Transparent film and optical compensatory film, polarizing plate and liquid-crystal display device employing it

• US 8,187,681 B2
• Filed: 03/24/2005
• Issued: 05/29/2012
• Est. Priority Date: 03/25/2004
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Nakayama, Hajime, Saitoh, Yukito
• Primary Examiner(s): Sample, David
• Assistant Examiner(s): GUGLIOTTA, NICOLE T
• Application Number:
  US10/594,041
• Publication Number:
  US 20070285603A1
• Time in Patent Office: 2,623 Days
• Field of Search: None
• US Class Current: 428/1.33
• CPC Class Codes: C08J 2301/12 Cellulose acetate
• CPC Class Codes: C08J 2365/00 Characterised by the use of macromolecular compounds obtained by reactions forming a carbon-to-carbon link in the main chain C08J2307/00 - C08J2357/00, C08J2361/00 take precedence; Derivatives of such polymers
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C09K 2323/035 Ester polymer, e.g. polycarbonate, polyacrylate or polyester
• CPC Class Codes: G02B 5/305 including organic materials, e.g. polymeric layers
• CPC Class Codes: G02F 1/133634 the refractive index Nz perpendicular to the element surface being different from in-plane refractive indices Nx and Ny, e.g. biaxial or with normal optical axis
• CPC Class Codes: G02F 1/13396 Spacers having different sizes
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 2203/04 wavelength independent

Abstract

A novel transparent film is disclosed. Re (λ) and Rth (λ) of the film defined by the following formulae (I) and (II) satisfy the following formulae (III) and (IV):
Re(λ)=(nx−ny)×d,  (I)
Rth(λ)={(nx+ny)/2−nz}×d,  (II)
0≦|Re(630)|≦50,  (III)
Rth(400)×Rth(700)≦0, and 0≦|Rth(700)−Rth(400)|≦150,  (IV)

• • wherein Re (λ) means an in-plane retardation value at a wavelength λ nm (unit: nm); Rth (λ) means a thickness-direction retardation value at a wavelength λ, nm (unit: nm); nx means a refractive index in the in-plane slow-axis direction; ny means a refractive index in the in-plane fast-axis direction; nz means a refractive index in the film thickness direction; and d means a thickness of the film.

Claims

1. A transparent film of which Re (λ

) and Rth (λ

) defined by following formulae (I) and (II) satisfy following formulae (III) and (IV);

Re(λ

)=(nx−

ny)×

d, 

 

(I)

Rth(λ

)={(nx+ny)/2−

nz}×

d, 

 

(II)

0≦

|Re(630)|≦

50, 

 

(III)

Rth(400)×

Rth(700)<

0, and 0≦

|Rth(700)−

Rth(400)|≦

150, 

 

(IV)

wherein Re (λ

) means an in-plane retardation value at a wavelength λ

nm (unit;

nm);

Rth (λ

) means a thickness-direction retardation value at a wavelength λ

nm (unit;

nm);

nx means a refractive index in the in-plane slow-axis direction;

ny means a refractive index in the in-plane fast-axis direction;

nz means a refractive index in the film thickness direction; and

d means a thickness of the film; and

wherein the transparent film comprises a compound which has an absorption in a UV region of from 200 to 400 nm and of which the wavelength dispersion of Re and Rth is larger on the shorter wavelength side.

2. The transparent film of claim 1, which comprises a thermoplastic norbornene resin.

3. The transparent film of claim 1, which comprises a cellulose acylate.

4. The transparent film of claim 3, wherein the cellulose acylate has a degree of acyl substitution of from 2.85 to 3.00.

5. The transparent film of claim 4, wherein the acyl substituent in the cellulose acylate comprises two selected from the group consisting of an acetyl group, a propionyl group and a butanoyl group;

and the degree of total acyl substitution is from 2.50 to 3.00.

6. The transparent film of claim 1, which comprises at least one compound capable of reducing Re(λ

) and Rth(λ

).

7. The transparent film of claim 1, which comprises at least one compound capable of reducing Re(λ

) and Rth(λ

) of the film and having an octanol-water partition coefficient (Log p value) of from 0 to 7, in an amount of from 0.01 to 30% by weight of the solid content of the film.

9. The transparent film of claim 1, having a thickness of from 10 to 120 μ

m.

10. An optical compensatory film comprising a transparent film of claim 1 and an optically-anisotropic layer having Re (630) of from 0 to 200 nm and |Rth (630)| of from 0 to 400 nm.

