Compositions: coating or plastic – Coating or plastic compositions – Marking
Reexamination Certificate
1999-04-30
2001-06-12
Klemanski, Helene (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Marking
C106S031890
Reexamination Certificate
active
06245137
ABSTRACT:
FIELD OF INVENTION
The present invention generally relates to inks, and more particularly, ink-jet ink compositions for improved image quality.
BACKGROUND OF THE INVENTION
The use of ink-jet printing systems has grown dramatically in recent years. This growth may be attributed to substantial improvements in print resolution and overall print quality, coupled with appreciable reduction in cost. Today's ink-jet printers offer acceptable print quality for many industrial, commercial, business, and residential applications at costs fully an order of magnitude lower than comparable products available just a few years ago. Notwithstanding their recent success, intensive research and development efforts continue toward improving the print quality of ink-jet images. Thus, challenge remains to further improve the performance of the ink-jet inks.
SUMMARY OF THE INVENTION
Generally, surfactants are molecules containing two distinct regions that can be classified as hydrophobic (oil-like, which do not favorably associate with water) and hydrophilic (water-like, that associate with water favorably). Surfactants may generally be described by Formula I, wherein R
1
is a hydrophobic group; L is a linking group which can be simply part of a molecule such as methylene, ether, ester or amide linkage; and R
2
is a hydrophilic group such as repeating units of ethylene glycol. It is known that use of surfactants in inks can improve attributes such as bleed control (or bleed alleviation). However, surfactants that improve chroma or color saturation are hereto unknown. The present invention relates to surfactants that help improve several of the image quality attributes, in particular chroma (i.e., color saturation), and ink-jet inks formulated with the same to produce inks exhibiting desirable properties such as improved chroma, bleed control, edge-acuity, and surface retention, thereby improving image quality.
Without subscribing to any particular theory, it is expected that surfactants that rapidly form large aggregate structures such as bilayers or vesicles on the surface of the media during the drying of ink film are useful in the practice of the invention. These structures (e.g., lamallae or vesicles) are not necessarily present in the inks but are formed at some point during drying of the solvents, thus resulting in the observed enhanced print attributes. The general description of surfactant behavior and expected critical packing parameter values is described below.
The colorants may be dye-based or pigment-based. As used herein, the term “pigment” refers to a colorant that is insoluble in the aqueous vehicle, and includes disperse dyes as well has pigments that are either dispersed with the aid of a dispersant or those that are self-dispersed.
The purity of all components is that employed in normal commercial practice for ink-jet ink compositions. Weight percents represent percent of the total ink composition, unless otherwise indicated.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to ink-jet inks formulated with surfactants capable of forming lamella phase, exhibiting improved image quality such as increased chroma, greater edgeacuity, enhanced bleed alleviation, and surface retention, across a range of media, when used in ink-jet inks for use in commercially available ink-jet printers such as DESKJET® printers, manufactured by Hewlett-Packard Company, of Delaware; and other commercially available home or office ink-jet printers.
Generally, surfactants are molecules containing two distinct regions that can be classified as hydrophobic (oil-like, that do not favorably associate with water) and hydrophilic (water-like, that associate with water favorably). It is known to those conversant in the art that use of surfactants in the inks can improve some attributes such as bleed alleviation. However, surfactants that improve chroma or color saturation are hereto unknown. The present invention relates to surfactants that help improve several of the image quality attributes, in particular chroma (i.e., color saturation), and ink-jet inks formulated with the same to produce inks exhibiting more than one of the desirable properties such as improved chroma, bleed control, edge-acuity, and surface retention, thereby improving image quality. More specifically, the invention relates to surfactants that form relatively large aggregated structures (micelles) of geometry other than spherical, hence fourth referred to as lamellae forming surfactants. Especially, surfactants that form lamellae or vesicle (bilayer) structures at some point during drying of the solvent are expected and noted to show these print attributes. Furthermore, it is not necessary for the present surfactants to exist in lamellae or vesicle form in the ink itself. The present surfactants have critical packing parameter (CPP—see Equation I) in a range from about ⅓ to 1.0; more preferably, from about 0.5 to about 1.0; and most preferably, from about 0.8 to about 1.0. Description of relation of surfactant behavior and critical packing parameter is available in literature such as “Surfactant Science technology by Drew Myres, 1088, VCH Publishers Inc. New Yrk, ISBN 0-89573-339-0. Although some surfactants that form vesicles show similar behavior, the invention does not necessarily require that vesicles be present in the inks.
The surfactants of the present invention are capable of forming large structures (e.g., lamellae phase) upon losing (e.g., drying-off) of the solvent on the print medium, the shape of which structure is determined by Equation I:
V
H
/l
c
a
0
=⅓ to 1, Equation I
Wherein
V
H
/l
c
a
0
is the critical packing parameter (CPP);
V
H
is the volume occupied by the hydrophobic groups in the micellar core,
L
c
is the length of the hydrophobic group (tail) in the core, and
a
0
is the cross-sectional area occupied by the hydrophilic group (head) at the micelle-solution interface.
The surfactants of the present invention have, bulky, hydrophobic groups, and small, close-packed hydrophilic groups and will tend to form lamellar or cylindrical micelles in aqueous media at some concentration in their phase diagram, which may not be the same as their concentration in ink.
Examples of surfactants capable of forming large structures (e.g., lamella phase) include, but are not limited to, surfactants wherein R
1
hydrophobic group (see Formula I) is a group or backbone with several groups of eight to fifty carbon units (C8-C50), e.g. steroidal such as cholesterol, stigmasterol, and derivatives thereof. Other surfactants expected to be within the scope of the present invention include those wherein R
1
is a set of two or more hydrophobic chains of 8 to 50 methylene or methine units in the same molecule and have polyhydroxy back bone such as glycerol, glucose, sorbitan, sucrose, mannose backbone, which may also serve as hydrophilic group. Other hydrophobic groups such as vitamin E combined with polar groups such as succinate show similar properties. More specific examples, include:
R
1
—L—R
2
Formula I
wherein
R
1
is Hydrophobic group of C8-C50; or sterol skeleton; or soy sterol; or fucosterol; or beta sitosterol; or campesterol; or stigmasterol; or cholesterol; or vitamin E; or sucrose disterate; or glyceryl C8-C50 esters, ethers amides; or sorbityl C8-C50 esters, esters, amides; or glucose C8-C50 esters, amides, ethers;
L is ether; ester; or amide; and
R
2
is carboxylate salt; sulfate; or phosphate.
More specifically, the surfactants of the present invention are selected from the group consisting of Generol, cholesterol, and vitamin E, and those wherein the polar group is a carboxylate, succinate, or PEG 3-1000 derivative.
Specific examples of surfactants according to the present invention include, but are not limited to:
Formula II
Formula III
Wherein Formula II is:
Wherein Formula III is:
Cholesterol (R
2
= H);
Cholic acid (R
2
= COOH).
Triolin (R
2
= triethylene glycol).
Formula IV
Formula V
Wherein Formula IV is:
Wherein Fo
Faison Veronica F.
Hewlett--Packard Company
Klemanski Helene
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