JP2018115325A - Magenta ink for inkjet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magenta ink that can give a sharp image having high glossiness while preventing uneven density or a white void in inkjet printing on a hardly-absorptive base material, showing excellent discharge stability after a long-term standby period, and giving excellent drying property even in high-speed printing, and an ink set achieving high color reproducibility while suppressing color mixture blur.SOLUTION: A magenta ink for inkjet is provided, comprising a pigment, a water-soluble organic solvent (A), a surfactant (B), and water. The pigment contains an azo pigment by 1 to 10 wt.% in the whole amount of the ink; the water-soluble solvent (A) contains a water-soluble organic solvent (A-1) showing a static surface tension of 22 to 32 mN/m at 25°C and an HLB value of 2.0 to 8.0 and having at least one hydroxyl group, by 5 to 50 wt.% in the whole amount of the ink; and the surfactant (B) contains a surfactant (B-1) having an HLB value of 1.5 to 8.0.SELECTED DRAWING: None

Description

  The present invention provides a clear print image with high gloss with little unevenness of density and white spots on a poorly permeable substrate when printing at high speed, excellent ejection stability after standing for a long time, and further difficult absorption The present invention relates to a magenta ink for ink jet capable of obtaining excellent drying properties on a substrate.

  Since digital printing does not require a plate like conventional offset printing and gravure printing, the production cost can be reduced by small lot printing and the size of the printing machine can be reduced, and it is used in various applications.

  There are two digital printing technologies currently used in the market. One is an electrophotographic method, which uses a powder or liquid toner for printing, and is a technology widely used in color printers, office multifunction devices, and the like. Another digital printing technology is the inkjet method, which is also used for various purposes including consumer printers.

  The ink jet method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording member and attaching them. This is an excellent printing technology that not only has the advantages of low noise and good operability, but also facilitates colorization.

  In addition to ink jet characteristics, many inks such as water-based inks, oil-based inks, solvent-based inks, and ultraviolet curable (UV) inks can be used, and printing can be performed on various printing media without contact. Since printing can be performed on paper other than paper, it is used not only for commercial printing but also for industrial printing such as sign / display printing.

  In industrial printing applications, printing presses capable of printing on plastic substrates such as polyvinyl chloride sheets and PET films using solvent-based inks and UV inks have actually been commercially available. However, in recent years, the demand for water-based inks has increased from the viewpoint of safety and environmental compatibility.

  As water-based inks for ink jets, as in Patent Documents 1 to 4, inks for special paper such as plain paper and photographic glossy paper have been developed for a long time. On the other hand, in recent years, further expansion of the application of the ink jet recording method is expected, and the need for direct printing on hardly-absorbable substrates such as art paper, coated paper, and fine coated paper is also 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.

  In particular, since the water-based ink has a high surface tension of water, the water-based ink hardly penetrates into a substrate having a low absorbency (not easily absorbable) as described above, and is very difficult to spread. Therefore, when water-based ink is printed on a hardly absorbable substrate, white spots due to insufficient wetting and spreading of the ink on the substrate are likely to occur. Further, since the surface tension of the water-based ink is high, the droplets coalesce on the base material at the time of landing, leading to deterioration of the image quality such as unevenness of the printed coating film.

  On the other hand, in order to expand the application of the ink jet system, high color rendering on the substrate is also required, and in particular, there is an increasing demand for color development and color gamut expansion of magenta ink. In general, quinacridone pigments and azo pigments are known as pigments used in magenta inks. However, quinacridone pigments have a low coloring power and do not have a satisfactory color reproduction range. On the other hand, azo pigments have a high coloring power and a wide color reproduction range, but they have poor stability to organic solvents, and in some cases, the pigments dissolve, and the original coloring property and gloss on the substrate cannot be expressed. there were. In addition, when an ink containing an azo pigment dissolved in an organic solvent is allowed to stand by for a long time in an inkjet head, the pigment is deposited in the process of water volatilizing and the ink is concentrated, causing nozzle clogging and the like. It was.

  In order to solve the above-mentioned problem, the present applicant has previously disclosed C.I. I. An ink using Pigment Red 150 and a basic organic compound was proposed. According to Patent Document 5, it is possible to obtain an ink-jet ink that has excellent red color reproducibility and excellent discharge stability without causing problems such as nozzle clogging. However, the ink disclosed in the example of Patent Document 5 has a high surface tension and insufficient wettability with respect to a hardly absorbable substrate, so that the ink is not filled and white spots occur or uneven density occurs. There is concern.

JP 2004-210996 A JP 2001-354888 A JP 2008-247951 A JP 2012-211260 A JP 2014-214277 A

  The object of the present invention is to provide ink jet printing on a hard-to-absorbent substrate, with no uneven density or white spots, a high gloss and clear image, excellent discharge stability after waiting for a long time, and high speed printing. It is an object of the present invention to provide a magenta ink for ink jet which can obtain excellent drying properties.

  Another object of the present invention is to provide an ink set containing the above-described magenta ink for ink jet which can suppress mixed color bleeding and realize high color reproducibility on a hardly absorbable substrate.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an azo pigment, a water-soluble organic solvent (a) having a specific static surface tension and an HLB value and having at least one hydroxyl group And found that the above-mentioned problems can be solved by an ink jet magenta ink containing a surfactant (B-1) having a specific HLB value and an ink set containing the ink jet magenta ink, and completed the present invention. It was.

  That is, the present invention is an ink-jet magenta ink containing at least a pigment, a water-soluble organic solvent (A), a surfactant (B), and water, wherein the pigment contains an azo pigment and the total amount of the ink-jet magenta ink. 1 to 10% by weight, the water-soluble organic solvent (A) has a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups The water-soluble organic solvent (A-1) having 5 to 50% by weight in the total amount of magenta ink for inkjet, and the surfactant (B) has a HLB value of 1.5 to 8.0. The present invention relates to an ink-jet magenta ink comprising an agent (B-1).

  The present invention also relates to the above-described magenta ink for ink jet, wherein the spectral reflectance of a coated product having a wet film thickness of 6 μm produced on a recording medium is 10% or less in a wavelength region of 480 to 580 nm. .

  In the present invention, the azo pigment may be C.I. I. The present invention relates to the inkjet magenta ink, which is CI Pigment Red 150.

  The present invention also relates to the magenta ink for ink jet, wherein the water-soluble organic solvent (A-1) contains at least one compound having a boiling point of 190 to 250 ° C. under 1 atm.

  The present invention also relates to the magenta ink for ink jet, wherein the compound having a boiling point of 190 to 250 ° C. under 1 atm is an alkanediol having 4 to 6 carbon atoms.

  In the present invention, the water-soluble organic solvent (A-1) contains at least one glycol alkyl ether having a boiling point of 100 to 250 ° C. under 1 atm. It relates to ink.

  The present invention also relates to the above magenta ink for ink jet, wherein the dynamic surface tension at 10 msec calculated by the maximum bubble pressure method is 25 to 35 mN / m.

  Moreover, the present invention further includes a (meth) acrylic copolymer having a weight average molecular weight of 15,000 to 50,000, which contains at least a monomer containing an aromatic ring in the copolymer composition as a pigment dispersion resin. And magenta ink for inkjet.

  The present invention also relates to the above-described magenta ink for ink jet, wherein the surfactant (B-1) contains at least one polyether-modified polydimethylsiloxane.

  The present invention also relates to the above-described magenta ink for inkjet, wherein the polyether-modified polydimethylsiloxane has a polyether group in a side chain of the polydimethylsiloxane chain.

  The present invention is also an inkjet ink set including at least cyan ink, yellow ink, and magenta ink, wherein the cyan ink and yellow ink contain at least one surfactant (B-1), and the magenta The present invention relates to an ink set, wherein the ink is the inkjet magenta ink.

  The present invention also relates to a method for producing an ink-jet printed matter, wherein the ink-jet magenta ink or the ink set is printed on a hardly absorbable substrate.

  According to the present invention, in inkjet printing on a hardly absorbable substrate, there is no uneven density or white spot, a high gloss and clear image is obtained, excellent discharge stability after waiting for a long time, and high speed printing. However, it is possible to provide a magenta ink for ink jet which can obtain excellent drying properties.

