JP6686366B2 - Ink, image forming method, image forming apparatus, and image formed article - Google Patents

Description

  The present invention relates to an ink, an image forming method, an image forming apparatus, and an image formed article.

2. Description of the Related Art In recent years, image forming methods are rapidly becoming popular because they can easily record color images and have low running costs.
Regarding the ink used in the image forming method, an aqueous pigment ink in which a pigment is made into fine particles and dispersed in water is drawing attention. Since the pigment has a composition similar to that of a colorant used in a general commercial printing ink, it is expected that the texture of a printed matter can be brought close to that of commercial printing. However, when the aqueous pigment ink is used to record on coated paper for commercial printing or publication printing, there is a problem that beading occurs because the ink is not absorbed in time.

Therefore, the applicant of the present application has previously proposed an inkjet recording ink containing water, a water-soluble organic solvent, a surfactant and a colorant (see Patent Documents 1 and 2). As the water-soluble organic solvent, a polyhydric alcohol having an equilibrium water content of 30% by mass or more at a temperature of 23 ° C. and a relative humidity of 80% and a predetermined amide compound are used. As the surfactant, at least one selected from silicone-based surfactants, fluorine-based surfactants, and acetylene glycol-based surfactants is used.
However, in these proposals, the relationship between the dynamic surface tension of the ink at the surface life of 15 msec by the maximum bubble pressure method and the static surface tension of the ink is not optimized, and therefore the ink is a nozzle of an ink head. There is a problem that the ink-repellent film on the plate is easily wetted and the ejection stability is lowered due to the adhesion of the ink to the nozzle.

  An object of the present invention is to provide an ink capable of performing high-quality recording with suppressed beading and good image density and ejection stability not only on plain paper but also on general-purpose printing paper. And

The ink of the present invention as a means for solving the above problems is an ink containing at least a colorant, an organic solvent, and water,
At least one organic solvent having a solubility parameter of 9 or more and less than 11.8 is contained as the organic solvent, and the content of the organic solvent having the solubility parameter of 9 or more and less than 11.8 is 20% by mass or more based on the total amount of the ink. Yes,
The dynamic surface tension A of the ink at a temperature of 25 ° C. and a surface life of 15 msec according to the maximum bubble pressure method is 34.0 mN / m or less, and the dynamic surface tension A and the static surface tension of the ink at 25 ° C. B is characterized by satisfying the following expression: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%.

  ADVANTAGE OF THE INVENTION According to the present invention, it is possible to provide not only plain paper but also general-purpose printing paper with ideal quality in which beading is suppressed and good quality recording is possible, and which has good image density and ejection stability. can do.

FIG. 1 is a schematic diagram showing an example of an ink container. FIG. 2 is a schematic diagram including the case of the ink container of FIG. FIG. 3 is a perspective view showing an example of the image forming apparatus. FIG. 4 is a diagram illustrating an example of the image forming apparatus. FIG. 5 is a schematic enlarged view showing an example of the inkjet head of the image forming apparatus.

(ink)
The ink of the present invention contains a colorant, an organic solvent, and water, preferably a surfactant and a water-dispersible resin, and further contains other components as necessary.

The ink contains at least one organic solvent having a solubility parameter of 9 or more and less than 11.8 as the organic solvent, and the content of the organic solvent having a solubility parameter of 9 or more and less than 11.8 is 20 with respect to the total amount of the ink. Mass% or more,
The dynamic surface tension A of the ink at a temperature of 25 ° C. and a surface life of 15 msec according to the maximum bubble pressure method is 34.0 mN / m or less, and the dynamic surface tension A and the static surface tension of the ink at 25 ° C. B is characterized by satisfying the following expression: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%. As a result, it is possible to secure sufficient wettability of the ink to the recording medium, and further, the ink quickly penetrates the coated paper having a coating layer such as general-purpose printing paper, which has a poor ink absorption property, to the paper surface. In the drying process after the ink has landed, the pigment agglomerates rapidly and the viscosity can be increased, so that beading can be suppressed.

The dynamic surface tension A of the ink at a surface life of 15 msec according to the maximum bubble pressure method at 25 ° C. is 34.0 mN / m or less, preferably 30.0 mN / m or less, and preferably 25.0 mN / m or more and 30.0 mN / m. The following is more preferable.
By setting the dynamic surface tension A to 34.0 mN / m or less, the wettability and penetrability of general-purpose printing paper are improved, and the effect of reducing beading and color bleeding is enhanced. Further, it is possible to improve the coloring property and the occurrence of white spots on plain paper.
The dynamic surface tension of the ink at a surface life of 15 msec according to the maximum bubble pressure method can be measured at 25 ° C. using, for example, SITA DynoTester (manufactured by SITA).

The dynamic surface tension A and the static surface tension B of the ink at 25 ° C. satisfy the following equation: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%. It is preferable to satisfy the following formula: 12.0% ≦ [(A−B) / (A + B)] × 100 ≦ 17.0%.
The dynamic surface tension A and the static surface tension B of the ink at 25 ° C. satisfy the following equation: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%. By filling the ink, the balance between the dynamic surface tension A and the static surface tension B in the ink can be optimized, and the water-repellent film on the nozzle plate of the inkjet head becomes hard to wet, so that the ejection stability can be secured. In addition, it is possible to obtain extremely stable ink that does not cause nozzle omission in continuous ejection.
As described above, after drying with an ink containing at least one organic solvent having a predetermined solubility parameter value and a predetermined amount or more, the relationship between the dynamic surface tension A and the static surface tension B satisfies a predetermined range. Since the pigment is uniformly fixed near the surface of the paper, it is possible to obtain a highly colored image in which beading and color bleeding are suppressed, and it is possible to achieve a high gamut coverage.
The static surface tension B of the ink at 25 ° C. is preferably 20.0 mN / m or more and 30.0 mN / m or less.
When the static surface tension is 20.0 mN / m or more and 30.0 mN / m or less, the ink permeability can be enhanced, the cockling and curling reduction effect can be enhanced, and the penetration and the penetration in plain paper printing can be improved. Good drying.
The static surface tension of the ink can be measured at 25 ° C. by using, for example, a fully automatic surface tension meter (CBVP-Z, manufactured by Kyowa Interface Science Co., Ltd.).

The gamut coverage ratio reproduced with the ink is a value indicating how much the gamut volume of the evaluation color covers (includes) the gamut volume of the target color. Specifically, in the evaluation color and the target color, eight plot points of C, M, Y, R, G, B, Bk, and W on the L ^* a ^* b ^* color space are represented by straight lines. Then, the lightness L ^* is projected on the a ^* b ^* plane. Next, in the color gamut area in which six points C, M, Y, R, G, and B projected on the a ^* b ^* plane for each lightness L ^* are connected by a straight line, the color gamut of the evaluation color is obtained. The ratio of the value (inclusive volume) obtained by integrating the area and the area of the region in which the gamut area of the target color overlaps in the lightness direction and the gamut volume of the target color (inclusive volume / gamut volume of the target color), That is, the gamut coverage rate is used for evaluation.
The target color uses a color reproduction area in the L ^* a ^* b ^* color space defined by “ISO-compliant 2011 for Japan color sheet-fed printing 2011 (abbreviation: Japan Color 2011 coated paper)”.
Here, the L ^* a ^* b ^* color space can be measured, for example, using a spectral densitometer (X-Rite 939, manufactured by X-Rite) at a D50 light source, no filter, and a viewing angle of 2 °. it can.

Therefore, in the present invention, the colorant is any one selected from carbon black pigment, phthalocyanine pigment, quinacridone pigment, monoazo pigment, and disazo pigment,
It is preferable that the gamut cover ratio reproduced by using the ink covers 90% or more of the gamut cover ratio defined by Japan Color 2011 coated paper.
By covering the gamut coverage ratio of 90% or more reproduced by using the ink, it is possible to obtain a highly colored image comparable to the offset printing.

<Organic solvent>
As the organic solvent, at least one organic solvent having a solubility parameter of 9 or more and less than 11.8 is contained. By containing the organic solvent having the solubility parameter of 9 or more and less than 11.8, it becomes possible to suppress the occurrence of beading even on general-purpose printing paper.

Here, the solubility parameter (SP value) is a numerical value indicating how easily each of them is soluble. The SP value is represented by a force of attraction between molecules, that is, a square root of cohesive energy density CED (Cohesive Energy Density). The CED is the amount of energy required to evaporate 1 mL.
The solubility parameter (SP value) is defined by the regular solution theory introduced by Hildebrand, and is a measure of the solubility of a binary system solution.
Although there are various theories about the method of calculating the SP value, the Fedors method generally used in the present invention is used.
The SP value can be calculated using the following formula (B) by the Fedors method.
SP value (dissolution parameter) = (CED value) ^1/2 = (E / V) ^1/2 ... formula (B)
In the above formula (B), E is a molecular cohesive energy (cal / mol), V is a molecular volume (cm ³ / mol), and when the evaporation energy of atomic groups is Δei and the molar volume is Δvi, the following formula ( C) and the formula (D).
E = ΣΔei ... Expression (C)
V = ΣΔvi ... Formula (D)

The data described in "Basic Theory of Adhesion" (Minori Imoto, published by Kobunshi Kogakukai, Chapter 5) is used as various data of the above calculation method, evaporation energy Δei and molar volume Δvi of each atomic group. be able to.
In addition, as for those such as -CF ₃ group, which do not show a value, R.I. F. Fedors, Polym. Eng. Sci. 14, 147 (1974).

  The organic solvent having a solubility parameter (SP value) of 9 or more and less than 11.8 is at least one selected from an amide compound represented by the following general formula (I) and an oxetane compound represented by the following general formula (II). Is more preferable.

[General Formula (I)]
However, in the general formula (I), R ′ represents an alkyl group having 4 to 6 carbon atoms.
[General Formula (II)]
However, in the general formula (II), R ″ represents an alkyl group having 1 to 2 carbon atoms.

  Specific examples of the amide compound represented by the general formula (I) or the oxetane compound represented by the general formula (II) include the following compounds.

[Structural formula (1), SP value: 9.03]

[Structural formula (2), SP value: 9.00]

[Structural formula (3), SP value: 8.96]

[Structural formula (4), SP value: 11.3]

[Structural formula (5), SP value: 11.79]

  As the organic solvent, in addition to the amide compound represented by the general formula (I) and the oxetane compound represented by the general formula (II), the organic solvent has a solubility parameter (SP value) of 11.8 or more and 14.0 or less. It is preferable to use a polyhydric alcohol and a penetrant having a solubility parameter (SP value) of 9 or more and less than 11.8.

Examples of the polyhydric alcohol having a solubility parameter (SP value) of 11.8 or more and 14.0 or less include 3-methyl-1,3-butanediol (SP value: 12.05) and 1,2-butanediol ( SP value: 12.8), 1,3-butanediol (SP value: 12.75), 1,4-butanediol (SP value: 12.95), 2,3-butanediol (SP value: 12. 55), 1,2-propanediol (SP value: 13.5), 1,3-propanediol (SP value: 13.72), 1,2-hexanediol (SP value: 11.8), 1, 6-hexanediol (SP value: 11.95), 3-methyl-1,5-pentanediol (SP value: 11.8), triethylene glycol (SP value: 12.12), diethylene glycol (SP value: 13) .02) And the like. These may be used alone or in combination of two or more.
Among these, 3-methyl-1,3-butanediol (SP value: 12.05), 1,2-butanediol (SP value: 12.8), 1,3-butanediol (SP value: 12. 75), 1,4-butanediol (SP value: 12.95), 2,3-butanediol (SP value: 12.55), 1,2-propanediol (SP value: 13.5), 1, 3-Propanediol (SP value: 13.72) is preferable, and 1,2-butanediol (SP value: 12.8) and 1,2-propanediol (SP value: 13.5) are more preferable.

The total content of the polyhydric alcohol having the solubility parameter (SP value) of 11.8 or more and 14.0 or less, the amide compound represented by the general formula (I) and the oxetane compound represented by the general formula (II) is the total amount of the ink. On the other hand, it is preferably 30% by mass or more and 60% by mass or less.
When the content is 30% by mass or more, beading on general-purpose printing paper and color bleeding between colors may be suppressed, and when the content is 60% by mass or less, image quality is good and ink viscosity is high. It becomes appropriate and the ejection stability becomes good.

