JP2007161982A - Ink composition for inkjet recording, ink cartridge using the same, recording method, recording system and recorded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition for inkjet recording, which shows a low viscosity despite of its high concentration of solid components, secures a high OD-value/fixability as one of printing characteristics and is capable of securing reliability in terms of recovery from clogging, high-temperature jetting stability, etc. <P>SOLUTION: The ink composition for inkjet recording contains a self-dispersing pigment and two kinds of resin particles each having a glass transition temperature (Tg) of below 0°C, wherein the self-dispersing pigment and the two kinds of the resin particles are contained as solid components and account for ≥10 wt.% in total. The two kinds of resin particles both have OH groups within the molecule and share a common skeleton. The ink composition for inkjet recording further contains both an inorganic alkali and an organic alkali. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is an ink for ink jet recording which can ensure reliability such as low viscosity, high OD value / fixing property, clogging recovery property, ejection stability at high temperature, etc. while being a high solid content ink. The present invention relates to a composition, an ink cartridge using the composition, a recording method, a recording system, and a recorded matter.

  Conventionally, many ink jet recording methods using an ink composition containing a pigment dispersion and a resin emulsion have been used (Patent Documents 1, 2, and 3).

However, the composition of the ink composition in the conventional ink jet recording method is difficult to ensure the characteristics such as high OD value and fixability in the low-viscosity ink, clogging recovery, and ejection stability at high temperature. It is.
Japanese Patent Laid-Open No. 1-217088 Japanese Patent Laid-Open No. 3-60068 JP-A-4-18462 Japanese translation of PCT publication No. 2003-535949

  Therefore, the present invention realizes a low viscosity while being a high solid content ink, ensures a high OD value and fixability as printing characteristics, and further improves reliability such as clogging recovery and ejection stability at high temperatures. It is an object of the present invention to provide an ink composition for ink jet recording that can also ensure the above.

  Another object of the present invention is to provide an ink cartridge, a recording method, a recording system, and a recorded matter using the above-described excellent ink composition for inkjet recording.

The present invention relates to the following 1. The object is achieved by providing the invention.
1. An ink composition for ink jet recording comprising a self-dispersing pigment and two resin particles having a glass transition point (Tg) of less than 0 ° C,
The self-dispersing pigment and the two types of resin particles contain a total content of 10% by weight or more, and both the two types of resin particles have an OH group in the molecule and have the same skeleton. Ink composition for inkjet recording.

The present invention also provides the following 2. -15. Each invention is provided.
2. 2. The ink composition for ink jet recording according to 1, wherein at least one of the two kinds of resin particles is blended in the form of an emulsion obtained by emulsion polymerization of an unsaturated monomer.

  3. 3. The ink composition for ink jet recording according to 1 or 2, wherein the content of the self-dispersing pigment is 6% by weight or more in the ink composition.

  4). The two kinds of resin particles include a first resin particle having a particle size in the range of 40 to 70 nm and a second resin particle having a particle size in the range of 110 to 190 nm and a glass transition point of 10 ° C. or less. 4. The ink composition for ink jet recording according to any one of 1 to 3 above.

  5. 5. The ink composition for ink jet recording according to 4, wherein the first resin particles are both composed of a styrene-acrylic skeleton molecule or an acrylic skeleton molecule.

  6). 6. The ink composition for inkjet recording according to 4 or 5, wherein the content of the first resin particles is 0.5 to 2% by weight in the ink composition.

  7). 7. The ink composition for ink jet recording according to any one of 4 to 6, wherein the content of the second resin particles is 2 to 5% by weight in the ink composition.

  8). 8. The ink composition for ink jet recording according to any one of 4 to 7, wherein a weight ratio of the first resin particles to the second resin particles (the former: the latter) is 1:10 to 10: 1. .

  9. Furthermore, the ink composition for inkjet recording in any one of Claims 1-8 which contains both an inorganic alkali and an organic alkali as an alkali additive.

  10. Furthermore, the ink composition for inkjet recording in any one of said 1-9 containing an acetylene glycol type surfactant.

  11. Furthermore, the ink composition for inkjet recording in any one of said 1-10 containing water-soluble glycols.

  12 An ink cartridge comprising the ink composition for ink jet recording according to any one of 1 to 11 above.

  13. 12. A recording method for forming an image using the ink composition for ink jet recording according to any one of 1 to 11 above.

  14 A recording system for forming an image using the ink composition for ink jet recording according to any one of 1 to 11 above.

