JP7773370B2 - Metallized film and method of manufacturing same - Google Patents

Description

The present invention relates to a metallized film and a method for manufacturing a metallized film.

Metalized films are used as conductive materials in a wide range of fields, including film capacitors, electromagnetic wave shielding, battery current collectors, and printed circuit boards.

For example, semiconductor integrated circuit elements (hereinafter sometimes referred to as "semiconductor elements") used as computer microprocessors and the like have become increasingly sophisticated and multifunctional in recent years. This has led to a demand for narrower pitches between terminals on semiconductor elements, and for package substrates, which are printed wiring boards on which semiconductor elements are mounted, to have finer wiring patterns, making copper, with its low resistance, an ideal material for this purpose.

The wiring patterns on printed wiring boards have traditionally been formed by etching the copper film on copper-clad laminates. Etching methods include subtractive and semi-additive processes. The subtractive process involves removing unnecessary copper film from copper-clad laminates to form circuits. The areas that should remain as wiring are covered with ink or paint, and the copper film is then etched using metal-corrosive chemicals to form the required circuits. On the other hand, the semi-additive process involves adding circuit patterns to insulating layer boards later. A resist is formed on the areas where the pattern should not be formed, and plating is then applied to form the pattern.

In recent years, printed wiring boards used in electronic devices have become smaller and lighter, and as components are mounted more densely in smaller spaces, there has been a demand for fine-pitch circuits.

Copper foil and metallized film are used as wiring materials, but to meet these requirements, metallized film with a thinner copper film is preferably used (for example, Patent Document 1).

In mobile communication devices, it has been common to shield electromagnetic waves by laminating an electromagnetic wave shielding film over the wiring and chip sections. Electromagnetic wave shielding is achieved by applying a conductive adhesive to a metal-coated film that has an insulating layer and a conductive layer. Copper or silver is used as the metal for the metal-coated film.

In recent years, mobile communication devices have become required to process large amounts of signals in order to achieve faster internet speeds. Therefore, in order to process such large amounts of signals, the signal processing speed of semiconductor elements has also increased, resulting in increased electromagnetic noise being generated from semiconductor elements and signal lines.

These electromagnetic noises interfere with antenna components built into mobile communication devices, causing malfunctions. Therefore, shielding films with better shielding properties are needed to shield the electromagnetic noise that accompanies increased speeds. Shielding performance is determined by the type and thickness of the shielding material; silver and copper, with their high conductivity and magnetic permeability, are preferred, along with thick metal layers. To actually shield signals in the 1 GHz band, a metal layer resistance of 500 mΩ/ ^m² or less is required; for example, copper requires a thickness of 0.08 μm or more. Meanwhile, shielded objects come in a variety of shapes, including semiconductor chips and cases, and the shielding film must be bonded to these objects without gaps, requiring shape-conforming properties. Thick metal layers and films are undesirable because they wrinkle during bonding, making it difficult to conform to the shape. Therefore, electromagnetic wave shielding films have been proposed requiring a metal layer thickness of 0.08 to 2.0 μm and a film thickness of 4 to 75 μm (see, for example, Patent Document 2).

Copper has low resistance and is used as a wiring material for circuit boards. Because it can be thickened more cheaply than silver, it is essential for electromagnetic wave shielding materials with high shielding performance. Copper vapor deposition metallized film is manufactured by depositing copper of the desired thickness onto a resin film using plating or vapor deposition methods (including sputtering).

However, copper is susceptible to surface oxidation, and this oxidation progresses during the process from production to post-processing. When the metallized film is attached to a circuit board using an adhesive, the residual surface oxidation can cause peeling at the surface oxidation film interface. Furthermore, when plating using the semi-additive method, the copper of the metallized film is used as a seed layer. However, if surface oxidation progresses, this can increase resistance, making the current supply unstable and resulting in uneven film thickness. While a cleaning process using an acidic solution is effective in removing the surface oxidation layer, the copper is etched during the cleaning process, potentially resulting in a significant reduction in film thickness or even complete loss for copper films less than 1 μm thick. To prevent this, a rust inhibitor treatment primarily containing a benzoazole compound is typically applied (see, for example, Patent Document 3).

However, if the rust inhibitor remains on the copper film surface, it can cause interfacial peeling. Furthermore, the acidic cleaning process used to remove the rust inhibitor etches the copper surface, making it unsuitable for thin films.

Therefore, to solve this problem, studies have been conducted to obtain anti-corrosion properties by providing a separate metal layer on the copper surface (for example, Patent Documents 4 and 5).

