Uniaxially stretched multi-layer laminate film, polarizing plate comprising same, optical member for liquid crystal display device, and liquid crystal display device

摘要

A uniaxially stretched multi-layer laminate film that exhibits a high polarization performance of 99.5% or more in a simpler configuration than before, a polarizing plate that is composed of the same, an optical member for a liquid crystal display device, and a liquid crystal display device are provided. Namely, in the uniaxially stretched multi-layer laminate film in which a first layer and a second layer are alternately laminated, the uniaxially stretched multi-layer laminate film includes an intermediate layer that has a thickness of 2 μm or more and 30 μm or less; the first layer is composed of a polyester containing a naphthalene dicarboxylic acid ester; the second layer is composed of a copolymer polyester and is an optically isotropic layer that has an average refractive index of 1.50 or more and 1.60 or less; the first layer, the second layer, both first and second layers, or the intermediate layer contains a visible light absorbent, which has a weight loss of less than 10% when it is kept at 300° C. for 1 hour, in an amount of 200 ppm or more and 2500 ppm or less on the basis of the weight of the layer; the uniaxially stretched multi-layer laminate film has a polarization degree of 99.5 or more; and the average transmittance Ts for S-polarized light in a wavelength range of 400 nm to 800 nm is 60% or more.

主权项

1. A uniaxially stretched multi-layer laminate film, in which a first layer and a second layer are alternately laminated, comprising an intermediate layer which is inside of the alternately laminated configuration of the first and second layers and which has a thickness of 2 μm or more and 30 μm or less, wherein
(1) the first layer is composed of a polyester containing a naphthalene dicarboxylic acid ester, (2) the second layer is composed of a copolymer polyester and is an optically isotropic layer having an average refractive index of 1.50 or more and 1.60 or less, (3) the first layer, the second layer, both first and second layers, or the intermediate layer contains a visible light absorbent that exhibits a weight loss of less than 10% when the visible light absorbent is kept at 300° C. for 1 hour, in an amount of 200 ppm or more and 2500 ppm or less on the basis of the weight of each layer, and (4) the uniaxially stretched multi-layer laminate film has a polarization degree (P %) represented by the following equation (1) of 99.5 or more and an average transmission Ts of 60% or more for S-polarized light in a wavelength range of 400 nm to 800 nm,
Polarization degree(P)={(Ts−Tp)/(Tp+Ts)}×100  (1) wherein Tp represents an average transmission for P-polarized light in a wavelength range of 400 nm to 800 nm and Ts represents an average transmission for S-polarized light in a wavelength range of 400 nm to 800 nm.