Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2001-03-06
2003-05-20
Hess, Bruce H. (Department: 1774)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C428S195100
Reexamination Certificate
active
06565205
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink jet printing method using a porous ink jet recording element.
BACKGROUND OF THE INVENTION
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water and an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink jet recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-receiving layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
An important characteristic of ink jet recording elements is their need to dry quickly after printing. To this end, porous recording elements have been developed which provide nearly instantaneous drying as long as they have sufficient thickness and pore volume to effectively contain the liquid ink. For example, a porous recording element can be manufactured by cast coating, in which a particulate-containing coating is applied to a support and is dried in contact with a polished smooth surface.
EP 1,029,702 discloses an ink jet recording element comprising a support having thereon a gelatin subbing layer and a coating dispersion of silica and PVA. However, there is a problem with this element in that the gloss is lower than one would like.
It is an object of this invention to provide an ink jet printing method using a porous ink jet recording element that, when printed with dye-based inks, provides better hues and higher gloss. It is another object of this invention to provide an ink jet printing method using a porous ink jet recording element that has an acid-free surface, which is desirable for archival printing applications.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with the invention which comprises an ink jet printing method, comprising the steps of:
A) providing an ink jet printer that is responsive to digital data signals;
B) loading the printer with an ink jet recording element comprising a support having thereon a porous image-receiving layer comprising particles in a binder, the particles having a primary particle size of from about 7 to about 40 nm in diameter which may be aggregated up to about 300 nm, the image-receiving layer being coated from an acidic aqueous dispersion, and the recording element containing a subbing layer between the support and the porous image-receiving layer, the subbing layer comprising a basic material which is capable of raising the surface pH of the image-receiving layer at least about 2 pH units;
C) loading the printer with an ink jet ink composition; and
D) printing on the image-receiving layer using the ink jet ink composition in response to the digital data signals.
Better hues and a higher gloss are obtained by printing on a porous ink jet recording element with dye-based inks in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
The ink-receiving layer employed in the invention contains particles so that the layer is porous in order to obtain very fast ink drying. The pores formed between the particles must be sufficiently large and interconnected so that the printing ink passes quickly through the layer and away from the outer surface to give the impression of fast drying. At the same time, the particles must be arranged in such a way so that the pores formed between them are sufficiently small that they do not scatter visible light.
The particles may be in the form of primary particles or in the form of secondary aggregated particles. The aggregates are comprised of smaller primary particles about 7 to about 40 nm in diameter, and being aggregated up to about 300 nm in diameter. The pores in a dried coating of such aggregates fall within the range necessary to ensure low optical scatter yet have sufficient ink solvent uptake. The particles useful in the invention may be inorganic or organic and may be manufactured by various methods and are commercially available for an image-receiving layer.
Examples of particles useful in the invention include alumina, boehmite, clay, calcium carbonate, titanium dioxide, calcined clay, alumino-silicates, silica, barium sulfate, or polymeric beads. The particles may be porous or nonporous. In a preferred embodiment of the invention, the particles are metallic oxides such as alumina, boehmite or cationically-modified silica. Such particles are preferred because they possess cationic surfaces, which are capable of binding anionic ink jet printing dyes, rendering printed images resistant to dye migration due to water and high humidity conditions. Such particles are considered to possess a cationic charge in aqueous dispersions if the pH of the dispersion is maintained below the particle point of zero charge. The point of zero charge of such particles is above pH 7, so that stable dispersions of such particles are maintained under acidic conditions. For example, stable aqueous dispersions of fumed alumina generally possess a pH of around 4 or lower.
In a preferred embodiment of the invention, the image-receiving layer is coated from an acidic aqueous dispersion having a pH below about 5, more preferably at a pH below about 4.
Any basic material may be used in the subbing layer employed in the invention as long as it is compatible with the subbing layer polymer. In a preferred embodiment, the basic material comprises sodium hydroxide or triethanolamine. In another preferred embodiment, the basic material is capable of raising the surface pH of the image-receiving layer at least above about 4.
In yet another preferred embodiment of the invention, the subbing layer comprises a mixture of a basic material and a polymer. Any polymer may be used in this layer, as long as it is compatible with the basic material. For example, gelatin, poly(vinyl alcohol) or an acrylic latex polymer may be used.
While any amount of basic material may be used in the subbing layer, in general, the subbing layer comprises from about 10-30% by weight of the basic material.
In a preferred embodiment of the invention, the binder in the image-receiving layer is a hydrophilic polymer such as poly(vinyl alcohol), poly(vinyl pyrrolidone), gelatin, cellulose ethers, poly(oxazolines), poly(vinylacetamides), partially hydrolyzed poly(vinyl acetate/vinyl alcohol), poly(acrylic acid), poly(acrylamide), poly(alkylene oxide), sulfonated or phosphated polyesters and polystyrenes, casein, zein, albumin, chitin, chitosan, dextran, pectin, collagen derivatives, collodian, agar-agar, arrowroot, guar, carrageenan, tragacanth, xanthan, rhamsan and the like. In still another preferred embodiment of the invention, the hydrophilic polymer is poly(vinyl alcohol), hydroxypropyl cellulose, hydroxypropyl methyl cellulose, gelatin, or a poly(alkylene oxide). In yet still another preferred embodiment, the hydrophilic binder is poly(vinyl alcohol). The binder should be chosen so that it is compatible with the aforementioned particles.
The amount of binder used should be sufficient to impart cohesive strength to the ink jet recording element, but should also be minimized so that the interconnected pore structure formed by the aggregates is not filled in by the binder. In a preferred embodiment of the invention, the weight ratio of the binder to the total amount of particles is from about 1:20 to about 1:5.
Since the image-receiving layer is a porous layer comprising particles, the void volume must be sufficient to absorb all of the printing ink. For example, if a porous layer has 60 volume % open pores, in order to instantly absorb 32 cc/M
2
of ink, it must have a physical thickness of at least about 54 &mgr;m.
The support for the ink jet recording element used in the invention can be any o
Bermel Alexandra D.
Martin Colin
Shaw-Klein Lori J.
Cole Harold E.
Eastman Kodak Company
Grendzynski Michael
Hess Bruce H.
Leipold Paul A.
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