JP6136726B2 - Water-based magenta ink for inkjet - Google Patents

Description

  The present invention relates to a water-based magenta ink for ink jet excellent in color reproducibility and ejection stability.

  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, the color pigments used in pigment inks, especially Pigment Red 122 and Pigment Bio Red 19, which are pigments used in magenta, have weak coloring power and sufficiently satisfy the color reproduction range compared to magenta dyes. It wasn't possible.

  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. Patent Document 1 discloses an ink using Pigment Red 150, which is an azo pigment that solves these problems. However, Pigment Red 150 is a reddish magenta pigment, and the Japan color that is the standard of the printing color cannot be represented by a single color. Although it is possible to represent a Japanese magenta color by mixing with other colors at the time of printing, there has been a problem that color misalignment may occur due to blurring of printing conditions and the like.

JP 2010-195909

  An object of the present invention is to provide an ink-jet magenta ink having excellent color reproducibility and ejection stability.

That is, the present invention is at least a pigment, a jet magenta ink containing an organic solvent, water, looking contains at least two kinds of pigments having different hues as the pigment,
The first pigment is Pigment Red 150,
The second of the pigment is, whether it is Pigment Red 31,
Any one of pigment blue 15: 3 and pigment blue 15: 4;
The organic solvent is 1,2-propanediol or 1,3-propanediol, and contains 1,2-propanediol or 1,3-propanediol in an amount of 5 to 50% by weight based on the total amount of the ink;
And, a second pigment, when containing Pigment Red 31,
The weight ratio of the first pigment: second pigment is 1: 2 to 1: 6,
When the second pigment contains Pigment Blue 15: 3 or Pigment Blue 15: 4
The first pigment: second pigment weight ratio is 4: 1 to 40: 1 magenta ink for inkjet (however, the first pigment, the second pigment, and the pigment dispersant are dispersed at the same time). Except in the case of
The present invention also relates to the above magenta ink for ink jet, wherein the second pigment is Pigment Red 31.
The present invention also relates to the above magenta ink for ink jet, wherein the second pigment is a pigment selected from any one of Pigment Blue 15: 3 and Pigment Blue 15: 4.
The present invention also relates to the above-described magenta ink for inkjet, wherein both the first and second pigments are dispersed in the ink by a pigment dispersant.

  According to the present invention, it has become possible to provide a magenta ink for inkjet excellent in color reproducibility and ejection stability.

 Hereinafter, the present invention will be described with reference to preferred embodiments. Unless otherwise specified, “parts” and “%” represent “parts by weight” and “% by weight”, respectively.

 In addition, the color value used in the present invention is a value obtained by measuring a printed matter coated on a white substrate so that the wet film thickness is 6 to 10 μm under the conditions of a D50 light source and a 2 ° visual field. . Although it does not specifically limit as a white base material, It is preferable to use a coated paper.

  The present invention is characterized in that the magenta color of Japan color is reproduced by using two kinds of pigments having different hues.

 As the first pigment, a pigment having a hue angle h of 0 to 25 in the CIE1976 color system and a chroma C * of 75 or more on the recording medium is used. Color reproducibility can be improved by using pigments with high saturation. Any pigment having the above-described hue can be used as the pigment to be used, but it is preferable to use a pigment selected from Pigment Red 146, 150, 185, 245, 266. Most preferred is Pigment Red 150.

 As the second pigment, a pigment having a hue angle h of 220 to 350 and a chroma C * of 50 or more in the CIE1976 color system on the recording medium is used. Preferably, a pigment having a hue angle h of 320 to 350 and a chroma C * of 50 or more or a pigment having a hue angle h of 220 to 250 and a chroma C * of 50 or more is used. Any pigment having the above-mentioned hue can be used as the pigment to be used, but as pigments having a hue angle h of 320 to 350 and a saturation C * of 50 or more, pigment red 31, 122, hue A copper phthalocyanine pigment is preferably used as the pigment having an angle h of 220 to 250 and a chroma C * of 50 or more. As the copper phthalocyanine pigment, a pigment selected from pigment blue 15: 3 and 15: 4 is preferably used.