  15. A recorded matter in which an image is formed using the ink composition for inkjet recording according to any one of 1 to 11 above.

  According to the present invention, although it is a high solid content ink, it achieves a low viscosity, ensures a high OD value / fixability as printing characteristics, and further improves reliability such as clogging recovery and ejection stability at high temperatures. The ink composition for inkjet recording which can also ensure this is provided.

  In addition, according to the present invention, there are provided an ink cartridge, a recording method, a recording system, and a recorded matter using the excellent ink composition for inkjet recording.

  Hereinafter, the ink composition for ink jet recording according to the present invention will be described based on preferred embodiments thereof.

  The ink composition for ink-jet recording of the present invention is a recording liquid for discharging as droplets from a printer head of an ink-jet printer in order to record and form images such as characters and figures on a recording medium such as paper by a so-called ink-jet recording method. (Hereinafter, the ink composition for ink jet recording of the present invention may be simply referred to as “the ink composition of the present invention”).

  As described above, the ink composition of the present invention is an ink composition for ink jet recording comprising a self-dispersing pigment and two resin particles having a glass transition point (Tg) of less than 0 ° C. The dispersion type pigment and the two kinds of resin particles contain a total of 10% by weight or more as a solid content, and both the two kinds of resin particles have an OH group in the molecule and have the same skeleton.

  Since the ink composition of the present invention has such a configuration, it achieves a low viscosity while being a high solid content ink, and has a high OD value (Optical Density) and fixing property as printing characteristics. Reliability such as clogging recovery and discharge stability at high temperatures can also be ensured.

The self-dispersing pigment used in the present invention (hereinafter referred to as “component A: self-dispersing pigment (A)”) has —COOH, —CHO, —OH, —SO ₃ H and these on the surface of the pigment. A pigment treated so as to have one or more functional groups (dispersibility-imparting groups) selected from the group consisting of salts in a water-based ink composition without adding a dispersant separately. It can be uniformly dispersed. The term “dispersed” as used herein refers to a state in which the self-dispersing pigment (A) is stably present in water without a dispersant, and is not only in a dispersed state but also dissolved. It also includes those in state. The ink composition containing the self-dispersing pigment (A) is more stable in dispersion than a normal ink composition containing a non-self-dispersing pigment other than the self-dispersing pigment (A) and a dispersing agent. In addition, since the viscosity of the ink composition is moderate, it is possible to contain a larger amount of pigment, and in particular, images such as characters and figures having excellent color development properties on plain paper can be formed. Can do. Further, the ink composition containing the self-dispersing pigment (A) does not cause a decrease in fluidity even when a penetrant effective for improving the printing quality (described later) is blended. The print quality can be improved by using together.

  As the pigment capable of forming the self-dispersing pigment (A), the same pigments as those used in ordinary ink jet recording ink compositions are used. For example, carbon black, azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment , Phthalocyanine pigment, perylene pigment, perinone pigment, quinacridone pigment, thioindigo pigment, isoindolinone pigment, quinofullerone pigment, dioxazine pigment, anthraquinone pigment, nitro pigment, nitroso pigment, aniline black and other organic pigments, titanium white, zinc white, lead Inorganic pigments such as white, carbon black, bengara, vermilion, cadmium red, yellow lead, ultramarine, cobalt blue, cobalt violet, and zinc chromate are included. Further, any pigment that is not described in the color index can be used as long as it can be dispersed in the aqueous phase. Of these, azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene pigments, perinone pigments, quinacridone pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, dioxazine pigments, and anthraquinone pigment systems are used. It is preferable. The “pigment” means a particulate solid that is usually insoluble in water, solvent, oil, or the like.

  In order to prepare the self-dispersing pigment (A), a functional group or a molecule containing a functional group is coordinated to the surface of the pigment by chemical treatment such as vacuum plasma or chemical treatment, and chemical bonding such as grafting is performed. Can be obtained. For example, it can be obtained by the method described in JP-A-8-3498. Further, as the self-dispersing pigment (A), a commercially available product can be used. Preferred examples include “Microjet CW1” manufactured by Orient Chemical Industries, Ltd., and “CAB-O-” manufactured by Cabot Corporation. JET 200 "," CAB-O-JET 300 "and the like.

