MX2008004294A - Aryltricarboxyl-attached pigment-based inks with improved slewing decap - Google Patents

Abstract

Compositions, systems, and methods for ink-jet printing having improved slewing decap time can comprise a pigment having an aryltricarboxyl group covalently attached thereto;at least 12 wt%of an anti-slewing decap cosolvent selected from the group consisting of 2-pyrrolidone, derivatized 2-pyrrolidone, and mixtures thereof;and a liquid vehicle.

Description

INKS BASED ON PIGMENTOS UNIDOS A ARILTRICARBOXILO WITH DESTAPADURA SESGADA IMPROVED Field of the Invention The present invention relates generally to pigment-based inkjet imaging. More particularly, the present invention relates to inkjet ink compositions, based on pigments attached to aryltricarboxyl, and to methods for printing inkjet images with improved biased uncovering.

BACKGROUND OF THE INVENTION There are several reasons why inkjet printing has become a popular way of recording images on various media surfaces, particularly plain paper. Some of these reasons include low printer noise, high-speed recording capability, and multi-color recording. Additionally, these advantages can be obtained at a relatively low price to consumers. However, although there has been great improvement in inkjet printing, accompanying this improvement are increased demands by consumers in this area, for example, higher speeds, higher resolution, color image formation complete, increased stability, higher image quality, etc. As new inkjet inks are developed, there are several traditional features that are considered when evaluating ink for use in conjunction with a printing surface or other inks. These features include edge sharpness and optical density of the image on the surface, control of the color black shift, color black absorption, halo control, dry time of the ink on the substrate, adhesion to the substrate, lack of deviation in ink droplet placement, presence of all points, acceptable time of skewed uncovering, ink resistance after drying to water and other solvents, long-term storage stability, and long-term reliability without corrosion or bogilla jam . Although the above list of characteristics provides a respectable goal to achieve, there are difficulties associated with satisfying all of the above characteristics. Frequently, the inclusion of a proposed ink component to satisfy one of the above characteristics may prevent another characteristic from being fulfilled. In this way, most commercial inks for use in inkjet printers represent a compromise in an attempt to achieve at least an adequate response in satisfy all the requirements listed above. A problem associated with reduced line quality and reduced graphic accuracy of certain pigment-based inkjet inks is directly related to a problem known as capping or uncovering. The term "uncovering" is intended to be understood both here and in the appended claims as referring to the inability of an inkjet ink to remain fluid in air exposure which can lead to degradation of print quality. . To avoid the problems associated with uncovering, the inkjet or inkjet pens are periodically triggered at different times when printed on a desired substrate, resulting in wasted ink in inkjet. The time between the two shots is called the bias time. In this way, by increasing the bias time, less inkjet ink is wasted and the inkjet printer and architecture or inkjet print pen does not have to work as hard and therefore can be improved the performance A method for increasing the bias time which is known in the prior art is to increase the kinetic energy of the drop ejected from the pencil. However, the increase in kinetic energy also tends to increase the spray, drop weight and / or other features that degrade the quality of the image. Certain types of pigments that are otherwise very good with respect to print quality, for example, under runoff, low absorption, low halo, fast throughput, excellent line quality, etc., often have an unacceptably low bias time. . When the biased uncovering time is very short, heavy sizzle is regulated to maintain good print quality that will greatly reduce the printer's performance. In this way, it would be beneficial to provide ink formulations, for ink injection, based on pigments, which have a prolonged biased uncovering time.

Detailed Description of the Preferred Modes Before the particular embodiments of the present invention are described and narrated, it is to be understood that this invention is not limited to the particular process and materials described herein since these may vary to some degree. It is also to be understood that the terminology used herein is used for the purpose of describing only particular embodiments and is not intended to be limiting, since the scope of the present invention will be defined only by the appended claims and equivalents thereto. .

