US 12,443,812 B2
Color display, authentication medium, and method for determining authenticity of color display
Keitaro Sugihara, Tokyo (JP)
Assigned to TOPPAN INC., Tokyo (JP)
Filed by TOPPAN INC., Tokyo (JP)
Filed on Oct. 7, 2022, as Appl. No. 17/961,788.
Application 17/961,788 is a continuation of application No. PCT/JP2021/015016, filed on Apr. 9, 2021.
Claims priority of application No. 2020-070966 (JP), filed on Apr. 10, 2020.
Prior Publication US 2023/0031501 A1, Feb. 2, 2023
Int. Cl. G06K 7/14 (2006.01); B42D 25/30 (2014.01); B42D 25/328 (2014.01); G02B 27/42 (2006.01)
CPC G06K 7/1417 (2013.01) [B42D 25/30 (2014.10); B42D 25/328 (2014.10); G06K 7/1413 (2013.01); G02B 27/4205 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A color display, comprising:
an embossed layer;
a high refractive index layer; and
a protective layer, laminated in this order, wherein
the high refractive index layer has a highest refractive index among these layers,
the embossed layer includes a first region (A) having a periodic structure with a period at least smaller than a center wavelength of visible light,
a plurality of the first regions (A), each having a strip shape, are connected to each other at their longitudinal end sides, the first regions (A) being offset from each other in a direction perpendicular to a longitudinal direction of the strip shape, as viewed via a display surface, and
a periodic direction of the periodic structure is parallel to the longitudinal direction, wherein
the embossed layer includes the first region (A) having a strip shape configured with a first periodic structure and a second region (B) configured with a second periodic structure including a plurality of different periods, a plurality of the first regions (A) and a plurality of the second regions (B) being alternately arranged at least in the longitudinal direction or the direction perpendicular to the longitudinal direction, and the second region (B) has a dimension smaller than that of the first region (A),
a color image is formed at the observation angle at which the zeroth-order diffracted light emitted from the first region (A) is observed, and a grayscale image is formed at the observation angle at which the first-order diffracted light emitted from the second region (B) is observed,
a position of a viewpoint for observing the color image formed of the first region (A) is an observation position,
the color display has a first position and a second position relative to a rotation axis normal to a plane in which the color display extends,
the second position is a position shifted from the first position by rotating the color display by 90° about the rotation axis,
the color display, when oriented in the first position, displays a first color image (1) having a first color to the observation position,
the color display, when oriented in the second position, displays a second color image (2) having a second color to the observation position,
the first region (A) includes a second sub-region (A2) which locally includes a plurality of periods,
the second sub-region (A2) is formed as an authentication code having a same color in both the first position and the second position, and
the authentication code is used as a machine-readable authentication code for determining authenticity.