JP2007002059A - Water-based ink composition for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink which is a pigment ink excellent in light resistance and water resistance and is excellent in storage stability and to provide a water-based ink composition which does not cause plugging due to the drying of ink at ejection nozzle tips and therefore always ensures good ejection response and ejection stability. <P>SOLUTION: The water-based ink composition is one essentially consisting of water, a water-soluble organic solvent, and a pigment and containing a compound represented by formula (I) (wherein M is an alkali metal, an ammonium group, or an organoammonium group; and n is 0 or 1). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-based ink suitable for printing, writing, recorders, and inkjet recording, and in particular, can obtain an image having excellent image fastness such as water resistance and light resistance, excellent storage stability, and printing. The present invention relates to a water-based ink composition excellent in ejection stability without clogging of the head at the time.

  Inkjet recording, which records images by ejecting liquid ink from nozzles, is capable of printing on plain paper, easy to cope with colorization, low driving noise, and low power consumption In recent years, it has been rapidly spreading as a printer for outputting documents and images created by a computer. Recent advances in inkjet recording technology have made it possible to obtain high-quality images similar to photographs, but in addition to these, durability of images such as water resistance and light resistance, and ejection stability during high-speed printing, etc. The required performance has been diversified.

  Currently, there are ink jet recording systems in which a large amount of ink using a dye is used as a colorant (Japanese Patent Laid-Open No. 05-19489: Patent Document 1, Japanese Patent Laid-Open No. 09-003380: Patent Document 2, Japanese Patent Laid-Open No. Hei 2). 11-158424 gazette: patent documents 3). However, although inks using dyes have good color development and a wide color reproduction range, they are often inferior in water resistance and light resistance, so that the light resistance of recorded images often becomes a problem. Further, since the dye is water-soluble, the water resistance of the recorded image may be a problem.

  In order to improve the fastness of these recorded images, a water-based ink composition has been proposed in which a pigment having excellent light resistance and water resistance as compared with a dye is used as a colorant. In pigment inks for inkjet recording, in order to prevent clogging of the ink, the pigment is dispersed at least to an average particle size of 0.2 μm or less and the upper limit of particle size distribution is approximately 0.6 μm. It is necessary to ensure storage stability.

  Therefore, when a pigment is used as a colorant for an aqueous ink composition, it is dispersed in an aqueous medium using a disperser in the presence of a so-called pigment dispersant such as various water-soluble synthetic polymers and surfactants. Need to be stabilized.

  For example, in Patent Document 4 (Japanese Patent Laid-Open No. 64-6074) and Patent Document 5 (Japanese Patent Laid-Open No. 4-149286), an acidic carbon black and a dispersant (an anionic surfactant or a polymer dispersant) and An aqueous pigment ink composition containing a buffer is described. Patent Document 6 (JP-A-3-210373) describes an ink-jet ink composition containing acidic carbon black having a volatile content of 3.5 to 8% by weight and a water-soluble resin. Patent Document 7 (Japanese Patent Laid-Open No. 3-134073) describes an ink jet recording liquid containing neutral or basic carbon black and a water-soluble resin. However, when a surfactant or a polymer dispersant is used as a dispersant, there is a problem that dispersion tends to become unstable due to the interaction between a solvent or an additive added to adjust ink characteristics and the dispersant. is there.

  Further, a method for hydrophilizing a pigment without using a dispersant has been studied. For example, Patent Document 8 (Japanese Patent Laid-Open No. 9-286938) discloses an aqueous pigment ink containing no dispersant using oxidized carbon black oxidized with hypohalous acid or a salt thereof. Further, an ink using a hydrophilic pigment in which a hydrophilic group is introduced on the surface of carbon black using an aromatic group or an alkyl group as a linking group (Japanese Patent Publication No. 10-510862: Patent Document 9 and Japanese Patent Publication No. 10-510863: Patent Document). 10) etc. are presented.

  By using the above dispersion method, it is possible to disperse and stabilize the pigment in the aqueous medium. However, in the on-demand type ink jet printer, there is no problem of drying in the nozzle that is always ejected during printing. However, it is rare that all nozzles are ejecting, and in that case, the ink is dried by non-ejection nozzles, so that the pigments aggregate due to dispersion of the pigment due to moisture evaporation, or pigment particles are formed on the nozzle surface. It may adhere. In order to prevent this phenomenon, the printer is provided with a maintenance mechanism based on suction and wiping operations. However, if the operation becomes frequent, the amount of ink consumption increases. In order to prevent this phenomenon from the ink side, it has been disclosed to add a hygroscopic agent to the aqueous ink composition. Patent Document 11 (Japanese Patent Laid-Open No. 2004-75730) discloses the use of pantothenate as a hygroscopic agent in order to prevent clogging at the nozzles of inkjet ink. (Application No. 2005-076034) discloses an example in which a self-dispersible pigment having a hydrophilic group on the surface and a pantothenate are used in combination to solve the above-mentioned problems.

