WO2019176612A1 - Electromagnetic absorber composition, three-dimensionally molded article formed from electromagnetic absorber, electronic component and electronic device using same, and methods for producing electronic component and electronic device - Google Patents

Abstract

This three-dimensionally molded article formed from an electromagnetic absorber is molded using an electromagnetic absorber composition containing a binder resin and iron oxide which is an electromagnetic wave absorbing material which magnetically resonates in millimeter-wave and higher frequency bands. The three-dimensionally molded article is molded into a thin-wall structure capable of covering an electronic member and satisfies the relational expression d × V^1/3 > 0.4, where d (mm) represents the wall thickness of the three-dimensionally molded article, and V (%) represents the volume content percentage of the electromagnetic wave absorbing material contained in the three-dimensionally molded article. Moreover, the electromagnetic wave transmission attenuation in the millimeter-wave and higher frequency bands is 10dB or greater.

Description

Electromagnetic wave absorber composition, electromagnetic wave absorber three-dimensional structure, electronic component and electronic device using the same, and method for manufacturing the electronic component and electronic device

The present invention relates to an electromagnetic wave absorber that absorbs millimeter wave electromagnetic waves, and more particularly, an electromagnetic wave absorber composition, an electromagnetic wave absorber three-dimensional structure, an electronic component and an electronic device using the same, and the electronic component And an electronic device manufacturing method.

With the development of wireless communication technology represented by mobile phones, various devices and sensors are being connected to the network wirelessly. In the medical field, devices are becoming cordless from the viewpoint of infection prevention, and medical devices are starting to be connected wirelessly. These communications require high-speed and large-capacity communication over a relatively short distance, and have a high use frequency. As the number of devices using such high frequencies increases, there is an increased risk of malfunctions in electronic devices and communications due to malfunctions caused by noise generated from the devices and interference between the noise and the electromagnetic waves used. Furthermore, in recent years, the installation of millimeter wave radar for the purpose of preventing collision accidents of automobiles has begun. Since malfunctions in these medical and automotive devices affect human life, there should be no malfunction. Therefore, there is a need to apply an electromagnetic wave absorber as a countermeasure against so-called EMC (Electromagnetic Compatibility) countermeasures to circuit elements and transmission lines that emit and receive millimeter-wave electromagnetic waves. It is growing.

In order to suppress high-frequency noise, an electromagnetic wave absorbing sheet that uses magnetic loss of a magnetic material that has been conventionally used is less effective, and a resonant electromagnetic wave absorbing sheet that uses a conductive material is required (Patent Document 1). Non-Patent Document 1). However, direct contact of a conductive material with a conductive circuit element or transmission path is not suitable because it causes a short circuit. Even if the conductive layer of the resonance type electromagnetic wave absorbing sheet is prevented from directly touching the circuit element or the transmission path by the adhesive to be applied to the circuit element or the transmission path, the sheet is cut and punched to a desired size. When used, the conductive layer is exposed on the cut surface, and there is a risk of short-circuiting the circuit by contacting this portion. Furthermore, the danger of a short circuit due to the loss of the conductive material cannot be eliminated.

On the other hand, the iron oxide magnetic material is a non-conductive material, and there is no danger of a short circuit. In recent years, it has been found that epsilon-type iron oxide has an electromagnetic wave absorption ability in the millimeter wave band, and the absorption frequency can be controlled by the substitution element and the substitution amount (Patent Documents 2 and 3). Furthermore, it is known that hexagonal ferrite also has an electromagnetic wave absorption ability in the millimeter wave band (Patent Document 4).

JP 2007-81119 A (Patent No. 4881613) JP 2008-60484 A (Patent No. 4787978) JP 2008-277726 A (Patent No. 4859791) JP 2007-250823 A (Japanese Patent No. 4673380)

By the way, when a sheet-like electromagnetic wave absorber is bonded to a circuit element or transmission line that is desired to prevent the influence of noise or noise with adhesive or the like to suppress noise, the shape of the electromagnetic wave absorber sheet is usually a circuit. Since the shape is difficult to follow the surface shape of the element or the transmission path, the sheet may be peeled off. Moreover, since the size of a circuit element or a transmission line is small, handling of an electromagnetic wave absorber sheet may be difficult. Furthermore, depending on the material and roughness of the surface of the circuit element, the adhesive may not stick, or the adhesive may come into contact with the circuit element or the transmission path.

Also, the noise suppression effect correlates with the amount of electromagnetic wave absorbing material present in the traveling direction of the electromagnetic wave that becomes noise, and the greater the amount of electromagnetic wave absorbing material, the higher the noise suppressing effect. Therefore, the noise suppression effect is reduced by the thickness of the electromagnetic wave absorber and the uneven distribution of the electromagnetic wave absorbing material, and noise may leak.

The present invention solves the above-mentioned conventional problems, and can absorb an electromagnetic wave absorber securely to a noise source or to a circuit element or a transmission path to prevent the influence of noise without leaking the electromagnetic wave. A three-dimensional modeled body is provided.

The electromagnetic wave absorber composition of the present invention is an electromagnetic wave absorber composition used for forming an electromagnetic wave absorber three-dimensional structure having an electromagnetic wave transmission attenuation amount of 10 dB or more in a millimeter wave band or higher frequency band. And an electromagnetic wave absorbing material and a binder resin, wherein the electromagnetic wave absorbing material is an iron oxide that magnetically resonates in a frequency band equal to or higher than a millimeter wave band, and the thickness of the electromagnetic wave absorber three-dimensional structure is d When forming as (mm), if the volume content of the electromagnetic wave absorbing material in the electromagnetic wave absorber composition is V (%), a relational expression of d × V ^1/3 > 0.4 is established.