The penetrant preferably has a solubility parameter of 9 or more and less than 11.8, and examples thereof include a polyol compound having 8 to 11 carbon atoms and a glycol ether compound.
Among these, 1,3-diol compounds represented by the following general formula (VII) are preferable, and 2-ethyl-1,3-hexanediol [SP value: 10.6], 2,2,4-trimethyl- 1,3-Pentanediol [SP value: 10.8] is particularly preferable.

[General Formula (VII)]
However, in the general formula (VII), R ′ is a methyl group or an ethyl group, R ″ is a hydrogen atom or a methyl group, and R ″ ′ is an ethyl group or a propyl group.

  Examples of other polyol compounds include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1,2-diol And so on.

  The content of the penetrant is preferably 0.5% by mass or more and 4% by mass or less, and more preferably 1% by mass or more and 3% by mass or less, based on the total amount of the ink. When the content is 0.5% by mass or more, the effect of penetrating the ink is obtained, and the effect on the image quality is obtained. On the other hand, when the content is 4% by mass or less, the initial viscosity of the ink becomes appropriate.

The content of the organic solvent having the solubility parameter of 9 or more and less than 11.8 is 20% by mass or more, and preferably 20% by mass or more and 60% by mass or less, based on the total amount of the ink.
When the content is 20% by mass or more, the occurrence of beading on general-purpose printing paper is suppressed, and the effect of suppressing color bleeding between colors is improved. On the other hand, when the content is 60% by mass or less, the image quality is improved, the ink viscosity is appropriate, and the ejection stability is improved.

The organic solvent preferably does not contain “a polyhydric alcohol having an equilibrium water content of 30% or more at a temperature of 23 ° C. and a relative humidity of 80%”.
The equilibrium water content is maintained at a temperature of 23 ° C. ± 1 ° C. and a relative humidity of 80% ± 3% in a desiccator using a saturated aqueous solution of potassium chloride / sodium chloride, and 1 g of each organic solvent is weighed in the desiccator. The petri dish was stored and the equilibrium water content was calculated from the following formula.
Equilibrium water content (%) = (water content absorbed in organic solvent / organic solvent + water content absorbed in organic solvent) x 100
When "polyhydric alcohol having an equilibrium water content of 30% or more at a temperature of 23 ° C. and a relative humidity of 80%" is contained as the organic solvent, it can be applied to coated paper having a coating layer such as general-purpose printing paper and having poor ink absorption. As a result, the permeation of the ink is delayed, the drying of the ink after landing on the paper is delayed, and beading may occur.
The above-mentioned “polyhydric alcohol having an equilibrium water content of 30% or more at a temperature of 23 ° C. and a relative humidity of 80%” is disclosed in JP2012-207202A (Patent Document 1) and JP2014-94998A (Patent Document 2). It is used in etc.
Examples of the “polyhydric alcohol having an equilibrium water content of 30% or more at a temperature of 23 ° C. and a relative humidity of 80%” include 1,2,3-butanetriol (equilibrium water content: 38%), 1,2,4. -Butanetriol (equilibrium water content: 41%), glycerin (equilibrium water content: 49%, SP value 16.38), diglycerin (equilibrium water content: 38%), triethylene glycol (equilibrium water content: 39%, SP value 15.4), tetraethylene glycol (equilibrium water content: 37%), diethylene glycol (equilibrium water content: 43%), 1,3-butanediol (equilibrium water content: 35%) and the like.

<Colorant>
It is preferable to use a water-dispersible pigment as the colorant. A dye may be used in combination for the purpose of adjusting the color tone, but it is preferable to use it within a range that does not deteriorate the weather resistance.
The pigment in the water-dispersible pigment includes an organic pigment and an inorganic pigment.
Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, carbon black and the like. Among these, carbon black is preferable.

The carbon black (Pigment Black 7) may be manufactured by a known method such as a contact method, a furnace method, or a thermal method, and examples thereof include channel black, furnace black, gas black, and lamp black.
Examples of commercial products of the carbon black include Regal (registered trademark), Black Pearls (registered trademark), Elftex (registered trademark), Monarch (registered trademark), Regal (registered trademark), Mogul (registered trademark), and Vulcan (registered trademark). Carbon black available from Cabot Corporation under the registered trademark (for example, Black Pearls 2000, 1400, 1300, 1100, 1000, 900, 880, 800, 700, 570, Black Pearls). L, Elftex 8, Monarch 1400, same 1300, same 1100, same 1000, same 900, same 880, same 800, same 700, Mogul L, Regal 330, same 400, same 660, Vulcan P); S NSIJET Black SDP100 (SENSIENT Co., Ltd.), (made by SENSIENT Inc.) SENSIJET Black SDP1000, (manufactured by SENSIENT Inc.) SENSIJET Black SDP2000 and the like. These may be used alone or in combination of two or more.

Examples of the organic pigment include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are preferable.
Examples of the azo pigment include azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, and the like. Examples of the polycyclic pigments include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinofuraron pigments. Examples of the dye chelates include basic dye chelates and acid dye chelates.

  Specific examples of the organic pigment include C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104. , 108, 109, 110, 117, 120, 128, 139, 150, 151, 155, 153, 180, 183, 185, 213, C.I. I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2,53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108 ( Cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, C.I. I. Pigment Violet 1 (Rhodamine Lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3 (phthalocyanine blue), 16, 17: 1, 56, 60, 63; C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36 and the like. These may be used alone or in combination of two or more.

The specific surface area of the pigment is appropriately selected depending on the intended purpose without any limitation, but it is preferably 10 m ² / g or more and 1,500 m ² / g or less, and 20 m ² / g or more and 600 m ² / g or less. It is more preferably 50 m ² / g or more and 300 m ² / g or less.
If the desired specific surface area is not met, adjust the pigment to a smaller particle size by size reduction or milling (eg ball milling, or jet milling, or sonication). You can
The volume average particle diameter of the pigment is preferably 10 nm or more and 200 nm or less in the ink.

As the water-dispersible pigment, (1) a surfactant dispersion in which a pigment is dispersed with a surfactant, (2) a resin dispersion in which a pigment is dispersed with a resin, and (3) a resin coating dispersion in which the surface of the pigment is coated with a resin (4) Self-dispersing pigments having a hydrophilic group provided on the surface of the pigment.
Among these, the resin-coated pigment obtained by coating the surface of the pigment of (3) with a resin and the hydrophilic surface of the pigment of (4) have high storage stability over time and can suppress an increase in viscosity upon evaporation of water. Self-dispersed pigments provided with groups are preferred.

As the self-dispersing pigment (4) having a hydrophilic functional group, anionically charged pigments are preferable. Examples of the anionic functional _{group, -COOM, -SO 3 M, -PO} 3 HM, -PO 3 M 2, -CONM 2, -SO 3 NM 2, -NH-C 6 H 4 -COOM, -NH- _{C 6 H 4 -SO 3 M,} -NH-C 6 H 4 -PO 3 HM, -NH-C 6 H 4 -PO 3 M 2, -NH-C 6 H 4 -CONM 2, -NH-C 6 such as H ₄ -SO ₃ NM ₂ and the like. Examples of the counter ion M include alkali metal ions and quaternary ammonium ions. Of these, quaternary ammonium ions are preferable.

Examples of the quaternary ammonium ion include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, benzyltrimethylammonium ion, benzyltriethylammonium ion and tetrahexylammonium ion. And tetraethylammonium ion, tetrabutylammonium ion, benzyltrimethylammonium ion and the like. Among these, tetrabutylammonium ion is preferable.
It is presumed that the self-dispersing pigment having the hydrophilic functional group and the quaternary ammonium ion exhibits affinity even in water-rich ink and in organic solvent-rich ink in which water is evaporated, and the dispersion of the pigment can be stably maintained. To be done.

  Among the self-dispersing pigments, the ink using the pigment modified with at least one of the geminal bisphosphonic acid group and the geminal bisphosphonic acid group has excellent redispersibility after drying, and thus suspends printing for a long time. Even if the water content of the ink near the inkjet head nozzle evaporates, the ink does not become clogged, and good printing can be easily performed with a simple cleaning operation. Furthermore, since the storage stability with time is high and the increase in viscosity upon evaporation of water is suppressed, the ink adherence and ejection reliability in the head maintenance device are also very excellent.

Specific examples of the phosphonate group or phosphonate group include any of the following structural formulas (i) to (iv).
However, in the structural formula (iii), X ⁺ represents Li ⁺ , K ⁺ , Na ⁺ , NH ₄ ⁺ , N (CH ₃ ) ₄ ⁺ , N (C ₂ H ₅ ) ₄ ⁺ , N (C ₃ H). ₇ ) ₄ ⁺ and N (C ₄ H ₉ ) ₄ ⁺ .
However, in the structural formula (iv), X ⁺ represents Li ⁺ , K ⁺ , Na ⁺ , NH ₄ ⁺ , N (CH ₃ ) ₄ ⁺ , N (C ₂ H ₅ ) ₄ ⁺ , N (C ₃ H). ₇ ) ₄ ⁺ and N (C ₄ H ₉ ) ₄ ⁺ .

-Modification of pigment surface-
Here, the modification treatment of the pigment surface will be described by taking the case of a geminal bisphosphonic acid group as an example. Examples of the reforming method include the following method A and method B.
[Method A]
20 g of carbon black, 20 mmol of a compound represented by the following structural formula (v) or structural formula (vi), and 200 mL of ion-exchanged high-purity water are mixed in a Silverson mixer (6000 rpm) under a room temperature environment. If the pH of the resulting slurry is higher than 4, add 20 mmol nitric acid. After 30 minutes, sodium nitrite (20 mmol) dissolved in a small amount of ion-exchanged pure water is slowly added to the above mixture. Further, when heated to 60 ° C. with stirring and reacted for 1 hour, a modified pigment in which a compound represented by the following structural formula (v) or structural formula (vi) is added to carbon black is produced. Then, the pH is adjusted to 10 with an aqueous NaOH solution, and a modified pigment dispersion is obtained after 30 minutes. Next, ultrafiltration with a dialysis membrane is performed using the dispersion and ion-exchanged high-purity water, and further ultrasonic dispersion is performed to obtain a modified pigment dispersion having concentrated solids.

[Method B]
A ProcessAll 4HV mixer (4 L) is charged with 500 g of dry carbon black, 1 L of ion-exchanged pure water and 1 mol of a compound represented by the following structural formula (v) or structural formula (vi). The mixture is then vigorously mixed for 10 minutes at 300 rpm while warming to 60 ° C. To this, 20% aqueous sodium nitrite solution [1 molar equivalent based on the compound of structural formula (v) or the compound of structural formula (vi)] was added over 15 minutes and mixed for 3 hours while heating to 60 ° C. Stir.
The reaction product was taken out while diluting it with 750 mL of ion-exchanged high-purity water, and the obtained modified pigment dispersion and ion-exchanged high-purity water were subjected to ultrafiltration with a dialysis membrane, followed by ultrasonic dispersion to concentrate the solid content. A modified pigment dispersion is obtained. Furthermore, when there are many coarse particles, it is desirable to remove them using a centrifuge or the like.

[Structural formula (v)]

[Structural formula (vi)]

A pH adjuster may be added to the obtained modified pigment dispersion, if necessary. As the pH adjuster, the same one as the pH adjuster of the ink described later can be used. Among ^{_{these, Na +, N (CH 3}} ) 4 +, N (C 2 H 5) 4 +, N (C 3 H 7) 4 +, N (C 4 H 9) 4 + being preferred.
When the treatment with the pH adjuster is performed, at least a part of the compound of the structural formula (v) or the structural formula (vi) is a salt thereof (a compound corresponding to the structural formula (iii) or the structural formula (iv)). ).

As the resin-coated pigment obtained by coating the surface of the pigment of (3) with a resin, a polymer emulsion in which the pigment is contained in polymer particles is preferable.
The polymer emulsion in which the pigment is contained in the polymer particles is one in which the pigment is encapsulated in the polymer particles, or one in which the pigment is adsorbed on the surface of the polymer particles. In this case, it is not necessary that all the pigments be encapsulated or adsorbed, and the pigments may be dispersed in the emulsion as long as the effects of the present invention are not impaired.
Examples of the polymer forming the polymer emulsion (polymer in the polymer fine particles) include vinyl-based polymers, polyester-based polymers, polyurethane-based polymers, and the like. Particularly preferably used polymers are vinyl-based polymers and polyester-based polymers. The polymers disclosed in JP 2000-53897 A and JP 2001-139849 A can be cited.

