Electromagnetic wave absorbing film, device for producing same, and near-field electromagnetic wave absorber

Abstract

The invention relates to an electromagnetic wave absorbing film, an apparatus for manufacturing the same, and a near-field electromagnetic wave absorber. The electromagnetic wave absorbing film has a plastic film and a metal thin film formed on one surface of the plastic film, the metal thin film has a plurality of substantially parallel linear traces formed in two directions at irregular widths and intervals, and the linear traces have high-density regions and low-density regions alternately in each direction. The high-density area is in a grid shape through intersection of linear traces in two directions.

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave absorbing film and a near-field electromagnetic wave absorber which have high radiated noise absorbing capability in a wide frequency range of 100 MHz to 5 GHz and can be used without grounding, and an apparatus for manufacturing the electromagnetic wave absorbing film. Background Art

[0002] In order to prevent erroneous operation caused by electromagnetic wave noise emitted by electronic components in various communication devices or electronic devices, various electromagnetic wave absorbers have been put into practical use. Under such circumstances, the inventor proposed a metal film-plastic composite film with linear traces and reduced anisotropy of electromagnetic wave absorption ability through Japanese Patent No. 4685977, characterized in that it has a plastic film and a single-layer or multi-layer metal film arranged on at least one side of the plastic film, and a plurality of substantially parallel and discontinuous linear traces are formed on the metal film in two directions with irregular widths and intervals. Japanese Patent No. 4685977 records that if multiple metal film-plastic composite films with linear traces are stacked directly or via a dielectric layer, the electromagnetic wave absorption ability will be improved. Although the metal film-plastic composite film with linear traces in Japanese Patent No. 4685977 has excellent conduction noise absorption ability in a wide frequency range, it may not be sufficient for the radiation noise absorption ability at a frequency band below 1 GHz.

[0003] Japanese Patent No. 5203295 discloses an electromagnetic wave absorbing film, characterized in that the electromagnetic wave absorbing film is formed by laminating a magnetic composite film having a plastic film and a magnetic metal thin film provided on at least one side of the plastic film, and a non-magnetic composite film having a plastic film and a non-magnetic metal thin film provided on at least one side of the plastic film, wherein a plurality of substantially parallel and discontinuous linear traces are formed in at least one direction with irregular lengths, widths and intervals on at least one metal film of the magnetic metal thin film and the non-magnetic metal thin film, wherein the linear traces have an average width of 1 to 100 μm and an average interval of 1 to 100 μm, and more than 90% of the linear traces have a width in the range of 0.1 to 1,000 μm. Japanese Patent No. 5203295 states that an electromagnetic wave absorbing film having a surface resistance of 1 to 377 Ω / □ for the magnetic metal thin film and a surface resistance of 377 to 10,000 Ω / □ for the non-magnetic metal thin film has excellent electromagnetic wave noise absorption in the near field.

[0004] However, it is known that the electromagnetic wave noise absorption in Japanese Patent No. 5203295 is so-called conduction noise absorption, and there is a frequency that maximizes the radiation noise in a wide frequency range from less than 1 GHz to several GHz. Therefore, when the electromagnetic wave absorbing film is put into practical use, grounding (GND) is required to prevent the radiation of the maximized noise.

[0005] International Publication No. WO2012 / 090586 discloses a near-field electromagnetic wave absorber, which is formed by bonding multiple electromagnetic wave absorbing films, and the multiple electromagnetic wave absorbing films are formed by forming a metal film on one side of a plastic film, characterized in that the metal film of at least one electromagnetic wave absorbing film not only has a thin film layer of a magnetic metal, but also has a plurality of substantially parallel and discontinuous linear traces formed in two directions with irregular widths and intervals on the metal film of at least one electromagnetic wave absorbing film. International Publication No. WO2012 / 090586 records that the metal film of each electromagnetic wave absorbing film has a surface resistance in the range of 50 to 1500Ω / □ after the linear traces are formed. The near-field electromagnetic wave absorber also has excellent conduction noise absorption capability in a wide frequency range from less than 1GHz to several GHz. However, it is known that the near-field electromagnetic wave absorber of International Publication No. WO2012 / 090586 has a frequency at which the radiation noise is maximized. Therefore, similarly to Japanese Patent No. 5203295, when the near-field electromagnetic wave absorber is put to practical use, grounding (GND) is required in order to prevent radiation of maximized noise.

[0006] Japanese Patent No. 5559668 discloses an electromagnetic wave absorber which is formed by laminating a plurality of electromagnetic wave absorbing films via a dielectric in front of an electromagnetic wave reflector. The electromagnetic wave absorber is characterized in that:

[0007] Each electromagnetic wave absorbing film is formed by forming a conductive layer on one side of a plastic film.

[0008] The conductive layer of each electromagnetic wave absorbing film has a surface resistance in the range of 100 to 1000 Ω / □.

[0009] The surface resistance of the conductive layer of the front electromagnetic wave absorbing film is greater than the surface resistance of the conductive layer of the next electromagnetic wave absorbing film by more than 100Ω / □.

[0010] (a) when there are two electromagnetic wave absorbing films, the ratio of the distance between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film to the distance between the second electromagnetic wave absorbing film and the electromagnetic wave reflector is 100:30 to 80:70,

[0011] (b) when there are three or more electromagnetic wave absorbing films, the ratio of the interval between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film to the interval between the second electromagnetic wave absorbing film and the third electromagnetic wave absorbing film is 100:30 to 80:70,

[0012] A plurality of substantially parallel and discontinuous linear traces are formed in two directions with irregular widths and intervals on the conductive layer of the electromagnetic wave absorbing film.

[0013] More than 90% of the widths of the linear traces are within a range of 0.1 to 100 μm and are 1 to 50 μm on average, and intervals between the linear traces are within a range of 0.1 to 200 μm and are 1 to 100 μm on average.

[0014] Japanese Patent No. 5559668 states that since the surface resistance of the conductive layer of the front electromagnetic wave absorbing film is greater than that of the conductive layer of the next electromagnetic wave absorbing film by more than 100Ω / □, it has a significantly higher electromagnetic wave absorbing capacity and the anisotropy of the electromagnetic wave absorbing capacity is reduced compared with the case where multiple electromagnetic wave absorbing films with the same surface resistance are simply stacked. However, since the electromagnetic wave absorber has a structure in which multiple electromagnetic wave absorbing films are stacked via a dielectric in front of an electromagnetic wave reflector (aluminum plate), it is suitable for ETC, FRID and the like, but cannot be used as a near-field electromagnetic wave absorber attached to electronic components and the like. Summary of the invention

[0015] Therefore, a first object of the present invention is to provide an electromagnetic wave absorbing film which has a high radiated noise absorbing capability in a wide frequency range of, for example, 100 MHz to 5 GHz and can be used without being grounded.

[0016] A second object of the present invention is to provide a near-field electromagnetic wave absorber which has a high radiation noise absorption capability in a wide frequency range of, for example, 100 MHz to 5 GHz and can be used without being grounded.

[0017] A third object of the present invention is to provide an apparatus capable of efficiently manufacturing the above-mentioned electromagnetic wave absorbing film.

[0018] As a result of in-depth research in view of the above-mentioned purpose, the inventors found the following situation and thus conceived the present invention, which is as follows: (a) if linear traces are intermittently formed in a manner in which areas with high density of linear traces and areas with low density are alternately arranged in each of two directions, instead of forming linear traces in two directions on the entire surface of the metal film, the high-density areas of the linear traces are distributed in a grid shape by the intersection of the linear traces in the two directions, and an electromagnetic wave absorption film with high radiation noise absorption ability in a wide frequency range of, for example, 100 MHz to 5 GHz is obtained; (b) by combining an electromagnetic wave absorption film having high-density areas of linear traces in a grid shape and an electromagnetic wave absorption film having linear traces in two directions formed on the entire surface of the metal film, a near-field electromagnetic wave absorber having higher radiation noise absorption ability in a wide frequency range of, for example, 100 MHz to 5 GHz can be obtained; and (c) in an apparatus for forming linear traces in two directions on the entire surface of the metal film, by changing the shape or driving method of the pattern roller, areas with high density of linear traces and areas with low density can be alternately formed in each of the two directions.

[0019] That is, the electromagnetic wave absorbing film of the present invention comprises a plastic film and a metal thin film formed on one side of the plastic film.

[0020] The metal film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals.

[0021] In each direction, there are alternately high-density regions where the linear traces are formed at high density and low-density regions where the linear traces are formed at low density,

[0022] The high-density area of ​​the linear traces is distributed in a lattice shape by the intersection of the linear traces in two directions.

[0023] Preferably, in each direction, the surface resistivity of the high-density region is 30 to 200 Ω / □, and the surface resistivity of the low-density region is 0 to 20 Ω / □.

[0024] Preferably, the length ratio of the high-density region to the low-density region in each direction is 5 / 1 to 1 / 5.

[0025] Preferably, in each direction, the length of the high-density region is 0.2-10 mm, and the length of the low-density region is 0.2-10 mm.

[0026] The first device of the present invention for manufacturing the above-mentioned electromagnetic wave absorbing film is characterized by comprising:

[0027] two pattern rollers;

[0028] a mechanism for conveying the plastic film in a manner that the metal film is in sliding contact with two pattern rollers; and

[0029] A pressing roller pressing the metal film against the pattern roller,

[0030] The two pattern rollers are inclined to opposite sides of the plastic film in the surface in sliding contact with the metal film.

