JP7653761B2 - Electromagnetic wave shielding film, printed wiring board with electromagnetic wave shielding film, and method for producing same - Google Patents

Description

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

In order to shield electromagnetic noise generated from the printed wiring board or from external electromagnetic noise, an electromagnetic shielding film having an insulating resin layer and an electromagnetic shielding layer may be provided on the surface of the printed wiring board via an insulating film (coverlay film) (see, for example, Patent Document 1). The electromagnetic shielding layer has, for example, a metal layer for shielding electromagnetic waves and a conductive adhesive layer for electrically connecting the metal layer to the printed circuit of the printed wiring board. The conductive adhesive layer contains resin and conductive particles. The conductive adhesive layer is formed, for example, by applying a conductive adhesive paint containing resin, conductive particles, and a solvent to the surface of the metal layer.

When providing the electromagnetic shielding film on the surface of the printed wiring board, the printed wiring board with insulating film and the electromagnetic shielding film are overlapped so that the insulating film and the conductive adhesive layer are in contact, temporarily fixed, and then thermocompression bonded. At this time, part of the conductive adhesive layer of the electromagnetic shielding film contacts the printed circuit (ground) of the printed wiring board through the through hole formed in the insulating film, electrically connecting the metal layer and the printed circuit of the printed wiring board.

JP 2017-220592 A

As the conductive particles, metal particles having high conductivity such as copper particles, silver particles, copper particles coated with silver, etc. However, when metal particles are used as the conductive particles, the following problems may occur.
- Metal particles have a high specific gravity and therefore tend to settle in conductive adhesive paints, and there is a possibility that they may settle in the flow passages of the coating machine, so a special coating method is required to form a stable film.
- Metal particles have a large particle size distribution, so the content of metal particles is increased in order to ensure the number of particles that contribute to the electrical connection between the printed circuit and the metal layer. As the content increases, the resin film itself contains many small metal particles that do not contribute to the connection, which reduces the flexibility of the resin film itself, and the relatively increased metal particles with larger particle sizes act as spacers, reducing the ease of temporary fixing and adhesion between the conductive adhesive layer of the electromagnetic shielding film and the surface of the printed wiring board. As a result, the workability during mounting decreases, and when gas is generated inside during the solder flow process or reflow process, the adhesion is insufficient, causing the conductive adhesive layer to peel off and blistering. In addition, due to the low adhesion, problems such as the electromagnetic shielding film peeling off from the printed wiring board occur during chemical resistance tests and solvent resistance tests. On the other hand, if the content of metal particles is reduced, the connection between the electromagnetic shielding film and the printed circuit of the printed wiring board cannot be made or becomes unstable, making it difficult to achieve both adhesion and electrical connectivity.

The present invention aims to provide an electromagnetic wave shielding film, a printed wiring board with an electromagnetic wave shielding film, and a method for manufacturing the same, which can stably form an electromagnetic wave shielding layer even using a general-purpose method, has excellent adhesion to the printed circuit of a printed wiring board, does not cause defects such as abnormalities during the solder flow process or reflow process, and has excellent electrical connectivity.

The present invention has the following aspects.
[1] An insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer,
The electromagnetic wave shielding film, wherein the electromagnetic wave shielding layer comprises resin particles having a conductive film formed by coating the surfaces of the resin particles with a conductive film.
[2] The electromagnetic wave shielding film according to [1], wherein the ratio of the mass of the conductive film to the total mass of the resin particles with the conductive film is 5 mass % or more and 50 mass % or less.
[3] The electromagnetic wave shielding film according to [1] or [2], wherein the specific gravity of the resin particles with the conductive film is 1.00 or more and 3.00 or less.
[4] The electromagnetic wave shielding film according to any one of [1] to [3], wherein the specific gravity of the resin particles is 0.90 or more and 3.00 or less.
[5] The electromagnetic wave shielding film according to any one of [1] to [4], wherein the resin particles contain at least one resin selected from the group consisting of an acrylic resin, a urethane resin, a nylon resin, and a silicone resin.
[6] The electromagnetic wave shielding film according to any one of [1] to [5], wherein the specific gravity of the conductive film is 2.50 or more and 22.0 or less.
[7] The electromagnetic shielding film according to any one of [1] to [6], wherein the conductive film contains at least one metal selected from the group consisting of gold, silver, and copper.
[8] The electromagnetic wave shielding film according to any one of [1] to [7], wherein the conductive film contains two or more different metals.
[9] The electromagnetic wave shielding film according to any one of [1] to [8], wherein the average particle size of the resin particles with the conductive film is from 0.5 μm to 20 μm.
[10] The electromagnetic shielding film according to any one of [1] to [9], wherein the conductive film includes a sputtered film.
[11] The electromagnetic shielding film according to any one of [1] to [9], wherein the conductive film includes a plating film.
[12] The electromagnetic wave shielding film according to any one of [1] to [11], wherein the coefficient of variation in particle size distribution of the resin particles with a conductive film is 0.5% or more and 27% or less.
[13] The electromagnetic wave shielding layer has a metal layer adjacent to the insulating resin layer and a conductive adhesive layer adjacent to the metal layer on the opposite side to the insulating resin layer,
The electromagnetic wave shielding film according to any one of [1] to [12], wherein the conductive adhesive layer contains the conductive film-attached resin particles.
[14] The electromagnetic wave shielding film according to [13], wherein the conductive adhesive layer is an anisotropic conductive adhesive layer.
[15] An insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer,
a method for producing an electromagnetic wave shielding film, the electromagnetic wave shielding layer having a metal layer adjacent to the insulating resin layer and a conductive adhesive layer adjacent to the metal layer on a side opposite to the insulating resin layer,
A method for producing an electromagnetic wave shielding film, comprising applying a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film onto the metal layer to form the conductive adhesive layer.
[16] A printed wiring board having a printed circuit provided on at least one surface of a substrate;
an insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided;
[15] The electromagnetic wave shielding film according to any one of [1] to [14], which is adjacent to the insulating film on the opposite side to the printed wiring board and in which the electromagnetic wave shielding layer is in contact with the insulating film;
A printed wiring board with an electromagnetic wave shielding film.
[17] A printed wiring board having a printed circuit provided on at least one surface of a substrate and an insulating film provided with an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided;
[1] to [14] and an electromagnetic wave shielding film according to any one of [1] to [14],
The insulating film and the electromagnetic wave shielding layer are overlapped so as to be in contact with each other, and then thermocompression bonded to each other.

The present invention provides an electromagnetic wave shielding film, a printed wiring board with an electromagnetic wave shielding film, and a manufacturing method thereof, which can stably form an electromagnetic wave shielding layer even using a general-purpose method, has excellent adhesion to the printed circuit of a printed wiring board, does not cause defects such as abnormalities during the solder flow process or reflow process, and has excellent electrical connectivity.

1 is a cross-sectional view showing a first embodiment of an 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. 1 is a cross-sectional view showing one embodiment of a printed wiring board with an electromagnetic wave shielding film of the present invention. 4A to 4C are cross-sectional views showing a manufacturing process of the printed wiring board with the electromagnetic shielding film of FIG. 3. FIG. 5(A) is a plan view showing a flexible printed wiring board with an insulating film for evaluating connectivity to measure the minimum connection diameter, FIG. 5(B) is a cross-sectional view taken along line A-A in FIG. 5(A), and FIG. 5(C) is a cross-sectional view taken along line B-B in FIG. 5(A). FIG. 6(A) is a plan view showing a test piece used for measuring the minimum connection diameter, and FIG. 6(B) is a cross-sectional view taken along the line CC of FIG. 6(A).

The following definitions of terms apply throughout the specification and claims.
The term "isotropically conductive adhesive layer" refers to a conductive adhesive layer that has conductivity in the thickness direction and the surface direction.
The term "anisotropic conductive adhesive layer" refers to a conductive adhesive layer that has conductivity in the thickness direction but not in the surface direction.
The term "conductive adhesive layer having no conductivity in the planar direction" refers to a conductive adhesive layer having a surface resistance of 1×10 ⁴ Ω/□ or more.
The average particle diameter of the resin particles with a conductive film (conductive particles) is a value obtained by randomly selecting 30 particles from a microscopic image of the particles, measuring the minimum and maximum diameters of each particle, defining the median of the minimum and maximum diameters as the particle diameter of one particle, and then arithmetically averaging the particle diameters of the 30 measured particles.
The coefficient of variation of the resin particles with a conductive film (conductive particles) is a CV value (%) calculated by randomly selecting 30 particles from a microscopic image of the particles, determining the standard deviation σ and average particle diameter D for the particle diameters of the 30 particles, and using the following formula:
CV=σ/D×100
The specific gravity of the resin particles with a conductive film (conductive particles) is a value measured at a temperature of 23° C. in accordance with Method A of JIS K7112:1999.
The 10% compression strength of the resin particles with a conductive film (conductive particles) is calculated from the results of measurement using a micro compression tester, according to the following formula (α).
C(x)=2.48P/πd ² ...(α)
where C(x) is the 10% compressive strength (MPa), P is the test force (N) at 10% displacement of the particle diameter, and d is the particle diameter (mm).
The thickness of a film (carrier film, release film, insulating film, etc.) or coating (insulating resin layer, conductive adhesive layer, etc.) is the average value of the thickness measured at five randomly selected locations using a digital length measuring machine (Mitutoyo Corporation, Litematic VL-50-B).
The thickness of the metal layer is determined by measuring the thickness at five randomly selected locations by X-ray fluorescence analysis in accordance with JIS K0119:2008, and averaging the measured values.
The storage modulus is calculated from the stress applied to the measurement object and the strain detected, and is measured as one of the viscoelastic properties using a dynamic viscoelasticity measuring device that outputs the value as a function of temperature or time.
The surface resistance is a surface resistivity measured by a method conforming to JIS K 7194:1994, JIS R 1637:1998, and JIS K 6911:2006.
The dimensional ratios in FIGS. 1 to 4 are different from the actual ones for the sake of convenience of explanation.

