JP6979152B1 - Water-based inkjet ink set and printed matter manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printed matter containing a water-based inkjet magenta ink having excellent dispersion stability and ejection stability, which is also excellent in image quality, color development and color reproducibility, and which does not cause discoloration or fading over time. , A set of the above-mentioned water-based inkjet magenta ink and water-based inkjet yellow ink is provided. A naphthol-based mixed crystal pigment, an alkanediol having 4 to 6 carbon atoms, and a basic organic compound having a pKa value of 9.5 or less are contained, and the boiling point at 1 atm is 240 ° C. or higher. An inkjet ink set containing an aqueous inkjet magenta ink having an organic solvent content of 8% by mass or less and an aqueous inkjet yellow ink containing an alkane diol having 4 to 6 carbon atoms, wherein the pKa value is 9. An inkjet ink set that defines the amount of a basic organic compound having 5 or less and the alkane diol having 4 to 6 carbon atoms. [Selection diagram] None

Description

An embodiment of the present invention relates to an ink set containing a water-based inkjet magenta ink and a water-based inkjet yellow ink, and a method for producing a printed matter using the ink set.

The inkjet printing method is a method of forming an image and / or characters on the recording medium by flying and landing minute droplets of ink from the inkjet head on the recording medium, and does not require a plate. It is a feature. Compared to the electrophotographic method, which is another printing method that does not require a plate, the inkjet printing method is superior in terms of price and size of printing equipment, running cost at the time of printing, high-speed printing characteristics, etc., and future growth is expected. It is expected.

The inks used in the inkjet printing method are diverse, such as oil-based, solvent-based, active energy ray-curable, and water-based. Further, the active energy ray-curable inkjet printing method is becoming widespread because it can be printed on a non-permeable substrate such as plastic or glass, has excellent resistance to printed matter, and can realize high-speed printing. However, in recent years, regulations on polymerizable monomers have been promoted from the viewpoint of dealing with harmful effects on the environment and humans. Against this background, there is a demand for replacement of active energy ray-curable inks with water-based inks, and demand is increasing.

Further, in recent years, with the remarkable improvement in the performance of the inkjet head, it is expected that the inkjet printing method will be developed in the industrial printing market and the package printing market, in which the plate printing method such as the offset printing method has been conventionally used. In the above printing market, the productivity and color reproducibility of printed matter are very important. For example, many spot color inks are used in the offset printing method, and printed matter with excellent color reproduction area is printed. Therefore, in order to achieve practical use of the inkjet printing method in the above printing market, excellent colors are used. Achieving reproducibility is important.

As described above, as a market demand in recent years, there is a growing demand for water-based (water-based) inks that can effectively enjoy the above-mentioned advantages of the inkjet printing method and also have excellent color reproducibility.

In order to realize excellent color reproducibility, it is important how much color reproduction potential the colorants used, particularly the three colors of yellow, cyan, and magenta, which are process colors, have. As described in Patent Document 1, it is possible to use special color ink in the inkjet printing method in order to improve the color reproducibility, but the price and size of the printing apparatus, which are the advantages of the inkjet printing method. From this point of view, it is not a preferable measure. Therefore, what is used as the colorant of the above three colors is very important.

Generally, colorants are roughly classified into dyes and pigments. Of these, dyes have the advantages of good color development and low cost, but have the disadvantages of being inferior in water resistance, light resistance, etc., and easily discolored. In the industrial printing market and the package printing market described above, these drawbacks can often be fatal, and the inks used in those markets use pigments as colorants.

Generally, pigments used in magenta ink include laked azo pigments, naphthol-based azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments and the like. Of these, naphthol-based azo pigments (hereinafter, also simply referred to as "naphthol-based pigments") are relatively inexpensive, have high coloring power, and often have superior properties to the other pigments listed above. It is widely used as a colorant for inkjet inks. On the other hand, the naphthol pigment has a drawback that the dispersion stability is poor and the ejection stability from the inkjet head is poor.

For example, in Patent Document 2, C.I. I. Pigment Red 150 and the C.I. I. A pigment composition obtained by simultaneously synthesizing a compound different from Pigment Red 150 is disclosed. According to Patent Document 2, a pigment composition having good dispersion stability can be obtained, but there is a problem that the effect of improving the dispersion stability cannot be obtained depending on the material used in combination with the pigment composition. be.

Further, although Patent Document 3 discloses an aqueous inkjet magenta ink that does not form a solid solution (mixed crystal) with each other and contains two kinds of pigments having different hue angles, it is not always good from the viewpoint of versatility of the base material. It wasn't something like that. Specifically, the above-mentioned water-based inkjet magenta ink has a problem that the color development property is poor with respect to the high-quality paper often used in the industrial printing market.

As mentioned above, color reproducibility is very important in the industrial printing market and the package printing market, but in particular, red with high light resistance as a sales promotion design, corporate color of a company, national color of an emerging country, etc. Color is often required. Generally, the red color is formed by superimposing the process colors yellow and magenta, but from the viewpoint of improving the color reproducibility of the red region, it is essential to improve the color reproducibility and color development of the base magenta ink. It is essential. Conventionally, in order to obtain a printed matter having excellent secondary color reproducibility, in addition to the method using the special color ink described above, a processing liquid is applied to the recording medium, and the recording medium is dried every time one color is printed. Techniques such as doing have been taken. However, in either method, it was inevitable that the printing equipment would become larger and the price would increase.

For example, in Patent Document 4, a good image, particularly a good hue image, is realized in addition to light resistance and water resistance by forming an ink set in which a cyan, magenta, and yellow ink composition containing a specific colorant is combined. It is suggested that you can do it.
However, in Patent Document 4, the quinacridone pigment used in the magenta ink composition is inferior in color development. Even if the quinacridone pigment is changed to a naphthol-based pigment, there is a problem that a sufficient hue cannot be obtained depending on the organic solvent or the like used in combination, and further, fading of the printed matter occurs.

Japanese Unexamined Patent Publication No. 2009-24702 Japanese Unexamined Patent Publication No. 2010-195907 Japanese Unexamined Patent Publication No. 2017-155092 Japanese Unexamined Patent Publication No. 2008-291103

The present invention has been made to solve the above problems, and an object thereof includes a water-based inkjet magenta ink having excellent dispersion stability and ejection stability, and further to improve image quality, color development and color reproducibility. It is an object of the present invention to provide a set of the above-mentioned water-based inkjet magenta ink and water-based inkjet yellow ink, which can obtain a printed matter which is excellent and does not cause discoloration or fading over time.

As a result of diligent research to solve the above problems, the present inventors include a basic organic compound having a specific pKa value, an alkanediol having 4 to 6 carbon atoms, and a naphthol-based mixed crystal pigment. We have found that the above problems can be solved by an inkjet ink set containing magenta ink in which the amount of organic solvent having a high boiling point is limited and yellow ink containing alkanediol having 4 to 6 carbon atoms, and completed the present invention. rice field.

That is, the present invention is a water-based inkjet ink set containing a water-based inkjet magenta ink and a water-based inkjet yellow ink.
The water-based inkjet magenta ink contains magenta pigment (A), a basic organic compound, a water-soluble organic solvent (SM), and water.
The magenta pigment (A) contains a mixed crystal pigment (A-1) containing two or more kinds of pigments having a structure represented by the following general formula (1).
The content of the mixed crystal pigment (A-1) is 1 to 10% by mass in the total amount of the water-based inkjet magenta ink.
The basic organic compound contains 0.1 to 1.25% by mass of the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in the total amount of the aqueous inkjet magenta ink.
The water-soluble organic solvent (SM) contains 1 to 30% by mass of an alkanediol having 4 to 6 carbon atoms in the total amount of the water-based inkjet magenta ink.
The content of the organic solvent having a boiling point of 240 ° C. or higher under 1 atm is 8% by mass or less in the total amount of the aqueous inkjet magenta ink.
The water-based inkjet yellow ink contains a pigment, a water-soluble organic solvent (SY), and water.
The water-soluble organic solvent (SY) contains 1 to 30% by mass of an alkanediol having 4 to 6 carbon atoms in the total amount of the water-based inkjet yellow ink.
The present invention relates to a water-based inkjet ink set in which the content of an organic solvent having a boiling point of 240 ° C. or higher at 1 atm is 8% by mass or less based on the total amount of the water-based inkjet yellow ink.

（一般式（１）中、Ｒ¹、Ｒ²、及びＲ³は、それぞれ独立して、水素原子、炭素数１〜２のアルキル基、炭素数１〜２のアルコキシ基、アニリド基、カルバモイル基、メトキシカルボニル基、エトキシカルボニル基、アミノ基、ニトロ基、スルホンアミド基、メチルアミノスルホニル基、またはエチルアミノスルホニル基のいずれかである。また、Ｒ⁴は、水素原子、炭素数１〜２のアルキル基、または下記一般式（２）で表される構造を有する基のいずれかである。） General formula (1):

(In the general formula (1), R ¹ , R ² and R ³ are independently hydrogen atoms, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an anilide group and a carbamoyl group, respectively. , A methoxycarbonyl group, an ethoxycarbonyl group, an amino group, a nitro group, a sulfonamide group, a methylaminosulfonyl group, or an ethylaminosulfonyl group. In addition, R ⁴ is a hydrogen atom having 1 to 2 carbon atoms. It is either an alkyl group or a group having a structure represented by the following general formula (2).)

（一般式（２）中、Ｒ⁵は、水素原子、塩素原子、臭素原子、炭素数１〜２のアルキル基、炭素数１〜２のアルコキシ基、アミノ基、またはニトロ基のいずれかである。また、Ｒ⁶及びＲ⁷は、それぞれ独立して、水素原子、塩素原子、臭素原子、炭素数１〜２のアルキル基、炭素数１〜２のアルコキシ基、アミノ基、またはニトロ基のいずれかであるか、Ｒ⁶とＲ⁷とが互いに結合し、イミダゾリジノン環を形成している。また、＊の部分は結合手である。） General formula (2):

(In the general formula (2), R ⁵ is any one of a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an amino group, or a nitro group. In addition, each of R ⁶ and R ⁷ is independently a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an amino group, or a nitro group. Or, R ⁶ and R ⁷ are bonded to each other to form an imidazolidinone ring. The * part is a bond.)

Further, in the present invention, the difference between the static surface tension of the water-based inkjet magenta ink at 25 ° C. and the static surface tension of the water-based inkjet yellow ink at 25 ° C. is 3 mN / m or less. Regarding water-based inkjet ink sets.

Further, in the present invention, the pigment having the structure represented by the above general formula (1) is C.I. I. The water-based inkjet ink set according to the above description, comprising at least one selected from the group consisting of Pigment Red 31, 32, 146, 147, 150, 176, and 269.

Further, in the present invention, the pigment having the structure represented by the above general formula (1) is C.I. I. The water-based inkjet ink set described above, comprising Pigment Red 150.

Further, in the present invention, the water-based inkjet yellow ink contains the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in an amount of 0.1 to 1.25 mass in the total amount of the water-based inkjet yellow ink. % With respect to the water-based inkjet ink set described above.

The present invention also relates to the above-mentioned water-based inkjet ink set, wherein the water-based inkjet magenta ink and / or the water-based inkjet yellow ink contains amino alcohols. When the pKa value of the amino alcohols at 25 ° C. is 9.5 or less, the amino alcohols correspond to the basic organic compound (B).

The present invention also relates to a method for producing a printed matter, which comprises a step of ejecting the above-mentioned water-based inkjet ink set from an inkjet head and printing it on a recording medium.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to obtain a printed matter containing a water-based inkjet magenta ink having excellent dispersion stability and ejection stability, which is also excellent in image quality, color development and color reproducibility, and which does not cause discoloration or fading over time. It is possible to provide a set of the above-mentioned water-based inkjet magenta ink and water-based inkjet yellow ink.

Hereinafter, the water-based inkjet ink set of the present invention (hereinafter, also simply referred to as “ink set”) will be described with reference to preferred embodiments. In the present specification, the "aqueous medium" means a medium composed of at least a liquid containing water. Further, "chromatic color" generally refers to all colors other than colors having no saturation (black, light black (gray), and white).

<Aqueous inkjet ink set>
The ink set of the present invention includes a water-based inkjet magenta ink and a water-based inkjet yellow ink. The water-based inkjet magenta ink (hereinafter, also simply referred to as “magenta ink”) contains a magenta pigment (A), a water-soluble organic solvent (SM), a basic organic compound, and water, and contains the magenta pigment (hereinafter, simply referred to as “magenta ink”). A) contains 1 to 10% by mass of a mixed crystal pigment (A-1) consisting of two or more kinds of pigments having a structure represented by the following general formula (1) in the total amount of the magenta ink, and is basic. The organic compound contains 0.1 to 1.5% by mass of the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in the total amount of the magenta ink, and the water-soluble organic solvent (SM). However, the content of the organic solvent containing 1 to 30% by mass of alkanediol having 4 to 6 carbon atoms in the total amount of the magenta ink and having a boiling point of 240 ° C. or higher at 1 atm is the total amount of the magenta ink. Medium 8% by mass or less. In addition, the water-based inkjet yellow ink (hereinafter, also simply referred to as “yellow ink”) contains a pigment, a water-soluble organic solvent (SY), and water, and has the number of carbon atoms as the water-soluble organic solvent (SY). It contains 4 to 6 alcandiols in an amount of 1 to 30% by mass based on the total amount of the above yellow ink.

General formula (1):

In the above general formula (1), R ¹ , R ² and R ³ are independently hydrogen atoms, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an anilide group and a carbamoyl group. , A methoxycarbonyl group, an ethoxycarbonyl group, an amino group, a nitro group, a sulfonamide group, a methylaminosulfonyl group, or an ethylaminosulfonyl group. Further, R ⁴ is either a hydrogen atom, an alkyl group having 1 to 2 carbon atoms, or a group having a structure represented by the following general formula (2).

General formula (2):

In the above general formula (2), R ⁵ is any one of a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an amino group, or a nitro group. .. Further, R ⁶ and R ⁷ are independently any of a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an amino group, or a nitro group. Or, R ⁶ and R ⁷ are bonded to each other to form an imidazolidinone ring. In addition, the part marked with * is a bond.

Generally, in inkjet printing using a water-based ink, a secondary color is formed by bringing two types of water-based inks having different hues into contact with each other on a recording medium. At that time, for example, when a poorly permeable base material or a non-permeable base material is used as the recording medium, when inkjet printing is performed at high speed, or when the printing rate of the printed matter is high, the printing medium is used. The inks of the above will come into contact with each other in a wet state. In such a case, the colorant in the ink aggregates, causing a bias in the distribution of the colorant in the ink droplets, resulting in uneven shading, or the aggregation increases the particle size of the colorant. Phenomena such as deterioration of color development and color reproducibility may occur.

On the other hand, the pigment having the structure represented by the general formula (1) is difficult to disperse and stabilize as compared with, for example, a quinacridone-based pigment generally used in an aqueous inkjet magenta ink. Further, it is known that the mixed crystal pigment has a smaller primary particle size than the pigment itself constituting the mixed crystal pigment.

Therefore, the mixed crystal pigment (A-1) composed of two or more kinds of pigments having a structure represented by the above general formula (1) used in the magenta ink constituting the ink set of the present invention is a conventionally known pigment. Compared to the magenta ink used, it is very difficult to stabilize the dispersed state. As a result, the magenta ink containing the mixed crystal pigment (A-1) tends to cause unevenness in shades of secondary colors and deterioration of color development and color reproducibility.

