JP2014091795A - Inkjet ink, method of producing inkjet ink, ink cartridge, inkjet printing method, and inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink having excellent discharge stability.SOLUTION: An inkjet ink includes water, a water-soluble organic solvent, a colorant, and a polyol in which an amount of the polyol dissolved in water under normal conditions (25°C, 1 atm) is 10wt% or less, and when a dissolved oxygen concentration is 1, the weight ratio of a dissolved nitrogen concentration is 10 or more.

Description

  The present invention relates to an inkjet ink, a method for manufacturing an inkjet ink, an ink cartridge, an inkjet printing method, and an inkjet printing apparatus.

  In recent years, in wide format printing, an ink jet that forms a desired image on a recording medium by ejecting ink from a head toward the recording medium has been widely used. Examples of inks used in inkjet printers include solvent inks based on aqueous solvents or organic solvents, photocured inks that are cured by exposure to light, latex inks based on water, and wax inks that are solid at room temperature. is there.

  In an ink jet printer, ink is ejected from a small-diameter ejection port formed in the head. Therefore, when the dissolved oxygen concentration in the ink increases, bubbles are likely to be generated, and when bubbles are generated, ejection becomes unstable. When the dissolved oxygen concentration is 5 ppm or less, ejection can be performed almost stably. However, when the dissolved oxygen concentration is 7 ppm or more, ink mistakes are likely to occur, and ink scattering tends to occur.

  Conventionally, the relationship between the amount of dissolved oxygen and the ejection stability of the head has been investigated in detail. The amount of dissolved oxygen in the degassed ink that provides good head ejection performance shows a substantially constant value in any report.

  Patent Document 1 and Patent Document 2 describe maintenance liquids for ink jet printers that contain glycol ethers and glycol esters and have a dissolved oxygen amount of 45 mg / l to 10 mg / l. Patent Document 3 describes that the ink is desirably degassed, and preferably has a dissolved oxygen concentration of 5 ppm or less.

JP 2008-274016 A JP 2010-99874 A JP 2006-77232 A

  By the way, there is a demand for ink that is more excellent in ejection stability. For example, in a latex ink using titanium oxide having high sedimentation properties and high surface activity, oxygen tends to dissolve in the ink, and the dissolved oxygen concentration tends to be high. Therefore, it is necessary to improve the ejection stability of such ink.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an ink jet ink excellent in ejection stability. For example, an ink having excellent ejection stability is provided even for an ink in which a binder resin is suspended or suspended (hereinafter also referred to as “latex ink”) or an ink containing a white pigment that easily settles. .

  The ink-jet ink according to the present invention contains water, a water-soluble organic solvent, a coloring material, a polyol having a solubility in water of 10 wt% or less in a standard state (25 ° C., 1 atm), and a dissolved oxygen concentration of 1. The weight ratio of the dissolved nitrogen concentration is 10 or more.

  By including the polyol, the dissolved oxygen concentration is reduced, and the weight ratio of the dissolved nitrogen concentration when the dissolved oxygen concentration is 1 can be adjusted to be 10 or more. As described above, the ink having a low dissolved oxygen concentration is less likely to generate bubbles. If air bubbles are generated, the pigment and binder resin in the ink are aggregated to lead to ejection failure. However, according to the present invention, since air bubbles are not easily generated, aggregation is unlikely to occur and the ejection stability is excellent. Therefore, it is possible to provide an ink jet ink excellent in ejection stability.

  The inkjet ink according to the present invention may further include a binder resin, and the binder resin may be emulsion or suspension.

  In the ink in which the binder resin is emulsified or suspended in water and a water-soluble organic solvent, the ink tends to aggregate more easily, but in the present invention, since the dissolved oxygen concentration is sufficiently low, the aggregation is difficult to occur. Excellent discharge stability. Accordingly, it is possible to provide a latex ink having excellent ejection stability.

  In the inkjet ink according to the present invention, the dissolved oxygen concentration may be 5 mg / l or less, and the dissolved nitrogen concentration may be 20 mg / l or less.

  If the dissolved oxygen concentration and the dissolved nitrogen concentration are in this range, bubbles are less likely to be generated, and thus the discharge stability is more excellent.

  In the inkjet ink according to the present invention, the polyol preferably has 7 to 11 carbon atoms.

  By containing the polyol, the dissolved oxygen concentration can be further reduced. Therefore, the discharge stability is more excellent.

  In the ink-jet ink according to the present invention, the polyol is more preferably 2-ethyl-1,3-hexanediol or 2,2,4-trimethyl-1,3-pentanediol.

  By containing the polyol, the dissolved oxygen concentration can be further reduced. Therefore, the discharge stability is more excellent.

  In the inkjet ink according to the present invention, the polyol content is more preferably 0.1 to 7 wt%.

  By being 0.1 wt% or more, the effect of reducing the dissolved oxygen concentration by the polyol can be sufficiently obtained. In addition, the polyol is difficult to dissolve in water, but can be easily dissolved if it is 7 wt% or less, so that it becomes easy to produce the ink jet ink according to the present invention.

  More preferably, the inkjet ink according to the present invention further includes glycol ethers.

  When the latex ink further contains glycol ethers, the ink can be made more suitable for inkjet applications.

  In the inkjet ink according to the present invention, the coloring material may be titanium oxide.

  An ink containing titanium oxide as a color material is generally used as a white ink. However, such an ink tends to settle more easily and discharge stability tends to deteriorate. However, according to the present invention, it is possible to provide a white ink that suppresses aggregation and is superior in ejection stability.

  In the inkjet ink according to the present invention, it is more preferable that the titanium oxide is surface-modified with a graft polymer.

  Dispersibility of titanium oxide is improved by being surface-modified with the graft polymer.

  In the inkjet ink according to the present invention, the particle diameter of the titanium oxide is more preferably 10 nm or more and 80 nm or less.

  Since such titanium oxide hardly aggregates, the discharge stability is more excellent.

  In the ink-jet ink according to the present invention, the binder resin is more preferably at least one selected from the group consisting of an aqueous polyester resin, an aqueous polyurethane resin, an aqueous acrylic resin, and an aqueous vinyl chloride resin. It can be suitably used as a latex ink.

  In the inkjet ink according to the present invention, the water-soluble organic solvent is glycerin, trimethylolpropane, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2 , 3-butanediol, 1,4-butanediol, 3-methyl-1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-hexanediol, 2 More preferred is at least one selected from the group consisting of -pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, tetramethylurea and urea.

  By forming an image with ink containing such a water-soluble organic solvent, the gloss of the surface of the image can be improved.

  More preferably, the inkjet ink according to the present invention further includes a polyalkylene glycol surfactant having an HLB (hydrophilic / lipophilic ratio) of 13 to 20.

  Since the dissolved oxygen concentration can be further reduced, the discharge stability is further improved.

  The method for producing an ink-jet ink according to the present invention dissolves from water, a water-soluble organic solvent, a coloring material, and a polyol having a solubility in water of 10 wt% or less in a standard state (25 ° C., 1 atm). It includes a deoxygenation step of removing oxygen.

  When the deoxygenation step is performed, the oxygen in the air tends to be easily taken up, but since the polyol is contained, it becomes difficult to take in oxygen and the dissolved oxygen concentration can be lowered. Therefore, it is possible to provide an ink jet ink excellent in ejection stability.

  The ink cartridge according to the present invention contains the ink-jet ink according to the present invention in a container.

  Printing can be performed with an ink jet ink having excellent ejection stability.

  The inkjet printing method according to the present invention is characterized by printing using the inkjet ink according to the present invention.

  Since the ejection stability of the inkjet ink used is excellent, high-quality inkjet printing can be performed.

  An ink jet printing apparatus according to the present invention includes the ink cartridge according to the present invention.

  Since the ejection stability of the inkjet ink to be ejected is excellent, high-quality inkjet printing can be performed.

  According to the present invention, it is possible to provide an ink that is excellent in ejection stability. For example, latex ink and latex ink containing a white pigment that easily settles are excellent in ejection stability.

It is a figure which shows an example of the apparatus which measures a dissolved nitrogen concentration. It is a figure which shows an example of the apparatus which measures a dissolved nitrogen concentration. It is a figure which shows one Embodiment of the ink cartridge which concerns on this invention. FIG. 4 is a diagram including a case (exterior) of the ink cartridge of FIG. 3. It is a figure which shows the structure of one Embodiment of the inkjet printing apparatus which concerns on this invention. 1 is an element diagram of an inkjet head provided in an embodiment of an inkjet printing apparatus according to the present invention. It is principal part sectional drawing of the direction between channels of the inkjet head shown in FIG.

[Ink-jet ink]
The ink-jet ink according to the present invention contains water, a water-soluble organic solvent, a coloring material, and a polyol having a solubility in water of 10 wt% or less in a standard state (25 ° C., 1 atm bar (10 ⁵ Pa)). The weight ratio of the dissolved nitrogen concentration when the oxygen concentration is 1 is 10 or more. That is, the polyol is soluble in water until it reaches 10 wt% in the standard state.

  Polyols with a water solubility of 10 wt% or less in the standard state have a low solubility in water, so the proportion of oxygen taken into water is reduced, contributing to stabilization of the dissolved oxygen content, and the dissolved oxygen content after storage It is thought that the increase in Further, by increasing the dissolved nitrogen concentration, dissolved oxygen is replaced with dissolved nitrogen, and the dissolved oxygen concentration can be reduced.

  If the dissolved oxygen concentration is low, generation of minute bubbles inside the ink supply module can be suppressed. If ink is ejected while the bubbles remain inside, when the pressure is applied to the ink, the bubbles absorb the pressure applied to the ink, and a normal ejection state cannot be obtained. In the present invention, a polyol having low solubility in water is contained in the ink, and then, for example, nitrogen is blown into the ink, and the dissolved oxygen in the ink is replaced with nitrogen as much as possible, whereby the dissolved oxygen concentration is set to 1. When the weight ratio of the dissolved nitrogen concentration is 10 or more, these problems are solved. In this way, it is possible to suppress instability of ejection characteristics due to oxygen and to maintain ink ejection stability. That is, once the dissolved oxygen concentration is adjusted to a low level by the method described later, the above-described polyol prevents oxygen from being newly dissolved in the ink, so that the dissolved oxygen concentration in the ink can be kept low. .

(Dissolved oxygen concentration and dissolved nitrogen concentration)
The weight ratio of the dissolved nitrogen concentration when the dissolved oxygen concentration is 1 should be 10 or more, and the higher the better. The upper limit of the ratio is not particularly limited, but is, for example, 25, more preferably 100. By replacing oxygen in the ink with nitrogen, those skilled in the art can easily improve the ratio.

  In the inkjet ink according to the present invention, the dissolved oxygen concentration is preferably 5 mg / l or less, and the dissolved nitrogen concentration is preferably 20 mg / l or less. The dissolved oxygen concentration is more preferably 2 mg / l or less, and further preferably 1 mg / l or less. The lower limit value of the dissolved oxygen concentration is not particularly limited, and the lower the better, the better. For example, it may be 0.1 mg / l. Further, the lower limit value of the dissolved nitrogen concentration is, for example, 1.0 mg / l. When the dissolved oxygen concentration is 5 mg / l or less, generation of minute bubbles inside the ink supply module can be suppressed.

  The method for adjusting the dissolved oxygen concentration is not particularly limited, and examples thereof include a method of degassing ink under reduced pressure, a method of degassing by irradiating ultrasonic waves, and a method of degassing with a hollow fiber membrane.

  Also, the dissolved oxygen concentration after reducing the dissolved oxygen by purging nitrogen inside the container of various solvents that are the raw materials of the ink, the tank used in the ink manufacturing process, and the inside of the manufactured ink container. Can be controlled.

