Energy curable ink compositions and methods thereof

Abstract

An energy curable ink composition comprising: from 2% to 20% by weight, based on the total weight of (a), (b), (c) and (d), of a pigment; from 5% to 30% by weight, based on the total weight of (a), (b), (c) and (d), of a cellulose ester resin; from 40% to 91% by weight, based on the total weight of (a), (b), (c) and (d), of one or more multifunctional acrylates; and 2% to 10% by weight, based on the total weight of (a), (b), (c) and (d), of a free radical photoinitiator; wherein the composition has a viscosity of from 2,000 mPa-s to 6,000 mPa-s as measured according to ASTM D4287 using a cone plate viscometer (BYK CAP 2000 +) at a rotor 2 at a rotational speed of 100 rpm, and a method for preparing the same.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to energy-curable ink compositions, and more specifically, to energy-curable ink compositions for offset or lithographic printing applications. Background Technology

[0002] Lithography is a common method for printing or marking images on an image-receiving medium. In a typical lithography process, image areas and non-image areas are formed on the surface of the image carrier (which can be a plate, cylinder, or strip). Image areas correspond to the areas on the final printed matter on the image-receiving medium that are occupied by the printed or marked material (such as ink), while non-image areas (such as background areas) correspond to the areas on the final printed matter on the image-receiving medium that are not occupied by the printed or marked material. Traditional lithography and offset lithography techniques use permanently patterned printing plates and are therefore generally considered useful only for printing large quantities of the same image in long-running prints (such as magazines, newspapers, etc.).

[0003] Offset / flatbed printing inks are available in a variety of formulations to meet diverse application scenarios and performance requirements. A key characteristic of offset ink formulations is ink viscosity, ensuring clean transfer of the ink across the transfer and printing rollers of proofing / printing presses. The ink must also avoid harmful ink splattering. Other factors include a fluid carrier medium containing selected UV-curable monomers and oligomers, as well as coloring pigments or dyes. Another important aspect of the ink is the resin or polymer binder, along with other additives for wetting and surface modification purposes.

[0004] Resin or polymeric binders are a major cause of tackiness, and this can be even more pronounced with UV curing media or diluents such as low-viscosity monomers, oligomers, and other highly branched, curable reactive UV monomers. However, one problem with offset / lithographic printing inks is that the resins (e.g., acrylates, polyurethanes, or other polymeric resins) have single or limited compatibility with the substrate. That is, they cannot adhere to a variety of substrates (e.g., metal substrates, paper, Tyvek, vinyl, PVC, polyolefins, etc.), and problems can include adhesion, wetting, and long-term performance issues such as image quality and durability. One solution is to use two or more resins / binders to address these performance problems. Furthermore, polymeric resins can sometimes interfere with UV / electron beam curing because they absorb UV energy light. To address this, photoinitiators can be added to the formulation to improve curing efficiency.

[0005] Therefore, there is still a need for an offset / lithographic printing ink composition that achieves a good balance of properties including adhesion, wettability, image quality and durability, while being compatible with a variety of substrates and providing better UV curing with minimal or no need for photoinitiators (in the case of electron beam curing). Summary of the Invention

[0006] This document discloses an energy-curable ink composition. The energy-curable ink composition comprises: 2% to 20% by weight of pigment based on the total weight of (a), (b), (c), and (d); 5% to 30% by weight of cellulose ester resin based on the total weight of (a), (b), (c), and (d); 40% to 91% by weight of one or more polyfunctional acrylates based on the total weight of (a), (b), (c), and (d); and 2% to 10% by weight of free radical photoinitiator based on the total weight of (a), (b), (c), and (d); wherein the composition has a viscosity of 2,000 mPa⁻² to 6,000 mPa⁻², as measured according to ASTM D4287 using a cone-plate viscometer (BYK CAP 2000+) with rotor #2 at 100 rpm.

[0007] The embodiments herein further disclose a printing method. The method includes providing an ink composition disclosed herein; depositing the ink composition onto a substrate; and curing the ink composition by irradiation with ultraviolet light to form a cured ink.

[0008] Further features and advantages of the embodiments will be described in the following detailed description, and some of these features and advantages will become apparent to those skilled in the art from that description or by practicing the embodiments described herein. It should be understood that the foregoing and following descriptions depict various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. Detailed Implementation

[0009] Detailed embodiments of energy-curable ink compositions, their application methods, and printing methods thereof will now be provided. Energy-curable ink compositions can be used in lithography or offset printing. However, it should be noted that this is merely an illustrative description of the embodiments disclosed herein. These embodiments are applicable to other technologies susceptible to problems similar to those discussed above.

