JP6467701B2 - 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. 9 is a cross-sectional view showing an example of a manufacturing process of a 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, an anisotropic conductive adhesive layer 116 covering the surface of the metal thin film layer 114, and insulation. A release film 118 (carrier film) covering the second surface of the protective layer 112.
The anisotropic conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is adhered to the surface of the insulating film 140 and cured. Further, the anisotropic conductive adhesive layer 116 is electrically connected to the printed circuit 134 through a through hole 142 formed in the insulating film 140.

For example, as shown in FIG. 9, 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 anisotropic conductive adhesive layer 116 of the electromagnetic wave shielding film 110 is in contact with them, and these are hot-pressed on the surface of the insulating film 140. Bonding the anisotropic conductive adhesive layer 116 and electrically connecting the anisotropic 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.

  However, in the flexible printed wiring board 101 with the electromagnetic wave shielding film, the electromagnetic thin film 114 is bent and deformed along the shape of the unevenness in the portion with the unevenness such as the through hole 142 portion. Are prone to cracks. The anisotropic conductive adhesive layer 116 has conductivity in the thickness direction but does not have conductivity in the surface direction. Therefore, when a crack occurs in the metal thin film layer 114, the metal thin film layer 114 and the anisotropic conductivity are formed. The resistance of the electromagnetic wave shielding layer composed of the adhesive layer 116 is increased, and the shielding effect of electromagnetic wave noise by the electromagnetic wave shielding layer is lowered.

JP, 2014-112576, A

  The present invention provides an electromagnetic wave shielding film and a flexible printed wiring board with an electromagnetic wave shielding film that can maintain an electromagnetic wave noise shielding effect even when a metal thin film layer is cracked, and a method for producing the same.

The present invention has the following aspects.
(1) An insulating protective layer, a metal thin film layer having a surface resistance of 0.01 to 0.3Ω, and an isotropic conductive adhesive layer that includes a conductive filler and has a surface resistance of 1 to 100Ω in order. Equipped with an electromagnetic shielding film.
(2) The electromagnetic wave shielding film according to (1), wherein a ratio of the conductive filler is 30 to 80% by volume in 100% by volume of the isotropic conductive adhesive layer.
(3) The electromagnetic wave shielding film according to (1) or (2), wherein the isotropic conductive adhesive layer includes conductive particles and conductive fibers as the conductive filler.
(4) The electromagnetic wave shielding film according to any one of (1) to (3), further comprising a first release film provided on the surface of the insulating protective layer.
(5) The electromagnetic wave shielding film according to (4), further comprising a second release film provided on the surface of the isotropic conductive adhesive layer.
(6) A method for producing an electromagnetic wave shielding film according to (5), comprising the following steps (a) to (d).
(A) A step of forming an insulating protective layer on one surface of the first release film.
(B) The process of obtaining the 1st laminated body provided with the 1st release film, the insulating protective layer, and the metal thin film layer in order by forming a metal thin film layer on the surface of the said insulating protective layer. .
(C) A second laminate comprising a second release film and an isotropic conductive adhesive layer in this order by forming an isotropic conductive adhesive layer on one surface of the second release film. Obtaining.
(D) A step of bonding the first laminated body and the second laminated body so that the metal thin film layer and the isotropic conductive adhesive layer are in contact with each other.
(7) A flexible printed wiring board provided with a printed circuit on at least one side of a 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 The isotropic conductive adhesive layer is attached to the electromagnetic wave shielding film of any one of (1) to (3), and the isotropic conductive adhesive layer is formed in the through-hole formed in the insulating film. A flexible printed wiring board with an electromagnetic wave shielding film electrically connected to the printed circuit through the wiring board.
(8) The manufacturing method of the flexible printed wiring board with an electromagnetic wave shielding film which has the following process (e)-(g).
(E) 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 the side where the printed circuit is provided; The process of obtaining the flexible printed wiring board with a film.
(F) After the step (e), the isotropic conductive adhesion of the flexible printed wiring board with an insulating film and the electromagnetic wave shielding film of any one of (1) to (4) to the surface of the insulating film The isotropic conductive adhesive layer is adhered to the surface of the insulating film by stacking the adhesive layers so that they are in contact with each other and hot pressing them, and the isotropic conductive adhesive layer is attached to the through-holes. Electrically connecting to the printed circuit through.
(G) A step of peeling off the first release film after the step (f) when the electromagnetic wave shielding film includes a first release film.

