TWI823254B - Electromagnetic wave shielding film and printed circuit board with electromagnetic wave shielding film - Google Patents

Abstract

The present invention provides a high-generality and practical electromagnetic wave shielding film which still performs good adaptation and maintains low connecting resistance value under hot-humid climate. The electromagnetic wave shielding film is made up of successively stacking insulating resin layer, shielding film and electrically conductive adhesive. The said electrically conductive adhesive is made from the combination of electrically conductive adhesive which contains adhesive ingredient and conducting particles. The water absorption rate of the said adhesive ingredient is lower than 2.0%. The said adhesive ingredient contains thermosetting resin. The said thermosetting resin contains the epoxy resins which has the structural formula as the general formula (1) shown below and performs 170~400g/eq epoxy equivalent.

(In the formula (1) above, R₁ represents Hydrocarbyl with l to 35 carbon atoms; R₂ represents Hydrogen or Methyl group; n represents integers 1 to 10.)

Description

Electromagnetic wave shielding film and printed circuit board with electromagnetic wave shielding film

The invention relates to an electromagnetic wave shielding film and a printed circuit board with an electromagnetic wave shielding film.

In order to shield (shield) electromagnetic wave noise generated from a flexible printed circuit board (hereinafter also referred to as FPC) and electromagnetic wave noise from the outside, it is known to have an insulating resin layer and a metal film layer (hereinafter also referred to as a shielding layer or electromagnetic wave shielding layer). ) and an electromagnetic wave shielding film of a conductive adhesive layer are bonded to a flexible printed circuit board via an insulating film (hereinafter also referred to as a cover film).

In this method, the conductive adhesive layer of the electromagnetic wave shielding film of the printed circuit board and the ground circuit of the printed circuit board are connected through the opening provided in the insulating film covering the ground circuit and are shielded.

As the conductive adhesive composition constituting the conductive adhesive layer of the electromagnetic wave shielding film, various conductive adhesive compositions are known (see, for example, Patent Documents 1 and 2).

Prior technical documents patent documents

Patent Document 1: JP Unexamined Publication No. 2019-196458

Patent Document 2: JP Patent No. 5854248

In view of this, our inventors devoted themselves to further research, and began to carry out research and development and improvement, hoping to solve the above problems with a better invention, and after continuous testing and modification, the present invention came out.

In addition, for electromagnetic wave shielding films, in addition to the bending resistance and heat resistance required for the entire flexible printed circuit board, durability that can maintain high adhesion and low connection resistance in a high temperature and high humidity environment is also required.

However, when the electromagnetic wave shielding film is placed in a high temperature and high humidity environment, the adhesive layer deteriorates over time and the adhesion is reduced, and the metal conductive particles and the shielding layer are oxidized. The problem is that the connection resistance value cannot be maintained low after being exposed to the environment.

The above-mentioned Patent Document 1 describes improving the adhesion in a high-temperature and high-humidity environment by using a specific proportion of the adhesive composition, but does not specifically mention the connection resistance value when placed in a high-temperature and high-humidity environment. There is room for improvement from the viewpoint of providing an electromagnetic wave shielding film that can exhibit good adhesion and maintain a low connection resistance value even after being left in a high-temperature and high-humidity environment.

In addition, the above-mentioned Patent Document 2 describes that by using surface-coated conductive fine particles, it is possible to provide a conductive adhesive having high connection reliability even after moist heat treatment over time. However, in the above-mentioned Patent Document 2, In the technology, there are problems that the selection of conductive fine particles becomes complicated, the manufacturing cost also increases, and the versatility is lacking.

Therefore, the purpose of the present invention is to provide a highly versatile and practical electromagnetic wave shielding film that can exhibit good adhesion and maintain low connection resistance even after being placed in a high temperature and high humidity environment.

As a result of intensive research conducted by the inventors of the present invention in order to solve the above-mentioned problems, they found that it is possible to provide an adhesive component that exhibits a specific water absorption rate as a conductive adhesive layer used in a conductive adhesive layer constituting an electromagnetic wave shielding film. The present invention has been completed by forming an electromagnetic wave shielding film that can solve the above-mentioned problems by forming a thermosetting resin containing a specific epoxy resin as a component of the adhesive composition.

The present invention includes the following aspects.

[1] An electromagnetic wave shielding film, which is composed of an insulating resin layer, a shielding layer, and a conductive adhesive layer sequentially laminated. The conductive adhesive layer is made of conductive resin containing an adhesive component and conductive particles. It is formed from an adhesive composition, the water absorption rate of the adhesive component is less than 2.0%, the adhesive component contains a thermosetting resin, and the thermosetting resin contains a formula represented by the following formula (1) An epoxy resin with a structural formula and an epoxy equivalent weight of 170~400g/eq.

(In the above [Formula (1)], R ₁ represents a hydrocarbon group having 1 to 35 carbon atoms, R ₂ represents hydrogen or a methyl group, and n represents an integer of 1 to 10.)

[2] Based on the electromagnetic wave shielding film described in [1], the adhesive component contains 30 to 70 mass % of the epoxy resin.

[3] Based on the electromagnetic wave shielding film described in [1] or [2], the epoxy equivalent is 215 to 400 g/eq.

[4] The electromagnetic wave shielding film according to any one of [1] to [3], wherein R ₁ in the general formula (1) is a structure containing an alicyclic hydrocarbon or an aromatic hydrocarbon. hydrocarbyl.

[5] Based on the electromagnetic wave shielding film described in [3] or [4], the epoxy equivalent is 250~400g/eq.

[6] The electromagnetic wave shielding film according to any one of [1] to [5], wherein the adhesive component contains a rubber component.

[7] The electromagnetic wave shielding film according to [6], wherein the acid value of the rubber component is 20 mgKOH/g or less.

[8] The electromagnetic wave shielding film according to [6] or [7], wherein the epoxy equivalent of the rubber component is 0.05 eq/kg or more.

[9] In the electromagnetic wave shielding film according to any one of [6] to [8], the glass transition temperature of the rubber component is 10°C or higher.

[10] A printed circuit board with an electromagnetic wave shielding film, comprising: a printed circuit board provided with a printed circuit on at least one side of the substrate; and an insulating film connected to the side of the printed circuit board provided with the printed circuit The surfaces are adjacent; and the electromagnetic wave shielding film according to any one of [1] to [9], which is arranged such that the conductive adhesive layer is adjacent to the insulating film.

According to the present invention, a practical electromagnetic wave shielding film with high versatility can be provided, which can exhibit good adhesion and maintain a low connection resistance value even after being placed in a high temperature and high humidity environment.

[Invention]

1: Electromagnetic wave shielding film

10: Insulating resin layer

2: Flexible printed circuit board with electromagnetic wave shielding film

20:Shielding layer

22: Conductive adhesive layer

24: Anisotropic conductive adhesive layer

24a: Adhesive

24b: Conductive particles

26: Isotropic conductive adhesive layer

26a: Adhesive

26b: Conductive particles

3: Flexible printed circuit board with insulating film

30: First release film

32:Substrate layer

34: Adhesive layer/release agent layer

40: Second release film

42:Substrate layer

44: Release agent layer/adhesive layer

50:Flexible printed circuit board

52:Basilar membrane

54: Print circuit

60:Insulating film

62:Through hole

[Fig. 1] is a cross-sectional view showing one embodiment of the electromagnetic wave shielding film; [Fig. 2] is a cross-sectional view showing another embodiment of the electromagnetic wave shielding film; [Fig. 3] shows the manufacturing process of the electromagnetic wave shielding film of Fig. 1 A cross-sectional view of the manufacturing process of steps (A1-1) to (A1-4) according to one embodiment; [Fig. 4] shows the step (A2-) as another embodiment of the manufacturing process of the electromagnetic wave shielding film of Fig. 1 1) A cross-sectional view of the manufacturing process of (A2-2); [FIG. 5] is a cross-sectional view showing the manufacturing process of step (A2-3) as another embodiment of the manufacturing process of the electromagnetic wave shielding film of FIG. 1; [FIG. Fig. 6] is a cross-sectional view showing the manufacturing process of step (A2-4) as another embodiment of the manufacturing process of the electromagnetic wave shielding film of Fig. 1; [Fig. 7] is a diagram showing a printed circuit board with an electromagnetic wave shielding film. Cross-sectional view of embodiment; [Fig. 8] is a cross-sectional view showing the manufacturing process of the printed circuit board with electromagnetic wave shielding film of Fig. 7.

