Although the first thermally conductive layer 80 and the second thermally conductive layer 90 are shown in FIG. 5 as being located on the same layer, in some implementations, the first thermally conductive layer 80 and the second thermally conductive layer 90 may be located on different layers.

The second thermally conductive layer 90 may be physically connected to the common power supply line 70 with a second connection layer 92 therebetween. When the second thermally conductive layer 90 is physically connected to the common power supply line 70, heat transferred to the common power supply line 70 may be diffused to the second thermally conductive layer 90 through the second connection layer 92.

For example, the second thermally conductive layer 90 and the second connection layer 92 may diffuse heat applied to the common power supply line 70 due to laser energy applied in a process of curing of the seal 400 after the lower substrate 100 is adhered to the upper substrate 300, in a similar manner as the first thermally conductive layer 80 and the first connection layer 82. However, since the end surface 80E of the first thermally conductive layer 80 is exposed to the outside of the panel whereas the second thermally conductive layer 90 does not have a portion exposed to the outside, the first thermally conductive layer 80 may perform a main heat dissipation function and the second thermally conductive layer 90 may perform an auxiliary heat dissipation function.