[0031] Linear trace forming areas and linear trace non-forming areas are alternately arranged on the outer circumferential surface of each pattern roller in the circumferential direction.

[0032] The linear trace forming region has a plurality of high hardness particles on the surface.

[0033] In one embodiment of the present invention, the linear trace non-formation region of the pattern roller is retracted radially inward from the linear trace formation region. Preferably, the retraction distance Dh of the linear trace non-formation region is 1 mm or more.

[0034] In another embodiment of the present invention, the linear trace non-forming region does not have high hardness particles. In this case, the radius of the linear trace non-forming region may be the same as or smaller than the radius of the linear trace forming region.

[0035] The second device of the present invention for manufacturing the electromagnetic wave absorbing film is characterized by comprising:

[0036] Two pattern rollers, having a plurality of high hardness particles on the entire outer circumference;

[0037] a mechanism for conveying the plastic film along the pattern roller; and

[0038] The pressing rollers are arranged on both sides of each pattern roller.

[0039] The two pattern rollers are inclined to opposite sides of the plastic film in the surface in sliding contact with the metal film.

[0040] The second device includes a device for driving each pattern roller and / or a pressing roller on both sides of each pattern roller in a direction perpendicular to the metal film so that each pattern roller intermittently slides in contact with the metal film.

[0041] The near-field electromagnetic wave absorber of the present invention comprises at least one layer of plastic film and a first metal film and a second metal film, and is characterized in that:

[0042] The first metal film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, the linear traces alternately having high-density regions and low-density regions in each direction, and the high-density regions are distributed in a lattice shape on the entire surface of the first metal film due to the intersection of the linear traces in two directions.

[0043] A plurality of substantially parallel and discontinuous linear traces are formed on the entire surface of the second metal film in two directions with irregular widths and intervals.

[0044] Preferably, in the near-field electromagnetic wave absorber of the present invention, in each direction of the linear traces of the first metal film, the surface resistivity of the high-density area is 30 to 200 Ω / □, and the surface resistivity of the low-density area is 0 to 20 Ω / □.

[0045] Preferably, in the near-field electromagnetic wave absorber of the present invention, the length ratio of the high-density region to the low-density region in each direction on the first metal film is 5 / 1 to 1 / 5.

[0046] Preferably, in the near-field electromagnetic wave absorber of the present invention, the length of the high-density region in each direction on the first metal film is 0.2-10 mm, and the length of the low-density region is 0.2-10 mm.

[0047] Preferably, the near-field electromagnetic wave absorber of the present invention comprises: (a) a first metal film with linear traces, having a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and alternatingly having high-density regions in which the linear traces are formed with high density and low-density regions in which the linear traces are formed with low density in each direction, and the high-density regions are distributed in a lattice shape by the intersection of the linear traces in two directions; and (b) a second metal film with linear traces, having a plurality of substantially parallel and discontinuous linear traces in two directions formed on the entire surface with irregular widths and intervals.

[0048] Preferably, in the near-field electromagnetic wave absorber of the present invention,

[0049] The first metal film comprises: a first linear trace group having the high-density area of ​​the linear traces and the low-density area of ​​the linear traces alternately in a first direction; and a second linear trace group having the high-density area of ​​the linear traces and the low-density area of ​​the linear traces alternately in a second direction different from the first direction,

[0050] Due to the overlap of the first linear trace group and the second linear trace group, overlapping portions of the high-density regions, overlapping portions of the high-density regions and the low-density regions, and overlapping portions of the low-density regions are formed on the first metal film.

[0051] The repeated parts of the high-density regions are distributed in a dotted pattern.

[0052] The repeated parts of the high-density regions and the repeated parts of the high-density regions and the low-density regions are combined to form a lattice pattern.

[0053] The overlapping parts of the low-density regions are distributed in a dotted pattern.

[0054] Preferably, the near-field electromagnetic wave absorber of the first embodiment of the present invention has a structure formed by bonding a first electromagnetic wave absorbing film and a second electromagnetic wave absorbing film, wherein the first electromagnetic wave absorbing film has the first metal film on a single side of a plastic film, and the second electromagnetic wave absorbing film has the second metal film on a single side of a plastic film.

[0055] Preferably, in the near-field electromagnetic wave absorber according to the first embodiment of the present invention, the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film are bonded together with the first metal thin film and the second metal thin film being inside.

[0056] Preferably, the near-field electromagnetic wave absorber according to the second embodiment of the present invention includes the first metal thin film and the second metal thin film on both sides of a plastic film.

[0057] Preferably, in the electromagnetic wave absorbing film and the near-field electromagnetic wave absorber of the present invention, the crossing angle of the linear traces in two directions is 30 to 90°.

[0058] Preferably, in the electromagnetic wave absorbing film and the near-field electromagnetic wave absorber of the present invention, the thickness of the metal thin film is 20 to 100 nm.

[0059] Preferably, in the electromagnetic wave absorbing film and the near-field electromagnetic wave absorber of the present invention, the metal thin film is made of aluminum.

[0060] Preferably, in the electromagnetic wave absorbing film and the near-field electromagnetic wave absorber of the present invention, the width W of the linear traces is in the range of 0.1 to 100 μm and is 1 to 50 μm on average, and the interval I of the linear traces is in the range of 0.1 to 500 μm and is 1 to 200 μm on average.

[0061] The electromagnetic wave absorbing film of the present invention is formed by overlapping a metal film with a group of linear traces in two directions of high-density areas and low-density areas having linear traces alternately, and has a high-density area. The linear traces are distributed in a grid-like manner, so it has a high radiation noise absorption capacity in a wide frequency range of 100MHz to 5GHz. In addition, the near-field electromagnetic wave absorber of the present invention is formed by combining an electromagnetic wave absorbing film in which high-density linear trace areas are distributed in a grid-like manner and an electromagnetic wave absorbing film in which linear traces are formed on the entire surface of the metal film, so it has a higher radiation noise absorption capacity. The electromagnetic wave absorbing film and near-field electromagnetic wave absorber of the present invention having such characteristics can efficiently suppress electromagnetic wave noise by being attached to electronic components of various electronic devices and communication devices such as personal computers, mobile phones, and smart phones without grounding.

[0062] The device of the present invention is obtained by (a) replacing the pattern roller in a device for forming linear marks on the entire surface of a metal film with a pattern roller having linear mark forming areas and linear mark non-forming areas alternately arranged in a circumferential direction on the outer surface, or by (b) adding a device for driving the pattern roller and at least one of the pressing rollers on both sides of the pattern roller in a direction perpendicular to the metal film to the device for forming linear marks on the entire surface of the metal film. Therefore, the electromagnetic wave absorbing film of the present invention can be effectively manufactured with a relatively simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] FIG. 1( a ) is a plan view schematically showing an example of a first linear trace group constituting the electromagnetic wave-absorbing film of the present invention.

[0064] FIG. 1( b ) is a cross-sectional view taken along line AA of FIG. 1( a ).

[0065] Figure 2 This is a plan view schematically showing another example of the first linear trace group constituting the electromagnetic wave-absorbing film of the present invention.

[0066] Figure 3 It is a plan view schematically showing an example of the second linear trace group constituting the electromagnetic wave absorbing film of the present invention.

[0067] Figure 4 This is a plan view schematically showing an example of the electromagnetic wave absorbing film of the present invention.

[0068] Figure 5 It is schematically indicated Figure 4 A plan view of section A in the high-density repeating section is shown.

[0069] FIG6(a) is a cross-sectional view showing an example of the near-field electromagnetic wave absorber according to the first embodiment of the present invention.

[0070] FIG6(b) is a cross-sectional view showing the arrangement of the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film constituting the near-field electromagnetic wave absorber shown in FIG6(a).

[0071] FIG6(c) is a plan view showing an example of a metal thin film with linear traces of the second electromagnetic wave-absorbing film.

[0072] Figure 7 This is a cross-sectional view showing the arrangement of the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film constituting another example of the near-field electromagnetic wave absorber according to the first embodiment of the present invention.

[0073] Figure 8 It is a cross-sectional view showing a near-field electromagnetic wave absorber according to a second embodiment of the present invention.

[0074] FIG. 9( a ) is a perspective view showing an example of a manufacturing apparatus for the second electromagnetic wave-absorbing film used in the present invention.

[0075] FIG9(b) is a top view showing the device of FIG9(a).

[0076] FIG9(c) is a BB cross-sectional view of FIG9(b).

[0077] FIG9(d) is a partially enlarged plan view for explaining the principle of forming a linear trace inclined with respect to the film running direction.

[0078] FIG9(e) is a partial plan view showing the inclination angles of the pattern roller and the pressing roller relative to the film in the apparatus of FIG9(a).

[0079] Fig.10 It is a perspective view showing another example of the manufacturing apparatus of the second electromagnetic wave-absorbing film of the present invention.

[0080] FIG. 11( a ) is a schematic cross-sectional view showing an example of a pattern roll used in a first apparatus for producing a first electromagnetic wave-absorbing film of the present invention.

[0081] FIG. 11( b ) is a partially enlarged cross-sectional view showing a linear trace formation region of the pattern roller shown in FIG. 11( a ).

[0082] Fig.12 This is a partial cross-sectional view of the linear trace formation region and the linear trace non-formation region of the pattern roller shown in FIG. 11( a ) developed in the circumferential direction.

[0083] Fig.13 This is a schematic cross-sectional view showing another example of the pattern roll used in the first apparatus for producing the first electromagnetic wave-absorbing film of the present invention.

