Polymer film and preparation method of polymer solution

• US 8,304,040 B2
• Filed: 01/26/2005
• Issued: 11/06/2012
• Est. Priority Date: 01/26/2004
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Sasada, Yasuyuki
• Primary Examiner(s): Ortiz, Angela
• Assistant Examiner(s): Zhang, Ruiyun
• Application Number:
  US11/041,978
• Publication Number:
  US 20050163923A1
• Time in Patent Office: 2,841 Days
• Field of Search: 428/1.33, 428/1.54, 349117-118, 349/122, 106/171.1, 264207-208
• US Class Current: 428/1.33
• CPC Class Codes: C08J 2301/10 Esters of organic acids
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08L 1/10 Esters of organic acids , i.e. acylates
• CPC Class Codes: C08L 1/12 Cellulose acetate
• CPC Class Codes: C09K 2323/035 Ester polymer, e.g. polycarbonate, polyacrylate or polyester
• CPC Class Codes: 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
• 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

Abstract

A polymer is swollen in a first tank. The swelling temperature is in the range of −10 to 50° C. The mixture is cooled in a first cooling vessel to the range of −100 to −10° C., and thereafter heated in a heating device to the range of 0 to 57° C. The polymer is cellulose acylate in which a degree of substitution of the acyl group for hydroxyl group is at least 2.87. A film obtained from the cellulose acylate has a negative value of ΔRe and a positive value of ΔRth, and |ΔRth| is at least 10 nm. ΔRe and ΔRth are respective difference of Re and Rth at the measurement thereof with use of wavelengths between 700 nm and 400 nm. The film is used adequately as a birefringence film, a protective film for a polarizing filter in a liquid crystal display.

Claims

1. A polymer film having an in-plane retardation Re(n) and a thickness retardation Rth(n) measured with use of a light of wavelength n (unit;

nm), wherein;

Δ

Re is calculated by Re(700)−

Re(400);

Δ

Rth is calculated by Rth(700)−

Rth(400), a sign of said Δ

Rth being opposite to that of said Δ

Re; and

the polymer comprises cellulose acylate, and the cellulose acylate has a degree of acylation of at least 2.87.

2. A polymer film as defined in claim 1, wherein said Δ

Rth satisfies a formula of 10 nm≦

|Δ

Rth|≦

1000 nm.

3. A polymer film as defined in claim 1, wherein said Δ

Re is a negative value.

4. A polymer film as defined in claim 1, wherein said polymer film is used as a retardation filter in a liquid crystal display including a liquid crystal layer sandwiched between a pair of orientation layers, and said retardation filter is oppositely disposed over one of said orientation layers to said liquid crystal layer.

5. A polymer film as defined in claim 1, wherein said polymer film is used as a protective film for a polarizing filter, and said protective film is adhered to at least one surface of a polarized film of said polarizing filter.

6. The polymer film as defined in claim 1, wherein said cellulose acylate has a degree of substitution of acetyl groups in the range of 0.0 to 3.0.

7. The polymer film as defined in claim 1, wherein said cellulose acylate has a degree of substitution of acyl groups, in which the number of carbon atoms is from 3 to 22, in the range of 0.0 to 3.0.

8. The polymer film as defined in claim 1, wherein said polymer film is produced from a polymer solution which is prepared from a mixture containing a polymer and a solvent, and a method of preparing said polymer solution comprising:

(a) regulating a temperature of said mixture in a range of −

10°

C. to 50°

C. such that said polymer swells;

(b) cooling said mixture after the swelling, such that said temperature of said mixture is in the range of −

100°

C. to −

10°

C.; and

(c) heating said mixture after the cooling, such that said temperature of said mixture is in the range of 0°

C. to 57°

C.

9. The polymer film as defined in claim 8, wherein said solvent comprises a chlorinated solvent.

10. The polymer film as defined in claim 8, wherein said cooling (b) is performed under an increased pressure, and said method further comprises:

(d) pressurizing and heating said mixture after said heating (c), under a pressure from 0.2 MPa to 30 MPa, such that said temperature of said mixture is in a range of 60°

C. to 240°

C.

11. The polymer film as defined in claim 10, wherein the cooling (b) is performed under an increased pressure by using a screw pump, and the pressurizing in the step of pressurizing and heating (d), is performed by using a screw pump.