[0010] In embodiments herein, the energy-curable ink composition comprises (a) a pigment, (b) a cellulose ester resin, (c) one or more polyfunctional acrylates, and (d) a free radical photoinitiator. In one or more embodiments herein, the energy-curable ink composition comprises 2% to 20% by weight of pigment based on the total weight of (a), (b), (c), and (d). All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the energy-curable ink composition comprises 2% to 18% by weight, 3% to 15% by weight, 5% to 15% by weight, or 5% to 13% by weight of pigment based on the total weight of (a), (b), (c), and (d).

[0011] Pigments are components used to provide color to energy-curable ink compositions, and are primarily colored pigments. Examples of pigments may include organic and / or inorganic pigments already used in conventional printing ink compositions. In some embodiments, the pigment is selected from inorganic pigments, organic pigments, or combinations thereof. In other embodiments, the pigment is an organic pigment.

[0012] Examples of organic pigments may include, for example, perylene and perylene ketone compound pigments, quinacridone compound pigments, phthalocyanine compound pigments, anthraquinone compound pigments, phthalon-based compound pigments, dioxazine compound pigments, isoindolinone compound pigments, methenyl and azometenyl compound pigments, diketopyrrolopyrrole compound pigments, insoluble azo compound pigments, and condensed azo compound pigments.

[0013] Examples of inorganic pigments include, for example, titanium dioxide, zinc sulfide, white lead, zinc oxide, lithopone, antimony trioxide, basic lead sulfate, basic lead silicate, barium sulfate, calcium carbonate, gypsum, silicon dioxide, carbon black, iron oxide black, cobalt violet, cinnabar, molybdenum orange, red lead, ferric oxide, chrome yellow, cadmium yellow, zinc chromate, ochre yellow, chromium oxide, ultramarine blue, Prussian blue, and cobalt blue. Specific examples of pigments (organic or inorganic) may include yellow pigments such as diazo yellow (pigment yellow 12, 13, 14, 17, and 1) and Hansa yellow; magenta pigments such as Brilliant Carmine 6B, Lake Red C, and Watching Red; cyan pigments such as phthalocyanine blue, phthalocyanine green, and basic blue; and black pigments such as carbon black.

[0014] In embodiments described herein, the energy-curing ink composition comprises a cellulose ester resin. In some embodiments, based on the total weight of (a), (b), (c), and (d), the energy-curing ink composition comprises 5% to 30% by weight of a cellulose ester resin. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, based on the total weight of (a), (b), (c), and (d), the energy-curing ink composition comprises 5% to 27.5% by weight, 5% to 25% by weight, or 6% to 20% by weight of a cellulose ester resin.

[0015] The cellulose ester resin may be cellulose acetate propionate resin, cellulose acetate butyrate resin, or a combination thereof. In some embodiments, the average degree of substitution (DSOH) of the cellulose ester resin is 0 to 1.2, and the average degree of substitution (DSAC) of the acetyl substituents is 0.05 to 0.5. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the average degree of substitution (DSOH) of the cellulose ester resin is 0.1 to 1.0, 0.1 to 0.75, 0.1 to 0.6, or 0.2 to 0.5, and the average degree of substitution (DSAC) of the acetyl substituents is 0.05 to 0.4, 0.05 to 0.3, 0.05 to 0.25, or 0.05 to 0.2.

[0016] In some embodiments, the cellulose ester resin comprises at least 50% by weight of cellulose acetate propionate (CAP) resin. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, based on the total amount of cellulose ester resin, the cellulose ester resin comprises at least 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 97.5%, or 99% by weight of cellulose acetate propionate (CAP) resin. In other embodiments, based on the total amount of cellulose ester resin, the cellulose ester resin comprises 55% to 99% by weight, 60% to 99% by weight, 65% to 99% by weight, 70% to 99% by weight, 75% to 99% by weight, 80% to 99% by weight, 85% to 99% by weight, 90% to 99% by weight, or 95% to 99% by weight of cellulose acetate propionate (CAP) resin and 1% to 45% by weight, 1% to 40% by weight, 1% to 35% by weight, 1% to 30% by weight, 1% to 25% by weight, 1% to 20% by weight, 1% to 15% by weight, 1% to 10% by weight, or 1% to 5% by weight of cellulose acetate butyrate (CAB) resin. In a further embodiment, the cellulose ester resin is cellulose acetate propionate (CAP) resin (i.e., 100% by weight based on the total amount of cellulose ester resin).

