JP6943704B2 - Resistor film for λ / 4 type radio wave absorber and λ / 4 type radio wave absorber - Google Patents

Description

The present invention includes a resistance film for a λ / 4 type radio wave absorber capable of producing a λ / 4 type radio wave absorber exhibiting excellent durability, and a resistance film for the λ / 4 type radio wave absorber. / 4 type radio wave absorber.

In recent years, mobile communication devices such as mobile phones and smartphones have rapidly become widespread, and many electronic devices have come to be installed in automobiles and the like. Problems such as malfunction of electronic devices occur frequently. Various radio wave absorbers are being studied as measures to prevent such radio interference and malfunction. For example, in Patent Document 1, a perfect reflector is attached to the back surface of a dielectric spacer having a thickness of approximately λ / 4 (where λ represents the wavelength of radio waves in the dielectric), and ion play is provided on the front surface. A λ / 4 type radio wave absorber having a resistance film prepared by dielectricing, vapor deposition, sputtering or the like is disclosed.

Japanese Unexamined Patent Publication No. 5-114813

The conventional λ / 4 type radio wave absorber has a structure in which conductive layers such as ITO (tin-doped indium oxide), a dielectric, and aluminum, which are resistance films, are laminated. This ITO is often formed on a polymer film such as a polyethylene terephthalate (PET) film for reasons such as cost reduction. Since the polymer film cannot be heated at a high temperature, ITO cannot be formed by heating, and the film is formed in an amorphous state. Amorphous films have high resistivity and low durability and chemical stability in the atmosphere. Therefore, usually, the film-formed ITO film is annealed and crystallized in a subsequent process to improve the physical characteristics of the film.

However, since the annealing temperature of the polymer film cannot be increased, annealing at a relatively low temperature for a long time, for example, at 140 ° C. for 2 hours, is required. Therefore, if a metal film that does not require an annealing step can be used as a resistance film instead of ITO, annealing after film formation becomes unnecessary, and significant productivity improvement and cost reduction can be expected. Further, ITO contains a large amount of indium, but indium is a metal that is expected to be used in a larger amount than the reserves, and there is a concern about resource depletion. Therefore, the development of a resistance coating material to replace ITO is expected.

However, many metal films are inferior in durability in the atmosphere when used as a resistance film for a λ / 4 type radio wave absorber having 376.7 Ω / □, and the radio wave absorption of the λ / 4 type radio wave absorber. There is a problem that the amount may decrease over time. The surface resistance value of the resistance film for the λ / 4 type radio wave absorber must be 376.7Ω / □ ± 10%.

In view of the above situation, the present invention has a resistance film for a λ / 4 type radio wave absorber capable of producing a λ / 4 type radio wave absorber exhibiting excellent durability, and the λ / 4 type radio wave absorber. It is an object of the present invention to provide a λ / 4 type radio wave absorber including a resistance film for use.

In one embodiment of the present invention, a resistance film for a λ / 4 type radio wave absorber made of an alloy containing 5% by weight or more of molybdenum is provided.

According to one embodiment of the present invention, a resistance film for a λ / 4 type radio wave absorber capable of producing a λ / 4 type radio wave absorber exhibiting excellent durability, and the λ / 4 type radio wave absorber. It is possible to provide a λ / 4 type radio wave absorber including a resistance film for use.

The present inventors investigated the cause of inferior durability when a metal film was used as a resistance film for a λ / 4 type radio wave absorber. As a result, it was found that the surface resistance value of the resistance film constituting the λ / 4 type radio wave absorber greatly fluctuates with time, which is one of the causes of the decrease in radio wave absorption.
So far, alloys such as stainless steel (iron / chromium alloy, SUS) and nickel / chromium alloys, and metals such as titanium have been studied as a resistance film for a λ / 4 type radio absorber that replaces ITO. For example, when SUS or a nickel-chromium alloy is used as the resistance film, a passivation film having a thickness of 10 nm or less is formed on the surface of the resistance film and is stabilized. However, if such a resistance film is left unattended, salt (chlorine ions) in the atmosphere adheres to the surface, so that the passivation film is destroyed, the resistance film itself is damaged, and the surface resistance value fluctuates. It was thought to be. Further, for example, when titanium is used as the resistance film, the film thickness of titanium is as thin as about 1 nm. Therefore, if the resistance film is left unattended, titanium is oxidized by oxygen in the atmosphere and titanium oxide is oxidized from the surface. It was considered that the surface resistance value would fluctuate due to being replaced by.

