Polycarbonate resin and transparent film formed therefrom

1. A transparent film having a birefringence of more than 0.001, comprising:

a polycarbonate resin which comprises:

a first structural unit derived from a dihydroxy compound represented by a general formula (1);

a second structural unit derived from a dihydroxy compound represented by a general formula (2); and

a third structural unit derived from at least one, a dihydroxy compound represented by general formula (5)

wherein the dihydroxy compound represented by the general formula (1) is 9,9-[4-(2-hydroxyethoxy)phenyl]fluorene,

wherein the first structural unit accounts for 18% by mole or more of the polycarbonate resin, and

wherein the polycarbonate resin has a reduced viscosity of 0.30 dL/g or higher

wherein the general formula (1), R 1 to R 4 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1-20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 6-20 carbon atoms, or a substituted or unsubstituted aryl group having 6-20 carbon atoms, X represents a substituted or unsubstituted alkylene group having 2-10 carbon atoms, a substituted or unsubstituted cycloalkylene group having 6-20 carbon atoms, or a substituted or unsubstituted arylene group having 6-20 carbon atoms, and m and n each independently are an integer of 0-5;

wherein the general formula (3), R 5 represents a substituted or unsubstituted, monocyclic cycloalkylene group having 4-20 carbon atoms;

wherein the general formula (4), R 6 represents a substituted or unsubstituted, monocyclic cycloalkylene group having 4-20 carbon atoms;

wherein the general formula (5), R 7 represents a substituted or unsubstituted alkylene group having 2-10 carbon atoms, and p is an integer of 2 to 15;

wherein the general formula (6), R 11 represents either an alkyl group having 2-20 carbon atoms or the group represented by a formula (7).

2. The transparent film according to claim 1 , wherein the transparent film has been stretched at least in one direction.

3. The transparent film according to claim 1 , wherein the transparent film has a refractive index as measured with sodium D-line (589 nm) in the range of 1.57 to 1.62.

4. The transparent film according to claim 1 , wherein the transparent film satisfies expression (5),

0.5 ≦R 450 /R 550≦1.0  (5)

wherein the equation (5), R450 represents a retardation measured at a wavelength of 450 nm and R550 represents a retardation measured at a wavelength of 550 nm.

5. The transparent film according to claim 1 , wherein the transparent film has a thickness of 80 μm or less.

6. The transparent film according to claim 1 , wherein the transparent film satisfies one of expressions (6) to (8);

nx>ny=nz   (6)

nx>ny>nz   (7)

nx>nz>ny   (8)

wherein nx and ny represent refractive indexes in two in-plane directions, nz represents a refractive index in a thickness-direction of the transparent film.

7. The transparent film according to claim 1 , wherein the transparent film satisfies expressions (9) and (10);

NZ= ( nx−nz )/( nx−ny )=0.2 to 8  (9)

Δ nd =( nx−ny )· d= 30 to 400 nm  (10)

wherein nx and ny represent refractive indexes in two in-plane directions, nz represents a refractive index in a thickness-direction, and d represents a thickness of the transparent film.

8. The transparent film according to claim 1 , wherein the transparent film has a water absorption higher than 1.0% by weight.

9. The transparent film according to claim 1 , wherein the transparent film has a photoelastic coefficient of 40×10 −12 Pa −1 or less.

10. A polarizing plate comprising the transparent film according to claim 1 and a polarizer thereon.