Electromagnetic-wave-absorbing film and its production apparatus, and near-field electromagnetic wave absorber comprising such electromagnetic-wave-absorbing film

Abstract

An electromagnetic wave absorbing film of the present invention comprises a plastic film and a metal film formed on one side of the plastic film. The metal film has a plurality of substantially parallel linear marks formed in two directions with irregular widths and intervals. In each direction, the linear marks alternately have high-density regions and low-density regions. By the intersection of the linear marks in the two directions, the high-density regions of the linear marks become a grid.

Description

Electromagnetic Wave Absorbing Film, Manufacturing Apparatus Thereof, and Near-Field Electromagnetic Wave Absorber Having the Electromagnetic Wave Absorbing Film The present invention relates to an electromagnetic wave absorbing film and a near-field electromagnetic wave absorber, and an apparatus for manufacturing the electromagnetic wave absorbing film. The electromagnetic wave absorbing film has, for example, a high radiation noise absorption ability in a wide frequency range of 100 MHz to 5 GHz and can be used without connecting to a ground point. In order to prevent malfunctioning and the like caused by electromagnetic wave noise emitted from electronic components in various communication machines or electronic machines, various electromagnetic wave absorbers have been put into practical use. Under such circumstances, the present inventor proposed, in Japanese Patent No. 4685977, a metal thin film-plastic composite film with linear marks having reduced anisotropy of electromagnetic wave absorption ability, which is characterized by having a plastic film and a single-layer or multi-layer metal thin film provided on at least one surface of the plastic film, and a plurality of substantially parallel and intermittent linear marks formed on the metal thin film in two directions with irregular widths and intervals. Japanese Patent No. 4685977 describes that if a plurality of metal thin film-plastic composite films with linear marks are laminated directly or with a dielectric layer interposed therebetween, the electromagnetic wave absorption ability is improved. Although the metal thin film-plastic composite film with linear marks of Japanese Patent No. 4685977 has excellent conductive noise absorption ability in a wide frequency range, the radiation noise absorption ability in a frequency band of less than 1 GHz is not necessarily sufficient. Japanese Patent No. 5203295 discloses an electromagnetic wave absorbing film, which is characterized by laminating a magnetic composite film and a non-magnetic composite film. The magnetic composite film has a plastic film and a magnetic metal thin film provided on at least one surface of the plastic film, and the non-magnetic composite film has a plastic film and a non-magnetic metal thin film provided on at least one surface of the plastic film. On at least one of the magnetic metal thin film and the non-magnetic metal thin film, a plurality of substantially parallel and intermittent linear marks are formed in at least one direction with irregular lengths, widths and intervals. The linear marks 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 marks have a width within the range of 0.1 to 1000 μm. Japanese Patent No. 5203295 describes that an electromagnetic wave absorbing film having a surface resistance of the magnetic metal thin film of 1 to 377 Ω / □ and a surface resistance of the non-magnetic metal thin film of 377 to 10000 Ω / □ exhibits excellent absorption of electromagnetic wave noise in the near field. However, the absorption of electromagnetic wave noise in Japanese Patent No. 5203295 is the so-called absorption of conductive noise, and it is known that there is a frequency at which the radiation noise in a wide frequency range of less than 1 GHz to several GHz is maximized. Therefore, when putting this electromagnetic wave absorbing film into practical use, in order to prevent the radiation of the maximized noise, it is necessary to connect to a ground point (GND). WO2012 / 090586 discloses a near-field electromagnetic wave absorber formed by bonding a plurality of electromagnetic wave absorption films. The electromagnetic wave absorption film is formed by depositing a metal thin film on one side of a plastic film. It is characterized in that not only at least one metal thin film of the electromagnetic wave absorption film has a magnetic metal thin film layer, but also a plurality of substantially parallel discontinuous linear traces are formed on the metal thin film of at least one electromagnetic wave absorption film in two directions with irregular widths and intervals. WO2012 / 090586记载有:各電磁波吸收膜的金屬薄膜在形成線狀痕後具有50~1500Ω / □的範圍內的表面電阻。该近场电磁波吸收体亦在未满1GHz至数GHz的宽广频率范围中的传导噪音的吸收能力上表现优异。然而,已知在WO2012 / 090586号的近场电磁波吸收体中,存在有关于辐射噪音最大化的频率。因此,与日本专利第5203295号同样的,要将该近场电磁波吸收体加以实用化时,为了防止最大化的噪音的辐射,需要连接至接地点(GND)。 Japanese Patent No. 5559668 discloses an electromagnetic wave absorber formed by laminating a plurality of electromagnetic wave absorption films隔着介电体在电磁波反射体之前。其特征在于各电磁波吸收膜在塑料膜的一面上形成导体层,各电磁波吸收膜的导体层具有100~1000Ω / □范围内的表面电阻,最前方的电磁波吸收膜的导体层的表面电阻比第二前方的电磁波吸收膜的导体层的表面电阻大上100Ω / □以上,并且,(a)在前述电磁波吸收膜为二片的情况下,第一个电磁波吸收膜与第二个电磁波吸收膜的间隔和前述第二个电磁波吸收膜与前述电磁波反射体的间隔的比为100:30~80:70;(b)在前述电磁波吸收膜为三片以上的情况下,第一个电磁波吸收膜与第二个电磁波吸收膜的间隔和前述第二个电磁波吸收膜与第三个电磁波吸收膜的间隔的比为100:30~80:70;在前述电磁波吸收膜的导体层上,在两个方向中以不规则的宽度及间隔形成有实质平行的多个断断连续的线状痕,前述线状痕的90%以上在0.1~100μm的范围内,且平均为1~50μm,前述线状痕的间隔在0.1~200μm的范围内,且平均为1~100μm。 需要说明的是,原文中“隔着介电体在电磁波反射体之前”表述不太准确和完整,可能影响理解,你可根据实际情况进一步调整完善。Japanese Patent No. 5559668 describes that: since the surface resistance of the conductor layer of the foremost electromagnetic wave absorption film is 100 Ω / □ or more greater than the surface resistance of the conductor layer of the second foremost electromagnetic wave absorption film, compared with the case of simply laminating a plurality of electromagnetic wave absorption films having the same surface resistance, it not only has significantly higher electromagnetic wave absorption ability, but also the anisotropy of the electromagnetic wave absorption ability is reduced. However, since this electromagnetic wave absorber has a structure in which a plurality of electromagnetic wave absorption films are laminated隔着a dielectric in front of an electromagnetic wave reflector (aluminum plate), although it is applicable to uses such as ETC and FRID, it cannot be used as a near-field electromagnetic wave absorber to be attached to electronic components, etc. (Object of the Invention) Therefore, a first object of the present invention is to provide an electromagnetic wave absorption film that has high radiation noise absorption ability, for example, in a wide frequency range of 100 MHz to 5 GHz, and can be used without connecting to a ground point. A second object of the present invention is to provide a near-field electromagnetic wave absorber that has high radiation noise absorption ability, for example, in a wide frequency range of 100 MHz to 5 GHz, and can be used without connecting to a ground point. A third object of the present invention is to provide a device that can efficiently manufacture the above-mentioned electromagnetic wave absorption film. (Summary of the Invention) As a result of in-depth research in view of the above objects, the present inventor has found that (a) if linear marks are intermittently formed in such a manner that regions with a higher density of linear marks and regions with a lower density are alternately arranged in each of the two directions, instead of forming linear marks in two directions over the entire surface of the metal thin film, the high-density regions of the linear marks can be distributed in a grid pattern by the intersection of the linear marks in the two directions, and an electromagnetic wave absorption film having high radiation noise absorption ability in a wide frequency range of, for example, 100 MHz to 5 GHz can be obtained. (b) By combining an electromagnetic wave absorption film having a high-density region of linear marks in a grid pattern with an electromagnetic wave absorption film having linear marks formed in two directions over the entire surface of the metal thin 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 a device for forming linear marks in two directions over the entire surface of the metal thin film, by changing the shape or driving method of the pattern roller, regions with a higher density of linear marks and regions with a lower density can be alternately formed in each of the two directions, and the present invention has been conceived. That is, an electromagnetic wave absorbing film of the present invention has a plastic film and a metal thin film formed on one surface of the aforementioned plastic film, and the aforementioned metal thin film has a plurality of linearly shaped marks formed in two directions with irregular widths and intervals and substantially parallel to each other; in each direction, there are alternately provided a high-density region where the aforementioned linearly shaped marks are formed at a high density and a low-density region where the aforementioned linearly shaped marks are formed at a low density; by the intersection of the linearly shaped marks in two directions, the high-density regions of the linearly shaped marks are distributed in a grid pattern. In each direction, preferably, the surface resistivity of the aforementioned high-density region is 30 to 200 Ω / square, and the surface resistivity of the aforementioned low-density region is 0 to 20 Ω / square. The length ratio of the aforementioned high-density region to the aforementioned low-density region in each direction is preferably 5 / 1 to 1 / 5. In each direction, preferably, the length of the aforementioned high-density region is 0.2 to 10 mm, and the length of the aforementioned low-density region is 0.2 to 10 mm. The first device of the present invention for manufacturing the above-mentioned electromagnetic wave absorbing film includes: two pattern rollers; means for conveying the aforementioned plastic film in such a manner that the aforementioned metal thin film is in sliding contact with the two pattern rollers; and a pressing roller that presses the aforementioned metal thin film against the aforementioned pattern rollers; wherein, the two pattern rollers are inclined in opposite directions with respect to the width direction of the aforementioned plastic film within the plane of sliding contact with the aforementioned metal thin film; on the outer peripheral surface of each pattern roller, a linearly shaped mark forming region and a linearly shaped mark non-forming region are alternately provided in the circumferential direction; the aforementioned linearly shaped mark forming region has a plurality of high-hardness fine particles on its surface. In an embodiment of the present invention, the aforementioned linearly shaped mark non-forming region of the aforementioned pattern roller retreats inward in the radial direction with respect to the aforementioned linearly shaped mark forming region. The retreat distance Dh of the aforementioned linearly shaped mark non-forming region is preferably 1 mm or more. In another embodiment of the present invention, the aforementioned linearly shaped mark non-forming region does not have high-hardness fine particles. In this case, the radius of the aforementioned linearly shaped mark non-forming region may be the same as that of the aforementioned linearly shaped mark forming region or may be smaller. The second device of the present invention for manufacturing the above-mentioned electromagnetic