JP2005286191A - Laminated electromagnetic wave absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated electromagnetic wave absorber that is formed by laminating a conductive electromagnetic wave reflecting layer upon an electromagnetic wave absorbing layer which absorbs unnecessary electromagnetic waves from the inside and outside of a resin-made enclosure, has such an adhesive property that the absorber can be stuck on the surface of an unnecessary electromagnetic wave radiating source, such as the high-speed arithmetic element etc., and such an adhesive strength that the absorber does not fall down even when the absorber is stuck to the horizontal glass ceiling surface of the resin-made enclosure. <P>SOLUTION: In the laminated electromagnetic wave absorber, a conductive electromagnetic wave reflecting layer is laminated upon an electromagnetic wave absorbing layer which absorbs unnecessary electromagnetic waves from the inside and outside of the resin-made enclosure, an adhesive agent layer is laminated upon the outside of the electromagnetic wave reflecting layer through an insulator layer, and releasable film layers are respectively laminated upon the outside of the electromagnetic wave absorbing layer and the outside of the adhesive agent layer. The electromagnetic wave absorbing layer has such an adhesive property that the layer can closely adhere to at least the surface of the high-speed arithmetic element and the adhesive agent layer has such an adhesive strength that the layer can adhere to at least the horizontal glass ceiling surface of the resin-made enclosure and does not fall down from the ceiling surface. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laminated electromagnetic wave absorber having an electromagnetic wave absorbing layer and an electromagnetic wave reflecting layer, and in particular, an electromagnetic wave absorptive and electromagnetic wave that can be affixed to an upper surface of a housing and an unnecessary electromagnetic wave radiation source such as a high-speed arithmetic element. The present invention relates to a laminated electromagnetic wave absorber having excellent shielding properties.

In recent years, with the progress of the use of electromagnetic waves such as broadcasting, mobile communication, radar, mobile phones, and wireless LANs, electromagnetic waves are scattered in the living space, and problems such as electromagnetic interference and malfunction of electronic devices are frequently occurring. In particular, electromagnetic waves in the vicinity of electromagnetic fields that cause interference and resonance phenomenon caused by unnecessary electromagnetic waves (noise) radiated from elements and printed circuit board patterns inside the equipment that generate electromagnetic waves, and reduce the performance and reliability of the equipment, In addition, heat radiation countermeasures against an increase in the amount of heat generated by increasing the speed of arithmetic elements are becoming urgent.
As a method for solving these problems, a reflection method in which the generated noise is reflected and returned to the generation source, a bypass method in which the noise is guided to a stable potential surface (grounding portion, etc.), a shield method, or the like Has been taken.
However, with recent high-density mounting due to the demand for smaller and lighter equipment, the space for mounting noise countermeasure components has decreased, and with the drive voltage reduction due to the demand for power saving, the power supply system has been switched from other media. A structure that is easy to couple high-frequency, and is susceptible to high-frequency due to the narrowness of the clock signal due to the demand for rapid increase in processing speed. Because of the rapid increase in the frequency band to be used, both methods are sufficiently compatible with both electromagnetic field countermeasures and heat radiation countermeasures in the vicinity of electromagnetic fields, for example, because they are placed in an environment that is susceptible to mutual influence. The current situation is not.

  In order to solve these problems, electromagnetic wave absorbers that convert noise generated from elements and printed circuit board patterns in resin casings into thermal energy and electromagnetic wave absorbers that combine this with reflective layers that reflect noise have begun to be used. Yes. The electromagnetic wave absorber absorbs noise electromagnetic wave energy generated using magnetic loss characteristics and converts it into thermal energy to suppress reflection and transmission inside the housing, and emits the substrate pattern and element terminal as an antenna It is necessary to have a function of lowering the electromagnetic energy level by deteriorating the antenna effect by adding impedance to the electromagnetic energy to be generated, and those having these functions sufficiently are desired.

In order to cope with such problems, a sheet-like electromagnetic wave absorbing layer having a flexibility obtained by mixing an electromagnetic wave energy loss material and a holding material, and an organic fiber cloth is electrolessly plated with a highly conductive metal material. A flexible thin electromagnetic wave absorber (for example, see Patent Document 1) in which radio wave reflection layers are laminated has been proposed.
In addition, in order to prevent leakage of electromagnetic waves to the outside of the equipment, a metal plate is installed as an electromagnetic shielding material, or the casing is made conductive to impart electromagnetic shielding performance. In order to solve the problem that the reflected and scattered electromagnetic wave fills the inside of the device and promotes electromagnetic interference and the problem of electromagnetic interference between multiple substrates installed inside the device, a conductive support, There has been proposed an electromagnetic wave interference suppressor (see, for example, Patent Document 2) in a form in which a green soft magnetic layer made of soft magnetic powder and an organic binder is laminated.
Furthermore, an electromagnetic wave absorbing layer in which an electromagnetic wave absorbing filler is dispersed in a silicone resin is laminated on at least one surface of the electromagnetic wave reflecting layer in which the conductive filler is dispersed in the silicone resin. An electromagnetic wave absorber (see, for example, Patent Document 3) is disclosed, has high electromagnetic wave absorption performance and high electromagnetic wave shielding performance, and reflects the properties of the silicone resin itself, so that processability, flexibility, weather resistance, and heat resistance are achieved. It is said that it will be excellent.