  Examples of the method for measuring the dissolved oxygen concentration of ink-jet ink include the Ostwald method (see Experimental Chemistry Course 1, Basic Operation [1], page 241, 1: 2075, Maruzen), the method of measuring by the mass spectrum method, Examples include an oxygen concentration meter and a colorimetric analysis method. Moreover, it can measure simply even if it uses a commercially available dissolved oxygen concentration meter.

  Next, the dissolved nitrogen concentration method and measuring apparatus will be described.

  Regarding the method for measuring the dissolved nitrogen concentration, the method described in JP2010-216943A can be mentioned.

  This method is a method of measuring the dissolved nitrogen concentration by the thermal conductivity detection method through the hydrogen removal step using a platinum group catalyst, but only the method of the dissolved nitrogen concentration by the latter thermal conductivity detection method. It may be used.

  A specific measurement method will be described with reference to FIGS. 1 and 2 are diagrams showing an example of an apparatus for measuring a dissolved nitrogen concentration (refer to JP 2010-216943 for each member).

  In FIG. 1, the ink is supplied to a thermal conductivity detector 100, and the dissolved nitrogen concentration in the ink is measured by the thermal conductivity detector 100.

  A method for measuring the dissolved nitrogen concentration by the thermal conductivity detector 100 will be described with reference to FIG. First, the valve 124 is opened, purge gas (carbon dioxide gas, argon gas, etc.) of the purge gas supply source 120 is supplied from the purge gas supply line 122 to the measurement chamber 110, and the measurement chamber 110 is filled with the purge gas. In this state, the TCD 112 measures the thermal conductivity of the purge gas and outputs the measured value to the amplifier 130 as a signal. At this time, since the inside of the measurement chamber 110 is filled with a specific purge gas, the signal output from the TCD 112 to the amplifier 130 is stable with the thermal conductivity of the purge gas. The signal output from the TCD 112 is sent to the controller 132 via the amplifier 130. In the controller 132, when the signal output from the TCD 112 is stable, that is, when the purge in the measurement chamber 110 is completed, the valve 124 is closed and the supply of the purge gas to the measurement chamber 110 is stopped.

  When ink is supplied to the sample chamber 102 in a state where the measurement chamber 110 is filled with purge gas, dissolved nitrogen in the ink passes through the diaphragm 112 and moves to the measurement chamber 110. When nitrogen gas moves from the sample chamber 102 to the measurement chamber 110, the purge gas in the measurement chamber 110 is discharged to the gas discharge line 114 by the transferred nitrogen gas. The TCD 112 measures the thermal conductivity according to the nitrogen gas concentration in the measurement chamber 110, and outputs the measured value as a signal to the controller 132 via the amplifier 130. The speed at which the purge gas in the measurement chamber 110 is replaced with nitrogen gas is proportional to the nitrogen partial pressure of the dissolved gas in the sample chamber 102. For this reason, the controller 132 obtains the nitrogen partial pressure in the sample chamber 102 from the change rate of the signal output from the TCD 112, and obtains the dissolved nitrogen concentration of the ink based on the obtained nitrogen partial pressure.

(Water-soluble organic solvent)
Specific examples of the water-soluble organic solvent include the following.

  Glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1, Polyhydric alcohols such as 2,3-butanetriol, 2-methyl-2,4-pentanediol, petriol, 3-methoxy-3-methyl-1-butanediol; ethylene glycol monoethyl ether, ethylene glycol Polyhydric alcohol alkyl ethers such as nobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, dipropylene Polyhydric alcohol aryl ethers such as glycol monobutyl ether, tripropylene glycol monobutyl ether, diethylene glycol isobutyl ether, triethylene glycol isobutyl ether, diethylene glycol isopropyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2 -Pyrrolidone Nitrogen-containing heterocyclic compounds such as 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; amides such as formamide, N-methylformamide, N, N-dimethylformamide; monoethanolamine, diethanolamine, tri Amines such as ethanolamine, monoethylamine, diethylamine, and triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane, thiodiethanol, and thiodiglycol; propylene carbonate, ethylene carbonate, trimethylolpropane, tetramethylurea, urea, and the like .

  Among these water-soluble organic solvents, glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butane Diol, 1,5-pentanediol, tetraethylene glycol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, polyethylene glycol, 1,2,4-butanetriol, 1,2,6-hexane Triol, thiodiglycol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone are preferred. These are excellent in solubility and prevention of poor jetting characteristics due to water evaporation.

(Color material)
Examples of the color material contained in the ink jet ink according to the present invention include water-soluble dyes, oil-soluble dyes, dyes such as disperse dyes, pigments, and the like. Oil-soluble dyes and disperse dyes are preferable from the viewpoint of good adsorption and encapsulation, and pigments are preferably used from the light resistance of the obtained image.

  Examples of pigments include carbon black as a black pigment, and examples of color pigments include anthraquinone, phthalocyanine blue, phthalocyanine green, diazo, monoazo, pyranthrone, perylene, heterocyclic yellow, quinacridone, and (thio) indigoid. .

  Examples of phthalocyanine blue include copper phthalocyanine blue and its derivatives (Pigment Blue 15).

  Examples of quinacridone include Pigment Orange 48, Pigment Orange 49, Pigment Red 122, Pigment Red 192, Pigment Red 202, Pigment Red 206, Pigment Red 207, Pigment Red 209, Pigment Violet 19 and Pigment Violet 42.

  Examples of anthraquinone include pigment red 43, pigment red 194 (perinone red), pigment red 216 (brominated pyrantrone red) and pigment red 226 (pyrantron red).

  Examples of pyrerin include Pigment Red 123 (Bell Million), Pigment Red 149 (Scarlet), Pigment Red 179 (Maroon), Pigment Red 190 (Red), Pigment Violet, Pigment Red 189 (Yellow Shade Red), and Pigment Red 224. Can be mentioned.

  Examples of thioindigoid include Pigment Red 86, Pigment Red 87, Pigment Red 88, Pigment Red 181, Pigment Red 198, Pigment Violet 36, and Pigment Violet 38.

  Examples of heterocyclic yellow include pigment yellow 117 and pigment yellow 138.

  Examples of other colored pigments are described in The Color Index, Third Edition (The Society of Dyer's and Colorists, 1982).

  The ink-jet ink according to the present invention may contain titanium oxide as a color material.

  Titanium oxide includes a rutile type and an anatase type, but may be appropriately selected according to the purpose, and may be any type of titanium oxide.

  The particle diameter of titanium oxide is not particularly limited, but fine particles of 10 nm or more and 80 nm or less are preferable. The reason for this is that the specific gravity of titanium oxide is 4 to 5 and an average of about 4.5, and it is easy to settle, but the small particle size increases the self-dispersibility and further improves the dispersion stability.

  Titanium oxide has three crystal forms: anatase (Anatase), rutile (Rutile) and brookite (Brookite). Of these, rutile and anatase are used industrially, while brookite is only taken up academically and has no industrial use.

  As for the arrangement of atoms in the titanium oxide crystal, six O atoms are coordinated around one Ti atom in the three crystal forms, and an octahedral ridge is formed by the O atoms. A rutile crystal has a structure in which two edges of an octahedron are shared and extend in a chain shape in the c-axis direction. Considering the expansion space of the electron cloud, it is considered that the structure is such that Ti atoms are sandwiched between gaps filled with large O atoms.

  Rutile is an octahedral two-ridge shared chain structure in the c-axis direction as described above, but brookite is a three-ridge shared structure and anatase is a four-ridge shared structure.

The crystal unit cell unit cell has a structure containing two chemical units of rutile TiO ₂ , eight brookites and four anatases. The unit cell and crystal system data for the three crystals are shown in Table 1 below. Rutile and anatase are tetragonal and brookite is orthorhombic. The volume per mole increases in the order of rutile, brookite, and anatase.

  Pauling's electronegativity is widely used for the ionicity and covalentness of chemical bonds of crystal constituent atoms. There are reports on the ionicity of Ti-O bonds, such as 50% by Kiriyama, 43% by Grant, and 63% by Beohm (Titanium oxide properties and applied technology by Kiyono Seino, Gihodo Publishing Co., Ltd.). Is considered a half-half bond. Further, it is said that the ionicity decreases as the number of shared octahedral edges increases, and the ionicity decreases in the order of rutile, brookite, and anatase, and the sharing becomes stronger.

As for the chemical properties of titanium oxide, both anatase and rutile are soluble in hydrofluoric acid, hot concentrated sulfuric acid and dissolved alkali salts, but not in other acids, alkalis, water, organic solvents and the like. Further, a highly reactive gas such as HF, SO ₃ , Cl ₂ , and H ₂ S does not react with titanium oxide at room temperature and normal pressure, but reacts with HF at a high temperature to become TiF ₄ . Furthermore, it reacts with a halogen such as Cl _{2 at a} high temperature in the presence of a reducing agent to produce a titanium halide such as TiCl ₄ . Further, it is reduced with H ₂ , CO ₂ or the like at a high temperature to change to a lower oxide.

  Titanium oxide may react with other substances under special conditions like this, but it is extremely stable under normal use conditions, and there is no danger of combustion or explosion.

  In addition, since both the sulfuric acid method and the chlorine method are subjected to heat treatment at 800 to 1100 ° C. in the manufacturing process, titanium oxide itself is essentially not deteriorated by heating at 800 ° C. or less.

  The physical properties of titanium oxide are as follows.

(1) Electrical conductivity Titanium oxide is a complete insulator at room temperature, but acts as an n-type semiconductor when appropriate energy is applied from outside such as heating or ultraviolet irradiation.

(2) Thermal transition Among the three crystal forms of titanium oxide, rutile is the most stable, and anatase and brookite are transformed into rutile by heating. In the absence of a transfer control agent or accelerator, anatase transfers to rutile at 915 ± 15 ° C or higher, and brookite transfers to rutile at 650 ° C or higher.

  Since this reaction is irreversible, it does not transfer to anatase or brookite. Rutile melts at 1825 ° C. when further heated.

  Titanium oxide is preferably ultrafine titanium oxides TTO-51 (20 nm) and TTO-55 (35 nm) from Ishihara Sangyo, and various materials are commercially available from Fuji Titanium and DuPont.

  When titanium oxide is used as a coloring material, it is more preferable that titanium oxide is surface-modified with a graft polymer. Dispersibility of titanium oxide is improved by being surface-modified with the graft polymer. Although the kind of polymer and the method of surface modification are not specifically limited, An example is shown in an Example.

  When the color material contained in the inkjet ink according to the present invention is a pigment, a pigment in which at least one hydrophilic group is bonded to the pigment surface directly or via another atomic group may be used. It can be stably dispersed without using a dispersant.

  As the pigment having a hydrophilic group introduced on the surface, those having ionicity are preferable, and those having an anionic charge or those having a cationic charge are suitable.

Examples of the anionic hydrophilic group, for _{example, -COOM, -SO 3 M, -PO} 3 HM, -PO 3 M 2, -SO 2 NH 2, -SO 2 NHCOR ( where, M in the formula is a hydrogen atom, R represents an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a naphthyl group which may have a substituent. It is done. In the present invention, among these, it is particularly preferable to use a pigment having —COOM or —SO ₃ M bonded to the surface.

  Examples of a method for obtaining an anionically charged pigment include a method of oxidizing a pigment with sodium hypochlorite, a method of sulfonation, a method of reacting a diazonium salt, and the like.

  As the hydrophilic group charged to the cation, for example, a quaternary ammonium group can be used. More preferably, a pigment in which at least one of the quaternary ammonium groups listed below is bonded to the pigment surface is used.

  When the color material contained in the inkjet ink according to the present invention is a pigment, a pigment dispersion in which the pigment is dispersed in an aqueous medium with a dispersant can also be used. As a preferable dispersant, a known dispersant used for preparing a pigment dispersion can be used, and examples thereof include the following.

Polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Polymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styne-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic Acid copolymer-alkyl acrylate ester copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate -Maleic acid ester copolymer, vinyl acetate Rotonic acid copolymer, vinyl acetate-acrylic acid copolymer, etc.

  Further, the nonionic or anionic dispersant used for dispersing the pigment can be appropriately selected according to the pigment type or the ink formulation. For example, as the nonionic dispersant, polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene Polyoxyethylene alkyl ethers such as oxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyoxyethylene α Naphthyl ether, polyoxyethylene β naphthyl ether, polyoxyethylene monostyryl phenyl ether, polyoxyethylene distyryl phenyl ether, polyoxyethylene Examples thereof include xylethylene alkyl naphthyl ether, polyoxyethylene monostyryl naphthyl ether, polyoxyethylene distyryl naphthyl ether, polyoxyethylene polyoxypropylene block copolymer, and the like. Further, a dispersant obtained by replacing a part of each polyoxyethylene with polyoxypropylene, and a dispersant obtained by condensing a compound having an aromatic ring such as polyoxyethylene alkylphenyl ether with formalin or the like can also be used.

  The HLB of the nonionic dispersant is preferably 12 or more and 20.5 or less, more preferably 13 or more and 20 or less. If the HLB is 12 or more, the dispersion stability is good because the dispersant is well adapted to the dispersion medium. If the HLB is 20.5 or less, the dispersant is easily adsorbed to a pigment such as titanium oxide. Dispersion stability is improved.

  Anionic dispersants include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene monostyryl phenyl ether sulfate, polyoxyethylene distyryl phenyl ether sulfate, polyoxyethylene alkyl ether phosphorus Acid salt, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene monostyryl phenyl ether phosphate, polyoxyethylene distyryl phenyl ether phosphate, polyoxyethylene alkyl ether carboxylate, polyoxyethylene alkyl phenyl ether Carboxylate, polyoxyethylene monostyryl phenyl ether carboxylate, polyoxyethylene distyryl phenyl ether carboxylate, naphthalene Lulfonate formalin condensate, melanin sulfonate formalin condensate, dialkyl sulfosuccinic acid ester salt, sulfosuccinic acid alkyl disalt, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α-olefin sulphonate, alkylbenzene sulfone Examples thereof include acid salts, alkylnaphthalene sulfonates, alkyl sulfonates, N-acyl amino acid salts, acylated peptides, soaps and the like. Of these, sulfates and phosphates of polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, and polyoxyethylene distyryl phenyl ether are particularly preferable.

  The addition amount of the dispersant is preferably 10 wt% or more and 50 wt% or less of the pigment. If the added amount of the dispersant is 10 wt% or more of the pigment, the storage stability of the pigment dispersion and the ink is good, and the dispersion can be performed in a short time, and if it is 50 wt% or less, the viscosity of the ink is high. Since it is not too high, the discharge stability is improved.

  In addition, a resin-coated color material can also be suitably used as the color material.

  An ink using a resin-coated color material is a polymer emulsion in which a color material is contained in polymer fine particles. In the present specification, “containing a color material” means either or both of a state in which a color material is enclosed in polymer fine particles and a state in which the color material is adsorbed on the surface of the polymer fine particles.

  In addition, when the ink-jet ink according to the present invention includes a resin-coated color material, it is not necessary that all of the color material be encapsulated or adsorbed in the polymer fine particles. Part of the coloring material may be dispersed in the emulsion.

  The color material may be any color material that is insoluble or hardly soluble in water and can be adsorbed by the polymer. In this specification, “water-insoluble or poorly water-soluble” means that a coloring material does not dissolve 10 parts by weight or more with respect to 100 parts by weight of water at 20 ° C. It means that separation or sedimentation of coloring material is not observed. Examples of the color material contained in the polymer fine particles include dyes such as oil-soluble dyes and disperse dyes, pigments, and the like. Oil-soluble dyes and disperse dyes are preferable from the viewpoint of good adsorption and encapsulation, but pigments are preferably used from the light resistance of the obtained image.

  As the polymer that forms the polymer emulsion, for example, vinyl polymers, polyester polymers, polyurethane polymers, and the like can be used. Particularly preferred polymers are vinyl polymers and polyester polymers, and specific examples thereof include those disclosed in JP-A Nos. 2000-53897 and 2001-139849.

  Moreover, 10-200 mass parts is preferable with respect to 100 mass parts of polymers, and, as for the compounding quantity of the coloring material with respect to a polymer, 25-150 mass parts is more preferable. The average particle diameter of the polymer fine particles containing the colorant is preferably 20 nm or more and 80 nm or less in the ink.

  The content of the polymer fine particles with respect to the total amount of the ink is preferably 8 to 20% by mass, more preferably 8 to 12% by mass in terms of solid content in the ink.

  The color material contained in the ink-jet ink according to the present invention is more preferably a pigment, but as for the resin-coated color material, a dye is also suitable as well as the pigment.

  An example of a water-soluble dye used for a resin-coated color material is shown below. Those having excellent water resistance and light resistance are preferably used. Examples of water-soluble dyes include acid dyes, food dyes, direct dyes, basic dyes, and reactive dyes.

  Examples of acid dyes and food dyes include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142; C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254 289; I. Acid Blue 9, 29, 45, 92, 249; I. Acid Black 1, 2, 7, 24, 26, 94; I. Food Yellow 3, 4; I. Food red 7, 9, 14; I. Food black 1, 2 etc. are mentioned.

  Examples of direct dyes include C.I. I. Direct yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144; I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227; I. Direct orange 26, 29, 62, 102; I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202; I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171 etc. are mentioned.

Examples of basic dyes include C.I. I. Basic yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 64, 65, 67, 70, 73, 77, 87, 91; C.I. I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70, 73, 78, 82, 102, 104, 109, 112; I. Basic blue 1, 3, 5, 7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93, 105, 117, 120, 122, 1
24, 129, 137, 141, 147, 155; I. Basic black 2, 8 etc. are mentioned.

  Examples of reactive dyes include C.I. I. Reactive black 3, 4, 7, 11, 12, 17; I. Reactive Yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67; I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97; I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95 etc. are mentioned.

(Binder resin)
The ink-jet ink according to the present invention contains a binder resin, and the binder resin is more preferably emulsion or suspension. Such an ink is used to improve the fixability, scratch resistance, and gloss of the color material when printed on a medium.

  The binder resin is more preferably at least one selected from the group consisting of an aqueous polyester resin, an aqueous polyurethane resin, an aqueous acrylic resin, and an aqueous vinyl chloride resin. It can be suitably used as a latex ink.

  In this specification, the binder resin forming the latex ink is referred to as polymer latex. The polymer latex refers to a polymer that can be dispersed as a polymer emulsion in a solvent containing a continuous phase in an aqueous system in the presence of a surfactant.

  Examples of the polymer latex include a polymer latex obtained by emulsion polymerization of an ethylenically unsaturated monomer. From the viewpoint of dispersion stability, the polymer latex is preferably a vinyl polymer latex. These polymer latexes may be used alone or in combination of two or more.

The polymer latex contained in the inkjet ink according to the present invention has a structural unit represented by the following formula (1) in order to improve the fixing property of the color material when printed on a medium.
—CH ₂ —C (R ¹ ) (COO—R ² —) — (1)
In the formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² may have a substituent, which has 7 to 22 carbon atoms, preferably 7 to 18 carbon atoms, more preferably an arylalkyl group having 7 to 12 carbon atoms, or 6 to 22 carbon atoms, preferably Represents an aryl group having 6 to 18 carbon atoms, more preferably 6 to 12 carbon atoms. The substituent may contain a hetero atom. Examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom.

Specific examples of R ² include a benzyl group, a phenethyl group (phenylethyl group), a phenoxyethyl group, a diphenylmethyl group, and a trityl group.

  Specific examples of the substituent include preferably an alkyl group, an alkoxy group or an acyloxy group, a hydroxyl group, an ether group, an ester group or a nitro group having 1 to 9 carbon atoms.

  As the structural unit represented by the formula (1), a structural unit derived from benzyl (meth) acrylate is particularly preferable from the viewpoint of developing high gloss.

  The structural unit represented by the formula (1) is preferably obtained by polymerizing a monomer represented by the following formula (1-1).

CH ₂ = CR ¹ COOR ² (1-1)
(In the formula, R ¹ and R ² are the same as described above.)
Specifically, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, phenoxyethyl (meth) acrylate, 1-naphthalyl acrylate, 2-naphthalyl (meth) acrylate, phthalimidomethyl ( Polymerizing (meth) acrylate, p-nitrophenyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-acryloyloxyethylphthalic acid, etc. Thus, a polymer having the structural unit represented by the formula (1) can be synthesized. Among these, benzyl (meth) acrylate is particularly preferable. These can be used alone or in admixture of two or more.

  As used herein, “(meth) acryl” means “acryl”, “methacryl”, or a mixture thereof.

  When the inkjet ink according to the present invention includes a binder resin, the binder resin preferably includes a structural unit derived from the salt-forming group-containing monomer (a) from the viewpoint of improving dispersibility when an emulsion is formed. The structural unit derived from the salt-forming group-containing monomer (a) can be obtained by polymerizing the salt-forming group-containing monomer, but after polymerization of the polymer, the salt-forming group (anionic group or cationic group) is added to the polymer chain. ) May be introduced. Examples of the salt-forming group include an anionic group such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and a cationic group such as an amino group and an ammonium group.

  As the salt-forming group-containing monomer (a), (a-1) an anionic monomer and (a-2) a cationic monomer are preferable.

  (A-1) As an anionic monomer, 1 or more types chosen from the group which consists of an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer are mentioned.

  Examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.

  Examples of unsaturated sulfonic acid monomers include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. Can be mentioned.

  Examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl A phosphate etc. are mentioned.

  Among the above anionic monomers, unsaturated carboxylic acid monomers are preferable, and acrylic acid and methacrylic acid are more preferable from the viewpoints of ink viscosity and dischargeability.

  (A-2) As a cationic monomer, 1 or more types chosen from the group which consists of an unsaturated tertiary amine containing vinyl monomer and an unsaturated ammonium salt containing vinyl monomer are mentioned.

  Examples of the unsaturated tertiary amine-containing monomer include N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, and N, N. -Dimethylaminopropyl (meth) acrylamide, vinylpyrrolidone, 2-vinylpyridine, 4-vinylpyridine, 2-methyl-6-vinylpyridine, 5-ethyl-2-vinylpyridine and the like.

  Examples of unsaturated ammonium salt-containing monomers include N, N-dimethylaminoethyl (meth) acrylate quaternized product, N, N-diethylaminoethyl (meth) acrylate quaternized product, N, N-dimethylaminopropyl (meth). Examples include acrylate quaternized products.

  Among the cationic monomers, N, N-dimethylaminoethyl (meth) acrylate, NN-dimethylaminopropyl (meth) acrylamide and vinyl pyrrolidone are preferable.

  The salt-forming group-containing monomer (a) can be used alone or in admixture of two or more.

  When the inkjet ink according to the present invention contains a binder resin, the binder resin further preferably contains a structural unit derived from the salt-forming group-containing monomer (a) and a structural unit derived from the macromer (b), and contains a salt-forming group. One or more selected from the group consisting of a structural unit derived from the monomer (a), a structural unit derived from the macromer (b), a hydrophobic monomer (c), a hydroxyl group-containing monomer (d), and an oxyalkylene group-containing monomer (e) It is particularly preferable to include a structural unit derived from the monomer.

  The structural unit derived from the macromer (b) is used from the viewpoint of improving storage stability and scratch resistance, and can be obtained by polymerizing a macromer having a polymerizable functional group at one end.

