Inkjet printing method using integrated spot color and process color

Abstract

To provide a unique ink color set of a process color and a spot color providing a combination for surprisingly and unexpectedly beneficial performance improvement when being used in an inkjet printing process.SOLUTION: A method for producing a printed image on a substrate includes the steps of: selecting no more than eight process color from a color set of known process ink; providing two or more spot color to form the color set including the process color and the spot color; and optionally printing an image using the formed color set. A ratio of the number of the spot color to the number of the process color is at least 0.5:1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62 / 309,673, filed March 17, 2016, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for printing images using an inkjet printer, and more particularly to a method for producing durable printed images on a substrate using both spot and process colors, and to an inkjet printer for use in the method, a durable ink color set, and a method for extending the color gamut of a process ink color set using both spot and process colors. [Background technology]

[0003] background Inkjet printing systems are widely used in a variety of fields to produce printed images on a variety of substrates. Conventional color inkjet printers use a basic process ink color set, typically containing four to eight process colors, to create the color variations necessary to print a desired image. One well-known process ink color set includes four basic colors: cyan, yellow, magenta, and black, and is called the CMYK color set or CMYK process color method. Generally, the process colors in a process color set are typically combined in varying amounts to produce a variety of printed colors. Typically, in inkjet printers, the CMYK colors are not actually mixed together to form the desired color; instead, very small droplets of different colored inks are deposited adjacent to each other on the page. The human eye tends to blend the individual ink droplets from a distance to create a "mixed" color area. The range of possible colors printed by a printing process is called the process's "color gamut."

[0004] Using these methods, color inkjet printers are generally able to reproduce a sufficient number of colors. In an effort to expand the gamut of the CMYK color set, other process inks are added to produce other process color sets / methods, such as CMYKRGB and CMYKOG. Unfortunately, the gamut of most of these color sets is much smaller than the range of all colors that can be displayed. The gamut of a process color printer is smaller than the gamut produced by traditional printing presses, such as offset, flexographic, gravure, and screen printing presses. For example, flesh-tone colors are not easily produced using the CMYK color method, nor are fluorescent and metallic colors.

[0005] Additionally, many specialty colors cannot be easily created using traditional process ink color sets. Some specialty colors are also called spot colors (also known as house colors or brand colors). These spot colors are typically customer-specific multi-pigmented colors associated with a particular company, product, and / or brand name. Spot colors are generally created at the molecular level and are constructed by bending the tints, hues, and shades of various colors. Examples include Kodak®, IBM®, and others. This includes the precise hues of red and yellow used in Coca-Cola Blue® or Coca-Cola Red. Traditional ink color sets generally cannot reproduce the vividness of spot colors. This is because, unlike spot color printing, which involves applying a single area of ​​premixed spot color, all colors in traditional process printing overlap. This is because the colors are composed of dots of process inks that are used in combination. CMYK inkjet printers encounter processing problems when trying to achieve some of these special colors. Also, because there can be slight differences between CMYK ink lots, even if a special color ink is obtained once, it may not be possible to achieve it after another ink lot is used. Therefore, the color gamut provided by conventional ink color sets leaves much room for improvement.

[0006] In addition to color gamut defects, conventional ink color sets / methods produce printed images that are insufficient for various applications. For example, process ink image durability is known to be an issue. Particularly for applications involving large-scale signage, such as outdoor signage like traffic signs, printed images produced from conventional ink color sets are known to fade over time, exhibit reduced reflectance, day-to-night color variations, and / or exhibit other visual qualities, such as a decrease in color vividness and color contrast. These parameters are particularly relevant to traffic signs due to the strict regulations regarding traffic signs. Furthermore, conventional images are said to suffer from consistency issues. That is, these images exhibit defects such as color banding and other types of color variations. In some cases, these types of defects are difficult to recognize initially due to the composition of the process color inks used.

[0007] Also, conventional printers may contain several process color channels and a small number of spot color channels (compared to the number of process color channels). If spot colors need to be added (as is often the case), one or more spot color channels must be washed out with a cleaning solvent (often referred to as a long-term archiving process). The long-term archiving process takes a long time and generates a lot of waste in ink and cleaning solvent. Additionally, increased use of cleaning solvents has a significant negative impact on the lifespan of the printer.

[0008] U.S. Patent Application Publication No. 2012 / 0090488 discloses that spot colors can be used to reproduce expensive brand colors to supplement traditional process colors for printed images and packaging. The publication also discloses that a printing press can use spot colors and high-fidelity process inks (at least three native colors and black) to print a single brand color and overlay it on other colors to produce wide color gamut, halftone color reproduction. The publication further discloses a method for printing a logo on a substrate, including (i) printing the spot color using spot inks and (u) printing the remainder of the image using the substituted original process ink set. Such a method may alternatively include the steps of (in) [sic] reading the spectral characteristics of the inks, (iv) determining whether any colors in the image can be identified by the color management method from the palette of the default process ink set, (v) processing the out-of-palette colors using spot colors and the standard process ink set, and (vi) applying tone scale value increments (TVIs) to the process color set. However, the publication only focuses on issues related to extending the color gamut of conventional ink color sets, and does not address durability, consistency, control, or printer lifespan, etc.

[0009] Other references also relate to extending the color gamut of traditional ink color sets and methods, many of which add process inks to existing color sets, and some of which use process colors in an attempt to simulate spot colors. Some references include U.S. Patent No. 6,717,699, U.S. Patent No. 7,004,562, U.S. Patent No. 7,032,517, U.S. Patent No. 8,955,940, and U.S. Patent Application Publication Nos. 2015 / 0158317 and 2015 / 0339552. However, these references do not address the extended color gamut process. There is no mention of integrating spot colors into the process set.