 The total amount of the first pigment and the second pigment contained in the ink is preferably 1% by weight or more and 10% by weight or less based on the total weight of the ink. Within this range, it is possible to exhibit high color reproducibility for various printing substrates. More preferably, it is 2 to 8% by weight, and further preferably 3 to 6% by weight.

 The blending ratio of the first pigment and the second pigment is such that when the pigment having a hue angle h of 320 to 350 and a chroma C * of 50 or more is used as the second pigment, the first pigment is the first pigment. It is preferable to use less than the second pigment (weight ratio). More preferably, the ratio of the first pigment: second pigment = 1: 1.5-5, and still more preferably the ratio of the first pigment: second pigment = 1: 2-4. When a pigment having a hue angle h of 220 to 250 and a chroma C * of 50 or more is used as the pigment of the second pigment, the second pigment is less than the first pigment and the second pigment is contained. The amount is preferably 0.5% by weight or less in the ink. More preferably, it is 0.3 weight% or less, More preferably, it is 0.3 weight% or less. By setting these ranges, the magenta color reproducibility can be further enhanced.

 In order to maintain the stability of the magenta ink of the present invention for a long period, it is preferable to use the pigment dispersed in the ink medium. As a method for dispersing the pigment, there are a method in which the pigment is surface-modified by oxidation treatment or the like and the pigment is dispersed without a dispersant, and a method in which the pigment is dispersed using a surfactant or resin as a dispersant. In the present invention, it is preferable to disperse the pigment using a dispersant in order to disperse the two pigments more stably. If different dispersion methods are used for the two kinds of pigments, they may interfere with each other, resulting in a decrease in dispersion stability and a decrease in ejection stability.

 Examples of the pigment dispersant include an acrylic resin, a styrene acrylic resin, a maleic acid resin, a styrene maleic resin, an α-olefin maleic resin, a urethane resin, and an ester resin. Among these, it is preferable to use an acrylic resin or a styrene acrylic resin. It is possible to maintain a more stable dispersion state by using the same resin type for the two types of pigments.

 The acid value of the pigment dispersant is preferably 50 to 400 mg KOH / g. If the acid value is less than 50 mgKOH / g, the resin is difficult to dissolve in water, and the viscosity of the ink increases, which may affect ejection. Moreover, even when it is larger than 400 mgKOH / g, the interaction between the resins may be strengthened and the viscosity may be increased. The acid value of the pigment dispersant is more preferably 100 to 350 mgKOH / g, and further preferably 150 to 300 mgKOH / g.

 The weight average molecular weight of the pigment-dispersed resin is preferably 5,000 to 100,000. If the molecular weight is less than 5,000, the dispersion stability may decrease, and if the molecular weight exceeds 100,000, ejection may be affected. More preferably, the molecular weight is 10,000 to 50,000, and still more preferably the molecular weight is 15,000 to 30,000.

 The ratio of pigment to pigment dispersant is preferably 2/1 to 100/1. When the ratio of the pigment dispersant is larger than 2/1, the viscosity of the ink tends to increase. On the other hand, if it is less than 100/1, the dispersibility may be lowered and the stability may be lowered. The ratio of the pigment to the pigment dispersant is more preferably 4/1 to 50/1, further preferably 5/1 to 25/1, and most preferably 10/1 to 20/1.

 An organic solvent is used in the inkjet ink of the present invention. When an organic solvent is not used, ink drying around the ink jet nozzle is very fast, causing non-ejection. Only one type of organic solvent may be selected and used, or a plurality of solvents may be used in combination for adjusting the permeability to the substrate, the viscosity, and the like.

 As the organic solvent, an alkanediol having 3 to 8 carbon atoms is preferably used. Alkanediol has an effect of preventing drying around the ink jet nozzle, prevents nozzle missing during printing, and improves the stability of continuous printing. Further, since the wettability with respect to the substrate is also good, it is effective in improving the image quality.

 Examples of the alkanediol having 3 to 8 carbon atoms include 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2-methyl- 1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 2,2-dimethyl-1,3-propanediol, 1,2-hexanediol, 1, 6-hexanediol, 2,5-hexanediol, 3,5-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,2-heptanediol, 1, Examples include 7-heptanediol, 2,6-heptanediol, 1,2-octanediol, 1,8-octanediol, 2-methyl-1,3-hexanediol, and the like. Among these, it is preferable to use 1,2-propanediol and 1,3-propanediol in order to improve the storage stability and ejection stability of the ink.

