Electromagnetic wave absorbing film and manufacturing device thereof, and near-field electromagnetic wave absorber having electromagnetic wave absorbing film

Abstract

To provide an electromagnetic wave absorbing film and a near-field electromagnetic wave absorber that have high radiation noise absorption capability in a wide frequency range from 100 MHz to 5 GHz and can be used without connecting a ground, as well as an apparatus for manufacturing the electromagnetic wave absorbing film.SOLUTION: An electromagnetic wave absorbing film includes a plastic film and a thin metal film formed on one surface thereof, the thin metal film has a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and alternating regions in each direction in which the linear scratches are formed at high density and regions in which the linear scratches are formed at low density, the high density regions form a lattice pattern due to intersection of the linear scratches in both directions.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave absorbing film and near-field electromagnetic wave absorber that have high radiated noise absorbing capability in a wide frequency range, for example from 100 MHz to 5 GHz, and can be used without connecting a ground, and to an apparatus for manufacturing such an electromagnetic wave absorbing film. [Background technology]

[0002] In order to prevent malfunctions caused by electromagnetic noise emitted from electronic components in various communication devices and electronic devices, various electromagnetic wave absorbers have been put to practical use. Under such circumstances, the present inventor proposed in Japanese Patent No. 4685977 (Patent Document 1) a metal thin film-plastic composite film with linear scratches, which has a plastic film and a single-layer or multi-layer metal thin film provided on at least one surface of the plastic film, and is characterized in that a large number of substantially parallel and intermittent linear scratches are formed in two directions with irregular widths and intervals on the metal thin film, and has reduced anisotropy of electromagnetic wave absorption ability. Patent Document 1 describes that the electromagnetic wave absorption ability is improved when multiple sheets of metal thin film-plastic composite films with linear scratches are laminated directly or via a dielectric layer. The metal thin film-plastic composite film with linear scratches of Patent Document 1 has excellent conductive noise absorption ability in a wide frequency range, but its radiated noise absorption ability in a frequency band below 1 GHz is not necessarily sufficient.

[0003] Japanese Patent No. 5203295 (Patent Document 2) discloses an electromagnetic wave absorbing film which is formed by laminating a magnetic composite film having a plastic film and a magnetic metal thin film provided on at least one surface thereof, and a non-magnetic composite film having a plastic film and a non-magnetic metal thin film provided on at least one surface thereof, and is characterized in that a large number of substantially parallel and intermittent linear scratches are formed in at least one direction with irregular lengths, widths and intervals on at least one of the magnetic metal thin film and the non-magnetic metal thin film, the linear scratches have an average width of 1 to 100 μm and an average interval of 1 to 100 μm, and 90% or more of the linear scratches have a width within the range of 0.1 to 1,000 μm. Patent Document 2 describes that an electromagnetic wave absorbing film in which the surface resistance of the magnetic metal thin film is 1 to 377 Ω / □ and the surface resistance of the non-magnetic metal thin film is 377 to 10,000 Ω / □ is excellent in absorbing electromagnetic wave noise in the near field.

[0004] However, the absorption of electromagnetic noise in Patent Document 2 is the absorption of so-called conducted noise, and it has been found that there exists a frequency range in which the radiation noise is maximized, from less than 1 GHz to several GHz. Therefore, when this electromagnetic wave absorbing film is put to practical use, it is necessary to connect it to a ground (GND) in order to prevent the radiation of maximized noise.

[0005] WO 2012 / 090586 (Patent Document 3) discloses a near-field electromagnetic wave absorber formed by bonding a plurality of electromagnetic wave absorbing films each having a metal thin film formed on one side of a plastic film, characterized in that the metal thin film of at least one of the electromagnetic wave absorbing films not only has a thin film layer of a magnetic metal, but also has a large number of intermittent linear scratches with irregular widths and intervals that are substantially parallel to each other and formed in two directions on the metal thin film of at least one of the electromagnetic wave absorbing films. Patent Document 3 describes that the metal thin film of each electromagnetic wave absorbing film has a surface resistance in the range of 50 to 1500 Ω / □ after the linear scratches are formed. This near-field electromagnetic wave absorber also has excellent conductive noise absorption ability in a wide frequency range from less than 1 GHz to several GHz. However, it has been found that there is a frequency at which radiation noise is maximized. Therefore, as with Patent Document 2, when this near-field electromagnetic wave absorber is put into practical use, it is necessary to connect a ground (GND) to prevent the radiation of maximized noise.

[0006] Japanese Patent No. 5559668 (Patent Document 4) discloses an electromagnetic wave absorber formed by laminating a plurality of electromagnetic wave absorbing films in front of an electromagnetic wave reflector with a dielectric therebetween, in which each electromagnetic wave absorbing film is formed by forming a conductive layer on one surface of a plastic film, the conductive layer of each electromagnetic wave absorbing film has a surface resistance within a range of 100 to 1000 Ω / □, the surface resistance of the conductive layer of the foremost electromagnetic wave absorbing film is 100 Ω / □ or more higher than the surface resistance of the conductive layer of the next electromagnetic wave absorbing film, (a) when the electromagnetic wave absorbing films are two, the ratio of the distance between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film and the distance between the second electromagnetic wave absorbing film and the electromagnetic wave reflector is 100:30 to 80:70, and (b) The electromagnetic wave absorber is characterized in that, when the number of the electromagnetic wave absorbing films is three or more, the ratio of the distance between the first electromagnetic wave absorbing film and the second electromagnetic wave absorbing film to the distance between the second electromagnetic wave absorbing film and the third electromagnetic wave absorbing film is 100:30 to 80:70, a large number of substantially parallel intermittent linear scratches with irregular widths and intervals are formed in two directions on the plastic film side of the electromagnetic wave absorbing film, 90% or more of the widths of the linear scratches are in the range of 0.1 to 100 μm and 1 to 50 μm on average, and the intervals of the linear scratches are in the range of 0.1 to 200 μm and 1 to 100 μm on average. Patent Document 4 describes that since the surface resistance of the conductive layer of the foremost electromagnetic wave absorbing film is 100 Ω / □ or more higher than the surface resistance of the conductive layer of the next electromagnetic wave absorbing film, not only is the electromagnetic wave absorbing ability significantly higher than that of a case where multiple electromagnetic wave absorbing films with the same surface resistance are simply laminated, but the anisotropy of the electromagnetic wave absorbing ability is reduced. However, this electromagnetic wave absorber has a structure in which multiple electromagnetic wave absorbing films are laminated with a dielectric between them in front of an electromagnetic wave reflector (aluminum plate), so although it is suitable for applications such as ETC and RFID, it cannot be used as a near-field electromagnetic wave absorber to be attached to electronic components, etc. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 4685977 [Patent Document 2] Patent No. 5203295 [Patent Document 3] WO 2012 / 090586 publication [Patent Document 4] Patent No. 5559668 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, a first object of the present invention is to provide an electromagnetic wave absorbing film that has high radiation noise absorption capability in a wide frequency range, for example, from 100 MHz to 5 GHz, and can be used without connecting a ground.

[0009] A second object of the present invention is to provide a near-field electromagnetic wave absorber that has a higher radiation noise absorption capability in a wide frequency range, for example, from 100 MHz to 5 GHz, and can be used without connecting a ground.

[0010] A third object of the present invention is to provide an apparatus capable of efficiently producing the above-mentioned electromagnetic wave-absorbing film. [Means for solving the problem]

[0011] As a result of intensive research in view of the above object, the present inventors have discovered that (a) instead of forming linear scratches in two directions all over the surface of a metal thin film, if linear scratches are formed intermittently so that areas of high and low linear scratch density are arranged alternately in each of two directions, the intersection of linear scratches in both directions results in high-density areas of linear scratches being distributed in a lattice pattern, and an electromagnetic-wave-absorbing film having high radiant noise absorbing ability in a wide frequency range, for example, from 100 MHz to 5 GHz, can be obtained, (b) by combining an electromagnetic-wave-absorbing film having high-density areas of linear scratches in a lattice pattern with an electromagnetic-wave-absorbing film in which linear scratches in two directions are formed all over the surface of the metal thin film, a near-field electromagnetic wave absorber having even higher radiant noise absorbing ability in a wide frequency range, for example, from 100 MHz to 5 GHz can be obtained, and (c) in an apparatus for forming linear scratches in two directions all over the surface of a metal thin film, areas of high and low linear scratch density can be formed alternately in each of two directions by changing the shape or driving method of a pattern roll., and have thus conceived the present invention.

[0012] That is, the electromagnetic-wave-absorbing film of the present invention comprises a plastic film and a thin metal film formed on one side of the plastic film, the thin metal film having a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and alternating between areas in which the linear scratches are formed at a high density and areas in which the linear scratches are formed at a low density in each direction, and the high-density areas of the linear scratches are distributed in a lattice pattern due to the intersection of the linear scratches in both directions.

