JP6658675B2 - Water-based inkjet ink - Google Patents

Description

  The present invention has no white spots due to insufficient ink wettability, and no bleeding or uneven coagulation due to coalescence of ink droplets having different hues on a printing substrate such as a poorly absorbable substrate. The present invention relates to an aqueous ink-jet ink capable of producing a high-quality printed matter, and having excellent storage stability and excellent dischargeability from an ink-jet nozzle.

  Unlike conventional plate printing such as offset printing, digital printing does not require a plate, so that cost reduction and space saving can be realized. In particular, the ink jet recording method is to directly discharge and attach ink droplets from a very fine nozzle to a recording member to obtain characters and images. According to this method, there is an advantage that the noise of the device to be used is small, operability and colorization are easy, and a paper base material can be used as a recording member. Widely used as.

  Also, with the improvement of inkjet technology, it is expected to be used as an output device for digital printing in industrial applications. In fact, devices that print solvent inks and UV inks on plastic base materials such as polyvinyl chloride and PET are commercially available. ing. However, in recent years, restrictions on the use of solvents and monomers have been promoted from the viewpoint of consideration and response to harm to the environment and people, and the demand for water-based inks has increased instead.

  As water-based inks for ink jets, as described in Patent Literatures 1, 2, and 3, printing on special paper such as plain paper or glossy photographic paper has been developed for a long time. On the other hand, in recent years, the use of the ink jet recording system is expected to expand, and the need for direct printing on hard-to-absorbable base materials such as art paper, coated paper, and finely coated paper is increasing.

  However, water, which is the main solvent of the aqueous ink, has a high surface tension, so it is difficult to spread on the poorly absorbable substrate as described above and hardly penetrates into the substrate. When printing on, white spots caused by insufficient wetting and spread, and bleeding and uneven aggregation due to color boundaries caused by coalescence of undried ink droplets having different hues, This has led to poor image quality.

  Generally, a surfactant is used for improving the wet spreadability. For example, Patent Document 4 discloses an ink in which polyoxyethylene alkyl ether is used as a surfactant to suppress image defects such as feathering, improve image quality, and suppress a decrease in ejection characteristics from an inkjet nozzle. It has been disclosed. Indeed, according to this method, a feathering suppression effect can be seen with respect to a highly water-absorbing base material such as XEROX 4200 paper used in Patent Document 4, but it is an object of the present invention. For hardly-absorbable substrates such as coated paper, white spots, blurring of color boundaries and uneven coagulation cannot be suppressed. It is considered that the above-mentioned surfactant cannot sufficiently spread the ink by wetting and spread the ink droplets due to insufficient drying property.

  As described above, conventionally, especially for poorly absorbable base materials, it is possible to produce high-quality printed matter without white spots, color boundary bleeding and uneven coagulation, and excellent in dischargeability from an inkjet nozzle. There was no inkjet ink present.

JP 2001-354888 A JP 2004-210996 A JP 2008-247941 A JP 2012-21260 A

  The present invention has been made in order to solve the above-described problems, and an object thereof is to form a white spot due to insufficient ink wettability on a printing base material such as a poorly absorbable base material, and a different hue. A water-based inkjet ink capable of producing high-quality printed matter free from color boundary bleeding and uneven aggregation due to coalescence of ink droplets, and having excellent storage stability and dischargeability from an inkjet nozzle. It is in.

  Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-described problems, and have found that an organic solvent having a specific HLB value is used in combination with a surfactant, thereby completing the present invention.

That is, the present invention relates to an aqueous inkjet ink containing at least a pigment, a pigment-dispersed resin, a binder resin, a water-soluble organic solvent, and a surfactant (A),
The binder resin is a water-soluble resin having an acid value of 1 to 80 mgKOH / g,
The water-soluble organic solvent contains a water-soluble organic solvent having an HLB value of not more than 8 by the Griffin method of 8 or less based on the total amount of the aqueous inkjet ink,
The surfactant (A) contains an acetylenic diol-based surfactant (a1) having an HLB value of 3 or less by a Griffin method ,
A water-based ink-jet ink characterized in that the content of the acetylene diol-based surfactant (a1) having an HLB value of 3 or less is 0.5 to 5.0% by weight based on the total amount of the water- based ink-jet ink.

  The present invention also relates to the aqueous inkjet ink described above, wherein the surfactant (A) further contains a polysiloxane-based surfactant (a2) having an HLB value of 4 or less by a Griffin method. .

  The present invention also provides the aqueous inkjet ink as described above, wherein the surfactant (A) further contains a polysiloxane-based surfactant (a3) having an HLB value of 8 to 20 by a Griffin method. About.

  Further, the present invention provides a ratio of the content of the polysiloxane surfactant (a2) having the HLB value of 4 or less to the content of the acetylene diol surfactant (a1) having the HLB value of 3 or less. Is from 0.2: 1.0 to 3.3: 1.0.

  Further, the present invention relates to the content of the polysiloxane-based surfactant (a3) having the HLB value of 8 or more and 20 or less, and the content of the acetylene diol-based surfactant (a1) having the HLB value of 3 or less. A ratio of 0.1: 1.0 to 2.0: 1.0.

  The present invention also relates to the aqueous inkjet ink described above, wherein the water-soluble organic solvent having an HLB value of 8 or less contains a polyol solvent.

The present invention also relates to the aqueous inkjet ink described above, wherein the water-soluble resin has an alkyl chain having 8 to 36 carbon atoms .

  The present invention also relates to the above-mentioned aqueous inkjet ink, wherein the content of the water-soluble resin is 0.5 to 10% by weight based on the total amount of the aqueous inkjet ink.

  The present invention also relates to a printed matter obtained by printing the above-described aqueous inkjet ink on a substrate.

  According to the present invention, on a printing base material such as a poorly absorbable base material, there is no white spots due to insufficient wettability of the ink, and there is no bleeding or uneven aggregation due to the coalescence of ink droplets having different hues. Thus, it has become possible to provide a water-based inkjet ink that can produce high-quality printed matter, and that has excellent storage stability and dischargeability from an inkjet nozzle.

  Hereinafter, preferred embodiments of the inkjet ink (hereinafter, also simply referred to as “ink”) of the present invention will be described in detail. It should be noted that the present invention is not limited to the embodiments described below, and also includes modified examples implemented without changing the gist of the present invention. Unless otherwise specified, “parts” and “%” represent “parts by weight” and “% by weight”.

