Water-based flexographic ink and its applications

Abstract

To provide an aqueous flexographic ink that prevents ink from being transferred to an unintended portion of printed material that should not be printed, and demonstrates excellent blocking resistance, and also excels in ink stability, substrate adhesion, and laminate strength.SOLUTION: An aqueous flexographic ink comprises a coloring pigment, an extender pigment, a binder resin and a liquid medium, the coloring pigment comprising an organic pigment and / or carbon black. Relative to the total mass of the aqueous flexographic ink, the coloring pigment is 12-30 mass% and the extender pigment is 1-15 mass%. The binder resin comprises an aqueous urethane resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an aqueous flexographic ink, a printed matter obtained by printing the ink on a substrate 1, and a laminate laminate having an adhesive layer and a substrate 2 on a printed layer of the printed matter.

[0002] More specifically, the present invention relates to an aqueous flexographic ink printed on a plastic substrate, an aqueous flexographic ink having excellent properties such as plate - wrapping property and blocking property, a printed matter, and a laminate.

Background Art

[0003] For packaging printing of foods and sanitary products, various printing methods such as gravure printing, flexographic printing, offset printing, inkjet printing, silk - screen printing, roll - coater printing, etc. are widely used as methods for imparting patterns. In particular, for flexible packaging materials using a plastic film as a substrate, the gravure printing method or the flexographic printing method has been used. Flexographic printing is a type of relief printing, in which ink is adhered to a resin relief plate via an anilox roll, and then the ink is transferred from the relief plate to a plastic substrate or the like. In particular, flexographic ink is excellent in high - speed printing property, and since flexographic printing is relief printing, even a small amount of ink transfer can reproduce fine characters and sharp expressions, so it is useful. Furthermore, in recent years, not only the improvement of the beauty of printed patterns, but also the reduction of environmental load by reducing the amount of organic solvent discharged during printing, prevention of solvent fires and other safety requirements, and further reduction of residual solvents in the package have increased the demand, and aqueous flexographic inks have attracted attention.

[0004] Water-based flexographic inks have generally been used for paper substrates such as corrugated cardboard and paper bags. However, water-based flexographic inks used for paper substrates are designed based on drying by hot air (called a hot air dryer) and drying by penetration into the paper substrate, and the paper substrate allows for accelerated drying. On the other hand, with plastic substrates, drying by penetration cannot be expected, making drying poorly likely, and there has been a concern that blocking (a phenomenon in which ink bleeds to the back) may occur between the printed layer and the plastic substrate. Furthermore, in flexographic printing, the ink is transferred from the anilox roll to the relief plate and then from the relief plate to the substrate, so depending on the printing conditions and environmental factors such as temperature and humidity, there were concerns such as plate entanglement (printing smudges). It should be noted that the above-mentioned plate entanglement is more likely to occur during long printing times and is a challenge for flexographic printing suitability. Printing entanglement is a phenomenon where ink seeps not only into the raised parts of the printing plate, but also into the sides and other parts (recesses), and the ink accumulated in the recesses causes ink to transfer to areas of the printed material that are not meant to be printed (non-printed areas). Furthermore, in water-based flexographic inks containing water-based urethane resin, the stringing property of the water-based urethane resin makes it easier for ink to transfer to non-printed areas. Stringing is a phenomenon where the viscosity of the water-based urethane resin causes the ink to string when it transfers from the plate to the substrate. This phenomenon causes the ink to drip down to the sides of the raised parts of the plate, making printing entanglement more likely.

[0005] In recent years, water-based urethane resins have been used as the main binder resin in water-based flexographic inks, particularly because they exhibit good adhesion to plastic substrates. Such printed materials are often further laminated to form laminated structures, which are then used as packaging bags for food, pharmaceuticals, and other products. For example, Patent Documents 1 and 2 disclose technological developments related to water-based urethane resins for inks.

[0006] As a technique to improve the above-mentioned plate-binding properties, a technology relating to aqueous flexographic inks containing glycol solvents and glycol monoalkyl ether solvents has been disclosed (Patent Document 3). However, if the amount of glycol solvent and glycol monoalkyl ether solvent used is reduced in order to improve environmental compatibility, there is a concern that the above-mentioned plate-binding properties may deteriorate. Furthermore, a technology relating to an aqueous flexographic ink containing polyether has been disclosed as a similar technique to improve the plate-binding properties (Patent Document 4). In this case, increasing the polyether content to improve plate-binding properties may cause the ink film itself to become softer, raising concerns about a decrease in blocking resistance. In other words, further performance improvements are desired for water-based flexographic inks that can simultaneously solve the problems of ink entanglement and blocking. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2008-49706 [Patent Document 2] Japanese Patent Publication No. 2005-272587 [Patent Document 3] Japanese Patent Publication No. 2019-203051 [Patent Document 4] Japanese Patent Publication No. 2020-066698 [Overview of the project] [Problems that the invention aims to solve]

[0008] Conventional water-based flexographic inks containing water-based urethane resin have the problem that the stringiness of the water-based urethane resin makes it easy for the ink to transfer to non-printing areas, making it difficult to maintain plate adhesion during long printing sessions. Maintaining blocking resistance at the same time was also a challenge.

