Optical device with a dichroic polarizer and a multilayer optical film

• US 6,111,697 A
• Filed: 01/13/1998
• Issued: 08/29/2000
• Est. Priority Date: 01/13/1998
• Status: Expired due to Term

• Current Assignee: 3M Innovative Properties Company (3M Company)
• Original Assignee: 3M Innovative Properties Company (3M Company)
• Inventors: Hebrink, Timothy J., Kausch, William L., Merrill, William W., Williams, Brian H.
• Primary Examiner(s): Schuberg, Darren E.
• Application Number:
  US09/006,468
• Time in Patent Office: 959 Days
• Field of Search: 359/483, 359/485, 359/487, 359/488, 359/490, 359/493, 359/497, 359/498, 359/500, 252/585
• US Class Current: 359/487.02
• CPC Class Codes: G02B 5/3041 comprising multiple thin layers, e.g. multilayer stacks
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers

Abstract

An optical device includes a dichroic polarizer and a multilayer optical film, such as a reflective polarizer or mirror. The multilayer optical film is made using polymers which may allow for the simultaneous orientation of the dichroic and reflective polarizers. The multilayer optical film often contains a set of birefringent first layers and a set of second layers, which may have an isotropic index of refraction. The dichroic polarizers is a polyvinyl alcohol film with a dichroic dye. The multilayer optical film and dichroic polarizer can be stretched at temperatures of 130° C. or less to orient the two films without substantial cracking of the dichroic polarizer. When an optional second polymer is combined with the polyvinyl alcohol, the multilayer optical film and dichroic polarizer can be stretched at temperatures of about 160° C. without substantial cracking of the dichroic polarizer.

Claims

1. An optical polarizer, comprising:

a dichroic polarizer; and

a reflective polarizer positioned in the same optical path as the dichroic polarizer, the reflective polarizer comprising

a plurality of first optical layers comprising a first copolyester, the first copolyester being semicrystalline and birefringent, the first copolyester comprising carboxylate subunits and glycol subunits, wherein 70 to 100 mol % of the carboxylate subunits are first carboxylate subunits, 0 to 30 mol % of the carboxylate subunits are first comonomer carboxylate subunits, 70 to 100 mol % of the glycol subunits are first glycol subunits, and 0 to 30 mol % of the glycol subunits are first comonomer glycol subunits, and wherein at least 0.5 mol % of the combined carboxylate and glycol subunits of the first copolyester are first comonomer carboxylate subunits, first comonomer glycol subunits, or a combination thereof; and

a plurality of second optical layers comprising a second polymer having an in-plane birefringence of about 0.04 or less, at 632.8 nm, after the reflective polarizer has been formed.

2. The optical polarizer of claim 1, wherein at least 2.5 mol % of the combined carboxylate and glycol subunits of the first copolyester are first comonomer carboxylate subunits, first comonomer glycol subunits, or a combination thereof.

3. The optical polarizer of claim 1, wherein the second polymer comprises a second copolyester.

4. The optical polarizer of claim 3, wherein the second copolyester comprises carboxylate subunits and glycol subunits, the carboxylate subunits comprising 20 to 100 mol % second carboxylate subunits and 0 to 80 mol % second comonomer carboxylate subunits, the glycol subunits comprising 40 to 100 mol % second glycol subunits and 0 to 60 mol % second comonomer glycol subunits, wherein 10 mol % or more of the combined carboxylate and glycol subunits of the second copolyester are second comonomer carboxylate subunits, second comonomer glycol subunits, or a combination thereof.

5. The optical polarizer of claim 4, wherein 0.01 to 2.5 mol % of the combined carboxylate and glycol subunits of the second copolyester are second comonomer carboxylate subunits derived from compounds having three or more carboxylate or ester functionalities, second comonomer glycol subunits derived from compounds having three or more hydroxy functionalities, or a combination thereof.

6. The optical polarizer of claim 4, wherein the glycol subunits are derived from 70 to 100 mol % C2-C4 diols and 0 to 30 mol % second comonomer glycol subunits derived from one or more of 1,6-hexanediol, trimethylol propane, neopentyl glycol, or a combination thereof;

and the carboxylate subunits are 20 to 100 mol % naphthalate subunits, 0 to 80 mol % terephthalate or isophthalate subunits or mixtures thereof, and 0 to 30 mol % of second comonomer carboxylate subunits derived from phthalic acid, t-butyl-isophthalic acid, lower alkyl esters of these acids, or a combination thereof;

wherein at least 0.5 mol % of the combined carboxylate and glycol subunits of the second copolyester are second comonomer carboxylate subunits, second comonomer glycol subunits, or a combination thereof.

