent layer 20b is within the above range, the second release film 20 is more easily peeled in the step (h) described later.

(Thickness of electromagnetic shielding film)
10-45 micrometers is preferable and, as for the thickness (except a release film) of the electromagnetic wave shielding film 10, 10-30 micrometers is more preferable. If the thickness of the electromagnetic wave shielding film 10 (excluding the release film) is 10 μm or more, it is difficult to break when the first release film 18 is peeled off. When the thickness of the electromagnetic shielding film 10 (excluding the release film) is 45 μm or less, the flexible printed wiring board with the electromagnetic shielding film can be thinned.

(Method for producing electromagnetic shielding film)
The electromagnetic wave shielding film of the present invention can be produced, for example, by a method having the following steps (a) to (e).
(A) A step of forming an insulating protective layer on one surface of the first release film.
(B) A step of forming a metal thin film layer on the surface of the insulating protective layer.
(C) By forming a primer layer on the surface of the metal thin film layer, a first laminate having a first release film, an insulating protective layer, a metal thin film layer, and a primer layer in order is obtained. Process.
(D) The process of obtaining the 2nd laminated body provided with the 2nd release film and the conductive adhesive layer in order by forming a conductive adhesive layer in the single side | surface of a 2nd release film.
(E) The process of bonding a 1st laminated body and a 2nd laminated body so that a primer layer and a conductive adhesive layer may contact.

  Hereinafter, a method for producing the electromagnetic wave shielding film 10 shown in FIG. 1 will be described with reference to FIGS.

(Process (a))
As shown in FIG. 2, the insulating protective layer 12 is formed on the surface of the release agent layer 18 b of the first release film 18.

The insulating protective layer 12 can be formed by applying and curing a paint containing a thermosetting resin and a curing agent, applying a paint containing a thermoplastic resin, and a film obtained by melt-molding a thermoplastic resin. The method of sticking etc. are mentioned. From the viewpoint of heat resistance during soldering or the like, a method of applying and curing a paint containing a thermosetting resin and a curing agent is preferable.
The paint containing a thermosetting resin and a curing agent may contain a solvent and other components as necessary.

When the insulating protective layer 12 is formed by applying a paint, the insulating protective layer 12 can be made relatively thin. In addition, since the hardened | cured material of a thermosetting resin is hard, intensity | strength becomes inadequate when the insulating protective layer 12 is made thin. As described above, when the storage elastic modulus at 160 ° C. of the insulating protective layer 12 is in the range of 5 × 10 ⁶ to 1 × 10 ⁸ Pa, the balance between flexibility and strength and heat resistance is good. Become.

The storage elastic modulus of the insulating protective layer 12 is controlled by selecting the type and composition of a thermosetting resin, a curing agent, etc. from the viewpoint of toughness resulting from the crosslink density and the crosslink structure. This is done by adjusting the storage modulus.
In addition, the storage elastic modulus is adjusted by adjusting the curing conditions such as temperature and time when the thermosetting resin is cured, or a thermoplastic resin such as a thermoplastic elastomer is added as a component having no thermosetting property. Can be adjusted by.

(Process (b))
As shown in FIG. 2, a metal thin film layer 14 is formed on the surface of the insulating protective layer 12.

  Examples of the method for forming the metal thin film layer 14 include a method of forming a metal thin film by physical vapor deposition, CVD, plating, and the like, a method of attaching a metal foil, and the like. From the viewpoint that the metal thin film layer 14 having excellent surface conductivity can be formed, a method of forming the metal thin film by physical vapor deposition, CVD, plating, or the like is preferable. The thickness of the metal thin film layer 14 can be reduced and the thickness can be reduced. However, the method by physical vapor deposition is more preferable because the metal thin film layer 14 having excellent conductivity in the plane direction can be formed and the metal thin film layer 14 can be easily formed by a dry process.

(Process (c))
As shown in FIG. 2, the primer layer 15 is formed on the surface of the metal thin film layer 14, and the 1st laminated body 10a is obtained.

