Patent ID: 7510771

Claim:
A polymer interlayer comprising: a first polymer sheet comprising a plasticized poly(vinyl butyral); a second polymer sheet comprising a plasticized poly(vinyl butyral), wherein the amount of plasticizer in said plasticized poly(vinyl butyral) of said second polymer sheet is at least 10 parts per hundred greater than the amount of plasticizer in said plasticized poly(vinyl butyral) of said first polymer sheet, wherein said second polymer sheet has a residual hydroxyl content per weight percentage that is at least 2% lower than the residual hydroxyl content per weight percentage of said first polymer sheet, wherein said first polymer sheet and said second polymer sheet are in direct contact with each other, and wherein said first polymer sheet and said second polymer sheet each have a residual acetate content of less than 5 mol percent; and, a third polymer sheet disposed in direct contact with said second polymer sheet, wherein said third polymer sheet comprising plasticized poly(vinyl butyral) and wherein the amount of plasticizer in said plasticized poly(vinyl butyral) of said second polymer sheet is at least 10 parts per hundred greater than the amount of plasticizer in said plasticized poly(vinyl butyral) of said third polymer sheet.