JP2017165982A - Aqueous inkjet ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous inkjet ink capable of forming a high quality printed matter without whitening due to lack of wettability of the ink and color boundary bleeding or aggregation unevenness due to coalescence of ink drops with different color tones on a printing substrate such as hardly absorptive substrate and excellent in storage stability or discharging property from an inkjet nozzle.SOLUTION: There is provided an aqueous inkjet ink containing at least a pigment, a water soluble organic solvent and a surfactant (A), the water soluble organic solvent having HLB value by a Griffin method of 8 or less of 10 to 50 wt.% based on total amount of the aqueous inkjet ink as the water soluble organic solvent and the surfactant (A) contains an acetylenediol-based surfactant having HLB value by the Griffin method (a1) of 3 or less.SELECTED DRAWING: None

Description

  The present invention has no white spots due to insufficient wettability of ink on a printing substrate such as a hardly absorbable substrate, and no blurring or aggregation of color boundaries due to coalescence of ink droplets having different hues. The present invention relates to a water-based inkjet ink that can produce a high-quality printed matter and that has excellent storage stability and dischargeability from an inkjet nozzle.

  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. In particular, the ink jet recording method is a method in which ink droplets are directly ejected and adhered to a recording member from very fine nozzles to obtain characters and images. According to this method, there is an advantage that the noise of the apparatus to be used is small, operability and colorization are easy, and the paper base can be used as a recording member. Is widely used.

  In addition, the improvement of inkjet technology is expected to be used as an output device for digital printing in industrial applications, and devices for printing solvent inks and UV inks on plastic substrates 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 environmental and human hazards, and demand for water-based inks is increasing instead.

  As ink-jet water-based inks, as disclosed in Patent Documents 1, 2, and 3, special paper such as plain paper and photographic glossy paper has been developed for a long time. On the other hand, in recent years, the application of the ink jet recording method is expected to be expanded, and the need for direct printing on hardly absorbable substrates such as art paper, coated paper, and fine coated paper is increasing.

  However, water, which is the main solvent for water-based inks, has high surface tension, so it is difficult to spread and penetrate into the above difficult-to-absorbent substrate, and it is difficult to penetrate into the substrate. When printing on, white spots caused by insufficient wetting spread, and bleeding and aggregation unevenness in the color boundary caused by undried ink droplets with different hues coalesce occur, It led to a drop in image quality.

  In general, a surfactant is used to improve wettability. For example, Patent Document 4 discloses an ink that uses polyoxyethylene alkyl ether as a surfactant to suppress image defects such as feathering and improve image quality, and also suppresses deterioration in ejection characteristics from an inkjet nozzle. It is disclosed. Certainly, according to this method, although a feathering suppression effect is seen for a highly water-absorbing substrate such as XEROX 4200 paper used in Patent Document 4, it is a problem in the present invention. For a hard-to-absorb base material such as coated paper, white spots, color boundary bleeding and aggregation unevenness cannot be suppressed. This is considered to be because the surfactant cannot sufficiently wet and spread the ink, and the ink droplets are likely to coalesce due to insufficient drying properties.

  As described above, conventionally, it is possible to produce a high-quality printed material that is free of white spots, color boundary blurring, and unevenness of aggregation, particularly with respect to a hardly absorbable base material, and is excellent in water dischargeability from an inkjet nozzle. Inkjet ink was not present.

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

  The present invention has been made to solve the above-mentioned problems, and its purpose is to have white spots caused by insufficient wettability of ink and different hues on a printing substrate such as a hardly absorbent substrate. Providing water-based inkjet inks that are capable of producing high-quality prints that are free from blurring and coagulation unevenness due to ink droplet coalescence, and that are excellent in storage stability and ejectability from inkjet nozzles. There is.

  The inventors of the present invention have made extensive studies to solve the above-mentioned problems, found that an organic solvent having a specific HLB value and a surfactant are used in combination, and have completed the present invention.

  That is, the present invention is a water-based inkjet ink containing at least a pigment, a water-soluble organic solvent, and a surfactant (A), wherein the water-soluble organic solvent has an HLB value of 8 or less by the Griffin method as the water-soluble organic solvent. The solvent is contained in an amount of 10 to 50% by weight based on the total amount of the water-based inkjet ink, and the surfactant (A) contains an acetylenic diol surfactant (a1) having an HLB value of 3 or less according to the Griffin method. The present invention relates to an aqueous inkjet ink.

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

  Further, in the present invention, the surfactant (A) further contains a polysiloxane surfactant (a3) having an HLB value of 8 to 20 according to the Griffin method. About.

  Further, the present invention is characterized in that the content of the acetylenic diol surfactant (a1) having an HLB value of 3 or less is 0.5 to 5.0% by weight with respect to the total amount of the water-based inkjet ink. The present invention relates to the aqueous inkjet ink described above.

  Moreover, this invention is ratio of content of the polysiloxane type surfactant (a2) whose said HLB value is 4 or less, and content of the acetylene diol type surfactant (a1) whose said HLB value is 3 or less. Is 0.2: 1.0 to 3.3: 1.0, and relates to the water-based inkjet ink described above.