<Electromagnetic wave shielding film>
A first aspect of the present invention is an electromagnetic wave shielding film having an insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer, the electromagnetic wave shielding layer including resin particles with a conductive film in which the surfaces of the resin particles are coated with a conductive film.

Fig. 1 is a cross-sectional view showing an electromagnetic wave shielding film 1 according to a first embodiment. Fig. 2 is a cross-sectional view showing an electromagnetic wave shielding film 1 according to a second embodiment.
Both the electromagnetic wave shielding film 1 of the first embodiment and the second embodiment have an insulating resin layer 10, an electromagnetic wave shielding layer 20 adjacent to the insulating resin layer 10, a carrier film 30 adjacent to the insulating resin layer 10 on the side opposite the electromagnetic wave shielding layer 20, and a release film 40 adjacent to the insulating resin layer 20 on the side opposite the insulating resin layer 10.
In the electromagnetic wave shielding film 1 of the first embodiment, the electromagnetic wave shielding layer 20 has a metal layer 22 adjacent to the insulating resin layer 10 and an anisotropic conductive adhesive layer 24 adjacent to the release film 40 .
In the electromagnetic wave shielding film 1 of the second embodiment, the electromagnetic wave shielding layer 20 has a metal layer 22 adjacent to the insulating resin layer 10 and an isotropic conductive adhesive layer 26 adjacent to the release film 40 .
From the viewpoints of excellent transmission characteristics, a small content of conductive-coated resin particles, and cost advantages, an electromagnetic wave shielding film 1 in which the conductive adhesive layer is the anisotropic conductive adhesive layer 24 is preferred.

The thickness of the electromagnetic shielding film 1 (excluding the carrier film 30 and the release film 40) is preferably 3 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less. If the thickness of the electromagnetic shielding film 1 excluding the carrier film 30 and the release film 40 is equal to or more than the lower limit of the above range, the film is less likely to break when the carrier film 30 is peeled off. If the thickness of the electromagnetic shielding film 1 excluding the carrier film 30 and the release film 40 is equal to or less than the upper limit of the above range, the printed wiring board with the electromagnetic shielding film can be made thin.

(Insulating resin layer)
The insulating resin layer 10 becomes a protective layer for the metal layer 22 after the electromagnetic wave shielding film 1 is attached to the surface of an insulating film provided on the surface of a flexible printed wiring board and the carrier film 30 is peeled off from the electromagnetic wave shielding film 1.

Examples of the insulating resin layer 10 include a coating film formed by applying a paint containing a thermosetting resin and a curing agent and semi-curing or curing the paint; a coating film formed by applying a paint containing a thermoplastic resin and drying the paint; and a layer made of a film formed by melt-molding a composition containing a thermoplastic resin. From the viewpoint of heat resistance when subjected to the solder reflow process, a coating film formed by applying a paint containing a thermosetting resin and a curing agent and semi-curing or curing the paint is preferred.

Examples of the thermosetting resin include amide resin, epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet-curable acrylate resin, etc. As the thermosetting resin, amide resin and epoxy resin are preferred from the viewpoint of excellent heat resistance.
The curing agent may be a known curing agent suitable for the type of thermosetting resin.
Examples of the thermoplastic resin include aromatic polyether ketone, polyimide, polyamide imide, polyamide, polysulfone, polyether sulfone, polyphenylene sulfone, polyphenylene sulfide, polyphenylene sulfide sulfone, and polyphenylene sulfide ketone.

The insulating resin layer 10 may contain either or both of a colorant (pigment, dye, etc.) and a filler in order to conceal the printed circuit of the printed wiring board or to impart design features to the printed wiring board with the electromagnetic wave shielding film.
As either or both of the colorant and the filler, a pigment or a filler is preferred from the viewpoints of weather resistance, heat resistance, and hiding power, and from the viewpoints of hiding power and design of the printed circuit, a black pigment, a combination of a black pigment with another pigment, or a combination of a black pigment with a filler is more preferred.
The insulating resin layer 10 may contain a flame retardant.
The insulating resin layer 10 may contain other components as necessary within the range that does not impair the effects of the present invention.

From the viewpoint of electrical insulation, the surface resistance of the insulating resin layer 10 is preferably 1×10 ⁶ Ω/□ or more, and from the viewpoint of practical use, the surface resistance of the insulating resin layer 10 is preferably 1×10 ¹⁹ Ω/□ or less.
The thickness of the insulating resin layer 10 is preferably 1.0 μm or more and 20 μm or less, more preferably 2.0 μm or more and 15 μm or less, and even more preferably 3.0 μm or more and 8.0 μm or less. If the thickness of the insulating resin layer 10 is 1.0 μm or more, the insulating resin layer 10 can fully function as a protective layer. If the thickness of the insulating resin layer 10 is 2.0 μm or more, the thickness variation in the surface of the insulating resin layer 10 can be suppressed, and performance and productivity can be improved. If the thickness of the insulating resin layer 10 is 3.0 μm or more, the insulating resin layer 10 is less likely to break. If the thickness of the insulating resin layer 10 is 20 μm or less, the pressing conditions can be relaxed, and the insulating resin layer 10 and the electromagnetic wave shielding layer 20 are less likely to break, thereby preventing a decrease in shielding characteristics. If the thickness of the insulating resin layer 10 is 15 μm or less, the conformability to the step of the printed wiring board is improved. If the thickness of the insulating resin layer 10 is 8.0 μm or less, the electromagnetic wave shielding film 1 can be made thin.

(Electromagnetic wave shielding layer)
The electromagnetic wave shielding layer 20 has a metal layer 22 and a conductive adhesive layer (anisotropic conductive adhesive layer 24 or an isotropic conductive adhesive layer 26) adjacent to the metal layer 22 on the side opposite the insulating resin layer 10, and therefore has sufficiently high electromagnetic wave shielding properties.

Metal layer:
The metal layer 22 is a layer made of metal. The metal layer 22 is formed so as to extend in the planar direction, and therefore has electrical conductivity in the planar direction and functions as a layer that blocks electromagnetic waves, etc.

Examples of the metal layer 22 include a deposition layer formed by physical vapor deposition (vacuum deposition, sputtering, ion beam deposition, electron beam deposition, etc.) or CVD (chemical vapor deposition), a plating layer formed by plating, metal foil, etc. In that the metal layer 22 can be made thin and has excellent conductivity in the surface direction even if it is thin, the metal layer 22 is preferably a deposition layer or a plating layer. In that the metal layer 22 can be easily formed by a dry process, the metal layer 22 is more preferably a deposition layer, and a deposition layer formed by physical vapor deposition is even more preferable.

Examples of metals constituting the metal layer 22 include aluminum, silver, copper, gold, conductive ceramics, etc. Among these, silver or copper is preferable from the viewpoint of electrical conductivity.
Among the metal layers 22, a metal vapor deposition layer is preferred because it has high electromagnetic wave shielding properties and is easy to form a thin metal film, and a silver vapor deposition layer or a copper vapor deposition layer is more preferred.

The surface resistance of the metal layer 22 is preferably 0.001 Ω/□ or more and 1 Ω/□ or less, and more preferably 0.001 Ω/□ or more and 0.5 Ω/□ or less. If the surface resistance of the metal layer 22 is equal to or greater than the lower limit of the above range, the metal layer 22 can be made sufficiently thin. If the surface resistance of the metal layer 22 is 1 Ω/□ or less, the electromagnetic wave shielding properties can be sufficiently exhibited. If the surface resistance of the metal layer 22 is 0.5 Ω/□ or less, the effect on the transmission characteristics of the printed wiring board can be reduced.

The thickness of the metal layer 22 is preferably 0.01 μm or more and 5 μm or less, and more preferably 0.05 μm or more and 3 μm or less. If the thickness of the metal layer 22 is equal to or more than the lower limit of the above range, the electromagnetic noise shielding effect is further improved. If the thickness of the metal layer 22 is equal to or less than the upper limit of the above range, the electromagnetic shielding film 1 can be made thinner. In addition, the productivity and flexibility of the electromagnetic shielding film 1 are improved.

Anisotropic conductive adhesive layer:
The anisotropic conductive adhesive layer 24 has conductivity in the thickness direction, has no conductivity in the planar direction, and has adhesiveness.
The anisotropic conductive adhesive layer 24 has the advantage that the amount of conductive-coated resin particles can be reduced, and as a result, the flexibility and adhesion of the electromagnetic wave shielding film 1 can be further improved, and costs can be reduced.
Since the anisotropic conductive adhesive layer 24 has no conductivity in the planar direction, the electromagnetic wave shielding layer 20 has little effect on the transmission characteristics of the printed wiring board, making it possible to produce a printed wiring board with an electromagnetic wave shielding film having small transmission loss.

The anisotropic conductive adhesive layer 24 may be, for example, a layer made of a conductive adhesive. A thermosetting conductive adhesive layer containing a thermosetting resin 24a and conductive film-attached resin particles 24b is preferable as the anisotropic conductive adhesive layer 24, because it can exhibit heat resistance after curing and can easily maintain adhesion and electrical connection with the printed circuit of the printed wiring board during thermocompression bonding. The thermosetting anisotropic conductive adhesive layer 24 may be in an uncured state or in a B-stage state.
In the present invention, in the conductive adhesive layer, a thermoplastic resin may be used instead of the thermosetting resin, or a thermosetting resin and a thermoplastic resin may be used in combination.

