JP2023169906A - Aqueous flexographic ink, printed matter, and layered body - Google Patents

Abstract

To provide an aqueous flexographic ink that is superior in print compatibility (such as plate clinging) and blocking resistance and reduces the overprinting uneven dots on printed matter.SOLUTION: An aqueous flexographic ink contains an aqueous urethane resin and water. The aqueous urethane resin has an acid group and contains a structural unit derived from polyethylene glycol. The weight-average molecular weight of the aqueous urethane resin is 8,000 to 24,000. The structural unit derived from polyethylene glycol constitutes 30-60 mass% of the total mass of the aqueous urethane resin.SELECTED DRAWING: None

Description

The present invention relates to water-based flexographic inks, printed materials, and laminates.

The flexographic printing method is a type of letterpress printing, in which ink is transferred to a resin letterpress plate via an anilox roll, and then the ink is transferred again from the letterpress plate to a plastic substrate, etc., and has excellent high-speed printing performance. , it is possible to reproduce fine letters and sharp patterns even with a small amount of ink transfer. Flexographic printing has traditionally been used primarily for printing on paper substrates such as cardboard and paper bags, but recently there has been an increasing need for packaging materials using plastic films.

In the flexographic printing method, the number of times, time, or distance from when ink is supplied to the substrate is transferred is long, so depending on the printing environment, there are concerns about printing problems such as plate entanglement and poor transfer. "Plate entanglement" is a printing defect in which ink deposits are formed on the convex portions and concave portions of the flexographic plate, causing ink to transfer to areas on the printing substrate that are not originally intended for printing.

In printing with water-based flexographic ink, the above-mentioned "plate entanglement" occurs when the ink tends to dry on the flexographic plate. Therefore, it is necessary to suppress the drying of the ink, and additives that retard the drying of the ink, organic solvents with a high boiling point (slow solvents), and the like are used. However, when printing on plastic film, unlike printing on paper base materials, it is not possible to dry the medium (water or organic solvent) by penetrating the base material, so blocking may occur due to the medium remaining in the printing layer. . Therefore, the design of flexo ink requires a unique design depending on the printing method.

Patent Document 1 discloses a water-based flexo ink containing 1 to 20% by mass of a polyether polyol having a number average molecular weight of 200 to 7,000 in addition to the binder resin as a means to improve plate entanglement properties. . However, with this ink, since the polyol remains when printed on a plastic film, the printed layer may become brittle, and depending on the storage conditions, there is a concern that blocking resistance may deteriorate.

Furthermore, Patent Document 2 discloses that, as a means to improve plate entanglement, an aqueous flexographic ink containing 6 to 30% by mass of a glycol solvent and/or glycol monoalkyl ether solvent with a boiling point of 130 to 280°C in the total ink mass is used. is proposed. However, while further improvements in printability (plate entanglement properties) and blocking resistance are desired, there is a problem in achieving both the above physical properties and suppression of overlapping halftone dot unevenness.

JP2020-066698A JP2019-203051A

It is an object of the present invention to provide a water-based flexographic ink that has good printability (plate entanglement properties, etc.) and anti-blocking properties, and further causes less uneven halftone dots in printed matter.

As a result of intensive studies in view of the above problems, the present inventors discovered that the problems could be solved by using a predetermined water-based flexographic ink, and the present invention was completed.

That is, the present invention is a water-based flexo ink containing a water-based urethane resin and water,
The aqueous urethane resin has an acid group and contains a structural unit derived from polyethylene glycol,
The present invention relates to a water-based flexo ink, wherein the water-based urethane resin has a weight average molecular weight of 8,000 to 24,000.

The present invention also relates to the above-mentioned water-based flexo ink containing 30 to 60% by mass of structural units derived from polyethylene glycol in the total mass of the water-based urethane resin.

The present invention also relates to the above-mentioned water-based flexographic ink containing 37 to 60% by mass of structural units derived from polyethylene glycol in the total mass of the water-based urethane resin.

The present invention also relates to the above water-based flexo ink, wherein the water-based urethane resin has an acid value of 5 to 30 mgKOH/g.

The present invention further relates to the aqueous flexographic ink described above, which contains less than 6% by mass of a glycol solvent and/or glycol monoalkyl ether solvent having a boiling point of 130 to 280° C. in the total mass of the ink.

The present invention also relates to a printed matter having a printing layer made of the above water-based flexographic ink on a substrate.

The present invention also relates to a laminate having a base material 1, a printing layer made of the water-based flexo ink described above, and a base material 2 in this order.