  The water-based ink composition containing at least water, a water-soluble organic solvent, and a pigment can ensure normal dispersion stability by the above-described dispersion method, but when ink drying occurs with a non-ejection nozzle, The pigment may aggregate or pigment particles may adhere to the nozzle surface due to the dispersion failure of the pigment accompanying water evaporation. When used in an ink jet recording method, if the ink is left unprinted for a long period of time, the ink forms an aggregate at the tip of the discharge nozzle, and there is a problem that it does not recover even if a recovery operation such as suction occurs. This is remarkable in a fine discharge nozzle used in an inkjet recording apparatus with a small amount of ink droplets for high-definition printing.

  On the other hand, the water-based ink composition of the present invention does not cause the above problem and can maintain good dispersion stability. Usually, water-based ink compositions contain highly hygroscopic glycerin as a wetting agent in order to prevent the evaporation of moisture in the above open system, but it is difficult to suppress the evaporation of moisture, and in order to prevent evaporation There is also a method of adding a compound having a stronger hygroscopic effect to the ink composition, but the present invention prevents moisture from evaporating at the tip of the discharge nozzle and agglomeration, and is good for continuously supplied ink. It is possible to secure the ink ejection stability by imparting the characteristic of being dispersed (defined as redispersibility in the present invention).

  The phenolic compound of the general formula (I) used in the present invention is a dye auxiliary agent for dissolving a cationic dye in Patent Document 13 (Japanese Patent Laid-Open No. 2002-265830), and a dye compound in Patent Document 14 (Japanese Patent Laid-Open No. 10-88043). In water-based inks, water-insoluble monoglycol ether, water-insoluble polyglycol ether, water-insoluble N-substituted 2-pyrrolidone, water-insoluble monoglycol ester, water-insoluble polyglycol ester, etc. While we have been studying the prevention of pigment aggregation at the time of water evaporation with water-based pigment-based ink, the ink added with the compound of the present invention prevents aggregation even when the water is evaporated, It was found that the ink was imparted with a characteristic of being well redispersed, leading to the present invention. This is because the phenolic hydroxyl group or carboxyl group of the compound of the present invention repels each other with the hydrophilic group on the surface in the case of an anionic group of the dispersant or a self-dispersing pigment, thereby preventing the progress of aggregation. I thought it was because there was.

Japanese Patent Laid-Open No. 05-194889 Japanese Patent Laid-Open No. 09-003380 JP-A-11-158424 JP-A 64-6074 JP-A-4-149286 JP-A-3-210373 JP-A-3-134073 Japanese Patent Laid-Open No. 9-286938 Japanese National Patent Publication No. 10-510862 Japanese National Patent Publication No. 10-510863 JP 2004-75730 A Japanese Patent Application No. 2005-076034 JP 2002-265830 A JP-A-10-88043

  The present invention has been made in view of the above-described prior art, and is a pigment-based ink having excellent light resistance and water resistance, providing an ink having excellent storage stability, and clogging due to ink drying at the tip of the discharge nozzle. It is an object of the present invention to provide a water-based ink composition that is used in an ink jet recording system that does not occur and always has good ejection response and ejection stability.

The present inventors have studied the water-based ink composition, particularly the water-based ink composition for inkjet recording from various angles, and as a result, have found that the above-described object can be achieved by the present invention described below.
That is, the present invention
(1) An aqueous ink composition containing at least water, a water-soluble organic solvent, and a pigment, wherein the aqueous ink composition contains a compound represented by the following general formula (I): .

（但し Ｍはアルカリ金属、アンモニウム又は有機アンモニウムを表し、ｎは０又は１である）
（２）前記一般式（Ｉ）で表される化合物の含有量がインク全重量に対し０．０１以上１０．０ｗｔ％未満であることを特徴とする（１）に記載の水性インク組成物である。
（３）前記顔料が、親水性基を表面に有する自己分散可能な顔料であることを特徴とする（１）に記載の水性インク組成物である。
（４）自己分散可能な顔料が、カーボンブラックを親水化することにより得られる顔料であることを特徴とする（３）に記載の水性インク組成物である。
（５）さらに界面活性剤を含有することを特徴とする（１）ないし（４）いずれかに記載の水性インク組成物である。
（６）界面活性剤の含有量がインク全重量に対し０．０１以上２．０ｗｔ％未満であることを特徴とする（５）に記載の水性インク組成物である。
（７）界面活性剤が、アニオン性界面活性剤および／またはノニオン性界面活性剤であることを特徴とする（５）または（６）に記載の水性インク組成物である。

(However, M represents an alkali metal, ammonium, or organic ammonium, and n is 0 or 1.)
(2) The aqueous ink composition according to (1), wherein the content of the compound represented by the general formula (I) is 0.01 or more and less than 10.0 wt% with respect to the total weight of the ink. is there.
(3) The aqueous ink composition according to (1), wherein the pigment is a self-dispersible pigment having a hydrophilic group on the surface.
(4) The water-based ink composition as described in (3), wherein the self-dispersible pigment is a pigment obtained by hydrophilizing carbon black.
(5) The water-based ink composition as described in any one of (1) to (4), further comprising a surfactant.
(6) The water-based ink composition as described in (5), wherein the content of the surfactant is 0.01 or more and less than 2.0 wt% with respect to the total weight of the ink.
(7) The aqueous ink composition as described in (5) or (6), wherein the surfactant is an anionic surfactant and / or a nonionic surfactant.

