JP2000101284A - Electromagnetic wave absorbing body and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thin, light weight, and flexible characteristic while excellent in mechanical strength for high absorbing performance, by providing an electromagnetic wave absorbing layer comprising an organic silane compound whose main components are soft-magnetic particles and a binder on a support body. SOLUTION: An electromagnetic wave absorbing layer 2 is formed on a support body 1 such as a paper, paper with high polymer resin such as polyolefine laminated, cloth, metal, glass. The electronic wave absorbing body using soft-magnetic oxide material such as MnZn ferrite is laminated by bonding, an adhesive agent, or heat-pressure bonding. Another support body 1 may be laminated on the electromagnetic wave absorbing layer 2 side. Here, the content of organic silane compound 0.1-10 pts.wt. relative to a soft-magnetic particle 100 pts.wt. with the organic silane compound added into the electromagnetic wave absorbing layer, an interface reinforcing effect between the soft-magnetic particles, and the binder is provided for improved coat characteristics such as tensile strength and bending characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave absorber and a method for producing the same, and more particularly, to a film-shaped electromagnetic wave absorber having flexibility, strength and high electromagnetic wave absorption, and a method for producing the same.

[0002]

2. Description of the Related Art With the spread of mobile phones, personal computers, and various types of electronic devices equipped with microcomputers, mutual interference of electromagnetic waves, interference, malfunction, or information stealing has become a technical and social problem. .
As a countermeasure against such electromagnetic wave interference, an electromagnetic wave shielding material using a conductive material or an electromagnetic wave absorber using a soft magnetic material is used.

[0003] The former electromagnetic wave shielding material converts electromagnetic wave energy into eddy current, and prevents the electromagnetic wave from entering the inside of the device and radiating to the outside of the device. For example, a technique such as coating with a hydrophilic paint is used. However, there is a disadvantage that the trapped electromagnetic waves easily cause interference inside the device, and the shielding effect is reduced unless the device is completely covered. On the other hand, if the gap is sufficiently shielded, another problem occurs in that the heat dissipation of the electronic device is reduced.

For this reason, an electromagnetic wave absorber that absorbs electromagnetic waves to reduce reflected waves and transmitted waves has been receiving attention. The electromagnetic wave absorber converts electromagnetic wave energy into heat energy through spin inversion of a soft magnetic material or movement of a domain wall to reduce the intensity of transmitted or reflected electromagnetic waves. Soft ferrite sintered bodies usually used as electromagnetic wave absorbers are heavy and brittle, and thus have difficulty in workability, and their electromagnetic wave absorption performance sharply decreases in a high frequency range, so that their application range is limited.

On the other hand, an electromagnetic wave absorbing material obtained by dispersing an electromagnetic wave absorbing material in a matrix such as resin or rubber and molding it by extrusion or the like has excellent workability, but it is difficult to fill the electromagnetic wave absorbing material with high density. For this reason, it was difficult to obtain high electromagnetic wave absorption performance. In addition, as the electronic devices become smaller and thinner, the electromagnetic wave absorbers are required to be thinner and lighter and have excellent electromagnetic wave absorption performance.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been proposed to provide an electromagnetic wave absorber which is thin and lightweight, is flexible, has excellent mechanical strength, is excellent in workability, and has a high absorption performance, and an electromagnetic wave absorber having the same. It is an object to provide a manufacturing method.

[0007]

Means for Solving the Problems The electromagnetic wave absorber of the present invention is an electromagnetic wave absorber having, on a support, an electromagnetic wave absorbing layer mainly composed of soft magnetic particles and a binder. It is further characterized by containing an organic silane compound.

[0008] The method for producing an electromagnetic wave absorber of the present invention comprises:
A method for producing an electromagnetic wave absorber, comprising a step of applying a coating mainly composed of soft magnetic particles and a binder on a support and drying the coating to form an electromagnetic wave absorbing layer, wherein the electromagnetic wave absorbing layer further comprises an organic silane. It is characterized by containing a compound.

The organic silane compound used in the present invention is preferably a compound represented by the following general formula (1). X-Si (-Y) (-Z) -V (1) (However, in the above general formula (1), X, Y and Z
Are H, Cl, NH ₂ , R, OR, and OR, respectively.
¹ represents any one of -OR ^2, may be the same or different. V is H, Cl, NH ₂ , SH, N
It represents any one of CO, R, epoxy group and acrylic acid group. R, R ¹ and R ^{2 each} represent any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. And may be the same or different, and furthermore, these R, R ¹ and R ² are Cl, NH ₂ , N
HR ^w , NR ^w ₂ , SH, NCO, epoxy group and acrylic acid group may be added. Here, R ^w represents any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. )

[0010] The content of the organic silane compound is 0.1 to 10 parts by weight per 100 parts by weight of the soft magnetic particles.
It is desirable that the amount be not more than part by weight. If the amount is less than 0.1 part by weight, the effect of dispersibility and high density filling of the soft magnetic particles cannot be obtained,
Further, the strength of the electromagnetic wave absorbing layer cannot be obtained. On the other hand, if it exceeds 10 parts by weight, plasticization of the coating film proceeds, and the mechanical strength decreases. In addition, since the number of matrix components increases, the effect of high-density packing cannot be obtained. In any case, when the filling density of the soft magnetic particles is low, the electromagnetic wave absorbing effect is reduced. R, R ¹ , R ² and R ^w in the organic silane compound preferably have about 1 to 26 carbon atoms. If it exceeds 26, the solubility at the time of preparing the coating material for the electromagnetic wave absorbing layer decreases.

