JP7707775B2 - Solvent-based laminating flexographic inks and their applications. - Google Patents

Description

The present invention relates to a solvent-based flexographic ink for lamination, and its printed matter and laminate.

Flexographic inks are widely used for printing patterns to impart beauty and functionality to printed materials, but in recent years, the demands placed on printing inks have become more diverse year by year, due to the diversity of packaging materials, the sophistication of packaging technology, and environmental initiatives in terms of legal restrictions on organic solvents.

Flexographic inks, particularly those used for the printing layer of laminated laminates, often use urethane resin to maintain and improve the strength of the laminate. This is because urethane resin allows for flexible coating film design, from hard and tough to flexible and elastic, by selecting isocyanates, polyols, etc.

There are three methods for creating laminated bodies: extrusion lamination, dry lamination, and solventless lamination. For light packaging materials such as snack foods, the extrusion lamination method is often used from the perspective of running costs. When creating a laminate, an anchor layer, a melt-adhesive olefin resin, and a sealant base material are layered on top of the printed material, but it is generally difficult to obtain strong laminate strength with this layering structure.

It has been known that printing inks using urethane resins and vinyl chloride copolymer resins, mainly consisting of polyester polyols, improve adhesion and laminate strength on plastic substrates such as OPP film, PET film, and NY film (Patent Documents 1 and 2).

While the above printing inks often use ester-based organic solvents, the resin plates used in flexographic printing have low resistance to these ester-based solvents, which causes problems such as the plates swelling during long-run printing and the tendency for changes in density in printed matter. Furthermore, printing inks using urethane resins that primarily contain the above polyester polyols do not dissolve sufficiently in alcohol-based solvents. As a result, the printing defect known as plate tangling, in which ink accumulates on the relief plate, has yet to be resolved.

JP 2016-130297 A WO2018/003596 Publication Pamphlet

The present invention aims to provide a flexographic ink that has good plate adhesion in flexographic printing and excellent lamination strength in extrusion lamination and other processes.

As a result of extensive research, the inventors of the present application discovered that the above problems could be solved by using the solvent-based flexographic ink for lamination described below, and thus came up with the present invention.

That is, the present invention is a solvent-based flexographic ink for lamination containing a urethane resin and a solvent,
The present invention relates to a solvent-based flexographic ink for lamination, wherein the urethane resin contains structural units derived from a polyether polyol and/or structural units derived from an aliphatic diol, and has a urethane bond concentration of 2.6 or more and 5.0 or less (mmol/g).

The present invention also relates to the above-mentioned solvent-based flexographic ink for lamination, in which the urethane resin contains structural units derived from a polyether polyol and structural units derived from an aliphatic diol, and the mass ratio of the structural units derived from the polyether polyol to the structural units derived from the aliphatic diol is 5:95 to 95:5.

The present invention also relates to the above-mentioned solvent-based flexographic ink for lamination, in which the aliphatic diol has a branched structure.

The present invention also relates to the above-mentioned solvent-based flexographic ink for lamination, which further contains at least one resin selected from the group consisting of cellulose-based resins, polyvinyl acetal resins, and rosin resins.

The present invention also relates to the above-mentioned solvent-based flexographic ink for lamination, which further contains a chelating crosslinker and/or a plasticizer.

In addition, the present invention is a method for producing a liquid crystal display device, wherein the solvent includes an ester-based organic solvent and an alcohol-based organic solvent,
The mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is from 60:40 to 5:95.

The present invention also relates to a printed matter having a printed layer made of the above-mentioned solvent-based flexographic ink for lamination on a substrate 1.

The present invention also relates to a laminate having an adhesive layer and a substrate 2, in that order, on the printed layer of the printed matter.

The present invention makes it possible to provide a flexographic ink that has good plate adhesion in flexographic printing and excellent lamination strength in extrusion lamination and other processes.

The following examples are provided to explain the embodiments of the present invention in detail, but the following examples are merely representative examples of the embodiments of the present invention, and the present invention is not limited to these examples as long as they do not exceed the gist of the present invention.

The present invention is a solvent-based flexographic ink for lamination that contains a urethane resin.
A part or the whole of the urethane resin contains structural units derived from a polyether polyol and/or an aliphatic diol, and has a urethane bond concentration of 2.6 or more and 5.0 or less (mmol/g).
The inclusion of the urethane resin provides the effect of imparting appropriate solubility and flexibility, which is believed to contribute to improving properties such as printability and lamination strength.

In this specification, "flexographic ink" may be referred to simply as "ink" or "printing ink," but these terms have the same meaning. The layer formed from flexographic ink is referred to as the "printing layer" or "ink film."

(urethane resin)
The urethane resin is preferably contained in an amount of 3 to 25% by mass, and more preferably 5 to 22% by mass, of the total mass of the ink as a non-volatile component. The ink of the present invention may contain two or more kinds of urethane resins in combination.

The urethane resin in the present invention is preferably one obtained by reacting a polyether polyol and/or an aliphatic diol with a polyisocyanate, and reacting the urethane polymer having a terminal isocyanate group with an alcohol or a polyamine. The mass ratio of the structural units derived from the polyether polyol to the structural units derived from the aliphatic diol is preferably 5:95 to 95:5, more preferably 90:10 to 25:75, and even more preferably 80:20 to 40:60. This is to improve lamination suitability and plate entanglement. The weight average molecular weight of the urethane resin is preferably 2000 to 90,000, and even more preferably 4000 to 70,000 or 4000 to 55,000. This is because it is possible to achieve both lamination strength and plate entanglement performance during flexographic printing.

