a sheet of polyvinyl alcohol-type matrix including vinylene polymer blocks, the sheet defining a pass polarization axis and a block polarization axis perpendicular to the pass polarization axis, light having an electrical vector parallel to the pass polarization axis being substantially transmitted through the sheet and light having an electrical vector parallel to the block polarization axis being substantially absorbed by the vinylene polymer blocks, the sheet having an intrinsic absorption spectrum such that, when crossed with an identical sheet and illuminated with a cold cathode fluorescent tube (CCFT) light source, the sheet transmits light having an a* co-ordinate with a magnitude of less than 2 and a b* co-ordinate with a magnitude of less than 2, wherein the a* and b* co-ordinates are measured accordingly to the CIELAB color system,

a concentration of vinylene polymer blocks having a chain length n less than or equal to 9 being greater than a concentration of vinylene polymer blocks having a chain length greater than 9.