TW201819183A - Electromagnetic wave shielding material - Google Patents

Abstract

An electromagnetic wave shielding material is provided, capable of realizing excellent followability to a high level difference. An electromagnetic wave shielding material is provided, characterized in that a conductive paste layer 13 and a conductive adhesion layer 14 are laminated in this order in the direction of the thickness of a substrate 11 on one side of the substrate 11, wherein the substrate 11 is made of a dielectric resin film, and the tensile elongation of the substrate 11 is 100% or more.

Description

   Electromagnetic wave shielding material   

The present invention relates to an electromagnetic wave shielding material that can be used for electromagnetic wave shielding of a printed circuit board or the like.

In portable electronic devices such as mobile phones, printed circuit boards on which electronic components are accumulated are widely used. In addition, in order to prevent malfunction of electronic equipment caused by the influence of electromagnetic wave noise, an electromagnetic wave shielding material is used.

For example, Patent Document 1 describes an electromagnetic wave shielding sheet, which is an electromagnetic wave shielding sheet including an insulating layer, a conductive layer, and an adhesive layer. The conductive layer contains a resin and a conductive filler. The surface resistance is 100 mΩ / □ or less. The electrical conductivity is It is 1 × 10 ⁶ S / m or more.

In addition, Patent Document 2 describes an electromagnetic wave shielding film including a metal layer having a layer thickness of 0.5 to 12 μm and a conductive anisotropic adhesive layer in a laminated state.

[Prior Art Literature]

[Patent Literature]

Patent Document 1: Japanese Patent Application Laid-Open No. 2015-138813

Patent Document 2: Japanese Patent Application Laid-Open No. 2015-109449

As the printed substrate, a rigid rigid substrate with an insulating substrate, a flexible flexible substrate with a flexible substrate, and a rigid flexible substrate (rigid-flexible substrate) including a flexible portion and a rigid portion are known. In the case where there is a high level difference such as a boundary portion of a portion with a different substrate thickness, when the electromagnetic wave shielding material is adhered to the printed substrate, if the electromagnetic wave shielding material does not sufficiently follow the level difference of the printed substrate, a gap is generated at the level difference. There are problems such as electromagnetic wave intrusion or leakage, water intrusion, and dust adhesion. If the electromagnetic wave shielding material is forced to follow the step, the electromagnetic wave shielding characteristics may be deteriorated due to breakage or damage of the conductive layer constituting the electromagnetic wave shielding material.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an electromagnetic wave shielding material that is excellent in followability even with a high level difference.

In order to solve the above-mentioned problem, the present invention provides an electromagnetic wave shielding material, characterized in that a conductive paste is sequentially laminated on one side of a substrate formed of a dielectric resin film along a thickness direction of the substrate Layer and the conductive adhesive layer, the tensile elongation of the substrate is 100% or more.

The conductive paste layer preferably contains silver nano particles having a particle diameter of less than 1 μm.

The tensile elongation of the substrate is preferably 100% or more and 300% or less.

The substrate is preferably formed of a solvent-soluble polyfluoreneimide film.

The substrate is preferably formed of a polyfluoreneimide film, which is formed using a polyfluoreneimide material having aromatic units having 3 or more carbon atoms between aromatic units.

The thickness of the conductive adhesive layer is preferably 15 μm or less.

The conductive adhesive layer is preferably a conductive anisotropic adhesive layer.

The conductive adhesive layer preferably contains polyurethane.

The total thickness from the substrate to the conductive adhesive layer is preferably 6 μm to 20 μm.

The substrate is preferably supported on a surface opposite to a side on which the conductive paste layer and the conductive adhesive layer are laminated by a support film that can be peeled from the substrate.

The present invention also provides a mobile phone including the electromagnetic wave shielding material.

The present invention also provides an electronic device including the electromagnetic wave shielding material.

According to the electromagnetic wave shielding material of the present invention, it is possible to provide an electromagnetic wave shielding material which is excellent in followability even with a high level difference.

10‧‧‧Electromagnetic wave shielding material

11‧‧‧ Substrate

12‧‧‧ Anchor layer

13‧‧‧ conductive paste layer

14‧‧‧ conductive adhesive layer

20‧‧‧Layer of electromagnetic wave shielding material

21‧‧‧ support body membrane

22‧‧‧ peeling film

30‧‧‧ Detection substrate

31‧‧‧Terminal

32‧‧‧ Flexible substrate section

33‧‧‧Hard substrate department

FIG. 1 is a schematic cross-sectional view showing an example of an electromagnetic wave shielding material of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a method for evaluating a step difference followability in an example.

Hereinafter, preferred embodiments of the present invention will be described.

