Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
1998-05-22
2002-08-20
Eickholt, Eugene (Department: 2854)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C101S491000
Reexamination Certificate
active
06435678
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods and formulations that improve the performance of aqueous inks which utilize pigments as colorants and which are useful for ink jet printing applications. Specifically, this invention relates to incorporating hardeners into ink receiving layers (IRL's), printing the above receivers with pigmented inks, and then treating the printed image with a solution which also contain hardeners.
BACKGROUND OF THE INVENTION
The formulations and methods employed in ink jet imaging involve the application of liquid ink droplets in a pixel-by-pixel manner to an ink-receiving element. There are numerous schemes that may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired image. In one process, known as continuous ink jet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while unimaged droplets are caught and returned to the ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant, which is molecularly dispersed or solvated by the carrier medium. The carrier medium can be a liquid or a solid at room temperature. A commonly used carrier medium is water or a mixture of water and organic cosolvents. Each individual dye molecule is surrounded by molecules of the carrier medium. In dye-based inks, no particles are observable under the microscope. Although there have been many recent advances in the art of dye-based ink jet inks, such inks still suffer from deficiencies such as low optical densities on plain paper and poor lightfastness. When water is used as the carrier medium, such inks also generally suffer from poor waterfastness.
Pigment-based inks have been gaining in popularity as a means of addressing these limitations. In pigment-based inks, the colorant exists as discrete particles. These pigment particles are usually treated with addenda known as dispersants or stabilizers, which serve to keep the pigment particles from agglomerating and/or settling out. Pigment-based inks suffer from a different set of deficiencies than dye-based inks. One deficiency is related to the observation that pigment-based inks interact differently with specially coated papers and films, such as the transparent films used for overhead projection and the glossy papers and opaque white films used for high quality graphics and pictorial output. In particular, it has been observed that pigment-based inks produce imaged areas that are entirely on the surface of coated papers and films. This results in images which have poor dry and wet adhesion properties, resulting in images which can be easily smudged.
Commonly owned U.S. patent application Ser. No. 08/847,858, filed Apr. 28, 1997, entitled “Pigmented Ink Jet Inks Containing Aldehydes” of Martin et al., and U.S. patent application Ser. No. 08/896,520 filed Apr. 28, 1997, entitled “Pigmented Ink Jet Inks Containing Olefins” of Martin et al., disclose ink jet ink formulations containing compounds with aldehyde, blocked aldehyde and active olefinic functional groups. However, these references do not teach the use of a solution that is separate and distinct from the ink, nor do they teach treating the ink receiver to improve waterfastness of the image.
SUMMARY OF THE INVENTION
The present invention discloses that improved waterfastness, and wet adhesion are observed when gelatin and/or cross-linkable polymeric coated papers or films containing one or more hardeners are printed with a pigmented ink jet ink and the printed image is then treated with a solution containing one or more hardeners. Hardening agents are defined as any additive which causes chemical cross-linking. It is advantageous to cross-link the coating prior to applying the hardener solution to the printed image to prevent the image from migrating or running when the hardener solution is applied over it. The hardener solution can be added in a variety of ways, for example, via a printhead, spray-bar, or by submersion in a hardener bath. Methods and apparatuses for applying the hardener solution are disclosed in U.S. patent application Ser. No. 09/083,673, filed May, 22, 1998, entitled “Printing Apparatus With Spray Bar For Improved Durability” of Wen et al., U.S. patent application Ser. No. 09/083,070, filed May 22, 1998, entitled “Printing Apparatus With Processing Tank” of Wen et al., and U.S. patent application Ser. No. 09/083,876, filed May 22, 1998, entitled “Ink Jet Printing Apparatus With Print Head For Improved Image Quality” of Wen et al.,
The present invention provides a method of improving the durability of an ink jet ink image comprising the steps of:
a) providing an ink jet ink receiving layer containing hardener;
b) image-wise depositing pigment-based ink jet ink on the hardener-containing ink receiving layer; and then
c) applying to the ink receiving layer a solution comprising a hardener that is the same or different from the hardener in the ink receiving layer.
Also provided is an ink jet ink receiver comprising:
a support;
on the support, an ink jet ink receiving layer containing a hardener;
on the ink receiving layer, an image formed by pigmented ink jet ink deposited thereon; and
a solution applied to the ink receiving layer, said solution comprising a hardener that is the same or different from the hardener in the ink receiving layer.
Thus, the present invention relates to inkjet receivers containing one or more hardeners, and treatment of the printed image with a hardener solution where the solution contains one or more hardeners. When hardener solutions of the present invention are applied after printing with pigmented inks onto glossy papers and films containing an imaging layer consisting of gelatin or cross-linkable polymers, the inkjet images exhibit excellent waterfastness, wet adhesion, and image quality properties throughout the image.
DETAILED DESCRIPTION OF THE INVENTION
The hardeners in the ink-receiving layer and in the hardener solution may include organic hardener compounds, inorganic hardener compounds or combinations of both. Concentrations of hardeners in the ink-receiving layer can range from 0.10 to 5.0 weight percent, preferably 0.10 to 3.0 weight percent. Concentrations of hardeners in the hardener solution can range from 0.10 to 5.0 weight percent, preferably 0.25 to 2.0 weight percent.
Preferred hardeners include formaldehyde and compounds that contain two or more aldehyde functional groups such as glyoxal, gluteraldehyde and the like. Other preferred hardeners include compounds that contain blocked aldehyde functional groups such as aldehydes of the type tetrahydro-4-hydroxy-5-methyl-2(1H)-pyrimidinone polymers (Sequa SUNREZ® 700), polymers of the type having a glyoxal polyol reaction product consisting of 1 anhydroglucose unit: 2 glyoxal units (SEQUAREZ® 755 obtained from Sequa Chemicals, Inc.), DME-Melamine non-fomaldehyde resins such as Sequa CPD3046-76 obtained from Sequa Chemicals Inc., 2,3-dihydroxy-1,4-dioxane (DHD), and the like. Blocked hardeners are substances, usually derived from the active hardener, that release the active compound under appropriate conditions (The Theory of the Photographic Process, 4
th
Edition, T. H. James, 1977, Macmillan Publishing CO., page 81). All are employed at concentrations ranging from 0.10 to 5.0 weight percent of active ingredients in the solution and/or in the ink-receiving layer.
Other preferred hardeners are compounds that contain active olefinic functional groups such as bis-(vinylsulfonyl)-methane (BVSM), bis-(vinylsulfonyl-methyl)ether (BVSME), 1,3,5-triacryloylhexahydro-s-triazine, and the like. In the context of the present invention, a
Erdtmann David
Romano Charles E.
Cole Harold E.
Eastman Kodak Company
Eickholt Eugene
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