JP6690773B1 - Electromagnetic wave shielding sheet, and electromagnetic wave shielding wiring circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding sheet having high cleaning resistance, excellent high frequency shielding property, and good insulating property, and a wired circuit board using the electromagnetic wave shielding sheet. An interface of the metal layer in contact with the adhesive layer has a Flop Index (FI) calculated by the formula (1). Is 50 or less and X represented by the formula (2) is less than 1.0, which is solved by the electromagnetic wave shielding sheet. [Selection diagram] Figure 1

Description

  The present invention relates to an electromagnetic wave shielding sheet and an electromagnetic wave shielding wiring circuit board, for example, an electromagnetic wave shielding sheet suitable for being used by being joined to a part of a component that emits an electromagnetic wave, and an electromagnetic wave using the electromagnetic wave shielding sheet. The present invention relates to a shielded printed circuit board.

  Various electronic devices such as mobile terminals, PCs, servers, etc. have a built-in printed circuit board such as a printed wiring board. An electromagnetic wave shield structure is provided on these printed circuit boards in order to prevent malfunction due to an external magnetic field or radio waves and to reduce unnecessary radiation from electric signals.

  With the increase in the transmission speed of transmission signals, the electromagnetic wave shielding sheet is also required to reduce the electromagnetic wave shielding property (hereinafter, high frequency shielding property) corresponding to high frequency noise and the transmission loss in the high frequency region (hereinafter, also referred to as transmission characteristic). ing. Patent Document 1 discloses a configuration in which a metal layer having a thickness of 0.5 to 12 μm and an anisotropic conductive adhesive layer are provided in a laminated state. Then, it is described that, with this configuration, electric field waves, magnetic field waves, and electromagnetic waves traveling from one surface side to the other surface side of the electromagnetic wave shielding sheet are well shielded and the transmission loss is reduced.

International Publication No. 2013/077108 Japanese Patent Laid-Open No. 2019-121731

2. Description of the Related Art In recent years, in electronic devices typified by mobile phones, along with the increase in transmission speed of transmission signals, the electromagnetic wave shielding sheets on the printed circuit boards built therein are also required to have high-frequency shielding properties. Therefore, it has been preferable to use a metal layer having a thickness of 0.5 to 12 μm as the conductive layer of the electromagnetic wave shield sheet as described in Patent Document 1.
However, merely using a metal layer having a thickness of 0.5 to 12 μm, the electromagnetic wave shielding sheet cannot exhibit sufficient high frequency shielding property in the high frequency band, and the electromagnetic wave shielding sheet has more excellent high frequency shielding property. In order to achieve this, it has been required to further improve the metal layer.
In Patent Document 2, the surface of the shield layer of the electromagnetic wave shielding film (equivalent to the electromagnetic wave shielding sheet) on the adhesive layer side is to be adjusted to a certain range of the average length Rsm of the roughness curve element according to JIS B 0601: 2013. Thus, the ground wiring provided on the printed circuit board and the shield layer are grounded well, and the high frequency shielding property is realized.

  In the mounting process of electronic equipment, the electromagnetic wave shielding printed circuit board may be exposed to the cleaning process mainly for the purpose of removing dirt, dust and the like. In order to remove all dirt, dust and the like adhering to the electromagnetic wave shielding wired circuit board, a plurality of chemical agents having water-based property, oil-based property, acidic property or alkaline property are used in the cleaning process. At that time, there was a problem that the electromagnetic wave shield layer was not sufficiently resistant to decomposition and dissolution with respect to cleaning chemicals, and the electromagnetic wave shield layer was damaged.

  In addition, the electromagnetic wave shield sheet is usually provided with an insulating protective layer on one surface of the shield layer in order to prevent connection other than between the shield layer and the ground wiring. When the insulating property of the protective layer is not sufficiently high, or when the steep irregularities of the shield layer by heat pressing penetrate the protective layer, when the protective layer of the electromagnetic wave shield layer contacts a member other than the ground wiring, There was a problem that connections other than between the shield layer and the ground wiring occurred.

  The present invention has been made in view of the above background, and an object thereof is to use an electromagnetic wave shielding sheet having high cleaning resistance, excellent high frequency shielding property, and good insulating property, and the electromagnetic wave shielding sheet. The present invention is to provide a wired circuit board.

As a result of earnest studies by the present inventor, they found that the problems of the present invention can be solved in the following aspects, and completed the present invention.
That is, the electromagnetic wave shielding sheet according to the present invention has a laminate having an adhesive layer, a metal layer, and a protective layer in this order, and the interface of the metal layer in contact with the adhesive layer is calculated by the formula (1). Flop Index (FI) is 50 or less, and X represented by the formula (2) is less than 1.0.

(L ^* _{15 °} , L ^* _{45 °} , and L ^* _{110 °} are offset angles from the specular reflection light of the light incident at an angle of 45 ° with respect to the normal direction of the interface between the metal layer in contact with the adhesive layer. 15 °, 45 °, which is a 110 ° ^{L * a} * ^b * color system defined by JIS Z8729 of ^{L *.)}

(Sz is the maximum height of the metal layer determined according to ISO 25178, and T is the thickness of the protective layer.)

  According to the present invention, there is an excellent effect that it is possible to provide an electromagnetic wave shield sheet that exhibits high cleaning resistance, excellent high-frequency shieldability, and good insulation, and an electromagnetic wave shielded wired circuit board.

It is sectional drawing which illustrated the electromagnetic wave shield sheet which concerns on this embodiment. It is a figure which showed FI measurement system and FI behavior of two surfaces which differ in the steepness and order of unevenness. FIG. 7 is a schematic cross-sectional view of a cut portion showing an example of an electromagnetic wave shielding wired circuit board according to a description of an indentation effect of non-conductive particles. FIG. 3 is a schematic cross-sectional view of a section showing an example of an electromagnetic wave shielding wired circuit board according to the present embodiment. It is two types of sectional views with which the relation of thickness T of a protective layer and maximum height Rz of a metal layer differs.

Hereinafter, an example of an embodiment to which the present invention is applied will be described. It should be noted that the sizes and ratios of the respective members in the following drawings are for convenience of explanation and are not limited to these. Further, in the present specification, the description “arbitrary number A to arbitrary number B” includes the number A as a lower limit value and the number B as an upper limit value in the range. Further, the "sheet" in this specification includes not only a "sheet" defined in JIS but also a "film". The numerical values specified in this specification are values obtained by the method disclosed in the embodiment or the example.

<Electromagnetic wave shield sheet>
The electromagnetic wave shield sheet of the present invention has a laminate including at least an adhesive layer, a metal layer, and a protective layer in this order. FIG. 1 is a sectional view illustrating an electromagnetic wave shield sheet 10 according to an embodiment of the present invention. As shown in FIG. 1, the electromagnetic wave shield sheet 10 has a laminated body including an adhesive layer 1, a metal layer 2 and a protective layer 3 in this order, and the metal layer 2 includes an adhesive layer 1 and a protective layer 3. It is located in between.
That is, the electromagnetic wave shielding sheet according to the present invention has a laminate having an adhesive layer, a metal layer, and a protective layer in this order, and the interface of the metal layer in contact with the adhesive layer is Flop calculated by the formula (1). Index (FI) is 50 or less, using the maximum height Sz determined according to ISO 25178-2: 2012 at the interface of the metal layer in contact with the adhesive layer, and the thickness T of the protective layer, Since X represented by the formula (2) is less than 1.0, particularly in a printed circuit board that transmits a high frequency (for example, 100 MHz to 50 GHz) signal, high cleaning resistance and excellent high frequency shielding property are exhibited. be able to.
For the electromagnetic wave shield sheet 10, for example, a wiring circuit board that is an adherend and the surface on the adhesive layer 1 side are bonded to each other to form an electromagnetic wave shield layer, and an electromagnetic wave shielding wired circuit board is manufactured. That is, of the surfaces of the metal layer 2, the surface facing the signal wiring and the ground wiring in the printed circuit board is the surface that is in close contact with the adhesive layer 1.

