JP2017186472A - Aqueous inkjet ink composition and inkjet method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous inkjet ink composition excellent in clogging resistance in a head and allowing formation of an image with excellent rubbing resistance, and an inkjet method.SOLUTION: The aqueous inkjet ink composition relating to an embodiment of the present invention comprises a resin, a nitrogen-containing solvent having an SP value difference of 3 or less with respect to the resin, and water. The content of the nitrogen-containing solvent is 2 to 9 pts.mass with respect to 1 pt.mass of the resin, and a content of an organic solvent having a standard boiling point of 280°C or higher is 3 mass% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water-based inkjet ink composition and an inkjet method.

  The ink jet recording method is capable of recording high-definition images with a relatively simple device, and has been rapidly developed in various fields. Among them, various studies have been made on ejection stability and the like. For example, Patent Document 1 discloses a step of heating a non-ink-absorbing or low-absorbing recording medium to a temperature range of 40 ° C. to 60 ° C. to discharge droplets of a water-based inkjet ink composition, and a recording medium. And a step of drying the water-based ink composition ejected onto the recording medium by heating to a temperature range of 40 ° C. or more and 90 ° C. or less.

JP 2011-201230 A

  Conventionally, a resin is added to a water-based inkjet ink composition (hereinafter simply referred to as an ink composition) used for recording on a non-ink-absorbing or low-absorbing recording medium in order to give a recorded material having excellent abrasion resistance. ing. The resin is dissolved and dispersed in the ink composition as resin particles (resin emulsion).

  When the ink stays in the pressure chamber due to the influence of bubbles or the like generated in the ink jet head, the ink composition is easily dried by receiving heat from the platen. As a result, there is a problem that the resin emulsion resin contained in the ink composition is welded to the head wall surface and clogging occurs. At present, the resin deposited on the wall of the head cannot be removed even after cleaning. In addition, there is a problem that the ink composition is dried and the clogging is caused in the ink jet head left at the time when printing is stopped.

  In particular, from the viewpoint of increasing the drying speed of the ink composition on a non-ink-absorbing or low-absorbing recording medium and forming an abrasion-resistant image, when the ink composition does not contain a high-boiling solvent, an inkjet head The ink tends to dry inside, and the above-described problems are likely to occur. As described above, improvement in abrasion resistance and improvement in clogging resistance in the head are in a trade-off relationship, and it has been difficult to achieve both.

  The present invention has been made to solve at least a part of the above-described problems, and is a water-based inkjet ink composition and inkjet method capable of forming an image excellent in clogging resistance in a head and excellent in abrasion resistance. The purpose is to provide.

  The present inventors diligently studied to solve the above problems. As a result, the ratio of the content of the combination of the ink resin and the nitrogen-containing solvent having a SP value of 3 or less is 2 to 9 parts by mass of the nitrogen-containing solvent with respect to 1 part by mass of the resin. It has been found that the resin is sufficiently dissolved and easily formed into a film, has excellent abrasion resistance, and the resin deposited in the head is difficult to remove by cleaning and difficult to recover.

  One aspect of the present invention includes a resin, a nitrogen-containing solvent having a SP value difference of 3 or less with respect to the resin, and water, and the content of the nitrogen-containing solvent is 2 to 9 masses per 1 part by mass of the resin. Part, and the content of the organic solvent having a standard boiling point of 280 ° C. or higher is 3% by mass or less.

  In the present invention, the ratio of the combination of the resin and the nitrogen-containing solvent having a SP value of 3 or less is 2 to 9 parts by mass of the nitrogen-containing solvent with respect to 1 part by mass of the resin. The nitrogen-containing solvent can stably dissolve the resin therein, and the aggregation of the resin and the adhesion of the resin to the inner wall of the head due to the drying of the ink composition can be suppressed, and the ejection stability can be improved. In the present invention, the content of the organic solvent having a normal boiling point of 280 ° C. or higher is 3% by mass or less, so that the drying property of the ink can be improved, and the resin is easily formed into a film on the recording medium, and the rub resistance is improved. it can.

  Preferably, the mass ratio of the nitrogen-containing solvent to the total mass of the organic solvent contained in the water-based inkjet ink composition is 0.2 to 0.7. By setting the mass ratio of the nitrogen-containing solvent to the total mass of the organic solvent in the above range, the nitrogen-containing solvent can stably dissolve the resin, and the resin agglomerates due to drying of the ink composition and the resin on the inner wall of the head. Welding can be suppressed.

  Preferably, the mass ratio of the total mass of the organic solvent contained in the water-based inkjet ink composition to the mass of the water is 0.2 to 0.7. By setting the mass ratio of the total mass of the organic solvent to the mass of water in the above range, the nitrogen-containing solvent can stably dissolve the resin in the ink composition, and the resin agglomerates by drying the ink composition. In addition, the welding of the resin to the inner wall of the head can be suppressed.

  Preferably, the content of the nitrogen-containing solvent is 3 to 30% by mass. By setting the content of the nitrogen-containing solvent within the above range, the nitrogen-containing solvent can stably dissolve the resin in the ink composition, and the resin agglomerates and the resin on the inner wall of the head due to drying of the ink composition. Can be suppressed.

  Preferably, the content of the resin is 1 to 15% by mass. When the resin content is less than 1% by mass, the abrasion resistance tends to be inferior. When the resin content exceeds 15% by mass, the nitrogen-containing solvent cannot stably dissolve the resin, and the resin tends to be welded in the head by drying the ink composition.

  Preferably, the surfactant contains at least one of a silicone-based surfactant, an acetylene glycol-based surfactant, and a fluorine-based surfactant. By the combination of the nitrogen-containing solvent and these surfactants, even when the resin is welded to the inner wall of the head, the welded resin can be peeled off from the inner wall of the head and redissolved in the nitrogen-containing solvent.

