Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-12-02
2002-05-21
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C347S105000, C347S106000, C428S323000, C428S328000, C428S329000, C428S330000, C428S331000
Reexamination Certificate
active
06391427
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a substantially transparent, porous ink jet image-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-recording 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. Medical images, such as radiographic images, are typically viewed on a blue transparent support.
An important characteristic of ink jet receivers is their need to dry quickly after printing. To this end, porous receivers 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 receiver 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.
When a porous receiver of the type described is coated and dried on a transparent support, optical scatter within the coating produces a white appearance. In medical imaging applications, blue transparencies are desired for radiographic imaging. However, when a porous fumed oxide coating is deposited on a transparent, blue-tinted support, it appears white when viewed in reflection, which is undesirable.
EP 813,978 relates to an ink jet recording element comprising an ink absorption layer containing solid fine particles, a binder and oil drops. However, there is a problem using this ink absorption layer on a transparent support in that an objectionable white appearance results due to scattering of visible light, as described above.
It is an object of this invention to provide a substantially transparent ink jet receiver in which the white appearance due to scattering of visible light is reduced. It is another object of this invention to provide a substantially transparent ink jet receiver which has a fast dry time.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with the invention which comprises an ink jet recording element, prior to image recording, comprising a substantially transparent support having thereon an image-recording layer comprising a polymeric binder, a colorant, and porous, colorless aggregates of particles having a primary particle size of from about 7 to about 40 nm in diameter and being aggregated up to about 300 nm.
Another embodiment of the invention relates to an ink jet printing process comprising:
a) providing an ink jet recording element as described above, and
b) applying liquid ink droplets thereon in an image-wise manner.
By use of the invention, a fast-drying image can be produced which has a reduced white appearance due to scattering of visible light.
DETAILED DESCRIPTION OF THE INVENTION
Particles useful in the invention include alumina, boehmite, clay, calcium carbonate, titanium dioxide, calcined clay, aluminosilicates, silica, barium sulfate, or polymeric beads. In a preferred embodiment of the invention, the particles are metallic oxides, such as alumina. While many types of inorganic and organic particles are manufactured by various methods and commercially available for an ink receiving layer, porosity is necessary 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 most preferred particle type providing the above requirements are aggregates of small particles. The aggregates are typically 150-300 nm in dimension and are comprised of smaller primary particles about 7-40 nm in diameter. The pores in a dried coating of such aggregates fall within the range necessary to ensure low optical scatter yet sufficient ink vehicle uptake.
Silica and alumina fumed oxides are well known, and alumina fumed oxides are preferred. Fumed oxides are available in dry form or as dispersions of the aggregates mentioned above.
In a preferred embodiment of the invention, the polymeric binder is a hydrophilic polymer. Examples of such hydrophilic materials include, but are not limited to, polyvinyl alcohols and their derivatives, polyvinyl pyrrolidone, sulfonated or phosphated polyesters, cellulose ethers and their derivatives, poly(2-ethyl-2-oxazoline), gelatin, casein, zein, albumin, chitin, chitosan, dextran, pectin, collagen derivatives, collodian, agar-agar, arrowroot, guar, carrageenan, tragacanth, xanthan, rhamsan, sulfonated polystyrenes, acrylamides and their derivatives, poly(alkylene oxides) and the like. In a preferred embodiment of the invention the hydrophilic polymer is poly(vinyl alcohol), hydroxypropyl cellulose, hydroxypropyl methyl cellulose or a poly(alkylene oxide).
The binder material 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 receiver, 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 volume ratio of binder to particles is from about 1:4 to about 1:2.
Since the image-recording 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.
Suitable support materials useful in the invention include polymeric film materials such as tinted or untinted poly(ethylene terephthalate), polyethylene naphthalate, poly-1,4-cyclohexane dimethylene terephthalate, polyvinyl chloride, polyimide, polycarbonate, polystyrene, cellulose acetate, or cellulose acetate propionate. In a preferred embodiment of the invention, the support is poly(ethylene terephthalate). Such film materials may be pretreated with an adhesion promoting layer, an antistatic layer, or a curl control layer as known in the art.
The support generally has a thickness of from about 50 to about 500 &mgr;m, preferably from about 75 to 300 &mgr;m. Antioxidants, antistatic agents, plasticizers, and other known additives may be incorporated into the support, if desired.
In order to improve the adhesion of the image-recording layer to the support, the surface of the support may be subjected to a corona-discharge treatment prior to applying the image-recording layer.
Furthermore, if the colorant in the image-recording layer is a dye chosen to match the color of the tinted transparency, a clear support may be used with the image-recording layer providing both the desired background color and ink receptive properties.
Colorants useful in the invention can be classified as either dyes or pigments. If a dye is used, the dye molecules are dispersed or solvated by the liquid or solid medium, so that each individual dye molecule is surrounded by molecules of the liquid or solid medium. Dyes are soluble in aqueous and organic solvents, thus particles are not observable under a microscope. If a pigment is used, discrete particles are dispersed in a liquid or solid medium. Each particle consists of many dye molecules held together by strong intermolecular forces. Pigment-based col
Derry Scott E.
Dillenbeck Eric L.
Gallo Elizabeth A.
Shaw-Klein Lori J.
Cole Harold E.
Eastman Kodak Company
Schwartz Pamela R.
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