JP2017061608A - Inkjet magenta ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet magenta ink having excellent printability with respect to, among general printing base materials, a hardly absorbing base material such as coated paper, art paper and lightly coated paper, that is, an inkjet magenta ink having high color developability and glossiness, discharge stability from an inkjet nozzle and storage stability.SOLUTION: The inkjet magenta ink comprises at least a pigment, a pigment dispersing resin, a water-soluble organic solvent and water. The pigment comprises C.I. pigment red 150; the pigment dispersing resin comprises a (meth)acrylic copolymer having a weight average molecular weight of 15000 to 50000 and containing at least a monomer (A) having an aromatic ring in the copolymer composition; and the water-soluble organic solvent comprises at least an alkane diol having 3 to 6 carbon atoms and having a boiling point of 190°C or higher.SELECTED DRAWING: None

Description

  The present invention is excellent in printing suitability for difficult-to-absorbable substrates such as coated paper, art paper and fine coated paper among general printing substrates, that is, high color developability and high glossiness, and from inkjet nozzles. The present invention relates to an ink jet magenta ink excellent in ejection stability and storage stability.

  Unlike conventional plate printing such as offset printing, digital printing does not require a plate making film or plate making, so it can achieve cost reduction and speedup and is expected to be widely used in the future. ing.

  Among digital printing, the inkjet recording method is a recording method in which ink droplets are directly ejected from a very fine nozzle and adhered to a recording member to obtain characters and images. According to this method, the noise of the device to be used is obtained. In addition to being small and easy to operate, it has the advantages of being easy to color, and being able to use plain paper as a recording member, so it is widely used as an output device in offices and homes.

  On the other hand, industrial applications are expected to be used as output devices for digital printing due to improvements in inkjet technology, compared to non-absorbent substrates (plastic substrates such as polyvinyl chloride and PET) with solvent inks and UV inks. However, printing machines capable of printing even have been commercially available. However, in recent years, use restrictions on solvents and monomers have been promoted from the viewpoint of consideration and response to harmfulness to the environment and humans, and the demand for water-based ink is increasing.

  As ink-jet water-based inks, as described in Patent Documents 1, 2, and 3, the development of inks in which special printing paper such as plain paper or photographic glossy paper has been developed for a long time. On the other hand, in recent years, the application of the ink jet recording method is expected to be expanded, and the need for direct printing on hardly-absorbable substrates such as art paper, coated paper, and fine coated paper is increasing. However, conventional water-based inks perform drawing by absorbing droplets on paper, and therefore, when printed on a substrate having low water absorption, the image is blurred and cannot be used.

  Furthermore, in addition to the above-described printability on the hard-to-absorbent substrate, in order to expand the use, high color rendering on the paper surface is also required. Especially, demand for color development and color gamut expansion of magenta ink is required. Is growing. In general, quinacridone pigments and azo pigments are known as magenta pigments. However, quinacridone pigments have low coloring power, and the color reproduction range is not sufficiently satisfactory. On the other hand, azo pigments have high coloring power and a wide color reproduction range, but it is difficult to stabilize the dispersion. In particular, in order to have printability on difficult-to-absorbent substrates as described above, organic solvents are blended in the ink. Then, there is a problem that pigment aggregation is caused and the original color developability of the azo pigment cannot be expressed.

  Patent Document 4 discloses C.I. as a magenta pigment. I. An ink-jet ink excellent in red color reproducibility by using CI Pigment Red 150 is presented. However, this method does not have printability on a hardly absorbent substrate such as art paper, coated paper, and fine coated paper, so that ink is not buried on the paper surface and white spots occur. Color developability cannot be obtained. Further, pigment aggregation is caused at the time of drying after printing, and there is a concern that the glossiness of the coating film surface and the color developability are lowered.

  On the other hand, Patent Document 5 proposes an ink-jet magenta ink having excellent color development properties by blending two kinds of specific pigments. However, even with this method, there is a concern that the printability is not satisfactory with respect to a substrate having a low absorbency as described above, and an excellent color developability cannot be obtained.

Japanese Patent No. 4764562 Japanese Patent No. 4595281 JP 2008-247951 A JP 2014-214277 A JP 2014-208777 A

  The object of the present invention is to provide excellent printability for non-absorbable substrates such as coated paper, art paper and fine coated paper among general printing substrates, that is, high color developability and high glossiness, and inkjet nozzles. It is an object of the present invention to provide an inkjet magenta ink having excellent ejection stability and storage stability.

That is, the present invention is an inkjet magenta ink containing at least a pigment, a pigment dispersion resin, a water-soluble organic solvent, and water,
The pigment is C.I. I. Pigment Red 150,
The pigment-dispersed resin contains a monomer (A) containing at least an aromatic ring in the copolymer composition, and includes a (meth) acrylic copolymer (X) having a weight average molecular weight of 15,000 to 50,000,
The water-soluble organic solvent contains an alkanediol having 3 to 6 carbon atoms having a boiling point of 190 ° C. or higher, and relates to an inkjet magenta ink.

  The present invention also relates to the above-described inkjet magenta ink, wherein the average secondary particle diameter (D50) of the pigment in the ink is 115 nm to 185 nm.

  In the present invention, the (meth) acrylic copolymer (X) further contains (meth) acrylic acid (B) in the copolymer composition, and the content of the monomer (A) containing the aromatic ring. Is 5% by weight to 50% by weight with respect to the (meth) acrylic copolymer, and the content of the monomer (A) containing the aromatic ring and the (meth) acrylic acid (B) The total amount of the ink-jet magenta ink is 10% to 85% by weight with respect to the (meth) acrylic copolymer.

