KR100897309B1 - Electromagnetic wave absorptive film and its fabrication - Google Patents

Abstract

The present invention discloses an electromagnetic wave absorbing film that absorbs electromagnetic waves by destructive interference, wherein the film has a single layer and / or double layer wave-absorbing and / or wave reflection embedded therein. a compound layer containing particles, whose thickness is 1/4 n times the wavelength of the electromagnetic wave to be absorbed, and a reflective layer covered on one side of the compound layer and having a higher refractive index than the compound layer ).

Electromagnetic wave absorption film

Description

Electromagnetic wave absorbing film and manufacturing method therefor {ELECTROMAGNETIC WAVE ABSORPTIVE FILM AND ITS FABRICATION}

1 is a simplified diagram showing the correlation between the electromagnetic wave absorbing film and the product to be shielded.

Figure 2 is a simplified diagram showing the reflection and absorption of the bi-layer reflective particles in the composite layer of the electromagnetic wave absorbing film according to the present invention.

3 is a simplified diagram showing single layer wave reflecting particles, double layer wave reflecting particles and single layer wave absorbing particles embedded in a carrier of a composite layer of an electromagnetic wave absorbing film according to the present invention.

4 is a schematic diagram showing single layer wave reflecting particles, double layer wave reflecting particles, single layer wave absorbing particles, and double layer wave absorbing particles embedded in a carrier of the composite layer of the electromagnetic wave absorbing film according to the present invention.

5 is a manufacturing flowchart of the electromagnetic wave absorbing film according to the present invention.

Figure 6 is a simplified diagram showing an electromagnetic wave absorbing film covered on the antenna of the mobile phone according to the present invention.

Figure 7 shows another application example of the present invention.

The present invention relates to an EMI protection material, and more particularly to an electromagnetic wave absorbing film that absorbs electromagnetic waves by destructive interference. Moreover, this invention relates to the manufacturing method of such an electromagnetic wave absorption film.

With the rapid development of advanced technologies, a variety of computer and digital communication devices and consumer electronics have been announced and introduced to the market. There is a trend in the market to manufacture electronic products at a relatively higher frequency. As a result, consumers have a high chance of exposing their bodies to the harmful effects of electromagnetic waves, which can result in high risk of leukemia, brain tumors, DNA destructive disease and other diseases. Studies show that electromagnetic waves above 60 Hz are harmful to DNA in human cells. Some other foreign research mentions the effects of cell phones on the human brain, such as temporary memory loss and poor behavior. As the bad effects of electromagnetic waves continue to be discovered, the discovery of electromagnetic shielding materials has become an important research topic in different fields.

Regular electromagnetic wave shielding materials include electric field shielding materials and magnetic field shielding materials. In addition, there is an electromagnetic interference (EMI) protective material made from a mixture of metal fibers and other natural and synthetic fibers. Organic composite materials are coated on various materials, such as metals, plastics, magnesium alloys, titanium alloys, aluminum alloys, wood, ceramics, to change their surface properties, which achieves EMI protection.

 However, conventional EMI protection materials generally have certain thicknesses that limit their coverage. Nowadays, there is a tendency to develop cellular telephones and other electronic products with light, thin, short and small features. When conventional EMI protection materials are used in small mobile electronics, electromagnetic waves are still leaking.

Therefore, it is desirable to provide an electromagnetic wave absorbing film which eliminates the above-mentioned problems.

The present invention has been accomplished under these circumstances. One object of the present invention is to provide an electromagnetic wave absorbing film using the electromagnetic wave characteristics of the phase offset (phase offset) to cancel and absorb the electromagnetic wave in the structure of the electromagnetic wave absorbing film and a method of manufacturing the same.

It is still another object of the present invention to provide an electromagnetic wave absorbing film having a practical thin thickness for use in any of a variety of products for effectively absorbing electromagnetic waves and a method of manufacturing the same.

It is still another object of the present invention to provide an electromagnetic wave absorbing film and a method of manufacturing the same, which eliminates the installation of ground without causing electrical connection.