The content of the binder is desirably 5 to 12 parts by weight based on 100 parts by weight of the soft magnetic particles. If the amount is less than 5 parts by weight, it is brittle and mechanical strength cannot be obtained, and if it exceeds 12 parts by weight, the matrix component becomes excessively large,
The packing density of the soft magnetic particles decreases.

The average particle size of the soft magnetic particles is 0.02 μm
It is desirable that the thickness be at least 30 μm. 0.02 μm
If it is less than 1, although the packing density increases, the shrinkage of the electromagnetic wave absorbing layer after drying is large, and the shape of the electromagnetic wave absorber deteriorates and cracks are easily generated. If it exceeds 30 μm, the filling property of the soft magnetic particles is reduced, the electromagnetic wave absorption performance is reduced and the physical properties of the coating film are reduced, and the soft magnetic particles are liable to sediment when formed into a paint in the manufacturing process. Stability decreases.

The electromagnetic wave absorber of the present invention may have a plurality of electromagnetic wave absorbing layers. In this case, the support may be laminated together, or the electromagnetic wave absorbing layer may be peeled off from the support and only the electromagnetic wave absorbing layer may be laminated.

In the electromagnetic wave absorber of the present invention, by adding an organic silane compound to the electromagnetic wave absorbing layer, the effect of reinforcing the interface between the soft magnetic particles and the binder is obtained, and the physical properties of the coating film such as tensile strength and flexural rigidity are obtained. Is improved. When the properties of the coating film are improved, the thickness of the electromagnetic wave absorbing layer is, for example, several tens μm to several hundred μm.
Even if it is as thin as m, sufficient mechanical strength can be obtained.
It is also possible to handle only the electromagnetic wave absorbing layer.

The addition of the organic silane compound improves the dispersibility of the soft magnetic particles in the coating, and as a result,
The filling property of the soft magnetic particles in the dried electromagnetic wave absorbing layer is enhanced. That is, the void volume in the electromagnetic wave absorbing layer is reduced, and even when stress is applied from the outside, the frequency of destruction starting from the void portion is reduced, and the coating film properties are also improved from this surface.
When the filling rate of the soft magnetic particles is improved, the magnetic permeability of the electromagnetic wave absorbing layer as a bulk is improved, and the electromagnetic wave absorbing performance is enhanced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The electromagnetic wave absorber of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view showing the basic structure of the electromagnetic wave absorber of the present invention. FIG. 1A shows a structure in which an electromagnetic wave absorbing layer 2 is formed on a support 1. FIG.
(B) is an electromagnetic wave absorber composed of only the electromagnetic wave absorbing layer 2 which is separated from each other.

FIG. 2 shows an example in which the electromagnetic wave absorber of the present invention is configured as a laminate. The lamination may be performed by any method such as an adhesive or a pressure-sensitive adhesive, or thermocompression bonding. Of these, FIG.
(A) to (c) show an electromagnetic wave absorber having the structure of FIG.
They are stacked with their front and back sides changed. FIG.
1D shows a structure in which a support 1 is further laminated on the electromagnetic wave absorbing layer 2 side of the electromagnetic wave absorber having the structure shown in FIG. FIG.
(E) is obtained by further laminating the electromagnetic wave absorber of FIG. 2 (d).

FIG. 2F shows a structure in which the electromagnetic wave absorbing layer 2 is further laminated on the electromagnetic wave absorbing layer 2 side of the electromagnetic wave absorber of FIG. 1A. The electromagnetic wave absorber of FIG. 2F can be manufactured by repeating the application and drying of the electromagnetic wave absorbing layer 2 twice. Alternatively, the electromagnetic wave absorber having the structure shown in FIG. 1B may be laminated on the electromagnetic wave absorber having the structure shown in FIG. As for the direction of the lamination, the electromagnetic wave absorbing layers 2 on both surfaces of the support 1 may be provided in addition to the structure shown in FIG.

FIG. 2G shows a laminate of two electromagnetic wave absorbers having the structure shown in FIG. 1B. FIG. 2H is FIG.
The electromagnetic wave absorber having the structure shown in FIG. By laminating the layers in this manner, the electromagnetic wave absorbing performance is further improved.

