Copper foil for electromagnetic wave shield, method for producing same, and electromagnetic wave shield

Abstract

Provided is a copper foil for an electromagnetic wave shield in which high corrosion resistance is obtained and in which surface wettability is controlled. A copper foil (50) for an electromagnetic wave shield according to one embodiment of the present invention comprises a copper foil base body (10) and a surface treatment layer (40) formed on one or both surfaces of the copper foil base body (10), wherein: the surface treatment layer (40) is provided with a nickel layer (20) containing nickel or a nickel-phosphorus alloy, and a hydrophilic rust prevention treatment layer (30) formed on the surface of the nickel layer (20) on the side opposite from the surface facing the copper foil base body (10); and when the surface roughness of a surface (40a) of the surface treatment layer (40) is measured in conformance with the method specified in ISO 25178, the developed surface area ratio Sdr is 0.01-20%, and the peak density Spd [1 / μm2] of peaks is 0.5-10.

Description

Copper foil for electromagnetic wave shielding, its manufacturing method, and electromagnetic wave shielding

[0001] The present invention relates to a copper foil used for an electromagnetic wave shield that can be used in electronic devices, etc., a method for producing the same, and an electromagnetic wave shield using the copper foil for electromagnetic wave shielding.

[0002] In recent years, signals have become increasingly high-frequency, increasing the demand for electromagnetic wave shields to be installed in electronic devices. Copper (Cu) has high electrical conductivity and therefore excellent shielding properties, and copper foils are widely used as electromagnetic wave shields. Copper foils used as electromagnetic wave shields are required to have higher corrosion resistance than before due to increased performance and multi-functionality. However, since it is difficult to ensure corrosion resistance with copper alone, the surface is sometimes treated with nickel (Ni) (see Patent Document 5).

[0003] Furthermore, when copper foil is used to shield electromagnetic waves in electronic devices, it is often coated with an adhesive layer on the surface of the copper foil. Therefore, high adhesion between the copper foil and the adhesive layer is required. To improve adhesion between the copper foil and the adhesive layer, it is necessary to increase the surface free energy, i.e., surface wettability, of the copper foil surface. However, the surface of nickel-treated copper foil is usually hydrophobic, resulting in low surface wettability and poor adhesion of adhesive layers, etc.

[0004] In recent years, electromagnetic wave shields have increasingly been used as emergency shields by being attached to electronic devices. Therefore, long-term storage of copper foils for electromagnetic wave shielding is required in preparation for sudden demand. During such long-term storage, oxidation and discoloration due to moisture adsorbed on the copper foil surface become a significant problem. Meanwhile, Patent Document 1 discloses copper foils with controlled surface wettability, but does not consider controlling the surface wettability of copper foils that have been subjected to corrosion-resistant treatments such as nickel treatment.

[0005] Furthermore, Patent Documents 2 to 4 disclose surface-treated copper foils for circuits that utilize the anchor effect to improve adhesion to insulating resin substrates. However, when the surface free energy of the copper foil is increased enough to obtain the anchor effect, the surface wettability becomes too high, and it has become clear that the copper foil is oxidized and discolored by moisture adsorbed on the copper foil surface. Furthermore, Patent Document 5 discloses an electromagnetic wave shielding composite using Ni-treated copper foil, but does not mention surface wettability, and it has become clear that the same problem occurs.

[0006] Japanese Patent No. 6246398 International Publication No. 2022 / 255420 Japanese Patent No. 7177956 Japanese Patent No. 6905157 Japanese Patent No. 5000792

[0007] In order to solve the above-mentioned problems, an object of the present invention is to provide a copper foil for electromagnetic shielding having high corrosion resistance and controlled surface wettability, an electromagnetic shield using the copper foil for electromagnetic shielding, and a method for producing the copper foil for electromagnetic shielding.

[0008] The copper foil for electromagnetic shielding according to one embodiment of the present invention is a copper foil having a copper foil substrate and a surface treatment layer formed on one or both sides of the copper foil substrate, the surface treatment layer comprising a nickel layer containing nickel or a nickel-phosphorus alloy, and a hydrophilic rust-proofing treatment layer formed on the side of the nickel layer opposite to the side facing the copper foil substrate, and the surface roughness of the surface treatment layer, when measured in accordance with the method specified in ISO 25178, is such that the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

[0009] An electromagnetic wave shield according to another aspect of the present invention comprises the electromagnetic wave shielding copper foil according to the above aspect and an adhesive layer bonded to the surface of the electromagnetic wave shielding copper foil having the surface treatment layer.

[0010] A method for producing a copper foil for electromagnetic shielding according to another embodiment of the present invention comprises a nickel plating step of applying nickel plating treatment to both sides or one side of a copper foil substrate, the nickel plating treatment including a non-uniform nickel plating treatment for forming an uneven shape and a uniform nickel plating treatment for forming a smooth surface, to form a nickel layer on the copper foil substrate, and a rust prevention treatment step of applying a hydrophilic rust prevention treatment to the surface of the nickel layer to form a hydrophilic rust prevention treatment layer on the nickel layer, wherein the surface roughness of the surface of the hydrophilic rust prevention treatment layer is such that, when measured in accordance with the method specified in ISO 25178, the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

[0011] According to the present invention, it is possible to provide an electromagnetic wave shielding copper foil having high corrosion resistance and controlled surface wettability, an electromagnetic wave shield using the electromagnetic wave shielding copper foil, and a method for producing the electromagnetic wave shielding copper foil.

