Retardation film and utilization thereof

A retardation film, comprising:

• a polymer material including at least one cellulose derivative having a monomeric unit of formula (1),
• where R1, R2, and R3 in the formula (1) are each independently hydrogen, an aliphatic alkyl group or an aromatic acyl group;
• and
• a plurality of inorganic particles,
• wherein the retardation film has an in-plane retardation Re(550) of 105 nm to 160 nm, a reverse wavelength dispersion property Re(450)/Re(550) of 0.80 to 0.89, and a thickness of 20 μm to 50 μm,
• the cellulose derivative has a total degree of substitution D1 of 2.00 to 210 for substitution by an aliphatic alkyl group, and a degree of substitution D2 of 0.30 to 1.00 for substitution by an aromatic acyl 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 acyl group in the polymer material.