JP2009235155A - Ink composition, and inkjet recording method and recorded matter using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition having high printing quality to various recording media and excellent in reliability such as storage stability and printing stability, and a recording method and recorded matter using the same. <P>SOLUTION: The ink composition comprises at least water, a pigment coated with a water-insoluble polymer, a glycol ether whose HLB value calculated by the Davis method is 4.2-8.0, and a 1,2-alkanediol. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink composition, an ink jet recording method, and a recorded matter.

  The ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. Due to recent advances in inkjet recording technology, the inkjet recording method has been used for high-definition image recording (printing), which has been the field of photography and offset printing. High-quality recording is required not only for paper and dedicated paper for ink-jet recording (matte and glossy) but also for recording media such as printing paper, synthetic paper, and film.

  As the coloring material, a dye or a pigment is used. In particular, a water-soluble dye is often used for color inks because of high color saturation, transparency, and high solubility in water. However, such dyes generally have insufficient light resistance and gas resistance, and because they are water-soluble, there are also problems with water resistance. The recorded matter has a drawback that the recorded image has poor storage stability. On the other hand, a colorant insoluble in water is advantageous in terms of water resistance. In particular, among pigments that are insoluble in water, pigments are such color materials that are excellent in light resistance, gas resistance, and water resistance. Therefore, pigment inks that take advantage of these color material properties are being developed.

  On the other hand, water-based pigment inks for ink-jet recording have high color developability, glossiness, low bleeding, and other print quality, discharge stability characteristics that prevent ejection from the head nozzle, and ink storage stability. It is required to be satisfied at the same time.

  However, if the pigment concentration in the ink is increased in order to enhance the color developability, the viscosity increase, clogging characteristics, ejection stability characteristics, and ink storage stability are impaired. Also, if the ink permeability is increased to suppress bleeding and increase the printing speed, the ink penetrates into the recording medium, making it difficult for the ink to remain on the surface of the recording medium. There was a problem that the color developability was impaired.

  For such problems, for the purpose of improving color developability and bleeding, polymer fine particles are contained (see Patent Document 1), inorganic fine particles are contained (see Patent Document 2), and a colorant is contained. Use an ink containing a water-insoluble vinyl polymer dispersion (see Patent Document 3), an acetylene glycol surfactant (see Patent Document 4 and Patent Document 5), and a branched chain having a specific bivalent chain length. The addition of alcohol (see Patent Document 6) has been proposed.

JP 2001-123098 A JP-A-11-209671 JP 2004-75988 A JP-A-4-239068 JP-A-6-322307 JP 2003-96345 A J.T.Davies and E.K.Rideal, “Interface Phenomena” 2nd ed. Academic Press, New York 1963

  However, in the above-described known ink composition, depending on the combination of the color material and the water-soluble organic solvent used, the storage stability and ejection stability of the ink may be reduced, and the print quality, ink storage stability, There were still problems in achieving both discharge properties.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is excellent in reliability such as storage stability and ejection stability, and for various recording media, particularly plain paper. Another object of the present invention is to provide an ink composition suitable for use in an ink jet recording method capable of obtaining high color developability and excellent print quality with little bleeding.

  As a result of intensive studies, the inventors have at least water, a pigment coated with a water-insoluble polymer as a coloring material, a glycol ether having an HLB value calculated by the Davis method of 4.2 to 8.0, The present inventors have found that an ink composition comprising 1,2-alkanediol can solve the above problems. The present invention is based on such knowledge, and the configuration of the present invention is as follows.

  Application Example 1 At least water, a pigment coated with a water-insoluble polymer, a glycol ether having an HLB value calculated by the Davis method of 4.2 to 8.0, 1,2-alkanediol, An ink composition comprising:

  [Application Example 2] The ink composition according to [Application Example 1], wherein the alkyl group of the glycol ether has a branched structure.

  [Application Example 3] According to [Application Example 1] or [Application Example 2], the content of the glycol ether is 0.1 to 6% by weight based on the total amount of the ink composition. Ink composition.

