Electromagnetic wave shielding composition

Abstract

Provided is an electromagnetic wave shielding composition with which an EMI shielding effect can be enhanced. This electromagnetic wave shielding composition contains: (A) silver particles; and (B) a first solvent having a boiling point of less than

Description

[Technical Field]

[0001] The present invention relates to a component for shielding electromagnetic waves used to form an electromagnetic wave shielding layer for electronic components mounted on a substrate. [Previous Technology]

[0002] Electronic devices such as mobile phones, smartphones, laptops, and tablets have built-in circuit boards on which electronic components such as power amplifiers, Wi-Fi / Bluetooth modules, and flash memory are mounted. These electronic components may malfunction due to external electromagnetic waves. Conversely, some electronic components may also become sources of electromagnetic noise, causing other electronic components to malfunction.

[0003] In the field of electronic devices, advancements in development have led to the integration of multiple components, such as System-on-a-Chip (SoC), System-in-Package (SiP), and Multi-Chip Module (MCM), into a single component, resulting in increasingly smaller and thinner electronic devices. With this miniaturization and thinning of electronic devices, the protection against electromagnetic interference (EMI) is increasingly important for components such as baseband components, radio frequency (RF) components, wireless components, analog devices, and power management components.

[0004] A shielding layer made of a metal plate is formed on an electronic component to block electromagnetic waves, or a three-layer shielding layer consisting of a stainless steel (SUS) layer, a copper (Cu) layer, and a stainless steel (SUS) layer is formed on the outer surface of the electronic component by sputtering.

[0005] Using a metal plate shielding layer is difficult to meet the requirements of miniaturization or thinning of electronic devices. Moreover, the shielding layer formed by sputtering has different thicknesses on the top and side. If the thickness of the shielding layer formed on the top and side is to be uniform, sputtering will consume time and increase costs.

[0006] Besides sputtering, the shielding layer can also be formed by spray coating on the surface of electronic components. For example, Patent Document 1 discloses an EMI shielding composition for forming a shielding layer by spray sputtering on the surface of electronic components. The EMI shielding composition disclosed in Patent Document 1 includes (a) thermoplastic resins such as phenoxy resin and vinylene resin and / or thermosetting resins such as epoxy resin and acrylic resin, (b) a solvent or a reactive diluent such as 2-phenoxyethyl acrylate, and (c) conductive particles such as silver particles. Patent Document 1 describes that the EMI shielding composition is used to seal functional modules disposed on a substrate using a spray coating machine or a dispersion / ejection machine. [Prior Art Documents] [Patent Documents]

[0007] Patent Document 1: Japanese Patent Publication No. 2017-520903 [Summary of the Invention]

[0008] [The problem the invention aims to solve]

[0009] The shielding layer is required to improve the EMI shielding effect.

[0010] One aspect of the present invention aims to provide a component for shielding electromagnetic waves that can further improve the EMI shielding effect. [Means for solving the problem]

[0011] In order to solve the aforementioned problems, the present invention includes the following aspects.

[0012] The first aspect of the present invention is a composition for shielding electromagnetic waves, characterized by comprising: (A) silver particles, and (B) a first solvent having at least one structure selected from the group of structures represented by the following formula (1) and the following formula (2) and having a boiling point not exceeding 200°C.

[0013]

[0014] (In formula (1), R1 is an alkyl group with 2 to 3 carbon atoms having a double bond between carbon atoms).

[0015]

[0016] (In formula (2), R2 is an alkylene group with 2 to 3 carbon atoms).

[0017] A second embodiment of the present invention is an electronic component that uses the aforementioned electromagnetic wave shielding composition. [Effects of the Invention]

[0018] According to the present invention, a component for shielding electromagnetic waves with low specific resistance and improved EMI shielding effect can be provided.

Implementation Method

[0019] Hereinafter, the components for shielding electromagnetic waves disclosed herein will be described based on embodiments. However, the embodiments shown below are illustrative examples to concretize the technical concept of the present invention, and the present invention is not limited to the components for shielding electromagnetic waves described below.

