# US 8,568,893 B2 · Birefringent film and polarizer

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- Number: US 8,568,893 B2
- Document ID: US8568893B2
- Status: Granted
- Kind: B2
- Application number: 12/918,642
- Filed: 2009-01-27
- Published: 2010-12-30
- Granted: 2013-10-29
- Earliest claimed: 2008-02-20
- Assignees: Nitto Denko Corporation
- Applicants: Tomoyuki Hirayama; Toshiyuki Iida; Yutaka Ohmori; Satoru Suzuki; Miyuki Kurogi; Hisae Shimizu
- Inventors: Tomoyuki Hirayama; Toshiyuki Iida; Yutaka Ohmori; Satoru Suzuki; Miyuki Kurogi; Hisae Shimizu
- Web page: https://patentgrep.com/patent/US8568893B2

## CPC

- G02B 5/3083: {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)}
- C08G 63/547: Hydroxy compounds containing aromatic rings
- G02B 1/04: made of organic materials, e.g. plastics (G02B1/08 takes precedence)
- C09K 2323/031: Polarizer or dye
- C09K 2323/035: Ester polymer, e.g. polycarbonate, polyacrylate or polyester
- C09K 2323/06: Substrate layer characterised by chemical composition
- 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}
- Y10T 428/31786: Of polyester [e.g., alkyd, etc.]
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C09K: MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An ester-based polymer to be used in the present invention has at least a repeating unit represented with the general formula (I). A and B are substituents substituted on a stilbene group. R1 is a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group. R2 is a linear or branched alkyl group having 2 to 10 carbon atoms. R3 to R6 each independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group. n is an integer of 2 or more.

## Claims

### Claim 1

A birefringent film comprising an ester-based polymer having at least a repeating unit represented by the following formula (I):
wherein A and B each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group; a and b each independently represents any one of integers of 0 to 4; R1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group; R2 represents a linear or branched alkyl group having 2 to 10 carbon atoms; R3 to R6 each independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group; and n represents an integer of 2 or more.

### Claim 2 (depends on 1)

The birefringent film according to claim 1, wherein R1 is a methyl group, and R2 is a linear or branched alkyl group having 2 to 4 carbon atoms in the above formula (I).

### Claim 3 (depends on 1)

The birefringent film according to claim 1, wherein R3 to R6 each independently represents a linear or branched alkyl group having 1 to 4 carbon atoms in the above formula (I).

### Claim 4 (depends on 3)

The birefringent film according to claim 3, wherein the ester-based polymer having at least a repeating unit represented by the formula (I) or (II) has a glass transition temperature of 100° C. or higher and 300° C. or lower.

### Claim 5 (depends on 1)

The birefringent film according to claim 1, wherein the ester-based polymer having at least a repeating unit represented by the formula (I) or (II) has a glass transition temperature of 100° C. or higher and 300° C. or lower.

### Claim 6

A birefringent film comprising a copolymer ester-based polymer having at least a repeating unit represented by the following formula (II):
wherein R1 represents a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted aryl group; R2 represents a linear or branched alkyl group having 2 to 10 carbon atoms; R3 to R6 each independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a substituted or unsubstituted aryl group; R7 and R8 are respectively the same as those for R1 and R2; R9 to R12 are respectively the same as those for R3 to R6; and l and m are integers of 2 or more.

### Claim 7 (depends on 6)

The birefringent film according to claim 6, wherein the value of l/(l+m) is from 0.3 to 0.8 in the copolymer ester-based polymer represented by the formula (II).

### Claim 8 (depends on 6)

The birefringent film according to claim 6, wherein the ester-based polymer having at least a repeating unit represented by the formula (I) or (II) has a glass transition temperature of 100° C. or higher and 300° C. or lower.

### Claim 9 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

A polarizing element comprising the birefringent film according to any one of claims 1 to 8 and a polarizer.

### Claim 10 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

A polarizing element comprising the birefringent film according to any one of claims 1 to 8, a first adhesive layer, a polarizer, a second adhesive layer and a transparent protective film, laminated in order of the birefringent film, the first adhesive layer, the polarizer, the second adhesive layer and the transparent protective film.

### Claim 11 (depends on 1, 2, 3, 4, 5, 6, 7, 8)

A polarizing element comprising a laminate of the birefringent film according to any one of claims 1 to 8 and a base material, a first adhesive layer, a polarizer, a second adhesive layer and a transparent protective film, laminated in order of the laminate of the birefringent film, the base material, the first adhesive layer, the polarizer, the second adhesive layer and the transparent protective film.