Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
2000-12-28
2002-11-05
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031600, C106S031580, C106S031860
Reexamination Certificate
active
06475271
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention is directed to an aqueous ink composition. More specifically, the present invention is directed to aqueous ink compositions comprising a low boiling point alcohol or thiol as a substrate penetrant additive for use in ink jet printing processes. In addition, the present invention is also directed to an ink jet printing process wherein an aqueous ink composition comprising a low boiling point alcohol or thiol is used in the production of single or multicolor images.
2. Description of Related Art
Ink jet printing is a non-impact printing method that produces droplets that are deposited on a print substrate (recording medium) such as plain paper, coated paper, transparent film (transparency), or textile in response to electronic digital signals. Thermal or bubble jet drop-on-demand ink jet printers have found broad applications as output for personal computers in the office and at home.
In existing thermal ink jet printing processes, the printhead typically comprises one or more ink jet ejectors, each ejector includes a channel communicating with an ink supply chamber, or manifold, at one end and having an opening at an opposite end, referred to as a nozzle. A thermal energy generator, usually a resistor, is located in each of the channels at a predetermined distance from the nozzles. The resistors are individually addressed with a current pulse to momentarily vaporize the ink within each respective channel to form a bubble that expels an ink droplet. As the bubble grows, the ink rapidly bulges from the nozzle and is momentarily contained by the surface tension of the ink as a meniscus. This is a very temporary phenomenon, and the ink is quickly propelled toward a print sheet. As the bubble begins to collapse, the ink remaining in the channel between the nozzle and the bubble starts to move toward the collapsing bubble, causing volumetric contraction of the ink at the nozzle resulting in the separation of the bulging ink from the nozzle as a droplet. The acceleration of the ink out of the nozzle while the bubble is growing provides sufficient momentum and velocity to propel the ink droplet in a substantially straight-line direction towards a print substrate, such as a piece of paper. Subsequently, the ink channel refills by capillary action and is ready for the next repeating thermal ink jet process. Thermal ink jet processes are well known and described in, for example, U.S. Pat. Nos. 4,251,824, 4,410,889, 4,412,224, 4,463,359, 4,532,530, 4,601,777, 5,139,574, 5,145,518, and 5,281,261, the entire disclosures of which are incorporated herein by reference. Because the droplet of ink is emitted only when the resistor is actuated, this type of thermal ink jet printing is known as “drop-on-demand” printing. Other types of drop-on-demand printing such as piezoelectric ink jet printing and acoustic ink jet printing are also known.
Continuous ink jet printing is also known. In continuous ink jet printing systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. Multiple orifices or nozzles can be used to increase imaging speed and throughput. The ink is perturbed while being ejected from an orifice, causing the ink to break up into droplets at a fixed distance from the orifice. At the point of break-up, the electrically charged ink droplets pass through an applied electrode that switches on and off in accordance with digital data signals. Charged ink droplets pass through a controllable electric field that adjusts the trajectory of each ink droplet in order to direct it to either a gutter for ink deletion and recirculation or to a specific location on a recording substrate (print substrate) to create images.
In an ink jet printing apparatus, the printhead typically comprises a linear array of ejectors, and the printhead moves relative to the surface of the print substrate, either by moving the print substrate relative to a stationary printhead, or vice-versa, or both. In some types of apparatuses, at least a relatively small print head supplied with an ink moves across a print sheet numerous times in swaths in order to complete an image. For multi-color ink jet printing, a set of printheads and ink (e.g. cyan, magenta, yellow and black) can move across the print substrate numerous times in swathes and disperse selected inks in any desired patterns (e.g., 1/8, 1/4, 1/2, fulltone (1/1)) according to digital signals. The speed of this type of single or multiple color ink jet printing on a substrate is determined by the moving speed of the printheads across the print substrate, ink jetting frequency (or frequency response), and the desired number of swathes needed for printing. The printing speed of this type of ink jet apparatus can be increased if two or more print heads are budded together to form a partial-width array printhead for printing each ink in a monochrome or multi-color ink jet printing system. The partial-width ink jet printhead has more ink jet nozzles per printhead, and can deliver a large number of ink droplets across the substrate in a swath in a short period of time. Monochrome or multi-color ink jet printing apparatuses using one or several partial-width printheads may have a faster printing speed than current commercial ink jet printers.
Alternatively, a printhead that consists of an array of ejectors (e.g., several butted printheads to give a full-width array printhead) and extends the full width of the print substrate may pass an ink down once onto the print substrate to give full line images, in what is known as a “full-width array printer.” When the printhead and the print substrate are moved relative to each other, image-wise digital data is used to selectively activate the thermal energy generators in the ink jet printhead over time so that the desired image will be created on the print substrate at a fast speed. For multi-color inkjet printing, several full-width array printheads and inks (e.g., cyan, magenta, yellow, and black) can be used to deliver multiple color inks onto a print substrate. This type of multi-color ink jet printing process is capable of printing multiple color images and monochrome color images on a print substrate at a much faster speed (e.g., more than five pages of full color images per minute) than current commercial color ink jet printers.
In multicolor ink jet printing processes, several inks can be printed on a print substrate. In some instances, two different inks can be printed next to each other. Intercolor bleed can occur if the inks are not dried properly or if the printing process is too fast for the inks to set. Undesired ink mixing on a print substrate, especially on the surface of a plain paper, can cause distorted images near the border of two inks. After the inks dry, the border of the two inks can appear irregular with poor edge sharpness (or raggedness) due to the invasion of one ink into the other. Such bleed images are visibly unattractive. This phenomenon is generally called intercolor bleed. Intercolor bleed occurs particularly when a darker colored ink (such as a black ink) and a lighter colored ink (such as a yellow ink, a cyan ink, a magenta ink, or the like) are printed next to each other, because of the high contrast between the two colors. Intercolor bleed can also occur when two color inks are printed next to each other (for example yellow ink next to magenta ink, yellow ink next to cyan ink, magenta ink next to cyan ink or the like). The severity of the intercolor bleed generally is affected by the type and composition of the ink, absorption rate of the ink on a print substrate, printhead design, ink drop mass, ink dot size and method and speed of printing. As a result, there is a need to reduce intercolor bleed and to produce high quality multicolor ink jet images on print substrates, including plain and coated papers, transparencies, textiles and other desired substrates.
U.S. Pat. No. 5,091,005, the disclosure of which is totally incorporated herein by reference, discloses inks comprising, by
Faison Veronica F.
Klemanski Helene
Oliff & Berridg,e PLC
Xerox Corporation
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