JP7472552B2 - Overcoat and print materials - Google Patents

Description

The present invention relates to an overcoat agent and a printed matter using the same.

In flexible packaging and other packaging that uses film substrates such as polyester film, nylon film, and polyolefin film, printing ink is printed to add design, beauty, or product information. Printing on film substrates can be broadly divided into front printing, where printing is done directly on the surface of the film, and back printing, where ink is printed on the back side of the film. When packaging is done with front printing, the printed layer is placed on the outermost side and can be directly observed with the naked eye. On the other hand, when packaging is done with back printing, the outermost side is the film substrate, and the printed layer is sandwiched between the substrate and a thermoplastic substrate called a sealant (called a laminate). Therefore, unlike front printing, packaging with back printing has the difference that the printed layer can be seen through the film substrate.

Since a surface-printed printed composition forms a printing ink layer on the outermost surface, it often has a poorer gloss and is also inferior in abrasion resistance and heat resistance compared to the above-mentioned film substrate (Patent Document 1). On the other hand, a reverse-printed printed composition (laminate laminate) is characterized in that the physical properties of the film substrate itself are effectively utilized in the outermost layer of the package, making it easier to obtain high gloss and abrasion resistance compared to a surface-printed printed composition in which the outermost layer of the package is a printing layer. However, this method requires printing ink onto the substrate and then attaching another film onto the printing layer, which is a time-consuming process, and in addition, the physical properties due to the process, such as adhesion between the film substrate and the printing layer and delamination (floating), are often insufficient, and there are also cost issues due to the need for adhesives and lamination processes.

Therefore, in order to impart high gloss and heat resistance to surface-printed structures or packages, a method of forming a protective layer on the surface of the surface-printed layer using an overcoat agent has been investigated. This method is expected to impart gloss and scratch resistance to the same degree as laminates without the need for complicated manufacturing processes as with laminates.
However, as conventional overcoating agents, a urethane resin-based coating agent (Patent Document 2), an acrylic resin-based coating agent (Patent Document 3), an amide resin-based coating agent (Patent Document 4), a polylactic acid-based overcoating agent (Patent Document 5), and the like have been proposed, but all of them have room for improvement in terms of gloss, heat resistance, and even odor, compared to laminated bodies.

JP 2019-119824 A JP 2018-145283 A Patent No. 5828196 JP 2016-079306 A JP 2003-147265 A

The present invention aims to provide an overcoat agent that can achieve high gloss equivalent to or greater than that of the film surface of a laminate, in addition to various physical properties such as adhesion, heat resistance, and odor, even in surface-printed compositions.

As a result of extensive research into the problem, the inventors discovered that the problem could be solved by using the overcoat agent described below, which led to the creation of the present invention.

That is, the present invention provides an overcoat agent for forming a transparent protective layer disposed on a print layer, the overcoat agent containing a binder resin and an isocyanate curing agent,
the binder resin contains a polyester-based resin in an amount of 30% by mass or more of the entire binder resin, and the polyester-based resin contains structural units derived from a dibasic acid and a polyhydric alcohol in an amount of 50% by mass or more of the entire polyester-based resin,
The present invention relates to an overcoat agent, wherein either or both of the binder resin and the isocyanate curing agent have at least one cyclic structure selected from an aromatic group, an alicyclic group and a pyranose group.

The present invention also relates to the above overcoat agent, in which the content of the cyclic structure is 7 to 50 mass% of the total mass of the solid content of the overcoat agent.

The present invention also relates to the above overcoat agent, in which the ester bond concentration of the polyester resin is 0.5 mmol/g to 12.0 mmol/g.

The present invention also relates to the above overcoat agent, in which the isocyanate curing agent contains an adduct type isocyanate compound and/or a biuret type isocyanate compound.

The present invention also relates to the above overcoat agent, in which the binder resin further contains a cellulose-based resin, and the mass ratio of the polyester-based resin to the cellulose-based resin is 90:10 to 30:70.

The present invention also relates to the above overcoat agent, in which the content of the cyclic structure is 15 to 40 mass% of the total mass of the solid content of the overcoat agent.

The present invention also relates to a printed matter having, in order, a substrate, a printed layer, and a transparent protective layer formed from the above-mentioned overcoat agent.

The present invention makes it possible to provide an overcoat agent that can exhibit high gloss equal to or greater than that of the film surface of a laminate, in addition to various physical properties such as adhesion, heat resistance, and odor.
In addition, it is now possible to produce printed matter with performance equal to or better than that of laminated laminates, even in surface printing configurations, which was previously difficult, and this can contribute to simplifying lamination and other manufacturing processes, reducing costs, and reducing _CO2 emissions by reducing the amount of plastic base material used.

The following describes in detail an embodiment of the present invention. However, the following description of the embodiment or requirements is merely an example of how the present invention can be implemented, and the present invention is not limited to these details as long as it does not exceed the gist of the invention.

The present invention relates to an overcoat agent for forming a transparent protective layer disposed on a printed layer. The transparent protective layer preferably has a surface gloss value (60°) of 80 to 135.
The overcoat agent includes a binder resin containing a polyester resin and an isocyanate curing agent. The polyester resin in the overcoat agent imparts flexibility and adhesion, and the isocyanate curing agent imparts heat resistance and scratch resistance. In order to improve the gloss value and adhesion, the binder resin and/or the isocyanate curing agent have a cyclic structure, and the cyclic structure includes at least one selected from the group consisting of an aromatic group, an alicyclic group, and a pyranose group. The content of the cyclic structure is preferably 7 to 50% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 40% by mass of the total mass of solids in the overcoat agent. The solid content refers to the total mass of non-volatile components of the overcoat agent.

The gloss value referred to in this invention refers to the value measured according to JIS Z8741, and is the measured value at an incidence angle of 60°. The gloss value can be measured, for example, using a Micro-TRI-glossmeter manufactured by BYK-Gardner, under measurement conditions of an incidence angle of 60° and a receiving angle of 60°.

(Content of Cyclic Structure)
The content of the cyclic structure can be calculated by the following formula.
Content of cyclic structure (%) = Sum of atomic weights of all atoms constituting the cyclic structure in one molecule of raw material / Molecular weight of raw material Here, the raw material refers to compounds constituting an overcoat agent such as a binder resin or an isocyanate-based hardener, and all atoms constituting the cyclic structure in one molecule of raw material means the carbon atoms and hydrogen atoms constituting the cyclic structure itself, such as an aromatic ring or a cyclo ring, and is defined as not including atoms of groups substituted on or adjacent to the cyclic structure, such as a methyl group or a nitro group.
For example, in the case of a xylylene diisocyanate-trimethylolpropane adduct compound (XDI-TMP adduct) which is an isocyanate curing agent, the total molecular weight is 698.7, but there are three cyclic structures which are aromatic groups, and the total molecular weight of these is 228.3, so the content of the cyclic structures is 228.3/698.7=33%.
The content of the cyclic structure in the total mass of the solid content of the overcoat agent is obtained by multiplying the content of the cyclic structure in each molecule by the ratio of the molecule in the solid content of the overcoat agent.