  The present invention is also characterized in that the (meth) acrylic copolymer (X) further contains a monomer (C) containing an alkyl chain having 10 to 30 carbon atoms in the copolymer composition. The present invention relates to an inkjet magenta ink.

  The present invention also relates to the above-described inkjet magenta ink, wherein the water-soluble organic solvent contains at least an alkanediol having 3 or 4 carbon atoms.

  The present invention is also an inkjet ink set including at least cyan ink, yellow ink, and magenta ink, wherein the cyan ink includes a copper phthalocyanine pigment, and the yellow ink includes C.I. I. The present invention relates to an ink set comprising a pigment selected from CI Pigment Yellow 14, 74, 120, and 150, wherein the magenta ink is the inkjet magenta ink.

  The present invention also relates to an ink jet printing method, wherein the ink jet magenta ink is printed on a hardly absorbent substrate.

  According to the present invention, among general printing substrates, it has excellent printability for difficult-to-absorbent substrates such as coated paper, art paper and fine coated paper, that is, high color development and high glossiness, and from inkjet nozzles. An ink jet magenta ink having excellent ejection stability and storage stability can be provided.

  Hereinafter, the present invention will be described with reference to preferred embodiments.

  The present invention relates to C.I. I. Pigment Red 150, (meth) acrylic pigment-dispersed resin with a specific structure, and C3-C6 alkanediol having a boiling point of 190 ° C. or higher are combined to make it difficult to absorb coated paper, art paper, fine coated paper, etc. The ink jet magenta ink is excellent in printability on a porous substrate, has high color development properties and high glossiness, and is excellent in ejection stability from ink jet nozzles and storage stability.

  As explained above, generally poorly absorbable substrates such as coated paper, art paper and finely coated paper have poor ink absorbability, so the solvent used is permeable to the substrate and dried by evaporation If the property is poor, the solvent remains on the base material, so that dots are connected to each other, blurring occurs, and a clear image cannot be obtained. On the other hand, since these substrates have a low surface tension of the substrate itself, it is known that it is not easy to sufficiently spread the ink on these substrates. If the ink does not have sufficient wettability, the printed portion is not sufficiently filled with the ink and white spots or the like are likely to occur, so that the original color developability of the pigment cannot be expressed. As described above, in order to perform printing on these hardly absorbable substrates, it is necessary to sufficiently ensure the wettability and drying property of the ink.

  In particular, since water has a very high surface tension among solvents, it is difficult to get wet and the contribution of penetration is low. Therefore, it is very difficult to obtain sufficient wettability and dryness of water-based ink.

  In general, a water-soluble organic solvent is used for the purpose of improving the wettability and drying property of water-based ink. Since the water-soluble organic solvent has a lower surface tension than water, it is indispensable for improving the wettability on the hardly absorbent substrate. Further, by using a water-soluble organic solvent having high hydrophobicity, it is possible to improve the drying property by permeation. Furthermore, it is also possible to improve the drying property of the ink by volatilization by using a highly volatile water-soluble organic solvent having a low boiling point. However, if the drying property of the ink is too high, the ink is dried before the dots are wet and spread on the substrate, and the printing portion is not completely filled with the ink, and white spots occur. Further, since the dots are dried before being sufficiently wet and spread, a uniform ink coating film cannot be formed, resulting in unevenness on the surface of the coating film, resulting in a decrease in gloss. Therefore, in order to obtain excellent printability on a hardly absorbent substrate, it is necessary to control the wettability and drying property of the ink on the substrate.

  On the other hand, C.I. which is a magenta pigment used in the present invention. I. Pigment Red 150 is a pigment having particularly high color reproducibility and excellent color reproducibility among azo pigments. However, as described above, C.I. I. Pigment Red 150 is difficult to disperse and stabilize, especially in the presence of the water-soluble organic solvent described above, when water is volatilized when the ink coating film after printing is dried and the ink is concentrated, pigment aggregation is caused. Problems such as a decrease in color developability occur. In addition, even when the inkjet printer is kept on standby for a certain period of time while the inkjet head is filled with ink, water evaporates in the vicinity of the inkjet nozzle and causes pigment aggregation, leading to problems such as non-ejection.

  As a result of diligent investigations, the inventors of the present invention have made a magenta ink excellent in printability on a hardly-absorbable substrate, having high color developability and gloss after drying, and excellent in ejection stability and storage stability. As C.I. I. Pigment Red 150, a (meth) acrylic copolymer having a weight average molecular weight of 15,000 to 50,000 containing a monomer containing an aromatic ring as a pigment dispersion resin in the copolymer composition, and a boiling point of 190 ° C. or more as a water-soluble organic solvent It discovered that the said subject could be solved by using a C3-C6 alkanediol, and came to this invention.

  The reason why it is possible to obtain an inkjet magenta ink excellent in printability to a hardly-absorbable substrate by the above method, that is, high color developability and high glossiness, ejection stability from an inkjet nozzle, and storage stability is clear. However, the following can be considered. The pigment dispersion resin used in the present invention is a (meth) acrylic copolymer having an aromatic ring in the structure and having a molecular weight in a suitable range. Therefore, even in the presence of a water-soluble organic solvent, the aromatic ring in the pigment-dispersed resin is firmly adsorbed to the aromatic ring in the pigment, and further has a molecular weight within a suitable range, so that the ink is concentrated in the drying process. It is also considered that the pigment aggregation due to the detachment of the pigment dispersion resin is suppressed, and the decrease in color developability and glossiness is suppressed.

