Gravure or flexographic inks, and printed materials and laminates using them.

Abstract

To provide black ink for gravure or flexographic printing which has good highlight transition property, can stably reproduce a design of characters and ruled lines even in long run printing in printing of a packaging material, has good blocking resistance after printing, and is excellent in laminate strength.SOLUTION: Gravure or flexographic ink contains carbon black, a binder resin, an organic solvent, water and a fatty amide, wherein the binder resin contains a urethane resin and a polyvinyl acetal resin, and the urethane resin contains a polyester-derived structural unit composed of a dibasic acid and diol.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to gravure or flexo ink, printed matter using the same, and laminates.

Background Art

[0002] Gravure or flexo ink (hereinafter also referred to as printing ink) is widely used for the purpose of imparting cosmetic properties and functional properties to paper or plastic substrates. When these inks are used for packaging materials, especially when used for packages such as food packaging materials, generally, after printing these inks on a substrate such as a plastic film to obtain printed matter, the obtained printed matter is laminated with another plastic film. A laminated body obtained by laminating is used.

[0003] Such printing ink is mainly composed of a pigment as a coloring material, a binder resin that disperses the pigment and controls printing suitability and lamination suitability, a solvent that controls the viscosity and drying property of the ink, and an auxiliary agent that complements various performances. Among coloring materials, ink using carbon black in particular is widely used not only for reproducing the black design of packaging materials but also for information display by forming characters and ruled lines.

[0004] The above-mentioned information display design is generally a part with a small ruled line area called a highlight part, and the ink receiving part of the plate used for gravure or flexo printing also becomes small. Therefore, especially during long-run printing, there is a problem of poor highlight transferability in which the stability of ink transfer from the plate to the film deteriorates with printing, and ruled lines cannot be formed. This occurs particularly when the pigment dispersion in the ink is not sufficient or when the solubility of the ink in an organic solvent is poor.

[0005] To address the above challenges, binder resins are widely selected to optimize ink dispersibility and solvent solubility. In particular, vinyl chloride vinyl acetate copolymer resins are used as binder resins suitable for pigment dispersion in printing inks. However, these resins do not have sufficient solubility in alcohol-based solvents, which can lead to transfer problems, especially in highlight areas during long-run printing. Furthermore, in flexographic printing, ester-based solvents can damage flexographic resin plates, so the solvent composition is primarily alcohol-based. Therefore, vinyl chloride vinyl acetate copolymer resins, which have low compatibility with alcohol, are generally not used.

[0006] Polyurethane resins are widely used as binder resins in printing inks. They offer a wide range of raw material options, making it easy to adjust the structure and control properties such as solubility in ink solvents and laminate properties. However, they have the drawback of poor pigment dispersibility. Therefore, they are often used in combination with dispersion resins as described above.

[0007] As shown in Patent Documents 1 and 2, there are examples of using polyvinyl butyral resin (hereinafter also referred to as PVB) as a resin that has broad solubility and pigment dispersibility in ester-based and alcohol-based solvents to form inks for packaging materials. However, in the case of black ink, the aforementioned poor transferability often leads to insufficient density in printed materials. If the amount of pigment added is increased to resolve the insufficient density, there is a problem that the printability, post-printing blocking resistance, and lamination strength decrease. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2014-62138 [Patent Document 2] Japanese Patent Publication No. 2021-80402 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0009] The problem that this invention aims to solve is to provide a black ink for gravure or flexographic printing that has good highlight transfer properties, can stably reproduce character and line designs in packaging material printing even in long-run printing, has good blocking resistance after printing, and further has excellent lamination strength. [Means for solving the problem]

[0010] In light of the above-mentioned problems, the inventors conducted thorough research and, as a result, found that the following methods can solve the problems, leading to the present invention.

[0011] In other words, the present invention relates to a gravure or flexographic ink containing carbon black, a binder resin, an organic solvent, water, and a fatty acid amide, The binder resin comprises a urethane resin and a polyvinyl acetal resin. The present invention relates to a gravure or flexographic ink in which the urethane resin contains polyester-derived structural units consisting of a dibasic acid and a diol.

[0012] The present invention also relates to the above-mentioned gravure or flexographic ink, wherein the average particle size of the carbon black is 10 to 120 nm.

[0013] The present invention also relates to the above-mentioned gravure or flexographic ink, wherein the diol contains at least one selected from the group consisting of 1,2-propanediol, 2-methyl-1,3-propanediol, and butylethylpropanediol.