The overcoat agent of the present invention is preferably used for surface printing. In this specification, surface printing refers to the case where, when printing on a paper or plastic substrate, the printing ink and the overcoat agent are printed on the substrate in that order, and the printed pattern can be confirmed from the printed surface. The transparent protective layer made of the overcoat agent becomes the outermost layer in the printed matter of the present invention. Each material constituting the overcoat agent of the present invention will be described below.

<Binder resin>
The binder resin refers to a resin that is the main component contained in the overcoat agent, and the total amount of the binder resin contains polyester resin at 30% by mass or more, and preferably at 50% by mass or more. The binder resin preferably has the above-mentioned cyclic structure, and the cyclic structure is selected from an aromatic group (aromatic cyclic structure), an alicyclic group (alicyclic cyclic structure), and a pyranose group (pyranose cyclic structure). The cyclic structure is preferably contained in an amount of 5 to 60% by mass, and more preferably 20 to 50% by mass, of the total mass of the binder resin.

<Polyester Resin>
The polyester resin is not particularly limited as long as it contains 50% by mass or more of structural units derived from dibasic acid and polyhydric alcohol in the total mass of the polyester resin, and is appropriately produced by a known method. The polyester resin preferably has at least one cyclic structure selected from an aromatic group, an alicyclic group, and a pyranose group, as described above. The cyclic structure is preferably an aromatic group and/or an alicyclic group. The content of the cyclic structure in the polyester resin is preferably 1 to 80% by mass, more preferably 10 to 50% by mass. Examples of the polyester resin include polyester resins obtained by reacting a polyhydric alcohol with a carboxylic acid using a known esterification polymerization reaction, and alkyd resins described below.

The weight average molecular weight of the polyester resin is preferably 500 to 100,000, and more preferably 2,000 to 50,000. This is because it provides good adhesion and blocking resistance, as well as work efficiency and printability in the ink printing process.

Examples of alicyclic alcohols among polyhydric alcohols include 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, spiroglycol, isosorbide, etc. Monofunctional alcohols such as cyclohexanol, cyclohexaneethanol, 4-tert-butylcyclohexanol, menthol, 2-ethyl-4-(2,2,3-trimethyl-3-cyclopentenyl)-2-buten-1-ol, 4-isopropylcyclohexanol, and 2-(tert-butyl)cyclohexanol can also be used in combination.
The polyhydric alcohols can be used alone or in combination of two or more kinds.

Among the polyhydric alcohols, aromatic alcohols include 1,4-benzenedimethanol, 1,3-bis(2-hydroxyethoxy)benzene, 1,2-bis(2-hydroxyethoxy)benzene, 1,4-bis(2-hydroxyethoxy)benzene, hydroquinone, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, etc., which can be used alone or in combination of two or more.

Among the dibasic acids, alicyclic dibasic acids include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,1-cyclopentanediacetic acid, and decahydro-1,4-naphthalenedicarboxylic acid.

Among the dibasic acids, aromatic dibasic acids include phthalic acid, isophthalic acid, terephthalic acid, 1,2-phenylene diacetic acid, 1,3-phenylene diacetic acid, 1,4-phenylene diacetic acid, 4-(carboxymethyl)benzoic acid, etc., which can be used alone or in combination of two or more.

In addition, polyhydric alcohols that do not have a cyclic structure and dibasic acids that do not have a cyclic structure can also be used in the above polyester resins.

Examples of polyhydric alcohols that do not have an alicyclic structure include, but are not limited to, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-butyl-1,3propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 1,2-pentanediol, 3-methyl-1,5-pentanediol, hexanediol, octanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, 1,2,4-butanetriol, sorbitol, and pentaerythritol.

Dibasic acids that do not have a cyclic structure include, but are not limited to, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and phthalic acid. If necessary, monobasic acids such as formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, oleic acid, and linoleic acid may be used in combination.

Furthermore, acid anhydrides may be used, such as succinic anhydride, methyl succinic anhydride, 2,2-dimethyl succinic anhydride, butyl succinic anhydride, isobutyl succinic anhydride, hexyl succinic anhydride, octyl succinic anhydride, dodecenyl succinic anhydride, phenyl succinic anhydride, glutaric anhydride, 3-allyl glutaric anhydride, 2,4-dimethyl glutaric anhydride, 2,4-diethyl glutaric anhydride, butyl glutaric anhydride, and hexyl glutaric anhydride. maleic anhydride, 2-methylmaleic anhydride, 2,3-dimethylmaleic anhydride, butylmaleic anhydride, pentyl maleic anhydride, hexyl maleic anhydride, octyl maleic anhydride, decyl maleic anhydride, dodecyl maleic anhydride, 2,3-dichloromaleic anhydride, phenyl maleic anhydride, 2,3-diphenylmaleic anhydride, itaconic anhydride, citraconic anhydride, phthalic anhydride, 4-methylphthalic anhydride, daclinic anhydride, phthalic ... Examples of the anhydrides include mer acid, 1,2,3,6-tetrahydrophthalic anhydride, 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride, 3-methyl-1,2,3,6-tetrahydrophthalic anhydride, 4-methyl-1,2,3,6-tetrahydrophthalic anhydride, methylbutenyl-1,2,3,6-tetrahydrophthalic anhydride, chlorendic anhydride, head acid anhydride, biphenyl dicarboxylic anhydride, himic anhydride, endomethylene-1,2,3,6-tetrahydrophthalic anhydride, methyl-3,6-endomethylene-1,2,3,6-tetrahydrophthalic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, methylcyclohexene dicarboxylic anhydride, trimellitic anhydride, 1,8-naphthalenedicarboxylic anhydride, and octahydro-1,3-dioxo-4,5-isobenzofuran dicarboxylic anhydride.

