JP2019183063A - Water-based inkjet ink and manufacturing method of printed matter - Google Patents

Abstract

An object of the present invention is to provide a water-based ink-jet ink which can prevent ejection failure, obtain high-quality printed matter having high drying properties, abrasion resistance, and substrate adhesion, and have excellent storage stability. An object of the present invention is to provide an aqueous inkjet ink set. Another object of the present invention is to provide a method for producing a printed matter, which can provide a printed matter excellent in fineness. An aqueous inkjet ink containing a pigment (A), a polymer compound (B), a water-soluble organic solvent (C), and a surfactant (D), wherein the water-soluble organic solvent (C) is ethylene It contains glycol and / or 1,3-propanediol (c1) and a water-soluble organic solvent (c2) having a specific static surface tension, and has a glass transition temperature and a boiling point of 240 ° C. of the polymer compound (B). An aqueous ink jet ink in which the amount of the water-soluble organic solvent, the weighted average of the boiling points of the water-soluble organic solvent (C), and the conditions relating to the amounts of the respective components are specified. [Selection diagram] None

Description

  Embodiments of the present invention relate to a method for producing a water-based inkjet ink and printed matter.

  Unlike conventional plate-type printing such as offset printing, digital printing does not require a plate, so that cost reduction and space saving can be realized. Further, among digital printing, the ink jet printing method is to obtain characters or images by ejecting and adhering ink droplets from a very fine nozzle onto a substrate. This method is widely used as an output device in offices or homes because it has the advantages of low noise in the printing press, excellent operability, and easy colorization.

  In addition, due to improvements in inkjet technology, it is expected to be used as an output device for digital printing in industrial applications. Actually, ink jet printers for plastic substrates such as polyvinyl chloride and polyethylene terephthalate (PET) are commercially available. Until now, solvent ink or UV ink has been used in inkjet printing for industrial use. However, in recent years, regulations on solvents and monomers, which are the main components of the ink, have been promoted in consideration of and consideration for environmental and human hazards. Demand is increasing.

  Conventionally, water-based inks for ink jet printing are intended for printing on plain paper and ink jet exclusive paper (see Patent Documents 1, 2, and 3). On the other hand, in recent years, as the application of the ink jet printing method is expected to be expanded as described above, it is represented by hardly absorbable paper base materials such as art paper, coated paper, fine coated paper, polypropylene, polyethylene, nylon and the like. There is an increasing need for direct printing on non-absorbing substrates (hereinafter, the above-mentioned substrates and the like are collectively referred to as “difficult / non-absorbing substrates”).

  Difficult / non-absorbable substrates are less permeable to water-based inks or do not penetrate at all compared to plain paper and inkjet paper. There is a problem that it is easy to get worse. Specifically, omission due to insufficient wetting and spreading of the water-based ink, and color boundary bleeding and aggregation unevenness due to coalescence of ink droplets having different hues are likely to occur. In particular, when printing on a non-absorbent substrate or when performing high-speed printing on a difficult / non-absorbent substrate, other water-based ink droplets are successively deposited before drying the water-based ink droplets. The above-mentioned problem becomes more remarkable because it is given. Therefore, even in the case of printing on a non-absorbent substrate and high-speed printing on a difficult / non-absorbent substrate, in order to solve the above-mentioned problems and obtain a printed material with excellent image quality, conventionally, as in Patent Document 4, A technique for improving the volatility of water-based ink by using a water-soluble organic solvent having a low boiling point has been used. In addition, in order to improve the lack of wet spreadability of the water-based ink, a water-soluble organic solvent having a low surface tension and / or a surfactant is often used (see Patent Documents 5 and 6).

  On the other hand, in recent years, studies aiming at higher resolution are being promoted in order to produce high-quality printed matter in connection with the expansion of application and technology improvement of inkjet printing. In order to increase the resolution, it is necessary to reduce the amount of ink droplets ejected from the nozzles, and the nozzle diameter (nozzle diameter) tends to decrease accordingly.

  When printing a water-based ink with improved volatility as in Patent Document 4 using an inkjet head having a small nozzle diameter, ejection failure becomes a major issue. Specifically, when waiting for a print job or when an inkjet head with nozzles mounted without capping is held or stored for a long period of time, the water-based ink dries and adheres at the nozzle interface, and the water-based ink is restarted when printing is resumed. May not discharge properly. In particular, when the water-based ink is completely fixed and the nozzle is clogged, it cannot be restored to the original state even if a head cleaning liquid or the like is used. These risks increase as the nozzle diameter of the inkjet head becomes smaller.

  In order to prevent ejection failure, for example, as in Patent Document 7, a method of adding a predetermined amount of a high boiling point solvent such as glycerin to water-based ink is common. However, when a high-boiling solvent is added to water-based ink, the time until the water-based ink dries becomes longer, so the above-mentioned problem is worsened when printing on a difficult / non-absorbable substrate, resulting in image quality. Prints inferior to.

  Further, as a method of suppressing ejection failure, a method of reducing solid content in ink that causes sticking is also conceivable. However, the solid content in the ink is specifically a pigment, a binder resin, a pigment dispersion resin, and the like, and by reducing the amount of these components, the image density of the printed matter is reduced, and the scratch resistance is deteriorated. There is a risk of lowering the adhesion of the base material, deteriorating storage stability, and the like. In particular, when a water-soluble organic solvent having a low surface tension and / or a surfactant is used in combination as in Patent Documents 5 and 6, these problems become more prominent. The reason for this is that these materials are relatively hydrophobic and may easily destroy the dispersion and / or dissolution state of the solids.

  As described above, conventionally, it is possible to prevent ejection failure when waiting for a long time or storing an ink jet head on which a nozzle is mounted without capping for a predetermined time, and in particular, a difficult / non-absorbent substrate. In printing on a paper, there was no water-based inkjet ink that was able to obtain a high-quality printed matter having high drying properties, scratch resistance and substrate adhesion, and excellent storage stability.

JP 2001-354888 A JP 2004-210996 A JP 2008-247951 A JP 2006-017126 A JP 2012-052041 A JP 2014-205768 A JP 2001-354889 A

  SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to perform ejection when waiting for a predetermined period of time or when standing by or storing an inkjet head on which a nozzle is mounted without capping. In addition to preventing defects, it is possible to obtain high-quality printed materials with high drying properties, scratch resistance and substrate adhesion, especially when printing on difficult and non-absorbable substrates, and also excellent storage stability. It is to provide an aqueous inkjet ink. Another object of the present invention is to provide a water-based inkjet ink set that can provide a printed matter having excellent sharpness and visibility in addition to the above. Another object of the present invention is to provide a method for producing a printed matter using the water-based inkjet ink, which can suitably solve the above-mentioned problems and can obtain a printed matter having excellent delicateness.

  As a result of extensive research by the inventors, a water-soluble organic solvent having a specific structure and a water-soluble organic solvent having a specific surface tension are used in combination, and the water-soluble organic solvent, pigment, and It has been found that the above-described problems can be solved by an aqueous inkjet ink that defines the blending amount of the molecular compound and an aqueous inkjet ink set that includes the aqueous inkjet ink. Furthermore, the present inventors have found that the above-mentioned problems can be suitably solved by a method for producing a printed material that defines an inkjet head on which the water-based inkjet ink is mounted, and have completed the present invention.

That is, the present invention is a water-based inkjet ink comprising a pigment (A), a polymer compound (B), a water-soluble organic solvent (C), and a surfactant (D),
The glass transition temperature of the polymer compound (B) is −100 to 40 ° C.,
The water-soluble organic solvent (C) comprises ethylene glycol and / or 1,3-propanediol (c1) and a water-soluble organic solvent (c2) having a static surface tension at 25 ° C. of 20 to 37 mN / m. And the content of the water-soluble organic solvent having a boiling point of 240 ° C. or higher at 1 atm is 5% by mass or less based on the total amount of the water-based inkjet ink,
The water-soluble organic solvent (C) has a weighted average value of boiling points at 1 atm of 130 ° C. or more and less than 180 ° C.,
The content of the pigment (A) is WA (mass%), the content of the polymer compound (B) is WB (mass%), the ethylene glycol and / or 1,3-propanediol with respect to the total amount of the water-based inkjet ink. When the content of (c1) is WC1 (mass%) and the content of the water-soluble organic solvent (c2) whose static surface tension at 25 ° C. is 20 to 37 mN / m is WC2 (mass%), The present invention relates to an aqueous inkjet ink in which WA, WB, WC1, and WC2 satisfy all of the following formulas (1) to (5).

3 ≤ WA ≤ 18 (1)
5 ≤ WB ≤ 25-WA (2)
10 ≦ WC1 + WC2 ≦ 40 (3)
0.25 ≦ WC1 / (WA + WB) ≦ 1.75 (4)
1.5 ≦ WC2 / WC1 ≦ 5 (5)

  The present invention also relates to the above water-based inkjet ink, wherein the water-soluble organic solvent (c2) having a static surface tension at 25 ° C. of 20 to 37 mN / m contains a 1,2-alkanediol having 3 to 6 carbon atoms. .

  The present invention also relates to the above aqueous inkjet ink, wherein the ethylene glycol and / or 1,3-propanediol (c1) contains ethylene glycol.

  Moreover, this invention relates to the said water-based inkjet ink whose content of the said surfactant (D) is 0.5-5.5 mass% in water-based inkjet ink whole quantity.

Further, the present invention is an aqueous inkjet ink set comprising two or more types of aqueous inkjet inks having different hues from each other,
Each of the two or more types of water-based inkjet inks is the above-mentioned water-based inkjet ink, and the water-based inkjet ink set in which at least one of the two or more types of water-based inkjet inks is a white ink.

The present invention also includes a step of discharging the aqueous inkjet ink or the aqueous inkjet ink set from an inkjet head to adhere to a printing substrate, and a step of drying the printing substrate to which the aqueous inkjet ink has adhered. A method for producing a water-based inkjet ink print comprising:
The present invention relates to a method for producing a water-based inkjet ink print, wherein the nozzle diameter of the inkjet head is 15 to 25 μm and the design resolution of the inkjet head is 600 dpi or more.

  Moreover, this invention relates to the printed matter formed by printing the said water-based inkjet ink or the said water-based inkjet ink set on a base material.

