Patent Publication Number: US-6665095-B1

Title: Apparatus for hybrid printing

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 60/117,889, filed Jan. 29, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention is generally in the field of digital printing systems. More specifically, the present invention relates to a system and method useful for ink-jet printing onto substrates. The present invention is directed to ink-jet printing onto textiles and other materials printed in an industrial environment using spot color, process color and hybrid color printing modes. 
     BACKGROUND OF THE INVENTION 
     Textiles having a printed pattern thereon are used in many different items. Clothing, fabrics for furniture upholstery, automotive upholstery, window treatments, and bedroom furnishings, such as bedspreads, sheets and pillow cases, are just a few of the uses for these textiles. In addition to textiles, other materials have used printed patterns, such as wall coverings, floor coverings and signage. These patterns on the printed textiles and other materials may include many different colors, several of which may be very vivid and striking. 
     Typically, these printed textiles are produced using standard printing presses. After determining the colors to be used, screens or other mechanical forms are made for each color and these mechanical forms are placed in the press. Next, a fabric is placed on the press and colorants are added to the press. The press then applies the colorants onto the fabric via the mechanical forms to produce the desired pattern. 
     Generally, the fixed costs for preparing the screens or other mechanical forms and setting up the presses are spread over long production runs for the textile or other material being printed and are, therefore, very reasonable on a per yard basis. Therefore, the technology used to make these printed textiles has changed very little over the years. However, these fixed costs can be very high. If only small quantities of the printed textile or other material are produced, the cost per yard produced can be very expensive. However, smaller quantities are needed when producing a variety of different colored samples and patterns to help with market assessment of the desired pattern. Since not all designed patterns are accepted by the market, print producers have had an aversion to preparing pre-production samples of very many patterns. Additionally, the time needed to change from one colored pattern to another is extensive. 
     Therefore, there is a need for a system and process which is capable of producing printed textiles which significantly reduces the fixed costs and preparation time, thereby allowing a plurality of samples to be produced in an inexpensive manner and to be produced on a just-in-time basis. 
     Digital color printing is one possible alternative for low cost production of textile samples. Digital color printing of documents has been known for some time. Digital color printers, including ink-jet printing systems, are widely used in many different fields to produce documents and presentations having the added benefit of color. However, due to the limited number of color cartridges that may be used in a digital printer, typically four to eight, current printers are limited in the colors they can recreate. To enhance the number of printable colors, current digital color printers use a “process color” method when printing to expand upon the colors in the color cartridges. 
     In a “process color” method, the digital color printer uses “process colors,” in which either three (cyan, magenta and yellow) or four (plus black) primary ink colors which comprise a process color set. These primary ink colors are commonly referred to by their initials C, M, Y and K, respectively. In addition, other process color sets, such as (C, M, Y, K, green, and orange) or (C, M, Y, K, light cyan, and light magenta), are known in the art. Generally, the process colors in a process color set are used to produce a wide range of printed colors by combining various amounts of each of the process colors in the form of adjacent or superimposed dots. C, M and Y are subtractive primary ink colors and may be combined to form most other ink colors. 
     Spot color printing involves application of solid areas of pre-mixed ink rather than overlapping multiple inks (C, M, Y and K) to create colors. For example, the deposition of an ink having the pre-mixed color of IBM® blue onto a substrate would be a spot color process. 
     The range of possible colors that may be printed by a printing process is referred to as the “gamut” of the process. Unfortunately, the gamut of most printing processes is much smaller than the total range of colors that can be seen. Specifically, the gamut of process color printers is smaller than the possible gamuts produced by traditional printing presses, such as offset, flexographic, gravure and screen printing presses, which print with pre-mixed or “spot” color inks. In other words, ink-jet printing systems relying on process color techniques cannot produce colors that match exactly many of the desired colors (i.e., IBM® blue, Coca-Cola® red or colors designed by fashion designers and produced by specific textiles dyes or pigments) one sees in everyday life. Therefore, ink-jet printing systems are not able to reproduce many of the vivid and striking colors currently seen on most textile patterns. As various industries, such as the textile industry, begin to transition from traditional press technology to digital printing technology, the restricted color gamut of process color devices will dampen the rate of adoption of digital printing. 
     Therefore, what is needed is a combination of spot color printing with digital printing which will provide the same color gamut expected by the users of traditional presses as well the benefits that are inherent to digital printing, such as short run printing, just-in-time production, and distributed printing, among others. 
     SUMMARY OF THE INVENTION 
     The present invention provides a system and method for digital printing which is useful for ink-jet printing onto various substrates. Even more specifically, the present invention is directed to ink-jet printing onto textiles using a spot color printing mode, a process color printing mode, and/or a hybrid of both spot and process color printing modes. The present invention uses standard colorants, including textile dyes and pigments, thereby allowing the system to be used in existing manufacturing plants. As used herein, the term “dye” is meant to include all dyes and pigments. Next, the present invention includes methods of formulating ink-jet inks wherein these dyes are purified using a system specifically designed to selectively remove unwanted impurities, such as particulates, dissolved molecules, and ions, from the dyes and to formulate these dyes into inks capable of being used in an ink-jet printing process. 
     After the dyes have been purified, they are placed into and shipped in specially designed containers to a color kitchen, which may be located at the manufacturing plant. The containers are designed to not only prevent impurities, including air, from entering the container and to prevent expiration of water from within, but also such that they may be easily connected to the color kitchen. The color kitchen is designed to mix the purified dye stock solutions with water and optionally other additives to form the inks needed to reproduce a particular color, i.e., a spot color. The determination of the colors to be used is performed using a recipe creation software which analyzes the colors to be printed and selects which formulations of dyes should be mixed together to form the colors needed to reproduce the selected colors in the pattern to be printed. Next, the color kitchen dispenses the appropriate purified dye stock solutions, generates the selected ink-jet ink formulations into specially designed containers or ink jet cartridges. These containers are preferably designed to include a removable connector that allows the color kitchen to dispense the purified dye stock solutions, water and additives into the container. The same connector, when attached to these containers allows the container to be used directly in an ink-jet printing system. Additionally, the containers are preferably designed to ensure that no impurities are able to get into the dispensed inks and therefore clog the ink-jet printing system nozzles or destabilize the inks. 
     In general, because ink-jet printing systems currently print with no more than 6 to 8 colors, and because many printed textiles have patterns containing more than eight colors, the present invention also includes a hybrid color management software which directs the printer to use a spot color process to exactly reproduce some colors of the desired pattern while using a process color process to reproduce the remaining, less important colors of the pattern, thereby allowing the reproduction of a printed textile using a digital printing process. 
     Therefore, the present invention is capable of digitally printing a pattern onto a substrate using standard printing dyes. The present invention also provides a filtration system which is capable of purifying standard printing dyes into stable solutions that can be used in a color kitchen. Additionally, the present invention includes containers which are designed to transport purified dyes solutions or pigment dispersions to a color kitchen without impurities entering the container while also permitting the dyes to be introduced into the color kitchen. The present invention provides a color kitchen which mixes the purified dye solutions into the necessary colors as determined using a recipe creation software program. Additionally, the present invention provides a second container which is adaptable to fit onto the color kitchen while also being adaptable to fit onto an ink-jet printing system. Finally, the present invention is capable of using both a spot color printing mode and a process color printing mode to reproduce a desired printed pattern on a textile and digitally printing that pattern onto a textile to produce more pattern colors than there are ink colors on the printing system. 
     These and other features and advantages of the present invention will become apparent after a review of the following detailed description of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  is a functional block diagram illustrating a system of the present invention wherein dyes are purified, mixed and dispensed into containers capable of acting as printer cartridges for an ink-jet printing system. 
