JP5705460B2 - Electromagnetic wave absorber, method for producing electromagnetic wave absorber, and electronic device - Google Patents

Description

  The present invention relates to an electromagnetic wave absorber, a manufacturing method thereof, and an electronic device, and more particularly, to an electromagnetic wave absorber having reflow resistance, a manufacturing method thereof, and an electronic device including the electromagnetic wave absorber.

  In electronic devices such as computers, communication devices, and video cameras, unnecessary electromagnetic waves such as high-frequency noise are generated from printed wiring boards and cables inside the electronic devices, which causes malfunctions of the electronic devices and other electronic devices. Unnecessary electromagnetic waves may affect electronic devices.

  Therefore, conventionally, a technique has been proposed in which an electromagnetic wave shielding material using a metal thin film as an electromagnetic wave shielding layer is attached to a printed wiring board or a cable. The electromagnetic shielding material is composed of a metal thin film and an adhesive resin layer, and shields unnecessary electromagnetic waves by the metal thin film.

  In recent years, solder reflow has been adopted as a method for connecting electronic components to a printed wiring board to which an electromagnetic wave shielding material is attached. In solder reflow, a solder paste is printed in advance on a printed wiring board, electronic parts are mounted on the printed circuit board, and the solder is melted by placing it in a reflow furnace at a high temperature atmosphere of about 260 ° C. (reflow treatment) ) Soldering method.

  In general, since an adhesive resin does not have good heat resistance, an electromagnetic wave shielding material having an adhesive resin layer is not suitable for high-temperature reflow treatment. Therefore, an electromagnetic wave shielding material having a heat-resistant and flame-retardant adhesive resin layer has been proposed (see Patent Document 1).

  The electromagnetic wave shielding material disclosed in Patent Document 1 can be applied to a printed wiring board or the like that performs reflow treatment by using a highly heat-resistant and flame-retardant adhesive resin layer.

  Recently, a member having flexibility (flexibility) such as a flexible printed circuit board (FPC) or a flat cable has been adopted as a member to which the electromagnetic wave shielding material is attached. However, since the electromagnetic shielding material using a metal thin film is inferior in flexibility, the metal thin film may be torn or peeled off while being bent together with the FPC. Therefore, it is difficult to apply an electromagnetic shielding material using a metal thin film to a member that requires flexibility such as FPC.

  Therefore, a method for preventing the influence of unnecessary electromagnetic waves by an electromagnetic wave absorber which is a means different from the electromagnetic wave shielding material using a metal thin film has been proposed.

  Hereinafter, a conventional electromagnetic wave absorber will be described with reference to FIG. FIG. 5 is a cross-sectional view of a conventional electromagnetic wave absorber.

  As shown in FIG. 5, the conventional electromagnetic wave absorber 1000 includes a base material layer 100 and a magnetic powder-containing resin layer 200 formed on the base material layer 100. The magnetic powder-containing resin layer 200 is a resin in which magnetic powder is contained.

  The electromagnetic wave absorber 1000 configured as described above is attached to an FPC or the like with an adhesive. Thereby, since unnecessary electromagnetic waves generated from the electronic device can be absorbed by the magnetic powder-containing resin layer 200, the influence of unnecessary electromagnetic waves can be suppressed. Moreover, since the magnetic powder-containing resin layer 200 is made of magnetic powder and synthetic resin and has flexibility, problems such as breakage and peeling do not occur even if bending is repeated together with the FPC.

  Further, as this type of electromagnetic wave absorber, a noise suppression sheet in which a surface protective layer is formed on at least one surface of a magnetic powder-containing resin layer has also been proposed (see Patent Document 2). According to this noise suppression sheet, the problem due to the combination of the noise suppression sheet and pasting of another member can be solved.

JP 2007-294918 A JP 2009-158694 A

  However, when a conventional electromagnetic wave absorber is attached to a printed wiring board such as an FPC and a reflow process is performed by applying solder reflow, the magnetic powder-containing resin layer swells and an abnormal appearance occurs in the electromagnetic wave absorber. There's a problem.

  To solve this problem, it may be possible to apply an electromagnetic wave absorber to the printed circuit board after reflow treatment. However, considering productivity, the electromagnetic wave absorber is applied to the printed circuit board in advance. In addition, it is preferable to perform the reflow process by mounting electronic components on this.

  Therefore, there is a problem that it is difficult to perform reflow processing in solder reflow on a printed wiring board or the like to which a conventional electromagnetic wave absorber is attached.

  The present invention has been made to solve such a problem, and an object thereof is to provide an electromagnetic wave absorber that can withstand a reflow process.

  In order to solve the above problems, an aspect of the electromagnetic wave absorber according to the present invention is an electromagnetic wave absorber including a base material layer and an electromagnetic wave absorption layer, and is provided between the base material layer and the electromagnetic wave absorption layer. A binder layer made of a heat-resistant resin that can withstand reflow treatment is formed.

  Thereby, since the electromagnetic wave absorbing layer is protected by the binder layer, even if the reflow process is performed, the electromagnetic wave absorber does not have an appearance abnormality such as swelling or peeling.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, it is preferable that the thickness of the electromagnetic wave absorption layer is 10 μm or more and 100 μm or less.

  Thereby, electromagnetic wave absorption performance can be made suitable.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, it is preferable that a surface resistance value of the electromagnetic wave absorption layer is 20Ω / □ or more and 170Ω / □ or less.

  Thereby, electromagnetic wave absorption performance can be made suitable.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, it is preferable that the electromagnetic wave absorption layer contains carbon black and magnetic metal particles.

  Thereby, desired electromagnetic wave absorption performance can be obtained easily.

  Furthermore, in one embodiment of the electromagnetic wave absorber according to the present invention, the resin constituting the binder layer is preferably a polyester resin.

  Thereby, while being able to improve adhesiveness with a base material layer, the binder layer which has reflow resistance can be comprised easily.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, the binder layer is preferably crosslinked by a crosslinking agent. Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, the cross-linking agent is preferably an isocyanate-based cross-linking agent.

  Thereby, since the molecular structure of a binder layer can be densified, the heat resistance and reflow resistance of an electromagnetic wave absorber can be improved. In addition, since an electromagnetic wave absorber excellent in adhesive strength and excellent in flexibility and impact resistance can be obtained, it is suitable for a printed wiring board having flexibility such as FPC.

  Furthermore, in one embodiment of the electromagnetic wave absorber according to the present invention, it is preferable that the thickness of the binder layer is 3 μm or more and 50 μm or less.

  Thereby, the adhesiveness between a base material layer and an electromagnetic wave absorption layer can be made suitable.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, the amount of the crosslinking agent added is preferably 3 to 16 parts by weight with respect to 30 parts by weight of the resin in the binder layer.

  Thereby, the adhesiveness and flexibility between a base material layer and an electromagnetic wave absorption layer can be made suitable.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, it is preferable that a flame retardant is added to the binder layer. Further, in one aspect of the electromagnetic wave absorber according to the present invention, a flame retardant layer in which a flame retardant is added to a predetermined synthetic resin on a surface of the electromagnetic wave absorption layer opposite to the side on which the binder layer is formed. Is preferably formed.

  Thereby, the flame retardance of an electromagnetic wave absorption layer can be improved.

  Furthermore, in one aspect of the electromagnetic wave absorber according to the present invention, an adhesive layer is preferably formed on the electromagnetic wave absorption layer.

  Thereby, an electromagnetic wave absorber can be easily affixed to electromagnetic wave generating members, such as FPC.