(Alkyd resin)
Examples of alkyd resins include alkyd resins synthesized by polycondensation of carboxylic acid compounds, fatty acids (or animal and vegetable oils), and alcohol compounds, and alkyd resins obtained by reacting animal and vegetable oils or their fatty acid monoesters with carboxylic acid compounds, followed by esterification of alcohol compounds. All of these are alkyd resins modified from fats and oils.
The alkyd resin used in the present invention preferably has a hydroxyl value of 5 to 200 mgKOH/g, more preferably 20 to 150 mgKOH/g. The weight average molecular weight of the alkyd resin is preferably 500 to 100,000, more preferably 2,000 to 50,000. The content of cyclic structures in the alkyd resin is preferably 1 to 80% by mass, more preferably 10 to 50% by mass.

The carboxylic acid compound used in the alkyd resin is preferably a polybasic acid such as a dibasic acid, and suitable examples of the dibasic acid include the aromatic carboxylic acids (including anhydrides) and alicyclic carboxylic acids (including anhydrides). Among these, aromatic carboxylic acids (including anhydrides) are preferred, and suitable examples of such compounds include phthalic anhydride, phthalic acid, isophthalic acid, and terephthalic acid.

The alcohol compounds used in the alkyd resin preferably include alicyclic alcohols, aromatic alcohols, and alcohols not having a cyclic structure, and the same as those mentioned above can be preferably used. Among them, it is preferable to use an alcohol not having a cyclic structure, and as the alcohol, preferably, as a dihydric alcohol compound, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, 1,2-hexanediol, 1,5-hexanediol, 2,5-hexanediol, cyclohexanedimethanol, nepentyl glycol, etc. can be mentioned.
Examples of trihydric or higher alcohol compounds include aliphatic polyhydric alcohols such as (mono-, di-, or tri)glycerin, (mono-, di-, or tri)trimethylolethane, (mono-, di-, or tri)trimethylolpropane, (mono-, di-, or tri)trimethylolalkane, (mono-, di-, or tri)pentaerythritol, and sorbitol.

The above-mentioned animal and vegetable oils include hemp seed oil, linseed oil, perilla oil, oiticica oil, olive oil, cacao oil, kapok oil, kaya oil, mustard oil, apricot kernel oil, tung oil, kukui oil, walnut oil, poppy seed oil, sesame oil, safflower oil, radish seed oil, soybean oil, safflower oil, camellia oil, corn oil, rapeseed oil, niger oil, rice bran oil, palm oil, castor oil, sunflower oil, grape seed oil, almond oil, pine seed oil, cottonseed oil, coconut oil, peanut oil, and dehydrated castor oil.

The fatty acid may be a mixed fatty acid, and preferred examples of the fatty acid include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, linolenic acid, palmitic acid, and stearic acid.

The fatty acid monoester may be an alkyl ester formed from the fatty acid and an alcohol, and preferred examples of the alcohol include alkanols such as methanol, ethanol, propanol, isopropanol, butanol, and isobutanol.

(Ester bond concentration)
In an embodiment of the present invention, the polyester resin preferably has an ester bond concentration of 0.5 mmol/g to 12.0 mmol/g, and more preferably 4.0 mmol/g to 10.5 mmol/g, because this provides good adhesion, blocking resistance, solubility in organic solvents, and the like.
The ester bond concentration here is a value calculated by the following formula (1).
Equation (1) Ester bond concentration (mmol/g)=total number of moles of ester bonds in polyester resin (mmol)/total mass of solid content in polyester resin (g)
As described above, the ester bond concentration represents the number of moles of ester bonds relative to the total amount of polyester resin. For example, in the case of polyethylene terephthalate, a repeating unit formed by polycondensation of terephthalic acid and ethylene glycol has a repeating unit molecular weight of 192 (166 + 62 - 2 × 18 = 192) obtained by subtracting dehydration from the molecular weight of terephthalic acid (166) and the molecular weight of ethylene glycol (62), and contains 2 mol of ester bonds, so the ester bond density is calculated as 2/192 = 0.0104 mol/g = 10.4 mmol/g.

<Cellulosic resin>
In the overcoat agent of the present invention, it is preferable to use a cellulose-based resin in combination in order to improve gloss and heat resistance. Specifically, nitrocellulose, cellulose acetate propionate, cellulose acetate butyrate, hydroxyalkylcellulose, carboxyalkylcellulose, etc. are mentioned, and the alkyl group may be, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a pentyl group, a hexyl group, etc., and the alkyl group may further have a substituent. Among them, cellulose acetate propionate, cellulose acetate butyrate, and nitrocellulose are preferable. The molecular weight is preferably 5,000 to 300,000 in weight average molecular weight, more preferably 10,000 to 200,000, and even more preferably 10,000 to 100,000. In addition, it is preferable that the glass transition temperature is 100°C to 160°C.

(Nitrocellulose)
Nitrocellulose is preferably obtained by reacting natural cellulose with nitric acid to replace three hydroxyl groups in the six-membered ring of the anhydrous glucopyranose group in the natural cellulose with nitric acid groups to obtain a nitric acid ester, and the weight-average molecular weight is preferably in the same range as above. In addition, the average degree of polymerization is preferably in the range of 35 to 480, more preferably 50 to 200. When the average degree of polymerization is 50 or more, the strength of the ink film is improved, and the abrasion resistance and kneading resistance are improved, which is preferable. In addition, when the average degree of polymerization is 200 or less, the solubility in the solvent, the low-temperature stability of the ink, and the compatibility with the co-used resin are improved, which is preferable. In addition, the nitrogen content is preferably 10.5 to 12.5% by mass.

In one embodiment, the binder resin preferably contains the polyester resin and the cellulose resin. In this case, the ratio of the polyester resin to the cellulose resin is preferably 90:10 to 30:70 by mass, and more preferably 70:30 to 40:60 by mass. The polyester resin preferably contains an alkyd resin. The cellulose resin preferably contains nitrocellulose. The binder resin preferably contains 70% by mass or more of the polyester resin and the cellulose resin, and more preferably 80% by mass or more.

<Concomitant Resin>
In the embodiment of the present invention, the binder resin is also suitable for use in combination with other resins in addition to the above polyester resins and cellulose resins, and examples thereof include, but are not limited to, polyurethane resins, polyamide resins, vinyl chloride resins such as vinyl chloride-vinyl acetate copolymer resins and vinyl chloride-acrylic copolymer resins, rosin resins, ethylene-vinyl acetate copolymer resins, vinyl acetate resins, acrylic resins, styrene resins, dammar resins, styrene-maleic acid copolymer resins, styrene-acrylic copolymer resins, terpene resins, phenol-modified terpene resins, ketone resins, cyclized rubbers, chlorinated rubbers, butyral, polyacetal resins, petroleum resins, and modified resins thereof. These resins may be used alone or in combination of two or more.

