Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-09-13
2001-10-16
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S211100, C428S478200, C428S478800, C428S479600, C428S500000, C347S105000
Reexamination Certificate
active
06303212
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an ink jet image-recording element which yields printed images with excellent image stability over a wide range of humidity conditions.
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-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.
While a wide variety of different types of image-recording elements for use with ink jet devices have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness. The requirements for an image recording medium or element for ink jet recording are very demanding.
It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, an ink jet recording element must:
Be readily wetted so there is no puddling, i.e., coalescence of adjacent ink dots, which leads to nonuniform density
Exhibit no image bleeding
Provide maximum printed optical densities
Exhibit the ability to absorb high concentrations of ink and dry quickly to avoid elements blocking together when stacked against subsequent prints or other surfaces
Provide a high level of gloss and avoid differential gloss
Exhibit no discontinuities or defects due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like
Not allow unabsorbed dyes to aggregate at the free surface causing dye crystallization, which results in bloom or bronzing effects in the imaged areas
Have an optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light
Provide image stability under high-humidity conditions
Image stability is an important concern for inkjet prints. In particular, dyes used in the printing process may continue to migrate over time during storage of a printed image. The migration process typically occurs more quickly under conditions of high relative humidity since inkjet dyes are water soluble and materials used to manufacture inkjet media are often easily plasticized by water. Within a given dye set, the individual dyes may migrate or bleed at different rates due to differences in solubility or molecular dimensions. As a result, areas which are originally printed as neutral densities may acquire a colored tint over time. Such a phenomenon is especially objectionable in a medical application such as a radiographic image, since a neutral gray scale is expected and a colored tint is typically unacceptable in any area of the print.
U.S. Pat. No. 4,547,405 relates to an ink jet receiver comprising an ink jet recording layer which contains a polymeric latex of a block copolymer of polyvinyl alcohol and polyvinyl (benzyl ammonium chloride). However, there is a problem with this material in that, under high humidity conditions, the image stability is not as good as one would like.
Other prior art references such as U.S. Pat. No. 5,916,673 discloses that trivalent salts or ions of Group IIIb metals may be added to ink jet recording sheets for the purpose of improving waterfastness of images without compromising lightfastness. However, it has been found that such salts or ions of metals in reality actually contribute to poorer color stability under high humidity conditions.
It is an object of this invention to provide an ink jet receiver in which the color does not shift under high humidity conditions.
SUMMARY OF THE INVENTION
These and other objects are achieved in accordance with the invention which comprises an ink jet recording element comprising a support having thereon an image-recording layer comprising a binder and a polymeric mordant, the image-recording layer providing a total concentration of charged polymeric binding sites greater than about 3×10
26
/m
3
, and the image-receiving layer having a concentration of salts providing charges, opposite to the charge of the binding sites, of less than about 5.8×10
26
charges/m
3
, the salt having a molecular weight of less than 10,000 grams/mole.
By use of the invention, an image can be produced which has improved image stability under high humidity conditions.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, it has been found that a specific combination of minimum mordant content and maximum ionic content must be simultaneously satisfied in order to eliminate objectionable color shift under high humidity conditions. This invention is useful in inkjet receivers which are comprised primarily of swellable polymers or those which are comprised primarily of inorganic particles.
In a preferred embodiment of the invention, the concentration of salts providing charges, opposite to the charge of said binding sites, is less than about 1.0×10
26
charges/m
3
. In another preferred embodiment of the invention, the concentration of salts providing charges, opposite to the charge of said binding sites, is less than about 5.0×10
24
charges/m
3
.
Any polymeric mordant can be used in the image-recording layer of the invention provided it has the binding site concentration noted above. For example, there may be used a cationic polymer, e.g., a polymeric quartenary ammonium compound, or a basic polymer, such as poly(dimethylaminoethyl)-methacrylate, polyalkylenepolyamines, and products of the condensation thereof with dicyanodiamide, amine-epichlorohydrin polycondensates; lecithin and phospholipid compounds. Examples of mordants useful in the invention include: vinylbenzyl trimethyl ammonium chloride/ethylene glycol dimethacrylate; vinylbenzyl trimethyl ammonium chloride/divinyl benzene; poly(diallyl dimethyl ammonium chloride); poly(2-N,N,N-trimethylammonium)ethyl methacrylate methosulfate; poly(3-N,N,N-trimethylammonium)propyl methacrylate chloride; a copolymer of vinylpyrrolidinone and vinyl(N-methylimidazolium chloride; and hydroxyethylcellulose derivitized with (3-N,N,N-trimethylammonium) propyl chloride. In a preferred embodiment, the mordant is a polymeric quaternary ammonium compound.
During the synthesis of the polymeric mordant, impurities may be introduced in the form of salts. Examples of the source of these salts include the starting reagents, by-products of pH adjustment and undesired side reactions. It has been found that when the amount of these salts is reduced to a certain level, then improved image stability under high humidity conditions can be obtained.
In a preferred embodiment of the invention, the binder is a hydrophilic material. Such hydrophilic materials include naturally-occurring hydrophilic colloids and gums such as gelatin, albumin, guar, xantham, acacia, chitosan, starches and their derivatives, functionalized proteins, functionalized gums and starches, and cellulose ethers and their derivatives, polyvinyloxazoline and polyvinylmethyloxazoline, polyoxides, polyethers, poly(ethylene imine), poly(acrylic acid), poly(methacrylic acid), n-vinyl amides including polyacrylamide and polyvinylpyrrolidone, and poly(vinyl alcohol), its derivatives and copolymers. In a preferred embodiment, the hydrophilic binder is gelatin.
The hydrophilic material which may be employed in the image-recording layer may be present in any amount which is effective for the intended purpose. In general, it may be pr
Ghyzel Peter J.
Shaw-Klein Lori
Cole Harold E.
Eastman Kodak Company
Hess Bruce H.
Shewareged B.
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