JPH09186486A - Electromagnetic-wave absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the transmissivity of light and the absorbing characteristics of electromagnetic waves compatible and to improve the absorbing characteristics for high frequencies by providing the continuous pattern layer of the closed circuit by the thin-film fine line of a magnetic body and a transparent conducting film layer on a transparent organic macromolecular film. SOLUTION: On a transparent organic macromolecular film 11, a continuous pattern 12 of the closed circuit by the thin-film fine line of a magnetic body and a transparent conducting film 13 are provided. A pair of the transparent organic macromolecular films 11 of electromagnetic-wave absorbing bodies are stuck together through the transparent organic macromolecular plate agent having the relative dielectric constant ε: 3.0-8.0, wherein transparent adhesive agent layers are provided on both surfaces. As the transparent organic macromolecular film 11 having the relative dielectric constant ε: 3.0-8.0, for example, polyethylene terephthalate, vinyl chloride and the like can be listed. It is recommendable that the thickness is 0.3-3.0mm. The magnetic body, is for example, FeCo, ferrite and the like. The transparent conducting film 13 is, for example, indium titanate, tin oxide and the like.

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 for absorbing harmful electromagnetic waves emitted from a display device such as a computer.

[0002]

2. Description of the Related Art In recent years, the use of computers has expanded explosively, and the time for staring at display devices has been increasing. Attendant on this, the damage of electromagnetic waves emitted from a computer, especially a display device, has been medically noticed. On the other hand, electromagnetic interference has become a serious problem, such as radiated electromagnetic noise causing damage to wireless communication devices. For such a problem, a combination of a metal mesh and a dielectric plate has been commercialized under the name of VDT filter or the like, particularly as an absorber of a display device. These products show that when the light transmittance is increased (high aperture ratio), the electromagnetic wave absorption characteristics deteriorate, and the frequency is several hundreds.
It is known that when the frequency is higher than MHz, the absorption characteristic is deteriorated and the absorption effect for higher harmonics of the display device is significantly decreased.

[0003]

DISCLOSURE OF THE INVENTION The present invention has two problems of the VDT filter composed of the metal mesh and the dielectric plate as described above, that the light transmittance and the electromagnetic wave absorption characteristic are not compatible with each other. For the purpose of improving the deterioration of absorption characteristics for electromagnetic waves of 100 MHz or more,
The problem is to improve the absorption characteristics especially for high frequencies.

[0004]

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, the present invention relates to an electromagnetic wave absorber comprising a transparent organic polymer film and a continuous pattern layer of a closed circuit formed by thin magnetic thin film lines and a transparent conductive film layer.

Next, the present invention will be described with reference to the drawings. FIG.
Is a cross-sectional view of the electromagnetic wave absorber according to one embodiment of the present invention (along line AB in FIG. 2), and FIG. 2 is a diagram showing an example of a closed circuit pattern of the electromagnetic wave absorber according to one embodiment of the present invention. 1 in the figure
Reference numeral 1 denotes a base film, which is made of a transparent film such as polyethylene terephthalate (PET), saran resin (trade name), and vinyl chloride (PVC), and has a thickness of 60 to 300 μm.
m. Reference numeral 12 denotes a continuous pattern layer of a closed circuit formed by thin magnetic thin film wires. The magnetic material is, for example, Fe.
Co, ferrite, permalloy, etc., which are formed into a thin film, for example, about 0.05 to 2.0 μm, on the surface of the base film by a method such as a sputtering method or a vacuum deposition method.

The method for forming a continuous closed circuit pattern of a magnetic material is not particularly limited. For example, after forming a magnetic material film on a base film, an etching pattern is screen-printed and etched by a wet method to form a pattern. There are methods such as forming. The width of the thin film thin wire is preferably 0.01 to 0.3 mm.

The pattern in the present invention needs to have a structure in which a part of the closed circuit is connected, and it functions as a circuit in which a current induced in the closed circuit by a high frequency electromagnetic wave flows to the ground point. Even if this ground point does not function sufficiently, it is possible to shield the electromagnetic wave by converting the current vibration induced by the vibration of the electric field and the magnetic field of the electromagnetic wave into heat and absorbing it by the impedance of the closed circuit. Become. By specifying the shape and size of this closed circuit pattern, it is possible to selectively absorb electromagnetic waves having a wavelength corresponding to the shape.

Reference numeral 13 denotes a transparent conductive film layer, which is made of ITO (Indiu).
A conductor such as m-Tin Oxide) or tin oxide is formed on the magnetic film in the form of a thin film, for example, about 0.03 to 0.5 μm by a method such as a sputtering method or a vacuum deposition method.

Reference numeral 14 is a protective film for the surface of the transparent conductive film, which is provided as necessary, and may be coated on the surface with a method such as saran resin (trade name), polyethylene, or the like. Its thickness is about 60 to 300 μm. The surface of the protective film has a diameter of 2 in order to enhance the absorption effect.
Approximately 4 mm concave recesses or depth 10-30 μ
You may provide the notch of the V-shaped straight line of m at intervals of 1-3 mm.

In the present invention, an electromagnetic wave absorber can also be obtained by bonding a pair of the transparent organic polymer films described above to each other with a transparent adhesive layer interposed therebetween. The patterns of the electromagnetic wave absorbers to be laminated may be the same or different.

Examples of the material capable of forming such a transparent adhesive layer include (meth) acrylic UV-curable adhesives and epoxy adhesives. These substances are used, for example, in roll coaters. A transparent adhesive layer can be formed by applying the composition to the surface of the adhesive surface by screen printing or screen printing, and then performing ultraviolet curing and / or heat curing.

