JP2005154548A - Ink composition, recording method using the same and printed product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which reduces bleeding with resect to plain paper and recycled paper used in general offices and at home and can be printed on two sides of the paper. <P>SOLUTION: The ink composition comprises at least a coloring material, resin fine particles which do not form a film at ambient temperature, a nonionic surface active agent, and a 1,2-alkanediol and/or a glycol ether. It is preferred that the resin fine particles have a glass transition temperature (Tg) of ≥10°C and a minimum film-forming temperature (MFT) of ≥25°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention is an ink composition that has less bleeding and can be printed on both front and back surfaces of plain paper and recycled paper used in general offices and homes, and is particularly suitable for use in an ink jet recording system. Relates to the composition.

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. As the ink, there is known an ink composition that generally includes a coloring material serving as a colorant, water, a water-soluble organic solvent, a surfactant, and the like.
However, with these ink compositions, bleeding occurs particularly when printed on plain paper or recycled paper, and a recorded matter exhibiting sufficient color development cannot be obtained, and ink is reflected on the back surface of the paper due to ink penetration, There was a problem that double-sided printing was difficult.
In general, if the ink permeability is suppressed, the color developability of the recorded image can be improved. However, when an ink composition with suppressed penetration is used, the drying property of the ink on the recording medium decreases. Therefore, when printing using a plurality of inks as in color printing, inks that remain without being dried on the recording medium are mixed with each other to form color bleed, which significantly deteriorates the image quality.

Accordingly, a method has been proposed in which a polymer emulsion in which water-insoluble or hardly soluble color material is contained in polymer fine particles as a color material is used, and the color material stays on the paper surface to obtain an image with little show-through (Patent Document 1 and 2).
Also proposed is a method to reduce bleeding and color bleeding while improving color development by suppressing ink penetration and reducing ink fluidity on the paper surface with an ink composition containing alginic acid or alginate. (See Patent Document 3).
Furthermore, a method for suppressing image bleeding using an ink composition including a colorant which is a charged particle and a resin emulsion having the same polarity as the colorant has been proposed (see Patent Document 4).

JP 2003-96345 A JP 2003-226827 A JP 2003-176432 A JP 2000-351931 A

However, since an ink composition using a polymer emulsion (colored polymer emulsion) in which a polymer fine particle contains a water-insoluble or hardly soluble colorant is insufficient in color developability, the ink composition is used to obtain a desired concentration. A high-concentration colored polymer emulsion is required, and there are problems in ensuring physical property values (viscosity) suitable for the ink jet recording system and reliability such as clogging.
In addition, in the ink composition containing alginic acid or alginate, the ink viscosity rapidly increases as the water in the ink evaporates. There was a problem that the discharge rate became high and the discharge became unstable.
Furthermore, in an ink composition including a colorant that is a charged particle and a resin emulsion having the same polarity as the colorant, the resin emulsion forms a film at an ambient temperature, so that sufficient color developability may not be obtained. There was a problem in the storage stability of the ink.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is an ink composition that can be printed on both front and back surfaces with little bleeding on plain paper and recycled paper. An object of the present invention is to provide an ink composition suitable for use in an ink jet recording system.

As a result of intensive studies, the inventor is characterized by containing at least a coloring material, resin fine particles that do not form a film at ambient temperature, a nonionic surfactant, and 1,2-alkanediol and / or glycol ether. The inventors have obtained knowledge that an ink composition can solve the above problems. The present invention is based on such knowledge, and the configuration of the present invention is as follows.
(1) An ink composition comprising at least a colorant, resin fine particles that do not form a film at ambient temperature, a nonionic surfactant, and 1,2-alkanediol and / or glycol ether.
(2) The ink composition according to (1), wherein the resin fine particles have a glass transition temperature (Tg) of 10 ° C. or higher and a minimum film-forming temperature (MFT) of 25 ° C. or higher.
(3) The ink composition according to (1), wherein the resin fine particles have an average particle size of 100 to 300 nm.
(4) The ink composition according to any one of (1) to (3), wherein the resin fine particles are contained in an amount of 0.5 to 10% by weight based on the total amount of the ink composition.
(5) Any one of (1) to (4), wherein the resin fine particles are selected from an acrylic resin emulsion, a vinyl acetate resin emulsion, a vinyl chloride resin emulsion, and a styrene-acrylic resin emulsion The ink composition described in 1.
(6) The ink composition as described in any one of (1) to (5), which is used in an ink jet recording system.
(7) A recording method for performing printing by attaching the ink composition according to any one of (1) to (6) to a recording medium.
(8) An ink jet recording method, wherein printing is performed by discharging a droplet of the ink composition according to any one of (1) to (6) and attaching the droplet to a recording medium.
(9) A recorded matter recorded by the recording method according to (7) or (8).