  According to the present invention, when waiting for a predetermined time or when an inkjet head equipped with a nozzle without capping is kept on standby or stored for a long time, ejection failure is prevented, and printing on particularly difficult and non-absorbent substrates is possible. In addition, it is possible to obtain a high-quality printed matter having high drying properties, scratch resistance and adhesion to a substrate, and further to provide an aqueous inkjet ink having excellent storage stability. Further, according to the present invention, in addition to the above, it is possible to provide an aqueous inkjet ink set from which a printed matter excellent in sharpness and visibility can be obtained. In addition, the present invention can provide a method for producing a printed matter using the water-based inkjet ink, which can suitably solve the above-described problems and obtain a printed matter with excellent delicateness.

  Below, the manufacturing method of water-based inkjet ink and printed matter which are embodiment (henceforth "this embodiment") of this invention is demonstrated in detail. In addition, this invention is not limited to the following embodiment, The modification implemented in the range which does not change the summary of this invention is also contained. Unless otherwise specified, “parts” and “%” represent “parts by mass” and “mass%”, respectively.

  As explained in the prior art, in order to obtain printed matter with excellent image quality, it is excellent in dryness and wettability even when printing on non-absorbent substrates and high-speed printing on difficult / non-absorbent substrates. Ink design is required. In addition, it is necessary to add a certain amount or more of pigments and polymer compounds in order to produce printed matter with excellent image density, scratch resistance and substrate adhesion, and to make water-based inks with excellent storage stability. There is. However, just increasing the amount of water or a low-boiling water-soluble organic solvent to improve the drying property as in the past causes drying and fixing of the water-based ink at the nozzle interface, resulting in ejection failure. Risk increases. In addition, when a water-soluble organic solvent having a low surface tension and / or a surfactant is used to improve the wetting and spreading property, the dispersion of the pigment and the polymer compound and / or the dissolution state of the polymer compound may be destroyed. The drying and fixing of the water-based ink at the interface occurs, and the possibility of ejection failure increases. Of course, the risk increases as the amount of pigment and polymer compound in the water-based ink increases. In addition, these water-based inks that are liable to cause ejection failures also exhibit poor storage stability due to dispersion and / or dissolution state breakdown.

  As a result of intensive studies by the present inventors to solve the above problems, a water-soluble organic solvent having a specific structure and a water-soluble organic solvent having a specific surface tension are used in combination, and the water-soluble organic solvent, It has been found that the above problems can be solved by defining the blending amount and / or blending ratio of the pigment and the polymer compound. Below, the outline | summary of embodiment of this invention is demonstrated.

<Water-based inkjet ink>
In the present embodiment, in particular, a static surface tension at 25 ° C. of 20 to 20 is obtained in order to obtain a printed matter with excellent image quality even when printing on a non-absorbent substrate or high-speed printing on a difficult / non-absorbent substrate. A water-soluble organic solvent (c2) of 37 mN / m (hereinafter also simply referred to as “low surface tension solvent (c2)”) and a surfactant (D) are used in combination. By using both in combination, the water-based ink droplets are suitably spread even on a difficult / non-absorbable substrate, and the surfactant (D) oriented on the droplet surface allows Unification is suppressed. As a result, it is possible to obtain a printed matter with excellent image quality that is free from omission, color boundary bleeding, and aggregation unevenness.

  In addition, when glycerin (boiling point: 290 ° C.), diethylene glycol (boiling point: 244 ° C.), polyethylene glycol (boiling point: about 250 ° C.) or the like, which is conventionally used as a moisturizing agent, is excessively used, the drying properties of the droplets on the substrate deteriorate. As a result, the image quality may deteriorate. Therefore, in the water-based ink of the present embodiment, the amount of the water-soluble organic solvent having a boiling point of 240 ° C. or higher at 1 atm, and the weighted average value of the boiling point of the water-soluble organic solvent (C) at 1 atm, In particular, deterioration of image quality during printing on a non-absorbent substrate or during high-speed printing on a difficult / non-absorbent substrate is prevented. Specifically, the content of the water-soluble organic solvent having a boiling point of 240 ° C. or higher under 1 atm is set to 5% by mass or less (5% by mass or less if not included) in the total amount of the ink. The weighted average value of the boiling points of the water-soluble organic solvent (C) at 1 atm is 130 ° C. or higher and lower than 180 ° C.

  On the other hand, using the low surface tension solvent (c2) and the surfactant (D), the amount of the water-soluble organic solvent having a boiling point of 240 ° C. or higher and the weighted average value of the boiling points of the water-soluble organic solvent (C) were limited. As described above, the water-based ink is liable to be dried and fixed at the nozzle interface. In particular, when the nozzle diameter is reduced, the phenomenon occurs remarkably. In addition, these water-based inks that are liable to dry and stick tend to have poor storage stability.

  Therefore, in the present embodiment, as the water-soluble organic solvent (C), in addition to the low surface tension solvent (c2), ethylene glycol and / or 1,3-propanediol (c1) (hereinafter referred to as “specific diol (c1)” Also called). These water-soluble organic solvents have boiling points at 1 atm of 197 ° C. and 214 ° C., respectively, and are less volatile than water, but have a very high hydrophilicity due to the close molecular structure to that of water. It has the property that the dispersion and / or dissolution state of the polymer compound is not easily destroyed. Therefore, the specific diol (c1) remains in the water-based ink after the water and the low-boiling water-soluble organic solvent are volatilized together with the low surface tension solvent (c2) and the surfactant (D). These solvent molecules are present so as to cover the pigment and the polymer compound, thereby suppressing the dispersion and / or dissolution state of the pigment and the polymer compound, and drying and fixing at the nozzle interface, and storage stability. It is thought that the deterioration of the can be prevented.

In order to suitably express the above effects, it is desired to define the solid content and the amounts of the respective solvents, and the ratio thereof. The inventors satisfy the following formulas (1) to (5) with respect to the blending amounts of the pigment (A), the polymer compound (B), the specific diol (c1), and the low surface tension solvent (c2). In addition to the image density, scratch resistance, drying property, and image quality of the printed matter, it was found that the water-based ink prepared in 1) can satisfy all of the ejection failure suppression and storage stability.
3 ≤ WA ≤ 18 (1)
5 ≤ WB ≤ 25-WA (2)
10 ≦ WC1 + WC2 ≦ 40 (3)
0.25 ≦ WC1 / (WA + WB) ≦ 1.75 (4)
1.5 ≦ WC2 / WC1 ≦ 5 (5)

  In the above formulas (1) to (5), WA is the content of the pigment (A), WB is the content of the polymer compound (B), WC1 is the content of the specific diol (c1), and WC2 is the low surface tension. It is content of a solvent (c2), and all are represented by the mass% with respect to the water-based ink whole quantity.

  By adjusting the amount of the pigment (A) so as to satisfy the above formula (1) and the amount of the polymer compound (B) so as to satisfy the above formula (2), the image density, scratch resistance, The substrate adhesion can be achieved with a suitable balance. In addition, by keeping the amount of solids in the above range, it is possible to prevent the occurrence of ejection failure due to drying and fixing of an excessive amount of solids, and the deterioration of the storage stability of ink due to the aggregation of an excessive amount of pigment. it can.

  In addition, by adjusting the total amount of the specific diol (c1) and the low surface tension solvent (c2) so as to satisfy the above (3), in particular, printing on a non-absorbent substrate and difficulty / non-absorbability It is possible to achieve both dryness of printed matter and image quality in high-speed printing on a substrate.

  Further, by adjusting the ratio of the solid content, the specific diol (c1), and the low surface tension solvent (c2) so as to satisfy the above formulas (4) and (5), the balance among the three can be achieved. It becomes suitable, and the effect of suppressing the dispersion and / or dissolution state breakdown by the ethylene glycol and / or 1,3-propanediol (c1) can be sufficiently exhibited. As a result, it is possible to suppress ejection failure and improve storage stability while maintaining the image density, scratch resistance, substrate adhesion, drying property, and image quality of the printed material. In addition, the specific diol (c1) has a high static surface tension, and water-based inks containing these excessively have poor wetting and spreading properties on difficult and non-absorbable substrates, resulting in insufficient ink filling in printed matter. Occurrence of bleeding, aggregation unevenness, etc. occurs in color boundaries due to omission, drying deterioration, and coalescence of ink droplets. Therefore, in this embodiment, in order to improve the wet spreading property of the water-based ink with respect to the printing substrate and suppress the occurrence of the above problems, ethylene glycol and / or 1,3-propanediol (c1) and a low surface tension solvent (c2) ) And the ratio are adjusted so as to satisfy the above formulas (3) and (5).

  In the present embodiment, in addition to the above, the glass transition temperature of the polymer compound is further defined as −100 to 40 ° C. By setting the glass transition temperature of the polymer compound (B) within the above range, a continuous film (printed material layer) can be formed on the substrate, and the elasticity of the film is optimized. Will improve. On the other hand, a polymer compound having a lower glass transition temperature has a higher film-forming property, and when the polymer compound waits for a long time in a non-printing state, or when the ink jet head is not capped and stored for a long time, the polymer compound. There is a possibility that the water-based ink containing the ink dries and adheres at the nozzle interface. Therefore, in the present embodiment, the specific diol (c1) is used in combination to prevent drying and sticking at the nozzle interface. Further, although the detailed reason is unknown, the polymer compound (B) having a glass transition temperature in the above range has high affinity with the low surface tension solvent (c2) and does not localize in the water-based ink. It is thought that it can exist uniformly. As a result, it is considered that microscopic drying and sticking at the nozzle interface can be suppressed, and further ejection failure suppression and storage stability improvement can be realized.

  As described above, it prevents discharge failure when waiting for a predetermined time or when an inkjet head equipped with a nozzle without capping is stored or stored for a long period of time. Therefore, it is possible to produce a high-quality printed matter that is free from aggregation unevenness and excellent in scratch resistance and substrate adhesion. Furthermore, in order to obtain an ink excellent in storage stability, a low surface tension solvent (c2) and a surfactant (D) are used in combination with ethylene glycol and / or 1,3-propanediol (c1), and Optimize the blending amount and ratio including pigments and polymer compounds. In addition, said mechanism is inference and does not limit this invention at all.

  Subsequently, each main component of the water-based ink of the present embodiment will be described below.

<Pigment (A)>
In the water-based ink of this embodiment, any of an inorganic pigment and an organic pigment can be used as the pigment (A). Examples of inorganic pigments include titanium oxide, zinc white, zinc sulfide, white lead, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, black iron oxide, cadmium red, red bean, molybdenum red , Molybdate orange, chrome vermilion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine, bituminous, cobalt blue, cerulean blue , Cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet.

  Examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, dye lake pigments, and fluorescent pigments.

  Specific examples of the color index include C.I. I. Pigment Blue 1, 2, 3, 15: 1, 15: 3, 15: 4, 15: 6, 16, 21, 22, 60, 64, and the like.

  As magenta pigments, C.I. I. Pigment Red 5, 7, 9, 12, 31, 48, 49, 52, 53, 57, 97, 112, 120, 122, 146, 147, 149, 150, 168, 170, 177, 178, 179, 184, 185, 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282; I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50 and the like.

  Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like.

Examples of the black pigment include carbon black (CI Pigment Black 7) produced by a furnace method or a channel method. For example, these carbon blacks have a primary particle diameter of 11 to 40 nm, a specific surface area by BET method of 50 to 400 m ² / g, a volatile content of 0.5 to 10% by mass, a pH value of 2 to 10 and the like. Those having characteristics are preferred. Specifically, as a commercial product having such characteristics, No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (above, manufactured by Mitsubishi Chemical); RAVEN1255 (made by Colombian Carbon); REGA330R, 400R, 660R, MOGUL L, ELFTEX415 (above, made by Cabot) Nexex90, Nipex150T, Nipex160IQ, Nipex170IQ, Nipex75, Printex85, Printex95, Printex90, Printex35, PrintexU (manufactured by Evonik Degussa) and the like, and any of them can be preferably used.

  In addition to carbon black, examples of the black pigment that can be used in the present embodiment include aniline black, lumogen black, and azomethine azo black. Further, a plurality of chromatic color pigments such as the above-mentioned cyan pigments, magenta pigments, yellow pigments, and the following brown pigments and orange pigments may be used to form black pigments.

  Examples of white pigments include titanium oxide (CI Pigment White 6) and zinc white (CI Pigment White 4), and titanium oxide is preferably used from the viewpoints of concealability and availability. In addition, as the titanium oxide, either anatase type or rutile type can be used, but it is preferable to use the rutile type in order to improve the concealability of the printed matter. Furthermore, although what was manufactured by any methods, such as a chlorine method and a sulfuric acid method, may be selected, Since the whiteness is high, the titanium oxide manufactured by the chlorine method is used preferably.

  The titanium oxide used in this embodiment is preferably one that has been surface-treated with an inorganic compound and / or an organic compound. Examples of inorganic compounds include compounds of silicon (Si), aluminum, zirconium, tin, antimony, titanium, and hydrated oxides thereof. Examples of organic compounds include polyhydric alcohols, alkanolamines or derivatives thereof, higher fatty acids or metal salts thereof, and organometallic compounds. Among these, a polyhydric alcohol or a derivative thereof is preferably used because it can highly hydrophobize the titanium oxide surface and improve the storage stability of the ink.

  In the present embodiment, it is also preferable to use hollow resin particles as the white pigment. The hollow resin particles have a specific gravity (apparent density) smaller than that of titanium oxide and the like, and can easily suppress sedimentation over time, so that an ink having excellent storage stability can be obtained. Further, in order to obtain a white ink having both storage stability and concealment properties, hollow resin particles and titanium oxide may be used in combination as the pigment (A).

  Examples of pigments other than cyan, magenta, yellow, black, and white include C.I. I. Pigment Green 7, 10, 36; C.I. I. Pigment Brown 3, 5, 25, 26; C.I. I. Pigment Orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71, and the like.

  In this embodiment, as above-mentioned, 3-18 mass% of pigments (A) are contained with respect to the ink whole quantity. More preferably, it is 3.5 mass% or more and 15 mass% or less, More preferably, it is 4 mass% or more and 12 mass% or less. By setting the content to 3% by mass or more, it is possible to produce a printed matter having an excellent image density even when using an absorptive base material such as high-quality paper and exclusive inkjet paper. Moreover, by setting it as 18 mass% or less, the balance with specific diol (c1) becomes favorable, and while ensuring the storage stability of ink, discharge failure can be suppressed suitably. Furthermore, it does not adversely affect the substrate adhesion of the printed matter.

  In addition to the printed matter with high pigment concentration, the content of the pigment (A) takes into account the specific gravity (apparent density) of the pigment (A) from the viewpoint of obtaining an ink having excellent storage stability and ejection stability. Is preferably determined. Specifically, when the apparent density of the pigment (A) is DA, WA / DA is preferably 1.5 to 6.0, more preferably 1.8 to 5.0, and more preferably 2 It is especially preferable that it is 0.0-4.5. The “apparent density” in the present specification is a density including the volume of voids inside the pigment, and in the case of a pigment without the voids, it is the same as the true density. The apparent density can be measured by, for example, a gas phase substitution method.

<Polymer compound (B)>
The inkjet ink of this embodiment contains a polymer compound (B). In the present specification, the “polymer compound” is a compound in which a unit structure (monomer) is connected via a covalent bond, and the weight average molecular weight measured by the method described later is 1,000 or more. Refers to things.

  In general, emulsions, water-soluble resins, and hydrosols, which are intermediate forms, are known as forms of polymer compounds used in inkjet inks. In the present specification, “emulsion” refers to a form in which an emulsifier is adsorbed on the surface of resin fine particles and dispersed in a dispersion medium. In addition, “hydrosol” is a form in which acidic and / or basic functional groups present in a resin are present in a dispersion medium in a neutralized state, while having particle properties, At least a portion is swollen and dissolved. In the present embodiment, any of the above may be used as the polymer compound (B).

  Among these, the emulsion contains a high molecular weight resin, can reduce the viscosity of the ink, and can contain a larger amount of resin in the ink, and thus is suitable for increasing the resistance of the printed matter.

  Further, when a hydrosol and a water-soluble resin are used as the polymer compound (B), the weight average molecular weight is preferably in the range of 10,000 to 80,000, and in the range of 20,000 to 50,000. More preferably, it is within. A weight average molecular weight of 10,000 or more is preferable because the scratch resistance of the printed material can be made suitable. A weight average molecular weight of 80,000 or less is preferable because the ejection stability from the inkjet head can be maintained in a suitable state.

  In addition, the weight average molecular weight of a high molecular compound (B) can be measured by a conventional method. For example, a value measured as a weight average molecular weight in terms of polystyrene measured using TSKgel column (manufactured by Tosoh Corporation) and GPC equipped with an RI detector (manufactured by Tosoh Corporation, HLC-8120GPC) using THF as a developing solvent. It is.

  As above-mentioned, in this embodiment, the glass transition temperature of a high molecular compound (B) is -100-40 degreeC, More preferably, it is -90-15 degreeC, More preferably, it is -80--10 degreeC. As described above, the polymer compound (B) having the glass transition temperature has excellent adhesion to the substrate and high affinity with the low surface tension solvent (c2), and further drying and fixing at the nozzle interface. Can be suppressed.

  In addition, the said glass transition temperature is obtained by the measurement based on JISK7121 using the differential scanning calorimeter DSC-60 (made by Shimadzu Corporation Corp.), for example. Specifically, a sample placed in an aluminum sample container is heated at 10 ° C./min, and a DSC curve is measured. Note that indium is used for temperature calibration. In the obtained endothermic peak, a tangent line having a point at which it begins to deviate from the base line and a point at which the slope has settled down after the peak rise is drawn, and the intersection of the tangent line and the base line is defined as the glass transition temperature.

  As described above, in this embodiment, when the content mass% of the pigment (A) with respect to the total amount of the ink is WA, and the content mass% of the polymer compound (B) having a glass transition temperature of −100 to 40 ° C. is WB, The WB is 5 to (25-WA) mass%. More preferably, it is 6- (23-WA) mass%, More preferably, it is 7- (21-WA) mass%. By making WB 5% by mass or more, it becomes possible to produce a printed matter having excellent image density, scratch resistance, and substrate adhesion, and the amount of the polymer compound (B) relative to the pigment (A) is suitable. And the scratch resistance of the printed matter is improved. Moreover, by setting it as (25-WA) mass% or less, the rapid viscosity rise and solidification at the time of ink drying can be suppressed, and the discharge defect can be further suppressed.

  Further, the ratio of the content mass% of the pigment (A) to the content mass% of the polymer compound (B) represented by WA / WB is preferably 0.20 or more and 3.50 or less, more preferably. It is 0.25 or more and 3.20 or less. With the water-based ink within the above range, the pigment (A) can be sufficiently protected by the polymer compound (B) in the printed material, and thus a printed material having excellent scratch resistance can be produced.

  In this embodiment, the types of resins that can be used as the polymer compound (B) are exemplified by acrylic resins, styrene acrylic resins, urethane resins, acrylic urethane resins, polyester resins, styrene butadiene resins, vinyl chloride. Resin, polyolefin resin, and the like, and any of them may be used alone, or two or more kinds of resins may be used in combination. In particular, considering that the storage stability of the ink and the scratch resistance of the printed material can be made suitable, and that the material selectivity is wide and the affinity with the low surface tension solvent (c2) can be arbitrarily adjusted, acrylic resin, styrene One or more materials selected from acrylic resins, urethane resins, acrylic urethane resins, polyester resins, and polyolefin resins are preferably used. Moreover, from the point which is excellent also in the base-material adhesiveness with respect to a various base material, 1 or more types of materials selected from a styrene acrylic resin, a urethane type resin, and an acrylic urethane type resin are especially suitable.

  In the present embodiment, the configuration of the polymer compound (B) is not particularly limited, and for example, a random structure, a block structure, a comb structure, a star structure, or the like can be arbitrarily used.

  The polymer compound (B) may be used for any application as long as the glass transition temperature is −100 to 40 ° C. However, a polymer compound used as a pigment (A) such as hollow resin particles, or a polymer compound used as a surfactant (D) as described later (for example, a polyoxyalkylene alkyl ether surfactant) Is excluded. Specifically, the polymer compound (B) can be used for additives such as pigment dispersion resins, binder resins, waxes, and thickeners. Especially, it is preferable to use as binder resin and / or a wax from the point which can provide abrasion resistance suitably for printed matter. It is particularly preferable to use it as a binder resin.

  The polymer compound (B) preferably has an acid value of 0 to 100 mgKOH / g. More preferably, it is 5-80 mgKOH / g, More preferably, it is 10-50 mgKOH / g. An acid value of 100 mgKOH / g or less is preferable because a printed matter having excellent water resistance can be obtained.