[0013] It is preferable that the surface resistivity in each direction of the high density region is 30 to 200 Ω / □, and the surface resistivity of the low density region is 0 to 20 Ω / □.

[0014] The length ratio between the high density region and the low density region in each direction is preferably 5 / 1 to 1 / 5.

[0015] It is preferable that the length of the high density region is 0.2 to 10 mm in each direction, and the length of the low density region is 0.2 to 10 mm in each direction.

[0016] A first apparatus of the present invention for producing the electromagnetic wave-absorbing film comprises: Two pattern rolls, a means for conveying the plastic film so that the metal thin film is in sliding contact with two pattern rolls; a press roll for pressing the metal thin film against the pattern roll; the two pattern rolls are inclined to opposite sides with respect to the width direction of the plastic film within the plane in sliding contact with the metal thin film, The outer peripheral surface of each pattern roll is provided with linear-scratch-formed regions and linear-scratch-free regions alternately in the circumferential direction, The linear scratch forming region is characterized in that it has a large number of high-hardness fine particles on its surface.

[0017] In one embodiment of the present invention, the linear-scratch-free region of the pattern roll is recessed radially inward from the linear-scratch-free region. The recession distance Dh of the linear-scratch-free region is preferably 1 mm or more.

[0018] In another embodiment of the present invention, the linear-scratch-free region does not have high-hardness fine particles. In this case, the radius of the linear-scratch-free region may be the same as the radius of the linear-scratch-formed region, but may be smaller.

[0019] A second apparatus of the present invention for producing the electromagnetic wave-absorbing film comprises: Two pattern rolls having a large number of high-hardness fine particles on the entire outer circumferential surface, a means for conveying the plastic film along the pattern roll; and a presser roll disposed on both sides of each pattern roll, the two pattern rolls are inclined to opposite sides with respect to the width direction of the plastic film within the plane in sliding contact with the metal thin film, The method is characterized by comprising a device for driving at least one of each pattern roll and the pressure rolls on both sides thereof in a direction perpendicular to the thin metal film so that each pattern roll comes into sliding contact with the thin metal film intermittently.

[0020] The near-field electromagnetic wave absorber of the present invention has at least one plastic film layer and first and second metal thin films, said first metal thin film has a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and in each direction has alternating regions where the linear scratches are formed at a high density and regions where the linear scratches are formed at a low density, and the high density regions are distributed in a lattice pattern by the intersection of the linear scratches in both directions, The second thin metal film is characterized in that a large number of substantially parallel intermittent linear scratches are formed in two directions with irregular widths and intervals on the entire surface thereof.

[0021] In the near-field electromagnetic wave absorber of the present invention, it is preferable that the surface resistivity of the high-density region is 30 to 200 Ω / □ and the surface resistivity of the low-density region is 0 to 20 Ω / □ in each direction of the linear scratches in the first metal thin film.

[0022] In the near-field electromagnetic wave absorber of the present invention, the length ratio of the high density region to the low density region in each direction in the first metal thin film is preferably 5 / 1 to 1 / 5.

[0023] In the near-field electromagnetic wave absorber of the present invention, it is preferable that the length of the high density region in each direction in the first metal thin film is 0.2 to 10 mm, and the length of the low density region is 0.2 to 10 mm.

[0024] The near-field electromagnetic wave absorber of the first embodiment of the present invention preferably has a structure in which a first electromagnetic wave absorbing film having the first metal thin film on one side of a plastic film and a second electromagnetic wave absorbing film having the second metal thin film on one side of a plastic film are bonded together.

[0025] In the near-field electromagnetic wave absorber of the first embodiment of the present invention, the first and second electromagnetic wave absorbing films are preferably bonded together with the first and second thin metal films facing inwards.

[0026] The near-field electromagnetic wave absorber of the second embodiment of the present invention preferably has the first and second thin metal films on both sides of a single plastic film.

[0027] In the electromagnetic wave absorbing film and near-field electromagnetic wave absorber of the present invention, the crossing angle between the linear scratches in two directions is preferably 30 to 90°.

[0028] In the electromagnetic wave absorbing film and near-field electromagnetic wave absorber of the present invention, the metal thin film preferably has a thickness of 20 to 100 nm.

[0029] In the electromagnetic wave absorbing film and near-field electromagnetic wave absorber of the present invention, the metal thin film is preferably made of aluminum.

[0030] In the electromagnetic wave absorbing film and near-field electromagnetic wave absorber of the present invention, it is preferred that the width W of the linear scratches is in the range of 0.1 to 100 μm and is 1 to 50 μm on average, and the interval I between the linear scratches is in the range of 0.1 to 500 μm and is 1 to 200 μm on average. Effect of the Invention

[0031] The electromagnetic wave absorbing film of the present invention is formed by forming a bidirectional linear scratch group having alternating high-density and low-density regions of the linear scratches so as to overlap one metal thin film, and has a linear scratch distribution in which the high-density regions extend in a lattice pattern, and therefore has high radiation noise absorbing ability in a wide frequency range, for example, from 100 MHz to 5 GHz. The near-field electromagnetic wave absorber of the present invention is formed by combining an electromagnetic wave absorbing film in which high-density regions are distributed in a lattice pattern with an electromagnetic wave absorbing film in which linear scratches are formed on the entire surface of the metal thin film, and therefore has even higher radiation noise absorbing ability. The electromagnetic wave absorbing film and near-field electromagnetic wave absorber of the present invention having such characteristics can be attached to electronic components in various electronic devices and communication devices such as personal computers, mobile phones, and smartphones without connecting a ground, to suppress electromagnetic wave noise.

[0032] The apparatus of the present invention can be obtained by (a) replacing the pattern roll in an apparatus that forms linear scratches all over the entire surface of a metal thin film with a pattern roll having linear scratch-formed areas and linear scratch-free areas that are provided alternately in the circumferential direction on its outer peripheral surface, or (b) adding a device that drives the pattern roll and at least one of the pressure rolls on either side of it in a direction perpendicular to the metal thin film to an apparatus that forms linear scratches all over the entire surface of a metal thin film, and therefore has a relatively simple structure and can efficiently produce the electromagnetic-wave-absorbing film of the present invention. [Brief description of the drawings]