  As will be apparent from the following detailed and specific description, when the aqueous ink composition obtained in the examples is used, it is a clear image having high density without blurring and excellent in water resistance and light resistance. The printed image can be obtained with any printing paper, and the image has excellent dryness. Further, the water-based ink compositions obtained by the examples are excellent in storage stability, and can perform inkjet recording with high ejection reliability even after storage for a long period of time and after printing is stopped. It has an extremely excellent effect.

Hereinafter, the invention will be described in more detail.
The present invention is an aqueous ink composition containing at least water, a water-soluble organic solvent, and a pigment, and is characterized by containing a compound represented by the following general formula (I).

（但し、Ｍはアルカリ金属、アンモニウム又は有機アンモニウムを表し、ｎは０又は１である）

(However, M represents an alkali metal, ammonium, or organic ammonium, and n is 0 or 1.)

  Specific examples of the compound represented by the general formula (I) include resorcin, phloroglucin, 1,2,4-trihydroxybenzene, pyrogallol, α-resorcinic acid, β-resorcinic acid, γ-resorcinic acid, 2,4 , 6-trihydroxybenzoic acid, 2,3,4-trihydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid (garlic acid), and the like, alkali metal salts, ammonium salts, or organic ammonium salts. Examples of organic ammonium include trimethyl-2-oxyethylammonium, tetraethylammonium, monoethanolammonium, diethanolammonium, and triethanolammonium. These can be used alone or in combination. The compound represented by the general formula (I) is blended in an amount of 0.01 to 10.0% by weight, preferably 0.1 to 5.0% by weight, based on the total amount of the recording ink. If the amount is less than 0.01% by weight, it is difficult to obtain an aggregation preventing effect. If the amount is more than 10.0% by weight, the added salt does not completely dissolve, the solid content in the ink increases, the ink viscosity increases, and the ejection response increases. Make it worse.

  In addition, the water-soluble organic solvent used in the present invention forms a main solvent together with water, has compatibility with water, and does not have an undesirable interaction with other components in the ink composition. As long as it is a thing, it will not specifically limit. The water-soluble organic solvent is used for the purpose of making the ink have desired physical properties, for preventing the ink from drying, and for improving the dissolution stability. For example, the following water-soluble organic solvents are used. The These water-soluble organic solvents may be used alone or in combination.

Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol having a molecular weight of 600 or less, 1,3-propylene glycol, isopropylene glycol, isoptylene glycol, 1, 4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, mesoerythritol, pentaerythritol, etc.
Glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monobutyl ether, propylene glycol Examples include monoethyl ether, ethylene glycol monophenyl ether, and ethylene glycol monobenzyl ether.

Examples of nitrogen-containing heterocyclic compounds include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, and γ-butyrolactone. ,
Examples of amides include formamide, N-methylformamide, N, N-dimethylformamide,
Examples of amines include monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine.
Examples of sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiethanol and the like.
Other examples include propylene carbonate and ethylene carbonate.

  Among these organic solvents, diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, dipropylene glycol, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1 , 3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2-pyrrolidone and N-methyl-2-pyrrolidone are preferred. These are excellent in solubility and prevention of poor jetting characteristics due to water evaporation.

  These water-soluble organic solvents may be used alone or in combination of two or more. The content of the water-soluble organic solvent is 1 to 60 wt%, more preferably 5 to 40 wt%, based on the total weight of the recording ink.

The pigment used in the present invention is not particularly limited, and an inorganic pigment and an organic pigment can be used.
As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments). , Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like.

  The type of carbon black used as a raw material is not particularly limited. Any of the above-mentioned acidic carbon black, neutral carbon black, and alkaline carbon black can be used.

