JP2019001955A - Aqueous inkjet ink composition - Google Patents

Abstract

To provide an aqueous inkjet ink composition excellent in prevention of occurrence of mottling and occurrence of strike-through during printing.SOLUTION: An aqueous inkjet ink composition comprises a water-soluble organic solvent, water, a pigment and a pigment dispersant. In the ink composition, the water-soluble organic solvent contains one or more kinds of a and/or one or more kinds of b in an amount of 20 mass% or more or alternatively, one or more kinds of a and/or one or more kinds of b, and c in an amount of 20 mass% or more as given below: a: a solvent has an amount of the solvent dissolved in water of 50 g or more, has one or less OH group in one molecule, and has surface tension of 35 mN/m or less and a SP value of 10.0(cal/cm)or less; b: a solvent has an amount of the solvent dissolved in water of 50 g or more, has two OH groups in one molecule, and has surface tension of 35 mN/m or less and a SP value of 12.5(cal/cm)or less; and c: a solvent has an amount of the solvent dissolved in water of 50 g or more, has three or more OH groups in one molecule, and has surface tension of 60 mN/m or more and an SP value of 15.0(cal/cm)or more.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous inkjet ink composition.

  When printing on plain paper or coated paper for ink jet printing using water-based ink-jet ink, especially in areas where the printing rate is high on these papers, image quality declines due to the occurrence of mottling, There may be a case where the back-through occurs due to the ink soaking into the back side. These tendencies are prominent in portions exhibiting secondary or higher colors.

  It is known to adjust the composition of the water-soluble organic solvent in order to prevent the occurrence of motering as in the ink-jet ink compositions described in Patent Documents 1 and 2. However, no consideration has been given to preventing the occurrence of show-through in a portion with a high printing rate on the paper.

JP 2017-31272 A International Publication No. 2015/020128

  The problem to be solved by the present invention is not only to prevent the occurrence of motering during printing in the water-based inkjet ink composition, but also to prevent the occurrence of show-through in a portion where the printing rate on the paper is high, Furthermore, it is to achieve both improvement in storage stability and ejection stability of the inkjet ink composition.

The present inventors have found that the above-mentioned problems can be solved by containing a specific amount of a specific water-soluble organic solvent as the organic solvent, and have completed the present invention.
In an aqueous inkjet ink composition containing a water-soluble organic solvent, water, a pigment, and a pigment dispersant,
As the water-soluble organic solvent, one or more of the following water-soluble organic solvents a and / or one or more of the water-soluble organic solvents of the following b are contained in a total of 20% by mass or more in the ink composition. Or one or more of the following water-soluble organic solvents a and / or one or more of the following water-soluble organic solvents b, and further containing the water-soluble organic solvent c below, A water-based inkjet ink composition containing a total of 20% by mass or more of organic solvents in the ink composition.
a. The amount dissolved in 100 g of water at 20 ° C. is 50 g or more, has no OH group in one molecule, or has one OH group, has a surface tension of 35 mN / m or less, and an SP value of 10. 0 (cal / cm ³ ) A water-soluble organic solvent that is ^0.5 or less.
b. The amount dissolved in 100 g of water at 20 ° C. is 50 g or more, has two OH groups in one molecule, has a surface tension of 35 mN / m or less, and an SP value of 12.5 (cal / cm ³ ) ⁰ Water-soluble organic solvent that is ^.5 or less.
c. The amount dissolved in 100 g of water at 20 ° C. is 50 g or more, has 3 or more OH groups in one molecule, has a surface tension of 60 mN / m or more, and an SP value of 15.0 (cal / cm ³ ). Water-soluble organic solvent that is ^0.5 or more.

  The water-based ink-jet ink composition of the present invention is excellent in prevention of occurrence of motoring and back-through, even when printing is performed on plain paper or coated paper for ink-jet printing so that the printing rate is high. An aqueous inkjet ink composition having excellent stability and storage stability can be provided.

