Uniaxially oriented birefringent article having a structured surface

• US 20060204720A1
• Filed: 12/23/2004
• Published: 09/14/2006
• 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., Tarnowski, Catherine P., Brott, Robert L., Merrill, William Ward, Benson, Olester Jr., Kowitz, David A.
• Application Number:
  US11/184,022
• Publication Number:
  US 20060204720A1
• Time in Patent Office: Days
• US Class Current: 428/156
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: Y10T 428/24479 including variation in thickness

Abstract

An article, such as a film, comprising a body portion and a surface portion is provided. The body portion has (i) a first 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 body. The surface portion comprises a linear geometric feature disposed on the first surface of the body in a direction substantially parallel to the first in-plane axis of the polymeric body. The article has (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 n₂ and n₃ are substantially the same but substantially different from n₁; and wherein the uniaxially oriented polymeric film has a relative birefringence of 0.3 or less and wherein the ratio of the thickness of the body to the height of the geometric feature is at least 2.

Claims

1. A uniaxially oriented structured surface polymeric film comprising:

(a) a polymeric body having (i) a first 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; and

(b) a linear structured feature disposed on the first surface of the polymeric body in a direction substantially parallel to the first in-plane axis of the polymeric film;

wherein the uniaxially oriented polymeric film has (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; and

wherein the uniaxially oriented polymeric film has a relative birefringence of 0.3 or less and wherein the ratio of the thickness of the body to the height of the geometric feature is at least 2.

2. The polymeric film of claim 1 wherein the film comprises a multilayer film having a plurality of layers of different polymeric composition.

3. The polymeric film of claim 1 wherein the polymeric film has a total thickness and the geometric feature has a base width and wherein the thickness of the body of the polymeric film to the base width of the feature is greater than about 3.

4. The polymeric film of claim 1 wherein the geometric feature comprises a micro-feature.

5. The polymeric film of claim 1 having a retained shape parameter of at least 0.1.

6. A roll of the film of claim 1 comprising a plurality of plies of the film wound upon themselves such that the first surface a specific ply of the film contacts the second surface of a next ply of the film.