《Metal layer》
The metal layer of the present invention has a function of imparting high frequency shielding properties to the electromagnetic wave shielding sheet. The interface of the metal layer on the side in contact with the adhesive layer has a Flop Index (FI) calculated by the formula (1) of 50 or less, and X represented by the formula (2) is less than 1.0. And

(L ^* _{15 °} , L ^* _{45 °} , and L ^* _{110 °} are offset angles from the specular reflection light of the light incident at an angle of 45 ° with respect to the normal direction of the interface between the metal layer in contact with the adhesive layer. 15 °, 45 °, which is a 110 ° ^{L * a} * ^b * color system defined by JIS Z8729 of ^{L *.)}

(Sz is the maximum height of the metal layer determined according to ISO 25178, and T is the thickness of the protective layer.)
Details of FI and Sz, and details of effects obtained by these controls will be described later.

[Flop Index (FI)]
Flop Index (FI) is a parameter calculated by Expression (1).

The FI measurement system is shown in FIG. The FI radiates light (incident light) at an incident angle of 45 ° with respect to the direction perpendicular to the surface to be measured, detects light reflected at a constant angle (regular reflection light) by a detector, and digitizes it. It is calculated using the lightness L ^* . L ^* is the lightness L ^* in the L ^* a ^* b ^* color system specified by JIS Z8729, and L ^* _{15 °} , L ^* _{45 °} , and L ^* _{110 °} are measured in the direction perpendicular to the surface to be measured. On the other hand, it is L ^* observed at offset angles of 15 °, 45 °, and 110 ° from the specularly reflected light of light incident at an angle of 45 °.
The FI is an index for evaluating the roughness of the surface to be measured and the orderliness of the surface roughness. As shown in FIG. 2B, in the case where the surface of the object to be measured has large irregularities and is disordered, the incident light is reflected (scattered) at all angles, so that the angle dependence of the detected light amount becomes small. As a result, the value of FI calculated by the equation (1) becomes a small value. On the other hand, as shown in FIG. 2C, when the unevenness of the surface to be measured is gentle and the order is high, the incident light is strongly reflected at a constant angle, and therefore the angle dependence of the detected light amount. Grows. In particular, among the lights observed at the offset angles of 15 °, 45 °, and 110 ° described above, the light amount of 15 ° is large, so that the FI has a large value.

  As a result of earnest studies, the inventor has found that the cleaning resistance of the electromagnetic wave shielding sheet is improved by setting the FI of the metal layer to 50 or less. When the FI of the metal layer is 50 or less, it means that the metal layer surface has irregularities having sufficient steepness and disorder. The adhesive layer provided on the surface of the metal layer having the above-mentioned state enters into the unevenness of the surface of the metal layer which is steep and highly disordered, and the adhesion between the metal layer and the adhesive layer becomes strong. Therefore, even when the electromagnetic wave shielding sheet and the electromagnetic wave shielding wired circuit board are exposed to cleaning chemicals, chemicals do not flow into the interface between the metal layer and the adhesive layer, and it is possible to suppress the occurrence of defects such as delamination. it can. In addition, since there is no inflow of chemicals between the metal layer and the adhesive layer, especially when the cleaning chemical has acid or alkalinity, it is possible to suppress discoloration and corrosion of the metal layer. The invention exhibits excellent wash resistance. The FI of the metal layer is more preferably 30 or less, further preferably 10 or less. Moreover, 0 or more is preferable.

  Regarding the mechanism that brings about the effect of the invention, the above-mentioned mechanism involves estimation, and the mechanism that exerts the effect is not limited at all.

[Sz of metal layer]
The maximum height Sz is a parameter defined by ISO25178, and represents the distance from the highest point to the lowest point on the measurement surface. The maximum height Sz is a parameter obtained by expanding the maximum height Rz, which is a two-dimensional roughness parameter, into three dimensions. When a cross section of a surface is extracted and the roughness is discussed, Sz and Rz can be regarded as synonymous.

In the electromagnetic wave shielding sheet of the present invention, the value X represented by the formula (2) formed by the maximum height Sz (μm) of the surface of the metal layer in contact with the adhesive layer and the thickness T (μm) of the protective layer is 1 It is less than 0.0, and more preferably less than 0.97.
When X is less than 1.0, the insulating property of the electromagnetic wave shield layer is improved. As shown in FIG. 5A, when X is 1.0 or more, the thickness T of the protective layer becomes smaller than the maximum height Rz of the metal layer (synonymous with Sz), and therefore the unevenness of the metal layer Penetrates the protective layer, and the metal layer is electrically connected to a place other than the ground wiring. On the other hand, as shown in FIG. 5B, when X is less than 1.0, the thickness T of the protective layer is larger than the maximum height Rz of the metal layer (synonymous with Sz), and therefore the metal The unevenness of the layer does not penetrate the protective layer, and the outermost surface of the electromagnetic wave shield layer has improved insulation.

(Sz is the maximum height of the metal layer determined according to ISO 25178, and T is the thickness of the protective layer.)

  The factor of X being 1.0 or more is, for example, when the height of the unevenness of the surface of the metal layer in contact with the protective layer is higher than the thickness of the protective layer, or when the protective layer is formed by coating or the like, coating defects occur. It is assumed that when the metal layer is generated, a metal layer is formed on the protective layer by plating or the like, and the metal layer is formed along the shape of the defect. The coating defects described above may occur, for example, when a resin composition to which particles having an average particle diameter larger than the thickness of the protective layer are added is applied. The factors that cause X to be 1.0 or more are just examples.

[Control method of FI and Sz]
The method of controlling FI and Sz on the surface of the metal layer is, for example, a method of forming a protective layer having irregularities from a resin composition containing particles and then forming a metal layer on the protective layer by plating, sputtering, or the like. A method of forming a metal layer by plating or spattering after spraying particles on a protective layer formed from an object, blasting or plasma irradiation of the protective layer surface, electron beam treatment, chemical solution treatment, or embossing to make it uneven After forming the metal layer, a method of forming a metal layer on the protective layer by plating, sputtering, or the like, a method of depositing roughening particles on the metal foil surface to form a roughened surface, JP-A No. 2017-13473. A method of polishing a metal surface using the described buff, a method of polishing a metal surface using a polishing cloth, a metal layer by a method such as plating on a carrier material having desired unevenness. Method of forming by transferring the irregularities of the carrier material, the shot blast method of blowing an abrasive on the metal surface by compressed air, and a method of transferring a press addressed uneven shape mold having a desired uneven metal foil. The method of controlling FI and Sz on the surface of the metal layer is not limited to the exemplified method, and a conventionally known method can be applied.

[Thickness of metal layer]
The thickness of the metal layer is preferably 0.3 to 10 μm. When the thickness of the metal layer is 0.3 to 10 μm, the high frequency shielding property and the thinness of the electromagnetic wave shielding sheet can both be achieved. The thickness of the metal layer is more preferably 0.5 to 5 μm.

[Metal layer component]
As the metal layer, for example, a metal foil, a metal vapor deposition film, a metal plating film or the like can be used.
The metal used for the metal foil is preferably a conductive metal such as aluminum, copper, silver or gold, and one kind of metal or an alloy of plural metals can be used. From the viewpoint of high-frequency shielding property and cost, copper, silver and aluminum are more preferable, and copper is further preferable. For copper, for example, it is preferable to use a rolled copper foil or an electrolytic copper foil.
As the metal used for the metal vapor deposition film and the metal plating film, it is preferable to use one kind of a conductive metal such as aluminum, copper, silver and gold, or an alloy of a plurality of metals, more preferably copper and silver. One surface or both surfaces of the metal foil, the metal vapor deposition film, and the metal plating film may be coated with a metal or an organic substance such as a rust preventive agent.