<Isocyanate hardener>
In the overcoat agent of the present invention, an isocyanate curing agent is used to improve heat resistance. In order to improve gloss, it is preferable that the isocyanate curing agent has a cyclic structure. Specifically, polyisocyanate compounds and modified isocyanate compounds can be suitably used as the isocyanate curing agent. Specifically, the modified isocyanate compound is preferably a dimeric allophanate type isocyanate compound, a trimer biuret type isocyanate compound, an adduct type isocyanate compound, and an isocyanurate type isocyanate compound. The biuret type isocyanate compound is an isocyanate compound having a structure in which urea is dimerized. In addition, the isocyanurate type isocyanate compound refers to an isocyanate compound that is a cyclic trimer of a polyisocyanate compound. The adduct type isocyanate compound refers to an adduct of a polyisocyanate compound and a polyhydric alcohol, and examples thereof include a reaction product of xylylene diisocyanate and trimethylolpropane.
As the polyisocyanate compound, diisocyanates are preferred, and aromatic diisocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, etc., alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate, isophorone diisocyanate, etc., aliphatic diisocyanates such as hexamethylene diisocyanate, etc., and aromatic aliphatic diisocyanates such as α,α,α',α'-tetramethylxylylene diisocyanate, etc. are preferred.
Specific examples of commercially available modified isocyanate compounds include Duranate 24A-100, 22A-75P, TPA-100, TKA-100, and P301-75E (manufactured by Asahi Kasei Corporation), Takenate D-160N, D-170N, D-110N, and D-101 (manufactured by Mitsui Chemicals), and Desmodur N3200, N3600, Z4470BA, and L75(C) (manufactured by Covestro).
The isocyanate curing agent preferably contains 5 to 50% by mass of a cyclic structure, more preferably 20 to 40% by mass. The cyclic structure preferably has an alicyclic group and/or an aromatic group. The isocyanate curing agent preferably has an isocyanate group (NCO) content as specified in JIS K6806 of 3 to 30% (mass %), more preferably 5 to 25%.

The isocyanate curing agent is preferably blended in an amount of 0.2 to 8 equivalents per equivalent of the crosslinkable functional group (such as a hydroxyl group or an amino group) of the binder resin, and more preferably 0.8 to 3 equivalents. The ratio of the binder resin to the isocyanate curing agent used is preferably 95:5 to 10:90 by mass, and even more preferably 90:10 to 20:80 by mass. Within this range, sufficient crosslink density is obtained, and heat resistance is good.
After applying the overcoat agent, it is preferable to perform aging to enhance reactivity. Here, aging refers to storage at a constant temperature and humidity for several hours to several days. Aging may be performed under conditions for a normal isocyanate curing agent, for example, 1 to 10 days at room temperature or 1 to 3 days at 40°C.

<Additives>
The overcoat agent of the present invention may appropriately contain conventionally known additives. In producing the overcoat agent, additives such as a wetting agent, an adhesion aid, a leveling agent, an antifoaming agent, an antistatic agent, a viscosity modifier, a chelating crosslinking agent, a trapping agent, an antiblocking agent, wax components other than those mentioned above, and a silane coupling agent may be used as necessary.

<Organic Solvent>
The overcoat agent of the present invention preferably contains an organic solvent as a liquid medium (organic solvent-based overcoat agent). Although not limited to the following, the organic solvent used may be a known organic solvent such as an aromatic organic solvent such as toluene or xylene, a ketone-based organic solvent such as methyl ethyl ketone or methyl isobutyl ketone, ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, an ester-based organic solvent, an alcohol-based organic solvent such as methanol, ethanol, n-propanol, isopropanol, or n-butanol, or a glycol ether-based solvent such as ethylene glycol monopropyl ether or propylene glycol monomethyl ether, or may be used in combination. Among them, an organic solvent that does not contain an aromatic organic solvent such as toluene or xylene (non-toluene-based organic solvent) is more preferable. More preferably, an organic solvent consisting of an ester-based organic solvent or an alcohol-based organic solvent is preferable. In this case, the glycol ether-based organic solvent may be contained in an amount of 6% by mass or less in 100% by mass of the overcoat agent. The overcoat agent of the present invention may contain water as a liquid medium, but the content of water is preferably 0.1 to 5% by mass in 100% by mass of the liquid medium. However, it is not limited to these.

(Production of Overcoat Agent)
The overcoat agent is not particularly limited in the manufacture, and may be manufactured by adding a binder resin solution in which a binder resin and an organic solvent are dissolved or dispersed, and a solvent to an agitator equipped with an agitator blade, a rotor, etc., and mixing and stirring the mixture. The agitation speed is not particularly limited, and can be 50 to 300 rpm. In order to improve the handling and application properties of the overcoat agent, a solvent can be appropriately added. The isocyanate curing agent can be added at the beginning, but depending on the storage conditions and the type of isocyanate curing agent, it is preferable to mix it just before use. Since the overcoat agent is used by a printing method, etc., the viscosity is preferably 20 to 200 mPa·s.

(Overcoat application and printing)
The overcoat agent of the present invention can be applied by a known printing method. For example, gravure printing, flexographic printing, microgravure printing, etc. can be mentioned, and gravure printing is preferred. In the gravure printing method, the overcoat agent enters the recesses that become the image areas engraved on the surface of a cylindrical cylinder, and after the overcoat agent of the non-image areas is scraped off with a metal plate called a doctor, the overcoat agent remaining in the recesses of the cylinder is transferred onto the printing film to form a coating layer. The amount of overcoat agent applied can be controlled by the depth of the recesses. The coating on the printing film can be applied multiple times, taking into consideration the film properties such as drying after coating, gloss of the coating film, scratch resistance, and high-temperature hot water resistance. The amount of coating and the number of coatings can be appropriately selected as the form of use of the overcoat agent. The thickness of the transparent protective layer formed by the overcoat agent of the present invention is preferably 0.5 to 10 μm, more preferably 1 to 6 μm.

The drying temperature of the applied overcoat agent is preferably 40 to 80°C. If necessary, the resulting print can be aged at room temperature to 40°C for about 1 to 10 days to become a print with a tough transparent protective layer.

The overcoat agent of the present invention is applied onto the printing layer formed by the printing ink to form a printed matter. The printing ink is preferably a printing ink consisting of a binder resin, a pigment, a solvent, and, if necessary, additives. Although not limited to the following, it is preferable that the printing ink contains, as the binder resin constituting the printing ink, a urethane resin, a polyamide resin, an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, a nitrocellulose resin, a chlorinated polypropylene resin, an ethylene-vinyl acetate copolymer resin, a vinyl acetate resin, a polyester resin, an alkyd resin, a rosin-based resin, a rosin-modified maleic acid resin, a ketone resin, a cyclized rubber, a chlorinated rubber, a butyral, a petroleum resin, or the like. Among them, it is more preferable that the printing ink contains at least one selected from the group consisting of a urethane resin, a polyamide resin, an acrylic resin, a vinyl chloride-vinyl acetate copolymer resin, and a nitrocellulose resin. In particular, a printing ink containing a urethane resin is even more preferable because it has good adhesion to a film substrate.