  [Application Example 4] Any of [Application Example 1] to [Application Example 3], in which the content of the 1,2-alkanediol is 1/2 to 5/1 by weight with respect to the glycol ether. The ink composition according to claim 1.

  [Application Example 5] Any one of [Application Example 1] to [Application Example 4], wherein the 1,2-alkanediol is contained in an amount of 1 to 20% by weight based on the total amount of the ink composition. Item 4. The ink composition according to item.

  [Application Example 6] The ink composition according to any one of [Application Example 1] to [Application Example 5], wherein the alkyl group of the glycol ether is a 2-ethylhexyl group.

  [Application Example 7] The ink composition according to any one of [Application Example 1] to [Application Example 6], wherein the ink composition further includes a nonionic surfactant.

  [Application Example 8] The application example according to any one of [Application Example 1] to [Application Example 7], wherein the pigment is included in an amount of 0.5 wt% to 10 wt% with respect to the total amount of the ink composition. Ink composition.

  [Application Example 9] An inkjet recording method for performing printing by attaching the ink composition according to any one of [Application Example 1] to [Application Example 8] to a recording medium.

  Application Example 10 Printing is performed by ejecting droplets of the ink composition according to any one of [Application Example 1] to [Application Example 8] and attaching the droplets to a recording medium. An inkjet recording method.

  [Application Example 11] A recorded matter recorded by the inkjet recording method according to [Application Example 9] or [Application Example 10].

  According to the present invention, the ink composition has excellent reliability such as storage stability and ejection stability, and has excellent color quality and excellent print quality with little bleeding on various recording media, particularly plain paper. Product, an ink jet recording method using an ink composition having such characteristics, and a beautiful recorded matter obtained by this recording method.

  Hereinafter, the ink composition of the present invention will be described in detail based on preferred embodiments thereof.

  The ink composition of the present invention comprises at least water, a pigment coated with a water-insoluble polymer, a glycol ether having an HLB value calculated by the Davis method of 4.2 to 8.0, and 1,2- And alkanediol.

[Color material]
The color material of the present invention is a pigment coated with at least a water-insoluble polymer, and the water-insoluble polymer used in the color material is a block copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group. A polymer comprising a resin and containing at least a monomer having a salt-forming group, and having a solubility in 100 g of water at 25 ° C. of less than 1 g after neutralization.

  Monomers having hydrophobic groups are methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl. Methacrylic acid esters such as methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, vinyl esters such as vinyl acetate, vinylcyan compounds such as acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, Vinyltoluene, 4-t-butylstyrene, chlorost Emissions, vinyl anisole, include aromatic vinyl monomers such as vinyl naphthalene, may also be used alone, or a combination of two or more kinds.

  Examples of the monomer having a hydrophilic group include polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, and ethylene glycol / propylene glycol monomethacrylate. These can be used alone or in admixture of two or more. In particular, polyethylene glycol (2-30) monomethacrylate, polyethylene glycol (1-15) / propylene glycol (1-15) monomethacrylate, polypropylene glycol (2-30) methacrylate, methoxypolyethylene glycol (2-30) methacrylate, methoxy Glossiness of a printed image is improved by using a monomer component constituting a branched chain such as polytetramethylene glycol (2-30) methacrylate and methoxy (ethylene glycol / propylene glycol copolymer) (1-30) methacrylate. .

  Monomers having a salt-forming group include acrylic acid, methacrylic acid, styrene carboxylic acid, maleic acid, etc., and each can be used alone or in combination of two or more.

  Furthermore, a macromonomer such as a styrene macromonomer or a silicone macromonomer having a polysynthetic functional group at one end, or other monomers can be used in combination.

  The water-insoluble polymer of the present invention can be obtained by copolymerizing monomers by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, and the solution polymerization method is particularly preferable. In this case, a known radical polymerization agent or polymerization chain transfer agent may be added.

