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 200°C and having at least one structure selected from the group consisting of a structure represented by formula (1) and a structure represented by formula (2). Said electromagnetic wave shielding composition may further contain (C) a dispersant, wherein the content of the (B) first solvent may be in the range of 5-150 parts by mass with respect to 100 parts by mass of the (A) silver particles.

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave shielding composition for forming an electromagnetic wave shielding layer on electronic components, etc., mounted on a substrate. [Background technology]

[0002] Electronic devices such as mobile phones, smartphones, laptops, and tablet devices are equipped with circuit boards that contain electronic devices such as power amplifiers, Wi-Fi / Bluetooth modules, and flash memories. These electronic components may malfunction due to external electromagnetic waves. Conversely, electronic components may become a source of electromagnetic noise, causing other electronic components to malfunction.

[0003] In the field of electronic devices, the development of high integration technologies that integrate multiple components into one component, such as system-on-chip (SoC), system-in-package (SiP), and multi-chip module (MCM), is progressing, and electronic devices are becoming smaller and thinner. As electronic devices become smaller and thinner, there is an increasing need to protect against electromagnetic interference (hereinafter also referred to as "EMI") between components such as baseband components, radio frequency (RF) components, wireless components, analog devices, and power management components.

[0004] Electronic components have a shielding layer made of a metal plate to block electromagnetic waves, and a triple shielding layer made of, for example, a stainless steel (SUS) layer / copper (Cu) layer / stainless steel (SUS) layer is formed on the outer surface of the electronic component by sputtering.

[0005] It is difficult for a shielding layer made of a metal plate to satisfy the demand for smaller and thinner electronic devices. Also, the thickness of the shielding layer formed by sputtering differs between the top (upper surface) and the sides (side surfaces), and if you try to make the thickness of the shielding layer formed on the top (upper surface) and the sides (side surfaces) uniform, the sputtering takes a long time and the cost can rise.

[0006] In addition to sputtering, the shielding layer can also be formed by spray coating on the surface of an electronic component. For example, Patent Document 1 discloses an EMI shielding composition for forming a shielding layer on the surface of an electronic component by spray coating. The EMI shielding composition disclosed in Patent Document 1 includes (a) a thermoplastic resin such as a phenoxy resin or vinylidene resin and / or a thermosetting resin such as an epoxy resin or an 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 encapsulates a functional module arranged on a substrate using a spray coating machine or a dispersion / squirting machine. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2017-520903 Summary of the Invention [Problem to be solved by the invention]

[0008] The shielding layer is required to further improve the EMI shielding effect.

[0009] An object of one aspect of the present invention is to provide an electromagnetic wave shielding composition that can further improve the EMI shielding effect. [Means for solving the problem]

[0010] The means for solving the above problems are as follows, and the present invention includes the following aspects.

[0011] A first aspect of the present invention is a composition for electromagnetic shielding, comprising (A) silver particles and (B) a first solvent having at least one structure selected from the group consisting of a structure represented by the following formula (1) and a structure represented by the following formula (2), and having a boiling point of less than 200°C.

[0012] [ka]

[0013] (In formula (1), R 1 is an alkyl group having 2 to 3 carbon atoms and a double bond between carbon atoms.

[0014] [ka]

[0015] (In formula (2), R 2 is an alkylidene group having 2 to 3 carbon atoms.

[0016] A second aspect of the present invention is an electronic part using the electromagnetic wave shielding composition. Effect of the Invention

[0017] According to the present invention, it is possible to provide an electromagnetic wave shielding composition that can reduce the resistivity and further enhance the EMI shielding effect. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The electromagnetic shielding composition according to the present disclosure will be described below based on embodiments, however, the embodiments shown below are merely examples for embodying the technical concept of the present invention, and the present invention is not limited to the electromagnetic shielding composition described below.