In this case, a general organic pigment or a composite pigment obtained by coating inorganic pigment particles with an organic pigment or carbon black can be preferably used. The composite pigment can be produced by a method of depositing an organic pigment in the presence of inorganic pigment particles, a mechanochemical method of mechanically milling an inorganic pigment and an organic pigment, or the like.
Further, if necessary, a layer of an organosilane compound formed from polysiloxane or alkylsilane may be provided between the inorganic pigment and the organic pigment to improve the adhesiveness between them.

The organic pigment and the inorganic pigment are not particularly limited and can be appropriately selected and used from the above-mentioned ones.
The mass ratio of the inorganic pigment particles to the organic pigment or carbon black as a colorant is preferably 3: 1 to 1: 3, more preferably 3: 2 to 1: 2.
When the amount of the colorant is small, the coloring property and the coloring power may be lowered, and when the amount of the colorant is large, the transparency and the color tone may be deteriorated.
Coloring material particles obtained by coating such inorganic pigment particles with an organic pigment or carbon black include silica / carbon black composite materials manufactured by Toda Kogyo Co., Ltd., silica / phthalocyanine PB15: 3 composite materials, silica / disazo yellow composite materials, Silica / quinacridone PR122 composite material and the like can be preferably used because the primary average particle size is small.
Here, when the inorganic pigment particles having a primary particle diameter of 20 nm are coated with an equal amount of the organic pigment, the primary particle diameter of the pigment is about 25 nm. If a suitable dispersant can be used to disperse even the primary particles, a very fine pigment-dispersed ink having a dispersed particle diameter of 25 nm can be produced.
In the composite pigment, not only the organic pigment on the surface contributes to the dispersion but also the property of the inorganic pigment at the center appears through a thin layer of the organic pigment having a thickness of 2.5 nm, so that both can be dispersed and stabilized at the same time. The choice of pigment dispersant is also important.

  The content of the colorant is preferably 1% by mass or more and 15% by mass or less and more preferably 2% by mass or more and 10% by mass or less with respect to the total amount of the ink. When the content is 1% by mass or more, sufficient color developability and image density of ink can be obtained. On the other hand, when the content is 15% by mass or less, the viscosity of the ink does not increase and the ejection property does not deteriorate, which is economically preferable.

<Water>
As the water, for example, deionized water, ultrafiltered water, reverse osmosis water, pure water such as distilled water, or ultrapure water can be used.
The content of the water in the ink is not particularly limited and can be appropriately selected according to the purpose.

<Surfactant>
The surfactant preferably contains a polyether-modified siloxane compound.
By using the polyether-modified siloxane compound as a surfactant, the ink becomes hard to wet the ink repellent layer of the nozzle plate of the ink head, ejection failure due to ink sticking to the nozzle is prevented, and ejection stability is improved.

  The polyether-modified siloxane compound has the following general formula (III) from the viewpoints of dispersion stability not impaired by the combination of the colorant and the organic solvent, low dynamic surface tension, permeability, and leveling property. To (VI) are preferred.

[General Formula (III)]
However, in the said General formula (III), m shows the integer of 0-23, n shows the integer of 1-10. a shows the integer of 1-23, b shows the integer of 0-23. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[General Formula (IV)]
However, in said general formula (IV), m shows the integer of 1-8, c and d show the integer of 1-10. R ₂ and R ₃ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[General formula (V)]
In the general formula (V), e represents an integer from 1 to 8, _{R 4} represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

[General formula (VI)]
However, in the general formula (VI), f represents an integer of 1 to 8. R ₅ represents a polyether group represented by the following general formula (A).

[General formula (A)]
However, in the general formula (A), g represents an integer of 0 to 23, h represents an integer of 0 to 23, and g and h are not 0 at the same time. R ₆ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

  Examples of the polyether-modified siloxane compound represented by the general formula (III) include, but are not limited to, compounds represented by the following structural formulas.

[Structural Formula (VI)]

[Structural Formula (VII)]

[Structural Formula (VIII)]

[Structural Formula (IX)]

[Structural Formula (X)]

[Structural Formula (XI)]

[Structural Formula (XII)]

[Structural Formula (XIII)]

  Examples of the polyether-modified siloxane compound represented by the general formula (IV) include, but are not limited to, compounds represented by the following structural formulas.

[Structural Formula (XIV)]

  Examples of the polyether-modified siloxane compound represented by the general formula (V) include, but are not limited to, compounds represented by the following structural formulas.

[Structural formula (XV)]

  Examples of the polyether-modified siloxane compound represented by the general formula (VI) include, but are not limited to, compounds represented by the following structural formulas.

[Structural Formula (XVI)]

[Structural Formula (XVII)]

[Structural Formula (XVIII)]

  As the polyether-modified siloxane compound, those synthesized appropriately may be used, or commercially available products may be used.

The method for synthesizing the polyether-modified siloxane compound is not particularly limited and may be appropriately selected depending on the intended purpose. For example, descriptions in Japanese Patent No. 5101598, Japanese Patent No. 5032325, Japanese Patent No. 5661229, etc. Can be referred to.
Specifically, it can be synthesized by subjecting (A) polyether and (B) organohydrogensiloxane to a hydrosilylation reaction.
Polyethers of the component _{(A), - (C n H 2n O} ) - ( In the formula, n represents 2 to 4.) Shows a polyoxyalkylene polymer represented by.
As the polyoxyalkylene polymer unit, for example, oxyethylene units _{- (C 2 H 4 O)} -, oxypropylene units _{- (C 3 H 6 O)} -, oxybutylene units _{- (C 4 H 8 O)} -, Or the mixed unit etc. thereof are mentioned. The oxyalkylene units may be arranged by any method and can form either a block structure or a random copolymer structure, but it is preferable to form a random copolymer group. The polyoxyalkylene preferably contains both an oxyethylene unit (C ₂ H ₄ O) and an oxypropylene unit (C ₃ H ₆ O) in the random copolymer.

The organohydrogensiloxane of the component (B) is an organopolysiloxane containing at least one silicon-bonded hydrogen (SiH) per molecule. Examples of the organopolysiloxane include (R ₃ SiO _0.5 ), (R ₂ SiO), (RSiO _1.5 ), and (SiO ₂ ) (wherein, R is independently an organic group or Any number or combination of siloxy units (which are hydrocarbon groups).
When R of (R ₃ SiO _0.5 ), (R ₂ SiO) and (RSiO _1.5 ) of the organopolysiloxane is a methyl group, the siloxy units are M units, D units and T, respectively. Shown as a unit. On the other hand, (SiO ₂ ) siloxy units are shown as Q units.
The organohydrogensiloxane has a similar structure but has at least one SiH present on the siloxy unit.
Methyl-based siloxy units in the organohydrogensiloxane, ^{"M H"} siloxy units _(R 2 _{HSiO 0.5),} ^{"D H"} siloxy units (RHSiO), ^{"T H"} siloxy units _{(HSiO 1.5)} Can be represented as including.
The organohydrogensiloxane can include a condition that it contains at least one siloxy unit SiH, any number of ^{M, M H, D, D} H, T, T H, or Q siloxy units.

The component (A) and the component (B) are reacted by a hydrosilylation reaction. The hydrosilylation reaction is appropriately selected depending on the intended purpose without any limitation, but it is preferable to add a hydrosilylation catalyst.
The hydrosilylation catalyst is not particularly limited and may be appropriately selected depending on the intended purpose. And so on.
The content of the hydrosilylation catalyst is preferably 0.1 ppm to 1,000 ppm, more preferably 1 ppm to 100 ppm, based on the weight of the component (A) and the component (B).

The hydrosilylation reaction can be carried out without dilution or in the presence of a solvent, but it is preferably carried out in the presence of a solvent.
Examples of the solvent include alcohols (eg, methanol, ethanol, isopropanol, butanol, or n-propanol), ketones (eg, acetone, methyl ethyl ketone, or methyl isobutyl ketone); aromatic hydrocarbons (eg, benzene, toluene, Or xylene); aliphatic hydrocarbon (eg, heptane, hexane, or octane); glycol ether (eg, propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol n-butyl ether, propylene glycol n-propyl ether, or ethylene). Glycol n-butyl ether), halogenated hydrocarbon (for example, dichloromethane, 1,1,1-trichloroethane, methylene chloride, or chloroform), dimethyl Rusuruhokishido, dimethylformamide, acetonitrile, tetrahydrofuran, gasoline, mineral spirits, naphtha, and the like. These may be used alone or in combination of two or more.

The amounts of the component (A) and the component (B) used in the hydrosilylation reaction are not particularly limited and can be appropriately adjusted according to the purpose, and the amount of all unsaturated groups in the component (A) can be adjusted. Is represented by a molar ratio with the SiH content of the component (B). The amount of polyether unsaturated groups is preferably 20 mol% or less, and more preferably 10 mol% or less, based on the SiH molar amount of the organohydrogensiloxane. preferable.
The hydrosilylation reaction is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a batch method, a semi-continuous method and a continuous method. For example, a continuous method using a plug flow reactor may be used. It can be carried out.

Examples of commercially available products of the polyether-modified siloxane compound include 71ADDITIVE, 74ADDITIVE, 57ADDITIVE, 8029ADDITIVE, 8054ADDITIVE, 8211ADDITIVE, 8019ADDITIVE, 8526ADDITIVE, FZ-2123, FZ-2191; , TSF4441, TSF4445, TSF4446, TSF4450, TSF4452, TSF4460 (all manufactured by Momentive Performance Materials); Silface SAG002, Silface SAG003, Silface SAG005, Silface SAG503A, Sylface SAG008, Silface SJM003 ( BYGO-345, BYK-347, TEGO Wet KL245, TEGO Wet 250, TEGO Wet 260, TEGO Wet 265, TEGO Wet 270, TEGO Wet 280 (both manufactured by Evonik); BYK-348, BYK-375, BYK-377 (all manufactured by Big Chemie Japan) and the like can be mentioned. These may be used alone or in combination of two or more.
Among these, TEGO Wet 270 (manufactured by Evonik) and Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) are preferable.

  As the surfactant, in addition to the polyether-modified siloxane compound, a fluorine-based surfactant, a silicone-based surfactant, an acetylene glycol or an acetylene alcohol-based surfactant may be used in combination.

  The content of the surfactant is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less, based on the total amount of the ink. When the content is 0.001% by mass or more and 5% by mass or less, the ink becomes difficult to wet the ink repellent layer of the nozzle plate of the ink head, ejection defects due to ink nozzle adhesion are prevented, and ejection stability is improved. The effect is obtained.

<Water dispersible resin>
The water-dispersible resin has excellent film forming properties (image forming properties), high water repellency, high water resistance, and high weather resistance, and is suitable for image recording with high water resistance and high image density (high color development). It is useful.
Examples of the water-dispersible resin include condensation type synthetic resins, addition type synthetic resins, and natural polymer compounds. These may be used alone or in combination of two or more.

Examples of the condensed synthetic resin include polyester resin, polyurethane resin, polyepoxy resin, polyamide resin, polyether resin, poly (meth) acrylic resin, acryl-silicone resin, and fluorine resin.
Examples of the addition-based synthetic resin include polyolefin resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl ester resin, polyacrylic acid resin, unsaturated carboxylic acid resin, and the like.
Examples of the natural polymer compound include celluloses, rosins, and natural rubber.
Among these, fluororesins and acrylic-silicone resins are preferable.

The fluororesin is preferably a fluororesin having a fluoroolefin unit, and more preferably a fluorine-containing vinyl ether resin composed of a fluoroolefin unit and a vinyl ether unit.
As the fluoroolefin unit is not particularly limited and may be appropriately selected depending on the purpose, for _{example, -CF 2 CF 2 -, -} CF 2 CF (CF 3) -, - CF 2 CFCl- and Can be mentioned.
The vinyl ether unit is appropriately selected depending on the intended purpose without any limitation, and examples thereof include compounds represented by the following structural formulas.