A schematic cross-sectional view of the electromagnetic wave shielding material of the present embodiment is shown in FIG. 1. This electromagnetic wave shielding material 10 has a structure in which a conductive paste layer 13 and a conductive adhesive layer are sequentially laminated on one surface of a substrate 11 formed of a dielectric resin film along the thickness direction of the substrate.接 剂 层 14。 Connection layer 14. When the electromagnetic wave shielding material 10 is adhered to a printed circuit board or the like as an adherend, since the outer surface is the dielectric base material 11, it is not necessary to further provide an electrically insulating coating material on the outer surface.

(Base material)

The base material 11 is an insulating layer formed of a dielectric resin film. Examples of the resin film constituting the base material 11 include a polyimide resin film, a polyester resin film, and a polyimide resin film. When the base material 11 is formed of a polyimide resin film, it has high mechanical strength, heat resistance, insulation, and solvent resistance, which are characteristics of a polyimide resin, and is chemically stable until it reaches about 260 ° C. Yes, it is suitable.

Examples of the polyimide include a thermosetting polyimide produced in a dehydration condensation reaction by heating a polyamic acid, and a non-dehydration condensation type solvent-soluble solvent-soluble polymer.醯 imine. As a method for producing a polyimide film, a generally known method is as follows: A diamine and a carboxylic dianhydride are reacted in a polar solvent to synthesize a polyimide acid as a precursor of the imine, and heat is used. Or the catalyst dehydrates and cyclizes the polyamidic acid to make the corresponding polyimide. However, it is preferable that the heat treatment temperature in the step of imidization is in a temperature range of 200 ° C to 300 ° C. When the heating temperature is lower than this temperature, fluorene imidization may not proceed, which is not preferable. In the case where the heating temperature is higher than the above temperature, thermal decomposition of the compound may occur, which is not preferable.

In order to further improve the flexibility of the substrate 11, an extremely thin polyimide film having a thickness of less than 10 m is preferred. When a thin polyimide film is laminated on one surface of the support film 21 to form the substrate 11, the polyimide film itself is easy to be transported continuously along the longitudinal direction even if the mechanical strength of the polyimide film is low, which is preferable of. As the support film 21, a resin film for general use, such as a polyethylene terephthalate (PET) resin film, is preferred from the viewpoint of both price and heat-resistant temperature performance. However, the heat-resistant temperature of PET is not as high as that of polyimide, so it is impossible to adopt a method of coating the imine precursor on PET and the imidization of polyimide.

The solvent-soluble polyfluorene imine has a polyfluorene imine-imidization and is soluble in a solvent. Therefore, after coating a coating liquid obtained by dissolving the polyfluorene in a solvent, the temperature can be lower than 200 ° C. The film is formed by evaporating the solvent at a low temperature. Therefore, in the case where the substrate 11 is formed of a solvent-soluble polyimide film, a thin-film resin film of a polyimide film can be formed by the following method, which is applying on one side of the support film 21 After being a non-dehydration condensation type solvent-soluble polyfluorene imide coating liquid, it is dried at a heating temperature of less than 200 ° C. In addition, the anchor layer 12, the conductive paste layer 13, the conductive adhesive layer 14, and the like can be continuously formed on one side of the support body film 21 while the same support body film 21 is conveyed in the longitudinal direction. Thereby, the electromagnetic wave shielding material 10 can also be produced in a roll-to-roll manner, which is excellent in processability and productivity.

The non-dehydration-condensation type solvent-soluble polyfluorene imide used for the substrate 11 is not particularly limited, and a commercially available coating solution of a solvent-soluble polyfluorene imine can be used. Specific examples of commercially available solvent-soluble polyimide coating solutions include Solpit 6,6-PI (Solpit Industries, Ltd.), Q-IP-0895D (PI R & D Co., LTD), and PIQ (Hitachi). Chemical Industry), SPI-200N (Nippon Steel Chemical), RIKACOAT SN-20, RIKACOAT PN-20 (Nippon Physico Chemical), etc. The method for applying the solvent-soluble polyamine coating solution to the support film 21 is not particularly limited. For example, a die coater, a blade coater, a lip coater, or the like can be used. The coating machine performs coating.

The thickness of the substrate 11 (for example, the thickness of the polyimide film) is preferably 1 μm to 9 μm. When the polyfluorene imide film is made into a film having a thickness of less than 0.8 μm, the mechanical strength of the produced film is weak, and therefore it is technically difficult. In addition, if the thickness of the substrate 11 exceeds 10 μm, it is difficult to obtain the electromagnetic shielding material 10 that is thin and has excellent step-followability. Moreover, when the thickness of the base material 11 is thinner than about 7 micrometers, it is difficult to adjust the tension at the time of being wound by a roll. Therefore, it is preferable to form a base 11 by laminating a thin polyimide film on one surface of the support film 21. Alternatively, it is preferable to form the conductive adhesive layer 14, the conductive paste layer 13, the anchor layer 12, and the like on the release film 22 in advance, and then further form the base material 11.