Examples of the thermosetting resin 24a include epoxy resin, phenol resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet-cured acrylate resin, etc. Epoxy resin is preferable because of its excellent heat resistance. The epoxy resin may contain a rubber component (nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, etc.
The thermosetting resin 24a may contain other components (such as a curing agent, a curing accelerator, and a reaction initiator) as necessary, as long as the effects of the present invention are not impaired.

Examples of the thermoplastic resin used for the anisotropic conductive adhesive layer 24 include the same thermoplastic resins as those listed for the insulating resin layer 10 .
The anisotropic conductive adhesive layer 24 may contain cellulose resin and microfibril (glass fiber, etc.) in order to increase the strength and improve the punching characteristics of the anisotropic conductive adhesive layer 24. The anisotropic conductive adhesive layer 24 may contain other components (flame retardant, antiblocking agent, adhesion improver, dispersant, etc.) as necessary within a range that does not impair the effects of the present invention.

The conductive film-attached resin particles 24b are conductive particles having a core-shell structure in which the surfaces of the resin particles are coated with a conductive film, and therefore have a lower specific gravity than metal particles, making it easier to control the particle size distribution and allowing the compression strength of the particles to be reduced.
Examples of the resin material of the resin particles include acrylic resin, urethane resin, nylon resin, silicone resin, etc. The resin material of the resin particles may be one type or two or more types. The resin particles preferably contain at least one type selected from the group consisting of acrylic resin, urethane resin, nylon resin, and silicone resin, because the resin particles are inexpensive and easily available, and resin particles having a narrow particle size range are easily manufactured.
When the resin particles require heat resistance and solvent resistance, it is preferable to use crosslinked resin particles, and when flexibility is required, it is preferable to use uncrosslinked resin particles.

Examples of materials for the conductive film in the conductive film-coated resin particles 24b include gold, silver, copper, platinum, nickel, palladium, and aluminum.
The conductive film preferably contains at least one metal selected from the group consisting of gold, silver, and copper, because this improves the conductivity of the conductive film and allows the electromagnetic wave shielding layer 20 to be more reliably electrically connected to the printed circuit. In order to improve the performance of the conductive film, the conductive film may contain two or more different metals. For example, in order to improve adhesion and uniformity, the conductive film may be formed by forming a metal film such as gold, silver, or copper on a nickel film as an anchor.

As the conductive film in the conductive film-coated resin particles 24b, a plated film or a vapor deposition film is preferred because it is easy to manufacture resin particles with a conductive film having a core-shell structure. Furthermore, among vapor deposition films, a sputtered film formed by sputtering such as barrel sputtering is more preferred because it is inexpensive.

The average particle diameter of the conductive film-attached resin particles 24b is preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 15 μm or less, and even more preferably 3 μm or more and 10 μm or less. If the average particle diameter of the conductive film-attached resin particles 24b is 1 μm or more, a uniform conductive film can be formed on the resin particles, and the electrical connection of the electromagnetic wave shielding layer 20 to the printed circuit can be easily ensured. If the average particle diameter of the conductive film-attached resin particles 24b is 2 μm or more, the surface area per unit mass of the resin particles can be reduced, and the ratio of the mass of the conductive film to the total mass of the conductive film-attached resin particles 24b can be reduced, so that the conductive film-attached resin particles 24b with low specific gravity and high dispersibility can be manufactured inexpensively. If the average particle diameter of the conductive film-attached resin particles 24b is 3 μm or more, the anisotropic conductive adhesive layer can be thickened, and the in-plane thickness fluctuation can be suppressed, thereby stabilizing performance and productivity. If the average particle size of the conductive film-attached resin particles 24b is equal to or less than the upper limit of the range, the anisotropic conductive adhesive layer 24 can be made thin, making it possible to reduce the thickness of the electromagnetic wave shielding film.

The coefficient of variation in the particle size distribution of the conductive film-attached resin particles 24b is preferably 0.5% to 27%, more preferably 1% to 25%, and even more preferably 2% to 20%. If the coefficient of variation of the conductive film-attached resin particles 24b is equal to or greater than the lower limit of the range, the manufacturing cost of the conductive film-attached resin particles can be reduced. If the coefficient of variation of the conductive film-attached resin particles 24b is equal to or less than the upper limit of the range, the content of particles with a larger particle diameter that act as a spacer between the surface of the printed wiring board and the resin surface of the electromagnetic wave shielding layer 20 and particles with a smaller particle diameter that do not contribute to electrical connection and reduce the flexibility of the anisotropic conductive adhesive layer 24 can be reduced, and the adhesion between the surface of the printed wiring board and the electromagnetic wave shielding layer 20 can be further improved. In addition, the conductive film-attached resin particles 24b can be more uniformly dispersed in the conductive adhesive paint, and the distribution of the conductive film-attached resin particles 24b in the anisotropic conductive adhesive layer 24 can be more uniform. As a result, it is possible to ensure adhesion between the printed wiring board and the electromagnetic wave shielding layer, and it is possible to more stably manufacture the electromagnetic wave shielding layer 20, which can more reliably electrically connect the electromagnetic wave shielding layer 20 to the printed circuit.

The specific gravity of the resin particles 24b with conductive film is preferably 1.00 or more and 3.00 or less, and more preferably 1.10 or more and 2.00 or less. When the specific gravity of the resin particles 24b with conductive film is equal to or more than the lower limit of the above range, the conductivity is excellent. When the specific gravity of the resin particles 24b with conductive film is equal to or less than the upper limit of the above range, the dispersibility of the resin particles 24b with conductive film is excellent, and it becomes easy to form a uniform electromagnetic wave shielding layer.

The specific gravity of the resin particles is preferably 0.90 or more and 3.00 or less, and more preferably 0.95 or more and 2.00 or less. If the specific gravity of the resin particles is equal to or more than the lower limit of the above range, the resin particles can be easily obtained. If the specific gravity of the resin particles is equal to or less than the upper limit of the above range, the specific gravity of the resin particles with conductive film can be reduced.

The specific gravity of the conductive film is preferably 2.50 or more and 22.0 or less, more preferably 7.30 or more and 20.0 or less, and even more preferably 7.50 or more and 12.0 or less. If the specific gravity of the conductive film is 2.50 or more and 22.0 or less, the conductive film has excellent conductivity, the specific gravity of the conductive film-attached resin particles is kept low, and the distribution of the conductive film-attached resin particles 24b in the anisotropic conductive adhesive layer 24 is easily uniform, and the anisotropic conductive adhesive layer 24 can be easily manufactured. If the specific gravity of the conductive film is 7.30 or more and 20.0 or less, the conductivity is further improved, so that the ratio of the mass of the conductive film to the total mass of the conductive film-attached resin particles 24b can be lowered to improve dispersibility, and the amount of the conductive film-attached resin particles 24b added can be reduced to improve adhesion. If the specific gravity of the conductive film is 7.50 or more and 12.0 or less, the conductive film-attached resin particles 24b can be easily manufactured.

The ratio of the mass of the conductive film to the total mass of the resin particles 24b with conductive film is preferably 2.5% by mass or more and 50% by mass or less, more preferably 4% by mass or more and 30% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less. If the ratio of the mass of the conductive film is equal to or more than the lower limit of the range, the conductivity of the resin particles with conductive film is improved, and the electromagnetic wave shielding layer 20 can be more reliably electrically connected to the printed circuit. If the ratio of the mass of the conductive film is 50% by mass or less, the specific gravity of the resin particles with conductive film is kept low, and the distribution of the resin particles with conductive film in the anisotropic conductive adhesive layer 24 is easily uniform, and the anisotropic conductive adhesive layer 24 can be easily manufactured. If the ratio of the mass of the conductive film is 30% by mass or less, the effect on the compressive strength of the resin particles is small, and the resin particles 24b with conductive film are deformed during thermocompression bonding, improving adhesion, and improving heat resistance, chemical resistance, and solvent resistance in the solder flow process and reflow process.

The 10% compressive strength of the conductive film-attached resin particles 24b is 40 MPa or less, preferably 0.25 MPa or more and 19.0 MPa or less, and more preferably 0.5 MPa or more and 7.0 MPa or less. If the 10% compressive strength of the conductive film-attached resin particles 24b is 19.0 MPa or less, the conductive film-attached resin particles 24b are easily deformed during thermocompression bonding. Therefore, even if the conditions such as the press pressure, press temperature, and press time during thermocompression bonding are not strict, the resin of the anisotropic conductive adhesive layer 24 is easily in contact with the printed wiring board with the insulating film, and sufficient adhesion can be ensured. As a result, defects such as breakage and deformation in the insulating resin layer 10, the metal layer 22, and the printed wiring board are suppressed, and the workability is also excellent. If the 10% compressive strength of the conductive film-attached resin particles 24b is 7.0 MPa or less, the adhesion is further improved, and the heat resistance, chemical resistance, and solvent resistance in the solder flow process and reflow process are improved. In addition, workability is further improved by enabling compression bonding with a short press time. If the 10% compressive strength of the conductive film-attached resin particles 24b is 0.25 MPa or more, there is no risk of deformation during film formation of the anisotropic conductive adhesive layer 24, resulting in a decrease in performance. If the 10% compressive strength of the conductive film-attached resin particles 24b is 0.5 MPa or more, the anisotropic conductive adhesive layer 24 is likely to be reliably electrically connected to the printed circuit of the printed wiring board through the through holes of the insulating film without a significant loss in the pressure applied to the metal layer 22 during thermocompression bonding.