As the support 1, paper, paper laminated with a polymer resin such as polyolefin, polymer resin,
Cloth, nonwoven fabric, metal, glass and the like are used. Among these, a polymer resin which can obtain a thin strength is preferably employed. The polymer resin is not particularly limited, but polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefins such as polyethylene and polypropylene, and fluorine obtained by substituting part or all of hydrogen of these polyolefins with fluorine. Resins, cellulose derivatives such as cellulose triacetate and cellulose diacetate, vinyl resins such as polyvinyl chloride,
Examples thereof include vinylidene resins such as polyvinylidene chloride, polycarbonate, polyphenylene sulfide, polyamideimide, and polyimide. The surface of the polymer resin may be subjected to a release treatment with a silicone resin or the like.
These polymer resins are preferably in the form of a plate or a film. In the case of a plate, the thickness is about several hundred μm to several mm, and in the case of a film, the thickness is about several μm to several hundred μm.

The material of the soft magnetic particles used for the electromagnetic wave absorbing layer is not particularly limited, and may be FeSi, FeNi, FeSiA.
Metal soft magnetic material such as 1, MnZn ferrite, MgZn
Oxide soft magnetic materials such as ferrite and NiZn ferrite are exemplified.

The binder used in the electromagnetic wave absorbing layer is not particularly limited, but any of a thermoplastic resin, a thermosetting resin, a reactive resin and the like can be used. As the molecular weight of the resin, the number average molecular weight is 5,000 to 200,
000 are preferred, and 10,000 to 10
The one of 000 is more preferred.

Examples of the thermoplastic resin include vinyl chloride resin, vinyl acetate resin, vinyl fluoride resin, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer. Polymer, vinyl chloride-acrylonitrile copolymer, vinylidene chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, acrylate-vinyl chloride-vinylidene chloride copolymer, methacrylate-vinyl chloride copolymer Coalesce, methacrylate-vinylidene chloride copolymer, methacrylate-
Ethylene copolymer, acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, polyurethane resin, polyester polyurethane resin, polyester resin, polycarbonate polyurethane resin, polycarbonate resin, polyamide resin, polyvinyl butyral resin, cellulose derivative (cellulose acetate butyrate) , Cellulose diacetate, cellulose triacetate, cellulose propionate, nitrocellulose, etc.), styrene butadiene copolymer, polyester resin, amino resin, various synthetic rubbers, and the like.

Examples of the thermosetting resin and the reactive resin include phenol resin, epoxy resin, polyurethane curable resin, urea formaldehyde resin, melamine resin, alkyd resin, silicone resin, polyamine resin, high molecular weight polyester resin and isocyanate. Examples thereof include a mixture of a prepolymer, a mixture of a polyester polyol and a polyisocyanate, a mixture of a low molecular weight glycol, a high molecular weight diol, and an isocyanate, and a mixture of these resins. Among these resins, it is preferable to use a polyurethane resin, a polycarbonate resin, a polyester resin, an acrylonitrile-butadiene copolymer, which is considered to impart flexibility.

These resins include -SO ₃ M, -OSO ₃ M, -COOM, and -SO ₃ M in order to improve the dispersibility of the soft magnetic particles.
Alternatively, it is desirable to contain a polar functional group such as —PO (OM ′) ₂ (where M is H or Li, Ka, N
an alkali metal such as a, M ′ is H or Li, Ka, Na
Represents an alkali metal or alkyl group). Other polar functional groups include -NR ₁ R ₂ and -NR ₁ R ₂ R
₃ ⁺ X ^- as the side chain type having an end group of,> NR ₁ R ₂
⁺ X ^- there is such a main chain type (wherein R _1, R _2, R
₃ is a hydrogen atom or a hydrocarbon group, X ^- is fluorine,
Halogen ions such as chlorine, bromine and iodine or inorganic,
Represents an organic ion). In addition, -OH, -SH,-
It may be a polar functional group such as CN or an epoxy group. The content of these polar functional groups is 10 ^-1 to 10 ^-8 mol / g, preferably 10 ^-2 to 10 ^-6 mol / g. These organic binders can be used alone,
It is also possible to use more than one kind in combination.

