PRODUCTION METHOD OF OPTICAL FILM

PROBLEM TO BE SOLVED: To provide a production method of an optical film which suppresses occurrence of bright-spot foreign matters sufficiently even when an optical film containing a phase difference increasing agent is produced over a long time.SOLUTION: A production method of an optical film includes a first step of forming a film by using a resin solution containing a transparent resin and a solid phase difference increasing agent of a number average molecular weight of 50-1,000, and a second step of subjecting the film to a specified treatment, while carrying the film in an enclosed first region, to form an optical film. In the second step, the average temperature of the first region is 20°C or more lower than a glass transition temperature Tg of the transparent resin, and a collection member capable of collecting the scattering of the phase difference increasing agent is arranged in one or more parts in the first region, including low-temperature parts 30°C or more lower than the average temperature. 【課題】位相差上昇剤を含有する光学フィルムを長期間にわたって製造しても、輝点異物の発生を充分に抑制した光学フィルムの製造方法を提供することを目的とする。【解決手段】透明性樹脂と数平均分子量５０〜１０００の固体状の位相差上昇剤とを含む樹脂溶液を用いて、フィルムを作製する第１工程と、前記フィルムを、囲まれた第１領域内を搬送しながら、前記フィルムに所定の処理を施して、光学フィルムを作製する第２工程とを備え、前記第２工程において、前記第１領域内の平均温度が、前記透明性樹脂のガラス転移温度Ｔｇより２０℃低い温度以上であって、前記第１領域内の、前記平均温度より３０℃以上低い低温箇所等に、前記位相差上昇剤の飛散物を捕集可能な捕集部材を１箇所以上設ける光学フィルムの製造方法である。【選択図】図１