In the above, the aliphatic diol does not include polyether polyol. Aliphatic diol refers to a substituted or unsubstituted alkane diol (alkylene glycol).

The urethane resin may contain structural units derived from polyols other than those mentioned above (other polyols). Examples of other polyols include polyester polyols (including polylactone polyols), polycarbonate polyols, polyolefin polyols, castor oil polyols, and hydrogenated castor oil polyols.
Polyester polyol is preferable because it can ensure solubility in ester-based solvents and alcohol-based solvents.

(Polyether polyol)
Suitable examples of polyether polyols include polymers or copolymers of methylene oxide, ethylene oxide, propylene oxide, tetrahydrofuran, etc. These may be used alone or in combination of two or more. More specifically, it is preferable to include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytrimethylene glycol, and copolymers thereof, and it is even more preferable to include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

The polyether polyols may be used alone or in combination of two or more kinds. The number average molecular weight of the polyether polyol is preferably 200 to 5000, more preferably 200 to 4000. This is because blocking resistance and solubility can be ensured.

(Aliphatic diol)
The aliphatic diol does not include polyether polyols. The aliphatic diol refers to a substituted or unsubstituted alkanediol (alkylene glycol), and the alkanediol preferably has 2 to 10 carbon atoms, and examples of suitable alkanediols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 3,3,5-trimethylpentanediol, 2,4-diethyl-1,5-pentanediol, 1,12-octadecanediol, 1-monoglyceride, 2-monoglyceride, 1-monoglycerin ether, 2-monoglycerin ether, dimer diol, and hydrogenated dimer diol.

Among the above aliphatic diols, aliphatic diols having a branched structure are preferred, and examples thereof include 2-butyl-2-ethyl-1,3-propanediol (hereinafter also referred to as BEPG), 2-methyl-1,3-propanediol (hereinafter also referred to as MPO), 3-methyl-1,5-pentanediol (hereinafter also referred to as MPD), neopentyl glycol (hereinafter also referred to as NPG), 1,2-propylene glycol (hereinafter also referred to as PG), 2,4-diethyl-1,5-pentanediol, 1,3-butanediol, dipropylene glycol, etc. Among them, it is preferred to use at least one diol having a branched structure selected from MPO, MPD, BEPG, NPG, PG, and 2,4-diethyl-1,5-pentanediol, and it is more preferred to use NPG and/or BEPG, and it is particularly preferred to use BEPG. This is because it improves lamination strength and blocking properties.

As the polyisocyanate, a diisocyanate is preferred, and various known aromatic, aliphatic, or alicyclic diisocyanates can be used as such compounds. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylsilyl diisocyanate, 1,3,4-trimethylsilyl diisocyanate, 1,4,5 ...4,5-trimethylsilyl diisocyanate, 1,4,5-trimethylsilyl diisocyanate, 1,4,5-trimethylsilyl diisocyanate, 1,4,5-trimethylsilyl diisocyanate, 1,4,5-trimethylsilyl diiso Representative examples include methylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate in which the carboxyl group of a dimer acid is converted to an isocyanate group. These can be used alone or in a mixture of two or more. Among them, isophorone diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate are preferred, and 4,4'-diphenylmethane diisocyanate is even more preferred from the viewpoint of lamination suitability.

The polyamine is preferably an organic diamine, and examples of such diamines include ethylenediamine, propylenediamine, hexamethylenediamine, isophoronediamine, and dicyclohexylmethane-4,4'-diamine. In addition, amines having a hydroxyl group in the molecule, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropyldiamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine, can also be used. These organic diamines can be used alone or in combination of two or more, with isophoronediamine being preferred. Furthermore, polyfunctional amines having three or more amino groups, such as diethylenetriamine, iminobispropylamine (IBPA, 3,3'-diaminodipropylamine), N-(3-aminopropyl)butane-1,4-diamine (spermidine), 6,6-iminodihexylamine, 3,7-diazanonane-1,9-diamine, and N,N'-bis(3-aminopropyl)ethylenediamine, can also be used in combination with the above organic diamines.

(Urethane bond concentration)
The urethane bond concentration may be, for example, a value calculated by the method described in JP-A-2016-130297.

Urethane bond concentration = {( _W1 x _OH1 + _W2 x _OH2 + ... + _Wi x _OHi ) x 1000}/(56100 x S) Formula (1)

In formula (1), each is as follows.
W ₁ : Weight of polyol 1
OH ₁ : hydroxyl value of polyol 1
W2: weight of polyol 2
OH ₂ : hydroxyl value of polyol 2
W _i : weight of polyol i
OH _i : hydroxyl value of polyol i
S: Weight of urethane resin solids

Simply put, when there is an excess of isocyanate groups, it can be understood as the number of moles of hydroxyl groups modified (urethane bonded) by the isocyanate groups, and when there is an excess of hydroxyl groups, it is the number of moles of isocyanate groups modified by the hydroxyl groups.

For example, the urethane bond concentration is a value expressed by the following formula.
When (NCO molar equivalent/OH molar equivalent)>1

Equation (1) Urethane bond concentration (mmol/g)=total number of moles of hydroxyl groups (mmol)/total solid content (g)

Here, the total number of moles of hydroxyl groups refers to the total number of moles of hydroxyl groups contained in the polymer polyol, aliphatic diol, and other polyols used in the reaction to form the urethane, and the total solid content refers to the total mass of non-volatile components that become the polyurethane resin.

