Ink composition and printing method

Abstract

To provide a DALI white ink composition which is cured by an LED source, gives a printed matter having acceptable opacity and fastness, and can be successfully transferred to an acceptive base material from an anilox roller, and a method for printing an ink composition.SOLUTION: A white ink composition contains an ink vehicle containing at least one compound selected from an acrylate monomer, a methacrylate monomer, an acrylate oligomer and a methacrylate oligomer, at least one polyol adhesive resin that is solid at 25°C, at least one photoinitiator, and at least one white coloring agent.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a radiation-curable white ink composition that can be used, for example, in digital offset printing processes. [Background technology]

[0002] Ink-based digital printing uses digital offset printing systems, also known as Digital Advanced Lithography Imaging ("DALI") systems. DALI systems are configured to perform lithography printing using lithography inks to form images based on digital image data that can vary from one image to the next. In other words, variable image data is used to generate an image on a substrate that can change with each subsequent rendering of the image on the substrate in the imaging process.

[0003] For example, a digital offset printing process may involve transferring a radiation-curable ink onto a portion of an imaging member, such as an imaging cylinder or printing plate, that is coated with dampening fluid. Areas of the dampening fluid are selectively removed by exposure to a focused radiation source (e.g., a laser light source) to form pockets. In this manner, a temporary pattern of dampening fluid is formed on the imaging member. Ink is then applied to the imaging member and retained in the pockets to form an ink image. The ink surface is then contacted with a substrate, and the ink image is transferred from the imaging member to the substrate. The dampening fluid may then be removed from the imaging member, a new uniform layer of dampening fluid is applied, and the process is repeated.

[0004] Digital offset printing inks differ from traditional inks because they are designed to meet the demanding rheological specifications imposed by the lithographic printing process while being compatible with system component materials and meeting the functional requirements of subsystem components, including wetting and transfer. White inks, in particular, have very high pigment concentrations to achieve relatively high opacity. In addition, white ink applications often require thicker ink layers to cover relatively large areas compared to colored inks. The thicker the ink layer, the more difficult it is to obtain good ink transfer between the anilox roller, the imaging member, and the final substrate. These differences can make meeting the demanding rheological specifications of white inks more challenging than colored inks.

[0005] Previous DALI white ink compositions were often designed for and cured using Hg (D-bulb) light sources. Light-emitting diodes (LEDs), such as those centered around peak central emissions of about 365, 385, 395, and 405 nm, as well as several other LED lamps with peak central emissions below about 365 nm and above about 405 nm, are rapidly replacing Hg curing sources, with LED lamps typically being lower cost, generating less heat, and being more environmentally friendly, among other reasons. However, many conventional DALI ink compositions remain unsuitable for LED curing. There remains a need to develop a DALI white ink composition that can be cured with an LED source and successfully transferred from an anilox roller to a receiving substrate, with the resulting print having acceptable opacity and robustness. Summary of the Invention

[0006] An embodiment of the present disclosure relates to a white ink composition comprising an ink vehicle including at least one compound selected from acrylate monomers, methacrylate monomers, acrylate oligomers, and methacrylate oligomers, at least one polyol adhesive resin that is solid at 25°C, at least one photoinitiator, and at least one white colorant.

[0007] Another embodiment of the present disclosure relates to a method for variable lithographic printing, the method including applying dampening fluid to an imaging member surface, forming a latent image by removing dampening fluid from selective locations on the imaging member surface to form hydrophobic non-image areas and hydrophilic image areas, developing the latent image by applying a white ink composition to the hydrophilic image areas, and transferring the developed latent image to a receiving substrate. The white ink composition includes an ink vehicle including at least one compound selected from acrylate monomers, methacrylate monomers, acrylate oligomers, and methacrylate oligomers, at least one polyol adhesive resin that is solid at 25°C, at least one photoinitiator, and at least one white colorant.

[0008] The white ink of the present disclosure may provide one or more of the following advantages: The ink may be compatible with materials it comes into contact with, including, for example, imaging members, dampening fluids, and other cured or uncured inks. The ink may meet subsystem functional specifications, including providing suitable wetting and transfer properties. The imaged ink may be transferred from the anilox roller to the imaging medium and from the imaging medium to the final substrate. The ink may uniformly wet the blanket material and transfer from the blanket to the substrate. The ink may provide efficient transfer of the imaging layer, such as 90% transfer by weight of the imaging layer. The ink may reduce or prevent ghost images appearing in subsequent prints. The ink may exhibit improved adhesion to certain substrates, such as substrates comprising at least one material selected from biaxially oriented polyethylene terephthalate (commercially available as MYLAR®), biaxially oriented polypropylene ("BOPP"), polyethylene, and other polymers or transparent polymers, compared to otherwise identical inks without the polyol resin additive of the present disclosure. The white ink may provide a tack-free, high-opacity print after curing with UV LED radiation and / or have good chemical resistance. It may provide a non-yellowing composition before and / or after radiation curing. It may also provide an average tack (measured over 10 minutes) ranging from about 55 to about 70 g-m. The ink may provide good anilox roller acceptance and high transfer from the anilox roller to a receiving substrate such as a transparent polymer substrate (e.g., a MYLAR substrate).

[0009] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present teachings, as claimed. [Brief explanation of the drawings]

[0010] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and, together with the description, serve to explain the principles of the present teachings.

[0011] [Figure 1]FIG. 1 illustrates an example of a system for digital advanced lithography imaging that can be used to print the white ink of the present disclosure.

[0012] It should be noted that some details of the figures have been simplified and strict structural accuracy, detail, and scale are not maintained, but are drawn to facilitate understanding of the embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0013] Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals are used to designate the same elements throughout. In the following description, reference is made to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments in which the present teachings may be practiced. Accordingly, the following description is by way of example only.

[0014]

[0003] Embodiments of the present disclosure relate to a white ink composition. The white ink composition includes an ink vehicle containing at least one compound selected from acrylate monomers, methacrylate monomers, acrylate oligomers, and methacrylate oligomers. The white ink composition further includes at least one polyol adhesive resin that is solid at 25°C, at least one photoinitiator, and at least one white colorant. Additional components may also be included, as discussed below. Ink Vehicle

[0015] The ink vehicle used in the composition of the present disclosure may include at least one compound selected from acrylate monomers, methacrylate monomers, acrylate oligomers, and methacrylate oligomers. In one embodiment, the ink vehicle includes both at least one acrylate or methacrylate monomer and at least one acrylate or methacrylate oligomer. The use of oligomers may enable faster crosslinking of the ink. The oligomer-to-monomer ratio may be adjusted to provide a desired balance between crosslinking speed and viscosity. In one embodiment, the ink is not compatible with water.

[0016] Any suitable acrylate and methacrylate monomers can be used, including mono- or multi-functional acrylate monomers, mono- or multi-functional methacrylate monomers, or combinations thereof. Exemplary acrylate monomers include polyester acrylate, acid-modified epoxy diacrylate, trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, and glycerol derivative triacrylate (e.g., EBECRYL 5500 from Allnex). Other triacrylate, monoacrylate, diacrylate, tetraacrylate, pentaacrylate, hexaacrylate, and higher-functional acrylate monomers, and various combinations thereof, can also be used as vehicles in the ink composition.