The present invention has made it possible to provide a water-based flexographic ink that has good printability (plate entanglement, etc.) and anti-blocking properties, and also has less uneven halftone dots in printed matter.

"Overlapping halftone dot unevenness" is a phenomenon in which the halftone dot gain of the base changes unevenly and appears uneven when overprinting is performed. This phenomenon tends to occur when the film has a relatively high degree of surface treatment, such as PET film, and there is unevenness in the degree of treatment within the surface of the film. Note that "overlapping halftone dot unevenness" is observed when overlapping printing is performed, and is a different issue from "dot gain" which is determined based on a single hue.

Embodiments of the present invention will be described in detail below, but the explanation of the matters described below is an example of the embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist thereof.

In the following description, water-based flexo ink may be simply referred to as "flexo ink" or "ink", but these terms have the same meaning. Furthermore, a printing layer made of water-based flexographic ink may be simply referred to as a "printing layer," "ink film," "ink coating," or "ink layer," but these terms have the same meaning.

The water-based flexo ink of the present invention uses a predetermined water-based urethane resin as the water-based binder resin. It can be expected that the ink re-dissolving property will be improved and the plate entanglement property will be improved. Furthermore, it is possible to suppress uneven halftone dots and to expect good anti-blocking properties. Binder resin refers to a binding resin contained in ink. Note that "aqueous" may be in a water-soluble state or in an emulsion state.

<Water-based urethane resin>
The aqueous urethane resin used in the present invention has an acid group and contains structural units derived from a polyol, the polyol contains polyethylene glycol, and the weight average molecular weight of the aqueous urethane resin is 8,000 to 24,000. It is preferably from 13,000 to 21,000, more preferably from 15,000 to 19,000. The range is preferable from the viewpoint of achieving both blocking resistance, printability, and suppression of overlapping halftone dot unevenness.

The water-based urethane resin mentioned above may be a water-based urethane resin synthesized from polyol, polyhydroxy acid and polyisocyanate, or a chain formed by polyamine and a urethane prepolymer having an isocyanate group at the end synthesized from polyol, hydroxy acid and polyisocyanate. A preferred embodiment is a water-based urethane resin containing an extended polyurethane urea structure. However, it is not limited to these.

In addition, if the water-based urethane resin has acid groups, the above-mentioned weight average molecular weight range, and the content of the structural unit derived from polyethylene glycol described below at the same time, it will act as a cohesive structure and improve plate entanglement and blocking resistance. It is thought that this can further improve the quality and suppress the unevenness of overlapping halftone dots. In addition, it is more preferable that the following acid value requirements are met, and overlapping halftone dot unevenness can be particularly suppressed.
The above action is thought to be due to the fact that water-soluble sites exist uniformly to some extent within the molecules of the water-based urethane resin, contributing to the solubility of the entire urethane resin, but this action/function specifically limits the present invention. It's not something you do.

The acid value of the aqueous urethane resin is preferably 5 to 30 mgKOH/g, more preferably 10 to 28 mgKOH/g, and still more preferably 15 to 25 mgKOH/g. This is because the ability to suppress uneven halftone dots and plate entanglement of the water-based flexographic ink is improved.

In addition, in relation to acid groups, when a water-based urethane resin having an acid value within the above range is used as a binder resin for preprinting (base) ink, unevenness tends not to occur even if additional ink is overprinted. . Although this phenomenon is presumed to be due to the interaction between the acid groups of the resin and the active functional groups of the surface-treated film, the present invention is not limited by this consideration.

From the viewpoint of achieving both printability and lamination strength, the number of urethane bonds in the aqueous urethane resin is preferably 1.4 to 3.0 mmol/g, more preferably 1.8 to 2.6 mmol/g.

(polyol)
The polyol used in the synthesis of the aqueous urethane resin serves as a structural unit of the urethane resin, and the polyol has polyethylene glycol as an essential component.
Polyols other than polyethylene glycol include, but are not limited to, polyester polyols, polyether polyols (excluding polyethylene glycol), polylactone polyols, polycarbonate polyols, polyolefin polyols, dimer diols, hydrogenated dimer diols, diethylene glycol, trimethylene glycol. , triethylene glycol, propylene glycol, butylene glycol, hexamethylene glycol, neopentyl glycol, 1,4 cyclohexanedimethanol, 1,4 cyclohexanediol, trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol, penta Examples include erythritol. These polyols may be used alone or in combination of two or more.
The aqueous urethane resin preferably contains a structural unit consisting of polyethylene glycol and at least one polyol selected from polyester polyol, polyether polyol (excluding polyethylene glycol), and polycarbonate polyol.
The number average molecular weight of the polyester polyol, polyether polyol (excluding polyethylene glycol) and polycarbonate polyol is preferably 400 to 5,000 or 600 to 2,000.

