Optical laminate, polarizing plate, and image device display
An optical laminate includes two optically anisotropic layers, an A-plate and a C-plate, in which the adhesiveness between the layers, the liquid crystal alignment of the C-plate, and the adhesiveness between the A-plate and a pressure-sensitive adhesive, are excellent. The optical laminate includes first and second optically anisotropic layers which are A-plate and C-plate formed of a first and second liquid crystal compound, respectively, and a mixed layer disposed between the layers, including components derived from the first and second liquid crystal compounds, and an optical alignment compound, in which a surface energy of the first optically anisotropic layer on a side opposite to the mixed layer is 25 mN/m or more, and where a component in a depth direction is analyzed with time-of-flight type secondary ion mass spectrometry while irradiating ion beams from a surface of the optical laminate on the first, toward the second, optically anisotropic layer.
1. An optical laminate comprising:
a first optically anisotropic layer formed of a first liquid crystal compound;
a second optically anisotropic layer formed of a second liquid crystal compound that is different from the first liquid crystal compound; and
a mixed layer in direct contact with, and disposed between, the first optically anisotropic layer and the second optically anisotropic layer, the mixed layer including a component derived from the first liquid crystal compound and a component derived from the second liquid crystal compound,
wherein the first optically anisotropic layer is an A-plate,
the A-plate satisfying one of two Expressions (A1) and (A2):
nx>ny≈nz Expression (A1)
ny<nx≈nz Expression (A2)
where nx is a refractive index in the slow axis direction in the layer plane (i.e., the direction in which the refractive index becomes a maximum in the plane), ny is a refractive index in the direction in-plane orthogonal to the in-plane slow axis direction, and nz is a refractive index in the layer thickness direction,
a surface energy of a surface of the first optically anisotropic layer on a side opposite to a mixed layer side is 25 mN/m or more,
the second optically anisotropic layer is a C-plate,
the C-plate satisfying one of two Expressions (C1) and (C2):
nz>nx≈ny Expression (C1)
nz<nx≈ny Expression (C2)
the mixed layer further includes a photo-alignment compound which has a horizontal alignment function, and
the following conditions are satisfied by the optical laminate in which a component in a depth direction of the optical laminate is analyzed with time-of-flight type secondary ion mass spectrometry while irradiating ion beams from a surface of the optical laminate on a first optically anisotropic layer side toward a second optically anisotropic layer side,
condition 1: where a depth position in the mixed layer, at which a secondary ion intensity derived from the photo-alignment compound is maximum, is defined as a peak position, a depth position which is on the first optically anisotropic layer side from the peak position, where a secondary ion intensity that is half of the secondary ion intensity at the peak position is exhibited, is defined as a first position, and a depth position which is on the second optically anisotropic layer side from the peak position, where a secondary ion intensity that is half of the secondary ion intensity at the peak position is exhibited, is defined as a second position, secondary ions derived from the first liquid crystal compound and the second liquid crystal compound are detected at any depth position in a region between the first position and the second position, and
condition 2: where a distance between the first position and the peak position is defined as a first distance and a distance between the second position and the peak position is defined as a second distance, a ratio of the second distance is less than 50% with respect to a total distance of the first distance and the second distance.
2. The optical laminate according to claim 1 ,
where a position in a middle of the first position and the second position is defined as a third position, and where a depth position which is located between the first position and the second position and is on a second position side from the third position is defined as a specific depth position, secondary ions derived from the first liquid crystal compound and the second liquid crystal compound are detected at any depth position in a region between the first position and the specific depth position.
3. The optical laminate according to claim 1 ,
wherein a thickness of the mixed layer is 1 to 1,000 nm.
4. The optical laminate according to claim 1 ,
wherein a thickness of the mixed layer is 10 to 500 nm.
5. The optical laminate according to claim 1 ,
wherein the first liquid crystal compound and the second liquid crystal compound are liquid crystal compounds having a polymerizable group.
6. A polarizing plate comprising:
the optical laminate according to claim 1 ; and
a polarizer.
7. An image display device comprising the optical laminate according to claim 1 .
8. An image display device comprising the polarizing plate according to claim 6 .
9. The optical laminate according to claim 2 ,
wherein a thickness of the mixed layer is 1 to 1,000 nm.
10. The optical laminate according to claim 2 ,
wherein a thickness of the mixed layer is 10 to 500 nm.
11. The optical laminate according to claim 2 ,
wherein the first liquid crystal compound and the second liquid crystal compound are liquid crystal compounds having a polymerizable group.
12. The optical laminate according to claim 3 ,
wherein a thickness of the mixed layer is 10 to 500 nm.
13. The optical laminate according to claim 3 ,
wherein the first liquid crystal compound and the second liquid crystal compound are liquid crystal compounds having a polymerizable group.