[0010] While references may teach the use of modified ink color sets to expand color gamut, there remains a need for improved ink color sets and methods therefor that provide a beneficial combination of significant further color gamut expansion as well as improvements in printed image durability, printed image consistency, control, and printer longevity (reduction / elimination of long-term archiving processes). Summary of the Invention [Means for solving the problem]

[0011] In one embodiment, the present invention relates to a method for producing a printed image (or forming a color set) on a substrate. The method includes the steps of selecting eight or fewer process colors from a known process ink color set, providing two or more spot colors, and forming a color set including the process colors and the spot colors, wherein the ratio of the number of spot colors to the number of process colors is at least 0.5:1, and optionally the number of spot colors is equal to or greater than the number of process colors. Optionally, the method includes printing an image using the formed color set, preferably using at least one process color and / or at least one spot color of the color set. In some cases, one or more spot colors correspond to an unselected member of the known process ink color set. Some of the spot colors may correspond to an unselected member of the known process ink color set. In some embodiments, the provided spot colors include additional spot colors, and the additional spot colors do not correspond to an unselected member of the known process ink color set. The selecting step may include selecting three or fewer process colors from the known process ink color set. In some cases, the formed color set includes at least four colors, optionally three or fewer colors comprising process colors, and optionally two or more colors comprising spot colors. In one embodiment, the formed color set includes at least five spot colors, or six spot colors and two process colors. Preferably, the spot colors include at least one of spot yellow and spot black. The ratio of the number of spot colors to the number of process colors can be at least 1:1. The printed image can have an outdoor weatherability of at least 5 years (when used with a suitable overlay film). The formed color set can have a color gamut with at least 10% more units than a known process ink color set, where units are measured using Colorthink Pro 3.0.The formed color set can have a color gamut of at least 200,000 units. Preferably, printing is performed using a driver that recognizes each spot color as a corresponding member of a color set of known process inks, and the driver further distinguishes each spot color from its respective corresponding member of the color set of known process inks (using colors appropriately). The present invention also relates to printed images produced by the method of the present invention.

[0012] In one embodiment, the present invention relates to an inkjet printer. The printer includes color channels, e.g., at least three color channels, each containing a respective color. Six or fewer, e.g., three or fewer, channels can contain process colors, and two or more, e.g., at least five, channels can contain spot colors. The ratio of the number of spot colors (or channels containing spot colors) to the number of process colors (or channels containing process colors) can be at least 0.5:1. The number of spot colors may be equal to or greater than the number of process colors. Preferably, the printer includes at least six channels, with three or fewer colors constituting the process colors and two or more colors constituting the spot colors, e.g., printer. The printer includes six channels containing spot colors, optionally including spot yellow and spot black, and two channels containing process colors. The ratio of channels containing spot colors to channels containing process colors can be at least 1:1. The process colors can be members selected from a color set of known process inks. Preferably, the printer includes a driver, and the printer may not include subtanks.

[0013] The present invention also relates, in some embodiments, to a method for printing a durable image on a traffic sign, comprising providing a color set. The color set comprises six or fewer process colors and two or more spot colors. The number of spot colors may be equal to or greater than the number of process colors. The ratio of the number of spot colors to the number of process colors may be at least 0.5:1. The method further comprises printing an image using the color set, wherein the printed image may have the characteristics described herein. The formed color set may have a color gamut as described herein.

[0014] The present invention also relates to a method for generating a durable ink color set, including the steps of: 1) identifying a known process ink color set including at least four colors; 2) selecting two or more process colors from the known process ink color set; and 3) substituting each selected process color with a spot color corresponding to the respective process color to form an improved ink color set. The ratio of the number of substitute spot colors to the number of process colors in the improved ink color set can be at least 0.5:1. The present invention also relates to a method for expanding the color gamut of a process ink color set including at least one process color. The method can include the steps of providing a known process ink color set including at least one process color and combining the at least one process color with two or more spot colors to form the improved ink color set. In the improved ink color set, the ratio of the number of spot colors to the number of process colors can be at least 0.5:1. The improved ink color set has a color gamut as described herein. The method may further include selecting one or more colors from the process ink color set and substituting each selected process color with a spot color corresponding to the respective process color to form an improved ink color set.

[0015] The present invention also relates to a method of producing a printed image on a substrate, comprising the steps of providing a color set and printing the image using the color set. The color set may include up to six process colors and two or more spot colors, and the ratio of the number of spot colors to the number of process colors may be at least 0.5:1. The printed image may have the characteristics described herein. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a CIELAB diagram showing the color gamut of a conventional CMYK color set relative to the color gamut of the ink color set / method of the present invention. [Figure 2] FIG. 1 illustrates the color gamut of a conventional CMYK color set relative to the color gamut of the ink color set / method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] overview The present invention relates to a unique ink color set of process and spot colors that, when used in inkjet printing processes, provides a surprising and unexpectedly beneficial combination of improved performance. These benefits include significant additional color gamut expansion as well as improved printing performance. These include improvements in image durability (weather resistance), print image consistency, and printer lifespan. The present invention also provides improved printer spot color printing performance, such as the ability to use more spot colors than conventional printers, e.g., two or more spot colors, three or more spot colors, four or more spot colors, five or more spot colors, or six or more spot colors. While some conventional ink color sets use one or two spot colors along with some process colors to achieve slight improvements in color gamut expansion, these conventional color sets cannot achieve the above combination of advantageous improvements.

[0018] Typically, color inkjet printers use a basic process ink color set to combine various amounts of each process color to produce a range of printed colors, commonly referred to as the "color gamut." In recent years, efforts have been made to expand the color gamut for printed images and packaging by using spot colors that reproduce expensive brand colors to supplement traditional process colors (see, for example, U.S. Patent Application Publication No. 2012 / 0090488). In this case, (a small number of) spot colors are added to a known process ink color set and used in place of the process color combination previously used to mimic the spot color. However, these recent efforts primarily teach the use of only one or two spot colors, specifically, spot red and spot orange, to supplement a process color set, e.g., a CMYKOG color set. Thus, two spot colors and four process colors are used. Furthermore, the references make no mention of spot colors or the combination of spot colors and process colors in terms of overall printed image durability (outdoor weatherability), printed image consistency, control, and / or printer lifespan. Importantly, the relationship between the number of spot colors and the number of process colors in an ink color set / method, and the impact of such relationship on the characteristics of the printed image, is not explored or explained in the reference(s).

[0019] Ink color set and printing process It has now been discovered that, in addition to expanding the color gamut, the use of ink color sets containing a large number of spot colors (in inkjet printing processes) has a beneficial effect on the properties of the resulting printed image, such as durability. Furthermore, the durability of process ink images is known to be problematic. Conventional printed images are known to fade over time, exhibit reduced reflectance, change color between day and night, and / or exhibit other reductions in visual quality, such as color contrast and color vividness.