However, the present inventors are magenta inks using the above mixed crystal pigment (A-1) because the magenta ink and the yellow ink each contain 1 to 30% by mass of alkanediol having 4 to 6 carbon atoms. However, it was found that the deterioration of the dispersed state at the time of mixing can be suppressed. Although the detailed principle is not clear, the difference between the SP value (solubility parameter) of the structure represented by the above general formula (1) and the SP value of the alkanediol having 4 to 6 carbon atoms is small; the carbon number thereof. Although the alkanediols 4 to 6 are water-soluble organic solvents, they have a relatively long alkyl group exhibiting hydrophobicity; they form hydrogen bonds in the structure represented by the above general formula (1). It is considered that the alkanediol having 4 to 6 carbon atoms in the magenta ink behaves to protect the mixed crystal pigment (A-1) due to the presence of a plurality of solvents, hydroxyl groups, carbonyl groups, azo bonds, etc. Be done.

Further, the presence of the basic organic compound (B) having a specific pKa value makes it difficult to form a strong intramolecular interaction between the mixed crystal pigment (A-1) and the pigment in the yellow ink. As a result, it is considered that the dispersion state of each other is not adversely affected during mixing, and the distribution of each pigment in the ink droplets is less likely to be biased. As described above, the ink set of the present invention does not cause agglomeration of pigments, which leads to deterioration of color development and color reproducibility, and does not cause unevenness in shading even when contacted on a recording medium. It is presumed that a printed matter having excellent color development, color reproducibility, and image quality can be obtained.

When a magenta ink containing a magenta pigment having no above-mentioned structure is used, it is possible to print a printed matter that satisfies either the color development property and the color reproducibility and the image quality quality, but it satisfies both of them. That is difficult.

For example, when a naphthol pigment other than a mixed crystal pigment is used as the magenta pigment, or when a quinacridone mixed crystal pigment is used as the magenta pigment, the printed matter is inferior in color reproducibility in the red color region. Further, for example, when a diketopyrrolopyrrole pigment is used as the magenta pigment, it is very difficult to achieve both the dispersion stability of the magenta ink containing the diketopyrrolopyrrole pigment and the image quality.

As described above, in the present invention, a naphthol-based mixed crystal pigment having a specific structure and a basic organic compound having a specific pKa value are used in combination, and an alkanediol having 4 to 6 carbon atoms is contained in an amount of 1 to 30% by mass. Further, the magenta ink in which the boiling point of the organic solvent to be used in combination is specified is combined with the yellow ink containing 1 to 30% by mass of alkanediol having 4 to 6 carbon atoms in order to achieve both of the above characteristics.

Hereinafter, the magenta ink and the yellow ink included in the ink set of the present invention will be described in detail.

<Magenta pigment (A)>
The magenta ink constituting the ink set of the present invention contains a magenta pigment (A) as a colorant, and the magenta pigment (A) is a pigment having two or more kinds of structures represented by the above general formula (1). Includes a mixed crystal pigment (A-1) containing (hereinafter, also simply referred to as “naphthol-based mixed crystal pigment (A-1)”).

It is generally known that naphthol-based pigments have excellent color-developing properties, but also have poor dispersion stability due to their molecular structure. Further, the mixed crystal pigment has improved optical characteristics such as color development and color reproducibility as compared with the case where each pigment constituting the mixed crystal pigment is used alone, but the dispersion stability may be deteriorated. Are known. Therefore, a mixed crystal pigment containing two or more kinds of naphthol pigments (hereinafter, also referred to as “naphthol mixed crystal pigment” in the present specification) has the above-mentioned poor dispersion stability, which is a characteristic of the mixed crystal pigment. Due to the characteristics of the naphthol pigment itself, the dispersed state is easily destroyed by the delicate change in the balance in the water-based ink, and the above-mentioned unevenness of shading, color development and color reproducibility during the formation of the secondary color are observed. Decline is likely to occur.

On the other hand, in the present invention, the structure of the naphthol pigment constituting the mixed crystal pigment is defined, and as will be described later, it is used in combination with the basic organic compound (B) having a specific pKa value, and further in magenta ink. By limiting the amount of the high boiling point organic solvent in the above, while suppressing the above-mentioned phenomenon, the excellent optical characteristics which are the characteristics of the naphthol-based mixed crystal pigment are exhibited, the dispersion stability and the ejection stability are improved, and It is possible to manufacture printed matter having excellent color development and color reproducibility.

As used herein, the term "mixed crystal" refers to a compound in which two or more compounds are fused with each other to form a uniform solid phase as a whole, and is also called a solid solution. On the other hand, it is clearly distinguished from a simple mixture of the two or more compounds.

Whether or not the pigment forms a mixed crystal can be easily verified by X-ray diffraction analysis or the like. When a sample is simply a mixture of a plurality of pigments, the obtained X-ray diffraction pattern is a superposition of the X-ray diffraction patterns of each pigment, and the intensity of each diffraction peak is the compounding ratio of each pigment. Depends on. On the other hand, when a plurality of pigments form a mixed crystal, an X-ray diffraction pattern different from the case where the plurality of pigments are simply mixed can be obtained. Specifically, phenomena such as the acquisition of a new diffraction peak, the intensity of each diffraction peak not depending on the blending ratio of the pigment, and the increase in the half-value width of the diffraction peak can be seen.

Further, the naphthol-based mixed crystal pigment can be produced, for example, by the method described in JP-A-2005-107147 and JP-A-2010-195907.

The pigment constituting the naphthol-based mixed crystal pigment (A-1) may contain a pigment other than the pigment having the structure represented by the general formula (1). However, in the present invention, from the viewpoint of color development and color reproducibility of printed matter, the naphthol-based mixed crystal pigment (A-1) is a mixed crystal pigment composed of two or more pigments having a structure represented by the general formula (1). Is preferable.

As a specific example of the pigment having the structure represented by the general formula (1), C.I. I. Pigment Red 17, 22, 23, 31, 32, 114, 146, 147, 150, 170, 176, 184, 185, 245, 266, 268, 269.

On the other hand, among the compounds having the structure represented by the general formula (1), in the above general formula (1), R ¹ is a methoxy group and R ² is hydrogen from the viewpoint of color development and dispersion stability. A compound which is an atom and R ³ is an anilide group is preferable, and the naphthol-based pigment constituting the naphthol-based mixed crystal pigment has R ¹ as a methoxy group, R ² as a hydrogen atom, and R ^{3 in the above general formula (1).} It is particularly preferable that the compound consists only of a compound which is an anilide group. As a specific example of the compound in which ^{R 1} is a methoxy group, R ² is a hydrogen atom, and R ³ is an anilides group in the general formula (1), C.I. I. Pigment Red 31, 32, 146, 147, 150, 176, 269 and the like.

Further, in the present invention, as the naphthol-based mixed crystal pigment (A-1), C.I. I. Pigment Red 150 has a structure represented by the above general formula (1), and in the general formula (1), R ¹ is a methoxy group, R ² is a hydrogen atom, and R ³ is anilides. It is particularly preferable to use a mixed crystal pigment composed of a compound as a group.

A naphthol-based mixed crystal pigment (A-1) is used as a component of C.I. I. When Pigment Red 150 is included, the above-mentioned C.I. I. As a naphthol-based pigment to be mixed with Pigment Red 150, C.I. I. It is preferable to select one or more selected from the group consisting of Pigment Red 31, 32, 146, 147, 176, and 269. Above all, from the viewpoint of coloring power, C.I. I. It is more preferable to select one or more selected from the group consisting of Pigment Red 31, 32, 146, 147, and 269, and from the viewpoint of color reproducibility and coloring power in the red color region, C.I. I. Pigment Red 31 and / or C.I. I. It is particularly preferred to use Pigment Red 269.

As the naphthol-based mixed crystal pigment (A-1), C.I. I. When the Pigment Red 150 and other naphthol-based pigments are mixed and crystallized, the above-mentioned C.I. I. The blending amount of Pigment Red 150 is preferably 0.1 to 99 mol%, more preferably 10 to 80 mol%, and 20 to 70 mol% in the naphthol-based mixed crystal pigment (A-1). It is particularly preferable to have. By keeping the blending amount within the above range, it is possible to achieve both coloring power (particularly, color development property when printed on a permeable substrate), dispersion stability, and ejection stability.

Further, from the viewpoint of obtaining a printed matter having excellent color development and color reproducibility regardless of the recording medium used, the content of the naphthol-based mixed crystal pigment (A-1) contained in the magenta ink is the total amount of the magenta ink. It is preferably 0.5 to 10% by mass, more preferably 1 to 9% by mass, and particularly preferably 2 to 8% by mass.

<Other magenta ink pigments>
In the present invention, the magenta pigment (A) is a pigment other than the naphthol-based mixed crystal pigment (A-1) (hereinafter, from the viewpoint of obtaining a printed matter having excellent color development and color reproducibility regardless of the recording medium used. Also referred to as "other magenta ink pigments") may be used in combination.

As the above-mentioned other pigments for magenta ink, orange pigments, magenta pigments, violet pigments and the like can be suitably used, and magenta pigments and / or violet pigments are included from the viewpoint of obtaining a printed matter having excellent color reproducibility in the red region. Is particularly suitable. When a magenta pigment and / or a violet pigment is used as a pigment for magenta ink other than the naphthol-based mixed crystal pigment (A-1), the blending amount thereof is the naphthol-based mixed crystal pigment (A-1). It is preferably 10 to 100% by mass, and particularly preferably 20 to 70% by mass, based on the total amount of the mixture.

Examples of orange pigments that can be used with the naphthol-based mixed crystal pigment (A-1) include C.I. I. Pigment Orange 13, 16, 17, 22, 24, 34, 36, 38, 40, 43, 51, 60, 62, 64, 71, 72, 73 and the like. Among them, C.I. I. One or more selected from the group consisting of Pigment Orange 36, 38, 43, 60, 62, 64, and 72 can be preferably used.

Examples of magenta pigments that can be used together with the naphthol-based mixed crystal pigment (A-1) include naphthol-based pigments (excluding those that are mixed-crystal pigments), quinacridone-based pigments, and diketopyrrolopyrrole-based pigments. Be done. Specifically, as the naphthol-based pigment, those listed above as specific examples of the naphthol-based pigment constituting the naphthol-based mixed crystal pigment (A-1), and as the quinacridone-based pigment, C.I. I. Pigment Red 122, 202, 207, 209, etc., as a diketopyrrolopyrrole pigment, C.I. I. Pigment Red 254, 255 and the like.
Above all, the naphthol-based pigment (however, since the dispersed state of the naphthol-based mixed crystal pigment (A-1) is not easily destroyed and the color reproducibility when mixed with the above-mentioned naphthol-based mixed crystal pigment (A-1) is excellent. , A mixed crystal pigment) or a quinacridone-based pigment can be preferably used, for example, C.I. I. One or more selected from the group consisting of Pigment Red 31, 32, 122, 146, 147, 150, 176, 185, 202, 209, 282, and 269 can be preferably used.

Further, to exemplify a violet pigment that can be used together with the naphthol-based mixed crystal pigment (A-1), C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 42, 43, 50 and the like. Among them, C.I. I. One or more selected from the group consisting of Pigment Violet 19, 23, 32, and 42 can be preferably used.

Among the other magenta ink pigments exemplified and selected above, benzimidazolone pigments, quinacridone pigments, naphthol pigments (excluding mixed crystal pigments), diketopyrrolopyrrole pigments, and One or more selected from the group consisting of dioxazine pigments is preferably selected. Since each of the pigments has a structure similar to that of the naphthol-based mixed crystal pigment (A-1), it is difficult to destroy the dispersed state of the naphthol-based mixed crystal pigment (A-1) and the dispersion stability is excellent. This is because the magenta ink can be obtained. These pigments are also suitable from the viewpoint of color reproducibility of printed matter. Above all, it is more preferable to use a quinacridone pigment and / or a naphthol pigment (however, the naphthol pigment is excluded from a mixed crystal pigment) in combination.

When a naphthol-based mixed crystal pigment (A-1) is used in combination with a quinacridone pigment and / or a naphthol pigment (however, the naphthol pigment is not a mixed crystal pigment), the blending amount of the quinacridone pigment or the naphthol pigment is determined. It is preferably 0.1 to 50% by mass, more preferably 1 to 30% by mass, based on 100% by mass of the naphthol-based mixed crystal pigment (A-1). Within the above range, the dispersion stability is improved, and the color development and color reproducibility of the printed matter are improved regardless of the recording medium.

<Pigments in yellow ink>
The pigment contained in the yellow ink constituting the ink set of the present invention is not particularly limited, and conventionally known pigments can be used. Among them, one selected from the group consisting of isoindoline pigments, isoindolinone pigments, quinoxalin-based azo pigments, and benzimidazolone-based azo pigments from the viewpoint of obtaining printed matter having excellent image quality, color development and color reproducibility. It is preferable to use the above in an amount of 50% by mass or more based on the total amount of the pigment contained in the yellow ink. Further, it is particularly preferable that the isoindoline pigment is contained in an amount of 50% by mass or more in the total amount of the pigment contained in the yellow ink and 1 to 10% by mass in the total amount of the yellow ink.

Generally, an isoindoline pigment is known as a pigment having a strong coloring power, but when combined with a magenta ink containing a naphthol-based mixed crystal pigment and not containing the above-mentioned amount of alcandiol having 4 to 6 carbon atoms, a red color region is formed. Saturation, color reproducibility and image quality of the color region may be deteriorated. Furthermore, there is a risk that the printed matter will fade over time. The reason is not clear, but the formation of an interaction between the naphthol-based mixed crystal pigment in magenta ink and the isoindoline pigment in yellow ink cannot be suppressed, and the original color development of the pigment cannot be exhibited. Can be considered.
On the other hand, in the present invention, by combining with the magenta ink having the above-mentioned configuration, even a yellow ink containing an isoindoline pigment does not cause agglomeration of the pigment which leads to deterioration of color development and color reproducibility. In addition, a printed matter having excellent color development, color reproducibility, and image quality can be obtained.

As an isoindoline pigment, C.I. I. Pigment Yellow 139, 185, C.I. I. Pigment Orange 66, 69 and the like. Among these pigments, C.I. I. Pigment Yellow 139 and / or 185 is preferably included. C. I. It is particularly preferred to include Pigment Yellow 185. C. I. Pigment Yellow 185 has high coloring power and color reproducibility, and due to the effect of alcandiol having 4 to 6 carbon atoms described later, the dispersed state is maintained even when mixed with magenta ink containing a naphthol-based mixed crystal pigment. Easy to stabilize. As a result, the interaction between the naphthol-based mixed crystal pigment and the isoindoline pigment is suppressed, the transparency of the yellow ink and the color development of the magenta ink are maintained, and high color reproducibility can be exhibited in the red color region.

On the other hand, as a pigment other than the isoindoline pigment that can be used for the yellow ink, for example, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 9, 12, 13, 14, 17, 49, 55, 65, 73, 74, 83, 87, 109, 110, 120, 124, 127, 138, Examples thereof include 150, 151, 154, 155, 168, 169, 170, 171 and 180, 213.

As the pigments listed above, only one kind may be used, or two or more kinds may be used in combination. Further, when two or more kinds are used in combination, a mixed crystal pigment may be used. Further, when two or more kinds of pigments are not in a mixed crystal state, that is, they have different crystal structures, the two or more kinds of pigments may be mixed and dispersed from the beginning by a method described later or the like. The pigment dispersions dispersed separately may be mixed later.

From the viewpoint of color development, color reproducibility, and dispersion stability of the yellow ink, the total amount of the pigment contained in the yellow ink is preferably 1 to 10% by mass based on the total amount of the yellow ink. It is more preferably 5 to 9.5% by mass. Further, considering the dispersion stability of the yellow ink and the ejection stability from the inkjet head, it is particularly preferably 2 to 8% by mass, and most preferably 3 to 6% by mass.

As an example of a combination of a naphthol-based mixed crystal pigment (A-1) contained in magenta ink and a pigment contained in yellow ink, which can suitably exhibit the effects of the present invention, C.I. I. Pigment Red 150 and C.I. I. Pigment Red 31, 32, 146, 147, and C.I. I. Pigment Yellow 139 and / or 185 in combination.