Specific examples of the pigment preferably used in the present invention include the following. For black, carbon black (CI Pigment Black 7) such as furnace black, lamp black, acetylene black and channel black, or metals such as copper and iron (CI Pigment Black 11), oxidation Examples thereof include metal oxides such as titanium, hydroxides, sulfides, carbonates, phosphates, sulfates, organometallic compounds such as phthalocyanines, and organic pigments such as aniline black (CI Pigment Black 1).
Specific examples of carbon black include # 10B, # 20B, # 30, # 33, # 40, # 44, # 45, # 45L, # 50, # 55, # 95, # 260, ## manufactured by Mitsubishi Chemical Corporation. 900, # 1000, # 2200B, # 2300, # 2350, # 2400B, # 2650, # 2700, # 4000B, CF9, MA8, MA11, MA77, MA100, MA220, MA230, MA600, MCF88, etc .; Monarch made by Cabot 120, Monarch 700, Monarch 800, Monarch 880, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, Mogal L, Legal 99R, Legal 250R, Legal 300R, Legal 330R, Legal 400R, Legal 500R and Legal 660R, etc .; Made of plastic Printex A, Printex G, Printex U, Printex V, Printex 55, Printex 140U, Printex 140V, Special Black 4, Special Black 4A, Special Black 5, Special Black 6, Special Black 100, Special Black 250 Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, and the like.

  Further, for color use, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 81, 83 (Disazo Yellow HR) ), 95, 97, 98, 100, 101, 104, 408, 109, 110, 117, 120, 138, 153, C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B (Ca)), 48: 3 (Permanent Red 2B (Sr)), 48: 4 (Permanent Red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63 : 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (Quinacridone magenta), 123 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, CI. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue E), 16, 17: 1, 56, 60, 63, C.I. I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like.

  As a dispersant for using these pigments as a colorant for an aqueous ink composition, there are usual anionic surfactants and polymer dispersants. As anionic surfactants, JP-A-8-199100 is known. Polyoxyethylene alkyl ether sulfate salts, polyoxyethylene alkyl phenyl ether sulfate salts, polyoxyethylene allyl ether sulfate salts, polymer dispersants, such as proteins such as gelatin and casein, and natural rubber such as gum arabic , Glucoxide such as saponin, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, lignin sulfonate, natural polymers such as ceramic, polyacrylate, styrene-acrylic acid copolymer salt, vinyl naphthalene- Crylic acid copolymer salt, styrene-maleic acid copolymer salt, vinyl naphthalene-maleic acid copolymer salt, sodium salt of β-naphthalenesulfonic acid formalin condensate, anionic polymer such as polyphosphoric acid, polyvinyl alcohol Nonionic polymers such as polyvinyl pyrrolidone and polyethylene glycol can be used, and one or more of these can be used in combination. The addition amount is preferably 0.1 to 20% by weight, more preferably 1 to 10% by weight, based on the total weight of the ink.

  The self-dispersible pigment having at least one hydrophilic group on the surface of the present invention has a hydrophilic functional group on the surface, does not contain a so-called polymer dispersant or surfactant, and is itself dispersed in a solvent. Possible pigments are used. As the hydrophilic functional group possessed by the pigment, any nonionic, anionic or cationic hydrophilic functional group can be used, and in particular, a carboxyl group, a hydroxyl group, a sulfonic acid group, or a phosphoric acid group alone or in combination of two or more. A combination is preferable, and among these, a carboxyl group alone or two or more combinations including a carboxyl group are more preferable. When it has a carboxyl group, a sulfonic acid group, or a phosphoric acid group, it can be used as it is in a free acid state, but it is more advantageous in terms of dispersibility that a part or all of it forms a salt, which is preferable. As the substance forming the salt, various basic substances can be used, but an alkali metal, ammonium, or an organic ammonium compound alone or a combination of two or more kinds is preferable. As a pigment into which a hydrophilic functional group is introduced, both inorganic and organic pigments can be used.

  It is also possible to use a commercially available product as a self-dispersible pigment having the hydrophilic group on the surface preferably used in the present invention. As a preferred example, a black self-dispersing pigment is a carboxyl group modified by Cabot Corporation. Type CAB-O-JET300, sulfone group-modified type CAB-O-JET200, BONJET BLACK CW-1, CW-2, etc. manufactured by Orient Chemical Industry Co., Ltd. Examples thereof include pigment dispersions of CAB-O-JET250C (cyan), CAB-O-JET260M (magenta), CAB-O-JET270Y (yellow), and the like.

  The number average particle diameter of the pigment dispersed particles in the ink is adjusted to a range of 15 to 110 nm, preferably 20 to 90 nm. If the number average particle diameter is less than 15 nm, the recorded product has a sense of transparency, and a sufficient optical density cannot be obtained. On the other hand, if it exceeds 110 nm, the particles are likely to settle, and the storage stability of the ink tends to be lowered.

  The content of the pigment in the ink composition is preferably 2 to 10% by weight, more preferably about 3 to 8% by weight. If the pigment content is less than 2% by weight, the printing or writing concentration is insufficient, and if it exceeds 10% by weight, the pigment is likely to aggregate, causing precipitation during long-term storage, and the ejection stability being poor.