  As described in the prior art, water, which is the main solvent of the water-based ink, has a high surface tension, and has a property that it is difficult to spread to the base material, resulting in poor image quality such as white spots, color boundary bleeding and uneven coagulation. Cause. In order to improve the image quality, it is effective to lower the surface tension of the ink. Generally, a surfactant or a hydrophobic water-soluble solvent is added to the ink to reduce the surface tension. I have. However, if the surface tension is merely reduced, the ink droplets that have spread and wet are united with each other, so that the color boundary is also blurred and uneven coagulation is generated, which does not lead to improvement in image quality. In addition, if the above-mentioned material is used excessively, other problems such as agglomeration of the pigment in the ink leading to a decrease in storage stability, and deterioration of the ejection property due to overflow of the ink from the inkjet nozzle may occur. Will happen.

  As a result of intensive studies by the present inventors to solve the above problems, the present inventors have found that the above problems can be solved by using an organic solvent having a specific HLB value and a surfactant in combination.

  One of the features of the present invention is to use an acetylenic diol-based surfactant (a1) having an HLB value of 3 or less by the Griffin method. The HLB value is an index indicating the hydrophilicity / hydrophobicity of the material. An acetylenic diol-based surfactant (a1) having a particularly low HLB value can be used for an ink in a very short time of several tens of microseconds or less after landing on a recording medium. It is considered that the liquid crystal is oriented on the surface of the liquid droplets, remarkably improves the wettability of the ink, and suppresses the coalescence of the liquid droplets from immediately after landing to the initial stage. Further, it is considered that the surface area of the ink droplets is increased by spreading the ink droplets quickly, and the efficiency of drying and penetration into the base material is improved, which also contributes to the suppression of coalescence of the ink droplets.

  On the other hand, when a material having a small HLB as described above, that is, a material having a high hydrophobicity is used for an aqueous ink, problems such as separation over time and deterioration of storage stability due to affecting other materials will occur. Therefore, in the present invention, a certain amount of a water-soluble organic solvent having an HLB value of 8 or less is added to solve the above problem. By using a water-soluble organic solvent having a moderate hydrophobicity, the acetylenic diol-based surfactant (a1) is compatible with the ink and can be stably present without separation, and can be used for other materials. Is considered to be minimized, and as a result, storage stability and ejection property are improved.

  As described above, in order to obtain a high-quality printed matter without white spots, color boundary bleeding, and uneven aggregation, and to obtain an ink having excellent storage stability and ejection properties, it has a specific HLB value. It is essential to use an organic solvent and a surfactant together. Note that the above mechanism is an inference and does not limit the present invention in any way.

  The main components of the present embodiment will be described below.

<Acetylene diol-based surfactant (a1)>
As described above, one of the features of the present invention is to use an acetylenic diol-based surfactant (a1) having an HLB value of 3 or less by the Griffin method. The preferred HLB value is 1.0 or more and 2.9 or less, and more preferably 2.0 or more and 2.8 or less. As described above, the acetylenic diol surfactant (a1) having an HLB value of 3 or less is excellent in the alignment speed on the ink droplet surface, so that the wettability is improved and the coalescence of the droplets is suppressed. It is considered possible. In addition, when used in combination with a water-soluble organic solvent having an HLB value of 8 or less, it becomes possible to maintain the storage stability and dischargeability of the ink at a suitable level.

The HLB (Hydrophile-Lipophile Balance) value is one of the parameters indicating the hydrophilicity / hydrophobicity of the material. There are various methods for calculating the HLB value, such as the Griffin method, the Davis method, and the Kawakami method. In the present invention, the HLB value is calculated using the Griffin method.

  Generally, the Griffin method is used for a nonionic material and is known to indicate the degree of hydrophilicity / hydrophobicity thereof. The Griffin method is obtained by the following formula (1) using the molecular weight of the target material. . Note that the smaller the HLB value, the higher the hydrophobicity of the material, and the larger the HLB value, the higher the hydrophilicity of the material.

General formula (1):
HLB value = 20 × (total molecular weight of hydrophilic portion) ÷ (molecular weight of material)

  The amount of the acetylenic diol-based surfactant (a1) having an HLB value of 3 or less is preferably 0.5% by weight or more and 5.0% by weight or less, more preferably 0.7% by weight, based on the total amount of the ink. % To 4% by weight, more preferably 1.0% to 3.0% by weight. When the content is 0.5% by weight or more, the function as a surfactant can be sufficiently exhibited, and when the content is 5.0% by weight or less, the storage stability and ejection property of the ink are maintained at suitable levels. It is possible to do.

  Specific examples of the acetylenic diol-based surfactant (a1) having an HLB value of 3 or less that can be used in the present invention include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, , 5,8,11-Tetramethyl-6-dodecin-5,8-diol, hexadec-8-yne-7,10-diol, 4,7-dipropyl-dec-5-yne-4,7-diol, 6,9-dimethyl-tetradec-7-yne-6,9-diol, 3,6-diisopropyl-2,7-dimethyloct-4-yn-3,6-diol, octadeca-9-yne-8,11 -Diol, 7,10-dimethylhexadec-8-in-7,10-diol, 5,8-dibutyldodec-6-yne-5,8-diol, 4,7-diisobutyl-2,9-dimethyl- Dec-5- Down-4,7-diol, 5,14- diethyl-8,11-dimethyl-oct dec-9-in-8,11-diol, and the like. Above all, from the viewpoint of compatibility with the aqueous ink, 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, hexadec-8-yne-7,10-diol, 6,9-dimethyl It is preferred to use -tetradec-7-yne-6,9-diol. The above compounds may be used alone or in combination of two or more. Further, as the above compound, a compound synthesized by a known synthesis method may be used, or a commercially available product may be used.

<Polysiloxane-based surfactant>
In the present invention, it is preferable to use a polysiloxane-based surfactant in addition to the acetylenic diol-based surfactant (a1) having an HLB value of 3 or less. In general, a polysiloxane-based surfactant is preferable because it has a lower orientation speed on a liquid surface and can further improve color boundary bleeding and uneven aggregation, as compared with an acetylene diol-based surfactant. Further, by using a polysiloxane-based surfactant, it is possible to impart water repellency and rub resistance to the printed matter, and it is also possible to control the surface tension and ejection property of the ink, and it is preferably used from the above viewpoint.

  In the present invention, a polysiloxane-based surfactant (a2) having an HLB value of 4 or less and / or a polysiloxane-based surfactant (a3) having an HLB value of 8 or more and 20 or less are prepared by adding an HLB value of 3 or less. It is preferable to use it with a certain acetylenic diol-based surfactant (a1). The HLB value of the polysiloxane surfactant is also calculated using the Griffin method.