  Macromer (b) includes (b-1) a styrenic macromer having a polymerizable functional group at one end, (b-2) an alkyl (meth) acrylate macromer having a polymerizable functional group at one end, and (b- 3) One or more selected from the group consisting of silicone macromers having a polymerizable functional group at one end are preferred. The polymerizable functional group present at one terminal is preferably an acryloyloxy group or a methacryloyloxy group, and a polymer having a macromer-derived structural unit can be obtained by copolymerization thereof.

  (B-1) A styrenic macromer having a polymerizable functional group at one end includes a styrene homopolymer having a polymerizable functional group at one end, and styrene and other monomers having a polymerizable functional group at one end The copolymer of these is mentioned.

  Examples of the other monomer include (1) acrylonitrile, (2) (meth) acryl having 1 to 22 carbon atoms, preferably 1 to 18 carbon atoms, and optionally having a hydroxy group and having an alkyl group. Acid esters, (3) aromatic ring-containing monomers other than styrene, and the like.

  (2) Specific examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (iso Or tertiary) butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) stearyl (meth) acrylate, and the like.

  In the present specification, “(iso or tertiary)” and “(iso)” are the case where the branched structure represented by “iso” or “tertiary” is present or not present (normal). Both are shown.

  (3) As aromatic ring-containing monomers other than styrene, for example, α-methylstyrene, vinyltoluene, vinylnaphthalene, ethylvinylbenzene, 4-vinylbiphenyl, 1,1-diphenylethylene, benzyl (meth) acrylate, Examples thereof include vinyl monomers having an aromatic ring having 6 to 22 carbon atoms such as phenoxyethyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate.

  These may be used alone or in combination of two or more.

  (B-1) The content of the structural unit derived from styrene in the styrenic macromer is preferably 60 wt% or more, more preferably 70 wt% or more, and particularly preferably 90 wt% or more from the viewpoint of storage stability. Examples of commercially available (b-1) styrenic macromers include trade names of Toa Gosei Co., Ltd., AS-6, AS-6S, AN-6, AN-6S, HS-6, HS-6S. Etc.

  (B-2) An alkyl (meth) acrylate macromer having a polymerizable functional group at one end has an alkyl (meth) acrylate homopolymer having a polymerizable functional group at one end, and a polymerizable functional group at one end. And a copolymer of an alkyl (meth) acrylate and another monomer. Preferably, it is a C1-C8 alkyl (meth) acrylate macromer, for example, a methyl methacrylate macromer, a butyl acrylate macromer, an isobutyl methacrylate macromer, etc. are mentioned.

(B-3) The silicone-based macromer having a polymerizable functional group at one end is preferably a macromer represented by the following formula (3).
_{CH 2 = C (CH 3)} -COOC 3 H 6 - [Si _{(CH 3) 2} O] _{t -Si (CH 3) 3 ···} (3)
(Wherein t represents a number of 8 to 40)
The number average molecular weight of the macromer (b) is preferably 1,000 to 10,000, and preferably 2,000 to 8,000 from the viewpoint of keeping the viscosity low while increasing the copolymerization ratio in order to increase the dispersion stability. Further preferred.

  The number average molecular weight of the macromer is a value measured by gel permeation chromatography using polystyrene as a standard substance and tetrahydrofuran containing 50 mmol / L acetic acid as a solvent.

  The structural unit derived from the hydrophobic monomer (c) is used from the viewpoint of storage stability and scratch resistance, and can be obtained by polymerizing the hydrophobic monomer. A monomer may be introduced.

As the hydrophobic monomer (c), (c-1) (meth) acrylate having an alkyl group having 1 to 22 carbon atoms or (c-2) an aromatic group-containing monomer represented by the following formula (4) is preferable. .
_{^{CH 2 = C (R 3)}} -R 4 ··· (4)
(In the formula, R ³ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, and R ⁴ represents an aromatic group-containing hydrocarbon group having 6 to 22 carbon atoms.)
(C-1) As a (meth) acrylate having an alkyl group having 1 to 22 carbon atoms, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, (iso or tertiary) butyl (Meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, (iso) stearyl (meth) acrylate, Examples include heenyl (meth) acrylate.

  (C-2) As the aromatic group-containing monomer represented by the formula (4), from the viewpoint of scratch resistance, styrene, vinyl naphthalene, α-methylstyrene, vinyl toluene, ethyl vinyl benzene, 4-vinyl biphenyl, One or more selected from 1,1-diphenylethylene is preferred. Among these, from the viewpoint of scratch resistance and storage stability, one or more selected from the group consisting of styrene, α-methylstyrene, and vinyltoluene are more preferable.

  The structural unit derived from the hydroxyl group-containing monomer (d) enhances dispersion stability and exhibits an excellent effect of improving marker resistance in a short time when printed, and polymerizes the hydroxyl group-containing monomer. Can be obtained. For example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polyethylene glycol (n = 2 to 30, n represents the average number of moles added of the oxyalkylene group; the same applies hereinafter) (meth) acrylate Polypropylene glycol (n = 2-30) (meth) acrylate, poly (ethylene glycol (n = 1-15) / propylene glycol (n = 1-15)) (meth) acrylate, polyethylene glycol methacrylate 2-ethylhexyl ether, etc. Is mentioned. Among these, 2-hydroxyethyl (meth) acrylate, polyethylene glycol monomethacrylate, polyethylene glycol methacrylate 2-ethylhexyl ether, and polypropylene glycol methacrylate are preferable.

The oxyalkylene group-containing monomer (e) is a monomer represented by the following formula (5).
CH ₂ = C (R ⁵ ) COO (R ⁶ O) pR ⁷ (5)
(Wherein R ⁵ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R ⁶ is a divalent hydrocarbon group having 1 to 30 carbon atoms which may have a hetero atom, and R ⁷ is a hetero atom. The monovalent hydrocarbon group having 1 to 30 carbon atoms that may be present, p represents the average number of moles added, and is 1 to 60, preferably 1 to 30.)
The structural unit derived from the oxyalkylene group-containing monomer (e) is used from the viewpoint of enhancing the ejection stability of the water-based ink, and can be obtained by polymerizing the monomer represented by the above formula (5).

In the formula (5), examples of the hetero atom that R ⁶ or R ⁷ may have include a nitrogen atom, an oxygen atom, a halogen atom, and a sulfur atom.

Representative examples of the group represented by R ⁶ or R ⁷ include aromatic groups having 6 to 30 carbon atoms, heterocyclic groups having 3 to 30 carbon atoms, alkylene groups having 1 to 30 carbon atoms, and the like. It may have a substituent. These groups may be a combination of two or more. Examples of the substituent include an aromatic group, a heterocyclic group, an alkyl group, a halogen atom, and an amino group.

As R ⁶ , a phenylene group which may have a substituent having 1 to 24 carbon atoms, an aliphatic alkylene group having 1 to 30 carbon atoms, preferably 1 to 20 carbon atoms, and an aromatic ring having 7 carbon atoms. An alkylene group having 4 to 30 carbon atoms having a -30 alkylene group and a heterocycle is preferred. Particularly preferable specific examples of the R ⁶ O group include an oxyethylene group, an oxy (iso) propylene group, an oxytetramethylene group, an oxyheptamethylene group, an oxyhexamethylene group, or a carbon number of 2 or more of these oxyalkylenes. ˜7 oxyalkylene groups and oxyphenylene groups.

R ⁷ includes a phenyl group, an aliphatic alkyl group having 1 to 30 carbon atoms, preferably an aliphatic alkyl group having 1 to 20 carbon atoms, an alkyl group having 7 to 30 carbon atoms having an aromatic ring, or an alkyl group having 4 to 30 carbon atoms having a heterocycle. An alkyl group is preferred. More preferred examples of R7 include methyl group, ethyl group, (iso) propyl group, (iso) butyl group, (iso) pentyl group, (iso) hexyl group, (iso) octyl group, (iso) decyl group, C1-C12 alkyl groups, such as an (iso) dodecyl group, a phenyl group, etc. are mentioned.

  Specific examples of the component (e) include methoxypolyethylene glycol (p in Formula 2 is 1 to 30) (meth) acrylate, methoxypolytetramethylene glycol (p = 1 to 30) (meth) acrylate, ethoxypolyethylene glycol (p = 1-30) (meth) acrylate, (iso) propoxypolyethylene glycol (p = 1-30) (meth) acrylate, butoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxypolyethylene glycol (p = 1-30) (meth) acrylate, phenoxypolyethylene glycol (p = 1-30) (meth) acrylate, methoxypolypropylene glycol (p = 1-30) (meth) acrylate, methoxy (ethylene glycol / propylene glycol copolymer) p = 1-30, in which ethylene glycol moiety is 1-1: 20) (meth) acrylate, phenoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, in which ethylene glycol moiety is 1 ˜1: 20) (meth) acrylate and the like. Among these, methoxypolyethylene glycol (p = 1-30) (meth) acrylate, octoxypolyethylene glycol (p = 1-30) (meth) acrylate, phenoxypolyethylene glycol (p = 1-30) (meth) acrylate , Phenoxy (ethylene glycol / propylene glycol copolymer) (p = 1-30, in which the ethylene glycol moiety is 1-1: 20) (meth) acrylate is preferred.

  The polymer used in the present invention contains a monomer represented by the above formula (1-1), preferably a salt-forming group-containing monomer (a), more preferably a macromer (b), particularly preferably a hydrophobic monomer ( c) obtained by copolymerizing a monomer mixture (hereinafter referred to as “monomer mixture”) containing one or more monomers selected from the group consisting of a hydroxyl group-containing monomer (d) and an oxyalkylene group-containing monomer (e). Those are preferred.

  The monomer content represented by the above formula (1-1) in the monomer mixture, or the content of the structural unit represented by the above formula (1) in the polymer is determined by the scratch resistance and glossiness of the aqueous ink. From the viewpoint of improvement and dispersion stability, it is preferably 10 to 80 wt%, more preferably 25 to 80 wt%, and particularly preferably 25 to 75 wt%.

  Content of the salt-forming group-containing monomer (a) in the monomer mixture (content as an unneutralized amount; hereinafter, calculated as an unneutralized amount for the salt-forming group-containing monomer), or salt-forming group-containing monomer in the polymer The content of the structural unit derived from (a) is preferably from 3 to 30 wt%, more preferably from 5 to 25 wt%, from the viewpoints of improvement in print density and gloss when used as a water-based ink and good dispersion stability. Particularly preferably, it is 5 to 20 wt%.

  The weight ratio of [the structural unit represented by the formula (1) / the structural unit derived from the salt-forming group-containing monomer (a)] is preferably 10/1 to 1 from the viewpoint of improving the dispersibility and gloss of the polymer. / 1, more preferably 5/1 to 1/1.

  The content of the macromer (b) in the monomer mixture or the content of the structural unit derived from the macromer (b) in the polymer is preferably 0 to 50 wt. From the viewpoint of storage stability and scratch resistance when used as a water-based ink. %, More preferably 5 to 35 wt%, particularly preferably 5 to 30 wt%.

  The weight ratio of [the structural unit represented by the formula (1) / the structural unit derived from the macromer (b)] is preferably 10/1 to 1 from the viewpoint of improving the storage stability, scratch resistance and gloss of the polymer. 1/1, more preferably 5/1 to 1/1.

  The content of the hydrophobic monomer (c) in the monomer mixture or the content of the structural unit derived from the hydrophobic monomer (c) in the polymer is preferably from the viewpoint of storage stability and scratch resistance when used as a water-based ink. Is 0 to 40 wt%, more preferably 0 to 20 wt%.

  The content of the hydroxyl group-containing monomer (d) in the monomer mixture or the content of the structural unit derived from the hydroxyl group-containing monomer (d) in the polymer is preferably 0 to 40 wt. From the viewpoint of dispersion stability when the aqueous ink is used. %, More preferably 0 to 20 wt%.