However, in any technique, the structure of the electromagnetic wave absorber is such that a powder of magnetic loss material such as ferrite or a powder of dielectric loss material such as carbon is uniformly filled in rubber or plastic. However, the degree of filling is limited, and at the same time, there is a problem in flexibility to cope with various shapes of the mounted structure.
In particular, as an electromagnetic wave absorber for the high density and highly integrated portion of the electronic device elements inside the electronic device, a member having electromagnetic wave absorption performance, high resistance and high insulation, and heat conduction performance is required. There is no member having these three performances, and in the case of this application, flexibility, heat resistance, flame retardancy and the like are further required, but none of these performances are satisfied at the same time. In particular, in an absorber having an electromagnetic wave reflection function, the installation location is limited, and for example, it is a fact that installation on a top surface of a resin casing cannot be performed sufficiently.
Japanese Patent No. 3097343 Japanese Patent Laid-Open No. 7-212079 JP 2002-329995 A

  In view of the above-mentioned problems, the object of the present invention is to absorb unnecessary electromagnetic waves from inside and outside of a resin casing, and in a laminated electromagnetic wave absorber in which a conductive electromagnetic wave reflecting layer is laminated on an electromagnetic wave absorbing layer, A laminated electromagnetic wave absorber that has adhesiveness that can be affixed on an unnecessary electromagnetic radiation source, and has an adhesive force that does not drop even if it is affixed to a horizontal glass-like ceiling surface of a resin casing. , Laminated electromagnetic wave absorber excellent in electromagnetic wave absorbability, electromagnetic wave shielding property, and further, by enabling high filling of magnetic loss material, it is excellent in electromagnetic wave absorption, thermal conductivity, flame retardancy, less temperature dependence, Another object of the present invention is to provide a laminated electromagnetic wave absorber that is soft, has excellent adhesion strength, has high resistance and high insulation characteristics, and has no sticking restrictions.

  As a result of intensive studies to solve such problems, the present inventor has found that the electromagnetic wave absorbing layer contains at least a binder having an adhesive property that can adhere to an unnecessary electromagnetic radiation source such as a high-speed computing element, and the adhesive layer is at least a resin. A laminated electromagnetic wave absorber that has adhesive strength that does not drop even if it is attached to the horizontal glass-like ceiling surface of a plastic casing, is placed on the top surface of a plastic casing, on a high-speed computing element, etc. It becomes a laminated electromagnetic wave absorber with excellent electromagnetic wave absorbability and electromagnetic wave shielding properties that can be pasted, and further, by enabling high filling of magnetic loss materials, it has excellent electromagnetic wave absorption, thermal conductivity, flame retardancy, The present invention has been completed by finding that it can be a laminated electromagnetic wave absorber that has low temperature dependence, is soft, has excellent adhesion strength, has high resistance and high insulation characteristics, and has no sticking restrictions.

  That is, according to the first aspect of the present invention, a conductive electromagnetic wave reflection layer is laminated on an electromagnetic wave absorption layer that absorbs unnecessary electromagnetic waves from inside and outside the resin casing, and an insulator layer is interposed outside the electromagnetic wave reflection layer. A laminated electromagnetic wave absorber in which a pressure-sensitive adhesive layer is laminated, and a release film layer is laminated on each of the outer side of the electromagnetic wave absorbing layer and the outer side of the pressure-sensitive adhesive layer, and the electromagnetic wave absorbing layer has an adhesive property that can adhere to at least a high-speed computing element. And a pressure-sensitive adhesive layer is provided at least on a horizontal glass ceiling surface and has an adhesive force that does not fall.

  According to the second invention of the present invention, there is provided a laminated electromagnetic wave absorber characterized in that in the first invention, an insulating layer is provided between the electromagnetic wave absorbing layer and the electromagnetic wave reflecting layer.

  According to the third invention of the present invention, in the first or second invention, the electromagnetic wave absorbing layer is filled with electromagnetic wave absorption into a silicone gel having a penetration of JIS K2207-1980 (50 g load) of 5 to 200. A laminated electromagnetic wave absorber characterized by being filled with an agent is provided.

