Gravure Ink

Abstract

The present invention aims to provide a method for manufacturing printed materials that has special effects in terms of blocking resistance, storage stability, plate cover resistance, and lamination suitability. [Solution] The above problem is solved by a gravure ink having a binder resin, silica, and an organic solvent, wherein the silica is surface-coated with polyethylene wax and / or paraffin wax, or by a gravure ink in which the silica content in the total mass of the gravure ink is 0.1 to 5% by mass.

Description

Technical Field

[0001] The present invention relates to gravure ink. It also relates to a printed matter having a printing layer and a laminate.

Background Art

[0002] In conventional gravure inks, various additives are used to improve the adhesion to substrates such as the friction resistance and blocking resistance of printed matters, gloss, etc. Among them, silica is known to contribute not only to the appearance but also to the improvement of printing suitability and printing effect by improving the slipperiness and trapping property of the ink, and to the improvement of the blocking resistance of printed matters. However, it has been known that when silica is directly added to the ink, the dispersion stability is low, and the uniformity of the ink and the stability during long-term storage are impaired.

[0003] For example, in Patent Document 1, a gravure ink containing a pigment, a urethane resin, polyvinyl butyral and / or a chlorinated polyolefin resin, silica particles and an organic solvent was invented, achieving good printing suitability and blocking resistance in an environmentally friendly ink. Also, in Patent Document 2, a paint product containing silica as a matting agent was invented, achieving the adjustment of a coating film with little variation in gloss. Furthermore, in Patent Document 3, the development of an adhesive tape excellent in fingerprint resistance and scratch resistance was achieved using silica treated with a silane coupling agent.

[0004] However, those that satisfy all of blocking resistance, storage stability, plate fogging property, and lamination suitability have not yet been invented.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

[0006] The object of the present invention is to provide a gravure ink that has blocking resistance, storage stability, plate cover resistance, and lamination suitability. [Means for solving the problem]

[0007] In other words, the present invention relates to a gravure ink having a binder resin, silica, and an organic solvent, The present invention relates to a gravure ink characterized in that the silica is surface-coated with polyethylene wax and / or paraffin wax.

[0008] In other words, the present invention relates to a gravure ink in which the silica content is 0.1 to 5% by mass relative to 100% by mass of the total mass of the gravure ink.

[0009] In other words, the present invention relates to a gravure ink in which the silica content is 1 to 35% by mass relative to 100% by mass of the binder resin solids.

[0010] In other words, the present invention relates to a gravure ink in which the binder resin comprises a urethane resin containing constituent units derived from a dibasic acid.

[0011] In other words, the present invention relates to a gravure ink in which the binder resin further comprises a vinyl chloride copolymer resin and / or a cellulose-based resin.

[0012] In other words, the present invention relates to a gravure ink in which the ignition loss of silica is 14% by mass or less.

[0013] In other words, the present invention relates to a printed material having a printed layer formed from the gravure ink on a substrate 1.

[0014] In other words, the present invention relates to a laminate having, in sequence, a substrate 1, a printed layer formed from the gravure ink, and a substrate 2. [Effects of the Invention]

[0015] The present invention makes it possible to provide a gravure ink that has blocking resistance, storage stability, plate cover resistance, and lamination suitability. [Modes for carrying out the invention]

[0016] The embodiments of the present invention will be described in detail below, but the description of the constituent elements described below is just one example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist of the invention.

[0017] Hereafter, gravure ink may be abbreviated as simply "ink," but they are synonymous. In this specification, "solids" refers to the total mass of nonvolatile components in the total mass of gravure ink.

[0018] <Gravure Ink> This invention relates to a gravure ink. More particularly, to a gravure ink having a binder resin, silica, and an organic solvent, wherein the silica is surface-coated with polyethylene wax and / or paraffin wax. It is presumed that using the above-mentioned silica in a gravure ink will improve blocking resistance, as well as improve dispersion stability in the ink and thus storage stability. Furthermore, using a good ink with improved dispersion stability and no sedimentation tends to improve plate coverage (streaking). In addition, it is thought that the lamination suitability of printed materials will improve. Due to these features, the gravure ink of the present invention is expected to gain high praise in the printing industry. The use of the gravure ink according to the present invention is particularly effective in printing packaging materials, and is expected to exhibit superior performance compared to conventional inks in terms of improved print quality and durability. This will enable the provision of attractive products to consumers and is expected to contribute to improved market competitiveness. Note that this consideration is based solely on speculation and does not limit any inventions in any way.

[0019] Here, "silica surface-coated with polyethylene wax or paraffin wax" refers to silica particles whose surfaces are coated with polyethylene wax or paraffin wax, which tends to improve the dispersibility of the silica particles and maintain the uniformity of the ink.