In describing and claiming the present invention, the following terminology will be used. The singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. In this way, for example, the reference to "a dye" includes reference to one or more of these materials. As used herein, "carrier" refers to ink vehicles or liquid carriers that include liquid compositions that can be used to deliver dyes to a substrate. Liquid carriers are well known in the art, and a wide variety of ink vehicles may be used in accordance with embodiments of the present invention. These ink vehicles may include a mixture of a variety of different agents, including without limitation, surfactants, solvents, co-solvents, buffers, biocides, viscosity modifiers, sequestering agents, stabilizing agents, and water. The vehicles may also carry other solids (other than dyes) as part of the vehicle, such as polymers, UV curable materials, plasticizers, latex particles, etc., in some embodiments. "Bias" refers to the period of time as long as an inkjet pen or pencil is in an active mode, for example, uncovered, and is between the shot of the ink drops. Typically, droplet trickling on the substrate to produce an image is performed while the inkjet architecture is uncovered. However, each boguilla does not always fire within the period of time where the filler begins to appear. In this way, non-image-forming droplets are fired to keep the bogies cool between the imaging activity. In this way, the longer the biased uncovering time of a given inkjet ink in a given inkjet pen or pencil, the less ink is wasted during the imaging process and the greater the performance of the ink. printer. "Biased anti-uncovering co-solvents" may include co-solvents that are added to an ink vehicle and performs the function of improving skew uncovering performance, for example, increased time between shots of drops. Typically, they are solvents with high and low vapor pressure and excellent water miscibility. As used herein, "colored", when referring to inkjet inks, refers to non-black ink compositions. For example, typical colored ink compositions include cyan, magenta, yellow and mixtures thereof.

As used in this"Pigment" refers to a coloring particle that is at least substantially insoluble in the ink vehicle in which it is used. As used herein, "functionalized" refers to pigment particles that have a compound chemically bound by covalent bonds. This is in contrast to pigment particles that have compounds bound by ionic bonds or other weaker intermolecular forces. The pigments bound to aryltricarboxyl according to the embodiment of the present invention are pigments which are functionalized with aryltricarboxylic groups, for example, aryltricarboxylic acid groups and / or aryltricarboxylate groups. When referring to an "aryltricarboxyl" group (including aryltricarboxylic acids and aryltricarboxylates), it is understood that the term "tri" refers to at least three carboxyl groups present in a common aryl group. Thus, tricarboxyl includes tetracarboxyl, pentatricarboxyl, etc., since each of these functional groups includes at least three carboxyl groups present in a common aryl group. It is further understood that the aryl group can be any individual aryl group such as benzene, naphthalene, biphenyl, etc. Any atom of intervention between two aryl groups will be considered multiple aryl groups. In other words, if multiple aryl groups are present, in order to qualify as an aryl-carboxylic group as defined herein, at least one of the multiple aryl groups will include at least three carboxyl groups. As used herein, "bleed" refers to the tendency of the ink to run into, and mix with, adjacently printed inks. Shifting typically occurs before adjacently printed inks dry completely on a substrate. The degree of shifting will depend on a variety of factors such as the drying speed of the ink, ink guímica, for example, the presence of reactive or non-reactive mechanisms of shift control, and type of substrate, among other variables . In accordance with embodiments of the present invention, the shifting can be reduced without the use of an ink reactive mechanism, although reactive ink mechanisms can also be used. The term "halo" or "halo effect" refers to a white or grayish band which may appear on the black surface and colored inks which occur as a result of the migration of the liguid or dye. "Absorption" refers to the migration of the ink of an image between the paper fibers, thereby creating a damaged edge. One edge or more damaged between two printed inks is indicative of increased absorption. As used herein, "carboxyl," or "carboxyl group," or the like, refers to a carboxylic acid group (COOH) or a carboxylate salt thereof (COOM). Appropriate counterions (M) for the salt may include alkali metals such as sodium, lithium or potassium; positively charged amines such as NH 4 +, (CH 3) 4 N +, (CH 3) 3 NH 4 +; or similar. The concentrations, quantities, and other numerical data may be presented herein in an interval format. It is to be understood that this interval format is used only for convenience and brevity and should be interpreted flexibly to include not only the numerical values explicitly cited as the range limits, but also to include all individual or sub-numerical values. intervals covered within that range as if each numerical value and sub-interval were cited explicitly. For example, a weight range of about 1% to about 20% should be construed to include not only the concentration limits explicitly cited from 1% to about 20%, but also includes individual concentrations such as 2%, 3%, 4 %, and sub-intervals such as 5% to 15%, 10% to 20%, etc.