  The polysiloxane-based surfactant (a2) having an HLB value of 4 or less has a high orientation in the ink among the polysiloxane-based surfactants and is excellent in surface tension lowering ability. It has the effect of improving. On the other hand, a polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less is an acetylene diol-based surfactant (a1) having an HLB value of 3 or less or a polysiloxane surfactant having an HLB value of 4 or less. Compared with the agent (a2), it has a particularly excellent effect of suppressing coalescence of droplets. As described above, in the present invention, it is particularly preferable to use both the polysiloxane surfactant (a2) having an HLB value of 4 or less and the polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less. .

  The polysiloxane-based surfactant suitably used in the present invention is a compound represented by the following general formula (2) or (4).

General formula (2):

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

General formula (3):

In the general formula (3), m is an integer of 1 to 6, n is an integer of 0 to 50, o is an integer of 0 to 50, and n + o is an integer of 1 or more. R ₃ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a (meth) acryl group.

General formula (4):

In the general formula (4), r represents an integer of 1 to 80. R ₁ is represented by the general formula (3).

  The compound represented by the general formula (2) has a large contribution to the adjustment of the surface tension, wettability and dischargeability of the ink. Further, the compound represented by the general formula (4) has an effect of suppressing coalescence of ink droplets on a substrate and increasing storage stability (stability of surface tension) of the ink. In the present invention, the above-mentioned materials can be appropriately selected and used in consideration of the HLB value.

  As the polysiloxane-based surfactants represented by the general formulas (2) and (4), those synthesized by a known synthesis method or commercially available products may be used. Examples of commercial products of the compound represented by the general formula (2) include SF8428, FZ-2162, 8032 ADDITIVE, SH3749, FZ-77, L-7001, L-7002, and FZ-2104 manufactured by Dow Corning Toray. FZ-2110, F-2123, SH8400, SH3773M; BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 manufactured by BYK Chemie Co .; KF-351A, KF-352A, KF-353, KF-354L, KF355A, KF-615A, KF-640, KF-642, KF-643 manufactured by Chemical Industry Co., Ltd .; Silface SAG series manufactured by Nissin Chemical Industry Co., Ltd. But It is below.

  Examples of commercial products of the compound represented by the general formula (4) include BY16-201 and SF8427 manufactured by Dow Corning Toray Co., Ltd .; BYK-331, BYK-333, BYK-UV3500 manufactured by BYK Chemie; Evonik Degussa Tegoglide 410, Tegoglide 432, Tegoglide 435, Tegoglide 440, Tegoglide 450, and the like.

<Polysiloxane-based surfactant (a2) having an HLB value of 4 or less>
As described above, the polysiloxane-based surfactant (a2) having an HLB value of 4 or less mainly contributes to ink wettability, and the HLB value is 2.0 or more and 3.8 or less. It is more preferable that it is 2.4 or more and 3.6 or less.

  The addition amount of the polysiloxane surfactant (a2) having an HLB value of 4 or less is preferably 0.1% by weight or more and 4.0% by weight or less, more preferably 0.1% by weight or less, based on the total weight of the ink. It is from 5% by weight to 3.0% by weight, more preferably from 1.0% by weight to 2.5% by weight. When the content is within the above range, it is possible to obtain an ink having excellent wettability to a substrate, and excellent in ejection property and storage stability.

  When the content of the acetylenic diol-based surfactant (a1) having an HLB value of 3 or less is set to 1, the content ratio of the polysiloxane-based surfactant (a2) having an HLB value of 4 or less is as follows. , 0.2 to 3.3 are preferred, 0.4 to 2.5 are more preferred, and particularly preferred is 0.5 to 1.5. In general, when a plurality of surfactants are used in combination, it is considered that the compatibility of each surfactant in the aqueous ink is changed, and by controlling the content ratio within the above range, the compatibility of each surfactant is considered. It is believed that the solubility is favorable.

  Since the polysiloxane surfactant (a2) of the present invention having an HLB value of 4 or less is a material that contributes to the wettability of the ink as described above, the general formula (2) that greatly contributes to the surface tension of the ink is used. It is particularly preferred to have a structure represented by

<Polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less>
The polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less is mainly used for suppressing coalescence of droplets on a substrate, and has an HLB value of 10 or more. It is more preferably 18 or less, more preferably 12 or more and 16 or less.

  The addition amount of the polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less is preferably 0.05% by weight or more and 1.0% by weight or less, more preferably 0.1% by weight or less based on the total weight of the ink. % By weight to 0.8% by weight, more preferably 0.2% by weight to 0.7% by weight. When the content is within the above range, coalescence of the ink droplets on the base material hardly occurs, and an ink excellent in storage stability and ejection property can be obtained.

  Further, when the content of the acetylene diol-based surfactant (a1) having an HLB value of 3 or less is set to 1, the content ratio of the polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less is set. Is preferably from 0.1 to 2.0, more preferably from 0.15 to 1.5, and even more preferably from 0.2 to 1.0. It is considered that by keeping the content ratio within the above range, the compatibility of each surfactant becomes suitable.

  The polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less according to the present invention is a material that contributes to the suppression of coalescence between ink droplets on a substrate as described above, and has the general formula (4) It is particularly preferred to have a structure represented by the formula:

<Other surfactants>
In the present invention, a surfactant other than the above can be used as long as the above effects are not inhibited. Various surfactants are known according to the intended use, but they maintain the surface tension of the ink at a suitable level and ensure wettability and dischargeability, and coexist stably with hydrophilic materials. From the viewpoints, acetylene-based, glycol ether-based, and fluorine-based surfactants other than those described above can be used.

<Water-soluble organic solvent>
As described above, the present invention is characterized in that a water-soluble organic solvent having an HLB value of 8 or less is contained in an amount of 10 to 50% by weight based on the total amount of the ink. It is considered that the water-soluble organic solvent having an HLB value of 8 or less has a function of making a surfactant having a small HLB value used together compatible with water. Therefore, it is preferable to use one having a small HLB value within a range that does not impair the hydrophilicity. Specifically, the HLB value is preferably 1 or more and 7.8 or less, and particularly preferably 2 or more and 7.6 or less. The HLB value of the water-soluble organic solvent is also calculated using the Griffin method.