Examples of a method for forming the primer layer 15 include a method in which a primer including a synthetic rubber containing a carboxy group is applied and dried as necessary.
The primer may contain a solvent and other components (an adhesion promoter, a curing agent, a curing accelerator, a recognition colorant, etc.) as necessary.

  The viscosity of the primer is preferably 1 to 100 mPa · s, and more preferably 5 to 50 mPa · s. When the viscosity of the primer is 1 mPa · s or more, the primer layer 15 is easily formed. If the viscosity of the primer is 100 mPa · s or less, the primer penetrates and is absorbed into the metal thin film layer 14, and as a result, the adhesion and conductivity between the metal thin film layer 14 and the conductive adhesive layer 16 are improved.

(Process (d))
As shown in FIG. 3, the conductive adhesive layer 16 is formed on the surface of the release agent layer 20b of the second release film 20, and the second laminate 10b is obtained.

Examples of the method for forming the conductive adhesive layer 16 include a method of applying a conductive adhesive composition.
As the conductive adhesive composition, one containing the above-described thermosetting adhesive and conductive particles 22 is used.

(Process (e))
As shown in FIG. 4, the first laminate 10a and the second laminate 10b are bonded together so that the primer layer 15 and the conductive adhesive layer 16 are in contact with each other.

  The first laminated body 10a and the second laminated body 10b are bonded together by, for example, hot pressing with a press machine (not shown) or the like. By hot pressing, at least part of the carboxy group of the carboxy group-containing synthetic rubber contained in the primer layer 15 is electronically, chemically or mechanically bonded to the material of the metal thin film layer 14 and / or the material of the conductive adhesive layer 16. To join.

(Function and effect)
In the electromagnetic wave shielding film 10 described above, since the primer layer 15 exists between the metal thin film layer 14 and the conductive adhesive layer 16, the gap between the metal thin film layer 14 and the conductive adhesive layer 16 is present. High adhesion.

(Other embodiments)
The electromagnetic wave shielding film of the present invention is not limited to the embodiment of FIG. 1 as long as it includes an insulating protective layer, a metal thin film layer, a primer layer, and a conductive adhesive layer in this order.
For example, when the tackiness of the surface of the conductive adhesive layer 16 is small, the second release film 20 may be omitted.
When the insulating protective layer 12 has sufficient flexibility and strength, the first release film 18 may be omitted.
In the case where the release film has sufficient release properties only with the release film main body, the release film may not have a release agent layer.

<Flexible printed wiring board with electromagnetic shielding film>
FIG. 5 is a cross-sectional view showing an example of the flexible printed wiring board with an electromagnetic wave shielding film of the present invention.
The flexible printed wiring board 1 with an electromagnetic wave shielding film includes a flexible printed wiring board 30, an insulating film 40, and an electromagnetic wave shielding film 10 from which a release film is peeled off.
The flexible printed wiring board 30 has a printed circuit 34 provided on at least one side of a base film 32.
The insulating film 40 is provided on the surface of the flexible printed wiring board 30 on the side where the printed circuit 34 is provided.
The conductive adhesive layer 16 of the electromagnetic wave shielding film 10 is bonded to the surface of the insulating film 40 and cured. In addition, the conductive adhesive layer 16 is electrically connected to the printed circuit 34 through a through hole (not shown) formed in the insulating film 40.

In the vicinity of the printed circuit 34 (signal circuit, ground circuit, ground layer, etc.) excluding the portion with the through hole, the metal thin film layer 14 of the electromagnetic wave shielding film 10 is interposed via the insulating film 40 and the conductive adhesive layer 16. It is spaced and opposed.
The separation distance between the printed circuit 34 and the metal thin film layer 14 excluding the portion having the through hole is substantially equal to the sum of the thickness of the insulating film 40 and the thickness of the conductive adhesive layer 16. The separation distance is preferably 30 to 200 μm, and more preferably 60 to 200 μm. When the separation distance is smaller than 30 μm, the impedance of the signal circuit is lowered. Therefore, in order to have a characteristic impedance such as 100Ω, the line width of the signal circuit has to be reduced, and the variation in the line width causes the variation in the characteristic impedance. Thus, the reflection resonance noise due to the impedance mismatch is easily applied to the electric signal. If the separation distance is larger than 200 μm, the flexible printed wiring board 1 with an electromagnetic wave shielding film becomes thick, and the flexibility is insufficient.

