Image display apparatus including a cholesteric liquid crystal layer having a pitch gradient structure and AR glasses
Provided are: an image display apparatus in which the utilization efficiency of a virtual image is high and the virtual image having high brightness uniformity can be displayed to be superimposed on a real image; and AR glasses including the image display apparatus. The image display apparatus includes: a display element; one or more cholesteric liquid crystal layers that reflect a display image of the display element; and a transparent reflection element that reflects the image reflected by the cholesteric liquid crystal layer to the cholesteric liquid crystal layer, in which at least one of the cholesteric liquid crystal layers has a structure having a region where a surface pitch changes in a thickness direction.
1. An image display apparatus comprising:
a display element;
a cholesteric liquid crystal layer that reflects an image displayed by the display element and is obtained by immobilizing a cholesteric liquid crystalline phase; and
a transparent reflection element that reflects the image of the display element reflected by the cholesteric liquid crystal layer to the cholesteric liquid crystal layer,
wherein one or more cholesteric liquid crystal layers are provided and at least one of the cholesteric liquid crystal layers has a pitch gradient structure that is a structure having a region where a helical pitch of a helical structure of the cholesteric liquid crystalline phase changes,
the cholesteric liquid crystal layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from a liquid crystal compound changes while continuously rotating in at least one in-plane direction,
in the thickness direction of the cholesteric liquid crystal layer, the helical pitch is continuously increased,
a length of a single period of the liquid crystal alignment pattern is 0.1 to 10 μm, the single period being a length, in the one in-plane direction, over which a direction of the optical axis derived from the liquid crystal compound rotates by 180° in the one in-plane direction, and the direction of an optical axis derived from the liquid crystal compound changing while continuously rotating in the one in-plane direction, and
an angle between a normal line of the cholesteric liquid crystal layer and an incidence direction of a virtual image into the cholesteric liquid crystal layer is more than 45°.
2. The image display apparatus according to claim 1 ,
wherein a plurality of the cholesteric liquid crystal layers having different the helical pitches are provided.
3. The image display apparatus according to claim 1 ,
wherein all of the cholesteric liquid crystal layers have the pitch gradient structure.
4. The image display apparatus according to claim 1 ,
wherein a selective reflection wavelength range of the cholesteric liquid crystal layer having the pitch gradient structure is 80 nm or more.
5. The image display apparatus according to claim 4 ,
wherein only one cholesteric liquid crystal layer is provided.
6. The image display apparatus according to claim 1 ,
wherein a retardation plate is provided between the display element and the cholesteric liquid crystal layer.
7. The image display apparatus according to claim 6 ,
wherein the retardation plate is a λ/4 wave plate.
8. AR glasses comprising:
the image display apparatus according to claim 1 .
9. The image display apparatus according to claim 2 ,
wherein a permutation of lengths of the helical pitches and a permutation of lengths of the single periods in the liquid crystal alignment patterns match each other in the plurality of cholesteric liquid crystal layers having different the helical pitches.