[0017] In one or more embodiments herein, the CAP resin has an average degree of substitution (DSOH) of 0 to 1.2 for unsubstituted hydroxyl groups, an average degree of substitution (DSAC) of 0.05 to 0.5 for acetyl groups, and an average degree of substitution (DSPr) of 1.3 to 2.8 for propionyl groups. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the CAP resin has an average degree of substitution (DSOH) of 0.1 to 1.0, 0.1 to 0.75, 0.1 to 0.6, or 0.2 to 0.5 for unsubstituted hydroxyl groups, an average degree of substitution (DSAC) of 0.05 to 0.4, 0.05 to 0.3, 0.05 to 0.25, or 0.05 to 0.2 for acetyl groups, and an average degree of substitution (DSPr) of 1.5 to 2.8, 1.75 to 2.8, 2.0 to 2.8, or 2.2 to 2.8 for propionyl groups.

[0018] For cellulose esters, the level of substitution is typically expressed as the degree of substitution (DS), which is the average number of non-OH substituents in each aglycone unit (AGU). Typically, conventional cellulose contains three substituted hydroxyl groups in each AGU unit. As used herein, the term "degree of substitution" or "DS" refers to the average number of substituents in each aglycone ring of the cellulose polymer, with a maximum degree of substitution of 3.0. Because DS is a statistical average, a value of 1 does not guarantee that each AGU has a single substituent. In some cases, unsubstituted aglycone units may be present, some may have two substituents while others have three, and typically, the value will be a non-integer. Total DS is defined as the average number of all substituents in each aglycone unit. The degree of substitution per AGU can also refer to a specific substituent, such as hydroxyl (DSOH) or acetyl (DSAC).

[0019] In some embodiments, the cellulose ester resin has a falling ball viscosity of 0.1 to 5 seconds as measured according to ASTM D1343. All individual values ​​and sub-ranges are included and disclosed herein. For example, in some embodiments, the cellulose ester resin may have a falling ball viscosity of 0.1 to 5, 0.1 to 2.5, 0.1 to 1, or 0.1 to 0.5 seconds as measured according to ASTM D1343. In further embodiments herein, the cellulose ester resin is a CAP with a falling ball viscosity of 0.1 to 5 seconds as measured according to ASTM D1343. All individual values ​​and sub-ranges are included and disclosed herein. For example, in some embodiments, the cellulose ester resin is a CAP with a falling ball viscosity of 0.1 to 5, 0.1 to 2.5, 0.1 to 1, or 0.1 to 0.5 seconds as measured according to ASTM D1343.

[0020] In one or more embodiments herein, the cellulose ester resin is cellulose acetate propionate (CAP) having an average degree of substitution (DSOH) of 0 to 1.2 for unsubstituted hydroxyl groups, an average degree of substitution (DSAC) of 0.05 to 0.5 for acetyl groups, an average degree of substitution (DSPr) of 1.3 to 2.8 for propionyl groups, and a falling ball viscosity of 0.1 to 5 seconds as measured according to ASTM D1343. In one or more embodiments herein, the cellulose ester resin comprises at least 50% by weight of cellulose acetate propionate (CAP) having an average degree of substitution (DSOH) of 0 to 1.2 for unsubstituted hydroxyl groups, an average degree of substitution (DSAC) of 0.05 to 0.5 for acetyl groups, an average degree of substitution (DSPr) of 1.3 to 2.8 for propionyl groups, and a falling ball viscosity of 0.1 to 5 seconds as measured according to ASTM D1343. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the cellulose ester resin is cellulose acetate propionate (CAP) having an average degree of substitution (DSOH) of 0.1 to 1.0, 0.1 to 0.75, 0.1 to 0.6, or 0.2 to 0.5 for unsubstituted hydroxyl groups, an average degree of substitution (DSAC) of 0.05 to 0.4, 0.05 to 0.3, 0.05 to 0.25, or 0.05 to 0.2 for acetyl groups, an average degree of substitution (DSPr) of 1.5 to 2.8, 1.75 to 2.8, 2.0 to 2.8, or 2.2 to 2.8 for propionyl groups, and a falling ball viscosity of 0.1 to 5, 0.1 to 2.5, 0.1 to 1, or 0.1 to 0.5 seconds as measured according to ASTM D1343.