Regarding the technical means of our inventors, several preferred embodiments are described in detail below along with the drawings, so as to provide readers with a thorough understanding and recognition of the present invention.

Hereinafter, the electromagnetic wave shielding film of the present invention will be described in detail. However, the description of the constituent elements described below is an example of one embodiment of the present invention and is not limited to these contents.

The following definitions of terms apply in this specification and the scope of the patent application.

The "isotropic conductive adhesive layer" refers to a conductive adhesive layer having conductivity in the thickness direction and the surface direction.

The "anisotropic conductive adhesive layer" refers to a conductive adhesive layer that is conductive in the thickness direction but does not have conductivity in the surface direction.

"A conductive adhesive layer that is not conductive in the surface direction" refers to a conductive adhesive layer with a surface resistance of 1×10 ⁴ Ω or more.

The average particle diameter of the conductive particles is a value obtained by randomly selecting 30 conductive particles from a microscope image of the conductive particles, measuring the minimum diameter and the maximum diameter of each conductive particle, and dividing the minimum diameter and the maximum diameter. The median value is the particle diameter of one particle and is obtained by taking the arithmetic mean of the measured particle diameters of 30 conductive particles.

The film thickness of the film (release film, insulating film, etc.), coating film (insulating resin layer, conductive adhesive layer, etc.), shielding layer (electromagnetic wave shielding layer), etc. is determined by observing the cross-section of the measurement object using a microscope and measuring 5 locations. thickness and average the value.

When the surface resistance is less than 10 ⁶ Ω/□, use a low-resistance resistivity meter (such as Mitsubishi Chemical Corporation, Loresta GP, ASP probe) by the four-terminal method (based on JIS K 7194: 1994 and JIS R 1637: 1998 method), when the surface resistivity is 10 ⁶ Ω/□ or more, use a high resistance resistivity meter (such as Mitsubishi Chemical Corporation, Hiresta UP, URS probe) by the double loop method (according to JIS K 6911: 2006 method) to determine the surface resistivity.

(Electromagnetic wave shielding film)

The electromagnetic wave shielding film of the present invention is formed by laminating an insulating resin layer, a shielding layer and a conductive adhesive layer in sequence.

The conductive adhesive layer is formed using a conductive adhesive composition containing an adhesive component and conductive particles.

The water absorption rate of the adhesive component is less than 2.0%.

The adhesive component contains thermosetting resin.

The thermosetting resin contains an epoxy resin having a structural formula represented by the following general formula (1) and having an epoxy equivalent weight of 170 to 400 g/eq.

(In the above [Formula (1)], R ₁ represents a hydrocarbon group having 1 to 35 carbon atoms, R ₂ represents hydrogen or a methyl group, and n represents an integer of 1 to 10.)

FIG. 1 is a cross-sectional view showing one embodiment of the electromagnetic wave shielding film of the present invention.

2 is a cross-sectional view showing another embodiment of the electromagnetic wave shielding film of the present invention.

The electromagnetic wave shielding film 1 has: an insulating resin layer 10; a shielding layer 20 adjacent to the insulating resin layer 10; a conductive adhesive layer 22 adjacent to the side of the shielding layer 20 opposite to the insulating resin layer 10; and an insulating resin layer. The first release film 30 adjacent to the side opposite to the shielding layer 20 of 10; and the second release film 40 adjacent to the side opposite to the shielding layer 20 of the conductive adhesive layer 22.

The electromagnetic wave shielding film 1 of the first embodiment is an example in which the adhesive layer 22 is an anisotropic conductive adhesive layer 24 .

The electromagnetic wave shielding film 1 of the second embodiment is an example in which the adhesive layer 22 is an isotropic conductive adhesive layer 26.

<Insulating resin layer>

The insulating resin layer 10 is a protective layer for the shielding layer 20 after the electromagnetic wave shielding film 1 is attached to the surface of an insulating film provided on the surface of the printed circuit board and the first release film 30 is peeled off.

Examples of the insulating resin layer 10 include: a coating film formed by applying a composition containing a thermosetting resin and a curing agent and semi-curing or curing it; applying and drying a coating liquid containing a thermosetting resin, a curing agent and a solvent; Semi-cured or cured coating film, etc. As the insulating resin layer 10 , from the viewpoint of further improving the adhesion between the insulating resin layer 10 and the shielding layer 20 , it is preferable to apply a coating liquid containing a resin material (a combination of a thermosetting resin and a curing agent) and a solvent and dry it. And the coating film formed by semi-curing or curing it as needed.

Examples of the thermosetting resin include amide resin, epoxy resin, phenolic resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet curing acrylate resin, and the like. As the thermosetting resin, amide resin and epoxy resin are preferred because of their excellent heat resistance.

Examples of the curing agent include known curing agents corresponding to the type of thermosetting resin.

The insulating resin layer 10 may contain either or both of a colorant (pigment, dye, etc.) and a filler in order to hide the printed circuit of the printed circuit board with the electromagnetic wave shielding film or to provide design to the printed circuit board with the electromagnetic wave shielding film. By.

As either or both of the colorants and fillers, pigments or fillers are preferred from the viewpoints of weather resistance, heat resistance, and concealability, and black pigments and fillers are more preferred from the viewpoints of concealment and design of printed circuits. or combinations of black pigments with other pigments or fillers.

The insulating resin layer 10 may contain other components as necessary within a 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. From a practical viewpoint, 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 0.1 μm or more and 30 μm or less, more preferably 0.5 μm or more and 20 μm or less, and still more preferably 3 μm or more and 15 μm or less. If the insulating resin layer 10 If the thickness is more than the lower limit of the above range, the insulating resin layer 10 can fully function as a protective layer. If the thickness of the insulating resin layer 10 is equal to or less than the upper limit of the above range, the electromagnetic wave shielding film 1 can be made thinner.

<Shielding layer (electromagnetic wave shielding layer))>

The shielding layer 20 is not particularly limited as long as it has conductivity, and may be a metal film, a conductive film composed of conductive particles, or the like.

The shielding layer 20 is formed to expand in the plane direction, and therefore has conductivity in the plane direction, and functions as an electromagnetic wave shielding layer and the like.

Examples of the metal constituting the metal film include one selected from nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, and zinc, or an alloy containing one or more of these. Among these, copper and copper-containing alloys are preferred from the viewpoints of shielding properties and economical efficiency.

Examples of methods for forming a metal film include a vapor deposition film formed by physical vapor deposition (vacuum vapor deposition, sputtering, ion beam vapor deposition, electron beam vapor deposition, etc.) or chemical vapor deposition, a plated film formed by plating, Metal foil etc. Among them, a vacuum evaporated film or a sputtered film formed by a vacuum film forming method (vacuum evaporation method, sputtering method, etc.) or a plating film formed by an electroplating method is preferable from the viewpoint of excellent conductivity in the plane direction. A vapor-deposited film using a vacuum vapor deposition method is more preferable from the viewpoint that the thickness can be reduced, the conductivity in the plane direction is excellent even if the thickness is thin, and the film can be easily formed by a dry process. In addition, the metal film may be a metal foil formed by rolling processing, or a metal foil based on electrolysis (for example, a special electrolytic copper foil, etc.).

When the shielding layer is a conductive film composed of conductive particles, the conductive particles may be, for example, particles of carbon, silver, copper, nickel, solder, or the like. In addition, the conductive particles may be silver-coated copper particles in which copper powder is silver-plated, or insulating particles such as resin balls or glass beads are metal-plated. These conductive particles can be used alone or in combination of two or more types.

The shape of the conductive particles may be any of spherical, needle-like, fibrous, flaky, or dendritic, but from the viewpoint of forming a layer, the flake-like shape is preferred.

The thickness of the shielding layer 20 is 0.01 μm or more and 3 μm or less, preferably 0.05 μm or more and 2 μm or less, and more preferably 0.1 μm or more and 1.5 μm or less. If the thickness of the shielding layer 20 is 0.01 μm or more, the shielding effect of electromagnetic wave noise becomes better. If the thickness of the shielding layer 20 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 productivity and flexibility of the electromagnetic wave shielding film 1 are improved.

The surface resistance of the shielding layer 20 is preferably 0.001Ω or more and 1Ω or less, and more preferably 0.001Ω or more and 0.1Ω or less. If the surface resistance of the shielding layer 20 is not less than the lower limit of the above range, the shielding layer 20 can be made sufficiently thin. If the surface resistance of the shielding layer 20 is equal to or less than the upper limit of the above range, the shielding layer 20 can fully function as an electromagnetic wave shielding layer.

