Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-04-28
2001-02-27
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031860, C106S031890
Reexamination Certificate
active
06193792
ABSTRACT:
The present invention is directed to improved ink compositions. More specifically, the present invention is directed to aqueous ink compositions which exhibit good performance in ink jet printing processes. One embodiment of the present invention is directed to an ink composition which comprises (a) water, (b) a surfactant of the formula
wherein the molecular weight of the polypropylene oxide block is about 900 and the ethylene oxide blocks constitute about 80 percent by weight of the molecule, (c) colored pigment particles, and (d) uncolored precipitated colloidal silica particles, wherein the ink has a pH of at least about 7.5 when measured at about 25° C.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are two types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The relatively large size of the transducer prevents close spacing of the nozzles, and physical limitations of the transducer result in low ink drop velocity. Low drop velocity seriously diminishes tolerances for drop velocity variation and directionality, thus impacting the system's ability to produce high quality copies. Drop-on-demand systems which use piezoelectric devices to expel the droplets also suffer the disadvantage of a slow printing speed.
Another type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of dropon-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to evaporate almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the hydrodynamic motion of the ink stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the “bubble jet” system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the some high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280° C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses on the resistor. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The resistive layer encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action. This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be refired after 100 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet processes are well known and are described in, for example, U.S. Pat. No. 4,601,777, U.S. Pat. No. 4,251,824, U.S. Pat. No. 4,410,899, U.S. Pat. No. 4,412,224, and U.S. Pat. No. 4,532,530, the disclosures of each of which are totally incorporated herein by reference.
European Patent Publication EP 0 823 464 A1, the disclosure of which is totally incorporated herein by reference, discloses the use of a recording liquid for water based inkjet with pigment and colloidal silica, wherein prints recorded on plain paper exhibit good clearness, high quality, water resistance, and light resistance. Optionally, the ink can also contain an anionic or nonionic surfactant, such as fatty acid salts, alkyl sulfuric esters, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfuric succinates, alkyl diaryl ether disulfonates, alkyl phosphates, polyoxyethylene alkyl ether sulfonates, polyoxyethylene alkyl aryl ether sulfonates, naphthalene sulfonic acid formaldehyde condensations, polyoxyethylene alkyl phosphoric acid esters, glycerol borate fatty acid esters, polyoxyethylene glycerol fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene-oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerol fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkyl amines, fluorine types, silicon types, and the like, with one specific example provided being EMULGEN 420, obtained from Kao Corporation.
U.S. Pat. No. 5,221,332 (Kohimeier), the disclosure of which is totally incorporated herein by reference, discloses an ink composition which comprises an aqueous liquid vehicle, a colorant, and silica particles in an amount of from about 0.1 to about 5 percent by weight. The inks are particularly suited for ink jet printing processes, including thermal ink jet printing processes, and exhibit increased drop volume and increased drop velocity when employed in ink jet printing processes.
U.S. Pat. No. 4,877,451 (Winnik et al.), the disclosure of which is totally incorporated herein by reference, discloses ink jet ink compositions comprising water, a solvent, and a plurality of colored particles comprising hydrophilic porous silica particles to the surfaces of which dyes are covalently bonded through silane coupling agents.
U.S. Pat. No. 5,378,574 (Winnik et al.), the disclosure of which is totally incorporated herein by reference, discloses ink jet inks and liquid developers containing colored particles comprising hydrophilic porous silica particles to the surfaces of which dyes are covalently bonded through silane coupling agents.
U.S. Pat. No. 5,145,518 (Winnik et al.), the disclosure of which is totally incorporated herein by reference, discloses an ink composition which comprises an aqueous liquid vehicle and particles of an average diameter of 100 nanometers or less which comprise micelles of block copolymers of the formula ABA, wherein A represents a hydrophilic se
Byorick Judith L.
Faison Veronica F.
Klemanski Helene
Xerox Corporation
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