Impedance matching film for radio wave absorber, film with impedance matching film for radio wave absorber, radio wave absorber, and laminate for radio wave absorber

Abstract

The impedance matching film 10 contains a metal element and a non-metal element. The impedance matching film 10 has a thickness of 10 nm to 200 nm. The impedance matching film 10 has a sheet resistance of 200 Ω / □ or more. In the impedance matching film 10, the content of oxygen atoms based on the number of atoms is less than 50%.

Description

Technical Field

[0001] The present invention relates to an impedance matching film for a radio wave absorber, a film with an impedance matching film for a radio wave absorber, a radio wave absorber, and a laminate for a radio wave absorber. Background Art

[0002] Conventionally, there is known a technique for achieving impedance matching by using an alloy in a resistor film for a radio wave absorber so as to match the impedance on the surface of the radio wave absorber with the characteristic impedance of air.

[0003] For example, Patent Document 1 proposes a λ / 4 type resistor coating for a radio wave absorber, which includes an alloy containing 5 wt% or more of molybdenum. In the λ / 4 type resistor coating for a radio wave absorber, the surface resistance value is adjusted to a predetermined range with a film thickness of 5 nm to 6 nm by adjusting the nickel content and chromium content of the alloy.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-56562 Summary of the invention

[0007] Problems to be solved by the invention

[0008] Patent Document 1 measures the temporal change in the surface resistance value of a resistor coating at 25° C. On the other hand, Patent Document 1 does not evaluate the temporal change in the surface resistance value of a resistor coating when exposed to a high temperature environment (eg, an environment of 80° C.).

[0009] In view of such circumstances, the present invention provides a novel impedance matching film for a radio wave absorber which is advantageous in suppressing a change in sheet resistance from the viewpoint of impedance matching when exposed to a high temperature environment.

[0010] Means used to solve problems

[0011] The present invention provides an impedance matching film for a radio wave absorber, wherein the impedance matching film for a radio wave absorber comprises a metal element and a non-metal element, and

[0012] Having a thickness of 10nm to 200nm,

[0013] Has a sheet resistance of more than 200Ω / □, and

[0014] The content of oxygen atoms based on the number of atoms is less than 50%.

[0015] In addition, the present invention provides a film with an impedance matching film for a radio wave absorber, wherein the film with an impedance matching film for a radio wave absorber has:

[0016] Base material, and

[0017] The above-mentioned radio wave absorber uses an impedance matching film.

[0018] In addition, the present invention provides a radio wave absorber, wherein the radio wave absorber has:

[0019] Impedance matching film for the above-mentioned radio wave absorber;

[0020] Conductors that reflect radio waves; and

[0021] A dielectric layer is disposed between the impedance matching film for the radio wave absorber and the conductor in a thickness direction of the impedance matching film for the radio wave absorber.

[0022] In addition, the present invention provides a laminate for a radio wave absorber, wherein the laminate for a radio wave absorber has:

[0023] The above-mentioned impedance matching film for the radio wave absorber; and

[0024] A dielectric layer is disposed so as to be in contact with the impedance matching film for the radio wave absorber in a thickness direction of the impedance matching film for the radio wave absorber.

[0025] Effects of the Invention

[0026] The impedance matching film for a radio wave absorber is advantageous in suppressing a change in sheet resistance when exposed to a high temperature environment from the viewpoint of impedance matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a cross-sectional view showing an example of the impedance matching film for the radio wave absorber of the present invention.

[0028] Figure 2A It is a cross-sectional view showing an example of the radio wave absorber of the present invention.

[0029] Figure 2B To express Figure 2A sectional view of a modified example of the radio wave absorber shown.

[0030] Figure 2C To express Figure 2A 2 is a cross-sectional view of another modified example of the radio wave absorber shown.

[0031] Figure 3 It is a cross-sectional view showing another example of the radio wave absorber of the present invention.

[0032] Figure 4AIt is a cross-sectional view showing another example of the radio wave absorber of the present invention.

[0033] Figure 4B It is a cross-sectional view showing an example of the laminate for the radio wave absorber of the present invention.

[0034] Figure 5A It is a cross-sectional view showing another example of the radio wave absorber of the present invention.

[0035] Figure 5B It is a cross-sectional view showing another example of the laminate for the radio wave absorber of the present invention. DETAILED DESCRIPTION

[0036] Embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the present invention is not limited to the following embodiments.

[0037] like Figure 1 As shown, the impedance matching film for radio wave absorber 10 is provided by, for example, a film 15 with an impedance matching film for radio wave absorber. The impedance matching film for radio wave absorber 10 is a resistive film. The film 15 with an impedance matching film for radio wave absorber has a substrate 22 and the impedance matching film for radio wave absorber 10. The impedance matching film for radio wave absorber 10 is formed on, for example, one main surface of the substrate 22.

[0038] The impedance matching film 10 contains metal elements and non-metal elements. Moreover, the impedance matching film 10 has a thickness of 10 nm to 200 nm and has a sheet resistance of more than 200 Ω / □. In addition, the content of oxygen atoms based on the atomic number of the impedance matching film 10 is less than 50%. Therefore, the indium tin oxide (ITO) film is not included in the impedance matching film 10. It should be noted that in this specification, semi-metal elements such as silicon, germanium, arsenic, antimony, and tellurium are regarded as non-metal elements. The impedance matching film 10 is, for example, a resistive coating adjusted so that the impedance expected from its front surface is equal to the characteristic impedance of a plane wave.