[0021] In addition to the above, in some embodiments herein, the cellulose ester resin may have a glass transition temperature (Tg) of 120°C to 170°C. All individual values ​​and sub-ranges are included and disclosed herein. For example, in some embodiments, the cellulose ester resin may have a Tg of 120°C to 165°C or 130°C to 165°C. In other embodiments, the cellulose ester resin is cellulose acetate propionate (CAP) having a glass transition temperature (Tg) of 120°C to 170°C. All individual values ​​and sub-ranges are included and disclosed herein. For example, in some embodiments, the cellulose ester resin is cellulose acetate propionate (CAP) having a Tg of 120°C to 165°C or 130°C to 165°C.

[0022] In embodiments described herein, the energy-curing ink composition further comprises one or more polyfunctional acrylates. In some embodiments, based on the total weight of (a), (b), (c), and (d), the energy-curing ink composition comprises 40% to 91% by weight of one or more polyfunctional acrylates. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, based on the total weight of (a), (b), (c), and (d), the energy-curing ink composition comprises 45% to 90%, 50% to 90%, or 55% to 85% by weight of one or more polyfunctional acrylates.

[0023] One or more polyfunctional acrylates may be difunctional, trifunctional, tetrafunctional, pentafunctional, hexafunctional, or combinations thereof. In some embodiments, the molecular weight of one or more polyfunctional acrylates is from 90 g / mol to 1,000 g / mol. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, one or more polyfunctional acrylates have a molecular weight of 150 g / mol to 750 g / mol, 200 g / mol to 700 g / mol, or 250 g / mol to 650 g / mol. Molecular weight can be calculated according to the test methods described below.

[0024] Examples of multifunctional acrylates include, but are not limited to: triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, neopentyl glycol diacrylate, dimethyloltricyclodecane diacrylate, bisphenol A EO (ethylene oxide) adduct diacrylate, bisphenol A PO (Propylene oxide) adduct diacrylates, hydroxy-neopentyl ester neopentyl glycol diacrylates, propoxylated neopentyl glycol diacrylates, alkoxylated dimethyloltricyclodecane diacrylates, polytetramethylene glycol diacrylates, trimethylolpropane triacrylates, EO-modified trimethylolpropane triacrylates, tri(propylene glycol) triacrylates, caprolactone-modified trimethylolpropane triacrylates, pentaerythritol triacrylates, pentaerythritol tetraacrylates, pentaerythritol ethoxytetraacrylates, dipentaerythritol hexaacrylates, bis(trimethylolpropane) tetraacrylates, glycerol propoxytetraacrylates, dipentaerythritol pentaacrylates, dipentaerythritol monohydroxy pentaacrylates, alkyl acyl-modified dipentaerythritol pentaacrylates, and caprolactam-modified dipentaerythritol hexaacrylates. In some embodiments, the one or more polyfunctional acrylates are trifunctional acrylates, pentafunctional acrylates, or combinations thereof. In other embodiments, the one or more polyfunctional acrylates are trifunctional acrylates, pentafunctional acrylates, or combinations thereof, wherein the molecular weight of the one or more polyfunctional acrylates is from 90 g / mol to 1,000 g / mol (optionally, 150 g / mol to 750 g / mol, 200 g / mol to 700 g / mol, or 250 g / mol to 650 g / mol). In further embodiments, the one or more polyfunctional acrylates are at least two triacrylates selected from the group consisting of: trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, tri(propylene glycol) triacrylate, caprolactone-modified trimethylolpropane triacrylate, and pentaerythritol triacrylate, and pentaacrylates selected from the group consisting of: dipentaerythritol pentaacrylate, dipentaerythritol monohydroxy pentaacrylate, and alkyl acyl-modified dipentaerythritol pentaacrylate. The at least two triacrylates will be different from each other.

[0025] In embodiments described herein, the energy-curable ink composition further comprises a photoinitiator. In some embodiments, the energy-curable ink composition comprises 2% to 10% by weight of a free radical photoinitiator. All individual values ​​and subranges are included and disclosed herein. For example, in some embodiments, the energy-curable ink composition comprises 2% to 8% by weight or 3% to 6% by weight of a free radical photoinitiator.