<Basic organic compound (B)>
The magenta ink constituting the ink set of the present invention preferably contains the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in an amount of 0.1 to 1.25% by mass based on the total amount of the magenta ink. Contains 0.1 to 1.0% by mass. The "basic organic solvent (B)" in the present specification includes water-soluble organic solvents described later that satisfy the above pKa value condition. Even if the compound is not a water-soluble organic solvent, the compound is included in the basic organic compound (B) if the above pKa value condition is satisfied.

Generally, in a water-based ink, the dispersed state of the pigment is maintained by the charge repulsion generated between the pigment particles, and the dispersion stability is ensured. As a method of maintaining dispersion stability for a long period of time, there is a method of adjusting the pH of the ink to neutral to weakly basic. By maintaining the pH at neutral to weakly basic, the ion concentration in the electric double layer covering the pigment surface can be increased, the repulsive force of the electric double layer can be increased, and a large repulsive force can be generated between the pigment particles. However, some basic organic compounds are strongly basic, and by using these compounds in combination with the naphthol-based mixed crystal pigment (A-1), the naphthol-based mixed crystal pigment (A-) is used. The dispersion stability of 1) may be deteriorated, and the discharge stability may be deteriorated accordingly. Furthermore, when a large amount of a strongly basic basic organic compound is added to magenta ink containing a naphthol-based mixed crystal pigment (A-1), the present inventors add to the above phenomenon, especially in a red-colored printed matter. It has been found that deterioration of color reproducibility and image quality (unevenness of shading), and discoloration and / or fading over time may occur.

On the other hand, by using the basic organic compound (B) having a pKa value of 9.5 or less, the color reproducibility and image quality are excellent, and discoloration and discoloration occur with time, especially in the red color region. We have also found that magenta ink with excellent dispersion stability can be obtained. Although the detailed factors are unknown, it is said that the acid dissociation constant (pKa value) is moderately small and the organic compound suppresses the damage to the naphthol-based mixed crystal pigment (A-1). Conceivable. Further, when the magenta ink is mixed with the yellow ink described above, a basic organic compound (B) is used so as to suppress contact between the naphthol-based mixed crystal pigment (A-1) molecule and the pigment molecule in the yellow ink. ) Moves, preventing the formation of strong intermolecular interactions between the two.

From the above viewpoint, the pKa value of the basic organic compound (B) is preferably 8.5 or less. By using a compound having an appropriately small pKa value, it is possible to suppress excessive pH fluctuation of the ink with respect to the amount of addition, suppress deterioration of color reproducibility and image quality in red-colored printed matter, and suppress deterioration of image quality over time. It is easy to prevent discoloration and discoloration and to secure dispersion stability at the same time. The lower limit of the pKa value of the basic organic compound (B) is not particularly limited, but is preferably 3 or more, more preferably 4.5 or more, and particularly preferably 6.5 or more.

Specific examples of the basic organic compound (B) include diethanolamine (pKa = 8.9), methyldiethanolamine (pKa = 8.5), triethanolamine (pKa = 7.8), and 1-amino-2-propanol. (PKa = 9.4), Diisopropanolamine (pKa = 9.0), Triisopropanolamine (pKa = 8.0), Trishydroxymethylaminomethane (pKa = 8.1), Imidazole (pKa = 7.0) ), And aniline (pKa = 4.6). Among the above, the magenta ink ejection stability is improved, the image quality of the printed matter is improved and fading over time can be prevented, the solubility in an aqueous medium is high, and the safety to the human body is high. The basic organic compound (B) preferably contains amino alcohols (alkanolamines), and particularly preferably contains triethanolamine having a small pKa value. It should be noted that only one kind of the above compound may be used, or two or more kinds thereof may be used in combination. As an example of the case where two or more kinds are used in combination, a basic organic compound having a pKa value of 8.5 or less (for example, triethanolamine) and a basic organic compound having a pKa value of more than 8.5 (for example, 1-amino-) 2-Propanol and / or diisopropanolamine) in combination.

In addition, in this specification, pKa can be measured by a known method. Specifically, it is a value measured in a 25 ° C. environment by a potentiometric titration method using water as a solvent using a potentiometric titration device AT-710S manufactured by Kyoto Electronics Industry Co., Ltd.

In some embodiments, the molecular weight of the basic organic compound (B) contained in the magenta ink is preferably 500 or less, more preferably 300 or less, and particularly preferably 200 or less. The molecular weight is preferably 50 or more, more preferably 75 or more, and particularly preferably 100 or more. By using the basic organic compound (B) having the above molecular weight, overdrying and residual of the basic organic compound (B) at the time of printing can be prevented, and the color reproducibility, image quality, and drying property of the printed matter can be improved. It is possible to obtain excellent ink. Further, although the details are unknown, the basic organic compound (B) having the above molecular weight causes less damage to the naphthol-based mixed crystal pigment (A-1), and it is possible to improve the dispersion stability of the magenta ink.

As described above, the content of the basic organic compound (B) in the magenta ink is 0.1 to 1.25% by mass in the total amount of the magenta ink. If it is 0.1% by mass or more, it is easy to secure dispersion stability for a long period of time, and even when water volatilizes on the inkjet head nozzle, the naphthol-based mixed crystal pigment contained in magenta ink ( Since the dispersed state of A-1) is not destroyed, a printed matter having excellent color reproducibility and image quality can be obtained in the red color region, and deterioration of the printed matter due to nozzle omission or the like can be prevented. .. Further, by adding 1.25% by mass or less, it is possible to prevent discoloration and discoloration of the printed matter over time. Further, depending on the material used as the basic organic compound (B), a compound having a high boiling point also exists. Therefore, by setting the content to 1.25% by mass or less, the drying property of the ink does not deteriorate, and the printed matter is printed. There is no need to reduce the production speed of. Further, from the viewpoint of more preferably exhibiting the above effects, in some embodiments, the content of the basic organic compound (B) is 0.1 to 1.0% by mass in the total amount of magenta ink. preferable.

It should be noted that any component such as a pH adjuster and / or a surfactant, which will be described later, is also included in the basic organic compound (B) if it corresponds to the basic organic compound satisfying the pKa. Further, the magenta ink contains the "pigment dispersion resin and / or the binder resin" having an acid group as an arbitrary component, and the pKa is used as the "pigment dispersion resin and / or the binder resin" having an acid group. When the "pigment dispersion resin and / or binder resin" neutralized by the satisfying basic organic compound is used, the basic organic compound satisfying the pKa used for neutralization (hereinafter, "basic organic compound (hereinafter," basic organic compound (hereinafter, "basic organic compound") b2) ”) is also included in the basic organic compound (B).
However, it is generally considered that the basic organic compound (b2) forms an intramolecular interaction with the "pigment dispersion resin and / or binder resin" having an acid group. Therefore, in some embodiments, the amount obtained by subtracting the amount of the basic organic compound (b2) from the total amount of the basic organic compound (B) contained in the magenta ink is 0.1 to 1.0% by mass. Is preferable. Hereinafter, the basic organic compound (B) other than the basic organic compound (b2) may be referred to as a basic organic compound (b1).

The basic organic compound (b1) and the basic organic compound (b2) may be the same compound or different compounds from each other. When they are the same compound, the basic organic compound (b1) and the basic organic compound (b2) are preferably amino alcohols (alkanolamines), and more preferably triethanolamine. When they are different compounds, as a combination of the basic organic compound (b1) and the basic organic compound (b2), for example, a basic organic compound having a pKa value of 8.5 or less and a basic organic compound having a pKa of more than 8.5 are basic. Combinations with organic compounds; combinations of triethanolamine with basic organic compounds other than triethanolamine, and the like.

The basic organic compound may contain a basic organic compound having a pKa value of more than 9.5, but as described above, the basic organic compound having a pKa value of more than 9.5 is the present invention. Since the effect may be hindered, the compounding amount should be small. Specifically, when the basic organic compound contains a basic organic compound having a pKa value of more than 9.5, the content of the basic organic compound having a pKa value of more than 9.5 is the total amount of magenta ink. Of the above, it is preferably more than 0% by mass and 0.5% by mass or less, and more preferably more than 0% by mass and 0.3% by mass or less. The total content of the basic organic compound (the total content of the basic organic compound (B) and the basic organic compound having a pKa value of more than 9.5) is 0.1 to 1 in the total amount of magenta ink. It is preferably 2.0% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.1 to 1.25% by mass. As a specific example, the content of the basic organic compound (B) is 0.1 to 1.0% by mass in the total amount of magenta ink, and the total content of the basic organic compounds (basic organic compound (basic organic compound ()). Examples thereof include magenta ink having a total content of B) and a basic organic compound having a pKa value of more than 9.5) of 1.5% by mass or less.

On the other hand, when an isoindoline pigment is used as the pigment contained in the yellow ink, the dispersion stability is improved when a basic organic compound exhibiting strong basicity is added, as in the case of the naphthol-based mixed crystal pigment (A-1). It is easy to get worse. As a matter of course, when a yellow ink containing a basic organic compound showing strong basicity and magenta ink are mixed, the above-mentioned deterioration of dispersion stability and red color are caused by the basic organic compound showing strong basicity. It is considered that deterioration of color reproducibility and image quality (unevenness of shading), and discoloration and / or fading over time occur in the printed matter of. From the above viewpoint, it is preferable that the yellow ink also contains the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C.

The suitable pKa value, suitable molecular weight, specific examples, blending amount, etc. of the basic organic compound (B) contained in the yellow ink are the same as those of the magenta ink described above. That is, the yellow ink preferably contains the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in an amount of 0.1 to 1.25% by mass based on the total amount of the aqueous inkjet yellow ink. Further, the pKa value is more preferably 8.5 or less. Further, it is preferable that the yellow ink contains amino alcohols (for example, triethanolamine) as the basic organic compound (B).

<Organic solvent with a boiling point of 240 ° C or higher>
The magenta ink has a boiling point of 240 ° C. or higher at 1 atm, and the content of the organic solvent (hereinafter, also referred to as “high boiling point organic solvent”) is 8% by mass or less (0% by mass) in the total amount of the magenta ink. May be).
The "organic solvent" in the present specification includes, in addition to the water-soluble organic solvent described later, a solvent that is not the water-soluble organic solvent (however, a solvent that is liquid at 25 ° C. and 1 atm). do.

In general, with an ink in which an excessive amount of the high boiling point organic solvent is present, the high boiling point organic solvent tends to remain in the printed matter after printing, which may deteriorate the image quality such as uneven shading. In addition, when a permeable substrate is used as the recording medium, the high boiling point organic solvent may permeate and diffuse inside the recording medium together with the naphthol-based mixed crystal pigment (A-1), which may lead to a decrease in concentration. be. In addition, since the high boiling point organic solvent generally has high hygroscopicity, when the printed matter is stored for a long period of time, the high boiling point organic solvent may absorb moisture in the atmosphere. Here, when the boiling point of the basic organic compound (B) used is high, it is considered that a part of the basic organic compound (B) also remains in the printed matter. In that case, the basic organic compound (B) elutes in the water absorbed by the high boiling point organic solvent and diffuses into the printed matter, damaging the naphthol-based mixed crystal pigment (A-1) contained in the magenta ink. Can be considered. As a result of the above, in a printed matter produced by using an ink in which an excessive amount of high boiling point organic solvent is present, discoloration and discoloration may occur over time. Therefore, in the present invention, the phenomenon is suppressed by setting the content of the high boiling point organic solvent in the magenta ink to a certain amount or less.

From the above viewpoint, the smaller the content of the high boiling point organic solvent is, the better, for example, it is more preferably 3% by mass or less, and particularly preferably 1.5% by mass or less in the total amount of magenta ink.

In the present specification, the boiling point at 1 atm can be measured by using a thermal analyzer such as DSC (Differential Scanning Calorimetry).

Further, also in the yellow ink constituting the ink set of the present invention, it is preferable that the amount of the high boiling point organic solvent is small. This is because the magenta ink and the yellow ink are mixed on the recording medium when the red-colored printed matter is produced using the ink set of the present invention. The suitable blending amount of the high boiling point organic solvent contained in the yellow ink is the same as that of the magenta ink described above.

Subsequently, in detail, the common materials in the magenta ink, the yellow ink, and the inks of other colors (hereinafter, collectively referred to as simply “inks”) constituting the ink set of the present invention will be described in detail below. explain.

<Water-soluble organic solvent>
The magenta ink and the yellow ink constituting the ink set of the present invention each contain 1 to 30% by mass of an alkanediol having 4 to 6 carbon atoms as a water-soluble organic solvent. The detailed principle is not clear, but as mentioned above, when the magenta ink and the yellow ink are mixed, the dispersed state of each pigment can be stabilized, and good color development, color reproducibility, and image quality can be obtained. It is thought that it can be expressed. From the viewpoint of further stabilizing the dispersed state of the pigment and improving the image quality, color reproducibility, and color development of the printed matter, the amount of alcandiol having 4 to 6 carbon atoms contained in the magenta ink and the yellow ink is It is more preferably 3 to 30% by mass based on the total amount of the ink, and further preferably 3 to 25% by mass from the viewpoint of drying property.

The term "water-soluble organic solvent" as used herein refers to a solvent having a solubility in water of 5 g / 100 gH ₂ O or more and a liquid at 25 ° C. and 1 atm. Further, among the above-mentioned basic organic compounds (B), those satisfying the above-mentioned solubility conditions are also included in the water-soluble organic solvent.

Examples of alkanediols having 4 to 6 carbon atoms are 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3. -Pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,3- Examples thereof include butanediol, 3-methyl-1,5-pentanediol and the like. Among them, the structure in which the hydroxyl group is localized at one end of the structure has a high affinity for both the aqueous medium and the pigment surface, and by further stabilizing the pigment dispersibility, the image quality and color reproduction of the printed matter are reproduced. It can be preferably used because it improves the properties and color development. Specifically, 1,2-alkanediol such as 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol is suitable. Further, 1,2-hexanediol can be particularly preferably used because it has a good balance between hydrophobicity and hydrophilicity and can improve discharge stability.

As the magenta ink and the yellow ink, in addition to the above-mentioned alkanediol having 4 to 6 carbon atoms, other water-soluble organic solvents can be used in combination. Among them, a printed matter having excellent image quality and drying property can be obtained, an ink having excellent compatibility with a binder resin and a surfactant described later, a water-soluble organic solvent itself having a low viscosity, and an ink having excellent ejection stability can be obtained. Further, a water-soluble organic solvent having one or two hydroxyl groups is preferably selected from the viewpoint of not inhibiting the above-mentioned effect of 1,2-alkanediol. Among them, alcohol-based solvents, glycol ether-based solvents, polyalkylene glycol-based solvents and the like can be particularly preferably used.

As other water-soluble organic solvents that can be used in the present invention,
Examples of the monohydric alcohol solvent include ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 3-butanol, isobutanol, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol and the like. but,
Ethylene glycol, propylene glycol (1,2-propanediol), 1,3-propanediol, 1,2-heptanediol as dihydric alcohol solvents (other diol solvents) excluding alkanediol having 4 to 6 carbon atoms. Etc.,
As a trivalent or higher alcohol solvent (polyol solvent), glycerin, 1,2,4-butanetriol, diglycerin and the like can be used.
As glycol ether-based solvents, 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, diethylene glycol monoisopropyl ether, Diethylene Glycol Monoisobutyl Ether, Triethylene Glycol Monomethyl Ether, Triethylene Glycol Monoethyl Ether, Triethylene Glycol Monopropyl Ether, Triethylene Glycol Monobutyl Ether, Tetraethylene Glycol Monomethyl Ether, Dipropylene Glycol Monomethyl Ether, Diethylene Glycol Dimethyl Ether, Triethylene Glycol Dimethyl Ether , Tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl butyl ether, triethylene glycol methyl butyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol methyl ethyl ether. , Tetraethylene glycol butylmethyl ether, propylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, propylene glycol dimethyl ether, tripropylene glycol dimethyl ether, etc.
Diethylene glycol, dipropylene glycol, etc. are used as polyalkylene glycol solvents.
As chain amide-based solvents, N, N-dimethylformamide, 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-ethyl Hexoxypropionamide, N, N-dimethyl-β-octoxypropionamide, N, N-diethyl-β-butoxypropionamide, N, N-diethyl-β-pentoxypropionamide, N, N-diethyl-β -Hexoxypropionamide, N, N-diethyl-β-heptoxypropionamide, N, N-diethyl-β-octoxypropionamide, etc.
As the cyclic amide solvent, 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone and the like can be used.
As the cyclic carbamate solvent, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone and the like can be used.
Each is listed, but not limited to these.