[0017] Examples of suitable commercially available polyester acrylate monomers include Sartomer CN294E, Sartomer CD-501, Sartomer CN9014, Sartomer CN2282, and Sartomer CN2256, and 1.10 g / cm 3Examples of suitable commercially available trimethylolpropane triacrylate monomers include EBECRYL 853, a low viscosity polyester triacrylate having a specific gravity of 1.02, an APHA color of 200, and a viscosity of 80 cps at 25°C. These polyester acrylate monomers may be useful for wetting pigments and improving the tack and / or viscosity of the composition. Examples of suitable commercially available trimethylolpropane triacrylate monomers include SR-492, SR-501, SR-444, SR-454, SR-499, SR-502, SR-9035, and SR-415 manufactured by Sartomer, and EBECRYL 853 and EBECRYL 5500 manufactured by Allnex. Trimethylolpropane triacrylate has a refractive index of 1.474, a viscosity of 1.06 g / cm. 3 Sartomer SR-492 is a 3 mole propoxylated trimethylolpropane triacrylate with a refractive index of 1.459, a viscosity of 1.05 g / cm 3 Sartomer SR-501 is a 6 mole propoxylated trimethylolpropane triacrylate with a refractive index of 1.4567, a viscosity of 1.048 g / cm 3 A suitable commercially available example of pentaerythritol triacrylate has a refractive index of 1.4801, a viscosity of 1.162 g / cm 3 An example of a suitable commercially available ethoxylated trimethylolpropane triacrylate is Sartomer SR-444, which has a specific gravity of 1.025, a Tg of 103°C, an APHA color of 50, and a viscosity of 520 cps at 25°C. An example of a suitable commercially available ethoxylated trimethylolpropane triacrylate is 3 mole ethoxylated trimethylolpropane triacrylate, which has a refractive index of 1.4689, a viscosity of 1.103 g / cm 3 Sartomer SR-454, a 6 mole ethoxylated trimethylolpropane triacrylate, has a specific gravity of 1.001, a Tg of 120°C, an APHA color of 55, and a viscosity of 60 cps at 25°C, a refractive index of 1.4691, and a viscosity of 1.106 g / cm 3Sartomer SR-499, a 9 mole ethoxylated trimethylolpropane triacrylate, has a specific gravity of 1.02, a Tg of -8°C, an APHA color of 50, and a viscosity of 85 cps at 25°C, a refractive index of 1.4691, and a viscosity of 1.11 g / cm 3 Sartomer SR-502, a 15 mole ethoxylated trimethylolpropane triacrylate, having a specific gravity of 1.00, a Tg of -19°C, an APHA color of 140, and a viscosity of 130 cps at 25°C, a refractive index of 1.4695, and a viscosity of 1.113 g / cm 3 Sartomer SR-9035, a 20 mole ethoxylated trimethylolpropane triacrylate, having a specific gravity of 1.00, a Tg of -32°C, an APHA color of 60, and a viscosity of 168 cps at 25°C, a refractive index of 1.4699, and a viscosity of 1.115 g / cm 3 An example of a suitable commercially available glycol-derivatized triacrylate is Sartomer SR-415, which has a specific gravity of 1.07 g / cm, a Tg of -40°C, an APHA color of 55, and a viscosity of 225 cps at 25°C. 3 A commercially available example of an acid-modified epoxy diacrylate is CN118, available from Sartomer, Exton, Pennsylvania. CN118 has a density of 9.47 lb / gallon, a refractive index of 1.529 at 25°C, a T g , and has a viscosity of 80,000 cps at 25°C.

[0018] Curable acrylate oligomers that can be used in the ink composition as a vehicle can include polyester acrylate oligomers, such as difunctional polyester acrylate oligomers, trifunctional polyester acrylate oligomers, and tetrafunctional polyester acrylate oligomers; acrylated urethane oligomers, such as difunctional acrylated urethane oligomers, trifunctional urethane acrylate oligomers, and tetrafunctional urethane acrylate oligomers; and aliphatic acrylate ester oligomers.

[0019] Examples of commercially available acrylate oligomers include Sartomer CN294E, CN2256, CN2282, CN9014, CN309, CN9010, CN2261, CN750, and CN2264. Sartomer CN294E is a tetrafunctional acrylated polyester oligomer that is a clear liquid with a specific gravity of 0.93 and a viscosity of 4,000 cps at 60°C. Sartomer CN2256 is a difunctional polyester acrylate oligomer with a refractive index of 1.5062, a Tg of -22°C, a tensile strength of 675 psi, and a viscosity of 11,000 cps at 60°C. Sartomer CN2282 is a tetrafunctional acrylated polyester that is a clear liquid with a specific gravity of 1.15 and a viscosity of 2,500 cps at 60°C. Sartomer CN9014 is a difunctional acrylated urethane and is a non-transparent liquid with a specific gravity of 0.93 and a viscosity of 19,000 cps at 60°C. Sartomer CN309 is an oligomer containing acrylate esters derived from an aliphatic hydrophobic backbone, in other words, an aliphatic acrylate ester. CN309 is a transparent liquid with a specific gravity of 0.92, a density of 7.68 lb / gal, a surface tension of 26.3 dynes / cm, a viscosity of 150 cps at 25°C, and a viscosity of 40 cps at 60°C. CN9010 has a viscosity of 1.201 g / cm at 25°C. 3 CN2261 is an aliphatic urethane acrylate oligomer having a density of 1.14 g / cm at 25°C, a refractive index of 1.495 at 25°C, a Tg of 103°C, and a viscosity of 2,650 cps at 60°C. 3 CN750 is a trifunctional polyester acrylate oligomer having a density of 1.3 g / cm at 25°C, a refractive index of 1.512 at 25°C, a Tg of 56°C, and a viscosity of 2,280 cps at 60°C. 3CN2264 is a trifunctional chlorinated polyester acrylate oligomer having a density of 9.67 lb / gallon at 25° C., a refractive index of 1.511 at 25° C., a Tg of 43° C., and a viscosity of 1,250 cps at 60° C. Further examples of commercially available acrylate oligomers include EBECRYL 8405, EBECRYL 8411, EBECRYL 8413, EBECRYL 8465, EBECRYL 8701, EBECRYL 9260, EBECRYL 546, EBECRYL 657, EBECRYL 809, and EBECRYL 2870, all from Allnex. EBECRYL 8405 is a tetrafunctional urethane acrylate diluted at 80% by weight in 1,6-hexanediol diacrylate (HDDA) and is a clear liquid with a Gardner color of 2 and a viscosity of 4,000 cps at 60°C. EBECRYL 8411 is a difunctional urethane acrylate diluted at 80% by weight in isobornyl acrylate (IBOA) and is a clear liquid with a viscosity range of 3,400 to 9,500 cps at 65°C. EBECRYL 8413 is a difunctional urethane acrylate diluted at 67% by weight in IBOA and is a clear liquid with a viscosity of 35,000 cps at 60°C. EBECRYL 8465 is a trifunctional urethane acrylate diluted at 80% by weight in IBOA and is a clear liquid with a Gardner color of 2 and a viscosity of 21,000 cps at 60°C. EBECRYL 8701 is a trifunctional urethane acrylate that is a clear liquid with a Gardner color of 2 and a viscosity of 4,500 cps at 60°C. EBECRYL 9260 is a trifunctional urethane acrylate that is a clear liquid with a Gardner color of 2 and a viscosity of 4,000 cps at 60°C. EBECRYL 546 is a trifunctional polyester acrylate that is a clear liquid with a Gardner color of 1.5 and a viscosity of 350,000 cps at 25°C. EBECRYL 657 is a tetrafunctional polyester acrylate that is a clear liquid with a Gardner color of 4 and a viscosity of 125,000 cps at 25°C.EBECRYL 809 is a trifunctional polyester acrylate that is a clear liquid with a Gardner color of 3 and a viscosity of 1,300 cps at 60° C. EBECRYL 2870 is 1.10 g / cm at 25° C. 3 and a viscosity of 4,100 cps at 60°C. Further examples of commercially available acrylate oligomers include those having a viscosity of 1.14 g / cm 3 and a viscosity of about 1,000 to about 2,000 cps at 25°C.