[0020] <Binder resin> The binder resin refers to the binder resin in the present invention. For example, urethane resins, cellulose-based resins, polyamide resins, vinyl chloride copolymer resins, etc. are preferably cited. It is preferably a thermoplastic resin soluble in an organic solvent. Further, the content of the binder resin in the total mass of the gravure ink is preferably 20 to 80% by mass, more preferably 25 to 75% by mass, and still more preferably 30 to 70% by mass.

[0021] <Urethane resin> The binder resin in the present invention preferably contains a urethane resin. The urethane resin is considered to provide flexibility and durability and exhibit excellent adhesion to various printing substrates. Preferred forms of the urethane resin include urethane resins obtained by the reaction of a polyol and a polyisocyanate, urethane prepolymers having an isocyanate group at the terminal, which are condensation reaction products of a polyol and a polyisocyanate, and urethane resins (urethane urea resins) obtained by the reaction (referred to as chain extension) of a polyamine. The urethane resin used in the present invention can be synthesized, for example, by the methods described in JP-A-2016-150942, JP-A-2013-213109 or JP-A-2020-147720. The urethane resin of the present invention preferably contains a structural unit derived from a polyester polyol, which is a condensation reaction product of a dibasic acid and a diol.

[0022] When the gravure ink of the present invention contains a urethane resin, the total content of the urethane resin solid content in the total solid content of the gravure ink is preferably 15 to 65% by mass, more preferably 17 to 63% by mass, and still more preferably 20 to 60% by mass. Further, the total content of the urethane resin solid content in the total solid content of the binder resin is preferably 20 to 100% by mass, more preferably 30 to 95% by mass, and still more preferably 40 to 90% by mass. By being within the above ranges, the storage stability, plate doubling property, and lamination suitability are improved. The weight average molecular weight (Mw) of the urethane resin is preferably 10,000 to 200,000, more preferably 11,000 to 180,000, and still more preferably 12,000 to 150,000. Further, the amine value of the urethane resin is preferably 1 to 20 mgKOH / g, more preferably 1.5 to 15 mgKOH / g, and still more preferably 1.7 to 10 mgKOH / g.

[0023] <Polyol> Examples of the polyol include polyester polyol, polyether polyol, polycaprolactone diol, polycarbonate polyol, polyolefin polyol, castor oil polyol, hydrogenated castor oil polyol, dimer diol, and hydrogenated dimer diol. Among them, polyester polyol or polyether polyol is preferable, and polyester polyol is particularly preferable. There is a tendency for the plate doubling property and lamination suitability to be improved. These polyols may be used in combination.

[0024] <Polyester polyol> The polyester polyol is preferably a condensation product of a dibasic acid and a diol. By using a polyester polyol, which is a condensation product of a dibasic acid and a diol, as the polyol, the urethane resin contains constituent units derived from the dibasic acid. The weight-average molecular weight of the polyester polyol is preferably 400 to 10,000. Furthermore, it is preferable that the total mass of the polyol contains 50% by mass or more of polyester polyol, and more preferably 70% by mass or more.

[0025] <Dibasic acid> Dibasic acids specifically include adipic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, oxalic acid, succinic acid, malonic acid, glutaric acid, dimer acid, pimelic acid, superiic acid, azelaic acid, trimellitic acid, pyromellitic acid, etc. In particular, the inclusion of sebacic acid and dimer acid is preferred. This improves lamination suitability and blocking resistance. The content of dibasic acid-derived constituent units is preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 40% by mass or more, based on the total mass of polyols constituting the urethane resin. A coating film with a balanced combination of flexibility and toughness is formed, and lamination suitability tends to improve.

[0026] <Diol> The diol constituting the above polyester polyol preferably includes both branched and linear diols. This results in a tough coating film for the urethane resin, improving blocking resistance and lamination suitability. Here, a linear diol refers to a diol that does not have substituents such as branched alkyl groups, and suitable examples include alkylene glycol, dialkylene glycol, and trialkylene glycol. A branched diol refers to a diol in which at least one hydrogen atom of the hydrocarbon group of alkylene glycol is substituted with an atom other than hydrogen. Since linear diols impart crystallinity and branched diols impart flexibility, urethane resins using these form a well-balanced coating film, improving blocking resistance, plate coverage, and lamination suitability.

[0027] Suitable branched diols 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, and dipropylene glycol. In the present invention, it is preferable to use at least one branched diol selected from MPO, MPD, BEPG, NPG, PG, and 2,4-diethyl-1,5-pentanediol, more preferably NPG and / or BEPG, and even more preferably NPG.