     FIG. 1 b  is a functional block diagram illustrating a system of the present invention wherein printer cartridges are inserted into an ink-jet printing system for digitally printing a pattern onto a substrate. 
     FIG. 2 shows an exemplary embodiment of a purification system useful in the present invention. 
     FIG. 3 is a functional block diagram illustrating an exemplary color kitchen in accordance with the present invention. 
     FIGS. 4 a  and  4   b  show a side view and a top view, respectively, of a container useful in the present invention. 
     FIG. 5 shows a cap/adapter useful in the present invention. 
     FIG. 6 is a flow chart illustrating an exemplary quality control method in accordance with the present invention. 
     FIG. 7 is a flowchart that illustrates an exemplary hybrid color management method of the present invention. 
    
    
     DETAILED DESCRIPTION 
     The present invention provides a system and method for using digital printing technology to print patterns onto textiles and other materials, which heretofore could only be generated using standard printing presses. The system includes a plurality of different features, each of which is an important part of the overall system. 
     As shown in FIGS. 1 a  and  1   b , the first part of the present invention comprises a method and apparatus  10  for purifying dyes such that they are able to be used in a digital printing system, such as an ink-jet printing system  100 . It is desirable to use known textile colorants  20  in the present invention since, as discussed above, one of the uses for this system is for economically producing samples of many different types of printed textiles. The standard colorants  20  are purified and formulated into purified stock dye solutions or pigment dispersions  30  using a purification system. By using standard colorants  20 , a textile printing company can use the same colorants  20  for both ink-jet printing, which would include proof sampling and short run production, and on-press production printing. This eliminates the need for sourcing expensive specialty dyes, which may not accurately reflect the color of the textile dye, thereby creating discrepancies between the sample produced and the large production run. 
     The next part of the system comprises the means by which the purified stock dye solutions  30  are transported to the textile manufacturing plant without contamination of these solutions  30 . While it is contemplated that the dyes will be purified ex situ, it is possible for the purification system to be located in situ. However, in most instances, after the dyes have been purified into purified stock dye solutions  30 , it is desired to ensure that contamination does not occur between the purification site and the manufacturing site. By using containers designed to prevent contamination, the present invention helps ensure that the solutions will be able to be used in an ink-jet printing system. Additionally, the containers are preferably designed such that the purified dye can be withdrawn from the container and added to a color kitchen, to be discussed hereafter, without contamination of the solution. 
     Once the purified dye stock solutions  30  have been loaded into the color kitchen  40 , they can be formulated into inks that can be used in an ink-jet printing system  100 . As used herein, the term “color kitchen” is defined as a system designed to mix one or more purified dye stock solutions or dispersions with additives and either water or a solvent to form an ink capable of being used in an ink-jet printer. 
     While the color kitchen  40  may be located ex situ, it is contemplated that each manufacturing plant incorporating the present system will have its own color kitchen  40 . This allows production of ink-jet inks having short-term stability, unlike typical ink-jet inks, which have shelf-lives of  6  months or longer. This “just-in-time” ink production helps to significantly reduce ink development time and cost, thus making the development of inks utilizing hundreds of different colorants feasible. The color kitchen  40  takes the purified dye solutions  30  and mixes them with water and other additives  35  to form the inks to be used by the ink-jet printing system  100 . These ink-jet ink sets  60  are dispensed by the color kitchen  40  into containers  70 , which are then sealed. These containers  70  may be specially designed containers which may also be installed directly onto the ink-jet printing system  100 . 
     The colors of the inks to be produced in the color kitchen  40  are determined using a recipe creation program module  50  which analyzes the colors to be produced and determines which mixture of dyes will be needed. Additionally, if the pattern or design to be printed has more design colors than the ink-jet printing system  100  has ink colors, then a Hybrid Color Management program module  90  may be used to invoke a hybrid printing mode. In a hybrid printing mode, a hybrid color set comprising spot colors and process colors is loaded into the ink-jet printing system  100 . The spot colors are used to print selected design colors in a spot color mode, while the process colors are used in combination with themselves and/or with the spot colors to print other design colors in a process color mode. Finally, a textile CAD program module  80  may be used to provide input data to the color kitchen  40  and the ink-jet printing system  100 . 
     The first part of the system and process of the present invention is the purification of standard dyes. Typically, standard dyes have impurities within the dye which prevent these dyes from being used directly in a digital printing system, such as an ink-jet printing system. Custom purification is therefore usually required to allow the standard dyes to be used in a digital printing system. The purification removes from the dye both inorganic and organic materials that prove detrimental to ink stability and ink performance in both the printing head and print quality. 
     The standard colorants that may be used in the present invention preferably have a low viscosity (1 to 20 cps) and may be reactive dyes, acid dyes, VAT dyes, dispersed dyes or pigments. However, the dyes are preferably reactive dyes. 
     Reactive dyes useful in the present invention include, but are not limited to, CI Reactive Yellow 7, CI Reactive Yellow 18, CI Reactive Yellow 22, CI Reactive Yellow 55, CI Reactive Yellow 86, CI Reactive Orange 4, CI Reactive Orange 12, CI Reactive Orange 13, CI Reactive Orange 35, CI Reactive Orange 66, CI Reactive Red 2, CI Reactive Red 3, CI Reactive Red 5, CI Reactive Red 6, CI Reactive Red 11, CI Reactive Red 31, CI Reactive Green 8, CI Reactive Blue 4, CI Reactive Blue 5, CI Reactive Blue 9, CI Reactive Blue 13, CI Reactive Blue 49, CI Reactive Blue 63, CI Reactive Blue 71, CI Reactive Blue 72, CI Reactive Blue 62, CI Reactive Blue 96, CI Reactive Blue 99, CI Reactive Blue 109, CI Reactive Blue 122, CI Reactive Blue 140, CI Reactive Blue 161, CI Reactive Blue 162, CI Reactive Blue 163, CI Reactive Blue 166, CI Reactive Blue 198, CI Reactive Violet 1, CI Reactive Brown 9, CI Reactive Brown 10, CI Reactive Brown 17, CI Reactive Brown 22, CI Reactive Brown 23, CI Reactive Black 8, and CI Reactive Black 14. 
     Acid dyes useful in the present invention include, but are not limited to, CI Acid Yellow 3, CI Acid Yellow 5, CI Acid Yellow 23, CI Acid Yellow 36, CI Acid Yellow 73, CI Acid Yellow 210, CI Acid Orange 7, CI Acid Orange 8, CI Acid Orange 60, CI Acid Orange 63, CI Acid Orange 142, CI Acid Red 52, CI Acid Red 87, CI Acid Red 357, CI Acid Green 1, CI Acid Green 26, CI Acid Blue 9, CI Acid Blue 254, CI Acid Violet 90, CI Acid Brown 26, CI Acid Brown 268, CI Acid Brown 269, CI Acid Black 194, and CI Acid Black 210. 
     VAT dyes useful in the present invention include, but are not limited to, CI Vat Yellow 4, CI Vat Blue 1, CI Vat Brown, CI Solubilized Vat Yellow 2, CI Solubilized Vat Yellow 4, CI Solubilized Vat Yellow 45, CI Solubilized Vat Orange 1, CI Solubilized Vat Orange 5, CI Solubilized Vat Orange 11, Cl Solubilized Vat Red 1, Cl Solubilized Vat Red 2, CI Solubilized Vat Red 10, CI Solubilized Vat Green 1, CI Solubilized Vat Green 30, CI Solubilized Vat Blue 1, CI Solubilized Vat Blue 2, CI Solubilized Vat Blue 5, CI Solubilized Vat Blue 6, CI Solubilized Vat Violet 2, Cl Solubilized Vat Violet 3, CI Solubilized Vat Violet 8, CI Solubilized Vat Brown 1, CI Solubilized Vat Black 1, CI Solubilized Vat Black 2, and CI Solubilized Vat Black 25. 