  The ink for inkjet recording of the present invention may preferably contain a surfactant. The surfactant used here is not used as a so-called pigment dispersant, but is intended to assist the dispersion stability of the dispersed pigment, or to allow the ink to penetrate into the paper as the recording medium. Is to do. Examples of the surfactant that can be used in the inkjet recording ink of the present invention include various anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and the like. Anionic surfactants and nonionic surfactants.

  The anionic surfactant preferably contains a polyoxyalkylene alkyl ether carboxylate surfactant, a polyoxyalkylene alkyl ether sulfonate salt, or a polyoxyalkylene aryl ether sulfonate surfactant. Examples of the polyoxyalkylene alkyl ether carboxylate surfactant include ECT-3NEX, ECTD-3NEX, ECTD-6NEX, ECT-3, ECT-7, AKYPO RLM 45NV (CHEM-Y) manufactured by Nikko Chemicals, AKYPO RLM45 (CHEM-Y), AKYPO RLM100NV (CHEM-Y), AKYPO RLM100 (CHEM-Y), etc. can be used, and polyoxyalkylene alkyl ether sulfonate or polyoxyalkylene aryl ether sulfonate surfactant As examples, NICOLL SBL-44 manufactured by Nikko Chemicals, Hightenol N-07, Hightenol N-08, Hightenol N-17, Hightenol NE-05, Hightenol NE- 15, Hightenol NF-13, Hightenol 08E, Hightenol 12, Hightenol 18E, etc. can be used. In particular, when ECTD-3NEX, ECTD-6NEX, or Haitenol 18E is used, good recording quality is exhibited.

  Nonionic surfactants include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene alkyl allyl ether such as polyoxyethylene dodecyl phenyl ether; polyoxyethylene oleyl ether, polyoxyethylene lauryl ether Such as polyoxyethylene alkyl ether; polyoxyalkylene alkyl ether; ether type such as polyoxyethylene oleic acid; polyoxyethylene oleic acid ester, polyoxyethylene distearic acid ester, sorbitan laurate, sorbitan monostearate, sorbitan mono Esters such as oleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate Other fluoroalkyl ester, and the like fluorine-containing surfactants such as perfluoroalkyl carboxylates.

  The addition amount of these surfactants is preferably about 0.01 to 2.0% by weight, more preferably about 0.1 to 1.5% by weight of the ink composition. An addition amount in this range improves the dispersion stability and has the effect of penetrating the ink into the paper as the recording medium. If it exceeds 2.0% by weight, the bleeding increases.

  On the other hand, in the present invention, a diol and / or diethylene glycol monoalkyl ether having a solubility of 0.1 to 4.5% by weight in water at 25 ° C. is 0.1 to 10. By adding 0% by weight, the wettability of the ink to the inner wall of the head ink channel is improved, and ejection stability and frequency stability can be obtained even with a small amount of addition.

A diol having a solubility of at least 4.5 parts by weight in 100 parts by weight of water at 25 ° C. has a high solubility and therefore hardly exhibits a function as a penetrant. In contrast, penetrants having a solubility of less than 0.1-4.5% by weight in water at 25 ° C. have the advantage of very high permeability instead of low solubility. Therefore, a highly penetrating ink can be obtained by combining a penetrant having a solubility of less than 0.1 to 4.5% by weight in water at 25 ° C. with another solvent or another surfactant. It becomes possible to create.

  Examples of the diol and / or diethylene glycol monoalkyl ether having a solubility of less than 0.1 to 4.5% by weight in 25 ° C. water include 2-ethyl-1,3-hexanediol, 2,2,4- Examples include trimethyl-1,3-pentanediol, 1,2,4-trimethyl-1,3-pentanediol, 2,4-diethyl-1,5-pentanediol, and diethylene glycol monohexyl ether. Ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and 2,4-diethyl-1,5-pentanediol are particularly preferred.

  The content of the diol and / or diethylene glycol monoalkyl ether in the ink composition is preferably 0.1 to 4.5% by weight, more preferably about 0.5 to 3% by weight. When the content of the diol and / or diethylene glycol monoalkyl ether is less than 0.1% by weight, the effect on the ink permeability or wettability is insufficient, and when it exceeds 4.5% by weight, the undissolved content is contained in the ink. This causes separation and pigment aggregation.

  In addition, the ink composition according to the present invention has a preservative, a fungicide, a pH adjuster, a dye dissolution aid, an antioxidant, a conductivity adjuster, a surface tension adjuster, and an oxygen absorption agent to improve various properties. Agents and the like.

  Preferred examples of antiseptics and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-benzisothiazoline-3-one (Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel LV of ICI) and the like.

  Examples of pH adjusters, dye solubilizers and antioxidants include amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, lithium hydroxide. Inorganic salts such as ammonium hydroxide, quaternary ammonium hydroxide (such as tetramethylammonium), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate, and other phosphates, or N-methyl-2-pyrrolidone, allophanate, methyl Examples include allophanates such as allophanate, burettes such as burette, dimethyl burette, and tetramethyl burette, and L-ascorbic acid and salts thereof.