  Furthermore, by using a C3-C6 alkanediol having a boiling point in a suitable range as a water-soluble organic solvent, it is possible to express optimum wettability and drying on a hardly absorbent substrate. Become. Therefore, it is possible to form a printed portion with less white spots on the hardly absorbent substrate. I. It is considered that it is possible to express the original excellent coloring property of CI Pigment Red 150.

  C. used as a pigment of the inkjet magenta ink of the present invention. I. The content of CI Pigment Red 150 is preferably in the range of 1 to 10% by weight in the ink composition from the viewpoint of securing excellent color developability on the printed coating film. More preferably, it is 3 to 8% by weight.

  In the inkjet magenta ink of the present invention, the average secondary particle diameter (D50) of the pigment in the ink is preferably 115 nm to 210 nm, more preferably 115 nm, from the viewpoint of ensuring excellent color developability on the printed coating film. ˜185 nm, particularly preferably 115 nm to 170 nm. In order to keep the average secondary particle diameter within the preferred range, the pigment dispersion treatment process may be controlled as described later, for example, change of disperser and grinding media conditions, adjustment of dispersion treatment time, after dispersion treatment There exists a method of making it settle in said average secondary particle diameter range by classifying process of this.

  The secondary particle diameter of the pigment in the present invention can be measured by a conventional method. Specifically, it can be measured by diluting the ink with ion-exchanged water using a particle size distribution measuring device (Nikkiso Microtrac UPA EX-150).

<Pigment dispersion resin> ((Meth) acrylic copolymer (X))
The pigment-dispersed resin used in the present invention is a (meth) acrylic copolymer (X) having a weight average molecular weight of 15,000 to 50,000, which contains at least an aromatic ring-containing monomer (A) in the copolymer composition. It is characterized by. The weight average molecular weight of the pigment-dispersed resin is more preferably 15000 to 35000 from the viewpoint of ensuring excellent pigment dispersion stability and ejection stability. When the weight average molecular weight is less than 15000, sufficient dispersion stabilization of the pigment cannot be ensured, and pigment aggregation occurs at the time of drying, and the glossiness and color developability are liable to occur. On the other hand, if the weight average molecular weight exceeds 50,000, the ink viscosity is likely to increase when water volatilizes. In particular, when the ink jet printer is kept on standby for a certain period, the ink viscosity increases when water is volatilized in the vicinity of the ink jet nozzle and the ink is concentrated, leading to problems such as non-ejection.

  The weight average molecular weight of the pigment-dispersed resin in the present invention can be measured by a conventional method. As an example, using a TSKgel column (manufactured by Tosoh Corp.), GPC equipped with an RI detector (manufactured by Tosoh Corp., HLC-8120GPC) was measured as a weight average molecular weight in terms of polystyrene measured using THF as a developing solvent. can do.

The ((meth) acrylic copolymer (X)) used in the present invention is a (meth) acrylic copolymer containing at least an aromatic ring-containing monomer (A) in the copolymer composition. Features. Examples of the aromatic ring structure include phenyl group, naphthyl group, anthryl group, tolyl group, xylyl group, mesityl group, anisyl group and the like. Of these, a phenyl group and a tolyl group are preferable from the viewpoint of dispersion stability of the pigment.
Examples of the monomer (A) containing the aromatic ring include styrene, α-methylstyrene, phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, 2,4-dimethylstyrene, Examples thereof include pn-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, and the like. In the present invention, among the above, styrene and α-methylstyrene are preferably selected.

  The content of the ((meth) acrylic copolymer (X)) used in the present invention in the copolymer of the monomer (A) containing an aromatic ring is 4 to 4 from the viewpoint of dispersion stability of the pigment. It is preferable that it is 65 weight%, More preferably, it is 5-50 weight%. In the present invention, the expression of the monomer content in the copolymer does not mean the monomer remaining in the polymer, but the monomer-derived part contained in the copolymer. Say ratio. Since the monomer becomes a copolymer by addition polymerization (no detachment), the raw material charge ratio of the monomer, the content of parts derived from the monomer of the copolymer, and the single amount of the copolymer The body content is the same.

  Furthermore, the ((meth) acrylic copolymer (X)) used in the present invention is preferably a (meth) acrylic copolymer containing (meth) acrylic acid (B) in the copolymer composition. The monomer (A) containing the aromatic ring and the (meth) acrylic from the viewpoint of improving the color developability by improving the dispersibility of the pigment and suppressing the decrease in gloss by suppressing the pigment aggregation at the time of drying. The total content of the acid (B) is preferably 10% by weight to 95% by weight and more preferably 10% by weight to 85% by weight with respect to the (meth) acrylic copolymer.