In order to achieve these and other objects of the present invention, an electromagnetic wave absorbing film has particles embedded therein, the composite layer having a thickness of 1 / 4n times the wavelength of the electromagnetic wave to be absorbed, and on one side of the composite layer. It includes a reflective layer that is covered by and has a refractive index greater than that of the composite layer. In addition, the method for producing an electromagnetic wave absorbing film includes the steps of (1) preparing a molten polymer; (2) mixing the particles into the molten polymer; (3) shaping the mixture of molten polymer and particles to form a composite layer whose thickness is 1 / 4n of the wavelength of the electromagnetic wave to be absorbed; And (4) forming a reflective layer on one side of the composite layer having a refractive index greater than that of the composite layer.

The electromagnetic wave absorbing film according to the present invention absorbs electromagnetic waves by using destructive interference. The so-called destructive interference causes two reversed wave trains of some wavelengths to meet each other so that the peaks of one burst can overlap each other on the wave troughs of another burst. This neutralizes the two tears.

1 is a simplified diagram showing the correlation between the electromagnetic wave absorbing film and the product to be shielded. As illustrated, the electromagnetic wave absorbing film includes a composite layer 1 and a reflective layer 2 covered on one side, that is, on the top side, of the composite layer 1. The composite layer 1 comprises a carrier 12 and particles 14 embedded in the carrier 12. The carrier 12 is made from a polymeric material. The thickness of the composite layer 1 is 1/4 n times the wavelength of the electromagnetic wave to be absorbed, i.e., the requirement for destructive interference, so that the reflected wave travel course is 1 / 2n times the wavelength when the incident wave is reflected by the obstacle. (Where n is a natural number). If the difference between the forward travel course and the reflective travel course is 1 / 2n of the wavelength, then the peak of the reflected burst overlaps the fracture of the forward burst so that the tear can be neutralized.

The particles 14 may be reflective particles, including single layer reflective particles 16 and double layer reflective particles 18. Bilayer reflective particles 18 include an inner layer 182 of wave absorbing material and an outer layer 184 of wave reflecting material as shown in FIG. 2. The inner layer 182 of the wave absorbing material may be obtained from silicon carbide, porphyries, andesite, infrared ceramics, tourmaline, and the like. The outer layer 184 of wave reflecting material may be metal. When incident electromagnetic waves encounter the double layer reflective particles 18, a portion of the relatively lower energy incident electromagnetic waves is reflected toward the second double layer reflective particles 18 by the outer layer 184 of the wave reflective material and is relatively more A portion of the low energy reflected electromagnetic waves is reflected towards the third double layer reflective particles 18 by the outer layer 184 of the wave reflecting material of the second double layer reflective particles 18, which is repeated over and over. Or similarly to the bulkhead, it is possible to neutralize the reflected electromagnetic waves. The other portion of the relatively stronger energy incident electromagnetic wave is absorbed by the inner layer 182 of the wave absorbing material of the first double layer reflective particles 18 and then passes through the first double layer reflective particles 18 that are encountered. The portion of the electromagnetic wave is greatly weakened in energy and reflected by the outer layer 184 of the wave reflecting material of another double layer reflective particle 18. Through repeated reflection and absorption, the incident electromagnetic waves are neutralized in the near future.

The aforementioned particles 14 include wave absorbing particles 21 formed of the wave absorbing material held by the composite layer 1 as shown in FIG. 3. The composite layer 1 holds the wave absorbing particles 21, the single layer reflective particles 16, and the double layer reflective particles 18 embedded in the carrier 14 to form a honeycomb structure. This design eliminates the possibility of electrical connection of the single layer reflective particles 16 due to the high installed density of the single layer reflective particles 16.

Referring to FIG. 4, the wave absorbing particles 21 of the present invention may be the double layer wave absorbing particles 22. This bilayer wave absorbing particle 22 comprises an inner layer 222 of a wave reflecting material obtained from a metal, for example, and an outer layer of a wave absorbing material obtained from, for example, silicon carbide, rock, andesite, infrared ceramic or tourmaline. do. When the electromagnetic wave meets one double layer wave absorbing particle 22, the outer layer 224 of the wave absorbing material of the double layer wave absorbing particle 22 absorbs the energy of the incident electromagnetic wave, and one double layer wave absorbing particle 22. The inner layer 222 of the wave reflecting material reflects the reduced incident electromagnetic wave, in which residual energy of the reflected electromagnetic wave is absorbed again by the outer layer 224 of the wave absorbing material of the double layer wave absorbing particle 22. To help.