  One embodiment of an electronic device according to the present invention includes a printed wiring board on which one embodiment of the electromagnetic wave absorber is stacked.

  Thereby, the electromagnetic wave absorber can absorb unnecessary electromagnetic waves in the electronic device.

  Moreover, the one aspect | mode of the manufacturing method of the electromagnetic wave absorber which concerns on this invention is the 1st resin solution application | coating process which apply | coats the 1st resin solution containing the metal on the release sheet, and said 1st resin. An electromagnetic wave absorbing layer forming step of forming an electromagnetic wave absorbing layer by subjecting the solution to heat treatment; and a second resin that coats a second resin solution containing a heat resistant resin that can withstand reflow treatment on the electromagnetic wave absorbing layer A solution coating step, a binder layer forming step of forming a binder layer by subjecting the second resin solution to a heat treatment, a base material layer disposed on the binder layer, and the electromagnetic wave absorbing layer and the base material layer And a base material layer laminating step for laminating them with a binder layer, and a release sheet peeling step for peeling the release sheet from the electromagnetic wave absorbing layer.

  Thereby, the electromagnetic wave absorber which has reflow resistance and flexibility can be manufactured.

  According to the electromagnetic wave absorber according to the present invention, since the binder layer made of a heat-resistant resin that can withstand the reflow treatment is formed between the base material layer and the electromagnetic wave absorption layer, the reflow treatment is performed. Even if it does, the problem of the appearance abnormality in an electromagnetic wave absorber does not arise. Therefore, an electromagnetic wave absorber having reflow resistance and flexibility can be provided.

  In addition, according to the electronic device according to the present invention, since it has a printed wiring board laminated with an electromagnetic wave absorber having reflow resistance and flexibility, solder reflow can be performed on the printed wiring board, The electromagnetic wave absorber can absorb unnecessary electromagnetic waves in the electronic device. Thereby, generation | occurrence | production of malfunction of an electronic device can be suppressed.

Sectional drawing of the electromagnetic wave absorber which concerns on the 1st Embodiment of this invention The flowchart in the manufacturing method of the electromagnetic wave absorber which concerns on the 1st Embodiment of this invention Sectional drawing of the electromagnetic wave absorber which concerns on the 2nd Embodiment of this invention. Sectional drawing of the electromagnetic wave absorber which concerns on the 3rd Embodiment of this invention. Sectional view of conventional electromagnetic wave absorber

  Hereinafter, an electromagnetic wave absorber, a manufacturing method thereof, and an electronic device according to embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
First, an electromagnetic wave absorber according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a cross-sectional view of an electromagnetic wave absorber according to the first embodiment of the present invention.

(Whole structure of electromagnetic wave absorber)
As shown in FIG. 1, the electromagnetic wave absorber 10 according to the first embodiment of the present invention is a film-like (sheet-like) electromagnetic wave absorber laminated on a printed wiring board such as an FPC or a cable, A base material layer 1, an electromagnetic wave absorption layer 2, and a binder layer 3 formed between the base material layer 1 and the electromagnetic wave absorption layer 2 are provided.

  The electromagnetic wave absorber 10 according to the present embodiment is an electromagnetic wave absorber in which each layer is made of a predetermined synthetic resin made of a polymer compound, and has a layer made of only a metal such as a metal vapor deposition layer or a metal foil. Not. That is, when a material such as a metal or an inorganic compound is used for each layer of the electromagnetic wave absorber 10 according to the present embodiment, each layer is configured by mixing a synthetic resin and a metal or an inorganic compound so as to have flexibility. .

  Hereinafter, the configuration of each layer of the electromagnetic wave absorber 10 according to the present embodiment will be described in detail.

(Base material layer)
The base material layer 1 in the present embodiment is composed of a resin film made of a synthetic resin having flexibility and insulating properties and heat resistance. The base material layer 1 is a layer that is exposed to the outside when the electromagnetic wave absorber is laminated on a printed wiring board such as an FPC or a cable. Therefore, it is preferable to have predetermined heat resistance with respect to various heat treatment processes such as a reflow process in the manufacturing process of the electronic device.

  In this embodiment, the base material layer 1 has heat resistance that can withstand at least the temperature of the reflow treatment. In this case, considering the temperature at the time of reflow treatment, the heat resistance of the base material layer 1 is, for example, left for 2 minutes at a temperature of 260 ° C. or left for 60 minutes in a temperature environment of 200 ° C. In such a case, it is preferable that the base material layer 1 is heat resistant so that the base material layer 1 does not dissolve and does not shrink or stretch.

  Specifically, as such a base material layer 1, a polypropylene film, a crosslinked polyethylene film, a polyester film, a polybenzimidazole film, an aramid film, a polyimide film (PI film), a polyimide amide film, a polyetherimide film, a polyphenylene Examples thereof include a sulfide film (PPS film) and a polyethylene naphthalate film. From the viewpoint of heat resistance, it is preferable to use a PI film, a polyimide amide film, a polyetherimide film, or a PPS film as the base material layer 1. In particular, the PI film not only has the property of extremely high heat resistance, but also has high strength and excellent electrical insulation, and thus is suitable as a base material layer for an electromagnetic wave absorber.

  Moreover, it is preferable that the film thickness of the base material layer 1 shall be 10 micrometers or more and 50 micrometers or less. This is because when the film thickness of the base material layer 1 is less than 10 μm, the mechanical strength as the base material layer becomes weak, and the base material layer may tear or curl during the manufacturing process of the electromagnetic wave absorber. It is. On the other hand, when the film thickness of the base material layer 1 exceeds 50 μm, the flexibility of the electromagnetic wave absorber as a whole is lowered, so that it is difficult to laminate the FPC so that bending is repeated. Furthermore, when the film thickness of the base material layer 1 exceeds 50 μm, the entire electromagnetic wave absorber becomes bulky, and the storability and transportability are also lowered.

  That is, it is thought that the reflow resistance and heat resistance of the entire electromagnetic wave absorber can be improved by increasing the thickness of the base material layer 1. However, if the film thickness of the base material layer 1 is too thick, the flexibility of the entire electromagnetic wave absorber is drastically deteriorated. Therefore, it is not preferable to increase the thickness of the base material layer 1 alone.

  In addition, you may perform surface modification processing, such as a corona treatment, with respect to the surface which contacts the binder layer 3 of the base material layer 1. FIG. In the corona treatment, the surface of the treated substrate is modified by irradiating the treated substrate with corona discharge. By performing the surface modification treatment, it is possible to improve the adhesion of the surface of the base material layer 1 in contact with the binder layer 3.

(Binder layer)
As shown in FIG. 1, the binder layer 3 in this embodiment is sandwiched between a base material layer 1 and an electromagnetic wave absorption layer 2. The binder layer 3 in the present embodiment is made of a synthetic resin having heat resistance that can withstand a reflow process. In this way, by inserting the binder layer 3 made of a resin having reflow resistance between the base material layer 1 and the electromagnetic wave absorbing layer 2, the electromagnetic wave absorbing layer 2 swells even if reflow treatment is performed. There will be no problems such as going up. That is, the binder layer 3 functions as a binder that binds the base material layer 1 and the electromagnetic wave absorption layer 2 and also functions to protect the electromagnetic wave absorption layer 2 and prevent deformation of the electromagnetic wave absorption layer 2 due to heat. Have

  Specifically, the binder layer 3 does not cause swelling or peeling of the electromagnetic wave absorber 10 after a reflow test to be described later, and changes in appearance such as a synthetic resin flowing out on a printed wiring board such as an FPC. It does not occur. Even when the binder layer 3 is softened or partially melted during the reflow test, the electromagnetic wave absorber does not swell or peel off after the test (after cooling), and the synthetic resin bleeds. If it is not taken out, it has heat resistance to withstand reflow treatment.

