Processes and apparatus for making transversely drawn films with substantially uniaxial character
First Claim
Patent Images
1. 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.
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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.
120 Citations
31 Claims
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1. A method of processing a film, the method comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method of forming an optical film, the method comprising:
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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. - View Dependent Claims (17, 18, 19, 20, 21)
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22. A method of processing a film, the method comprising:
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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. - View Dependent Claims (23, 24, 25, 26, 27)
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28. A method of processing a film, the method comprising:
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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 λ
1/2 where λ
is the transverse direction draw ratio. - View Dependent Claims (29, 30, 31)
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Specification