JP7261577B2 - Water-based gravure ink - Google Patents

Description

The present invention relates to aqueous gravure inks.

Gravure printing is a printing method that uses a gravure plate having ink-receiving cells to transfer ink to a printing medium. The printing quality can be controlled by changing the cell depth and cell spacing (number of lines), and high-definition printing is possible.
The gravure _ink used in gravure printing aims to improve the working environment, and non-toluene oil-based ink is used. In addition, there are problems from the viewpoint of disaster prevention, and also from the viewpoint of residual solvents when used in food-related applications. In addition, since gravure printing uses a large amount of oil-based ink, there is a problem that it is difficult to meet market needs for a wide variety of products and small lots.
Therefore, gravure printing using water-based ink has attracted attention. However, the water-based ink has a problem that it is difficult to obtain a high-quality printed matter due to poor adhesion to the printing medium due to poor drying and poor wetting of the ink onto the printing plate surface due to surface tension.

A technique of blending a resin emulsion into ink is known to improve physical properties of a coating film such as adhesion to a printing medium.
For example, Patent Document 1 describes an ink suitable for gravure printing that is excellent in ink stability, printability, and coating film physical properties. A water-based printing ink using as a vehicle a resin emulsion having a particle size distribution in which particles having a particle size in the range of 50 to 600 nm account for 60% by weight or more of all particles is disclosed. In the example, the water-based printing ink was diluted with water to a Zahn cup viscosity of #3-25 seconds, and printed on a vinyl chloride wallpaper raw fabric coated with foamed vinyl chloride sol. C. for 45 seconds in a hot air oven, and evaluated the physical properties (adhesion, water resistance, abrasion resistance, chemical resistance) of the coating film after the heating and foaming process.

JP-A-10-204361

In recent years, the use of resin film as a printing medium is increasing, but if the printed image is damaged or peeled off, the value of the product will be reduced. There is a demand for high adhesion of printed images to
However, the water-based ink described in Patent Document 1 is said to have excellent physical properties of the coating film after the printed matter is heated and foamed at 220° C., and is used under temperature conditions at which the polymer particles in the ink soften or melt. In addition, the adhesiveness is insufficient for low or non-low liquid absorbing printing media such as PET film and polypropylene film, which are subject to heat treatment.
In addition, with oil-based gravure inks and water-based gravure inks with a high alcohol content, the antiseptic properties of the ink are secured by oil-based solvents and alcohols, but with water-based gravure inks with a high water content, antiseptic and rust-preventive properties tend to be inferior. There is The storage stability is affected when bacteria and the like increase in the ink. In order to improve this problem, antiseptic properties may be ensured by adding antiseptic compounds to water-based gravure inks containing a large amount of water. Patent document 1 lists preservatives, antifungal agents, and antibacterial agents as ingredients that can be added, but does not describe their types or their effects.
An object of the present invention is to provide a water-based gravure ink which is excellent in ink adhesion and storage stability and which can produce high-quality prints.

The present inventors have found that in a water-based gravure ink containing pigment particles A and polymer particles B, the average particle diameter and polydispersity index of each of pigment particles A and polymer particles B are adjusted to specific ranges, and antiseptic properties It has been found that the above problems can be solved by containing a compound.
That is, the present invention provides a water-based gravure ink containing pigment particles A, polymer particles B, an antiseptic compound, and water, wherein the pigment particles A have an average particle diameter of 140 nm or more and 550 nm or less, and The polydispersity index in the diameter distribution is 0.08 or more and 0.32 or less,
The average particle size of the polymer particles B is 30 nm or more and 220 nm or less, and the polydispersity index in the particle size distribution of the polymer particles B is 0.08 or more and 0.32 or less,
Provided is a water-based gravure ink, wherein the antiseptic compound is one or more selected from isothiazoline compounds, aromatic alcohol compounds, and pyrithione metal complexes.

According to the present invention, it is possible to provide a water-based gravure ink that is excellent in ink adhesion and storage stability, and that can produce high-quality prints.

[Water-based gravure ink]
The water-based gravure ink of the present invention (hereinafter also referred to as "the ink of the present invention") is a water-based gravure ink containing pigment particles A, polymer particles B, an antiseptic compound, and water, wherein the pigment particles A have an average particle diameter of is 140 nm or more and 550 nm or less, and the polydispersity index in the particle size distribution of the pigment particles A is 0.08 or more and 0.32 or less,
The average particle size of the polymer particles B is 30 nm or more and 220 nm or less, and the polydispersity index in the particle size distribution of the polymer particles B is 0.08 or more and 0.32 or less,
The antiseptic compound is one or more selected from isothiazoline compounds, aromatic alcohol compounds, and pyrithione metal complexes.

According to the water-based gravure ink of the present invention, it is possible to obtain high-quality prints with excellent ink adhesion and storage stability. Although the reason is not clear, it is considered as follows.
The ink of the present invention contains pigment particles A and polymer particles B having a specific average particle size and a small polydispersity index.
When the polydispersity index of the pigment particles A is small, the particle size distribution becomes narrow, so that the pigment particles A are uniformly fixed on the surface of the printing medium with a more uniform size and less surface unevenness. As a result, it is considered that the adhesion of the pigment particles A is improved.
The polymer particles B are considered to have the same function as the pigment particles A. If the polydispersity index of the polymer particles B is small, the particle size distribution becomes narrow, and the polymer particles B have a more uniform size on the surface of the printing medium. It is thought that the adhesiveness is improved because the toner is uniformly fixed with less unevenness on the surface.
In addition, by using a specific antiseptic compound, the pigment particles A and polymer particles B can be stabilized without the antiseptic compound being adsorbed to the pigment particles A and polymer particles B due to moderate ionicity and hydrophobicity. Since the ink can be retained and the growth of bacteria can be suppressed, the stability of the ink is improved without agglomeration during the process of forming the printing surface. is formed and fixed, so it is considered that the adhesion is improved.
Furthermore, since the particle size distribution of the pigment particles A and the polymer particles B is narrow, the particles have a uniform particle size.
As a result, it is thought that the ink adhesion and storage stability are excellent, and high-quality printed matter can be obtained.