[0084] FIG. 14( a ) is a schematic diagram showing a state in which a pattern roller is in a raised position in a second manufacturing apparatus for manufacturing the first electromagnetic wave-absorbing film of the present invention.

[0085] FIG14(b) is a schematic diagram showing a state where the pattern roller is in a lowered position in the second manufacturing apparatus for manufacturing the first electromagnetic wave-absorbing film of the present invention.

[0086] Fig.15 This is a microscope photograph of the first electromagnetic wave-absorbing film of Example 1.

[0087] FIG. 16( a ) is a plan view showing a system for evaluating the conduction noise absorption capability of an electromagnetic wave absorbing film (near-field electromagnetic wave absorber).

[0088] FIG16(b) is a cross-sectional view showing a system for evaluating the conduction noise absorption capability of an electromagnetic wave absorbing film (near-field electromagnetic wave absorber).

[0089] Fig.17 is the noise absorption rate P of the first electromagnetic wave absorbing film of Example 1 loss / P in of charts.

[0090] Fig.18 This is a photograph showing the accumulated radiation noise of the first electromagnetic wave-absorbing film of Example 1 in the range of 100 MHz to 5 GHz.

[0091] Fig.19 The noise absorption rate P of the near-field electromagnetic wave absorber of Example 2 is shown in FIG. loss / P in of charts.

[0092] Fig. 20 This is a photograph showing the accumulated radiation noise of the near-field electromagnetic wave absorber of Example 2 in the range of 100 MHz to 5 GHz.

[0093] Fig.21 This is a microscope photograph of the first electromagnetic wave-absorbing film of Example 3.

[0094] Fig. 22 is the noise absorption rate P of the first electromagnetic wave absorbing film of Example 3 loss / P in of charts.

[0095] Fig.23 This is a photograph showing the accumulated radiation noise of the first electromagnetic wave-absorbing film of Example 3 in the range of 100 MHz to 5 GHz.

[0096] Fig.24 is the noise absorption rate P of the near-field electromagnetic wave absorber of Example 4 loss / P inof charts.

[0097] Fig.25 This is a photograph showing the accumulated radiation noise of the near-field electromagnetic wave absorber of Example 4 in the range of 100 MHz to 5 GHz.

[0098] Fig.26 is the noise absorption rate P of the first electromagnetic wave absorbing film of Comparative Example 1 loss / P in of charts.

[0099] Fig. 27 This is a photograph showing the accumulated radiation noise of the first electromagnetic wave-absorbing film of Comparative Example 1 in the range of 100 MHz to 5 GHz.

[0100] Fig.28 is the noise absorption rate P of the near-field electromagnetic wave absorber of Comparative Example 2 loss / P in of charts.

[0101] Fig.29 This is a photograph showing the accumulated radiation noise of the near-field electromagnetic wave absorber of Comparative Example 2 in the range of 100 MHz to 5 GHz.

[0102] Description of Reference Numerals

[0103] 1…Near-field electromagnetic wave absorber

[0104] 10, 10a, 10b…Plastic film

[0105] 11, 11a, 11b…Metallic thin film

[0106] 11a…The first metal film with linear traces

[0107] 11b…The second metal film with linear traces

[0108] 12, 12a, 12b…Linear traces

[0109] 2a, 2b, 32a, 32b ... pattern roller for manufacturing the second electromagnetic wave absorbing film

[0110] 3a, 3b, 103a, 103b ... press roller

[0111] 20…Adhesive layer

[0112] 100a…First electromagnetic wave absorbing film

[0113] 100b…second electromagnetic wave absorbing film

[0114] 102 ... an example of a pattern roller used in a first device for manufacturing a first electromagnetic wave absorbing film

[0115] 102a ... roller body

[0116] 102b…Linear trace formation area

[0117] 102c…Linear trace non-formation area

[0118] 102d…High hardness particles

[0119] 102e…Fixed layer

[0120] 112…High-density area

[0121] 113…Low-density area

[0122] 114…The high-density regions are repeated

[0123] 115…The overlapping parts of high-density and low-density regions

[0124] 116…Repetitions of low-density regions

[0125] 122 ... Another example of the pattern roller used in the first device for manufacturing the first electromagnetic wave absorbing film

[0126] 122a…Roller body

[0127] 122b…Large outer diameter area

[0128] 122c…Small outer diameter area

[0129] 122d…Linear trace formation area

[0130] 132 ... pattern roller used in the second device for manufacturing the first electromagnetic wave absorbing film

[0131] α1…Central angle of the linear trace formation area

[0132] α2…Central angle of the area where the linear trace is not formed

[0133] R…Radius of the roller body

[0134] R1…Radius of the large outer diameter area

[0135] R2…Radius of the small outer diameter area DETAILED DESCRIPTION

[0136] Embodiments of the present invention will be described in detail with reference to the accompanying drawings. Unless otherwise specified, the description related to one embodiment is also applicable to other embodiments. In addition, the following description is not restrictive, and various changes can be made within the scope of the technical concept of the present invention.

[0137] [1] Electromagnetic wave absorbing film

[0138] FIG. 1(a) is a plan view schematically showing an example of a first linear trace group constituting the electromagnetic wave absorbing film of the present invention, and FIG. 1(b) is a cross-sectional view taken along the line AA of FIG. 1(a). On a metal film 11 formed on one side of a plastic film 10, a plurality of substantially parallel linear traces 12a are formed with irregular widths and intervals along one direction (first direction) F1, and high-density regions 112 where the linear traces 12a are formed and low-density regions 113 where the linear traces 12a are substantially not formed are alternately arranged along one direction F1. Here, the linear traces 12a in the plurality of high-density regions 112 alternately arranged along one direction F1 are collectively referred to as a "first linear trace group", and the metal film 11 having the first linear trace group is referred to as a "first metal film with linear traces 11a". The high-density regions 112 and low-density regions 113 of the linear traces 12a alternately formed along the direction F1 form a stripe pattern. In addition, the lengths La1 and La2 of the high-density region 112 and the low-density region 113 of the linear trace 12a in the direction F1 are determined according to the manufacturing method and the device.

[0139] (1) Plastic film

[0140] The resin forming the plastic film 10 is not particularly limited as long as it has insulation and sufficient strength, flexibility and processability, and examples thereof include polyester (polyethylene terephthalate, etc.), polyarylene sulfide (polyphenylene sulfide, etc.), polyethersulfone, polyetheretherketone, polycarbonate, acrylic resin, polystyrene, polyolefin (polyethylene, polypropylene, etc.), etc. Among them, polyethylene terephthalate (PET) film is preferred from the viewpoint of strength and cost. The thickness of the plastic film 10 may be about 10 to 100 μm, but in order to make the electromagnetic wave absorbing film and the near-field electromagnetic wave absorber as thin as possible, it is preferably about 10 to 30 μm.

[0141] (2)Metal film

[0142] The metal film 11 is made of a non-magnetic metal or a magnetic metal. Examples of non-magnetic metals include aluminum, copper, and silver. Examples of magnetic metals include nickel and chromium. These metals are of course not limited to monomers but may also be alloys. From the perspective of cost and corrosion resistance, aluminum is preferred. The metal film 11 can be formed by known methods such as sputtering and vacuum evaporation. From the perspective of controlling the degree of processing of linear traces, the thickness of the metal film 11 is preferably 20 to 100 nm, more preferably 30 to 90 nm, and most preferably 40 to 80 nm.

[0143] (3) The first linear trace group

[0144] As described above, in each high-density region 112 of the first metal film 11a with linear traces, a plurality of linear traces 12a substantially parallel to the metal film 11 are formed with irregular widths and intervals along one direction F1. As shown in FIG. 1(b), the linear traces 12a have various widths W and intervals I in the lateral direction orthogonal to the orientation direction F1 thereof. The width W and interval I of the linear traces 12a are both determined based on the height (original height) of the surface S of the metal film 11 before the linear traces are formed. In addition, the depth of the linear traces 12a is exaggerated in FIG. 1(b) for the purpose of explanation.

[0145] The width W of the linear trace 12a is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm, further preferably in the range of 0.5 to 50 μm, and most preferably in the range of 0.5 to 20 μm. In addition, the average width Wav of the linear trace 12a is preferably 1 to 50 μm, more preferably 2 to 50 μm, and most preferably 5 to 30 μm. The interval I of the linear trace 12a is preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.5 to 200 μm, further preferably in the range of 1 to 100 μm, and most preferably in the range of 1 to 50 μm. In addition, the average interval Iav of the linear trace 12a is preferably 1 to 200 μm, more preferably 5 to 100 μm, and most preferably 10 to 80 μm. When calculating the width W and the average width Wav, the interval I and the average interval Iav of the linear traces 12a, the linear traces 12a with a width of up to 0.1 μm are counted. The same shall apply unless otherwise specified.

[0146] The length Ls of the linear trace 12a depends not only on the sliding contact conditions (mainly the relative speed between the pattern roller and the plastic film and the contact angle between the plastic film and the pattern roller), but also on the length of the high-density region 112. Since the longitudinal gap of the linear trace 12a is sometimes also located in the high-density region 112, the length Ls of the linear trace 12a is the same as or less than the length La1 of the high-density region 112.

