JPWO2008026743A1 - Gradient junction conductive film, high-frequency transmission line using the same, and high-frequency filter - Google Patents

Abstract

An object of the present invention is to provide a conductive film having a frequency dependency of a high-frequency transmission rate, a high-frequency transmission line including the conductive film, and a high-frequency filter. The present invention has first and second metal thin films 11a and 11b having different electrical resistances on at least one surface of a plastic film 10, and the boundary between the first and second metal thin films 11a and 11b has a thick metal composition ratio. This is a gradient junction conductive film having a gradient composition layer 12 ′ that changes in the vertical direction.

Description

  The present invention relates to a conductive film in which two kinds of metal thin films are joined with a composition gradient, and a high-frequency transmission line and a high-frequency filter using the conductive film.

  High-frequency transmission lines are used in information processing equipment such as personal computers and wireless communication equipment such as mobile phones. Conventionally, as a high-frequency transmission line, a coaxial cable in which a dielectric substrate 200 is interposed between a linear inner conductor 100 and an outer conductor 100 ′ as shown in FIG. 26, or a metal having a square cross section as shown in FIG. A waveguide consisting of a tube 100 is used. However, coaxial cables and waveguides transmit high-frequency signals with a predetermined attenuation factor, and the transmission characteristics are isotropic (same in both directions).

  In addition, a high-frequency transmission line (FIG. 28) provided with a pair of strip-like conductor lines 110 and 110 parallel to one surface of the dielectric substrate 210, ground conductors 120 and 120 provided on both surfaces of the dielectric substrate 210, and a conductor at the center. A high-frequency transmission line with 110 (FIG. 29), a ground conductor 120 on one surface of the dielectric substrate 210, and a high-frequency transmission line with a strip-shaped conductor 110 on the other surface (FIG. 30), on one surface of the ceramic dielectric substrate 210 There is a high-frequency transmission line (FIG. 31) or the like in which a strip-shaped conductor 110 is provided and ground conductors 120 and 120 are disposed on both sides thereof. Japanese Patent Application Laid-Open No. 7-336113 discloses a high-frequency transmission line having a conductor film having a thickness of 1.14 to 2.75 times the skin depth at a used frequency, and having a structure shown in FIGS. 28 and 31, for example.

  However, as described in JP-A-7-336113, even when a conductor film is formed on the ceramic dielectric substrate 210, the high-frequency transmission rate (input amplitude / output amplitude) increases or becomes zero depending on the frequency. In addition, there is no difference in characteristics (having anisotropy) depending on the transmission direction of the high-frequency signal. By utilizing the frequency dependence and anisotropy of such a high-frequency transmission rate, a high-frequency filter with extremely good demultiplexing characteristics can be obtained.

  Accordingly, an object of the present invention is to provide a conductive film having a frequency dependency of a high-frequency transmission rate, a high-frequency transmission line having such a conductive film, and a high-frequency filter.

  As a result of diligent research in view of the above object, the present inventor has found that, in a conductive film having at least two metal thin films on a plastic film, when the boundary between the metal thin films is a gradient composition layer, the frequency of the high frequency transmission rate is The inventors have found that dependency can be obtained, and have arrived at the present invention.

  That is, the gradient bonded conductive film of the present invention has first and second metal thin films having different electric resistances on at least one surface of a plastic film, and the boundary between the first and second metal thin films has a metal composition ratio. It has a gradient composition layer that changes in the thickness direction.

  In such a gradient bonded conductive film, it is preferable that the boundary between the plastic film and the metal thin film is also a gradient composition layer in which the proportion of the metal decreases from the metal thin film to the plastic film. The first metal thin film is preferably a vapor deposition film, a plating film or a foil, and the second metal thin film is preferably a vapor deposition film or a plating film.

In a preferred embodiment of the present invention, the second metal thin film has an electric resistance of 2 × 10 ⁻⁶ Ω · cm or more larger than that of the first metal thin film. In this case, it is preferable that the first metal thin film is made of copper and the second metal thin film is made of nickel.

In another preferred embodiment of the present invention, the first metal thin film has an electric resistance of 2 × 10 ⁻⁶ Ω · cm or more larger than that of the second metal thin film. In this case, it is preferable that the first metal thin film is made of nickel and the second metal thin film is made of copper.

  In the case where the first metal thin film has an electric resistance larger than that of the second metal thin film and vice versa, the thickness of the metal thin film having the smaller electric resistance is set to the metal having the larger electric resistance. The ratio is preferably 2/1 to 20/1 with respect to the thickness of the thin film. In particular, when both the first and second metal thin films are vapor-deposited films, the ratio is more preferably 3/1 to 15/1. When both the first and second metal thin films are vapor deposition films, the thickness of the metal thin film having the higher electrical resistance is 10 to 70 nm, and the thickness of the metal thin film having the lower electrical resistance is 0.1 to It is preferably 1 μm.

It is preferable that a large number of fine holes having an average opening diameter of 0.5 to 50 μm are formed in at least the first and second metal thin films. The average distribution density of the micropores is preferably 1 × 10 ⁴ to 2 × 10 ⁵ holes / cm ² . The plastic film is preferably made of polyethylene terephthalate or polyimide.

  The high-frequency transmission line of the present invention comprises two spaced apart inclined conductive films in parallel.

  The two graded junction conductive films are either (1) on the same surface of the dielectric substrate, (2) on the opposite inner surface of the U-shaped dielectric substrate, or (3) orthogonal to the L-shaped dielectric substrate. It is preferable to be disposed anywhere on the inner surface.

  The high frequency filter of this invention comprises the said high frequency transmission line.

  Since the gradient junction conductive film of the present invention has a frequency dependency of a high frequency transmission rate, a desired high frequency signal can be efficiently used when used in a high frequency transmission line used in various information processing devices and wireless communication devices such as aircraft and automobiles. In addition to being able to transmit, transmission of a high-frequency signal having a specific frequency can be made zero. Such a high-frequency transmission line is expected to be applied as an antenna, for example, an antenna for an electronic tag. In addition, if the configuration has anisotropy of high-frequency transmission, for example, a high-frequency filter having a simple structure that can transmit a transmission signal but does not transmit a reception signal is obtained, and application as a hacker prevention filter or the like is expected. .