<Pigment Particle A>
Pigment particles A used in the ink of the present invention may be either inorganic pigment particles or organic pigment particles.
Examples of inorganic pigments constituting the pigment particles A include carbon black and metal oxides. Among black inks, carbon black is preferred. Examples of carbon black include furnace black, thermal lamp black, acetylene black, channel black and the like. White inks include white pigments such as metal oxides such as titanium dioxide, zinc oxide, silica, alumina, and magnesium oxide.
Examples of organic pigments constituting the pigment particles A include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments. be done.
The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, red, blue, orange, and green can be used in the chromatic ink.

When using a white pigment, titanium dioxide is preferred from the viewpoint of dispersibility. The crystal structure of titanium dioxide includes rutile type, anatase type, and brookite type, but rutile type titanium oxide is preferable from the viewpoint of crystal stability, hiding property, and availability.
Although untreated titanium dioxide can be used, surface-treated titanium dioxide is preferred from the viewpoint of obtaining good dispersibility. Surface treatment of titanium dioxide includes surface treatment with inorganic substances such as alumina, silica, zinc oxide, zirconia, and magnesium oxide, and known hydrophobizing agents such as titanium coupling agents, silane coupling agents, and higher fatty acid metal salts. It may be surface-treated.
The average primary particle size of titanium dioxide is preferably 140 nm or more, more preferably 150 nm or more, and still more preferably 200 nm or more as the arithmetic mean of the major diameters of the primary particles from the viewpoint of whiteness, and from the viewpoint of hiding power. , preferably 450 nm or less, more preferably 400 nm or less, and still more preferably 350 nm or less.
Commercially available examples of rutile-type titanium dioxide include the trade names of Typaque R, CR, and PF series manufactured by Ishihara Sangyo Co., Ltd., the trade names of R series manufactured by Sakai Chemical Industry Co., Ltd., and the trade names of JR manufactured by Tayca Corporation. , MT series, trade name: KURONOS KR series manufactured by Titan Kogyo Co., Ltd., trade name: TR series manufactured by Huntsmann, and the like.

Preferred forms of the pigment particles A used in the present invention include self-dispersing pigment particles and pigment particles containing a pigment in a polymer. The form of pigment particles contained in a polymer, that is, polymer particles A containing a pigment (hereinafter also referred to as “pigment-containing polymer particles A”) is preferred. In the present specification, the "pigment-containing polymer particles A" refer to a form in which the polymer contains the pigment, a form in which a part of the pigment is exposed on the surface of the particles composed of the polymer and the pigment, and a form in which the polymer is adsorbed on a part of the pigment. Including particles such as morphology.
The self-dispersing pigment particles are those in which one or more anionic hydrophilic groups or cationic hydrophilic groups are bonded directly or via other atomic groups to the surface of the pigment, using a surfactant or polymer. means pigment particles that are dispersible in an aqueous medium without

(Average particle size of pigment particles A)
The average particle size of the pigment particles A in the ink of the present invention is 140 nm or more and 550 nm or less from the viewpoint of improving the adhesion and storage stability of the ink. The average particle diameter of the pigment particles A can be adjusted by pulverizing and dispersing by a known method.
The average particle size of the pigment particles A is preferably 150 nm or more, more preferably 200 nm or more, still more preferably 250 nm or more, and is preferably 500 nm or less, more preferably 490 nm or less, still more preferably 450 nm or less.
The average particle diameter of pigment particles A is measured by the method described in Examples.

(Polydispersity index in particle size distribution of pigment particles A)
The polydispersity index in the particle size distribution of the pigment particles A in the ink of the present invention is 0.08 or more and 0.32 or less from the viewpoint of improving the adhesion and storage stability of the ink.
"Polydispersity Index (PDI)" is an index for evaluating the width of the particle size distribution, and is measured by a dynamic light scattering method. Chapter 1 Light Scattering” (Kyoritsu Shuppan, edited by The Society of Polymer Science), or J. Am. Chem. Phys. , 70(B), 15 Apl. , 3965 (1979).
From the same viewpoint as above, the polydispersity index of the pigment particles A is preferably 0.10 or more, more preferably 0.11 or more, still more preferably 0.12 or more, and preferably 0.30 or less. It is more preferably 0.29 or less, still more preferably 0.27 or less.
The polydispersity index of Pigment Particle A is measured by the method described in Examples.
The average particle size and polydispersity index of the pigment particles A can be adjusted by adjusting the primary particle size of the pigment and dispersion conditions such as dispersion strength and dispersion time when the pigment is dispersed in a medium such as water. Moreover, it is also possible to select and use a commercial product that satisfies the average particle size and polydispersity index.

(Polymer Constituting Pigment Particle A)
The polymer constituting the pigment particles A may be either a water-soluble polymer or a water-insoluble polymer, but a water-insoluble polymer is more preferable. That is, the pigment particles A are more preferably water-insoluble polymer particles A containing a pigment.
The water-insoluble polymer refers to a polymer whose dissolved amount is less than 10 g when it is dried at 105° C. for 2 hours and has reached a constant weight and dissolved in 100 g of water at 25° C. until it is saturated. The amount is preferably 5 g or less, more preferably 1 g or less. In the case of an anionic polymer, the dissolved amount is the dissolved amount when the anionic groups of the polymer are 100% neutralized with sodium hydroxide.
As the polymer to be used, one or more selected from vinyl resins, polyester resins, polyurethane resins, and the like can be mentioned. A vinyl resin obtained by addition polymerization of is preferred. A polymer crosslinked with a crosslinking agent can also be used.
From the viewpoint of improving the storage stability of the ink, the polymer constituting the pigment particles A is preferably a vinyl-based resin obtained by addition polymerization of a vinyl monomer.
As the vinyl-based resin, an acrylic resin containing (a1) a structural unit derived from an ionic monomer and (a2) a structural unit derived from a nonionic monomer is preferable.

