JP2002241679A - Electromagnetic wave absorbing coating material, electromagnetic wave absorbing material and method for applying the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave absorbing coating material having improved durability while keeping the electromagnetic wave absorbing performance especially in GHz region, an electromagnetic wave reflecting coating material, an electromagnetic wave absorbing material and a method for the application of the materials. SOLUTION: The electromagnetic wave absorbing material is composed of an electrically conductive coating object 1 and an electromagnetic wave absorbing coating film 2 formed on the coating object and produced by dispersing iron carbonyl powder in a modified polyester resin consisting of a copolymer of isobutyl methacrylate and butyl acrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint which is applied to a surface of a building or a structure or a case of an electronic device to prevent unnecessary reflected electromagnetic waves of electromagnetic waves.

[0002]

2. Description of the Related Art There is a problem that electromagnetic waves are reflected on buildings or structures, and the reflected electromagnetic waves interfere with equipment utilizing electromagnetic waves. As a countermeasure, an electromagnetic wave absorbing panel or an electromagnetic wave absorbing sheet as an electromagnetic wave absorber is attached to the surface of a building or a structure. Further, there is a concern that an electronic device emits an electromagnetic wave, which may cause other electronic devices to malfunction or adversely affect human health. As a countermeasure, an electromagnetic wave absorbing panel or an electromagnetic wave absorbing sheet is attached to the back surface (electronic device side) of the case of the electronic device. The electromagnetic wave absorbing panel or sheet is composed of an outer absorbing layer and an inner reflecting layer. The absorbing layer contains a magnetic loss material such as a ferrite powder, and the incident electromagnetic wave is absorbed as a magnetic loss. The reflection layer is made of a material that reflects electromagnetic waves, such as iron and aluminum, and has a low sheet resistance, so that the incident electromagnetic waves generate eddy currents and are reflected. With such a configuration, electromagnetic waves incident on the building or structure are absorbed by the absorber layer,
Alternatively, the light is reflected by the reflection layer in the opposite phase to the incident electromagnetic wave, cancels the incident electromagnetic wave, and suppresses the reflection from the building or the structure. As the performance of the electromagnetic wave absorbing panel or the electromagnetic wave absorbing sheet, assuming that Ho is the intensity of the reflected electromagnetic wave and Hi is the intensity of the incident electromagnetic wave, the reflection loss (dB) = − 20 · log (Ho / H
The reflection loss obtained from the equation (i) is generally required to be 20 dB or more. Electromagnetic wave absorbing panels or sheets may be plate-shaped or sheet-shaped, but these plate-shaped or sheet-shaped electromagnetic wave absorbing panels or sheets may be attached to curved or irregularly shaped surfaces. Have difficulty. Therefore, an electromagnetic wave absorbing material is applied by applying an electromagnetic wave absorbing paint to the irregularly shaped surface.

[0003]

The performance required of the conventional electromagnetic wave absorber is mainly the absorption of the electromagnetic wave in the MHz range. For example, the ferrite powder is contained in a resin, and the electromagnetic wave is applied to the ferrite powder. Electromagnetic wave absorbers to be absorbed have been used. However, in recent years, since the frequency used for electronic devices has been increasing, the frequency of harmonic electromagnetic waves generated from electronic devices has been in the GHz range, and conventional electromagnetic wave absorbers that absorb ferrite powder with electromagnetic waves have been used. There is a problem that sufficient electromagnetic wave absorption performance cannot be obtained. JP-A-10-7867 discloses an example of an electromagnetic wave absorbing paint which solves such a problem and provides a sufficient electromagnetic wave absorbing performance even in a GHz region. An electromagnetic wave-absorbing resin composition (that is, an electromagnetic wave-absorbing paint) containing the above dielectric loss material is described. The electromagnetic wave absorbing paint exhibits intended electromagnetic wave absorbing characteristics at an input impedance set so as to be adapted by directly applying the electromagnetic wave reflecting paint to a material such as a metal which reflects electromagnetic waves. However, if an anticorrosive paint such as paint is applied to the surface of a material that reflects electromagnetic waves such as metal, the anticorrosive paint layer functions as a dielectric and is set to be compatible with direct application to metal. The electromagnetic wave absorbing paint having the specified input impedance cannot exhibit the expected electromagnetic wave absorbing characteristics. For this reason, there has been a problem that the thickness of the anticorrosion paint layer must be measured for each surface to be applied and an electromagnetic wave absorbing paint having an input impedance suitable for the thickness must be prepared.

