Bond it between the cover glass and sensor, when the screen is off, you'll not see the viewing area, and the whole display will be completely black. Like the below pictures.
OCA products meet the appearance requirements of human display applications: high-end, atmospheric, beautiful, scientific and technological sense, to create an integrated visual sense, that can shock at the first glance. Grab the eye of the consumer.
Seamless special OCA to make your display nicer and higher end. This technology is widely used in the design of smart homes, smartwatches and other products that pursue a beautiful appearance.
If you want to learn more,please contact me at Helen@kingtechlcd.com