As a result of diligent studies, the present inventors reduced the fluctuation of the surface resistance value of the resistance film even when it was left in the atmosphere when the resistance film was formed using an alloy containing 5% by weight or more of molybdenum. Then, they found that a λ / 4 type radio wave absorber exhibiting excellent durability could be manufactured, and completed the present invention.

The resistance film for a λ / 4 type radio wave absorber according to an embodiment of the present invention is made of an alloy containing 5% by weight or more of molybdenum. As a result, it is possible to manufacture a λ / 4 type radio wave absorber that exhibits excellent durability by reducing fluctuations in the surface resistance value of the resistance film even when left in the atmosphere. The content of molybdenum in the alloy constituting the resistance film for the λ / 4 type radio wave absorber is preferably 7% by weight or more, more preferably from the viewpoint of obtaining the λ / 4 type radio wave absorber exhibiting excellent durability. Is 9% by weight or more, more preferably 11% by weight or more, still more preferably 13% by weight or more, particularly preferably 15% by weight or more, and most preferably 16% by weight or more. The molybdenum content is preferably 30% by weight or less, more preferably 25% by weight or less, still more preferably 20% by weight or less.

As described above, according to one embodiment of the present invention, it is possible to provide a λ / 4 type radio wave absorber that exhibits excellent durability. The reason for this is not necessarily clear, but it is thought that the alloy containing 5% by weight or more of molybdenum improves the corrosion resistance not only in an oxidizing atmosphere but also in a reducing atmosphere.

The alloy is not particularly limited as long as it contains 5% by weight or more (preferably within the above range) of molybdenum, but λ / can produce a λ / 4 type radio wave absorber exhibiting excellent durability. From the viewpoint of obtaining a resistance film for a type 4 radio wave absorber, an alloy containing nickel, chromium and molybdenum is preferable. Alloys containing nickel, chromium and molybdenum include, for example, Hastelloy B-2, B-3, C-4, C-2000, C-22, C-276, G-30, N, W, X and the like. Various grades can be mentioned.

Among them, from the viewpoint of obtaining a λ / 4 type radio wave absorber that exhibits more excellent durability, the nickel content is 40% by weight or more, the chromium content is 1% by weight or more, and the molybdenum content is 5% by weight. % Or more is more preferred. When the alloy contains nickel, chromium, and molybdenum, the nickel content is 45% by weight or more, the chromium content is 3% by weight or more, and / or the molybdenum content is 7% by weight or more from the same viewpoint. Is even more preferable. It is even more preferable that the nickel content is 47% by weight or more, the chromium content is 5% by weight or more, and / or the molybdenum content is 9% by weight or more. It is particularly preferable that the nickel content is 50% by weight or more, the chromium content is 10% by weight or more, and / or the molybdenum content is 11% by weight or more. It is very preferable that the nickel content is 53% by weight or more, the chromium content is 12% by weight or more, and / or the molybdenum content is 13% by weight or more. It is particularly preferable that the nickel content is 55% by weight or more, the chromium content is 15% by weight or more, and / or the molybdenum content is 15% by weight or more. Most preferably, the nickel content is 57% by weight or more, the chromium content is 16% by weight or more, and / or the molybdenum content is 16% by weight or more.
When the alloy contains nickel and chromium, the nickel content is preferably 80% by weight or less, more preferably 70% by weight or less, from the viewpoint of obtaining a λ / 4 type radio wave absorber exhibiting more excellent durability. , More preferably 65% by weight or less. And / or the chromium content is preferably 50% by weight or less, more preferably 40% by weight or less, still more preferably 35% by weight or less.

