Provided are a polarizer comprising a polyvinyl alcohol-based film and having an endothermic peak of 50° C. to 60° C. when measured by differential scanning calorimetry at a temperature increase rate of 10° C./min; a polarizing plate comprising a polarizer and a first protective film and a second protective film laminated on one surface and the other surface of the polarizer, respectively, and having an initial shrinkage initiation temperature greater than 70° C. and less than or equal to 90° C. during thermomechanical analysis; and an optical display device comprising same.

A cover for a display panel is provided. The cover for a display panel includes a cover film; a first adhesive layer on the cover film; a polarizer on a side of the first adhesive layer away from the cover film; a phase difference layer on a side of the polarizer away from the first adhesive layer; a second adhesive layer on a side of the phase difference layer away from the polarizer; and an ultra-thin glass and an opaque filler layer on a side of the second adhesive layer away from the phase difference layer. The opaque filler layer includes an opaque material. The opaque filler layer abuts at least a portion of a periphery of the ultra-thin glass.

An all-around curved polarizer for an all-around curved display device comprises a polarizing layer, a first protective layer and a second protective layer. The first protective layer is arranged on a side of the polarizing layer adjacent to the all-around curved display device and has a first coefficient of thermal expansion. The second protective layer is disposed on the other side of the polarizing layer opposite to the all-around curved display device, and has a second coefficient of thermal expansion, and the second coefficient of thermal expansion is greater than the first coefficient of thermal expansion of the first protective layer.

An all-around curved polarizer for an all-around curved display device comprises a polarizing layer, a first protective layer and a second protective layer. The first protective layer is arranged on a side of the polarizing layer adjacent to the all-around curved display device and has a first coefficient of thermal expansion. The second protective layer is disposed on the other side of the polarizing layer opposite to the all-around curved display device, and has a second coefficient of thermal expansion, and the second coefficient of thermal expansion is greater than the first coefficient of thermal expansion of the first protective layer.

The optical element for a low frequency band includes a substrate including a first main face and a second main face, the substrate having birefringence, and an antireflection film located on the first main face, wherein the low frequency band is lower than a reststrahlen band of the antireflection film, wherein an absolute value of a difference between a first refractive index and a second refractive index of the substrate in the low frequency band is 0.2 or more, and wherein a thickness of the substrate is 15 μm or more and 4000 μm or less.

The optical element for a low frequency band includes a substrate including a first main face and a second main face, the substrate having birefringence, and an antireflection film located on the first main face, wherein the low frequency band is lower than a reststrahlen band of the antireflection film, wherein an absolute value of a difference between a first refractive index and a second refractive index of the substrate in the low frequency band is 0.2 or more, and wherein a thickness of the substrate is 15 μm or more and 4000 μm or less.

A polarizing film including a polarizer that is a cured product of a polymerizable liquid crystal composition is provided. The polymerizable liquid crystal composition contains both a polymerizable liquid crystal compound having at least one polymerizable group and a dichroic coloring matter. The polarizer is laminated on a surface, having a pore size of 0.45 nm to 0.57 nm, of a base material. The pore size is obtained by converting, into a diameter, an average free volume radius calculated by a positron lifetime measurement method in which the positron lifetime is measured by irradiating the surface with positrons with an injection energy of 3 kV.

A polarizing film including a polarizer that is a cured product of a polymerizable liquid crystal composition is provided. The polymerizable liquid crystal composition contains both a polymerizable liquid crystal compound having at least one polymerizable group and a dichroic coloring matter. The polarizer is laminated on a surface, having a pore size of 0.45 nm to 0.57 nm, of a base material. The pore size is obtained by converting, into a diameter, an average free volume radius calculated by a positron lifetime measurement method in which the positron lifetime is measured by irradiating the surface with positrons with an injection energy of 3 kV.

An optical polymer material includes an alternating copolymer made of a monomer of a styrene derivative and a monomer of a maleimide derivative, and has a nonlinear property in which the photoelastic coefficient of the optical polymer material decreases to a predetermined value with increase in composition ratio of the styrene derivative, and rises above the predetermined value with further increase in composition ratio of the styrene derivative. A composition ratio of the styrene derivative is within a predetermined range. An absolute value of the photoelastic coefficient is equal to or smaller than a first absolute value within the predetermined range of the composition ratio, and an absolute value of the intrinsic birefringence is equal to or smaller than a second absolute value of the optical polymer material within the predetermined range of the composition ratio.

An optical polymer material includes an alternating copolymer made of a monomer of a styrene derivative and a monomer of a maleimide derivative, and has a nonlinear property in which the photoelastic coefficient of the optical polymer material decreases to a predetermined value with increase in composition ratio of the styrene derivative, and rises above the predetermined value with further increase in composition ratio of the styrene derivative. A composition ratio of the styrene derivative is within a predetermined range. An absolute value of the photoelastic coefficient is equal to or smaller than a first absolute value within the predetermined range of the composition ratio, and an absolute value of the intrinsic birefringence is equal to or smaller than a second absolute value of the optical polymer material within the predetermined range of the composition ratio.