[0009] The present invention aims to provide an aqueous flexographic ink that exhibits good plate-binding properties and blocking resistance, as well as good ink stability, substrate adhesion, and laminate strength. [Means for solving the problem]

[0010] As a result of diligent research, the inventors of the present invention have found that the above problems can be solved by using an aqueous flexographic ink containing a predetermined aqueous urethane resin, pigment, and extender pigment, and have completed the present invention.

[0011] In other words, the present invention relates to an aqueous flexographic ink comprising a coloring pigment, an extender pigment, a binder resin, and a liquid medium, The aforementioned coloring pigment comprises an organic pigment and / or carbon black. The aqueous flexographic ink contains 12 to 30% by mass of the coloring pigment and 1 to 15% by mass of the extender pigment, The present invention relates to a water-based flexographic ink in which the binder resin includes a water-based urethane resin.

[0012] Furthermore, the present invention relates to the above-mentioned aqueous flexographic ink, wherein the extender pigment comprises one or more extender pigments selected from the group consisting of barium sulfate, calcium carbonate, magnesium carbonate, kaolin clay, and silica.

[0013] Furthermore, in this invention, the liquid medium is water. This invention relates to the above-mentioned water-based flexographic ink, wherein the water-based flexographic ink contains 30 to 70% by mass of water relative to the total mass of the water-based flexographic ink.

[0014] Furthermore, the present invention relates to the aqueous flexographic ink wherein the aqueous urethane resin has an acid value, and the weight-average molecular weight of the aqueous urethane resin is 5,000 to 50,000.

[0015] Furthermore, the present invention relates to the above-mentioned aqueous flexographic ink, wherein the content of aqueous urethane resin is 1 to 15% by mass relative to the total mass of the aqueous flexographic ink.

[0016] The present invention also relates to the aqueous flexographic ink wherein the aqueous urethane resin has a structural unit derived from at least one polyol selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol.

[0017] The present invention also relates to a printed matter obtained by printing the above aqueous flexographic ink on a substrate 1.

[0018] The present invention also relates to a laminate laminate having an adhesive layer and a substrate 2 in this order on a printing layer made of the above aqueous flexographic ink.

Effects of the Invention

[0019] According to the present invention, it has become possible to provide an aqueous flexographic ink having good plate sticking properties and blocking resistance, and further having good ink stability, substrate adhesion, and laminate strength.

Modes for Carrying Out the Invention

[0020] Examples will be given below to explain 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] In the following description, the "aqueous flexographic ink" of the present invention may sometimes be simply described as "ink" or "aqueous ink", which are synonymous.

[0022] <Coloring Pigment> The coloring pigment used in the aqueous flexographic ink of the present invention contains organic pigments and / or carbon black. Examples of such coloring pigments include organic pigments and carbon black similar to those used in general inks, paints, and recording materials. Examples of organic pigments include azo, phthalocyanine, anthraquinone, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindoline, quinophthalone, azomethine azo, dicutopyrrolopyrrole, and isoindoline pigments. The coloring pigment (including organic pigments and / or carbon black) can be any of the pigments listed as CI pigments in the color index. Furthermore, the carbon black (CIPigment Black 7) is preferably made of carbon nanoparticles with a diameter of approximately 50 to 500 nm, manufactured under industrial quality control. In the above, the coloring pigment should be contained in an amount of 12 to 30% by mass relative to the total mass of the ink, preferably 13 to 25% by mass, and more preferably 13 to 20% by mass.