[0026] Examples of suitable free radical photoinitiators may include, but are not limited to, α-hydroxyketone photoinitiators (including α-hydroxyketone photoinitiators sold under the trademarks IRGACURE™ 184, IRGACURE™ 500, DAROCUR™ 1173, and IRGACURE™ 2959, manufactured by BASF, or α-hydroxyketone photoinitiators sold under the trademarks OMNIRAD™ 184, OMNIRAD™ 500, OMNIRAD™ 1173, and OMNIRAD™ 2959, manufactured by IGM Group BV Waalwijk, The Netherlands), α-aminoketone photoinitiators (including α-aminoketone photoinitiators IRGACURE™ 369, IRGACURE™ 379, IRGACURE™ 907, and IRGACURE™ 1300, manufactured by BASF), and bis(acylphosphine) photoinitiators (including those sold under the trademarks IRGACURE™ 819, IRGACURE™ 2959, and IRGACURE™ 2959, manufactured by BASF). The 819DW and IRGACURE™ 2022 are bisacylphosphine photoinitiators manufactured by BASF. Other suitable photoinitiators include monoacylphosphine oxides and bisacylphosphine oxides, such as 2,4,6-trimethylbenzoyl diphenylphosphine oxide (manufactured by BASF, brand name LUCIRIN™ TPO); ethyl-2,4,6-trimethylbenzoyl phenylphosphine ester (manufactured by BASF, brand name LUCIRIN™ TPO-L); monoacylphosphine and bisacylphosphine photoinitiators (e.g., IRGACURE™ 1700, IRGACURE™ 1800, IRGACURE™ 1850 and DAROCUR™ 4265, manufactured by BASF), benzyl dimethyl ketal photoinitiators (e.g., IRGACURE™ 651, manufactured by BASF), and oligomeric [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone] (which can be ESACURE™ KIP150 (available from Lamberti); Type II Norrish photoinitiators (e.g., benzophenone, 2-isopropylthioxanthanone, 4-isopropylthioxanthanone, 2,4-dimethylthioxanthanone, and 2,4-diethylthioxanthanone), and combinations thereof. In some embodiments, the free radical photoinitiator is an α-hydroxyketone photoinitiator.

[0027] In one or more embodiments herein, the energy-curable ink composition may further comprise one or more fillers. Suitable fillers may include, but are not limited to, amorphous diatomaceous earth, fumed silica and crystalline silica, clay, wax, aluminum silicate, magnesium aluminum silicate, talc, mica, exfoliating clay, calcium carbonate and calcium silicate, gypsum, barium sulfate, zinc, zinc calcium molybdate, zinc oxide, calcium, barium, strontium phosphosilicates and borosilicates, barium metaborate monohydrate, etc. In some embodiments, the filler may be clay, wax, talc, calcium carbonate, or combinations thereof. In some embodiments, the one or more fillers may be present in the energy-curable ink composition of this disclosure in an amount from about 0% to about 20% by weight, for example, from about 2% to about 16% by weight, from about 3% to about 15% by weight, from about 3% to about 8% by weight, or from about 8% to about 15% by weight, based on the total weight of the ink composition.

[0028] As measured according to ASTM D4287 using a cone-plate viscometer (BYK CAP 2000+) with rotor #2 at 100 rpm, the energy-curing ink compositions described herein have a viscosity of 2,000 mPa⁻¹ to 6,000 mPa⁻¹. In some embodiments, as measured according to ASTM D4287 using a cone-plate viscometer (BYK CAP 2000+) with rotor #2 at 100 rpm, the energy-curing ink compositions described herein have a viscosity of 2,000 mPa⁻¹ to 5,500 mPa⁻¹, 2,000 mPa⁻¹ to 5,000 mPa⁻¹, 2,500 mPa⁻¹ to 6,000 mPa⁻¹, or 3,000 mPa⁻¹ to 6,000 mPa⁻¹. As measured according to ASTM D4287 using a cone-plate viscometer (BYK CAP 5000+) with rotor #3 at 100 rpm, the energy-curing ink compositions described herein have a viscosity of 5,000 mPa⁻² to 20,000 mPa⁻². In some embodiments, as measured according to ASTM D4287 using a cone-plate viscometer (BYK CAP 2000+) with rotor #2 at 100 rpm, the energy-curing ink compositions described herein have a viscosity of 5,000 mPa⁻² to 17,500 mPa⁻², 5,000 mPa⁻² to 15,000 mPa⁻², or 5,000 mPa⁻² to 12,500 mPa⁻².