The surface resistance value of the resistance film for the λ / 4 type radio wave absorber must be 376.7Ω / □ ± 10%. Based on this surface resistance value, the thickness of the resistance film for the λ / 4 type radio wave absorber is determined. For example, if SUS or a nickel-chromium alloy is used to obtain this surface resistance value, the film thickness of the resistance film must be 1 to 4 nm, and if titanium is used to obtain this surface resistance value, the resistance film must be formed. It is necessary to set the film thickness of 1 to 2 nm. (Note that copper and silver having high conductivity need to have a film thickness of about 0.3 nm.) However, when a resistance film is formed by a method such as sputtering, a film thickness of 4 nm or less is stably formed. It is extremely difficult to do.
On the other hand, alloys having a nickel content of 40% by weight or more, a chromium content of 1% by weight or more, and a molybdenum content of 5% by weight or more (more preferably, nickel content, chromium content and For alloys with a molybdenum content within the above range), the surface resistance value can be adjusted to 376.7 Ω / □ ± 10% by setting the film thickness to 5 to 6 nm. If the film thickness is 5 to 6 nm, a film can be stably formed by sputtering or the like, which has a merit in manufacturing. Since the above-mentioned resistance film can be stably produced, performance unevenness due to each resistance film can be caused. It can be suppressed.

In one embodiment of the present invention, examples of metals other than nickel, chromium and molybdenum that can form an alloy include iron, cobalt, tungsten, manganese and titanium. When the alloy contains nickel, chromium and molybdenum, the upper limit of the total content of metals other than nickel, chromium and molybdenum is preferably 45% by weight, more preferably 40% by weight from the viewpoint of durability of the resistance film. , More preferably 35% by weight, even more preferably 30% by weight, particularly preferably 25% by weight, and very preferably 23% by weight. The total content of metals other than nickel, chromium and molybdenum is, for example, 1% by weight or more.

When the alloy constituting the resistance film contains iron, it is preferably 25% by weight or less, more preferably 20% by weight or less, still more preferably 15% by weight or less, for example, from the viewpoint of durability of the resistance film. Weight% or more. When the alloy constituting the resistance film contains cobalt and / or manganese, each of them independently, preferably 5% by weight or less, more preferably 4% by weight or less, still more preferably, from the viewpoint of durability of the resistance film. It is 3% by weight or less, for example, 0.1% by weight or more. When the alloy constituting the resistance film contains tungsten, it is preferably 8% by weight or less, more preferably 6% by weight or less, still more preferably 4% by weight or less, for example, from the viewpoint of durability of the resistance film. Weight% or more.

The alloy constituting the resistance film may contain silicon and / or carbon, and the content thereof is independently, for example, 1% by weight or less or 0.5% by weight or less, for example, 0.01. Weight% or more.

The resistance film for a λ / 4 type radio wave absorber according to an embodiment of the present invention can be produced by, for example, a method such as ion plating, vapor deposition, or sputtering. In one embodiment of the present invention, in the case of an alloy containing nickel, chromium, and molybdenum within the above range, the film thickness of the resistance film can be 5 to 6 nm, so that the resistance film is stable by the above production method. It is possible to suppress performance unevenness due to each resistance film.

It has a resistance film for a λ / 4 type radio wave absorber, a dielectric, and a radio wave reflection film, which is one embodiment of the present invention, and the resistance film for a λ / 4 type radio wave absorber and the radio wave reflection film are , The λ / 4 type radio wave absorber arranged at a position λ / 4 away from the dielectric is another embodiment of the present invention.

By using the resistance film for a λ / 4 type radio wave absorber according to an embodiment of the present invention, a λ / 4 type radio wave absorber exhibiting excellent durability can be manufactured.
Specifically, for example, a resistance film for a λ / 4 type radio wave absorber, a dielectric, and a radio wave reflecting film according to an embodiment of the present invention are used, and a resistance film for a λ / 4 type radio wave absorber and a radio wave. A λ / 4 type radio wave absorber can be obtained by arranging the reflective film at a position λ / 4 away from the dielectric material. Here, λ represents the wavelength of the radio wave in the dielectric.