(a1) The ionic monomer is preferably an anionic monomer, and examples thereof include carboxylic acid monomers and sulfonic acid monomers. Among these, carboxylic acid monomers are more preferred, and one or more selected from acrylic acid and methacrylic acid are even more preferred.
(a2) Nonionic monomer is a monomer having high affinity with water and water-soluble organic solvents, preferably polyalkylene glycol (meth) acrylate, alkoxypolyalkylene glycol (meth) acrylate, methoxypolyethylene glycol (n = 1 30) (meth)acrylates are more preferred. Examples of commercially available nonionic monomers include NK Ester M series manufactured by Shin-Nakamura Chemical Co., Ltd., Blenmer PE series, PME series, 50PEP series, and 50POEP series manufactured by NOF Corporation.

The polymer constituting the pigment particles A may further contain (a3) a structural unit derived from a hydrophobic monomer. (a3) Hydrophobic monomers include alkyl (meth)acrylates, aromatic group-containing monomers, and macromonomers having a polymerizable functional group at one end.
The alkyl (meth)acrylate preferably has an alkyl group having 6 to 18 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, (iso)propyl (meth)acrylate, (iso or tertiary ly)butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (iso)octyl (meth)acrylate and the like.
As the aromatic group-containing monomer, a vinyl-based monomer having an aromatic group having 6 to 22 carbon atoms is preferable, and a styrene-based monomer, an aromatic group-containing (meth)acrylate, and the like are more preferable. Styrene-based monomers are preferably styrene, 2-methylstyrene, α-methylstyrene, vinyltoluene, divinylbenzene and the like, and aromatic group-containing (meth)acrylates are preferably benzyl (meth)acrylate and the like.

(Content of Each Structural Unit in Polymer Constituting Pigment Particle A)
From the viewpoint of improving the dispersion stability of the ink, the contents of the structural units derived from the components (a1) to (a3) in the polymer constituting the pigment particle A are as follows.
The content of component (a1) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less. , more preferably 20% by mass or less.
The content of component (a2) is preferably 20% by mass or more, more preferably 40% by mass or more, still more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. , and more preferably 85% by mass or less.
The content of component (a3) is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

(Production of Polymer Constituting Pigment Particle A)
The polymer constituting the pigment particles A can be produced by copolymerizing a monomer mixture containing (a1) an ionic monomer, (a2) a nonionic monomer, etc., by a known solution polymerization method or the like.
The weight-average molecular weight of the polymer is preferably 3,000 or more, more preferably 5,000 or more, and still more preferably 10,000 or more, from the viewpoint of improving ink dispersion stability and adhesion to a printing medium, and , preferably 100,000 or less, more preferably 50,000 or less, and still more preferably 30,000 or less.
The acid value of the polymer is preferably 100 mgKOH/g or more, more preferably 150 mgKOH/g or more, still more preferably 200 mgKOH/g or more, and preferably 350 mgKOH, from the viewpoints of pigment dispersibility and polymer adsorptivity. /g or less, more preferably 300 mgKOH/g or less, still more preferably 250 mgKOH/g or less.
The weight average molecular weight and acid value can be measured by the methods described in Examples.

(Production of pigment-containing polymer particles A)
Pigment-containing polymer particles A can be efficiently produced as a dispersion by a method including the following step I. Furthermore, it may be produced by a method having the following steps II and III. If step I does not contain an organic solvent, step II can be omitted. Step III is optional.
Step I: A step of dispersing a mixture containing a polymer, a pigment, and, if necessary, an organic solvent, a neutralizing agent, a surfactant, etc. to obtain a dispersion of pigment-containing polymer particles Step II: In Step I A step of removing the organic solvent from the resulting dispersion to obtain an aqueous dispersion of pigment-containing polymer particles Step III: Mixing the dispersion obtained in Step I or the aqueous dispersion obtained in Step II with a cross-linking agent and cross-linking to obtain an aqueous dispersion of cross-linked polymer particles containing a pigment

When the polymer constituting the pigment particles A is an anionic polymer having an anionic group, a neutralizing agent may be used to neutralize the anionic group in the polymer. When a neutralizing agent is used, neutralization is preferably carried out so that the pH is 7 or more and 11 or less. Examples of neutralizing agents include bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia and various amines. Moreover, the polymer may be neutralized in advance.
From the viewpoint of improving the dispersion stability of the ink, the degree of neutralization of the anionic groups of the polymer is preferably 10 mol% or more and 100 mol% or less, more preferably 20 mol% or more and 90 mol% or less, relative to the anionic groups. Preferably, 30 mol % or more and 80 mol % or less is more preferable.
Here, when the polymer has an anionic group, the degree of neutralization can be determined by the following formula as the equivalent amount of the neutralizing agent to the anionic group of the polymer. When the use equivalent of the neutralizing agent is 100 mol % or less, it is synonymous with the degree of neutralization. If the use equivalent of the neutralizing agent exceeds 100 mol%, it means that the neutralizing agent is excessive with respect to the acid groups of the polymer, and the degree of neutralization of the polymer at this time is regarded as 100 mol%. .
Use equivalent of neutralizing agent (mol%) = [{adding mass of neutralizing agent (g) / equivalent of neutralizing agent} / [{weighted average acid value of polymer (mgKOH/g) x mass of polymer (g) }/(56×1000)]]×100

When the polymer constituting the pigment-containing polymer particles A has an anionic group, the cross-linking agent is preferably a compound having a functional group that reacts with the anionic group. and compounds having two or more oxazoline groups in the molecule and compounds having two or more isocyanate groups in the molecule. Among these, compounds having 2 to 4 epoxy groups in the molecule are preferred, and trimethylolpropane polyglycidyl ether is more preferred.
The crosslinking ratio of the acid component in the polymer constituting the pigment-containing polymer particles A is preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 20 mol%, from the viewpoint of improving the storage stability of the ink. and preferably 80 mol % or less, more preferably 70 mol % or less, still more preferably 60 mol % or less.

