JP2009108245A - Ink composition and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which can form a good printed image excellent in preservability and preventing blurring or feathering from occurring in the printed image, and can keep a stable dispersion state even using a pigment, especially to provide an ink composition which provides good discharge stability in inkjet recording, and can form a good printed image stably even in a case of forming a large number of images. <P>SOLUTION: This ink composition comprising a pigment dispersoid dispersed in an aqueous medium comprises a block copolymer which is hydrophilic at a room temperature and becomes amphipathic on heating at a temperature expressing hydrophobicity or above. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink composition suitable for various image recording apparatus inks such as various printing methods, ink jet methods, and electrophotographic methods, and an ink jet recording apparatus using the same.

  In recent years, digital printing technology, represented by inkjet technology, has made remarkable progress. In particular, ink-jet technology that is compact and can perform recording easily with low power consumption enables high-quality printing with the advancement of nozzle miniaturization and ink ejection methods, and the image quality is approaching that of silver halide photography. is there. However, since dye ink is used in the ink jet technique, bleeding may occur in the image ejected on the recording medium when the multi-color dye ink is superimposed. In addition, a phenomenon (feathering) in which the ink ejected onto the recording medium oozes out in the fiber direction of the recording medium due to a capillary phenomenon may be observed.

  In order to solve the feathering, an ink (Patent Document 1) containing a dye, a water-soluble vehicle, and particles having an average diameter of 100 nm or less has been reported. However, although bleeding and feathering were reduced by this ink, the printed image had low weather resistance, and there was a problem in long-term storage of the printed image.

  As means for solving these problems, it has been proposed to use pigment-dispersed ink instead of dye ink (Patent Document 2).

In general, pigment ink is used as a dispersion in which a pigment is dispersed by a polymer compound. When an image is formed by an ink jet printer on coated paper coated with kaolin or the like using pigment ink, bleeding and feathering are reduced. However, when the pigment ink has a long storage period before printing, the dispersed state tends to be lowered, and when the dispersed state ink that partially aggregates is used, stable ejection may not be obtained. . This tendency is particularly strong in ink jet recording in which ejection is performed by applying thermal energy. In addition, when a large amount of image is formed using such dispersed ink, ink ejection becomes unstable and a good image may not be obtained.
No. 2957324 US Patent No. 5,085,698

  An object of the present invention is to maintain a stable dispersion state even when a pigment is used, to form a good print image, to suppress bleeding and feathering that occur in the print image, and to have excellent storage stability. Another object of the present invention is to provide an ink composition capable of forming a printed image. In particular, it is an object of the present invention to provide an ink composition that can provide good ejection stability in ink jet recording and can stably form a good image even when a large amount of image is formed. And it is providing the inkjet recording device using this.

  The present inventors in an ink in which a pigment dispersion composed of an amphiphilic dispersion resin having a hydrophobic part and a hydrophilic part adhering to the surface of a hydrophobic pigment and a pigment is dispersed in an aqueous medium. Thus, in order to suppress the occurrence of aggregation in the pigment dispersion, the following findings were obtained as a result of intensive studies. When the dispersion resin constituting the pigment dispersion is detached from the pigment surface by vibration or heating, it is very rare that the once removed dispersion resin adheres again to the site of the detached pigment surface. Dispersion resin that does not constitute the pigment dispersion has hydrophobic parts attracting each other and agglomerating to form micelles in the aqueous medium. In the aqueous medium, the dispersion resin having the hydrophobic part as a free end is It can be said that it hardly exists. For this reason, it is difficult for another dispersion resin to adhere to the site where the dispersion resin is detached and maintain the dispersed state, and the pigment dispersion tends to aggregate at the site where the dispersion resin is detached. Obtained knowledge. Then, the ink contains a hydrophobic developing block polymer that has hydrophilicity in the ink at room temperature and develops hydrophobicity and becomes amphiphilic in the ink heated to a predetermined temperature. It was found that the aggregation of the pigment dispersion that occurs at the temperature of 1 can be suppressed. Based on these findings, the present invention has been completed.

  In the ink composition in which a pigment dispersion is dispersed in an aqueous medium, the present invention contains a block polymer that is hydrophilic at room temperature and is heated to a temperature higher than the hydrophobic expression temperature to have amphiphilic properties. And an ink composition.

  The present invention relates to an ink jet recording apparatus that performs ink jet recording by discharging the ink composition from a discharge port.

  The ink composition of the present invention can maintain a stable dispersion state even when a pigment is used, and can form a good print image with excellent storage stability. Bleeding and feathering can be suppressed. By using the ink composition of the present invention, good ejection stability can be obtained in an ink jet recording apparatus, and a good image can be stably formed even when a large amount of image is formed.

  The ink composition of the present invention contains a hydrophobic expressible block polymer in which a pigment dispersion is dispersed in an aqueous medium, is hydrophilic at room temperature, and is heated above the hydrophobic expression temperature to have amphiphilic properties. .

[Aqueous medium]
Examples of the aqueous medium contained in the ink composition of the present invention include water and a mixture of water and a water-soluble organic solvent. The water is preferably ion-exchanged water, pure water or ultrapure water from which metal ions or the like have been removed.

  Specific examples of the water-soluble organic solvent include the following. Polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol and glycerin. Polyhydric alcohol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; Nitrogen-containing solvents such as N-methyl-2-pyrrolidone, substituted pyrrolidone and triethanolamine. In addition, monohydric alcohols such as methanol, ethanol and isopropyl alcohol can be used for the purpose of accelerating the drying of the aqueous dispersion on the recording medium.

  In addition, organic solvents that are soluble in these water-soluble organic solvents can also be used. Examples of the organic solvent include hydrocarbon solvents, aromatic solvents, ether solvents, ketone solvents, ester solvents, amide solvents, and the like.