When (NCO molar equivalent/OH molar equivalent)<1

Equation (2) Urethane bond concentration (mmol/g)=total number of moles of isocyanate groups (mmol)/total solid content (g)

The total number of moles of isocyanate groups herein refers to the total number of moles of isocyanate groups contained in the polyisocyanate used in the reaction to form urethane.

<Urea bond concentration>
The urea binding concentration is a value represented by the following formula.
When a prepolymer having a terminal isocyanate group is synthesized under the above condition of (NCO molar equivalent/OH molar equivalent)>1 and then chain-extended with a polyamine to give a polyurethane resin having an amino group at its terminal, the polyurethane resin is represented by the following formula (3).

Equation (3) Urea bond concentration (mmol/g)=[total number of moles of isocyanate groups (mmol)−total number of moles of hydroxyl groups (mmol)]/total solid content (g)

When a prepolymer having a terminal isocyanate group is synthesized under the above condition of (NCO molar equivalent/OH molar equivalent)>1 and then chain-extended with a polyamine to give a polyurethane resin having an isocyanate group at its terminal, the polyurethane resin is represented by the following formula (4).

Equation (4) Urea bond concentration (mmol/g)=(total number of moles of amino groups (mmol))/total solid content (g)

The total number of moles of amino groups herein refers to the total number of moles of amino groups contained in the polyamine used to form urea bonds by reacting with a prepolymer having a terminal isocyanate group.

The urethane resin in the present invention preferably has a urethane bond concentration of 2.6 to 5.0 (mmol/g), more preferably 2.8 to 4.5 (mmol/g), and even more preferably 3.0 to 4.2 (mmol/g). This composition improves the laminate strength and plate adhesion during flexographic printing.

The urethane resin in the present invention preferably has a urea bond concentration of 1.0 or less (mmol/g), 0.7 or less (mmol/g), or 0.5 or less (mmol/g). ("or less" includes the case of 0.0 (mmol/g).) This is to improve plate adhesion.

The urethane resin may or may not have a urea bond. When a urea bond is present, the manufacturing method is not particularly limited, but it is preferable that the total number of amino groups in the chain extender and reaction terminator is within the range of 0.2 to 1.5 when the number of isocyanate groups in the prepolymer having isocyanate groups at the terminals obtained by reacting a polyol and/or an aliphatic diol with a polyisocyanate is 1.

For example, if the urethane resin has a straight-chain structure, both ends of the straight-chain structure are called end groups. If the urethane resin has a branched structure, the ends including the ends of the branches are also called end groups.
The terminal group is not particularly limited, but among them, the terminal group is preferably an alkyl group and/or a hydroxyl group, and when it has a hydroxyl group, the hydroxyl value of the urethane resin is preferably 0.1 to 35 mgKOH/g, and more preferably 0.5 to 20 mgKOH/g. When it has an alkyl group as the terminal group, it preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and even more preferably 1 to 5 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tertiary butyl group, a pentyl group, and a hexyl group.

In one embodiment, in order to introduce a hydroxyl group or an alkyl group into the terminal of a urethane resin, a method can be mentioned in which a polyol is reacted with a polyisocyanate to obtain a urethane prepolymer having a terminal isocyanate group, and then a polymerization terminator is used to introduce a terminal structure derived from the polymerization terminator.
When it is desired to introduce an alkyl group into the isocyanate terminal after the reaction, it is preferable to use a monoalcohol as a polymerization terminator, and a monoalcohol having 1 to 8 carbon atoms such as ethanol, isopropanol, normal propanol, butanol, and hexanol is suitable. Note that, in cases where structural isomers having multiple carbon atoms exist, these structural isomers are also included.
In order to introduce a hydroxyl group into the terminal of the urethane resin, it is preferable to use a diol or amino alcohol as a polymerization terminator, and suitable examples of the diol include ethylene glycol, propylene glycol, 1,3-propanediol, and 1,4-butanediol, and suitable amino alcohols include 2-ethanolamine, 4-butanolamine, and 3-propanolamine, and are preferably amino alcohols having 1 to 8 carbon atoms. Note that, in cases where structural isomers having a plurality of carbon atoms exist, these structural isomers are also included.
Another suitable method is to react the above polyol with a polyisocyanate so that the hydroxyl value of the polyol is in excess to obtain a urethane resin having hydroxyl groups at its terminals.

(Cellulosic resin)
The cellulose-based resin is preferably a nitric acid ester obtained by reacting natural cellulose with nitric acid to replace three hydroxyl groups in a six-membered ring of an anhydrous glucopyranose group in the natural cellulose with nitric acid groups. The weight-average molecular weight is preferably 10,000 to 100,000, and more preferably 10,000 to 80,000. This improves the strength of the ink film, and improves the solubility in the solvent, the low-temperature stability of the ink, and the compatibility with the co-used resin. The nitrogen content in the cellulose-based resin is preferably 10.5 to 12.5% by mass. This is because the affinity to alcohol-based solvents is high and the suitability for flexographic printing is good.
In addition, cellulose acetate propionate and cellulose acetate butyrate are also preferably used.
The cellulose-based resin is contained in an amount of preferably 0.5 to 15 mass %, and more preferably 1.5 to 12 mass %, based on the total mass of the ink as the total mass of non-volatile components.