[0028] The linear diol is preferably an alkylene glycol, and suitable examples of such compounds include ethylene glycol (also written as EG), diethylene glycol, 1,3-propanediol (also written as 1,3-PD), 1,4-butanediol (also written as 1,4-BD), 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, triethylene glycol, and the like. Among these, linear diols with 8 or fewer carbon atoms, preferably 6 or fewer carbon atoms, are preferred, with EG, 1,3-PD, 1,4-BD, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and the like being preferred. Furthermore, from the viewpoint of blocking resistance, EG, 1,3-PD, and 1,4-BD are more preferred.

[0029] <Polyether polyol> Examples of polyether polyols include polyether polyols that are polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, etc. Among these, polytetramethylene glycol, polypropylene glycol, and polyethylene glycol are preferred, and the number average molecular weight is preferably 500 to 10,000.

[0030] <Polyisocyanate> The polyisocyanate preferably contains a diisocyanate. Examples of such diisocyanates include aliphatic diisocyanates such as tetramethylene diisocyanate, isopropyl diisocyanate, methylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate. Alicyclic diisocyanates such as cyclohexane-1,4-diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanates obtained by converting the carboxyl group of a dimer acid to an isocyanate group; Examples include aromatic diisocyanates such as α,α,α',α'-tetramethylxylylene diisocyanate, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyli isocyanate, dimethyldiphenylmethane diisocyanate, tetramethyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, o-xylylene diisocyanate, and 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate. Among these, alicyclic or aromatic aliphatic diisocyanates are preferred from the viewpoint of ease of reaction control and a good balance of performance in the resulting urethane resin, and isophorone diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate are particularly preferred. At least one type of diisocyanate may be used, and two or more types can be used in combination.

[0031] <Polyamine> Diamines are preferred as polyamines, and suitable 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-hydroxyethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypyropyrethylenediamine, and di-2-hydroxypyropyrethylenediamine, can also be suitably used. These diamines can be used individually or in combination of two or more, but isophoronediamine is preferred. Furthermore, it is also preferable to use polyamines 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, in combination with the above-mentioned diamines.

[0032] <Other binder resins> There are various types of binder resins, including cellulose resins, polyamide resins, vinyl chloride copolymer resins, rosin resins, vinyl acetate resins, acrylic resins, styrene resins, styrene-maleic acid copolymer resins, polyester resins, alkyd resins, ketone resins, polyacetal resins, petroleum resins, dammar resins, terpene resins, cycloplastic rubbers, chlorinated rubbers, polyolefin resins, phenolic resins, silicone resins, epoxy resins, xylene resins, coumarone indene resins, amino resins, petroleum resins, and modified resins thereof. These resins can be used in combination. The binder resin used in the present invention is not particularly limited as long as it is used in liquid inks applied to printing methods using printing plates for ordinary gravure inks, but it is preferable to include vinyl chloride copolymer resin and cellulose resin. Furthermore, it is preferable to include vinyl chloride copolymer resin and / or cellulose resin in addition to urethane resin. The mass ratio of urethane resin to the total mass of vinyl chloride copolymer resin and cellulose resin is preferably 99:1 to 1:99, and more preferably 90:10 to 50:50. In particular, vinyl chloride copolymer resin is preferred from the viewpoint of print coverage and lamination suitability.

[0033] <Vinyl chloride copolymer resin> In the present invention, the binder resin may also preferably contain a vinyl chloride copolymer resin from the viewpoint of plate coverage and lamination suitability. The vinyl chloride copolymer resin is not particularly limited as long as it contains structural units derived from vinyl chloride and structural units derived from other monomers. For example, vinyl chloride-vinyl acetate copolymer resin and vinyl chloride-acrylic copolymer resin are preferred. The content of vinyl chloride copolymer resin in the total mass of gravure ink is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and even more preferably 5 to 40% by mass. This tends to improve lamination suitability.

[0034] <Vinyl chloride-vinyl acetate copolymer resin> The vinyl chloride-vinyl acetate copolymer resin contains vinyl chloride units and vinyl acetate units. It is also preferable that it contains vinyl alcohol units. The mass ratio of vinyl chloride units to vinyl acetate units (vinyl chloride units:vinyl acetate units) is preferably 98:2 to 70:30, and more preferably 95:5 to 80:20, from the viewpoint of improving the blocking resistance of the coating film and suppressing a decrease in adhesion to the support (substrate) film. The weight-average molecular weight is preferably 5,000 to 50,000, and more preferably 10,000 to 35,000.

[0035] <Vinyl chloride-acrylic copolymer resin> The vinyl chloride-acrylic copolymer resin mainly consists of a copolymer resin of vinyl chloride monomer and acrylic monomer, and it is preferable that the acrylic monomer contains (meth)acrylate hydroxyalkyl ester to improve adhesion to the substrate and solubility in organic solvents. The acrylic monomer may be incorporated into the main chain of polyvinyl chloride in a block or random manner, or it may be graft polymerized into the side chain of polyvinyl chloride. The vinyl chloride-acrylic copolymer resin preferably has a weight-average molecular weight of 10,000 to 100,000, and more preferably 30,000 to 70,000. It is also preferable that the hydroxyl value be 20 to 200 mg KOH / g and the glass transition temperature be 50°C to 90°C.