It is sectional drawing which shows the gradient joining electrically conductive film by one Example of this invention. FIG. 2 is an enlarged cross-sectional view showing a portion A in FIG. FIG. 2 is an enlarged cross-sectional view schematically showing a portion A ′ of FIG. 1 (b). FIG. 2 is an enlarged cross-sectional view schematically showing a portion A ″ in FIG. 1 (b). It is sectional drawing which shows the gradient joining electrically conductive film by another Example of this invention. It is an expanded sectional view which shows the B section of Fig.2 (a). FIG. 3 is an enlarged cross-sectional view schematically showing a portion B ′ in FIG. FIG. 3 is an enlarged cross-sectional view schematically showing a portion B ″ in FIG. It is sectional drawing which shows the gradient joining electrically conductive film by another Example of this invention. FIG. 4 is an enlarged cross-sectional view schematically showing a portion C in FIG. It is sectional drawing which shows the gradient joining electrically conductive film by another Example of this invention. FIG. 5 is an enlarged cross-sectional view schematically showing a D part in FIG. 4 (a). It is sectional drawing which shows the gradient joining electrically conductive film by another Example of this invention. FIG. 6 is an enlarged cross-sectional view schematically showing an E portion in FIG. It is a perspective view which shows the gradient joining electrically conductive film by another Example of this invention. It is a perspective view which shows the gradient joining electrically conductive film by another Example of this invention. It is a perspective view which shows the gradient joining electrically conductive film by another Example of this invention. 1 is a perspective view showing a high frequency transmission line according to an embodiment of the present invention. It is a perspective view which shows the high frequency transmission line by another Example of this invention. It is a perspective view which shows the high frequency transmission line by another Example of this invention. It is a perspective view which shows the high frequency transmission line by another Example of this invention. It is a perspective view which shows the high frequency transmission line by another Example of this invention. It is a schematic perspective view which shows the high frequency filter by one Example of this invention. It is the schematic which shows the state which connected the oscillator and the receiver to the high frequency transmission line. It is a circuit diagram which shows roughly the structure of the oscillator used for the measurement of a high frequency transmissibility. It is the schematic which shows the signal pattern at the time of transmitting so that a signal may be output from the (+) side from an oscillator. It is the schematic which shows the signal pattern at the time of transmitting so that a signal may be output from the (-) side from an oscillator. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of Example 1. It is a fragmentary sectional view which shows the connection structure to the high frequency transmission line of Example 2. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of Example 2. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of Example 3. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of Example 4. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of the comparative example 1. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of the comparative example 2. It is a graph which shows the relationship between a frequency and a high frequency transmissibility about the high frequency transmission line of the comparative example 3. It is a perspective view which shows the example of the conventional high frequency transmission line. It is a perspective view which shows another example of the conventional high frequency transmission line. It is a perspective view which shows another example of the conventional high frequency transmission line. It is a perspective view which shows another example of the conventional high frequency transmission line. It is a perspective view which shows another example of the conventional high frequency transmission line. It is a perspective view which shows another example of the conventional high frequency transmission line.

[1] Gradient junction conductive film
(1) Structure FIG. 1 shows an example of a gradient junction conductive film of the present invention. The first and second metal thin films 11a and 11b are uniformly formed on one surface of the plastic film 10, and the boundary between the metal thin films 11a and 11b is the composition ratio of the first metal and the second metal. Is a gradient composition layer 12 ′ that changes in the thickness direction. In the gradient composition layer 12 ′, the metal composition ratio is preferably changed substantially continuously. Although it is not limited, it is preferable that the boundary portion between the plastic film 10 and the metal thin film 11a is a gradient composition layer 12 in which the proportion of metal decreases from the metal thin film 11a to the plastic film 10. In the gradient composition layer 12, it is more preferable that the ratio of the metal changes substantially continuously. (C) of FIG. 1 schematically shows a state in which the second metal atom 11b ′ partially enters between the first metal atoms 11a ′, and (d) shows the first metal atom 11a ′. 1 schematically shows a state in which the film partially enters between plastic molecules 10 ′ of the film 10.

  FIG. 2 shows another example of the gradient junction conductive film. The gradient bonded conductive film of this example is the same as that shown in FIG. 1 except that the first metal thin film 11a is bonded to the plastic film 10 via the adhesive layer 13. Since the adhesive layer 13 is provided, the first metal thin film 11a may be a metal foil. FIG. 2 (c) schematically shows a state in which the second metal atom 11b ′ partially enters between the first metal atoms 11a ′, and FIG. A state in which one metal atom 11a ′ does not enter between plastic molecules 10 ′ of the film 10 is schematically shown.

  FIG. 3 shows still another example of the gradient junction conductive film. The gradient bonded conductive film of this example is the same as that shown in FIG. 1 except that a large number of fine holes 14 are provided in the first and second metal thin films 11a and 11b. As will be described later, the large number of fine holes 14 are formed by a roll having diamond fine particles on the surface, and thus have various depths, but need not penetrate through the plastic film 10.

  FIG. 4 shows still another example of the gradient junction conductive film. In the gradient bonded conductive film of this example, the first and second metal thin films 11a and 11b are uniformly formed on both surfaces of the plastic film 10, and a large number are formed on the first and second metal thin films 11a and 11b on one surface. The same as that shown in FIG.

  FIG. 5 shows still another example of the gradient junction conductive film. In this example, the first and second metal thin films 11a and 11b are formed on both surfaces of the plastic film 10, and a large number of the fine holes 14 substantially penetrate the conductive film. It is considered that the metal thin films 11a and 11b are plastically deformed during the formation of the through holes and enter the micro holes 14.

  FIG. 6 shows still another example of the gradient junction conductive film. The gradient bonded conductive film of this example is shown in FIG. 1 except that two laminated metal strip thin films (consisting of first and second metal thin films 11a and 11b) are formed on one surface of a plastic film 10 in parallel. Is the same.

  FIG. 7 shows still another example of the gradient junction conductive film. In this example of the gradient bonding conductive film, one laminated metal strip thin film (consisting of the first and second metal thin films 11a and 11b) is formed on one surface of the plastic film 10, and the laminated metal thin film (first film) is formed on the other surface. 1 is the same as that shown in FIG. 1 except that the first and second thin metal films 11a and 11b are uniformly formed.

  FIG. 8 shows still another example of the gradient junction conductive film. The gradient bonded conductive film of this example is shown in FIG. 1, except that three laminated metal strip thin films (each consisting of first and second metal thin films 11a and 11b) are provided on one surface of the plastic film 10. Is the same.