  The content of the oxyalkylene group-containing monomer (e) in the monomer mixture, or the content of the structural unit derived from the oxyalkylene group-containing monomer (e) in the polymer is preferably from the viewpoint of ejection stability when a water-based ink is used. Is 0 to 50 wt%, more preferably 10 to 40 wt%.

  When the inkjet ink according to the present invention contains a binder resin, and the binder resin has a salt-forming group, the salt-forming group derived from the salt-forming group-containing monomer is neutralized with a conventionally known neutralizing agent. Use. The degree of neutralization of the salt-forming group is preferably 10 to 200%, more preferably 20 to 150%, and particularly preferably 50 to 150%.

  The degree of neutralization can be determined by the following formula when the salt-forming group is an anionic group.

{[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [acid value of polymer (KOH mg / g) × polymer weight (g) / (56 × 1000)]} × 100
When the salt-forming group is a cationic group, it can be determined by the following formula.

[[Weight of neutralizing agent (g) / equivalent of neutralizing agent] / [amine value of polymer (HCL mg / g) × polymer weight (g) / (36.5 × 1000)]] × 100
The acid value and amine value can be calculated from the constituent unit of the water-insoluble vinyl polymer. Alternatively, it can also be determined by a method in which a polymer is dissolved in an appropriate solvent (for example, methyl ethyl ketone) and titrated.

  The weight average molecular weight of the polymer used in the present invention is preferably from 5,000 to 500,000, more preferably from 10,000 to 400,000, particularly preferably from 10,000 to 300,000, from the viewpoint of gloss.

  In addition, the weight average molecular weight of the polymer is measured using polystyrene as a standard substance by gel chromatography using dimethylformamide containing 60 mmol / L phosphoric acid and 50 mmol / L lithium bromide as a solvent.

(Manufacture of polymer latex)
An example of the manufacturing method of the inkjet ink containing polymer latex is shown. The polymer latex contains a monomer represented by the above formula (1-1) in the presence of a surfactant and / or a reactive surfactant, and further contains a salt-forming group-containing monomer (a), a macromer ( It is obtained by emulsion polymerization of a monomer mixture containing b), a hydrophobic monomer (c), a hydroxyl group-containing monomer (d), and / or an oxyalkylene group-containing monomer (e) by a conventional method.

  Reactive surfactants have one or more unsaturated double bonds capable of radical polymerization in the molecule, and have excellent monomer emulsifying properties, making them useful for the production of water dispersions with excellent stability. It is.

  Examples of the reactive surfactant include at least one hydrophobic group such as a linear or branched alkyl group or alkenyl group having 8 to 30 carbon atoms, preferably 12 to 22, an ionic group, an oxyalkylene group, or the like. Those having at least one hydrophilic group and anionic or nonionic are preferred.

  Specific examples of reactive surfactants include, for example, sulfosuccinate esters (for example, Kao Corporation, Latemul S-120P, S-180A, Sanyo Chemical Co., Ltd., Eleminol JS-2), and alkylphenol ethers. (For example, the product made from Dai-ichi Kogyo Seiyaku Co., Ltd., Aqualon HS-10, RN-20 etc.) is mentioned.

  The D50 of the polymer latex obtained by emulsion polymerization (accumulated value of 50% calculated from the small particle side in the frequency distribution of scattering intensity) is 500 nm from the viewpoint of storage stability, glossiness, and scratch resistance of the aqueous dispersion. The following is preferable, 300 nm or less is further preferable, and 100 nm or less is particularly preferable. Moreover, from the ease of manufacture, the lower limit is preferably 10 nm or more, and more preferably 20 nm or more. From these viewpoints, 10 to 500 nm is preferable, 20 to 300 nm is more preferable, and 20 to 100 nm is particularly preferable.

  Further, D90 (cumulative 90% value calculated from the small particle side in the scattering intensity frequency distribution) of the polymer latex is preferably 2000 nm or less from the viewpoint of increasing the storage stability of the dispersion by reducing coarse particles. The following is more preferable, and 500 nm or less is particularly preferable. Further, the lower limit is preferably 20 nm or more, and more preferably 50 nm or more, from the viewpoint of ease of production.

  In addition, the measurement of D50 and D90 is performed on the same conditions as the above using the laser particle analysis system ELS-8000 of the said Otsuka Electronics Co., Ltd.

  Next, the minimum film-forming temperature (MTF: Minimum Film-Forming Temperature) of the polymer latex will be described. The polymer latex preferably has a minimum film-forming temperature (MTF) of room temperature or lower, preferably 0 ° C. or lower. If the film formation of the polymer latex is set at room temperature or lower, particularly 0 ° C. or lower, the binding of the paper fibers automatically proceeds without any special treatment such as heating or drying of the image-formed image support. preferable.

  The polymer latex having an MFT of 0 ° C. or lower spreads the resin on the medium, and can fix the pigment as the color material on the recording medium. As described above, MFT is preferably 0 ° C. or lower, and more preferably −10 ° C. or lower in order to effectively exhibit the effect.

  Here, “minimum film temperature (MFT)” is transparent when an aqueous polymer latex obtained by dispersing polymer latex in water is cast thinly on a metal plate such as aluminum and the temperature is raised. Defined as the lowest temperature at which a continuous film is formed.

  Specifically, the MFT is a value measured by an MFT measuring device such as “Film-forming temperature test device” (manufactured by Imoto Seisakusho Co., Ltd.), “TP-801 MFT tester” (manufactured by Tester Sangyo Co., Ltd.). . Moreover, it can also measure with the measuring method shown by JISK6828-1: 2096. The MFT is, for example, controlling the Tg (glass transition point) of the resin particles, particularly when the resin particles are a copolymer, the ratio (addition ratio) of the monomer forming the copolymer, etc. It can be adjusted by changing it. Furthermore, in order to prepare low MFT resin particles, a film-forming aid can be added to the high MFT resin particles. This is because the film formation temperature of the resin particles, that is, the MFT can be lowered by the addition of the film forming aid.

(Polyol)
The ink-jet ink according to the present invention contains a polyol having a solubility in water of 10 wt% or less in a standard state (25 ° C., 1 atm). The polyol functions as a dissolved oxygen inhibitor.

  The polyol contained in the ink-jet ink according to the present invention may be 10 wt% or less when dissolved in water in a standard state (25 ° C., 1 atm). By having low solubility in water, that is, oily, the amount of oxygen dissolved in water can be reduced.

  Also, among polyols having a solubility in water of 10 wt% or less in a standard state (25 ° C., 1 atm), polyols having 7 to 11 carbon atoms are more preferable. The dissolved oxygen concentration can be further lowered. Furthermore, examples of such polyols include 2-ethyl-1,3 hexanediol and 2,2,4-trimethyl 1,3 pentanediol. These may be used alone or in combination.

  The content of the polyol in the total amount of the inkjet ink according to the present invention is preferably 0.1 wt% or more, and more preferably 0.5 wt% or more. By being 0.1 wt% or more, it is possible to sufficiently obtain the effect of reducing the dissolved oxygen concentration due to the fact that the inkjet ink according to the present invention contains a polyol. Further, the content of the polyol in the total amount of the inkjet ink according to the present invention is preferably 20 wt% or less, more preferably 10 wt% or less, and even more preferably 7 wt% or less. Since the solubility of the polyol is low, if it is 20 wt% or less, it becomes easier to produce the ink-jet ink according to the present invention.

  The present inventors have found that polyol has an effect of suppressing an increase in dissolved oxygen concentration in the ink. Oxygen is more polar and more soluble in water than nitrogen. Polyols with a solubility in water of 10 wt% or less have a side like an oily substance and have a low polarity with oxygen. Therefore, by adding a blending amount up to the solubility limit and replacing the ink with nitrogen, The state in which the amount of oxygen remains reduced can be maintained.

  The polyol also functions as a penetrant. If the amount added is less than the lower limit, the ink will have poor permeability to the media and will be rubbed with a roller during transport, causing smudges, or when transported for printing, ink will adhere to the transport belt and smear will occur. It cannot be used for high-speed printing. If the addition amount is greater than or equal to the upper limit, the printed dot diameter is increased, and the line width of the characters is increased or the image definition is decreased.

(Glycol ethers)
When the inkjet ink according to the present invention is a latex ink, it preferably includes glycol ethers. Latex ink can be suitably used by inkjet. This is because the inclusion of glycol ethers can control the wetting and penetrability of ink on the medium and further expand the application range as an inkjet ink.

  Examples of glycol ethers include polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Polyhydric alcohols such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, diethylene glycol isobutyl ether, triethylene glycol isobutyl ether, diethylene glycol isopropyl ether Ethers and the like.

(Surfactant)
The ink-jet ink according to the present invention may further contain a surfactant. This is for improving the dispersibility of the coloring material, the binder resin, and the like.

  Examples of the surfactant include a polyalkylene glycol surfactant. The polyalkylene glycol surfactant is an ethylene oxide adduct. It is also effective to substitute a part of ethylene oxide with an alkylene oxide such as propylene oxide or butylene oxide as long as water solubility can be maintained. The substitution rate is preferably 50% or less.

  The HLB (hydrophilic new oil ratio) of the polyalkylene glycol surfactant is preferably 12 or more and 20 or less, more preferably 13 or more and 20 or less. When the HLB is 12 or more, the familiarity of the surfactant with the dispersion medium is improved and the dispersion stability is improved. When the HLB is 20 or less, the surfactant is easily adsorbed to the pigment. , Dispersion stability is improved.

(Other additives)
In addition to the components described above, the inkjet ink according to the present invention may contain other additives as long as the effects of the present invention are not impaired. Examples of other additives include an antifungal agent, an antirust agent, and a pH adjuster.

  By using 1,2-benzisothiazolin-3-one as an antifungal agent, it is possible to provide an ink having an excellent antifungal effect while ensuring reliability such as storage stability and ejection stability. In particular, in combination with the wetting agent of the present invention, even if the addition amount is conventionally difficult to suppress the generation of bacteria and sputum, the effect can be sufficiently exerted, by suppressing the addition amount In addition, since phenomena such as particle aggregation and ink thickening can be prevented, ink performance can be exhibited over a long period of time. The amount of 1,2-benzisothiazolin-3-one added is preferably 0.01 to 0.04 parts by weight of the total amount of ink as the active ingredient amount. If it is 0.01 part by weight or more, the antifungal property will be good. If it is 0.04 parts by weight or less, particle aggregation can be suppressed when the ink is stored for a long period of time (for example, 2 years at room temperature, 1 to 3 months at 50 to 60 ° C.). On the other hand, if the amount is larger than 0.04 parts by weight, there may be a problem of long-term storage stability such as an increase in ink viscosity of 50% to 100% of the initial viscosity, and the initial printing performance may not be maintained.

  As the pH adjuster, any substance can be used as long as the pH can be adjusted to 7 or more without adversely affecting the ink to be prepared.

  Examples thereof include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium. Other examples include aminopropanediol derivatives such as hydroxides, alkali metal carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate. Aminopropanediol derivatives are water-soluble organic basic compounds such as 1-amino-2,3-propanediol, 1-methylamino-2,3-propanediol, 2-amino-2-methyl-1, Examples thereof include 3-propanediol and 2-amino-2-ethyl-1,3-propanediol, and particularly preferred examples include 2-amino-2-ethyl-1,3-propanediol.

  Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Moreover, a water-soluble ultraviolet absorber, a water-soluble infrared absorber, etc. can be added according to the purpose of the inkjet ink.

[Method for producing ink-jet ink]
The ink-jet ink according to the present invention can be obtained by mixing water, a water-soluble organic solvent, a coloring material, and a polyol having a solubility in water of 10 wt% or less in a standard state (25 ° C.).