[0039] Since the impedance matching film 10 has a thickness of 10nm to 200nm, it is easy to maintain the desired sheet resistance from the perspective of impedance matching when exposed to a high temperature environment (for example, 80°C). This is because, even if the impedance matching film is degraded near the surface in a high temperature environment, the volume occupied by the degraded portion in the impedance matching film 10 is small. On the other hand, the resistor coating for the λ / 4 type radio wave absorber described in Patent Document 1 has a film thickness of 5nm to 6nm, for example. Since the resistor coating is thin, when the surface of the resistor coating is degraded in a high temperature environment, the volume occupied by the degraded portion in the resistor coating is large, which has a great impact on the characteristics of the resistor coating used for impedance matching. Therefore, it is difficult to say that the technology described in Patent Document 1 is beneficial to suppressing the change in the sheet resistance of the resistor coating from the perspective of impedance matching when exposed to a high temperature environment.

[0040] The thickness of the impedance matching film 10 may be greater than or equal to 11 nm, greater than or equal to 13 nm, or greater than or equal to 15 nm.

[0041] The thickness of the impedance matching film 10 is 200 nm or less. This can suppress the warping of the impedance matching film 10 and prevent cracks from being easily generated in the impedance matching film 10. The thickness of the impedance matching film 10 may be 180 nm or less, 160 nm or less, or 150 nm or less.

[0042] Since the impedance matching film 10 has a sheet resistance of 200Ω / □ or more, the radio wave absorber provided by using the impedance matching film 10 can easily exhibit the desired radio wave absorption performance.

[0043] The sheet resistance of the impedance matching film 10 may be 220Ω / □ or more, 250Ω / □ or more, or 280Ω / □ or more.

[0044] The upper limit of the sheet resistance of the impedance matching film 10 is not limited to a specific value. The sheet resistance of the impedance matching film 10 may vary according to the characteristics of other structures of the radio wave absorber. In one example of the radio wave absorber, the sheet resistance of the impedance matching film 10 is, for example, 600Ω / □ or less. The sheet resistance of the impedance matching film 10 may be 580Ω / □ or less, 550Ω / □ or less, or 520Ω / □ or less. For example, in the case where the radio wave absorber does not include lossy materials such as dielectric loss materials and magnetic loss materials, the upper limit of the sheet resistance of the impedance matching film 10 may be adjusted within such a range. In another example of the radio wave absorber, the sheet resistance of the impedance matching film 10 is, for example, 10MΩ (megaohm) / □ or less, 8MΩ / □ or less, 5MΩ / □ or less, or 3MΩ / □ or less. For example, in the case where the radio wave absorber includes lossy materials such as dielectric loss materials or magnetic loss materials, the upper limit of the sheet resistance of the impedance matching film 10 may be adjusted within such a range.

[0045] The impedance matching film 10 has, for example, a 0.40×10 -3 The resistivity is Ω·cm or more. Thus, the impedance matching film 10 has a thickness of 10 nm to 200 nm and is likely to have a desired sheet resistance from the viewpoint of impedance matching.

[0046] The resistivity of the impedance matching film 10 can be 0.44×10 -3 Ω·cm or more, can be 0.50×10 -3 Ω·cm or more, and can also be 0.56×10 -3 Ω·cm or more.

[0047] The upper limit of the resistivity of the impedance matching film 10 is not limited to a specific value. The resistivity of the impedance matching film 10 may be changed according to the characteristics of other structures of the radio wave absorber. In one example of the radio wave absorber, the resistivity of the impedance matching film 10 is, for example, 8.0×10 -3 Ω·cm or less. The resistivity of the impedance matching film 10 can be 7.7×10 -3 Ω·cm or less, which can be 7.3×10 -3 Ω·cm or less, and can also be 7×10 -3 Ω·cm or less. For example, in the case where the radio wave absorber does not include lossy materials such as dielectric loss materials and magnetic loss materials, the upper limit of the resistivity of the impedance matching film 10 can be adjusted within such a range. In another example of the radio wave absorber, the resistivity of the impedance matching film 10 is, for example, 150Ω·cm or less, 100Ω·cm or less, 80Ω·cm or less, or 50Ω·cm or less. For example, in the case where the radio wave absorber includes lossy materials such as dielectric loss materials and magnetic loss materials, the upper limit of the resistivity of the impedance matching film 10 can be adjusted within such a range.

[0048] In the impedance matching film 10, the sheet resistance change rate Cs determined by the following formula (1) is, for example, 30% or less. In the formula (1), Ri [Ω / □] is the initial sheet resistance of the impedance matching film 10, and Rt [Ω / □] is the sheet resistance of the impedance matching film 10 after the impedance matching film 10 is kept at an ambient temperature of 80° C. for 24 hours. In the impedance matching film 10, if the sheet resistance change rate Cs is 30% or less, it is easy to maintain its radio wave absorption performance even if the radio wave absorber is exposed to a high temperature environment. The most preferred sheet resistance change rate Cs is 0%.

[0049] Cs[%]=100×|Rt-Ri| / Ri Formula (1)

[0050] The sheet resistance change rate Cs in the impedance matching film 10 may be 28% or less, 25% or less, or 23% or less.