The electromagnetic wave absorber three-dimensional structure of the present invention is an electromagnetic wave absorber three-dimensional structure formed using the electromagnetic wave absorber composition of the present invention, wherein the electromagnetic wave absorber three-dimensional structure is It is shaped into a thin-walled structure that can cover an electronic member, the thickness of the electromagnetic wave absorber three-dimensional structure is d (mm), and the volume content of the electromagnetic wave absorbing material contained in the electromagnetic wave absorber three-dimensional structure is Assuming V (%), a relational expression of d × V ^1/3 > 0.4 is established, and the electromagnetic wave transmission attenuation in a frequency band equal to or higher than the millimeter wave band is 10 dB or higher.

The electronic component of the present invention includes an electronic member coated with the electromagnetic wave absorber three-dimensional structure of the present invention.

The electronic device of the present invention includes the electronic component of the present invention.

The method for producing an electronic component of the present invention includes a step of preparing the electromagnetic wave absorber composition of the present invention, a step of forming an electromagnetic wave absorber three-dimensional structure using the electromagnetic wave absorber composition, A step of bonding the electromagnetic wave absorber three-dimensional structure to an electronic member and covering it.

The electronic device manufacturing method of the present invention includes a step of incorporating the electronic component manufactured by the electronic component manufacturing method of the present invention into the electronic device.

According to the present invention, using an iron oxide that is a non-conductive material as an electromagnetic wave absorbing material, an electromagnetic wave absorber three-dimensional structure having a thin structure is formed, and the thickness of the electromagnetic wave absorber three-dimensional structure, By controlling the volume content of the electromagnetic wave absorbing material in the electromagnetic wave absorber three-dimensional structure to a specific relationship, an electromagnetic wave absorber that does not cause a short circuit and that does not leak noise can be provided. .

FIG. 1 is a schematic cross-sectional view showing an example of a three-dimensional structure of an electromagnetic wave absorber according to the present embodiment. FIG. 2 is a schematic cross-sectional view illustrating another example of the electromagnetic wave absorber three-dimensional structure according to the present embodiment. FIG. 3 is a schematic cross-sectional view showing an example of a part of the electronic component of the present embodiment. FIG. 4 is a schematic cross-sectional view showing another example of a part of the electronic component of the present embodiment. FIG. 5 is a graph showing the electromagnetic wave transmission attenuation amount at a frequency of 76 GHz of the electromagnetic wave absorbers of Examples and Comparative Examples. FIG. 6 is a diagram showing an electromagnetic wave absorption spectrum of the electromagnetic wave absorbers of Example 1 and Comparative Example 3.

The composition for an electromagnetic wave absorber disclosed in the present application is a composition for an electromagnetic wave absorber used for forming an electromagnetic wave absorber three-dimensional structure having an electromagnetic wave transmission attenuation amount of 10 dB or more in a frequency band of a millimeter wave band or higher. An electromagnetic wave absorbing material and a binder resin, wherein the electromagnetic wave absorbing material is an iron oxide that magnetically resonates in a frequency band greater than or equal to a millimeter wave band, and the thickness of the electromagnetic wave absorber three-dimensional structure is d When forming as (mm), if the volume content of the electromagnetic wave absorbing material in the electromagnetic wave absorber composition is V (%), a relational expression of d × V ^1/3 > 0.4 is established.

Using the electromagnetic wave absorber composition, an electromagnetic wave absorber three-dimensional structure having a thin-walled structure is formed, and the thickness of the electromagnetic wave absorber three-dimensional structure and the above-mentioned electromagnetic wave absorber three-dimensional structure By controlling the volume content of the electromagnetic wave absorbing material to the above relationship, an electromagnetic wave absorber that does not cause a short circuit and that does not leak noise can be provided.

The electromagnetic wave absorbing material is preferably hexagonal ferrite containing at least one selected from the group consisting of Sr and Ba. Further, the electromagnetic wave absorbing material is hexagonal ferrite containing Sr, and it is more preferable that a part of Fe site of the hexagonal ferrite containing Sr is substituted with Al. The hexagonal ferrite is a non-conductive iron oxide that magnetically resonates in a frequency band above the millimeter wave band. By replacing a part of the Fe site of the hexagonal ferrite containing Sr with Al, electromagnetic wave absorption is achieved. This is because the magnetic resonance frequency to be carried can be changed and the thermal stability is excellent.

The electromagnetic wave absorbing material is epsilon-type iron oxide, and a part of the Fe site of the epsilon-type iron oxide is preferably substituted with at least one selected from the group consisting of Al, Ga, and In. . The epsilon-type iron oxide is a non-conductive iron oxide that magnetically resonates in a frequency band equal to or higher than the millimeter wave band, and a part of the Fe site is at least one selected from the group consisting of Al, Ga and In. This is because the magnetic resonance frequency responsible for electromagnetic wave absorption can be changed by substitution.

The binder resin preferably contains at least one selected from the group consisting of an active energy ray curable resin, a thermosetting resin, a thermoplastic resin, and a rubber-like resin. This is because by using the binder resin, an electromagnetic wave absorber three-dimensional structure having a thin-walled structure can be formed by various methods.

The electromagnetic wave absorber three-dimensional structure disclosed in the present application is an electromagnetic wave absorber three-dimensional structure formed using the electromagnetic wave absorber composition disclosed above, and the electromagnetic wave absorber three-dimensional structure Is formed into a thin-walled structure capable of covering an electronic member, the thickness of the electromagnetic wave absorber three-dimensional structure is d (mm), and the volume of the electromagnetic wave absorbing material contained in the electromagnetic wave absorber three-dimensional structure is included. When the rate is V (%), a relational expression of d × V ^1/3 > 0.4 is established, and the electromagnetic wave transmission attenuation amount in the frequency band of the millimeter wave band or higher is 10 dB or higher.