[0020] Methacrylate analogs of any of the acrylate monomers or acrylate oligomers disclosed herein can be used in the compositions of the present disclosure. Such methacrylate analogs can be used in place of or in addition to the acrylate monomers and / or acrylate oligomers described herein. The reaction rate of methacrylates is typically about two orders of magnitude slower than that of their acrylate counterparts. However, they can provide improved properties, such as improved adhesion and / or flexibility of cured images.

[0021] The monomer and / or oligomer can be present in any suitable amount. In embodiments, the monomer, oligomer, or combination thereof is added in an amount of from about 10 to about 85 wt %, from about 30 to about 80 wt %, or from about 50 to about 70 wt %, based on the total weight of the curable ink composition.

[0022] In one embodiment, the composition of the present disclosure includes at least one acrylate monomer and at least one acrylate oligomer. Any of the acrylate monomers and oligomers described above may be used. As an example, the acrylate monomer may be a propoxylated trimethylolpropane triacrylate monomer, and the acrylate oligomer may be a tetrafunctional polyester acrylate oligomer.

[0023] In some embodiments, a co-reactive monomer can be added in addition to or instead of the acrylate monomers described above. The co-reactive monomer is added to control the polarity of the ink vehicle. Specific examples of such co-reactive monomers include, but are not limited to, a functional water-soluble aromatic urethane acrylate compound (available from CYTEC as EBECRYL 2003), a difunctional compound polyethylene glycol diacrylate (available from CYTEC as EBECRYL 11), and a trifunctional compound polyether triacrylate (available from CYTEC as EBECRYL 12). polyol

[0024] The white ink composition of the present disclosure may include at least one polyol adhesive resin. Any suitable polyol that functions as an adhesive, is compatible with the white ink composition, and is solid at 25°C or above may be used. In one embodiment, the polyol adhesive resin has a T of about 80°C to about 150°C, or about 85°C to about 120°C, or about 85°C to about 100°C. g T exceeding 75 degrees, such as g In particular, polyols may impart adhesion of the white ink to certain polymer substrates, such as substrates comprising one or more of biaxially oriented polyethylene terephthalate (commercially available as MYLAR®), biaxially oriented polypropylene ("BOPP"), polyethylene, and other polymers.

[0025] A commercially available polyol adhesive resin that is solid at 25°C is Variplus sk, available from Evonik Industries (Essen, Germany). This commercially available polyol has a glass transition temperature of about 90°C, a hydroxyl number of about 325 mg KOH / g, and a viscosity of about 1.15 g / cm. 3 The polyol adhesive of the present disclosure is distinguishable from copolyols known to modify or enhance the surface wetting properties of inks, such as dimethicone copolyol. In one embodiment, the composition of the present disclosure does not include a polyol surfactant, such as dimethicone copolyol.

[0026] The amount of polyol adhesive resin in the ink composition can be any amount suitable for white inks. As mentioned above, white inks often use a higher percentage of pigment than colored inks, which can make it difficult to incorporate additional solids while maintaining ink stability over time. This is especially true considering that DALI inks typically have a high viscosity, which allows the ink to effectively print images and allows substantial transfer of the ink from the blanket to the receiving substrate in the DALI printing process. A concentration of TiO2 pigment in a DALI ink that provides a desired balance of both ink stability and opacity is, for example, about 40% or more TiO2 pigment, such as about 45% or more TiO2 pigment by weight, or about 50% or more TiO2 pigment by weight. Some solid polyols, including VariPlus SK, can withstand temperatures above about 80°C. g The polyols have a high solids content, which makes it difficult to solubilize the DALI ink monomer and oligomer carrier components at room temperature (approximately 23°C for purposes of this application) given their already high solids content. However, applicants have determined that incorporating an effective amount of additional solids in the form of solid polyols is achievable with these compositions and processes at room temperature. It is desirable to be able to obtain stable compositions at relatively low temperatures, such as around room temperature, because excessive heating of radiation-curable components, including acrylate monomers and oligomers, can lead to T g While melt solubilization of some polyols, including VariPlus SK, above about 80°C can lead to undesirable thermally induced or chemically initiated radical polymerization reactions. Furthermore, excess polyol, which is solid at room temperature, can also interfere with the desired rheology and flow properties of the ink generated in the DALI printing process, including ink dosing and acceptance from the ink loader to the anilox roller where the ink is present. The inks of the present disclosure are stable and exhibit promising rheology and flow properties.

[0027] Exemplary polyol adhesive resin concentrations in the white inks of the present disclosure can range from about 2% to about 20% by weight, or from about 5% to about 15% by weight, or from about 5% to about 10% by weight, based on the total weight of the ink composition. Photoinitiator

[0028] Any suitable photoinitiator compatible with the white ink composition and suitable for polymerizing the specific oligomers and monomers used in the ink vehicle may be used. The photoinitiator may render the ink radiation-curable using a suitable radiation source, such as light in the ultraviolet spectrum. In one embodiment, the photoinitiator is a free-radical photoinitiator. Exemplary photoinitiators include 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholino-4-ylphenyl)butan-1-one, 1-hydroxycyclohexylphenyl ketone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinenate (TPO-L), 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO), and oligomeric alpha hydroxy ketones such as oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone].

[0029] Examples of such photoinitiators are commercially available as IRGACURE 379, IRGACURE 184, and IRGACURE 819, available from Ciba Specialty Chemicals. IRGACURE 379 is 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholino-4-yl-phenyl)butan-1-one with a molecular weight of 380.5. IRGACURE 184 is 1-hydroxy-cyclohexyl-phenyl-ketone with a molecular weight of 204.3. IRGACURE 819 is bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide with a molecular weight of 418.5. An example of a commercially available oligomeric alpha hydroxyketone photoinitiator is Esacure KIP 150, which is oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], available from Lamberti Technologies. An example of a commercially available 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide is OMNIRAD™ TPO, available from IGM Resins (Charlotte, North Carolina).

[0030] The photoinitiator can be selected for use with the particular wavelength used for curing. For example, TPO photoinitiators work well at 395 nm. Any suitable wavelength range that can be emitted with sufficient intensity to cure the ink can be used. For example, wavelengths in the range of about 300 nm to about 450 nm, such as about 365 nm to about 405 nm, can be used for curing, as well as wavelengths outside this range.

[0031] In one embodiment, multiple different photoinitiators, such as two, three, or more photoinitiators, can be used in a single ink composition. For example, two, three, or four of any of the photoinitiators listed above can be used. By way of example, a mixture of commercially available photoinitiators suitable for white ink compositions can be used. A specific example is Omnirad 2100, which is a blend of Omnirad 819 and Omnirad TPO-L. Another suitable mixture of photoinitiators is Omnirad BL 724, which contains a mixture of 2-hydroxy-2-methylpropiophenone, 2,3-dihydro-6-(2-hydroxy-2-methyl-1-oxopropyl)-1,1,3-trimethyl-3-[4-(2-hydroxy2-methyl-1-oxopropyl)phenyl]-1H-indene, 2,3-dihydro-5-(2-hydroxy-2-methyl-1-oxopropyl)-1,1,3-trimethyl-3-[4-(2-hydroxy2-methyl-1-oxopropyl)phenyl]-1H-indene, ethylphenyl(2,4,6-trimethylbenzoyl)phosphinate, 2,2-dimethoxy-1,2-diphenylethan-1-one, 3-hydroxy-3-phenylbutan-2-one (isomers), and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, which is commercially available from IGM Available commercially from Resins, BV.

[0032] The total of all photoinitiators may be present in an amount of from 1 to about 10% by weight of the ink composition, such as from about 3 to about 8% by weight, or from about 5 to about 7% by weight.