Japanese Patent Application Laid-Open No. 2007-245645 JP 2011-35213 A Japanese Patent Application Publication No. 5-28835 JP 2016-153214 A Patent No. 4463442

However, many metals used in anti-corrosion layers form a dense oxide film on their surface, giving them a relatively high electrical resistivity. As the thickness increases, there are concerns that the surface resistance will increase, and that the dense metal oxide film may inhibit etching, leaving residue and resulting in poor patterning. In addition, when the metal layer used in the anti-corrosion layer oxidizes, losing its metallic luster and turning into a relatively transparent oxide film, the color of the underlying copper becomes visible, resulting in a change from the metallic luster of the initial anti-corrosion layer, and this may be interpreted as abnormal discoloration.

In view of the above, the objective of the present invention is to provide a metallized film that exhibits minimal changes in resistance and color before and after a moisture resistance test.

As a result of intensive research in light of the above-mentioned problems, the inventors have developed a metallized film and a method for manufacturing the same that exhibits minimal change in resistance and color before and after a moisture resistance test by adjusting the thickness of the titanium layer to an appropriate thickness.

That is, the present invention relates to a metallized film having a copper layer and an anticorrosion layer, in this order from the film side, on at least one surface of the film, wherein the anticorrosion layer contains at least one selected from the group consisting of metallic titanium, titanium oxide, and mixtures thereof, and wherein the surface resistance change rate after 3 days in an 85°C, 85% RH environment is 20% or less, and the color difference ΔE after 3 days in said environment is 6.5 or less.

The present invention also relates to a method for producing a metallized film, in which the copper layer and anti-corrosion layer are formed by vacuum deposition or sputtering.

The present invention makes it possible to obtain a metallized film that exhibits minimal change in resistance and color before and after a moisture resistance test, as well as a method for manufacturing the same.

1 is a cross-sectional schematic view of a metallized film of the present invention. 1 is a cross-sectional schematic view of a metallized film of the present invention.

The present invention is described in detail below.

<Metallized film>
A preferred embodiment of the present invention is a metallized film having a copper layer and an anticorrosive layer, in this order, on at least one surface of the film, the anticorrosive layer containing at least one selected from the group consisting of metallic titanium, titanium oxide, and mixtures thereof, and having a surface resistance change rate of 20% or less after 3 days in an 85°C, 85% RH environment and a color difference ΔE of 6.5 or less after 3 days in the same environment. A more preferred embodiment of the metallized film has a copper layer and an anticorrosive layer made of metallic titanium, titanium oxide, or a mixture thereof on at least one surface of the film (Figure 1). Thus, it is more preferred that the anticorrosive layer be made of metallic titanium, titanium oxide, or a mixture thereof.

<Copper layer>
The copper layer according to the present invention is an aggregate of one or more laminated copper layers each having copper as the main component, where the main component is more than 80 atomic % when the entire layer is taken as 100 atomic %.

The thickness of the copper layer in the present invention is preferably 0.05 μm or more and 3.0 μm or less, and more preferably 0.2 μm or more and 1.5 μm or less.

For electromagnetic wave shielding applications, a copper layer of 0.05 μm or more provides shielding performance, while a layer of 0.2 μm or more provides even better electromagnetic wave shielding performance. For electronic circuit formation applications, a copper layer of 0.1 μm or more ensures conductivity during plating using the semi-additive method, while a layer of 0.2 μm or more ensures high conductivity. On the other hand, to form fine patterns on printed circuit boards using the semi-additive method, a relatively thin copper layer is necessary. Considering the cost constraints associated with forming the copper layer, a copper layer thickness of 3.0 μm or less is preferred, with a thickness of 1.5 μm or less being even more desirable.

Vacuum deposition methods include induction heating deposition, resistance heating deposition, laser beam deposition, and electron beam deposition. Any deposition method can be used, but electron beam deposition is preferred due to its high film formation rate. The film may be cooled during deposition to prevent the temperature from rising.

<Rust prevention layer>
The anticorrosion layer in the present invention preferably contains at least one selected from the group consisting of metallic titanium, titanium oxide, and mixtures thereof, and more preferably consists of metallic titanium, titanium oxide, or a mixture thereof.

The anticorrosion layer is preferably formed on the copper layer on at least one side of the film by sputtering, a physical vapor deposition method, and is preferably deposited using a target whose main component is metallic titanium. "Main component" refers to a component that accounts for more than 80 atomic % when the entire target is taken as 100 atomic %. In other words, it is preferable that the anticorrosion layer contains more than 80 atomic % of titanium out of 100 atomic % of the metal elements contained in the anticorrosion layer. The film may be cooled during deposition to prevent the temperature from rising.

After the anti-corrosion layer is formed, some of the metallic titanium oxidizes in reaction with the atmosphere, forming titanium oxide, which has a high anti-corrosion effect. Because the titanium oxide film suppresses internal oxidation, layers with different oxygen concentrations are formed along the depth direction, resulting in the entire anti-corrosion layer being a mixture of metallic titanium and titanium oxide. If the anti-corrosion layer is thick, the surface layer will be made up of titanium oxide, and areas further from the surface will contain metallic titanium. If the anti-corrosion layer is thin, titanium oxide will make up most of the entire layer.