  In addition, the ink composition according to the present invention may contain an ultraviolet absorber. Examples of such commercially available products include Tinuvin 328, 900, 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024 manufactured by Ciba Geigy.

  In addition, the ink composition according to the present invention may include a viscosity modifier. Specific examples thereof include rosins, alginic acids, polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, polyacrylate, polyvinyl pyrrolidone, gum arabic starch and the like.

Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite. Depending on the purpose, a water-soluble ultraviolet absorber, a water-soluble infrared absorber, and a surfactant can be added.

  The recording ink according to the present invention can be used for writing instrument ink and ink jet recording ink. As the ink jet recording method, there are a recording method in which mechanical energy is applied to ink to eject droplets, and a recording method in which thermal energy is applied to ink and ink droplets are ejected by foaming of the ink. The recording ink of the present invention can be suitably used. When used for ink jet recording, the ink preferably has a characteristic that it can be ejected from an ink jet head. From the viewpoint of ejection properties from an inkjet head, the surface tension of the ink is preferably 20 to 60 mN / m, and more preferably 25 to 50 mN / m. The viscosity is preferably 1.5 to 10.0 mPa · s, more preferably 2.0 to 8.0 mPa · s. The pH is preferably 6.0 to 11.0, and more preferably 6.5 to 10.0, in order to ensure the dispersion stability of the pigment particles in the ink.

  Examples and Comparative Examples of the present invention are shown below, but the present invention is not limited to these. In addition, the amount (%) of each component described in the examples is based on weight. An ink composition having the following composition was prepared.

[Example 1]
First, a pigment dispersion was prepared and mixed according to the following formulation. This mixture was placed in a 1 liter vessel, 900 g of zirconia beads having a diameter of 0.7 mm were added, and the mixture was dispersed for 20 hours in a batch tabletop sand mill manufactured by Campe. A dispersion (A) was obtained.
Pigment Red 122 30 parts (FASTOGEN SUPER MAGENTA RG manufactured by Dainippon Ink, Inc.)
30 parts of styrene-acrylic acid copolymer aqueous ammonium solution (20%) (John Crill 679 manufactured by Johnson Polymer Co., Ltd.)
Glycerin 10 parts Ion-exchanged water 130 parts An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8. Thereafter, filtration was performed with a membrane filter having an average pore diameter of 1.2 μm to obtain an aqueous ink composition.
Pigment dispersion (A) 25 parts phloroglucin 1 part glycerin 6 parts diethylene glycol 18 parts 2-ethyl-1,3-hexanediol 2 parts 1,2-benzisothiazolin-3-one 0.15 parts (Proxel LV 20 manufactured by Avicia) %liquid)
47.85 parts of ion exchange water

[Example 2]
First, a pigment dispersion was prepared and mixed according to the following formulation. This mixture was placed in a 1 liter vessel, 900 g of zirconia beads having a diameter of 0.7 mm were added, and the mixture was dispersed for 20 hours in a batch tabletop sand mill manufactured by Campe. A dispersion (B) was obtained.
Pigment Blue 15: 3 30 parts (LIONOL BLUE FG-7351 manufactured by Toyo Ink Co., Ltd.)
Polyoxyethylene lauryl ether sulfate triethanolammonium salt (NICOLL SBL-4T manufactured by Nikko Chemicals) 6 parts Glycerin 10 parts Ion-exchanged water 154 parts Except for using the following composition, the pH was adjusted to 10% lithium hydroxide. A water-based ink composition was obtained by changing to 9 with an aqueous solution. Thereafter, filtration was performed with a membrane filter having an average pore diameter of 1.2 μm to obtain an aqueous ink composition.
Pigment dispersion (B) 20 parts Resorcin 1 part Glycerin 6 parts Triethylene glycol 17 parts 2-Ethyl-1,3-hexanediol 2 parts ECTD-3NEX 0.5 parts (anionic surfactant manufactured by Nikko Chemicals)
1,5-benzoisothiazolin-3-one 0.15 part (Proxel LV 20% solution manufactured by Avicia)
53.35 parts of ion exchange water

[Example 3]
First, a pigment dispersion was prepared and mixed according to the following formulation. This mixture was placed in a 1 liter vessel, 900 g of zirconia beads having a diameter of 0.7 mm were added, and the mixture was dispersed for 20 hours in a batch tabletop sand mill manufactured by Campe. A dispersion (C) was obtained.
30 parts of Pigment Yellow 138 (LIONOGEN YELLOW 1010 manufactured by Toyo Ink)
30 parts of styrene-maleic anhydride copolymer aqueous ammonium solution (20%) (SMA grade 2000, manufactured by Sartomer)
Glycerin 10 parts Ion-exchanged water 130 parts An ink composition having the following formulation was prepared and adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8. Thereafter, filtration was performed with a membrane filter having an average pore diameter of 1.2 μm to obtain an aqueous ink composition.
Pigment dispersion (C) 20 parts 1,2,4-trihydroxybenzene 1 part glycerin 6 parts diethylene glycol 18 parts 2-ethyl-1,3-hexanediol 2 parts Hightenol N-08 1.0 part (Daiichi Kogyo) Anionic surfactant manufactured by Pharmaceutical Co., Ltd.
1,5-benzoisothiazolin-3-one 0.15 part (Proxel LV 20% solution manufactured by Avicia)
51.85 parts of ion exchange water

