| abstract |
[PROBLEMS] To provide not only excellent transparency and heat resistance, but also desired properties such as mechanical strength and molding processability, and when it does not contain a nitrogen atom, further low coloration properties, and particularly high optical properties. To provide a low birefringence material having isotropic properties. The low birefringence material of the present invention is, for example, an acrylic copolymer having a lactone ring structure giving a positive phase difference and a structural unit giving a negative phase difference, under the following conditions: (A) The glass transition temperature (Tg) is 100 ° C. or higher; (B) The total light transmittance of the film made of the copolymer is 85% or more; (C) The phase difference per 100 μm thickness in the plane direction of the film is 10 nm or less, and the phase difference per 100 μm thickness in the plane direction after the film is stretched 1.5 times; The difference from the phase difference per 100 μm thickness in the surface direction of the film is 20 nm or less; Satisfied. [Selection figure] None |