Demand for optimum brightness, better visibility, and lower power consumption for illuminating automotive instrument panels and displays has been steadily increasing. Printed clear or matte plastic films have been used to provide necessary local diffusion of light to hide the lamps and structural details behind the display, while transmitting light where illumination is needed. Such films may be limited in meeting the necessary functionality, without additional lighting and surface treatments to reach adequate brightness and contrast levels.
Recent developments of advanced display films for the LCD TV and Monitor markets enabled the extension of certain light management capabilities of such films to the automotive displays and instrument panels. This paper addresses the introduction of polycarbonate (PC) films comprising engineered surface features for improved contrast and brightness. Optical functionality is accomplished through the creation of optical elements such as micro-lens arrays, lenticular or prismatic matrices on the surface of the film. Such films are particularly attractive for applications utilizing LEDs for illumination.
In this paper two types of films are evaluated; a film with micro-lens array on the surface, and a film with random matte texture as reference. The films were screen-printed with patterns simulating those used in typical instrument panels, placed on a test backlight module, and corresponding brightness and contrast of the display were assessed qualitatively and quantitatively using light intensity measurements.
Compared to standard matte finish, films with engineered micro-lens surface features had less glare, better hiding power, and were three times better in contrast under ambient and transmitted lighting conditions; thus increasing brightness and contrast of the module at the same power level, or potentially reducing power consumption for the same brightness performance.