[Aperture]
The metal layer may have a plurality of openings. By having the openings, the solder reflow resistance is improved. By having an opening, when the electromagnetic wave shielding wiring circuit board is subjected to solder reflow processing, the volatile components contained in the polyimide film of the wiring circuit board or the coverlay adhesive escape to the outside, and the coverlay adhesive and the electromagnetic wave shielding sheet. It is possible to suppress the occurrence of the appearance defect due to the interfacial peeling.

  The shape of the opening viewed from the surface of the metal layer may be a perfect circle, an ellipse, a quadrangle, a polygon, a star, a trapezoid, a branch, or any other shape, as required. From the viewpoint of manufacturing cost and ensuring the toughness of the metal layer, the shape of the opening is preferably a perfect circle or an ellipse.

[Aperture ratio of metal layer]
The aperture ratio of the metal layer is preferably in the range of 0.10 to 20% and can be calculated by the following formula (3).
Formula (3)
(Aperture ratio [%]) = (Area of opening per unit area) / (Area of opening per unit area + Area of non-opening per unit area) × 100

When the aperture ratio is 0.10% or more, the volatile components during the solder reflow treatment can be sufficiently escaped, the appearance deterioration due to the interfacial peeling of the coverlay adhesive and the electromagnetic wave shield sheet, and the deterioration of the connection reliability. Is preferable because it can suppress
On the other hand, when the aperture ratio is 20% or less, the amount of electromagnetic noise passing through the aperture can be reduced and the shielding property can be improved, which is preferable. The range of the aperture ratio that makes the solder reflow resistance and the high-frequency shield property compatible with each other at a high level is more preferably 0.30 to 15%, further preferably 0.50 to 6.5%.

  The measurement of the aperture ratio is, for example, using an image magnified 500 to 2000 times with a laser microscope and a scanning electron microscope (SEM) perpendicular to the surface direction of the metal layer, binarizing the aperture and the non-aperture, It can be obtained by setting the number of pixels of binarized color per unit area as each area.

[Method for manufacturing metal layer having openings]
As a method for producing a metal layer having an opening, a conventionally known method can be applied. A method of forming a pattern resist layer on a metal foil and etching the metal foil to form an opening (i), a predetermined method A method (ii) in which an anchor agent is screen-printed in a pattern and metal plating is performed only on the anchor agent-printed surface, a manufacturing method (iii) described in JP-A-2015-63730, and the like can be applied.
That is, a water-soluble or solvent-soluble ink is pattern-printed on a support, a metal vapor deposition film is formed on the surface of the ink, and the pattern is removed. A metal layer having an opening with a carrier can be obtained by forming a release layer on the surface and performing electrolytic plating. Among them, a method for forming an opening for forming a pattern resist layer and etching a metal foil (i) However, it is preferable because the shape of the opening can be precisely controlled. However, the shape of the opening may be controlled by any other method, and the method for manufacturing the metal layer is not limited to the etching method (i).

<Adhesive layer>
The adhesive layer has a function of laminating the electromagnetic wave shielding sheet on the wiring circuit board and adhering the electromagnetic wave shielding sheet to the wiring circuit board when manufacturing the electromagnetic wave shielding wiring circuit board.

  The adhesive layer can be formed using a resin composition. The resin composition contains a binder resin. As the binder resin, either a thermoplastic resin, or a thermosetting resin and a curing agent can be used. As the adhesive layer, either a non-conductive adhesive layer or a conductive adhesive layer can be used, and the conductive adhesive layer exhibits conductivity by containing a conductive filler or the like.

As the conductive adhesive layer, either an isotropic conductive adhesive layer or an anisotropic conductive adhesive layer can be used. The isotropic conductive adhesive layer has conductivity in the vertical direction and the horizontal direction when the electromagnetic wave shield sheet is placed horizontally. Further, the anisotropic conductive adhesive layer has conductivity only in the vertical direction when the electromagnetic wave shield sheet is placed horizontally.
The conductive adhesive layer may be either isotropically conductive or anisotropically conductive, and is preferably anisotropically conductive because the cost can be reduced.

[Thermoplastic resin]
As the thermoplastic resin, polyolefin resin, vinyl resin, styrene / acrylic resin, diene resin, terpene resin, petroleum resin, cellulose resin, polyamide resin, polyurethane resin, polyester resin, polycarbonate resin, polyimide resin, liquid crystal Examples thereof include polymers and fluororesins. Although not particularly limited, a material having a low dielectric constant and a low dielectric loss tangent is preferable from the viewpoint of transmission loss, and a material having a low dielectric constant is preferable from the viewpoint of characteristic impedance, and examples thereof include a liquid crystal polymer and a fluorine resin.
The thermoplastic resins may be used alone or in combination of two or more.

[Thermosetting resin]
The thermosetting resin is a resin having a plurality of functional groups capable of reacting with the curing agent. Functional group, for example, hydroxyl group, phenolic hydroxyl group, acid anhydride group, methoxymethyl group, carboxyl group, amino group, epoxy group, oxetanyl group, oxazoline group, oxazine group, aziridine group, thiol group, isocyanate group, blocked Examples thereof include isocyanate groups, blocked carboxyl groups, silanol groups and the like. The thermosetting resin is, for example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane resin, polyurethane urea resin, epoxy resin, oxetane resin, phenoxy resin, polyimide resin, polyamide resin, polyamideimide resin, phenol resin. Known resins such as resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins and fluororesins can be mentioned.
The thermosetting resins can be used alone or in combination of two or more.

  Among these, polyurethane resin, polyurethane urea resin, polyester resin, epoxy resin, phenoxy resin, polyimide resin, polyamide resin, and polyamideimide resin are preferable from the viewpoint of washing resistance.

[Curing agent]
The curing agent has a plurality of functional groups capable of reacting with the functional group of the thermosetting resin. Examples of the curing agent include known compounds such as epoxy compounds, acid anhydride group-containing compounds, isocyanate compounds, aziridine compounds, amine compounds, phenol compounds and organometallic compounds.
The curing agents can be used alone or in combination of two or more.

  The curing agent is preferably contained in an amount of 1 to 50 parts by weight, more preferably 3 to 40 parts by weight, still more preferably 3 to 30 parts by weight, based on 100 parts by weight of the thermosetting resin.

  The thermoplastic resin and the thermosetting resin can be used alone or in combination of both.

[Conductive filler]
The conductive filler has a function of imparting conductivity to the adhesive layer. As the material of the conductive filler, for example, conductive metals such as gold, platinum, silver, copper and nickel and alloys thereof, and fine particles of a conductive polymer are preferable, and silver is more preferable in terms of price and conductivity.
Further, instead of the fine particles of a single material, composite fine particles having a core of metal or resin and having a coating layer coating the surface of the core are also preferable from the viewpoint of cost reduction. Here, the nucleus is preferably selected from nickel, silica, copper and alloys thereof, and resin, which are inexpensive. The coating layer is preferably a conductive metal or a conductive polymer. Examples of the conductive metal include gold, platinum, silver, nickel, manganese, indium, and the like, and alloys thereof. Examples of the conductive polymer include polyaniline and polyacetylene. Among these, silver is preferable in terms of price and conductivity.

The shape of the conductive filler is not limited as long as desired conductivity is obtained. Specifically, for example, a spherical shape, a flake shape, a leaf shape, a dendritic shape, a plate shape, a needle shape, a rod shape, and a grape shape are preferable. Further, two kinds of conductive fillers having different shapes may be mixed.
The conductive filler can be used alone or in combination of two or more kinds.