  According to a fourth aspect of the present invention, there is provided the laminated electromagnetic wave absorber according to any one of the first to third aspects, wherein the electromagnetic wave reflection layer is an aluminum metal layer.

  According to a fifth aspect of the present invention, there is provided the laminated electromagnetic wave absorber according to any one of the first to fourth aspects, wherein the pressure-sensitive adhesive layer is an acrylic resin pressure-sensitive adhesive layer. .

  According to a sixth aspect of the present invention, there is provided the laminated electromagnetic wave absorber according to any one of the first to fifth aspects, wherein the insulator layer is a polyethylene terephthalate resin layer.

  The laminated electromagnetic wave absorber of the present invention has a special layer structure in which a release film layer, an electromagnetic wave absorption layer, an electromagnetic wave reflection layer, an insulator layer, an adhesive layer, and a release film layer are laminated in this order. The product can be used in any way, for example, it can be attached to the horizontal glass surface of the casing on an unnecessary electromagnetic radiation source such as a high-speed computing element, It has the effect of excellent shielding properties.

  The laminated electromagnetic wave absorber of the present invention has an electromagnetic wave absorbing layer and an electromagnetic wave reflecting layer of a conductor, and a release film layer, an electromagnetic wave absorption layer, an electromagnetic wave reflection layer, an insulator layer, an adhesive layer, and a release film layer are laminated in this order. It is a laminated body. Hereinafter, each layer and layer configuration will be described in detail.

1. Each layer of laminated body (1) Electromagnetic wave absorbing layer The electromagnetic wave absorbing layer used in the laminated electromagnetic wave absorber of the present invention is not particularly limited as long as it has an electromagnetic wave absorbing effect. However, the electromagnetic wave absorbing property, thermal conductivity, flame retardancy are not limited. It is preferable that it is excellent in heat resistance, has low temperature dependency, is soft, has excellent adhesion strength, has high resistance and high insulation characteristics, and has an effect of having no sticking limitation. For example, (a) soft ferrite described below, A composite material in which (b) flat soft magnetic metal powder, (c) magnetite, etc. are contained in (d) silicone resin is preferable.

(A) Soft ferrite The soft ferrite that can be used for the electromagnetic wave absorbing layer of the present invention exhibits a magnetic function even with a weak excitation current. Although it does not specifically limit as a soft ferrite, Ni-Zn system ferrite, Mn-Zn system ferrite, Mn-Mg system ferrite, Cu-Zn system ferrite, Ni-Zn-Cu ferrite, Fe-Ni-Zn -Cu-based, Fe-Mg-Zn-Cu-based, and Fe-Mn-Zn-based soft ferrites are mentioned. Among these, Ni-- from the balance of electromagnetic wave absorption characteristics, thermal conductivity, price, etc. Zn-based ferrite is preferred.

The shape of the soft ferrite is not particularly limited, and can be a desired shape such as a spherical shape, a fibrous shape, or an indefinite shape. In the present invention, since it can be filled with a high filling density and higher thermal conductivity can be obtained, it is preferably spherical. When the soft ferrite is spherical, the particle size can be filled at a high packing density, and the blending operation can be facilitated by preventing aggregation of the particles.
By using the Ni—Zn ferrite in such a shape, it does not cause inhibition of curing of the silicone gel described later, is excellent in dispersibility in the silicone gel material, and exhibits a certain degree of thermal conductivity.

Furthermore, the particle size distribution _{D 50} of the soft ferrite, 1 to 30 [mu] m, preferably 10 to 30 [mu] m. The particle size distribution D ₅₀ of 500MHz frequencies below is less than 1μm soft ferrite tends to electromagnetic wave absorption performance is lowered, more than 30μm when look like smoothness of the electromagnetic wave absorber is poor, undesirable .
Here, the particle size distribution D _50, shows the range of particle size value when it becomes 50% by total weight of smaller particle sizes determined by a particle size distribution meter.

The soft ferrite used in the present invention needs to be treated with a non-functional silane compound in order to suppress the influence of residual alkali ions existing on the surface of the soft ferrite. Soft ferrite is used by blending it into silicone, which will be described later. Residual alkali ions existing on the surface of the ferrite may cause curing inhibition in the condensation type or addition type curing mechanism of the silicone. If it is caused, the soft ferrite cannot be highly filled, and further the dispersion of the filled soft ferrite becomes insufficient.
By treating the surface of the soft ferrite with a non-functional group silane compound, the pH of the soft ferrite surface-treated with the non-functional group silane compound is 8.5 or less, preferably 8.2 or less, more preferably 7. It is preferable to make it 8-8.2. By setting the pH of the soft ferrite to 8.5 or less, the inhibition of curing of the silicone is suppressed, and it can be applied to any silicone. In addition, the familiarity between soft ferrite and silicone is improved, and as a result, the amount of soft ferrite in silicone is increased, and at the same time, the mixing property with the heat conductive filler is increased, and a uniform molded body can be obtained.