(Water-soluble organic solvent)
As the water-soluble organic solvents (a) to (c) below that constitute the aqueous inkjet ink composition of the present invention, the following can be used. In combination with the following other water-soluble organic solvents, the surface tension, SP value, and solubility in water are shown in Table 1 below.
a. Examples thereof include diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, diethylene glycol diethyl ether, tripropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, and diethylene glycol monoethyl ether acetate.
b. Examples thereof include dipropylene glycol, tripropylene glycol, 1,2-pentanediol, 1,2-hexanediol, and the like.
c. Examples thereof include glycerin and diglycerin.

The above-mentioned water-soluble organic solvents a to c are used in one or more of them, and examples of combinations include those from a to one or more and / or b to one or more, and those further using c in combination. It is done. These water-soluble organic solvents are blended so that the total amount is 20% by mass or more, preferably 20 to 60% by mass, and more preferably 23 to 40% by mass in the aqueous inkjet ink composition. When it is less than 20% by mass, it is particularly difficult to prevent the showthrough.
However, rather than using the water-soluble organic solvent c above, only one or more water-soluble organic solvents a and / or one or more water-soluble organic solvents b are used without using the water-soluble organic solvent c. This tends to be preferable at least in terms of preventing the occurrence of motoring.

(Other water-soluble organic solvents)
In addition to the water-soluble organic solvents a to c, other water-soluble organic solvents that do not satisfy the requirements a to c can be blended within a range not impairing the effects of the present invention. However, it is preferable not to mix them in terms of preventing the occurrence of motoring and the occurrence of breakthrough.
Examples of such other water-soluble organic solvents include monoalcohols, polyhydric alcohols, lower alkyl ethers of polyhydric alcohols, ketones, ethers, esters, nitrogen-containing compounds, and the like. it can. These may be used alone or in combination of two or more.

  Specific examples of the monoalcohols include methanol, ethanol, n-propanol, n-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, n-nonyl alcohol, n-decanol, and these. Isomers, cyclopentanol, cyclohexanol and the like, and preferably an alcohol having an alkyl group with 1 to 6 carbon atoms.

  Specific examples of the polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, , 2-cyclohexanediol, heptanediol, octanediol, 1,9-nonanediol, 1,10-decanediol, pentaerythritol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, tetrapropylene glycol, thiodiglycol, etc. Is mentioned.

  Specific examples of the lower alkyl ethers of the polyhydric alcohol include ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, ethylene glycol isopropyl ether, ethylene glycol isobutyl ether. , Propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether etc And the like.

Specific examples of the ketones include acetone, methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diisopropyl ketone, cyclopentanone, and cyclohexanone.
Specific examples of the ethers include isopropyl ether, n-butyl ether, tetrahydrofuran, tetrahydropyran, 1,4-dioxane and the like.
Examples of the esters include propylene carbonate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, ethyl butyrate, dibutyl phthalate, dioctyl phthalate, and ε-caprolactone, ε -Cyclic esters such as caprolactam.
Examples of the nitrogen-containing compound include urea, pyrrolidone, N-methyl-2-pyrrolidone, octyl pyrrolidone and the like.
The content of the other water-soluble organic solvent is preferably 0 to 20% by mass in the aqueous inkjet ink composition.
In addition, it is also possible not to mix propylene carbonate.

Moreover, in order to further improve the dryness adjustment and the prevention of occurrence of motering, an alkylene glycol derivative having a flash point of 50 to 150 ° C. other than diethylene glycol dialkyl ether can be used in combination.
Examples of the alkylene glycol derivative having a flash point of 50 to 150 ° C. include (poly) ethylene glycol dialkyl ethers such as ethylene glycol diethyl ether, ethylene glycol dimethyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, (Poly) propylene glycol dialkyl ethers such as propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, propylene glycol diethyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl (Poly) polypropylene glycol monoalkyl ether such as ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, di (Poly) polypropylene glycol monoalkyl ether monoalkyl ester such as propylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol (Poly) ethylene glycol monoethers such as nobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, (Poly) ethylene glycol monoester such as ethylene glycol monomethyl acetate, ethylene glycol monoethyl acetate, ethylene glycol monobutyl acetate, diethylene glycol monomethyl acetate, triethylene glycol monomethyl acetate, ethylene glycol diacetate, diethylene glycol diacetate, (Poly) ethylene glycol diester such as reethylene glycol diacetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol propyl ether acetate, triethylene glycol Examples include (poly) ethylene glycol monoether monoesters such as monobutyl ether, triethylene glycol ethyl ether acetate, and triethylene glycol butyl ether acetate.
Further, the total amount of the organic solvent is preferably an amount that occupies 20.0 to 60.0% by mass in the total ink composition. When the total amount exceeds 60.0% by mass, the printability of the resulting ink is deteriorated. On the other hand, when the total amount is less than 20.0% by mass, the viscosity of the ink is increased, and the ink from the nozzle This is not preferable because the dischargeability tends to decrease.