  Further, according to the present invention, it is possible to provide an ink set including the above-described magenta ink for ink jet which can suppress mixed color bleeding and realize high color reproducibility in a hardly absorbable substrate.

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

  In the present invention, an azo pigment, a water-soluble organic solvent (A-1) having a specific static surface tension and an HLB value and having one or more hydroxyl groups, and a surfactant (B) having a specific HLB value -1) is used in ink jet printing on difficult-to-absorbent substrates, there is no uneven density or white spots, and a high-gloss and clear image is obtained, which is excellent in ejection stability after waiting for a long time. Ink jet magenta ink (hereinafter, also simply referred to as ink) capable of obtaining excellent drying properties even in high-speed printing.

  As described in the prior art, the water-based ink generally has a very high surface tension of water contained as a main component, and therefore, it is difficult to wet and spread on the substrate. In addition, it is known that the hard-to-absorbent substrate has a low surface tension itself, and the ink is less likely to wet and spread than other substrates. When printing on these hardly absorbent substrates using an inkjet head, if the surface tension of the ink is high, etc., if the wettability on the substrate is insufficient, adjacent ink droplets that have landed , They are united before spreading sufficiently on the substrate, resulting in uneven density. In addition, white spots occur due to ink not being buried on the base material, and gloss defects occur due to unevenness on the printed coating film because dots are not smooth.

  Furthermore, since the hard-to-absorbent substrate is difficult for water-based ink to permeate, printing troubles due to poor drying of the ink are likely to occur. In particular, when the wettability of the ink on the base material is insufficient, the area where the ink droplet contacts the base material may be small, and drying defects are likely to occur. As described above, it is very important to improve the wettability of the ink in order to obtain excellent print image quality and drying property on the hardly absorbent substrate.

  On the other hand, azo pigments are pigments with high color development and excellent color reproducibility, but they are not stable to organic solvents, especially highly hydrophobic organic solvents, and are highly hydrophobic organic to improve ink wettability. When used in combination with a solvent, there is a problem that the original color developability and gloss cannot be expressed because the pigment dissolves in these solvents. Another problem is that when the ink is concentrated in the inkjet head for a long time, the azo pigment dissolved in the highly hydrophobic water-soluble organic solvent is deposited in the process of concentrating the ink, causing nozzle clogging and the like, resulting in non-ejection. there were.

  As described above, conventionally, an ink using an azo pigment is difficult to be used in combination with a highly hydrophobic organic solvent, and there has been a problem that printing image quality and drying property on a hardly absorbent substrate are inferior. As a result of intensive studies by the present inventors on this problem, an azo pigment, a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups And a water-soluble organic solvent (A) containing the water-soluble organic solvent (A-1) (hereinafter also simply referred to as “water-soluble organic solvent (A-1)”), and further having an HLB value of 1.5. The above-mentioned problem can be solved by using a surfactant (B) containing a surfactant (B-1) (hereinafter also referred to simply as “surfactant (B-1)”) of ˜8.0. I found. With the above configuration, it is excellent in printing image quality such as density unevenness, white spots, glossiness, and sharpness of printed matter even when printing on a hard-to-absorbent substrate, and has a suitable drying property even in high-speed printing, The reason why a magenta ink excellent in ejection stability after standing for a long time can be obtained is as follows.

  In this invention, the wettability of the ink with respect to a hardly absorbable base material can be improved by using the water-soluble organic solvent which has the static surface tension and HLB value of a specific range. However, it cannot prevent the azo pigment from dissolving as described above. Therefore, in the present invention, the water-soluble organic solvent is a compound having one or more hydroxyl groups, and the surfactant is further used in combination with a surfactant having a specific HLB value.

  Although details of the mechanism are not clear, azo pigments have an amide bond and a hydroxyl group in the molecular structure, and are considered to be easily linked to each other by a hydrogen bond with a water-soluble organic solvent having one or more hydroxyl groups. On the other hand, the HLB value of the surfactant used in the present invention is close to that of the water-soluble organic solvent. In general, those having similar HLB values are easily miscible with each other, so that it is considered that a large amount of the surfactant is present in the vicinity of the water-soluble organic solvent around the azo pigment. Therefore, it is considered that a highly hydrophobic surfactant is present around the azo pigment via the water-soluble organic solvent, and this is considered to prevent the dissolution of the azo pigment.

  On the other hand, since the HLB values close to each other are easy to mix with each other as described above, a part of the surfactant of the present invention is compatible with the water-soluble organic solvent, and the ink droplets land on the substrate. At this time, there is a possibility that the whole amount of the surfactant is not oriented at the droplet interface. Therefore, it is considered that a part of the added surfactant does not function as a surfactant, but in the present invention, the ink wettability is mainly secured by the water-soluble organic solvent, so that the ink wettability is improved. Is not considered to have any adverse effect. On the other hand, if the entire amount of the surfactant functions, the wettability becomes too good, and there is a possibility that the ink droplets are united before drying.

  As described above, the water-soluble organic solvent and the surfactant having the parameters stipulated in the present invention contribute to solving the problems of the present invention with an exquisite balance. It is considered that it is possible to obtain excellent printing image quality and drying property even on a hardly absorbent substrate while maintaining the properties and gloss.

  The main components of the ink according to the embodiment of the present invention will be described below.

<Pigment>
The content of the azo pigment used as the pigment of the magenta ink for inkjet according to the present invention ensures excellent sharpness and gloss on the printed matter, and the water-soluble organic solvent (A-1) and the surfactant (B-1). From the viewpoint of making the blending balance with the ink suitable, it is preferably in the range of 1 to 10% by weight relative to the total amount of ink. More preferably, it is 2 to 9% by weight, and particularly preferably 3 to 8% by weight.

  In the present invention, as the azo pigment, C.I. I. It is preferably at least one selected from CI Pigment Red 31, 146, 147, 150, 266, and 269. All of the above-mentioned pigments are also known as naphthol AS pigments. Compared to other azo pigments, they have better stability to highly hydrophobic organic solvents, have ether bonds and amino groups in their structures, and are water-soluble. Since the interaction with the volatile organic solvent (A-1) is considered to be strong, the effects of the present invention can be exhibited particularly suitably. Moreover, it is easy to adjust the spectral reflectance in a wavelength region of 480 to 580 nm, which will be described later, to 10% or less regardless of the type and amount of the water-soluble organic solvent (A-1) and the surfactant (B-1). Among the pigments exemplified above, at least C.I. C. is shown because of the sharpness of the image and particularly high color reproducibility when used as an ink set. I. It is particularly preferable to include CI Pigment Red 150.

  C. I. Pigment Red 150 is obtained by a coupling reaction of 3-amino-4-methoxybenzanilide and 3-hydroxy-2-naphthamide, and is commercially available C.I. I. It is known that a part of the raw material remains in Pigment Red 150 (see Patent Document 5). Since these raw materials also contain amino groups and hydroxyl groups, it is considered that the above-described interaction with the water-soluble organic solvent (A-1) and the surfactant (B-1) is caused. If the amount of raw materials contained as these impurities is large, C.I. I. Since the amount of the water-soluble organic solvent (A-1) or surfactant (B-1) that interacts with Pigment Red 150 is reduced, the blending balance of the material may be lost. In order to sufficiently exhibit the above, it is preferable to reduce the amount of these impurities. In the present invention, the content of 3-amino-4-methoxybenzanilide and 3-hydroxy-2-naphthamide is preferably 8000 ppm or less, more preferably 6000 ppm or less, respectively, based on the total amount of ink. More preferably, each is 4000 ppm or less, and particularly preferably 3000 ppm or less. In addition, content of the said impurity can be measured by HPLC method, for example.

<Water-soluble organic solvent (A-1)>
The magenta ink for inkjet according to the present invention is a water-soluble organic solvent (A) having a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups. The organic solvent (A-1) is contained in an amount of 5 to 50% by weight in the total amount of magenta ink for inkjet.

  The static surface tension of the ink of the present invention refers to the surface tension measured by the Wilhelmy method (plate method, vertical plate method) in an environment of 25 ° C. The static surface tension of the water-soluble organic solvent (A-1) used in the ink of the present invention is preferably 22 mN / m or more and 32 mN / m or less, more preferably 24 mN / m or more and 30 mN / m or less. preferable.