(Polyether polyol)
The polyether polyol (polyethylene glycol will be described later) is a compound having a plurality of hydroxyl groups and an ether structure. The polyether polyol is not particularly limited as long as it is a polyol having a polyether structure, and suitable examples include polypropylene glycol, polytrimethylene glycol, polytetramethylene glycol, and polyether polyols obtained by copolymerization thereof. The polyether polyol may have a branched structure or a plurality of hydroxyl groups. In addition, polyglycerin such as triglycerin, polyoxyethylene glycerin, polyoxypropylene glyceryl ether, polyoxyethylene polyoxypropylene glyceryl ether, polyoxyethylene polyoxypropylene trimethylol propane, polyoxypropylene diglyceryl ether, polyoxyethylene poly Also included are oxypropylene pentaerythritol ether, polyoxypropylene sorbitol, and the like.
Among the above, polypropylene glycol and polytetramethylene glycol are preferred, and polytetramethylene glycol is more preferred.

(polyethylene glycol)
The polyethylene glycol is a compound having multiple hydroxyl groups and two or more ethylene oxide units (-OCH ₂ --CH ₂ --). Compared to water solubilization using only polyhydroxy acid, which will be described later, by using polyethylene glycol in combination, both contribute to water solubilization and can maintain good printability while suppressing the occurrence of overlapping halftone dot unevenness. The number average molecular weight of the ethylene oxide repeating unit in this compound is preferably 400 or more and 5000 or less. The content of structural units derived from polyethylene glycol in the total mass of the aqueous urethane resin is preferably 30 to 60% by mass, more preferably 33 to 60%, still more preferably 37 to 55% by mass, and It is preferably 38 to 50% by weight, particularly preferably 40 to 50% by weight.

(Polyhydroxy acid)
The polyhydroxy acid mentioned above is not limited to the following, but a polyol containing a carboxyl group can be used. Preferred examples of the polyhydroxy acid include dimethylolalkanoic acids such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, and 2,2-dimethylolvaleric acid. These can be used alone or in combination of two or more. Polyhydroxy acid is used in the manufacturing process of water-based urethane resin, and carboxyl groups hardly react with isocyanate groups, and isocyanate groups react only with hydroxyl groups, so carboxyl groups are present in the side chains of the resulting water-based urethane resin. Aqueous urethane resin having acid groups is obtained. In particular, dimethylolpropionic acid and 2,2-dimethylolbutanoic acid are preferred from the viewpoint of reactivity and solubility. It is preferable that the acid groups of the water-based urethane resin are neutralized to make them water-based. Constituent units derived from polyethylene glycol also contribute to improving the hydrophilicity of urethane resins.

(Polyisocyanate)
Preferred examples of the polyisocyanate used in the synthesis of the aqueous urethane resin include aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, and the like. Note that these may form a trimer to form an isocyanurate ring structure.
Aromatic diisocyanates include 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzylisocyanate, dialkyldiphenylmethane diisocyanate, and tetraalkyl Examples include diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, and tolylene diisocyanate.
Examples of the aliphatic diisocyanate include butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, and the like.
Examples of alicyclic diisocyanates include cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, and norbornane diisocyanate. , m-tetramethylxylylene diisocyanate, hydrogenated 4,4-diphenylmethane diisocyanate, and dimer diisocyanate obtained by converting the carboxyl group of dimer acid into an isocyanate group.
Among these, at least one member selected from the group consisting of tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, and hexamethylene diisocyanate is preferred. These polyisocyanates can be used alone or in combination of two or more.

(Polyamine)
Compounds that can be used as the polyamine include various known amines, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, di-2-hydroxypropylethylenediamine, ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and dimer diamine obtained by converting the carboxyl group of dimer acid into an amino group. etc., and these can be used alone or in combination of two or more.

(reaction terminator)
In the synthesis of the aqueous urethane resin, a reaction terminator can also be used in combination with the above polyamine. Examples of such reaction terminators include dialkylamines such as di-n-dibutylamine, monoethanolamine, diethanolamine, 2-amino-2-methyl-1-propanol, tri(hydroxymethyl)aminomethane, 2-amino -2-ethyl-1,3-propanediol, N-di-2-hydroxyethylethylenediamine, N-di-2-hydroxyethylpropylenediamine, N-di-2-hydroxypropylethylenediamine and other hydroxyl group-containing amines, Further examples include monoamine-type amino acids such as glycine, alanine, glutamic acid, taurine, aspartic acid, aminobutyric acid, valine, aminocaproic acid, aminobenzoic acid, aminoisophthalic acid, and sulfamic acid.

