Optical film

• US 8,877,304 B2
• Filed: 06/17/2008
• Issued: 11/04/2014
• Est. Priority Date: 06/19/2007
• Status: Active Grant

• Current Assignee: Teijin Chemicals Ltd. (Teijin Limited)
• Original Assignee: Teijin Chemicals Ltd. (Teijin Limited)
• Inventors: Motoyoshi, Tetsuya, Ando, Masatoshi, Ueno, Makoto, Nishijima, Akiko
• Primary Examiner(s): Blackwell, Gwendolyn
• Assistant Examiner(s): Zhang, Ruiyun
• Application Number:
  US12/452,180
• Publication Number:
  US 20100104777A1
• Time in Patent Office: 2,331 Days
• Field of Search: 428/1.1, 428/1.31, 428/412, 428/64.7, 349/75, 349/117, 349/96, 349/98, 528/206, 528/196, 528/204
• US Class Current: 428/1.31
• CPC Class Codes: C08G 64/1608 saturated
• CPC Class Codes: C08J 2369/00 Characterised by the use of polycarbonates; Derivatives of polycarbonates
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C09K 2323/00 Functional layers of liquid crystal optical display excluding electroactive liquid crystal layer characterised by chemical composition
• CPC Class Codes: C09K 2323/031 Polarizer or dye
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133637 characterised by the wavelength dispersion
• CPC Class Codes: Y10T 428/31507 Of polycarbonate

Abstract

It is an object of the present invention to provide an optical film which has reverse chromatic dispersibility that its retardation becomes smaller as the wavelength becomes shorter and a low photoelastic constant.

The optical film is made of a polycarbonate copolymer containing a unit (A) represented by the following formula:

• • wherein R₁ and R₂ are each independently a hydrogen atom, hydrocarbon group having 1 to 10 carbon atoms or the like, R₃ and R₄ are each independently a hydrocarbon group having 1 to 10 carbon atoms or the like, “m” and “n” are each independently an integer of 0 to 4, and “p” and “q” are each independently an integer of 0 or more,
    and a unit (B) represented by the following formula:

• • wherein R₅ to R₈ are each independently a hydrogen atom or alkyl group having 1 to 10 carbon atoms,
    the (A/B) molar ratio of the unit (A) to the unit (B) is 10/90 to 90/10 and which satisfies the following expression (1):
    R(450)<R(550)<R(650)  (1)
  • wherein R(450), R(550) and R(650) are retardation values within the plane of the film at wavelengths of 450 nm, 550 nm and 650 nm, respectively.

Claims

1. An optical film which is made of a polycarbonate copolymer consisting essentially of a unit (A2) represented by the following formula:

2. The film according to claim 1 which satisfies the following expressions (2) and (3):

0<

R(450)/R(550)<

1 

 

(2)

1.01<

R(650)/R(550)<

2 

 

(3).

3. The film according to claim 1 which is a retardation film.

4. A liquid crystal display comprising the retardation film of claim 3.

5. A circularly polarizing film which comprises the film of claim 1 and a polarizing layer.

6. A display element comprising the circularly polarizing film of claim 5 as an antireflection film.