  The HLB value of the water-soluble organic solvent (A-1) used in the present invention needs to be 2.0 to 8.0. By keeping the HLB value within the above range, the miscibility with the surfactant (B-1) can be made suitable, and the sharpness and glossiness on the hard-to-absorbent substrate are improved, and at the long-term standby time. In this case, an ink excellent in ejection stability can be obtained without causing nozzle clogging. The HLB value of the water-soluble organic solvent (A-1) is 3.0 to 8.0 from the viewpoint of making the above miscibility more suitable and ensuring ejection stability, sharpness and glossiness. It is more preferably 3.0 to 6.0 from the viewpoint that an ink having high definition and gloss can be obtained.

  The HLB (Hydrophile-Lipophile Balance) value is one of the parameters representing the hydrophilicity / hydrophobicity of the material. The smaller the value, the higher the hydrophobicity of the material, and the higher the value, the higher the hydrophilicity of the material. There are various methods for calculating the HLB value, such as the Griffin method, the Davis method, and the Kawakami method, and various methods for actual measurement are known. However, in the present invention, the structure of a compound such as a water-soluble organic solvent is used. When clearly understood, the HLB value is calculated using the Griffin method. The Griffin method is a method for obtaining the HLB value as shown in the following formula (1) using the molecular structure and molecular weight of the target material.

Formula (1):

HLB value = 20 × (sum of molecular weight of hydrophilic portion) ÷ (molecular weight of material)

  On the other hand, when a compound with an unknown structure is included as in the surfactant described later, for example, “Surfactant Handbook” (Nishi Ichiro et al., Sangyo Tosho Co., Ltd., 1960) p. The HLB value of the surfactant can be experimentally determined by the following method described in H.324. Specifically, after dissolving 0.5 g of the surfactant in 5 mL of ethanol, the solution was titrated with a 2 wt% aqueous phenol solution while stirring at 25 ° C., and the end point was when the solution became cloudy. . When the amount of the phenol aqueous solution required up to the end point is A (mL), the HLB value can be calculated by the following formula (2).

Formula (2):

HLB value = 0.89 × A + 1.11

  The content of the water-soluble organic solvent (A-1) in the present invention ensures glossiness, sharpness, and drying properties on the hardly-absorbable substrate, and the azo pigment and the surfactant (B-1). From the viewpoint of making the blending balance suitable, it is preferably contained in the total amount of magenta ink for ink jetting by 5 to 50% by weight, more preferably from 10 to 45% by weight, and from 15 to 40% by weight. Is more preferable. Particularly preferably, the content is 20 to 35% by weight. By setting the content in the above range, the temporal stability of the ink can be improved.

  The water-soluble organic solvent (A-1) is a water-soluble organic solvent having a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups. Any solvent can be used. For example, 3-methoxy-1-butanol, 3-methyl-3-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, 1,2-butanediol, 1 , 2-pentanediol, 1,2-hexanediol and the like, but are not limited thereto.

  In the present invention, an ink containing only one type of water-soluble organic solvent corresponding to the water-soluble organic solvent (A-1) may be used, or an ink containing two or more types of water-soluble organic solvents (A-1). It may be. However, two or more types of water-soluble organic solvents corresponding to the water-soluble organic solvent (A-1) may be contained in the ink from the viewpoint of arbitrarily controlling white spots and dryability on the hardly absorbent substrate. preferable. When the ink contains two or more types of water-soluble organic solvents (A-1), at least one of them preferably has an HLB value of 3.0 to 6.0.

  When the ink of the present invention contains two or more types of water-soluble organic solvents (A-1), and one or more of them are water-soluble organic solvents having an HLB value of 3.0 to 6.0, the HLB value is The content of the water-soluble organic solvent that is 3.0 to 6.0 is preferably 1 to 25% by weight, more preferably 3 to 20% by weight, and 5 to 15% by weight in the total amount of the ink. It is particularly preferred that By being within the above range, it is possible to obtain an ink having particularly excellent drying properties without inhibiting the interaction with the azo pigment and the surfactant.

  The water-soluble organic solvent (A-1) in the present invention has a pressure of 1 atm from the viewpoint of ensuring the discharge stability after being kept on standby for a long time on the inkjet head and obtaining excellent drying properties on the hardly absorbent substrate. It is preferable to contain at least one compound having a boiling point of 190 to 250 ° C. Among the compounds having the boiling point, from the viewpoint of improving the discharge stability by making the interaction with the azo pigment suitable, and obtaining an ink excellent in printing image quality and drying property, it has 4 carbon atoms. It is particularly preferred to use ˜6 alkanediols. The content of the alkanediol having 4 to 6 carbon atoms is preferably 5 to 50% by weight, more preferably 10 to 45% by weight, and more preferably 15 to 40% by weight in the total amount of magenta ink for inkjet. Is more preferable. Particularly preferred is 20 to 35% by weight.

  In addition, the surfactant (B-1) that is not miscible with the water-soluble organic solvent (A-1) has a function of easily orienting uniformly at the ink interface, so that wetting on the hardly absorbable substrate is achieved. From the viewpoint of further improving the properties and obtaining an ink having excellent printing image quality and drying properties, the water-soluble organic solvent (A-1) is a glycol alkyl ether having a boiling point of 100 to 250 ° C. under 1 atm. It is preferable to contain at least one kind. The content of glycol alkyl ethers having a boiling point of 100 to 250 ° C. at 1 atm is preferably 0.5 to 25% by weight and more preferably 1 to 20% by weight in the total amount of magenta ink for inkjet. preferable. Particularly preferred is 2 to 15% by weight. If the boiling point exceeds 250 ° C., it may remain in the printed material after the drying step, which may cause deterioration of color developability and gloss. Glycol alkyl ethers having a boiling point of 100 to 200 ° C. at 1 atm. It is particularly preferable to use it.

<Other water-soluble organic solvents>
In the ink of the present invention, a water-soluble organic solvent other than the water-soluble organic solvent (A-1) can be used as long as the quality is not impaired. As water-soluble organic solvents other than the water-soluble organic solvent (A-1), 1,2-propanediol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1, 4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, glycerin, dipropylene glycol, 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, 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 methyl ether Methyl ether, tetraethylene glycol butyl methyl ether, 2-pyrrolidone, N- methylpyrrolidone, N- ethylpyrrolidone, but 3-methyl-2-oxazolidinone, and the like are not limited thereto.

  A compound having a boiling point of 250 ° C. to 400 ° C. is used as a water-soluble organic solvent other than the water-soluble organic solvent (A-1) for the purpose of improving moisture retention on the ink jet head and ensuring ejection stability. be able to. The content is preferably 0 to 5% by weight based on the total amount of ink. “0% by weight” means that the compound is not contained.

<Surfactant (B-1)>
The magenta ink for inkjet according to the present invention is characterized by containing at least one surfactant (B-1) having an HLB value of 1.5 to 8.0 as the surfactant (B). As the surfactant, various compounds such as acetylene-based, silicon-based, acrylic-based, and fluorine-based surfactants are known. Any compound having an HLB value of 1.5 to 8.0 can be used. These surfactants can be used alone or in combination.

  While improving the miscibility with the water-soluble organic solvent (A-1), the non-mixed surfactant (B-1) is uniformly oriented at the ink interface, and the wettability on the hardly absorbent substrate is improved. From the viewpoint of further improving and ensuring excellent printing image quality, the HLB value of the surfactant (B-1) needs to be 1.5 to 8.0, and is 2.0 to 7.0. Is more preferable. Most preferably, it is 2.5-6.0. If the HLB value is 8.0 or less, the surfactant (B-1) that is not miscible with the water-soluble organic solvent (A-1) is not miscible with water, which is the main component, and the ink interface. Therefore, the wettability on the hardly absorbent substrate can be improved.

  As the surfactant (B-1) used in the present invention, a silicon surfactant and / or an acetylene surfactant is used from the viewpoint of interaction with the water-soluble organic solvent (A-1). It is preferable to use at least a silicon-based surfactant. Further, it is particularly preferable to use polyether-modified polydimethylsiloxane as a silicon-based surfactant, and among polyether-modified polydimethylsiloxanes, a polyether group has a side chain of the polydimethylsiloxane chain and / or both ends. It is very preferable to use one. Further, from the viewpoint that the surfactant (B-1) that is not mixed with the water-soluble organic solvent (A-1) at the time of landing has a high orientation speed at the ink interface, and particularly excellent print image quality can be obtained. Most preferably, a siloxane surfactant having an ether group in the side chain of the polydimethylsiloxane chain is used.