[Example 4]
A water-based ink composition was obtained in the same manner as in Example 1 except that the following composition was used, and the pH was adjusted to 9 with a 10% aqueous lithium hydroxide solution. Thereafter, filtration was performed with a membrane filter having an average pore diameter of 1.2 μm to obtain an aqueous ink composition.
25 parts of sulfonic acid group addition type carbon black dispersion (CAB-O-JET200 manufactured by Cabot Specialty Chemicals, Inc.)
2,4,6-trihydroxybenzoic acid 1 part glycerin 6 parts diethylene glycol 18 parts 2-ethyl-1,3-hexanediol 2 parts polyoxyethylene octylphenol ether 0.5 parts (Nonal 310, manufactured by Toho Chemical Industry Co., Ltd.)
1,5-benzoisothiazolin-3-one 0.15 part (Proxel LV 20% solution manufactured by Avicia)
47.35 parts of ion exchange water

[Example 5]
A recording ink was prepared in the same manner as in Example 1 except that the following composition was used, and the pH was adjusted to 9 with a 10% aqueous solution of lithium hydroxide. Then, it filtered with the membrane filter with an average hole diameter of 5 micrometers, and obtained the water-based ink composition.
Carboxyl group-added carbon black dispersion 35 parts (Orient Chemical Industries, Ltd. BonJet CW-1)
α-resorcinic acid 1 part glycerin 6 parts diethylene glycol 18 parts 2-ethyl-1,3-hexanediol 2 parts ECTD-6NEX 0.5 parts (anionic surfactant manufactured by Nikko Chemicals)
1,5-benzoisothiazolin-3-one 0.15 part (Proxel LV 20% solution manufactured by Avicia)
Ion exchange water 37.35 parts

[Example 6]
A recording ink was prepared in the same manner as in Example 1 except that the following composition was used, and the pH was adjusted to 9 with a 10% aqueous solution of lithium hydroxide. Thereafter, filtration was performed with a membrane filter having an average pore diameter of 1.2 μm to obtain an aqueous ink composition.
35 parts of sulfonic acid group addition type magenta dispersion (CAB-O-JET260M manufactured by Cabot Specialty Chemicals, Inc.)
Glycerin 6 parts Triethylene glycol 17 parts 2-Ethyl-1,3-hexanediol 2 parts 2-Pyrrolidone 2 parts Hightenol 18E 1 part (Daiichi Kogyo Seiyaku Co., Ltd. anionic surfactant)
Pegnol TH-8 0.3 part (nonionic surfactant manufactured by Toho Chemical Industry Co., Ltd.)
1,5-benzoisothiazolin-3-one 0.15 part (Proxel LV 20% solution manufactured by Avicia)
44.55 parts of ion exchange water

[Comparative Example 1]
A recording ink was prepared by changing the pH to 9 with lithium hydroxide in the same manner as in Example 1 except that the following composition was used. Thereafter, filtration was performed with a membrane filter having an average pore diameter of 1.2 μm to obtain an aqueous ink composition.
Pigment dispersion liquid of Example 1 (A) 25 parts Glycerin 6 parts Diethylene glycol 18 parts 2-ethyl-1,3-hexanediol 2 parts Antifungal agent Proxel LV (20% liquid) 0.15 parts Ion-exchanged water 48.85 Part

[Comparative Example 2]
A water-based ink composition was prepared by adjusting the pH to 9 with lithium hydroxide in the same manner as in Example 1 except that the following composition was used.
Pigment dispersion (B) of Example 2 20 parts Glycerin 6 parts Triethylene glycol 17 parts 2-ethyl-1,3-hexanediol 2 parts ECTD-3NEX 0.5 part (anionic surfactant manufactured by Nikko Chemicals)
Antifungal agent Proxel LV (20% solution) 0.15 parts Ion-exchanged water 54.35 parts

[Comparative Example 3]
A water-based ink composition was prepared by adjusting the pH to 9 with lithium hydroxide in the same manner as in Example 1 except that the following composition was used.
Pigment dispersion (C) of Example 3 20 parts Glycerin 6 parts Diethylene glycol 18 parts Antifungal agent Proxel LV (20% liquid) 0.15 parts Ion-exchanged water 55.85 parts

[Comparative Example 4]
In Example 1, an aqueous ink composition was prepared in the same manner as in Example 1 except that CI Acid Red 35 (solid content concentration 4%) was used instead of the pigment dispersion (A).