  The content of the aqueous medium is preferably in the range of 20 to 95% by mass in the ink composition. More preferably, it is the range of 30-90 mass%. The total content of the water-soluble organic solvent and the organic solvent is preferably 50% by mass or less in the aqueous medium.

[Pigment dispersion]
The pigment dispersion in the ink composition of the present invention contains a pigment and an amphiphilic dispersion resin that can be dispersed in an aqueous medium at least at room temperature, and has a micelle structure.

[Dispersion resin]
The dispersion resin contained in the pigment dispersion has a so-called amphipathic property having hydrophilicity and hydrophobicity at least at room temperature. Here, the amphiphilic property has affinity for both inorganic and organic solvents. The dispersion resin has an amphipathic property at least at room temperature, so that it is bonded or attached to the surface of the pigment that is hydrophobic, hydrated with the aqueous medium, and stably dispersed in the aqueous medium at room temperature. Can do.

  The dispersion resin having such an amphiphilic property is not limited as long as it has a hydrophilic functional group and a hydrophobic substituent, but binds to a hydrophobic block segment that hardly forms a bond with a water molecule, and to a water molecule. Is preferably a block polymer having a hydrophilic block segment that easily forms. The hydrophobic block segment adheres to the surface of the pigment at least at room temperature, and the hydrophilic block segment hydrates to form a stable pigment dispersion. Furthermore, the amphiphilic block polymer may have another ionic block segment other than the hydrophobic block segment and the hydrophilic hydrophobic block segment.

  Specific examples of the hydrophilic functional group of the dispersion resin include a sulfone group, a carboxyl group, a hydroxyl group, an ammonium group, an amino group, an imino group, an ether group, and salts thereof. Examples of these salts include cation salts such as lithium salts, sodium salts, potassium salts, calcium salts, and anion salts such as hydrochlorides, sulfates, chlorine salts, bromine salts, and iodine salts.

  In addition, examples of the hydrophobic substituent of the dispersion resin include linear, branched or cyclic saturated hydrocarbon groups such as methyl group, ethyl group, propyl group, butyl group, and pentyl group, phenyl group, and naphthyl group. And aromatic groups such as anthracenyl group (is it an anthryl group?) And an azulenyl group.

  In the case where the dispersion resin is a block polymer, the hydrophilic block segment preferably has a repeating unit having a hydrophilic functional group that easily forms a bond with a water molecule. The repeating unit may be composed of one type or two or more types of monomers, but those having a single repeating unit are preferable because the effect obtained by the function becomes remarkable. The hydrophilic block segment preferably has a polyalkenyl ether structure in the main chain. Specifically, the hydrophilic functional group is the same as those exemplified as the hydrophilic functional group or salt thereof in the dispersion resin. It is preferable to have a thing. Specific examples of the hydrophilic block segment include those having the repeating units exemplified below. In the following chemical formula, R is preferably, for example, a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, or a propyl group.

  In addition, the hydrophobic block segment preferably has a repeating unit having a hydrophobic substituent that hardly forms a bond with a water molecule. The repeating unit may be composed of one type or two or more types of monomers, but those having a single repeating unit are preferable because the effect obtained by the function becomes remarkable. The hydrophobic block segment preferably has a polyalkenyl ether structure in the main chain, and specifically has the same hydrophobic substituent as that exemplified as the hydrophobic substituent in the dispersion resin. It is preferable. Specific examples of the hydrophobic block segment include those exemplified below. In the following chemical formula, R is preferably, for example, a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, or a propyl group.

  The molecular weight of the dispersion resin preferably has a narrow distribution width in order to form a stable pigment dispersion so that a stable printed image and ejection characteristics can be obtained. The average molecular weight (Mn) of the dispersion resin is preferably 1,000 or more and 1,000,000 or less, and more preferably 1,000 or more and 100,000 or less in order to suppress an increase in the viscosity of the ink composition.

  As a content ratio of the hydrophilic block segment and the hydrophobic block segment in the dispersion resin, the molecular weight of the hydrophobic block segment is preferably 10 to 90% with respect to the molecular weight of the dispersion resin. If the molecular weight of the hydrophobic block segment is 10% or more, it is possible to suppress the dispersion resin from being dissolved in the medium and reducing the adsorptivity to the pigment. Moreover, if the molecular weight of the hydrophobic block segment is 90%, sufficient dispersibility can be imparted to the dispersion resin.

  As a method for synthesizing the dispersion resin, any method may be used as long as each block segment is bonded. In order to obtain a dispersion resin having a uniform molecular weight, it is preferable to use a living polymerization method. Specific examples of the living polymerization method include a method by Aoshima et al. (Polymer Bulletin, 15, 417 to 423 (1986), JP-A-11-322942, JP-A-11-322866) and the like. be able to.

  The content of such a dispersion resin is 0.1 part by mass or more and 99.9 parts by mass or less with respect to 1 part by mass of the pigment from the viewpoint of the viscosity of the ink composition and the print density. preferable.

[Pigment]
The pigment contained in the pigment dispersion may be either an inorganic pigment or an organic pigment. Specific examples of the inorganic pigment include the following. Oxide pigments such as cobalt blue, celsian blue, cobalt violet, cobalt green, zinc white, titanium white, light red, chromium oxide green, and mars black. Hydroxide pigments such as billijan, yellow ocher and alumina white. Silica pigments such as ultramarine, talc and white carbon, metal powders such as gold powder, silver powder and bronze powder, carbon black and the like. Specific examples of the organic pigment include the following. β-naphthol-based azo pigments, naphthol-AS-based azo pigments, monoazo-type or disazo-type acetoacetate allylide-type azo pigments, pyrazone-type azo pigments, condensation-type azo pigments, and the like. Phthalocyanine pigments, subphthalocyanine pigments, porphyrin pigments, quinacridone pigments, isoindoline pigments, isoindolinone pigments. Slen pigments, perylene pigments, perinone pigments, thioindigo pigments, dioxazine pigments, quinophthalone pigments, diketopyrrolopyrrole pigments.