  Further, the ((meth) acrylic copolymer (X)) of the present invention preferably contains a monomer (C) containing an alkyl chain having 10 to 30 carbon atoms in the copolymer composition. By setting the number of carbon atoms of the alkyl group to 10 to 30, it is possible to realize a low viscosity and further dispersion stabilization of the pigment dispersion. The alkyl chain having 10 or more carbon atoms may be linear or branched, but is preferably linear. Examples of the alkyl chain include decyl group (C10), lauryl group (C12), myristyl group (C14), cetyl group (C16), stearyl group (C18), aralkyl group (C20), behenyl group (C22), lignoceryl group (C24). ), Serotoyl group (C26), montanyl group (C28), merisyl group (C30) and the like. From the viewpoint of ensuring high glossiness and color developability and ensuring excellent ejection stability, the alkyl chain preferably has 10 to 25 carbon atoms, particularly preferably 10 to 15 carbon atoms. If the alkyl chain has 10 or more carbon atoms, the dispersion stability is improved, and it is possible to obtain a printed matter having high glossiness and color developability by suppressing pigment aggregation during drying. In some cases, the discharge stability may deteriorate.

  The content contained in the copolymer of the monomer (C) containing an alkyl chain having 10 to 30 carbon atoms contained in ((meth) acrylic copolymer (X)) used in the present invention is: From the viewpoint of ensuring a print image quality excellent in gloss and color developability, it is preferably 5% by weight to 50% by weight, more preferably 20% by weight to 45% by weight, and 30% by weight to 45% by weight. It is particularly preferred that

  The acid value of the pigment-dispersed resin used in the present invention is preferably 30 to 400 mgKOH / g. If the acid value is less than 30 mg KOH / g, the resin is difficult to dissolve in water, and thus the viscosity of the ink is increased, which may affect ejection. Moreover, even if it is a case where it is larger than 400 mgKOH / g, the interaction between resin becomes strong and a viscosity may become high. The acid value of the pigment dispersion resin is more preferably 100 to 300 mgKOH / g.

  The pigment-dispersed resin used in the present invention is preferably neutralized with an acid group in the resin in order to increase the solubility in water. As the base, organic bases such as aqueous ammonia, dimethylaminoethanol, diethanolamine, and triethanolamine, and inorganic bases such as lithium hydroxide, sodium hydroxide, and potassium hydroxide can be used. When an organic base is used, the base is volatilized when the ink is dried, which may improve the water resistance of the printed matter.

  In the present invention, the weight ratio of the pigment dispersion resin to the pigment is preferably 1.5 / 1 to 100/1. When the ratio of the pigment dispersion resin is larger than 1.5 / 1, the viscosity of the ink is increased. On the other hand, if it is less than 100/1, the dispersibility stability is lowered. From the viewpoint of securing excellent dispersion stability and obtaining a print image quality having high glossiness and color developability, the ratio of the pigment to the pigment dispersion resin is more preferably 2/1 to 20/1, more preferably 2.5 /. 1 to 10/1, particularly preferably 3/1 to 10/1.

<Water-soluble organic solvent>
The ink-jet magenta ink of the present invention has an optimal wet and dry property on a hardly-absorbable substrate, and from the viewpoint of ensuring excellent print image quality with few white spots and ejection stability from the ink-jet nozzle. It is characterized by containing a C3-C6 alkanediol whose boiling point is 190 degreeC or more as an ionic organic solvent. When the boiling point is lower than 190 ° C., the ink dries before spreading sufficiently on the hardly absorbent substrate, leading to problems such as white spots. Moreover, when it does not have sufficient wettability, problems, such as a high glossiness not being obtained, arise by impairing the smoothness of a printed coating film. Furthermore, since the moisture retention is insufficient, the ejection stability may be impaired. On the other hand, when the number of carbon atoms is smaller than 3, the wettability is insufficient on the hardly-absorbable substrate, leading to problems that the original color developability of the pigment cannot be expressed due to the occurrence of white spots or the like. Further, when the number of carbon atoms is larger than 6, the solubility in water is lowered, so that when water volatilizes on the ink jet nozzle, insolubilization may lead to problems such as non-ejection.

  Any solvent having 3 to 6 carbon atoms having a boiling point of 190 ° C. or higher can be used alone or in combination. For example, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3-butanediol, 1,2-butanediol 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,2-hexanediol, 1,6 -Hexanediol etc. are mentioned. From the viewpoint of ensuring excellent wettability and drying on a hardly absorbent substrate, it is more preferable to use an alkanediol having 3 to 4 carbon atoms having a boiling point of 190 ° C. or higher. Particularly preferred is 1,3-propanediol.

  In addition, organic solvents other than those described above can be used singly or in combination as long as the content is within a suitable range that does not reduce the effect of the present invention. When using together, it is preferable that the ratio of a C3-C6 alkanediol with respect to the total amount of the organic solvent in ink is 70 to 99 weight%, More preferably, it is 80 to 95 weight%.

  Other organic solvents 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, dipropylene glycol monomethyl ether, dipropylene glycol Monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene Glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol methyl ethyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl Chirueteru, tetraethylene glycol butyl ether, propylene glycol dimethyl ether, tripropylene glycol dimethyl ether and the like.

  Further, a water-soluble nitrogen-containing solvent can be added for the purpose of improving the penetration and adhesion to the hardly absorbent substrate.

  Nitrogen-containing solvents include 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, N, N-dimethyl-β-methoxypropionamide, N , N-dimethyl-β-ethoxypropionamide, N, N-dimethyl-β-butoxypropionamide, N, N-dimethyl-β-pentoxypropionamide, N, N-dimethyl-β-hexoxypropionamide, N , N-dimethyl-β-heptoxypropionamide, N, N-dimethyl-β-2-ethylhexoxypropionamide, N, N-dimethyl-β-octoxypropionamide, N, N-diethyl-β-butoxy Propionamide, N, N-diethyl-β-pentoxypropionamide, N, N-diethyl-β- Examples include hexoxypropionamide, N, N-diethyl-β-heptoxypropionamide, N, N-diethyl-β-octoxypropionamide, and the like.