(Pigment)
As the pigment constituting the aqueous ink-jet ink composition of the present invention, known inorganic pigments and organic pigments conventionally used in aqueous ink-jet ink compositions can be used.
Specific examples of conventionally known inorganic pigments include carbon black, titanium oxide, zinc white, zinc oxide, tripone, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate, calcium carbonate, silica, and alumina. , Cadmium red, Bengal, Molybdenum red, Chrome vermilion, Molybdate orange, Yellow lead, Chrome yellow, Cadmium yellow, Yellow iron oxide, Titanium yellow, Chromium oxide, Pyridian, Cobalt green, Titanium cobalt green, Cobalt chrome green, Ultramarine blue Ultramarine blue, bitumen, cobalt blue, cerulean blue, manganese violet, cobalt violet, mica and the like.
Specific examples of organic pigments include azo, azomethine, polyazo, phthalocyanine, quinacridone, anthraquinone, indigo, thioindigo, quinophthalone, benzimidazolone, isoindoline, and isoindolinone. Organic pigments are listed, and specific examples are shown by color index. Pigment Black 7, Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 60, Pigment Green 7, 36, Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 149, 168, 177, 178, 179, 206, 207, 209, 242, 254, 255, Pigment Violet 19, 23, 29, 30, 37 , 40, 50, Pigment Yellow 12, 13, 14, 17, 20, 24, 4, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, Pigment orange 36, 43, 51, 55, 59, 61, 71, 74, and the like.
These pigments can be used alone or in combination of two or more, and the amount used is preferably 1.0 to 10.0% by mass, more preferably based on the total amount of the water-based inkjet ink composition. Is 2.0-7.0 mass%. When the amount of the pigment used is less than 1.0% by mass, the coloring power tends to be insufficient. On the other hand, when it exceeds 10.0% by mass, the viscosity increases and the fluidity of the ink tends to decrease.

(Pigment dispersant)
Next, a known pigment dispersant can be used as the pigment dispersant constituting the aqueous inkjet ink composition of the present invention. The pigment dispersant has both a group having affinity for the pigment and a group having affinity for the solvent.
In the present invention, the pigment dispersant having a group having an affinity for a solvent or the like is preferably a resin. For example, an acrylic resin, a styrene acrylic resin, a maleic acid resin, a styrene maleic resin, an α-olefin maleic resin, a urethane resin, Examples include ester resins. Among them, it is preferable to use an acrylic resin or a styrene acrylic resin from the viewpoint of stabilizing the pigment dispersion.
As the group having affinity for the pigment, a structure of the pigment or a group close to the structure / polarity of the pigment is used, and examples thereof include a carboxyl group and an amino group.

(Acrylic resin)
An acrylic resin can be blended in the aqueous inkjet ink composition of the present invention. Examples of the acrylic resin include a copolymer composed of a monomer having a polar group such as (meth) acrylic acid and a monomer such as (meth) acrylate that is soluble in water or an aqueous organic solvent. . Such (meth) acrylates include, for example, alkyl (meth) acrylates such as ethyl, propyl, or butyl (meth) acrylate; hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl (meth) acrylate, etc. Examples thereof include hydroxyalkyl (meth) acrylate.
These acrylic resins may be used alone or in combination of two or more.

The amount of the acrylic resin used is preferably 0.5 to 5.0% by mass, more preferably 1.0 to 4.0% by mass, and even more preferably 1.5% with respect to the total amount of the aqueous inkjet ink composition. It is -3.0 mass%.
If the total amount of acrylic resin used is less than 0.5% by mass, the fixability to the substrate is not sufficient and bleeding may occur, whereas if it exceeds 5.0% by mass, the solid content will increase excessively. There is a possibility that the discharge stability is lowered.

