Electromagnetic wave shielding composition

Abstract

Provided is an electromagnetic wave shielding composition capable of improving EMI shielding effect. The electromagnetic wave shielding composition comprises (A) silver particles; and (B) a first solvent having at least one structure selected from the structure represented by formula (1) and the structure represented by formula (2), and having a boiling point of less than 200°C. The electromagnetic wave shielding composition may further comprise (C) a dispersant, and the above-mentioned (B) first solvent may be in a range of 5 parts by mass or more and 150 parts by mass or less relative to 100 parts by mass of the above-mentioned (A) silver particles.

Description

Technical Field

[0001] The present invention relates to an electromagnetic shielding composition for forming an electromagnetic shielding layer on an electronic component mounted on a substrate. Background Art

[0002] Electronic devices such as mobile phones, smartphones, laptop computers, and tablet computers are built onto the substrates of these devices, including power amplifiers, Wi-Fi / Bluetooth modules, and flash memory. These electronic components can malfunction due to external electromagnetic waves. Conversely, these electronic components can become a source of electromagnetic noise, potentially causing malfunctions in other electronic components.

[0003] In the field of electronic devices, the development of high-integration technologies that integrate multiple components into a single unit, such as system-on-chip (SoC), system-in-package (SiP), and multi-chip module (MCM), is progressing, leading to increasingly smaller and thinner electronic devices. With this trend toward smaller and thinner electronic devices, the need for protection against electromagnetic interference (EMI) between components such as baseband components, radio frequency (RF) components, wireless components, analog devices, and power management components is increasing.

[0004] In electronic components, a shielding layer using a metal plate is formed to block electromagnetic waves. For example, a three-layer shielding layer of stainless steel (SUS) layer, copper (Cu) layer, and stainless steel (SUS) layer is formed on the outer surface of the electronic component from the inside by sputtering.

[0005] Shielding layers made of metal plates are difficult to meet the demands for miniaturization and thinning of electronic devices. Furthermore, shielding layers formed by sputtering often have different thicknesses on the top (upper surface) and sides (lateral surfaces). Making the thickness of the shielding layers uniform across the top (upper surface) and sides can be time-consuming and expensive.

[0006] In addition to sputtering, the shielding layer can also be formed by spraying on the surface of the electronic component. For example, Patent Document 1 discloses an EMI shielding composition for forming a shielding layer by spraying on the surface of the electronic component. The EMI shielding composition disclosed in Patent Document 1 includes (a) a thermoplastic resin such as a phenoxy resin, a vinylidene resin (Japanese original: ビニリデン) resin and / or a thermosetting resin such as an epoxy resin and an acrylic resin, (b) a reactive diluent such as a solvent or 2-phenoxyethyl acrylate, and (c) conductive particles such as silver particles. Patent Document 1 records that the EMI shielding composition uses a sprayer or a dispersion / spraying machine to seal the functional module arranged on the substrate.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application No. 2017-520903 Summary of the Invention

[0010] Problems to be solved by the invention

[0011] The shielding layer is required to further improve the EMI shielding effect.

[0012] An object of one embodiment of the present invention is to provide an electromagnetic shielding composition capable of further improving the EMI shielding effect.

[0013] Means for solving problems

[0014] Means for solving the above-mentioned problems are as follows, and the present invention includes the following aspects.

[0015] A first embodiment of the present invention is an electromagnetic shielding composition, characterized in that it contains: (A) silver particles; and (B) a first solvent having at least one structure selected from the structure represented by the following formula (1) and the structure represented by the following formula (2), and having a boiling point of less than 200°C.

[0016] [Chemical Formula 1]

[0017]

[0018] (In formula (1), R 1 It is an alkyl group having 2 to 3 carbon atoms and having a double bond between carbon atoms.

[0019] [Chemical Formula 2]

[0020]

[0021] (In formula (2), R 2 It is an alkylidene group having 2 to 3 carbon atoms.

[0022] A second aspect of the present invention is an electronic component using the electromagnetic shielding composition.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to provide an electromagnetic shielding composition that can reduce resistivity and further improve EMI shielding effect. DETAILED DESCRIPTION

[0025] Hereinafter, the electromagnetic shielding composition of the present invention will be described based on the embodiments. However, the embodiments shown below are for exemplifying the technical concept of the present invention, and the present invention is not limited to the following electromagnetic shielding composition.