<Water-soluble organic solvent (C)>
As described above, in this embodiment, the specific diol (c1) and the low surface tension solvent (c2) are used in combination. Moreover, the sum total (WC1 + WC2) of both solvent is 10 mass% or more and 40 mass% or less with respect to the ink whole quantity. The value of WC1 + WC2 is more preferably 15% by mass or more and 35% by mass or less, and further preferably 20% by mass or more and 33% by mass or less. By setting WC1 + WC2 to 10% by mass or more, wetting and spreading properties of the water-based ink on the printing substrate are ensured, and a printed matter with no omission is obtained. Moreover, the ink excellent in drying property can be obtained by setting it as 40 mass% or less. Further, by setting WC1 + WC2 within the above range, the ink has excellent ejection stability.

  In the water-based ink of this embodiment, the mass ratio (WC2 / WC1) of the content of the low surface tension solvent (c2) to the content of the specific diol (c1) is 1.5 to 5. By keeping the blending ratio of both solvents in the above range, the effect of inhibiting the dispersion and / or dissolution state of the ethylene glycol and / or 1,3-propanediol (c1) can be improved, and the result As a result, an ink having excellent ejection properties and storage stability can be obtained. The value of WC2 / WC1 is preferably 2 to 4.5, and more preferably 2.5 to 4.

  In addition, as described above, the water-based ink of the present embodiment has a water-soluble organic solvent (C) having a boiling point of 240 ° C. or higher at 1 atm as the water-soluble organic solvent (C), and 5% by mass or less based on the total amount of the ink. And the weighted average value of the boiling points of the water-soluble organic solvent in the ink under 1 atm is 130 ° C. or higher and lower than 180 ° C. As content of the water-soluble organic solvent whose boiling point is 240 degreeC or more, 3 mass% or less is more preferable, and 1 mass% or less is especially preferable. “The content is 5% by mass or less” means that the water-soluble organic solvent having a boiling point of 240 ° C. or higher is not included or, when included, the content is 5% by mass or less. The weighted average value of the boiling points of the water-soluble organic solvent (C) in the ink under 1 atm is more preferably 135 ° C. or more and 170 ° C. or less, and particularly preferably 140 ° C. or more and 160 ° C. or less. By satisfying these conditions, it is possible to obtain an ink excellent in drying property and image quality. The low surface tension solvent (c2) having a boiling point of 240 ° C. or higher under 1 atm is also included in the “water-soluble organic solvent having a boiling point of 240 ° C. or higher under 1 atm”.

  Here, the boiling point under 1 atm can be measured by a known method. Moreover, the weighted average value of the boiling points of the water-soluble organic solvent (C) under 1 atm is calculated for each water-soluble organic solvent, and the mass relative to the total water-soluble organic solvent (C) under 1 atm. It is a value obtained by adding the product of the ratio and the sum.

  As described above, the water-based ink of the present embodiment contains ethylene glycol and / or 1,3-propanediol (c1) as an essential component. Either one of these solvents may be used, or both may be used in combination. Among these, it is preferable to contain at least ethylene glycol because it has higher hydrophilicity and has a high effect of inhibiting the dispersion and / or dissolution state of the pigment and the polymer compound.

  In this embodiment, the blending amount of the specific diol (c1) is preferably 2 to 16% by mass, and more preferably 5 to 13% by mass with respect to the total amount of the ink. By being within the above range, in addition to the effect of suppressing the dispersion of solid content and / or dissolution state, it is possible to further improve the drying property of the ink droplets, and to obtain a printed matter particularly excellent in drying property and image quality. it can.

  The low surface tension solvent (c2) used in the present embodiment is a solvent having a static surface tension at 25 ° C. of 20 to 37 mN / m. In addition, as said static surface tension, Preferably it is 20-36 mN / m, More preferably, it is 20-35.5 mN / m. By keeping the static surface tension within the above range, wetting of ink droplets on the substrate is suitable for printing on non-absorbent substrates and high-speed printing on difficult / non-absorbent substrates. Therefore, it is possible to obtain a printed matter excellent in drying property and image quality. The static surface tension at 25 ° C. can be measured by, for example, a liquid contact test of a platinum plate by the Wilhelmi method at 25 ° C. An example of the measuring machine is CBVPZ manufactured by Kyowa Interface Science Co., Ltd.

Specific examples of the low surface tension solvent (c2) that can be suitably used in the present embodiment include propylene glycol (1,2-propanediol), 1,2-butanediol, 1,2-pentanediol, 1,2 -Hexanediol, 1,3-butanediol, 3-ethyl-1,2-hexanediol, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol Monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, diethylene glycol monoisobuty Ether, ethylene glycol monoallyl ether, diethylene glycol monobenzyl ether, dipropylene glycol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monopropyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol Examples include dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether acetate, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol (3-methyl-3-methoxybutanol), and the like. . In addition, said compound may use only 1 type and may use 2 or more types together.
In the present embodiment, among the solvents exemplified above, as the low surface tension solvent (c2), propylene glycol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 3-ethyl- 1,2-alkanediols such as 1,2-hexanediol; diethylene glycol monoalkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoisopropyl ether and diethylene glycol monobutyl ether; propylene glycol monoalkyls such as propylene glycol monomethyl ether and propylene glycol monopropyl ether A solvent containing at least one selected from the group consisting of ether; 3-methoxy-1-butanol and 3-methoxy-3-methylbutanol can be suitably used. . Although details are unknown, the above-mentioned solvent is difficult to destroy the dispersion and / or dissolution state of the pigment and the polymer compound, so that the ink is excellent in storage stability and dischargeability.

  In particular, in the present embodiment, among the solvents that can be suitably used as exemplified above, it is more preferable that the low surface tension solvent (c2) contains alkanediol. This is because alkanediol has a structure similar to that of the specific diol (c1) and does not adversely affect the storage stability and ejection stability of the ink. In a more preferred embodiment, it is preferable that the alkanediol contains 1,2-alkanediol, among which propylene glycol, 1,2-butanediol, 1,2-pentanediol, or 1,2-hexane. It is highly preferred to include a diol. 1,2-Alkanediol has a hydroxyl group, which is a hydrophilic unit, and an alkyl group, which is a hydrophobic unit, and has a high affinity for water, and can particularly improve the storage stability and ejection stability of ink. On the other hand, the surface tension of the ink can be reduced to a suitable range. As a result, the wettability of the ink is also improved, and it is considered that a printed matter having excellent image quality and scratch resistance can be produced.

  In this embodiment, the blending amount of the low surface tension solvent (c2) is preferably 6 to 30% by mass, more preferably 15 to 30% by mass, and further preferably 15 to 30% by mass with respect to the total amount of the ink. 25% by mass. By being within the above range, in addition to improving the wettability of the ink, the dispersion of solids by the specific diol (c1) and / or the effect of inhibiting the destruction of the dissolved state is not hindered. Ink can be obtained.

  In the water-based ink of the present embodiment, a conventionally known water-soluble organic solvent can be arbitrarily selected and used in addition to the specific diol (c1) and the low surface tension solvent (c2). Examples of water-soluble organic solvents that can be suitably selected in addition to the two solvents include 2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl-1,5. -Pentanediol, 1,6-hexanediol, glycerin, diethylene glycol, triethylene glycol, dipropylene glycol, 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, 3-methyl-2-oxazolidinone and the like. When these organic solvents are used, they are used within the above-described conditions regarding the amount of the water-soluble organic solvent having a boiling point of 240 ° C. or higher and the weighted average value of the boiling points of the water-soluble organic solvent (C). Furthermore, it is preferable to use in the range which does not inhibit the effect by specific diol (c1) and a low surface tension solvent (c2).

<Surfactant (D)>
In the present embodiment, the surfactant (D) is used for the purpose of adjusting the surface tension and ensuring the wetting and spreading property on the substrate, particularly the difficult / non-absorbable substrate. As the surfactant (D), there are various types of surfactants such as siloxane surfactants, acetylene surfactants, acrylic surfactants, fluorine surfactants, polyoxyalkylene alkyl ether surfactants, and the like. Things are known. From the viewpoint of sufficiently reducing the surface tension of the ink and ensuring excellent wetting and spreading properties, it is preferable to use a siloxane-based surfactant and / or an acetylene-based surfactant. The addition amount of the surfactant is preferably 0.5% by mass or more and 5.5% by mass or less, more preferably 1% by mass or more and 5% by mass or less, still more preferably 1% by mass or more and 4% by mass with respect to the total mass of the ink. It is below mass%. By setting the content to 0.5% by mass or more, the function as a surfactant can be sufficiently exerted, and by setting the content to 5.5% by mass or less, ink storage stability and ejection stability are suitable. Can be maintained at level.

<Pigment dispersion resin>
In order to maintain the stability of the ink for a long time, the pigment (A) in the present embodiment is used by being dispersed in the ink. As a method for dispersing the pigment, there are a method in which the surface of the pigment is modified by oxidation treatment or resin coating and the like, and a method in which the pigment is dispersed without a dispersant, and a method in which a surfactant or resin is used as a dispersant for dispersion. In the present embodiment, it is preferable to disperse the pigment (A) using a pigment dispersion resin from the viewpoint of improving the gloss of the printed matter and obtaining an ink having more excellent storage stability and dischargeability. When a pigment dispersion resin is used, a resin corresponding to the polymer compound (B) may be used as the pigment dispersion resin.

  The type of the pigment dispersion resin is not particularly limited. For example, acrylic resin, styrene acrylic resin, maleic acid resin, styrene maleic resin, urethane resin, ester resin, amide resin, imide resin Etc. Among these, from the viewpoint of strengthening the adsorption to the pigment (A) and stabilizing the pigment dispersion, one or more resins selected from acrylic resins, styrene acrylic resins, urethane resins, and ester resins Is preferably used. There is no particular limitation on the configuration, and for example, a random structure, a block structure, a comb structure, a star structure, or the like can be arbitrarily used.

  In addition, it is preferable to use a pigment-dispersed resin having a C10-C36 alkyl group in the resin skeleton from the viewpoint of the storage stability of the ink and the compatibility with the low surface tension solvent (c2). In addition, as a method of synthesizing a resin having an alkyl group, a method of condensing an alcohol and / or an amine having an alkyl group to a functional group such as a carboxylic acid having a basic resin skeleton, and a monomer having an alkyl group at the time of resin synthesis And a method of synthesizing a resin having an alkyl group by using.

  The molecular weight of the pigment-dispersed resin is preferably in the range of 1,000 to 100,000, more preferably in the range of 5,000 to 50,000. By setting the weight average molecular weight within the above range, the pigment (A) can be stably dispersed in water and the ejection stability can be improved. In addition, the weight average molecular weight of pigment dispersion resin can be measured similarly to the case of said high molecular compound (B).

