Magnetic sheet, module comprising same, and portable device comprising same
Provided herein is a magnetic sheet. The magnetic sheet according to one embodiment of the present invention includes a magnetic layer formed of crushed pieces of a magnetic body to improve flexibility of the magnetic sheet, and a thin film coating layer formed on at least one surface of the magnetic layer to maintain the magnetic layer in a sheet shape and buffer an external force applied to the crushed pieces of the magnetic body. According to the present invention, since the magnetic sheet is improved in mechanical strength properties, such as a tensile property, a bending property, and the like, to have significantly superior flexibility, degradation of physical properties, such as magnetic permeability and the like, caused by physical damage such as unintended cracks in the magnetic body provided in the magnetic sheet can be prevented even in the process of storing, transferring, and attaching the magnetic sheet to a target object and during usage of an electronic device provided with the target object to which the magnetic sheet is attached, and the magnetic sheet can be attached to a target surface of the target object with a superior adhering force even when a stepped portion is present at the surface, and at the same time, the magnetic sheet can block the influence of a magnetic field on parts of a portable terminal device or a human body of a user using the portable terminal device, significantly increase transmission and reception efficiencies and distances of a data and/or wireless power signal, and maintain the above-described performance for a long period of time, such that the magnetic sheet can be widely used in various portable devices such as mobile devices, smart appliances, devices for the Internet of Things, and the like.
1. A magnetic sheet comprising:
a magnetic layer formed of crushed pieces of a magnetic body to improve flexibility of the magnetic sheet; and
a thin film coating layer formed on at least one surface of the magnetic layer to maintain the magnetic layer in a sheet shape and buffer an external force applied to the crushed pieces of the magnetic body, wherein the thin film coating layer has a thickness of 10 μm or less and is a single layer formed of ethylene propylene diene monomer (EPDM) rubber.
2. The magnetic sheet of claim 1 , wherein the thin film coating layer partially or completely infiltrates into a space between at least some adjacent pieces of the magnetic body.
3. The magnetic sheet of claim 1 , wherein a single layer of the magnetic layer has a thickness in a range of 1 to 30 μm.
4. The magnetic sheet of claim 1 , wherein:
the magnetic sheet includes a magnetic body made of a soft magnetic material; and
the soft magnetic material includes a metallic soft magnetic material or ferrite.
5. The magnetic sheet of claim 4 , wherein:
the metallic soft magnetic material includes one or more selected from the group consisting of a Ni—Co-based alloy, a Fe—Ni-based alloy, a Fe—Cr-based alloy, a Fe—Al-based alloy, a Fe—Si-based alloy, a Fe—Si—B-based alloy, and a Fe—Si—B—Cu—Nb-based alloy; and
the ferrite includes one or more selected from the group consisting of Mn—Zn-based ferrite, Ni—Zn-based ferrite, Ni—Co-based ferrite, Mg—Zn-based ferrite, Cu—Zn-based ferrite, and cobalt-substituted Y or Z hexagonal-based ferrite.
6. A low-frequency antenna comprising:
an antenna core;
a magnetic sheet including
a magnetic layer formed of crushed pieces of a magnetic body to improve flexibility of the magnetic sheet, and
a thin film coating layer formed on at least one surface of the magnetic layer to maintain the magnetic layer in a sheet shape and buffer an external force applied to the crushed pieces of the magnetic body, the thin film coating layer having a thickness of 10 μm or less and being a single layer formed of ethylene propylene diene monomer (EPDM) rubber, the magnetic sheet being attached to one surface or both surfaces of the antenna core; and
a coil wound on an outer surface of each of the antenna core and the magnetic sheet.
7. A wireless power transmission (WPT) module comprising:
an antenna unit including an antenna for WPT; and
a magnetic field unit having at least one magnetic sheet including
a magnetic layer formed of crushed pieces of a magnetic body to improve flexibility of the magnetic sheet, and
a thin film coating layer formed on at least one surface of the magnetic layer to maintain the magnetic layer in a sheet shape and buffer an external force applied to the crushed pieces of the magnetic body, the thin film coating layer having a thickness of 10 μm or less and being a single layer formed of ethylene propylene diene monomer (EPDM) rubber, the at least one magnetic sheet being disposed on one surface of the antenna unit and configured to improve a characteristic of the antenna for WPT and focus a magnetic flux toward the antenna for WPT.
8. The WPT module of claim 7 , wherein the antenna unit further includes at least one of an antenna for near-field communication (NFC) and an antenna for magnetic secure transmission (MST).