In the ink jet circle, it is typically desired that all ink droplets printed on a substrate appear substantially similar to each other so that high quality images can be produced. Inherently working against this objective is the fact that the ink is not injected continuously from an inkjet argument during the image forming process, ie there is a period of bias where the print holes between each series are uncovered. of injection. When they are uncovered, the inks tend to crimp very quickly due in part to the sticking hole sizes of the injection argument. This phenomenon is known as biased uncovering. When the inkjet inks begin to crimp in a print hole, the print quality that can be achieved is decreased. It is known that the filling that occurs during bias can be substantially prevented by systematically firing the pencil in the form of a "sizzle" process when the pencil is not printing on the target substrate in order to keep the ink cool. print hole. This sizzling process wastes a certain amount of inkjet ink and time. In other words, in order to keep the hole in the inkjet pen cool and ready for printing when a If the pencil is in an active mode of printing, the pencil will waste some ink and time to avoid the hole filling. Accordingly, it is generally known that pigment-based inks can provide better optical density and better text printing quality compared to black inks based on dyes. In particular, certain inkjet inks, based on functionalized pigments, can produce excellent image quality, but the biased uncovering time of some of these types of inks is unacceptably low. Specifically, the pigments which are functionalized on the surface (by covalent bonding) with aryltricarboxylic groups, and more particularly, pigments functionalized with 3, 4, 5-benzenetricarboxylic acids or 3, 4, 5-benzenetricarboxylates provide excellent pigment quality. image, but typically contribute to lowering the biased uncovering time when formulated in an inkjet ink composition. In accordance with this problem, it has been recognized that by including a high load of 2-pyrrolidone, the unbent destapling time can be significantly increased without significantly reducing print quality. For a high load, it is proposed that it be at least 12% by weight. More specifically, a charge of 2-pyrrolidone of 12% by weight at about 25% by weight provides acceptable results. In a specific embodiment, the charge of 2-pyrrolidone may be about 16% by weight. According to these findings, an inkjet ink composition may comprise a pigment having an aryltricarboxylic group covalently bonded thereto; at least 12% by weight of a biased anti-uncovering co-solvent selected from the group consisting of 2-pyrrolidone, derivatized 2-pyrrolidone, and mixtures thereof; and a liquid vehicle. In another embodiment, a method for increasing the biasing time of a inkjet ink inkjet without significant uncovering may comprise providing an inkjet ink, charging the inkjet ink in an inkjet argument, configuring the inkjet architecture to allow for a bias of at least 3 seconds between shots without the requirement of architectural capping during bias. The inkjet ink may comprise a pigment having an aryltricarboxylic group covalently bonded thereto; at least 12% by weight of a biased anti-uncovering co-solvent selected from the group consisting of 2-pyrrolidone, derivatized 2-pyrrolidone, and mixtures thereof; and a liquid vehicle. In another embodiment, a printing system of High quality images with reduced biased uncovering may comprise an inkjet ink, and an inkjet architecture, configured to fire non-image-producing drops of the inkjet ink at intervals of at least 3 seconds when the argument is made. Inkjet is uncovered and is not actively forming images. The inkjet ink may comprise a pigment having an aryltricarboxylic group covalently bonded thereto; at least 12% by weight of a biased anti-uncovering co-solvent selected from the group consisting of 2-pyrrolidone, derivatized 2-pyrrolidone, and mixtures thereof; and a liquid vehicle. As mentioned, the pigments with aryltricarboxyl functional groups provide excellent text quality and excellent optical density on plain paper compared to many other similar pigments. It has excellent performance with respect to high performance and text quality. Although this pigment has been useful in more traditional printing processes, for example, different from inkjet imaging, it has not been used successfully in inkjet techniques due to poor uncoating. For example, the uncovering of this pigment using more traditional inkjet ink vehicles has been less of a second, which is unacceptable for a typical commercial inkjet printer. In other words, although this pigment can be used quite easily in other applications that do not have the same demands inherently present with the inkjet architecture, it is not a simple process of taking a known vehicle of ink used in