JP6935187B2 - Electromagnetic wave shield film and its manufacturing method, and printed wiring board with electromagnetic wave shield film - Google Patents

Description

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

From an insulating resin layer and a conductive layer composed of a metal thin film layer and a conductive adhesive layer adjacent to the insulating resin layer in order to shield electromagnetic noise generated from a flexible printed wiring board and electromagnetic noise from the outside. An electromagnetic wave shielding film may be provided on the surface of a flexible printed wiring board (see, for example, Patent Document 1).

The insulating resin layer in the electromagnetic wave shielding film is required to have heat resistance and high hardness. Therefore, the insulating resin layer is made of a cured product of a thermosetting resin such as an amide resin or an epoxy resin. For the insulating resin layer made of a cured product of a thermosetting resin, a coating liquid containing a thermosetting resin such as an amide resin or an epoxy resin, a curing agent, and a solvent is applied to one side of the first release film. Formed by drying.

Japanese Unexamined Patent Publication No. 2016-086120

However, the thermosetting resin is an oligomer or a monomer before curing, and the curing agent is also a compound having a low molecular weight. Therefore, the wettability of the coating liquid on the surface of the first release film is poor, and defects due to repelling or unevenness of the coating liquid are likely to occur in the insulating resin layer.
Further, since the coating liquid containing the thermosetting resin and the curing agent has a short pot life, the insulating resin layer cannot be stably formed over a long period of time.

The present invention is an electromagnetic wave shielding film having an insulating resin layer having heat resistance, high hardness and few defects; the insulating resin layer having heat resistance, high hardness and few defects is stable over a long period of time. 2. A printed wiring board with an electromagnetic wave shielding film having an insulating resin layer having heat resistance, high hardness, and few defects.

The present invention has the following aspects.
<1> An electromagnetic wave shielding film having an insulating resin layer and a conductive layer adjacent to the insulating resin layer, wherein the insulating resin layer contains a polyamide-imide.
<2> The electromagnetic wave shielding film of <1>, wherein the polyamide-imide has a glass transition temperature of 250 to 350 ° C.
<3> The electromagnetic wave shielding film of <1> or <2>, wherein the number average molecular weight Mn of the polyamide-imide is 5000 to 35000.
<4> The conductive layer has a metal thin film layer adjacent to the insulating resin layer and a conductive adhesive layer which is the outermost layer of the conductive layer on the opposite side of the insulating resin layer. ~ <3> Electromagnetic wave shield film.
<5> The electromagnetic wave shielding film according to any one of <1> to <3>, wherein the conductive layer is an isotropic conductive adhesive layer.
<6> The electromagnetic wave shielding film according to any one of <1> to <5>, further comprising a first release film of the insulating resin layer adjacent to the conductive layer on the opposite side.
<7> The electromagnetic wave shielding film according to any one of <1> to <6>, further comprising a second release film adjacent to the conductive layer on the side opposite to the insulating resin layer.
<8> The method for producing the electromagnetic wave shielding film of <6>; the insulating resin layer is obtained by applying a coating liquid containing the polyamide-imide and a solvent to one side of the first release film and drying the film. A method for producing an electromagnetic wave shielding film, wherein a conductive layer adjacent to the insulating resin layer is provided.
<9> A printed wiring board provided with a printed circuit on at least one side of the substrate; an insulating film adjacent to the surface of the printed wiring board on the side where the printed circuit is provided; the conductive layer is adjacent to the insulating film. An electromagnetic wave shield having the electromagnetic wave shield film according to any one of <1> to <6>, wherein the conductive layer is electrically connected to the printed circuit through a through hole formed in the insulating film. Printed wiring board with film.

The electromagnetic wave shielding film of the present invention has an insulating resin layer having heat resistance, high hardness, and few defects.
According to the method for producing an electromagnetic wave shielding film of the present invention, an insulating resin layer having heat resistance, high hardness, and few defects can be stably formed over a long period of time.
The printed wiring board with an electromagnetic wave shielding film of the present invention has an insulating resin layer having heat resistance, high hardness, and few defects.

It is sectional drawing which shows one Embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the other embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the other embodiment of the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the manufacturing process of the electromagnetic wave shielding film of FIG. It is sectional drawing which shows one Embodiment of the printed wiring board with the electromagnetic wave shielding film of this invention. It is sectional drawing which shows the manufacturing process of the printed wiring board with the electromagnetic wave shielding film of FIG.

The definitions of the following terms apply throughout the specification and claims.
The "isotropic conductive adhesive layer" means a conductive adhesive layer having conductivity in the thickness direction and the surface direction.
The "anisotropic adhesive layer" means a conductive adhesive layer that has conductivity in the thickness direction and does not have conductivity in the surface direction.
The “conductive adhesive layer having no conductivity in the plane direction” means a conductive adhesive layer having a surface resistance of 1 × 10 ⁴ Ω or more.
The arithmetic mean roughness Ra measures the roughness curve of the test piece using a laser microscope, and is based on JIS B 0601: 2013 (corresponding international standard ISO 4287: 1997, Amd. 1: 2009) from this roughness curve. It is a value obtained by
For the average particle size of the conductive particles, 30 conductive particles were randomly selected from the microscopic image of the conductive particles, and the minimum and maximum diameters of each conductive particle were measured, and the minimum and maximum diameters were determined. The median value of is taken as the particle size of one particle, and the measured particle size of the 30 conductive particles is calculated and averaged.
The thickness of the film (release film, insulating film, etc.), coating film (insulating resin layer, conductive adhesive layer, etc.), metal thin film layer, etc. was determined by observing the cross section of the measurement target using a microscope at 5 locations. It is a value obtained by measuring the thickness and averaging it.
The storage elastic modulus is calculated from the stress applied to the measurement target and the detected strain, and is measured as one of the viscoelastic properties by using a dynamic viscoelastic measuring device that outputs as a function of temperature or time.
For the surface resistance, two thin film metal electrodes (length 10 mm, width 5 mm, distance between electrodes 10 mm) formed by depositing gold on quartz glass are used, and an object to be measured is placed on the electrodes to be measured. It is the resistance between the electrodes measured with a measurement current of 1 mA or less by pressing a region of 10 mm × 20 mm of the object to be measured with a load of 0.049 N from above the object.

<Electromagnetic wave shield film>
FIG. 1 is a cross-sectional view showing a first embodiment of the electromagnetic wave shielding film of the present invention, FIG. 2 is a cross-sectional view showing a second embodiment of the electromagnetic wave shielding film of the present invention, and FIG. It is sectional drawing which shows the 3rd Embodiment of the electromagnetic wave shielding film of this invention.
The electromagnetic wave shield film 1 of the first embodiment, the second embodiment, and the third embodiment has the insulating resin layer 10; the conductive layer 20 adjacent to the insulating resin layer 10; and the conductive layer 20 of the insulating resin layer 10. It has a first release film 30 adjacent to the opposite side; and a second release film 40 adjacent to the insulating resin layer 10 of the conductive layer 20.