Nonfunctional functional silane compounds for surface treatment of soft ferrite that can be used in the present invention include methyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, and phenyltriethoxysilane. , Diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane and the like. Among these, dimethyldimethoxysilane and methyltrimethoxysilane are preferable. These non-functional group silane compounds can be used alone or in combination of two or more.
As a silane compound for the surface treatment of the soft ferrite of the present invention, if a normal silane coupling agent or an epoxy resin surface treatment agent used for the surface treatment of fillers is used, the hardness changes that the hardness increases in an environmental test under heating. If it occurs, cracks and the like due to thermal decomposition occur, and the shape cannot be maintained, resulting in appearance damage.

  The method for treating the surface of the soft ferrite with the non-functional group silane compound is not particularly limited, and a surface treatment method for an inorganic compound with a normal silane compound or the like can be used. For example, soft ferrite is immersed and mixed in a methyl alcohol solution of about 5% by weight of dimethyldimethoxysilane, then water is added to the solution for hydrolysis treatment, and the resulting processed product is pulverized with a Henschel mixer or the like. It is obtained by mixing. The non-functional group-based silane compound is preferably about 0.2 to 10% by weight with respect to the soft ferrite.

(B) Flat soft magnetic metal powder (b) Flat soft magnetic metal powder that can be used in the electromagnetic wave absorbing layer of the present invention is a material having an effect of having stable energy conversion efficiency in a high frequency band.
(B) The flat soft magnetic metal powder is not particularly limited as long as it has soft magnetism and can be flattened by mechanical treatment, but has high magnetic permeability and low self-oxidation property. Also, a shape having a high aspect ratio (a value obtained by dividing the average particle diameter by the average thickness) is desirable. Specific metal powders include Fe-Ni alloy system, Fe-Ni-Mo alloy system, Fe-Ni-Si-B system, Fe-Si alloy system, Fe-Si-Al alloy system, Fe-Si-. B alloy, Fe—Cr alloy, Fe—Cr—Si alloy, Co—Fe—Si—B alloy, Al—Ni—Cr—Fe alloy, Si—Ni—Cr—Fe alloy, etc. Magnetic metals are exemplified, and among these, Al or Si—Ni—Cr—Fe based alloys are particularly preferred from the viewpoint of low self-oxidation. These may be used alone or in combination of two or more.

Autooxidation can be determined from the rate of change in weight of a sample after an exposure test in the air under heating. Those having a weight change rate of 0.3% or less after being exposed to an atmosphere of 200 ° C. for 300 hours are preferable. If the flat soft magnetic metal powder has low self-oxidation property, even if a highly permeable silicone gel or the like is used as a binder resin, it will not deteriorate over time due to changes in ambient environmental conditions such as humidity. . Therefore, there is an advantage that any binder resin can be used.
Furthermore, if the self-oxidation property is low, there is no danger of dust explosion, and it has the advantage that it can be stored in a large amount as a non-hazardous material and can be handled easily and production efficiency can be increased.

The aspect ratio of the flat soft magnetic metal powder is preferably 10 to 150, more preferably 17 to 20.
Further, the average thickness of the flat soft magnetic metal powder is preferably 0.01 to 1 μm. When the thickness is less than 0.01 μm, the dispersibility in the resin is deteriorated, and the particles are not sufficiently aligned in one direction even when an orientation treatment is performed by an external magnetic field. Even with materials of the same composition, magnetic properties such as magnetic permeability are lowered, and magnetic shield properties are also lowered. On the contrary, when the average thickness exceeds 1 μm, the filling rate decreases. Further, since the aspect ratio is small, the influence of the demagnetizing field is increased, and the magnetic permeability is lowered, so that the shield characteristics are insufficient.
The particle size distribution _{D 50} of the flat soft magnetic metal powder, 8～42Myuemu is preferred. Particle size reduces the energy conversion efficiency distribution D ₅₀ of less than 8 [mu] m, and decreases the mechanical strength of the particles exceeds 42 .mu.m, if it is mechanically mixed easily damaged.
Here, the particle size distribution D _50, shows the range of particle size value when it becomes 50% by total weight of smaller particle sizes determined by a particle size distribution meter.