[0033] The particular photoinitiator used can affect the color of the white ink. For example, many photoinitiators can cause undesirable coloration of the ink (e.g., the ink can turn yellow) if used in excessively large amounts. As an example, using all four of IRGACURE 379, IRGACURE 819, IRGACURE 184, and ESACURE KIP 150 in the amounts shown in Table 3 allows for the formation of a white ink, but excessive use of any one of these four can cause undesirable discoloration (e.g., yellowing). Furthermore, it can be advantageous to select different photoinitiators to enable light absorption over a wider absorption range. Thus, using multiple photoinitiators can provide advantages in white ink systems. coloring agent

[0034] In one embodiment, the colorant used in the white ink of the present disclosure is selected from one or more dyes, one or more pigments, or a mixture of dyes and pigments. Any suitable dye or pigment that provides the desired white coloration can be selected, provided that it can be dispersed or dissolved in the ink composition and is compatible with the other ink components. In one embodiment, a pigment is used. In certain embodiments, the colorant herein comprises one or more white pigments of varying degrees of opacity, including, for example, titanium dioxide pigments, lithopone pigments (e.g., CI Pigment White 5), zinc oxide white, which may themselves be slightly colored or uncolored, or other inorganic white pigments. In an embodiment, the pigment herein is selected from the group consisting of titanium dioxide pigments, lithopone pigments, zinc oxide pigments, and combinations thereof.

[0035] In embodiments, the ink compositions herein comprise a white pigment as a primary colorant and, optionally, one or more additional pigments. In embodiments, the ink composition is a background ink, which means an ink that, when printed, provides an ink layer, in embodiments a white ink layer, and an image can be printed on top of the white ink layer. In embodiments, the white ink background layer can be "opaque" (i.e., the substrate does not show through) or "transparent" (i.e., the substrate shows through the printed layer). Opacity can be achieved by varying the pigment loading in the ink or by printing several layers on top of each other. To achieve transparency, less pigment can be added to the ink, or an ink rheology can be selected to allow for thinner layers on the substrate. In embodiments, the ink composition can contain two or more colorants, including a selected ratio of a high opacity colorant to a low opacity colorant, in embodiments, a selected ratio of a high opacity pigment and a low opacity pigment.

[0036] In embodiments, one or more low opacity pigments may be selected. The low opacity pigments may be white or non-white. In embodiments, a non-white low opacity pigment may be combined with one or more additional colorants to provide a white ink composition (i.e., an ink composition that prints a white image or layer).

[0037] In embodiments, the low opacity pigment is selected from the group consisting of brilliant white pigment Lithopone B301, cobalt green (sometimes known as Rinman green or zinc green), translucent green pigments, and combinations thereof.

[0038] In embodiments, the high opacity pigment is selected from the group consisting of titanium dioxide pigments, natural titanium dioxide pigments, synthetic titanium dioxide pigments, and combinations thereof. Synthetic titanium dioxide pigments, such as rutile titanium dioxide pigments, can be produced, for example, by the sulfate process or the chloride process. Titanium dioxide pigments can be surface modified or treated with one or more of alumina and other aluminum products, synthetic amorphous silica and other silicon products, and zirconium products, and can also include organic (and / or other) treatments to aid dispersibility, stability, and other performance metrics, including rheology, optical properties, weatherability, and lightfastness, in various end uses such as paints, coatings, and inks. Examples of suitable titanium dioxide pigments include TI-PURE® R706 and TI-PURE 6300, both available from Chemours Company TT, LLC, and KRONOS 2064 and KRONOS 2066 titanium dioxide pigments, both available from Kronos International, Inc.

[0039] The amount of pigment used can be any amount suitable for a white ink. As noted above, white inks often use higher proportions of pigment than colored inks. Exemplary pigment loadings for white inks of the present disclosure at 23° C. can range from about 40% to about 65% by weight, or from about 40% to about 60% by weight, or from about 45% to about 55% by weight, based on the total weight of the ink composition.

[0040] The total non-curable solids loading, which may include optional non-curable solids such as pigments, polyol adhesive resins, and fillers (e.g., clay or silica fillers), may range from about 45% to about 70% by weight, such as about 50% to about 65% by weight, at room temperature (about 23° C.). These solids ranges are selected so that the resulting rheology and tack of the ink allows for the desired inking onto the anilox roller and substantial transfer of the ink from the anilox roller to the receiving blanket and then to the receiving substrate to enable a printed image, and when the printed image ink is radiation cured, the desired opacity and adhesion properties of the printed image can be achieved. Optional ingredients

[0041] The ink compositions of the present disclosure may include one or more optional additional ingredients, such as heat stabilizers, in-can stabilizers, viscosity modifiers, fillers, and dispersants.

[0042] An exemplary heat stabilizer is Sartomer CN3216, an acrylate stabilizing additive having a specific gravity of 1.113 at 25°C and a viscosity of 1,100 cP at 25°C. Other examples of stabilizers include sterically hindered nitroxyl radicals, such as those disclosed in U.S. Patent Publication No. 2003 / 073762 or European Patent Publication No. 1235863, the disclosures of both of which are incorporated herein by reference in their entireties. Examples of typical radical scavengers that prevent gelation of UV-curable compositions with minimal impact on cure rate are bis(1-oxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate (Irgastab® UV 10) and 4-hydroxy-1-oxy-2,2,6,6-tetramethylpiperidine. Yet another stabilizer composition includes a stabilizer blend of a sterically hindered nitroxyl radical and a quinone methide, as disclosed in U.S. Pat. No. 7,723,398, the disclosure of which is incorporated herein by reference in its entirety.

[0043] One or more different thermal stabilizers may be used. The thermal stabilizer may be present in any suitable amount. Exemplary amounts include from about 0.1 to about 5% by weight of the ink composition, such as from about 0.2 to about 3% by weight, or from about 0.4 to about 1% by weight.

[0044] Any suitable in-can stabilizer can be used. The in-can stabilizer functions to reduce the level of free radicals, thereby potentially preventing undesired polymerization in the composition during storage. One example of a commercially available in-can stabilizer is Genorad 16, available from Rahn AG (Zurich, Switzerland).

[0045] Any filler suitable for adjusting the viscosity of the ink composition and otherwise compatible with the printing process may optionally be used. Exemplary fillers include organic and inorganic clays and silica. Commercially available examples of such fillers include CLAYTONE HY, an organoclay available from Southern Clay Products, and silica-based materials such as AEROSIL 200 from Degussa. One or more different fillers may be used. For example, either clay or silica alone, or a combination of both, may be used.

[0046] The total filler may be present in an amount of from about 0 to about 6% by weight of the ink composition, such as from about 0.2 to about 4% by weight, or from about 1 to about 2% by weight, based on the total weight of the ink composition.

[0047] The optional dispersant component can include any suitable or desired dispersant, including, but not limited to, high molecular weight AB diblock copolymers such as EFKA® 4340, available from BASF SE, and DISPERBYK® 2100, available from Byk-Chemie GmbH, or mixtures thereof. In certain embodiments, the dispersant mixture includes cyclohexanedimethanol diacrylate (such as CD406®, available from Sartomer USA, LLC) and at least one additional component, such as EFKA® 4340, a high molecular weight dispersant with an AB-diblock copolymer structure, available from BASF SE. In an exemplary embodiment, the dispersant is a polymeric dispersant, such as SOLSPERSE® 39000, available from The Lubrizol Corporation. Another commercially available dispersant is K-SPERSE A504, available from King Industries, Norfolk, Connecticut.

[0048] The dispersant can be added in any suitable amount based on the weight of the composition, such as, for example, about 1% to about 20% by weight, about 2% to about 10% by weight, or about 3% to about 8% by weight, etc. The amount of dispersant can vary depending on the amount of pigment used.

[0049] Any other ingredients suitable for use in DALI inks may also be optionally included in the compositions of the present disclosure. Those skilled in the art will be able to readily determine other ingredients that can be used.