[0019] The electromagnetic shielding composition according to the first embodiment of the present invention is a composition for electromagnetic shielding, characterized by comprising (A) silver particles and (B) a first solvent having at least one structure selected from the group consisting of a structure represented by the following formula (1) and a structure represented by the following formula (2), and having a boiling point of less than 200°C.

[0020] [ka]

[0021] In formula (1), R 1 In formula (1), R is an alkyl group having 2 to 3 carbon atoms and a double bond between carbon atoms. 1 Specific examples of R include vinyl, 1-propenyl, 2-propenyl (allyl), and isopropenyl. 1 is preferably an isopropenyl group.

[0022] [ka]

[0023] In formula (2), R 2 is an alkylidene group having 2 to 3 carbon atoms. 2 is represented as an alkylidene group including the double bond in formula (2). 2 Specific examples of the alkylidene group including the double bond in formula (2) include an ethylidene group, a propylidene group, and an isopropylidene group. Of these, an isopropylidene group is preferred.

[0024] The electromagnetic shielding composition according to the first embodiment of the present invention contains (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, and therefore has high volatility, and the specific resistance of the shielding layer formed from the electromagnetic shielding composition is small, thereby enabling an improvement in the EMI shielding effect. (B) The first solvent may be a solvent having a structure represented by formula (1) or a solvent having a structure represented by formula (2), and it is sufficient that the boiling point is less than 200°C. (B) The first solvent may contain both a solvent having a structure represented by formula (1) and a solvent having a structure represented by formula (2), and it is sufficient that both have boiling points less than 200°C.

[0025] The EMI shielding effect of the shielding layer is expressed by the reflection loss (dB). The reflection loss can be calculated by the following formula (I). In the following formula (I), K is expressed by the following formula (II) and is the ratio of the impedance of the space to the impedance of the shielding layer. The smaller the resistivity of the shielding layer, i.e., the higher the conductivity, the lower the impedance of the shielding layer and the smaller the ratio of the impedance of the space to the impedance of the shielding layer, resulting in a higher reflection loss (dB) and a higher EMI shielding effect of the shielding layer. The shielding layer obtained from the electromagnetic shielding composition according to the first embodiment of the present invention has a low resistivity and can have a high EMI shielding effect.

[0026]

number

[0027]

number

[0028] (A) Silver particles In the electromagnetic shielding composition, the (A) silver particles are blended as conductive particles to shield electromagnetic waves. The average particle size of the (A) 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. When the (A) silver particles have an average particle size in the range of 30 nm to 350 nm, the sedimentation of the silver particles in the electromagnetic shielding composition can be suppressed and the dispersion state of the silver particles in the composition can be maintained, making it easy to form a shielding layer with enhanced EMI shielding effect.

[0029] The average particle size of silver particles can be measured, for example, by observation using a scanning electron microscope (hereinafter also referred to as "SEM"). For example, an SEM photograph or SEM image of silver particles is obtained at a magnification of 10,000 to 20,000 times, the outline of the silver particles present in the SEM photograph or SEM image is approximated to a perfect circle, the diameter of the perfect circle is measured, and the arithmetic average value of the diameters of any 50 silver particles can be determined as the average particle size.

[0030] The silver particles may have any shape, such as a spherical shape, a scaly shape, or a needle shape. When the silver particles have a scaly or needle shape, the average major axis length of the scaly or needle shape can be regarded as the average particle size. From the viewpoint of suppressing settling in the electromagnetic shielding composition, it is preferable that the (A) silver particles are spherical.

[0031] Specifically, silver powder manufactured by Metalor Technologies USA (product names: P620-7, P620-24) and silver powder manufactured by DOWA Electronics Co., Ltd. (product name: Ag nano powder-2) can be used as the silver particles.

[0032] The (A) silver particles are contained in the electromagnetic shielding composition in an amount, calculated as solid content, preferably in the range of 35% by mass or more and 95% by mass or less, and may be contained in the range of 40% by mass or more and 90% by mass or less.