When the support body film 21 is not used and the base material 11 formed of only a thin polyimide film is used, the thickness is preferably about 1 μm to 9 μm.

In addition, in order to improve the followability of the step to the printed circuit board as an adherend, the base material 11 of the present embodiment preferably has a high tensile elongation. The tensile elongation of the base material 11 is preferably 100% or more. The upper limit of the tensile elongation of the substrate 11 is not particularly limited, and may be 300% or less. The elastic modulus of the base material 11 is preferably 1.0 GPa or more and 2.5 GPa or less. When the base 11 having a high tensile elongation is formed of a polyimide film, for example, it is preferably formed using a polyimide material having aromatic units having 3 or more carbon atoms between aromatic units. Polyimide film. Furthermore, the aliphatic unit preferably contains a polyalkyleneoxy group having an alkylene group having about 1 to 10 carbon atoms.

Moreover, it is preferable that the water vapor transmission rate of the polyimide film used for the base material 11 of this embodiment is 500 g / m ² ‧ days or more. In the case where the water vapor transmission rate is less than 500 g / m ² ‧ days, after the printed circuit board is covered with the electromagnetic wave shielding material 10, in the heating step such as solder reflow, the residual solvent from each layer or the outgassing of the adhesive outgas), water vapor generated by rapid heating of water in the film, etc., peeling may occur between layers. There is no particular upper limit for the water vapor transmission rate, but as long as the same material is used, the water vapor transmission rate is inversely proportional to the thickness. Therefore, when the thickness is reduced and the water vapor transmission rate is increased, it is preferably within the above-mentioned thickness range.

(Support body membrane)

When the electromagnetic wave shielding material 10 is used, the support film 21 can be peeled from the base material 11. Examples of the base material of the support film 21 include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; Polyolefin film such as propylene and polyethylene. The thickness of the support film 21 is not particularly limited to the entire thickness of the electromagnetic wave shielding material 10 when it is used by being coated on a printed circuit board, and is not particularly limited, but is usually about 12 μm to 150 μm.

When the base material of the support body film 21 is, for example, a base material such as polyethylene terephthalate (PET) itself has a certain degree of releasability, the support body film 21 may not be subjected to a peeling treatment. The substrate 11 formed of the applied dielectric thin film resin film is directly laminated, and a peeling treatment may be performed on the surface of the support film 21 in order to make the substrate 11 easier to peel. In addition, when the base material of the support film 21 does not have releasability, a peeling treatment may be performed by applying a release agent such as an amino alkyd resin or a silicone resin, followed by heating and drying. . The release agent applied to the support film 21 preferably does not use a silicone resin. When a silicone resin is used as a release agent, a part of the silicone resin is transferred to the surface of the base material 11 which is in contact with the surface of the support film 21, and the silicone resin is transferred to the conductive adhesive through the inside of the electromagnetic shielding material 10 The surface of the adhesive layer 14 may weaken the adhesive force of the conductive adhesive layer 14.

(Anchor layer)

In the electromagnetic wave shielding material 10 of the present embodiment, in order to improve the adhesion between the substrate 11 and the conductive paste layer 13, the anchor layer 12 may be used. The anchor layer 12 is an adhesive layer of a thin film which adheres the base material 11 and the conductive paste layer 13. When the adhesiveness between the conductive paste layer 13 and the substrate 11 is sufficient, the anchor layer 12 may be omitted. In the case where the conductive paste layer 13 is formed by applying and heating the conductive paste on the anchor layer 12, it is necessary to use an adhesive resin having excellent heat resistance as the material of the anchor layer 12.

Preferred examples of the adhesive resin used for the anchor layer 12 include thermoplastic resins such as polyester resins, polyurethane resins, (meth) acrylic resins, polyethylene resins, polystyrene resins, and polyamide resins; epoxy resins; Thermosetting resins such as resins, amine-based resins, polyimide resins, and (meth) acrylic resins. As the adhesive resin of the anchor layer 12, an adhesive resin composition in which a polyester resin composition having an epoxy group is crosslinked is particularly preferable; or a polyurethane resin is mixed as a curing agent. Adhesive resin composition of epoxy resin and the like. Therefore, the anchor layer 12 has harder physical properties than the substrate 11 formed of a thin film of a polyimide film. The polyester resin composition having an epoxy group is not particularly limited. For example, an epoxy resin (its uncured resin) having two or more epoxy groups in one molecule and two or more carboxyl groups in one molecule can be used. Obtained by the reaction of a polycarboxylic acid. For the crosslinking of the epoxy-based polyester resin composition, a crosslinking agent for an epoxy resin that reacts with an epoxy group can be used.