The average particle diameter of the conductive filler is a D ₅₀ average particle diameter, and from the viewpoint of ensuring sufficient conductivity, it is preferably 2 μm or more, more preferably 5 μm or more, and further preferably 7 μm or more. On the other hand, from the viewpoint of compatibility with the thinness of the adhesive layer, it is preferably 30 μm or less, more preferably 20 μm or less, and further preferably 15 μm or less. The D ₅₀ average particle diameter can be determined by a laser diffraction / scattering method particle size distribution measuring device or the like.

  The content of the conductive filler in the adhesive layer is preferably 35 to 90% by weight, more preferably 39 to 70% by weight, and further preferably 40 to 65% by weight. When the content is 35% by weight or more, the connection between the adhesive layer and the ground wiring becomes good, so that the high frequency shielding property and the cooling / heating cycle reliability are improved. On the other hand, when it is 90% by weight or less, solder reflow resistance and transmission characteristics are improved.

  The resin composition is a silane coupling agent, a rust preventive, a reducing agent, an antioxidant, a pigment, a dye, a tackifier resin, a plasticizer, and an ultraviolet absorber as optional components for the purpose of improving desired physical properties and imparting functions. Agents, defoamers, leveling adjusters, fillers, flame retardants, etc. can be added.

  The resin composition can be obtained by mixing the materials described above and stirring. For stirring, a known stirring device such as a Dispermat or a homogenizer can be used.

  A known method can be used for producing the adhesive layer. For example, a method of forming an adhesive layer by coating a resin composition on a peelable sheet and drying it, or extruding the resin composition into a sheet using an extruder such as a T-die. It can also be formed by.

  Examples of the coating method include gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, dip coating method. A known coating method such as a method can be used. It is preferable to perform a drying step during coating. In the drying step, a known drying device such as a hot air dryer or an infrared heater can be used.

  The thickness of the adhesive layer is not particularly limited, but is preferably smaller than Sz on the surface of the metal layer. When the thickness of the adhesive layer is smaller than Sz on the surface of the metal layer, when the electromagnetic wave shielding sheet is adhered to the printed wiring board, the tip of the metal layer unevenness easily comes into contact with the ground wiring. Among them, when the thickness of the adhesive layer is 1 to 20 μm, the thin film property, the adhesiveness to the base material, and the connection (contact) to the ground wiring can be compatible, which is particularly preferable.

《Protective layer》
The protective layer is located on the surface of the electromagnetic wave shielding wiring circuit board including the electromagnetic wave shielding sheet and the wiring circuit board, and the metal layer or the adhesive layer comes into contact with the cleaning chemicals when cleaning the electromagnetic wave shielding wiring circuit board. And has a function of blocking the electrical connection between the metal layer and the external conductor by coating the metal layer.

  The protective layer can be formed using a resin composition. The resin composition contains a binder resin. As the binder resin, either a thermoplastic resin, or a thermosetting resin and a curing agent can be used.

  The weight average molecular weight of the binder resin is preferably 10,000 or more. When the weight average molecular weight of the binder resin is 10,000 or more, decomposition and dissolution of the coating film when exposed to cleaning chemicals can be suppressed, and cleaning resistance is improved. The weight average molecular weight of the binder resin is more preferably 30,000 or more, further preferably 50,000 or more. Further, the weight average molecular weight of the binder resin is preferably 500,000 or less from the viewpoint of improving the compatibility and dispersibility with other components contained in the protective layer.

[Thermoplastic resin]
As the thermoplastic resin, polyolefin resin, vinyl resin, styrene / acrylic resin, diene resin, terpene resin, petroleum resin, cellulose resin, polyamide resin, polyurethane resin, polyester resin, polycarbonate resin, polyimide resin, liquid crystal Examples thereof include polymers and fluororesins. Although not particularly limited, a material having a low dielectric constant and a low dielectric loss tangent is preferable from the viewpoint of transmission loss, and a material having a low dielectric constant is preferable from the viewpoint of characteristic impedance, and examples thereof include a liquid crystal polymer and a fluorine resin.
The thermoplastic resins may be used alone or in combination of two or more.

[Thermosetting resin]
The thermosetting resin is a resin having a plurality of functional groups capable of reacting with the curing agent. Functional group, for example, hydroxyl group, phenolic hydroxyl group, methoxymethyl group, carboxyl group, amino group, epoxy group, oxetanyl group, oxazoline group, oxazine group, aziridine group, thiol group, isocyanate group, blocked isocyanate group, blocked Examples thereof include a carboxyl group and a silanol group. The thermosetting resin is, for example, acrylic resin, maleic acid resin, polybutadiene resin, polyester resin, polyurethane resin, polyurethane urea resin, epoxy resin, oxetane resin, phenoxy resin, polyimide resin, polyamide resin, polyamideimide resin, phenol resin. Known resins such as resins, alkyd resins, amino resins, polylactic acid resins, oxazoline resins, benzoxazine resins, silicone resins and fluororesins can be mentioned.
The thermosetting resins can be used alone or in combination of two or more.

  Among these, polyurethane resin, polyurethane urea resin, polyester resin, epoxy resin, phenoxy resin, polyimide resin, polyamide resin, and polyamideimide resin are preferable from the viewpoint of solder reflow resistance.

[Curing agent]
The curing agent has a plurality of functional groups capable of reacting with the functional group of the thermosetting resin. Examples of the curing agent include known compounds such as epoxy compounds, acid anhydride group-containing compounds, isocyanate compounds, aziridine compounds, amine compounds, phenol compounds and organometallic compounds.
The curing agents can be used alone or in combination of two or more.

  The curing agent is preferably contained in an amount of 1 to 50 parts by weight, more preferably 3 to 40 parts by weight, still more preferably 3 to 30 parts by weight, based on 100 parts by weight of the thermosetting resin.

  The thermoplastic resin and the thermosetting resin can be used alone or in combination of both.

[Non-conductive particles]
The protective layer preferably contains non-conductive particles. The non-conductive particles have the function of improving the insulating property of the protective layer, and also having the function of assisting the grounding of the metal layer and the ground wiring by pushing the metal layer during hot pressing.

  When the electromagnetic wave shield sheet is adhered to the printed wiring board, a heat press is mainly used. At the time of heat pressing, the electromagnetic wave shield sheet and the printed wiring board are pressed from above and below by the heat press board as shown in FIG. Receive pressure. At that time, the non-conductive particles 4 contained in the protective layer 3 receive the pressure from the hot press machine and transmit the pressure to the metal layer 2. As a result, the metal layer 2 is pushed into the adhesive layer 1 side, and finally contacts the ground wiring 5. Due to this action, the metal layer 2 and the ground wiring 5 are electrically connected, and the electromagnetic wave shield layer 12 can exhibit an excellent high-frequency shield property.

  Examples of the non-conductive particles include non-conductive ceramics, pigments, dyes and the like, and ceramics are preferable because they have high hardness and can transfer the pressure applied during hot pressing to the metal layer without relaxing.

Among the non-conductive particles, non-conductive particles having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more are preferable. When the volume resistivity of the non-conductive particles is 1.0 × 10 ¹⁰ Ω · cm or more, the insulating property of the protective layer can be further improved. The volume resistivity of the substance contained in the non-conductive particles is more preferably 1.0 × 10 ¹² Ω · cm or more, further preferably 1.0 × 10 ¹⁴ Ω · cm or more. Materials having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more include aluminum dioxide (alumina), zirconium dioxide (zirconia), silicon dioxide (silica), boron carbide, aluminum nitride, boron nitride, magnesium oxide (magnesia). , Titanium oxide, and other ceramics. Among them, a more preferable substance is zirconium dioxide (ZrO ₂ ; volume resistivity 1.0 × 10 ¹² Ω · cm), and a further preferable substance is silica (SiO ₂ ; volume). The resistivity is 1.0 × 10 ¹⁴ Ω · cm). The volume resistivity of the substance contained in the non-conductive particles can be measured according to JIS C2141.