[0012] Fig. 1 is a schematic diagram of an electromagnetic shielding copper foil having a surface treatment layer formed on one side of a copper foil substrate according to one embodiment of the present invention. Fig. 2 is a cross-sectional view showing the configuration of an electromagnetic shielding copper foil having a surface treatment layer formed on one side of a copper foil substrate according to one embodiment of the present invention. Fig. 3 is a cross-sectional view showing the configuration of an electromagnetic shielding copper foil having a surface treatment layer formed on both sides of a copper foil substrate according to another embodiment of the present invention. Fig. 4 is a schematic diagram showing a method for producing an electromagnetic shielding copper foil according to one embodiment of the present invention.

[0013] An electromagnetic wave shielding copper foil according to one embodiment of the present invention will be described with reference to Fig. 1. The embodiment described below is merely an example of the present invention. Various modifications or improvements can be made to this embodiment, and such modifications or improvements can also be included in the present invention.

[0014] 1, the copper foil 50 for electromagnetic shielding according to this embodiment is a copper foil having a copper foil substrate 10 and a surface treatment layer 40 on one or both sides of the copper foil substrate 10, the surface treatment layer 40 comprising a nickel layer 20 containing nickel or a nickel-phosphorus alloy, and a hydrophilic rust-proofing treatment layer 30 formed on the surface of the nickel layer 20 opposite to the surface facing the copper foil substrate 10. The surface roughness of the surface 40a of the surface treatment layer 40, when measured in accordance with the method specified in ISO 25178, is such that the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

[0015] With this configuration, the electromagnetic wave shielding copper foil 50 according to this embodiment not only has high corrosion resistance, but also has good oxidation resistance and long-term storage stability because the surface wettability can be controlled within a suitable range.

[0016] The electromagnetic wave shielding copper foil 50 in FIG. 1 is an example in which the surface treatment layer 40 is formed on one of the two surfaces of the copper foil, but the electromagnetic wave shielding copper foil according to the present invention is not limited to this example.

[0017] The electromagnetic shielding copper foil according to this embodiment will be described in further detail below with reference to Fig. 2. The electromagnetic shielding copper foil 50 in Fig. 2 is an example in which a surface treatment layer 40 is formed on one of the two surfaces of a copper foil substrate 10, and the electromagnetic shielding copper foil 50' in Fig. 3 is an example in which a surface treatment layer 40 is formed on both surfaces of the copper foil substrate 10.

[0018] (Copper Foil) The thickness and type of the copper foil substrate 10, which is the raw material for the electromagnetic wave shielding copper foil 50 according to this embodiment, are not particularly limited and can be appropriately determined based on the thickness required for the final electromagnetic wave shielding, etc. The thickness of the copper foil substrate 10 may be in the general thickness range of 6 μm to 75 μm. Furthermore, if the type of copper foil substrate 10 is a copper foil substrate generally known as a double-sided smooth copper foil, the surface roughness can be easily controlled.

[0019] (Surface Treatment Layer) The surface treatment layer 40 comprises a nickel layer 20 containing nickel or a nickel-phosphorus alloy formed on the surface of the copper foil substrate 10, which is the raw material, and a hydrophilic rust-proofing treatment layer 30 formed on the surface of the nickel layer 20 opposite to the surface facing the copper foil substrate 10. The surface treatment layer 40 can be formed by subjecting the above-mentioned copper foil substrate 10 to a nickel plating treatment and a hydrophilic rust-proofing treatment in this order.

[0020] (Nickel Layer) The nickel layer 20 is formed on one or both sides of the copper foil substrate 10. When treating one side, it may be the S side (shiny side, the side that faces the drum during production of electrolytic copper foil) or the M side (matte side, the side that faces the deposition side during production of electrolytic copper foil) of the copper foil substrate 10. Since the copper foil substrate 10 generally tends to curl toward the M side, it is preferable to form the nickel layer 20 on the S side to reduce curling, but the nickel layer may be formed on either side depending on the actual production conditions.

[0021] The thickness of the nickel layer 20 is not particularly limited, but may be 10 nm or more and 300 nm or less, or 10 nm or more and 80 nm or less. If the thickness of the nickel layer 20 is 10 nm or more, improved corrosion resistance can be expected. If the thickness of the nickel layer 20 is 300 nm or less, curling of the copper foil surface due to internal stress of the nickel is less likely to occur, improving handleability during production. If the thickness is 80 nm or less, in addition to the above effects, the specific conductivity of the copper foil surface is more likely to be reduced, making it easier to further improve electromagnetic wave shielding properties.

[0022] When forming the nickel layer 20, for example, it can be formed by using a non-uniform nickel plating process that forms an uneven shape and a uniform nickel plating process that forms a smooth surface. The non-uniform nickel plating process and the uniform nickel plating process may be performed in either order, or they may be performed alternately. Either method can adjust the surface roughness according to the present embodiment.

[0023] (Hydrophilic Rust-Proof Treatment Layer) The hydrophilic rust-proof treatment layer 30 is formed by performing a hydrophilic rust-proof treatment on the surface of the nickel layer 20 opposite the surface facing the copper foil substrate 10. This hydrophilic rust-proof treatment may also be performed on the surface of the copper foil substrate that is not treated with the nickel layer. The rust-proof treatment may be hydrophilic and rust-proof, and examples thereof include plating treatments containing metals such as chromium (Cr) or zinc (Zn), and surface treatments using silane coupling agents, benzotriazole, phosphates, etc. Considering the balance between rust-preventive performance and surface free energy, the hydrophilic rust-proof treatment layer 30 preferably contains chromium as a single element or an alloy. Chromium plating methods include chromate immersion treatments and electroplating.

[0024] Examples of the silane coupling agent include epoxy silane coupling agents, amino silane coupling agents, vinyl silane coupling agents, methacrylic silane coupling agents, acrylic silane coupling agents, azole silane coupling agents, styryl silane coupling agents, ureido silane coupling agents, mercapto silane coupling agents, sulfide silane coupling agents, and isocyanate silane coupling agents. One type of silane coupling agent may be used alone, or two or more types may be used in combination.