 Other usable solvents include glycerin, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol mono Butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, diethylene glycol methyl ethyl ether Ter, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol butyl methyl ether, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, and other glycol ether solvents, 2-pyrrolidone, Nitrogen-containing solvents such as N-methylpyrrolidone, N-ethylpyrrolidone, N-methyloxazolidinone, N-ethyloxazolidinone, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropionamide, and cyclic ester solvents such as γ-butyrolactone and ε-caprolactone.

 Among these solvents, it is preferable to use an alkanediol and a glycol ether solvent in combination because the wettability and drying property of the ink can be adjusted to desired characteristics. As the glycol ether solvent, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, and dipropylene glycol monomethyl ether are preferable.

 The content of the solvent in the ink is preferably 5% by weight or more and 50% by weight or less based on the total weight of the ink. If it is less than 5% by weight, non-ejection may occur due to drying around the ink jet nozzle. If it exceeds 50% by weight, the drying property of the ink is deteriorated and the productivity of the printed matter may be lowered. More preferably, they are 10 weight% or more and 45 weight% or less, More preferably, they are 15 weight% or more and 40 weight% or less, Most preferably, they are 20 weight% or more and 35 weight% or less.

 The water content is preferably 30 to 90% by weight in the ink, more preferably 40 to 80% by weight.

 In order to increase the resistance of the printed material, a binder resin can be further added in the present invention. Water-soluble resins and fine resin particles are generally known as binder resins for water-based inks. In general, resin fine particles have a higher molecular weight than water-soluble resins, and can achieve high resistance. In addition, the resin fine particles can lower the ink viscosity, and a larger amount of resin can be blended in the ink. Therefore, the resin fine particles are suitable for increasing the resistance of the ink-jet ink. Examples of the resin include acrylic resin, urethane resin, styrene butadiene resin, vinyl chloride resin, and polyolefin resin.

 By increasing the glass transition temperature (Tg) of the binder resin, it is possible to improve resistance such as abrasion resistance and chemical resistance, preferably in the range of 50 to 120 ° C, more preferably in the range of 80 to 100 ° C. It is good to do. When the temperature is lower than 50 ° C., sufficient resistance cannot be obtained, and the ink coating film may be peeled off from the printed matter in practical use. In addition, when the temperature is higher than 120 ° C., the coating film becomes very hard, and cracking and cracking may occur on the printed surface when the printed material is bent.

 The content of the binder resin in the ink is in the range of 2% by weight to 30% by weight, preferably in the range of 3% by weight to 20% by weight, based on the total weight of the ink in solid content, More preferably, it is in the range of 4 wt% to 15 wt%.

 In addition to the above-described components, the ink of the present invention may be an ink having a desired physical property value, if necessary, and additives such as leveling agents, antifoaming agents, thickeners, pH adjusters, preservatives, etc. Can be added as appropriate. The additive amount of these additives is 0.01% by weight or more and 10% by weight or less, preferably 0.05% by weight or more and 5% by weight or less, more preferably 0.1% by weight or more and 3% by weight or less based on the total weight of the ink. .

 The ink of the present invention may be used in a single color, but can also be used as an ink set in which a plurality of colors are combined according to the application. The combination is not particularly limited, but a full color image can be obtained by using three colors of cyan, magenta, and yellow. Moreover, black feeling can be improved by adding black ink, and the visibility of a character etc. can be raised. Furthermore, color reproducibility can be improved by adding colors such as orange and green. When printing on a print medium other than white, a clear image can be obtained by using white ink together.

 Known printing media can be used for printing with the ink jet ink of the present invention. For example, paper media such as high-quality paper, coated paper, art paper, cast paper, synthetic paper, and ink-jet paper, and plastic media such as polyvinyl chloride sheets, PET films, and PP films. These may have a smooth print medium surface or an uneven surface, or may be transparent, translucent, or opaque. Further, two or more of these print media 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.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, “parts” and “%” represent “parts by weight” and “% by weight”, respectively, unless otherwise specified. In addition, Examples 1-5, 7, and 8 are reference examples.

