Retardation film and utilization thereof

19:

• The retardation film of claim 18, wherein at least one of R1, R2, and R3 in the formula (1) is an aromatic group.

20:

• The retardation film of claim 19, wherein the cellulose derivative has a total degree of substitution D1 of 2.00 to 2.70 for substitution by a saturated aliphatic group or an unsaturated aliphatic group, and a degree of substitution D2 of 0.30 to 1.00 for substitution by an aromatic group, satisfying D1+D2≦3.0 in the cellulose derivative, and the polymer material has a total degree of substitution D3 of 0.40 to 0.50 for substitution by an aromatic group in the polymer material.

21:

• The retardation film of claim 19, wherein the aromatic group is an aromatic acyl group.

22:

• The retardation film of claim 18, wherein the retardation film has a photoelastic coefficient of less than 42.0×10−12 m2/N.

23:

• The retardation film of claim 18, wherein the inorganic particles comprise an inorganic material having an unsaturated bond.

24:

• The retardation film of claim 18, wherein the inorganic particles comprise an inorganic material having an acryloyl group.

25:

• The retardation film of claim 18, wherein the inorganic particles are included in an amount of from 5 parts by weight to 40 parts by weight with respect to 100 parts by weight of the cellulose derivative.

26:

• The retardation film of claim 18, wherein the inorganic particles comprise silica particles.

27:

• The retardation film of claim 18, wherein the inorganic particles have an average particle diameter of 5 nm to 30 nm.

28:

• The retardation film of claim 18, wherein the inorganic particles are spherical particles.

29:

• The retardation film of claim 18, wherein the cellulose derivative includes a saturated aliphatic group in the formula (1) which is an aliphatic alkyl group.

30:

• The retardation film of claim 29, wherein the aliphatic alkyl group is an ethyl group.

31:

• The retardation film of claim 18, wherein the at least one cellulose derivative comprises a plurality of cellulose derivatives.

32:

• The retardation film of claim 31, wherein each of the cellulose derivatives has a total degree of substitution D1 of 2.00 to 2.70 for substitution by a saturated aliphatic group or an unsaturated aliphatic group, and a degree of substitution D2 of 0.30 to 1.00 for substitution by an aromatic group, satisfying D1+D2≦3.0 in each of the cellulose derivatives, and the polymer material has a total degree of substitution D3 of 0.40 to 0.50 for substitution by an aromatic group in the polymer material.

33:

• The retardation film of claim 31, wherein each of the cellulose derivatives has a total degree of substitution D1 of 2.30 to 2.60 for substitution by a saturated aliphatic group or an unsaturated aliphatic group, and a degree of substitution D2 of 0.35 to 0.70 for substitution by an aromatic group, satisfying D1+D2≦3.0 in each of the cellulose derivatives, and the polymer material has a total degree of substitution D3 of 0.44 to 0.48 for substitution by an aromatic group in the polymer material.

34:

• A circular polarizer plate, comprising:
• one or more of the retardation film of claim 18.

35:

• An image display device, comprising:
• the circular polarizer plate of claim 34.

36:

• A method of manufacturing the retardation film of claim 18, comprising:
• drawing a production film comprising the polymer material at a draw ratio of 20% to 200%.

37:

• The method of claim 36, wherein the drawing is conducted at a temperature in a range of from (Tg−30) ° C. to (Tg+30) ° C., where Tg is a glass transition temperature of the production film.