Using the electromagnetic wave absorber composition, an electromagnetic wave absorber three-dimensional structure having a thin-walled structure is formed, and the thickness of the electromagnetic wave absorber three-dimensional structure and the above-mentioned electromagnetic wave absorber three-dimensional structure By controlling the volume content of the electromagnetic wave absorbing material to the above relationship, even when the thickness of the electromagnetic wave absorber three-dimensional structure changes during modeling, it is possible to ensure a certain level of electromagnetic wave absorption performance, noise. An electromagnetic wave absorber without leakage can be provided.

The volume resistivity of the electromagnetic wave absorber three-dimensional structure is preferably 10 ¹⁰ Ωcm or more. This is because the occurrence of a short circuit can be reliably prevented.

Further, the electronic component disclosed in the present application is an electronic component including an electronic member covered with the electromagnetic wave absorber three-dimensional structure disclosed above. By covering the electronic member with the electromagnetic wave absorber three-dimensional structure, EMC (electromagnetic compatibility) of the electronic component can be ensured. In other words, the above-mentioned electronic components are resistant to the electromagnetic waves emitted from them from affecting other devices and systems, and to operate satisfactorily even when receiving electromagnetic waves from other devices and systems. Can be secured.

The electromagnetic wave absorber three-dimensional structure is preferably in contact with and followed the surface of the electronic member. This is because noise leakage can be prevented more reliably and the EMC (electromagnetic compatibility) of the electronic component can be further improved.

The electromagnetic wave absorber three-dimensional structure may have a non-contact portion with respect to the surface of the electronic member. This is because, depending on the surface shape of the electronic member, it may be difficult to form the electromagnetic wave absorber three-dimensional structure into a shape in which the electromagnetic wave absorber is brought into contact with the surface of the electronic member.

Examples of the electronic member include a circuit element and a transmission line.

Further, the electronic device disclosed in the present application is an electronic device including the electronic component disclosed above. By providing the electronic component, EMC (electromagnetic compatibility) of the electronic device can be ensured.

Moreover, the manufacturing method of the electronic component disclosed by this application forms the electromagnetic wave absorber three-dimensional structure using the process for preparing the electromagnetic wave absorber composition disclosed above and the electromagnetic wave absorber composition. A process and a process of bonding and covering the electromagnetic wave absorber three-dimensional structure to an electronic member. With the above manufacturing method, an electronic component having high EMC (electromagnetic compatibility) can be manufactured.

Further, the electronic device manufacturing method disclosed in the present application includes a step of incorporating the electronic component manufactured by the electronic component manufacturing method disclosed above into the electronic device. With the above manufacturing method, an electronic device with high EMC (electromagnetic compatibility) can be manufactured.

(Embodiment of composition for electromagnetic wave absorber)
First, an embodiment of the electromagnetic wave absorber composition will be described. The electromagnetic wave absorber composition of the present embodiment is used to form an electromagnetic wave absorber three-dimensional structure having an electromagnetic wave transmission attenuation amount of 10 dB or more in a frequency band equal to or higher than a millimeter wave band, and an electromagnetic wave absorbing material and a binder. Resin, and the electromagnetic wave absorbing material is an iron oxide that magnetically resonates in a frequency band equal to or higher than a millimeter wave band, and the thickness of the electromagnetic wave absorber three-dimensional structure is formed as d (mm), When the volume content of the electromagnetic wave absorbing material in the electromagnetic wave absorber composition is V (%), the relational expression d × V ^1/3 > 0.4 is established.

Hereinafter, each component contained in the composition for electromagnetic wave absorber will be described.

<Electromagnetic wave absorbing material>
The electromagnetic wave absorbing material is an iron oxide that magnetically resonates in a frequency band greater than or equal to the millimeter wave band. Specifically, the following hexagonal ferrite or the following epsilon type iron oxide can be used. The volume content V (%) of the electromagnetic wave absorbing material in the composition for electromagnetic wave absorber is d × V ^1/3 > when the thickness of the electromagnetic wave absorber three-dimensional structure is formed as d (mm). Adjustment is made so that a relational expression of 0.4 is established.

[Hexagonal ferrite]
As the hexagonal ferrite, hexagonal ferrite containing at least one selected from the group consisting of Sr and Ba can be used. Further, it is more preferable that a part of the Fe site of the hexagonal ferrite containing Sr is substituted with Al. The hexagonal ferrite has a magnetoblumbite type crystal structure and is represented by a general formula: AFe ₁₂ O ₁₉ , and A in the general formula represents at least one selected from the group consisting of Sr and Ba. The hexagonal ferrite can change the magnetic resonance frequency responsible for electromagnetic wave absorption by substituting a part of Fe site with a trivalent Al metal element.

The details of the hexagonal ferrite are disclosed in the aforementioned Patent Document 4 (Japanese Patent Laid-Open No. 2007-250823).

[Epsilon-type iron oxide]
As the epsilon-type iron oxide, epsilon-type iron oxide in which a part of the Fe site is substituted with at least one selected from the group consisting of Al, Ga and In can be used. The epsilon-type iron oxide has an ε-phase crystal structure, is represented by a general formula: ε-Fe ₂ O ₃ , and part of the Fe site is at least one selected from the group consisting of Al, Ga, and In. By substituting, the magnetic resonance frequency responsible for electromagnetic wave absorption can be changed.

The details of the above epsilon-type iron oxide are disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2008-60484) and Patent Document 3 (Japanese Patent Laid-Open No. 2008-277726).

<Binder resin>
The binder resin is used as a matrix material when the electromagnetic wave absorbing material is dispersed and fixed to form an electromagnetic wave absorber three-dimensional structure, specifically, an active energy ray curable resin, At least one selected from the group consisting of thermosetting resins, thermoplastic resins and rubber-like resins can be used.

