The uneven surface of the electroconductive substrate may preferably have {TAIL ~ a center line average surface roughness} (Ra of 15 300 nm when scanned in a direction parallel to the linear projections and a center line average surface roughness Ra of 20 600 nm when scanned in {HEAD ~ a direction} perpendicular to the linear projections 
The uneven surface of the electroconductive substrate may preferably have { TAIL ~ a center line average surface roughness } ( Ra of 15 300 nm when scanned in a direction parallel to the linear projections and a center line average surface roughness Ra of 20 600 nm when scanned in { HEAD ~ a direction } perpendicular to the linear projections
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