From the viewpoint of improving adhesion, the content of the polymer that constitutes the pigment particles A in the ink of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and still more preferably 0.2% by mass or more. It is 3% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less.
The mass ratio [polymer/pigment] of the polymer constituting the pigment particles A to the pigment in the ink of the present invention is preferably 0.2/99.8 to 70/30, from the viewpoint of improving the storage stability of the ink. More preferably 0.5/99.5 to 60/40, still more preferably 1/99 to 50/50.

Specific examples of vinyl-based resins that are polymers used in the production of pigment particles A include polyacrylic acids such as "Aron AC-10SL" (manufactured by Toagosei Co., Ltd.), "Joncryl 67" and "Joncryl 611", "Joncryl 678", "Joncryl 680", "Joncryl 690", "Joncryl 819" (manufactured by BASF Japan Ltd.) and other styrene-acrylic resins.

<Polymer particles B>
The ink of the present invention contains polymer particles B containing no pigment (hereinafter referred to as "polymer particles B") from the viewpoint of improving adhesion by forming a film on a printing medium. The polymer particles B are preferably water-insoluble polymer particles that do not contain a pigment and are composed of a polymer alone.
Examples of polymers constituting the polymer particles B include vinyl resins, polyester resins, polyurethane resins, polystyrene resins, styrene-acrylic resins, and the like. One or more selected from resins, polyester resins, and polyurethane resins are preferable, and vinyl resins are more preferable. A polymer crosslinked with a crosslinking agent can also be used.
Polymer particles B are preferably used as an aqueous dispersion in which they are dispersed in water. Polymer particles B may be appropriately synthesized or may be commercially available.

The vinyl-based resin is preferably a water-insoluble vinyl-based resin obtained by copolymerizing a monomer mixture B containing (b1) an ionic monomer and (b2) a hydrophobic monomer.
The component (b1) is the same as the component (a1), but among them, anionic monomers are preferable, carboxylic acid monomers are more preferable, and acrylic acid monomers are more preferable from the viewpoint of improving ink adhesion and storage stability. and one or more selected from methacrylic acid is more preferable.
Component (b2) includes alkyl (meth)acrylates, aromatic group-containing monomers, and macromonomers similar to component (a3). Among these, alkyl (meth)acrylates are preferable, and those having an alkyl group having 1 to 22 carbon atoms, preferably 1 to 10 carbon atoms are more preferable, and the above-exemplified compounds are more preferable, and methyl (meth)acrylate and A combined use with 2-ethylhexyl (meth)acrylate is even more preferred.

(Content of Each Structural Unit in Polymer Constituting Polymer Particle B)
The contents of the structural units derived from the components (b1) and (b2) in the polymer constituting the polymer particles B are as follows from the viewpoint of improving the adhesion and storage stability of the ink.
The content of component (b1) is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less. , more preferably 15% by mass or less.
The content of component (b2) is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, and preferably 99% by mass or less, more preferably 97% by mass or less. , more preferably 95% by mass or less.

The polymer can be produced by copolymerizing a monomer mixture containing (b1) an ionic monomer, (a2) a nonionic monomer, etc., by a known solution polymerization method or the like.
Examples of commercially available dispersions of polymer particles B include "Neocryl A1127" (manufactured by DSM Neo Resins, anionic self-crosslinking aqueous acrylic resin) and "Joncryl 390" (manufactured by BASF Japan Ltd.). Acrylic resins such as "WBR-2018" and "WBR-2000U" (manufactured by Taisei Fine Chemical Co., Ltd.) and other urethane resins, and styrene such as "SR-100" and "SR102" (manufactured by Nippon A&L Co., Ltd.) - butadiene resins, "Joncryl 7100", "Joncryl 7600", "Joncryl 734", "Joncryl 780", "Joncryl 537J", "Joncryl 538J", "Joncryl PDX-7164", "Joncryl Styrene-acrylic resins such as Kryl PDX-7775 (manufactured by BASF Japan Ltd.).

(Average particle size of polymer particles B)
The average particle size of the polymer particles B is 30 nm or more and 220 nm or less from the viewpoint of improving ink adhesion and storage stability.
From the same viewpoint as above, the average particle size of the polymer particles B is preferably 32 nm or more, more preferably 40 nm or more, still more preferably 50 nm or more, and is preferably 200 nm or less, more preferably 180 nm or less, and still more preferably. is 150 nm or less.
Moreover, the average particle size of the polymer particles B is preferably smaller than the average particle size of the pigment particles A from the viewpoint of improving the adhesion and storage stability of the ink. From the same viewpoint as above, the difference between the average particle diameter of the polymer particles B and the average particle diameter of the pigment particles A is preferably 70 nm or more, more preferably 100 nm or more, still more preferably 150 nm or more, and even more preferably 180 nm or more. and is preferably 350 nm or less, more preferably 320 nm or less, still more preferably 290 nm or less.

(Polydispersity index in particle size distribution of polymer particles B)
The polydispersity index in the particle size distribution of polymer particles B is 0.08 or more and 0.32 or less from the viewpoint of improving ink adhesion and storage stability.
"Polydispersity Index (PDI)" has the same meaning as above.
From the same viewpoint as above, the polydispersity index of the polymer particles B is preferably 0.09 or more, more preferably 0.10 or more, still more preferably 0.11 or more, and preferably 0.30 or less. It is more preferably 0.29 or less, still more preferably 0.28 or less.
The average particle diameter and polydispersity index of polymer particles B are measured by the methods described in Examples.
The average particle size and polydispersity index of the polymer particles B can be adjusted by adjusting the dispersion conditions such as dispersion strength and dispersion time when the polymer is dispersed in a medium such as water. Moreover, it is also possible to select and use a commercial product that satisfies the above average particle size and polydispersity index.