[0050] Any of the optional ingredients discussed herein may be excluded from the composition, hi one example, one or more of the fillers or heat stabilizers are excluded from the composition.

[0051] The inks of the present disclosure have complex viscosities ranging from about 300 Pa·s to about 900 Pa·s, such as from about 350 Pa·s to about 700 Pa·s, or from about 400 Pa·s to about 620 Pa·s, measured at 25°C, an angular frequency of 100 rad / s, and a constant applied % oscillatory strain, which may be from about 0.5% to about 5%. The complex viscosity of the inks was evaluated at 25°C and a 500 micrometer gap on a DHR-2 rheometer (TA Instruments) equipped with 25 mm parallel plates. A frequency sweep with data ranging from 0.1 to 100 rad / s over a semi-decade period was generated. Because the inks have relatively high viscosities, a strain sweep was performed prior to the frequency sweep to determine the % oscillatory strain used during the frequency sweep. For high viscosity DALI inks, it is preferable to apply a dynamic oscillatory strain test to the sample prior to the frequency sweep test to ensure that the frequency sweep test is performed in an appropriate manner so that the complex viscosity is determined at or near the upper linear viscoelastic limit of the ink. For a parallel plate configuration in a rheometer, the applied (or measured) strain (deformation of the sample) is a unitless relationship of the radius r of the plate and the sample being tested divided by the thickness h of the sample multiplied by the deflection θ (in radians) of one of the moving plates relative to the sample: Applied Oscillatory Strain % is the applied strain * 100% (e.g., 0.01 strain = 1% strain).

number

[0052] In one embodiment, after curing with UV LED radiation, the inks of the present disclosure can produce tack-free or substantially tack-free prints. For example, the average tack (measured over 10 minutes) can range from about 55 g-m to about 70 g-m at 32°C after curing with UV LED. Curing can be achieved, for example, at about 1 W / cm. 2 Intensity and 35mJ / cm 2 This can be achieved with a 395 nm LED lamp (measured with a UV Power Puck® II from EIT using the UV-A2 channel) providing an energy dose of 1000 kJ / s, resulting in an immediate tack-free print. Note that ink tack is a measure of ink cohesion before curing and is different from print tackiness or tack, which is measured after curing has occurred.

[0053] The ink compositions of the present disclosure can be prepared by any desired or suitable method. Methods for combining the components described herein to form ink compositions will be readily apparent to those skilled in the art. Printing method

[0054] The present disclosure also relates to a printing method, which is carried out on a system for variable lithography using the ink compositions described herein.

[0055] As shown in FIG. 1 , an exemplary system 100 can include an imaging member 110. While the imaging member 110 in the embodiment shown in FIG. 1 is a drum, this exemplary description should not be construed to exclude embodiments in which the imaging member 110 includes a plate, a belt, or other known or later-developed configurations. The imaging member has a reimageable surface that can be formed of a material that provides the desired properties for forming and releasing ink images. Exemplary materials include silicones such as polydimethylsiloxane (PDMS), fluorosilicones, and / or fluoropolymer elastomers such as VITON®. Other suitable materials may also be used. In one embodiment, the reimageable surface can be formed of a relatively thin layer on a mounting layer, with the thickness of the relatively thin layer being selected to balance printing or marking performance, durability, and manufacturability.

[0056] The imaging member 110 is used to apply an ink image to an image receiving medium substrate 114 at a transfer nip 112. The transfer nip 112 is formed by an impression roller 118, which applies pressure toward the imaging member 110 as part of an image transfer mechanism 160. The image receiving medium substrate 114 can be any suitable medium to which an ink image can be transferred, including, for example, paper, polymer (e.g., plastic), metal, or composite sheet film. For example, suitable polymer substrates can include polymeric materials such as biaxially oriented polyethylene terephthalate (commercially available as MYLAR®), biaxially oriented polypropylene ("BOPP"), polyethylene, and other polymers. The polymeric substrate can be transparent, translucent, or opaque, depending on the material used for the substrate. In one embodiment, the image receiving medium substrate 114 includes a transparent polymer such as biaxially oriented polyethylene terephthalate, biaxially oriented polypropylene ("BOPP"), polyethylene, or a mixture thereof. The exemplary system 100 can be used to produce images on a wide variety of image receiving medium substrates.

[0057] The exemplary system 100 includes a dampening fluid system 120, which generally includes a series of rollers, which may be considered dampening rollers or dampening units, for uniformly wetting the reimageable surface of the imaging member 110 with dampening fluid. The purpose of the dampening fluid system 120 is to deliver a layer of dampening fluid having a generally uniform and controlled thickness to the reimageable surface of the imaging member 110. Suitable dampening fluids are well known in the art and, as described in more detail below, may comprise primarily water, optionally with small amounts of isopropyl alcohol or ethanol added to reduce surface tension and lower the evaporation energy required to support subsequent laser patterning. Small amounts of certain surfactants may also optionally be added to the dampening fluid. Alternatively, other suitable dampening fluids may be used to improve performance in ink-based digital lithography systems. An exemplary dampening fluid includes water, NOVEC® 7600 (1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3-hexafluoropropoxy)pentane, CAS#870778-34-0.), and D4 (octamethylcyclotetrasiloxane).

[0058] As the dampening fluid is dispensed onto the reimageable surface of the imaging member 110 via the meter, the thickness of the dampening fluid may be measured using a sensor 125. The sensor 125 may provide feedback to control the dispensing of the dampening fluid via the meter onto the reimageable surface of the imaging member 110 by the dampening fluid system 120.

[0059] After the dampening fluid is applied to the reimageable surface of the imaging member 110, an optical patterning subsystem 130 may be used to selectively form a latent image in the uniform dampening fluid layer. Any suitable patterning technique for imaging the dampening fluid layer may be used. One suitable exemplary patterning process uses a laser to image the dampening fluid. Mechanisms affecting the patterning process performed by the optical patterning subsystem 130 of the exemplary system 100 are known in the art. Briefly, application of optical patterning energy from the optical patterning subsystem 130 selectively removes portions of the dampening fluid layer to form hydrophobic non-image areas and hydrophilic image areas.

[0060] Following patterning of the dampening fluid layer on the imaging member 110 by the optical patterning subsystem 130, the patterned layer is presented to the inker subsystem 140. The inker subsystem 140 is used to apply a uniform layer of ink, such as any of the inks of the present disclosure, onto the patterned dampening fluid layer. The inker unit 140 further includes a heated ink bath whose temperature is regulated by a temperature control module (not shown). The inker subsystem 140 may use an anilox roller to meter the offset lithography ink of the present disclosure onto one or more ink forming rollers that contact the reimageable surface layer of the imaging member 110. Separately, the inker subsystem 140 may include other conventional elements, such as a series of metering rollers, to provide a precise delivery rate of ink to the reimageable surface. The inker subsystem 140 may deposit ink on imaged portions of the reimageable surface where dampening fluid has been removed (sometimes referred to herein as "pockets"), while ink does not adhere to portions of the reimageable surface where dampening fluid remains.

[0061] The cohesiveness and viscosity of the ink present on the reimageable surface of the imaging member 110 can then be altered by cooling the ink. Cooling can be achieved by any suitable means, such as by using one or more physical cooling mechanisms and / or via chemical cooling. One example of cooling by physical means is convection cooling by blowing cool air onto the reimageable surface, such as from one or more jets 180, after the ink composition has been applied to the imaging member 110 and before the ink composition is transferred to the final substrate 114. Instead of, or in addition to, cooling the ink by convection, the surface of the imaging member 110 can be directly cooled to maintain the reimageable surface at a desired temperature (e.g., 10-30°C) and cool the ink by thermal conduction. Any other suitable means can be used to cool the ink.