[0020] By using more colors and process colors in a ratio of at least 0.5:1, and optionally using an ink color set in which the number of spot colors is equal to or greater than the number of process colors, a more durable image can be produced. This type of durable image can be particularly advantageous when used in applications involving large signage, such as outdoor signage such as traffic signs. Durability is particularly relevant to traffic signs because of the strict regulations. Without being limited by theory, it is believed that the use of a greater amount of spot colors and the actual composition of the spot colors contributes to improved performance characteristics of the image. For example, the spot colors can contain more stable pigments (compared to the pigments of the process colors) and / or UV stabilizers, which can contribute to improved performance characteristics of the image.

[0021] In addition to durability benefits, the ink color sets and methods of the present invention provide unexpected improvements in the consistency of printed images. Traditional images, for example, those printed using process ink color sets such as CMYK, suffer from defects such as color streaks and other types of color variations. This can cause defects. In some cases, these types of defects are initially difficult to recognize due to the printing process (overlay of process ink spots) and / or the actual makeup of the process color inks used. However, using the ink color sets and methods of the present invention, defects such as color streaks and other types of color variations are much easier to recognize. Without being limited by theory, it is believed that defects are more noticeable because more spot colors are printed directly (e.g., not overlaid). This improved recognition beneficially improves the consistency and quality control of printed images. Additionally, the inventors have found that better image control is provided by using the ink color sets of the present invention due to the improved ease of adjusting the properties and opacity of the spot colors. In some cases, the large number of spot colors in the ink color sets of the present invention can be easily printed by setting the opacity (coverage) percentage to provide a monochrome (single) color print. In contrast, conventional process color sets often rely on pre-set profiles that must be calibrated on each specific substrate sheet. These beneficial combinations of image performance characteristics achieved by the ink color sets and methods of the present invention were unexpected.

[0022] Additionally, by using spot colors and process colors as described herein, the ink color sets and methods of the present invention provide surprising improvements in printer life and overall process efficiency, e.g., inks and / or wash solvents. This is particularly useful when many spot colors are required to print an image. In these cases, substituting spot colors for process colors provides advantages with printer life by allowing more spot colors to be used in the color set, reducing / eliminating the need for long-term archiving processes. As noted above, the reference(s) fail to recognize the impact of spot colors, or the combination of spot colors and process colors, on the resulting image.

[0023] Thus, in one embodiment, the present invention relates to a method for producing a printed image on a substrate. The method includes the steps of selecting eight or fewer process colors from a color set of known process inks, e.g., seven or fewer, six or fewer, five or fewer, four or fewer, three or fewer, or two or fewer, and providing one or more spot colors, e.g., two or more, three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more, and forming a color set. The color set includes the (selected) process colors and the (provided) spot colors. In one embodiment, the formed color set includes a total of at least three colors (combining the process colors and the spot colors), e.g., at least four, at least five, at least six, at least seven, or at least eight colors. The method may further include printing an image using the formed color set. However, in some cases, the method of the present invention includes forming the color set and / or a printer in which the color set is used, regardless of whether an image is printed. Preferably, the printing of the image uses at least one process color and / or at least one spot color of the color set. The present invention also contemplates printed images formed using the ink color sets / methods of the present invention. As described herein, using an ink color set that includes more spot colors than process colors provides an unexpected combination of benefits.

[0024] Generally speaking (and in the embodiments described herein), the ratio of the number of spot colors to the number of process colors can be at least 0.5:1, e.g., at least 1:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at least 4:1, or at least 5:1. In some cases, the ratio of the number of spot colors to the number of process colors is greater than 0.5:1, e.g., greater than 1:1, greater than 1.5:1, greater than 2:1, or greater than 2.5:1. , greater than 3:1, greater than 4:1, or greater than 5:1. In some cases, the number of spot colors in the formed color set may be greater than (or optionally equal to) the number of process colors. These limitations and ranges are applicable to the color sets / processes described herein.

[0025] Known process ink color sets can be very diverse. A known process ink color set can include any number of known process colors, for example, one or more, two or more, three or more, or four or more. Numerous process ink color sets have been in use for some time. Examples include the CMYK, CMYKOG, CMYKRGB, and CcMmYK color sets (where "c" and "m" represent lighter shades of cyan and magenta, respectively). This list is not intended to be limiting. Broadly speaking, a known process ink color set can be any color set that includes known process colors. In one embodiment, a known process ink color set does not include any spot colors. In one embodiment, a known ink color set is a CMYK color set.

[0026] One important feature of the present invention is the use of a large number of spot colors, preferably a larger number (compared to the number of process colors). For example, the ratio of the number of spot colors to the number of process colors can be as described herein. Numerous combinations of spot colors and process colors are possible, as long as the ratio of the number of spot colors to the number of process colors is at least 0.5:1 (greater than 0.5:1). For example, a formed color set can include two spot colors and one process color; three spot colors and one process color; three spot colors and two process colors; four spot colors and one, two, or three process colors; five spot colors and one, two, three, or four process colors; or six spot colors and one, two, three, four, or five process colors. Preferably, a formed color set includes five spot colors and three process colors, or six spot colors and two process colors.

[0027] In some preferred embodiments, the spot color(s) correspond to one of the unselected members of the known process ink color set. Thus, in contrast to simply adding the spot color to the known process ink color set (where both the spot color and the corresponding process color are present in the color set), the spot color substitutes for one or more of the colors originally present in the known process ink color set, e.g., the spot color replaces the respective process color. In the method of the present invention, the spot color is used as both a spot color and a process color. In preferred embodiments, at least some spot colors are provided as both the respective spot color and the substituted process color during a printing run. If the associated process color was previously used, the respective spot color is used. For example, if the known process ink color set is a CMYK color set, Y and / or K color can be substituted with spot yellow and / or spot black. Then, during a printing run, spot yellow is used as both spot yellow and Y, and spot black is used as spot black and K. The inventors have found that the color gamut can be advantageously expanded by substituting some spot colors for the corresponding process colors. Without being limited by theory, it is believed that spot colors can have a higher degree of color depth. Thus, increasing the color depth provides greater depth in the colors formed through combinations using these spot colors (in an inkjet printing process). In some embodiments, the ink color set includes one or more additional spot colors in addition to the spot color(s) corresponding to one of the unselected colors. Includes color.