The content of the conductive film-attached resin particles 24b in the anisotropic conductive adhesive layer 24 is preferably 0.2% by mass or more and 30% by mass or less, and more preferably 0.4% by mass or more and 20% by mass or less, relative to the total mass of the anisotropic conductive adhesive layer 24. If the content of the conductive film-attached resin particles 24b is equal to or more than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 24 is improved, and the electromagnetic shielding properties and electrical connectivity are improved. If the content of the conductive film-attached resin particles 24b is equal to or less than the upper limit of the above range, the adhesion of the anisotropic conductive adhesive layer 24 is improved, and the flexibility of the electromagnetic wave shielding film 1 is improved. In addition, the manufacturing cost of the electromagnetic wave shielding film 1 is reduced.

The storage modulus of the anisotropic conductive adhesive layer 24 at 180°C is preferably ^1x103 Pa or more and ^5x107 Pa or less, more preferably ^5x103 Pa or more and ^1x107 Pa or less. If the storage modulus of the anisotropic conductive adhesive layer 24 at 180°C is equal to or more than the lower limit of the above range, the anisotropic conductive adhesive layer 24 has a more appropriate hardness, and the pressure loss in the anisotropic conductive adhesive layer 24 during thermocompression bonding can be reduced. As a result, the anisotropic conductive adhesive layer 24 and the printed circuit of the printed wiring board are sufficiently bonded, and the anisotropic conductive adhesive layer 24 is more reliably electrically connected to the printed circuit of the printed wiring board through the through hole of the insulating film. If the storage modulus of the anisotropic conductive adhesive layer 24 at 180°C is ^5x107 Pa or less, the flexibility of the electromagnetic wave shielding film 1 is improved. As a result, the electromagnetic wave shielding film 1 is easily sunk into the through-hole of the insulating film, and the anisotropic conductive adhesive layer 24 passes through the through-hole of the insulating film and is reliably electrically connected to the printed circuit of the printed wiring board. If the storage modulus of the anisotropic conductive adhesive layer 24 at 180°C is 1 x ¹⁰⁷ Pa or less, the conductive film-attached resin particles 24b can be easily deformed.

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. If the surface resistance of the anisotropic conductive adhesive layer 24 is equal to or more than the lower limit of the above range, the content of the conductive film-attached resin particles 24b can be kept low. In addition, the influence of the electromagnetic wave shielding layer 20 on the transmission characteristics of the printed wiring board is small, and a printed wiring board with an electromagnetic wave shielding film having small transmission loss can be manufactured. 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 practical problem with the anisotropy.

The thickness of the anisotropic conductive adhesive layer 24 is preferably 1 μm or more and 25 μm or less, and more preferably 2 μm or more and 15 μm or less. If the thickness of the anisotropic conductive adhesive layer 24 is 1 μm or more, the adhesion of the anisotropic conductive adhesive layer 24 can be ensured. If the thickness of the anisotropic conductive adhesive layer 24 is 2 μm or more, the thickness variation within the plane of the anisotropic conductive adhesive layer 24 can be suppressed, and performance and productivity can be stabilized. If the thickness of the anisotropic conductive adhesive layer 24 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film 1 can be made thinner. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

Isotropically conductive adhesive layer:
The isotropically conductive adhesive layer 26 has electrical conductivity in the thickness direction and the surface direction, and also has adhesiveness.
The isotropic conductive adhesive layer 26 has the advantage that the number of conductive paths is increased, resulting in high stability of electrical connection and higher electromagnetic shielding properties of the electromagnetic shielding film 1. In addition, by using the conductive film-attached resin particles 26b, the flexibility of the isotropic conductive adhesive layer 26 can be improved, and by reducing the ratio of metal components in the isotropic conductive adhesive layer 26, the effect of the electromagnetic shielding layer 20 on the transmission characteristics of the printed wiring board can be reduced.

The isotropic conductive adhesive layer 26 may be, for example, a layer made of a conductive adhesive. A thermosetting conductive adhesive layer containing a thermosetting resin 26a and conductive film-attached resin particles 26b is preferred because it can exhibit heat resistance after curing and is easy to maintain a conductive path during thermocompression bonding.
The thermosetting resin 26a contained in the isotropic conductive adhesive layer 26 may be the same as the thermosetting resin 24a contained in the anisotropic conductive adhesive layer 24, and the preferred forms are also the same.

The conductive film-attached resin particles 26b are the conductive film-attached resin particles having the above-mentioned core-shell structure, similar to the conductive film-attached resin particles 24b contained in the anisotropic conductive adhesive layer 24, and the preferred form is also the same.
The average particle diameter of the conductive film-attached resin particles 26b in the isotropically conductive adhesive layer 26 is preferably 0.5 μm or more and 10 μm or less, more preferably 0.5 μm or more and 5 μm or less, and even more preferably 0.5 μm or more and 3 μm or less. If the average particle diameter of the conductive film-attached resin particles 26b is equal to or more than the lower limit of the above range, the manufacturing cost of the conductive film-attached resin particles 26b can be reduced. If the average particle diameter of the conductive film-attached resin particles 26b is equal to or less than the upper limit of the above range, the number of contact points of the conductive film-attached resin particles 26b increases, and the conductivity in the three-dimensional direction can be stably improved.

The content of the conductive film-attached resin particles 26b in the isotropic conductive adhesive layer 26 is preferably 5% by mass or more and 60% by mass or less, and more preferably 9% by mass or more and 50% by mass or less, relative to the total mass of the isotropic conductive adhesive layer 26. If the proportion of the conductive film-attached resin particles 26b is equal to or more than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 is good. If the proportion of the conductive film-attached resin particles 26b is equal to or less than the upper limit of the above range, the adhesion and fluidity (ability to conform to the shape of the through holes in the insulating film) of the isotropic conductive adhesive layer 26 are good. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

The storage modulus of the isotropically conductive adhesive layer 26 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. The reason why this range is preferable is the same as that of the anisotropically conductive adhesive layer 24.

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. If the surface resistance of the isotropic conductive adhesive layer 26 is equal to or more than the lower limit of the above range, the content of the conductive film-attached resin particles 26b is kept low, the viscosity of the conductive adhesive does not become too high, and the applicability is further improved. In addition, the fluidity of the isotropic conductive adhesive layer 26 (ability to follow the shape of the through holes in the insulating film) can be further ensured. If 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 isotropic conductive adhesive layer 26 is preferably 1 μm or more and 20 μm or less, more preferably 2 μm or more and 17 μm or less, and even more preferably 4 μm or more and 15 μm or less. If the thickness of the isotropic conductive adhesive layer 26 is equal to or greater than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 is good, and the electromagnetic wave shielding properties can be fully exhibited. In addition, the fluidity (ability to follow the shape of the through holes of the insulating film) of the isotropic conductive adhesive layer 26 can be ensured, the through holes of the insulating film can be sufficiently filled with the conductive adhesive, and adhesion can be ensured. If the thickness of the isotropic conductive adhesive layer 26 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film 1 can be made thin. In addition, the flexibility of the electromagnetic wave shielding film 1 is improved.

(Carrier film)
The carrier film 30 is a support that reinforces and protects the insulating resin layer 10 and the electromagnetic wave shielding layer 20, and improves the handleability of the electromagnetic wave shielding film 1. In particular, when a film having a thickness of 10 μm or less is used as the insulating resin layer 10, the presence of the carrier film 30 can prevent the insulating resin layer 10 from breaking.
After the electromagnetic wave shielding film 1 is attached to a printed wiring board or the like, the carrier film 30 is peeled off from the insulating resin layer 10 .

The carrier film 30 used in this embodiment has a carrier film body 32 and a release agent layer 34 provided on the surface of the carrier film body 32 facing the insulating resin layer 10.

The resin material of the carrier film body 32 may be polyethylene terephthalate (hereinafter sometimes referred to as "PET"), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, liquid crystal polymer, etc. As the resin material, PET is preferred from the standpoint of heat resistance (dimensional stability) and price when manufacturing the electromagnetic wave shielding film 1.

The carrier film body 32 may contain either or both of a colorant (pigment, dye, etc.) and a filler.
As either the colorant or the filler, or both, a color different from that of the insulating resin layer 10 is preferable, since it can be clearly distinguished from the insulating resin layer 10 and it is easy to notice any remaining part of the carrier film 30 after thermocompression bonding. A white pigment, a filler, a combination of a white pigment and another pigment, or a combination of a white pigment and a filler is more preferable.

The storage modulus of the carrier film main body 32 at 180°C is preferably ^8x107 Pa or more and ^5x109 Pa or less, and more preferably ^1x108 Pa or more and ^8x108 Pa or less. When the storage modulus of the carrier film main body 32 at 180°C is equal to or more than the lower limit of the above range, the carrier film 30 has an appropriate hardness, which can reduce pressure loss in the carrier film 30 during thermocompression bonding and prevent breakage of the electromagnetic wave shielding film 1. When the storage modulus of the carrier film main body 32 at 180°C is equal to or less than the upper limit of the above range, the flexibility of the carrier film 30 is good, and the ability of the electromagnetic wave shielding film 1 to conform to steps on a printed wiring board is improved.

The thickness of the carrier film body 32 is preferably 12 μm or more and 100 μm or less, and more preferably 20 μm or more and 75 μm or less. If the thickness of the carrier film body 32 is equal to or greater than the lower limit of the above range, the handling properties of the electromagnetic shielding film 1 are good. If the thickness of the carrier film body 32 is equal to or less 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 shielding film 1 is thermocompression bonded to the surface of the insulating film. In addition, the conformability of the electromagnetic shielding film 1 to steps on the printed wiring board is improved.

The release agent layer 34 is formed by treating the surface of the carrier film body 32 with a release agent. By having the release agent layer 34 on the carrier film 30, when the carrier film 30 is peeled off from the insulating resin layer 10, the carrier film 30 is easily peeled off and the insulating resin layer 10 is 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 0.01 μm or more and 30 μm or less, and more preferably 0.05 μm or more and 20 μm or less. If the thickness of the release agent layer 34 is within the above range, the carrier film 30 becomes even easier to peel off.