  The total amount of the water-soluble organic solvent used in the present invention in the ink composition is preferably 5% by weight or more and 65% by weight or less. From the viewpoint of ensuring sufficient wettability and drying on a hardly absorbent base material in order to obtain ejection stability from the inkjet nozzle and excellent printability, the total amount of the water-soluble organic solvent is 10% by weight or more 55 More preferably, it is 20% by weight or more and 50% by weight or less. Especially preferably, it is 30 to 50 weight%. If the total amount of the water-soluble organic solvent is less than 5% by weight, the moisture retention of the ink is insufficient, and the ejection stability may be impaired. Moreover, the wettability on a hardly absorbable base material may fall. If the total content of the water-soluble organic solvent is more than 65% by weight, the viscosity of the ink becomes high, and the ejection stability may be impaired. Further, the storage stability and drying property of the ink are not suitable for practical use, and the print quality may be deteriorated.

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

  The content of water that can be used in the present invention is preferably in the range of 20 to 90% by weight of the total weight of the ink.

<Binder resin>
The inkjet magenta ink of the present invention is a binder resin (however, a (meth) acrylic copolymer (X)) in order to increase the drying property of the ink on the poorly permeable substrate and the coating film resistance of the printed matter. Except in some cases). It is preferable to use water-dispersible resin fine particles as the binder resin. 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 reduce the viscosity of the ink and can be blended with a larger amount of resin in the ink, so that it can be said that the resin fine particles are suitable for enhancing the resistance of the ink-jet ink. Examples of the resin fine particles include acrylic, urethane, styrene butadiene, vinyl chloride, and polyolefin.

  The content of the binder resin in the ink composition as described above is preferably in the range of 1 to 20% by weight of the total weight of the ink in terms of non-volatile content.

<Surfactant>
In the inkjet magenta ink of the present invention, a surfactant can be used for the purpose of adjusting the surface tension and ensuring the wettability on the hardly absorbent substrate. As the surfactant, various types of acetylene-based, silicon-based, acrylic-based, fluorine-based and the like are known, but if the surface tension is too low, the nozzle surface of the inkjet head gets wet with ink, Adjustment of the surface tension of the ink is very important because it impairs the ejection stability. It is preferable to use an acetylene-based, silicon-based, or fluorine-based surfactant from the viewpoint of ensuring optimum wettability on a difficult-to-absorbent substrate and stable ejection from the inkjet nozzle, and acetylene-based, especially acetylenic diol-based It is particularly preferable to use the surfactant. As an example of the addition amount of the surfactant, 0.1 wt% or more and 5 wt% or less is preferable with respect to the total weight of the ink. In addition, a plurality of surfactants may be used in combination.

<Other ingredients>
In addition to the above-described components, the inkjet magenta ink of the present invention may be appropriately added with additives such as an antifoaming agent and an antiseptic agent in order to obtain an ink having desired physical properties as required. it can. As an example of the addition amount of these additives, 0.01% by weight or more and 10% by weight or less is preferable with respect to the total weight of the ink.

<Ink set>
The inkjet magenta ink of the present invention may be used in a single color, but it 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, yellow, and magenta. 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.

  For each ink constituting the ink jet ink set of the present invention, any of known organic pigments and inorganic pigments can be used. Among these, when used in a combination of cyan, yellow and magenta, examples of cyan pigments include copper phthalocyanine pigments such as C.I. I. Pigment Blue 15: 3 and 15: 4 are selected from C.I. I. It is preferable to use a pigment selected from CI Pigment Yellow 14, 74, 120, and 150. As the magenta ink, high color reproducibility can be obtained by using the magenta ink of the present invention in combination.

<Ink preparation method>
Examples of the method for preparing 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 dispersant 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 organic solvent or an appropriately selected additive component as listed above is added to this pigment dispersion, and the mixture is stirred and filtered as necessary to obtain the ink of the present invention. And

  In the ink preparation method of the present invention, as described above, a pigment dispersion obtained by carrying out a dispersion treatment is used for ink preparation, but before the dispersion treatment carried out during the preparation of the pigment dispersion. It is effective to perform premixing. 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 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).

  In the pigment premixing and dispersion treatment, the pigment dispersant may be dissolved or dispersed only in water, or may be dissolved or dispersed in a mixed solvent of an organic solvent and water.

  As the pigment contained in the ink of the present invention, it is preferable to use a pigment having an optimum particle size distribution as described above. In order to obtain a pigment having a desired particle size distribution, the following method may be mentioned. Reduce the size of the grinding media of the disperser mentioned above, change the material of the grinding media, increase the filling rate of the grinding media, change the shape of the stirring member (agitator), dispersion This is a combination of increasing the processing time, classifying with a filter or a centrifugal separator after dispersion processing, and the like. In order to keep the pigment in the present invention in the above preferred particle size range, the size of the grinding media of the disperser is preferably 0.1 to 3 mm in diameter. Further, glass, zircon, zirconia, and titania are preferably used as the material for the grinding media.

<Non-absorbable substrate>
The hardly absorbent substrate used in the present invention is a recording medium that hardly absorbs water or has a low absorption rate. Examples thereof include paper media such as coated paper, cast coated paper, art paper, and fine coated paper, and plastic media such as polyvinyl chloride sheet, PET film, and PP film. 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.