wave absorbing film includes: two pattern rollers that have a plurality of high-hardness fine particles on the entire outer peripheral surface; means for conveying the aforementioned plastic film along the aforementioned pattern rollers; and pressing rollers arranged on both sides of each pattern roller; wherein, the two pattern rollers are inclined in opposite directions with respect to the width direction of the aforementioned plastic film within the plane of sliding contact with the aforementioned metal thin film; and the aforementioned device includes: a device for driving each pattern roller and / or the pressing rollers on both sides of the pattern roller in the vertical direction with respect to the aforementioned metal thin film in such a manner that each pattern roller intermittently slides in contact with the aforementioned metal thin film. The near-field electromagnetic wave absorber of the present invention has at least one plastic film and first and second metal thin films. Among them, the aforementioned first metal thin film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and in each direction, the aforementioned linear traces alternately have high-density regions and low-density regions. By the intersection of the linear traces in the two directions, the aforementioned high-density regions are distributed in a grid pattern over the entire surface of the aforementioned first metal thin film; on the entire surface of the aforementioned second metal thin film, a plurality of discontinuous linear traces substantially parallel in two directions are formed with irregular widths and intervals. In the near-field electromagnetic wave absorber of the present invention, in each direction of the aforementioned linear traces in the aforementioned first metal thin film, preferably, the surface resistivity of the aforementioned high-density region is 30 to 200 Ω / square, and the surface resistivity of the aforementioned low-density region is 0 to 20 Ω / square. In the near-field electromagnetic wave absorber of the present invention, the length ratio of the aforementioned high-density region to the aforementioned low-density region in each direction in the aforementioned first metal thin film is preferably 5 / 1 to 1 / 5. In the near-field electromagnetic wave absorber of the present invention, preferably, the length of the aforementioned high-density region in each direction in the aforementioned first metal thin film is 0.2 to 10 mm, and the length of the aforementioned low-density region is 0.2 to 10 mm. The near-field electromagnetic wave absorber of the present invention preferably has (a) a first metal thin film with linear traces, which 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 with high density and a low-density region where the linear traces are formed with low density. By the intersection of the linear traces in the two directions, the aforementioned high-density regions are distributed in a grid pattern, (b) a second metal thin film with linear traces, which has a plurality of discontinuous linear traces substantially parallel in two directions formed on the entire surface with irregular widths and intervals. In the near-field electromagnetic wave absorber of the present invention, the aforementioned first metal thin film with linear traces has: a first group of linear traces, which alternately has the aforementioned high-density region of the linear traces and the aforementioned low-density region of the linear traces in the first direction; and a second group of linear traces, which alternately has the aforementioned high-density region of the linear traces and the aforementioned low-density region of the linear traces in a second direction different from the aforementioned first direction; by the coincidence of the aforementioned first and second groups of linear traces, on the aforementioned metal thin film, there are formed overlapping portions of the aforementioned high-density regions with each other, overlapping portions of the aforementioned high-density region and the aforementioned low-density region, and overlapping portions of the aforementioned low-density regions with each other; the overlapping portions of the aforementioned high-density regions with each other are distributed in a dot pattern; the overlapping portions of the aforementioned high-density regions with each other and the overlapping portions of the aforementioned high-density region and the aforementioned low-density region together form a grid-like pattern; the overlapping portions of the aforementioned low-density regions with each other are distributed in a dot pattern. The near-field electromagnetic wave absorber according to the first embodiment of the present invention preferably has the following structure: a first electromagnetic wave absorption film having the aforementioned first metal thin film on one surface of a plastic film, and a second electromagnetic wave absorption film having the aforementioned second metal thin film on one surface of a plastic film are bonded together. In the near-field electromagnetic wave absorber according to the first embodiment of the present invention, preferably, the aforementioned first and second electromagnetic wave absorption films are bonded together with the aforementioned first and second metal thin films on the inside. The near-field electromagnetic wave absorber according to the second embodiment of the present invention preferably has the following structure: the aforementioned first and second metal thin films are provided on both surfaces of a single plastic film. In the electromagnetic wave absorption film and the near-field electromagnetic wave absorber of the present invention, preferably, the crossing angle of the linear traces in two directions is 30 to 90°. In the electromagnetic wave absorption film and the near-field electromagnetic wave absorber of the present invention, preferably, the thickness of the aforementioned metal thin film is 20 to 100 nm. In the electromagnetic wave absorption film and the near-field electromagnetic wave absorber of the present invention, preferably, the aforementioned metal thin film is made of aluminum. In the electromagnetic wave absorption film and the near-field electromagnetic wave absorber of the present invention, preferably, the width W of the aforementioned linear trace is in the range of 0.1 to 100 μm, and the average is 1 to 50 μm, and the interval I of the aforementioned linear traces is in the range of 0.1 to 500 μm, and the average is 1 to 200 μm. (Effect of the invention) The electromagnetic wave absorption film of the present invention is formed by overlapping a two-directional linear trace group having high-density regions and low-density regions with linear traces alternately on a single metal thin film, and has a linear trace distribution in which the high-density regions extend in a grid pattern. Therefore, for example, it has high radiation noise absorption ability in a wide frequency range from 100 MHz to 5 GHz. Further, the near-field electromagnetic wave absorber of the present invention is composed of an electromagnetic wave absorption film in which the high-density linear trace regions are distributed in a grid pattern and an electromagnetic wave absorption film having linear traces formed on the entire surface of the metal thin film. Therefore, it has higher radiation noise absorption ability. The electromagnetic wave absorption film and the near-field electromagnetic wave absorber of the present invention having such characteristics do not need to be connected to a ground point, can be attached to electronic components in various electronic devices and communication devices such as personal computers, mobile phones, and smartphones, and can effectively suppress electromagnetic wave noise. The device of the present invention is obtained by (a) replacing the pattern roll in the device for forming linear traces on the entire surface of the metal thin film with a pattern roll having linear trace forming regions and linear trace non-forming regions alternately provided in the circumferential direction on the outer peripheral surface, or (b) adding a device for driving at least one of the pattern roll and the pressing rolls on both sides of the pattern roll in the vertical direction with respect to the metal thin film in the device for forming linear traces on the entire surface of the metal thin film. Therefore, the electromagnetic wave absorption film of the present invention can be efficiently manufactured with a relatively simple structure. The embodiments of the present invention will be described in detail with reference to the accompanying drawings. Unless otherwise specified, the description of one embodiment can also be applied to other embodiments. Also, the following description is not restrictive, and various modifications can be made within the scope of the technical idea of the present invention. [1] Electromagnetic wave absorption film Fig. 1a is a plan view schematically showing an example of the first linear trace group constituting the electromagnetic wave absorption film of the present invention, and Fig. 1b is a sectional view taken along line A-A of Fig. 1a. On the metal thin film 11 formed on one surface of the plastic film 10, in one direction (first direction) F 1 a plurality of substantially parallel linear traces 12a are formed with irregular widths and intervals, and along one direction F 1 high-density regions 112 where the linear traces 12a are formed and low-density regions 113 where substantially no linear traces 12a are formed are alternately arranged. Here, all the linear traces 12a in the plurality of high-density regions 112 alternately arranged in one direction F 1 are collectively referred to as the "first linear trace group", and the metal thin film 11 having the first linear trace group is referred to as the "first metal thin film with linear traces" 11a. Along the direction F of the linear traces 12a 1 the alternately formed high-density regions 112 and low-density regions 113 form stripes. In addition, the direction F of the linear traces 12a 1 the lengths La 1 and La 2 of the high-density regions 112 and low-density regions 113 are determined according to the manufacturing method and apparatus. (1) Plastic film The resin forming the plastic film 10 is not particularly limited as long as it has insulation, sufficient strength, flexibility, and processability. For example, polyester (such as polyethylene terephthalate), polyarylene sulfide (such as polyphenylene sulfide), polyethersulfone, polyetheretherketone, polycarbonate, acrylic resin, polystyrene, polyolefin (such as polyethylene, polypropylene), etc. can be mentioned. Among them, from the viewpoints of strength and cost, a polyethylene terephthalate (PET) film is preferred. The thickness of the plastic film 10 can be made about 10 to 100 μm, but in order to make the electromagnetic wave absorption film and the near-field electromagnetic wave absorber as thin as possible, it is preferably about 10 to 30 μm. (2) Metal thin film The metal thin film 11 is composed of a non-magnetic metal or a magnetic metal. Examples of the non-magnetic metal include aluminum, copper, silver, etc. Examples of the magnetic metal include nickel, chromium, etc. These metals can of course be not only monomers but also alloys. From the viewpoints of cost and corrosion resistance, aluminum is preferred. The metal thin film 11 can be formed by well-known methods such as sputtering method, vacuum evaporation method, etc. From the viewpoint of controlling the processing degree of the linear marks, the thickness of the metal thin film 11 is preferably 