  The silicon-based surfactant having a polyether group in the side chain of the polydimethylsiloxane chain, most preferably used in the present invention, is a compound represented by the following general formula (3).

General formula (3):

In general formula (3), p is an integer of 0 or more, and q is an integer of 1 or more. R ₁ represents the following general formula (4), and R ₂ represents an alkyl group having 1 to 6 carbon atoms.

General formula (4):

In general formula (4), m is an integer of 1 to 6, n is an integer of 0 to 50, o is an integer of 0 to 50, and n + o is represented by an integer of 1 or more. R ₃ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a (meth) acryl group. Further, the order of the ethylene oxide group and the propylene oxide group in the general formula (4) may be random.

  On the other hand, the silicon-based surfactant having a polyether group at both ends of the polydimethylsiloxane chain, which is preferably used in the present invention as the surfactant (B-1), is a compound represented by the general formula (5). .

General formula (5):

In general formula (5), r is an integer of 1-80. R ₁ represents the general formula (4).

  Moreover, as above-mentioned, it is also preferable to use an acetylenic diol type-surfactant as surfactant (B-1). The acetylene diol surfactant has a very high orientation speed to the ink interface, improves the ink wettability on the hard-to-absorbent substrate, and smoothes the dots to obtain a printed matter with high gloss. Is possible. Further, the acetylenic diol surfactant having an HLB value in the above preferred range has an effect of improving the permeability of ink droplets and improving the drying property on a hardly absorbent substrate.

  Examples of the acetylenic diol surfactant suitably used in the present invention include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,5,8,11-tetramethyl-6. -Dodecin-5,8-diol, hexadec-8-in-7,10-diol, 6,9-dimethyl-tetradec-7-in-6,9-diol, 7,10-dimethylhexadeca-8-in -7,10-diol and its ethylene oxide and / or propylene oxide adducts. However, it is preferable not to have an ethylene oxide group and / or a propylene oxide group from the viewpoint that the HLB value can be within the above-mentioned preferable range and the protective function of the azo pigment is considered to be good.

  In the ink of the present invention, the surfactant (B-1) that is not miscible with the water-soluble organic solvent (A-1) is oriented at a suitable amount and speed to the ink interface to ensure excellent print image quality and drying properties. In view of the above, it is particularly preferable to use a silicon surfactant and an acetylenic diol surfactant in combination as the surfactant (B-1).

  The content of the surfactant (B-1) in the magenta ink for inkjet according to the present invention is preferably 0.1 to 10% by weight based on the total amount of the ink. More preferably, it is 0.5-8 weight%, More preferably, it is 1-6 weight%.

<Pigment dispersion resin>
When the azo pigment is used in the present invention, it is preferable to use it dispersed in the ink in order to maintain the stability of the ink for a long period of time and to ensure the ejection stability after standby. 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 an ink having better storage stability and ejection stability, it is preferable to disperse the pigment using a pigment dispersion resin.

  Examples of the pigment dispersion resin include (meth) acrylic resin, maleic acid resin, α-olefin maleic acid resin, urethane resin, and ester resin. Among them, it is preferable to use a (meth) acrylic resin from the viewpoint that the configuration can be easily changed and adjusted so that the interaction between the azo pigment and the water-soluble organic solvent (A-1) can be assisted. . In addition, the pigment dispersion is improved by strengthening the adsorption of the pigment and stabilizing the pigment dispersion, and the pigment-dispersed resin provides excellent discharge stability and excellent color development on a hardly absorbable substrate. From the viewpoint of ensuring, it is preferable to include a (meth) acrylic resin including an aromatic ring-containing monomer in the copolymer composition among acrylic resins. In this specification, “(meth) acrylic resin” means a methacrylic monomer (for example, methacrylic acid, methyl methacrylate, butyl methacrylate, ethyl hexyl methacrylate, lauryl methacrylate, stearyl methacrylate, benzyl methacrylate, methacrylic acid). Phenoxyethyl acid), acrylic monomers (eg, acrylic acid, methyl acrylate, butyl acrylate, ethyl hexyl acrylate, lauryl acrylate, stearyl acrylate, benzyl acrylate, phenoxyethyl acrylate), styrene monomers ( For example, it means a resin having at least one of styrene, methylstyrene, methoxystyrene and the like as a constituent component.

  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.

  The molecular weight of the pigment-dispersed resin used in the present invention is preferably 5,000 to 100,000. When the molecular weight is 5000 or less, sufficient dispersion stabilization cannot be ensured, and pigment aggregation is caused at the time of drying, so that glossiness and color developability are lowered, and ejection failure after a long standby is likely to occur. When the molecular weight is 100,000 or more, the ink viscosity is likely to increase when water is volatilized. In particular, when the ink jet printer is kept on standby for a long period of time, the ink viscosity increases when water evaporates near the ink jet nozzle and the ink is concentrated, leading to problems such as non-ejection. In order to ensure ejection stability and to obtain an excellent print image quality, the molecular weight is more preferably 15000 to 50000, and particularly preferably 15000 to 40000.

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

  Furthermore, the pigment dispersion resin of the present invention preferably contains a monomer containing an alkyl chain having 8 to 30 carbon atoms in the copolymer composition. Improves dispersion stability, ensures ejection stability from inkjet heads, and maintains dispersion stability of pigments in the drying process on difficult-to-absorbent substrates even from pigment-dispersed resins, improving color development and gloss From the viewpoint of expression, it preferably contains an alkyl chain having 10 to 28 carbon atoms, and particularly preferably contains an alkyl chain having 12 to 24 carbon atoms.

  The alkyl chain having 8 or more carbon atoms may be linear or branched, but is preferably linear. Examples of the alkyl chain include an ethylhexyl group (C8), a decyl group (C10), a lauryl group (C12), a myristyl group (C14), a cetyl group (C16), a stearyl group (C18), an aralkyl group (C20), and a behenyl group (C22). ), Lignoceryl group (C24), serotoyl group (C26), montanyl group (C28), merisyl group (C30) and the like.

  The acid value of the pigment-dispersed resin used in the present invention is preferably 30 to 400 mgKOH / g. By keeping the acid value within the above range, it is preferable because the solubility of the pigment-dispersed resin in the ink can be ensured and the ink viscosity can be suppressed within a suitable range. 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.

  The ratio of the pigment dispersion resin to the pigment in the present invention 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 tends to increase. On the other hand, if it is less than 100/1, the dispersibility stability may be lowered. From the viewpoint of securing excellent dispersion stability and obtaining a printing image quality having high color development and gloss, the ratio of the pigment to the pigment dispersion resin is more preferably 2/1 to 20/1, further preferably 2.5 / 1. 10/1, particularly preferably 3/1 to 10/1.

<Binder resin>
In the magenta ink for ink jet of the present invention, a binder resin can be used in order to increase the drying property of the ink on the poorly permeable substrate and the coating film resistance of the printed matter. In the present invention, the “binder resin” is used to bring the printed material into close contact with the hardly absorbent substrate and to impart friction resistance and water resistance to the printed material. Further, it may have a function of stabilizing the dispersion state of the azo pigment in the ink, but does not have the function as the pigment dispersion resin described above. Whether or not the target resin has a function as a pigment-dispersed resin can be confirmed, for example, by preparing magenta ink by the method of Examples described later and evaluating its storage stability.

  As binder resins for water-based inks, water-soluble resins and resin fine particles are generally classified. In general, resin fine particles have a higher molecular weight than water-soluble resins and can achieve high resistance. However, once the film is formed, it is difficult to re-dissolve, so when ink is kept on standby for a long time on an inkjet head. In addition, there is a concern that nozzle clogging may occur. Therefore, in the ink of the present invention, it is preferable to use a water-soluble resin as the binder resin, which can ensure the ejection stability after standing for a long time.

  Examples of the water-soluble binder resin used in the present invention include (meth) acrylic, styrene (meth) acrylic, urethane, styrenebutadiene, vinyl chloride, and polyolefin. It is preferable to use a (meth) acrylic resin from the viewpoint of ensuring ejection stability from the inkjet nozzle.