<Conductive adhesive layer>

The conductive adhesive layer 22 is a layer for bonding the electromagnetic wave shielding film 1 to the printed circuit board with an insulating film.

The conductive adhesive layer 22 is a conductive adhesive layer for electrically connecting the electromagnetic wave shielding film 1 and the printed circuit board.

The conductive adhesive layer is conductive at least in the thickness direction and has adhesive properties.

Examples of the conductive adhesive layer include the anisotropic conductive adhesive layer 24 which has conductivity in the thickness direction but does not have conductivity in the plane direction, or has conductivity in the thickness direction and the plane direction. Isotropic conductive adhesive layer 26. As the conductive adhesive layer, the anisotropic conductive adhesive layer 24 is preferable from the viewpoint that it has no conductivity in the plane direction but has good transmission characteristics and the flexibility of the electromagnetic wave shielding film 1 becomes good. As the conductive adhesive layer, the isotropic conductive adhesive layer 26 is preferred because it can fully function as an electromagnetic wave shielding layer.

The conductive adhesive layer is formed using a conductive adhesive composition containing an adhesive component including a thermosetting resin and conductive particles.

<<Adhesive ingredients>>

The water absorption rate of the adhesive component is less than 2.0%.

The adhesive component contains thermosetting resin.

The thermosetting resin contains an epoxy resin having a structural formula represented by the following general formula (1) and having an epoxy equivalent weight of 170 to 400 g/eq.

(In the above [Formula (1)], R ₁ represents a hydrocarbon group having 1 to 35 carbon atoms, R ₂ represents hydrogen or a methyl group, and n represents an integer of 1 to 10.)

R ₁ (hydrocarbon group having 1 to 35 carbon atoms) in the above [formula (1)] is not particularly limited. For example, it may be an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, or an aromatic hydrocarbon group. Alternatively, it may be a hydrocarbon group composed of an appropriate combination of these.

Examples of R ₁ include the following group [Formula 2].

R ₂ in the above [Formula (1)] is more preferable since the methyl group is more hydrophobic than hydrogen and therefore can reduce the hygroscopicity of the adhesive component.

In addition, an epoxy resin having a structural formula represented by the general [Formula (1)] and exhibiting an epoxy equivalent weight of 170 to 400 g/eq (in this specification, this epoxy resin is also referred to as "Specific epoxy resin") may contain one type or two or more types.

By using an epoxy resin with a polyfunctional structure represented by the above [Formula (1)] as the epoxy resin, the crosslinking density of the conductive adhesive layer during curing can be increased and the conductive particles can be stably fixed. This conductive adhesive layer ensures excellent connectivity.

The adhesive component preferably contains 30 to 70% by mass of a specific epoxy resin.

If the content of the specific epoxy resin in the adhesive component is 30% by mass or more, the problem of failure to ensure connectivity due to poor curing can be effectively prevented. In addition, if the content is 70% by mass or less, the problem of failure to ensure connectivity due to the influence of moisture absorption can be effectively prevented.

Specific epoxy resins exhibit an epoxy equivalent weight of 170~400g/eq.

By limiting the epoxy equivalent weight, the OH group (hydrophilicity) and functional group R ₁ (hydrophobicity) of the ring-opened epoxy during curing can be optimized.

If the epoxy equivalent is too small, the hydrophobic effect of the functional group _R1 will be insufficient, and the conductive particles may be oxidized due to moisture absorption, resulting in poor connectivity. On the other hand, if the epoxy equivalent is too large, there will be fewer OH groups, poor adhesion and cross-linking properties, and possibly poor connectivity.

The epoxy equivalent is preferably 190 g/eq or more, more preferably 215 g/eq or more, still more preferably 245 g/eq or more, particularly preferably 250 g/eq or more, and preferably 300 g/eq or less.

The epoxy equivalent can be measured in accordance with JIS K7236:2001.

In the present invention, by making the water absorption rate of the adhesive component in the conductive adhesive layer less than 2.0% and blending a specific epoxy resin into the adhesive component, the deterioration of the conductive adhesive layer can be suppressed. , oxidation caused by moisture absorption of the conductive particles and the shielding layer can form an electromagnetic wave shielding film that can maintain a low connection resistance value even in a high temperature and high humidity environment.

The adhesive component may contain epoxy resins other than specific epoxy resins and other thermosetting resins other than epoxy resins within a range that does not affect the effects of the present invention.

Examples of other thermosetting resins include phenolic resin, amino resin, alkyd resin, urethane resin, synthetic rubber, ultraviolet curing acrylic resin, and the like.

In addition, the adhesive component contains a curing agent in addition to the above-mentioned thermosetting resin.

Examples of the curing agent include latent curable adhesives that are cured by reacting with a thermosetting resin under heating.

As curing agents, there are additive curing agents having multiple functional groups capable of reacting with thermosetting resins, and catalyst curing agents such as cations or anions that release the strain energy of epoxy groups. Since the storage stability of the adhesive component is good, a catalyst-type curing agent is preferred.

The content of the catalyst curing agent in the adhesive component is preferably 0.1 parts by mass or more and 50 parts by mass or less, more preferably 0.5 parts by mass or more and 30 parts by mass or less, and still more preferably 1 part by mass relative to 100 parts by mass of the thermosetting resin. More than 10 parts by mass and less than 10 parts by mass.

In addition, as components other than the thermosetting resin that can be contained in the adhesive component, in addition to the above-mentioned curing agent, various components such as rubber components, tackifiers, curing accelerators, stress reducing agents (stress relaxants), etc. .

The adhesive component may contain a rubber component (carboxyl-modified nitrile rubber, acrylic rubber, etc.) for imparting flexibility, a tackifier, etc. In addition, the adhesive component may also contain a curing accelerator, a stress reducing agent (stress relaxant), etc.

The acid value of the rubber component contained in the adhesive component is preferably 20 mgKOH/g or less from the viewpoint of adhesion and water absorption. In addition, the epoxy equivalent of the rubber component is preferably 0.05 eq/kg or more and 1 eq/kg or less from the viewpoint of reactivity with the epoxy resin. In addition, the glass transition temperature of the rubber component is preferably 10° C. or higher.

By making the adhesive component contain a rubber component that meets the above requirements, it is possible to provide an electromagnetic wave shielding film that exhibits good adhesion and maintains a low connection resistance value for a longer period of time even after being placed in a high temperature and high humidity environment. .

Examples of stress reducing agents include acrylonitrile butadiene rubber (NBR), acrylic rubber, styrene butadiene rubber, vinyl acetate resin, silicone resin, and the like.

The content of the low-stress agent in the adhesive component is preferably 10 mass% or more and 80 mass% or less, and more preferably 30 mass% or more and 70 mass% in 100 mass% of the adhesive component (solid content) before curing. %the following. If the content of the stress reducing agent is within the above range, the conductive adhesive layer will have excellent flexibility.

The water absorption rate of the adhesive component is less than 2.0%.

By limiting the water absorption of the adhesive components, the mixing conditions for other components other than the specific epoxy resin are also limited.

If the water absorption rate of the adhesive component is too high, for example, the oxidation of the conductive particles is accelerated and the connectivity is deteriorated. In addition, expansion occurs due to the vaporization of water, and the heat resistance is also deteriorated. On the other hand, if the water absorption rate of the adhesive component is too low, the compatibility with the epoxy resin will deteriorate.

The water absorption rate of the adhesive component can be determined as follows according to JIS K 7209.

[water absorption rate]

Coat the adhesive component on the PET substrate and heat it at 150°C for 1 hour to create a cured layer.

The test piece composed of this cured layer was exposed to conditions of 85° C., 48 hours, and a relative humidity of 85%. Then, the mass change of the test piece, that is, the difference between the initial mass and the mass after exposure to water, is measured and obtained, and expressed as a percentage of the initial mass.

<<Conductive particles>>

The conductive adhesive composition forming the conductive adhesive layer contains conductive particles in addition to the above-mentioned adhesive components.

As shown in FIG. 1 , the anisotropic conductive adhesive layer 24 includes, for example, an adhesive 24 a containing the above resin and conductive particles 24 b.

As shown in FIG. 2 , the isotropic conductive adhesive layer 26 includes, for example, an adhesive 26 a containing the above-mentioned resin and conductive particles 26 b.

