JP5559668B2 - Electromagnetic wave absorber - Google Patents

Description

  The present invention relates to an electromagnetic wave absorber having high electromagnetic wave absorbing ability.

  Shielding materials that prevent leakage and entry of electromagnetic waves are used in systems for electronic devices and communication devices such as personal computers, mobile phones, toll road automatic toll collection systems (ETC), RFID systems, and wireless LANs. The shielding material is required not only to absorb electromagnetic waves in a wide range of frequencies well, but also to have a small change (anisotropy) in electromagnetic wave absorption capability according to the incident direction. Especially in systems using circularly polarized waves such as ETC, both TE waves (electromagnetic waves whose electric field components are perpendicular to the incident surface) and TM waves (electromagnetic waves whose magnetic field components are perpendicular to the incident surface) are both efficient. A shielding material that absorbs is required.

Japanese Patent Laid-Open No. 6-120689 (Patent Document 1) is a multilayer type radio wave absorber in which a resistive film having an appropriate surface resistance and dielectrics are alternately arranged and a dielectric lined with a radio wave reflector on the back side. An electromagnetic wave absorber is disclosed in which the resistance film and the dielectric are made of a transparent material, and the electric wave reflector is made of a structure or material that transmits light. Each resistive film has a surface resistance of 377 Ω / □ (free-space radio wave characteristic impedance) ± 10% in the direction of radio wave arrival, and the dielectric lined with a radio wave reflector is λ _g / 4 (λ _g is radio wave) The thickness of the In Example 5, which is the only example showing a multilayer structure, three 0.5 mm thick PET plates on which a metal oxide film having a surface resistance of 377 Ω / □ ± 10% is formed as a resistance film are equally spaced by 10 mm. The distance between the innermost resistive film and the dielectric lined with a radio wave reflector is 10 mm. Even if a plurality of resistive films having a surface resistance of about 377Ω / □ are arranged in front of the radio wave reflector, the radio wave absorption ability is improved, but it is still insufficient and further improvement is desired.

Japanese Patent Laid-Open No. 6-208989

  Accordingly, an object of the present invention is to provide an electromagnetic wave absorber having high electromagnetic wave absorbing ability.

As a result of earnest research in view of the above object, the present inventor found that the electromagnetic wave absorber in which a plurality of electromagnetic wave absorbing films are arranged in front of the electromagnetic wave reflector, (a) the first electromagnetic wave absorbing film is more than the next electromagnetic wave absorbing film. When having a large surface resistance, a significantly higher electromagnetic wave absorption ability can be obtained than when having the same surface resistance, (b) When the interval between the electromagnetic wave absorbing film and the interval between the electromagnetic wave absorbing film and the electromagnetic wave reflector are different, When the electromagnetic wave absorbing ability is further improved, and (c) a large number of intermittent linear traces substantially parallel with irregular widths and intervals are formed in a plurality of directions on the plastic film side of the electromagnetic wave absorbing film, The inventors have discovered that the ability to absorb electromagnetic waves is further improved than the case where no trace is formed, and have arrived at the present invention.

That is, the electromagnetic wave absorber of the present invention is formed by laminating a plurality of electromagnetic wave absorbing films through a dielectric before the electromagnetic wave reflector.
Each electromagnetic wave absorbing film is formed by forming a conductor layer on one side of a plastic film,
The conductive layer of each electromagnetic wave absorbing film has a surface resistance in the range of 100 to 1000 Ω / □, and the surface resistance of the conductive layer of the previous electromagnetic wave absorbing film is the surface of the conductive layer of the next electromagnetic wave absorbing film. 100 Ω / □ or more larger than the resistance
(a) When the number of the electromagnetic wave absorbing films is two, the ratio between the distance between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film and the distance between the second electromagnetic wave absorbing film and the electromagnetic wave reflector is 100: 30 to 100: 70, and (b) when there are three or more electromagnetic wave absorbing films, an interval between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film, and the second electromagnetic wave absorbing film, The ratio of the distance to the third electromagnetic wave absorbing film is 100: 30 to 100: 70,
A number of intermittent linear traces substantially parallel with irregular widths and intervals are formed in a plurality of directions on the plastic film side of the electromagnetic wave absorbing film,
90% or more of the width of the linear traces is in the range of 0.1 to 100 μm, and the average is 1 to 50 μm, and the interval of the linear traces is in the range of 0.1 to 200 μm, and the average is 1 to 100 μm. characterized in that there.

The electromagnetic wave absorber according to the first embodiment has a layer configuration of a first electromagnetic wave absorbing film / dielectric / second electromagnetic wave absorbing film / dielectric / electromagnetic wave reflector, and the first and second electromagnetic wave absorbers. The conductive layer of the film has a surface resistance of 100 to 1000 Ω / □, and the conductive layer of the first electromagnetic wave absorbing film has a surface that is 100 Ω / □ or more larger than the conductive layer of the second electromagnetic wave absorbing film. Has resistance . The ratio between the distance between the distance and the second electromagnetic wave absorption film of the first and second electromagnetic wave absorbing film and the electromagnetic wave reflector 100: 30 to 100: 70.

The electromagnetic wave absorber according to the second embodiment has a layer configuration of a first electromagnetic wave absorbing film / dielectric / second electromagnetic wave absorbing film / dielectric / third electromagnetic wave absorbing film / dielectric / electromagnetic wave reflector. The conductive layer of the first to third electromagnetic wave absorbing films has a surface resistance of 100 to 1000 Ω / □, and the conductive layer of the first electromagnetic wave absorbing film is conductive of the second electromagnetic wave absorbing film. It has a surface resistance that is 100 Ω / □ or more greater than the body layer. The conductor layer of the third electromagnetic wave absorbing film preferably has a surface resistance that is 100 Ω / □ or more larger than that of the second electromagnetic wave absorbing film . The ratio between the distance interval between the second and third electromagnetic wave absorption film of the first and second electromagnetic wave absorbing film 100: 30 to 100: 70. The ratio of the distance between the third electromagnetic wave absorbing film and the electromagnetic wave reflector and the distance between the second and third electromagnetic wave absorbing films is preferably 100: 30 to 100: 70.

The linear traces of each electromagnetic wave absorbing film are oriented in two directions, and the crossing angle is preferably 30 to 90 ° .

  The at least one electromagnetic wave absorbing film may be composed of a plurality of electromagnetic wave absorbing film pieces having different surface resistances. By using a plurality of electromagnetic wave absorbing film pieces having different surface resistances, the adverse effect of non-uniformity in the surface resistance of the electromagnetic wave absorbing film is reduced.

The electromagnetic wave absorber of the present invention is formed by laminating a plurality of electromagnetic wave absorbing films made of a plastic film having a conductive layer via a dielectric, and the conductive layer of each electromagnetic wave absorbing film is 100 to 1000 Ω / □. The surface resistance of the conductive layer of the previous electromagnetic wave absorbing film having a surface resistance within the range is 100 Ω / □ or more larger than the surface resistance of the conductive layer of the next electromagnetic wave absorbing film, The ratio between the interval between the second electromagnetic wave absorbing film and the interval between the second electromagnetic wave absorbing film and the electromagnetic wave reflector or the third electromagnetic wave absorbing film is 100: 30 to 100: 70, and the electromagnetic wave since intermittent linear scratches of many substantially parallel with irregular widths and intervals on the plastic film side of the absorbing film is formed in a plurality of directions, simply a plurality of electromagnetic wave absorption film having the same surface resistance Not only has a significantly higher electromagnetic wave absorption capability as compared with the case of layers, the anisotropy of electromagnetic wave absorption capability is decreased. The electromagnetic wave absorber of the present invention having such characteristics can be used for a wide range of applications that require high electromagnetic wave absorption ability such as ETC and FRID.

