Optical film of cellulose ester and cellulose ether for vertical alignment liquid crystal displays

Patent metadata

Field	Value
Publication number	US-9523794-B2
Application number	US-201414772271-A
Country	US
Kind code	B2
Filing date	Feb 7, 2014
Priority date	Mar 7, 2013
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

The optical film contains cellulose ester and cellulose ether. The cellulose ester satisfies formulae 2.0≦X+Y≦3.0 and 0≦Y≦1.6. X is an acetyl group, and Y is a propionyl group and/or a butyryl group. The mass ratio of the cellulose ester to the cellulose ether is 99.0:1.0 to 55.0:45.0. Retardations Ro and Rt of the film are 20 to 130 nm and 100 to 300 nm, respectively, and expressed as Ro=(nx−ny)×d and Rt={(nx+ny)/(2−nz)}×d. nx is an in-plane refractive index of a film in a slow axis direction, ny is an in-plane refractive index of a film in a fast axis direction, nz is a refractive index of a film in a thickness direction, and d is a thickness of a film.

First claim

The invention claimed is:

1. An optical film, comprising cellulose ester and cellulose ether, wherein
the cellulose ester satisfies formulae (1), and (2):

[Mathematical formula 1]
2.0≦ X+Y≦ 3.0  (1)

0≦ Y≦ 1.6  (2)

wherein X is a substitution degree of an acetyl group, and Y is a substitution degree of a propionyl group, a butyryl group, or the propionyl group and the butyryl group;
a mixing ratio of the cellulose ester and the cellulose ether (cellulose ester:cellulose ether) is 99.0:1.0 to 55.0:45.0 mass ratio; and
retardations Ro, and retardation Rt expressed in formulae (3), and (4):

[Mathematical formula 2]
Ro =( nx−ny )× d   (3)

Rt ={( nx+ny )/(2− nz )}× d   (4)

wherein nx is an in-plane refractive index of a film in a slow axis direction, ny is an in-plane refractive index of a film in a fast axis direction, nz is a refractive index of a film in a thickness direction, and d is a thickness nm of a film,

are 20 to 130 nm, and 100 to 300 nm, respectively.

2. The optical film according to claim 1 ,
wherein the mixing ratio of the cellulose ester and the cellulose ether (cellulose ester:cellulose ether) is 95.0:5.0 to 60.0:40.0 mass ratio.

3. The optical film according to claim 1 ,
wherein the cellulose ester satisfies formula (5):

[Mathematical formula 3]
0≦ Y≦ 0.9  (5).

4. The optical film according to claim 1 , further comprising
1.0 to 30.0 parts by mass of a plasticizer based on 100 parts by mass in total of cellulose ester and cellulose ether.

5. The optical film according to claim 4 ,
wherein the plasticizer is at least one selected from the group consisting of a carbohydrate derivative, a polyester compound, and a resin having a negative birefringence.

6. The optical film according to claim 1 , further comprising
a hydrogen bonded compound.

7. A polarizing plate, comprising
the optical film according to claim 1 , and a polarizer,
wherein the optical film and the polarizer are bonded by an active energy ray curable adhesive.

8. A vertical alignment (VA) type liquid crystal display,
wherein the polarizing plate according to claim 7 is provided at least on one surface of a liquid crystal cell.

Assignees

• Konica Minolta Inc

Inventors

• Kaneko Yuki
• Nishimura Masumi

Classifications

• C08J5/18 Primary

  Manufacture of films or sheets · CPC title

• G02B5/3083

  Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001) · CPC title

• G02B5/3033

  in the form of a thin sheet or foil, e.g. Polaroid · CPC title

• G02B1/08 Primary

  made of polarising materials · CPC title

• G02B5/32

  Holograms used as optical elements · CPC title