The thickness of the carrier film 30 is preferably 12 μm or more and 125 μm or less, and more preferably 25 μm or more and 100 μm or less. If the thickness of the carrier film 30 is equal to or greater than the lower limit of the above range, the handling properties of the electromagnetic shielding film 1 are good. If the thickness of the carrier film 30 is equal to or less 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 shielding film 1 is thermocompression bonded to the surface of the insulating film. In addition, the conformability of the electromagnetic shielding film 1 to steps on the printed wiring board is improved.

(Release film)
The release film 40 protects the conductive adhesive layer and is effective in preventing blocking and improving sliding properties when the electromagnetic shielding film 1 is wound into a roll or cut into sheets and stacked. The release film 40 is peeled off from the conductive adhesive layer before the electromagnetic shielding film 1 is attached to a printed wiring board or the like.

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

Examples of the resin material of the release film body 42 include the same resin material as that of the carrier film body 32 .
The release film body 42 may contain a colorant, a filler, and the like.
The thickness of the release film body 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and even more preferably 20 μm or more and 100 μm or less.

The release agent layer 44 is formed by treating the surface of the release film body 42 with a release agent. By having the release agent layer 44 on the release film 40, when the release film 40 is peeled off from the conductive adhesive layer, the release film 40 is easily peeled off and the conductive 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 0.01 μm or more and 30 μm or less, and more preferably 0.05 μm or more and 20 μm or less. If the thickness of the release agent layer 44 is within the above range, the release film 40 becomes even easier to peel off.

In the electromagnetic shielding film 1 described above, the conductive particles contained in the electromagnetic shielding layer are resin particles with a conductive film. The resin particles with a conductive film have a smaller specific gravity than metal particles and are less likely to settle in the conductive adhesive paint or in the flow path of the coating machine, so that the electromagnetic shielding layer can be stably formed even with a general-purpose coating method. In addition, the particle size distribution of the resin particles with a conductive film is easier to control than that of metal particles, and the particle size distribution can be made sharper. Therefore, the ratio of the resin particles with a conductive film with a small particle size that do not contribute to the connection and the resin particles with a conductive film with a larger particle size that acts like a spacer is low, and the temporary fixation and adhesion between the conductive adhesive layer of the electromagnetic shielding film and the surface of the printed wiring board are improved. As a result, when gas is generated inside during the solder flow process or reflow process, the conductive adhesive layer does not peel off and no swelling occurs. In addition, since the resin particles with a conductive film with a particle size that contributes to the connection increase, the electrical connection between the electromagnetic shielding film and the printed circuit of the printed wiring board is excellent even if the content of the resin particles with a conductive film is reduced.

Other Embodiments
The electromagnetic wave shielding film of this embodiment has an insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer, and the electromagnetic wave shielding layer may contain resin particles with a conductive film, and is not limited to the first and second embodiments shown in the figures.
For example, if the insulating resin layer 10 has sufficient flexibility and strength, the carrier film 30 may be omitted.
The electromagnetic wave shielding layer does not necessarily have to have a metal layer, and may be, for example, an electromagnetic wave shielding film made of an isotropic conductive adhesive layer adjacent to an insulating resin layer.
If the adhesive strength of the surface of the conductive adhesive layer is low, the release film 40 may be omitted.
The carrier film 30 does not need to have the release agent layer 34 if the carrier film body 32 has sufficient releasability or is a film having self-adhesive properties.
The carrier film 30 may have an adhesive layer instead of the release agent layer 34 .
The release film 40 does not need to have the release agent layer 44 if the release film body 42 has sufficient releasability or is a film having self-adhesive properties.
The release film 40 may have an adhesive layer instead of the release agent layer 44 .

<Method of manufacturing electromagnetic wave shielding film>
A second aspect of the present invention is a method for producing an electromagnetic wave shielding film having an insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer, the electromagnetic wave shielding layer having a metal layer adjacent to the insulating resin layer and a conductive adhesive layer adjacent to the metal layer on the opposite side to the insulating resin layer. In the second aspect of the present invention, a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film is applied onto the metal layer to form a conductive adhesive layer.

An example of a method for producing the electromagnetic wave shielding film 1 of the first embodiment is the following method (A1). The method (A1) is a method including the following steps (A1-1) to (A1-4).
Step (A1-1): A step of forming an insulating resin layer 10 on one surface of a carrier film 30.
Step (A1-2): A step of forming a metal layer 22 on the surface of the insulating resin layer 10 opposite to the carrier film 30.
Step (A1-3): A step of forming an anisotropic conductive adhesive layer 24 on the surface of the metal layer 22 opposite to the insulating resin layer 10.
Step (A1-4): A step of laminating a release film 40 on the surface of the anisotropic conductive adhesive layer 24 opposite to the metal layer 22.
Each step of the method (A1) will be described in detail below.

The method for forming the insulating resin layer 10 in the step (A1-1) may be, for example, the following method.
A method in which a coating material containing a thermosetting resin and a curing agent is applied to the surface of the carrier film 30 on the release agent layer 34 side, and then semi-cured or cured.
A method of applying paint containing a thermoplastic resin to the surface of the carrier film 30 on the release agent layer 34 side, and then drying the paint.
A method of directly laminating a film formed by extrusion molding a composition containing a thermoplastic resin onto the surface of the carrier film 30 on which the release agent layer 34 is formed.
Among these methods, from the standpoint of heat resistance during soldering, etc., a method in which a paint containing a thermosetting resin and a curing agent is applied to the surface of the carrier film 30 on the release agent layer 34 side and then semi-cured or cured is preferred.
Examples of a method for applying the coating material include methods using various coaters such as a die coater, a gravure coater, a roll coater, a curtain flow coater, a spin coater, a bar coater, a reverse coater, a kiss coater, a fountain coater, a rod coater, an air doctor coater, a knife coater, a blade coater, a cast coater, and a screen coater.
When semi-curing or curing the thermosetting resin, it is sufficient to heat it using a heater such as a heater or an infrared lamp, or it may be irradiated with ultraviolet rays using an ultraviolet irradiator.

Methods for forming the metal layer 22 in step (A1-2) include a method for forming a vapor-deposited film by physical vapor deposition or CVD (chemical vapor deposition), a method for forming a plated film by plating, and a method for attaching a metal foil. From the viewpoint of forming a metal layer 22 with excellent conductivity in the surface direction, a method for forming a vapor-deposited film by physical vapor deposition or CVD, or a method for forming a plated film by plating is preferred. From the viewpoints of being able to form a thin metal layer 22, being able to form a metal layer 22 with excellent conductivity in the surface direction even if it is thin, and being able to form the metal layer 22 simply by a dry process, a method for forming a vapor-deposited film by physical vapor deposition or CVD is more preferred, and a method for forming a vapor-deposited film by physical vapor deposition is even more preferred.

In step (A1-3), a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film is applied to the surface of the metal layer 22 opposite the insulating resin layer 10. The conductive adhesive paint may, for example, contain a thermosetting resin 24a, resin particles with a conductive film 24b, and a solvent.
Examples of solvents contained in the conductive adhesive paint include esters (butyl acetate, ethyl acetate, methyl acetate, isopropyl acetate, ethylene glycol monoacetate, etc.), ketones (methyl ethyl ketone, methyl isobutyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, etc.), alcohols (methanol, ethanol, isopropanol, butanol, propylene glycol monomethyl ether, propylene glycol, etc.), toluene, etc.
Examples of a method for applying the conductive adhesive coating material include methods using various coaters such as a die coater, gravure coater, roll coater, curtain flow coater, spin coater, bar coater, reverse coater, kiss coater, fountain coater, rod coater, air doctor coater, knife coater, blade coater, cast coater, and screen coater.
The anisotropic conductive adhesive layer 24 is formed by volatilizing the solvent from the applied conductive adhesive paint.

In the step (A1-4), the release film 40 is laminated on the surface of the anisotropic conductive adhesive layer 24 opposite the metal layer 22 such that the release agent layer 44 is in contact with the anisotropic conductive adhesive layer 24.
After laminating the release film 40 onto the anisotropic conductive adhesive layer 24, the laminate consisting of the carrier film 30, the insulating resin layer 10, the metal layer 22, the anisotropic conductive adhesive layer 24 and the release film 40 may be subjected to a pressure treatment to increase the adhesion between the layers.
Heating may be performed simultaneously with the pressure treatment.

The electromagnetic wave shielding film 1 of the first embodiment may be produced by the following method (A2). The method (A2) is a method including the following steps (A2-1) to (A2-4).
Step (A2-1): A step of forming an insulating resin layer 10 on one surface of a carrier film 30.
Step (A2-2): A step of forming a metal layer 22 on the surface of the insulating resin layer 10 opposite to the carrier film 30 to obtain a laminate I.
Step (A2-3): A step of forming an anisotropic conductive adhesive layer 24 on one surface of a release film 40 to obtain a laminate II.
Step (A2-4): A step of bonding the laminate I and the laminate II together so that the metal layer 22 of the laminate I and the anisotropic conductive adhesive layer 24 of the laminate II are in contact with each other.

Steps (A2-1) and (A2-2) are the same as steps (A1-1) and (A1-2) in the method (A1).

In step (A2-3), a conductive adhesive paint is applied to the surface of the release film 40 on which the release agent layer 44 is provided. The solvent is evaporated from the applied conductive adhesive paint to form the anisotropic conductive adhesive layer 24. The conductive adhesive paint and the application method are the same as those in step (A1-3) in the method (A1).

When laminating laminate I and laminate II in step (A2-4), a pressure treatment may be performed to increase the adhesion between laminate I and laminate II. The pressure conditions are the same as those in the pressure treatment in step (A1-4). Heating may also be performed in step (A2-4) as in step (A1-4).