The dielectric is not particularly limited, and a dielectric used for a conventionally known λ / 4 type radio wave absorber such as an organic foam, an organic polymer sheet, or an organic polymer film can be used.
The radio wave reflecting film is not particularly limited, and a radio wave reflecting film used for a conventionally known λ / 4 type radio wave absorber such as an aluminum thin film can be used.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

In the following Examples and Comparative Examples, the thickness was measured as follows. The metal content per unit area obtained by comparing the intensity of characteristic X-rays generated when the surface of a metal thin film is irradiated with X-rays by a fluorescent X-ray analyzer with a standard sample is divided by the density of the metal. The thickness of the metal thin film was calculated.

(Example 1)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. A resistance film made of Hastelloy C-276 having a thickness of 5 nm was formed on the PET film at an output of 2.4 kW by DC magnetron sputtering using a Hastelloy C-276 target.
Hastelloy C-276 has a nickel content of 57% by weight, a chromium content of 16% by weight, a molybdenum content of 16% by weight, an iron content of 6.5% by weight, and a cobalt content of 2.5% by weight. % Or less, tungsten content is 4.3% by weight, manganese content is 1% by weight or less, silicon content is 0.08% by weight or less, and carbon content is 0.01% by weight or less.

The surface resistance value of the obtained resistance film was measured by the 4-terminal method using a surface resistance meter (manufactured by MITSUBISHI CHEMICAL ANALYTECH, trade name "Loresta-EP") and found to be 355.0 Ω / □ ( initial value).

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured by a four-terminal method using a surface resistance meter (manufactured by MITSUBISHI CHEMICAL ANALYTECH, trade name "Loresta-EP") every time from the start of standing. The results are shown in Table 1.

(Example 2)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. A resistance film made of Hastelloy X having a thickness of 5 nm was formed on a PET film at an output of 2.4 kW by DC magnetron sputtering using a Hastelloy G-30 target.
Hastelloy X has a nickel content of 43% by weight, a chromium content of 30% by weight, a molybdenum content of 5.5% by weight, an iron content of 15.0% by weight, and a cobalt content of 2% by weight or less. , Tungsten content is 2.5% by weight, manganese content is 1.5% by weight or less, silicon content is 1% by weight or less, and carbon content is 0.3% by weight or less.

When the surface resistance value of the obtained resistance film was measured in the same manner as in Example 1, it was 353.2 Ω / □ (initial value).

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured in the same manner as in Example 1 every time after the start of leaving. The results are shown in Table 2.

(Example 3)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. A resistance film made of Hastelloy B-3 having a thickness of 5 nm was formed on a PET film at an output of 2.4 kW by DC magnetron sputtering using a Hastelloy B-3 target.
Hastelloy B-3 has a nickel content of 67% by weight, a chromium content of 1.5% by weight, a molybdenum content of 28.5% by weight, an iron content of 1.5% by weight, and a cobalt content of 1.5% by weight. The tungsten content is 3% by weight or less, the manganese content is 3% by weight or less, the silicon content is 0.1% by weight or less, and the carbon content is 0.01% by weight or less.

When the surface resistance value of the obtained resistance film was measured in the same manner as in Example 1, it was 340.1 Ω / □ (initial value).

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured in the same manner as in Example 1 every time after the start of leaving. The results are shown in Table 3.

(Comparative Example 1)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. SUS310S with a thickness of 2 nm (iron content: 51% by weight, chromium content: 25% by weight, nickel content: 20% by weight) at an output of 6.5 kW by DC magnetron sputtering using a SUS310S target on a PET film. %) Formed a resistance film.

When the surface resistance value of the obtained resistance film was measured in the same manner as in Example 1, it was 335.0Ω / □ (initial value).