  As the non-conductive particles, any shape can be used as long as it can realize the above-mentioned metal layer pushing mechanism, but it is preferably a lump, an irregular shape, a substantially spherical shape, a spherical shape, a true spherical shape. Is preferred. The non-conductive particles may be porous or may have voids inside as long as they can realize the above-described metal layer pushing mechanism.

The protective layer preferably contains 3 to 80% by weight of non-conductive particles. When the content of the non-conductive particles in the protective layer is 3% by weight or more, the insulating property is improved, and when it is 80% by weight or less, the film forming property is improved. The non-conductive particles contained in the protective layer are more preferably 10 to 60% by weight, and particularly preferably 20 to 40% by weight.
From the viewpoint of the insulating property of the protective layer, the content ratio of the non-conductive particles having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more is preferably 85 to 100 wt% in 100 wt% of the non-conductive particles.

The average particle size of the non-conductive particles is not particularly limited as long as the FI of the metal layer surface calculated by the formula (1) and the X calculated by the formula (2) can be set to desired values. The range of 1 to 50 μm is preferable because both high-frequency shielding property and insulating property can be realized. The thickness is more preferably 4 to 20 μm, still more preferably 6 to 14 μm.
The average particle diameter can be determined by a laser diffraction / scattering particle size distribution measuring device or the like.

  The ratio (average particle diameter / thickness) of the average particle diameter (μm) of the non-conductive particles to the protective layer thickness (μm) is preferably in the range of 1/4 to 1.5 / 1. When the ratio of the average particle diameter of the non-conductive particles to the thickness of the protective layer is in the range of 1/4 to 1.5 / 1, the high frequency shielding property and the insulating property are improved. When (average particle diameter / thickness) is 1.5 / 1 or less, non-conductive particles fly out from the protective layer to generate voids, and plating is performed via the voids, whereby the protective layer It is possible to suppress the formation of a metal layer that penetrates through, and improve the insulating property. On the other hand, when the (average particle size / thickness) is 1/4 or more, the effect of the non-conductive particles pushing in the metal layer during hot pressing becomes stronger, the connection with the ground wiring is improved, and the electromagnetic wave shielding property is improved. It is preferable because

The resin composition is a silane coupling agent, an anticorrosive agent, a reducing agent, an antioxidant, a tackifying resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling adjuster, a filler, and a flame retardant as optional components. Can be mixed.
Further, a pigment or the like other than the non-conductive particles can be added for the purpose of coloring the protective layer and enhancing the designability as long as the function as the protective layer is not hindered. Such pigments include carbon black, carbon graphite, carbon nanotubes, graphene and the like. It is preferable to add carbon black, carbon graphite, carbon nanotubes, graphene, etc. within the range of the addition amount at which a good evaluation of "practical" or higher is obtained in the insulation evaluation described later.

  The resin composition can be obtained by mixing the materials described above and stirring. For stirring, a known stirring device such as a Dispermat or a homogenizer can be used.

  A known method can be used for producing the protective layer. For example, a method of forming a protective layer by coating the resin composition on a peelable sheet and drying it, or extruding the resin composition into a sheet shape using an extruder such as a T-die. It can also be formed.

  Examples of the coating method include gravure coating method, kiss coating method, die coating method, lip coating method, comma coating method, blade method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, dip coating method. A known coating method such as a method can be used. It is preferable to perform a drying step during coating. In the drying step, a known drying device such as a hot air dryer or an infrared heater can be used.

  Further, as the protective layer, a film formed by molding an insulating resin such as polyester, polycarbonate, polyimide, polyamideimide, polyamide, polyphenylene sulfide, or polyether ether ketone can also be used.

  The thickness of the protective layer is preferably 2 to 20 μm. When the thickness of the protective layer is 2 to 20 μm, dissolution of the protective layer after exposure to cleaning chemicals and peeling from the metal layer can be suppressed.

  The electromagnetic wave shield sheet can include other functional layers in addition to the adhesive layer, the metal layer, and the protective layer. The other functional layer is a layer having a function such as hard coat property, water vapor barrier property, oxygen barrier property, thermal conductivity, low dielectric constant, high dielectric constant property or heat resistance.

  The electromagnetic wave shielding sheet of the present invention can be used in various applications where it is necessary to shield electromagnetic waves. For example, it can be used not only for flexible printed wiring boards, but also for rigid printed wiring boards, COFs, TABs, flexible connectors, liquid crystal displays, touch panels and the like. Further, it can also be used as a member for blocking electromagnetic waves of a case of a personal computer, a wall of a building material, a building glass such as a window glass, a vehicle, a ship, an aircraft and the like.

  The electromagnetic wave shield sheet of the present invention, when the thermoplastic resin is used as the binder resin in the adhesive layer, the contained thermoplastic resin exists in a solid state, and the thermoplastic resin is melted by the printed circuit board and hot press, and cooled. A desired adhesive strength can be obtained by solidifying again later.

  In the electromagnetic wave shielding sheet of the present invention, when a thermosetting resin is used as the binder resin in the adhesive layer, the contained thermosetting resin and curing agent are present in an uncured state (B stage), and the wiring circuit board and the heat By curing with a press (C stage), a desired adhesive strength can be obtained. The uncured state includes a semi-cured state in which a part of the curing agent is cured.

  The electromagnetic wave shield sheet is generally stored in a state in which a peelable sheet is attached to the adhesive layer and the protective layer in order to prevent foreign matter from adhering.

  The peelable sheet is a sheet obtained by subjecting a base material such as paper or plastic to a known peeling treatment.

<Electromagnetic wave shielding printed circuit board>
An electromagnetic wave shielding wired circuit board includes an electromagnetic wave shielding layer formed from the electromagnetic wave shielding sheet of the present invention, a cover coat layer, a circuit pattern having signal wiring and ground wiring, and a wiring circuit board having an insulating base material. .
The printed circuit board has a circuit pattern having a signal wiring and a ground wiring on the surface of an insulating base material, and protects the signal wiring and the ground wiring from insulation on the printed circuit board by at least one of the ground wiring. After forming a cover coat layer having a via in the part, and placing the adhesive layer surface of the electromagnetic wave shield sheet on the cover coat layer, the electromagnetic wave shield sheet is hot pressed to flow the adhesive layer inside the via. It can be manufactured by adhering it to the ground wiring.

An example of the electromagnetic wave shielding wired circuit board of the present invention will be described with reference to FIG.
The electromagnetic wave shield layer 12 is configured to include the adhesive layer 1, the metal layer 2, and the protective layer 3.

  The cover coat layer 8 is an insulating material that covers the signal wiring of the printed circuit board and protects it from the external environment. The cover coat layer is preferably a polyimide film with a thermosetting adhesive, a thermosetting or UV-curable solder resist, or a photosensitive coverlay film, and more preferably a photosensitive coverlay film for fine processing. For the cover coat layer, a known resin having heat resistance and flexibility such as polyimide is generally used. The thickness of the cover coat layer is usually about 10 to 100 μm.

  The circuit pattern includes a ground wiring 5 for grounding and a signal wiring 6 for sending an electric signal to an electronic component. Both are generally formed by etching a copper foil. The thickness of the circuit pattern is usually about 1 to 50 μm.