20 to 100 nm, more preferably 30 to 90 nm, and most preferably 40 to 80 nm. (3) First group of linear marks As described above, in each high-density region 112 of the first metal thin film 11a with linear marks, in one direction F 1 a plurality of linear marks 12a substantially parallel to the metal thin film 11 are formed with irregular widths and intervals. As shown in Fig. 1b, the linear marks 12a have various widths W and intervals I in the transverse direction orthogonal to their arrangement direction F 1 The width W and interval I of the linear marks 12a are both obtained based on the height (original height) of the surface S of the metal thin film 11 before forming the linear marks. In addition, for the sake of illustration, the depth of the linear marks 12a is exaggerated in Fig. 1b. The width W of the linear marks 12a is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm, still more preferably in the range of 0.5 to 50 μm, and most preferably in the range of 0.5 to 20 μm. Also, the average width Wav of the linear marks 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 marks 12a is preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.5 to 200 μm, still more preferably in the range of 1 to 100 μm, and most preferably in the range of 1 to 50 μm. Also, the average interval Iav of the linear marks 12a is preferably 1 to 200 μm, more preferably 5 to 100 μm, and most preferably 10 to 80 μm. In addition, when calculating the width W and average width Wav and interval I and average interval Iav of the linear marks 12a, the linear marks 12a are counted up to a width of 0.1 μm. The same applies hereinafter unless otherwise specified. The length Ls of the linear marks 12a is determined not only by the sliding contact conditions (mainly the relative speed between the pattern roller and the plastic film, and the contact angle of the plastic film relative to the pattern roller), but also by the length of the high-density region 12. Since the long-side direction gap of the linear marks 12a is located within the high-density region 112, the length Ls of the linear marks 12a is the same as or less than the length La 1 of the high-density region 112 1 。 (a) Formation density of the first linear marks Generally speaking, if the processing degree of the linear marks increases, the width W (proportional to the depth) of the linear marks will become larger and the interval I will become smaller. Therefore, the proportion (density) of the linear marks in the metal thin film 11 will become larger. Therefore, the processing degree of the linear marks can be expressed by the density of the linear marks. However, the linear marks are not only very small but also of different lengths and are formed at a high density, so it is difficult to directly measure the density of the linear marks. Therefore, focusing on the fact that the density of the linear marks increases and the surface resistivity and light transmittance of the metal thin film 11 also increase, the density of the linear marks is evaluated by the surface resistivity and light transmittance of the metal thin film 11. Although no linear marks 12a are shown in the region 113 in Fig. 1a, according to the manufacturing method, it is likely that, for example, as shown in Fig. 2, a small number of linear marks 12a are also formed in the region 113. However, as long as the processing degree of the linear marks 12a is low, the effects of the present invention can be fully obtained. Therefore, the case where a small number of linear marks 12a are formed in the region 113 is also included in the scope of the present invention. Therefore, in order to also include the case where a small number of linear marks 12a are formed in the region 113, the region 113 is referred to as the "low-density region of linear marks" or simply as the "low-density region" instead of the "region without linear marks". Along with this, the high-density region 112 where the linear marks are formed at a high density is referred to as the "high-density region of linear marks" or simply as the "high-density region". (i) Surface resistivity The surface resistivity of the metal thin film 11 in the high-density region 112 is preferably 30 to 200 Ω / sq. If the surface resistivity of the metal thin film 11 in the high-density region 112 is less than 30 Ω / sq or exceeds 200 Ω / sq, the electromagnetic wave absorption film cannot exhibit sufficient electromagnetic wave absorption ability. On the other hand, the surface resistivity of the metal thin film 11 in the low-density region 113 is preferably 0 to 20 Ω / sq. In addition, the lower limit of 0 Ω / sq is the same as the surface resistivity of the metal thin film itself. That is, it is also possible that no linear marks 12a are formed in the metal thin film 11 in the low-density region 113. If the surface resistivity of the metal thin film 11 in the low-density region 113 exceeds 20 Ω / sq, the effect of providing the low-density region 113 becomes insufficient. More preferably, the surface resistivity of the metal thin film 11 in the high-density region 112 is 30 to 150 Ω / sq, and the surface resistivity of the metal thin film 11 in the low-density region 113 is 0 to 15 Ω / sq. When the high-density region 112 and the low-density region 113 are very small, it is difficult to measure their respective surface resistivities. Therefore, under the same conditions as the high-density region 112 in the metal thin film with linear scratches formed alternately in one direction as shown in Fig. 1a, the surface resistivity of the metal thin film with linear scratches formed over the entire surface is measured and used as the surface resistivity Rs1 of the high-density region 112. Also, the surface resistivity Rs of the metal thin 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 almost 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. (ii) Light transmittance The light transmittance of the metal thin film 11 in the high-density region 112 is preferably 3 to 10%, more preferably 4 to 8%. Also, the light transmittance of the metal thin film 11 in the low-density region 113 is preferably 0 to 2.5%, more preferably 0 to 2%. In addition, a light transmittance of 0% is a state where no linear scratches 12a are formed at all. In addition, the light transmittance 11 of the metal thin film 11 in the high-density region 112 is related to the surface resistivity. (b) Lengths of the high-density region and the low-density region In the direction F of the linear scratch 12a 1 the length La of the high-density region 112 1 is preferably 0.2 to 10 mm, and the length La of the low-density region 113 2 is preferably 0.2 to 10 mm. If the length La of the high-density region 112 1 is less than 0.2 mm, or the length La of the low-density region 113 2 exceeds 10 mm, the electromagnetic wave absorption ability will be too low. On the other hand, if the length La of the high-density region 112 1 exceeds 10 mm, or the length La of the low-density region 113 2 is less than 0.2 mm, the effect of providing the low-density region 113 will be insufficient, and the radiation noise absorption ability of the electromagnetic wave absorption film will become low. The length La of the high-density region 112 1 is more preferably 1 to 5 mm, and the length La of the low-density region 113 2 is more preferably 1 to 5 mm. Along the direction F of the linear scratch 12a 1 , the length ratio La of the high-density region 112 to the low-density region 113 1 / La 2 is preferably 5 / 1 to 1 / 5. If the length ratio La 1 / La 2 is less than 1 / 5, the electromagnetic wave absorption ability will be too low. Also, if the length ratio La 1 / La 2 exceeds 5 / 1, the effect of setting the low-density region 113 will be insufficient, and the radiation noise absorption ability of the electromagnetic wave absorption film will become low. From the viewpoint of the isotropy of the electromagnetic wave absorption ability, the length ratio La 1 / La 2 is more preferably 2 / 1 to 1 / 2, and particularly preferably 1 / 1. (4) Second linear mark group Fig. 3 is a plan view schematically showing an example of the first linear mark shown in Fig. 1 and the second linear mark group constituting the electromagnetic wave absorption film of the present invention. The second linear mark group is formed in a manner that repeats on the metal thin film 11 on which the first linear mark group is formed. As will be described later, the (second) direction F of the linear mark 12b in the second linear mark group 2 must be different from the (first) direction F of the linear mark 12a in the first linear mark group 1 . In addition, the range of the width W, average width Wav, interval I, and average interval Iav of the linear mark 12b in the second linear mark group can be the same as the range in the first linear mark group. Also, the range of the surface resistivity and light transmittance of the high-density region 112 and low-density region 113 in the second linear mark group, and the range of the length and ratio thereof can also be the same as the range in the first linear mark group. The length La of the high-density region 112 in the first linear mark group 1 can be the same as or different from the length Lb of the high-density region 112 in the second linear mark group 1 . In the case of being different, the ratio La 1 / Lb 1Preferably, it is 1 / 2 to 2 / 1, more preferably 2 / 3 to 3 / 2. In addition, even 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 can be the same as that in the first linear trace group. That is to say, the second linear trace group can be the same as the first linear trace group except for the direction of the linear traces. (5) Structure of the electromagnetic wave absorption film Fig. 4 is a plan view schematically showing an example of the electromagnetic wave absorption film 100 of the present invention having both a first linear trace group and a second linear trace group. By overlapping the first and second linear trace groups, a repeating portion 114 of high-density regions 112 with each other, a repeating portion 115 of a high-density region 112 and a low-density region 113, and a repeating portion 116 of low-density regions 113 with each other are formed on the metal thin film 11. Hereinafter, the repeating portion 114 of high-density regions 112 with each other is simply referred to as "high-density repeating portion", the repeating portion 115 of a high-density region 112 and a low-density region 113 is referred to as "high-density - low-density repeating portion", and the repeating portion 116 of low-density regions 113 with each other is referred to as "low-density repeating portion". The high-density repeating portion 114 is distributed in a dot pattern, but the high-density repeating portion 114 and the high-density - low-density repeating portion 115 together form a grid pattern. Also, the low-density repeating portion 116 is distributed in a dot pattern. In the high-density repeating portion 114, as schematically shown in Fig. 5, the linear trace 12a of the first linear trace group and the linear trace 12b of the second linear trace group cross at a crossing angle θs. The crossing angle θs of the linear traces 12a, 12b is preferably 30 to 90°, more preferably 60 to 90°, most preferably 80 to 90°, and particularly preferably 90°. As the crossing angle approaches 90°, the electromagnetic wave absorption ability becomes isotropic. In Fig. 5, Ls 1 、Ls 2 respectively represent the lengths of the linear traces 12a, 12b. The length Ls of the linear trace 12a 1 may also be different from the length Ls of the linear trace 12b 2 , but if they are the same, the electromagnetic wave absorption ability will be isotropic and is preferable. In the case where the length Ls of the linear trace 12a 1 is different from the length Ls of the linear trace 12b 2 , the length ratio Ls 1 / Ls 2 is preferably 1 / 2 to 2 / 1, more preferably 2 / 3 to 3 / 2. In the high-density - low-density repeating portion 115, mainly one of the linear traces 12a and 12b is formed, and the other is hardly formed. Therefore, the high-density - low-density repeating portion 115 exhibits a lower conduction noise absorption ability than the high-density repeating portion 114, but helps to improve the radiation noise absorption ability. In each high-density - low-density repeating portion 115, almost all of the linear traces are arranged in one direction, but almost all of the linear traces in adjacent high-density - low-density repeating portions 115 are arranged in directions with a crossing angle difference θs. Therefore, the electromagnetic wave absorption ability of the entire electromagnetic wave absorption film is almost isotropic. In the low-density repeating portion 116, the linear traces 12a and 12b are hardly formed. Therefore, it has a function close to that of the metal thin film 11 itself and exhibits a relatively large radiation noise absorption ability. 