[0033] [Figure 1(a)] FIG. 2 is a plan view showing typically one example of a first group of linear scratches that constitute the electromagnetic-wave-absorbing film of the present invention. [Figure 1(b)] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 2] FIG. 11 is a plan view showing typically another example of the first group of linear scratches that constitutes the electromagnetic-wave-absorbing film of the present invention. [Diagram 3] FIG. 4 is a plan view showing typically one example of a second group of linear scratches that constitutes the electromagnetic-wave-absorbing film of the present invention. [Figure 4] FIG. 1 is a plan view illustrating a schematic example of an electromagnetic wave-absorbing film of the present invention. [Diagram 5] 5 is a plan view showing a schematic diagram of a portion A in the high-density region overlapping portion shown in FIG. 4. [Figure 6(a)] 1 is a cross-sectional view showing an example of a near-field electromagnetic wave absorber according to a first embodiment of the present invention. [Figure 6(b)] FIG. 7 is a cross-sectional view showing an arrangement of first and second electromagnetic wave absorbing films that constitute the near-field electromagnetic wave absorber shown in FIG. [Figure 6(c)] FIG. 2 is a plan view showing an example of a linear-scratched thin metal film of a second electromagnetic-wave-absorbing film. [Figure 7] FIG. 11 is a cross-sectional view showing an arrangement of first and second electromagnetic wave absorbing films constituting another example of the near-field electromagnetic wave absorber according to the first embodiment of the present invention. [Figure 8] FIG. 4 is a cross-sectional view showing a near-field electromagnetic wave absorber according to a second embodiment of the present invention. [Figure 9(a)] FIG. 2 is a perspective view showing an example of an apparatus for producing the second electromagnetic-wave-absorbing film of the present invention. [Figure 9(b)] FIG. 9(b) is a plan view showing the device of FIG. [Figure 9(c)] FIG. 9B is a cross-sectional view taken along line BB of FIG. [Figure 9(d)] FIG. 13 is a partially enlarged plan view for explaining the principle by which linear scratches inclined with respect to the traveling direction of the film are formed. [Figure 9(e)] FIG. 9(b) is a partial plan view showing the inclination angles of the pattern roll and the pressure roll with respect to the film in the apparatus of FIG. [Figure 10] FIG. 11 is a perspective view showing another example of the apparatus for producing the second electromagnetic-wave-absorbing film of the present invention. [Figure 11(a)] FIG. 2 is a schematic cross-sectional view showing an example of a pattern roll used in a first apparatus for producing a first electromagnetic-wave-absorbing film of the present invention. [Figure 11(b)] FIG. 12 is a partially enlarged cross-sectional view showing a linear scratch formation region of the pattern roll shown in FIG. [Figure 12] 12 is a partial cross-sectional view of the pattern roll shown in FIG. 11(a) in which a linear-scratch-formed region and a linear-scratch-non-formed region are developed in the circumferential direction. FIG. [Figure 13] FIG. 2 is a schematic cross-sectional view showing another example of a pattern roll used in the first apparatus for producing the first electromagnetic-wave-absorbing film of the present invention. [Figure 14(a)] FIG. 2 is a schematic view showing a state in which a pattern roll is in a raised position in a second production apparatus for producing the first electromagnetic-wave-absorbing film of the present invention. [Figure 14(b)] FIG. 2 is a schematic view showing a state in which a pattern roll is in a lowered position in a second production apparatus for producing the first electromagnetic-wave-absorbing film of the present invention. [Figure 15] 1 is a micrograph of a first electromagnetic-wave-absorbing film of Example 1. [Figure 16(a)] FIG. 1 is a plan view showing a system for evaluating the conductive noise absorption ability of an electromagnetic wave absorbing film (near-field electromagnetic wave absorber). [Figure 16(b)]FIG. 1 is a cross-sectional view showing a system for evaluating the conductive noise absorption ability of an electromagnetic wave absorbing film (near-field electromagnetic wave absorber). [Figure 17] 1 is a graph showing the noise absorption ratio Ploss / Pin of the first electromagnetic-wave-absorbing film of Example 1. [Figure 18] FIG. 2 is a photograph showing accumulated radiation noise in the range of 100 MHz to 5 GHz of the first electromagnetic-wave-absorbing film of Example 1. [Figure 19] 13 is a graph showing a noise absorption ratio Ploss / Pin of the near-field electromagnetic wave absorber of Example 2. [Figure 20] 13 is a photograph showing the accumulated radiation noise in the range of 100 MHz to 5 GHz of the near-field electromagnetic wave absorber of Example 2. [Figure 21] 1 is a microscope photograph of a first electromagnetic-wave-absorbing film of Example 3. [Figure 22] 13 is a graph showing the noise absorption ratio Ploss / Pin of the first electromagnetic-wave-absorbing film of Example 3. [Figure 23] FIG. 13 is a photograph showing the accumulated radiation noise in the range of 100 MHz to 5 GHz of the first electromagnetic-wave-absorbing film of Example 3. [Figure 24] 13 is a graph showing a noise absorption ratio Ploss / Pin of the near-field electromagnetic wave absorber of Example 4. [Diagram 25] 13 is a photograph showing the accumulated radiation noise in the range of 100 MHz to 5 GHz of the near-field electromagnetic wave absorber of Example 4. [Figure 26] 1 is a graph showing the noise absorption ratio Ploss / Pin of the first electromagnetic-wave-absorbing film of Comparative Example 1. [Figure 27] 1 is a photograph showing accumulated radiation noise in the range of 100 MHz to 5 GHz of the first electromagnetic-wave-absorbing film of Comparative Example 1. [Figure 28] 13 is a graph showing a noise absorption ratio Ploss / Pin of the near-field electromagnetic wave absorber of Comparative Example 2. [Figure 29] 13 is a photograph showing the accumulated radiation noise in the range of 100 MHz to 5 GHz of the near-field electromagnetic wave absorber of Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] The present invention will be described in detail with reference to the accompanying drawings, and the description of one embodiment of the present invention is applicable to other embodiments unless otherwise specified. Furthermore, the following description is not limiting, and various modifications may be made within the scope of the technical idea of ​​the present invention.

[0035] [1] Electromagnetic wave absorbing film Fig. 1(a) is a plan view showing a schematic example of a first group of linear scratches constituting the electromagnetic-wave-absorbing film of the present invention, and Fig. 1(b) is a cross-sectional view taken along the line AA of Fig. 1(a). A thin metal film 11 formed on one surface of a plastic film 10 has a large number of substantially parallel linear scratches 12a formed in one direction F1 with irregular widths and intervals, and regions 112 in which the linear scratches 12a are formed and regions 113 in which the linear scratches 12a are not formed are alternately arranged along the one direction F1. The linear scratches 12a formed in the multiple regions 112 alternately arranged in the one direction F1 are collectively referred to as the "first group of linear scratches", and the thin metal film 11 having the first group of linear scratches is referred to as the "thin metal film 11a with first linear scratches". The regions 112 and regions 113 alternately formed along the direction F1 of the linear scratches 12a form a striped pattern. The lengths La1 and La2 of the regions 112 and 113 in the direction F1 of the linear scratches 12a are determined by the manufacturing method and device.

[0036] (1) Plastic film The resin forming the plastic film 10 is not particularly limited as long as it has sufficient strength, flexibility and processability as well as insulation, and examples thereof include polyester (polyethylene terephthalate, etc.), polyarylene sulfide (polyphenylene sulfide, etc.), polyethersulfone, polyetheretherketone, polycarbonate, acrylic resin, polystyrene, polyolefin (polyethylene, polypropylene, etc.). Among them, polyethylene terephthalate (PET) film is preferred from the viewpoint of strength and cost. The thickness of the plastic film 10 may be about 10 to 100 μm, but is preferably about 10 to 30 μm in order to make the near-field electromagnetic wave absorber as thin as possible.

[0037] (2) Metal thin film The thin metal film 11 is made of a non-magnetic metal or a magnetic metal. Examples of non-magnetic metals include aluminum, copper, and silver. Examples of magnetic metals include nickel and chromium. Of course, these metals are not limited to simple substances, and may be alloys. From the viewpoints of cost and corrosion resistance, aluminum is preferable. The thin metal film 11 can be formed by a known method such as a sputtering method or a vacuum deposition method. From the viewpoint of controlling the degree of processing of linear scratches, the thickness of the thin metal film 11 is preferably 20 to 100 nm, more preferably 30 to 90 nm, and most preferably 40 to 80 nm.

[0038] (3) First group of linear marks As described above, in each region 112 of the first linear-scratched thin metal film 11a, a large number of linear scratches 12a that are substantially parallel to the thin metal film 11 are formed in one direction F1 with irregular widths and intervals. As shown in FIG. 1(b), the linear scratches 12a have various widths W and intervals I in the direction perpendicular to their orientation direction (lateral direction). The widths W and intervals I of the linear scratches 12a are both determined based on the height (original height) of the surface S of the thin metal film 11 before the linear scratches are formed. Note that the depth of the linear scratches 12a is exaggerated in FIG. 1(b) for the sake of explanation.

[0039] The width W of the linear scratches 12a is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm, even more preferably in the range of 0.5 to 50 μm, and most preferably in the range of 0.5 to 20 μm. The average width Wav of the linear scratches 12a is preferably in the range of 1 to 50 μm, more preferably in the range of 2 to 50 μm, and most preferably in the range of 5 to 30 μm. The interval I of the linear scratches 12a is preferably in the range of 0.1 to 500 μm, more preferably in the range of 0.5 to 200 μm, even more preferably in the range of 1 to 100 μm, and most preferably in the range of 1 to 50 μm. The average interval Iav of the linear scratches 12a is preferably in the range of 1 to 200 μm, more preferably in the range of 5 to 100 μm, and most preferably in the range of 10 to 80 μm. In addition, when calculating the width W and average width Wav of the linear scratches 12a, and the interval I and average interval Iav, the linear scratches 12a up to a width of 0.1 μm were counted.

[0040] The length Ls of the linear scratches 12a is determined not only by the sliding contact conditions (mainly the relative speed between the roll and the plastic film, and the winding angle of the plastic film around the roll) but also by the length of the region 112. Since a longitudinal gap of the linear scratches 12a may be located within the region 112, the length Ls of the linear scratches 12a is the same as or less than the length La1 of the region 112.

[0041] (a) Density of first linear scratches Generally, as the degree of linear scratch processing increases, the width W (proportional to the depth) of the linear scratches increases and the interval I decreases, so the proportion (density) of the linear scratches in the thin metal film 11 increases. Therefore, the degree of linear scratch processing can be expressed by the density of the linear scratches. However, since the linear scratches are not only very small but also irregular and formed at high density, it is difficult to directly measure the density of the linear scratches. Therefore, focusing on the fact that the surface resistivity and light transmittance of the thin metal film 11 also increase as the density of the linear scratches increases, the density of the linear scratches is evaluated by the surface resistivity or light transmittance of the thin metal film 11.