[0020] The composition for shielding electromagnetic waves in 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 of structures represented by the following formula (1) and the following formula (2) and having a boiling point of not reaching 200°C.

[0021]

[0022] In formula (1), R1 is an alkyl group with 2 to 3 carbon atoms having a double bond between carbon atoms. Specific examples of R1 in formula (1) include vinyl, 1-propenyl, 2-propenyl (allyl), and isopropenyl. R1 is preferably isopropenyl.

[0023]

[0024] In formula (2), R2 is an alkylene group having 2 to 3 carbon atoms. R2 in formula (2) also represents an alkylene group that also contains the double bond in formula (2). In formula (2), as a specific example of R2, it represents an alkylene group that also contains the double bond in formula (2), for example being ethylene, propylene, or isopropylene. Among these, isopropylene is preferred.

[0025] The electromagnetic wave shielding composition of the first embodiment of the present invention contains (B) a first solvent having at least one structure selected from the group consisting of the structure represented by formula (1) and the structure represented by formula (2) and having a boiling point not exceeding 200°C. Therefore, it has high volatility, which can reduce the specific resistance of the shielding layer formed by the electromagnetic wave shielding composition and improve the EMI shielding effect. (B) The first solvent may be a solvent having the structure represented by formula (1) or a solvent having the structure represented by formula (2), as long as the boiling point does not exceed 200°C. (B) The first solvent may also contain both a solvent having the structure represented by formula (1) and a solvent having the structure represented by formula (2), as long as both have a boiling point not exceeding 200°C.

[0026] The EMI shielding effect of the shielding layer is represented by the reflection loss (dB). The reflection loss can be calculated using the following formula (I). In the following formula (I), K is the ratio of the spatial impedance to the impedance of the shielding layer, expressed by the following formula (II). The smaller the specific resistance of the shielding layer, that is, the higher its conductivity, the lower the impedance of the shielding layer, and the lower the ratio of the spatial impedance to the impedance of the shielding layer, thus increasing the reflection loss (dB) and improving the EMI shielding effect of the shielding layer. The shielding layer obtained from the electromagnetic wave shielding composition of the first embodiment of the present invention has a small specific resistance, which improves the EMI shielding effect.

[0027] In the aforementioned calculation formula (I), R represents the reflection loss (dB), and K is expressed as the ratio of the space impedance to the impedance of the shielding layer as shown in the following calculation formula (II).

[0028] In the aforementioned calculation formula (II), ZO represents the impedance of the space and ZS represents the impedance of the shielding layer.

[0029] (A) In the composition for shielding electromagnetic waves using silver particles, (A) silver particles are formulated as conductive particles to shield electromagnetic waves. (A) The average particle size of the silver particles is preferably in the range of 30 nm to 350 nm, more preferably in the range of 40 nm to 300 nm, and even more preferably in the range of 50 nm to 250 nm. (A) If the average particle size of the silver particles is in the range of 30 nm to 350 nm, the sedimentation of silver particles in the composition for shielding electromagnetic waves is suppressed, the dispersion state of silver particles in the composition can be maintained, and a shielding layer with improved EMI shielding effect can be easily formed.

[0030] The average particle size of silver particles can be determined by observation using, for example, a scanning electron microscope (SEM). For example, SEM photographs or images of silver particles are obtained at a magnification of 10,000 to 20,000. The outlines of the silver particles present in the SEM photographs or images are approximated as perfect circles, and the diameter of the perfect circle is measured. The arithmetic mean of the diameters of any 50 silver particles is taken as the average particle size.

[0031] The shape of the silver particles can be spherical, scaly, needle-like, or any other shape. When the shape of the silver particles is scaly or needle-like, the average long axis of the scaly or needle-like shape can be set as the average particle size. Based on the viewpoint of suppressing sedimentation in the composition for shielding electromagnetic waves, (A) the silver particles are preferably spherical.

[0032] Specifically, the silver particles may be silver powder manufactured by Metalor Technologies USA (product name: P620-7, P620-24) or silver powder manufactured by DOWA Electronics Co., Ltd. (product name: Ag nano powder-2).