  Further, the present invention provides a content of the polysiloxane surfactant (a3) having the HLB value of 8 or more and 20 or less, and a content of the acetylenediol surfactant (a1) having the HLB value of 3 or less. The ratio is 0.1: 1.0 to 2.0: 1.0.

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

  The present invention further relates to the aqueous inkjet ink as described above, further comprising a water-soluble resin having an alkyl chain having 8 to 36 carbon atoms.

  The present invention also relates to the aqueous inkjet ink as described above, 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 printing substrates such as hardly absorbable substrates, there are no white spots due to insufficient wettability of ink and unevenness in color boundaries due to coalescence of ink droplets having different hues. In addition, it is possible to provide a water-based inkjet ink that can produce a high-quality printed matter and that is excellent in storage stability and ejectability from an inkjet nozzle.

  Hereinafter, preferred embodiments of the inkjet ink of the present invention (hereinafter also simply referred to as “ink”) will be described 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, “part” and “%” represent “part by weight” and “% by weight”.

  As explained in the prior art, water, which is the main solvent of water-based ink, has a high surface tension and has a characteristic that it is difficult to spread on the base material, resulting in deterioration in image quality such as white spots, blurring of color boundaries and uneven aggregation. Cause. In order to improve image quality, it is effective to reduce the surface tension of the ink. Generally, surfactants and hydrophobic water-soluble solvents are added to the ink to reduce the surface tension. Yes. However, merely reducing the surface tension causes the ink droplets that have spread out to coalesce to each other, so that bleeding and aggregation unevenness occur at the color boundary, which does not lead to improvement in image quality. In addition, if the above materials are used excessively, other problems such as aggregation of the pigment in the ink leading to a decrease in storage stability, or deterioration of the ejection performance due to the ink overflowing from the inkjet nozzles. It will occur.

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

  One feature of the present invention is to use an acetylenic diol surfactant (a1) having an HLB value of 3 or less according to the Griffin method. The HLB value is an index representing the hydrophilicity / hydrophobicity of the material. The acetylenic diol surfactant (a1) having a particularly small HLB value can be used in an extremely small time of several tens of microseconds or less after landing on the recording medium. It is considered that the liquid crystal is oriented on the surface of the droplets, remarkably improves the wettability of the ink, and suppresses coalescence of the droplets immediately after landing. In addition, it is considered that the surface area of the ink droplets increases rapidly by spreading the ink droplets and that the efficiency of drying and penetration into the base material is improved, thereby contributing to the suppression of the coalescence of the ink droplets.

  On the other hand, when a material having a small HLB, that is, a strong hydrophobic property is used for water-based ink as described above, problems such as separation over time and deterioration in storage stability due to influence on other materials arise. 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 problems. By using a water-soluble organic solvent that is moderately hydrophobic, the acetylenic diol surfactant (a1) is compatible with the ink and can be stably present without separation, and to other materials. It is thought that the storage stability and dischargeability are improved as a result.

  As described above, in order to obtain an ink that is capable of producing a high-quality printed matter that is free from white spots, blurs in color boundaries, and has no aggregation unevenness, and has a specific HLB value, the ink has excellent storage stability and ejection properties. It is essential to use an organic solvent and a surfactant in combination. In addition, said mechanism is inference and does not limit this invention at all.

  The main components of this embodiment will be described below.

<Acetylene diol-based surfactant (a1)>
As described above, one feature of the present invention is to use the acetylenic diol surfactant (a1) having an HLB value of 3 or less according to the Griffin method. A preferable 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 orientation speed to the ink droplet surface, thereby improving wettability and suppressing droplet coalescence. It is considered possible. Further, when used in combination with a water-soluble organic solvent having an HLB value of 8 or less, it is possible to maintain ink storage stability and ejection properties at suitable levels.

The HLB (Hydrophile-Lipophile Balance) value is one of the parameters representing 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.

  In general, the Griffin method is used in nonionic materials and is known to express the degree of hydrophilicity / hydrophobicity, and 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 higher the HLB value, the higher the hydrophilicity of the material.

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

  The addition amount of the acetylenic diol 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. If it is 0.5% by weight or more, the function as a surfactant can be fully expressed, and if it is 5.0% by weight or less, the storage stability and ejection property of the ink are maintained at suitable levels. It becomes possible to do.

  Specific examples of the acetylenic diol surfactant (a1) having an HLB value of 3 or less that can be used in the present invention include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, , 5,8,11-tetramethyl-6-dodecin-5,8-diol, hexadec-8-in-7,10-diol, 4,7-dipropyl-dec-5-in-4,7-diol, 6,9-dimethyl-tetradec-7-in-6,9-diol, 3,6-diisopropyl-2,7-dimethyloct-4-yne-3,6-diol, octadec-9-in-8,11 -Diol, 7,10-dimethylhexadec-8-in-7,10-diol, 5,8-dibutyldodec-6-in-5,8-diol, 4,7-diisobutyl-2,9-dimethyl- Deca-5 Down-4,7-diol, 5,14- diethyl-8,11-dimethyl-oct dec-9-in-8,11-diol, and the like. Among these, 2,5,8,11-tetramethyl-6-dodecine-5,8-diol, hexadec-8-in-7,10-diol, and 6,9-dimethyl are preferred from the viewpoint of compatibility with water-based inks. It is preferable to use -tetradec-7-in-6,9-diol. In addition, said compound may use only 1 type and may use 2 or more types together. Moreover, what was synthesize | combined by the well-known synthesis | combining method may be used for said compound, and a commercial item may be used for it.