(Neutralizer)
In order to make the water-based urethane resin water-based, the acid groups in the side chains are preferably neutralized with a basic compound. The basic compounds include sodium hydroxide, potassium hydroxide, ammonia, methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, ethanolamine, propanolamine, diethanolamine, N-methyldiethanolamine, dimethylamine, diethylamine. , triethylamine, N,N-dimethylethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, morpholine, etc., and these may be used alone or in combination. The above combinations are used. Ammonia is preferred from the viewpoint of water resistance of printed matter, residual odor, etc.

(Manufacture of water-based urethane resin)
The aqueous urethane resin used in the present invention is appropriately manufactured by a known method. Examples include a method in which urethane resin is synthesized in an organic solvent that is inert to isocyanates and is hydrophilic, and then the organic solvent is replaced with water, and a non-solvent synthesis method in which the synthesis reaction is performed without using an organic solvent. It will be done. For example, the method described in Japanese Unexamined Patent Publication No. 2013-234214 can be used as appropriate.

<Other resins>
The water-based flexographic ink of the present invention may additionally contain "other resins" in addition to the water-based urethane resin. Examples of other resins include water-based urethane resins that do not meet the above requirements for water-based urethane resins, water-based acrylic modified urethane resins, water-based acrylic resins, water-based styrene-acrylic acid copolymer resins, water-based styrene-maleic acid copolymer resins, and water-based ethylene resins. - Acrylic acid copolymer resin, aqueous polyester resin, aqueous shellac, aqueous rosin-modified maleic acid resin, aqueous vinyl chloride-vinyl acetate copolymer resin, aqueous vinyl chloride-acrylic acid copolymer resin, aqueous chlorinated polypropylene resin, aqueous hydroxyethyl cellulose Preferred examples include resins, aqueous hydroxypropyl cellulose resins, and aqueous butyral resins. These resins can be used alone or in combination of two or more.

(Organic solvent)
The aqueous flexo ink of the present invention contains water as a volatile component, and preferably has the highest content of water among the volatile components, but may contain an organic solvent as long as it does not interfere with its purpose and effects. When an organic solvent is included, it is preferably an alcohol-based organic solvent, a glycol-based organic solvent, or a glycol ether-based organic solvent.
Examples of alcohol-based organic solvents include ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, t-butanol, 2-methyl-2-propanol, etc. Examples of organic solvents include ethylene glycol and propylene glycol, and examples of glycol ether organic solvents include ethylene glycol monopropyl ether, diethylene glycol monopropyl ether, propylene glycol monopropyl ether, and diethylene glycol monopropyl ether.
In the aqueous flexographic ink of the present invention, since poor drying can be suppressed, the total content of organic solvents is preferably 20% by mass or less, more preferably 15% by mass or less, and 10% by mass or less. It is more preferable to use it in an amount of % by mass or less. The preferred content of the organic solvent may be 0% by mass, but is preferably 0.2% by mass or more, more preferably 0.5% by mass or more.

(Glycol solvent and/or glycol monoalkyl ether solvent with a boiling point of 130 to 280°C)
When the aqueous flexo ink of the present invention contains an organic solvent, among the above organic solvents, a glycol solvent and/or a glycol monoalkyl ether solvent having a boiling point of 130 to 280°C is preferred.
The total content of the glycol solvent and/or glycol monoalkyl ether solvent is preferably 6% by mass or less, more preferably 5% by mass or less, and 3% by mass or less based on the total mass of the aqueous flexo ink. It is more preferable to use it in The preferred content of the organic solvent may be 0% by mass, but is preferably 0.2% by mass or more, more preferably 0.5% by mass or more.
When the content of the glycol solvent and/or glycol monoalkyl ether solvent with a boiling point of 130 to 280°C is within this range, plate entanglement caused by drying of the ink on the flexo plate is suppressed, and furthermore, the residue after printing is dried is suppressed. Since the amount of solvent is reduced, plate entanglement and blocking resistance are improved, and overlapping halftone dot unevenness is suppressed.

<Glycol solvent>
Suitable examples of the glycol solvent having a boiling point of 130 to 280°C include propylene glycol, butylene glycol and other alkylene glycols, dipropylene glycol, diethylene glycol and other dialkylene glycols, tripropylene glycol, triethylene glycol and other trialkylene glycols. Can be mentioned. Among them, it is preferable to use at least one selected from propylene glycol, butylene glycol, dipropylene glycol, and tripropylene glycol.