     Dispersed dyes useful in the present invention include, but are not limited to, CI Disperse Yellow 3, CI Disperse Yellow 23, CI Disperse Yellow 42, CI Disperse Yellow 54, CI Disperse Yellow 82, CI Disperse Yellow 86, CI Disperse Yellow 119, CI Disperse Yellow 238, CI Disperse Yellow 239, CI Disperse Orange 1, CI Disperse Orange 3, CI Disperse Orange 25, CI Disperse Orange 153, CI Disperse Red 1, CI Disperse Red 4, CI Disperse Red 9, CI Disperse Red 13, CI Disperse Red 11, CI Disperse Red 60, CI Disperse Red 167, CI Disperse Red 364, CI Disperse Red 375, CI Disperse Blue 3, CI Disperse Blue 14, CI Disperse Blue 56, CI Disperse Blue 60, CI Disperse Blue 72, CI Disperse Blue 79, CI Disperse Blue 134, CI Disperse Blue 160, CI Disperse Blue 359, CI Disperse Blue 360, CI Disperse Violet 1, CI Disperse Violet 17, CI Disperse Violet 105, CI Disperse Brown 28 and CI Disperse Brown 27. 
     Pigments useful in the present invention include, but are not limited to, CI Pigment Yellow 1, CI Pigment Yellow 3, CI Pigment Yellow 14, CI Pigment Yellow 17, CI Pigment Yellow 83, CI Pigment Yellow 101, CI Pigment Yellow 1110, CI Pigment Yellow 185, CI Pigment Orange 13, CI Pigment Orange 16, CI Pigment Orange 49, CI Pigment Red 48, CI Pigment Red 49, CI Pigment Red 57, CI Pigment Red 81, CI Pigment Red 112, CI Pigment Red 122, CI Pigment Red 146, CI Pigment Red 150, CI Pigment Red 170, CI Pigment Red 202, CI Pigment Red 206, CI Pigment Red 207, CI Pigment Green 7, CI Pigment Green 36, CI Pigment Blue 15, CI Pigment Blue 15.1, CI Pigment Blue 15.3, CI Pigment Blue 61, CI Pigment Violet 19, CI Pigment Violet 42, CI Pigment Black 7, and CI Pigment Black 31. 
     Examples of other dyes that may be used in the present invention include, but are not limited to, CI Ingrain Blue 2, CI Ingrain Blue 5, CI Ingrain Blue 14, triarylmethyl dyes, such as Malachite Green Carbinol base {4-(dimethylamino)-_-[4-(dimethylamino)phenyl]-_-phenyl-benzene-methanol}, Malachite Green Carbinol hydrochloride {N-4-[[4-(dimethylamino)phenyl-methylene]-2,5-cyclohexyldien-1-ylidene]-N-methyl-methanaminium chloride or bis[p-(dimethylamino)phenyl]phenyl-methylium chloride}, and Malachite Green oxalate {N-4-[[4-(dimethylamino)-phenyl]-phenylmethylene]-2,5-cyclohexyldien-1-ylidene]-N-methyl-methanaminium chloride or bis[p-(dimethylamino)-phenyl]phenyl-methylium oxalate}; monoazo dyes, such as Cyanine Black, Chrysoidine [Basic Orange 2; 4-(phenylazo)-1,3-benzenediamine monohydrochloride], Victoria Pure Blue BO, Victoria Pure Blue B, basic fuschin and β-Naphthol Orange; thiazine dyes, such as Methylene Green, zinc chloride double salt [3,7-bis(dimethylamino)-6-nitrophenothiazin-5-ium chloride, zinc chloride double salt]; oxazine dyes, such as Lumichrome (7,8-dimethylalloxazine); naphthalimide dyes, such as Lucifer Yellow CH {6-amino-2-[(hydrazino-carbonyl)amino]-2,3-dihydro-1,3-dioxo-1H-benz[de]iso-quinoline-5,8-disulfonic acid dilithium salt}; azine dyes, such as Janus Green B {3-(diethylamino)-7-[[4-(dimethyl-amino)phenyl]azo]-5-phenylphenazinium chloride}; cyanine dyes, such as Indocyanine Green {Cardio-Green or Fox Green; 2-[7-[1,3-dihydro-1,1-dimethyl-3-(4-sulfobutyl)-2H-benz[e]indol-2-ylidene]-1,3,5-heptatrienyl]-1,1-dimethyl-3-(4-sulfobutyl)-1H-benz[e]indolium hydroxide inner salt sodium salt}; indigo dyes, such as Indigo {Indigo Blue or Vat Blue 1; 2-(1,3-dihydro-3-oxo-2H-indol-2-ylidene)-1,2-dihydro-3H-indol-3-one}; coumarin dyes, such as 7-hydroxy-4-methyl-coumarin (4-methylumbelliferone); benzimidazole dyes, such as Hoechst 33258 [bisbenzimide or 2-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)2,5-bi-1H-benzimidazole trihydro-chloride pentahydrate]; paraquinoidal dyes, such as Hematoxylin {Natural Black 1; 7,11b-dihydrobenz[b]-indeno[1,2-d]pyran-3,4,6a,9,10(6H)-pentol}; fluorescein dyes, such as Fluoresceinamine (5-aminofluorescein); diazonium salt dyes, such as Diazo Red RC (Azoic Diazo No. 10 or Fast Red RC salt; 2-methoxy-5-chlorobenzenediazonium chloride, zinc chloride double salt); azoic diazo dyes, such as Fast Blue BB salt (Azoic Diazo No. 20; 4-benzoylamino-2,5-diethoxy-benzene diazonium chloride, zinc chloride double salt); phenylenediamine dyes, such as Disperse Yellow 9 [N-(2,4-dinitrophenyl)-1,4-phenylenediamine or Solvent Orange 53]; diazo dyes, such as Disperse Orange 13 [Solvent Orange 52; 1-phenylazo-4-(4-hydroxyphenylazo)naphthalene]; anthra-quinone dyes, such as Disperse Blue 3 [Celliton Fast Blue FFR; 1-methylamino-4-(2-hydroxyethylamino)-9,10-anthraquinone], Disperse Blue 14 [Celliton Fast Blue B; 1,4-bis(methylamino)-9,10-anthraquinone], and Alizarin Blue Black B (Mordant Black 13); trisazo dyes, such as Direct Blue 71 {Benzo Light Blue FFL or Sirius Light Blue BRR; 3-[(4-[(4-[(6-amino-1-hydroxy-3-sulfo-2-naphthalenyl)azo]-6-sulfo-1-naphthalenyl)-azo]-1-naphthalenyl)azo]-1,5-naphthalenedisulfonic acid tetrasodium salt}; xanthene dyes, such as 2,7-dichloro-fluorescein; proflavine dyes, such as 3,6-diaminoacridine hemisulfate (Proflavine); sulfonaphthalein dyes, such as Cresol Red (o-cresolsulfonaphthalein); phthalocyanine dyes, such as Copper Phthalocyanine {Pigment Blue 15; (SP-4-1)-[29H,31H-phthalocyanato(2-)-N 29 ,N 30 ,N 31 ,N 32 ]copper}; carotenoid dyes, such as trans-β-carotene (Food Orange 5); carminic acid dyes, such as Carmine, the aluminum or calcium-aluminum lake of carminic acid (7-a-D-glucopyranosyl-9,10-dihydro-3,5, 6,8-tetrahydroxy-1-methyl-9,10-dioxo-2-anthracene-carbonylic acid); azure dyes, such as Azure A [3-amino-7-(dimethylamino)phenothiazin-5-ium chloride or 7-(dimethyl-amino)-3-imino-3H-phenothiazine hydrochloride]; and acridine dyes, such as Acridine Orange [Basic Orange 14; 3,8-bis(dimethylamino)acridine hydrochloride, zinc chloride double salt] and Acriflavine (Acriflavine neutral; 3,6-diamino-10-methylacridinium chloride mixture with 3,6-acridine-diamine). Other examples of dyes include leuco dyes such as aminotriarylmethanes, aminoxanthenes, aminothioxanthenes, amino-9,10-dihydroacridines, aminophenoxazines, aminophenothiazines, aminodihydrophenazines, aminodiphenylmethanes, leuco indamines, aminohydrocinnamic acids (cyanoethanes, leucomethines), hydrazines, leuco indigoid dyes, amino-2,3-dihydroanthraquinones, phenethylanilines, 10-acyl-aminodihydrophenazines, 10-acyl-aminophenothiazines, 10-acyl-aminophenoxazines and aminotriarylmethanes wherein the methane hydrogen has been replaced by an alkylthio, benzylthio, 2-phenylhydrazino, or alkoxycarbonyl group. 
