JP2019056022A - Aqueous ink, ink cartridge, recording apparatus, and recording method - Google Patents

Abstract

To provide an aqueous ink that comprises an aqueous medium and resin particles dispersed in the aqueous medium and can improve storage-resistant offset properties yet maintaining the dry fixability, as compared with when polyester resin particles containing polyester as the relevant resin particles are used alone.SOLUTION: The aqueous ink comprises: an aqueous medium; polyester resin particles dispersed in the aqueous medium and containing polyester; and resin particles dispersed in the aqueous medium and containing a first resin. The glass transition point Tg2 of the first resin is 30°C or more lower than the glass transition point Tg1 of the polyester, the weight-average molecular weight Mw2 of the first resin is more than the weight-average molecular weight Mw1 of the polyester, and the content of the resin particles is less than the content of the polyester resin particles.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous ink, an ink cartridge, a recording apparatus, and a recording method.

  Ink-jet recording water-based inks in which resin particles are added in addition to an aqueous medium and a colorant are known.

  Patent Document 1 discloses a water-based ink containing polyester resin particles (A) and polymer particles containing a pigment, wherein the content of the hydrophilic polymer in the polymer of the polymer particles containing the pigment is 90% by mass. The above water-based ink for ink-jet recording is disclosed.

  Patent Document 2 discloses a water-based ink containing a colorant and polyester resin particles, in which the polyester contained in the polyester resin particles contains an alcohol component containing a divalent or trivalent alicyclic alcohol, and a carboxylic acid. A water-based ink is disclosed, which is a polyester (A) obtained by polycondensation of components with an acid value of the polyester (A) of 5 mgKOH / g or more and 50 mgKOH / g or less.

JP2015-0985552A Japanese Patent Laid-Open No. 2017-025263

  An object of the present invention is to maintain an aqueous medium and resin particles dispersed in the aqueous medium, while maintaining dry fixability as compared to the case where polyester resin particles containing polyester are used alone as the resin particles. An object of the present invention is to provide a water-based ink that can improve storage offset resistance.

  Specific means for solving the above-described problems include the following modes.

  The invention according to claim 1 includes an aqueous medium, polyester resin particles dispersed in the aqueous medium and containing polyester, and resin particles dispersed in the aqueous medium and containing a first resin, The glass transition point of the first resin is 30 ° C. lower than the glass transition point of the polyester, the weight average molecular weight of the first resin is higher than the weight average molecular weight of the polyester, and the content of the resin particles However, the water-based ink is less than the content of the polyester resin particles.

  The invention according to claim 2 is the water-based ink according to claim 1, further comprising a compound having infrared absorptivity.

  The invention according to claim 3 is the water-based ink according to claim 2, wherein the compound having infrared absorbing property is contained in the polyester resin particles.

  The invention according to claim 4 is the water-based ink according to any one of claims 1 to 3, wherein a ratio of a weight average molecular weight of the first resin to a weight average molecular weight of the polyester is 2 or more. .

  The invention according to claim 5 is the water-based ink according to any one of claims 1 to 4, wherein the glass transition point of the first resin is lower by 30 ° C. or more than the glass transition point of the polyester.

  The invention according to claim 6 is according to any one of claims 1 to 5, wherein a ratio of the content of the polyester resin particles to the total of the polyester resin particles and the resin particles is 55% by mass or more. Water-based ink.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the total amount of the polyester resin particles and the resin particles is 3% by mass or more and 5% by mass or less of the total amount of the water-based ink. Water-based ink.

  An invention according to an eighth aspect is an ink cartridge containing the water-based ink according to any one of the first to seventh aspects.

  An invention according to a ninth aspect is a recording apparatus including the water-based ink according to any one of the first to seventh aspects, and an ink applying unit that applies the water-based ink to a recording medium.

  The invention according to claim 10 contains the water-based ink according to claim 2 or 3 and irradiates the water-based ink applied to the recording medium with infrared rays by applying the water-based ink to the recording medium. And an infrared irradiating means.

  The invention according to an eleventh aspect is a recording method including an ink application step of applying the water-based ink according to any one of the first to seventh aspects to a recording medium.

  The invention according to claim 12 includes: an ink application step for applying the aqueous ink according to claim 2 or 3 to a recording medium; and an infrared irradiation step for irradiating the aqueous ink applied to the recording medium with infrared rays. Recording method.

  The invention according to claim 13 is the recording method according to claim 11 or 12, wherein the recording medium is a low permeability medium.

  According to the inventions according to claims 1 to 7, the aqueous resin and the resin particles dispersed in the aqueous medium, and the polyester resin particles containing polyester as the resin particles are used in comparison with the case where the resin particles are used alone. Provided is a water-based ink capable of improving storage offset resistance while maintaining fixability.

  According to the inventions according to claims 8 to 13, the aqueous ink includes an aqueous medium and resin particles dispersed in the aqueous medium, and the polyester resin particles containing polyester are used alone as the resin particles. Thus, an ink cartridge, a recording apparatus, or a recording method that can improve storage offset resistance while maintaining dry fixing properties is provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment.

  Embodiments of the invention will be described below. These descriptions and examples illustrate embodiments and do not limit the scope of the invention.

  In the present disclosure, when referring to the amount of each component in the composition, when there are a plurality of substances corresponding to each component in the composition, the plurality of the substances present in the composition unless otherwise specified. It means the total amount of substance.

<Water-based ink>
The aqueous ink according to the present embodiment includes an aqueous medium, polyester resin particles containing polyester, and resin particles containing a first resin. The polyester resin particles and the resin particles are dispersed in an aqueous medium, The glass transition point Tg2 of the first resin is 30 ° C. or more lower than the glass transition point Tg1 of the polyester, the weight average molecular weight Mw2 of the first resin is higher than the weight average molecular weight Mw1 of the polyester, The content of the resin particles is less than the content of the polyester resin particles with respect to the total amount of the water-based ink.

  Conventionally, in order to give the image itself strength while suppressing the influence on the ink ejection property for image formation by an ink jet method using non-curable water-based ink, a particle size of about several nanometers to several hundred nanometers A technique is known in which an emulsion in which resin particles having a water content are dispersed in an aqueous medium is added to ink. Here, as a measure for improving the dry fixability of the formed image, a method of lowering the glass transition point (Tg) of the resin forming the emulsion, or a solvent added to the water-based ink for improving the moisture retention or penetrability Thus, a method for increasing the plasticity of the resin is known. Usually, an emulsion refers to a dispersion solution in which both the dispersoid and the dispersion medium are liquid, but here, it is used as a term including so-called latex.

  Here, by using the water-based ink introduced with the above-described measures for improving the dry fixability, image formation by an inkjet method is performed on a non-penetrating or low-penetrating recording medium such as coated paper having a resin layer on the surface of the recording medium. In this case, an offset defect (storage offset) occurs when the formed image is transferred to another recording medium or an image formed on another recording medium when the recording medium on which the image is formed is stacked or rolled. There was a request to suppress more.

  On the other hand, in the water-based ink according to the present embodiment, polyester resin particles containing polyester are used alone by containing two types of resin particles each having a specific glass transition point Tg and a specific weight average molecular weight Mw. As compared with the case of using in the above, the storage offset resistance can be improved while maintaining the dry fixability. The reason for this can be estimated as follows. First, in an ink image containing resin particles, the resin particles are fused during drying, and the ink image is formed into a film and fixed. However, a resin having a low Tg is more advantageous for dry fixability. On the other hand, the resin particles having a low Tg tend to exhibit adhesiveness even after drying and fixing, and the image strength against stress such as peeling or bending when forming an image is low. For this reason, it is estimated that the adhesiveness of the image surface can be suppressed while securing the fixing property by using a resin having a high Tg in combination and increasing the proportion of the resin having a high Tg. For image strength, an approach of strengthening by increasing the molecular weight of a resin having a low Tg is effective. On the other hand, when the molecular weight of the resin having a high Tg is increased, the fixability is further deteriorated. From the above, it is presumed that the balance between the fixability and the storage offset resistance can be achieved by using a resin having a low Tg and a high molecular weight and a resin having a higher Tg and a lower molecular weight.