Examples of conductive particles include particles of metal (silver, platinum, gold, copper, nickel, palladium, aluminum, solder, etc.), graphite powder, fired carbon particles, plated fired carbon particles, and metal-coated particles. Core-shell resin particles, etc. From the viewpoint of high conductivity, metal particles are preferable, and from the viewpoint of low cost, copper particles are more preferable.

The average particle diameter of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 26 μm or less, and more preferably 4 μm or more and 16 μm or less. If the average particle diameter of the conductive particles 24b is not less than the lower limit of the above range, the stability of electrical connection will be improved and it will be difficult for the conductive particles 24b to Since the fluidity of the resin of the anisotropic conductive adhesive layer 24 is impaired, it is possible to ensure that the insulating film of the anisotropic conductive adhesive layer 24 follows the shape of the through hole. If the average particle diameter of the conductive particles 24b is less than the upper limit of the above range, the conductive particles 24b will not hinder the contact between the resin of the anisotropic conductive adhesive layer 24 and the surface of the adherend, and sufficient contact can be ensured. of tightness.

The average particle diameter of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 1 μm or less. If the average particle diameter of the conductive particles 26 b is equal to or greater than the lower limit of the above range, the frequency of contact of the conductive particles 26 b increases, and the conductivity in the three-dimensional direction can be stably improved. If the average particle diameter of the conductive particles 26 b is less than the upper limit of the above range, the conductive particles 26 b will not hinder the contact between the resin of the isotropic conductive adhesive layer 26 and the surface of the adherend, and sufficient contact can be ensured. of tightness.

The proportion of the conductive particles 24b in the anisotropic conductive adhesive layer 24 is preferably 1 volume % or more and 30 volume % or less out of 100 volume % of the anisotropic conductive adhesive layer 24 , and more preferably 2 Volume % or more and 10 volume % or less. When the proportion of the conductive particles 24b is equal to or greater than the lower limit of the above range, the conductivity of the anisotropic conductive adhesive layer 24 becomes good. When the proportion of the conductive particles 24b is less than the upper limit of the above range, the adhesiveness and fluidity (the ability to follow the shape of the through-hole of the insulating film) of the anisotropic conductive adhesive layer 24 become good. . In addition, the flexibility of the electromagnetic wave shielding film 1 becomes better.

The proportion of the conductive particles 26b in the isotropic conductive adhesive layer 26 is preferably 50 volume % or more and 80 volume % or less, and more preferably 60 volume % out of 100 volume % of the isotropic conductive adhesive layer 26 Volume % or more and 70 volume % or less. When the proportion of the conductive particles 26 b is equal to or greater than the lower limit of the above range, the conductivity of the isotropic conductive adhesive layer 26 becomes good. When the proportion of the conductive particles 26b is less than the upper limit of the above range, the adhesiveness and fluidity (the ability to follow the shape of the through-hole of the insulating film) of the isotropic conductive adhesive layer 26 become good. . In addition, the flexibility of the electromagnetic wave shielding film 1 becomes better.

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 not less than the lower limit of the above range, the content of the conductive particles 24 b is suppressed to be low. If the surface resistance of the anisotropic conductive adhesive layer 24 is below the upper limit of the above range, there is no problem with anisotropy in practical terms.

The surface resistance of the isotropic conductive adhesive layer 26 is preferably from 0.05Ω to 2.0Ω, and more preferably from 0.1Ω to 1.0Ω. If the surface resistance of the isotropic conductive adhesive layer 26 is not less than the lower limit of the above range, the content of the conductive particles 26 b is suppressed to a low level, and the viscosity of the conductive adhesive does not become too high. The coating properties are further improved. In addition, the fluidity (the ability to follow the shape of the through-hole of the insulating film) of the isotropic conductive adhesive layer 26 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 anisotropic conductive adhesive layer 24 is preferably 2 μm or more and 25 μm or less, and more preferably 5 μm or more and 20 μm or less. If the thickness of the anisotropic conductive adhesive layer 24 is not less than the lower limit of the above range, the fluidity of the anisotropic conductive adhesive layer 24 (the ability to follow the shape of the through-hole of the insulating film) can be ensured. ), the through-holes of the insulating film can be fully filled with conductive adhesive. In addition, the distance between the electromagnetic wave shielding layer 20 and the printed circuit can be enlarged, and the transmission characteristics can be improved. 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 becomes better.

The thickness of the isotropic conductive adhesive layer 26 is preferably 2 μm or more and 20 μm or less, and more preferably 3 μm or more and 10 μm or less. When the thickness of the isotropic conductive adhesive layer 26 is more than the lower limit of the above range, the adhesion becomes good. In addition, the fluidity of the isotropic conductive adhesive layer 26 (the ability to follow the shape of the through-holes of the insulating film) can be ensured, and the through-holes of the insulating film can be fully filled with the conductive adhesive. Can ensure bending resistance, even if it is bent repeatedly, all directions The homogeneous conductive adhesive layer 26 will not break either. 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 thinner. In addition, the flexibility of the electromagnetic wave shielding film 1 becomes better. In addition, the isotropic conductive adhesive layer 26 having a higher surface resistance than the electromagnetic wave shielding layer 20 has a thinner film thickness, thereby improving transmission characteristics.

<First release film>

The first release film 30 serves as a protective film for the insulating resin layer 10 and makes the electromagnetic wave shielding film 1 easy to handle. The first release film 30 is peeled off from the insulating resin layer 10 after the electromagnetic wave shielding film 1 is attached to the printed circuit board with an insulating film.

The first release film 30 has, for example, a base material layer 32 and an adhesive layer or a release agent layer 34 provided on the surface of the base material layer 32 on the insulating resin layer 10 side. In addition, in this specification, the adhesive layer or the release agent layer 34 is also expressed as the adhesive layer/release agent layer 34.

The first release film 30 may be provided with an adhesive layer/release agent layer 34 directly on the surface of the base material layer 32, or may be provided with an adhesive layer/release agent layer 34 on the surface of the insulating resin layer 10, and then The base material layer 32 is adhered to the surface of the adhesive layer/release agent layer 34, thereby providing the adhesive layer/release agent layer 34 on the surface of the base material layer 32.

Examples of the resin material of the base layer 32 include polyethylene terephthalate (hereinafter also referred to as PET), polyethylene naphthalate, polyethylene isophthalate, and poly(p-ethylene terephthalate). Butylene phthalate, polyolefin, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, polyvinylidene chloride, synthetic rubber, Liquid crystal polymers, etc. As the resin material, PET is preferred from the viewpoint of heat resistance (dimensional stability) and price when manufacturing the electromagnetic wave shielding film 1 .

Base material layer 32 may contain colorants or fillers.

The thickness of the base layer 32 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, still more preferably 25 μm or more and 100 μm or less. When the thickness of the base material layer 32 is equal to or greater than the lower limit of the above range, the handleability of the electromagnetic wave shielding film 1 becomes good. If the base material layer 32 is thick If the temperature is below the upper limit of the above range, when the electromagnetic wave shielding film 1 is hot-pressed onto a printed circuit board with an insulating film, heat is easily transmitted to the conductive adhesive layer 22 .

An adhesive layer 34 or a release agent layer 34 is disposed between the base material layer and the insulating resin layer.

The first release film 30 has an adhesive layer or a release agent layer 34, so that when the second release film 40 is peeled off from the conductive adhesive layer 22 or the electromagnetic wave shielding film 1 is bonded to the printed surface by heat pressing. When using a circuit board or the like, peeling of the first release film 30 from the insulating resin layer 10 can be suppressed, and the first release film 30 can fully function as a protective film.

As the adhesive, a known adhesive may be used.

In addition, the release agent layer 34 is formed by subjecting the surface of the base material layer 32 to a release treatment using a release agent. The first release film 30 has the release agent layer 34 . Therefore, when the first release film 30 is peeled off from the insulating resin layer 10 , the first release film 30 is easily peeled off and the insulating resin layer 10 is not easily broken.

As the release agent, a known release agent may be used.

The thickness of the adhesive layer 34 is preferably from 0.05 μm to 50.0 μm, and more preferably from 0.1 μm to 25.0 μm. If the thickness of the adhesive layer 34 is within the above range, the surface of the first release film 30 will have appropriate adhesiveness.

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

<Second release film>

The second release film 40 is used to protect the conductive adhesive layer 22 and make the electromagnetic wave shielding film 1 have good operability. The second release film 40 is peeled off from the conductive adhesive layer 22 before the electromagnetic wave shielding film 1 is attached to the printed circuit board with an insulating film.