     Once the dyes have been selected, they are then purified and formulated into purified dye stock solutions. These purified dye stock solutions are formed by using a purification system designed to remove the undesirable contaminants. However, some of the impurities located within a dye are beneficial, such as salts which are used as pH buffers, so the purification system is preferably designed to remove only those impurities which adversely affect the quality of the purified dye stock solution. After the impurities are removed, the dyes are formulated into purified dye stock solutions by mixing the purified dyes with water and specially selected buffer materials to keep the solutions stable prior to being formed into ink-jet inks. 
     In general, there are several different types of purification systems that may be used to remove the impurities. Examples of purification systems include filtration, ion exchange, precipitation, electrodialysis, and centrifugation. However, the preferred purification system is a filtration system. 
     There are several filtration methods that may be used with the present invention, including, but not limited to, crossflow filtration and throughflow filtration, of which the preferred method is crossflow filtration. Both methods can be used to separate different types of species, ranging from large particles to small molecules and ions. The type of species to be separated determines the type of membrane system to be used. These membrane systems include, but are not limited to, microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. Because dye molecules are mid-sized molecules (molecular weight of about 500), it is preferred to select a filtration system that can remove both large particles and small molecules. Moreover, because not all of the impurities in a dye are detrimental to its performance as an ink, the system should be capable of removing certain impurities, and leaving the beneficial ones behind. Finally, it is desirable to select a filtration system that will minimize the risk of clogging and degradation of the membrane. For these reasons, the preferred filtration system is a crossflow membrane filtration system. 
     As shown in FIG. 2, in a cross-flow membrane filtration system  200 , the dye undergoes a two step process. In the first step, a membrane  270  is chosen which uses size exclusion to remove the larger impurities. In the second step, a different membrane  270  is chosen which is capable of removing the smaller sized impurities. 
     The cross-flow membrane filtration system  200  comprises a dye inlet  210 , a first outlet  220 , and a recirculation outlet  230 . The system  200  also includes a cross-flow filtration area  240  which includes a lower plate  250  and an upper plate  260  which sandwich the membrane  270 . Bolts or other fastening means are used to ensure that the membrane  270  remains in place during the filtration step since the dyes are usually filtered at elevated speeds and pressures, which create significant forces upon the membrane  270 . Additionally, a pump  285 , pressure gauges  290  and pressure regulating valves  295  may be used to control flow of the fluids through the system  200 . 
     The output from the first outlet  220  and the recirculation outlet  230  will change depending upon which filtration step is occurring. During the first filtration step, the larger particles are trapped by the membrane  270  and are recirculated to the recirculation outlet  230  where they are removed. The partially purified dye and smaller particles pass through the membrane  270  and out through the first outlet  220 . In the second filtration step, a second membrane  270  is used which has a different pore size and selectivity characteristics. During this step, the smaller impurities and water pass through the membrane  270  and exit the system  200  through the first outlet  220 . The impurity laden water that has exited the system is replaced with clean distilled water. The addition of clean water to replace impure water is typically known as diafiltration. Purified dye is trapped by the membrane  270  and passes through to the recirculation outlet  230  along with the clean water, where it is collected in a container (not shown) and mixed with water and buffers to produce the purified dye stock solution. If the purification is performed off-site and the color kitchen  40  is located at the textile manufacturing plant, then the stock solutions need to be transported to the color kitchen  40 . Preferably, the containers used are designed to help prevent contamination of the purified stock solutions during transport. In general, it is desired to keep air out of the containers and keep water from expiring from the purified stock solution. 
     Alternatively, the filtration apparatus may be designed such that the two different membranes  270  are arranged in series, which the larger pore size membrane located in the first position. The filtration apparatus would then include three outlets. Materials not passing through the first membrane would be discarded through the first outlet as these materials would comprise the larger impurities. Materials passing through the second membrane would be discarded through the third outlet as comprising the smaller impurities. The purified dyes would be removed from the second outlet. 
     The membranes  270  used are mainly chosen based upon their pore size. However, the membranes  270  are also preferably able to be modified, such as by pH adjustment, to selectively keep or remove only some of the impurities, thereby allowing the beneficial impurities to remain in the dye solution. Preferably, the microfiltration membranes used for crossflow filtration are SUPOR™ membranes. They are polyethersulfone membranes manufactured by Gelman Sciences in Ann Arbor, Mich., and are distributed by VWR Scientific Products. The pore size of the microfiltration membranes is 0.2 μm. 
     Additionally, the ultrafiltration membranes currently used for crossflow filtration may be obtained from Sepratech in Rock Hill, S.C. and are listed under the designations G5, G10, and G20. They are thin film composite membranes. The membrane is composed of two layers: a thin film of membrane at the top which is responsible for the actual separation, and a comparatively thicker layer of backing material at the bottom which provides support. The G5, G10, and G20 membranes are rated at different molecular weight cutoffs. However, it must be kept in mind that molecular weight cutoffs should be used as guidelines and not as absolute boundaries; the G5 will have the lowest amount of passage and the G20 will have the highest amount of passage, but the specific molecules that would pass through the membranes can only be determined by experiment. It has been determined that a large percentage (95-99%) of dye molecules are retained by these particular membranes. 
     After the standard dyes have been purified and formulated into purified stock solutions, these solutions are dispensed into containers and shipped to sites that have color kitchens  40 . Additionally, the additives  35  needed to be mixed with the purified stock solutions  30  are also shipped to the sites that have a color kitchen  40 . The purified stock solutions  30  and the additives  35  are combined in the color kitchen  40  to form ink-jet inks. Process color ink-jet inks are generally purchased as standard off-the-shelf items. 
     The present invention also includes specially designed containers which are capable of preventing contamination and water expiration during shipment, but also allow for ready dispensing of the stock solutions into the color kitchen  40  without significant risk of decontamination. 