  Hereinafter, the components, composition, manufacturing method, and the like of the water-based ink according to this embodiment will be described in more detail.

[Polyester resin particles]
The polyester resin particles contained in the water-based ink according to this embodiment have a glass transition point Tg1 that is 30 ° C. higher than the glass transition point Tg2 of the first resin contained in the resin particles, and are contained in the resin particles. The polyester which has the weight average molecular weight Mw1 lower than the weight average molecular weight Mw2 of 1st resin is contained.

  The type of the polyester contained in the polyester resin particles (hereinafter also simply referred to as “polyester”) is not limited as long as it has the glass transition point Tg1 and the weight average molecular weight Mw1.

  As the polyester, for example, a polyester synthesized by a polycondensation reaction such as a polycarboxylic acid, a polyol, and an ester compound thereof (oligomer and / or prepolymer) is used.

  A polyol is a compound containing two or more hydroxyl groups in one molecule, and includes, for example, a diol containing two hydroxyl groups in one molecule, a triol or tetraol containing three or more hydroxyl groups in one molecule, and the like. . These polyols may be used alone or in combination of two or more.

  Examples of the diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, and 2,2-dimethyl- 1,3-propanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,4-pentanediol, 3,3-dimethyl-1,2-butanediol, 2- Ethyl-2-methyl-1,3-propanediol, 1,2-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 2-methyl-2,4-pentane Diol, 2,2-diethyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 1,7-heptanediol, -Methyl-2-propyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2-ethyl-1,3-hexanediol, 1,2-octanediol, 1,8-octane Diol, 2,2,4-trimethyl-1,3-pentanediol, 1,4-cyclohexanedimethanol, hydroquinone, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol, poly (oxy Tetramethylene) glycol, polyester polyol, 4,4′-dihydroxyphenylsulfone, and the like.

  Examples of polyols such as triol and tetraol include glycerin, pentaerythritol, tetramethylol benzoguanamine, tetraethylol benzoguanamine, hexamethylol melamine, hexaethylol melamine and the like.

  A polycarboxylic acid is a compound containing two or more carboxyl groups in one molecule, and includes, for example, aliphatic, alicyclic or aromatic polycarboxylic acids, and alkyl esters thereof. Examples of the polycarboxylic acid include dicarboxylic acid containing two carboxy groups in one molecule, and tricarboxylic acid or tetracarboxylic acid containing three or more carboxy groups in one molecule. These polycarboxylic acids may be used alone or in combination of two or more.

  Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, dimethylmalonic acid, adipic acid, pimelic acid, α, α-dimethylsuccinic acid, acetone dicarboxylic acid, sebacic acid, and 1,9-nonanedicarboxylic acid. Acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, phthalic acid, isophthalic acid, terephthalic acid, 2-butyl terephthalic acid, tetrachloroterephthalic acid, acetylenedicarboxylic acid, poly (ethylene terephthalate) dicarboxylic acid, 1,2- Examples include cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, ω-poly (ethylene oxide) dicarboxylic acid, and p-xylylene dicarboxylic acid.

  Examples of the tricarboxylic acid and tetracarboxylic acid include trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid. These polycarboxylic acids may be subjected to dehydration condensation in the form of alkyl esters, acid chlorides or acid anhydrides.

  The polyester contained in the polyester resin particles is not limited to a case where a polycondensate such as a polycarboxylic acid and a polyol is contained alone, and any polyester having a main chain skeleton composed of an ester bond can be used. .

  The polyester contained in the polyester resin particles preferably contains an aromatic ring in its molecular structure. This is because when the polyester contains an aromatic ring, when the polyester resin particles contain an infrared absorbent described later, precipitation of the infrared absorbent can be suppressed and the infrared absorbing performance of the water-based ink can be improved. Examples of a method for synthesizing a polyester having an aromatic ring in the molecular structure include a method using a dicarboxylic acid having an aromatic ring as a polycarboxylic acid, a method using a bisphenol compound or an alkylene oxide adduct thereof as a polyol, and those And the like.

  Examples of the dicarboxylic acid having an aromatic ring include phthalic acid, isophthalic acid, terephthalic acid, 2-butyl terephthalic acid, tetrachloroterephthalic acid, poly (ethylene terephthalate) dicarboxylic acid, and p-xylylene dicarboxylic acid.

  The bisphenol compound used as the polyol is a compound having a bisphenol type structure, and examples thereof include bisphenol A, bisphenol B, bisphenol C, bisphenol E, and bisphenol F. An alkylene oxide adduct of a bisphenol compound is a compound obtained by adding alkylene oxide to at least one of the terminal hydroxyl groups of a bisphenol compound. As a polyol used for the synthesis | combination of a polyester resin particle, the ethylene oxide or propylene oxide adduct of bisphenol A is preferable.

  From the above viewpoint, the content of the aromatic ring with respect to the total amount of the polyester is preferably 10% by mass or more, and more preferably 20% by mass or more. The upper limit of the aromatic ring content relative to the total amount of polyester is not particularly limited, and is, for example, 60% by mass or less.

  The polyester may use at least one of a polycarboxylic acid having a dissociable group and a polyol from the viewpoint of improving dispersibility in an aqueous medium. Examples of the dissociable group include an anionic group, and a sulfonic acid group is preferable. The dissociable group is introduced into the polyester, for example, by using a dicarboxylic acid or diol having a sulfonic acid group as a raw material for the polyester.

  The molecular structure of the polyester contained in the polyester resin particles is qualitatively and quantitatively determined by a known method. For example, the water-based ink is subjected to separation, neutralization, washing, drying, etc. by centrifugation or filtration, and the recovered resin is subjected to nuclear magnetic resonance spectroscopy (NMR) or Fourier transform infrared spectroscopy. By analyzing by a method such as (FT-IR) or reactive pyrolysis GC / MS method, the type and molar ratio of each structural unit constituting the molecular structure of the polyester is determined. According to this method, the molecular structure of the resin contained in the resin particles is also qualitatively and quantitatively determined.

  The glass transition point Tg (Tg1) of the polyester contained in the polyester resin particles is preferably 50 ° C. or higher and 80 ° C. or lower, and more preferably 60 ° C. or higher and 78 ° C. or lower. When the glass transition point Tg1 of the polyester is 50 ° C. or higher, the storage offset resistance of the water-based ink is further improved. Further, when the glass transition point Tg1 of the polyester is 80 ° C. or less, the drying property of the water-based ink is further improved.

  The glass transition point Tg1 of the polyester is controlled by adjusting the type and amount of the polycondensable monomer used for the synthesis of the polyester.

  The glass transition point Tg is measured by differential scanning calorimetry in accordance with ASTM D3418, and the DSC obtained in the first heating process using a differential scanning calorimeter (manufactured by Shimadzu Corporation: DSC-60A). The temperature at the intersection of the extension line of the base line and the rising line in the endothermic part of the curve is the glass transition point Tg.

  The weight average molecular weight Mw (Mw1) of the polyester contained in the polyester resin particles is preferably 5000 or more and 100,000 or less, and more preferably 1500 or more and 50,000 or less. When the weight average molecular weight Mw of the polyester is 5000 or more, the film strength when the polyester is used as a coating film is excellent. When the weight average molecular weight Mw1 is 100,000 or less, the solubility in an organic solvent is excellent, and the viscosity of the polyester solution dissolved in the organic solvent can be suppressed, so that it is easy to disperse in an aqueous medium when producing an aqueous ink. .

  The weight average molecular weight Mw is a value measured by gel permeation chromatograph (GPC). Specifically, molecular weight measurement by GPC is performed with a THF solvent using “HLC-8120GPC” manufactured by Tosoh Corporation as a measuring device and a column “TSKgel SuperHM-M (15 cm)” manufactured by Tosoh Corporation. The weight average molecular weight Mw is calculated using a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample from this measurement result. However, since the accuracy is not obtained in the region where the weight average molecular weight Mw is 100,000 or more, when there is a peak in the region of 100,000 or more, it was uniformly calculated as 100,000.

