Abstract: A method of transparentizing a cellulosic substrate which is suitable for use as a mailer or envelope having at least one transparentized portion is provided. The method includes the application of a transparentizing composition to a substrate by a flexographic printing apparatus in which one or more of the transparentizing composition, the substrate, and the transfer rollers of the printing apparatus are preferably cooled prior to application in order to raise the viscosity of the composition and allow more of the composition to be transferred to the substrate surface. A primer composition may also be applied to the substrate prior to application of the transparentizing composition in order to aid in penetration of the transparentizing composition.

Abstract: The invention described in the specification relates to latent image printing and developing systems and to substrates containing latent images. High quality latent images are prepared by a printing method which deposits a layer containing organic-based dye particles and organic-based developer particles, each having a particle size of from about 2 to about 6 microns, on a substrate. The image is then developed by contacting the substantially invisible image of dye and developer particles with an oxygenated solvent from an imaging device. Multicolor, vivid images are obtained as a result of the image printing and developing system of the invention.

Abstract: An optically variable device for use on security documents to deter unauthorized reproduction is provided which contains a warning message that is not readily apparent to an observer but that reproduces as a visible warning message when copied. The device comprises a pattern of light reflecting surfaces which comprise a reflection diffraction grating having a plurality of grooves that vary in orientation and blaze angle. In an alternative embodiment, a machine-readable optically variable device is provided in which the pattern of specularly light-reflecting surfaces produces a machine-readable message in response to light impinging on the device.