1. A printing device comprising: a thermal head that transfers overcoat ink provided on an ink sheet onto a surface of printing paper; and a controller that causes the thermal head to perform the transfer based on pattern data, wherein the pattern data is data in which a first pattern and a second pattern are arranged alternately in a primary scanning direction and a secondary scanning direction, the first pattern includes a rectangular block of high tonal value pixels, a frame-like group of low tonal value pixels surrounding the rectangular block, and a group of high tonal pixels surrounding the group of low tonal value pixels, and the second pattern includes a rectangular block of low tonal value pixels, a group of high tonal value pixels surrounding the rectangular block, and a frame-like group of low tonal pixels surrounding the group of high tonal value pixels.