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 high-density repeating portion 114 and attenuates there. In the electromagnetic wave absorption film 100 of the present invention, the high-density repeating portions 114 are distributed in a grid pattern across the high-density - low-density repeating portions 115 due to the crossing of the linear traces 12a and 12b. Therefore, the high-density regions 112 are also distributed in a grid pattern on the metal thin film 11. Due to the grid pattern distribution of the high-density regions 112, the electromagnetic wave absorption film 100 of the present invention can exhibit good radiation noise absorption ability while ensuring sufficient conduction noise absorption ability. [2] Near-field electromagnetic wave absorber The near-field electromagnetic wave absorber of the present invention is characterized by having at least one plastic film and first and second metal thin films. The first metal thin film has a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and in each direction, the linear traces alternately have high-density regions and low-density regions. Due to the crossing of the linear traces in the two directions, the high-density regions are distributed in a grid pattern over the entire surface of the first metal thin film, and on the entire surface of the second metal thin film, a plurality of intermittently formed substantially parallel linear traces are formed in two directions with irregular widths and intervals. Specifically, the near-field electromagnetic wave absorber of the present invention preferably has: (a) a first metal thin film with linear traces, the metal thin film having a plurality of substantially parallel linear traces formed in two directions with irregular widths and intervals, and in each direction having a high-density region where the linear traces are formed with a high density and a low-density region where the linear traces are formed with a low density. Due to the crossing of the linear traces in the two directions, the high-density regions are distributed in a grid pattern; and (b) a second metal thin film with linear traces, the metal thin film having a plurality of intermittently formed substantially parallel linear traces in two directions with irregular widths and intervals formed over the entire surface. Preferably, the aforementioned first metal thin film with linear marks has: a first group of linear marks that alternately have the aforementioned high-density regions of the linear marks and the aforementioned low-density regions of the linear marks in a first direction; and a second group of linear marks that alternately have the aforementioned high-density regions of the linear marks and the aforementioned low-density regions of the linear marks in a second direction different from the aforementioned first direction; by the coincidence of the aforementioned first and second groups of linear marks, there are formed repeating portions of the aforementioned high-density regions with each other, repeating portions of the aforementioned high-density regions and the aforementioned low-density regions, and repeating portions of the aforementioned low-density regions with each other on the aforementioned metal thin film; the repeating portions of the aforementioned high-density regions with each other are distributed in a dot shape; the repeating portions of the aforementioned high-density regions with each other and the repeating portions of the aforementioned high-density regions and the aforementioned low-density regions together form a grid-like pattern; the repeating portions of the aforementioned low-density regions with each other are distributed in a dot shape. (1) First Embodiment As an example of a near-field electromagnetic wave absorber according to the first embodiment of the present invention, as shown in FIGS. 6a and 6b, a first electromagnetic wave absorption film 100a having a first metal thin film 11a with linear marks on a plastic film 10a and a second electromagnetic wave absorption film 100b having a second metal thin film 11b with linear marks on a plastic film 10b are bonded together with a bonding layer 20 interposed therebetween. In this example, since the first and second metal thin films 11a and 11b with linear marks face each other, in order to prevent the two from being electrically connected, the adhesive layer 20 is a non-conductive layer. If the adhesive layer 20 is made very thin, the first and second metal thin films 11a and 11b with linear marks will be electromagnetically coupled. Although the adhesive layer 20 can be formed by an adhesive, it can also be formed by heat sealing or a double-sided tape. The second electromagnetic wave absorption film 100b can be the same as the first electromagnetic wave absorption film 100a except that a plurality of substantially parallel linear marks are formed on the entire surface of the metal thin film 11 in two directions with irregular widths and intervals. FIG. 6c shows an example of the metal thin film 11b with linear marks of the second electromagnetic wave absorption film 100b. The width W of the linear marks 12 in the second metal thin film 11b with linear marks is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm, still more preferably in the range of 0.5 to 50 μm, and most preferably in the range of 0.5 to 20 μm. Also, the average width Wav of the linear marks 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 marks 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. Also, the average interval Iav of the linear marks 12 is preferably 1 to 200 μm, more preferably 5 to 100 μm, and most preferably 10 to 80 μm. The length Ls of the linear marks 12 in the second metal thin film 11b with linear marks is determined according to the sliding contact conditions (mainly the relative speed between the pattern roller and the plastic film). Therefore, 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 marks 12 is not particularly limited, and in practical use, it can be on the order of 1 to 100 mm, preferably 2 to 10 mm. The crossing angle θs of the linear marks 12 in two directions in the second metal thin film 11b with linear marks is preferably 30 to 90°, more preferably 45 to 90°, most preferably 60 to 90°, and particularly preferably 90°. As shown in Fig. 7, the first and second electromagnetic wave absorbing films 100a and 100b may be bonded in such a way that the metal thin films 11a and 11b with linear marks are located on the same side of each plastic film, instead of facing the first and second metal thin films 11a and 11b with linear marks. (2) Second Embodiment Fig. 8 shows a near-field electromagnetic wave absorber according to the second embodiment of the present invention. The near-field electromagnetic wave absorber is composed of a plastic film 10 and first and second metal thin films 11a and 11b with linear marks provided on both sides of the plastic film 10. The first and second metal thin films 11a and 11b with linear marks themselves may be the same as those in the first embodiment. [3] Manufacturing Apparatus for Electromagnetic Wave Absorbing Film Since the first metal thin film with linear marks has a more complex structure than the second metal thin film with linear marks, the manufacturing apparatus for the second electromagnetic wave absorbing film with the second metal thin film with linear marks will be described first. (1) Manufacturing Apparatus for Second Electromagnetic Wave Absorbing Film Figures 9a to 9e show an example of an apparatus for manufacturing the second electromagnetic wave absorbing film 100b. The illustrated apparatus includes: (a) a reel 21 that unwinds a plastic film 10 having a metal thin film; (b) a first pattern roller 2a that is disposed obliquely with respect to the width direction of the plastic film 10; (c) a first pressing roller 3a that is disposed on the upstream side of the first pattern roller 2a on the side opposite to the first pattern roller 2a; (d) a second pattern roller 2b that is inclined in a direction opposite to the first pattern roller 2b with respect to the width direction of the plastic film 10 and is disposed on the same side as the first pattern roller 2a; (e) a second pressing roller 3b that is disposed on the downstream side of the second pattern roller 2b on the side opposite to the second pattern roller 2b; (f) a reel 24 that winds back the plastic film 10' (second electromagnetic wave absorbing film 100b) having a metal thin film with linear marks formed thereon. A plurality of guide rollers 22 and 23 are disposed at specified positions. Each of the pattern rollers 2a and 2b is supported by support rollers (e.g., rubber rollers) 5a and 5b to prevent bending. In the apparatus shown in Figure 9a, one pressing roller 3a and 3b is disposed near each of the pattern rollers 2a and 2b, but a pair of pressing rollers 3a and 3b may also be disposed on both sides of each of the pattern rollers 2a and 2b. As shown in Figure 9c, each of the pressing rollers 3a and 3b contacts the metal thin film of the plastic film 10 at a position lower than the sliding contact position with each of the pattern rollers 2a and 2b. Therefore, the plastic film 10 is pressed toward each of the pattern rollers 2a and 2b. By adjusting the height of each of the pressing rollers 3a and 3b under this condition, the pressing force of each of the pattern rollers 2a and 2b on the metal thin film can be adjusted. Specifically, if the position of each of the pressing rollers 3a and 3b is lowered, the pressing force of each of the pattern rollers 2a and 2b on the metal thin film of the plastic film 10 increases, so the linear marks formed on the metal thin film become deeper (the degree of processing of the metal thin film increases). On the contrary, if the position of each of the pressing rollers 3a and 3b is raised, the pressing force of each of the pattern rollers 2a and 2b on the metal thin film of the plastic film 10 decreases, so the linear marks formed on the metal thin film become shallower (the degree of processing of the metal thin film decreases). Generally, the deeper the linear marks become, the less the amount of metal remaining on the metal thin film, so the surface resistivity of the metal thin film with linear marks increases. Therefore, the surface resistivity of the metal thin film with linear marks can be adjusted by changing the pressing force of each of the pattern rollers 2a and 2b