[0051] The non-metallic element contained in the impedance matching film 10 is not limited to a specific element as long as the impedance matching film 10 has a thickness of 10 nm to 200 nm and has a sheet resistance of 200 Ω / □ or more. The non-metallic element contained in the impedance matching film 10 is, for example, at least one element selected from the group consisting of B, C, N, O, F, Si, S, and Ge. In this case, when the impedance matching film 10 is exposed to a high temperature environment, it is easy to more reliably maintain a desired sheet resistance from the viewpoint of impedance matching.

[0052] The metal element contained in the impedance matching film 10 is not limited to a specific element as long as the impedance matching film 10 has a thickness of 10 nm to 200 nm and a sheet resistance of 200 Ω / □ or more. The metal element contained in the impedance matching film 10 is, for example, at least one element selected from the group consisting of Ni, Cr, Ti, W, Mo, Cu, Al, Sn, Pd, Ta, Rh, Au, Mg, Fe, Mn, Co, and V. In this case, when the impedance matching film 10 is exposed to a high temperature environment, it is easy to more reliably maintain a desired sheet resistance from the viewpoint of impedance matching.

[0053] The metal element contained in the impedance matching film 10 may be at least one element selected from the group consisting of Ni, Cr, Mo and Ti. In this case, when the impedance matching film 10 is exposed to a high temperature environment, it is easy to more reliably maintain a desired sheet resistance from the viewpoint of impedance matching.

[0054] The content of the metal element contained in the impedance matching film 10 based on the number of atoms is not limited to a specific value. The content is greater than 0%, and may be 5% or more, 10% or more, 15% or more, or 20% or more. The content of the metal element contained in the impedance matching film 10 based on the number of atoms is, for example, 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less.

[0055] When the metal element contained in the impedance matching film 10 includes at least one element selected from the group consisting of Ni, Cr, Mo, and Ti, the total content of Ni, Cr, Mo, and Ti based on the number of atoms is, for example, 10% or more. In this case, when the impedance matching film 10 is exposed to a high temperature environment, it is easy to more reliably maintain a desired sheet resistance from the viewpoint of impedance matching.

[0056] In the impedance matching film 10, the total content of Ni, Cr, Mo and Ti based on the number of atoms may be 11% or more, 13% or more, or 15% or more. In the impedance matching film 10, the total content of Ni, Cr, Mo and Ti based on the number of atoms may be, for example, 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less.

[0057] The substrate 22 plays a role as a support body for supporting the impedance matching film 10, for example. The impedance matching film 10 is formed on one main surface of the substrate 22 by, for example, sputtering using a predetermined target material. In this case, for example, a predetermined target material containing a metal element and a non-metal element is used. In addition to the composition of the target material, the impedance matching film 10 can be formed in a manner in which the content of oxygen atoms based on the number of atoms is less than 50% by adjusting predetermined conditions such as the ratio of the volume flow rate of an active gas such as oxygen to the volume flow rate of a gas supplied to the surrounding of the substrate 22 during sputtering. The impedance matching film 10 can be formed by a method such as ion plating or coating (for example, bar coating) according to the situation.

[0058] like Figure 2A As shown, a radio wave absorber 1a can be provided using an impedance matching film 10. The radio wave absorber 1a includes the impedance matching film 10, a conductor 30, and a dielectric layer 20. The conductor 30 reflects radio waves. The dielectric layer 20 is disposed between the impedance matching film 10 and the conductor 30 in the thickness direction of the impedance matching film 10.

[0059] The radio wave absorber 1a is, for example, a λ / 4 type radio wave absorber. The radio wave absorber 1a is designed so that when a radio wave of wavelength λ0 to be absorbed is incident on the radio wave absorber 1a, the radio wave generated by the reflection on the surface of the impedance matching film 10 (surface reflection) and the radio wave generated by the reflection on the conductor 30 (back reflection) interfere with each other. In the λ / 4 type radio wave absorber, as shown in the following formula (2), the thickness t of the dielectric layer and the relative dielectric constant ε of the dielectric layer are used to calculate the relative dielectric constant ε of the dielectric layer. r The wavelength λ0 of the electromagnetic wave to be absorbed is determined. That is, by appropriately adjusting the relative dielectric constant and thickness of the dielectric layer, the wavelength of the electromagnetic wave to be absorbed can be set. In formula (2), sqrt(ε r ) represents the relative dielectric constant ε r The square root of .

[0060] λ0=4t×sqrt(ε r ) Formula (2)

[0061] Since the radio wave absorber 1a has the impedance matching film 10, even when the radio wave absorber 1a is exposed to a high temperature environment, it is easy to maintain the desired radio wave absorption performance.

[0062] The sheet resistance of the impedance matching film 10 is determined in the design of the radio wave absorber so that the impedance expected from the front surface of the impedance matching film 10 is equal to the characteristic impedance of the plane wave using, for example, the transmission theory. In the radio wave absorber, the sheet resistance required for the impedance matching film 10 may be changed depending on the assumed incident angle of the radio wave incident on the radio wave absorber.

[0063] The conductor 30 is not particularly limited as long as it can reflect and absorb the radio waves of the target object, and has a predetermined conductivity. Figure 2A As shown, the conductor 30 is formed in a layer shape, for example. In this case, the conductor 30 has a sheet resistance lower than that of the impedance matching film 10. The conductor 30 may have a shape other than a layer shape.

[0064] The conductor 30 contains, for example, indium tin oxide. In this case, the conductor 30 tends to have high transparency.