  The acid value of the polyester contained in the polyester resin particles is, for example, preferably from 5 mgKOH / g to 50 mgKOH / g, and more preferably from 10 mgKOH / g to 40 mgKOH / g. When the acid value of the polyester is 5 mgKOH / g or more, the dispersibility of the polyester resin particles in an aqueous medium is excellent. When the acid value of the polyester is 50 mgKOH / g or less, when the polyester resin particles have an infrared absorber described later, separation of the infrared absorber from the polyester resin particles is suppressed, and the infrared absorption performance of the water-based ink is further improved. To do.

  The acid value is measured according to a neutralization titration method according to JIS K0070: 1992. That is, an appropriate amount of a sample is taken, 100 ml of a solvent (tetrahydrofuran) and a few drops of an indicator (phenolphthalein solution) are added, and shaken well until the sample is dissolved on a water bath. This solution is titrated with a 0.1 mol / l potassium hydroxide ethanol solution, and the end point is when a light red color of the indicator lasts for 30 seconds. When the acid value is A, the sample amount is S (g), the 0.1 mol / l potassium hydroxide ethanol solution used for the titration is B (ml), and f is the factor of the 0.1 mol / l potassium hydroxide ethanol solution. , A = (B × f × 5.611) / S, and the acid value is calculated.

(Compound having infrared absorptivity)
The polyester resin particles preferably contain a compound having infrared absorptivity (also referred to as “infrared absorber”). This is because when the polyester resin particles contain an infrared absorber, the drying time of the image formed on the recording medium is shortened.

  The infrared absorber contained in the polyester resin particles is not particularly limited as long as it is a compound that can absorb radiation in the infrared region (for example, 700 nm or more and 2500 nm or less, near infrared region), for example, squarylium pigment, croconium pigment, And naphthalocyanine dyes, cyanine dyes, aminium dyes, and the like.

（一般式（Ｉ）中、Ｒ^１ａ、Ｒ^１ｂ、Ｒ^１ｃ及びＲ^１ｄはそれぞれ独立にアルキル基又はアリール基を表す。）

（一般式（ＩＩ）中、Ｒ^２ａ、Ｒ^２ｂ、Ｒ^２ｃ及びＲ^２ｄはそれぞれ独立にアルキル基を表し、Ｒ^２ａとＲ^２ｂとが互いに連結して環を形成してもよく、Ｒ^２ｃとＲ^２ｄとが互いに連結して環を形成してもよい。） Specific examples of the infrared absorber include, for example, squarylium dyes represented by the following general formula (I) or general formula (II), but are not limited to the following compounds.

(In general formula (I), R ^1a , R ^1b , R ^1c and R ^1d each independently represents an alkyl group or an aryl group.)

(In the general formula ^(II), R ^2a, R ^{2b, R 2c} and ^{R 2d} represent each independently an alkyl ^group, may form a ring with ^{R 2a} and ^{R 2b} each ^other, and ^{R 2c} R ^2d may be linked to each other to form a ring.)

In the infrared absorbent, the maximum absorption wavelength (λ _max ) in the tetrahydrofuran solution is preferably 760 nm or more and 1200 nm or less, and more preferably 780 nm or more and 1100 nm or less. Further, the molar extinction coefficient (ε _max ) at the maximum absorption wavelength (λ _max ) in the tetrahydrofuran solution of the infrared absorber is 1 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or more and 6 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or less. It is preferably 2 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or more and 6 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ or less.

  What is necessary is just to manufacture the dispersion liquid of the polyester resin particle containing an infrared absorber by a well-known manufacturing method, for example, a phase inversion emulsification method, an impregnation method, etc. The phase inversion emulsification method prepares a solution in which an infrared absorber and a resin are dissolved in an organic solvent, neutralizes the resin by adding a neutralizing agent, and then gradually mixes water to both the infrared absorber and the resin. Is a method of preparing a dispersion liquid in which particles containing ss are dispersed. The impregnation method is a method of impregnating the particles with the infrared absorbent by mixing a solution in which the particles are dispersed with a solution in which the infrared absorbent is dissolved in an organic solvent, and gradually removing the organic solvent.

  The polyester resin particles may contain additives other than polyester and infrared absorber. Examples of the additive include a compound having an ultraviolet absorbing ability (for example, a benzotriazole compound, a benzophenone compound, etc.), a colorant, a neutralizer, a surfactant, a dispersion stabilizer, and the like.

  The average particle size of the polyester resin particles contained in the water-based ink is preferably 10 nm to 150 nm, more preferably 10 nm to 120 nm, and still more preferably 10 nm to 100 nm. When the average particle size of the polyester resin particles is 10 nm or more, the water-based ink dischargeability is further improved. Further, when the average particle size of the polyester resin particles is 150 nm or less, the droplet ejection characteristics when recording by the ink jet method are excellent.

  In addition, the average particle diameters of the polyester resin particles, the resin particles containing the first resin, the colorant-containing particles, and the like included in the water-based ink according to this embodiment are measured using a scanning electron microscope (SEM). . More specifically, target particles recovered by performing freeze-drying treatment subsequent to centrifugation, washing, and quick freezing using liquid nitrogen are observed using an SEM. Next, 100 particles are randomly extracted from the obtained image, and the average value of the lengths of the major and minor axes of each particle is used as the particle size of each particle, and the particle size of the 100 particles is averaged. Thus, the average particle diameter of the particles is calculated.

<Resin particles>
The resin particles contained in the water-based ink according to the present embodiment have a glass transition point Tg2 that is 30 ° C. lower than the glass transition point Tg1 of the polyester contained in the polyester resin particles, and the polyester particles contained in the polyester resin particles. A first resin having a weight average molecular weight Mw2 higher than the weight average molecular weight Mw1 is contained.

  The type of the first resin contained in the resin particles (hereinafter also simply referred to as “resin”) is not limited as long as it has the glass transition point Tg2 and the weight average molecular weight Mw2. Examples of the resin include polyurethane, polyester, polyvinyl, polyamide, polyurea, epoxy resin, and polycarbonate. The resin preferably contains at least one selected from polyester, polyurethane, and polyvinyl, and preferably contains polyester or polyurethane, from the viewpoint of adhesion to a general recording medium.

(Polyurethane)
The polyurethane contained in the resin particles is not particularly limited, and examples thereof include polyether polyurethane, polycarbonate polyurethane, and polyester polyurethane. These polyurethanes are obtained by reacting a polyol such as polyether polyol, polycarbonate polyol or polyester polyol with polyisocyanate.

  Examples of the polyether polyol include those obtained by addition polymerization of alkylene oxide to a compound having two or more active hydrogen atoms. Examples of the compound having two or more active hydrogen atoms include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylene glycol, 1,3-butanediol, 1,4-butanediol, and 1,6-hexanediol. Glycerin, trimethylolethane, trimethylolpropane and the like. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, styrene oxide, epichlorohydrin, and tetrahydrofuran.

  Examples of the polycarbonate polyol include those obtained by reacting a carbonate and polyol, and those obtained by reacting phosgene with bisphenol A and the like. Examples of the carbonate ester include methyl carbonate, dimethyl carbonate, ethyl carbonate, diethyl carbonate, cyclocarbonate, diphenyl carbonate, and the like. Examples of the polyol include the aforementioned polyols.

    Examples of polyester polyols include those obtained by esterifying low molecular weight polyols and polycarboxylic acids, polyesters obtained by ring-opening polymerization of cyclic ester compounds such as ε-caprolactone, and copolymerized polyesters thereof. Etc. Examples of the low molecular weight polyol include ethylene glycol and propylene glycol. Examples of the polycarboxylic acid include succinic acid, adipic acid, sebacic acid, dodecanedicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, anhydrides or ester-forming derivatives thereof.

    Examples of polyisocyanates include aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and naphthalene diisocyanate; hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate Examples thereof include aliphatic or alicyclic diisocyanates such as isocyanate and 2,2,4-trimethylhexamethylene diisocyanate.

  Polyurethane resin particles containing polyurethane can be produced by a production method generally used conventionally. For example, the polyurethane resin particles are produced by the following method. First, an isocyanate-terminated urethane prepolymer is produced by reacting a polyol and a polyisocyanate in an equivalent ratio in which an isocyanate group becomes excessive in the absence of a solvent or in the presence of an organic solvent. Next, the anionic group in the isocyanate-terminated urethane prepolymer is neutralized with a neutralizing agent as necessary, and then reacted with a chain extender such as polyamine, and finally the organic solvent in the system is removed as necessary. It can be obtained by removing.