An example of a method for producing the electromagnetic wave shielding film 1 of the second embodiment is the following method (B1).
The method (B1) is similar to the method (A1) except that an isotropic conductive adhesive layer 26 is formed instead of the anisotropic conductive adhesive layer 24.
The electromagnetic wave shielding film 1 of the second embodiment may be produced by a method (B2), which is the same as the method (A2) except that an isotropic conductive adhesive layer 26 is formed instead of the anisotropic conductive adhesive layer 24.

(Action and Effect)
In the method for producing the electromagnetic wave shielding film 1 described above, a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film is applied, and therefore the electromagnetic wave shielding film 1 can be produced easily by a general-purpose method with the same effect as in the first embodiment. In addition, an electromagnetic wave shielding film 1 that has excellent flexibility and adhesion and has excellent electrical connectivity with the printed circuit of a printed wiring board can be produced even if the content of the resin particles with a conductive film is reduced.

Other Embodiments
The manufacturing method of the electromagnetic wave shielding film of this embodiment is a method of forming a conductive adhesive layer by applying a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film, and is not limited to the above-mentioned methods (A1), (A2), (B1), and (B2) as long as the conductive particles are the above-mentioned resin particles with a conductive film.

<Printed wiring board with electromagnetic shielding film>
A third aspect of the present invention is a printed wiring board with an electromagnetic wave shielding film, comprising: a printed wiring board having a printed circuit provided on at least one side of a substrate; an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided; and an electromagnetic wave shielding film of the first aspect of the present invention adjacent to the side of the insulating film opposite the printed wiring board, with an electromagnetic wave shielding layer in contact with the insulating film.

FIG. 3 is a cross-sectional view showing one embodiment of a printed wiring board with an electromagnetic wave shielding film according to this aspect.
The printed wiring board 2 with an electromagnetic wave shielding film includes a flexible printed wiring board 50, an insulating film 60, and the electromagnetic wave shielding film 1 of the first embodiment.
The flexible printed wiring board 50 has a printed circuit 54 provided on at least one surface of a base film 52 .
The insulating film 60 is provided on the surface of the flexible printed wiring board 50 on which 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. In addition, the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through a through hole (not shown) formed in the insulating film 60.
In the printed wiring board 2 with the electromagnetic wave shielding film, the carrier film and the release film have been peeled off from the electromagnetic wave shielding film 1 .

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) except for the part with the through hole, the metal layer 22 of the electromagnetic shielding film 1 is arranged opposite and spaced apart via the insulating film 60 and the anisotropic conductive adhesive layer 24.

(Flexible Printed Circuit Board)
The flexible printed wiring board 50 is formed by processing the copper foil of a copper-clad laminate into a desired pattern by a known etching method to form a printed circuit 54 .
Examples of copper-clad laminates include those in which copper foil is attached to one or both sides of a base film 52 via an adhesive layer (not shown); and those in which a resin solution or the like that forms a base film 52 is cast onto the surface of the copper foil.
Examples of materials for the adhesive layer include epoxy resins, polyesters, polyimides, polyamideimides, polyamides, phenolic resins, urethane resins, acrylic resins, and melamine resins.
The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

The base film 52 is preferably a heat-resistant film, and more preferably a polyimide film, a polyetherimide film, a polyphenylene sulfide film, an aromatic polyether ketone film, or a liquid crystal polymer film.
From the viewpoint of electrical insulation, the surface resistance of the base film 52 is preferably 1×10 ⁶ Ω/□ or more, and from the viewpoint of practical use, the surface resistance of the base film 52 is preferably 1×10 ¹⁹ Ω/□ or less.
The thickness of the base film 52 is preferably 5 μm or more and 200 μm or less, and from the viewpoint of flexibility, is more preferably 6 μm or more and 50 μm or less, and even more preferably 10 μm or more and 25 μm or less.

Examples of the copper foil constituting the printed circuit 54 include rolled copper foil and electrolytic copper foil, and from the viewpoint of flexibility, rolled copper foil is preferred. The printed circuit 54 is used as a signal circuit, a ground circuit, a ground layer, etc.
The thickness of the copper foil is preferably 1 μm or more and 50 μm or less.
The ends (terminals) of the printed circuit 54 in the longitudinal direction are exposed and not covered by the insulating film 60 or the electromagnetic shielding film 1 for soldering, connector connection, component mounting, and the like.

(Insulating film)
The insulating film 60 (coverlay film) is an insulating film body (not shown) having an adhesive layer (not shown) formed on one side thereof 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, and is preferably 1×10 ¹⁹ Ω/□ or less from the viewpoint of practical use.
The insulating film body is preferably a heat-resistant film, such as a polyimide film, a polyetherimide film, a polyphenylene sulfide film, an aromatic polyether ketone film, or a liquid crystal polymer film.
The thickness of the insulating film body is preferably 1 μm or more and 100 μm or less from the viewpoint of flexibility.
Examples of materials for the adhesive layer include epoxy resins, polyesters, polyimides, polyamideimides, polyamides, phenolic resins, urethane resins, acrylic resins, melamine resins, polystyrene, polyolefins, etc. The epoxy resins may contain a rubber component (nitrile rubber, acrylic rubber, etc.) for imparting flexibility.
The thickness of the adhesive layer is preferably from 1 μm to 100 μm, and more preferably from 1.5 μm to 60 μm.

The shape of the opening of the through hole formed in the insulating film 60 is not particularly limited. Examples of the shape of the opening of the through hole include a circle, an ellipse, a rectangle, etc.

(Action and Effect)
In the printed wiring board 2 with electromagnetic wave shielding film described above, the conductive particles contained in the electromagnetic wave shielding layer of the electromagnetic wave shielding film are resin particles with a conductive film, and therefore have the same effect as the first aspect, resulting in excellent adhesion and electrical connectivity with the printed circuit of the printed wiring board.

Other Embodiments
The printed wiring board with electromagnetic wave shielding film of this embodiment need only have a printed wiring board having a printed circuit on at least one side of a substrate, an insulating film adjacent to the side of the printed wiring board on which the printed circuit is provided, and an electromagnetic wave shielding film of the first embodiment of the present invention adjacent to the side of the insulating film opposite the printed wiring board, with a conductive adhesive layer in contact with the insulating film, and is not limited to the embodiment shown in the figures.
For example, the flexible printed wiring board 50 may have a ground layer on the back surface side. The flexible printed wiring board 50 may have printed circuits 54 on both sides, and the insulating film 60 and the electromagnetic wave shielding film 1 may be attached to both sides.
Instead of the flexible printed wiring board 50, a rigid printed circuit board that has no flexibility may be used.
The electromagnetic wave shielding film 1 of the second embodiment may be used in place of the electromagnetic wave shielding film 1 of the first embodiment.

<Method of manufacturing a printed wiring board with an electromagnetic wave shielding film>
A fourth aspect of the present invention is a method for producing a printed wiring board with an electromagnetic wave shielding film, comprising overlapping a printed wiring board having a printed circuit provided on at least one side of a substrate and an insulating film adjacent to the side of the printed wiring board on which the printed circuit is provided, and an electromagnetic wave shielding film of the first aspect of the present invention, and thermocompression bonding the insulating film and the electromagnetic wave shielding layer in contact with each other.

The printed wiring board 2 with an electromagnetic wave shielding film can be produced, for example, by a method including the following steps (a) to (e) (see FIG. 4).
Step (a): A step of providing an insulating film 60 having a through hole 62 formed at a position corresponding to the printed circuit 54 on the surface of the flexible printed wiring board 50 on which the printed circuit 54 is provided, thereby obtaining a printed wiring board 3 with an insulating film.
Step (b): After step (a), the printed wiring board 3 with the insulating film and the electromagnetic wave shielding film 1 from which the release film 40 has been peeled off are overlapped so that the anisotropic conductive adhesive layer 24 is in contact with the surface of the insulating film 60, and then temporarily fixed together.
Step (c): After step (b), a step of thermocompression bonding the temporarily fixed printed wiring board 3 with the insulating film and the electromagnetic wave shielding film 1 from which the release film 40 has been peeled off.
Step (d): After step (c), a step of peeling off the carrier film 30 when the carrier film 30 is no longer needed.
Step (e): If necessary, a step of fully curing the anisotropic conductive adhesive layer 24 after step (d).
Each step will be described in detail below with reference to FIG.

Step (a):
Step (a) is a step of laminating an insulating film 60 on a flexible printed wiring board 50 to obtain a printed wiring board 3 with an insulating film.
Specifically, first, an insulating film 60 having through holes 62 formed in positions corresponding to the printed circuits 54 is laid on the flexible printed wiring board 50. Next, an adhesive layer (not shown) of the insulating film 60 is adhered to the surface of the flexible printed wiring board 50, and the adhesive layer is cured to obtain the printed wiring board 3 with the insulating film. 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 fully cured in step (d).
The adhesive layer is bonded and cured by, for example, thermocompression bonding using a press (not shown) or the like.

Step (b):
Step (b) is a step of thermocompression bonding the electromagnetic wave shielding film 1 to the printed wiring board 3 with the insulating film under mild conditions.
Specifically, the electromagnetic wave shielding film 1 from which the release film 40 has been peeled off is placed on the printed wiring board 3 with the insulating film, and they are thermocompression bonded under mild conditions. This makes it possible to temporarily fix the position of the electromagnetic wave shielding film 1 relative to the printed wiring board 3 with the insulating film. Step (b) eliminates the need for alignment near the high-temperature press used in step (c), and thus makes it possible to omit dangerous work.