[0029] The embodiments described herein also disclose a printing method using the energy-curable ink composition described herein. The method includes: providing the energy-curable ink composition described herein; depositing the energy-curable ink composition onto a substrate; and curing the energy-curable ink composition by irradiation with ultraviolet light to form a cured ink. Exemplary substrates may include any substrate capable of receiving a printed image, whether smooth or non-smooth, such as paper, plastics (e.g., polyethylene, polypropylene), mylar, vinyl, metallized paper, folded cardboard, kraft paper, transparent substrates, metallic substrates, textured cardboard, textured plastics, uncoated paper, or labels. In the embodiments described herein, the cured ink may exhibit an IPA (Intense Pulsed Abrasion) of more than 100 cycles at a 500 g hammerhead value.

[0030] Test methods Falling ball viscosity Falling ball viscosity was measured according to ASTM D1343. Results are reported in seconds.

[0031] molecular weight The molecular weight of polyfunctional acrylates can be calculated from the molecular mass of each atom. The results are reported in g / mol.

[0032] Glass transition temperature (Tg) The resin sample was placed in a differential scanning calorimeter (TA Instruments DSC Q2000 V24.9 Build121). During the first heating cycle, the sample was heated from 30°C to 150°C at a rate of 10°C / min under a nitrogen atmosphere. The sample was then rapidly cooled to 30°C. For the second heating cycle, the sample was heated under the same conditions as in the first heating cycle. The midpoint of the second heating cycle was reported as the sample's Tg. Results were reported in °C.

[0033] Ink viscosity The viscosity of the ink composition was measured according to ASTM 4287 using a cone-plate viscometer (BYK-CAP 2000+) with rotor No. 2 or No. 3 at 100 RPM. Results were reported in millipascal-seconds (mPa·s).

[0034] Resin viscosity The viscosity of the resin was measured according to ASTM D3835. Results are reported in centipoises (cps).

[0035] Viscosity at a specified shear rate Viscosity was measured according to ASTM D2196 Method A. Viscosity is reported in mPa·s.

[0036] viscosity Using an inkometer equipped with two rubber rollers rotating at 400 rpm, 5 g of ink is applied to the top roller, and the ink is rubbed against the second roller at the same speed. The instrument is calibrated to sense ink transfer and the ease with which ink is transferred from one roller to another, and will provide a value in the range of 1 to 10.

[0037] IPA dual friction Typically, the IPA double friction test consists of an arm with a hammer that oscillates back and forth (double friction cycle) across the ink surface. The test stops once the ink begins to peel off, and the number of cycles is recorded. The ink passes the friction test if it passes 100 cycles. The test continues up to 200 cycles, meaning no failures occur after 200 cycles. A piece of coarse cotton cloth soaked in 5 g of IPA is placed over a 500 g hammer and a stroke counter set to 0 to record the number of back-and-forth movement cycles or one double friction cycle.

[0038] Print quality The appearance evaluation of printing inks is based on the uniformity of the ink on the metal substrate, color density, and any coating defects such as cracking, pinholes, orange peel-like defects, and spots. Quality ratings are as follows: .

[0039] Optical density The Datacolor 500 instrument is first calibrated for total internal reflection using white ceramic tiles and for total absorption using black ceramic tiles. Samples containing ink are then tested. The instrument provides optical color density in the range of 0 to 3. Units are dimensionless.

[0040] Adhesion Adhesion was measured according to ASTM D3359, and the results were summarized in grades 0-5 as specified in the ASTM method. Example

[0041] The following specific examples illustrate the process and performance characteristics related to energy-curable ink compositions and their components. Inventional and comparative examples are provided below, with details of formulations and results provided in the tables below.

[0042] Table 1 – Raw Materials .

[0043] Table 2 – Resin Properties .

[0044] The energy-curable ink composition was formulated according to the following procedure: The resin was mixed with TA-1, PA, and TA-2. A photoinitiator was added to the resin mixture along with a flow additive. The weight percentages of each component are shown in Table 3 below. Examples of the invention: IE1, IE4, and IE7 used CAP as the resin. CE2 and CE3 used A-81 as the resin. CE5 and CE8 used V-AP as the resin. CE6 used E-546 as the resin.

[0045] Table 3 – Energy-curable ink compositions .