In the electromagnetic wave shielding film 1 of the first embodiment, the conductive layer 20 has a metal thin film layer 22 adjacent to the insulating resin layer 10 and an anisotropic conductive adhesive layer 24 adjacent to the second release film 40. This is an example of having.
In the electromagnetic wave shielding film 1 of the second embodiment, the conductive layer 20 has a metal thin film layer 22 adjacent to the insulating resin layer 10 and an isotropic conductive adhesive layer 26 adjacent to the second release film 40. This is an example of having.
The electromagnetic wave shielding film 1 of the third embodiment is an example in which the conductive layer 20 is composed of only the isotropic conductive adhesive layer 26.

(Insulating resin layer)
The insulating resin layer 10 serves as a base (base) when forming the metal thin film layer 22, and the electromagnetic wave shielding film 1 is attached to the surface of the insulating film provided on the surface of the flexible printed wiring board, and the first mold release is performed. After the film 30 is peeled off, it becomes a protective layer of the metal thin film layer 22.
The insulating resin layer 10 contains a polyamide-imide.
The polyamide-imide preferably has solvent solubility, and is commercially available by Lomax (registered trademark) HR-11NN, HR-12N2, HR-13NX, HR-14ET, HR-15ET, HR-16NN (manufactured by Toyobo Co., Ltd.). , HPC-5000, HPC-5012, HPC-1000, HPC-5020, HPC-3010, HPC-6000, HPC-9000 (manufactured by Hitachi Kasei Co., Ltd.) and the like can be preferably used.

The glass transition temperature of the polyamide-imide is preferably 250 to 350 ° C. When the glass transition temperature of the polyamide-imide is at least the lower limit of the above range, the heat resistance is good. When the glass transition temperature of the polyamide-imide is not more than the upper limit of the above range, the film forming property is good.
The number average molecular weight Mn of the polyamide-imide is preferably 5000 to 35000, more preferably 1000 to 28000. When the number average molecular weight Mn of the polyamide-imide is at least the lower limit of the above range, the film strength is tough. When the number average molecular weight Mn of the polyamide-imide is not more than the upper limit of the above range, the film forming property is good.

The insulating resin layer 10 preferably contains a polyamide-imide having a repeating unit represented by the following formula (1).

Ar is an arylene group or a group having an arylene group. As Ar, -Ph-, -Ph-CH _2- Ph-, -Ph-Ph-, -Ph-O-Ph-, _{-Ph-C (CH 3} ) _2- Ph-, -Ph-SO _2- Ph-, -Ph-O-Ph-O-Ph-, -Ph-C (CH ₃ ) _{2 -Ph-C (CH 3} ) ₂ -Ph- and the like can be mentioned. However, Ph is a phenylene group which may have a substituent (alkyl group, haloalkyl group, halogen atom, etc.).

As the insulating resin layer 10, a coating film formed by applying a coating liquid containing polyamide-imide and a solvent and drying it is preferable.
The insulating resin layer 10 may contain a colorant or a filler in order to conceal the printed circuit of the printed wiring board with the electromagnetic wave shielding film and to impart designability to the printed wiring board with the electromagnetic wave shielding film.
The insulating resin layer 10 may contain a flame retardant.
The insulating resin layer 10 may contain other components, if necessary, as long as the effects of the present invention are not impaired.

The storage elastic modulus of the insulating resin layer 10 at 180 ° C. ^{is preferably 5 × 10 6} Pa or more and 5 × 10 ¹⁰ Pa or less, and more preferably 1 × 10 ⁷ Pa or more and 1 × 10 ¹⁰ Pa or less. When the storage elastic modulus of the insulating resin layer 10 at 180 ° C. is equal to or higher than the lower limit of the above range, the insulating resin layer 10 has a more appropriate hardness, and the pressure loss in the insulating resin layer 10 during hot pressing is achieved. Can be further reduced. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more sufficiently bonded, and the conductive adhesive layer is reliably electrically connected by the printed circuit of the printed wiring board through the through hole of the insulating film. Will be done. When the storage elastic modulus of the insulating resin layer 10 at 180 ° C. is not more than the upper limit of the above range, the flexibility of the electromagnetic wave shielding film 1 is further improved. As a result, the electromagnetic wave shield film 1 is more likely to sink into the through hole of the insulating film, and the conductive adhesive layer is reliably electrically connected through the through hole of the insulating film by the printed circuit of the printed wiring board. ..

The surface resistance of the insulating resin layer 10 ^{is preferably 1 × 10 6} Ω or more from the viewpoint of electrical insulation. The surface resistance of the insulating resin layer 10 ^{is preferably 1 × 10 19} Ω or less from a practical point of view.
The thickness of the insulating resin layer 10 is preferably 0.1 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 20 μm or less. When the thickness of the insulating resin layer 10 is at least the lower limit of the above range, the insulating resin layer 10 can sufficiently exert the function as a protective layer. When the thickness of the insulating resin layer 10 is not more than the upper limit of the above range, the electromagnetic wave shielding film 1 can be thinned.

From the following points, the surface irregularities of the surface of the first release film 30 may be transferred to the surface of the insulating resin layer 10.
-Make scratches and the like generated on the surface of the insulating resin layer 10 inconspicuous.
-Suppresses specular reflection of light from a flexible printed wiring board with an electromagnetic wave shield film around optical sensors (CCD image sensor of camera module, CMOS image sensor, etc.).

(Conductive layer)
The conductive layer 20 includes a metal thin film layer 22 adjacent to the insulating resin layer 10 and a conductive adhesive layer (irregular conductive adhesive layer 24) which is the outermost layer of the conductive layer 20 on the opposite side of the insulating resin layer 10. Alternatively, a conductive layer (I) having an isotropic conductive adhesive layer 26); or a conductive layer (II) composed of only the isotropic conductive adhesive layer 26 can be mentioned. As the conductive layer 20, the conductive layer (I) is preferable because it can sufficiently function as an electromagnetic wave shielding layer.

(Metal thin film layer)
The metal thin film layer 22 is a layer made of a metal thin film. Since the metal thin film layer 22 is formed so as to spread in the plane direction, it has conductivity in the plane direction and functions as an electromagnetic wave shield layer or the like.

Examples of the metal thin film layer 22 include a vapor deposition film formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam deposition, electron beam deposition, etc.) or CVD, a plating film formed by plating, a metal foil, and the like. A thin-film deposition film and a plating film are preferable from the viewpoint of excellent surface-direction conductivity, and even if the thickness is thin, the surface-direction conductivity is excellent and can be easily formed by a dry process. A vapor-deposited film is more preferable, and a thin-film film by physical vapor deposition is further preferable.