The role of such an anticorrosion layer is to protect the underlying copper layer. A high resistance change rate after a humidity test is undesirable, as it indicates that corrosion of the copper layer has occurred. Therefore, it is preferable that the resistance change rate be 20% or less. From the viewpoint of the resistance change rate, a thicker anticorrosion layer is preferable, but from the viewpoint of color difference ΔE, a thinner film thickness is preferable, as it reduces the change in color difference ΔE. The color difference ΔE is determined by applying a colorimeter from the anticorrosion layer side, measuring the reflected light including specular reflection light using the L ^* a ^* b ^* color system, and calculating the value using the following formula. A color difference ΔE of 6.5 or less is considered to be acceptable and is determined to be non-existent.

Measured values before humidity resistance test in an 85°C, 85% RH environment (L ₀ , a ₀ , b ₀ )
Measured values (L, a, b) after humidity resistance test in an 85°C, 85% RH environment.

The thickness of the anticorrosion layer in the present invention is preferably 2 nm to 8 nm, more preferably 3 nm to 5 nm, and even more preferably 3 nm to 4 nm. When the anticorrosion layer thickness is 2 nm to 8 nm, it is more likely to achieve a surface resistance change rate of 20% or less and a color difference ΔE of 6.5 or less even after 3 days in an 85°C, 85% RH environment. Furthermore, when the anticorrosion layer thickness is 3 nm to 5 nm, it is more likely to achieve a surface resistance change rate of 20% or less and a color difference ΔE of 6.5 or less even after 7 days in an 85°C, 85% RH environment. Furthermore, when the anticorrosion layer thickness is 3 nm to 4 nm, it is more likely to achieve a surface resistance change rate of 20% or less and a color difference ΔE of 6.5 or less even after 28 days in an 85°C, 85% RH environment.

When a copper film formed by vacuum deposition or sputtering is exposed to the atmosphere, a copper oxide film forms on the copper film's surface. Because the CuO in the copper oxide film has an acicular structure and is not a dense film, forming a titanium film on the CuO makes it difficult to form a uniform, dense anti-corrosion layer, which can weaken the anti-corrosion effect. Therefore, in order to improve the anti-corrosion effect, it is preferable to sputter an anti-corrosion layer using titanium without exposing the copper layer formed in a vacuum to the atmosphere.

Meanwhile, in the production of metallized films, it can be difficult to form a titanium anticorrosion layer on a copper film without exposure to the atmosphere due to constraints on the structure and film-forming performance of the manufacturing equipment. Considering production capacity and manufacturing costs, it is preferable to form the copper film by vacuum deposition and the titanium anticorrosion layer in a continuous, single-pass line without exposing the film to the atmosphere. However, allowing the copper film formed by vacuum deposition or sputtering to be exposed to the atmosphere simplifies the manufacturing equipment and process, allowing the metallized film to be obtained more efficiently in terms of time and energy. To efficiently obtain a metallized film while maintaining favorable anticorrosion effects, a metallized film manufacturing method can also be used in which the copper layer is vapor-deposited and then exposed to the atmosphere, followed by copper sputtering again in a vacuum, followed by titanium sputtering without exposing the film to the atmosphere.

If one is only concerned with the anti-rust effect, it is possible to re-sputter nickel, chromium, or titanium instead of copper to thicken the copper film surface before sputtering titanium onto the surface exposed to the atmosphere. However, sputtering a metal other than copper before sputtering titanium may increase the surface resistance or significantly change the surface color.

When copper sputtering is performed on a copper surface exposed to the atmosphere, it is preferable that the sputtered copper thickness be 1 nm or more. By performing Cu sputtering to a thickness of 1 nm or more, the brittle copper oxide present on the copper surface exposed to the atmosphere is also removed, and a sputtered copper film is formed on top of it. Then, by continuously sputtering titanium on the sputtered copper film without exposing it to the atmosphere, a stable anti-corrosion layer can be obtained.

The thickness of the anticorrosion layer of the present invention can also be determined by the reflectance of light immediately after deposition. If the reflectance of the metal layer of the anticorrosion layer at a wavelength of 800 nm is 82% or higher, and the ratio R800/R300 (the reflectance at a wavelength of 800 nm, R800), to the reflectance at a wavelength of 300 nm, R300, is between 5.0 and 10.0, then even after three days in an 85°C, 85% RH environment, the surface resistance change rate can be 20% or less and the color difference ΔE can be 6.5 or less. Because the anticorrosion layer is thin immediately after deposition, it is difficult to directly measure its thickness. However, the optimal thickness of the anticorrosion layer can be easily determined by checking its reflectance.