[0065] The content of tin oxide in the indium tin oxide of the conductor 30 is, for example, 5 mass % to 15 mass %. In this case, the conductor 30 can be formed from stable polycrystalline indium tin oxide by annealing. As a result, when the radio wave absorber 1a is exposed to a high temperature environment for a long time, the desired radio wave absorption performance can be more reliably exhibited.

[0066] The conductor 30 may contain at least one selected from the group consisting of aluminum, copper, iron, aluminum alloys, copper alloys, and iron alloys. In this case, it is easy to achieve desired conductivity while reducing the thickness of the conductor 30.

[0067] The thickness of the conductor 30 is not limited to a specific thickness. For example, when the conductor 30 is indium tin oxide, the conductor 30 has a thickness of, for example, 20 nm to 200 nm, preferably 50 nm to 150 nm. Thus, the radio wave absorber 1a can exert the desired radio wave absorption performance, and cracks are less likely to occur in the conductor 30.

[0068] When the conductor 30 is at least one selected from the group consisting of aluminum, copper, iron, aluminum alloys, copper alloys, and iron alloys, the conductor 30 has a thickness of, for example, 30 nm to 100 μm, and preferably 50 nm to 50 μm.

[0069] The dielectric layer 20 has a relative dielectric constant of, for example, 2.0 to 20.0. In this case, the thickness of the dielectric layer 20 can be easily adjusted, and the radio wave absorption performance of the radio wave absorber 1a can be easily adjusted. The relative dielectric constant of the dielectric layer 20 is, for example, the relative dielectric constant at 10 GHz measured by the cavity resonance method.

[0070] The dielectric layer 20 is formed of a predetermined polymer, for example. The dielectric layer 20 includes, for example, at least one polymer selected from the group consisting of ethylene-vinyl acetate copolymer, vinyl chloride resin, polyurethane resin, acrylic resin, acrylic polyurethane resin, polyethylene, polypropylene, polysiloxane, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, and cycloolefin polymer. In this case, it is easy to adjust the thickness of the dielectric layer 20, and the manufacturing cost of the radio wave absorber 1a can be kept low. The dielectric layer 20 can be made, for example, by hot pressing a predetermined resin composition.

[0071] The dielectric layer 20 may be formed as a single layer or may be formed by a plurality of layers formed of the same or different materials. When the dielectric layer 20 has n layers (n is an integer greater than or equal to 2), the relative dielectric constant of the dielectric layer 20 is determined, for example, as follows. The relative dielectric constant ε of each layer is measured: i (i is an integer from 1 to n). Next, the relative dielectric constant ε of each layer to be measured is i Multiply by the thickness of the layer t i The ratio of the thickness T of the dielectric layer 20 to the total thickness T is used to obtain ε i ×(t i / T). By transforming all layers of ε i ×(t i / T) is added to determine the relative dielectric constant of the dielectric layer 20.

[0072] like Figure 2A As shown, the dielectric layer 20 includes, for example, a first layer 21, a second layer 22, and a third layer 23. The first layer 21 is disposed between the second layer 22 and the third layer 23. The first layer 21 includes, for example, at least one polymer selected from the group consisting of ethylene-vinyl acetate copolymer, vinyl chloride resin, polyurethane resin, acrylic resin, acrylic polyurethane resin, polyethylene, polypropylene, polysiloxane, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, polyimide, and cycloolefin polymer.

[0073] In the radio wave absorber 1a, the second layer 22 also serves as the base material of the impedance matching film 10. The second layer 22 is disposed, for example, at a position closer to the conductor 30 than the impedance matching film 10. Figure 2BAs shown, the second layer 22 can be arranged at a position farther away from the conductor 30 than the impedance matching film 10. In this case, the dielectric layer 20 is formed by the first layer 21 and the third layer 23. In this case, the impedance matching film 10 and the dielectric layer 20 are protected by the second layer 22, and the radio wave absorber 1a has high durability. In this case, for example, the impedance matching film 10 can be in contact with the first layer 21. The second layer 22 also serves as an auxiliary material for adjusting the thickness of the impedance matching film 10 with high precision. The material of the second layer 22 is, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), acrylic resin (PMMA), polycarbonate (PC), polyimide (PI) or cycloolefin polymer (COP). Among them, from the perspective of good heat resistance, dimensional stability and balance of manufacturing cost, the material of the second layer 22 is preferably PET.

[0074] The substrate 22 has a thickness of, for example, 10 μm to 150 μm, preferably 15 μm to 100 μm. Thus, the substrate 22 has low bending rigidity, and when the impedance matching film 10 is formed, the generation of wrinkles or deformation in the substrate 22 can be suppressed.

[0075] In the radio wave absorber 1a, the third layer 23 supports, for example, a layered conductor 30. In this case, the layered conductor 30 is, for example, a metal foil or an alloy foil. The layered conductor 30 can be formed on the third layer 23 by, for example, sputtering, ion plating, or coating (for example, bar coating). The third layer 23 is, for example, disposed in the radio wave absorber 1a at a position closer to the impedance matching film 10 than the layered conductor 30, and constitutes a part of the dielectric layer 20. It should be noted that, as Figure 2C As shown, the third layer 23 may be disposed at a position farther from the impedance matching film 10 than the layered conductor 30. In this case, for example, the layered conductor 30 is in contact with the first layer 21.

[0076] As the material of the third layer 23, for example, the materials exemplified as the material of the second layer 22 can be used. The material of the third layer 23 may be the same as or different from the material of the second layer 22. From the viewpoint of good balance between heat resistance, dimensional stability and manufacturing cost, the material of the third layer 23 is preferably PET.