(Polyvinyl acetal resin)
The polyvinyl acetal resin is an acetal cyclized product of reacting polyvinyl alcohol with an aldehyde such as butyraldehyde and/or formaldehyde, and preferably contains vinyl alcohol units, vinyl acetate units, and an acetal ring group. The polyvinyl acetal resin preferably contains 60 to 90% by mass of acetal rings, 5 to 30% by mass of vinyl alcohol units, and 0.5 to 10% by mass of vinyl acetate units, and is more preferably a polyvinyl butyral resin having a butyral ring as the acetal ring.
The weight average molecular weight of the polyvinyl acetal resin is preferably 10,000 to 100,000, and more preferably 10,000 to 80,000. The glass transition point of the polyvinyl acetal resin is preferably 50 to 80°C, and more preferably 60 to 75°C.

(rosin resin)
The rosin resin refers to a resin having a structural unit derived from a rosin acid (e.g., abietic acid, neoabietic acid, palustric acid, pimaric acid, isopimaric acid, dehydroabietic acid) as a main component. Here, the main component means 50% by mass or more. The rosin acid or rosin resin may be hydrogenated.
The rosin resin is preferably at least one selected from the group consisting of rosin-modified phenolic resins, rosin ester resins, rosin-modified maleic acid resins, and polymerized rosin resins.
The acid value of the rosin resin is preferably 5 to 350 mgKOH/g, more preferably 20 to 350 mgKOH/g, and further preferably 60 to 320 mgKOH/g.
The softening point of the rosin resin is preferably 60 to 180° C., and more preferably 80 to 160° C. In this specification, the softening point is a value measured by the ring and ball method, and can be measured in accordance with JIS K2207.

The rosin resin is preferably a rosin ester, which is an ester condensation resin of a low molecular weight polyol having a molecular weight of 1,000 or less and a rosin acid. The low molecular weight polyol preferably has 2 to 4 hydroxyl groups in one molecule (hereinafter sometimes abbreviated as bifunctional to tetrafunctional) and a molecular weight of 50 to 500. As such a low molecular weight polyol, for example, bifunctional low molecular weight polyols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,10-decanediol, etc.; trifunctional low molecular weight polyols such as glycerin and trimethylolpropane; and tetrafunctional low molecular weight polyols such as erythritol and pentaerythritol are preferably used. Among them, trifunctional and/or tetrafunctional low molecular weight polyols are preferred.
The weight average molecular weight of the rosin ester is preferably 500 to 2,000, and more preferably 500 to 1,500.

(Other resins)
Resins other than those mentioned above may be contained within a range that does not impair the effects of the present invention. Examples of such resins include acrylic resins, polyamide resins, chlorinated rubbers, cyclized rubbers, vinyl chloride, vinylidene chloride, vinyl chloride-vinyl acetate copolymers, polyester resins, ketone resins, ethylene-vinyl acetate resins, ethylene-vinyl alcohol resins, styrene-maleic acid resins, casein, and alkyd resins.

(Chelating Crosslinker)
In the present invention, in order to improve lamination suitability and blocking resistance, it is preferable to use a chelating crosslinking agent. The chelating crosslinking agent is preferably an organic titanium compound having a Ti-O-C type bond in one molecule. Specific examples include titanium chelates such as titanium alkoxide and titanium acylate.
It is preferable to use a titanium chelate, and representative examples of titanium chelates include titanium alkoxides such as tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, tetramethyl titanate, and tetrastearyl titanate, and titanium chelates such as triethanolamine titanate, titanium acetylacetate, titanium ethylacetoacetate, titanium lactate, octylene glycol titanate, and titanium tetraacetylacetonate. Among these, organic titanium compounds such as titanium chelates generally require heating to complete the crosslinking reaction, but are less likely to hydrolyze at room temperature and have excellent stability, making them suitable for use in inks and suitable for use. The chelating crosslinking agent is preferably contained in an amount of 0.1 to 8% by mass, and more preferably 0.5 to 5% by mass, based on the total mass of the ink.

(Plasticizer)
In the present invention, it is preferable to use a plasticizer. This is because the flexibility of the ink film is improved, and the lamination suitability and plate adhesion are improved. Specific examples include citrate esters, castor oil, phthalate esters, polyesters, epoxidized vegetable oils, phosphate esters, and sulfonamides. Among these, citrate esters, epoxidized vegetable oils, phosphate esters, and sulfonamides are preferable, and citrate esters are more preferable.
The content of the plasticizer in the total ink mass is preferably 0.1 to 10 mass %, more preferably 0.5 to 8 mass %, and even more preferably 0.8 to 5 mass %.

(Other additives)
The ink of the present invention may contain additives such as a leveling agent, an antifoaming agent, a wax, a silane coupling agent, a light stabilizer, silica particles, an infrared absorbing agent, an ultraviolet absorbing agent, an aromatic agent, a flame retardant, and a curing agent, as necessary.

(Pigment)
The ink preferably contains a pigment, but the pigment to be used is not particularly limited. Any of organic pigments, inorganic pigments, and extender pigments can be used, but inorganic pigments containing titanium oxide are preferred, and extender pigments such as silica, barium sulfate, kaolin, clay, calcium carbonate, and magnesium carbonate are preferred. Organic pigments made of organic compounds and organometallic complexes are preferred.
When a white pigment such as titanium oxide is contained, the content of the white pigment is preferably 10 to 80 mass % of the total mass of the ink, and more preferably 30 to 60 mass %. When an organic pigment or other chromatic pigment other than a white pigment is contained, the content of the white pigment is preferably 5 to 50 mass % of the total mass of the ink, and more preferably 10 to 40 mass %.

(Organic pigments)
Examples of the organic pigment include, but are not limited to, soluble azo pigments, insoluble azo pigments, azo pigments, phthalocyanine pigments, halogenated phthalocyanine pigments, anthraquinone pigments, anthanthrone pigments, dianthraquinonyl pigments, anthrapyrimidine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, dioxazine pigments, isoindolinone pigments, quinophthalone pigments, azomethine azo pigments, flavanthrone pigments, diketopyrrolopyrrole pigments, isoindoline pigments, indanthrone pigments, and carbon black pigments.