[0014] The present invention also relates to the above-mentioned gravure or flexographic ink, wherein the urethane resin further contains structural units derived from polyether.

[0015] The present invention also relates to the above-mentioned gravure or flexographic ink, wherein the fatty acid amide has an aliphatic hydrocarbon group having 10 to 25 carbon atoms.

[0016] The present invention further relates to the gravure or flexographic ink described above, which contains an isocyanate-based curing agent.

[0017] The present invention also relates to a printed matter having a printed layer formed from the above-described gravure or flexographic ink on a substrate 1.

[0018] The present invention also relates to a laminate having a substrate 2 further on the printed layer of the above-described printed matter.

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a gravure or flexographic printing ink (hereinafter sometimes simply referred to as "ink") that has good highlight transferability, can stably reproduce the characters and ruled lines of packaging materials even in long-run printing, has good blocking resistance after printing, and further has excellent laminate strength.

Embodiments for Carrying Out the Invention

[0020] Examples will be given below to describe the embodiments of the present invention in detail. However, the matters described below are examples or representative examples of the embodiments of the present invention, and the present invention is not limited to these contents as long as it does not exceed the gist thereof.

[0021] <Carbon black> The ink of the present invention contains carbon black as a pigment. Specifically, C.I. Pigment Black 7 is preferable. The average particle diameter of the carbon black is preferably 20 to 120 nm, more preferably 23 to 100 nm, and still more preferably 25 to

[100] nm. When the average particle diameter of the carbon black is within the above range, good pigment dispersibility and a clear hue can be obtained. Here, the above average particle diameter is the arithmetic average diameter obtained by observing carbon black particles with an electron microscope.

[0022] <Binder resin> The ink of the present invention contains a urethane resin and a polyvinyl acetal resin as binder resins.

[0023] <Urethane resin> In the ink of the present invention, the urethane resin has a function of improving printing suitability and laminate strength. The urethane resin is a resin having a urethane bond. For example, a urethane resin composed of a polyol and a polyisocyanate, and a urethane polymer of terminal isocyanate composed of a polyol and an isocyanate, and a chain extender such as a polyamine are reacted. Examples of the urethane urea resin obtained thereby include those described in JP-A-2013-256551, JP-A-2018-127545, and JP-A-2013-213109. The polyol used for the synthesis of the urethane resin preferably contains a structural unit derived from a polyester composed of a dibasic acid and a diol (hereinafter also referred to as a polyester polyol), and further contains a structural unit derived from a polyether (hereinafter also referred to as a polyether polyol). By containing a structural unit derived from a polyester, the adhesiveness to the substrate becomes good. In addition, by having a structural unit derived from a polyether, the solubility in an organic solvent increases and the printing suitability becomes good.

[0024] The dibasic acid used for the polyester polyol is preferably one having 2 to 20 carbon atoms such as sebacic acid, adipic acid, azelaic acid, succinic acid, decanoic acid, dimer acid, etc. Among them, at least one selected from the group consisting of adipic acid, sebacic acid, succinic acid, and dimer acid is more preferable.

[0025] The diol component of the polyester polyol used preferably contains a branched diol. Examples of such branched diols include 1,2-propanediol, butylethylpropanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2,4-diethyl-1,5-pentanediol, 1,3-butanediol, and dipropylene glycol. In particular, from the viewpoint of improving blocking resistance, it is more preferable to include at least one selected from the group consisting of 1,2-propanediol, 2-methyl-1,3-propanediol, and butylethylpropanediol.

[0026] The polyether polyol is not limited to the following, but it is preferable to use, for example, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytrimethylene glycol, and polyether polyols which are copolymers thereof.

[0027] The number-average molecular weights of polyester polyols and polyether polyols are, independently, preferably in the range of 500 to 5,000.

[0028] Examples of the polyisocyanates mentioned above include various known aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates commonly used in the production of polyurethane resins. These may also be in the form of trimers with an isocyanurate ring structure.

[0029] Examples of aromatic or aroliphatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyli isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylenedi isocyanate, 1,4-phenylenedi isocyanate, tolylene diisocyanate, xylylene diisocyanate, and m-tetramethylxylylene diisocyanate.

[0030] Examples of aliphatic diisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0031] Examples of alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, and dimer isocyanates obtained by converting the carboxyl groups of dimer acids to isocyanate groups.

[0032] Preferably, the polyisocyanate is selected from the group consisting of tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, and trimers of hexamethylene diisocyanate. These polyisocyanates can be used individually or in combination of two or more.