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

In addition, in this specification, the release agent layer or the adhesive layer 44 is also expressed as the release agent layer/adhesive layer 44.

Examples of the resin material of the base material layer 42 include the same resin material as the resin material of the base material layer 32 of the first release film 30 .

Base material layer 42 may contain colorants or fillers.

The thickness of the base material layer 42 is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 150 μm or less, and still more preferably 25 μm or more and 100 μm or less.

A release agent layer 44 or an adhesive layer 44 is disposed between the base material layer 42 and the conductive adhesive layer 22 .

The release agent layer 44 is formed by subjecting the surface of the base material layer 42 to a release treatment using a release agent. The second release film 40 has a release agent layer 44. Therefore, when the second release film 40 is peeled off from the conductive adhesive layer 22, the second release film 40 is easily peeled off, and the conductive adhesive layer 22 is not easily peeled off. break.

As the release agent, a known release agent may be used.

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

As the adhesive layer 44, the same adhesive layer as the adhesive layer 34 described in the column of the above <first release film> can be used.

<Constitution of electromagnetic wave shielding film>

In the present invention, the electromagnetic wave shielding film only needs to have at least an insulating resin layer, a shielding layer and a conductive adhesive layer. The electromagnetic wave shielding film may include a first release film and a second release film, or may not.

For this reason, in this specification, the first release film and/or the second release film may be included in the insulating resin layer, shielding layer, and conductive adhesive layer and are called electromagnetic wave shielding films. Or, it does not include these release films and is called an electromagnetic wave shielding film.

<Thickness of electromagnetic wave shielding film>

The thickness of the electromagnetic wave shielding film 1 (excluding the release film) is preferably 5 μm or more and 45 μm or less, and more preferably 5 μm or more and 30 μm or less. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is more than the lower limit of the above range, the first release film 30 will not be easily broken when peeling off. If the thickness of the electromagnetic wave shielding film 1 (excluding the release film) is equal to or less than the upper limit of the above range, the printed circuit board with the electromagnetic wave shielding film can be made thinner.

(Method for manufacturing electromagnetic wave shielding film)

As a first embodiment of the manufacturing method of the electromagnetic wave shielding film of the present invention, there is, for example, a manufacturing method based on the following method (A1). In addition, in the following method (A1), as an electromagnetic wave shielding film, the electromagnetic wave shielding film in which the adhesive layer shown in FIG. 1 is the anisotropic conductive adhesive layer 24 is used as an example, However, it is not limited to this adhesive layer. The manufacturing method described below is equally applicable regardless of whether the adhesive layer is an isotropic conductive adhesive layer 27 or an adhesive layer 22 that does not contain conductive particles.

Method (A1) is specifically a method having the following steps (A1-1) to (A1-4).

Hereinafter, method (A1) will be described based on FIG. 3 .

Step (A1-1): a step of forming the insulating resin layer 10 on one surface of the first release film 30 .

Step (A1-2): a step of forming the shielding layer 20 on the surface of the insulating resin layer 10 opposite to the first release film 30 .

Step (A1-3): a step of forming the anisotropic conductive adhesive layer 24 on the surface of the shielding layer 20 opposite to the insulating resin layer 10 .

Step (A1-4): a step of laminating the second release film 40 on the surface of the anisotropic conductive adhesive layer 24 opposite to the shielding layer 20 .

Each step of the method (A1) will be described in detail below.

As a method of forming the insulating resin layer 10 in the step (A1-1), for example, the following method is preferable: from the viewpoint of heat resistance during soldering, etc., it is preferable to use the adhesive layer/release agent of the first release film 30 The surface on the layer 34 side is coated with a paint containing a thermosetting resin and a curing agent, and is semi-cured or cured.

As the coating method of the above-mentioned coating, for example, a die coater, a gravure coater, a roll coater, a curtain coater, a spin coater, a rod coater, a reverse coater, a dosing coater, or a spray coater can be used. Machine, rod coater, air knife coater, blade coater, blade coater, cast coater, screen coater and other coating machine methods.

When semi-curing or curing the thermosetting resin, heating may be performed using a heater, an infrared lamp, or the like.

In the step (A1-2), the shielding layer 20 is formed on the surface of the insulating resin layer 10 opposite to the first release film 30 .

Examples of methods for forming the shielding layer 20 include a method using a vacuum film forming method (vacuum evaporation, sputtering), a method using an electroplating method, a method using a metal foil (copper foil), and the like.

When the film thickness of the shielding layer 20 is less than 3 μm, from the viewpoint that the shielding layer 20 can be formed with a desired film thickness and surface shape, a method of forming a vapor-deposited film by vacuum evaporation or a method of forming a plated film by electroplating is preferable. method. From the viewpoint that the shielding layer 20 can be formed with high gas permeability and can easily release the gas generated inside under high temperature conditions to the outside, and the shielding layer 20 can be easily formed by a dry process, it is more preferable to form the vapor deposition by vacuum evaporation. Coating method.

When the film thickness of the shielding layer 20 is 3 μm or more, deterioration of the insulating resin layer 10 due to the thermal process of vacuum evaporation never occurs, and the shielding layer having a desired film thickness can be easily formed. From the viewpoint of 20, it is preferable to perform a lamination process using pressure and/or heating so that the insulating resin layer 10 and the metal foil (copper foil) are in contact with each other.

Here, the pressure in the pressure treatment is preferably 0.1 kPa or more and 100 kPa or less, more preferably 0.1 kPa or more and 20 kPa or less, still more preferably 1 kPa or more and 10 kPa or less.

Heating may be performed simultaneously with pressure treatment. The heating temperature at this time is preferably -30°C or more and +50°C or less from the glass transition temperature of the semi-cured or cured insulating resin layer, and more preferably 50°C or more and 150°C or less.

In step (A1-3), a conductive adhesive paint containing an adhesive 24a, conductive particles 24b and a solvent is applied to the surface of the shielding layer 20 opposite to the insulating resin layer 10.

The solvent is volatilized by the applied conductive adhesive paint, thereby forming the anisotropic conductive adhesive layer 24 .

Examples of the solvent contained in the adhesive paint include esters (butyl acetate, ethyl acetate, methyl acetate, isopropyl acetate, ethylene glycol monoacetate, etc.), ketones (methyl ethyl acetate, etc.) ketone, methyl isobutyl ketone, acetone, methyl isobutyl ketone, cyclohexanone, etc.), alcohols (methanol, ethanol, isopropyl alcohol, butanol, propylene glycol monomethyl ether, propylene glycol monomethyl ether, etc.), etc.

The method of applying the conductive adhesive is the same as the method of applying the paint in step (A1-1).

In step (A1-4), the second release film 40 is laminated on the anisotropic conductive adhesive layer such that the release agent layer/adhesive layer 44 is in contact with the anisotropic conductive adhesive layer 24. The surface of the agent layer 24 opposite to the electromagnetic wave shielding layer 20 .

After the second release film 40 is laminated on the anisotropic conductive adhesive layer 24, in order to improve the adhesion between the layers, the first release film 30, the insulating resin layer 10, and the shielding layer may also be 20. The laminate composed of the anisotropic conductive adhesive layer 24 and the second release film 40 is subjected to a lamination process using pressure and/or heating.

The pressurizing conditions are the same as the pressurizing treatment in step (A1-2). In addition, in the process (A1-4), you may perform heat processing similarly to the process (A1-2).

In addition, in the method (A1), an example in which the lamination process is performed in steps (A1-2) and (A1-4) is described, but the stage at which the lamination process is performed is not limited to this.

As a second embodiment of the manufacturing method of the electromagnetic wave shielding film of the present invention, there is, for example, a manufacturing method based on the following method (A2).

Method (A2) is specifically a method having the following steps (A2-1) to (A2-4).

Hereinafter, the method (A2) will be described based on Figures 4 to 6 . The steps (A2-1) to (A2-2) are shown in FIG. 4 , the step (A2-3) is shown in FIG. 5 , and the step (A2-4) is shown in FIG. 6 .

Step (A2-1): a step of forming the insulating resin layer 10 on one surface of the first release film 30 .

Step (A2-2): a step of forming the shielding layer 20 on the surface of the insulating resin layer 10 opposite to the first release film 30 to form the laminated body (p1).

Step (A2-3): a step of forming the anisotropic conductive adhesive layer 24 on the second release film 40 to form the laminate (p2).

Step (A2-4): Connect the laminated body (p1) and the laminated body (p2) so that the shielding layer 20 of the laminated body (p1) and the anisotropic conductive adhesive layer 24 of the laminated body (p2) are in contact with each other. Fitting process.