In the present invention, a pair of transparent organic polymer films having an electromagnetic wave absorber comprising a transparent organic polymer film, a continuous pattern layer of a closed circuit formed by thin magnetic thin film lines, and a transparent conductive film layer. By bonding the two through the transparent organic polymer plate material having a relative dielectric constant ε: 3.0 to 8.0 having transparent adhesive layers provided on both surfaces thereof,
It can also be an electromagnetic wave absorber.

Examples of the transparent organic polymer plate material having a relative dielectric constant ε: 3.0 to 8.0 include polyvinyl chloride, nylon, saran resin and the like, and the thickness thereof is 0.
It is preferably 3 to 3.0 mm.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited to these examples.

Example 1 An electromagnetic wave absorber as shown in FIG. 1 was manufactured. Numeral 11 is a transparent polyethylene terephthalate (PET) film for forming an absorber, having a thickness of 120 μm. On this PET film, 0.2 μm thick FeCo
A magnetic thin film 12 of was formed by a sputtering method. Then, an etching pattern was screen-printed on the magnetic thin film, and wet etching was performed using a hydrochloric acid-based etching solution to form the pattern shown in FIG. The major axis (center diameter) of the pattern is 2.0 mm, and the minor axis (center diameter) is 1.0
mm, and the pattern width was 0.2 mm. The transparent conductor 13 made of ITO is formed on the magnetic thin film pattern.
Thin film of 0.04 μm was formed by the sputtering method.

Further, a Saran resin (trade name) film 14 was laminated on the transparent conductor thin film. The resin surface was provided with a recess having a diameter of 2 mm on the entire surface to prevent reflection.

The characteristics of the electromagnetic wave absorber obtained as described above were measured by the measuring system shown in FIG. In the figure, 21 is a spectrum analyzer, 22 is a tracking generator,
23 is an amplifier, 24 is a near magnetic field probe, 25 is an electromagnetic wave source antenna, 26 is a sealed box to be tested, and 27 is an electromagnetic wave absorber to be measured. FIG. 3 shows the relationship between the frequency (GHz) and the transmission attenuation amount (dB). The transmission attenuation amount is the difference between the signal levels detected by the near magnetic field probe depending on the presence or absence of the electromagnetic wave absorber to be measured. 20d at peak frequency
An absorption effect exceeding B was confirmed.

Example 2 A pair of electromagnetic wave absorbers obtained in Example 1 (same pattern)
Were pasted together via a transparent adhesive layer made of an acrylic ultraviolet curing agent to produce the electromagnetic wave absorber shown in FIG. The bonding surface at this time is a surface on which no pattern is formed as shown in the figure. The results of measuring the characteristics of the electromagnetic wave absorber by the same method as in Example 1 are shown in FIG.

Example 3 One pair of electromagnetic wave absorbers obtained in Example 1 (same pattern)
With a transparent adhesive layer on both sides, the relative dielectric constant ε:
The transparent organic polymer plate material (thickness: 1.2 mm) made of polyvinyl chloride of 4.0 was bonded to each other to manufacture an electromagnetic wave absorber. The results of measuring the characteristics of the electromagnetic wave absorber by the same method as in Example 1 are shown in FIG.

[0020]

The electromagnetic wave absorber of the present invention has a high visible light aperture ratio, and the absorption effect of high frequency electromagnetic waves can select the frequency band by patterning, and can shield the unnecessary electromagnetic wave noise at low cost. Excellent electromagnetic wave absorption V
A DT filter can be provided. And for VDT work that is concerned about the impact on the human body
Supplying the DT filter can eliminate the health concerns for workers engaged in this work, and its industrial value is high.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of an electromagnetic wave absorber according to an embodiment of the present invention.

FIG. 2 is a diagram showing a magnetic pattern of an electromagnetic wave absorber according to an embodiment of the present invention.

FIG. 3 is a diagram showing frequency-transmission attenuation amount characteristics of the electromagnetic wave absorber according to the first embodiment.

FIG. 4 is a diagram showing a cross section of an electromagnetic wave absorber obtained by laminating two electromagnetic wave absorbers of the present invention.

FIG. 5 is a diagram showing frequency-transmission attenuation amount characteristics of an electromagnetic wave absorber in Example 2.

FIG. 6 is a view showing a cross section of an electromagnetic wave absorber obtained by bonding two electromagnetic wave absorbers of the present invention with a transparent polymer plate material having transparent adhesive layers provided on both surfaces thereof.

FIG. 7 is a diagram showing frequency-transmission attenuation amount characteristics of an electromagnetic wave absorber in Example 3.

FIG. 8 is a diagram showing an outline of a measurement system for measuring the absorption characteristics of the electromagnetic wave absorber of the present invention.

[Explanation of symbols]

 11: Transparent Organic Polymer Film 12: Patterned Magnetic Film 13: Transparent Conductor Film 14: Protective Film 15: Adhesive Layer 16: Transparent Polymer Plate 21: Spectrum Analyzer 22: Tracking Generator 23: Amplifier 24 : Near magnetic field probe 25: Electromagnetic wave source antenna 26: Sealed box under test 27: Electromagnetic wave absorber under test

Claims (3)

[Claims] 1. An electromagnetic wave absorber comprising a transparent organic polymer film, a continuous pattern layer of a closed circuit formed by a thin film of a magnetic material, and a transparent conductive film layer. 2. An electromagnetic wave absorber formed by laminating a pair of transparent organic polymer films according to claim 1 through a transparent adhesive layer. 3. A transparent organic polymer having a relative permittivity ε: 3.0 to 8.0 in which a pair of transparent organic polymer films of the electromagnetic wave absorber according to claim 1 are provided with transparent adhesive layers on both sides thereof. An electromagnetic wave absorber that is laminated with a polymer plate material film.