[0025] (Developed Surface Area Ratio Sdr and Peak Density Spd) When the surface roughness of the surface 40a of the surface treatment layer 40 is measured in accordance with the method specified in ISO 25178, the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less. Here, the developed surface area ratio Sdr represents the degree to which the developed area (surface area) of the defined region has increased relative to the area of ​​the defined region. On a completely smooth surface, the area of ​​the defined region and the developed area are the same, so Sdr is zero. On a surface with irregularities, the developed area is larger than the area of ​​the defined region, so Sdr is large. Furthermore, the peak density Spd represents the number of convex portions present in a given area.

[0026] If the developed surface area ratio Sdr of the surface 40a of the surface treatment layer 40 is 0.01% or more, the surface free energy of the surface treatment layer 40 is unlikely to decrease, and therefore the surface wettability is unlikely to decrease. If the developed surface area ratio Sdr is 20% or less, it is easy to prevent a decrease in oxidation resistance due to excessive trapping of moisture, etc. on the copper foil surface. Furthermore, the developed surface area ratio Sdr may be 7.9% or less. Within this range, the surface free energy of the surface 40a can be more suitably controlled.

[0027] The peak density Spd [1 / μm ２ If the peak density Spd [1 / μm ２ If Spd[1 / μm] is 10 or less, not only is it easy to control the surface free energy, but it is also difficult to trap moisture and the like excessively, so that it is easy to suppress a decrease in oxidation resistance. ２ ] may be 1.5 or more and 8.0 or less. Within this range, the surface free energy of the surface 40a can be controlled more suitably.

[0028] The surface 40a of the surface treatment layer 40 may have an arithmetic mean roughness Sa [μm] of 0.05 to 0.18 when measured in accordance with the method specified in ISO 25178. Within this range, not only can the surface free energy be suitably controlled, but also appearance defects such as rubbing during the manufacturing process of the copper foil and the electromagnetic wave shield can be reduced.

[0029] As shown in FIG. 4( c), the electromagnetic shielding copper foil 50 according to this embodiment, after the nickel layer 20 is formed, has numerous very fine convex portions from a microscopic perspective, as represented by the Spd value, and has a nearly flat surface from a macroscopic perspective, as represented by the Sdr value. When a hydrophilic rust-proofing treatment is applied to the surface of such a nickel layer 20, the convex portions are more susceptible to the rust-proofing treatment than the flat portions. Therefore, as shown in FIG. 4( d), the thickness of the hydrophilic rust-proofing layer 30 is greater in the convex portions, making them hydrophilic. On the other hand, the flat portions are hydrophobic because they do not have the hydrophilic rust-proofing layer 30 or the thickness of the hydrophilic rust-proofing layer 30 is very small. Therefore, the surface 40 a of the electromagnetic shielding copper foil 50 according to this embodiment is in a state in which both hydrophilic and hydrophobic portions are present. This is believed to enable the surface 40 a of the electromagnetic shielding copper foil 50 according to this embodiment to have a surface free energy that can achieve both surface wettability and corrosion resistance.

[0030] (Method of Measuring Surface Roughness) The developed surface area ratio Sdr, the peak density Spd, and the arithmetic mean roughness Sa of the surface 40a of the electromagnetic wave shielding copper foil 50 according to this embodiment can be measured for the surface of the surface treatment layer 40 using a laser microscope in accordance with ISO25178.

[0031] (Ratio of Nickel Content to the Sum of Nickel Content and Chromium Content) The ratio of the nickel content to the sum of the nickel content and the chromium content in the surface treatment layer 40 according to this embodiment may be 90 mass % or more. Under such conditions, it becomes easier to control the surface free energy of the surface 40a of the surface treatment layer 40.

[0032] (Method for Measuring Nickel and Chromium Contents) The nickel and chromium contents in the surface treatment layer 40 according to this embodiment can be measured by analyzing a certain surface of the surface treatment layer 40 using fluorescent X-ray analysis. Specifically, the nickel and chromium contents are quantified using calibration curves obtained from known standard samples of these metals. From the obtained nickel and chromium contents, the ratio of the nickel content to the sum of the nickel content and the chromium content in the surface treatment layer 40 is calculated.

[0033] (Surface Free Energy) The surface free energy of the surface 40a of the surface treatment layer 40 in the electromagnetic shielding copper foil 50 according to this embodiment may be 41 mN / m or more and 64 mN / m or less. If the surface free energy is 41 mN / m or more, when the surface 40a of the electromagnetic shielding copper foil 50 is bonded to an adhesive layer to form an electromagnetic shield, adhesion to the adhesive layer is likely to be improved. If the surface free energy is 64 mN / m or less, adhesion of moisture to the surface 40a is suppressed, and therefore deterioration of oxidation resistance and long-term storage stability is likely to be prevented.

[0034] (Method for Measuring Surface Free Energy) The surface free energy of the surface 40a of the surface treatment layer 40 according to this embodiment can be measured using a dyne pen. A dyne pen is a pen equipped with ink having a specific surface free energy. When a straight line is drawn on the surface of a sample with the dyne pen, if the surface repels the ink, this means that the surface has a lower surface free energy than the ink, and if the ink is absorbed, this means that the surface has a surface free energy equal to or greater than that of the ink.

[0035] The surface free energy is evaluated based on whether a straight line drawn with a dyne pen on the surface 40a blends with the surface. First, dyne pens with different surface free energies, such as 41 mN / m, 44 mN / m, 48 mN / m, 56 mN / m, 60 mN / m, 64 mN / m, and 68 mN / m, are prepared. Next, five 5 cm straight lines are drawn on the surface 40a with the dyne pen in order of decreasing surface free energy. Next, the drawn straight lines are visually observed, and the surface free energy of the dyne pen where all five lines blend with the surface is recorded. The highest surface free energy among the recorded surface free energies is taken as the surface free energy of the copper foil.

