Optical stack

An optical stack comprising:

• an optical film;
• and
• an optical adhesive adhered to the optical film and comprising a first major surface facing away from the optical film, the first major surface comprising a plurality channels formed therein, each channel comprising a side wall extending upwardly beyond a portion of the first major surface adjacent the channel to define a ridge substantially co-extensive with the channel along at least a portion of a length of the channel, such that when the optical stack is placed on a support surface with the first major surface of the optical adhesive contacting the support surface, the optical stack bonds to the support surface and may be removed from, or slidingly repositioned on, the support surface without damage to the optical adhesive or the support surface, and upon application of at least one of heat and pressure, the optical stack substantially permanently bonds to the support surface and the plurality of channels and ridges substantially disappear.

An automotive windshield comprising an optical stack disposed between, and bonded to, an interior glass substrate and an exterior glass substrate, the optical stack comprising:

• an optical film comprising a plurality of alternating first and second polymeric layers numbering at least 50 in total, each first and second polymeric layer having an average thickness less than about 500 nm;
• and
• a first optical adhesive bonding the optical film to the interior glass substrate, the first optical adhesive having an average thickness in the range of about 10 micrometers to about 100 micrometers and comprising a sound absorbing property for reducing noise in an interior of a motor vehicle, such that a ratio of a loss modulus G″ to a storage modulus G′ of the optical adhesive for frequencies in a range from about 1000 Hz to about 3200 Hz is greater than about 0.3.