The process (A2-1) and the process (A2-2) are the same as the said process (A1-1) and the process (A1-2) respectively.

In step (A2-3), the thermosetting adhesive 24a and conductive particles including conductive particles 24b are coated not on the shielding layer 20 but on the surface of the second release film 40 on which the release agent layer/adhesive layer 44 is provided. The process is the same as the above-mentioned step (A1-3) except that the anisotropic conductive adhesive layer 24 is formed by using a flexible adhesive coating.

In the lamination of the laminated body (p1) and the laminated body (p2) in the step (A2-4), a pressure-based method for improving the adhesion between the laminated body (p1) and the laminated body (p2) may also be implemented. of lamination. The pressurizing conditions are the same as the pressurizing treatment in step (A1-4). In addition, in the process (A2-4), you may perform heat processing similarly to the process (A1-4).

<Effect>

The electromagnetic wave shielding film 1 of this embodiment uses an adhesive component exhibiting a specific water absorption rate as the conductive adhesive composition used in the conductive adhesive layer constituting the electromagnetic wave shielding film, and the adhesive component contains A thermosetting resin containing a specific epoxy resin can exhibit good adhesion and maintain a low connection resistance value even after being placed in a high temperature and high humidity environment.

<Other embodiments>

The electromagnetic wave shielding film in the present invention is not limited as long as it has an insulating resin layer, a shielding layer adjacent to the insulating resin layer, and a conductive adhesive layer adjacent to the side of the shielding layer opposite to the insulating resin layer. The embodiment shown in the figure.

For example, the number of insulating resin layers may be two or more.

The first release film may have a release agent layer instead of the adhesive layer.

The second release film may have an adhesive layer instead of the release agent layer.

The first release film or the second release film may not have an adhesive layer or a release agent layer, and may be composed of only a base material layer.

When the insulating resin layer has sufficient flexibility and strength, the first release film may be omitted.

When the surface viscosity of the conductive adhesive layer is low, the second release film may be omitted.

(Printed circuit board with electromagnetic wave shielding film)

The printed circuit board with an electromagnetic wave shielding film of the present invention includes: a printed circuit board provided with a printed circuit on at least one side of the substrate; an insulating film adjacent to the surface of the printed circuit board provided with the printed circuit; And the above-mentioned electromagnetic wave shielding film of the present invention is provided with a conductive adhesive layer adjacent to the insulating film.

7 is a cross-sectional view showing the first embodiment of the printed circuit board with an electromagnetic wave shielding film obtained by the manufacturing method of the present invention.

The flexible printed circuit board with electromagnetic wave shielding film 2 includes a flexible printed circuit board 50 , an insulating film 60 , and the electromagnetic wave shielding film 1 of the first embodiment.

The flexible printed circuit board 50 is provided with a printed circuit 54 on at least one side of the base film 52 .

The insulating film 60 is provided on the surface of the flexible printed circuit board 50 on the side where the printed circuit 54 is provided.

The anisotropic conductive adhesive layer 24 of the electromagnetic wave shielding film 1 is adhered to 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 flexible printed circuit board 2 with the electromagnetic wave shielding film, the second release film 40 is peeled off from the anisotropic conductive adhesive layer 24 .

When the first release film 30 is not required in the flexible printed circuit board 2 with the electromagnetic wave shielding film, the first release film 30 is peeled off from the insulating resin layer 10 .

In the vicinity of the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) except for the portion with the through hole, the shielding layer 20 of the electromagnetic wave shielding film 1 is sandwiched between the insulating film 60 and the anisotropic conductive adhesive layer 24 They are arranged facing each other separately.

The separation distance between the printed circuit 54 and the shielding layer 20 except for the portion with the through hole is substantially equal to the sum of the thickness of the insulating film 60 and the thickness of the anisotropic conductive adhesive layer 24 . The separation distance is preferably from 15 μm to 200 μm, and more preferably from 30 μm to 200 μm. If separated If the distance is less than 15 μm, in order to adjust the characteristic impedance of the signal circuit, the line width of the signal circuit must be reduced, and it will be technically difficult to achieve stable manufacturing of the printed circuit 54 . If the separation distance exceeds 200 μm, the flexible printed circuit board 2 with the electromagnetic wave shielding film becomes thicker and has insufficient flexibility.

<Flexible printed circuit board>

The flexible printed circuit board 50 processes the copper foil of the copper-clad laminate into a desired pattern by a known etching method to form a printed circuit (power circuit, ground circuit, ground layer, etc.).

Examples of the copper-clad laminate include a laminate in which copper foil is bonded to one or both sides of the base film 52 via an adhesive layer (not shown); and a resin for forming the base film 52 is cast on the surface of the copper foil. Laminated boards obtained from solutions, etc.

Examples of materials for the adhesive layer include epoxy resin, polyester, polyamide imide, polyamide imide, polyamide, phenolic resin, polyurethane resin, acrylic resin, melamine resin, and the like.

The thickness of the adhesive layer is preferably 0.5 μm or more and 30 μm or less.

<<Base membrane>>

As the base film 52, a heat-resistant film is preferable, a polyimide film or a liquid crystal polymer film is more preferable, and a polyimide film is even more preferable.

From the viewpoint of electrical insulation, the surface resistance of the base film 52 is preferably 1×10 ⁶ Ω or more. From a practical viewpoint, 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. From the viewpoint of flexibility, it is more preferably 6 μm or more and 25 μm or less, and further preferably 10 μm or more and 25 μm or less.

<<Printed circuit>>

Examples of the copper foil constituting the printed circuit 54 (signal circuit, ground circuit, ground layer, etc.) include rolled copper foil, electrolytic copper foil, and the like. From the viewpoint of flexibility, rolled copper foil is preferred.

The thickness of the copper foil is preferably 1 μm or more and 50 μm or less, and more preferably 7 μm or more and 35 μm or less.

The longitudinal end portions (terminals) of the printed circuit 54 are not covered by the insulating film 60 or the electromagnetic wave shielding film 1 for soldering, connector connection, component mounting, etc.

<Insulation film>

The insulating film 60 is obtained by forming an adhesive layer (not shown) on one side of an insulating film main body (not shown) by applying an adhesive, sticking an adhesive sheet, or the like.

From the viewpoint of electrical insulation, the surface resistance of the main body of the insulating film is preferably 1×10 ⁶ Ω or more. From a practical viewpoint, the surface resistance of the main body of the insulating film is preferably 1×10 ¹⁹ Ω or less.

As the insulating film main body, a heat-resistant film is preferred, a polyimide film or a liquid crystal polymer film is more preferred, and a polyimide film is even more preferred.

The thickness of the insulating film main body is preferably 1 μm or more and 100 μm or less, and from the viewpoint of flexibility, it is more preferably 3 μm or more and 25 μm or less.

Examples of materials for the adhesive layer include epoxy resin, polyester, polyamide imide, polyamide imide, polyamide, phenolic resin, polyurethane resin, acrylic resin, melamine resin, polystyrene, Polyolefin, etc. The epoxy resin may contain a rubber component (carboxyl-modified nitrile rubber, etc.) for imparting flexibility.

The thickness of the adhesive layer is preferably 1 μm or more and 100 μm or less, and more preferably 1.5 μm or more and 60 μm or less.

The shape of the opening of the through hole is not particularly limited. Examples of the shape of the opening of the through hole 62 include a circular shape, an elliptical shape, a quadrangular shape, and the like.

(Method for manufacturing printed circuit board with electromagnetic wave shielding film)

The method for manufacturing a printed circuit board with an electromagnetic wave shielding film of the present invention includes the step of press-bonding a printed circuit board with a printed circuit on at least one side of a substrate and the electromagnetic wave shielding film of the present invention via an insulating film. During crimping, the insulating film is brought into close contact with the surface of the printed circuit board on which the printed circuit is provided, and the insulating film is brought into close contact with the adhesive layer of the electromagnetic wave shielding film.

Method for Manufacturing a Printed Circuit Board with an Electromagnetic Wave Shielding Film of the Invention After the electromagnetic wave shielding film is manufactured by the above-mentioned method for manufacturing an electromagnetic wave shielding film of the invention, the following steps (a) and (b) are performed.

Step (a): a step of providing an insulating film on the surface of the side of the printed circuit board on which the printed circuit is provided to obtain a printed circuit board with an insulating film.