[0033] (A) The silver particles in the composition for shielding electromagnetic waves are preferably contained in the range of 35% to 95% by mass, or in the range of 40% to 90% by mass, when converted to solids.

[0034] (A) Silver particles may also be dispersed in a masterbatch in a second solvent (D) other than (B) the first solvent. The masterbatch is formed by pre-dispersing silver particles in the first solvent (B) and / or the second solvent (D) to form a slurry. In the composition for shielding electromagnetic waves, by using a masterbatch containing (A) silver particles, the silver particles (A) are less likely to settle in the composition for shielding electromagnetic waves, and are more likely to maintain a moderately dispersed state in the composition.

[0035] The master batch may contain one or more solvents, including (B) the first solvent and / or (D) the second solvent other than (B) the first solvent. The master batch may also contain both (B) the first solvent and (D) the second solvent other than (B) the first solvent. The second solvent other than (B) the first solvent may be at least one selected from the group consisting of ethylene glycol monophenyl ether (EPH), butyl carbitol acetate (BCA), and butyl carbitol (BC). One or more solvents may be used for (B) the first solvent or (D) the second solvent. The amount of (B) the first solvent or (D) the second solvent contained in the master batch may be sufficient to suppress the sedimentation of (A) silver particles contained in the master batch and maintain a slurry-like consistency.

[0036] (B) In the composition for shielding electromagnetic waves using a first solvent, (B) the first solvent is preferably limonene or terpinene. If (B) the first solvent is limonene or terpinene, it has high volatility, and the resistivity of the shielding layer formed by the composition for shielding electromagnetic waves is low, which can improve the EMI shielding effect.

[0037] Limonene is represented by the following formula (3), has the structure represented by the aforementioned formula (1), and has a boiling point of 176°C.

[0038]

[0039] The terpinene is represented by the following formula (4), has the structure represented by the aforementioned formula (2), and has a boiling point of 184°C.

[0040]

[0041] (B) The first solvent in the composition for shielding electromagnetic waves preferably contains between 5 and 150 parts by mass relative to 100 parts by mass of silver particles (A). By containing the first solvent (B) in the composition for shielding electromagnetic waves in between 5 and 150 parts by mass relative to 100 parts by mass of silver particles (A), a shielding layer can be formed in a substantially uniformly dispersed state of the silver particles (A). By evaporating the first solvent (B), a shielding layer with high EMI shielding effect can be formed. The amount of the first solvent (B) contained in the composition for shielding electromagnetic waves is preferably between 6 and 140 parts by mass relative to 100 parts by mass of silver particles (A), and more preferably between 7 and 130 parts by mass.

[0042] (C) Dispersant The composition for shielding electromagnetic waves preferably includes (C) dispersant. Because the composition for shielding electromagnetic waves includes (C) dispersant, the dispersibility of (A) silver particles can be improved, sedimentation can be suppressed, and a shielding layer with high EMI shielding effect can be formed.

[0043] In the composition for shielding electromagnetic waves, based on good compatibility with either (B) the first solvent or (D) the second solvent, the dispersant in (C) is preferably selected from at least one of the group consisting of acrylic dispersants, phosphate ester dispersants, and multifunctional ionic dispersants. The dispersant in component (C) may also be a carboxylic acid dispersant. Examples of acrylic dispersants include, for example, polyisobutyl methacrylate. Examples of phosphate ester dispersants include, for example, BYK-145 manufactured by BYK CHEMIE. Examples of multifunctional ionic dispersants include, for example, the MALIALIM (registered trademark) series or SC1015F of the MALIALIM (registered trademark) SC series manufactured by Nippon Oil Co., Ltd. The dispersants in the MALIALIM (registered trademark) series manufactured by Nippon Oil Co., Ltd. are multifunctional comb-type dispersants having ionic groups in the main chain and polyoxyalkylene chains in the side chains. Examples of carboxylic acid-based dispersants include CRODA's dicarboxylic acid weak base anionic dispersant (brand name: HypermerKD-57). Examples of phosphate ester-based dispersants include CRODA's phosphate ester-based dispersant (brand name: CRODAFOS O3A).