another field. of inkjet printing, adding this pigment to the vehicle, and expecting it to be printable using the inkjet printing argument. This would not be the case due to the significant biased uncovering problems associated with this particular type of pigment. The use of high loads of 2-pyrrolidone has solved this inherent problem. The pigment that binds to the aryltricarboxyl group can be almost any commercially available pigment that provides acceptable printing characteristics. In one embodiment, the base pigment is a carbon black pigment. Carbon black pigments suitable for use in the present invention include, without limitation, carbon black, graphite, vitreous carbon, charcoal, and combinations thereof. In one aspect of the present invention, the carbon pigment is a carbon black pigment. These carbon black pigments can be manufactured by a variety of known methods such as a channel method, a contact method, an oven method, an acetylene method, or a thermal method, and are commercially available from vendors such as Cabot Corporation, Columbian Chemicals Company, Degussa AG, and E.I. DuPont de Nemours and Company. Suitable carbon black pigments include, without limitation, Cabot pigments such as MONARCH 1400, MONARCH 1300, MONARCH 1100, MONARCH 1000, MONARCH 900, MONARCH 880, MONARCH 800, MONARCH 700, BP-700, CAB-O-JET 200, and CAB-O-JET 300; Columbian pigments such as RAVEN 7000, RAVEN 5750, RAVEN 5250, RAVEN 5000, and RAVEN 3500; Degussa pigments such as black color FW 200, RAVEN FW2, RAVEN FW2V, RAVEN FW 1, RAVEN FW 18, RAVEN S160, RAVEN FW S170, Special Black 6, Special Black 5, Special Black 4A, Special Black 4, PRINTEX U, PRINTEX 140U, PRINTEX V, and PRINTEX 140V; and TIPURE R-101 available from Dupont. Typically, the carbon pigments of the present invention can be from about 10 nm to about 10 microns and in one aspect can be from 10 nm to about 500 nm in diameter, although sizes outside this range can be used if the pigment can remain scattered and provide adequate color properties. Typically, the base carbon is covalently linked by aryltricarboxyl groups to become dispersible in an aqueous vehicle. Although the use of carbon black pigments is an example of the modalities of the present invention, in other embodiments, the base pigment may be a color pigment. The base color pigments which may be used include, but are not limited to, cyan, magenta, yellow, and other secondary colors such as red, orange, green, blue and violet. These chemically linked aryltricarboxy dispersants impart not only improved dispersion properties to the ink composition, but also contribute to a high degree of color black and color to color shift control, reduced absorption, improved halo, and general sharpness of image border. Those skilled in the art will recognize that these aryltricarboxyl groups may be present in acid form or may also be present in their salt form, depending on the components in the inkjet ink composition. In a detailed aspect of the present invention, the dispersant can have the following guise structure (Formula I) where the "*" indicates a point of attachment to the carbon pigment, either directly or through a known separating group, as follows : * -Ar- (COOM) Formula I where Ar is aryl, n is at least 3, for example, 3-5, and M is H or a monovalent cation, for example, Na +, Li +, K +, or positively charged organic species such as NH 4 +, ( CH3) 4N +, or (CH3) 3NH4 +. Example structures that can be prepared and attached to a black pigment according to Formula I are shown as follows: It is noted that all of the above examples are aryltricarboxyl groups since they each include at least three carboxyl groups in a common aryl group as defined at the moment. It is also noted that the biphenyl groups shown above are considered to be an individual aryl group because there are no intervening atoms between the two benzene groups. Additionally, although all of the example formulations shown above are in the carboxylic acid state, it is recognized that the hydrogen of each carboxylic acid can be replaced by a monovalent cation to form a salt thereof, as described in Formula I. In an additional note, the functional groups defined in Formula I and by way of example above can be attached to carbon black pigment surfaces using amino or other reactive binding mechanisms. For example, a 1-amino-3, 4, 5-benzenetricarboxylic acid can be used to bind a 3,4,5-benzenetricarboxylic acid to the surface of a pigment, which results in an l-pigment-3, 4 acid. , 5-benzenetricarboxylic acid. In this example, the amino group can act as a leaving group which facilitates binding to the pigment. Noting this, these pigments can be functionalized in the carbon pigment by any of several known methods. For example, U.S. Patent Nos. 5,554,739 and 5,707,432, each of which is hereby incorporated by reference in its entirety to the degree consistent with the