Method of treating interlayer material

A method of fabricating a maximum number of individual sheets of substantially uniform thickness of trapezoidal shape of a flexible material of plastic composition suitable for use as an interlayer for laminated windows having a graded coating along an upper portion thereof from a continuous ribbon of clear, flexible interlayer material of plastic composition having a substantially uniform thickness comprising:

• (1) cutting successive portions of said continuous ribbon of clear, flexible interlayer material into a number of interfitting sheets of trapezoidal shape while supporting each said successive portion of said continuous ribbon in such a manner as to avoid wrinkling and differential stretching thereof during its cutting from said ribbon,
• (2) orienting each of said sheets of trapezoidal shape so formed into a predetermined orientation and positioning each said sheet in turn while at said predetermined orientation in a predetermined position with respect to apparatus to apply a coating composition along a preselected longitudinal portion only of said sheet of trapezoidal shape,
• (3) applying a coating of graded intensity along said longitudinal portion only of said sheet of trapezoidal shape in such a manner that the intensity of said coating decreases transversely of the length of said longitudinal edge portion away from the longitudinal edge of said sheet,
• and
• (4) continuing to support said sheet of trapezoidal shape in such a manner as to avoid wrinkling and differential stretching thereof during said coating applying step, whereby each said coated sheet of trapezoidal shape with a coating of graded intensity so produced has a substantially uniform thickness and is smooth and has a substantially uniform stress throughout its entire extent.