  Examples of these pigments include black, cyan, magenta, and yellow pigments that are commercially available.

  Black pigment: Raven1060, Raven1080, Raven1170, Raven1200, Raven1250, Raven1255, Raven1500, Raven2000, Raven3500, Raven5250, Raven5750. Raven7000, Raven5000 ULTRAII, Raven1190 ULTRAII (above, Colombian Carbon Co., Ltd.), Black Pearls L, MOGUL-L. Regal 400R, Regal 660R, Regal 330R, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1300, Monarch 1400 (above, manufactured by Cabot Corporation). Color Black FW1, Color Black FW2, Color Black FW200, Color Black 18, Color Black S160, Color Black S170, Special Black 4. Special Black 4A, Special Black 6, Printex35, PrintexU, Printex140U, PrintexV, Printex140V (manufactured by Degussa). No. 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation).

  Cyan pigment: C.I. I. Pigment Blue-1, C.I. I. Pigment Blue-2, C.I. I. Pigment Blue-3, C.I. I. Pigment Blue-15, C.I. I. Pigment Blue-15: 2. C. I. Pigment Blue-15: 3, C.I. I. Pigment Blue-15: 4, C.I. I. Pigment Blue-16, C.I. I. Pigment Blue-22, C.I. I. Pigment Blue-60.

  Magenta pigment: C.I. I. Pigment Red-5, C.I. I. Pigment Red-7, C.I. I. Pigment Red-12, C.I. I. Pigment Red-48, C.I. I. Pigment Red-48: 1. C. I. Pigment Red-57, C.I. I. Pigment Red-112, C.I. I. Pigment Red-122, C.I. I. Pigment Red-123, C.I. I. Pigment Red-146. C. I. Pigment Red-168, C.I. I. Pigment Red-184, C.I. I. Pigment Red-202, C.I. I. Pigment Red-207.

  Yellow pigment: C.I. I. Pigment Yellow-12, C.I. I. Pigment Yellow-13, C.I. I. Pigment Yellow-14, C.I. I. Pigment Yellow-16, C.I. I. Pigment Yellow-17. C. I. Pigment Yellow-74, C.I. I. Pigment Yellow-83, C.I. I. Pigment Yellow-93, C.I. I. Pigment Yellow-95, C.I. I. Pigment Yellow-97. C. I. Pigment Yellow-98, C.I. I. Pigment Yellow-114, C.I. I. Pigment, Yellow-128, C.I. I. Pigment Yellow-129, C.I. I. Pigment Yellow-151. C. I. Pigment Yellow-154.

  In the ink composition of the present invention, a pigment that can be self-dispersed in an aqueous medium can also be used. Examples of the water dispersible pigment include those using a steric hindrance effect in which a polymer is adsorbed on the pigment surface and those using electrostatic repulsion. Specifically, CAB-0-JET200, CAB-0-JET300 (manufactured by Cabot Corporation), Microjet Black CW-1 (manufactured by Orient Chemical Co., Ltd.) and the like can be mentioned as commercially available products.

  The pigment may be subjected to a surface treatment with a polymer or a low molecular compound for the purpose of improving dispersibility.

[Block polymer]
The block polymer used in the present invention has hydrophilicity at room temperature and is amphiphilic when heated to a temperature higher than the hydrophobic expression temperature. Hydrophilicity in the block polymer is imparted by water molecules bonded to the surface, and at a temperature equal to or higher than the hydrophobic expression temperature, a part thereof is preferably changed from a hydrated state to a dehydrated state and changed to hydrophobic. Here, having hydrophilicity at room temperature means the property that the block polymer dissolves in water at 0.1% by mass or more at room temperature (23 ° C.), and dissolution means stirring water and the block polymer. Thereafter, it can be said that the mixed liquid maintains a uniform appearance even after the flow has subsided.

  The hydrophobic expression temperature is a temperature at which the block polymer develops amphipathic properties, a temperature at which a part thereof transitions from a hydrated state to a dehydrated state, and the block polymer dissolved in water is deposited. This is the temperature at which the transition can be confirmed. The hydrophobic expression temperature of the block polymer is a temperature exceeding room temperature, preferably 35 ° C. or more, and more preferably 40 ° C. or more in order to obtain a stable behavior at room temperature. Moreover, since it is the behavior in an aqueous system, it is preferable that hydrophobic expression temperature is 100 degrees C or less.

  Such a block polymer is hydrophilic at room temperature and has a hydrophilic block segment that retains hydrophilicity even when heated above the hydrophobic expression temperature, and has hydrophilicity at room temperature and develops hydrophobicity upon heating. It is preferable to have a hydrophobic expressible block segment.

  The block polymer is hydrophilic at room temperature, and the hydrophilic block segment and the hydrophobic expressible block segment are in a hydrated state in which water molecules are bonded to the surface thereof. When the hydrophobic expressible block polymer is heated to a temperature equal to or higher than the hydrophobic expression temperature, the hydrophilic block segment maintains a hydration state in a state where water molecules bound to the surface are bound, and maintains hydrophilicity. On the other hand, in the hydrophobic expressive block segment, the water molecules bonded to the surface are dehydrated and the hydrophobicity is expressed on the polymer surface. Hydrophobic sites are adsorbed to the pigment and dispersed in an aqueous medium in an environment at or above the hydrophobic expression temperature. Thus, the hydrophobicity of the hydrophobically expressing block segment is not due to a change in the chemical molecular structure accompanying changes in the polymer backbone or substituents, but due to a change in the hydration state of the surface due to a change in conformation due to thermal stimulation. Is. For this reason, after the hydrophobic expressible block segment has once adhered to the pigment surface to form a pigment dispersion, the hydrophobic expressible block segment becomes hydrophilic by reheating or cooling, and the hydrophobic expressible block polymer becomes the pigment. It is considered relatively difficult to desorb from the surface.