The weighted average value of the boiling point of the water-soluble organic solvent (SM) contained in magenta ink at 1 atm and the weighted average value of the boiling point of the water-soluble organic solvent (SY) contained in yellow ink at 1 atm are , 100 to 235 ° C, more preferably 120 to 210 ° C, and particularly preferably 120 to 195 ° C, respectively. Further, considering the image quality for a non-permeable substrate such as a plastic substrate, it is particularly preferable that the temperature is 120 to 180 ° C., respectively. When the weighted average value of the boiling point under 1 atm is 100 ° C. or higher, the ejection stability from the inkjet head is improved, and the color development and color reproducibility when printed on a penetrating substrate are improved. Further, when the weighted average value of the boiling point is 235 ° C. or less, the image quality is good without causing drying failure on the recording medium and preventing the remaining water-soluble organic solvent from causing bleeding between ink droplets. In addition, the adhesion to impermeable substrates such as plastic substrates and the scratch resistance of printed matter are improved. The weighted average value of the boiling point shall include the water-soluble organic solvent having a boiling point of 240 ° C. or higher under 1 atm. When there are two or more types of water-soluble organic solvents contained in the water-based inkjet ink, the weighted average value of the boiling points under 1 atm is the boiling point at 1 atm calculated for each water-soluble organic solvent. , It is a value obtained by adding the multiplication value with the mass ratio to the total amount of the water-soluble organic solvent. On the other hand, when the water-soluble organic solvent contained in the water-based inkjet ink is only one kind of alcandiol having 4 to 6 carbon atoms, the "weighted average value of boiling points" is set to "(4 to 6 carbon atoms). It shall be read as "boiling point (of alcandiol)".

Further, from the viewpoint of keeping the weighted average value of the boiling point within the above range, the blending amount of the water-soluble organic solvent having a boiling point of 100 to 220 ° C. under 1 atm is 50 with respect to the total amount of the water-soluble organic solvent in the ink. It is preferably 7% by mass or more, more preferably 70% by mass or more, and particularly preferably 85% by mass or more, respectively.

The content of the water-soluble organic solvent (SM) contained in the magenta ink and the content of the water-soluble organic solvent (SY) contained in the yellow ink may be 1 to 30% by mass with respect to the total amount of the ink, respectively. preferable. Further, from the viewpoint of ensuring ejection stability on the inkjet head and obtaining printed matter having excellent adhesion, dryness, and image quality even with a non-permeable substrate, the content should be 3 to 27% by mass, respectively. Is more preferable, and it is particularly preferable that each is 5 to 25% by mass.

<Pigment dispersion resin>
As a method for stably dispersing and holding the pigment contained in each ink constituting the ink set of the present invention, (1) a method of covering at least a part of the pigment surface with a pigment dispersion resin, (1) 2) A method of adsorbing a water-soluble and / or water-dispersible surfactant on the pigment surface, (3) A hydrophilic functional group is chemically and physically introduced on the pigment surface without a dispersion resin or a surfactant. Examples thereof include a method of dispersing in ink (self-dispersing pigment).

For each ink constituting the ink set of the present invention, the method (1) above, that is, the method using a pigment dispersion resin is preferably selected. This is because the covering ability of the pigment-dispersed resin to the pigment and the charge of the pigment-dispersed resin can be easily adjusted by selecting and examining the polymerizable monomer composition and the molecular weight constituting the resin, so that the pigment is fine. However, it is possible to impart dispersion stability, and further, it is possible to obtain a printed matter having excellent ejection stability, color development property, and color reproducibility.

The type of the pigment dispersion resin is not particularly limited, and for example, (meth) acrylic resin, styrene (meth) acrylic resin, (anhydrous) maleic acid resin, styrene (anhydrous) maleic acid resin, olefin (anhydrous) maleic acid resin, and the like. Urethane resin, ester resin (polycondensate of polyvalent carboxylic acid and polyhydric alcohol) and the like can be used, but the present invention is not limited thereto. Above all, use one or more selected from the group consisting of (meth) acrylic resin, styrene (meth) acrylic resin, urethane resin, and ester resin in terms of the size of material selectivity and ease of synthesis. Is preferable. Further, from the viewpoint of improving the dispersion stability and ejection stability of the ink, it is preferable to use a resin of the same type as the binder resin described later.

In the present specification, "(meth) acrylic resin" means an acrylic resin, a methacrylic resin, or an acrylic-methacrylic resin. Here, the "acrylic-methacrylic resin" means a resin using acrylic acid and / or acrylic acid ester and methacrylic acid and / or methacrylic acid ester as a polymerizable monomer. Further, "(anhydrous) maleic acid" means maleic anhydride or maleic acid.

The pigment dispersion resin described above can be synthesized by a known method or a commercially available product can be used. Further, the structure is not particularly limited, and for example, a resin having a random structure, a block structure, a comb-shaped structure, a star-shaped structure, or the like can be used. Further, as the pigment dispersion resin, a water-soluble resin may be selected or a water-insoluble resin may be selected. The "water-insoluble resin" refers to a resin in which the target pigment dispersion resin is not transparent to the naked eye at 25 ° C. by 1% by mass.

When a water-soluble resin is used as the pigment dispersion resin, its acid value is preferably more than 100 mgKOH / g and 450 mgKOH / g or less, and more preferably 120 to 400 mgKOH / g. Particularly preferably, it is 150 to 350 mgKOH / g. By setting the acid value within the above range, it is possible to maintain the dispersion stability of the pigment, and it is possible to stably eject the pigment from the inkjet head. In addition, it becomes possible to maintain the ejection stability on the inkjet head. Further, it is preferable from the viewpoint that the solubility of the pigment-dispersed resin in water can be ensured and the viscosity of the pigment-dispersed liquid can be suppressed by making the interaction between the pigment-dispersed resins suitable.

On the other hand, when a water-insoluble resin is used as the pigment dispersion resin, its acid value is preferably 0 to 100 mgKOH / g, more preferably 5 to 90 mgKOH / g, and further preferably 10 to 80 mgKOH / g. preferable. When the acid value is within the above range, a printed matter having excellent drying property and scratch resistance can be obtained.

The acid value of the resin can be measured by a known device. The acid value of the resin in the present specification is a value measured by a potentiometric titration method using AT-610 manufactured by Kyoto Electronics Industry Co., Ltd. according to JIS K 2501. As an example of a specific measurement method, AT-610 manufactured by Kyoto Denshi Kogyo Co., Ltd. is used, the resin is dissolved in a mixed solvent of toluene-ethanol, then titrated with a potassium hydroxide solution, and the acid value is determined from the titration to the end point. There is a method of calculating.

Further, from the viewpoint of improving the adsorption ability to the pigment and ensuring the dispersion stability, it is preferable to introduce an aromatic group into the pigment dispersion resin. In particular, in the case of magenta ink, the aromatic ring structure contained in the naphthol mixed crystal pigment (A-1) and the aromatic ring structure contained in the pigment dispersion resin interact with each other to cause the naphthol mixed crystal pigment (A-). The adsorption capacity of the pigment-dispersed resin with respect to 1) is significantly improved. As a result, even if the pigment is finely dispersed, it is possible to secure the dispersion stability, the ejection stability, and the color reproducibility of the printed matter for a long period of time. Examples of the aromatic group include, but are not limited to, a phenyl group, a naphthyl group, an anthryl group, a tolyl group, a xylyl group, a mesitylene group, an anisyl group and the like. Of these, a phenyl group, a naphthyl group and a tolyl group are preferable from the viewpoint of sufficiently ensuring dispersion stability.

From the viewpoint of achieving both dispersion stability, print quality, and drying property of magenta ink, the content of the monomer containing an aromatic ring is preferably 5 to 75% by mass, preferably 5 to 75% by mass, based on the total amount of the pigment dispersion resin. It is more preferably 65% by mass, and even more preferably 10 to 50% by mass.

Further, in addition to the aromatic group, it is particularly preferable to introduce an alkyl group having 8 to 36 carbon atoms into the pigment dispersion resin. This is because by setting the number of carbon atoms of the alkyl group to 8 to 36, it is possible to reduce the viscosity of the pigment dispersion liquid, improve the dispersion stability, and realize the ejection stability. The number of carbon atoms of the alkyl group is more preferably 10 to 30, and even more preferably 12 to 24 carbon atoms. Further, the alkyl group can be either linear or branched as long as it has 8 to 36 carbon atoms, but a linear group is preferable. As the linear alkyl group, ethylhexyl group (C8), lauryl group (C12), myristyl group (C14), cetyl group (C16), stearyl group (C18), araquil group (C20), behenyl group (C22), Lignoceryl group (C24), cellotoyl group (C26), montanyl group (C28), meliscil group (C30), dotriacontanyl group (C32), tetratriacontanyl group (C34), hexatriacontanyl group (C36) And so on.

The content of the monomer containing an alkyl chain having 8 to 36 carbon atoms is 5 to 60% by mass with respect to the total amount of the pigment dispersion resin from the viewpoint of achieving both low viscosity of the pigment dispersion and scratch resistance of the printed matter. It is preferably 10 to 55% by mass, more preferably 15 to 50% by mass, and particularly preferably 15 to 50% by mass.

When a water-soluble resin is used as the pigment dispersion resin, it is preferable that the acid group in the resin is neutralized with a base in order to increase the solubility in the ink. Whether or not the amount of the base added is excessive can be confirmed, for example, by preparing a 10% by mass aqueous solution of the pigment-dispersed resin and measuring the pH of the aqueous solution. From the viewpoint of improving the dispersion stability of the ink, the pH of the aqueous solution is preferably 7 to 11, and more preferably 7.5 to 10.5.

Examples of the base for neutralizing the pigment dispersion resin include organic amine solvents such as triethylamine, monoethanolamine, diethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, and aminomethylpropanol, aqueous ammonia, and water. Examples include, but are not limited to, alkali metal hydroxides such as lithium oxide, sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate and potassium carbonate. ..

When a water-soluble resin is used as the pigment dispersion resin, its weight average molecular weight is preferably in the range of 1,000 to 500,000, more preferably in the range of 5,000 to 40,000, 10. It is more preferably in the range of 000 to 35,000, and particularly preferably in the range of 15,000 to 30,000. When the weight average molecular weight is in the above range, the pigment is stably dispersed in water, and it is easy to adjust the viscosity when applied to ink. When the weight average molecular weight is 1,000 or more, the pigment dispersion resin is difficult to dissolve in the water-soluble organic solvent added to the ink, so that the adsorption of the pigment dispersion resin to the pigment is strengthened and the dispersion stability is increased. Is improved. When the weight average molecular weight is 50,000 or less, the viscosity at the time of dispersion is suppressed to a low level, the dispersion stability of the ink and the ejection stability from the inkjet head are improved, and stable printing over a long period of time becomes possible.

The blending amount of the pigment dispersion resin is preferably 1 to 100% by mass with respect to the blending amount of the pigment. By setting the ratio of the pigment dispersion resin within the above range, the viscosity of the pigment dispersion liquid is suppressed, and the dispersion stability and ejection stability of the ink are improved. The ratio of the pigment to the pigment dispersion resin is more preferably 2 to 50% by mass, and particularly preferably 4 to 45% by mass.

<Dispersion aid>
A dispersion aid may be used in combination from the viewpoint of significantly improving the dispersion stability and ejection stability of the pigment and also improving the color reproducibility of the printed matter by enabling fine dispersion of the pigment. The dispersion aid is a material that contributes to improving the adsorption rate of the pigment dispersion resin or the surfactant with respect to the pigment. In the present invention, conventionally known materials can be arbitrarily used as the dispersion aid, and in particular, a compound called a dye derivative can be preferably used. The dye derivative is a compound in which a substituent is introduced into the organic dye molecule, and the organic dye includes a monoazo dye, a disuazo dye, a polyazo dye, an anthraquinone dye, an isoindolinone dye, and an isoindoline dye. , Quinacridone dye, quinophthalone dye, dioxazine dye, diketopyrrolopyrrole dye, slene dye, thioindigo dye, naphthalocyanine dye, phthalocyanine dye, perinone dye, perylene dye, benzimidazolone dye , Metal complex dyes and the like. The above-mentioned "dye" is a general term for pigments and dyes.

When the dispersion aid is used in the present invention, the blending amount thereof is preferably 0.1 to 10% by mass, particularly preferably 0.5 to 5% by mass, based on the blending amount of the pigment. When it is 0.1% by mass or more, the addition ratio to the pigment becomes a sufficient amount, and the dispersion stability, the ejection stability and the color reproducibility of the printed matter are improved. Further, when the content is 10% by mass or less, the pigment miniaturization does not proceed more than necessary, so that the dispersion stability is improved and the deterioration of the light resistance of the printed matter can be prevented.

<Binder resin>
Each ink constituting the ink set of the present invention preferably contains a binder resin in order to improve scratch resistance, color development, and color reproducibility of the printed matter.

The "binder resin" in the present specification is a resin used for binding a layer of printed matter (printed matter layer, ink layer) to a recording medium. As described above, each ink may contain a pigment-dispersed resin, but when the resin contained in each ink is a water-soluble resin, which of the pigment-dispersed resin and the binder resin corresponds to the resin. Shall be distinguished by the adsorption rate for the pigment. That is, a resin having an adsorption rate with respect to the pigment of 50% by mass or more with respect to the total blending amount is determined to be a pigment dispersion resin, and a resin having an adsorption rate of less than 50% by mass is determined to be a binder resin.

As an example of a method for measuring the adsorption rate on a pigment, a water-based ink diluted with water is subjected to a centrifugal separation treatment (for example, at 30,000 rpm for 4 hours) to separate the pigment and the supernatant liquid. Then, when the solid content contained in the supernatant liquid is measured, if the solid content is 50% by mass or more with respect to the total amount of the resin having the same composition contained in the ink, the resin is a binder resin. Judge.

As the form of the binder resin, a water-soluble resin and resin fine particles (a form of a water-insoluble resin) are generally known, and in the present invention, either one may be selected and used, or both may be used in combination. May be good. For example, the resin fine particles have a higher molecular weight than the water-soluble resin, can improve the scratch resistance of the printed matter, and are also excellent in the image quality of the printed matter. Further, when printing on a permeable substrate, the voids on the surface of the recording medium can be effectively filled, so that the color development and color reproducibility of the printed matter are improved. On the other hand, an ink using a water-soluble resin as a binder resin has excellent ejection stability. In the present specification, the "water-soluble resin" refers to a resin that is not the above-mentioned water-insoluble resin, that is, a resin in which a 25 ° C., 1% by mass water mixture of the target resin is transparent to the naked eye. ..

Each ink constituting the ink set of the present invention, particularly magenta ink, preferably contains a binder resin having an acid value of 1 to 80 mgKOH / g as the binder resin. Further, by ensuring the dispersion stability of the naphthol-based mixed crystal pigment (A-1) and rapidly moving to the gas-liquid interface, a printed matter having excellent image quality can be obtained, and further, the permeability of uncoated paper or the like can be obtained. When a base material is used, the binder resin contained in magenta ink is contained in the magenta ink from the viewpoint of producing a printed matter having excellent color development and color reproducibility by rapidly moving so as to fill the voids on the surface of the base material. The acid value is preferably 3 to 60 mgKOH / g, particularly preferably 5 to 40 mgKOH / g. The acid value of the binder resin can be measured in the same manner as the acid value of the pigment-dispersed resin.