The above urethane resin can be obtained by known methods, such as those disclosed in JP-A-62-153366, JP-A-62-153367, JP-A-1-236289, JP-A-2-64173, JP-A-2-64174, and JP-A-2-64175. Specifically, the urethane resin is produced by a two-stage method in which a polyol and a diisocyanate compound are reacted in a ratio that results in an excess of isocyanate groups to obtain a prepolymer having terminal isocyanate groups, and the obtained prepolymer is reacted with a chain extender and/or a reaction terminator in a suitable solvent, or a one-stage method in which a polyol, a diisocyanate compound, a chain extender, and/or a reaction terminator are reacted at once in a solvent. Of these methods, the two-stage method is preferred to obtain a uniform urethane resin.

The printing ink may contain additives, such as pigment dispersants, leveling agents, defoamers, leveling agents, waxes, trapping agents, plasticizers, infrared absorbers, ultraviolet absorbers, anti-blocking agents, antistatic agents, and flame retardants.

As pigments, any of the C.I. pigments listed in the Color Index that can be generally used in printing inks and paints can be used. Examples include colored pigments such as titanium oxide, red iron oxide, Prussian blue, ultramarine blue, carbon black, and graphite, and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc. Furthermore, examples of organic pigments include soluble azo pigments, insoluble azo pigments, azo chelate pigments, condensed azo pigments, copper phthalocyanine pigments, and condensed polycyclic pigments. The content of these pigments in the printing ink can be 0.5 to 50% by weight.

The organic solvents used in the printing ink can be the same as those that can be used in the overcoat agent described above, and known alcohol-based organic solvents, ketone-based organic solvents, ester-based organic solvents, aliphatic hydrocarbon-based organic solvents, and alicyclic hydrocarbon-based organic solvents can be used. Taking into consideration the solubility of the urethane resin and the co-resin, the drying property during printing, etc., it is preferable to use them in a mixture.

The printing ink can be produced by a known method of dispersing a pigment using a resin, a solvent, etc. For example, a pigment dispersion is produced by dispersing a pigment in a solvent using a urethane resin, a co-resin, a dispersant, etc., and the resulting pigment dispersion is mixed with resins, additives, etc. as necessary.

(Base material)
The substrate used in the present invention may suitably be a plastic substrate on a film, a paper substrate, etc. Among them, the use of a plastic substrate is preferred, and since a process such as heat sealing is required, a plastic substrate having thermoplastic properties is preferred.
Examples of plastic substrates include polyethylene, polypropylene and other polyolefin substrates, polyethylene terephthalate, polylactic acid and other polyester substrates, polystyrene substrates, polystyrene-based resins such as AS resin and ABS resin, polycarbonate substrates, polyamide substrates, polyvinyl chloride substrates, various substrates such as polyvinylidene chloride, cellophane substrates, paper substrates, aluminum foil substrates, etc., or film- or sheet-shaped 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. 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.

The above-mentioned plastic substrates include (1) plastic substrates made of a single type, and (2) multi-layered plastic substrates made of multiple types of plastic substrates. In the present invention, a multi-layered plastic substrate is preferable from the viewpoints of toughness, moisture resistance, etc. Furthermore, in the present invention, the multi-layered plastic substrate is preferably a multi-layered plastic substrate having heat sealability (thermoplasticity) on the side opposite to the printed side. When a multi-layered plastic substrate is used, it is possible to easily make a bag without post-processing after applying an overcoat agent, which has the advantage of simplifying the packaging manufacturing process.

Examples of the configuration of multilayer plastic substrates include two-layer structures such as PET/CPP, OPP/CPP, and Ny/CPP; three-layer structures such as PET/aluminum/CPP, PET/Ny/CPP, Ny/PET/CPP, and Ny/vapor-deposited PET/CPP; and four-layer structures such as PET/aluminum/Ny/CPP, which are laminated via an anchor coating agent and adhesive. Even with such multilayer plastic substrates, it is preferable to subject the printing surface to corona treatment, frame treatment, plasma treatment, etc., as this improves the adhesion of the printing ink layer.

Plastic substrates can be laminated together by known methods, such as the extrusion lamination method, which uses an anchor coating agent such as an imine, polybutadiene, or titanium-based agent and laminates molten polyethylene resin, or the dry lamination method, which applies an adhesive such as a urethane adhesive and laminates the substrate. Multilayer plastic substrates obtained by the dry lamination method are particularly preferred for applications that require resistance to high-temperature hot water.

The printed matter of the present invention is formed by printing a printing ink layer and an overcoat agent in that order on a plastic substrate. As mentioned above, it is preferable to use a heat-sealable multilayer film as the plastic substrate in terms of ease of post-processing.

The packaging obtained in this way can be widely used as packaging material for foods, medicines, etc. In addition, because the front-printed structure exhibits excellent resistance to high-temperature hot water, it can also be used in applications that require high resistance with the conventional reverse-printed structure.

The present invention will be described in detail below with reference to examples, but 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 3, 6, 8, 10, and 12 are reference examples.

(Molecular Weight and Molecular Weight Distribution)
The weight average molecular weight (Mw), number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) were measured by gel permeation chromatography (GPC) and calculated as molecular weights using polystyrene as a standard substance. The measurement conditions are shown below.
GPC device: Showa Denko Shodex GPC-104
Columns: The following columns were used in series connection:
Showa Denko Shodex LF-404 x 2 Showa Denko Shodex LF-G x 2
Detector: RI (differential refractometer)
Measurement conditions: column temperature 40°C
Eluent: tetrahydrofuran Flow rate: 0.3 mL/min

(Hydroxyl value)
In the following, the hydroxyl value was measured according to the method described in JIS K0070 (1992).

(Glass-transition temperature)
The glass transition temperature (Tg) was measured using a DSC-TA60 (differential scanning calorimeter) manufactured by Shimadzu Corporation. Approximately 2 mg of a sample obtained by drying the binder resin composition was weighed on an aluminum pan, and the aluminum pan was set in a DSC measurement holder. The endothermic peak of the chart obtained under the temperature increase condition of 5°C/min was read. The peak temperature at this time was taken as the glass transition temperature.

