Transparent Film And Optical Compensatory Film, Polarizing Plate And Liquid-Crystal Display Device Employing It

• US 20070285603A1
• Filed: 03/24/2005
• Published: 12/13/2007
• Est. Priority Date: 03/25/2004
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Saitoh, Yukito, Nakayama, Hajime
• Granted Patent: US 8,187,681 B2
• Time in Patent Office: Days
• US Class Current: 349/118
• 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.

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 consists of substantially two selected from 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.

8. The transparent film of claim 1, which contains at least one compound of any of the following formulae (1) 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;

9. The transparent film of claim 1, which comprises at least one compound capable of lowering |Rth (700)−

Rth (400)| of the film.

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

m.

11. 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.

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

19. The transparent film of claim 3, wherein the acyl substituent in the cellulose acylate consists of substantially two selected from an acetyl group, a propionyl group and a butanoyl group;

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

20. A polarizing plate comprising at least one of a transparent film or an optical film of claim 11, and a polarizer, wherein the transparent film is 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.

13. 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.

14. A liquid-crystal display device comprising a liquid-crystal cell, which has a pair of substrates disposed to face each other and having an electrode on at least one of them, and a liquid-crystal layer sandwiched between the pair of substrates and comprising a nematic liquid-crystal material, wherein the liquid-crystal molecules of the nematic liquid-crystal material are aligned substantially in parallel to the surface of the pair of substrates in a black state and wherein the product of the thickness d (μ

m) and the refractivity anisotropy Δ

n, Δ

n·

d, of the liquid-crystal layer falls within the range from 0.2 and 1.0 μ

m, first and second polarizing films disposed to sandwich the liquid-crystal cell between them, and a transparent film is disposed between at least one of the first and second polarizing films and the liquid-crystal cell,

wherein Re (λ

) and Rth (λ

) of the transparent film, as 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.

15. The liquid-crystal display device of claim 14, further comprising first and second optical compensatory films,

wherein the first polarizing film, the second optical compensatory film, the first optical compensatory film, the liquid-crystal cell, the transparent film and the second polarizing film are disposed in this order, Re of the second optical compensatory film is not greater than 100 nm and the thickness-direction retardation Rth thereof is not greater than 200 nm, the refractivity anisotropy of the first optical compensatory film is negative and the optical axis thereof is substantially in parallel to the layer face, the slow axis of the first optical compensatory film is parallel to the transmission axis of the first polarizing film and to the slow axis direction of the liquid-crystal cell in a black display, and Re of the first optical compensatory film falls within the range from 50 nm to 400 nm.

16. The liquid-crystal display device of claim 15, wherein at least one of the first optical compensatory film and the second optical compensatory film comprises at least one discotic liquid-crystal compound.

17. The liquid-crystal display device of claim 14 further comprising first and second optical compensatory film,

wherein the first polarizing film, the second optical compensatory film, the first optical compensatory film, the liquid-crystal cell, the transparent film and the second polarizing film are disposed in this order, Re of the second optical compensatory film is not greater than 100 nm and the thickness-direction retardation Rth thereof is not greater than 200 nm, Re of the first optical compensatory film falls within the range from 100 nm to 300 nm, and Nz of the first optical compensatory film, defined as Nz=(nx−

nz)/(nx−

ny), falls within the range from 0.2 to 0.8 where nx and ny are the in-plane refractive index of the film (nx≧

ny), nz is the thickness-direction refractive index of the film, and d is the thickness of the film.

18. The liquid-crystal display device of claim 17, wherein at least one of the first optical compensatory film and the second optical compensatory film is a biaxially-stretched film.