     These specially designed containers may be any shape or size as long as they prevent contamination of the purified stock solutions and additives. While the containers may be rigid, preferably they comprise collapsible bags made from a material that is substantially impervious to air contaminants and moisture. Materials suitable for this purpose include, but are nor limited to, plastics and/or foils. Preferably, the material for the bags comprises a laminate including at least one foil layer. Foils may be used to not only provide a substantially impervious layer to air, other gasses and moisture, but the foil also helps eliminate light, which might degrade the purified dye stock solutions. 
     Additionally, the containers include a specially designed fitting which serves two purposes. The first is the introduction of the solutions into the container in a manner which prevents contamination of the just-purified dye stock solution. Therefore, the fitting is preferably designed to be connected with the purification apparatus outlet such that after purification, the dye stock solutions are immediately dispensed into the container and sealed. The containers are then shipped to the color kitchen  40 . As further described below, a typical color kitchen  40  includes a plurality of reservoir tanks which hold the different purified dye stock solutions  30  and additives  35 . Therefore, the container fittings must also be capable of dispensing the purified dye stock solutions  35  into their respective reservoir tank without contamination. 
     One feature of the present invention is the on-demand, on-site formulation of final ink-jet inks. This will provide quick and efficient preparation of ink-jet formulations for colors needed to print specific designs. The purified dye stock solutions  30 , additives and water  35  may be mixed in any proportion to produce the desired ink color. This is accomplished using a color kitchen  40 . Color kitchens are currently used in the production of conventional printing inks and pastes. However, heretofore, these color kitchens have not been made commercially available to produce ink-jet inks, which contain various additives not normally associated with conventional inks and pastes. Ink-jet additives, which may include, but are not limited to, a solution in water or a base solvent containing co-solvents, surfactants, viscosity modifiers, biocides, corrosion inhibitors, resins, and/or buffers may then be dispensed with the stock dye solution to provide a final ink having ink-jettable characteristics. An additional advantage of this just-in-time ink production method is that the final ink requires only short term stability. 
     The final ink may be placed into a specially designed ink container or reservoir and capped. As will be discussed in more detail below, the specially designed ink container preferably comprises a collapsible plastic pouch into which the color kitchen  40  dispenses purified dye stock solutions  30 , additives and water or solvent  35 , depending upon the type of dye being used. Additionally, the containers may also be used as ink feed reservoirs for the ink-jet printing system  100 . These containers also minimize the amount of air contacting the final ink, and thereby minimize the risk of contamination from air-borne particulates. Therefore, the color kitchen  40  is preferably designed to be able to be used with these unique ink containers. 
     FIG. 3 shows a functional block diagram of an exemplary color kitchen  40  that is used in accordance with the present invention. The color kitchen  40  is used to mix purified dye stock solutions  30  and ink-jet additive  35  to provide a final ink-jettable ink, such as a spot color ink  60 . The color kitchen  40  includes a plurality of feed reservoirs  310  which hold a number (e.g., 12) of the dye stock solutions  30  and also has extra reservoirs  310  containing the ink-jet additives and either water or solvent  35 . 
     The exemplary color kitchen  40  is controlled by a computerized system generally comprising a processor  302  and a number of software program modules and data  309  stored in a memory  304  coupled to the processor  302 . Program modules include routines, operating systems  308 , application programs modules (such as Recipe Creation program module  305 , Ink Data Encoding program module  306  and Control System program module  307 ), data structures, and other software or firmware components. Specifically, the Recipe Creation program module  305  comprises computer executable instructions for controlling the creation of the mixing recipes of dye stock solutions  30  and ink-jet additives  35 . The Ink Data Encoding program module  306  comprises computer executable instructions for creating ink data and generating an output representing the ink data that may be encoded on a container  330  used to store the ink. As used herein, “ink data” refers to the amount and color of the ink that is contained in a container. The Ink Data Encoding program module  306  creates ink data for the spot color inks produced by the color kitchen  40 , which will also be used in the ink-jet printing system  100 . Also, the Control System program module  307  comprises computer executable instructions for controlling mid-level and low-level indicators on the feed reservoirs  310 , which are operable to detect fluid levels. The processor  302  executes the computer-executable instructions of the various program modules described above. 
     The color kitchen  40  also includes one or more input interfaces  314  for communicating with and managing one or more input devices. An input device may comprise a keyboard, mouse, touch-screen, microphone, or other signal generating device, or another computer executing a program module, such as a computer aided design (CAD) program module  80 . Thus, via an input interface  314 , the color kitchen  40  may receive design data relating to a particular print design. As used herein, “design data” refers to information relating to the colors and quantities of inks required to print a design. Design data may also include information relating to the type, color and dimensions of the substrate on which the design will be printed. The colors to be printed in a design are referred to as either target colors or design colors. For purposes of the present invention, the terms “target colors” and “design colors” are used interchangeably. Design data may be stored in data files  309  in the memory  304  of the color kitchen  40 . The Recipe Creation program module  305  may then process the design data to determine the identity and quantity of each dye stock solution  30  and the ink-jet additives  35  required to create a spot color ink  60  that matches a selected design color. 
     In processing the design data, the Recipe Creation program module  305  deconstructs the target colors into constituent mother colors, taking into account the color values of the selected mother colors and of the unprinted substrate. The color kitchen  40  may be capable of storing the characteristics of 1000 or more ink colors and their recipes in its memory. Recipe Creation program modules are well known in the art and are generally available off-the-shelf (i,e., Gretag MacBeth or DataColor). An output interface  316  allows the processor  302 , controlled by the operating system  308  in conjunction with the Recipe Creation program module  305 , to communicate with the mechanical components (not shown) of the color kitchen  40  in order to control the dispensing of appropriate amounts of dye stock solutions  30  and ink-jet additives  35  into the containers  330 . 
     It is preferred that each purified stock solution be dispensed with an accuracy of plus or minus 0.01 grams when dispensing 5 grams or less, and plus or minus 0.02 grams at over 5 grams. The range of ink formulated per ink color can range from about 50 ml to tens of liters or more. The dispensed dye stock solutions  30  and additives  35  are then mixed in the container  330  or reservoir by mechanical agitation or other means. Although color kitchens are common in industries such as textiles, where printing takes place with traditional presses, the exemplary color kitchen  40  used for the method of ink-jet printing described herein is designed with unique capabilities. Such capabilities are in-line filtration of sub-micrometer particles; isolation of the dye stock solutions, additives and dispensed and mixed final inks from atmospheric contamination and debris; and automated encoding of the containers  330  or reservoirs with ink data that identifies the color and volume or weight of the contents and that may be communicated to an ink-jet printing system  100 . 
     When formulating the ink-jet inks using the color kitchen  40 , it is important to adjust the viscosity of the processing fluids used when making the final ink-jet inks. These fluids include the purified dye stock solutions  30 , additives and water  35 . If the viscosity of the ink is too low, splatter problems could develop when placing the ink into the ink container  330  using the color kitchen  40 . Also, too low of a viscosity could result in the formation of small droplets in the container  330 , which could also interfere with the printing process. 
     Conversely, if the viscosity of the ink-jet ink is too high, the ink will not flow through the in-line filters at an acceptable pressure drop. This would require the use of a pump having an unacceptably high output pressure. Accordingly, it is preferred to optimize the rheology of the various solutions which are dispensed in the color kitchen  40  to produce an ink-jet ink which does not splatter during dispensing into the ink-jet containers  330  while also flowing through the in-line filters at an acceptable pressure drop. 
     The color kitchen  40  also includes a plurality of tubes  312  which feed the purified stock solution  30 , additives and water or solvent  35  from the reservoirs  310  to a plurality of dispensing nozzles  320 . The dispensing nozzles  320  basically comprise the outlets from the plurality of tubes  312 . Then, as each ink is formulated, the necessary purified stock solutions  30 , additives and water or solvent  35  are fed from the reservoirs  310 , through the tubes  312  and out from the nozzles  320  into the container  330 . 