The specific surface area of the flat soft magnetic metal powder is preferably 0.8 to 1.2 m ² / g. Since the flat soft magnetic metal powder is a material that performs an energy conversion function by electromagnetic induction, the higher the specific surface area, the higher the energy conversion efficiency can be maintained. However, the larger the specific surface area, the weaker the mechanical strength. Therefore, it is necessary to select the optimum range. When the specific surface area is less than 0.8 m ² / g, high filling is possible, but the energy exchange function is low, and when it exceeds 1.2 m ² / g, it is easy to break when mechanically mixed, and shape retention becomes difficult, Even if the filling is high, the energy exchange function is low.
Here, the specific surface area is a value measured by a BET measuring device.

  The tap density of the flat soft magnetic metal powder is preferably 0.55 to 0.75 g / ml. Moreover, it is preferable that the surface of these metal magnetic body flat shaped powder is given antioxidant.

The flat soft magnetic metal powder used in the present invention is preferably used after being microencapsulated. When the flat soft magnetic metal powder is combined and filled with soft ferrite or the like, the dielectric breakdown strength tends to be lowered together with the volume resistance. By performing microencapsulation, it is possible to prevent this decrease in dielectric breakdown strength and at the same time improve the strength.
The method of microencapsulation is not particularly limited, and may be a method of covering the surface of the flat soft magnetic metal powder to a certain thickness and using a material that does not hinder the energy conversion function of the flat soft magnetic metal powder. Any method may be used.
For example, gelatin is used as a material for coating the surface of a flat soft magnetic metal powder, and the soft magnetic metal powder is dispersed in a toluene solution in which gelatin is dissolved, and then the toluene is volatilized and the capsule is coated with the soft magnetic metal powder with gelatin. Flattened soft magnetic metal powder can be obtained. In this case, for example, a microencapsulated material having a gelatin weight of 20% and a flat soft magnetic metal powder with a weight ratio of about 80% is obtained having a particle size of about 100 μm, and dielectric breakdown of an electromagnetic wave absorber using the microencapsulated material is obtained. The strength can be improved about twice that without microencapsulation.

(C) Magnetite (c) Magnetite that can be used in the electromagnetic wave absorbing layer of the present invention is iron oxide (Fe ₃ O ₄ ), and when used together with the soft ferrite, imparts flame retardancy to the electromagnetic wave absorber. At the same time, the thermal conductivity can be improved, and further, the electromagnetic wave absorption effect of the entire electromagnetic wave absorber can be improved by the synergistic effect by adding the magnetic properties of magnetite.
Particle size distribution _{D 50} of magnetite, 0.1 to 0.4 [mu] m is preferred. It may enable highly filled soft ferrite by the particle size distribution D ₅₀ of the magnetite to about one-tenth of the particle size distribution D ₅₀ of the soft ferrite. The particle size distribution D ₅₀ of the magnetite becomes difficult to handle and is less than 0.1 [mu] m, it becomes impossible to highly filled with soft ferrite exceeds 0.4 .mu.m.
Here, the particle size distribution D _50, shows the range of particle size value when it becomes 50% by total weight of smaller particle sizes determined by a particle size distribution meter.

  The shape of the magnetite is not particularly limited, and can be a desired shape such as a spherical shape, a fibrous shape, or an indefinite shape. In the present invention, in order to obtain high flame resistance, octahedral fine particles are preferable. When magnetite is octahedral fine particles, the specific surface area is large and the effect of imparting flame retardancy is high.

(D) Silicone (d) Silicone that can be used in the electromagnetic wave absorbing layer of the present invention functions as a binder for the soft ferrite, flat soft magnetic metal powder, magnetite, and the like, and has the temperature dependency of the electromagnetic wave absorbing layer. It has a function that enables use in a wide temperature range of -20 to 150 ° C. (D) As silicone, what is conventionally used as various silicone materials conventionally known and marketed can be selected suitably, and can be used. Therefore, any of a heat curing type or a room temperature curing type, a condensation type or an addition type, etc. can be used. In addition, the group bonded to the silicon atom is not particularly limited, and examples thereof include alkyl groups such as methyl group, ethyl group, and propyl group, cycloalkyl groups such as cyclopentyl group and cyclohexyl group, vinyl groups, and allyl groups. In addition to aryl groups such as alkenyl groups, phenyl groups, and tolyl groups, those in which the hydrogen atoms of these groups are partially substituted with other atoms or linking groups can be mentioned.

The silicone used in the electromagnetic wave absorber of the present invention may be in a gel state. For example, a silicone having a penetration of JIS K2207-1980 (50 g load) of 5 to 200 after curing can be used. Use of such a soft silicone gel is advantageous in adhesion when used as a molded body.
By using such silicone, the electromagnetic wave absorbing layer used in the present invention has at least adhesiveness capable of being in close contact with the high-speed arithmetic element.