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 includes at least a colorant, resin fine particles that do not form a film at ambient temperature, a nonionic surfactant, and 1,2-alkanediol or glycol ether.
Hereinafter, each component will be described in detail.

[Color material]
The ink composition of the present invention contains a color material as a colorant, and examples of the color material include dyes and pigments.

  As the dye, an acid dye, a direct dye, a reactive dye, and a basic dye can be used without any particular limitation. For example, C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9, 45, 249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive black 3, 4, 35, etc. can be used.

  Examples of the pigment include 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, 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. can be used.

These pigments may be used as a pigment dispersion dispersed in an aqueous medium by a dispersant, or a dispersibility-imparting group (hydrophilic functional group and / or salt thereof) may be directly or alkyl group, alkyl ether group, Indirectly bonded via an aryl group or the like, processed as a self-dispersing pigment that is dispersed and / or dissolved in an aqueous medium without a dispersant, and as a pigment dispersion liquid dispersed in an aqueous medium, an ink composition It is preferable to mix.
These pigments preferably have an average particle size in the range of 50 to 250 nm from the viewpoint of storage stability of the ink and prevention of nozzle clogging.
Furthermore, these pigments are preferably contained in the ink of the present invention in the range of 2 to 15% by weight. If the content is less than 2% by weight, the print density (coloring property) may be insufficient, and if the content is more than 15% by weight, there is a problem in reliability such as nozzle clogging or unstable discharge. May occur.

[Resin fine particles]
The ink composition of the present invention contains fine resin particles that do not form a film at ambient temperature. The resin particles in the present invention do not form a film at the ambient temperature in the room, so that the particles remain on the paper as they are, and high color development on plain paper or recycled paper is realized by the action of causing pigment particles to exist on the paper surface.
Here, the presence or absence of film formation at ambient temperature was determined by thinly applying an aqueous solution or aqueous dispersion obtained by dissolving or dispersing resin particles in water on a metal plate such as aluminum and drying at ambient temperature. Judging by observing the condition. Those that form a film at ambient temperature form a transparent continuous film, and those that do not form a film at ambient temperature become a white powder.

  These resins are preferably one or more selected from the group consisting of acrylic resins, vinyl acetate resins, vinyl chloride resins, and styrene-acrylic resins. These resins can be used in either a single phase structure or a multiphase structure (core-shell type).

  Furthermore, the resin fine particles used in the present invention are preferably blended in the ink composition in the form of emulsion of resin fine particles. The reason for this is that even if the resin fine particles are added to the ink composition as they are, dispersion of the resin particles may be insufficient, so that the emulsion form is preferable for the production of the ink composition.

The emulsion of resin fine particles can be obtained by a known emulsion polymerization method. For example, it can be obtained by emulsion polymerization of an unsaturated monomer (such as an unsaturated vinyl monomer) in water containing a polymerization initiator and a surfactant.
Examples of unsaturated monomers include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl cyanide compounds generally used in emulsion polymerization. Examples include monomers, halogenated monomers, olefin monomers, and diene monomers. Furthermore, specific examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate. Acrylic acid esters such as dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl Methacrylate, n-hexyl methacrylate, 2-ethyl Hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, methacrylic esters such as phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, and vinyl esters such as vinyl acetate; vinyl such as acrylonitrile and methacrylonitrile Cyanides; halogenated monomers such as vinylidene chloride and vinyl chloride; simple aromatic vinyl such as styrene, α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene Olefins such as ethylene and propylene, dienes such as butadiene and chloroprene, vinyl ethers, vinyl ketones and vinyl pyrrolides Vinyl monomers such as ethylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid; acrylamides such as acrylamide, methacrylamide and N, N′-dimethylacrylamide; 2-hydroxy Examples thereof include hydroxyl group-containing monomers such as ethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate, and these can be used alone or in combination of two or more.

