Polymer interlayers with low mottle and reduced iceflower defects

A polymer interlayer that resists formation of optical defects, the polymer interlayer comprising:

• a first polymer layer;
• and
• a second polymer layer;
• wherein said first polymer layer is disposed on a first side of said second polymer layer,
• wherein a surface of the first side of said second polymer layer includes a surface roughness, defined by an RSM value, of greater than 500 microns,
• wherein said polymer interlayer has a mottle value of less than 1.0.

A method of forming a polymer interlayer that resists formation of optical defects, said method comprising the steps of:

• (a) extruding a first polymer layer through a co-extrusion die;
• (b) extruding a second polymer layer through the co-extrusion die;
• and
• (c) extruding a third polymer layer through the co-extrusion die;
• wherein upon said extruding of steps (a), (b), and (c), the first polymer layer is positioned between the second and third polymer layers,
• wherein during said extruding of step (a) said first polymer layer has a first storage modulus value, wherein during said extruding of step (b) said second polymer layer has a second storage modulus value, and wherein a difference between the first storage modulus value and the second storage modulus value is less than about 45,000 Pa,
• wherein upon said extruding of steps (a), (b), and (c), the polymer interlayer has a mottle value of less than 1.0.