[0077] The third layer 23 has a thickness of, for example, 10 μm to 150 μm, preferably 15 μm to 100 μm. Thus, the bending rigidity of the third layer 23 is low, and when the layered conductor 30 is formed, the generation of wrinkles or deformation in the third layer 23 can be suppressed. It should be noted that the third layer 23 can be omitted according to circumstances.

[0078] The first layer 21 may be composed of a plurality of layers. Figure 2B or Figure 2C As shown, when the first layer 21 is in contact with at least one of the impedance matching film 10 and the layered conductor 30 , the first layer 21 may be composed of a plurality of layers.

[0079] The first layer 21 may or may not have adhesive properties. When the first layer 21 has adhesive properties, the adhesive layer may be configured to contact at least one of the two main surfaces of the first layer 21, or the adhesive layer may not be configured to contact the two main surfaces. When the first layer 21 does not have adhesive properties, the adhesive layer is preferably configured to contact the two main surfaces of the first layer 21. It should be noted that, when the dielectric layer 20 includes the second layer 22, even if the second layer 22 does not have adhesive properties, the adhesive layer may not be configured to contact the two main surfaces of the second layer 22. In this case, the adhesive layer may be configured to contact one main surface of the second layer 22. When the dielectric layer 20 includes the third layer 23, even if the third layer 23 does not have adhesive properties, the adhesive layer may not be configured to contact the two main surfaces of the third layer 23. The adhesive layer may be configured to contact at least one main surface of the third layer 23.

[0080] The radio wave absorber 1a is designed to absorb radio waves of a desired wavelength. There is no particular limitation on the type of radio waves that the radio wave absorber 1a can absorb. The radio waves that the radio wave absorber 1a can absorb may be, for example, millimeter waves or submillimeter waves of a specific frequency band.

[0081] The radio wave absorber 1a may include at least one of a dielectric loss material and a magnetic loss material. In other words, the radio wave absorber 1a may be a dielectric loss type radio wave absorber or a magnetic loss type radio wave absorber. In this case, the sheet resistance required by the impedance matching film 10 tends to be high. The dielectric layer 20 may include at least one of a dielectric loss material and a magnetic loss material. In addition, the material forming the impedance matching film 10 may be a magnet.

[0082] The electromagnetic wave absorber 1a can be changed from various viewpoints. For example, the electromagnetic wave absorber 1a can be Figure 3 The radio wave absorber 1b shown, Figure 4A The radio wave absorber 1c shown or Figure 5A The radio wave absorbers 1b, 1c and 1d are configured similarly to the radio wave absorber 1a except for the parts specifically described. The components of the radio wave absorbers 1b, 1c and 1d that are the same as or correspond to the components of the radio wave absorber 1a are denoted by the same reference numerals, and detailed descriptions thereof are omitted. The description of the radio wave absorber 1a is also applicable to the radio wave absorbers 1b, 1c and 1d as long as there is no technical contradiction.

[0083] like Figure 3As shown in FIG. 1 , the radio wave absorber 1 b further includes an adhesive layer 40 a. In the radio wave absorber 1 b , the conductor 30 is disposed between the dielectric layer 20 and the adhesive layer 40 a.

[0084] For example, the radio wave absorber 1b can be attached to the article by bringing the adhesive layer 40a into contact with a predetermined article and pressing the radio wave absorber 1b against the article. Thus, an article with a radio wave absorber can be obtained.

[0085] The adhesive layer 40a contains, for example, a rubber adhesive, an acrylic adhesive, a polysiloxane adhesive, or a urethane adhesive. The radio wave absorber 1b may also have a diaphragm (not shown). In this case, the diaphragm covers the adhesive layer 40a. The diaphragm is typically a film that can maintain the adhesive force of the adhesive layer 40a when covering the adhesive layer 40a and can be easily peeled off from the adhesive layer 40a. The diaphragm is, for example, a film made of a polyester resin such as PET. By peeling off the diaphragm, the adhesive layer 40a is exposed, and the radio wave absorber 1b can be attached to an object.

[0086] In the radio wave absorber, the dielectric layer 20 may have adhesion to the conductor 30. For example, Figure 4A As shown, in the radio wave absorber 1c, the dielectric layer 20 has a plurality of layers including an adhesive layer 40b. The adhesive layer 40b is in contact with the conductor 30. The adhesive layer 40b contains, for example, a rubber adhesive, an acrylic adhesive, a silicone adhesive, or a urethane adhesive. The adhesive layer 40b is, for example, disposed between the first layer 21 and the conductor 30.

[0087] like Figure 4A As shown, the dielectric layer 20 further has an adhesive layer 40c. The adhesive layer 40c is, for example, in contact with the second layer 22. The radio wave absorber 1c can be modified so that the adhesive layer 40c is in contact with the impedance matching film 10. The adhesive layer 40c contains, for example, a rubber adhesive, an acrylic adhesive, a polysiloxane adhesive, or a urethane adhesive. The adhesive layer 40c is, for example, disposed between the first layer 21 and the second layer 22.

[0088] The radio wave absorber 1c can be, for example, Figure 4B The radio wave absorber laminate 50a shown is manufactured. The radio wave absorber laminate 50a includes an impedance matching film 10 and a dielectric layer 20. The dielectric layer 20 is disposed so as to be in contact with the impedance matching film 10 in the thickness direction of the impedance matching film 10.

