PROCESSES AND APPARATUS FOR MAKING TRANSVERSELY DRAWN FILMS WITH SUBSTANTIALLY UNIAXIAL CHARACTER

• US 20100254002A1
• Filed: 06/21/2010
• Published: 10/07/2010
• Est. Priority Date: 05/31/2001
• Status: Active Grant

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Wheatley, John A., Merrill, William Ward, Ruff, Andrew T., Jackson, Jeffery N., Krueger, Dennis L.
• Granted Patent: US 9,314,961 B2
• Time in Patent Office: Days
• US Class Current: 359/487
• CPC Class Codes: B29C 2793/009 after shaping
• CPC Class Codes: B29C 55/08 transverse to the direction of feed
• CPC Class Codes: B29C 55/20 Edge clamps
• CPC Class Codes: B29C 69/001 a shaping technique combined with cutting, e.g. in parts or slices combined with rearranging and joining the cut parts for reinforced material B29C70/545; B29C49/4278, B29C51/268 take precedence
• CPC Class Codes: B29K 2067/003 PET, i.e. poylethylene terephthalate
• CPC Class Codes: B29K 2995/0051 mono-axially
• CPC Class Codes: B29L 2011/00 Optical elements, e.g. lenses, prisms
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid
• CPC Class Codes: Y10S 425/041 Reshape

Abstract

A stretcher for substantially uniaxially orienting a film includes a plurality of gripping members to hold opposing edge portions of the film, paths along which the gripping members travel to stretch the film in a stretching region, and a drive mechanism to convey the film and gripping members along a machine direction. At least a portion of the paths in the stretching region define diverging, curvilinear courses disposed in-plane. The paths are configured such that during the stretching an extent of uniaxial character, U, is between zero and unity and a minimum value of an extent of uniaxial character, U, is at least 0.70 over a final portion of the stretching after achieving a TDDR of 2.5. U is defined as U=(1/MDDR−1)/(TDDR^1/2−1), wherein TDDR is greater than 4 at an end of the stretching region.

Claims

1. A roll of multilayer optical film, the roll comprising a substantially uniaxially-oriented multilayer optical film, wherein at least one layer of the multilayer optical film has indices of refraction in a length direction and a thickness direction that are substantially the same, but substantially different from an index of refraction in a width direction.

2. The roll of claim 2, wherein the multilayer optical film is a reflective polarizer.

3. A stretcher for processing a film, the stretcher comprising:

means for receiving a film;

means for grasping edge portions of the film;

means for conveying the film in a machine direction; and

means for moving the opposing edge portions along diverging, substantially parabolic paths to form a stretched film.

4. An apparatus for processing a film, the apparatus comprising:

conveying means for conveying a film along a machine direction within a stretching region of the apparatus, the conveying means comprising gripping means for holding opposing edge portions of the film, a portion of the conveying means providing diverging curvilinear paths to stretch the film; and

isolated takeaway means for grasping opposing takeaway regions of the film and taking the film from the conveyor directly from the stretching region and conveying the film further along in the machine direction.

5. The apparatus of claim 4, further comprising slitting means for slitting a stretched portion of the film between the opposing edge portions and the opposing takeaway regions to form selvages.