[0023] <Body pigments> The aqueous flexographic ink of the present invention contains an extender pigment in an amount of 1 to 15% by mass relative to the total mass of the ink. The inclusion of an extender pigment is expected to improve ink stability, plate adhesion, and blocking resistance. Preferably, the extender pigment used is one or more pigments selected from the group consisting of barium sulfate, calcium carbonate, magnesium carbonate, kaolin clay, and silica. By including these extender pigments within this range, both blocking resistance and plate adhesion can be achieved. Among these, barium sulfate is preferred from the viewpoint of ink stability. The extender pigments, such as barium sulfate, preferably have an average particle size of 0.01 to 0.9 μm, and more preferably 0.1 to 0.7 μm. Here, the average particle size refers to the measurement by electron microscopy, which can be measured, for example, by taking the average of 10 randomly selected extender pigment particles using a field emission scanning electron microscope (JEOL JSM-7000F). Furthermore, the oil absorption capacity of the extender pigments, such as barium sulfate, is preferably 8 to 40 ml / 100g, and more preferably 15 to 30 ml / 100g. This is because within these ranges, the ink adhesion, blocking resistance, and stability of the aqueous flexographic ink are improved.

[0024] The above-mentioned extender pigment must be contained in an amount of 1 to 15% by mass relative to the total mass of the ink, preferably 3 to 13% by mass, and more preferably 5 to 10% by mass. This is because within these ranges, the plate adhesion, blocking resistance, and stability of the water-based flexographic ink are improved.

[0025] As described above, by including a predetermined amount of coloring pigment and extender pigment, stringiness in the ink is suppressed, which in turn contributes to improved plate adhesion, improved blocking resistance, and other benefits.

[0026] <Binder resin, water-based urethane resin> The aqueous flexographic ink of the present invention contains a binder resin from the viewpoint of adhesion to plastic substrates and lamination strength. Furthermore, the binder resin must contain an aqueous urethane resin. The aqueous urethane resin has an acid value that can be neutralized, preferably 20 to 65 mg KOH / g. In addition, the glass transition temperature is preferably -30 to 0°C. Here, the glass transition temperature refers to the temperature at which Tanδ is at its maximum value in dynamic viscoelasticity measurement. The glass transition temperature can be measured using a dynamic viscoelasticity measuring device DVA-200 manufactured by IT Measurement Control Co., Ltd. after the aqueous urethane resin has been dried to form a dry coating film. By setting the glass transition temperature within this range, blocking resistance is improved and lamination suitability is enhanced. The hydroxyl value of the aqueous urethane resin is preferably 1 to 15 mg KOH / g. The hydroxyl value can also be adjusted by controlling the amount of polyamine, as described later.

[0027] <Weight-average molecular weight and content of water-based urethane resin> The weight-average molecular weight of the aqueous urethane resin is preferably 5,000 to 50,000, more preferably 6,000 to 40,000, and even more preferably 10,000 to 30,000. Furthermore, the content of aqueous urethane resin in the aqueous flexographic ink is preferably 1 to 15% by mass, more preferably 3 to 13% by mass, and even more preferably 5 to 10% by mass, based on the total mass of the aqueous flexographic ink. This is because it improves blocking resistance and lamination suitability.

[0028] <Composition of water-based urethane resin> As the above-mentioned aqueous urethane resin, an aqueous urethane resin that is a reaction product of a polyol, a polyhydroxy acid, and a polyisocyanate is preferred. Also preferred is an aqueous urethane resin whose chain is extended by reacting a urethane prepolymer having isocyanate groups at the terminals, which is a reaction product of a polyol, a polyhydroxy acid, and a polyisocyanate, with a polyamine.

[0029] <Polyol> The polyols mentioned above do not include polyhydroxy acids, which will be discussed later. While not limited to the following, suitable examples of polyols include polyester polyols, polyether polyols, polylactone polyols, polycarbonate polyols, polyolefin polyols, dimer ols, and hydrogenated dimer ols. These polyols may be used individually or in combination of two or more. The aqueous urethane resin preferably contains constituent units derived from at least one polyol selected from polyester polyols, polyether polyols, and polycarbonate polyols. The number-average molecular weight of the polyol is preferably 500 to 5000.

[0030] <Polyether polyol> Suitable examples of the above-mentioned polyether polyols include polyethylene glycol, polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, and copolymers thereof. It is preferable that the aqueous urethane resin contains constituent units made from these. The aqueous urethane resin preferably contains constituent units derived from polyethylene glycol, preferably in an amount of 0.1 to 25% by mass, more preferably 2 to 15% by mass, and even more preferably 2 to 10% by mass, based on the total mass of the aqueous urethane resin.

[0031] <Polyester Polyol> The above-mentioned polyester polyol is a diol obtained by reacting a dibasic acid with a diol. Among these, a diol obtained by reacting a dibasic acid with a branched diol is preferred. Suitable dibasic acids include sebacic acid, adipic acid, and succinic acid, and the branched diol refers to a form in which at least one hydrogen atom on the carbon of an alkylene glycol has a substituent. Specifically, it is preferable to contain at least one selected from propylene glycol, 3-methyl-1,5-pentanediol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and 2-methyl-1,3-propanediol in an amount of 50% by mass or more in the total mass of the diol. However, the embodiments of the polyester polyol are not limited to these.