It is sectional drawing which shows the electromagnetic wave absorption film which does not have a linear trace. It is sectional drawing which shows the electromagnetic wave absorption film which has a linear trace in a conductor layer. It is sectional drawing which shows the electromagnetic wave absorption film which has a linear trace on a plastic surface. It is a fragmentary top view which shows an example of a linear trace. It is a fragmentary top view which shows the other example of a linear trace. It is a fragmentary top view which shows the other example of a linear trace. It is a fragmentary top view which shows the other example of a linear trace. It is a partial top view which shows the composite electromagnetic wave absorption film which consists of a striped electromagnetic wave absorption film piece which does not have a linear trace. It is a partial top view which shows the composite electromagnetic wave absorption film which consists of a striped electromagnetic wave absorption film piece which has a linear trace. It is a partial top view which shows the composite electromagnetic wave absorption film which consists of a rectangular electromagnetic wave absorption film piece which has a linear trace. It is sectional drawing which shows the electromagnetic wave absorption film in which the protective layer was provided on the conductor layer and the linear trace. It is a perspective view which shows an example of the manufacturing apparatus of an electromagnetic wave absorption film. FIG. 9 is a plan view showing the device of FIG. 8 (a). FIG. 9 is a sectional view taken along line BB in FIG. 8 (b). It is a partial enlarged plan view for demonstrating the principle in which the linear trace inclined with respect to the advancing direction of a film is formed. FIG. 9 is a partial plan view showing the inclination angles of the pattern roll and the presser roll with respect to the film in the apparatus of FIG. 8 (a). It is a fragmentary sectional view which shows the other example of the manufacturing apparatus of an electromagnetic wave absorption film. It is a perspective view which shows the further another example of the manufacturing apparatus of an electromagnetic wave absorption film. It is a perspective view which shows the further another example of the manufacturing apparatus of an electromagnetic wave absorption film. It is a perspective view which shows the further another example of the manufacturing apparatus of an electromagnetic wave absorption film. In the electromagnetic wave absorber of a comparative example , it is sectional drawing which shows arrangement | positioning of two electromagnetic wave absorption films which do not have a linear trace, and a reflecting plate. FIG. 14 is an exploded perspective view showing the configuration of the electromagnetic wave absorber shown in FIG. In the electromagnetic wave absorber of a comparative example , it is sectional drawing which shows arrangement | positioning of two electromagnetic wave absorption films and reflectors which have a linear trace in a conductor layer. In the electromagnetic wave absorber of the present invention, it is a cross-sectional view showing the arrangement of two electromagnetic wave absorbing films having a linear mark on a plastic surface and a reflector. FIG. 17 is an exploded perspective view showing a configuration of the electromagnetic wave absorber of FIGS. 15 and 16. In the electromagnetic wave absorber of the present invention, it is an exploded plan view showing an example of a combination of two electromagnetic wave absorbing films having linear traces. In the electromagnetic wave absorber of the present invention, it is an exploded plan view showing another example of a combination of two electromagnetic wave absorbing films having linear traces. FIG. 6 is an exploded plan view showing still another example of a combination of two electromagnetic wave absorbing films having linear traces in the electromagnetic wave absorber of the present invention. In the electromagnetic wave absorber of a comparative example , it is sectional drawing which shows arrangement | positioning of the three electromagnetic wave absorption films and reflectors which do not have a linear trace. FIG. 20 is an exploded perspective view showing the configuration of the electromagnetic wave absorber shown in FIG. In the electromagnetic wave absorber of a comparative example , it is sectional drawing which shows arrangement | positioning of the three electromagnetic wave absorption films which have a linear trace in a conductor layer, and a reflecting plate. In the electromagnetic wave absorber of the present invention, it is a cross-sectional view showing the arrangement of three electromagnetic wave absorbing films having a linear trace on a plastic surface and a reflector. FIG. 23 is an exploded perspective view showing a configuration of the electromagnetic wave absorber shown in FIGS. 21 and 22. FIG. In the electromagnetic wave absorber of the present invention, it is an exploded plan view showing an example of a combination of three electromagnetic wave absorbing films having linear traces. In the electromagnetic wave absorber of the present invention, it is an exploded plan view showing another example of a combination of three electromagnetic wave absorbing films having linear traces. FIG. 5 is an exploded plan view showing still another example of a combination of three electromagnetic wave absorbing films having linear traces in the electromagnetic wave absorber of the present invention. FIG. 5 is an exploded plan view showing still another example of a combination of three electromagnetic wave absorbing films having linear traces in the electromagnetic wave absorber of the present invention. FIG. 5 is an exploded plan view showing still another example of a combination of three electromagnetic wave absorbing films having linear traces in the electromagnetic wave absorber of the present invention. FIG. 5 is an exploded plan view showing still another example of a combination of three electromagnetic wave absorbing films having linear traces in the electromagnetic wave absorber of the present invention. It is the schematic which shows the apparatus which evaluates the electromagnetic wave absorption capability of an electromagnetic wave absorber. 6 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 1 . 2 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Example 1. FIG. 6 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 2 . 3 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Example 2. FIG. 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 3 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 4 . 6 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 5 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 6 . 10 is a graph showing the peak absorptance and peak frequency of the electromagnetic wave absorber of Comparative Example 7 . 10 is a graph showing the peak absorptance and peak frequency of the electromagnetic wave absorber of Comparative Example 8 . 6 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Example 3. FIG. 6 is a graph showing the electromagnetic wave absorption rate at 5.8 GHz of the electromagnetic wave absorber of Example 4 . 6 is a graph showing an electromagnetic wave absorption rate at 5.8 GHz of the electromagnetic wave absorber of Example 5 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 9 . 10 is a graph showing the peak absorptance and peak frequency of the electromagnetic wave absorber of Comparative Example 10 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 11 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 12 . 14 is a graph showing the peak absorptance and peak frequency of the electromagnetic wave absorber of Comparative Example 13 . 14 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 14 . 6 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Example 6. FIG. 16 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 15 . 16 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 16 . 18 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 17 . 16 is a graph showing an electromagnetic wave absorption rate at 2.5 GHz of the electromagnetic wave absorber of Comparative Example 17 . 19 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 18 . 16 is a graph showing an electromagnetic wave absorption rate at 2.5 GHz of the electromagnetic wave absorber of Comparative Example 18 . 20 is a graph showing an electromagnetic wave absorption rate at 2.5 GHz of the electromagnetic wave absorber of Comparative Example 19 . 6 is a graph showing an electromagnetic wave absorption rate at 5.8 GHz of the electromagnetic wave absorber of Example 7 . 10 is a graph showing an electromagnetic wave absorption rate at 2.5 GHz of the electromagnetic wave absorber of Comparative Example 20 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 20 . 10 is a graph showing the peak absorption rate and peak frequency of the electromagnetic wave absorber of Comparative Example 21 .

  DESCRIPTION OF EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the accompanying drawings. Unless otherwise specified, the description relating to one embodiment is applicable to other embodiments. The following description is not limited, and various modifications may be made within the scope of the technical idea of the present invention.

[1] electromagnetic wave absorbing film
(1) First electromagnetic wave absorbing film
The first electromagnetic wave absorbing film 100 is obtained by forming a conductor layer 11 on one surface of a plastic film 10 as shown in FIG.

(a) Plastic film The resin forming the plastic film 10 is not particularly limited as long as it has sufficient strength, flexibility, and processability as well as properties and insulation properties. For example, polyester (polyethylene terephthalate, etc.), polyarylene sulfide (polyphenylene) Sulfide), polyether sulfone, polyether ether ketone, polycarbonate, acrylic resin, polystyrene, polyolefin (polyethylene, polypropylene, etc.) and the like. The thickness of the plastic film 10 may be about 10 to 100 μm.

(b) Conductor layer The conductor layer 11 is made of a thin film of a conductive metal or a transparent conductive metal oxide. The conductive metal film becomes transparent as it becomes thinner. Therefore, the conductor layer 11 may be transparent or opaque. In order to exhibit excellent electromagnetic wave absorbing ability, the surface resistance of the conductor layer 11 is 100 to 1000 Ω / □, preferably 200 to 1000 Ω / □, and more preferably 250 to 800 Ω / □. The surface resistance can be measured by a direct current two-terminal method. When the surface resistance of the conductor layer 11 is out of the range of 100 to 1000 Ω / □, even if a plurality of electromagnetic wave absorbing films are combined with an electromagnetic wave reflector, high electromagnetic wave absorbing ability cannot be obtained. The conductor layer 11 can be formed by a known method such as a sputtering method or a vacuum deposition method.

Examples of the conductive metal include nickel, aluminum, and chromium. Of course, these metals are not limited to simple substances, but may be alloys. The aluminum thin film also has good conductivity, but it is difficult to make the film thickness (surface resistance) uniform. On the other hand, a nickel thin film is suitable for the purpose of the present invention because it has good conductivity and a uniform surface resistance distribution. The thickness of the metal thin film needs to be set so that the surface resistance is in the range of 100 to 1000 Ω / □, specifically 10 to 20 nm is preferable , and 10 to 15 nm is more preferable. If the thickness of the metal thin film is less than 10 nm, the surface resistance is too large, and if the thickness of the metal thin film exceeds 20 nm, the surface resistance is too small. In addition, when forming a linear trace in a metal thin film, since the surface resistance of a metal thin film can be adjusted with a linear trace, a metal thin film can be formed thicker. Specifically, the thickness of the metal thin film may be about 0.01 to 1 μm.

Examples of the transparent conductive metal oxide include indium tin oxide (ITO), zinc oxide (ZnO), and tin oxide (SnO ₂ ). The thickness of the transparent conductive metal oxide thin film needs to be set so that the surface resistance is in the range of 100 to 1000 Ω / □, specifically 0.05 to 1 μm is preferable , and 0.1 to 1 μm is more preferable. .

(2) Second electromagnetic wave absorbing film
The second electromagnetic wave absorbing film 110 has a conductor layer 11 on one surface of the plastic film 10, and has linear traces 12 in a plurality of directions on the conductor layer 11 or on the opposite plastic surface. FIG. 2 shows an electromagnetic wave absorbing film 110 in which a linear mark 12 is formed on the conductor layer 11, and FIG. 3 shows an electromagnetic wave absorbing film 120 in which the linear mark 12 is formed on the plastic surface opposite to the conductive layer 11. Show. The electromagnetic wave absorber of the present invention has an electromagnetic wave absorbing film 120.

  In any case, the substantially parallel and intermittent linear marks 12 are formed with irregular widths and intervals in a plurality of directions. FIG. 4 shows an example of a plurality of linear marks 12. A number of substantially parallel and intermittent linear marks 12a and 12b formed on the other surface of the conductor layer 11 or the plastic film 10 (the surface not having the conductor layer 11) are formed in a plurality of directions (example shown in the figure). In two directions) with irregular widths and intervals. For the sake of explanation, the depth of the linear mark 12 is exaggerated in FIGS. The linear traces 12 oriented in two directions have various widths W and intervals I. The interval I means an interval in both the alignment direction (longitudinal direction) of the linear marks 12 and the direction (lateral direction) perpendicular thereto. Both the width W and the interval I of the linear marks 12 are determined by the height (original height) of the surface S of the plastic film 10 before the linear marks are formed. Since the linear scar 12 has various widths W and intervals I, the electromagnetic wave absorbing film 1 can efficiently absorb electromagnetic waves having a wide range of frequencies.

  90% or more of the width W of the linear scar 12 is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 50 μm, and most preferably in the range of 0.1 to 20 μm. The average width Wav of the linear marks 12 is preferably 1 to 50 μm, more preferably 1 to 20 μm, and most preferably 1 to 10 μm.

  The interval I between the linear marks 12 is preferably in the range of 0.1 to 200 μm, more preferably in the range of 0.1 to 100 μm, most preferably in the range of 0.1 to 50 μm, and 0.1 to 20 μm. It is particularly preferred that it is within the range. The average interval Iav of the linear marks 12 is preferably 1 to 100 μm, more preferably 1 to 50 μm, and most preferably 1 to 20 μm.

  Since the length L of the linear mark 12 is determined by the sliding contact condition (mainly the relative speed between the roll and the film and the winding angle of the film on the roll), the length L is almost the same unless the sliding contact condition is changed. Yes (approximately equal to the average length). The length of the linear mark 12 is not particularly limited, and may be about 1 to 100 mm practically.

  The acute crossing angle (hereinafter also referred to simply as “crossing angle” unless otherwise specified) θs of the two-way linear marks 12a and 12b is preferably 30 to 90 °, more preferably 45 to 90 °, and 60 to 90 ° is most preferred. By adjusting the sliding contact conditions (sliding contact direction, peripheral speed ratio, etc.) between the plastic film 10 and the pattern roll, linear shapes with various crossing angles θs as shown in Fig. 5 (a) to Fig. 5 (c) Trace 12 is obtained. The alignment of the linear marks is not limited to two directions, and may be three or more directions. 5 (a) is composed of orthogonal line marks 12a and 12b, and the line mark 12 in FIG. 5 (b) is composed of line marks 12a and 12b intersecting at 60 °. The linear trace 12 of c) is composed of linear traces 12a, 12b and 12c in three directions.