[0042] In FIG. 1(a), no linear scratches 12a are shown in the region 113, but depending on the manufacturing method, linear scratches 12a are often formed slightly in the region 113 as shown in FIG. 2, for example. However, the effect of the present invention can be obtained sufficiently if the degree of processing of the linear scratches 12a is low, so the case where linear scratches 12a are formed slightly in the region 113 is also within the scope of the present invention. Therefore, to include the case where linear scratches 12a are formed slightly, the region 113 will be called a "low-density region of linear scratches" or simply a "low-density region" rather than a "wireless scratch region". Accordingly, the region 112 where linear scratches are formed at a high density will be called a "high-density region of linear scratches" or simply a "high-density region".

[0043] (i) Surface resistivity The surface resistivity of the metal thin film 11 in the high-density region 112 is preferably 30 to 200 Ω / □. If the surface resistivity of the metal thin film 11 in the high-density region 112 is less than 30 Ω / □ or more than 200 Ω / □, the electromagnetic wave absorbing film cannot exhibit sufficient electromagnetic wave absorbing 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 / □. The lower limit of 0 Ω / □ is the same as the surface resistivity of the metal thin film itself. That is, the linear scratches 12a may not be formed at all on 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 is more than 20 Ω / □, 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 / □, and the surface resistivity of the metal thin film 11 in the low-density region 113 is 0 to 15 Ω / □.

[0044] When the high density region 112 and the low density region 113 are very fine, it is difficult to measure the surface resistivity of each. Therefore, the surface resistivity of the metal thin film on which linear scratches are formed all over is measured under the same conditions as the high density region 112 in the metal thin film on which linear scratches are formed alternately in one direction as shown in Figure 1 (a), and this is taken as the surface resistivity Rs1 of the high density region 112. In addition, the surface resistivity Rs0 of the metal thin film 11 on which no linear scratches are formed is measured. The surface resistivity Rs2 of the low density region 113 can be calculated from the surface resistivities Rs1 and Rs0.

[0045] (ii) Light transmittance The light transmittance of the metal thin film 11 in the high density region 112 is preferably 3 to 10%, and more preferably 4 to 8%. The light transmittance of the metal thin film 11 in the low density region 113 is preferably 0 to 2.5%, and more preferably 0 to 2%. Note that a light transmittance of 0% is a state in which no linear scratches 12a are formed at all. Note that the light transmittance of the metal thin film 11 in the high density region 112 correlates with the surface resistivity.

[0046] (b) Length of high and low density regions In the direction F1 of the linear scratches 12a, the length La1 of the high-density region 112 is preferably 0.2 to 10 mm, and the length La2 of the low-density region 113 is preferably 0.2 to 10 mm. If the length La1 of the high-density region 112 is less than 0.2 mm or the length La2 of the low-density region 113 exceeds 10 mm, the electromagnetic wave absorbing ability is too low. On the other hand, if the length La1 of the high-density region 112 exceeds 10 mm or the length La2 of the low-density region 113 is less than 0.2 mm, the effect of providing the low-density region 113 is insufficient, and the radiation noise absorbing ability of the electromagnetic wave absorbing film decreases. The length La1 of the high-density region 112 is more preferably 1 to 5 mm, and the length La2 of the low-density region 113 is more preferably 1 to 5 mm.

[0047] Along the direction F1 of the linear scratches 12a, the length ratio La1 / La2 between the high density regions 112 and the low density regions 113 is preferably 5 / 1 to 1 / 5. If the length ratio La1 / La2 is less than 1 / 5, the electromagnetic wave absorbing ability is too low. If the length ratio La1 / La2 exceeds 5 / 1, the effect of providing the low density regions 113 is insufficient, and the radiated noise absorbing ability of the electromagnetic wave absorbing film decreases. From the viewpoint of isotropy of the electromagnetic wave absorbing ability, the length ratio La1 / La2 is more preferably 2 / 1 to 1 / 2, and particularly preferably 1 / 1.

[0048] (4) Second group of linear marks Fig. 3 is a plan view showing typically an example of a second linear scratch group constituting the electromagnetic-wave-absorbing film of the present invention together with the first linear scratch group shown in Fig. 1. The second linear scratch group is formed so as to overlap on the metal thin film 11 on which the first linear scratch group is formed. As will be described later, the direction F2 of the linear scratches 12b in the second linear scratch group needs to be different from the direction F1 of the linear scratches 12a in the first linear scratch group. The ranges of the width W, average width Wav, interval I and average interval Iav of the linear scratches 12b in the second linear scratch group may be the same as those in the first linear scratch group. The ranges of the surface resistivity and light transmittance of the high-density regions 112 and low-density regions 113 in the second linear scratch group, as well as the ranges of their lengths and ratios, may also be the same as those in the first linear scratch group.

[0049] The length La1 of the high-density region 112 in the first group of linear scratches and the length Lb1 of the high-density region 112 in the second group of linear scratches may be the same or different. If different, the ratio La1 / Lb1 is preferably 1 / 2 to 2 / 1, and more preferably 2 / 3 to 3 / 2. Even if different, the linear scratch densities of the high-density region 112 and low-density region 113 in the second group of linear scratches may be the same as those in the first group of linear scratches. In short, the second group of linear scratches may be the same as the first group of linear scratches except for the direction of the linear scratches.

[0050] (5) Structure of the electromagnetic wave absorbing film 4 is a plan view showing typically one example of the electromagnetic-wave-absorbing film 100 of the present invention having both a first group of linear scratches and a second group of linear scratches. Due to the overlapping of the first and second groups of linear scratches, on the metal thin film 11, overlapping parts 114 between high-density regions 112 are distributed in a dot pattern, overlapping parts 115 between high-density regions 112 and low-density regions 113 are distributed in a lattice pattern via the overlapping parts 114 between high-density regions 112, and overlapping parts 116 between low-density regions 113 are distributed in a dot pattern.

[0051] In the high-density region overlapping portion 114, the linear scratches 12a of the first linear scratch group and the linear scratches 12b of the second linear scratch group intersect at a crossing angle θs, as shown typically in Fig. 5. The crossing angle θs of the linear scratches 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 θs approaches 90°, the electromagnetic wave absorption ability becomes isotropic.

[0052] In Fig. 5, Ls1 and Ls2 indicate the lengths of the linear scratches 12a and 12b, respectively. The length Ls1 of the linear scratches 12a and the length Ls2 of the linear scratches 12b may be different, but it is preferable that they are the same because the electromagnetic wave absorption ability becomes isotropic. When the length Ls1 of the linear scratches 12a and the length Ls2 of the linear scratches 12b are different, the length ratio Ls1 / Ls2 is preferably 1 / 2 to 2 / 1, more preferably 2 / 3 to 3 / 2.

[0053] In the high-density region-low-density region overlapping portions 115, one of the linear scratches 12a, 12b is mainly formed, and the other linear scratches are hardly formed. Therefore, the conductive noise absorbing ability is lower than that of the high-density region overlapping portions 114, but the radiative noise absorbing ability is improved. In each high-density region-low-density region overlapping portion 115, most of the linear scratches are oriented in one direction, but in adjacent high-density region-low-density region overlapping portions 115, most of the linear scratches are oriented in a direction different by the crossing angle θs, so that the electromagnetic-wave absorbing ability of the electromagnetic-wave absorbing film as a whole is approximately isotropic.

[0054] In the low-density region overlapping portion 116, the linear scratches 12a, 12b are hardly formed, so it has a function similar to that of the metal thin film 11 itself, and exhibits a large radiation noise absorption capacity. The current generated from the electromagnetic noise absorbed in the low-density region overlapping portion 116 flows to the adjacent high-density region-low-density region overlapping portion 115 and high-density region overlapping portion 114, and is attenuated there.

[0055] In the electromagnetic-wave-absorbing film 100 of the present invention, the intersections of the linear scratches 12a, 12b cause the high-density region-high-density region overlapping parts 114 to be distributed in a lattice pattern via the high-density region-low-density region overlapping parts 115, and so the high-density regions 112 are distributed in a lattice pattern on the metal thin film 11. The lattice-like distribution of the high-density regions 112 makes it possible to exhibit good radiative noise absorbing ability while ensuring sufficient conductive noise absorbing ability.

[0056] [2] Near-field electromagnetic wave absorber The near-field electromagnetic wave absorber of the present invention comprises: (a) a first metal thin film with linear scratches having a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and having alternating areas in each direction where the linear scratches are formed at a high density and areas where the linear scratches are formed at a low density, the high-density areas being distributed in a lattice pattern due to the intersection of the linear scratches in both directions; and (b) a second metal thin film with linear scratches, in which a large number of substantially parallel intermittent linear scratches in two directions are formed over the entire surface with irregular widths and intervals.

