Low Tg multilayer optical films
First Claim
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1. An optical film, comprising:
- (a) a plurality of first optical layers, each first optical layer comprising high refractive index birefringent polymers, wherein the polymers in the first optical layers comprise the polymerization product of an aromatic carboxylated comonomer and a sufficient amount of a glycol comonomer derived from 50–
100 mol % of diols having a carbon chain length of C6 or longer; and
(b) a plurality of second optical layers disposed in a repeating sequence with the plurality of first optical layers, each second optical layer comprising low refractive index polymers, wherein such polymers have a Tg below room temperature.
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Abstract
Multilayer optical films are comprised of materials with glass transition temperatures below room temperature (<30° C.). The high refractive index polymers are unique in that they exhibit mechanical properties similar to other low Tg semi-crystalline polymers, yet have significant birefringence (>0.05) when strain induced oriented. Novel combinations of comonomers for thermoplastics control the rate of crystallinity for improved processability and flexibility, giving the films crease and crumple recovery advantages.
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Citations
36 Claims
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1. An optical film, comprising:
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(a) a plurality of first optical layers, each first optical layer comprising high refractive index birefringent polymers, wherein the polymers in the first optical layers comprise the polymerization product of an aromatic carboxylated comonomer and a sufficient amount of a glycol comonomer derived from 50–
100 mol % of diols having a carbon chain length of C6 or longer; and(b) a plurality of second optical layers disposed in a repeating sequence with the plurality of first optical layers, each second optical layer comprising low refractive index polymers, wherein such polymers have a Tg below room temperature. - View Dependent Claims (2, 3, 4, 5, 11, 20, 21, 23, 25, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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6. A bank note, comprising:
(a) an optical film, comprising; (i) a plurality of first optical layers, each first optical layer comprising high refractive index birefringent polymers, wherein the polymers in the first optical layers comprise carboxylate subunits and glycol subunits derived from 50–
100 mol % of diols having a carbon chain length of C6 or longer; and(ii) a plurality of second optical layers disposed in a repeating sequence with the plurality of first optical layers, each second optical layer comprising low refractive index polymers, wherein such low refractive index polymers have a TgL below room temperature. - View Dependent Claims (7, 8, 9, 12, 13, 14, 15, 22, 24, 26)
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10. An optical film obtained by orienting a multi-layered film, wherein the film is comprised of:
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(a) a plurality of first optical layers, each- first optical layer being oriented and comprising high refractive index birefringent polymers, wherein the polymers in the first optical layer comprise at least 50 mol % of terephthalate comonomer subunits and 50–
100 mol % of glycol comonomer subunits, wherein the glycol subunits are derived from diols comprising a carbon chain length of C6 or longer; and(b) a plurality of second optical layers disposed in a repeating sequence with the plurality of first optical layers, each second optical layer comprising low refractive index polymers, wherein such polymers have a TgL below room temperature, with the proviso that TgH is less than TgL. - View Dependent Claims (16, 17, 18, 19)
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36. An optical film, comprising:
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(a) a plurality of first optical layers, each first optical layer comprising high refractive index birefringent polymers, wherein the polymers in the first optical layer comprise at least 50 mol % of terephthalate comonomer subunits and 50–
100 mol % of glycol comonomer subunits, wherein the glycol subunits are derived from diols having a carbon chain length of C6 or longer and wherein the refractive indices of the polymers in the first optical layer exhibit a strain induced birefringence between at least one in-plane axis and the axis normal to the film plane of at least 0.05; and(b) a plurality of second optical layers disposed in a repeating sequence with the plurality of first optical layers, each second optical layer comprising low refractive index polymers, wherein such polymers have a Tg below room temperature.
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Specification