The thickness of the anchor layer 12 is preferably about 0.05 μm to 1 μm. With such a film thickness, a sufficient adhesive force with the conductive paste layer 13 can be obtained. When the thickness of the anchor layer 12 is 0.05 μm or less, the adhesion between the substrate 11 and the conductive paste layer 13 may decrease. In addition, if the thickness of the anchor layer 12 exceeds 1 μm, the cost increases, which is not preferable.

(Conductive paste layer)

For the formation of the conductive paste layer 13, a conductive paste in which a conductive filler is mixed in a resin composition serving as a binder is used. The conductive paste preferably contains one or more selected from the group of conductive fillers consisting of conductive metal fine particles, carbon nanotubes, and carbon fibers, and a binder resin composition. As the conductive metal fine particles, fine metal powders such as copper, silver, nickel, and aluminum are used. However, from the viewpoint of high conductivity and low price, it is preferable to use fine powders of copper or silver or nano particles having a particle size of less than 1 μm (copper nano Rice particles, silver nano particles, etc.). In addition, carbon nanotubes and carbon nanofibers which are carbon nanoparticle having conductivity can also be used. The volume resistivity of the conductive paste layer 13 after firing is preferably 1.5 × 10 ^-5 Ω · cm or less. The surface resistivity of the conductive paste layer 13 after firing is preferably 0.3 Ω / □ or less.

In order to suppress the firing temperature of the conductive paste to a low temperature in a temperature range of 150 ° C to 250 ° C, the average particle diameter of the metal fine particles is preferably in a range of 1 nm to 120 nm, and more preferably in a range of 1 nm to 100 nm. By including such metal fine particles in the conductive paste layer 13, not only can a thin film be formed, but also the fine particles can be melt-bonded with each other, and the electrical conductivity can be improved at the same time. In addition, by covering the surface of the metal fine particles with an organic molecular layer, the dispersibility in a solvent can be improved. In the heating and firing step of the conductive paste, the metal particles are brought into contact with each other on the surface, so that the conductive paste layer 13 exhibits conductivity.

The conductive paste is heated and fired. For example, by heating to about 150 ° C to 250 ° C, the organic molecular layer on the surface of the coated metal particles is detached and evaporated to remove it. Therefore, the firing temperature is preferably at the Boiling point range.

When the conductive paste is fired, when the support film 21 or the release film 22 is used, in order to suppress the thermal degradation of these resin films, the firing temperature is preferably lower, and preferably 150 ° C to 180 °. ℃.

As the binder resin composition to be used in combination with a conductive filler in a conductive paste, polyester resin, (meth) acrylic resin, polyethylene resin, polystyrene resin, polyamide resin, and the like are preferably exemplified. Thermoplastic resin; thermosetting resin such as epoxy resin, amine-based resin, polyimide resin, (meth) acrylic resin.

For the conductive paste, conductive adhesives such as conductive metal particles, carbon nanotubes, and carbon nanofibers are mixed into these binder resin compositions, and an organic solvent such as alcohol or ether may be added to adjust the viscosity as required. The viscosity can be adjusted by the addition amount (mixing ratio) of the organic solvent. When an adhesive resin composition is mixed with a conductive paste, when an electromagnetic wave shielding material for FPC is adhered to a step, the crack can be prevented and the conductivity can be prevented from being impaired even when stretched.

The thickness of the conductive paste layer 13 after firing is preferably about 0.1 μm to 2 μm, and more preferably about 0.3 μm to 1 μm. When the thickness of the conductive paste layer 13 after firing is thinner than 0.1 m, it is difficult to obtain high electromagnetic wave shielding performance. On the other hand, if the thickness of the conductive paste layer 13 after firing is thicker than 2 μm, the cost increases, which is not preferable.

(Conductive adhesive layer)

The conductive adhesive layer 14 is an adhesive layer for attaching the electromagnetic wave shielding material 10 to an adherend such as a printed circuit board. The conductive adhesive layer 14 is preferably a thermosetting adhesive layer by heating and pressing, rather than an adhesive layer that exhibits pressure-sensitive adhesiveness at ordinary temperature. Thereby, even when a printed circuit board is bent repeatedly, it is hard to reduce adhesive force.

Examples of the thermosetting adhesive used for the conductive adhesive layer 14 include an acrylic adhesive, a polyurethane adhesive, an epoxy adhesive, a rubber adhesive, and a silicone adhesive. A thermosetting adhesive generally used for adhesives and the like. In addition, it is preferable to use a thermosetting adhesive having flame retardance by mixing a flame retardant such as a phosphorus-based or bromine-based flame retardant, and the like is not particularly limited. It is also possible to use a urethane resin as a thermosetting adhesive. The urethane resin is a polyol compound or a polyisocyanate compound using a phosphorus-containing compound as a raw material for polyurethane, and the molecular structure of the resin contains phosphorus. The thermosetting conductive adhesive layer 14 preferably contains a phosphorus-containing polyurethane resin composition and an epoxy resin.

