Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
2001-06-29
2002-06-04
Beck, Shrive P. (Department: 1762)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C427S411000, C427S414000, C428S511000, C521S050000
Reexamination Certificate
active
06399156
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for forming an ink jet recording element, more particularly to a process for forming an ink jet recording element with a uniform protective overcoat.
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, 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-forming layer. Again typically, the ink-receiving layer is either a porous layer that imbibes the ink via capillary action or a polymer layer that swells to absorb the ink.
Ink jet prints, prepared by printing onto ink jet recording elements, are subject to environmental degradation. They are especially vulnerable to water smearing and light fade. For example, since ink jet dyes are water-soluble, they can migrate from their location in the image layer when water comes in contact with the receiver after imaging. Highly swellable hydrophilic layers can take an undesirably long time to dry slowing printing speed, and will dissolve when left in contact with water, destroying printed images. Porous layers speed the absorption of the ink vehicle, but often suffer from insufficient gloss and severe light fade.
In order to reduce the vulnerability of ink jet prints to water damage without resorting to a costly and time-consuming lamination step, receivers with a fusible porous particle topcoat and processes to produce them have been developed. In order to obtain uniform coatings, the coated fluid should have sufficient viscosity or mechanical integrity so that impingement of air during the drying process does not disturb the uniformity of the coated layer. This has generally been accomplished by using hydrophilic polymers that either boost viscosity such as polyvinyl alcohol, or polymers that can be gelled by chilling such as gelatin. There is a problem with this technique, however, in that upon fusing the layer, the hydrophilic binder impairs water resistance.
EP 0 858 905 A1 discloses a process for preparing an ink jet recording element by forming a porous outermost layer by heat treatment of a particulate thermoplastic resin. However, there is a problem with this process in that the coated layer does not set when coated, so that the layer may not always be uniform.
U.S. Pat. No. 5,925,712 discloses a coating composition of a powdered thermoplastic polymer, a water-soluble cationic polymer and a nonionic or cationic latex binder. However, there is a problem with this element in that water-soluble polymers degrade the water resistance of the layer containing them.
It is an object of this invention to provide a process for preparing an ink jet recording element that has an uppermost porous, ink-transporting layer that can be coated from an aqueous solution. It is a further object to provide a process wherein a coated particle dispersion will gel uniformly upon coating prior to the drying stage. Another object is to provide a process for forming a uniform coated layer of particles without the need for a gelling or thickening hydrophilic polymer binder. Still another object is to provide a process for producing a coated porous pass-through layer of thermoplastic particles that will provide a uniformly thick protective layer upon fusing.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with the invention comprising a method for making a porous ink jet recording element having a uniform, protective layer comprising coating on a support the following layers in order:
a) a porous, image-receiving layer containing a diffusible coagulant, and
b) a layer containing a dispersion of particles which are capable of forming a particle gel with a coagulant;
c) the diffusible coagulant thereby diffusing into the layer containing the dispersion of particles, causing the layer to set to a particle gel; and
d) drying the element to obtain a uniform, protective layer on top of the porous, image-receiving layer.
By use of the invention, a porous, ink jet recording element is obtained that has a uniformly thick protective layer upon fusing.
DETAILED DESCRIPTION OF THE INVENTION
Particles which are capable of forming a particle gel with a coagulant which may be used in the invention include those which have ionic functionalities on their surfaces, such as ionomer particles, particles which have adsorbed anionic or cationic surfactants, polyelectrolytes, etc. In a preferred embodiment of the invention, the particles are anionomer particles. In yet another preferred embodiment, the anionomer particles are urethane anionomer particles.
Urethane anionomer particles which may be used in the process of the invention can be water-dispersible, segmented polyurethanes having the following formula:
wherein:
R
1
is represented by one or more of the following structures:
A is derived from a polyol, such as a) a dihydroxy polyester obtained by esterification of a dicarboxylic acid, such as succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic, isophthalic, terephthalic, tetrahydrophthalic acid, and the like, and a diol, such as ethylene glycol, propylene-1,2-glycol, propylene-1,3-glycol, diethylene glycol, butane-1,4-diol, hexane-1,6-diol, octane-1,8-diol, neopentyl glycol, 2-methyl propane-1,3-diol, or the various isomeric bis-hydroxymethylcyclohexanes; b) a dihydroxy polylactone, such as polymers of &egr;-caprolactone and one of the above mentioned diols; c) a dihydroxy polycarbonate obtained, for example, by reacting one of the above-mentioned diols with diaryl carbonates or phosgene; or d) a dihydroxy polyether, such as a polymer or copolymer of styrene oxide, propylene oxide, tetrahydrofuran, butylene oxide or epichlorohydrin;
R
2
represents a substituted or unsubstituted alkyl group of from about 1 to about 12 carbon atoms or a substituted or unsubstituted aryl group of from about 6 to about 24 carbon atoms;
R
3
represents an alkyl group of from about 1 to about 12 carbon atoms substituted with phosphonate, carboxylate or sulfonate groups, such as dimethylol propionic acid;
w is an integer of from about 10 to about 60 weight %;
x is an integer of from about 20 to about 40 weight %;
y is an integer of from about 50 to about 80 weight %; and
z is an integer of from about 0 to about 10 weight %.
In a preferred embodiment of the invention, the polyurethane has a number average molecular weight of from about 5,000 to about 100,000, more preferably from 10,000 to 50,000. The water-dispersible polyurethane employed in the invention may be prepared as described in “Polyurethane Handbook”, Hanser Publishers, Munich Vienna, 1985.
As used herein, a porous, image-receiving layer is one which is usually composed of inorganic or organic particles bonded together by a binder. The amount of particles in this type of coating is often far above the critical particle volume concentration, which results in high porosity in the coating. During the ink jet printing process, ink droplets are rapidly absorbed into the coating through capillary action and the image is dry-to-touch right after it comes out of the printer. Therefore, porous coatings allow a fast “drying” of the ink and produce a smear-resistant image.
In a preferred embodiment of the invention, the porous image-receiving layer comprises from about 20% to about 100% of particles and from about 0% to about 80% of a polymeric binder, preferably from about 80% to about 95% of particles and from about 20% to about 5% of a polymeric binder, such as poly(vinyl alcohol), poly(vinyl pyrrolidinone), poly(vinyl acetate) or copolymers thereof or gelatin. The porous, image-receiving layer can also contain polymer micr
Wexler Allan
Yacobucci Paul D.
Beck Shrive P.
Cole Harold E.
Eastman Kodak Company
Fletcher, III William Phillip
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