(2) Plastic film The resin constituting the plastic film 10 is not particularly limited. For example, polyester, polyphenylene sulfide, polyamide, polyimide, polyamideimide, polyethersulfone, polyetheretherketone, polycarbonate, acrylic resin, polystyrene, ABS resin , Polyurethane, fluororesin, polyolefin (polyethylene, polypropylene, etc.), polyvinyl chloride, thermoplastic elastomer and the like. Among them, highly heat-resistant resins such as polyester, polyphenylene sulfide, polyamide, polyimide, polyamideimide, polyethersulfone and polyetheretherketone are preferable, and polyester and polyimide are particularly preferable.

(a) Polyester film Examples of the polyester include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate (PBN). Of these, PET films and PBT films are preferred because they are commercially available at low cost.

(i) PET film
The PET film is a saturated polyester film basically composed of ethylene glycol and terephthalic acid. A diol component other than ethylene glycol and a cambonic acid component other than terephthalic acid may be included as long as the characteristics are not impaired. Commercially available PET films have a dielectric constant of about 3 (10 ⁶ Hz), a dielectric loss tangent of about 0.01 to 0.02 (10 ⁶ Hz), a melting point of about 250 to 270 ° C., and a glass transition temperature of about 70 to 80 ° C. . The dielectric constant and dielectric loss tangent are measured by ASTM D150, the melting point is measured by ASTM D4591, and the glass transition temperature is measured by JIS K7121 (the same applies hereinafter).

(ii) PBT film
The PBT film is basically a saturated polyester film composed of 1,4-butanediol and terephthalic acid. A diol component other than 1,4-butanediol and a cambonic acid component other than terephthalic acid may be included as long as the physical properties are not impaired. Commercially available PBT films have a dielectric constant of about 3-4 (10 ⁶ Hz), a dielectric loss tangent of about 0.02 (10 ⁶ Hz), a melting point of about 220-230 ° C., and a glass transition temperature of about 20-45 ° C. . The thermal contraction rate (measured under the condition of heating to 150 ° C. for 10 minutes) of the PBT film is preferably 2% or less for both MD (longitudinal direction) and TD (lateral direction). A PBT film having a thermal shrinkage rate of 2% or less can be produced, for example, by an air-cooled inflation molding method described in JP-A-2004-268257.

(iii) Other additive components Polyester is thermoplastic such as polyphenylene sulfide, polyamide, polyimide, polyamideimide, polyethersulfone, polyetheretherketone, polycarbonate, polyurethane, fluororesin, polyolefin, polyvinyl chloride, thermoplastic elastomer, etc. A resin may be contained. The content of the other thermoplastic resin is preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and 5 to 10% by mass, based on 100% by mass of the entire polyester. Particularly preferred. If necessary, stabilizers such as plasticizers, antioxidants and UV absorbers, antistatic agents, surfactants, colorants such as dyes and pigments, lubricants for improving fluidity, inorganic filling You may contain additives, such as an agent, suitably.

(b) Polyimide film Polyimide is basically composed of a dehydration condensation reaction product of aromatic tetracarboxylic dianhydride and aromatic diamine, and dehydration condensation of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether. What has a reaction material as a main component is preferable. Commercially available polyimide has a dielectric constant of about 3.4 (10 ⁶ Hz) and a dielectric loss tangent of about 0.01 (10 ⁶ Hz). The polyimide may contain other thermoplastic resins and additives. The content of the other thermoplastic resin is preferably 5 to 20% by mass based on 100% by mass of the entire polyimide.

(c) Laminated film The plastic film 10 is not limited to a single layer, and may be a laminated film. For example, a laminated film can be formed by thermally fusing different plastic films or bonding them through an adhesive layer such as polyethylene.

(d) Film thickness The thickness of the plastic film 10 is not particularly limited, but is preferably about 4 to 50 μm for practical use. It is technically difficult to make the thickness of the plastic film 10 less than about 4 μm, and when it exceeds about 50 μm, the gradient junction conductive film becomes too thick.

(3) Metal thin film The first and second metal thin films 11a and 11b have different electric resistances. The electric resistance of the first metal thin film 11a may be greater than that of the second metal thin film 11b, or vice versa. The difference in electrical resistance between the first and second metal thin films 11a and 11b is preferably 2 × 10 ⁻⁶ Ω · cm or more at room temperature, more preferably 4 × 10 ⁻⁶ Ω · cm or more.

As the metal forming the first and second metal thin films 11a and 11b, copper [resistivity (20 ° C.): 1.6730 × 10 ⁻⁶ Ω · cm], aluminum [resistivity (20 ° C.): 2.6548 × 10 ⁻⁶ Ω · cm], Silver [Resistivity (20 ° C): 1.59 × 10 ^-6 Ω · cm], Gold [Resistivity (20 ° C): 2.35 × 10 ^-6 Ω · cm], Platinum [Resistivity (20 ° C) ): 10.6 × 10 ^-6 Ω · cm], nickel [resistivity (20 ° C): 6.84 × 10 ^-6 Ω · cm], iron [resistivity (20 ° C): 9.71 × 10 ^-6 Ω · cm], Cobalt [Resistivity (20 ° C): 6.24 × 10 ^-6 Ω · cm], Magnesium [Resistivity (20 ° C): 4.45 × 10 ^-6 Ω · cm], Titanium [Resistivity (20 ° C): 42 × 10 ^-6 Ω · cm], chromium [resistivity (0 ° C): 12.9 × 10 ^-6 Ω · cm], zinc [resistivity (20 ° C): 5.916 × 10 ^-6 Ω · cm], gallium [resistivity ( 20 ° C): 17.4 × 10 ^-6 Ω · cm], Molybdenum [Resistivity (0 ° C): 5.2 × 10 ^-6 Ω · cm], Palladium [Resistivity (20 ° C): 10.8 × 10 ^-6 Ω · cm ], Tin [resistivity ^{0 ℃): 11.0 × 10 -6} Ω · cm], and the like alloys thereof.

  The metal forming the first and second metal thin films 11a and 11b can be selected from the above so that the electric resistance is different. As a preferred combination, the first metal thin film 11a is made of copper and / or aluminum, and the second metal thin film 11b is made of at least one selected from the group consisting of nickel, zinc, tin, titanium, cobalt, iron and chromium. The combination, and the first metal thin film 11a is made of at least one selected from the group consisting of nickel, zinc, tin, titanium, cobalt, iron and chromium, and the second metal thin film 11b is made of copper and / or aluminum. Is mentioned. Among these, a combination in which the first metal thin film 11a is made of copper, the second metal thin film 11b is made of nickel, and a combination in which the first metal thin film 11a is made of nickel and the second metal thin film 11b is made of copper is more preferable. .