The conductive fine particles to be mixed in the conductive adhesive layer 14 are not particularly limited, and conventionally known conductive fine particles can be applied. Examples include: carbon black; metal fine particles made of metals such as silver, nickel, copper, and aluminum; and composite metal fine particles coated with other metals on the surface of these metal fine particles. One or two of these may be appropriately selected. Used above.

In the above-mentioned conductive adhesive, the conductive fine particles exhibit electrical conductivity by contacting the conductive fine particles with each other and by contacting the conductive fine particles with the conductive paste layer and the printed circuit board as an adherend. Therefore, if a large amount of a conductive substance is contained, excellent conductivity can be obtained, but the adhesion force is reduced. If the content of the conductive substance is decreased, the adhesion force is increased, but the conductivity is reduced. This has the opposite problem. Therefore, the compounding amount of the conductive fine particles is usually about 10 to 100 parts by weight, and more preferably 30 to 80 parts by weight, based on 100 parts by weight of the adhesive (solid content).

As the conductive adhesive constituting the conductive adhesive layer 14, a conductive anisotropic adhesive containing conductive fine particles is preferred. As this conductive anisotropic adhesive, a known substance can be used. For example, an adhesive containing an insulating thermosetting resin such as epoxy resin as a main component and dispersed with conductive fine particles can be used. Examples of the conductive fine particles used in the conductive anisotropic adhesive include, for example, one or two or more kinds of metal fine particles such as gold, silver, zinc, tin, and solder; or metal-coated ones. Resin particles. The shape of the conductive fine particles is preferably dendritic or acicular. With such a shape, when a printed circuit board to be adhered is heated and pressurized by a crimping member, conductive particles can be bite into the conductor wiring of the printed circuit board with a low applied pressure, thereby reducing the conductive anisotropy Resistance between the anisotropic adhesive layer and the conductor wiring.

The adhesive force of the conductive adhesive is not particularly limited, and the measurement method is based on the test method described in JIS Z 0237. Under conditions of a peeling angle of 180 degrees and a peeling speed of 300 mm / minute, the adhesion force to the surface of the adherend is preferably in a range of 5 N / inch to 30 N / inch. When the adhesive force is less than 5 N / inch, for example, the electromagnetic wave shielding material 10 adhered to the printed circuit board may peel off or float. There are no particular restrictions on the conditions for the heat and pressure bonding of the printed substrate. For example, it is preferable to perform the hot pressing for 60 minutes at a temperature of 160 ° C. and a pressure of 4.5 MPa.

The thickness of the conductive adhesive layer 14 is preferably 15 μm or less. Thereby, the total thickness of the electromagnetic wave shielding material 10 including the thickness of the conductive adhesive layer 14 becomes thin, and the step followability improves. If the thickness of the conductive adhesive layer 14 is greater than 15 μm, it is not possible to cope with the reduction in thickness of information terminals in recent years, and the cost is increased, which is not preferable.

(Light absorbent)

In order to impart light-shielding properties to the electromagnetic wave shielding material 10, a light absorber may be included in any of the layers constituting the electromagnetic wave shielding material 10 other than the support film 21 and the release film 22. Examples of the layer capable of containing a light absorber for this purpose include, for example, one or two or more of the substrate 11, the anchor layer 12, the conductive paste layer 13, and the conductive adhesive layer 14. Examples of the light absorber include one or more selected from the group consisting of non-conductive carbon black, graphite, aniline black, cyanine black, titanium black, black iron oxide, chromium oxide, and manganese oxide. Black pigment or color pigment. In order to improve the appearance in a state where the electromagnetic wave shielding material 10 is adhered to an adherend such as a printed circuit board, it is preferable that one or both of the base material 11 and the anchor layer 12 that become the outside of the electromagnetic wave shielding material 10 contain a light absorber.

After the support film 21 and the release film 22 are removed, the light transmittance of the electromagnetic wave shielding material 10 is preferably 5% or less. Examples of the light transmittance include visible light transmittance and total light transmittance. When the base material 11 is formed of a solvent-soluble polyfluorene imide film, the base material 11 may contain a light absorber.

In order to effectively reduce the light transmittance, among light absorbers, black pigments such as carbon black are preferred. The light absorber formed of a black pigment or a colored pigment is preferably contained in any layer in an amount of 0.1% to 30% by weight. The black pigment or the colored pigment preferably has an average particle diameter of the primary particles observed by SEM of about 0.02 μm to 0.1 μm. The thickness of the light-absorbing agent-containing layer is preferably larger than the particle diameter of the light-absorbing agent so that the fine particles of the light-absorbing agent are not exposed. In addition, as the black pigment, silicon dioxide particles or the like may be immersed in a black colorant so that only the surface layer portion is black, or it may be formed of a black coloring resin or the like so that the entirety is made of black. In addition, the black pigment may include, in addition to pure black, particles exhibiting an approximately black color such as grayish black, dark brown, or dark green, and may be used as long as it is a dark color that is difficult to reflect light.