[0032] <Polycarbonate polyol> As the above-mentioned polycarbonate polyol, a polycondensate product obtained by transesterification of a diol made of alkylene glycol and a carbonate compound is preferred. However, the manufacturing method and the diol are not limited. Furthermore, the polycarbonate polyol is preferably an alicyclic and / or aliphatic polycarbonate diol. It is preferable that the carbonate compound is a polycarbonate polyol having a branched diol structure such as 3-methyl-1,5-pentanediol. The carbonate compound is not particularly limited, but examples include dialkyl carbonates, diaryl carbonates, or alkylene carbonates. Specific examples of carbonate compounds include dialkyl carbonates such as dimethyl carbonate, diethyl carbonate, and dibutyl carbonate, diaryl carbonates such as diphenyl carbonate, and alkylene carbonates such as ethylene carbonate.

[0033] <Other polyols> Other polyols besides those mentioned above can react with polyisocyanates, and these may also be the starting diols for polyether polyols and polycarbonate polyols. Examples include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butynediol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, diethylene glycol, polypropylene glycol, dipropylene glycol, trimethylolpropane, and bis(2-hydroxypropylaniline), which can be used individually or in combination of two or more.

[0034] <Polyisocyanate> Suitable examples of the above-mentioned polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, and alicyclic diisocyanates. These may also be in the form of trimers with an isocyanurate ring structure. Examples of aromatic 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, and tolylene diisocyanate. Examples of aliphatic diisocyanates include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. Examples of alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, norbornane diisocyanate, m-tetramethylxylylene diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, and dimer isocyanates obtained by converting the carboxyl groups of dimer acids to isocyanate groups. Preferably, the polyisocyanate is selected from tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, and trimers of hexamethylene diisocyanate. These polyisocyanates can be used individually or in combination of two or more.

[0035] <Polyhydroxy acids> The polyhydroxy acids mentioned above are not limited to those listed below, but polyols containing carboxyl groups can be used. For example, dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolpentanoic acid are preferred. These can be used individually or in combination of two or more. The polyhydroxy acid is used in the manufacturing process of aqueous urethane resin, and its carboxyl group is introduced into the resulting urethane resin, giving it an acid value. The carboxyl group can be neutralized with the following neutralizing agent to make the urethane resin aqueous.

[0036] <Neutralizing agent> To make urethane resin aqueous, it is preferable to neutralize the carboxyl groups in the urethane resin with a basic compound. Examples of basic compounds include sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, ethanolamine, propanolamine, diethanolamine, N-methyldiethanolamine, dimethylamine, diethylamine, triethylamine, NN-dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, and morpholine, which can be used individually or in combination of two or more. Depending on the type of basic compound, the affinity for the urethane resin solution or the stability after aqueous conversion may differ, so it is necessary to select appropriately. Of these, ammonia and alkyl-substituted amines are preferred in terms of the water resistance of the printed material and residual odor, and ammonia is even more preferred.

[0037] <Polyamine> The urethane resin used in the present invention may be a urethane prepolymer having terminal isocyanate groups that has been chain-extended with a polyamine. The following are preferred as polyamines, for example, organic diamines containing hydroxyl groups such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine, as well as organic diamines that do not contain hydroxyl groups, such as ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and dimeramine obtained by converting the carboxyl groups of dimer acid to amino groups.

[0038] <Synthesis method for water-based urethane resin> Urethane resins can be manufactured by known methods as appropriate. Examples include the acetone method, which uses an organic solvent that is inert to isocyanate and hydrophilic, and solvent-free synthesis methods that do not use any solvents. For example, the method described in Japanese Patent Application Publication No. 2013-234214 can be used as appropriate.

[0039] <Additives for water-based flexographic inks> The above-mentioned aqueous flexographic ink may contain additives, such as pigment dispersants, pigment derivatives, neutralizing agents, leveling agents, defoaming agents, waxes, silane coupling agents, antiblocking agents, thickeners, rheology modifiers, rust inhibitors, preservatives, plasticizers, infrared absorbers, ultraviolet absorbers, fragrances, and flame retardants.

[0040] <Liquid medium, water> In the present invention, the aqueous flexographic ink contains a liquid medium, the liquid medium being mainly composed of water. To avoid reducing the ink's adherence to the ink plate, it is preferable that the aqueous flexographic ink contains 30 to 70% by mass of water relative to its total mass. It is even more preferable that the water content be 40 to 60% by mass or 45 to 58% by mass.