  From the viewpoint of water dispersibility, the acid value of the polyurethane is preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, and 50 mgKOH / g or less.

  Examples of the form of the polyurethane resin particles include a dispersion in which polyurethane resin particles are dispersed in water, and may contain a dispersant such as a surfactant as necessary. The aqueous dispersion of polyurethane resin particles also acts as a fixing emulsion in order to fix the ink droplets ejected from the ink jet nozzles on the recording medium and obtain an image having excellent uniformity.

  As a polyurethane resin particle, what was synthesize | combined suitably may be used and a commercial item may be used. Examples of commercially available polyurethane resin particles include Acryt (trademark) series including Acryt (trademark) WBR-016U (manufactured by Taisei Fine Chemical Co., Ltd., polyether polyol-based polyurethane resin particles or polyurethane shell-core core shell of polyacrylic core). Hybrid polyurethane resin fine particles having a structure, etc.), U-coat series, or Permarin series (manufactured by Sanyo Chemical Industries, Ltd., polycarbonate polyol or polyether polyol-based polyurethane resin particles). These may be used individually by 1 type and may use 2 or more types together.

(polyester)
The polyester contained in the resin particles is not particularly limited as long as each of the glass transition point Tg2 and the weight average molecular weight Mw2 is contained in the above range. For example, in the term of the polyester contained in the polyester resin particles described above, The polyesters described may be used.

  When the water-based ink according to this embodiment includes particles containing polyester as resin particles, the polyester is synthesized and emulsified or dispersed so as to have a specific glass transition point Tg2 and a weight average molecular weight Mw2. You may use and a commercial item may be used.

(Polyvinyl)
The polyvinyl contained in the resin particles is not particularly limited, and a polymer containing a structural unit derived from a monomer containing an unsaturated ethylene group may be used. Specific examples of polyvinyl include, for example, a structural unit derived from (meth) acrylic acid and a structural unit derived from one or more monomers selected from (meth) acrylic acid esters, vinyl chloride, and vinyl acetate. Polymers.

  Resin particles containing an acrylic polymer can be produced, for example, by copolymerizing a mixture of (meth) acrylic acid and (meth) acrylic acid ester by a known polymerization method. As the polymerization method, an emulsion polymerization method, a suspension polymerization method and the like are preferable, and an emulsion polymerization method is more preferable. As the resin particles containing the acrylic polymer, those appropriately synthesized may be used, or commercially available products may be used.

(Characteristics of resin particles)
The glass transition point Tg2 of the first resin contained in the resin particles is not particularly limited as long as the difference from the glass transition point Tg1 of the polyester is 30 ° C. or more. For example, Tg2 is 10 ° C. or more and 55 ° C. or less. It is preferably 20 ° C. or higher and 45 ° C. or lower. The glass transition point Tg2 of the first resin is controlled, for example, by adjusting the type and usage of the structural unit constituting the first resin.

  The weight average molecular weight Mw2 of the first resin is preferably from 20,000 to 2,000,000, and more preferably from 50,000 to 1,500,000. When the weight average molecular weight Mw2 of the first resin is 20,000 or more, the film strength when used as a coating film is excellent. When the weight average molecular weight Mw2 is 2 million or less and the glass transition point Tg2 is in the above desired range, it is possible to secure the fusion property of the resin particles in the ink solvent when the first resin is used as particles. .

  When the first resin has an acid value, the acid value is, for example, preferably from 5 mgKOH / g to 50 mgKOH / g, and more preferably from 10 mgKOH / g to 40 mgKOH / g. Resin particles containing the first resin having an acid value of 5 mgKOH / g or more are excellent in dispersibility in an aqueous medium. Resin particles containing the first resin having an acid value of 50 mgKOH / g or less are excellent in dispersion stability in a mixed solvent of water and a water-soluble solvent such as an ink solvent.

  The average particle size of the resin particles contained in the water-based ink is preferably 10 nm to 150 nm, more preferably 10 nm to 120 nm, and still more preferably 10 nm to 100 nm. When the average particle diameter of the resin particles is 10 nm or more, the water-based ink ejection properties are further improved. Further, when the average particle diameter of the resin particles is 150 nm or less, the droplet ejection characteristics when recording by the ink jet method are excellent.

  The glass transition point Tg2, the weight average molecular weight Mw2 and the acid value of the first resin contained in the resin particles, and the average particle diameter of the resin particles are measured according to the measurement method described above.

  The glass transition point Tg2 of the first resin contained in the resin particles is preferably 33 ° C. or more lower than the glass transition point Tg1 of the polyester contained in the polyester resin particles, more preferably 40 ° C. or more. This is because when the difference between the glass transition point Tg2 of the first resin and the glass transition point Tg1 of the polyester is in the above range, the dry fixing property / storage offset resistance is more excellent. Although an upper limit is not restrict | limited, For example, it is preferable that the difference of the glass transition point Tg1 of polyester and the glass transition point Tg2 of 1st resin is less than 60 degreeC from a viewpoint of adhesiveness suppression of an image.

  The ratio of the weight average molecular weight Mw2 of the first resin contained in the resin particles to the weight average molecular weight Mw1 of the polyester contained in the polyester resin particles is preferably 2 or more, and more preferably 4 or more. This is because when the ratio of the weight average molecular weight Mw2 of the first resin to the weight average molecular weight Mw1 of the polyester is within the above range, the dry fixability / storage offset resistance is more excellent. Although the upper limit is not limited, for example, from the viewpoint of image strength, the ratio of the weight average molecular weight Mw2 of the first resin to the weight average molecular weight Mw1 of the polyester is preferably 6 or less.

  The content of the polyester resin particles in the water-based ink and the content of the resin particles containing the first resin are not particularly limited as long as the polyester resin particles are contained in a larger amount than the resin particles. The proportion of the total of the particles and the resin particles is preferably 55% by mass or more, and more preferably 70% by mass or more. Although an upper limit is not restrict | limited, It is preferable from a fixed viewpoint that the ratio which occupies for the sum total of the polyester resin particle of the polyester resin particle and the said resin particle exists in the range of 80 mass% or less.

  In the present embodiment, from the viewpoint of improving the adhesion of the substrate to the coated paper, the total content of the resin particles containing the polyester resin particles and the first resin is 1% by mass or more to the total amount of the water-based ink. The mass is preferably 2% by mass or less, more preferably 2% by mass or more and 4% by mass or less, and further preferably 3% by mass or more and 4% by mass or less.

[Aqueous medium]
The aqueous medium contained in the aqueous ink is water or a mixed solvent containing water as a main solvent. The mixed solvent is, for example, a mixture of water and a water-soluble organic solvent.

  The water is preferably purified water such as distilled water, ion-exchanged water, or ultrafiltrated water from the viewpoint of suppressing contamination with impurities or generation of microorganisms. Examples of the water-soluble organic solvent include alcohols, polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, and sulfur-containing solvents.

  The content of water is preferably 40% by mass or more and 80% by mass or less, and more preferably 50% by mass or more and 80% by mass or less with respect to the total mass of the water-based ink. The content of the water-soluble organic solvent is preferably 50% by mass or less and more preferably 40% by mass or less with respect to the total mass of the water-based ink. The lower limit of the content of the water-soluble organic solvent is not limited. For example, the content is preferably 0.1% by mass or more, and more preferably 1% by mass or more with respect to the total mass of the aqueous ink.

[Colorant]
Examples of the colorant include pigments and dyes, and pigments are preferable from the viewpoint of light resistance of an image.

  When a pigment is used as the colorant, it is preferable to use a pigment dispersant together. Examples of the pigment dispersant include known polymer dispersants and surfactants. One type of pigment dispersant may be used, or two or more types may be used in combination. The polymer dispersant may contain, for example, a resin selected from polyester, polyurethane and polyvinyl, and any of polyester, polyurethane and polyvinyl contained in the aforementioned resin particles may be used. Although the content of the pigment dispersant varies depending on the type of pigment and the type of pigment dispersant, it cannot be generally stated, but it is preferably 0.1% by mass to 100% by mass with respect to the pigment content.

