Window system and light guiding film therein

1. A light guiding film comprising:

a film base, having a first side and a second side opposite the first side; and

at least one microstructure, disposed on the first side or the second side of the film base, and comprising a first surface and a second surface above the first surface, wherein a first inclination angle is between the first surface and a reference plane, the reference plane is perpendicular with the film base, a second inclination angle is between the second surface and the reference plane;

whereby a plurality of incident light beams becomes a plurality of output light beams after passing through the light guiding film, an output angle is defined as the angle between the output light beam and the light guiding film, the output angle is defined as 0 degree when the output light beam is downward and parallel with the light guiding film, the output angle is defined as 180 degrees when the output light beam is upward and parallel with the light guiding film, the total energy of the output light beams with the output angles from 85 to 120 degrees is more than 40% of the total energy of the output light beams with the output angles from 0 to 180 degrees.

2. The light guiding film as claimed in claim 1 , wherein the light guiding film is attached to a glass of a window of a room, the incident light beams are the sunlight beams outside the room, and the output light beams inside the room.

3. The light guiding film as claimed in claim 1 , wherein the cross section of the at least one microstructure is substantially triangle.

4. The light guiding film as claimed in claim 3 , wherein the at least one microstructure further comprises a curved chamfer, the curved chamfer is disposed between the first surface and the second surface, and adjacent to the first surface and the second surface.

5. The light guiding film as claimed in claim 1 , wherein the incident light beams are downward, and more than 50% of the output light beams are upward.

6. The light guiding film as claimed in claim 1 , wherein an incident angle is defined as the angle between the incident light beam and the reference plane, the incident angle is defined as positive when the incident light beam is downward, the incident angles of the incident light beams are from 30 to 60 degrees.

7. The light guiding film as claimed in claim 1 , wherein the value of the first inclination angle is different from that of the second inclination angle.

8. The light guiding film as claimed in claim 1 , wherein the at least one microstructure is disposed on the second side of the film base, the value of the first inclination angle is between 21 to 25 degrees, and the value of the second inclination angle is between 20 to 28 degrees.

9. The light guiding film as claimed in claim 8 , wherein the at least one microstructure faces the incident light beams.

10. The light guiding film as claimed in claim 8 , wherein the value of the first inclination angle is 23 degrees, and the value of the second inclination angle is 24 degrees.

11. The light guiding film as claimed in claim 1 , wherein the at least one microstructure is disposed on the second side of the film base, the value of the first inclination angle is between 17 to 23 degrees, and the value of the second inclination angle is between 35 to 45 degrees.

12. The light guiding film as claimed in claim 11 , wherein the at least one microstructure faces the incident light beams.

13. The light guiding film as claimed in claim 11 , wherein the value of the first inclination angle is 20 degrees, and the value of the second inclination angle is 40 degrees.

14. The light guiding film as claimed in claim 1 , wherein the at least one microstructure is disposed on the first side of the film base, the value of the first inclination angle is between 3 to 5 degrees, and the value of the second inclination angle is between 27 to 33 degrees.

15. The light guiding film as claimed in claim 14 , wherein the second side of the film base faces the incident light beams.

16. The light guiding film as claimed in claim 14 , wherein the value of the first inclination angle is 4 degrees, and the value of the second inclination angle is 30 degrees.

17. The light guiding film as claimed in claim 1 , wherein the total energy of the output light beams with the output angles from 85 to 120 degrees is more than 50% of the total energy of the output light beams with the output angles from 0 to 180 degrees.

18. The light guiding film as claimed in claim 1 , wherein the total energy of the output light beams with the output angles from 85 to 120 degrees is more than 60% of the total energy of the output light beams with the output angles from 0 to 180 degrees.

19. The light guiding film as claimed in claim 1 , wherein the total energy of the output light beams with the output angles from 85 to 120 degrees is more than 70% of the total energy of the output light beams with the output angles from 0 to 180 degrees.

20. A window system comprising:

a first protective plate;

a second protective plate, fixed to the first protective plate; and

a light guiding film disposed in an accommodating space between the first protective plate and the second protective plate, the light guiding film being attached to the first protective plate or the second protective plate, and comprising:

a film base, having a first side and a second side opposite the first side; and

at least one microstructure, disposed on the first side or the second side of the film base, and comprising a first surface and a second surface above the first surface, wherein a first inclination angle is between the first surface and a reference plane, the reference plane is perpendicular with the film base, a second inclination angle is between the second surface and the reference plane;

whereby a plurality of incident light beams becomes a plurality of output light beams after passing through the light guiding film, an output angle is defined as the angle between the output light beam and the light guiding film, the output angle is defined as 0 degree when the output light beam is downward and parallel with the light guiding film, the output angle is defined as 180 degrees when the output light beam is upward and parallel with the light guiding film, the total energy of the output light beams with the output angles from 85 to 120 degrees is more than 40% of the total energy of the output light beams with the output angles from 0 to 180 degrees.

21. The window system as claimed in claim 20 , wherein the incident light beams are the sunlight beams outside a room, and the output light beams inside the room.

22. The window system as claimed in claim 20 , wherein the first protective plate, the second protective plate, the film base, and the at least one microstructure are light transmissible, and the second protective plate faces the incident light beams.

23. The window system as claimed in claim 20 , wherein the material of the first protective plate and the second protective plate are glass.

24. The window system as claimed in claim 20 , wherein the first side of the film base is attached to the first protective plate, the at least one microstructure is disposed on the second side of the film base, the value of the first inclination angle is between 21 to 25 degrees, and the value of the second inclination angle is between 20 to 28 degrees.

25. The window system as claimed in claim 20 , wherein the first side of the film base is attached to the first protective plate, the at least one microstructure is disposed on the second side of the film base, the value of the first inclination angle is between 17 to 23 degrees, and the value of the second inclination angle is between 35 to 45 degrees.

26. The window system as claimed in claim 20 , wherein the second side of the film base is attached to the second protective plate, the at least one microstructure is disposed on the first side of the film base, the value of the first inclination angle is between 3 to 5 degrees, and the value of the second inclination angle is between 27 to 33 degrees.