<Printing method>
As a method for printing the ink-jet ink of the present invention, a method in which ink is ejected from the nozzles of an ink-jet head and ink droplets are deposited on a printing substrate is used.

  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.

<Example of production of pigment dispersion resin 1>
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 reaction vessel was heated to 110 ° C., and 30 parts of styrene as a polymerizable monomer, 55 parts of acrylic acid, 15 parts of 2-ethylhexyl methacrylate, and 6 parts of V-601 (manufactured by Wako Pure Chemical Industries) as a polymerization initiator. The mixture was added dropwise over 2 hours to conduct a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, then 0.6 part of V-601 (manufactured by Wako Pure Chemical Industries) was added, and the reaction was further continued at 110 ° C. for 1 hour to obtain a dispersion resin 1 solution. It was. Further, after cooling to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization, and 100 parts of water was added to make it aqueous. Then, it heated to 100 degreeC or more, butanol was azeotroped with water, butanol was distilled off, and it adjusted so that solid content might be 50%. As a result, an aqueous solution having a solid content of 50% of the pigment dispersion resin 1 was obtained.

<Production Examples of Pigment Dispersing Resin 2-19>
An aqueous solution having a solid content of 50% of the pigment dispersion resins 2 to 19 was obtained in the same manner as the pigment dispersion resin 1 except that the monomers listed in Table 1 were used as the polymerizable monomers.

Abbreviations listed in Table 1 are as follows.
St: Styrene AA: Acrylic acid MAA: Methacrylic acid 2EHMA: 2-Ethylhexyl methacrylate LMA: Lauryl methacrylate SMMA: Stearyl methacrylate VA: Behenyl acrylate MTA: Montanyl acrylate

<Example of production of magenta pigment dispersion 1 (MB1)>
As a pigment, C.I. I. 20 parts of Pigment Red 150, 8 parts of an aqueous solution of Pigment Dispersion Resin 1 and 72 parts of water were mixed, predispersed with a disper, and then filled with 1800 g of zirconia beads having a diameter of 0.5 mm and having a capacity of 0.6 L Was used to obtain a magenta pigment dispersion 1 (MB1).

<Production Examples of Magenta Pigment Dispersions 2 to 23 (MB2 to MB23)>
Except for using the raw materials shown in Table 2, pigment dispersion was performed in the same manner as for magenta pigment dispersion 1 (MB1) to obtain magenta pigment dispersions 2 to 23 (MB2 to MB23).

Abbreviations listed in Table 2 are as follows.
P. R. 150: C.I. I. Pigment Red 150
P. R. 122: C.I. I. Pigment Red 122

<Production Example of Cyan Pigment Dispersion Liquid 1 (CB1)>
As a pigment, C.I. I. 20 parts of Pigment Blue 15: 3, 10 parts of an aqueous solution of Pigment Dispersion Resin 9 and 70 parts of water were mixed, predispersed with a disper, and filled with 1800 g of zirconia beads having a diameter of 0.5 mm, 0.6 L This dispersion was carried out using a dyno mill of No. 1 to obtain Cyan Pigment Dispersion Liquid 1 (CB1).

<Production Example of Yellow Pigment Dispersion Liquid 1 (YB1)>
As a pigment, C.I. I. 20 parts of Pigment Yellow 14, 10 parts of an aqueous solution of Pigment Dispersion Resin 9 and 70 parts of water were mixed, predispersed with a disper, and filled with 1800 g of zirconia beads having a diameter of 0.5 mm and having a capacity of 0.6 L Was subjected to main dispersion to obtain a yellow pigment dispersion 1 (YB1).

<Production Example of Yellow Pigment Dispersion Liquid 2 (YB2)>
As a pigment, C.I. I. Pigment dispersion was carried out in the same manner as in Yellow Pigment Dispersion Liquid 1 (YB1) except that Pigment Yellow 74 was used to obtain Yellow Pigment Dispersion Liquid 2.

<Production Example of Yellow Pigment Dispersion Liquid 1 (YB3)>
As a pigment, C.I. I. Pigment dispersion was performed in the same manner as in Yellow Pigment Dispersion 1 (YB1), except that Pigment Yellow 120 was used, and Yellow Pigment Dispersion 3 was obtained.

<Production Example of Yellow Pigment Dispersion Liquid 4 (YB4)>
As a pigment, C.I. I. Pigment dispersion was performed in the same manner as in Yellow Pigment Dispersion Liquid 1 (YB1) except that Pigment Yellow 150 was used, and Yellow Pigment Dispersion Liquid 4 was obtained.

<Production Example of Yellow Pigment Dispersion Liquid 5 (YB5)>
As a pigment, C.I. I. Except for using Pigment Yellow 154, pigment dispersion was performed in the same manner as Yellow Pigment Dispersion Liquid 1 (YB1) to obtain Yellow Pigment Dispersion Liquid 5.

<Production example of magenta ink 1 (M1)>
20 parts of magenta pigment dispersion (MB1), 40 parts of 1,3-propanediol, 0.5 parts of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration with a membrane filter was performed to remove coarse particles that cause clogging of the head, and magenta ink 1 (M1) was prepared.

<Production example of magenta inks 2-39 (M2-39)>
Using the raw materials shown in Table 3, magenta inks 2-39 (M2-39) were prepared in the same manner as in the production example of magenta ink 1 (M1).