  Preferably, the standard boiling point of the nitrogen-containing solvent is 180 ° C. or higher and lower than 280 ° C. Thereby, volatilization of the nitrogen-containing solvent contained in the ink composition in the head can be prevented, and nozzle clogging can be prevented. Further, when the ink composition adheres to the recording medium, the nitrogen-containing solvent can be quickly volatilized, and sufficient image quality can be obtained on a recording medium that is non-ink-absorbing or low-absorbing.

  One embodiment of the present invention is an inkjet method including a step of ejecting the above-described aqueous inkjet ink composition from a nozzle of an inkjet head and attaching it to a recording medium. Thereby, it is possible to improve ejection stability while forming an image having abrasion resistance.

  Preferably, the surface temperature of the recording medium when the water-based inkjet ink composition is attached to the recording medium is 70 ° C. or less. By making the surface temperature of the recording medium in the adhering step as low as 70 ° C. or lower, drying of the ink composition inside the ink jet head can be suppressed, and resin welding to the inner wall of the head can be prevented.

  Preferably, the method includes a step of drying the recording medium after the step of attaching the aqueous inkjet ink composition to the recording medium, and the surface temperature of the recording medium in the step is 70 ° C. or higher. Thereby, the resin contained in the ink composition is welded and solidified on the recording medium, and an image having abrasion resistance is formed on the recording medium.

  Preferably, the ink-jet head includes a pressure chamber and an element that applies pressure to the pressure chamber to discharge the water-based ink-jet ink composition from the nozzle, and the position facing the outlet communicating with the nozzle in the pressure chamber. The element is arranged at a place other than. In such an ink jet head, by using the ink composition described above, it is possible to suppress the resin from being welded to the inner wall of the ink jet head, to improve the clogging property, and to provide an image having abrasion resistance with respect to the recording medium. Can record.

  For example, the method includes a step of attaching a reaction liquid containing an aggregating agent that aggregates the components of the water-based inkjet ink composition to the recording medium.

  For example, it is preferable to perform recording for 1 hour or more without performing a step of applying pressure to the inkjet head from the outside and discharging the aqueous inkjet ink composition from the nozzle. Alternatively, it is preferable to perform recording without performing a step of applying pressure to the inkjet head from the outside and discharging the aqueous inkjet ink composition from the nozzle during recording. Furthermore, it is preferable to perform a step of applying an external pressure to the inkjet head and discharging the aqueous inkjet ink composition from the nozzle before or after recording. Even in such a case, by using the ink composition described above, the resin is prevented from welding to the inner wall of the inkjet head, the clogging property is improved, and the recording medium is rub-resistant. Images can be recorded.

It is the schematic of the inkjet head of this embodiment. It is the schematic of the inkjet apparatus used for the inkjet method of this embodiment.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary. However, the present invention is not limited to this, and the gist thereof is described below. Various modifications are possible without departing from the scope. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, positional relationships such as up, down, left and right are based on the positional relationships shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

[Ink composition]
The ink composition of the present embodiment includes a resin, a nitrogen-containing solvent having an SP value difference of 3 or less with respect to the resin, and water, and the content of the nitrogen-containing solvent is 2 to 9 parts by mass with respect to 1 part by mass of the resin. It is a water-based inkjet ink composition which is a mass part, and whose content of the organic solvent having a standard boiling point of 280 ° C. or higher is 3% by mass or less.

  When the ink stays in the pressure chamber due to the influence of bubbles or the like generated in the ink jet head, the ink composition is easily dried by receiving heat from the platen. As a result, there is a problem that the resin emulsion resin contained in the ink composition is welded to the head wall surface and clogging occurs. The resin welded to the wall surface of the head has a problem in that it cannot be eliminated by wiping or flushing the nozzle plate, and it cannot be sufficiently eliminated by suction cleaning. In addition, there is a problem that the ink composition is dried and the clogging is caused in the ink jet head left at the time when printing is stopped.

  Such a problem is closely related to the ease of welding of the resin. From the viewpoint of the abrasion resistance of the recorded material, it is desirable that the resin be easily welded onto the recorded material. For this reason, improvement in abrasion resistance and improvement in clogging resistance in the head are in a trade-off relationship, and it is difficult to achieve both.

  In contrast, in the ink composition of the present embodiment, the content ratio of the combination of the resin and the nitrogen-containing solvent whose SP value is within 3 is 2 to 9 mass of the nitrogen-containing solvent with respect to 1 mass part of the resin. By setting it as a part, the nitrogen-containing solvent can stably dissolve the resin in the ink composition, and the welding of the resin in the head due to the drying of the ink composition can be suppressed. The resin welded in the head is not easily removed by cleaning and is not easily recovered. In addition, the ink composition of the present embodiment can improve the drying property of the ink because the content of the organic solvent having a standard boiling point of 280 ° C. or higher is 3% by mass or less, and the resin can be easily formed into a film on the recording medium. Abrasion resistance can be improved. As a result, the ink composition of the present embodiment achieves both improved abrasion resistance and improved clogging resistance in the head. Hereinafter, each component contained in the ink composition will be described.

[Color material]
A pigment or dye can be used as the color material, but a pigment is preferably used. Although it does not specifically limit as a pigment, For example, the following are mentioned.

  Although it does not specifically limit as a black pigment, For example, it is No. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B, etc. (Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (above, Columbia Carbon, Carbon 1 Rubbi 400, Carbon Co. Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (Cabot Corp. CA Kol. , Color B lack FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color B1ack S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A , Special Black 4 (manufactured by Degussa).

  Although it does not specifically limit as a white pigment, For example, C.I. I. Pigment White 6, 18, 21, and white inorganic pigments of titanium oxide, zinc oxide, zinc sulfide, antimony oxide, magnesium oxide, and zirconium oxide. In addition to the white inorganic pigment, white organic pigments such as white hollow resin particles and polymer particles can also be used.