  In both cases where the first metal thin film 11a has an electric resistance larger than that of the second metal thin film 11b and vice versa, the thickness of the metal thin film having the smaller electric resistance is set to the thickness of the metal thin film having the larger electric resistance. The ratio is preferably 2/1 to 20/1 with respect to the thickness of the metal thin film. In particular, when both the first and second metal thin films 11a and 11b are vapor deposition films, it is more preferable to set this ratio to 3/1 to 15/1.

  In any case where the first metal thin film 11a has an electric resistance larger than that of the second metal thin film 11b and vice versa, the thickness of the metal thin film having the smaller electric resistance is preferably 0.1 to 35 μm, The thickness of the metal thin film having the larger resistance is preferably 0.01 to 20 μm. However, when both the first and second metal thin films 11a and 11b are vapor deposition films, the thickness of the metal thin film having the smaller electric resistance is preferably 0.1 to 1 μm, more preferably 0.15 to 0.7 μm, and more preferably 0.2 to 0.6 μm. The thickness of the metal thin film having the larger electric resistance is preferably 10 to 70 nm, and more preferably 20 to 60 nm. If the thickness of the metal vapor-deposited film having the smaller electrical resistance is less than 0.1 μm, the high-frequency transmission characteristics are poor. On the other hand, if it exceeds 1 μm, the frequency dependency of the high-frequency transmission rate is poor.

  The first metal thin film 11a is preferably formed by vapor deposition, plating or foil, and the second metal thin film 11b is preferably formed by vapor deposition or plating. Metal vapor deposition films are usually crystalline, have high purity, and excellent oxidation resistance.

(4) Gradient composition layer
(a) Metal Thin Film—Plastic Film For example, as shown in FIG. 1, in the graded composition layer 12, metal atoms 11 a ′ partially enter between plastic molecules 10 ′ of the film 10. Accordingly, the composition ratio (concentration) of the metal atoms 11a ′ decreases from the metal thin film 11a to the plastic film 10. The decrease in the composition ratio of the metal atoms 11a ′ is preferably almost continuous in the thickness direction. “Substantially continuous” means that the composition ratio of the metal atoms 11a ′ in the thickness direction changes substantially monotonically, but this condition does not necessarily have to be satisfied locally. In the graded composition layer 12, the concentration of the metal atoms 11a ′ decreases, so it is considered that an amorphous phase is formed.

(b) First metal thin film-second metal thin film For example, as shown in FIG. 1, in the gradient composition layer 12 ′, the second metal atoms 11b ′ partially enter between the first metals 11a ′. is doing. Accordingly, the composition ratio (concentration) of the first metal 11a ′ decreases from the first metal thin film 11a to the second metal thin film 11b, and the second metal atom 11b ′ is reduced from the second metal thin film 11b to the first metal thin film 11b. It decreases toward the metal thin film 11a. Even in the gradient composition layer 12 ′, the change in the metal composition ratio is preferably substantially continuous in the thickness direction. In the graded composition layer 12 ′, the concentration of both metal atoms 11a ′ and 11b ′ is gradually changed, so it is considered to be amorphous.

  For the conductive film having the amorphous gradient composition layers 12 and 12 ', a clear reason is unknown, but an amplification band having a high-frequency transmission rate of 100% or more and an attenuation band having a high-frequency transmission rate of almost 0%. Is expressed.

(5) Micropores In order to obtain excellent high-frequency transmission characteristics, it is preferable to form micropores 14 in the gradient bonding conductive film. As shown in FIG. 3 and FIG. 4, it is preferable that the fine holes 14 penetrate at least the metal thin films 11a and 11b. The fine hole 14 may reach the middle of the plastic film 10 as long as it penetrates the metal thin films 11a and 11b. Further, as shown in FIG. 5, the fine hole 14 may penetrate the gradient junction conductive film 1.

  The average opening diameter of the micropores 14 is preferably 0.1 to 100 μm, and more preferably 0.5 to 50 μm. It is technically difficult to make the average opening diameter of the fine holes 14 less than 0.1 μm. On the other hand, if the average opening diameter of the fine holes 14 exceeds 100 μm, the strength of the gradient bonding conductive film 1 may be reduced. In order to have good transmission loss, the upper limit of the average aperture diameter is particularly preferably 20 μm, and most preferably 10 μm. The average opening diameter is obtained by measuring and averaging the diameters of all the fine holes 14 in five regions of 50 μm × 50 μm at arbitrary positions of the gradient bonding conductive film using an atomic force microscope.

The average distribution density of the micropores 14 is preferably 500 / cm ² or more, and more preferably 5 × 10 ³ / cm ² or more. If the average distribution density of the fine holes 14 is less than 500 / cm ² , transmission loss increases. The reason is not clear, but it is presumed that eddy currents are generated in the vicinity of the fine holes 14 during transmission of the high-frequency signal. In order to have a good transmission loss, the average distribution density of the fine pores 14 is particularly preferably in the range of 1 × 10 ⁴ ~3 × 10 ⁵ cells ^{/ cm 2, 1 × 10 4} ~2 × 10 5 cells / cm ² Most preferably. The average distribution density of the fine holes 14 is obtained by counting the number of fine holes 14 in five regions of 50 μm × 50 μm at arbitrary positions of the gradient junction conductive film using an atomic force microscope, and averaging the obtained values. Then, it is calculated by converting to the number per 1 cm ² .

  As shown in FIG. 5, when the fine hole 14 penetrates the inclined bonding conductive film, the metal thin films 11 a and 11 b are plastically deformed and enter the wall surface of the fine hole 14. This further reduces transmission loss.

(6) Adhesive layer The adhesive layer 13 is, for example, polyurethane resin, epoxy resin, acrylic resin, ethylene-vinyl alcohol copolymer (EVA), polyvinyl acetal resin [eg, polyvinyl formal, polyvinyl butyral (PVB), modified PVB, etc.] , Vinyl chloride resin, hot melt adhesive, sealant film and the like.