On the other hand, the glass transition temperature of the binder resin contained in each ink can be selected, for example, as follows according to the required characteristics. Specifically, it improves ejection stability and scratch resistance of printed matter, and is also excellent in drying property and blocking resistance (a phenomenon in which a print layer sticks to another recording medium when a recording medium after printing is stacked). In order to obtain the printed ink, the glass transition temperature is preferably 60 to 140 ° C, more preferably 70 to 135 ° C, and particularly preferably 80 to 130 ° C.

On the other hand, when printing on a non-permeable substrate such as a plastic substrate, the glass transition temperature is preferably −120 to 45 ° C., preferably −80, from the viewpoint of image quality and adhesion. The temperature is more preferably ~ 25 ° C, and particularly preferably −60 to 15 ° C.

The glass transition temperature is a value measured using a DSC (Differential Scanning Calorimetry), and can be measured as follows, for example, according to JIS K7121. Approximately 2 mg of a sample obtained by drying the resin is weighed on an aluminum pan, and the aluminum pan is set in a holder in a DSC measuring device (for example, DSC-60Plus manufactured by Shimadzu Corporation) as a test container. Then, the temperature at the intersection of the baseline on the low temperature side and the tangent at the inflection point read from the obtained DSC chart obtained by measuring under the heating condition of 5 ° C./min is referred to as the glass transition temperature in the present specification. do.

Types of binder resin used in the present invention include (meth) acrylic resin, styrene (meth) acrylic resin, urethane resin, urethane / (meth) acrylic composite resin, styrene butadiene resin, vinyl chloride resin, and styrene (anhydrous) maleic acid resin. , Ester resin, polyolefin resin and the like. Above all, from the viewpoint of obtaining an ink having excellent dispersion stability and ejection stability, the binder resin is composed of (meth) acrylic resin, styrene (meth) acrylic resin, urethane resin, urethane / acrylic composite resin, and polyolefin resin. It is preferable to use one or more resins selected from the group. Further, in general, urethane resin, urethane / acrylic composite resin, and polyolefin resin have a low glass transition temperature, and are therefore preferably selected from the viewpoint of adhesion to impermeable substrates such as plastic substrates and image quality.

Further, from the viewpoints of adhesion to a plastic substrate, scratch resistance of printed matter, color development and color reproducibility when printed on a penetrating substrate, and blocking resistance, as a binder resin, a polyolefin resin and (meth ) It is preferable to include one or more resins selected from an acrylic resin, a styrene (meth) acrylic resin, a urethane resin, and a urethane / acrylic composite resin.

As a result of diligent studies by the present inventors, when polyolefin resin fine particles are used as the binder resin, the color reproducibility and image quality of the printed matter and the dispersion stability of the ink are improved depending on the conditions, and over time. It was found that the discoloration of the printed matter can be prevented.
Specifically, in magenta ink, the amine value of the naphthol-based mixed crystal pigment (A-1) is Am (PA) [mgKOH / g], and the naphthol-based mixed crystal pigment (A-1) is contained in the total amount of the ink. The amount is C (PA) [mass%], the acid value of the olefin resin fine particles is Av (RO) [mgKOH / g], and the content of the olefin resin fine particles in the total amount of ink is C (RO) [mass%]. The acid value / amine value ratio represented by the following formula (3) ^{is preferably 0.5 × 10 -4} to 15 × 10 ^-4 , and 1.5 × 10 ^-4 to 10 ×. It is particularly preferable that it is 10 ^-4. Although the detailed factor is unknown, the acid group present in the olefin resin fine particles and the naphthol-based mixed crystal pigment (A-1) having an amine structure interact with each other, and the naphthol-based mixed crystal pigment (A) It is considered that the presence of the olefin resin fine particles around -1) can prevent the aggregation of the naphthol-based mixed crystal pigment (A-1).

Equation (3):
Acid value / amine value ratio = {Av (RO) x C (RO)} ÷ {Am (PA) x C (PA)}

The above binder resin can be synthesized by a known method or a commercially available product can be used. Further, the structure is not particularly limited, and for example, a resin having a random structure, a block structure, a comb-shaped structure, a star-shaped structure, or the like can be used.

When a water-soluble resin is used as the binder resin in the present invention, its weight average molecular weight ensures stability of ejection from the inkjet nozzle, and the printed matter has excellent adhesion and scratch resistance to various recording media. It is preferably 5,000 to 50,000 from the viewpoint of obtaining the above, and 8,000 to 45,000 from the viewpoint of excellent color development and color reproducibility when printed on a penetrating substrate. It is more preferably 10,000 to 40,000.

In the present specification, the weight average molecular weight of the resin is a polystyrene-equivalent value that can be measured by, for example, a method according to JIS K 7252. As an example of a specific measurement method, there is a method of measuring using a GPC measuring device (HLC-8120GPC manufactured by Tosoh Corporation) equipped with a TSKgel column manufactured by Tosoh Corporation and a THF as a developing solvent. Can be mentioned.

The content of the binder resin with respect to the total amount of the ink is preferably 1 to 15% by mass, more preferably 2 to 12% by mass, and further preferably 4 to 10% by mass in terms of solid content. By setting the amount of the binder resin within the above range, the dispersion stability and the ejection stability are not deteriorated, and the printed matter has scratch resistance, dryness, image quality, and color development when printed on a penetrating substrate. It is possible to obtain an ink having excellent properties and color reproducibility.

In addition, an ink having excellent dispersion stability and ejection stability, good adhesion to a plastic substrate and good image quality, and excellent color development and color reproducibility when printed on a penetrating substrate can be obtained. From this viewpoint, the content of the binder resin having an acid value of 1 to 80 mgKOH / g is preferably 20 to 100% by mass, more preferably 35 to 100% by mass, based on the total amount of the binder resin in the ink. Particularly preferably 50 to 100% by mass.

<Surfactant>
In the present invention, it is preferable to contain one or more surfactants from the viewpoint of obtaining an ink having excellent ejection stability, image quality of printed matter, drying property and the like. Further, it is preferable to use a nonionic surfactant as the surfactant. Generally, various nonionic surfactants are known, such as acetylenediol-based, acetylene alcohol-based, siloxane-based, acrylic-based, fluorine-based, and polyoxyalkylene-based, depending on the application. , An acetylene diol-based surfactant, a siloxane-based surfactant, and one or more nonionic surfactants selected from the group consisting of a polyoxyalkylene-based surfactant represented by the following general formula (4). It is more preferable to contain an acetylene diol-based and / or a siloxane-based surfactant, and it is particularly preferable to contain a siloxane-based surfactant. In particular, in the case of magenta ink, the acetylene diol-based surfactant and the siloxane-based surfactant are naphthol-based mixed crystal pigments (A-1) present in the ink droplets after landing on the recording medium. It is considered that the interface is rapidly oriented to the gas-liquid interface and the recording medium-droplet interface without being affected by. As a result, the wettability of magenta ink can be improved and the ink droplets can be quickly smoothed even on a non-permeable substrate. In addition to the improvement in drying property, bleeding and uneven shading between droplets can be realized. It is possible to obtain a printed matter having excellent image quality with a small amount of ink. In addition to the above, when a siloxane-based surfactant is used, the scratch resistance of the printed matter is also improved, and although the details are unknown, magenta is used when printing on a penetrating base material such as uncoated paper. A printed matter having excellent color development and color reproducibility can be obtained without causing excessive penetration and diffusion of ink. In particular, in the present invention, although the details are unknown, since a water-based ink having excellent ejection stability in addition to the improvement of the above-mentioned characteristics can be obtained, at least in magenta ink, an acetylene diol-based surfactant and a siloxane-based surfactant are obtained. It is preferable to use in combination with.

Suitable acetylene diol-based surfactants include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,5,8,11-tetramethyl-6-dodecyne-. 5,8-diol, hexadeca-8-in-7,10-diol, 6,9-dimethyl-tetradeca-7-in-6,9-diol, 7,10-dimethylhexadeca-8-in-7, Examples include, but are not limited to, 10-diols and their ethylene oxide and / or propylene oxide adducts.

Further, as a siloxane-based surfactant that can be preferably used, for example, a siloxane-based surfactant in which one or more ethylene oxide groups and / or one or more propylene oxide groups are introduced into the side chains and / or both ends of the polydimethylsiloxane chain. Examples include surfactants. Specifically, 8032ADDITIVE, FZ-2104, FZ-2120, FZ-2122, FZ-2162, FZ-2164, FZ-2166, FZ-2404, FZ-7001, FZ-7002, manufactured by Toray Dow Corning Co., Ltd. FZ-7006, L-7001, L-7002, SF8427, SF8428, SH3748, SH3749, SH3771M, SH3772M, SH3773M, SH3775M, SH8400, BYK-331, BYK-333, BYK-345, BYK-346, manufactured by Big Chemie. BYK-347, BYK-348, BYK-349, BYK-UV3500, BYK-UV3510, BYK-UV3530, BYK-UV3570, Ebonic's TEGO Wet 240, TEGO Wet 250, TEGO Wet 260, TEGO Wet 270, TEGO 280, TEGO Glide 410, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, KF-351A, KF-352A, KF-353, KF-354L, KF-355 manufactured by Shin-Etsu Chemical Co., Ltd. 615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, X-22- 4515, Silface SAG series of Nissin Chemical Industry Co., Ltd. and the like can be mentioned.

Further, as a polyoxyalkylene-based surfactant that can be preferably used, for example, a compound represented by the following general formula (4) can be mentioned.

General formula (4):
RO- (EO) m- (PO) n-H

In the above general formula (4), R has an alkyl group having 8 to 22 carbon atoms, an alkenyl group having 8 to 22 carbon atoms, an alkylcarbonyl group having 8 to 22 carbon atoms, or an alkyl carbonyl group having 8 to 22 carbon atoms. Represents an alkenylcarbonyl group. The R may have a branched structure. Further, EO represents an ethylene oxide group and PO represents a propylene oxide group. m indicates the average number of added moles of EO and is a number of 2 to 50, and n indicates the average number of added moles of PO and is a number of 0 to 50. When n is not 0, the addition order of (EO) m and (PO) n does not matter, and the addition may be block or random.

Among the surfactants exemplified above, those having a hydrophilic ethylene oxide group are particularly preferably selected.

Further, from the viewpoint that an ink having excellent dispersion stability and ejection stability can be obtained and a printed matter having excellent image quality without bleeding or uneven shading can be obtained, a surfactant having an HLB value of 0 to 5 is used. It is particularly preferable to include a surfactant having an HLB value of 0 to 4.

In particular, in addition to dispersion stability and ejection stability, a printed matter having excellent image quality with less bleeding between ink droplets and uneven shading on a non-permeable substrate such as a plastic substrate can be obtained, and at the same time. , A surfactant having an HLB value of 0 to 5 (preferably 0 to 4) from the viewpoint of obtaining a printed matter having excellent color development and color reproducibility on a permeable base material such as uncoated paper. It is preferable to use in combination with a surfactant having an HLB value of 6 to 18 (preferably 7 to 18, particularly preferably 8 to 16).

When a compound represented by the above general formula (4) is used as the surfactant, its HLB value is preferably 13 or less, and more preferably 10 or less. By setting the content within the above range, a printed matter having excellent image quality without bleeding or uneven shading can be obtained with respect to the non-penetrating base material and the poorly permeable base material.

The HLB (Hydrophile-Lipophile Balance) value is one of the parameters indicating the hydrophilicity / hydrophobicity of the material, and the smaller the value, the higher the hydrophobicity, and the larger the value, the higher the hydrophilicity. Various methods for calculating the HLB value from the chemical structure are known, and various methods for actually measuring the HLB value are also known. However, in the present invention, as in the case of acetylenediol-based surfactants and polyoxyalkylene-based surfactants, If the structure of the compound is clearly known, the HLB value is calculated using the Griffin method. The Griffin method is a method of calculating an HLB value using the following formula (5) using the molecular structure and molecular weight of the target material.

Equation (5):
HLB value = 20 × (total molecular weight of hydrophilic part) ÷ (molecular weight of material)

On the other hand, when a compound having an unknown structure is contained, such as a siloxane-based surfactant, for example, p. The HLB value of the surfactant can be determined experimentally by the following method described in 324. Specifically, after dissolving 0.5 g of a surfactant in 5 mL of ethanol, the solution is titrated with a 2 mass% phenol aqueous solution while stirring at 25 ° C., and the end point is where the solution becomes turbid. .. When the amount of the aqueous phenol solution required up to the end point is A (mL), the HLB value can be calculated by the following formula (6).

Equation (6):
HLB value = 0.89 × A + 1.11

The content of the surfactant is preferably 0.2 to 4% by mass with respect to the total amount of the ink. More preferably, it is 0.5 to 2% by mass.

<Water>
As the water contained in each ink, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions. The content thereof is preferably in the range of 20 to 90% by mass based on the total mass of the ink.

<Other ingredients>
In addition to the above components, additives such as defoaming agents, thickeners, preservatives, infrared absorbers, and ultraviolet absorbers are appropriately added in order to obtain inks having desired physical property values as needed. be able to. As an example of the addition amount of these additives, 0.01 to 10% by mass or less is preferable in the total amount of the ink.

It is preferable that each ink contains substantially no polymerizable monomer. Here, "substantially not contained" means that the ink is not intentionally added, and does not exclude a small amount of contamination or generation during manufacturing and storage of the ink. Specifically, the content of the polymerizable monomer is preferably 1% by mass, and particularly preferably 0.5% by mass or less, based on the total amount of the ink.

<Ink manufacturing method>
The ink composed of the above-mentioned components can be produced by a known method. In particular, from the viewpoint of obtaining an ink having excellent dispersion stability and ejection stability, after producing a pigment dispersion liquid containing a pigment in advance, the pigment dispersion liquid and the constituent materials of the ink (basic organic compound, water-soluble organic) are used. A manufacturing method of mixing (solvent or the like) is preferably selected. An example of an ink manufacturing method will be described below, but as described above, the manufacturing method is not limited to the following.

(1) Production of Pigment Dispersion Liquid (1-1) Method of Dispersion Treatment Using Pigment Dispersion Resin, which is a Water-Soluble Resin When a water-soluble resin is used as the pigment dispersion resin, the pigment dispersion resin, water, and if necessary. To prepare a pigment-dispersed resin aqueous solution by mixing and stirring with a water-soluble organic solvent. A pigment, a dispersion aid, additional water, and a (additional) water-soluble organic solvent, if necessary, are added to the pigment dispersion resin aqueous solution, mixed and stirred (premixed), and then a disperser is used. Perform distributed processing. Then, if necessary, centrifugation, filtration, and adjustment of the solid content are performed to obtain a pigment dispersion liquid.

(1-2) Method for Dispersion Treatment Using Pigment Dispersion Resin, which is a Water-Insoluble Resin In addition, when producing a dispersion liquid of a pigment coated with a pigment dispersion resin, which is a water-insoluble resin, an organic solvent such as methyl ethyl ketone is prepared in advance. A pigment-dispersed resin solution is prepared by dissolving the pigment-dispersed resin in the mixture and neutralizing the pigment-dispersed resin, if necessary. To the pigment dispersion resin solution, a pigment, water, a dispersion aid, a water-soluble organic solvent, and an additional organic solvent are added as necessary, mixed and stirred (premixed), and then dispersed using a disperser. Perform processing. Then, the organic solvent is distilled off by vacuum distillation, and if necessary, centrifugation, filtration, and adjustment of the solid content are performed to obtain a pigment dispersion liquid.

In the above methods (1-1) and (1-2), the disperser used in the dispersion treatment of the pigment may be any generally used disperser, and for example, a ball mill, a roll mill, a sand mill, etc. Examples include bead mills and nanomizers. Among the above, bead mills are preferably used, and specifically, they are commercially available under trade names such as super mills, sand grinders, agitator mills, grain mills, dyno mills, pearl mills and cobol mills.