The insulating base material 9 is a support for a circuit pattern, and is preferably a bendable plastic such as polyester, polycarbonate, polyimide, polyphenylene sulfide, or liquid crystal polymer, and more preferably liquid crystal polymer or polyimide. Among these, a liquid crystal polymer having a low relative dielectric constant and a low dielectric loss tangent is more preferable in consideration of the use of a wired circuit board that transmits a high frequency signal.
When the printed circuit board is a rigid wiring board, the constituent material of the insulating base material is preferably glass epoxy. By providing such an insulating base material, the printed circuit board can have high heat resistance.

The hot pressing of the electromagnetic wave shield sheet 10 and the printed circuit board is generally performed under conditions of a temperature of about 150 to 190 ° C., a pressure of about 1 to 3 MPa, and a time of about 1 to 60 minutes. The adhesive layer 1 and the cover coat layer 8 are brought into close contact with each other by hot pressing. The thermosetting resin reacts and cures by the hot pressing, and becomes the electromagnetic wave shield layer 12.
In addition, in order to promote curing, post-curing may be performed at 150 to 190 ° C. for 30 to 90 minutes after hot pressing.

The opening area of the via 11 is preferably 0.8 mm ² or less, 0.008 mm ² or more. By setting the above range, the area of the ground wiring can be narrowed, and the printed wiring board can be downsized.
The shape of the via is not particularly limited, and any shape such as a circle, a square, a rectangle, a triangle, and an amorphous shape can be used according to the application.

  It is preferable that the electromagnetic wave shield layers are laminated on both surfaces of the printed circuit board, because leakage of electromagnetic waves can be suppressed more effectively. In addition, the electromagnetic wave shielding layer in the electromagnetic wave shielding wired circuit board of the present invention can be used as a ground circuit in addition to shielding electromagnetic waves, thereby omitting a part of the ground circuit and reducing the area of the printed circuit board. As a result, cost can be reduced and it can be incorporated in a narrow area in the housing.

  Further, the signal wiring is not particularly limited, and it can be used for either a single end including one signal wiring or a differential circuit including two signal wirings. preferable. On the other hand, when the circuit pattern area of the printed circuit board is limited and it is difficult to form the ground circuits in parallel, the ground circuit is not provided beside the signal circuit and the electromagnetic wave shield layer is used as the ground circuit. A printed wiring board structure having a ground in the thickness direction can also be used.

  The electromagnetic wave shielding wired circuit board of the present invention is preferably provided (mounted) in an electronic device such as a notebook PC, a mobile phone, a smartphone, a tablet terminal, etc., in addition to a liquid crystal display, a touch panel, etc.

  Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. In addition, "part" in the examples means "part by weight", and "%" means "% by weight".

  The acid value of the resin, the weight average molecular weight (Mw), the glass transition temperature (Tg), and the average particle diameters of the conductive filler and the non-conductive particles were measured by the following methods.

<< Measurement of acid value of binder resin >>
The acid value was measured according to JIS K0070. About 1 g of a sample is precisely weighed in a ground-in stopper Erlenmeyer flask, and 100 ml of a tetrahydrofuran / ethanol (volume ratio: tetrahydrofuran / ethanol = 2/1) mixed solution is added and dissolved. To this, phenolphthalein reagent solution was added as an indicator and titrated with a 0.1N alcoholic potassium hydroxide solution, and the end point was when the indicator held a pink color for 30 seconds. The acid value was calculated by the following formula (unit: mgKOH / g).
Acid value (mgKOH / g) = (5.611 × a × F) / S
However,
S: Amount of sample (g)
a: Consumption of 0.1N alcoholic potassium hydroxide solution (ml)
F: titer of 0.1N alcoholic potassium hydroxide solution

<< Measurement of weight average molecular weight (Mw) of binder resin >>
The weight average molecular weight (Mw) was measured by GPC (gel permeation chromatography) "HPC-8020" manufactured by Tosoh Corporation. GPC is a liquid chromatography in which a substance dissolved in a solvent (THF; tetrahydrofuran) is separated and quantified by the difference in its molecular size. The measurement in the present invention was performed by connecting two "LF-604" (Showa Denko KK: GPC column for rapid analysis: 6 mm ID x 150 mm size) in series to the column, using a flow rate of 0.6 ml / min and a column temperature. The weight average molecular weight (Mw) was determined at 40 ° C. in terms of polystyrene.

<Glass transition temperature (Tg) of binder resin>
The Tg was measured by differential scanning calorimetry (“DSC-1” manufactured by METTLER TOLEDO).

<< Measurement of average particle size of conductive filler and non-conductive particles >>
The D ₅₀ average particle diameter is a numerical value obtained by measuring the conductive filler and the non-conductive particles with a tornado dry powder sample module using a laser diffraction / scattering particle size distribution analyzer LS13320 (manufactured by Beckman Coulter, Inc.). And the cumulative value in the cumulative particle size distribution is a particle size of 50%. The refractive index was set to 1.6.

Then, the material used in the Example is shown below.
"material"
Binder resin 1: acid value 5 mg KOH / g, weight average molecular weight 54,000, Tg -5 ° C polyurethane urea resin (manufactured by Toyochem Co., Ltd.)
Binder resin 2: Polyurethane urea resin (manufactured by Toyochem) having an acid value of 5 mgKOH / g, a weight average molecular weight of 5,000 and a Tg of -14 ° C.
Binder resin 3: Polyurethane urea resin (manufactured by Toyochem Co., Ltd.) having an acid value of 5 mgKOH / g, a weight average molecular weight of 11,500 and a Tg of -11 ° C.
Binder resin 4: Polyurethane urea resin (manufactured by Toyochem) having an acid value of 5 mgKOH / g, a weight average molecular weight of 32,000 and a Tg of -9 ° C.
-Epoxy compound: "JER828" (bisphenol A type epoxy resin epoxy equivalent = 189 g / eq) manufactured by Mitsubishi Chemical Co.-Aziridine compound: "Chemite PZ-33" manufactured by Nippon Shokubai Co., Ltd.-Non-conductive particles 1: Sunsphere H-121
(D ₅₀ average particle diameter: 12.0 μm, SiO ₂ ; content ratio of volume resistivity 1.0 × 10 ¹⁴ Ω · cm 99%. AGC SITEC Co., Ltd.)
-Non-conductive particles 2: Sunsphere NP-100
(D ₅₀ average particle diameter: 8.0 μm, SiO ₂ ; volume resistivity 1.0 × 10 ¹⁴ Ω · cm content 99%. AGC SITEC Co., Ltd.)
-Non-conductive particles 3: Sunsphere H-51
(D ₅₀ average particle diameter: 5.0 μm, SiO ₂ ; content ratio of volume resistivity 1.0 × 10 ¹⁴ Ω · cm 99%. AGC SITEC Co., Ltd.)
・ Non-conductive particles 4: Sunsphere H-31
(D ₅₀ average particle diameter: 3.0 μm, SiO ₂ ; content ratio of volume resistivity 1.0 × 10 ¹⁴ Ω · cm 99%. AGC SITEC Co., Ltd.)
-Non-conductive particles 5: Sunsphere H-201
(D ₅₀ average particle diameter: 15.0 μm, SiO ₂ ; content ratio of volume resistivity 1.0 × 10 ¹⁴ Ω · cm 99%. AGC SITEC Co., Ltd.)
-Non-conductive particles 6: Zirconia beads NZ10SP
(D ₅₀ average particle diameter: 12.0 μm, ZrO ₂ ; content rate of volume resistivity 1.0 × 10 ¹² Ω · cm 88%. Manufactured by Niimi Sangyo Co., Ltd.)
-Non-conductive particles 7: GC # 1000
(D ₅₀ average particle size: 11.9 μm, SiC; content rate of volume resistivity 1.0 × 10 ⁶ Ω · cm 92%. Fujimi Incorporated)
Conductive filler: Composite fine particles (dendritic fine particles in which 10 parts by weight of silver is coated on 100 parts by weight of copper as a core) D ₅₀ Average particle diameter: 11.0 μm Fukuda Metal Foil & Powder Co., Ltd. Carrier material Attached Copper Foil A1: Electrolytic copper foil with a copper carrier having a thickness of 2.5 μm. An opening of 30 μmφ is formed by the etching process so that the opening ratio is 6.5%.