  In general, the reflow process is performed at a temperature of about 260 ° C. for several minutes. Before the reflow process, in order to bond the printed wiring board and the electromagnetic wave absorber, a pressure press is performed at a temperature of 150 to 200 ° C. to 150 ° C. There is a step of performing a heat treatment for about 1 hour at a temperature around 1C. Therefore, it is preferable that the material of the binder layer 3 has heat resistance that does not change the appearance even when left in a temperature environment of 200 ° C. for 60 minutes.

  Moreover, even if the binder layer 3 is inserted between the base material layer 1 and the electromagnetic wave absorbing layer 2, it is necessary to maintain the flexibility of the entire electromagnetic wave absorber 10, so that the binder layer 3 has a certain flexibility. It is preferable to adjust the material, film thickness, and the like so as to have them.

  Examples of the material for the binder layer 3 include synthetic resins such as polyester resin, epoxy resin, phenol resin, urethane resin, and acrylic resin.

  Among these synthetic resins, a more preferable material for the binder layer 3 is a material having high heat resistance, and is an acrylic resin, a polyester resin, or an epoxy resin. In consideration of not only heat resistance but also adhesion to the base material layer 1, it is preferable to use a polyester resin, particularly a saturated polyester resin. Moreover, it is preferable to use an epoxy resin from a heat resistant and heat shrinkable viewpoint. However, since the temperature management at the time of storage etc. is complicated, the epoxy resin is more preferable than the epoxy resin from the viewpoint of production management.

  Moreover, in this embodiment, it is preferable that a crosslinking agent is added to the synthetic resin of the binder layer 3, and the said synthetic resin is bridge | crosslinked and the binder layer 3 is comprised. Furthermore, the binder layer 3 is preferably a synthetic resin obtained by adding a crosslinking agent to a thermoplastic resin, that is, a thermoplastic and thermosetting synthetic resin. In this way, by forming the binder layer 3 by cross-linking the synthetic resin, the molecular structure of the binder layer 3 can be made dense, so that the heat resistance of the binder layer 3 can be improved. Thereby, the reflow resistance of the electromagnetic wave absorption layer 2 can be improved. Moreover, by using the binder layer 3 formed by crosslinking a synthetic resin, not only can heat resistance and reflow resistance be improved, but also an electromagnetic wave absorber excellent in adhesive strength, flexibility and impact resistance. Can be obtained.

  As a crosslinking agent used for the binder layer 3, when the resin which comprises the binder layer 3 is a polyester resin, it is preferable to use an isocyanate type crosslinking agent. In particular, the heat resistance and adhesiveness of the binder layer 3 can be further improved by using a polyfunctional type isocyanate-based crosslinking agent. Examples of the isocyanate-based crosslinking agent include Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd.), Aquanate AQ200 (manufactured by Nippon Polyurethane Industry Co., Ltd.), Barnock DN955 (manufactured by DIC Corporation), and the like. In particular, among the polyfunctional types, it is preferable to use a non-yellowing type isocyanate crosslinking agent.

  However, when a crosslinking agent is used for the binder layer 3, it is preferable to use a saturated polyester resin instead of an unsaturated polyester resin. This is because if an unsaturated polyester resin is used to crosslink with an isocyanate-based cross-linking agent, shrinkage due to heat treatment is large and internal stress may remain.

  Thus, in this embodiment, even if it is a case where the polyester resin considered that it is generally difficult to use is considered as a material which comprises the electromagnetic wave absorber 10, when the temperature of reflow processing is considered, it is used for reflow processing. A tolerable electromagnetic wave absorber 10 can be obtained.

  In addition, an aluminum chelate crosslinking agent can also be used as a crosslinking agent used for the synthetic resin constituting the binder layer 3. In this case, an acrylic resin, a polyester resin, or an epoxy resin can be used as the material of the binder layer 3, and the binder layer 3 can be obtained by blending an aluminum chelate crosslinking agent into these resins. Epoxy crosslinking agents can also be used.

  When the binder layer 3 is formed using a crosslinking agent, the amount of the crosslinking agent added is preferably about 3 to 16 parts by weight with respect to 30 parts by weight of the synthetic resin of the binder layer 3. This is because when the addition amount of the crosslinking agent is less than 3 parts by weight with respect to 30 parts by weight of the synthetic resin, the heat resistance of the obtained binder layer 3 is reduced, and the base material layer 1 and the electromagnetic wave absorption layer 2 This is because the adhesiveness (binding property) between them may be insufficient. On the other hand, when the addition amount of the crosslinking agent exceeds 16 parts by weight with respect to 30 parts by weight of the synthetic resin, the obtained electromagnetic wave absorber 10 becomes too hard and the flexibility of the entire electromagnetic wave absorber may be reduced. .

  Furthermore, it is preferable to use a catalyst when the synthetic resin constituting the binder layer 3 is crosslinked using a crosslinking agent. Examples of the catalyst include amine-based catalysts, tin-based catalysts, organic antimony-based catalysts, and organic bismuth-based catalysts. Moreover, these catalysts can also be mix | blended suitably and can be used. As the catalyst for crosslinking, an amine catalyst is particularly preferably used, and specific examples include triethylenetetramine, diethylaminopropylamine, polyamide resin, imidazoles, metaphenylenediamine, and polythioether. By crosslinking using an amine catalyst, the crosslinking density is increased, the softening point of the resulting binder layer 3 can be increased, and the heat resistance of the binder layer 3 can be further improved. The softening point of such a binder layer is preferably 260 ° C. or higher.

  When the binder layer 3 is crosslinked using a catalyst, the amount of the catalyst added is preferably about 4 to 25 parts by weight with respect to 100 parts by weight of the crosslinking agent. This is because if the added amount of the catalyst is less than 4 parts by weight with respect to 100 parts by weight of the crosslinking agent, the speed at which the binder layer 3 is cured may be too slow. On the other hand, when the addition amount of the catalyst exceeds 25 parts by weight with respect to 100 parts by weight of the cross-linking agent, the reaction becomes too fast and the pot life (pot life) of the resin solution may be too short.

  Moreover, it is preferable that the film thickness of the binder layer 3 shall be 3 micrometers or more and 50 micrometers or less. This is because when the film thickness of the binder layer 3 is less than 3 μm, the adhesiveness (binding property) between the base material layer 1 and the electromagnetic wave absorbing layer 2 is lowered, and the obtained electromagnetic wave absorber 10 can withstand reflow treatment. This is because there is a risk of being lost. On the other hand, even if the thickness of the binder layer 3 is larger than 50 μm, not only the adhesion between the base material layer 1 and the electromagnetic wave absorbing layer 2 is improved, but also a solvent remains in the binder layer 3, which is reflowed. There is a possibility that the adhesiveness of the binder layer 3 may be deteriorated by vaporizing during processing to form voids (pores).

  In addition, as a synthetic resin used for the binder layer 3, it is preferable to use the crosslink density formation type synthetic resin whose weight average molecular weight is 50,000 or less. When the binder layer 3 is formed using a crosslinking agent, it is preferable to use a crosslinking density forming type synthetic resin having a weight average molecular weight of 50,000 or less before crosslinking with the crosslinking agent. The crosslink density forming type refers to a type that is three-dimensionally cross-linked with the polyfunctional isocyanate-based cross-linking agent described above.