7. The optical polarizer of claim 4, wherein the second copolyester comprises glycol subunits derived from 85 to 99.99 mol % C2-C4 diols and 0.01 to 5 mol % branching monomer molecules and carboxylate subunits derived from 5 to 95 mol % cyclohexane dicarboxylic acid or lower alkyl esters thereof and 5 to 95 mol % tertiary-butyl isophthalic acid or lower alkyl esters thereof.

8. The optical polarizer of claim 4, wherein the first and second carboxylate subunits are the same.

9. The optical polarizer of claim 1, wherein, after the multilayer reflective polarizer is formed, the first copolyester has an in-plane birefringence of 0.1 or greater at 632.8 nm.

10. The optical polarizer of claim 1, wherein the first carboxylate subunits are naphthalate or terephthalate subunits.

11. The optical polarizer of claim 1, further comprising one or more non-optical layers.

12. The optical polarizer of claim 1, wherein the first copolyester has in-plane indices of 1.83 or less and which differ from each other by 0.20 or greater when measured with 632.8 nm light.

13. The optical polarizer of claim 1, wherein the reflective polarizer is formed by drawing the first and second layers in at least one draw direction to a particular draw ratio and, after drawing, the first optical layers of the reflective polarizer have an index of refraction in the draw direction is at least 0.02 units less, as measured at 632.8 nm, than an index of refraction in the draw direction of a similarly constructed polyethylene naphthalate layer which has a same in-plane birefringence at 632.8 nm.

14. The optical polarizer of claim 1, wherein 1 to 30 mol % of the glycol subunits are first comonomer glycol subunits.

15. The optical polarizer of claim 1, wherein the dichroic polarizer comprises polyvinyl alcohol and a dichroic dye material.

16. The optical polarizer of claim 15, wherein the dichroic polarizer further comprises an additional polymer.

17. The optical polarizer of claim 16, wherein the dichroic polarizer is formed by removal of a solvent from a dispersion of polyvinyl alcohol and the additional polymer in the solvent.

18. The optical polarizer of claim 17, wherein the solvent is water.

28. The optical polarizer of claim 15, wherein the dichroic polarizer is disposed on the reflective polarizer and the dichroic polarizer and reflective polarizer were simultaneously oriented by stretching at a processing temperature without substantial cracking of the dichroic polarizer.

19. A method of making an optical polarizer, comprising:

forming a reflective polarizer, the reflective polarizer comprising a plurality of first optical layers comprising a first copolyester, the first copolyester being semicrystalline and birefringent, the first copolyester comprising carboxylate subunits and glycol subunits, wherein 70 to 100 mol % of the carboxylate subunits are first carboxylate subunits, 0 to 30 mol % of the carboxylate subunits are first comonomer carboxylate subunits, 70 to 100 mol % of the glycol subunits are first glycol subunits, and 0 to 30 mol % of the glycol subunits are first comonomer glycol subunits, and wherein at least 0.5 mol % of the combined carboxylate and glycol subunits of the first copolyester are first comonomer carboxylate subunits, first comonomer glycol subunits, or a combination thereof; and

a plurality of second optical layers comprising a second polymer having an in-plane birefringence of about 0.04 or less, at 632.8 nm, after the reflective polarizer film has been formed;

forming a dichroic polarizer on the reflective polarizer, the dichroic polarizer comprising polyvinyl alcohol and a dichroic dye material; and

stretching the dichroic polarizer and reflective polarizer to orient the dichroic and reflective polarizers at a temperature of about 130°

C. or less, without substantial cracking of the dichroic polarizer.

20. The method of claim 19, wherein the temperature at which the dichroic and reflective polarizers are stretched is about 130°