  The hydrophobic expressible block segment preferably has a repeating unit having a heat-sensitive substituent that binds to a water molecule at room temperature and releases the water molecule at a specific temperature or higher. The repeating unit may be composed of one type or two or more types of monomers, but those having a single repeating unit are preferable because the effect obtained by the function becomes remarkable. The hydrophobic expressible block segment preferably has a polyalkenyl ether structure in the main chain, and preferably has a heat-sensitive substituent as a side chain. Specifically, the thermofunctional substituent is preferably an oligoether chain having a molecular weight of 119 or more or an alkyl chain having a hydroxyl group at the terminal.

  Specific examples of the hydrophobic expressive block segment of the block polymer used in the present invention include those exemplified below. In the following chemical formula, m and n are preferably integers of 20 or more from the viewpoint of hydrophobic expression.

  Specific examples of the hydrophilic block segment of the block polymer include the same as those exemplified in the hydrophilic block segment in the dispersion resin.

  The molecular weight of the block polymer preferably has a narrow distribution width in order to form a stable pigment dispersion so that a stable printed image and ejection characteristics can be obtained. The average molecular weight (Mn) of the block polymer is preferably from 1,000 to 3,000,000, and more preferably from 1,000 to 1,000,000 in order to suppress an increase in the viscosity of the ink composition.

  As a content ratio of the hydrophilic block segment and the hydrophobic expressible block segment in the block polymer, the molecular weight of the hydrophobic expressible block segment is preferably 10 to 90% with respect to the molecular weight of the block polymer. When the molecular weight of the hydrophobic expressive block segment is 10% or more, it is possible to suppress the block polymer from being dissolved in the medium and reducing the adsorptivity to the pigment. Moreover, if the molecular weight of the hydrophobic expressible block segment is 90%, sufficient dispersibility can be imparted to the block polymer.

  As a method for synthesizing the block polymer, any method may be used as long as it is a method in which block segments are combined. In order to obtain a polymer having a uniform molecular weight, it is preferable to use a living polymerization method. Specific examples of the living polymerization method include the same methods as those exemplified in the method for synthesizing the dispersion resin.

  The content of such a block polymer is preferably 30% by mass or less with respect to the entire ink composition from the viewpoint of the viscosity of the ink composition and the printing density to be obtained, and is preferably 0.1% by mass or more and 20% by mass. % Or less is more preferable.

[Additive]
Additives may be added to the ink composition of the present invention in order to add various functions as long as the functions of the above substances are not impaired. Specific examples of the additive include the following. A pH adjusting agent for stabilizing the dispersibility of the ink and the stability of the ink in the recording apparatus. A penetrant that accelerates ink penetration into recording media and accelerates apparent drying. An antifungal agent that prevents wrinkles in the ink. A chelating agent that blocks metal ions in the ink and prevents metal precipitation at the nozzle and insoluble matter in the ink. An antifoaming agent that prevents the generation or generation of bubbles during the recording liquid circulation or movement. In addition, an antioxidant, a viscosity modifier, a conductive agent, an ultraviolet absorber, a crosslinking agent activated by application of heat or electromagnetic waves, an acid generator, and a polymerization initiator. The content of these additives in the ink composition is preferably 50% by mass or less, and more preferably 30% by mass or less.

[Method for producing ink composition]
Examples of the method for producing the ink composition of the present invention include a dispersion step of preparing a pigment dispersion in which a pigment is dispersed as a pigment dispersion in an aqueous solvent, and a method of adding a block polymer to the pigment dispersion. Can do. As the dispersion step, a pigment, a dispersion resin, a method of dispersing water using a disperser, etc., a dispersion resin, a pigment, and an organic solvent are mixed with a disperser to form an oil phase, and then water or an aqueous solution is added A phase inversion emulsification method of mixing and emulsifying can be used. In order to form a stable pigment dispersion with a uniform particle size, the phase inversion emulsification method is preferred. Examples of the organic solvent used in the phase inversion emulsification method include the following. Normal hexane, toluene, xylene, chloroform, tetrahydrofuran, dioxane, ethyl acetate, methyl ethyl ketone, acetone acetonitrile, propanol, butanol, N, N-dimethyl sulfoxide. Ethylene glycol, diethylene glycol, triethylene glycol, N-methyl-2-pyrrolidone, substituted pyrrolidone, triethanolamine, N, N-dimethylformamide, ethanol, methanol. These solvents can be used alone or in combination of two or more. The solvent used in the phase inversion emulsification method may be removed by distillation or filtration after phase inversion emulsification.

  Examples of the disperser used for the preparation of the pigment dispersion include an ultrasonic homogenizer, a jet mill, a pressure homogenizer, a colloid mill, a ball mill, a sand mill, and a paint shaker. These may be used alone or in combination.