[Comparative Example 5]
In Example 2, a water-based ink composition was prepared in the same manner as in Example 2 except that CI Acid Blue 9 (solid content concentration 3%) was used instead of the pigment dispersion (B).

[Comparative Example 6]
In Example 3, a water-based ink composition was prepared in the same manner as in Example 3 except that CI Acid Yellow 23 (solid content concentration 3%) was used instead of the pigment dispersion (A).

Next, the following tests were conducted on Examples 1 to 6 and Comparative Examples 1 to 6. The test results are shown in Table 1 described later.
1) Sharpness of image A thermal inkjet type nozzle diameter of 45 μm, an inkjet printer having a 300 dpi nozzle, and an inkjet printer having a nozzle diameter of 33 μm and a 128 dpi nozzle using a laminated PZT for pressurizing a liquid chamber flow channel are commercially available. Prints on three types of printing paper, recycled paper, fine paper, and bond paper, and visually determines the blur of the border of the two-color overlap, blurring of the image, color tone, and density of the printed image to visually clarify the image. evaluated.
Evaluation Criteria A: Clear printing without occurrence of bleeding on all papers.
○: Whisker-like bleeding occurs on some paper (recycled paper).
Δ: Whisker-like bleeding occurs on all papers.
X: The blur has occurred so that the outline of the character is not clear.
2) Water resistance of the image The print image sample is immersed in water at 30 ° C for 1 minute, and the change in the image density before and after the treatment is measured with a Macbeth densitometer. The water resistance (color resistance%) is obtained by the following formula. It was. In Table 1, ○ indicates a case where the water resistance (% of color resistance) is less than 10% in any of the three types of printing paper, Δ indicates a case where it is 10% or more and less than 30%, and × indicates The case where it is 30% or more is shown.
Colorfastness (%) = [1− (Image density after processing / Image density before processing)] × 100
3) Light resistance of the image The printed image sample was irradiated with a xenon feed meter at a black panel temperature of 63 degrees for 3 hours, and the change in image density before and after processing was measured with a Macbeth densitometer. %). In Table 1, ◯ indicates a case where the light resistance (% of color resistance) is less than 5% in any of the three types of printing paper, △ indicates a case where the value is 5% or more and less than 30%, and X indicates The case where it is 30% or more is shown.
Colorfastness (%) = [1− (Image density after processing / Image density before processing)] × 100
4) Dryability of image The filter paper was pressed against the image after printing under certain conditions, and the time until the ink was not transferred to the filter paper was measured. When dried within 10 seconds, ○, 10-20 seconds were evaluated as Δ, and 20 seconds or more were evaluated as ×.
5) Storage stability Each recording ink is put in a polyethylene container and stored for 3 months under the conditions of -20 ° C, 5 ° C, 20 ° C and 70 ° C, and the surface tension, viscosity, and precipitate deposit after storage. The presence or absence of was investigated. In Table 1, the case where there is no change in physical properties and the like under any condition is shown as ◯, the case where there is no precipitation but the change in physical properties is large, and the case where precipitation is recognized.
6) Reliability during printing pause
Use an inkjet printer equipped with a PZT-driven head with a nozzle diameter of 30 μm and a 128 dpi nozzle, and check how much it can be recovered even if printing is stopped without performing caps, cleaning, etc. The reliability was evaluated based on whether the jetting direction was shifted or the weight of the ejected liquid droplets was changed during the time. In Table 1, when there is no particular problem with 600 seconds of printing pause, ○ mark, when 600 seconds of printing pause, the change in droplet weight is small and the deviation in jetting direction is small, Δ mark, printing pause within 600 seconds The case where remarkable clogging occurred was indicated as x.

Claims (7)

A water-based ink composition containing at least water, a water-soluble organic solvent, and a pigment, wherein a compound represented by the following general formula (I) is contained.

(However, M represents an alkali metal, ammonium, or organic ammonium, and n is 0 or 1.)   2. The aqueous ink composition according to claim 1, wherein the content of the compound represented by the general formula (I) is 0.01 or more and less than 10.0 wt% with respect to the total weight of the ink. The aqueous ink composition according to claim 1, wherein the pigment is a self-dispersible pigment having a hydrophilic group on its surface. The water-based ink composition according to claim 3, wherein the self-dispersible pigment is a pigment obtained by subjecting carbon black to a hydrophilic treatment.   The aqueous ink composition according to claim 1, further comprising a surfactant. The aqueous ink composition according to claim 5, wherein the content of the surfactant is 0.01 or more and less than 2.0 wt% with respect to the total weight of the ink. The aqueous ink composition according to claim 5 or 6, wherein the surfactant is an anionic surfactant and / or a nonionic surfactant.