MULTIPLE DRAW GAP LENGTH ORIENTATION PROCESS

• US 20080083998A1
• Filed: 10/06/2006
• Published: 04/10/2008
• Est. Priority Date: 10/06/2006
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Merrill, William W., Lindeman, David D.
• Application Number:
  US11/539,304
• Publication Number:
  US 20080083998A1
• Time in Patent Office: Days
• US Class Current: 264/1.34
• CPC Class Codes: B29C 55/065 in several stretching steps
• CPC Class Codes: B29D 11/00 Producing optical elements, e.g. lenses or prisms grinding or polishing of optical elements B24B; constructional form of optical elements G02B; optical parts of spectacles G02C7/00
• CPC Class Codes: B29K 2995/0034 Polarising

Abstract

A method of forming an optical film includes stretching a polymer film in first draw gap of a first length along a machine direction, at a first draw ratio; and further stretching the polymer film in second draw gap along a machine direction, wherein the step of stretching in the first draw gap is isolated from the step of stretching in the second draw gap.

Claims

1. A method of forming an optical film, the method comprising:

stretching a polymer film in first draw gap of a first length along a machine direction, at a first draw ratio; and

further stretching the polymer film in second draw gap along a machine direction, wherein the step of stretching in the first draw gap is isolated from the step of stretching in the second draw gap.

2. The method of claim 1 wherein the isolation is accomplished by quenching the polymer film.

3. The method of claim 1 wherein the isolation is accomplished by a roll positioned between the first draw gap and the second draw gap.

4. The method of claim 1 wherein the optical film is substantially uniaxial.

5. The method of claim 1 wherein the stretching step is performed using a length orienter.

6. The method of claim 1 further comprising heat setting the polymer film.

7. The method of claim 1 wherein the second draw gap has a second length, and the second length is equal to the first length.

8. The method of claim 1 wherein the second draw gap has a second length, and the second length is not equal to the first length.

9. The method of claim 1 wherein the step of stretching the polymer film in the second draw gap comprises stretching the polymer film at a second draw ratio, and the second draw ratio is equal to the first draw ratio.

10. The method of claim 1 wherein the step of stretching the polymer film in the second draw gap comprises stretching the polymer film at a second draw ratio, and the second draw ratio is not equal to the first draw ratio.

11. The method of claim 1 wherein

the step of stretching the polymer film in the first draw gap comprises stretching the polymer film between a first slow roll and a first fast roll;

and

the step of stretching the polymer film in the second draw gap comprises stretching the polymer film between a second slow roll and a second fast roll.

12. The method of claim 11 wherein a center roll acts as both the first fast roll and the second slow roll.

13. The method of claim 11 further comprising an intervening isolating roll between the first fast roll and the second slow roll.

14. The method of claim 1 wherein

the step of stretching the polymer film in the first draw gap comprises stretching the polymer film at a first average temperature;

and

the step of stretching the polymer film in the second draw gap comprises stretching the polymer film at a second average temperature,

wherein the second average temperature is greater than the first average temperature.

15. The method of claim 1 wherein at least one of the first draw ratio or the second draw ratio is greater than about 1.5 and the optical film has an extent of uniaxial character U greater than about 0.7.

16. The method of claim 1 further comprising stretching the polymer film in n number of draw gaps, wherein the first draw ratio λ

* is set according to an equation

λ

_final=(λ

*)ⁿ

where a final desired draw ratio is λ

_final.

17. The method of claim 1 further comprising stretching the polymer film in n number of draw gaps, wherein the first length L_j is set according to an equation

L_j=L[(λ

*)<sup>(−

1/2)</sup>−

1](λ

*)<sup>[−

(k−

1)/2</sup>]/[(λ

*)<sup>(−

n/2)</sup>−

1]

where L is a total of length of a sum of effective draw gaps, the first draw ratio is λ

*, and a number of fast rolls is k.