[0026] The electromagnetic shielding composition according to the first embodiment of the present invention is characterized by comprising: (A) silver particles; and (B) a first solvent having at least one structure selected from the group consisting of the structure represented by the following formula (1) and the structure represented by the following formula (2), and having a boiling point of less than 200°C.

[0027] [Chemical Formula 3]

[0028]

[0029] In formula (1), R 1 is an alkyl group having 2 to 3 carbon atoms and having a double bond between carbon atoms. 1 Specific examples include vinyl, 1-propenyl, 2-propenyl (allyl), and isopropenyl. 1 Isopropenyl is preferred.

[0030] [Chemical Formula 4]

[0031]

[0032] In formula (2), R 2 is an alkylidene group having 2 to 3 carbon atoms. 2 The alkylidene group represented by also includes the double bond in formula (2). In formula (2), R 2 Specific examples of alkylidene groups include ethylidene, propylidene and isopropylidene, among which isopropylidene is preferred.

[0033] The electromagnetic shielding composition of the first embodiment of the present invention includes (B) a first solvent having at least one structure selected from the structure represented by formula (1) and the structure represented by formula (2) above, and having a boiling point of less than 200°C. Therefore, it has high volatility, and the resistivity of the shielding layer formed by the electromagnetic shielding composition is reduced, which can improve the EMI shielding effect. The first solvent (B) can be a solvent having a structure represented by formula (1) above or a solvent having a structure represented by formula (2) above, and the boiling point can be less than 200°C. The first solvent (B) can include both a solvent having a structure represented by formula (1) above and a solvent having a structure represented by formula (2) above, and the boiling points of both solvents can be less than 200°C.

[0034] The shielding effect of the shielding layer on EMI is represented by reflection loss (dB). The reflection loss can be calculated by the following calculation formula (I). In the following calculation formula (I), K is represented by the following calculation formula (II), which is the ratio of the impedance of the space to the impedance of the shielding layer. The smaller the resistivity of the shielding layer, that is, the higher the conductivity, the lower the impedance of the shielding layer, the more the ratio of the impedance of the space to the impedance of the shielding layer is reduced, and the higher the reflection loss (dB), the EMI shielding effect of the shielding layer can be improved. The resistivity of the shielding layer obtained by the electromagnetic wave shielding composition of the first embodiment of the present invention is small, which can improve the EMI shielding effect.

[0035] [Mathematical formula 1]

[0036]

[0037] In the above calculation formula (I), R represents the return loss (dB), and K represents the ratio of the impedance of the space to the impedance of the shield layer as shown in the following calculation formula (II).

[0038] [Mathematical formula 2]

[0039]

[0040] In the above calculation formula (II), Z0 represents the impedance of the space, Z S Indicates the impedance of the shielding layer.

[0041] (A) Silver particles

[0042] In the electromagnetic shielding composition, (A) silver particles are incorporated as conductive particles to block electromagnetic waves. The average particle size of the (A) silver particles is preferably within a range of 30 nm to 350 nm, more preferably within a range of 40 nm to 300 nm, and even more preferably within a range of 50 nm to 250 nm. When the average particle size of the (A) silver particles is within a range of 30 nm to 350 nm, settling of the silver particles in the electromagnetic shielding composition can be suppressed, maintaining the dispersed state of the silver particles in the composition, and facilitating the formation of a shielding layer with enhanced EMI shielding effectiveness.

[0043] The average particle size of the silver particles can be measured, for example, by observation using a scanning electron microscope (hereinafter referred to as "SEM"). For example, a SEM photograph or SEM image of the silver particles can be obtained at a magnification of 10,000 to 20,000 times. The outline of the silver particles in the SEM photograph or SEM image can be approximated to a perfect circle, the diameter of the perfect circle is measured, and the arithmetic mean of the diameters of 50 random silver particles is taken as the average particle size.

[0044] The silver particles may be spherical, flaky, or acicular in shape. When the silver particles are flaky or acicular, the average value of the major axis of the flaky or acicular shape may be used as the average particle diameter. From the perspective of sedimentation in the electromagnetic shielding composition, the silver particles (A) are preferably spherical.

[0045] Specifically, as the silver particles, silver powder (product name: P620-7, P620-24) manufactured by Metalor Technologies USA, Inc., or silver powder (product name: Ag nano powder-2) manufactured by DOWA Electronics Co., Ltd. can be used.

