Active reflective polarizer, liquid crystal display employing the same and method for the same

1. An optical device comprising:

a magnetic material layer magnetized in a first direction, the magnetic material layer reflecting electromagnetic radiation having a magnetic field component parallel to the first direction and transmitting electromagnetic radiation having a magnetic field component perpendicular to the first direction.

2. The optical device of claim 1 , wherein the magnetic material layer is formed of a plurality of magnetic particles and a transparent insulating medium in which the plurality of magnetic particles are embedded without agglomeration between the plurality of magnetic particles.

3. The optical device of claim 2 , wherein each of the plurality of magnetic particles is surrounded by a transparent insulating shell or a transparent polymer-type insulating surfactant.

4. The optical device of claim 2 , wherein the plurality of magnetic particles have a sphere, oval, square, rectangle, cylinder, elliptical or arbitrary shape.

5. The optical device of claim 2 , wherein the plurality of magnetic particles comprise one or more of a ferromagnetic material, a superparamagnetic material, a paramagnetic material, a diamagnetic material, and a ferrimagnetic material.

6. The optical device of claim 2 , wherein the plurality of magnetic particles are selected from the group consisting of titanium, cobalt, iron, nickel, aluminum, barium, platinum, sodium, strontium, magnesium, dysprosium, manganese, gadolinium, sliver, copper, chromium, cobalt-platinum (Co x Pt y ), iron-platinum (Fe v Pt z ), MnZn(Fe 2 O 4 ) 2 , Mn Fe 2 O 4 , Fe 3 O 4 , Fe 2 O 3 and Sr 8 CaRe 3 Cu 4 O 24 , Co x Zr y Nb z , Ni x Fe y Nb z , Co x Zr y Nb z Fe v , wherein x, y, z and v present a composition rate.

7. The optical device of claim 2 , wherein the plurality of magnetic particles have a diameter within a range of 1 to 1000 nm.

8. The optical device of claim 1 , wherein the magnetic material layer is magnetized in the first direction when a magnetic field is applied thereto and continues to be magnetized in the first direction after the magnetic field is removed therefrom.

9. The optical device of claim 1 , wherein the magnetic material layer is first magnetized in the direction only while a magnetic field is applied thereto.

10. The optical device of claim 1 , wherein the magnetic material layer has a thickness greater than a magnetic decay length of the magnetic material layer.

11. The optical device of claim 1 , further comprising insulating layers on opposite surfaces of the magnetic material layer.

12. The optical device of claim 1 , further comprising a transparent substrate above which the magnetic material layer is provided.

13. The optical device of claim 1 , wherein the magnetic material layer is formed of a magnetic thin film having a thickness less than a micrometer.

14. The optical device of claim 1 , wherein the magnetic material layer comprises magnetic polymers.

15. The optical device of claim 1 , wherein the magnetic material layer is formed of a mixture of different particles of magnetic and transparent insulating materials.

16. The optical device of claim 1 further comprising a transparent protective film coated on a surface of the magnetic material layer.

17. The optical device of claim 1 further comprising an electrically conductive element disposed to at least one side of the magnetic material layer to apply a magnetic field to the magnetic material layer.

18. The optical device of claim 17 further comprising a power supply connected to the electrically conductive element.

19. The optical device of claim 17 , wherein the electrically conductive element has a plurality of wires arranged on the magnetic material layer.

20. The optical device of claim 19 , wherein spaces between adjacent wires of the plurality of wires are filled with transparent insulating material.

21. The optical device of claim 17 , wherein the electrically conductive element is a transparent plate electrode.

22. A method of producing polarized electromagnetic radiation, comprising:

magnetizing a magnetic material layer in a first direction;

receiving electromagnetic radiation at the magnetic material layer;

reflecting a first component of the electromagnetic radiation having a magnetic field component parallel to the first direction; and

transmitting a second component of the electromagnetic radiation having a magnetic field component perpendicular to the first direction.

23. A method of producing polarized electromagnetic radiation, comprising:

receiving electromagnetic radiation at a magnetic material layer magnetized in a first direction;

reflecting a first component of the electromagnetic radiation having a magnetic field component parallel to the first direction; and

transmitting a second component of the electromagnetic radiation having a magnetic field component perpendicular to the first direction.

24. A liquid crystal panel comprising:

a liquid crystal layer; and

a polarizer comprising a magnetic material layer magnetized in a first direction, the magnetic material layer reflecting light having a magnetic field component parallel to the first direction and transmitting light having a magnetic field component perpendicular to the first direction toward the liquid crystal layer.

25. A liquid crystal display comprising:

a liquid crystal layer;

a backlight unit which provides light;

a polarizer disposed between the backlight unit and the liquid crystal layer, the polarizer comprising a magnetic material layer magnetized in a first direction, the magnetic material layer reflecting a first component of the light having a magnetic field component parallel to the first direction and transmitting a second component of the light having a magnetic field component perpendicular to the first direction.