In the above methods (1-1) and (1-2), as a method of controlling the particle size distribution of the pigment dispersion liquid, the size of the pulverized media used in the above-mentioned disperser is adjusted, and the material of the pulverized media is changed. To increase the filling rate of the crushed media, change the shape of the stirring member (agitator), lengthen the dispersion treatment time, classify by filtration or centrifugation after the dispersion treatment, and these. A combination of methods can be mentioned. In order to keep the pigment within a suitable particle size distribution range, the diameter of the pulverized media of the disperser is preferably 0.1 to 3 mm. Further, as the material of the crushing media, glass, zircon, zirconia and titania are preferably used.

(1-3) Method of Grinding and Kneading Using Pigment Dispersion Resin Further, in the present invention, the method of grinding and kneading shown below can also be preferably used. After kneading the pigment, the pigment dispersion resin, the water-soluble organic solvent, the inorganic salt, and if necessary, the dispersion aid with a kneader, water is added to the obtained mixture, and the mixture / stirring is performed. Then, the inorganic salt and, if necessary, the water-soluble organic solvent are removed by centrifugation, filtration, and washing, and the solid content is further adjusted to obtain a pigment dispersion liquid.

The kneader used in the above method (1-3) may be any disperser that is generally used, but a high-viscosity mixture can be kneaded to form a pigment dispersion liquid containing fine pigments. A kneader or a remix is preferably used because a printed matter having excellent quality, color development and color reproducibility can be obtained. By adjusting the temperature at the time of kneading, the particle size distribution of the obtained pigment dispersion can be controlled.

Further, as the inorganic salt, sodium chloride, barium chloride, potassium chloride, sodium sulfate, potassium sulfate and the like can be preferably used.

(2) Preparation of ink To the pigment dispersion obtained above, the constituent materials of the ink (basic organic compound, water-soluble organic solvent, binder resin, surfactant, water, etc.) are added, and the mixture is stirred and mixed. If necessary, the mixture may be stirred and mixed while heating in the range of 40 to 100 ° C.

(3) Removal of coarse particles The coarse particles contained in the above mixture are removed by a method such as filtration or centrifugation to obtain ink. As a method for filtration separation, a known method can be appropriately used, but when a filter is used, the opening diameter thereof is preferably 0.3 to 5 μm, more preferably 0.5 to 3 μm. Further, when performing filtration, the filter may be a single type or a plurality of types may be used in combination.

<Ink characteristics>
It is preferable to adjust the viscosity of each of the inks constituting the ink set of the present invention to 3 to 20 mPa · s at 25 ° C. In this viscosity region, stable ejection characteristics are exhibited not only in a head having a frequency of 4 to 10 KHz but also in a head having a high frequency of 10 to 70 KHz. In particular, by setting the viscosity at 25 ° C. to 4 to 10 mPa · s, stable ejection can be achieved even when used for an inkjet head having a design resolution of 600 dpi or more. The viscosity can be measured by a conventional method. Specifically, an E-type viscometer (TVE25L-type viscometer manufactured by Toki Sangyo Co., Ltd.) can be used for measurement using 1 mL of ink.

In addition, the inks constituting the ink set of the present invention each have a static surface tension of 18 to 35 mN / m at 25 ° C. from the viewpoint that the ink can be stably ejected and a printed matter having excellent image quality can be obtained. It is preferably 20 to 32 mN / m, and particularly preferably 20 to 32 mN / m. The static surface tension refers to the surface tension measured by the Wilhelmy method in an environment of 25 ° C. Specifically, CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. can be used, and measurement can be performed using a platinum plate.

In particular, in the case of the present invention, in order to prevent color mixing due to the union of magenta ink and yellow ink, improve color development and color reproducibility in the red color region, and improve image quality, the magenta ink is static. The difference between the surface tension and the static surface tension of the yellow ink is preferably 0 to 3 mN / m, and more preferably 0 to 2 mN / m.

Further, from the viewpoint of obtaining excellent image quality by quickly getting wet and spreading on the recording medium after landing on the recording medium, the inks constituting the ink set of the present invention are each 50 ms by the maximum foam pressure method. The dynamic surface tension in the above is preferably 25 to 36 mN / m, more preferably 26 to 34 mN / m, and particularly preferably 27 to 32 mN / m. The dynamic surface tension in the present specification is a value measured in an environment of 25 ° C. using a bubble pressure dynamic surface tension meter BP100 manufactured by Kruss.

The above-mentioned static surface tension and dynamic surface tension can be controlled, for example, by adjusting the type and amount of the water-soluble organic solvent and the surfactant.

<Hue of ink coated material>
As described above, the ink set of the present invention can obtain a printed matter having excellent color reproducibility. From the viewpoint of obtaining a printed matter having particularly excellent color development and color reproducibility, the magenta ink preferably has a hue angle ∠H ° measured by the following method in the range of 330 to 360 °, and is also a yellow ink. The hue angle ∠H ° is preferably in the range of 70 to 105 °.

The hue angle ∠H ° of the ink is measured by applying a wet film thickness of 6 μm on a recording medium and drying the coated product. Specifically, K control coater K202 manufactured by Matsuo Sangyo Co., Ltd., wire bar No. After applying the ink using No. 1, it is dried in an oven at 80 ° C. for 1 minute or more to prepare a coated product. Then, using i1Pro2 manufactured by X-rite, measurement was performed under the conditions of light source D50, viewing angle 2 ° and CIE color system, and the obtained a * and b * values were used to ∠H ° = tan ^-1. It is obtained by (b * / a *) +180 (when a * <0) or ∠H ° = tan ^-1 (b * / a *) +360 (when a *> 0). For coating, for example, UPM Finesse Gloss paper manufactured by UPM is used as a recording medium.

As standards or standards related to color, for example, Japan Color (Japan offset sheet-fed printing color standard), Fogra (German printing related standard), SWOP (US off-wheel printing standard), etc., offset printing international standard (ISO 12647-2) Compliant standards are known. The magenta ink and the yellow ink satisfying the above-mentioned hue angle can satisfy each of the above-mentioned printing color standards or standards, and a printed matter having excellent color development and color reproducibility can be obtained.

Further, the spectral reflectance of the coated product of magenta ink is 10% or less in the wavelength region of 480 to 580 nm because a printed matter having excellent image density and excellent color reproducibility in the red region can be obtained. It is preferable that the spectral reflectance of the coated product of the yellow ink is 10% or less in the wavelength region of 380 to 480 nm. The spectral reflectance of the printed matter is calculated by the method specified in ISO 5-3: 2009. Specifically, it can be measured using i1Pro2 manufactured by X-rite in the same manner as the above-mentioned hue angle ∠H °.

Since the color characteristics of the pigment change depending on the dispersion state, for example, the measurement should be performed using a pigment dispersion produced by the same method as the magenta pigment dispersion 1 or the yellow pigment dispersion 1 of Examples described later. Is preferable. As a specific method for measuring the hue angle, after diluting the pigment dispersion with water so that the pigment concentration becomes 3% by mass, recording is performed by the same method as for the ink coating product having a wet thickness of 6 μm. Apply on the medium. Then, the hue angle and the spectral reflectance of the obtained coated material are measured by the method described above.

<Inks other than yellow ink and magenta ink>
The ink set of the present invention may contain inks other than magenta ink and yellow ink (also referred to as "inks of other colors" in the present specification) from the viewpoint of obtaining printed matter having excellent color reproducibility. Above all, it is preferable to include cyan ink and / or violet ink and black ink as the inks of the other colors.

<Cyan ink>
Cyan ink contains cyan pigment and water. Examples of the cyan pigment contained in the cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15: 6, 16, 22, 60 and the like. In the cyan ink, the total content of the pigments listed above is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass in the total amount of the pigments contained in the cyan ink. % Or more, and particularly preferably 95% by mass or more. The total content of the pigments listed above may be 100% by mass with respect to the total amount of the pigments used. Above all, when used in combination with magenta ink having a hue angle ∠Hm ° of the coated object of 330 to 360 °, C.I. I. It is preferable to include one or more selected from the group consisting of Pigment Blue 15: 3 and 15: 4.

On the other hand, when used in combination with magenta ink having a hue angle ∠Hm ° of the coated product of 0 to 45 °, only three types of ink, yellow ink, magenta ink, and cyan ink, which are the embodiments of the present invention, are used. From the viewpoint that a printed matter having excellent color reproducibility can be produced even with an ink set containing the chromatic color ink, C.I. I. It is preferable to use a cyan ink containing one or more selected from the group consisting of Pigment Blue 15: 6 and 60.

From the viewpoint of color reproducibility and image density, the content of the cyan pigment contained in the cyan ink is preferably 0.1 to 10% by mass, preferably 1 to 9.5% by mass, based on the total amount of the cyan ink. Is more preferable.

In addition to the cyan pigment and water, the cyan ink may contain a water-soluble organic solvent, a pigment dispersion resin, a dispersion aid, a binder resin, a surfactant, a basic organic compound, and other components. The details regarding these components are the same as in the case of the magenta ink and the yellow ink described above.

<Violet ink>
Violet ink contains violet pigment and water. Examples of the violet pigment contained in the violet ink include C.I. I. Pigment Violet 1, 3, 23, 27, 32, 36, 37, 38 and the like. In the violet ink, the total content of the pigments listed above is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass in the total amount of the pigments contained in the violet ink. % Or more, and particularly preferably 95% by mass or more. The total content of the pigments listed above may be 100% by mass with respect to the total amount of the pigments used. Above all, the ink set containing the magenta ink and the yellow ink of the present invention has the viewpoint of producing a printed matter having excellent color reproducibility. I. It is preferred to include one or more selected from the group consisting of Pigment Violet 3, 23, 27, and 32.

From the viewpoint of color reproducibility and image density, the content of the violet pigment contained in the violet ink is preferably 0.1 to 10% by mass, preferably 1 to 9.5% by mass, based on the total amount of the violet ink. Is more preferable.

In addition to the violet pigment and water, the violet ink may contain a water-soluble organic solvent, a pigment dispersion resin, a dispersion aid, a binder resin, a surfactant, a basic organic compound, and other components. The details regarding these components are the same as in the case of the magenta ink and the yellow ink described above.

In the present specification, cyan ink and violet ink are distinguished by the color index name of the pigment mainly contained in the ink. That is, C.I. I. The ink containing the pigment blue pigment is cyan ink, and the main component is C.I. I. Ink containing pigment violet pigment is referred to as violet ink. In addition, C.I. I. Pigment Blue Pigment and C.I. I. In the case of an ink containing the same amount of pigment violet pigment, the hue angle ∠H ° of the ink coated product with a wet film thickness of 6 μm produced in the same manner as in the case of the above yellow ink is 200 ° or more and less than 260 °. Cyan ink is used as an ink, and violet ink is used as an ink having a temperature of 260 ° or more and less than 330 °. However, as the main component, C.I. I. Pigment blue pigment and / or C.I. I. Even if the ink contains a pigment violet pigment, if the hue angle ∠H ° of the ink-coated product is less than 200 °, it is assumed to be a green ink described later, and the ∠H ° is 330 ° or more. In this case, it shall be the magenta ink described above. Here, the main component refers to the pigment having the highest content based on the total amount of the pigment.

<Other color inks>
In order to improve the color reproducibility in the entire color region, the ink set of the present invention can be further combined with red ink, orange ink, green ink, brown ink and the like. When red ink is used, the pigment contained in the red ink may be, for example, C.I. I. Pigment Red 177, 254, 255, and C.I. I. One or more selected from the group consisting of Pigment Orange 73 is preferably used. When orange ink is used, the pigment contained in the orange ink may be, for example, C.I. I. Pigment Orange 5, 13, 16, 34, 36, 38, 43, 62, 64, 67, 71, 72 and C.I. I. One or more selected from the group consisting of Pigment Red 17, 49: 2,112, 149, 178, 188 and 264 is preferably used. When green ink is used, the pigment contained in the green ink may be, for example, C.I. I. One or more selected from the group consisting of Pigment Greens 7, 36 and 58 is preferably used.

In addition, light-colored inks such as light yellow ink, light cyan ink, light magenta ink, and light black (gray) ink, which are inks having a low pigment concentration, can also be used in combination depending on the application and image quality.
When light magenta ink or light yellow ink is used in combination, it is preferable to use the pigment used in magenta ink and yellow ink. In that case, it is particularly preferable to use the naphthol-based mixed crystal pigment (A-1) and the basic organic compound (B) in combination in the light magenta ink.

<Black ink>
It is also possible to include black ink in the ink set. By using black ink together, it is possible to obtain a higher-definition image that is excellent in character expression and contrast expression.

Examples of the black pigment contained in the black ink include organic pigments such as aniline black, lumogen black and azomethine black, and inorganic pigments such as carbon black and iron oxide. Further, a plurality of color pigments such as the above-mentioned magenta pigment, yellow pigment, and cyan pigment can be used as a composite black.

As the carbon black pigment, carbon black produced by the furnace method or the channel method is suitable. Among these carbon blacks, the primary particle size is 11 to 40 mμm (nm), the specific surface area by the BET method is 50 to 400 m ² / g, the volatile content is 0.5 to 10% by mass, and the pH value is 2 to 2. Those having characteristics such as 10 are suitable. Examples of commercially available products having such characteristics include No. 25, 30, 33, 40, 44, 45, 52, 850, 900, 950, 960, 970, 980, 1000, 2200B, 2300, 2350, 2600; MA7, MA8, MA77, MA100, MA230 (manufactured by Mitsubishi Chemical Corporation) ), RAVEN760UP, 780UP, 860UP, 900P, 1000P, 060UP, 1080UP, 1255 (manufactured by Bill La Carbon), REGAL330R, 400R, 660R, MOGUL L (manufactured by Cabot), NipponeX160IQ, 170IQ, 35,75; , 40, 45, 55, 75, 80, 85, 90, 95, 300; SpecialBlack350, 550; Neurox305, 500, 505, 600, 605 (manufactured by Orion Engineered Carbons), etc., all of which are preferably used. be able to.

The amount of the black pigment contained in the black ink is preferably 0.1 to 10% by mass, more preferably 1 to 9.5% by mass, based on the total amount of the black ink.

<White ink>
The ink set can also contain white ink. By using white ink together, a printed matter having good visibility can be formed on a transparent recording medium or a recording medium having low brightness. In particular, by using it in combination with magenta ink and yellow ink according to the embodiment of the present invention, it is possible to obtain clear and high-definition printed matter even on the above-mentioned recording medium as in the case of printing on a white medium. Become.

White pigments that can be used for white ink include inorganic white pigments and organic white pigments. Among them, examples of the inorganic white pigment include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, fine powder silicic acid, silicas such as synthetic silicates, calcium silicate and alumina. Alumina hydrate, titanium oxide, zinc oxide, talc, clay and the like can be mentioned. Titanium oxide is most preferable from the viewpoint of hiding power and coloring power.

The average particle size of the white pigment is preferably 50 to 500 nm. By keeping the average particle size within the above range, it is possible to achieve both hiding property, dispersion stability, and ejection stability. It is more preferably 100 to 400 nm.

The amount of the white pigment contained in the white ink is preferably 3 to 50% by mass, more preferably 5 to 30% by mass, based on the total amount of the white ink.

<Manufacturing method of printed matter>
The method for producing a printed matter using the ink set of the present invention includes a step of ejecting each ink of the ink set from an inkjet head and printing on a recording medium, and further includes a step of drying each printed ink. It is preferable to include it. In the present invention, different inkjet heads may be prepared for each ink constituting the ink set for printing, or printing may be performed using an inkjet head capable of ejecting two or more types of ink. Further, it is also possible to use one inkjet head and perform printing while changing the inks constituting the ink set each time.