<Polysiloxane surfactant>
In the present invention, it is preferable to use a polysiloxane surfactant in combination with the acetylenic diol surfactant (a1) having an HLB value of 3 or less. In general, polysiloxane surfactants are preferred because they have a slower orientation rate on the liquid surface than acetylenic diol surfactants, and can further improve color boundary bleeding and aggregation unevenness. In addition, by using a polysiloxane surfactant, water repellency and friction resistance can be imparted to the printed matter, and the surface tension and dischargeability of the ink can be controlled.

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

  The polysiloxane surfactant (a2) having an HLB value of 4 or less has a fast orientation in ink among the polysiloxane surfactants and is excellent in surface tension reducing ability. Has the effect of improving. On the other hand, the polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less is an acetylenic diol 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 droplet coalescence suppressing effect. From the 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 surfactant suitably used in the present invention is a compound represented by the following general formula (2) or general formula (4).

General formula (2):

In 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 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 represented by an integer of 1 or more. R ₃ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a (meth) acryl group.

General formula (4):

In general formula (4), r shows the integer of 1-80. R ₁ is represented by the general formula (3).

  The compound represented by the general formula (2) greatly contributes to the adjustment of the surface tension, wettability, and dischargeability of the ink. In addition, the compound represented by the general formula (4) has an effect of increasing the coalescence restraint between ink droplets on the substrate and the storage stability (surface tension stability) of the ink. In the present invention, the above materials can be appropriately selected and used in consideration of the HLB value.

  As the polysiloxane surfactants represented by the general formulas (2) and (4), those synthesized by a known synthesis method may be used, or commercially available products may be used. Examples of commercially available compounds represented by the general formula (2) include SF8428, FZ-2162, 8032ADDITIVE, SH3749, FZ-77, L-7001, L-7002, and FZ-2104 manufactured by Toray Dow Corning. FZ-2110, F-2123, SH8400, SH3773M; BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 manufactured by BYK-Chemie Corporation; 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 of Nisshin Chemical Industry, etc. But It is below.

  Moreover, as an example of a commercial item of the compound represented by the general formula (4), BY16-201, SF8427 manufactured by Toray Dow Corning, BYK-331, BYK-333, BYK-UV3500 manufactured by BYK Chemie, Inc., Evonik Degussa Examples thereof include Tegoglide 410, Tegoglide 432, Tegoglide 435, Tegoglide 440, Tegoglide 450, and the like.

<Polysiloxane surfactant (a2) having an HLB value of 4 or less>
As described above, the polysiloxane surfactant (a2) having an HLB value of 4 or less mainly contributes to the wettability of the ink, and the HLB value is 2.0 or more and 3.8 or less. Preferably, 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 0.8% by weight or less with respect to the total weight of the ink. 5% by weight or more and 3.0% by weight or less, more preferably 1.0% by weight or more and 2.5% by weight or less. By keeping the content in the above range, it is possible to obtain an ink having excellent wettability with respect to the base material and excellent in dischargeability and storage stability.

  The ratio of the content of the polysiloxane surfactant (a2) having an HLB value of 4 or less when the content of the acetylenic diol surfactant (a1) having an HLB value of 3 or less is 1. 0.2 to 3.3 is preferable, 0.4 to 2.5 is more preferable, and 0.5 to 1.5 is particularly preferable. In general, when a plurality of surfactants are used in combination, it is considered that the compatibility of each surfactant in the water-based ink is changed. By keeping the content ratio within the above range, the phase of each surfactant is changed. It is considered that the solubility is suitable.

  Since the polysiloxane surfactant (a2) having an HLB value of 4 or less according to the present invention 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. It is particularly preferable 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 the substrate, and the HLB value thereof is 10 or more. More preferably, it is 18 or less, More preferably, it is 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, based on the total weight of the ink. % By weight or more and 0.8% by weight or less, more preferably 0.2% by weight or more and 0.7% by weight or less. By keeping the content within the above range, it is possible to obtain an ink that is less likely to cause coalescence of ink droplets on the substrate and that is excellent in storage stability and dischargeability.

  The ratio of the content of the polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less when the content of the acetylenic diol surfactant (a1) having an HLB value of 3 or less is 1. Is preferably 0.1 to 2.0, more preferably 0.15 to 1.5, and still more preferably 0.2 to 1.0. It is considered that the compatibility of each surfactant becomes suitable when the content ratio falls within the above range.