The hue of the organic pigment is preferably at least one selected from the group consisting of black pigments, cyan pigments, green pigments, red pigments, purple pigments, yellow pigments, orange pigments, and brown pigments.Furthermore, at least one or more selected from the group consisting of black pigments, cyan pigments, red pigments, and yellow pigments are preferable.Specific examples of organic pigments are shown by C.I. numbers of the Color Index International (abbreviated as C.I.).
Preferably, C.I. Pigment Red 57:1, C.I. Pigment Red 48:1, C.I. Pigment Red 48:2, C.I. Pigment Red 48:3, C.I. Pigment Red 146, C.I. Pigment Red 242, C.I. Pigment Yellow 83, C.I. Pigment Yellow 14, C.I. Pigment Orange 38, C.I. Pigment Orange 13, C.I. Pigment Yellow 180, C.I. Pigment Yellow 139, C.I. Pigment Red 185, C.I. Pigment Red 122, C.I. Pigment Red 178, C.I. Pigment Red 149, C.I. Pigment Red 144, C.I. C.I. Pigment Red 166, C.I. Pigment Violet 23, C.I. Pigment Violet 37, C.I. Pigment Blue 15, C.I. Pigment Blue 15:1, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4, C.I. Pigment Blue 15:6, C.I. Pigment Green 7, C.I. Pigment Orange 34, C.I. Pigment Orange 64, C.I. Pigment Black 7, and it is preferable to use one or more of them.

Inorganic pigments include titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, aluminum particles, mica, bronze powder, chrome vermilion, yellow lead, cadmium yellow, cadmium red, ultramarine, Prussian blue, red iron oxide, yellow iron oxide, and iron black. Aluminum can be either leafing or non-leafing type, with the non-leafing type being preferred.

(Titanium oxide pigment)
In the present invention, the titanium oxide pigment may have a crystal structure of any of anatase type, rutile type, and brookite type. Among them, rutile type titanium oxide is preferable because it has good pigment dispersibility. In industrial production of titanium oxide, rutile ore or ilmenite ore (FeTiO3) is used as a raw material. There are two main production methods, the chlorine method and the sulfuric acid method, and either method may be used.
In order to improve printability, it is preferable that the titanium oxide pigment is surface-treated, and in particular, that the titanium oxide pigment is surface-treated with at least one metal selected from the group consisting of Si, Al, Zn, Zr and oxides thereof.

The oil absorption amount as measured by the method specified in JIS K5101 is preferably 14 to 35 ml/100 g, and more preferably 17 to 32 ml/100 g. The average particle size (median particle size) as measured by a transmission electron microscope is preferably 0.2 to 0.3 μm. Multiple types of titanium oxide pigments may be used in combination.
In the flexographic ink of the present invention, in addition to the titanium oxide pigment, other inorganic pigments and organic pigments can also be used in combination.

(Organic Solvent)
The flexographic ink preferably contains an organic solvent. The organic solvent may be an alcohol-based organic solvent, an ester-based organic solvent, a glycol-based organic solvent, or the like, and is preferably a mixed solvent. The organic solvent is preferably contained in an amount of 30 to 85% by mass based on the total mass of the flexographic ink. As the alcohol-based organic solvent, ethanol, isopropyl alcohol, n-propyl alcohol, n-butanol, isobutanol, or the like is preferred, and as the ester-based organic solvent, ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, or the like is preferred. As the glycol ether-based organic solvent, ethylene glycol mono n-butyl ether, propylene glycol monopropyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, or the like is preferred.
The mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is preferably 60:40 to 5:95, more preferably 50:50 to 15:85, and even more preferably 40:60 to 25:75. By setting the mass ratio within this range, it is possible to obtain good plate adhesion without corroding the resin plate used for the flexographic ink.

(Method of manufacturing flexographic ink)
The flexographic ink of the present invention can be produced, for example, by previously mixing an organic pigment, a urethane resin, other resins, an organic solvent, and the like using a stirring mixer, and then subjecting the mixture to a pigment dispersion process using a dispersing machine such as a beads mill, and then mixing the resulting dispersion with a chelating crosslinking agent and a plasticizer.
A common dispersing machine is used to produce the pigment dispersion. For example, a roller mill, a ball mill, a pebble mill, an attritor, a bead mill (sand mill, gamma mill, etc.), etc. can be used. Among them, production using a bead mill dispersing machine such as a sand mill is preferred.