[0046] The viscosity of the ink composition was measured and is shown in Table 4. The ink composition was applied to LDPE, tin, or aluminum using a 3-inch square precision tool with gaps of 0.5 to 6 mils, resulting in an ink thickness ranging from 10 to 25 micrometers. The coated substrates were cured under a UV-A lamp using a Fusion laboratory UV tower at 300 watts / cm and a conveyor speed of 25 fpm. The ink cured immediately, and performance characteristics (tack, IPA bifriction, print quality, optical density, and adhesion) were measured. The results are shown in Table 4.

[0047] Table 4 – Results .

[0048] As shown in Table 4, it has been unexpectedly found that the energy-curing ink formulation of the present invention exhibits improved viscosity compared to the comparative examples, and shows improved IPA bifriction, print quality and optical density during curing.

[0049] The dimensions and values ​​disclosed herein should not be construed as strictly limited to the precise numerical values ​​stated. Rather, unless otherwise specified, each such dimension is intended to represent the stated value and a functionally equivalent range around that value. For example, a dimension disclosed as “40 mm” is intended to represent “approximately 40 mm”.

[0050] Unless expressly excluded or otherwise limited, every reference cited herein (if any), including any cross-referenced or related patent or application and any patent application or patent claiming priority or benefit to this application, is hereby incorporated in its entirety by reference. Reference to any reference does not imply that it is prior art relating to any invention disclosed or claimed herein, nor does it imply that it, alone or in any combination with any other reference, teaches, suggests, or discloses any such invention. Furthermore, where any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in any reference incorporated by reference, the meaning or definition given to that term in this document shall prevail.

[0051] While specific embodiments of the invention have been described and illustrated, it will be apparent to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Therefore, the appended claims are intended to cover all such changes and modifications that fall within the scope of the invention.

Claims

1. An energy-curable ink composition comprising: a. 2% to 20% by weight of pigment based on the total weight of (a), (b), (c) and (d); b. 5% to 30% by weight of cellulose ester resin based on the total weight of (a), (b), (c) and (d); c. 40% to 91% by weight of one or more polyfunctional acrylates based on the total weight of (a), (b), (c), and (d); and d. 2% to 10% by weight of free radical photoinitiator based on the total weight of (a), (b), (c) and (d); The composition has a viscosity of 2,000 mPa-s to 6,000 mPa-s, as measured using a cone-plate viscometer (BYK CAP 2000+) with rotor #2 at 100 rpm, according to ASTM D4287.

2. The composition of claim 1, wherein the cellulose ester resin comprises at least 50% by weight cellulose acetate propionate (CAP), wherein the cellulose acetate propionate has an average degree of substitution (DSOH) of 0 to 1.2 for hydroxyl substituents, an average degree of substitution (DSAc) of 0.05 to 0.5 for acetyl substituents, an average degree of substitution (DSPr) of 1.3 to 2.8 for propionyl substituents, and a falling ball viscosity of 0.1 to 5 seconds as measured according to ASTM D1343.

3. The composition of claim 1 or 2, wherein the one or more polyfunctional acrylates are trifunctional acrylates, pentafunctional acrylates, or combinations thereof.

4. The composition according to claims 1-3, wherein the molecular weight of the one or more polyfunctional acrylates is from 90 g / mol to 1,000 g / mol.

5. The composition of claims 1-4, wherein the one or more polyfunctional acrylates are at least two triacrylates selected from the group consisting of: trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, tri(propylene glycol) triacrylate, caprolactone-modified trimethylolpropane triacrylate, and pentaerythritol triacrylate, and pentaacrylates selected from the group consisting of: dipentaerythritol pentaacrylate, dipentaerythritol monohydroxy pentaacrylate, and alkyl acyl-modified dipentaerythritol pentaacrylate.

6. The composition according to claims 1-5, wherein the photoinitiator is an α-hydroxyketone photoinitiator.

7. The composition according to claims 1-6, wherein the pigment is selected from inorganic pigments, organic pigments, or combinations thereof.

8. The composition according to claims 1-7, wherein the composition further comprises one or more fillers.

9. A printing method, the method comprising: Provide the ink composition according to claims 1-8; The ink composition is deposited onto the substrate; as well as The ink composition is cured by irradiating it with ultraviolet light to form a cured ink.

10. The method of claim 9, wherein the cured ink exhibits an IPA dual friction 500 g hammer value of more than 100 cycles.