present invention, describe methods for functionalizing carbon materials. using diazonium salts. In a detailed aspect of the present invention, the functionalized pigment comprises from about 1% to about 20% by weight of the ink jet ink composition, and can frequently comprise from about 2% to about 6% by weight of the composition of inkjet ink. When an ink-jet ink is used to print against the ink-jet inks of the present invention, colored or black pigments or dyes can be used. The percentages by weight of the pigment in these secondary inks may be approximately the same as quoted with respect to the functionalized carbon pigments described above, or any other concentration generally known in the art. When colored dyes are used in the colored inkjet ink to be printed against the inkjet ink containing aryltricarboxyl, the dye may typically be present in the inkjet ink of 1% by weight to about 10. % in weigh. With respect to the liquid or ink carriers described herein, the components discussed are generally relevant to both pigment-based inkjet inks and dye-based inkjet inks. In this way, to the extent that both types of ink are analyzed in the present, the analysis of these vehicles is applicable to both types of ink. The inkjet ink compositions of the present invention are typically prepared in an aqueous formulation or ink vehicle which may include water, co-solvents, surfactants, buffering agents, biocides, sequestering agents, viscosity modifiers, humectants, binders. , and / or other known additives. In one aspect of the present invention, the ink vehicle may comprise from about 70% to about 98% by weight of the inkjet ink composition. Additionally, other than the vehicle's liguids, solids may also be dispersed in the vehicle, such as polymers, photocurable materials, plasticizers, latex particles, etc. As described, co-solvents may be included in the ink jet compositions of the present invention. Co-solvents suitable for use in the present invention include water-soluble organic co-solvents, but are not limited to, aliphatic alcohols, aromatic alcohols, diols, glycol ethers, poly (glycol) -ethers, lactams, formamides, acetamides, long chain alcohols, ethylene glycol, propylene glycol, diethylene glycols, triethylene glycols, glycerin, dipropylene glycols, glycol butyl ethers, polyethylene glycols, polypropylene glycols, amides, ethers, carboxylic acids, esters, organosulfides, organosulphoxides, sulfones, alcohol derivatives, carbitol, butyl carbitol, cellosolve, ether derivatives, amino alcohols and ketones. For example, co-solvents may include primary aliphatic alcohols of 30 carbons or less, primary aromatic alcohols of 30 carbons or less, secondary aliphatic alcohols of 30 carbons or. less, secondary aromatic alcohols of 30 carbons or less, 1,2-diols of 30 carbons or less, 1,3-diols of 30 carbons or less, 1,5-diols of 30 carbons or less, ethylene glycol alkyl ethers, propylene glycol-alkene-ethers, poly (ethylene glycol) -alkyl-ethers,. higher homologs of poly (ethylene glycol) -alkyl ethers, poly (propylene glycol) -alkyl ethers, higher homologues of poly (propylene glycol) -alkyl ethers, lactams, substituted formamides, unsubstituted formamides, substituted acetamides, and unsubstituted acetamides. Specific examples of co-solvents that are preferably employed in the practice of this invention include, but are not limited to, 1,5-pentanediol, 2-pyrrolidone, 2-ethyl-2-hydroxymethyl-1,3-propanediol. , diethylene glycol, 3-methoxybutanol, and 1,3-dimethyl-2-imidazolidinone. Co-solvents can be added to reduce the water evaporation rate of the ink to minimize the jamming or other properties of the ink such as viscosity, pH, surface tension, optical density, and print quality. The concentration of the co-solvent may vary from about 0 wt% to about 50 wt%, and in one embodiment is from about 15% to about 40 wt%. According to embodiments of the present invention, the liquefied carrier can include at least 12% by weight of the co-solvent 2-pyrrolidone. In another embodiment, the 2-pyrrolidone may be present from 12% by weight to 20% by weight. In yet another embodiment, the 2-pyrrolidone may be present from 14% by weight to 18% by weight. The high charge of 2-pyrrolidone may be present only as non-derivatized 2-pyrrolidone, (with other optional co-solvents), only as a derivatized 2-pyrrolidone, for example, l-methyl-2-pyrrolidone, 3-methyl- 2-pyrrolidone, 4-methyl-2-pyrrolidone, 5-methyl-2-pyrrolidone, l-ethyl-2-pyrrolidone, 3-ethyl-2-pyrrolidone, 4-ethyl-2-pyrrolidone, 5-ethyl-2- pyrrolidone, 5- (hydroxylmethyl) -2-pyrrolidone, 1- (2-hydroxyethyl) -2-pyrrolidone, etc., or as a mixture of 2-pyrrolidone and derivatized 2-pyrrolidone. Various damping agents may also be optionally used in the inkjet ink compositions of the present invention. Typical buffering agents include pH control solutions such as inorganic and organic buffering agents.