  The electromagnetic wave absorbing layer of the present invention can be blended with other components within the range and type that do not impair the object of the present invention. Examples of such other components include a catalyst, a curing retarder, a curing accelerator, and a colorant.

  The electromagnetic wave absorbing layer used in the present invention is preferably a layer in which the above components (a) to (d) are used in combination according to the purpose. For example, the purpose is (i) high resistance and high insulation (a ), (C) and (d), (ii) an electromagnetic wave absorption layer consisting of (b), (c) and (d) for high electromagnetic wave absorption in the 2-4 GHz band, (iii) ) It can be used as an electromagnetic wave absorbing layer comprising (a), (b), (c) and (d) for the purpose of broadband frequency characteristics.

  In the electromagnetic wave absorbing layer comprising (a), (c) and (d) for the purpose of (i) above, the composition ratio of each component was (a) surface-treated with a non-functional silane compound. It is preferable to blend so as to contain 60 to 90% by weight of soft ferrite, (c) 3 to 25% by weight of magnetite, and (d) 7 to 15% by weight of silicone. In the electromagnetic wave absorbing layer composed of (b), (c) and (d) for the purpose of (ii) above, the composition ratio of each component is (b) 60 to 70% by weight of flat soft magnetic metal powder, It is preferable to blend so as to contain (c) 3 to 10% by weight of magnetite and (d) 20 to 37% by weight of silicone. In the electromagnetic wave absorbing layer composed of (a), (b), (c) and (d) for the purpose of (iii) above, the composition ratio of each component is (a) a non-functional group silane compound. 40-60% by weight of the surface-treated soft ferrite, (b) 20-30% by weight of flat soft magnetic metal powder, (c) 3-10% by weight of magnetite, and (d) 7-25% by weight of silicone. It is preferable to blend in.

  As described above, the electromagnetic wave absorbing layer used in the present invention is obtained from a mixture in which silicone is highly filled with soft ferrite, flat soft magnetic metal powder, magnetite and the like. Usually, ferrite, flat soft magnetic metal powder, magnetite are mixed with silicone rubber. When the inorganic filler such as the above is highly filled, the viscosity becomes high and roll kneading, banbury kneading, and kneader kneading are difficult. Even if kneading is carried out, the viscosity of the compound is high, and compression molding cannot form a uniform thickness. However, when silicone gel is used, kneading with a chemical mixer is easy even if high filling is performed. This makes it easy to form a sheet having a uniform thickness. Moreover, since the surface of soft ferrite is treated with a non-functional group silane compound, there is an effect that kneading and the like can be easily performed. In addition, when silicone is highly filled with ferrite and kneaded in a roll, the strength of holding the ferrite of the silicone is insufficient, the cohesion is lost, and further, the compound adheres to the roll and a uniform compound cannot be formed. Since the surface is treated with a non-functional group-based silane compound, it is excellent in dispersibility in silicone and has an effect of facilitating molding of a ferrite-containing sheet or the like. Moreover, when using what made the flat soft magnetic metal powder microcapsule has an effect which makes kneading | mixing etc. easier.

  The shape of the electromagnetic wave absorbing layer is not particularly limited, and can be a desired shape according to the application. For example, when making it into a sheet form, it is preferable that thickness is 0.5 mm-5.0 mm, and you may use it individually or 2-3 sheets.

(2) Electromagnetic wave reflection layer In the laminated electromagnetic wave absorber of the present invention, by providing the electromagnetic wave absorption layer and the reflection layer, the continuous reflection attenuation due to the shielding effect and the electromagnetic wave absorption layer can be easily produced at low cost and even in a thin sheet product. The thermal energy conversion can improve the attenuation performance of electromagnetic energy. The electromagnetic wave reflection layer is not particularly limited, and a conductor such as aluminum, copper, and stainless steel can be used. The electromagnetic wave reflection layer may be an aluminum foil or an aluminum layer deposited on a resin film or the like.
The reflective layer used in the present invention may be laminated directly on the electromagnetic wave absorbing layer, or may be laminated on the electromagnetic wave absorbing layer via an insulator layer.

(3) Insulator layer In the laminated electromagnetic wave absorber of the present invention, it is necessary to provide an insulator layer on the electromagnetic wave reflecting layer laminated on the electromagnetic wave absorbing layer. The insulator layer is made of an insulating material such as a polyethylene terephthalate (PET) resin film, a polypropylene resin film, a polystyrene resin film, and the like, and can suppress the decrease in dielectric breakdown strength of the electromagnetic wave absorber and at the same time improve its strength. .
Moreover, an insulator layer can also be provided between the electromagnetic wave absorption layer and the electromagnetic wave reflection layer as necessary.
The thickness of the insulator layer is preferably 25 to 75 μm.
Note that an acrylic resin adhesive or the like can be used for laminating the insulator layers.