  The weight average molecular weight of the binder resin used in the present invention is 3000 to 50000 from the viewpoint of securing the discharge stability from the ink jet nozzle and obtaining excellent coating film resistance even on a hardly absorbent substrate. Preferably, it is 5000-40000. Particularly preferably, it is 10,000 to 30,000. When the weight average molecular weight exceeds 50000, when the water in the ink volatilizes at the end face of the ink jet nozzle, the ink tends to thicken and may cause non-ejection.

  The weight average molecular weight of the binder resin in the present invention can be measured by a conventional method. The measuring method of the weight average molecular weight of the binder resin in the present invention is as follows. The weight average molecular weight is a polystyrene-converted weight average molecular weight measured by using TSKgel column (manufactured by Tosoh Corporation) and GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with an RI detector using THF as a developing solvent. .

  In the present invention, it is possible to further improve resistance such as abrasion resistance and chemical resistance by increasing the glass transition temperature (Tg) of the binder resin. The glass transition temperature (Tg) of the binder resin is preferably in the range of 40 to 120 ° C, more preferably in the range of 50 to 110 ° C. When the glass transition temperature (Tg) is 50 ° C. or higher, better resistance can be easily obtained, and this is preferable from the viewpoint of suppressing peeling of printing from a printed matter in practice. Further, when the glass transition temperature (Tg) is 110 ° C. or less, it is easy to maintain the hardness of the coating film in an appropriate range, which is preferable from the viewpoint of suppressing cracking and cracking of the printed surface when the printed material is bent. .

  The glass transition temperature is a value obtained using a DSC (differential scanning calorimeter) and can be measured, for example, as follows. About 2 mg of a sample obtained by drying the binder resin composition is weighed on an aluminum pan, the test container is set on a DSC measurement holder, and the endothermic peak of the chart obtained under a temperature rising condition of 5 ° C./min is read. The peak temperature at this time is defined as the glass transition temperature in the present specification.

  The acid value of the binder resin used in the present invention is preferably 1 to 100 mgKOH / g, and more preferably 5 to 60 mgKOH / g, from the viewpoint of improving resistance such as water resistance and chemical resistance.

  The content of the binder resin in the ink composition as described above is preferably in the range of 1 to 20% by weight and more preferably 3 to 15% by weight based on the total weight of the ink in terms of non-volatile content.

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

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

<Other ingredients>
In addition to the above-described components, the ink of the present invention can 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. 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.

<Dynamic surface tension of ink>
The magenta ink for inkjet according to the present invention is an ink at 10 msec calculated by the maximum bubble pressure method in order to obtain an excellent print image quality that does not have white spots or shading unevenness immediately after landing on a hardly absorbent substrate. The dynamic surface tension is preferably 25 to 35 mN / m. Specifically, using a bubble pressure dynamic surface tension meter BP100 (manufactured by Kruss) using the maximum bubble pressure method, the dynamic surface tension at 25 ° C. is measured and calculated from the dynamic surface tension at a lifetime of 10 msec. It is possible.

<Ink set>
The magenta ink for inkjet according to 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, 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.

  When the ink jet ink set of the present invention is used in combination of cyan, yellow, and magenta, a suitable pigment type is selected from the viewpoint of excellent color reproducibility when printed on a hardly absorbent substrate. That is, as a cyan pigment, C.I. I. Pigment Blue 15: 3 and 15: 4 are preferable, and yellow pigments include C.I. I. Pigment Yellow 14, 74, 120, and 150 are preferably used, and more preferably C.I. I. Pigment Yellow 14 and 74. Further, from the viewpoint of suppressing mixed color bleeding and obtaining high color reproducibility, C.I. having high dissolution stability in water-soluble organic solvents. I. It is particularly preferable to use CI Pigment Yellow 14. By using the magenta ink of the present invention in combination as the magenta ink, high color reproducibility can be obtained.

  In addition, cyan ink and yellow ink are used from the viewpoint of having excellent wettability on a hard-to-absorbent substrate and suppressing mixed color bleeding between droplets when used as a combination of cyan, yellow, and magenta as an inkjet ink set. However, it is preferable that at least one surfactant (B-1) having an HLB value of 8 or less is contained and combined with the magenta ink of the present invention.

  Furthermore, in order to improve the wettability at the time of landing on a hardly absorbent substrate and achieve excellent print image quality and color reproducibility, when using in combination with cyan, yellow, magenta as an inkjet ink set, the maximum bubble pressure method It is preferable that the dynamic surface tension at 10 msec calculated by the above is 25 to 35 mN / m for any ink.

<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-dispersed resin and water are mixed, and after mixing and stirring, dispersion processing is performed using a dispersion means described later, and centrifugation is performed as necessary. A desired pigment dispersion is obtained. 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 absorbable base material used in the present invention is a base material that hardly absorbs water or has a slow absorption rate, and the Bristow method (J. TAPPI paper pulp test method No. 51-87) shown below. The base material whose absorption coefficient with respect to water measured by 1 is 0-0.6 ml / m < ² > msec < ^1/2 > is represented. Specific examples include paper media such as coated paper, art paper, finely coated paper, and cast coated 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, and after printing, an adhesive may be provided on the printing surface.

The above absorption coefficient can be measured, for example, by using an automatic scanning liquid absorption meter manufactured by Kumagai Riki Kogyo Co., Ltd. Specifically, the relationship between the water absorption amount (ml / m ² ) and the square root of contact time (msec ^1/2 ) obtained using the above device and water for a contact time of 100 to 1000 milliseconds. Therefore, the slope of the straight line obtained by the least square method is taken as the absorption coefficient.

<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.

<Spectral reflectance of ink coating>
The magenta ink of the present invention preferably has a spectral reflectance of 10% or less in a wavelength region of 480 to 580 nm in a coated product having a wet film thickness of 6 μm produced on a recording medium. As described above, in the magenta ink of the present invention, the balance of the azo pigment, the water-soluble organic solvent (A-1), and the surfactant (B-1) is considered as an important factor. It has been found that the range of formulas for obtaining a suitable balance varies depending on the type of azo pigment. Although the detailed factors are unknown, the balance of the blending amount is lost due to the aggregation of a part of the azo pigment in the ink, and the good color developability and color inherent in the azo pigment is caused by aggregation. It is considered that the reproducibility cannot be expressed sufficiently. In particular, when printing on a hardly absorbable substrate, it is considered that quality deterioration such as color developability and color reproducibility is likely to appear.

  If the above aggregation is severe, the presence or absence of aggregation can be determined by, for example, measuring the particle diameter of the ink, but if the pigment is partly aggregated, it cannot be confirmed by the above measurement. Thus, as a result of intensive studies by the present inventors, it was found that even a small amount of aggregation can be judged significantly by measuring the spectral reflectance in the wavelength region of 480 to 580 nm. This is because the components removed from the ink by drying have little effect on the reflectance in the above wavelength range, so the values hardly change between the wet coated film and the dried film. By suppressing the spectral reflectance of a coated product having a wet film thickness of 6 μm produced on a medium to 10% or less in a wavelength region of 480 to 580 nm, a water-soluble organic solvent (A-1) or a surfactant (B It is possible to obtain a magenta ink that has a wide range of prescriptions that can maintain the balance with -1) and that can exhibit the good color development and color reproducibility inherent in azo pigments.

  Specific examples of the method for measuring the spectral reflectance in the present invention include K control coater K202, wire bar no. The magenta ink of the present invention was coated on a recording medium using No. 1 and then dried in an air oven at 60 ° C. for 3 minutes to prepare a coated material. The spectral reflectance on the coated material was measured by X-rite. The method of measuring using i1Pro2 manufactured by the company is mentioned. In measuring the spectral reflectance, the wavelength range of 480 to 580 nm is measured at an interval of 10 nm, and the spectral reflectance needs to be 10% or less in all the regions.

As the above-mentioned coated product, for example, a solid image printed on a recording medium may be used by adjusting the ink discharge amount so that the wet film thickness becomes 6 ± 0.3 μm using an inkjet printer. The recording medium is not particularly limited as long as it is white, but it is preferably an OK top coat + (US basis weight 104.7 g / m ² ) manufactured by Oji Paper Co., Ltd.