[0004] Japanese Patent Publication No. 2612592 describes a method of applying an electromagnetic wave absorbing paint to solve such a problem. This method involves applying an electromagnetic wave reflecting paint made of a synthetic resin containing a dielectric loss material onto an anticorrosion coating applied to the surface of a building or structure, and then applying an electromagnetic wave absorbing paint containing ferrite powder. It is. According to this method, even if the anticorrosive paint is applied to the surface of the building or structure, or even if the surface of the building or structure is a nonmetal such as concrete or plastic,
Since the electromagnetic wave reflecting paint reflects the electromagnetic wave, the electromagnetic wave absorbing paint applied to the surface thereof can exhibit the desired electromagnetic wave absorbing characteristics. However, in this method, the durability of the electromagnetic wave reflecting paint or the electromagnetic wave absorbing paint cannot be said to be sufficient, and there has been a problem particularly in outdoor use where the environment is severe.
Accordingly, an object of the present invention is to provide an electromagnetic wave absorbing paint, an electromagnetic wave absorber, and a method for applying the same, which have improved durability while maintaining electromagnetic wave absorbing performance particularly in the GHz range.

[0005]

According to a first aspect of the present invention, there is provided an electromagnetic wave in which a solvent contains at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and carbonyl iron powder. Absorbent paint.

[0006] The second invention of the present application is to provide an electromagnetic wave absorbing coating in which carbonyl iron powder is dispersed in a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate on a conductive object to be coated. An electromagnetic wave absorber characterized by the following. Here, the conductive object to be coated is an object to be coated having at least the surface on which the electromagnetic wave absorbing coating film is formed having conductivity, and the characteristics of the material inside the object are not limited. In order to make the surface of the object to be conductive, the object to be coated itself is formed of a conductive material, or a conductive film is formed by painting or plating.

[0007] A third invention of the present application is to provide an electromagnetic wave reflection coating film in which a conductive substance is dispersed in a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate on an insulating object to be coated. An electromagnetic wave absorber comprising an electromagnetic wave absorbing coating in which carbonyl iron powder is dispersed in a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate on the electromagnetic wave reflecting coating. Here, the insulative object to be coated is an object to be coated having at least a surface on which the above-mentioned electromagnetic wave reflection coating film is formed having insulating properties, and the characteristics of the material inside the object are not limited. In order to make the surface of the object to be insulated, the object to be coated itself is formed of an insulating material, or an insulating film is formed by painting or plating.

In a fourth aspect of the present invention, an electromagnetic wave absorbing coating comprising a solvent and at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate and carbonyl iron powder is coated with a conductive coating. An application method of an electromagnetic wave absorber characterized by being applied to the surface of a painted object.

The fifth invention of the present application is directed to an electromagnetic wave reflecting coating in which a solvent contains at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and a conductive substance. An electromagnetic wave reflecting coating is formed by applying the coating on the surface of a coated object, and then a solvent contains at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and carbonyl iron powder. An electromagnetic wave absorber is applied by applying an absorbing paint on the surface of the electromagnetic wave reflecting coating to form an electromagnetic wave absorbing coating.

In the present invention, for example, isopropyl alcohol, kerosene or acetone is used as the solvent.