(4) Adhesive layer In the laminated electromagnetic wave absorber of the present invention, an adhesive having an adhesive force that does not drop and adheres to at least a horizontal glass surface ceiling surface outside the insulator layer laminated on the electromagnetic wave reflecting layer. An agent layer is provided. By providing such a pressure-sensitive adhesive layer, it can be applied to the top and side surfaces of the housing, and the application range can be expanded.
The pressure-sensitive adhesive of the pressure-sensitive adhesive layer is not particularly limited, but an acrylic resin pressure-sensitive adhesive can be used.
Furthermore, what is obtained by providing an adhesive layer / release film on one of the insulator layers such as a PET film and integrally forming it is preferable.

(5) Release Film Layer In the laminated electromagnetic wave absorber of the present invention, a release film layer is provided on the outside of the electromagnetic wave absorption layer and the outside of the pressure-sensitive adhesive layer. For the release film layer, an insulating film such as a PET resin film, a polypropylene resin film, or a polystyrene resin film is used, and the thickness is preferably 20 to 30 μm. The release film layer is laminated with the tackiness of the silicone gel of the electromagnetic wave absorbing layer and the adhesive force of the adhesive layer.

2. Laminated structure and usage method of laminated body The laminated electromagnetic wave absorber of the present invention is obtained by laminating each of the above-mentioned layers. For example, it becomes a laminated body having a cross-sectional view as shown in FIG. In FIG. 1, 1 is an electromagnetic wave absorption layer, 2 is an electromagnetic wave reflection layer, 3 is an insulator layer, 4 is an adhesive layer, and 5 and 6 are release film layers.
In using the laminated electromagnetic wave absorber of the present invention, the electromagnetic wave absorbing layer / electromagnetic wave reflecting layer is always laminated in the order in which the unnecessary electromagnetic waves are incident. Examples of use will be described with reference to FIGS. For example, when an unnecessary electromagnetic radiation source from a high-speed computing element, a cable, a pattern, or the like can be specified, that is, when the high-speed computing element 11 on the substrate 10 is identified as an unnecessary electromagnetic radiation source in FIG. The release film 5 outside the electromagnetic wave absorption layer 1 is peeled off on the element 11, and is directly attached to the high-speed arithmetic element in the direction of the arrow (enlarged view of 11) due to the tack property of the electromagnetic wave absorption layer 1. Even when an unnecessary electromagnetic radiation source cannot be specified and can be attached to the substrate, the release film 5 outside the electromagnetic wave absorption layer 1 can be peeled off and attached to the substrate. In the case where the substrates have a multilayer structure, they can be laminated between the substrates. For example, in the case where an adhesive layer is attached to the lower side of the substrate located on the upper side, that is, in FIGS. In order to prevent the influence of unnecessary electromagnetic waves from the high-speed computing elements 11, 12 of the substrate 10 on the substrate 10 ′, the release film 6 on the outer side of the adhesive layer 4 is peeled off, and the arrow on the lower side of the substrate 10 ′ Adhesive layer 4 is stuck in the direction of. Further, when the unnecessary electromagnetic radiation source cannot be specified and cannot be attached to the substrate, that is, in FIG. 4, which of the cables, patterns, elements, etc. on the substrate 15 in the housing 20 is the unnecessary electromagnetic radiation source. If it cannot be specified and cannot be attached even in shape, the release film 6 outside the adhesive layer 4 is peeled off, and the adhesive layer 4 is attached to the top plate 21 of the housing in the direction of the arrow. Prevents reflection and transmission of unwanted electromagnetic waves to the outside of the housing. As described above, the laminated electromagnetic wave absorber according to the present invention is a product of one form and can be applied to cases of any unnecessary radio wave radiation sources.

The present invention will be described in detail based on examples, but the present invention is not limited to these examples. In addition, the physical-property value in an Example was measured with the following method.
(1) Penetration: Determined according to JIS K 2207-1980.
(2) Magnetic loss (permeability): Measured using a magnetic permeability & inductivity measurement system (S-parameter system coaxial tube er, μr measuring instrument system manufactured by Anritsu & Keycom).
(3) Volume resistance: measured in accordance with JIS K 6249.
(4) Dielectric breakdown strength: measured in accordance with JIS K 6249.
(5) Thermal conductivity: determined in accordance with the QTM method (Kyoto Electronics Industry Co., Ltd.).
(6) Flame retardancy: measured in accordance with UL94.
(7) Heat resistance: Leave at a constant temperature of 150 ° C., measure the penetration and thermal conductivity, and observe changes with time. The time until a change is observed.
(8) Absorption rate: Measured with a near-field electromagnetic wave absorbing material measuring device (manufactured by Keycom).