[0089] According to the radio wave absorber laminate 50a, the dielectric layer 20 has adhesiveness on, for example, the main surface away from the impedance matching film 10. In this case, for example, by bringing the dielectric layer 20 into contact with the conductor 30 and pressing the radio wave absorber laminate 50a onto the conductor 30, the radio wave absorber laminate 50a can be attached to the conductor 30, thereby manufacturing the radio wave absorber 1c.

[0090] like Figure 4B As shown, in the radio wave absorber laminate 50 a , the dielectric layer 20 has a plurality of layers including, for example, an adhesive layer 40 b . The adhesive layer 40 b is disposed farthest from the impedance matching film 10 among the plurality of layers constituting the dielectric layer 20 .

[0091] The radio wave absorber laminate 50a may also have a diaphragm (not shown). In this case, the diaphragm covers the adhesive layer 40b. The diaphragm is typically a film that can maintain the adhesive force of the adhesive layer 40b when covering the adhesive layer 40b and can be easily peeled off from the adhesive layer 40b. The diaphragm is, for example, a film made of a polyester resin such as PET. By peeling off the diaphragm, the adhesive layer 40b is exposed, and the radio wave absorber laminate 50a can be attached to the conductor 30.

[0092] like Figure 5A As shown, in the radio wave absorber 1d, the first layer 21 is in contact with the conductor 30. The first layer 21 has, for example, adhesiveness to the conductor 30. The first layer 21 is in contact with, for example, the second layer 22. The first layer 21 has, for example, adhesiveness to the second layer 22. The radio wave absorber 1d may be modified so that the first layer 21 is in contact with the impedance matching film 10. In this case, the first layer 21 has, for example, adhesiveness to the impedance matching film 10.

[0093] The radio wave absorber 1d can be, for example, Figure 5B The radio wave absorber laminate 50b shown is manufactured. The radio wave absorber laminate 50b includes an impedance matching film 10 and a dielectric layer 20. The dielectric layer 20 is disposed so as to be in contact with the impedance matching film 10 in the thickness direction of the impedance matching film 10.

[0094] In the radio wave absorber laminate 50b, the dielectric layer 20 has adhesiveness on the main surface away from the impedance matching film 10. For example, the first layer 21 has adhesiveness. For example, by making the first layer 21 contact with the conductor 30 and pressing the radio wave absorber laminate 50b on the conductor 30, the radio wave absorber laminate 50b can be attached to the conductor 30 to produce the radio wave absorber 1d.

[0095] The radio wave absorber laminate 50b may also have a diaphragm (not shown). In this case, the diaphragm covers the surface of the dielectric layer 20 that should be in contact with the conductor 30. The diaphragm is typically a film that can maintain the adhesive force of the surface of the dielectric layer 20 that should be in contact with the conductor 30 when covering the surface of the dielectric layer 20 that should be in contact with the conductor 30, and can be easily peeled off from the dielectric layer 20. The diaphragm is, for example, a film made of a polyester resin such as PET. By peeling off the diaphragm to expose the surface of the dielectric layer 20 that should be in contact with the conductor 30, the radio wave absorber laminate 50b can be attached to the conductor 30.

[0096] The radio wave absorber laminate is not limited to a specific configuration as long as it includes the impedance matching film 10 and the dielectric layer 20 and the dielectric layer 20 is arranged in contact with the impedance matching film 10 in the thickness direction of the impedance matching film 10 .

[0097] [Example]

[0098] Hereinafter, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples. First, the evaluation method for the examples and comparative examples will be described.

[0099] [X-ray diffraction]

[0100] The thickness of the impedance matching film of the film with an impedance matching film of each example and comparative example was measured by an X-ray reflectivity method using an X-ray diffraction apparatus (manufactured by Rigaku Corporation, product name: RINT2200).

[0101] [TEM-EDX]

[0102] A focused ion beam (FIB) processing observation device (manufactured by Hitachi High-Technologies Corporation, FB-2200) was used to prepare a sample for TEM-EDX from the impedance matching film of the embodiment and the comparative example by the FIB microsampling method. The thickness of the sample is 80nm. The TEM-EDX device was used to perform EDX on a specific area of ​​the cross section of the sample to investigate the content of each element based on the number of atoms. The results are shown in Table 1. The TEM-EDX device is composed of a TEM (manufactured by JEOL Ltd., product name: JEM-2800) and an EDX device (manufactured by Thermo Fisher Scientific, product name: NORAN System 7). The area where EDX is performed is an area with a length of 400nm in a direction perpendicular to the thickness direction at the center of the impedance matching film in the thickness direction.

[0103] [Resistivity]

[0104] The initial sheet resistance Ri [Ω / □] of the impedance matching film of each Example and Comparative Example was measured by eddy current measurement according to JIS Z2316 using a non-contact resistance measuring device (manufactured by Napson, product name: NC-80MAP). In each Example and Comparative Example, the resistivity was determined by calculating the product of the thickness of the impedance matching film measured as above and the initial sheet resistance Ri [Ω / □] of the impedance matching film measured as above. The results are shown in Table 1.

[0105] [Heating test]

[0106] The films with impedance matching films of each example and comparative example were exposed to an environment of 80°C for 24 hours. Then, the sheet resistance Rt [Ω / □] of the impedance matching films of each example and comparative example after the heating test was measured by eddy current measurement method according to JIS Z 2316 using a non-contact resistance measuring device (manufactured by Napson, product name: NC-80MAP). The sheet resistance change rate Cs of the impedance matching film of each example was calculated based on the above formula (1) from the measurement results and the initial sheet resistance Ri [Ω / □] of the impedance matching film measured as described above. The results are shown in Table 1.