  The pigment coated with the water-insoluble polymer of the present invention is obtained by, for example, dissolving the water-insoluble polymer in an organic solvent such as methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethyl ketone, and dibutyl ether. By adding a colorant, then adding a neutralizing agent and water, kneading, and dispersing to prepare an oil-in-water dispersion and removing the organic solvent from the resulting dispersion. It can be obtained as an aqueous dispersion. For the kneading and dispersing treatment, for example, a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, a high-speed stirring type disperser, or the like can be used.

  The neutralizing agent is preferably a tertiary amine such as ethylamine or trimethylamine, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia or the like, and the pH of the resulting aqueous dispersion is preferably 6-10.

  The water-insoluble polymer to be coated is preferably a polymer having a weight average molecular weight of about 10,000 to 150,000 from the viewpoint of stably dispersing a colorant, particularly a pigment. The weight average molecular weight can be measured by a molecular weight analysis method by gel permeation chromatography (GPC).

  As the pigment used in the color material of the present invention, existing pigments described in “Dye Handbook” (publisher: Maruzen Co., Ltd.) and the like can be used.

  As the pigment that can be used in the present invention, any of known inorganic pigments and organic pigments can be used, and pigments such as Pigment Yellow, Pigment Red, Pigment Violet, Pigment Blue, and Pigment Black described in the Color Index. In addition, phthalocyanine-based, azo-based, anthraquinone-based, azomethine-based, condensed ring-based pigments can be exemplified. Further, organic pigments such as yellow No. 4, 5, 205, 401; orange 228, 405; blue No. 1, 404, etc., titanium oxide, zinc oxide, zirconium oxide, iron oxide, ultramarine blue, bitumen, Examples thereof include inorganic pigments such as chrome oxide. For example, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, 155, 174, 180, 198, C.I. I. Pigment Red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184,202,209, C.I. I. Pigment Bio Red 1,3,5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, C.I. I. Pigment Black 1, 7, etc., and an ink composition can also be formed using a plurality of pigments.

  These pigments are preferably contained in the ink of the present invention in the range of 0.5 wt% to 10 wt%. If the content is less than 0.5% by weight, the print density (color developability) may be insufficient. If the content is more than 10% by weight, glossiness on glossy media, nozzle clogging, ejection failure, etc. There may be a problem in reliability such as stability.

  Furthermore, the ratio of the pigment and the water-insoluble polymer is in the ratio of pigment: water-insoluble polymer = 1: 0.2 to 1: 1, so that dispersion stability, ink storage stability, nozzle clogging prevention, etc. From the viewpoint of glossiness on glossy media. Specifically, if the amount of water-insoluble polymer is less than 20% of the pigment, stable dispersion cannot be achieved, and aggregation of the pigment occurs. This is because of deterioration.

  Further, from the viewpoint of coloring and glossiness on glossy media, the volume average particle diameter of the pigment in the ink is preferably in the range of 50 nm to 150 nm. These average particle diameters can be obtained by particle diameter measurement using a Microtrac UPA150 (manufactured by Microtrac) or a particle size distribution analyzer LPA3100 (manufactured by Otsuka Electronics Co., Ltd.).

  The pigment coated with the water-insoluble polymer of the present invention may have a shape in which a part of the pigment is exposed without being completely covered with the water-insoluble polymer.

[Glycol ether]
The ink composition of the present invention contains a glycol ether in a specific range of the HLB value, so that the wettability / penetration speed can be controlled without being affected by the type of the recording medium so much. It is possible to obtain a clear printed image with high color development and little bleeding. In addition, the combination with 1,2-alkanediol having compatibility with glycol ether, which will be described later, improves the affinity for water as the main solvent, and gives problems to the dispersion of the water-insoluble polymer described above. Therefore, excellent print quality, storage stability, and ejection stability can be ensured at the same time.

  Here, the HLB value of the glycol ether used in the present invention is a value for evaluating the hydrophilicity of the compound proposed by Davis et al. The value calculated by the equation (1).

