Stock material or miscellaneous articles – Ink jet stock for printing – Plural ink receptive layers
Reexamination Certificate
2000-05-22
2003-11-18
Schwartz, Pamela R. (Department: 1774)
Stock material or miscellaneous articles
Ink jet stock for printing
Plural ink receptive layers
C428S032260, C428S032270, C428S032290, C428S032300, C428S032380
Reexamination Certificate
active
06649233
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to inkjet ink imaging, particularly inkjet ink image recording elements.
BACKGROUND OF THE INVENTION
In a typical inkjet 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 or a polyhydric alcohol or a mixed solvent of water and other water miscible solvents such as a monohydric alcohol or a polyhydric alcohol.
The recording elements typically comprise a support or a support material having on at least one surface thereof one or more ink-receiving or image-forming layers. The elements include those intended for reflection viewing, which usually have an opaque support, and those intended for viewing by transmitted light, which usually have a transparent support.
While a wide variety of different types of image-recording elements for use with inkjet ink 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 inkjet recording are very demanding.
It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, the 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.
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 be sufficiently insoluble in typical ink solvents to avoid development of 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 optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light.
Inkjet ink image recording elements often have an overcoat or top layer coated on top of another ink-absorbing layer, particularly if the underlying layer contains gelatin or polymer. The overcoat layer can have various functions, such as to provide physical protection, reduce tackiness, provide a glossy appearance, offer an ink-receptive surface, carry specific components or allow easier manufacture. Overcoat layers are usually relatively thin in comparison to the thick underlying layer typically used for ink-jet receivers, often in the order of one micron in thickness and can comprise a variety of materials, including cellulose derivatives.
Methylcellulose and its derivatives possess characteristic thermal gelling, surfactant, non-ionic, thickening, film-forming, and adhesive properties coupled with extremely low toxicity. In addition, it is possible to adapt these materials to specific end uses by controlling the type and ratio of their modifying substituents as described in “Industrial Gums. Polysaccharides and their derivatives”, Whistler, R. L., Academic press, Inc, 2nd edition, 1973. Thus, they have found application in a wide range of products including use in inkjet ink recording media.
U.S. Pat. No. 5,789,070 describes an image recording element for inkjet ink images comprising, in the following order, a support, a base layer and a top layer, wherein:
the base layer comprises a hydrophilic material e.g. gelatin;
the top layer is ink receptive and comprises a cationically modified cellulose ether having the structure:
wherein
R represents C
n
H
2n+1
;
X represent halide; and
n is 1 to 30.
The present invention is concerned with improving the drying time of an image recording element for inkjet ink images.
It has been found that if the polymer e.g. gelatin laydown of an underlying ink-absorbing layer is increased, the time taken to dry a printed image (measured as the density of an image transferred to a piece of plain paper sandwiched to the printed image immediately after it exits the inkjet printer) can be reduced. However, to achieve a significant improvement in this measure, the polymer laydown in the ink-absorbing layer has to be almost doubled (e.g. 13.9 g/m
2
compared to 7.6 g/m
2
). This also results in an undesirable variability in gloss levels produced by different printed colours (signified by an increase in differential gloss, that is, the standard deviation of the gloss measurements taken from eight different colours).
The invention solves the problems associated with increasing the polymer content of an underlying ink-absorbing layer and avoids a large increase in the polymer content of the recording element.
SUMMARY OF THE INVENTION
The invention provides an image recording element for inkjet ink images comprising, in the following order,
a support;
an absorbent base layer; and,
a top layer which is ink receptive and comprises one or more hydrophilic polymers, gelatin, a crosslinking agent for gelatin and a humectant.
The addition of gelatin, a crosslinking agent for gelatin and a humectant to a conventional overcoat layer consisting of hydrophilic polymers results in a significant improvement in both dry time and differential gloss.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the recording element can be opaque, translucent, or transparent. Thus, the supports utilized in the recording element of the present invention are not particularly limited and various supports may be employed. Accordingly, plain papers, coated papers e.g. resin-coated papers, various plastics including a polyester-type resin such as poly(ethylene terephthalate), poly(ethylene naphthalate) and polyester diacetate, a polycarbonate-type resin, a fluorine-type resin such as ETFE, metal foil, and various glass materials can be employed as supports. When the supports are transparent, a transparent recording element can be obtained and used as a transparency in an overhead projector.
The supports employed in the present invention must be self-supporting. By “self-supporting” is meant a support material such as a sheet of film that is capable of independent existence in the absence of a supporting support.
The thickness of the support can be from 12 to 500 &mgr;m, preferably from 75 to 300 &mgr;m.
If desired, in order to improve the adhesion of the base layer to the support, the surface of the support may be corona-discharge-treated prior to applying the solvent-absorbing layer to the support or, alternatively, an undercoating, such as a layer formed from a halogenated phenol or a partially hydrolyzed vinyl chloride-vinyl acetate copolymer can be applied to the surface of the support.
The base layer is primarily intended as a sponge layer for the absorption of ink solvent. As such, it is primarily composed of hydrophilic or porous materials. It may have a thickness of 3 to 60 &mgr;m.
Hydrophilic materials include gelatin, acetylated gelatin, phthalated gelatin, oxidized gelatin, chitosan, poly(alkylene oxide), poly(vinyl alcohol), modified poly(vinyl alcohol), sulfonated polyester, partially hydrolyzed poly(vinylacetate/vinyl alcohol), poly(acrylic acid), poly(1-vinylpyrrolidone), poly(sodium styrene sulfonate), poly(2-acrylamido-2-methane sulfonic acid), and polyacrylamide and mixtures of these materials. Copolymers of these polymers with hydrophobic monomers may also be used.
The hydrophilic material may be coated to provide a laydown of 3 to 60 g/m
2
, preferably 5 to 12 g/m
2
.
Other materials useful in the base layer include cellulose derivatives, gum derivatives, chitin starch, or other materials which are obvious to those skilled in the a
Cole Harold E.
Eastman Kodak Company
Schwartz Pamela R.
LandOfFree
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