The electromagnetic wave shielding film of the present invention can maintain the electromagnetic noise shielding effect even if a crack occurs in the metal thin film layer.
According to the method for producing an electromagnetic wave shielding film of the present invention, it is possible to produce an electromagnetic wave shielding film that can maintain an electromagnetic noise shielding effect even if a crack occurs in the metal thin film layer.
The flexible printed wiring board with an electromagnetic wave shielding film of the present invention can maintain an electromagnetic noise shielding effect even if a crack occurs in the metal thin film layer.
According to the method for producing a flexible printed wiring board with an electromagnetic wave shielding film of the present invention, it is possible to produce a flexible printed wiring board with an electromagnetic wave shielding film capable of maintaining an electromagnetic noise shielding effect even if a crack occurs in the metal thin film layer.

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)-(b) in the manufacturing method of the electromagnetic wave shield film of this invention. It is sectional drawing which shows an example of the process (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 a perspective view which shows the model case of the electromagnetic wave shield layer used in order to approximate the whole resistance of the electromagnetic wave shield layer before a crack arises in a metal thin film layer. It is a perspective view which shows the model case of the electromagnetic wave shield layer used in order to approximate the whole resistance of the electromagnetic wave shield layer after a crack produced in the metal thin film layer. 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 (e)-(g) 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.
For the average fiber length of the conductive fibers, 30 conductive fibers were randomly selected from the electron microscope image of the conductive fibers, the fiber length was measured for each conductive fiber, and the measured 30 conductive fibers were measured. This is a value obtained by arithmetically averaging the fiber lengths.
For the average fiber diameter of the conductive fibers, 30 conductive fibers were randomly selected from the electron microscopic image of the conductive fibers, the minimum diameter and the maximum diameter were measured for each conductive fiber, and the minimum diameter and maximum diameter were measured. Is the value obtained by arithmetically averaging the measured fiber diameters of 30 conductive fibers.
The specific surface area of the conductive particles and the conductive fibers is a value calculated by immersing degassed particles or the like 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, an isotropic conductive adhesive layer 16 covering the surface of the metal thin film layer 14, and an insulating film. The first release film 18 that covers the second surface of the protective protective layer 12 and the second release film 20 that covers the surface of the isotropic 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 0.01 to 0.3Ω, preferably 0.02 to 0.2Ω, and more preferably 0.05 to 0.1Ω. When the surface resistance of the metal thin film layer 14 is 0.01Ω 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 0.3Ω or less, it can sufficiently function as an electromagnetic wave shielding layer.

(Isotropic conductive adhesive layer)
The isotropic conductive adhesive layer 16 has conductivity in the thickness direction and the surface direction, and has adhesiveness.
The isotropic conductive adhesive layer 16 can sufficiently function as an electromagnetic wave shielding layer as compared with an anisotropic conductive adhesive layer having conductivity in the thickness direction and not having conductivity in the surface direction.

  The isotropic conductive adhesive layer 16 includes a conductive filler. The isotropic conductive adhesive layer 16 preferably includes the conductive particles 22 as a conductive filler from the viewpoint of the conductivity in the thickness direction and the plane direction, and the conductivity in the plane direction is further improved and the surface resistance is improved. It is more preferable that the conductive particles 22 and the conductive fibers 24 are included as the conductive filler because the strength of the isotropic conductive adhesive layer 16 is increased and cracks are not easily generated.

  Further, in the isotropic conductive adhesive layer 16, the surface conductivity is further improved, the surface resistance is lowered, and the strength of the isotropic conductive adhesive layer 16 is increased, resulting in cracks. From the difficult point, the direction of the conductive fiber 24 in the fiber direction is biased toward the surface direction of the isotropic conductive adhesive layer 16 rather than the thickness direction of the isotropic conductive adhesive layer 16, that is, the conductive fiber. 24 is preferably oriented in the surface direction of the isotropic conductive adhesive layer 16.

The isotropic conductive adhesive layer 16 is preferably a thermosetting isotropic conductive adhesive layer from the viewpoint that heat resistance can be exhibited after curing.
The thermosetting isotropic conductive adhesive layer 16 includes, for example, a thermosetting adhesive, conductive particles 22, and conductive fibers 24. The isotropic 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 (carboxyl-modified nitrile rubber or the like) for imparting flexibility, a tackifier or the like.
The thermosetting adhesive may contain a cellulose resin and microfibril (such as glass fiber) in order to increase the strength of the isotropic 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 isotropic conductive adhesive layer 16, baked carbon particles that are hard and spherical are preferred.