<Film>
The film used in the present invention is a thin film made from a polymer such as a synthetic resin.

Films suitable for use in the present invention include, for example, polyester films, and among polyester films, polyethylene terephthalate films, polyethylene naphthalate films, polyimide films, polyphenylene sulfide films, and polypropylene films. Of these, polyethylene terephthalate films are more preferred. These films may be used alone or in combination. Films with a coating of resin, adhesive, etc. on the surface may also be used.

The thickness of such a film is preferably between 1 μm and 200 μm. The appropriate film thickness varies depending on the application. For example, when used for electromagnetic shielding of micro-coaxial cables, a film thickness of less than 1 μm may cause the film to deform or tear when wrapped around the micro-coaxial cable. Furthermore, a thickness of more than 10 μm may result in reduced flexibility due to the increased diameter of the micro-coaxial cable. For another application, when using a film for electromagnetic shielding gaskets to prevent EMI (electromagnetic interference), a thickness of less than 10 μm may cause the film to deform or tear due to the stress applied during gasket fabrication. Furthermore, a thickness of more than 50 μm may result in the gasket itself being too thick and unsuitable for space-saving applications, and the film's rigidity may be so great that it loses its flexibility. When using metallized films in printed circuit boards or touch sensors other than those mentioned above, a film thickness of 50 μm or more and 200 μm or less is generally preferred, as it can be maintained as a substrate and provide satisfactory electrical properties.

<Buffer layer>
The metallized film of the present invention may have a buffer layer between the film and the copper layer. By providing a buffer layer, it is expected that the adhesion between the film and the copper layer will be improved. Furthermore, in the case of a polyimide film, the buffer layer also serves as a copper diffusion barrier into the film, and is expected to prevent a decrease in adhesion due to copper diffusion. As the buffer layer, it is preferable to form a metal layer on the film by a sputtering method. Sputtering allows for a thinner buffer layer, making it ideal for electromagnetic wave shielding applications where thinner layers are required.

The buffer layer is preferably a metal layer containing one or more elements selected from the group consisting of copper, nickel, titanium, nichrome, and chromium. When the film is made of a material that allows copper to diffuse, such as polyimide, selecting a material that inhibits copper diffusion into the film can prevent a decrease in adhesion. It is important to maintain the surface of the metal selected for the buffer layer, such as nickel, titanium, chromium, or nichrome, without oxidizing it before forming the copper layer on top. Specifically, after forming the metal layer as a buffer layer by sputtering, it is important to form the copper film while maintaining a vacuum without exposing it to the atmosphere. If the surface of the metal selected for the buffer layer, such as nickel, titanium, chromium, or nichrome, oxidizes, a stable metal oxide film is formed, which makes it difficult to form a metal bond with the interface with the copper layer formed on top, resulting in insufficient adhesion and possible peeling of the copper layer from the buffer layer. Therefore, it is important to prevent oxidation of the metal selected for the buffer layer, such as nickel, titanium, chromium, or nichrome.

The thickness of the buffer layer is preferably 5 nm to 40 nm, and more preferably 10 nm to 20 nm. A thickness of less than 5 nm may result in insufficient adhesion. On the other hand, a thickness of more than 40 nm increases the average crystal grain size of the buffer layer formed by sputtering. Depending on the type of metal, the copper layer formed on top of it may be affected by the size of the crystal grain size of the buffer layer, resulting in a larger average crystal grain size for the copper layer, making it difficult to control. Furthermore, for metals other than copper, a thickness of more than 40 nm makes it difficult to remove by copper etching, and a two-stage etching process may be required, in which an additional etching process dedicated to the buffer metal is added after the copper etching process.

The present invention will be described below based on examples. However, the present invention is not limited to these examples, and these examples may be modified or altered based on the spirit of the present invention, and such modifications are not excluded from the scope of the invention.

(Magnetron sputtering)
The film was placed in a batch-type vacuum deposition apparatus (EBH-800 manufactured by ULVAC), and a target of 50 mm x 550 mm was used. The vacuum level was adjusted to 5 x 10 ^-1 Pa or less in an argon gas atmosphere, and DC power was applied continuously for a time until a predetermined metal film thickness was achieved.

Alternatively, the film was placed in a roll-type vacuum deposition apparatus (EWC-060 manufactured by ULVAC), and a target of 70 mm x 550 mm was used. The vacuum level was adjusted to 1 x 10 ^-2 Pa or less in an argon gas atmosphere, and a DC power source was applied to form a metal layer.

Unless otherwise specified, sputtering and vacuum deposition were performed consecutively, and no contact with the air was allowed between the deposition of the buffer layer, copper layer, and anti-corrosion layer.