(Electromagnetic wave absorbing layer)
The electromagnetic wave absorbing layer 2 in the present embodiment has a function of absorbing electromagnetic waves, particularly radio waves, and is composed of a synthetic resin and an electromagnetic wave absorbing material.

  Examples of the synthetic resin constituting the electromagnetic wave absorbing layer 2 include polyurethane resin, acrylic resin, polyester resin, polyamide resin, silicone resin, fluorine resin, ethylene resin, styrene butadiene resin, nitrile butadiene resin, or epoxy resin. Considering the stability of the electromagnetic wave absorption performance, it is preferable to use a urethane resin as the synthetic resin of the electromagnetic wave absorption layer 2.

  Moreover, as the electromagnetic wave absorbing material constituting the electromagnetic wave absorbing layer 2, carbon black and magnetic metal are used.

  Carbon black having a particle size of 10 nm to 300 μm is preferably used. In particular, from the viewpoint of electromagnetic wave absorption performance, it is preferable to use carbon black obtained by blending large particles having a particle size of about 1 μm to 300 μm and small particles having a particle size of less than 1 μm. Moreover, since the scaly particles having a particle diameter of about 1 μm to 300 μm (the long diameter of the scaly particles) have a wide surface area, they have excellent electromagnetic wave absorbing performance and can form the thin electromagnetic wave absorbing layer 2 depending on the shape thereof. . The particle diameter can be confirmed by observing with an electron microscope.

  As the magnetic metal material, magnetic metal particles (magnetic metal powder) such as iron silicon alloy, iron aluminum silicon alloy, iron nickel alloy, and magnetite can be used. The shape of the magnetic metal may be any shape such as a scale shape, a rod shape, a needle shape, a spherical shape, and an indeterminate shape, but it is preferable to use a scale-like magnetic metal from the viewpoint of electromagnetic wave absorption performance.

  The particle diameter of the magnetic metal particles is preferably 0.01 μm to 300 μm, and particularly preferably 0.2 μm to 100 μm. The particle diameter of the magnetic metal particles refers to the length of the longest diagonal line (major diameter) when the shape of the magnetic metal particles is other than a sphere, for example, when the shape is a scale.

  The content of carbon black and magnetic metal in the electromagnetic wave absorbing layer 2 is 50 to 200 parts by weight with respect to 100 parts by weight of the synthetic resin constituting the electromagnetic wave absorbing layer 2, and the magnetic metal The content of is preferably 50 to 100 parts by weight. If the carbon black content is less than 50 parts by weight with respect to 100 parts by weight of the synthetic resin, sufficient electromagnetic wave absorption performance cannot be obtained, and 200 parts by weight with respect to 100 parts by weight of the synthetic resin. This is because if it exceeds, the performance as an electromagnetic wave shield (electromagnetic wave reflection performance) becomes strong, and the electromagnetic wave absorption performance may not be obtained. On the other hand, when the carbon black content exceeds 200 parts by weight with respect to 100 parts by weight of the synthetic resin, there is a balance with the magnetic metal content, but the electromagnetic wave absorbing layer 2 itself may become brittle. On the other hand, when the content of the magnetic metal is less than 50 parts by weight with respect to 100 parts by weight of the synthetic resin of the electromagnetic wave absorbing layer 2, there is a possibility that sufficient electromagnetic wave absorbing performance cannot be obtained. Even if it exceeds 100 parts by weight with respect to parts by weight, the electromagnetic wave absorption performance is not improved so much, which is disadvantageous in terms of cost, and the flexibility of the electromagnetic wave absorption layer 2 may be reduced.

  In the present embodiment, the electromagnetic wave absorbing layer 2 may be configured by adding a cross-linking agent as necessary and crosslinking the synthetic resin. As such a crosslinking agent, for example, an isocyanate-based crosslinking agent is preferably used, and in particular, a polyfunctional type isocyanate-based crosslinking agent is preferably used in the same manner as the binder layer 3. Thereby, the heat resistance and adhesiveness of the electromagnetic wave absorption layer 2 can be improved. Examples of the isocyanate-based crosslinking agent include Coronate HL (manufactured by Nippon Polyurethane Industry Co., Ltd.), Aquanate AQ200 (manufactured by Nippon Polyurethane Industry Co., Ltd.), Barnock DN955 (manufactured by DIC Corporation), and the like. In particular, among the polyfunctional types, it is preferable to use a non-yellowing type isocyanate crosslinking agent.

  In addition, when comprising the electromagnetic wave absorption layer 2 using a crosslinking agent, it is preferable that the addition part number of a crosslinking agent adds about 1-20 weight part with respect to 100 weight part of urethane resins.

  In the present embodiment, the electromagnetic wave absorbing layer 2 preferably has a surface resistance value of 10Ω / □ or more and 200Ω / □ or less. If the surface resistance value of the electromagnetic wave absorbing layer 2 is less than 10Ω / □, the electromagnetic wave shielding performance is enhanced and the electromagnetic wave is reflected instead of absorbing the electromagnetic wave, and the reflected electromagnetic wave may cause malfunction of the electronic device. is there. Moreover, when the surface resistance value of the electromagnetic wave absorption layer 2 exceeds 200 Ω / □, sufficient electromagnetic wave absorption performance cannot be obtained, and malfunction of electronic equipment may occur due to insufficient electromagnetic wave absorption. In addition, the more preferable surface resistance value of the electromagnetic wave absorption layer 2 is 20Ω / □ or more and 170Ω / □ or less.

  Moreover, in this embodiment, it is preferable that the film thickness of the electromagnetic wave absorption layer 2 is 5 micrometers or more and 100 micrometers or less. If the film thickness of the electromagnetic wave absorbing layer 2 is less than 5 μm, sufficient electromagnetic wave absorbing performance may not be obtained. Moreover, even if the film thickness of the electromagnetic wave absorption layer 2 exceeds 100 μm, the electromagnetic wave absorption performance is not improved so much, which is not preferable in terms of cost. A more preferable film thickness of the electromagnetic wave absorbing layer 2 is 10 μm or more and 50 μm or less.

  In addition, as electromagnetic wave absorption performance of the electromagnetic wave absorption layer 2 according to the present embodiment, when the electromagnetic wave absorber 10 is laminated on an FPC or the like, at least 1 to 1 electromagnetic waves are generated with respect to an unlaminated product in a 300 to 800 MHz band. Any effect that reduces about 2 dB may be used. The electromagnetic wave absorbing performance may be such that the electromagnetic wave is reduced by 2 dB or more.

  In the present embodiment, the electromagnetic wave absorption performance of the electromagnetic wave absorber 10 can be measured using a radio wave absorption performance measurement S21 method and a Keycom-type near-field radio wave absorption measurement device according to IEC-62333.

(Effect of electromagnetic wave absorber)
As described above, the electromagnetic wave absorber 10 according to the first embodiment of the present invention includes the binder layer 3 made of a heat-resistant resin that can withstand reflow treatment, between the base material layer 1 and the electromagnetic wave absorption layer 2. ing. Thereby, even if the reflow process is performed on the electromagnetic wave absorber 10, no abnormal appearance such as swelling or peeling is observed in the electromagnetic wave absorber 10. Therefore, the electromagnetic wave absorber 10 having flexibility that can withstand the reflow treatment can be provided.