  The acid value of the pigment dispersion resin is preferably 100 to 400 mgKOH / g. When the acid value is 100 mgKOH / g or more, the pigment dispersion resin is easily dissolved in water, which is the main component, and the viscosity of the pigment dispersion can be kept low. Moreover, if it is 400 mgKOH / g or less, the compatibility defect of a pigment dispersion resin and a low surface tension solvent (c2) can be prevented, and the storage stability of ink can be maintained at a suitable level. The acid value of the pigment-dispersed resin is preferably 150 to 350 mgKOH / g. The acid value of the pigment-dispersed resin was titrated with a potassium hydroxide ethanol solution (0.1 mol / L) using, for example, an automatic potentiometric titrator AT-710S manufactured by Kyoto Electronics Industry Co., Ltd. It can be calculated from the titration amount.

  Further, in order to increase the solubility of the pigment-dispersed resin in water, it is preferable that the acid group in the resin is neutralized with a base. Examples of the base that can be used include ammonia water, organic bases such as dimethylaminoethanol, diethanolamine, and triethanolamine, and inorganic bases such as lithium hydroxide, sodium hydroxide, and potassium hydroxide.

  When using pigment dispersion resin, it is preferable that the content is 1-50 mass% with respect to a pigment (A). By keeping the ratio of the pigment dispersion resin in the above range, the viscosity of the pigment dispersion and the ink can be kept low, and the dispersibility and storage stability can be improved. As content of the pigment dispersion resin with respect to a pigment (A), More preferably, it is 2-45 mass%, More preferably, it is 3-40 mass%, Most preferably, it is 4-35 mass%.

<Water>
As water contained in the ink of the present embodiment, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions. The water content in the present embodiment is preferably 20% by mass or more and 90% by mass or less with respect to the total amount of ink.

<Other ingredients>
In addition to the above components, the ink according to the present embodiment is appropriately added with additives such as an antifoaming agent, a pH adjusting agent, and an antiseptic agent in order to obtain an ink having a desired physical property value as necessary. be able to. The addition amount of these additives is preferably 0.01% by mass or more and 10% by mass or less with respect to the total mass of the ink.

<Ink set>
The ink of the present embodiment may be used in a single color, but in the form of an aqueous inkjet ink set (hereinafter also simply referred to as “ink set”) in which two or more types of aqueous inkjet inks having different hues are combined according to the application. Can also be used. The combination is not particularly limited, but a full-color image can be obtained by using three colors of cyan, yellow, and magenta. Moreover, black feeling can be improved by adding black ink, and the visibility of a character etc. can be raised. Furthermore, color reproducibility can be improved by adding colors such as orange and green.

  In this specification, “the hues are different from each other” means that the hue of a printed matter with a printing rate of 100% is measured using a colorimeter (eXact standard manufactured by X-rite), observation light source: D50, observation field of view: 2 °. , White reference: Abs, measurement mode: M0, and the color difference (ΔE) calculated from the obtained CIE-L * a * b * values is 30 or more.

  In the ink set of the present embodiment, it is preferable that at least one of the inks constituting the ink set is white ink from the viewpoint that the sharpness and visibility of the printed matter can be remarkably improved. For example, a clear image can be obtained by printing a combination of white ink and black ink on a transparent film substrate, which is an example of a non-permeable substrate. Especially, characters printed with black ink, etc. Since the sharpness and visibility can be improved, they are preferably combined.

  Among them, the effect of inhibiting the destruction of the dispersed state by the specific diol (c1) is high. Especially, even when printing on a non-absorbent substrate or high-speed printing on a difficult / non-absorbent substrate, image density, image quality, and sharpness And a printed matter having excellent visibility, C.I. I. Pigment Blue 15: 3, 15: 4, cyan ink using a cyan pigment selected from 15: 6, C.I. I. Pigment Red 31, 122, 146, 147, 150, 185, 202, 209, 266, 282, C.I. I. Magenta ink using a magenta pigment selected from Pigment Violet 19, C.I. I. Pigment Yellow 14, yellow ink using yellow pigment selected from 74, 120, 150, and 185, and one or more color inks selected from black ink using carbon black, and white ink using titanium oxide It is preferable to use the set.

<Ink preparation method>
Examples of the method for preparing the ink of the present embodiment composed of the components described above include the following methods, but the present embodiment is not limited thereto. First, after mixing and stirring the pigment (A), water, and, if necessary, a pigment dispersion resin, if necessary, a dispersion treatment is performed using a dispersion means described later, and if necessary, centrifugation is performed. By performing the treatment, a pigment dispersion is obtained. In production of the pigment dispersion, a polymer compound (B), a water-soluble organic solvent (C), and / or a surfactant (D) that do not correspond to the pigment dispersion resin may be added as necessary. . Next, a polymer compound (B), a water-soluble organic solvent (C), a surfactant (D), and other components as necessary are added to the pigment dispersion. The ink of this embodiment is obtained by stirring and mixing while applying heat as necessary, followed by filtration.

  In the case of producing a pigment dispersion by carrying out a dispersion treatment, any dispersing machine may be used as long as it is a commonly used dispersing machine. Examples thereof include a ball mill, a roll mill, a sand mill, a bead mill, and a nanomizer. Among these, a bead mill is preferably used.

  The pigment (A) contained in the ink of the present embodiment preferably has the following volume 50% diameter (d50) in the ink from the viewpoint of improving the effect of suppressing the destruction of the dispersed state by the specific diol (c1). In order to obtain the pigment (A) having a desired volume 50% diameter, for example, the following method may be mentioned. Reduce the size of the grinding media of the disperser as mentioned above; change the material of the grinding media; increase the filling rate of the grinding media; change the shape of the stirring member (agitator); Increasing the processing time; classifying with a filter or a centrifuge after dispersion processing; and a combination of these methods. In order to keep the pigment in the present embodiment in the above preferred particle size range, the size of the grinding media of the disperser is preferably 0.1 to 3 mm in diameter. Further, glass, zircon, zirconia, titania and the like are preferably used as the material for the grinding media.

  From the above viewpoint, the volume 50% diameter of the pigment (A) in the ink of the present embodiment is preferably 20 to 400 nm, more preferably 35 to 350 nm, and still more preferably 50 to 300 nm. The 50% volume diameter is a median diameter that can be measured using Nanotrac UPA EX-150 (manufactured by Microtrack Bell) using ink diluted with water.

<Method for producing printed matter>
In general, as a method for printing inkjet ink, a method is used in which ink is ejected from nozzles of an inkjet head and ink droplets are deposited on a printing substrate. Inkjet printers equipped with the inkjet head and used for printing are roughly classified into two types depending on the printing style. One is a “shuttle scan type” in which the head reciprocates on the printing substrate while ejecting ink, and the other is where the position of the head that ejects ink is fixed, and the printing substrate passes under the head. This is a “line pass type” that ejects ink when performing the process.

  The line pass type can perform high-speed printing as compared with the shuttle scan type, and can be expected to replace an existing high-speed printing machine such as offset printing. However, “discarding” that is performed in the shuttle scan type cannot be performed, and depending on the printed pattern, a nozzle that does not eject ink for a long time is generated.

  As described above, particularly in a line pass type printer, there is a problem of eliminating the trade-off between increasing the printing speed and suppressing ejection failure.

  Moreover, regarding the ink jet head mounted on the ink jet printer, generally, the higher the design resolution, the better the image quality of the printed matter. In particular, by using a head having a design resolution of 600 dpi or more, it becomes possible to produce a printed matter with excellent image quality. On the other hand, in order to set the design resolution of the ink jet head to 600 dpi or more, it is preferable to set the interval between adjacent nozzles to about 42 μm or less and the nozzle diameter to the same or less. As the nozzle diameter is reduced, the amount of ejected ink droplets is reduced, and the fineness of the obtained image is improved. On the other hand, there is a tendency that ink droplets are easily removed due to poor wetting and spreading. In addition, the smaller the nozzle diameter, the easier it is to lead to ejection failure even if a small amount of ink is dried and fixed.

  In response to the above, as a result of intensive studies by the present inventors, a printed matter is produced by mounting the water-based ink described above on an inkjet head having a nozzle diameter of 15 to 25 μm and a design resolution of 600 dpi or more. The present inventors have found that the above problems can be suitably solved. That is, for the water-based ink containing the low surface tension solvent (c2) and the surfactant (D), the amount of the water-soluble organic solvent having a boiling point of 240 ° C. or higher, and the weighted average value of the boiling points of the water-soluble organic solvent (C) By limiting the above, it is possible to sufficiently wet and spread ink droplets even on a difficult / non-absorbable substrate. As a result, it is possible to obtain a printed matter that is excellent in image density and fineness, with no omission and no blurring or cohesion unevenness in the color boundary. Furthermore, by using a water-based ink in which the above material is combined with ethylene glycol and / or 1,3-propanediol (c1), the occurrence of drying and sticking at the nozzle interface can be remarkably suppressed, and the nozzle diameter is small. Even in the case of a head, it is possible to produce a printed matter without causing ejection failure.

  As described above, the design resolution of the inkjet head used in the method for producing a printed matter using the water-based ink of the present embodiment is preferably 600 to 1,600 dpi, and more preferably 1,200 to 1,600 dpi. The nozzle diameter of the inkjet head used for printing is preferably 15 to 25 μm, more preferably 15 to 20 μm. By using an inkjet head having a finer nozzle diameter, it is possible to reduce the ejection amount of ink droplets, and it is possible to produce a printed material with higher image quality and higher sensitivity.

<Printing substrate>
The ink of this embodiment can be particularly suitably used for a difficult / non-absorbable substrate. As described above, the “difficult / non-absorbable substrate” in the present specification is a general term for a hardly-absorbent paper substrate, a non-absorbent substrate, etc., and does not absorb water or has a slow absorption rate. It is a printing substrate. Specifically, the water absorption coefficient measured by the Bristow method (J. TAPPI paper pulp test method No. 51-87) is 0 to 0.6 ml / m ² · msec ^1/2. It corresponds to a non-absorbent substrate. The above absorption coefficient can be measured, for example, by using an automatic scanning liquid absorption meter manufactured by Kumagai Riki Kogyo Co., Ltd. Specifically, the relationship between the water absorption amount (ml / m ² ) and the square root of contact time (msec ^1/2 ) obtained using the above device and water for a contact time of 100 to 1000 milliseconds. Therefore, the slope of the straight line obtained by the least square method is taken as the absorption coefficient.