Examples of the metal constituting the metal thin film layer 22 include aluminum, silver, copper, gold, and conductive ceramics. Copper is preferable from the viewpoint of electrical conductivity, and conductive ceramics is preferable from the viewpoint of chemical stability.

The surface resistance of the metal thin film layer 22 is preferably 0.001 Ω or more and 1 Ω or less, and more preferably 0.001 Ω or more and 0.1 Ω or less. When the surface resistance of the metal thin film layer 22 is equal to or higher than the lower limit of the above range, the metal thin film layer 22 can be sufficiently thinned. When the surface resistance of the metal thin film layer 22 is not more than the upper limit of the above range, it can sufficiently function as an electromagnetic wave shielding layer.

The thickness of the metal thin film layer 22 is preferably 0.01 μm or more and 1 μm or less, and more preferably 0.05 μm or more and 1 μm or less. When the thickness of the metal thin film layer 22 is 0.01 μm or more, the conductivity in the plane direction is further improved. When the thickness of the metal thin film layer 22 is 0.05 μm or more, the shielding effect of electromagnetic noise is further improved. When the thickness of the metal thin film layer 22 is not more than the upper limit of the above range, the electromagnetic wave shield film 1 can be thinned. In addition, the productivity and flexibility of the electromagnetic wave shielding film 1 are improved.

(Conductive adhesive layer)
The conductive adhesive layer has at least conductivity in the thickness direction and has adhesiveness.
As the conductive adhesive layer, the anisotropic conductive adhesive layer 24 which has conductivity in the thickness direction and does not have conductivity in the surface direction, or has conductivity in the thickness direction and the surface direction, etc. The anisotropic conductive adhesive layer 26 can be mentioned. As the conductive adhesive layer in the conductive layer (I), the conductive adhesive layer can be thinned and the amount of conductive particles can be reduced, and as a result, the electromagnetic wave shielding film 1 can be thinned, and the electromagnetic wave shielding film 1 can be used. The anisotropic conductive adhesive layer 24 is preferable from the viewpoint of improving the property. As the conductive adhesive layer in the conductive layer (I), the isotropic conductive adhesive layer 26 is preferable from the viewpoint that it can sufficiently function as an electromagnetic wave shielding layer.

As the conductive adhesive layer, a thermosetting conductive adhesive layer is preferable because it can exhibit heat resistance after curing. The thermosetting conductive adhesive layer may be in an uncured state or in a B-staged state.
The thermosetting anisotropic conductive adhesive layer 24 contains, for example, a thermosetting adhesive 24a and conductive particles 24b.
The thermosetting isotropic conductive adhesive layer 26 contains, for example, a thermosetting adhesive 26a and conductive particles 26b.

Examples of the thermosetting adhesive include those containing a thermosetting resin having adhesiveness and a curing agent.
Examples of the thermosetting resin include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet curable acrylate resin and the like. As the thermosetting resin, an epoxy resin is preferable because it has excellent heat resistance.
Examples of the curing agent include known curing agents depending on the type of thermosetting resin.

When the thermosetting resin is an epoxy resin, the thermosetting adhesive may contain a rubber component (carboxy-modified nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, and the like.
The thermosetting adhesive may contain a flame retardant if necessary.
The thermosetting adhesive may contain a cellulose resin, microfibrils (glass fiber, etc.) in order to increase the strength of the conductive adhesive layer and improve the punching characteristics.
The thermosetting adhesive may contain other components, if necessary, as long as the effects of the present invention are not impaired.

Examples of the conductive particles include metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.) particles, graphite powder, calcined carbon particles, plated calcined carbon particles, and the like. As the conductive particles, metal particles are preferable, and copper particles are preferable from the viewpoint that the conductive adhesive layer has an appropriate hardness and the pressure loss in the conductive adhesive layer during hot pressing can be reduced. More preferred.

The average particle size of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 26 μm or less, and more preferably 4 μm or more and 16 μm or less. When the average particle size of the conductive particles 24b is at least the lower limit of the above range, the thickness of the anisotropic conductive adhesive layer 24 can be secured, and sufficient adhesive strength can be obtained. When the average particle diameter of the conductive particles 24b is equal to or less than the upper limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (following the shape of the through holes of the insulating film) can be ensured, and the insulating film The inside of the through hole can be sufficiently filled with the conductive adhesive.

The average particle size of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 1 μm or less. When the average particle diameter of the conductive particles 26b is equal to or greater than the lower limit of the above range, the number of contact points of the conductive particles 26b increases, and the conductivity in the three-dimensional direction can be stably increased. When the average particle diameter of the conductive particles 26b is equal to or less than the upper limit of the above range, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through holes of the insulating film) can be ensured, and the insulating film The inside of the through hole can be sufficiently filled with the conductive adhesive.

The proportion of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 1% by volume or more and 30% by volume or less, preferably 2% by volume or more and 10% by volume, out of 100% by volume of the anisotropic conductive adhesive layer 24. The following is more preferable. When the ratio of the conductive particles 24b is equal to or higher than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 24 becomes good. When the proportion of the conductive particles 24b is not more than the upper limit of the above range, the adhesiveness and fluidity (following the shape of the through hole of the insulating film) of the anisotropic conductive adhesive layer 24 are improved. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

The proportion of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 50% by volume or more and 80% by volume or less, preferably 60% by volume or more and 70% by volume, out of 100% by volume of the isotropic conductive adhesive layer 26. The following is more preferable. When the ratio of the conductive particles 26b is equal to or higher than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good. When the proportion of the conductive particles 26b is not more than the upper limit of the above range, the adhesiveness and fluidity (following the shape of the through hole of the insulating film) of the isotropic conductive adhesive layer 26 are improved. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

The storage elastic modulus of the conductive adhesive layer at 180 ° C. ^{is preferably 1 × 10 3} Pa or more and 5 × 10 ⁷ Pa or less, and more preferably 5 × 10 ³ Pa or more and 1 × 10 ⁷ Pa or less. When the storage elastic modulus of the conductive adhesive layer at 180 ° C. is equal to or higher than the lower limit of the above range, the conductive adhesive layer has a more appropriate hardness, and the conductive adhesive layer at the time of hot pressing The pressure loss in can be further reduced. As a result, the conductive adhesive layer and the printed circuit of the printed wiring board are more sufficiently bonded, and the conductive adhesive layer is reliably electrically connected by the printed circuit of the printed wiring board through the through hole of the insulating film. Will be done. When the storage elastic modulus of the conductive adhesive layer at 180 ° C. is not more than the upper limit of the above range, the flexibility of the electromagnetic wave shielding film 1 is further improved. As a result, the electromagnetic wave shield film 1 is more likely to sink into the through hole of the insulating film, and the conductive adhesive layer is reliably electrically connected through the through hole of the insulating film by the printed circuit of the printed wiring board. ..

