OPTICAL FILM, REFLECTION TYPE POLARIZING PLATE USING THE OPTICAL FILM, AND LUMINANCE ENHANCING FILM

摘要

PROBLEM TO BE SOLVED: To provide an optical film excellent in polarization characteristic and having high luminance-improvemnt performance.

SOLUTION: The optical film contains a polyethylene naphthalate system resin (P) and a thermoplastic resin (S). The thermoplastic resin (S) is obtained from (a) 20 to 40 mass% of a vinyl cyanide system monomer, (b) 40 to 80 mass% of an aromatic vinyl system monomer and (c) 0 to 20 wt.% of the other monomer capable of copolymerizing with (a) and (b) ((a)+(b)+(c)=100 mass%) and the thermoplastic resin (S) has a weight average molecular weight of 150,000 to 230,000, an average refractive index of 1.545 to 1.575. The optical film has morphology having sea-island structure which is constituted of a phase (I) essentially composed of the polyethylene naphthalate system resin (P) and a phase (II) essentially composed of the thermoplastic resin (S). Either the phase (I) or the phase (II) is a dispersion phase, an aspect ratio of the dispersion phase is two or more and a volume ratio of the phase (I) to the phase (II)((I)/(II)) is 10/90 to 90/10.

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