[Active energy ray curable resin]
Examples of the active energy ray curable resin include urethane acrylate, acrylic resin acrylate, and epoxy acrylate. When the active energy ray-curable resin is used as the binder resin, an electromagnetic wave absorber three-dimensional structure can be produced by an optical modeling method using a three-dimensional printer.

More specifically, bifunctional or higher polyfunctional ethylenically unsaturated monomers can be used, for example, linear or branched alkylene glycol di (meth) acrylate having 10 to 25 carbon atoms, alkylene glycol tri (meth). Acrylate [for example, tripropylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 3-methyl- 1,5-pentanediol di (meth) acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di (meth) acrylate, pentaerythritol tri (meth) acrylate, etc.], having 10 to 30 carbon atoms Alicyclic ring-containing di (meth) acrylate [for example, dimethylol tricyclodeca Di (meth) acrylate, etc.] or the like can be used. These may be used alone or in combination of two or more.

[Thermosetting resin]
As the thermosetting resin, for example, phenol resin, urea resin, melamine resin, epoxy resin, unsaturated polyester resin, alkyd resin, silicon resin, polyurethane and the like can be used. When the thermosetting resin is used as the binder resin, an electromagnetic wave absorber three-dimensional structure can be produced by a heat compression molding method.

[Thermoplastic resin]
Examples of the thermoplastic resin include polyethylene, polypropylene, polystyrene, ABS resin, methyl methacrylate resin, polyvinyl chloride, polyamide, polyethylene terephthalate, polybutylene terephthalate, and polycarbonate. When the thermoplastic resin is used as the binder resin, an electromagnetic wave absorber three-dimensional structure can be produced by an injection molding method.

[Rubber resin]
As the rubber-like resin, for example, urethane rubber, silicone rubber, fluorine rubber or the like which is a thermosetting elastomer can be used. When the rubber-like resin is used as the binder resin, an electromagnetic wave absorber three-dimensional structure can be produced by a heat compression molding method.

<Photopolymerization initiator>
When the active energy ray-curable resin is used as the binder resin, a photopolymerization initiator is added to the electromagnetic wave absorber composition. The photopolymerization initiator is for initiating a polymerization reaction or crosslinking reaction of a monomer by active energy rays, and the electromagnetic wave absorber composition contains the photopolymerization initiator, for example, a three-dimensional printer. The composition for electromagnetic wave absorber released using can be cured by irradiation with active energy rays.

The active energy ray irradiated to the photopolymerization initiator can be appropriately selected from, for example, ultraviolet rays, near ultraviolet rays, visible rays, infrared rays, far infrared rays and the like.

The photopolymerization initiator is not particularly limited as long as the polymerization can be initiated with low energy, and is a benzoin compound having 14 to 18 carbon atoms [for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isobutyl. Ethers, etc.], acetophenone compounds having 8 to 18 carbon atoms [for example, acetophenone, 2,2-diethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 2-hydroxy- 2-methyl-phenylpropan-1-one, diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, etc.], carbon number 4-19 anthraquinone compounds [eg, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-chloroanthraquinone, 2-amylanthraquinone, etc.], thioxanthone compounds having 13 to 17 carbon atoms [eg, 2,4-diethylthioxanthone , 2-isopropylthioxanthone, 2-chlorothioxanthone, etc.], ketal compounds having 16 to 17 carbon atoms (for example, acetophenone dimethyl ketal, benzyldimethyl ketal, etc.), benzophenone compounds having 13 to 21 carbon atoms (for example, benzophenone, 4-benzoyl, etc.) -4'-methyldiphenyl sulfide, 4,4'-bismethylaminobenzophenone, etc.], acylphosphine oxide compounds having 22 to 28 carbon atoms [for example, 2,4,6-trimethylbenzoyl-diphenyl -Phosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, etc.], and these compounds Can be used. These may be used alone or in combination of two or more.

The amount of the photopolymerization initiator added may be 3.0 to 15 parts by mass when the total mass of the electromagnetic wave absorber composition is 100 parts by mass. When two or more kinds of the photopolymerization initiators are used in combination, the addition amount is determined as the total addition amount of each photopolymerization initiator.

<Surface conditioner>
When the active energy ray curable resin is used as the binder resin, a surface conditioner is added to the electromagnetic wave absorber composition. Thereby, the surface tension of the said composition for electromagnetic wave absorbers can be adjusted to an appropriate range. By adjusting the surface tension of the composition for electromagnetic wave absorbers to an appropriate range, an optically shaped article with good dimensional accuracy can be obtained. In order to obtain this effect, the amount of the surface conditioner added may be 0.005 to 3.0 parts by mass when the total mass of the electromagnetic wave absorber composition is 100 parts by mass.

As the surface conditioner, a silicone compound or the like can be used, and examples of the silicone compound include a silicone compound having a polydimethylsiloxane structure. Specific examples include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, and polyaralkyl-modified polydimethylsiloxane. More specifically, the product names include BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-315, BYK-320, BYK-322, BYK-323, manufactured by BYK Chemie. BYK-325, BYK-330, BYK-331, BYK-333, BYK-337, BYK-344, BYK-370, BYK-375, BYK-377, BYK-UV3500, BYK-UV3510, BYK-UV3570; Evonik Japan-made TEGO-Rad2100, TEGO-Rad2200N, TEGO-Rad2250, TEGO-Rad2300, TEGO-Rad2500, TEGO-Rad2600, TEGO-Rad2700; Kyoeisha Chemical Co., Ltd. Granol 100, Granol 115, Gu Nord 400, Granol 410, Granol 435, Granol 440, Granol 450, B-1484, a Polyflow ATF-2, KL-600, UCR-L72, UCR-L93 or the like can be used. These may be used alone or in combination of two or more. When two or more kinds of the surface conditioners are used in combination, the addition amount is determined as the total addition amount of each surface conditioner.