[0036] (Electromagnetic Wave Shielding) An electromagnetic wave shield according to another aspect of the present invention comprises the copper foil for electromagnetic wave shielding according to the above aspect and an adhesive layer bonded to the surface of the copper foil for electromagnetic wave shielding having the surface treatment layer. The surface free energy of the surface treatment layer of the copper foil for electromagnetic wave shielding according to the present invention easily satisfies the surface free energy required for a general adhesive layer. Therefore, adhesion to the adhesive layer can be improved.

[0037] (Method for Manufacturing Copper Foil for Electromagnetic Wave Shielding) The method for manufacturing the copper foil 50 for electromagnetic wave shielding according to this embodiment includes a nickel plating process of performing nickel plating on both or one side of the copper foil substrate 10, including a non-uniform nickel plating process for forming an uneven shape and a uniform nickel plating process for forming a smooth surface, to form a nickel layer 20 on the copper foil substrate 10, and a rust prevention process of performing a hydrophilic rust prevention treatment on the surface of the nickel layer 20 to form a hydrophilic rust prevention treatment layer 30 on the nickel layer 20. The surface roughness of the surface 40a of the hydrophilic rust prevention treatment layer 30, when measured in accordance with the method specified in ISO 25178, is such that the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

[0038] As the copper foil substrate, it is preferable to use electrolytic copper foil or rolled copper foil, which has a smooth and glossy surface without large irregularities, as a raw material. Among them, electrolytic copper foil is preferred from the viewpoints of productivity and cost. Furthermore, it is preferable to use electrolytic copper foil. The surface of the drum-shaped cathode used in the production of electrolytic copper foil is polished with a buff of #1000 to #2500.

[0039] Next, one or both sides of the prepared copper foil substrate are subjected to nickel plating. As an example of a preferred manufacturing method, the nickel layer 20 can be formed by a non-uniform nickel plating process that forms an uneven shape and a uniform nickel plating process that forms a smooth surface. The non-uniform nickel plating process and the uniform nickel plating process may be performed in either order, or may be performed alternately.

[0040] As an example, as shown in FIG. 4, a method for manufacturing a copper foil for electromagnetic shielding will be described in which one surface of a copper foil substrate 10 is subjected to a non-uniform nickel plating process to form a non-uniform nickel plating 21 (FIG. 4(b)), and then a uniform nickel plating process is performed to form a uniform nickel plating 22 (FIG. 4(c)), thereby forming a nickel layer 20.

[0041] For example, plating conditions that can form fine irregularities can be selected for the non-uniform nickel plating process to form the non-uniform nickel plating 21. Specific examples of such conditions include electroplating performed at a high current density for a short time using a plating solution that does not contain boric acid or the like. While boric acid or the like is typically used as an additive for uniform nickel plating baths, non-uniform plating can be achieved by deliberately omitting boric acid or the like. Furthermore, in electroplating, the surface roughness can be controlled by varying the current density and treatment time. In particular, electroplating performed at a high current density for a short time can instantly plate nickel on copper foil in a burnt-like manner. Plating under the above conditions can produce non-uniform nickel plating, i.e., multiple fine irregularities on the surface, as shown in FIG. 4(b). An example of conditions for the non-uniform nickel plating process is shown below.

[0042] (Heterogeneous nickel plating conditions) Bath composition: nickel sulfate (10 to 80 g / L in terms of nickel atoms) Bath pH: 2.5 to 5.5 Bath temperature: 20 to 60°C Current density: 10 to 20 A / dm ２ Current application time: 0.1 to 0.5 seconds

[0043] Next, as shown in FIG. 4( c), a uniform nickel plating process is performed on the surface on which the non-uniform nickel plating 21 has been formed. Examples of the uniform nickel plating process include ordinary electrolytic plating, electroless plating, and sputtering. The nickel plating in this case may be an alloy containing phosphorus. By performing such a uniform nickel plating process, a uniform nickel plating 22 can be formed that conforms to the fine uneven shape formed by the non-uniform nickel plating process. In this way, the nickel layer 20 can be formed. An example of the conditions for the uniform nickel plating process is shown below.

[0044] (Uniform nickel plating conditions) Bath composition: nickel sulfate (20 to 60 g / L in terms of nickel atoms), boric acid (10 to 40 g / L), sodium hypophosphite monohydrate (PO ２ (Converted to 1 to 15 g / L for Ni alloys containing phosphorus) Bath pH: 3 to 5 Bath temperature: 15 to 60°C Current density: 0.5 to 5.0 A / dm ２ Current application time: 2 to 50 seconds

[0045] The nickel layer 20 can be formed on one or both sides of the copper foil substrate 10. When treating one side, it may be on the S side or the M side of the copper foil substrate 10. Since the copper foil substrate 10 generally tends to curl toward the M side, it is preferable to form the nickel layer 20 on the S side in order to reduce curling, but the nickel layer 20 may be appropriately selected depending on the actual manufacturing situation.

[0046] Next, a rust prevention treatment step is performed in which the surface of the nickel layer 20 is subjected to a hydrophilic rust prevention treatment to form a hydrophilic rust prevention layer 30 on the nickel layer 20. The rust prevention treatment may be hydrophilic and rust-resistant, and examples thereof include plating treatments containing metals such as chromium or zinc, and surface treatments using silane coupling agents or benzotriazole. Considering the balance between rust prevention performance and surface free energy, the hydrophilic rust prevention treatment is preferably treatment using chromium alone or an alloy. Examples of chromium plating methods include chromate immersion treatment and electroplating. When chromium is electroplated, the following two types of plating conditions are given as examples.