<Production of adhesive layer 1>
100 parts of binder resin 1, 10 parts of epoxy compound, and 0.5 part of aziridine compound are charged into a container in terms of solid content, and a mixed solvent (toluene: isopropyl alcohol = 2: 1 ( (Weight ratio)) was added and the mixture was stirred with a disper for 10 minutes to obtain a resin composition.

  The resin composition was coated on a peelable sheet with a bar coater to a dry thickness of 6.0 μm, and dried in an electric oven at 100 ° C. for 2 minutes to obtain an adhesive layer 1.

<Production of adhesive layer 2>
100 parts by weight of binder resin 1, 75 parts by weight of conductive filler, 10 parts by weight of epoxy compound and 0.5 parts by weight of aziridine compound in terms of solid content were charged into a container, and a mixed solvent (toluene: toluene: Isopropyl alcohol = 2: 1 (weight ratio)) was added and the mixture was stirred with a disper for 10 minutes to obtain a resin composition.

  An adhesive layer 2 was obtained by applying the resin composition on a peelable sheet with a bar coater to a dry thickness of 6 μm and drying it in an electric oven at 100 ° C. for 2 minutes.

[Example 1]
100 parts of the binder resin 1, 30 parts of the epoxy compound, 7.5 parts of the aziridine compound, and 31.4 parts of the non-conductive particles 1 are added in terms of solid content, and stirred for 10 minutes with a disper to obtain a resin composition 1. It was The resulting resin composition 1 was applied to a peelable sheet (thickness: 50 μm) using a bar coater so that the dry thickness was 11.5 μm, and dried for 2 minutes in an electric oven at 100 ° C. to form a protective layer. 1 was formed.

  Then, a copper plating layer (2.5 μm), which is a metal layer, was formed on the surface of the obtained “Release Sheet / Protective Layer 1” where the protective layer 1 was exposed. The copper plating layer was formed by an electrolytic plating method, the electrolytic solution used was copper sulfate, and current was applied at 25 ° C. for 7 minutes.

By bonding the adhesive layer 1 to the formed metal layer surface, an electromagnetic wave shield sheet composed of "peelable sheet / protective layer 1 / metal layer (plating layer) / adhesive layer 1 / peelable sheet" was obtained. The metal layer and the adhesive layer 1 were attached to each other at a temperature of 90 ° C. and a pressure of 3 kgf / cm ² with a heat laminator.

[Examples 2 to 17, and 21 to 23, Comparative Examples 1 and 2]
As shown in Tables 1 and 2, except that the types of the adhesive layer, the metal layer, and the protective layer were changed, the same procedure as in Example 1 was performed to obtain Examples 2 to 17, 21 to 23, and Comparative Example. The electromagnetic wave shield sheets 1 and 2 were obtained. When the FI on the surface of the metal layer after forming the copper plating layer was different from the target value, the FI was adjusted by appropriately buffing or polishing the surface.

[Example 18]
100 parts of the binder resin 1, 30 parts of the epoxy compound, 7.5 parts of the aziridine compound, and 31.4 parts of the non-conductive particles 1 are added in terms of solid content, and stirred for 10 minutes with a disper to obtain a resin composition 1. It was The resulting resin composition 1 was applied to a copper foil A1 with a carrier material using a bar coater so that the dry thickness was 11.5 μm, and dried for 2 minutes in an electric oven at 100 ° C. to form a protective layer 14. Then, a peelable sheet was attached to the protective layer 14.

Next, the carrier material of the carrier-added copper foil A1 was peeled off, the copper foil surface was buffed, and the FI of the copper foil surface was adjusted to the value shown in Table 2 to obtain a metal layer. By sticking the adhesive layer 1 on the surface of the metal layer after polishing, an electromagnetic wave shield sheet composed of "peelable sheet / protective layer 1 / metal layer (copper foil) / adhesive layer 1 / peelable sheet" was obtained. . The metal layer and the adhesive layer 1 were attached to each other at a temperature of 90 ° C. and a pressure of 3 kgf / cm ² with a heat laminator.

[Example 19]
100 parts of binder resin 1, 30 parts of epoxy compound, 7.5 parts of aziridine compound, 31.4 parts of non-conductive particles 1 are added in terms of solid content, and resin composition 1 is obtained by stirring for 10 minutes with a disper. It was The resulting resin composition 1 was applied to a peelable sheet (thickness: 50 μm) using a bar coater so that the dry thickness was 11.5 μm, and dried for 2 minutes in an electric oven at 100 ° C. to form a protective layer. 1 was formed.

  Next, a copper layer was formed on the exposed surface of the obtained "peelable sheet / protective layer 1" with the protective layer 1 exposed to form a metal layer.

By bonding the adhesive layer 1 to the formed metal layer surface, an electromagnetic wave shield sheet composed of "peelable sheet / protective layer 1 / metal layer (sputter layer) / adhesive layer 1 / peelable sheet" was obtained. The metal layer and the adhesive layer 1 were attached to each other at a temperature of 90 ° C. and a pressure of 3 kgf / cm ² with a heat laminator.

[Example 20]
100 parts of binder resin 1 in terms of solid content, 30 parts of epoxy compound, 7.5 parts of aziridine compound, 31.4 of non-conductive particles 1 were added, and a resin composition 1 was obtained by stirring for 10 minutes with a disper. . The resulting resin composition 1 was applied to a peelable sheet (thickness: 50 μm) using a bar coater so that the dry thickness was 11.5 μm, and dried for 2 minutes in an electric oven at 100 ° C. to form a protective layer. 1 was formed.

  Next, a copper vapor deposition process was performed on the exposed surface of the protective layer 1 of the obtained “peelable sheet / protective layer 1” to form a metal layer.

By bonding the adhesive layer 1 to the formed metal layer 1 side, an electromagnetic wave shield sheet composed of "peelable sheet / protective layer 1 / metal layer (deposition layer) / adhesive layer 1 / peelable sheet" was obtained. . The metal layer and the adhesive layer 1 were attached to each other at a temperature of 90 ° C. and a pressure of 3 kgf / cm ² with a heat laminator.

  Regarding the obtained electromagnetic wave shielding sheet, the thickness of each layer and the FI of the metal layer were measured by the following methods.

<< Measurement of thickness of each layer >>
The thicknesses of the adhesive layer, metal layer, and protective layer of the electromagnetic wave shield sheet were measured by the following method.
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet was peeled off, the exposed adhesive layer and the polyimide film (“Kapton 200EN” manufactured by Toray-Dupont Co., Ltd.) were bonded together, and hot pressed for 30 minutes at 2 MPa and 170 ° C. . After cutting this into a size of about 5 mm in width and 5 mm in length, 0.05 g of epoxy resin (Petropoxy 154, manufactured by Maltaux Co.) was dropped on a slide glass, and an electromagnetic wave shield sheet was adhered to the slide glass / electromagnetic wave shield. A laminate having a sheet / polyimide film structure was obtained. The obtained laminate was cut and processed from the polyimide film side by ion beam irradiation using a cross section polisher (SM-09010 manufactured by JEOL Ltd.) to obtain a measurement sample of an electromagnetic wave shield sheet after hot pressing.

  The thickness of each layer was measured from the observed enlarged image of the cross section of the obtained measurement sample using a laser microscope (VK-X100, manufactured by Keyence Corporation). The magnification was 500 to 2000 times. With respect to the thickness T of the protective layer, the perpendicular distance passing through one point of the protective layer closest to the adhesive layer from the outermost surface of the protective layer of the electromagnetic wave shielding sheet in the enlarged image as T was taken as T.