  There is no restriction | limiting in particular about the order to mix. As for the temperature to mix, 5-50 degreeC is more preferable.

  Further, additives such as a wetting agent, a dispersing agent, an antifoaming agent, an antifungal agent, and a chelating agent can be contained. There is no restriction | limiting in particular in the mixing method of each of these components.

  An example of the contents of water, a water-soluble organic solvent, a color material, and a binder resin in the ink-jet ink is as follows.

  The content of the color material is preferably 1 to 20 wt%, more preferably 2 to 13 wt%, and particularly preferably 3 to 10 wt% from the viewpoint of printing density.

  The content of the binder resin is preferably 0.5 to 15 wt%, more preferably 1 to 10 wt%, and particularly preferably 2 to 8 wt% from the viewpoint of scratch resistance and gloss.

  The weight ratio of the binder resin to the color material [binder resin / color material] is preferably 1/10 to 10/1, more preferably 1/5 to 5/1, from the viewpoint of high printing density, scratch resistance, and gloss. Preferably, 1/3 to 3/1 is particularly preferable, and 1/2 to 2/1 is most preferable.

  The preferred surface tension (20 ° C.) of the inkjet ink according to the present invention is preferably 30 to 70 mN / m, more preferably 35 to 68 mN / m when the inkjet ink is a water dispersion. Is preferably 25 to 50 mN / m, more preferably 27 to 45 mN / m. “Aqueous dispersion” means a slow penetrating ink that has a low decrease in surface tension due to a surfactant, and “water-based ink” means a super penetrating ink that has a decrease in surface tension due to a surfactant. It's expensive.

  In the case where the inkjet ink according to the present invention is an aqueous dispersion (coloring material dispersion), the viscosity (20 ° C.) at a solid content of 10 wt% is 2 in order to obtain a good viscosity when an aqueous ink is used. -6 mPa · s is preferable, and 2 to 5 mPa · s is more preferable. In the case of water-based ink, the viscosity (20 ° C.) is preferably 2 to 12 mPa · s, and more preferably 2.5 to 10 mPa · s in order to maintain good ejection properties. The pH of the water-based ink is preferably 4-10.

  The inkjet ink production method according to the present invention includes water, a water-soluble organic solvent, a coloring material, and a polyol having a solubility in water of 10 wt% or less in a standard state (25 ° C., 1 atm). It includes a deoxygenation step for removing dissolved oxygen. When the deoxygenation step is performed, the oxygen in the air tends to be easily taken up, but since the polyol is contained, it becomes difficult to take in oxygen and the dissolved oxygen concentration can be lowered. Therefore, it is possible to provide an ink jet ink excellent in ejection stability.

  The specific method of the deoxygenation step for reducing the dissolved oxygen concentration is not particularly limited, but the method of degassing the ink under reduced pressure, the method of degassing by irradiating with ultrasonic waves, or degassing with a hollow fiber membrane. The method to be worried about is mentioned.

〔media〕
The media (recording medium) to be printed with the ink-jet ink according to the present invention includes a vinyl chloride sheet, a PET sheet, a tarpaulin (tent cloth) sheet, a coated paper or an untreated polypropylene resin, glass, metal, and these. This is a molded product.

〔ink cartridge〕
The ink cartridge according to the present invention contains the ink-jet ink according to the present invention in a container. Moreover, it has the other member etc. which were suitably selected as needed.

  The container is not particularly limited, and its shape, structure, size, material and the like can be appropriately selected according to the purpose. For example, the container has at least an ink bag formed of an aluminum laminate film, a resin film, or the like. The thing etc. are mentioned suitably.

  Next, the ink cartridge will be described with reference to FIGS. Here, FIG. 3 is a view showing an embodiment of the ink cartridge according to the present invention, and FIG. 4 is a view including a case (exterior) of the ink cartridge of FIG.

  As shown in FIG. 3, the ink cartridge 200 is filled into the ink bag 241 from the ink inlet 242 and exhausted, and then the ink inlet 242 is closed by fusion. In use, the needle of the apparatus main body is pierced into the ink discharge port 243 made of a rubber member and supplied to the apparatus.

  The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminate film. As shown in FIG. 4, the ink bag 241 is usually housed in a plastic cartridge case 244 and is detachably mounted on various ink jet recording apparatuses.

  The ink cartridge according to the present invention contains the ink-jet ink according to the present invention and can be used by being detachably mounted on various ink jet recording apparatuses, and is also detachably mounted on the ink jet recording apparatus of the present invention described later. It is particularly preferable to use them.

[Inkjet printing method, inkjet printing apparatus]
The ink jet printing apparatus according to the present invention includes the ink cartridge according to the present invention. Since the ejection stability of the inkjet ink to be ejected is excellent, high-quality inkjet printing can be performed.

  Further, the ink jet printing apparatus according to the present invention may include ink flying means, and further includes other means appropriately selected as necessary, for example, stimulus generation means, control means, and the like.

  The inkjet printing method according to the present invention performs printing using the inkjet ink according to the present invention.

  Since the ejection stability of the inkjet ink used is excellent, high-quality inkjet printing can be performed.

  In addition, the ink jet printing method according to the present invention may include an ink flying process, and further includes other processes appropriately selected as necessary, for example, a stimulus generation process, a control process, and the like.

  The ink jet printing method according to the present invention can be preferably carried out by the ink jet printing apparatus of the present invention, and the ink flying step can be suitably carried out by an ink flying means. Further, the other steps can be suitably performed by other means appropriately provided in the ink jet printing apparatus.

  The ink flying process is a process of recording an image on a recording medium by applying a stimulus to the inkjet ink according to the present invention to fly the inkjet ink.

  The ink flying means is means for applying a stimulus to the ink-jet ink according to the present invention, causing the ink-jet ink to fly, and recording an image on a recording medium. The specific configuration of the ink flying means is not particularly limited, and examples thereof include various nozzles for ejecting ink.

  In one form of the ink jet printing apparatus according to the present invention, at least a part of the liquid chamber portion, the fluid resistance portion, the vibration plate, and the nozzle member of the ink jet head may be formed of a material containing at least one of silicone and nickel. preferable.

  The nozzle diameter of the inkjet nozzle is preferably 30 μm or less, and preferably 1 to 20 μm.

  In one form of the ink jet printing apparatus according to the present invention, the ink jet printing apparatus has a sub tank for supplying ink onto the ink jet head, and the sub tank is replenished with ink from the ink cartridge through the supply tube. It is preferable to configure.

In the ink jet printing method according to the present invention, the maximum ink adhesion amount is more preferably 8 to ²⁰ g / m ² at a resolution of 300 dpi or more.

  The stimulus applied to the ink-jet ink can be generated by, for example, a stimulus generating unit, and the stimulus can be appropriately selected according to the purpose, and examples thereof include heat, pressure, vibration, light, and the like. . These may be used individually by 1 type and may use 2 or more types together. 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, a light, and the like. For example, an electric heat such as a piezoelectric actuator such as a piezoelectric element and a heating resistor. Examples include a thermal actuator that uses a phase change caused by film boiling of a liquid using a conversion element, a shape memory alloy actuator that uses a metal phase change caused by a temperature change, and an electrostatic actuator that uses an electrostatic force.

  There is no restriction | limiting in particular as a method of flying the ink for inkjet, It changes according to the kind etc. of irritation | stimulation.

  For example, when the stimulus is “heat”, the following method is exemplified. First, thermal energy corresponding to the recording signal is applied to the ink-jet ink in the recording head using, for example, a thermal head. Then, bubbles are generated in the inkjet ink by the thermal energy. Due to the pressure of the bubbles, the inkjet ink can be ejected and ejected as droplets from the nozzle holes of the recording head.

  Further, when the stimulus is “pressure”, for example, the following method may be mentioned. First, by applying a voltage to a piezoelectric element bonded to a position called a pressure chamber in the ink flow path in the recording head, the piezoelectric element is bent and the volume of the pressure chamber is reduced, so that the nozzle of the recording head The ink can be ejected and ejected as droplets from the holes.

  For example, the size of the droplets of the inkjet ink to be ejected is preferably 1 to 40 pl.

  The ejection speed of inkjet ink is preferably 5 to 20 m / s.

  The nozzle drive frequency when ejecting the inkjet ink is preferably 1 kHz or more.

  The resolution of the image formed by the inkjet ink is preferably 300 dpi or more.

  The control means is not particularly limited as long as it can control the movement of each means described above, and can be appropriately selected according to the purpose. For example, devices such as a sequencer and a computer can be mentioned.

  One mode for carrying out the ink jet printing method according to the present invention by the ink jet printing apparatus according to the present invention will be described with reference to FIG. FIG. 5 is a diagram showing a configuration of an embodiment of the ink jet printing apparatus according to the present invention.

  As shown in FIG. 5, in the inkjet printing apparatus 101, a carriage 133 is moved in the main scanning direction by a guide rod 131 and a stay (not shown) that are horizontally mounted on left and right side plates (not shown). The main scanning motor (not shown) moves and scans in the direction indicated by the arrow in FIG.

  The carriage 133 is provided with a recording head 134 composed of four ink jet recording heads that eject ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward.

  Examples of the inkjet printing head constituting the recording head 134 include a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase caused by a temperature change. A shape memory alloy actuator using a change, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for discharging ink can be used.

  The carriage 133 is equipped with sub-tanks (not shown) for each color for supplying ink of each color to the recording head 134. The sub tank is supplied with ink jet ink according to the present invention from an ink cartridge 200 loaded in an ink cartridge loading section (not shown) via an ink supply tube (not shown).

  When a near-end remaining amount of ink in the sub tank is detected, a required amount of ink is supplied from the ink cartridge 200 to the sub tank.

  In this ink jet printing apparatus, when the ink in the ink cartridge 200 is used up, the casing of the ink cartridge 200 can be disassembled and only the ink bag inside can be replaced. Further, the ink cartridge 200 can supply ink stably even when the ink cartridge 200 is vertically placed and has a front loading configuration. Therefore, even when the upper part of the ink jet printing apparatus 101 is closed and installed, for example, even when it is stored in a rack or an object is placed on the upper surface of the ink jet printing apparatus 101, the ink cartridge 200 is used. Can be easily exchanged.

  Here, an example is described in which the present invention is applied to a serial (shuttle type) ink jet printing apparatus that is scanned by a carriage, but the present invention can be similarly applied to a line type ink jet printing apparatus having a line type head.

  Next, an ink jet head provided in an embodiment of the ink jet printing apparatus according to the present invention will be described.

  FIG. 6 is an element diagram of an ink jet head provided in an ink jet printing apparatus according to an embodiment of the present invention, and FIG.

  The inkjet head includes an ink supply port (not shown) (supplying ink from the front surface direction to the back direction (back surface direction of the paper) in FIG. 6) and a frame 10 formed with a carving that becomes a common liquid chamber 12; The flow resistance plate 21, the flow path plate 20 having the communication port 23 communicating with the nozzle 31 and the engraving to be the fluid resistance portion 21 and the pressurized liquid chamber 22, the nozzle plate 30 forming the nozzle 31, the convex portion 61, the diaphragm portion 62, and the ink A diaphragm 60 having an inflow port 63, a laminated piezoelectric element 50 bonded to the diaphragm 60 via an adhesive layer 70, and a base 40 to which the laminated piezoelectric element 50 is fixed are provided. The base 40 is made of a barium titanate ceramic, and the laminated piezoelectric elements 50 are arranged in two rows and joined.

  The laminated piezoelectric element 50 includes a lead zirconate titanate (PZT) piezoelectric layer 51 having a thickness of 10 to 50 μm / layer, and an internal electrode layer 52 made of silver and palladium (AgPd) having a thickness of several μm / layer. Are stacked alternately. The internal electrode layer 52 is connected to the external electrode 53 at both ends.