  Further, the boiling point of the water-soluble organic solvent is preferably in the range of 180 ° C. to 250 ° C. at 1 atm, more preferably 180 ° C. to 230 ° C. By using a water-soluble organic solvent having a boiling point of 180 ° C. or higher, drying of the ink in contact with the outside air at the nozzle interface of the inkjet head can be suppressed, and as a result, the ejection stability of the ink is improved. Further, by setting the boiling point to 250 ° C. or less, drying on the printing base material can be maintained at a preferable level, and a decrease in image quality such as blurring of color boundaries and uneven coagulation can be further suppressed.

Specific examples of the water-soluble organic solvent having an HLB value of 8 or less that can be suitably used in the present invention include 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2-methyl. -1,3-propanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl- Polyol-based solvents such as 1,5-pentanediol, 1,2-hexanediol, and 1,6-hexanediol;
Propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene Propylene glycol monoether solvents such as glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, and tripropylene glycol monobutyl ether;
Propylene glycol diether solvents such as propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, and tripropylene glycol dimethyl ether; and methoxy butanol solvents such as 3-methoxy-1-butanol and 3-methoxy-3-methylbutanol. Among the above, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2-methyl-1,3, which are solvents having a boiling point at 180 ° C. or higher and 250 ° C. or lower at 1 atm. -Propanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5- Pentanediol, 1,2-hexanediol, 1,6-hexanediol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monomethyl ether are particularly preferable. It is preferably used.

  In the present invention, it is particularly preferable to select a polyol-based solvent from the solvents preferably used as exemplified above. An ink using a polyol-based solvent having an HLB value of 8 or less has particularly excellent storage stability and ejection properties as compared with a case where a water-soluble organic solvent having an HLB value of 8 or less is used. It is speculated that the polyol solvent has multiple hydroxyl groups and forms hydrogen bonds between the hydroxyl groups of the acetylenic diol surfactant used in combination and the oxygen atoms of the polysiloxane surfactant. By doing so, it is considered that the compatibility effect between the surfactant and water is further enhanced.

  Further, it is most preferable to use a 1,2-alkanediol as the polyol solvent. The 1,2-alkanediol has a hydroxyl unit serving as a hydrophilic unit and an alkyl group serving as a hydrophobic unit localized, and has a high affinity for water, while reducing the surface tension of the ink to a suitable range. It is considered that the resulting printed matter has improved wettability of the ink and excellent image quality. Among the compounds exemplified above, 1,2-butanediol, 1,2-pentanediol, and 1,2-hexanediol are exemplified as the 1,2-alkanediol having an HLB value of 8 or less, which is most preferably used in the present invention. be able to.

  As described above, the content of the water-soluble organic solvent having an HLB value of 8 or less needs to be 10% by weight or more and 50% by weight or less based on the total amount of the ink, preferably 15% by weight or more and 40% by weight or less. More preferably, the content is 20% by weight or more and 30% by weight or less. When the content is 10% by weight or more, a surfactant having a small HLB value can be sufficiently compatibilized, and storage stability and ejection property can be secured. When the content is 50% by weight or less, the viscosity of the ink can be kept in a suitable range, and the ejection property can be improved.

  The water-soluble organic solvent having an HLB value of 8 or less is a material for compatibilizing the acetylene diol-based surfactant (a1) having an HLB value of 3 or less. Is also an important point. The content of the water-soluble organic solvent having an HLB value of 8 or less is preferably 5 to 100 when the content of the acetylene diol-based surfactant (a1) having an HLB value of 3 or less is 1, It is more preferably from 10 to 70, particularly preferably from 15 to 40. By keeping the content ratio of the two within the above range, the acetylene diol-based surfactant (a1) having an HLB value of 3 or less can be suitably dissolved in the ink.

  In addition, a water-soluble organic solvent other than the above can be used alone or in combination of two or more as long as the content of the present invention is within a preferable range that does not decrease the effect of the present invention. Specifically, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol-2-ethylhexyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol methyl Ethyl ether, diethylene glycol methyl butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, triethylene glycol methyl ethyl ether, triethylene glycol methyl Butyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol methyl butyl ether, glycerin, 2-pyrrolidone, N-methyloxazolidinone, γ-butyrolactone , Ε-caprolactone, etc., but are not limited thereto.

<Water-soluble resin>
In the present invention, it is preferable to add a binder resin from the viewpoint of improving the coating film resistance of the printed matter. In general, a water-soluble resin and resin fine particles are known as a binder resin used for an inkjet ink. Among them, the resin fine particles have a higher molecular weight than the water-soluble resin, and the resin fine particles can lower the viscosity of the ink and can contain a larger amount of the resin in the ink. Suitable for enhancing. Examples of the type of resin used as the resin fine particles include acrylic, styrene-acryl, urethane, styrene-butadiene, vinyl chloride, and polyolefin-based resins. Above all, acrylic-based and styrene-acrylic resin fine particles are preferably used in consideration of the storage stability of the ink and the durability of the printed matter.

  However, when the binder resin in the ink is resin fine particles, it is necessary to consider the minimum film forming temperature (MFT) of the resin fine particles. When resin particles having a low MFT are used, the MFT of the resin particles is further reduced by the water-soluble organic solvent added to the ink, and even at room temperature, the resin particles fuse and agglomerate. Clogging may occur. In the case of resin fine particles, once formed into a film, they do not re-dissolve in the ink, so that the ejected property is impaired by the fixed resin component. In order to avoid the above problem, it is preferable that the MFT of the resin fine particles be adjusted to 60 ° C. or higher by adjusting the monomers constituting the resin fine particles. The MFT can be measured by, for example, an MFT tester manufactured by Tester Sangyo Co., Ltd.

  In the present invention, the resin itself has solubility, so that clogging in the ink jet head nozzle is unlikely to occur and the ejection property is excellent. By selecting a constituent material, it can function as a compatibilizer for a surfactant having a low HLB value. In view of the fact that a water-soluble resin can be used, it is preferable to use a water-soluble resin as the binder resin.

  Among them, it is particularly preferable that the water-soluble resin has an alkyl chain which is a hydrophobic unit and has 8 to 36 carbon atoms. This is because the water-soluble resin having the hydrophobic unit can function as a compatibilizer for a surfactant having a low HLB value as described above, and the image quality during printing and the storage stability of the ink are further improved.