  As the addition step, a method of adding the block polymer as it is to the pigment dispersion obtained in the dispersion step, a method of adding an aqueous block polymer solution, and adding a hydrophobic developing block polymer dissolved in an organic solvent and diluted And the like. In this addition step, the pigment dispersion and the block polymer may be mixed and dispersed using a disperser. Specifically, as the disperser used in the addition step and the organic solvent used for diluting the block polymer, the same ones as exemplified as the disperser and the organic solvent used in the dispersion step can be used. The organic solvent used for dilution may be removed after the addition step by distillation or filtration using a microfiltration membrane, an ultrafiltration membrane, a nanofiltration membrane, a reverse osmosis membrane, or the like.

  Moreover, the addition process which adds a block polymer can be performed prior to a dispersion | distribution process, and a pigment, a dispersion resin, and an aqueous medium can also be added and disperse | distributed to the aqueous solvent of the obtained block polymer.

[Ink composition]
The function of the ink composition of the present invention will be described below with an example.

  As shown in FIG. 1, the block polymer 11 contained in an example of the ink composition of the present invention is composed of a hydrophobic developing block segment 12 and a hydrophilic block segment 13. In an aqueous medium at room temperature, the hydrophobic expressible block segment 12 and the hydrophilic block segment 13 are in a hydrated state with water molecules 14 attached or bonded to their surfaces. Has hydrophilicity. In an aqueous medium at or above the hydrophobic expression temperature, the hydrophobic expression block segment is dehydrated to become the hydrophobic block segment 120 and transferred to the amphiphilic block polymer 110. With the passage of time, the hydrophobic block segments 120 aggregate and form stable micelles 111 in an aqueous medium.

  Further, as shown in FIG. 2, the pigment dispersion 20 contained in the ink composition has a pigment 21 and a dispersion resin 22 attached or bonded to the surface of the pigment 21, and dispersed in an aqueous medium. Yes. Among the dispersion resins, those that are not attached to the pigment attract and aggregate the hydrophobic block segments to form a stable micelle 25 having a spherical structure or an almost spherical structure that is associated with the hydrophobic block segments inside. ing.

  In the aqueous solvent at room temperature containing the pigment dispersion 20 and the micelle 25, the block polymer 11 is hydrophilic, and there are many in the vicinity of the hydrophilic block segment of the dispersion resin 22 and the vicinity of the micelle 25. Is attached. The pigment dispersion containing or adhering such a block polymer in the vicinity forms a micelle or reverse micelle structure, which can be confirmed by an electron microscope.

  When part of the dispersion resin 22 is detached from the pigment dispersion 20 by heating in an aqueous medium having a hydrophobic expression temperature or higher, an amphiphilic substance that is not micelles is formed in the vicinity of the pigment from which the dispersion resin has been detached. Block polymer 110 is present. For this reason, the amphiphilic hydrophobic block polymer 110 adheres to the portion of the pigment 21 from which the dispersion resin has been detached, thereby forming the hydrophobic block polymer-attached pigment dispersion 200, and the dispersion resin is detached and the pigment is exposed. Suppresses aggregation of the pigment dispersion by the surface. The dispersion resin 22 released from the pigment may form a micelle 30 together with the surrounding amphiphilic block polymer 110.

[Recording method]
The ink composition of the present invention can be used for pattern formation in various image devices such as various printing methods, ink jet methods, electrophotographic methods, and semiconductor processes, and the ink jet method is particularly preferable. The ink jet method may be any one of a thermal ink jet method, a piezo ink jet method using a piezoelectric element, or the like, and may be a continuous type or an on-demand type. The ink jet method may be a recording method in which ink is ejected to an intermediate transfer member and then transferred to a recording medium such as paper.

When the ink composition of the present invention is used in an ink jet method, in order to suppress color bleeding and feathering in a printed image and to exhibit excellent fixability, an aqueous solvent is immediately applied from the ink ejected on the recording medium. It is preferable to remove and promote aggregation of the pigment dispersion. Examples of the method for promoting the aggregation of the pigment dispersion include the following methods.
(A) Increase in viscosity due to a sudden phase change or aggregation of insoluble components due to thermal stimulation caused by the difference between the temperature of the ink at the time of ejection from the ink jet recording apparatus and the temperature of the ink on the recording medium adhered by ejection. How to produce.
(B) A dark room from the ink jet recording apparatus to the time of ejection is exposed to visible light by ejection, or polymerized functional groups contained in the ink are polymerized by electromagnetic wave stimulation from an electromagnetic wave irradiation apparatus provided in the ink jet recording apparatus. A method of causing thickening or aggregation of insoluble components in the material.
(C) A method in which the pH of the ink is different from the pH of the recording medium, the ink adheres to the recording medium, and the pH of the ink is changed to cause the ink to thicken due to a phase change or to aggregate insoluble components.
(D) A phase change in the ink due to a change in the concentration of the ink due to a difference between the concentration of the ink upon ejection from the inkjet recording apparatus and the concentration after the aqueous solvent contained in the ejected ink is evaporated or absorbed by the recording medium. A method of causing thickening due to or aggregation of insoluble components.

  These methods are not limited to one method, and can be used in appropriate combination.

  Examples of means for giving a stimulus to such ink include a means for using a stimulus-imparting substance having responsiveness to each of the above stimuli and mixing or contacting it with the ink. Specifically, when agglomeration is caused by the change in pH of (c) above, a method of driving a stimulus imparting substance capable of adjusting the ink to a corresponding pH onto a recording medium using an ink jet apparatus can be mentioned. . Furthermore, a more stable image can be formed by controlling the amount of the stimulating substance.

  Alternatively, the ink may contain the stimulus imparting substance as a dye or a pigment. For example, color bleeding can be improved by using an ink that stimulates any of the multicolor inks (cyan-magenta-yellow-black ink (CMYK)) used in the color ink jet method.

[Inkjet recording apparatus]
The ink jet recording apparatus of the present invention is not particularly limited as long as it performs ink jet recording by discharging the ink composition from the discharge port.