In the present invention, since the modified polyester resin is dissolved in a solvent, isobutyl methacrylate (isobutyl-methacrylat) in the copolymer of the modified polyester resin is used.
The composition ratio of e) and butyl acrylate is preferably from 1/1 to 3/1 in terms of the weight ratio of solids. When this ratio exceeds 3/1, the degree of polymerization of the resulting modified polyester resin becomes excessively large, so that it becomes difficult to dissolve in a solvent, which is not preferable. On the other hand, if the ratio is less than 1/1 (it is easy to dissolve in a solvent), the degree of polymerization is too small, and it is not possible to obtain the characteristics specific to the modified polyester resin described below. This modified polyester resin has a molecular weight of 1,000,000 or more and is 100% of a general polymer.
The molecular structure is not linear, it is a long-chain type, and it is in a three-dimensional entangled state like a rubber ball. When solidified, it has a three-dimensional graft-type structure with stereoregularity, and it is a tough and stable coating. It becomes a film. Further, this modified polyester resin is rich in rheological performance and has fluidity, and takes in magnetic powder such as iron powder into a ladder-like high-performance structure to protect it from oxidation and deterioration. Further, this modified polyester resin is used in other ABS.
Compared with resin and polyethylene resin, the addition of magnetic powder such as iron powder has extremely small "elongation reduction" and is excellent in flexibility, and it has excellent adhesiveness to not only metal surfaces but also concrete and mortar surfaces Is good. This is because this modified polyester resin has a carboxyl group (C
This is because Ca, which is a main component of concrete or mortar, and H of the carboxyl group react with each other to form a strong chemical bond.

The carbonyl iron powder used in the present invention is obtained by thermally decomposing carbonyl iron, which is an organic intermetallic compound, and has a substantially spherical shape and an average particle diameter of 6 μm or less. It is also preferably used in the method, has good dispersibility in the modified polyester resin, and is preferably used in the case where the modified polyester resin is mixed at a high concentration.

The thickness of the applied electromagnetic wave absorbing paint after drying is determined by the frequency (ie, wavelength) of the electromagnetic wave to be treated.
In order to make the incident electromagnetic wave reflected by the reflection layer in the opposite phase to the incident electromagnetic wave and cancel out the incident electromagnetic wave in the electromagnetic wave absorbing paint, a film thickness of λg / 4 (λg
Is the wavelength of the electromagnetic wave in the electromagnetic wave absorbing paint), and the variation in the film thickness must be as small as possible. The thickness of the applied electromagnetic wave absorbing paint after drying is t
mm, the variation is t ± 0.3 m in the present invention.
m, preferably t ± 0.2 mm, and more preferably t ± 0.1 mm.

The electromagnetic wave absorbing coating composition of the present invention, in which the solvent contains at least the modified polyester resin and carbonyl iron powder, absorbs electromagnetic waves due to the magnetic loss of the carbonyl iron powder, and has an electric conductivity to the carbonyl iron powder. Therefore, there is also an effect of absorbing electromagnetic waves as resistance loss. In addition, the modified polyester resin constituting the electromagnetic wave absorbing paint 2 is a huge lump of carbon atoms when viewed at the electronic level forming the source of the electromagnetic wave, and the innumerable carbon atoms prevent the reflection of the electromagnetic wave and prevent the electromagnetic wave. It functions as a resistor that converts it into heat energy and absorbs it. Due to the functions of the carbonyl iron powder and the modified polyester resin, the electromagnetic wave absorbing paint of the present invention exhibits excellent electromagnetic wave absorption.

The thickness of the electromagnetic wave reflection paint is preferably thicker in terms of electromagnetic wave reflection performance, but is preferably thinner in terms of construction. In the present invention, in consideration of both of them, the film thickness after drying of the electromagnetic wave reflection paint applied to the flat surface to be coated is 15 to 5 minutes.
0 μm, preferably 20 to 40 μm, and more preferably 25 to 35 μm.