  As explained above, C.I. I. Use of at least one selected from CI Pigment Red 31, 146, 147, 150, 266, and 269, regardless of the type and amount of the water-soluble organic solvent (A-1) and the surfactant (B-1) The spectral reflectance in the wavelength region of 480 to 580 nm can be within the above range, which is preferable.

  For the same pigment, as a method of keeping the spectral reflectance in the wavelength range of 480 to 580 nm within the above range, for example, adjusting the dispersion time and the grinding media of the disperser, and using the above pigment dispersion resin and its type and amount Adjusting a dispersion aid such as a pigment derivative.

  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 inside of the reaction vessel was heated to 110 ° C., and 30 parts of acrylic acid as a polymerizable monomer, 40 parts of methyl methacrylate, 30 parts of lauryl 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 example of pigment dispersion resins 2 to 6>
An aqueous solution having a solid content of 50% in the pigment dispersion resins 2 to 6 was obtained in the same manner as in 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-MMA: Methyl methacrylate-2EHA: 2-ethylhexyl acrylate-STMA: Stearyl methacrylate

<Synthesis of acetylene diol surfactants>
By using the method described in JP-A-2002-356451, Example 1 and using methyl isoamyl ketone as a raw material ketone, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol (Acetylene diol 1) was synthesized. The acetylene range all 1 has an HLB value of 2.7. Similarly, 2,4,7,9-tetramethyl-5-decyne-4,7-diol (acetylenediol 2) was synthesized by using methyl isobutyl ketone as a raw material ketone. The acetylene range 2 has an HLB value of 3.0.

  In the examples, Surfynol 440 (manufactured by Air Products Japan, HLB value = 8.0) and Surfynol 465 (manufactured by Air Products Japan, HLB value = 13.0), which are commercially available products, are also used as acetylene diol interfaces. Used as activator.

<Synthesis example of polyether-modified siloxane 1>
In a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, 360 g of ethylene glycol allyl methyl ether and 0.5 g of a 0.5 mass% toluene solution of chloroplatinic acid were charged and replaced with nitrogen gas. After heating the inside of the reaction vessel to 70 ° C., 480 g of hexadecamethyloctasiloxane in which both ends of the siloxane chain are hydrogen atoms was added dropwise over 30 minutes. Next, the inside of the reaction vessel was heated to 110 ° C. and held for 3 hours with stirring to react the materials. After completion of the reaction, the low-boiling fraction was distilled off under reduced pressure to obtain polyether-modified siloxane 1. The polyether-modified siloxane 1 is represented by the structure of the general formula (5), r = 6, and R ₁ is m = 3, n = 2, o = 0, R _{3 in the} general formula (4). = CH ₃ . The HLB value of the compound is 7.5.

<Synthesis example of polyether-modified siloxane 2>
Polyether modified except that the amount of ethylene glycol allyl methyl ether added is 180 g and 200 g of heptamethyltrisiloxane in which one hydrogen atom is bonded to the central silicon atom is used instead of hexadecamethyloctasiloxane. Polysiloxane surfactant 2 was obtained by the same method as siloxane 1. The polyether-modified siloxane 2 is represented by the structure of the general formula (3), where p = 0, q = 1, R ₂ = CH ₃ , and R ₁ is m = 3 in the general formula (4), n = 1, o = 0, R ₃ = CH ₃ . The HLB value of the compound is 4.6.

<Synthesis example of polyether-modified siloxane 3>
Polyether except that the addition amount of ethylene glycol allyl methyl ether was 360 g, and 240 g of octamethylheptanetetrasiloxane having two hydrogen atoms bonded to the central silicon atom was used instead of hexadecamethyloctasiloxane. Polysiloxane surfactant 3 was obtained by the same method as modified siloxane 1. The polyether-modified siloxane 3 is represented by the structure of the general formula (3), p = 0, q = 2, R ₂ = CH ₃ , and R ₁ is m = 3 in the general formula (4), n = 1, o = 0, R ₃ = CH ₃ . The HLB value of the compound is 7.5.

<Synthesis example of polyether-modified siloxane 4>
In the same manner as in the polyether-modified siloxane 1, except that the amount of ethylene glycol allyl methyl ether added was 640 g and dotriacontyl hexadecasiloxane 480 g in which both ends of the siloxane chain were hydrogen atoms was used, Activator 4 was obtained. The polyether-modified siloxane 4 is represented by the structure of the general formula (5), r = 14, and R ₁ is m = 3, n = 1, o = 0, R _{3 in the} general formula (4). = CH ₃ . The HLB value of the compound is 1.9.

<Synthesis example of polyether-modified siloxane 5>
Polyether modified except that the amount of ethylene glycol allyl methyl ether added is 180 g and 200 g of heptamethyltrisiloxane in which one hydrogen atom is bonded to the central silicon atom is used instead of hexadecamethyloctasiloxane. A polysiloxane surfactant 5 was obtained by the same method as for siloxane 1. The polyether-modified siloxane 4 is represented by the structure of the general formula (3), p = 0, q = 1, R ₂ = CH ₃ , and R ₁ is m = 3 in the general formula (4), n = 2, o = 0, R ₃ = CH ₃ . The HLB value of the compound is 9.2.

<Synthesis Example of Polysiloxane Surfactant 6>
Polysiloxane surfactant in the same manner as in polyether-modified siloxane 1 except that the amount of ethylene glycol allyl methyl ether added was 640 g and 480 g of pentacontylpentacosanesiloxane having both siloxane chains hydrogen atoms were used. 6 was obtained. The polyether-modified siloxane 7 is represented by the structure of the general formula (5), r = 23, and R ₁ is m = 3, n = 1, o = 0, R _{3 in the} general formula (4). = CH ₃ . The HLB value of the compound is 1.2.

<Binder resin>
As a binder resin used in Examples, a water-soluble resin 1 (styrene: methacrylic acid: methyl methacrylate = 20: 5: 75 (weight ratio) random polymer, molecular weight: 16000, acid value: 33, Tg: 107 ° C. , Solid content: 40%).

<Example of production of magenta pigment dispersion 1>
As a pigment, C.I. I. 20 parts of Pigment Red 150, 10 parts of an aqueous solution of Pigment Dispersion Resin 1 and 70 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 2-14>
Pigment dispersion was carried out in the same manner as magenta pigment dispersion 1 except that the raw materials listed in Table 2 were used, and magenta pigment dispersions 2 to 14 (MB2 to MB14) were obtained.

Abbreviations listed in Table 2 are as follows.
・ P. R. 150: C.I. I. Pigment Red 150
・ P. R. 31: C.I. I. Pigment Red 31
・ P. R. 146: C.I. I. Pigment Red 146
・ P. R. 147: C.I. I. Pigment Red 147
・ P. R. 266: C.I. I. Pigment Red 266
・ P. R. 269: C.I. I. Pigment Red 269
・ P. R. 1: C.I. I. Pigment Red 1
・ P. R. 242: C.I. I. Pigment Red 242
・ P. R. 122: C.I. I. Pigment Red 122

<Example of production of cyan pigment dispersion 1>
As a pigment, C.I. I. 20 parts of Pigment Blue 15: 3, 10 parts of an aqueous solution of Pigment Dispersion Resin 2 and 70 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, 0.6 L capacity This dispersion was performed using a dyno mill of No. 1 to obtain a cyan pigment dispersion 1.

<Example of production of yellow pigment dispersion 1>
As a pigment, C.I. I. 20 parts of Pigment Yellow 74, 10 parts of an aqueous solution of Pigment Dispersion Resin 2 and 70 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 subjected to main dispersion to obtain a yellow pigment dispersion 1.
<Example of production of yellow pigment dispersion 2>
As a pigment, C.I. I. 20 parts of Pigment Yellow 14, 10 parts of an aqueous solution of Pigment Dispersion Resin 2 and 70 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 subjected to main dispersion to obtain a yellow pigment dispersion 2.

<Production Example of Magenta Ink 1 (M1) of Example 1>
Adjust the magenta pigment dispersion 1 to 20 parts, 25 parts of 1,2-butanediol, 10 parts of binder resin 1, 1 part of polyether-modified siloxane 2, and the rest to be 100 parts of the total ink. This was stirred with a disper until it was sufficiently uniform. Thereafter, filtration with a membrane filter was carried out to remove coarse particles causing clogging of the head, and magenta ink (M1) of Example 1 was prepared.