In another aspect of the present invention, various biocides may be used to inhibit the growth of undesirable microorganisms. Various non-limiting examples of suitable biocides include benzoate salts, sorbate salts, commercial products such as NUOSEPT (Nudex, Inc., a division of Huís America), 'UCARCIDE (Union Carbide), VANCIDE (RT Vanderbilt Co.), and PROXEL (ICI Americas) and other known biocides. Typically, these biocides comprise less than about 5% by weight of the inkjet ink composition and frequently from about 0.1% to about 0.25% by weight. In a further aspect of the present invention, binders that act to secure dyes in the substrate can be included. Binders suitable for use in the present invention typically have a molecular weight of about 100 to about 50,000 g / mol. Non-limiting examples include polyester, polyester-melanin, styrene-acrylic acid copolymers, styrene-acrylic acid-algayl acrylate copolymers, styrene-maleic acid copolymers, styrene-maleic acid-algae acrylate copolymers, styrene copolymers -methacrylic acid, styrene-methacrylic acid-alkyl acrylate copolymers, styrene-male-medium ester copolymers, vinyl naphthalene-acid copolymersacrylic, vinyl naphthalene-maleic acid copolymers, and salts thereof. In one aspect of the present invention, inkjet ink compositions may include surfactants. These surfactants may include water-soluble standard surfactants such as alkyl-polyethylene oxides, alkyl-phenyl-polyethylene oxides, polyethylene oxide block copolymers (PEO), acetylene PEO, PEO esters, PEO amines, PEO amides, and dimethicone copolyols. If used, the surfactants may be from 0.01% to about 10% by weight of the inkjet ink composition. Various combinations of nonionic, anionic and / or amphoteric surfactants may also be used. In another aspect of the present invention, pigmented colored inks containing pigments according to Formula I can be prepared as described above for black pigmented inks. Color inks include, but are not limited to, cyan, magenta, yellow, and other secondary colors such as red, orange, green, blue, and violet.