[0147] (a) Formation density of the first linear trace

[0148] Generally speaking, if the degree of processing of the linear trace increases, the width W (proportional to the depth) of the linear trace increases, and the interval I decreases, so the proportion (density) of the linear trace in the metal film 11 increases. Therefore, the degree of processing of the linear trace can be represented by the density of the linear trace. However, since the linear trace is not only very small but also irregular and formed at a high density, it is difficult to directly measure the density of the linear trace. Therefore, focusing on the fact that the surface resistivity and transmittance of the metal film 11 increase if the density of the linear trace increases, the density of the linear trace is evaluated by the surface resistivity or transmittance of the metal film 11.

[0149] In FIG. 1( a ), although no linear trace 12 a is shown in the region 113 , depending on the manufacturing method, for example, Figure 2 As shown, a small amount of linear traces 12a are often formed in the region 113. However, if the processing degree of the linear traces 12a is low, the effect of the present invention can be fully obtained, so the case where a small amount of linear traces 12a are formed in the region 113 is also within the scope of the present invention. Therefore, the region 113 is referred to as a "low-density region of linear traces" or simply "low-density region" to include the case where a small amount of linear traces 12a are formed in the region 113. Along with this, the high-density region 112 where linear traces are formed at a high density is referred to as a "high-density region of linear traces" or simply "high-density region".

[0150] (i) Surface resistivity

[0151] The surface resistivity of the metal film 11 in the high-density region 112 is preferably 30 to 200Ω / □. If the surface resistivity of the metal film 11 in the high-density region 112 is less than 30Ω / □ or greater than 200Ω / □, the electromagnetic wave absorption film cannot exert sufficient electromagnetic wave absorption capability. On the other hand, the surface resistivity of the metal film 11 in the low-density region 113 is preferably 0 to 20Ω / □. In addition, the lower limit of 0Ω / □ is the same as the surface resistivity of the metal film itself. That is, linear traces 12a can be completely formed on the metal film 11 in the low-density region 113. If the surface resistivity of the metal film 11 in the low-density region 113 is greater than 20Ω / □, the effect of setting the low-density region 113 will be insufficient. More preferably, the surface resistivity of the metal film 11 in the high-density region 112 is 30 to 150Ω / □, and the surface resistivity of the metal film 11 in the low-density region 113 is 0 to 15Ω / □.

[0152] In the case where the high-density region 112 and the low-density region 113 are very fine, it is difficult to measure their respective surface resistivities. Therefore, the surface resistivity of the metal film having linear traces formed on the entire surface under the same conditions as the high-density region 112 in the metal film having linear traces alternately formed in one direction as shown in FIG. 1(a) is measured, and is taken as the surface resistivity Rs1 of the high-density region 112. In addition, the surface resistivity Rs of the metal film 11a having the high-density region 112 and the low-density region 113 is measured. Since the surface resistivity Rs can be regarded as being approximately equal to the sum of the surface resistivities Rs1 and Rs2 of the high-density region 112 and the low-density region 113, the surface resistivity Rs2 of the low-density region 113 can be calculated from the surface resistivities Rs1 and Rs.

[0153] (ii) Light transmittance

[0154] The light transmittance of the metal film 11 in the high-density region 112 is preferably 3 to 10%, and more preferably 4 to 8%. In addition, the light transmittance of the metal film 11 in the low-density region 113 is preferably 0 to 2.5%, and more preferably 0 to 2%. In addition, the light transmittance of 0% is a state in which no linear traces 12a are formed. In addition, the light transmittance of the metal film 11 in the high-density region 112 is related to the surface resistivity.

[0155] (b) Length of high-density and low-density regions

[0156] In the direction F1 of the linear trace 12a, the length La1 of the high-density region 112 is preferably 0.2 to 10 mm, and the length La2 of the low-density region 113 is preferably 0.2 to 10 mm. If the length La1 of the high-density region 112 is less than 0.2 mm or the length La2 of the low-density region 113 is greater than 10 mm, the electromagnetic wave absorption capacity is too low. On the other hand, if the length La1 of the high-density region 112 is greater than 10 mm or the length La2 of the low-density region 113 is less than 0.2 mm, the effect of setting the low-density region 113 will be insufficient, and the radiation noise absorption capacity of the electromagnetic wave absorption film will be reduced. The length La1 of the high-density region 112 is more preferably 1 to 5 mm, and the length La2 of the low-density region 113 is more preferably 1 to 5 mm.

[0157] Along the direction F1 of the linear trace 12a, the length ratio La1 / La2 of the high-density region 112 and the low-density region 113 is preferably 5 / 1 to 1 / 5. If the length ratio La1 / La2 is less than 1 / 5, the electromagnetic wave absorption capacity is too low. In addition, if the length ratio La1 / La2 is greater than 5 / 1, the effect of providing the low-density region 113 will be insufficient, and the radiation noise absorption capacity of the electromagnetic wave absorption film will be reduced. From the perspective of the isotropy of the electromagnetic wave absorption capacity, the length ratio La1 / La2 is more preferably 2 / 1 to 1 / 2, and particularly preferably 1 / 1.

[0158] (4) The second linear trace group

[0159] Figure 3 It is a plan view schematically showing an example of a second linear trace group that constitutes the electromagnetic wave absorbing film of the present invention together with the first linear trace group shown in FIG1. ​​The second linear trace group is repeatedly formed on the metal film 11 on which the first linear trace group is formed. As described later, the (second) direction F2 of the linear traces 12b in the second linear trace group needs to be different from the (first) direction F1 of the linear traces 12a in the first linear trace group. In addition, the ranges of the width W, average width Wav, interval I and average interval Iav of the linear traces 12b in the second linear trace group may be the same as those of the first linear trace group. In addition, the ranges of the surface resistivity and transmittance of the high-density region 112 and the low-density region 113 in the second linear trace group and the ranges of their lengths and their ratios may also be the same as those of the first linear trace group.

[0160] The length La1 of the high-density region 112 in the first linear trace group and the length Lb1 of the high-density region 112 in the second linear trace group may be the same or different. In different cases, the ratio La1 / Lb1 is preferably 1 / 2 to 2 / 1, and more preferably 2 / 3 to 3 / 2. In addition, in different cases, the linear trace density of the high-density region 112 and the low-density region 113 in the second linear trace group may be the same as that in the first linear trace group. In short, the second linear trace group may be the same as the first linear trace group except for the direction of the linear traces.

[0161] (5) Structure of electromagnetic wave absorbing film

[0162] Figure 41 is a plan view schematically showing an example of an electromagnetic wave absorbing film 100 of the present invention having both a first linear trace group and a second linear trace group. Due to the overlap of the first linear trace group and the second linear trace group, overlapping portions 114 of high-density regions 112, overlapping portions 115 of high-density regions 112 and low-density regions 113, and overlapping portions 116 of low-density regions 113 are formed on the metal thin film 11. Hereinafter, the overlapping portions 114 of high-density regions 112 are simply referred to as "high-density overlapping portions", the overlapping portions 115 of high-density regions 112 and low-density regions 113 are referred to as "high-density-low-density overlapping portions", and the overlapping portions 116 of low-density regions 113 are referred to as "low-density overlapping portions".

[0163] Although the high-density repeating portion 114 is distributed in a dotted pattern, the high-density repeating portion 114 and the high-density-low-density repeating portion 115 are combined to form a lattice pattern. In addition, the low-density repeating portion 116 is distributed in a dotted pattern.

[0164] In the high-density repeating portion 114, as Figure 5 As schematically shown in FIG. 1 , the linear traces 12a of the first linear trace group and the linear traces 12b of the second linear trace group intersect at an intersection angle θs. The intersection angle θs of the linear traces 12a and 12b is preferably 30 to 90°, more preferably 60 to 90°, most preferably 80 to 90°, and particularly preferably 90°. As the intersection angle θs approaches 90°, the electromagnetic wave absorption capability becomes isotropic.

[0165] exist Figure 5 In FIG. 1 , Ls1 and Ls2 represent the lengths of the linear traces 12a and 12b, respectively. The length Ls1 of the linear trace 12a and the length Ls2 of the linear trace 12b may be different, but if they are the same, the electromagnetic wave absorption capacity is isotropic, which is preferred. When the length Ls1 of the linear trace 12a and the length Ls2 of the linear trace 12b are different, the length ratio Ls1 / Ls2 is preferably 1 / 2 to 2 / 1, and more preferably 2 / 3 to 3 / 2.

[0166] In the high-density-low-density repeating portion 115, one of the linear traces 12a and 12b is mainly formed, and the other linear trace is almost not formed. Therefore, although the high-density-low-density repeating portion 115 shows a lower conduction noise absorption capacity than the high-density repeating portion 114, it helps to improve the radiation noise absorption capacity. Although most of the linear traces in each high-density-low-density repeating portion 115 are oriented in one direction, since most of the linear traces in the adjacent high-density-low-density repeating portions 115 are oriented in different directions at a crossing angle θs, the electromagnetic wave absorption capacity of the entire electromagnetic wave absorption film is roughly isotropic.

[0167] Since the linear traces 12a and 12b are almost not formed in the low-density repeating portion 116, it has a function close to that of the metal film 11 itself and exhibits a large radiation noise absorption capability. The current generated by the electromagnetic wave noise absorbed by the low-density repeating portion 116 flows to the adjacent high-density-low-density repeating portion 115 and the high-density repeating portion 114 and is attenuated there.