(3) Third electromagnetic wave absorbing film Each electromagnetic wave absorbing film may be a combination of a plurality of electromagnetic wave absorbing film pieces. For example, the electromagnetic wave absorbing film 130 shown in FIG. 6 (a) is composed of three types of striped electromagnetic wave absorbing film pieces 100a ′, 100b ′, and 100c ′ having conductor layers having different surface resistances. By combining the electromagnetic wave absorbing film pieces having different surface resistances, functions equivalent to those of the electromagnetic wave absorbing film having a desired surface resistance can be exhibited. Of course, the number of electromagnetic wave absorbing film pieces to be combined is limited to three, and may be two or four or more. Preferred combinations include 785Ω / □ and 500Ω / □ and 785Ω / □, 500Ω / □ and 300Ω / □ and 500Ω / □, 300Ω / □ and 250Ω / □ and 300Ω / □, 250Ω / □ And combinations of 500Ω / □ and 250Ω / □. The width of each electromagnetic wave absorbing film piece 100a ′, 100b ′, 100c ′ is preferably in the range of 2 to 20 cm.

  Further, as shown in FIG. 6 (b), there is also an electromagnetic wave absorbing film 140 in which a plurality of striped electromagnetic wave absorbing film pieces 12A, 12B, and 12C in which linear traces are formed on the conductor layer or the plastic surface on the opposite side are combined. It can be used. The criteria for the combination are (a) exhibiting the same function as an electromagnetic wave absorbing film having a desired surface resistance, and (b) changing the orientation of the linear marks so as to reduce the anisotropy of the electromagnetic wave absorbing ability. It is. As in the example of FIG. 6 (a), the width of each electromagnetic wave absorbing film piece 12A, 12B, 12C is preferably in the range of 2 to 20 cm.

  FIG. 6 (c) shows an example of an electromagnetic wave absorbing film 150 formed by combining a plurality of rectangular electromagnetic wave absorbing film pieces 12A, 12B, and 12C. In this case as well, the criteria for the combination are (a) exerting the same function as the electromagnetic wave absorbing film having a desired surface resistance, and (b) the alignment of the linear marks so as to reduce the anisotropy of the electromagnetic wave absorbing ability. Is different.

(4) Protective layer As shown in FIG. 7, it is preferable to form protective layers 13a and 13b on the conductor layer 11 and the linear trace 12 if there are any. The protective layers 13a and 13b are preferably plastic hard coats or films. When using a film, it is preferable to adhere by a heat laminating method or a dry laminating method. The plastic hard coat can be formed, for example, by application of a photocurable resin and irradiation with ultraviolet rays. The thickness of each protective layer 13a, 13b is preferably about 10-100 μm.

[2] Apparatus for forming linear traces FIGS. 8 (a) to 8 (e) show an example of an apparatus for forming linear traces in two directions on a plastic film. The linear trace can be formed on either the conductor layer 11 or the plastic surface, and can be either before or after the formation of the conductor layer 11, so that the linear trace is simply formed on the plastic film 10 for simplicity of explanation. Taking a case as an example, a method of forming a linear trace will be described. In addition, when forming a linear trace in the plastic surface (surface on the opposite side to the conductive layer 11) of the commercially available plastic film 10 in which the conductive layer 11 has been formed in advance, the conductive layer 11 is formed during the formation of the linear trace. In order to prevent damage, it is preferable to form an overcoat on the conductor layer 11.

  The illustrated apparatus includes (a) a reel 21 for unwinding the plastic film 10, (b) a first pattern roll 2a disposed to be inclined with respect to the width direction of the plastic film 10, and (c) a first A first presser roll 3a disposed on the upstream side of the pattern roll 2a and on the opposite side thereof; and (d) a first pattern that is inclined in the direction opposite to the first pattern roll 2a with respect to the width direction of the plastic film 10. A second pattern roll 2b disposed on the same side as the roll 2a, (e) a second presser roll 3b disposed on the opposite side to the downstream side of the second pattern roll 2b, and (f) a linear shape. And a reel 24 for winding the plastic film 10 'with a mark. In addition, a plurality of guide rolls 22 and 23 are arranged at predetermined positions. Each pattern roll 2a, 2b is supported by backup rolls (for example, rubber rolls) 5a, 5b in order to prevent bending.

As shown in FIG. 8 (c), since the presser rolls 3a and 3b are in contact with the plastic film 10 at positions lower than the sliding contact positions with the pattern rolls 2a and 2b, the plastic film 10 is in contact with the pattern rolls 2a and 2b. Pressed. Each presser rolls 3a while satisfying this condition, by adjusting the height of 3b, each pattern roll 2a, can adjust the pressing force to 2b, also be adjusted even sliding contact distance which is proportional to the center angle theta _1.

  FIG. 8 (d) shows the principle that the linear marks 12 a are formed obliquely with respect to the traveling direction of the plastic film 10. Since the pattern roll 2a is inclined with respect to the traveling direction of the plastic film 10, the moving direction (rotating direction) of the hard fine particles on the pattern roll 2a is different from the traveling direction of the plastic film 10. Therefore, as shown by X, if the hard fine particles at point A on the pattern roll 2a come into contact with the plastic film 10 to form a mark B at an arbitrary time, the hard fine particles move to point A ′ after a predetermined time. , Mark B moves to point B ′. While the hard fine particles move from the point A to the point A ′, the traces are continuously formed, so that a linear trace 12 a extending from the point A ′ to the point B ′ is formed.

The direction and the crossing angle θs of the linear marks 12a, 12b formed by the first and second pattern rolls 2a, 2b are the angles of the pattern rolls 2a, 2b with respect to the plastic film 10 and / or the travel of the plastic film 10. It can be adjusted by changing the peripheral speed of each pattern roll 2a, 2b with respect to the speed. For example, when the peripheral speed a of the pattern roll 2a is increased with respect to the traveling speed b of the plastic film 10, the linear mark 12a is represented by a line segment C′D ′ as shown by Y in FIG. 8 (d). It can be 45 ° with respect to the direction of travel. Similarly, when the inclination angle θ ₂ of the pattern roll 2a with respect to the width direction of the plastic film 10 is changed, the peripheral speed a of the pattern roll 2a can be changed. The same applies to the pattern roll 2b. Therefore, the direction of the linear marks 12a and 12b can be changed by adjusting both the pattern rolls 2a and 2b.

Since each pattern roll 2a, 2b is inclined with respect to the plastic film 10, the plastic film 10 receives a force in the width direction by sliding contact with each pattern roll 2a, 2b. Therefore, in order to prevent the meandering of the plastic film 10, it is preferable to adjust the height and / or angle of each presser roll 3a, 3b with respect to each pattern roll 2a, 2b. For example, if the crossing angle θ ₃ between the axis of the pattern roll 2a and the axis of the presser roll 3a is appropriately adjusted, a widthwise distribution of the pressing force is obtained so as to cancel the force in the widthwise direction, thereby preventing meandering. it can. Further, adjustment of the distance between the pattern roll 2a and the presser roll 3a also contributes to prevention of meandering. In order to prevent the meandering and breaking of the plastic film 10, the rotation directions of the first and second pattern rolls 2a, 2b inclined with respect to the width direction of the plastic film 10 are the same as the traveling direction of the plastic film 10. Is preferred.

In order to increase the pressing force of the pattern rolls 2a and 2b on the plastic film 10, a third presser roll 3c may be provided between the pattern rolls 2a and 2b as shown in FIG. Sliding length of the plastic film 10 which is proportional to the center angle theta ₁ by a third pressing roll 3c also increases, linear scratches 12a, 12b becomes longer. Adjusting the position and inclination angle of the third presser roll 3c can also contribute to prevention of meandering of the plastic film 10.

  FIG. 10 shows an example of an apparatus for forming linear traces oriented in three directions as shown in FIG. 5 (c). This apparatus differs from the apparatus shown in FIGS. 8 (a) to 8 (e) in that a third pattern roll 2c parallel to the width direction of the plastic film 10 is disposed downstream of the second pattern roll 2b. The rotation direction of the third pattern roll 2c may be the same as or opposite to the traveling direction of the plastic film 10, but the reverse direction is preferable in order to efficiently form linear marks. The third pattern roll 2c arranged in parallel with the width direction forms a linear mark 12c extending in the traveling direction of the plastic film 10. The third presser roll 3d is provided on the upstream side of the third pattern roll 2c, but may be provided on the downstream side. The third pattern roll 2c may be provided upstream of the first pattern roll 2a or between the first and second pattern rolls 2a and 2b without being limited to the illustrated example.

  FIG. 11 shows an example of an apparatus for forming linear traces oriented in four directions. This apparatus is provided with a fourth pattern roll 2d between the second pattern roll 2b and the third pattern roll 2c, and a fourth presser roll 3e provided upstream of the fourth pattern roll 2d. This is different from the apparatus shown in FIG. By reducing the rotational speed of the fourth pattern roll 2d, the direction of the line mark 12a ′ (the line segment E′F ′) is changed to the width direction of the plastic film 10 as indicated by Z in FIG. 8 (d). Can be parallel.

  FIG. 12 shows another example of an apparatus for forming orthogonal linear marks as shown in FIG. 5 (a). This apparatus is different from the apparatuses shown in FIGS. 8 (a) to 8 (e) in that the second pattern roll 32b is arranged in parallel with the width direction of the plastic film 10. FIG. Accordingly, only the parts different from the apparatus shown in FIGS. 8 (a) to 8 (e) will be described below. The rotation direction of the second pattern roll 32b may be the same as or opposite to the traveling direction of the plastic film 10. The second presser roll 33b may be on the upstream side or the downstream side of the second pattern roll 32b. As shown by Z in FIG. 8 (d), this apparatus is suitable for forming linear traces orthogonal to the direction of the linear trace 12a '(line segment E'F') in the width direction of the film 10. ing.

The operating conditions that determine the depth, width, length, and spacing of the line marks as well as the inclination angle and crossing angle of the linear traces are the traveling speed of the plastic film 10, the rotational speed and inclination angle of the pattern roll, and the pressing force. is there. The running speed of the film is preferably 5 to 200 m / min, and the peripheral speed of the pattern roll is preferably 10 to 2,000 m / min. The inclination angle θ ₂ of the pattern roll is preferably 20 ° to 60 °, particularly about 45 °. The tension (proportional to the pressing force) of the film 10 is preferably 0.05 to 5 kgf / cm width.