As a pass method when ejecting an ink set from an inkjet head, a single pass method in which inkjet ink is ejected to a recording medium only once for printing, and a short shuttle in a direction perpendicular to the transport direction of the recording medium. Either the serial method of ejecting and printing while reciprocating the head may be adopted. However, in the case of the serial method, it is necessary to adjust the ejection timing in consideration of the movement of the inkjet head, and the landing position is likely to shift. Therefore, when printing the water-based inkjet ink of the present invention, a single-pass method, particularly a method in which a recording medium is passed under a fixed inkjet head, is preferably used.

There is no particular limitation on the method of ejecting each ink that constitutes the ink set, and known methods such as the drop-on-demand method (pressure pulse method) that uses the vibration pressure of the piezo element, and the method of heating the ink to form bubbles. However, a thermal inkjet (bubble jet (registered trademark)) method that utilizes the generated pressure can be used.

In addition, the amount of droplets of each ink ejected from the inkjet head is 0.2 to 30 picolitres, respectively, from the viewpoint of greatly reducing the drying load and improving color reproducibility and other image quality. It is preferably 1 to 20 picolitres, and more preferably 1 to 20 picolitres.

When drying each ink printed on the recording medium, it is preferable to use a mechanism for drying the ink on the recording medium. Examples of the drying method used in the drying mechanism include a heat drying method, a hot air drying method, an infrared ray (for example, an infrared ray having a wavelength of 700 to 2500 nm), a microwave drying method, and a drum drying method.

In the present invention, from the viewpoint of preventing the liquid component from boiling in the ink and obtaining a printed matter having excellent color reproducibility and image quality, when the heat drying method is adopted, the drying temperature is set to 35 to 100 ° C. When the hot air drying method is adopted, it is preferable that the hot air temperature is 50 to 250 ° C. From the same viewpoint, when the infrared drying method is adopted, it is preferable that 50% or more of the integrated value of the total output of infrared rays used for infrared irradiation is present in the wavelength region of 700 to 1500 nm.

Further, the above-mentioned drying method may be used alone, in combination of two or more, or in combination at the same time. For example, by using the heat drying method and the hot air drying method in combination, the ink can be dried more quickly than when each of them is used alone.

It is preferable to have a step of semi-drying the ink on the recording medium after printing each ink constituting the ink set on the recording medium and before printing the next ink.

As used herein, the term "semi-drying" means partial drying, and refers to a state in which the ink on the recording medium is partially dried but not completely dried. Specifically, the total amount of volatile components (water and water-soluble organic solvent) present in the ink after semi-drying is 10 to 80% by mass with respect to the total amount of volatile components present in the ink before semi-drying. Refers to the state of.

<Recording medium>
The recording medium for printing the ink set of the present invention is not particularly limited, and any known material such as a permeable base material, a poorly permeable base material, and a non-permeable base material can be used arbitrarily. As described above, the ink set of the present invention can obtain a printed matter having excellent image quality, color development and color reproducibility.

In the present specification, the permeability of the recording medium shall be judged by the amount of water absorption measured by the dynamic scanning liquid absorption meter. ^{Specifically, a recording medium having a water absorption of pure water of less than 1 g / m 2} at a contact time of 100 msec, which is measured by the following method, is referred to as a “non-permeable base material”, which is 1 g / m ² or more and 10 g / m ^2. A recording medium having a value of less than or less than 10 g / m ² is referred to as a “persistent base material”, and a recording medium having a value of 10 g / m 2 or more is referred to as a “permeable base material”.

The amount of water absorbed by the recording medium can be measured under the following conditions. A KM500win manufactured by Kumagai Riki Kogyo Co., Ltd. is used as a dynamic scanning liquid absorption meter, and pure water is used under the conditions shown below using a recording medium having a size of about 15 to 20 cm square under the conditions of 23 ° C. and 50% RH. The amount of metastasis is measured.
-Measurement method: Spiral Method
・ Measurement start radius: 20 mm
・ Measurement end radius: 60 mm
・ Contact time: 10 to 1,000 msec
・ Number of sampling points: 19 (measured so that they are approximately equal to the square root of the contact time)
・ Scanning interval: 7 mm
・ Speed switching angle of rotary table: 86.3 degrees ・ Headbox conditions: width 5 mm, slit width 1 mm

Examples of the permeable base material include non-coated paper such as stencil paper, medium-quality paper, wood-free paper and recycled paper, cotton, synthetic fiber woven fabric, silk, linen, non-woven fabric and leather, and leather. Of these, uncoated paper such as stencil paper, medium-quality paper, wood-free paper, and recycled paper is preferable from the viewpoint of obtaining printed matter having excellent color development and image quality.

Also, examples of non-permeable or impervious substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, polyvinyl alcohol, coated paper, art paper, etc. Examples thereof include coated paper base materials such as cast paper, metal base materials such as aluminum, iron, stainless steel, and titanium, and glass base materials.

The recording medium listed above may have a smooth surface, an uneven surface, or may be transparent, translucent, or opaque. Further, two or more kinds of these recording media may be bonded to each other. Further, a peeling adhesive layer or the like may be provided on the opposite side of the printed surface, or an adhesive layer or the like may be provided on the printed surface after printing. Further, the shape of the recording medium used in the method for producing an inkjet printed matter of the present invention may be a roll shape or a sheet-fed shape.

In addition, since the wettability of the ink is improved, the image quality, the color reproducibility and the dryness are improved, and the scratch resistance and the adhesion can be improved by making the surface of the printed matter uniform, the recording media listed above can be improved. On the other hand, it is also preferable to perform surface modification such as corona treatment and plasma treatment.

<Coating treatment>
The printed matter printed using the ink set of the present invention may be coated on the printed surface, if necessary. Specific examples of the coating treatment include coating / printing of the coating composition, laminating processing by a dry laminating method, a solvent-free laminating method, an extrusion laminating method, or the like, and any of them may be selected. Both may be combined.

When the printed matter is coated by coating / printing the coating composition, the coating / printing method includes a method of printing in a non-contact manner with a recording medium such as inkjet printing and a recording medium. On the other hand, either method of printing by abutting the coating composition on the surface may be adopted. Further, when a method of printing the coating composition in a non-contact manner with respect to a recording medium is selected, the coating composition contains substantially a colorant component excluding the pigment from the aqueous inkjet ink of the present invention. It is preferable to use no ink (clear ink).

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the following description, "part", "%" and "ratio" are based on mass unless otherwise specified.

<Production example of naphthol-based mixed crystal pigment 1>
As a base component, 23.4 parts of 3-amino-4-methoxybenzanilide was added to 364.4 parts of water, and the suspension was prepared by stirring well, and then ice was added to adjust the liquid temperature to 5 ° C. did. Then, 39.7 parts of 35% hydrochloric acid was added to the suspension, and the mixture was stirred for 1 hour. Then, an aqueous solution prepared by dissolving 7.1 parts of sodium nitrite in 22 parts of water was added, and the mixture was stirred for 1 hour to diazotize. Next, 1 part of sulfamic acid was added to the reaction mixture to eliminate nitrite, and then an aqueous solution consisting of 20.7 parts of sodium acetate, 1.8 parts of acetic acid and 165 parts of water was added to obtain a diazonium aqueous solution.
On the other hand, 18.0 parts of 3-hydroxy-2-naphthamide and 2.0 parts of N- (5-chloro-2-methoxyphenyl) -3-hydroxy-2-naphthamide were added as coupler components in a 25% aqueous sodium hydroxide solution. An aqueous coupler solution was prepared by adding to 31.8 parts and 414 parts of water and stirring well to completely dissolve the mixture.
Then, the coupler aqueous solution is added to the diazonium aqueous solution prepared above and stirred for 1 hour to complete the reaction, and then the mixture slurry is heat-treated to 70 ° C., further filtered and washed with water to obtain a naphthol-based mixed crystal pigment. A press cake of a pigment composition was obtained. Further, this press cake was dried under the conditions of 90 ° C. for 18 hours and then pulverized to obtain a naphthol-based mixed crystal pigment 1.

<Production example of naphthol-based mixed crystal pigments 2 to 13>
The naphthol-based mixed crystal pigments 2 to 13 were produced in the same manner as the above-mentioned naphthol-based mixed crystal pigment 1 except that the base component and the coupler component were changed as shown in Table 1.

The abbreviations of the compounds used in Table 1 are as follows. In Table 1, C.I. I. The blending amount of Pigment Red 150 is also described (however, excluding naphthol-based mixed crystal pigments 12 to 13 which do not contain CI Pigment Red 150 as a component).
・ TM-40: 3-amino-4methoxybenzanilide ・ TM-20: 3-amino-4methoxybenzamide ・ 2M-5NA: 2-methoxy-5-nitroaniline ・ Bonamide: 3-hydroxy-2-naphthamide ・ Naphthol AS: 3-Hydroxy-N-phenyl-2-naphthamide ・ Naphthol AS-BS: 3-Hydroxy-3'-nitro-2-naphthoanilide ・ Naphthol AS-LC: N- (4-chloro-2,5-dimethoxyphenyl) ) -3-Hydroxy-2-naphthamide-Naphthol AS-CA: N- (5-chloro-2-methoxyphenyl) -3-hydroxy-2-naphthamide-Naphthol AS-KB: 5'-chloro-3-hydroxy -2'-Methyl-2-naphthanilides

Further, the structures of the naphthol-based mixed crystal pigments 1 to 13 and C.I. I. Pigment No. The correspondence with is shown in Table 2.

It was confirmed that all of the naphthol-based mixed crystal pigments 1 to 13 were mixed crystals by X-ray diffraction analysis using an X-ray diffractometer (X'Pert PRO MRD) manufactured by PANalytical Co., Ltd.

<Production example of pigment dispersion resin>
93.4 parts of butanol was charged in a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser and a stirrer, and replaced with nitrogen gas. The inside of the reaction vessel is heated to 110 ° C., and a mixture of 30 parts of acrylic acid, 35 parts of styrene, 35 parts of lauryl methacrylate as a polymerizable monomer, and 6 parts of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator is added. The mixture was added dropwise over 2 hours to carry out a polymerization reaction. After completion of the dropping, the reaction was carried out at 110 ° C. for 3 hours, 0.6 part of V-601 was added, and the reaction was further continued at 110 ° C. for 1 hour. Then, after cooling the reaction system to room temperature, 39 parts of dimethylaminoethanol was added to neutralize, and then 100 parts of water was added. Then, the mixed solution is heated to 100 ° C. or higher to distill off butanol, and then water is used to adjust the solid content to 30% to obtain an aqueous solution of the pigment dispersion resin (solid content 30%). rice field. The weight average molecular weight of the pigment-dispersed resin measured by the method described above was 16,000, and the acid value was 230.

<Production example of magenta pigment dispersion liquid 1>
20 parts of naphthol-based mixed crystal pigment 1, 20 parts of an aqueous solution of a pigment dispersion resin (solid content 30%), and 60 parts of water are sequentially put into a mixing container equipped with a stirrer, and then premixed. Was done. Then, the magenta pigment dispersion 1 (pigment concentration 20%) was obtained by performing the main dispersion using a dynomill having a volume of 0.6 L filled with 1800 g of zirconia beads having a diameter of 0.5 mm.
The above-mentioned "aqueous solution" means a solution containing an aqueous solvent and a component dispersed and / or dissolved in the aqueous solvent.

<Production example of magenta pigment dispersion liquids 2 to 18>
Magenta pigment dispersions 2 to 13 (both have a pigment concentration of 20%) were produced in the same manner as the magenta pigment dispersion 1 except that the naphthol-based mixed crystal pigments 2 to 13 were used as the pigment. Further, magenta pigment dispersions 14 to 18 (all having a pigment concentration of 20%) were obtained in the same manner as in the magenta pigment dispersion 1 except that the pigments shown below were used.
-Magenta pigment dispersion 14: Toshiki Red 150TR (CI Pigment Red 150 manufactured by Tokyo Color Materials Co., Ltd.)
-Magenta Pigment Dispersion Liquid 15: Toshiki Red 269N (CI Pigment Red 269 manufactured by Tokyo Color Materials Co., Ltd.)
-Magenta pigment dispersion 16: Toshiki Red 31N (CI Pigment Tread 31 manufactured by Tokyo Color Materials Co., Ltd.)
Magenta Pigment Dispersion 17: FASTGEN SUPER MAGENTA RG (CI Pigment Red 122 manufactured by DIC Corporation)
-Magenta pigment dispersion 18: FASTGEN SUPER MAGENTA RY (quinacridone solid solution manufactured by DIC Corporation)

<Production example of azo mixed crystal pigment>
According to the method described in Example 6 of JP-A-2007-527458, C.I. I. Pigment Yellow 74 and C.I. I. A mixed crystal pigment containing Pigment Yellow 73 (hereinafter referred to as "azo mixed crystal pigment") was produced.

<Production example of isoindoline mixed crystal pigment>
According to the method described in Example 4 of JP-A-02-113074, C.I. I. Pigment Yellow 185 (isoindoline pigment) and C.I. I. A mixed crystal pigment containing Pigment Yellow 110 (hereinafter referred to as "isoindoline mixed crystal pigment") was produced.

<Production examples of yellow pigment dispersion liquids 1 to 10>
Yellow pigment dispersions 1 to 10 (both have a pigment concentration of 20%) were produced in the same manner as the magenta pigment dispersion 1 except that the yellow pigments shown below were used.
-Yellow pigment dispersion 1: SYMULER FAST YELLOW GFCONC (C.I. Pigment Yellow 12 manufactured by DIC Corporation)
-Yellow pigment dispersion liquid 2: SYMULER FAST YELLOW 4090G (manufactured by DIC Corporation, CI Pigment Yellow 14)
-Yellow pigment dispersion liquid 3: HANSA YELLOW 5GX01 (manufactured by Clariant, CI Pigment Yellow 74)
-Yellow Pigment Dispersion Solution 4: Irgazin Yellow L 1030 (CI Pigment Yellow 109, manufactured by BASF)
-Yellow Pigment Dispersion Solution 5: Irgazin Yellow D 1999 (BASF, CI Pigment Yellow 110)
-Yellow Pigment Dispersion Solution 6: Pariotrol Yellow D 0960 (manufactured by BASF, CI Pigment Yellow 138)
-Yellow pigment dispersion 7: Pariotrol Yellow D 1819 (manufactured by BASF, CI Pigment Yellow 139)
-Yellow Pigment Dispersion Liquid 8: Pariotor Yellow D 1155 (manufactured by BASF, CI Pigment Yellow 185)
-Yellow pigment dispersion 9: Isoindoline mixed crystal pigment produced above-Yellow pigment dispersion 10: Azo mixed crystal pigment produced above

<Production example of binder resin 1 (styrene (meth) acrylic water-soluble resin)>
93.4 parts of butanol was charged in a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser and a stirrer, and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and 5 parts of methacrylic acid, 30 parts of styrene, 30 parts of methyl methacrylate, 30 parts of butyl acrylate, 5 parts of stearyl methacrylate as a polymerizable monomer, and V-601 (as a polymerization initiator). A mixture of 6 parts (manufactured by Wako Junyaku) was added dropwise over 2 hours to carry out a polymerization reaction. After completion of the dropping, the reaction was carried out at 110 ° C. for 3 hours, 0.6 part of V-601 was added, and the reaction was further continued at 110 ° C. for 1 hour. Then, after cooling the reaction system to room temperature, 5.5 parts of dimethylaminoethanol was added to neutralize, and then 100 parts of water was added. Then, the mixed solution is heated to 100 ° C. or higher to distill off butanol, and then the solid content is adjusted to 30% with water to obtain a binder resin which is a styrene (meth) acrylic water-soluble resin. An aqueous solution of 1 (solid content 30%) was obtained. The weight average molecular weight of the binder resin 1 measured by the method described above was 16,500, the acid value was 30, and the glass transition temperature was 34 ° C.