The fluorine-containing vinyl ether resin composed of the fluoroolefin unit and the vinyl ether unit is preferably an alternating copolymer formed by alternately copolymerizing the fluoroolefin unit and the vinyl ether unit.
As such a fluorine-based resin, a properly synthesized resin may be used, or a commercially available product may be used. Examples of the commercially available product include Fluoronate FEM-500, FEM-600, Dickguard F-52S, F-90, F-90M, F-90N, and Aquafran TE-5A manufactured by Dainippon Ink and Chemicals, Inc .; Asahi Glass Co., Ltd. Lumiflon FE4300, FE4500, FE4400, Asahi Guard AG-7105, AG-950, AG-7600, AG-7000, AG-1100 and the like.

The water-dispersible resin may be used as a homopolymer, or may be used as a composite resin by being used as a copolymer, and any of single phase structure type, core shell type and power feed type emulsions Can be used.
As the water-dispersible resin, it is possible to use a resin which has a hydrophilic group and has self-dispersibility, or a resin which does not have dispersibility and which is dispersible with a surfactant or a resin having a hydrophilic group. . Among these, an ionomer of a polyester resin or a polyurethane resin or an emulsion of resin particles obtained by emulsion polymerization and suspension polymerization of an unsaturated monomer is most suitable. In the case of emulsion polymerization of an unsaturated monomer, a resin emulsion is prepared by reacting with unsaturated water, a polymerization initiator, a surfactant, a chain transfer agent, a chelating agent, and a pH adjusting agent. Therefore, the water-dispersible resin can be easily obtained, and the resin composition can be easily changed, so that the desired property can be easily produced.

  Examples of the unsaturated monomer include unsaturated carboxylic acids, monofunctional or polyfunctional (meth) acrylic acid ester monomers, (meth) acrylic acid amide monomers, and aromatic vinyl monomers. , Vinyl cyano compound monomers, vinyl monomers, allyl compound monomers, olefin monomers, diene monomers, oligomers having unsaturated carbon, etc., alone or in combination. You can It is possible to flexibly modify the properties by combining these monomers, and it is also possible to modify the properties of the resin by carrying out a polymerization reaction and a graft reaction using an oligomer type polymerization initiator.

Examples of the unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and the like.
Examples of the monofunctional (meth) acrylic acid ester monomers include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2 -Ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, methacryloxyethyl trimethyl ammonium. Salt, 3-me Cryloxypropyltrimethoxysilane, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate , Dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dimethylaminoethyl acrylate, acryloxyethyl trimethylammonium salt, and the like.

  As the polyfunctional (meth) acrylic acid ester monomers, for example, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1, 4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate, 2,2'-bis (4-methacryloxy) Diethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, polyethylene Glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate Acrylate, polypropylene glycol diacrylate, 2,2'-bis (4-acryloxyproproxyphenyl) propane, 2,2'-bis (4-acryloxydiethoxyphenyl) propane trimethylolpropane triacrylate, trimethylolethanetri Acrylate, tetramethylol methane triacrylate, ditrimethylol tetraacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate, Such as pentaerythritol hexaacrylate, and the like.

  Examples of the (meth) acrylic acid amide monomers include acrylamide, methacrylamide, N, N-dimethylacrylamide, methylenebisacrylamide, 2-acrylamido-2-methylpropanesulfonic acid and the like.

  Examples of the aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene, divinylbenzene and the like.

  Examples of the vinyl cyano compound monomers include acrylonitrile and methacrylonitrile.

Examples of the vinyl monomers include vinyl acetate, vinylidene chloride, vinyl chloride, vinyl ether, vinyl ketone, vinylpyrrolidone, vinylsulfonic acid or a salt thereof, vinyltrimethoxysilane, vinyltriethoxysilane and the like.
Examples of the allyl compound monomers include allylsulfonic acid salts thereof, allylamine, allyl chloride, diallylamine, diallyldimethylammonium salts and the like.
Examples of the olefin monomers include ethylene and propylene.
Examples of the diene monomers include butadiene and chloroprene.

  Examples of the oligomers having unsaturated carbon include styrene oligomers having methacryloyl groups, styrene-acrylonitrile oligomers having methacryloyl groups, methylmethacrylate oligomers having methacryloyl groups, dimethylsiloxane oligomers having methacryloyl groups, polyesters having acryloyl groups. Examples thereof include oligomers.

  Since the water-dispersible resin causes molecular chain breakage such as dispersion breakage or hydrolysis under strong alkaline or strong acidity, the pH is preferably 4 to 12, and particularly from the viewpoint of miscibility with a water-dispersible colorant. The pH is more preferably 6 to 11, and even more preferably 7 to 11.

The volume average particle diameter of the water-dispersible resin is related to the viscosity of the dispersion liquid, and for the same composition, the smaller the particle diameter, the larger the viscosity at the same solid content. The volume average particle diameter of the water-dispersible resin is preferably 50 nm or more so that the ink does not have an excessively high viscosity when made into an ink.
Further, when the particle diameter is several tens of μm, it becomes larger than the nozzle opening of the inkjet head and cannot be used. The presence of particles having a large particle size in the ink even if they are smaller than the nozzle opening deteriorates the ejection property. Therefore, the volume average particle diameter is more preferably 200 nm or less, still more preferably 150 nm or less, in order not to impair the ink ejection property.

The water-dispersible resin has a function of fixing the colorant on the paper surface, and is preferably formed into a film at room temperature to improve the fixability of the colorant. Therefore, the minimum film forming temperature (MFT) of the water-dispersible resin is preferably 30 ° C. or lower. Further, when the glass transition temperature of the water-dispersible resin is -40 ° C or lower, the viscosity of the resin film becomes strong and tack is generated on the printed matter, so that the glass transition temperature is -30 ° C or higher. It is preferable.
The content of the water-dispersible resin is preferably 0.5% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 8% by mass or less, based on the total amount of the ink.

<Other ingredients>
The other components are not particularly limited and may be appropriately selected as needed. Antioxidants, ultraviolet absorbers, oxygen absorbers, light stabilizers and the like can be mentioned.

-Foam suppressor-
The foam suppressor (defoaming agent) is used to suppress foaming by adding a very small amount to the ink. Here, the foaming means that the liquid becomes a thin film and wraps air. Characteristics such as surface tension and viscosity of ink are involved in the generation of bubbles. That is, a liquid having a high surface tension, such as water, is difficult to foam because the force that works to reduce the surface area of the liquid acts as much as possible. On the other hand, a high-viscosity, high-permeability ink is apt to foam due to its low surface tension, and bubbles generated due to the viscosity of the solution are easily maintained and are difficult to be defoamed.

Usually, the foam suppressor locally lowers the surface tension of the foam film to destroy the foam, or disperses the foam by injecting a foam inhibitor insoluble in the foam liquid on the surface of the foam liquid. When a polyether-modified siloxane compound having an extremely strong function of lowering the surface tension is used as the surfactant in the ink, the surface tension of the foam film is locally reduced even if the foam suppressor according to the former mechanism is used. It is not normally used because it cannot. Therefore, the latter foam suppressor that is insoluble in the foaming liquid is used, but in this case, the stability of the ink decreases due to the foam suppressor that is insoluble in the solution.
On the other hand, the foam suppressor represented by the following general formula (VIII) is not as strong in lowering the surface tension as the polyether-modified siloxane compound, but is highly compatible with the polyether-modified siloxane compound. For this reason, the foam suppressor is efficiently taken into the foam film, and the surface of the foam film is locally imbalanced due to the difference in surface tension between the polyether-modified siloxane compound and the foam suppressor, and the foam is destroyed. Conceivable.

  As the foam suppressor, a compound represented by the following general formula (A) is used.

<General formula (A)>
However, in the general formula (A), R ₄ and R ₅ are independently an alkyl group having 3 to 6 carbon atoms, and R ₆ and R ₇ are independently an alkyl group having 1 to 2 carbon atoms. And n is an integer of 1 to 6.

  Examples of the compound represented by the general formula (A) include 2,4,7,9-tetramethyldecane-4,7-diol, 2,5,8,11-tetramethyldodecane-5,8-. Examples include diols. Among these, 2,5,8,11-tetramethyldodecane-5,8-diol is preferable from the viewpoint of the foam-suppressing effect and the high compatibility with ink.

  The content of the foam suppressor is preferably 0.01% by mass or more and 10% by mass or less, and more preferably 0.1% by mass or more and 5% by mass or less, based on the total amount of the ink. When the content of the foam suppressor is 0.01% by mass or more, the effect of suppressing foam is obtained, and when the content of the foam suppressor is 10% by mass or less, good foam suppressing property is obtained, and the ink having the viscosity, the particle diameter and the like is obtained. The physical properties become appropriate.

-PH adjuster-
The pH adjuster is not particularly limited as long as it can adjust the pH to 7 to 11 without adversely affecting the ink to be prepared, and can be appropriately selected according to the purpose. For example, alcohol amine Examples thereof include hydroxides of alkali metal elements, hydroxides of ammonium, phosphonium hydroxides, carbonates of alkali metals, and the like. If the pH is less than 7 or more than 11, the amount of the inkjet head or the ink supply unit to be melted out is large, and defects such as alteration or leakage of ink and ejection failure may occur.
Examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol and the like.
Examples of the hydroxide of the alkali metal element include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like.
Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.
Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, potassium carbonate and the like.

− Antiseptic and antifungal agent −
Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, and sodium pentachlorophenol.

-Chelating reagent-
Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uramildiacetate.

-Rust preventive-
Examples of the rust preventive agent include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

-Antioxidant-
Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.

<Ink manufacturing method>
The ink of the present invention further needs to disperse or dissolve the colorant, the organic solvent, and the water, preferably the surfactant and the water-dispersible resin, and, if necessary, the other components in water. It is manufactured by stirring and mixing according to. The stirring and mixing can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, a stirrer using stirring blades, a magnetic stirrer, a high speed disperser, or the like.

-Ink physical properties-
The physical properties of the ink are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity and surface tension are preferably in the following ranges.
The viscosity of the ink at 25 ° C. is preferably 5 mPa · s to 25 mPa · s. More preferably, the viscosity at 25 ° C. is in the range of 6 mPa · s to 20 mPa · s. When the ink viscosity is 5 mPa · s or more, the effect of improving the printing density and the character quality can be obtained. On the other hand, by suppressing the ink viscosity to 25 mPa · s or less, the ejection property can be secured.
Here, the viscosity can be measured at 25 ° C. using a viscometer (RE-550L, manufactured by Toki Sangyo Co., Ltd.), for example.

The ink of the present invention is suitably used for either inkjet recording or spray coating.
The ink for ink-jet recording uses an ink-jet head as a pressure generating means for pressurizing the ink in the ink flow path by using a piezoelectric element to deform a vibration plate forming a wall surface of the ink flow path, thereby forming an ink flow path inner volume. Of a so-called piezo type that changes the temperature of the ink to eject ink droplets (see Japanese Patent Laid-Open No. 2-51734), or a so-called thermal type that heats the ink in the ink flow path using a heating resistor to generate bubbles. (See Japanese Patent Laid-Open No. 61-59911), the diaphragm forming the wall surface of the ink flow path and the electrode are arranged to face each other, and the diaphragm is deformed by the electrostatic force generated between the diaphragm and the electrode. Therefore, any ink jet head such as an electrostatic type (see Japanese Patent Laid-Open No. 6-71882) that changes the volume of the ink flow path to eject ink droplets It can be satisfactorily used in the printer for mounting.

(Ink container)
The ink container of the present invention contains the ink of the present invention in the container, and further has other members appropriately selected as necessary.
The container is not particularly limited, and its shape, structure, size, material and the like can be appropriately selected according to the purpose, and for example, an aluminum laminate film, an ink bag formed of a resin film or the like can be used at least. Preferable ones have.

Next, the ink container will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a diagram showing an example of the ink container, and FIG. 2 is a diagram including a case (exterior) of the ink container of FIG.
As shown in FIG. 1, the ink container 200 is filled into the ink bag 241 through the ink injection port 242, exhausted, and then the ink injection port 242 is closed by fusion. At the time of use, the ink discharge port 243 made of a rubber member is pierced with a needle of the apparatus main body and supplied to the apparatus.
The ink bag 241 is formed of a packaging member such as an aluminum laminated film having no air permeability. As shown in FIG. 2, the ink bag 241 is usually housed in a plastic cartridge case 244 and is detachably attached to various image forming apparatuses for use.