[0168] In the electromagnetic wave absorbing film 100 of the present invention, the high-density repeating portion 114 is distributed in a lattice shape via the high-density-low-density repeating portion 115 by the intersection of the linear traces 12a and 12b, so the high-density region 112 is also distributed in a lattice shape on the metal film 11. By the lattice distribution of the high-density region 112, the electromagnetic wave absorbing film 100 of the present invention can ensure sufficient conduction noise absorption capacity while also exerting good radiation noise absorption capacity.

[0169] [2] Near-field electromagnetic wave absorber

[0170] The near-field electromagnetic wave absorber of the present invention is characterized in that it has at least one plastic film and a first metal film and a second metal film.

[0171] The first metal film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, the linear traces alternately having high-density regions and low-density regions in each direction, and the high-density regions are distributed in a lattice shape on the entire surface of the first metal film due to the intersection of the linear traces in the two directions.

[0172] A plurality of substantially parallel and discontinuous linear traces are formed on the entire surface of the second metal film in two directions with irregular widths and intervals.

[0173] Specifically, the near-field electromagnetic wave absorber of the present invention preferably comprises: (a) a first metal film with linear traces, having a plurality of substantially parallel linear traces formed with irregular widths and intervals along two directions, and alternatingly having high-density regions in which the linear traces are formed with high density and low-density regions in which the linear traces are formed with low density in each direction, wherein the high-density regions are distributed in a grid pattern by the intersection of the linear traces in two directions; and (b) a second metal film with linear traces, having a plurality of substantially parallel and discontinuous linear traces in two directions formed with irregular widths and intervals on the entire surface.

[0174] The first metal film with linear traces preferably has:

[0175] a first linear trace group having the high-density area of ​​the linear trace and the low-density area of ​​the linear trace alternately in a first direction; and a second linear trace group having the high-density area of ​​the linear trace and the low-density area of ​​the linear trace alternately in a second direction different from the first direction,

[0176] By overlapping the first linear trace group and the second linear trace group, overlapping portions of the high-density regions, overlapping portions of the high-density regions and the low-density regions, and overlapping portions of the low-density regions are formed on the metal film.

[0177] The repeated parts of the high-density regions are distributed in a dotted pattern.

[0178] The repeated parts of the high-density regions and the repeated parts of the high-density regions and the low-density regions are combined to form a lattice pattern.

[0179] The overlapping parts of the low-density regions are distributed in a dotted pattern.

[0180] (1) First Embodiment

[0181] An example of a near-field electromagnetic wave absorber according to the first embodiment of the present invention is formed by bonding a first electromagnetic wave absorbing film 100a having a first metal thin film 11a with linear traces on a plastic film 10a and a second electromagnetic wave absorbing film 100b having a second metal thin film 11b with linear traces on a plastic film 10b via an adhesive layer 20, as shown in Fig. 6(a) and Fig. 6(b). In this example, since the first metal thin film 11a with linear traces and the second metal thin film 11b with linear traces are opposite to each other, the adhesive layer 20 is non-conductive to prevent conduction between the two. If the adhesive layer 20 is made very thin, electromagnetic coupling will occur between the first metal thin film 11a with linear traces and the second metal thin film 11b with linear traces. The adhesive layer 20 may be formed by an adhesive, but may also be formed by heat sealing or double-sided adhesive tape.

[0182] The second electromagnetic wave absorbing film 100b may be the same as the first electromagnetic wave absorbing film 100a except that a plurality of substantially parallel linear traces are formed in two directions with irregular widths and intervals on the entire surface of the metal thin film 11. Fig. 6(c) shows an example of the metal thin film 11b with linear traces of the second electromagnetic wave absorbing film 100b.

[0183] The width W of the linear traces 12 in the second metal film 11b with linear traces is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm, further preferably in the range of 0.5 to 50 μm, and most preferably in the range of 0.5 to 20 μm. In addition, the average width Wav of the linear traces 12 is preferably 1 to 50 μm, more preferably 2 to 50 μm, and most preferably 5 to 30 μm. The interval I of the linear traces 12 is preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.5 to 200 μm, most preferably in the range of 1 to 100 μm, and particularly preferably in the range of 1 to 50 μm. In addition, the average interval Iav of the linear traces 12 is preferably 1 to 200 μm, more preferably 5 to 100 μm, and most preferably 10 to 80 μm.

[0184] The length Ls of the linear trace 12 in the second metal film 11b with linear traces is determined by the sliding contact conditions (mainly the relative circumferential speed of the pattern roller and the plastic film), so as long as the sliding contact conditions are not changed, most of them are almost the same (almost equal to the average length). The length Ls of the linear trace 12 is not particularly limited, and can be about 1 to 100 mm, preferably 2 to 10 mm, from a practical point of view.

[0185] The intersection angle θs of the linear traces 12 in two directions in the second metal film 11 b with linear traces is preferably 30 to 90°, more preferably 45 to 90°, most preferably 60 to 90°, and particularly preferably 90°.

[0186] You can Figure 7 Instead of making the first metal film 11a with linear traces and the second metal film 11b with linear traces face each other, the first electromagnetic wave absorbing film 100a and the second electromagnetic wave absorbing film 100b are bonded in such a manner that the metal films 11a and 11b with linear traces are located on the same side of the plastic films as shown.

[0187] (2) Second Embodiment

[0188] Figure 8 The near-field electromagnetic wave absorber according to the second embodiment of the present invention is shown. The near-field electromagnetic wave absorber is composed of a plastic film 10 and a first metal film 11a with linear traces and a second metal film 11b with linear traces provided on both sides of the plastic film 10. The first metal film 11a with linear traces and the second metal film 11b with linear traces themselves can be the same as those in the first embodiment.

[0189] [3]Equipment for manufacturing electromagnetic wave absorbing film

[0190] Since the first metal thin film with linear traces has a more complex structure than the second metal thin film with linear traces, the manufacturing apparatus of the second electromagnetic wave absorbing film having the second metal thin film with linear traces will be described first.

[0191] (1) Second electromagnetic wave absorbing film manufacturing device

[0192] Figure 9(a) to Figure 9(e) An example of an apparatus for manufacturing a second electromagnetic wave absorbing film 100b is shown. The apparatus shown in the figure has: (a) a reel 21 for unwinding a plastic film 10 having a metal thin film; (b) a first pattern roller 2a arranged obliquely with respect to the width direction of the plastic film 10; (c) a first pressing roller 3a arranged on the upstream side of the first pattern roller 2a and on the opposite side of the first pattern roller 2a; (d) a second pattern roller 2b inclined in the opposite direction to the first pattern roller 2a with respect to the width direction of the plastic film 10 and arranged on the same side as the first pattern roller 2a; (e) a second pressing roller 3b arranged on the downstream side of the second pattern roller 2b and on the opposite side of the second pattern roller 2b; and (f) a reel 24 for winding up a plastic film 10' (second electromagnetic wave absorbing film 100b) having a metal thin film formed with linear traces. In addition, a plurality of guide rollers 22 and 23 are arranged at predetermined positions. Each pattern roller 2a, 2b is supported by a supporting roller (e.g., a rubber roller) 5a, 5b to prevent deflection. In the device shown in FIG9(a), a pressing roller 3a, 3b is arranged near each pattern roller 2a, 2b, but a pair of pressing rollers 3a, 3b may also be arranged on both sides of each pattern roller 2a, 2b.

[0193] As shown in FIG9(c), since each pressing roller 3a, 3b contacts the metal film of the plastic film 10 at a position lower than the sliding contact position with each pattern roller 2a, 2b, the plastic film 10 is pressed by each pattern roller 2a, 2b. By adjusting the height of each pressing roller 3a, 3b under the condition that this condition is satisfied, the pressing force of each pattern roller 2a, 2b on the metal film can be adjusted. Specifically, if the position of each pressing roller 3a, 3b is lowered, the pressing force of each pattern roller 2a, 2b on the metal film of the plastic film 10 increases, so the linear traces formed on the metal film become darker (the processing degree of the metal film will be improved). On the contrary, if the position of each pressing roller 3a, 3b is raised, the pressing force of each pattern roller 2a, 2b on the metal film of the plastic film 10 decreases, so the linear traces formed on the metal film of the plastic film 10 become shallower (the processing degree of the metal film will be reduced).

[0194] Generally speaking, the deeper the linear traces, the less metal remains on the metal film, so the surface resistivity of the metal film with linear traces increases. Therefore, the surface resistivity of the metal film with linear traces can be adjusted by changing the pressing force of each pattern roller 2a, 2b on the metal film of the plastic film 10. In addition, if the linear traces become deeper, the width of the linear traces becomes wider, so the intervals between the linear traces tend to become narrower. The pressing force of the plastic film 10 on each pattern roller 2a, 2b can also be adjusted by moving the position of each pattern roller 2a, 2b in the direction of the plastic film 10. The position movement of each pattern roller 2a, 2b can be performed by a driving device (not shown) installed on each pattern roller 2a, 2b.

[0195] FIG9(d) shows the principle of forming a linear trace 12 at an angle relative to the traveling direction of the plastic film 10. Since the pattern roller 2a is inclined relative to the traveling direction of the plastic film 10, the moving direction (rotation direction) of the hard particles on the pattern roller 2a is different from the traveling direction of the plastic film 10. Therefore, as shown by X, if it is assumed that at any time, the hard particles at point A on the pattern roller 2a contact the metal film of the plastic film 10 to form a trace B, then after a predetermined time, the hard particles move to point A' and the trace B moves to point B'. Since the trace B is continuously formed during the period when the hard particles move from point A to point A', a linear trace 12 extending from A' to B' is formed.