[0016]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a first embodiment of the present invention, in which an electromagnetic wave absorbing paint 2 is applied to a surface of a conductive object 1 to be coated. The work 1 is often made of a metal such as an iron plate, for example, but need not be a metal, and may be any conductive material. The electromagnetic wave absorbing paint 2
A modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate is dissolved in a solvent to form a liquid composition. Then, a carbonyl iron powder and a dispersant are mixed with the modified polyester resin to prepare the electromagnetic wave absorbing coating material 2. When the carbonyl iron powder is mixed with the liquid modified polyester resin, the carbonyl iron powder precipitates because of its large specific gravity. However, the carbonyl iron powder can be uniformly mixed without being precipitated by mixing the dispersant. Further, by adding an antioxidant to this modified polyester resin, it is possible to prevent oxidation when the modified polyester resin is dissolved in a solvent or when the obtained electromagnetic wave absorbing paint 2 is stored and used.

FIG. 2 is a cross-sectional view showing the configuration of the second embodiment of the present invention. An electromagnetic wave reflecting paint 3 is applied to the surface of an insulating object 1 to be coated. The electromagnetic wave absorbing paint 2 is applied to the surface of the electromagnetic wave reflecting paint 3. The workpiece 1 is
For example, concrete and wood are often used, but other materials may be used as long as they are insulating. Further, a coated (not conductive) conductive object (for example, a metal such as an iron plate) may be used. The electromagnetic wave reflection paint 3 is obtained by mixing a copper powder and a dispersant with a liquid composition comprising the same modified polyester resin and a solvent as the electromagnetic wave absorption paint 2 of the first embodiment. When the copper powder is mixed with the liquid composition of the modified polyester resin, the copper powder has a large specific gravity and precipitates. However, by mixing the dispersant, the copper powder does not precipitate and the copper powder can be uniformly mixed. Also, as in the first embodiment,
It is preferable to add an antioxidant. The electromagnetic wave absorbing paint 2 is the same as in the first embodiment.

(Example) Next, an example of the present invention will be described. Hereinafter, parts by weight are values on a solid after drying,
The indication is based on 100 parts by weight of the modified polyester resin. (However, Comparative Example 2 is excluded)

(Example 1-1-1) An example of the electromagnetic wave absorbing paint, the electromagnetic wave absorber, and the method of applying the same shown in FIG. 1 will be described. A steel plate having a thickness of 2.3 mm, a vertical dimension of 400 mm and a horizontal dimension of 300 mm was used as the object 1 to be coated. The electromagnetic wave absorbing paint 2 was prepared as follows. First, a modified polyester resin consisting of a copolymer of isobutyl methacrylate and n-butyl acrylate in which the composition ratio of isobutyl methacrylate and n-butyl acrylate is 2/1 by weight is added to a solid material in kerosene as a solvent. The liquid composition was dissolved by 30 wt% in conversion. Next, 300 parts by weight of carbonyl iron powder of grade ES manufactured by BASF was mixed with this liquid composition, and a known dispersant (for example, oleic acid or phosphate ester) was added. When the carbonyl iron powder is mixed with the liquid composition of the modified polyester resin, the carbonyl iron powder precipitates because the specific gravity of the carbonyl iron powder is large. did it. This BASF
The carbonyl iron powder of Grade ES manufactured by the company has an average particle size of 3.
0 to 4.5 μm, the mass% component is Fe> 97.7,
C <1.1, N <1.1, O <0.4, and 30 to 1
A high Q value is obtained at 00 MHz. Then, an antioxidant Ainol (manufactured by Shell Corp .:
(Trade name) was added to be 0.5 parts by weight. In addition, the order of such mixing (mixing) is not limited to the above, and may be an optimal order in consideration of functions, workability, and the like. The thus-prepared electromagnetic wave absorbing coating material 2 is applied to the surface of the object 1 by applying a roller 7 times, and after drying, the film thickness becomes 2
mm. Note that the number of times of application is not limited to seven, and may be applied by means other than a roller. FIG. 3 shows the electromagnetic wave absorbing paint 2 after the overcoating and drying.
2 shows a cross section of the outermost layer and the innermost layer. As described above, this modified polyester resin has a three-dimensional structure, is a long-chain type rubber-like shape, so that the carbonyl iron powder is wrapped in the modified polyester resin so that the carbonyl iron powder is exposed on the surface of each coating layer. The surface of each coating layer (that is, the modified polyester resin portion without carbonyl iron powder)
Functions as a protective insulating layer. In addition, since the carbonyl iron powder is not exposed on the surface of the outermost layer, insulation and corrosion resistance are excellent. FIG. 4 shows the electromagnetic wave absorber thus obtained.
5 is a graph showing a relationship between return loss and frequency. From the figure, it can be seen that the magnetic loss has a maximum value of 34 dB at 7.2 GHz.

