METHODS FOR FABRICATING OPTICAL MICROSTRUCTURES USING A CYLINDRICAL PLATFORM AND A RASTERED RADIATION BEAM

• US 20060275714A1
• Filed: 08/17/2006
• Published: 12/07/2006
• Est. Priority Date: 09/11/2003
• Status: Active Grant

• Current Assignee: Bright View Technologies Corporation (Tredegar Corporation)
• Original Assignee: Bright View Technologies, Inc. (Tredegar Corporation)
• Inventors: Wood, Robert L., Freese, Robert P., Rinehart, Thomas A.
• Granted Patent: US 7,763,417 B2
• Time in Patent Office: Days
• US Class Current: 430/321
• CPC Class Codes: B29D 11/00288 made by a rotating cylinder
• CPC Class Codes: G02B 3/0012 characterised by the manufacturing method
• CPC Class Codes: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 3/0043 Inhomogeneous or irregular arrays, e.g. varying shape, size, height
• CPC Class Codes: G02B 5/1857 using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams

Abstract

Optical microstructures, such as microlenses, are fabricated by rotating a cylindrical platform that includes a radiation sensitive layer thereon, about its axis, while simultaneously axially rastering a laser beam across at least a portion of the radiation sensitive layer. The cylindrical platform is also simultaneously translated axially while it is being rotated. The amplitude of the laser beam is continuously varied while rastering. The optical microstructures that are imaged in the radiation sensitive layer can be developed to provide a master for replicating a microlenses.

Claims

1. A method of fabricating optical microstructures comprising:

rotating a cylindrical platform that includes a radiation sensitive layer thereon about an axis thereof, while

simultaneously axially rastering a radiation beam across a portion of the radiation sensitive layer; and

while

simultaneously continuously translating the cylindrical platform and/or radiation beam axially relative to one another, to image the optical microstructures in a spiral pattern in the radiation sensitive layer.

2. A method according to claim 1 wherein simultaneously axially rastering comprises simultaneously axially rastering a radiation beam across a portion of the radiation sensitive layer while varying amplitude of the radiation beam to image the optical microstructures in the radiation sensitive layer.

3. A method according to claim 1 wherein simultaneously axially rastering comprises simultaneously axially rastering a radiation beam across at least a portion of the radiation sensitive layer while continuously varying amplitude of the radiation beam to image the optical microstructures in the radiation sensitive layer.

4. A method according to claim 1 wherein simultaneously axially rastering a radiation beam comprises simultaneously axially rastering a laser beam.

5. A method according to claim 4 wherein simultaneously axially rastering a laser beam comprises:

generating a continuous wave laser beam;

modulating the laser beam to vary an amplitude thereof; and

oscillating the laser beam to raster the laser beam across a portion of the radiation sensitive layer.

6. A method according to claim 1 wherein simultaneously axially rastering is performed at sufficient speed, relative to rotating, such that the radiation beam images an optical microstructure over a plurality of scans of the radiation beam.

7. A method according to claim 1 further comprising:

simultaneously varying a focal length of the radiation beam to at least partially compensate for radial variation in the cylindrical platform and/or thickness variation in the radiation sensitive layer.

8. A method according to claim 1 further comprising:

simultaneously varying a focal length of the radiation beam to image portions of the optical microstructures at varying depths in the radiation sensitive layer.

9. A method according to claim 1 wherein simultaneously axially rastering comprises:

simultaneously axially rastering a radiation beam along first and second opposite axial directions across a portion of the radiation sensitive layer to image the optical microstructures in the radiation sensitive layer along both the first and the second opposite axial directions.

10. A method according to claim 1 wherein simultaneously axially rastering comprises:

simultaneously axially rastering a radiation beam along first and second opposite axial directions across a portion of the radiation sensitive layer to image the optical microstructures in the radiation sensitive layer along the first axial direction and to blank the radiation beam along the second axial direction.

11. A method according to claim 1 wherein the cylindrical platform is at least about one foot in circumference and/or at least about one foot in axial length.

12. A method according to claim 11 wherein rotating is performed at angular velocity of at least about 1 revolution per minute.

13. A method according to claim 12 wherein simultaneously axially rastering is performed at frequency of at least about 1 kHz.