The self-dispersing pigment (A) is prepared, for example, as follows.
[Example of Preparation Method of Self-Dispersion Pigment (A) (Surface Oxidation Treatment-Sulfonation Treatment of Pigment)]
A pigment is added to the solvent, and this is subjected to high-speed shearing dispersion with a high-speed mixer or the like, or impact-dispersed with a bead mill or jet mill to obtain a slurry-like pigment dispersion. While slowly stirring the pigment dispersion, a treatment agent containing sulfur (sulfamic acid, fuming sulfuric acid, sulfuric acid, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, etc.) is added, and the pigment dispersion is heated to 60 to 200 ° C. Then, the dispersibility-imparting group is introduced on the pigment surface. After removing the solvent from the pigment dispersion, the treatment agent containing sulfur is removed by repeating washing with water, ultrafiltration, reverse osmosis, centrifugation, filtration and the like to obtain a self-dispersion pigment (A).

  The self-dispersing pigment (A) preferably has an average particle size of 10 to 300 nm, preferably 40 to 150 nm, from the viewpoint of improving the storage stability of the ink and preventing nozzle clogging. Further preferred.

  The content of the self-dispersing pigment (A) is preferably 6% by weight or more, more preferably 7 to 10% by weight in the ink composition of the present invention in that a sufficient OD value can be obtained. The self-dispersing pigment (A) is an ink having a total solid content of 10% by weight or more together with two kinds of resin particles (preferably contained in the form of emulsion) having a glass transition point (Tg) below 0 ° C. Contained in the composition.

  Other examples of the self-dispersing pigment (A) include pigments that have been surface oxidized by a hypochlorite oxidation method, an ozone oxidation treatment method (see Japanese Patent Application Publication No. 2003-535949: Patent Document 4, etc.), and the like. It is done.

  In the present invention, two kinds of resin particles having a glass transition point (Tg) of less than 0 ° C. are used. Here, of these two types of resin particles, one is a first resin particle (hereinafter referred to as B component: first resin particle (B)), and the other is a second resin particle (hereinafter referred to as “B”). C component: referred to as second resin particles (C)). The first resin particles (B) and the second resin particles (C) both have OH groups in the molecule and have the same skeleton.

  As the first resin particles (B), those having a particle diameter in the range of 40 to 70 nm are preferably used. When the particle size is less than 40 nm, the viscosity of the ink composition is increased, and there is a possibility that the ejection stability and clogging recovery properties may be insufficient. By using the first resin particles (B), the fixing property can be secured in a small amount, the ejection stability and the clogging recovery property can be secured while the viscosity of the ink composition is lowered, and the OD value is not lowered. Can be.

  The content of the first resin particles (B) is preferably 0.5 to 2% by weight in the ink composition. When the content exceeds 2% by weight, the viscosity of the ink composition is increased, the ejection stability and clogging recovery properties are insufficient, and the OD value may be lowered.

  On the other hand, as the second resin particles (C), those having a particle size in the range of 110 to 190 nm and a glass transition point (Tg) of 10 ° C. or less are preferably used. By setting the particle size within this range, an appropriate OD value and fixability can be improved, and by setting the Tg to 10 ° C. or less, the fixability can be sufficiently secured. In particular, those having a Tg of −10 ° C. or lower are more preferable from the viewpoint of improvement in fixability.

  The content of the second resin particles (C) is preferably 2 to 5% by weight in the ink composition. If the content exceeds 5% by weight, the viscosity of the ink composition increases, and the ejection stability and clogging recovery properties are insufficient.

  In the present invention, the glass transition point (Tg) can be measured using a usual method, for example, a thermal analyzer such as a differential scanning calorimeter (DSC). An example of the thermal analyzer is SSC5000 manufactured by Seiko Electronics. The glass transition point (Tg) can be evaluated as a calculated value of the glass transition point when the resin is a copolymer. The glass transition point (Tg) of the copolymer and the methodology for its evaluation are as follows. The glass transition point (Tg) of a copolymer having a specific monomer composition can be determined by calculation using the Fox equation. Here, the Fox formula is for calculating the Tg of the copolymer based on the Tg of the homopolymer of the monomer for each monomer forming the copolymer, The details are described in Bulletin of the American Physical Society, Series 2, Vol. 1, No. 3, p. 123 (1956). The concept of the term “calculated glass transition point” used in the specification of the present invention includes a glass transition point calculated by the Fox equation. For example, the Tg of the homopolymer of various monomers serving as the basis for calculating the Tg of the copolymer according to the Fox formula is, for example, Polymer Data Handbook Fundamentals (Polymer Society), pages 525-546. Or actual values measured by a normal method can be employed.

