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Optical bodies made with a birefringent polymer
| Details |
Inventors: Hebrink, Timothy J.; Condo, Peter D.; Merrill, William W.;
Assignee: 3M Innovative Properties Company (St. Paul, MN)
Primary Examiner: Chang; Audrey
Assistant Examiner: Curtis; Craig
Attorney, Agent or Firm: Black; Bruce E.
A optical body has at least two polymeric materials forming a reflective interface for at least one polarization of light. One optical body is a multilayer optical film that includes birefringent first optical layers and second optical layers interleaved with the first optical layers. Each first optical layer is formed using a polymer, such as a copolymer of polyethylene naphthalate. The second optical layers are formed so that they have a lower in-plane birefringence than the first optical layers for 632.8 nm light. Optical bodies can be used as, for example, polarizers and mirrors. The optical bodies can be formed using polymers that provide better index matching and are more easily protected from UV light without coloring the optical body. |
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DETAILED DESCRIPTION Generally, the present invention relates to optical bodies and their manufacture, as well as the use of the optical bodies in optical devices, such as polarizers and mirrors.
One embodiment is a multilayer optical film that includes birefringent first optical layers and second optical layers interleaved with the first optical layers.
Each first optical layer is formed using a copolymer of polyethylene naphthalate with less than 70 mol % of the carboxylate subunits being naphthalate subunits.
The second optical layers have a lower in-plane birefringence than the first optical layers for 632.
8 nm light.
The copolymer of the first optical layers can be a random or block copolymer.
The invention is also directed to methods of making and using the optical films and devices containing the optical films.
Another embodiment is a multilayer optical film that includes birefringent first optical layers and second optical layers interleaved with the first optical layers.
Each first optical layer is formed using a polymer (e.
g.
, a copolymer of polyethylene naphthalate) that is capable of yielding an in-plane birefringence of at least about 0.
16 for 632.
8 nm light after orienting the polymer at a temperature no more than about 5.
degree.
C.
above the glass transition temperature of the copolymer or, if desired, no greater than the glass transition temperature of the copolymer.
The second optical layers have a lower in-plane birefringence than the first optical layers for 632.
8 nm light.
Preferably, the polymer is capable of yielding an in-plane birefringence of at least 0.
18 for 632.
8 nm light, more preferably, at least 0.
19, after orienting the polymer at a temperature no more than about 5.
degree.
C.
above the glass transition temperature of the copolymer or, if desired, no greater than the glass transition temperature of the copolymer.
The invention is also directed to methods of making and using the optical films and devices containing the optical films.
Yet another embodiment is a multilayer optical film that includes birefringent first optical layers and second optical layers interleaved with the first optical layers
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