[0046] The electromagnetic shielding composition preferably contains the silver particles (A) in an amount of 35% to 95% by mass, and may contain the silver particles (A) in an amount of 40% to 90% by mass, based on solid content.

[0047] A masterbatch can be used, wherein the silver particles (A) are dispersed in the first solvent (B) and / or a second solvent (D) other than the first solvent (B). The masterbatch is obtained by pre-dispersing the silver particles in the first solvent (B) and / or the second solvent (D) to form a slurry. By using a masterbatch containing the silver particles (A) in the electromagnetic shielding composition, the silver particles (A) are less likely to settle in the electromagnetic shielding composition, and are more likely to be maintained in a properly dispersed state in the composition.

[0048] The (B) first solvent and / or the (D) second solvent other than the (B) first solvent contained in the masterbatch may be a single solvent or two or more solvents. The masterbatch may contain both the (B) first solvent and the (D) second solvent other than the (B) first solvent. The (D) second solvent other than the (B) first solvent may be, for example, at least one selected from ethylene glycol monophenyl ether (EPH), butyl carbitol acetate (BCA), and butyl carbitol (BC). The (B) first solvent or the (D) second solvent may be a single solvent or two or more solvents may be used in combination. The (B) first solvent or the (D) second solvent contained in the masterbatch may be an amount that can suppress the sedimentation of the (A) silver particles contained in the masterbatch and maintain the slurry state.

[0049] (B) First Solvent

[0050] In the electromagnetic shielding composition, the first solvent (B) is preferably limonene or terpinolene. Limonene or terpinolene, as the first solvent (B), has high volatility, reduces the resistivity of the shielding layer formed from the electromagnetic shielding composition, and enhances the EMI shielding effect.

[0051] Limonene is represented by the following formula (3), has the structure represented by the above formula (1), and has a boiling point of 176°C.

[0052] [Chemical Formula 5]

[0053]

[0054] Terpinolene is represented by the following formula (4), has the structure represented by the above formula (2), and has a boiling point of 184°C.

[0055] [Chemical Formula 6]

[0056]

[0057] The electromagnetic shielding composition preferably contains the first solvent (B) in an amount of 5 parts by mass to 150 parts by mass, relative to 100 parts by mass of the silver particles (A). By including the first solvent (B) in an amount of 5 parts by mass to 150 parts by mass, relative to 100 parts by mass of the silver particles (A), the shielding layer can be formed with the silver particles (A) substantially uniformly dispersed. As the first solvent (B) evaporates, a shielding layer with a high EMI shielding effect can be formed. The amount of the first solvent (B) contained in the electromagnetic shielding composition is preferably in a range of 6 parts by mass to 140 parts by mass, and more preferably in a range of 7 parts by mass to 130 parts by mass, relative to 100 parts by mass of the silver particles (A).

[0058] (C) Dispersant

[0059] The electromagnetic shielding composition preferably further comprises a dispersant (C). By including the dispersant (C) in the electromagnetic shielding composition, the dispersibility of the silver particles (A) can be improved, sedimentation can be suppressed, and a shielding layer with a high EMI shielding effect can be formed.

[0060] In the composition for electromagnetic wave shielding, from the viewpoint of good compatibility with (B) the first solvent or (D) the second solvent, the (C) dispersant is preferably at least one selected from an acrylic dispersant, a phosphate salt dispersant, and a polyfunctional ionic dispersant. The dispersant of component (C) can use a carboxylic acid dispersant. Examples of acrylic dispersants include polyisobutyl methacrylate. Examples of phosphate salt dispersants include BYK-145 manufactured by BYK Chemie. Examples of polyfunctional ionic dispersants include SC1015F of the MALIALIM (registered trademark) series or the MALIALIM (registered trademark) SC series manufactured by NOF Corporation. The dispersants of the MALIALIM (registered trademark) series manufactured by NOF Corporation are polyfunctional comb-type dispersants having an ionic group in the main chain and a polyoxyalkylene chain in the graft chain. Examples of carboxylic acid-based dispersants include CRODA's dicarboxylic acid weak anionic dispersants (product name: Hypermer KD-57), and phosphate-based dispersants include CRODA's phosphate-based dispersants (product name: CRODAFOS O3A).