  In the present invention, as the resin applicable to the first resin particle (B) and the second resin particle (C), both resin particles both have OH groups in the molecule and have the same skeleton. Although it does not restrict | limit in particular, For example, an acrylic resin, a urethane resin, an epoxy resin, a polyolefin resin etc. are mentioned. In particular, from the viewpoint of clogging recovery and printed matter fixability, the first resin particles (B) and the second resin particles (C) are both composed of styrene-acrylic skeleton molecules. On the other hand, from the viewpoint of improving the fixability of the ink composition to the recording medium, it is preferable that both the first resin particles (B) and the second resin particles (C) are composed of molecules of an acrylic skeleton.

  When these resins are used, the first resin particles (B) and the second resin particles (C) are used as one or more kinds as the same skeleton, and those having the skeleton described above are preferred. At least one of the first resin particles (B) and the second resin particles (C) is in the form of an emulsion (for example, so-called “acrylic emulsion”) of resin particles obtained by emulsion polymerization of an unsaturated monomer. It is preferable to be blended in the ink composition. The reason is that, even if the resin 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 is preferably an acrylic emulsion from the viewpoint of storage stability of the ink composition.

  An emulsion of resin particles (such as an acrylic emulsion) 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 ether, vinyl ketone, vinyl pyrrolide 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 Dimethacrylate, 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, , 2′-bis (4-methacryloxydiethoxyphenyl) propane and other dimethacrylate compounds, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate and other trimethacrylate compounds, methylenebisacrylamide, divinylbenzene and the like. Can be used alone or in admixture of two or more.

  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.

  In the present invention, the first resin particles (B) and the second resin particles (C) may be mixed with other components of the ink composition as fine particle powder, but preferably the resin particles are dispersed in an aqueous medium. It is preferably mixed with the other components of the ink composition after being in the form of an emulsion (polymer emulsion).

  The weight ratio (B / C) between the first resin particles (B) and the second resin particles (C) is in terms of clogging recovery, fixing properties, and color development (OD value). It is preferably 10/1 to 1/10.

  Moreover, as a 1st resin particle (B) and a 2nd resin particle (C), any of a single phase structure and a multiphase structure (core-shell type) can be used.

The first resin particles (B) and the second resin particles (C) are formed as emulsions in the ink composition of the present invention in terms of ink adjustment for adjusting uniform ink and ink stability. It is preferable to mix.
In the present invention, the term “resin particles” refers to particles in which a water-insoluble resin is dispersed in the form of particles in a dispersion medium mainly composed of water, or the water-insoluble resin is particles in a dispersion medium mainly composed of water. It means that which is dispersed in a shape, and further includes the dried product.
In the present invention, the term “emulsion” means a solid / liquid dispersion called dispersion, latex or suspension.

  In addition, the emulsion is preferably anionic from the viewpoint of improving the dispersion stability of the self-dispersing pigment (A) described above. From the same point of view, when a pigment having a cationic surface (for example, one dispersed with a cationic group by surface treatment) is used, the emulsion is preferably cationic.

An emulsion is manufactured as follows, for example.
[Emulsion production method example]
In a reaction vessel equipped with a dropping device, a thermometer, a water-cooled reflux condenser and a stirrer, 100 parts of ion-exchanged water is added, and 0.2 part of a polymerization initiator is added while stirring at a temperature of 70 ° C. in a nitrogen atmosphere. To this, a separately prepared monomer solution is dropped and subjected to a polymerization reaction to prepare a primary substance. Thereafter, at a temperature of 70 ° C., 2 parts of a 10% aqueous solution of a polymerization initiator is added to the primary substance and stirred, and a separately prepared reaction solution is added and stirred to cause a polymerization reaction to obtain a polymerization reaction product. . The polymerization reaction product is neutralized with a neutralizing agent and adjusted to have a pH of 8 to 8.5, then filtered through a 0.3 μm filter to remove coarse particles, and resin particles are made into dispersoids. To obtain an emulsion.

  As the polymerization initiator, those used for normal radical polymerization are used, for example, potassium persulfate, ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, Examples include peracetic acid, cumene hydroperoxide, t-butyl hydroxy peroxide, paramentane hydroxy peroxide, and the like. In particular, as described above, when the polymerization reaction is performed in water, a water-soluble polymerization initiator is preferable.

  Moreover, as an emulsifier used by a polymerization reaction, what is generally used as an anionic surfactant, a nonionic surfactant, or an amphoteric surfactant other than sodium lauryl sulfate is mentioned, for example.

  Examples of the chain transfer agent used in the polymerization reaction include t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, xanthogens such as dimethylxanthogen disulfide, diisobutylxanthogen disulfide, dipentene, indene, 1,4- Examples include cyclohexadiene, dihydrofuran, and xanthene.