  Although it does not specifically limit as a pigment used for yellow ink, For example, C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 167, 172, 180.

  Although it does not specifically limit as a magenta pigment, For example, C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or C.I. I. Pigment violet 19, 23, 32, 33, 36, 38, 43, 50.

  Although it does not specifically limit as a cyan pigment, For example, C.I. I. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16, 18, 22, 25, 60, 65, 66, C.I. I. Bat Blue 4, 60.

  In addition, the pigment used in color inks other than magenta, cyan, and yellow is not particularly limited. I. Pigment green 7,10, C.I. I. Pigment brown 3, 5, 25, 26, C.I. I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63.

  Although it does not specifically limit as a pearl pigment, For example, the pigment which has pearl luster and interference gloss, such as titanium dioxide covering mica, fish scale foil, and bismuth acid chloride, is mentioned.

  Although it does not specifically limit as a metallic pigment, For example, the particle | grains which consist of single bodies or alloys, such as aluminum, silver, gold | metal | money, platinum, nickel, chromium, tin, zinc, indium, titanium, copper, are mentioned.

  The content of the pigment is preferably 0.4 to 12% by mass, more preferably 1 to 8% by mass, and further preferably 2 to 5% by mass with respect to 100% by mass of the ink composition.

[Resin particles]
The ink composition of this embodiment includes resin particles of a resin having a SP value difference of 3 or less with respect to the nitrogen-containing solvent. By selecting such a resin, the nitrogen-containing solvent can stably dissolve the resin particles in the ink composition, and the resin agglomerates and the resin adheres to the inner wall of the head by drying the ink composition. Can be suppressed.

Here, the SP value in the present invention will be described. As the SP value, the Hansen solubility parameter is used. The Hansen solubility parameter is a three-dimensional space where the solubility parameter introduced by Hildebrand is divided into three components: a dispersion term δd, a polar term δp, and a hydrogen bond term δh. In the present invention, the SP value is represented by δ [(cal / cm ³ ) ^0.5 ], and a value calculated using the following formula is used.
δ [(cal / cm ³ ) ^0.5 ] = (δd ² + δp ² + δh ² ) ^0.5

  The dispersion term δd, the polar term δp, and the hydrogen bond term δh are demanded by Hansen and its successors, and are described in detail in Polymer Handbook (fourth edition), VII-698 to 711. In addition, Hansen solubility parameter values for many solvents and resins have been investigated, see, for example, Wesley L., et al. It is described in Archer, Industrial Solvents Handbook.

  The SP value of the resin can be adjusted by changing the type and mass ratio of monomers used for resin synthesis. The resin is not particularly limited. For example, (meth) acrylic acid, (meth) acrylic acid ester, acrylonitrile, cyanoacrylate, acrylamide, olefin, styrene, vinyl acetate, vinyl chloride, vinyl alcohol, vinyl ether, vinyl pyrrolidone, vinyl Examples include homopolymers or copolymers of pyridine, vinyl carbazole, vinyl imidazole, and vinylidene chloride, fluororesins, and natural resins. Among these, at least one of (meth) acrylic resin and styrene- (meth) acrylic acid copolymer resin is preferable, and at least one of acrylic resin and styrene-acrylic acid copolymer resin is more preferable. A styrene-acrylic acid copolymer resin is more preferable. In addition, said copolymer may be any form among a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer.

  Although said resin is not specifically limited, For example, it can obtain by the preparation method shown below, You may combine a some method as needed. As the preparation method, a polymerization catalyst (polymerization initiator) and a dispersant are mixed in a monomer of a component constituting a desired resin, and polymerization (emulsion polymerization) is performed. A resin having a hydrophilic portion is dissolved in water. A method of removing a water-soluble organic solvent by distillation after mixing a solution obtained by dissolving in a water-soluble organic solvent into water, and a solution obtained by dissolving a resin in a water-insoluble organic solvent together with a dispersant in an aqueous solution The method of mixing is mentioned.

  The resin content is preferably 1% by mass or more and 15% by mass or less, more preferably 2% by mass or more and 10% by mass, and further preferably 3% by mass or more and 7% by mass or less. By setting the resin content within the above range, the resin can be stably dissolved while improving the abrasion resistance, and the resin agglomerates and the resin adheres to the inner wall of the head by drying the ink composition. Can be suppressed.

〔water〕
The ink composition of this embodiment contains water. Examples of water include water from which ionic impurities have been removed as much as possible, such as pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, and ultrapure water. Further, when water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is used, generation of mold and bacteria can be prevented when the pigment dispersion and ink using the same are stored for a long period of time.

  The water content is not particularly limited, but the present invention preferably contains a larger amount of water than the solvent (organic solvent) described later. The ink is also called a “water-based ink” and has at least water as a main component as a solvent component contained in the ink. The water content is preferably 40 to 95% by mass, more preferably 45 to 90% by mass, and further preferably 50 to 80% by mass with respect to 100% by mass of the water-based ink composition. Preferably it is 55-75 mass%, More preferably, it is 60-70 mass%.

(Nitrogen-containing solvent)
The ink composition of the present embodiment includes a nitrogen-containing solvent having a SP value difference of 3 or less with respect to the resin of the resin particles, and the content of the nitrogen-containing solvent is 2 to 9 parts by mass with respect to 1 part by mass of the resin. Preferably, it is 2.5-8 mass parts, More preferably, it is 3-7 mass parts. By including 2 to 9 parts by mass of a nitrogen-containing solvent having an SP value difference of 3 or less with respect to 1 part by mass of the resin, the resin can be stably dissolved, and even when drying of the ink composition proceeds, It is possible to prevent the resin from aggregating and welding to the inner wall of the head. As a result, clogging in the vicinity of the nozzles of the head during ink jet recording is prevented, and the ejection stability of the ink composition tends to be more excellent. Further, the nitrogen-containing solvent has an effect of promoting the softening of the resin particles, and the adhesion tends to be improved even when the heating temperature is low.