Example 1-1-2 Example 1-1-2 was the same as Example 1-1-1 except that the carbonyl iron powder of Example 1-1-1 was changed to grade EN manufactured by BASF. Is the same.
The carbonyl iron powder of grade EN manufactured by BASF has an average particle diameter of 4.0 to 5.2 μm, and the mass% components are Fe> 97.5, C <0.9, N <0.9, O < 0.
4. FIG. 5 is a graph showing the relationship between the reflection loss and the frequency of the electromagnetic wave absorber obtained in this manner. From the figure, it can be seen that the magnetic loss has a maximum value of 39 dB at 7.8 GHz.

Example 1-2-1 Example 1-2-1 was the same as Example 1-1-1 except that the amount of carbonyl iron powder in Example 1-1-1 was changed to 200 parts by weight. It is. FIG. 6 is a graph showing the relationship between the reflection loss and the frequency of the electromagnetic wave absorber thus obtained. From the figure, it can be seen that the magnetic loss has a maximum value of 27 dB at 9.8 GHz.

(Example 1-2-2) Example 1-2-2 is the same as Example 1-1-2 except that the amount of carbonyl iron powder was changed to 200 parts by weight. Same as 1-1. FIG. 7 shows the electromagnetic wave absorber thus obtained.
5 is a graph showing the relationship between return loss and frequency. From the figure 1
It can be seen that the magnetic loss has a maximum value of 22 dB at 1 GHz.

(Example 2-1) An example of the electromagnetic wave reflecting paint, the electromagnetic wave absorbing paint, the electromagnetic wave absorber and the method of construction thereof shown in FIG. 2 will be described. The work 1 has a thickness of 40
A concrete plate having a vertical dimension of 400 mm and a horizontal dimension of 300 mm in mm was used. The electromagnetic wave reflection paint 3 was prepared as follows. First, a modified polyester resin comprising a copolymer of isobutyl methacrylate and n-butyl acrylate in which the composition ratio of isobutyl methacrylate and n-butyl acrylate is 2/1 by weight is added to a solid material in kerosene as a solvent. The liquid composition was dissolved by 30 wt% in conversion. Next, 250 parts by weight of copper powder was mixed with the liquid composition, and a known dispersant (for example, oleic acid or phosphate ester) was added. When the copper powder was mixed with the liquid composition of the modified polyester resin, the copper powder was precipitated because of its large specific gravity. However, by adding the dispersant, the copper powder was not precipitated, and the copper powder could be uniformly mixed. Then, to the composition thus obtained, 0.5 parts by weight of an antioxidant Ainol (trade name, manufactured by Shell Co.) was added. Note that the order of such mixing (mixing) is not limited to the above, and may be an optimal order in consideration of functions, workability, and the like. The electromagnetic wave reflecting paint 3 prepared in this manner was applied to the surface of the work 1 using an airless coater, and was applied so that the film thickness after drying was 30 μm. The application means is not particularly limited as long as air is not mixed into the coating film and the film thickness can be made uniform. It is not preferable that air enters the coating film because it also affects the characteristics of the film. Blowing with an airless coating machine is preferable because air can be prevented from entering the coating film, so that the coating film has a smooth surface. Then, the same electromagnetic wave absorbing coating material 2 as in Example 1-1-1 was applied to the surface of this electromagnetic wave reflecting coating material 3 by the same construction method as in Example 1-1-1.
The coating was performed so as to have the same film thickness after drying as -1. The relationship between the reflection loss and the frequency of the thus obtained electromagnetic wave absorber was measured, and the result was the same as that of Example 1-1-1.