[2] Method for Producing Gradient Bonded Conductive Film In the gradient bonded conductive film 1, the first metal thin film 11a is formed on one surface or both surfaces of the plastic film 10 by a vapor deposition method, a plating method, or a foil bonding method. The second metal thin film 11b is formed by plating. Since the gradient composition layer 12 ′ is formed between the first metal thin film 11a and the second metal thin film 11b, the gradient composition layer 12 is formed between the plastic film 10 and the first metal thin film 11a. There is no need. For example, in the gradient bonding conductive film 1 shown in FIG. 2, the first metal thin film 11a made of metal foil is bonded to the plastic film 10, and the second metal thin film 11b is formed by vapor deposition or plating.

(1) Metal thin film formation process
(a) Vapor deposition method Metal deposition is performed by, for example, physical vapor deposition such as vacuum vapor deposition, sputtering, or ion plating, chemical vapor deposition such as plasma CVD, thermal CVD, and photo CVD. Can do. From the viewpoint of economy, the vacuum deposition method is preferable.

  In order to improve the adhesion between the plastic film 10 and the deposited metal, the plastic film 10 may be subjected to a surface treatment that also serves as a cleaning in advance. The surface treatment includes mechanical treatment by blasting, embossing, etc .; physicochemical treatment by corona discharge, plasma, flame treatment, UV irradiation, etc .; chemical treatment by solvent, acidic solution, alkaline solution, etc. The film 10 after the surface treatment may be heated or vacuum heat treated to remove moisture and gas content in the film 10.

The vacuum vapor deposition method may be either a semi-continuous method (a method in which film feeding, vapor deposition and winding are performed in vacuum) or a continuous method (a method in which only vapor deposition is performed in vacuum). In either case, the metal vapor is condensed on the plastic film 10 or the first metal thin film 11a under a high vacuum of about 10 ⁻² Pa. The second metal thin film 11b is preferably deposited immediately after the first metal thin film 11a is deposited.

  In the case of a chemical vapor deposition method (CVD method), a plasma CVD method capable of forming a thin film at a low temperature is preferable. In the plasma CVD method, a metal vapor deposition layer is formed by generating plasma of a low-pressure reaction gas, or a metal vapor deposition layer is formed by decomposition of the reaction gas under reduced pressure. As starting materials, metal halides, organometallics, organometallic complexes, metal alcoholates, etc. are used, and reactive gases such as nitrogen, ammonia, dinitrogen monoxide, oxygen, carbon monoxide, methane, hydrogen, etc. are used as helium, argon, etc. Used together with the carrier gas.

When forming a copper vapor deposition layer, for example, copper acetylacetonate [Cu (acac) ₂ ] is used as a source gas. When forming a vapor deposition layer of aluminum, for example, trimethylaluminum (Al (CH ₃ ) ₃ ) is used as a source gas. Furthermore, when forming a nickel vapor deposition layer, for example, nickel chloride gas is used as a raw material gas.

(b) Plating method Plating is performed by electrolytic plating, electroless plating, or the like. The details of the plating method are disclosed in, for example, “Plating Technology Handbook” (edited by the Technical Committee of the Tokyo Sheet Metal Cooperative Association). After forming the electroless plating layer, the electrolytic plating layer may be formed.

  When the metal thin films 11a and 11b are formed by plating, an underlayer may be provided on the plastic film 10 or the first metal thin film 11a. In the case of electroless plating, the underlayer may be a metal vapor deposition layer, a polymer binder layer containing a plating catalyst, a polymer binder layer containing a catalyst precursor, or the like. The catalyst-containing underlayer is, for example, a polymer binder layer impregnated with a Pd catalyst, a polymer binder layer to which reducing metal particles (for example, colloids such as Ni, Co, Rh, and Pd) are added.

  For example, in the case of electroless copper plating, after first providing a conductive underlayer such as an antistatic agent, metal particles, a resin layer containing carbon, a conductive metal oxide layer, or a metal thin film layer on the plastic film 10 Soak in an electroless copper plating solution such as a copper sulfate plating bath. Since the composition itself of the electroless copper plating solution is known, its description is omitted. The copper plating layer may be formed only by the electroless plating method, but it is preferable to combine the electroless plating method and the electrolytic plating method in order to increase the efficiency. For example, an alkaline nickel solution is used for the electroless nickel plating, and for example, a watt bath or a sulfamic acid bath is used for the electrolytic nickel plating.

(c) In the case where a metal strip thin film is formed The metal strip thin films 11a and 11b as shown in FIGS. 6 to 8 are obtained by (i) uniformly forming the metal thin films 11a and 11b on the plastic film 10 and A method of applying a resist and etching after exposure; (ii) applying a photoresist so as to have a strip-shaped opening in advance on the plastic film 10; after exposure, forming metal thin films 11a and 11b by vapor deposition or plating; It can be formed by a method of removing the photoresist layer or the like.

(2) Formation of micropores As shown in FIGS. 3 to 5, when a large number of micropores 14 are formed in the metal thin films 11a and 11b of the gradient junction conductive film, a so-called porous processing method is used. The porous processing method is described in, for example, Japanese Patent No. 2063411, Japanese Patent No. 2547772, Japanese Patent No. 2643730, Japanese Patent No. 2703151, Japanese Patent Laid-Open No. 9-99492, Japanese Patent Laid-Open No. 9-57860, Japanese Patent Laid-Open No. 2002-059487, etc. ing. For example, the metal thin films 11a and 11b are on the first roll side between a first roll having a large number of Mohs hardness 5 or more having sharp corners attached to the surface and a second roll having a smooth surface. Then, the inclined bonding conductive film is passed under a uniform pressing force. As the second roll, for example, an iron-based roll, an iron-based roll subjected to Ni plating, Cr plating or the like, a stainless-based roll, a special steel roll, or the like can be used. The average opening diameter and average distribution density of the fine holes 14 can be adjusted by adjusting the particle diameter and density of the fine particles of the first roll. The pressing force between the first roll and the second roll determines the depth of the fine hole 14 and whether or not it penetrates the gradient bonding conductive film. The fine holes 14 are preferably provided uniformly in the gradient bonding conductive film 1. When forming the fine holes 14 at a high density, it is preferable to use a porous processing apparatus in which two or more units composed of first and second rolls are provided in tandem.

  When a large number of micropores 14 are formed, the wall surface metal thin films 11a and 11b of the micropores 14 are plastically deformed to at least partially cover the wall surfaces of the micropores 14.

[3] High-frequency transmission line The high-frequency transmission line of the present invention will be described in detail below.