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured in the same manner as in Example 1 every time after the start of leaving. The results are shown in Table 4.

(Comparative Example 2)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. A nickel-chromium alloy target is used on a PET film, and a nickel-chromium alloy with a thickness of 3.9 nm (nickel content is 80% by weight and chromium content is 20% by weight) at an output of 0.5 kW by DC magnetron sputtering. %) Formed a resistance film.

When the surface resistance value of the obtained resistance film was measured in the same manner as in Example 1, it was 500.8 Ω / □ (initial value). In the case of nickel-chromium alloy, it became difficult to adjust the thickness, and the initial surface resistance value became high.

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured in the same manner as in Example 1 every time after the start of leaving. The results are shown in Table 5.

(Comparative Example 3)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. A resistance film made of titanium having a thickness of 1 nm was formed on a PET film at an output of 3.6 kW by DC magnetron sputtering using a titanium target.

When the surface resistance value of the obtained resistance film was measured in the same manner as in Example 1, it was 365.4 Ω / □ (initial value).

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured in the same manner as in Example 1 every time after the start of leaving. The results are shown in Table 6.

(Comparative Example 4)
As a base material, a polyethylene terephthalate (PET) film having a thickness of 125 μm was prepared. A resistance film made of an alloy having a thickness of 5 nm was formed on a PET film at an output of 2.4 kW by DC magnetron sputtering using an alloy target.
The above alloy has a nickel content of 43% by weight, a chromium content of 31% by weight, a molybdenum content of 4.5% by weight, an iron content of 15.0% by weight, and a cobalt content of 2% by weight or less. , Tungsten content is 2.5% by weight, manganese content is 1.5% by weight or less, silicon content is 1% by weight or less, and carbon content is 0.3% by weight or less.

When the surface resistance value of the obtained resistance film was measured in the same manner as in Example 1, it was 351.9 Ω / □ (initial value).

The resistance film immediately after the film formation was left in the atmosphere at a temperature of 25 ° C. and a humidity of 40% Rh. The surface resistance value of the resistance film was measured in the same manner as in Example 1 every time after the start of leaving. The results are shown in Table 7.

From the above results, it can be seen that the surface resistance values of the resistance films in Examples 1 to 3 have hardly changed even after 26 days from the start of leaving. On the other hand, it can be seen that the surface resistance values of the resistance films of Comparative Examples 1 to 4 increase with time.
Furthermore, in the case of nickel-chromium alloys, it became difficult to adjust the thickness, and the initial surface resistance value became high.

According to the present invention, a resistance film for a λ / 4 type radio wave absorber capable of producing a λ / 4 type radio wave absorber exhibiting excellent durability, and a resistance film for the λ / 4 type radio wave absorber. A λ / 4 type radio wave absorber comprising the above, that is, a λ / 4 type radio wave absorber including the resistance film for the λ / 4 type radio wave absorber can be provided.

Claims (5)

Ri Do an alloy containing molybdenum 5% by weight or more, the alloy of nickel, an alloy containing chromium and molybdenum, nickel, the total content of metals other than chromium and molybdenum is 30 wt% or less, lambda / Resistance film for type 4 radio wave absorber. The resistance film for a λ / 4 type radio wave absorber according to claim 1 , wherein the nickel content in the alloy is 40% by weight or more, the chromium content is 1% by weight or more, and the molybdenum content is 5% by weight or more. The resistance film for a λ / 4 type radio wave absorber according to claim 2, which has a thickness of 5 nm or more. The resistance film for a λ / 4 type radio wave absorber according to any one of claims 1 to 3, wherein the surface resistance value is 376.7 Ω / □ ± 10%. The λ / 4 type radio wave absorber resistance film according to any one of claims 1 to 4 , a dielectric, and a radio wave reflection film, and the λ / 4 type radio wave absorber resistance film and the radio wave reflection A λ / 4 type radio wave absorber in which a film is arranged at a position λ / 4 away from the dielectric.