[0061] The (C) dispersant is preferably included in the electromagnetic shielding composition in an amount of 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the (A) silver particles. By including the (C) dispersant in the electromagnetic shielding composition in an amount of 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the (A) silver particles, the sedimentation of the (A) silver particles can be suppressed, and a shielding layer can be formed while the silver particles are substantially uniformly dispersed. This allows the formation of a shielding layer with low resistivity and high EMI shielding effect. The amount of the (C) dispersant contained in the electromagnetic shielding composition is preferably in a range of 1 part by mass or more and 8 parts by mass or less relative to 100 parts by mass of the (A) silver particles, and more preferably in a range of 1.5 parts by mass or more and 7 parts by mass or less.

[0062] The dispersant (C) may be included in a masterbatch in which the silver particles (A) are pre-dispersed in a slurry. The inclusion of the dispersant (C) in the masterbatch can suppress the sedimentation of the silver particles (A), allowing the shielding layer to be formed with the silver particles substantially uniformly dispersed, resulting in a shielding layer with a high EMI shielding effect. Even when the dispersant (C) is included in the masterbatch, the dispersant (C) may be included in an amount within a range of 0.5 parts by mass to 10 parts by mass per 100 parts by mass of the silver particles (A) contained in the electromagnetic shielding composition.

[0063] The electromagnetic wave shielding composition may include additives. As additives, for example, silane coupling agents, defoaming agents, etc. can be mentioned. The additives can be added to the electromagnetic wave shielding composition, and in the case of using a masterbatch, can be added to the masterbatch. The amount of the additive in the electromagnetic wave shielding composition is preferably within the range of 0.01 mass parts or more and 5 mass parts or less relative to 100 mass parts of the electromagnetic wave shielding composition, preferably within the range of 0.05 mass parts or more and 3 mass parts or less. In the case of adding to the masterbatch, the amount of the additive in the electromagnetic wave shielding composition to which the masterbatch is added is within the range of 0.01 mass parts or more and 5 mass parts or less relative to 100 mass parts of the electromagnetic wave shielding composition.

[0064] Silane coupling agents can be used to improve the heat resistance and bonding strength of the electromagnetic wave shielding composition. For example, various silane coupling agents such as epoxy, amino, vinyl, methacrylic, acrylic, and mercapto can be used. Among them, epoxy silane coupling agents having epoxy groups and methacrylic silane coupling agents having methacrylic groups are preferred. Specifically, epoxy silane coupling agents (3-glycidoxypropyltrimethoxysilane) (product name: KBM403) manufactured by Shin-Etsu Chemical Co., Ltd. and methacrylic silane coupling agents (3-methacryloyloxypropyltrimethoxysilane) (product name: KBM503) manufactured by Shin-Etsu Chemical Co., Ltd. can be used.

[0065] The defoaming agent is added to prevent the formation of bubbles in the electromagnetic shielding composition. For example, acrylic, silicone, and fluorosilicone defoaming agents can be used. Specifically, a silicone defoaming agent (product name: WACKER AF98 / 1000) manufactured by Wacker Asahika SeiSilicone Co., Ltd. can be used. When a silane coupling agent is added, it can be added in an amount within a range of 0.001 parts by mass to 5 parts by mass per 100 parts by mass of the silver particles (A).

[0066] Viscosity

[0067] The viscosity of the electromagnetic shielding composition, as measured at 25°C and 10 rpm using a rotational viscometer (Product No. TVE-22H) manufactured by Tokyo Keiki Co., Ltd., is preferably within the range of 10 mPa·s to 10,000 mPa·s, more preferably within the range of 20 mPa·s to 2,000 mPa·s, and even more preferably within the range of 30 mPa·s to 1,000 mPa·s. If the viscosity of the electromagnetic shielding composition, as measured at 25°C and 10 rpm, is within the range of 10 mPa·s to 10,000 mPa·s, the silver particles (A) are dispersed in the electromagnetic shielding composition, and a shielding layer having a high EMI shielding effect can be formed by spray coating.