  Thus, since the electromagnetic wave absorber 10 according to the present embodiment has reflow resistance, the electromagnetic wave absorbing layer 2 is considered to require a softening point of 260 ° C. or higher in the reflow treatment. However, in the present embodiment, the binder layer 3 is provided, and the binder layer 3 protects the electromagnetic wave absorption layer 2. Therefore, the synthetic resin material of the electromagnetic wave absorption layer 2 is generally used as 170 to 180. Even if one having a heat resistance of about 0 ° C. is used, the appearance abnormality of the electromagnetic wave absorber does not occur.

  Even when the binder layer 3 or the electromagnetic wave absorption layer 2 is softened or partially melted during the reflow process, these synthetic resins swell or peel off or bleed after the reflow process (after cooling). If you do not put out. Therefore, the resin used for the binder layer 3 and the electromagnetic wave absorption layer 2 may be a thermoplastic resin. More preferably, it is preferable to use a thermoplastic and thermosetting synthetic resin. In particular, both the resin of the binder layer 3 and the electromagnetic wave absorbing layer 2 are both thermoplastic, and by using a thermosetting synthetic resin, they have excellent adhesive strength, flexibility, impact resistance and heat resistance. An excellent electromagnetic wave absorber can be obtained.

  Moreover, since the binder layer 3 in the electromagnetic wave absorber 10 according to the present embodiment has flexibility, the flexibility of the entire electromagnetic wave absorber 10 can be maintained in the same manner as before even when the binder layer 3 is inserted. Therefore, in the electromagnetic wave absorber 10 according to the present embodiment, an adhesive is applied to the electromagnetic wave absorption layer 2 and the electromagnetic wave absorber 10 is attached to a flexible FPC or cable so that the base material layer 1 becomes an exposed surface. By attaching, a printed wiring board or a flat wiring cable that is flexible and can suppress generated electromagnetic waves can be obtained. Moreover, since the electromagnetic wave absorber 10 according to this embodiment has reflow resistance as described above, even if solder reflow is applied to the printed wiring board, the electromagnetic wave absorber 10 is swollen or peeled off. And no problems such as the synthetic resin flowing out on the printed wiring board. That is, the electromagnetic wave absorber 10 according to the present embodiment is an electromagnetic wave absorber configured to exhibit reflow resistance while maintaining flexibility.

  And by providing the printed wiring board etc. in which the electromagnetic wave absorber 10 which concerns on this embodiment was laminated | stacked in an electronic device, since the said electromagnetic wave absorber 10 can absorb the unnecessary electromagnetic wave in an electronic device, electronic Occurrence of malfunction of equipment can be suppressed.

(Method for producing electromagnetic wave absorber)
Next, the manufacturing method of the electromagnetic wave absorber 10 according to the first embodiment of the present invention will be described with reference to FIG. FIG. 2 is a flowchart of the manufacturing method of the electromagnetic wave absorber according to the first embodiment of the present invention.

  As shown in FIG. 2, first, a first resin solution (resin solution for electromagnetic wave absorbing layer), which is a resin solution for forming the electromagnetic wave absorbing layer 2, is applied on the release sheet (first resin solution). Application process: S11). Here, the release sheet is a sheet that has been surface-treated so that the synthetic resin does not adhere to other members, and more specifically, release paper or release film.

  As the first resin solution, a solution obtained by dissolving, dispersing, or emulsifying the above-described synthetic resin of the electromagnetic wave absorbing layer 2 with an organic solvent such as dimethylformamide, methyl ethyl ketone, toluene, xylene, or water is used. Further, a resin solution in which a hot melt resin is dissolved by heating without using a solvent can also be used.

  The above-mentioned crosslinking agent is added to the first resin solution as necessary. In addition to the crosslinking agent, a catalyst, a pigment, a flame retardant, an antioxidant, an ultraviolet absorber, and the like may be added. However, it is preferable to adjust to such an extent that the electromagnetic wave absorbing performance of the electromagnetic wave absorbing layer 2 is not hindered or the softening point is not greatly lowered.

  Moreover, the coating method of the 1st resin solution on a mold release sheet can use a knife coater, a pipe coater, or an extrusion coater. In addition, what is necessary is just to set the slit space | interval in the case of application | coating considering the thickness of the target electromagnetic wave absorption layer 2. FIG.

  Next, the first resin solution applied on the release sheet is heat-treated to form the electromagnetic wave absorption layer 2 (electromagnetic wave absorption layer forming step: S12).

  At this time, when a solvent is used for the first resin solution, the electromagnetic wave absorbing layer 2 is formed by drying at a temperature of 50 to 130 ° C. for about 30 seconds to 5 minutes using an oven or the like. Moreover, when using a crosslinking agent, in order to bridge | crosslink a synthetic resin, the heat processing for about 10 second-about 5 minutes are performed at the temperature of 130 to 200 degreeC.

  On the other hand, when no solvent is used for the first resin solution, the electromagnetic wave absorbing layer 2 is formed by cooling as it is. When a crosslinking agent is used, the above heat treatment or humidification treatment is performed in order to crosslink the synthetic resin.

  Next, a second resin solution (binder layer resin solution) that is a resin solution for forming the binder layer 3 is applied on the electromagnetic wave absorbing layer 2 formed on the release sheet (second resin). Solution coating step: S13).

  As a 2nd resin solution, it can obtain by performing the method similar to a 1st resin solution with respect to the synthetic resin of the binder layer 3 mentioned above. Moreover, you may use additives, such as a crosslinking agent, a catalyst, or a pigment, as needed similarly to the 1st resin solution.

  Next, the second resin solution applied on the electromagnetic wave absorption layer 2 is subjected to heat treatment to form the binder layer 3 (binder layer forming step: S14).

  The heat treatment of the second resin solution can be performed by the same method as the heat treatment of the first resin solution.

  Next, the base material layer 1 is superposed on the formed binder layer 3 so that the base material layer 1 and the electromagnetic wave absorption layer 2 are bonded together via the binder layer 3 (base material layer bonding step: S15). ).

  The bonding conditions may be matched to the characteristics of the synthetic resin constituting the binder layer 3. For example, the bonding is performed at a temperature of room temperature (10 ° C. to 25 ° C.) to 200 ° C. and a pressure of about 0.01 MPa to 10 MPa. Can do. Thereby, the laminated structure by which the base material layer 1, the binder layer 3, and the electromagnetic wave absorption layer 2 were laminated | stacked in this order on the release sheet can be obtained.

  In addition, in order to accelerate | stimulate the bridge | crosslinking of the synthetic resin in the electromagnetic wave absorption layer 2 or the binder layer 3 after that, you may perform aging for about 12 to 100 hours at the temperature of about 50 to 90 degreeC as needed. .

  Finally, a release sheet is peeled from the laminated structure of the base material layer 1, the binder layer 3, and the electromagnetic wave absorption layer 2 (release sheet peeling step: S16).

  By the above, the electromagnetic wave absorber 10 in which the binder layer 3 is formed between the base material layer 1 and the electromagnetic wave absorbing layer 2 can be obtained.

(Second Embodiment)
Next, an electromagnetic wave absorber 20 according to a second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of an electromagnetic wave absorber according to the second embodiment of the present invention.