A crosslinkable monomer having two or more polymerizable double bonds can also be used. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2 ′ -Diacrylate compounds such as bis (4-acryloxydiethoxyphenyl) propane, triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate Tetraacrylate compounds such as ditrimethylol tetraacrylate, tetramethylol methane tetraacrylate, pentaerythritol tetraacrylate, hexaacrylate compounds such as dipentaerythritol hexaacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol di Methacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate Methacrylate, 2, Examples include dimethacrylate compounds such as 2′-bis (4-methacryloxydiethoxyphenyl) propane, trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate, methylenebisacrylamide, and divinylbenzene. It can be used alone or in combination.
In addition to the polymerization initiator and surfactant used in emulsion polymerization, a chain transfer agent, further a neutralizing agent, and the like may be used according to a conventional method. In particular, ammonia and inorganic alkali hydroxides such as sodium hydroxide and potassium hydroxide are preferred as the neutralizing agent.

  On the other hand, when the average particle diameter of the resin fine particles in the present invention is in the range of 50 nm to 300 nm, the coloring material is retained on the paper surface and the effect of improving the color developability is exhibited, and the bleeding can be suppressed. When the average particle diameter of the resin fine particles is smaller than 50 nm, the effect of retaining the coloring material on the paper surface and the effect of suppressing bleeding are not effectively expressed. When the average particle diameter is larger than 300 nm, when used in the ink jet recording method. There is a problem with nozzle clogging and ejection stability. In addition, these average particle diameters can be obtained by particle size measurement using a Microtrac UPA150 (manufactured by Microtrac) or a particle size distribution analyzer LPA3100 (manufactured by Otsuka Electronics Co., Ltd.).

  In the present invention, the resin fine particles are present in the range of 0.5 to 10% by weight from the viewpoint of more effectively obtaining the effects of the present invention, ink jet proper physical property values, reliability (clogging, ejection stability, etc.) of the ink composition. It is preferable to be contained in the ink composition of the invention.

[Nonionic surfactant]
Nonionic surfactants are particularly preferable from the viewpoint of obtaining an ink composition with less foaming and foaming. Specific examples include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene nonylphenyl ether, polyoxyethylene nonionic surfactants, and polyoxyethylene nonylphenyl ethers. Ethers such as oxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxy Ethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, Esters such as bitane monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate, silicon surfactants such as dimethylpolysiloxane, other fluorine alkyl esters, perfluoroalkyl carboxylates, etc. Examples include fluorine-containing surfactants. Among these, acetylene glycol surfactants and acetylene alcohol surfactants are preferable in that print quality with less bleeding can be obtained. Further specific examples of the acetylene glycol surfactant and the acetylene alcohol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4- Examples include octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3ol, and are also commercially available. For example, Surfynol 104, 82, 465, 485 manufactured by Air Products, Examples include TG, Nissin Chemical's Olfin STG, Olfin E1010, and the like.

[Water-soluble organic solvent]
The ink composition of the present invention contains 1,2-alkanediol and / or glycol ether. These can suitably control the permeability and bleeding of the ink to the paper, and are also suitable for imparting ink drying properties.

  Specific examples of 1,2-alkanediol include 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol, 4-methyl-1,2-pentanediol and the like. Among these, 1,2-octanediol and 1,2-hexanediol can be preferably used. Specific examples of the glycol ether include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether. , Ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, triethylene Glycol mono-n-butyl ether, -Methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether , Dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether, and the like. Among these, diethylene glycol mono-n-butyl ether and triethylene glycol mono-n-butyl ether can be suitably used. These solvents may be used alone or in combination of two or more, and are preferably contained in the ink composition in an amount of 2 to 15% by weight from the viewpoint of ensuring appropriate permeability and drying properties.

  Further, for the purpose of preventing clogging in the vicinity of the nozzle of the inkjet head, it is preferable to add a water-soluble organic solvent having a wetting effect. 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 , (Sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose and other sugars, sugar alcohols, hyaluronic acids, ureas, etc., so-called solid wetting agents, etano C1-C4 alkyl alcohols such as methanol, butanol, propanol, isopropanol, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide Sorbitol, 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. From the viewpoint of ensuring appropriate physical properties (such as viscosity) of the ink composition, ensuring printing quality, and reliability. It is preferable that 10-50 weight% is contained in a composition.

  The water contained in the ink composition of the present invention is a main solvent, and it is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled 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 composition.

[Other]
Furthermore, the ink composition of the present invention preferably contains a pH adjuster.
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.

  If necessary, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid, etc. can be used as pH buffering agents, antifoaming agents, antioxidants Agents, ultraviolet absorbers, antiseptic / antifungal agents, and the like can also be added.

  The ink composition of the 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 excellent blurring and show-through and excellent print quality.

