Optical: systems and elements – Optical modulator – Light wave temporal modulation
Reexamination Certificate
2001-05-24
2003-04-15
Mack, Ricky (Department: 2873)
Optical: systems and elements
Optical modulator
Light wave temporal modulation
Reexamination Certificate
active
06549327
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a display. More specifically, the present invention is directed to a display having photochromic characteristics. One embodiment of the present invention is directed to a display comprising an arrangement of a plurality of optically anisotropic rotatable elements, each of said rotatable elements having a surface in contact with an enabling fluid, said rotatable elements being electrically dipolar in the presence of the enabling fluid and thus being subject to rotation upon application of an electric field, said rotatable elements being free to rotate in place but not free to translate substantially so as to disrupt the arrangement of rotatable elements, wherein a first portion of said surface contains a mixture of a chelating agent and a spiropyran material of the formula
wherein n is an integer representing the number of repeat —CH
2
— units and R is —H or —CH═CH
2
, and wherein a second portion of said surface contains substantially no spiropyran.
Photochromism in general is a reversible change of a single chemical species between two states having distinguishably different absorption spectra, wherein the change is induced in at least one direction by the action of electromagnetic radiation. The inducing radiation, as well as the changes in the absorption spectra, are usually in the ultraviolet, visible, or infrared regions. In some instances, the change in one direction is thermally induced. The single chemical species can be a molecule or an ion, and the reversible change in states may be a conversion between two molecules or ions, or the dissociation of a single molecule or ion into two or more species, with the reverse change being a recombination of the two or more species thus formed into the original molecule or ion. Photochromic phenomena are observed in both organic compounds, such as anils, disulfoxides, hydrazones, oxazones, semicarbazones, stilbene derivatives, o-nitrobenzyl derivatives, spiro compounds, and the like, and in inorganic compounds, such as metal oxides, alkaline earth metal sulfides, titanates, mercury compounds, copper compounds, minerals, transition metal compounds such as carbonyls, and the like. Photochromic materials are known in applications such as photochromic glasses, which are useful as, for example, ophthalmic lenses.
Electric reusable paper can be defined as any electronically addressable display medium that approximates paper in form and function. Electric reusable paper ideally is light-weight, thin, and flexible, and ideally it displays images indefinitely while consuming little or no power. In addition, electric reusable ideally is reusable so that the user is able to erase images and create new ones repeatedly. Preferably, electric reusable paper displays images using reflected light and allows a very wide viewing angle.
One form of electric paper uses a gyricon or rotating element display. Gyricon or twisting ball displays typically are display systems in which the display panel comprises rotatable elements such as cylinders, prisms, or spherical balls that have an optical and an electrical anisotropy as a result of each hemisphere surface having a different color and a electrical charge in contact with a liquid. These rotatable elements are typically embedded in a solid substrate and a slight space between each rotatable element and the substrate is filled with a liquid so that the elements are free to rotate in a changing electrical field but cannot migrate from one location to another. If, for example, one hemisphere of the rotatable element is black and the other is white, each pixel can be turned on and off by the electrical field applied to that location. Each pixel can be individually addressed, and a full page image can thus be generated.
Most commonly the solid substrate used in these displays is a gel, typically a silicone gel. The purpose of using this material lies in the remarkably large expansion in volume exhibited by gels when soaked in certain liquids refered to as plasticizing liquids. Thirty percent expansions are not uncommon when these materials are soaked in silicone oils. The rotatable elements do not expand when contacted by the plasticizing liquid, so a cavity opens up around each rotatable element when the gel is immersed in a plasticizing liquid. This space fills with the plasticizing liquid.
Other variations on these displays are also known, such as embodiments wherein the rotatable elements are individually enclosed in shells with the space between the inner surface of the shell and the outer surface of the rotatable element being filled with a dielectric liquid. The resultant capsules can then be dispersed in a second liquid, such as an optically clear epoxy, which can then be hardened. The resultant display is then in the form of a thin, paper-like sheet. Alternatively, the resultant display can easily be conformally coated on a non-planar surface for even greater flexibility of applications.
Other variations on these displays include using rotatable elements of other than ball or sphere shape, such as cylinders, prisms, or the like.
In some embodiments, the display comprises a thin substantially transparent sheet having many of the attributes of paper documents. It looks like paper, has ambient light valve behavior like paper (i.e. the brighter the ambient light, the more easily it may be seen), is flexible like paper, can be folded like paper, can be carried around like paper, can be written on like paper, can be copied like paper, and has nearly the archival memory of paper since the display typically retains an image indefinitely in the absence of an applied electric field. These embodiments are frequently referred to as “electric paper”. The display provides a reuseable (and thus environmentally friendly) substitute for ordinary paper. In other embodiments, the display device has a rigid structure incorporating an array of addressing electrodes. Upon application of an electrical field between electrodes located on opposite surfaces of the layer containing the bichromal elements, the elements rotate depending on the polarity of the field, presenting one or the other hemisphere to an observer.
U.S. Pat. No. 5,633,109 (Jennings et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition which comprises an aqueous liquid vehicle, a photochromic material, and a vesicle-forming lipid, wherein vesicles of the lipid are present in the ink.
U.S. Pat. No. 5,593,486 (Oliver et al.), the disclosure of which is totally incorporated herein by reference, discloses a hot melt ink composition comprising (a) an ink vehicle, said ink vehicle being a solid at about 25° C. and having a viscosity of from about 1 to about 20 centipoise at a temperature suitable for hot melt ink jet printing, said temperature being greater than about 45° C., (b) a photochromic material, (c) an optional colorant, and (d) an optional propellant.
U.S. Pat. No. 5,551,973 (Oliver et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition which comprises an aqueous phase, an oil phase, a photochromic material, and a surfactant, said ink exhibiting a liquid crystalline gel phase at a first temperature and a liquid microemulsion phase at a second temperature higher than the first temperature.
U.S. Pat. No. 5,759,729 (Martin et al.), the disclosure of which is totally incorporated herein by reference, discloses a toner composition for the development of electrostatic latent images which comprises particles comprising a mixture of a resin and a photochromic material. Another embodiment of the present invention is directed to a liquid developer composition for the development of electrostatic latent images which comprises a nonaqueous liquid vehicle and a photochromic material, wherein the liquid developer has a resistivity of from about 10
8
to about 10
11
ohm-cm and a viscosity of from about 25 to about 500 centipoise. Yet another embodiment of the present invention is directed t
Buncel Erwin
Chopra Naveen
Foucher Daniel A.
Kazmaier Peter M.
Patel Raj D.
Byorick Judith L.
Hindi Omar
Mack Ricky
Xerox Corporation
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