  0.1-10 micrometers is preferable and, as for the average particle diameter of the electroconductive particle 22, 0.2-1 micrometer is more preferable. 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 isotropic 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 secured. It can be sufficiently filled with a conductive adhesive.

0.2-50 m < ² > / g is preferable and, as for the specific surface area of the electroconductive particle 22, 0.5-20 m < ² > / g is more preferable. If the specific surface area of the electroconductive particle 22 is 0.2 m < ² > / g or more, the electroconductive particle 22 will be easy to obtain. 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 isotropic conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be further ensured.

  When the conductive filler is only the conductive particles 22, the proportion of the conductive particles 22 is preferably 30 to 80% by volume, more preferably 50 to 70% by volume, out of 100% by volume of the isotropic conductive adhesive layer 16. preferable. When the ratio of the conductive particles 22 is 30% by volume or more, the conductivity of the isotropic conductive adhesive layer 16 is stabilized. When the ratio of the conductive particles 22 is 80% by volume or less, the adhesiveness and fluidity of the isotropic conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) are improved. Moreover, the flexibility of the electromagnetic wave shielding film 10 is improved.

  Examples of the conductive fibers 24 include carbon nanofibers and nanowires of metals (copper, platinum, gold, silver, nickel, etc.). Since the thickness of the isotropic conductive adhesive layer 16 is as small as a micron level, the fiber diameter A thin carbon nanofiber is preferred. As carbon nanofibers, vapor grown carbon fibers are used because they are excellent in dispersibility and ensure the fluidity of the isotropic conductive adhesive layer 16 (followability to the shape of the through holes of the insulating film). preferable.

  0.5-5 micrometers is preferable and, as for the average fiber length of the conductive fiber 24, 1-3 micrometers is more preferable. When the average fiber length of the conductive fibers 24 is 0.5 μm or more, the conductivity and strength of the isotropic conductive adhesive layer 16 are further improved. When the average fiber length of the conductive fibers 24 is 5 μm or less, the adhesiveness and fluidity (trackability to the shape of the through holes of the insulating film) of the isotropic conductive adhesive layer 16 are improved.

  The average fiber diameter of the conductive fibers 24 is preferably 0.01 to 0.5 μm, and more preferably 0.05 to 0.3 μm. When the average fiber diameter of the conductive fibers is 0.01 μm or more, the conductivity and strength of the isotropic conductive adhesive layer 16 are further improved. When the average fiber diameter of the conductive fibers 24 is 0.5 μm or less, the adhesiveness and fluidity (trackability to the shape of the through holes of the insulating film) of the isotropic conductive adhesive layer 16 are improved.

  The aspect ratio of the conductive fiber 24 is preferably 5 to 300, and more preferably 10 to 100. When the aspect ratio of the conductive fiber is 5 or more, the conductivity and strength of the isotropic conductive adhesive layer 16 are further improved. When the aspect ratio of the conductive fiber is 300 or less, the adhesiveness and fluidity (followability to the shape of the through hole of the insulating film) of the isotropic conductive adhesive layer 16 are good.

2-50 m < ² > / g is preferable and, as for the specific surface area of the conductive fiber 24, 2-40 m < ² > / g is more preferable. If the specific surface area of the conductive fiber 24 is 2 m ² / g or more, the conductive fiber 24 is easily available. If the specific surface area of the conductive fiber 24 is 50 m ² / g or less, the oil absorption amount of the conductive fiber 24 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 isotropic conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be further ensured.

  When the conductive filler is the conductive particles 22 and the conductive fibers 24, the proportion of the conductive fibers 24 is preferably 3 to 30% by volume in 100% by volume of the isotropic conductive adhesive layer 16, and 5 to 5%. 20% by volume is more preferable. However, the total of the conductive particles 22 and the conductive fibers 24 is 30 to 80% by volume (preferably 50 to 70% by volume). When the proportion of the conductive fibers 24 is 3% by volume or more, the conductivity and strength of the isotropic conductive adhesive layer 16 are further improved. If the ratio of the conductive fibers 24 is 30% by volume or less, the viscosity of the conductive adhesive will not be too high, and the coating property will be good. Further, the fluidity of the isotropic conductive adhesive layer 16 (followability to the shape of the through hole of the insulating film) can be secured, and the through hole of the insulating film is sufficiently filled with the isotropic conductive adhesive layer 16. Can do.