  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 coalescence suppression of ink droplets on a substrate as described above, and is represented by the general formula (4 It is particularly preferred to have a structure represented by

<Other surfactants>
In the present invention, surfactants other than those described above can be used as long as the above effects are not impaired. Various surfactants are known depending on the application, but the surface tension of the ink is maintained at a suitable level to ensure wettability and ejection properties, and stably coexist with hydrophilic materials. In view of the capability, acetylene-based, glycol ether-based, 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 the 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. The water-soluble organic solvent having an HLB value of 8 or less is considered to have a function of compatibilizing a surfactant having a small HLB value in water. Therefore, it is preferable to use a material having a small HLB value within the range not impairing 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.

  The boiling point of the water-soluble organic solvent is preferably in the range of 180 ° C. or higher and 250 ° C. or lower at 1 atmosphere, and more preferably contains a water-soluble organic solvent that is 180 ° C. or higher and 230 ° C. or lower. 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, ink ejection stability is improved. Further, by setting the boiling point to 250 ° C. or less, it is possible to maintain drying on the printing substrate at a suitable level, and to further suppress deterioration in image quality such as color boundary bleeding and aggregation unevenness.

Specific examples of water-soluble organic solvents 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 solvents such as 1,5-pentanediol, 1,2-hexanediol, 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, tripropylene glycol monobutyl ether;
Examples include propylene glycol diether solvents such as propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, and tripropylene glycol dimethyl ether; methoxybutanol solvents such as 3-methoxy-1-butanol and 3-methoxy-3-methylbutanol. Among these, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3, which are solvents having a boiling point of 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- Particularly 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 Preferably used.

  In the present invention, it is particularly preferable to select a polyol solvent among the solvents preferably used exemplified above. An ink using a polyol solvent having an HLB value of 8 or less is particularly excellent in storage stability and ejection performance as compared with the case of using another water-soluble organic solvent having an HLB value of 8 or less. As expected, polyol solvents have multiple hydroxyl groups, and form 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 of the surfactant and water is further enhanced.

  Furthermore, it is most preferable to use 1,2-alkanediol as the polyol solvent. 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, while reducing the surface tension of the ink to a suitable range. It is considered that a printed matter having improved image wettability and excellent image quality can be obtained. Among the compounds exemplified above, 1,2-butanediol, 1,2-pentanediol and 1,2-hexanediol are listed as 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 to 50% by weight, preferably 15 to 40% by weight, based on the total amount of the ink. More preferably, it is 20 to 30 weight%. By setting it as 10 weight% or more, surfactant with a small HLB value can fully be compatibilized, and storage stability and discharge property can be ensured. Moreover, it is preferable for it to be 50% by weight or less because the ink viscosity can be kept within a suitable range and the discharge properties can be made favorable.

  Further, the water-soluble organic solvent having an HLB value of 8 or less is a material for compatibilizing the acetylenic diol 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 acetylenic diol surfactant (a1) having an HLB value of 3 or less is 1. More preferably, it is 10-70, and it is especially preferable that it is 15-40. By keeping the content ratio of both in the above range, the acetylenic diol surfactant (a1) having an HLB value of 3 or less can be suitably dissolved in the ink.

  In addition, if it is the range of suitable content of the grade which does not become small, the water-soluble organic solvent other than the above can be used alone or in combination. 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 and the like, but are not limited thereto.

<Water-soluble resin>
In this invention, it is preferable to add binder resin from the point which improves the coating-film resistance of printed matter. In general, water-soluble resins and resin fine particles are known as binder resins used in inkjet inks. Among these, 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 resin in the ink. Suitable for enhancing. Examples of the resin used as the resin fine particles include acrylic, styrene acrylic, urethane, styrene butadiene, vinyl chloride, and polyolefin. Among these, acrylic 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 fine particles having a low MFT are used, the MFT of the resin fine particles is further lowered by the water-soluble organic solvent added to the ink, and the resin fine particles cause fusion and aggregation even at room temperature. Clogging may occur. In the case of resin fine particles, once the film is formed, it is not re-dissolved in the ink, so that the ejectability 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 is set to 60 ° C. or higher by adjusting the monomer 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, since the resin itself is soluble, clogging at the ink jet head nozzle hardly occurs, and the discharge property is excellent. By selecting a constituent material, the resin can function as a compatibilizer for a surfactant having a low HLB value. In view of the point that can be achieved, it is preferable to use a water-soluble resin as the binder resin.

  Especially, it is especially preferable that the water-soluble resin has an alkyl chain that 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 ink are further improved.

The alkyl group in the water-soluble resin skeleton may be linear or branched, but is preferably linear. Linear alkyl groups include lauryl group (C12), myristyl group (C14), cetyl group (C16), stearyl group (C18), aralkyl group (C20), behenyl group (C22), lignoceryl group (C24), serotoyl Group (C26), Montanyl group (C
28), melicyl group (C30), dotriacontanoyl group (C32), tetratriacontanoyl group (C34), hexatriacontanoyl group (C36) and the like. Moreover, as carbon number of an alkyl group, Preferably it is C10-30, More preferably, it is C18-24.