The surface resistance of the anisotropic conductive adhesive layer 24 ^{is preferably 1 × 10 4} Ω or more and 1 × 10 ¹⁶ Ω or less, and more preferably 1 × 10 ⁶ Ω or more and 1 × 10 ¹⁴ Ω or less. When the surface resistance of the anisotropic conductive adhesive layer 24 is at least the lower limit of the above range, the content of the conductive particles 24b can be suppressed to a low level. If the surface resistance of the anisotropic conductive adhesive layer 24 is equal to or less than the upper limit of the above range, there is no problem in anisotropy in practical use.

The surface resistance of the isotropic conductive adhesive layer 26 is preferably 0.05 Ω or more and 2.0 Ω or less, and more preferably 0.1 Ω or more and 1.0 Ω or less. When the surface resistance of the isotropic conductive adhesive layer 26 is equal to or higher than the lower limit of the above range, the content of the conductive particles 26b is suppressed to a low level, the viscosity of the conductive adhesive does not become too high, and the coatability is further improved. It will be good. Further, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through hole of the insulating film) can be further ensured. When the surface resistance of the isotropic conductive adhesive layer 26 is equal to or less than the upper limit of the above range, the entire surface of the isotropic conductive adhesive layer 26 has uniform conductivity.

The thickness of the anisotropic conductive adhesive layer 24 is preferably 3 μm or more and 25 μm or less, and more preferably 5 μm or more and 15 μm or less. When the thickness of the anisotropic conductive adhesive layer 24 is equal to or greater than the lower limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (following the shape of the through hole of the insulating film) can be ensured. The inside of the through hole of the insulating film can be sufficiently filled with the conductive adhesive. When the thickness of the anisotropic conductive adhesive layer 24 is not more than the upper limit of the above range, the electromagnetic wave shielding film 1 can be thinned. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

The thickness of the isotropic conductive adhesive layer 26 is preferably 5 μm or more and 20 μm or less, and more preferably 7 μm or more and 17 μm or less. When the thickness of the isotropic conductive adhesive layer 26 is at least the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good, and the isotropic conductive adhesive layer 26 can sufficiently function as an electromagnetic wave shielding layer. In addition, the fluidity of the isotropic conductive adhesive layer 26 (following the shape of the through holes of the insulating film) can be ensured, and the inside of the through holes of the insulating film can be sufficiently filled with the conductive adhesive to withstand resistance. Foldability can be ensured, and the isotropic conductive adhesive layer 26 does not tear even if it is repeatedly bent. When the thickness of the isotropic conductive adhesive layer 26 is not more than the upper limit of the above range, the electromagnetic wave shielding film 1 can be thinned. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

(First release film)
The first release film 30 serves as a carrier film for the insulating resin layer 10 and the conductive layer 20, and improves the handleability of the electromagnetic wave shielding film 1. The first release film 30 is peeled off from the insulating resin layer 10 after the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like.

The first release film 30 has, for example, a base material layer 32 and a release agent layer 34 provided on the surface of the base material layer 32 on the insulating resin layer 10 side.

Examples of the resin material of the base material layer 32 include polyethylene terephthalate (hereinafter, also referred to as PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyvinylidene sulfide, polyamide, and ethylene-vinyl acetate. Examples thereof include polymers, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, and liquid crystal polymers. As the resin material, PET is preferable from the viewpoint of heat resistance (dimensional stability) and price when manufacturing the electromagnetic wave shielding film 1.
The base material layer 32 may contain a colorant or a filler.

The storage elastic modulus of the base material layer 32 at 180 ° C. ^{is preferably 8 × 10 7} Pa or more and 5 × 10 ⁹ Pa, and more preferably 1 × 10 ⁸ Pa or more and 8 × 10 ⁸ Pa. When the storage elastic modulus of the base material layer 32 at 180 ° C. is equal to or higher than the lower limit of the above range, the first release film 30 has an appropriate hardness, and the first release film during heat pressing The pressure loss in the film 30 can be reduced. When the storage elastic modulus of the base material layer 32 at 180 ° C. is equal to or less than the upper limit of the above range, the flexibility of the first release film 30 becomes good.

The thickness of the base material layer 32 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and further preferably 25 μm or more and 100 μm or less. When the thickness of the base material layer 32 is at least the lower limit of the above range, the handleability of the electromagnetic wave shielding film 1 is good. When the thickness of the base material layer 32 is not more than the upper limit of the above range, heat is easily transferred to the conductive adhesive layer when the conductive adhesive layer of the electromagnetic wave shielding film 1 is hot-pressed on the surface of the insulating film.

The release agent layer 34 is formed by subjecting the surface of the base material layer 32 to a mold release treatment with a release agent. Since the first release film 30 has the release agent layer 34, when the first release film 30 is peeled from the insulating resin layer 10, the first release film 30 can be easily peeled off, and the insulating resin. The layer 10 and the cured conductive adhesive layer are less likely to break.
As the release agent, a known release agent may be used.

The thickness of the release agent layer 34 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. When the thickness of the release agent layer 34 is within the above range, the first release film 30 can be more easily peeled off.

The arithmetic mean roughness Ra of the surface of the first release film 30 on the insulating resin layer 10 side is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less.
If the arithmetic mean roughness Ra of the surface of the first release film 30 on the insulating resin layer 10 side is equal to or greater than the lower limit of the above range, irregularities satisfying the following points are formed on the surface of the insulating resin layer 10. ..
-Make scratches and the like generated on the surface of the insulating resin layer 10 inconspicuous.
-Suppresses specular reflection of light from flexible printed wiring boards with electromagnetic wave shielding film around the optical sensor.
When the arithmetic average roughness Ra of the surface of the first release film 30 on the insulating resin layer 10 side is equal to or less than the upper limit of the above range, the adhesiveness between the first release film 30 and the insulating resin layer 10 is high. The first release film 30 is easily peeled off from the insulating resin layer 10 without becoming too much.

(Second release film)
The second release film 40 protects the conductive adhesive layer and improves the handleability of the electromagnetic wave shielding film 1. The second release film 40 is peeled off from the conductive adhesive layer before the electromagnetic wave shielding film 1 is attached to the printed wiring board or the like.

The second release film 40 has, for example, a base material layer 42 and a release agent layer 44 provided on the surface of the base material layer 42 on the conductive adhesive layer side.

Examples of the resin material of the base material layer 42 include those similar to the resin material of the base material layer 32.
The base material layer 42 may contain a colorant or a filler.
The thickness of the base material layer 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and further preferably 25 μm or more and 100 μm or less.

The release agent layer 44 is formed by subjecting the surface of the base material layer 42 to a mold release treatment with a release agent. Since the second release film 40 has the release agent layer 44, when the second release film 40 is peeled from the conductive adhesive layer, the second release film 40 can be easily peeled off and is conductive. The release adhesive layer is less likely to break.
As the release agent, a known release agent may be used.