on the metal thin film of the plastic film 10. In addition, if the linear marks become deeper, the linear marks become wider, so the interval between the linear marks tends to narrow. The pressing force of the plastic film 10 on each of the pattern rollers 2a and 2b can also be adjusted by moving the position of each of the pattern rollers 2a and 2b in the direction toward the plastic film 10. The position movement of each of the pattern rollers 2a and 2b can be performed by a driving device (not shown) installed on each of the pattern rollers 2a and 2b. FIG. 9d shows the principle that the linear mark 12 is formed to be inclined with respect to the traveling direction of the plastic film 10. Since the pattern roller 2a is inclined with respect to the traveling direction of the plastic film 10, the moving direction (rotating direction) of the hard microparticles on the pattern roller 2a is different from the traveling direction of the plastic film 10. Therefore, as shown by X, if the hard microparticles at point A on the pattern roller 2a contact the metal thin film of the plastic film 10 to form a mark B at any time point, after a specified time, the hard microparticles will move to point A', and the mark B will move to B'. During the process of the hard microparticles moving from point A to point A', the mark B will be continuously formed, so that the linear mark 12 extending from point A' to point B' is formed. The direction and the crossing angle θs of the linear mark 12 formed by using the first and second pattern rollers 2a and 2b can be adjusted by changing the angles of the respective pattern rollers 2a and 2b with respect to the plastic film 10 and / or the peripheral speeds of the respective pattern rollers 2a and 2b with respect to the conveying speed of the plastic film 10. For example, if the peripheral speed a of the pattern roller 2a with respect to the conveying speed b of the plastic film 10 is increased, as shown by Y in FIG. 9d, the linear mark 12 can be made to be at 45° with respect to the traveling direction of the plastic film 10 like the line segment C'D'. Similarly, if the inclination angle θ of the pattern roller 2a with respect to the width direction of the plastic film 10 is changed 2 , the peripheral speed a of the pattern roller 2a can be changed. The same applies to the pattern roller 2b. Therefore, by adjusting the two pattern rollers 2a and 2b, the direction of the linear mark 12 can be changed. Since the respective pattern rollers 2a and 2b are inclined with respect to the plastic film 10, the plastic film 10 will receive a force in the width direction due to the sliding contact with the respective pattern rollers 2a and 2b. Therefore, in order to prevent the plastic film 10 from meandering, it is preferable to adjust the height and / or the angle of the respective pressing rollers 3a and 3b with respect to the respective pattern rollers 2a and 2b. For example, if the crossing angle θ between the axis of the pattern roller 2a and the axis of the pressing roller 3a is appropriately adjusted 3 , the width direction distribution of the pressing force can be obtained in a manner that eliminates the force in the width direction, thereby preventing the plastic film 10 from meandering. In addition, the adjustment of the interval between the pattern roller 2a and the pressing roller 3a also helps to prevent the plastic film 10 from meandering. In order to prevent the plastic film 10 from meandering and breaking, it is preferable that the rotating directions of the first and second pattern rollers 2a and 2b inclined with respect to the width direction of the plastic film 10 are the same as the traveling direction of the plastic film 10. Figure 10 shows another example of a device for forming orthogonal linear marks. The difference between this device and the devices shown in FIGS. 9a to 9e is that the second pattern roller 32b is arranged parallel to the width direction of the plastic film 10 (perpendicular to the traveling direction). Therefore, only the parts different from the devices shown in FIGS. 9a to 9e will be described below. The rotation direction of the second pattern roller 32b can be the same as or opposite to the traveling direction of the plastic film 10. Also, the second pressing roller 33b can be located on the upstream side or the downstream side of the second pattern roller 32b. As shown by Z in FIG. 9d, this device is suitable for forming orthogonal linear marks by making the direction of the linear marks 12' (line segment E'F') in the width direction of the plastic film 10. The conveying 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 2000 m / min. The inclination angle θ of the pattern roller 2 is preferably 20° to 60°, particularly preferably about 45°. The tension of the film 10 (proportional to the compressive force) is preferably 0.05 to 5 kgf / cm width. The pattern roller is preferably a roller having fine particles with a Mohs hardness of 5 or more on the surface, and the fine particles have sharp corners. The pattern roller is preferably a diamond roller described in, for example, Japanese Patent Application Laid-Open No. 2002-59487. Since the width of the linear marks is determined by the particle diameter of the fine particles, more than 90% of the diamond fine particles preferably have a particle diameter in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm. The diamond fine particles are preferably attached to the roller surface at an area ratio of 30% or more. The fixing of the diamond fine particles is preferably carried out by a metal layer such as nickel. (2) Manufacturing device for the first electromagnetic wave absorption film (a) First manufacturing device Except that linear mark forming regions and linear mark non-forming regions are alternately provided in the circumferential direction on the outer peripheral surface of each pattern roller, and the aforementioned linear mark forming regions have a plurality of high-hardness fine particles on the surface, the aforementioned first manufacturing device has substantially the same structure as the manufacturing device for the second electromagnetic wave absorption film. Therefore, the above-mentioned pattern roller will be described in detail. FIG. 11a shows an example of each pattern roller used in the first manufacturing apparatus. The pattern roller 102 is composed of a pattern roller body 102a, a linear mark formation region 102b and a linear mark non-formation region 102c which are alternately formed on the outer peripheral surface of the pattern roller body 102a at a prescribed interval. As shown in FIG. 11b, the linear mark formation region 102b includes a plurality of high-hardness fine particles 102d and a fixing layer 102e that holds the high-hardness fine particles 102d. Similar to the manufacturing apparatus for the second electromagnetic wave absorption film described above, the high-hardness fine particles 102d are preferably diamond fine particles, and the fixing layer 102e is preferably a metal layer such as nickel. The linear mark non-formation region 102c is preferably (a) a region where the fixing layer 102e that holds the plurality of high-hardness fine particles 102d is not formed, or (b) a region composed only of the fixing layer 102e (without the high-hardness fine particles 102d) so that even when the metal thin film 11 comes to a proximity position due to the rotation of the pattern roller 102, linear marks are not formed or hardly formed on the metal thin film 11. The central angle α1 of the linear mark formation region 102b is preferably 30 to 90°, more preferably 45 to 90°. Also, the central angle α2 of the linear mark non-formation region 102c is preferably 30 to 90°, more preferably 45 to 90°. In the illustrated example, since four linear mark formation regions 102b and four linear mark non-formation regions 102c are alternately provided, α1 + α2 is 90°, but the form is not limited to this. As shown in FIG. 12, the circumferences D1 and D2 of the linear mark formation region 102b and the linear mark non-formation region 102c are determined by the central angles α1 and α2 of the two and the radius R of the roller body 102a, and are preferably 0.2 to 10 mm, and more preferably 1 to 5 mm, respectively. The radius R of the roller body 102a is preferably 3 to 6 cm. If the radius R exceeds 6 cm, the distance at which the pattern roller 102 slides on the metal thin film 11 is too long, and the high-density region of the linear marks cannot be set to be short. 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. Figure 13 shows another example of each pattern roll used in the first manufacturing apparatus. The pattern roll 122 has a roll body 122a, and the roll body 122a alternately has a large outer diameter region 122b and a small outer diameter region 122c along the outer peripheral surface. A linear scratch forming region 122d is formed on the large outer diameter region 122b of the roll body 122a. The small outer diameter region 122c functions as a linear scratch non-forming region. The linear scratch forming region 122d may be the same as the linear scratch forming region 102b in the above-described pattern roll 102. It is not necessary to form a fixing layer for holding a plurality of high-hardness fine particles in the small outer diameter region 122c, but from the viewpoint of manufacturing efficiency, a fixing layer for holding a plurality of high-hardness fine particles may also be formed in the small outer diameter region 122c. 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 scratch forming region 102b and the linear scratch non-forming region 102c in the above-described pattern roll 102. When a fixing layer for holding a plurality of high-hardness fine particles is also formed in the small outer diameter region 122c, the radius R of the large outer diameter region 122b 1 and the radius R of the small outer diameter region 122c 2 The difference Dh is preferably 1 mm or more. If the step difference Dh is less than 1 mm, there is a high possibility that the high-hardness fine particles in the small outer diameter region 122c will strongly slide on the metal thin film, and the density of the linear scratches in the low-density region of the obtained first electromagnetic wave absorption film will become too high. The step difference Dh is preferably 2 to 5 mm. The radius R of the large outer diameter region 122b of the pattern roll 122a 1 Is also preferably 3 to 6 cm, more preferably 3 to 5 cm. (b) Second manufacturing apparatus In addition to having a device for driving at least one of the pattern roll and the pressing roll relative to the metal thin film in the vertical direction in such a manner that the pattern rolls are intermittently slid on the metal thin film, the second manufacturing apparatus has substantially the same structure as the manufacturing apparatus for the second electromagnetic wave absorption film. Therefore, the vertical driving of the pattern roll and / or the pressing roll will be described in detail. Figures 14a and 14b show an example in which the rotation axes of a pair of pressing rolls 103a and 103b are fixed, and the rotation axis of the pattern roll 132 is driven relative to the metal thin film 11 in the vertical direction at regular time intervals by a driving device (not shown). The pattern roll 132 has a plurality of high-hardness fine particles on the entire outer peripheral surface, similar to the pattern rolls 2a and 2b used in the manufacturing apparatus for the second electromagnetic wave absorption film. The plastic film 10 is held at a certain height by a pair of pressing rolls 103a and 103b. In the state of Fig. 14a, the pattern roller 