The alkyl group in the water-soluble resin skeleton may be linear or branched, but is preferably a linear one. Examples of the linear alkyl group include lauryl group (C12), myristyl group (C14), cetyl group (C16), stearyl group (C18), aralkyl group (C20), behenyl group (C22), lignoceryl group (C24), and serotoyl. Group (C26), a montanyl group (C
28), a merissyl group (C30), a dotriacontanoyl group (C32), a tetratriacontanoyl group (C34), a hexatriacontanoyl group (C36) and the like. The alkyl group preferably has 10 to 30 carbon atoms, and more preferably 18 to 24 carbon atoms.

  Examples of the type of the water-soluble resin having an alkyl chain include an acrylic resin, a styrene acrylic resin, a urethane resin, and a polyolefin resin. Above all, in consideration of the storage stability of the ink and the resistance of the printed matter, an acrylic or styrene-acrylic water-soluble resin is preferably used as in the case of the resin fine particles. In the present invention, a water-soluble resin synthesized by a known synthesis method may be used, or a commercially available product may be 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.

  When a water-soluble resin is used as the binder resin, the weight average molecular weight is preferably in the range of 5,000 to 50,000, more preferably 10,000 to 40,000. By setting the weight average molecular weight to 5,000 or more, the coating film resistance of the printed matter can be improved, and by setting the weight average molecular weight to 50,000 or less, the ejection stability from the inkjet head can be improved. Can be something.

  The weight average molecular weight of the binder resin can be measured by a conventional method. For example, using a TSKgel column (manufactured by Tosoh Corporation) and a GPC equipped with an RI detector (manufactured by Tosoh Corporation, HLC-8120GPC), a value measured as a polystyrene-equivalent weight average molecular weight measured using THF as a developing solvent. It is.

  When selecting a water-soluble resin, the acid value is also important, and the acid value is preferably from 1 to 80 mgKOH / g, more preferably from 5 to 50 mgKOH / g. By setting the acid value to 1 mgKOH / g or more, the ink can be dissolved again even after it has solidified, thereby suppressing clogging on the nozzles of the inkjet head and improving printing stability. Further, when the acid value is 80 mgKOH / g or less, a printed matter excellent in water resistance can be obtained, which is preferable.

  The amount of the water-soluble resin to be added is preferably 0.5% by weight or more and 10% by weight or less, more preferably 1% by weight or more and 8% by weight or less, further preferably 2% by weight or more and 6% by weight or less based on the total amount of the ink. . When the amount of the water-soluble resin added is 0.5% by weight or more, a surfactant having a low HLB value can be sufficiently compatibilized, and the storage stability of the ink can be improved. When the content is 10% by weight or less, the viscosity of the ink can be suppressed to a suitable range, and the ink can be excellent in ejection property.

<Pigment>
In the present invention, any of an inorganic pigment and an organic pigment can be used as the pigment. Examples of inorganic pigments include titanium oxide, zinc white, zinc sulfide, lead white, calcium carbonate, sedimentable barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, black iron oxide, cadmium red, Bengala, and molybdenum red. , Molybdate orange, chrome vermillion, graphite, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, victoria green, ultramarine, navy blue, cobalt blue, cerulean blue , Cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet.

  Examples of the organic pigment include an azo pigment, a phthalocyanine pigment, an anthraquinone pigment, a quinacridone pigment, an isoindolinone pigment, a quinophthalone pigment, a dye lake pigment, and a fluorescent pigment.

  Illustrating specifically with a color index, C.I. I. Pigment Blue 1, 2, 3, 15: 1, 15: 3, 15: 4, 15: 6, 16, 21, 22, 60, 64 and the like.

  Examples of the magenta pigment include 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, 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282, C.I. I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50 and the like.

  As the yellow pigment, 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 produced by a furnace method and a channel method. For example, these carbon blacks have a primary particle diameter of 11 to 40 nm, a specific surface area by a BET method of 50 to 400 m2 / g, a volatile content of 0.5 to 10% by weight, and a pH value of 2 to 10 or the like. Are preferred. As a commercially available product having such characteristics, for example, 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical), RAVE1255 (manufactured by Columbian Carbon), REGA330R, 400R, 660R, MOGUL L, ELFTEX415 (manufactured by Cabot) ), Nipex90T, Nipex150T, Nipex160IQ, Nipex170IQ, Nipex75, Printex85, Printex95, Printex90, Printex35, PrintexU (all manufactured by Evonik Degussa) and the like, and any of them can be preferably used.

  In addition to carbon black, examples of black pigments that can be used in the present invention include aniline black, luminogen black, and azomethine azo black. In addition, a black pigment can be used by using a plurality of chromatic pigments such as the above-mentioned cyan pigment, magenta pigment, yellow pigment, brown pigment and orange pigment described below.

  Pigments other than cyan, magenta, yellow and black 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.

  The content of the pigment in the present invention is preferably 0.1% by weight or more and 15% by weight or less, more preferably 0.5% by weight or more and 10% by weight or less, and more preferably 1% by weight or more based on the total amount of the ink. Particularly preferred is 8% by weight or less.

<Pigment dispersion resin>
In order to maintain the stability of the ink for a long period of time, the above-mentioned pigment is used by being dispersed in the ink. The method of dispersing the pigment includes a method of modifying the surface of the pigment by oxidation treatment or resin coating, and dispersing the pigment without a dispersant, and a method of dispersing using a surfactant or a resin as a dispersant. In the present invention, it is preferable to disperse the pigment by using a pigment dispersing resin in order to improve the gloss of the printed matter and to make the ink more excellent in storage stability and dischargeability.

  The type of the pigment-dispersed resin is not particularly limited, and examples thereof include acrylic, styrene-acrylic, maleic, styrene-maleic, urethane, ester, amide, and imide resins. Among them, it is preferable to use one or more resins selected from acrylic resins, styrene acrylic resins, urethane resins, and ester resins from the viewpoint of strengthening the adsorption of the pigment and stabilizing the pigment dispersion. . 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.

  Further, it is preferable to use a pigment dispersion resin having an alkyl group having 10 to 36 carbon atoms in the resin skeleton from the viewpoint of storage stability of the ink and the compatibility with a surfactant having a small HLB value. In addition, as a method of synthesizing a resin having an alkyl group, a method of condensing an alcohol or an amine having an alkyl group with a functional group such as a carboxylic acid of a basic resin skeleton or a monomer having an alkyl group at the time of resin synthesis is used To synthesize a resin having an alkyl group.

