JP6089933B2 - Inkjet ink - Google Patents

Description

  The present invention relates to an inkjet ink excellent in red color reproducibility and excellent in ejection stability without causing problems such as clogging of 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, pigment inks using pigments instead of water-soluble dyes have been studied. 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. In Patent Document 1, the purity is increased by washing an azo pigment, which is used for ink-jet ink. By reducing the amount of impurities in this way, the possibility of precipitation of impurities can be reduced, but at a purity of 90%, the content of impurities is large and the possibility of precipitation still remains. In addition, pigments that have undergone special operations such as washing become expensive and have a problem in industrial use.

JP 2004-123866 JP

  An object of the present invention is to provide an inkjet ink that is excellent in red color reproducibility and excellent in ejection stability without causing problems such as clogging of inkjet nozzles.

また、前記塩基性有機化合物がアミノアルコール系化合物であることを特徴とする上記インクジェット用インキに関する。 That is, the present invention is an inkjet ink containing Pigment Red 150, a compound represented by the following general formula 1, a basic organic compound, an organic solvent, and water ,
The content of the basic organic compound with respect to the entire ink is 0.5 to 3% by weight, and
The organic solvent contains an alkanediol having 3 to 8 carbon atoms .
[General formula 1]

In addition, the present invention relates to the inkjet ink, wherein the basic organic compound is an amino alcohol compound.

In addition, the present invention relates to the above inkjet ink, wherein the content of the compound represented by Formula 1 in the ink is 10,000 ppm or less.
It is related with the said ink for inkjets characterized by content of a basic compound being 1 to 10 weight times of content of the compound represented by General formula 1.

  According to the present invention, it has become possible to provide an ink jet ink excellent in red color reproducibility and excellent in ejection stability without causing problems such as clogging of an ink jet nozzle.

  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 the present invention, Pigment Red 150 is used as a magenta pigment in order to improve color reproducibility in the red region. In addition, a basic organic compound and an organic solvent are used in order to suppress precipitation of the general formula 1, which is a constituent component of the pigment and causes nozzle clogging.

  Pigment Red 150, which is a pigment used in the present invention, has a higher coloring power than Pigment Red 122 and Pigment Bio Red 19, which are widely used in general ink-jet magenta inks, and is excellent in red color reproducibility. .

  The content of Pigment Red 150 in the ink is preferably 1% by weight or more and 10% by weight or less based on the total weight of the ink (100% by weight). 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 compound represented by the general formula 1 is a raw material for pigment synthesis contained in Pigment Red 150 and is known to remain in the pigment in a certain amount. The remaining amount can be reduced by washing the pigment, but there is a problem that the pigment is expensive. This compound is difficult to dissolve in water or a solvent, and even if it is once dissolved by an operation such as heating, it may precipitate in the ink when it is left for a long time or at a low temperature. When precipitation occurs, the nozzles of the inkjet head are clogged, causing non-ejection. The amount of the compound represented by the general formula 1 contained in the ink of the present invention is preferably 10,000 ppm or less with respect to the total amount of the ink. If it is this amount, it can be sufficiently dissolved by combining with a basic organic compound. More preferably, it is 8000 ppm or less, More preferably, it is 5000 ppm or less.
As a measuring method, it measures using HPLC method.

General formula (1)

  In order to dissolve this compound in ink and prevent nozzle clogging, the present invention contains a basic organic compound and an organic solvent as essential components. A basic inorganic compound has a low solubility of the compound of general formula 1 and has a risk of precipitation. Moreover, since a basic inorganic compound remains in a coating film, water resistance falls.

  As the basic organic compound, amino alcohol compounds and amine compounds can be preferably used. If a basic organic compound with high volatility is used, the basic organic compound volatilizes during printing, and the compound of general formula 1 may precipitate and cause non-ejection. A compound can be used more suitably. Examples of amine compounds include diethylamine, triethylamine, isopropylamine, diisopropylamine, butylamine, dibutylamine, tributylamine, and hexylamine. Examples of amino alcohol compounds include ethanolamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, diethanolamine, methyldiethanolamine, triethanolamine and the like. Among amino alcohol compounds, those having one or two hydroxyl groups are preferred. In the case of three or more, the volatilization becomes very slow, so that it remains in the coating film and may cause a decrease in resistance.

  The content of the basic organic compound is preferably 1 to 10 times the weight of the compound represented by the general formula 1 contained in the ink. Within this range, the compound represented by the general formula 1 can be completely dissolved, and other ink physical properties are not adversely affected. The amount is more preferably 2 to 9 times, and still more preferably 3 to 8 times. In view of the storage stability of the ink, the basic organic compound is preferably 3% by weight or less based on the total weight of the ink (100% by weight).

  An organic solvent is used in the inkjet ink of the present invention. Even if a basic organic compound is used, the compound represented by the general formula 1 is not completely dissolved in a medium containing only water, and nozzle clogging may occur. By increasing the solubility of the compound of general formula 1 using an organic solvent, it becomes possible to completely prevent precipitation. Only one type of organic solvent may be selected and used, or a plurality of solvents may be used in combination for adjusting the drying property and viscosity.