[0033] The polyamines are not limited to those listed below, but are preferably those with a molecular weight of 500 or less, and include diamine-based and polyfunctional amine-based polyamines. In addition to diamine-based chain extenders such as ethylenediamine, propylenediamine, hexamethylenediamine, pentamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and p-phenylenediamine, diamine-based chain extenders having hydroxyl groups such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypyropyrethylenediamine, di-2-hydroxypyropyrethylenediamine, and di-2-hydroxypropylethylenediamine can also be used. These chain extenders can be used individually or in combination of two or more. Polyfunctional amine-based chain extenders with three or more functions can also be used as needed. Specifically, examples include diethylenetriamine, iminobispropylamine (IBPA, 3,3'-diaminodipropylamine), triethylenetetramine, N-(3-aminopropyl)butane-1,4-diamine (spermidine), 6,6-iminodihexylamine, 3,7-diazanonane-1,9-diamine, and N,N'-bis(3-aminopropyl)ethylenediamine. Among these, isophoronediamine, hexamethylenediamine, and iminobispropylamine are preferred.

[0034] The polyamines described above may include compounds having primary and secondary monovalent amino groups. These compounds function as polymerization inhibitors to stop excessive reactions. Examples of such compounds include dialkylamines such as di-n-butylamine and amino alcohols such as 2-ethanolamine. Furthermore, when it is particularly desirable to introduce carboxyl groups into the polyurethane resin, amino acids such as glycine and L-alanine can be used as polymerization inhibitors. When using polymerization inhibitors, the polymerization inhibitor and chain extender may be used together to carry out the chain extension reaction, or the polymerization inhibitor may be added alone to carry out the polymerization termination reaction after the chain extension reaction has been carried out to some extent with the chain extender. On the other hand, molecular weight control is possible even without using polymerization inhibitors, but in this case, adding the prepolymer to a solution containing the chain extender is preferred in terms of reaction control.

[0035] The content of polyol-derived structural units in the urethane resin is preferably 5 to 95% by mass, more preferably 20 to 90% by mass, and even more preferably 30 to 85% by mass, based on the solid content mass of the urethane resin. Furthermore, the content of constituent units derived from polyester polyol is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 65% ​​by mass or more, based on the solid content mass of the urethane resin. In urethane resin, when the constituent units derived from polyols and those derived from polyester polyols are present in the above proportions, the ink exhibits excellent printability and lamination strength.

[0036] The urethane resin is preferably one with a weight-average molecular weight of 10,000 to 100,000, preferably with a glass transition temperature of 0°C or lower, more preferably -60°C to 0°C, and even more preferably -40°C to -5°C.

[0037] Furthermore, the urethane resin is preferably one that has amino groups and / or hydroxyl groups. If the urethane resin has amino groups, the amine value is preferably 0.5 to 30 mg KOH / g, and more preferably 1 to 20 mg KOH / g. If the urethane resin has hydroxyl groups, the hydroxyl value is preferably 0.5 to 30 mg KOH / g, and more preferably 1 to 20 mg KOH / g.

[0038] <Polyvinyl acetal resin> In the ink of the present invention, polyvinyl acetal resin is responsible for solubility in ester-based and alcohol-based solvents and for pigment dispersibility. Polyvinyl acetal resin can be obtained, for example, by condensation (acetalization) of polyvinyl alcohol and aldehydes. Examples of polyvinyl acetal resins include polyvinyl formal, polyvinyl acetal, polyvinyl propional, polyvinyl butyral, and polyvinyl hexyral, but in the present invention, polyvinyl butyral resin is preferred from the viewpoint of toughness and flexibility of the resin.

[0039] <Polyvinyl butyral resin> The polyvinylobutyral resin used in the present invention is obtained by reacting polyvinyl alcohol with butyraldehyde to form a butyral ring, and preferably contains vinyl alcohol units, vinyl acetate units, and a butyral ring, and more preferably contains 60 to 90% butyral rings. The weight-average molecular weight of the polyvinybutyral resin is preferably 10,000 to 100,000, more preferably 10,000 to 80,000. The glass transition temperature is preferably 50 to 80°C, more preferably 60 to 75°C. Within the above range, good pigment dispersibility and high solubility in esters and alcohols can be obtained.