[0044] (C) The dispersant in the composition for shielding electromagnetic waves is preferably contained in the range of 0.5 parts by mass to 10 parts by mass relative to 100 parts by mass of silver particles (A). By containing (C) the dispersant in the composition for shielding electromagnetic waves in the range of 0.5 parts by mass to 10 parts by mass relative to 100 parts by mass of silver particles (A), the sedimentation of silver particles (A) can be suppressed, and a shielding layer can be formed in a substantially uniformly dispersed state of silver particles, thereby forming a shielding layer with low specific resistance and high EMI shielding effect. The amount of (C) dispersant contained in the composition for shielding electromagnetic waves is preferably in the range of 1 part by mass to 8 parts by mass relative to 100 parts by mass of silver particles (A), and more preferably in the range of 1.5 parts by mass to 7 parts by mass.

[0045] (C) The dispersant may also be contained in the master batch in which the (A) silver particles are dispersed in a slurry form beforehand. When the master batch contains the (C) dispersant, it can suppress the sedimentation of the (A) silver particles, and form a shielding layer in a state of approximately uniform dispersion of the silver particles, thereby forming a shielding layer with high EMI shielding effect. When the (C) dispersant is contained in the master batch, it is sufficient to contain it in the range of 0.5 to 10 parts by mass relative to 100 parts by mass of the (A) silver particles contained in the composition for shielding electromagnetic waves.

[0046] The composition for shielding electromagnetic waves may also contain additives. Examples of additives include silane coupling agents or defoamers. Additives can be added to the composition for shielding electromagnetic waves, and can also be added to the master batch when using it. The amount of additive in the composition for shielding electromagnetic waves is preferably between 0.01 parts by weight and 5 parts by weight, more preferably between 0.05 parts by weight and 3 parts by weight, relative to 100 parts by weight of the composition for shielding electromagnetic waves. When added to the master batch, the amount of additive added to the composition for shielding electromagnetic waves in the master batch is also between 0.01 parts by weight and 5 parts by weight, relative to 100 parts by weight of the composition for shielding electromagnetic waves.

[0047] Silane coupling agents are formulated to improve the heat resistance or adhesion strength of components used for shielding electromagnetic waves. Various silane coupling agents, such as epoxy, amino, vinyl, methacrylic, acrylic, and mercapto-based agents, can be used. Among these, epoxy silane coupling agents with epoxy groups and methacrylic silane coupling agents with methacrylic groups are preferred. Specifically, epoxy silane coupling agents (3-glycidoxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. (product name: KBM403) and methacrylic silane coupling agents (3-methacryloxypropyltrimethoxysilane) manufactured by Shin-Etsu Chemical Co., Ltd. (product name: KBM503) can be used.

[0048] Defoamers are formulated to prevent the formation of air bubbles in components used for shielding electromagnetic waves. Examples of defoamers include acrylic, silicone, and fluorosilicone defoamers. Specifically, silicone defoamers manufactured by Asahi Kasei WACKER SILICONE Co., Ltd. (product name: WACKER AF98 / 1000) can be used. When adding a silane coupling agent, it can be added in a range of 0.001 parts by weight to 5 parts by weight relative to 100 parts by weight of (A) silver particles.

[0049] The viscosity of the component for shielding electromagnetic waves is preferably measured using a rotational viscometer (part number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd., at 25°C and 10 rpm, in the range of 10 mPa·s to 10,000 mPa·s, more preferably in the range of 20 mPa·s to 2,000 mPa·s, and even more preferably in the range of 30 mPa·s to 1,000 mPa·s. If the viscosity of the component for shielding electromagnetic waves, measured at 25°C and 10 rpm, is in the range of 10 mPa·s to 10,000 mPa·s, then (A) silver particles dispersed in the component for shielding electromagnetic waves can form a shielding layer with high EMI shielding effect by spray coating.