(Release film)

In order to protect the conductive adhesive layer 14, a release film 22 may be provided on the surface of the conductive adhesive layer 14. The peeling film 22 can be peeled from the conductive adhesive layer 14 when the electromagnetic wave shielding material 10 is used. Examples of the base material of the release film 22 include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polypropylene, Polyolefin film such as polyethylene. These substrate films are coated with a release agent such as an amino alkyd resin or a silicone resin, and then heat-dried to perform a release treatment. The release agent applied to the release film 22 preferably does not use a silicone resin. When a silicone resin is used as the release agent, the adhesive force of the conductive adhesive layer 14 may be weakened. The thickness of the peeling film 22 is not included in the overall thickness of the electromagnetic wave shielding material 10 when it is used by being adhered to a printed circuit board. Therefore, the thickness is not particularly limited, but is generally about 12 μm to 150 μm.

The total thickness of the electromagnetic wave shielding material 10 is preferably in the range of 6 μm to 20 μm, and more preferably 8 μm to 15 μm. Here, the total thickness of the electromagnetic shielding material 10 refers to the total thickness from the substrate 11 to the conductive adhesive layer 14, and includes the thickness of the substrate 11 and the thickness of the conductive adhesive layer 14.

(Printed substrate)

Examples of the printed substrate shielded by the electromagnetic wave of the present invention include rigid rigid substrates with insulating substrates, flexible flexible substrates with insulating substrates, and rigid flexible substrates (rigid-flexible substrates) including flexible portions and rigid portions. Wait. Examples of the step difference include 50 μm or more, and further 300 μm or more.

The electromagnetic wave shielding material laminated body 20 in which one or both of the support film 21 or the release film 22 is laminated on one or both sides of the electromagnetic wave shielding material 10 is operable even if the total thickness of the electromagnetic wave shielding material 10 is thin. Also excellent. When the electromagnetic wave shielding material 10 is adhered to the adherend printed board, at least the peeling film 22 is peeled off and removed, and then the surface of the conductive adhesive layer 14 is opposed to the adherend. When the step followability is required, the electromagnetic wave shielding material 10 and the adherend are laminated in a state where the total thickness after removing the support film 21 and the release film 22 is thin. After that, the conductive adhesive layer 14 is preferably thermally cured by heating and pressing to adhere the electromagnetic wave shielding material 10 to the adherend.

The electronic device shielded by the electromagnetic wave of the present invention is not particularly limited, and examples thereof include a mobile phone, a notebook personal computer, a portable terminal, and a tablet terminal. These electronic devices may include a printed circuit board to which the electromagnetic wave shielding of the present invention is adhered.

[Example]

Hereinafter, the present invention will be specifically described by way of examples.

(Example 1)

A polyethylene terephthalate (PET) film having a thickness of 50 μm subjected to a peeling treatment on one side was used as a support film. On one side of the support film, a solvent-soluble polyimide coating solution was cast and dried to a thickness of 4 μm after drying, and a dielectric thin film resin film was laminated to form a film. The coating solution of the solvent-soluble polyfluorene imide is a solid component of the solvent-soluble polyfluorene imide with a tensile elongation of 140% after drying, and is mixed with 1% by weight of non-conductive carbon. Black is obtained as a black pigment as a light absorber. In addition, in order to measure the tensile elongation of the substrate, a substrate for measuring the tensile elongation was produced in the same manner as the substrate for the production of an electromagnetic shielding material, and the substrate was peeled from the support film, according to IPC. -The method of TM-650 2.4.19, and the tensile elongation was measured, and the result was 140%.

A conductive paste prepared by mixing silver particles having a particle size of 10 to 40 nm as a conductive filler and a binder resin is applied to a substrate laminated on one side of a support film and dried. The subsequent thickness was 0.25 μm, and then firing was performed at a temperature of 150 ° C. to form a conductive paste layer. The volume resistivity of the dried conductive paste layer was measured, and the value was 1.5 × 10 ^-5 Ω · cm or less.

Separately, with respect to 100 parts by weight of a 40% solution (manufactured by Toyobo: UR3575) of a phosphorus-containing polyurethane resin, 3.9 parts by weight of a polyfunctional epoxy resin solution (manufactured by Toyobo: HY-30) was sequentially added, and the average particle size was 2.1 parts by weight of 16nm fumed silica (manufactured by AEROSIL, Japan: R972), 0.42 parts by weight of silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd .: KBM-403), silver mixed with copper (household) Manufactured by Tian Industry: RD-MS3) 26 parts by weight, diluted with methyl ethyl ketone and toluene, stirred and kneaded to obtain a conductive adhesive solution. The proportion of silver mixed with copper is about 60.8 parts by weight based on 100 parts by weight of the adhesive (solid component) in which the phosphorus-containing polyurethane resin and the polyfunctional epoxy resin are combined. A conductive adhesive layer was laminated on the conductive paste layer so that the obtained conductive adhesive solution had a thickness of 4 μm after drying to obtain the electromagnetic wave shielding material of Example 1.