     Recirculation means (not shown) may be provided to ensure that the contents of the reservoirs  310  are maintained in a homogeneous state to ensure a uniform concentration. If recirculation means are used, these means will preferably include a recirculation pump that removes a solution from one of the reservoirs  310 , pumps it through a filter (not shown) and returns it to its reservoir  310 . Preferably, the return solution is returned to the reservoir  310  at a location such that it is not immediately pulled back into the recirculation line. Preferably, the return solution is allowed to mix into the contents of the reservoir  310  to help ensure that the contents of the reservoir  310  are at a substantially uniform concentration and that the contents have a substantially consistent residence time prior to being used. 
     If the return line is located at the top of the reservoir  310 , possible foaming could occur. Foaming would occur if the liquid level in the reservoir  310  dropped below the level of the return line, thereby creating a spatial gap. Then, as the return solution is placed into the reservoir  310 , the spatial gap would cause foaming as the return solution contacted the contents of the reservoir  310 . This foaming would result in the contents of the reservoir  310  not being at a substantially uniform concentration. 
     Conversely, if the return line is located at the bottom of the reservoir  310 , possible “short circuiting” could occur as the return liquid is immediately drawn out of the outlet, resulting in an extended residence time for the remainder of the contents in the reservoir  310 . Accordingly, unique design considerations should be taken into account if recirculation means are used. 
     Preferably, the color kitchen  40  also includes a control system which includes the previously mentioned mid-level and low-level indicators (not shown) on the feed reservoirs  310 . These indicators will alert the operator when the level of a fluid reaches a point whereby more fluid may be added. Additionally, if the fluid level of any reservoir  310  gets too low, the control system may be designed to warn the operator that fluid must be added and/or that the color kitchen  40  must be automatically shut down, thereby preventing waste caused from producing ink-jet dyes that do not have the correct formulation. As mentioned, operation of the control system is controlled by the Control System program module  307 . 
     The containers  330  into which the ink-jettable inks are dispensed are preferably designed to ensure that no contamination occurs. As shown in FIG. 4 a , the container  330  is designed with a grip  410  which is preferably located near the color kitchen nozzle  320 . The containers  330  are preferably collapsible, as shown in FIG. 4 b , but will expand as they are filled. As already discussed, preferably these containers  330  comprise collapsible pouches into which the ink-jet inks are dispensed. 
     By using collapsible pouches, the same size pouch can be used for a wide range of ink volumes since the amounts of each ink will depend on the requirements of the selected pattern. In addition, the collapsible pouches help reduce the amount of air contacting the inks when they are fed to the printer, thereby minimizing foaming and the necessity to de-gas the ink within the printer&#39;s feed system. 
     Also, as shown in FIG. 5, preferably the containers  330  are designed to have cap/adapters  500  that can readily receive dispensed ink components, while also later being able to be connected directly to the ink-jet printing system  100 . Accordingly, one the ink is dispensed into the container  330  by the color kitchen  40 , these containers  330  may be loaded directly onto an ink-jet printing system  100 . These cap/adapters  500  include threads  510  which correspond to the threads  420  on the container  330 . Additionally, the cap/adapter  500  includes a rubber septum  520  which seals the container  330  and prevents air from entering and water from expiring from the container  330 . Preferably, the cap/adapter  500  is designed such that when hand-tightened onto the container  330 , there will be no leaks. 
     FIG. 6 is a flow chart illustrating an exemplary quality control method  600  used in accordance with the present invention. The exemplary method  600  begins at starting block  601  and progresses to step  602 , where an spot color ink-jet ink is created at a color kitchen  40 . At step  604 , the spot color ink is placed in a container  330  by the color kitchen  40 , as previously described. Next, at step  606  the container  330  storing the spot color ink is encoded with ink data. Ink data may be generated by a component of the color kitchen  40 , such as the exemplary Ink Data Encoding program module  306  described above. Those skilled in the art will appreciate that the Ink Data Encoding program module  306 , or an equivalent thereof, may also be executed by a distinct system, such as a desktop, laptop, or handheld computer system, that is in communication with and operated in conjunction with the color kitchen  40 . Alternately, ink data may be created manually by the operator of the color kitchen. 
     The Ink Data Encoding program module  306  may interact with the Recipe Creation program module  305  to determine a color reference, such as an LAB value, for the ink-jet ink. The Ink Data Encoding program  306  may then generate an encoded output, such as a bar code or a digital representation of the ink data. The encoded output may be encoded on the container  330  that stores the spot color ink. Encoding the ink data, or a representation thereof, on the container  330  may comprise affixing a bar code to the container  330 , such as by way of a printed label, or storing digital data in a computer-readable memory device attached to the container  330 . Those skilled in the art will appreciate that suitable computer-readable memory devices include RAM, ROM, EPROM, EEPROM, flash memory cards, digital video disks, Bernoulli cartridges, and the like. Still, any type of computer chip including a memory may be affixed to, or otherwise associated with, the container  330 . 
     Those skilled in the art will also recognize that the color kitchen  40 , or other system for generating the ink data, will include an appropriate output device, such as a printer or a data communication device, for encoding the ink data on the container  330 . For example, a printer may be used to print a bar code label, which may be manually attached to the container  330 . Alternately, the Ink Data Encoding program module  306  may be programmed to interact with a data communication device in order to automatically transfer digital ink data to a computer readable memory device associated with the container  330 , via a data communications link. Other methods and systems for encoding ink data on the container  330 , such as by stamping or melting a code onto the surface of the container  330 , may be contemplated by those skilled in the art. Such other methods for encoding ink data onto the container  330  are considered to be within the spirit and scope of the present invention. 
     After the ink data is encoded on the container  330 , the exemplary method  600  continues at step  608 , where the container  330  is delivered to the ink-jet printing system  100 . The color kitchen  40  may be remotely located from the ink-jet printing system  100 , requiring that the containers be delivered to the ink-jet printing system  100  by freight or some other transport method. Preferably, however, the color kitchen  40  may be situated in the same location as the ink-jet printing system  100 . As mentioned, proximity of the color kitchen  40  and the ink-jet printing system. 100  allows production of ink-jet inks having short-term stability, which have significantly reduced development times and costs. 
     At step  610 , the ink data from the container  330  is input to the ink-jet system  100 . Ink data may be input to the ink-jet printing system  100  in a variety of well-known ways. For example, if the ink data is encoded on the container  330  by way of a bar code, a conventional bar code reader may be coupled to the ink-jet printing system  100  as an input device. Alternately, if the ink data is encoded on the container  330  by way of a computer readable medium, an appropriate input device for reading the ink data may be coupled to the ink-jet printing system  100 . Appropriate input devices for reading ink data may comprise optical memory reading devices, magnetic memory reading devices, and the like. Furthermore, ink data may be input into the ink-jet printing system  100  by way of a keyboard, a touch screen, a mouse, a voice recognition unit including a microphone, or any other input device. 
     Ink data that is input to the ink-jet printing system  100  is stored in a data file  111  in the memory  112  of the ink-jet system  100  (see FIG.  1 ). The memory  112  may also store various program modules, such as an operating system  114 , a Hybrid Color Management program module  90 , a Quality Control program module  116 , and any other program module required to control or optimize the ink-jet printing system  100 . The memory  112  is coupled to a processor  120  that executes the computer-executable instructions of the described program modules. The processor  112  is also coupled to an input interface  122  for communicating with and managing various input devices and an output interface  124  for communicating with and managing various output devices. Output devices coupled to the ink-jet printing system  100  may include: a printer, such as an ink-jet printer, a dot matrix printer, a laser printer, and any other printing device; a display device; an audio device, such as a speaker, or an alarm; a light emitting device; and the like. 