  Among the above, specific examples of the hardly absorbent paper substrate include coated paper, art paper, cast paper, finely coated paper, and synthetic paper. Specific examples of non-absorbing substrates include plastic substrates such as polyvinyl chloride, PET, polypropylene, polyethylene, nylon, polystyrene, foamed styrene, polymethyl methacrylate (PMMA), and polycarbonate; metals such as aluminum and stainless steel Substrate; glass and the like can be mentioned. In addition, the difficult / non-absorbable base material in the present specification is not limited to the above base material. The ink-jet ink of the present embodiment can also be suitably used for materials other than difficult / non-absorbable substrates such as plain paper, fabric, and wood.

  Each of the above substrates may have a smooth surface, an uneven surface, or may be transparent, translucent, or opaque. Further, in order to further improve the ink base material adhesion and the image quality, a resin-coated one may be used. Further, two or more of these substrates may be bonded together. In addition, a peeling adhesive layer or the like may be provided on the opposite side of the printing surface, and an adhesive layer or the like may be provided on the printing surface after printing.

<Coating process>
When the water-based ink of the present embodiment is printed on a plastic substrate, the printing surface can be coated as necessary. Specific examples of the coating treatment include coating or printing of a coating composition; dry lamination method, solventless lamination method, extrusion lamination method, lamination by hot melt lamination, etc., and any of these may be selected. , You may combine both.

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

<Cyan pigment dispersion 1>
20 parts of LIONOGEN BLUE FG-7358G (CI Pigment Blue 15: 3, manufactured by Toyocolor Co., Ltd.) as a pigment, and styrene acrylic resin (styrene: acrylic acid: behenyl methacrylate = 35: 30: 35 (mass) as a pigment dispersion resin Ratio) random polymer, molecular weight: 16,000, glass transition temperature: 75 ° C., acid value: 250 mg KOH / g) aqueous solution (solid content 20%) 15 parts and 65 parts of water were mixed, Pre-dispersion treatment was performed with a stirrer. An aqueous solution of styrene acrylic resin was prepared using the method described in JP 2012-188581 A and Production Example 2.
Next, the obtained mixture was subjected to a main dispersion treatment using a 0.6 L dyno mill filled with 1800 g of zirconia beads having a diameter of 0.5 mm to obtain a cyan pigment dispersion 1.

<Yellow pigment dispersion 2>
A yellow pigment dispersion 2 was obtained in the same manner as the cyan pigment dispersion 1, except that the pigment was changed to LIONOL YELLOW TT-1405G (CI Pigment Yellow 14, manufactured by Toyocolor Co., Ltd.).

<Magenta pigment dispersion 3>
A magenta pigment dispersion 3 was obtained in the same manner as in the cyan pigment dispersion 1, except that the pigment was changed to FASTOGEN Super Magenta RTS (CI Pigment Red 122, manufactured by DIC).

<Black pigment dispersion 4>
A black pigment dispersion 4 was obtained in the same manner as the cyan pigment dispersion 1 except that the pigment was changed to Printex 85 (carbon black, manufactured by Orion Engineered Carbons).

<White pigment dispersion 5>
As a pigment, 40 parts of Taipei CR-90 (titanium oxide, manufactured by Ishihara Sangyo Co., Ltd.), 10 parts of an aqueous pigment dispersion resin solution (20% solid content) used for the preparation of cyan pigment dispersion 1, and 50 parts of water are mixed. Then, preliminary dispersion treatment was performed with a disper.
Next, the obtained mixture was subjected to a main dispersion treatment using a 0.6 L dynomill solution filled with 1800 g of zirconia beads having a diameter of 0.5 mm to obtain a white pigment dispersion 5.

<Example of production of binder resin 1 (styrene acrylic resin)>
In a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a refluxer, 40 parts of ion-exchanged water and 0.2 part of Aqualon KH-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier were charged. On the other hand, as a polymerizable monomer, 0.5 part of 2-hydroxyethyl methacrylate, 83.2 parts of butyl acrylate, 15.3 parts of styrene, 1.0 part of sodium styrenesulfonate, 53 parts of ion-exchanged water, and as an emulsifier Aqualon KH-10 (Daiichi Kogyo Seiyaku Co., Ltd.) 1.8 parts was separately mixed with a stirrer to prepare an emulsion.

  After taking 5 parts of the emulsified liquid and adding it to the above reaction vessel, the temperature inside the reaction vessel (internal temperature) was raised to 60 ° C. and sufficiently purged with nitrogen, and further 5% aqueous solution of potassium persulfate. 3 parts and 4 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added to initiate the polymerization reaction. After starting the reaction, while maintaining the internal temperature at 60 ° C., a mixture of the rest of the emulsion (95 parts), 2 parts of a 5% aqueous solution of potassium persulfate and 6 parts of a 1% aqueous solution of anhydrous sodium bisulfite, The solution was added dropwise over 1.5 hours, and stirring was further continued for 2 hours. Thereafter, the internal temperature was cooled to 30 ° C., and diethylaminoethanol was added to adjust the pH to 8.5. Furthermore, the aqueous dispersion (solid content 40%) of binder resin 1 was obtained by adjusting solid content to 40% with ion-exchange water. In addition, the glass transition temperature of the binder resin 1 measured using the differential scanning calorimeter DSC-60 (made by Shimadzu Corp.) was -32 degreeC.

<Example of production of binder resin 2 (styrene acrylic resin)>
As in the case of the binder resin 1, except that 0.5 parts of 2-hydroxyethyl methacrylate, 65.0 parts of butyl acrylate, 33.5 parts of styrene, and 1.0 part of sodium styrenesulfonate were used as the polymerizable monomer. Thus, an aqueous dispersion (solid content 40%) of binder resin 2 was obtained. The glass transition temperature of binder resin 2 measured in the same manner as in the case of binder resin 1 was −9 ° C.

In addition, the high molecular compound (B) used by the Example and the comparative example is as showing below.
・ High Loss M-141 (acrylic resin, manufactured by Starlight PMC, glass transition temperature 15 ° C., solid content 46%)
NeoCryl A-1127 (acrylic resin, DSM Coating Resins, glass transition temperature 5 ° C., solid content 44%)
Juliano W-600 (acrylic urethane resin, Arakawa Chemical Industries, glass transition temperature -55 ° C., solid content 35%)
Juliano W-321 (urethane resin, Arakawa Chemical Industries, glass transition temperature -60 ° C., solid content 34.5%)
NeoRez R-600 (urethane resin, manufactured by DSM Coating Resins, glass transition temperature -77 ° C, solid content 33%)
・ Superflex 150 (urethane resin, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., glass transition temperature 40 ° C., solid content 30%)
Elitel KT-0507 (polyester resin, manufactured by Unitika Ltd., glass transition temperature -25 ° C., solid content 25%)
・ High loss QE-1042 (styrene acrylic resin, manufactured by Seiko PMC, glass transition temperature 53 ° C., solid content 40.5%)
・ Viniblanc 700 (vinyl chloride resin, manufactured by Nissin Chemical Industry Co., Ltd., glass transition temperature 70 ° C., solid content 30%)

Moreover, the water-soluble organic solvent (C) used by the Example and the comparative example and the abbreviation described in Tables 1-3 are as showing below.
1,3-PD: 1,3-propanediol (boiling point: 214 ° C., surface tension: 47.1 mN / m)
EG: ethylene glycol (boiling point: 197 ° C., surface tension: 48.4 mN / m)
1,2-HexD: 1,2-hexanediol (boiling point: 223 ° C., surface tension: 25.9 mN / m)
1,2-PenD: 1,2-pentanediol (boiling point: 210 ° C., surface tension: 27.7 mN / m)
1,2-BD: 1,2-butanediol (boiling point: 194 ° C., surface tension: 31.6 mN / m)
1,2-PG: propylene glycol (boiling point: 188 ° C., surface tension: 35.1 mN / m)
MMB: 3-methyl-3-methoxybutanol (boiling point: 174 ° C., surface tension: 29.7 mN / m)
PGM: propylene glycol monomethyl ether (boiling point: 121 ° C., surface tension: 23.5 mN / m)
MB: 3-methoxy-1-butanol (boiling point: 161 ° C., surface tension: 28.9 mN / m)
PNP: propylene glycol monopropyl ether (boiling point: 150 ° C., surface tension: 25.9 mN / m)
IPDG: Diethylene glycol monoisopropyl ether (boiling point: 207 ° C., surface tension: 29.9 mN / m)
BDG: Diethylene glycol monobutyl ether (boiling point: 230 ° C., surface tension: 27.9 mN / m)
3-ethyl-1,2-hexanediol (boiling point: 244 ° C., surface tension: 31.2 mN / m)
NMP: N-methylpyrrolidone (boiling point: 202 ° C., surface tension: 40.3 mN / m)
2-pyrrolidone (boiling point: 245 ° C., surface tension: 45.0 mN / m)
・ Glycerin (boiling point: 290 ° C., surface tension: 62.0 mN / m)

  In Examples and Comparative Examples, Surfynol 465 (acetylenediol surfactant, manufactured by Nissin Chemical Industry Co., Ltd.) was used as the surfactant (D).

<Production Examples of Inks 1C, 1M, 1Y, 1K>
15.0 parts of Cyan Pigment Dispersion 1, 17.5 parts of aqueous dispersion (solid content 40%) of Binder Resin 1 (7.0 parts in terms of solid content), 7.5 parts of ethylene glycol, propylene glycol 22.5 parts of monomethyl ether and 1.0 part of Surfynol 465 were sequentially added to the mixing container, and then water was added so that the total amount of ink was 100 parts. After these mixtures were stirred with a disper until sufficiently uniform, the obtained mixture was filtered with a membrane filter having a pore size of 1 μm to remove coarse particles that cause clogging of the head, thereby obtaining ink 1C.
Ink 1Y, 1M, and ink 1C were used in the same manner as ink 1C except that yellow pigment dispersion 2, magenta pigment dispersion 3, and black pigment dispersion 4 were used instead of cyan pigment dispersion 1. And 1K were obtained.

<Production Example of Inks 2 to 72>
According to the formulation shown in Tables 1-2, inks 2-72 (four colors of C, Y, M, and K, respectively) were produced in the same manner as in the production examples of inks 1C, 1M, 1Y, 1K.

  However, in Tables 1-2, the compounding quantity of a high molecular compound (B) is a solid content conversion value.