C. or less.

21. A method of making an optical polarizer, comprising:

forming a reflective polarizer, the reflective polarizer comprising a plurality of first optical layers comprising a first copolyester, the first copolyester being semicrystalline and birefringent, the first copolyester comprising carboxylate subunits and glycol subunits, wherein 70 to 100 mol % of the carboxylate subunits are first carboxylate subunits, 0 to 30 mol % of the carboxylate subunits are first comonomer carboxylate subunits, 70 to 100 mol % of the glycol subunits are first glycol subunits, and 0 to 30 mol % of the glycol subunits are first comonomer glycol subunits, and wherein at least 0.5 mol % of the combined carboxylate and glycol subunits of the first copolyester are first comonomer carboxylate subunits, first comonomer glycol subunits, or a combination thereof; and

a plurality of second optical layers comprising a second polymer having an in-plane birefringence of about 0.04 or less, at 632.8 nm, after the reflective polarizer film has been formed;

forming a dichroic polarizer on the reflective polarizer, the dichroic polarizer comprising polyvinyl alcohol, a second polymer and a dichroic dye; and

stretching the dichroic polarizer and reflective polarizer to orient the dichroic and reflective polarizers at a temperature of about 160°

C. or less, without substantial cracking of the dichroic polarizer.

22. The method of claim 21, wherein forming the dichroic polarizer comprises

forming a dispersion of polyvinyl alcohol and an additional polymer in a solvent;

coating a substrate with the dispersion;

removing the solvent to form a polymeric film; and

incorporating a dichroic dye material in the polymeric film.

23. The method of claim 22, wherein the substrate is the reflective polarizer.

24. The method of claim 22, wherein forming the dichroic polarizer further comprises

removing the polymeric film from the substrate;

and

adhering the polymeric film to the reflective polarizer.

25. An optical device, comprising:

a dichroic polarizer; and

a multilayer optical film positioned in the same optical path as the dichroic polarizer, the multilayer optical film comprising

a plurality of first optical layers comprising a first copolyester, the first copolyester comprising carboxylate subunits and glycol subunits, wherein 70 to 100 mol % of the carboxylate subunits are first carboxylate subunits, 0 to 30 mol % of the carboxylate subunits are first comonomer carboxylate subunits, 70 to 100 mol % of the glycol subunits are first glycol subunits, and 0 to 30 mol % of the glycol subunits are first comonomer glycol subunits, and wherein at least 0.5 mol % of the combined carboxylate and glycol subunits of the first copolyester are first comonomer carboxylate subunits, first comonomer glycol subunits, or a combination thereof; and

a plurality of second optical layers comprising a second polymer.

26. The optical device of claim 25, wherein the multilayer optical film comprises a reflective polarizer.

27. The optical device of claim 25, wherein the multilayer optical film comprises a mirror.

29. An optical polarizer, comprising:

a dichroic polarizer comprising a polymeric film containing polyvinyl alcohol and dichroic dye material; and

a reflective polarizer disposed adjacent to the dichroic polarizer and positioned in the same optical path as the dichroic polarizer, the reflective polarizer comprising

a plurality of first optical layers, each first optical layer comprising a copolyester having naphthalate subunits, wherein the copolyester is semicrystalline and birefringent, and

a plurality of second optical layers, each second optical layer comprising a second polymer having an in-plane birefringence of about 0.04 or less, at 632.8 nm, after the reflective polarizer has been formed;

wherein the copolyester and second polymer are selected to have a glass transition temperature that is sufficiently low to permit simultaneous orienting, by stretching at a processing temperature, of the polymeric film of the dichroic polarizer and the first and second optical layers of the reflective polarizer without generating cracks in the polymeric film.

30. The optical polarizer of claim 29, wherein the dichroic polarizer comprises a blend of polyvinyl alcohol and a second polymer.

31. The optical polarizer of claim 30, wherein the second polymer is selected from the group consisting of polyesters and polyvinyl pyrrolidone.

32. An optical polarizer, comprising:

a dichroic polarizer comprising a polymeric film containing polyvinyl alcohol and dichroic dye material; and

a reflective polarizer disposed adjacent to the dichroic polarizer and positioned in the same optical path as the dichroic polarizer, the reflective polarizer comprising

a plurality of first optical layers, each first optical layer comprising a copolyester having naphthalate subunits, wherein the first copolyester is semicrystalline and birefringent, and

a plurality of second optical layers, each second optical layer comprising a second polymer having an in-plane birefringence of about 0.04 or less, at 632.8 nm, after the reflective polarizer has been formed;

wherein the copolyester and second polymer are selected so that no portion of the dichroic polarizer can be removed in a crosshatched tape pull adhesion test.