US 11,886,071 B2
Light guide element comprising a diffraction element having a cholesteric liquid crystal layer with a pitch gradient
Fumitake Mitobe, Minamiashigara (JP); Katsumi Sasata, Minamiashigara (JP); Yukito Saitoh, Minamiashigara (JP); and Akiko Watano, Minamiashigara (JP)
Assigned to FUJIFILM Corporation, Tokyo (JP)
Filed by FUJIFILM Corporation, Tokyo (JP)
Filed on Sep. 30, 2022, as Appl. No. 17/937,272.
Application 17/937,272 is a continuation of application No. PCT/JP2021/011127, filed on Mar. 18, 2021.
Claims priority of application No. 2020-065845 (JP), filed on Apr. 1, 2020.
Prior Publication US 2023/0049424 A1, Feb. 16, 2023
Int. Cl. G02F 1/1335 (2006.01); G02F 1/137 (2006.01); G02B 27/01 (2006.01)
CPC G02F 1/133524 (2013.01) [G02F 1/13718 (2013.01); G02F 1/133504 (2013.01); G02B 27/0172 (2013.01)] 5 Claims
OG exemplary drawing
 
1. A light guide element comprising:
a light guide plate; and
a diffraction element that is disposed on a main surface of the light guide plate,
wherein the diffraction element includes a liquid crystal layer that is formed of a liquid crystal composition including a liquid crystal compound and 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,
a refractive index of the light guide plate is 1.70 or higher,
in a case where the refractive index of the light guide plate is represented by nd and a refractive index of the liquid crystal layer is represented by nk,
nk−nd≥0
is satisfied,
the liquid crystal layer is a cholesteric liquid crystal layer obtained by immobilizing a cholesteric liquid crystalline phase,
the cholesteric liquid crystal layer is a pitch gradient layer in which a helical pitch changes in a thickness direction, and
in a main surface of the liquid crystal layer in which the direction of the optical axis of the liquid crystal compound changes while continuously rotating in at least one in-plane direction, in a case where a length over which the direction of the optical axis of the liquid crystal compound rotates by 180° is set as a single period Λ, a helical pitch on one surface side of the pitch gradient layer is represented by P1, and a helical pitch on the other surface side of the pitch gradient layer is represented by P2,
P1<Λ<P2
is satisfied.