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US 6,939,499 B2Granted
Processes and apparatus for making transversely drawn films with substantially uniaxial character
Assignee3M Innovative Properties Company
InventorsWilliam Ward Merrill, Jeffery N. Jackson, Andrew T. Ruff, John A. Wheatley, Dennis L. Krueger
Life of this patent
Estimating the term…
Abstract
A process for stretching films is described. The process preferably stretches films in a uniaxial fashion. Preferably, optical films are stretched including multilayer optical films. Other aspects of the invention include a roll of stretched film and an apparatus for stretching films.
Claims31
A method of processing a film, the method comprising:
- conveying a film within a stretcher along a machine direction while holding opposing edge portions of the film;
- and
- stretching the film within the stretcher by moving the opposing edge portions along diverging, substantially parabolic paths to form a stretched film.
A method of forming an optical film, the method comprising:
- forming a multilayer film comprising alternating layers of different polymeric compositions;
- conveying the multilayer film into a stretcher along a machine direction while holding opposing edge portions of the multilayer film;
- and
- stretching the multilayer film within the stretcher by moving the opposing edge portions along diverging, substantially parabolic paths to form a multilayer optical film.
1 more element
A method of processing a film, the method comprising:
- conveying a film within a stretcher along a machine direction while holding opposing edge portions of the film;
- and
- stretching the film to a draw ratio in excess of four within the stretcher by moving the opposing edge portions along diverging, non-linear, coplanar paths to form a stretched film, wherein, during the stretching of the film, the minimum value of the extent of uniaxial character, U, is at least 0.8 over a final portion of the stretching after achieving a TDDR of 2.5 and U is less than 1 at the end of the stretching, wherein U is defined as
- U=(1/MDDR−1)/(TDDR1/2−1)
- wherein MDDR is the machine direction draw ratio corresponding to a divergence angle of the diverging paths and TDDR is the transverse direction draw ratio as measured between the diverging paths.
2 more elements
A method of processing a film, the method comprising:
- conveying a film within a stretcher along a machine direction while holding opposing edge portions of the film;
- and
- stretching the film within the stretcher by moving the opposing edge portions along diverging non-linear paths to form a stretched film, wherein, during the stretching of the film, the speed of the film along the machine direction decreases by a factor of approximately λ1/2 where λ is the transverse direction draw ratio.
Dependencies are inferred from the claim text.