[0196] The direction and the cross angle θs of the linear trace 12 formed by the first pattern roller 2a and the second pattern roller 2b can be adjusted by changing the angle of each pattern roller 2a, 2b relative to the plastic film 10 and / or the circumferential speed of each pattern roller 2a, 2b relative to the travel speed of the plastic film 10. For example, if the circumferential speed a of the pattern roller 2a relative to the travel speed b of the plastic film 10 is increased, the linear trace 12 can be made 45° relative to the travel direction of the plastic film 10 as shown in Y of Figure 9 (d). Similarly, if the inclination angle θ2 of the pattern roller 2a relative to the width direction of the plastic film 10 is changed, the circumferential speed a of the pattern roller 2a can be changed. This is also true for the pattern roller 2b. Therefore, the direction of the linear trace 12 can be changed by adjusting the two pattern rollers 2a, 2b.

[0197] Since each pattern roller 2a, 2b is inclined relative to the plastic film 10, the plastic film 10 is subjected to a force in the width direction through sliding contact with each pattern roller 2a, 2b. Therefore, in order to prevent the plastic film 10 from zigzagging, it is preferred to adjust the height and / or angle of each pressing roller 3a, 3b relative to each pattern roller 2a, 2b. For example, if the intersection angle θ3 between the axis of the pattern roller 2a and the axis of the pressing roller 3a is properly adjusted, the width distribution of the pressing force can be obtained so as to eliminate the force in the width direction, thereby preventing the plastic film 10 from zigzagging. In addition, adjusting the interval between the pattern roller 2a and the pressing roller 3a also helps to prevent the plastic film 10 from zigzagging. In order to prevent the plastic film 10 from zigzagging and breaking, the rotation direction of the first pattern roller 2a and the second pattern roller 2b inclined relative to the width direction of the plastic film 10 is preferably the same as the travel direction of the plastic film 10.

[0198] Fig.10 Another example of a device for forming orthogonal linear traces is shown. This device is similar to the device in that the second pattern roller 32b is arranged parallel to the width direction of the plastic film 10 (at right angles to the running direction). Figure 9(a) to Figure 9(e) Therefore, only the following description is relevant to Figure 9(a) to Figure 9(e) The second pattern roller 32b can rotate in the same direction as the traveling direction of the plastic film 10 or in the opposite direction to the traveling direction of the plastic film 10. In addition, the second pressing roller 33b can be located on the upstream side of the second pattern roller 32b or on the downstream side of the second pattern roller 32b. As shown in Z in FIG9(d), the direction of the linear trace 12' (line segment E'F') is set to the width direction of the plastic film 10, which is suitable for forming orthogonal linear traces.

[0199] The traveling speed of the plastic film 10 is preferably 5 to 200 m / min, and the peripheral speed of the pattern roller is preferably 10 to 2,000 m / min. The inclination angle θ2 of the pattern roller is preferably 20° to 60°, and particularly preferably about 45°. The tension of the plastic film 10 (proportional to the pressing force) is preferably in the range of 0.05 to 5 kgf / cm.

[0200] The pattern roller is preferably a roller having particles with a Mohs hardness of 5 or more and sharp corners on the surface, such as a diamond roller described in Japanese Patent Publication No. 2002-59487. The width of the linear trace is determined by the particle size of the particles, so preferably more than 90% of the diamond particles have a particle size in the range of 0.1 to 100 μm, more preferably a particle size in the range of 0.1 to 70 μm. The diamond particles are preferably attached to the roller surface at an area ratio of more than 30%. The fixing of the diamond particles is preferably carried out by a metal layer such as nickel.

[0201] (2) First Electromagnetic Wave Absorption Film Manufacturing Apparatus

[0202] (a) First Manufacturing Device

[0203] The first manufacturing device has a structure substantially the same as that of the second electromagnetic wave absorbing film manufacturing device, except that linear trace forming areas and linear trace non-forming areas are alternately provided in the circumferential direction on the outer circumferential surface of each pattern roller, and the linear trace forming areas have a plurality of high hardness particles on the surface. Therefore, the pattern rollers are described in detail.

[0204] FIG11(a) shows an example of each pattern roller used in the first manufacturing device. The pattern roller 102 is composed of a roller body 102a, a linear trace forming area 102b and a linear trace non-forming area 102c formed alternately at a predetermined interval on the outer peripheral surface of the roller body 102a. The linear trace forming area 102b has a plurality of high hardness particles 102d and a fixing layer 102e that holds the high hardness particles 102d as shown in FIG11(b). As in the manufacturing device of the second electromagnetic wave absorbing film, the high hardness particles 102d are preferably diamond particles, and the fixing layer 102e is preferably a metal layer such as nickel. The linear mark non-forming area 102c is preferably (a) an area where a fixed layer 102e that retains multiple high hardness particles 102d is not formed or (b) an area consisting only of a fixed layer 102e (without high hardness particles 102d), so that even when the metal film 11 reaches a close position due to the rotation of the pattern roller 102, no linear mark is formed on the metal film 11 at all or almost not.

[0205] The central angle α1 of the linear trace forming region 102b is preferably 30 to 90°, more preferably 45 to 90°. In addition, the central angle α2 of the linear trace non-forming region 102c is preferably 30 to 90°, more preferably 45 to 90°. In the example shown in the figure, four linear trace forming regions 102b and four linear trace non-forming regions 102c are alternately arranged, so α1+α2 is 90°, but it is not limited to this.

[0206] like Fig.12 As shown, the perimeter D1 of the linear trace forming region 102b and the perimeter D2 of the linear trace non-forming region 102c are determined by the central angles α1 and α2 thereof and the radius R of the roller body 102a, and are preferably 0.2 to 10 mm, and more preferably 1 to 5 mm.

[0207] The radius R of the roller body 102a is preferably 3 to 6 cm. If the radius R is greater than 6 cm, the distance of sliding contact between the pattern roller 102 and the metal film 11 is too long, and the linear trace high density area cannot be set shorter. On the other hand, if the radius R is less than 3 cm, the rigidity of the roller body 102a is insufficient. The radius R of the roller body 102a is more preferably 3 to 5 cm.

[0208] Fig.13 Another example of each pattern roller used in the first manufacturing device is shown. The pattern roller 122 has a roller body 122a, and the roller body 122a has a large outer diameter area 122b and a small outer diameter area 122c alternately along its outer circumference, and a linear trace forming area 122d is formed on the large outer diameter area 122b of the roller body 122a. The small outer diameter area 122c functions as a linear trace non-forming area. The linear trace forming area 122d can be the same as the linear trace forming area 102b in the above-mentioned pattern roller 102. Although it is not necessary to form a fixed layer holding a plurality of high hardness particles on the small outer diameter area 122c, a fixed layer holding a plurality of high hardness particles can also be formed on the small outer diameter area 122c from the viewpoint of manufacturing efficiency. The ratio of the central angles (circumferences) of the large outer diameter region 122b and the small outer diameter region 122c may be the same as the ratio of the central angles (circumferences) of the linear trace formation region 102b and the linear trace non-formation region 102c in the pattern roller 102 described above.

[0209] When a fixed layer holding a plurality of high-hardness particles is also formed on the small outer diameter region 122c, the difference Dh between the radius R1 of the large outer diameter region 122b and the radius R2 of the small outer diameter region 122c is preferably 1 mm or more. If the step difference Dh is less than 1 mm, the high-hardness particles in the small outer diameter region 122c are likely to strongly slide in contact with the metal film 11, and the density of the linear traces in the low-density region of the obtained first electromagnetic wave absorbing film becomes too high. The step difference Dh is more preferably 2 to 5 mm.

[0210] The radius R1 of the large outer diameter region 122b of the roller body 122a is also preferably 3 to 6 cm, and more preferably 3 to 5 cm.

[0211] (b) Second Manufacturing Apparatus

[0212] The second manufacturing device has a structure substantially the same as that of the second electromagnetic wave absorbing film manufacturing device, except that it has a device for driving at least one of the pattern roller and the pressing roller in a vertical direction relative to the metal film so that each pattern roller intermittently slides in contact with the metal film. Therefore, the vertical driving of the pattern roller and / or the pressing roller is described in detail.

[0213] Fig. 14 (a) and Fig. 14 (b) show an example in which the rotation axes of a pair of pressing rollers 103a and 103b are fixed and the rotation axis of a pattern roller 132 is driven at a certain time interval in a direction perpendicular to the metal film 11 by a driving device (not shown). The pattern roller 132 has a plurality of high-hardness particles on the entire outer peripheral surface, similarly to the pattern rollers 2a and 2b used in the manufacturing device of the second electromagnetic wave absorbing film. The plastic film 10 is maintained at a certain height by the pair of pressing rollers 103a and 103b.

[0214] In the state of FIG. 14(a), the pattern roller 132 is in an ascending position, and the pattern roller 132 is slightly pressed by the metal film 11 of the plastic film 10 and is in sliding contact with it, so that a linear trace is formed on the metal film 11. Next, if the pattern roller 132 reaches a descending position as shown in FIG. 14(b), since the pattern roller 132 is away from the metal film 11, no linear trace is formed on the metal film 11. Since the formation of linear traces is alternately performed by intermittent vertical driving of each pattern roller 132, the first linear trace group and the second linear trace group can be alternately formed along the linear trace direction on the metal film 11. The lengths of the high-density region and the low-density region in the first linear trace group and the second linear trace group can be adjusted by the time interval of the vertical driving of each pattern roller 132.