The electromagnetic wave shielding film 1 is temporarily fixed by, for example, thermocompression bonding using a press (not shown) or the like.
The pressing time for thermocompression bonding is preferably 5 seconds to 2 minutes, more preferably 5 seconds to 30 seconds. If the thermocompression bonding time is equal to or more than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be easily adhered to the surface of the insulating film 60. If the thermocompression bonding time is equal to or less than the upper limit of the above range, the manufacturing time for the printed wiring board 2 with the electromagnetic shielding film can be shortened.

The thermocompression pressing temperature (the temperature of the hot platen of the press) is preferably 50°C or higher and 150°C or lower, and more preferably 60°C or higher and 80°C or lower. If the thermocompression temperature is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be easily adhered to the surface of the insulating film 60. In addition, the thermocompression bonding time can be shortened. If the thermocompression bonding temperature is equal to or lower than the upper limit of the above range, the danger of the work can be reduced.

The pressure for thermocompression bonding is preferably 0.01 MPa or more and 1 MPa or less. If the pressure for thermocompression bonding is equal to or more than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60. In addition, the time for thermocompression bonding can be shortened. If the pressure for thermocompression bonding is equal to or less than the upper limit of the above range, the risk of the work can be reduced.

Step (c):
Step (c) is a step of thermocompression bonding the electromagnetic wave shielding film 1 to the printed wiring board 3 with the insulating film.
Specifically, the temporarily fixed printed wiring board 3 with the insulating film and the electromagnetic wave shielding film 1 are thermocompression bonded together, whereby the anisotropic conductive adhesive layer 24 is bonded to the surface of the insulating film 60, and the anisotropic conductive adhesive layer 24 is pressed into the through hole 62, filling the through hole 62 and electrically connecting to the printed circuit 54. In this way, a printed wiring board 2 with an electromagnetic wave shielding film is obtained.

The anisotropic conductive adhesive layer 24 is adhered and cured by, for example, thermocompression bonding using a press (not shown) or the like.
The pressing time for thermocompression bonding is preferably 20 seconds to 60 minutes, more preferably 30 seconds to 30 minutes. If the thermocompression bonding time is equal to or more than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be easily bonded to the surface of the insulating film 60. If the thermocompression bonding time is equal to or less than the upper limit of the above range, the manufacturing time of the printed wiring board 2 with the electromagnetic shielding film can be shortened.

The thermocompression pressing temperature (temperature of the hot platen of the press) is preferably 140°C or higher and 200°C or lower, and more preferably 170°C or higher and 190°C or lower. If the thermocompression temperature is equal to or higher than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be easily bonded to the surface of the insulating film 60. In addition, the thermocompression time can be shortened. If the thermocompression temperature is equal to or lower than the upper limit of the above range, deterioration of the electromagnetic wave shielding film 1, the flexible printed wiring board 50, etc. can be easily suppressed.

The pressure for thermocompression bonding is preferably 0.5 MPa or more and 20 MPa or less, and more preferably 1 MPa or more and 16 MPa or less. If the pressure for thermocompression bonding is equal to or more than the lower limit of the above range, the anisotropic conductive adhesive layer 24 is adhered to the surface of the insulating film 60. In addition, the time for thermocompression bonding can be shortened. If the pressure for thermocompression bonding is equal to or less 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 (d):
Step (d) is a step of peeling off the carrier film 30 .
Specifically, when the carrier film is no longer needed, the carrier film 30 is peeled off from the insulating resin layer 10 .

Step (e):
Step (e) is a step of fully curing the anisotropic conductive adhesive layer 24 .
When the time for the thermocompression bonding in step (c) is a short time of 20 seconds or more and 10 minutes or less, it is preferable to carry out main curing of the anisotropic conductive adhesive layer 24 between steps (c) and (d) or after step (d).
The anisotropic conductive adhesive layer 24 is fully cured by using a heating device such as an oven.
The heating time is from 15 minutes to 120 minutes, and more preferably from 30 minutes to 60 minutes. When the heating time is equal to or more than the lower limit of the above range, the anisotropic conductive adhesive layer 24 can be sufficiently cured. When the heating time is equal to or less than the upper limit of the above range, the manufacturing time of the printed wiring board 2 with the electromagnetic shielding film can be shortened.
The heating temperature (ambient temperature in the oven) is preferably 120° C. or higher and 180° C. or lower, and more preferably 120° C. or higher and 160° 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 equal to or lower 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.

(Action and Effect)
In the manufacturing method of the printed wiring board 2 with the electromagnetic wave shielding film described above, the conductive particles contained in the electromagnetic wave shielding layer of the electromagnetic wave shielding film are resin particles with a conductive film, and therefore, due to the same action effect as in the first aspect, it is possible to manufacture a printed wiring board 2 with an electromagnetic wave shielding film that has good adhesion and excellent electrical connectivity with the printed circuit of the printed wiring board.

Other Embodiments
The method for producing a printed wiring board with an electromagnetic wave shielding film of this embodiment may be a method in which a printed wiring board with an insulating film and an electromagnetic wave shielding film of the first embodiment of the present invention (however, if there is a release film adjacent to the electromagnetic wave shielding layer, the release film is peeled off) are superimposed and thermocompressed so that the insulating film and the electromagnetic wave shielding layer are in contact with each other, and is not limited to the above-mentioned embodiment.
If precise alignment is not required, step (b) may be omitted.
In the step (c), if the thermocompression bonding time is long enough to harden the anisotropic conductive adhesive layer 24, the step (e) can be omitted.

The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

(Specific gravity of conductive particles and resin particles)
The specific gravity of the conductive particles and the resin particles was measured at a temperature of 23° C. in accordance with Method A of JIS K7112:1999.

(Average particle size and coefficient of variation of conductive particles)
The average particle diameter of the conductive particles was determined by randomly selecting 30 particles from a microscopic image of the particles, measuring the minimum and maximum diameters of each particle, determining the median of the minimum and maximum diameters as the particle diameter of one particle, and taking the arithmetic mean of the measured particle diameters of the 30 particles.
The coefficient of variation (CV) of the conductive particles was calculated from the above formula by randomly selecting 30 particles from a microscopic image of the particles, determining the standard deviation σ and average particle diameter D for the particle diameters of the 30 particles.

(Thickness of metal layer, conductive adhesive layer)
The thickness of the metal layer was determined by measuring the thickness at five randomly selected locations using an eddy current thickness gauge and averaging the results.
The thickness of the conductive adhesive layer was determined by measuring the thickness at five randomly selected locations using a digital length measuring machine (Mitutoyo Corporation, Litematic VL-50-B) and averaging the results.

(Conductive particle dispersibility)
In each example, after preparing a conductive adhesive paint for forming a conductive adhesive layer, it was left to stand at 25°C for 1 hour, and the dispersibility of the resin particles with conductive film (conductive particles) in the conductive adhesive paint was visually confirmed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
⊚: The conductive particles do not settle or hardly settle at all.
◯: The conductive particles settle but can be redispersed by stirring.
×: The conductive particles settle and do not redisperse even when stirred.

(Temporary fixation)
The electromagnetic wave shielding film of each example and a 50 μm thick polyimide film were stacked with the conductive adhesive layer and the polyimide film facing each other, and were thermally compressed using a hot press device at a press temperature of 65° C., a press pressure of 0.1 MPa, and a press time of 10 seconds to temporarily fix the anisotropic conductive adhesive layer to the surface of the insulating film. The degree of adhesion between the electromagnetic wave shielding film and the 50 μm thick polyimide film was visually confirmed and evaluated according to the following evaluation criteria.
<Evaluation criteria>
⊚: The entire surface is adhered.
Good: There are some areas that are not adhered, but the film does not peel off.
△: Partially adhered, but easily peeled off.
×: Not adhered.

(Reflow heat resistance)
The electromagnetic wave shielding film of each example and a 50 μm thick polyimide film were stacked with the conductive adhesive layer and the polyimide film facing each other, and were thermocompression-bonded using a hot press device at a press temperature of 180° C., a press pressure of 5 MPa, and a press time of 120 seconds. After peeling off the carrier film, the flexible printed wiring board with the electromagnetic wave shielding film thermocompression-bonded was heated at a temperature of 150° C. for 1 hour using a high-temperature incubator to fully cure the anisotropic conductive adhesive layer, thereby obtaining a test specimen.
Next, according to the reflow temperature profile of the solder heat resistance test when using a lead-free solder alloy in JIS C60068-2-58:2006, the test specimen was passed through a reflow furnace set so as to pass the soldering conditions of preheating at 150° C. to 180° C. for 120 seconds, residence time at 220° C. for 60 seconds, and a maximum temperature of 250° C. This operation was repeated three times, and the insulating resin layer was visually observed and evaluated according to the following criteria.
<Evaluation criteria>
◯: No swelling occurred.
×: Blisters are observed.

(Solder flow heat resistance)
A test specimen was prepared in the same manner as in the reflow heat resistance test. The test specimen was floated in a solder bath at 288°C so that the solder was in contact with the insulating resin layer, and was then pulled out after 10 seconds. This operation was repeated three times, and the insulating resin layer was visually observed and evaluated according to the following criteria.
<Evaluation criteria>
◯: No swelling occurred.
×: Blisters are observed.