  The ink jet recording apparatus of the present invention is an ink jet recording apparatus that performs recording by ejecting ink droplets and attaching the droplets to a recording medium, and uses at least the ink composition having the above-described configuration as ink. . In the present invention, any recording apparatus employing any of the above-described inkjet recording methods can be used.

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

[Preparation of resin fine particles]
A resin dispersion (emulsion) having resin particles as dispersed particles was prepared by the following method. The presence or absence of film formation was judged visually by applying the emulsion thinly on an aluminum plate in an environment of room ambient temperature of about 25 ° C. Further, the particle diameter is a value of an average particle diameter measured by a particle size distribution measurement of Microtrac UPA150 (manufactured by Microtrac).

(Method for producing emulsion 1)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 1000 g of ion-exchanged water and 6.5 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. Maintaining the internal temperature at 70 ° C., adding 4 g of potassium persulfate as a polymerization initiator, dissolving, and previously stirring 450 g of ion exchange water, 2 g of sodium lauryl sulfate, 20 g of acrylamide, 550 g of styrene, 200 g of butyl acrylate, and 30 g of methacrylic acid The emulsion prepared in addition to the chemical conversion was continuously dropped into the reaction solution over 4 hours. After completion of the dropwise addition, aging was performed for 3 hours.
After cooling the obtained aqueous emulsion to room temperature, ion exchange water and ammonia water were added to adjust the solid content to 37% by weight and pH 8.
The obtained aqueous emulsion was confirmed not to form a film at room ambient temperature of about 25 ° C., and the average particle size of the resin particles was 70 nm.

(Method for producing emulsion 2)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 800 g of ion-exchanged water and 1 g of sodium lauryl sulfate, and the temperature was raised to 75 ° C. while purging with nitrogen under stirring. The internal temperature was kept at 75 ° C., 6 g of potassium persulfate was added as a polymerization initiator, and after dissolution, 450 g of ion exchange water, 2 g of sodium lauryl sulfate, 20 g of acrylamide, 600 g of methyl methacrylate, 215 g of butyl acrylate, and 30 g of methacrylic acid were added. The emulsion prepared in addition to stirring was continuously dropped into the reaction solution over 5 hours. After completion of the dropwise addition, aging was performed for 3 hours. The obtained aqueous emulsion was cooled to room temperature, and then ion-exchanged water and an aqueous sodium hydroxide solution were added to adjust the solid content to 40% by weight and pH 8.
It was confirmed that the obtained aqueous emulsion did not form a film at room ambient temperature of about 25 ° C., and the average particle size of the resin particles was 250 nm.

(Method for producing emulsion 3)
A reaction vessel equipped with a stirrer, a reflux condenser, a dropping device, and a thermometer was charged with 900 g of ion exchange water and 3 g of sodium lauryl sulfate, and the temperature was raised to 70 ° C. while purging with nitrogen under stirring. The internal temperature is kept at 70 ° C., 4 g of potassium persulfate is added as a polymerization initiator, and after dissolution, 450 g of ion exchange water, 3 g of sodium lauryl sulfate, 20 g of acrylamide, 300 g of styrene, 640 g of butyl acrylate, and 30 g of methacrylic acid are stirred in advance. The emulsion prepared in addition to the chemical conversion was continuously dropped into the reaction solution over 4 hours. After completion of the dropwise addition, aging was performed for 3 hours. The resulting aqueous emulsion was cooled to room temperature, and then ion-exchanged water and 5% aqueous sodium hydroxide solution were added to adjust the solid content to 40% by weight and pH 8.
The obtained aqueous emulsion was confirmed to form a film at a room ambient temperature of about 25 ° C., and the average particle size of the resin particles was 90 nm.

[Preparation of ink composition]
After mixing each component in the ratio shown in Table 1 and stirring for 2 hours at room temperature, the mixture was filtered through a membrane filter having a pore size of 5 μm, and each of the aqueous ink compositions of Examples 1 to 5 and Comparative Examples 1 and 2 was used. Prepared. However, the addition amounts shown in Table 1 are all expressed as weight percent concentrations, and the addition amounts of the pigment dispersion and the resin emulsion are expressed as solid content concentrations, respectively. The “remaining amount” of ion-exchanged water means adding ion-exchanged water so that the total amount of ink becomes 100 parts.

