{HEAD ~ The plurality} of {TAIL ~ linear projections} may preferably provide an uneven surface which has a center line average surface roughness Ra of 15 300 nm when scanned in a direction parallel to the linear projections, a center line average surface roughness Ra of 20 600 nm when scanned in a direction perpendicular to the linear projections, and an Ra/Ra ratio of at most 0.8 
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{ HEAD ~ The plurality } of { TAIL ~ linear projections } may preferably provide an uneven surface which has a center line average surface roughness Ra of 15 300 nm when scanned in a direction parallel to the linear projections , a center line average surface roughness Ra of 20 600 nm when scanned in a direction perpendicular to the linear projections , and an Ra / Ra ratio of at most 0.8
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