The weight-average molecular weight of the polymer constituting the polymer particles B is preferably 100,000 or more, more preferably 200,000 or more, and still more preferably 300,000 or more, from the viewpoint of improving ink adhesion and storage stability, and , preferably 2,500,000 or less, more preferably 1,000,000 or less, and still more preferably 600,000 or less.
The acid value of the polymer constituting the polymer particles B is preferably 20 mgKOH/g or more, more preferably 30 mgKOH/g or more, still more preferably 40 mgKOH/g or more, from the viewpoint of improving ink storage stability. is 70 mgKOH/g or less, more preferably 65 mgKOH/g or less, still more preferably 60 mgKOH/g or less.
The weight average molecular weight and acid value of the polymer are measured by the methods described in Examples.

<Preservative compound>
The inks of the present invention contain an antiseptic compound. The antiseptic compound used in the present invention is one or more selected from isothiazoline compounds, aromatic alcohol compounds, and pyrithione metal complexes. The antiseptic compound used in the present invention is more preferably an isothiazoline compound from the viewpoint of improving ink adhesion and storage stability. It is believed that these antiseptic compounds not only impart antiseptic performance to the ink, but also suppress aggregation of the ink to improve storage stability and improve the adhesion of the pigment particles A and polymer particles B to the printing medium. be done.

(isothiazoline compound)
An isothiazoline compound is a compound having a five-membered heterocyclic ring containing a nitrogen atom and a sulfur atom. Specific examples thereof include 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-ethyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-ethyl-4-isothiazolin-3-one, 4,5-dichloro-2-methyl-4-isothiazolin-3-one, 2-ethyl-4-isothiazolin-3-one, 2-n-octyl-4- isothiazolin-3-one, 5-chloro-2-ethyl-4-isothiazolin-3-one, 5-chloro-2-t-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-n- octyl-4-isothiazolin-3-one, 4,5-dichloro-2-cyclohexyl-4-isothiazolin-3-one, 1,2-benzisothiazolin-3-one, butyl-benzisothiazolin-3-one and the like. be done.
Among these are 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-ethyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2 -ethyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, 4,5-dichloro -2-Cyclohexyl-4-isothiazolin-3-one, and one or more selected from 1,2-benzisothiazolin-3-one and butyl-benzisothiazolin-3-one, and 1,2-benzisothiazolin-3 -one, butyl-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, and 2-n-octyl-4-isothiazolin -3-one is more preferred, and one or more selected from 1,2-benzisothiazolin-3-one and butyl-benzisothiazolin-3-one is more preferred.

(Aromatic alcohol compound)
Examples of aromatic alcohol compounds include benzyl alcohol, 2-phenylethanol, 2-phenoxyethanol, phenoxyisopropanol, 3-(4-chlorophenoxy)-1,2-propanediol and the like. Among these, one or more selected from 2-phenoxyethanol and phenoxyisopropanol are preferred, and 2-phenoxyethanol is more preferred.

(Pyrithione metal complex)
A pyrithione metal complex is a compound consisting of a combination of one or more pyrithione molecules and one or more metals, more specifically 2-pyridylthiol-1-oxide or di(2-pyridylthiol-1 -oxide) and other metal complexes of pyrithione compounds.
Metals of pyrithione metal complexes include lithium, sodium, potassium, magnesium, calcium, copper, zinc, bismuth, and the like.
Among these, a pyrithione sodium complex and a pyrithione zinc complex are preferred, and a pyrithione zinc complex is more preferred. Pyrithione zinc complexes are prepared by reacting 1-hydroxy-2-pyridinethione (pyrithionic acid) or its soluble salts with zinc salts such as zinc sulfate, as disclosed in US Pat. No. 2,809,971. can be obtained by
The above antiseptic compounds may be used alone or in combination of two or more.

<Surfactant>
In the present invention, it is preferable to further contain a surfactant from the viewpoint of improving the adhesion and storage stability of the ink.
The surfactant to be used is preferably a nonionic surfactant, more preferably one or more selected from acetylene glycol-based surfactants and silicone-based surfactants, from the viewpoint of wettability to the print medium, and acetylene glycol-based surfactants. It is more preferable to contain an active agent and a silicone-based surfactant.

As the acetylene glycol-based surfactant, from the same viewpoint as above, acetylene glycol having 8 to 22 carbon atoms and an ethylene adduct of the acetylene glycol are preferable, and acetylene glycol having 8 to 22 carbon atoms is more preferable. The number of carbon atoms in the acetylene glycol is preferably 10 or more, more preferably 12 or more, and is preferably 20 or less, more preferably 18 or less, and still more preferably 16 or less. Specifically, from the viewpoint of improving leveling properties, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, and 2,5-dimethyl-3-hexyne-2,5-diol, and ethylene oxide adducts of the acetylene glycol. Among these, 2,4,7,9-tetramethyl-5-decyne-4,7-diol is preferred.

HLB of the acetylene glycol-based surfactant is preferably 0 or more, more preferably 1 or more, still more preferably 2 or more, still more preferably 2.5 or more, and preferably 5 or less, more preferably 4.5. It is 5 or less, more preferably 4 or less, and even more preferably 3.5 or less.
Here, the HLB (Hydrophile-Lypophile Balance) value is a value that indicates the affinity of a surfactant for water and oil, and can be obtained from the following equation by Griffin's method.
HLB = 20 x [(molecular weight of hydrophilic group contained in surfactant)/(molecular weight of surfactant)]
Hydrophilic groups contained in surfactants include, for example, hydroxyl groups and ethyleneoxy groups.

Specific examples of these commercially available include Surfynol 104 (2,4,7,9-tetramethyl-5-decyne-4,7-diol, EO average addition moles Number: 0, HLB: 3.0), 104E (50% dilution of Surfynol 104 with ethylene glycol), 104PG-50 (50% dilution of Surfynol 104 with propylene glycol), Surfynol 420 (Surfinol 104 EO average added moles: 1.3, HLB: 4.7), Kawaken Fine Chemicals Co., Ltd. acetylenol E13T (EO average added moles: 1.3, HLB: 4.7), and the like.