[0041] <Organic solvents> In the present invention, an organic solvent may be used as the liquid medium for the aqueous flexographic ink, to the extent that it does not impair its purpose and effect. If used, it is preferably an alcohol-based organic solvent, a glycol-based organic solvent, or a glycol ether-based organic solvent. Examples of such organic solvents include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, t-butanol, and 2-methyl-2-propanol as alcohol-based organic solvents; ethylene glycol and propylene glycol as glycol-based organic solvents; and ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, propylene glycol monopropyl ether, and diethylene glycol monopropyl ether as glycol ether-based organic solvents. In the aqueous flexographic ink of the present invention, it is preferable to use an amount of 8% by mass or less, and more preferably 5% by mass or less, of the total mass of the ink, in order to control the wettability to the substrate.

[0042] <Method for manufacturing water-based flexographic ink> The aqueous flexographic ink of the present invention can be manufactured by dissolving and / or dispersing (pigment dispersion) a binder resin containing an aqueous urethane resin, a coloring pigment, and an extender pigment in a liquid medium and a specified amount of solvent. Subsequently, the aqueous flexographic ink can be manufactured by blending the obtained dispersion with additives, water, and, if necessary, a solvent.

[0043] For dispersing pigments, commonly used dispersers such as roller mills, ball mills, pebble mills, attritors, and sand mills can be used. Dispersion using a sand mill, gamma mill, or other bead mill is preferable.

[0044] If the water-based flexographic ink contains air bubbles or unexpectedly coarse particles, filtration or other treatments may be performed, and known filters can be used.

[0045] The viscosity of the aqueous flexographic ink produced by the above method is preferably in the range of 10 mPa·s or higher from the viewpoint of preventing pigment sedimentation and ensuring appropriate dispersion, and 1000 mPa·s or lower from the viewpoint of workability during ink production and printing. The above viscosity is measured at 25°C using a Type B viscometer. A viscometer manufactured by Tokimec or similar company can be used.

[0046] <Flexographic printing method> (Anilox roll) For the production of flexographic printed materials according to the present invention, the anilox roll used for flexographic printing can be a cell-engraved ceramic anilox roll, a chrome-plated anilox roll, or the like. To obtain printed materials with excellent dot reproducibility, an anilox roll with a line count of 5 times or more, preferably 6 times or more, the line count used for printing is used. For example, if the line count used is 75 lpi, an anilox roll of 375 lpi or more is required, and if the line count is 150 lpi, an anilox roll of 750 lpi or more is required. Regarding the anilox capacity, from the viewpoint of drying properties and blocking properties of the aqueous flexographic ink of the present invention, it should be 1 to 8 cm³. 3 / m 2 Capacity, preferably 2-6 cm 3 / m 2 This is an anilox roll.

[0047] <Flexographic printing method> (flexographic plate) The printing plates used in the flexographic printing process for the flexographic printed materials of the present invention include photosensitive resin plates that utilize UV ​​curing with a UV light source, and 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.

[0048] <Flexographic printing method> (printing press) 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.

[0049] <Base material 1, printed matter> The printed material in this embodiment has a printed layer formed on the surface of the substrate 1 by flexographic printing using the above-mentioned aqueous flexographic ink.

[0050] The base material 1 is preferably a plastic film, and the type and thickness of the plastic film are not particularly limited, but examples of film types include polyester films, nylon films, and polyolefin films, as well as metal oxide deposits thereof. In the case of polyolefin films, using a corona discharge treated polyolefin film having functional groups such as hydroxyl groups or carbonyl groups can yield better printed materials. The plastic film is preferably a uniaxially or biaxially stretched film. The printed material is always handled as a roll and, as necessary, subsequently cut to a specific size through lamination, slitting, etc.

[0051] <Laminated structure> The laminate of the present invention is obtained by further laminating an adhesive layer and a substrate 2 (second substrate) on the printed layer of the printed material of the present invention. The adhesive layer includes, but is not limited to, a urethane adhesive layer, an anchor coat layer, a molten resin layer, etc., as long as it is a layer having adhesive function. Examples of molten resins include low-density polyethylene, polypropylene, ethylene-vinyl acetate copolymer resin, etc., and examples of adhesives include imine-based, isocyanate-based, polybutadiene-based, titanate-based, etc. A specific example of a method for manufacturing the laminate is lamination. Examples of lamination methods include 1) an extrusion lamination method in which an anchor coat agent is applied to the printed layer, and then a molten resin is layered on top while simultaneously laminating a second substrate such as polyolefin, and 2) a dry lamination method in which an adhesive such as a urethane adhesive is applied to the printed layer, and then, if necessary, it is dried and bonded to the second substrate to form a laminate. [Examples]

[0052] Next, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to these embodiments and includes many other embodiments based on the spirit of the invention. Unless otherwise specified, "parts" and "%" are based on weight. Examples 2-5 and Example 11 are for reference only.