  As an example of the ink jet recording apparatus of the present invention, the ink jet recording apparatus shown in the block diagram of FIG. 3 can be given. The ink jet recording apparatus IJ shown in FIG. 3 includes a CPU 50 that controls the operation of the entire apparatus, an ink ejection element that generates energy for ejecting ink, an ink storage section that stores ink, and an ejection port that ejects ink (not shown). And a head 70 having a The program for controlling the CPU may be stored in the program memory 66, or may be stored in storage means such as an EEPROM (not shown) as so-called firmware. The head 70 is moved in the X and Y directions by the X direction driving motor 56 and the Y direction driving motor 58 which are controlled and moved by the driving signals from the X motor driving circuit 52 and the Y motor driving circuit 54, respectively, which received the control signal from the CPU. It is possible.

  Further, an X encoder 62 and a Y encoder 64 for detecting the position of the head are connected to the CPU 50, and position information of the head 70 is input to the CPU.

  Recording data such as image or character information itself to be recorded, or compressed or encoded information thereof is input to the CPU via a program memory 66 from recording data creating means (not shown). When the recording data is compressed or encoded information, the CPU can obtain the image or character information to be recorded by decompressing or expanding the recording data in the CPU.

  A drive signal is sent from the CPU that has received the recording data to the X-direction drive motor 56 and the Y-direction drive motor 58 via the X motor drive circuit 52 and the Y motor drive circuit 54, respectively. The operation of the X direction drive motor 56 and the Y direction drive motor 58 causes the head 70 to move to a position opposite to the position of the recording medium that ejects ink. Thereafter, in response to a control signal from the CPU, a drive signal is sent from the head drive circuit 60 to the ink ejection element, and ink is ejected based on the recording data. The CPU 50 controls the movement of the head to the opposing position on the recording medium that ejects ink and the ejection of ink based on this control program and the positional information from the X encoder 62 and the Y encoder 64. In this way, desired recording can be performed on the recording medium.

  In addition, an ink tank for loading a plurality of colors of ink can be installed in the head, and the above operation can be performed for each color of ink, so that multicolor drawing can be performed on the recording medium. In addition, the head can be equipped with a tank for loading the stimulating substance, and the ejection can be performed on the recording medium in parallel by the same operation as the ink ejection operation.

  Further, in the ink jet recording apparatus, the form can be changed as necessary. For example, the head 70 is not moved in the XY axis direction, but is moved in either the X axis direction or the Y axis direction, the recording medium is moved in the Y axis direction or the X axis direction, and recording is performed in conjunction with these. It can also be done.

  As an ink ejection element in the ink jet recording apparatus, an electrothermal converter, a thermal energy generating element such as a laser beam, a piezoelectric element, or the like can be used. In particular, a thermal energy generating element is preferable as an ink discharging element to which the above ink is applied, because high definition of recording can be obtained.

  In the ink jet recording apparatus using the thermal energy generating element, for example, in the case of an on-demand type, the electrothermal transducer disposed corresponding to the ink flow path exceeds the nucleate boiling corresponding to the ejection information. One drive signal giving a steep temperature rise is applied. As a result, heat energy is generated in the electrothermal transducer, and film boiling occurs on the heat acting surface of the head. As a result, bubbles in the liquid corresponding one-to-one with the drive signal can be formed.

  When the ink composition of the present invention is applied to an ink jet recording apparatus using a thermal energy generating element, the reason why ink ejection performance is improved is currently considered as follows. Since a thin film heater is used as the thermal energy generating element and the film boiling is used as a discharge energy generating source, it is considered that the temperature rises locally in the vicinity of the thin film heater. The dispersion resin adhering to the pigment at normal temperature may be detached from the vicinity of the pigment surface at high temperature, causing aggregation between the exposed pigment surfaces, which may cause problems in ejection performance. However, although the block polymer is water-soluble near room temperature, it becomes amphiphilic under high temperature conditions near the thin film heater, and adheres to the surface of the pigment from which the dispersed resin has peeled off faster than the developed hydrophobic sites aggregate. It is considered that the deterioration of the discharge performance is suppressed.

  The ink jet recording apparatus is not limited to a direct recording apparatus that directly ejects ink onto a recording medium, but is transferred to a recording medium such as paper after the ink is transferred to an intermediate transfer body on which a latent image is formed. The present invention can also be applied to an indirect recording apparatus using an indirect recording method.

  The ink composition of the present invention will be specifically described below in detail, but the technical scope of the present invention is not limited thereto. In the following, “part” means “part by mass”.

[Synthesis of block polymer]
[Synthesis Example 1]
<Diblock Polymer ₁ Composed of CH ₂ = CHOCH ₂ CH ₂ OCH ₃ : (MOVE: A Block) and CH ₂ = CHOCH ₂ CH ₂ OCH ₂ CH ₂ OCH ₃ : (MOEOVE: B Block)>
The inside of the glass container fitted with the three-way stopcock was purged with nitrogen, and then heated to 250 ° C. under a nitrogen gas stream to remove adsorbed water. The system was returned to room temperature, MOVE 6.0 mmol (mmol), ethyl acetate 16 mmol, 1-isobutoxyethyl acetate 0.1 mmol, and toluene 11 ml were added, and the reaction system was cooled while stirring. When the system temperature reached 0 ° C., 0.2 mmol of ethylaluminum sesquichloride (an equimolar mixture of diethylaluminum chloride and ethylaluminum dichloride) was added to initiate polymerization. The molecular weight was monitored in a time-sharing manner using molecular sieve column chromatography (GPC) to confirm the completion of polymerization of the A block.

