JP2012184334A - Aqueous inkjet ink - Google Patents

Abstract

A water-based inkjet ink composition and a printed matter that are excellent in dispersibility and storage stability, eliminate nozzle clogging over time, and enable high print quality.
An ink composition comprising at least two kinds of azo pigments, a pigment-dispersing resin, water, and a water-soluble solvent as coloring components, and having a specific structural formula that is a constituent of the two kinds of azo pigments A water-based inkjet ink, wherein the content of the compound having a water content is 400 ppm or less, and the water-soluble solvent is at least one selected from glycol ethers and diols.
[Selection figure] None

Description

  The present invention relates to an aqueous inkjet ink composition having excellent color reproducibility and excellent ejection stability, dispersibility, and storage stability from inkjet nozzles.

  Conventionally, in ink jet printing, water-based ink using a water-soluble dye as a colorant has been mainly used. However, the dye ink has a drawback of being inferior in weather resistance and water resistance. Accordingly, studies have been made on pigment inks that use pigments instead of water-soluble dyes. In recent years, inkjet printers using pigment inks have been put to practical use as large-format printers in the sign display market. However, C.I. which is a color pigment used for pigment ink, particularly a pigment used for magenta color. I. Pigment red 122 and C.I. I. Pigment Bio Red 19 had a weak coloring power as compared with the magenta color of the dye, and the color reproduction range was not sufficiently satisfactory.

  In recent years, azo pigments have attracted attention as magenta pigments that can solve these problems. However, this azo pigment has problems such as poor dispersibility and stability over time and causes nozzle clogging, and various studies have been conducted. For example, Patent Document 1 describes an ink-jet ink in which an azo pigment is extracted and washed with methanol, and a pigment having a purity of 90% or more calculated from the weight ratio before and after the azo pigment is used. However, when the purity is 90%, the general formula (1), which is the cause of nozzle clogging, precipitates with time and causes nozzle clogging. Furthermore, there was no description of the amount of the general formula (1) in the ink, which was insufficient to solve the nozzle clogging. Patent Document 2 describes an ink-jet ink using a pigment for the purpose of keeping the amount of impurities in an azo pigment to a certain amount or less. However, with this pigment, the aggregation between the pigments is strong and the dispersibility is insufficient. Also, penetration of glycol ethers and diols added to improve the print quality by eliminating the occurrence of beading and white streaks due to insufficient penetration and spread of ink droplets on hard-to-penetrate substrates such as coated paper There is a problem that the preservability with time deteriorates due to the solvent. Therefore, it was difficult to use it for inkjet ink.

JP 2004-123866 A Special table 2007-533802 gazette

  The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain good dispersibility and storage stability with inkjet ink, no nozzle clogging over time, and excellent print quality and color reproduction. The present invention provides an ink-jet ink having good properties and satisfying other properties required for the ink-jet ink in a well-balanced manner.

The above object is achieved by the present invention described below.

That is, the present invention is an ink composition comprising at least two kinds of azo pigments, a pigment dispersion resin, water, and a water-soluble solvent as coloring components, and is a general formula (1) that is a constituent component of the azo pigment. The water-based ink-jet ink composition according to claim 1, wherein the water-soluble solvent is at least one selected from glycol ethers and diols.
Moreover, 2nd invention is related with the inkjet ink composition of the said invention shown by general formula (2) in which said 2 types of azo pigments contain general formula (1) as a structural component.

The third invention is a C.I. azo pigment of the general formula (2) wherein X1 is a methoxy group, Y1 is a hydrogen atom and Z1 is a chlorine atom. I. Pigment Red 269 and C.I. wherein R1 is a hydrogen atom. I. Pigment Red 150, or C.I. in which X1 is a methyl group, Y1 is a hydrogen atom, and Z1 is a chlorine atom. I. Pigment Red 147, or C.I. in which X1 is a methoxy group, Y1 is a chlorine atom, and Z1 is a methoxy group. I. The present invention relates to the inkjet ink composition according to any one of the above inventions, which is a mixture of CI Pigment Red 146.
Moreover, 4th invention is related with the printed matter formed by printing the inkjet ink of the said invention.