The thickness of the release agent layer 44 is preferably 0.05 μm or more and 2.0 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. When the thickness of the release agent layer 44 is within the above range, the second release film 40 can be more easily peeled off.

(Thickness of electromagnetic wave shield film)
The thickness of the electromagnetic wave shielding film 1 (excluding the release film) is preferably 10 μm or more and 45 μm or less, and more preferably 10 μm or more and 30 μm or less. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is at least the lower limit of the above range, it is unlikely to break when the first release film 30 is peeled off. When the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is equal to or less than the upper limit of the above range, the printed wiring board with the electromagnetic wave shielding film can be thinned.

(Manufacturing method of electromagnetic wave shield film)
In the method for producing an electromagnetic wave shielding film of the present invention, a coating liquid containing polyamide-imide and a solvent is applied to one side of a first release film and dried to form an insulating resin layer, and then adjacent to the insulating resin layer. This is a method of providing a conductive layer to be used.

Examples of the method for producing the electromagnetic wave shielding film of the present invention include the method (α) having the following steps (a) to (c).
Step (a): A step of forming an insulating resin layer on one side of the first release film.
Step (b): A step of forming a conductive layer on the surface of the insulating resin layer after the step (a).
Step (c): After the step (b), a step of attaching the second release film to the surface of the conductive layer.

Further, as a method for producing the electromagnetic wave shielding film of the present invention, for example, a method (β) having the following steps (a'), (b'1), (b'2), and (c') can be mentioned.
Step (a'): A step of forming an insulating resin layer on one side of the first release film.
Step (b'1): By forming a metal thin film layer on the surface of the insulating resin layer, a first laminate having a first release film, an insulating resin layer, and a metal thin film layer in this order is obtained. Process.
Step (b'2): A second laminate having a second release film and a conductive adhesive layer in order by forming a conductive adhesive layer on one side of the second release film. The process of obtaining.
Step (c'): A step of laminating the first laminate and the second laminate so that the metal thin film layer and the conductive adhesive layer are in contact with each other.

Hereinafter, a method of manufacturing the electromagnetic wave shielding film 1 shown in FIG. 1 by the method (α) will be described with reference to FIG.

Step (a):
As shown in FIG. 4, a coating liquid containing polyamide-imide and a solvent is applied to one side of the first release film 30 and dried to form an insulating resin layer 10.
The polyamide-imide is a polyamide-imide having a repeating unit represented by the above formula (1).

Examples of the solvent include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, xylene, toluene, methyl ethyl ketone, cyclohexanone, cyclopentanone, ethanol, methanol, γ-butyrolactone, water, and a mixed solvent thereof. Xylene, toluene, methyl ethyl ketone, cyclohexanone, cyclopentanone, ethanol, methanol, γ-butyrolactone, water, and a mixed solvent thereof are preferable because they have good drying properties and a strong film can be easily obtained.
The coating liquid may contain a colorant, a filler, a flame retardant, or other components, if necessary.

Step (b):
As shown in FIG. 4, the metal thin film layer 22 is formed on the surface of the insulating resin layer 10 (step (b1)), and the anisotropic conductive adhesive layer 24 is formed on the surface of the metal thin film layer 22 (step (b2). )).

Examples of the method for forming the metal thin film layer 22 include a method of forming a vapor-deposited film by physical vapor deposition and CVD, a method of forming a plating film by plating, a method of attaching a metal foil, and the like. From the viewpoint that the metal thin film layer 22 having excellent surface conductivity can be formed, a method of forming a thin film by physical vapor deposition or CVD, or a method of forming a plating film by plating is preferable, and the thickness of the metal thin film layer 22 is reduced. A thin-film metal thin film layer 22 can be formed even if the thickness is thin and has excellent conductivity in the plane direction, and the thin-film metal layer 22 can be easily formed by a dry process. The method is more preferable, and the method of forming a thin-film deposition film by physical vapor deposition is further preferable.

Examples of the method for forming the anisotropic conductive adhesive layer 24 include a method of applying a thermosetting conductive adhesive composition to the surface of the metal thin film layer 22.
As the thermosetting conductive adhesive composition, one containing the thermosetting adhesive 24a and the conductive particles 24b is used.

Step (c):
As shown in FIG. 4, a second release film 40 is attached to the surface of the anisotropic conductive adhesive layer 24 to obtain an electromagnetic wave shielding film 1.

(Action effect)
In the electromagnetic wave shielding film 1 described above, since the insulating resin layer 10 contains a polyamide-imide having a repeating unit represented by the formula (1), it has heat resistance, high hardness, and few defects. It has an insulating resin layer 10.
Further, in the method for producing the electromagnetic wave shielding film 1 described above, a coating liquid containing a polyamide-imide having a repeating unit represented by the above formula (1) and a solvent on one side of the first release film 30. Is applied and dried to form the insulating resin layer 10. Therefore, the insulating resin layer having heat resistance, high hardness, and few defects can be stably formed over a long period of time.

That is, since the polyamide-imide having the repeating unit represented by the formula (1) is a material having heat resistance and high hardness, the insulating resin layer 10 containing the material has heat resistance and has high hardness. The hardness will be high. Further, since polyamide-imide has a high molecular weight, when the insulating resin layer 10 is formed, the coating liquid containing polyamide-imide has good wettability with respect to the surface of the first release film 30, and the coating liquid is repelled or uneven. Defects derived from the above are less likely to occur in the insulating resin layer 10.
Further, since the polyamide-imide having the repeating unit represented by the formula (1) has flame retardancy, the insulating resin layer 10 containing the polyamide-imide also has flame retardancy.

(Other embodiments)
The electromagnetic wave shielding film of the present invention is an electromagnetic wave shielding film having an insulating resin layer and a conductive layer adjacent to the insulating resin layer, and the insulating resin layer is a polyamide-imide having a repeating unit represented by the above formula (1). However, the embodiment is not limited to the illustrated example.
For example, the insulating resin layer may be two or more layers.
The first release film may have a pressure-sensitive adhesive layer instead of the release agent layer.
The first release film may have no release agent layer or pressure-sensitive adhesive layer and may consist only of a base material layer.
If the insulating resin layer has sufficient flexibility and strength, the first release film may be omitted.
If the surface of the conductive adhesive layer has little tackiness, the second release film may be omitted.