  The ink composition of the present invention is usually a water-based ink composition containing water, preferably ion-exchanged water, as a solvent.

  The ink composition of the present invention can also use an organic solvent in combination with water as a solvent. Such an organic solvent has compatibility with water, improves the penetrability of the ink composition into the recording medium and prevents clogging of the nozzles, and components in the ink composition such as a penetrant described later. Are preferable, for example, ethanol, methanol, butanol, propanol, isopropanol and other C1-C4 alkyl alcohols, 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 Cole mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-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, Glycol ethers such as dipropylene glycol mono-iso-propyl ether, 2-pyrrolidone, Lumamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, diacetin, triacetin, sulfolane and the like, and one or more of these are preferably used in the ink composition of the present invention at 0 to 10% by weight. be able to.

  The ink composition of the present invention preferably contains an acetylene glycol surfactant from the viewpoint of improving printing quality. Examples of such acetylene glycol surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 3,6-dimethyl-4-octyne-3,6-diol. 3,5-dimethyl-1-hexyne-3ol, or a substance obtained by adding an average of 1 to 30 ethyleneoxy groups or propyleneoxy groups to each of a plurality of hydroxyl groups in each of these substances. In addition, as the acetylene glycol surfactant, a commercially available product can be used, and examples thereof include “Surfinol 104PG50, 465” (all trade names, manufactured by Air Products and Chemicals, Inc.). These 1 type (s) or 2 or more types can be used.

  The content of the acetylene glycol surfactant is preferably 0.1 to 3% by weight, more preferably 0.5 to 1.5% by weight in the ink composition of the present invention.

  The ink composition of the present invention preferably contains a water-soluble glycol in order to prevent clogging of the nozzle and improve reliability. Examples of such water-soluble glycols include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol having a molecular weight of 2000 or less, trimethylene glycol, and isobutylene. A glycol etc. are mentioned, These 1 type (s) or 2 or more types can be used. In particular, glycerin is preferable from the viewpoint of improving clogging recovery.

  The content of the water-soluble glycol is preferably 1 to 30% by weight in the ink composition of the present invention.

The ink composition of the present invention preferably contains a penetrating agent in order to further improve the fixability to a recording medium and to improve the abrasion resistance of images such as characters and graphics to be recorded. Examples of such penetrants include 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,2-alkanediol (such as 1,2-hexanediol), and 1,6-hexane. Divalent alcohol such as diol, diethylene glycol mono-n-butyl ether (DEGmBE), diethylene glycol mono-t-butyl ether (DEGMTBE), triethylene glycol mono-n-butyl ether (TEGmBE), propylene glycol mono-n-butyl ether (PGmBE) , Dipropylene glycol mono-n-butyl ether (DPGmBE) and one or more selected from the group consisting of compounds represented by the following general formula (I) are preferable, and DEGmBE, TEGmBE, and DPGmBE are particularly preferable. In the following general formula (I), m and n represent the presence in the system, and PO and EO may be added in blocks or randomly.
RO- (PO) _m- (EO) _n- H (I)
(In the formula, R represents an alkyl group having 4 to 10 carbon atoms, PO represents a propyleneoxy group, and EO represents an ethyleneoxy group. M ≧ 1, n ≧ 0, m + n ≦ 20.)

  The content of the penetrant is preferably 1 to 20% by weight in the ink composition of the present invention in terms of improving the penetrability and quick-drying property of the ink composition and effectively preventing the occurrence of ink bleeding.

  In addition, the ink composition of the present invention may contain a surfactant other than the acetylene glycol surfactant in order to improve the abrasion resistance of images such as characters and figures, as in the penetrant. it can. Examples of such surfactants include, as amphoteric surfactants, lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine. Polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, non-ionic surfactants such as polyoctyl polyaminoethylglycine and other imidazoline derivatives Ethers such as ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxy Tylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate, etc. Examples thereof include silicon surfactants such as ester and dimethylpolysiloxane, fluorine-containing surfactants such as other fluorine alkyl esters and perfluoroalkyl carboxylates, and the use of one or more of these. it can.

  Further, like the water-soluble glycols, the ink composition of the present invention may contain a saccharide, an antifungal agent, and an antiseptic agent to prevent nozzle clogging.

  Examples of the saccharide include glucose, mannose, fructose, ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucosose, maltose, cellobiose, sucrose, trehalose, maltotriose, alginic acid and salts thereof, cyclodextrins, and celluloses. These can be used, and one or more of these can be used in the ink composition of the present invention, preferably at 0 to 15% by weight.