Excellent dispersibility is obtained with inkjet ink, inkjet ink has excellent printing characteristics and color reproducibility without nozzle clogging in continuous printing, and ink jet ink that satisfies other characteristics required for inkjet ink in a well-balanced manner is provided. The

It has been found that the inkjet ink of the present invention can realize stable ink ejection without nozzle clogging over time when the content of the general formula (1) in the ink is 400 ppm or less. The reason for this is not clear, but is considered as follows.
General formula (1)

（Ｒ_１は、水素原子、又はＹ_１のパラ位で結合する一般式（１）’であり、
一般式（１）’

(R ₁ is a hydrogen atom or general formula (1) ′ bonded at the para position of Y ₁ ;
General formula (1) '

Ｘ_１、Ｙ_１、Ｚ_１が、水素原子、塩素原子、アルキル基、アルコキシル基の何れかである）

X ₁ , Y ₁ , and Z ₁ are any one of a hydrogen atom, a chlorine atom, an alkyl group, and an alkoxyl group)

  The general formula (1) is hardly soluble in a highly hydrophilic solvent such as water or a water-soluble solvent, and precipitates with time when the ink is stored for a long time. Therefore, not containing the general formula (1) in the ink is effective in improving the stable ejection property. The method of bringing the amount of the general formula (1) in the ink within the above range is not particularly limited, and it is possible to use a pigment in which the amount of the general formula (1) is reduced by a pigment synthesis method or washing purification. it can. Preferably, the pigment is washed with an alkali.

However, as will be apparent from the examples described later, when the amount of the general formula (1) falls below a certain amount, the dispersibility of the ink deteriorates.
Accordingly, the present inventors have found that by mixing two kinds of azo pigments, high dispersibility can be maintained even when the general formula (1) in the ink is not more than a certain amount.

  It also contains glycol ethers and diols that are added to control the penetrability and wettability of droplets on the substrate and improve printing quality by mixing two kinds of azo pigments. However, it has been found that an increase in viscosity during storage with time can be suppressed.

The azo pigment used in the present invention includes all azo pigments having a known chemical structure, but it is preferable to mix two kinds of azo pigments represented by the general formula (2).
General formula (2)

（Ｒ_１は、水素原子又はＹ_１のパラ位で結合する一般式（１）’であり、
一般式（１）’

(R ₁ is a hydrogen atom or general formula (1) ′ bonded at the para position of Y ₁ ;
General formula (1) '

Ｘ_１、Ｙ_１、Ｚ_１が、水素原子、塩素原子、アルキル基、アルコキシル基の何れかである）

X ₁ , Y ₁ , and Z ₁ are any one of a hydrogen atom, a chlorine atom, an alkyl group, and an alkoxyl group)

Specifically, C.I. I. Pigment red 269 and C.I. I. Pigment red 150, or C.I. I. Pigment red 269 and C.I. I. Pigment red 147, or C.I. I. Pigment red 269 and C.I. I. Mixing with Pigment Red 146 is preferred. More preferably, C.I. I. Pigment red 269 and C.I. I. It is a mixture with Pigment Red 147. The mixing ratio is preferably in the range of 99: 1 to 90:10. More preferably, it is 97: 3 to 92: 8. The mixing method is not particularly limited, and may be either pigment synthesis / cleaning purification or dispersion. Preferably, it is at the time of pigment synthesis / cleaning purification.
The method for synthesizing the pigment is not particularly limited, and a known method can be used.

  The water-soluble solvent used in the present invention is used for the purpose of improving the wettability and penetrability to the substrate, eliminating beading and white streaks, and improving the printing quality.