[0057] (1) First embodiment An example of the near-field electromagnetic wave absorber according to the first embodiment of the present invention is formed by bonding a first electromagnetic-wave absorbing film 100a having a first linear-scratched metal thin film 11a on a plastic film 10a to a second electromagnetic-wave absorbing film 100b having a second linear-scratched metal thin film 11b on a plastic film 10b, as shown in Fig. 6(a) and Fig. 6(b). In this example, the first and second linear-scratched metal thin films 11a and 11b face each other, so the adhesive layer 20 is non-conductive to prevent electrical conduction between them. When the adhesive layer 20 is made very thin, the first and second linear-scratched metal thin films 11a and 11b are electromagnetically bonded. The adhesive layer 20 can be formed by an adhesive, but may also be formed by heat sealing or double-sided adhesive tape.

[0058] The second electromagnetic-wave-absorbing film 100b may be the same as the first electromagnetic-wave-absorbing film 100a, except that a large number of substantially parallel linear scratches are formed in two directions with irregular widths and intervals all over the entire surface of the thin metal film 11. Figure 6(c) shows an example of the thin metal film 11b with linear scratches of the second electromagnetic-wave-absorbing film 100b.

[0059] The width W of the linear scratches 12 in the second linearly scratched metal thin film 11b is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.1 to 70 μm, even more preferably in the range of 0.5 to 50 μm, and most preferably in the range of 0.5 to 20 μm. The average width Wav of the linear scratches 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 scratches 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. The average interval Iav of the linear scratches 12 is preferably 1 to 200 μm, more preferably 5 to 100 μm, and most preferably 10 to 80 μm.

[0060] The length Ls of the linear scratches 12 in the second linearly scratched thin metal film 11b is determined by the sliding contact conditions (mainly the relative peripheral speeds of the pattern roll and the plastic film), and so will for the most part be roughly the same (roughly equal to the average length) unless the sliding contact conditions are changed. The length Ls of the linear scratches 12 is not particularly limited, and in practice it may be around 1 to 100 mm, and preferably 2 to 10 mm.

[0061] The crossing angle θs of the linear scratches 12 in two directions in the second linearly scratched thin metal film 11b is preferably 30 to 90°, more preferably 45 to 90°, most preferably 60 to 90°, and particularly preferably 90°.

[0062] Instead of facing the first and second linear-scratch-provided metal thin films 11a, 11b, the first and second electromagnetic-wave-absorbing films 100a, 100b may be adhered so that each linear-scratch-provided metal thin film 11a, 11b is located on one side of each plastic film, as shown in Figure 7.

[0063] (2) Second embodiment 8 shows a near-field electromagnetic wave absorber according to a second embodiment of the present invention. This near-field electromagnetic wave absorber is composed of a plastic film 10 and first and second thin metal films 11a and 11b with linear scratches provided on both sides of the plastic film 10. The first and second thin metal films 11a and 11b with linear scratches themselves may be the same as those in the first embodiment.

[0064] [3] Manufacturing equipment for electromagnetic wave absorbing films Since the first thin metal film with linear scratches has a more complicated structure than the second thin metal film with linear scratches, a manufacturing apparatus for the second electromagnetic-wave-absorbing film having the second thin metal film with linear scratches will be described first.

[0065] (1) Second electromagnetic wave absorbing film manufacturing apparatus 9(a) to 9(e) show an example of an apparatus for producing the second electromagnetic-wave-absorbing film 100b. The apparatus shown in the figure has (a) a reel 21 for unwinding the plastic film 10 having a thin metal film, (b) a first pattern roll 2a arranged at an incline with respect to the width direction of the plastic film 10, (c) a first pressing roll 3a arranged on the upstream side of the first pattern roll 2a and on the opposite side thereto, (d) a second pattern roll 2b which is inclined in the opposite direction to the first pattern roll 2a with respect to the width direction of the plastic film 10 and is arranged on the same side as the first pattern roll 2a, (e) a second pressing roll 3b arranged on the downstream side of the second pattern roll 2b and on the opposite side thereto, and (f) a reel 24 for winding up the plastic film 10' having a thin metal film on which linear scratches are formed (the second electromagnetic-wave-absorbing film 100b). In addition, a number of guide rolls 22, 23 are arranged at predetermined positions. The pattern rolls 2a and 2b are supported by backup rolls (for example, rubber rolls) 5a and 5b to prevent deflection.

[0066] As shown in FIG. 9(c), the press rolls 3a and 3b come into contact with the thin metal film of the plastic film 10 at a position lower than the sliding contact position with the pattern rolls 2a and 2b, so that the plastic film 10 is pressed against the pattern rolls 2a and 2b. By adjusting the height of the press rolls 3a and 3b while satisfying this condition, the pressing force on the pattern rolls 2a and 2b can be adjusted. Specifically, when the positions of the press rolls 3a and 3b are lowered, the pressing force of the pattern rolls 2a and 2b against the thin metal film of the plastic film 10 increases, so that the linear marks formed on the thin metal film become deeper (the degree of processing of the thin metal film increases). Conversely, when the positions of the press rolls 3a and 3b are higher, the pressing force of the pattern rolls 2a and 2b against the thin metal film of the plastic film 10 decreases, so that the linear marks formed on the thin metal film of the plastic film 10 become shallower (the degree of processing of the thin metal film decreases). Generally, the deeper the linear scratches, the less metal remains in the metal thin film, and the surface resistivity of the metal thin film with linear scratches increases. Therefore, the surface resistivity of the metal thin film with linear scratches can be adjusted by changing the pressing force of each pattern roll 2a, 2b against the metal thin film of the plastic film 10. Note that as the linear scratches become deeper, the width of the linear scratches becomes wider, and therefore the distance between the linear scratches tends to become narrower. The pressing force of the plastic film 10 against each pattern roll 2a, 2b can also be adjusted by moving the position of each pattern roll 2a, 2b toward the plastic film 10. The position movement of each pattern roll 2a, 2b can be performed by a drive device (not shown) attached to each pattern roll 2a, 2b.

[0067] FIG. 9(d) shows the principle of linear scratches 12 formed obliquely to the traveling direction of the plastic film 10. Since the pattern roll 2a is inclined to the traveling direction of the plastic film 10, the moving direction (rotation direction) of the hard particles on the pattern roll 2a is different from the traveling direction of the plastic film 10. Therefore, as shown by X, if the hard particles at point A on the pattern roll 2a come into contact with the metal thin film of the plastic film 10 at any time and form a mark B, after a certain time, the hard particles move to point A' and the mark B moves to point B'. While the hard particles move from point A to point A', the marks are formed continuously, so that a linear scratch 12 extending from point A' to point B' is formed.

[0068] The direction and crossing angle θs of the linear scratches 12 formed by the first and second pattern rolls 2a, 2b can be adjusted by changing the angle of each pattern roll 2a, 2b with respect to the plastic film 10 and / or the peripheral speed of each pattern roll 2a, 2b with respect to the running speed of the plastic film 10. For example, by increasing the peripheral speed a of the pattern roll 2a with respect to the running speed b of the plastic film 10, the linear scratches 12 can be set at 45° with respect to the traveling direction of the plastic film 10 as shown by line segment C'D' in Y of FIG. 9(d). Similarly, by changing the inclination angle θ2 of the pattern roll 2a with respect to the width direction of the plastic film 10, the peripheral speed a of the pattern roll 2a can be changed. This is also true for the pattern roll 2b. Therefore, the direction of the linear scratches 12 can be changed by adjusting both pattern rolls 2a, 2b.

[0069] Since each pattern roll 2a, 2b is inclined with respect to the plastic film 10, the plastic film 10 receives a force in the width direction by sliding contact with each pattern roll 2a, 2b. Therefore, in order to prevent the plastic film 10 from meandering, it is preferable to adjust the height and / or angle of each press roll 3a, 3b with respect to each pattern roll 2a, 2b. For example, by appropriately adjusting the crossing angle θ3 between the axis of the pattern roll 2a and the axis of the press roll 3a, a width direction distribution of the pressing force is obtained so as to cancel the force in the width direction, thereby preventing meandering. In addition, adjustment of the interval between the pattern roll 2a and the press roll 3a also contributes to preventing meandering. In order to prevent meandering and breakage of the plastic film 10, it is preferable that the rotation direction of the first and second pattern rolls 2a, 2b inclined with respect to the width direction of the plastic film 10 is the same as the traveling direction of the plastic film 10.

[0070] FIG. 10 shows another example of an apparatus for forming orthogonal linear scratches. This apparatus differs from the apparatus shown in FIG. 9(a) to FIG. 9(e) in that the second pattern roll 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 apparatus shown in FIG. 9(a) to FIG. 9(e) will be described below. The rotation direction of the second pattern roll 32b may be the same as or opposite to the traveling direction of the plastic film 10. The second pressing roll 33b may be located upstream or downstream of the second pattern roll 32b. This apparatus is suitable for forming orthogonal linear scratches by aligning the direction of the linear scratches 12' (line segment E'F') with the width direction of the plastic film 10, as shown by Z in FIG. 9(d).