[0215] For the same reason as described above, the radius R of the pattern roller 132 is preferably 3 to 6 cm, and more preferably 3 to 5 cm.

[0216] Even if the pair of pressing rollers 103a and 103b are driven vertically instead of the pattern roller 132, the high-density region and the low-density region can be alternately formed. In addition, if the pattern roller 132 and the pair of pressing rollers 103a and 103b are driven vertically in opposite directions, that is, if the pair of pressing rollers 103a and 103b are lowered when the pattern roller 132 rises, and the pair of pressing rollers 103a and 103b are raised when the pattern roller 132 falls, the switching of the sliding contact between the pattern roller 132 and the metal film 11 can be accelerated, so that the high-density region and the low-density region can be narrowed (shortened in the direction of the linear trace).

[0217] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.

[0218] Example 1

[0219] (1) Manufacturing of the first electromagnetic wave absorbing film

[0220] In the device shown in FIG9(a), a pair of pattern rollers 102, 102 on which diamond particles having a particle size distribution of 50 to 80 μm are electrodeposited are used instead of a pair of pattern rollers 2a, 2b, and are set as a first manufacturing device. By means of the pattern roller 102 on the upstream side of the first manufacturing device, high-density regions and low-density regions of linear traces having the following characteristics are alternately formed in one direction on a 60 nm thick aluminum film vacuum-evaporated onto a 16 μm thick PET film, thereby producing a first linear trace group. Next, by means of the pattern roller 102 on the downstream side, under the same conditions as the first linear trace group, a second linear trace group having high-density regions and low-density regions of linear traces in another direction is produced in a manner overlapping with the first linear trace group, thereby obtaining a first electromagnetic wave absorbing film. The intersection angle θs of the linear traces in the first linear trace group and the second linear trace group is 90°. A microscope photograph of the first electromagnetic wave absorbing film is shown in FIG9(a). Fig.15 .

[0221] The linear traces in the first linear trace group and the second linear trace group have the same characteristics except for the direction as described below.

[0222] High density area

[0223] Line traces:

[0224] Width W range: 0.5~50μm

[0225] Average width Wav: 30μm

[0226] The range of the lateral spacing I is 1 to 50 μm.

[0227] Average lateral spacing Iav: 40μm

[0228] Average length Lav: 1mm

[0229] Length in orientation direction: 2mm

[0230] Low density area (1)

[0231] Length in orientation direction: 2mm

[0232] Note: (1) Since the linear traces are very small in the low-density region, only the length in the orientation direction of the low-density region was measured.

[0233] (a) Determination of surface resistivity

[0234] The surface resistivity Rs of a metal film having a first linear trace group, the first linear trace group having a high-density region and a low-density region of the linear traces, was measured. In addition, the surface resistivity of an aluminum film having linear traces formed on the entire surface under the same conditions as the high-density region was measured, and this surface resistivity was set as the surface resistivity Rs1 of the high-density region. The surface resistivity Rs2 of the low-density region was calculated from the surface resistivity Rs and Rs1. When measuring the surface resistivity, a sheet resistance / surface resistivity measuring instrument "EC-80P" of NAPSON CORPORATION was used. In addition, the surface resistivity of the second linear trace group having linear traces formed in a different direction was regarded as the same as the first linear trace group.

[0235] (b) Determination of light transmittance

[0236] The transmittance Lt of a metal film having a first linear trace group, the first linear trace group having a high-density area and a low-density area of ​​the linear traces, was measured. In addition, the transmittance of an aluminum film having linear traces formed on the entire surface under the same conditions as the high-density area was measured, and the transmittance was set as the transmittance Lt1 of the high-density area. The transmittance Lt2 of the low-density area was calculated from the transmittance Lt and Lt1. When measuring the transmittance, a through-type laser discrimination sensor (IB-30) manufactured by KEYENCE CO., LTD. was used. In addition, the transmittance of the second linear trace group was regarded as the same as that of the first linear trace group.

[0237] High density area

[0238] Surface resistivity: 90Ω / □

[0239] Light transmittance: 4.5%

[0240] Low density area

[0241] Surface resistivity: 8Ω / □

[0242] Light transmittance: 1.5%

[0243] (2) Determination of conducted noise absorption rate

[0244] A test piece TP1 (50 mm × 50 mm) is cut out from the first electromagnetic wave absorbing film. In the near-field electromagnetic wave evaluation system shown in FIG. 16 (a) and FIG. 16 (b), which is composed of a 50Ω microstrip line MSL (64.4 mm × 4.4 mm), an insulating substrate 200 supporting the microstrip line MSL, a ground electrode 201 bonded to the lower surface of the insulating substrate 200, conductive pins 202, 202 connected to both ends of the microstrip line MSL, a grid analyzer NA, and coaxial cables 203, 203 connecting the grid analyzer NA to the conductive pins 202, 202, the test piece TP is attached to the upper surface of the insulating substrate 200 by an adhesive in such a way that the center of the test piece TP1 coincides with the center of the microstrip line MSL. An incident wave of 0.1 to 6 GHz is input to the microstrip line MSL, and the power S of the reflected wave is measured. 11 and the power of the transmitted wave S 12 , according to S 11 and S 12 Calculate the noise absorption rate P loss / P in The results are shown in Fig.17 .Depend on Fig.17 It is clear that the noise absorption rate P of the electromagnetic wave absorbing film of Example 1 is loss / P in Although slightly inferior to Comparative Example 1 described later, it is sufficient in terms of balance with the radiation noise absorption capability.

[0245] (3) Measurement of radiated noise

[0246] The test piece TP2 (40 mm×40 mm) cut out from the first electromagnetic wave absorbing film was scanned in the frequency range of 0.03 GHz to 7 GHz using an EMC noise scanner (WM7400) manufactured by MORITATECH CO., LTD. to measure the radiation noise. Fig.18 The cumulative radiation noise of the test piece of Example 1 is shown in FIG. Fig.18 In the following photos of accumulated radiation noise, the positions of the test pieces are the same and therefore omitted.

[0247] Depend on Fig.18 It is clear that substantially no cumulative radiation noise of -10 dBm or more is observed in the frequency range of 100 MHz to 5 GHz. Therefore, it is confirmed that the first electromagnetic wave-absorbing film of Example 1 has excellent radiation noise absorption capability in the frequency range of 100 MHz to 5 GHz.

[0248] Example 2

[0249] (1) Manufacturing of the Second Electromagnetic Wave Absorbing Film

[0250] Using an apparatus having the structure shown in FIG. 9( a ) having pattern rollers 2a and 2b on which diamond particles having a particle size distribution of 50 to 80 μm are electrodeposited, linear traces of the following characteristics are formed in two directions on the entire surface of an aluminum film identical to that of Example 1, thereby obtaining a second electromagnetic wave absorbing film.

[0251] Width W range: 0.5~50μm

[0252] Average width Wav: 30μm

[0253] The range of the lateral spacing I: 1 to 5 μm

[0254] Average lateral spacing Iav: 40μm

[0255] Average length Lav: 1mm

[0256] Crossing angle θs: 90°

[0257] The surface resistivity and light transmittance of the second electromagnetic wave absorbing film having intersecting linear traces on the entire surface were measured by the same method as in Example 1 and the results were 25Ω / □ and 3%, respectively.

[0258] (2) Bonding of the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film

[0259] The second electromagnetic wave absorbing film was bonded to the first electromagnetic wave absorbing film produced in Example 1 by a non-conductive adhesive to produce a near-field electromagnetic wave absorber as shown in Fig. 6(a). The thickness of the adhesive layer 20 was 5 μm.

[0260] (3) Conducted noise absorption capacity and radiated noise absorption capacity of near-field electromagnetic wave absorbers

[0261] The noise absorption rate P of the near-field electromagnetic wave absorber was measured in the same manner as in Example 1. loss / P in The results after radiated noise are shown in Fig.19 and Fig. 20 .Depend on Fig.19 and Fig. 20 It is clear that the near-field electromagnetic wave absorber of Example 2 exhibits excellent radiation noise absorption capability and also has sufficient conduction noise absorption capability.

[0262] Example 3

[0263] (1) Manufacturing of the first electromagnetic wave absorbing film

[0264] In the apparatus shown in FIG. 9( a ), a pair of pattern rollers 132, 132 having a driving unit (not shown) for vertically driving the rotating shaft are used instead of the pair of pattern rollers 2a, 2b, and a second manufacturing apparatus is provided. Diamond particles having a particle size distribution of 50 to 80 μm are electrodeposited on the entire outer peripheral surface of each pattern roller 132, 132. Each pattern roller 132, 132 is driven to move up and down at a certain time interval while the plastic film 10 having the metal thin film 11 is moving.

[0265] By means of the pattern roller 132 on the upstream side of the second manufacturing device, high-density areas and low-density areas of linear traces having the following characteristics are alternately formed along one direction on the same aluminum film as in Example 1, thereby producing a first linear trace group. Next, by means of the pattern roller 132 on the downstream side, a second linear trace group having high-density areas and low-density areas of linear traces along different directions is produced in an overlapping manner with the first linear trace group under the same conditions as the first linear trace group, thereby obtaining a first electromagnetic wave absorbing film. The intersection angle θs of the linear traces in the first linear trace group and the second linear trace group is 90°. A microscope photograph of the first electromagnetic wave absorbing film is shown in FIG. Fig.21 .

[0266] The linear traces in the first linear trace group and the second linear trace group have the same characteristics except for the direction as described below.