[0033] A master batch in which the (A) silver particles are dispersed in the (B) first solvent and / or the (D) second solvent other than the (B) first solvent may be used. The master batch is prepared by dispersing silver particles in the (B) first solvent and / or the (D) second solvent in advance to form a slurry. By using a master batch containing the (A) silver particles in the electromagnetic shielding composition, the (A) silver particles are less likely to settle in the electromagnetic shielding composition, and it becomes easier to maintain a state in which they are appropriately dispersed in the composition.

[0034] The (B) first solvent and / or the (D) second solvent other than the (B) first solvent contained in the masterbatch may be one type of solvent or two or more types of 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 the group consisting of ethylene glycol monophenyl ether (EPH), butyl carbitol acetate (BCA), and butyl carbitol (BC). The (B) first solvent or the (D) second solvent may be one type of solvent or two or more types of solvents in combination. The (B) first solvent or the (D) second solvent contained in the masterbatch may be in an amount that can suppress the precipitation of the (A) silver particles contained in the masterbatch and maintain a slurry state.

[0035] (B) First Solvent In the electromagnetic shielding composition, the (B) first solvent is preferably limonene or terpinolene. When the (B) first solvent is limonene or terpinolene, the volatility is high, and the resistivity of the shielding layer formed from the electromagnetic shielding composition is low, thereby improving the EMI shielding effect.

[0036] Limonene is represented by the following formula (3), has a structure represented by the above formula (1), and has a boiling point of 176°C.

[0037] [ka]

[0038] Terpinolene is represented by the following formula (4), has a structure represented by the above formula (2), and has a boiling point of 184°C.

[0039] [ka]

[0040] The (B) first solvent is preferably contained in the electromagnetic shielding composition in an amount of 5 to 150 parts by mass relative to 100 parts by mass of the (A) silver particles. By containing the (B) first solvent in the electromagnetic shielding composition in an amount of 5 to 150 parts by mass relative to 100 parts by mass of the (A) silver particles, a shielding layer can be formed in a state in which the (A) silver particles are substantially uniformly dispersed, and the (B) first solvent volatilizes to form a shielding layer with high EMI shielding effect. The amount of the (B) first solvent contained in the electromagnetic shielding composition is preferably in the range of 6 to 140 parts by mass, more preferably in the range of 7 to 130 parts by mass relative to 100 parts by mass of the (A) silver particles.

[0041] (C) Dispersant The electromagnetic shielding composition preferably further contains a dispersant (C). By containing the dispersant (C) in the electromagnetic shielding composition, the dispersibility of the silver particles (A) can be improved and sedimentation can be suppressed, making it possible to form a shielding layer with high EMI shielding effect.

[0042] In the electromagnetic wave shielding composition, the dispersant (C) is preferably at least one selected from the group consisting of acrylic acid dispersants, phosphate ester salt dispersants, and polyfunctional ionic dispersants, since it has good compatibility with the first solvent (B) or the second solvent (D). The dispersant of the component (C) may be a carboxylic acid dispersant. An example of the acrylic dispersant is polyisobutyl methacrylate. An example of the phosphate ester salt dispersant is BYK-145 manufactured by BYK-Chemie. An example of the polyfunctional ionic dispersant is SC1015F of the Marialim (registered trademark) series or Marialim (registered trademark) SC series manufactured by NOF Corporation. The dispersant of the Marialim (registered trademark) series manufactured by NOF Corporation is a polyfunctional comb-type dispersant having an ionic group in the main chain and a polyoxyalkylene chain in the graft chain. An example of the carboxylic acid dispersant is a dicarboxylic acid weak anionic dispersant manufactured by CRODA (product name: Hypermer KD-57). An example of the phosphate ester salt dispersant is a phosphate ester dispersant manufactured by CRODA (product name: CRODAFOS O3A).

