Abstract: A display device includes: a first substrate including a display area and a pad area; a second substrate facing the first substrate, a touch portion on the second substrate, a first flexible circuit board coupled to the first substrate, a second flexible circuit board coupled to the touch portion, a first adhesive layer on the first flexible circuit board, and a second adhesive layer that attaches the first adhesive layer and the second flexible circuit board to each other. The first adhesive layer and the second adhesive layer are formed of different materials from each other.

Abstract: A connection substrate includes a first substrate including first and second upper pads, and an inner wire electrically connecting the first and second upper pads, and a second substrate including first and second lower pads connected to the first and second upper pads, respectively. The second substrate includes a first test point disposed at an end of a first test wire extending from the first lower pad, a second test point disposed at an end of a second test wire extending from the second lower pad, and a dummy test point disposed at an end of a dummy test wire branched from a predetermined position of the second test wire and extended. A length of the dummy test wire is determined such that a resistance value of the dummy test wire is equal to a resistance value of the first test wire.