(Image forming method and image forming apparatus)
The image forming method of the present invention includes at least an ink jetting step, and further includes other steps appropriately selected as necessary.
The image forming apparatus of the present invention includes at least an ink ejecting unit, and further includes other units appropriately selected as necessary.

  The image forming method of the present invention can be suitably carried out by the image forming apparatus of the present invention, and the ink jetting step can be suitably carried out by the ink jetting means. Further, the other steps can be suitably performed by the other means.

<Ink flight process and ink flight means>
The ink flying step is a step of applying a stimulus (energy) to the ink of the present invention to fly the ink and form an image on a recording medium.
The ink flying unit is a unit that applies a stimulus (energy) to the ink of the present invention to fly the ink and form an image on a recording medium. The ink ejecting means is not particularly limited, and examples thereof include various nozzles for ejecting ink.

  The stimulus (energy) can be generated by, for example, the stimulus generating means, and the stimulus is not particularly limited and can be appropriately selected according to the purpose, and heat (temperature), pressure, vibration, Examples include light. These may be used alone or in combination of two or more. Among these, heat and pressure are preferable.

  Examples of the stimulus generating means include a heating device, a pressurizing device, a piezoelectric element, a vibration generating device, an ultrasonic oscillator, and a light. Specifically, for example, a piezoelectric actuator such as a piezoelectric element or a heating resistor. Examples include a thermal actuator that uses a phase change due to film boiling of a liquid using an electrothermal conversion element such as, a shape memory alloy actuator that uses a metal phase change due to a temperature change, and an electrostatic actuator that uses an electrostatic force.

  The mode of flight of the ink is not particularly limited and varies depending on the type of the stimulus, for example, when the stimulus is “heat”, thermal energy corresponding to a recording signal is applied to the ink in the recording head. Is applied by using a thermal head or the like, bubbles are generated in the ink by the thermal energy, and the ink is ejected as droplets from the nozzle holes of the recording head by the pressure of the bubbles. Is mentioned. When the stimulus is “pressure”, for example, when a voltage is applied to a piezoelectric element bonded to a position called a pressure chamber in the ink flow path in the recording head, the piezoelectric element bends and the volume of the pressure chamber increases. And a method of ejecting and ejecting the ink as droplets from the nozzle holes of the recording head.

<Other steps and other means>
The other steps are appropriately selected depending on the intended purpose without any limitation, and examples thereof include a drying step and a controlling step.
The other means is not particularly limited and may be appropriately selected depending on the purpose, and examples thereof include a drying means and a control means.

-Drying process and drying means-
The drying step is a step of heating and drying a recording medium on which an image is recorded with the ink, and is performed by a drying unit.
The drying is not particularly limited, and can be appropriately selected according to the purpose, for example, an infrared drying device, a microwave drying device, a roll heater, a drum heater or warm air. In addition, in order to smooth the image-formed surface and fix the image, a fixing step of heating the image-forming surface to 100 ° C. or more and 150 ° C. or less to heat-fix may be provided.
By providing the fixing step, the glossiness and the fixability of the image recorded matter are improved. Here, as the heat fixing unit, a roller having a heated mirror surface, a drum heater, or the like is preferably used, and the roll heater or the mirror surface portion (smooth portion) of the drum heater can be brought into contact with the image forming surface. Regarding the heating temperature, a fixing roller heated to 100 to 150 ° C. is preferable in consideration of image quality, safety and economy.

-Control process and control means-
The control step is a step of controlling each of the steps, and is performed by a control means.
The control means is not particularly limited as long as it can control the movement of each means, and can be appropriately selected according to the purpose, and examples thereof include equipment such as a sequencer and a computer.

Here, one mode for carrying out the image forming method of the present invention by the image forming apparatus of the present invention will be described with reference to the drawings.
The image forming apparatus shown in FIG. 3 stocks an apparatus main body 101, a paper feed tray 102 for loading sheets attached to the apparatus main body 101, and a sheet attached to the apparatus main body 101 on which an image is recorded (formed). It has a paper discharge tray 103 and an ink cartridge loading section 104. It is possible to feed various recording media using the paper feed tray 102.
On the upper surface of the ink cartridge loading unit 104, an operation unit 105 such as operation keys and a display is arranged. The ink cartridge loading unit 104 has an openable / closable front cover 115 for attaching and detaching the ink cartridge 200.
As shown in FIGS. 4 and 5, in the main body 101 of the apparatus, a carriage 133 is slid in the main scanning direction by guide rods 131 and stays 132, which are guide members extending laterally on left and right side plates (not shown). It is movably held and moved and scanned in the direction of the arrow in FIG. 5 by a main scanning motor (not shown).
On the carriage 133, a recording head 134 including four inkjet recording heads for ejecting ink droplets of yellow (Y), cyan (C), magenta (M), and black (Bk) is formed. Are arranged in a direction intersecting with the main scanning direction, and the ink droplet ejection direction is set downward.
The inkjet recording head that constitutes the recording head 134 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change due to film boiling of a liquid using an electrothermal conversion element such as a heating resistor, and a metal phase due to a temperature change. A shape memory alloy actuator that uses change, an electrostatic actuator that uses electrostatic force, or the like provided as an energy generating unit for ejecting ink can be used.
Further, the carriage 133 is equipped with a sub tank 135 of each color for supplying the ink of each color to the recording head 134. Ink is supplied to the sub tank 135 from the ink cartridge 200 loaded in the ink cartridge loading unit 104 via an ink supply tube (not shown) to be replenished.

On the other hand, as a sheet feeding unit for feeding the sheets 142 stacked on the sheet stacking unit (pressure plate) 141 of the sheet feeding tray 102, a half-moon roller (feeding unit) that separates and feeds the sheets 142 one by one from the sheet stacking unit 141. The paper roller 143) and a separation pad 144 made of a material having a large friction coefficient are provided so as to face the paper roller 143, and the separation pad 144 is urged toward the paper roller 143.
As a transport unit for transporting the paper 142 fed from the paper feed unit below the recording head 134, a transport belt 151 for electrostatically attracting and transporting the paper 142, and a guide 145 from the paper feed unit. A counter roller 152 for nipping and conveying the sheet 142 sent through the conveyance belt 151 with the conveyance belt 151, and the sheet 142 conveyed substantially vertically above are changed in direction by approximately 90 ° and made to follow the conveyance belt 151. And a charging roller 156 serving as a charging unit for charging the surface of the transport belt 151. Has been.

  The transport belt 151 is an endless belt, is stretched between a transport roller 157 and a tension roller 158, and can be rotated in the belt transport direction. The conveyor belt 151 is, for example, a surface layer serving as a paper suction surface formed of a resin material having a thickness of about 40 μm, which is not subjected to resistance control, for example, a copolymer of tetrafluoroethylene and ethylene (ETFE), and the same surface layer as this surface layer. It has a back layer (medium resistance layer, ground layer) whose resistance is controlled by carbon as a material. On the back side of the conveyor belt 151, a guide member 161 is arranged so as to correspond to the printing area of the recording head 134. In addition, as a paper ejection unit for ejecting the paper 142 recorded by the recording head 134, a separation claw 171 for separating the paper 142 from the conveyor belt 151, a paper ejection roller 172, and a paper ejection roller 173 are provided. The discharge tray 103 is disposed below the discharge rollers 172.

A double-sided paper feeding unit 181 is detachably attached to the back surface of the apparatus main body 101. The double-sided paper feeding unit 181 takes in the paper 142 returned by the reverse rotation of the conveyor belt 151, reverses it, and feeds it again between the counter roller 152 and the conveyor belt 151. A manual paper feeding unit 182 is provided on the upper surface of the double-sided paper feeding unit 181.
In the image forming apparatus, the paper 142 is separated and fed one by one from the paper feed unit, and the paper 142 fed substantially vertically upward is guided by the guide 145, and is fed between the conveyor belt 151 and the counter roller 152. It is sandwiched between and transported. Further, the front end is guided by the transfer guide 153 and pressed against the transfer belt 151 by the front end pressing roller 155, and the transfer direction is changed by about 90 °.

At this time, the conveyor belt 151 is charged by the charging roller 156, and the sheet 142 is electrostatically adsorbed to the conveyor belt 151 and conveyed. Therefore, by driving the recording head 134 according to the image signal while moving the carriage 133, ink droplets are ejected onto the stopped paper 142 to record one line, and after the paper 142 is conveyed by a predetermined amount, Record the next line. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 142 has reached the recording area, the recording operation is ended and the sheet 142 is discharged to the sheet discharge tray 103.
Then, when the near end of the remaining amount of ink in the sub tank 135 is detected, a required amount of ink is supplied from the ink cartridge 200 to the sub tank 135.

In the image forming apparatus, when the ink in the ink cartridge 200 is used up, the housing of the ink cartridge 200 can be disassembled and only the internal ink bag can be replaced. In addition, the ink cartridge 200 can supply ink stably even if it is vertically installed and has a front loading configuration. Therefore, even when the apparatus main body 101 is closed and installed, for example, when the apparatus main body 101 is housed in a rack or an object is placed on the upper surface of the apparatus main body 101, the ink cartridge 200 is replaced. Can be done easily.
Here, the example applied to the serial type (shuttle type) image forming apparatus in which the carriage scans has been described, but the present invention can also be applied to a line type image forming apparatus including a line type head.

  INDUSTRIAL APPLICABILITY The image forming apparatus and the image forming method of the present invention can be applied to various recordings by an inkjet recording method, and are particularly suitable for an inkjet recording printer, a facsimile machine, a copying machine, a printer / fax / copier composite machine, and the like. Can be applied to.

(Image formation)
The image-formed product of the present invention has an image formed by using the ink of the present invention on a recording medium.

<Recording media>
The recording medium is appropriately selected depending on the intended purpose without any limitation, and examples thereof include plain paper, glossy paper, special paper, cloth, film, OHP sheet, and general-purpose printing paper.
The image-formed product has high image quality, no bleeding, excellent stability over time, and can be suitably used for various applications as a material on which various kinds of printing or images are recorded.
Among these, since the image quality (image density, saturation, beading, color bleed) is excellent, the glossiness is high, and the image having excellent smear fixing property can be recorded, the liquid absorption property is within a certain range. The general-purpose printing paper of is suitable, specifically, a recording medium having a coating layer on at least one surface of the support, and the surface having the coating layer is a dynamic scanning liquid absorption meter. net transfer amount of said to the recording medium of water is 2 ml / ^{m 2} or more 35 ml / ^{m 2} or less and preferably in the measured contact time 100 ms, and the amount of transferred to the recording medium of pure water at a contact time of 400ms is 3 ml / m ² or more 40 ml / ^{m 2} or less is a recording medium is preferred.
In the case of a recording medium in which the amount of pure water transferred is too small even with the above ink, beading (a phenomenon in which adjacent dots are attracted to each other to make the image appear jerky) and color bleed (bleeding between colors) If the recording medium has an excessively large amount of pure water transferred, the diameter of the ink dot after recording may be smaller than the desired diameter, and a solid image may not be filled.
Here, this dynamic scanning absorptometer (DSA, Paper and Paper Cooperative Journal, Vol. 48, May 1994, pp. 88-92, Shigeru Kuiga) shows the amount of liquid absorption in an extremely short time. It is a device that can accurately measure. In this dynamic scanning liquid absorption meter, (i) the speed of the liquid absorption is directly read from the movement of the meniscus in the capillary, (ii) the sample is made into a disc shape, and the liquid absorption head is spirally scanned on the sample. The measurement is automated by a method in which the scanning speed is automatically changed according to a set pattern and the measurement is performed by the number of points required for one sample. The liquid supply head for the paper sample is connected to the capillary via a Teflon (registered trademark) tube, and the position of the meniscus in the capillary is automatically read by an optical sensor. Specifically, the transfer amount of pure water was measured using a dynamic scanning liquid absorption meter (K350 series D type, manufactured by Kyowa Seiko Co., Ltd.). The transfer amount at the contact time of 100 ms can be calculated by interpolation from the measured transfer amount at the contact time near the contact time.
Commercial products can be used as the general-purpose printing paper having the liquid absorption property within a certain range, and examples of the commercially available products include POD gloss coat, OK top coat +, OK Kinto +, SA Kinto + (Oji Paper Co., Ltd. Co., Ltd.), Super MI Dal, Aurora Coat, Space DX (made by Nippon Paper Industries Co., Ltd.), α mat, Mucoat (made by Hokuetsu Paper Mills Co., Ltd.), Raicho Art, Thunderbird Super Art (made by Chuetsu Pulp Industry Co., Ltd.), Pearl Coat N (manufactured by Mitsubishi Paper Mills Ltd.) and the like can be mentioned.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Preparation example 1)
-Preparation of Surface Modified Black Pigment Dispersion (1)-
Black Pearls (registered trademark) 1000 (carbon black having a BET specific surface area of 343 m ² / g and DBPA 105 mL / 100 g) manufactured by Cabot Corporation 100 g, 100 mM of sulfanilic acid, and 1 L of ion-exchanged high-purity water at room temperature. 6,000 rpm).
When the pH of the resulting slurry was higher than 4, 100 mmol of nitric acid was added. After 30 minutes, sodium nitrite (100 mmol) dissolved in a small amount of ion exchanged pure water was slowly added to the above mixture. Further, the mixture was heated to 60 ° C. with stirring and reacted for 1 hour. A modified pigment in which sulfanilic acid was added to carbon black could be produced.
Next, the pH was adjusted to 9 with a 10% by mass tetrabutylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane was performed using the obtained dispersion containing a pigment bonded to at least one sulfanilic acid group or a tetrabutylammonium sulfanilic acid salt and ion-exchanged pure water. Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The surface treatment level of the obtained modified pigment dispersion was 0.75 mmol / g, and the volume average particle diameter measured by a particle size distribution measuring device (Nanotrack UPA-EX150 manufactured by Nikkiso Co., Ltd.) was 120 nm.