Among the above-mentioned binders, for example, a polyisocyanate or the like can be added as a curing agent for crosslinking and curing the curable resin. As the polyisocyanate, an adduct of trimethylolpropane and 2,4-tolylene diisocyanate (TDI) (for example, trade name Coronate L-50) is generally used, but 4,4-diphenylmethane diisocyanate (MDI) and hexane diisocyanate An adduct of an alkylene diisocyanate such as (HDI) may be used. In addition, polyglycidylamine compounds such as tetraglycidyl metaxylenediamine, tetraglycidyl-1,3-bisaminomethylcyclohexane, tetraglycidylaminodiphenylmethane, triglycidyl-p-aminophenol, and 2-dibutylamino-4,6-dimercapto Polythiol compounds such as substituted triazines, epoxy compounds such as triglycidyl isocyanurate, mixtures of epoxy compounds and isocyanate compounds, mixtures of epoxy compounds and oxazoline compounds, mixtures of imidazole compounds and isocyanate compounds, methyl nadic anhydride, etc. Any of them can be used. The mixing ratio of these curing agents to the curable resin is 0.5 to 80 with respect to 100 parts by weight of the curable resin.
Parts by weight, preferably 5 to 50 parts by weight. By adding the curing agent in this range, the bonding strength between the pigment such as soft magnetic particles and the binder is increased, and the mechanical strength of the electromagnetic wave absorbing layer is improved. These isocyanate compounds may be applied to the surface of the coating film after forming the coating film of the electromagnetic wave absorbing layer. In this case, the hardening is performed mainly in the vicinity of the surface of the electromagnetic wave absorbing layer, so that the pigment such as soft magnetic particles and the binder are prevented from falling off from the electromagnetic wave absorbing layer.

In the present invention, the electromagnetic wave absorbing layer contains an organic silane compound as an essential component. As the organic silane compound, a compound represented by the general formula (1) is preferably used. X-Si (-Y) (-Z) -V (1) (However, in the above general formula (1), X, Y and Z
Are H, Cl, NH ₂ , R, OR, and OR, respectively.
¹ represents any one of -OR ^2, may be the same or different. V is H, Cl, NH ₂ , SH, N
It represents any one of CO, R, epoxy group and acrylic acid group. R, R ¹ and R ^{2 each} represent any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. And may be the same or different, and furthermore, these R, R ¹ and R ² are Cl, NH ₂ , N
HR ^w , NR ^w ₂ , SH, NCO, epoxy group and acrylic acid group may be added. Here, R ^w represents any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. )

More specific compounds include vinyltrichlorosilane, vinyltris (β-methoxyethoxy)
Silane, vinyltriethoxysilane, vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylethoxysilane, β
-(3,4 epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxy Examples thereof include silane and γ-chloropropyltrimethoxysilane, but are not limited thereto.

A lubricant, if necessary, is added to the electromagnetic wave absorbing layer.
Other additives such as reinforcing pigments, conductive particles, antistatic agents, surfactants, stabilizers and the like can also be used. For these additives, conventional general materials and compounding ratios can be employed.

Examples of the lubricant include graphite, molybdenum disulfide, tungsten sulfide, fatty acids having about 2 to 26 carbon atoms, and these fatty acids and 2 to 26 carbon atoms.
Conventionally known fatty acid esters, terpene compounds, oligomers thereof, silicone oils, fluorine-based lubricants, etc., all of which can be used.

Examples of the reinforcing pigment include inorganic pigments such as silicon oxide, aluminum oxide, and calcium carbonate. The amount of the reinforcing pigment to be added is 20 parts by weight or less, preferably 10 parts by weight or less based on 100 parts by weight of the soft magnetic particles.

As the conductive particles and the antistatic agent, carbon black, graphite, metal particles, a surfactant and the like are employed.

As the lubricant, any of conventionally known nonionic, cationic, anionic or amphoteric lubricants may be used.

The solvent for preparing the coating material containing the above-mentioned soft magnetic particles, a binder and an organic silane compound as a main component is not particularly limited, and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, methanol, Alcohols such as ethanol, propanol and butanol, esters such as methyl acetate, ethyl acetate, propyl acetate, butyl acetate, ethyl lactate and ethylene glycol acetate; ethers such as diethylene glycol dimethyl ether, 2-ethoxyethanol, tetrahydrofuran and dioxane; benzene And aromatic hydrocarbon compounds such as toluene, xylene, and halogenated hydrocarbon compounds such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, and chlorobenzene. Can.

As a dispersing and kneading apparatus for preparing the coating material, a kneader, an agitator, a ball mill, a sand mill, a roll mill, an extruder, a homogenizer, an ultrasonic dispersing machine and the like are used, but are not limited thereto.

The coating method for forming the electromagnetic wave absorbing layer on the support is also not particularly limited, and may be air doctor coat, blade coat, wire bar coat, air knife coat, squeeze coat, impregnation coat, reverse roll coat, transfer roll coat, Gravure coat, kiss coat,
Any of the conventional methods such as cast coating, extrusion coating, die coating, and spin coating can be employed. By using these types of coating devices, it is possible to perform coating on one side or both sides of the support.

As shown in FIG. 2 (f), when a plurality of electromagnetic wave absorbing layers 2 are formed on one side of the support 1, a die coater having a plurality of lips is adopted, and simultaneous multilayer coating is performed. can do. . After applying the electromagnetic wave absorbing layer on the support, the organic solvent may be removed by drying with heated air or the like, and a curing treatment may be performed, if necessary, and then an upper electromagnetic wave absorbing layer may be further applied thereon.