(Example 1)
Particle size distribution D ₅₀ 10% to 30 μm Ni—Zn soft ferrite (BSE-828 (trade name) manufactured by Toda Kogyo Co., Ltd.) surface-treated with methyltrimethoxysilane 83% by weight soft ferrite, particle size distribution D ₅₀ 0.1% to 0.4 μm octahedral magnetite fine particles (KN-320 (trade name): manufactured by Toda Kogyo Co., Ltd.) 5% by weight, and JISK2207-1980 (50 g load) penetration is 150 Silicone gel (CF-5106 (trade name): manufactured by Toray Dow Corning Silicone Co., Ltd.) 12% by weight was mixed, vacuum degassed, and then poured between glass plates so as not to entrain air. Heat-press molding was performed for 1 minute to obtain an electromagnetic wave absorbing sheet having a thickness of 1 mm and a smooth surface.
Next, using the obtained electromagnetic wave absorbing sheet, a PET film release film having a thickness of 20 μm, an electromagnetic wave absorbing sheet, an aluminum foil, a PET film having a thickness of 50 μm, an adhesive layer having a thickness of 1 μm, and a thickness of 20 μm. A PET film release film was laminated in this order to obtain a laminated electromagnetic wave absorber. The near electromagnetic field electromagnetic wave absorption rate of this laminated electromagnetic wave absorber was measured. The result was A shown in FIG. In FIG. 5, for comparison, the value of the near electromagnetic field electromagnetic wave absorption rate of an electromagnetic wave absorber not laminated with aluminum foil is shown as B.
The obtained laminated electromagnetic wave absorber has a magnetic loss μ ″ (1 GHz): 4.0, volume resistance: 2 × 10 ¹¹ Ω · m, dielectric breakdown strength: 4.5 kV / mm, thermal conductivity: 1. 2 W / m · K, specific gravity: 2.8, penetration: 60, flame retardancy (UL94): equivalent to V-0, heat resistance: 1000 hours or more.

  The laminated electromagnetic wave absorber of the present invention has a release film layer, an electromagnetic wave absorption layer, an electromagnetic wave reflection layer, an insulator layer, an adhesive layer, and a release film layer laminated in this order. Can be affixed on devices and the like, and has an effect of being excellent in electromagnetic wave absorption and electromagnetic wave shielding properties. In particular, it can be used for absorbing unnecessary electromagnetic waves in nearby electromagnetic fields such as broadcasting, cellular phones, and wireless LANs. .

It is sectional drawing of an example of the laminated electromagnetic wave absorber of this invention. It is a figure explaining an example of the usage method of the lamination | stacking absorber of this invention. It is a figure demonstrated by an example of the usage method of the laminated | stacked absorber of this invention. It is a figure demonstrated by an example of the usage method of the laminated | stacked absorber of this invention. It is a figure which shows the measurement result of the near electromagnetic field electromagnetic wave absorptivity of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave absorption layer 2 Electromagnetic wave reflection layer 3 Insulator layer 4 Adhesive layer 5, 6 Peeling film layer 10, 10 ', 15 Board | substrate 11, 11', 12, 12 'High-speed arithmetic element 20 Case 21 Case top

Claims (6)

  Absorbs unnecessary electromagnetic waves from inside and outside of the resin casing. A conductive electromagnetic wave reflection layer is laminated on the electromagnetic wave absorption layer, and an adhesive layer is laminated outside the electromagnetic wave reflection layer via an insulator layer. And a laminated electromagnetic wave absorber in which a release film layer is laminated on the outside of the adhesive layer, the electromagnetic wave absorbing layer having at least adhesiveness that can adhere to the high-speed computing element, and the adhesive layer is at least a horizontal glass ceiling surface A laminated electromagnetic wave absorber, characterized in that it has an adhesive force that does not drop when stuck to a film.   The laminated electromagnetic wave absorber according to claim 1, further comprising an insulator layer between the electromagnetic wave absorbing layer and the electromagnetic wave reflecting layer.   The laminated electromagnetic wave absorber according to claim 1 or 2, wherein the electromagnetic wave absorbing layer is filled with an electromagnetic wave absorbing filler in a silicone gel having a penetration of JIS K2207-1980 (50 g load) of 5 to 200. .   The laminated electromagnetic wave absorber according to any one of claims 1 to 3, wherein the electromagnetic wave reflection layer is an aluminum metal layer.   The laminated electromagnetic wave absorber according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer is an acrylic resin pressure-sensitive adhesive layer.   The laminated electromagnetic wave absorber according to claim 1, wherein the insulator layer is a polyethylene terephthalate resin layer.

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