   The nitrogen-containing solvent is not particularly limited, and examples thereof include pyrrolidone, imidazolidinone, amide ether, pyridine, pyrazine, and pyridone. Pyrrolidone is preferable, and examples include 2-pyrrolidone, N-methyl-2-pyrrolidone, and N-ethyl-2-pyrrolidone. A nitrogen-containing solvent may be used individually by 1 type, and may use 2 or more types together.

  The content of the nitrogen-containing solvent is preferably 3% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 20% by mass or less, and further preferably 10% by mass with respect to the total amount of the ink composition. The content is 15% by mass or less. By setting the content of the nitrogen-containing solvent within the above range, the nitrogen-containing solvent can stably dissolve the resin in the ink composition, and the resin agglomerates and the resin on the inner wall of the head due to drying of the ink composition. Can be suppressed.

(Claim 7)
The standard boiling point of the nitrogen-containing solvent is preferably 180 ° C. or higher and lower than 280 ° C., more preferably 190 ° C. or higher and lower than 250 ° C., further preferably 200 ° C. or higher and lower than 250 ° C. Thereby, volatilization of the nitrogen-containing solvent contained in the ink composition in the head can be prevented, and nozzle clogging can be prevented. Further, when the ink composition adheres to the recording medium, the nitrogen-containing solvent can be quickly volatilized, and sufficient image quality can be obtained on a recording medium that is non-ink-absorbing or low-absorbing.

(Other organic solvents)
The ink in the present embodiment may further contain an organic solvent other than the nitrogen-containing solvent. Other organic solvents other than the above are not particularly limited, but specifically, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl Ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol Butyl ether, diethylene glycol mono-t-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono- n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol 2-butanol, tert-butanol, iso-butanol, n-pentanol, 2-penta Lumpur, 3-pentanol, and tert- alcohols or glycols such as pentanol. Another solvent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The mass ratio of the nitrogen-containing solvent to the total mass of the organic solvent contained in the ink composition is preferably 0.2 to 0.7, more preferably 0.3 to 0.6, and still more preferably 0.8. 4 to 0.5. By setting the mass ratio of the nitrogen-containing solvent to the total mass of the organic solvent in the above range, the nitrogen-containing solvent can stably dissolve the resin, and the resin agglomerates due to drying of the ink composition and the resin on the inner wall of the head. Welding can be suppressed.

  The mass ratio of the total mass of the organic solvent to the mass of water is preferably 0.2 to 0.7, more preferably 0.2 to 0.6, and still more preferably 0.3 to 0.5. is there. By setting the mass ratio of the total mass of the organic solvent to the mass of water in the above range, the nitrogen-containing solvent can stably dissolve the resin in the ink composition, and the resin agglomerates by drying the ink composition. In addition, the welding of the resin to the inner wall of the head can be suppressed.

  The preferable range of the normal boiling point of the other organic solvent is the same as that of the nitrogen-containing solvent, preferably 180 ° C. or higher and lower than 280 ° C., more preferably 190 ° C. or higher and lower than 250 ° C., further preferably 200 ° C. Above 250 ° C. Thereby, volatilization of the organic solvent contained in the ink composition in the head can be prevented, and nozzle clogging can be prevented. In addition, when the ink composition adheres to the recording medium, the organic solvent can be quickly volatilized, and sufficient image quality can be obtained on a non-ink-absorbing or low-absorbing recording medium.

  The total amount of the organic solvent including the nitrogen-containing solvent is preferably 5.0% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 25% by mass or less, and further preferably 15% by mass with respect to the total amount of the ink. % To 20% by mass.

(Solvent with a boiling point of 280 ° C or higher)
In the ink composition of the present embodiment, the content of the organic solvent having a standard boiling point of 280 ° C. or higher is 3% by mass or less. When the ink composition contains an organic solvent having a standard boiling point of 280 ° C. or higher, the drying property of the ink on the recording medium is significantly lowered. As a result, in various recording media, in particular, non-ink-absorbing or low-absorbing recording media, not only unevenness in image density is noticeable, but also ink fixing properties cannot be obtained.

  The content of the organic solvent having a standard boiling point of 280 ° C. or higher in the ink composition is preferably 2% by mass or less, more preferably 1% by mass or less, and further preferably 0.5% by mass or less with respect to the total mass of the ink composition. Preferably, 0% by mass or more and less than 0.1% by mass is particularly preferable, 0% by mass or more and less than 0.05% by mass is more preferable, 0% by mass or more and less than 0.01% by mass is even more preferable, and 0% by mass or more and 0% by mass or less. Most preferred is less than 0.001 mass%. When the content is in the above range, the recorded material using the ink composition is suppressed from being deteriorated by an organic solvent having a normal boiling point of 280 ° C. or more, and a recorded material having more excellent abrasion resistance is obtained. Can be obtained.

[Surfactant]
The ink composition of the present embodiment preferably contains a surfactant. The surfactant is not particularly limited, and examples thereof include acetylene glycol surfactants, fluorine surfactants, and silicone surfactants. Of these, acetylene glycol surfactants and silicone surfactants are preferred. By the combination of the nitrogen-containing solvent and these surfactants, even when the resin is welded to the inner wall of the head, the welded resin can be peeled off from the inner wall of the head and redissolved in the nitrogen-containing solvent.

