Abstract:
The present invention generally relates to colorants, and more particularly, waterfast ink-jet ink compositions containing the same. The colorants of this invention, when interacted with a second reactive fluid, provides high optical density and superior durability to acid and alkaline highlighter and wet smudge benefits.

Description:
FIELD OF INVENTION  
         [0001]    The present invention generally relates to colorants, and more particularly, waterfast ink-jet ink compositions containing the same. The colorants of this invention, when interacted with a second reactive fluid, provides high optical density and superior durability to acid and alkaline highlighter and wet smudge benefits.  
         BACKGROUND OF THE INVENTION  
         [0002]    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&#39;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 durability and permanence issues of ink-jet images, especially when the printed media is subjected to wetness. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURE  
       [0003]    [0003]FIG. 1 shows how the concentration of latex in the undercoat/fixer versus durability of a black pigment ink. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0004]    Definitions  
         [0005]    Fluid—includes either or both the reactant fluid and ink compositions.  
         [0006]    Reaction—means that the solubility or phase state of one or more components is changed as to immobilize the movement of at least one colorant on the print medium in the event that one fluid comes in contact with another fluid and interacts.  
         [0007]    Reactant Fluid—also known as a 5 th  pen fluid or fixer fluid. A fluid that is typically substantially devoid of color (i.e., the reactant fluid may contain no colorant (e.g., dye or pigment), or it may contain a colorant that does not absorb visible light but may absorb in either or both the IR or UV spectrums). The reactant fluid comprises a component (a molecule or complex, or a functional group in a molecule or complex) that is reactive with a component (a molecule or complex, or a functional group in a molecule or complex), including the colorant, in an ink thus providing for enhanced image integrity of printed areas created with the ink, such as, increased permanent (e.g. smearfastness); in the event that the reactant fluid and the ink are printed at least partially on a same pre-determined area on a print medium, or on pre-determined areas adjacent one another on a print medium. The reactive fluid is reactive with at least one ink formulated according to the present invention.  
         [0008]    Ink—a fluid containing at least one colorant, the ink absorbing in one or more regions (e.g., visible, IR, UV, etc.). Ink-jet printers typically contain an ink set with black, magenta, cyan, and yellow inks, commonly known as a 4-pen ink set. Additional pens with additional color inks may also be present.  
         [0009]    The present invention is directed to fluid sets, in particular for use in coloring applications, and more particularly for use in ink-jet printing. The present fluid set combines the benefits of interactive fluids while utilizing dyes providing enhanced image integrity to the ink-jet formula. The fluid set may be used in many applications of aqueous-based printing inks, in particular 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.  
         [0010]    Aqueous inks of this invention comprise, by weight, from about 0.5 to about 20 wt % colorant, preferably from about 1 to about 10%, and more preferably from about 1 to about 6 wt % colorant; from about 1 to about 40 wt % of one or more organic solvents; and optionally up to about 20 wt % of an additive independently selected from the group consisting of immobilizing agents, surfactants, buffers, biocides, and mixtures thereof.  
         [0011]    Colorants  
         [0012]    At least one of the inks of the present fluid set contains at least one colorant according to the present invention. Without being limited by theory, it is believed that the colorants of this invention interact with the reactive fluid, or 5 th  fluid, to bind on the media which provides the benefits referred to above.  
         [0013]    Colorants may be dye-based and/or pigments based. As used herein, the term ‘pigment’ refers to a colorant that is insoluble in the aqueous vehicle, and includes pigments that are either dispersed with the aid of covalently bonded polymers or small molecules or pigments that are dispersed by loosely associated polymer dispersants. In one embodiment herein, the dispersing agent contains a carboxylate salt that forms a double charge layer around the pigment particle. This charge will be destroyed by the acid component in the reactive fluid described below, and the pigment will no longer be water dispersed. In another preferred embodiment, the dispersant also contains an aromatic character, such as from styrene monomers which can favorably interact with the styrene components of the reactant fluid described below. Without being limited by theory, it is believed that the pi-pi interaction of the aromatic components in the latex reactive fluid and the binder and dispersion polymers in the ink provide the mechanical durability and wetfastness of this invention. Besides pigments, dyes are suitable for use herein. Preferred dyes are sulfonated dyes and Projet fixable dyes.  
         [0014]    Examples of self-dispersed pigments for use herein are those provided by Cabot Company under the Trade name Cabojet™. In particular, self-dispersed pigments utilizing covalently bound polymers containing styrene are most preferred.  
         [0015]    Reactions and Reactive Components or Reactive Agents  
         [0016]    The reactant fluids of this invention are preferably applied under the ink layer in the printing process using methods known in the art for 5 th  pen applications or by means of a roller application onto the media before printing.  