The thickness of the isotropic conductive adhesive layer 16 is preferably 5 to 20 μm, and more preferably 7 to 17 μm. If the thickness of the isotropic conductive adhesive layer 16 is 5 μm or more, the conductivity of the isotropic conductive adhesive layer 16 is further improved, and can sufficiently function as an electromagnetic wave shielding layer. In addition, the fluidity of the isotropic 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. The bendability can be secured and the isotropic conductive adhesive layer 16 will not be torn even if it is repeatedly bent. If the thickness of the isotropic conductive adhesive layer 16 is 20 μm or less, the electromagnetic shielding film 10 can be thinned. Moreover, the flexibility of the electromagnetic wave shielding film 10 is improved.

The surface resistance of the isotropic conductive adhesive layer 16 is 1 to 100Ω, preferably 1 to 50Ω, and more preferably 1 to 10Ω. If the surface resistance of the isotropic conductive adhesive layer 16 is more than 1 [Omega, fluidity of the isotropic conductive adhesive layer 16 is high, strength is higher toughness. If the surface resistance of the isotropic conductive adhesive layer 16 is 100Ω or less, even if a crack occurs in the metal thin film layer 14, the resistance of the electromagnetic wave shielding layer composed of the metal thin film layer 14 and the isotropic conductive adhesive layer 16 is reduced. As a result, the electromagnetic wave shielding film 10 can maintain the electromagnetic noise shielding effect.

(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 the electromagnetic wave shielding film 10 is produced.

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 isotropic conductive adhesive layer 16 of the electromagnetic wave shielding film 10 is applied to the surface of the insulating film provided on the surface of the flexible printed wiring board by hot pressing. When sticking, the isotropic 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, when the isotropic conductive adhesive layer 16 of the electromagnetic wave shielding film 10 is hot-pressed on the surface of the insulating film, the isotropic conductive adhesive layer 16 is formed. Heat is easily transmitted.

(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 includes the release agent layer 18b, the first release film 18 is peeled off from the insulating protective layer 12 in the step (g) described later. 18 easily peels off, and the insulating protective layer 12 and the isotropic 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 (g) described later.

(Second release film)
The second release film 20 protects the isotropic 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 isotropic 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 main body 20a on the side of the isotropic 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 isotropic conductive adhesive layer 16 in the step (g) described later. The release film 20 is easy to peel off, and the isotropic conductive adhesive layer 16 is difficult to break.
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. If 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 (g) 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 (d).
(A) A step of forming an insulating protective layer on one surface of the first release film.
(B) The process of obtaining the 1st laminated body provided with the 1st release film, the insulating protective layer, and the metal thin film layer in order by forming a metal thin film layer on the surface of an insulating protective layer.
(C) A second laminate comprising a second release film and an isotropic conductive adhesive layer in this order by forming an isotropic conductive adhesive layer on one surface of the second release film. Obtaining.
(D) A step of bonding the first laminate and the second laminate so that the metal thin film layer and the isotropic conductive adhesive layer are in contact with each other.

  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, the metal thin film layer 14 is formed on the surface of the insulating protective layer 12, and the 1st laminated body 10a is obtained.

  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. 3, the isotropic 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 isotropic 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, conductive particles 22 and conductive fibers 24 is used.

(Process (d))
As shown in FIG. 4, the first laminated body 10a and the second laminated body 10b are bonded so that the metal thin film layer 14 and the isotropic conductive adhesive layer 16 are in contact with each other.

  The first laminated body 10a and the second laminated body 10b are bonded to each other by a press machine (not shown) or the like because the conductive fibers 24 are easily oriented in the surface direction of the isotropic conductive adhesive layer 16. It is preferable to carry out by hot pressing.

(Function and effect)
In the electromagnetic wave shielding film 10 described above, the surface resistance of the metal thin film layer 14 is 0.3Ω or less and the surface resistance of the isotropic conductive adhesive layer 16 is 10Ω or less. Thus, even if a crack occurs in the metal thin film layer 14, the shielding effect of electromagnetic noise can be maintained.

