Method of making daylight redirecting window films employing embedded microstructures

A method of making a daylight redirecting window film, comprising:

• providing a first optically transmissive film having a generally smooth first broad area surface configured for light input and an opposing second broad area surface configured for light output;
• coating the first broad area surface with a layer of an optically transmissive adhesive,
• providing a second optically transmissive film approximately coextensive with the first optically transmissive film and comprising a first light redirecting layer disposed on a first side of the second optically transmissive film and a second light redirecting layer disposed on an opposite second side of the second optically transmissive film, wherein the first light redirecting layer comprises a periodic array of linear light redirecting structures extending parallel to an edge of the second optically transmissive film and defining a parallel array of linear channels each having a width of less than 50 micrometers, wherein the second light redirecting layer comprises a two-dimensional pattern of light scattering surface microstructures, wherein each of the linear light redirecting structures comprises a first side wall configured to reflect light using a total internal reflection, an opposing second side wall disposed at a distance from the first side wall, and a top wall joining the first and second side walls;
• positioning the second optically transmissive film relatively to the first optically transmissive film such that the first side of the second optically transmissive film is facing the second broad area surface of the first optically transmissive film;
• providing an optically transmissive adhesive layer between the first optically transmissive film and the second optically transmissive film;
• and
• bonding top portions of the linear light redirecting structures to the second broad area surface of the first optically transmissive film using the optically transmissive adhesive layer,
• wherein a combined thickness of the first optically transmissive film, the second optically transmissive film, the optically transmissive adhesive layer, and the layer of the optically transmissive adhesive is less than one millimeter.