As a method for laminating the electromagnetic wave absorber, pressure molding, pressure thermoforming, molding with an adhesive or a pressure-sensitive adhesive, or the like is employed. The electromagnetic wave absorbing layer may be impregnated and swelled with a solvent and then molded under pressure. The pressure conditions vary depending on the type of binder, the presence or absence of heating, the heating temperature, the number and thickness of the electromagnetic wave absorbers, but are generally selected from the range of 0.1 to 500 kg / cm ² . In the case of heat molding, the temperature is desirably 250 ° C. or less. For the press molding and the press thermoforming, an ordinary press device, a roll laminator, or the like is used.

The same molding method is used when the electromagnetic wave absorbing layer formed on the support is peeled off and the isolated electromagnetic wave absorbing layer is laminated.

The preparation of the coating material for the electromagnetic wave absorbing layer is carried out by mixing, dispersing and kneading the soft magnetic particles and, if necessary, other additives, binders and organic solvents.

[0042]

EXAMPLES Hereinafter, preferred examples of the present invention will be described in more detail with reference to comparative examples as appropriate, but the present invention is not limited to these examples.

Example 1 As a soft magnetic particle material, MgZn ferrite having the following characteristics was employed. Soft magnetic particle characteristics Fe / Mg / Zn composition 100 / 18.4 / 12 at
m% Average particle size 7.2 μm Screen residue (100 μm or more) Less than 0.1% Loss on drying 0.25% Coercive force 1.19 kA / m (15 Oe)

The composition of the soft magnetic particles was analyzed by a fluorescent X-ray method using an X-ray diffractometer (manufactured by Rigaku Corporation).
The content of each element assuming that the content of element e is 100 is shown by relative comparison. As the average particle diameter, an average value of the particle diameters of unit particles of 500 soft magnetic particles randomly extracted by observation with a transmission electron microscope (manufactured by JEOL Ltd.) was adopted. The sieve residue was sieved with pure running water using a sieve having a mesh size of 100 μm, and the remaining weight was weighed. The loss on drying was represented by the weight loss after heating and holding in a heating furnace at 150 ° C. for 60 minutes. The coercive force was measured by a sample vibration type magnetometer (manufactured by Tohoku Special Steel Co., Ltd.).

Preparation of Paint for Electromagnetic Wave Absorbing Layer These soft magnetic particles were mixed with γ-aminopropyltriethoxysilane as an organic silane compound and a polyester polyurethane resin as a binder by a ball mill, and homogeneously dispersed to form a paint. . The composition of the paint for the electromagnetic wave absorbing layer is shown below. MgZn ferrite particles 100 parts by weight Polyester polyurethane resin 10 parts by weight (UR-8200 manufactured by Toyobo Co., Ltd .; sodium sulfonate as a polar functional group is contained at a ratio of 1 × 10 ⁻⁴ mol / g) γ-aminopropyltriethoxysilane 1 part by weight Methyl ethyl ketone 30 parts by weight Toluene 10 parts by weight Immediately before application, 0.5 part by weight of a polyisocyanate (Coronate HL manufactured by Nippon Polyurethane Co.) was added to the composition and further mixed to obtain a coating for an electromagnetic wave absorbing layer. .

Formation of Electromagnetic Wave Absorbing Layer As an example, a coating for an electromagnetic wave absorbing layer was applied to one main surface side of a support made of a polypropylene film having a thickness of 50 μm using a knife coater. The coating thickness is 0.5m when wet
m and 0.2 mm after drying. An electromagnetic wave absorbing layer was formed through the steps of drying and curing at 60 ° C. for 20 hours. By cutting into an appropriate shape in this state, the electromagnetic wave absorber shown in FIG. 1A is completed.

In this example, in order to measure the mechanical strength of the electromagnetic wave absorbing layer alone, the electromagnetic wave absorbing layer was peeled from the support to obtain an electromagnetic wave absorbing body having the form shown in FIG. 1 (b).
As for the mechanical strength of the electromagnetic wave absorber of the electromagnetic wave absorbing layer alone, the breaking strength and the breaking elongation were evaluated using a tensile tester (manufactured by Shimadzu Corporation). The tensile test conditions are JIS-K-6
In accordance with No. 301, the measurement was performed under the condition of a tensile speed of 300 mm / min. The electromagnetic wave absorption characteristics of the electromagnetic wave absorbing layer or the electromagnetic wave absorber were evaluated by measuring the proximity electric field shielding effect using a cell proposed by Kansai Electronics Industry Promotion Center. The measurement result will be described later.

Examples 2 to 11 The same procedure as in Example 1 was repeated except that MgZn ferrite having the same composition as in Example 1 was used, and the average particle size and the composition of the coating for the electromagnetic wave absorbing layer were changed. Only the electromagnetic wave absorber was obtained.