(Vacuum deposition)
The film was placed in a batch-type vacuum deposition apparatus (EBH-800 manufactured by ULVAC), and an amount of copper to achieve the desired thickness was placed on the deposition boat. After that, the chamber was evacuated to a vacuum of 9.0 × 10 ⁻³ Pa or less, and the deposition boat was heated to carry out vacuum deposition to form a copper layer.

Alternatively, the film was placed in a roll-type vacuum deposition device (EWC-060 manufactured by ULVAC) and vacuum deposition was performed at a conveying speed and output conditions that resulted in the copper layer thickness being the specified value, forming a copper layer.

(Moisture resistance test)
The metallized film was cut to a size of approximately 300 mm x approximately 80 mm and attached to a plastic plate. The film was then placed face down in a thermo-hygrostat (THC-120 manufactured by IMV) at 85°C and 85% RH to prevent water droplets from adhering to the film, and left for a predetermined period of time.

(Surface resistance measurement, calculation of resistance change rate)
The metallized film was cut into a size of approximately 300 mm x approximately 80 mm, and the surface resistance was measured at 10 locations on the anticorrosive layer side (or the copper layer side if no anticorrosive layer was provided) using a simple low resistivity meter (Loresta (registered trademark) EP MCP-T360, manufactured by Mitsubishi Chemical Analytech Corporation) by the four-terminal method, and the average value was used as the surface resistance value.

The rate of change ΔR was calculated using the following formula from the surface resistance R ₀ before the humidity resistance test and the surface resistance R after the humidity resistance test at 85°C and 85% RH. If the calculated rate of change was 20% or less, it was judged as ◯, and if it exceeded 20%, it was judged as ×.
ΔR=(R−R ₀ )/R ₀ .

(Anti-rust layer thickness)
A sample was prepared in which only the anticorrosive layer was vapor-deposited onto the film, and the transmittance at a wavelength of 555 nm was measured using a transmittance meter (Portable Black-and-White Transmission Densitometer Ihac-T5 manufactured by Ihara Electronics Co., Ltd.). The metal thickness was calculated using the Beer-Lambert law, applying it to the following formula. The extinction coefficient used in the calculation was 2.56.

I: Amount of light after passing through the thin film
I ₀ : Initial light intensity k: Extinction coefficient
Z: Film thickness (nm)
λ: Wavelength (nm).

(Chromaticity measurement, calculation of color difference ΔE)
The chromaticity of the surface was measured using a color difference meter (CM-2500d manufactured by Konica Minolta) with specular reflection (incident angle 8°, reflection angle 8°) and the L ^* a ^* b ^* color system was used.

The measurement results were applied to the following formula to calculate the color difference ΔE.

Measured values before humidity resistance test in an 85°C, 85% RH environment (L ₀ , a ₀ , b ₀ )
Measurement values after humidity resistance test in an 85°C, 85% RH environment (L, a, b)
When the color difference ΔE was 6.5 or less, there was no color change and it was judged as ◯, and when it exceeded 6.5, there was a large color change and it was judged as ×.

(Measuring the reflectance of the metal layer)
The reflectance of the metal layer was measured under the following conditions using a UV-Visible-Near-Infrared Spectrophotometer V-670 manufactured by JASCO Corporation. From the obtained spectral data, the reflectance at a wavelength of 800 nm was defined as R800, and the reflectance at a wavelength of 300 nm was defined as R300, and the reflectance ratio R800/R300 was calculated.
Measurement mode: Reflectance mode (5°)
Measurement wavelength range: 300 to 1,000 nm
Data acquisition interval: 0.5 nm
Scanning speed: 1,000 nm/min
UV/Vis bandwidth: 5.0 nm
NIR bandwidth: 20.0 nm.

(electric field shielding performance measurement)
The electric field shielding performance (dB) at 1 GHz was measured using the KEC method with an E5071C ENA network analyzer (manufactured by Agilent) for microwave and millimeter-wave band evaluation. The upper measurement limit was determined by sandwiching a 3 mm-thick copper plate between the materials. A measured electric field shielding performance of 10 dB or less is considered to have almost no electromagnetic wave shielding effect, and an electromagnetic wave shielding material is required to have an electric field shielding performance of 10 dB or more. A change of approximately 20% in the electric field shielding performance E0/Ei (Ei: incident electric field (V/m), E0: transmitted electric field (V/m)) corresponds to a 2 dB change in the measured electric field shielding performance. Therefore, a change of 2.0 dB or less compared to the initial measurement value is considered acceptable and marked with a circle. A change of more than 2.0 dB is considered to indicate that the initial performance has not been maintained and is marked with an X.