  The acetylene glycol-based surfactant is not particularly limited, and examples thereof include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5- Selected from alkylene oxide adducts of decyne-4,7-diol and alkylene oxide adducts of 2,4-dimethyl-5-decyn-4-ol and 2,4-dimethyl-5-decyn-4-ol One or more are preferred. Although it does not specifically limit as a commercial item of acetylene glycol-type surfactant, For example, E series (A product made by Air Products Japan (Inc)) (Surfinol 465), such as Olfine 104 series and Olfine E1010, Surfinol 61 and Surfinol DF110D (trade names manufactured by Nissin Chemical Industry CO., Ltd.) can be used. One acetylene glycol surfactant may be used alone, or two or more acetylene glycol surfactants may be used in combination.

  The fluorosurfactant is not particularly limited. For example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, perfluoroalkyl betaine, A fluoroalkylamine oxide compound is mentioned. Although it does not specifically limit as a commercial item of a fluorochemical surfactant, For example, S-144, S-145 (made by Asahi Glass Co., Ltd.); FC-170C, FC-430, Fluorard-FC4430 (made by Sumitomo 3M Co., Ltd.) FSO, FSO-100, FSN, FSN-100, FS-300 (manufactured by Dupont); FT-250, 251 (manufactured by Neos). A fluorine-type surfactant may be used individually by 1 type, and may use 2 or more types together.

  Examples of silicone surfactants include polysiloxane compounds and polyether-modified organosiloxanes. Although it does not specifically limit as a commercial item of a silicone type surfactant, Specifically, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (above trade name, manufactured by Big Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF- 945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (all trade names, manufactured by Shin-Etsu Chemical Co., Ltd.) Etc.

  The content of the surfactant is preferably 0.1 to 2.0% by mass, more preferably 0.1 to 1.7% by mass, and further preferably 100% by mass with respect to 100% by mass of the ink composition. It is 0.1-1.5 mass%. When the content of the surfactant is 2.0% by mass or less, the abrasion resistance tends to be further improved. Further, when the content of the surfactant is 0.1% by mass or more, the embedding property of the obtained recorded matter tends to be further improved and the ejection stability tends to be further improved. Improving the ejection stability is easy to remove even if the resin is fixed, and it becomes possible to remove the fixed resin efficiently by head cleaning, etc. It is considered that the presence of the surfactant in the surface facilitates loosening of the fixed resin mass.

[Other ingredients]
The ink used in the present embodiment maintains its storage stability and ejection stability from the head, improves clogging, or prevents ink deterioration, solubilizing aid, viscosity adjusting agent, pH Various additives such as a modifier, an antioxidant, an antiseptic, an antifungal agent, a corrosion inhibitor, and a chelating agent for capturing metal ions that affect the dispersion can be appropriately added.

[Inkjet head]
FIG. 1 shows a schematic diagram of an ink jet head used in the ink jet method of the present embodiment. The ink jet head 2 according to the present embodiment includes a pressure chamber 21 and a piezoelectric element 23 that applies pressure to the pressure chamber 21 to discharge the ink composition from the nozzle 22. In the pressure chamber 21, the outlet 24 communicates with the nozzle 22. The piezoelectric element 23 is disposed at a place other than the position opposite to. In the case where the piezoelectric element 23 is provided immediately above the nozzle 22, the pushing force of the ink from the piezoelectric element 23 is transmitted to the resin 25 that is more directly fixed, so that the resin can be fixed. In the case where the piezoelectric element 23 is not provided immediately above the nozzle 22, it is difficult to eliminate the sticking of the resin, so that the present invention is particularly useful. The position of the pressure chamber 21 that faces the outlet 24 that communicates with the nozzle 22 is, as shown in FIG. 1, when the line is extended upward from the wall of the outlet 24 and is surrounded by the extension line and the extension line. It is an area. For example, in the head of FIG. 1, the outlet 24 is a portion having the same area as the nozzle 22 in the direction perpendicular to the direction in which ink is ejected. The fact that the piezoelectric element 23 is disposed in a place other than the position means that at least a part of the piezoelectric element 23 is not present in at least a part of this region. In this case, it is preferable in that the degree of freedom in designing the piezoelectric element and the pressure chamber is high.

  A plurality of pressure chambers 21 and piezoelectric elements 23 and nozzles 22 provided for each pressure chamber 21 may be provided in one head independently of each other. The piezoelectric element 23 changes the volume of the pressure chamber 21 by mechanical deformation. Instead of the piezoelectric element 23, an electrothermal conversion element that generates bubbles by discharging heat to generate ink may be used.

  When the solvent and water in the ink composition are volatilized from the nozzle, the composition in the ink composition is changed, and the resin dispersed in the ink is aggregated and welded to the inner wall of the cavity as shown in FIG. Such resin welding hinders the movement of the ink composition in the cavity, and as a result, causes a phenomenon that the ink is not ejected normally. In contrast, by using the ink composition of the present embodiment, the resin is difficult to weld in the cavity, and even if the resin is welded, the surfactant can remove (peel) it. It becomes. Therefore, even when the continuous printing time is long, the ink composition can be normally discharged, and in addition, it is possible to obtain a recorded matter having excellent abrasion resistance.

[Inkjet method]
The ink jet method of the present embodiment includes an attaching step of ejecting the ink composition from the nozzles of the ink jet head and attaching the ink composition to a recording medium. Thereby, it is possible to improve ejection stability while forming an image having abrasion resistance.

[Adhesion process]
The upper limit of the surface temperature of the recording medium in the attaching step is preferably 70 ° C. or less, more preferably 50 ° C. or less, further preferably 45 ° C. or less, particularly preferably 40 ° C. or less, and most preferably. It is 38 degrees C or less. The lower limit of the surface temperature of the recording medium in the attaching step is not limited, but is preferably 20 ° C. or higher, more preferably 25 ° C. or higher, further preferably 30 ° C. or higher, and particularly preferably 32 ° C. or higher. It is. Accordingly, since the radiant heat received from the platen is small or eliminated, drying and composition variation of the ink composition in the inkjet head can be suppressed, and the resin can be prevented from being welded to the inner wall of the head.