  As shown in FIG. 3, the electromagnetic wave absorber 20 according to the second embodiment of the present invention further includes an adhesive layer with respect to the electromagnetic wave absorber 10 according to the first embodiment of the present invention shown in FIG. 4. The components other than the adhesive layer 4 are the same as those of the electromagnetic wave absorber according to the first embodiment of the present invention. Therefore, in FIG. 3, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 3, the electromagnetic wave absorber 20 according to the second embodiment of the present invention is a film-like electromagnetic wave absorber laminated on a printed wiring board such as an FPC, a cable, etc., as in the first embodiment. A base material layer 1, an electromagnetic wave absorption layer 2, a binder layer 3 formed between the base material layer 1 and the electromagnetic wave absorption layer 2, and an adhesive layer 4 formed on the binder layer 3. Prepare. Each layer of the electromagnetic wave absorber 20 according to the present embodiment is also an electromagnetic wave absorber that has flexibility and includes a predetermined synthetic resin made of a polymer compound, and is used by being laminated on an FPC or the like.

  The adhesive layer 4 in this embodiment is for adhering to an electromagnetic wave generating member such as an FPC. By the adhesive layer 4, the electromagnetic wave absorber 20 can be easily attached to an electromagnetic wave generating member such as an FPC.

  As the adhesive layer 4, an epoxy resin, a phenol resin, a melamine resin, an acrylic resin, a polyester resin, an ultraviolet curable resin, a urethane resin, a silicone resin, or the like can be used. In the present embodiment, it is particularly preferable to use an epoxy resin having better heat resistance.

  Moreover, in order to manufacture the electromagnetic wave absorber 20 according to the present embodiment, the adhesive layer 4 is further formed on the electromagnetic wave absorbing layer 2 by applying each step shown in FIG. That is, after peeling off the release sheet, the adhesive layer 4 made of the predetermined material is applied and laminated on the exposed electromagnetic wave absorbing layer 2. In addition, about the coating method of the adhesive bond layer 4, a knife coater, a pipe coater, an extrusion coater etc. can be used. In addition, what is necessary is just to set the slit space | interval in the case of application | coating considering the thickness of the target adhesive bond layer 4. FIG.

  When an epoxy resin is used as the adhesive layer 4, the epoxy resin may be cured when heated, and may not be able to adhere to the FPC or the like. Therefore, it is preferable to store the epoxy resin at a low temperature of 10 ° C. or lower, and it is preferable not to apply heat until it is bonded to FPC or the like.

(Third embodiment)
Next, electromagnetic wave absorbers 30 and 31 according to a third embodiment of the present invention will be described with reference to FIGS. 4 (a) and 4 (b). FIG. 4A and FIG. 4B are cross-sectional views of an electromagnetic wave absorber according to the third embodiment of the present invention.

  As shown in FIG. 4A, the electromagnetic wave absorber 30 according to the third embodiment of the present invention is difficult for the binder layer 3 of the electromagnetic wave absorber 10 according to the first embodiment of the present invention shown in FIG. A flame retardant is added. In FIG. 4A, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4A, the electromagnetic wave absorber 30 according to the third embodiment of the present invention is in the form of a film laminated on a printed wiring board such as an FPC, a cable, or the like as in the first embodiment. It is an electromagnetic wave absorber, and includes a base material layer 1, an electromagnetic wave absorption layer 2, and a binder layer 35 formed between the base material layer 1 and the electromagnetic wave absorption layer 2.

  As described above, the binder layer 35 in the present embodiment is obtained by adding a flame retardant to the binder layer 3 shown in FIG. As the flame retardant, a phosphorus flame retardant or a halogen flame retardant can be used. From the environmental viewpoint, it is preferable to use a phosphorus-based flame retardant.

  The amount of the flame retardant added is preferably 40 to 120 parts by weight with respect to 30 parts by weight of the synthetic resin of the binder layer 35. When the amount of the flame retardant added is less than 40 parts by weight relative to 30 parts by weight of the synthetic resin, there is a possibility that sufficient flame retardant performance cannot be obtained. Moreover, when the addition amount of a flame retardant exceeds 120 weight part with respect to 30 weight part of the said synthetic resin, there exists a possibility that the binder layer 35 obtained may become weak.

  Thus, by adding a flame retardant to the binder layer 35, the flame retardancy of the electromagnetic wave absorbing layer 2 on the binder layer 35 can be improved. Therefore, the electromagnetic wave absorber 30 excellent in flame retardancy can be obtained with respect to the electromagnetic wave absorber 10 according to the first embodiment.

  Further, in the electromagnetic wave absorber 30 shown in FIG. 4A, a flame retardant is added to the binder layer 35, but without adding a flame retardant to the binder layer 35, as shown in FIG. The flame retardant layer 5 may be formed on 2.

  As shown in FIG. 4B, the electromagnetic wave absorber 31 according to the third embodiment of the present invention is different from the electromagnetic wave absorber 10 according to the first embodiment of the present invention shown in FIG. Furthermore, the flame retardant layer 5 is formed. In FIG. 4B, the same components as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 4B, an electromagnetic wave absorber 31 according to another third embodiment of the present invention has a base material layer 1, a binder layer 3, and an electromagnetic wave absorption layer 2 formed in this order. A flame retardant layer 5 in which a flame retardant is added to a synthetic resin is formed on the surface of the absorbent layer 2 opposite to the surface on which the binder layer 3 is formed.

  As the synthetic resin constituting the flame retardant layer 5, a polyester resin, an epoxy resin, a phenol resin, a urethane resin, an acrylic resin, or the like can be used. Moreover, the above-mentioned flame retardant can be used as the flame retardant. The amount of the flame retardant added can also be the same as that of the binder layer 35.

  The flame retardant layer 5 is subjected to heat treatment by applying a third resin solution (resin solution for the flame retardant layer), which is a resin solution for forming the flame retardant layer 5, on the formed electromagnetic wave absorbing layer 2. Thus, a film can be formed.

  Thus, the flame retardance of the electromagnetic wave absorbing layer 2 can also be improved by forming the flame retardant layer 5 on the electromagnetic wave absorbing layer 2. Therefore, the electromagnetic wave absorber 31 excellent in flame retardancy can be obtained.

  4 (a) and 4 (b) may be combined to have a structure in which the electromagnetic wave absorbing layer 2 is sandwiched between the flame retardant layer 5 and the binder layer 35 to which the flame retardant is added. Thereby, the flame retardance of the electromagnetic wave absorption layer 2 can be further improved.

  Moreover, in this embodiment, you may apply the adhesive bond layer 4 as shown in FIG. That is, in FIG. 4A, the adhesive layer 4 may be formed on the surface opposite to the binder layer 35 of the electromagnetic wave absorbing layer 2. Moreover, in FIG.4 (b), you may form the adhesive bond layer 4 in the surface on the opposite side to the electromagnetic wave absorption layer 2 of the flame retardant layer 5. FIG.

  Examples of the electromagnetic wave absorber according to the present invention will be described below.

(Test method)
Various test methods in each example were performed as follows.

(Reflow test)
The produced electromagnetic wave absorber was heat-treated at a temperature of 150 ° C. for 2 minutes, and then heat-treated at a temperature of 260 ° C. for 5 seconds. Thereafter, the external appearance of the electromagnetic wave absorber was visually observed to determine whether there was any abnormal appearance such as swelling or peeling.

(Heat resistance test)
The produced electromagnetic wave absorber was subjected to a heat treatment at a temperature of 200 ° C. for 60 minutes by a gear oven, and then visually changed in appearance and measured for electromagnetic wave absorption performance by the following method.