[0040] <Organic solvents> The printing ink of the present invention contains an organic solvent as a liquid medium. While not limited to the following, known organic solvents can be used, including ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, ester-based organic solvents, alcohol-based organic solvents such as methanol, ethanol, n-propanol, isopropanol, and n-butanol, and glycol ether-based solvents such as ethylene glycol monopropyl ether and propylene glycol monomethyl ether. These solvents may also be used in mixtures.

[0041] <Water> The printing ink of the present invention further contains water. The water content is preferably 0.1 to 10% by mass, more preferably 0.5 to 7% by mass, even more preferably 0.5 to 5% by mass, and particularly preferably 0.5 to 4% by mass of the total mass of the ink. The inclusion of a predetermined amount of water in the ink improves pigment dispersibility and enhances printability, such as ink transferability.

[0042] <Fatty acid amide> The printing ink of the present invention contains a fatty acid amide as an additive. The fatty acid amide preferably has an aliphatic hydrocarbon group having 10 to 25 carbon atoms. Furthermore, the fatty acid amide content is preferably 0.1 to 1% by mass, and more preferably 0.6 to 0.9% by mass, in the ink. The inclusion of a fatty acid amide in the ink provides good blocking resistance, and this effect is further improved when the content is within the above range.

[0043] <Additives> The printing ink of the present invention may contain, in addition to the above-mentioned fatty acid amide, conventionally known additives as appropriate. For example, pigment derivatives, dispersants, wetting agents, adhesion aids, leveling agents, defoaming agents, antistatic agents, viscosity modifiers, chelating crosslinking agents, trapping agents, antiblocking agents, wax components other than those listed above, silane coupling agents, etc., can be used.

[0044] <Isocyanate-based curing agent> The printing ink of the present invention preferably contains an isocyanate-based curing agent. Polyisocyanates and modified compounds thereof can be used as the isocyanate-based curing agent. Specifically, biuret, isocyanurate, and adduct forms of polyisocyanates are preferred, and diisocyanates are preferred as the polyisocyanates. Aromatic diisocyanates such as tolylene diisocyanate, alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate and isophorone diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate, and aromatic aliphatic diisocyanates such as α,α,α′,α′-tetramethylxylylene diisocyanate can be used. Examples of specific commercially available products include 24A-100, 22A-75, TPA-100, TSA-100, TSS-100, TAE-100, TKA-100, P301-75E, E402-808, E405-70B, AE700-100, D101, D201, A201H (manufactured by Asahi Kasei), Mytec Y260A (manufactured by Mitsubishi Chemical Corporation), Coronate HX, Coronate HL, Coronate L (manufactured by Nippon Polyurethane Co., Ltd.), and Desmodul N75MPA / X (manufactured by Bayer AG). Among these, isophorone diisocyanate and isophorone diisocyanate adducts and / or isocyanurates are preferred.

[0045] <Manufacturing of printing inks> The printing ink of the present invention can be manufactured by dissolving and / or dispersing a pigment and a binder resin in an organic solvent. Specifically, a pigment dispersion can be produced by mixing carbon black, polyurethane resin, polyvinyl acetal resin, and optionally a pigment dispersant, and dispersing the mixture in an organic solvent. The printing ink can then be manufactured by further blending the obtained pigment dispersion with a binder resin, fatty acid amide, water, isocyanate curing agent, and optionally other resins and additives. Commonly used pigment dispersers such as roller mills, ball mills, pebble mills, attritors, sand mills, and gamma mills can be used. Among these, manufacturing using a bead mill disperser such as a sand mill is preferred. The printing ink can be manufactured by appropriately adjusting the type and size of beads in the bead mill disperser, the bead filling rate, the dispersion processing time, viscosity, etc.

[0046] The viscosity of the printing ink of the present invention is preferably in the range of 10 to 1000 cps, more preferably in the range of 15 to 700 cps, and even more preferably in the range of 20 to 500 cps, when measured at 25°C with a B-type viscometer, in order to accommodate high-speed printing (50 to 300 m / min). The viscosity of the printing ink composition can be adjusted by appropriately selecting the type and amount of raw materials used, such as pigments, binder resins, and organic solvents. The viscosity of the ink can also be adjusted by adjusting the particle size and particle size distribution of the pigments in the ink.

[0047] <Printed material> One embodiment of the present invention is a printed article having a printed layer formed by printing the ink of the present invention onto a substrate 1. The printing is preferably performed by gravure printing or flexographic printing.