(1) First High Frequency Transmission Line In the first high frequency transmission line shown in FIG. 9, two strip-shaped inclined junction conductive films 1 and 1 are arranged in parallel on the upper surface of the dielectric substrate 2. The strip-shaped gradient bonding conductive films 1 and 1 are formed by slitting the gradient bonding conductive film 1 by a known method. Since the electric field concentrates between the two strip-shaped gradient junction conductive films 1, 1, a high-frequency signal can be transmitted efficiently. In order to obtain an excellent high-frequency transmission property, the dielectric substrate 2 preferably has a convex portion 20 between the two strip-shaped gradient junction conductive films 1 and 1. The strip-like gradient bonding conductive films 1 and 1 disposed on the support 2 may be provided with the metal thin film on the upper side or the lower side.

The width d ₁ of each of the gradient bonding conductive films 1 and ₁ is appropriately set according to the frequency and amplitude of the high-frequency signal, but is preferably 1 to 10 mm, and more preferably 1.5 to 7 mm. If the width d ₁ is 1mm or more, having a sufficient high-frequency signal transmission property. Further, even if the width d ₁ is more than 10 mm, further improvement in high-frequency signal transmission cannot be obtained.

The distance d ₂ between the _two strip-shaped gradient bonding conductive films 1 and 1 is preferably 1 to 10 mm, and more preferably 1.5 to 7 mm. If the distance d ₂ is less than 1 mm, the high-frequency signal transmission is insufficient, while if it exceeds 10 mm, the radiation loss is large. The height h of the convex portion 20 is preferably 1 to 10 mm, and more preferably 1.5 to 7 mm.

  The dielectric that forms the support 2 is made of, for example, a resin (which may be the same as the plastic film 10), ceramics such as alumina, or the like. In order to fix the gradient bonding conductive films 1 and 1 to the dielectric substrate 2, it is preferable that the adhesive layer 3 be interposed.

(2) Second high-frequency transmission line In the second high-frequency transmission line shown in FIG. 10, two strip-shaped inclined junction conductive films 1 and 1 are disposed on the opposing inner surface of a dielectric substrate 2 having a U-shaped cross section. ing. An electric field concentrates between the two strip-shaped gradient junction conductive films 1 and 1, and a high-frequency signal can be transmitted efficiently. As shown in FIG. 10, when the two strip-shaped gradient junction conductive films 1 and 1 have the metal thin films 11a and 11b on one side, it is preferable to arrange the two metal thin films 11b and 11b so as to face each other. The dielectric substrate 2 is not limited to the shape shown in the figure as long as the two strip-shaped gradient junction conductive films can be arranged to face each other.

The width of each inclined junction conductive film 1, 1 may be the same as that of the first high-frequency transmission line. The distance d ₃ between the two strip-like gradient bonding conductive films 1 and 1 is preferably 1 to 10 mm, and more preferably 1.5 to 7 mm. If the distance d ₃ is less than 1 mm, the high-frequency signal transmission is insufficient, while if it is more than 10 mm, the radiation loss is large.

(3) Third high-frequency transmission line In the third high-frequency transmission line shown in FIG. 11, two strip-shaped inclined junction conductive films 1 and 1 are disposed on the orthogonal inner surface of a dielectric substrate 2 having an L-shaped cross section. ing. An electric field concentrates between the two strip-shaped gradient junction conductive films 1 and 1, and a high-frequency signal can be transmitted efficiently. The dielectric substrate 2 is not limited to the shape shown in the figure as long as the two strip-like gradient junction conductive films 1 and 1 can be arranged so as to be orthogonal to each other.

The width of each inclined junction conductive film 1, 1 may be the same as that of the second high-frequency transmission line. The distance d ₄ between the two strip-shaped gradient bonding conductive films 1 and 1 is preferably 1 to 10 mm, and more preferably 1.5 to 7 mm. If the distance d ₄ is less than 1 mm, the high-frequency signal transmission is insufficient, while if it exceeds 10 mm, the radiation loss is large.

(4) Fourth High-Frequency Transmission Line The fourth high-frequency transmission line shown in FIG. 12 is a dielectric circular waveguide in which a cylindrical dielectric substrate 2 is covered with an inclined junction conductive film 1.

(5) Fifth high-frequency transmission line The fifth high-frequency transmission line shown in FIG. 13 is provided with a central conductor 1 made of a gradient bonded conductive film on the inner surface of a cylindrical dielectric substrate 2 and made of a gradient bonded conductive film on the outer surface. A coaxial line provided with a ground conductor 1 ′. What is necessary is just to set the internal diameter and outer diameter of a coaxial line suitably according to the frequency of a high frequency signal. A gradient junction conductive film may be used for only one of the center conductor 1 and the ground conductor 1 ′.

[4] High-frequency filter The high-frequency filter of the present invention has a simple structure obtained by providing an input terminal and an output terminal on any of the above-described high-frequency transmission lines. FIG. 14 shows an example of such a high frequency filter. When the second metal thin film 11b has an electric resistance larger than that of the first metal thin film 11a, it is preferable to provide the terminal 4 on the first metal thin film 11a. The high-frequency filter of the present invention has an excellent high-frequency transmission rate and anisotropy as necessary, and is useful as a band elimination filter or a hacker prevention filter.

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

Example 1
(1) Production of gradient bonded conductive film Biaxially stretched polyimide film [thickness: 25 μm, melting point: none, glass transition temperature: 280 ° C or higher, product name: “Kapton H” (manufactured by Toray Dubon Co., Ltd.)] A rolled copper foil having a thickness of 30 μm was bonded to one surface. A nickel layer having a thickness of 15 μm was formed on the copper foil by electrolytic plating. The obtained gradient bonded conductive film was slit so as to have a width of 5 mm.

(2) Production of a high-frequency transmission line Two parallel strip-like conductive films are bonded in parallel to a vinyl chloride resin support so that the polyimide film is on the support side, and the parallel-line high-frequency transmission line shown in FIG. (Length: 50 cm, distance d ₂ between _two strip-shaped gradient junction conductive films: 3 mm).

(3) Measurement of high frequency transmissibility
(a) Measuring spurious characteristics of high-frequency oscillators
(i) Fabrication of high-frequency transmission line for measuring spurious characteristics Biaxially stretched PET film [Thickness: 12μm, dielectric constant: 3.2 (1 MHz), dielectric loss tangent: 1.0% (1 MHz), melting point: 265 ℃, glass transition temperature : 75 ° C., trade name: “LUMIRROR” (manufactured by Toray Industries, Inc.)], a copper layer having a thickness of 0.3 μm was formed by vapor deposition. The obtained conductive film was slit so as to have a width of 5 mm. Two strip-shaped conductive films were bonded in parallel to a vinyl chloride resin support so that the PET film was on the support side, and a parallel line type high-frequency transmission line for measuring spurious characteristics was produced in the same manner as described above (long Length: 50 cm, distance d ₂ between the _two strip-like conductive films: 3 mm).