  As the colorant, particles may be formed of a pigment and a polymer dispersant. In this case, the polymer dispersant may enclose the pigment, or the polymer dispersant may cover a part of the surface of the pigment, and a part of the surface of the pigment may be exposed. A plurality of pigments may be contained in one particle.

  Examples of the pigment include a pigment that self-disperses in water (hereinafter referred to as “self-dispersing pigment”). The self-dispersing pigment refers to a pigment having a hydrophilic group on the pigment surface and being dispersed in water without the presence of a pigment dispersant. Examples of the self-dispersing pigment include all known self-dispersing pigments obtained by subjecting the pigment to surface modification treatment such as coupling agent treatment, polymer graft treatment, plasma treatment, oxidation treatment, and reduction treatment. Pigments.

  Examples of the pigment include so-called microcapsule pigments coated with a resin. Commercially available microcapsule pigments include DIC Corporation and Toyo Ink Corporation.

  Specific pigments such as red, green, brown, white, etc .; metallic luster pigments such as gold and silver; colorless or light extender pigments; plastic pigments; dyes or pigments on the surface of silica, alumina, or polymer beads And particles in which dyes are fixed; insoluble lakes of dyes; colored emulsions; colored latexes;

  When a dye is used as the colorant, it is preferable to make the dye into particles together with the above polymer dispersant, for example, a resin such as polyester, polyurethane, and polyvinyl, and to include the particles in the aqueous ink.

  When the colorant is contained in the aqueous ink in the form of particles, the average particle diameter of the colorant-containing particles is, for example, from 10 nm to 200 nm, and preferably from 50 nm to 150 nm. This is because when the average particle diameter of the colorant-containing particles is in the above range, the dispersibility in the water-based ink, the discharge property of the water-based ink, and the droplet ejection characteristics when recording by the ink jet method are excellent.

  The content of the colorant is preferably 1% by mass or more and 25% by mass or less, and more preferably 2% by mass or more and 20% by mass or less with respect to the total mass of the water-based ink.

[Additive]
The water-based ink according to this embodiment may contain various additives as necessary. Examples of the additive include a surfactant, a penetrating agent, a viscosity adjusting agent, a pH adjusting agent, a pH buffering agent, an antioxidant, an ultraviolet absorber, an antiseptic, and an antifungal agent. Further, the water-based ink may contain other resin particles that do not correspond to any of the aforementioned polyester resin particles and the aforementioned resin particles.

[Method for producing water-based ink]
The water-based ink according to the present embodiment is produced, for example, by stirring and mixing an aqueous medium, polyester resin particles, resin particles containing a first resin, a colorant, and, if necessary, an additive. The stirring and mixing may be performed using, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, a stirrer using a normal stirrer blade, a magnetic stirrer, a high-speed disperser, or the like.

  When producing the water-based ink, the polyester resin particles and the resin particles containing the first resin are mixed with other materials such as an aqueous medium or a colorant in the state of a resin emulsion in which water is dispersed as a dispersion medium. It is preferable to obtain a water-based ink. This is because the workability of preparing a water-based ink by blending with a water-soluble organic solvent, a colorant and water is excellent, and the dispersibility of the resin particles containing the polyester resin and the first resin is excellent.

[Physical properties of water-based ink]
The pH of the water-based ink according to this embodiment is preferably 6.5 or more and 10.5 or less, more preferably 7.0 or more and 10.0 or less, and still more preferably 8.0 or more and 10.0 or less. In this embodiment, the pH of the water-based ink is measured under an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

  The surface tension of the water-based ink according to this embodiment is preferably 20 mN / m or more and 40 mN / m or less, and more preferably 25 mN / m or more and 35 mN / m or less. In this embodiment, the surface tension of the water-based ink is measured using a Wilhelmy surface tension meter in an environment of a temperature of 23 ± 0.5 ° C. and a relative humidity of 55 ± 5%.

The viscosity of the water-based ink according to the present embodiment is preferably 1 mPa · s to 30 mPa · s, and more preferably 2 mPa · s to 20 mPa · s. In this embodiment, the viscosity of the water-based ink is measured under the conditions of a temperature of 23 ± 0.5 ° C. and a shear rate of 1400 s ⁻¹ using a TV-20 viscometer (Toki Sangyo Co., Ltd.) as a measuring device.

  The water-based ink according to this embodiment can be suitably used as, for example, an inkjet recording ink.

<Ink cartridge>
The ink cartridge according to the present embodiment is a cartridge that contains the water-based ink according to the present embodiment. The ink cartridge according to the present embodiment is provided in a form that can be attached to and detached from, for example, an ink jet recording apparatus.

<Recording apparatus and recording method>
The recording apparatus according to the present embodiment contains the water-based ink according to the present embodiment, an ink applying unit that applies the water-based ink to the recording medium, and an infrared irradiation unit that irradiates the water-based ink applied to the recording medium with infrared rays. With. The recording apparatus according to the present embodiment realizes a recording method including an ink application process for applying the water-based ink according to the present embodiment to a recording medium, and an infrared irradiation process for irradiating the water-based ink applied to the recording medium with infrared light. Is done.

  Examples of the ink application unit in the present embodiment include: an ejection unit that ejects ink by an inkjet method; an application unit using rolls, sprays, sponges, and the like; a printing unit using offset printing, screen printing, gravure printing, letterpress printing, and the like. It is done.

  The ink application unit in the present embodiment is preferably an ejection unit that ejects ink by an inkjet method. A recording apparatus and a recording method to which the ink jet system is applied are excellent in ejection stability by using the water-based ink according to the present embodiment.

  The recording apparatus according to the present embodiment includes an infrared irradiation unit as a drying unit that dries the aqueous ink applied to the recording medium. In the recording apparatus according to the present embodiment, as the drying unit, in addition to the infrared irradiation unit, a contact heating unit such as a heating roll, a heating drum, and a heating belt; a hot air blowing unit including a heating element and a blower; a combination thereof May be provided.

  Examples of the recording medium used in the recording apparatus and the recording method according to the present embodiment include plain paper, coated paper coated with resin, and a film made of resin, metal, glass, ceramics, silicon, rubber, or the like. And a known image recording medium such as a plate. In particular, from the viewpoint that the effect of the water-based ink according to the present embodiment is easily exhibited, a coated paper provided with a coating layer made of a paint or a synthetic resin on one or both sides of a paper substrate is preferably used. Examples of the coated paper include “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and “Aurora Coat” manufactured by Nippon Paper Industries Co., Ltd.

  The recording apparatus according to the present embodiment may include an ink cartridge that accommodates the water-based ink according to the present embodiment and is made into a cartridge so as to be attached to and detached from the recording apparatus.

  Hereinafter, an example of a recording apparatus and a recording method according to the present embodiment will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram illustrating an example of a recording apparatus according to the present embodiment. A recording apparatus 12 shown in FIG. 1 is an ink jet recording apparatus.

  A recording apparatus 12 shown in FIG. 1 includes a container 16 that accommodates a recording medium P before image recording, an endless conveyance belt 28 that is stretched around a driving roll 24 and a driven roll 26, and a housing 14. Ink discharge heads (ink discharge heads 30Y, 30M, 30C, 30K, collectively referred to as ink discharge heads 30), which are examples of ink application means, and infrared irradiation means (infrared irradiation devices 60Y, 60M, 60C, 60K) And collectively referred to as an infrared irradiation device 60) and a container 40 for storing the recording medium P after image recording.

  Between the container 16 and the transport belt 28 is a transport path 22 through which the recording medium P before image recording is transported. The transport path 22 includes a roll 18 for taking out the recording medium P one by one from the container 16, and a recording. A plurality of roll pairs 20 that convey the medium P are arranged. A charging roll 32 is disposed on the upstream side of the conveyance belt 28. The charging roll 32 is driven while sandwiching the conveyance belt 28 and the recording medium P with the driven roll 26, generates a potential difference with the grounded driven roll 26, and applies an electric charge to the recording medium P to convey the conveyance belt. 28 is electrostatically adsorbed.

  The ink discharge head 30 is disposed above the conveyance belt 28 so as to face the flat portion of the conveyance belt 28. A region where the ink discharge head 30 and the conveyance belt 28 face each other is a region where ink droplets are discharged from the ink discharge head 30.