132 is in the raised position, and the pattern roller 132 is slightly pressed against and slidably contacted with the metal thin film 11 facing the plastic film 10, so that linear marks are formed on the metal thin film 11. Then, if the pattern roller 132 comes to the lowered position as shown in Fig. 14b, the pattern roller 132 separates from the metal thin film 11, so that linear marks are not formed on the metal thin film 11. Thus, since the formation of linear marks is alternately performed by the intermittent vertical driving of each pattern roller 132, the first and second linear mark groups can be alternately formed on the metal thin film 11 in the direction of the linear marks. The lengths of the high-density regions and the low-density regions in the first and second linear mark groups can be adjusted by the time intervals of the vertical driving of each pattern roller 132. For the same reason as described above, the radius R of the pattern roller 132 is preferably 3 to 6 cm, more preferably 3 to 5 cm. Instead of the vertical driving of the pattern roller 132, the vertical driving of a pair of pressing rollers 103a and 103b can also be performed to alternately form high-density regions and low-density regions. Also, if the pattern roller 132 and a pair of pressing rollers 103a and 103b are vertically driven in opposite directions, that is, when the pattern roller 132 rises, the pair of pressing rollers 103a and 103b are lowered, and when the pattern roller 132 is lowered, the pair of pressing rollers 103a and 103b are raised, the switching of the sliding contact between the pattern roller 132 and the metal thin film 11 can be accelerated, and the high-density regions and the low-density regions can be narrowed (shortened in the direction of the linear marks). The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples. Example 1 (1) Manufacture of the first electromagnetic wave absorption film A first manufacturing apparatus was made by using a pair of pattern rollers 102, 102 electrically connected with diamond microparticles having a particle size distribution of 50 to 80 μm instead of the pair of pattern rollers 2a, 2b in the apparatus shown in Fig. 9a. By the pattern roller 102 on the upstream side of the first manufacturing apparatus, high-density regions and low-density regions of linear marks having the following characteristics were alternately formed in one direction on an aluminum thin film having a thickness of 60 nm formed on a PET film having a thickness of 16 μm by vacuum evaporation, and a first linear mark group was manufactured. Then, by the pattern roller 102 on the downstream side, under the same conditions as the first linear mark group, a second linear mark group was formed overlapping the first linear mark group, and a first electromagnetic wave absorption film was obtained. The second linear mark group has high-density regions and low-density regions of linear marks in different directions. The crossing angle θs of the linear marks in the first and second linear mark groups is 90°. A micrograph of the first electromagnetic wave absorption film is shown in Fig. 15. The linear marks in the first and second linear mark groups have the same characteristics except for the direction as described below. High-density area Linear marks: Range of width W: 0.5 to 50 μm Average width Wav: 30 μm Range of lateral direction interval I: 1 to 50 μm Average lateral direction interval Iav: 40 μm Average length Lav: 1 mm Length in the arrangement direction: 2 mm Low-density area (1) Length in the arrangement direction: 2 mm Note: (1) Since there are only a small number of linear marks in the low-density area, only the length in the arrangement direction of the low-density area is measured. (a) Measurement of surface resistivity Measure the surface resistivity Rs of the metal thin film having the first linear mark group, which has a high-density area and a low-density area of linear marks. Also, for the aluminum thin film with linear marks formed entirely under the same conditions as the high-density area, measure the surface resistivity of the aluminum thin film and use this surface resistivity as the surface resistivity Rs1 of the high-density area. Calculate the surface resistivity Rs2 of the low-density area based on the surface resistivity Rs and Rs1. For the measurement of the surface resistivity, use the sheet resistance / surface resistance measuring instrument "EC-80P" manufactured by NAPSON Co., Ltd. In addition, the surface resistivity of the second linear mark group formed in different directions is regarded as the same as that of the first linear mark group. (b) Measurement of light transmittance Measure the light transmittance Lt of the metal thin film having the first linear mark group, which has a high-density area and a low-density area of linear marks. Also, for the aluminum thin film with linear marks formed entirely under the same conditions as the high-density area, measure the light transmittance of the aluminum thin film and use this light transmittance as the surface resistivity Lt1 of the high-density area. Calculate the light transmittance Lt2 of the low-density area based on the light transmittance Lt and Lt1. For the measurement of the light transmittance, use the transmissive laser discrimination sensor "IB-30" manufactured by KEYENCE Corporation. In addition, the light transmittance of the second linear mark group is regarded as the same as that of the first linear mark group. High-density area Surface resistivity: 90 Ω / □ Light transmittance: 4.5% Low-density area Surface resistivity: 8 Ω / □ Light transmittance: 1.5% (2) Measurement of Conducted Noise Absorption Rate A test piece TP1 (50 mm × 50 mm) was cut out from the first electromagnetic wave absorption film. In the near-field electromagnetic wave evaluation system shown in FIGS. 16a and 16b, the test piece TP1 was attached to the upper surface of the insulating substrate 200 with an adhesive such that the center of the test piece TP1 was aligned with the center of the microstrip line MSL. The near-field electromagnetic wave evaluation system consisted of the following: a 50 Ω microstrip line MSL (64.4 mm × 4.4 mm), an insulating substrate 200 supporting the microstrip line MSL, a ground electrode 201 joined to the lower surface of the insulating substrate 200, conductive pins 202, 202 connected to both ends of the microstrip line MSL, a network analyzer NA, and coaxial cables 203, 203 connecting the network analyzer NA to the conductive pins 202, 202. An incident wave of 0.1 to 6 GHz was input to the microstrip line MSL, and the power S of the reflected wave 11 and the power S of the transmitted wave 12 were measured. Based on S 11 and S 12 the noise absorption rate P loss / P in was obtained. The results were shown in FIG. 17. It was clearly seen from FIG. 17 that the noise absorption rate P loss / P in of the electromagnetic wave absorption film of Example 1 was slightly worse than that of Comparative Example 1 described later, but it was sufficient in terms of the balance with the radiation noise absorption ability. (3) Measurement of Radiation Noise For a test piece TP2 (40 mm × 40 mm) cut out from the first electromagnetic wave absorption film, it was scanned in the frequency range of 0.03 GHz to 7 GHz with an EMC noise scanner (WM7400) manufactured by Morita Technical Co., Ltd. to measure the radiation noise. The cumulative radiation noise of the test piece of Example 1 was shown in FIG. 18. In addition, the position of the test piece was indicated by a white frame in FIG. 18. In the following photos of the cumulative radiation noise, the position of the test piece was the same, so it was omitted. It was clearly seen from FIG. 18 that substantially no cumulative radiation noise above -10 dBm was observed in the frequency range of 100 MHz to 5 GHz. Therefore, it was confirmed that the first electromagnetic wave absorption film of Example 1 had excellent radiation noise absorption ability in the frequency range of 100 MHz to 5 GHz. Example 2 (1) Manufacture of the second electromagnetic wave absorption film Using the apparatus having the structure shown in Fig. 9a with pattern rollers 2a and 2b electrically connected with diamond microparticles having a particle size distribution of 50 to 80 μm, linear marks in two directions with the following characteristics were formed over the entire surface of the aluminum thin film in the same manner as in Example 1, thereby obtaining the second electromagnetic wave absorption film. Range of width W: 0.5 to 50 μm Average width Wav: 30 μm Range of lateral interval I: 1 to 50 μm Average lateral interval Iav: 40 μm Average length Lav: 1 mm Crossing angle θs: 90° As a result of measuring the surface resistivity and light transmittance of the second electromagnetic wave absorption film having crossed linear marks over the entire surface by the same method as in Example 1, they were 25 Ω / square and 3%, respectively. (2) Bonding of the first and second electromagnetic wave absorption films The above-mentioned second electromagnetic wave absorption film was bonded to the first electromagnetic wave absorption film manufactured in Example 1 by a non-conductive adhesive, thereby manufacturing the near-field electromagnetic wave absorber shown in Fig. 6a. The thickness of the bonding layer 20 was 5 μm. (3) Conduction noise absorption ability and radiation noise absorption ability of the near-field electromagnetic wave absorber The noise absorption rate P loss / P in of the near-field electromagnetic wave absorber and the radiation noise were measured in the same manner as in Example 1, and the results are shown in Figs. 19 and 20, respectively. It can be clearly seen from Figs. 19 and 20 that the near-field electromagnetic wave absorber of Example 2 exhibits excellent radiation noise absorption ability and is also sufficient for the conduction noise absorption ability. Example 3 (1) Manufacture of the first electromagnetic wave absorption film In the apparatus shown in Fig. 9a, a pair of pattern rollers 132 and 132 having a drive unit (not shown) with a vertically driven rotary shaft were used instead of the pair of pattern rollers 2a and 2b to form a second manufacturing apparatus. Diamond microparticles having a particle size distribution of 50 to 80 μm were electrically connected to the entire outer peripheral surface of each of the pattern rollers 132 and 132. Each of the pattern rollers 132 and 132 was driven to move up and down at regular time intervals while the plastic film 10 having the metal thin film 11 was moving. Using the pattern roller 132 on the upstream side of the second manufacturing apparatus, in the same manner as in Example 1, a high-density region and a low-density region of linear marks having the following characteristics are alternately formed in one direction on the aluminum thin film to produce a first group of linear marks. Next, using the pattern roller 132 on the downstream side, under the same conditions as the first group of linear marks, a second group of linear marks is produced by overlapping with the first group of linear marks, and a first electromagnetic wave absorption film is obtained. The second group of linear marks has a high-density region and a low-density region of linear marks in different directions. The crossing angle θs of the linear marks in the first and second groups of linear marks is 90°. A micrograph of the first electromagnetic wave absorption film is shown in FIG. 21. The linear marks in the first and second groups of linear marks have the same characteristics except for the direction as described below. High-density region Linear marks: Width W range: 