(Flexible printed wiring board)
The flexible printed wiring board 30 is a printed circuit 34 (power supply circuit, ground circuit, ground layer, etc.) obtained by processing a copper foil of a copper clad laminate into a desired pattern by a known etching method.
As the copper clad laminate, one or both surfaces of the base film 32 are bonded with copper foil via an adhesive layer (not shown); a resin solution or the like that forms the base film 32 is cast on the surface of the copper foil. And the like.
Examples of the material for the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, polyurethane, acrylic resin, and melamine resin.
As for the thickness of an adhesive bond layer, 0.5-30 micrometers is preferable.

(Base film)
The base film 32 is preferably a heat resistant film, more preferably a polyimide film or a liquid crystal polymer film, and even more preferably a polyimide film.
The surface resistance of the base film 32 is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the base film 32 is preferably 1 × 10 ¹⁹ Ω or less from a practical point of view.
The thickness of the base film 32 is preferably 5 to 200 μm, more preferably 6 to 25 μm, and more preferably 10 to 25 μm from the viewpoint of flexibility.

(Printed circuit)
Examples of the copper foil constituting the printed circuit 34 (signal circuit, ground circuit, ground layer, etc.) include rolled copper foil, electrolytic copper foil, and the like, and rolled copper foil is preferred from the viewpoint of flexibility.
1-50 micrometers is preferable and, as for the thickness of copper foil, 18-35 micrometers is more preferable.
An end portion (terminal) in the length direction of the printed circuit 34 is not covered with the insulating film 40 or the electromagnetic wave shielding film 10 for solder connection, connector connection, component mounting, or the like.

(Insulating film)
The insulating film 40 is obtained by forming an adhesive layer (not shown) on one surface of a base film (not shown) by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the base film is preferably 1 × 10 ⁶ Ω or more from the viewpoint of electrical insulation. The surface resistance of the base film is preferably 1 × 10 ¹⁹ Ω or less from a practical point of view.
As a base film, the film which has heat resistance is preferable, a polyimide film and a liquid crystal polymer film are more preferable, and a polyimide film is further more preferable.
1-100 micrometers is preferable and, as for the thickness of a base film, 3-25 micrometers is more preferable from a flexible point.
Examples of the material for the adhesive layer include epoxy resin, polyester, polyimide, polyamideimide, polyamide, phenol resin, polyurethane, acrylic resin, melamine resin, polystyrene, and polyolefin. The epoxy resin may contain a rubber component (carboxy-modified nitrile rubber or the like) for imparting flexibility.
1-100 micrometers is preferable and, as for the thickness of an adhesive bond layer, 1.5-60 micrometers is more preferable.

  The shape of the opening of the through hole is not particularly limited. Examples of the shape of the opening of the through hole include a circle, an ellipse, and a quadrangle.

(Method for producing flexible printed wiring board with electromagnetic shielding film)
The flexible printed wiring board with an electromagnetic wave shielding film of the present invention can be produced, for example, by a method having the following steps (f) to (h).
(F) An insulating film having a through hole formed at a position corresponding to the printed circuit is provided on the surface of the flexible printed wiring board having the printed circuit on at least one side of the base film on which the printed circuit is provided. The process of obtaining a flexible printed wiring board.
(G) After the step (f), the flexible printed wiring board with an insulating film and the electromagnetic wave shielding film of the present invention are stacked so that the conductive adhesive layer is in contact with the surface of the insulating film, and these are hot-pressed. The process which adhere | attaches a conductive adhesive layer on the surface of an insulating film, and electrically connects a conductive adhesive layer to a printed circuit through a through-hole.
(H) The process of peeling a 1st release film after a process (g) and obtaining a flexible printed wiring board with an electromagnetic wave shielding film.