  Ink discharge heads 30Y, 30M, 30C, and 30K are respectively a head that records a Y (yellow) color image, a head that records an M (magenta) color image, a head that records a C (cyan) color image, and K This is a head for recording a (black) color image. The ink discharge heads 30Y, 30M, 30C, and 30K are arranged from the upstream side to the downstream side of the conveyance belt 28 in this order, for example. The ink ejection heads 30Y, 30M, 30C, and 30K are connected to the ink cartridges 31Y, 31M, 31C, and 31K of each color that are attached to and detached from the recording apparatus 12 through supply tubes (not shown), and the inks of the respective colors are supplied from the ink cartridge. Supplied to the discharge head.

  As the ink discharge head 30, for example, an effective recording area (arrangement area of nozzles that discharge ink) is longer than the width of the recording medium P (the length in the direction orthogonal to the conveyance direction of the recording medium P). And a carriage head that is shorter than the width of the recording medium P and moves in the width direction of the recording medium P to eject ink.

  As the ink jet system employed by the ink ejection head 30, a piezoelectric system that utilizes the vibration pressure of the piezoelectric element; a charge control system that ejects ink using electrostatic attraction; an electrical signal is converted into an acoustic beam and the ink is irradiated And an acoustic ink jet system that discharges ink using radiation pressure; a thermal ink jet system that heats ink to form bubbles and uses the generated pressure;

  The ink discharge head 30 is, for example, a low-resolution recording head (for example, a 600 dpi recording head) that discharges ink droplets in a range of 10 pL to 15 pL, and discharges ink droplets in a range of less than 10 pL. This is a recording head for high resolution (for example, a recording head of 1200 dpi). dpi means “dots per inch”.

  The recording apparatus 12 is not limited to a form including four ink ejection heads. The recording apparatus 12 may be configured to include five or more ink discharge heads obtained by adding intermediate colors to YMCK; and to record one color single image including one ink discharge head.

  On the downstream side of the ink discharge head 30, an infrared irradiation device 60 Y, 60 M, 60 C, 60 K (hereinafter also collectively referred to as “infrared irradiation device 60”) for each color ink discharge head above the transport belt 28. Is arranged.

  The infrared irradiation device 60 (an example of infrared irradiation means) is a device that irradiates the ink on the recording medium P with infrared rays to dry the ink, and is used when the ink is an infrared absorbing ink.

  The recording device 12 may include at least one of a contact heating unit and a hot air blowing unit as an ink drying unit instead of or together with the infrared irradiation unit 60. The contact heating means or the hot air blowing means is provided in the recording device 12 when the ink does not have infrared absorptivity. The contact-type heating means or hot air blowing means performs drying under conditions that raise the surface temperature of the recording medium to a range of 50 ° C. or higher and 120 ° C. or lower, for example.

  Examples of the light source of the infrared irradiation device 60 include a light emitting diode, a semiconductor laser, a surface emitting semiconductor laser, a halogen lamp, and a xenon lamp.

  As the infrared irradiation device 60, for example, a long infrared irradiation device in which an effective infrared irradiation region (arrangement region of a light source for irradiating infrared rays) is equal to or larger than the width of the recording region by the ink discharge head 30; And a carriage-type infrared irradiation device that moves in the width direction of the recording medium P and irradiates infrared rays.

The irradiation conditions of the infrared irradiation device 60 are set according to the infrared absorption performance of the ink, the amount of moisture in the ink, and the like. As the irradiation condition, the irradiation condition for drying the water content in the ink applied on the recording medium P to 10% by mass or less is preferable. Specifically, for example, a central wavelength of 700nm or more 1200nm or less (preferably not more than 780nm or 980 nm), irradiation intensity 0.1 J / cm ² or more 10J / cm ² or less (preferably 1 J / cm ² or more 3J / cm ² The irradiation time is from 0.1 milliseconds to 10 seconds (preferably from 10 milliseconds to 100 milliseconds).

  The recording device 12 is not limited to a mode including an infrared irradiation device for each color ink discharge head, and may be a mode including one infrared irradiation device on the downstream side of the most downstream ink discharge head.

  A peeling plate 34 is disposed on the downstream side of the infrared irradiation device 60 so as to face the drive roll 24. The peeling plate 34 peels the recording medium P from the conveyance belt 28.

  Between the conveyance belt 28 and the container 40 is a conveyance path 36 through which the recording medium P after image recording is conveyed, and a plurality of pairs of rolls 38 that convey the recording medium P are arranged in the conveyance path 36. .

  The operation of the recording device 12 will be described. The recording medium P before image recording is taken out one by one from the container 16 by the roll 18 and is conveyed to the conveying belt 28 by the plural roll pairs 20. Next, the recording medium P is electrostatically attracted to the conveyance belt 28 by the charging roll 32, and is conveyed below the ink discharge head 30 by the rotation of the conveyance belt 28. Next, ink is ejected from the ink ejection head 30 onto the recording medium P, and an image is recorded. Next, the ink on the recording medium P is irradiated with infrared rays from the infrared irradiation device 60, the ink generates heat by absorbing infrared rays, the ink temperature rises, and the ink is dried. Next, the recording medium P on which the ink is dried and the image is fixed is peeled off from the transport belt 28 by the peeling plate 34 and is transported to the container 40 by a plurality of roll pairs 38.

  The recording apparatus according to the present embodiment is not limited to a mode in which ink is directly applied to the recording medium from the ink applying unit, and after the ink is applied from the ink applying unit to the intermediate transfer member, the ink on the intermediate transfer member is applied to the recording medium. A form to be transferred may be used.

  The recording apparatus according to the present embodiment is not limited to a sheet-fed press using the recording apparatus 12 illustrated in FIG. 1 as an example, and may be a rotary press.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. In the following description, “part” and “%” are all based on mass unless otherwise specified.

<Preparation of water-based ink>
(Preparation of cyan dispersion)
In a reaction vessel, 6 parts of styrene, 11 parts of stearyl methacrylate, 4 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 5 parts of Plenmer PP-500 (manufactured by NOF Corporation), 5 parts of methacrylic acid, 2-mercapto A mixed solution of 0.05 part of ethanol and 24 parts of methyl ethyl ketone was prepared.

  On the other hand, 14 parts of styrene, 24 parts of stearyl methacrylate, 9 parts of styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.), 9 parts of Plenmer PP-500 (manufactured by NOF Corporation), 10 parts of methacrylic acid, 2-mercaptoethanol 0 A mixed solution consisting of .13 parts, 56 parts of methyl ethyl ketone and 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) was prepared and placed in a dropping funnel.

  Next, under a nitrogen atmosphere, the mixed solution in the reaction vessel was heated to 75 ° C. while stirring, and the mixed solution in the dropping funnel was gradually dropped over 1 hour. After 2 hours from the end of dropping, a solution prepared by dissolving 1.2 parts of 2,2′-azobis (2,4-dimethylvaleronitrile) in 12 parts of methyl ethyl ketone was added dropwise over 3 hours, and further at 75 ° C. for 2 hours, The solution was aged at 80 ° C. for 2 hours to obtain a methyl ethyl ketone solution of a water-insoluble polymer dispersant.

  A part of the obtained water-insoluble polymer dispersant solution was isolated by removing the solvent, the obtained solid content was diluted to 0.1% by mass with tetrahydrofuran, and the weight average molecular weight was measured by GPC. . As a result, the isolated solid content had a polystyrene equivalent weight average molecular weight of 25,000.

  Moreover, 5.0 g of the obtained water-insoluble polymer dispersant solution in terms of solid content, cyan pigment pigment blue 15: 3 (manufactured by Dainichi Seika Kogyo Co., Ltd.) 10.0 g, methyl ethyl ketone 40.0 g, 1 mol / L hydroxylation 8.0 g of sodium, 82.0 g of ion-exchanged water, and 300 g of 0.1 mm zirconia beads were supplied to the vessel and dispersed with a ready mill disperser (manufactured by IMEX Co., Ltd.) under a condition of 1000 rpm for 6 hours. The obtained dispersion was concentrated under reduced pressure until the methyl ethyl ketone was sufficiently distilled off with an evaporator, concentrated until the pigment concentration was 10%, and water-insoluble colored particles composed of a pigment whose surface was coated with a water-insoluble polymer dispersant, A cyan dispersion was obtained. The average particle size of the obtained cyan dispersion was 77 nm.