  Examples of the water-soluble resin having an alkyl chain include acrylic, styrene acrylic, urethane, and polyolefin. Among these, considering the storage stability of the ink and the durability of the printed matter, acrylic and styrene acrylic water-soluble resins are 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 or more and 50,000 or less, and more preferably in the range of 10,000 or more and 40,000 or less. When the weight average molecular weight is 5,000 or more, the coating film resistance of the printed matter can be improved, and when the weight average molecular weight is 50,000 or less, the ejection stability from the inkjet head is good. Can be anything.

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

  In selecting a water-soluble resin, the acid value is also important, and the acid value is preferably 1 to 80 mgKOH / g, more preferably 5 to 50 mgKOH / g. By setting the acid value to 1 mgKOH / g or more, the ink can be dissolved again even after the ink has solidified, clogging on the inkjet head nozzle is suppressed, and the printing stability is improved. An acid value of 80 mgKOH / g or less is preferable because a printed matter having excellent water resistance can be obtained.

  The addition amount of the water-soluble resin 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, and further preferably 2% by weight or more and 6% by weight or less with respect to the total amount of the ink. . If 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. Moreover, if it is 10 weight% or less, while being able to suppress an ink viscosity in a suitable range, it can be set as the ink excellent in discharge property.

<Pigment>
In the present invention, any of inorganic pigments and organic pigments can be used as the pigment. 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 rice, 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, cobalt violet, and the like.

  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, 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.

  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 produced by a furnace method or a channel method. For example, these carbon blacks have a primary particle size of 11 to 40 nm, a specific surface area of 50 to 400 m <2> / g according to the BET method, a volatile content of 0.5 to 10% by weight, a pH value of 2 to 10 and the like. Those having the following are preferred. As commercial products having such characteristics, for example, 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 invention include aniline black, lumogen black, and azomethine azo black. Further, a plurality of chromatic 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 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 pigment content 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 with respect to the total amount of the ink. 8% by weight or less is particularly preferable.

<Pigment dispersion resin>
In order to maintain the stability of the ink for a long period of time, the above pigment is used by being dispersed in the ink. As a method for dispersing the pigment, there are a method in which the pigment is surface-modified by oxidation treatment or resin coating, and the pigment is dispersed without a dispersant, or a method in which a surfactant or resin is used as a dispersant to disperse the pigment. In the present invention, it is preferable to disperse the pigment 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 kind of the pigment dispersion resin is not particularly limited, and examples thereof include acrylic, styrene acrylic, maleic acid, styrene maleic acid, 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 pigment adsorption 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-dispersed resin having an alkyl group having 10 to 36 carbon atoms in the resin skeleton from the viewpoint of the storage stability of the ink and the compatibility with the 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 amine having an alkyl group to a functional group such as a carboxylic acid having a basic resin skeleton, or a monomer having an alkyl group at the time of resin synthesis is used. Thus, a method of synthesizing a resin having an alkyl group can be mentioned.

  The molecular weight of the pigment-dispersed resin is preferably in the range of 1,000 to 100,000 in weight average molecular weight, and more preferably in the range of 5,000 to 50,000. Setting the weight average molecular weight within the above range is preferable because the pigment can be stably dispersed in water and the discharge stability can be improved. In addition, the weight average molecular weight of pigment dispersion resin can be measured similarly to the case of said binder resin.

  Moreover, it is preferable that the acid value of pigment dispersion resin is 50-400 mgKOH / g. If the acid value is 50 mgKOH / g or more, the pigment dispersion resin is easily dissolved in water, and the viscosity of the dispersion can be kept low. Moreover, if it is 400 mgKOH / g or less, interaction with surfactant can be made suitable and the raise of the viscosity of ink can be prevented. The acid value of the pigment dispersion resin is preferably 100 to 350 mgKOH / g, and more preferably 150 to 300 mgKOH / g.

  The pigment-dispersed resin is preferably neutralized with an acid group in the resin in order to increase the solubility in water. As the base, organic bases such as aqueous ammonia, dimethylaminoethanol, diethanolamine, and triethanolamine, and inorganic bases such as lithium hydroxide, sodium hydroxide, and potassium hydroxide can be used.

  The weight ratio of the pigment to the pigment dispersion resin is preferably 2/1 to 100/1. 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 stability such as viscosity and dispersion are improved. The ratio of the pigment to the pigment dispersion resin is more preferably 20/9 to 50/1, further preferably 5/2 to 25/1, and most preferably 20/7 to 20/1.

<Water>
As 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 ink.

<Other ingredients>
In addition to the above-described components, the ink of the present invention can be appropriately added with additives such as an antifoaming agent and an antiseptic agent in order to obtain an ink having a desired physical property value as necessary. The addition amount of these additives is preferably 0.01% by weight or more and 10% by weight or less based on the total weight of the ink.

<Recording medium>
The ink of this embodiment can be particularly suitably used for a hardly absorbent substrate. The hardly absorbent substrate is a recording medium that hardly absorbs water or has a slow absorption rate, and specifically, measured by the Bristow method (J.TAPPI paper pulp test method No. 51-87). The water absorption coefficient is 0 to 0.6 ml / m ² msec ^1/2 . 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.