[0036] In the following explanation, (meth)acrylic and (meth)acrylate refer to methacrylic and acrylic, methacrylate and acrylate, respectively.

[0037] The above acrylic monomers preferably include those having a hydroxyl group. Examples include hydroxyalkyl esters of (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate, as well as glycol mono(meth)acrylates such as polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and 1,4-cyclohexanedimethanol mono(meth)acrylate, caprolactone-modified (meth)acrylate, and hydroxyethylacrylamide. Among these, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl acrylate are more preferred because they improve solubility in solvents and improve the storage stability of the ink. These can be used individually or in combination of two or more. Other acrylic monomers may be included as needed.

[0038] <Cellulose resin> The gravure ink of the present invention may also preferably contain a cellulose-based resin. Examples of cellulose-based resins include acyl group-substituted celluloses such as nitrocellulose, cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate; alkyl group-substituted celluloses such as methylcellulose and ethylcellulose; and celluloses having hydroxyl groups such as benzylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and hydroxymethylpropylcellulose. Nitrocellulose is preferred as the cellulose-based resin, and acyl group-substituted cellulose and / or alkyl group-substituted cellulose are preferred from the viewpoint of improving adhesion to the substrate. Furthermore, the degree of hydroxyl group substitution of the cellulose-based resin is preferably about 30 to 85%. At least one type of cellulose-based resin may be used, and two or more types can be used in combination. The content of cellulose-based resin in the total mass of the gravure ink is preferably 1 to 50% by mass, more preferably 3 to 45% by mass, and even more preferably 5 to 40% by mass.

[0039] The weight-average molecular weight of the cellulose resin is preferably 10,000 to 500,000. As the molecular weight increases, it becomes more difficult to dissolve in organic solvents, and the viscosity tends to increase, limiting the amount that can be contained. Therefore, the weight-average molecular weight is more preferably 10,000 to 300,000, and even more preferably 10,000 to 100,000.

[0040] <Silica> The silica in this invention is characterized by being an inorganic fine particle mainly composed of silicon dioxide, with its surface coated with polyethylene wax and / or paraffin wax. In this invention, surface coating refers to the coating of part or all of the surface of the silica particle. It is presumed that the surface coating of the silica improves its compatibility with the binder resin and organic solvent, and stabilizes its dispersion state. To obtain the effects of this invention to the fullest extent, it is preferable to include a urethane resin among the binder resins, and further preferable to include a vinyl chloride copolymer resin and / or a cellulose resin. This tends to improve blocking resistance, storage stability, printability, and lamination suitability. There are no particular restrictions on the method for producing the inorganic fine particles mainly composed of silicon dioxide, but examples include dry methods such as combustion and wet methods such as sedimentation and gel methods. From the viewpoint of dispersibility and storage stability, a wet method is preferable, and those obtained by the gel method are particularly preferable.

[0041] In the present invention, the average particle size of silica is preferably 0.1 to 10 μm, more preferably 1 to 8 μm, and even more preferably 2 to 6 μm. When the average particle size of silica is within the above range, the blocking resistance tends to improve. In the present invention, the average particle size refers to the particle size measured by laser diffraction / scattering, for example, the particle size at a cumulative frequency of 50% in the particle size distribution measured using MicrotracMRB's MT3300EXII. The apparent specific gravity of silica is 0.05 to 1 g / cm³. 3 Preferably, it is 0.1 to 0.6 g / cm³. 3 It is preferable that it is [this].

[0042] In the present invention, the ignition loss of silica is preferably 14% by mass or less, more preferably 13.5% by mass or less, and even more preferably 13% by mass or less. Furthermore, the ignition loss of silica is preferably 3% by mass or more, more preferably 4% by mass or more, and even more preferably 7% by mass or more. In the present invention, the heat loss of silica is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. Furthermore, the heat loss of silica is preferably 0.1% by mass or more, and more preferably 1% by mass or more.

[0043] In the silica of the present invention, characterized in that inorganic fine particles mainly composed of silicon dioxide are surface-coated with polyethylene wax and / or paraffin wax, a preferred embodiment is that the ratio obtained by subtracting the heating loss from the ignition loss is preferably 1 to 15% by mass, and more preferably 3 to 10% by mass. This tends to improve storage stability and print coverage. In this invention, ignition loss is calculated by heating the sample at 1050°C for 1 hour and determining the percentage change (mass%) before and after heating, while heating loss is calculated by heating the sample at 110°C for 2 hours and determining the percentage change (mass%) before and after heating.