  Before attaching the ink composition, a step of attaching a reaction liquid containing an aggregating agent for aggregating the components of the ink composition to the recording medium may be provided. Thereby, the temperature of the recording medium in the attaching step can be lowered.

  The reaction solution attaching step is a step of attaching a reaction solution containing at least one of a polyvalent metal compound, an organic acid and a cationic resin to a recording medium. All of the polyvalent metal compound, organic acid and cationic resin contained in the reaction liquid react with the pigment contained in the ink composition, the pigment dispersion resin that can be contained in the ink composition, and the like, thereby aggregating the pigment. It has the function. Thereby, generation | occurrence | production of the bleeding etc. of the image recorded using an ink composition can be suppressed, and the image of the outstanding image quality is obtained.

[Drying process]
The ink jet method according to the present embodiment may include a drying step of drying the recording medium to which the ink composition is attached after the discharging step. As a result, the resin contained in the ink composition on the recording medium is melted, and a recorded matter with good embedding can be formed. At that time, the temperature of the recording medium in the drying step is preferably 50 to 150 ° C, more preferably 70 ° C to 120 ° C, and further preferably 80 ° C to 100 ° C. When the drying temperature is within the above range, the abrasion resistance tends to be further improved.

The ink jet method according to this embodiment may include a step of applying pressure to the ink jet head from the outside and discharging the ink composition from the nozzle. By providing this process, even when there is a concern that the resin is welded to the inner wall of the ink jet head, it is possible to suppress this and further improve the clogging property.
In the ink jet method according to this embodiment, it is preferable to perform recording for 1 hour or more without performing a step of applying pressure to the ink jet head from the outside and discharging the ink composition from the nozzle. This is preferable because the recording speed is not reduced by interrupting the recording in accordance with the process. Even in such a case, by using the ink composition described above, the resin is prevented from welding to the inner wall of the inkjet head, the clogging property is improved, and the recording medium is rub-resistant. Images can be recorded. Here, the pressure applied from the outside is suction (negative pressure) or applying a positive pressure upstream of the head. It is not ink discharge (flushing) due to the function of the head itself. That is, it is not discharging using the function of discharging ink from the head during recording. The recording time may not be continuous, and may be paused unless the ink composition is discharged from the nozzle by applying pressure to the inkjet head from the outside. That is, it is the cumulative time of recording. The recording time is preferably 1 hour or longer, more preferably 1.5 hours or longer, still more preferably 2 hours or longer. The upper limit of the recording time is not limited, but it is preferably 4 hours or less, more preferably 3 hours or less.
In addition, the ink jet method according to the present embodiment does not perform the step of applying an external pressure to the ink jet head during recording and discharging the ink composition from the nozzle during one recording. Is preferable. In addition, it is preferable to perform the step of applying pressure from the outside to the ink jet head and discharging the ink composition from the nozzle at least either before or after recording.

〔recoding media〕
Although it does not specifically limit as a recording medium used in the inkjet method of this embodiment, For example, an absorptive recording medium, a non-absorbing recording medium, or a low absorptive recording medium is mentioned. Among these, it is preferable to use a non-absorbing recording medium or a low-absorbing recording medium, and it is more preferable to use a non-absorbing recording medium. In the non-absorbing recording medium or the low-absorbing recording medium, the lower the absorption and the more the non-absorbing recording medium, the lower the embedding property due to the repelling of the water-based ink composition. Therefore, it is advantageous to use the inkjet method inkjet according to the present embodiment for such a recording medium.

Here, “low-absorbing recording medium” or “non-absorbing recording medium” refers to a recording medium having a water absorption of 10 mL / m ² or less from the start of contact to 30 msec in the Bristow method. This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method".

  Further, the non-absorbent recording medium or the low-absorbent recording medium can be classified by the wettability of the recording surface with respect to water. For example, a 0.5 μL water droplet is dropped on the recording surface of the recording medium, and the reduction rate of the contact angle (comparison of the contact angle at 0.5 ms after landing and the contact angle at 5 seconds) is measured. Can be characterized. More specifically, as a property of the recording medium, the non-absorbing property of the “non-absorbing recording medium” indicates that the above-mentioned reduction rate is less than 1%, and the low-absorbing property of the “low absorbing recording medium” This means that the rate of decrease of 1% or more and less than 5%. Moreover, absorptivity means that said reduction rate is 5% or more. In addition, a contact angle can be measured using portable contact angle meter PCA-1 (made by Kyowa Interface Science Co., Ltd.) etc.

  Although it does not specifically limit as a low absorptive recording medium, For example, the coated paper by which the coating layer for accepting oil-based ink was provided in the surface is mentioned. The coated paper is not particularly limited, and examples thereof include recording paper such as art paper, coated paper, and mat paper.

  The non-absorbent recording medium is not particularly limited. For example, a plastic film that does not have an ink absorbing layer, a paper that is coated with plastic on a substrate such as paper, or a plastic film that is bonded. Is mentioned. Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

In addition to the above recording medium, plates of metals such as iron, silver, copper, and aluminum,
A non-ink-absorbing or low-absorbing recording medium such as glass can also be used.

[Inkjet device]

  FIG. 1 is a schematic cross-sectional view of an ink jet apparatus used in the ink jet method according to the present embodiment. As shown in FIG. 1, the inkjet apparatus 1 includes an inkjet head 2, an IR heater 3, a platen heater 4, a curing heater 5, a cooling fan 6, a preheater 7, and a ventilation fan 8. Yes. The ink jet head 2 ejects an ink composition onto a recording medium, and the type shown in FIG. 1 can be used.