  Hereinafter, a method for producing a flexible printed wiring board with an electromagnetic wave shielding film will be described with reference to FIG.

(Process (f))
As shown in FIG. 6, an insulating film 40 in which a through hole 42 is formed at a position corresponding to the printed circuit 34 is overlaid on the flexible printed wiring board 30, and an adhesive layer of the insulating film 40 is placed on the surface of the flexible printed wiring board 30. A flexible printed wiring board 2 with an insulating film is obtained by bonding (not shown) and curing the adhesive layer. The adhesive layer of the insulating film 40 may be temporarily bonded to the surface of the flexible printed wiring board 30, and the adhesive layer may be fully cured in the step (g).
Adhesion and curing of the adhesive layer are performed by, for example, hot pressing with a press machine (not shown) or the like.

(Process (g))
As shown in FIG. 6, a conductive adhesive is applied to the surface of the insulating film 40 by superimposing the electromagnetic wave shielding film 10 from which the second release film 20 has been peeled off on the flexible printed wiring board 2 with an insulating film, followed by hot pressing. The precursor 16 of the flexible printed wiring board with an electromagnetic wave shielding film in which the layer 16 is bonded and the conductive adhesive layer 16 is electrically connected to the printed circuit 34 through the through hole 42 is obtained.

Adhesion and hardening of the conductive adhesive layer 16 are performed by, for example, hot pressing with a press machine (not shown) or the like.
The hot pressing time is 20 seconds to 60 minutes, and more preferably 30 seconds to 30 minutes. When the hot pressing time is 20 seconds or longer, the conductive adhesive layer 16 is bonded to the surface of the insulating film 40. If the time of hot press is 60 minutes or less, the manufacturing time of the flexible printed wiring board 1 with an electromagnetic wave shielding film can be shortened.

  140-190 degreeC is preferable and, as for the temperature of a hot press (temperature of the press plate of a press), 150-175 degreeC is more preferable. If the temperature of hot pressing is 140 ° C. or higher, the conductive adhesive layer 16 is bonded to the surface of the insulating film 40. In addition, the time for hot pressing can be shortened. When the temperature of the hot press is 190 ° C. or lower, deterioration of the electromagnetic wave shielding film 10, the flexible printed wiring board 30, and the like can be suppressed.

  The pressure of the hot press is preferably 10 MPa to 20 MPa, and more preferably 10 MPa to 16 MPa. If the pressure of hot press is 10 MPa or more, the conductive adhesive layer 16 is bonded to the surface of the insulating film 40. In addition, the time for hot pressing can be shortened. If the pressure of hot press is 20 MPa or less, damage to the electromagnetic shielding film 10, the flexible printed wiring board 30, etc. can be suppressed.

(Process (h))
As shown in FIG. 6, the 1st release film 18 is peeled from the insulating protective layer 12, and the flexible printed wiring board 1 with an electromagnetic wave shield film is obtained.

When the time of the hot press in the step (g) is a short time of 20 seconds to 10 minutes, the conductive adhesive layer 16 can be fully cured before or after the first release film 18 is peeled off. preferable.
The main curing of the conductive adhesive layer 16 is performed using a heating device such as an oven, for example.
The heating time is 15 to 120 minutes, preferably 30 to 60 minutes. If the heating time is 15 minutes or longer, the conductive adhesive layer 16 can be sufficiently cured. If heating time is 120 minutes or less, the manufacturing time of the flexible printed wiring board 1 with an electromagnetic wave shielding film can be shortened.
The heating temperature (atmosphere temperature in the oven) is preferably 120 to 180 ° C, more preferably 120 to 150 ° C. When the heating temperature is 120 ° C. or higher, the heating time can be shortened. If heating temperature is 160 degrees C or less, deterioration etc. of the electromagnetic wave shielding film 10, the flexible printed wiring board 30, etc. can be suppressed.
Heating is preferably performed without pressure from the point that a special apparatus need not be used.