（但し、［１］は親水基の基数を表し、［２］は疎水基の基数を表す）。
下記の表１に、代表的な親水基、及び疎水基の基数を例示する。

(However, [1] represents the number of hydrophilic groups and [2] represents the number of hydrophobic groups).
Table 1 below exemplifies the number of representative hydrophilic groups and hydrophobic groups.

  The ink composition of the present invention comprises glycol ether having an HLB value calculated by the Davis method of 4.2 to 8.0 as an essential component. The HLB value is preferably in the range of 4.2 to 8.0, more preferably in the range of 4.2 to 7.1. When the HLB value is less than 4.2, the hydrophobicity of the glycol ether increases, and the affinity with water as the main solvent may decrease, and the ink storage stability may deteriorate. If the HLB value is greater than 8.0, the effect of penetrating into the recording medium is reduced, and the effects of high color development and bleeding reduction may not be exhibited. Specific examples of the glycol ether include ethylene glycol monoisobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoisohexyl ether, diethylene glycol monohexyl ether, triethylene glycol monohexyl ether, diethylene glycol monoisohexyl ether, triethylene glycol mono Isohexyl ether, ethylene glycol monoisoheptyl ether, diethylene glycol monoisoheptyl ether, triethylene glycol monoisoheptyl ether, ethylene glycol monooctyl ether, ethylene glycol monoisooctyl ether, diethylene glycol monoisooctyl ether, triethylene glycol monoisooctyl Ether, ethi Glycol mono 2-ethylhexyl ether, diethylene glycol mono 2-ethyl hexyl ether, triethylene glycol mono 2-ethyl hexyl ether, diethylene glycol mono 2-ethyl pentyl ether, ethylene glycol mono 1-ethyl pentyl ether, ethylene glycol mono 2-methyl pentyl ether, Examples include diethylene glycol mono 2-methylpentyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, and tripropylene glycol monomethyl ether. These can be used 1 type or in mixture of 2 or more types.

  Furthermore, the ink composition of the present invention preferably has a branched structure in the alkyl group of the glycol ether. When the ink composition contains a glycol ether having a branched structure in the alkyl group, an excellent recorded matter with high color development and little bleeding can be obtained regardless of the recording medium. Specifically, ethylene glycol monoisohexyl ether, diethylene glycol monoisohexyl ether, triethylene glycol monoisohexyl ether, ethylene glycol monoisoheptyl ether, diethylene glycol monoisoheptyl ether, triethylene glycol monoisoheptyl ether, ethylene glycol mono Isooctyl ether, diethylene glycol monoisooctyl ether, triethylene glycol monoisooctyl ether, ethylene glycol mono 2-ethylhexyl ether, diethylene glycol mono 2-ethylhexyl ether, triethylene glycol mono 2-ethylhexyl ether, diethylene glycol mono 2-ethylpentyl ether, Ethylene glycol mono 1-ethyl Inch ether, ethylene glycol mono-2-methylpentyl ether, diethylene glycol mono-2-methylpentyl ether, and the like.

  In order to further improve the color developability, the alkyl group is more preferably a 2-ethylhexyl group as the branched structure of the glycol ether. Specifically, ethylene glycol mono 2-ethyl hexyl ether, diethylene glycol mono 2-ethyl hexyl ether, triethylene glycol mono 2-ethyl hexyl ether, diethylene glycol mono 2-ethyl pentyl ether, ethylene glycol mono 1-ethyl pentyl ether, ethylene glycol mono 2 -Methyl pentyl ether, diethylene glycol mono 2-methyl pentyl ether, etc. are mentioned, and ethylene glycol mono 2-ethyl hexyl ether, diethylene glycol mono 2-ethyl hexyl ether, triethylene glycol mono 2-ethyl hexyl ether and the like are particularly preferable.

