| 摘要 |
A document includes paper having an average surface roughness of at least about 0.5 microns and including one or more optical brighteners, and includes at least one image thereon wherein the at least one image includes clear binder and light absorbing material that absorbs light only at wavelengths below 350 nm. The image is substantially not detectable to a naked human eye through differential gloss or exposure to light having wavelengths of 365 nm or more, but may be revealed to the naked human eye by exposing the document to light having a wavelength at which the light absorbing material absorbs light.
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