[0068] Thixotropic index Ti (5rpm / 50rpm)

[0069] The thixotropic index Ti of the electromagnetic wave shielding composition is preferably in the range of 1 or more and 6 or less, more preferably in the range of 1.2 or more and 5.0 or less. The thixotropic index is the ratio of the viscosity measured at 25°C at a rotation speed of 5 rpm to the viscosity measured at 50 rpm using a rotational viscometer (product number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd. The thixotropic index Ti is an index that measures the dependence of the viscosity on the shear rate (rotation speed of the viscometer) and the viscosity and represents thixotropy. The Ti value of a Newtonian fluid such as water, whose viscosity does not change even when the shear rate changes, is 1. When the Ti value is less than 1, it means that the viscosity is smaller when the shear force is small than when the shear force is large, and when the Ti value is greater than 1, it means that the viscosity is larger when the shear force is large than when the shear force is large. The larger the Ti value, the more thixotropic it is. If the Ti value of the electromagnetic wave shielding composition is in the range of 1 or more and 6 or less, a shielding layer with a high EMI shielding effect can be formed by spray coating (spraying).

[0070] Method for producing electromagnetic shielding composition

[0071] The electromagnetic wave shielding composition can be produced, for example, by mixing (A) silver particles, (B) a first solvent, (C) a dispersant as needed, and additives as needed, and stirring and mixing them using a known apparatus. Examples of known apparatuses include a Henschel mixer, a roller mill, and a three-roll mill. (A) Silver particles, (B) a first solvent, and (C) a dispersant as needed can be added to the apparatus simultaneously for mixing, or a portion can be added to the apparatus first for mixing, and then the remaining portion can be added to the apparatus for mixing.

[0072] Masterbatch manufacturing method

[0073] Regarding the masterbatch, a slurry-like masterbatch can be produced by premixing and stirring (A) silver particles with (B) a first solvent and / or (D) a second solvent other than the (B) first solvent. The masterbatch may contain (C) a dispersant and may also contain the above additives as needed. The (A) silver particles, (B) first solvent, and / or (D) second solvent contained in the masterbatch can be stirred and mixed using the above-mentioned well-known devices.

[0074] Coating method

[0075] The electromagnetic wave shielding composition can be spray-coated on electronic components, etc., to form a shielding layer on the outer surface of the electronic components, etc. In addition, the electromagnetic wave shielding composition can be coated on electronic components, for example, using a conventionally well-known sprayer, etc. In addition, the electromagnetic wave shielding composition can be filled in an aerosol can, etc., for coating. The thickness of the shielding layer formed by spray-coating the electromagnetic wave shielding composition on the electronic components can be in the range of 5 μm or more and 30 μm or less, can also be in the range of 5 μm or more and 20 μm or less, and can also be in the range of 5 μm or more and 10 μm or less.

[0076] Resistivity

[0077] The resistivity of the shielding layer formed by spray-coating the electromagnetic wave shielding composition should be 30 μΩ·cm or less, preferably 25 μΩ·cm or less, more preferably 20 μΩ·cm or less, even more preferably 10 μΩ·cm or less, particularly preferably 7 μΩ·cm or less, and can be 1 μΩ·cm or more. The smaller the resistivity of the shielding layer formed by spray-coating the electromagnetic wave shielding composition, that is, the higher the conductivity, the lower the impedance of the shielding layer, the smaller the ratio of the impedance of the space to the impedance of the shielding layer, and the higher the reflection loss (dB), and the EMI shielding effect of the shielding layer can be improved.

[0078] The resistivity can be measured, for example, as follows: The electromagnetic wave shielding composition is spray-coated on an alumina substrate in a specific size and length, dried in a hot air dryer at 200 °C for 30 minutes, and the shielding layer thus formed is measured by the four-terminal method using a multimeter (product number: model 2001) manufactured by TOYO Corporation.

[0079] Electronic components

[0080] The electromagnetic wave shielding composition can be applied to electronic components by spraying or the like. Examples of electronic components using the electromagnetic wave shielding composition include power amplifiers, Wi-Fi / Bluetooth modules, and flash memory used in electronic devices such as mobile phones, smart phones, laptop computers, and tablet terminals. When the electromagnetic wave shielding composition is used in electronic components, the electromagnetic wave shielding composition can be applied to each electronic component and then each electronic component can be mounted on a substrate. Alternatively, the electromagnetic wave shielding composition can be applied after each electronic component is mounted on a substrate.

[0081] Example

[0082] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0083] The following raw materials were used to produce the electromagnetic shielding compositions of Examples and Comparative Examples.