<Production Examples of Inks 1W to 16W>
40 parts of white pigment dispersion 5, 17.5 parts of aqueous dispersion of binder resin 1 (solid content 40%) (7.0 parts in terms of solid content), 7.5 parts of ethylene glycol, propylene glycol monomethyl ether 22.5 parts and Surfinol 465 1.0 parts were sequentially added to the mixing container, and water was added so that the total amount of ink was 100 parts. After these mixtures were stirred with a disper until sufficiently uniform, the obtained mixture was filtered with a membrane filter having a pore size of 1 μm to remove coarse particles that cause clogging of the head, thereby obtaining ink 1W.
Moreover, according to the mixing | blending of Table 3, it carried out similarly to the manufacture example of the ink 1W, and manufactured the ink 2W-16W.

  However, in Table 3, the compounding quantity of a high molecular compound (B) is a solid content conversion value.

<Examples 1-73, Comparative Examples 1-25>
The following evaluation was performed using the produced inks 1 to 72 (four colors of C, Y, M, and K, respectively) and the inks 1W to 16W. The evaluation results are as shown in Tables 1-3.

<Evaluation 1: Evaluation of ink storage stability>
For each color of ink 1 to 72 (four colors of C, Y, M, and K, respectively) and inks 1W to 16W, using an E-type viscometer (TVE-20L manufactured by Toki Sangyo Co., Ltd.), The viscosity was measured under the condition of a rotation speed of 50 rpm. This ink is put into a sealed container, stored in a thermostat at 70 ° C. and accelerated over time, and then the viscosity is measured again using the above apparatus, and the change in the viscosity of the ink before and after aging is calculated. Storage stability was evaluated. The criteria are as follows, and AA, A, and B evaluations are practical areas. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.
AA: Change rate of viscosity after storage for 4 weeks was less than ± 5% A: Change rate of viscosity after storage for 2 weeks was less than ± 5%, but change rate of viscosity after storage for 4 weeks was ± 5% B: Viscosity change rate after storage for 1 week was less than ± 5%, but viscosity change rate after storage for 2 weeks was ± 5% or more C: Viscosity change rate after storage for 1 week Was more than ± 5%

<Evaluation 2A: Evaluation of color development (image density)>
An ink jet ejection device was prepared by arranging four Kyocera heads (KJ4B-1200 model, design resolution 1200 dpi, nozzle diameter: 20 μm) in the transport direction of the printing substrate. From the upstream side, black, cyan, magenta, And filled with yellow ink. Moreover, FOR # 20 (biaxially stretched polypropylene film, thickness 20 μm) manufactured by Futamura Chemical Co., Ltd. was prepared as a printing substrate.
Each of the printing substrates was conveyed at a constant speed and passed through the lower part of the head. At that time, ink was ejected from each head under printing conditions of a frequency of 20 kHz, 1200 × 1200 dpi, and a drop volume of 2.5 pL, and an image in which a 5 cm × 5 cm printing rate 100% solid patch was adjacent to each color was printed. After printing, the printed matter was quickly put into an air oven at 70 ° C. and dried for 2 minutes to obtain a solid patch printed matter. The solid density (OD value) of the obtained printed matter was measured from the surface (ink printing surface side), and the color developability (image density) was evaluated. For color measurement, eXact standard manufactured by X-rite, observation light source: D50, observation field of view: 2 °, density: status E, white standard: Abs, measurement mode: M0 were used. The evaluation criteria are as shown in Table 4 below, and AA, A, and B evaluations are in a practical range. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.

<Evaluation 2B: Evaluation of concealment (image brightness)>
The same inkjet discharge apparatus as that used in Evaluation 2A was used, and inks 1W to 16W were filled. Moreover, FOR # 20 manufactured by Futamura Chemical Co., Ltd. was prepared as a printing substrate. Then, a solid patch printed material having a printing rate of 5 cm × 5 cm and a printing rate of 100% was produced under the same printing conditions as in evaluation 2A.
Each of the obtained solid patch prints of inks 1W to 16W is overlaid on the solid patch print of ink 1K prepared in Evaluation 2A, and the lightness (L * value) is measured under the same colorimetric conditions as in Evaluation 2A. Thus, the hiding property (image brightness of white ink) was evaluated. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range.
A: Lightness (L *) value was 75 or more A: Lightness (L *) value was 67 or more and less than 75 B: Lightness (L *) value was 60 or more and less than 67 C: Lightness ( L *) value was less than 60

<Evaluation 3: Evaluation of solid part missing>
The solid patch printed matter produced in Evaluation 2A and Evaluation 2B was used, and the omission was evaluated by confirming the omission degree with a magnifying glass and visual observation. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.
A: No omission was observed with the loupe or visual observation. A: Occasional omission was observed with the loupe, but no omission was observed with the visual inspection. B: Occasional visual observation was observed. Omission was seen

<Evaluation 4: Evaluation of blurring between colors>
Using the solid patch printed material produced in Evaluation 2A, the degree of blurring at the boundary between each color was confirmed with a magnifying glass and visual observation to evaluate the blurring at the boundary. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range.
AA: No blurring was observed at the boundary between colors with the loupe and visual observation A: A slight blurring was observed at the boundary between colors with the loupe, but was not observed with visual observation B: Slight blurring was observed in the boundary between colors C: Bleeding was clearly observed at the boundary between colors.

<Evaluation 5: Evaluation of uneven aggregation>
Printing conditions similar to those of Evaluation 2A and Evaluation 2B, and a printing rate of 10% to 100% for each color of cyan, magenta, yellow, black, and white using FOR # 20 manufactured by Phutamura Chemical Co., Ltd. as the printing substrate A gradation pattern with 10% increments was printed. After printing, it was immediately put into a 70 ° C. air oven and dried for 2 minutes to obtain a gradation printed matter. The degree of uneven aggregation was evaluated by confirming the degree of uneven aggregation of the printed portions with a printing rate of 20%, 50%, and 80% with a loupe. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.
AA: No agglomeration unevenness was observed with a magnifying glass or visual observation at any of the printing ratios of 20, 50, and 80%. Was observed but was not visually observed. B: Slight uneven aggregation was visually observed at any one or more of the printing rates of 20, 50, and 80%. C: Printing rate of 20, 50, and 80%. In any one or more of the above, there was obvious aggregation unevenness visually.

<Evaluation 6: Evaluation of drying property>
Prints a solid image with a printing rate of 300% using the same printing conditions as evaluation 2A, and using FOR # 20 manufactured by Futamura Chemical Co., Ltd. as a printing substrate, and multiplying the printing rates of cyan, magenta, and yellow by 100%. did. After printing, it was quickly put into a 70 ° C. air oven, heated for a predetermined time, and then touched with a finger to evaluate the drying property of the printed matter. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range.
AA: The ink did not adhere to the finger even if it was touched with the finger 10 seconds after the oven was charged. A: The ink adhered to the finger 10 seconds after the oven was charged, but did not adhere after 15 seconds. B: Oven Ink adhered to the finger after 15 seconds from charging, but did not adhere after 20 seconds. C: Ink adhered to the finger even 20 seconds after charging into the oven.

<Evaluation 7: Evaluation of scratch resistance>
The same inkjet discharge device as that used in Evaluation 2A was used, and each color of ink 1 to 72 (four colors C, Y, M, and K, respectively) and inks 1W to 16W were filled. Further, FOR # 20 manufactured by Futamura Chemical Co., Ltd. was used as a printing substrate, and a 100% solid image of 20 cm × 2 cm was printed for each color. After printing, it was quickly put into an air oven at 70 ° C. and dried for 2 minutes to obtain a solid print.
This solid print is set on a Gakushin type anti-friction fastness tester (manufactured by Tester Sangyo Co., Ltd.) set with a cotton cloth for rubbing (gold width 3), and after reciprocating 10 times while applying a load of 200 g, the surface of the print The degree of ink peeling and the degree of ink adhesion to the gold width No. 3 were visually confirmed, and scratch resistance was evaluated. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.
AA: The surface of the printed material was not changed, and no color transfer to the gold width 3 was observed. A: The surface of the printed material was not changed, but the color transfer to the gold width 3 was confirmed. B: On the surface of the printed material Scratches were observed, and color transfer to gold width 3 was also confirmed. C: The printed surface was scraped off, and there was a portion where the film substrate was exposed.

<Evaluation 8: Evaluation of substrate adhesion>
A solid print was produced using the same printing conditions and evaluation ink as in Evaluation 7 using FOR # 20 manufactured by Futamura Chemical Co., Ltd. and FE2001 # 16 (polyester film) manufactured by Futamura Chemical Co., Ltd. as printing substrates.
With respect to this printed matter, 10 × 10 square grid-like cuts were made so as to form a square of 2 mm square while preventing the film substrate from being broken. A cellophane tape (manufactured by Nichiban Co., Ltd.) was strongly pressure-bonded so as to cover the cuts, and then peeled off at a stroke in a direction perpendicular to the printed matter. And the base-material adhesion | attachment was evaluated by confirming visually the mass number which the layer of the printed material peeled from the base material. Evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.
AA: All 100 cells did not peel from the substrate at all.
A: 90 squares or more and less than 100 squares did not peel from the base material in 100 squares B: 80 squares or more and less than 90 squares did not peel from the base material in 100 squares C: Peeled from the base material in 100 squares The number of cells that were not done was less than 80 cells

<Evaluation 9A: Evaluation of intermittent discharge performance using a printing press>
In the same printing apparatus as in Evaluation 2A, five types of the following two types of inkjet heads were mounted. Thereafter, black, cyan, magenta, yellow, and white inks were filled from the upstream side, respectively. After filling, a nozzle check pattern is printed (drop volume: head A: 5 pL, head B: 2.5 pL), and after confirming that ink is correctly discharged from all nozzles, it is predetermined in an environment of 25 ° C. The nozzle check pattern was printed again after waiting for no time discharge. The intermittent ejection performance was evaluated by visually confirming whether nozzle missing occurred after waiting. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range. In Tables 1 and 2, only the result of the worst color among the four evaluated colors is shown.
AA: No nozzle missing even after printing after waiting for 3 hours A: No nozzle missing even after printing after waiting for 2 hours, but nozzle missing occurs when printing after waiting for 3 hours B: No nozzle missing even after printing after waiting for 1 hour, but nozzle missing occurred when printing after waiting for 2 hours C: Nozzle missing 1-9 after printing after waiting for 1 hour This was occurring

The ink jet head used in Evaluation 9A and Evaluation 10 described below is as follows.
Head A: Kyocera head (KJ4B-QA model, design resolution 600 dpi, nozzle diameter: 25 μm)
Head B: Kyocera head (KJ4B-1200 model, design resolution 1200 dpi, nozzle diameter: 20 μm)

<Evaluation 9B: Evaluation of intermittent discharge performance using discharge evaluation machine>
A magenta ink was filled in each pulse injector manufactured by Cluster Technology Co., Ltd., on which an evaluation head having a nozzle with a nozzle diameter of 15 μm was set. After confirming that the ink was ejected normally, the pulse injector was put on standby for a predetermined time in an environment of 25 ° C. Thereafter, after a drive waveform signal for performing one drop ejection was transmitted four times, FORMA # 20 manufactured by Phutamura Chemical Co., Ltd. was quickly laid on the lower portion of the nozzle, and a drive waveform signal for performing one drop ejection was again transmitted once. At that time, intermittent ejection performance was evaluated by confirming whether ink droplets were normally ejected on FOR # 20. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range. The same test was also performed with an evaluation head having nozzles with a nozzle diameter of 25 μm and a nozzle diameter of 40 μm.
AA: Ink was ejected on FOR # 20 even after waiting for 3 hours. A: Ink was ejected on FOR # 20 after waiting for 2 hours, but not ejected after waiting for 3 hours. B: 1 Ink was discharged on FOR # 20 after waiting for a time, but not discharged after waiting for 2 hours. C: No ink was discharged on FOR # 20 even after waiting for 1 hour.