Example 1
Titanium was vapor-deposited to a thickness of 5 nm as a buffer layer by magnetron sputtering using a batch vacuum deposition apparatus (ULVAC EBH-800) on a 16 μm thick biaxially oriented polyethylene terephthalate film (Toray Industries, Inc., "Lumirror (registered trademark)" type: F68). The sputtering output was 5.0 kW using a DC power supply. A titanium 99.9% by weight sputtering target was used. Copper was then vacuum-deposited to a thickness of 100 nm by vacuum deposition. A copper 99.9% by weight raw material was used for the deposition. Titanium was then vapor-deposited to a thickness of 2 nm by magnetron sputtering as a rust-preventive layer. The sputtering output was 2.0 kW using a DC power supply. A titanium 99.9% by weight sputtering target was used.

The surface resistance _R0 of the metallized film produced in this manner was measured before a humidity resistance test in an 85°C, 85% RH environment and was found to be 0.252 Ω/□. Furthermore, the surface chromaticity ( _L0 , _a0 , _b0 ) before a humidity resistance test in an 85°C, 85% RH environment was measured and found to be (88.19, 13.85, 16.79). Furthermore, the reflectance R800 of the metal layer at a wavelength of 800 nm on the anticorrosive layer side was 91%, and the ratio R800/R300 was 5.0. Furthermore, the electric field shielding performance was measured and found to be 54.6 dB.

After that, humidity resistance tests were conducted in an environment of 85°C and 85% RH for 3, 7, and 28 days, and then the surface resistance, color, and electric field shielding performance of each sample were measured and a judgment was made based on the results.

After three days of humidity resistance testing, the surface resistance was 0.251 Ω/□, and the calculated change rate was -0.4%, resulting in a rating of Good. Meanwhile, the surface chromaticity (L, a, b) measured after humidity resistance testing in an 85°C, 85% RH environment was (84.87, 16.37, 21.58), and the calculated color difference ΔE was 6.36, resulting in a rating of Good. Furthermore, the electric field shielding performance measurement result was 54.1 dB, a change of -0.5 dB, resulting in a rating of Good.

After seven days of humidity resistance testing, the surface resistance was 0.268 Ω/□, and the calculated change rate was 6.3%, resulting in a rating of Good. Meanwhile, the surface chromaticity (L, a, b) measured after humidity resistance testing in an 85°C, 85% RH environment was (69.85, 17.86, 24.10), and the calculated color difference ΔE was 20.15, resulting in a rating of Bad. Furthermore, the electric field shielding performance measurement result was 55.6 dB, a change of 1.0 dB, resulting in a rating of Good.

After 28 days of humidity resistance testing, the surface resistance was 0.471 Ω/□, and the calculated rate of change was 87.0%, resulting in an X rating. Meanwhile, the surface chromaticity (L, a, b) measured after humidity resistance testing in an 85°C, 85% RH environment was (77.74, 15.28, 22.49), and the calculated color difference ΔE was 12.00, resulting in an X rating. Furthermore, the electric field shielding performance measurement result was 47.8 dB, a change of -6.8 dB, resulting in an X rating.

(Examples 2 and 12)
Metallized films were prepared and evaluated in the same manner as in Example 1, except that the substrate and anticorrosive layer thicknesses were as shown in Table 1 and the sputtering power for the anticorrosive layer was 3.1 kW. The results are shown in Tables 1 and 2.

Example 3
Metallized films were prepared and evaluated in the same manner as in Example 1, except that the thickness of the anticorrosive layer was set as shown in Table 1 and the sputtering power for the anticorrosive layer was set to 4.2 kW. The results are shown in Tables 1 and 2.

(Examples 4 to 7)
Metallized films were prepared and evaluated in the same manner as in Example 1, except that the thickness of the anticorrosive layer was set as shown in Table 1 and the sputtering power for the anticorrosive layer was set to 5.0 kW. The results are shown in Tables 1 and 2.

(Example 8)
Titanium was deposited as a buffer layer to a thickness of 5 nm on a 16 μm thick biaxially oriented polyethylene terephthalate film (Toray Industries, Inc., "Lumirror (registered trademark)" type: F68) by magnetron sputtering using a batch vacuum deposition apparatus (ULVAC, EBH-800). The sputtering output was 5.0 kW using a DC power supply. Copper was then vacuum-deposited to a thickness of 100 nm by vacuum deposition. After leaving the film exposed to the atmosphere for 8 hours, titanium was again deposited as a rust-preventive layer to a thickness of 5 nm by magnetron sputtering using a batch vacuum deposition apparatus (ULVAC, EBH-800). The sputtering output was 5.0 kW using a DC power supply. The evaluation results of the produced film are shown in Tables 1 and 2.