Abbreviations listed in Table 3 are as follows.
1,2-PD: 1,2-propanediol (boiling point: 188.2 ° C.)
1,3-PD: 1,3-propanediol (boiling point: 214 ° C.)
1,2-BD: 1,2-butanediol (boiling point: 191 ° C.)
1,3-BD: 1,3-butanediol (boiling point: 203 ° C.)
1,5-PenD: 1,5-pentanediol (boiling point: 242 ° C.)
1,2-HexD: 1,2-hexanediol (boiling point: 224 ° C.)
EDG: Diethylene glycol monoethyl ether (boiling point: 196 ° C)
BDG: Diethylene glycol monobutyl ether (boiling point: 230 ° C.)
EG: ethylene glycol (boiling point: 197.3 ° C)
Activator: Surfynol 440 (Air Products, acetylenic diol activator)

<Production example of cyan ink 1 (C1)>
20 parts of magenta pigment dispersion (CB1), 30 parts of 1,3-propanediol, 0.5 parts of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration with a membrane filter was performed to remove coarse particles that would cause clogging of the head, thereby preparing cyan ink 1 (C1).

<Example of production of yellow ink 1 (Y1)>
20 parts of yellow pigment dispersion (YB1), 30 parts of 1,3-propanediol, 0.5 parts of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration was carried out with a membrane filter to remove coarse particles which cause clogging of the head, thereby producing yellow ink 1 (Y1).

<Example of production of yellow ink 1 (Y2)>
20 parts of yellow pigment dispersion (YB2), 30 parts of 1,3-propanediol, 0.5 part of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration was carried out with a membrane filter to remove coarse particles causing the clogging of the head, and yellow ink 2 (Y2) was prepared.

<Example of production of yellow ink 3 (Y3)>
20 parts of yellow pigment dispersion (YB3), 30 parts of 1,3-propanediol, 0.5 parts of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration was carried out with a membrane filter to remove coarse particles causing the clogging of the head, thereby producing yellow ink 3 (Y3).

<Example of production of yellow ink 4 (Y4)>
20 parts of yellow pigment dispersion (YB4), 30 parts of 1,3-propanediol, 0.5 part of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), and 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration was carried out with a membrane filter to remove coarse particles causing the clogging of the head, thereby producing yellow ink 4 (Y4).

<Example of production of yellow ink 5 (Y5)>
20 parts of yellow pigment dispersion (YB5), 30 parts of 1,3-propanediol, 0.5 part of activator (Acetylenediol-based activator Surfynol 440 manufactured by Air Products), 100 parts of the whole ink with the rest as water And stirred with a disper until it was sufficiently uniform. Thereafter, filtration was carried out with a membrane filter to remove coarse particles causing the clogging of the head, thereby producing yellow ink 5 (Y5).

<Evaluation of inkjet ink>
The following evaluation was performed about the produced magenta ink 1-39 (M1-39). The evaluation results obtained are shown in Table 4.

<Evaluation of average secondary particle size of ink>
The average secondary particle size (D50) of magenta ink was evaluated using a particle size distribution measuring machine (Nikkiso Microtrac UPA EX-150).

<Evaluation of ink storage stability>
The viscosity of magenta ink was measured using an E-type viscometer (TVE-20L manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. under the condition of a rotation speed of 50 rpm. This ink was stored in a thermostat at 70 ° C. and accelerated with time, and the change in the viscosity of the ink before and after aging was evaluated. The evaluation criteria are as follows, and AA, A, and B evaluation are practical areas.
AA: Viscosity change rate after storage for 4 weeks is less than ± 5% A: Viscosity change rate after storage for 2 weeks is less than ± 5% B: Viscosity change rate after storage for 1 week is less than ± 5% C: Storage for 1 week Later viscosity change rate is more than ± 5%

<Evaluation of white spots>
Solid printing with a printing rate of 100% was performed by ejecting ink under the printing conditions of a frequency of 20 kHz and 600 × 600 dpi using an inkjet ejection device equipped with a head (QA06NTB) manufactured by Kyocera Corporation. Printing is performed using OK Top Coat + (coated paper) manufactured by Oji Paper Co., Ltd. as the printing substrate. After printing, the printed material is dried for 3 minutes using a 50 ° C. air oven. And visually confirmed. Evaluation criteria are as follows, and A and B evaluations are practical areas.
A: No white spots are observed with a magnifying glass or visually. B: White spots are slightly observed with a loupe, but no white spots are visually observed. C: White spots are clearly observed visually.

<Evaluation of dryness>
Observe the occurrence of mottling of the printed material after printing with the same printing conditions and printing substrate as in the above evaluation, using a printing substrate with a printing rate of 100% and drying the printed material for 3 minutes using a 50 ° C air oven after printing. Then, the drying property was evaluated. Evaluation criteria are as follows, and A and B evaluations are practical areas.
A: Almost no mottling, and no density unevenness in the printed material B: Slight mottling, but no density unevenness in the printed material C: Mottling clearly occurs, and the printed material Density unevenness is occurring

<Color development evaluation>
Solid printing with a printing rate of 100% was performed using the same printing conditions and printing substrate as in the above evaluation, and the density was measured using a spectral densitometer (manufactured by X-RITE). The evaluation criteria were as follows. The evaluation criteria are as follows, and AA, A, and B evaluations are practical areas.
AA: OD value 1.6 or more A: OD value 1.5 or more and less than 1.6 B: OD value 1.4 or more and less than 1.5 C: OD value less than 1.4