[0053] 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. Tosoh Corporation Guard Column HXL-H TSKgel G5000HXL manufactured by Tosoh Corporation TSKgel G4000HXL manufactured by Tosoh Corporation TSKgel G3000HXL manufactured by Tosoh Corporation TSKgel G2000HXL manufactured by Tosoh Corporation Detector: RI (Differential Refractometer) Measurement conditions: Column temperature 40°C Eluent: Tetrahydrofuran Flow rate: 1.0mL / min

[0054] <Example 1 of water-based urethane resin (P1) synthesis> In a reactor equipped with a thermometer, stirrer, reflux condenser, stirring device, and nitrogen gas introduction tube, 30.5 parts of polytetramethylene glycol with a number average molecular weight of 2000, 25.0 parts of polyethylene glycol with a number average molecular weight of 2000, 1.3 parts of cyclohexanedimethanol, 9.2 parts of dimethylolbutanoic acid, 6.5 parts of bis(2-hydroxypropyl)aniline, 0.2 parts of trimethylolpropane, and 125 parts of methyl ethyl ketone were mixed and stirred while 27.4 parts of isophorone diisocyanate were added dropwise over 1 hour, and the mixture was reacted at 80°C for 6 hours. Next, while cooling, 2.5 parts of 28% aqueous ammonia and 526 parts of deionized water were gradually added dropwise to the solvent-type urethane resin to neutralize it and make it water-soluble. After further removing the methyl ethyl ketone under reduced pressure by distillation, water was added to adjust the solid content, thereby obtaining an aqueous urethane resin (P1) (weight average molecular weight approximately 40,000).

[0055] Aqueous urethane resins P2 and P5 were synthesized in the same manner as in Synthesis Example 1, except that the raw material compounds shown in Table 1 were used. Neutralization with 28% aqueous ammonia was carried out in the same manner as in Synthesis Example 1, so as to be equivalent to the carboxyl groups derived from dimethylolbutanoic acid.

[0056] <Example 3 of water-based urethane resin (P3) synthesis> In a reactor equipped with a thermometer, stirrer, reflux condenser, agitator, and nitrogen gas introduction tube, 49.1 parts of poly(3-methyl-1,5-pentaneadipate)diol with a number average molecular weight of 2000, 5.0 parts of polyethylene glycol with a number average molecular weight of 2000, 9.2 parts of dimethylolbutanoic acid, and 32.1 parts of isophorone diisocyanate were reacted in 80 parts of methyl ethyl ketone for 6 hours while introducing nitrogen gas to obtain a terminal isocyanate prepolymer. After cooling to 40°C, 40 parts of acetone were added to obtain a solvent solution of the terminal isocyanate prepolymer. Next, 175.4 parts of the obtained terminal isocyanate prepolymer solution were gradually added at room temperature to a mixture of 4.5 parts of 2-hydroxyethylethylenediamine and 80 parts of acetone, and reacted at 50°C for 3 hours to obtain a solvent-type urethane resin solution. Next, 3.7 parts of 28% aqueous ammonia and 300 parts of deionized water were gradually added to the solvent-type urethane resin solution to neutralize it and make it water-soluble. After further removing all of the methyl ethyl ketone and acetone under azeotropic distillation, water was added to adjust the solid content, thereby obtaining aqueous urethane resin (P3) (weight-average molecular weight approximately 30,000).

[0057] Aqueous urethane resin P4 was synthesized in the same manner as in Synthesis Example 3, except that a polycarbonate diol with a number average molecular weight of 2000 was used instead of a poly(3-methyl-1,5-pentaneadipate)diol with a number average molecular weight of 2000, and the amounts shown in Table 1 were used. Neutralization with 28% aqueous ammonia was carried out in the same manner as in Synthesis Example 2, so as to be equivalent to the carboxyl groups derived from dimethylolbutanoic acid.

