Method of preparing conductive magnetic composite sheet and antenna device

1. A method of preparing a conductive magnetic composite sheet, the method comprising:

preparing a magnetic sheet comprising a magnetic powder and a binder resin;

stacking the magnetic sheet and a first conductive foil; and

applying heat and pressure to the obtained stack to bond the magnetic sheet and the first conductive foil,

wherein the magnetic sheet comprises 70 wt % to 90 wt % of the magnetic powder, and 6 wt % to 12 wt % of a polyurethane-based resin, 0.5 wt % to 2 wt % of an isocyanate-based hardener, and 0.3 wt % to 1.5 wt % of an epoxy-based resin, as the binder resin, based on the total weight of the magnetic sheet.

2. The method of claim 1 , wherein the step of applying heat and pressure to the stack is performed at a pressure of 5 MPa to 30 MPa and a temperature of 150° C. to 200° C.

3. The method of claim 1 , wherein the stacking step and the step of applying heat and pressure to the stack are performed by a roll-to-roll process, which is performed at a roll temperature of 150° C. to 200° C., a roll pressure of 5 MPa to 30 MPa, and a speed of 1 m/min to 5 m/min by using 2 to 10 pairs of rolls.

4. The method of claim 1 , wherein the magnetic sheet is an unsintered sheet with a thickness of 10 μm to 3,000 μm having flexibility.

5. The method of claim 1 , wherein the magnetic sheet has a magnetic permeability of 100 to 300 when measured during applying an alternating current with a frequency of 3 MHz to the magnetic sheet, a magnetic permeability of 80 to 270 when measured during applying an alternating current with a frequency of 6.78 MHz to the magnetic sheet, and a magnetic permeability of 60 to 250 when measured during applying an alternating current with a frequency of 13.56 MHz to the magnetic sheet.

6. The method of claim 1 , wherein the conductive magnetic composite sheet has a peel strength between the magnetic sheet and the first conductive foil of 0.6 kgf/cm or more after subjected to heat-treatment twice, the heat-treatment including heating from 30° C. to 240° C. at a constant rate for 200 seconds and then cooling from 240° C. to 130° C. at a constant rate for 100 seconds.

7. The method of claim 1 , wherein the binder resin is a thermosetting resin, and

the binder resin bonds the magnetic sheet to the first conductive foil while being cured in the step of applying heat and pressure to the stack.

8. The method of claim 7 , wherein the conductive magnetic composite sheet has a peel strength between the magnetic sheet and the first conductive foil of 0.6 kgf/cm or more after subjected to heat-treatment twice, the heat-treatment including heating from 30° C. to 240° C. at a constant rate for 200 seconds and then cooling from 240° C. to 130° C. at a constant rate for 100 seconds,

wherein the magnetic sheet is an unsintered sheet with a thickness of 10 μm to 3,000 μm having flexibility, and

the magnetic sheet has a magnetic permeability of 100 to 300 when measured during applying an alternating current with a frequency of 3 MHz to the magnetic sheet; a magnetic permeability of 80 to 270 when measured during applying an alternating current with a frequency of 6.78 MHz to the magnetic sheet; a magnetic permeability of 60 to 250 when measured during applying an alternating current with a frequency of 13.56 MHz to the magnetic sheet;

a thickness change of 5% or less and a magnetic permeability change of 5% or less after subjected to heat-treatment twice, the heat-treatment being composed of heating from 30° C. to 240° C. at a constant rate for 200 seconds and then cooling from 240° C. to 130° C. at a constant rate for 100 seconds;

a thickness change of 5% or less and a magnetic permeability change of 5% or less after immersed in a 2 N hydrochloric acid solution for 30 minutes; and a thickness change of 5% or less and a magnetic permeability change of 5% or less after immersed in a 2 N sodium hydroxide solution for 30 minutes.

9. The method of claim 1 , wherein the first conductive foil has a first primer layer formed on its one side, and the magnetic sheet and the first conductive foil are stacked such that one side of the magnetic sheet is in contact with the first primer layer of the first conductive foil.

10. The method of claim 9 , wherein the first primer layer has a thickness of 0.01 μm to 1 μm.

11. The method of claim 9 , wherein the first primer layer comprises a thermosetting resin, and the thermosetting resin in the first primer layer is cured in the step of applying heat and pressure to the stack.

