Abstract: An identification medium includes a first layer, and a second layer disposed thereon in a manner of overlapping with the first layer. The first layer is capable of reflecting one of clockwise circular polarized light and counterclockwise circular polarized light and allowing to pass therethrough the remaining circular polarized light. The second layer is capable of reflecting at least a portion of circular polarized light having the same rotation direction as that of the circular polarized light that the first layer reflects, and allowing to pass therethrough circular polarized light having an opposite rotation direction to that of the circular polarized light reflected by the first layer. A ratio (Ssf2/S2) of Ssf2 defined by the following formula (2) relative to S2 defined by the following formula (1) is more than 0.

Abstract: A display medium including a first layer, a second layer, and a third layer, wherein: a part or an entirety of the first layer, a part or an entirety of the second layer, and a part or an entirety of the third layer are stacked in a thickness direction in this order; the first layer is a layer that is capable of reflecting circularly polarized light having a rotation direction D1 and allowing to pass therethrough circularly polarized light having a rotation direction D2, which is a direction opposite to the rotation direction D1; the second layer is a phase difference layer; and the third layer is a layer that is capable of reflecting circularly polarized light whose rotation direction is the rotation direction D1 and allowing to pass therethrough circularly polarized light whose rotation direction is the rotation direction D2.

Abstract: An identification medium includes a first layer, and a second layer disposed thereon in a manner of overlapping with the first layer. The first layer is capable of reflecting one of clockwise circular polarized light and counterclockwise circular polarized light and allowing to pass therethrough the remaining circular polarized light. The second layer is capable of reflecting at least a portion of circular polarized light having the same rotation direction as that of the circular polarized light that the first layer reflects, and allowing to pass therethrough circular polarized light having an opposite rotation direction to that of the circular polarized light reflected by the first layer. A ratio (Ssf2/S2) of Ssf2 defined by the following formula (2) relative to S2 defined by the following formula (1) is more than 0.

Abstract: An optical film, wherein a photoelastic coefficient thereof is 1.5×10?13 (dyn/cm2)?1 or less, an in-plane retardation Re(560) thereof at a wavelength of 560 nm is 1.0 nm or less, an absolute value of a thickness-direction retardation Rth(560) thereof at a wavelength of 560 nm |Rth(560)| is 1.0 nm or less, a change of a ratio Re(560)/d that is a ratio of the in-plane retardation Re(560) at a wavelength of 560 nm relative to a thickness d, the change being a result of storage at a temperature of 60° C. and a humidity of 90% for 4 hours, is 0.5×10?5 or less, and a change of a ratio Rth(560)/d that is a ratio of the thickness-direction retardation Rth(560) at a wavelength of 560 nm relative to the thickness d, the change being a result of storage at a temperature of 60° C. and a humidity of 90% for 4 hours, is 0.5×10?5 or less.

Abstract: An optical film having a heat resistance of 120° C. or higher, a tear strength of 1.5 N/mm or more, a water vapor transmission rate of 50 g/m2·day or less, and having absolute values |Re| and |Rth| of an in-plane retardation Re and a thickness-direction retardation Rth each being 1 nm or less; and a polarizing plate having the same. Preferably, the optical film includes a polymer containing a block A having the unit (a) of the hydrogenated product of the aromatic vinyl compound; and a copolymer block B having the unit (a) of the hydrogenated product of the aromatic vinyl compound and the unit (b) of the hydrogenated product of the diene compound.

Abstract: An optical film, wherein a photoelastic coefficient thereof is 1.5×10?13 (dyn/cm2)?1 or less, an in-plane retardation Re(560) thereof at a wavelength of 560 nm is 1.0 nm or less, an absolute value of a thickness-direction retardation Rth(560) thereof at a wavelength of 560 nm |Rth(560)| is 1.0 nm or less, a change of a ratio Re(560)/d that is a ratio of the in-plane retardation Re(560) at a wavelength of 560 nm relative to a thickness d, the change being a result of storage at a temperature of 60° C. and a humidity of 90% for 4 hours, is 0.5×10?3 or less, and a change of a ratio Rth(560)/d that is a ratio of the thickness-direction retardation Rth(560) at a wavelength of 560 nm relative to the thickness d, the change being a result of storage at a temperature of 60° C. and a humidity of 90% for 4 hours, is 0.5×10?3 or less.

Abstract: An optical film formed of a resin containing a polymer having a molecular weight of 100,000 or more, the optical film having a heat resistance of 140° C. or higher, a pencil hardness of F or higher, a water vapor transmission rate of 50 g/m2·day or less, and having absolute values |Re| and |Rth| of an in-plane retardation Re and a thickness-direction retardation Rth each being 3 nm or less; and a polarizing plate including the same. The polymer preferably includes a block A having the unit (a) of the hydrogenated product of the aromatic vinyl compound; and a copolymer block B having the unit (a) of the hydrogenated product of the aromatic vinyl compound and the unit (b) of the hydrogenated product of the diene compound.

Abstract: An optical film having a heat resistance of 120° C. or higher, a tear strength of 1.5 N/mm or more, a water vapor transmission rate of 50 g/m2·day or less, and having absolute values |Re| and |Rth| of an in-plane retardation Re and a thickness-direction retardation Rth each being 1 nm or less; and a polarizing plate having the same. Preferably, the optical film includes a polymer containing a block A having the unit (a) of the hydrogenated product of the aromatic vinyl compound; and a copolymer block B having the unit (a) of the hydrogenated product of the aromatic vinyl compound and the unit (b) of the hydrogenated product of the diene compound.

Abstract: A method for manufacturing a phase difference film having specific optical properties from a pre-stretch film that includes a resin layer (a) made of a resin A containing polycarbonate and a resin layer (b) made of a resin B having a negative intrinsic birefringence, wherein the pre-stretch film has a property of exhibiting a phase difference that varies depending on temperatures. The method includes a stretching step of performing uniaxial stretching two or more times at different temperatures and in different directions, so that a resin layer having a specific plane orientation coefficient is obtained by stretching the resin layer (a), and a resin layer having specific birefringence and specific Nz coefficient is obtained by stretching the resin layer (b). The resin A has a specific glass transition temperature TgA, and the TgA and a glass transition temperature TgB of the resin B satisfy a specific relationship.