[0071] The running speed of the plastic film 10 is preferably 5 to 200 m / min, and the peripheral speed of the pattern roll is preferably 10 to 2,000 m / min. The inclination angle θ2 of the pattern roll is preferably 20° to 60°, and more preferably about 45°. The tension of the film 10 (proportional to the pressing force) is preferably 0.05 to 5 kgf / cm width.

[0072] The pattern roll is preferably a roll having sharp corners and fine particles with a Mohs hardness of 5 or more on the surface, such as the diamond roll described in JP-A-2002-59487. The width of the linear scratches is determined by the particle size of the fine particles, so 90% or more of the diamond fine particles preferably have a particle size within the range of 0.1 to 100 μm, more preferably a particle size within the range of 0.1 to 70 μm. The diamond fine particles are preferably attached to the roll surface with an area ratio of 30% or more. The diamond fine particles are preferably fixed by a layer of metal such as nickel.

[0073] (2) First electromagnetic wave absorbing film manufacturing apparatus (a) First manufacturing equipment The first production apparatus has basically the same structure as the second electromagnetic-wave-absorbing film production apparatus, except that linear scratch-formed regions and linear scratch-non-formed regions are provided alternately in the circumferential direction on the outer circumferential surface of each pattern roll, and the linear scratch-formed regions have a large number of high-hardness fine particles on their surfaces. Therefore, the above-mentioned pattern rolls will be described in detail.

[0074] Fig. 11(a) shows an example of each pattern roll used in the first manufacturing apparatus. This pattern roll 102 comprises a roll body 102a, and linear scratch-formed regions 102b and linear scratch-unformed regions 102c formed alternately at a predetermined interval on the outer peripheral surface of the roll body 102a. The linear scratch-formed region 102b comprises a large number of high-hardness fine particles 102d and a fixing layer 102e for holding the particles, as shown in Fig. 11(b). As in the second electromagnetic-wave-absorbing film manufacturing apparatus described above, the high-hardness fine particles 102d are preferably diamond fine particles, and the fixing layer 102e is preferably a layer of a metal such as nickel. The linear scratch non-forming region 102c is preferably (a) a region where the fixing layer 102e holding a large number of high-hardness particles 102d is not formed, or (b) a region consisting only of the fixing layer 102e (not having high-hardness particles 102d), so that no or almost no linear scratches are formed on the metal thin film 11 even when the metal thin film 11 comes into close proximity due to the rotation of the pattern roll 102.

[0075] The central angle α1 of the linear-scratch-formed regions 102b is preferably 30 to 90°, and more preferably 45 to 90°. The central angle α2 of the linear-scratch-free regions 102c is preferably 30 to 90°, and more preferably 45 to 90°. In the illustrated example, four linear-scratch-formed regions 102b and four linear-scratch-free regions 102c are alternately provided, so α1+α2 is 90°, but is not limited to this.

[0076] As shown in FIG. 12, the circumferential lengths D1, D2 of the linear-scratch-formed region 102b and the linear-scratch-free region 102c are determined by their center angles α1, α2 and the radius R of the roll body 102a, and are generally preferably 0.2 to 10 mm, and more preferably 1 to 5 mm, respectively.

[0077] The radius R of the roll body 102a is preferably 3 to 6 cm. If the radius R exceeds 6 cm, the distance over which the pattern roll 102 slides against the metal thin film 11 is too long, making it impossible to set the high density linear scratch region short. On the other hand, if the radius R is less than 3 cm, the rigidity of the roll body 102a is insufficient. It is more preferable that the radius R of the roll body 102a is 3 to 5 cm.

[0078] FIG. 13 shows another example of each pattern roll used in the first manufacturing apparatus. This pattern roll 112 has a roll body 112a having a large outer diameter region 112b and a small outer diameter region 112c alternately along the outer circumferential surface, and a linear scratch formation region 112d formed in the large outer diameter region 112b of the roll body 112a. The linear scratch formation region 112d may be the same as the linear scratch formation region 102b in the above-mentioned pattern roll 102. Although it is not necessary to form a fixing layer that holds a large number of high-hardness fine particles in the small outer diameter region 112c, a fixing layer that holds a large number of high-hardness fine particles may also be formed in the small outer diameter region 112c from the viewpoint of manufacturing efficiency. The ratio of the central angle (circumferential length) between the large outer diameter region 112b and the small outer diameter region 112c may be the same as the ratio of the central angle (circumferential length) between the linear scratch formation region 102b and the linear scratch non-formation region 102c in the above-mentioned pattern roll 102.

[0079] When a fixing layer holding a large number of high-hardness fine particles is also formed in the small outer diameter region 112c, the difference Dh between the radius R1 of the large outer diameter region 112b and the radius R2 of the small outer diameter region 112c is preferably 1 mm or more. If the step Dh is less than 1 mm, the high-hardness fine particles in the small outer diameter region 112c are likely to come into strong sliding contact with the metal thin film 11, and the density of linear scratches in the low-density region of the obtained first electromagnetic-wave-absorbing film becomes too high. It is more preferable that the step Dh is 2 to 5 mm.

[0080] The radius R1 of the large outer diameter region 112b of the roll body 112a is also preferably 3 to 6 cm, and more preferably 3 to 5 cm.

[0081] (b) Second manufacturing equipment The second production apparatus has basically the same structure as the second production apparatus for the electromagnetic-wave-absorbing film, except that it comprises a device for driving at least one of the pattern roll and the pressure roll in a direction perpendicular to the thin metal film so that each pattern roll is in sliding contact with the thin metal film intermittently. Therefore, the vertical driving of the pattern roll and / or the pressure roll will be described in detail.

[0082] 14(a) and 14(b) show an example in which the rotation shafts of a pair of press rolls 103a, 103b are fixed, and the rotation shaft of a pattern roll 122 is driven by a drive device (not shown) in a direction perpendicular to the thin metal film 11 at regular time intervals. The pattern roll 122 has a large number of high-hardness fine particles on its entire outer circumferential surface, similar to the pattern rolls 2a, 2b used in the second electromagnetic-wave-absorbing film manufacturing apparatus. The plastic film 10 is held at a constant height by the pair of press rolls 103a, 103b.

[0083] In the state shown in Fig. 14(a), the pattern roll 122 is in the raised position and is slightly pressed against and in sliding contact with the thin metal film 11 of the plastic film 10, so that linear scratches are formed on the thin metal film 11. Next, when the pattern roll 122 reaches the lowered position as shown in Fig. 14(b), the pattern roll 122 moves away from the thin metal film 11, so that no linear scratches are formed on the thin metal film 11. In this way, the formation of linear scratches is alternated by the intermittent vertical drive of each pattern roll 122, so that the first and second groups of linear scratches can be alternately formed in the thin metal film 11 in the linear scratch direction. The lengths of the high-density and low-density regions in the first and second groups of linear scratches can be adjusted by the time interval between the vertical drives of each pattern roll 122.

[0084] For the same reason as above, the radius R of the pattern roll 122 is also preferably 3 to 6 cm, and more preferably 3 to 5 cm.

[0085] High density regions and low density regions can be formed alternately by vertically driving the pair of pressure rolls 103a, 103b instead of vertically driving the pattern roll 122. Also, by vertically driving the pattern roll 122 and the pair of pressure rolls 103a, 103b in the opposite directions, that is, by lowering the pair of pressure rolls 103a, 103b when the pattern roll 122 rises and raising the pair of pressure rolls 103a, 103b when the pattern roll 122 descends, the sliding contact between the pattern roll 122 and the metal thin film 11 can be switched quickly, so that the high density regions and low density regions can be narrowed (shortened in the linear scratch direction).

[0086] The present invention will be described in more detail by the following examples, but the present invention is not limited thereto.

[0087] Example 1 (1) Manufacturing of a first electromagnetic wave absorbing film A pair of pattern rolls 102, 102 on which diamond fine particles with a particle size distribution of 50 to 80 μm were electrodeposited in place of the pair of pattern rolls 2a, 2b in the apparatus shown in FIG. 9(a) was used as a first manufacturing apparatus. The upstream pattern roll 102 of the first manufacturing apparatus formed high-density and low-density regions of linear scratches having the following characteristics alternately in one direction on an aluminum thin film with a thickness of 60 nm vacuum-deposited on a PET film with a thickness of 16 μm, thereby producing a first linear scratch group. Next, the downstream pattern roll 102 produced a second linear scratch group having high-density and low-density regions of linear scratches in another direction by overlapping the first linear scratch group under the same conditions as the first linear scratch group, thereby obtaining a first electromagnetic-wave-absorbing film. The crossing angle θs of the linear scratches in the first and second linear scratch groups was 90°. A micrograph of this first electromagnetic-wave-absorbing film is shown in FIG. 15.

