COLORLESS FLUORESCENT NANOPARTICLES FOR TRANSPARENCIES
Original Publication Date: 1992-Jun-30
Included in the Prior Art Database: 2004-Apr-06
Xerox Disclosure Journal
A colorless coating composition for use in xerographic transparency stock as a reference and registration stripe is disclosed. Alternatively the colorless coating may be used over the entire transparency sheet surface. The coating composition is comprised of an aqueous dispersion of fluorescent nanoparticles. The fluorescent nanoparticles are comprised of small, diameter less than 50 nanometers, silicated polymeric micelles to which fluorescent dyes are covalently bonded. The silicated polymeric micelles are comprised of aggregates of block copolymers, for example, ABA type, having a hydrophobic core and a hydrophilic shell into which a silica network has been incorporated. Reactive fluorescent dyes are subsequently grafted to the hydrophobic shells of the aggregates. A suitable reactive fluorescent dye chromophore should satisfy the following conditions: has adequate water solubility; absorbs ultraviolet light but not visible light; emits fluorescent light that is detectable by a machine sensor chosen for this purpose; has good thermal and photonic stability; is non-toxic; and is reactive to hydroxyl or amino functional groups on solid particle surfaces in aqueous media. Advantages of the colorless nanoparticle containing coating compositions include: enables "stripeless" transparency stock; enables invisible document identification or encoding; and enables a simple coating process in transparency manufacture. Silicated nanoparticles provide stable dispersions in aqueous media that reduce environmental impacts of preparation, use and disposal of such coating fluids. Siliczted nanoparticles may also be used in place of silica particles used in conventional xerographic transparencies for friction control. Example prepsxations of nanoparticles and nanoparticle containing transparency stock fo 1 lows.