Optical laminate, polarizing plate, and image display device
According to the present invention, provided are an optical laminate which has excellent adhesiveness between two optically anisotropic layers, and in which an A plate or a layer obtained by fixing a twist-aligned liquid crystal phase, which is as an optically anisotropic layer, has excellent liquid crystal alignment properties, a polarizing plate, and an image display device. An optical laminate of the present invention has: a first optically anisotropic layer formed of a first liquid crystal compound; a second optically anisotropic layer formed of a second liquid crystal compound; and a mixed layer which is disposed between the first optically anisotropic layer and the second optically anisotropic layer and contains a component derived from the first liquid crystal compound and a component derived from the second liquid crystal compound, the first optically anisotropic layer is a C plate, the second optically anisotropic layer is an A plate or a layer obtained by fixing a twist-aligned liquid crystal phase, the mixed layer further contains a photo-alignment compound, and in an analysis of components of the optical laminate in a depth direction by time-of-flight secondary ion mass spectrometry with ion beam irradiation from a surface of the optical laminate on a first optically anisotropic layer side toward a second optically anisotropic layer side, predetermined requirements are satisfied.
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; and
a mixed layer which is disposed between the first optically anisotropic layer and the second optically anisotropic layer and contains 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 a C plate,
the second optically anisotropic layer is an A plate or a layer obtained by fixing a twist-aligned liquid crystal phase,
the mixed layer further contains a photo-alignment compound, and
in an analysis of components of the optical laminate in a depth direction by time-of-flight secondary ion mass spectrometry with ion beam irradiation from a surface of the optical laminate on a first optically anisotropic layer side toward a second optically anisotropic layer side, both the following conditions 1 and 2 are satisfied,
Condition 1: in a case where a depth position of the mixed layer where a secondary ion intensity derived from the photo-alignment compound is maximum is set as a peak position, a depth position closer to the first optically anisotropic layer than the peak position, which exhibits a secondary ion intensity that is half of the secondary ion intensity at the peak position, is set as a first position, and a depth position closer to the second optically anisotropic layer than the peak position, which exhibits a secondary ion intensity that is half of the secondary ion intensity at the peak position, is set 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: in a case where a distance between the first position and the peak position is set as a first distance and a distance between the second position and the peak position is set as a second distance, the second distance is 50% or greater of a total of the first distance and the second distance.
2. The optical laminate according to claim 1 ,
wherein in a case where an intermediate position between the first position and the second position is set as a third position, and
a depth position closer to the second position than the third position, which is between the first position and the second position, is set 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 the mixed layer has a thickness of 1 to 1,000 nm.
4. The optical laminate according to claim 3 ,
wherein the mixed layer has a thickness of 10 to 500 nm.
5. The optical laminate according to claim 1 ,
wherein the photo-alignment compound in the mixed layer has a horizontal alignment function.
6. 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.
7. A polarizing plate comprising:
the optical laminate according to claim 1 ; and
a polarizer.
8. An image display device comprising:
the polarizing plate according to claim 7 .
9. An image display device comprising:
the optical laminate according to claim 1 .