[0047] (Cr plating condition 1) Bath composition: chromium (VI) oxide (2 to 10 g / L in terms of Cr) Bath pH: 1.5 to 3.0 Bath temperature: 20 to 40°C Current density: 2.0 to 8.0 A / dm ２ Current application time: 2 to 5 seconds

[0048] (Cr plating condition 2) Bath composition: chromium (VI) oxide (2 to 10 g / L in terms of Cr), zinc sulfate heptahydrate (30 to 150 ppm in terms of Zn), sodium hydroxide (10 to 30 g / L) Bath pH: 9.0 to 12.0 Bath temperature: 30 to 40°C Current density: 2.0 to 8.0 A / dm ２ Current application time: 2 to 5 seconds

[0049] In the method for producing the copper foil for electromagnetic shielding according to this embodiment, the surface roughness of the surface 40a of the copper foil for electromagnetic shielding 50 is, when measured in accordance with the method specified in ISO 25178, such that the developed surface area ratio Sdr is 0.01% or more and 20% or less, the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

[0050] When the developed surface area ratio Sdr of the surface 40a is 0.01% or more, the surface free energy of the surface treatment layer is unlikely to decrease, and therefore the surface wettability is unlikely to decrease. When the developed surface area ratio Sdr is 20% or less, it is easy to prevent a decrease in oxidation resistance due to excessive trapping of moisture, etc. on the copper foil surface. Furthermore, when the peak density Spd is 0.5 or more and 10 or less, the surface wettability can be suitably controlled.

[0051] Furthermore, the copper foil surface-treated by the method for producing a copper foil for electromagnetic shielding according to this embodiment can be suitably used as an electromagnetic shield. Specifically, for example, the copper foil for electromagnetic shielding can be attached to a common adhesive such as an acrylic, epoxy, or urethane adhesive filled with a conductive filler, and then attached to the housing of an electronic device in the form of a release film.

[0052] Although the embodiments of the present invention have been described above, the above embodiments are merely examples of the present invention. The present invention includes all aspects encompassed by the concept of the present invention and the scope of the claims, and various modifications can be made within the scope of the present invention.

[0053] The present invention will be described in more detail below with reference to Examples and Comparative Examples. The electromagnetic wave shielding copper foils of Examples 1 to 28 and Comparative Examples 1 to 11 were obtained by the following procedure.

[0054] (Example 1) (1) Copper Foil Substrate A roll of electrolytic copper foil (double-sided smooth copper foil) having a thickness of 12 μm was produced as a copper foil substrate, which is a raw material for producing copper foil for electromagnetic wave shielding, using the following cathode and anode and a copper sulfate electrolyte having the following composition under the following electrolysis conditions. The surface of the electrolytic copper foil produced here was adjusted so that the ten-point average roughness Rzjis defined in JIS B 0601:2001 was 2.0 μm on both sides.

[0055] <Cathode and anode> Cathode: Titanium rotating drum with surface roughness adjusted by buffing with #1000 to #2000 grit Anode: Dimensionally stable anode DSA (registered trademark) <Electrolyte composition> Copper sulfate pentahydrate: 80 g / L in terms of copper (atom) Sulfuric acid: 60 g / L Chlorine concentration: 15 mg / L (Additives) ・3-mercapto-1-propanesulfonic acid sodium: 2.5 mg / L ・Hydroxyethyl cellulose: 10 mg / L ・Low molecular weight glue (molecular weight 3000): 50 mg / L <Electrolysis conditions> Solution temperature: 60°C Current density: 40 A / dm ２

[0056] (2) Formation of Surface Treatment Layer A surface treatment layer consisting of a nickel layer and a hydrophilic rust-proofing layer was formed on the S-side of the copper foil substrate. First, a non-uniform nickel plating was formed by electroplating at a high current density for a short time. Then, the surface on which the non-uniform nickel plating had been formed was plated with a nickel-phosphorus alloy by a uniform nickel plating process to form a nickel layer. The thickness of the nickel layer was 50 nm. The plating conditions are shown below.

[0057] (Heterogeneous nickel plating conditions) Bath composition: nickel sulfate (25 g / L in terms of nickel atoms) Bath pH: 3.0 Bath temperature: 25°C Current density: 10 A / dm ２ Current application time: 0.1 s

[0058] (Uniform nickel plating conditions) Bath composition: nickel sulfate (25 g / L in terms of nickel atoms), boric acid (30 g / L), sodium hypophosphite monohydrate (PO ２ (equivalent to 5 g / L for Ni alloys containing phosphorus) Bath pH: 3.8 Bath temperature: 25°C Current density: 2.0 A / dm ２ Current application time: 13s

[0059] Finally, the surface on which the nickel layer was formed was subjected to chrome plating as a hydrophilic rust-proofing treatment to form a hydrophilic rust-proofing layer, thereby obtaining the copper foil for electromagnetic wave shielding of Example 1.

[0060] Examples 2 to 5 Electromagnetic shielding copper foils of Examples 2 to 5 were obtained in the same manner as in Example 1, except that the current application time for non-uniform nickel plating was changed as shown in Table 1.

[0061] Examples 6 to 8 Electromagnetic shielding copper foils of Examples 6 to 8 were obtained in the same manner as in Example 1, except that a plating bath was used in which sodium hypophosphite monohydrate was omitted from the conditions for uniform nickel plating, thereby plating nickel alone, and the current application time for non-uniform nickel plating was changed as shown in Table 1.

