US 12,392,947 B2
Optical laminate, light guide element, and image display device
Hiroshi Sato, Minami-ashigara (JP); Yukito Saitoh, Minami-ashigara (JP); and Katsumi Sasata, Minami-ashigara (JP)
Assigned to FUJIFILM Corporation, Tokyo (JP)
Filed by FUJIFILM Corporation, Tokyo (JP)
Filed on Apr. 9, 2021, as Appl. No. 17/226,329.
Application 17/226,329 is a continuation of application No. PCT/JP2019/039755, filed on Oct. 9, 2019.
Claims priority of application No. 2018-193490 (JP), filed on Oct. 12, 2018.
Prior Publication US 2021/0223448 A1, Jul. 22, 2021
Int. Cl. G02B 5/30 (2006.01); F21V 8/00 (2006.01); G02B 27/01 (2006.01)
CPC G02B 5/3016 (2013.01) [G02B 6/0023 (2013.01); G02B 6/005 (2013.01); G02B 6/0056 (2013.01); G02B 27/0172 (2013.01)] 18 Claims
OG exemplary drawing
 
1. An optical laminate comprising:
a first cholesteric liquid crystal layer and a second cholesteric liquid crystal layer that each selectively reflect a red light which is light in a wavelength range of 620 to 750 nm, a green light which is light in a wavelength range of 495 to 570 nm, or a blue light which is light in a wavelength range of 420 to 490 nm, have a helical structure in which a liquid crystal compound is helically turned and laminated, have a liquid crystal alignment pattern in which a direction of an optical axis derived from the liquid crystal compound continuously rotates in at least one in-plane direction, and selectively reflect light in a wavelength range of a same color,
wherein in the first cholesteric liquid crystal layer and the second cholesteric liquid crystal layer,
helical pitches as lengths in a thickness direction over which the liquid crystal compound that is helically turned and laminated in the cholesteric liquid crystal layer turns by 360° are different from each other,
turning directions of circularly polarized light to be reflected are the same,
rotation directions of the direction of the optical axis derived from the liquid crystal compound that continuously rotates in at least one in-plane direction in the liquid crystal alignment pattern are the same,
a length of a longer helical pitch of the helical pitches is 1.05 to 1.45 times with respect to a length of a shorter helical pitch of the helical pitches, and
in a case where, in the liquid crystal alignment pattern, a length over which the direction of the optical axis derived from the liquid crystal compound rotates by 180° in the one in-plane direction in which the direction of the optical axis derived from the liquid crystal compound changes while continuously rotating is set as a single period,
lengths of the single periods in the liquid crystal alignment pattern of the first cholesteric liquid crystal layer and the liquid crystal alignment pattern of the second cholesteric liquid crystal layer are the same.