<Glycol monoalkyl ether solvent>
Examples of glycol monoalkyl ether solvents having a boiling point of 130 to 280°C include propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether and other propylene glycol monoalkyl ethers, dipropylene glycol monoethyl ether, and dipropylene. Glycol monomethyl ether Other dipropylene monoalkyl ethers, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether Other tripropylene glycol monoalkyl ethers, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and other diethylene glycol monoalkyl ethers are preferably mentioned, and it is preferable to use at least one selected from the above.

(Additive)
The ink of the present invention may contain additives such as pigments, antifoaming agents, thickeners, leveling agents, waxes, and ultraviolet absorbers, as well as organic solvents such as alcohols, ketones, and esters, as necessary. be able to.

<Curing agent>
By crosslinking the water-based urethane resin using a curing agent, the water-based flexographic ink of the present invention can have the effects of improving adhesion to the substrate, laminating strength, and water resistance of the ink coating. Since the aqueous urethane resin has acidic groups such as carboxyl groups, it is preferable to use a hydrazine compound, a carbodiimide compound, or an epoxy compound as the curing agent.
As the hydrazine compound, adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide and other dihydrazide compounds are preferred.
The carbodiimide compound is a compound having a carbodiimide group, and examples thereof include Carbodilite E-02, E-03A, SV-02, V-02, V02-L2, and V-04 manufactured by Nisshinbo.
The epoxy compound refers to a compound having an epoxy group, and includes, for example, alicyclic epoxies such as Adeka Resin EP-4000, EP-4005, and 7001 manufactured by ADEKA.
The curing agent is preferably used in an amount of 0.1 to 5% by weight, more preferably 0.1 to 3% by weight, based on the total weight of the water-based flexographic ink.

(Manufacture of water-based flexo ink)
An example of a method for producing water-based flexo ink is, for example, after mixing pigment, water-based urethane resin, and water, dispersion treatment (kneading) is performed using a ball mill, sand mill, other bead mill, attritor, etc., and then additives, etc. There is a way to mix it up. For example, the method described in Japanese Unexamined Patent Publication No. 2013-234214 can be used as appropriate. In kneading, a pigment dispersant can also be used if necessary.

(Base material 1)
The base material that can be used for the printed matter of the present invention may be a plastic base material or a paper base material, and although there is no particular limitation, plastic base materials are preferable.For example, polyolefins such as polyethylene and polypropylene, polyethylene terephthalate, polycarbonate, and Examples include film-like base materials made of polyesters such as lactic acid, polystyrene resins such as polystyrene, AS resins, and ABS resins, nylon, polyamide, polyvinyl chloride, polyvinylidene chloride, cellophane, or composite materials thereof. Further, a vapor deposition substrate in which an inorganic compound such as silica, alumina, or aluminum is vapor-deposited on a polyethylene terephthalate or nylon film may also be used, and the vapor-deposited surface may be coated with polyvinyl alcohol or the like. It is preferable that the surface to be printed (the surface in contact with the printing layer) of the base material is subjected to an adhesion treatment, and the adhesion treatment includes, for example, corona discharge treatment, ultraviolet/ozone treatment, plasma treatment, oxygen plasma treatment, Examples include primer treatment. For example, in corona discharge treatment, hydroxyl groups, carboxyl groups, carbonyl groups, etc. are expressed on the substrate. Since hydrogen bonds can be utilized, it is preferable that the ink contains a compound having a functional group such as a hydroxyl group, an amino group, or a carbodiimide group.

(Base material 2)
The base material 2 used in the present invention may be the same as the base material 1 or may be different. Preferably, it is an unstretched plastic film. This is to provide a heat sealing function.

The viscosity of the water-based flexo ink produced by the above method is 10 mPa·s or more from the viewpoint of preventing pigment sedimentation and moderate dispersion, and 1000 mPa·s or less from the viewpoint of workability efficiency during ink production and printing. It is preferable that there be. Note that the above viscosity is a viscosity measured at 25° C. using a B-type viscometer manufactured by Tokimec.

<Flexographic printing method> (Anilox roll)
As the anilox used for flexographic printing used in the method for producing a flexographic printed matter of the present invention, a ceramic anilox roll with cell engraving, a chrome-plated anilox roll, etc. can be used. In order to obtain a printed matter with excellent dot reproducibility, an anilox roll having a line count of at least 5 times, preferably at least 6 times, the number of plate lines used during printing is used. For example, if the plate number used is 75 lpi, an anilox roll of 375 lpi or more is required, and if the plate number used is 150 lpi, an anilox roll of 750 lpi or more is required. Regarding the anilox capacity, the anilox roll has a capacity of 1 to 8 cc/m ² , preferably 2 to 6 cc/m ² from the viewpoint of drying properties and blocking properties of the aqueous flexographic ink of the present invention.