<< Measurement of FI >>
The FI of the metal layer of the electromagnetic wave shield sheet was measured by the following method.
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet was peeled off, and the exposed adhesive layer was washed off with acetone to expose the metal layer. The adhesive layer was removed, and the surface of the exposed metal layer was measured for L ^* _{15 °} , L ^* _{45 °} , and L ^* _{110 °} using a multi-angle colorimeter (BYK-made, BYK-mac i23 mm measurement aperture). Then, the FI was calculated based on the equation (1). In addition, the measurement was performed by arranging the multi-angle colorimeter so that the major axis direction of the multi-angle colorimeter and the MD direction of the electromagnetic wave shield sheet were aligned. The MD direction refers to the coating direction when applying the resin composition. The measurement was performed under the conditions of a light source of D50 and a visual field of 2 °.

<< Measurement of Sz >>
The maximum height Sz of the metal layer of the electromagnetic wave shield sheet was measured by the following method.
The peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet was peeled off, and the exposed adhesive layer was washed off with acetone to expose the metal layer. The adhesive layer was removed, and the exposed surface of the metal layer was subjected to measurement data acquisition using a laser microscope (VK-X100, manufactured by Keyence Corporation) (objective lens magnification: 50 times). The acquired measurement data was loaded into analysis software (analysis application "VK-H1XA" equipped with ISO 25178 surface texture measurement module "VK-H1XR", both manufactured by KEYENCE CORPORATION), and ISO25178 surface texture measurement was executed (conditions: S-filter; 1 μm, L-filter; 0.2 mm). In one measurement visual field, measurement is performed in five areas, and similar measurement is performed in five visual fields by changing the measurement visual field. The average value of the measurement data of 25 areas in total was taken as the maximum height Sz of the metal layer. For the metal layer having an opening on the surface, the opening was excluded from the measurement range when ISO 25178 surface texture measurement was performed.

  The obtained electromagnetic wave shielding sheet was evaluated for cleaning resistance, high frequency shielding property, and insulating property by the following methods.

<Washing resistance>
The peelable sheet on the adhesive layer side of the electromagnetic wave shielding sheet having a width of 40 mm and a length of 40 mm is peeled off, and the exposed adhesive layer is pressure-bonded with Kapton 500H having a width of 50 mm and a length of 50 mm at 170 ° C., 2.0 MPa, and 30 minutes. Then, it was heat-cured to obtain a sample. On the protective layer side of the electromagnetic shielding sheet of the obtained sample, a cross-cut guide was used according to JIS K5400, and 100 cross-cuts having an interval of 1 mm were produced. Then, it is immersed in a solvent type cleaning liquid "Zestoron FA +" (manufactured by Zestoron) for 20 minutes, and an ultrasonic cleaning machine "UT-205HS" (manufactured by SHARP) is used to set the output to 100% and perform ultrasonic treatment for 2 minutes. After that, the sample was taken out, washed with distilled water and then dried. The cleaning solution was changed to "10% by weight hydrochloric acid aqueous solution", "10% by weight aqueous sodium hydroxide solution", "Pine Alpha ST-100S (manufactured by Arakawa Chemical Co., Ltd.)", and compared to the newly prepared cross-cut test piece. The process of sonication to cleaning was performed. The adhesive tape was strongly pressure-bonded to the cross section of each test piece, the end of the tape was peeled off at an angle of 45 °, and judgment was made based on the number of peeled cross sections and the state of the cross section according to the following criteria.

⊚: All the test pieces have less than 5 cross-cuts. Very good.
◯: In all the test pieces, the number of cross-cuts was 5 or more and less than 15. Good.
Δ: In any of the test pieces, the number of peeled grids was 15 or more and less than 35. Practical is possible.
X: The number of peeled grids in any one of the test pieces was 35 or more. Not practical.

<High frequency shielding>
The high frequency shielding property is based on ASTM D4935, and the coaxial tube type shield effect measurement system manufactured by Keycom is used to irradiate the electromagnetic wave under the condition of 100 MHz to 15 GHz, and the attenuation amount of the electromagnetic wave which is attenuated by the electromagnetic wave shielding sheet is measured. However, the notation is made according to the following criteria. The measured value of the attenuation amount is decibel (unit: dB).

⊚: The amount of attenuation when irradiated with an electromagnetic wave of 15 GHz is less than −55 dB, which is extremely good.
◯: Attenuation amount at the time of electromagnetic wave irradiation of 15 GHz is −55 dB or more and less than −50 dB, which is good.
Δ: Attenuation amount at the time of electromagnetic wave irradiation of 15 GHz is −50 dB or more and less than −45 dB, which is practical.
X: Attenuation amount at the time of electromagnetic wave irradiation of 15 GHz is -45 dB or more, which is not practical.

<Insulation>
Peel off the peelable sheet on the adhesive layer side of the electromagnetic wave shield sheet with a width of 50 mm and a length of 100 mm, and press-bond the exposed adhesive layer and Kapton 300H with a width of 70 mm and a length of 120 mm at 170 ° C., 2.0 MPa, and 30 minutes. Then, it was heat-cured to obtain a test piece. The surface resistance value of the insulating layer of the test piece was measured using a ring probe URS of "HIRESTA UP MCP-HT800" manufactured by Mitsubishi Chemical Analytech. The evaluation criteria are as follows.

⊚: 1.0 × 10 ⁹ Ω / □ or more Very good.
◯: 1.0 × 10 ⁷ Ω / □ or more, less than 1.0 × 10 ⁹ Ω / □, good.
Δ: 1.0 × 10 ⁵ Ω / □ or more but less than 1.0 × 10 ⁷ Ω / □ Practically acceptable.
×: Less than 1.0 × 10 ⁵ Ω / □ Practical use is not possible.

1 Adhesive Layer 2 Metal Layer 3 Protective Layer 4 Non-Conductive Particles 5 Ground Wiring 6 Signal Wiring 7 Electromagnetic Wave Shielding Wiring Circuit Board 8 Cover Coat Layer 9 Insulating Substrate 10 Electromagnetic Wave Shielding Sheet 11 Via 12 Electromagnetic Wave Shielding Layer 13 Heat Press Plate 14 Peelable sheet

Claims (5)

An adhesive layer, a metal layer, a laminate having a protective layer in this order,
The interface of the metal layer in contact with the adhesive layer has a Flop Index (FI) calculated by the formula (1) of 50 or less and X represented by the formula (2) of less than 1.0. Electromagnetic wave shield sheet.

(L ^* _{15 °} , L ^* _{45 °} , and L ^* _{110 °} are offset angles from the specular reflection light of the light incident at an angle of 45 ° with respect to the normal direction of the interface between the metal layer in contact with the adhesive layer. 15 °, 45 °, which is a 110 ° ^{L * a} * ^b * color system defined by JIS Z8729 of ^{L *.)}

(Sz is the maximum height of the metal layer determined according to ISO 25178, and T is the thickness of the protective layer.)   The electromagnetic wave shield sheet according to claim 1, wherein the metal layer has a thickness of 0.3 to 10 µm. The electromagnetic wave shielding sheet according to claim 1, wherein the protective layer contains non-conductive particles having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more.   The electromagnetic wave shield sheet according to any one of claims 1 to 3, wherein the protective layer contains a binder resin having a weight average molecular weight of 10,000 or more. An electromagnetic wave shielding wiring comprising: an electromagnetic wave shielding layer formed from the electromagnetic wave shielding sheet according to claim 1; a cover coat layer; and a wiring board having a signal wiring and an insulating base material. Circuit board.