  As long as these performances do not deteriorate, resins that are soluble in water-soluble or water-soluble organic solvents other than the acrylic resins, such as vinyl chloride resins, vinyl chloride-vinyl acetate resins, and ethylene-vinyl acetate resins. It is also possible to use a resin, a styrene-acrylic resin, a styrene-maleic acid resin, a cellulose resin, a maleic acid resin, or the like in combination.

(Other ingredients)
Furthermore, in the water-based inkjet ink composition of the present invention, other resins can be added as necessary within the range that does not impair the effects of the present invention. Furthermore, acetylene-based surfactants, plasticizers, surface conditioning Various additives such as an agent, an ultraviolet light inhibitor, a light stabilizer, and an antioxidant can be used.

(Production of aqueous ink-jet ink composition)
Next, a method for producing the water-based inkjet ink composition of the present invention using these materials will be described.
The aqueous inkjet ink composition of the present invention includes, for example, a wet circulation mill, a bead mill, a ball mill, a sand mill, an attritor, a roll mill, a DCP mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, and a high pressure homogenizer (microfluidizer). , Nanomizer, Ultimateizer, Genus PY, DeBEE2000, etc.) and a pearl mill.

(Use)
The water-based ink-jet ink composition of the present invention can be used for well-known applications, and is particularly suitable for use on the surface layer of plain paper or coated paper for ink-jet printing.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” means “mass%” and “part” means mass part.

<Alkali-soluble resin varnish>
25 parts by mass of a copolymer of acrylic acid / stearyl acrylate / styrene = 25/30/45 having a glass transition temperature of 40 ° C., a weight average molecular weight of 30,000, and an acid value of 185 mgKOH / g, and 4.9 parts by mass of potassium hydroxide It was dissolved in a mixed solution with 70.1 parts by mass of water to obtain an alkali-soluble resin varnish having a solid content of 25%.

<Water-based pigment ink base>
(Water-based yellow pigment ink base)
74 parts by mass of water was added to 16 parts by mass of the alkali-soluble resin varnish and mixed to prepare a resin varnish for pigment dispersion. To this varnish, 10 parts by mass of a yellow pigment (trade name Nova Palm Yellow 4G01, manufactured by Clariant) was further added, stirred and mixed, and then kneaded with a wet circulation mill to prepare an aqueous yellow ink base.

(Water-based magenta pigment ink base)
74 parts by mass of water was added to 16 parts by mass of the alkali-soluble resin varnish and mixed to prepare a resin varnish for pigment dispersion. To this varnish, 10 parts by mass of a magenta pigment (trade name Inkjet Magenta E5B02, manufactured by Clariant) was added, mixed with stirring, and then kneaded with a wet circulation mill to prepare an aqueous magenta pigment ink base.

(Water-based cyan pigment ink base)
74 parts by mass of water was added to 16 parts by mass of the alkali-soluble resin varnish and mixed to prepare a resin varnish for pigment dispersion. To this varnish was further added 10 parts by mass of a cyan pigment (trade name Heliogen Blue L7101F, manufactured by BASF), mixed with stirring, and then kneaded with a wet circulation mill to prepare an aqueous cyan pigment ink base.

(Water-based black pigment ink base)
74 parts by mass of water was added to 16 parts by mass of the alkali-soluble resin varnish and mixed to prepare a resin varnish for pigment dispersion. To this varnish, 10 parts by mass of carbon black (trade name Printex 90, manufactured by Daicel Evonik) was further added, stirred and mixed, and then kneaded with a wet circulation mill to prepare an aqueous black pigment ink base.

<Surfactant>
Surfynol 465 (active ingredient 100%, HLB13, manufactured by Nissin Chemical Industry Co., Ltd.)