<Flexo printing method> (Flexo plate)
The plate used for flexographic printing used in the method for producing a flexographic printed matter of the present invention includes a photosensitive resin plate that utilizes ultraviolet curing by a UV light source or an elastomer material plate that uses a direct laser engraving method. Regardless of the method of forming the image area of the flexographic plate, a plate having a screening line number of 75 lpi or more is used. Any sleeve or cushion tape for pasting the plate can be used.

<Flexo printing method> (printing machine)
Flexo printing machines include CI-type multicolor flexo printing machines and unit-type multicolor flexo printing machines, and ink supply systems include chamber type and two-roll type, and known printing machines can be used. can.

(Laminated body, method for manufacturing the laminate)
The laminate of the present invention has a film layer further laminated in this order to the printed layer of the above-mentioned printed matter. Note that the laminate is preferably a laminate including an adhesive layer, and is preferably a laminate including a base material 1, a printed layer, an adhesive layer, and a base material 2 in this order. Examples of the adhesive layer include a layer made of an anchor coating agent, a urethane laminating adhesive, a molten resin, and the like. 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 laminates. Examples include adhesives, and there are those containing organic solvents and those without solvents. Furthermore, examples of the molten resin include molten polyethylene.
Examples of methods for manufacturing the laminate include ordinary extrusion lamination, in which molten polyethylene resin is laminated on the printed layer via various anchor coating agents such as imine, isocyanate, polybutadiene, and titanium. ) method, dry lamination method or non-solvent lamination method in which a urethane adhesive or other adhesive is applied to the printed surface and a plastic film is laminated on top of that, and the direct lamination method in which molten polypropylene is directly pressed onto the printed surface and laminated. etc., can be obtained by a known lamination process.

Hereinafter, the present invention will be specifically explained by giving Examples, Comparative Examples, etc. In the following description, "parts" indicate parts by mass. "%" represents mass % unless otherwise specified.

The weight average molecular weight was determined by measuring the molecular weight distribution using a GPC (gel permeation chromatography) device (GPC-104 manufactured by Shodex Co., Ltd.) and as a converted molecular weight using polystyrene as a standard substance. The measurement conditions are shown below.
Column: Two Shodex LF-404 were used connected in series.
Detector: ShodexRI-74S (differential refractometer)
Measurement conditions: Column temperature 40℃
Eluent: Tetrahydrofuran Flow rate: 0.3 mL/min

The acid value is the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 g of resin solid content, and the dried resin is diluted with a potential difference in a potassium hydroxide/ethanol solution according to the method described in JIS K2501. Calculated by titration.

[Synthesis example 1]
Polytetramethylene glycol (“PTMG1000”) with a number average molecular weight of 1000 (hydroxyl value 112.2 mgKOH/g) 25 was placed in a 4-necked 2000 ml flask equipped with a reflux condenser, a dropping funnel, a gas introduction tube, a stirrer, and a thermometer. .6 parts, polyethylene glycol (``PEG1000'') with a number average molecular weight of 1000 (hydroxyl value 112.2 mgKOH/g) 16.9, polyethylene glycol (``PEG600'') with a number average molecular weight 600 (hydroxyl value 187.0 mgKOH/g) 27.7 parts of dimethylolbutanoic acid ("DMBA") and 5.4 parts of dimethylolbutanoic acid ("DMBA") were charged, the inside of the flask was purged with dry nitrogen, and while stirring, 24.4 parts of isophorone diisocyanate ("IPDI") was added and gradually heated to 100 °C. The temperature rose to . The reaction was further carried out for 180 minutes to obtain an aqueous urethane resin. Next, 50 parts of isopropyl alcohol was added while cooling, and then 350 parts of ion-exchanged water containing 6.7 parts of 10% ammonia water was added, and aqueous urethane resin WU1 solution (weight average molecular weight 16,700) with a solid content of 20% by mass was added. Obtained 500 copies.

[Synthesis Examples 2 to 14]
Aqueous urethane resin WU2 to WU14 solutions were obtained in the same manner as in Synthesis Example 1 using the parts and charging ratios listed in Table 1.

[Comparative synthesis examples 1 and 2]
Aqueous urethane resin WU15 and WU16 solutions were obtained in the same manner as in Synthesis Example 1 using the parts and charging ratios listed in Table 1.