FIG. 5 is a perspective view showing a model case of an electromagnetic wave shielding layer composed of the metal thin film layer 14 and the isotropic conductive adhesive layer 16 before the metal thin film layer 14 is cracked.
The electromagnetic wave shielding layer in the model case is a laminate of a metal thin film layer 14 having a width of 10 mm and a length of 20 mm and an isotropic conductive adhesive layer 16 having a width of 10 mm and a length of 20 mm.
Since the surface resistance Rms of the metal thin film layer 14 is a resistance between two electrodes having a length of 10 mm and a distance between the electrodes of 10 mm, the total resistance in the length direction (20 mm) of the metal thin film layer 14, that is, the resistance of the circuit is , 2Rms which is twice the surface resistance Rms.
Since the surface resistance Rcs of the isotropic conductive adhesive layer 16 is a resistance between two electrodes having a length of 10 mm and a distance between electrodes of 10 mm, the length of the isotropic conductive adhesive layer 16 in the length direction (20 mm) is as follows. The total resistance is similarly 2Rcs.
If the electromagnetic shielding layer is regarded as a parallel circuit of the metal thin film layer 14 and the isotropic conductive adhesive layer 16, the total resistance R1 in the length direction of the electromagnetic shielding layer before the crack is generated is the resistance of the parallel circuit, That is, it is represented by the following formula (1).
R1 = 2 × Rms · Rcs / (Rms + Rcs) (1)

FIG. 6 is a perspective view showing a model case of the electromagnetic wave shielding layer composed of the metal thin film layer 14 and the isotropic conductive adhesive layer 16 after the metal thin film layer 14 is cracked.
It is assumed that a crack having a gap of 0.2 mm occurs in the center in the length direction of the metal thin film layer 14 in the width direction.
The electromagnetic shielding layer includes a parallel circuit including a metal thin film layer 14 having a width of 10 mm and a length of 9.9 mm and an isotropic conductive adhesive layer 16, and an isotropic conductive adhesive layer having a width of 10 mm and a length of 0.2 mm. If a circuit composed of 16 and a parallel circuit composed of a metal thin film layer 14 having a width of 10 mm and a length of 9.9 mm and an isotropic conductive adhesive layer 16 are considered to be connected in series, a crack occurs. The total resistance R2 in the length direction of the electromagnetic wave shielding layer after is expressed by the following formula (2).
R2 = 2 × 0.99 × Rms · Rcs / (Rms + Rcs) + 0.02 × Rcs (2)

  When the surface resistance Rms of the metal thin film layer 14 is 0.3Ω which is the maximum value and the surface resistance Rcs of the isotropic conductive adhesive layer 16 is 100Ω which is the maximum value, the length of the electromagnetic wave shielding layer before the crack is generated The total resistance R1 in the length direction is 0.598Ω, and the total resistance R2 in the length direction of the electromagnetic wave shielding layer after the crack is generated is 2.538Ω. Thus, the increase in resistance of the electromagnetic wave shielding layer due to the occurrence of cracks in the metal thin film layer 14 is suppressed to 10 times or less, and the shielding effect of electromagnetic wave noise can be maintained.

  On the other hand, when the surface resistance Rms of the metal thin film layer 14 is 0.3Ω, which is the maximum value, and the surface resistance Rcs of the isotropic conductive adhesive layer 16 is 1000Ω which exceeds the maximum value, the electromagnetic wave shield before cracks are generated. The overall resistance R1 in the length direction of the layer is 0.600Ω, and the overall resistance R2 in the length direction of the electromagnetic wave shielding layer after the crack is generated is 20.540Ω. As described above, when the surface resistance Rcs of the isotropic conductive adhesive layer 16 exceeds the maximum value, the metal thin film layer 14 is cracked, so that the resistance of the electromagnetic wave shielding layer is greatly increased. As a result, the electromagnetic noise is shielded. The effect is reduced.