[0048] Gravure printing (Gravure version) In the gravure printing described above, the gravure plate is a cylindrical metal plate, and recesses are created in each color by engraving, etching, or laser. There are no restrictions on the use of engraving or laser, and they can be set as desired according to the design. Line screens of 75 to 200 are used as appropriate, with higher line screens allowing for finer printing. The thickness of the printed layer is preferably 0.1 μm to 100 μm.

[0049] (printing machine) In a gravure printing press, each printing unit is equipped with the aforementioned gravure plate and doctor blade. There are numerous printing units, and units can be configured to accommodate organic solvent-based printing inks and image inks. Each unit has an oven drying unit. Printing is performed by rotary press using a roll printing method. The type of plate and doctor blade are selected as appropriate, according to the specifications.

[0050] <Flexographic printing> (Flexographic version) The plates used for the above flexographic printing include photosensitive resin plates that utilize UV ​​curing with a UV light source, or elastomer material plates that use a direct laser engraving method. Regardless of the method of forming the image portion of the flexographic plate, a screen ruling of 75 lpi or higher is used. Any type of sleeve or cushioning tape can be used to attach the plate.

[0051] (printing machine) Flexographic printing presses include CI-type multi-color flexographic printing presses and unit-type multi-color flexographic printing presses. Ink supply methods include chamber type and two-roll type, and the appropriate printing press can be used.

[0052] <Base material 1> The substrate 1 preferably has a wettability index of 30 to 60 dyne / cm on the printed surface (the surface in contact with the printing layer), and more preferably 35 to 55 dyne / cm. The wettability index is a value measured using a wettability index standard solution according to the method described in JIS K6768. The substrate 1 that can be used in the printed material of the present invention includes, for example, polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polycarbonate, and polylactic acid, polystyrene-based resins such as polystyrene, AS resin, and ABS resin, nylon, polyamide, polyvinyl chloride, polyvinylidene chloride, cellophane, paper, aluminum, or a film-like substrate made of these composite materials. Furthermore, a vapor-deposited substrate obtained by vapor-depositing inorganic compounds such as silica, alumina, and aluminum onto polyethylene terephthalate or nylon film can also be used, and the vapor-deposited surface may be further coated with polyvinyl alcohol or the like. It is preferable that the substrate 1 is treated to facilitate adhesion such that the wettability index of the surface in contact with the printed layer falls within the above range. Examples of such facilitating adhesion treatments include corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, and primer treatment. For example, corona discharge treatment causes hydroxyl groups, carboxyl groups, carbonyl groups, etc., to appear on the substrate. It is preferable that the ink contains compounds having functional groups such as hydroxyl groups and amino groups, as hydrogen bonding can be utilized.

[0053] <Laminate> A laminate can be obtained by sequentially laminating a film layer to the printed layer of the printed material described above. Preferably, the laminate includes an adhesive layer, and a laminate comprising a base material 1, a printed layer, an adhesive layer, and a base material 2 in that order is preferred. The adhesive layer may consist of an anchor coating agent, a urethane-based laminate adhesive, or a molten resin. Examples of anchor coating agents (AC agents) include imine-based AC agents, isocyanate-based AC agents, polybutadiene-based AC agents, and titanium-based AC agents. Examples of urethane-based laminate adhesives include polyether-urethane-based laminate adhesives and polyester-based laminate adhesives, which can contain organic solvents or be solvent-free. Examples of molten resins include molten polyethylene. Laminates can be manufactured using known lamination processes, such as the conventional extrusion lamination method, which involves laminating molten polyethylene resin onto a printed layer via various anchor coating agents such as imine-based, isocyanate-based, polybutadiene-based, and titanium-based agents; the dry lamination method or non-solvent lamination method, which involves applying an adhesive such as urethane-based to the printed surface and then laminating a plastic film on top of it; or the direct lamination method, which involves directly pressing molten polypropylene onto the printed surface.

[0054] <Base material 2> Substrate 2 can be the same as that of substrate 1, and may be the same or different. Among these, unstretched polyethylene, unstretched polypropylene, nylon substrate, aluminum foil substrate, and aluminum vapor-deposited substrate are preferred. [Examples]

[0055] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. It is not. Furthermore, unless otherwise noted, parts and % in this invention refer to parts by mass and mass. Represents a percentage. Note that Example 10 is for reference only.

[0056] (Hydroxyl value) The measurements were taken according to the method described in JIS K0070.

