| abstract |
A thin optical film with high hygrothermal durability and high front contrast, includes cellulose acylate whose degree of substitution of acyl group is from 2.0 to 2.6 and at least one optical performance developer, wherein the cellulose acylate has a mannose content of 0.2% by mass or less, and the optical film has a thickness of 40 μm or thinner and satisfies: n M A ≧M B ×1.1 Formula In n C A ≧C B ×1.1 Formula IIn n wherein, A denotes the depthwise region ranging from one surface up to 2 μm depth of the optical film, and B denotes the depthwise region ranging from the other surface up to 2 μm depth, and M A and M B represent the mannose content in regions A and B; C A and C B represent the content of the optical performance developer in regions A and B; and M A , M B , C A and C B are given in % by mass. |