[0028] It is noted that transparency can be an issue when using spot colors as process colors. Generally, brand color inks are not tested for transparency because they are not used in process sets. Typically, process inks must be transparent to reveal the underlying color so as to form a two-color overprint. Therefore, in an exemplary embodiment of the present invention, when substituting a spot color for a process color, the spot color ink can be made sufficiently transparent to facilitate the use of overprints.

[0029] In one embodiment, the spot colors of the ink color set include at least one of spot yellow and spot black (spot yellow and / or spot black). The inventors have made the surprising discovery that including spot yellow and / or spot black in an ink color set provides a significant expansion of the color gamut. Without being limited by theory, it is believed that the spot black color has more color depth, and this color depth blends particularly well with spot yellow and other process colors.

[0030] In some cases, use of the ink color sets / methods of the present invention provides an expansion of a printer's capabilities to print multiple spot colors. For example, by using the ink color sets of the present invention, spot color printing capabilities, e.g., the ability to print multiple spot colors, are significantly expanded, e.g., by at least 10%, at least 25%, at least 40%, at least 50%, at least 75%, or at least 100%. In some cases, spot colors may occupy more than two channels of an eight-channel printer, e.g., four or more, five or more, or six or more. This capability is highly desirable in the traffic sign industry, as it allows more spot colors to be printed without having to physically increase the number of ink channels.

[0031] In some cases, the ink color set formed has a color gamut volume of at least 200,000 units, e.g., at least 225,000, at least 250,000, at least 275,000, at least 300,000, at least 325,000, at least 350,000, at least 375,000, at least 400,000, at least 425,000, at least 450,000, at least 475,000, at least 500,000, at least 525,000, at least 550,000, at least 575,000, at least 600,000, at least 650,000, or at least 700,000 units, when measured using a ColorThink Pro 3.0 imaging software system, available from CHROMiX, Inc. (Seattle, Washington), a well-known system used to measure color gamut. In terms of range, the ink color set formed has a gamut volume in the range of 200,000 units to 1,000,000 units, e.g., 300,000 units to 900,000 units, 450,000 units to 900,000 units, 450,000 units to 750,000 units, 500,000 units to 700,000 units, 500,000 units to 600,000 units, or 525,000 units to 575,000 units.

[0032] In one embodiment, the ink color set formed may have at least 10%, e.g., at least 20%, at least 25%, at least 30%, at least 35%, at least 37%, at least 40%, at least 45%, at least 50%, at least 60%, or at least 75% more unit increase over a similar known ink color set without the required number of spot colors. The improved contrast and reflectance found also make the ink color set highly suitable for use in large sign applications, particularly traffic signs. The discussion regarding the measurement of expansion is applicable to ink color sets and method and printer embodiments of the present invention.

[0033] In some cases, the ink color sets formed provide color gamuts with similar numerical ranges and limits, but the CIELAB system (and CIELAB units) can be used.

[0034] 1 and 2 also illustrate the color gamut expansion demonstrated by the color set of the present invention compared to a conventional CMYK color set. In particular, FIG. 1 compares the gamut comparison of a conventional CMYK color set with an improved color set using two spot colors in accordance with the present invention as substitutes for their respective process colors on a CIELAB diagram. The darker lines represent the gamut of the conventional CMYK color set. The lighter lines represent the gamut of the color set of the present invention. As shown, the new color set represents a 37% increase in overall color gamut. While there may be slight losses in some color regions in some cases, the surprisingly beneficial expansion of the gamut in other regions outweighs the slight color loss.

[0035] Figure 2 is a plot using another imaging system, the ColorThink Pro 3.0 system. Figure 2 compares a conventional CMYK color set with an improved color set in accordance with the present invention, which uses two spot colors as substitutes for each process color. In Figure 2, the lighter lines represent the gamut of the conventional CMYK color set. The darker (thicker) lines represent the gamut of the color set of the present invention.

[0036] In some cases, the printing process of the present invention uses a driver that recognizes the colors of a color set to facilitate printing operations. Preferably, the driver recognizes each spot color as a corresponding member of a known process ink color set and is able to distinguish each spot color from its respective corresponding member of the known process ink color set. In some cases, the driver is configured to use a spot color as both a process color and a spot color. The driver has the ability (as described herein) to use a spot color as a substitute for a specific process color listed in the design file.

[0037] In other embodiments, some of the spot colors may simply be added to a color set. For example, a spot color may exist with a corresponding member of a process ink set. For example, an ink color set may include a process color C (cyan) along with a spot blue and a spot red. In such an ink color set, the spot blue color is associated with the C process color. In other cases, some of the spot colors may not be associated with any of the process colors in the process ink set. For example, an ink color set may include process colors C and M (magenta) along with a spot black, a spot yellow, and a spot white. In such an ink color set, the spot colors are not directly associated with the C and M process colors.

[0038] In some embodiments, the present invention relates to methods for printing particularly durable images on traffic signs. As noted above, printing standards and regulations for large signs are much more stringent than for printing on other substrates, such as textiles or packaging. These methods may include providing an ink color set(s) as described herein, for example, an ink color set including six or fewer process colors and two or more spot colors. The number of spot colors may be greater than the number of process colors, and / or the ratio of the number of alternative spot colors to the number of process colors in the improved ink color set may be greater than the number of process colors in the present invention. The method may be as described herein. The method further includes printing an image using the color set, for example by using at least one process color and at least one spot color of the color set.

[0039] In one embodiment, the image is printed using at least one of spot yellow and spot black (spot yellow and / or spot black). In addition to the advantages discussed above for these colors (among others), the use of spot yellow and spot black offers certain advantages for outdoor signage. For example, the use of spot yellow and / or spot black allows for an expanded color gamut in certain areas that are advantageous for signage, such as highly visible colors.