Specific examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, triethylene Glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monobutyl ether, propylene glycol monopropyl ether, propylene Glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, and the like.
Specific examples of diols include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, Examples include 1,2-hexanediol, 1,6-hexanediol, and 2-methyl-2,4-pentanediol.
Of these, the most effective are diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-hexanediol. 2-methyl-2,4-pentanediol.
These solvents may be used alone or in combination.

  The ink-jet ink of the present invention comprises a pigment-dispersed resin and water in addition to the pigment and water-soluble solvent defined in the present invention described above, and each of these components will be described below.

  As the pigment dispersion resin contained in the ink jet ink of the present invention, conventionally known ones can be used, but (meth) acrylic acid copolymers are generally used. This is because the charge repulsion occurs when the (meth) acrylic acid copolymer adsorbed on the pigment surface is ionized, so that the pigment repels between the pigments in an aqueous solvent, and a stable pigment dispersion state can be maintained. .

  As water contained in the ink-jet ink of the present invention, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

  Further, in addition to the above components, the ink of the present invention is a surface conditioner, antifoaming agent, water-dispersible resin fine particles, water-dispersed wax, preservative, etc. in order to obtain an ink having desired physical properties as required. Can be added as appropriate.

  Examples of the method for producing the ink of the present invention comprising the components described above include the following methods, but the present invention is not limited to these. First, a pigment is added to an aqueous medium in which at least a pigment dispersion resin and water are mixed, and after mixing and stirring, dispersion processing is performed using a dispersion means described later, and centrifugation is performed as necessary. To obtain a desired pigment dispersion. Next, if necessary, a water-soluble solvent or an appropriately selected additive component as listed above is added to this pigment dispersion, followed by stirring, and if necessary, filtering to obtain the ink of the present invention. To do.

  In the ink production method of the present invention, as described above, a pigment dispersion obtained by carrying out a dispersion treatment is used for the preparation of the ink, but before the dispersion treatment carried out during the preparation of the pigment dispersion. It is effective to perform premixing. That is, premixing may be performed by adding a pigment to an aqueous medium in which at least a pigment dispersion resin and water are mixed. Such a premixing operation is preferable because it improves wettability of the pigment surface and promotes adsorption of the dispersant to the pigment surface.

The disperser used in the above-described pigment dispersion treatment may be any disperser that is generally used, and examples thereof include a ball mill, a roll mill, a sand mill, a bead mill, and a nanomizer. Among these, a bead mill is preferably used. Examples of such include a super mill, a sand grinder, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).
Furthermore, in the pigment premixing and dispersion treatment described above, the pigment dispersion resin may be dissolved or dispersed only in water, or may be dissolved or dispersed in a mixed solvent of a water-soluble solvent and water.

A well-known thing can be used for the base material which prints the inkjet ink of this invention demonstrated above. For example, high-quality paper, coated paper, art paper, cast paper, synthetic paper, or film can be used. The surface of the substrate may be a smooth surface, an uneven surface, or transparent, translucent, or opaque.
Further, two or more of these substrates may be bonded to each other. Furthermore, a peeling adhesive layer or the like may be provided on the opposite side of the printing surface, or an adhesive layer or the like may be provided on the printing surface after printing.

[Example]
Hereinafter, the present invention will be described specifically by way of examples. In the examples, “part” represents “part by weight” and “%” represents “% by weight”.