  The content of the glycol ether is in the range of 0.1% by weight to 6% by weight with respect to the total amount of the ink composition from the viewpoints of high color developability of the ink composition, bleeding reduction effect, ink storage stability, and ejection reliability. It is preferable that it is contained. If it is less than 0.1% by weight, the penetrability and drying properties of the ink composition become poor, and it is difficult to obtain a clear image, and the print density (coloring property) may be insufficient. On the other hand, if it exceeds 6% by weight, the viscosity of the ink becomes high and it becomes difficult to discharge stably, or the solubility in the ink composition cannot be obtained and the stable storage stability for a long time may not be obtained.

[1,2-alkanediol]
The ink composition of the present invention comprises 1,2-alkanediol as an aqueous organic solvent compatible with the glycol ether.

  Here, “compatible” means that among the components constituting the ink composition, the mixture of the glycol ether and 1,2-alkanediol is completely dissolved in the ink composition using water as the main solvent. The combination of each material and the ratio of each material is meant.

  By including this 1,2-alkanediol in the ink composition, the solubility in the ink composition with the glycol ether can be increased, and the ink storage stability and ejection stability can be improved. Moreover, since it becomes easy to increase the content of the glycol ether in the ink composition, it is possible to contribute to further improvement in printing quality.

  Specific examples of 1,2-alkanediol include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 4- A 1,2-alkanediol having 4 to 8 carbon atoms such as methyl-1,2-pentanediol is preferred. In particular, C6-C8 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol are preferable from the viewpoints of solubility in water and compatibility with the glycol ether. The addition amount of 1,2-alkanediol is preferably 1/2 to 5/1 by weight with respect to the glycol ether from the viewpoint of compatibility with the glycol ether. Further, from the viewpoint of compatibility with the glycol ether, ink storage stability, and ejection stability, it is preferably added in the range of 1% by weight to 20% by weight with respect to the total amount of the ink composition. If it is less than 1% by weight, it may make it difficult to produce a compatibility effect with the glycol ether. If it is more than 20% by weight, the viscosity of the ink becomes high and stable ejection becomes difficult, and it is stable for a long time. Ink storability may not be obtained.

[Nonionic surfactant]
The ink composition of the present invention further comprises a nonionic surfactant.
By containing a nonionic surfactant, the surface tension of the ink composition can be easily adjusted to a desired value, and ink permeability can be improved with respect to various recording media, particularly plain paper. .

  Specific examples of nonionic surfactants include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene phenyl ethers and the like, and among nonionic surfactants, An acetylene glycol-based surfactant is preferable in that an ink composition with almost no foaming can be obtained, and both ejection stability and print quality can be achieved. It is particularly preferable when used for inkjet recording. Examples of acetylene glycol surfactants include Surfynol 420, 440, 465, 485, 104, STG (product of Air Products), Olfine PD001, PD002W, SPC, E1004, E1010 (product of Nissin Chemical Industry Co., Ltd.) ), Acetylenol E00, E40, E100, LH (product of Kawaken Fine Chemical Co., Ltd.) and the like. Examples of the polyether-modified siloxanes include BYK-346, 347, 348, and UV3530 (Bic Chemie product). One or more of these can be used in the ink composition, and the surface tension is preferably adjusted to 20 mN / m to 40 mN / m. In the ink composition, 0.1% by weight to 3% is preferable. 0.0% by weight is contained.

[Ink composition]
The ink composition of the present invention is preferably a water-based ink in which the main solvent of the ink is water from the viewpoint of safety and handling, and the water is ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, etc. It is preferable to use pure water or ultrapure water. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide in order to prevent the generation of mold and bacteria and enable long-term storage of the ink.

  Furthermore, since the ink composition of the present invention is an ink composition suitable for the ink jet recording method, it preferably contains a humectant, a penetration enhancer, and a pH adjuster.