[0040] In some embodiments, particularly with respect to printing traffic signs, the use of spot colors allows for the use of more spot colors in a printer. In printing traffic signs, there are at least four different (primary) spot colors, including green (or Warboy green), red, blue, and brown in the traffic sign industry. The number of ink channels in a printer may be limited, for example, there may be fewer than 10 channels. For printers with fewer than 10 ink channels, it may be difficult to print all the primary spot colors together with process colors, for example, CMYK. By substituting some process ink channels, the printing performance of spot colors can be significantly improved as described herein.

[0041] The present invention also relates to a durable ink color set and a method for generating the same. The method may include identifying a known process ink color set including at least four colors. The known process ink colors are described herein. In some embodiments, the method includes selecting one or more, e.g., two or more, process colors from the known process ink color set and substituting spot colors for each selected process color to form an improved ink color set. The spot colors may correspond to each process color. In these methods, the known ink set is modified to substitute process inks with spot colors similar to the process inks to be replaced. For example, starting with a known CMYK system, C, Y, and K process colors may be substituted with spot blue, spot yellow, and spot black colors. Preferably, the number of substituted spot colors relative to the number of process colors in the improved ink color set is as described herein. Substituting process inks with spot inks provides the unexpected advantages described herein.

[0042] In some cases, substitution includes identifying one or more process colors selected for substitution and determining corresponding substitute spot colors, which are then substituted for the selected process colors, e.g., the substitute spot color(s) substituting for the selected process color(s) to form an improved ink color set (as described herein).

[0043] The present invention also contemplates expanding the color gamut of a known process ink color set, e.g., a process ink color set that includes at least one (original) process color. The method may include providing a known process ink color set and combining two or more spot colors with the process color(s) to form an improved color ink set. The ratio of the number of spot colors to the number of process colors in the improved ink color set is as described herein. The combination of spot colors and process colors unexpectedly allows for significant expansion of the color gamut. These expansions are quantified and described herein.

[0044] Combining process and spot colors can be achieved using the methods / techniques described herein.

[0045] In one embodiment, the present invention generally relates to a method for producing a printed image on a substrate. The method includes providing a color set including six or fewer process colors and two or more spot colors, where the ratio of the number of spot colors to the number of process colors is as described herein. The method further includes printing an image using the color set, e.g., using at least one process color and at least one spot color of the color set.

[0046] Generally speaking, the method steps described herein can be used in combination with other steps, features, and / or characteristics described herein. Similarly, the color ink set features and characteristics described herein can be combined with other features and characteristics described herein.

[0047] Inkjet printer In addition to the above-described methods and color sets, the present invention also relates to an inkjet printer. The inkjet printer includes, among other components, multiple color channels, e.g., at least three channels, at least four channels, at least five channels, at least six channels, at least seven channels, at least eight channels, at least nine channels, or at least ten channels. Each channel includes or is associated with a respective ink or ink color. A channel may hold or contain a respective ink used to generate an image. Six or fewer channels, e.g., five or fewer, four or fewer, three or fewer, or two or fewer channels, include process colors. In preferred embodiments, four, three, or two channels include process colors. Two or more channels, e.g., three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more channels, include spot colors. The number of channels containing spot colors (and thus the number of spot colors used by the printer(s)) can be greater than the number of channels containing process colors (and thus the number of process colors used by the printer(s)). In some cases, the ratio of channels containing spot colors to channels containing process colors is as described herein with respect to the number of spot and process colors. By using more spot color channels, the printer of the present invention provides a surprising improvement in printer life and overall process efficiency. For example, in many applications, more spot colors are required to print an image. Because the printer of the present invention uses a greater number of spot color channels, the need to replace channels, e.g., by removing one spot color and substituting another, is minimized or reduced. Therefore, the waste of ink and cleaning solvents required for channel replacement (a long-term storage process) is also minimized or reduced. Furthermore, the use of aggressive cleaning solvents can be reduced, with attendant benefits in printer life.

[0048] In some embodiments, a stable printing system can be provided using known printing processes, where spot colors can be printed in a tone scale of vignettes as solids for logos and brand names, providing high fidelity color images (with process colors). In some of these embodiments, changes to a given print job will only require changes to the print stations with other spot colors included in the next print job.

[0049] In some preferred embodiments, the printer includes at least six channels, with three or fewer colors comprising process colors and two or more colors comprising spot colors, and preferably the printer includes six channels comprising spot colors and two channels comprising process colors.

[0050] In one embodiment, the spot color channel includes at least one of spot yellow and spot black (spot yellow and / or spot black), and thus the printer of the present invention provides the advantages described above with respect to these colors (among others).

[0051] The process colors, in some embodiments, are selected from a color set of known process inks, some of which are described herein.

[0052] The printer of the present invention may further include a driver, which may operate as described herein. In addition to the color channels, the printer of the present invention may further include other well-known printer components, such as, for example, cartridge adapters, dryers, etc.

[0053] In one embodiment, the printer of the present invention does not include subtanks. Subtanks are generally containers known to function as reservoirs for storing a quantity of ink (in addition to the ink stored in the cartridge). Typically, each channel has a subtank associated with it. In some cases, the subtank(s) allow the printer to continue printing images when one or more channels are low for a respective ink cartridge. The printer is configured to send an alert when each channel is low for a respective ink. The subtank(s) allow the printer to continue printing when one or more channels are low for an ink. However, subtank(s) require significant space in the printer assembly. Also, subtank(s) increase waste during long-term storage processes, particularly due to ink loss. Because the printer of the present invention effectively uses spot colors as described, the long-term storage process is reduced or eliminated, and the increased waste associated with subtank(s) can be advantageously avoided.

[0054] Performance characteristics Use of the ink color sets / methods of the present invention provides significant improvements, particularly in color gamut expansion, process efficiency, and printed image quality.

[0055] Because the ink color sets of the present invention are used to print images, the printed images generally have improved durability. For example, the printed images can have an outdoor weatherability of at least 5 years, e.g., at least 5.5 years, at least 6 years, at least 6.5 years, at least 7 years, at least 7.5 years, at least 8 years, at least 8.5 years, at least 9 years, at least 10 years, at least 12 years, at least 14 years, or at least 15 years, when a suitable overlay film is used with the printed image.

[0056] In some embodiments, color differences are significantly reduced using the ink color sets / methods of the present invention. One way to quantify these differences is ΔE, a known description of color difference (often in the CIELAB color space). The change can be measured before and after durability or weathering tests, and ΔE can be calculated from the before and after measurements.