  Examples of the antifungal agent / preservative include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazoline-3 -On (AVECIA's Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like, and one or more of these are preferably added to the ink composition of the present invention in an amount of 0.00. It can be used at 01 to 0.5% by weight.

  The ink composition of the present invention preferably contains a chelating agent such as EDTA from the viewpoint of ensuring reliability such as prevention of clogging and ejection stability, and the ink composition of the present invention preferably contains 0.01 to It can be used at 0.5% by weight.

  In the ink composition of the present invention, when the surface of the self-dispersing pigment (A) is anionic, the pH is preferably 6 to 11 from the viewpoint of improvement in printing density and liquid stability. More preferably, it is 10.

  In order to make the pH of the ink composition of the present invention within the above range, as additives, inorganic alkalis such as sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia, triethanolamine, ethyldiethanolamine, diethyl It is preferable to contain alkali additives such as organic alkalis such as tertiary amines having 6 to 10 carbon atoms such as ethanolamine and tripropanolamine.

  Here, the alkali additive that can be used in the ink composition of the present invention is a combination of at least one inorganic alkali and at least one organic alkali used in combination with clogging recovery and waste liquid system. It is preferable from the viewpoint of improving reliability such as redispersibility. In particular, it is preferable to contain both potassium hydroxide as the inorganic alkali and tripropanolamine as the organic alkali. These alkali additives can be used preferably in an amount of 0.01 to 2% by weight in the ink composition of the present invention.

  The ink composition of the present invention can further contain various additives such as a surface tension adjusting agent, a viscosity adjusting agent, an antioxidant, an ultraviolet absorber, an antifoaming agent, and an oxygen absorber, if necessary. These 1 type (s) or 2 or more types are used.

  The surface tension of the ink composition of the present invention is preferably 20 to 40 mN / m, and more preferably 25 to 34 mN / m, from the viewpoint of improving ejection stability and increasing reliability. In order to make the surface tension within the above range, the surface tension adjusting agent may be contained. The surface tension of the ink composition is measured according to JIS K 3211.

  The ink composition of the present invention preferably has a viscosity at 20 ° C. of 2 to 10 mPa · s, particularly 3 to 6 mPa · s, from the viewpoint of improving ejection stability and improving reliability. In order to bring the viscosity of the ink composition within the above range, the viscosity modifier may be contained. Examples of the viscosity modifier include rosins, alginic acids, polyvinyl alcohol, hydroxypropylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, polyacrylate, polyvinylpyrrolidone, gum arabic starch and the like.

  The ink composition of the present invention can be prepared using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, or a roll mill. In preparing the ink composition of the present invention, it is preferable to remove coarse particles. For example, particles (300 nm or more) are removed by filtering a mixture (ink) obtained by blending the above-described components with a filter such as a metal filter or a membrane filter. By performing such treatment, a highly reliable ink composition that does not clog the nozzle can be obtained.

  The ink composition of the present invention is not limited to the color type and the like, and various color ink compositions (cyan, magenta, yellow, light cyan, light magenta, dark yellow, red, green, blue, orange, Violet, etc.), black ink composition, light black ink composition and the like. In use, the ink composition of the present invention is used alone or as an ink set composed of a plurality of types thereof, or from one or more types of the ink composition of the present invention and one or more types of other ink compositions. Can be used as an ink set.

  The ink composition of the present invention is not particularly limited as a recording medium for forming the image, and can be applied to various recording media such as plain paper, inkjet special paper, plastic, film, metal, and the like. it can.

  Moreover, according to this invention, the ink cartridge provided with the ink composition mentioned above is provided. The ink cartridge of the present invention can ensure the usability and handling of the ink composition.

  The present invention also provides a recording method for forming an image on a recording medium using the ink composition described above. In one embodiment of the recording method of the present invention, printing is performed by ejecting the droplets of the ink composition described above by an inkjet recording method and attaching the droplets to a recording medium. By implementing the recording method of the present invention, it is possible to secure high OD value and fixability as printing characteristics, and to realize reliability such as clogging recovery and ejection stability at high temperatures.

  According to the present invention, there is also provided a recorded matter in which an image is formed on a recording medium using the ink composition described above. The recorded matter of the present invention has a high OD value and fixability.

  Further, according to the present invention, it is possible to provide a recording system for forming an image using the above-described ink composition, and in particular, a recording apparatus such as an ink jet printer using the ink composition according to the above-described embodiment and other recording systems. It can be suitably provided.