(Other embodiments)
The electromagnetic wave shielding film of the present invention only needs to be provided with an insulating protective layer, a metal thin film layer having a specific surface resistance, and an isotropic conductive adhesive layer having a specific surface resistance in this order. The embodiment is not limited.
For example, when the tackiness of the surface of the isotropic 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. 7 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 isotropic conductive adhesive layer 16 of the electromagnetic wave shielding film 10 is adhered to the surface of the insulating film 40 and cured. Further, the isotropic 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 having the through hole, the metal thin film layer 14 of the electromagnetic wave shielding film 10 is provided with the insulating film 40 and the isotropic conductive adhesive layer 16. Are arranged opposite to each other.
The separation distance between the printed circuit 34 and the metal thin film layer 14 excluding the portion having the through hole is the sum of the thickness of the insulating film 40 and the thickness of the isotropic 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 (carboxyl-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 (e) to (g).
(E) 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 the side where the printed circuit is provided. The process of obtaining a flexible printed wiring board.
(F) After the step (e), the flexible printed wiring board with an insulating film and the electromagnetic wave shielding film of the present invention are overlaid so that the isotropic conductive adhesive layer contacts the surface of the insulating film, and these are heated. The step of bonding the isotropic conductive adhesive layer to the surface of the insulating film by pressing and electrically connecting the isotropic conductive adhesive layer to the printed circuit through the through hole.
(G) The process of peeling a 1st release film after a process (f) 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 (e))
As shown in FIG. 8, 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 (f).
Adhesion and curing of the adhesive layer are performed by, for example, hot pressing with a press machine (not shown) or the like.

(Process (f))
As shown in FIG. 8, the electromagnetic shielding film 10 from which the second release film 20 has been peeled is superimposed on the flexible printed wiring board 2 with an insulating film, and is hot-pressed, so that the surface of the insulating film 40 is isotropically conductive. The precursor 3 of the flexible printed wiring board with an electromagnetic wave shielding film in which the adhesive layer 16 is bonded and the isotropic conductive adhesive layer 16 is electrically connected to the printed circuit 34 through the through hole 42 is obtained.

The isotropic conductive adhesive layer 16 is bonded and cured by, for example, hot pressing with a press (not shown) or the like.
The hot pressing time is 20 seconds to 60 minutes, and more preferably 30 seconds to 30 minutes. If the hot pressing time is 20 seconds or more, the isotropic conductive adhesive layer 16 is adhered 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 the hot press is 140 ° C. or higher, the isotropic 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 pressing is 10 MPa or more, the isotropic 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 (g))
As shown in FIG. 8, the 1st release film 18 is peeled from the insulating protective layer 12, and the flexible printed wiring board 1 with an electromagnetic wave shielding film is obtained.

When the hot pressing time in the step (f) is a short time of 20 seconds to 10 minutes, the isotropic conductive adhesive layer 16 is fully cured before or after the first release film 18 is peeled off. It is preferable.
The main curing of the isotropic 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 more, the isotropic 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, the surface resistance of the metal thin film layer 14 is 0.3Ω or less and the surface resistance of the isotropic conductive adhesive layer 16 is 10Ω or less. Even if the metal thin film layer 14 is cracked, the electromagnetic noise shielding effect can be maintained.

(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).

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 is 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. The laminated body 10a was obtained.

Step (c):
A mixture of an epoxy resin (manufactured by DIC, EXA-4816) and a curing agent (manufactured by Ajinomoto Fine Techno Co., PN-23) as a curable epoxy resin on the surface of the release agent layer 20b of the second release film 20 In addition, silver particles (manufactured by DOWA Electronics, AG 6-11, average particle size: 3.6 μm, specific surface area: 0.21 m ² / g, true density: 10.5 g / cm ³ ) and carbon nano particles as conductive particles 22 Fiber (manufactured by Showa Denko KK, VGCF, average fiber length: 6 μm, average fiber diameter: 0.15 μm, aspect ratio: 60, specific surface area: 13 m ² / g, true density: 2.1 g / cm ³ ) solvent (methyl ethyl ketone) The conductive adhesive composition dissolved or dispersed in) is applied using a die coater, the solvent is evaporated, and the isotropic conductive adhesive layer 16 (thickness: 10 μm, silver particles: 8% by volume, carbon nanofibers: 15 vol%, surface resistivity: 80 [Omega) on the ridges thereby to obtain a second laminate 10b.

Step (d):
The first laminated body 10a and the second laminated body 10b are stacked so that the metal thin film layer 14 and the isotropic conductive adhesive layer 16 are in contact with each other, and a hot press apparatus (VFPC-05R, manufactured by Vigor Corporation) is attached. The electromagnetic wave shielding film 10 was obtained by hot pressing at a temperature of 90 ° C. and a pressure of 2 MPa for 3 seconds.

Step (e):
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 (f):
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 isotropic conductive 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 precursor 3 of the flexible printed wiring board with an electromagnetic wave shielding film is heated at a temperature of 170 ° C. for 30 minutes using a high-temperature thermostatic chamber (manufactured by Enomoto Kasei Co., Ltd., HT210). Cured.

Step (g):
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.