  The pattern roll is preferably a roll having fine particles with a Mohs hardness of 5 or more having sharp corners on its surface, such as a diamond roll described in JP-A-2002-59487. Since the width of the linear mark is determined by the particle size of the fine particles, 90% or more of the diamond fine particles preferably have a particle size in the range of 1 to 100 μm, and more preferably in the range of 10 to 50 μm. The diamond fine particles are preferably attached to the roll surface at an area ratio of 30% or more.

[3] Electromagnetic wave absorber The electromagnetic wave absorber of the present invention comprises a plurality of electromagnetic wave absorbing films (a number of intermittent linear shapes substantially parallel to the plastic film with irregular widths and intervals ) in front of the electromagnetic wave reflector. And a conductive layer of each electromagnetic wave absorbing film has a surface resistance in the range of 100 to 1000 Ω / □, and The surface resistance of the conductor layer of the electromagnetic wave absorbing film is 100 Ω / □ or more larger than the surface resistance of the conductor layer of the next electromagnetic wave absorbing film. The surface resistance of the conductor layer of each electromagnetic wave absorbing film is preferably 200 to 1000Ω / □, more preferably 250 to 800Ω / □, and the difference in surface resistance between adjacent electromagnetic wave absorbing films is preferably 200Ω / □ or more , and 300Ω / □. □ or more is more preferable.

  The dielectric is preferably a plastic plate, foam, honeycomb structure or the like. Regardless of the number of electromagnetic wave absorbing films and the presence or absence of linear marks, the total thickness of the dielectrics that determine the distance between adjacent electromagnetic wave absorbing films and the distance between the electromagnetic wave absorbing film and the electromagnetic wave reflector is the wavelength λ of the electromagnetic wave to be absorbed. On the other hand, it is generally preferable that the range includes λ / 8 to λ / 4. When the frequency of the electromagnetic wave to be absorbed is small (for example, 2.5 GHz), the total thickness of the dielectric is preferably λ / 4, but when the frequency of the electromagnetic wave to be absorbed is large (for example, 5.8 GHz), the total thickness of the dielectric is λ / 8 is preferred. In general, there is an allowable range of ± 40% with respect to the range of λ / 8 to λ / 4, preferably an allowable range of ± 20%, and more preferably an allowable range of ± 10%.

(1) Example of Electromagnetic Wave Absorber The electromagnetic wave absorber shown in FIGS. 13 and 14 is formed by laminating two electromagnetic wave absorbing films 100a and 100b in front of the electromagnetic wave reflector 200 via a dielectric. This electromagnetic wave absorber has a layer structure of first electromagnetic wave absorption film 100a / dielectric 30a / second electromagnetic wave absorption film 100b / dielectric 30b / electromagnetic wave reflector 200. The conductor layers 11a and 11b of the electromagnetic wave absorbing films 100a and 100b may be on the same side or opposite sides of the plastic film 10. In the present invention, (a) the surface resistance of the conductor layers 11a and 11b of the first and second electromagnetic wave absorbing films 100a and 100b is in the range of 100 to 1000 Ω / □, and (b) the conductor layer 11a The surface resistance needs to be 100 Ω / □ or more larger than the surface resistance of the conductor layer 11b. That is, the surface resistance of the conductor layer 11a is in the range of 200 to 1000 Ω / □, the surface resistance of the conductor layer 11b is in the range of 100 to 900 Ω / □, and the surface resistance of the conductor layer 11a is 100 Ω / □ or more larger than the surface resistance of the conductor layer 11b. If the conditions (a) and (b) are not satisfied at the same time, high electromagnetic wave absorbing ability is not obtained. The surface resistance of the conductor layers 11a and 11b is preferably 200 to 1000Ω / □, and more preferably 250 to 800Ω / □. Also it is preferable surface resistance than 200 [Omega / □ or greater surface resistance of the conductive layer 11a is electrically conductive layer 11b, and more preferably 300 [Omega / □ or greater.

The thickness of the dielectric 30a knocked spacing D ₁ of the the first electromagnetic wave absorbing film 100a and a second electromagnetic wave absorbing film 100b, the thickness of the dielectric 30b and the second electromagnetic wave absorption film 100a and an electromagnetic wave reflector 200 determine the distance D _2. The ratio of the distance D ₁ / spacing D ₂ is 100: 30 to 100: 70. When the above conditions (a) and (b) are satisfied and the ratio of the distance D ₁ / the distance D ₂ is within this range, the highest electromagnetic wave absorbing ability can be obtained. The ratio of the distance D ₁ / the distance D ₂ is preferably 100: 40 to 100: 60, more preferably 100: 45 to 100: 55, and ideally 100: 50.

In the first and second electromagnetic wave absorbing films, linear marks are formed on the opposite side of the conductor layer. As shown in FIG. 15, when the linear scar 12 is formed on the side of the conductor layers 11a, 11b of the electromagnetic wave absorbing films 110a, 110b, and as shown in FIG. 16, the linear scar 12 is an electromagnetic wave absorbing film 120a, In any case where it is formed on the plastic surface of 120b, the above conditions (a) and (b) must be satisfied, and the ratio of the distance D ₁ / the distance D ₂ needs to be within the above range. Sometimes linear scratches are formed, the surface resistance of the conductive layer 11a and 11b are 100~1000Ω / □, preferably 200~1000Ω / □, 250~800Ω / □, more preferably, also the conductive layer 11a surface resistance conductor layer 11b increases 100 [Omega / □ or higher than the surface resistance of, is preferably 200 [Omega / □ or greater, more preferably 300 [Omega / □ or greater.

  In the case shown in FIG. 15, the surface resistance of the conductor layers 11a and 11b of the electromagnetic wave absorbing films 110a and 110b can be adjusted by the linear trace 12, and the electromagnetic wave is attenuated by the gap of the linear trace 12. Further, in the case shown in FIG. 16, there is an advantage that the transparency of the conductor layers 11a and 11b of the electromagnetic wave absorbing films 120a and 120b is not affected by the linear marks 12. In both cases of FIGS. 15 and 16, as shown in FIG. 17, the first electromagnetic wave absorbing film 110a (120a) / dielectric 30a / second electromagnetic wave absorbing film 110b (120b) / dielectric 30b / electromagnetic wave reflector It has 200 layer structure.

  FIG. 18 (a) and FIG. 18 (b) show examples of combinations of linear traces of two electromagnetic wave absorbing films constituting the electromagnetic wave absorber. By changing the orientation of the linear traces and the crossing angle θs of the two electromagnetic wave absorbing films 110a (120a) and 110b (120b) according to the frequency to be absorbed, the anisotropy of the electromagnetic wave absorbing ability is reduced and excellent. Electromagnetic wave absorption ability is obtained. For example, if the crossing angle θs of linear traces is 60 °, an electromagnetic wave absorbing film having excellent electric field absorption ability can be obtained, and if the crossing angle θs of linear traces is 90 °, an electromagnetic wave absorbing film having excellent magnetic field absorption ability can be obtained. It is done. Therefore, for example, the first electromagnetic wave absorbing film 110a (120a) having a crossing angle θs of linear traces of 60 ° and the second electromagnetic wave absorbing film 110b (120b) having a crossing angle θs of linear traces of 90 ° are combined. The electromagnetic wave absorber shown in FIG. 18 (c) is excellent in both electric field absorption ability and magnetic field absorption ability.

(2) Another Example of Electromagnetic Wave Absorber The electromagnetic wave absorber shown in FIGS. 19 and 20 has three electromagnetic wave absorbing films 100a, 100b, and 100c placed in front of the electromagnetic wave reflector 200 through dielectrics 30a, 30b, and 30c. And laminated. This electromagnetic wave absorber has a layer structure of a first electromagnetic wave absorbing film 100a / dielectric 30a / second electromagnetic wave absorbing film 100b / dielectric 30b / third electromagnetic wave absorbing film 100c / dielectric 30c / electromagnetic wave reflector 200. Have. The conductor layers 11a, 11b, and 11c of the electromagnetic wave absorbing films 100a, 100b, and 100c may all be on the same side or the opposite side of the plastic film 10. In the present invention, (a) the surface resistance of the conductor layers 11a, 11b, 11c of the first to third electromagnetic wave absorbing films 100a, 100b, 100c is in the range of 100-1000 Ω / □, and (b) The surface resistance of the conductor layer 11a needs to be 100 Ω / □ or more larger than the surface resistance of the conductor layer 11b. If the conditions (a) and (b) are not satisfied at the same time, high electromagnetic wave absorbing ability is not obtained. The surface resistance of each conductor layer 11a, 11b, 11c is preferably 200 to 1000Ω / □, and more preferably 250 to 800Ω / □. Also it is preferable surface resistance than 200 [Omega / □ or greater surface resistance of the conductive layer 11a is electrically conductive layer 11b, and more preferably 300 [Omega / □ or greater. Furthermore, the surface resistance of the conductor layer 11c is preferably 50Ω / □ or more larger than the surface resistance of the conductor layer 11b, more preferably 100Ω / □ or more, most preferably 200Ω / □ or more, most preferably 300Ω / □ or more. Large is particularly preferred. The surface resistance of the conductor layer 11c may be the same as the surface resistance of the conductor layer 11a.

The thickness of the dielectric 30a knocked spacing D ₁ of the the first electromagnetic wave absorbing film 100a and a second electromagnetic wave absorbing film 100b, the thickness of the dielectric 30b is a second electromagnetic wave absorbing film 100a and a third electromagnetic wave absorbing determining the distance D ₂ between the film 100c, the thickness of the dielectric 30c determines the distance D ₃ between the third electromagnetic wave absorbing film 100c and the electromagnetic wave reflector 200. The ratio of the interval D ₁ / the interval D ₂ is 100: 30 to 100: 70 . The ratio of the distance D ₃ / the distance D ₂ is also preferably 100: 30 to 100: 70. When the above conditions (a) and (b) are satisfied and the ratio of the distance D ₁ / the distance D _{2 and} the ratio of the distance D ₃ / the distance D ₂ are within these ranges, the highest electromagnetic wave absorption ability is obtained. It is done. The ratio of the distance D ₁ / the distance D ₂ is preferably 100: 40 to 100: 60, more preferably 100: 45 to 100: 55, and ideally 100: 50. The ratio of the distance D ₃ / the distance D ₂ is more preferably 100: 40 to 100: 60, most preferably 100: 45 to 100: 55, and ideally 100: 50. Distance D ₁ and the distance D ₃ may be the same.