  The present invention suitably provides each of the embodiments described above, but is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and test examples of the present invention. However, the present invention is not limited to the examples.

<Preparation of ink composition>
Each component was added in the composition shown below to make the total amount 100 g. Thereafter, the mixture was stirred at room temperature for 2 hours and filtered through a membrane filter (trade name, manufactured by Nihon Millipore Limited) having a pore size of 5 μm to prepare an ink composition (aqueous ink) of Example 1.

Pigment dispersion: 7% by weight (pigment solid content)
("MicroJet CW1" (trade name) manufactured by Orient Chemical Industry Co., Ltd .; prepared according to one preparation method example of the self-dispersing pigment (A) described above, and the average particle diameter of the pigment is 110 nm)
Emulsion (1): 1% by weight
(Tg of resin particles: −5 ° C., particle size: 50 nm, molecular skeleton: styrene-acrylic system containing OH group, prepared according to one example of production method of emulsion described above)
Emulsion (2): 2.5% by weight
(Tg of resin particle: −15 ° C., particle size: 130 nm, molecular skeleton: styrene-acrylic system containing OH group, prepared according to one example of production method of emulsion described above)
Surfynol 104PG50: 0.5% by weight
(Product name, Air Products and Chemicals. Inc.)
Surfynol 465: 1% by weight
(Product name, Air Products and Chemicals. Inc.)
・ Glycerin: 7% by weight
・ Triethylene glycol monobutyl ether: 2% by weight
・ 1,2-hexanediol: 4% by weight
・ Ultra pure water: remaining amount

The emulsions (1) and (2) are aqueous dispersions of resin particles in which the dispersion medium is water and the dispersoid is resin particles. In addition, the weight% of emulsion represents the density | concentration (resin solid content) as a resin particle. Tg is a value measured by differential thermal analysis using a thermal analyzer SSC5000 (manufactured by Seiko Electronics Co., Ltd.). An ink composition prepared in the same manner as in Example 1 except that the molecular skeleton of the emulsion (2) was acrylic ( no OH group contained ) was evaluated as Comparative Example 1.

  Using the ink compositions thus prepared, various printings were performed with a resolution of 360 dpi using an inkjet printer PX-V700 (manufactured by Seiko Epson Corporation). As recording media, four types of paper, Copyplus (manufactured by Hammermill), Xerox 4024 (manufactured by Xerox), Xerox P (manufactured by Fuji Xerox), and special plain paper (manufactured by Seiko Epson Corporation) are used. Printing was performed, and the evaluation and test items shown below were evaluated using the obtained sample (recorded material).

Evaluation / Test: Discharge stability Continuous printing of solid and ruled line patterns was performed in a 40 ° C. environment. A nozzle check was performed before continuous printing, and evaluation was started after confirming the fillability. After that, cleaning was performed each time as a recovery operation when there was a disturbance during printing due to missing dots or ink scattering or bending. The number of cleanings required for 100 pages of continuous printing in A4 size was used as a result, and the determination was made based on the following criteria.

Evaluation A: Zero cleaning times.
Evaluation B: Number of cleanings 1 or 2 times.
Evaluation C: Number of cleanings is 3 times or more.

Evaluation / test: Clogging recovery property A nozzle check was performed before leaving the product, the filling property was confirmed and it was confirmed that normal printing was possible, and then printing was stopped. Thereafter, the printer was left at room temperature (25 ° C.) for 6 months. After leaving, printing was resumed, and cleaning operation was performed until there was no ejection failure and printing equivalent to that before leaving was obtained. The number of cleaning operations was evaluated according to the following criteria.

Evaluation AA: Printing equivalent to that before standing was obtained by 0 to 2 cleaning operations.
Evaluation A: Printing equivalent to that before standing was obtained by 3 to 5 cleaning operations.
Evaluation B: Printing equivalent to that before standing was obtained by 6 to 10 cleaning operations.
Evaluation C: Printing equivalent to that before standing was not obtained after 11 cleaning operations.

Evaluation / Test: Abrasion resistance (line marker resistance)
After printing, the sample (recorded material) was naturally dried for 24 hours, and then the printed characters were rubbed at a writing pressure of 300 g / 15 mm using a yellow aqueous fluorescent pen ZEBRA PEN2 (registered trademark) manufactured by Zebra to check for the presence of stains. It was observed visually. The result was determined based on the following criteria.