         [0017]    The reactant fluids herein contain from about 6 to 50%, preferably about 10 to about 20% by wt of glycolic acid, from about 12 to about 50%, preferably 15 to 40%, by wt of cationic latex, and from 0 to about 50% by wt of glycerol. Succinic acid, or other organic acids may be substituted for glycolic acid. In one embodiment, the cationic latex is a dispersed styrene butadiene particle. Other examples of suitable hydrophobic latexes include those with a polyurethane or polyacrylate backbone.  
         [0018]    The reactive fluid, in addition to water and the reactant agent described above, may also contain one or more of the same ingredients and in the same % amounts commonly formulated into inks. For instance, solvents, surfactants, amphiphiles, biocides, buffers may be present in the reactive fluids of this invention.  
         [0019]    The fluids of the present invention may comprise from about 1 to about 40 wt % of at least one organic solvent. More preferably the fluids comprise from about 1 to about 25 wt % of at least one organic solvent with from about 5 to about 15 wt % being the more preferred. Optionally, one or more water-soluble surfactants/amphiphiles (0 to about 40 wt %, preferably about 0.1 to about 5 wt %) may be present. The inks of this invention have a pH in the range of from about 7 to about 11, preferably from about 8 to about 10, more preferably from about 8 to about 9. The reactive fluids of this invention have a pH in the range of from about 2.5 to about 7, preferably from about 3 to about 6, more preferably from about 4 to about 5.  
         [0020]    Aqueous Vehicle  
         [0021]    All concentrations herein are expressed in weight percentages, unless otherwise indicated. The purity of all components is that employed in normal commercial practice for ink-jet inks. All cited documents and patents are hereby incorporated by reference.  
         [0022]    Other ingredients added to the inks of this invention should be compatible with the above colorants employed in this invention. Likewise, other ingredients added to the reaction fluids of this invention should be compatible with the above reactive agents employed in this invention. These other ingredients are generally present, if at all, at levels of from 0% to about 20% by wt of composition.  
         [0023]    The aqueous vehicle is water or a mixture of water and at least one water-soluble organic solvent, as is well-known in the art. Selection of a suitable mixture depends on requirements of the specific application, such as the desired surface tension and viscosity, the selected colorant or reactive agent, drying time of the ink-jet fluid, and the type of print medium onto which the fluid will be printed. For a discussion of inks and their properties, see  The Printing Manual,  5 th  Ed., Leach et al. (Chapman and Hall, 1993). See also U.S. Pat. Nos. 2,833,736; 3,607,813,; 4,104,061; 4,770,706; and 5,026,755.  
         [0024]    The water soluble organic solvents suitably employed in the present ink-jet ink compositions include any of, or a mixture of two or more, of such compounds as nitrogen-containing ketones, such as 2-pyrrolidinone, N-methyl-2-pyrrolidinone (NMP), 1,3-dimethylimidazolid-2-one, and octyl-pyrrolidinone; diols such as ethanediols (e.g., 1,2-ethanediol), propanediols (e.g., 1,2-propanediol, 1,3-propanediol), butanediols (e.g., 1,2-butanediol, 1,3-butanediol, 1,4-butanediol), pentanediols (e.g., 1,2-pentanediol, 1,5-pentanediol), hexanediols (e.g., 1,2-hexanediol, 1,6-hexandiol, 2,5-hexanediol), heptanediols (e.g., 1,2-heptanediol, 1,7-heptanediol), octanediols (e.g., 1,2-octanediol, 1,8-octanediol); triolos such as 2-ethyl2-hydroxymethyl-1,3-propanediol and ethylhydroxypropanediol (EHPD); and glycol ethers and thioglycol ethers, commonly employed in ink-jet inks such as polyalkylene glycols such as polyethylene glycols (e.g., diethylene glycol (DEG), triethylene glycol, tetraethylene glycol), polypropylene glycols (e.g., dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polymeric glycols (e.g., PEG 200, PEG 300, PEG 400, PPG 400) and thiodiglycol. Prefereably 2-pyrrlidinone, NMP, DEG, EHPD and 1,5-pentanediol are employed in the practice of this invention with 2-pyrrolidinone, DEG and 1,5-pentanediol being the most preferred solvents.  
         [0025]    Suitable surfactants may be nonionic or anionic when used in the fluid vehicle. Examples of suitable nonionic surfactants include, secondary alcohol ethoxylates (e.g., Tergitol series available form Union Carbide Co.), nonionic fluoro surfactants (such as FC-170C available from 3M), nonionic fatty acid ethoxylate surfactants (e.g., Alkamul PSMO-20 available from Rhone-Poulenc), fatty amide ethoxylate surfactants (e.g., Aldamide L-203 available from Rhone-Poulenc), and acetylenic polyethylene oxide surfactants (e.g., Surfynol series, available from Air Products &amp; Chemicals, Inc.). Examples of anionic surfactants include alkyldiphenyloxide surfactants (such as Calfax available from Pilot), and Dowfax (e.g., Dowfax 8390 available from Dow), and fluorinated surfactants (Fluorad series available form 3M). Cationic surfactants may be used in the reactive fluid which interacts with the ink vehicle and/or ink vehicle colorant. Cationic surfactants that may be used include betaines (e.g., Hartofol CB-45 available from Hart Product Corp., Mackam OCT-50 available form McIntyre Group Ltd., Amisoft series available from Ajinomoto), quaternary ammonium compounds (e.g., Glucquat series available from Amerchol, Bardac and Barquat series available from Lonza), cationic amine oxides (e.g., Rhodamox series available form Rhone-Poulenc, Barlox series available from Lonza) and imidazoline surfactants (e.g., Miramine series available from Rhone-Poulenc, Unamine series available from Lonza).  