[0062] (Uniform nickel plating conditions) Bath composition: nickel sulfate (25 g / L in terms of nickel atoms), boric acid (30 g / L) Bath pH: 3.8 Bath temperature: 25°C Current density: 2.0 A / dm ２ Current application time: 13s

[0063] (Examples 9 to 11) Electromagnetic shielding copper foils of Examples 9 to 11 were obtained in the same manner as in Example 1, except that the surface to be plated was the M side of the copper foil and the current application time for the non-uniform nickel plating treatment was changed as shown in Table 1.

[0064] (Examples 12 and 13) Electromagnetic shielding copper foils of Examples 12 and 13 were obtained in the same manner as in Example 1, except that the surfaces to be plated were both the S and M surfaces of the copper foil, and the current application time for the non-uniform nickel plating treatment was changed as shown in Table 1. Note that the evaluations described below were performed on both the S and M surfaces.

[0065] (Examples 14 and 15) Electromagnetic shielding copper foils of Examples 14 and 15 were obtained in the same manner as in Example 1, except that a uniform nickel plating was formed on the S-side of the copper foil substrate, and then a non-uniform nickel plating was formed to form a nickel layer, and the current application time for the non-uniform nickel plating treatment was changed as shown in Table 1.

[0066] (Examples 16 to 22) Electromagnetic shielding copper foils of Examples 16 to 22 were obtained in the same manner as in Example 1, except that the conditions for the uniform nickel plating treatment and the thickness of the nickel layer were changed as shown in Table 1.

[0067] Examples 23 to 25 Electromagnetic wave shielding copper foils of Examples 23 to 25 were obtained in the same manner as in Example 1, except that the hydrophilic rust-proofing treatment was changed as shown in Table 1.

[0068] Examples 26 to 28 Electromagnetic shielding copper foils of Examples 26 to 28 were obtained in the same manner as in Example 1, except that the ratio of the nickel content to the sum of the nickel content and the chromium content contained in the surface treatment layer consisting of the nickel layer and the hydrophilic rust-proofing treatment layer was changed as shown in Table 1.

[0069] Comparative Example 1 An electromagnetic shielding copper foil of Comparative Example 1 was obtained in the same manner as in Example 1, except that the non-uniform nickel plating treatment was not carried out.

[0070] Comparative Examples 2 and 3 Electromagnetic shielding copper foils of Comparative Examples 2 and 3 were obtained in the same manner as in Example 1, except that the conditions for non-uniform nickel plating were changed as shown in Table 1.

[0071] Comparative Example 4 An electromagnetic wave shielding copper foil of Comparative Example 4 was obtained in the same manner as in Comparative Example 2, except that the M side of the copper foil was used as the surface to be plated.

[0072] (Comparative Examples 5 and 6) An electromagnetic shielding copper foil of Comparative Example 5 was obtained by the manufacturing method described in Patent Document 1. An electromagnetic shielding copper foil of Comparative Example 6 was obtained in the same manner as in Comparative Example 5, except that the above-mentioned uniform nickel plating treatment was carried out as a general nickel plating treatment to impart corrosion resistance to the copper foil substrate.

[0073] (Comparative Examples 7 and 8) An electromagnetic shielding copper foil of Comparative Example 7 was obtained by the manufacturing method described in Patent Document 3. Moreover, an electromagnetic shielding copper foil of Comparative Example 8 was obtained in the same manner as in Comparative Example 7, except that the above-mentioned uniform nickel plating treatment was carried out as a general nickel plating treatment in order to impart corrosion resistance to the copper foil substrate.

[0074] (Comparative Examples 9 and 10) An electromagnetic shielding copper foil of Comparative Example 9 was obtained by the manufacturing method described in Patent Document 4. Moreover, an electromagnetic shielding copper foil of Comparative Example 10 was obtained in the same manner as in Comparative Example 9, except that the above-mentioned uniform nickel plating treatment was carried out as a general nickel plating treatment in order to impart corrosion resistance to the copper foil substrate.

[0075] Comparative Example 11 An electromagnetic wave shielding copper foil of Comparative Example 11 was obtained by the copper foil manufacturing method described in Patent Document 5.

[0076] (Ratio of Nickel Content to the Sum of Nickel Content and Chromium Content) For the copper foils for electromagnetic shielding of Examples 1 to 28 and Comparative Examples 1 to 11, the nickel and chromium contents in the surface treatment layer were measured by X-ray fluorescence analysis using a ZSX Primus IV X-ray fluorescence analyzer manufactured by Rigaku Corporation.

[0077] The nickel and chromium contents were quantified for the surface-treated copper foil of each example and comparative example using calibration curves obtained from known standard samples of nickel and chromium. From the obtained nickel and chromium contents, the ratio of the nickel content to the sum of the nickel content and the chromium content was calculated. The results are shown in Table 1.

[0078]

[0079] (Calculation of developed surface area ratio Sdr, peak density Spd, and arithmetic mean roughness Sa) For the copper foils for electromagnetic shielding of Examples 1 to 28 and Comparative Examples 1 to 11, the developed surface area ratio Sdr, peak density Spd, and arithmetic mean roughness Sa of the surface treatment layer were measured in accordance with ISO 25178 using a confocal laser microscope VK-X3100 manufactured by Keyence Corporation.

[0080] The objective lens magnification of the confocal laser microscope was 100x, the scan mode was laser focal, the measurement size was 2048px x 1536px, the measurement quality was high precision, and the pitch was 0.08µm. The developed surface area ratio Sdr, peak density Spd, and arithmetic mean roughness Sa were calculated using the following filter processing and calculation conditions. The results are shown in Table 1.

