Transmissive liquid crystal diffraction element

A transmissive liquid crystal diffraction element comprising:

• a plurality of optically-anisotropic layers that are formed of a liquid crystal composition including a liquid crystal compound in a thickness direction,
• wherein the optically-anisotropic layer has a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound changes while continuously rotating in at least one in-plane direction,
• the one in-plane directions of the plurality of optically-anisotropic layers are parallel to each other,
• in at least two optically-anisotropic layers adjacent to each other among the plurality of optically-anisotropic layers, a rotation direction of the optical axis in the liquid crystal alignment pattern of one optically-anisotropic layer and a rotation direction of the optical axis in the liquid crystal alignment pattern of the other optically-anisotropic layer are opposite to each other,
• in cross-sectional images of the plurality of optically-anisotropic layers obtained by observing cross-sections taken in a thickness direction parallel to the one in-plane direction with a scanning electron microscope, the plurality of optically-anisotropic layers have bright portions and dark portions extending from one surface to another surface,
• tilt angles of the dark portions of the plurality of optically-anisotropic layers change in order in the thickness direction,
• in at least one of the plurality of optically-anisotropic layers, the liquid crystal compound is twisted and aligned in the thickness direction, and twisted angle in the thickness direction is less than 360 degrees, and
• an in-plane retardation Δn×d of each of the plurality of optically-anisotropic layers satisfies 0.7×(λ/2)nm≤Δnλ×d≤1.3×(λ/2) nm, where λ represents a wavelength of an incident light.