12. The method of claim 11 , wherein the thermosetting resin comprises a bisphenol A-type epoxy resin, a cresol novolac-type epoxy resin, or a tetrakis(glycidyloxyphenyl)ethane-type epoxy resin.

13. A method of preparing a conductive magnetic composite sheet, the method comprising:

preparing a magnetic sheet comprising a magnetic powder and a binder resin;

stacking a first conductive foil, the magnetic sheet and a second conductive foil; and

applying heat and pressure to the obtained stack to bond the first conductive foil, the magnetic sheet and the second conductive foil together,

wherein the magnetic sheet comprises 70 wt % to 90 wt % of the magnetic powder, and 6 wt % to 12 wt % of a polyurethane-based resin, 0.5 wt % to 2 wt % of an isocyanate-based hardener, and 0.3 wt % to 1.5 wt % of an epoxy-based resin, as the binder resin, based on the total weight of the magnetic sheet.

14. The method of claim 13 , wherein the binder resin is a thermosetting resin, and the binder resin bonds the first conductive foil, the magnetic sheet and the second conductive foil together while being cured in the step of applying heat and pressure to the stack.

15. The method of claim 13 , wherein the first conductive foil has a first primer layer formed on its one side, the second conductive foil has a second primer layer formed on its one side,

the magnetic sheet and the first conductive foil are stacked such that one side of the magnetic sheet is in contact with the first primer layer of the first conductive foil, the magnetic sheet and the second conductive foil are stacked such that the other side of the magnetic sheet is in contact with the second primer layer of the second conductive foil,

the first primer layer and the second primer layer comprise a thermosetting resin, and

the thermosetting resins in the first and second primer layers are cured in the step of applying heat and pressure to the stack.

16. A method of preparing an antenna device, the method comprising:

preparing a magnetic sheet comprising a magnetic powder and a binder resin;

stacking the magnetic sheet and a first conductive foil;

applying heat and pressure to the obtained stack to bond the magnetic sheet and the first conductive foil; and

etching the first conductive foil to form an antenna pattern therein,

wherein the magnetic sheet comprises 70 wt % to 90 wt % of the magnetic powder, and 6 wt % to 12 wt % of a polyurethane-based resin, 0.5 wt % to 2 wt % of an isocyanate-based hardener, and 0.3 wt % to 1.5 wt % of an epoxy-based resin, as the binder resin, based on the total weight of the magnetic sheet.

17. The method of claim 16 , wherein the binder resin is a thermosetting resin, and the binder resin bonds the magnetic sheet and the first conductive foil while being cured in the step of applying heat and pressure to the stack.

18. The method of claim 16 , wherein the first conductive foil has a first primer layer formed on its one side, the magnetic sheet and the first conductive foil are stacked such that one side of the magnetic sheet is in contact with the first primer layer of the first conductive foil, the first primer layer comprises a thermosetting resin, and the thermosetting resin in the first primer layer is cured in the step of applying heat and pressure to the stack.

19. The method of claim 16 , wherein the magnetic sheet is an unsintered sheet with a thickness of 10 μm to 3,000 μm having flexibility, and

the magnetic sheet has a magnetic permeability of 100 to 300 when measured during applying an alternating current with a frequency of 3 MHz to the magnetic sheet; a magnetic permeability of 80 to 270 when measured during applying an alternating current with a frequency of 6.78 MHz to the magnetic sheet; a magnetic permeability of 60 to 250 when measured during applying an alternating current with a frequency of 13.56 MHz to the magnetic sheet;

a thickness change of 5% or less and a magnetic permeability change of 5% or less after subjected to heat-treatment twice, the heat-treatment including heating from 30° C. to 240° C. at a constant rate for 200 seconds and then cooling from 240° C. to 130° C. at a constant rate for 100 seconds;

a thickness change of 5% or less and a magnetic permeability change of 5% or less after immersed in a 2 N hydrochloric acid solution for 30 minutes; and a thickness change of 5% or less and a magnetic permeability change of 5% or less after immersed in a 2 N sodium hydroxide solution for 30 minutes.