  The ink jet apparatus shown in FIG. 1 includes an IR heater 3 and a platen heater 4 for heating the recording medium when the ink composition is discharged from the ink jet head 2. When the recording medium is heated in the ink composition attaching step, at least one of the IR heater 3 and the platen heater 4 may be used.

  If the IR heater 3 is used, the recording medium can be heated from the inkjet head 2 side. Thereby, although the inkjet head 2 is also easily heated at the same time, the temperature can be raised without being affected by the thickness of the recording medium as compared with the case where the inkjet head 2 is heated from the back surface of the recording medium such as the platen heater 4. If the platen heater 4 is used, the recording medium can be heated from the side opposite to the inkjet head 2 side. Thereby, the inkjet head 2 becomes comparatively difficult to be heated. However, as described above, the temperature of the recording medium by the IR heater 3 and the platen heater 4 is preferably 38 ° C. or less, more preferably 35 ° C. or less, and it can be set to room temperature without being operated. Further preferred. Thereby, since the radiant heat received from the IR heater 3 and the platen heater 4 is small or eliminated, the drying and composition variation of the ink composition in the ink jet head can be suppressed, and the resin can be prevented from being welded to the inner wall of the head.

  The curing heater 5 is for drying and solidifying the ink composition recorded on the recording medium. When the curing heater 5 heats the recording medium on which the image is recorded, moisture contained in the ink composition is evaporated and scattered more quickly, and a film is formed by the polymer particles contained in the ink composition. The In this manner, the dried ink is firmly fixed (adhered) on the recording medium, and a high-quality image excellent in abrasion resistance can be obtained in a short time. The drying temperature by the curing heater 5 is preferably 40 ° C to 120 ° C, more preferably 60 ° C to 100 ° C, and further preferably 80 ° C to 90 ° C.

  The inkjet device 1 may have a cooling fan 6. After drying, the ink composition on the recording medium is cooled by the cooling fan 6 so that a film can be formed on the recording medium with good adhesion.

  Further, the ink jet apparatus 1 may include a preheater 7 that preheats (preheats) the recording medium before the ink composition is ejected onto the recording medium. Furthermore, the inkjet apparatus 1 may include a ventilation fan 8 so that the ink composition attached to the recording medium is dried more efficiently.

[Control method of recording apparatus]
The present embodiment may be a control method for a recording apparatus (inkjet apparatus). For example, when performing the above-described recording method using the above-described recording apparatus, the control unit included in the recording apparatus performs recording by controlling the recording apparatus to perform the above-described recording method.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. The present invention is not limited in any way by the following examples.

(Preparation of ink composition)
Each material was mixed with the composition (mass%) shown in Table 1 below, and stirred sufficiently to obtain ink compositions of Examples, Comparative Examples, and Reference Examples.

  In this example, the reaction solution having the composition shown in Table 2 was used.

  As shown in Table 1, for each ink composition, recording was performed while changing the conditions of the recording test and the head configuration, and gloss, rubbing resistance, clogging, continuous printing, and bleeding were evaluated. Hereinafter, the conditions of the recording test, the configuration of the head, and details of each evaluation test will be described.

(Recording test)
A modified machine of an ink jet printer (trade name PX-G930, manufactured by Seiko Epson Corporation) was filled with the ink composition and the reaction liquid. Specifically, the reaction liquid and ink used in the test were filled into each nozzle row. The modified machine is equipped with a platen heater. The recording medium discharged from the printer was secondarily dried in an oven. As a recording medium, Toray PET film “Lumirror S10” was used.
In Table 1, in the example using the reaction liquid, the reaction liquid is first deposited as a pattern with an adhesion amount of ² mg / inch ² , the recording medium is reversely fed and reset, and the ink is deposited on the pattern. It was.
The ink was adhered at a resolution of 720 dpi horizontal and 720 dpi vertical, with an adhesion amount of 7 mg / inch ² , and a pattern was recorded. Adhesion of the reaction liquid and ink was performed by setting the surface temperature of the recording medium to the primary drying temperature in the table.
After completion of the adhesion, the recording medium was discharged from the printer and secondarily dried in an oven at the temperature shown in the table for 2 minutes.

(Head configuration)
In Table 1, the head 1 is the type of head shown in FIG. 1 in which the piezoelectric element 23 is not located at a position facing the ink outlet 24 of the pressure chamber 21. The head 2 is a head in which the piezoelectric element is in a position facing the ink outlet of the pressure chamber. In FIG. 1, the piezoelectric element 23 is disposed immediately above the nozzle 22.

(Glossy)
After recording by the above recording test, the gloss of the pattern was measured with a gloss meter (manufactured by Konica Minolta). The glossiness was measured at 45 ° glossiness. The evaluation criteria are shown below.
A Glossiness 80 or more B Glossiness 20 or more and less than 80 C Glossiness less than 20

(Abrasion resistance)
After recording by the above recording test, the recording surface of the recorded material left for 1 hour in a laboratory at room temperature (25 ° C.) is used as a Gakushin type friction fastness tester AB-301 (trade name, manufactured by Tester Sangyo Co., Ltd.). Was used to evaluate the abrasion resistance by confirming the state of peeling of the recording surface and the state of ink transfer to the cotton cloth when rubbed 20 times with a cotton cloth under a load of 200 g. The evaluation criteria are shown below.
A: No damage or peeling.
B: Those having scratches or peeling of 1% or less of the stroke area.
C: Those having scratches or peeling exceeding 1% of the stroke area.