[0088] The linear scratches in the first and second groups of linear scratches had the same characteristics except for their direction, as follows: high density area Linear marks: Width W range: 0.5~50μm Average width Wav: 30μm Range of lateral spacing I: 1 to 50 μm Average lateral spacing Iav: 40μm Average length Lav: 1 mm Length in the direction of orientation: 2 mm low density area (1) Length in the direction of orientation: 2 mm Note: (1) Since the linear scratches are very small in the low-density region, only the length in the orientation direction of the low-density region was measured.

[0089] (a) Measurement of surface resistivity The surface resistivity of the aluminum thin film on which linear scratches were formed all over the surface was measured under the same conditions as the high-density region in the first group of linear scratches in which linear scratches were formed in one direction, and this was designated as the surface resistivity Rs1 of the high-density region. In addition, the surface resistivity Rs0 of the aluminum thin film on which no linear scratches were formed was measured, and the surface resistivity Rs2 of the low-density region was calculated from the obtained surface resistivities Rs1 and Rs0. The surface resistivity was measured using a sheet resistance / surface resistivity meter "EC-80P" manufactured by Napson Corporation. The surface resistivity of the second group of linear scratches was considered to be the same as that of the first group of linear scratches.

[0090] (b) Measurement of light transmittance The light transmittance of the aluminum thin film on which linear scratches were formed on the entire surface was measured under the same conditions as the high-density region in the first linear scratch group, and this was taken as the surface resistivity Lt1 of the high-density region. In addition, the light transmittance Lt0 of the aluminum thin film on which no linear scratches were formed was measured, and the light transmittance Lt2 of the low-density region was calculated from the obtained light transmittances Lt1 and Lt0. A transmission type laser discrimination sensor (IB-30) manufactured by Keyence Corporation was used to measure the light transmittance. The light transmittance of the second linear scratch group was considered to be the same as that of the first linear scratch group.

[0091] high density area Surface resistivity: 90Ω / □ Light transmittance: 4.5% low density area Surface resistivity: 8Ω / □ Light transmittance: 1.5%

[0092] (2) Conduction noise absorption rate measurement A test piece TP1 (50 mm×50 mm) was cut out from the first electromagnetic-wave-absorbing film. In a near-field electromagnetic wave evaluation system shown in FIG. 16(a) and FIG. 16(b) including a 50Ω 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, the test piece TP was attached to the upper surface of the insulating substrate 200 with an adhesive so that the center of the test piece TP1 coincided with the center of the microstrip line MSL. An incident wave of 0.1 to 6 GHz was input to the microstrip line MSL, and the power S of the reflected wave was measured. 11 and the power of the transmitted wave S 21 Measure S 11 and S 21 From noise absorption rate P loss / P in The results are shown in Fig. 17. As is clear from Fig. 17, the noise absorption ratio P loss / P in was inferior to Comparative Example 1 described later, but was sufficient in terms of the balance with the radiation noise absorption ability.

[0093] (3) Measurement of radiated noise A test piece TP2 (40 mm×40 mm) cut out from the first electromagnetic-wave-absorbing film was scanned at frequencies in the range of 0.03 GHz to 7 GHz by an EMC noise scanner (WM7400) manufactured by Morita Tech Co., Ltd., to measure the radiated noise. Fig. 18 shows the accumulated radiated noise of the test piece of Example 1. The position of the test piece is indicated by a white frame in Fig. 18. In the following photographs of the accumulated radiated noise, the position of the test piece is the same, so it is omitted.

[0094] 18 , accumulated radiation noise of −10 dBm or more was not substantially observed within the frequency range of 100 MHz to 5 GHz, confirming that the first electromagnetic-wave-absorbing film of Example 1 has excellent radiant noise absorbing capability in the frequency range of 100 MHz to 5 GHz.

[0095] Example 2 (1) Manufacturing the second electromagnetic wave absorbing film Using an apparatus having the structure shown in Fig. 9(a) having pattern rolls 2a, 2b on which diamond particles having a particle size distribution of 50 to 80 µm were electrodeposited, bidirectional linear scratches having the following characteristics were formed all over the surface of the same aluminum thin film as in Example 1, thereby obtaining a second electromagnetic-wave-absorbing film. Width W range: 0.5~50μm Average width Wav: 30μm Range of lateral spacing I: 1 to 5 μm Average lateral spacing Iav: 40μm Average length Lav: 1 mm Intersection angle θs: 90°

[0096] The surface resistivity and light transmittance of the second electromagnetic-wave-absorbing film having intersecting linear scratches all over its surface were measured by the same methods as in Example 1, and were found to be 25 Ω / □ and 3%, respectively.

[0097] (2) Adhesion of the first and second electromagnetic wave absorbing films The second electromagnetic-wave-absorbing film was adhered with a non-conductive adhesive to the first electromagnetic-wave-absorbing film produced in Example 1, to produce the near-field electromagnetic wave absorber shown in Fig. 6(a). The thickness of the adhesive layer 20 was 5 µm.

[0098] (3) Conduction noise absorption capacity and radiation noise absorption capacity of near-field electromagnetic wave absorbers As in Example 1, the noise absorption rate P loss / P inThe results of measuring the noise and radiation noise are shown in Figures 19 and 20, respectively. As is clear from Figures 19 and 20, the near-field electromagnetic wave absorber of Example 2 exhibited excellent radiated noise absorbing ability, and also had sufficient conductive noise absorbing ability.

[0099] Example 3 (1) Manufacturing of a first electromagnetic wave absorbing film A second manufacturing apparatus was prepared by using a pair of pattern rolls 102, 102 having a drive unit (not shown) that drives the rotation shaft vertically instead of the pair of pattern rolls 2a, 2b in the apparatus shown in Fig. 9(a). Diamond fine particles having a particle size distribution of 50 to 80 μm were electrodeposited on the entire outer circumferential surface of each pattern roll 102, 102. Each pattern roll 102, 102 was driven by moving up and down at regular time intervals while the plastic film 10 having the metal thin film 11 was moving.

[0100] The pattern roll 122 on the upstream side of the second production apparatus formed high-density and low-density regions of linear scratches having the following characteristics alternately in one direction on the same aluminum thin film as in Example 1, to produce a first group of linear scratches. The pattern roll 122 on the downstream side then formed a second group of linear scratches having high-density and low-density regions of linear scratches in another direction by overlapping the first group of linear scratches under the same conditions as the first group of linear scratches, to obtain a first electromagnetic-wave-absorbing film. The crossing angle θs of the linear scratches in the first and second groups of linear scratches was 90°. A micrograph of this first electromagnetic-wave-absorbing film is shown in Fig. 21.

[0101] The linear scratches in the first and second groups of linear scratches had the same characteristics except for their direction, as follows: high density area Linear marks: Width W range: 0.5~50μm Average width Wav: 35μm Range of lateral spacing I: 1 to 50 μm Average lateral spacing Iav: 30μm Average length Lav: 1 mm Length in the direction of orientation: 2 mm low density area (1) Length in the direction of orientation: 2 mm Note: (1) Since the linear scratches are very small in the low-density region, only the length in the orientation direction of the low-density region was measured.

[0102] The surface resistivity and light transmittance of the high-density region and the low-density region in the first group of linear scratches were measured by the same method as in Example 1. The surface resistivity and light transmittance of the second group of linear scratches were considered to be the same as those of the first group of linear scratches. high density area Surface resistivity: 150Ω / □ Light transmittance: 6% low density area Surface resistivity: 3Ω / □ Light transmittance: 1%

[0103] (2) Conduction noise absorption capacity and radiation noise absorption capacity of the first electromagnetic wave absorbing film As in Example 1, the noise absorption rate P loss / P in The measurement results of the noise and radiation noise are shown in Figures 22 and 23, respectively. As is clear from Figures 22 and 23, the first electromagnetic-wave-absorbing film of Example 3 not only exhibited excellent radiated noise absorbing capability, but also had sufficient conducted noise absorbing capability.

[0104] Example 4 (1) Adhesion of the first and second electromagnetic wave absorbing films The first electromagnetic-wave-absorbing film of Example 3 was bonded to the second electromagnetic-wave-absorbing film of Example 2 with a non-conductive adhesive to produce the near-field electromagnetic wave absorber shown in Fig. 6(a). The thickness of the adhesive layer was 5 µm.