(Embodiment 2-2) The embodiment 2-2 is the same as the embodiment 2
1 coated object 1 is a paint Epotal N manufactured by Kansai Paint Co., Ltd.
o.600 (trade name) (anticorrosion paint) has a film thickness of 270-3 after drying
This is a steel plate coated to a thickness of 40 μm and having a thickness of 2.3 mm, a vertical dimension of 400 mm and a horizontal dimension of 300 mm, and is otherwise the same as Example 2-1. The relationship between the reflection loss and the frequency of the thus obtained electromagnetic wave absorber was measured, and the result was the same as that of Example 1-1-1.

(Example 2-3) Coating object 1 of Example 2-1
And the film thickness and the like of the electromagnetic wave reflecting paint 3 were changed as follows, and the other conditions were the same as in Example 2-1. The work 1 is 80 mm thick, 400 mm long and 300 mm wide.
The surface of the object to be coated was formed in a sawtooth shape as shown in FIG. In FIG. 8, the d dimension is the depth dimension from the serrated peak 1a to the serrated valley bottom 1b, and the w dimension is the width dimension of the serrated peak 1a. In this embodiment, w = 1.0 to 1.0. 1.3 mm, d = 1.2 to 1.5
mm. The electromagnetic wave reflecting paint 3 is the same as that of Example 2-1 and is applied with a brush, a roller or an airless gun, and after drying, the film thickness (the film thickness measured from the intermediate position between the top 1a and the bottom 1b in FIG. 8) is 2 0.6 mm. As described above, since the modified polyester resin of the electromagnetic wave reflection paint 3 has a large molecular weight of 1,000,000 or more, even if the surface to be coated has a saw-tooth-shaped uneven surface as described above, Has good leveling properties. Also in the present embodiment, the surface after applying and drying the electromagnetic wave reflecting paint 3 becomes substantially smooth, irregular reflection of the electromagnetic wave is prevented, and the electromagnetic wave absorbing performance of the electromagnetic wave absorber after applying the electromagnetic wave absorbing paint 2 can be maintained. When the relationship between the reflection loss and the frequency of the electromagnetic wave absorber obtained in this way was measured, the result was the same as that of Example 1-1-1.

The modified polyester resin of the electromagnetic wave reflecting paint and the electromagnetic wave absorbing paint thus obtained is
As described above, it is excellent in flexibility, has good adhesion to metal and concrete surfaces, forms a tough and stable coating film, and does not expose carbonyl iron powder to the surface of the outermost layer. Therefore, even when an outdoor exposure test (one year in the seaside area) was performed, any of the electromagnetic wave absorbers in the above Examples did not have any abnormality such as pinholes or peeling of the paint, and the durability was good.