  The ink composition of the present invention preferably contains a water-soluble organic solvent having a moisturizing effect for the purpose of preventing clogging in the vicinity of the nozzle of the inkjet head. Specifically, for example, glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2-butene Polyhydric alcohols such as 1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucitol (Sorbit), sugars such as maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, so-called solid wetting agents such as sugar alcohols, hyaluronic acids, ureas, ethanol Alkyl alcohols having 1 to 4 carbon atoms such as methanol, butanol, propanol, isopropanol, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, Examples include sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like. These water-soluble organic solvents having a wetting effect can be used singly or in combination of two or more in the ink from the viewpoint of ensuring appropriate physical properties (such as viscosity), printing quality, and reliability of the ink. It is preferably contained in an amount of 10% to 50% by weight.

  As the pH adjuster, it is possible to use alkali metal hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide, amines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine. Although it is possible, it preferably contains at least one pH adjusting agent selected from alkali metal hydroxides, ammonia, triethanolamine, and tripropanolamine, and is preferably adjusted to pH 6-10. If the pH is out of this range, the material constituting the ink jet printer will be adversely affected, and the clogging recoverability will deteriorate.

  Further, an antifoaming agent, an antioxidant, an ultraviolet absorber, an antiseptic / antifungal agent and the like can be added as necessary.

  In addition, the viscosity of the ink composition of the present invention is preferably 25 cPs or less at 25 ° C. from the viewpoint of ensuring ejection stability in the ink jet recording apparatus. More preferably, it is 15 cPs or less.

<Recording method and recorded material>
The ink composition of the present invention can be suitably used for writing instruments such as pens, stamps and the like, but can be more suitably used as an ink composition for inkjet recording. In the present invention, the ink jet recording system means a system in which an ink composition is ejected as droplets from a fine nozzle and the droplets are attached to a recording medium. This will be specifically described below.

  As a first method, there is an electrostatic suction method, which applies a strong electric field between the nozzle and the acceleration electrode placed in front of the nozzle, and continuously ejects ink from the nozzle in the form of droplets. This is a method in which a print information signal is applied to the deflection electrode while the ink droplet is flying between the deflection electrodes for recording, or a method in which the ink droplet is ejected in response to the print information signal without being deflected.

  The second method is a method in which ink droplets are forcibly ejected by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. The ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is given to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which a pressure and a print information signal are simultaneously applied to an ink liquid by a piezoelectric element to eject and record ink droplets.

  The fourth method is a method in which the ink liquid is rapidly expanded in volume by the action of heat energy, and the ink liquid is heated and foamed with a microelectrode in accordance with a print information signal to eject and record ink droplets.

  Any of the above methods can be used in the ink jet recording method using the ink composition of the present invention.

  The recorded matter of the present invention is recorded at least using the above ink composition. By using the ink composition of the present invention, the recorded matter has a sufficient print density and exhibits excellent print quality.

<Example>
EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these Examples.

[Adjustment of colorant dispersion]
A colorant dispersion having dispersed particles of a colorant coated with a water-insoluble polymer was prepared by the following method.

(Synthesis of water-insoluble polymers 1 to 3)
In a reaction vessel sufficiently substituted with nitrogen gas using 20 parts by weight of an organic solvent (methyl ethyl ketone), 0.03 part by weight of a polymerization chain transfer agent (2-mercaptoethanol), a polymerization initiator, and each monomer shown in Table 2. The mixture was polymerized with stirring at 75 ° C., 0.9 part by weight of 2,2′-azobis-2,4-dimethylvaleronitrile dissolved in 40 parts by weight of methyl ethyl ketone was added to 100 parts by weight of the monomer component, and the mixture was heated at 80 ° C. The polymer solution was obtained by aging for 1 hour.

(Dispersion Y)
5 parts obtained by drying the polymer solution obtained as water-insoluble polymer 1 under reduced pressure was dissolved in 15 parts of methyl ethyl ketone, and the polymer was neutralized with an aqueous sodium hydroxide solution. Furthermore, C.I. I. 15 parts of Pigment Yellow 74 was added and kneaded with a disperser while adding water. After 100 parts of ion-exchanged water was added to the kneaded mixture and stirred, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed, whereby a yellow pigment having a solid content concentration of 20% by weight was removed. An aqueous dispersion was obtained. At this time, the weight ratio of pigment: water-insoluble polymer was 1: 0.5.