In Table 1, PTMG1000 is polytetramethylene ether glycol with an average molecular weight of 1000, PEG1000 is polyethylene glycol with an average molecular weight of 1000, PEG600 is polyethylene glycol with an average molecular weight of 600, PEG400 is polyethylene glycol with an average molecular weight of 400, DMBA is dimethylolbutyric acid, and DMPA is polyethylene glycol with an average molecular weight of 400. Dimethylolpropionic acid, IPDI stands for isophorone diisocyanate.

In addition, the urethane bond density of each urethane resin was 2.2 mmol/g.

<Preparation of printing ink (black ink)>
(Black ink Example 1a) (S-1)
20 parts of carbon black, 50 parts of aqueous urethane resin WU1 solution, 19.3 parts of distilled water, 5 parts of normal propanol, 3 parts of propylene glycol, and 0.3 parts of 10% ammonia water were dispersed for 10 minutes in an Eiger mill (manufactured by Eiger). Then, 0.2 parts of a surface conditioner, 0.05 parts of an antifoaming agent, 2 parts of polyethylene wax, and 0.2 parts of adipine dihydrazide were added to obtain a water-based flexographic ink composition. The water-based flexo ink composition was adjusted to 15 seconds using a Zahn cup #4 (manufactured by Rigosha) using a mixed solvent of water/isopropyl alcohol = 1/1 to obtain a water-based flexo ink composition for evaluation. Ta.

[Examples 2a to 20a] (S-2 to S-20)
According to the method of Example 1, S-2 to S-20 were similarly produced using the aqueous urethane resin solutions obtained in Synthesis Examples 2 to 14. The composition is shown in Table 2.

[Comparative Examples 1aa, 2aa] (C-1, C-2)
According to the method of Example 1, C-1 and C-2 were similarly produced using the aqueous urethane resin solutions obtained in Comparative Synthesis Examples 15 and 16. The composition is shown in Table 2.

<Preparation of printing ink (white ink)>
(White ink Example 1b) (WS-1)
37 parts of titanium oxide, 42 parts of aqueous urethane resin WU1 solution, 10.3 parts of distilled water, 5 parts of normal propanol, 3 parts of propylene glycol, and 0.3 parts of 10% ammonia water were dispersed for 10 minutes in an Eiger mill (manufactured by Eiger). Then, 0.2 parts of a surface conditioner, 0.05 parts of an antifoaming agent, 2 parts of polyethylene wax, and 0.2 parts of adipine dihydrazide were added to obtain a water-based flexographic ink composition. The water-based flexo ink composition was adjusted to 15 seconds using a Zahn cup #4 (manufactured by Rigosha) using a mixed solvent of water/isopropyl alcohol = 1/1, and the water-based flexo ink composition for evaluation was prepared as WS-. I got 1.

[Examples 2b to 20b] (WS-2 to WS-20)
According to the method of Example 1, WS-2 to WS-20 were similarly produced using the aqueous urethane resin solutions obtained in Synthesis Examples 2 to 14. The composition is shown in Table 3.

[Comparative Examples 1bb, 2bb] (WC-1, WC-2)
According to the method of Example 1, WC-1 and WC-2 were similarly produced using the aqueous urethane resin solutions obtained in Comparative Synthesis Examples 15 and 16. The composition is shown in Table 3.

Using the ink obtained above, tests were conducted on plate entanglement, blocking resistance, and overlapping halftone dot unevenness.

<Print suitability (plate entanglement) evaluation>
An ink with an adjusted viscosity was printed on the treated surface of a commercially available single-sided corona-treated polyethylene terephthalate film (hereinafter referred to as PET, thickness 12 μm) using a flexo printing machine at a speed of 65 m/min.
On the treated surface of a commercially available single-sided corona-treated polyethylene terephthalate film (hereinafter referred to as PET, thickness 12 μm) using a flexo printing machine (black ink anilox condition: 900 LPI, 3 cc/m ² , white ink anilox condition: 300 LPI, 9 cc/m ² ) A printed matter was obtained by printing for 1000 m at a speed of 65 m/min, and the printing suitability (plate entanglement property) was evaluated by observing the 5% halftone dot area of the printed matter. The drying conditions for the printing layer were an intercolor dryer at 80°C and a tunnel dryer at 80°C.
(Evaluation criteria)
A: A clear image is formed with no visible thickening of the 5% halftone dot area. (excellence)
B: Slight thickening was observed in the 5% halftone dot area, and the halftone dots were not connected to each other. (Good)
C: The shape of the 5% halftone dot area is distorted, and some connections between the halftone dots (dot bridges) are observed. (Available for use)
D: 5% The shape of the halftone dot area is distorted and the connection of halftone dots (dot bridge) is clearly observed (defective)
The practical level evaluation is A to C.