Water-based inkjet ink compositions of Examples 1 to 31 and Comparative Examples 1 to 9 were prepared using various pigment ink bases so as to have the composition shown in Table 2 below.
Printing evaluation of water-based inkjet ink composition (storage stability)
The aqueous pigment-type inkjet ink compositions of Examples 1-31 and Comparative Examples 1-9 were filled in glass bottles and allowed to stand at 60 ° C. for 7 days, and then the viscosity of the aqueous pigment-type inkjet ink composition was measured. The storage stability was evaluated.
Evaluation criteria ○: Change rate from initial viscosity is less than 10%
Δ: Change rate from initial viscosity is 10% or more and less than 20% ×: Change rate from initial viscosity is 20% or more

(Discharge stability)
The aqueous ink-jet ink compositions of Examples 1 to 31 and Comparative Examples 1 to 9 are packed in an evaluation printer cartridge equipped with a Seiko Epson head and printed on photographic paper <Glossy> (Seiko Epson). The discharge stability was evaluated.
Evaluation criteria ○: There is no printing disturbance and can be ejected stably. △: There is some printing disturbance but it can be ejected. ×: There is printing disorder and it cannot be ejected stably.

(Motoring)
The ink compositions for water-based inkjets of Examples 1 to 31 and Comparative Examples 1 to 9 are packed in an evaluation printer cartridge equipped with a Seiko Epson head and printed on a Mitsubishi IJ form (Mitsubishi Paper Corporation). It was visually evaluated whether or not motering occurred for the secondary color.
Evaluation criteria ○: No irregularities on the print surface and good image quality Δ: Some unevenness on the print surface, inconspicuous ×: Conspicuous unevenness on the entire print surface, poor image quality

(Betrayal)
The ink compositions for water-based inkjets of Examples 1 to 31 and Comparative Examples 1 to 9 were packed in a cartridge for an evaluation printer equipped with a head manufactured by Seiko Epson, and a solid image was displayed on a Mitsubishi IJ foam (manufactured by Mitsubishi Paper Industries). Double-sided printing was performed, and the degree of ink penetration on the back side of the print was visually evaluated according to the following evaluation criteria.
Evaluation criteria ○: Slightly confirmed back-through △: Back-through can be confirmed, but image discrimination is possible even with double-sided printing ×: Back-through has been significantly confirmed, and image discrimination is possible with double-sided printing It is difficult

According to the results of Examples 1 to 31 shown in Table 2, if the water-based inkjet ink composition is in accordance with the composition of the present invention, the storage stability and the ejection stability are excellent, and the motoring Occurrence prevention and back-through prevention can be prevented.
On the other hand, according to Comparative Examples 1 to 9 in which the water-soluble organic solvents a and b are not used or are used in a small amount, at least motoring and strike-through occurred.

Claims (2)

In an aqueous inkjet ink composition containing a water-soluble organic solvent, water, a pigment, and a pigment dispersant,
As the water-soluble organic solvent, one or more of the following water-soluble organic solvents a and / or one or more of the water-soluble organic solvents of the following b are contained in a total of 20% by mass or more in the ink composition. Or one or more of the following water-soluble organic solvents a and / or one or more of the following water-soluble organic solvents b, and further containing the water-soluble organic solvent c below, A water-based inkjet ink composition containing a total of 20% by mass or more of organic solvents in the ink composition.
a. The amount dissolved in 100 g of water at 20 ° C. is 50 g or more, has no OH group in one molecule, or has one OH group, has a surface tension of 35 mN / m or less, and an SP value of 10. 0 (cal / cm ³ ) A water-soluble organic solvent that is ^0.5 or less.
b. The amount dissolved in 100 g of water at 20 ° C. is 50 g or more, has two OH groups in one molecule, has a surface tension of 35 mN / m or less, and an SP value of 12.5 (cal / cm ³ ) ⁰ Water-soluble organic solvent that is ^.5 or less.
c. The amount dissolved in 100 g of water at 20 ° C. is 50 g or more, has 3 or more OH groups in one molecule, has a surface tension of 60 mN / m or more, and an SP value of 15.0 (cal / cm ³ ). Water-soluble organic solvent that is ^0.5 or more. A is at least one selected from triethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, and diethyl glycol monobutyl ether, and b is 1,2-pentanediol, 1,2-hexanediol, di- The water-based inkjet ink composition according to claim 1, wherein at least one selected from propylene glycol and tripropylene glycol, and the c is at least one selected from glycerin or diglycerin.