  The molecular weight of the pigment-dispersed resin is preferably such that the weight average molecular weight is in the range of 1,000 to 100,000, and more preferably in the range of 5,000 to 50,000. When the weight average molecular weight is in the above range, the pigment can be stably dispersed in water, and the ejection stability can be improved. The weight average molecular weight of the pigment-dispersed resin can be measured in the same manner as in the case of the binder resin.

  The acid value of the pigment dispersion resin is preferably 50 to 400 mgKOH / g. When the acid value is 50 mgKOH / g or more, the pigment-dispersed resin is easily dissolved in water, and the viscosity of the dispersion can be kept low. Further, when the concentration is 400 mgKOH / g or less, the interaction with the surfactant can be made favorable, and the increase in the viscosity of the ink can be prevented. The acid value of the pigment dispersion resin is preferably from 100 to 350 mgKOH / g, more preferably from 150 to 300 mgKOH / g.

  Further, in order to increase the solubility in water, it is preferable that the acid group in the resin is neutralized with a base. As the base, an organic base such as aqueous ammonia, dimethylaminoethanol, diethanolamine, and triethanolamine, and an inorganic base such as lithium hydroxide, sodium hydroxide, and potassium hydroxide can be used.

  The weight ratio of the pigment to the pigment-dispersed resin is preferably from 2/1 to 100/1. When the ratio of the pigment-dispersed resin is within the above range, the viscosity of the pigment dispersion or the ink can be kept low, and the dispersibility, the viscosity, the stability such as the dispersion, and the like are improved. The ratio of the pigment to the pigment-dispersed resin is more preferably from 20/9 to 50/1, still more preferably from 5/2 to 25/1, and most preferably from 20/7 to 20/1.

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

<Other ingredients>
Further, in addition to the above components, additives such as an antifoaming agent and a preservative can be appropriately added to the ink of the present invention, if necessary, in order to obtain an ink having desired physical properties. The amount of these additives is preferably from 0.01% by weight to 10% by weight based on the total weight of the ink.

<Recording medium>
The ink of the present embodiment can be particularly suitably used for a poorly absorbable substrate. The poorly absorbable substrate is a recording medium that hardly absorbs water or has a low absorption rate, and specifically, is measured by the Bristow method (J. TAPPI paper pulp test method No. 51-87). , Having an absorption coefficient of 0 to 0.6 ml / m ² msec ^1/2 . The above absorption coefficient can be measured by using, for example, an automatic scanning liquid absorption meter manufactured by Kumagai Riki Kogyo Co., Ltd. Specifically, using the above-mentioned apparatus and water, a relationship diagram between a liquid absorption amount (ml / m ² ) obtained during a contact time of 100 to 1000 milliseconds and a square root of the contact time (msec ^1/2 ). Therefore, the gradient of the straight line obtained by the least square method is used as the absorption coefficient.

  Specific examples of the poorly-absorbable substrate include, for example, paper substrates such as coated paper, art paper, cast paper, finely coated paper, and synthetic paper; polycarbonate, hard PVC, soft PVC, polystyrene, foamed styrene, PMMA, and polypropylene. Plastic substrates such as polyethylene, PET, etc .; metal substrates such as aluminum and stainless steel; glass; and the like, but are not limited thereto. In addition, the inkjet ink of this embodiment can be suitably used for non-absorbent substrates such as plain paper, cloth, and wood.

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

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

<Production Example of Cyan Pigment Dispersion 1>
20 parts of LIONOGEN BLUE FG-7358G (CI Pigment Blue 15: 3, manufactured by Toyo Color) as a pigment, and styrene acrylic resin (styrene: acrylic acid: behenyl methacrylate = 35: 30: 35 (weight ratio)) as a pigment dispersion resin 15 parts of an aqueous solution of a random polymer (molecular weight: 16000, acid value: 250) (nonvolatile content: 20%) and 65 parts of water were mixed and predispersed by a disper, and then 1800 g of zirconia beads having a diameter of 0.5 mm was prepared. This dispersion was carried out using a 0.6 L Dynomill filled with, and a cyan pigment dispersion 1 was obtained.

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

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

<Production Example of Black Pigment Dispersion 4>
A black pigment dispersion 4 was obtained in the same manner as for the cyan pigment dispersion except that the pigment was changed to Print X85 (carbon black, manufactured by Orion Engineered Carbons).

<Production example of water-soluble resin 1>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 93.4 parts of butanol and replaced with nitrogen gas. The reaction vessel was heated to 110 ° C., and a mixture of 20 parts of styrene as a polymerizable monomer, 10 parts of methacrylic acid, 70 parts of methyl methacrylate, and 9 parts of V-601 (manufactured by Wako Pure Chemical Industries) as a polymerization initiator was applied for 2 hours. Then, a polymerization reaction was performed. After the completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, and then 0.9 parts of V-601 (manufactured by Wako Pure Chemical Industries, Ltd.) was added. . The weight average molecular weight of the pigment-dispersed resin was about 12,000.
After cooling to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization, and then 100 parts of water was added to make the mixture aqueous. Thereafter, the mixture is heated to 100 ° C. or higher, butanol is azeotropically distilled with water, and then the butanol is distilled off. Then, the solid content is adjusted to 50%. ) Got.

<Production examples of water-soluble resins 2 to 4>
An aqueous solution (solid content of 50%) of the water-soluble resins 2 to 4 was obtained by using the same synthesis method as the water-soluble resin 1 except that the materials and amounts shown in Table 1 were used as the polymerizable monomers. Was.

Table 1

<Synthesis of acetylenic diol surfactant>
Utilizing the method described in JP-A-2002-356451, Example 1, and using methyl isoamyl ketone as a raw material ketone, 2,5,8,11-tetramethyl-6-dodecine-5,8-diol Was synthesized. The compound has an HLB value of 2.7. Similarly, by using di-n-propyl ketone (4-heptanone) as a raw material ketone, 4,7-dipropyl-dec-5-yne-4,7-diol (HLB value = 2.7) was obtained. By using methylhexyl ketone (2-octanone), 7,10-dimethylhexadec-8-in-7,10-diol (HLB value = 2.4) is converted to 2,2 by using methyl isobutyl ketone. 4,7,9-Tetramethyl-5-decyne-4,7-diol (HLB value = 3.0) was synthesized.