  The laminated piezoelectric element 50 is divided onto comb teeth by half-cut dicing, and is used as a drive unit 56 and a support unit 57 (non-drive unit) one by one (FIG. 7).

  The outer end of one of the two external electrodes 53 (continuous to one end of the internal electrode layer 52 in the front or back direction (the back side of the paper) in the figure) is cut out so as to be divided by half-cut dicing. The length is limited by such processing, and these become a plurality of individual electrodes 54. The other is conductive without being divided by dicing, and becomes the common electrode 55.

  An FPC 80 is soldered to the individual electrode 54 of the drive unit. Further, the common electrode 55 is provided with an electrode layer at the end of the laminated piezoelectric element and is wound around to join the Gnd electrode of the FPC 80. A driver IC (not shown) is mounted on the FPC 80, thereby controlling application of drive voltage to the drive unit 56.

  The diaphragm 60 includes a thin film diaphragm portion 62, an island-shaped convex portion (island portion) 61 that joins the laminated piezoelectric element 50 that forms the driving portion 56 formed at the center portion of the diaphragm portion 62, and a support (not shown). A thick film portion including a beam to be joined to the portion and an opening to be an ink inflow port 63 are formed by stacking two Ni plating films by an electroforming method. The diaphragm portion has a thickness of 3 μm and a width of 35 μm (one side).

  The bond between the island-shaped convex portion 61 of the diaphragm 60 and the movable portion 56 of the laminated piezoelectric element 50 and the bond between the diaphragm 60 and the frame 10 are bonded by patterning the adhesive layer 70 including a gap material. ing.

  As the flow path plate 20, a silicon single crystal substrate was used, and the engraving to be the fluid resistance portion 21 and the pressurized liquid chamber 22 and the through-hole to be the communication port 23 at the position relative to the nozzle 31 were patterned by an etching method.

  The portion left by etching becomes the partition wall 24 of the pressurized liquid chamber 22. Further, in this head, a portion for narrowing the etching width is provided, and this is used as the fluid resistance portion 21.

  The nozzle plate 30 is formed of a metal material, for example, an Ni plating film formed by an electroforming method, and has a large number of nozzles 31 that are fine discharge ports for flying ink droplets. The inner shape (inner shape) of the nozzle 31 is formed in a horn shape (may be a substantially cylindrical shape or a substantially frustum shape). The diameter of the nozzle 31 is about 20 to 35 μm as the diameter on the ink droplet outlet side. The nozzle pitch of each row is 150 dpi.

  The ink ejection surface (nozzle surface side) of the nozzle plate 30 is provided with a water-repellent treatment layer that has been subjected to a water-repellent surface treatment (not shown). Ink, such as PTFE-Ni eutectoid plating, electrodeposition coating of fluororesin, vapor-deposited fluororesin (for example, fluorinated pitch), baking after solvent coating of silicon resin and fluororesin A water-repellent film selected according to the physical properties is provided to stabilize the ink droplet shape and flight characteristics so as to obtain high-quality image quality. Among these, for example, various materials are known as the fluororesin, but a modified perfluoropolyoxetane (manufactured by Daikin Industries, Ltd., trade name: OPTOOL DSX) has a thickness of 30 to 100 mm. Thus, good water repellency can be obtained by vapor deposition.

  The frame 10 that forms the engraving that becomes the ink supply port and the common liquid chamber 12 is made by resin molding.

  In the ink jet head configured as described above, by applying a driving waveform (pulse voltage of 10 to 50 V) to the driving unit 56 in accordance with the recording signal, displacement in the stacking direction occurs in the driving unit 56, and the nozzle plate 30. The pressurized liquid chamber 22 is pressurized via the pressure to increase the pressure, and ink droplets are ejected from the nozzle 31.

  Thereafter, the ink pressure in the pressurizing liquid chamber 22 decreases with the end of ink droplet ejection, and negative pressure is generated in the pressurizing liquid chamber 22 due to the inertia of the ink flow and the discharge process of the drive pulse, and the ink is filled. Move to the process. At this time, the ink supplied from the ink tank flows into the common liquid chamber 12, passes from the common liquid chamber 12 through the ink inlet 63, passes through the fluid resistance portion 21, and is filled into the pressurized liquid chamber 22.

  The fluid resistance portion 21 is effective in damping the residual pressure vibration after ejection, but becomes resistant to the maximum filling (refill) due to surface tension. By appropriately selecting the fluid resistance portion, it is possible to balance the attenuation of the residual pressure and the refill time, and to shorten the time (drive cycle) until the transition to the next ink droplet ejection operation.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in the embodiments are also included. It is included in the technical scope of the present invention.

  Hereinafter, although the Example and comparative example of this invention are shown, this invention is not limited to these. In addition, the amount of each component described in the examples is based on weight.

[Synthesis example of polymer graft colorant]
(Synthesis Example 1 (Titanium Oxide Dispersion))
(A) Synthesis of titanium oxide provided with an organic group having a vinyl group 300.0 g of ethanol and 20.0 g of deionized water were put into a 1 L glass reaction vessel, and acetic acid was added dropwise while stirring at 150 rpm. The pH was adjusted to 4.5. Next, after adding 200 g of titanium oxide R-960 (manufactured by Dupont) and stirring at 150 rpm for 30 minutes, a solution in which 20 g of 3- (trimethoxysilyl) propyl methacrylate was dissolved in 80 g of ethanol was added in about 1 hour. After dropping, the mixture was stirred at 60 ° C. for 4 hours.

  Next, the dispersion obtained by returning to room temperature and stirring was centrifuged at 5000 rpm for 30 minutes and decanted. The obtained white powder was charged with 400 mL of ethanol, stirred and redispersed, and then the obtained dispersion was centrifuged at 5000 rpm for 30 minutes and decanted. The obtained white powder was left to stand overnight, dried, and then vacuum-dried at 70 ° C. for 4 hours to obtain a surface-treated titanium oxide having no chargeable group (amino group) and having an organic group having a vinyl group added thereto. Obtained.

(B) Introduction of graft polymer chain onto titanium oxide particle surface (synthesis of grafted titanium oxide)
Next, 100.0 g of lauryl methacrylate, 300.0 g of paraffin hydrocarbon neothiozole (manufactured by Chuo Kasei Co., Ltd.), 96.0 g of the above-mentioned surface-treated titanium oxide, and 0.600 g of AIBN were put into a 1 L pressurized reaction vessel. After nitrogen substitution and pressurization with nitrogen to 0.1 MPa, dispersion was performed for 30 minutes while stirring at 300 rpm.

  Then, it heated to 75 degreeC in about 1 hour, and stirred at 75 degreeC for 7 hours. Next, the dispersion obtained by returning to room temperature and stirring was centrifuged at 10,000 rpm for 30 minutes and decanted. The obtained white powder was charged with 600 mL of isooctane, stirred and redispersed, and then centrifuged at 10,000 rpm for 30 minutes and decanted twice.

  Furthermore, after standing overnight and drying, it was vacuum-dried at 70 ° C. for 4 hours to obtain a polymer-grafted titanium oxide. When the grafted titanium oxide was subjected to thermogravimetric analysis, the weight loss was 9.3% (GT).

(Synthesis Example 2 (carbon black dispersion))
90 g of carbon black with a CTAB specific surface area of 150 m ² / g and DBP oil absorption of 100 ml / 100 g is added to 3000 ml of 2.5 N normal sodium sulfate solution, stirred at a temperature of 60 ° C. and a speed of 300 rpm, and reacted for 10 hours for oxidation treatment. Was done. The reaction solution was filtered, and the carbon black separated by filtration was neutralized with a sodium hydroxide solution and subjected to ultrafiltration. The obtained carbon black (G-K) was washed with water, dried, and dispersed in pure water to 20 wt%.

[Synthesis example of polymer inclusion color material]
(Synthesis Example 3)
After sufficiently replacing the inside of the 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas introduction tube, reflux tube and dropping funnel with nitrogen gas, 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, 4.0 g of polyethylene glycol methacrylate, 4.0 g of styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6) and 0.4 g of mercaptoethanol were charged, 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 hydroxyethyl methacrylate, styrene macromer (Toa Gosei (
Co., Ltd., trade name: AS-6) 36.0 g, mercaptoethanol 3.6 g, azobisdimethylvaleronitrile 2.4 g, and methyl ethyl ketone 18 g mixed solution were dropped into the flask over 2.5 hours. After completion of dropping, a mixed solution of 0.8 g of azobisdimethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 g of azobisdimethylvaleronitrile was added and further aging was performed 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 having a solid content concentration of 50%.

(Synthesis Example 4 (phthalocyanine polymer inclusion dispersion))
After 28 g of the polymer solution prepared in Synthesis Example 3, 26 g of phthalocyanine pigment, 13.6 g of 1 mol / L potassium hydroxide solution, 20 g of methyl ethyl ketone, and 30 g of ion-exchanged water were sufficiently stirred, they were kneaded using a three-roll mill. The obtained paste was put into 200 g of ion-exchanged water and stirred sufficiently, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a cyan polymer fine particle dispersion (P-Cy). The particle size was 156 nm.

(Synthesis Example 5 (Titanium oxide polymer inclusion dispersion))
After sufficiently stirring 28 g of the polymer solution prepared in Synthesis Example 3, 26 g of titanium oxide (Ishihara Sangyo TTO-51 particle size 20 nm), 13.6 g of 1 mol / L potassium hydroxide solution, 20 g of methyl ethyl ketone, and 30 g of ion-exchanged water. And kneading using a three-roll mill. The obtained paste was put into 200 g of ion-exchanged water and sufficiently stirred, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a white polymer fine particle dispersion (PT). The particle size was 50 nm.

[Production example of resin-dispersed coloring material]
(Production Example 1)
150 g of titanium oxide (TTO-55 manufactured by Ishihara Sangyo Co., Ltd., particle size 35 nm), Solsperse 43000 (manufactured by Lubrizol), 3.0%, Solsperse 44000 (manufactured by Lubrizol), 3.0%, distilled water After mixing 738 g and pre-dispersing this mixture, it was circulated and dispersed for 20 hours in a disk-type bead mill (Shinmaru Enterprises KDL type, media: 0.3 mmφ zirconia ball used), and titanium oxide (RT) A pigment dispersion was obtained.

(Production Example 2 (Dimethylquinacridone pigment dispersion))
C. I. 150 g of Pigment Red 122, Solsperse 43000 (manufactured by Lubrizol), 3.38%, Solsperse 44000 (manufactured by Lubrizol), 3.38%, and 738 g of distilled water were mixed, and this mixture was pre-dispersed. Then, it was circulated and dispersed for 20 hours in a disk-type bead mill (Shinmaru Enterprises KDL type, media: 0.3 mmφ zirconia ball used) to obtain a dimethylquinacridone pigment dispersion (RM).

[Synthesis of polymer latex (binder resin)]
(Synthesis Example 6)
After fully replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, 10 g of Aqualon RN-20 (Daiichi Kogyo Seiyaku), 1 g of potassium persulfate and pure 286 g of water was charged and the temperature was raised to 65 ° C. Next, 150 g of methyl methacrylate, 100 g of 2-ethylhexyl acrylate, 20 g of acrylic acid, 20 g of vinyltriethoxysilane, 10 g of Aqualon RN-20, 10 g of potassium persulfate 10 g of Aqualon RN-20, 4 g of potassium persulfate and pure water 398.3 g of the mixed solution was dropped into the flask over 2.5 hours. The mixture was further heated and aged at 80 ° C. for 3 hours and then cooled, and the pH was adjusted to 7 to 8 with potassium hydroxide. The particle diameter of the resin measured using Microtrac UPA was 130 nm. The minimum film-forming temperature (MTF) was 0 ° C. (P-1).