[0050] Rheological Index Ti (5rpm / 50rpm) The rheological index Ti of components used for shielding electromagnetic waves is preferably in the range of 1 to 6, and more preferably in the range of 1.2 to 5.0. The rheological index is the ratio of viscosity measured at 25°C at 5 rpm to viscosity measured at 50 rpm using a rotational viscometer (e.g., Tokyo Keiki Co., Ltd.) at 25°C. The rheological index Ti measures the dependence of shear rate (viscometer rotation number) on viscosity, representing rheological properties. A Ti value of 1 indicates that the viscosity of a Newtonian fluid, like water, remains unchanged even when the shear rate is changed. A Ti value less than 1 indicates that the viscosity at lower shear forces is less than that at higher shear forces, and a Ti value greater than 1 indicates that the viscosity at lower shear forces is greater than that at higher shear forces. A higher Ti value indicates greater rheological properties. If the Ti value of the components used to shield electromagnetic waves is in the range of 1 to 6, a shielding layer with high EMI shielding effect can be formed by spray coating.

[0051] Method for Manufacturing a Component for Shielding Electromagnetic Waves The component for shielding electromagnetic waves can be manufactured by, for example, mixing (A) silver particles, (B) a first solvent, (C) a dispersant as needed, and additives as needed, using a conventional apparatus. A Henschel mixer, a roller mill, a three-roll mill, etc., can be used as a conventional apparatus. (A) silver particles, (B) a first solvent, and (C) a dispersant as needed can be added to the apparatus simultaneously and mixed, or a portion of them can be added to the apparatus first and mixed, with the remainder added later and mixed.

[0052] Method for manufacturing masterbatch: The masterbatch can be prepared into a slurry-like masterbatch by pre-mixing (A) silver particles, (B) a first solvent and / or (D) a second solvent other than (B) the first solvent. The masterbatch may also contain (C) a dispersant, and may also contain the aforementioned additives as needed. The (A) silver particles, (B) the first solvent and / or (D) the second solvent contained in the masterbatch can be mixed using the aforementioned conventional apparatus.

[0053] The coating method involves spraying a component for shielding electromagnetic waves onto electronic components, thereby forming a shielding layer on the outer surface of the electronic components. Furthermore, the component for shielding electromagnetic waves can be applied to the electronic components using, for example, a conventional spray coating machine. Alternatively, the component for shielding electromagnetic waves can be filled into a can or similar container for coating. The thickness of the shielding layer formed by spraying the component for shielding electromagnetic waves onto the electronic components can be in the range of 5 μm to 30 μm, or 5 μm to 20 μm, or 5 μm to 10 μm.

[0054] The resistivity of the shielding layer formed by spray coating of the electromagnetic wave shielding components is preferably 30 Ω·cm or less, more preferably 25 Ω·cm or less, even more preferably 20 Ω·cm or less, and even more preferably 10 Ω·cm or less, particularly preferably 7 Ω·cm or less, and may also be 1 Ω·cm or more. The lower the resistivity of the shielding layer formed by spray coating of the electromagnetic wave shielding components, that is, the higher the conductivity, the lower the impedance of the shielding layer, the lower the ratio of the impedance of the space to the impedance of the shielding layer, the higher the reflection loss (dB), and the better the EMI shielding effect of the shielding layer.

[0055] The resistivity can be measured, for example, by spraying a component for shielding electromagnetic waves onto an alumina substrate at a specific size and length, drying it in a hot air dryer at 200°C for 30 minutes to form a shielding layer, using a multimeter (model number: 2001) manufactured by Tungyang Technology Co., Ltd., using the 4-terminal method.

[0056] Electromagnetic wave shielding components for electronic components can be applied to electronic components by spray coating or similar methods. Examples of electronic components using electromagnetic wave shielding components include power amplifiers, Wi-Fi / Bluetooth modules, and flash memory used in electronic devices such as mobile phones, smartphones, laptops, and tablets. When applying electromagnetic wave shielding components to electronic components, the components can be applied to each electronic component before mounting them onto a substrate, or the components can be mounted on the substrate before applying the electromagnetic wave shielding components. [Example]

[0057] The present invention will be specifically described below by way of examples. The present invention is not limited to these examples.