(Example 2)

A non-conductive carbon black was added to the solvent-soluble polyimide coating solution having a tensile elongation of 120% after drying to form a base material. Except that the base material was obtained in the same manner as in Example 1, Example 2 was obtained. Electromagnetic wave shielding material.

(Example 3)

A non-conductive carbon black was not added to the solvent-soluble polyimide coating solution having a tensile elongation of 170% after drying, and a base material was formed so that the thickness after drying was 4 μm. A coating liquid for forming an anchor layer was applied on the material so that the thickness after drying was 0.5 μm, and an anchor layer was laminated. The coating liquid for forming the anchor layer was mixed with light. The non-conductive carbon black of the black pigment of the absorbent and the polyester-based resin composition having a heat-resistant temperature of 260 ° C to 280 ° C, and thereafter, a conductive paste layer and a conductive adhesive layer are formed on the anchoring layer. Except for the above, the electromagnetic wave shielding material of Example 3 was obtained in the same manner as in Example 1.

(Example 4)

An electromagnetic wave shielding material of Example 4 was obtained in the same manner as in Example 1 except that the thickness of the conductive paste layer was 0.8 μm.

(Comparative example 1)

A non-conductive carbon black was added to a solvent-soluble polyimide coating solution having a tensile elongation of 50% after drying to form a base material, and Comparative Example 1 was obtained in the same manner as in Example 1 except that a substrate was formed. Electromagnetic wave shielding material.

(Comparative example 2)

An electromagnetic shielding material of Comparative Example 2 was obtained in the same manner as in Example 1 except that a silver vapor-deposited film having a thickness of 0.08 μm was provided instead of the laminated conductive paste layer.

(Comparative example 3)

An electromagnetic shielding material of Comparative Example 3 was obtained in the same manner as in Example 3 except that an electrolytic copper foil having a thickness of 12 μm was provided on the anchor layer instead of the conductive paste layer.

(Comparative Example 4)

A comparison was made in the same manner as in Example 3 except that a polyimide film formed of a thermosetting polyimide having a thickness of 10 μm and a tensile elongation of 62% was used as a base material without using a support film. The electromagnetic wave shielding material of Example 4.

(Evaluation method of step-followability)

As shown in FIG. 2, a detection substrate 30 having a rigid substrate portion 33 and a terminal portion 31 provided on a flexible substrate portion 32 is prepared, and an electromagnetic wave shielding material 10 is stacked thereon. The length between the terminal portions 31 formed on both ends of the flexible substrate portion 32 is 50 mm. The height of the step formed by the rigid substrate portion 33 with respect to the flexible substrate portion 32 is 0.3 mm (300 μm) and the width is 30 mm. The length of the rigid substrate portion 33 is 30 mm, and the length of the opening portion 35 between the terminal portion 31 and the rigid substrate portion 33 is 10 mm from the left and right.

An exposed portion 34 for measuring the resistance between the terminals is left on the terminal portion 31. An end portion of the electromagnetic wave shielding material 10 covers a part of the terminal portion 31, and the surface of the conductive adhesive of the electromagnetic wave shielding material 10 according to the opening portion 35. The covering method was superimposed, and hot pressing was performed under the conditions of 160 ° C., 2.5 MPa, and 65 minutes to obtain a follow-up evaluation sample. Observe the cross-section of the obtained sample, and mark it as "○" when the electromagnetic wave shielding material follows the central step; the non-following, electromagnetic wave shielding material floats from the detection substrate to create a gap, or the electromagnetic wave is shielded at the corner of the step. The case where the film of the material is broken is denoted by "×".

(Evaluation method of conductivity)

A digital multimeter (TFF Keithley Instruments, model: 2100/100) was used to measure the terminal-to-terminal resistance of both ends of the sample obtained in the evaluation method of the step-following follow-up property, and the less than 1Ω was marked as "○". 1Ω or more and less than 2Ω are referred to as "△", and 2Ω or more are referred to as "×".

(Evaluation method of heat resistance)

The obtained electromagnetic wave shielding material was hot-pressed to a polyimide film having a thickness of 25 μm under conditions of 160 ° C., 2.5 MPa, and 65 minutes to obtain a sample for evaluating heat resistance. The test piece was cut into a size of 2.5 cm × 5 cm, immersed in a solder bath at 290 ° C. for 10 seconds, and then lifted. The appearance of the electromagnetic wave shielding material after the solder bath was immersed was visually inspected for abnormalities such as deformation or shrinkage. The abnormality and goodness were recorded as "○", and the abnormality was observed as "x".