0.5 to 50 μm Average width Wav: 35 μm Lateral direction interval I range: 1 to 50 μm Average lateral direction interval Iav: 30 μm Average length Lav: 1 mm Length in the alignment direction: 2 mm Low-density region (1) Length in the alignment direction: 2 mm Note: (1) Since there are only a small number of linear marks in the low-density region, only the length in the alignment direction of the low-density region is measured. In the same manner as in Example 1, the surface resistivity and light transmittance of the high-density region and the low-density region in the first group of linear marks are measured. In addition, the surface resistivity and light transmittance of the second group of linear marks are considered to be the same as those of the first group of linear marks. High-density region Surface resistivity: 150 Ω / square Light transmittance: 6% Low-density region Surface resistivity: 3 Ω / square Light transmittance: 1% (2) Conduction noise absorption ability and radiation noise absorption ability of the first electromagnetic wave absorption film The noise absorption rate P of the first electromagnetic wave absorption film is the same as in Example 1 loss / P in and the measurement results of the radiation noise are shown in FIGS. 22 and 23, respectively. It can be clearly seen from FIGS. 22 and 23 that the first electromagnetic wave absorption film of Example 3 exhibits excellent radiation noise absorption ability and is also sufficient for the conduction noise absorption ability. Example 4 (1) Bonding of the first and second electromagnetic wave absorption films The first electromagnetic wave absorption film of Example 3 is bonded to the second electromagnetic wave absorption film of Example 2 by a non-conductive adhesive to produce a near-field electromagnetic wave absorber shown in Fig. 6a. The thickness of the bonding layer 20 is 5 μm. (2) Conduction noise absorption ability and radiation noise absorption ability of the near-field electromagnetic wave absorber The noise absorption rate P of the near-field electromagnetic wave absorber is the same as in Example 1 loss / P in The measurement results of the conduction noise and the radiation noise are shown in FIGS. 24 and 25, respectively. It can be clearly seen from FIGS. 24 and 25 that the near-field electromagnetic wave absorber of Example 4 exhibits excellent radiation noise absorption ability and is also sufficient for the conduction noise absorption ability. Comparative Example 1 For test pieces TP1 and TP2 cut from a piece of the second electromagnetic wave absorption film manufactured in Example 2, the noise absorption rate P loss / P in and the radiation noise were measured in the same manner as in Example 1. The results are shown in FIGS. 26 and 27, respectively. It can be clearly seen from FIGS. 26 and 27 that although the electromagnetic wave absorption film of Comparative Example 1 exhibits excellent conduction noise absorption ability, its radiation noise absorption ability is significantly inferior to that of Example 1 and Example 3. Comparative Example 2 For test pieces TP1 and TP2 cut from a near-field electromagnetic wave absorber formed by bonding two pieces of the second electromagnetic wave absorption film manufactured in Example 2, the noise absorption rate P loss / P in and the radiation noise were measured in the same manner as in Example 1. The results are shown in FIGS. 28 and 29, respectively. It can be clearly seen from FIGS. 28 and 29 that although the near-field electromagnetic wave absorber of Comparative Example 2 exhibits good conduction noise absorption ability, its radiation noise absorption ability is significantly inferior to that of Example 2 and Example 4. 1: Near-field electromagnetic wave absorber 2a, 2b: Pattern rollers 3a, 3b: Press rollers 5a, 5b: Support rollers 10, 10a, 10b, 10’: Plastic films 11: Metal thin film 11a: First metal thin film with linear marks 11b: Second metal thin film with linear marks 12, 12a, 12b: Linear marks 20: Adhesive film 21: Reel 22: Guide roller 23: Guide roller 24: Reel 32b: Second pattern roller 33b: Second press roller 100: Electromagnetic wave absorption film 100a: First electromagnetic wave absorption film 100b: Second electromagnetic wave absorption film 102: Pattern roller 102a: Pattern roller body 102b: Linear mark formation area 102c: Linear mark non-formation area 102d: High-hardness fine particles 102e: Fixed layer 103a, 103b: Press rollers 112: High-density area 113: Low-density area 114: High-density repetition part (repetition part of high-density areas with each other) 115: High-density - low-density repetition part (repetition part of high-density area and low-density area) 116: Low-density repetition part (repetition part of low-density areas with each other) 122: Pattern roller 122a: Roller body 122b: Large outer diameter area 122c: Small outer diameter area 122d: Linear mark formation area 132: Pattern roller α1: Central angle of linear mark formation area α2: Central angle of linear mark non-formation area θs: Crossing angle θ 1 , θ 2 : Tilt angle θ 3 : Crossing angle D 1 , D 2 : Circumference Dh: Step difference F 1 : Direction (first direction) F 2 : Direction (second direction) I: Interval La 1 , La 2 : Length Lb 1 , Lb 2 : Length Ls: Length Ls 1 , Ls 2 : Length R: Radius R of the roller body 1 : Radius R of the large outer diameter area 2 :Radius S of the small outer diameter region: Surface W: Width FIG. 1a is a plan view schematically showing an example of a first linear mark group constituting the electromagnetic wave absorption film of the present invention. FIG. 1b is a sectional view taken along line A-A of FIG. 1a. FIG. 2 is a plan view schematically showing another example of the first linear mark group constituting the electromagnetic wave absorption film of the present invention. FIG. 3 is a plan view schematically showing an example of a second linear mark group constituting the electromagnetic wave absorption film of the present invention. FIG. 4 is a plan view schematically showing an example of the electromagnetic wave absorption film of the present invention. FIG. 5 is a plan view schematically showing part A in the high-density repeating portion shown in FIG. 4. FIG. 6a is a sectional view showing an example of a near-field electromagnetic wave absorber according to a first embodiment of the present invention. FIG. 6b is a sectional view showing the arrangement of the first and second electromagnetic wave absorption films constituting the near-field electromagnetic wave absorber shown in FIG. 6a. FIG. 6c is a plan view showing an example of a metal thin film with linear marks of the second electromagnetic wave absorption film. FIG. 7 is a sectional view showing the arrangement of the first and second electromagnetic wave absorption films constituting another example of the near-field electromagnetic wave absorber according to the first embodiment of the present invention. FIG. 8 is a sectional view showing a near-field electromagnetic wave absorber according to a second embodiment of the present invention. FIG. 9a is a perspective view showing an example of a manufacturing apparatus for the second electromagnetic wave absorption film of the present invention. FIG. 9b is a plan view showing the apparatus of FIG. 9a. FIG. 9c is a sectional view taken along line B-B of FIG. 9b. FIG. 9d is a partially enlarged plan view for explaining the principle of forming linear marks inclined with respect to the traveling direction of the film. FIG. 9e is a partial plan view showing the inclination angles of the pattern roll and the pressing roll with respect to the film in the apparatus of FIG. 9a. FIG. 10 is a perspective view showing another example of a manufacturing apparatus for the second electromagnetic wave absorption film of the present invention. FIG. 11a is a schematic sectional view showing an example of a pattern roll used in a first apparatus for manufacturing the first electromagnetic wave absorption film of the present invention. FIG. 11b is a partially enlarged sectional view showing the linear mark forming region of the pattern roll shown in FIG. 11a. FIG. 12 is a partial sectional view after unfolding the linear mark forming region and the non-linear mark forming region of the pattern roll shown in FIG. 11a in the circumferential direction. FIG. 13 is a schematic sectional view showing another example of a pattern roll used in a first apparatus for manufacturing the first electromagnetic wave absorption film of the present invention. FIG. 14a is a schematic view showing a state where the pattern roll is in the raised position in a second manufacturing apparatus for manufacturing the first electromagnetic wave absorption film of the present invention. FIG. 14b is a schematic view showing a state where the pattern roll is in the lowered position in a second manufacturing apparatus for manufacturing the first electromagnetic wave absorption film of the present invention. FIG. 15 is a micrograph of the first electromagnetic wave absorption film of Example 1. FIG. 16a is a plan view showing a system for evaluating the conductive noise absorption ability of an electromagnetic wave absorption film (near-field electromagnetic wave absorber). FIG. 16b is a sectional view showing a system for evaluating the conductive noise absorption ability of an electromagnetic wave absorption film (near-field electromagnetic wave absorber).FIG. 17 shows the noise absorption rate P of the first electromagnetic wave absorption film of Example 1. loss / P in The chart of. FIG. 18 is a photograph showing the cumulative radiation noise in the range of 100 MHz to 5 GHz of the first electromagnetic wave absorption film of Example 1. FIG. 19 shows the noise absorption rate P of the near-field electromagnetic wave absorber of Example 2 loss / P in The chart of. FIG. 20 is a photograph showing the cumulative radiation noise in the range of 100 MHz to 5 GHz of the near-field electromagnetic wave absorber of Example 2. FIG. 21 is a microscope photograph of the first electromagnetic wave absorption film of Example 3. FIG. 22 shows the noise absorption rate P of the first electromagnetic wave absorption film of Example 3 loss / P in The chart of. FIG. 23 is a photograph showing the cumulative radiation noise in the range of 100 MHz to 5 GHz of the first electromagnetic wave absorption film of Example 3. FIG. 24 shows the noise absorption rate P of the near-field electromagnetic wave absorber of Example 4 loss / P in The chart of. FIG. 25 is a photograph showing the cumulative radiation noise in the range of 100 MHz to 5 GHz of the near-field electromagnetic wave absorber of Example 4. FIG. 26 shows the noise absorption rate P of the first electromagnetic wave absorption film of Comparative Example 1 loss / P in The chart of. FIG. 27 is a photograph showing the cumulative radiation noise in the range of 100 MHz to 5 GHz of the first electromagnetic wave absorption film of Comparative Example 1. FIG. 28 shows the noise absorption rate P of the near-field electromagnetic wave absorber of Comparative Example 2 loss / P in The chart of. FIG. 29 is a photograph showing the cumulative radiation noise in the range of 100 MHz to 5 GHz of the near-field electromagnetic wave absorber of Comparative Example 2. Domestic deposit information (please note in the order of deposit institution, date, number) None Foreign deposit information (please note in the order of deposit country, institution, date, number) None 11a: First metal thin film with linear marks 12a: Second metal thin film with linear marks 112: High-density area 113: Low-density area F 1 : Direction (first direction) La 1 ,La 2 : Length Ls: Length