In the first to third electromagnetic wave absorbing films, linear marks are formed on the opposite side of the conductor layer. When the linear trace 12 is formed on the side of the conductor layers 11a, 11b, and 11c of the electromagnetic wave absorbing films 110a, 110b, and 110c as shown in FIG. 21, and the linear trace 12 is an electromagnetic wave as shown in FIG. In any case where the films are formed on the plastic surfaces of the absorbent films 120a, 120b, 120c, the above conditions (a) and (b) must be satisfied, and the ratio of the distance D ₁ / the distance D ₂ is within the above range. is there. The ratio of the distance D ₃ / the distance D ₂ is also preferably within the above range. In the case shown in FIG. 21, the surface resistance of the conductive layers 11a, 11b, and 11c of the electromagnetic wave absorbing films 110a, 110b, and 110c can be adjusted by the linear trace 12, and the electromagnetic wave is attenuated by the gap of the linear trace 12 can get. Further, in the case shown in FIG. 22, there is an advantage that the transparency of the conductor layers 11a, 11b, 11c of the electromagnetic wave absorbing films 120a, 120b is not affected by the linear marks 12. In both cases of FIGS. 21 and 22, as shown in FIG. 23, the first electromagnetic wave absorbing film 110a (120a) / dielectric 30a / second electromagnetic wave absorbing film 110b (120b) / dielectric 30b / third It has a layer structure of electromagnetic wave absorbing film 110c (120c) / dielectric 30c / electromagnetic wave reflector 200.

Sometimes linear scratches 12 are formed, each conductive layer 11a, 11b, the surface resistance of 11c is 100~1000Ω / □, preferably 200~1000Ω / □, 250~800Ω / □, more preferably, the surface resistance of the conductive layer 11a is greater 100 Omega / □ or higher than the surface resistance of the conductive layer 11b, is preferably 200 [Omega / □ or greater, more preferably 300 [Omega / □ or greater. Furthermore, the surface resistance of the conductor layer 11c is preferably 50Ω / □ or more larger than the surface resistance of the conductor layer 11b, more preferably 100Ω / □ or more, most preferably 200Ω / □ or more, most preferably 300Ω / □ or more. Large is particularly preferred. The surface resistance of the conductor layer 11c may be the same as the surface resistance of the conductor layer 11a.

  FIG. 24 (a) to FIG. 24 (f) show examples of combinations of linear marks of three electromagnetic wave absorbing films constituting the electromagnetic wave absorber. By changing the crossing angle θs of the linear marks of the three electromagnetic wave absorbing films 110a (120a), 110b (120b), and 110c (120c) according to the frequency to be absorbed, excellent electromagnetic wave absorbing ability can be obtained.

  In the example shown in FIG. 24 (a), the crossing angle θs of the linear marks in the first and third electromagnetic wave absorbing films 110a (120a) and 110c (120c) is 60 °, and the second electromagnetic wave absorbing film 110b ( The crossing angle θs of the linear marks in 120b) is 90 °. When the crossing angle θs of the linear marks is 60 °, an electromagnetic wave absorbing film having excellent electric field absorption ability is obtained. When the crossing angle θs of the linear marks is 90 °, an electromagnetic wave absorbing film having excellent magnetic field absorption ability is obtained. The electromagnetic wave absorber shown in FIG. 24 (a) is excellent in both electric field absorption ability and magnetic field absorption ability. In the example shown in FIG. 24 (b), conversely, the crossing angle θs of the linear marks in the first and third electromagnetic wave absorbing films 110a (120a) and 110c (120c) is 90 °, and the second electromagnetic wave absorbing film The crossing angle θs of the linear marks at 110b (120b) is 60 °. The electromagnetic wave absorber of this example is also excellent in both electric field absorption capability and magnetic field absorption capability.

  In the example shown in FIG. 24 (c), the crossing angles θs of the linear marks in the first to third electromagnetic wave absorbing films 110a (120a), 110b (120b), and 110c (120c) are all 90 °. In this case, the linear scars in the first and third electromagnetic wave absorbing films 110a (120a) and 110c (120c) intersect with the linear scars in the second electromagnetic wave absorbing film 110b (120b) at 45 °. Is preferred. The electromagnetic wave absorber of this example has an excellent magnetic field absorption ability.

  In the example shown in FIG. 24 (d), the crossing angles θs of the linear marks in the first to third electromagnetic wave absorbing films 110a (120a), 110b (120b), and 110c (120c) are all 60 °. In this case, the direction of the linear marks in the first and third electromagnetic wave absorbing films 110a (120a) and 110c (120c) is orthogonal to the direction of the linear marks in the second electromagnetic wave absorbing film 110b (120b). Is preferred. The electromagnetic wave absorber of this example has an excellent electric field absorption ability.

  In the example shown in FIG. 24 (e) and FIG. 24 (f), a combination of an electromagnetic wave absorbing film having a linear trace crossing angle θs of 90 ° and an electromagnetic wave absorbing film having a linear trace crossing angle θs of 45 ° is used. . Even if an electromagnetic wave absorbing film having a crossing angle θs of 45 degrees is used instead of an electromagnetic wave absorbing film having a line mark crossing angle θs of 60 °, the electromagnetic wave absorber has good electric field absorption ability and magnetic field absorption ability. Is obtained.

  The linear mark crossing angles θs of the exemplary electromagnetic wave absorbing films 110a (120a), 110b (120b), and 110c (120c) were 45 °, 60 °, and 90 °, but the present invention is of course not limited thereto. Other crossing angles θs within 30-90 ° can also be used. Research has shown that the crossing angle θs is preferably 360 / even. Therefore, 30 °, 36 °, 45 °, 60 ° and 90 ° are preferable. Here, since there is a manufacturing error in the intersection angle θs, it is generally within ± 5 °, preferably within ± 3 ° of the target value. For example, when the crossing angle θs is 60 °, it may be in the range of 55 to 65 °. Further, when the crossing angle θs is 90 °, it may be within a range of 85 to 90 °. In the case of an electromagnetic wave absorber having a three-layer electromagnetic wave absorbing film, the linear mark crossing angle θs of the outer electromagnetic wave absorbing film is preferably 60 ° or 90 °.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

Comparative Example 1
An electromagnetic wave absorbing film 100a (surface resistance: 785Ω) formed by forming a 10 nm-thick Ni thin film 11a on a 120 μm-thick PET film 10a from the electromagnetic wave absorber test piece TP (32 cm × 52 cm) shown in FIG. ), An electromagnetic wave absorbing film 100b (surface resistance: 283Ω) formed by forming a 15 nm thick Ni thin film 11b on a 120 μm thick PET film 10b, and an aluminum plate 200 having a thickness of 2 mm. Spacing D ₁ of the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b is 20 mm, the interval D ₂ between the electromagnetic wave absorption film 100b and the aluminum plate 200 was 10 mm.

  The electromagnetic wave absorbing ability of this test piece TP was evaluated using the apparatus shown in FIG. This apparatus includes a dielectric holder 62 having a thickness of 2 cm, a transmitting antenna 63a and a receiving antenna 63b that are 100 cm away from the holder 62, and a network analyzer 64 that is connected to the antennas 63a and 63b. First, an aluminum plate (32 cm x 52 cm x 2 mm) is fixed to the front surface (antenna side) of the holder 62, and the incident angle θi is changed from 10 ° to 60 ° from the antenna 63a at 10 ° intervals. An electromagnetic wave (circularly polarized wave) having a frequency of 0.25 GHz was irradiated at a frequency interval of 0.25 GHz, the reflected wave was received by the antenna 63b, and the reflected power was measured by the network analyzer 64. Next, the test piece TP was fixed to the front surface of the holder 62 instead of the aluminum plate, and the reflected power was measured in the same manner as described above. Assuming that the reflected power measured using an aluminum plate is equal to the incident power, the reflection coefficient (reflected power / incident power) RC is obtained, and the return loss (return loss) is calculated by RL (dB) = 20 log (1 / RC). ) RL (dB) was obtained. Since the return loss at each incident angle θi varies depending on the frequency, the electromagnetic wave absorption obtained at the frequency (peak frequency) when the return loss is maximized was taken as the peak absorption rate.

The measured peak absorption rate and peak frequency are shown in FIG. As is apparent from FIG. 26, the TE wave peak absorptance was about 13 to 38 dB and the TM wave peak absorptance was about 11 to 49 dB in the incident angle range of 10 to 60 °. From this result, the electromagnetic wave absorbing film 100a having the high resistance Ni thin film 11a is arranged on the front side, the electromagnetic wave absorbing film 100b having the low resistance Ni thin film 11b is arranged on the rear side, and the ratio of D ₁ / D ₂ is set. It was found that the 2/1 electromagnetic wave absorber has a high electromagnetic wave absorbing ability.

Example 1
For the electromagnetic wave absorbing film 100a used in Comparative Example 1 , an apparatus having a structure shown in FIG. 12 having pattern rolls 32a and 32b electrodeposited with diamond fine particles having a particle size distribution of 50 to 80 μm was used. A line-shaped trace having a crossing angle of 90 ° was formed on the surface on which 11a was not formed. In addition, an apparatus having the structure shown in FIG. 8 (a) having pattern rolls 2a and 2b in which diamond fine particles having a particle size distribution of 50 to 80 μm are electrodeposited on the electromagnetic wave absorbing film 100b used in Comparative Example 1 is used. Bidirectional traces having a crossing angle of 60 ° were formed on the surface (the surface on which the Ni thin film 11b was not formed). The characteristics of the linear marks in the obtained electromagnetic wave absorbing films 120a and 120b with linear marks were as follows.
Width W range: 0.5-5μm
Average width Wav: 2μm
Range in the lateral direction I: 2 to 30 μm
Average lateral direction interval Iav: 10μm
Average length Lav: 5 mm
Crossing angle θs: 90 ° and 60 °

The electromagnetic wave absorber shown in FIG. 16 was prepared in the same manner as in Comparative Example 1 except that these electromagnetic wave absorbing films 120a and 120b with linear traces were used, and the peak absorption rate in the incident angle range of 10 ° to 60 ° and Peak frequency was measured. The results are shown in FIG. As is clear from FIG. 27, the peak absorption rate of the TE wave was about 15 to 54 dB, and the peak absorption rate of the TM wave was about 12 to 36 dB. In addition, the TE wave peak absorptance was generally higher than that of Comparative Example 1 in this incident angle range. From this result, the electromagnetic wave absorption film 120a having the high resistance Ni thin film 11a is on the front side, the electromagnetic wave absorption film 120b having the low resistance Ni thin film 11b is on the rear side, and the ratio of D ₁ / D ₂ is 2/1 The electromagnetic wave absorbers having linear traces in two directions on the plastic surface side of the respective electromagnetic wave absorption films 120a and 120b have higher electromagnetic wave absorption ability than the electromagnetic wave absorber of Comparative Example 1 in which no linear traces are formed. I understood that.

