| 摘要 |
<p>An identification code is formed in a code formation area provided on a substrate. The code formation area is divided into a plurality of data cells. A plurality of dots are bonded with the substrate in such a manner that each of the dots is arranged in a predetermined data cell selected from the data cells. Each dot includes a projection formed in a peripheral portion of the dot and a flat portion formed in a center of the dot encompassed by the peripheral portion. The ratio of the thickness of the projection to the thickness of the flat portion is greater than 4 and smaller than 7. This structure improves the bonding strength of each dot with respect to the substrate.</p> |