[0043] The (C) dispersant is preferably contained in the electromagnetic shielding composition in an amount of 0.5 to 10 parts by mass relative to 100 parts by mass of the (A) silver particles. By containing the (C) dispersant in the electromagnetic shielding composition in an amount of 0.5 to 10 parts by mass relative to 100 parts by mass of the (A) silver particles, settling of the (A) silver particles can be suppressed, and a shielding layer can be formed in a state in which the silver particles are substantially uniformly dispersed, and a shielding layer having low resistivity and high EMI shielding effect can be formed. The amount of the (C) dispersant contained in the electromagnetic shielding composition is preferably in the range of 1 to 8 parts by mass, more preferably in the range of 1.5 to 7 parts by mass, relative to 100 parts by mass of the (A) silver particles.

[0044] The (C) dispersant may be contained in a master batch in which the (A) silver particles are dispersed in a slurry state in advance. When the master batch contains the (C) dispersant, the sedimentation of the (A) silver particles can be suppressed, and a shielding layer can be formed in a state in which the silver particles are dispersed approximately uniformly, thereby forming a shielding layer with high EMI shielding effect. Even when the (C) dispersant is contained in the master batch, it is sufficient that the dispersant is contained in a range of 0.5 parts by mass to 10 parts by mass relative to 100 parts by mass of the (A) silver particles contained in the electromagnetic shielding composition.

[0045] The electromagnetic shielding composition may contain an additive. Examples of additives include a silane coupling agent and an antifoaming agent. The additive may be added to the electromagnetic shielding composition, or may be added to the masterbatch when a masterbatch is used. The amount of the additive in the electromagnetic shielding composition is preferably in the range of 0.01 to 5 parts by mass, and preferably in the range of 0.05 to 3 parts by mass, relative to 100 parts by mass of the electromagnetic shielding composition. Even when the additive is added to the masterbatch, the amount of the additive in the electromagnetic shielding composition to which the masterbatch has been added may be in the range of 0.01 to 5 parts by mass, relative to 100 parts by mass of the electromagnetic shielding composition.

[0046] The silane coupling agent can be blended to enhance the heat resistance and adhesive strength of the electromagnetic shielding composition. For example, various silane coupling agents such as epoxy, amino, vinyl, methacryl, acrylic, and mercapto can be used. Among these, epoxy silane coupling agents having an epoxy group and methacryl silane coupling agents having a methacryl group are preferred. Specifically, an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane) (product name: KBM403) manufactured by Shin-Etsu Chemical Co., Ltd., a methacryl silane coupling agent (3-methacryloxypropyltrimethoxysilane) (product name: KBM503) manufactured by Shin-Etsu Chemical Co., Ltd., and the like can be used.

[0047] The defoaming agent is blended to prevent the generation of bubbles in the electromagnetic shielding composition, and for example, acrylic, silicone, and fluorosilicone defoaming agents can be used. Specifically, a silicone defoaming agent (product name: WACKER AF98 / 1000) manufactured by Wacker Asahi Kasei Silicone Co., Ltd. can be used. When a silane coupling agent is added, it can be added in an amount of 0.001 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the (A) silver particles.

[0048] viscosity The viscosity of the electromagnetic shielding composition, measured at 25°C and 10 rpm using, for example, a rotational viscometer (product number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd., is preferably 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 electromagnetic shielding composition measured at 25°C and 10 rpm is in the range of 10 mPa·s to 10,000 mPa·s, the (A) silver particles will be dispersed in the electromagnetic shielding composition, and a shielding layer with high EMI shielding effect can be formed by spray application.

