Method of making uniaxially oriented articles having structured surfaces

• US 20060138702A1
• Filed: 12/23/2004
• Published: 06/29/2006
• Est. Priority Date: 12/23/2004
• Status: Abandoned Application

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Ouderkirk, Andrew J., Biernath, Rolf W., Merrill, William Ward, Benson, Olester Jr., Kowitz, David A.
• Application Number:
  US11/184,028
• Publication Number:
  US 20060138702A1
• Time in Patent Office: Days
• US Class Current: 264/288.400
• CPC Class Codes: B29C 55/04 uniaxial, e.g. oblique
• CPC Class Codes: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 5/045 Prism arrays
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001

Abstract

A process for uniaxially orienting articles having a structured surface comprising a geometric feature is described. The process comprises a step of orienting the article in a direction substantially parallel to a first in-plane axis of the article.

Claims

1. A method of making an oriented, structured surface polymeric film, comprising the steps of:

(a) providing a polymeric film having (i) a first structured surface and a second surface, and (ii) first and second in-plane axes that are orthogonal with respect to each other and a third axis that is mutually orthogonal to the first and second in-plane axis in a thickness direction of the polymeric film, wherein the first structured surface has a geometric feature disposed thereon in a direction substantially parallel to the first in-plane axis; and

subsequently

(b) uniaxially orienting the polymeric film in a direction substantially parallel to the first in-plane axis of the polymeric film.

2. A method according to claim 1, wherein step (b) comprises stretching the polymeric film in a direction substantially parallel to the first in-plane axis.

3. A method according to claim 1, wherein step (b) comprises moving opposing edge portions of the polymeric film along diverging substantially parabolic paths.

4. A method according to claim 1, wherein the polymeric film is stretched in step (b) to a stretch ratio of at least about 1.1.

5. A method according to claim 1 wherein the polymeric film is stretched in step (b) to a stretch ratio of at least 1.5 and wherein the ratio of the larger to smaller of the stretch ratios along the second in-plane axis and the third axis is 1.4 or less.

6. A method according to claim 1, wherein geometric feature is elongate and is disposed on the first structured surface in a direction substantially parallel to the first in-plane axis.

7. A method according to claim 1 wherein the polymeric film has an initial dimension along the third axis and an initial dimension along the second in-plane axis prior to step (b) and the polymeric film has a stretched dimension along the third axis and a stretched dimension along the second in-plane axis, and wherein, after stretching the polymeric film to a ratio of stretched dimension along the second in-plane axis/to initial dimension along the second in-plane axis defined as λ

in step (b), the stretched polymeric film has a ratio of stretched dimension along the third axis/initial dimension along the third axis of approximately KT/λ

^0.5.

8. A method according to claim 1, wherein step (b) comprises stretching the polymeric film along paths that are substantially symmetrical about a center axis of the film.

9. A method according to claim 1, wherein the oriented polymeric film comprises at least one layer having (i) a first index of refraction (n₁) along the first in-plane axis, (ii) a second index of refraction (n₂) along the second in-plane axis, and (iii) a third index of refraction (n₃) along the third axis, wherein n₁≠

n₂ and n₁≠

n₃ and n₂ and n₃ are substantially equal to one another relative to their differences with n₁.

10. A method according to claim 1, wherein the film comprises a multilayer film having a plurality of layers of different polymeric composition.

11. A method according to claim 1 wherein the polymeric film has a first orientation state prior to stretching and a second orientation state, different than the first orientation state, after orientation.