Method for manufacturing a wide band polarization film

• US 6,252,640 B1
• Filed: 12/04/1998
• Issued: 06/26/2001
• Est. Priority Date: 01/10/1998
• Status: Expired due to Term

• Current Assignee: LG Cable & Machinery Limited (LG Corporation)
• Original Assignee: LG Cable & Machinery Limited (LG Corporation)
• Inventors: Kim, Tae Min, Hwang, Hee Nam, Kim, In Sun, Kim, Yang Kook, Kim, Sung Tae
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US09/205,932
• Time in Patent Office: 935 Days
• Field of Search: 349/96, 349/98, 349/175, 349/185, 349/187
• US Class Current: 349/96
• CPC Class Codes: C09K 19/00 Liquid crystal materials
• CPC Class Codes: G02B 5/3016 involving passive liquid crystal elements optical properties of liquid crystals G02F1/0063; polarising elements associated with active liquid crystal devices G02F1/133528
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence

Abstract

The present invention relates to a method for manufacturing a polarization film for a liquid crystal display and, more particularly, to a method for manufacturing a polarization film having improved wide band characteristics and improved reflectivity by binding together plural liquid crystal films having different selective light-reflecting central wavelengths.

Claims

1. A method for manufacturing a polarization film having wide band characteristics, comprising:

(a) forming two or more photopolymerized, cholesteric liquid crystal films having selective light-reflecting central wavelengths different from one another comprising,

(1) forming a coated liquid crystal layer by coating cholesteric liquid crystals having selective light-reflecting central wavelengths different from one another on respective substrates,

(2) adding photopolymerization initiator to the coated liquid crystal layer, and

(3) irradiating the coated liquid crystal layer; and

(b) binding together the two or more liquid crystal films so that the selective light-reflecting central wavelengths of the films do not neighbor one another;

wherein the cholesteric liquid crystals are produced by adding nematic liquid crystals to the cholesteric liquid crystals with a definite selective light-reflecting central wavelength at predetermined mixing ratios, and

wherein the cholesteric liquid crystal are coated on the substrate after being dissolved in non-polar solvent.

2. The method according to claim 1, further comprising the step of separating the polymerized liquid crystal films from said substrates before binding the films together.

3. The method according to claim 1, wherein the amount of nematic liquid crystals mixed with the cholesteric liquid crystals is more than 1% by weight.

4. The method according to claim 1, wherein the amount of the photopolymerization initiator added to the coated liquid crystal layer is more than 0.1% by weight.

5. The method according to claim 1, wherein the substrates include polyethyleneterephthalate films.

6. The method according to claim 1, wherein the binding of the two or more liquid crystal films is performed through thermal binding.

7. The method according to claim 1, wherein the binding of the two or more liquid crystal films is performed using an adhesive.

8. The method according to claim 7, wherein the adhesive has a refractive index equal or similar to that of the liquid crystal.

9. The method according to claim 1, wherein the irradiation step comprises irradiating with an ultraviolet ray of 365 nm.

10. The method according to claim 1, wherein the mixing ratio of said cholesteric liquid crystals to said nematic liquid crystals is in the range of about 0.9:

1 to 9.5;

1.

11. A liquid crystal display element having a liquid crystal cell between two glass substrates, wherein on the outside of the respective glass substrates, lamination type wide-band polarization films produced according to claim 1 are each disposed.

12. The method according to claim 1, wherein the non-polar solvent is selected from the group consisting of toluene and cyclohexane.

13. A method for manufacturing a polarization film having wide band characteristics, comprising:

(a) forming two or more photopolymerized, cholesteric liquid crystal films having selective light-reflecting central wavelengths different from one another comprising,

(1) forming a coated liquid crystal layer by coating cholesteric liquid crystals having selective light-reflecting central wavelengths different from one another on respective substrates,

(2) adding photopolymerization initiator to the coated liquid crystal layer, and

(3) irradiating the coated liquid crystal layer; and

(b) binding together the two or more liquid crystal films so that the selective light-reflecting central wavelengths of the films do not neighbor one another; and

(c) mounting a quarter wave (λ

/4) retardation film on top of the bound liquid crystal films;

wherein the cholesteric liquid crystals are produced by adding nematic liquid crystals to the cholesteric liquid crystals with a definite selective light-reflecting central wavelength at predetermined mixing ratios, and

wherein the cholesteric liquid crystal are coated on the substrate after being dissolved in non-polar solvent.

14. The method according to claim 13, further comprising separating the polymerized liquid crystal films from said substrates before binding the films together.

15. The method according to claim 13, wherein the amount of nematic liquid crystals mixed with the cholesteric liquid crystals is more than 1% by weight.

16. The method according to claim 13, wherein the amount of the photopolymerization initiator added to the coated liquid crystal layer is more than 0.1% by weight.

17. The method according to claim 13, wherein the substrates include polyethyleneterephthalate films.

18. The method according to claim 13, wherein the binding of the two or more liquid crystal films is performed through thermal binding.

19. The method according to claim 13, wherein the binding of the two or more liquid crystal films is performed using an adhesive.

20. The method according to claim 19, wherein the adhesive has a refractive index equal or similar to that of the liquid crystal.

21. The method according to claim 13, wherein the irradiation step comprises irradiating with an ultraviolet ray of 365 nm.

22. The method according to claim 13, wherein the mixing ratio of said cholesteric liquid crystals to said nematic liquid crystals is in the range of about 0.9:

1 to 9.5;

1.

23. A liquid crystal display element having a liquid crystal cell between two glass substrates, wherein on the outside of the respective glass substrates, lamination type wide-band polarization films produced according to claim 13 are each disposed.

24. The method according to claim 13, wherein the non-polar solvent is selected from the group consisting of toluene and cyclohexane.