[0049] Thixotropy index Ti (5rpm / 50rpm) The thixotropy index Ti of the electromagnetic shielding composition is preferably in the range of 1 to 6, more preferably in the range of 1.2 to 5.0. The thixotropy index is the ratio of the viscosity measured at 25°C at 5 rpm to the viscosity measured at 50 rpm using, for example, a rotational viscometer (product number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd. The thixotropy index Ti is an index that measures the dependency of viscosity on shear rate (the rotation rate of the viscometer) 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 smaller than 1, it indicates that the viscosity is smaller when the shear force is small than when the shear force is large, and when the Ti value is larger than 1, it indicates that the viscosity is larger when the shear force is small than when the shear force is large. The larger the Ti value, the more thixotropic the composition is. When the Ti value of the electromagnetic shielding composition is in the range of 1 to 6, a shielding layer with a high EMI shielding effect can be formed by spray application.

[0050] Method for producing electromagnetic wave shielding composition The electromagnetic wave shielding composition can be produced, for example, by blending (A) silver particles, (B) the first solvent, if necessary (C) a dispersant, and if necessary, additives, and stirring and mixing them using a known device. Examples of known devices that can be used include a Henschel mixer, a roll mill, and a triple roll mill. (A) silver particles, (B) the first solvent, and if necessary (C) a dispersant may be simultaneously charged into the device and mixed, or a portion of them may be charged into the device first and mixed, and the remainder may be charged into the device later and mixed.

[0051] Masterbatch manufacturing method The master batch can be produced in a slurry state by previously stirring and mixing (A) silver particles and (B) first solvent and / or (D) second solvent other than (B) first solvent. The master batch may contain (C) dispersant and may contain the above-mentioned additives as necessary. The (A) silver particles and (B) first solvent and / or (D) second solvent contained in the master batch can be stirred and mixed using the above-mentioned known device.

[0052] Application Method The electromagnetic shielding composition can be spray-coated onto electronic components and the like to form a shielding layer on the outer surface of the electronic components and the like. The electromagnetic shielding composition can be coated onto electronic components, for example, using a conventionally known spray coating machine. The electromagnetic shielding composition may be filled into an aerosol can and then coated. The thickness of the shielding layer formed by spray-coating the electromagnetic shielding composition onto an electronic component may be in the range of 5 μm to 30 μm, 5 μm to 20 μm, or 5 μm to 10 μm.

[0053] specific resistance The resistivity of the shielding layer formed by spraying the electromagnetic wave shielding composition is 30 m It is sufficient if the resistance is less than Ω·cm, and preferably 25 m Ω·cm or less, and more preferably 20 m Ω·cm or less, and even more preferably 10 m Ω·cm or less, and particularly preferably 7 m Ω cm or less, 1 m The smaller the resistivity of the shielding layer formed by spraying the electromagnetic shielding composition, i.e., the higher the conductivity, the lower the impedance of the shielding layer, and the smaller the ratio of the impedance of the space to the impedance of the shielding layer, resulting in an increased return loss (dB) and an increased EMI shielding effect of the shielding layer.

[0054] The resistivity can be measured, for example, by spraying the electromagnetic shielding composition onto an alumina substrate in a specific size and length, and then drying the resulting shielding layer in a hot air dryer at 200°C for 30 minutes, using a multimeter (model number: 2001) manufactured by Toyo Technical Corporation, using a four-terminal method.

[0055] Electronic Components The electromagnetic shielding composition can be applied to electronic components by spray application or the like. Examples of electronic components for which the electromagnetic shielding composition is used include power amplifiers, Wi-Fi / Bluetooth modules, flash memories, and the like used in electronic devices such as mobile phones, smartphones, notebook computers, and tablet terminals. When the electromagnetic shielding composition is used for electronic components, the electromagnetic shielding composition may be applied to each electronic component and then each electronic component may be mounted on a substrate, or the electromagnetic shielding composition may be applied after each electronic component is mounted on a substrate. EXAMPLES

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0057] The following raw materials were used to produce the electromagnetic shielding compositions of the Examples and Comparative Examples.