(Flexographic printing)
In the packaging material of the present invention, the printing layer obtained by the flexographic printing method has the characteristics of low film thickness and high density, excellent reproducibility of fine characters and sharp color reproduction, and less solvent emission during printing than gravure printing, which is also effective from the viewpoint of environmental consideration. Flexographic printing is a printing method in the field of packaging material printing, and is a letterpress printing method. The flexographic printing layer may be formed by a known method, for example, ink is supplied from an ink supply part to an anilox roll by a doctor chamber method, a two-roll method, an ink fountain method, etc., and then the ink is transferred to the raised part of a printing plate made of resin or rubber, and this ink is transferred to a printing material passing between the impression cylinder and the printing medium to form a flexographic printing layer.
Examples of the plate include a photosensitive resin plate that utilizes ultraviolet curing by a UV light source, and an elastomer material plate that uses a direct laser engraving method. Regardless of the method for forming the image part of the flexographic plate, a plate with a screening line count of 75 lpi or more is used.
As the anilox roll, a ceramic anilox roll with cell engraving, a chrome-plated anilox roll, etc. can be used. In order to obtain a print with excellent dot reproducibility, an anilox roll having a number of lines 5 or more times, preferably 6 or more times, the number of lines used in printing is used. For example, when the number of lines used is 75 lpi, an anilox roll of 375 lpi or more is required, and when the number of lines used is 150 lpi, an anilox roll of 750 lpi or more is required. The anilox roll has an anilox capacity of 1 to 10 cc/ ^m3 , preferably 2 to 9 cc/ ^m3 .
In order to obtain the properties of the packaging material of the present invention, it is preferable to use a 80 to 175 lpi plate and a 200 to 1400 lpi anilox roll for the flexographic printing layer. The obtained flexographic printing layer preferably has a film thickness of 0.5 to 10 μm, and more preferably 1 to 8 μm.

(printing machine)
The flexographic printing press includes a CI type multi-color flexographic printing press, a unit type multi-color flexographic printing press, and the like, and the ink supply system includes a chamber system and a two-roll system, and an appropriate printing press can be used.

(Base material 1)
The flexographic ink of the present invention is printed on a substrate 1 to form a printed matter.
Substrates to which the flexographic ink of the present invention can be applied include polyethylene, polypropylene and other polyolefin substrates, polycarbonate substrates, polyester substrates (polyethylene terephthalate, polylactic acid, etc.), polystyrene substrates, polystyrene-based substrates such as AS resin or ABS resin, polyamide substrates, polyvinyl chloride substrates, various substrates such as polyvinylidene chloride, cellophane substrates, paper substrates, aluminum foil substrates, etc., or film or sheet substrates made of composite materials of these. Among these, polyester substrates and polyamide substrates having high glass transition temperatures are preferably used.

The above-mentioned substrate may be coated with a metal oxide or the like by vapor deposition and/or with polyvinyl alcohol, for example, GL-AE manufactured by Toppan Printing Co., Ltd., in which aluminum oxide is vapor-deposited on the substrate surface, or IB-PET-PXB manufactured by Dai Nippon Printing Co., Ltd., may be mentioned. Furthermore, substrates treated with additives such as antistatic agents and ultraviolet protection agents, or substrates whose surfaces have been corona-treated or low-temperature plasma-treated may also be used as required.

(Base material 2)
The substrate 2 may be the same as or different from the substrate 1. A thermoplastic substrate (sometimes called a sealant) is preferable, and a non-oriented polyethylene substrate, a non-oriented polypropylene substrate, a non-oriented polyester substrate, or the like is preferable.

In the present invention, "for lamination" means a form of use in which a laminate has, in this order, a substrate 1, a printed layer formed from the ink of the present invention, and a substrate 2; a laminate having, in this order, a substrate 1, a printed layer, an adhesive layer, and a substrate 2 is more preferable.

(Laminate)
The laminate of the present invention is obtained by providing an adhesive layer on the printed layer of a printed matter printed with flexographic ink, and laminating it with a substrate 2. Representative examples of lamination processing include extrusion lamination, dry lamination, non-solvent lamination, etc. Extrusion lamination is a method in which an anchor coating agent is applied to the printed layer of a printed matter, and molten polyethylene resin, molten polypropylene resin, etc. are extruded thereon and simultaneously laminated with the substrate. Dry lamination and non-solvent lamination are methods in which an adhesive is applied to the printed layer of a printed matter, dried, and laminated with a sealant by thermocompression. The difference between the dry lamination and non-solvent lamination is whether or not an organic solvent or other volatile medium is contained.

The present invention will be described in detail below with reference to examples, but the following embodiments are merely examples of the present invention and the present invention is not limited to these examples. In the present invention, parts and % represent parts by mass and % by mass unless otherwise noted.
It should be noted that Examples 21, 24, and 29 are reference examples.

<Method of measuring number average molecular weight (Mn) and mass average molecular weight (Mw)>
The number average molecular weight (Mn) and the mass average molecular weight (Mw) were determined by GPC (gel permeation chromatography). The molecular weight distribution was measured using "Shodex GPC System-21" manufactured by Showa Denko K.K.
The molecular weight was calculated in terms of polystyrene under the following measurement conditions:
Column: The following columns are connected in series.
Tosoh Corporation, TSKgel Super AW2500,
Tosoh Corporation, TSKgel Super AW3000,
Tosoh Corporation, TSKgel Super AW4000,
TSK gelguard column Super AWH, manufactured by Tosoh Corporation
Detector: RI (differential refractometer),
Measurement conditions: column temperature 40°C,
Eluent: Tetrahydrofuran Reference material: Polystyrene Flow rate: 0.5 mL/min

<Method for measuring hydroxyl value>
It was determined according to the method described in JIS K0070.

[Synthesis Example 1] (Synthesis of urethane resin P1)
A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube was charged with 20 parts of ethyl acetate, 16 parts of polypropylene glycol (hereinafter abbreviated as PPG) having a number average molecular weight of 1000, 10 parts of 2-butyl-2-ethyl-1,3-propanediol (hereinafter abbreviated as BEPG), 24 parts of 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as 4,4-MDI), and 0.003 parts of tin 2-ethylhexanoate, and reacted for 3 hours at 80°C under a nitrogen stream. Then, 5 parts of ethyl acetate and 25 parts of isopropanol (hereinafter abbreviated as IPA) were added and cooled to obtain a urethane resin P1 solution with a solid content of 50% and a mass average molecular weight of 14,000.