[0057] For example, when tested, the printed image (or durability) formed by the method of the present invention The image (with the image) may have a ΔE of less than 5.0, e.g., less than 4.75, less than 4.5, less than 4.25, less than 4.0, less than 3.75, less than 3.5, less than 3.25, less than 3.0, less than 2.75, less than 2.5, less than 2.25, less than 2.0, less than 1.75, less than 1.5, less than 1.0, less than 0.75, less than 0.5, or less than 0.25. In a preferred embodiment, ΔE is less than 3.5. The test may be xenon weathering (XePVL) for a specific time period, e.g., 4,000 hours, as defined by ASTM G155-13 or ASTM D4956-13 (2016 or current year).

[0058] In certain embodiments, the dark green image formed by the methods of the present invention has a ΔE of less than 3.75, e.g., less than 3.5, less than 3.25, less than 3.0, less than 2.75, less than 2.5, less than 2.25, less than 2.0, less than 1.75, less than 1.5, less than 1.0, less than 0.75, less than 0.5, or less than 0.25, when tested under xenon weathering conditions as described herein.

[0059] In other embodiments, the green image formed by the methods of the present invention has a ΔE of less than 3.75, e.g., less than 3.5, less than 3.25, less than 3.0, less than 2.75, less than 2.5, less than 2.25, less than 2.0, less than 1.75, less than 1.5, less than 1.0, less than 0.75, less than 0.5, or less than 0.25, when tested under xenon weathering conditions as described herein.

[0060] In other embodiments, the yellow image formed by the methods of the present invention has a ΔE of less than 3.5, e.g., less than 3.25, less than 3.0, less than 2.75, less than 2.5, less than 2.25, less than 2.0, less than 1.75, less than 1.5, less than 1.0, less than 0.75, less than 0.5, or less than 0.25, when tested under xenon weathering conditions as described herein.

[0061] Printing Process The structure of the printing step used in the method of the present invention can vary greatly. The art is replete with teachings regarding the printing process itself. Examples are disclosed in U.S. Patent No. 6,637,860, the entire contents of which are incorporated herein by reference.

[0062] Example Example 1 A dark green image was printed using a color ink set in accordance with the present invention. The color ink set included Process C and M along with spot yellow and spot black. A comparative image was produced in a similar manner, but using a conventional CMYK color ink set. The printed dark green image of the present invention had a ΔEof of 2.4 after 4,000 hours of xenon weathering as determined by ASTM G155-13 and ASTM D4956-13 (2016 or current year). In contrast, a comparative image tested under the same conditions had a ΔEof of 3.5.

[0063] Example 2 A green image was printed using a color ink set in accordance with the present invention. The color ink set included Process C and M along with spot yellow and spot black. A comparative image was produced in a similar manner, but using a conventional CMYK color ink set. The printed green image of the present invention had a ΔEof of 3.1 after 4,000 hours of xenon weathering as determined by ASTM G155-13 and ASTM D4956-13 (2016 or current year). In contrast, a comparative image tested under the same conditions had a ΔEof of 3.5.

[0064] Example 3 A yellow image was printed using a color ink set in accordance with the present invention. The color ink set included Process C and M along with spot yellow and spot black. A comparative image was produced in a similar manner, but using a conventional CMYK color ink set. The printed yellow image of the present invention had a ΔEof of 3.1 after 4,000 hours of xenon weathering as determined by ASTM G155-13 and ASTM D4956-13 (2016 or current year). In contrast, a comparative image tested under identical conditions had a ΔEof of 3.5.

[0065] The following embodiments are possible: All combinations of features and embodiments are possible. Embodiment 1: A method for producing a printed image (or generating a color set) on a substrate, comprising the steps of selecting eight or fewer process colors from a color set of known process inks, providing two or more spot colors, and forming a color set comprising the process colors and the spot colors, wherein the ratio of the number of spot colors to the number of process colors is at least 0.5:1, and the method further comprises optionally printing an image using the formed color set.

[0066] Embodiment 2: The embodiment of embodiment 1, wherein one or more of the spot colors corresponds to one of the unselected members of a color set of known process inks.

[0067] Embodiment 3: An embodiment according to any one of embodiments 1 and 2, wherein the provided spot colors include an additional spot color, and the additional spot color does not correspond to one of the non-selected members of the color set of known process inks.

[0068] Embodiment 4: The embodiment of any one of embodiments 1 to 3, wherein some of the spot colors correspond to unselected members of a color set of known process inks.

[0069] Embodiment 5: An embodiment according to any one of embodiments 1 to 4, wherein the printing step includes printing the image using at least one process color and / or at least one spot color of the color set.

[0070] Embodiment 6: The embodiment of any one of embodiments 1 to 5, wherein the selecting step includes selecting no more than three process colors from a color set of known process inks.

[0071] Embodiment 7: The embodiment of any one of embodiments 1-6, wherein the formed collar set comprises at least four collars.

[0072] Embodiment 8: The embodiment of any one of embodiments 1 to 7, wherein three or fewer colors comprise process colors and two or more colors comprise spot colors.

[0073] Embodiment 9: The embodiment of any one of embodiments 1 to 8, wherein the formed color set includes at least five spot colors.

[0074] Embodiment 10: The embodiment of any one of embodiments 1 to 9, wherein the formed color set includes six spot colors and two process colors.

[0075] Embodiment 11: The embodiment of any one of embodiments 1 to 10, wherein the spot color includes at least one of spot yellow and spot black.

[0076] Embodiment 12: The embodiment of any one of embodiments 1 to 11, wherein the ratio of the number of spot colors to the number of process colors is at least 1:1.

[0077] Embodiment 13: The embodiment of any one of embodiments 1-12, wherein the printed image has an outdoor weather resistance of at least 5 years.

[0078] Embodiment 14: The embodiment of any one of embodiments 1 to 13, wherein the formed color set has a color gamut of at least 200,000 units as measured using Colorthink Pro 3.0.

[0079] Embodiment 15: An embodiment described in any one of embodiments 1 to 14, wherein the formed color set has a color gamut with at least 10% more units than the color set of known process inks, the units being measured using Colorthink Pro 3.0.