[0044] The silica content in the total mass of the gravure ink is preferably 0.1 to 5% by mass, more preferably 0.3 to 4% by mass, and even more preferably 0.5 to 3% by mass. When the silica content in the total mass of the gravure ink is within the above range, blocking properties, storage stability, and plate coverage tend to improve. Furthermore, the silica content per 100% by mass of the binder resin solids is preferably 1 to 35% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 25% by mass. When the silica content per 100% by mass of the binder resin solids is within the above range, blocking properties, storage stability, and plate coverage tend to improve further.

[0045] <Pigments> The gravure ink in the present invention may also preferably contain a pigment as a coloring agent. As the pigment, inorganic or organic pigments are preferred, and the CI pigments listed in the color index can be used as appropriate. Examples of organic pigments include, but are not limited to, soluble azo, insoluble azo, azo, phthalocyanine, halogenated phthalocyanine, anthraquinone, anthensrone, dianthaquinonyl, anthrapyrimidine, perylene, perinone, quinacridone, thioindigo, dioxazine, isoindolinone, quinophthalone, azomethine azo, flavanthrone, diketopyrrolopyrrole, isoindoline, and indanthrone pigments. Furthermore, it is preferable to use at least one or a combination of two or more. Examples of inorganic pigments include titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, aluminum hydroxide, chromium oxide, silica, carbon black, aluminum, and mica. From the viewpoint of coloring power, opacity, chemical resistance, and weather resistance, titanium dioxide is preferred as a white pigment, and titanium dioxide with a basic pigment surface is even more preferred. Aluminum is available in powder or paste form, but from the viewpoint of handling and safety, it is preferred to use it in paste form, and it may be either leafing or non-leafing. Barium sulfate, calcium carbonate, and aluminum hydroxide are called extender pigments and are used as fillers to improve fluidity, strength, and optical properties. When the gravure ink of the present invention contains pigments, it is preferable that they be included in a proportion of 1 to 50% by mass of the total mass of the gravure ink, and more preferably in a proportion of 3 to 25% by mass.

[0046] <Organic solvents> The organic solvents used in this invention are selected to maximize the performance of the gravure ink composition. These solvents include a wide variety of types, such as ester-based, alcohol-based, ketone-based, and aromatic solvents. Specific examples include ester-based solvents such as ethyl acetate, n-propyl acetate, isopropyl acetate, isobutyl acetate, propylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate, and alcohol-based solvents such as methanol, ethanol, n-propanol, isopropanol, and n-butanol. Aromatic solvents such as toluene and xylene, and ketone-based solvents such as methyl ethyl ketone and methyl isobutyl ketone are also used. These organic solvents are preferably mixed and used in consideration of their solubility and drying properties with respect to the binder resin. Among these, organic solvents that do not contain aromatic organic solvents (non-toluene organic solvents) are more preferable. Even more preferable are organic solvents that do not contain aromatic organic solvents and / or ketone organic solvents. Furthermore, a mixed solvent of ester-based and alcohol-based organic solvents is preferable because it improves printability. Furthermore, the preferred mass ratio of ester-based organic solvents to alcohol-based organic solvents (ester-based organic solvent / alcohol-based organic solvent) is 40 / 60 to 90 / 10. The organic solvent is preferably present in a total amount of 15% to 95% by mass of the gravure ink.

[0047] <Additives> The gravure ink of the present invention may optionally contain additives such as leveling agents, defoaming agents, waxes, silane coupling agents, plasticizers, light stabilizers, infrared absorbers, ultraviolet absorbers, fragrances, flame retardants, and curing agents. Preferably, the additives are present in an amount of 0.05 to 5% by mass of the total solid content of the gravure ink.

[0048] <Manufacturing of gravure inks> A preferred method for producing the gravure ink of the present invention involves dissolving and / or dispersing a binder resin and silica in an organic solvent. Specifically, it is preferable to mix the binder resin, silica, organic solvent, and optionally pigments and additives using a stirring mixer, then disperse the mixture using a disperser, and then optionally add and mix the binder resin, various additives, and organic solvents to the resulting dispersion. Dispersers such as ball mills, attritors, and sand mills, which are commonly used in the production of printing inks, can be used.

[0049] <Printed material> A preferred form of the printed material in the present invention is having a printed layer formed from the gravure ink described in claim 1 on a substrate 1. The method for manufacturing the printed material is not particularly limited as long as it is a general gravure ink printing method, but for example, the printed material can be manufactured as appropriate by the methods described in Japanese Patent Application Publication No. 2021-091894, Japanese Patent Application Publication No. 2024-86082 and Japanese Patent Application Publication No. 2020-147720.

[0050] <Laminate> A preferred form of the laminate in the present invention is to have a substrate 1, a printed layer formed from the gravure ink described in claim 1, and a substrate 2 in that order. Specifically, it can be manufactured as appropriate by the methods described in Japanese Patent Publication No. 2021-091894, Japanese Patent Publication No. 2024-86082, and Japanese Patent Publication No. 2020-147720.