(Cross cut test)
A 1 mm × 1 mm square grid cut is made on the electromagnetic wave absorbing layer surface of the produced electromagnetic wave absorber (the number of grids is 100). Next, the adhesive tape was strongly pressed at the place where the cuts were made on the grid, and the ends of the adhesive tape were rapidly peeled off at an angle of about 45 °, and the number of grids remaining in 100 pieces was counted.

(Evaluation item)
Moreover, the physical property value of each evaluation item in each Example was measured as follows.

(Surface resistance value)
The surface resistance value of the electromagnetic wave absorbing layer surface in the prepared electromagnetic wave absorber (when the adhesive layer is provided, before applying the adhesive layer) was measured using a surface resistance measuring instrument Lorester EP (Mitsubishi Chemical).

(Electromagnetic wave absorption)
The electromagnetic wave absorption performance of the produced electromagnetic wave absorber was measured by a radio wave absorption performance measurement S21 method according to IEC-62333 using a Keycom-type near-field radio wave absorption measurement device. Moreover, when reducing electromagnetic waves by 1 dB, it describes as -1 dB. The measurement wavelength region was 300 to 1000 MHz.

  In addition, as electromagnetic wave absorption performance, since the electromagnetic wave absorber according to each example shows the performance of lowering to the lower right (improving electromagnetic wave absorption performance) as the frequency increases, 300 MHz is shown when the performance is −6 dB or less at 1000 MHz. Stable and excellent electromagnetic wave absorption performance of −1 dB or less is exhibited in the entire wavelength region of ˜800 MHz. Further, even when the performance of -3 dB to -6 dB is shown at 1000 MHz, it is -1 dB or less in the entire wavelength region of 300 MHz to 800 MHz, and usually does not cause electromagnetic interference, but electromagnetic interference may occur depending on conditions. is there. Moreover, when the performance of -3 dB or more is shown at 1000 MHz, there is a high possibility that it will be -1 dB or more in the entire wavelength region of 300 MHz to 800 MHz, and there is a high possibility of causing electromagnetic interference. Therefore, when the value of the electromagnetic wave absorption performance at 1000 MHZ is −6 dB or less, it is “◯”, when it is −3 to −6 dB, “Δ”, and when it is −3 dB or more, it is “x”.

(Layer thickness)
The film thickness of each layer was measured using a dial gauge (“DIGMATIC MICROMETER APB-2C” manufactured by Mitutoyo Corporation). The film thickness of each layer was calculated as follows.

Film thickness of electromagnetic wave absorbing layer = film thickness of electromagnetic wave absorbing layer with release paper−thickness of release paper film thickness of binder layer = thickness of electromagnetic wave absorber (base material layer + binder layer + electromagnetic wave absorbing layer)
-Film thickness of base material layer-Film thickness of electromagnetic wave absorbing layer

(Flame retardance)
The flame retardancy of the electromagnetic wave absorber was tested according to UL-94 VTM-0, and a pass / fail judgment was made.

(Example 1)
First, on a release paper (manufactured by Lintec Corporation), the following resin solution for electromagnetic wave absorption layer was applied with a bar coater and dried at 120 ° C. for 1 minute to form an electromagnetic wave absorption layer having a film thickness of 30 μm. . In addition, the electromagnetic wave absorption layer of a present Example crosslinks a thermoplastic polyurethane resin with trifunctional isocyanate, and has thermosetting property and thermoplasticity.

(Resin solution for electromagnetic wave absorbing layer)
10 parts by weight of urethane resin 10 parts by weight of carbon black particles 10 parts by weight of magnetic metal particles (scale-like: iron aluminum silicon alloy) 1 part by weight of isocyanate-based crosslinking agent
(Coronate HL: manufactured by Nippon Polyurethane Industry Co., Ltd.)
80 parts by weight of dimethylformamide

  Next, on the electromagnetic wave absorption layer, the following binder layer resin solution was applied with a bar coater and dried at a temperature of 120 ° C. for 30 seconds to form a binder layer having a thickness of 20 μm. In addition, the binder layer of a present Example crosslinks a thermoplastic polyester resin with trifunctional isocyanate, and has thermosetting property and thermoplasticity.

(Resin solution for binder layer)
Polyester resin (saturated polyester resin, molecular weight 50,000 or less) 63 parts by weight Isocyanate-based crosslinking agent 12 parts by weight
(Coronate HL: manufactured by Nippon Polyurethane Industry Co., Ltd.)
2 parts by weight of amine catalyst
(Rezamin HI-299: manufactured by Dainichi Seika Kogyo Co., Ltd.)
Ethyl acetate 37 parts by weight Toluene 7 parts by weight

  Next, a PI film (Kapton 100EN, manufactured by Toray DuPont Co., Ltd., film thickness 30 μm) is prepared as a base material layer, the PI film is overlaid on the binder layer, and a nip roll is used at a temperature of 120 ° C. The base material layer and the electromagnetic wave absorbing layer were bonded to each other through a binder layer at a pressure of 0.4 MPa. Next, after aging for 72 hours at a temperature of 70 ° C., an electromagnetic wave absorber was obtained by peeling the release paper.

(Example 2)
In Example 1, the thickness of the electromagnetic wave absorption layer was 30 μm, but in Example 2, the thickness of the electromagnetic wave absorption layer was 15 μm. In addition, the electromagnetic wave absorber was obtained like Example 1 except the film thickness of the electromagnetic wave absorption layer.

(Example 3)
In Example 1, the synthetic resin of the binder layer resin solution was a urethane resin, but in Example 3, the synthetic resin of the binder layer resin solution was an acrylic resin. That is, Example 3 is obtained by changing the resin solution for the binder layer in Example 1 as follows. In addition, the electromagnetic wave absorber was obtained like Example 1 except the resin solution for binder layers.

(Resin solution for binder layer)
Acrylic resin 30 parts by weight Aluminum chelate crosslinking agent 2 parts by weight
(TA101K: manufactured by DIC Corporation)
Ethyl acetate 35 parts by weight Toluene 35 parts by weight

Example 4
In Example 4, a flame retardant layer was formed on the electromagnetic wave absorbing layer in the electromagnetic wave absorber obtained in Example 1. Specifically, on the electromagnetic wave absorbing layer in the electromagnetic wave absorber of Example 1, the following flame retardant layer resin solution was applied with a pipe coater, dried at 120 ° C. for 30 seconds, and the film thickness was 50 μm. A flame retardant layer was formed. In addition, it is the same as Example 1 except a flame retardant layer.

(Resin solution for flame retardant layer)
Urethane resin 13 parts by weight Flame retardant (phosphorous flame retardant: nitrogen, phosphorus condensate) 26 parts by weight Pigment (black) 2 parts by weight Dimethylformamide 20 parts by weight Methyl ethyl ketone 40 parts by weight

(Example 5)
In Example 1, the catalyst for the electromagnetic wave absorbing layer was an amine catalyst, but in Example 5, the catalyst for the electromagnetic wave absorbing layer was tin octylate (Chrisbon Accel T81, manufactured by DIC Corporation). That is, in Example 1, Example 5 changes the catalyst of an electromagnetic wave absorption layer from an amine catalyst to octyl tin. In addition, the electromagnetic wave absorber was obtained like Example 1 except the catalyst of the electromagnetic wave absorption layer.