<Production example of binder resin 2 ((meth) acrylic resin fine particles)>
In a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, 20 parts of toluene, 7.5 parts of methacrylic acid and 7.5 parts of methyl methacrylate as a polymerizable monomer, and 2,2'-as a polymerization initiator. 0.9 part of azobisisobutyronitrile and 3.6 parts of 2- (dodecylthiocarbonothio oilthio) -isobutyric acid were charged and replaced with nitrogen gas. The inside of the reaction vessel was heated to 75 ° C. and a polymerization reaction was carried out for 3 hours to obtain a copolymer (A block) composed of methacrylic acid and methyl methacrylate.

After completion of the above polymerization reaction, after cooling the reaction system to room temperature, 60 parts of toluene and 60 parts of methyl methacrylate and 25 parts of lauryl methacrylate as polymerizable monomers were added to the reaction vessel and replaced with nitrogen gas. did. Then, by heating the inside of the reaction vessel to 75 ° C. and carrying out a polymerization reaction for 3 hours, an AB block polymer in which a copolymer (B block) composed of methyl methacrylate and lauryl methacrylate is added to the A block. (Binder resin 2) was obtained.
Then, the reaction system was cooled to room temperature, 9.3 parts of dimethylaminoethanol was added to the reaction vessel for neutralization, and then 200 parts of water was added. Next, the mixed solution is heated to distill off toluene, and then water is used to adjust the solid content to 30%, whereby the aqueous dispersion of the binder resin 2 which is the (meth) acrylic resin fine particles ( Solid content 30%) was obtained. The weight average molecular weight of the binder resin 2 measured by the method described above was 19,500, the acid value was 46, and the glass transition temperature was 42 ° C.

<Production example of binder resin 3 (olefin resin fine particles)>
Except for using high wax 4052E manufactured by Mitsui Chemicals Co., Ltd. as the polyethylene oxide wax, the same method as described in paragraph No. 0103 of JP-A-2019-14237 is used with the oxide polyolefin resin fine particles having an acid value of 20 mgKOH / g. An aqueous dispersion of the binder resin 3 (solid content 26%) was produced.

<Manufacturing examples of water-based inkjet magenta inks 1 to 54 and water-based inkjet yellow inks 1 to 25>
The materials described below were sequentially added to the mixing vessel while stirring with a stirrer, and stirred until sufficiently uniform. Then, filtration was performed with a membrane filter having a pore size of 1 μm to obtain an aqueous inkjet magenta ink 1.
・ Magenta pigment dispersion 1 (pigment concentration 20%) 20 parts ・ Aqueous solution of binder resin 1 (solid content 30%) 16.7 parts ・ 1,2-butanediol 15 parts ・ Surfinol 420 1 part ・ Triethanolamine 1 Part ・ Proxel GXL 0.05 part ・ Ion-exchanged water 46.25 part

Further, the water-based inkjet magenta inks 2 to 54 were produced by the same method as the water-based inkjet magenta ink 1 except that the materials shown in Table 3 below were used. Further, water-based inkjet yellow inks 1 to 25 were obtained by the same method as the water-based inkjet magenta ink 1 except that the materials shown in Table 4 below were used.

Tables 3 to 4 also describe the surface tension of the water-based inkjet ink measured using CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. The materials listed in Tables 3 to 4 are as follows. Further, in Tables 3 to 4, the units of the items other than the "amount of organic solvent having a boiling point of 240 ° C. or higher" and the "boiling point weighted average value of the organic solvent" are all parts by mass.
(Water-soluble organic solvent)
1,2-BD: 1,2-butanediol (boiling point: 191 ° C)
1,3-BD: 1,3-butanediol (boiling point: 214 ° C)
1,2PenD: 1,3-pentanediol (boiling point: 206 ° C)
1,2HexD: 1,2-hexanediol (boiling point: 224 ° C)
1,2-PD: 1,2-propanediol (boiling point: 188 ° C)
-DEG: Diethylene glycol (boiling point: 244 ° C)
-GY: Glycerin (boiling point: 290 ° C)
(Surfactant)
・ S. 420: Surfinol 420 (acetylene diol-based surfactant manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 4.0)
・ S. 465: Surfinol 465 (acetylene diol-based surfactant manufactured by Nissin Chemical Industry Co., Ltd., HLB value: 13.2)
TW280: TEGO Wet 280 (siloxane-based surfactant manufactured by Evonik, HLB value: 3.5)
(PH regulator)
-Triethanolamine (pKa value: 7.8, boiling point: 335 ° C)
-Diethanolamine (pKa value: 8.9, boiling point: 269 ° C)
-Im: Imidazole (pKa value = 7.0, boiling point: 257 ° C.)
-DiPA: Diisopropanolamine (pKa value = 9.0, boiling point: 250 ° C.)
1Am2Pr: 1-amino-2-propanol (pKa value = 9.4, boiling point: 159 ° C)
DMAE: dimethylaminoethanol (pKa value: 9.9, boiling point: 133 ° C.)
CHA: Cyclohexylamine (pKa value: 10.6, boiling point: 134 ° C)
(others)
-Proxel GXL: 1,2-benzoisothiazole-3-one solution (preservative) manufactured by Arch Chemicals Co., Ltd.

[Evaluation of magenta ink]
The water-based inkjet magenta inks 1 to 54 produced above were evaluated 1 to 2 as shown below. The evaluation results are as shown in Table 5. Table 5 also describes the evaluation of the ink set described later and the sample number of the yellow ink combined with the magenta ink at that time, but the evaluations 1 and 2 are the magenta inks constituting the ink set. Evaluation was performed using only ink.

<Evaluation 1: Evaluation of dispersion stability>
The average secondary particle diameter (D50) of the pigments in the water-based inkjet magenta inks 1 to 54 produced above was measured at 25 ° C. using Nanotrack UPA-EX150 manufactured by Microtrac Bell. This ink was stored in a thermostat at 70 ° C., accelerated over time for a predetermined period, and then D50 was measured again at 25 ° C. to confirm changes before and after time to evaluate the dispersion stability. The evaluation criteria are as follows, and the evaluation criteria values 2 to 3 are set as the practical range.
3: The rate of change in D50 after storage for 2 weeks was less than ± 5%. The rate of change in D50 after storage for 1: 1 week was less than ± 5%, but the rate of change in viscosity after storage for 2 weeks was ± 5%. The rate of change in D50 after storage for 1: 1 week was ± 5% or more.

<Evaluation 2: Evaluation of discharge stability>
An inkjet head KJ4B-QA (manufactured by Kyocera Corporation, design resolution 600 dpi) was installed on a conveyor capable of transporting a recording medium, and the water-based inkjet magenta inks 1 to 54 produced above were filled therein. After printing the nozzle check pattern and confirming that there was no nozzle omission, the product was allowed to stand by for a predetermined time in an environment of 25 ° C. After that, the nozzle check pattern was printed again and the number of missing nozzles was counted to evaluate the ejection stability. The evaluation criteria are as follows, and the evaluation criteria values 2 to 4 are set as the practical range.
4: Nozzle omission even after waiting for 3 hours 3: Nozzle omission even after waiting for 2 hours, but nozzle omission after waiting for 3 hours Nozzle omission occurred at all even after waiting for 2: 1 hour, but after waiting for 2 hours, one or more nozzles were missing. Waiting for 1: 1 hour. Later, one or more nozzles were missing.

[Evaluation of ink set]
Subsequently, the magenta inks 1 to 54 and the yellow inks 1 to 25 produced above were used as ink sets in the combinations shown in Tables 5 to 6, respectively, and the evaluations 3 to 7 shown below were carried out.

<Evaluation 3: Evaluation of red image quality>
The inkjet printing apparatus used in Evaluation 2 was filled with the magenta ink and yellow ink manufactured above in the combinations shown in Tables 5 to 6, respectively, and then with a drop volume of 12 pL, Oji Paper Co., Ltd. OK top coat + (coating). On paper, a basis weight of 104.7 g / m ² ), a gradation patch image in which the printing rate was changed every 10% with a total printing rate of 20 to 200% was printed. The printing rate of magenta ink and the printing rate of yellow ink in each patch were the same. For example, a patch having a total printing rate of 80% is an image in which the printing rate of magenta ink is 40% and the printing rate of yellow ink is 40%. The gradation patch image was put into a 70 ° C. air oven within 10 seconds after printing and dried for 1 minute to obtain a printed matter for image quality evaluation. Then, the image quality of the coated paper was evaluated by visually observing the presence or absence of shading unevenness of the obtained printed matter for image quality evaluation. The evaluation criteria were as follows, and the evaluation criteria values 2 to 3 were set as the practical area. 3: No unevenness in shading was observed at any printing rate. 2: Uneven shading was observed in patches with a total printing rate of 120% or less. However, some patches with a total print rate of 130% or more showed uneven shading. 1: Even patches with a total printing rate of 120% showed uneven shading.

<Evaluation 4: Evaluation of red color gamut>
The inkjet printing apparatus used in Evaluation 2 was filled with the magenta ink and yellow ink produced above in the combinations shown in Tables 5 to 6, respectively, and then with a drop volume of 12 pL, Oji Paper Co., Ltd. OK Top Coat + (coating). A solid image (an image printed so as to have a magenta printing rate of 100% and a yellow printing rate of 100%) was printed on paper with a basis weight of 104.7 g / m ^2). The solid image was obtained as a printed matter for hue / color gamut evaluation by putting the printed matter in an air oven at 70 ° C. and drying it for 1 minute within 10 seconds after printing. Then, the red color gamut was evaluated by measuring the saturation C of the obtained printed matter for hue / color gamut evaluation. Using eXact manufactured by X-Rite, the light source is D50, the viewing angle is 2 °, the density status is ISO Status T, and the density white standard is the absolute value, and the a * value and b * value are measured, and the following formula (8) ) To calculate the saturation C.

Equation (8):
C = √ (a * ² + b * ² )

The evaluation criteria in the red color gamut evaluation are as follows, and the evaluation reference values 2 to 4 are set as the practical range.
4: Saturation C is 100 or more and 3: Saturation C is 98 or more and less than 100 2: Saturation C is 96 or more and less than 98 1: Saturation C is less than 96

<Evaluation 5: Evaluation of red density (coated paper)>
The density on the coated paper was evaluated by measuring the optical density (OD value) of the printed matter for hue / color gamut evaluation produced in Evaluation 4. An eXact manufactured by X-RITE was used, the light source was D50, the viewing angle was 2 °, the density status was ISO Status T, and the density white standard was an absolute value. The evaluation criteria are as follows, and the evaluation criteria values 2 to 3 are set as the practical range. 3: OD value 1.65 or more 2: OD value 1.45 or more and less than 1.65 1: OD value less than 1.45

<Evaluation 6: Evaluation of red density (high quality paper)>
The inkjet printing apparatus used in Evaluation 2 was filled with the magenta ink and yellow ink produced above in the combinations shown in Tables 5 to 6, respectively, and then the drop volume was 12 pL, and the OK Prince (high quality paper) manufactured by Oji Paper Co., Ltd. was used. A solid image (an image printed so as to have a magenta printing rate of 100% and a yellow printing rate of 100%) was printed on top. For a solid image printed on woodfree paper, the printed matter is placed in an air oven at 70 ° C. within 10 seconds after printing, dried for 1 minute, and then taken out from the air oven. By measuring the value), the concentration on the woodfree paper was evaluated. The evaluation criteria are as follows, and the evaluation criteria values 2 to 3 are set as the practical range. 3: OD value 1.00 or more 2: OD value 0.90 or more and less than 1.00 1: OD value less than 0.90

<Evaluation 7: Evaluation of fading of printed matter>
The L * value, a * value and b * value of the hue / color gamut evaluation printed matter produced in evaluation 4 were measured with the same equipment and conditions as in evaluation 4. Next, the solid image is allowed to stand indoors and under a fluorescent lamp for 24 hours, then L *, a * and b * are measured in the same manner, and the color difference ΔE is calculated by the following formula (9) to obtain a printed matter. The fading was evaluated.

Equation (9):
ΔE = √ (ΔL * ² + Δa * ² + Δb * ² )

In the above equation (9), ΔL *, Δa *, and Δb * are the differences between the L * value, the a * value, and the b * value before and after being left for 24 hours, respectively.

The evaluation criteria for evaluating the fading of printed matter are as follows, and the evaluation reference values 2 to 3 are set as the practical range.
3: ΔE is less than 2 2: ΔE is 2 or more and less than 3 1: ΔE is 3 or more

[Examples 1 to 61, Comparative Examples 1 to 19]
The results of the above evaluation are as shown in Tables 5-6.

Claims (7)

A water-based inkjet ink set containing water-based inkjet magenta ink and water-based inkjet yellow ink.
The water-based inkjet magenta ink contains a magenta pigment (A), a basic organic compound, a water-soluble organic solvent (SM), and water.
The magenta pigment (A) contains a mixed crystal pigment (A-1) containing two or more kinds of pigments having a structure represented by the following general formula (1).
The content of the mixed crystal pigment (A-1) is 1 to 10% by mass in the total amount of the water-based inkjet magenta ink.
The basic organic compound contains 0.1 to 1.25% by mass of the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in the total amount of the aqueous inkjet magenta ink.
The water-soluble organic solvent (SM) contains 1 to 30% by mass of an alkanediol having 4 to 6 carbon atoms in the total amount of the water-based inkjet magenta ink.
The content of the organic solvent having a boiling point of 240 ° C. or higher under 1 atm is 8% by mass or less in the total amount of the aqueous inkjet magenta ink.
The water-based inkjet yellow ink contains a pigment, a water-soluble organic solvent (SY), and water.
The water-soluble organic solvent (SY) contains 1 to 30% by mass of an alkanediol having 4 to 6 carbon atoms in the total amount of the water-based inkjet yellow ink.
A water-based inkjet ink set in which the content of an organic solvent having a boiling point of 240 ° C. or higher at 1 atm is 8% by mass or less based on the total amount of the water-based inkjet yellow ink.

General formula (1):

(In the general formula (1), R ¹ , R ² and R ³ are independently hydrogen atoms, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an anilide group and a carbamoyl group, respectively. , A methoxycarbonyl group, an ethoxycarbonyl group, an amino group, a nitro group, a sulfonamide group, a methylaminosulfonyl group, or an ethylaminosulfonyl group. In addition, R ⁴ is a hydrogen atom having 1 to 2 carbon atoms. It is either an alkyl group or a group having a structure represented by the following general formula (2).)

General formula (2):

(In the general formula (2), R ⁵ is any one of a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an amino group, or a nitro group. In addition, each of R ⁶ and R ⁷ is independently a hydrogen atom, a chlorine atom, a bromine atom, an alkyl group having 1 to 2 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, an amino group, or a nitro group. Or, R ⁶ and R ⁷ are bonded to each other to form an imidazolidinone ring. The * part is a bond.) The water-based inkjet according to claim 1, wherein the difference between the static surface tension of the water-based inkjet magenta ink at 25 ° C. and the static surface tension of the water-based inkjet yellow ink at 25 ° C. is 3 mN / m or less. Ink set. The pigment having the structure represented by the general formula (1) is C.I. I. The water-based inkjet ink set according to claim 1 or 2, which comprises at least one selected from the group consisting of Pigment Red 31, 32, 146, 147, 150, 176, and 269. The pigment having the structure represented by the general formula (1) is C.I. I. The water-based inkjet ink set according to any one of claims 1 to 3, which comprises Pigment Red 150. Claimed that the water-based inkjet yellow ink contains 0.1 to 1.25% by mass of the basic organic compound (B) having a pKa value of 9.5 or less at 25 ° C. in the total amount of the water-based inkjet yellow ink. The water-based inkjet ink set according to any one of 1 to 4. The water-based inkjet ink set according to any one of claims 1 to 5, wherein the water-based inkjet magenta ink and / or the water-based inkjet yellow ink contains amino alcohols. A method for producing a printed matter, which comprises a step of ejecting the water-based inkjet ink set according to any one of claims 1 to 6 from an inkjet head and printing it on a recording medium.