Example 12 An electromagnetic wave absorber was manufactured in the same manner as in Example 1. The electromagnetic wave absorbing layers of the electromagnetic wave absorber were overlapped with each other, and thermocompression bonded at 120 ° C. using a heating roll type laminator. Thereafter, the support is peeled off to obtain an electromagnetic wave absorber of the type shown in FIG. 2 (f) in which only two electromagnetic wave absorbing layers are laminated, and the support is peeled off to obtain an electromagnetic wave absorber having only two electromagnetic wave absorbing layers. Was.

Embodiment 13 According to the previous embodiment 12, only the type (n) shown in FIG.
= 3), and the support was peeled off to obtain an electromagnetic wave absorber having only three electromagnetic wave absorbing layers.

Comparative Example 1 A coating for an electromagnetic wave absorbing layer having a composition from which the organic silane compound was removed was prepared from the coating for an electromagnetic wave absorbing layer of Example 1, and the other conditions were the same as those of Example 1. An absorber was obtained.

Reference Example 1 An electromagnetic wave absorber of Reference Example 1 was obtained in the same manner as in Example 1 except that an organic silane compound was added in excess of the desired content of the organic silane compound.

[Reference Examples 2-3] Except for using a binder amount smaller or larger than the desired binder content,
The electromagnetic wave absorbers of Reference Examples 2 and 3 were obtained according to the same manner as in Example 1.

[Reference Examples 4 and 5] The electromagnetic wave absorbers of Reference Examples 4 and 5 were the same as in Example 1 except that soft magnetic particles smaller or larger than the desired soft magnetic particle size were used. I got

Table 1 shows the measurement results of the electromagnetic wave absorbers of the above Examples, Comparative Examples and Reference Examples together with the coating composition for the electromagnetic wave absorbing layer and the average particle size of the soft magnetic particles.

[0056]

[Table 1]

Examination of presence / absence and content of organosilane compound A series of samples of Examples 1 to 5, Comparative Example 1 and Reference Example 1 show that the presence / absence of the organosilane compound to the electromagnetic wave absorbing layer and the content thereof were determined. The effect of the electromagnetic wave absorber on the mechanical strength was studied.

FIG. 3 is a graph showing the relationship between the content of the organic silane compound and the rigidity of the electromagnetic wave absorber. The content of the organic silane compound is 0.1 to 100 parts by weight of the soft magnetic particles.
The electromagnetic wave absorbing layers of Examples 1 to 5 in the range of 10 to 10 parts by weight all show a value of 1.5 MPa or more. On the other hand, the sample of Comparative Example 1 in which the content of the organic silane compound was 0,
It is clear that the sample of Reference Example 1 in which the content of the organic silane compound exceeds 10 parts by weight has lower rigidity of the electromagnetic wave absorber than that of the example.

FIG. 4 is a graph showing the relationship between the content of the organic silane compound and the elongation at break of the electromagnetic wave absorber. The content of the organic silane compound is based on 100 parts by weight of the soft magnetic particles.
The electromagnetic wave absorbers of Examples 1 to 5 and Reference Example 1 each containing 0.1 part by weight or more show an elongation of 12% or more. On the other hand, the electromagnetic wave absorber of Comparative Example 1, which did not contain the organic silane compound, was broken at an elongation of about 8%.

Generally, when the rigidity of the electromagnetic wave absorber is large,
Since breaking requires a large stress, the breaking resistance is improved. However, even if only the strength is high, the electromagnetic wave absorber becomes hard and brittle, and the degree of freedom against distortion such as bending is reduced. The degree of freedom for this strain can be evaluated by tensile elongation. Therefore, the desirable mechanical strength of the electromagnetic wave absorbing layer is that both the rigidity and the tensile elongation are large. It can be seen that the electromagnetic wave absorbers of Examples 1 to 5 in which the content of the organic silane compound is in the range of 0.1 to 10 parts by weight satisfy this condition. The electromagnetic wave absorber of Reference Example 1 is inferior to these Examples in terms of rigidity.

Examination of the Binder Content Next, the series of samples of Examples 1, 6 and 7 and Reference Examples 2 and 3 show that the content of the binder in the electromagnetic wave absorber, that is, the electromagnetic wave absorbing layer, was reduced by the electromagnetic wave absorption. The effects on the mechanical strength of the body and the electromagnetic wave suppression characteristics were investigated.

FIG. 5 is a graph showing the relationship between the content of the binder and the rigidity of the electromagnetic wave absorber. From this graph, the electromagnetic wave absorbers of Examples 1 and 6 to 7 in which the content of the binder is in the range of 5 to 12 parts by weight based on 100 parts by weight of the soft magnetic particles, and Reference Example 3 of 15 parts by weight All exhibit a rigidity of 1.5 MPa or more. On the other hand, the rigidity of the electromagnetic wave absorber of Reference Example 2 having a content of 3 parts by weight is inferior to these.