(ii) Spurious characteristic measurement As shown in FIG. 15, a high-frequency oscillator 5 is connected to one end of conductive films 1 '' and 1 '' of a high-frequency transmission line for spurious characteristic measurement via a connection cable 70, and the other end. A high-frequency receiver 6 was connected to. A terminating resistor R (100Ω) for preventing reflected waves was provided immediately before the receiver 6. As shown in FIG. 16, the high-frequency oscillator 5 includes a voltage-controlled oscillator (VCO) 51, three high-frequency oscillation modules 52, 52 ′, 52 ″ and 2 which are switched according to the frequency of the signal to be transmitted. A plurality of high-frequency amplifiers 53 and 53 ′ are provided. The high frequency oscillator 5 can transmit signals in the range of 100 to 200 MHz, 260 to 550 MHz, and 600 to 1,050 MHz. Signals of 100, 200, 300, 500, 700 and 1,000 MHz were transmitted from the oscillator 5, and the spurious characteristics were examined. The results are shown in Table 1. The high-frequency oscillator 5 generates less harmonics and has no spurious other than the harmonics.

(b) Transmission coefficient setting The oscillator 5 and the receiver 6 were connected by a connection cable 70 (see FIG. 15), and a signal having a frequency of 120 to 1,050 MHz with an output amplitude of 1.0 V was transmitted from the oscillator 5. As shown in FIG. 17A, when the signal is transmitted from the output terminals 50, 50 of the oscillator 5 so that the signal is output from the (+) side (signal pattern 1), as shown in FIG. Input amplitude for both cases where the signal is transmitted from the output terminals 50, 50 of the oscillator 5 so that the signal is output from the (−) side (signal pattern 2: phase shifted by 1/2 wavelength with respect to signal pattern 1). Asked. According to the formula: transfer coefficient = input amplitude (V) / output amplitude (V), the transfer coefficient at each measurement frequency was obtained, and a frequency-transfer coefficient curve was created for each of the signal patterns 1 and 2.

(c) Measurement of high-frequency transmissibility The high-frequency oscillator 5 and the high-frequency receiver 6 are connected to the high-frequency transmission line having the band-like inclined junction conductive film produced in (2) above, and the terminating resistor R (100Ω) ) Is provided immediately before the receiver 6 (see FIG. 15). A 120 to 1,050 MHz signal (signal patterns 1 and 2) oscillated with an output amplitude (V) of 1.0 V was transmitted from the oscillator 5, and an input amplitude (V) was obtained. Using the transfer coefficient obtained from the above frequency-transfer coefficient curve, the high-frequency transfer rate (%) at each measurement frequency is expressed by the formula: high-frequency transfer rate (%) = input amplitude (V) / (output amplitude (V) × transfer coefficient ) × 100. The result of plotting the relationship between the frequency and the high frequency transmissibility is shown in FIG. From FIG. 18, it can be seen that the regions of 430 to 490 MHz and 650 to 750 MHz are substantially removed from the signal pattern 2. When the signal pattern 1 was transmitted, the transmission was excellent particularly in the region of 700 to 1,050 MHz. Among them, the high-frequency transmission rate was 100% or more in the region of 710 to 810 MHz and 940 to 1,050 MHz.

Example 2
A copper layer having a thickness of 0.3 μm was formed on one surface of the PET film by a vapor deposition method, and a nickel layer having a thickness of 40 nm was formed. The obtained gradient bonded conductive film was slit so as to have a width of 5 mm. A parallel line type high-frequency transmission line was prepared in the same manner as in Example 1 except that two strip-like inclined conductive films were bonded in parallel to a vinyl chloride resin support so that the nickel layer was on the support side (long). Length: 50 cm, the distance d ₂ between the _two strip-shaped gradient junction conductive films: 3 mm). As shown in FIG. 19, the PET film 10 and the support 2 at both ends of the high-frequency transmission line are removed, and the insulator 8 is joined to the adhesive layer 3 under the nickel layer 11b, and the lip clip 7 is used. The high-frequency transmission rate (%) was examined in the same manner as in Example 1 except that the high-frequency oscillator 5 and the high-frequency receiver 6 were connected to the copper layer 11a of the gradient junction conductive films 1 and 1. The results are shown in FIG. From FIG. 20, it can be seen that the region of 670 to 840 MHz is almost removed from the signal pattern 2. With respect to both signal patterns 1 and 2, the transmissibility in the region of 260 to 400 MHz and 950 to 1,050 MHz was excellent. In particular, with respect to the signal pattern 2, the high-frequency transmission rate was 100% or more in the region of 260 to 380 MHz and 970 to 1,050 MHz.

Example 3
In the same manner as in Example 2, a 0.3 μm thick copper layer and a 40 nm thick nickel layer were formed on one surface of the PET film. Between the first roll (electrodeposited with a synthetic diamond fine particle having a particle size of 15 to 30 μm) and the second roll made of metal, the metal thin film is the first roll. It was allowed to pass side by side. The obtained porous gradient bonding conductive film has micropores formed only in the nickel layer and the copper layer, the average aperture diameter of the micropores is 3 μm, and the average distribution density of micropores is 5 × 10 ⁴ pieces / cm ^2. Met. The porous gradient bonding conductive film was slit to a width of 5 mm, and a parallel line type high frequency transmission line was produced in the same manner as in Example 1. About this high frequency transmission line, it carried out similarly to Example 2, and investigated the high frequency transmissibility (%). The results are shown in FIG. From FIG. 21, it can be seen that the region of 680 to 740 MHz is almost removed from the signal pattern 2. With respect to the signal patterns 1 and 2, the transmissibility in the region of 260 to 400 MHz and 780 to 860 MHz was excellent. In particular, for the signal pattern 2, the high-frequency transmission rate was 100% or more in the regions of 260 to 400 MHz, 760 to 840 MHz, and 990 to 1,050 MHz.