[0058] [Table 1]

[0059] The abbreviations for each raw material compound in Table 1 represent the following compounds:

[0060] PTG2000: Polytetramethylene glycol (polyether polyol) with a number-average molecular weight of 2000. PEG2000: Polyethylene glycol (polyether polyol) with a number-average molecular weight of 2000. PMPA2000: Poly(3-methyl-1,5-pentaneadipate)diol with a number-average molecular weight of 2000 PC2000: Polycarbonate diol with a number-average molecular weight of 2000. DMBA: Dimethylolbutanoic acid Bis-HPA: Bis(2-hydroxypropylaniline) CHDM: 1,4-Cyclohexanedimethanol TMP: Trimethylolpropane AEA: 2-hydroxyethylethylenediamine IPDI: Isophorone diisocyanate

[0061] <Example 1: Preparation of Ink S1> 45.0 parts of aqueous urethane resin P1 solution, 20.0 parts of CI pigment blue 15:3 (Toyo Color Co., Ltd. blue pigment), 10 parts of barium sulfate, 2.0 parts of polyethylene wax, 0.1 parts of defoaming agent, 0.2 parts of dihydrazide adipic acid, 0.2 parts of aqueous ammonia, 17.5 parts of water, 2.0 parts of n-propanol, and 3.0 parts of propylene glycol were added. The mixture was stirred with a stirrer for 10 minutes, and then dispersed for 10 minutes using an Eiger Mill (Eiger Co., Ltd. bead mill), a bead mill disperser, to prepare ink S1 of Example 1. In the above, the barium sulfate used had the following properties. Average particle size 0.3μm, oil absorption 20ml / 100g

[0062] <Preparation of inks for Examples 2-20 and Comparative Examples 1-5> Inks S2 to S20 of Examples 2 to 20 were prepared by dispersing the raw materials and their proportions as shown in Table 2 using an Eiger mill (bead mill manufactured by Eiger) for 10 minutes, except that the raw materials and their proportions were used. In addition, inks T1 to T5 of Comparative Examples 1 to 5 were prepared by dispersing the raw materials and their proportions as shown in Table 3 using an Eiger mill (bead mill manufactured by Eiger) for 10 minutes, except that the raw materials and their proportions were used, except that the raw materials and their proportions were used.

[0063] [Table 2-1]

[0064] [Table 2-2]

[0065] [Table 3]

[0066] The annotations in the table indicate the following: JONCRYL63D: Water-based acrylic resin manufactured by BASF Japan. CI Pigment Yellow 14 Yellow Organic Pigment CI Pigment Red 57:1 Red Organic Pigment CI Pigment Black 7 Carbon Black Calcium carbonate: extender pigment Magnesium carbonate: Body pigment Kaolin clay: Body pigment Silica: extender pigment

[0067] <Evaluation Methods and Criteria> The following evaluations were performed using the inks obtained in the above examples and comparative examples.

[0068] (Flexographic printing) The inks obtained in the above examples and comparative examples were used on a flexographic plate (photosensitive resin plate, KODAK FLEX CEL NXH digital flexographic plate, plate thickness 1.14 mm, line count 150 lpi) and an anilox roll (900 lpi, 3 cm²). 3 / m 2Printing was performed on a plastic film (corona-treated polyester (PET) substrate (Toyobo Co., Ltd. E5100, 12 μm thick) at a speed of 200 m / min using a flexographic printing press (MIRAFLEX CM) equipped with the following equipment: The printed material was obtained. The drying conditions for the printed layer were 100°C for the intercolor dryer and 100°C for the tunnel dryer.

[0069] (1) Edition-related The inks obtained in the above examples and comparative examples were evaluated for their plate adhesion in the 1% halftone area after printing 2000 m of corona-treated polyester (PET) substrate (Toyobo E5100, 12 μm thick) at a printing speed of 200 m / min. The evaluation criteria are shown below. Practical levels are AB and C. A: No thickening of the halftone dots is observed, and a clear image is formed. (Excellent) B: Slight thickening is observed in the 1% halftone area, and the halftone dots are not connected. (Good) C: The shape of the halftone dots is distorted, and some dot bridging is observed. (Usable) D: 1% The shape of the halftone dots is distorted, and dot bridges (connections between dots) are clearly visible (defective).

[0070] (2) Ink stability The inks obtained in the above examples and comparative examples were stored at a constant temperature of 40°C for 3 months. Then, the viscosity over time (at 25°C) was measured using a Zahn cup No. 4, and the difference from the final (initial) viscosity was evaluated. The evaluation criteria are shown below. Practical levels are AB and C. A: Products where the difference between the finished viscosity and the viscosity over time is less than 2 seconds. B: Products where the difference between the finished viscosity and the viscosity over time is 2 seconds or more but less than 4 seconds. C: Products where the difference between the finished viscosity and the viscosity over time is 4 seconds or more but less than 6 seconds. D: Products where the difference between the finished viscosity and the viscosity over time is 6 seconds or more but less than 8 seconds. E: Products where the difference between the finished viscosity and the viscosity over time is 8 seconds or more.