(Comparative Example 1-1) A comparative example of the electromagnetic wave absorbing paint, the electromagnetic wave absorber and the method of applying the same shown in FIG. 1 will be described. Comparative Example 1-1 is the same as Example 1-1-1 except that the electromagnetic wave absorbing coating material 2 of Example 1-1-1 was changed as follows. The electromagnetic wave absorbing paint 2
In the electromagnetic wave absorbing paint 2 of Example 1-1-1, instead of carbonyl iron powder, a Ni—Zn ferrite powder having an average particle diameter of 20 to 30 μm and an initial magnetic permeability μ _i = 800 (T-314 manufactured by Hitachi Metals) And the amount of the Ni—Zn-based ferrite powder was 300 parts by weight.
The coating was the same as the electromagnetic wave absorbing coating material 1-1 of Example 1-1, and the thickness after drying was the same as that of Example 1-1-1. The solid line graph in FIG. 9 shows the relationship between the reflection loss and the frequency of the electromagnetic wave absorber thus obtained. As can be seen from this graph, the maximum value of the magnetic loss is 3.8 at 3.8 GHz.
Example 1-1-1 or Example 1-1
Very small compared to 2. Therefore, the same electromagnetic wave absorbing paint 2 as described above was applied so that the film thickness after drying was 6 mm. The broken line graph in FIG. 9 shows the relationship between the reflection loss and the frequency of the electromagnetic wave absorber obtained in this manner. As can be seen from this graph, the maximum value of the magnetic loss is 19 dB at 3.8 GHz, which is larger than the above-mentioned one having a dried film thickness of 2 mm. However, the construction in which the film thickness after drying is 6 mm is problematic in that the amount of paint used and the number of man-hours increase and the cost becomes high, and it is difficult to make the film thickness uniform. Construction on vertical and supine surfaces is extremely difficult (the actual construction surface is more vertical and supine than horizontal) and is not practical.

Comparative Example 1-2 Comparative Example 1-2 is the same as Example 1
2-1 is the same as Example 1-2-1, except that the electromagnetic wave absorbing paint 2 of 2-1 was changed as follows. The electromagnetic wave absorbing paint 2 of the Example 1-2-1 was used.
In place of the carbonyl iron powder of grade EN manufactured by BASF, an initial magnetic permeability μ _i = 2 with an average particle diameter of 2 to 3 μm.
000 Ni-Zn ferrite powder (DL-
2S), the amount of the Ni—Zn-based ferrite powder was 200 parts by weight, and the other conditions were the same as those of the electromagnetic wave absorbing coating material 2 of Example 1-2-1.
It was constructed to be 2 mm, the same as -2-1. The solid line graph in FIG. 10 shows the relationship between the reflection loss and the frequency of the electromagnetic wave absorber obtained in this manner. As can be seen from this graph, the maximum value of the magnetic loss is 4.3 d at 7 GHz.
B, which is extremely small as compared with Example 1-2-1 or Example 1-2-2. Therefore, the same electromagnetic wave absorbing paint 2 as described above was applied so that the film thickness after drying was 6 mm. FIG.
The broken line graph shows the relationship between the return loss and the frequency of the electromagnetic wave absorber obtained in this manner. As can be seen from this graph, the maximum value of the magnetic loss is 2 at 4.3 GHz.
It is 1 dB, which is larger than the above-mentioned one having a thickness of 2 mm after drying. However, as in Comparative Example 1-1, there is a problem of construction and cost, which is not practical.

Comparative Example 2 Comparative Example 2 is the same as Example 1-1-1 except that the electromagnetic wave absorbing coating material 2 of Example 1-1-1 was changed as follows. The parts by weight are solid values. The electromagnetic wave absorbing paint 2 was prepared in Comparative Example 1-1.
In place of the modified polyester resin in the electromagnetic wave absorbing paint 2, a resin consisting of 40 parts by weight of Epicoat 828 (manufactured by Shell Chemical), 10 parts by weight of xylene, and 20 parts by weight of versamide 140 (manufactured by Henkel Hakusui) was used.
A mixture obtained by mixing 300 parts by weight of carbonyl iron powder of grade ES manufactured by BASF with respect to 00 parts by weight and adding a known dispersant (for example, oleic acid or phosphate ester) was used. Then, in the same manner as in Example 1-1-1, the electromagnetic wave absorbing coating material 2 was applied to the surface of the object 1 by a roller, and was applied so that the film thickness after drying was 2 mm. The relationship between the reflection loss and the frequency of the thus obtained electromagnetic wave absorber was measured, and the result was the same as that of Example 1-1-1. However, when an outdoor exposure test was conducted in the beach area, 282
After a day (about 9 months), the electromagnetic wave absorbing paint 2 swelled, and the durability was not good.