(Pigment production example)
100 parts of 3-amino-4-methoxybenzanilide was dispersed in 1500 parts of water, ice was added to adjust the temperature to 0-5 ° C., 120 g of 35% aqueous hydrochloric acid was added, and the mixture was stirred for 10 minutes. Thereafter, 29 g of sodium nitrite was dissolved in water and added, and after stirring for 60 minutes, 4 g of sulfamic acid was added to eliminate nitrous acid. Further, 100 g of sodium acetate and 150 g of 90% acetic acid were added to obtain a diazonium salt solution.
Separately, 139 g of N- (5-chloro-2-methoxyphenyl) -3-hydroxy-2-naphthalenecarboxamide was dissolved at 90 ° C. together with 1500 g of water and 50 g of sodium hydroxide, and then water was added to adjust the temperature. A coupler solution was prepared at 20 ° C.
This coupler solution was added to the diazonium salt solution whose temperature was adjusted to 20 ° C. or lower to conduct a coupling reaction, and stirred for 1 hour. The obtained pigment slurry was heat-treated at 90 ° C., filtered and washed with water, dried at 100 ° C., and C.I. I. 218 g of Pigment Red 269 was obtained.
In a similar manner, without using N- (5-chloro-2-methoxyphenyl) -3-hydroxy-2-naphthalenecarboxamide, N- (4-chloro-2,5-dimethoxyphenyl) -3- Using 153 g of hydroxy-2-naphthalenecarboxamide, C.I. I. 221 g of Pigment Red 146 was obtained.

  The obtained C.I. I. Pigment Red 269 99g and C.I. I. 1 g of Pigment Red 146 was suspended in 2000 g of water, and 50 g of sodium hydroxide was added and stirred. After heat treatment at 35 ° C., filtration, washing with water, drying at 100 ° C., C.I. I. Pigment red 269 and C.I. I. A 99: 1 alkali-washed azo pigment of CI Pigment Red 146 was obtained.

(Production example of pigment dispersion resin)
A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 93.4 parts of butanol and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and a mixture of 35.0 parts of lauryl methacrylate, 35.0 parts of styrene, 30.0 parts of acrylic acid, and 6.0 parts of V-601 (manufactured by Wako Pure Chemical Industries) was added for 2 hours. Over the course of the polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, and then 0.6 part of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and the reaction was further continued at 110 ° C. for 1 hour to prepare a pigment dispersion resin 1 solution. Obtained. The weight average molecular weight of the pigment dispersion resin 1 was about 16000.
Further, after cooling to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization. This is the amount that neutralizes 100% of acrylic acid. Furthermore, 293.4 parts of water was added to make it aqueous. Thereafter, butanol was removed. 1 g of this was sampled, heated and dried at 180 ° C. for 20 minutes to measure the non-volatile content, and water was added so that the non-volatile content of the previously aqueous resin solution was 20%. As a result, an aqueous solution having a non-volatile content of 20% of the pigment dispersion resin 1 was obtained.

(Production example of pigment dispersion)
A total of 20 parts of azo pigment washed with alkali, 35 parts of water-dispersed solution of pigment dispersion resin 1 and 45 parts of water were charged into a mayonnaise bottle, predispersed with a disper, and then 250 parts of zirconia beads having a diameter of 0.8 mm were dispersed in a dispersion medium. And this dispersion was performed for 2 hours with a paint shaker to obtain a pigment dispersion.

(Ink production example)
17 parts of the obtained pigment dispersion, 1 part of Surfynol 465 (Air Products and Chemicals Inc.) as a polyalkoxylate of an acetylene glycol surfactant, 47 parts of 1,2-propanediol, and triethylene glycol monomethyl ether 1 part, 5 parts of diethylene glycol monobutyl ether and 29 parts of water were mixed, and ink was prepared by filtering through a 1 μm glass filter.

(Measurement of amount of general formula (1) in ink)
1.5 g of the obtained ink and 5 mL of methanol were mixed, centrifuged at 14,000 rpm for 30 minutes, and the supernatant was filtered through a 0.2 μm membrane filter to obtain a sample solution.

  30 μL of the sample solution was injected into high performance liquid chromatography and detected by a 240 nm photo-dye autoarray detector (separation column: TSKgel ODS-80TS, eluent: solution A (5 mol diammonium phosphate / methanol = 90/10 ) And liquid B (methanol / water = 95/5), the flow rate: 0.8 mL / min), and the amount of the general formula (1) in the ink was confirmed.

(Production example of printed matter)
The ink was filled in a cartridge of an inkjet printer (Epson "PM-750C"), coated paper (+ Oji Paper Co., Ltd. OK top coat, basis weight 104.7g / ^{m 2)} performs a print to, an evaluation printed matter Produced.