(Minimum connection diameter)
A flexible printed wiring board 100 with an insulating film for connectivity evaluation (hereinafter, referred to as "evaluation wiring board 100") shown in Figures 5(A) to 5(C) was prepared. The evaluation wiring board 100 is formed by laminating a base film (polyimide film) 152 having a thickness of 25 μm, a printed circuit 154 formed by etching a copper foil having a thickness of 12.5 μm, an adhesive layer 156 having a thickness of 25 μm, and an insulating film (polyimide film) 160 having a thickness of 12.5 μm in this order. In the evaluation wiring board 100, two rectangular printed circuits 154 of 20 mm x 3 mm are placed in parallel with an interval of 3 mm. In the insulating film 160 and the adhesive layer 156, one connection test through hole 162 and one resistance measurement through hole 164 having a diameter of 2 mm are formed at positions corresponding to both ends of each printed circuit 154. The distance between the centers of the connection test through holes 162 and the resistance measurement through holes 164 was 15 mm, the distance between the centers of the connection test through holes 162 was 6 mm, and the distance between the centers of the resistance measurement through holes 164 was 6 mm. In addition, the positions of the printed circuit 154 corresponding to the connection test through holes 162 and the resistance measurement through holes 164 were surface treated with a nickel layer having a thickness of 0.5 μm and a gold layer having a thickness of 0.05 μm.
Ten evaluation wiring boards 100 were prepared with connection test through holes 162 having diameters ranging from 0.1 mm to 1.0 mm in increments of 0.1 mm.

As shown in Fig. 6(A) and Fig. 6(B), the electromagnetic wave shielding film (shielding film 201) of each example and each evaluation wiring board 100 were stacked with the conductive adhesive layer (conductive adhesive layer 224) and the insulating film 160 facing each other so that the connection test through hole 162 was covered and the resistance measurement through hole 164 was not covered, and they were thermocompressed using a hot press device at a press temperature of 180°C, a press pressure of 5 MPa, and a press time of 120 seconds. After peeling off the carrier film, the evaluation wiring board 100 to which the shielding film 201 was thermocompressed was heated at a temperature of 150°C for 1 hour using a high-temperature incubator to fully cure the conductive adhesive layer 224 on the insulating resin layer (insulating resin layer 210), thereby obtaining a flexible printed wiring board (test specimen) with an electromagnetic wave shielding film.
A tester was placed against the resistance measurement through hole 164 of each test specimen to measure the resistance value of wiring-electromagnetic wave shielding layer-wiring, and among the test specimens with a resistance value of 1 Ω or less, the one with the smallest diameter of the connection test through hole 162 was determined as the minimum connection diameter.

Example 1
A coating material for forming an insulating resin layer was prepared by dissolving 100 parts by mass of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, jER (registered trademark) 1001), 2 parts by mass of 2-methyl-4-ethylimidazole, and 4 parts by mass of carbon black in 300 parts by mass of a solvent (methyl ethyl ketone).
As a carrier film, a PET film (manufactured by Toyobo Co., Ltd., CN200, thickness: 50 μm) was prepared.
A thermosetting conductive adhesive coating material was prepared by dissolving or dispersing, by stirring, 85 parts by mass of a thermosetting adhesive (a mixture of 100 parts by mass of a urethane resin (Byron UR-3500, manufactured by Toyobo Co., Ltd.) and 5.3 parts by mass of a curing agent (jER 1031S, manufactured by Mitsubishi Chemical Corporation)) and 15 parts by mass of the conductive particles (resin particles with conductive film) shown in Table 1 in 100 parts by mass of a solvent (a mixture of 100 parts by mass of methyl ethyl ketone and 100 parts by mass of toluene).

The coating material for forming an insulating resin layer was applied to the surface of the release agent layer of the carrier film, heated at 100°C for 2 minutes to dry the coating material, and then heated at 120°C for 48 hours in a high-temperature incubator to fully harden the coating material, thereby forming an insulating resin layer (thickness: 10 μm).
Copper was physically deposited on the surface of the insulating resin layer by electron beam deposition to form a metal layer (deposited film, thickness: 0.5 μm).
A thermosetting conductive adhesive paint was applied to the surface of the metal layer using a die coater, and the solvent was volatilized to bring it to a B-stage, thereby forming an anisotropic conductive adhesive layer (thickness: 4 μm) and obtaining an electromagnetic wave shielding film.
The evaluation results of the conductive particle dispersibility and the minimum connection diameter are shown in Table 1.

(Examples 2 to 23)
An electromagnetic wave shielding film was produced in the same manner as in Example 1, except that the type and content of the conductive particles used and the thickness of the conductive adhesive layer were changed as shown in Table 1, and the adhesion and the minimum connection diameter were evaluated. The results are shown in Table 1.

(Comparative Examples 1 to 3)
An electromagnetic wave shielding film was produced in the same manner as in Example 1, except that copper particles were used as the conductive particles and the content of the conductive particles and the thickness of the conductive adhesive layer were changed as shown in Table 1, and the adhesion and the minimum connection diameter were evaluated. The results are shown in Table 1.

In Table 1, "mass ratio C/S" refers to the mass ratio of the core to the shell in the conductive particles. "PMMA" refers to polymethyl methacrylate.

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

1. Electromagnetic wave shielding film,
2. Printed wiring board with electromagnetic wave shielding film,
3. Printed wiring board with insulating film,
10 insulating resin layer,
22 metal layer,
20 electromagnetic wave shielding layer,
24 anisotropic conductive adhesive layer,
24a thermosetting resin,
24b Resin particles with conductive film,
26 isotropic conductive adhesive layer,
26a thermosetting resin,
26b Resin particles with conductive film,
30 carrier film,
32 carrier film body,
34 release agent layer,
40 Release film,
42 release film body,
44 release agent layer,
50 Flexible printed wiring board,
52 base film,
54 printed circuits,
60 insulating film,
62 through hole.

Claims (15)

An insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer,
the electromagnetic wave shielding layer includes resin particles having a conductive film formed directly on the surface of the resin particles to coat the resin particles,
the electromagnetic wave shielding layer has a metal layer adjacent to the insulating resin layer and an isotropic conductive adhesive layer adjacent to the metal layer on the opposite side to the insulating resin layer,
the isotropically conductive adhesive layer contains the conductive film-attached resin particles,
the average particle size of the resin particles with a conductive film is 0.5 μm or more and 10 μm or less,
The electro-magnetic wave shielding film, wherein the coefficient of variation in particle size distribution of the resin particles with the conductive film is 0.5% or more and 27% or less. An insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer,
the electromagnetic wave shielding layer includes resin particles having a conductive film formed directly on the surface of the resin particles to coat the resin particles,
the electromagnetic wave shielding layer has a metal layer adjacent to the insulating resin layer and an anisotropic conductive adhesive layer adjacent to the metal layer on the opposite side to the insulating resin layer,
the anisotropic conductive adhesive layer contains the conductive film-attached resin particles,
The average particle size of the resin particles with a conductive film is 1 μm or more and 20 μm or less,
The electro-magnetic wave shielding film, wherein the coefficient of variation in particle size distribution of the resin particles with the conductive film is 0.5% or more and 27% or less. 3. The electromagnetic shielding film according to claim 1 , wherein a ratio of a mass of the conductive film to a total mass of the resin particles with the conductive film is 5 mass % or more and 50 mass % or less. The electromagnetic wave shielding film according to claim 1 , wherein the specific gravity of the resin particles with the conductive film is 1.00 or more and 3.00 or less. 5. The electromagnetic wave shielding film according to claim 1 , wherein the resin particles have a specific gravity of 0.90 or more and 3.00 or less. 6. The electromagnetic wave shielding film according to claim 1 , wherein the resin particles contain at least one resin selected from the group consisting of an acrylic resin, a urethane resin, a nylon resin, and a silicone resin. The electromagnetic wave shielding film according to any one of claims 1 to 6 , wherein the specific gravity of the conductive film is 2.50 or more and 22.0 or less. The electromagnetic wave shielding film according to any one of claims 1 to 7 , wherein the conductive film contains at least one metal selected from the group consisting of gold, silver, and copper. The electromagnetic wave shielding film according to claim 1 , wherein the conductive film contains two or more different metals. The electromagnetic wave shielding film according to claim 1 , wherein the conductive film comprises a sputtered film. The electromagnetic shielding film according to claim 1 , wherein the conductive film comprises a plating film. An insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer,
a method for producing an electromagnetic wave shielding film, the electromagnetic wave shielding layer having a metal layer adjacent to the insulating resin layer and an isotropic conductive adhesive layer adjacent to the metal layer on a side opposite to the insulating resin layer,
a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film formed directly on the surface of the resin particles to cover the resin particles is applied onto the metal layer to form the isotropic conductive adhesive layer;
the average particle size of the resin particles with a conductive film is 0.5 μm or more and 10 μm or less,
The electroconductively coated resin particles have a particle size distribution coefficient of variation of 0.5% or more and 27% or less. An insulating resin layer and an electromagnetic wave shielding layer adjacent to the insulating resin layer,
a method for producing an electromagnetic wave shielding film, the electromagnetic wave shielding layer having a metal layer adjacent to the insulating resin layer and an anisotropic conductive adhesive layer adjacent to the metal layer on a side opposite to the insulating resin layer,
a conductive adhesive paint containing a thermosetting resin or a thermoplastic resin and resin particles with a conductive film formed directly on the surface of the resin particles to cover the resin particles is applied onto the metal layer to form the anisotropic conductive adhesive layer;
The average particle size of the resin particles with a conductive film is 1 μm or more and 20 μm or less,
The electroconductively coated resin particles have a particle size distribution coefficient of variation of 0.5% or more and 27% or less. A printed wiring board having a printed circuit provided on at least one surface of a substrate;
an insulating film adjacent to a surface of the printed wiring board on which the printed circuit is provided;
The electromagnetic wave shielding film according to any one of claims 1 to 11 , which is adjacent to the insulating film on a side opposite to the printed wiring board, and the electromagnetic wave shielding layer is in contact with the insulating film;
A printed wiring board with an electromagnetic wave shielding film. a printed wiring board having a printed circuit provided on at least one surface of a substrate and an insulating film provided with an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided;
The electromagnetic wave shielding film according to any one of claims 1 to 11 ,
The insulating film and the electromagnetic wave shielding layer are overlapped so as to be in contact with each other, and then thermocompression bonded to each other.

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