14. A method according to claim 1 wherein rotating and simultaneously axially rastering are performed continuously for at least about 1 hour.

15. A method according to claim 14 wherein rotating and simultaneously axially rastering are performed continuously for at least about 1 hour to fabricate at least about one million optical microstructures.

16. A method according to claim 1 wherein the optical microstructures comprise microlenses.

17. A method according to claim 1 further comprising:

developing the optical microstructures that are imaged in the radiation sensitive layer to provide an optical microstructure master.

18. A method according to claim 1 wherein the cylindrical platform also includes a substrate on the radiation sensitive layer that is transparent to the radiation beam and wherein simultaneously axially rastering comprises simultaneously axially rastering a radiation beam through the substrate that is transparent thereto across a portion of the radiation sensitive layer to image the optical microstructures in the radiation sensitive layer.

19. A method according to claim 18 wherein the radiation sensitive layer is a negative photoresist layer such that portions of the negative photoresist layer that are exposed to the radiation beam remain after development.

20. A method according to claim 1 wherein the radiation sensitive layer is a negative photoresist layer such that portions of the negative photoresist layer that are exposed to the radiation beam remain after development.

21. A method according to claim 18 wherein the substrate is a flexible substrate.

22. A method according to claim 1 wherein rotating comprises:

rotating a cylindrical platform that includes thereon a radiation sensitive layer sandwiched between a pair of outer layers about an axis thereof.

23. A method according to claim 22 wherein simultaneously axially rastering is followed by:

removing at least one of the outer layers.

24. A method according to claim 22 wherein the pair of outer layers comprises a first outer layer adjacent the cylindrical platform and a second outer layer remote from the cylindrical platform that is transparent to the radiation beam, and wherein simultaneously axially rastering comprises simultaneously axially rastering the radiation beam through the second outer layer across at least a portion of the radiation sensitive layer to image the optical microstructures in the radiation sensitive layer.

25. A method according to claim 24 wherein the radiation sensitive layer is a negative photoresist layer.

26. A method according to claim 23 wherein the removing comprises:

separating the first outer layer from the cylindrical platform; and

separating the first outer layer from the radiation sensitive layer.

27. A method of fabricating optical microstructures comprising:

rotating a cylindrical platform that includes a radiation sensitive layer thereon about an axis thereof, while

simultaneously axially rastering a laser beam across a portion of the radiation sensitive layer while continuously varying amplitude of the laser beam; and

while

simultaneously translating the cylindrical platform and/or laser beam axially relative to one another, to image the optical microstructures in the radiation sensitive layer.

28. A method according to claim 27 wherein simultaneously axially rastering is performed at sufficient speed, relative to rotating, such that the laser beam images an optical microstructure over a plurality of scans of the laser beam.

29. A method according to claim 27 further comprising:

simultaneously varying a focal length of the laser beam.

30. A method according to claim 29 wherein simultaneously axially rastering comprises:

simultaneously axially rastering a laser beam along first and second opposite axial directions across a portion of the radiation sensitive layer to image the optical microstructures in the radiation sensitive layer along the first axial direction and to blank the laser beam along the second axial direction.

31. A method according to claim 30 wherein the cylindrical platform is at least about one foot in circumference and/or at least about one foot in axial length.

32. A method according to claim 31 wherein rotating and simultaneously axially rastering are performed continuously for at least about 1 hour to fabricate at least about one million optical microstructures.

33. A method according to claim 32 wherein the optical microstructures comprise microlenses.

34. A method according to claim 33 further comprising:

developing the microlenses that are imaged in the radiation sensitive layer to provide a microlens master.

35. A method according to claim 27 wherein the radiation sensitive layer is a negative photoresist layer such that portions of the negative photoresist layer that are exposed to the radiation beam remain after development;

and

wherein the cylindrical platform also includes a substrate on the negative photoresist layer that is transparent to the laser beam and wherein simultaneously axially rastering comprises simultaneously axially rastering a laser beam through the substrate that is transparent thereto across a portion of the negative photoresist layer to image the optical microstructures in the negative photoresist layer.

36. A method according to claim 35 wherein the cylindrical platform also includes a release layer between the negative photoresist layer and the cylindrical platform.