  Specific examples of difficult-to-absorbent substrates include paper substrates such as coated paper, art paper, cast paper, finely coated paper, and synthetic paper; polycarbonate, hard vinyl chloride, soft vinyl chloride, polystyrene, foamed polystyrene, PMMA, polypropylene Examples include, but are not limited to, plastic substrates such as polyethylene and PET; metal substrates such as aluminum and stainless steel; and glass. In addition, the inkjet ink of this embodiment can be used suitably also for things other than a hardly absorptive base materials, such as plain paper, a fabric, and wood.

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

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

<Example of production of 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 (weight ratio) as a pigment dispersion resin Random polymer, molecular weight: 16000, acid value: 250) 15 parts of an aqueous solution (non-volatile content 20%) and 65 parts of water were mixed and predispersed with a disper, and then 1800 g of zirconia beads having a diameter of 0.5 mm This dispersion was performed using a 0.6 L capacity dyno mill filled with a cyan pigment dispersion 1.

<Example of production 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 Toyocolor Co., Ltd.).

<Example of production 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 PigmentRed 122, manufactured by DIC).

<Example of production of black pigment dispersion 4>
A black pigment dispersion 4 was obtained in the same manner as the cyan pigment dispersion, except that the pigment was changed to PrintX85 (carbon black, manufactured by Orion Engineered Carbons).

<Production example of water-soluble resin 1>
A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 93.4 parts of butanol and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and 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 took 2 hours. Then, the polymerization reaction was carried out. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, 0.9 part of V-601 (manufactured by Wako Pure Chemical Industries) was added, and the reaction was further continued at 110 ° C. for 1 hour to obtain a resin 1 solution. . When the weight average molecular weight of the pigment-dispersed resin was measured, it was about 12,000.
Furthermore, after cooling to room temperature, 37.1 parts of dimethylaminoethanol was added and neutralized, and then 100 parts of water was added to make it aqueous. Thereafter, the mixture is heated to 100 ° C. or higher, butanol is azeotroped with water to distill off butanol, and the aqueous solution of water-soluble resin 1 (solid content 50%) is adjusted by adjusting the solid content to 50%. )

<Production example of water-soluble resins 2 to 4>
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 monomer, an aqueous solution (solid content 50%) of the water-soluble resins 2 to 4 was obtained. It was.

Table 1

<Synthesis of acetylene diol surfactants>
By using the method described in JP-A-2002-356451, Example 1 and using methyl isoamyl ketone as a raw material ketone, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol Was synthesized. In addition, the HLB value of the said compound is 2.7. Similarly, 4,7-dipropyl-dec-5-yne-4,7-diol (HLB value = 2.7) is obtained by using di-n-propyl ketone (4-heptanone) as a raw material ketone. By using methylhexyl ketone (2-octanone), 7,10-dimethylhexadec-8-in-7,10-diol (HLB value = 2.4) can be obtained by using methyl isobutyl ketone. 4,7,9-Tetramethyl-5-decyne-4,7-diol (HLB value = 3.0) was synthesized.

  In Examples, commercially available Surfynol 440 (Air Products, HLB value = 8.0) and Surfynol 465 (Air Products, HLB value = 13.0) are also acetylenic diol surfactants. Used as.

<Synthesis example of polysiloxane surfactant 1>
In a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, 360 g of ethylene glycol allyl methyl ether and 0.5 g of a 0.5 wt% toluene solution of chloroplatinic acid were charged and replaced with nitrogen gas. After heating the inside of the reaction vessel to 70 ° C., 480 g of hexadecamethyloctasiloxane in which both ends of the siloxane chain are hydrogen atoms was added dropwise over 30 minutes. Next, the inside of the reaction vessel was heated to 110 ° C. and held for 3 hours with stirring to react the materials. After completion of the reaction, the low-boiling fraction was distilled off under reduced pressure to obtain polyether-modified siloxane 1. The polyether-modified siloxane 1 is represented by the structure of the general formula (4), 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 Surfactant 2>
The amount of addition of ethylene glycol allyl methyl ether was 180 g, and polysiloxane type except that 200 g of heptamethyltrisiloxane having one hydrogen atom bonded to the central silicon atom was used instead of hexadecamethyloctasiloxane. Polysiloxane surfactant 2 was obtained in the same manner as surfactant 1. The polyether-modified siloxane 1 is represented by the structure of the general formula (2), p = 0, q = 1, R ₂ = CH ₃ , and R ₁
In the general formula (3), m = 3, n = 1, o = 0, and R ₃ = CH ₃ . The HLB value of the compound is 4.6.

<Synthesis example of polysiloxane 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 was used in place of hexadecamethyloctasiloxane. Polysiloxane surfactant 3 was obtained in the same manner as system surfactant 1. The polyether-modified siloxane 3 is represented by the structure of the general formula (4), 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 Big Chemie, HLB value = 10.1) was also used as a polysiloxane surfactant.