Examples of silicone surfactants include dimethylpolysiloxane, polyether-modified silicone, amino-modified silicone, carboxy-modified silicone, methylphenylpolysiloxane, fatty acid-modified silicone, alcohol-modified silicone, aliphatic alcohol-modified silicone, epoxy-modified silicone, fluorine-modified Examples include silicone, cyclic silicone, and alkyl-modified silicone. Among these, polyether-modified silicone is preferable from the viewpoint of wettability to the printing medium.
Polyether-modified silicones include PEG-3 dimethicone, PEG-9 dimethicone, PEG-9 PEG-9 dimethicone, PEG-9 methyl ether dimethicone, PEG-10 dimethicone, PEG-11 methyl ether dimethicone, PEG/PPG-20/22 Butyl ether dimethicone, PEG-32 methyl ether dimethicone, PEG-9 polydimethylsiloxyethyl dimethicone, lauryl PEG-9 polydimethylsiloxyethyl dimethicone and the like. Among these, PEG-11 methyl ether dimethicone is particularly preferred.
Specific examples of commercially available silicone surfactants include Silicone KF-6011, KF-6012, KF-6013, KF-6015, KF-6016, KF-6017 and KF from Shin-Etsu Chemical Co., Ltd. -6028, KF-6038, KF-6043, TEGO wet240, TEGO wet270 manufactured by Evonik Japan Co., Ltd., and the like.

Surfactants may contain other surfactants than those described above. Other surfactants preferably include anionic surfactants, nonionic surfactants other than the above, and amphoteric surfactants.
The above surfactants can be used alone or in combination of two or more.

<Other ingredients>
The ink of the present invention may contain various additives such as a water-soluble organic solvent, a pH adjuster, a viscosity adjuster, an antifoaming agent, and an antirust agent as optional components depending on its use.

(Content of each component in aqueous gravure ink)
The content of each component in the ink of the present invention is as follows from the viewpoint of improving the adhesion and storage stability of the ink. Here, the ink means the one prepared so that it can be used for printing as it is, and indicates the content of each component in the ink in this state.
The content of the pigment particles A in the ink of the present invention is preferably 2% by mass or more, more preferably 5% by mass or more, still more preferably 8% by mass or more, and even more preferably 10% by mass or more, and It is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less, and even more preferably 28% by mass or less.
The content of the polymer particles B in the ink of the present invention is preferably 2% by mass or more, more preferably 4% by mass or more, still more preferably 5% by mass or more, from the viewpoint of improving the adhesion of the ink, and , preferably 25% by mass or less, more preferably 20% by mass or less, and still more preferably 15% by mass or less.
In the ink of the present invention, the mass ratio of polymer particles B to pigment particles A [polymer particles B/pigment particles A] is preferably 0.2 or more, more preferably 0.3 or more, from the viewpoint of ink stability. It is more preferably 0.4 or more, and preferably 3 or less, more preferably 2 or less, and still more preferably 1 or less.
The content of the antiseptic compound in the ink of the present invention is preferably 0.002% by mass or more, more preferably 0.004% by mass or more, still more preferably 0.01% by mass or more, and still more preferably 0.04%. % by mass or more, more preferably 0.06% by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less.

The content of surfactants, particularly nonionic surfactants, in the ink of the present invention is preferably 0.1% by mass or more, more preferably 0.2% by mass, from the viewpoint of improving wettability to printing media. Above, more preferably 0.5% by mass or more, preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less.
The content of the acetylene glycol-based surfactant in the ink of the present invention is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably, from the viewpoint of improving wettability to a printing medium. is 0.7% by mass or more, and preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3.5% by mass or less.
The mass ratio of the acetylene glycol-based surfactant to the total amount of the acetylene glycol-based surfactant and the silicone surfactant in the ink of the present invention [acetylene glycol-based surfactant/total amount of surfactant] is preferably 0. .1 or more, more preferably 0.2 or more, still more preferably 0.3 or more, and preferably 1.2 or less, more preferably 1 or less, still more preferably 0.8 or less.
The water content in the ink of the present invention is preferably 50% by mass or more, more preferably 52% by mass or more, still more preferably 55% by mass or more, and preferably 70% by mass or less, more preferably 68% by mass. % by mass or less, more preferably 65% by mass or less.

The Zahn cup viscosity of the ink of the present invention at 20°C is preferably 10 seconds or more, more preferably 12 seconds or more, still more preferably 13 seconds or more, from the viewpoint of improving the adhesion and storage stability of the ink, and , preferably 25 seconds or less, more preferably 20 seconds or less, still more preferably 18 seconds or less.
The pH of the ink of the present invention at 20°C is preferably 5.5 or higher, more preferably 6.0 or higher, and still more preferably 6.5 or higher, from the viewpoint of improving dispersion stability. From the viewpoint of skin irritation, it is preferably 11.0 or less, more preferably 10.5 or less, and even more preferably 10.0 or less.

<Print media>
The ink of the present invention may be used for gravure printing without any particular limitation, but from the viewpoint of adhesion, it is suitable for low liquid absorption or non-low liquid absorption printing media. For example, low liquid absorption paper such as coated paper, art paper, synthetic paper, processed paper; non-low liquid absorption resin film such as polyester film, polyethylene film, polypropylene film, polystyrene film, vinyl chloride film, nylon film, etc. is mentioned. Among these, it is preferable to use a resin film, which has a limited heating temperature, as the print medium because it has excellent adhesion without being heated to a high temperature.
In recent years, the use of resin films as printing media has been increasing, and the ink of the present invention has excellent adhesion to resin films as well. As the resin film, a polyester film and a polypropylene film are preferable from the viewpoint of suitability for post-processing such as punching after manufacturing a printed matter. These resin films may be biaxially stretched films, uniaxially stretched films, or non-stretched films.
Moreover, from the viewpoint of improving the suitability for gravure printing, a resin film subjected to surface treatment by electrical discharge processing such as corona discharge treatment or plasma discharge treatment may be used.

In the following Production Examples, Examples, and Comparative Examples, "parts" and "%" are "mass parts" and "mass%" unless otherwise specified. Each physical property was measured by the following method.