(Preparation of magenta dispersion)
Among these, a magenta dispersion was obtained in the same manner except that the cyan pigment Pigment Blue 15: 3 (manufactured by Dainichi Seika) was changed to the magenta pigment FASTOGEN SUPER MAGENTAJM02 (manufactured by DIC Corporation). The average particle size of the obtained magenta dispersion was 85 nm.

(Preparation of polyester resin fine particle dispersion emulsion E-1)
25 parts of methyl ethyl ketone was added to 10 parts of polyester PES1 (Mitsubishi Chemical Corporation, glass transition point Tg 1: 77 ° C., weight average molecular weight Mw 1: 18000, acid value 14), and the mixture was stirred and mixed. Next, a 10% by mass aqueous solution of sodium hydroxide was added with stirring, 0.9 equivalent of all carboxy groups contained in the polyester resin P05 (degree of neutralization 90%). Next, 130 parts of water was gradually added while stirring, and water was mixed. After the mixture becomes nearly uniform, a distillation tube and a vacuum pump are attached to the flask, and the mixture is heated to 40 ° C to 50 ° C and depressurized while stirring. Part was distilled off. The operation of concentrating while replacing the organic solvent with water was repeated until the odor of the organic solvent disappeared while adjusting the amount of water added so that the solid content concentration calculated from the material did not exceed 12% by mass. The concentrate was filtered through a 230 mesh nylon mesh to obtain Emulsion E-1. The solid content was 12% by mass and the particle size was 57 nm.

(Manufacture of water-based ink)
After mixing the following components in respective amounts, coarse particles were removed with a 5 μm filter to produce cyan water-based ink 1 and magenta water-based ink 1, and the water-based ink set of Example 1 was manufactured. The percentages of the following components indicate the content ratio (mass ratio) with respect to the total amount of the water-based ink.
Preparation of cyan water-based ink 1;
・ Cyan dispersion: 4% (converted to solid content)
Emulsion E-1 containing polyester resin particles: 3% (solid content conversion)
Emulsion E-2 containing resin particles containing the first resin: 2% (in terms of solid content)
(Acrit WBR-016U, manufactured by Taisei Fine Chemical Co., Ltd.)
・ Propylene glycol (Wako Pure Chemical Industries, Ltd.): 25%
・ Propylene glycol monobutyl ether: 3%
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.): 0.7%
・ Orphine E1004 (manufactured by Nissin Chemical Industry Co., Ltd.): 0.3%
・ HITEC E6314 (manufactured by Toho Chemical Co., Ltd.): 0.5% (converted to solid content)
-Ion-exchanged water: A total amount of 100% was added. For the magenta water-based ink 1, a magenta water-based ink 1 was obtained in the same manner except that the cyan dispersion 4% was changed to a magenta dispersion 5%. .

  Here, the emulsion E-1 contains particles (average particle size 57 nm) of polyester PES1 (glass transition point Tg 1: 77 ° C., weight average molecular weight Mw 1: 18000) as polyester resin particles. Emulsion E-2 contains particles (average particle size 30 nm) of polyurethane resin PU1 (glass transition point Tg 2: 20 ° C., weight average molecular weight Mw 2: 45000) as resin particles containing the first resin. .

[Example 2]
A water-based ink set was prepared according to the method of Example 1 except that Emulsion E-3 (Permarine UA150, manufactured by Sanyo Chemical Industries, Ltd.) was used instead of Emulsion E-2. Emulsion E-3 contains particles (average particle size 70 nm) of polyurethane resin PU2 (glass transition point Tg 2: 34 ° C., weight average molecular weight Mw 2: 100,000) as resin particles containing the first resin.

[Example 3]
A water-based ink set was prepared according to the method of Example 1, except that Emulsion E-4 (Acrit WEM-202U, manufactured by Taisei Fine Chemical Co., Ltd.) was used instead of Emulsion E-2. Emulsion E-4 contains particles (average particle size 33 nm) of polyurethane resin PU3 (glass transition point Tg 2: 34 ° C., weight average molecular weight Mw 2: 100,000) as resin particles containing the first resin.

[Example 4]
A water-based ink set was prepared according to the method of Example 1 except that Emulsion E-5 was used instead of Emulsion E-2. In Emulsion E-5, the polyester resin of the preparation E-1 is replaced with polyester PES2 (glass transition point Tg 2: 45 ° C., weight average molecular weight Mw 2: 40000, acid value 13) as resin particles containing the first resin. A liquid was prepared in the same manner except that.

[Example 5]
An aqueous ink set was prepared according to the method of Example 1 except that Emulsion E-6 was used instead of Emulsion E-2. Emulsion E-6 was prepared by using polyester PES3 (Mitsubishi Chemical Corporation, glass transition point Tg2: 47 ° C., weight average molecular weight Mw2: 100,000) as a resin particle containing the first resin. ) Particles (average particle size 85 nm).

[Example 6]
A water-based ink set was prepared according to the method of Example 1, except that 2.75% of emulsion E-1 was contained in terms of solid content and 2.25% of emulsion E-2 was contained in terms of solid content.

[Comparative Example 1]
A water-based ink set was prepared according to the method of Example 1 except that Emulsion E-2 was not used and Emulsion E-1 was contained at 4% in terms of solid content.

[Comparative Example 2]
A water-based ink set was prepared according to the method of Example 1 except that the emulsion E-2 was not used and the emulsion EA-1 was contained in an amount of 4% in terms of solid content. Emulsion EA-1 contains polyester PES4 particles (average particle size 80 nm) of polyester PES4 (manufactured by Mitsubishi Chemical Corporation, glass transition point Tg 1: 66 ° C., weight average molecular weight Mw 1: 100,000).

[Comparative Example 3]
A water-based ink set was prepared according to the method of Example 1 except that Emulsion E-1 was not used and that Emulsion E-2 was contained at 5% in terms of solid content.

[Comparative Example 4]
A water-based ink set was prepared according to the method of Example 1 except that Emulsion E-1 was contained at 2.5% in terms of solid content and Emulsion E-2 was contained at 2.5% in terms of solid content.

[Comparative Example 5]
A water-based ink set was prepared according to the method of Example 1 except that Emulsion EA-2 (Acrit WEM-031U, manufactured by Taisei Fine Chemical Co., Ltd.) was used instead of Emulsion E-2. Emulsion EA-2 contains particles of polyurethane-acrylic hybrid resin PU4 (glass transition point Tg 2: 50 ° C., weight average molecular weight Mw 2: 100,000) as the first resin particles.

[Comparative Example 6]
Instead of the PES1 resin in the production example of the emulsion E-1, an emulsion EA-3 using PES5 (manufactured by Mitsubishi Chemical Corporation, glass transition point Tg1: 79 ° C., weight average molecular weight Mw1: 62000, acid value 14) is used. A water-based ink set was prepared according to the method of Example 1 except that. Emulsion EA-3 contains polyester PES5 particles (average particle size 60 nm) as polyester resin particles.

[Example 7]
A water-based ink was prepared according to the method of Example 1 except that Emulsion E-7 prepared by the following method and having polyester resin particles containing an infrared absorber dispersed therein was used instead of Emulsion E-1. A set was prepared.

  5 g of polyester PES1 was added to the flask, and 8 ml of methyl ethyl ketone (MEK) was further added and stirred. An amount of a 10% aqueous solution of sodium hydroxide to neutralize 0.8 equivalent of the total amount of carboxylic acid contained in polyester PES1 was added with stirring. To this solution, 40 mg of squarylium dye as an infrared absorber and 1.0 ml of tetrahydrofuran (THF) were added and dissolved. While continuing to stir, 12 ml of water was gradually added. In addition, as squarylium pigment | dye, the compound (I-1) represented by the following structural formula was used.