<Production Examples of Inks 1C, 1M, 1Y, 1K>
20 parts of the cyan pigment dispersion 1, 25 parts of 1,2-butanediol, and 1 part of 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol were sequentially added to the mixing container, The ink was adjusted by adding water to 100 parts, and stirred with a disper until it was sufficiently uniform. Then, it filtered with the membrane filter with a hole diameter of 1 micrometer, the coarse particle | grains causing the head clogging was removed, and ink 1C was produced.
Ink 1Y, 1M, and 1K 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 in place of cyan pigment dispersion 1. Produced.

<Production example of inks 2-49>
Inks 2 to 49 (four colors of C, Y, M, and K, respectively) were produced in the same manner as in the production example of ink 1C using the raw materials shown in Tables 2 to 4.

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

<Evaluation 1: Evaluation of white areas in solid portions>
Using the inkjet discharge device equipped with a head (QA06NTB) manufactured by Kyocera Corporation, the cyan ink of 1C to 49C was discharged under printing conditions of a frequency of 20 kHz and 600 × 600 dpi, and solid printing with a printing rate of 100% was performed. In addition, UPM Fines Gloss paper (coated paper) was used as a printing substrate. After printing, the printed material was dried for 3 minutes using an air oven at 50 ° C., and white spots were evaluated by checking the degree of white spots of the printed material with a magnifying glass and visually. The evaluation criteria are as follows, and ◎, ○, and Δ evaluations are practical areas.
◎: No white spots were observed with the loupe and visually observed ○: White spots were slightly observed with the loupe, but no white spots were visually observed Δ: Slightly white spots were visually observed ×: Obviously white spots were seen visually

<Evaluation 2: Evaluation of blurring between colors>
An ink jet discharge apparatus in which four Kyocera heads (QA06NTB) were arranged in the transport direction of the printing base material was prepared, and inks of cyan, magenta, yellow, and black were filled from the upstream side. Subsequently, the same printing substrate as in Evaluation 1 was prepared, and the lower part of the head was passed at a constant speed. At that time, ink was ejected from each head under printing conditions of a frequency of 20 kHz and 600 × 600 dpi, and a 100% solid patch of 1 cm × 1 cm was printed so that each color was adjacent. After printing, the printed matter was dried for 3 minutes using an air oven at 50 ° C., and the degree of blurring at the boundary between solid colors was confirmed with a magnifying glass and visually to evaluate the blurring at the boundary. The evaluation criteria are as follows, and ◎, ○, and Δ evaluations are practical areas.
◎: No blurring was observed at the boundary between colors with the loupe or visual observation ○: Slight blurring was observed at the boundary between colors with the loupe, but was not observed with visual observation △: Slight blurring was observed between the colors X: Bleeding was clearly observed at the boundary between colors.

<Evaluation 3: Evaluation of aggregation unevenness>
A gradation pattern was printed with the same printing base material and printing conditions as in Evaluation 1 so that the printing ratio was 10% from 10% to 100% for each color of cyan, magenta, yellow, and black. After printing, the printed matter is dried for 3 minutes using a 50 ° C air oven, and the degree of unevenness of the printed part with a printing rate of 20%, 50%, and 80% is confirmed with a magnifier and visually to evaluate the unevenness of aggregation. went. The evaluation criteria are as follows, and ◎, ○, and Δ evaluations are practical areas. In Tables 2 to 4, only the results of the worst color among the four colors evaluated are shown.
◎: No flocculation or visual agglomeration was observed at any of the printing ratios of 20, 50, 80%. ◯: Aggregation at the loupe at any one of the printing ratios of 20, 50, 80%. Unevenness was observed but not visually observed. Δ: Slightly agglomerated unevenness was visually observed at any one or more of the printing rates of 20, 50, and 80%. X: Printing rate of 20, 50, At any one of the 80% or more, there was obvious aggregation unevenness visually.

<Evaluation 4: Evaluation of ejectability>
Solid printing with a printing rate of 100% was performed 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 kept on standby for a certain period of time in an environment of 25 ° C., and then solid printing with a printing rate of 100% was performed again with the same printing base material and printing conditions. At that time, the ejection property was evaluated by confirming visually and loupe whether the solid start portion was printed. The evaluation criteria are as follows, and ◎, ○, and Δ evaluations are practical areas. In Tables 2 to 4, only the results of the worst color among the four colors evaluated are shown.
◎: Even after printing after waiting for 3 hours, no chipping was found at the beginning of hitting. ○: After printing after waiting for 3 hours, chipping was found at the starting portion, but waiting for 2 hours. Occasionally, no chipping was observed. Δ: When printing was performed after waiting for 2 hours, chipping was observed at the beginning of the strike, but chipping was not observed when waiting for 2 hours. However, there was a chipping at the beginning

<Evaluation 5: Evaluation of drying property>
Using the same ejection device, printing substrate, and printing conditions as those in Evaluation 2, 100% solids of cyan, magenta, and yellow were multiplied to print a solid of 300% printing rate. After heating for a predetermined time using a 50 ° C. air oven, the printed material was touched with a finger to evaluate the drying property of the printed material. The evaluation criteria are as follows, and ◎, ○, and Δ evaluations are practical areas.
◎: After 1 minute from the introduction of the oven, the ink did not adhere even when touched with a finger. ○: The ink adhered to the finger 1 minute after the introduction of the oven, but did not adhere after 2 minutes. Ink adhered to the finger after 2 minutes, but did not adhere after 3 minutes. X: Ink adhered to the finger even after 3 minutes from the introduction of the oven.