[Synthesis Examples 2 to 16] (Synthesis of urethane resins P2 to P16)
Urethane resins P2 to P16 were obtained in the same manner as in Synthesis Example 1, except that the raw materials and their charging ratios shown in Table 1 were used. The abbreviations shown in the table stand for the following.
NPG/AdA: Polyester polyol, a condensation product of neopentyl glycol and adipic acid, number average molecular weight 400
PPG: Polypropylene glycol (number average molecular weights of 3,000, 1,000 and 200 were used)
PEG: Polyethylene glycol, number average molecular weight 1,000
PTMG: Polytetramethylene ether glycol, number average molecular weight 1,000
1,3PD: 1,3-propanediol PG: 1,2-propylene glycol MPO: 2-methyl-1,3-propanediol NPG: neopentyl glycol TDI: tolylene diisocyanate IPDI: isophorone diisocyanate IPDA: isophorone diamine AEA: N-(2-aminoethyl)ethanolamine

[Synthesis Example 17] (Synthesis of urethane resin P17)
A four-neck flask equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen gas inlet tube was charged with 20 parts of ethyl acetate, 16 parts of polypropylene glycol having a number average molecular weight of 1000, 10 parts of 2-butyl-2-ethyl-1,3-propanediol, 23.5 parts of 4,4'-diphenylmethane diisocyanate, and 0.003 parts of tin 2-ethylhexanoate, and reacted for 3 hours at 80 ° C. under a nitrogen stream, 5 parts of ethyl acetate was added and cooled to obtain a solution of terminal isocyanate prepolymer. Next, 0.5 parts of isophorone diamine (hereinafter also abbreviated as IPDA) was gradually added to the obtained solution of terminal isocyanate prepolymer at room temperature, and then reacted at 50 ° C. for 1 hour. Then, 25 parts of isopropanol was added and cooled to obtain a urethane resin P15 solution having a solid content of 50% and a mass average molecular weight of 52000.

[Synthesis Example 18] (Synthesis of urethane resin P18)
Urethane resin P18 was obtained in the same manner as in Synthesis Example 17, except that the raw materials and the charging ratios thereof shown in Table 1 were used.

Comparative Synthesis Examples 1 to 3 (Synthesis of urethane resins PP1 to PP3)
Urethane resins PP1 to PP3 were obtained in the same manner as in Synthesis Example 1, except that the raw materials and their charging ratios shown in Table 1 were used.

[Example 1] (Production of ink S1)
20 parts of urethane resin P1 solution, 15 parts of C.I. Pigment Blue 15:4 (manufactured by Toyo Color Co., Ltd.: LIONOL BLUE FG-7400-G), 10 parts of cellulose-based resin solution (manufactured by Inabata Sangyo Co., Ltd.: DHX4-6, nitrogen content is 10.5 to 12.5% by mass, weight average molecular weight 22000) (solid content 50%, ethyl acetate/IPA = 50/50), and 10 parts of ethyl acetate were mixed and dispersed for 20 minutes with a bead mill to obtain a pigment dispersion. The obtained pigment dispersion was stirred and mixed with 33 parts of IPA, 1 part of tetraisopropyl titanate, and 1 part of acetyl tributyl citrate to obtain flexographic ink S1.

[Examples 2 to 29] (Production of Inks S2 to S29)
Flexographic inks S2 to S29 were obtained in the same manner as in Example 1, except that the raw materials and compositions were changed to those shown in Table 2.
Polyvinyl acetal resin solution: Mobital B20H manufactured by Kuraray Co., Ltd., solid content 50%, (ethyl acetate/IPA=50/50), weight average molecular weight about 23,000, vinyl alcohol unit 18-21% by mass, glass transition temperature 64° C.
Rosin resin solution: Arakawa Chemical's Malkied No. 33, solids content 50%, ethyl acetate/IPA = 50/50)

[Comparative Examples 1 to 3] (Production of Inks SS1 to SS3)
Flexographic inks SS1 to SS3 were obtained in the same manner as in Example 1, except that the raw materials and compositions were changed to those shown in Table 2.

[Preparation of printed matter using ink S1]
The viscosity of Ink S1 was adjusted by dilution with a mixed solvent of n-propyl acetate/n-propyl alcohol = 30/70 to a viscosity of 14 seconds (at 25 ° C.) in a Zahn cup #4 (manufactured by Rigo Co., Ltd.). Then, using a flexographic printing proofing machine equipped with a flexographic plate (150 LPI) and an anilox roll (120 LPI, 3.0 cc/m2), printing was performed on the corona-treated surface of a single-sided corona-treated polypropylene (OPP) film (Pylen P2161 manufactured by Toyobo Co., Ltd.) at a speed of 50 m/min, and dried at 50 to 60 ° C. to obtain an OPP print using Ink S1.

[Preparation of prints using inks S2 to S29 and inks SS1 to SS3]
OPP prints were obtained using inks S2 to S29 and inks SS1 to SS3, respectively, in the same manner as in the example of the print using ink S1, except that inks S2 to S29 and inks SS1 to SS3 were used.

The following evaluations were carried out using the inks and printed matter obtained in the above examples and comparative examples. The evaluation results are shown in Table 2.