Example 4
A nickel layer having a thickness of 50 nm was formed on one surface of the PET film by a vapor deposition method, and a copper layer having a thickness of 0.45 μm was formed. Fine pores were formed in the obtained gradient bonded conductive film in the same manner as in Example 3. The obtained porous gradient bonding conductive film had micropores formed only in the copper layer and nickel layer, the average aperture diameter of micropores was 3 μm, and the density of micropores was 5 × 10 ⁴ pieces / cm ^2. It was. The porous gradient bonding conductive film was slit so as to have a width of 5 mm. A parallel-line type high-frequency transmission line was prepared in the same manner as in Example 1 except that two strip-shaped porous gradient bonding conductive films were bonded in parallel to a vinyl chloride resin support so that the PET film was on the support side. (Length: 50 cm, distance d ₂ between _two strip-shaped gradient junction conductive films: 3 mm). About this high frequency transmission line, it carried out similarly to Example 1, and investigated the high frequency transmissibility (%). The results are shown in FIG. From FIG. 22, it can be seen that the region of 480 to 530 MHz is substantially removed for the signal pattern 1 and the region of 650 to 700 MHz is substantially removed for the signal pattern 2. With respect to the signal pattern 1, the transmission was excellent in the region of 130 to 160 MHz, 260 to 300 MHz, 380 to 400 MHz, 650 to 720 MHz, and 920 to 1,000 MHz. With respect to the signal pattern 2, the transmission was excellent in the region of 130 to 180 MHz, 260 to 360 MHz, 450 to 500 MHz, 750 to 820 MHz, and 960 to 990 MHz.

Comparative Example 1
A conductive film was formed in the same manner as in Example 1 except that the nickel layer was not formed on the copper foil. This conductive film was slit to a width of 5 mm, and a high-frequency transmission line was produced in the same manner as in Example 1 except that the PI film was bonded in parallel to the support made of vinyl chloride resin so that the PI film was on the support side. About this high frequency transmission line, it carried out similarly to Example 1, and investigated the high frequency transmissibility (%). The results are shown in FIG. Since this conductive film did not have a gradient composition layer, a region having a high-frequency transmission rate of 0% did not appear.

Comparative Example 2
A gradient bonded conductive film was prepared in the same manner as in Example 1, and then heated from the nickel layer side at 500 ° C. to eliminate the gradient composition layer. Using the obtained metal film (nickel / copper), a high-frequency transmission line was produced in the same manner as in Example 1 except that the nickel layer was bonded in parallel to a vinyl chloride resin support so that the nickel layer was on the support side. About this high frequency transmission line, it carried out similarly to Example 1, and investigated the high frequency transmissibility (%). The results are shown in FIG. Since this conductive film did not have a gradient composition layer, a region having a high-frequency transmission rate of 0% did not appear.

Comparative Example 3
An alloy of 10 atomic% iron and 90 atomic% copper was deposited on one surface of the PET film at a thickness of 5,000 mm. The obtained conductive film was slit to have a width of 5 mm, and a high-frequency transmission line was produced in the same manner as in Example 1 except that the PET film was adhered in parallel to the vinyl chloride resin support so that the PET film was on the support side. About this high frequency transmission line, it carried out similarly to Example 1, and investigated the high frequency transmissibility (%). The results are shown in FIG. Since this electrically conductive film does not have a gradient composition layer, the overall high frequency transmission rate was inferior to the high frequency transmission lines of Examples 1 to 4.

Claims (19)

A gradient bonded conductive film having first and second metal thin films having different electrical resistances in order from the bottom on at least one surface of a plastic film, wherein the metal composition ratio is thick at the boundary between the first and second metal thin films. There is a gradient composition layer that changes in a direction, a gradient junction conductive film. 2. The gradient bonded conductive film according to claim 1, wherein a boundary between the plastic film and the first metal thin film is also a gradient composition layer in which a proportion of the metal decreases from the first metal thin film to the plastic film. A graded junction conductive film. 3. The gradient bonding conductive film according to claim 1, wherein the first metal thin film is a vapor deposition film, a plating film, or a foil, and the second metal thin film is a vapor deposition film or a plating film. Tilted junction conductive film. 4. The gradient junction conductive film according to claim 1, wherein the second metal thin film has an electric resistance that is 2 × 10 ⁻⁶ Ω · cm or more larger than that of the first metal thin film. Tilted junction conductive film. 5. The gradient junction conductive film according to claim 4, wherein the first metal thin film is made of copper and the second metal thin film is made of nickel. 6. The gradient junction conductive film according to claim 4, wherein a thickness ratio of the first metal thin film to the second metal thin film is 2/1 to 20/1. film. 7. The graded junction conductive film according to claim 4, wherein the first metal thin film has a thickness of 0.1 to 1 [mu] m, and the second metal thin film has a thickness of 10 to 70 nm. A graded junction conductive film. 4. The gradient junction conductive film according to claim 1, wherein the first metal thin film has an electric resistance larger by 2 × 10 ⁻⁶ Ω · cm or more than the second metal thin film. Tilted junction conductive film. 9. The gradient junction conductive film according to claim 8, wherein the first metal thin film is made of nickel and the second metal thin film is made of copper. The gradient junction conductive film according to claim 8 or 9, wherein the thickness ratio of the second metal thin film to the first metal thin film is 2/1 to 20/1. film. 11. The graded junction conductive film according to claim 8, wherein the first metal thin film has a thickness of 10 to 70 nm, and the second metal thin film has a thickness of 0.1 to 1 μm. A graded junction conductive film. The gradient junction conductive film according to any one of claims 1 to 11, wherein a plurality of fine holes having an average opening diameter of 0.5 to 50 µm are formed in at least the first and second metal thin films. An inclined bonding conductive film. 13. The gradient junction conductive film according to claim 12, wherein the average distribution density of the micropores is 1 × 10 ⁴ to 2 × 10 ⁵ holes / cm ² . 14. The gradient bonded conductive film according to claim 1, wherein the plastic film is made of polyethylene terephthalate or polyimide. A high-frequency transmission line comprising two spaced-apart inclined junction conductive films according to any one of claims 1 to 14 in parallel. 16. The high-frequency transmission line according to claim 15, wherein the two inclined junction conductive films are arranged on the same surface of the dielectric substrate. 16. The high frequency transmission line according to claim 15, wherein the two inclined junction conductive films are disposed on opposing inner surfaces of a U-shaped dielectric substrate in cross section. 16. The high-frequency transmission line according to claim 15, wherein the two inclined junction conductive films are arranged on orthogonal inner surfaces of a dielectric substrate having an L-shaped cross section. 19. A high frequency filter comprising the high frequency transmission line according to claim 15.

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