[0071] (3) Adhesion to the substrate Each ink obtained in the above examples and comparative examples was printed on OPP film (stretched polypropylene film, P-216 1, 30 μm, manufactured by Toyobo Co., Ltd.), and a 10 mm wide cellophane tape manufactured by Nichiban Co., Ltd. was attached to the printed material, and a peel test was performed. The state of ink transfer (removal) to the cellophane tape was visually evaluated according to the following criteria. The evaluation criteria are shown below. Practical levels are AB and C. A: The ink did not transfer to the cellophane tape at all. B: Less than 5% ink transfer was observed on the cellophane tape. C: Ink transfer of 5% to less than 10% was observed on the cellophane tape. D: Ink transfer of 10% to less than 50% was observed on the cellophane tape. E: More than 50% ink transfer was observed on the cellophane tape.

[0072] (4) Blocking resistance Each ink obtained in the above examples and comparative examples was printed on OPP film (P-2161 above), and a 4cm x 4cm sample was taken. The printed surface of this sample was placed against the untreated surface of an unprinted film of the same size, and a pressure of 10kgf was applied at 40°C for 12 hours. The ink removal and resistance felt when the sample was peeled off were observed. The evaluation criteria are shown below. Practical levels are AB and C. A: No ink transfer was observed from the printed material, and there was no resistance when peeling it off. B: No ink transfer was observed from the printed material, but there was resistance when peeling it off. C: Ink transfer was observed from the printed material, covering less than 10% of the area. D: Ink transfer from the printed material was observed in an area of ​​10% to less than 50%. E: Ink transfer from the printed material was observed over 50% of the surface area.

[0073] (5) Lamination strength Each of the inks obtained in the above examples and comparative examples was printed onto OPP film (P-2161 above), and an imine-based anchor coating agent (EL-420, manufactured by Toyo Morton Co., Ltd.) was applied to the printed material. Using an extrusion laminating machine, the material was laminated to CPP film (sealant film) via polyethylene melted at 315°C to obtain a laminated product (extrusion lamination method). The processed product was cut to a width of 15 mm, and the peel strength when the ink side and the sealant film side were separated was measured using an Intesco 201 universal tensile tester. The evaluation criteria are shown below. Practical levels are AB and C or higher. A: Those with a peel strength of 0.9 N / 15 mm or higher. B: Those with a peel strength of 0.7 N / 15 mm or more and less than 0.9 N / 15 mm. C: Products with a peel strength of 0.5 N / 15 mm or more, and less than 0.7 N / 15 mm. D: Peel strength of 0.3 N / 15 mm or more, and less than 0.5 N / 15 mm. E: Products with a peel strength of less than 0.3 N / 15 mm

[0074] As shown in Table 2 (2-1 to 2-2), the examples yielded inks that were above practical levels in all aspects: plate adhesion, blocking resistance, and lamination strength, confirming that these inks are suitable for flexographic printing on plastic substrates. On the other hand, as shown in Table 3, the comparative example inks fell below practical levels in one or more of the following aspects: plate adhesion, blocking resistance, and lamination strength.

Claims

1. A water-based flexographic ink comprising a coloring pigment, an extender pigment, a binder resin, and a liquid medium, The aforementioned coloring pigment comprises an organic pigment and / or carbon black. The aforementioned extender pigment is barium sulfate with an oil absorption capacity of 8 to 40 ml / 100 g. The aqueous flexographic ink contains 12 to 30% by mass of the coloring pigment and 5 to 15% by mass of the barium sulfate, The binder resin comprises an aqueous urethane resin, The content of the aqueous urethane resin is 3 to 15% by mass relative to the total mass of the aqueous flexographic ink. It is for lamination. Water-based flexographic ink.

2. The liquid medium is water. The aqueous flexographic ink according to claim 1, comprising 30 to 70% by mass of water based on the total mass of the aqueous flexographic ink.

3. The aqueous flexographic ink according to claim 1 or 2, wherein the aqueous urethane resin has an acid value, and the weight-average molecular weight of the aqueous urethane resin is 5,000 to 50,000.

4. The aqueous flexographic ink according to any one of claims 1 to 3, wherein the aqueous urethane resin has constituent units derived from at least one polyol selected from the group consisting of polyester polyol, polyether polyol, and polycarbonate polyol.

5. A printed article obtained by printing an aqueous flexographic ink according to any one of claims 1 to 4 onto a substrate 1.

6. A laminated body having an adhesive layer and a substrate 2 sequentially on a printing layer made of the aqueous flexographic ink described in claim 5.

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