Evaluation A: No dirt is produced even if the same part is rubbed twice.
Evaluation B: Dirt does not occur until one rubbing, but dirt occurs after two rubbing.
Evaluation C: Dirt is generated by rubbing once.

Evaluation / Test: Optical density (OD value)
After printing, the sample (recorded material) was left for 1 hour in a general environment. After standing, the optical density of the solid portion was measured using a Gretag densitometer (manufactured by Gretag Co., Ltd.) and judged based on the following criteria. The value is the average value of each paper.

Evaluation A: Optical density is 1.3 or more.
Evaluation B: Optical density is less than 1.3.

[Comparative Examples 2 and 3]
An ink composition was prepared with the same composition as that of the ink composition of Example 1 except for the following points. Each ink composition was evaluated in the same manner as in Example 1.
Comparative Example 2: 2% by weight of emulsion (1) was used without using emulsion (2).
Comparative Example 3: The emulsion (2) was used at 3.5% by weight without using the emulsion (1).

  Resin particles of the emulsions (1) and (2) used in the pigment dispersion in Example 1 having a molecular skeleton of styrene-acrylic (both containing OH groups) and acrylic (both containing OH groups) An ink composition was prepared in the same manner as in Example 1 except that it was changed to the above, and the same evaluation was performed.

The composition of the composition similar to that of the ink composition of Example 1, with 0.1% by weight of potassium hydroxide (inorganic alkali) and 0.2% by weight of tripropanolamine (organic alkali) as alkali additives.
Ink compositions were prepared in the same manner as in Example 1, and the same evaluation was performed.

Evaluation results
Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 2
Discharge stability: A A A A A
Clogging recovery: A C B B A
Abrasion resistance (line marker resistance): A A B C A
Optical density (OD value): A A B A A

Evaluation results
Example 3
Discharge stability: A
Clogging recovery: AA
Abrasion resistance (line marker resistance): A
Optical density (OD value): A

  The present invention realizes a low viscosity while being a high solid content ink, ensures a high OD value and fixability as printing characteristics, and further provides reliability such as clogging recovery and ejection stability at high temperatures. The present invention has industrial applicability as an ink composition for ink jet recording that can be secured, and an ink cartridge, a recording method, a recording system, and a recorded matter using such an ink composition for ink jet recording.

Claims (15)

An ink composition for ink jet recording comprising a self-dispersing pigment and two resin particles having a glass transition point (Tg) of less than 0 ° C,
The self-dispersing pigment and the two types of resin particles contain a total content of 10% by weight or more, and both the two types of resin particles have an OH group in the molecule and have the same skeleton. Ink composition for inkjet recording.   The ink composition for inkjet recording according to claim 1, wherein at least one of the two kinds of resin particles is blended in the form of an emulsion obtained by emulsion polymerization of an unsaturated monomer.   The ink composition for ink jet recording according to claim 1 or 2, wherein the content of the self-dispersing pigment is 6% by weight or more in the ink composition.   The two kinds of resin particles include a first resin particle having a particle size in the range of 40 to 70 nm and a second resin particle having a particle size in the range of 110 to 190 nm and a glass transition point of 10 ° C. or less. The ink composition for inkjet recording according to claim 1, comprising:   The ink composition for ink jet recording according to claim 4, wherein the first resin particles are both composed of a styrene-acrylic skeleton molecule or an acrylic skeleton molecule.   The ink composition for inkjet recording according to claim 4 or 5, wherein the content of the first resin particles is 0.5 to 2% by weight in the ink composition.   The ink composition for inkjet recording according to any one of claims 4 to 6, wherein the content of the second resin particles is 2 to 5% by weight in the ink composition.   The ink composition for ink jet recording according to any one of claims 4 to 7, wherein a weight ratio (the former: the latter) of the first resin particles and the second resin particles is 1:10 to 10: 1. object.   Furthermore, the ink composition for inkjet recording in any one of Claims 1-8 which contains both an inorganic alkali and an organic alkali as an alkali additive.   Furthermore, the ink composition for inkjet recording in any one of Claims 1-9 containing an acetylene glycol type surfactant.   Furthermore, the ink composition for inkjet recording in any one of Claims 1-10 containing water-soluble glycols.   An ink cartridge comprising the ink composition for ink jet recording according to claim 1.   The recording method which forms an image using the ink composition for inkjet recording in any one of Claims 1-11.   The recording system which forms an image using the ink composition for inkjet recording in any one of Claims 1-11. A recorded matter in which an image is formed using the ink composition for inkjet recording according to claim 1.