(Example 6)
In Example 1, an isocyanate cross-linking agent was added to the electromagnetic wave absorbing layer resin solution to form an electromagnetic wave absorbing layer, but in Example 6, an isocyanate cross-linking agent was not added to the electromagnetic wave absorbing layer resin solution. An electromagnetic wave absorbing layer was formed. That is, although the electromagnetic wave absorption layer in Example 6 is a thermoplastic resin, the electromagnetic wave absorption layer in Examples 1 to 5 is a thermoplastic resin and a thermosetting resin because it is formed by adding a crosslinking agent. is there. At this time, the heat resistance of the synthetic resin of the electromagnetic wave absorbing layer in Example 6 was about 170 to 180 ° C. In addition, the electromagnetic wave absorber was obtained like Example 1 except the presence or absence of the crosslinking agent of the resin solution for electromagnetic wave absorption layers.

(Comparative Example 1)
Comparative Example 1 is an electromagnetic wave absorber produced in Example 1 without forming a binder layer. Specifically, the electromagnetic wave absorbing layer resin solution used in Example 1 was applied on the PI film used in Example 1 to form an electromagnetic wave absorbing layer having a thickness of 30 μm.

(Comparative Example 2)
In Comparative Example 2, an electromagnetic wave absorber was prepared by removing magnetic metal particles from the electromagnetic wave absorbing layer in Example 1. In addition, it is the same as Example 1 except the presence or absence of a magnetic metal particle.

  The performance of the electromagnetic wave absorber in each Example and Comparative Example obtained as described above is shown in Table 1 below.

  As shown in Table 1, in the electromagnetic wave absorber according to Comparative Example 1 having no binder layer, the electromagnetic wave absorber was swollen in the reflow test and the heat resistance test, and an appearance abnormality was observed. On the other hand, in the electromagnetic wave absorbers according to Examples 1 to 6, no abnormal appearance was observed in the reflow test and the heat resistance test.

  Further, in the electromagnetic wave absorber according to Comparative Example 1, although the number of grids with the electromagnetic wave absorbing layer remaining could not be accurately counted in the cross grid test, most of the 100 grids were peeled off. Oops. On the other hand, in the electromagnetic wave absorber which concerns on Examples 1-6, peeling of the electromagnetic wave absorption layer did not generate | occur | produce at all in the cross cut test, and it has confirmed that the electromagnetic wave absorber excellent in adhesiveness was obtained.

  Moreover, when the film thickness of the electromagnetic wave absorption layer was reduced as in the electromagnetic wave absorber according to Example 2, the electromagnetic wave absorption performance was reduced, but no appearance abnormality was observed in the reflow test and the heat resistance test. In addition, even if reflow resistance can be improved by forming a binder layer as in Comparative Example 2, a desired electromagnetic wave absorbing performance can be obtained unless magnetic metal particles are contained in the electromagnetic wave absorbing layer. In the first place, it cannot function as an electromagnetic wave absorber.

  Moreover, even if it comprises the synthetic resin of a binder layer with an acrylic resin like the electromagnetic wave absorber which concerns on Example 3, it can be set as the electromagnetic wave absorber excellent in reflow resistance and adhesiveness similarly to another Example. it can.

  Moreover, it can be set as the electromagnetic wave absorber which has the outstanding flame retardance by forming a flame retardant layer like the electromagnetic wave absorber which concerns on Example 4. FIG.

  Further, like the electromagnetic wave absorber according to Example 5, even when tin octylate is used as the catalyst of the electromagnetic wave absorption layer, an electromagnetic wave absorber excellent in reflow resistance and adhesiveness can be obtained as in the other examples. .

  Moreover, it can be set as the electromagnetic wave absorber excellent in reflow resistance and adhesiveness similarly to another Example, without adding a crosslinking agent like the electromagnetic wave absorber which concerns on Example 6. FIG. However, the electromagnetic wave absorber which has heat resistance in the temperature more than reflow processing temperature can be obtained by adding a crosslinking agent like Examples 1-5.

  As mentioned above, although the electromagnetic wave absorber which concerns on this invention, and its manufacturing method have been demonstrated based on embodiment and an Example, this invention is not limited to said embodiment and Example. For example, it is possible to arbitrarily combine the components and functions in each embodiment and example without departing from the spirit of the present invention, and forms obtained by subjecting each embodiment and example to various modifications conceived by those skilled in the art. The embodiment realized by the above is also included in the present invention.

  The electromagnetic wave absorber according to the present invention is useful for a flexible printed wiring board or a wiring member such as a cable, or an electronic device having these wiring members.

DESCRIPTION OF SYMBOLS 1 Base material layer 2 Electromagnetic wave absorption layer 3, 35 Binder layer 4 Adhesive layer 5 Flame retardant layer 10, 20, 30, 31 Electromagnetic wave absorber

Claims (14)

An electromagnetic wave absorber comprising a base material layer and an electromagnetic wave absorption layer,
Between the base material layer and the electromagnetic wave absorption layer, a binder layer composed of a resin having a softening point of 260 ° C. or higher in the reflow process is formed ,
The electromagnetic wave absorbing layer is an electromagnetic wave absorber having a softening point of less than 260 ° C. in a reflow process . The electromagnetic wave absorber according to claim 1, wherein a film thickness of the electromagnetic wave absorbing layer is 5 μm or more and 100 μm or less. The electromagnetic wave absorber according to claim 1 or 2, wherein a surface resistance value of the electromagnetic wave absorbing layer is 20Ω / □ or more and 170Ω / □ or less. The electromagnetic wave absorber according to claim 1, wherein the electromagnetic wave absorption layer includes carbon black and magnetic metal particles. The resin constituting the binder layer, Ri polyester resins der,
The electromagnetic wave absorber according to any one of claims 1 to 4, wherein the resin constituting the electromagnetic wave absorption layer is a urethane resin . The electromagnetic wave absorber according to claim 1, wherein the binder layer is crosslinked by a crosslinking agent. The electromagnetic wave absorber according to claim 6, wherein the crosslinking agent is an isocyanate-based crosslinking agent. The electromagnetic wave absorber according to claim 1, wherein the binder layer has a thickness of 3 μm or more and 50 μm or less. The electromagnetic wave absorber according to claim 6 or 7, wherein an addition amount of the crosslinking agent is 3 to 16 parts by weight with respect to 30 parts by weight of the resin in the binder layer. The electromagnetic wave absorber according to any one of claims 1 to 9, wherein a flame retardant is added to the binder layer. The flame retardant layer in which a flame retardant is added to a predetermined synthetic resin is formed on the surface of the electromagnetic wave absorbing layer opposite to the side on which the binder layer is formed. The electromagnetic wave absorber as described in the item. The electromagnetic wave absorber according to claim 1, wherein an adhesive layer is formed on the electromagnetic wave absorption layer. An electronic apparatus comprising a printed wiring board on which the electromagnetic wave absorber according to any one of claims 1 to 12 is laminated. A first resin solution application step of applying a first resin solution containing metal on a release sheet;
An electromagnetic wave absorbing layer forming step of forming an electromagnetic wave absorbing layer having a softening point of less than 260 ° C. in a reflow process by performing a heat treatment on the first resin solution;
On the electromagnetic wave absorbing layer, and a second resin solution application step of applying a second resin solution containing the tree butter,
A binder layer forming step of applying a heat treatment to the second resin solution to form a binder layer having a softening point of 260 ° C. or higher in the reflow process ;
A base material layer is disposed on the binder layer, and the electromagnetic wave absorbing layer and the base material layer are bonded together by a binder layer,
A release sheet peeling step of peeling the release sheet from the electromagnetic wave absorbing layer. A method for producing an electromagnetic wave absorber.

Images