[0057] (Amine value) The amine value was determined according to the following method in accordance with JIS K0070, using the equivalent amount of hydrochloric acid and the same amount of potassium hydroxide in milligrams required to neutralize the amino groups contained in 1 g of resin. 0.5 to 2 g of the sample was accurately weighed (sample solid content: Sg). 50 mL of a methanol / methyl ethyl ketone = 60 / 40 (mass ratio) mixed solution was added to the accurately weighed sample and dissolved. Bromophenol blue was added to the resulting solution as an indicator, and the solution was titrated with 0.2 mol / L ethanolic hydrochloric acid solution (titer: f). The endpoint was defined as the point where the color of the solution changed from green to yellow, and the amine value was determined using the titration volume (A mL) at this point, according to the following formula (Equation 2). (Equation 2) Amine value = (A × f × 0.2 × 56.108) / S [mgKOH / g]

[0058] (Weight average molecular weight) The weight-average molecular weight was determined by measuring the molecular weight distribution using a GPC (gel permeation chromatography) instrument (HLC-8220, manufactured by Tosoh Corporation) and calculating the converted molecular weight using polystyrene as the standard substance. The measurement conditions are shown below. Columns: The following columns were used, connected in series. TSKgel SuperAW2500 manufactured by Tosoh Corporation TSKgel SuperAW3000 manufactured by Tosoh Corporation TSKgel SuperAW4000 manufactured by Tosoh Corporation TSKgel guardcolumn SuperAWH, manufactured by Tosoh Corporation. Detector: RI (Differential Refractometer) Measurement conditions: Column temperature 40°C Eluent: Tetrahydrofuran Flow rate: 1.0mL / min

[0059] <Synthesis of urethane resin> [Synthesis Example 1] (Synthesis of urethane resin PU1) 90 parts of a polyester polyol (hereinafter referred to as MPO / AdA) with a number average molecular weight of 2,000, which is a condensate of 2-methyl-1,3-propanediol (MPO) and adipic acid (AdA), 14 parts of a polyether polyol with a number average molecular weight of 1,000, which is a polymer of propylene glycol, 25 parts of isophorone diisocyanate (hereinafter referred to as IPDI), and 32 parts of ethyl acetate were mixed and reacted at 90°C for 5 hours under a nitrogen atmosphere to obtain a urethane prepolymer with terminal isocyanates. Next, 6 parts of isophoronediamine (IPDA), 2 parts of N-(2-aminoethyl)ethanolamine (AEA), 1 part of dibutylamine (DBA), and 290 parts of mixed solvent 1 (ethyl acetate / isopropanol = 70 / 30 (mass ratio)) were stirred and mixed, and the resulting urethane prepolymer of the terminal isocyanate was gradually added at 40°C. The mixture was reacted at 80°C for 1 hour to obtain a solution of urethane resin PU1 with a solid content of 30%, an amine value of 8.3 mg KOH / g, a hydroxyl value of 7.2 mg KOH / g, and a weight-average molecular weight of 58,000.

[0060] [Synthesis Examples 2-5 and Comparative Synthesis Example 1] (Synthesis of urethane resins PU2-5 and PPU1) Using the raw materials shown in Table 1, solutions of urethane resins PU2-5 and PPU1 were obtained using the same method as in Synthesis Example 1.

[0061] [Table 1]

[0062] The abbreviations used in Table 1 are as follows: BEPG / AdA: A polyester polyol, a condensate of butylethylpropanediol and adipic acid, with a number-average molecular weight of 2,000. • PG / AdA: A polyester polyol formed by the condensation of 1,2-propanediol and adipic acid, with a number-average molecular weight of 2,000. MPD / AdA: A polyester polyol formed by the condensation of 3-methyl,1,5-pentanediol and adipic acid, with a number-average molecular weight of 2,000. • PPG: Polypropylene glycol, number average molecular weight 1,000 and 2,000

[0063] The abbreviations used in the following examples and comparative examples are as follows: • PVB solution: A 30% solids solution of polyvinyl butyral resin (glass transition temperature 70°C, weight-average molecular weight 50,000) containing vinyl alcohol units, vinyl acetate units, and vinyl butyral units, with 73% by mass of butyral rings, prepared using an ethyl acetate / isopropanol = 1 / 1 mixed solvent. • Vinyl chloride-vinyl acetate solution: 30% solids ethyl acetate solution of vinyl chloride-vinyl acetate copolymer resin (Solvine TA3, manufactured by Nisshin Chemical Co., Ltd.) • Fatty acid amide solution: 20% solid content ethyl acetate solution of fatty acid amide (Amid P, manufactured by Kao Chemical Co., Ltd.) • Isocyanate curing agent: 50% solid content ethyl acetate solution of hexamethylene diisocyanate adduct.

