PROCESSES FOR IMPROVED OPTICAL FILMS
First Claim
1. A method of forming an optical film having a useful central 60% portion with a caliper variation of about 5% or less of an average thickness of the film, the method comprising:
- selecting a draw ratio λ
in a first in-plane stretch direction;
setting an effective draw gap defined by a length L and a width W; and
stretching a polymer film at the draw ratio and effective draw gap, the effective draw gap being set such that the stretching step fits into one of two regimes,the first regime referred to as a uniaxial regime and characterized by a β
equal to or less than about 1.0; and
the second regime referred to as a planar extension regime and characterized by a β
equal to or greater than about 10.0.
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Accused Products
Abstract
A method of forming an optical film results in a film having a useful central 60% portion with a caliper variation of about 5% or less of an average thickness of the film. The method includes selecting a draw ratio λ in a first in-plane stretch direction, setting an effective draw gap defined by a length L and a width W, and stretching a polymer film at the draw ratio and effective draw gap. The effective draw gap is set such that the stretching step fits into one of two regimes, the first regime referred to as a uniaxial regime and characterized by a β equal to or less than about 1.0; and the second regime referred to as a planar extension regime and characterized by a β equal to or greater than about 10.0. The disclosure also describes an optical film formed by the method.
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Citations
24 Claims
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1. A method of forming an optical film having a useful central 60% portion with a caliper variation of about 5% or less of an average thickness of the film, the method comprising:
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selecting a draw ratio λ
in a first in-plane stretch direction;setting an effective draw gap defined by a length L and a width W; and stretching a polymer film at the draw ratio and effective draw gap, the effective draw gap being set such that the stretching step fits into one of two regimes, the first regime referred to as a uniaxial regime and characterized by a β
equal to or less than about 1.0; andthe second regime referred to as a planar extension regime and characterized by a β
equal to or greater than about 10.0. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An optical film having a useful central 60% portion with a caliper variation of about 5% or less of an average thickness of the film, produced by a process method comprising:
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selecting a draw ratio λ
in a first in-plane stretch direction;setting an effective draw gap defined by a length L and a width W; and stretching a polymer film at the draw ratio and effective draw gap, the effective draw gap being set such that the stretching step fits into one of two regimes, the first regime referred to as a uniaxial regime and characterized by a β
equal to or less than about 1.0; andthe second regime referred to as a planar extension regime and characterized by a β
equal to or greater than about 10.0. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of forming an optical film having a useful central 60% portion with a caliper variation of about 5% or less of an average thickness of the film, the method comprising:
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selecting an effective draw gap defined by a length L and a width W; setting a draw ratio λ
in a first in-plane stretch direction; andstretching a polymer film at the draw ratio and effective draw gap, the draw ratio being set such that the stretching step fits into one of two regimes, the first regime referred to as a uniaxial regime and characterized by a β
equal to or less than about 1.0; andthe second regime referred to as a planar extension regime and characterized by a β
equal to or greater than about 10.0.
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21. A method of increasing a uniaxial orientation of an optical film comprising:
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providing a drawn film having an initial breadth dimension and direction; constraining the drawn film in a direction substantially perpendicular to the breadth direction while not constraining the drawn film in the breadth direction; and heating the drawn film above a glass transition temperature of at least one component thereof to allow for a reduction of the initial breadth. - View Dependent Claims (22, 23, 24)
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Specification