The following evaluations were performed on the ink compositions of Examples 1 to 5 and Comparative Examples 1 and 2 prepared in Table 1.
(Test 1) Character and solid prints were printed with a color developing inkjet printer EM-930C (manufactured by Seiko Epson Corporation) at a resolution of 720 dpi. As recording media, Xerox P, Xerox R (trade name: manufactured by Fuji Xerox Co., Ltd., Xerox 4024 (trade name: Xerox Co. (USA)), Recycle Cut R-100 (trade name: manufactured by Oji Paper Co., Ltd.) After printing, the recorded material was allowed to stand for 1 hour in a general environment, and the OD value of the solid portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). The measured results were judged based on the following criteria, and the judgment was made by taking an average of evaluations on various papers.
A: When the OD value is 1.30 or more for all papers B; When the OD value is 1.20 or more and less than 1.30 C; When the OD value is less than 1.20

(Test 2) Bleeding Bleeding of outlines of characters printed in Test 1 was determined based on the following criteria.
A: When the recorded material is magnified 5 times with a stereomicroscope, blurring is not recognized.
B: When the recorded material is viewed at a distance of 30 cm from the eyes, blurring is not recognized.
C: Bleeding is conspicuous when the recorded material is viewed 30 cm away from the eyes.

(Test 3) The OD value of the back side of the solid portion printed in the show-through test 1 was measured, and the show-through was determined based on the following criteria.
A: When the back surface OD value is less than 0.03 B: When the back surface OD value is 0.03 or more and less than 0.06 C; When the OD value is 0.06 or more

(Test 4) Storage stability In a state where 50 g of the ink composition was put in an aluminum pack, it was left in an environment of 70 ° C. for 1 week. After standing, whether or not foreign matter (precipitate) has been generated, and for those that have no foreign matter, further changes in physical properties (viscosity, surface tension, pH, resin particle size) are determined based on the following criteria: did.
A: There is no generation of foreign matter and no change in physical properties.
B: Foreign matter is not generated, but the physical properties slightly change.
C: Foreign matter is generated or the physical properties are remarkably changed.

(Test 5) Using each ink composition prepared for ejection stability, solid and line patterns were continuously printed with an inkjet printer EM-930C at room temperature. The number of cleanings of the printer nozzle that is performed as a return operation to normal printing when ink dots are missing or bent in 100 pages of printing was evaluated and determined based on the following criteria.
A: Zero cleaning.
B: Cleaning 1 or 2 times.
C: Cleaning 3 times or more.

(Test 6) Clogging Ink jet printer EM-930C was used to fill each head with ink, and after confirming that the ink composition was discharged from all nozzles, the ink cartridge was not present and the home It was left in a 40 ° C. environment for one week at a position outside the position (the head was displaced from the position of the cap provided on the printer and the head was not capped). After being allowed to stand, the number of cleanings required until the ink composition was discharged again from all nozzles was examined, and a determination was made based on the following criteria.
A: One cleaning.
B: 2 to 5 cleanings.
C: Cleaning 6 times or more.

  The above evaluation determination results are summarized in Table 2.

As is apparent from Table 2, according to the ink composition of the present invention, there is provided an ink composition capable of printing on both the front and back sides with a clear image and less bleeding even on recorded paper on plain paper or recycled paper. The
In addition, the ink composition of the present invention is excellent in ejection stability and storage stability, and has good recovery from nozzle clogging in inkjet recording printers. It is an ink composition suitable for use.

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

Claims (9)

  An ink composition comprising at least a coloring material, resin fine particles that do not form a film at ambient temperature, a nonionic surfactant, and 1,2 alkanediol and / or glycol ether.   2. The ink composition according to claim 1, wherein the resin fine particles have a glass transition temperature (Tg) of 10 ° C. or higher and a minimum film-forming temperature (MFT) of 25 ° C. or higher.   The ink composition according to claim 1, wherein the resin fine particles have an average particle diameter of 50 to 300 nm.   The ink composition according to claim 1, wherein the resin fine particles are contained in an amount of 0.5 to 10% by weight based on the total amount of the ink composition.   The ink composition according to claim 1, wherein the resin fine particles are selected from an acrylic resin emulsion, a vinyl acetate resin emulsion, a vinyl chloride resin emulsion, and a styrene-acrylic resin emulsion. Stuff.   The ink composition according to claim 1, wherein the ink composition is used in an ink jet recording system.   A recording method for performing printing by adhering the ink composition according to claim 1 to a recording medium.   An ink jet recording method, wherein printing is performed by discharging a droplet of the ink composition according to claim 1 and attaching the droplet to a recording medium.   A recorded matter recorded by the recording method according to claim 7.