The various different particles can be used independently and mixed in the polymer carrier of the composite layer to meet different requirements.

The above-mentioned reflective layer 2 is provided on the top face of the composite layer 1 in order to reflect the electromagnetic wave passing through the composite layer 1 onto the composite layer 1. Therefore, the material of the reflective layer 2 is selected according to the structure of the carrier 12 of the composite layer 1, so that the refractive index n 1 of the reflective layer 2 can be larger than the refractive index n 2 of the carrier 12. This design allows the electromagnetic waves to move from denser media to denser media in order to greatly increase the chance of reflecting electromagnetic waves back to the composite layer 1 under the Brewsten angle. Generally, alloys are used to form the reflective layer 2. The alloy is formed of aluminum, nickel, iron, cobalt and copper. In addition, small amounts of manganese may be added to the alloy. Alternatively, the reflective layer 2 may comprise a plurality of metal layers, including aluminum layers, nickel layers, iron layers, copper layers and cobalt layers, which may be stacked together.

A method of manufacturing the electromagnetic wave absorbing film will be described below with reference to FIGS. 5 and 1 again. This manufacturing procedure

S1: preparing a molten polymer for a given carrier,

S2: mixing particles into the molten polymer, wherein the particles are monolayer reflective particles 16, bilayer reflective particles 18, monolayer wave absorbing particles 21, bilayer wave absorbing particles 22 and / or May be a combination thereof,

S3: shaping the mixture of molten polymer to form a predetermined composite layer 1 according to the predetermined thickness through the extrusion process, and

S4: forming the reflective layer 2 by vacuum sputtering or electroplating on one side of the composite layer 1 thus obtained, i.e., the top surface.

It includes.

In addition, a further step, S5, can be used to coat the glue layer 24 on the other side of the composite layer 1, ie the bottom side. Alternatively, the glue layer 24 may be covered on one side of the reflective layer 2 facing the composite layer 1 for bonding. Before coating the glue layer 24 on the reflecting layer 2, the electrical insulating layer 26 is formed on the reflecting layer 2 such that the bonding of the glue layer 24 prevents electrical connection as shown in FIG. 1. It must be covered.

6 is an application diagram of the present invention showing an electromagnetic wave absorbing film covered on an antenna of a cellular phone. Since cellular phones transmit signals to the base station by radio via an antenna, the antenna is a site where electromagnetic waves are generated. As shown in Fig. 6, the electromagnetic wave absorbing film denoted by the reference numeral 5 covers the antenna 3 and the fastener 4 fixing the antenna 3 to the case of the cellular phone, and at the same time occurs in the cellular phone. It leaves the transverse width "a" unshielded so that the electromagnetic waves can pass through it. This width "a" is a multiple that is divisible by the wavelength of the electromagnetic wave generated in the cellular phone. In addition, this width "a" extends in a direction away from the side to which the user's body can contact.

Figure 7 shows another application example of the present invention. According to this application example, the electromagnetic wave absorbing film 5 is coupled to the inner wall of the mobile phone case 7.

In addition, the electromagnetic wave absorbing film 5 may be formed directly on the surface of the component part of the cellular phone case in order to absorb the electromagnetic wave. In this case, the reflective layer is first formed on the inner wall of the component part, and then the composite layer is coated on the reflective layer. Those skilled in the art will readily be able to accomplish this modified method.

As indicated above, the present invention provides an electromagnetic wave absorbing film that neutralizes electromagnetic waves using wave phase offset characteristics, wave reflections, and wave absorption, which is a conventional method of shielding electromagnetic waves using a metal shield directly. Eliminates complex grounding arrangements as used in the method. Based on the phase offset, even one composite layer is sufficient to eliminate the electromagnetic waves. Therefore, the present invention can make the electromagnetic interference protection material as thin as possible.