[0081] Image processing: averaging, 3 x 3, median S filter: none F-operation: plane tilt correction L filter: 0.025 μm Calculation target area: 100 μm x 100 μm Load area ratio in load curve: 10% and 90%

[0082] (Evaluation of Corrosion Resistance) A salt spray test was conducted to evaluate the corrosion resistance of the electromagnetic shielding copper foils of Examples 1 to 28 and Comparative Examples 1 to 11. First, five test specimens were prepared for each Example and Comparative Example, with the surface of the surface treatment layer of the copper foil masked with tape to a size of 5 × 12 cm. The unmasked portion of the test specimen was the test surface. Next, each of these test specimens was placed in a salt spray tester. The test surface of each test specimen was subjected to salt spray using a 5% sodium chloride aqueous solution at a temperature of 25°C in accordance with JIS Z 2371:2015. Thereafter, the test surface was visually observed after 48 hours and 72 hours to confirm whether or not corrosion had occurred on the surface.

[0083] A sample that had corroded after 48 hours was given a score of 1, a sample that had corroded after 72 hours was given a score of 2, and a sample that had not corroded after 72 hours was given a score of 3. Finally, the average score of five copper foils was calculated for each example and comparative example, and a sample with an average score of 2 or more was judged to have corrosion resistance. The results are shown in Table 1.

[0084] (Evaluation of Long-Term Storage Stability) A constant temperature and humidity test was conducted to evaluate the long-term storage stability of the electromagnetic shielding copper foils of Examples 1 to 28 and Comparative Examples 1 to 11. First, two 5 cm square pieces were cut out of each of the electromagnetic shielding copper foils of the Examples and Comparative Examples. Next, the surface treatment layer of one of the cut copper foils was placed on the surface opposite to the surface treatment layer of the other copper foil to prepare a test piece. The test piece was prepared in this state to simulate the normal storage state of electromagnetic shielding copper foil (since electromagnetic shielding copper foils are usually stored in a rolled state, the surface treatment layer of the copper foil is placed on the surface opposite to the surface treatment layer of the other copper foil). Next, the test piece was placed in a constant temperature and humidity chamber at a temperature of 65°C and a relative humidity of 90% RH, and the condition of the test piece after 72 hours was visually observed. The test piece was observed by observing the surface treatment layer on the inner side of the two overlapping copper foils to determine whether discoloration had occurred. Those that did not discolor were rated A (pass), and those that did discolor were rated B (fail). The results are shown in Table 1.

[0085] (Measurement of Surface Free Energy) The surface free energy of the surface treatment layer side of the electromagnetic shielding copper foils of Examples 1 to 28 and Comparative Examples 1 to 11 was measured using a dyne pen. First, dyne pens with values ​​of 41 mN / m, 44 mN / m, 48 mN / m, 56 mN / m, 60 mN / m, 64 mN / m, 68 mN / m, and 73 mN / m were prepared. Five 5-cm straight lines were drawn with the dyne pen on the copper foil surface of each Example and Comparative Example for each surface free energy. Then, the ink was visually observed to determine whether it had adhered to the copper foil surface. The surface energy of the copper foil with the highest surface free energy among the five lines on which the ink had adhered was determined. The results are shown in Table 1.

[0086] (Evaluation) As can be seen from Table 1, the copper foils of Examples 1 to 28 not only had excellent corrosion resistance and long-term storage stability, but also had surface free energy within a suitable range. In contrast, the copper foils of Comparative Examples 1 to 4, 6, 8, 10, and 11 had excellent corrosion resistance, but insufficient long-term storage stability and excessive surface free energy. Furthermore, the copper foils of Comparative Examples 5, 7, and 9 had insufficient corrosion resistance and long-term storage stability, and also had excessive surface free energy.

[0087] The reasons for these results are thought to be as follows: The copper foil of Comparative Example 1 was not subjected to a non-uniform nickel plating treatment, and therefore the surface roughness could not be adequately controlled, and it is thought that a hydrophilic rust-proofing layer was formed over the entire surface of the nickel layer. This resulted in a large surface free energy, which made it easier for moisture to be trapped, and therefore, it is thought that this deteriorated the long-term storage stability.

[0088] In the copper foils of Comparative Examples 2 to 4, the current density or current application time of the non-uniform nickel plating process was outside the preferred range, which is believed to have prevented control of either or both of Sdr and Spd. Therefore, it is believed that the surface wettability of the copper foil increased, making it easier for moisture to be trapped, resulting in poor long-term storage stability. More specifically, in Comparative Example 2, the current application time of the non-uniform nickel plating was too long, which is believed to have caused both Sdr and Spd to increase too much. In Comparative Example 3, the current density of the non-uniform nickel plating was high and the current application time was short. Therefore, although convex features were formed on the surface, resulting in an Sdr of 11.0%, the number of such features was small, and Spd was less than 0.5. In Comparative Example 4, the current application time of the non-uniform nickel plating on the M side of the copper foil was long, which is believed to have increased surface roughness, resulting in an Sdr of 4.0% but an Spd greater than 10.

[0089] In the copper foil of Comparative Example 5, it is believed that the Spd was less than 0.5 because no nickel layer was formed. Therefore, it is believed that the surface free energy could not be controlled, and both the corrosion resistance and long-term storage stability were significantly reduced. On the other hand, in the copper foil of Comparative Example 6, the copper foil substrate was subjected to a nickel plating treatment, but the surface roughness was not controlled. Therefore, although the corrosion resistance was improved compared to Comparative Example 5, it is believed that the surface free energy could not be suitably controlled, and the long-term storage stability was reduced.

[0090] In the copper foil of Comparative Example 7, the Spd was less than 0.5 because no nickel layer was formed. Therefore, not only was the corrosion resistance effect of the nickel layer not obtained, but the surface free energy could not be controlled, and both the corrosion resistance and long-term storage stability were significantly reduced. On the other hand, in the copper foil of Comparative Example 8, the copper foil substrate was nickel-plated, but the surface roughness was not controlled. Therefore, although the corrosion resistance was improved compared to Comparative Example 7, the surface free energy could not be suitably controlled, and the long-term storage stability was reduced.