(1) Measurement of weight-average molecular weight of polymer Gel chromatography method using a solution obtained by dissolving phosphoric acid and lithium bromide in N,N-dimethylformamide at concentrations of 60 mmol/L and 50 mmol/L, respectively, as an eluent. [Tosoh Corporation GPC apparatus (HLC-8320GPC), Tosoh Corporation columns (TSKgel SuperAWM-H, TSKgel SuperAW3000, TSKgel guardcolumn Super AW-H), flow rate: 0.5 mL / min], the molecular weight is known as a standard substance monodisperse polystyrene kit [PStQuick B (F-550, F-80, F-10, F-1, A-1000), PStQuick C (F-288, F-40, F-4, A-5000, A -500), manufactured by Tosoh Corporation].
A sample to be measured was obtained by mixing 0.1 g of the resin with 10 mL of the eluent in a glass vial, stirring with a magnetic stirrer at 25° C. for 10 hours, and using a syringe filter (DISMIC-13HP PTFE 0.2 μm, Advantech Co., Ltd.). and used after filtration.

(2) Measurement of solid content concentration of pigment water dispersion and polymer emulsion Using an infrared moisture meter "FD-230" (manufactured by Kett Science Laboratory Co., Ltd.), 5 g of the measurement sample is dried at 150 ° C., measurement mode 96 ( After drying under the conditions of monitoring time 2.5 minutes/fluctuation width 0.05%), the water content (%) of the measurement sample was measured, and the solid content concentration was calculated by the following formula.
Solid content concentration (%) = 100 - moisture of measurement sample (%)

(3) Pigment aqueous dispersion, measurement of average particle size and polydispersity index of particles in polymer emulsion Cumulant average particle size using a laser particle analysis system (manufactured by Otsuka Electronics Co., Ltd., model number: ELS-8000, cumulant analysis) was measured, and the average particle size of the cumulants was taken as the average particle size of the particles in the aqueous pigment dispersion and the polymer emulsion. The polydispersity index was also determined.
A dispersion diluted with water so that the concentration of particles to be measured was 5×10 ⁻³ mass % was used as a measurement sample. The measurement conditions were a temperature of 25° C., an angle between the incident light and the detector of 90°, and 100 integration times, and the refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

Production Example 1 (Production of Aqueous Pigment Dispersion 1 Containing Pigment-Containing Polymer Particles A1)
Weigh 236 parts of ion-exchanged water in a 2 L flask, styrene-acrylic polymer (manufactured by BASF, trade name: Joncryl 690, weight average molecular weight: 16500, acid value: 240 mgKOH / g, Tg: 105 ° C.) 60 parts, 36.5 parts of 5N sodium hydroxide solution (sodium neutralization degree of 60 mol %) was added. The mixture was stirred at 200 rpm for 2 hours using an anchor blade to obtain 332.5 parts of an aqueous polymer solution (solid content concentration: 19.9%).
554 parts of zirconia beads with a diameter of 0.8 mm (manufactured by Nikkato Co., Ltd., trade name: XTZ balls) (filling rate of beads: 30% by volume) were placed in a 500 ml plastic container, and 25.1 parts of an aqueous polymer solution and titanium dioxide as a pigment were added. (manufactured by Ishihara Sangyo Co., Ltd., product name: CR-90, chlorine method titanium oxide (rutile type), average primary particle size 250 nm, Al Si treatment) 200 parts, 194.9 parts of ion-exchanged water are added, paint Dispersion was carried out for 2 hours using a shaker (manufactured by Asada Iron Works Co., Ltd., trade name: PS-1943). After that, the zirconia beads were removed with a 200-mesh wire mesh, and a pigment aqueous dispersion 1 containing pigment-containing polymer particles A1 having a solid concentration of 50% (pigment content: 48.8%, average particle size: 154 nm, polydispersity index: 0.11) 974 parts.

Production Examples 2-5 (Production of Aqueous Pigment Dispersions 2-5 Containing Pigment-Containing Polymer Particles A2-A5)
Aqueous pigment dispersions 2 to 5 containing pigment-containing polymer particles A2 to A5 having a solid content of 50% were prepared in the same manner as in Production Example 1, except that the pigment dispersion conditions were changed as shown in Table 1. got Table 1 shows the results.

Example 1 (Preparation of aqueous gravure ink 1)
52.5 parts of aqueous pigment dispersion 1 containing pigment-containing polymer particles 1 obtained in Production Example 1 was placed in a production container so as to have the ink composition shown in Table 2 (pigment in ink: 25%, pigment particles A: equivalent to 26%), polymer emulsion P1 (manufactured by BASF, trade name: Joncryl PDX-7775, styrene-acrylic polymer emulsion, average particle size 73 nm, acid value 55 mgKOH / g, polydispersity index 0.11, Solid concentration: 45%, polymer particles B in the ink: 26.7 parts (corresponding to 12%) was added and stirred at 150 rpm.
Further, an acetylene glycol-based surfactant (2,4,7,9-tetramethyl-5-decyne-4,7-diol (HLB: 3.0), manufactured by Nissin Chemical Industry Co., Ltd., trade name: Surfynol 104 , effective content 100%) 1.0 parts, polyether-modified silicone surfactant (manufactured by Evonik, trade name: TEGO wet240, effective content 100%) 0.5 parts, antiseptic compound A1 (manufactured by Lonza Japan Co., Ltd. , trade name: Proxel LV (S), 1,2-benzisothiazolin-3-one, active content 20%) 0.10 parts and 19.2 parts of ion-exchanged water are added and stirred at room temperature for 30 minutes. After that, it was filtered through a stainless wire mesh (200 mesh) to obtain Ink 1. Table 2 shows the results. The total amount of each component in Table 2 is 100 parts.

Examples 2-12, Comparative Examples 1-6 (Preparation of aqueous gravure inks 2-12, 31-36)
Aqueous gravure inks 2 to 12 and 31 to 36 were prepared in the same manner as in Example 1, except that the conditions were changed to those shown in Table 2.