Comparative Example 2
Separately from Comparative Example 1 , the 10 nm thick Ni thin film 11a formed on the 120 μm thick PET film 10a had a surface resistance of 500Ω. An electromagnetic wave absorber was prepared in the same manner as in Comparative Example 1 except that this electromagnetic wave absorbing film 100a was used on the front side, and the peak absorptance and peak frequency in the incident angle range of 10 ° to 60 ° were the same as in Comparative Example 1. It was measured. The results are shown in FIG. As apparent from FIG. 28, the peak absorption rate of the TE wave was about 14 to 37 dB, and the peak absorption rate of the TM wave was about 12 to 36 dB. From this result, the electromagnetic wave absorbing film 100a having the high resistance Ni thin film 11a is arranged on the front side, the electromagnetic wave absorbing film 100b having the low resistance Ni thin film 11b is arranged on the rear side, and the ratio of D ₁ / D ₂ is set. It was found that the 2/1 electromagnetic wave absorber has a high electromagnetic wave absorbing ability.

Example 2
In the same manner as in Example 1 , two-way linear traces having an intersecting angle of 90 ° were formed on the plastic surface (the surface on which the Ni thin film 11a was not formed) of the electromagnetic wave absorbing film 100a used in Comparative Example 2 . Further, in the same manner as in Example 1 , two-way linear traces having an intersection angle of 60 ° were formed on the plastic surface (the surface on which the Ni thin film 11b was not formed) of the electromagnetic wave absorbing film 100b used in Comparative Example 2 . The electromagnetic wave absorber shown in FIG. 16 was prepared in the same manner as in Comparative Example 1 except that these electromagnetic wave absorbing films 120a and 120b with linear traces were used, and the peak absorption rate in the incident angle range of 10 ° to 60 ° and Peak frequency was measured. The results are shown in FIG. As apparent from FIG. 29, the peak absorption rate of the TE wave was about 15 to 55 dB, and the peak absorption rate of the TM wave was about 12 to 34 dB. In addition, the TE wave peak absorptance was generally higher than that of Comparative Example 2 in this incident angle range. From this result, the electromagnetic wave absorption film 120a having the high resistance Ni thin film 11a is on the front side, the electromagnetic wave absorption film 120b having the low resistance Ni thin film 11b is on the rear side, and the ratio of D ₁ / D ₂ is 2/1 The electromagnetic wave absorbers having linear traces in two directions on the plastic surface side of the respective electromagnetic wave absorbing films 120a and 120b have higher electromagnetic wave absorption ability than the electromagnetic wave absorber of Comparative Example 2 in which no linear traces are formed. I understood that.

Comparative Example 3
Separately from Comparative Example 1 , a 10 nm thick Ni thin film 11b formed on a 120 μm thick PET film 10b had a surface resistance of 300Ω. An electromagnetic wave absorber was prepared in the same manner as in Comparative Example 1 except that this electromagnetic wave absorbing film 100b was used on the rear side, and the peak absorption rate and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. . The results are shown in FIG. As apparent from FIG. 30, the TE wave peak absorptance was about 14 to 46 dB, and the TM wave peak absorptance was about 12 to 42 dB. From this result, the electromagnetic wave absorbing film 100a having the high resistance Ni thin film 11a is arranged on the front side, the electromagnetic wave absorbing film 100b having the low resistance Ni thin film 11b is arranged on the rear side, and the ratio of D ₁ / D ₂ is set. It was found that the 2/1 electromagnetic wave absorber has a high electromagnetic wave absorbing ability.

Comparative Example 4
The distance D ₁ between the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b is 10 mm, the distance D ₂ between the electromagnetic wave absorbing film 100b and the aluminum plate 200 is 20 mm, and the ratio of D ₁ / D ₂ is 1/2. Other than that, an electromagnetic wave absorber was prepared in the same manner as in Comparative Example 3, and the peak absorption rate and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 31, the TE wave peak absorptance was about 8 to 15 dB, and the TM wave peak absorptance was about 15 to 32 dB. In this incident angle range, the peak absorptance of TE wave and TM wave was lower than that of Comparative Example 3 as a whole. From this result, it was found that when the ratio of D ₁ / D ₂ was changed from 2/1 to 1/2, the electromagnetic wave absorbing ability of the electromagnetic wave absorber was relatively lowered. Now, the distance between the case of a high resistance than the electromagnetic wave absorbing film 100b on the rear side electromagnetic wave absorbing film 100a on the front side, the distance D ₁ of the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b is an electromagnetic wave absorbing film 100b and the reflection plate 200 larger than D ₂ it can be seen electromagnetic wave absorbing power of the electromagnetic wave absorber is high.

Comparative Example 5
The distance D ₁ between the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b is 15 mm, the distance D ₂ between the electromagnetic wave absorbing film 100b and the aluminum plate 200 is 15 mm, and the ratio of D ₁ / D ₂ is 1/1. Other than that, an electromagnetic wave absorber was prepared in the same manner as in Comparative Example 3, and the peak absorption rate and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 32, the peak absorption rate of the TE wave was about 16 to 20 dB, and the peak absorption rate of the TM wave was about 20 to 34 dB. From this result, it was found that when the ratio of D ₁ / D ₂ was changed from 2/1 to 1/1, the electromagnetic wave absorbing ability of the electromagnetic wave absorber was relatively lowered. However, the degree of decrease in electromagnetic wave absorption ability was smaller than that of Comparative Example 4 in which the ratio of D ₁ / D ₂ became 1/2.

Comparative Example 6
An electromagnetic wave absorber was prepared in the same manner as in Comparative Example 3 except that an electromagnetic wave absorbing film having a surface resistance of 300Ω was used as the front electromagnetic wave absorbing film 100a, and an electromagnetic wave absorbing film having a surface resistance of 785Ω was used as the electromagnetic wave absorbing film 100b on the rear side. The peak absorptance and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 33, the peak absorption rate of the TE wave was about 10 to 17 dB, and the peak absorption rate of the TM wave was about 12 to 52 dB. From this result, it can be seen that when the electromagnetic wave absorbing film 100a on the front surface side has a lower resistance than the electromagnetic wave absorbing film 100b on the rear surface side, the electromagnetic wave absorbing ability of the electromagnetic wave absorber is reduced to an insufficient level.

Comparative Example 7
The distance D ₁ between the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b is 10 mm, the distance D ₂ between the electromagnetic wave absorbing film 100b and the aluminum plate 200 is 20 mm, and the ratio of D ₁ / D ₂ is 1/2. Other than that, an electromagnetic wave absorber was prepared in the same manner as in Comparative Example 6, and the peak absorption rate and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 34, the TE wave peak absorptance was about 8 to 12 dB, and the TM wave peak absorptance was about 12 to 50 dB. From this result, when the electromagnetic wave absorption film 100a on the front side has a lower resistance than the electromagnetic wave absorption film 100b on the rear side, the ratio of D ₁ / D ₂ is reduced from 2/1 to 1/2. It was found that the performance was further reduced.

Comparative Example 8
The distance D ₁ between the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b is 15 mm, the distance D ₂ between the electromagnetic wave absorbing film 100b and the aluminum plate 200 is 15 mm, and the ratio of D ₁ / D ₂ is 1/1. Other than that, an electromagnetic wave absorber was prepared in the same manner as in Comparative Example 6, and the peak absorption rate and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 35, the TE wave peak absorptance was about 7 to 14 dB, and the TM wave peak absorptance was about 16 to 32 dB. From this result, in the case from the electromagnetic wave absorbing film 100b of an electromagnetic wave absorbing film 100a on the front side rear side of the low resistance, the ratio of D ₁ / D ₂ is from 1/1 to 2/1, the electromagnetic wave absorption of electromagnetic wave absorber It was found that the performance was further reduced. However, the degree of decrease in electromagnetic wave absorption ability was smaller than that of Comparative Example 7 in which the ratio of D ₁ / D ₂ was halved.

Example 3
Bidirectional traces having a crossing angle of 60 ° were formed on the plastic surface of the electromagnetic wave absorbing film 100a having a surface resistance of 785Ω in the same manner as in Example 1 . Further, bi-directional linear traces having a crossing angle of 90 ° were formed in the same manner as in Example 1 on the plastic surface of the electromagnetic wave absorbing film 100b having a surface resistance of 300Ω. The electromagnetic wave absorber shown in FIG. 16 was prepared in the same manner as in Comparative Example 3 except that these electromagnetic wave absorbing films 120a and 120b with linear traces were used, and the peak absorption rate in the incident angle range of 10 ° to 60 ° and Peak frequency was measured. The results are shown in FIG. As is clear from FIG. 36, the peak absorption rate of the TE wave was about 12 to 22 dB, and the peak absorption rate of the TM wave was about 15 to 42 dB. The anisotropy of the TE wave and TM wave peak absorptance was smaller than that of Comparative Example 3 in this incident angle range. From this result, the electromagnetic wave absorption film 120a having the high resistance Ni thin film 11a is on the front side, the electromagnetic wave absorption film 120b having the low resistance Ni thin film 11b is on the rear side, and the ratio of D ₁ / D ₂ is 2/1 Thus, it was found that the electromagnetic wave absorber having the two-way linear traces on the plastic surface side of each of the electromagnetic wave absorbing films 120a and 120b has a small anisotropy and a high electromagnetic wave absorbing ability.