(Preparation example 2)
-Preparation of Surface Modified Black Pigment Dispersion (2)-
In ProcessAll 4HV mixer (4 L), Black Pearls (registered trademark) 880 (carbon black having 220 m ² / g of BET specific surface area 220 m ² / g and 105 mL / 100 g of DBPA) manufactured by Cabot Corporation is ion-exchanged with 1 L of pure water and 4-aminobenzoic acid 1 Molar was added. The mixture was then mixed vigorously at 300 rpm for 10 minutes while warming to 60 ° C. A 20% by mass aqueous sodium nitrite solution [1 molar equivalent based on 4-aminobenzoic acid] was added thereto over 15 minutes. While heating to 60 ° C., the mixture was stirred for 3 hours. The reaction product was taken out while diluting it with 750 mL of ion-exchanged pure water.
Next, the pH was adjusted to 9 with a 10% by mass tetrabutylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane was performed using the obtained modified pigment dispersion containing a pigment bound to at least one aminobenzoic acid group or tetrabutylammonium aminobenzoate salt and ion-exchanged high-purity water. went. Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The surface treatment level of the obtained dispersion was 0.5 mmol / g, and the volume average particle diameter measured by a particle size distribution analyzer (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) was 104 nm.

(Preparation example 3)
-Preparation of surface-modified black pigment dispersion (3)-
In ProcessAll 4HV mixer (4L), Black Pearls (registered trademark) 880 (carbon black having BET specific surface area 220 m ² / g and DBPA 105 mL / 100 g) manufactured by Cabot Corporation (500 g), ion-exchanged high pure water 1 L, and 4-aminobenzoic acid. 175 mmol was added. The mixture was then mixed vigorously at 300 rpm for 10 minutes while warming to 60 ° C. To this was added a 20% by weight aqueous sodium nitrite solution [175 mmole based on 4-aminobenzoic acid] over 15 minutes. While heating to 60 ° C., the mixture was stirred for 3 hours. The reaction product was taken out while diluting it with 750 mL of ion-exchanged pure water.
Next, the pH was adjusted to 9 with a 10 mass% tetraethylammonium hydroxide aqueous solution to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane is performed using the modified pigment dispersion containing the pigment bound to at least one aminobenzoic acid group or aminobenzoic acid tetraethylammonium salt and ion-exchanged pure water. It was Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The surface treatment level of the obtained dispersion was 0.35 mmol / g, and the volume average particle size measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) was 114 nm.

(Preparation example 4)
-Preparation of surface-modified black pigment dispersion (4)-
1 kg of a self-dispersion carbon black Aqua-Black 162 (manufactured by Tokai Carbon Co., Ltd., pigment solid content: 19.2% by mass) was acid-deposited with a 0.1 N HCl aqueous solution. Then, the pH was adjusted to 9 with a 40% by mass benzyltrimethylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane was carried out using the modified pigment dispersion containing the pigment bound to at least one carboxylic acid group or carboxylic acid benzyltrimethylammonium salt and ion-exchanged pure water. . Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 100 nm.

(Preparation example 5)
-Preparation of Surface Modified Black Pigment Dispersion (5)-
SENSIJET Black SDP2000 (manufactured by SENSIENT, pigment solid content 14.5% by mass) 1 kg of a pigment dispersion was acid-deposited with 0.1N HCl aqueous solution. Then, the pH was adjusted to 9 with a 10% by mass tetrabutylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, using the obtained at least one carboxylic acid group, sulfonic acid group or carboxylic acid tetrabutylammonium salt, a modified pigment dispersion containing a pigment bonded to a sulfonic acid tetrabutylammonium salt, and ion-exchanged high-purity water. Ultrafiltration was performed using a dialysis membrane. Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured with a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 120 nm.

(Preparation example 6)
-Preparation of surface-modified magenta pigment dispersion (1)-
1 kg of SENSIJET SMART Magenta 3122BA (Pigment Red 122 surface-treated dispersion, pigment solid content 14.5% by mass, manufactured by SENSIENT) was subjected to acid precipitation with 0.1N HCl aqueous solution. Then, the pH was adjusted to 9 with a 10% by mass aqueous tetraethylammonium hydroxide solution to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane is performed using the modified pigment dispersion containing the pigment combined with at least one aminobenzoic acid group or tetraethylammonium aminobenzoate salt obtained and ion-exchanged pure water. Then, ultrasonic dispersion was further performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150 manufactured by Nikkiso Co., Ltd.), and it was 104 nm.

(Preparation Example 7)
—Preparation of Surface Modified Cyan Pigment Dispersion (1) —
1 kg of SENSIJET SMART Cyan 3154BA (Pigment Blue 15: 4 surface-treated dispersion, pigment solid content 14.5% by mass, manufactured by SENSIENT Co.) was subjected to acid precipitation with 0.1N HCl aqueous solution. Then, the pH was adjusted to 9 with a 40% by mass benzyltrimethylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane was performed using the modified pigment dispersion containing the pigment bonded to at least one aminobenzoic acid group or benzyltrimethylammonium aminobenzoate salt and ion-exchanged high-purity water. went. Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 116 nm.

(Preparation Example 8)
-Preparation of Surface Modified Yellow Pigment Dispersion (1)-
SENSIJET SMART Yellow 3074BA (Pigment Yellow 74 surface treatment dispersion, pigment solid content 14.5% by mass, manufactured by SENSIENT) 10% by mass tetrabutylammonium hydroxide solution (methanol solution) to adjust the pH to 30. After minutes, a modified pigment dispersion was obtained.
Next, ultrafiltration using a dialysis membrane was performed using the obtained modified pigment dispersion containing a pigment bound to at least one aminobenzoic acid group or tetrabutylammonium aminobenzoate salt and ion-exchanged high-purity water. Then, ultrasonic dispersion was further performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 145 nm.

(Preparation Example 9)
<Preparation of polymer particle dispersion containing carbon black pigment>
-Preparation of polymer solution A-
After thoroughly replacing the inside of a 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas introduction tube, a reflux tube, and a dropping funnel with nitrogen gas, 11.2 g of styrene, 2.8 g of acrylic acid, and 12.0 g of lauryl methacrylate. , Polyethylene glycol methacrylate 4.0 g, styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6) 4.0 g, and mercaptoethanol 0.4 g were mixed, and the temperature was raised to 65 ° C.
Next, 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxylethyl methacrylate, styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6). A mixed solution of 36.0 g, mercaptoethanol 3.6 g, azobismethylvaleronitrile 2.4 g, and methyl ethyl ketone 18 g was dropped into the flask over 2.5 hours. After the dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging for 1 hour at 65 ° C., 0.8 g of azobismethylvaleronitrile was added and further aging for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution A having a concentration of 50% by mass.

-Preparation of carbon black pigment-containing polymer particle dispersion-
28 g of the polymer solution A, C.I. I. After 42 g of carbon black (FW100, manufactured by Degussa), 13.6 g of a 1 mol / L potassium hydroxide aqueous solution, 20 g of methyl ethyl ketone, and 13.6 g of ion-exchanged water were sufficiently stirred, they were kneaded using a roll mill. The obtained paste was put into 200 g of pure water, stirred sufficiently, the methyl ethyl ketone and water were distilled off using an evaporator, and this dispersion was further subjected to polyvinylidene fluoride having an average pore size of 5.0 μm in order to remove coarse particles. The mixture was filtered under pressure with a membrane filter to obtain a carbon black pigment-containing polymer particle dispersion having a pigment solid content of 15% by mass and a solid content concentration of 20% by mass.
The volume average particle diameter of the polymer fine particles in the obtained carbon black pigment-containing polymer particle dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 104 nm.

(Preparation Example 10)
-Preparation of Surface Modified Black Pigment Dispersion (6)-
1 kg of COJ400 (manufactured by Cabot, pigment solid content 15% by mass) pigment dispersion was acid-deposited with a 0.1 N HCl aqueous solution. Then, the pH was adjusted to 9 with a 10% by mass tetrabutylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, using the obtained at least one carboxylic acid group, sulfonic acid group or carboxylic acid tetrabutylammonium salt, a modified pigment dispersion containing a pigment bonded to a sulfonic acid tetrabutylammonium salt, and ion-exchanged high-purity water. Ultrafiltration was performed using a dialysis membrane. Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 105 nm.

(Preparation Example 11)
-Preparation of surface-modified magenta pigment dispersion (2)-
0.5 kg of COJ465M (manufactured by Cabot, 15% by mass of pigment solids) pigment dispersion and 0.5 kg of COJ480V (manufactured by Cabot, 15% by mass of pigment solids) pigment dispersion were acid-deposited with 0.1N HCl aqueous solution. . Then, the pH was adjusted to 9 with a 10% by mass aqueous tetraethylammonium hydroxide solution to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane is performed using the modified pigment dispersion containing the pigment combined with at least one aminobenzoic acid group or tetraethylammonium aminobenzoate salt obtained and ion-exchanged pure water. Then, ultrasonic dispersion was further performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 100 nm.

(Preparation Example 12)
-Preparation of surface-modified cyan pigment dispersion (2)-
1 kg of COJ450C (manufactured by Cabot, pigment solid content: 15% by mass) pigment dispersion was acid-deposited with a 0.1N HCl aqueous solution. Then, the pH was adjusted to 9 with a 40% by mass benzyltrimethylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane was performed using the modified pigment dispersion containing the pigment bonded to at least one aminobenzoic acid group or benzyltrimethylammonium aminobenzoate salt and ion-exchanged high-purity water. went. Furthermore, ultrasonic dispersion was performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 111 nm.

(Preparation example 13)
-Preparation of Surface Modified Yellow Pigment Dispersion (2)-
1 kg of COJ470Y (manufactured by Cabot, pigment solid content 15% by mass) was subjected to acid precipitation with a 0.1 N HCl aqueous solution. Then, the pH was adjusted to 9 with a 40% by mass benzyltrimethylammonium hydroxide solution (methanol solution) to obtain a modified pigment dispersion after 30 minutes.
Next, ultrafiltration using a dialysis membrane was performed using the obtained modified pigment dispersion containing a pigment bound to at least one aminobenzoic acid group or tetrabutylammonium aminobenzoate salt and ion-exchanged high-purity water. Then, ultrasonic dispersion was further performed to obtain a modified pigment dispersion in which the pigment solid content was concentrated to 20% by mass.
The volume average particle diameter of the obtained dispersion was measured with a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.), and it was 130 nm.