[0058] The following raw materials were used when manufacturing the components for shielding electromagnetic waves in the embodiments and comparative examples.

[0059] (A) Silver particles A1: Spherical, average particle size 100nm, silver filler, manufactured by Metalor Technologies USA, part number: P620-24 A2: Spherical, average particle size 60nm, silver filler, manufactured by DOWA Electronics Co., Ltd., part number: Ag nanopowder-2 A3: Spherical, average particle size 200nm, silver filler, manufactured by Metalor Technologies USA, part number: P620-7 (A) The average particle size of the silver particles is determined by observation using, for example, a scanning electron microscope (SEM). Fifty particles are randomly selected from SEM photographs or images at magnifications of 10,000x to 20,000x. The outline of each particle is approximately a perfect circle, and the diameter of the perfect circle is measured. The arithmetic mean of these circles is taken as the average particle size. When the shape of the silver particles is flake-like (scaly), the average long axis of any 50 particles is taken as the average particle size.

[0060] (B') The third solvent (B') is different from the first solvent (B) described below, and does not have at least one structure selected from the structure represented by formula (1) and the structure represented by formula (2) described above, 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). B'1: Butylcarbitol (BC) (90~100% by mass of diethylene glycol monobutyl ether), manufactured by Daishin Chemical Co., Ltd., boiling point 247°C B'2: Terpineol, manufactured by Kobayashi Fragrance Co., Ltd., boiling point 219°C B'3: Ethylene glycol monobutyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 171°C

[0061] (B) First Solvent (B) The first solvent has at least one structure selected from the structure represented by formula (1) and the structure represented by formula (2) above, and its boiling point does not reach 200°C. B4: Limonene, manufactured by Japan Terpenes Chemical Co., Ltd., boiling point 176°C B5: Terpinene, manufactured by Japan Terpenes Chemical Co., Ltd., boiling point 184°C

[0062] (C) Dispersant C1: Polyisobutyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd.; C2: Phosphate ester salt dispersant, manufactured by BYK CHEMIE Co., Ltd., product number: BYK-145; C3: Multifunctional ionic dispersant, manufactured by Nippon Oil Co., Ltd., MALIALIM (registered trademark) SC1015F

[0063] Examples 1 to 12 and Comparative Examples 1 to 5: Each raw material was mixed and dispersed using a 3-roll mill in the proportions shown in Tables 1 and 2 below to manufacture a composition for shielding electromagnetic waves.

[0064] Example 13 Except for the use of a masterbatch in which the silver filler (A) of silver particles (A1) is dispersed in terpinene (B) first solvent to form a slurry, a composition for shielding electromagnetic waves was manufactured in the same manner as in Example 1. The masterbatch contained 6.0 parts by mass of (B) first solvent relative to 100 parts by mass of the silver filler (A1) of silver particles (A1). Specifically, relative to 100 parts by mass of the silver filler (A1) of silver particles (A1) in the masterbatch, the raw materials other than the silver filler were mixed in the proportions shown in Table 2 below, and a composition for shielding electromagnetic waves was manufactured in the same manner as in Example 1.

[0065] The viscosity of each component used for shielding electromagnetic waves in the examples and comparative examples was measured using a rotational viscometer (part number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd., at 25°C, at rotational speeds of 1 rpm, 5 rpm, 10 rpm, 50 rpm, and 100 rpm. The results are shown in Tables 1 and 2.

[0066] Rheological Index Ti (5 rpm / 50 rpm) The rheological index Ti (5 rpm / 50 rpm) of each component for shielding electromagnetic waves in the Examples and Comparative Examples was determined using a rotational viscometer (part number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd., and the ratio of the viscosity measured at 25°C at 5 rpm to the viscosity measured at 50 rpm was calculated. The results are shown in Tables 1 and 2.