(Synthesis Example 7)
After fully replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, 10 g of Aqualon RN-20 (Daiichi Kogyo Seiyaku), 1 g of potassium persulfate and pure 286 g of water was charged and the temperature was raised to 65 ° C. Next, 150 g of methyl methacrylate, 100 g of 2-ethylhexyl acrylate, 20 g of acrylic acid, 40 g of hexyltrimethoxysilane, 10 g of Aqualon RN-20, 10 g of potassium persulfate 10 g of Aqualon RN-20, 4 g of potassium persulfate and pure water 398.3 g of the mixed solution was dropped into the flask over 3 hours. The mixture was further heated and aged at 80 ° C. for 3 hours and then cooled, and the pH was adjusted to 7 to 8 with potassium hydroxide. The particle diameter of the resin measured using Microtrac UPA was 148 nm. The minimum film-forming temperature (MTF) was 0 ° C. (P-2).

(Synthesis Example 8)
After fully replacing the inside of the flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel with nitrogen gas, 100 g of pure water, 3 g of sodium dodecylbenzenesulfonate and 1 g of polyethylene glycol nonylphenyl ether were added. First, 1 g of ammonium persulfate and 0.2 g of sodium hydrogen sulfite were added, and the temperature was raised to 60 ° C. Next, 30 g of butyl acrylate, 40 g of methyl methacrylate, 1:20 g of butyl methacrylate, 10 g of vinylsilane triol potassium salt and 1 g of 3-methacryloxypropylmethyldimethoxysilane were dropped into the flask over 3 hours. At this time, polymerization was carried out by adjusting the polymerization reaction solution to pH 7 with an aqueous ammonia solution. The particle diameter of the resin measured using Microtrac UPA was 160 nm. The minimum film-forming temperature (MTF) was 0 ° C. (P-3).

[Production of latex ink]
The inks of Examples and Comparative Examples were prepared using the prepared six types of pigment dispersions and binder resins. An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 9. Then, it filtered with the membrane filter whose average hole diameter is 0.8 micrometer, and obtained the ink composition (inkjet ink).

(Ink Preparation Example 1)
9 wt% (solid content) of polymer grafted titanium oxide (GT) synthesized in Synthesis Example 1
Polymer latex (P-1) (solid content 45%) 8wt%
3-methyl-1,3-butanediol 12wt%
Glycerin 10wt%
2-pyrrolidone 2wt%
Diethylene glycol isobutyl ether 10wt%
2-ethyl-1,3-hexanediol 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
Amine compound (2-amino-2-ethyl-1,3-propanediol) 0.1 wt%
Ion exchange water was added to make 100%.

(Ink Preparation Example 2)
Polymer grafted carbon black (G-K) synthesized in Synthesis Example 2 8 wt% (solid content)
Polymer latex (P-2) (45% solid content) 6 wt%
1,3-butanediol 10wt%
Glycerin 13wt%
2-pyrrolidone 1wt%
Triethylene glycol isobutyl ether 10wt%
2,2,4-Trimethyl-1,3-pentanediol 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
Amine compound (triethanolamine) 0.1wt%
Ion exchange water was added to make 100%.

(Ink Preparation Example 3)
Polymer-encapsulated phthalocyanine (P-Cy) synthesized in Production Example 4 8 wt% (solid content)
Polymer latex (P-3) (solid content 45%) 10 wt%
Glycerin 20wt%
Diethylene glycol isobutyl ether 10wt%
2-ethyl-1,3-hexanediol 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
Amine compound (triethanolamine) 0.1wt%
Ion exchange water was added to make 100%.

(Ink Preparation Example 4)
Polymer-encapsulated titanium oxide (PT) synthesized in Synthesis Example 5 8 wt% (solid content)
Polymer latex (P-1) (solid content 45%) 5 wt%
3-methyl-1,3-butanediol 10wt%
Glycerin 15wt%
Triethylene glycol isobutyl ether 10wt%
2-ethyl-1,3-hexanediol 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
Amine compound (lithium hydroxide) 0.1wt%
Ion exchange water was added to make 100%.

(Ink Preparation Example 5)
Resin-dispersed titanium oxide (RT) produced in Production Example 1 8 wt% (solid content)
Polymer latex (P-2) (45% solid content) 6 wt%
1,6-hexanediol 10wt%
Glycerin 13wt%
2-pyrrolidone 1wt%
Triethylene glycol isobutyl ether 10wt%
2,2,4-Trimethyl-1,3-pentanediol 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
Amine compound (2-amino-2-ethyl-1,3-propanediol) 0.1 wt%
Ion exchange water was added to make 100%.

(Ink Preparation Example 6)
Resin-dispersed quinacridone (RM) produced in Production Example 2 8 wt% (solid content)
Polymer latex (P-3) (45% solid content) 6 wt%
Glycerin 14wt%
Dipropylene glycol 10wt%
Diethylene glycol isobutyl ether 10wt%
2-ethyl-1,3-hexanediol 2wt%
Polyalkylene glycol surfactant (Asahi Denka) 1wt%
Amine compound (lithium hydroxide) 0.1wt%
Ion exchange water was added to make 100%.

[Deoxygenation process]
Each ink from Ink Preparation Examples 1 to 6 is subjected to a step of adjusting the dissolved oxygen amount. The dissolved oxygen amount is 5 mg / l or less, the dissolved nitrogen concentration is 20 mg / l or less, and the dissolved oxygen concentration is 1. The ratio (weight ratio) of the dissolved nitrogen concentration was 10 or more.

  Specifically, using a hollow fiber membrane degassing module manufactured by Mitsubishi Rayon, dissolved oxygen while blowing nitrogen gas into the ink at a degassing vacuum pressure of 90 kPa (degasing MAX using ULVAC DAP-6D). Deaeration was performed until the concentration was 1 mg / l or less and the dissolved nitrogen concentration was 20 mg / l or less.

  The dissolved oxygen concentration and dissolved nitrogen concentration of each ink are as shown in Table 2 below. The inks prepared in this manner were used as inks of Examples 1 to 6 (Table 2).

Further, the inks of Comparative Examples 1 to 6 were prepared by changing the inks of Ink Preparation Examples 1 to 6 as follows.
Comparative Example 1 An ink was prepared with the same composition as in Ink Preparation Example 1, except that 2-ethyl-1,3-hexanediol was omitted. The deaeration process was performed similarly to the Example.
Comparative Example 2 An ink was produced with the same composition as in Example 2, except that 2,2,4-trimethyl-1,3-pentanediol was omitted. The deaeration process was performed similarly to the Example.
Comparative Example 3 The ink prepared in Example 3 was used without going through a degassing step.
Comparative Example 4 The ink prepared in Example 4 was used without going through a degassing step.
Comparative Example 5 With the ink prepared in Example 5, the dissolved oxygen content and the dissolved nitrogen content were adjusted to the values shown in Table 3.
Comparative Example 6 With the ink prepared in Example 6, the dissolved oxygen content and dissolved nitrogen content were adjusted to the values shown in Table 3.

  Each dissolved oxygen concentration and dissolved nitrogen concentration are shown in Table 3.

  The viscosity and surface tension of each ink shown in the examples are as shown in Table 4.

  The viscosity and surface tension of each ink shown in the comparative example are as shown in Table 5.

  Next, the ejection characteristics of the inks of Examples and Comparative Examples were evaluated. The evaluation test was performed by changing the frequency using a jet property tester Jet Lyzer (T318 / S128 / P16 manufactured by Miki). The results are shown in Tables 6 and 7 below with a round mark if the discharge is good, but a triangle mark if the mist is large, and when the discharge is not good.

  Next, the image characteristics of the inks of Examples and Comparative Examples were evaluated.

[Print quality evaluation test]
Using an inkjet printer “JV5” (Mimaki Engineering Co., Ltd., product name), GEN5 (Ricoh Co., Ltd.) is attached to the head, and white vinyl gloss media “SPC-0482 (Nichiei Chemical Co., Ltd., product name)” In addition, each of the inks of Examples 1 to 6 and Comparative Examples 1 to 6 and Mimaki Engineering genuine latex ink were ejected from each of the five heads, and the printed matter was printed on the media paper tube while printing under the following printing conditions. Then, the printed surface after winding was visually confirmed to check for the occurrence of bleeding, and the printing speed at this time is shown in Table 8. The printing density is the ink per unit area. The coating amount was set as a reference.

(Evaluation item)
The image characteristics of the printed image were evaluated by the following five items.

(1) Feathering (2) Color bleed (3) Beading (4) Image image (5) Glossiness (Printing conditions)
(1) Draft: 540 × 1080 dpi / high speed mode (2) Fine: 720 × 1080 dpi / high speed mode heater temperature:
I Preheater: 40 ° C
II Platen heater: 40 ° C
III After heater: 50 ℃
(Latex ink)
MIMAKI LX ink: KCMY 4 colors

These results are shown in Table 9.
Evaluation items for image sharpness (1) Feathering and (2) Criteria for judging color bleed: Double circle: Clear printing without bleeding on all paper.

    Circle: Some paper (recycled paper) has whiskers.

  Triangle: All paper has whisker-like blurring.

  X: The bleeding is so large that the outline of the character is not clear.

(3) Beading The degree of beading of the green solid image portions of the examples and comparative examples was visually observed, and the rank was evaluated according to the following criteria.

〔Evaluation criteria〕
5: Uniform printing without occurrence of beading.

    4: The occurrence of beading is slightly observed, but it is at a level that does not matter at all.

    3: The occurrence of beading is recognized, but the image quality is not impaired.

    2: The occurrence of beading is clearly observed.

    1: Significant beading is observed.

(4) Evaluation of image density The optical density of the magenta image portion of the example and the comparative example was measured with X-Rite 932 and evaluated according to the following criteria.

〔Evaluation criteria〕
Double circle: Magenta image density 1.6 or more Circle: Magenta image density 1.3 or more Triangle: Magenta image density 1.0 or more X: Magenta image density less than 1.0 (5) Evaluation of glossiness Examples and Comparative Examples The degree of glossiness of the image area was visually observed and evaluated according to the following criteria.

〔Evaluation criteria〕
Double circle: High gloss.

    Circle: Glossy.

  X: Glossiness is not recognized.

  The present invention can be used for inkjet printing.

Claims (10)

  The weight ratio of dissolved nitrogen concentration when water, water-soluble organic solvent, coloring material, and polyol dissolved in water in the standard state (25 ° C., 1 atm) are 10 wt% or less and the dissolved oxygen concentration is 1. An ink-jet ink characterized by being 10 or more.   The inkjet ink according to claim 1, further comprising a binder resin, wherein the binder resin is emulsion or suspended.   The inkjet ink according to claim 1 or 2, wherein the dissolved oxygen concentration is 5 mg / l or less and the dissolved nitrogen concentration is 20 mg / l or less.   The ink for inkjet according to any one of claims 1 to 3, wherein the polyol has 7 to 11 carbon atoms.   The inkjet ink according to claim 2, further comprising glycol ethers.   The inkjet ink according to any one of claims 1 to 5, further comprising a polyalkylene glycol surfactant having an HLB (hydrophilic / lipophilic ratio) of 13 to 20.   Including a deoxygenation step of removing dissolved oxygen from water, a water-soluble organic solvent, a coloring material, and a polyol containing 10 wt% or less of dissolved water in a standard state (25 ° C., 1 atm). A method for producing an inkjet ink, which is characterized.   An ink cartridge comprising the ink-jet ink according to claim 1 contained in a container.   7. An ink jet printing method comprising printing using the ink jet ink according to claim 1.   An ink jet printing apparatus comprising the ink cartridge according to claim 8.

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