Electromagnetic shielding material
View Patent ↗Provided is an electromagnetic wave shielding material including a multilayer structure in which at least one metal foil and at least two resin layers are closely laminated, wherein both surfaces of each metal foil are closely laminated to the resin layers; wherein each metal foil satisfies the following relationship with each of the two resin layers adjacent to the metal foil: 0.02≤V M /V M′ ≤1.2, in which: V M is a volume fraction of the metal foil relative to a total volume of the metal foil and the resin layer; V M′ is (σ R −σ R′ )/(σ M +σ R −σ R′ ); σ M is a true stress (MPa) of the metal foil at breakage when a tensile stress is applied to the metal foil; σ R is a true stress (MPa) of the resin layer at breakage when a tensile stress is applied to the resin layer; and σ R′ is a true stress (MPa) of the resin layer when a logarithmic strain same as a logarithmic strain at breakage of the metal foil is applied to the resin layer.
1. An electromagnetic wave shielding material comprising a multilayer structure in which at least one metal foil and at least two resin layers are laminated,
wherein both surfaces of each metal foil are laminated to the resin layers;
wherein the at least two resin layers are free from glass fibers therein; and
wherein each metal foil satisfies the following relationship with each of the two resin layers adjacent to the metal foil:
0.02 ≤V M /V M′ ≤1.2, in which:
V M is a volume fraction of the metal foil relative to a total volume of the metal foil and the at least two resin layers;
V M′ is (σ R −σ R′ )/(σ M +σ R −σ R′ );
σ M is a true stress (MPa) of the metal foil at breakage when a tensile stress is applied to the metal foil;
σ R is a true stress (MPa) of the resin layer at breakage when a tensile stress is applied to the resin layer; and
σ R′ is a true stress (MPa) of the resin layer when a logarithmic strain same as a logarithmic strain at breakage of the metal foil is applied to the resin layer.
2. The electromagnetic wave shielding material according to claim 1 , wherein each metal foil satisfies the following relationship with each of the two resin layers adjacent to the metal foil:
0.2 ≤V M /V M′ ≤0.6.
3. The electromagnetic wave shielding material according to claim 1 , wherein each metal foil forming the electromagnetic wave shielding material has a thickness of 4 μm to 100 μm.
4. The electromagnetic wave shielding material according to claim 1 , wherein each resin layer forming the electromagnetic wave shielding material has a thickness of 4 μm to 250 μm.
5. The electromagnetic wave shielding material according to claim 1 , wherein the metal foil and the resin layers forming the electromagnetic wave shielding material are closely laminated by thermocompression bonding without interposing an adhesive layer.
6. The electromagnetic wave shielding material according to claim 1 , wherein a total thickness of the at least one metal foil is 100 μm or less, and a total thickness of the resin layers is 500 μm or less.
7. A method for producing an electromagnetic wave shielding molded article comprising molding the electromagnetic wave shielding material according to claim 1 .
8. The method for producing the electromagnetic wave shielding molded article according to claim 7 , wherein the molding is carried out by pressure forming.
9. The electromagnetic wave shielding material according to claim 1 , wherein the at least two resin layers are free from fiber reinforcing materials therein.
10. The electromagnetic wave shielding material according to claim 1 , wherein the at least two resin layers comprise polyethylene terephthalate (PET).
11. The electromagnetic wave shielding material according to claim 10 , wherein the at least one metal foil comprises copper.