(test results)

For Examples 1 to 4 and Comparative Examples 1 to 4, the above-mentioned evaluation method was used to evaluate the electromagnetic wave shielding material, and the obtained evaluation results are shown in Tables 1 to 2. The presence of "none" in the column of thickness means that the layer is absent. In the columns of the polyimide material of the polyimide substrate, "PI1", "PI2", "PI3", "PI4", and "PI5" refer to Examples 1, 2, and 2, respectively. Polyimide used in Example 3, Comparative Example 1, and Comparative Example 4.

As can be seen from the results of the followability tests shown in Tables 1 to 2, when the tensile elongation of the base material is 100% or more, the followability and conductivity are good. That is, when the tensile elongation of the base material is 100% or less, it is impossible to completely follow the step of the detection substrate, a gap may be formed between the detection substrate, or the conductive paste layer may be broken. The conductivity is deteriorated.

In addition, when the vapor-deposited film is a conductive layer as in Comparative Example 2, the conductive layer lacks flexibility. Therefore, even if the tensile elongation of the base material is 100% or more, the step difference of the detection substrate cannot be completely followed. Gaps occur between the detection substrates, or cracks or breaks occur in the conductive layer, and followability and conductivity are deteriorated.

In addition, when a metal foil is used as a conductive layer as in Comparative Example 3, the conductive layer lacks elongation. Therefore, even if the tensile elongation of the substrate is 100% or more, it cannot completely follow the step difference of the detection substrate, Gaps occur between the detection substrates, or cracks or breaks occur in the conductive layer, and followability and conductivity are deteriorated.

In the cases of Examples 1 to 4, since the conductive layer was used as the conductive paste layer, the adhesive was filled in the voids of the nano-silver particles after firing, so that flexibility was generated, and the conductive layer followed the step. Therefore, even if the polyimide film of the base material is stretched, the continuity is not lost, and an electromagnetic wave shielding material with good step-followability can be obtained.

In addition, in the case where a dense conductive film such as a metal foil or a vapor-deposited film is used as the conductive layer as in Comparative Examples 2 and 3, water vapor is generated by moisture in the base film generated during rapid heating of a solder bath or the like. , Or outgassing caused by unreacted materials, low-molecular components, etc., cannot pass through, resulting in poor appearance such as foaming. That is, the conductive layer was made of a conductive paste as in Examples 1 to 4. As a result, there were voids in the conductive layer after firing. Therefore, the above-mentioned moisture, outgassing, and the like can pass through, even under rapid heating. An electromagnetic wave shielding material having good heat resistance can be obtained without causing appearance defects such as foaming.

In addition, in Comparative Example 4 in which a polyimide film having a large thickness and a tensile elongation of 100% or less was used as a base material, the heat resistance was also deteriorated. This is considered to be due to the base material having a large thickness. Caused by a large amount of gas and low gas permeability.

Claims (12)

    An electromagnetic wave shielding material, characterized in that a conductive paste layer and a conductive adhesive are sequentially laminated on one side of a substrate formed of a dielectric resin film along a thickness direction of the substrate. Layer, the substrate has a tensile elongation of 100% or more.         The electromagnetic wave shielding material according to item 1 of the scope of patent application, wherein the conductive paste layer includes silver nano particles having a particle diameter of less than 1 μm.         The electromagnetic wave shielding material according to item 1 or 2 of the scope of patent application, wherein the tensile elongation of the substrate is 100% or more and 300% or less.         The electromagnetic wave shielding material according to any one of claims 1 to 3, wherein the substrate is formed of a solvent-soluble polyfluoreneimide film.         The electromagnetic wave shielding material according to any one of claims 1 to 4, wherein the base material is formed of a polyimide film, and the polyimide film has a number of carbon atoms between aromatic units. It is formed of a polyimide material having 3 or more aliphatic units.         The electromagnetic wave shielding material according to any one of claims 1 to 5, wherein the thickness of the conductive adhesive layer is 15 μm or less.         The electromagnetic wave shielding material according to any one of claims 1 to 6, wherein the conductive adhesive layer is a conductive anisotropic adhesive layer.         The electromagnetic wave shielding material according to any one of claims 1 to 7, wherein the conductive adhesive layer includes polyurethane.         The electromagnetic wave shielding material according to any one of claims 1 to 8, wherein a total thickness from the substrate to the conductive adhesive layer is 6 μm to 15 μm.         The electromagnetic wave shielding material according to any one of claims 1 to 9, wherein the substrate is on a side where the conductive paste layer and the conductive adhesive layer are laminated. The opposite surface is supported by a support film that can be peeled from the substrate.         A mobile phone includes the electromagnetic wave shielding material according to any one of claims 1 to 10.         An electronic device includes the electromagnetic wave shielding material according to any one of claims 1 to 10.