Example 9
Titanium was deposited as a buffer layer to a thickness of 5 nm on a 16 μm thick biaxially oriented polyethylene terephthalate film (Toray Industries, Inc., "Lumirror (registered trademark)" type: F68) by magnetron sputtering using a batch vacuum deposition apparatus (ULVAC, EBH-800). The sputtering output was 5.0 kW using a DC power supply. Copper was then vacuum-deposited to a thickness of 100 nm by vacuum deposition. After leaving the film exposed to the atmosphere for 8 hours, copper was again deposited to a thickness of 1 nm by magnetron sputtering using a batch vacuum deposition apparatus (ULVAC, EBH-800). Titanium was then deposited to a thickness of 5 nm as a rust-preventive layer by magnetron sputtering without being exposed to the atmosphere. The sputtering output was 2.0 kW for copper sputtering and 5.0 kW for titanium sputtering, using the same DC power supply for both copper and titanium. The evaluation results of the produced films are shown in Tables 1 and 2.

Example 10
A metallized film was prepared and evaluated in the same manner as in Example 2, except that no buffer layer was provided. The results are shown in Tables 1 and 2.

Example 11
Metallized films were prepared and evaluated in the same manner as in Example 2, except that the substrate and anticorrosive layer thicknesses were as shown in Table 1 and copper was vacuum-deposited to a thickness of 1,000 nm. The results are shown in Tables 1 and 2.

(Comparative Example 1)
Titanium was vapor-deposited to a thickness of 5 nm as a buffer layer by magnetron sputtering using a batch vacuum deposition apparatus (EBH-800 manufactured by ULVAC) on a 16 μm thick biaxially oriented polyethylene terephthalate film (manufactured by Toray Industries, Inc., "Lumirror (registered trademark)" type: F68). The sputtering output was 5.0 kW using a DC power supply. Copper was then vacuum-deposited to a thickness of 100 nm by vacuum deposition. No anticorrosion layer was then formed.

The surface resistance _R0 of the metallized film produced in this manner was measured before a humidity resistance test in an 85°C, 85% RH environment and was found to be 0.213 Ω/□. Furthermore, the surface chromaticity ( _L0 , a0, _b0 ) before a humidity resistance test in an 85°C, 85% RH environment was measured and found to be (88.47, _13.29 , 16.18). Furthermore, the reflectance R800 of the metal layer at a wavelength of 800 nm on the copper layer side was 94%, and the ratio R800/R300 was 3.5. Furthermore, the electric field shielding performance was measured and found to be 54.5 dB.

After that, humidity resistance tests were conducted in an environment of 85°C and 85% RH for 3, 7, and 28 days, and then the surface resistance, color, and electric field shielding performance of each sample were measured and a judgment was made based on the results.

After three days of humidity resistance testing, the surface resistance was 0.723 Ω/□, and the calculated change rate was 239%, resulting in an X rating. Meanwhile, the surface chromaticity (L, a, b) measured after humidity resistance testing in an 85°C, 85% RH environment was (57.43, 10.89, 21.44), and the calculated color difference ΔE was 31.57, resulting in an X rating. Furthermore, the electric field shielding performance measurement result was 44.0 dB, a change of -10.5 dB, resulting in an X rating.

After seven days of humidity resistance testing, the surface resistance was beyond the resistivity meter's range and could not be measured, resulting in an X rating. Meanwhile, the surface chromaticity (L, a, b) measured after humidity resistance testing in an 85°C, 85% RH environment was (50.65, 6.80, 20.03), and the calculated color difference ΔE was 38.57, resulting in an X rating. Furthermore, the electric field shielding performance fluctuated below 10 dB, making it difficult to determine a numerical value, but since there was almost no electric field shielding effect below 10 dB, it was deemed to be 0 dB. The change was -54.5 dB, resulting in an X rating.

After 28 days of humidity resistance testing, the surface resistance was beyond the resistivity meter's range and could not be measured, resulting in an X. Meanwhile, an attempt was made to measure the surface chromaticity (L, a, b) after humidity resistance testing in an 85°C, 85% RH environment, but the metal film had fallen off due to corrosion, making it impossible to measure, resulting in an X. Furthermore, the electric field shielding performance fluctuated below 10 dB, making it difficult to determine a numerical value, but since there was almost no electric field shielding effect below 10 dB, it was deemed to be 0 dB. The change was -54.5 dB, resulting in an X.

(Comparative Examples 2 and 3)
Metallized films were prepared and evaluated in the same manner as in Example 1, except that the thickness of the anticorrosive layer was as shown in Table 1. The results are shown in Tables 1 and 2. For both Comparative Examples 2 and 3, the surface resistance was beyond the range of the low-efficiency meter and could not be measured 7 and 28 days after the humidity resistance test. Similarly, the electric field shielding performance was measured at 10 dB or less, and the measured values fluctuated, making it difficult to determine a numerical value. However, since there was almost no electric field shielding effect below 10 dB, it was considered to be 0 dB. Furthermore, the surface chromaticity was not measurable 28 days after the humidity resistance test because the metal film had fallen off due to corrosion.