11. A polarizing plate comprising an optical compensatory film of claim 10, and a polarizer.

15. The liquid-crystal display device of claim 12, wherein the transparent film is a transparent film of claim 1.

8. A transparent film of which Re (λ

) and Rth (λ

) defined by following formulae (I) and (II) satisfy following formulae (III) and (IV);

Re(λ

)=(nx−

ny)×

d, 

 

(I)

Rth(λ

)={(nx+ny)/2−

nz}×

d, 

 

(II)

0≦

|Re(630)|≦

50, 

 

(III)

Rth(400)×

Rth(700)<

0, and 0≦

|Rth(700)−

Rth(400)|≦

150, 

 

(IV)

wherein Re (λ

) means an in-plane retardation value at a wavelength λ

nm (unit;

nm);

Rth (λ

) means a thickness-direction retardation value at a wavelength λ

nm (unit;

nm);

nx means a refractive index in the in-plane slow-axis direction;

ny means a refractive index in the in-plane fast-axis direction;

nz means a refractive index in the film thickness direction; and

d means a thickness of the film;

wherein the transparent film contains at least one compound of any of the following formulae (2) to (19) capable of reducing Re(λ

) and Rth(λ

) of the film and having an octanol-water partition coefficient (Log p value) of from 0 to 7, in an amount of from 0.01 to 30%, by weight of the solid content of the film;

12. A liquid-crystal display device, which comprises a transparent film of which Re (λ

) and Rth (λ

) defined by the following formulae (I) and (II) satisfy the following formulae (III) and (IV);

Re(λ

)=(nx−

ny)×

d, 

 

(I)

Rth(λ

)={(nx+ny)/2−

nz}×

d, 

 

(II)

0≦

|Re(630)|≦

50, 

 

(III)

Rth(400)×

Rth(700)<

0, and 0≦

|Rth(700)−

Rth(400)|≦

150, 

 

(IV)

wherein Re (λ

) means an in-plane retardation value at a wavelength λ

nm (unit;

nm);

Rth (λ

) means a thickness-direction retardation value at a wavelength λ

nm (unit;

nm);

nx means a refractive index in the in-plane slow-axis direction;

ny means a refractive index in the in-plane fast-axis direction;

nz means a refractive index in the film thickness direction; and

d means a thickness of the film; and

wherein the liquid-crystal display device employs an IPS mode.

14. The liquid-crystal display device of claim 12, wherein the light leakage value in the black state of the device is at most 0.022% at an azimuth angle of 45 degrees and at a polar angle of 60 degrees.

16. The liquid-crystal display device of claim 12, wherein the transparent film is a transparent film of claim 8.

17. The liquid-crystal display device of claim 12, wherein the transparent film is a transparent film of claim 13.

18. The liquid-crystal display device of claim 12, wherein the transparent film comprises a thermoplastic norbornene resin.

19. The liquid-crystal display device of claim 12, wherein the transparent film comprises a cellulose acylate.

20. The liquid-crystal display device of claim 19, wherein the cellulose acylate has a degree of acyl substitution of from 2.85 to 3.00.

21. The liquid-crystal display device of claim 20, wherein the acyl substituent in the cellulose acylate comprises two selected from the group consisting of an acetyl group, a propionyl group and a butanoyl group;

and the degree of total acyl substitution is from 2.50 to 3.00.

22. The liquid-crystal display device of claim 12, wherein the transparent film comprises at least one compound capable of reducing Re(λ

) and Rth(λ

).

23. The liquid-crystal display device of claim 12, wherein the transparent film comprises at least one compound capable of reducing Re(λ

) and Rth(λ

) of the film and having an octanol-water partition coefficient (Log p value) of from 0 to 7, in an amount of from 0.01 to 30% by weight of the solid content of the film.

24. The liquid-crystal display device of claim 12, wherein the transparent film comprises at least one compound capable of lowering |Rth (700)−

Rth (400)| of the film.

25. The liquid-crystal display device of claim 12, wherein the transparent film has a thickness of from 10 to 120 λ

m.

26. The liquid-crystal display device of claim 12, further comprising an optically-anisotropic layer having Re (630) of from 0 to 200 nm and |Rth (630)| of from 0 to 400 nm.

13. A transparent film of which Re (λ

) and Rth (λ

) defined by following formulae (I) and (II) satisfy following formulae (III) and (IV);

Re(λ

)=(nx−

ny)×

d, 

 

(I)

Rth(λ

)={(nx+ny)/2−

nz}×

d, 

 

(II)

0≦

|Re(630)|≦

50, 

 

(III)

Rth(400)×

Rth(700)<

0, and 0≦

|Rth(700)−

Rth(400)|≦

150, 

 

(IV)

wherein Re (λ

) means an in-plane retardation value at a wavelength λ

nm (unit;

nm);

Rth (λ

) means a thickness-direction retardation value at a wavelength λ

, nm (unit;

nm);

nx means a refractive index in the in-plane slow-axis direction;

ny means a refractive index in the in-plane fast-axis direction;

nz means a refractive index in the film thickness direction; and

d means a thickness of the film;

wherein the transparent film comprises a compound capable of reducing optical anisotropy; and

wherein the mean content of the compound in the part of 10% of the overall thickness from the surface of at least one side of the film is from 80 to 99% of the mean content of the compound in the center part of the film.