(Comparative Example 1)
Steps (a) to (b):
In the same manner as in Example 1, a first laminate was obtained.

Step (c):
On the surface of the release agent layer of the second release film, a mixture of an epoxy resin (manufactured by DIC, EXA-4816) and a curing agent (manufactured by Ajinomoto Fine Techno Co., PN-23) as a curable epoxy resin, conductive Baked carbon particles (CR2-800SR, manufactured by Air Water Bell Pearl Co., Ltd., average particle size: 5.0 μm, specific surface area: 0.8 m ² / g, true density: 1.34 g / cm ³ ) as solvent particles 22 A conductive adhesive composition dissolved or dispersed in (methyl ethyl ketone) is applied using a die coater, the solvent is evaporated, and an isotropic conductive adhesive layer (thickness: 10 μm, calcined carbon particles: 75 volumes) %, Carbon nanofiber: 10% by volume, surface resistance: 620Ω) to obtain a second laminate.

Step (d):
An electromagnetic wave shielding film was obtained in the same manner as in Example 1 except that the second laminate obtained in the step (c) of Comparative Example 1 was used as the second laminate.

Steps (e) to (g):
A flexible printed wiring board with an electromagnetic wave shielding film was obtained in the same manner as in Example 1 except that the electromagnetic wave shielding film obtained in the step (d) of Comparative Example 1 was used as the electromagnetic wave shielding film.

  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 16 Isotropic 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 Conductive particle DESCRIPTION OF SYMBOLS 24 Conductive fiber 30 Flexible printed wiring board 32 Base film 34 Printed circuit 40 Insulating film 42 Through-hole 101 Flexible printed wiring board with an electromagnetic shielding film 110 Electromagnetic shielding film 112 Insulating protective layer 114 Metal thin film layer 11 6 Anisotropic Conductive Adhesive Layer 118 Release Film 130 Flexible Printed Wiring Board 132 Base Film 134 Printed Circuit 140 Insulating Film 142 Through-hole

Claims (7)

A first release film;
An insulating protective layer having a thickness of 10 μm or less formed by applying a paint containing resin ;
A metal thin film layer having a surface resistance of 0.01 to 0.3Ω,
An electromagnetic wave shielding film comprising a conductive filler and an isotropic conductive adhesive layer having a surface resistance of 1 to 100Ω in contact with each other.   The electromagnetic wave shielding film according to claim 1, wherein a ratio of the conductive filler is 30 to 80% by volume in 100% by volume of the isotropic conductive adhesive layer.   The electromagnetic wave shielding film according to claim 1 or 2, wherein the isotropic conductive adhesive layer includes conductive particles and conductive fibers as the conductive filler. The electromagnetic wave shielding film according to any one of claims 1 to 3 , further comprising a second release film provided on a surface of the isotropic conductive adhesive layer. A method for producing the electromagnetic wave shielding film according to claim 4 ,
The manufacturing method of the electromagnetic wave shielding film which has the following process (a)-(d).
(A) The process of apply | coating the coating material containing resin to the single side | surface of a 1st release film, and forming the insulating protective layer 10 micrometers or less in thickness .
(B) By forming a metal thin film layer having a surface resistance of 0.01 to 0.3Ω on the surface of the insulating protective layer, a first release film, an insulating protective layer, a metal thin film layer, The process of obtaining the 1st laminated body which contacted and was equipped in order.
(C) By forming an isotropic conductive adhesive layer on one side of the second release film, the second release film and the conductive filler are included, and the isotropic conductivity having a surface resistance of 1 to 100Ω. obtaining a second laminate having in turn contact the sexual adhesive layer.
; (D) first laminate and the second laminate, wherein a first of said isotropic conductive adhesive layer of the metal thin film layer and the second stack of laminates are in contact The process of pasting together. 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 any one of claims 1 to 3, wherein the isotropic 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 isotropic 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 (e)-(g).
(E) 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 the side where the printed circuit is provided; The process of obtaining the flexible printed wiring board with a film.
(F) After the step (e), 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 formed on the surface of the insulating film with the isotropic conduction. The isotropic conductive adhesive layer is adhered to the surface of the insulating film, and the isotropic conductive adhesive layer is adhered to the surface of the insulating film by stacking the adhesive adhesive layers so that they are in contact with each other. Electrically connecting to the printed circuit through a hole.
After (g) pre-Symbol step (f), the step of removing the first release film.

Images