The following filler and dispersant can be further added to the electromagnetic wave absorber composition.

<Filler>
By adding the filler, the electromagnetic wave absorption characteristics of the electromagnetic wave absorber can be improved. Examples of the filler that can be used include metal particles, metal fibers, carbon, carbon nanotubes, and carbon nanocoils whose surfaces are covered with an insulator layer.

<Dispersant>
By adding the dispersing agent, the above-described electromagnetic wave absorbing material can be uniformly arranged in the electromagnetic wave absorber without uneven distribution, so that the electromagnetic wave absorption characteristics of the electromagnetic wave absorber are improved. As the dispersant, a polymer dispersant having an Mw of 1,000 or more is preferably used. Examples of the polymer dispersant include trade names such as DISPERBYK-101 and DISPERBYK-102 manufactured by BYK Chemie; EFKA4010 and EFKA4046 manufactured by Fuka Additive; Disperse Aid 6 and Disperse Aid 8 manufactured by Sannopco Various Solsperse dispersants such as SOLSPERS 3000 and 5000 manufactured by Noveon; Adeka Pluronic L31 and F38 manufactured by ADEKA; Ionette S-20 manufactured by Sanyo Chemical Industries; Disparon KS- manufactured by Enomoto Kasei Co., Ltd. 860, 873SN etc. are mentioned. These may be used alone or in combination of two or more.

The amount of the dispersant added is preferably 0.05 to 15 parts by mass when the total mass of the electromagnetic wave absorber composition is 100 parts by mass. When two or more kinds of the dispersants are used in combination, the addition amount is determined as the total addition amount of each dispersant.

The electromagnetic wave absorber composition can be prepared by uniformly dispersing and mixing the above components. By uniformly dispersing each of the above components, the electromagnetic wave absorbing material can be prevented from being unevenly distributed and an electromagnetic wave absorber free from noise leakage can be produced. Although the said mixing method is not specifically limited, For example, the mixing method using a kneader, an extruder, a roll mill etc. is preferable.

(Embodiment of electromagnetic wave absorber three-dimensional structure)
Next, an embodiment of the electromagnetic wave absorber three-dimensional structure will be described. The electromagnetic wave absorber three-dimensional structure of the present embodiment is an electromagnetic wave absorber three-dimensional structure formed using the electromagnetic wave absorber composition disclosed in the above-described embodiment, and is thin enough to cover an electronic member When the thickness of the electromagnetic wave absorber three-dimensional structure is d (mm) and the volume content of the electromagnetic wave absorbing material included in the electromagnetic wave absorber three-dimensional structure is V (%) The relational expression d × V ^1/3 > 0.4 is established, and the electromagnetic wave transmission attenuation amount in the frequency band equal to or higher than the millimeter wave band is 10 dB or higher.

When forming the electromagnetic wave absorber three-dimensional structure using the electromagnetic wave absorber composition, it is difficult to always make the thickness of the electromagnetic wave absorber three-dimensional structure completely uniform. Therefore, the thickness of the electromagnetic wave absorber three-dimensional structure may vary. That is, a thin part and a thick part may occur in the electromagnetic wave absorber three-dimensional structure. In this case, the content of the electromagnetic wave absorbing material contained in the thin part is less than the content of the electromagnetic wave absorbing material contained in the thick part, and the electromagnetic wave absorption characteristics in the thin part are deteriorated. That is, when the electromagnetic wave passes through the thin portion, the electromagnetic wave absorbing effect is reduced because the thickness through which the electromagnetic wave passes is reduced. As a result, unnecessary electromagnetic waves leak from the inside of the device to the outside, which may adversely affect the external device.

On the other hand, when the thickness of the electromagnetic wave absorber three-dimensional structure is d (mm) and the volume content of the electromagnetic wave absorbing material included in the electromagnetic wave absorber three-dimensional structure is V (%), d When the relational expression of × V ^1/3 > 0.4 is satisfied, even if the thickness of the electromagnetic wave absorber three-dimensional structure changes during modeling, the entire area of the electromagnetic wave absorber three-dimensional structure is above a certain level. Therefore, an electromagnetic wave absorber with low noise leakage can be realized. Specifically, an electromagnetic wave absorber that secures an electromagnetic wave transmission attenuation of 10 dB or more can be realized. If the electromagnetic wave transmission attenuation is less than 10 dB, there is a high possibility that noise leakage will affect peripheral electronic devices.

The above relational expression is derived by the present inventors through experiments and the like. For example, when the wall thickness d is constant, it means that the volume content V is set to a certain value or more. When the volume content V is constant, it means that the wall thickness d is set to a certain value or more.

In addition, since the electromagnetic wave absorber three-dimensional structure can be formed in advance according to the surface shape of various electronic members and the casing of the electronic member, the electromagnetic wave absorber three-dimensional structure is an electronic member using the electromagnetic wave absorber three-dimensional structure. Can be installed at any time.

By forming the electromagnetic wave absorber three-dimensional structure using the electromagnetic wave absorber composition containing the non-conductive iron oxide and the binder resin, the volume resistivity of the electromagnetic wave absorber three-dimensional structure is increased. It can be 10 ¹⁰ Ωcm or more. Thereby, the said electromagnetic wave absorber three-dimensional structure can be made into a nonelectroconductive material, and generation | occurrence | production of a short circuit can be prevented reliably.

The method for producing the electromagnetic wave absorber three-dimensional structure is not particularly limited, but can be selected from various production methods according to the type of binder resin used in the above-described electromagnetic wave absorber composition. For example, when producing an electromagnetic wave absorber three-dimensional structure by an optical modeling method, an active energy ray curable resin, a photopolymerization initiator, a surface conditioner, and further, if necessary, a filler and a dispersant are used in appropriate combination. Can do. In this case, an electromagnetic wave absorber three-dimensional structure can be easily formed with high modeling accuracy by an inkjet optical modeling method (MJM modeling method) using an inkjet printer as a three-dimensional printer. In this case, it is necessary to adjust the viscosity of the electromagnetic wave absorber composition to an appropriate discharge viscosity of the ink jet printer.