[0051] <Base material 1> The substrates to which this invention can be applied are not limited to plastic substrates, paper substrates, metals, etc. Examples of plastic substrates include polyamide resins such as nylon 6, nylon 66, and nylon 46 (Ny), polyester resins such as polyethylene phthalate (PET), polyethylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate, biodegradable resins such as polyhydroxycarboxylic acids like polylactic acid, aliphatic polyester resins such as polyethylene succinate and polybutylene succinate, cellulose resins such as diacetylcellulose and triacetylcellulose, polyolefin resins such as polypropylene (PP) and polyethylene, polyimide resins, polyarylate resins, or mixtures thereof. Among these, films made of polyester, polyamide, and polypropylene are particularly suitable. These films may be unstretched or stretched films, and their manufacturing methods are not limited. The thickness of the substrate is also not particularly limited, but is usually in the range of 1 to 500 μm.

[0052] <Base material 2> Substrate 2 is the same as that of substrate 1, and may be the same or different. It is preferable that it be a thermoplastic substrate (sometimes referred to as a sealant), and unoriented polyethylene substrates, unoriented polypropylene substrates, unoriented polyester substrates, etc., are preferred. [Examples]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to these examples unless it exceeds the essence of the invention. In the present invention, parts and % refer to parts by mass and mass %, respectively, unless otherwise noted.

[0054] (Measurement methods for various measurement parameters) (Weight average molecular weight Mw) The weight-average molecular weight (Mw) was determined by measuring the molecular weight distribution using a GPC (gel permeation chromatography) instrument (HLC-8220, manufactured by Tosoh Corporation) and calculating the converted molecular weight using polystyrene as the standard substance. The measurement conditions are shown below. Columns: The following columns were used, connected in series. TSKgelSuperAW2500 manufactured by Tosoh Corporation TSKgel SuperAW3000 manufactured by Tosoh Corporation TSKgelSuperAW4000 manufactured by Tosoh Corporation TSKgelguard Column Super AWH manufactured by Tosoh Corporation Detector: RI (Differential Refractometer) Measurement conditions: Column temperature 40°C Eluent: Tetrahydrofuran Flow rate: 1.0mL / min

[0055] (Synthesis Example 1) (Synthesis of Polyester Polyurethane Resin Solution) In a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 30.4 parts by mass of polyester polyol PO1 (a condensate of 1,3-PD:NPG:sebacic acid = 1:1:4 (mass ratio) dissolved in ethyl acetate with a solid content of 73.5%, number average molecular weight 3000), 0.1 parts by mass of 1,3-PD, 3.7 parts by mass of isophorone diisocyanate (hereinafter also abbreviated as IPDI), and 0.01 parts by mass of catalyst (stannous ethylhexylate 2) were charged. The mixture was reacted at 90°C for 3 hours under a nitrogen stream, 1.1 parts by mass of ethyl acetate and 6.5 parts by mass of n-propyl acetate were added, and the mixture was cooled to obtain a solution of terminal isocyanate prepolymer. Next, to a solution prepared by mixing 1.6 parts by mass of isophorone diamine (hereinafter also abbreviated as IPDA), 0.2 parts of dibutylamine (hereinafter also abbreviated as DBA), 21.2 parts of ethyl acetate, 6.5 parts of n-propyl acetate, and 28.7 parts of isopropyl alcohol, the entire amount of the terminal isocyanate prepolymer solution obtained above was gradually added at room temperature, and then the mixture was reacted at 40°C for 1 hour to obtain a polyester polyurethane resin solution (solid content 28% by mass, weight-average molecular weight Mw 60000).

[0056] (Synthesis Example 2) (Synthesis of Polyether Polyurethane Resin Solution) In a four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 22.4 parts by mass of polypropylene glycol (hereinafter abbreviated as PPG, number average molecular weight 3000), 8 parts by mass of ethyl acetate, 0.1 parts by mass of 1,3-PD, 3.7 parts by mass of IPDI, and 0.01 parts by mass of catalyst (stannous ethylhexyl 2-ethylhexylate) were charged and reacted at 90°C for 3 hours under a nitrogen stream. Then, 1.1 parts by mass of ethyl acetate and 6.5 parts by mass of n-propyl acetate were added and the mixture was cooled to obtain a solution of terminal isocyanate prepolymer. Next, to a solution of 1.6 parts by mass of IPDA, 0.2 parts of DBA, 21.2 parts of ethyl acetate, 6.5 parts of n-propyl acetate, and 28.7 parts of isopropyl alcohol, the entire amount of the obtained terminal isocyanate prepolymer solution was gradually added at room temperature and reacted at 40°C for 1 hour to obtain a polyether polyurethane resin solution (solid content 28% by mass, weight average molecular weight Mw 60000).