[0080] Embodiment 16: An embodiment described in any one of embodiments 1 to 15, wherein the printing step uses a driver, the driver recognizes each spot color as a corresponding element of a color set of known process inks, and the driver distinguishes each spot color from its respective corresponding element of the color set of known process inks.

[0081] Embodiment 17: A printed image produced through the method according to any one of embodiments 1 to 16.

[0082] Embodiment 18: An inkjet printer comprising color channels each containing a respective color, wherein six or fewer channels contain process colors and two or more channels contain spot colors, and wherein the ratio of channels containing spot colors to channels containing process colors is at least 0.5:1.

[0083] Embodiment 19: An embodiment according to embodiment 18, wherein the printer includes at least three color channels.

[0084] Embodiment 20: The embodiment of any one of embodiments 18-19, wherein three or fewer channels include process colors.

[0085] Embodiment 21: An embodiment according to any one of embodiments 18 to 20, wherein the printer includes at least six channels, three or fewer colors constituting process colors and two or more colors constituting spot colors.

[0086] Embodiment 22: An embodiment according to any one of embodiments 18 to 21, wherein the ratio of channels containing spot colors to channels containing process colors is at least 1:1.

[0087] Embodiment 23: An embodiment described in any one of embodiments 18 to 22, wherein at least five channels include spot colors.

[0088] Embodiment 24: An embodiment according to any one of embodiments 18 to 23, wherein the printer includes six channels containing spot colors and two channels containing process colors.

[0089] Embodiment 25: The embodiment of any one of embodiments 18-24, wherein the spot color includes at least one of spot yellow and spot black.

[0090] Embodiment 26: The embodiment of any one of embodiments 18 to 25, wherein the process color is a member selected from a color set of known process inks.

[0091] Embodiment 27: An embodiment described in any one of embodiments 18 to 26, further comprising a driver.

[0092] Embodiment 28: An embodiment described in embodiment 27, wherein the recognition device recognizes each spot color and uses each recognized spot color as a corresponding unselected member of a color set of known process inks.

[0093] Embodiment 29: The embodiment according to any one of embodiments 18 to 28, wherein the printer does not include a sub-tank.

[0094] Embodiment 30: A method for printing a durable image on a traffic sign, comprising providing a color set including six or fewer process colors and two or more spot colors, wherein the ratio of the number of spot colors to the number of process colors is at least 0.5:1, and further comprising printing an image using the color set, wherein the printed image has an outdoor weather resistance of at least 5 years.

[0095] Embodiment 31: The embodiment of embodiment 30, wherein the printing step includes printing the image using at least one process color and / or at least one spot color of the color set.

[0096] Embodiment 32: An embodiment described in any one of embodiments 30 and 31, wherein the two or more spot colors include at least one of spot yellow and spot black.

[0097] Embodiment 33: The embodiment of any one of embodiments 30 to 32, wherein the formed color set has a color gamut of at least 200,000 units as measured using Colorthink Pro 3.0.

[0098] Embodiment 34: An embodiment described in any one of embodiments 30 to 33, wherein the formed color set has a color gamut with at least 10% more units than the color set of known process inks, the units being measured using Colorthink Pro 3.0.

[0099] Embodiment 35: A print image generated through any one of embodiments 30 to 34.

[0100] Embodiment 36: A method for generating a durable ink color set, comprising the steps of: 1) identifying a known process ink color set including at least four colors; 2) selecting two or more process colors from the known process ink color set; and 3) substituting each selected process color with a spot color corresponding to the respective process color to form an improved ink color set, wherein the ratio of the number of substituted spot colors to the number of process colors in the improved ink color set is at least 0.5:1.

[0101] Embodiment 37: Alternative spot colors are each a process color and an alternative spot color. 37. The embodiment of embodiment 36, wherein the LA is used for both the LA and the LA.

[0102] Embodiment 38: A method for expanding the color gamut of a process ink color set, comprising the steps of providing a known process ink color set comprising at least one process color, and combining two or more spot colors with the at least one process color to form an improved color ink set, wherein the ratio of the number of spot colors to the number of process colors in the improved ink color set comprising the at least one process color is at least 1:1.

[0103] Embodiment 39: The embodiment of embodiment 38, wherein the improved ink color set has a color gamut of at least 200,000 units as measured using Colorthink Pro 3.0.

[0104] Embodiment 40: An embodiment described in any one of embodiments 38 and 39, wherein the improved ink color set has a color gamut with at least 10% more units than the color set of the known process ink, the units being measured using Colorthink Pro 3.0.

[0105] Embodiment 41: The embodiment of any one of embodiments 38 to 40, further comprising selecting one or more colors from a process ink color set.

[0106] Embodiment 42: An embodiment described in any one of embodiments 38 to 41, further comprising a step of substituting each selected process color with a spot color corresponding to the respective process color to form an improved ink color set.

[0107] Embodiment 43: A printed image produced using the improved color ink set of any one of embodiments 38-41.

[0108] Embodiment 44: A method for producing a printed image on a substrate, comprising providing a color set including six or fewer process colors and two or more spot colors, wherein the ratio of the number of spot colors to the number of process colors is at least 0.5:1, and the method further comprises printing the image using the color set.

[0109] Embodiment 45: The embodiment of embodiment 44, wherein the printed image has an outdoor weatherability of at least 5 years.

[0110] Embodiment 46: A printed image produced using the improved color ink set of any one of embodiments 44 and 45.

[0111] Although the present invention has been described in detail, modifications within the spirit and scope of the present invention will be readily apparent to those skilled in the art. In view of the foregoing discussion, relevant knowledge and references in the art have been set forth above with respect to the background art and specific content of the invention, and all of these disclosures are incorporated herein by reference. It should also be understood that the embodiments and portions of various embodiments of the present invention, and the various features mentioned below and / or the appended claims, may be combined or interchanged in whole or in part. In the above description of various embodiments, embodiments referring to other embodiments may be appropriately combined with other embodiments, as will be understood by those skilled in the art.

Claims

1. 1. A method for generating a color set, comprising: selecting eight or fewer process colors from a color set of known process inks; providing two or more spot colors; forming a color set including the process colors and the spot colors, wherein the ratio of the number of the spot colors to the number of the process colors is at least 0.5:1; and optionally printing an image on a substrate using the formed color set.