Step (b): When the electromagnetic wave shielding film has a second release film, after peeling off the second release film from the electromagnetic wave shielding film, the printed circuit board with the insulating film and the electromagnetic wave shielding film are coated with a conductive adhesive layer The process of overlapping and pressing the insulating film in such a manner that it contacts the surface of the insulating film to bond a conductive adhesive layer to the surface of the insulating film to obtain a printed circuit board with an electromagnetic wave shielding film.

As a more preferred embodiment, the method for manufacturing a printed circuit board with an electromagnetic wave shielding film of the present invention includes the following steps (a) to (d).

Step (a): a step of providing an insulating film on the surface of the side of the printed circuit board on which the printed circuit is provided to obtain a printed circuit board with an insulating film.

Step (b): When the electromagnetic wave shielding film has a second release film, after peeling off the second release film from the electromagnetic wave shielding film, the printed circuit board with the insulating film and the electromagnetic wave shielding film are coated with a conductive adhesive layer A process in which the conductive adhesive layer is pressed onto the surface of the insulating film by overlapping and pressing it in contact with the surface of the insulating film to obtain a printed circuit board with an electromagnetic wave shielding film.

Process (c): When the electromagnetic wave shielding film has a first release film, when the first release film is not required after the process (b), a process of peeling off the first release film from the electromagnetic wave shielding film.

Step (d): When the adhesive contained in the conductive adhesive layer is a thermosetting adhesive, as necessary, between steps (a) and (b), or after step (c) The process of formally solidifying the conductive adhesive layer.

Hereinafter, a method of manufacturing a flexible printed circuit board with an electromagnetic wave shielding film will be described with reference to FIG. 8 .

<Process (a)>

As shown in FIG. 8 , an insulating film 60 having through holes 62 formed at positions corresponding to the printed circuits 54 is superimposed on the flexible printed circuit board 50 , and an adhesive layer of the insulating film 60 is bonded to the surface of the flexible printed circuit board 50 . (illustration omitted), and the adhesive layer is cured, thereby obtaining the flexible printed circuit board 3 with an insulating film. The adhesive layer of the insulating film 60 may be temporarily bonded to the surface of the flexible printed circuit board 50 and the adhesive layer may be formally cured in step (d).

The adhesive layer is bonded and solidified by, for example, hot pressing using a press (not shown) or the like.

<Process (b)>

As shown in FIG. 8 , the electromagnetic wave shielding film 1 with the second release film 40 peeled off is stacked on the flexible printed circuit board 3 with an insulating film and pressed (preferably hot pressed) to obtain the surface pressure of the insulating film 60 . The flexible printed circuit board 2 with the electromagnetic wave shielding film is connected to the anisotropic conductive adhesive layer 24 and the anisotropic conductive adhesive layer 24 is electrically connected to the printed circuit 54 through the through hole 62 .

In the diagram of step (b) in FIG. 8 , the printed circuit 54 is composed of a ground circuit 54 a and a signal circuit 54 b (illustration of 54 a and 54 b is omitted).

The anisotropic conductive adhesive layer 24 is bonded by, for example, hot pressing using a press (not shown) or the like.

The time of hot pressing is preferably 20 seconds or more and 60 minutes or less, more preferably 30 seconds or more and 30 minutes or less.

The temperature of hot pressing (the temperature of the hot plate of the press) is preferably 140°C or more and 210°C or less, and more preferably 150°C or more and 190°C or less.

The pressure of hot pressing is preferably 0.5 MPa or more and 20 MPa or less, and more preferably 1 MPa or more and 16 MPa or less.

<Process (c)>

As shown in FIG. 8 , when the first release film 30 is not required, the first release film 30 is peeled off from the insulating resin layer 10 .

<Effect>

The printed circuit board with an electromagnetic wave shielding film 2 of this embodiment has the characteristics of the electromagnetic wave shielding film of the present invention described above. The shielding layer is a printed circuit board with an electromagnetic wave shielding film that is well grounded to the ground circuit of the printed circuit board.

<Other embodiments>

It should be noted that the printed circuit board with the electromagnetic wave shielding film in the present invention only needs to have a printed circuit board, an insulating film adjacent to the surface of the side of the printed circuit board on which the printed circuit is provided, and an adhesive layer and an insulating film. The electromagnetic wave shielding film may be adjacent to the film and is not limited to the illustrated embodiment.

For example, the flexible printed circuit board may also have a ground layer on the back side. In addition, the flexible printed circuit board may also have printed circuits on both sides, and insulating films and electromagnetic wave shielding films adhered to both sides.

A rigid printed circuit board without flexibility may also be used instead of the flexible printed circuit board.

The electromagnetic wave shielding film 1 of the second embodiment or the like may be used instead of the electromagnetic wave shielding film 1 of the first embodiment.

[Example]

Hereinafter, although an Example is given and this invention is demonstrated further in detail, the scope of this invention is not limited to these Examples.

The structural formulas [formula (a)] to [formula (f)] of the epoxy resin used in each example are shown below.

[Formula (a)]~[Formula (f)]

(Example 1)

<The ratio of adhesive paint for the insulating resin layer>

As the adhesive paint contained in the insulating resin layer, 20.6 parts by mass of bisphenol A type epoxy resin (jER (registered trademark) 828 manufactured by Mitsubishi Chemical Corporation), flexible epoxy resin (epoxy resin (DIC 60.7 parts by mass of the company's EXA-4816)), 16.7 parts by mass of the curing agent (Sho-amine Parts by mass and 4.9 parts by mass of carbon black were dissolved in 200 parts by mass of a solvent (methyl ethyl ketone) to prepare a paint for an insulating resin layer.

<The proportion of adhesive paint for the conductive adhesive layer>

As the adhesive paint contained in the conductive adhesive layer, an epoxy resin (EPICLON HP7200L manufactured by DIC Corporation) having the structural formula represented by the above [Formula (1)] is used (for the specific structural formula, refer to the above formula ( a))) 79 parts by mass, acrylate polymer (Teisan Resin SG-P3 (Tg12°C, acid value 0 mgKOH/g, epoxy equivalent 0.21 eq./kg)), manufactured by Nagase Chemicals Co., Ltd., 20 parts by mass, imidazole Conductive adhesive was produced by mixing 1 part by mass of an epoxy resin curing agent (Curezol 2P4MZ (2 phenyl 4 methyl imidazole) manufactured by Shikoku Kasei Co., Ltd.) and 20 parts by mass of copper particles (average particle diameter 5.02 μm). Adhesive coating for the adhesive layer. The mixing ratio of the adhesive paint of the conductive adhesive layer is as shown in the following [Table 1].

<Production of electromagnetic wave shielding film>

A first release film was prepared in which an adhesive layer composed of an acrylic adhesive was placed on one side of a PET film (CN200 manufactured by Toyobo Co., Ltd., film thickness: 50 μm).

On the surface of the adhesive layer of the first release film, the coating material for the insulating resin layer is applied using a die coater and then dried to form an insulating resin layer (10 μm).

Next, copper was physically evaporated by electron beam evaporation on the surface of the insulating resin layer opposite to the first release film to form a shielding layer (film thickness: 300 nm) composed of a copper evaporated film.

Next, the adhesive paint of the conductive adhesive layer is coated on the surface of the shielding layer opposite to the insulating resin layer using a die coater, and then dried to form a conductive adhesive layer (film thickness 5μm).

Prepare the first product in which a release layer is provided on one side of a PET film (T157, manufactured by Lintec, thickness of the release film body: 50 μm, thickness of the release agent layer: 0.1 μm) using a non-silicon-based release agent. 2. Release film.

The above-mentioned second release film is pasted on the surface of the above-mentioned conductive adhesive layer on the opposite side to the shielding layer in such a manner that the above-mentioned release agent layer is in contact with the above-mentioned conductive adhesive layer, thereby obtaining the electromagnetic wave shielding film of Example 1. .

<Production of printed circuit boards with electromagnetic wave shielding film>

The insulating adhesive composition was applied to the surface of a polyimide film (main body of the insulating film) with a thickness of 25 μm so that the dry film thickness became 25 μm to form an adhesive layer and obtain an insulating film (thickness: 50 μm). A through hole (hole diameter: 800 μm) is formed in the printed circuit at a position corresponding to the ground circuit.

A printed circuit board in which a printed circuit was formed on the surface of a polyimide film (base film) with a thickness of 12 μm was prepared.

The insulating film is adhered to the printed circuit board by hot pressing to obtain a printed circuit board with an insulating film.