  Next, a distillation tube and a vacuum pump were attached to the flask, and the solution was heated to 30 ° C. or higher and 35 ° C. or lower and the pressure was reduced while stirring to distill off part of the organic solvent and water. In the course of distilling off the organic solvent, the operation of adding water and the concentration operation were repeated until the solid content concentration did not exceed 13% until the organic solvent odor disappeared. The concentrated solution was filtered through a 0.45 μm filter to obtain a dispersion. The solid content of this dispersion was measured, and based on the obtained solid content, water was added to the dispersion to adjust the solid concentration to 10% by mass, thereby obtaining Emulsion E-7. The average particle size of the polyester resin particles contained in the emulsion E-7 was 60 nm. Moreover, the density | concentration in emulsion solid content of the squarylium pigment | dye (infrared absorber) in the emulsion E-7 was 1.5 mass%.

[Example 8]
A water-based ink set was prepared according to the method of Example 4 except that Emulsion E-7 in which polyester resin particles containing an infrared absorbent were dispersed was used instead of Emulsion E-1.

[Comparative Example 7]
A water-based ink set was prepared according to the method of Comparative Example 4 except that Emulsion E-7 prepared in Example 6 was used instead of Emulsion E-1.

[Comparative Example 8]
A water-based ink set was prepared according to the method of Comparative Example 5 except that the emulsion E-7 prepared in Example 7 was used instead of the emulsion E-1.

<Evaluation of water-based ink>
(Drying)
The dryness of each aqueous ink set produced in Examples 1 to 6 and Comparative Examples 1 to 6 was evaluated. Each water-based ink set was refilled with cyan and magenta cartridges of an inkjet printer (Seiko Epson Corporation, PX-1004). A solid patch (5 cm square) was printed on coated paper (Oji Paper Co., Ltd., OK Top Coat +) using an inkjet printer. The solid patch is a graphic created on Word 2016, which is software made by Microsoft, and the color is designated by R / G / B = 0/0/255. The printed coated paper was placed on a hot plate set at 60 ° C. and dried for a set time. Another coated paper (manufactured by Oji Paper Co., Ltd., OK Top Coat +) was superimposed on the solid patch printing surface of the coated paper immediately after drying. While applying a pressure of ² kg / cm ² , the stacked coated paper was shifted by 2 cm at a speed of 1 cm per second. The degree of color transfer in the area where the pressure was released and the coated paper was in contact with the solid patch was measured using a colorimeter (X-Rite 939, manufactured by X-Rite).

As a result of the measurement, when the optical density (OD value) of the overlapped coated paper was 0.03 or less, it was determined that the solid patch was dried. Change the drying time of the coated paper on which the solid patch is printed, and perform the above-mentioned drying determination. For each water-based ink, the shortest of the times determined that the solid patch printed on the coated paper has dried (the shortest) The drying fixability was evaluated based on the following evaluation criteria based on the shortest drying time obtained.
-Evaluation criteria-
A: The shortest drying time is less than 7 seconds B: The shortest drying time is 7 seconds or more and less than 10 seconds C: The shortest drying time is 10 seconds or more

For the water-based inks of Examples 6 and 7 and Comparative Examples 7 and 8 in which the polyester resin particles include an infrared absorber, instead of drying on a hot plate, an infrared laser irradiation drying device (Fuji Xerox Co., Ltd., paper feed speed) Except for drying the solid patch printed on the coated paper by infrared irradiation (center wavelength: 817 nm, irradiation intensity: 3.0 J / cm ² ) to the solid patch using a drying speed of 20 m / min. According to the method, a drying test was performed.

In addition, with respect to the water-based inks of Examples 6 and 7 and Comparative Examples 7 and 8, the dry fixability was evaluated based on the following evaluation criteria.
-Evaluation criteria-
A1: The optical density (OD value) of the overlaid coated paper is 0.03 or less. B1: The optical density (OD value) of the overlaid coated paper is larger than 0.03.

(Storage offset resistance)
Similar to the dry fixability test, two coated papers (manufactured by Oji Paper Co., Ltd.) using an ink jet printer (Seiko Epson Corporation, PX-1004) equipped with a cartridge containing each blue ink. A solid patch (5 cm square) was printed on OK top coat +). Next, the printed coated paper was placed on a hot plate set at 40 ° C. for 2 minutes to dry the solid patch. Thereafter, the two coated papers were put together so that the solid patch print portions were in contact with each other and then placed on a flat surface. A pressure of 3 kg / cm ² was applied to the upper surface (non-printed surface) of the two coated papers that were superposed and left for 17 hours in an environment of a temperature of 22 ° C. and a humidity of 50%. After the test was completed, the portion where the two solid patches of coated paper were superimposed was peeled off. The state of the solid patch was visually observed, and the storage offset resistance was evaluated based on the following evaluation criteria.
-Evaluation criteria-
A: Solid patch is not peeled B: Solid patch is slightly peeled C: Solid patch is peeled off, white part is conspicuous

  As shown in Table 1, the glass transition point Tg2 of the first resin is 30 ° C. or lower lower than the glass transition point Tg1 of the polyester, the weight average molecular weight Mw2 of the first resin is higher than the weight average molecular weight Mw1 of the polyester, and In the aqueous inks of Examples 1 to 6, the content of the resin particles containing the first resin with respect to the total amount of the aqueous ink is less than the content of the polyester resin particles with respect to the total amount of the aqueous ink, the polyester resin particles containing polyester It was found that the storage offset resistance can be improved while maintaining the dry fixability as compared with Comparative Examples 1 and 2 in which is used alone. Furthermore, as shown in Table 1, in the water-based inks of Examples 1 to 6, when the glass transition point Tg2 of the first resin exceeds a temperature 30 ° C. lower than the glass transition point Tg1 of the polyester, When the weight average molecular weight Mw2 is less than or equal to the weight average molecular weight Mw1 of the polyester, or when the content of the resin particles containing the first resin is greater than or equal to the content of the polyester resin particles, It was found that storage offset resistance could be improved while maintaining.

12 recording apparatus, 14 housing, 16, 40 container, 18 roll, 20, 38 roll pair, 22, 36 transport path, 24 drive roll, 26 driven roll, 28 transport belt, 30Y, 30M, 30C, 30K ink ejection head (Example of ink applying means), 31Y, 31M, 31C, 31K ink cartridge, 32 charging roll, 34 release plate, 60Y, 60M, 60C, 60K Infrared irradiation device (an example of infrared irradiation means), P recording medium.

Claims (13)

An aqueous medium;
Polyester resin particles dispersed in the aqueous medium and containing polyester;
Resin particles dispersed in the aqueous medium and containing a first resin;
Including
The glass transition point of the first resin is 30 ° C. lower than the glass transition point of the polyester,
The weight average molecular weight of the first resin is higher than the weight average molecular weight of the polyester;
The content of the resin particles is less than the content of the polyester resin particles,
Water based ink.   The aqueous ink according to claim 1, further comprising a compound having infrared absorptivity.   The water-based ink according to claim 2, wherein the compound having infrared absorptivity is contained in the polyester resin particles.   The water-based ink according to any one of claims 1 to 3, wherein a ratio of a weight average molecular weight of the first resin to a weight average molecular weight of the polyester is 2 or more.   The water-based ink according to any one of claims 1 to 4, wherein a glass transition point of the first resin is lower by 30 ° C or more than a glass transition point of the polyester.   The water-based ink according to any one of claims 1 to 5, wherein a ratio of the content of the polyester resin particles to the total of the polyester resin particles and the resin particles is 55% by mass or more.   The aqueous ink according to claim 1, wherein the total amount of the polyester resin particles and the resin particles is 3% by mass or more and 5% by mass or less of the total amount of the aqueous ink.   An ink cartridge containing the water-based ink according to claim 1.   A recording apparatus comprising the water-based ink according to claim 1, and an ink applying unit that applies the water-based ink to a recording medium. Ink application means for containing the water-based ink according to claim 2 or 3 and applying the water-based ink to a recording medium;
Infrared irradiation means for irradiating the water-based ink applied to the recording medium with infrared rays;
A recording apparatus comprising:   A recording method comprising an ink application step of applying the water-based ink according to claim 1 to a recording medium. An ink application step of applying the water-based ink according to claim 2 or 3 to a recording medium;
An infrared irradiation step of irradiating the water-based ink applied to the recording medium with infrared rays;
A recording method. The recording method according to claim 11 or 12, wherein the recording medium is a low permeability medium.

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