When the above-mentioned thermosetting resin and rubber-like resin are used as the binder resin, an electromagnetic wave absorber three-dimensional structure can be produced by a heat compression molding method. Moreover, when using the above-mentioned thermoplastic resin as said binder resin, an electromagnetic wave absorber three-dimensional molded item can be produced by the injection molding method.

Next, an embodiment of the electromagnetic wave absorber three-dimensional structure will be described with reference to the drawings. 1A and 1B and FIGS. 2A and 2B are schematic cross-sectional views illustrating specific examples of the electromagnetic wave absorber three-dimensional structure according to the present embodiment manufactured according to the surface shape of a specific electronic member. The manufacturing method of the electromagnetic wave absorber three-dimensional structure is not particularly limited, and depending on the type of binder resin used in the above-described electromagnetic wave absorber composition, an optical modeling method using a three-dimensional printer, a heat compression molding method The injection molding method can be appropriately selected.

The electromagnetic wave absorber three- dimensional structures 11 and 12 shown in FIGS. 1A and 1B have a thin-walled structure and are formed in a cup shape so as to cover an electronic member. The thickness d of the electromagnetic wave absorber three- dimensional structures 11 and 12 shown in FIGS. 1A and 1B is formed substantially uniformly.

On the other hand, the electromagnetic wave absorber three- dimensional structure 21 and 22 shown in FIGS. 2A and 2B have a thin structure and are formed in a cup shape so as to cover the electronic member. 22 has thick portions 21a and 22a and thin portions 21b and 22b, respectively.

The electromagnetic wave absorber three- dimensional structures 11, 12, 21, and 22 shown in FIGS. 1A and 1B and FIGS. 2A and 2B have a thickness d (mm) and the electromagnetic wave absorber three- dimensional structures 11, 12, 21, and 22. Since the relational expression d × V ^1/3 > 0.4 is established between the volume content V (%) of the electromagnetic wave absorbing material contained in the material, as shown in FIGS. Even if the thickness changes, the electromagnetic wave transmission attenuation amount of 10 dB or more in the frequency band of the millimeter wave band or higher can be ensured in the entire region of the electromagnetic wave absorber three-dimensional structure, and noise leakage can be ensured. There can be no electromagnetic wave absorber.

(Embodiments of electronic component and electronic device)
Subsequently, an embodiment of an electronic component will be described. The electronic component of this embodiment includes an electronic member covered with the electromagnetic wave absorber three-dimensional structure disclosed in the above-described embodiment. Moreover, the electronic device of this embodiment is provided with the electronic component of this embodiment.

Since the electronic member constituting the electronic component is covered with the electromagnetic wave absorber three-dimensional structure, EMC (electromagnetic compatibility) of the electronic component can be ensured. Moreover, since the said electronic device is equipped with the said electronic component which ensured EMC, EMC can be ensured also as the whole electronic device.

Examples of the electronic member covered with the electromagnetic wave absorber three-dimensional model include a circuit element and a transmission path. Examples of the circuit element include a transistor, a diode, a resistor, a capacitor, an inductor, and a battery. Examples of the transmission path include wiring, a printed circuit board, a connector, a socket, and the like. Moreover, as said electronic component, the circuit board provided with the circuit element, the transmission line, etc. corresponds, for example.

As the electronic device, for example, a communication device, a sensor, a medical device, a millimeter wave radar, or the like using wireless communication technology is applicable.

Next, an embodiment of the electronic component will be described with reference to the drawings. FIGS. 3A and 3B and FIGS. 4A and 4B are schematic cross-sectional views showing a part of an electronic component (for example, a circuit board) of this embodiment provided with a circuit element covered with an electromagnetic wave absorber three-dimensional structure. In FIG. 3A, the circuit element 13 has shown a part of electronic component coat | covered with the electromagnetic wave absorber three-dimensional structure 11 shown in FIG. 1A. In FIG. 3B, the circuit element 14 has shown a part of electronic component coat | covered with the electromagnetic wave absorber three-dimensional structure 12 shown in FIG. 1B. 4A shows a part of an electronic component in which the circuit element 23 is covered with the electromagnetic wave absorber three-dimensional structure 21 shown in FIG. 2A. 4B shows a part of an electronic component in which the circuit element 24 is covered with the electromagnetic wave absorber three-dimensional structure 22 shown in FIG. 2B. More specifically, FIGS. 3 and 4 show a part of a circuit board, for example.

3A and 4A, the electromagnetic wave absorber three- dimensional structures 11 and 21 are in contact with and follow the surface of the circuit elements 13 and 23. On the other hand, in FIG. 3B and FIG. 4B, the electromagnetic wave absorber three- dimensional structures 12 and 22 have non-contact portions with respect to the surfaces of the circuit elements 14 and 24, respectively.

Next, an embodiment of a method for manufacturing an electronic component will be described. The manufacturing method of the electronic component of this embodiment forms an electromagnetic wave absorber three-dimensional structure using the step of preparing the electromagnetic wave absorber composition disclosed in the above embodiment and the electromagnetic wave absorber composition. And a step of bonding and covering the electromagnetic wave absorber three-dimensional structure to the electronic member. With the above manufacturing method, an electronic component having high EMC (electromagnetic compatibility) can be manufactured. Moreover, in the said manufacturing method, since the said electromagnetic wave absorber three-dimensional structure can be produced in a process different from an electronic member, the influence of the heat | fever and pressurization at the time of manufacturing the said electromagnetic wave absorber three-dimensional structure is an electronic member. It does not reach. Furthermore, since the electromagnetic wave absorber three-dimensional structure does not include a conductive layer and has a volume resistivity of 10 ¹⁰ Ωcm or more, there is no possibility of short circuit even if it contacts a circuit element or a transmission line.