Example 4
The same electromagnetic wave absorber as in Example 3 was prepared except that D1 was 4 mm and D2 was 2 mm, and the electromagnetic wave absorption rate at 5.8 GHz was measured in an incident angle range of 10 ° to 60 °. The results are shown in FIG. As is apparent from FIG. 37, the electromagnetic wave absorption rate of the TE wave was about 12 to 52 dB, and the electromagnetic wave absorption rate of the TM wave was about 4 to 25 dB. From this result, even if D1 and D2 are small, the electromagnetic wave absorbing film 120a having the high resistance Ni thin film 11a is on the front side, and the electromagnetic wave absorbing film 120b having the low resistance Ni thin film 11b is on the rear side, D ₁ / It was found that the electromagnetic wave absorber having a D ₂ ratio of 2/1 and having linear traces in two directions on the plastic surface side of the respective electromagnetic wave absorbing films 120a and 120b has a high electromagnetic wave absorbing ability.

Example 5
In the same manner as in Example 1 , two-way linear marks having a crossing angle of 45 ° were formed on the plastic surface of the electromagnetic wave absorbing film having a surface resistance of 300Ω to produce the electromagnetic wave absorbing film 120b. An electromagnetic wave absorber having the same structure as in Example 4 was prepared except that the electromagnetic wave absorbing film 120a having a surface resistance of 785Ω formed in two directions with a 90 ° crossing angle and the electromagnetic wave absorbing film 120b was combined, and 10 The electromagnetic wave absorptivity at 5.8 GHz was measured in the incident angle range of ° -60 °. The results are shown in FIG. As is clear from FIG. 38, the electromagnetic wave absorption rate of the TE wave was about 16 to 37 dB, and the electromagnetic wave absorption rate of the TM wave was about 4 to 28 dB. From this result, the electromagnetic wave absorption film 120a having the high-resistance Ni thin film 11a is on the front side and the low-resistance Ni even if the crossing angle of the linear trace of one electromagnetic wave absorption film is 45 ° and D1 and D2 are small. The electromagnetic wave absorbing film 120b having the thin film 11b is on the rear side, the ratio of D ₁ / D ₂ is 2/1, and the electromagnetic wave absorbing film having bi-directional linear marks on the plastic surface side of each of the electromagnetic wave absorbing films 120a and 120b The body was found to have a high ability to absorb electromagnetic waves.

Comparative Example 9
The distance D ₁ between the electromagnetic wave absorbing film 120a and the electromagnetic wave absorbing film 120b is 10 mm, the distance D ₂ between the electromagnetic wave absorbing film 120b and the aluminum plate 200 is 20 mm, and the ratio of D ₁ / D ₂ is 1/2. Except that, the electromagnetic wave absorber shown in FIG. 16 was produced in the same manner as in Example 3 . In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As apparent from FIG. 39, the peak absorption rate of the TE wave was about 8 to 16 dB, and the peak absorption rate of the TM wave was about 17 to 28 dB. From this result, it was found that when the ratio of D ₁ / D ₂ was changed from 2/1 to 1/2, the electromagnetic wave absorbing ability of the electromagnetic wave absorber was relatively lowered. Now, the distance between the case of a high resistance than the electromagnetic wave absorbing film 120b on the rear side electromagnetic wave absorbing film 120a on the front side, the distance D ₁ of the electromagnetic wave absorbing film 120a and the electromagnetic wave absorbing film 120b is an electromagnetic wave absorbing film 120b and the reflection plate 200 larger than D ₂ it can be seen electromagnetic wave absorbing power of the electromagnetic wave absorber is high.

Comparative Example 10
The distance D ₁ between the electromagnetic wave absorbing film 120a and the electromagnetic wave absorbing film 120b is 15 mm, the distance D ₂ between the electromagnetic wave absorbing film 120b and the aluminum plate 200 is 15 mm, and the ratio of D ₁ / D ₂ is 1/1. Except that, the electromagnetic wave absorber shown in FIG. 16 was produced in the same manner as in Example 3 . In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 40, the peak absorption rate of the TE wave was about 12 to 22 dB, and the peak absorption rate of the TM wave was about 15 to 42 dB. From this result, it was found that when the ratio of D ₁ / D ₂ was changed from 2/1 to 1/1, the electromagnetic wave absorbing ability of the electromagnetic wave absorber was relatively lowered. However, the degree of decrease in electromagnetic wave absorption ability was smaller than that of Comparative Example 9 in which the ratio of D ₁ / D ₂ became 1/2.

Comparative Example 11
An electromagnetic wave absorber having the same structure as in Example 3 was prepared except that the surface resistance of the electromagnetic wave absorbing film 100a was 300Ω and the surface resistance of the electromagnetic wave absorbing film 100b was 785Ω, and the peak absorption rate in the incident angle range of 10 ° to 60 °. The peak frequency was measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 41, the peak absorption rate of the TE wave was about 11 to 18 dB, and the peak absorption rate of the TM wave was about 15 to 36 dB. From this result, it can be seen that if the surface resistance of the electromagnetic wave absorbing film 100a on the front side is smaller than the surface resistance of the electromagnetic wave absorbing film 100b on the rear side, a sufficiently high electromagnetic wave absorbing ability cannot be obtained even if linear marks are formed. .

Comparative Example 12
The same electromagnetic wave absorbing film 100c as the electromagnetic wave absorbing film 100a is disposed between the electromagnetic wave absorbing film 100b of the electromagnetic wave absorber of Comparative Example 1 and the aluminum plate 200, and the interval D ₁ between the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b, and distance D ₂ between the electromagnetic wave absorption film 100b and the electromagnetic wave absorbing film 100c, the electromagnetic wave absorption film 100c and the interval D ₃ each 20 mm of the aluminum plate 200, 10 mm, and a _{20 mm, D 1 / D 2} / D 3 The electromagnetic wave absorber shown in FIG. In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 42, the peak absorption rate of the TE wave was about 12 to 28 dB, and the peak absorption rate of the TM wave was about 26 to 36 dB. Also, the TM wave peak absorptance was generally high in this incident angle range. From this result, even in the case of an electromagnetic wave absorber having three electromagnetic wave absorbing films, if the surface resistance of the first electromagnetic wave absorbing film 100a is larger than the surface resistance of the second electromagnetic wave absorbing film 100b, excellent electromagnetic wave absorbing ability is obtained. You can see that It can also be seen that setting the ratio of D ₁ / D ₂ to 2/1 and the ratio of D ₃ / D ₂ to 2/1 is preferable for obtaining high electromagnetic wave absorption ability.

Comparative Example 13
The distances D ₁ , D ₂ and D ₃ were 10 mm, 10 mm and 30 mm, respectively, and the ratio of D ₁ / D ₂ / D ₃ was 1/1/3, as in Comparative Example 12, and FIG. The electromagnetic wave absorber shown in FIG. In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 43, the TE wave peak absorptance was about 12 to 28 dB, and the TM wave peak absorptance was about 26 to 36 dB. From this result, even in the case of an electromagnetic wave absorber having three electromagnetic wave absorbing films, if the surface resistance of the first electromagnetic wave absorbing film 100a is larger than the surface resistance of the second electromagnetic wave absorbing film 100b, excellent electromagnetic wave absorbing ability is obtained. You can see that

Comparative Example 14
An electromagnetic wave absorber shown in FIG. 19 was produced in the same manner as in Comparative Example 12 except that the surface resistances of the electromagnetic wave absorbing film 100a, the electromagnetic wave absorbing film 100b, and the electromagnetic wave absorbing film 100c were 283Ω, 785Ω, and 283Ω, respectively. In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 44, the peak absorption rate of the TE wave was about 8 to 15 dB, and the peak absorption rate of the TM wave was about 15 to 27 dB. From this result, even in the case of an electromagnetic wave absorber having three electromagnetic wave absorbing films, if the surface resistance of the first electromagnetic wave absorbing film 100a is smaller than the surface resistance of the second electromagnetic wave absorbing film 100b, the electromagnetic wave absorbing ability is sufficiently high. It can be seen that cannot be obtained.

Example 6
Electromagnetic wave absorbing film 100a, electromagnetic wave absorbing film 100b, and electromagnetic wave absorbing film 100c, in the same manner as in Comparative Example 12 , except that the crossing angles are 60 °, 90 ° and 60 °, respectively, forming linear traces in two directions. An electromagnetic wave absorber shown in FIG. 22 was produced. In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 45, the peak absorption rate of the TE wave was 12 to 32 dB, and the peak absorption rate of the TM wave was about 22 to 52 dB. In this incident angle range, the peak absorptance of TM wave was high overall. From this result, even in the case of an electromagnetic wave absorber having three electromagnetic wave absorbing films, if the surface resistance of the first electromagnetic wave absorbing film 100a is larger than the surface resistance of the second electromagnetic wave absorbing film 100b, excellent electromagnetic wave absorbing ability is obtained. You can see that It can also be seen that setting the ratio of D ₁ / D ₂ to 2/1 and the ratio of D ₃ / D ₂ to 2/1 is preferable for obtaining high electromagnetic wave absorption ability.

Comparative Example 15
The intervals D ₁ , D _2, and D ₃ were 20 mm, 20 mm, and 20 mm, respectively, and the ratio of D ₁ / D ₂ / D ₃ was 1/1/1, as in Example 6, and FIG. The electromagnetic wave absorber shown in FIG. In the incident angle range of 10 ° to 60 °, the peak absorption rate and peak frequency of this electromagnetic wave absorber were measured in the same manner as in Comparative Example 1 . The results are shown in FIG. As is clear from FIG. 46, the TE wave peak absorptance was about 13 to 43 dB, and the TM wave peak absorptance was about 16 to 39 dB. From this result, even in the case of an electromagnetic wave absorber having three electromagnetic wave absorbing films, if the surface resistance of the first electromagnetic wave absorbing film 100a is larger than the surface resistance of the second electromagnetic wave absorbing film 100b, excellent electromagnetic wave absorbing ability is obtained. You can see that However, the electromagnetic wave absorption ability was inferior to that of Example 6 in which the ratio of D ₁ / D ₂ was 2/1 and the ratio of D ₃ / D ₂ was 2/1.