  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 to 50% by weight with respect to the total weight of the ink. When the amount is less than 5% by weight, the compound represented by the general formula 1 is not sufficiently dissolved in the ink, which may cause precipitation. 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 5 weight% or less, Most preferably, they are 35 weight% or more.

  The pigment red 150 of the present invention is preferably used by being dispersed in an ink medium composed of an organic solvent and water in order to maintain the stability of the ink for a long period of time. 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 order to obtain a more stable ink, it is preferable to disperse the pigment using a pigment dispersion resin.

  Examples of the pigment dispersion resin 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.

  The acid value of the pigment dispersion resin is preferably 50 to 400 mgKOH / 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 dispersion resin 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. When the molecular weight is less than 5000, the dispersion stability may be lowered, and when the molecular weight is more than 100,000, the 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 weight ratio of the pigment to the pigment dispersion resin is preferably 2/1 to 100/1. When the ratio of the pigment dispersion resin 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 dispersion resin is more preferably 4/1 to 50/1, further preferably 5/1 to 25/1, and most preferably 10/1 to 20/1.

  An amine or the like may be used to make the resin water-soluble when using a pigment-dispersed resin, but this is used to neutralize acidic groups of the dispersed resin, and the resin and amine are present in an associated state. Therefore, the compound of general formula 1 cannot be dissolved by this amine. To dissolve the compound of general formula 1, it is necessary to add an excess of amine.

  About water content, 30 to 90 weight% is preferable in an ink, and 40 to 80 weight% is further more preferable.

  In order to increase the resistance of the printed matter, a binder resin can be further added to the ink of 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.
(Example 8 is a reference example.)

(Example 1)
After mixing 20 parts of 150A (Pigment Red 150, manufactured by Tokyo Color Materials Co., Ltd.), 6 parts of pigment dispersion resin (styrene acrylic resin, acid value 200 mgKOH / g), and 74 parts of water, and predispersing with a disper. Then, this dispersion was performed for 2 hours using a 0.6 L dyno mill filled with 1800 g of zirconia beads having a diameter of 0.5 mm to obtain a pigment dispersion.

25 parts of the pigment dispersion, 0.5 parts of triethylamine, 30 parts of propylene glycol, 5 parts of diethylene glycol monobutyl ether, 1 part of Surfinol 465 and 38.5 parts of water are sequentially added to the mixing vessel while stirring with a disper Until homogeneous. 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. Quantification of the compound represented by the general formula 1 in the ink was performed by high performance liquid chromatography. Fill the line-pass inkjet printer with the ink-jet ink you have created and Pigment Yellow 74, and use 600 x 600 dpi on high-quality paper (NPI, Nippon Paper Industries Co., Ltd., basis weight 64.0 g / m ² ). A color chart pattern was printed at a resolution of 1 to produce a printed matter for evaluation.

(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 red hue defined by Japan Color 2007 for sheet-fed printing, and it was evaluated whether the red of Japan Color 2007 was reproducible. The evaluation criteria are as follows.
○: A color gamut equivalent to or better than Japan color ×: A color gamut narrower than Japan color

(Continuous discharge)
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

(Clogged nozzle)
The prepared inkjet ink was filled into an inkjet head and allowed to stand at a specified temperature for 2 weeks. Then, a nozzle check pattern was printed using this inkjet head, and the presence or absence of nozzle clogging was confirmed. The evaluation criteria are as follows.
◎: No nozzle clogging occurs even after storage at 5 ℃ ○: No nozzle clogging occurs after storage at room temperature ×: Nozzle clogging occurs after storage at room temperature

(water resistant)
The evaluation printed matter was rubbed 5 times with a cotton swab soaked in water and subjected to a resistance test. Evaluation was performed based on the degree of color transfer of the ink to the swab after rubbing. The evaluation criteria are as follows.
◎: No color transfer to cotton swabs ○: Slight color transfer to cotton swabs X: Cotton swabs are clearly colored

(Examples 2 to 10, Comparative Examples 1 to 3)
In the same manner as in Example 1, inks were prepared using the raw materials shown in Table 1 and evaluated.
(150TR: Pigment Red 150 manufactured by Tokyo Color Material Industries Co., Ltd.)

Claims (4)

Pigment Red 150, an inkjet ink containing a compound represented by the following general formula 1, a basic organic compound, an organic solvent, and water ,
The content of the basic organic compound with respect to the entire ink is 0.5 to 3% by weight, and
The ink for ink-jet recording, wherein the organic solvent contains an alkanediol having 3 to 8 carbon atoms .
[General formula 1]

  2. The ink-jet ink according to claim 1, wherein the basic organic compound is an amino alcohol compound.   3. The inkjet ink according to claim 1, wherein the content of the compound represented by the general formula 1 in the ink is 10,000 ppm or less.   4. The inkjet ink according to claim 1, wherein the content of the basic compound is 1 to 10 times the content of the compound represented by the general formula 1.