Claims

1. An electromagnetic wave absorbing film comprising a plastic film and a metal thin film formed on one side of the plastic film, wherein the metal thin film has a plurality of substantially parallel linear marks formed in two directions with irregular widths and intervals; in each direction, the linear marks alternately have high-density regions and low-density regions; the high-density regions have a surface resistivity of 30 to 200 Ω / □ to form high-density linear marks, and the low-density regions have a surface resistivity of 0 to 20 Ω / □ to form low-density linear marks; the length ratio of the high-density regions to the low-density regions in each direction is 5 / 1 to 1 / 5; the high-density regions are distributed in a grid pattern by the intersection of the linear marks in the two directions.

2. The electromagnetic wave absorbing film as described in claim 1, wherein: The intersection angle of the linear marks in the two directions is 30° to 90°.

3. The electromagnetic wave absorbing film as described in claim 1 or 2, wherein: The width of the aforementioned linear marks is in the range of 0.1 to 100 μm, with an average of 2 to 50 μm, and the spacing of the aforementioned linear marks is in the range of 0.1 to 500 μm, with an average of 10 to 100 μm.

4. An apparatus for manufacturing an electromagnetic wave absorbing film, the electromagnetic wave absorbing film comprising a plastic film and a metal film formed on one side of the plastic film, the metal film having a plurality of substantially parallel linear grooves formed in two directions with irregular widths and intervals, wherein in each direction the linear grooves alternately have high-density regions and low-density regions, the high-density regions having a surface resistivity of 30 to 200 Ω / □ to form the high-density linear grooves, and the low-density regions having a surface resistivity of 0 to 20 Ω / □ to form the low-density linear grooves, the length ratio of the high-density regions to the low-density regions in each direction being 5 / 1 to 1 / 5, and the high-density regions being distributed in a grid pattern by the intersection of the linear grooves in the two directions; the apparatus comprising: two pattern rollers; a means for conveying the plastic film by means of sliding the metal film against the two pattern rollers; and a pressing roller that presses the metal film toward the pattern rollers; wherein... The two pattern rollers are inclined to opposite sides relative to the width direction of the plastic film in the surface where they slide against the metal film. On the outer peripheral surface of each pattern roller, a linear mark forming area and a linear mark non-forming area are alternately provided in the circumferential direction. The linear mark forming area has a plurality of high-hardness microparticles on its surface.

5. The apparatus for manufacturing an electromagnetic wave absorbing film as described in claim 4, wherein: The non-formed linear mark area of ​​the aforementioned pattern roller recedes inward toward the radial direction relative to the formed linear mark area.

6. The apparatus for manufacturing an electromagnetic wave absorbing film as described in claim 5, wherein: The non-formed area of ​​the aforementioned patterned roller is recessed by more than 1 mm in the radial direction relative to the formed area of ​​the aforementioned line mark.

7. An apparatus for manufacturing an electromagnetic wave absorbing film, the electromagnetic wave absorbing film comprising a plastic film and a metal film formed on one side of the plastic film, the metal film having a plurality of substantially parallel linear marks formed in two directions with irregular widths and intervals, wherein in each direction the linear marks alternately have high-density regions and low-density regions, the high-density regions having a surface resistivity of 30 to 200 Ω / □ to form the high-density linear marks, the low-density regions having a surface resistivity of 0 to 20 Ω / □ to form the low-density linear marks, the length ratio of the high-density regions to the low-density regions in each direction being 5 / 1 to 1 / 5, and the high-density regions being distributed in a grid pattern by the intersection of the linear marks in the two directions; the apparatus comprising: two pattern rollers having a plurality of high-hardness microparticles all over their outer peripheral surfaces; a means for conveying the plastic film along the pattern rollers; and pressing rollers disposed on both sides of each pattern roller; wherein... The two pattern rollers are inclined to opposite sides relative to the width direction of the plastic film within the surface where they slide against the metal film. The device includes a means for driving each pattern roller and / or the pressing rollers on both sides of the pattern rollers in the vertical direction relative to the metal film in such a way that each pattern roller intermittently slides against the metal film.

8. A near-field electromagnetic wave absorber, comprising at least one layer of plastic film and first and second metal thin films, wherein, The aforementioned first metal thin film has a plurality of substantially parallel linear marks formed in two directions with irregular widths and intervals, and in each direction there are alternating high-density regions where the aforementioned linear marks are formed with high density and low-density regions where the aforementioned linear marks are formed with low density. The aforementioned high-density regions have a surface resistivity of 30 to 200 Ω / □, and the aforementioned low-density regions have a surface resistivity of 0 to 20 Ω / □. The length ratio of the aforementioned high-density regions to the aforementioned low-density regions in each direction is 5 / 1 to 1 / 5. The aforementioned high-density regions are distributed in a grid pattern by the intersection of the aforementioned linear marks in the two directions. On the entire surface of the aforementioned second metal thin film, a plurality of substantially parallel discontinuous linear marks are formed in two directions with irregular widths and intervals.

9. The near-field electromagnetic wave absorber as described in claim 8, wherein: A first electromagnetic wave absorbing film having the aforementioned first metal thin film on one side of a plastic film, and a second electromagnetic wave absorbing film having the aforementioned second metal thin film on one side of a plastic film, are bonded together.

10. The near-field electromagnetic wave absorber as described in claim 9, wherein: The first and second metal films are used as the inner side, and the first and second electromagnetic wave absorbing films are bonded together.

11. The near-field electromagnetic wave absorber as described in claim 8, wherein: The aforementioned first and second metal films are present on both sides of a plastic film.

12. The near-field electromagnetic wave absorber as described in claim 8, wherein: The intersection angle of the linear marks in the two directions in each of the aforementioned first and second metal films is 30 to 90°.

13. The near-field electromagnetic wave absorber as described in claim 8, wherein: The width of the aforementioned linear marks in the first and second metal films is in the range of 0.1 to 100 μm, with an average of 2 to 50 μm, and the spacing of the aforementioned linear marks is in the range of 0.1 to 500 μm, with an average of 10 to 100 μm.

14. A near-field electromagnetic wave absorber as described in any one of claims 8 to 13, wherein: The aforementioned first metal thin film comprises: a first group of linear traces, which alternately comprises a high-density region of linear traces and a low-density region of linear traces in a first direction; and a second group of linear traces, which alternately comprises a high-density region of linear traces and a low-density region of linear traces in a second direction different from the first direction; by overlapping the aforementioned first and second groups of linear traces, the aforementioned metal thin film is formed with repeating portions of the aforementioned high-density regions, repeating portions of the aforementioned high-density regions and the aforementioned low-density regions; the repeating portions of the aforementioned high-density regions are distributed in a dotted pattern; the repeating portions of the aforementioned high-density regions and the repeating portions of the aforementioned high-density regions and the aforementioned low-density regions together form a grid-like texture; the repeating portions of the aforementioned low-density regions are distributed in a dotted pattern.

Images