The details of each notation in Table 2 are as follows.
(polymer emulsion)
· P1: manufactured by BASF, trade name: Joncryl PDX-7775, acrylic polymer emulsion, average particle size 73 nm, polydispersity index 0.11
・P2: manufactured by ADEKA Co., Ltd., trade name: ADEKA BONDITTER HUX-564, polyurethane emulsion, average particle size 180 nm, polydispersity index 0.20
・P3: Takamatsu Oil Co., Ltd., trade name: Pesresin A-645GH, polyester emulsion, average particle size 34 nm, polydispersity index 0.28
・ P4: Seiko PMC Co., Ltd., trade name: KE-1062, styrene acrylic emulsion, average particle size 93 nm, polydispersity index 0.06
・ P5: manufactured by ADEKA Co., Ltd., trade name: ADEKA BONDTER HUX-232, polyurethane emulsion, average particle size 25 nm, polydispersity index 0.33
The solid content (polymer particle B) concentration of polymer emulsions P1 to P5 is all 45%.
(antiseptic compound)
・ A1: manufactured by Lonza Japan Co., Ltd., product name: Proxel LV (S), 1,2-benzisothiazolin-3-one, active ingredient 20%
· A2: Sigma Aldrich, trade name: ProClin950, a mixture of 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, effective content 9.5%
・ A3: Tokyo Chemical Industry Co., Ltd., 2-n-octyl-4-isothiazolin-3-one, effective content 100%
・ A4: manufactured by Lonza Japan Co., Ltd., product name: DENSIL DN, butyl-benzisothiazolin-3-one, active ingredient 100%
・ A5: manufactured by Lonza Japan Co., Ltd., product name: Zinc Omdine ZOE, zinc pyrithione, effective content 55%
・ A6: Tokyo Chemical Industry Co., Ltd., 2-phenoxyethanol, effective content 100%

Using inks 1 to 12 obtained in Examples 1 to 12 and inks 31 to 36 obtained in Comparative Examples 1 to 6, the following printing test was performed to evaluate adhesion and storage stability. Table 2 shows the results.
<Print test>
Using the inks obtained in Examples and Comparative Examples, gravure printing was performed on the corona discharge-treated surface of a PET film (trade name: FE-2001, #12, manufactured by Futamura Chemical Co., Ltd.).
Printing was performed using a desktop gravure printing test machine (manufactured by Matsuo Sangyo Co., Ltd., trade name: K printing proofer) with an attached electronic engraving plate (line number 175 lines / inch, plate depth 31 μm). Solid with 100% halftone dots. After printing and drying on a hot plate (60° C.) for 5 minutes, a printed matter was obtained.

<Evaluation of Adhesion>
An adhesive tape (trade name: Cellotape (registered trademark), CT-15S, 15 mm width, manufactured by Nichiban Co., Ltd.) was attached to the solid printed portion, and the peeled area of the printed matter after peeling was evaluated according to the following indices.
A: Peeling area 0% or more and less than 5% B: Peeling area 5% or more and less than 10% C: Peeling area 10% or more and less than 20% D: Peeling area 20% or more and less than 50% E: Peeling area 50% or more In addition, C If there is more than this, there is no problem in terms of practical use.

<Evaluation of storage stability>
The inks obtained in Examples and Comparative Examples were stored in a constant temperature bath set at 40° C. for one month, and the rate of change from the initial average particle size was evaluated using the following index.
Particle size change rate (%)=[(Average ink particle size after storage/Average ink particle size before storage)−1]×100
A: Particle size change rate of 0% or more and less than 5% B: Particle size change rate of 5% or more and less than 10% C: Particle size change rate of 10% or more and less than 20% D: Particle size change rate of 20% or more and less than 50% E: Grain size change rate of 50% or more If C or more, there is no problem in terms of practical use.

Table 2 shows that the water-based gravure inks of Examples 1-12 are superior to the water-based gravure inks of Comparative Examples 1-6 in ink adhesion and ink storage stability. From this, it can be seen that high-quality gravure prints can be obtained by using the water-based gravure ink of the present invention.

Claims (7)

An aqueous gravure ink comprising pigment particles A, polymer particles B, an antiseptic compound, and water,
The pigment particles A are polymer particles A containing a pigment, the polymer constituting the polymer particles A is one or more selected from vinyl resins, polyester resins, and polyurethane resins, and the average particle diameter of the polymer particles A is is 200 nm or more and 450 nm or less , and the polydispersity index in the particle size distribution of the polymer particles A is 0.08 or more and 0.32 or less,
The polymer constituting the polymer particles B is one or more selected from vinyl resins, polyester resins, and polyurethane resins, and the average particle size of the polymer particles B is 30 nm or more and 180 nm or less, and the polymer particles B are grains. The polydispersity index in the diameter distribution is 0.08 or more and 0.32 or less,
The antiseptic compound is 1,2-benzisothiazolin-3-one, butyl-benzisothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3 - one or more selected from 2-n-octyl-4-isothiazolin-3-one,
The content of the polymer particles A in the ink is 5% by mass or more and 40% by mass or less,
The content of the polymer particles B in the ink is 5% by mass or more and 25% by mass or less,
A water-based gravure ink , wherein the content of the antiseptic compound in the ink is 0.01% by mass or more and 1% by mass or less . 2. The water-based gravure ink according to claim 1, wherein the polymer constituting the polymer particles A is a vinyl resin. The water-based gravure ink according to claim 2, wherein the vinyl resin is a styrene-acrylic resin. The water-based gravure ink according to any one of claims 1 to 3, wherein the mass ratio of polymer particles B to polymer particles A in the ink [polymer particles B/polymer particles A] is 0.2 or more and 3 or less. 5. The water-based gravure ink according to any one of claims 1 to 4 , further comprising a nonionic surfactant. 6. The water-based gravure ink according to claim 5 , wherein the nonionic surfactant is one or more selected from acetylene glycol-based surfactants and silicone-based surfactants. The water-based gravure ink according to claim 5 or 6 , wherein the content of the nonionic surfactant is 0.1% by mass or more and 5% by mass or less.