(Example 1)
20 parts of Pigment Red 146 as pigment, 6 parts of pigment dispersant (styrene acrylic resin, acid value 200 mgKOH / g) and 74 parts of water are mixed, predispersed with a disper, and then filled with 1800 g of zirconia beads with a diameter of 0.5 mm The main dispersion was performed for 2 hours using a 0.6 L dyno mill, to obtain a pigment dispersion (PR146). In the same manner, a dispersion was produced using Pigment Red 122 as a pigment to obtain a pigment dispersion (PR122).

Disperse 10 parts of pigment dispersion (PR146), 30 parts of pigment dispersion (PR122), 30 parts of propylene glycol, 5 parts of diethylene glycol monobutyl ether, 1 part of Surfinol 465, and 19 parts of water into a mixing vessel with a disper. Were added sequentially and stirred until it was sufficiently uniform. Thereafter, filtration with a membrane filter was performed to remove coarse particles that would cause clogging of the head, and the inkjet ink of the present invention was prepared. The ink-jet ink created is filled in a line-pass type ink-jet printer, and a color chart pattern is printed on the coated paper (OK Topcoat N manufactured by Oji Paper Co., Ltd., basis weight 104.7 g / m ² ) at a resolution of 600 x 600 dpi. A printed matter for evaluation was prepared.

(Evaluation of color reproducibility)
The printed matter for evaluation was measured using a spectrophotometer (manufactured by X-rite), and the color reproduction region in the L * a * b * color space was plotted and evaluated. The obtained color reproduction region was compared with the magenta hue defined by Japan Color 2007 for sheet-fed printing, and it was evaluated whether the magenta of Japan Color 2007 was reproducible. The evaluation criteria are as follows.
◎: Indicates a color gamut equivalent to or better than Japan color ○: Indicates a color gamut equivalent to Japan color ×: Indicates a color gamut narrower than Japan color

(Discharge stability evaluation)
Continuous printing was performed with the line pass type ink jet printer, and the time until nozzle missing occurred was measured. The evaluation criteria are as follows.
◎: No nozzle missing within 10 minutes ○: No nozzle missing within 1 minute ×: No nozzle missing within 1 minute

(Examples 2 to 12, Comparative Examples 1 and 2)
Ink jet inks having the compositions shown in Table 1 were prepared according to Example 1 and evaluated in the same manner.

As shown in Table 1, it was shown that the color reproducibility was good for the ink using the first pigment and the second pigment in combination. Particularly, those using Pigment Red 150 as the first pigment had good color reproducibility. Further, as in Examples 1 to 10, it was shown that the ink in which both the first pigment and the second pigment are dispersed by the pigment dispersant has high ejection stability. In Examples 11 and 12, since the resin-dispersed pigment and the self-dispersed pigment are used in combination, the dispersion stability is lowered and the ejection stability is lowered.

Claims (4)

At least a pigment, a jet magenta ink containing an organic solvent, water, looking contains at least two kinds of pigments having different hues as the pigment,
The first pigment is Pigment Red 150,
The second of the pigment is, whether it is Pigment Red 31,
Any one of pigment blue 15: 3 and pigment blue 15: 4;
The organic solvent is 1,2-propanediol or 1,3-propanediol, and contains 1,2-propanediol or 1,3-propanediol in an amount of 5 to 50% by weight based on the total amount of the ink;
And, a second pigment, when containing Pigment Red 31,
The weight ratio of the first pigment: second pigment is 1: 2 to 1: 6,
When the second pigment contains Pigment Blue 15: 3 or Pigment Blue 15: 4
The first pigment: second pigment weight ratio is 4: 1 to 40: 1 magenta ink for inkjet (however, the first pigment, the second pigment, and the pigment dispersant are dispersed at the same time). Except in the case of Second pigments, jet magenta ink of claim 1 wherein the Pigment Red 31. 2. The magenta ink for ink-jet recording according to claim 1, wherein the second pigment is a pigment selected from either pigment blue 15: 3 or pigment blue 15: 4. The magenta ink for inkjet according to any one of claims 1 to 3, wherein both the first and second pigments are dispersed in the ink by a pigment dispersant.