[0267] High density area

[0268] Line traces:

[0269] Width W range: 0.5~50μm

[0270] Average width Wav: 35μm

[0271] The range of the lateral spacing I is 1 to 50 μm.

[0272] Average lateral spacing Iav: 30μm

[0273] Average length Lav: 1mm

[0274] Length in orientation direction: 2mm

[0275] Low density area (1)

[0276] Length in orientation direction: 2mm

[0277] Note: (1) Since the linear traces are very small in the low-density region, only the length in the orientation direction of the low-density region was measured.

[0278] The surface resistivity and light transmittance of the high-density region and the low-density region in the first linear trace group were measured by the same method as in Example 1. The surface resistivity and light transmittance of the second linear trace group were considered to be the same as those of the first linear trace group.

[0279] High density area

[0280] Surface resistivity: 150Ω / □

[0281] Light transmittance: 6%

[0282] Low density area

[0283] Surface resistivity: 3Ω / □

[0284] Light transmittance: 1%

[0285] (2) Conducted noise absorption capacity and radiated noise absorption capacity of the first electromagnetic wave absorbing film

[0286] The noise absorption rate P of the first electromagnetic wave absorbing film was measured in the same manner as in Example 1. loss / P in The results after radiated noise are shown in Fig. 22 and Fig.23 .Depend on Fig. 22 and Fig.23 It is clear that the first electromagnetic wave-absorbing film of Example 3 exhibits excellent radiation noise absorption capability and also has sufficient conduction noise absorption capability.

[0287] Example 4

[0288] (1) Bonding of the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film

[0289] The near-field electromagnetic wave absorber shown in Fig. 6(a) was produced by bonding the first electromagnetic wave absorbing film of Example 3 to the second electromagnetic wave absorbing film of Example 2 with a non-conductive adhesive. The thickness of the adhesive layer 20 was 5 μm.

[0290] (2) Conducted noise absorption capacity and radiated noise absorption capacity of near-field electromagnetic wave absorbers

[0291] The noise absorption rate P of the near-field electromagnetic wave absorber was measured in the same manner as in Example 1. loss / P in The results after radiated noise are shown in Fig.24 and Fig.25 .Depend on Fig.24 and Fig.25 It is clear that the near-field electromagnetic wave absorber of Example 4 exhibits excellent radiation noise absorption capability and also has sufficient conduction noise absorption capability.

[0292] Comparative Example 1

[0293] The noise absorption coefficients P were measured for the test pieces TP1 and TP2 cut out from the second electromagnetic wave-absorbing film produced in Example 2 by the same method as in Example 1. loss / P in and radiation noise. The results are shown in Fig.26 and Fig. 27 .Depend on Fig.26 and Fig. 27 It is clear that although the electromagnetic wave absorbing film of Comparative Example 1 exhibits excellent conduction noise absorption capability, its radiated noise absorption capability is significantly inferior to that of Examples 1 and 3.

[0294] Comparative Example 2

[0295] The noise absorption coefficient P was measured by the same method as in Example 1 for the test pieces TP1 and TP2 cut out from the near-field electromagnetic wave absorber formed by bonding two second electromagnetic wave absorbing films produced in Example 2. loss / P in and radiation noise. The results are shown in Fig.28 and Fig.29 .Depend on Fig.28 and Fig.29 It is clear that although the near-field electromagnetic wave absorber of Comparative Example 2 exhibits good conduction noise absorption capability, its radiation noise absorption capability is obviously inferior to that of Examples 2 and 4.

Claims

1. An electromagnetic wave absorbing film, characterized in that: A plastic film and a metal thin film formed on one side of the plastic film, The metal film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals. The linear traces have high-density areas and low-density areas alternately in each direction. The high-density regions are distributed in a grid pattern by the intersection of linear traces in two directions.

2. The electromagnetic wave absorbing film according to claim 1, characterized in that: The surface resistivity of the high-density region is 30 to 200 Ω / □, and the surface resistivity of the low-density region is 0 to 20 Ω / □.

3. The electromagnetic wave absorbing film according to claim 1, characterized in that: The intersection angle of the linear traces in two directions is 30 to 90°.

4. The electromagnetic wave absorbing film according to claim 1, characterized in that: The length ratio of the high-density region to the low-density region in each direction is 5 / 1 to 1 / 5.

5. The electromagnetic wave absorbing film according to any one of claims 1 to 4, characterized in that: The width of the linear traces is in the range of 0.1 to 100 μm and is 2 to 50 μm on average, and the interval between the linear traces is in the range of 0.1 to 500 μm and is 10 to 100 μm on average.

6. An apparatus for manufacturing an electromagnetic wave absorbing film, the electromagnetic wave absorbing film comprising a plastic film and a metal thin film formed on one side of the plastic film, the metal thin film having a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and the linear traces alternately having high-density regions and low-density regions in each direction, the high-density regions being distributed in a lattice shape by the intersection of the linear traces in the two directions, The manufacturing device is characterized by comprising: two pattern rollers; a mechanism for conveying the plastic film in a manner that the metal film is in sliding contact with two pattern rollers; and A pressing roller pressing the metal film against the pattern roller, The two pattern rollers are inclined to opposite sides of the plastic film in the surface in sliding contact with the metal film. Linear trace forming areas and linear trace non-forming areas are alternately arranged on the outer circumferential surface of each pattern roller in the circumferential direction. The linear trace forming region has a plurality of high hardness particles on the surface.

7. The manufacturing device of the electromagnetic wave absorbing film according to claim 6, characterized in that: The linear trace non-formation region of the pattern roller is retracted radially inwardly from the linear trace formation region.

8. The manufacturing device of the electromagnetic wave absorbing film according to claim 7, characterized in that: The linear trace non-formation region of the pattern roller is retracted inward in the radial direction by more than 1 mm relative to the linear trace formation region.

9. An apparatus for manufacturing an electromagnetic wave absorbing film, the electromagnetic wave absorbing film comprising a plastic film and a metal thin film formed on one side of the plastic film, the metal thin film having a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and the linear traces alternately having high-density regions and low-density regions in each direction, the high-density regions being distributed in a lattice shape by the intersection of the linear traces in the two directions, The manufacturing device is characterized by comprising: Two pattern rollers, having a plurality of high hardness particles on the entire outer circumference; a mechanism for conveying the plastic film along the pattern roller; and The pressing rollers are arranged on both sides of each pattern roller. The two pattern rollers are inclined to opposite sides of the plastic film in the surface in sliding contact with the metal film. The manufacturing device includes a device for driving each pattern roller and / or a pressing roller on both sides of each pattern roller in a direction perpendicular to the metal film so that each pattern roller intermittently comes into sliding contact with the metal film.

10. A near-field electromagnetic wave absorber, comprising at least one plastic film and a first metal film and a second metal film, characterized in that: The first metal film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and in each direction, alternately has a high-density region where the linear traces are formed at a high density and a low-density region where the linear traces are formed at a low density, and the high-density region is distributed in a lattice shape by the intersection of the linear traces in the two directions. A plurality of substantially parallel and discontinuous linear traces are formed on the entire surface of the second metal film in two directions with irregular widths and intervals.

11. The near-field electromagnetic wave absorber according to claim 10, characterized in that: The surface resistivity of the high-density region is 30 to 200 Ω / □, and the surface resistivity of the low-density region is 0 to 20 Ω / □.

12. The near-field electromagnetic wave absorber according to claim 10, characterized in that: The length ratio of the high-density region to the low-density region in each direction on the first metal film is 5 / 1 to 1 / 5.

13. The near-field electromagnetic wave absorber according to claim 10, characterized in that: A first electromagnetic wave absorbing film and a second electromagnetic wave absorbing film are bonded. The first electromagnetic wave absorbing film has the first metal thin film on one side of a plastic film, and the second electromagnetic wave absorbing film has the second metal thin film on one side of a plastic film.

14. The near-field electromagnetic wave absorber according to claim 13, characterized in that: The first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film are bonded to the inner sides of the first metal film and the second metal film.

15. The near-field electromagnetic wave absorber according to claim 10, characterized in that: The first metal thin film and the second metal thin film are provided on both sides of a plastic film.

16. The near-field electromagnetic wave absorber according to claim 10, characterized in that: The intersection angle of the linear traces in two directions of each of the first metal thin film and the second metal thin film is 30 to 90 degrees.

17. The near-field electromagnetic wave absorber according to claim 10, characterized in that: The width of the linear traces of the first metal thin film and the second metal thin film is in the range of 0.1 to 100 μm and is 2 to 50 μm on average, and the interval between the linear traces is in the range of 0.1 to 500 μm and is 10 to 100 μm on average.

18. The near-field electromagnetic wave absorber according to any one of claims 10 to 17, characterized in that: The first metal film has: a first linear trace group having the high-density area of ​​the linear traces and the low-density area of ​​the linear traces alternately in a first direction; and a second linear trace group having the high-density area of ​​the linear traces and the low-density area of ​​the linear traces alternately in a second direction different from the first direction, Due to the overlap of the first linear trace group and the second linear trace group, overlapping portions of the high-density regions, overlapping portions of the high-density regions and the low-density regions, and overlapping portions of the low-density regions are formed on the first metal film. The repeated parts of the high-density regions are distributed in a dotted pattern. The repeated parts of the high-density regions and the repeated parts of the high-density regions and the low-density regions are combined to form a lattice pattern. The overlapping parts of the low-density regions are distributed in a dotted pattern.

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