(Production Example 1)
-Preparation of acrylic-silicone polymer particle dispersion-
After thoroughly replacing the inside of a 1 L flask equipped with a mechanical stirrer, a thermometer, a nitrogen gas introduction tube, a reflux tube, and a dropping funnel with nitrogen gas, a reactive anionic surfactant (Latemur S-180, Kao Corporation) 8.0 g (manufactured by the company) and 350 g ion-exchanged water were added and mixed, and the temperature was raised to 65 ° C. After heating, 3.0 g of t-butyl peroxobenzoate and 1.0 g of sodium isoascorbate, which are reaction initiators, were added, and after 5 minutes, 45 g of methyl methacrylate, 160 g of 2-ethylhexyl methacrylate, 5 g of acrylic acid, butyl methacrylate. 45 g, cyclohexyl methacrylate 30 g, vinyltriethoxysilane 15 g, reactive anionic surfactant (Latemur S-180, manufactured by Kao Co., Ltd.) 8.0 g, and ion-exchanged water 340 g are mixed and added dropwise over 3 hours. I went.
Then, the mixture was heat-aged at 80 ° C. for 2 hours, cooled to room temperature and adjusted to pH 7-8 with sodium hydroxide.
Next, ethanol was distilled off using an evaporator and the water content was adjusted to prepare 730 g of polymer particle dispersion of Production Example 1 having a solid content of 40% by mass.
The volume average particle diameter of the obtained polymer particle dispersion was measured by a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.) and found to be 125 nm.

(Example 1)
<Preparation of ink>
In a container equipped with a stirrer, 20.00 parts by mass of 3-n-butoxy-N, N-dimethylpropanamide of structural formula (1), 25.00 parts by mass of 1,2-propanediol, 2,2,4- Trimethyl-1,3-pentanediol 2.00 parts by mass, polyether modified siloxane compound of structural formula (VII) 1.00 parts by mass, and 2,4,7,9-tetramethyldecane-4,7-diol 0. .50 parts by mass was added, and the mixture was stirred for 30 minutes to make it uniform.
Next, 0.05 part by mass of antifungal agent (Proxel GXL, manufactured by Avicia), 0.20 part by mass of 2-amino-2-ethyl-1,3-propanediol, and surface-modified black pigment dispersion of Preparation Example 1. 37.50 parts by mass of body 1 and the remaining amount of pure water were added to make 100 parts by mass, and the mixture was stirred for 60 minutes to make the ink uniform.
The obtained ink was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore diameter of 1.2 μm to remove coarse particles and dust, to prepare an ink of Example 1.

(Example 2)
In a container equipped with a stirrer, 40 parts by mass of 3-ethyl-3-hydroxymethyloxetane of structural formula (4), 2 parts by mass of 2,2,4-trimethyl-1,3-pentanediol and structural formula (IX) 2 parts by mass of the polyether-modified siloxane compound and 0.5 parts by mass of 2,4,7,9-tetramethyldecane-4,7-diol were added, and the mixture was stirred for 30 minutes to make the mixture uniform.
Next, 0.05 part by mass of antifungal agent (Proxel GXL, manufactured by Abyssia), 0.2 part by mass of 2-amino-2-ethyl-1,3-propanediol, surface-modified black pigment dispersion of Preparation Example 1 37.5 parts by mass of the body 1 and the remaining pure water were added, and the mixture was stirred for 60 minutes to make it uniform.
Further, 5 parts by mass of the acrylic-silicone polymer particle dispersion of Production Example 1 was added and stirred for 30 minutes to make the ink uniform.
The obtained ink was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, to prepare an ink of Example 2.

(Examples 3 to 19 and Comparative Examples 1 to 8)
In the same manner as in Example 1 or Example 2, the organic solvent, the surfactant, and the defoaming agent shown in Tables 1 to 6 below were mixed and stirred. Then, the antifungal agent, the pH adjuster, and the water-dispersible colorant (pigment dispersion) were mixed and stirred, and further, the water-dispersible resin was mixed and stirred to make the ink uniform.
The obtained ink was pressure-filtered with a polyvinylidene fluoride membrane filter having an average pore diameter of 1.2 μm to remove coarse particles and dust, to prepare each ink of Examples 3 to 19 and Comparative Examples 1 to 8. .

Abbreviations in Tables 1 to 6 have the following meanings.
* SENSIJET SMART Magenta 3122BA: manufactured by SENSIENT (surface-treated pigment dispersion)
* SENSIJET SMART Cyan 3154BA: manufactured by SENSIENT (surface-treated pigment dispersion)
* SENSIJET SMART Yellow 3074BA: manufactured by SENSIENT (surface-treated pigment dispersion)
* SENSIJET Black SDP2000: manufactured by SENSIENT (surface-treated pigment dispersion)
* Fluorine resin emulsion: Asahi Glass Co., Ltd., Lumiflon FE4300, solid content 50% by mass, average particle size 150 nm, MFT = 30 ° C or less * Organic solvent represented by the following structural formula (1)

[Structural formula (1), SP value: 9.03]
* Organic solvent represented by the following structural formula (4)

[Structural formula (4), SP value: 11.3]

* Polyether-modified siloxane compound represented by the following structural formula (VII)

[Structural Formula (VII)]
* Polyether-modified siloxane compound represented by the following structural formula (IX)

[Structural Formula (IX)]
* Polyether-modified siloxane compound represented by the following structural formula (X)

[Structural Formula (X)]

* TEGO Wet270: Polyether-modified siloxane compound (Evonik, 100% by weight of active ingredient)
* Silface SAG503A: Polyether-modified siloxane compound (manufactured by Nisshin Chemical Industry Co., Ltd., active ingredient 100% by mass)
* Unidyne DSN403N: Polyoxyethylene perfluoroalkyl ether (manufactured by Daikin Industries, Ltd., active ingredient 100% by mass)
* Zonyl FS-300: Polyoxyethylene perfluoroalkyl ether (DuPont, active ingredient 40% by mass)
* Surfynol 104E: Acetylene glycol compound (manufactured by Nisshin Chemical Industry Co., Ltd., 100% by mass of active ingredient)
* Softanol EP-7025: higher alcohol ethoxylate compound (Nippon Shokubai Co., Ltd., active ingredient 100% by mass)
* Proxel GXL: 1,2-benzisothiazolin-3-one main component antifungal agent (manufactured by Avicia, 20% by mass, containing dipropylene glycol)

  Next, the ink physical properties of the inks of Examples 1 to 19 and Comparative Examples 1 to 8 were measured as follows. The results are shown in Table 7.

<Viscosity measurement>
The viscosity of the ink was measured at 25 ° C. using a viscometer (RE-550L, manufactured by Toki Sangyo Co., Ltd.).

<PH measurement>
The pH of the ink was measured at 25 ° C. using a pH meter (HM-30R type, manufactured by TOA-DKK Co., Ltd.).

<Dynamic surface tension measurement>
The dynamic surface tension of the ink of the present invention was measured at 25 ° C. using a SITA_DynoTester (manufactured by SITA) at a surface life of 15 msec according to the maximum bubble pressure method.

<Static surface tension>
The static surface tension of the ink was measured at 25 ° C. using an automatic surface tension meter (DY-300, manufactured by Kyowa Interface Science Co., Ltd.).

-Image formation-
Using an image forming apparatus (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) under environmental conditions adjusted to 23 ° C. ± 0.5 ° C. and 50 ± 5% RH, the piezo element of the piezo element is adjusted so that the ink ejection amount becomes even. The drive voltage was changed so that the same amount of ink was attached to OK top coat + (basis weight 104.7 g / m ² ) manufactured by Oji Paper Co., Ltd. as a recording medium.

  Next, various characteristics of Examples 1 to 19 and Comparative Examples 1 to 8 were evaluated as described below. The results are shown in Table 8.

<Image density>
A chart with 64 point characters "black square" created by Microsoft Word2000 was printed on MyPaper (manufactured by Ricoh Co., Ltd.) as a recording medium, and the "black square" portion of the printing surface was measured by a spectral densitometer (X -Rite 939, manufactured by X-Rite Co., Ltd.), and the color was evaluated according to the following evaluation criteria. The print mode was changed from "plain paper-standard fast" mode to "no color correction" from the plain paper user setting with the driver attached to the printer.
The “black square” is a character (code) in which the square is filled in black, but it cannot be used and is therefore expressed as “black square”.
〔Evaluation criteria〕
A: Black: 1.25 or more, Yellow: 0.8 or more, Magenta: 1.00 or more, Cyan: 1.05 or more B: Black: 1.20 or more and less than 1.25, Yellow: 0.75 or more 0. Less than 8, Magenta: 0.95 to less than 1.00 full, Cyan: 1.0 to less than 1.05 C: Black: 1.15 to less than 1.20 Yellow: 0.70 to less than 0.75, Magenta : 0.90 or more and less than 0.95 full, Cyan: 0.95 or more and less than 1.00 D: Black: less than 1.15, Yellow: less than 0.70, Magenta: less than 0.95, Cyan less than 0.95

<Beading>
The recording medium was changed to OK Top Coat + (basis weight 104.7 g / m ² ) manufactured by Oji Paper Co., Ltd., and the print mode was changed from “Glossy paper-clean” mode to “No color correction” with the driver attached to the printer. Using the above mode, a solid image was printed in the same manner as the image density, and the density unevenness (beading) of the solid image was visually observed and judged according to the following evaluation criteria.
〔Evaluation criteria〕
A: None at all B: Slightly present C: Fairly present D: Violent * The black solid image is very difficult to see with the naked eye, so it was observed with an optical microscope at a magnification of 40 times.

<Discharge stability-1: Intermittent discharge evaluation>
Continuously print 200 sheets of a chart that fills 5% of the area of A4 size paper per color created with Microsoft Word 2000 with a solid image on MyPaper (manufactured by Ricoh Co., Ltd.). evaluated. As the print mode, a mode in which the "plain paper-standard fast" mode was changed to "no color correction" from the user setting for plain paper using the driver attached to the printer was used.
〔Evaluation criteria〕
A: No discharge turbulence B: Some discharge turbulence C: Discharge turbulence or no discharge

<Discharge stability-2: Nozzle plate ink repellency time>
In an environment adjusted to a temperature of 23 ± 0.5 ° C. and a relative humidity of 50% ± 5%, 50 g of each ink was placed in a 50 mL beaker and used in an image forming apparatus (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.). Take out the nozzle plate of the head, sandwich it with tweezers, soak it in the ink at a speed of 315 mm / min, and measure the ink repellency time (ink closing time) from the ink repellant layer of the nozzle plate when taken out at the same speed, The following criteria evaluated. The ink repellent layer is Optool DSX manufactured by Daikin Industries, Ltd.
〔Evaluation criteria〕
A: Ink repellency time is less than 10 seconds B: Ink repellency time is 10 seconds or more and less than 30 seconds C: Ink repellency time is 30 seconds or more and less than 60 seconds D: Ink repellency time is 60 seconds or more Since the plate is easily wet with ink, the nozzles are easily missed in continuous ejection evaluation.

<Gamut cover rate>
C, M, Y, R, G patches with 6 or more hues of C, M, Y, R, G, and B created by Microsoft Word2000 in an area ratio of 10% to 100% , And the chart including the patch of 8 steps or more in which K is added from 0% to 100% to the area ratio 100% patch of B, is output to Lumiart Gloss 130 gsm (manufactured by STORE ENSO) as a recording medium, and the spectrum is output. The L ^* a ^* b ^* color space was measured using a densitometer (X-Rite 939, manufactured by X-Rite Co., Ltd.).
Next, in the color gamut area in which six points C, M, Y, R, G, and B projected on the a ^* b ^* plane for each lightness L ^* are connected by a straight line, the color gamut of the evaluation color is obtained. A value (inclusive volume) of a value obtained by integrating the area and the area of a region in which the gamut area of the target color overlaps in the lightness direction (inclusive volume), and the gamut volume of the target color (inclusive volume / gamut volume of the target color), That is, the gamut coverage rate was obtained. The gamut cover rate of 90% or more is a pass level.
As the target color, a color reproduction area in the L ^* a ^* b ^* color space defined by “ISO-compliant 2011 Japan sheet-for-sheet printing 2011 (abbreviation: Japan Color 2011 coated paper)” was used.

