Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2001-10-09
2004-04-13
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
Reexamination Certificate
active
06719423
ABSTRACT:
FIELD OF THE INVENTION
The invention relates in general to image recording and printing in an apparatus including an ink jet device for forming a particulate ink image on an member. In particular, ink particles in a liquid ink image on the member are concentrated by an applied field, a mechanism is provided for selectively removing excess liquid from the concentrated particles, and the concentrated particles are subsequently transferred to a receiver.
BACKGROUND OF THE INVENTION
High resolution digital input imaging processes are desirable for superior quality printing applications, especially high quality color printing applications. As is well known, such processes may include electrostatographic processes using small-particle dry toners, e.g., having particle diameters less than about 7 micrometers, electrostatographic processes using nonaqueous liquid developers (also known as liquid toners) in which particle size is typically of the order of 0.1 micrometer or less, and ink jet processes using nonaqueous or aqueous-based inks. The less commonly used nonaqueous ink jet technology has an advantage over aqueous-based ink jet technology in that an image formed on a receiver requires relatively little drying energy and therefore dries relatively rapidly.
The most widely used high resolution digital commercial electrostatographic processes involve electrophotography. Although capable of high process speeds and excellent quality printing, electrophotographic processes utilizing dry or liquid toners are inherently complicated, and require expensive, bulky and complex equipment. Moreover, due to their complex nature, electrophotographic processes and electrophotographic machines tend to require significant maintenance.
Digital ink jet processes have the inherent potential to be simpler, less costly, and more reliable than digital electrophotographic processes. Generally, it is usual for ink to be fed through a nozzle, the diameter of which nozzle being a major factor in determining the droplet size and hence the image resolution on a recording surface. There are two major classes of ink jet printing, namely, continuous ink jet printing and drop-on-demand ink jet printing. Continuous printing utilizes the nozzle to produce a continuous stream of electrically charged droplets, some of which droplets are selectively delivered to the recording surface, the remainder being electrostatically deflected and collected in a sump for reuse. Drop-on-demand ink jet printing produces drops from a small nozzle only as required to generate an image, the drops being produced and ejected from the nozzle by local pressure or temperature changes in the liquid in the immediate vicinity of the nozzle, e.g., using a piezoelectric device, an acoustic device or a thermal process controlled in accordance with digital data signals. In order to produce a gray scale image, variable numbers of drops are delivered to each imaging pixel. Typically, an ink jet head of an ink jet device includes a plurality of nozzles. In most commercial ink jet systems, aqueous-based inks containing dye colorants in relatively low concentrations are used. As a result, high image densities are difficult to achieve, image drying is not trivial, and images are not archival because many dyes are disadvantageously subject to fading. Moreover, the quality of an aqueous-based ink jet image is strongly dependent upon the properties of the recording surface, and will for example be quite different on a porous paper surface than on a smooth plastic receiver surface. By contrast, the quality of an electrophotographic toner image is relatively insensitive to the recording surface, and the toner colorants in both dry and liquid electrophotographic developers are generally finely divided or comminuted pigments that are stable against fading and able to give high image densities.
To overcome problems associated with fading and low image densities associated with dyed aqueous-based inks, pigmented aqueous-based inks have been disclosed in which a pigmented material is colloidally dispersed. Typically, a relatively high concentration of pigmented material is required to produce the desired highest image densities (Dmax). Exemplary art pertaining to pigmented aqueous-based inks includes the recently issued Lin et al. patent (U.S. Pat. No. 6,143,807) and the Erdtmann et al. patent (U.S. Pat. No. 6,153,000). Generally, pigmented inks have a much greater propensity to clog or modify the opening jet(s) of a drop-on-demand type of ink jet head than do dyed inks, especially for the narrow diameter jets required for high resolution drop-on-demand ink jet imaging, e.g., at 600 dots per inch. Drop-on-demand printers do not have a continuous high pressure in the nozzle, and modification of the nozzle behavior by deposition of pigment particles is strongly dependent on local conditions in the nozzle. In continuous ink jet printers using pigmented inks, the relatively high concentrations of pigment typically affects the droplet breakup which tends to result in nonuniform printing.
Pigmented nonaqueous inks having particle sizes smaller than 0.1 micrometer for use in ink jet apparatus are disclosed in the Romano et al. patent (U.S. Pat. No. 6,053,438), and the Santilli et al. patent (U.S. Pat. No. 6,166,105).
A deficiency associated with most high resolution conventional ink jet devices that deposit ink directly on to a (porous) paper receiver sheet is an unavoidable tendency for image spreading, with a concomitant resulting degradation of resolution and sharpness of the image produced. As a drop of deposited liquid ink is absorbed, capillary forces tend to draw the ink along the surface and into the microchannels between paper fibers, thereby causing a loss of resolution. Inasmuch as the colorant concentration of a dyed aqueous-based ink tends to be low, there is a comparatively large proportion of liquid vehicle which must be absorbed from each drop. This also holds true for the case of pigmented aqueous-based inks, for which particle sizes may be sub-micron, i.e., such very small particles can be swept along by the carrier liquid as it spreads in the paper, thereby compromising high resolution imaging quality. In addition to capillary spreading by liquid absorption in a receiver, spreading may also be a problem if the carrier liquid is not readily absorbed by a receiver, e.g., if the receiver is a coated specialty paper used in a high resolution conventional ink jet device that deposits ink directly on to a receiver. The spreading is strongly dependent upon the surface energies of the coating on the paper and of the ink. Unusual particle size distributions such as disclosed in the above-cited Lin et al. patent (U.S. Pat. No. 6,143,807) may be useful with pigmented aqueous-based inks, perhaps to mitigate the effects of image spread.
An intermediate transfer element or member may be used with an ink jet device in which device one or more colored inks may be deposited via ink jet on to the surface of the intermediate and subsequently co-transferred to a receiver such as a paper sheet. In the Anderson patent (U.S. Pat. No. 5,099,256) an intermediate member having a thermally conductive silicone surface that is rough to prevent image spreading is heated to dehydrate an aqueous-based ink jet image formed thereon prior to transfer of the ink jet image to a receiver. The Okamato et al. patent (U.S. Pat. No. 5,598,195) discloses an ink jet recording method, in which a voltage pulse applied to an electrode in an ink jet recording head and an opposing electrode disposed on the opposite side of an intermediate recording material produces a Coulomb force that causes an ink to be jetted on to the intermediate recording material. The Xu patent (U.S. Pat. No. 5,746,816) discloses an aqueous liquid ink containing an insoluble dye. Such an ink containing an insoluble dye is used in the Hale et al. patent (U.S. Pat. No. 5,830,263) which discloses a method in which a liquid ink containing a heat activated dye is imagewise deposited via an ink jet device on an intermediate memb
Chowdry Arun
May John Walter
Tombs Thomas Nathaniel
Do An H.
Kessler Lawrence P.
Meier Stephen D.
NexPress Solutions LLC
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