Examples The following examples illustrate the modalities of the invention that are currently better known. However, it is to be understood that the following is only exemplary and illustrative of the application of the principles of the present invention. Numerous modifications and alternative compositions, methods and systems may be contemplated by those skilled in the art without departing from the spirit and scope of the present invention. The appended claims are intended to cover these modifications and arrangements. Thus, while the present invention has been described above with particularity, the following examples provide additional detail in conjunction with what is currently judged to be the most practical and preferred embodiments of the present invention.

Example 1.- Preparation of Ink Vehicle Two inkjet ink vehicles were prepared according to Table 1, as follows: High boiling point co-solvents which are readily dissolvable in water, including co-solvents which are generally used in the art to improve the unclogging performance. Examples include glycerol, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, Dantocol DHE, ethylhydroxymethylpropanediol, 1,2-pentanediol, 1- (2-hydroxyethyl) -2-imidazolidinone, N-methylmorpholine-N-oxide, tetraethylene glycol, 2-methyl-l, 3-propanediol, mixtures thereof, etc. 2 Standard solvents frequently used in thermal inkjet ink techniques. Examples include lipoic ethoxylated glycol-1, etc.

Example 2.- Performance of Biased Unplugging. Biased unbinding performance tests were carried out using various formulations of ink containing pigment with structure of Formula I and type 1 ink vehicle and type 2 ink vehicle by allowing Multiple predetermined biases occur (eg 1 second, 2 seconds, 3 seconds, etc.) multiple times before printing the thin line with precise edges. Since the filing typically exhibits jamming or failed firing of injection holes, when the filing occurs, the quality of the line is significantly reduced. Each of the printed characters is compared to determine if acceptable print quality was achieved. Another noticeable failure in the accuracy of the line is considered to be a failure. The biased uncovering time is determined by evaluating the lines that have acceptable print quality comparable to the lines that have unacceptable print quality. For example, if a line has acceptable print quality after 5 seconds of bias, and unacceptable print quality after 6 seconds of printing, then the biased uncovering time is 5 seconds. By comparing the biased uncovering time between the various inks of the type 1 ink vehicle and the type 2 ink vehicle, it was found that the uncovering time for type 1 ink was generally less than one second, whereas time biased uncovering for type 2 ink was generally about 8 seconds or greater. This dramatic improvement in the biased uncovering time that was achieved by increasing the load of 2-pyrrolidone (2P) in inkjet ink from 10% by weight to 16% by weight was unexpected due to the relatively high vapor pressure of this co-solvent as compared to many of the uncoated co-solvents. In other words, typically 2-pyrrolidone is not considered to be a solvent that contributes significantly to skewed unclogging performance, even when increasing its level at a very high load (replacing the more traditional co-solvents of biased uncoating), dramatic improvement was achieved, that is, from < 1 second to 8 seconds. Additionally, the image quality or other performance marks that were incurred by including this high load of 2-pyrrolidone in the inkjet ink formulation seemed insignificant.

Example 3.- Performance of Biased Detachment for Pigments Joined to Arylmonocarboxyl, Arildicarboxyl and Polymer Biased uncovering performance tests were conducted as before using ink formulations containing pigments attached to arylmonocarboxyl, arylcarboxyl and polymer in vehicle type 1 ink and type 2 ink vehicle. biased uncovering of these inks was found to be at least 6 seconds. No uncovering difference was observed for inks with type 1 ink vehicle and type 2 ink vehicle.

It indicates that the regress of 2-pyrrolidone for the uncovering performance is not necessary for polymer-bound pigments and types of pigments where there are less than three carboxyl groups present in a common aryl group. It will be understood that the arrangements referred to above are illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements can be contemplated without departing from the spirit and scope of the present invention insofar as the present invention has been shown in the figures and described above in conjunction with the exemplary embodiments of the invention. It will be apparent to those skilled in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth in the claims.

Claims (10)

1. CLAIMS 1. Inkjet ink composition, characterized in that it comprises: (a) a pigment having an aryltricarboxylic group covalently bonded thereto; (b) at least 12% by weight of a biased anti-uncovering co-solvent selected from the group consisting of 2-pyrrolidone, derivatized 2-pyrrolidone, and mixtures thereof; and (c) a liquid vehicle.
2. 2. Inkjet ink according to claim 1, characterized in that the aryltricarboxyl group is an aryltricarboxylic acid, a benzenetricarboxylic group, a naphthalenetricarboxylic group, a biphenyltricarboxyl group, an aryltetracarboxyl group, an arylpentacarboxyl group, or an , 5-benzenetricarboxylic acid which has the pigment which binds in position 1 of 3, 4, 5-benzenetricarboxylic acid.
3. 3. Inkjet ink according to claim 1, characterized in that the aryltricarboxyl group is a salt having a sodium, lithium, potassium or a positively charged amine as its counter ion.
4. 4. Inkjet ink according to claim 1, characterized in that the pigment is carbon black.
5. 5. Inkjet ink according to claim 1, characterized in that the biased anti-uncovering co-solvent consists essentially of 2-pyrrolidone.
6. 6. Inkjet ink according to claim 1, characterized in that the biased anti-uncovering co-solvent is present from 12% by weight to 25% by weight.
7. 7. Inkjet ink according to claim 1, characterized in that the ink jet composition can be allowed to be biased for at least 5 seconds without a substantial reduction in print quality.
8. 8. Inkjet ink according to claim 1, characterized in that the inkjet ink composition can be allowed to bias undercut for at least 8 seconds without a substantial reduction in print quality.
9. 9. System for printing high quality images with reduced skewed uncovering, characterized by comprising: (a) an inkjet ink as in one of claims 1 to 8; and (b) an inkjet architecture configured to trigger non-image-producing drops of the ink-jet ink at intervals of at least 5 seconds when the ink-jet architecture is uncovered and is not actively forming images.
10. 10. Method for increasing the bias time of an inkjet ink inkjet without significant uncovering, characterized by comprising: (a) providing an inkjet ink as in one of claims 1 to 8; (b) charging the inkjet ink in an inkjet argument; and (c) configuring the inkjet argument to allow a bias of at least 5 seconds between the shot without the requirement of architecture overlap during the bias.