<Printed wiring board with electromagnetic wave shield film>
FIG. 5 is a cross-sectional view showing an embodiment of a printed wiring board with an electromagnetic wave shielding film of the present invention.
The flexible printed wiring board 2 with an electromagnetic wave shielding film includes a flexible printed wiring board 50, an insulating film 60, and an electromagnetic wave shielding film 1 of the first embodiment.
The flexible printed wiring board 50 is provided with a printed circuit 54 on at least one side of the base film 52.
The insulating film 60 is provided on the surface of the flexible printed wiring board 50 on the side where the printed circuit 54 is provided.
The anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film 1 is adhered to and cured on the surface of the insulating film 60. Further, the anisotropic conductive adhesive layer 24 is electrically connected to the print circuit 54 through a through hole (not shown) formed in the insulating film 60.
In the flexible printed wiring board 2 with the electromagnetic wave shielding film, the second release film 40 is peeled off from the anisotropic conductive adhesive layer 24.
When the first release film 30 is no longer needed in the flexible printed wiring board 2 with the electromagnetic wave shielding film, the first release film 30 is peeled off from the insulating resin layer 10.

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) excluding the portion having the through hole, the metal thin film layer 22 of the electromagnetic wave shielding film 1 forms the insulating film 60 and the anisotropic conductive adhesive layer 24. They are arranged so as to face each other apart from each other.
The separation distance between the printed circuit 54 and the metal thin film layer 22 excluding the portion having the through hole is substantially equal to the sum of the thickness of the insulating film 60 and the thickness of the anisotropic conductive adhesive layer 24. The separation distance is preferably 30 μm or more and 200 μm or less, and more preferably 60 μm or more and 200 μm or less. If the separation distance is smaller than 30 μm, the impedance of the signal circuit becomes low. Therefore, in order to have a characteristic impedance such as 100Ω, the line width of the signal circuit must be reduced, and the variation in the line width is the variation in the characteristic impedance. Therefore, the reflected resonance noise due to the impedance mismatch can easily get on the electric signal. If the separation distance is larger than 200 μm, the flexible printed wiring board 2 with the electromagnetic wave shielding film becomes thick, and the flexibility becomes insufficient.

(Flexible printed wiring board)
The flexible printed wiring board 50 is a printed circuit (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, a copper foil is attached to one or both sides of the base film 52 via an adhesive layer (not shown); a resin solution or the like forming the base film 52 is cast on the surface of the copper foil. Things etc. can be mentioned.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamide-imide, polyamide, phenol resin, urethane resin, acrylic resin, and melamine resin.
The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

(Base film)
As the base film 52, a film having heat resistance is preferable, a polyimide film and a liquid crystal polymer film are more preferable, and a polyimide film is further preferable.
The surface resistance of the base film 52 ^{is preferably 1 × 10 6} Ω or more from the viewpoint of electrical insulation. The surface resistance of the base film 52 ^{is preferably 1 × 10 19} Ω or less from a practical point of view.
The thickness of the base film 52 is preferably 5 μm or more and 200 μm or less, more preferably 6 μm or more and 25 μm or less, and more preferably 10 μm or more and 25 μm or less from the viewpoint of flexibility.

(Print circuit)
Examples of the copper foil constituting the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) include rolled copper foil, electrolytic copper foil, and the like, and rolled copper foil is preferable from the viewpoint of flexibility.
The thickness of the copper foil is preferably 1 μm or more and 50 μm or less, and more preferably 18 μm or more and 35 μm or less.
The end (terminal) of the print circuit 54 in the length direction is not covered with the insulating film 60 or the electromagnetic wave shielding film 1 because of solder connection, connector connection, component mounting, and the like.

(Insulation film)
The insulating film 60 has an adhesive layer (not shown) formed on one side of the insulating film main body (not shown) by applying an adhesive, attaching an adhesive sheet, or the like.
The surface resistance of the insulating film body ^{is preferably 1 × 10 6} Ω or more from the viewpoint of electrical insulation. The surface resistance of the insulating film body ^{is preferably 1 × 10 19} Ω or less from a practical point of view.
As the insulating film main body, a film having heat resistance is preferable, a polyimide film and a liquid crystal polymer film are more preferable, and a polyimide film is further preferable.
The thickness of the insulating film body is preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 25 μm or less from the viewpoint of flexibility.
Examples of the material of the adhesive layer include epoxy resin, polyester, polyimide, polyamide-imide, polyamide, phenol resin, urethane resin, acrylic resin, melamine resin, polystyrene, polyolefin and the like. The epoxy resin may contain a rubber component (carboxy-modified nitrile rubber, etc.) for imparting flexibility.
The thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, and more preferably 1.5 μm or more and 60 μm or less.

The shape of the opening of the through hole is not particularly limited. Examples of the shape of the opening of the through hole 62 include a circle, an ellipse, and a quadrangle.

(Manufacturing method of printed wiring board with electromagnetic wave shield film)
The printed wiring board with an electromagnetic wave shielding film of the present invention can be manufactured, for example, by a method having the following steps (d) to (g).
Step (d): A step of providing an insulating film having through holes formed at positions corresponding to the printed circuit on the surface of the printed wiring board on the side where the printed circuit is provided to obtain a printed wiring board with the insulating film.
Step (e): After the step (d), the printed wiring board with the insulating film and the electromagnetic wave shielding film of the present invention from which the second release film is peeled off are brought into contact with the surface of the insulating film by the conductive adhesive layer. By stacking them in such a manner and heat-pressing them, a conductive adhesive layer is adhered to the surface of the insulating film, and the conductive adhesive layer is electrically connected to the printed circuit through a through hole to generate an electromagnetic wave. The process of obtaining a printed wiring board with a shield film.
Step (f): A step of peeling off the first release film when the first release film is no longer needed after the step (e).
Step (g): A step of main curing the anisotropic conductive adhesive layer between the steps (e) and the step (f), or after the step (f), if necessary.

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

(Step (d))
As shown in FIG. 6, an insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 is superposed on the flexible printed wiring board 50, and an adhesive layer of the insulating film 60 is formed on the surface of the flexible printed wiring board 50. A flexible printed wiring board 3 with an insulating film is obtained by adhering (not shown) and curing the adhesive layer. The adhesive layer of the insulating film 60 may be temporarily adhered to the surface of the flexible printed wiring board 50, and the adhesive layer may be mainly cured in the step (g).
The adhesive layer is adhered and cured by, for example, hot pressing with a press machine (not shown) or the like.

(Step (e))
As shown in FIG. 6, an electromagnetic wave shielding film 1 from which the second release film 40 has been peeled off is placed on the flexible printed wiring board 3 with an insulating film and heat-pressed to form an anisotropic conductivity on the surface of the insulating film 60. A flexible printed wiring board 2 with an electromagnetic wave shielding film is obtained in which the adhesive layer 24 is adhered and the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62.

Adhesion and curing of the anisotropic conductive adhesive layer 24 are performed, for example, by hot pressing with a press machine (not shown) or the like.
The hot pressing time is 20 seconds or more and 60 minutes or less, more preferably 30 seconds or more and 30 minutes or less. When the heat pressing time is equal to or greater than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60. Further, the insulating resin layer 10 is sufficiently cured, and the peeling force at the interface between the insulating resin layer 10 and the first release film 30 is sufficiently reduced. When the heat pressing time is equal to or less than the upper limit of the above range, the manufacturing time of the flexible printed wiring board 2 with the electromagnetic wave shielding film can be shortened.