FIG. 6 is a graph showing the relationship between the content of the binder and the elongation at break of the electromagnetic wave absorber. From this graph,
Examples 1 and 6 to 7 in which the content of the binder is 5 parts by weight or more and 12 parts by weight with respect to 100 parts by weight of the soft magnetic particles, and 15 parts by weight of the electromagnetic wave absorber of Reference Example 3 Shows an elongation of 12% or more of 1.5 MPa or more. On the other hand, the elongation of the electromagnetic wave absorber of Reference Example 2 having a content of 3 parts by weight was inferior to these and was brittle.

FIG. 7 is a graph showing the binder content and the effect of suppressing electromagnetic waves. 5 parts by weight or more of binder 12
It can be seen that the electromagnetic wave absorbers of Examples 1 and 6 to 7 in the range of parts by weight show an excellent electromagnetic wave suppressing effect at each frequency. On the other hand, the electromagnetic wave absorbers of Comparative Examples 2 and 3 in which the content of the binder is 3 parts by weight and 15 parts by weight do not reach the effect of suppressing the electromagnetic wave absorbers of the examples.

Accordingly, it can be seen that the content range of the binder satisfying both the mechanical strength and the electromagnetic wave suppressing effect of the electromagnetic wave absorber is 5 to 12 parts by weight based on 100 parts by weight of the soft magnetic particles.

Examination of Average Particle Size of Soft Magnetic Particles A series of samples of Example 1, Examples 8 to 11, and Reference Examples 4 to 5 show that the average particle size of soft magnetic particles is
That is, the effect of the electromagnetic wave absorbing layer on the coating strength was examined.

FIG. 8 is a graph showing the relationship between the average particle size of the soft magnetic particles and the rigidity of the electromagnetic wave absorber. Average particle size is 30μ
m and a strong coating film of 1.5 MPa or more can be obtained. 3
If it exceeds 0 μm, it is considered that the filling ratio of the soft magnetic particles in the coating film does not increase, the film structure has many voids, and the coating film is broken by a slight stress.

FIG. 9 is a graph showing the relationship between the average particle size of the soft magnetic particles and the elongation at break of the electromagnetic wave absorber. When the average particle size is 0.02 μm or more, an elongation at break of 12% or more is obtained. On the other hand, the electromagnetic wave absorber of Reference Example 4 having an average particle size of 0.01 μm breaks at an elongation of 10%. this is,
When the average particle size is less than 0.02 μm, although the filling rate of the soft magnetic particles in the coating film tends to increase, the volume change when the coating film is dried is large, and stress concentration to a specific portion of the coating film easily occurs, This is considered to be because cracks easily occur in the dried coating film.

From the results shown in FIGS. 8 and 9, the average particle size of the soft magnetic particles satisfying the mechanical strength of the electromagnetic wave absorber is 0.1.
It is understood that the range of from 02 μm to 30 μm is preferable.

Examination of the Number of Laminated Electromagnetic Wave Absorbing Layers From the measurement results of Example 1 and Examples 12 to 13, the effect of the number of laminated electromagnetic wave absorbing layers on the mechanical strength of the electromagnetic wave absorber was examined.

FIG. 10 shows the result. Even with a single-layer electromagnetic wave absorber, good values are obtained, such as a stiffness of the coating film of 1.5 MPa or more and an elongation to breakage of 12% or more. However, by laminating the electromagnetic wave absorbing layer, these values are further improved, and the mechanical strength is improved. This is presumably because the laminated structure reduces the probability of overlapping of defective portions such as voids in the coating film, and complements each other's strength.

Although the method for producing the electromagnetic wave absorber of the present invention has been described in detail above, these are merely examples, and the present invention is not limited to these examples. That is, it goes without saying that the type of the organic silane compound, the type of the soft magnetic particles and the binder, the layered structure, and the like, or the coating thickness and the coating method can be appropriately changed. As a support, in addition to a film-like or plate-like substrate,
The present invention can also be applied to housings of various electronic devices.

[0073]

As is apparent from the above description, according to the electromagnetic wave absorber and the method for producing the same of the present invention, by adding an organic silane compound to the electromagnetic wave absorbing layer, the rigidity, tensile strength, An electromagnetic wave absorbing layer balanced in all aspects of the electromagnetic wave suppressing effect can be obtained. Therefore, the electromagnetic wave absorbing layer can be put to practical use by itself, with the electromagnetic wave absorbing layer peeled off from the support, and a thin and lightweight electromagnetic wave absorber of about several tens to several hundreds of micrometers or less can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a basic configuration of an electromagnetic wave absorber of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example in which the electromagnetic wave absorber of the present invention is configured as a laminate.

FIG. 3 is a graph showing the relationship between the content of an organic silane compound and the rigidity of an electromagnetic wave absorber.

FIG. 4 is a graph showing the relationship between the content of an organic silane compound and the elongation at break of an electromagnetic wave absorber.

FIG. 5 is a graph showing the relationship between the binder content and the rigidity of the electromagnetic wave absorber.

FIG. 6 is a graph showing the relationship between the content of a binder and the elongation at break of an electromagnetic wave absorber.