[0084] (A) Silver particles

[0085] A1: Spherical, average particle size 100 nm, silver filler, manufactured by Metalor Technologies USA, product number: P620-24

[0086] A2: Spherical, average particle size 60 nm, silver filler, manufactured by DOWA Electronics Co., Ltd., product number: Ag nano powder-2

[0087] A3: Spherical, average particle size 200 nm, silver filler, manufactured by Metalor Technologies USA, product number: P620-7

[0088] (A) Average particle size of silver particles: Observe using a scanning electron microscope (SEM). 50 particles are randomly selected from SEM photographs or images taken at magnifications of 10,000x to 20,000x. The contour of each particle is approximated to a perfect circle. The diameter of the perfect circle is measured, and the arithmetic mean is taken as the average particle size. If the silver particles are flaky (scaly), the average long axis diameter of the 50 randomly selected particles is taken as the average particle size.

[0089] (B') Third Solvent

[0090] The third solvent (B') differs from the first solvent (B) described below, does not have at least one structure selected from the structure represented by formula (1) and the structure represented by formula (2), and has a boiling point of 200°C or higher. The third solvent (B') may be the same as or different from the second solvent (D) other than the first solvent (B).

[0091] B'1: Butyl carbitol (BC) (90-100% by mass of diethylene glycol monobutyl ether), manufactured by Daishin Chemical Co., Ltd., boiling point 247°C

[0092] B'2: Terpineol, manufactured by Kobayashi Fragrance Co., Ltd., boiling point 219°C

[0093] B'3: Ethylene glycol monobutyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 171°C

[0094] (B) First Solvent

[0095] (B) The first solvent has at least one structure selected from the group consisting of the structure represented by the above formula (1) and the structure represented by the above formula (2), and has a boiling point of less than 200°C.

[0096] B4: Limonene, manufactured by Japan Terpene Chemical Co., Ltd., boiling point 176°C

[0097] B5: Terpinolene, manufactured by Nippon Terpene Chemical Co., Ltd., boiling point 184°C

[0098] (C) Dispersant

[0099] C1: Polyisobutyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd.

[0100] C2: Phosphate-based dispersant, manufactured by BYK-Chemie, product number: BYK-145

[0101] C3: Multifunctional ionic dispersant, manufactured by NOF Corporation, MALIALIM (registered trademark) SC1015F

[0102] Examples 1 to 12, Comparative Examples 1 to 5

[0103] The respective raw materials were mixed and dispersed using a three-roll mill so as to have the blending ratios shown in Tables 1 and 2 below, thereby producing electromagnetic shielding compositions.

[0104] Example 13

[0105] An electromagnetic shielding composition was produced in the same manner as in Example 1, except that a slurry-like masterbatch was used, in which the silver filler A1, which is the silver particles (A), was pre-dispersed in terpinolene, which is the first solvent (B). The masterbatch contained 6.0 parts by mass of the first solvent (B) per 100 parts by mass of the silver filler A1, which is the silver particles (A). Specifically, an electromagnetic shielding composition was produced in the same manner as in Example 1, with the raw materials other than the silver filler being incorporated in the proportions shown in Table 2 below, relative to 100 parts by mass of the silver filler A1, which is the silver particles (A) in the masterbatch.

[0106] Viscosity measurement

[0107] The viscosity of each electromagnetic shielding composition in Examples and Comparative Examples was measured at 25°C at rotation speeds of 1 rpm, 5 rpm, 10 rpm, 50 rpm, and 100 rpm using a rotational viscometer (Product No.: TVE-22H) manufactured by Tokyo Keiki Co., Ltd. The results are shown in Tables 1 and 2.

[0108] Thixotropic index Ti (5rpm / 50rpm)

[0109] The thixotropic index Ti (5 rpm / 50 rpm) of each electromagnetic shielding composition in Examples and Comparative Examples was determined by using a rotational viscometer (Product No.: TVE-22H) manufactured by Tokyo Keiki Co., Ltd., and calculating the ratio of the viscosity measured at 5 rpm at 25°C to the viscosity measured at 50 rpm. The results are shown in Tables 1 and 2.