[0064] <Manufacturing of gravure inks> [Example 1] Manufacturing of Gravure Ink GB1 Forty parts of urethane resin PU1, ten parts of PVB solution, ten parts of CI pigment black 7 (average particle size 25 μm), 22.2 parts of n-propyl acetate, and ten parts of isopropanol were mixed and dispersed in a bead mill for 20 minutes to obtain a pigment dispersion. To the obtained pigment dispersion, 0.8 parts of fatty acid amide (18 carbon atoms) solution, three parts of isocyanate curing agent, two parts of propylene glycol monomethyl ether, and two parts of water were stirred and mixed to obtain gravure ink GB1.

[0065] [Examples 2-11] Manufacturing of gravure inks GB2-GB11 Gravure inks GB2 to GB11 were obtained using the same method as in Example 1, except that the raw materials and formulations were changed as shown in Table 2.

[0066] [Comparative Examples 1-7] Manufacturing of Gravure Inks GBB1-GBB7 Gravure inks GBB1 to GBB7 were obtained using the same method as in Example 1, except that the raw materials and formulations shown in Table 2 were changed.

[0067] <Manufacturing of flexographic inks> [Example 12] (Manufacturing of flexographic ink FB1) 40 parts of urethane resin PU1, 10 parts of PVB solution, 12 parts of CI pigment black 7 (average particle size 25 μm), 8 parts of n-propyl acetate, and 22.2 parts of isopropanol were mixed and dispersed in a bead mill for 20 minutes to obtain a pigment dispersion. To the obtained pigment dispersion, 0.8 parts of fatty acid amide (18 carbon atoms) solution, 3 parts of isocyanate curing agent, 2 parts of propylene glycol monomethyl ether, and 2 parts of water were stirred and mixed to obtain flexographic ink FB1.

[0068] [Examples 13-16] (Manufacturing of flexographic inks FB2-FB5) Flexographic inks FB2 to FB5 were obtained using the same method as in Example 12, except that the raw materials and formulations shown in Table 3 were changed. Note that the average particle size of CI Pigment Black 7 in Table 3 is 25 μm, and the number of carbon atoms in the fatty acid amide is 18.

[0069] [Comparative Examples 8-12] (Manufacturing of flexographic inks FBB1-FBB5) Flexographic inks FBB1 to FBB5 were obtained using the same method as in Example 9, except that the raw materials and formulations shown in Table 3 were changed.

[0070] <Evaluation of printing inks> The highlight transfer properties were evaluated using the printing inks obtained in the examples and comparative examples. Furthermore, printed materials and laminated structures were prepared using the above printing inks, and their blocking resistance and lamination strength were evaluated. The evaluation method is as follows. The results are shown in Tables 2 and 3.

[0071] [Highlight transferability of gravure inks] The viscosity of the gravure ink was adjusted to 16 seconds using a mixed solvent of ethyl acetate / isopropanol = 7 / 3 (Zaan Cup #3, manufactured by Rigosha, 25°C). Under high temperature conditions of 30°C, printing was performed on the treated surface of a biaxially oriented polypropylene (CPP) film (Futamura Chemical Co., Ltd. FOR, 20 μm thick) that had been corona discharge treated on one side, using a gravure printing press equipped with a gravure plate. The gravure plate had a halftone gradient pattern, and the printing speed was set to 200 m / min. The percentage of the area of ​​streaking in the printed pattern in the highlight (halftone area 5% to 10%) printed areas of the printed material was evaluated visually. (Evaluation Criteria) A (Excellent): No smudging, and no stains on non-printed areas. B (Good): Scratching is visible in less than 5% of the area. C (Acceptable): Scratching is observed in an area ratio of 10% or more, but less than 10%. D (Unacceptable): Scratching is visible in more than 10% of the area.

[0072] [Highlight transferability of flexographic inks] The viscosity of the flexographic ink was adjusted to 16 seconds using a mixed solvent of ethyl acetate / isopropanol = 3 / 7 (Zaan Cup #4, manufactured by Rigosha, 25°C). Under high temperature conditions of 30°C, printing was performed on the treated surface of a biaxially oriented polypropylene (CPP) film (Futamura Chemical Co., Ltd. FOR, 20 μm thick) that had been corona-discharged on one side, using a flexographic printing press equipped with a flexographic plate. The flexographic plate had a halftone gradient pattern, and the printing speed was set to 200 m / min. For the printed material, the percentage of the area of ​​streaking in the printed pattern in the highlight (halftone area 5% to 10%) printed areas was visually evaluated. The evaluation criteria were the same as those for the highlight transferability of gravure inks.