(Function and effect)
In the flexible printed wiring board 1 with the electromagnetic wave shielding film described above, since the electromagnetic wave shielding film 10 includes the primer layer 15 between the metal thin film layer 14 and the conductive adhesive layer 16, the metal thin film layer 14. Between the metal thin film layer 14 and the conductive adhesive layer 16 is suppressed, and the metal thin film layer 14 and the printed circuit 34 are electrically and reliably connected by the conductive adhesive layer 16.
Note that the primer layer 15 is insulative and is considered to hinder electrical connection between the metal thin film layer 14 and the conductive adhesive layer 16. However, since the primer layer 15 is a thin layer and a part of the primer layer 15 penetrates and is absorbed by the metal thin film layer 14, the primer layer 15 is actually formed of a conductive adhesive and the metal thin film layer 14. The electrical connection between the layers 16 is not significantly disturbed. Rather, as a result of suppressing the peeling between the metal thin film layer 14 and the conductive adhesive layer 16, the conductivity between the metal thin film layer 14 and the printed circuit 34 is improved as compared with the case where the primer layer 15 is not provided.

(Other embodiments)
The flexible printed wiring board with an electromagnetic wave shielding film of the present invention only needs to include a flexible printed wiring board, an insulating film, and the electromagnetic wave shielding film of the present invention, and is not limited to the illustrated embodiment.
For example, the flexible printed wiring board may have a ground layer on the back side. The flexible printed wiring board may have a printed circuit on both sides, and an insulating film and an electromagnetic wave shielding film may be attached to both sides.

  Examples are shown below. In addition, this invention is not limited to an Example.

(Storage modulus)
The storage elastic modulus was measured using a dynamic viscoelasticity measuring apparatus (Rheometric Scientific, Inc., RSAII).

(viscosity)
The viscosity of the primer was measured using a B-type viscometer (model LVT) under conditions of room temperature (25 ° C.) and a rotation speed of 3 to 60 rpm.

(Peel test)
The electromagnetic wave shielding film was subjected to a peeling test using a strength tester (manufactured by Imada Seisakusho, SV-55C-20H) under the conditions of 180 ° C. peeling direction and a tensile speed of 50 mm / min, and the interface where peeling occurred was confirmed. .

(Presence or absence of carbon atoms in the metal thin film layer)
About the cross section of the metal thin film layer of an electromagnetic wave shielding film, the presence or absence of the carbon atom was confirmed using the electronic probe microanalyzer (the JEOL company make, JXA-8100).

Example 1
As the first release film 18 and the second release film 20, a polyethylene terephthalate film whose one surface was release-treated with a non-silicone release agent (manufactured by Lintec, T157, thickness: 50 μm, at 160 ° C. Storage modulus: 6 × 10 ⁸ Pa) was prepared.

Step (a):
On the surface of the release agent layer 18b of the first release film 18, a solvent-soluble amide resin (TPAE-617C, manufactured by T & K Toka Co., Ltd.) and a curing agent (toluene diisocyanate) are dissolved in N, N-dimethylformamide. The coating material was applied, heated at 150 ° C. for 0.4 hours to cure the amide resin, and the insulating protective layer 12 (thickness: 5 μm, storage elastic modulus at 160 ° C .: 8 × 10 ⁶ Pa, surface resistance: 8 × 10 ¹² Ω).

Step (b):
Copper was physically vapor-deposited on the surface of the insulating protective layer 12 by an electron beam vapor deposition method to form a vapor-deposited film (metal thin film layer 14) having a thickness of 0.07 μm and a surface resistance of 0.3Ω.

Step (c):
A primer (viscosity: acrylonitrile-butadiene copolymer rubber (Nipol 1072J, manufactured by Nippon Zeon Co., Ltd.), an epoxy resin and an imidazole curing agent dissolved in a solvent (methyl ethyl ketone) on the surface of the metal thin film layer 14 as a synthetic rubber containing carboxy group. 26 mPa · s) was applied and heated at 100 ° C. for 5 minutes to form a primer layer 15 (thickness: 0.2 μm) to obtain a first laminate 10a.