[0062] In addition to cooling the ink, any other suitable means may be used to modify the cohesiveness and viscosity of the ink present on the reimageable surface of the imaging member 110. For example, a curing mechanism may be used, including optical or light curing, thermal curing, drying, or various forms of chemical curing. One such optional mechanism may involve the use of a rheology (complex viscoelastic coefficient) control subsystem 150. The rheology control system 150 may, for example, form a partially crosslinked core of ink on the reimageable surface to increase the ink cohesion to the reimageable surface layer.

[0063] After cooling, the ink is transferred from the reimageable surface of the imaging member 110 to the image receiving medium substrate 114 using a transfer subsystem 160. Transfer occurs when the substrate 114 passes through the nip 112 between the imaging member 110 and the impression roller 118 such that the ink in the pockets of the reimageable surface of the imaging member 110 comes into physical contact with the substrate 114. The adhesive properties of the ink can be modified as the viscosity of the ink changes, such as during cooling of the ink or during partial UV curing using a rheology control system 150. The modified adhesive properties of the ink cause the ink to adhere to the substrate 114 and separate from the reimageable surface of the imaging member 110.

[0064] An optional final curing may be performed after transfer of the ink image to the substrate 114. Final curing of the ink image on the substrate 114 may be achieved by any suitable method, such as by exposing the ink image to ultraviolet light and / or heat.

[0065] In certain offset lithography systems, an offset roller, not shown in Figure 1, may first receive the ink image pattern from the imaging member 110 and then transfer the ink image pattern to the substrate 114 according to an indirect transfer method. Such offset rollers and indirect transfer techniques are well known in the art.

[0066] Following transfer of the majority of the ink to the substrate 114, any residual ink and / or residual dampening fluid may be removed from the reimageable surface of the imaging member 110, preferably without scraping or significantly abrading the surface. An air knife (not shown) may be used to remove the residual dampening fluid. However, it is expected that some ink residue may remain. Removal of such remaining ink residue may be achieved through the use of some form of cleaning subsystem 170. In one embodiment, the cleaning subsystem 170 includes at least a first cleaning member, such as a viscous or sticky member, in physical contact with the reimageable surface of the imaging member 110, which removes the residual ink and any remaining small amounts of surfactant compound from the dampening fluid on the reimageable surface of the imaging member 110. The sticky or sticky member may then be contacted with a smooth roller to which the residual ink may be transferred from the viscous or sticky member, after which the ink is stripped from the smooth roller by, for example, a doctor blade.

[0067] Any other suitable mechanism capable of facilitating cleaning of the reimageable surface of the imaging member 110 may be used. Cleaning residual ink and dampening fluid from the reimageable surface of the imaging member 110 may reduce or prevent the formation of ghost images (also known as "ghosting") in the proposed system. Once cleaned, the reimageable surface of the imaging member 110 is again presented to the dampening fluid system 120, which applies a fresh layer of dampening fluid to the reimageable surface of the imaging member 110, and the process is repeated.

[0068] Careful control of the temperature and pressure conditions in the transfer nip 112 can assist in the transfer of the ink image. By way of example, the transfer efficiency of the ink from the reimageable surface of the imaging member 110 to the substrate 114 (which may comprise a transparent polymer or any of the other substrate materials described herein) can be 90% or greater by weight of the ink image, e.g., 95% or greater, e.g., 98% or greater, e.g., at or near 100%. [Example]

[0069] [Table 1]

[0070] The materials used in the inks of the present invention in Table 1 are illustrative examples and are not meant to limit the spirit or scope of the present invention.

[0071] The pigment formulation of K-sperse A504 was fixed at approximately 10.8% AOP (additive to pigment, weight percent), however inks with similar formulations and a very similar range of rheology, adhesion, and cure properties could be achieved with other suitable dispersants and other AOP levels (%). Examples 1 to 10

[0072] [Table 2]

[0073] Example 1

[0074] To a 1000 mL stainless steel jacketed vessel equipped with a quick desorption line to a Julabo circulating bath with active cooling was added 20.40 g of CN2282 manufactured by Sartomer Corporation, 52.48 g of CN118 manufactured by Sartomer Corporation, 40.00 g of SR501 manufactured by Sartomer Corporation, 22.76 g of K-sperse A504 manufactured by King Industries, and 4.00 g of Genorad 16 manufactured by Rahn Corporation. The vessel was placed on an HCPS 1 / 16 mill unit, available from Hockmeyer Equipment Corporation, equipped with a 4-inch wide anchor impeller. The vessel was first heated to 80°C without stirring, then heated with stirring at 100 RPM until the temperature of the ink base components passed 80°C and reached a temperature of approximately 93°C, after which the vessel was mixed for approximately 60 minutes. Once the ink components were homogeneous and deaerated, 14.00 g of Omnirad TPO (manufactured by IGM Resins) and 4.36 g of Additol LX (manufactured by Allnex Corporation) were added to the vessel while mixing at 100 RPM. The temperature of the mixture was maintained at 93°C with mixing for 45 minutes, and the first UV ink base solution appeared homogeneous and air-free. At this point, 32.00 g of VariPlus SK (manufactured by Evonik Industries), which had been pre-pulverized, was slowly added to the vessel while the components were being mixed with an anchor impeller at 100 RPM. After the VariPlus SK addition, stirring of the vessel contents continued for one hour, revealing a second UV ink base solution that appeared homogeneous and air-free. At this point, 210 g of CI Pigment White 8 TiO2 pigment (manufactured by Chemours Company) was slowly added to the vessel, and the mixture was stirred for one hour to form Component Mixture 1A. The anchor impeller was replaced with a 40 mm diameter high shear Cowles blade and then mixed at 5000 RPM for approximately 1 hour to form Component Mixture 1 B. The thoroughly mixed component mixture was then qualitatively transferred to a Buhler TRIAS 300 three-roll mill.Here, component mixture 1B was first passed through a three-roll mill at an inner roll temperature of 35°C, roll separation forces of rollers 1-2 and 2-3 of 50 and 50 N / mm, and an input apron roll speed of 300 RPM to form component mixture 1C, which was collected in a 250 mL glass amber bottle.

[0075] Example 2

[0076] Inks, the compositions of which are outlined in Table 2A, were prepared in a 400 gram batch size in the same manner as Example 1, except that Additol LX was not used. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 2A was formed at the end of low shear mixing using an anchor impeller. Component Mix 2B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 2C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0077] Example 3

[0078] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component mixture 3A was formed at the end of low shear mixing using an anchor impeller. Component mixture 3B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 3C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0079] Example 4

[0080] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 4A was formed at the end of low shear mixing using an anchor impeller. Component Mix 4B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 4C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0081] Example 5

[0082] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 5A was formed at the end of low shear mixing using an anchor impeller. Component Mix 5B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 5C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0083] Example 6

[0084] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component mixture 6A was formed at the end of low shear mixing using an anchor impeller. Component mixture 6B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 6C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0085] Example 7

[0086] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 7A was formed at the end of low shear mixing using an anchor impeller. Component Mix 7B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 7C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0087] Example 8

[0088] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 8A was formed at the end of low shear mixing using an anchor impeller. Component Mix 8B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 8C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0089] Example 9

[0090] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 9A was formed at the end of low shear mixing using an anchor impeller. Component Mix 9B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 9C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0091] Example 10

[0092] Inks, the compositions of which are outlined in Table 2A, were prepared in 400 gram batch sizes in the same manner as in Example 2. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component mixture 10A was formed at the end of low shear mixing using an anchor impeller. Component mixture 10B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 10C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle. Examples 11 to 16

[0093] [Table 3]

[0094] Example 11

[0095] Inks, the compositions of which are outlined in Table 2B, were prepared in 400 gram batches in the same manner as Example 10, except that KRONOS 2066 was used instead of Ti Pure Pigment. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component mixture 11A was formed at the end of low shear mixing using an anchor impeller. Component mixture 11B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 11C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0096] Example 12