The electromagnetic wave shielding film of the above-mentioned Example 1 with the second release film peeled off is overlapped and peeled off on the printed circuit board with the insulating film, and is hot-pressed for 30 minutes using a hot-pressing device under the conditions of hot plate temperature: 180°C and load: 3MPa. A conductive adhesive layer is bonded to the surface of the insulating film.

The first release film is peeled off from the insulating resin layer to obtain a printed circuit board with an electromagnetic wave shielding film.

<Measurement of water absorption (%) of adhesive components>

Coat the adhesive component on the PET substrate and heat it at 150°C for 1 hour to create a cured layer.

The test piece composed of this cured layer was exposed to conditions of 85° C., 48 hours, and a relative humidity of 85%. Then, the mass change of the test piece, that is, the difference between the initial mass and the mass after exposure to water, is measured and obtained, and is expressed as a percentage of the initial mass.

The measurement results of the water absorption rate of the adhesive component used in Example 1 are shown below [Table 1].

<Evaluation of printed circuit boards with electromagnetic wave shielding film>

Regarding the electromagnetic wave shielding film-equipped printed circuit board of Example 1 obtained as described above, the connection resistance before and after storage in a high-temperature and high-humidity environment was measured to evaluate the connectivity. The storage conditions are 2 modes: 500 hours and 1000 hours in an environment of 85°C and 85% humidity. Connectivity was evaluated by the following method.

[Connectivity evaluation]

In a printed circuit board with an electromagnetic wave shielding film, the electrical connection between the wiring, the shielding layer, and the wiring is measured via the electromagnetic wave shielding film present in the through hole (also called a connection hole).

Put the tester in contact with the printed circuit board with the electromagnetic wave shielding film, and measure the resistance value between the wiring-shielding layer-wiring.

The connection resistance value was evaluated based on the following standards.

○: Less than 300mΩ

△：300mΩ or more and less than 1000mΩ

×: 1000mΩ or more

The evaluation results of the connectivity of the printed wiring board with the electromagnetic wave shielding film of Example 1 are shown in the following [Table 1].

(Example 2~Example 11)

In Example 1, except that each condition of the conductive adhesive layer was changed as shown in [Table 1] and [Table 2], the electromagnetic wave-coated electromagnetic wave-coated electromagnetic waves of Examples 2 to 11 were produced in the same manner as in Example 1. Shielding film for printed circuit boards.

In Example 2, EPICLON HP7200HHH manufactured by DIC Corporation was used as the epoxy resin (for the specific structural formula, refer to the above formula (a))).

In Example 3, NC3000 manufactured by Nippon Kayaku Co., Ltd. was used as the epoxy resin (for the specific structural formula, refer to the above formula (b))).

In Example 4, NC2000-L manufactured by Nippon Kayaku Co., Ltd. was used as the epoxy resin (for the specific structural formula, refer to the above formula (c))).

In Example 5, EPPN-201 manufactured by Nippon Kayaku Co., Ltd. was used as the epoxy resin (for the specific structural formula, refer to the above formula (d))).

In Example 10, Teisan Resin SG-70L (Tg-13°C, acid value 5 mgKOH/g, no epoxy equivalent) manufactured by Nagase Chemicals Co., Ltd. was used as the acrylate polymer.

The water absorption rate of the adhesive component used in Example 2 to Example 11 was measured by the same method as Example 1. The results are shown in [Table 1] and [Table 2].

In addition, the same evaluation as in Example 1 was performed on the printed circuit boards with electromagnetic wave shielding films produced in Examples 2 to 11. The results are shown in [Table 1] and [Table 2].

(Comparative Example 1~Comparative Example 3)

In Example 1, printed circuit boards with electromagnetic wave shielding films of Comparative Examples 1 to 3 were produced in the same manner as in Example 1, except that each condition of the conductive adhesive layer was changed as shown in [Table 1]. .

In Comparative Example 1, jER1001 manufactured by Mitsubishi Chemical Corporation was used as the epoxy resin (for the specific structural formula, refer to the above formula (e))).

In Comparative Example 2, jER157S70 manufactured by Mitsubishi Chemical Corporation was used as the epoxy resin (for the specific structural formula, refer to the above formula (f))).

In Comparative Example 3, Teisan Resin SG-280 (Tg-29°C, acid value 30 mgKOH/g, no epoxy equivalent) manufactured by Nagase Chemicals Co., Ltd. was used as the acrylate polymer.

The water absorption rate of the adhesive component used in Comparative Examples 1 to 3 was measured in the same manner as in Example 1. The results are shown in [Table 2].

In addition, the same evaluation as in Example 1 was performed on the printed circuit boards with electromagnetic wave shielding films produced in Comparative Examples 1 to 3. The results are shown in [Table 2].

[Table 1]

[Table 2]

It can be seen from the above examples that the electromagnetic wave shielding film of the present invention can reliably exhibit good adhesion and maintain low connection resistance even after 500 hours after being placed in a high temperature and high humidity environment.

In addition, it was found that when a specific rubber component is contained in an adhesive component, good adhesion can be exhibited and a low connection resistance value can be maintained even if the elapsed time is 1000 hours.

(industrial applicability)

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

In summary, the technical means disclosed in the present invention can indeed effectively solve the problems of conventional knowledge and achieve the expected purposes and effects. They have not been published in publications or publicly used before the application and are of long-term progress. They are truly worthy of the title. The invention described in the Patent Law is correct. I have submitted the application in accordance with the law. I sincerely pray that Jun will review it carefully and grant a patent for the invention. I am deeply grateful.

However, the above are only several preferred embodiments of the present invention, and should not be used to limit the scope of the present invention. That is, all equivalent changes and modifications made based on the patent scope of the present invention and the content of the invention specification are It should still fall within the scope of the patent of this invention.

1: Electromagnetic wave shielding film

10: Insulating resin layer

20:Shielding layer

22: Conductive adhesive layer

24: Anisotropic conductive adhesive layer

24a: Adhesive

24b: Conductive particles

30: First release film

32:Substrate layer

34: Adhesive layer/release agent layer

40: Second release film

42:Substrate layer

44: Release agent layer/adhesive layer

Claims (12)

An electromagnetic wave shielding film, which is formed by laminating an insulating resin layer, a shielding layer and a conductive adhesive layer in sequence. The conductive adhesive layer uses a conductive adhesive containing an adhesive component and conductive particles. The adhesive component is formed of a composition, and the water absorption rate of the adhesive component calculated in accordance with JIS K 7209 is less than 2.0% and 0.6% or more. The adhesive component contains a thermosetting resin, and the thermosetting resin contains the following general properties: An epoxy resin having a structural formula represented by [Formula (1)] and exhibiting an epoxy equivalent weight of 170 to 400 g/eq,

In the above [Formula (1)], R ₁ represents a hydrocarbon group having 1 to 35 carbon atoms, R ₂ represents hydrogen or a methyl group, and n represents an integer of 1 to 10. The electromagnetic wave shielding film according to claim 1, wherein the adhesive component contains 30 to 70 mass % of the epoxy resin. The electromagnetic wave shielding film according to claim 1, wherein R ₁ in the formula (1) is a hydrocarbon group containing a structure of an alicyclic hydrocarbon or an aromatic hydrocarbon. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the epoxy equivalent is 215~400g/eq. The electromagnetic wave shielding film according to claim 4, wherein the epoxy equivalent is 250~400g/eq. The electromagnetic wave shielding film according to claim 5, wherein the epoxy equivalent is 275~400g/eq. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the adhesive component contains a rubber component. The electromagnetic wave shielding film according to claim 7, wherein the acid value of the rubber component is 20 mgKOH/g or less. The electromagnetic wave shielding film according to claim 7, wherein the epoxy equivalent of the rubber component is 0.05 eq/kg or more. The electromagnetic wave shielding film according to claim 7, wherein the glass transition temperature of the rubber component is 10°C or higher. The electromagnetic wave shielding film according to any one of claims 1 to 3, wherein the adhesive component contains a catalyst curing agent, and the catalyst curing agent is The content is 0.1 parts by mass or more and 10 parts by mass or less. A printed circuit board with an electromagnetic wave shielding film, comprising: a printed circuit board provided with a printed circuit on at least one side of the substrate; and an insulating film facing the surface of the printed circuit board on which the printed circuit is provided. adjacent; and the electromagnetic wave shielding film according to any one of claims 1 to 11, which is arranged such that the conductive adhesive layer is adjacent to the insulating film.

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