<Production Example of Magenta Ink (M2 to 54) of Examples 2 to 54>
Using the raw materials listed in Tables 3 to 5, magenta inks (M2 to M54) of Examples 2 to 54 were prepared in the same manner as in the magenta ink production example of Example 1.

<Production Example of Magenta Inks (M55 to M67) of Comparative Examples 1 to 13>
Magenta inks (M55 to M67) of Comparative Examples 1 to 13 were prepared in the same manner as in the magenta ink production example of Example 1 using the raw materials shown in Table 6.

Abbreviations listed in Tables 3-6 are as follows.
1,2-BD: 1,2-butanediol (boiling point: 191 ° C., surface tension: 31.6 mN / m, HLB value: 7.6)
1,2-PenD: 1,2-pentanediol (boiling point: 206 ° C., surface tension: 27.7 mN / m, HLB value: 6.5)
1,2-HexD: 1,2-hexanediol (boiling point: 224 ° C., surface tension: 26.4 mN / m, HLB value: 5.8)
DPM: Dipropylene glycol monomethyl ether (boiling point: 189.6 ° C., surface tension: 28.6 mN / m, HLB value: 2.3)
MB: 3-methoxy-1-butanol (boiling point: 157 ° C., surface tension: 29.3 mN / m, HLB value = 6.3)
PGM: propylene glycol monomethyl ether (boiling point: 120 ° C., surface tension: 2 6.7 mN / m, HLB value: 3.8)
1,2-PD: 1,2-propanediol (boiling point: 188.2 ° C., surface tension: 35.1 mN / m, HLB value: 8.9)
1,4-BD: 1,4-butanediol (boiling point: 230 ° C., surface tension: 43.3 mN / m, HLB value: 7.6)
DPDM: Dipropylene glycol dimethyl ether (boiling point: 175 ° C., surface tension: 25.9 mN / m, HLB value: 0.0)
DPMP: dipropylene glycol monopropyl ether (boiling point: 212 ° C., surface tension: 25.6 mN / m, HLB value: 1.9)
BDG: diethylene glycol monobutyl ether (boiling point: 230 ° C., surface tension: 2 7.9 mN / m, HLB value: 13.0)
GLY: glycerin (boiling point: 290 ° C., surface tension: 62.3 mN / m, HLB: 11.1)

<Creation of yellow ink 1 (Y1)>
20 parts of yellow pigment dispersion 1, 25 parts of 1,2-butanediol, 10 parts of binder resin 1, 1 part of polyether-modified siloxane 3 and the rest as water are adjusted so that the total ink is 100 parts. This was 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). The dynamic surface tension at 10 msec calculated by the maximum bubble pressure method of the prepared ink was 35 to 45 mN / m.

<Creation of yellow ink 2 (Y2)>
20 parts of yellow pigment dispersion 1, 20 parts of 1,2-butanediol, 5 parts of 1,2-hexanediol, 10 parts of binder resin 1, 1 part of acetylenediol 2, 1 part of polyether-modified siloxane 2 The remaining ink was adjusted so that the total amount of ink was 100 parts, and this was 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. The dynamic surface tension at 10 msec calculated by the maximum bubble pressure method of the prepared ink was 25 to 35 mN / m.

<Creation of yellow ink 3 (Y3)>
20 parts of yellow pigment dispersion 2, 20 parts of 1,2-butanediol, 5 parts of 1,2-hexanediol, 10 parts of binder resin 1, 1 part of acetylenediol 2, 1 part of polyether-modified siloxane 2 The remaining ink was adjusted so that the total amount of ink was 100 parts, and this was 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). The dynamic surface tension at 10 msec calculated by the maximum bubble pressure method of the prepared ink was 25 to 35 mN / m.

<Cyan ink 1 (C1) creation>
15 parts of cyan pigment dispersion 1, 25 parts of 1,2-butanediol, 10 parts of binder resin 1, 1 part of polyether-modified siloxane 3 and the rest as water are adjusted so that the total ink is 100 parts. This was 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). The dynamic surface tension at 10 msec calculated by the maximum bubble pressure method of the prepared ink was 35 to 45 mN / m.

<Cyan ink 2 (C2) creation>
15 parts of cyan pigment dispersion 1, 20 parts of 1,2-butanediol, 5 parts of 1,2-hexanediol, 10 parts of binder resin 1, 1 part of acetylenediol 2, 1 part of polyether-modified siloxane 2 The remaining ink was adjusted so that the total amount of ink was 100 parts, and this was 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. The dynamic surface tension at 10 msec calculated by the maximum bubble pressure method of the prepared ink was 25 to 35 mN / m.

<Evaluation of inkjet ink>
The following evaluation was performed about the produced magenta ink (M1-M54) of Examples 1-54. The obtained evaluation results are shown in Tables 3-5, 7, and 8. Moreover, the following evaluation was similarly performed about the produced magenta ink (M55-M67) of Comparative Examples 1-13. The results obtained are shown in Tables 6 and 8.

<Evaluation of ink storage stability>
The viscosity of the magenta inks M1 to M67 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 evaluations were considered as 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 dynamic surface tension of ink>
The dynamic surface tension of magenta ink at 10 msec was evaluated using a bubble pressure dynamic surface tension meter BP100 (manufactured by Kruss) using a maximum bubble pressure method. The meanings of the symbols described in Tables 3 to 4 are as follows.
A: Dynamic surface tension is 25 to 35 mN / m
B: Dynamic surface tension is 35 to 45 mN / m

<Evaluation of spectral reflectance of coated material>
K control coater K202 manufactured by Matsuo Sangyo Co., Ltd. 1 and magenta inks M1 to 67 were coated on Oji Paper's OK top coat + (rice basis weight 104.7 g / m ² ), and then dried in an air oven at 60 ° C. for 3 minutes. Was made. Next, using i1Pro2 manufactured by X-rite, spectral reflectance was evaluated by measuring the spectral reflectance of the prepared coated product at 10 nm intervals in the wavelength range of 480 to 580 nm. The meanings of the symbols described in Tables 3 to 4 are as follows.
A: Spectral reflectance was 10% or less in the entire wavelength region of 480 to 580 nm.
B: Spectral reflectance was higher than 10% at one or more points in the wavelength range of 480 to 580 nm.

<Evaluation of unevenness of printed matter>
Ink is discharged onto Oji Paper's OK top coat + (US basis weight 104.7 g / m ² ) using a Kyocera head (QA06NTB) equipped with an inkjet discharge device under printing conditions of 20 kHz and 600 x 600 dpi. By doing so, solid printing with a printing rate of 60%, 80%, and 100% was performed. After printing, it was dried for 3 minutes using a 60 ° C. air oven, and then the density unevenness of the printed material was confirmed with a loupe. The evaluation criteria are as follows, and AA, A, and B evaluations were considered as practical areas.
AA: Density unevenness did not occur at any printing rate A: No shading unevenness occurred at a printing rate of 80% or less, but slight shading unevenness was observed at a printing rate of 100% B: Printing When the printing rate was 60% or less, there was no occurrence of shading unevenness, but slight shading unevenness occurred when the printing rate was 80 to 100%. C: Slight shading unevenness occurred when the printing rate was 60%. The density unevenness was clearly generated at 80 to 100%. D: The density unevenness was clearly generated at the printing rate of 60%.

<Evaluation of white spots on printed materials>
The degree of white spots of a solid printed material having a printing rate of 100%, which was created by the above-described evaluation of unevenness in density, was confirmed with a magnifying glass and visual observation. The evaluation criteria are as follows, and A and B evaluations are in a practical range.
A: No white spots were observed with the loupe and visually. B: White spots were slightly observed with the loupe, but no white spots were visually observed. C: White spots were clearly observed visually.

