Circularly polarizing plate, method for producing same, broadband lambda/4 plate, organic electroluminescent display device, and liquid crystal display device

A broadband λ/4 plate comprising:

• a λ/2 plate having a slow axis in a direction forming an angle of 22.5°±10° relative to a reference direction;
• and
• a λ/4 plate having a slow axis in a direction forming an angle of 90°±20° relative to the reference direction,
• wherein the λ/2 plate and the λ/4 plate have different wavelength dispersions,
• an NZ factor of the λ/2 plate is 1.00±0.05, and
• an NZ factor of the λ/4 plate is 0.00±0.05, wherein
• the NZ factor is a value represented by (nx−nz)/(nx−ny), where nx represents a refractive index in a direction in which the maximum refractive index is given among directions perpendicular to the thickness direction (in-plane directions), ny represents a refractive index in one of the in-plane directions that is orthogonal to the nx direction, and nz represents a refractive index in a thickness direction.

A method for producing a circularly polarizing plate, comprising the steps of:

• stretching a first pre-stretch film including a layer formed of a material having a positive intrinsic birefringence value in one direction to obtain a λ/2 plate having a slow axis in a stretching direction;
• stretching a second pre-stretch film including a layer formed of a material having a negative intrinsic birefringence value in one direction to obtain a λ/4 plate having a slow axis in a direction perpendicular to a stretching direction;
• bonding a polarizing film and the λ/2 plate together such that a slow axis of the λ/2 plate forms an angle of 22.5°±10° relative to an absorption axis of the polarizing film;
• and
• bonding the λ/2 plate and the λ/4 plate together such that a slow axis of the λ/4 plate forms an angle of 90°±20° relative to the absorption axis of the polarizing film, wherein
• the λ/2 plate and the λ/4 plate have different wavelength dispersions,
• an NZ factor of the λ/2 plate is 1.00±0.05, and
• an NZ factor of the λ/4 plate is 0.00±0.05, wherein
• the NZ factor is a value represented by (nx−nz)/(nx−ny), where nx represents a refractive index in a direction in which the maximum refractive index is given among directions perpendicular to the thickness direction (in-plane directions), ny represents a refractive index in one of the in-plane directions that is orthogonal to the nx direction, and nz represents a refractive index in a thickness direction.

A method for producing a circularly polarizing plate, comprising the steps of:

• stretching a first pre-stretch film including a layer formed of a material having a positive intrinsic birefringence value in one direction to obtain a λ/2 plate having a slow axis in a stretching direction;
• forming a layer containing a discotic liquid crystalline molecule on a supporting body, orienting the discotic liquid crystalline molecule, and fixing the discotic liquid crystalline molecule to obtain a λ/4 plate;
• bonding a polarizing film and the λ/2 plate together such that a slow axis of the λ/2 plate forms an angle of 22.5°±10° relative to an absorption axis of the polarizing film;
• and
• bonding the λ/2 plate and the λ/4 plate together such that a slow axis of the λ/4 plate forms an angle of 90°±20° relative to the absorption axis of the polarizing film, wherein
• the λ/2 plate and the λ/4 plate have different wavelength dispersions,
• an NZ factor of the λ/2 plate is 1.00±0.05, and
• an NZ factor of the λ/4 plate is 0.00±0.05, wherein
• the NZ factor is a value represented by (nx−nz)/(nx−ny), where nx represents a refractive index in a direction in which the maximum refractive index is given among directions perpendicular to the thickness direction (in-plane directions), ny represents a refractive index in one of the in-plane directions that is orthogonal to the nx direction, and nz represents a refractive index in a thickness direction.