  In the examples, commercially available Surfynol 440 (manufactured by Air Products, HLB value = 8.0) and Surfynol 465 (manufactured by Air Products, HLB value = 13.0) are also acetylenic diol-based surfactants. Used as

<Synthesis example of polysiloxane-based surfactant 1>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 360 g of ethylene glycol allyl methyl ether and 0.5 g of a 0.5% by weight toluene solution of chloroplatinic acid, and the atmosphere was replaced with nitrogen gas. After the inside of the reaction vessel was heated to 70 ° C., 480 g of hexadecamethyloctasiloxane in which both ends of the siloxane chain were hydrogen atoms were added dropwise over 30 minutes. Next, the above-described material was reacted by heating the inside of the reaction vessel to 110 ° C. and holding the mixture for 3 hours while stirring. After the completion of the reaction, polyether-modified siloxane 1 was obtained by distilling off low boiling components under reduced pressure. The polyether-modified siloxane 1 is represented by the structure of the general formula (4), where r = 6, and R ₁ is m = 3, n = 1, o = 0, R _{3 in the} general formula (3). = CH ₃ . The HLB value of the compound is 3.8.

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

<Synthesis example of polysiloxane-based surfactant 3>
A polysiloxane was used except that 500 g of diethylene glycol allyl methyl ether was used in place of ethylene glycol allyl methyl ether, and 180 g of hexamethyltrisiloxane in which both ends of the siloxane chain were hydrogen atoms were used instead of hexadecamethyloctasiloxane. Polysiloxane-based surfactant 3 was obtained in the same manner as for surfactant-based surfactant 1. The polyether-modified siloxane 3 is represented by the structure of the general formula (4), where r = 1, and R ₁ is m = 3, n = 2, o = 0, R _{3 in the} general formula (3). = CH ₃ . The HLB value of the compound is 19.5.

  In the examples, Tegowet 280 (manufactured by Evonik Degussa, HLB value = 3.5), Tegoglide 440 (manufactured by Evonik Degussa, HLB value = 13.5) and BYK-333 (manufactured by BYK Chemie, HLB value = 10.1) was also used as a polysiloxane-based surfactant.

<Examples of manufacturing inks 1C, 1M, 1Y, and 1K>
20 parts of cyan pigment dispersion 1, 25 parts of 1,2-butanediol, and 1 part of 2,5,8,11-tetramethyl-6-dodecine-5,8-diol were sequentially charged into a mixing vessel, Water was added to adjust the total amount of the ink to 100 parts, and the mixture was stirred with a disper until the ink became sufficiently uniform. Thereafter, the mixture was filtered with a membrane filter having a pore size of 1 μm to remove coarse particles that might cause clogging of the head, thereby producing ink 1C.
The inks 1Y, 1M, and 1K were prepared in the same manner as the ink 1C except that the yellow pigment dispersion 2, the magenta pigment dispersion 3, and the black pigment dispersion 4 were used instead of the cyan pigment dispersion 1, respectively. Produced.

<Production Examples of Inks 2 to 49>
Inks 2 to 49 (4 colors of C, Y, M, and K, respectively) were produced in the same manner as in Production Example of Ink 1C using the raw materials described in Tables 2 to 4.

<Examples 1 to 45, Comparative Examples 1 to 4>
The following evaluation was performed using the produced inks 1 to 49. The evaluation results are as shown in Tables 2 to 4.

<Evaluation 1: Evaluation of blank area in solid portion>
Using a Kyocera head (QA06NTB) equipped with an inkjet ejector, the above-described cyan ink of 1C to 49C was ejected under a printing condition of a frequency of 20 kHz and 600 × 600 dpi, and solid printing at a printing rate of 100% was performed. In addition, UPM Finess Gloss paper (coated paper) was used as a printing base material. After printing, the printed matter was dried using a 50 ° C. air oven for 3 minutes, and the degree of white spots on the printed matter was visually checked with a loupe to evaluate white spots. The evaluation criteria are as follows, and the evaluations of △, △, and Δ are the practically usable areas.
◎: No white spots were observed with the loupe and visually ○: Slight white spots were seen with the loupe, but no white spots were visually observed Δ: Slight white spots were visually observed ×: Clear white spots were seen visually

<Evaluation 2: Evaluation of bleeding between colors>
An inkjet discharge device was prepared in which four heads (QA06NTB) manufactured by Kyocera were arranged side by side in the transport direction of the printing substrate, and cyan, magenta, yellow, and black inks were filled from the upstream side. Subsequently, the same printing substrate as in Evaluation 1 was prepared, and passed under the head at a constant speed. At that time, ink was ejected from each head under a printing condition of a frequency of 20 kHz and 600 × 600 dpi, and 100% solid patches of 1 cm × 1 cm were printed so that each color was adjacent. After printing, the printed matter was dried using a 50 ° C. air oven for 3 minutes, and the degree of blurring between the solid colors was visually checked with a loupe and visually to evaluate the border blurring. The evaluation criteria are as follows, and the evaluations of △, △, and Δ are the practically usable areas.
：: No border bleeding was observed between the loupe and the eye. ×: Boundary between colors was clearly observed visually

<Evaluation 3: Evaluation of uneven aggregation>
Using the same printing substrate and printing conditions as in Evaluation 1, a gradation pattern was printed for each color of cyan, magenta, yellow, and black from 10% to 100% in 10% increments. After printing, the printed matter is dried for 3 minutes using a 50 ° C. air oven, and the degree of agglomeration unevenness of a printed portion having a printing ratio of 20%, 50%, or 80% is visually confirmed with a loupe and visually evaluated. went. The evaluation criteria are as follows, and the evaluations of △, △, and Δ are the practically usable areas. Tables 2 to 4 show only the result of the worst color among the four colors evaluated.
：: No agglomeration unevenness was observed with the loupe and visually at any of the printing rates of 20, 50, and 80%. ：: Aggregation was observed with the loupe at any one or more of the printing rates of 20, 50, and 80%. Unevenness was observed, but not visually observed. Δ: Slight aggregation unevenness was visually observed at any one or more of the printing rates of 20, 50, and 80%. X: Printing rate of 20, 50, In any one or more of 80%, uneven coagulation was clearly observed visually.