[0073] [Blocking resistance of printing inks] The printed material obtained from the highlight transfer evaluation was cut to a size of 4 cm x 4 cm. The printed surface of the cut sample was superimposed on the untreated surface of a 20 μm thick polypropylene film of the same size to create a test specimen. A load of 10 kgf was applied to the test specimen in an atmosphere of 40°C and 80% relative humidity. After 24 hours, the films were separated, and the degree of ink peeling from the printed surface was visually assessed. (Evaluation Criteria) A (Excellent): The ink film does not peel off, and there is no peeling resistance. B (Good): The ink film does not peel off, and the peeling resistance is low. C (Acceptable): The peeling area of ​​the ink film is 1% or more and less than 5%, and the peeling resistance is low. D (Not acceptable): The peeling area of ​​the ink film is 5% or more, or the peeling resistance is high.

[0074] [Manufacturing of laminated materials] On the printed layer obtained by highlight transfer evaluation, a urethane-based laminate adhesive (TM320 / CAT13B, 30% solids ethyl acetate solution, manufactured by Toyo Morton Co., Ltd.) was applied to a coating amount of 2.0 g / m2 after drying, and after drying, an unstretched polyethylene (PE) film with a thickness of 50 μm was laminated onto the adhesive layer to obtain a laminate.

[0075] [Lamination strength] The resulting laminate was left to stand for 4 days at a temperature of 30°C and a relative humidity of 50%. After standing, the laminate was cut into 15 mm wide strips, and a 90-degree peel test was performed using a tensile testing machine at a tensile speed of 300 mm / min to measure the laminate strength (N / 15 mm). (Evaluation Criteria) A (Excellent): Lamination strength of 1.5N / 15mm or higher B (Good): Lamination strength of 1.0 N / 15 mm or more, and less than 1.5 N / 15 mm. C (Acceptable): Lamination strength of 0.5 N / 15 mm or more, and less than 1.0 N / 15 mm. D (Not acceptable): Lamination strength is less than 0.5N / 15mm

[0076] [Table 2]

[0077] [Table 3]

[0078] From the above results, the printing inks corresponding to the embodiments of the present invention exhibit good highlight transfer properties and blocking resistance, and high laminate strength can be obtained in laminated printed materials using these inks. In particular, Examples 1 and 12, which use gravure ink GB1 and flexographic ink FB1, are especially excellent in highlight transfer properties, blocking resistance, and laminate strength. In contrast, GBB1 and FBB1, which are made only from urethane resin, GBB2 and FBB2, which use vinyl chloride-vinyl acetate copolymer, GBB5 and FBB4, which do not use water, and GBB6, which uses CI pigment red 146, have poor highlight transfer properties. Furthermore, GBB4 and FBB3, which do not use fatty acid amide solution, have poor blocking resistance. In addition, GBB3, which uses PU composed only of PPG, and GBB7 and FBB5, which use only PVB, have low laminate strength.

Claims

1. A gravure or flexographic ink containing carbon black, binder resin, organic solvent, water, and fatty acid amide, The binder resin comprises a urethane resin and a polyvinyl acetal resin. The aforementioned urethane resin contains a polyester-derived structural unit consisting of a dibasic acid and a diol. The diol contains at least one selected from the group consisting of 1,2-propanediol, 2-methyl-1,3-propanediol, and butylethylpropanediol. A gravure or flexographic ink in which the content of the polyester-derived constituent units is 65% by mass or more, based on the solid content mass of the urethane resin.

2. The gravure or flexographic ink according to claim 1, wherein the average particle size of the carbon black is 20 to 120 nm.

3. The gravure or flexographic ink according to claim 1 or 2, wherein the urethane resin further contains structural units derived from polyether.

4. The gravure or flexographic ink according to any one of claims 1 to 3, wherein the fatty acid amide has an aliphatic hydrocarbon group having 10 to 25 carbon atoms.

5. Furthermore, the gravure or flexographic ink according to any one of claims 1 to 4 contains an isocyanate-based curing agent.

6. A printed article having a printed layer formed on a substrate 1 from gravure or flexographic ink as described in any one of claims 1 to 5.

7. A laminate having a substrate 2 further on the printed layer of the printed material according to claim 6.

Images