Subsequently, an embodiment of a method for manufacturing an electronic device will be described. The electronic device manufacturing method of the present embodiment includes a step of incorporating the electronic component manufactured by the electronic component manufacturing method disclosed in the above embodiment into the electronic device. With the above manufacturing method, an electronic device with high EMC (electromagnetic compatibility) can be manufactured.

Hereinafter, the present invention will be described in detail based on examples. However, the present invention is not limited to the following examples.

Example 1
<Preparation of composition for electromagnetic wave absorber>
The following components were kneaded with a pressure batch kneader to prepare an electromagnetic wave absorber composition A of this example in which the volume content V of hexagonal ferrite magnetic powder as an electromagnetic wave absorbing material was 51%. The hexagonal ferrite magnetic powder having the following composition formula has a magnetic resonance frequency responsible for electromagnetic wave absorption adjusted to 76 G (Hz).
(1) Hexagonal ferrite magnetic powder (composition formula: SrFe _10.56 Al _1.44 O ₁₉ )
(2) Silicone rubber (trade name “KE-541-U” manufactured by Shin-Etsu Chemical Co., Ltd.)

<Production of electromagnetic wave absorber three-dimensional structure>
Using the electromagnetic wave absorber composition A produced above, a sheet-shaped electromagnetic wave absorption of 12 cm in length, 12 cm in width, and 2 mm in thickness d by a heat compression molding method at a temperature of 165 ° C. using a hydraulic press machine. A three-dimensional body (electromagnetic wave absorber) was prepared. The value of d × V ^1/3 of the electromagnetic wave absorber of this example is 1.60.

(Example 2)
<Preparation of composition for electromagnetic wave absorber>
The following components were kneaded with a pressure-type batch kneader to prepare an electromagnetic wave absorber composition B of this example in which the volume content V of epsilon-type iron oxide magnetic powder as an electromagnetic wave absorbing material was 40%. The epsilon-type iron oxide magnetic powder having the following composition formula is prepared by adjusting the magnetic resonance frequency responsible for electromagnetic wave absorption to 76 G (Hz).
(1) Epsilon-type iron oxide magnetic powder (composition formula: ε-Ga _0.46 Fe _1.54 O ₃ )
(2) Silicone rubber (trade name “KE-541-U” manufactured by Shin-Etsu Chemical Co., Ltd.)

<Production of electromagnetic wave absorber three-dimensional structure>
Using the electromagnetic wave absorber composition B produced above, a sheet-like electromagnetic wave absorption of 12 cm in length, 12 cm in width, and 2 mm in thickness d by a heat compression molding method at a temperature of 165 ° C. using a hydraulic press. A three-dimensional body (electromagnetic wave absorber) was prepared. The value of d × V ^1/3 of the electromagnetic wave absorber of this example is 1.47.

(Example 3)
<Preparation of composition for electromagnetic wave absorber>
The following components were kneaded with a heating extruder to prepare an electromagnetic wave absorber composition C of this example in which the volume content V of the hexagonal ferrite magnetic powder as an electromagnetic wave absorbing material was 47%. The following hexagonal ferrite magnetic powder is the same as that used in Example 1.
(1) Hexagonal ferrite magnetic powder (composition formula: SrFe _10.56 Al _1.44 O ₁₉ )
(2) Polycarbonate (trade name “Panlite” manufactured by Teijin Limited)

<Production of electromagnetic wave absorber three-dimensional structure>
Using the electromagnetic wave absorber composition C produced above, a sheet-like electromagnetic wave absorber three-dimensional structure (electromagnetic wave absorber) having a length of 12 cm, a width of 12 cm, and a thickness of d: 1 mm is formed by injection molding. Produced.
The value of d × V ^1/3 of the electromagnetic wave absorber of this example is 0.78.

(Comparative Example 1)
An electromagnetic wave absorber three-dimensional structure was produced in the same manner as in Example 1 except that the thickness d of the electromagnetic wave absorber three-dimensional structure (electromagnetic wave absorber) was changed to 0.5 mm. The value of d × V ^{1/3 in} this comparative example is 0.40.

(Comparative Example 2)
An electromagnetic wave absorber three-dimensional structure (electromagnetic wave absorber) was produced in the same manner as in Example 2 except that the thickness d of the electromagnetic wave absorber three-dimensional structure was changed to 0.5 mm. The value of d × V ^{1/3 in} this comparative example is 0.37.

(Comparative Example 3)
An electromagnetic wave absorber three-dimensional structure (electromagnetic wave absorber) was produced in the same manner as in Example 3 except that the thickness d of the electromagnetic wave absorber three-dimensional structure was changed to 0.5 mm. The value of d × V ^{1/3 in} this comparative example is 0.39.

Next, the electromagnetic wave transmission attenuation of the three-dimensional electromagnetic wave absorber (electromagnetic wave absorber) produced in Examples 1 to 3 and Comparative Examples 1 to 3 was measured using a free space method. Specifically, using an millimeter wave network analyzer “ME7838A” (product name) manufactured by Anritsu Corporation, an electromagnetic wave absorber is irradiated with an input wave (millimeter wave) of a predetermined frequency from a transmitting antenna via a dielectric lens. And the electromagnetic waves which permeate | transmit with the receiving antenna arrange | positioned at the back side of the electromagnetic wave absorber were measured. The intensity of the applied electromagnetic wave and the intensity of the transmitted electromagnetic wave were grasped as voltage values, and the electromagnetic wave transmission attenuation amount was determined in dB from the intensity difference.