(Comparative Example 4)
Titanium was vapor-deposited to a thickness of 5 nm as a buffer layer by magnetron sputtering using a batch vacuum deposition apparatus (ULVAC EBH-800) on a 16 μm thick biaxially oriented polyethylene terephthalate film (Toray Industries, Inc., "Lumirror (registered trademark)" type: F68). The sputtering output was 5.0 kW using a DC power supply. Copper was then vacuum-deposited to a thickness of 100 nm by vacuum deposition. Titanium was then vapor-deposited to a thickness of 10 nm as a rust-preventive layer by magnetron sputtering. The sputtering output was 5.0 kW using a DC power supply. The evaluation results of the produced films are shown in Tables 1 and 2.

(Comparative Example 5)
A 16 μm thick biaxially oriented polyethylene terephthalate film (Toray Industries, Inc., "Lumirror (registered trademark)" type: F68) was vacuum-deposited with copper to a thickness of 200 nm by vacuum deposition using a roll-type vacuum deposition apparatus (ULVAC, EWC-060). Subsequently, a 50-fold methanol-diluted solution of a benzotriazole-based rust inhibitor (Tatsuta Electric Wire Co., Ltd., "Pal C": an approximately 10% alcohol solution of an approximately 2:1 mixture of benzotriazole and its monoethanolamine salt) was applied using a 200-mesh gravure coater and dried at 70°C to complete the benzotriazole treatment on the surface. The evaluation results of the prepared film are shown in Tables 1 and 2.

1 film 2 buffer layer 3 copper layer 4 anti-corrosion layer

Claims (17)

A metallized film having a copper layer and a rust-preventive layer in this order from the film side on at least one surface of the film,
the anticorrosion layer contains at least one selected from the group consisting of metallic titanium, titanium oxide, and mixtures thereof, the thickness of the anticorrosion layer is 2 nm or more and 8 nm or less, and the reflectance of the anticorrosion layer side at a wavelength of 800 nm is 82% or more,
A metallized film having a surface resistance change rate of 20% or less on the rust-preventive layer side after 3 days in an 85°C, 85% RH environment, and a color difference ΔE of 6.5 or less after 3 days in said environment. The metallized film of claim 1, wherein the anticorrosive layer is made of titanium metal, titanium oxide, or a mixture thereof. the anticorrosive layer side has a reflectance of 82% or more at a wavelength of 800 nm;
3. The metallized film according to claim 1, wherein the ratio R800/R300 of the reflectance R800 at a wavelength of 800 nm to the reflectance R300 at a wavelength of 300 nm is 5.0 or more and 10.0 or less. 4. The metallized film according to claim 1 , wherein the surface resistance change rate on the anticorrosive layer side after 7 days in an 85°C, 85% RH environment is 20% or less, and the color difference ΔE after 7 days in said environment is 6.5 or less. 5. The metallized film according to claim 1, wherein the anticorrosive layer has a thickness of 3 nm or more and 5 nm or less. 6. The metallized film according to claim 1 , wherein the surface resistance change rate of the anticorrosive layer side after 28 days in an 85°C, 85% RH environment is 20% or less, and the color difference ΔE after 28 days in said environment is 6.5 or less. 7. The metallized film according to claim 1, wherein the anticorrosive layer has a thickness of 3 nm or more and 4 nm or less. 8. The metallized film of claim 1, further comprising a buffer layer between the copper layer and the film. 9. The metallized film of claim 8 , wherein the buffer layer comprises at least one selected from the group consisting of copper, titanium, nickel, nichrome, and chromium. 10. The metallized film according to claim 1, wherein the copper layer has a thickness of 0.05 μm or more and 3.0 μm or less. 11. The metallized film according to claim 1, wherein the film is made of at least one material selected from the group consisting of polyester, polyimide, polyphenylene sulfide, and polypropylene. 12. The metallized film of claim 1, wherein the thickness of the film is 1 μm or more and 200 μm or less. 13. The metallized film of claim 1, wherein the thickness of the film is 1 μm or more and 10 μm or less. 13. The metallized film of claim 1, wherein the thickness of the film is 10 μm or more and 50 μm or less. 13. The metallized film of claim 1, wherein the thickness of the film is 50 μm or more and 200 μm or less. 16. The method for producing a metallized film according to claim 1, wherein the copper layer and the anticorrosive layer are formed by vacuum deposition or sputtering. 17. A method for producing a metallized film according to claim 16 , wherein after vapor deposition of a copper layer, the film is exposed to the atmosphere, copper sputtering is again performed in a vacuum, and then titanium sputtering is performed continuously without being exposed to the atmosphere.