[0058] (A) Silver particles A1: Spherical, average particle size 100 nm, silver filler, manufactured by Metalor Technologies USA, product number: P620-24 A2: Spherical, average particle size 60 nm, silver filler, manufactured by DOWA Electronics Co., Ltd., product number: Ag nano powder-2 A3: Spherical, average particle size 200 nm, silver filler, manufactured by Metalor Technologies USA, product number: P620-7 (A) The average particle size of silver particles was measured by observing with a scanning electron microscope (SEM), randomly selecting 50 particles from SEM photographs or SEM images at magnifications of 10,000 to 20,000, approximating the outline of each particle to a perfect circle, measuring the diameter of the perfect circle, and taking the arithmetic average value as the average particle size. When the silver particles are in the form of flakes (scales), the average diameter was taken as the average major axis value of 50 random particles.

[0059] (B') Third Solvent The (B') third solvent is different from the (B) first solvent described below, does not have at least one structure selected from the structure represented by the formula (1) and the structure represented by the formula (2), and has a boiling point of 200° C. or higher. The (B') third solvent may be the same as or different from the (D) second solvent other than the (B) first solvent. B'1: Butyl carbitol (BC) (90 to 100% by mass of diethylene glycol monobutyl ether), manufactured by Taishin Chemical Co., Ltd., boiling point 247°C B'2: Terpineol, manufactured by Kobayashi Perfume Co., Ltd., boiling point 219°C B'3: Ethylene glycol monobutyl ether, manufactured by Tokyo Chemical Industry Co., Ltd., boiling point 171°C

[0060] (B) First Solvent The first solvent (B) has at least one structure selected from the group consisting of the structure represented by the formula (1) and the structure represented by the formula (2), and has a boiling point of less than 200°C. B4: Limonene, manufactured by Nippon Terpene Chemical Co., Ltd., boiling point 176°C B5: Terpinolene, manufactured by Nippon Terpene Chemical Co., Ltd., boiling point 184°C

[0061] (C) Dispersant C1: Polyisobutyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd. C2: Phosphate ester salt dispersant, manufactured by BYK-Chemie, product number: BYK-145 C3: Multifunctional ionic dispersant, Marialim (registered trademark) SC1015F, manufactured by NOF Corporation

[0062] Examples 1 to 12, Comparative Examples 1 to 5 The raw materials were mixed and dispersed using a three-roll mill so as to obtain the blending ratios shown in Tables 1 and 2 below, to produce compositions for electromagnetic shielding.

[0063] Example 13 An electromagnetic shielding composition was produced in the same manner as in Example 1, except that a master batch in which the (A) silver filler A1, which is silver particles, was previously dispersed in the (B) first solvent terpinolene to form a slurry was used. The master batch contained 6.0 parts by mass of the (B) first solvent per 100 parts by mass of the (A) silver filler A1, which is silver particles. Specifically, the electromagnetic shielding composition was produced in the same manner as in Example 1, with each raw material other than the silver filler being in the blending ratio shown in Table 2 below per 100 parts by mass of the (A) silver filler A1, which is silver particles in the master batch.

[0064] Viscosity measurement The viscosity of each of the electromagnetic wave shielding compositions in the Examples and Comparative Examples was measured at 25° C. and rotational speeds of 1 rpm, 5 rpm, 10 rpm, 50 rpm, and 100 rpm using a rotational viscometer (product number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd. The results are shown in Tables 1 and 2.

[0065] Thixotropy index Ti (5rpm / 50rpm) The thixotropy index Ti (5 rpm / 50 rpm) of each of the electromagnetic wave shielding compositions in the Examples and Comparative Examples was calculated by calculating the ratio of the viscosity measured at 25° C. and 50 rpm using a rotational viscometer (product number: TVE-22H) manufactured by Tokyo Keiki Co., Ltd. The results are shown in Tables 1 and 2.