<Evaluation 6: Evaluation of storage stability of ink>
About each color of ink 1-49, the viscosity was measured on the conditions of 25 degreeC and rotation speed 50rpm using the E-type viscosity meter (TVE-20L by Toki Sangyo Co., Ltd.). 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 ◎, ○, and Δ evaluations are practical areas. In Tables 2 to 4, only the results of the worst color among the four colors evaluated are shown.
◎: Viscosity change rate after storage for 4 weeks is less than ± 5% ○: Viscosity change rate after storage for 2 weeks is less than ± 5% △: Viscosity change rate after storage for 1 week is less than ± 5% ×: Storage for 1 week Later viscosity change rate is more than ± 5%

<Evaluation results of Examples and Comparative Examples>
Comparative Example 1 is 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 2,5 as an acetylenic diol surfactant (a1) having an HLB value of 3 or less. , 8,11-Tetramethyl-6-dodecine-5,8-diol, the solid whiteness of the printed matter, the aggregation unevenness, etc. were practical areas, but the ink ejection properties and storage stability Gave bad results. This is probably because the content of 1,2-butanediol, which is a solvent having an HLB value of 8 or less, was small, and the compatibility of the surfactant with ink was insufficient.

  On the other hand, in Comparative Example 2, instead of using the acetylenic diol surfactant (a1) having an HLB value of 3 or less, a polysiloxane surfactant (a2) having an HLB value of 4 or less, and an HLB value of 8 to In this system, polysiloxane surfactant (a3) No. 20 was used, and uneven aggregation was observed in the printed matter. Comparative Examples 3 and 4 were systems using an acetylenic diol surfactant having an HLB value greater than 3, and the printed material was observed to have color boundaries, uneven aggregation, and white spots in the solid portion.

  Examples 1-43 contain 10-50 weight% of water-soluble organic solvents whose HLB value is 8 or less with respect to the total amount of water-based inkjet ink, and acetylenediol type surfactant (a1) whose HLB value is 3 or less In the system containing white ink, white spots in prints, bleeding in color boundaries, uneven aggregation, and ink ejection, drying, and storage stability were all practical areas. Among them, Examples 39, 40, 42, 43, and 44 are surfactants, a polysiloxane surfactant (a2) having an HLB value of 4 or less, and a polysiloxane surfactant having an HLB value of 8 to 20. It is a system containing a surfactant (a3) in combination and containing a water-soluble resin having an alkyl chain having 8 to 36 carbon atoms, and it has been confirmed that the evaluation results are excellent in all evaluation items. .

  The water-based inkjet ink of the present invention and the method for producing a printed matter can obtain a high-quality image even on a hardly-absorbing substrate such as a coated paper, and particularly for high-speed printing for commercial printing using the substrate. It can be suitably used in high recording resolution ink jet printing.

Claims (10)

An aqueous inkjet ink comprising at least a pigment, a water-soluble organic solvent, and a surfactant (A),
The water-soluble organic solvent contains a water-soluble organic solvent having an HLB value of 8 or less according to the Griffin method, based on the total amount of the water-based inkjet ink,
The water-based inkjet ink, wherein the surfactant (A) contains an acetylenic diol surfactant (a1) having an HLB value of 3 or less according to the Griffin method.   The water-based inkjet ink according to claim 1, wherein the surfactant (A) further contains a polysiloxane surfactant (a2) having an HLB value of 4 or less according to the Griffin method.   The aqueous inkjet ink according to claim 1 or 2, wherein the surfactant (A) further contains a polysiloxane surfactant (a3) having an HLB value of 8 to 20 by the Griffin method.   The content of the acetylenic diol 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 water-based inkjet ink in any one.   The ratio of the content of the polysiloxane surfactant (a2) having an HLB value of 4 or less to the content of the acetylenic diol surfactant (a1) having an HLB value of 3 or less is 0.2. The water-based inkjet ink according to claim 2, wherein the ratio is 1.0 to 3.3: 1.0.   The ratio of the content of the polysiloxane surfactant (a3) having an HLB value of 8 or more and 20 or less and the content of the acetylenic diol surfactant (a1) having an HLB value of 3 or less is 0. The water-based inkjet ink according to claim 3, wherein the ratio is from 1: 1.0 to 2.0: 1.0.   The water-based inkjet ink according to any one of claims 1 to 6, wherein the water-soluble organic solvent having an HLB value of 8 or less contains a polyol solvent.   The water-based inkjet ink according to any one of claims 1 to 7, further comprising a water-soluble resin having an alkyl chain having 8 to 36 carbon atoms.   The water-based inkjet ink according to claim 8, wherein the content of the water-soluble resin is 0.5 to 10% by weight based on the total amount of the water-based inkjet ink.   A printed matter obtained by printing the aqueous inkjet ink according to claim 1 on a substrate.