Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2001-03-30
2002-10-22
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C347S096000, C347S101000
Reexamination Certificate
active
06467898
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to ink jet printing onto textiles, to the ink jet printing of wide web, large panel and other extended area substrates, and to the ink jet printing onto large area fabrics and other substrates on a high speed and commercial scale. The invention is particularly applicable to the printing of patterns onto fabric used in quilting such as mattress covers, comforters and bedspreads, and to the printing of signs, banners and other large area substrates. The invention is particularly related to the ink jet printing with ink compositions containing ultra-violet light (UV) curable and other polymerizable or otherwise stable inks.
BACKGROUND OF THE INVENTION
Needs have arisen for the printing of large banners, flags and signs in quantities that are not economical for many conventional printing processes. Proposals have been made to print such products from electronic source files that can be processed directly on the printing press or printing system, rather than through steps such as film image-setting and plate-making. One such process is that known as ink-jet printing. These processes have been attempted with modest success on surfaces such as vinyl, but printing with success onto textile surfaces has been even more limited. Such processes have been slow and lack reliability. The clogging of print heads in ink jet printing has been too frequent for use in wide width and large area substrates, and the processes used have not produced acceptable printing on textile materials.
Quilting, for example, is an art in which patterns are stitched through a plurality of layers of material over a two-dimensional area of the material. The multiple layers of material normally include at least three layers, one a woven primary or facing sheet that will have a decorative finished quality, one a usually woven backing sheet that may or may not be of a finished quality, and one or more internal layers of thick filler material, usually of randomly oriented fibers. The stitched patterns maintain the physical relationship of the layers of material to each other as well as provide ornamental qualities. Frequently, a combining of stitched patterns with printed patterns is desirable, such as in mattress covers and other quilt manufacture. Producing a printed pattern on a mattress cover requires the application of ink to fabric, which, unlike paper, plastic or other smooth surfaces, presents a texture, third dimension or depth, to the surface on which the printing is applied.
The printing of substrates that are more than several feet, or a meter, wide, referred to as the special category of “wide width” printing, into which category the printing of mattress ticking and most other quiltable materials would fall, is beyond many of the limitations of conventional printing methods. A number of technical problems exist that have deterred the development of the printing of wide fabrics such as mattress covers, upholstery, automobile seat cover fabrics, office partitions and other wide width substrates.
Wide width products are frequently printed in relatively small quantities. Traditional printing typically involves the creation of a plate, a mat, a screen, or some other permanent or at least tangible, physical image from which ink is transferred to the object being printed. Such images contribute a relatively high set up cost that is only economical where the number of identical copies of the product is large. At the other extreme, office printers, for example, print a single copy or a small number of copies of a given document or other item, and are currently of the type that uses no permanent, physical image transfer element, but which rather prints from a software or program controlled electronic image, which can be changed from product to product. Such “soft” image printing is sometimes referred to as direct digital printing, although the “soft” image need not necessarily be “digital” in the sense of a set of stored discrete numerical values. Ink jet printers are a common type of such “soft” image or digital printers in use today.
Ink jet printers print by projecting drops of ink on demand onto a substrate from one or more nozzles on one or more print heads. Office printers and other narrow width ink jet printers usually dispense water based or other solvent based inks onto the substrate by heating the ink and exploding bubbles of the ink out of the nozzles. These printers are commonly called bubble jet printers. The ink dries by evaporation of the solvent. Sometimes additional heat is used to evaporate the solvent and dry the ink. Printing onto wide width substrates with bubble type ink jet printers, or ink jet printers that use high temperature techniques to propel the ink, severely limits the life of the print head. The heat used to expel the ink and the evaporation of the solvents, particularly during downtime, and the thermal cycling of the heads, causes these print heads to clog or otherwise fail after as little as 20 milliliters of ink is dispensed. Office printers are, for example, often designed so that the print head is replaced every time a reservoir of ink is replenished. For this reason, for larger scale ink jet printing processes, such as wide width printing of films used for outdoor advertising, signage and architectural applications, print heads that use mechanical ink propulsion techniques are more common. Such mechanical print heads include piezo or piezo-crystal print heads, which convert electrical energy into intra-crystal vibrations that cause drops of ink to be ejected from print head nozzles.
Piezo print heads are particularly useful for applying inks that dry by polymerization which can be brought about after the ink leaves the print head and is deposited onto the substrate, usually by exposure to some form of energy medium such as electromagnetic or particle radiation. Inks have been formulated for ink jet printing that can be polymerized by exposure to a radiation curing source such as a focused beam of ultra violet light (UV) or high energy beams of electrons (EB). The inks generally incorporate stabilizers which prevent premature curing due to low levels of light exposure. Therefore, the inks usually require exposure to some threshold level of energy that is necessary to initiate a polymerization reaction. Unless exposed to such threshold energy levels, such inks do not polymerize and remain stable, with a low tendency to dry in the nozzles or elsewhere unless cured by adequate exposure to the energy medium.
Solvent based inks are primarily cured by evaporation of the solvents. Some solvent based inks cure only by air drying, while others require the application of heat to enhance the evaporation of the solvent. In some cases, heat will facilitate a chemical change or polymerization of the ink along with an evaporation of a solvent. Polymerizable inks include monomers and oligomers that polymerize, and other additives. UV curable inks polymerize when exposed to UV light at or above the threshold energy level. These UV curable ink formulations include photoinitiators which absorb light and thereby produce free radicals or cations which induce crosslinking between the unsaturation sites of the monomers, oligomers and polymers, as well as other additive components. Electron beam-cured inks do not require photoinhibitors because the electrons are able to directly initiate crosslinking.
Heat or air curable inks that are organic solvent based or water based inks often do not have as high a color intensity as UV curable or other polymerizable inks because the pigments or dyes that produce the color are somewhat diluted by the solvent. Furthermore, organic solvents can produce an occupational hazard, requiring costly measures be taken to minimize contact of the evaporating solvents by workers and to minimize other risks such as the risks of fire. Solvent based inks, whether applied with heat or not, tend to dry out and eventually clog ink jet nozzles. In addition, solvent based inks set by forming a chemical bond with the substrate, and
Badovinac Milan
Codos Richard N.
Collan William W.
Comerford Robert B.
Quattrociocchi Angelo
Barlow John
Do An H.
L&P Property Management Company
Wood Herron & Evans L.L.P.
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