[0110] Resistivity

[0111] For each electromagnetic shielding composition of the Examples and Comparative Examples, two tapes approximately 85 to 95 μm thick were attached parallel to each other at a 3 mm interval on an alumina substrate. The composition was then spray-coated between the two tapes to form a 3 mm width x 50 mm length x approximately 90 μm thickness. The composition was then dried in a hot air dryer at 200°C for 30 minutes to form a shielding layer. The resistivity of the shielding layer was measured using a multimeter (Product No. 2001) manufactured by TOYO Corporation using the four-terminal method. The results are shown in Tables 1 and 2.

[0112] [Table 1]

[0113]

[0114] [Table 2]

[0115]

[0116] As shown in Tables 1 and 2, the resistivity of each shielding layer formed by spray-coating the electromagnetic wave shielding compositions of Examples 1 to 13 is less than 5 μΩ·cm. The resistivity is small, that is, the conductivity is high, the impedance of the shielding layer is reduced, the reflection loss (dB) becomes higher, and the EMI shielding effect is high.

[0117] Each of the electromagnetic shielding compositions of Examples 1 to 13 had a viscosity within the range of 10 mPa·s to 10,000 mPa·s, as measured at rotation speeds of 1 rpm, 5 rpm, 10 rpm, 50 rpm, and 100 rpm at 25°C. (A) Silver particles were dispersed in the electromagnetic shielding composition, enabling spray coating. Furthermore, the electromagnetic shielding compositions of Examples 1 to 13 had a thixotropic index Ti within the range of 1 to 6, indicating thixotropy sufficient to form a shielding layer by spray coating.

[0118] Each electromagnetic shielding composition of Comparative Examples 1 to 5 contains a third solvent (B'). The third solvent (B') is a solvent that does not have the structure represented by formula (1) or the structure represented by formula (2) and has a boiling point of 200°C or higher, and is therefore a different solvent from the first solvent (B). The resistivity of each shielding layer formed by spray-coating each electromagnetic shielding composition of Comparative Examples 1 to 5 containing the third solvent (B') was greater than the resistivity of each shielding layer formed by spray-coating each electromagnetic shielding composition of Examples 1 to 13.

[0119] Industrial applicability

[0120] The electromagnetic wave shielding composition of the first embodiment of the present invention can be applied to electronic components by spraying (misting) to form a shielding layer, and can be applied to electronic components such as power amplifiers, Wi-Fi / Bluetooth modules, flash memories, etc. used in electronic devices such as mobile phones, smartphones, laptops, and tablet terminals.

Claims

1. An electromagnetic wave shielding composition, characterized in that Include: (A) silver particles; and (B) a first solvent having a structure represented by the following formula (2) and a boiling point of less than 200° C., The amount of the first solvent (B) is within a range of 5 parts by mass or more and 150 parts by mass or less relative to 100 parts by mass of the silver particles (A). In formula (2), R 2 It is an alkylidene group having 2 to 3 carbon atoms.

2. The electromagnetic shielding composition according to claim 1, wherein The (B) first solvent is terpinolene. 3 . The electromagnetic shielding composition according to claim 1 , further comprising (C) a dispersant.

4. The electromagnetic shielding composition according to claim 1 or 2, wherein The average particle size of the (A) silver particles is within a range of 30 nm to 350 nm.

5. The electromagnetic wave shielding composition according to claim 3, wherein The (C) dispersant is at least one selected from an acrylic dispersant and a polyfunctional ionic dispersant.

6. The electromagnetic wave shielding composition according to claim 1 or 2, wherein The shielding layer formed by spray-coating the electromagnetic wave shielding composition has a resistivity of 1 μΩ·cm or more and 30 μΩ·cm or less.

7. The electromagnetic wave shielding composition according to claim 1 or 2, wherein The electromagnetic shielding composition has a viscosity of 10 mPa·s or more and 10000 mPa·s or less measured at 25° C. and a rotation speed of 10 rpm.

8. The electromagnetic wave shielding composition according to claim 1 or 2, wherein The thixotropic index Ti of the electromagnetic shielding composition is within the range of 1 or more and 6 or less.

9. The electromagnetic wave shielding composition according to claim 1 or 2, wherein The electromagnetic shielding composition is a slurry-like masterbatch prepared by dispersing the (A) silver particles in the (B) first solvent and / or the (D) second solvent other than the (B) first solvent.

10. The electromagnetic wave shielding composition according to claim 9, wherein The masterbatch contains (C) a dispersant. 11 . An electronic component using the electromagnetic shielding composition according to claim 1 .

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