<Evaluation 10: Evaluation of nozzle blockage during long-term standby>
The ink jet head A or B was mounted on the same printing apparatus as in Evaluation 9A, and filled with magenta ink (M ink) or white ink (W ink), respectively. After filling, print a nozzle check pattern (drop volume: head A: 5 pL, head B: 2.5 pL), and after confirming that ink has been discharged accurately from all nozzles, 1 under a 25 ° C. environment. The printing device was put on standby without a head cap for a week. One week later, after purging about 10 mL of the same ink as that filled, a general maintenance operation of scraping off ink adhering to the nozzle surface was performed once. Thereafter, a nozzle check pattern was printed again, and the presence or absence of missing nozzles was confirmed (nozzle check 1).
For nozzles that have been confirmed to be missing in the nozzle check 1, a powerful maintenance operation is performed once, after all the ink in the inkjet head has been removed, 200 mL of cleaning liquid is purged and the cleaning liquid adhering to the nozzle surface is scraped off. Carried out. Thereafter, the same ink was again filled in the ink jet head, and then a nozzle check pattern was printed to confirm nozzle missing (nozzle check 2). As the cleaning liquid, a water-soluble organic solvent (C) contained in each ink was used except that all the components other than those having the largest amount were replaced with water. As a specific example, the cleaning liquid for ink 1C is a mixed solution of 22.5% by mass of propylene glycol monomethyl ether and 77.5% by mass of water.
In the nozzle check 1 and the nozzle check 2, the presence or absence of nozzle omission was confirmed to evaluate the nozzle blockage during long-term standby. The evaluation criteria are as follows, and A and B evaluations are in a practical range.
A: No nozzle missing in nozzle check 1 B: No nozzle missing in nozzle check 1, no nozzle missing in nozzle check 2 C: No nozzle missing in nozzle check 2

<Evaluation 11: Evaluation of clearness and visibility>
Using the same inkjet discharge apparatus as used in Evaluation 2A, the black ink (K ink) and the white ink (W ink) shown in Table 5 are arranged so that the color described in Table 5 is on the upstream side. Filled. FOR # 20 manufactured by Futamura Chemical Co., Ltd. was prepared as a printing substrate, and the inks were discharged in the same manner as in Evaluation 2A.
At that time, K ink printed a 4-point and 6-point MS Mincho character image mixed with hiragana and kanji, and W ink printed a 100% solid white image. In addition, printing was performed so that the image filled with the ink filled on the downstream side overlapped the image filled with the ink filled on the upstream side. Immediately after printing, the printed matter was put into a 70 ° C. air oven and dried for 2 minutes to prepare a letter / white solid printed matter.
The obtained character / white solid printed material was visually observed from the observation surface described in Table 5 to evaluate the sharpness and visibility. The evaluation criteria are as follows, and AA, A, and B evaluations are in a practical range.
AA: The 4-point and 6-point characters were both clear and readable.
A: Although the 4-point characters were slightly inferior in clarity, they were fully readable, and the 6-point characters were clear and clearly readable.
B: Characters of 4 points were inferior in clarity and could not be read. On the other hand, although the 6-point characters were slightly inferior, they could be read well.
C: Characters of 4 points and 6 points were inferior in clarity and could not be read.

  In Table 5, “back” as the observation surface represents that the printed material was observed from the film surface side, and “front” represents that the printed material was observed from the printing surface side.

<Evaluation results of Examples and Comparative Examples>
Comparative Example 1 and Comparative Example 21 were systems in which the content (WA) of the pigment (A) with respect to the total amount of ink was less than 3% by mass, resulting in poor color developability and hiding properties. On the contrary, Comparative Example 22 is a system in which WA exceeds 18% by mass, the storage stability, the intermittent discharge property when using a head having a minute nozzle diameter, and the substrate adhesion are poor, and the nozzle is blocked. Was observed. Also, in Comparative Examples 4 and 5 in which the glass transition temperature of the polymer compound B was outside the preferred range, poor substrate adhesion was observed.

  In Comparative Examples 2, 3, 23, and 24, the value of WB was outside the preferred range, and scratch resistance, deterioration of substrate adhesion, deterioration of intermittent ejection properties, and nozzle clogging were observed. In Comparative Example 13, the content and content ratio of the pigment (A), the polymer compound (B), and the water-soluble organic solvent (C) in the ink are suitable, but the surfactant (D) is contained. This was a non-system, and solid part omission, color boundary bleeding, and coagulation unevenness, which are considered to be caused by poor wettability of the water-based ink to the printing substrate, were observed.

  Other comparative examples were systems that did not suitably use the water-soluble organic solvent (C), and the results were that the quality of the printed matter, the drying property of the water-based ink, the intermittent ejection property, and the ejection property during long-term standby could not be satisfied. .

  On the other hand, Examples 1 to 63 are systems using the pigment (A), the polymer compound (B), the water-soluble organic solvent (C), and the surfactant (D) in suitable addition amounts. Stability, drying performance, intermittent ejection performance, nozzle blockability during long-term standby, color development of printed matter, solid portion omission, color boundary bleeding, cohesive unevenness, and scratch resistance were all practical areas.

  Moreover, Examples 64-73 shown in Table 5 are the systems which combined the black ink and white ink which were evaluated in Examples 1-63, and as a result of evaluation of clear and visibility, all are A or AA Level and good quality.

  The water-based inkjet ink which is an embodiment of the present invention uses an inkjet head having a minute nozzle diameter of 15 to 25 μm, and is printing on a non-absorbent substrate or high-speed printing on a difficult / non-absorbent substrate. In addition, an image having excellent image quality can be obtained. Further, by using an ink set containing the water-based inkjet white ink, a printed matter having excellent sharpness and visibility can be obtained. Furthermore, according to the method for producing a printed material according to an embodiment of the present invention using the water-based inkjet ink, a printed material having excellent delicateness can be obtained. Therefore, the water-based inkjet ink which is an embodiment of the present invention can be suitably used in high-speed and high-resolution inkjet printing for commercial printing using a difficult / non-absorbable substrate.

Claims (7)

An aqueous inkjet ink comprising a pigment (A), a polymer compound (B), a water-soluble organic solvent (C), and a surfactant (D),
The glass transition temperature of the polymer compound (B) is −100 to 40 ° C.,
The water-soluble organic solvent (C) comprises ethylene glycol and / or 1,3-propanediol (c1) and a water-soluble organic solvent (c2) having a static surface tension at 25 ° C. of 20 to 37 mN / m. And the content of the water-soluble organic solvent having a boiling point of 240 ° C. or higher at 1 atm is 5% by mass or less based on the total amount of the water-based inkjet ink,
The water-soluble organic solvent (C) has a weighted average value of boiling points at 1 atm of 130 ° C. or more and less than 180 ° C.,
The content of the pigment (A) is WA (mass%), the content of the polymer compound (B) is WB (mass%), the ethylene glycol and / or 1,3-propanediol with respect to the total amount of the water-based inkjet ink. When the content of (c1) is WC1 (mass%) and the content of the water-soluble organic solvent (c2) whose static surface tension at 25 ° C. is 20 to 37 mN / m is WC2 (mass%), A water-based inkjet ink in which WA, WB, WC1, and WC2 satisfy all of the following formulas (1) to (5).
3 ≤ WA ≤ 18 (1)
5 ≤ WB ≤ 25-WA (2)
10 ≦ WC1 + WC2 ≦ 40 (3)
0.25 ≦ WC1 / (WA + WB) ≦ 1.75 (4)
1.5 ≦ WC2 / WC1 ≦ 5 (5)   The water-based inkjet ink according to claim 1, wherein the water-soluble organic solvent (c2) having a static surface tension at 25 ° C of 20 to 37 mN / m contains 1,2-alkanediol having 3 to 6 carbon atoms.   The aqueous inkjet ink according to claim 1 or 2, wherein the ethylene glycol and / or 1,3-propanediol (c1) contains ethylene glycol.   The water-based inkjet ink in any one of Claims 1-3 whose content of the said surfactant (D) is 0.5-5.5 mass% in water-based inkjet ink whole quantity. A water-based inkjet ink set comprising two or more types of water-based inkjet inks having different hues from each other,
Each of the two or more types of water-based inkjet inks is the water-based inkjet ink according to any one of claims 1 to 4, and at least one of the two or more types of water-based inkjet inks is a white ink. set. A step of discharging the aqueous inkjet ink according to any one of claims 1 to 4 or the aqueous inkjet ink set according to claim 5 from an inkjet head to adhere to a printing substrate, and a printing base to which the aqueous inkjet ink is adhered A method for producing a water-based inkjet ink printed matter, comprising a step of drying the material,
A method for producing a water-based inkjet ink print, wherein the nozzle diameter of the inkjet head is 15 to 25 μm, and the design resolution of the inkjet head is 600 dpi or more.   The printed matter formed by printing the water-based inkjet ink in any one of Claims 1-4, or the water-based inkjet ink set of Claim 5 on a base material.