US 12,345,902 B2
Optical device and method of producing optical device
Yukari Oda, Tokyo (JP); Masashi Kawashita, Tokyo (JP); Yoshiko Ishimaru, Tokyo (JP); and Azusa Yamagishi, Tokyo (JP)
Assigned to TOPPAN INC., Tokyo (JP)
Filed by TOPPAN INC., Tokyo (JP)
Filed on Aug. 5, 2022, as Appl. No. 17/881,902.
Application 17/881,902 is a continuation of application No. PCT/JP2021/004369, filed on Feb. 5, 2021.
Claims priority of application No. 2020-020046 (JP), filed on Feb. 7, 2020.
Prior Publication US 2022/0381973 A1, Dec. 1, 2022
Int. Cl. G02B 5/18 (2006.01); G02B 5/22 (2006.01); G02B 5/28 (2006.01)
CPC G02B 5/1847 (2013.01) [G02B 5/1809 (2013.01); G02B 5/1866 (2013.01); G02B 5/22 (2013.01); G02B 5/28 (2013.01)] 10 Claims
OG exemplary drawing
 
1. An optical device, comprising
a concave-convex structure layer having a concavo-convex structure on a surface thereof, the concavo-convex structure being formed of either a plurality of convexities or a plurality of concavities which are arranged with a sub-wavelength period;
a high refractive index layer located on the concavo-convex structure and having a surface conforming to the concavo-convex structure, the high refractive index layer including first grating high refractive index portions located at a bottom of the concavo-convex structure and forming a first sub-wavelength grating and second grating high refractive index portions located at a top of the concavo-convex structure and forming a second sub-wavelength grating, the high refractive index layer being made of a material having a refractive index higher than that of the concavo-convex structure layer; and
a low refractive index layer located on the high refractive index layer and made of a material having a refractive index lower than that of the high refractive index layer, wherein
either of the concavo-convex structure layer and the low refractive index layer has absorptivity for light in a predetermined wavelength range; or
the optical device includes an additional layer having absorptivity for light in the predetermined wavelength range, wherein
when T1 represents a thickness of the first grating high refractive index portions, T2 represents a thickness of the second grating high refractive index portions, n1 represents a refractive index of a material of the high refractive index layer, n2 represents a refractive index of a material of the concavo-convex structure layer, n3 represents a refractive index of a material of the low refractive index layer, R1 represents an area ratio of the first grating high refractive index portions in a cross section including the first grating high refractive index portions and orthogonal to a thickness direction thereof, and R2 represents an area ratio of the second grating high refractive index portions in a cross section including the second grating high refractive index portions and orthogonal to a thickness direction thereof,
relations n1>n2, n1>n3, and R1+R2>1 are established; and
a ratio of a second parameter expressed by T2×{n1×R2+n3×(1−R2)} to a first parameter expressed by T1×{n1×R1+n2×(1−R1)} is 0.5 or more and 2.0 or less.