Step (d):
On the surface of the release agent layer 20b of the second release film 20, an epoxy resin (manufactured by DIC, EXA-4816) and a curing agent (manufactured by Ajinomoto Fine Techno Co., PN-23) are used as a latent curable epoxy resin. As a mixture and conductive particles 22, calcined carbon particles (air water bell pearl, CR1-2000, average particle size: 9 μm, specific surface area: 5 m ² / g, true density: 1.5 g / cm ³ ) are subjected to silver plating. An anisotropic conductive material is prepared by applying a conductive adhesive composition obtained by dissolving or dispersing a 1 μm-thickness in a solvent (methyl ethyl ketone) using a die coater and volatilizing the solvent to form a B stage. The conductive adhesive layer 16 (thickness: 10 μm, silver-plated baked carbon particles: 5 vol%, surface resistance: 5 × 10 ⁸ Ω) was formed to obtain a second laminate 10b.

Step (e):
The first laminated body 10a and the second laminated body 10b are stacked so that the primer layer 15 and the conductive adhesive layer 16 are in contact with each other, and a hot press apparatus (manufactured by Orihara Seisakusho, G-12) is used. Hot pressing was performed at a temperature of 60 ° C. and a pressure of 2 MPa for 1 minute to obtain an electromagnetic wave shielding film 10.

Step (f):
An insulating adhesive composition made of a nitrile rubber-modified epoxy resin is applied to the surface of a polyimide film (surface resistance: 1 × 10 ¹⁷ Ω) (base film) with a thickness of 25 μm so that the dry film thickness is 25 μm. Then, an adhesive layer was formed to obtain an insulating film 40 (thickness: 50 μm).

A flexible printed wiring board 30 having a printed circuit 34 formed on the surface of a 12 μm thick polyimide film (surface resistance: 1 × 10 ¹⁷ Ω) (base film 32) was prepared.
The insulating film 40 was affixed on the flexible printed wiring board 30 by hot press, and the flexible printed wiring board 2 with the insulating film was obtained.

Step (g):
The electromagnetic wave shielding film 10 from which the second release film 20 has been peeled is overlapped on the flexible printed wiring board 30, and a hot press apparatus (VIGOR, VFPC-05R) is used for 30 seconds at a temperature of 170 ° C. and a pressure of 15 MPa. It heat-pressed and the electroconductive adhesive layer 16 was adhere | attached on the surface of the insulating film 40, and the precursor 3 of the flexible printed wiring board with an electromagnetic wave shield film was obtained.
The conductive adhesive layer 16 is fully cured by heating the precursor 3 of the flexible printed wiring board with an electromagnetic wave shielding film at a temperature of 170 ° C. for 30 minutes using a high temperature thermostat (manufactured by Enomoto Kasei Co., Ltd., HT210). It was.

Step (h):
The 1st release film 18 was peeled from the insulating protective layer 12, and the flexible printed wiring board 1 with an electromagnetic wave shield film was obtained.
The electromagnetic wave shielding film 10 was subjected to a peel test. Peeling occurred at the interface between the reinforcing plate reinforcing the measurement sample and the insulating protective layer 12, and no peeling occurred between the metal thin film layer 14 and the conductive adhesive layer 16. Moreover, when the presence or absence of the carbon atom was measured about the cross section of the metal thin film layer 14, it was confirmed that the carbon atom was confirmed and a part of primer penetrate | infiltrated the metal thin film layer 14, and was absorbed.

(Comparative Example 1)
An electromagnetic wave shielding film was obtained in the same manner as in Example 1 except that no primer layer was provided.
The electromagnetic wave shielding film 10 was subjected to a peel test. Peeling occurred at the interface between the metal thin film layer 14 and the conductive adhesive layer 16. Moreover, when the presence or absence of a carbon atom was measured about the cross section of the metal thin film layer 14, a carbon atom was not confirmed.

  The electromagnetic wave shielding film of the present invention is useful as an electromagnetic wave shielding member in flexible printed wiring boards for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game machines, notebook computers, and medical devices.

DESCRIPTION OF SYMBOLS 1 Flexible printed wiring board with electromagnetic shielding film 2 Flexible printed wiring board with insulating film 3 Precursor of flexible printed wiring board with electromagnetic shielding film 10 Electromagnetic shielding film 10a First laminated body 10b Second laminated body 12 Insulating protective layer DESCRIPTION OF SYMBOLS 14 Metal thin film layer 15 Primer layer 16 Conductive adhesive layer 18 1st release film 18a Release film body 18b Release agent layer 20 2nd release film 20a Release film body 20b Release agent layer 22 Conductivity Particle 30 Flexible printed wiring board 32 Base film 34 Printed circuit 40 Insulating film 42 Through hole 101 Flexible printed wiring board with electromagnetic shielding film 110 Electromagnetic shielding film 112 Insulating protective layer 114 Metal thin film layer 116 118 release film conductive adhesive layer 130 a flexible printed circuit board 132 the base film 134 printed circuit 140 insulating film 142 through hole 144 gap

Claims (7)

Insulating protective layer, metal thin film layer, primer layer, and conductive adhesive layer in order,
The primer layer is, Ri layer der derived from primer comprising a synthetic rubber carboxylated,
The primer layer has a thickness of 0.05 to 1 μm,
Some of the primer is that is penetrated absorbed in the metal thin film layer, an electromagnetic wave shielding film. The electromagnetic wave shielding film according to claim 1, wherein the conductive adhesive layer is an anisotropic conductive adhesive layer. Wherein further comprising a first release film provided on the surface of the insulating protective layer, an electromagnetic wave shielding film according to claim 1 or 2. The electromagnetic wave shielding film according to claim 3 , further comprising a second release film provided on a surface of the conductive adhesive layer. A method for producing the electromagnetic wave shielding film according to claim 4 ,
The manufacturing method of the electromagnetic wave shield film which has the following process (a)-(e).
(A) A step of forming an insulating protective layer on one surface of the first release film.
(B) A step of forming a metal thin film layer on the surface of the insulating protective layer.
(C) By applying the primer having a viscosity of 1 to 100 mPa · s on the surface of the metal thin film layer to form a primer layer, a first release film, an insulating protective layer, a metal thin film layer, The process of obtaining the 1st laminated body provided with the primer layer in order.
(D) The process of obtaining the 2nd laminated body provided with the 2nd release film and the conductive adhesive layer in order by forming a conductive adhesive layer in the single side | surface of a 2nd release film.
(E) A step of bonding the first laminated body and the second laminated body so that the primer layer and the conductive adhesive layer are in contact with each other. A flexible printed wiring board provided with a printed circuit on at least one side of the base film;
An insulating film provided on the surface of the flexible printed wiring board on which the printed circuit is provided;
The electromagnetic shielding film according to claim 1 or 2 , wherein the conductive adhesive layer is adhered to a surface of the insulating film.
A flexible printed wiring board with an electromagnetic wave shielding film, wherein the conductive adhesive layer is electrically connected to the printed circuit through a through-hole formed in the insulating film. The manufacturing method of the flexible printed wiring board with an electromagnetic wave shielding film which has the following process (f)-(h).
(F) An insulating film in which a through hole is formed at a position corresponding to the printed circuit is provided on the surface of the flexible printed wiring board having the printed circuit on at least one side of the base film on the side where the printed circuit is provided; The process of obtaining the flexible printed wiring board with a film.
(G) After the step (f), the flexible printed wiring board with an insulating film and the electromagnetic wave shielding film according to any one of claims 1 to 3 are bonded to the surface of the insulating film with the conductive adhesive. The conductive adhesive layer is adhered to the surface of the insulating film by stacking the adhesive layers in contact with each other and heat-pressing them, and the conductive adhesive layer is passed through the through-holes to form the print. Electrical connection to the circuit.
(H) A step of peeling off the first release film after the step (g) when the electromagnetic wave shielding film includes a first release film.

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