         [0026]    Buffers may be used to modulate pH and they can be organic based biological buffers or inorganic buffers such as sodium phosphate. Furthermore, the buffer employed should provide a pH ranging from about 4 to about 9 in the practice of the invention. Examples of preferably employed organic buffers include Trizma base, available from companies such as Aldrich Chemical (Milwaukee, Wis.), 4-morpholinoethanesulfonic acid (MES) and 4-morpholinopropanesulfonic acid (MOPS).  
         [0027]    Any of the biocides commonly employed in ink-jet inks may be employed in the practice of the invention, such as NUOSEPT 95, available form Hals America (Piscataway, N.J.); Proxel GXL, available from Avecia (Wilmington, Del.); and glutaraldehyde, available from Union Carbide Company (Bound Brook, N.J.) under the trade designation UCARCIDEW 250. Proxel GXL is the preferred biocide.  
         [0028]    Printing Methods  
         [0029]    This invention also encompasses a method for inkjet printing with the colorants and 5 th  pen, reactive fluids discussed above. Alternatively, the latex reactive fluid may be deposited onto the substrate by any know means, including roller, spray painting, piezo, or other typical methods of applying a layer of material on a substrate.  
       EXAMPLES  
     Example 1  
       [0030]    [0030]FIG. 1 shows how the concentration of latex in the undercoat/fixer versus durability of a black pigment ink. The height of the bars represent how much ink smudged in various test (wet finger, hi-liter, etc.) High bars are worse than lower bars.  
         [0031]    A loading of 44% latex (solid bar) gives superior durability. At 24% latex (checkered bar), the formula provides for reliability, especially with a roller mechanism.  
         [0032]    Concentrations of 10% or lower(stripped bars) give lower durabilities.  
       Example 2  
       [0033]    [0033]                                             A representative Black pigment ink formula                Black (pigment based)   Wt %                       Cabojet 300 from Cabot     3%           Company           Joncryl 586   1.50%           Joncryl HPD 671   0.15           Zonyl FSO   0.10%           Surfactant   0.50%           2-Pyrrolidone     7%           1,6-hexanediol     2%           LEG-1   1.50%           Biocide   0.20%           Water     84%           PH   8.5-9.3                        
         [0034]    This formula uses an experimental polymer-attached pigment supplied to us by Cabot Corp.  
       Example 3  
       [0035]    [0035]                                             A repesentative reactive fluid formula                Reactive Fluid   Wt %                       Styrene Cationic Latex   24%           (49.2% solids pH 3.7)           Glycolic acid   12%           Glycerol   40%           Water   24%                        
       Example 4  
       [0036]    [0036]                                                                           Representative color ink formulas                Color Ink                       Formulas   Cyan   Magenta   Yellow                            Glycerol   7.5   7.5   7.5           Tris   0.2   0.2   0.2           Proxel GLX   0.2   0.2   0.2           2EG   5   5   5           EHPD   7.5   7.5   7.5           Tergitol 15S-7   0.5   0.5   0.5           Zonyl FSO-100   0.4   0.4   0.4           DB199 PJC1   1.7           PF Magenta 2-NH4       2.3           RR180pacified       0.4           PF Yellow2-NH4           1.3           DY132           1.6           PH   8.5   8.5   8.5                        
       Example 5  
       [0037]    [0037]                                             Representative color ink formula                                    Cabot self-dispersed    3.00%           pigment, dispersed with           covalently attached styrene           maleicanhdride           10% Joncryl 586B   15.00%           10% Joncryl 671    1.50%           Zonyl FSO    0.20%           Surfynol 61    1.00%           2-Pyrrolidone    7.00%           1,2-Hexanediol    4.00%           LEG-1    1.50%           Proxel GXL    0.20%           Water   Balance           pH   8.5-9.3                        
       Example 6  
       [0038]    [0038]                                                                                           Representative reactive fluid formulas                1   2   3   4   5   6                        glycolic acid   12.20%   12.00%   12.10%   48.60%   12.90%    0.00%       glycerol   7.50%   40.00%    0.00%    4.10%   51.30%   39.20%       cationic latex-   25.10%   24.00%   43.90%   20.50%   12.80%   23.40%       49.2% solids       pH 3.7       water   55.00%   24.00%   44.00%   26.60%   23.00%   37.30%