The temperature of the hot press (the temperature of the hot plate of the press machine) is preferably 140 ° C. or higher and 190 ° C. or lower, and more preferably 150 ° C. or higher and 175 ° C. or lower. When the temperature of the hot press is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60. Moreover, the time of hot pressing can be shortened. Further, the insulating resin layer 10 is sufficiently cured, and the peeling force at the interface between the insulating resin layer 10 and the first release film 30 is sufficiently reduced. When the temperature of the hot press is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, and the like can be suppressed.

The pressure of the hot press is preferably 0.5 MPa or more and 20 MPa or less, and more preferably 1 MPa or more and 16 MPa or less. When the pressure of the hot press is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60. Moreover, the time of hot pressing can be shortened. When the pressure of the hot press is not more than the upper limit of the above range, damage to the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be suppressed.

(Step (f))
As shown in FIG. 6, when the first release film is no longer needed, the first release film 30 is peeled off from the insulating resin layer 10.

(Step (g))
When the hot pressing time in the step (e) is as short as 20 seconds or more and 10 minutes or less, the anisotropic conductive adhesive layer is formed between the steps (e) and the step (f) or after the step (f). It is preferable to perform the main curing of 24.
The main curing of the anisotropic conductive adhesive layer 24 is performed using, for example, a heating device such as an oven.
The heating time is 15 minutes or more and 120 minutes or less, preferably 30 minutes or more and 60 minutes or less. When the heating time is equal to or greater than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be sufficiently cured. When the heating time is not more than the upper limit of the above range, the manufacturing time of the flexible printed wiring board 2 with the electromagnetic wave shielding film can be shortened.
The heating temperature (atmospheric temperature in the oven) is preferably 120 ° C. or higher and 180 ° C. or lower, and preferably 120 ° C. or higher and 150 ° C. or lower. When the heating temperature is equal to or higher than the lower limit of the above range, the heating time can be shortened. When the heating temperature is not more than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, and the like can be suppressed.
The heating is preferably performed without pressurization because it is not necessary to use a special device.

(Action effect)
Since the electromagnetic wave shielding film 1 is used in the flexible printed wiring board 2 with the electromagnetic wave shielding film described above, it has an insulating resin layer 10 having heat resistance, high hardness, and few defects. The insulating resin layer 10 also has flame retardancy.

(Other embodiments)
The printed wiring board with an electromagnetic wave shielding film of the present invention includes a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on the side where the printed circuit is provided, and a conductive layer adjacent to the insulating film and conductive. The layer may have the electromagnetic wave shielding film of the present invention electrically connected to the printed circuit through a through hole formed in the insulating film, and the embodiment is not limited to the illustrated example.
For example, the flexible printed wiring board may have a ground layer on the back surface side. Further, the flexible printed wiring board may have printed circuits on both sides, and an insulating film and an electromagnetic wave shielding film may be attached to both sides.
An inflexible rigid printed circuit board may be used instead of the flexible printed wiring board.
Instead of the electromagnetic wave shielding film 1 of the first embodiment, the electromagnetic wave shielding film 1 of the second embodiment, the electromagnetic wave shielding film 1 of the third embodiment, and the like may be used.

Examples are shown below. The present invention is not limited to the examples.

(Storage modulus)
The storage elastic modulus was measured using a dynamic viscoelasticity measuring device (Rheometric Scientific, Inc., RSAII) under the conditions of temperature: 180 ° C., frequency: 1 Hz, and heating rate: 10 ° C./min.

(Arithmetic Mean Roughness Ra)
For the arithmetic average roughness Ra of the surface of the first release film on the release agent layer side, a roughness curve was measured using a 3D measurement laser microscope (LEXT OLS4000 manufactured by OLYMPUS), and JIS was obtained from this roughness curve. It was determined based on B 0601: 2013 (corresponding international standard ISO 4287: 1997, Amd. 1: 2009).

(defect)
The insulating resin layer was visually observed and evaluated according to the following criteria.
◯: No defects due to repelling or unevenness of the coating liquid were observed in the insulating resin layer.
Δ: There was no repelling or defect of the coating liquid on the insulating resin layer, but some unevenness was observed.
X: Defects due to repelling or unevenness of the coating liquid were observed in the insulating resin layer.

(Heat-resistant)
The electromagnetic wave shield film from which the first release film and the second release film were peeled off was placed in a reflow furnace in which the internal temperature was set to 288 ° C. for 30 seconds. The electromagnetic wave shield film was taken out from the reflow furnace, visually observed, and evaluated according to the following criteria.
◯: No evidence of melting is seen in the insulating resin layer.
X: Evidence of melting is seen in the insulating resin layer.

(hardness)
Regarding the hardness of the insulating resin layer, pencil hardness test (JIS K5600-5-4, ISO15184, ASTM D3363 compliant, mechanical method: KT-VF2391 TQC WW tester, pencil used: Mitsubishi Pencil Uni 6B-6H, pencil tip load: 750g (7.35N), pencil scratching angle: 45 degrees, speed: 1.0 mm / s, distance: 7 mm), and the pencil hardness was measured.

(Flame retardance)
A test piece having a length of 200 mm and a width of 50 mm was cut out from the electromagnetic wave shield film from which the first release film and the second release film were peeled off. A thin material vertical combustion test (VTM test) was conducted in accordance with UL94 standards. The number of samples was 5. The judgment criteria are shown in Table 1.

(Example 1)
As the first release film and the second release film, a PET film (T157, manufactured by Lintec Corporation) whose one side was release-treated with a non-silicone release agent was prepared.

As a coating liquid for forming an insulating resin layer, a polyamideimide (manufactured by Toyo Boseki Co., Ltd., HR-22BL, glass transition temperature 335 ° C., solid content 20% by mass, γ-butyrolactone solution) having a repeating unit represented by the above formula (1). , 100 parts by mass of number average molecular weight Mn13000) and 2 parts by mass of carbon black were dissolved in 100 parts by mass of a solvent (γ-butyrolactone) to prepare a coating liquid.

As a thermosetting conductive adhesive composition, 100 parts by mass of a thermosetting adhesive (epoxy resin (DIC, EXA-4816)) and 20 parts by mass of a curing agent (Ajinomoto Fine Techno, PN-23). 40 parts by mass of conductive particles (copper particles having an average particle diameter of 7.5 μm) dissolved or dispersed in 200 parts by mass of a solvent (methyl ethyl ketone). I prepared it.

Step (a):
A coating liquid for forming an insulating resin layer is applied to the surface of the first release film on the release agent layer side, heated at 120 ° C. for 2 minutes, and the coating liquid is dried to obtain an insulating resin layer (thickness:: Storage elastic modulus at 5 μm and 180 ° C.: 2.0 × 10 ¹⁰ Pa) was formed.