[0057] [Example 1] (Manufacturing of gravure ink S1) Ten parts by mass of pigment (manufactured by Toyo Color Co., Ltd., product name LIONOL YELLOW 1422-G), eighteen parts by mass of polyester polyurethane resin solution, ten parts by mass of vinyl chloride-vinyl acetate copolymer resin solution (manufactured by Nisshin Chemical Industry Co., Ltd., product name Solvine TA5R, solids content 24% by mass), one part by mass of silica (manufactured by Mizusawa Chemical Co., Ltd., product name MIZUKASIL NP-8, paraffin wax surface coating treatment, loss on ignition 4% by mass), and twenty parts by mass of organic solvent were stirred and mixed. Then, after dispersion using a bead mill (sand mill), twenty parts by mass of polyester polyurethane resin solution and twenty-one parts by mass of organic solvent were added and stirred and mixed to prepare gravure ink S1. The organic solvent was a mixture of n-propyl acetate, isopropyl alcohol, and methylpropylene glycol, with a mass ratio of n-propyl acetate:isopropyl alcohol:methylpropylene glycol = 30:5:6.

[0058] [Examples 2-15, Comparative Examples 1-4] (Manufacturing of gravure inks S2-S15, T1-T4) Gravure inks S2-S15 and T1-T4 were obtained using the same method as for gravure ink S1, except that the raw materials and preparation weights were changed as described in Tables 1, 2-1, and 2-2. The abbreviations in the tables are as follows. • Cellulose resin solution: Nitrocellulose manufactured by ICI Novel Enterprises, product name DLX5-8, solids content 24% by mass • Polyethylene wax: BASF product name LUWAXA powder

[0059] (Printing with Gravure Ink S1) Using a gravure proofing machine equipped with a solid gravure printing plate for Helio 175 lines, the gravure ink S1 obtained in Example 1 was coated onto a PET (polyethylene terephthalate) film (manufactured by Toyobo Co., Ltd., product name: E-5102, film thickness: 12 μm) at a coating speed of 150 m / min so that the dry film thickness was approximately 2 μm. The film was then dried with hot air at 60°C (airflow 80%) to obtain a printed material having a printed layer formed from the gravure ink S1.

[0060] (Printing with gravure inks S2-S15, T1-T4) A printed material having a printed layer formed from each gravure ink was obtained using the same method as for printing with gravure ink S1, except that gravure ink S1 was replaced with gravure inks S2 to S15 and T1 to T4.

[0061] (Preparation of a laminate having a printed layer formed from gravure ink S1) In a printed material having a printed layer formed from the gravure ink S1 obtained above, a methanol solution (1% solid content by mass) of a butadiene-based anchor coating agent (EL451, manufactured by Toyo Morton Co., Ltd.) was applied to the printed layer formed from the gravure ink S1 and dried. Then, molten polyethylene (Sumikasen L417, manufactured by Sumitomo Chemical Co., Ltd.) was extruded at 320°C at a line speed of 100 m / min using an extrusion laminating machine (manufactured by Musashino Kikai Co., Ltd.) to a thickness of 15 μm, and a CPP film (FCMN, manufactured by Futamura Chemical Co., Ltd., with a film thickness of 20 μm) was bonded (laminated) onto the molten polyethylene to obtain a laminate having the printed layer formed from the gravure ink S1 and the substrate 2 in sequence.

[0062] (Preparation of a laminate having a printed layer formed from gravure inks S2-S15 and T1-T4) A laminate having sequentially formed printed layers and substrates 2, each made from a different gravure ink, was obtained in the same manner as the laminate having a printed layer formed from gravure ink S1, except that gravure ink S1 was changed to gravure inks S2 to S15 and T1 to T4.

[0063] (Measurement and evaluation) The printed materials and laminates obtained above were evaluated as follows. The evaluation results are shown in Tables 2-1 and 2-2.

