Antireflective member, optical element, display device, method of making stamper and method of making antireflective member using the stamper

An antireflective member having an uneven surface pattern, in which unit structures are arranged in three mutually intersecting directions at a period that is shorter than the shortest wavelength of an incoming light ray, on the surface of a substrate, the member satisfying the following Inequality (1a):

• Λ
• λ
• min
• <
• 1
• n
• ⁢
• ⁢
• i
• +
• n
• ⁢
• ⁢
• i
• ·
• sin
• ⁢
• ⁢
• θ
• ⁢
• ⁢
• i
• max
• (
• 1
• ⁢
• a
• )
• where λmin is the shortest wavelength of the incoming light ray;
• θimax is the largest angle of incidence of the incoming light ray, θimax being more than 0 degrees and less than 90 degrees;
• ni is the refractive index of an incidence medium, ns is the refractive index of the antireflective member;
• and Λ is the period of the uneven surface pattern in all of the three directions, wherein,
• each of the three directions is, among the tops of six raised portions being the closest to the top of a given raised portion and having a mutually equal distance from the top of the given raised portion, a direction interconnecting the tops of two raised portions between which the top of the given raised portion is interposed;
• the surface decreases in height in any direction from the top of the raised portion upon the surface, and the surface increases in height in any direction from the bottom of a recessed portion upon the surface;
• and
• the uneven surface pattern includes a saddle portion between the top of the given raised portion and the top of each of the closest six raised portions to the top of the given raised portion, wherein
• with respect to any raised portion and the recessed portion whose bottom is the closest to the top of the raised portion, if an axis of coordinates defined in the height direction of the uneven surface pattern is h-axis and if the height of the top of the raised portion is defined by htop, if the height of the bottom of the recessed portion is defined by hbottom, the height of the surface with respect to the bottom of the recessed portion is defined by h, an effective refractive index neff(h), represented as a function of h, satisfies the following Inequalities (1b):
• ns×0.93≦neff(hbottom)≦ns×1.07 and
• ni×0.93≦neff(htop)≦ni×1.07 (1b)
• and the effective refractive index neff(h) has three intersections with a function Neff(h) given by the following Equation (1c):
• Neff(h)={(eff(htop)−neff(hbottom))/(htop−hbottom)}×h+neff(hbottom) (1c).