(Examples 1-9)
According to the composition described in Table 1, the preparation of the dispersion, the preparation of the ink, the measurement of the amount of the general formula (1) in the ink, and the printed matter for evaluation were prepared in the same manner as in the above production example.

(Comparative Examples 1-9)
According to the composition described in Table 2, a dispersion was prepared, an ink was prepared, the amount of the general formula (1) in the ink was measured, and a printed matter for evaluation was prepared in the same manner as in the above production example.

  The following items were evaluated for the ink jet inks obtained in the above Examples and Comparative Examples. The results are shown in Table 3.

(Dispersibility of inkjet ink)
The dispersibility of the produced ink-jet ink was visually judged by the filterability of a 1 μm glass filter. If there was no clogging, it was rated as ○, if there was a slight clogging, and △ if there was a lot of clogging.

(Storage stability of inkjet ink)
After the ink was stored in a thermostat at 70 ° C. for 2 weeks and accelerated over time, the change in viscosity of the ink before and after aging was evaluated. When the change rate before and after storage at 70 ° C. for 2 weeks was within ± 10%, it was evaluated as “◯”, when ± 10% or more and ± 20% or less, Δ, and when ± 20% or more, ×.

(Evaluation of permeability and wettability to substrate)
In a solid printing part with a printing rate of 100%, the case where white stripes were clearly generated was visually evaluated as x, the case where white stripes were slightly generated was indicated as Δ, and the case where white stripes were not present was indicated as ○.

(Inkjet ink nozzle clogging)
The prepared ink-jet ink was filled in a cartridge of an ink-jet printer and allowed to elapse for 2 weeks at room temperature. Then, the printed matter printed before and after aging was compared to visually determine nozzle clogging. A comparison was made between the printed matter before and after the lapse of two weeks at room temperature.

As shown in Table 3, the amount of the general formula (1) in the ink is 400 ppm or less, and the ink using two kinds of azo pigments has no nozzle clogging and good dispersibility, and contains glycol ethers and diols. Even in this state, the storage stability was good.

Claims (4)

An ink composition comprising at least two kinds of azo pigments, a pigment dispersion resin, water, and a water-soluble solvent as a coloring component, which is a constituent of the two kinds of azo pigments, represented by the following general formula (1) A water-based inkjet ink composition, wherein the content in the ink is 400 ppm or less, and the water-soluble solvent is at least one selected from glycol ethers and diols.
General formula (1)

(R ₁ is a hydrogen atom or a general formula (1) ′ bonded at the para position of Y _1.
General formula (1) '

And X ₁ , Y ₁ and Z ₁ are any one of a hydrogen atom, a chlorine atom, an alkyl group and an alkoxyl group) The water-based inkjet ink composition according to claim 1, wherein the two kinds of azo pigments are represented by the following general formula (2) including the general formula (1) as a constituent component.
General formula (2)

(R ₁ is a hydrogen atom or general formula (1) ′ bonded at the para position of Y ₁ ;
General formula (1) '

X ₁ , Y ₁ , and Z ₁ are any one of a hydrogen atom, a chlorine atom, an alkyl group, and an alkoxyl group)   In the azo pigment of the general formula (2), C1 is a methoxy group, Y1 is a hydrogen atom, and Z1 is a chlorine atom. I. Pigment Red 269 and C.I. wherein R1 is a hydrogen atom. I. Pigment Red 150, or C.I. in which X1 is a methyl group, Y1 is a hydrogen atom, and Z1 is a chlorine atom. I. Pigment Red 147, or C.I. in which X1 is a methoxy group, Y1 is a chlorine atom, and Z1 is a methoxy group. I. The water-based inkjet ink composition according to claim 1 or 2, which is a mixture of CI Pigment Red 146.   A printed matter obtained by printing using the water-based inkjet ink according to any one of claims 1 to 3.