[0064] (Storage stability) For the gravure inks of Examples 1-15 and Comparative Examples 1-4, 100 ml glass sample bottles were placed and left to stand at 25°C for one week. The state of the ink was then visually inspected and evaluated. Here, separation refers to the separation mainly consisting of solvents that occur near the liquid surface, while precipitation refers to the separation mainly consisting of solids that occur near the bottom. 5 (Excellent): No ink sedimentation or separation is observed. 4 (Good): No ink sedimentation is observed, but slight separation is present. 3 (Acceptable): Slight ink sedimentation and separation are observed. 2 (Unacceptable): Ink sedimentation and separation are observed. 1 (Poor): Significant ink sedimentation and separation are observed. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0065] (Blocking resistance) For printed materials having a printed layer formed from the gravure inks of Examples 1-15 and Comparative Examples 1-4, the non-corona discharge treated surface of a PET (polyethylene terephthalate) film (manufactured by Toyobo Co., Ltd., product name: E-5102, film thickness: 12 μm) and the printed surface of the printed material were pressed together for 24 hours under conditions of 40°C and 5 kg / cm2, and then peeled off. The resistance during peeling and the peeling condition of the printed surface were evaluated. [Evaluation Criteria] 5 (Excellent): There is no peeling on the printed surface, and no resistance is felt when peeling. 4 (Good): There is no peeling on the printed surface, but resistance can be felt when peeling. 3 (Acceptable): Less than 20% slight peeling on the printed surface. 2 (Not acceptable): There is light peeling of 20% to less than 50% on the printed surface and / or heavy peeling. 1 (Poor): More than 50% peeling on the printed surface. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0066] (Pattern overlap) Printing was performed under the same conditions as when printing printed materials having a printed layer formed from gravure inks in Examples 1-15 and Comparative Examples 1-4. After 30 minutes from the start of printing, the area of ​​the non-image plate cover and streaks were visually inspected and evaluated. [Evaluation Criteria] 5 (Excellent): The area of ​​plate overlap is between 0% and 10% of the area of ​​the non-image plate, and no streaks are visible. 4 (Good): The area of ​​plate overlap is between 0% and 10% of the non-image plate area, but slight streaks are visible. 3 (Acceptable): The area covered by the image is between 10% and 30% of the area of ​​the non-image portion of the image plate, and some streaks are visible. 2 (Unacceptable): The area covered by the image plate is between 30% and 50% of the area of ​​the non-image plate, and streaks are visible. 1 (Poor): The area of ​​plate overhang is 50% or more of the area of ​​the non-image plate, and large streaks are visible. Note that values ​​3-5 are within a range that does not pose any practical problems.

[0067] (Lamination strength) Each laminate having a printed layer formed from the gravure inks of Examples 1-15 and Comparative Examples 1-4 was cut to a length of 150 mm and a width of 15 mm. The ink / PET film interface was peeled off at one end face to a width that could be held in place by the jig of a tensile testing machine, and the laminate strength in the 90° direction was measured using a tensile testing machine (Intesco small tensile testing machine) at a peeling speed of 300 mm / min. 5 (Excellent): Lamination strength of 1.5 N / 15 mm or higher 4 (Good): Lamination strength is 1.0 N / 15 mm or higher, and less than 1.5 N / 15 mm. 3 (Acceptable): Lamination strength of 0.8 N / 15 mm or more, and less than 1.0 N / 15 mm. 2 (Not acceptable): Lamination strength of 0.5N / 15mm or more, and less than 0.8N / 15mm. 1 (Inferior): Laminate strength less than 0.5 N / 15 mm Note that values ​​3-5 are within a range that does not pose any practical problems.

[0068] [Table 1]

[0069] [Table 2-1]

[0070] [Table 2-2]

[0071] Comparative Examples 1 and 2, which lacked surface coating with polyethylene wax and / or paraffin wax, Comparative Example 3, which contained neither silica nor inorganic fine particles mainly composed of silicon dioxide, and Comparative Example 4, in which inorganic fine particles mainly composed of silicon dioxide and polyethylene wax were added separately, failed to achieve any of the following properties: blocking resistance, storage stability, plate fogging, and lamination suitability. In contrast, Examples 1 to 15, which contained a binder resin, silica, and an organic solvent, and in which the silica was surface-coated with polyethylene wax and / or paraffin wax, exhibited performance at or above a practically acceptable level in all aspects of blocking resistance, storage stability, plate fogging, and lamination suitability. In other words, the present invention demonstrates that it is possible to provide a gravure ink that solves all the problems.

Claims

1. A gravure ink having a binder resin, silica, and an organic solvent, A gravure ink characterized in that the silica is surface-coated with polyethylene wax and / or paraffin wax.

2. The gravure ink according to claim 1, wherein the silica content in the total mass of the gravure ink is 0.1 to 5% by mass.

3. The gravure ink according to claim 1 or 2, wherein the silica content relative to 100% by mass of the binder resin solids is 1 to 35% by mass.

4. The gravure ink according to claim 1 or 2, wherein the binder resin comprises a urethane resin containing constituent units derived from a dibasic acid.

5. The gravure ink according to claim 1 or 2, wherein the binder resin further comprises a vinyl chloride copolymer resin and / or a cellulose-based resin.

6. The gravure ink according to claim 1 or 2, wherein the ignition loss of silica is 14% by mass or less.

7. A printed article having a printed layer formed from the gravure ink described in claim 1 on a substrate 1.

8. A laminate comprising, in sequence, a substrate 1, a printing layer formed from the gravure ink described in claim 1, and a substrate 2.

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