[0105] (2) Conduction noise absorption capacity and radiation noise absorption capacity of near-field electromagnetic wave absorbers As in Example 1, the noise absorption rate P loss / P inThe results of measuring the noise and radiation noise are shown in Figures 24 and 25, respectively. As is clear from Figures 24 and 25, the near-field electromagnetic wave absorber of Example 4 exhibited excellent radiated noise absorbing ability, and also had sufficient conductive noise absorbing ability.

[0106] Comparative Example 1 For test pieces TP1 and TP2 cut out from one sheet of the second electromagnetic-wave-absorbing film produced in Example 2, the noise absorption rate P loss / P in The results of measuring the conductive noise and radiated noise are shown in Fig. 26 and Fig. 27, respectively. As is clear from Fig. 26 and Fig. 27, the electromagnetic-wave-absorbing film of Comparative Example 1 exhibited excellent conductive noise absorbing ability, but its radiated noise absorbing ability was significantly inferior to Examples 1 and 3.

[0107] Comparative Example 2 For the test pieces TP1 and TP2 cut out from the near-field electromagnetic wave absorber formed by bonding two sheets of the second electromagnetic wave absorbing film produced in Example 2, the noise absorption rate P loss / P in The results of measuring the conductive noise and the radiated noise are shown in Fig. 28 and Fig. 29. As is clear from Fig. 28 and Fig. 29, the near-field electromagnetic wave absorber of Comparative Example 2 exhibited good conductive noise absorption ability, but the radiated noise absorption ability was significantly inferior to Examples 2 and 4. [Explanation of symbols]

[0108] 1. Near-field electromagnetic wave absorber 10, 10a, 10b... Plastic film 11,11a,11b...Metal thin film 12,12a,12b... Linear marks 2a, 2b, 32a, 32b... A pattern roll for producing a second electromagnetic wave absorbing film 3a, 3b, 103a, 103b... Presser roll 20...adhesive layer 100a First electromagnetic wave absorbing film 100b Second electromagnetic wave absorbing film 102 An example of a pattern roll used in the first apparatus for producing the first electromagnetic-wave-absorbing film 102a...Roll body 102b... Linear mark formation area 102c... Linear mark non-formation area 102d...High density fine particles 102e...Fixed layer 112...Another example of a pattern roll used in a first apparatus for producing a first electromagnetic-wave-absorbing film. 112a···Roll body 112b...Large outer diameter area 112c...Small outer diameter area 112d... Linear scar formation area 122... A pattern roll used in a second device for producing a first electromagnetic wave absorbing film. α1: central angle of linear scratch formation area α2: central angle of the region where no linear scratches are formed R: Radius of roll body R1: Radius of the large outer diameter area R2: Radius of small outer diameter area

Claims

1. 1. An electromagnetic-wave-absorbing film comprising a plastic film and a thin metal film formed on one side of said plastic film, said thin metal film having a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and alternating between areas in each direction where the linear scratches are formed at a high density and areas where the linear scratches are formed at a low density, and the high-density areas are formed in a lattice pattern by the intersection of the linear scratches in both directions.

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

3. 2. The electromagnetic-wave-absorbing film according to claim 1, wherein an intersecting angle between the linear scratches in two directions is 30 to 90°.

4. 2. The electromagnetic-wave-absorbing film according to claim 1, wherein a length ratio between the high-density region and the low-density region in each direction is 5 / 1 to 1 / 5.

5. 5. The electromagnetic-wave-absorbing film according to claim 4, wherein the length in each direction of the high-density region is 0.2 to 10 mm, and the length of the low-density region is 0.2 to 10 mm.

6. 2. The electromagnetic-wave-absorbing film according to claim 1, wherein the metal thin film has a thickness of 20 to 100 nm.

7. 2. The near-field electromagnetic wave absorber according to claim 1, wherein the metal thin film is made of aluminum.

8. 6. The electromagnetic-wave-absorbing film according to any one of claims 1 to 5, wherein the width of the linear scratches is in the range of 0.1 to 100 μm and is 2 to 50 μm on average, and the spacing between the linear scratches is in the range of 0.1 to 500 μm and is 10 to 100 μm on average.

9. An apparatus for manufacturing an electromagnetic-wave-absorbing film comprising a plastic film and a thin metal film formed on one surface of the plastic film, the thin metal film having a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and alternating regions in each direction in which the linear scratches are formed at a high density and regions in which the linear scratches are formed at a low density, the high-density regions being distributed in a lattice pattern due to the intersection of the linear scratches in both directions, Two pattern rolls, a means for conveying the plastic film so that the metal thin film is in sliding contact with two pattern rolls; a press roll for pressing the metal thin film against the pattern roll; the two pattern rolls are inclined to opposite sides with respect to the width direction of the plastic film within the plane in sliding contact with the metal thin film, The outer peripheral surface of each pattern roll is provided with linear-scratch-formed regions and linear-scratch-free regions alternately in the circumferential direction, An apparatus characterized in that the linear scratch forming area has a large number of high-hardness fine particles on its surface.

10. 10. An apparatus for producing an electromagnetic-wave-absorbing film according to claim 9, wherein the linear-scratch-free region of the pattern roll is set back radially inward from the linear-scratch-formed region.

11. 11. The electromagnetic-wave-absorbing film manufacturing apparatus according to claim 10, wherein the linear-scratch-free region of the pattern roll is set back from the linear-scratch-formed region by 1 mm or more radially inward.

12. 10. The apparatus for producing an electromagnetic-wave-absorbing film according to claim 9, wherein the linear-scratch-free region is a region that does not have high-hardness fine particles.

13. An apparatus for manufacturing an electromagnetic-wave-absorbing film comprising a plastic film and a thin metal film formed on one surface of the plastic film, the thin metal film having a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and alternating regions in each direction in which the linear scratches are formed at a high density and regions in which the linear scratches are formed at a low density, the high-density regions being distributed in a lattice pattern due to the intersection of the linear scratches in both directions, Two pattern rolls having a large number of high-hardness fine particles on the entire outer circumferential surface, a means for conveying the plastic film along the pattern roll; and a presser roll disposed on both sides of each pattern roll, the two pattern rolls are inclined to opposite sides with respect to the width direction of the plastic film within the plane in sliding contact with the metal thin film, The apparatus comprises a device for driving at least one of each pattern roll and the pressure rolls on both sides thereof in a direction perpendicular to the metal thin film so that each pattern roll is in sliding contact with the metal thin film intermittently.

14. A near-field electromagnetic wave absorber having at least one plastic film and first and second thin metal films, said first metal thin film has a large number of substantially parallel linear scratches formed in two directions with irregular widths and intervals, and in each direction has alternating regions where the linear scratches are formed at a high density and regions where the linear scratches are formed at a low density, and the high density regions are distributed in a lattice pattern by the intersection of the linear scratches in both directions, A near-field electromagnetic wave absorber characterized in that a large number of intermittent linear scratches which are substantially parallel to each other and have irregular widths and intervals are formed in two directions on the entire surface of said second thin metal film.

15. 15. The near-field electromagnetic wave absorber according to claim 14, wherein the surface resistivity of the high-density region is 30 to 200 Ω / □, and the surface resistivity of the low-density region is 0 to 20 Ω / □.

16. 15. The near-field electromagnetic wave absorber according to claim 14, wherein the length ratio of the high density region to the low density region in each direction in the first metal thin film is 5 / 1 to 1 / 5.

17. 15. The near-field electromagnetic wave absorber according to claim 14, wherein the length of the high-density region in each direction in the first metal thin film is 0.2 to 10 mm, and the length of the low-density region is 0.2 to 10 mm.

18. 15. The near-field electromagnetic wave absorber according to claim 14, characterized in that a first electromagnetic-wave absorbing film having the first metal thin film on one side of a plastic film, and a second electromagnetic-wave absorbing film having the second metal thin film on one side of a plastic film are bonded to each other.

19. 20. The near-field electromagnetic wave absorber according to claim 18, wherein the first and second electromagnetic wave absorbing films are bonded together with the first and second thin metal films facing inwards.

20. 15. The near-field electromagnetic wave absorber according to claim 14, comprising the first and second thin metal films on both sides of a single plastic film.

21. 15. The electromagnetic-wave absorbing film according to claim 14, wherein a crossing angle between linear scratches in two directions in each of the first and second metal thin films is 30 to 90°.

22. 15. The near-field electromagnetic wave absorber according to claim 14, wherein each of the first and second metal thin films has a thickness of 20 to 100 nm.

23. 15. The near-field electromagnetic wave absorber according to claim 14, wherein each of the first and second thin metal films is made of aluminum.

24. 24. The near-field electromagnetic wave absorber according to any one of claims 14 to 23, wherein the width of the linear scratches in the first and second metal thin films is within a range of 0.1 to 100 μm and is 2 to 50 μm on average, and the interval between the linear scratches is within a range of 0.1 to 500 μm and is 10 to 100 μm on average.

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