<Synthesis of polyurethane resin for printing ink>
[Synthesis Example 1] (Preparation of urethane resin PU1 solution)
150 parts of polyester polyol (PMPA) having a number average molecular weight of 1,000 obtained by reacting adipic acid with 3-methyl-1,5-pentanediol, 50 parts of polypropylene glycol (PPG700) having a number average molecular weight of 700, 103.4 parts of isophorone diisocyanate (IPDI), and 75.8 parts of ethyl acetate (EA) were reacted at 80° C. for 4 hours under a nitrogen stream to obtain a resin solution of a terminal isocyanate urethane prepolymer. Next, the above-mentioned resin solution of isocyanate-terminated urethane prepolymer was gradually added at 40° C. to a mixture of 44.6 parts of isophorone diamine (IPDA) and 736.2 parts of a mixed solvent of EA/isopropanol (IPA) = 50/50 (mass ratio), and then reacted at 80° C. for 1 hour to obtain a polyurethane resin solution PU1 having a solids content of 30%, an amine value of 9.5 mg KOH/g, a hydroxyl value of 0 mg KOH/g and a weight average molecular weight of 50,000.

[Synthesis Example 2] (Preparation of urethane resin PU2 solution)
200 parts of PPG700, 127 parts of IPDI, and 81.8 parts of EA were reacted under a nitrogen stream at 80°C for 4 hours to obtain a resin solution of a terminal isocyanate urethane prepolymer. Next, 49.5 parts of IPDA, 3 parts of 2-ethanolamine, and 803.9 parts of a mixed solvent of EA/IPA=50/50 (mass ratio) were mixed, to which the obtained resin solution of the terminal isocyanate urethane prepolymer was gradually added at 40°C, and then reacted at 80°C for 1 hour to obtain a polyurethane resin solution PU2 with a solid content of 30%, an amine value of 3.5 mgKOH/g, a hydroxyl value of 7.3 mgKOH/g, and a weight average molecular weight of 40,000.

<Synthesis of polyester resin for overcoat agent>
[Synthesis Example 3] (Preparation of Polyester Resin B Solution)
312.5 parts of terephthalic acid, 312.5 parts of isophthalic acid, 140.1 parts of ethylene glycol, and 234.9 parts of neopentyl glycol were charged into a reactor, and the mixture was gradually heated to 160-240°C while stirring under a nitrogen stream to carry out an esterification reaction. The reaction was carried out at 240°C for 1 hour or more, and when the acid value became 15 or less, the reactor was gradually depressurized to 1-2 Torr. When the predetermined viscosity was reached, the reaction was stopped and the resin was taken out. The weight average molecular weight of the obtained polyester resin B was 7,000 as measured by GPC, and the glass transition temperature was 53°C as measured by DSC. The hydroxyl value was 37.4 mgKOH/g, and the acid value was 0.2 mgKOH/g. The polyester resin B contains 100% by mass of the structural units derived from dibasic acid and polyhydric alcohol.

[Synthesis Example 4] (Preparation of Polyester Resin C Solution)
289.8 parts of terephthalic acid, 260.8 parts of isophthalic acid, 35.3 parts of sebacic acid, 90.9 parts of ethylene glycol, 209.1 parts of neopentyl glycol, and 114.1 parts of butyl ethyl propanediol were charged into a reactor, and the mixture was gradually heated to 160-240°C while stirring under a nitrogen stream to carry out an esterification reaction. The reaction was carried out at 240°C for 1 hour or more, and when the acid value became 15 or less, the reactor was gradually depressurized to 1-2 Torr. When the predetermined viscosity was reached, the reaction was stopped and the resin was taken out. The weight average molecular weight of the obtained polyester resin C was 26,000 as measured by GPC, and the glass transition temperature was 48°C as measured by DSC. The hydroxyl value was 10.2 mgKOH/g, and the acid value was 0.2 mgKOH/g. The polyester resin C contains 100% by mass of the constitutional units derived from dibasic acid and polyhydric alcohol.

[Synthesis Example 5] (Preparation of Polyester Resin D Solution)
286.2 parts of terephthalic acid, 200.3 parts of isophthalic acid, 104.5 parts of sebacic acid, 89.8 parts of ethylene glycol, 206.5 parts of neopentyl glycol, and 112.7 parts of butyl ethyl propanediol were charged into a reactor, and the mixture was gradually heated to 160-240°C while stirring under a nitrogen stream to carry out an esterification reaction. The reaction was carried out at 240°C for 1 hour or more, and when the acid value became 15 or less, the reactor was gradually depressurized to 1-2 Torr. When the predetermined viscosity was reached, the reaction was stopped and the resin was taken out. The weight average molecular weight of the obtained polyester resin D was 23,000 as measured by GPC, and the glass transition temperature was 30°C as measured by DSC. The hydroxyl value was 10.2 mgKOH/g, and the acid value was 0.2 mgKOH/g. The polyester resin D contains 100% by mass of the structural units derived from dibasic acid and polyhydric alcohol.

Comparative Synthesis Example 1 (Preparation of Acrylic Resin Solution)
In a reactor equipped with a reflux condenser, a dropping funnel, a gas inlet tube, a stirrer, and a thermometer, 40 parts of butyl methacrylate, 10 parts of methacrylic acid, 50 parts of 2-hydroxyethyl methacrylate, 40 parts of ethyl acetate (EA), and 40 parts of isopropyl alcohol (IPA) were charged while introducing nitrogen gas, and the temperature was raised to 90° C., and 1 part of azobisisobutyronitrile (AIBN) and 15 parts of EA were added and a polymerization reaction was carried out for 4 hours, and further 0.1 part of AIBN and 3 parts of EA were added and reacted for 2 hours to obtain an acrylic resin solution.
IPA was added to the resulting acrylic resin solution to adjust the solid content, yielding an acrylic resin solution with a solid content concentration of 30%, a weight average molecular weight of 30,000, an acid value of 65 mgKOH/g, and a hydroxyl value of 216 mgKOH/g.

Comparative Synthesis Example 2 (Preparation of Polyester Resin F Solution)
100 parts of DL-lactide, 100 parts of L-lactide, 0.2 parts of sodium isethionate, and 0.5 parts of tin octoate as a ring-opening polymerization catalyst were charged into a four-neck flask and heated at 180° C. for 2 hours under a nitrogen atmosphere to cause ring-opening polymerization, thereby obtaining Polyester Resin F having a solid content of 100%, a hydroxyl value of 2.5 mg KOH/g, and a weight average molecular weight of 59,000. Polyester Resin F does not contain any constituent units derived from a dibasic acid and a polyhydric alcohol.