[Extrusion Lamination Strength]
On the printed layer of the OPP film printed matter of the inks S1 to S29 (Examples) and SS1 to SS3 (Comparative Examples) obtained in the above Examples and Comparative Examples, a methanol solution containing 1% by mass of an imine-based anchor coating agent (EL420, manufactured by Toyo-Morton Co., Ltd.) was applied, and molten polyethylene (LC600A, manufactured by Japan Polyethylene Co., Ltd.) was extruded at 320°C at a line speed of 100 m/min using an extrusion laminator (manufactured by Musashino Kikai Co., Ltd.) to laminate at 20 μm, and at the same time, CPP (FCMN, 20 μm thick, manufactured by Futamura Chemical Co., Ltd.) was similarly laminated to obtain a laminate. After lamination, the laminate was cut into a length of 150 mm and a width of 15 mm, opened at the ink/OPP film interface, and the laminate strength in the 90° direction was measured using a tensile tester.

(Evaluation Criteria)
5: 1.2N/15mm or more (excellent)
4: 1.0N/15mm or more, less than 1.2N/15mm (good)
3: 0.8N/15mm or more, less than 1.0N/15mm (acceptable)
2: 0.5N/15mm or more, less than 0.8N/15mm (not acceptable)
1: Less than 0.5N/15mm (poor)
The practical level is 3 to 5.

[Blocking resistance]
The resulting print was cut into a size of 4 cm x 4 cm, and the printed surface of the cut sample was overlapped with the untreated surface of a 20 μm-thick polypropylene film of the same size to prepare a test piece. A load of 10 kgf was applied to the test piece in an atmosphere of 40° C. and 80% relative humidity, and after 48 hours, the films were peeled off and the state of ink peeling from the printed surface was visually judged.

(Evaluation Criteria)
5: The ink film does not peel off and there is no peeling resistance. 4: The ink film does not peel off and there is little peeling resistance. 3: The peeled area of the ink film is 1% or more and less than 5%.
2: The peeled area of the ink film is 5% or more and less than 50%.
1: The area of the ink film peeled off was 50% or more. Practical level is 3 to 5.

[Plate compatibility]
The inks S1 to S29 (Examples) and SS1 to SS3 (Comparative Examples) obtained in the above Examples and Comparative Examples were diluted and adjusted with a mixed solvent of n-propyl acetate/n-propyl alcohol = 30/70 to a viscosity of 14 seconds (at 25 ° C.) in Zahn cup #4 (manufactured by Rigo Co., Ltd.). Then, using a flexographic printing proofing machine equipped with a flexographic plate (150 LPI) and an anilox roll (1200 LPI, 3.0 cc/m2), printing was performed on the corona-treated surface of a single-sided corona-treated polypropylene (OPP) film (Pylen P2161 manufactured by Toyobo Co., Ltd.) at a speed of 50 m/min. The test was performed by visually evaluating the unevenness of the printed matter in the highlight (dot area 5% to 10%) printed portion after printing for 30 minutes using a flexographic plate having a halftone dot gradation pattern portion.
5: There is absolutely no unevenness in the highlighted printed areas.
4: The uneven area of the highlight printing portion is less than 5%.
3: The uneven area of the highlight printing portion is 5% or more and less than 25%.
2: The uneven area of the highlight printing portion is 25% or more and less than 50%.
1: The uneven area of the highlight printing portion is 50% or more.
The practical level is 3 to 5.

The above results show that the objective of the present application can be achieved by using the solvent-based flexographic ink for lamination of the present invention. In addition, when a urethane resin containing structural units derived from polyether polyol and/or aliphatic diol and having a urethane bond concentration of 2.6 to 5.0 (mmol/g) was used, superior results were obtained in terms of extrusion lamination strength, blocking resistance, and plate entanglement.

Claims (8)

A solvent-based flexographic ink for lamination containing a binder resin and a solvent,
the binder resin includes a urethane resin and at least one resin selected from the group consisting of a cellulose-based resin, a polyvinyl acetal resin, and a rosin resin;
the urethane resin contains a structural unit derived from a polyether polyol and/or a structural unit derived from an aliphatic diol, and has a urethane bond concentration of 2.6 or more and 5.0 or less (mmol/g);
the solvent includes an ester-based organic solvent and an alcohol-based organic solvent,
A solvent-based flexographic ink for lamination , wherein a mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is 60:40 to 5:95. 2. The solvent-based flexographic ink according to claim 1, wherein the content of the urethane resin is 66.6% by mass or more based on 100% by mass of the binder resin. A solvent-based flexographic ink for lamination containing a urethane resin and a solvent,
the urethane resin contains a structural unit derived from a polyether polyol and/or a structural unit derived from an aliphatic diol, has a urethane bond concentration of 2.6 or more and 5.0 or less (mmol/g) and a urea bond concentration of 0.3 or less (mmol/g);
the solvent includes an ester-based organic solvent and an alcohol-based organic solvent,
A solvent-based flexographic ink for lamination , wherein a mass ratio of the ester-based organic solvent to the alcohol-based organic solvent is 60:40 to 5:95. The solvent-based flexographic ink for lamination according to any one of claims 1 to 3, wherein the urethane resin contains a structural unit derived from a polyether polyol and a structural unit derived from an aliphatic diol, and the mass ratio of the structural unit derived from the polyether polyol to the structural unit derived from the aliphatic diol is 5:95 to 95:5. The solvent-based flexographic ink for lamination according to any one of claims 1 to 4 , wherein the aliphatic diol has a branched structure. The solvent-based flexographic ink for lamination according to any one of claims 1 to 5 , further comprising a chelating crosslinking agent and/or a plasticizer. A printed matter having a printed layer made of a solvent-based flexographic ink for lamination according to any one of claims 1 to 6 on a substrate 1. A laminate having an adhesive layer and a substrate 2, in that order, on the printed layer of the printed matter described in claim 7.