Liquid crystal diffraction element comprising an optical axis derived from a liquid crystal compound that continuously rotates in at least one in-plane direction, image display apparatus, and head mounted display

Abstract

Provided are a liquid crystal diffraction element, an image display apparatus, and a head mounted display where occurrence of a ghost in a head mounted display such as VR glasses can be suppressed. The liquid crystal diffraction element includes at least an optically-anisotropic layer that is formed of a liquid crystal composition including a liquid crystal compound, in which the optically-anisotropic layer has a liquid crystal alignment pattern in which an orientation of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction, in a case where a length over which the optical axis rotates by 180 degrees in the one direction is set as a single period, the single period gradually changes in the one direction, and in a case where an average period of 50 periods in the one direction from a period having a longest length of the single period is represented by Λa and a main surface of the optically-anisotropic layer in a region having a period shorter than or equal to the average period Λa is observed with an optical microscope, both of a ratio between a maximum value and a minimum value among widths of 30 continuous bright lines and a ratio between a maximum value and a minimum value among widths of 30 continuous dark lines in the region are 1.2 or less.