<Production of printing ink>
[Production Example 1] (Production of printing ink R1)
As the binder resin, 32 parts of urethane resin solution PU1 (solid content 30%), 3 parts of vinyl chloride-vinyl acetate copolymer resin (manufactured by Nissin Chemical Industry Co., Ltd., Solvine TAO, solid content 30%, EA solution), 1.0 part of chlorinated polypropylene resin (manufactured by Nippon Paper Industries Co., Ltd., 370M, chlorine content 30%, solid content 50%), 2 parts of polyethylene wax (manufactured by Mitsui Chemicals, Inc., Hiwax 320P, average particle size 2.5 μm, solid content 40% dispersion), 10 parts of indigo pigment (C.I. Pigment Blue 15:4), and 52 parts of a solution of methyl ethyl ketone (MEK) / n-propyl acetate (NPAC) / IPA = 40/40/20 (mass ratio) were mixed and dispersed for 15 minutes with an Eiger mill to obtain gravure ink R1.

[Production Examples 2 to 4] (Production of Printing Inks R2 to R4)
Printing inks R2 to R4 were obtained in the same manner as in Production Example 1, except that the raw materials and blending ratios shown in Table 1 were used.

The abbreviations and details of the raw materials in Table 1 are shown below.
Rosin maleic acid resin: rosin modified maleic acid resin. Arakawa Chemical Industries, Ltd., Malkid No. 5, solid content 30%, EA solution, softening point 145°C, hydroxyl value 0 mgKOH/g
Amide resin: a polyamide resin containing 50% by mass or more of structural units derived from dimer acid made from oleic acid and linoleic acid as raw materials, and having an amine value of 3.5 mgKOH/g. Weight average molecular weight: 6,000, solid content: 30%, IPA solution.
Cellulose resin: Nitrocellulose. Solid content 30%, EA/IPA solution, nitrogen content 11.5-12.2%, polymerization degree 35-45, hydroxyl value 175 mg KOH/g
Titanium oxide: Titanix JR-808, manufactured by Teika Corporation

<Preparation of Overcoat Agent>
[Example 1] (Preparation of overcoat agent S1)
Polyester resin A solution (polyester A) (castor oil, trimethylolpropane, phthalic anhydride as constituents, oil-modified alkyd resin with weight average molecular weight of 3300 and hydroxyl value of 109 mgKOH/g, aromatic group content of 11% by mass, solid content of 73%, EA solution) 7.8 parts, cellulose resin solution (cellulose resin) (solid content 30%, EA/IPA solution) 28.6 parts, XDI-TMP adduct (trimethylolpropane adduct of xylylene diisocyanate, Mitsui Chemicals, Takenate D-110N, solid content 33%) 20.8 parts, TEGO450 (EVONIC, TEGO Glide 450, polyether siloxane copolymer) 0.1 parts, EA 42.7 parts were mixed and stirred for 30 minutes with a disper to obtain an overcoat agent S1 with a solid content of 30%. The polyester resin A contains 77% by mass of structural units derived from a dibasic acid and a polyhydric alcohol based on the entire polyester resin A.

[Examples 2 to 22, Comparative Examples 1 to 7] (Preparation of overcoat agents S2 to S22, SS1 to SS7)
Overcoat agents S2 to S22 and SS1 to SS7 were obtained in the same manner as in Example 1, except that the raw materials and compounding ratios shown in Tables 2 and 3 were used.

The abbreviations and details of the raw materials in Tables 2 and 3 are shown below.
Polyester E: P-5010 manufactured by Kuraray Polyol Co., Ltd., a polyester resin which is a copolymer of 3-methyl-1,5-pentanediol and adipic acid, number average molecular weight 5,000, hydroxyl value 23 mgKOH/g
(Polyester resin E contains 100% by mass of structural units derived from a dibasic acid and a polyhydric alcohol based on the entirety of polyester resin E.)
XDI (xylylene diisocyanate)-TMP (trimethylolpropane) adduct: Takenate D-110N, manufactured by Mitsui Chemicals, Inc., solid content 33%, NCO content 12%
TDI (toluene diisocyanate)-TMP adduct: Desmodur L75 (C), manufactured by Sumika Bayer Urethane Co., Ltd., solid content 75%, NCO content 13%
HDI (hexamethylene diisocyanate)-TMP adduct: Asahi Kasei Chemicals Corporation, Duranate P301-75E, solid content 75%, NCO content 13%
HDI-biuret, manufactured by Asahi Kasei Chemicals Corporation, Duranate 24A-100, solids content 100%, NCO content 23.5%
IPDI: isophorone diisocyanate

The ester bond concentrations of the polyester resins synthesized and used above were as follows.
Polyester resin A: ester bond concentration 5.6 mmol/g
Polyester resin B: ester bond concentration 9.4 mmol/g
Polyester resin C: ester bond concentration 8.7 mmol/g
Polyester resin D: ester bond concentration 8.5 mmol/g
Polyester resin E: ester bond concentration 8.8 mmol/g
Polyester resin F: ester bond concentration 13.9 mmol/g

<Creation of printed matter using printing ink R2 and overcoat agent S1>
Each of the printing ink R2 and the overcoat agent S1 was diluted with a mixed solvent of EA/IPA (mass ratio 70/30) to a viscosity of 15 seconds at 25° C. in a Zahn cup #3 (manufactured by Rigo Co., Ltd.).
The diluted printing ink R2 was applied to a 30 μm thick polypropylene (OPP) film using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 50° C. to obtain a printed film.
Next, the diluted overcoat agent S1 was applied to the printing surface of the printed film prepared above using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 50° C., thereby obtaining a printed matter having a configuration of plastic substrate/printed layer/transparent protective layer.

<Preparation of printed matter using each printing ink and overcoat agent>
For each of the printing inks and overcoat agents obtained in the above manufacturing examples, examples, or comparative examples, printed materials having the same print configuration were produced in the same manner as in the production of the above printed materials, except that the printing inks and overcoat agents shown in Tables 2 and 3 were used.

<Characteristics evaluation>
The overcoat agents obtained in the above Examples and Comparative Examples and their printed matter were subjected to the following evaluations. The evaluation results are shown in Tables 2 and 3.

<Gloss>
The gloss values of the printed matter produced in the above Examples and Comparative Examples were measured from the transparent protective layer side using a Micro-TRI-glossmeter manufactured by BYK-Gardner at an incident angle of 60° and a receiving angle of 60°. The evaluation criteria are shown below.
A (excellent): Gloss value is 90 or more.
B (Acceptable): Gloss value is 80 or more and less than 90.
C (unacceptable): Gloss value is less than 80.
A and B are within the range where there is no practical problem.