[0066] specific resistance Each electromagnetic shielding composition of the Examples and Comparative Examples was applied to an alumina substrate by attaching two tapes of about 85 to 95 μm thickness in parallel with an interval of 3 mm, spraying the mixture between the two tapes to a width of 3 mm, length of 50 mm, and thickness of about 90 μm, and then drying the mixture in a hot air dryer at 200° C. for 30 minutes to form a shielding layer. The resistivity of the shielding layer was measured by a four-terminal method using a multimeter (model number: 2001) manufactured by Toyo Corporation. The results are shown in Tables 1 and 2.

[0067] [Table 1]

[0068] [Table 2]

[0069] As shown in Tables 1 and 2, each shielding layer formed by spraying each of the electromagnetic shielding compositions of Examples 1 to 13 had a resistivity of 5 Ω cm or less, i.e., a low resistivity, i.e., a high conductivity, a low impedance of the shielding layer, a high return loss (dB), and a high EMI shielding effect.

[0070] The electromagnetic shielding compositions of Examples 1 to 13 each had a viscosity measured at 25°C at rotation speeds of 1 rpm, 5 rpm, 10 rpm, 50 rpm, and 100 rpm that was within the range of 10 mPa·s to 10,000 mPa·s, and the (A) silver particles were dispersed in the electromagnetic shielding composition and could be spray-coated. Furthermore, the electromagnetic shielding compositions of Examples 1 to 13 each had a thixotropy index Ti within the range of 1 to 6, and had thixotropy that allowed a shielding layer to be formed by spray-coating.

[0071] Each of the electromagnetic shielding compositions of Comparative Examples 1 to 5 contains a third solvent (B'), which 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 different from the first solvent (B). Each of the shielding layers formed by spray-coating each of the electromagnetic shielding compositions of Comparative Examples 1 to 5 containing the third solvent (B') had a higher resistivity than each of the shielding layers formed by spray-coating each of the electromagnetic shielding compositions of Examples 1 to 13. [Industrial Applicability]

[0072] The electromagnetic wave shielding composition according to the first embodiment of the present invention can form a shielding layer by spraying onto electronic components, and can be suitably used for electronic components such as power amplifiers, Wi-Fi / Bluetooth modules, and flash memories used in electronic devices such as mobile phones, smartphones, notebook computers, and tablet terminals.

Claims

1. (A) silver particles; (B) a first solvent having at least one structure selected from the structures represented by the following formula (2) and a boiling point of less than 200° C., Electromagnetic wave shielding composition, wherein the (B) first solvent is present in an amount within the range of 5 parts by mass or more and 150 parts by mass or less per 100 parts by mass of the (A) silver particles. 【Chemistry 1】 (In formula (2), R 2 is an alkylidene group having 2 to 3 carbon atoms.)

2. 2. The electromagnetic shielding composition according to claim 1, wherein the first solvent (B) is terpinolene.

3. The electromagnetic shielding composition according to claim 1 or 2, further comprising a dispersant (C).

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

5. 4. The electromagnetic shielding composition according to claim 3, wherein the dispersant (C) is at least one selected from the group consisting of acrylic acid-based dispersants and polyfunctional ionic dispersants.

6. An electromagnetic wave shielding composition described in any one of claims 1 to 5, wherein the resistivity of a shielding layer formed by spraying the electromagnetic wave shielding composition is 1 μΩ·cm or more and 30 μΩ·cm or less.

7. An electromagnetic wave shielding composition described in any one of claims 1 to 6, having a viscosity measured at 25°C and a rotation speed of 10 rpm of 10 mPa·s or more and 10,000 mPa·s or less.

8. An electromagnetic wave shielding composition described in any one of claims 1 to 7, wherein the thixotropy index Ti is in the range of 1 or more and 6 or less.

9. 9. The electromagnetic shielding composition according to claim 1, wherein the (A) silver particles are dispersed in the (B) first solvent and / or a (D) second solvent other than the (B) first solvent to form a slurry-like master batch.

10. The electromagnetic shielding composition according to claim 9 , wherein the master batch comprises a dispersing agent (C).

11. An electronic part using the electromagnetic shielding composition according to any one of claims 1 to 10.

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