Optically diffusive film with elongated structures

An optically diffusive film comprising:

• a unitary optical layer comprising a first major surface and an opposing structured second major surface comprising a plurality of spaced apart elongated structures elongated along a same first direction and arranged at a substantially uniform density of between about 5 to 100 structures per square mm across the second major surface, each elongated structure comprising a peak such that in a plane of a cross-section of the elongated structure that comprises the peak and is parallel to:
• the first direction, the elongated structure has a length L1, a height variation of less than about 5% across a substantially flat top region having a length d, d/L1≥0.15, and a full width at half maximum W1;
• and
• a second direction orthogonal to the first direction, the elongated structure has a full width at half maximum W2, W2/W1≤0.6, wherein:
• a power spectral density of the structured second major surface has a first peak along the first direction having a first peak intensity I1 and a second peak along the second direction having a second peak intensity I2, 1≤I1/I2≤10,000.