(Dispersion M)
9 parts obtained by drying the polymer solution obtained as the water-insoluble polymer 2 under reduced pressure were dissolved in 45 parts of methyl ethyl ketone, and the polymer was neutralized with an aqueous sodium hydroxide solution. Furthermore, C.I. I. 18 parts of Pigment Red 122 was added and kneaded with a disperser while adding water. After 120 parts of ion-exchanged water was added to the kneaded product and stirred, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed, whereby a magenta pigment having a solid content concentration of 20% by weight was removed. An aqueous dispersion was obtained. At this time, the weight ratio of pigment: water-insoluble polymer was 1: 0.2.

(Dispersion C)
6 parts obtained by drying the polymer solution obtained as the water-insoluble polymer 3 under reduced pressure were dissolved in 20 parts of methyl ethyl ketone, and the polymer was neutralized with an aqueous sodium hydroxide solution. Furthermore, C.I. I. 10 parts of Pigment Blue 15: 3 was added and kneaded with a disperser while adding water. After 100 parts of ion-exchanged water was added to the kneaded product and stirred, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed to remove a cyan pigment having a solid content concentration of 20% by weight. An aqueous dispersion was obtained. At this time, the weight ratio of pigment: water-insoluble polymer was 1: 1.

[Preparation of ink]
Each component was mixed in the ratio shown in Table 3, stirred at room temperature for 2 hours, and then filtered through a membrane filter having a pore size of 5 μm to prepare each ink. However, the addition amounts shown in Table 3 are all expressed as weight percent concentrations, and the numbers in parentheses in the colorant dispersion represent the solid content concentration of the colorant. The “remaining amount” of ion-exchanged water means adding ion-exchanged water so that the total amount of ink becomes 100 parts.

  The following evaluation was performed using each ink prepared in Table 3.

(Test 1) Ink Storage Stability Each ink was compared at room temperature and 50 ° C. for 2 weeks, and the ink state (visually), the viscosity immediately after ink preparation, and the value after storage were compared. Judgment criteria are as follows.
S: The ink state is not aggregated / separated, and the viscosity fluctuation range is less than ± 5%.
A: The ink state is not aggregated / separated, and the viscosity fluctuation range is ± 5% or more and less than ± 10%. B: The ink state is not aggregated / separated, and the viscosity fluctuation range is ± 10% or more.
C: The ink state is aggregated or separated.

(Test 2) Discharge stability Each ink was mounted on PX-V600 (trade name, manufactured by Seiko Epson Corporation), which is an inkjet printer. A4 size Xerox-P (trade name, manufactured by Fuji Xerox Co., Ltd.) is used on the printing paper, and images with mixed text and fills are printed continuously at room temperature. The presence or absence of defects such as these was measured visually. Judgment criteria are as follows.
S: Flying bends / misses do not occur even after continuous printing up to 200 sheets.
A: Flying bends and omissions do not occur with continuous printing up to 200 sheets.
B: In continuous printing up to 100 sheets, flight bending / missing occurred, but there were less than 10 places.
C: At the time of continuous printing up to 100 sheets, 10 or more flying bends / misses occur.

(Evaluation 3) Print quality on plain paper / recycled paper Each ink was mounted on PX-V600 which is an inkjet printer. The print quality (character quality) due to the bleeding of characters when printing 4 to 20 points of Gothic characters on a plain paper / recycled paper in 1 point increments with a print setting of 360 dpi was evaluated. Furthermore, images with different fill densities in 5% increments from 5% to 100% with the same print settings were printed, and the print quality (filled image quality) due to shading unevenness of the printed matter was evaluated. In this evaluation, Xerox Premium Multipurpose 4024 (trade name, manufactured by Xerox Co., Ltd.), Xerox P (trade name, manufactured by Fuji Xerox Co., Ltd.), Hammermill Copy Plus (trade name, manufactured by International Paper) are regenerated as plain paper. Xeorx R (trade name, manufactured by Fuji Xerox Co., Ltd.) was used as paper, and the evaluation was performed visually. Judgment criteria are as follows.

