Method for producing an optical compensating resin film for a polarizing plate

1. A method of producing an optical compensating resin film for a polarizing plate comprising the steps in the sequence set forth as follows:

casting a resin exhibiting a glass transition temperature of 150 to 200° C. determined via DSC via a solution casting to form a film;

peeling the formed film;

conveying the film at a temperature of 55° C. or less for at least 90 seconds; and

stretching the film,

wherein the optical compensating resin film satisfies the following requirements:

Ro, defined by the formula Ro=(nx−ny)×d, is 20 to 300 nm at 23° C. and 55% relative humidity,

Rt, defined by the formula Rt=((nx+ny)/2−nz)×d, is 70 to 400 nm at 23° C. and 55% relative humidity; and

a crystallinity degree of said resin film is 0.15 or less:

wherein nx, ny, and nz each respectively represents the refractive index in the major axis x, y, and z direction of a refractive index ellipsoid, nx and ny each represents the refractive index in the in-plane direction of said resin film, nz represents the refractive index in the thickness direction, and d represents the film thickness in nm.

2. The method of producing an optical compensating resin film for a polarizing plate of claim 1 ,

wherein the resin used for the casting step exhibits a glass transition temperature of 170 to 185° C. determined via DSC; and

the film is kept at a temperature of 50° C. or less for at least 90 seconds in the conveying step of the film.

3. The method of producing an optical compensating resin film for a polarizing plate of claim 1 ,

wherein the resin employed in the optical compensating resin film is a cellulose ester.

4. The method of producing an optical compensating resin film for a polarizing plate of claim 3 ,

wherein the cellulose ester has an acyl group having 2 to 4 carbon atoms and simultaneously satisfies the following Formulas (I) and (II):

2.1 ≦X+Y≦ 2.6  (I)

1.0≦X≦2.6  (II)

wherein X represents the substitution degree of an acetyl group, and Y represents the substitution degree of a propionyl group or a butyryl group.

5. The method of producing an optical compensating resin film for a polarizing plate of claim 4 ,

wherein said cellulose ester is cellulose acetatee propionate.

6. The method of producing an optical compensating resin film for a polarizing plate of claim 5 ,

wherein the aforesaid cellulose acetate propionate satisfies the following Formulas (III) and (IV):

1.0≦X≦2.0  (III)

0.5≦Y≦1.3  (IV).

7. The method of producing an optical compensating resin film for a polarizing plate of claim 3 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

8. The method of producing an optical compensating resin film for a polarizing plate of claim 4 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

9. The method of producing an optical compensating resin film for a polarizing plate of claim 5 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

10. The method of producing an optical compensating resin film for a polarizing plate of claim 6 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

11. The method of producing an optical compensating resin film for a polarizing plate of claim 2 ,

wherein the resin employed in the optical compensating resin film is a cellulose ester.

12. The method of producing an optical compensating resin film for a polarizing plate of claim 11 ,

wherein the cellulose ester has an acyl group having 2 to 4 carbon atoms and simultaneously satisfies the following Formulas (I) and (II):

2.1 ≦X+Y≦ 2.6  (I)

1.0≦X≦2.6  (II)

wherein X represents a substitution degree of an acetyl group, and Y represents a substitution degree of a propionyl group or a butyryl group.

13. The method of producing an optical compensating resin film for a polarizing plate of claim 12 ,

wherein said cellulose ester is cellulose acetate propionate.

14. The method of producing an optical compensating resin film for a polarizing plate of claim 13 ,

wherein said cellulose acetate propionate satisfies the following Formulas (Ill) and (IV):

1.0≦X≦2.0  (III)

0.5≦Y≦1.3  (IV).

15. The method of producing an optical compensating resin film for a polarizing plate of claim 11 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

16. The method of producing an optical compensating resin film for a polarizing plate of claim 12 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

17. The method of producing an optical compensating resin film for a polarizing plate of claim 13 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.

18. The method of producing an optical compensating resin film for a polarizing plate of claim 14 ,

wherein the cellulose ester incorporates a plasticizer having an aromatic terminal ester group and is represented by the following Formula (1):

B-(G-A)n-G-B  Formula (1)

,wherein B represents a benzene monocarboxylic acid residual group; G represents an alkylene glycol residual group having 2 to 12 carbon atoms, an aryl glycol residual group having 6 to 12 carbon atoms, or an oxyalkylene glycol residual group having 4 to 12 carbon atoms, A represents an alkylene dicarboxylic acid residual group having 4 to 12 carbon atoms or an aryl dicarboxylic acid residual group having 6 to 12 carbon atoms, and n represents an integer of 1 or more.