While specific embodiments of the present invention have been described in detail for purposes of illustration, various modifications and improvements can be made without departing from the spirit and scope of the invention.

The present invention can be used to prevent harmful effects on the body of electromagnetic waves that may occur in electronic products such as mobile phones by providing an electromagnetic wave absorbing film that neutralizes electromagnetic waves using wave phase offset characteristics, wave reflection, and wave absorption.

Claims (21)

A composite layer having a plurality of particles embedded therein, wherein the thickness is 1 / 4n times the wavelength of the electromagnetic wave to be absorbed, where n is a natural number, and A reflective layer covered on one side of the composite layer, the refractive index being greater than the composite layer, The particles are selected from single layer wave absorbing particles, double layer wave absorbing particles, single layer wave reflecting particles, double layer wave reflecting particles, and combinations thereof. Electromagnetic wave absorption film. The electromagnetic wave absorbing film of claim 1, wherein the particles are wave reflecting particles. 3. The electromagnetic wave absorbing film of claim 2, wherein each of the wave reflecting particles comprises an inner layer of absorbing material and an outer layer of reflecting material surrounding the inner layer of the absorbing material. The electromagnetic wave absorbing film according to claim 1, wherein the particles include wave reflecting particles and wave absorbing particles different in diameter from the wave reflecting particles.  5. The electromagnetic wave absorbing film of claim 4, wherein each of the wave absorbing particles comprises an inner layer of reflective material and an outer layer of absorbing material surrounding the inner layer of reflective material. The electromagnetic wave absorbing film of claim 1, wherein the particles are wave absorbing particles. 7. The electromagnetic wave absorbing film of claim 6, wherein each of the wave absorbing particles comprises an inner layer of reflective material and an outer layer of absorbing material surrounding the inner layer of the reflective material. The electromagnetic wave absorbing film of claim 1, wherein the reflective layer is a metal layer. The electromagnetic wave absorbing film of claim 8, wherein the metal layer is selected from a group of materials including aluminum, nickel, iron, copper, and cobalt. 10. The electromagnetic wave absorbing film of claim 9, wherein the metal layer is formed on the composite layer by a coating procedure selected from one of vacuum sputtering and electroplating coating methods. The electromagnetic wave absorbing film of claim 1, wherein the composite layer is formed of a polymer. As a manufacturing method of an electromagnetic wave absorption film, (1) preparing a molten polymer, (2) mixing the particles into the molten polymer, (3) shaping the mixture of the molten polymer and the particles to form a composite layer whose thickness is 1 / 4n times the wavelength of the electromagnetic wave to be absorbed, where n is a natural number, and (4) forming a reflective layer on one side of the composite layer, wherein the reflective layer has a higher refractive index than the composite layer, Wherein said particle is selected from monolayer wave absorbing particles, bilayer wave absorbing particles, monolayer wave reflecting particles, bilayer wave reflecting particles, and combinations thereof. delete 13. The method of claim 12, wherein each of the bilayer wave reflecting particles comprises an inner layer of absorbent material and an outer layer of reflecting material surrounding the inner layer of the absorbent material. 13. The method of claim 12, wherein each of the bilayer wave absorbing particles comprises an inner layer of reflective material and an outer layer of absorbent material surrounding the inner layer of reflective material. The method of claim 12, wherein the reflective layer is a metal layer. The method of claim 16, wherein the metal layer is selected from the group of materials including aluminum, nickel, iron, copper, and cobalt. The method of claim 16, wherein the metal layer is formed on the composite layer by a coating procedure selected from one of vacuum sputtering and electroplating coating methods. 13. The method of claim 12, further comprising the step of covering an electrically insulating material layer on one side of the reflective layer facing the composite layer and covering a glue layer on the electrically insulating material layer facing the reflective layer (5). Way. 13. The method according to claim 12, further comprising covering (5) the glue layer on the other side of the composite layer facing the reflective layer. The method of claim 1, wherein the film is covered on the antenna of the mobile phone, leaving an unshielded gap for the electromagnetic wave generated in the mobile phone to pass through, the size of the gap is divided by the wavelength of the electromagnetic wave generated in the mobile phone Electromagnetic wave absorption film that is a possible multiple.

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