Ugly texture

Hi,
I have a graph as png file, 8192*2048 and looks ok with photo viewer. But when I add it to a plan as texture in Unity, it goes messy and really bad.
I already checked other answers and tried some change but nothing work.

Can someone help me ?

A distressed student


Are you sure ? My texture is actually 8192*2048 and Unity seems okay with that.
My problem is that planes are dynamically created with a C# script so if you know how to create UI image instead of plane as @saschandroid told me ?
My texture is also dynamically created with another C# script so if you know how to create Sprite as @saschandroid told me ?
Thanks for your answers