[Character quality]
S: No bleeding is seen in the characters at all points.
A: Slight bleeding is observed with characters of 5 points or less.
B: Due to bleeding, characters of 5 points or less appear thick.
C: The bleeding is remarkable and a character of 5 points or less cannot be determined.

[fill]
S: Almost no shading unevenness is observed in all filled images.
A: Slight shading unevenness is recognized in an image with a filling density of 100%, but there is no practical problem. Level B: Shading unevenness is recognized in an image with a filling density of 50% or more.
C: Light and shade unevenness is observed in all filled images.

(Evaluation 4) Evaluation of coloring property Each ink was mounted in PX-V600 which is an inkjet printer. An image with a fill density of 100% was printed at a print setting of 360 dpi, and the OD value (color developability) was evaluated. In this evaluation, Xerox Premium Multipurpose 4024 (trade name, manufactured by Xerox Co., Ltd.), Xerox P (trade name, manufactured by Fuji Xerox Co., Ltd.), Hammermill Copy Plus (trade name, manufactured by International Paper) are regenerated as plain paper. Xeorx R (trade name, manufactured by Fuji Xerox Co., Ltd.) was used as the paper. For evaluation of image quality, color measurement was performed using a Gretag densitometer (manufactured by Gretag Macbeth Co., Ltd.), and an average value of the OD values of the four papers was obtained for each ink composition. Judgment criteria are as follows.
S: When the OD value is 1.0 or more.
A: When the OD value is 0.95 or more and less than 1.0.
B: When the OD value is 0.90 or more and less than 0.95.
C: When the OD value is less than 0.90.

  The evaluation results of Tests 1 to 4 are summarized in Table 4.

表４から明らかなように、本発明のインク組成物によれば、優れた発色性と滲みを低減した印字品質を得ることが可能であって、かつ、保存安定性、吐出安定性も良好で信頼性が高く、インクジェット記録方法に用いるのに好適なインク組成物である。

As is apparent from Table 4, according to the ink composition of the present invention, it is possible to obtain excellent color developability and print quality with reduced bleeding, and excellent storage stability and ejection stability. The ink composition has high reliability and is suitable for use in an ink jet recording method.

  The present invention is not limited to the above-described embodiment, and can be applied to uses such as writing instrument ink and offset printing ink.

Claims (11)

  At least water, a pigment coated with a water-insoluble polymer, a glycol ether having an HLB value calculated by the Davis method of 4.2 to 8.0, and 1,2-alkanediol. An ink composition characterized by the above.   The ink composition according to claim 1, wherein the alkyl group of the glycol ether has a branched structure.   3. The ink composition according to claim 1, wherein the glycol ether content is 0.1 wt% to 6 wt% with respect to the total amount of the ink composition.   4. The content of the 1,2-alkanediol is 1/2 to 5/1 in a weight ratio with respect to the glycol ether. 5. Ink composition.   The ink composition according to any one of claims 1 to 4, wherein the 1,2-alkanediol is contained in an amount of 1 wt% to 20 wt% with respect to the total amount of the ink composition.   The ink composition according to claim 1, wherein the alkyl group of the glycol ether is a 2-ethylhexyl group.   The ink composition according to claim 1, further comprising a nonionic surfactant.   The ink composition according to any one of claims 1 to 7, wherein the pigment is contained in an amount of 0.5 to 10% by weight based on the total amount of the ink composition.   An ink jet recording method, wherein printing is performed by attaching the ink composition according to any one of claims 1 to 8 to a recording medium.   An ink jet recording method, wherein printing is performed by discharging a droplet of the ink composition according to any one of claims 1 to 8 and attaching the droplet to a recording medium.   11. Recorded matter recorded by the ink jet recording method according to claim 9 or 10.