Step (b1):
Copper was physically vapor-deposited on the surface of the insulating resin layer 10 by an electron beam vapor deposition method to form a metal thin film layer (deposited film, thickness: 0.07 μm, surface resistance: 0.3 Ω).

Step (b2):
A thermosetting conductive adhesive composition is applied to the surface of the metal thin film layer using a die coater, and the solvent is volatilized to form a B stage, whereby the anisotropic conductive adhesive layer (thickness: 7 μm, Copper particles: 4.5% by volume, storage elastic modulus at 180 ° C.: 1 × 10 ⁴ Pa) was formed.

Step (c):
A second release film was attached to the surface of the anisotropic conductive adhesive layer to obtain an electromagnetic wave shielding film as shown in FIG. The evaluation results are shown in Table 2.

Step (d):
An insulating adhesive composition made of a nitrile rubber-modified epoxy resin is applied to the surface of a 25 μm-thick polyimide film (surface resistance: 1 × 10 ^{17 Ω) (insulating film body) so that the dry film thickness is 25 μm.} Then, an adhesive layer was formed to obtain an insulating film (thickness: 50 μm). A through hole (hole diameter: 150 μm) was formed at a position corresponding to the ground of the print circuit 54.

A flexible printed wiring board in which a printed circuit was formed was prepared on the surface of a polyimide film (surface resistance: 1 × 10 ^{17 Ω) (base film) having a thickness of 12 μm.}
An insulating film was attached to the flexible printed wiring board by a hot press to obtain a flexible printed wiring board with an insulating film.

Step (e):
An electromagnetic wave shield film from which the second release film was peeled off was placed on a flexible printed wiring board with an insulating film, and a hot press device (G-12 manufactured by Orihara Seisakusho Co., Ltd.) was used to heat the hot plate temperature: 170 ° C. and pressure: 2 MPa. A flexible printed wiring board with an electromagnetic wave shielding film was obtained by temporarily adhering an anisotropic conductive adhesive layer to the surface of the insulating film by hot pressing for 120 seconds.

Steps (f), (g):
The anisotropic conductive adhesive layer was mainly cured by heating a flexible printed wiring board with an electromagnetic wave shielding film at a temperature of 160 ° C. for 1 hour using a high-temperature incubator (manufactured by Kusumoto Kasei Co., Ltd., HT210).
The first release film was peeled off from the insulating resin layer.

( Reference example )
HR-15ET (glass transition temperature 260 ° C., solid content 25% by mass, ethanol / toluene = 50/50 (mass ratio) solution, number average molecular weight Mn6000) manufactured by Toyo Boseki Co., Ltd. was used as the polyamideimide, and the solvent was ethanol / toluene =. An insulating resin layer (thickness: 5 μm, storage elastic modulus at 180 ° C.: 1.0 × 10 ¹⁰ Pa) was formed in the same manner as in Example 1 except that the ratio was changed to 50/50 (mass ratio), and an electromagnetic wave shield was formed. I got a film. The evaluation results are shown in Table 2.

(Example 2 )
HR-16NN manufactured by Toyobo Co., Ltd. (glass transition temperature 320 ° C., solid content 14% by mass, N-methylpyrrolidone solution, number average molecular weight Mn30000) was used as the polyamide-imide, except that the solvent was changed to N-methylpyrrolidone. example 1 and the insulating resin layer in the same manner (thickness: 5 [mu] m, storage elastic modulus at ^{180 ℃: 1.0 × 10 8 Pa} ) on the ridges thereby to obtain an electromagnetic wave shielding film. The evaluation results are shown in Table 2.

(Comparative Example 1)
As a coating liquid for forming an insulating resin layer, 100 parts by mass of a bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER (registered trademark) 828), 20 parts by mass of a curing agent (N-aminoethylpiperazine), 2-ethyl A coating solution was prepared in which 2 parts by mass of -4-methylimidazole and 2 parts by mass of carbon black were dissolved in 200 parts by mass of a solvent (methylethylketone).

An electromagnetic wave shield film was obtained in the same manner as in Example 1 except that the coating liquid for forming the insulating resin layer was changed. The evaluation results are shown in Table 2.

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

1 Electromagnetic wave shield film,
2 Flexible printed wiring board with electromagnetic wave shield film,
3 Flexible printed wiring board with insulating film,
10 Insulation resin layer,
20 conductive layer,
22 metal thin film layer,
24 anisotropic conductive adhesive layer,
24a thermosetting adhesive,
24b conductive particles,
26 Isotropic conductive adhesive layer,
26a Thermosetting adhesive,
26b Conductive particles,
30 First release film,
32 base material layer,
34 Release agent layer,
40 Second release film,
42 base material layer,
44 Release agent layer,
50 Flexible printed wiring board,
52 base film,
54 printed circuit,
60 Insulation film,
62 Through hole.

Claims (6)

Insulation resin layer and
The conductive layer adjacent to the insulating resin layer and
An electromagnetic wave shielding film having a first release film adjacent to the conductive layer on the opposite side of the insulating resin layer.
The insulating resin layer is a coating film containing polyamide-imide, and the insulating resin layer is a coating film containing polyamide-imide.
The glass transition temperature of the polyamide-imide is 250 to 350 ° C.
The number average molecular weight Mn of the polyamideimide, Ri 13000 to 35000 der,
The first release film has a release agent layer and
The insulating resin layer and said release layer is that Sessu, electromagnetic wave shielding film. The electromagnetic wave according to claim 1, wherein the conductive layer has a metal thin film layer adjacent to the insulating resin layer and a conductive adhesive layer which is the outermost layer of the conductive layer on the opposite side of the insulating resin layer. Shield film. The electromagnetic wave shielding film according to claim 1 or 2, wherein the conductive layer is an isotropic conductive adhesive layer. The electromagnetic wave shielding film according to any one of claims 1 to 3, further comprising a second release film adjacent to the conductive layer on the side opposite to the insulating resin layer. The method for producing an electromagnetic wave shielding film according to any one of claims 1 to 4.
A coating liquid containing the polyamide-imide and a solvent is applied to one side of the first release film and dried to form the insulating resin layer.
A method for manufacturing an electromagnetic wave shielding film, in which a conductive layer adjacent to the insulating resin layer is provided. A printed wiring board with a printed circuit on at least one side of the board,
An insulating film adjacent to the surface of the printed wiring board on the side where the printed circuit is provided, and
The invention according to any one of claims 1 to 4, wherein the conductive layer is adjacent to the insulating film, and the conductive layer is electrically connected to the printed circuit through a through hole formed in the insulating film. A printed wiring board with an electromagnetic wave shielding film, which has an electromagnetic wave shielding film.

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