<Evaluation 4: Evaluation of ejection property>
Solid printing was performed at a printing rate of 100% for each color of cyan, magenta, yellow, and black under the same printing substrate and printing conditions as in Evaluation 1. After printing, the inkjet discharge device was allowed to stand by for a certain period of time in an environment of 25 ° C., and then solid printing was performed again at a printing rate of 100% with the same printing base material and printing conditions. At that time, the dischargeability was evaluated by visually and loupe-checking whether the solid starting portion was printed. The evaluation criteria are as follows, and the evaluations of △, △, and Δ are the practically usable areas. Tables 2 to 4 show only the result of the worst color among the four colors evaluated.
：: No chipping was observed at the start of printing even after printing after waiting for 3 hours. ：: When printing after waiting for 3 hours, chipping was observed at the start of printing but waited for 2 hours. Occasionally, no chipping was observed. Δ: When printing after waiting for 2 hours, chipping was observed at the start of printing. However, no chipping was observed when waiting for 2 hours. ×: Printing after waiting for 1 hour. But there was a chip in the starting part

<Evaluation 5: Evaluation of dryness>
Using the same ejection device, printing substrate, and printing conditions as in Evaluation 2, the printing ratios of cyan, magenta, and yellow were each multiplied by 100% solid to print a solid printing ratio of 300%. After heating using a 50 ° C. air oven for a predetermined time, the dryness of the printed matter was evaluated by touching the printed matter with a finger. The evaluation criteria are as follows, and the evaluations of △, △, and Δ are the practically usable areas.
：: One minute after the oven was put, the ink did not adhere even when touched with a finger. ：: One minute after the oven was put, the ink adhered to the finger, but two minutes later, the ink did not adhere. The ink adhered to the finger after 2 minutes, but did not adhere after 3 minutes. ×: The ink adhered to the finger even after 3 minutes from turning on the oven.

<Evaluation 6: Evaluation of storage stability of ink>
The viscosity of each of the inks 1 to 49 was measured using an E-type viscometer (TVE-20L, manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. and 50 rpm. This ink was placed in a closed container, stored in a constant temperature oven at 70 ° C., and accelerated with time. Then, the viscosity was measured again using the above apparatus, and the change in the viscosity of the ink before and after the aging was calculated. The storage stability was evaluated. The criteria are as follows, and 、, △, and △ evaluations are practically usable areas. Tables 2 to 4 show only the result of the worst color among the four colors evaluated.
◎: Change in viscosity after storage for 4 weeks is less than ± 5% ：: Change in viscosity after storage for 2 weeks is less than ± 5% △: Change in viscosity after storage for 1 week is less than ± 5% ×: Storage for 1 week ± 5% or more change in viscosity after

<Evaluation results of Examples and Comparative Examples>
Comparative Example 1 was a system in which the content of a water-soluble organic solvent having an HLB value of 8 or less was less than 10% by weight, and acetylene diol-based surfactant (a1) having an HLB value of 3 or less was 2,5. By using, 8,11-tetramethyl-6-dodecine-5,8-diol, solid white spots and uneven cohesion of printed matter were in a practically usable range. Had bad results. This is probably because the content of 1,2-butanediol, a solvent having an HLB value of 8 or less, was small, and the compatibility of the surfactant with the ink was insufficient.

  On the other hand, in Comparative Example 2, instead of using an acetylene diol-based surfactant (a1) having an HLB value of 3 or less, a polysiloxane-based surfactant (a2) having an HLB value of 4 or less, and an HLB value of 8 to This is a system using a polysiloxane surfactant (a3) of No. 20, and uneven coagulation was observed in printed matter. Further, Comparative Examples 3 and 4 are systems using an acetylene diol-based surfactant having an HLB value larger than 3, and blurred color boundaries, uneven coagulation, and white spots on solid portions were observed in printed matter.

  In Examples 1 to 43, an acetylenic diol-based surfactant (a1) containing a water-soluble organic solvent having an HLB value of 8 or less based on the total amount of the aqueous inkjet ink and containing an HLB value of 3 or less was used. , And all of the white areas, blurred color boundaries, uneven cohesion, and ink dischargeability, drying properties, and storage stability of the printed matter were practically usable. Among them, Examples 39, 40, 42, 43, and 44 are, as surfactants, polysiloxane-based surfactants (a2) having an HLB value of 4 or less, and polysiloxane-based surfactants having an HLB value of 8 to 20. It is a system that uses a surfactant (a3) in combination and contains a water-soluble resin having an alkyl chain having 8 to 36 carbon atoms, and it was confirmed that very excellent evaluation results were obtained in all evaluation items. .

  The aqueous ink-jet ink of the present invention and the method for producing printed matter are capable of obtaining a high-quality image even on a poorly-absorbing substrate such as coated paper. In inkjet printing with high recording resolution, it can be suitably used.

Claims (9)

An aqueous inkjet ink containing at least a pigment, a pigment dispersion resin, a binder resin, a water-soluble organic solvent, and a surfactant (A),
The binder resin is a water-soluble resin having an acid value of 1 to 80 mgKOH / g,
A water-soluble organic solvent having an HLB value of 8 or less as a water-soluble organic solvent based on the total amount of the water-based inkjet ink, which has an HLB value of 8 or less;
The surfactant (A) contains an acetylenic diol-based surfactant (a1) having an HLB value of 3 or less by a Griffin method ,
A water-based inkjet ink characterized in that the content of the acetylene diol-based surfactant (a1) having an HLB value of 3 or less is 0.5 to 5.0% by weight based on the total amount of the water- based inkjet ink.   The aqueous inkjet ink according to claim 1, wherein the surfactant (A) further contains a polysiloxane-based surfactant (a2) having an HLB value of 4 or less according to a Griffin method.   3. The aqueous inkjet ink according to claim 1, wherein the surfactant (A) further contains a polysiloxane-based surfactant (a3) having an HLB value of 8 to 20 by a Griffin method.   The ratio of the content of the polysiloxane surfactant (a2) having the HLB value of 4 or less to the content of the acetylene diol surfactant (a1) having the HLB value of 3 or less is 0.2. : 1.0 to 3.3: 1.0.   The ratio of the content of the polysiloxane-based surfactant (a3) having an HLB value of 8 or more to 20 or less and the content of the acetylene diol-based surfactant (a1) having an HLB value of 3 or less is 0. The aqueous inkjet ink according to claim 3, wherein the ratio is 1: 1.0 to 2.0: 1.0. The aqueous inkjet ink according to any one of claims 1 to 5 , wherein the water-soluble organic solvent having an HLB value of 8 or less contains a polyol solvent. The aqueous inkjet ink according to any one of claims 1 to 6 , wherein the water-soluble resin has an alkyl chain having 8 to 36 carbon atoms. The aqueous inkjet ink according to any one of claims 1 to 7 , wherein the content of the water-soluble resin is 0.5 to 10% by weight based on the total amount of the aqueous inkjet ink. A printed matter obtained by printing the aqueous inkjet ink according to any one of claims 1 to 8 on a substrate.