<Glossy evaluation>
The same printing conditions as in the above evaluation, solid printing with a printing rate of 100% using a printing substrate, and after printing, the printed material was dried for 3 minutes using a 50 ° C. air oven to obtain a 60 ° glossiness of the printed material. Was measured and evaluated using a gloss meter. The evaluation criteria are as follows, and AA, A, and B evaluations are practical areas.
AA: Glossiness of 55 or more, excellent gloss uniformity on the printed surface A: Gloss value is 45-55, excellent gloss uniformity on the printed surface B: Gloss value is 45-55, The gloss of the printed surface is slightly uneven. C: The gloss value is 35 to 45, and the uniformity of the gloss on the printed surface is poor. D: The gloss value is 25 to 35, and the gloss of the printed surface is extremely poor.

<Evaluation of ejection stability>
The same printing conditions as in the above evaluation, solid printing with a printing rate of 100% using a printing substrate, and after waiting for the inkjet discharge device for a certain period of time in an environment of 25 ° C. after printing, the printing rate again under the same printing conditions 100% solid printing was performed, and visual evaluation was performed to determine whether nozzle missing occurred. The evaluation criteria are as follows, and AA, A, and B evaluations are practical areas.
AA: No nozzle missing even after printing after waiting for 3 hours A: No nozzle missing even after printing after waiting for 2 hours B: No nozzle missing even after printing after waiting for 1 hour No C: 1 to 9 nozzle missing occurs when printing after waiting for 1 hour D: 10 or more nozzle missing occurs when printing after waiting for 1 hour

<Evaluation of inkjet ink set>
Using the ink combinations listed in Table 5 as an ink set, an ink jet discharge device equipped with a head (QA06NTB) manufactured by Kyocera Corporation was used to discharge a color chart image by discharging ink under printing conditions of a frequency of 20 kHz and 600 × 600 dpi. Printing was done. Printing is performed using OK Top Coat + (coated paper) manufactured by Oji Paper Co., Ltd. as the printing substrate. After printing, the printed material is dried for 3 minutes using a 50 ° C. air oven. Evaluation was performed by measuring the color using a meter (manufactured by X-rite). The evaluation was performed by comparison with a color reproduction region defined by Japan Color 2007 for sheet-fed printing. The evaluation criteria are as follows, and AA, A, and B evaluations are practical areas.
AA: Color reproduction area greater than Japan color A: Color reproduction area equivalent to Japan color B: Color reproduction area slightly less than Japan color C: Color reproduction area much narrower than Japan color

  The evaluation results obtained by the above evaluation are shown in Table 6.

That is, the present invention is an inkjet magenta ink containing at least a pigment, a pigment dispersion resin, a water-soluble organic solvent, and water,
The pigment is C.I. I. Pigment Red 150,
The pigment-dispersed resin contains a monomer (A) containing at least an aromatic ring in the copolymer composition, and includes a (meth) acrylic copolymer (X) having a weight average molecular weight of 15,000 to 50,000,
Wherein the water-soluble organic solvent, see contains at least the boiling point of carbon number 3-4 is 190 ° C. or higher alkane diols,
C. above. I. The content of Pigment Red 150 is in the range of 1 to 10% by weight in the inkjet magenta ink, and relates to the inkjet magenta ink.

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. Examples 22 and 23 are reference examples.

Claims (7)

An inkjet magenta ink containing at least a pigment, a pigment dispersion resin, a water-soluble organic solvent, and water,
The pigment is C.I. I. Pigment Red 150,
The pigment-dispersed resin contains a monomer (A) containing at least an aromatic ring in the copolymer composition, and includes a (meth) acrylic copolymer (X) having a weight average molecular weight of 15,000 to 50,000,
An inkjet magenta ink, wherein the water-soluble organic solvent contains at least a C 3-6 alkanediol having a boiling point of 190 ° C. or higher.   The inkjet magenta ink according to claim 1, wherein an average secondary particle diameter (D50) of the pigment in the ink is 115 nm to 210 nm.   The (meth) acrylic copolymer (X) further contains (meth) acrylic acid (B) in the copolymer composition, and the content of the monomer (A) containing the aromatic ring is the above (meta) ) 4% to 65% by weight based on the acrylic copolymer, and the total content of the monomer (A) containing the aromatic ring and the (meth) acrylic acid (B) is The ink-jet magenta ink according to claim 1, wherein the content is 10% by weight to 95% by weight with respect to the (meth) acrylic copolymer.   The (meth) acrylic copolymer (X) further contains a monomer (C) containing an alkyl chain having 10 to 30 carbon atoms in the copolymer composition. Inkjet magenta ink according to any one of the above.   The inkjet magenta ink according to any one of claims 1 to 4, wherein the water-soluble organic solvent contains at least an alkanediol having 3 or 4 carbon atoms. An inkjet ink set including at least cyan ink, yellow ink, and magenta ink,
The cyan ink comprises a copper phthalocyanine pigment;
The yellow ink is C.I. I. A pigment selected from CI Pigment Yellow 14, 74, 120 and 150;
An ink set, wherein the magenta ink is the inkjet magenta ink according to any one of claims 1 to 5.   An inkjet printing method, comprising printing the inkjet magenta ink according to any one of claims 1 to 5 on a hardly absorbent substrate.