2. The method of claim 1 , wherein one or more of the spot colors corresponds to one of the unselected members of the known process ink color set.

3. 3. The method of claim 2, wherein the provided spot colors include an additional spot color, the additional spot color not corresponding to one of the non-selected members of the color set of the known process inks.

4. The method of any one of claims 1 to 3, wherein some of the spot colors correspond to unselected members of the known process ink color set.

5. The method of any one of claims 1 to 4, wherein the printing step comprises printing the image using at least one process color and / or at least one spot color of the color set.

6. The method of any one of claims 1 to 5, wherein the selecting step comprises selecting no more than three process colors from a set of known process ink colors.

7. The method of any one of claims 1 to 6, wherein the formed color set comprises at least four colors.

8. 8. The method of claim 7, wherein three or fewer of said colors comprise process colors and two or more of said colors comprise spot colors.

9. The method of any one of claims 1 to 8, wherein the formed color set comprises at least five spot colors.

10. The method according to any one of claims 1 to 9, wherein the formed color set comprises six spot colors and two process colors.

11. The method of any one of claims 1 to 10, wherein the spot colors include at least one of spot yellow and spot black.

12. The method according to any one of the preceding claims, wherein the ratio of the number of spot colors to the number of process colors is at least 1:

1.

13. The method of any one of claims 1 to 12, wherein the printed image has an outdoor weatherability of at least 5 years.

14. The method of any one of claims 1 to 13, wherein the formed color set has a color gamut of at least 200,000 units measured using Colorthink Pro 3.

0.

15. 15. The method of any one of claims 1 to 14, wherein the formed color set has a color gamut with at least 10% more units than the color set of the known process inks, the units being measured using Colorthink Pro 3.

0.

16. 16. The method of claim 1, wherein the printing step uses a driver that recognizes each spot color as a corresponding member of the known process ink color set, and the driver distinguishes each spot color from its respective corresponding member of the known process ink color set.

17. A printed image produced through the method of any one of claims 1 to 16.

18. An inkjet printer, each containing a color channel containing a respective color; six or fewer of said channels include process colors; two or more of said channels include spot colors; an inkjet printer wherein the ratio of the number of channels containing the spot colors to the number of channels containing the process colors is at least 0.5:1;

19. 20. The printer of claim 18, wherein the printer includes at least three color channels.

20. 20. A printer according to claim 18 or 19, wherein no more than three of the channels comprise process colours.

21. A printer according to any one of claims 18 to 20, wherein the printer comprises at least six channels, no more than three colours constituting process colours and two or more colours constituting spot colours.

22. A printer according to any one of claims 18 to 21, wherein the ratio of channels containing spot colours to channels containing process colours is at least 1:

1.

23. A printer according to any one of claims 18 to 22, wherein at least five of the channels include spot colours.

24. A printer according to any one of claims 18 to 23, wherein the printer comprises six channels containing spot colours and two channels containing process colours.

25. The printer of any one of claims 18 to 24, wherein the spot colors include at least one of spot yellow and spot black.

26. A printer according to any one of claims 18 to 25, wherein the process colours are selected members of a set of known process ink colours.

27. The printer of any one of claims 18 to 26, further comprising a driver.

28. The recognition device recognizes each spot color and compares each of the recognized spot colors with the previous spot color.

28. The printer of claim 27, wherein said known process inks are used as corresponding unselected members of said color set.

29. 1. A method for printing a durable image on a traffic sign, the method comprising: Six or fewer process colors; and two or more spot colors, wherein a ratio of the number of the spot colors to the number of the process colors is at least 0.5:1, the method further comprising: printing an image using said color set; The method wherein the printed image has an outdoor weatherability of at least 5 years.

30. 30. The method of claim 29, wherein the printing step includes printing the image using at least one process color and / or at least one spot color of the color set.

31. 31. The method of claim 29 or 30, wherein the two or more spot colors include at least one of spot yellow and spot black.

32. 32. The method of any one of claims 29 to 31, wherein the color set has a color gamut of at least 200,000 units as measured using Colorthink Pro 3.

0.

33. 33. The method of any one of claims 29 to 32, wherein the color set has a color gamut with at least 10% more units than the color set of the known process inks, the units being measured using Colorthink Pro 3.

0.

34. A printed image produced through the method of any one of claims 29 to 32.

35. 1. A method for producing a durable ink color set, said method comprising: 1) identifying a known process ink color set including at least four colors; 2) selecting two or more process colors from the set of known process ink colors; 3) substituting each selected process color with a corresponding spot color to form an improved ink color set; The method, wherein the ratio of the number of the alternative spot colors to the number of the process colors in the improved ink color set is at least 0.5:

1.

36. 36. The method of claim 35, wherein the alternate spot color is used as both the respective process color and the alternate spot color.

37. 1. A method for extending a color gamut of process ink colors including at least one process color, the method comprising: providing a color set of known process inks including at least one process color; combining two or more spot colors with said at least one process color to form an improved color ink set; A method wherein the ratio of the number of spot colors to the number of process colors in the improved ink color set is at least 0.5:

1.

38. 38. The method of claim 37, wherein the improved ink color set has a color gamut of at least 200,000 units as measured using Colorthink Pro 3.

0.

39. 39. The method of claim 37 or 38, wherein the improved ink color set has a color gamut with at least 10% more units than the known process ink color set, the units being measured using Colorthink Pro 3.

0.

40. 40. The method of any one of claims 37 to 39, further comprising the step of selecting one or more colors from the process ink color set.

41. 41. The method of claim 40, further comprising substituting each selected process color with a spot color corresponding to the respective process color to form the improved ink color set.

42. A printed image produced using the improved color ink set of any one of claims 37 to 41.

43. 1. A method for producing a printed image on a substrate, the method comprising: providing a color set, the color set comprising: Six or fewer process colors; two or more spot colors, wherein the ratio of the number of the spot colors to the number of the process colors is at least 0.5:1, and the method further comprises: and printing an image using said color set.

44. 44. The method of claim 43, wherein the printed image has an outdoor weatherability of at least 5 years.

45. 45. A printed image produced through the method of claim 43 or 44.

Images