<Blocking resistance>
Regarding the printed material obtained above, the surface with the printed layer of the printed material and the non-corona treated surface of the PET base material were overlapped, a load of 5 kg/cm ² was applied, and 24 hours passed in an environment of temperature 40°C and humidity 80% RH. Thereafter, the PET base material overlapped with the printed material was peeled off, and the blocking resistance was evaluated based on peel resistance or ink transfer area.
(Evaluation criteria)
A: No transfer of ink was observed from the printed matter, and there was no sense of resistance when peeled off.
B: No transfer of ink was observed from the printed matter, but there was a feeling of resistance during peeling.
C: Ink transfer was observed from the printed matter and was less than 10% of the area.
D: Transfer of ink from the printed matter was observed in an area of 10% or more and less than 50%.
E: Transfer of ink from the printed matter was observed over 50% or more of the area.
The practical level evaluation is A to C.

<Evaluation of overlapping halftone dots on PET film printed matter>
・Evaluation of black ink The viscosity-adjusted black ink was flexographic printed on commercially available single-sided PET film (anilox condition 900LPI, 3cc/m ² ), and white ink (anilox condition 300LPI, 9cc/m ² ) was overprinted. I got it. The black ink of the example was overprinted with 1b white ink, and the black ink of the comparative example was overprinted with 1bb white ink. The printing speed was 65 m/min, and the drying conditions for the printed layer were an intercolor dryer at 80°C and a tunnel dryer at 80°C.
The 50% color halftone/white solid overlapping portion of the obtained printed matter was cut out into a 10 cm x 10 cm square, and the halftone dot size at 9 points within the plane was measured. Evaluation was made using the maximum and minimum values of the measured halftone dot size and the in-plane halftone dot size change rate expressed by the following formula.
In-plane halftone dot size change rate [%] = ([maximum halftone dot size (μm)] - [minimum halftone dot size (μm)]) / [minimum halftone dot size (μm)]
(Evaluation criteria)
A: In-plane halftone dot size change rate [%] is less than 2%.
B: In-plane halftone dot size change rate [%] is 2% or more and less than 3%.
C: In-plane halftone dot size change rate [%] is 3% or more and less than 4%.
D: In-plane halftone dot size change rate [%] is 4% or more.
The practical level evaluation is A to C.
[Evaluation of white ink]
The viscosity-adjusted white ink was flexographically printed on a commercially available single-sided PET film (anilox condition: 900 LPI, 3 cc/m ² ), and black ink (anilox condition: 300 LPI, 9 cc/m ² ) was overprinted to obtain printed matter. The white ink of the example was overprinted with 1a black ink, and the ink of the comparative example was overprinted with 1aa black ink. The printing speed was 65 m/min, and the drying conditions for the printed layer were an intercolor dryer at 80°C and a tunnel dryer at 80°C.
The white ink was also evaluated in the same manner as the evaluation of the black ink using the white 50% halftone dot/black solid overlapping area of the obtained printed matter.
(Evaluation criteria)
A: In-plane halftone dot size change rate [%] is less than 2%.
B: In-plane halftone dot size change rate [%] is 2% or more and less than 3%.
C: In-plane halftone dot size change rate [%] is 3% or more and less than 4%.
D: In-plane halftone dot size change rate [%] is 4% or more.
The practical level evaluation is A to C.

Claims (7)

A water-based flexo ink containing a water-based urethane resin and water,
The aqueous urethane resin has an acid group and contains a structural unit derived from polyethylene glycol,
A water-based flexo ink, wherein the water-based urethane resin has a weight average molecular weight of 8,000 to 24,000. The water-based flexographic ink according to claim 1, which contains 30 to 60% by mass of structural units derived from polyethylene glycol in the total mass of the water-based urethane resin. The aqueous flexographic ink according to claim 1, which contains 37 to 60% by mass of structural units derived from polyethylene glycol in the total mass of the aqueous urethane resin. The water-based flexo ink according to any one of claims 1 to 3, wherein the water-based urethane resin has an acid value of 5 to 30 mgKOH/g. The aqueous flexographic ink according to any one of claims 1 to 3, further comprising less than 6% by mass of a glycol solvent and/or glycol monoalkyl ether solvent having a boiling point of 130 to 280°C in the total ink mass. A printed matter comprising a printing layer made of the aqueous flexographic ink according to any one of claims 1 to 3 on a substrate. A laminate comprising a base material 1, a printing layer made of the water-based flexographic ink according to any one of claims 1 to 3, and a base material 2 in this order.