As a result, the electromagnetic wave transmission attenuation at a frequency of 76 GHz is shown in Table 1 and FIG. In Table 1, in addition to the electromagnetic wave transmission attenuation, values of the electromagnetic wave absorbing material and the binder resin, the thickness d of the electromagnetic wave absorber, the volume content V of the electromagnetic wave absorbing material, and d × V ^1/3 are also shown. FIG. 6 shows the electromagnetic wave absorption spectra of Example 1 and Comparative Example 3.

From Table 1 and FIG. 5, the electromagnetic wave transmission attenuation amount of Examples 1 to 3 in which the value of d × V ^1/3 exceeded 0.4 was as high as 10 dB or more, and the electromagnetic wave from the coated electronic member was not covered. A comparative example in which the value of d × V ^1/3 is 0.4 or less, while it does not affect the electronic member, nor does it affect the electronic member covered by the electromagnetic wave from the electronic member outside the coating. The electromagnetic wave transmission attenuation of 1 to 3 is as low as 9 dB or less, the electromagnetic wave from the coated electronic member affects the electronic member outside the coating, and the electromagnetic wave from the electronic member outside the coating penetrates and affects the coated electronic member. I understand that This is because when the value of d × V ^1/3 exceeds 0.4, the amount of the electromagnetic wave absorbing material in the electromagnetic wave absorber can be secured more than a certain amount even if the thickness of the electromagnetic wave absorber is changed. It is thought that the electromagnetic wave transmission attenuation amount was achieved.

The present invention can be implemented in forms other than those described above without departing from the spirit of the present invention. The embodiments disclosed in the present application are merely examples, and the present invention is not limited thereto. The scope of the present invention is construed in preference to the description of the appended claims rather than the description of the above specification, and all modifications within the scope equivalent to the claims are construed in the scope of the claims. It is included.

The electromagnetic wave absorber composition and electromagnetic wave absorber three-dimensional structure disclosed in the present application absorb electromagnetic waves in a high frequency band above the millimeter wave band, provide no leakage of noise, and provide a non-conductive electromagnetic wave absorber. Therefore, it is useful for manufacturing an electronic component and an electronic device excellent in EMC.

11, 12, 21, 22 Electromagnetic wave absorber three- dimensional structure 21a, 22a Thick part 21b, 22b Thin part 13, 14, 23, 24 Circuit element

Claims (14)

1. An electromagnetic wave absorber composition used for forming an electromagnetic wave absorber three-dimensional structure having an electromagnetic wave transmission attenuation amount of 10 dB or more in a frequency band equal to or higher than a millimeter wave band,
   Including an electromagnetic wave absorbing material and a binder resin,
   The electromagnetic wave absorbing material is an iron oxide that magnetically resonates in a frequency band of a millimeter wave band or higher,
   When the thickness of the electromagnetic wave absorber three-dimensional structure is formed as d (mm), assuming that the volume content of the electromagnetic wave absorbing material in the electromagnetic wave absorber composition is V (%), d × V ^{1 / 3} > A composition for an electromagnetic wave absorber that satisfies a relational expression of> 0.4.
2. 2. The electromagnetic wave absorber composition according to claim 1, wherein the electromagnetic wave absorbing material is hexagonal ferrite containing at least one selected from the group consisting of Sr and Ba.
3. The electromagnetic wave absorbing material is hexagonal ferrite containing Sr;
   The composition for electromagnetic wave absorbers according to claim 1, wherein a part of the Fe site of the hexagonal ferrite containing Sr is substituted with Al.
4. The electromagnetic wave absorbing material is epsilon-type iron oxide,
   The composition for electromagnetic wave absorbers according to claim 1, wherein a part of the Fe site of the epsilon-type iron oxide is substituted with at least one selected from the group consisting of Al, Ga and In.
5. The electromagnetic wave absorption according to any one of claims 1 to 4, wherein the binder resin contains at least one selected from the group consisting of an active energy ray curable resin, a thermosetting resin, a thermoplastic resin, and a rubber-like resin. Body composition.
6. An electromagnetic wave absorber three-dimensional structure formed using the electromagnetic wave absorber composition according to any one of claims 1 to 5,
   The electromagnetic wave absorber three-dimensional structure is formed into a thin structure that can cover an electronic member,
   When the thickness of the electromagnetic wave absorber three-dimensional structure is d (mm) and the volume content of the electromagnetic wave absorbing material included in the electromagnetic wave absorber three-dimensional structure is V (%), d × V ^1/3 > A relational expression of 0.4 holds,
   An electromagnetic wave absorber three-dimensional structure in which an electromagnetic wave transmission attenuation in a frequency band equal to or higher than the millimeter wave band is 10 dB or more.
7. The electromagnetic wave absorber three-dimensional structure according to claim 6, wherein the volume resistivity is 10 ¹⁰ Ωcm or more.
8. An electronic component comprising an electronic member covered with the electromagnetic wave absorber three-dimensional structure according to claim 6 or 7.
9. The electronic component according to claim 8, wherein the electromagnetic wave absorber three-dimensional structure contacts and follows the surface of the electronic member.
10. The electronic component according to claim 8, wherein the electromagnetic wave absorber three-dimensional structure has a non-contact portion with respect to a surface of the electronic member.
11. The electronic component according to any one of claims 8 to 10, wherein the electronic member includes a circuit element and a transmission path.
12. An electronic device comprising the electronic component according to any one of claims 8 to 11.
13. Preparing the electromagnetic wave absorber composition according to any one of claims 1 to 5,
    Using the electromagnetic wave absorber composition, forming an electromagnetic wave absorber three-dimensional structure,
    A method of manufacturing an electronic component including a step of bonding and covering the electromagnetic wave absorber three-dimensional structure to an electronic member.
14. An electronic device manufacturing method including a step of incorporating the electronic component manufactured by the electronic component manufacturing method according to claim 13 into the electronic device.

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