Birefringence calculating method and birefringence calculating apparatus

A method for calculating a birefringence of a polymer in a birefringence calculating apparatus comprising a processor and a memory, comprising:

• an amorphous state generating step comprising accepting input of a parameter from an external device, generating a model of the polymer on the basis of the parameter, and bringing the model into an amorphous state;
• a stretching step comprising stretching the model brought into the amorphous state in the amorphous state generating step, carried out by the birefringence calculating apparatus;
• a birefringence calculating step comprising calculating a birefringence of the model stretched in the stretching step;
• an outputting step comprising outputting the birefringence calculated in the birefringence calculating step to a device, carried out by the birefringence calculating apparatus;
• and
• a determination step comprising determining whether the birefringence calculated in the birefringence calculating step satisfies a termination condition set in advance;
• outputting the birefringence in the outputting step when the termination condition is satisfied;
• and, when the termination condition is not satisfied, changing the parameter relating to the polymer, again generating a model of the polymer on the basis of the changed parameter, and calculating a birefringence, wherein simulation comprising the generating, stretching, calculating, outputting and determining steps is repeated, wherein different parameters apply to the generating step until a termination condition is met, and
• wherein the parameter change relating to the polymer is a change of monomers forming the polymer, or copolymerization of another kind of monomer,
• wherein the termination condition is that the birefringence is in a range defined by a preset upper threshold and a preset lower threshold, and
• when the calculated birefringence is larger than the upper threshold, side chain(s) having an aromatic hydrocarbon group is/are subject to a change in parameter relating to the monomer to lower birefringence,
• wherein the change in parameter relating to the monomer includes increasing the content of the aromatic hydrocarbon group and increasing the number of aromatic rings of the side chain(s) of the monomer, and when the calculated birefringence is smaller than the lower threshold, a main chain unit having an ether group is subject to a change in parameter relating to the monomer to increase birefringence,
• wherein the change in parameter relating to the monomer includes increasing the content of the ether group and increasing the number of oxygen atoms originating in the ether group of the main chain unit.