Aspects of the present invention are as follows, for example.
<1> An ink containing at least a colorant, an organic solvent, and water,
At least one organic solvent having a solubility parameter of 9 or more and less than 11.8 is contained as the organic solvent, and the content of the organic solvent having the solubility parameter of 9 or more and less than 11.8 is 20% by mass or more based on the total amount of the ink. Yes,
The dynamic surface tension A of the ink at 25 ° C. and the surface lifetime 15 msec by the maximum bubble pressure method is 34.0 mN / m or less, and the dynamic surface tension A and the static surface tension of the ink at 25 ° C. B is an ink characterized by satisfying the following expression: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%.
<2> The dynamic surface tension A of the ink at 25 ° C. and the surface lifetime 15 msec by the maximum bubble pressure method is 30.0 mN / m or less, and the dynamic surface tension A and the static temperature of the ink at 25 ° C. The surface tension B is the ink according to <1>, which satisfies the following formula: 12.0% ≦ [(A−B) / (A + B)] × 100 ≦ 17.0%.
<3> The ink according to any one of <1> to <2>, wherein the static surface tension B of the ink at 25 ° C. is 20.0 mN / m or more and 30.0 mN / m or less.
<4> The organic solvent having a solubility parameter of 9 or more and less than 11.8 is at least one selected from compounds represented by the following general formula (I) and the following general formula (II). The ink according to any one of 3>.
[General Formula (I)]
However, in the general formula (I), R ′ represents an alkyl group having 4 to 6 carbon atoms.
[General Formula (II)]
However, in the general formula (II), R ″ represents an alkyl group having 1 to 2 carbon atoms.
<5> The ink according to any one of <1> to <4>, wherein the organic solvent does not contain a polyhydric alcohol having an equilibrium water content of 30% or more at a temperature of 23 ° C. and a relative humidity of 80%.
<6> The ink according to any one of <1> to <5>, further containing a surfactant.
<7> The ink according to <6>, wherein the surfactant contains a polyether-modified siloxane compound.
<8> The ink according to <7>, wherein the polyether-modified siloxane compound is at least one selected from compounds represented by the following general formulas (III) to (VI).
[General Formula (III)]
However, in the said General formula (III), m shows the integer of 0-23, n shows the integer of 1-10. a shows the integer of 1-23, b shows the integer of 0-23. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General Formula (IV)]
However, in said general formula (IV), m shows the integer of 1-8, c and d show the integer of 1-10. R ₂ and R ₃ represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General formula (V)]
In the general formula (V), e represents an integer from 1 to 8, _{R 4} represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General formula (VI)]
However, in the general formula (VI), f represents an integer of 1 to 8. R ₅ represents a polyether group represented by the following general formula (A).
[General formula (A)]
However, in the general formula (A), g represents an integer of 0 to 23, h represents an integer of 0 to 23, and g and h are not 0 at the same time. R ₆ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
<9> The ink according to any one of <6> to <8>, in which the content of the polyether modified siloxane compound is 0.001% by mass or more and 5% by mass or less.
<10> The ink according to any one of <1> to <9>, wherein the colorant is a water-dispersible pigment.
<11> The ink according to <10>, wherein the water-dispersible pigment has a hydrophilic functional group on the surface, and the hydrophilic functional group is a quaternary ammonium salt.
<12> The ink according to <10>, wherein the water-dispersible pigment is a modified pigment modified with at least one of a geminal bisphosphonic acid group and a geminal bisphosphonic acid group.
<13> The ink according to any one of <10> to <12>, wherein the water-dispersible pigment is at least one selected from a black pigment, a cyan pigment, a magenta pigment, and a yellow pigment.
<14> The colorant is any one selected from carbon black pigments, phthalocyanine pigments, quinacridone pigments, monoazo pigments, and disazo pigments,
The ink according to any one of the items <1> to <13>, which has a gamut cover ratio reproduced by using the ink, and covers 90% or more of the gamut cover ratio defined by Japan Color 2011 coated paper. .
<15> The ink according to any one of <1> to <14>, further containing a water-dispersible resin.
<16> The ink according to any one of <1> to <15>, which is either for inkjet recording or spray coating.
<17> An ink container comprising the ink according to any one of <1> to <16> contained in a container.
<18> An ink for recording an image by applying the ink according to any one of <1> to <16> with at least one kind of stimulus selected from heat, pressure, vibration and light, and flying the ink. An image forming method including at least a flying step.
<19> An ink for recording an image by applying the ink according to any one of <1> to <16> with at least one kind of stimulus selected from heat, pressure, vibration, and light, and flying the ink. An image forming apparatus having at least a flying unit.
<20> An image-formed product comprising an image formed using the ink according to any one of <1> to <16> on a recording medium.
<21> Any of <12> to <16>, wherein the modified pigment is modified with at least one group selected from the following structural formulas (i), (ii), (iii) and (iv). The ink described in Crab.
However, in the structural formula (iii), X ⁺ represents Li ⁺ , K ⁺ , Na ⁺ , NH ₄ ⁺ , N (CH ₃ ) ₄ ⁺ , N (C ₂ H ₅ ) ₄ ⁺ , N (C ₃ H). ₇ ) ₄ ⁺ and N (C ₄ H ₉ ) ₄ ⁺ .
However, in the structural formula (iv), X ⁺ represents Li ⁺ , K ⁺ , Na ⁺ , NH ₄ ⁺ , N (CH ₃ ) ₄ ⁺ , N (C ₂ H ₅ ) ₄ ⁺ , N (C ₃ H). ₇ ) ₄ ⁺ and N (C ₄ H ₉ ) ₄ ⁺ .
<22> The ink according to any one of <10> to <16>, wherein the water-dispersible resin is either acrylic-silicone resin particles or fluorine-based resin particles.

  The ink according to any one of <1> to <16> and <21> to <22>, the ink container according to <17>, the image forming method according to <18>, and the <19>. According to the image forming apparatus described in the above and the image formed article described in the above <20>, it is possible to solve the above-mentioned problems in the related art and achieve the object of the present invention.

JP2012-207202A JP, 2014-94998, A

200 ink container 241 ink bag 242 ink inlet 243 ink outlet 244 cartridge case

Claims (19)

An ink containing at least a colorant, an organic solvent, and water,
At least one organic solvent having a solubility parameter of 9 or more and less than 11.8 is contained as the organic solvent, and the content of the organic solvent having the solubility parameter of 9 or more and less than 11.8 is 20% by mass or more based on the total amount of the ink. Yes,
The organic solvent having a solubility parameter of 9 or more and less than 11.8 is at least one selected from compounds represented by the following general formula (I) and the following general formula (II),
The organic solvent does not contain a polyhydric alcohol having an equilibrium water content of 30% or more at a temperature of 23 ° C. and a relative humidity of 80%,
The dynamic surface tension A of the ink at 25 ° C. and the surface lifetime 15 msec by the maximum bubble pressure method is 34.0 mN / m or less, and the dynamic surface tension A and the static surface tension of the ink at 25 ° C. B is an ink characterized by satisfying the following expression: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%.
[General Formula (I)]
However, in the general formula (I), R ′ represents an alkyl group having 4 to 6 carbon atoms.
[General Formula (II)]
However, in the general formula (II), R ″ represents an alkyl group having 1 to 2 carbon atoms. An ink containing at least a colorant, an organic solvent, a surfactant, and water,
The organic solvent contains at least one organic solvent having a solubility parameter of 9 or more and less than 11.8, and the content of the organic solvent having a solubility parameter of 9 or more and less than 11.8 is 20% by mass or more based on the total amount of the ink. Yes,
The organic solvent having a solubility parameter of 9 or more and less than 11.8 is at least one selected from compounds represented by the following general formula (I) and the following general formula (II),
The surfactant comprises a polyether modified siloxane compound,
The polyether-modified siloxane compound is at least one selected from compounds represented by the following general formulas (III) to (VI),
The dynamic surface tension A of the ink at 25 ° C. and the surface lifetime 15 msec by the maximum bubble pressure method is 34.0 mN / m or less, and the dynamic surface tension A and the static surface tension of the ink at 25 ° C. B is an ink characterized by satisfying the following expression: 10.0% ≦ [(A−B) / (A + B)] × 100 ≦ 19.0%.
[General Formula (I)]
However, in the general formula (I), R ′ represents an alkyl group having 4 to 6 carbon atoms.
[General Formula (II)]
However, in the general formula (II), R ″ represents an alkyl group having 1 to 2 carbon atoms.
[General Formula (III)]
However, in the said General formula (III), m shows the integer of 0-23, n shows the integer of 1-10. a shows the integer of 1-23, b shows the integer of 0-23. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General Formula (IV)]
However, in said general formula (IV), m shows the integer of 1-8, c and d show the integer of 1-10. R _Two And R _Three Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General formula (V)]
However, in the general formula (V), e represents an integer of 1 to 8 and R _Four Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General formula (VI)]
However, in the general formula (VI), f represents an integer of 1 to 8. R ₅ Represents a polyether group represented by the following general formula (A).
[General formula (A)]
However, in the general formula (A), g represents an integer of 0 to 23, h represents an integer of 0 to 23, and g and h are not 0 at the same time. R ₆ Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The ink according to claim 1, further comprising a surfactant. The ink according to claim 3, wherein the surfactant includes a polyether-modified siloxane compound. The ink according to claim 4, wherein the polyether-modified siloxane compound is at least one selected from compounds represented by the following general formulas (III) to (VI).
[General Formula (III)]
However, in the said General formula (III), m shows the integer of 0-23, n shows the integer of 1-10. a shows the integer of 1-23, b shows the integer of 0-23. R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General Formula (IV)]
However, in said general formula (IV), m shows the integer of 1-8, c and d show the integer of 1-10. R _Two And R _Three Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General formula (V)]
However, in the general formula (V), e represents an integer of 1 to 8 and R _Four Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
[General formula (VI)]
However, in the general formula (VI), f represents an integer of 1 to 8. R ₅ Represents a polyether group represented by the following general formula (A).
[General formula (A)]
However, in the general formula (A), g represents an integer of 0 to 23, h represents an integer of 0 to 23, and g and h are not 0 at the same time. R ₆ Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The ink according to claim 2, wherein the content of the polyether-modified siloxane compound is 0.001% by mass or more and 5% by mass or less. The dynamic surface tension A of the ink at 25 ° C. and the surface lifetime 15 msec by the maximum bubble pressure method is 30.0 mN / m or less, and the dynamic surface tension A and the static surface tension of the ink at 25 ° C. The ink according to any one of claims 1 to 6, wherein B and B satisfy the following formula: 12.0% ≤ [(A-B) / (A + B)] x 100 ≤ 17.0%. The ink according to claim 1, wherein the static surface tension B of the ink at 25 ° C. is 20.0 mN / m or more and 30.0 mN / m or less. The ink according to any one of claims 1 to 8, wherein the colorant is a water-dispersible pigment. The ink according to claim 9, wherein the water-dispersible pigment has a hydrophilic functional group on its surface, and the hydrophilic functional group is a quaternary ammonium salt. The ink according to claim 9, wherein the water-dispersible pigment is a modified pigment modified with at least one of a geminal bisphosphonic acid group and a geminal bisphosphonic acid group. The ink according to claim 9, wherein the water-dispersible pigment is at least one selected from a black pigment, a cyan pigment, a magenta pigment, and a yellow pigment. The colorant is any one selected from carbon black pigment, phthalocyanine pigment, quinacridone pigment, monoazo pigment, and disazo pigment,
  The ink according to any one of claims 1 to 12, wherein the gamut cover ratio reproduced using the ink covers 90% or more of the gamut cover ratio defined by Japan Color 2011 coated paper. The ink according to claim 1, further comprising a water-dispersible resin. The ink according to any one of claims 1 to 14, which is used for inkjet recording or spray coating. An ink container comprising the ink according to any one of claims 1 to 15 in a container. 16. An ink flying step of applying the ink according to any one of claims 1 to 15 with at least one stimulus selected from heat, pressure, vibration, and light, and flying the ink to record an image. And an image forming method. 16. At least an ink flight means for applying the ink according to any one of claims 1 to 15 with at least one kind of stimulus selected from heat, pressure, vibration, and light to fly the ink and record an image. An image forming apparatus characterized by. An image-formed product, comprising an image formed by using the ink according to claim 1 on a recording medium.