FIG. 7 is a graph showing the relationship between the content of a binder and the effect of suppressing electromagnetic waves.

FIG. 8 is a graph showing the relationship between the average particle size of soft magnetic particles and the rigidity of an electromagnetic wave absorber.

FIG. 9 is a graph showing the relationship between the average particle size of soft magnetic particles and the elongation at break of an electromagnetic wave absorber.

FIG. 10 is a graph showing the relationship between the number of laminated electromagnetic wave absorbing layers and rigidity and elongation at break.

[Explanation of symbols]

 1. Support, 2. Electromagnetic wave absorbing layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kietsu Iwabuchi 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Toshiaki Sugawara 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Koji Inomata 6-7-35 Kita Shinagawa, Shinagawa-ku, Tokyo F-term inside Sony Corporation (reference) 4F100 AB09 AB18 AB40 AH06B AK07 AK41 AK51 AL06B AS00B AT00A BA02 BA03 BA04 BA05 BA11 BA11B DE01B EH032 EH46 EH462 EJ003 EJ91 GB48 JD06B JD08 JD08B JD14 JD14B JK01 JK07 JK13 JK17 YY00B 5E321 BB21 BB32 BB51 BB53 GG11

Claims (13)

[Claims] 1. An electromagnetic wave absorber having an electromagnetic wave absorbing layer mainly composed of soft magnetic particles and a binder on a support, wherein the electromagnetic wave absorbing layer further contains an organic silane compound. Absorber. 2. The electromagnetic wave absorber according to claim 1, wherein the organic silane compound is a compound represented by the following general formula (1). X-Si (-Y) (-Z) -V (1) (However, in the above general formula (1), X, Y and Z
Are H, Cl, NH ₂ , R, OR, and OR, respectively.
¹ represents any one of -OR ^2, may be the same or different. V is H, Cl, NH ₂ , SH, N
It represents any one of CO, R, epoxy group and acrylic acid group. R, R ¹ and R ^{2 each} represent any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. And may be the same or different, and furthermore, these R, R ¹ and R ² are Cl, NH ₂ , N
HR ^w , NR ^w ₂ , SH, NCO, epoxy group and acrylic acid group may be added. Here, R ^w represents any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. ) 3. The content of the organic silane compound is 0.1 part by weight or more to 100 parts by weight of the soft magnetic particles.
The electromagnetic wave absorber according to claim 1, wherein the amount is 0 part by weight or less. 4. The electromagnetic wave absorber according to claim 1, wherein the content of the binder is 5 to 12 parts by weight based on 100 parts by weight of the soft magnetic particles. 5. The soft magnetic particles have an average particle size of 0.0
2. The electromagnetic wave absorber according to claim 1, wherein the thickness is 2 μm or more and 30 μm or less. 6. The electromagnetic wave absorber according to claim 1, wherein said electromagnetic wave absorber has a structure in which a plurality of said electromagnetic wave absorbing layers are laminated. 7. A method for producing an electromagnetic wave absorber, comprising a step of applying a coating mainly composed of soft magnetic particles and a binder on a support and drying the same to form an electromagnetic wave absorbing layer. Is a method for producing an electromagnetic wave absorber, further comprising an organic silane compound. 8. The method according to claim 7, wherein the organic silane compound is a compound represented by the following general formula (1). X-Si (-Y) (-Z) -V (1) (However, in the above general formula (1), X, Y and Z
Are H, Cl, NH ₂ , R, OR, and OR, respectively.
¹ represents any one of -OR ^2, may be the same or different. V is H, Cl, NH ₂ , SH, N
It represents any one of CO, R, epoxy group and acrylic acid group. R, R ¹ and R ^{2 each} represent any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. And may be the same or different, and furthermore, these R, R ¹ and R ² are Cl, NH ₂ , N
HR ^w , NR ^w ₂ , SH, NCO, epoxy group and acrylic acid group may be added. Here, R ^w represents any one of a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, an alicyclic saturated hydrocarbon group and an alicyclic unsaturated hydrocarbon group. ) 9. The content of the organic silane compound is 0.1 part by weight or more to 100 parts by weight of the soft magnetic particles.
The method for producing an electromagnetic wave absorber according to claim 7, wherein the amount is 0 part by weight or less. 10. The method for producing an electromagnetic wave absorber according to claim 7, wherein the content of the binder is 5 to 12 parts by weight based on 100 parts by weight of the soft magnetic particles. . 11. The soft magnetic particles have an average particle diameter of 0.1.
The method for producing an electromagnetic wave absorber according to claim 7, wherein the thickness is from 02 µm to 30 µm. 12. The method of manufacturing an electromagnetic wave absorber according to claim 7, further comprising a step of laminating a plurality of said electromagnetic wave absorbing layers. 13. The method for producing an electromagnetic wave absorber according to claim 7, further comprising a step of peeling off the electromagnetic wave absorbing layer from the support and laminating a plurality of obtained electromagnetic wave absorbing layers.