[0097] Inks, the compositions of which are outlined in Table 2B, were prepared in 400 gram batches in the same manner as Example 10, except that KRONOS 2064 was used instead of TI Pure Pigment. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component mixture 12A was formed at the end of low shear mixing using an anchor impeller. Component mixture 12B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 12C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0098] Example 13

[0099] Inks, the compositions of which are outlined in Table 2B, were prepared in 400 gram batches in the same manner as Example 2, except that the ink contained 5% by weight of polyester acrylate SP 283 and no Variplus SK or SR-501 monomers were added. During the ink preparation process, various UV ink bases and inks from different processes were prepared. Component mixture 13A was formed at the end of low shear mixing using an anchor impeller. Component mixture 13B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 13C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0100] Example 14

[0101] Inks, the compositions of which are outlined in Table 2B, were prepared in a 400 gram batch size in the same manner as Example 2, except that the ink contained 7.5 wt. % polyester acrylate SP 283, 2.66 wt. % Variplus SK, and no SR-501 monomer. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component Mix 14A was formed at the end of low shear mixing using an anchor impeller. Component Mix 14B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 14C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0102] Example 15

[0103] An ink, the composition of which is outlined in Table 2B, was prepared in a 400 gram batch size in the same manner as Example 2, except that the ink contained 10 wt. % polyester acrylate SP 283, 3.11 wt. % Variplus SK, and no SR-501 monomer. During the ink preparation process, various UV ink bases and inks from different processes were produced. Component mixture 15A was formed at the end of low shear mixing using an anchor impeller. Component mixture 15B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component mixture 15C was formed at the end of a three-roll milling process and collected in a 250 mL glass amber bottle.

[0104] Example 16

[0105] An ink, the composition of which is outlined in Table 2B, was prepared in the same manner as Example 13, except that a larger 13 kg batch size was made using a Dissolver Dispermat CN-10, available from VMA-GETZMANN GMBH, equipped with a 21 L stainless steel jacketed vessel and a 7-inch wide anchor impeller and a 4-inch diameter Cowles blade. During the ink preparation process, various UV ink bases and inks from different processes were made. Component Mix 16A was formed at the end of low shear mixing using the anchor impeller. Component Mix 16B was formed at the end of low shear mixing using a high shear mixing Cowles blade. Component Mix 16C was formed at the end of a three-roll milling process and collected in a 20 L high-density polyethylene pail.

[0106] Ink characteristics of the examples

[0107] Among other properties (e.g., resulting ink prints with good curing characteristics upon radiation exposure, more specifically UV LED radiation, and desired whiteness, color or near-color neutrality, and opacity characteristics on the resulting prints), inks with viscosity and rheology within a useful range are desirable features of the ink compositions described herein. Inks with too low a viscosity will cause undesirable image background problems, while inks with too high a viscosity will not flow as needed through the ink loader or onto and off the anilox roller during the blanket inking stage. Inks with too low a viscosity (ink cohesion) will have poor transfer from the blanket to the receiving substrate, adversely affecting print quality and taxing cleaning cycles of the printing system, while inks with too high a viscosity will accelerate blanket wear and limit blanket life, resulting in slower printing times and higher costs for customers.

[0108] The complex viscosity of the inks (from each of the triple-roll milled component "C" analogs of the illustrated examples) was evaluated using the same process described above for determining complex viscosity on a TA Instruments DHR-2 rheometer equipped with 25 mm parallel plates at 25°C and a 500 micron gap. A frequency sweep with a semi-decade of data from 0.1 to 100 rad / sec was generated.

[0109] The tack (ink cohesion) of the inks (from each of the triple-roll milled component "C" analogs of the illustrated examples) was determined using a Thwing-Albert Inkometer 1100, with the average tack determined on 1.3 mL of ink at 1200 RPM and 32°C over a 10-minute period, with the average tack calculated from the average of the tack values ​​generated every 20 seconds over the course of the measurement. Advantageously, the inks have an average tack over the 10-minute measurement period of about 45 to about 65 g-m. It is also a desirable property of these inks to have good tack stability (or low differential tack) over the course of the remaining 9-minute measurement cycle after the 60-second tack determination, such that the differential tack (the difference between the tack at 60 seconds and the tack at 600 seconds) is less than about 15 g-m. It is also desirable that little or no misting or spitting of the ink occurs during printing, based on a visual evaluation of the inner cover present to shield the rollers of the ink meter during the tests used to determine the adhesion properties of the ink.

[0110] [Table 4]

[0111] [Table 5]

[0112] The shortness index (for this purpose) is defined as the ratio of the viscosity of the ink between 1 rad / sec and 100 rad / sec at 25° C. The viscosity and tack results show that the example inks are within the useful range for printing.

[0113] Printing characteristics

[0114] Ink (from each of the three-roll milled component "C" analogs of the illustrated examples) was loaded into an apparatus equipped with an anilox roller (1000 lpi, 2.1 BCM, available from Impreglon Cellramic) maintained at a temperature of 45-50°C. There, the ink was first transferred to a blanket at room temperature, then transferred to a receiving transparent MYLAR® substrate, and then recirculated. Consequently, two chase sheets were created to estimate the residual ink left on the blanket from the initial ink transfer to the transparent Mylar® substrate. The transparent MYLAR® substrate and the two chase sheets containing the ink images were then cured at a speed of 1 m / sec using a Phoseon FireJet™ J-200 C 395 nm UV LED lamp. There was some variability among the example inks in the amount of ink transferred to the transparent MYLAR® or transparent BOPP substrate. As measured on cured prints on the transparent MYLAR® or transparent BOPP substrate on a black substrate, the L * The range was kept between 78 and 83.

[0115] The color characteristics and relative opacity of prints are measured using a D50 illuminant as well as OD Status T and CIELAB L. * a * b * The L of prints made on BOPP or transparent MYLAR® was determined using an X-Rite 528 spectrodensitometer (manufactured by X-Rite Corporation) measuring with two observers to generate the data. *was printed and evaluated first on a black substrate (Astrobrights® Eclipse Black™ paper) and then on a white substrate (Xerox® Digital Color Elite Gloss paper), and the % opacity of the print was calculated in this way. L * (Printed matter on a black background) / L * (printed matter on a white background) * 100

[0116] An advantage of the present invention is that the % opacity of prints made from LED-cured inks on transparent substrates is at least about 85, such as at least about 90, such as at least about 92. When opacity is determined in this manner, ·Opacity% approx. 1.1×L * (measured against a black substrate) was found.

[0117] In addition, LED-cured prints made on transparent substrates with white backgrounds were * and b * a, so that the magnitudes of are each less than about 2, e.g., less than 1. * and b * It is desirable that the a of a print made on a transparent substrate with a black background is medium or near medium in terms of * and b * corresponds to the size of

[0118] The print robustness tests performed included a fingernail scratch test, a tape adhesion test, a print tackiness test, and a chemical rub test using isopropanol. The resulting LED-cured prints should have good robustness, i.e., resistance to scratches such as fingernails, tack-freeness, and resistance to isopropanol solvents for at least 15 double rubs at room temperature.

[0119] When unprinted, there was no fastness data for the ink of Example 1. The inks of Examples 11 and 12 were also unprinted.

[0120] [Table 6]

[0121] The majority of the resulting prints made from the inks of Examples 2-10 and 13-16 were found to be tack-free, fingernail scratch resistant, have good adhesion on clear MYLAR® or clear BOPP substrates, and exhibit acceptable isopropanol double rubs. [Table 7]

[0122] The exemplary DALI ink composition described herein was developed to absorb light and be cured with a UV LED lamp. The ink exhibited good anilox roller acceptance and high transfer from the anilox roller to a receiving substrate, such as a transparent MYLAR® substrate. The resulting radiation-cured prints were tack-free immediately after curing and had acceptable robustness in ink adhesion to the substrate and solvent resistance. This was achieved by a combination of ingredients including, by way of example, a white pigment, a pigment dispersant, a tetrafunctional polyester acrylate, a high molecular weight acid-modified epoxy diacrylate, a 6-mol propoxylated trimethylolpropane triacrylate, an in-can stabilizer, a polyol resin, and at least one photoinitiator that absorbs in the wavelength range of the LED emission spectrum.