(Clogging)
Recording was performed for 10 minutes, the ink composition used for the recording was filled with the ink composition, and the cap was left open for one month. Thereafter, cleaning was performed three times to determine how many nozzles were missing. Cleaning was performed once by sucking 1 mL of ink per head from the nozzles having 180 nozzles. The evaluation criteria are shown below.
A: No nozzle missing B: Nozzle missing 1-5 C: Nozzle missing 6 or more

(Continuous printing)
Continuous printing for 2 hours was performed. During this time, flushing was performed for each pass, but suction cleaning was not performed. After printing, the number of nozzles in which ejection failure (non-ejection or flight bending) occurred was confirmed. The evaluation criteria are shown below.
A: No nozzle missing B: Nozzle missing 1-5 C: Nozzle missing 6 or more

(Smear)
For the evaluation of the aggregation unevenness, the same recorded material as that used in the above-mentioned abrasion resistance test was used. Ink aggregation within the solid pattern of the recorded matter was visually observed and evaluated according to the following evaluation criteria. This evaluation was performed in a laboratory at room temperature (25 ° C.). The evaluation criteria are shown below.
A: Aggregation unevenness was not recognized in the solid pattern.
B: Some aggregation unevenness was observed in the solid pattern.
C: Aggregation unevenness was substantially recognized as a whole in the solid pattern.

As shown in Table 1, the ink compositions of Examples were highly evaluated in terms of abrasion resistance, clogging, and continuous printing.
For example, Example 3 using the reaction solution, Example 4 with a primary drying temperature of 40 ° C., Example 5 using NMP (N-methyl-2-pyrrolidone) as a solvent, and Examples 1-4 are different. In any of Examples 6 employing the resin, as in Examples 1 and 2, the scuff resistance, clogging property, and continuous printing were highly evaluated.
Comparative Examples 1 to 4 in which the compounding ratio of the nitrogen-containing solvent / resin having an SP value of 3 or less falls outside the scope of the present invention was evaluated as low in at least one of abrasion resistance, clogging property, and continuous printing.
Compared with Example 1, Example 8 in which the addition amount of the surfactant was changed, and Examples 9 to 12 in which the type of the surfactant was changed were highly evaluated in terms of abrasion resistance, clogging, and continuous printing. It was.
Since Comparative Example 5 contained a high-boiling solvent, it had a clogging resistance, but had a low abrasion resistance.
In Comparative Example 6, since the difference in SP value between the nitrogen-containing solvent and the resin was greater than 3, the resin did not melt, resulting in low friction resistance.
In Comparative Example 7, the nitrogen-containing solvent / resin ratio was too small, and the abrasion resistance was low.

  DESCRIPTION OF SYMBOLS 1 ... Inkjet apparatus, 2 ... Inkjet head, 3 ... IR heater, 4 ... Platen heater, 5 ... Curing heater, 6 ... Cooling fan, 7 ... Pre-heater, 8 ... Ventilation fan, 21 ... Pressure chamber, 22 ... Nozzle, 23 ... piezoelectric element, 24 ... outlet, 25 ... resin.

Claims (14)

A resin, a nitrogen-containing solvent having a SP value difference of 3 or less with respect to the resin, and water,
The content of the nitrogen-containing solvent is 2 to 9 parts by mass with respect to 1 part by mass of the resin, and the content of the organic solvent having a standard boiling point of 280 ° C. or higher is 3% by mass or less.
A water-based inkjet ink composition. The mass ratio of the nitrogen-containing solvent to the total mass of the organic solvent contained in the water-based inkjet ink composition is 0.2 to 0.7.
The water-based inkjet ink composition according to claim 1. The mass ratio of the total mass of the organic solvent contained in the aqueous inkjet ink composition to the mass of the water is 0.2 to 0.7.
The water-based inkjet ink composition according to claim 1 or 2. The content of the nitrogen-containing solvent is 3 to 30% by mass,
The water-based inkjet ink composition as described in any one of Claims 1-3. The content of the resin is 1 to 15% by mass,
The water-based inkjet ink composition as described in any one of Claims 1-4. As a surfactant, it contains at least one of a silicone-based surfactant, an acetylene glycol-based surfactant, and a fluorine-based surfactant.
The water-based inkjet ink composition as described in any one of Claims 1-5. The normal boiling point of the nitrogen-containing solvent is 180 ° C. or higher and lower than 280 ° C.,
The water-based inkjet ink composition as described in any one of Claims 1-6. A step of discharging the water-based ink-jet ink composition according to any one of claims 1 to 7 from a nozzle of an ink-jet head and attaching it to a recording medium,
Inkjet method. The surface temperature of the recording medium when the aqueous inkjet ink composition is attached to the recording medium is 70 ° C. or less;
The inkjet method according to claim 8. A step of drying the recording medium after the step of attaching the water-based inkjet ink composition to the recording medium, and the surface temperature of the recording medium in the step is 70 ° C. or higher.
The inkjet method according to claim 8 or 9. The inkjet head includes a pressure chamber and an element that applies pressure to the pressure chamber to discharge the water-based inkjet ink composition from the nozzle, and is located in a location other than the position facing the outlet communicating with the nozzle in the pressure chamber. The element is arranged in
The inkjet method according to any one of claims 8 to 10. Attaching a reaction liquid containing a flocculant that agglomerates the components of the water-based inkjet ink composition to the recording medium,
The inkjet method according to any one of claims 8 to 11. Recording is performed for 1 hour or more without performing a step of applying pressure to the inkjet head from the outside and discharging the aqueous inkjet ink composition from the nozzle.
The inkjet method according to any one of claims 8 to 12.   Recording is performed without performing a step of applying an external pressure to the inkjet head to discharge the aqueous inkjet ink composition from the nozzle during recording, and the inkjet head is applied to the inkjet head at least before or after recording. The inkjet method according to any one of claims 8 to 12, wherein a step of applying pressure from the outside and discharging the aqueous inkjet ink composition from a nozzle is performed.

Images