[0091] In the copper foil of Comparative Example 9, the Sdr exceeded 150% due to the absence of a nickel layer and the roughening treatment applied to the copper foil substrate. Therefore, the surface free energy could not be controlled, and both the corrosion resistance and long-term storage stability were significantly reduced. On the other hand, in the copper foil of Comparative Example 10, the copper foil substrate was nickel-plated, but, like Comparative Example 9, the Sdr exceeded 150%. This is thought to be because the nickel plating conformed to the surface shape of the copper foil, resulting in almost no change in surface roughness. Therefore, although the uniform nickel plating improved corrosion resistance, the surface free energy could not be controlled appropriately, and long-term storage stability was reduced.

[0092] It is believed that the copper foil of Comparative Example 11 was not subjected to a non-uniform nickel plating treatment, and therefore a hydrophilic anti-rust treatment layer was formed over the entire surface, which resulted in a large surface free energy and made it easier for moisture to be trapped, thereby deteriorating the long-term storage stability.

[0093] For example, the present invention can take the following configuration: [1] A copper foil having a copper foil substrate and a surface treatment layer formed on one or both sides of the copper foil substrate, wherein the surface treatment layer comprises a nickel layer containing nickel or a nickel-phosphorus alloy, and a hydrophilic rust-proofing layer formed on the surface of the nickel layer opposite to the surface facing the copper foil substrate, and the surface roughness of the surface treatment layer, when measured in accordance with the method specified in ISO 25178, is such that the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２] is 0.5 or more and 10 or less. [2] The copper foil for electromagnetic shielding according to [1], wherein the nickel layer has a thickness of 10 nm or more and 300 nm or less. [3] The copper foil for electromagnetic shielding according to [1], wherein the nickel layer has a thickness of 10 nm or more and 80 nm or less. [4] The copper foil for electromagnetic shielding according to any one of [1] to [3], wherein the hydrophilic rust-proofing treatment layer contains chromium as a single element or an alloy. [5] The copper foil for electromagnetic shielding according to [4], wherein the ratio of the nickel content to the sum of the nickel content and the chromium content in the surface treatment layer is 90 mass % or more. [6] The copper foil for electromagnetic shielding according to any one of [1] to [5], wherein the surface treatment layer has a surface free energy of 41 mN / m or more and 64 mN / m or less. [7] An electromagnetic shield comprising the copper foil for electromagnetic shielding according to any one of [1] to [6], and an adhesive layer bonded to the surface of the copper foil for electromagnetic shielding having the surface treatment layer. [8] A method for producing a copper foil for electromagnetic shielding, comprising: a nickel plating step of applying nickel plating to both sides or one side of a copper foil substrate, the nickel plating step including a non-uniform nickel plating step for forming an uneven shape and a uniform nickel plating step for forming a smooth surface, to form a nickel layer on the copper foil substrate; and a rust prevention step of applying a hydrophilic rust prevention treatment to the surface of the nickel layer, to form a hydrophilic rust prevention treatment layer on the nickel layer, wherein the surface roughness of the surface of the hydrophilic rust prevention treatment layer is such that, when measured in accordance with the method specified in ISO 25178, the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

[0094] 10... Copper foil substrate 20... Nickel layer 21... Non-uniform nickel plating 22... Uniform nickel plating 30... Hydrophilic rust-proofing layer 40... Surface treatment layer 40a... Surface of surface treatment layer 50, 50'... Copper foil for electromagnetic wave shielding

Claims

1. A copper foil having a copper foil substrate and a surface treatment layer formed on one or both sides of the copper foil substrate, wherein the surface treatment layer comprises a nickel layer containing nickel or a nickel-phosphorus alloy, and a hydrophilic rust-proofing layer formed on the side of the nickel layer opposite to the side facing the copper foil substrate, and the surface roughness of the surface treatment layer, when measured in accordance with the method specified in ISO 25178, is such that the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

2. The copper foil for electromagnetic shielding according to claim 1, wherein the thickness of the nickel layer is 10 nm or more and 300 nm or less.

3. The copper foil for electromagnetic shielding according to claim 1, wherein the thickness of the nickel layer is 10 nm or more and 80 nm or less.

4. The copper foil for electromagnetic shielding according to any one of claims 1 to 3, wherein the hydrophilic anticorrosive treatment layer contains chromium as a simple substance or as an alloy.

5. The copper foil for electromagnetic shielding according to claim 4, wherein the ratio of the nickel content to the sum of the nickel content and the chromium content in the surface treatment layer is 90 mass % or more.

6. The copper foil for electromagnetic wave shielding according to any one of claims 1 to 3, wherein the surface treatment layer has a surface free energy of 41 mN / m or more and 64 mN / m or less.

7. An electromagnetic wave shield comprising the copper foil for electromagnetic wave shielding according to any one of claims 1 to 3 and an adhesive layer attached to the side of the copper foil for electromagnetic wave shielding having the surface treatment layer.

8. A method for producing copper foil for electromagnetic wave shielding, comprising: a nickel plating step of applying nickel plating to one or both sides of a copper foil substrate, the nickel plating step including a non-uniform nickel plating step for forming an uneven shape and a uniform nickel plating step for forming a smooth surface, to form a nickel layer on the copper foil substrate; and a rust prevention step of applying a hydrophilic rust prevention treatment to the surface of the nickel layer, to form a hydrophilic rust prevention treatment layer on the nickel layer, wherein the surface roughness of the surface of the hydrophilic rust prevention treatment layer is such that, when measured in accordance with the method specified in ISO 25178, the developed surface area ratio Sdr is 0.01% or more and 20% or less, and the peak density Spd [1 / μm ２ ] is 0.5 or more and 10 or less.

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