<Adhesion (tape adhesion resistance)>
For the printed matter produced in the above Examples and Comparative Examples, cellophane tape (12 mm wide) manufactured by Nichiban Co., Ltd. was applied to the transparent protective layer, and the degree of peeling of the printed layer or the transparent protective layer was evaluated when the tape was rapidly peeled off. The evaluation criteria are shown below.
A (Excellent): The printed layer or transparent protective layer does not peel off at all.
B (Fair): Less than 50% of the printed layer or transparent protective layer peels off.
C (unacceptable): 50% or more of the printed layer or transparent protective layer is peeled off.
A and B are within the range where there is no practical problem.

<Heat resistance>
The printed matter produced in the above examples and comparative examples was cut into pieces of 3 cm x 13 cm, and the glossy side of an aluminum foil (thickness 30 μm) cut to the same size was placed on the printed side of the printed matter. The aluminum foil was pressed with a pressure of 2 x 9.8 N/ ^cm2 at 120°C for 1 second using a Sentinel heat sealer, and the peeling of the printed layer or transparent protective layer when the aluminum foil was peeled off was visually judged. The evaluation criteria are shown below.
A (Excellent): No peeling at all at a seal bar temperature of 160°C.
B (Acceptable): Does not peel off at a seal bar temperature of 120°C, but peels off at 160°C.
C (unacceptable): Peeled off at a seal bar temperature of 120°C.
A and B are within the range where there is no practical problem.

<Odor>
[Volatile matter and odor test]
Immediately after printing, the prints obtained in the above Examples and Comparative Examples were cut into pieces measuring 12 cm wide x 22 cm long, sealed in a bottle, placed in an oven and kept at 60° C. for 12 hours.
The components in the bottle were analyzed by gas chromatography/mass spectrometry (GC/MS) in the same manner as above. The GC/MS device and column were as follows:
Apparatus: HP-GC6890N/MSD5973 (Agilent Technologies)/TDS (GERSTEL) Column: HP-5 (inner diameter 0.32 mm/length 60 m/film thickness 1.00 μm) (Agilent Technologies)
(Evaluation criteria)
A: No peaks due to organic matter were observed, and the printed matter was odorless.
B: A peak due to organic matter was observed, and the printed matter had a slight odor.
C: A peak due to organic matter was observed, and the printed matter had a strong odor.
The practical levels are A and B.

Reference Example 1: Evaluation of only surface-printed prints of printing ink
Each of the printing inks R3 was diluted with a mixed solvent of EA/IPA (mass ratio 70/30) so that the ink would have a viscosity of 15 seconds at 25° C. in a Zahn cup #3 (manufactured by Rigo Co., Ltd.).
The diluted printing ink R3 was applied to a 30 μm thick OPP film using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 50° C., to obtain a printed matter A1 with a surface print configuration.
The print A1 having a surface printing configuration was evaluated in the same manner as above, and the results were gloss: C, adhesion: A, heat resistance: C, and odor: A.

Reference Example 2: Evaluation of Laminated Body
Each of the printing inks R2 was diluted with a mixed solvent of EA/IPA (mass ratio 70/30) so that the ink would have a viscosity of 15 seconds at 25° C. in a Zahn cup #3 (manufactured by Rigo Co., Ltd.).
The diluted printing ink R2 was applied to a 30 μm thick OPP film using a gravure printing machine equipped with a gravure plate with a plate depth of 35 μm at a printing speed of 40 m/min and a dryer temperature of 50° C., to obtain a printed matter A2.
Next, using a dry laminator, a dry laminating adhesive (TM-340V/CAT-29B manufactured by Toyo-Morton) was applied onto the printed layer of printed matter A2, and then laminated with VMCPP (aluminum-vapor-deposited unoriented polypropylene film, thickness 25 μm) at a line speed of 40 m/min, to obtain a laminated body B1 laminated in the order of OPP substrate/printed layer/adhesive layer/VMCPP substrate.
The laminate B1 was evaluated in the same manner as above, and the results were gloss: B, adhesion: A, heat resistance: A, and odor: A. The gloss was evaluated from the OPP substrate side.

The above evaluation results show that by using the overcoat agent of the present invention, in the examples, it is possible to obtain printed matter with improved gloss of the transparent protective layer, better adhesion and heat resistance, and less odor, even without going through a lamination process, compared to conventional laminated laminates.
On the other hand, Comparative Example 1 did not contain an isocyanate curing agent, and was inferior in adhesion and heat resistance. Comparative Example 2 contained less than 30% by mass of polyester resin in the entire binder resin, and was inferior in gloss and heat resistance. Comparative Example 3 did not contain a ring structure, and was inferior in gloss. Comparative Example 4 did not contain 50% by mass or more of the constitutional unit derived from dibasic acid and polyhydric alcohol in the entire polyester resin, and the coating film was brittle, and was inferior in gloss, adhesion, and heat resistance. Comparative Example 5 did not contain polyester resin, and was inferior in heat resistance. Comparative Example 6 was an acrylic resin binder, and did not contain polyester resin, and was inferior in heat resistance, adhesion, and odor. Comparative Example 7 did not contain polyester resin, and was inferior in gloss and heat resistance.

Claims (5)

An overcoat agent for forming a transparent protective layer disposed on a print layer, the overcoat agent containing a binder resin and an isocyanate curing agent,
the binder resin contains a polyester-based resin in an amount of 30% by mass or more of the entire binder resin, and the polyester-based resin contains structural units derived from a dibasic acid and a polyhydric alcohol in an amount of 50% by mass or more of the entire polyester-based resin,
the binder resin further contains a cellulose-based resin, and a mass ratio of the polyester-based resin to the cellulose-based resin is 90:10 to 30:70;
the binder resin has at least one cyclic structure selected from an aromatic group, an alicyclic group, and a pyranose group,
The overcoat agent , wherein the content of the cyclic structure in the binder resin and the isocyanate curing agent is 7 to 50 mass % of the total mass of the solid contents in the overcoat agent . 2. The overcoat agent according to claim 1 , wherein the content of the cyclic structure is 15 to 40% by mass based on the total mass of the solid content of the overcoat agent. 3. The overcoat agent according to claim 1 , wherein the polyester resin has an ester bond concentration of 0.5 mmol/g to 12.0 mmol/g. 4. The overcoat agent according to claim 1 , wherein the isocyanate curing agent contains an adduct type isocyanate compound and/or a biuret type isocyanate compound. A printed matter having, in order, a substrate, a printed layer, and a transparent protective layer formed by the overcoat agent according to any one of claims 1 to 4 .