<Evaluation of gloss of printed matter>
The 60 ° glossiness of a solid printed matter having a printing rate of 100%, which was created by the above-described evaluation of unevenness in density, was measured and evaluated using a micro trigloss gloss meter (manufactured by Big Chemie Japan Co., Ltd.). The evaluation criteria are as follows, and AA, A, and B evaluations were considered as practical areas.
AA: Glossiness of 55 or more, and excellent uniformity of gloss on the printed surface A: Gloss value of 45-55, excellent uniformity of gloss on the printed surface B: Gloss value of 45-55 However, the gloss of the printed surface was slightly uneven. C: The gloss value was 35 to 45 and the uniformity of the gloss of the printed surface was poor. D: The gloss value was 25 to 35 and the printed surface. The uniformity of gloss was extremely poor

<Evaluation of print density>
The density of the solid printed material having a printing rate of 100%, which was created by the above-described evaluation of unevenness in density, was measured using a spectral densitometer (manufactured by X-RITE). The evaluation criteria are as follows, and AA, A, and B evaluations were considered as 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

<Evaluation of dryness of printed matter>
Solid printing with a printing rate of 100% was performed using the same printing conditions and printing substrate as in the above evaluation. After printing, after putting in 60 degreeC air oven, the printed material was evaluated for the drying property by touching the printed material with a finger every 10 seconds. The evaluation criteria are as follows, and AA, A, and B evaluations were considered as practical areas.
AA: 10 seconds after the oven was put in, no ink adhered even when touched with a finger. A: Ink deposited on the finger 10 seconds after the oven was put in, but 20 seconds later. B: From the oven put in. Ink adhered to the finger after 20 seconds, but did not adhere after 30 seconds. C: Ink adhered to the finger even 30 seconds after the oven was put

<Evaluation of ejection stability>
Magenta inks M1 to M67 were filled in an inkjet discharge device equipped with a head (QA06NTB) manufactured by Kyocera Corporation. After confirming that there was no nozzle omission, the inkjet discharge device was put on standby for a certain period of time in an environment of 25 ° C. After a certain time, a nozzle check pattern was printed and the number of missing nozzles was visually evaluated. The evaluation criteria are as follows, and AA, A, and B evaluations were considered as practical areas.
AA: No nozzle omission even after printing after waiting for 6 hours A: No nozzle omission even after printing after waiting for 4 hours, but when printing after waiting for 6 hours, no nozzle omission occurs One or more nozzles occurred B: No nozzle missing even after printing after waiting for 2 hours, but one nozzle missing occurred after printing after waiting for 4 hours C: 1 hour When printing after waiting, 1-9 nozzles were missing D: When printing after waiting for 1 hour, 10 or more nozzles were missing

<Evaluation of mixed color bleeding of inkjet ink set>
The ink combinations described in Tables 7 to 8 were used as ink sets, and filled into an ink jet discharge apparatus equipped with a head (QA06NTB) manufactured by Kyocera Corporation. A color chart image was printed by ejecting ink onto an OK topcoat (US basis weight 104.7 g / m ² ) manufactured by Oji Paper Co., Ltd. under printing conditions of a frequency of 30 kHz and 600 × 600 dpi. After printing, after drying for 3 minutes using an air oven at 60 ° C., the mixed color bleeding of the printed matter was evaluated visually and using a loupe. The evaluation criteria are as follows, and AA, A, and B evaluations were considered as practical areas.
A: No mixed color blur was observed with a loupe or visually. A: A slightly mixed color blur was observed with a loupe, but no mixed color blur was visually observed. B: A slight mixed color blur was visually observed. C: Obviously mixed color bleeding was seen visually

<Evaluation of hue of inkjet ink set>
Using the ink combinations described in Tables 7 to 8 as ink sets, the hue of the printed matter produced by the above printing method was evaluated by measuring the color using a spectrocolorimeter (manufactured by X-rite). The evaluation was performed by comparison with a color reproduction region defined by Japan Color 2011 for sheet-fed printing. The evaluation criteria are as follows, and AA, A, and B evaluations were considered as practical areas.
A: The color reproduction area was greater than Japan color. A: The color reproduction area was equivalent to Japan color. B: The color reproduction area was slightly less than Japan color. C: Color much narrower than Japan color. It was a reproduction area

  As described above, the magenta ink for ink-jet recording of the present invention provides high gloss and clear images without ink density unevenness and white spots in ink-jet printing on a difficult-to-absorbent substrate. It was also found that excellent drying properties can be obtained even with high-speed printing. Further, it was found that the ink set containing the magenta ink for inkjet according to the present invention can achieve high color reproducibility by suppressing mixed color bleeding in a hardly absorbable substrate.

That is, the present invention is an ink-jet magenta ink containing at least a pigment, a water-soluble organic solvent (A), a surfactant (B), and water, wherein the pigment contains an azo pigment and the total amount of the ink-jet magenta ink. 1 to 10% by weight, the water-soluble organic solvent (A) has a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups The water-soluble organic solvent (A-1) having 5 to 50% by weight in the total amount of magenta ink for inkjet, and the surfactant (B) has a HLB value of 1.5 to 8.0. look containing agent (B-1), wherein the surfactant is (B-1), characterized in that it comprises a silicon-based surfactant and the acetylene diol-based surfactant, an 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 1-18 and 21-23 are reference examples.

That is, the present invention is a magenta ink for inkjet containing at least a pigment, a water-soluble organic solvent (A), a surfactant (B), and water,
The pigment contains an azo pigment in an amount of 1 to 10% by weight based on the total amount of magenta ink for inkjet,
The water-soluble organic solvent (A) has a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups (A-1). ) In a total amount of magenta ink for inkjet,
The surfactant (B) includes a surfactant (B-1) having an HLB value of 1.5 to 7.0 ,
The surfactant (B-1) relates to a magenta ink for inkjet, wherein the surfactant (B-1) contains a silicon surfactant and an acetylenic diol surfactant.

Claims (12)

A magenta ink for ink-jet recording containing at least a pigment, a water-soluble organic solvent (A), a surfactant (B), and water,
The pigment contains an azo pigment in an amount of 1 to 10% by weight based on the total amount of magenta ink for inkjet,
The water-soluble organic solvent (A) has a static surface tension at 25 ° C. of 22 to 32 mN / m, an HLB value of 2.0 to 8.0, and one or more hydroxyl groups (A-1). ) In a total amount of magenta ink for inkjet,
The magenta ink for inkjet, wherein the surfactant (B) includes a surfactant (B-1) having an HLB value of 1.5 to 8.0.   2. The magenta ink for ink jet according to claim 1, wherein a spectral reflectance of a coated material having a wet film thickness of 6 μm produced on a recording medium is 10% or less in a wavelength region of 480 to 580 nm.   The azo pigment is C.I. I. The magenta ink for ink-jet recording according to claim 1, which is CI Pigment Red 150.   The magenta for inkjet according to any one of claims 1 to 3, wherein the water-soluble organic solvent (A-1) contains at least one compound having a boiling point of 190 to 250 ° C under 1 atm. ink.   The magenta ink for ink-jet recording according to claim 4, wherein the compound having a boiling point of 190 to 250 ° C under 1 atm is an alkanediol having 4 to 6 carbon atoms.   The water-soluble organic solvent (A-1) contains at least one glycol alkyl ether having a boiling point of 100 to 250 ° C under 1 atm, according to any one of claims 1 to 5. Magenta ink for inkjet.   The magenta ink for inkjet according to any one of claims 1 to 6, wherein a dynamic surface tension at 10 msec calculated by a maximum bubble pressure method is 25 to 35 mN / m.   The pigment dispersion resin further comprises a (meth) acrylic copolymer having a weight average molecular weight of 15,000 to 50,000, which contains at least a monomer containing an aromatic ring in the copolymer composition. 7. A magenta ink for inkjet according to any one of the above.   The magenta ink for inkjet according to any one of claims 1 to 8, wherein the surfactant (B-1) contains at least one polyether-modified polydimethylsiloxane.   10. The magenta ink for inkjet according to claim 9, wherein the polyether-modified polydimethylsiloxane has a polyether group in a side chain of the polydimethylsiloxane chain. An inkjet ink set including at least cyan ink, yellow ink, and magenta ink,
The cyan ink and yellow ink contain at least one surfactant (B-1),
An ink set, wherein the magenta ink is an inkjet magenta ink according to any one of claims 1 to 10.   An inkjet magenta ink according to any one of claims 1 to 10 or an ink set according to claim 11 is printed on a hardly absorbent substrate.