[0067] The electromagnetic wave shielding components of the specific resistance examples and comparative examples were attached to an alumina substrate. Two pieces of adhesive tape, approximately 85-95 μm thick, were adhered parallel to each other at 3 mm intervals. A spray coating was then applied between the two tapes, with a width of 3 mm × length of 50 mm × thickness of approximately 90 μm. The coating was then dried in a hot air dryer at 200°C for 30 minutes to form a shielding layer. The specific resistance of this shielding layer was measured using a multimeter (model 2001) manufactured by Tungyang Technology Co., Ltd., using the 4-terminal method. The results are shown in Tables 1 and 2.

[0068]

[0069]

[0070] As shown in Tables 1 and 2, the shielding layers formed by spraying the components of each shielding electromagnetic wave in Examples 1 to 13 have a resistivity of less than 5 Ω·cm. The resistivity is small, that is, the conductivity is high. The impedance of the shielding layer is reduced, the reflection loss (dB) is increased, and the EMI shielding effect is high.

[0071] The viscosity of each electromagnetic wave shielding composition in Examples 1 to 13, measured at 25°C with rotational speeds of 1 rpm, 5 rpm, 10 rpm, 50 rpm, and 100 rpm, is in the range of 10 mPa·s to 10,000 mPa·s. (A) Silver particles are dispersed in the electromagnetic wave shielding composition, allowing for spray coating. Furthermore, the rheological index Ti of the electromagnetic wave shielding compositions in Examples 1 to 13 is in the range of 1 to 6, exhibiting rheological properties that allow for the formation of a shielding layer through spray coating.

[0072] The electromagnetic wave shielding compositions of Comparative Examples 1 to 5 each contain a third solvent (B'). The third solvent (B') is a solvent that does not have the structure represented by formula (1) or formula (2) described above. Since it is a solvent with a boiling point of 200°C or higher, it is a different solvent from the first solvent (B). The resistivity of each shielding layer formed by spray coating of the electromagnetic wave shielding compositions of Comparative Examples 1 to 5 containing the third solvent (B') is greater than that of each shielding layer formed by spray coating of the electromagnetic wave shielding compositions of Examples 1 to 13. [Industrial Applicability]

[0073] The electromagnetic wave shielding composition of the first embodiment of the present invention can be sprayed onto electronic components to form a shielding layer, and can be appropriately used in electronic components such as power amplifiers, Wi-Fi / Bluetooth modules, and flash memory used in electronic devices such as mobile phones, smartphones, laptops, and tablet terminals.

Claims

1. A composition for shielding electromagnetic waves, characterized in that it comprises (A) silver particles and (B) a first solvent having at least one structure selected from the group consisting of a structure represented by formula (1) and a structure represented by formula (2) and having a boiling point not exceeding 200°C (in formula (1), R1 is an alkyl group having two to three carbon atoms with a double bond between carbon atoms) (in formula (2), R2 is an alkylene group having two to three carbon atoms).

2. The composition for shielding electromagnetic waves as claimed in claim 1, wherein the first solvent in (B) above is limonene or terpinene.

3. The composition for shielding electromagnetic waves as claimed in claim 1 or 2, wherein it further includes (C) a dispersant.

4. The composition for shielding electromagnetic waves as claimed in any of claims 1 to 3, wherein the first solvent in (B) is in the range of 5 to 150 parts by mass relative to 100 parts by mass of the silver particles in (A).

5. The electromagnetic wave shielding composition of any one of claims 1 to 4, wherein the average particle size of the silver particles in (A) is in the range of 30 nm to 350 nm.

6. The composition for shielding electromagnetic waves as claimed in any of claims 3 to 5, wherein the aforementioned dispersant (C) is selected from at least one of the group consisting of acrylic dispersants, phosphate salt dispersants and multifunctional ionic dispersants.

7. The composition for shielding electromagnetic waves as claimed in any of claims 1 to 6, wherein the aforementioned (A) silver particles are a slurry-like masterbatch dispersed in the aforementioned (B) first solvent and / or the aforementioned (D) second solvent other than the aforementioned (B) first solvent.

8. The composition for shielding electromagnetic waves as claimed in claim 7, wherein the aforementioned master batch contains (C) a dispersant.

9. An electronic component that uses a component for shielding electromagnetic waves as described in any one of claims 1 to 8.