     Data files  111  stored in the memory  112  of the ink-jet printing system  100  may also comprise design data relating to the target colors and quantities of inks required for a particular design to be printed. Design data may be input to the ink-jet printing system by way of any of the above-described input devices, or may be otherwise downloaded from a remote computer system. At step  612  the exemplary quality control method  600  compares the ink data from the container  330  with the design data to determine if any discrepancies exist between the spot color ink stored in the container  330  and a selected design color. 
     The comparison of ink data with design data may be performed by the Quality Control program module  116 . Generally, the ink data comprises a color reference, such as a LAB value for the spot color ink, and an indication of the quantity ink in the container  330 . The design data comprises information relating to the shape of the design and target color references, such as LAB values, for the target colors of the design. Design data may further comprise information relating to the printing mode to be used for printing the design and the type, dimensions and color value of the substrate on which the design is to be printed. Accordingly, the design data may be used to ensure that a spot color ink matches a selected design color and that there is a sufficient amount of the spot color ink required to print the design color. 
     The Quality Control program module  116  may thus comprise computer-executable instructions for examining the ink data to determine if selected target colors of the design can be reached (matched) by the spot color inks in the containers  330  and if enough ink is stored in the containers  330  to complete the design. In a spot color printing process, the determination as to whether the target colors can be reached involves comparing the color reference of the ink data from a single container  330  to the color reference of the selected target color. If the color reference of the ink data matches the color reference of the target color or differs from the color reference of the target color by less than a predetermined value, the target color will be considered to be reached by the spot color ink in the container  330 . 
     Returning to the description of FIG. 6, the exemplary method  600  continues at step  614  with a determination as to whether a discrepancy exists between the ink data and the design data. If no discrepancy exists, the method  600  continues to step  616 , where the ink-jet printing system  100  prepares for printing of the design. However, if a discrepancy exists, the method  600  proceeds to step  618 , where an error notification is generated. 
     As mentioned, the discrepancy may indicate that a selected target color of the design cannot be reached using a spot color ink stored in a containers  330  and/or that the quantity of a spot color ink stored in a container  330  is insufficient to properly print the design on the dimensions of the substrate. The discrepancy may also indicate that a spot color ink container has not been loaded into the proper location in the ink-jet printing system  100 . In addition, as previously mentioned, process color inks are typically purchased as off-the-shelf items. Process color ink containers may also be encoded with ink data. Ink data from process color ink containers may be used in the exemplary quality control method to ensure that the proper process color inks are loaded into the proper locations in the ink-jet printing system  100 . 
     The error message generated at step  618  will communicate information about the discrepancy to the operator or user of the ink-jet printing system  100 . The error message may be an audible alarm, a message printed on paper or displayed on a display device, or a display of the design showing how the design will appear if printed with the inks presently loaded onto the ink-jet printing system  100 . Other methods for generating an error message will occur to those of ordinary skill in the art and are therefore considered to be within the scope of the present invention. An error message may thus alert the user that a new spot color ink must be created in the color kitchen  40  or that the process color inks have been improperly loaded into the ink-jet printer. Subsequent to generating an error message at step  618  or preparing for printing of the design at step  616 , the exemplary method  600  ends at step  620 . 
     As mentioned, a unique feature of the ink-jet printing system  100  of the present invention is its ability to print in a hybrid color mode, using a hybrid color set. A hybrid color set comprises both spot color inks and process color inks. In an exemplary embodiment, the inventive hybrid printing functionality is provided by a Hybrid Color Management program module  90  (see FIG. 1 b ). The Hybrid Color Management program module  90  enables the printer to print a greater number of colors than the number of inks that are loaded onto the ink-jet printing system  100 . Thus, the Hybrid Color Management program module  90  permits hybrid ink-jet printing of a wide range of fabrics with colors that may be made to match those produced by production screen processes. 
     Conventional ink-jet printing systems are configured to print in a process color printing mode. Most commercially available color ink-jet printing systems print only four colors simultaneously. Some higher end ink-jet printing systems are capable of printing six or even eight colors simultaneously. Accordingly, prior art ink-jet printing systems were able to print up to a maximum of eight colors, or to print a range of process colors by combining up to eight ink colors. If such printers were configured to print in spot color mode, only eight spot colors could be achieved. 
     Many textile designs require greater than eight colors, which would require various substitutions of ink colors in an ink-jet printing system having only eight available spot color inks. Also, process color printing has a limited color gamut determined by the color values of the printed process colors. If a target color cannot be reached by combination of the process colors in a particular process color set, a spot color mode must be adopted. However, the Hybrid Color Management program module  90  of the present invention overcomes the limitations of both spot color mode and process color mode printing. 
     Generally described, the Hybrid Color Management program module  90  facilitates a method whereby a user selects important or dominant design colors that may be dispensed by the color kitchen  40 , as described above. When the design is printed, the important or dominant colors will be printed using a spot color mode. The less dominant design colors will be printed in a process color mode. Using a plurality of process colors in combination with themselves and/or with the spot colors, the Hybrid Color Management program module  90  will assist the user in selecting the color combinations needed to optimize color matching of the less-dominant design colors. 
     For example, with an eight color hybrid printing system that is to print a 16 color design, the user might select four ink colors as spot color inks to print the most important or dominant four design colors. Then the Hybrid Color Management program module  90  would be used to select four process ink colors, which when used in a process color printing mode in combination with each other and possibly with the four selected spot color inks, would provide optimum color matching of the 12 remaining design colors. 
     Before the Hybrid Color Management program module  90  is employed to determine a hybrid ink-jet ink color set, the design must be prepared for printing and the target colors of the design must be determined. Typically, a textile design is brought into digital form using CAD program modules  80 . After a design is brought into digital form, color separations are prepared. These separation files (one per color) can be used to drive a digital proofing printer. 
     In the course of the textile printing company&#39;s preparation of screens for production, separation files are typically modified by an expert in order to prepare them for driving digital screen engraving systems. These modifications take into account the selected screen mesh and type of screen (lacquer or galvano). Then, if a design color is to be printed at various intensities (gray scale), the engraving expert alters the separation files to provide desired visual effects. Although the work of the engraving expert does not effect color matching, the result does effect the appearance of the design. 
     Textile printing companies may proof either the just 10 separated design files or the separation files that have been modified by the engraving expert, following a step known as “colorizing.” Those skilled in the art will appreciate that proofing of the modified separation files will provide a closer match to the appearance of the production print. Separation files are colorized by a specialist who defines the target colors to be printed. Each textile printing company has a library of colors that are selected for each color field or a new color not in the library may be created for the design. 
     Usually, a design is prepared with more than one colorway, i.e., the same pattern with different design colors. The specialist uses calibrated monitors to visualize each colorway. Proof printing takes place after the colorways are prepared. When the color specialist is satisfied with the proof printing, design data is collected regarding the target colors for each colorway. Design data is later supplemented with information relating to the color, type and dimensions of the substrate on which the design will be printed, the printing mode that will be used to print the design, the dimensions of the design to be printed, etc. 
     After the design data for each selected colorway is input to the memory  112  of the ink-jet printing system  100 , the Hybrid Color Management program module  90  may be executed to assist the user in making decisions about what ink colors are needed to print the design. The method performed by the Hybrid Color Management program module  90  is generally illustrated in the flowchart of FIG.  7 . The exemplary method  700  begins at starting block  701  and progresses to step  702 , where the design data relating to the target colors of the design is received from memory. 