[0107] [Radio wave absorption performance]

[0108] With reference to JIS R 1679:2007, radio waves with a frequency of 60 GHz to 90 GHz were incident on the samples of each embodiment and each comparative example fixed on the sample holder at an incident angle of 0°, and the reflection attenuation at each frequency was determined using a vector network analyzer manufactured by Anritsu. The reflection attenuation is the absolute value |S| of the value calculated according to the following formula (3). In formula (3), P0 is the power of the transmitted radio wave when the radio wave is incident on the measurement object at a specified incident angle, and P i It is the power of the received radio wave in this case. It should be noted that, instead of the samples of each embodiment and each comparative example, an aluminum plate is fixed on a sample holder, and the reflection attenuation |S| when the radio wave is vertically incident on the plate is regarded as 0dB, which is used as the reference of the reflection attenuation |S| of each sample. The plate has a surface size of 30cm square, and the thickness of the plate is 5mm. The maximum value of the reflection attenuation |S| and the frequency (absorption peak frequency) representing the maximum value are determined for each sample. The results are shown in Table 2. If the maximum value of the reflection attenuation |S| is more than 10dB, it can be evaluated as having good radio wave absorption performance.

[0109] S[dB]=10×log|P i / P0| Formula (3)

[0110] <Example 1>

[0111] The impedance matching film of Example 1 was formed on a PET film having a thickness of 23 μm by sputtering using a target containing Cr (chromium), Ti (titanium), and O (oxygen) while supplying argon gas around the PET film. In this manner, the film with the impedance matching film of Example 1 was obtained.

[0112] An acrylic resin having a relative dielectric constant of 2.6 was molded into a thickness of 560 μm, thereby obtaining an acrylic resin layer. The film with an impedance matching film of Example 1 was overlapped on the acrylic resin layer so that the impedance matching film of the film with an impedance matching film of Example 1 was in contact with the acrylic resin layer. Next, a film with a reflector having a PET layer formed on both sides of an Al (aluminum) film with a thickness of 7 μm was obtained. In the film with a reflector, the thickness of the PET layer formed on one main surface of the aluminum film was 25 μm, and the thickness of the PET layer formed on the other main surface of the aluminum film was 9 μm. The film with a reflector was overlapped on the acrylic resin layer so that the 25 μm thick PET layer in the film with a reflector was in contact with the acrylic resin layer. In this way, the sample of Example 1 was obtained.

[0113] <Example 2>

[0114] On a PET film having a thickness of 23 μm, a target material containing Cr (chromium) was used, and sputtering was performed while supplying argon gas and nitrogen gas around the PET film, thereby forming an impedance matching film of Example 2. In this manner, a film with an impedance matching film of Example 2 was obtained. It is considered that oxygen was detected in the impedance matching film of Example 2 due to the influence of a small amount of residual oxygen that entered the chamber during sputtering.

[0115] A sample of Example 2 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 2 was used instead of the impedance matching film of Example 1.

[0116] <Example 3>

[0117] On a PET film having a thickness of 23 μm, a target material containing Hastelloy C-276 was used, and sputtering was performed while supplying argon gas and nitrogen gas around the PET film, thereby forming an impedance matching film of Example 3. In this way, a film with an impedance matching film of Example 3 was obtained. Hastelloy is a registered trademark of Hines International. It is believed that oxygen was detected in the impedance matching film of Example 3 due to the influence of a small amount of residual oxygen that entered the chamber during sputtering.

[0118] A sample of Example 3 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 3 was used instead of the impedance matching film of Example 1.

[0119] <Example 4>

[0120] The impedance matching film of Example 4 was formed on a PET film having a thickness of 23 μm by sputtering using a target containing Cu (copper), Ni (nickel), and Si (silicon) while supplying argon gas around the PET film.

[0121] A sample of Example 4 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 4 was used instead of the impedance matching film of Example 1.

[0122] <Example 5>

[0123] The impedance matching film of Example 5 was formed on a PET film having a thickness of 23 μm by sputtering using a target containing Cu (copper), Ni (nickel), and Si (silicon) while supplying argon gas around the PET film.

[0124] A sample of Example 5 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 5 was used instead of the impedance matching film of Example 1.

[0125] <Example 6>

[0126] The impedance matching film of Example 6 was formed on a PET film having a thickness of 23 μm by sputtering using a target containing Cu (copper), Ti (titanium), and Si (silicon) while supplying argon gas around the PET film.

[0127] A sample of Example 6 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 6 was used instead of the impedance matching film of Example 1.

[0128] <Example 7>

[0129] The impedance matching film of Example 7 was formed on a PET film having a thickness of 23 μm by sputtering using a target containing Cu (copper), Ti (titanium), and Si (silicon) while supplying argon gas around the PET film.

[0130] A sample of Example 7 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 7 was used instead of the impedance matching film of Example 1.

[0131] <Example 8>

[0132] On a PET film having a thickness of 23 μm, a target material containing Ti (titanium) and Mo (molybdenum) was used, and sputtering was performed while supplying argon gas and nitrogen gas around the PET film, thereby forming an impedance matching film of Example 8. It is considered that oxygen was detected in the impedance matching film of Example 8 due to the influence of a small amount of residual oxygen that entered the chamber during sputtering.

