OPTICAL FILM, ROLLED OPTICAL FILM, POLARIZING PLATE, LIQUID CRYSTAL DISPLAY DIVICE AND PRODUCING METHOD FOR OPTICAL FILM

摘要

The present invention provides an optical film with low contractile force and high modulus of elasticity. The optical film contains at least a compound having a repetitive unit and cellulose ester. The in-plane retardation (Re) at the wavelength of 590 nm is equal to or less than 10 nm. The modulus of elasticity is over 3.5 GPa. The compound having a repetitive unit is a condensation product of a polybasic acid and a polyhydric alcohol. Also, the optical film meets conditions (1) to (6) below: (1) as a polybasic acid, at least a polybasic acid with a carbon number equal to or less than 5 is included; (2) the average carbon number of the polybasic acid is equal to or greater than 3 and less than 6; (3) the average carbon number of the polyhydric alcohol is equal to or greater than 2 and equal to or less than 3; (4) the repetitive unit composed of the combination of a polybasic acid and a polyhydric alcohol has a carbon number equal to or greater than 4 and equal to or less than 9; (5) number average molecular weight is equal to or greater than 800 and equal to or less than 500; and (6) the hydroxyl value is less than 40 mgKOH/g.