Cellulose Acylate Film, Method of Producing the Same, Cellulose Derivative Film, Optically Compensatory Film Using the Same, Optically-Compensatory Film Incorporating Polarizing Plate, Polarizing Plate and Liquid Crystal Display Device

A cellulose derivative film, which comprises:

• a cellulose derivative containing a substituent having a polarizability anisotropy represented by following Equation (1) of 2.5×10−24 cm3 or greater;
• and
• at least one retardation regulator satisfying following Equation (11-1):
• Δα=αx−(αy+αz)/2 Equation (1)
• wherein αx is the largest component among characteristic values obtained after diagonalization of polarizability tensor;
• αy is the second largest component among characteristic values obtained after diagonalization of polarizability tensor;
• and
• αz is the smallest component among characteristic values obtained after diagonalization of polarizability tensor;
• and
• Rth(a)−Rth(0)/a≦−1.5, provided that 0.01≦a≦30, Equation (11-1)
• wherein Rth(a) represents Rth (nm) at a wavelength of 589 nm of a film having a film thickness of 80 μm, the film comprises:
• a cellulose acylate having a degree of acetyl substitution of 2.85;
• and a parts by mass of the at least one retardation regulator relative to 100 parts by mass of the cellulose acylate;
• Rth(0) represents Rth (nm) at a wavelength of 589 nm of a film having a film thickness of 80 μm, the film comprises:
• only a cellulose acylate having a degree of acetyl substitution of 2.85 without the at least one retardation regulator;
• and
• a represents parts by mass of the at least one retardation regulator relative to 100 parts by mass of the cellulose acylate.

An optically-compensatory film incorporating a polarizing plate, which comprises:

• (A) a long polarizing film which has an absorption axis in parallel with a longitudinal direction;
• (B) a long second phase difference film which comprises a cellulose acylate film that includes a substituent having a polarizability anisotropy Δα represented by following Expression (1) of 2.5×10−24 cm−3 or more, and which has a retardation in a thickness-direction Rth of −300 to −40 nm and an in-plane retardation Re of 50 nm or less, wherein an optical axis is not included in an in-plane film;
• and
• (C) a long first phase difference film which has a slow axis substantially orthogonal to a longitudinal direction, wherein the long first phase difference film is interposed between the long polarizing film and the long second phase difference film:
• Δα=αx−(αy+αz)/2 Expression (1)
• wherein, αx, αy and αz are each a characteristic value obtained after diagonalization of polarizability tensor, and satisfy αx≧αy≧αz.

An optically-compensatory film incorporating a polarizing plate, which comprises following (A), (B) and (C), in this order:

• (A) a long polarizing film which has an absorption axis in parallel with a longitudinal direction;
• (B) a long second phase difference film which comprises a cellulose acylate film that includes a substituent having a polarizability anisotropy Δα represented by following Expression (1) of 2.5×10−24 cm−3 or more, and which has a retardation in a thickness-direction Rth of −300 to −40 nm and an in-plane retardation Re of 50 nm or less, wherein an optical axis is not included in an in-plane film;
• and
• (C) a long first phase difference film which has a slow axis substantially orthogonal to a longitudinal direction:
• Δα=αx−(αy+αz)/2 Expression (1)
• wherein, αx, αy and αz are each a characteristic value obtained after diagonalization of polarizability tensor, and satisfy αx≧αy≧αz.

A liquid crystal display device, which comprises:

• a first polarizing film;
• a first phase difference area;
• a second phase difference area;
• a liquid-crystal layer containing liquid-crystal molecules;
• a liquid-crystal cell including a pair of substrates, in which the liquid-crystal layer is interposed between the pair of substrates;
• and
• a second polarizing film,
• wherein the liquid-crystal molecules contained in the liquid-crystal layer is aligned parallel to surfaces of the pair of substrates at a black display, and
• wherein a retardation in a thickness-direction Rth of the second phase difference area is from −300 to −40 nm.