[0133] A sample of Example 8 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 8 was used instead of the impedance matching film of Example 1.

[0134] <Example 9>

[0135] On a PET film having a thickness of 23 μm, a target material containing Ti (titanium) and Mo (molybdenum) was used, and sputtering was performed while supplying argon gas and nitrogen gas around the PET film, thereby forming an impedance matching film of Example 9. It is considered that oxygen was detected in the impedance matching film of Example 9 due to the influence of a small amount of residual oxygen that entered the chamber during sputtering.

[0136] A sample of Example 9 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 9 was used instead of the impedance matching film of Example 1.

[0137] <Example 10>

[0138] On a PET film having a thickness of 23 μm, sputtering was performed using a target material containing Ti (titanium) and Mo (molybdenum) while supplying argon gas and nitrogen gas around the PET film, thereby forming an impedance matching film of Example 10. It is considered that oxygen was detected in the impedance matching film of Example 10 due to the influence of a small amount of residual oxygen that entered the chamber during sputtering.

[0139] A sample of Example 10 was prepared in the same manner as in Example 1 except that the impedance matching film of Example 10 was used instead of the impedance matching film of Example 1.

[0140] <Comparative Example 1>

[0141] On a PET film having a thickness of 23 μm, a target containing Fe (iron), Cr (chromium), and Ni (nickel) was used, and sputtering was performed while supplying argon gas around the PET film, thereby forming an impedance matching film of Comparative Example 1. In this manner, a film with an impedance matching film of Comparative Example 1 was obtained.

[0142] A sample of Comparative Example 1 was prepared in the same manner as in Example 1 except that the impedance matching film of Comparative Example 1 was used instead of the impedance matching film of Example 1.

[0143] <Comparative Example 2>

[0144] On a PET film having a thickness of 23 μm, sputtering was performed using a target containing Ti (titanium) and Mo (molybdenum) while supplying argon gas around the PET film, thereby forming an impedance matching film of Comparative Example 2. It is believed that nitrogen and oxygen were detected in the impedance matching film of Comparative Example 2 due to the influence of a small amount of residual nitrogen and residual oxygen that entered the chamber during sputtering.

[0145] A sample of Comparative Example 2 was prepared in the same manner as in Example 1, except that the impedance matching film of Comparative Example 2 was used instead of the impedance matching film of Example 1.

[0146] As shown in Table 1, the sheet resistance change rate Cs of the impedance matching films of Examples 1 to 10 is less than 20%. In contrast, the sheet resistance change rates Cs of the impedance matching films of Comparative Examples 1 and 2 are 63% and 59%, respectively. The sheet resistance of the impedance matching films of Examples 1 to 10 indicates that the impedance matching films are not easily changed even when exposed to a high temperature environment.

[0147] As shown in Table 2, the samples of Examples 1 to 10 exhibited good radio wave absorption performance.

[0148]

[0149] Table 2

[0150]

Claims

1. An impedance matching film for a radio wave absorber, wherein: Impedance matching film for radio wave absorber Contains both metallic and non-metallic elements, and Having a thickness of 10nm to 200nm, Has a sheet resistance of more than 200Ω / □, and The content of oxygen atoms based on the number of atoms is less than 50%.

2. The impedance matching film for a radio wave absorber according to claim 1, wherein: The impedance matching film for the radio wave absorber has a 0.4×10 -3 Resistivity above Ω·cm.

3. The impedance matching film for a radio wave absorber according to claim 1 or 2, wherein: The non-metal element is at least one element selected from the group consisting of B, C, N, O, F, Si, S and Ge.

4. The impedance matching film for a radio wave absorber according to claim 1 or 2, wherein: The metal element is at least one element selected from the group consisting of Ni, Cr, Ti, W, Mo, Cu, Al, Sn, Pd, Ta, Rh, Au, Mg, Fe, Mn, Co and V.

5. The impedance matching film for a radio wave absorber according to claim 1 or 2, wherein: The metal element is at least one element selected from the group consisting of Ni, Cr, Mo and Ti.

6. The impedance matching film for a radio wave absorber according to claim 5, wherein: The total content of Ni, Cr, Mo and Ti based on the number of atoms is 10% or more.

7. The impedance matching film for a radio wave absorber according to claim 1 or 2, wherein: The impedance matching film for a radio wave absorber has a sheet resistance of 600Ω / □ or less.

8. The impedance matching film for a radio wave absorber according to claim 1 or 2, wherein: The impedance matching film for the radio wave absorber has a value of 8.0×10 -3 Resistivity below Ω·cm.

9. A film with an impedance matching film for a radio wave absorber, wherein: The film with impedance matching film for radio wave absorber has: Base material, and The impedance matching film for a radio wave absorber according to any one of claims 1 to 8.

10. A radio wave absorber, wherein: The radio wave absorber has: The impedance matching film for a radio wave absorber according to any one of claims 1 to 8; A conductor that reflects radio waves; and A dielectric layer is disposed between the impedance matching film for the radio wave absorber and the conductor in the thickness direction of the impedance matching film for the radio wave absorber.

11. A laminate for a radio wave absorber, wherein: The radio wave absorber laminate comprises: The impedance matching film for a radio wave absorber according to any one of claims 1 to 8; and A dielectric layer is disposed so as to be in contact with the impedance matching film for the radio wave absorber in a thickness direction of the impedance matching film for the radio wave absorber.

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