Comparative Example 16
The electromagnetic wave absorber shown in FIG. 22 was prepared in the same manner as in Example 6 except that the surface resistances of the electromagnetic wave absorbing film 120a, the electromagnetic wave absorbing film 120b, and the electromagnetic wave absorbing film 120c were 283Ω, 785Ω, and 283Ω, respectively, and 10 ° -60 ° The peak absorptance and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range. The results are shown in FIG. As is clear from FIG. 47, the peak absorption rate of the TE wave was about 8 to 17 dB, and the peak absorption rate of the TM wave was about 17 to 25 dB. From this result, even in the case of an electromagnetic wave absorber having three electromagnetic wave absorbing films having linear marks, it is sufficient if the surface resistance of the front electromagnetic wave absorbing film 120a is smaller than the surface resistance of the second electromagnetic wave absorbing film 120b. It can be seen that high electromagnetic wave absorbing ability cannot be obtained.

Comparative Example 17
An electromagnetic wave absorber having the same structure as Comparative Example 1 was prepared except that the surface resistance of the electromagnetic wave absorbing film 100a was 228Ω and the surface resistance of the electromagnetic wave absorbing film 100b was 137Ω (Ni thin film thickness: 20 nm), and 10 ° to 60 ° The peak absorption rate and peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of °. The results are shown in FIG. As is clear from FIG. 48, the peak absorption rate of the TE wave was about 10 to 38 dB, and the peak absorption rate of the TM wave was about 15 to 45 dB. Moreover, the electromagnetic wave absorptivity at 2.5 GHz was measured in an incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 49, the TE wave absorptance was about 7 to 16 dB, and the TM wave peak absorptance was about 5 to 23 dB. From these results, it can be seen that when the surface resistance of the electromagnetic wave absorbing film 100a on the front surface side is 50Ω or more larger than the surface resistance of the electromagnetic wave absorbing film 100b on the rear surface side, sufficiently high electromagnetic wave absorbing ability can be obtained.

Comparative Example 18
An electromagnetic wave absorber having the same configuration as that of Comparative Example 17 except that the arrangement order of the electromagnetic wave absorbing film 100a and the electromagnetic wave absorbing film 100b was reversed, and the peak absorption rate and the peak frequency were compared in an incident angle range of 10 ° to 60 °. Measured as in 1 . The results are shown in FIG. As is clear from FIG. 50, the peak absorption rate of the TE wave was about 6 to 8 dB, and the peak absorption rate of the TM wave was about 8 to 22 dB. Moreover, the electromagnetic wave absorptivity at 2.5 GHz was measured in an incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 51, the absorption rate of the TE wave was about 5.5 to 7.5 dB, and the peak absorption rate of the TM wave was about 7.5 to 11.5 dB. From these results, it can be seen that when the surface resistance of the electromagnetic wave absorbing film 100a on the front surface side is smaller than the surface resistance of the electromagnetic wave absorbing film 100b on the rear surface side, sufficiently high electromagnetic wave absorbing ability cannot be obtained.

Comparative Example 19
An electromagnetic wave absorber having the same structure as Comparative Example 1 except that the surface resistance of the electromagnetic wave absorbing film was set to 500Ω and the surface resistance of the electromagnetic wave absorbing film 100b was set to 300Ω, and an electromagnetic wave at 2.5 GHz in an incident angle range of 10 ° to 60 °. Absorptivity was measured. The results are shown in FIG. As is clear from FIG. 52, the TE wave absorptance was about 12 to 27 dB, and the TM wave peak absorptance was about 4 to 25 dB. From these results, it can be seen that when the surface resistance of the electromagnetic wave absorbing film 100a on the front surface side is larger than the surface resistance of the electromagnetic wave absorbing film 100b on the rear surface side, sufficiently high electromagnetic wave absorbing ability can be obtained at 2.5 GHz.

Example 7
Comparative example except that a two-way linear mark with a crossing angle of 60 ° is formed on the plastic surface of the electromagnetic wave absorbing film 100a, and a two-way linear mark with a crossing angle of 90 ° is formed on the plastic surface of the electromagnetic wave absorbing film 100b. An electromagnetic wave absorber having the same configuration as that of 19 was prepared, and the electromagnetic wave absorption rate at 5.8 GHz was measured in an incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 53, the electromagnetic wave absorption rate of TE waves was about 17 to 53 dB, and the electromagnetic wave absorption rate of TM waves was about 4 to 26 dB. From this result, if the surface resistance of the electromagnetic wave absorbing film 100a on the front side is larger than the surface resistance of the electromagnetic wave absorbing film 100b on the rear side, a sufficiently high electromagnetic wave absorbing ability can be obtained at 5.8 GHz even when linear traces are formed. I understand that.

Comparative Example 20
As shown in FIG. 6 (a), two electromagnetic wave absorbing film pieces 100a ′ having a surface resistance of 785Ω and one electromagnetic wave absorbing film piece 100b ′ having a surface resistance of 283Ω are arranged without gaps, and an average of 443Ω is obtained. A composite electromagnetic wave absorbing film 130a having a surface resistance was produced. Similarly, two electromagnetic wave absorbing film pieces 100a ′ having a surface resistance of 283Ω and one electromagnetic wave absorbing film piece 100b ′ having a surface resistance of 783Ω are arranged without gaps, and composite electromagnetic wave absorption having an average surface resistance of 367Ω. A film 130b was produced. An electromagnetic wave absorber having the same configuration as that of Comparative Example 1 except that these composite electromagnetic wave absorbing films 130a and 130b were used was produced, and an electromagnetic wave absorption rate at 2.5 GHz was measured in an incident angle range of 10 ° to 60 °. The results are shown in FIG. As apparent from FIG. 54, the electromagnetic wave absorption rate of the TE wave was about 12 to 33 dB, and the electromagnetic wave absorption rate of the TM wave was about 3 to 19 dB. Further, the peak absorption rate and the peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As apparent from FIG. 55, the peak absorption rate of the TE wave was about 16 to 40 dB, and the peak absorption rate of the TM wave was about 11 to 22 dB. From these results, even if a composite electromagnetic wave absorbing film consisting of a plurality of electromagnetic wave absorbing film pieces is used, the surface resistance of the composite electromagnetic wave absorbing film 130a on the front side is larger than the surface resistance of the composite electromagnetic wave absorbing film 130b on the rear side. It can be seen that a sufficiently high electromagnetic wave absorbing ability can be obtained.

Comparative Example 21
As shown in FIG. 6 (a), two electromagnetic wave absorbing film pieces 100a ′ having a surface resistance of 300Ω and one electromagnetic wave absorbing film piece 100b ′ having a surface resistance of 500Ω are arranged without gaps, and an average of 331Ω is obtained. A composite electromagnetic wave absorbing film 130b having a surface resistance was produced. A composite electromagnetic wave absorbing film 130a having an average surface resistance of 443Ω prepared in Comparative Example 20 was prepared, and an electromagnetic wave absorber having the same structure as Comparative Example 20 was prepared except that the composite electromagnetic wave absorbing film 130b having an average surface resistance of 331Ω was combined. The peak absorption rate and the peak frequency were measured in the same manner as in Comparative Example 1 in the incident angle range of 10 ° to 60 °. The results are shown in FIG. As is clear from FIG. 56, the peak absorption rate of the TE wave was about 16 to 41 dB, and the peak absorption rate of the TM wave was about 10 to 21 dB. Compared with the peak absorption rate of Comparative Example 20, the peak absorption rate of Comparative Example 21 was slightly higher. From these results, it can be seen that when the surface resistance of the composite electromagnetic wave absorbing film 130a on the front surface side is 100Ω or more higher than the surface resistance of the composite electromagnetic wave absorbing film 130b on the rear surface side, higher electromagnetic wave absorbing ability can be obtained.

The configurations of the electromagnetic wave absorbers of Examples and Comparative Examples are summarized in Table 1 below.

Table 1 (continued)

  Although the present invention has been described in detail with reference to the drawings, the present invention is of course not limited thereto, and various modifications can be made within the scope of the present invention. For example, not only a combination of electromagnetic wave absorbing films without linear traces, or an electromagnetic wave absorbing film having linear traces, but also an electromagnetic wave absorbing film without linear traces and an electromagnetic wave absorbing film having linear traces. Are also within the scope of the present invention.

100 ... Electromagnetic wave absorbing film
100a, 100b, 100c ... electromagnetic wave absorbing film without linear traces
110a, 110b, 110c ... Electromagnetic wave absorbing film having linear traces on the conductor layer
120a, 120b, 120c ... Electromagnetic wave absorbing film with linear marks on the plastic surface
130 ... Composite electromagnetic wave absorbing film comprising a plurality of electromagnetic wave absorbing film pieces without linear traces
140, 150 ... Composite electromagnetic wave absorbing film comprising a plurality of electromagnetic wave absorbing film pieces having linear marks
10, 10a, 10b, 10c ... Plastic film
11, 11a, 11b, 11c ... Conductor layer (metal thin film)
12, 12a, 12b, 12c, 12d ... linear marks
13a, 13b ... Protective layer
2a, 2b, 2c, 2d ... Pattern roll
3a, 3b, 3c, 3d, 3e ... Presser roll
30a, 30b, 30c ・ ・ ・ Dielectric
200 ... Reflector

Claims (2)

An electromagnetic wave absorber formed by laminating a plurality of electromagnetic wave absorbing films through a dielectric before an electromagnetic wave reflector,
Each electromagnetic wave absorbing film is formed by forming a conductor layer on one side of a plastic film,
The conductive layer of each electromagnetic wave absorbing film has a surface resistance in the range of 100 to 1000 Ω / □, and the surface resistance of the conductive layer of the previous electromagnetic wave absorbing film is the surface of the conductive layer of the next electromagnetic wave absorbing film. 100 Ω / □ or more larger than the resistance
(a) When the number of the electromagnetic wave absorbing films is two, the ratio between the distance between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film and the distance between the second electromagnetic wave absorbing film and the electromagnetic wave reflector is 100: 30 to 100: 70, and (b) when there are three or more electromagnetic wave absorbing films, an interval between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film, and the second electromagnetic wave absorbing film, The ratio of the distance to the third electromagnetic wave absorbing film is 100: 30 to 100: 70,
A number of intermittent linear traces substantially parallel with irregular widths and intervals are formed in a plurality of directions on the plastic film side of the electromagnetic wave absorbing film,
90% or more of the width of the linear traces is in the range of 0.1 to 100 μm, and the average is 1 to 50 μm, and the interval of the linear traces is in the range of 0.1 to 200 μm, and the average is 1 to 100 μm. electromagnetic wave absorber characterized in that there. 2. The electromagnetic wave absorber according to claim 1, wherein the linear traces of each electromagnetic wave absorption film are oriented in two directions, and the crossing angle is 30 to 90 °.

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