     Next at step  704 , a calibrated process color set is selected. Although a calibrated process color set may be selected automatically via software routines, it is preferable that a color expert manually select a calibrated process color set based his/her expertise. The memory  112  of the ink-jet printing system  100  will preferably store a number of calibrated process color sets. Calibration of a process color set is well known in the art and generally involves a process whereby each primary color in the process color set is printed in approximately twenty different intensities. For each printed intensity, a LAB color value is measured using a spectrophotometer. After the LAB values of the primary colors are measured, approximately one hundred to several hundreds of sample colors are printed and the LAB value for each sample color is measured. Finally, the difference in color value between each sample color and a corresponding primary color is calculated. This difference in color value is typically expressed as a “ΔE” value, which represents a distance between colors in color space. Based on the sample colors, colors may be predicted that are reachable using the process colors in the calibrated process color set in a process color printing mode. The concepts of color space, LAB values and ΔE values are well known to those skilled in the art and will therefore not be further described herein. 
     Once a calibrated process color set is selected, the exemplary method  700  advances to step  706 , where the differences in color value are determined between the design colors and the predicted colors reachable with the calibrated process color set in a process printing mode. Preferably, the determination of the differences in color values involves calculations of ΔE values. However, in an alternate embodiment, this determination may be made through visual inspection and comparison of the predicted colors and the design colors on a display device. If, at step  708 , the differences in color values between the design colors and the predicted colors is acceptable to the user (color expert), the method advances to step  709 , where the design is printed using the calibrated process color set in a process color mode. However, if the differences in color values between the design colors and the predicted colors is not acceptable, the method progresses to step  710 , where a plurality of spot colors are selected. 
     The spot colors may correspond to selected design colors, such as dominant or important target colors of the design. Again, selection of spot colors is preferably performed by a color expert based on expertise. By way of example, if a 16-color design is to be printed with an eight color ink-jet printer, the color expert may employ his or her color knowledge to determine how many and which design colors should be printed as spot colors. There will typically be the tendency to choose as spot colors the design colors that cover most of the fabric surface, since these colors have the most visual impact. Usually, the four most dominant design colors cover at least 60% of the surface. 
     Once a number of spot colors are selected, a reduced calibrated process color set is selected at step  712 . A reduced calibrated process color set includes the number of process colors as the original calibrated process color set (from step  704 ) reduced by the number of selected spot colors. Thus, if the original calibrated process color set included eight process colors and two spot colors were selected, the reduced calibrated process color set will include six process colors. A number of reduced calibrated process color sets may be stored in memory. Reduced calibrated process color sets are calibrated in the manner described above. 
     At step  714 , a hybrid color set is created that comprises the process colors of the reduced calibrated process color set and the selected spot colors. Then, at step  716 , the differences in color values are determined between the design colors and the predicted colors reachable with the hybrid color set in a process color printing mode. Using the hybrid color set in a process color printing mode may entail using only the process colors in the process color printing mode, or using the process colors in combination with one or more spot colors in the process printing mode. Those skilled in the art will appreciate that the predicted colors that are reachable in the process printing mode using only the process colors may be determined based on information relating to the reduced calibrated process color set. Those skilled in the art will also appreciate that the predicted colors that are reachable in the process printing mode using a combination of process colors and spot colors may be determined based on mathematical calculation and compensation of the information relating to the reduced calibrated process color set. 
     Again, the determination of the differences in color values preferably involves calculations of ΔE values. In a preferred embodiment of the present invention, ΔE values are displayed to the user of the ink-jet printing system via a display device. In this manner, the user may decide whether the difference between each printable color and the corresponding design color is significant enough as to be unacceptable. Of course, the decision as to whether a color value difference is unacceptable may be automated. For example, it is generally accepted in the art that a ΔE value greater than 3 translates into a visibly noticeable difference in color. Therefore, an automated decision may be made such that all ΔE values greater than 3 are considered to be unacceptable. 
     However, it is preferable to allow the user to control this decision because cost or time constraints or other external factors may dictate that a ΔE value of greater than 3 should be considered acceptable. Furthermore, it is also advantageous to provide the user with a display of the design as it would appear if printed with the hybrid color set. The user (color expert) may thus inspect the predicted design colors with the consequent errors side by side with the target design colors. 
     If at step  718  it is determined that the differences in color values between the design colors and the predicted colors reachable with the hybrid color set are acceptable, the design is printed in the hybrid color printing mode at step  720 . Again, printing in the hybrid color mode involves printing selected design colors in spot color mode and printing the remaining design colors in process color mode. 
     If at step  718  it is determined that the differences in color values between the design colors and the predicted colors are not acceptable, the method may return to either step  704 , where another calibrated process color set may be selected, to step  710 , where additional or other spot colors may be selected, or to step  712 , where another reduced calibrated process color set may be selected. The determination of whether to return to step  704 ,  710 , or  712  is preferably made by the color expert based on his/her color expertise. The method  700  is then repeated from either step  704 ,  710 , or  712 , as described above, until the design is printed in a process color mode at step  709  or until the design is printed in a hybrid color mode at step  720 . Subsequent to the design being printed, the exemplary method  700  ends at step  722 . 
     The exemplary hybrid printing method described above makes reference to the fact that a hybrid color set includes spot colors, as well process colors from a calibrated process color set. In accordance with an alternate embodiment of the present invention, a hybrid color set may be comprised entirely of spot colors. Any or all of the ink colors included in the hybrid color set may be used for printing in a spot color mode. In addition, any number of the spot colors in the hybrid color set may be combined in a process color printing mode to produce a gamut of printed colors. 
     As mentioned, printing of the design may first involve a proofing step. When the hybrid color set is loaded onto the ink-jet printing system  100 , a small amount of material (perhaps one repeat) may be printed and reviewed by the textile printing company&#39;s colorist, studio designer and/or customer. The reviewer may request that one or more design colors be slightly modified. In that case, a new color kitchen recipe may be created (determined by textile printing company staff off-line) for a new spot color. The new spot color would be characterized by a new color reference value, which would be encoded on its container as ink data. The new spot color would be added to the hybrid color set as a replacement for either a process color or a spot color. The design data for the design to be printed would also be updated with the new color reference information. 
     With the new hybrid color set and new design data, the Hybrid Color Management program module  90  would be employed to recalculate all process color tolerances and display the design as it would appear with the modified color. Also, the Hybrid Color Management program module  90  would reselect the process colors that would provide optimum color matching, taking into account the new spot color. Once proofing is complete, the ink-jet printing system  100  may be used to deposit the inks onto a fabric or other substrate, which is fed through the ink-jet system by conventional means. 
     While much of the description of the present invention has been directed to textile manufacturing, the present invention may also be used in other industries and with other substrates, such as wall coverings, floor coverings, signage, packaging materials, and labels. For example, as has been discussed previously, currently ink-jet printing systems are used to produce process color when printing color copies of documents. However, these copies are limited in quality and color based upon the lack of ink-jettable colors available for process color. However, by using the color kitchen and the Hybrid Spot/Process Color Management Program module discussed, the present invention is capable of generating hundreds of different colors of ink-jettable inks and, in combination with the hybrid color program module, can use these inks to accurately match thousands of different colors, thereby significantly increasing the usefulness and range of today&#39;s digital printers. Additionally, as printer technology increases further, to increase the number of ink-jet nozzles used, even more colors can be reproduced, thereby increasing the versatility of the present invention in all areas of color printing.