[0123] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein should be understood to encompass any and all subranges subsumed therein.

[0124] While the present teachings are described with respect to one or more implementations, variations and / or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. Additionally, while particular features of the present teachings may be disclosed with respect to only one of several implementations, such features may be combined with one or more other features of other implementations as may be desirable and advantageous for any given function or functions. Furthermore, to the extent that the terms "including," "includes," "having," "has," "with," or variations thereof are used in either the detailed description or the claims, such terms are intended to encompass such terms in a manner similar to the term "comprising." Furthermore, the term "about" in the discussion and claims herein indicates that the recited values ​​may be varied somewhat, provided that such variations do not result in incompatibility of the process or structure to the illustrated implementation. Finally, the term "exemplary" indicates that the description does not imply ideality, but is used as an example.

[0125] It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unprecedented alternatives, modifications, variations, or improvements may be subsequently made by those skilled in the art, which are intended to be encompassed by the following claims. Another aspect of the present invention may be as follows. 〔1〕 1. A white ink composition comprising: an ink vehicle comprising at least one compound selected from an acrylate monomer, a methacrylate monomer, an acrylate oligomer, and a methacrylate oligomer; at least one polyol adhesive resin that is solid at 25°C; at least one photoinitiator; and at least one white colorant. 〔2〕 The composition according to [1], wherein the ink vehicle comprises the acrylate oligomer and the acrylate monomer. 〔3〕 The composition according to [2] above, wherein the acrylate monomer is a propoxylated trimethylolpropane triacrylate monomer. 〔4〕 The composition according to [2] above, wherein the acrylate monomer is a tetrafunctional polyester acrylate oligomer. 〔5〕 The at least one polyol adhesive resin has a T g The composition according to [1] above, 〔6〕 The composition according to claim 1, wherein the at least one photoinitiator comprises 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. 〔7〕 The composition according to [1], wherein the at least one photoinitiator comprises a plurality of different photoinitiators. 〔8〕 The composition according to [1], further comprising at least one in-can stabilizer. 〔9〕 The composition according to [1], further comprising at least one polymeric dispersant. 〔10〕 The composition according to [1], further comprising at least one additional component selected from a heat stabilizer, a viscosity modifier, a filler, and combinations thereof. 〔11〕 The composition according to [1], wherein the at least one white colorant is a pigment, and the pigment is present at a concentration in the range of about 40% by weight to about 65% by weight, based on the total weight of the ink composition. 〔12〕 1. A method for variable lithographic printing, comprising: applying a dampening fluid to an imaging member surface; forming a latent image by removing the dampening fluid from selective locations on the imaging member surface to form hydrophobic non-image areas and hydrophilic image areas; developing the latent image by applying a white ink composition to the hydrophilic image areas; transferring the developed latent image to a receiving substrate; The white ink composition an ink vehicle comprising at least one compound selected from an acrylate monomer, a methacrylate monomer, an acrylate oligomer, and a methacrylate oligomer; at least one polyol adhesive resin that is solid at 25°C; at least one photoinitiator; and at least one white colorant. 〔13〕 The method according to claim 12, wherein the ink vehicle comprises the acrylate oligomer and the acrylate monomer. 〔14〕 13. The method according to claim 12, wherein the acrylate monomer is a propoxylated trimethylolpropane triacrylate monomer. 〔15〕 The method according to

[12] , wherein the acrylate monomer is a tetrafunctional polyester acrylate oligomer. 〔16〕 The at least one polyol adhesive resin has a T g The method according to

[12] above, comprising: 〔17〕 13. The method of claim 12, wherein the at least one photoinitiator comprises 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide. 〔18〕 13. The method of claim 12, further comprising at least one in-can stabilizer. 〔19〕 The method according to

[12] above, further comprising at least one polymeric dispersant. 〔20〕 The method according to

[12] above, wherein the white colorant is a pigment, and the pigment has a concentration in the range of about 40% by weight to about 65% by weight relative to the total weight of the ink composition.

Claims

1. 1. A white ink composition comprising: an ink vehicle comprising at least one compound selected from an acrylate monomer, a methacrylate monomer, an acrylate oligomer, and a methacrylate oligomer; at least one polyol adhesive resin that is solid at 25°C; at least one photoinitiator comprising 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide; at least one white colorant; at least one stabilizer comprising 4-hydroxy-1-oxy-2,2,6,6-tetramethylpiperidine; the at least one polyol adhesive resin has a concentration ranging from about 2% to about 20% by weight based on the total weight of the ink composition; the white ink composition has an average viscosity, measured over 10 minutes, of from about 45 g-m to about 65 g-m; and the at least one white colorant is a pigment, and the pigment is present in a concentration ranging from about 40% to about 65% by weight, based on the total weight of the ink composition; White ink composition.

2. The composition of claim 1 , wherein the ink vehicle comprises the acrylate oligomer and the acrylate monomer.

3. The composition of claim 2 wherein the acrylate monomer is a propoxylated trimethylolpropane triacrylate monomer.

4. The composition of claim 2 wherein the acrylate monomer is a tetrafunctional polyester acrylate oligomer.

5. The at least one polyol adhesive resin has a T of about 80° C. to about 150° C. g 10. The composition of claim 1, wherein

6. The composition of claim 1 , wherein the at least one photoinitiator comprises a plurality of different photoinitiators.

7. 10. The composition of claim 1 further comprising at least one in-can stabilizer.

8. The composition of claim 1 further comprising at least one polymeric dispersant.

9. 10. The composition of claim 1, further comprising at least one additional component selected from a heat stabilizer, a viscosity modifier, a filler, and combinations thereof.

10. 1. A method for variable lithographic printing, comprising: applying a dampening fluid to an imaging member surface; forming a latent image by removing the dampening fluid from selective locations on the imaging member surface to form hydrophobic non-image areas and hydrophilic image areas; developing the latent image by applying a white ink composition to the hydrophilic image areas; transferring the developed latent image to a receiving substrate; The white ink composition an ink vehicle comprising at least one compound selected from an acrylate monomer, a methacrylate monomer, an acrylate oligomer, and a methacrylate oligomer; at least one polyol adhesive resin that is solid at 25°C; at least one photoinitiator comprising 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide; at least one white colorant; at least one stabilizer comprising 4-hydroxy-1-oxy-2,2,6,6-tetramethylpiperidine; the at least one polyol adhesive resin has a concentration ranging from about 2% to about 20% by weight based on the total weight of the ink composition; the white ink composition has an average viscosity, measured over 10 minutes, of from about 45 g-m to about 65 g-m; and the at least one white colorant is a pigment, and the pigment is present in a concentration ranging from about 40% to about 65% by weight, based on the total weight of the ink composition; Method for variable lithographic printing.

11. The method of claim 10 , wherein the ink vehicle comprises the acrylate oligomer and the acrylate monomer.

12. The method of claim 10, wherein the acrylate monomer is a propoxylated trimethylolpropane triacrylate monomer.

13. The method of claim 10 wherein the acrylate monomer is a tetrafunctional polyester acrylate oligomer.

14. The at least one polyol adhesive resin has a T of about 80° C. to about 150° C. g 11. The method of claim 10, comprising:

15. The method of claim 10 further comprising at least one in-can stabilizer.

16. The method of claim 10 further comprising at least one polymeric dispersant.

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