As described above, the electromagnetic wave absorber of the embodiment is different from the electromagnetic wave absorbers of Comparative Examples 1-1 and 1-2 in that the electromagnetic loss absorbing paint 2 has a smaller magnetic loss despite the thin film thickness after drying. Large value. In other words, good electromagnetic wave absorption performance can be obtained even when applied thinly. Further, the electromagnetic wave absorber of the example has better durability than the electromagnetic wave absorber of Comparative Example 2.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples. The dimensions or mixing ratios (parts by weight) described in the examples are not limited to these, and may be set to the optimum dimensions or mixing ratios (parts by weight) in consideration of functions, workability, and the like. In the embodiment, the carbonyl iron powder of the electromagnetic wave absorbing coating material 2 is grade ES manufactured by BASF or grade EN manufactured by BASF. However, the present invention is not limited thereto. Good. The dispersants and antioxidants described in the examples are not limited to these, and the most suitable one may be selected in consideration of functions, workability, and the like. Further, in the example, the electromagnetic wave reflection paint 3 was 250 parts by weight of copper powder with respect to 100 parts by weight of the modified polyester resin.
It may be 0 parts by weight, or another conductive substance may be used in place of the copper powder. This conductive substance (including copper) may be in the form of powder, flakes, or fibers.

[0032]

According to the present invention, it is possible to provide an electromagnetic wave absorbing paint, an electromagnetic wave absorber, and a method for applying the same, which have improved durability while maintaining electromagnetic wave absorbing performance particularly in the GHz range.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a second exemplary embodiment of the present invention.

FIG. 3 is a cross-sectional view of an outermost layer of the electromagnetic wave absorbing coating material 2 of Example 1-1-1 and a layer inside the outermost layer.

FIG. 4 is a graph showing the relationship between the return loss and the frequency in Example 1-1-1.

FIG. 5 is a graph showing the relationship between the return loss and the frequency in Example 1-2-2.

FIG. 6 is a graph showing the relationship between the return loss and the frequency in Example 1-2-1.

FIG. 7 is a graph showing the relationship between the return loss and the frequency in Example 1-2-2.

FIG. 8 is a drawing showing a cross section of an object to be coated 1 of Example 2-3.

FIG. 9 is a graph showing the relationship between the return loss and the frequency in Comparative Example 1-1.

FIG. 10 is a graph showing the relationship between the return loss and the frequency in Comparative Example 1-2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Coated object, 1a Serrated peak, 1b Serrated valley, 2 Electromagnetic wave absorbing paint, 3 Electromagnetic reflecting paint

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J038 CG141 CH031 HA066 JC38 MA14 NA19 5E321 AA01 AA41 BB23 BB32 GG11

Claims (5)

[Claims] 1. An electromagnetic-wave-absorbing paint, characterized in that the solvent contains at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and carbonyl iron powder. 2. An electromagnetic wave absorber comprising an electromagnetic wave absorbing coating obtained by dispersing carbonyl iron powder in a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate on a conductive object. body. 3. An insulating object to be coated with an electromagnetic wave reflection coating in which a conductive substance is dispersed in a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, wherein the isobutyl methacrylate and butyl acrylate An electromagnetic wave absorber comprising an electromagnetic wave absorbing coating obtained by dispersing carbonyl iron powder in a modified polyester resin comprising a copolymer of 4. An electro-magnetic wave absorbing coating comprising a solvent and at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and carbonyl iron powder, is applied to the surface of a conductive object to be coated. A method for constructing an electromagnetic wave absorber. 5. An electro-magnetic wave reflecting paint comprising a solvent and at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and a conductive substance, is applied to the surface of the insulative workpiece. To form an electromagnetic wave reflecting coating film, and then, in a solvent, an electromagnetic wave absorbing coating material containing at least a modified polyester resin comprising a copolymer of isobutyl methacrylate and butyl acrylate, and carbonyl iron powder. A method for constructing an electromagnetic wave absorber, characterized in that an electromagnetic wave absorbing film is formed by coating the film on the surface of the film.