HIGH-CONTRAST POLARIZATION ELEMENT EXHIBITING UNIFORM TRANSMITTANCE AT RESPECTIVE WAVELENGTHS, AND POLARIZATION PLATE

摘要

[Problem] To provide: a high-contrast polarization element which exhibits a substantially constant transmittance at respective wavelengths in cases when the polarization element is disposed parallel to an absorption axis, and in cases when the polarization element is disposed orthogonal to the absorption axis; and a polarization plate. [Solution] This polarization element includes an iodine-containing base material which is capable of polarizing light, and which comprises a hydrophilic polymer that has adsorbed boric acid and been stretched. The polarization element is characterized by including: an organic compound which is in the form of a free acid, and which is represented by formula (1) (in formula (1): R₁ represents hydrogen, a halogen, a lower alkyl group, a lower alkoxyl group, or a carboxyl group; and k, m, and n individually represent 0 or 1, with the caveat that m+n 1); or a salt of said organic compound. The polarization element is further characterized in that: the luminosity corrected unit transmittance (Yc) when measured using the base material as the unit is in the range of 40.0-42.5%; the difference between the luminosity corrected unit transmittance (Ys) and the unit transmittance (Ts₄₆₀) at 460 nm is not more than 1.2%; the difference between the luminosity corrected unit transmittance (Ys) and the unit transmittance (Ts₅₅₀) at 550 nm is not more than 1%; the difference between the luminosity corrected unit transmittance (Ys) and the unit transmittance (Ts₆₁₀) at 610 nm is not more than 1%; the luminosity corrected orthogonal transmittance when measured after disposing two sheets of the base material orthogonally with respect to an absorption-axis direction is not more than 0.01%; and the average value (Tc Ave430-480) of the orthogonal transmittance at 430-480 nm when measured after disposing two sheets of the base material orthogonally with respect to the absorption-axis direction is not more than 0.03%.