Next, 6.0 mmol of MOEOVE was added as a monomer for the B block, and monitoring was performed using GPC to confirm the completion of polymerization of the B block. After completion of the polymerization of the B block, a 0.3 mass% ammonia / methanol aqueous solution was added to stop the polymerization reaction, and a toluene solution of a block polymer precursor was obtained. The toluene solution was washed with 0.6 mol / l dilute hydrochloric acid and pure water, and then the toluene was removed with an evaporator to obtain the intended diblock polymer. The compound was identified using ¹ H-NMR and GPC. The obtained compound was Mn = 17500 and Mw / Mn = 1.45. The polymerization ratio was A: B = 100: 95, and the hydrophobic expression temperature in a 10% by mass aqueous solution was 63 ° C. The hydrophobic expression temperature was obtained by measuring the cloud point in an aqueous solution.

[Synthesis Example 2]
_{<CH 2 = CHOCH 2 CH 2} OCH 2 CH 2 CH 3: and: (BuOVE A _{block), CH 2 = CHOCH 2 CH} 2 OCH 2 CH 2 OCH 3: diblock polymer 2 consisting of: (MOEOVE B block)>
Polymerization was carried out in the same manner as in Synthesis Example 1 except that BuOVE was used instead of MOVE used in the synthesis of the A block in Synthesis Example 1. The obtained compound was Mn = 15480 and Mw / Mn = 1.52. The polymerization ratio was A: B = 95: 93, and the transition temperature in a 10% by mass aqueous solution was 40 ° C. when measured with TAON023 manufactured by Kinotech Co., Ltd.

[Synthesis Example 3]
_{<CH 2 = CHOCH 2 CH 2} OCH 2 CH 2 CH 3: and: (BuOVE A _{block), CH 2 = CHOCH 2 CH} 2 CH 2 CH 2 OH: diblock polymer 3 consisting of: (Hove B block)>
The same as Synthesis Example 1 except that BuOVE was used instead of MOVE used for the synthesis of A block described in Synthesis Example 1 and CH ₂ = CHOCH ₂ CH ₂ OSiCH ₃ was used instead of MOEOVE of B block. Polymerization was carried out by the method. The obtained compound was Mn = 14500 and Mw / Mn = 1.58. The polymerization ratio was A: B = 96: 95, and the transition temperature in a 10% by mass aqueous solution was 40 ° C.

[Synthesis Example 4]
<Isobutyl vinyl ether and CH ₂ = CHOCH ₂ CH ₂ OPhPh: (IBVE-BPhOVE: random polymerization A block), 2-methoxyethyl vinyl ether (MOVE: B block), 4- (2-vinyloxy) benzoic acid (BBVE: C-block) triblock polymer 4>
The inside of the glass container fitted with the three-way stopcock was purged with nitrogen, and then heated to 250 ° C. under a nitrogen gas stream to remove adsorbed water. The system was returned to room temperature, IBVE 6 mmol (mmol), BPhOVE 6 mmol, ethyl acetate 16 mmol, 1-isobutoxyethyl acetate 0.1 mmol, and toluene 11 ml were added, and the reaction system was cooled while stirring. When the system temperature reached 0 ° C., 0.2 mmol of ethylaluminum sesquichloride (an equimolar mixture of diethylaluminum chloride and ethylaluminum dichloride) was added to initiate polymerization. The molecular weight was monitored in a time-sharing manner using molecular sieve column chromatography (GPC) to confirm the completion of random polymerization of the A block.

  Next, 4.0 mmol of MOVE was added as a B block component, and monitoring was performed using GPC to confirm the completion of polymerization of the B block.

After completion of the polymerization of the B block, a toluene solution of EBVE 3.0 mmol was added, and after 24 hours, a 0.3 mass% ammonia / methanol aqueous solution was added to stop the polymerization reaction, thereby obtaining a toluene solution of a block polymer precursor. The toluene solution was washed with 0.6 mol / l dilute hydrochloric acid and pure water, and then the toluene was removed by an evaporator and purified using methanol to obtain a block polymer precursor. Next, after the block polymer precursor was dissolved in dimethylformamide, 18.0 mmol of sodium hydroxide was added, and the mixture was stirred at room temperature for 72 hours to deprotect C-block ethylbenzoic acid. After completion of the reaction, the solid obtained by removing dimethylformamide with an evaporator was dissolved in chloroform, and the chloroform solution was washed with 0.6 mol / l dilute hydrochloric acid and water. After washing, the intended triblock polymer was obtained by removing chloroform with an evaporator. The compound was identified using ¹ H-NMR and GPC. Mn = 23000 and Mw / Mn = 1.41. The polymerization ratio was A: B: C = 100: 40: 15, and the polymerization ratio of the two monomers in the A block was 1: 1.

[Example 1]
5 parts of carbon black (PhilblackO: manufactured by Philips Petroleum Co.) and 5 parts of the triblock polymer 4 obtained in Synthesis Example 4 were co-dissolved in 100 parts of tetrahydrofuran and converted into an aqueous phase using 400 parts of distilled water. . 0.1 ml of 0.1N sodium hydroxide aqueous solution was added to this aqueous phase, and further dispersed for 10 minutes with an ultrasonic homogenizer, and then tetrahydrofuran was removed by distillation under reduced pressure. Thereafter, 10 parts of the diblock polymer 1 obtained in Synthesis Example 1 dissolved in 40 parts of distilled water was added at room temperature, followed by pressure filtration through a 1 μm filter to produce a pigment dispersion. Next, 67 parts of the above-mentioned pigment dispersion were mixed with 7 parts of glycerin, 5 parts of diethylene glycol, 7 parts of trimethylolpropane, 0.5 parts of acetylenol EH (manufactured by Kawaken Fine Chemicals), and 13.5 parts of ion-exchanged water. Thus, the intended ink composition 1 was obtained.

