Circularly polarizing plate, method for producing same, broadband lambda/4 plate, organic electroluminescent display device, and liquid crystal display device
A circularly polarizing plate including a polarizing film, a λ/2 plate having a slow axis in a direction forming an angle of 22.5°±10° relative to an absorption axis of the polarizing film, a λ/4 plate having a slow axis in a direction forming an angle of 90°±20° relative to the absorption axis of the polarizing film, in this order, 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; a method for producing the same, and a method for using the same.
1. A circularly polarizing plate comprising:
a polarizing film;
a λ/2 plate having a slow axis in a direction forming an angle of 22.5°±10° relative to an absorption axis of the polarizing film; and
a λ/4 plate having a slow axis in a direction forming an angle of 90°±20° relative to the absorption axis of the polarizing film, in this order, 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.
2. The circularly polarizing plate according to claim 1 , satisfying the following formula (A):
Reh(400)/Reh(550)<Req(400)/Req(550)
wherein Reh(400) is an in-plane phase difference of the λ/2 plate at a wavelength of 400 nm,
Reh(550) is an in-plane phase difference of the λ/2 plate at a wavelength of 550 nm,
Req(400) is an in-plane phase difference of the λ/4 plate at a wavelength of 400 nm, and
Req(550) is an in-plane phase difference of the λ/4 plate at a wavelength of 550 nm.
3. The circularly polarizing plate according to claim 1 , satisfying the following formula (B):
Req(400)/Req(550)−Reh(400)/Reh(550)=0.12±0.08
wherein Reh(400) is an in-plane phase difference of the λ/2 plate at a wavelength of 400 nm,
Reh(550) is an in-plane phase difference of the λ/2 plate at a wavelength of 550 nm,
Req(400) is an in-plane phase difference of the λ/4 plate at a wavelength of 400 nm, and
Req(550) is an in-plane phase difference of the λ/4 plate at a wavelength of 550 nm.
4. The circularly polarizing plate according to claim 1 , wherein the λ/4 plate includes a layer formed of a material having a negative intrinsic birefringence value.
5. The circularly polarizing plate according to claim 1 , wherein the λ/2 plate includes a layer formed of a material having a positive intrinsic birefringence value.
6. An organic electroluminescent display device comprising the circularly polarizing plate according to claim 1 .
7. A liquid crystal display device comprising the circularly polarizing plate according to claim 1 .
8. 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.
9. 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.
10. 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.