Optical laminate and optical device

An optical stack comprising:

• a first optical sheet having a first principal face with a concavo-convex structure and a second principal face at an opposite side from the first principal face;
• and
• an adhesive layer that is disposed on the first principal face of the first optical sheet, wherein,
• the concavo-convex structure includes a plurality of dents and flat portions between adjacent ones of the plurality of dents;
• the adhesive layer is in contact with the flat portions;
• a surface of the adhesive layer and the first principal face of the first optical sheet together define an internal space within each of the plurality of dents;
• and
• each of the plurality of dents satisfies 0.10≤(C−A)/C≤1.00 and 0.75≤(C−A)/(C−B), where A is a maximum height value of the adhesive layer existing in that dent;
• B is a minimum height value of the adhesive layer existing in that dent;
• and C is a depth of that dent.