  The obtained ink composition 1 was filled in a print head of an ink jet printer (BJF800, manufactured by Canon Inc.), and a discharge test was performed by visually confirming the discharge of droplets. The discharge state was good.

[Example 2]
An ink composition was prepared in the same manner as in Example 1 except that the diblock polymer 2 obtained in Synthesis Example 2 was used instead of the diblock polymer 1 obtained in Synthesis Example 1, and an ejection test was performed. It was. The discharge state was good.

[Example 3]
An ink composition was prepared in the same manner as in Example 1 except that the diblock polymer 3 obtained in Synthesis Example 3 was used instead of the diblock polymer 1 obtained in Synthesis Example 1, and an ejection test was performed. It was. The discharge state was good.

[Example 4]
Example 1 was used except that instead of the triblock polymer 4 obtained in Synthesis Example 4, a styrene-ethylene oxide block polymer (P124-1 SEO: manufactured by Soka Kagaku Co., Ltd.) (hereinafter referred to as block polymer 5) was used. Ink compositions were prepared in the same manner as described above.

  After heating and refluxing 100 g of the obtained ink composition at 100 ° C. for 24 hours, the mixture was filtered with a 0.1 μm filter, and the heat was tested on the filter. As a result, there was no filtrate on the filter.

[Example 5]
Example 4 except that 10 parts of the diblock polymer 1 obtained in Synthesis Example 1 dissolved in 40 parts of distilled water was used instead of 5 parts of the diblock polymer 1 dissolved in 45 parts of distilled water. An ink composition was prepared in the same manner as described above, and a heating test was performed. As a result, there was no filtrate on the filter.

[Example 6]
Example 4 except that 10 parts of the diblock polymer 1 obtained in Synthesis Example 1 dissolved in 40 parts of distilled water was used instead of 3 parts of the diblock polymer 1 dissolved in 47 parts of distilled water. An ink composition was prepared in the same manner as described above, and a heating test was performed. As a result, there was no filtrate on the filter.

[Comparative Example 1]
An ink composition was prepared in the same manner as in Example 4 except that only 50 parts of distilled water was used instead of 10 parts of the diblock polymer 1 obtained in 10 parts of Synthesis Example 1 dissolved in 40 parts of distilled water. Then, a heating test was conducted. As a result, a filtrate that was thought to be caused by carbon black was observed on the filter.

[Comparative Example 2]
Example 4 is different from Example 4 except that 30 parts of the block polymer 5 dissolved in 20 parts of distilled water is used in place of the 10 parts of the diblock polymer 1 obtained in Synthesis Example 1 dissolved in 40 parts of distilled water. Similarly, an ink composition was prepared and a heating test was performed. As a result, it became a high-viscosity sol-like liquid and could not be filtered.

  From the above results, it is confirmed that the ink composition of the present invention is excellent in dispersibility of the pigment dispersion, excellent in dispersibility, suppressed in dispersibility by heating, and particularly suitable for an ink jet recording apparatus using heat energy. did it.

It is a figure which shows the function of the block polymer of an example of the ink composition of this invention. It is a figure which shows the function of the pigment dispersion and block polymer of the ink composition of this invention. It is a schematic block diagram which shows an example of the inkjet recording device of this invention.

Explanation of symbols

11 Block polymer 12 Hydrophobic expressing block segment 13 Hydrophilic block segment 14 Water molecule 110 Amphiphilic hydrophobic expressing block segment 111, 25, 30 Micelle 120 Hydrophobic block segment 200 Hydrophobic block polymer adhering pigment dispersion 22 Dispersing resin 50 CPU
70 Head IJ Inkjet Recording Device

Claims (13)

  An ink composition comprising a block polymer that is hydrophilic at room temperature and heated to a temperature equal to or higher than a hydrophobic expression temperature and has an amphiphilic property in an ink composition in which a pigment dispersion is dispersed in an aqueous medium. object.   2. The ink composition according to claim 1, wherein the pigment dispersion has a pigment and a dispersion resin having an amphiphilic property capable of dispersing the pigment in an aqueous medium at least at room temperature.   The ink composition according to claim 1 or 2, wherein the block polymer has a function of adsorbing to a pigment and dispersing it in an aqueous medium in an environment at or above the hydrophobic expression temperature.   The ink composition according to any one of claims 1 to 3, wherein the block polymer exhibits hydrophobicity by dehydration at or above the hydrophobic expression temperature.   5. The block polymer according to claim 1, wherein the block polymer has a hydrophilic block segment that retains hydrophilicity at a hydrophobic expression temperature or higher and a hydrophobic expression block segment that exhibits hydrophobicity. 6. Ink composition.   6. The ink composition according to claim 5, wherein the hydrophobically expressing block segment has an oligoether chain having a molecular weight of 119 or more in the side chain.   The ink composition according to claim 5 or 6, wherein the hydrophobic expressible block segment has an alkyl chain having a hydroxyl group at a terminal at a side chain.   The ink composition according to any one of claims 5 to 7, wherein the hydrophobic expressible block segment has a polyalkenyl ether structure in the main chain.   The ink composition according to any one of claims 1 to 8, wherein the content of the block polymer is 30% by mass or less with respect to the whole ink composition.   The ink composition according to claim 1, wherein the dispersion resin contains an amphiphilic block polymer.   The ink composition according to claim 10, wherein the amphiphilic block polymer has a polyalkenyl ether structure in the main chain.   An ink jet recording apparatus that performs ink jet recording by discharging the ink composition according to claim 1 from a discharge port.   13. The ink jet recording apparatus according to claim 12, wherein the ink composition is boiled by applying thermal energy and ejected from an ejection port.

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