Optical member and image display device including optical member
The optical member of the present invention includes: a substrate; and a dot that is in contact with a surface of the substrate, in which the dot has wavelength selective reflecting properties, the dot is formed of a liquid crystal material having a cholesteric structure, the cholesteric structure has a stripe pattern including bright portions and dark portions in a cross-sectional view of the dot when observed with a scanning electron microscope, the dot includes a portion having a height which continuously increases to a maximum height in a direction moving from an end portion of the dot to the center of the dot, in the portion, an angle between a normal line perpendicular to a line, which is firmed using a first dark portion from a surface of the dot, and the surface is in a range of 70° to 90°, and the liquid crystal material includes a surfactant.
1. An optical member comprising:
a substrate; and
a dot that is in contact with a surface of the substrate,
wherein the dot has wavelength selective reflecting properties,
the dot is formed of a liquid crystal material having a cholesteric structure,
the cholesteric structure has a stripe pattern including bright portions and dark portions in a cross-sectional view of the dot when observed with a scanning electron microscope,
the dot includes a portion having a height which continuously increases to a maximum height in a direction moving from an end portion of the dot to the center of the dot,
regarding all the points of an inclined portion or a curved portion from said end portion of the dot, an angle between a normal line perpendicular to a line, which is formed using a first dark portion from a surface of the dot, and the surface of the dot is in a range of 70° to 90°, and
the liquid crystal material includes a surfactant.
2. The optical member according to claim 1 ,
wherein a plurality of the dots are provided in a pattern shape on the surface of the substrate.
3. The optical member according to claim 1 ,
wherein a diameter of the dot is 20 to 200 μm.
4. The optical member according to claim 1 ,
wherein a diameter of the dot is 30 to 120 μm.
5. The optical member according to claim 1 ,
wherein a value obtained by dividing the maximum height by the diameter of the dot is 0.13 to 0.30.
6. The optical member according to claim 1 ,
wherein in the end portion of the dot, an angle between the surface of the dot and the substrate is 27° to 62°.
7. The optical member according to claim 1 ,
wherein the surfactant is a fluorine surfactant.
8. The optical member according to claim 1 ,
wherein the liquid crystal material is a material obtained by curing a liquid crystal composition including a liquid crystal compound, a chiral agent, and the surfactant.
9. The optical member according to claim 1 ,
wherein the dot has wavelength selective reflecting properties in which a center wavelength is present in an infrared range.
10. The optical member according to claim 9 ,
wherein the dot has wavelength selective reflecting properties in which a center wavelength is present at a wavelength of 800 to 950 nm.
11. The optical member according to claim 1 which is transparent in a visible range.
12. An image display device comprising the optical member according to claim 11 .
13. The optical member according to claim 7 ,
wherein the surfactant comprises a compound represented by the following Formula (I):
(Hb 11 -Sp 11 -L 11 -Sp 12 -L 12 ) m11 -A 11 -L 13 -T 11 -L 14 -A 12 -(L 15 -Sp 13 -L 16 -Sp 14 -Hb 11 ) n11 Formula (I)
wherein L 11 , L 12 , L 13 , L 14 , L 15 , and L 16 each independently represent a single bond, —O—, —S—, —CO—, —COO—, —OCO—, —COS—, —SCO—, —NRCO—, or —CONR— (in Formula (I), R represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms),
Sp 11 , Sp 12 , Sp 13 , and Sp 14 each independently represent a single bond or an alkylene group having 1 to 10 carbon atoms,
A 11 and A 12 represent a monovalent to tetravalent aromatic hydrocarbon group, T 11 represents a divalent group or a divalent aromatic heterocyclic group represented by any one of the following formulae (X in T 11 represents an alkyl group having 1 to 8 carbon atoms, an alkoxy group, a halogen atom, a cyano group, or an ester group, Ya, Yb, Yc, and Yd each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and
o and p each independently represent an integer of 0 to 4),
Hb 11 represents a perfluoroalkyl group having 2 to 30 carbon atoms,
m11 and n11 each independently represent 0 to 3 and m11+n11≥1.
14. The optical member according to claim 7 ,
wherein Hb 11 -Sp 11 -L 11 -Sp 12 -L 12 and -L 15 -Sp 13 -L 16 -Sp 14 -Hb 11 present at the terminal of Formula (I) are a group represented by any one of the following formulae:
(C a F 2a+1 )—(C b H 2b )—O—;
(C a F 2a+1 )—(C b H 2b )—COO—;
(C a F 2a+1 )—(C b H 2b )—O—(C r H 2r )—O—;
(C a F 2a+1 )—(C b H 2b )—COO—(C r H 2r )—COO—; and
(C a F 2a+1 )—(C b H 2b )—OCO—(C r H 2r )—COO—,
wherein a represents an integer of 2 to 30, b represents an integer of 0 to 20, a+b represents 3 to 30, and r represents an integer of 1 to 10.
15. The optical member according to claim 7 ,
wherein the surfactant comprises the following compound
16. The optical member according to claim 8 ,
wherein the addition amount of the surfactant in the liquid crystal composition is 0.01 mass % to 10 mass %.
17. The optical member according to claim 15 ,
wherein the liquid crystal material is a material obtained by curing a liquid crystal composition including a liquid crystal compound, a chiral agent, and the surfactant.
18. The optical member according to claim 17 ,
wherein the addition amount of the surfactant in the liquid crystal composition is 0.01 mass % to 10 mass %.
19. The optical member according to claim 8 ,
wherein the liquid crystal compound is a combination of the following compounds:
20. The optical member according to claim 19 ,
wherein the surfactant comprises the following compound: