JP2005082607A - Aqueous recording liquid and recording method using the same - Google Patents

Abstract

In an inkjet printer capable of high-speed printing, an aqueous recording liquid which has practically sufficient drying properties without using a special drying apparatus and does not cause image deterioration such as image back-through or bleeding, and the like The recording method used is provided.
An ink composition contains at least a colorant that dissolves or disperses in water, water, a diol derivative having 8 or more carbon atoms, a compound containing a sulfur atom in a molecule, and a water-soluble organic solvent. A water-based recording solution. The aqueous recording liquid is accommodated in an ink cartridge and mounted on an ink jet printer, and discharged and ejected as droplets from a fine discharge port to form an image on a recording medium.
[Selection] Figure 1

Description

  The present invention relates to an aqueous recording liquid (ink) suitable for ink jet recording to which an on-demand method such as a piezo method or a thermal method or a continuous ejection method such as a charge control method is applied, and particularly has excellent characteristics as a color ink for plain paper. The present invention relates to an aqueous recording liquid comprising an aqueous ink composition having the following properties and used also as an aqueous writing instrument, recorder, and pen plotter.

  In recent years, inkjet recording systems have become widespread rapidly due to the advantages of small size, low price, low running cost, low noise, electrophotographic transfer paper, printing paper, typewriter paper, wire dot printer paper, word processor paper. Inkjet printers capable of printing on various non-coated plain paper such as letter paper and report paper are also on the market.

  In these ink jet printers, various proposals have been made for improving the absorptivity of the aqueous recording liquid (ink) so that a higher quality image can be obtained. However, it is difficult to satisfy all of the color reproducibility of the image, water resistance, light resistance, image drying property, image bleeding and ejection reliability. In particular, in the case of a color printer, even if there is no image quality deterioration in the yellow, magenta, and cyan single-color printing portions, image quality deterioration is likely to occur in the two-color overlapping portion of red, green, and blue.

  In particular, when drying is performed without using a fixing device, it is known that drying property is improved by increasing ink permeability (see, for example, Patent Document 1). However, since this method uses a large amount of surfactant, there is a problem in that it causes serious misery depending on the type of paper.

  In addition, when dialkylsulfosuccinic acid is used as the surfactant, it is said that the drying property of the ink is improved and the image deterioration is small (see, for example, Patent Document 2), but the pixel depends on the type of paper as the recording medium. There is a problem that the diameters are remarkably different and the image density is remarkably lowered, and the active agent is decomposed on the alkali side and the active effect is lost during storage.

  Furthermore, a quick-drying ink with reduced misery by improving the permeability using a surfactant that is an ethylene oxide adduct having an acetylene bond has been disclosed (for example, see Patent Document 3). However, an ink using a direct dye such as DBK168, for example, due to a colorant (dye) has a problem in that the drying speed is not improved because of a hydrophobic interaction with the dye.

  In addition, an ink in which a strongly basic substance is added to improve print drying is disclosed (for example, see Patent Document 4). However, although rosin-sized acidic paper is effective, it has no effect on paper using alkyl ketene dimer or alkenyl sulfosuccinic acid as a sizing agent. Even in the case of acid paper, there is no effect in the two-color overlapping portion.

  Or the ink characterized by containing a polyhydric alcohol derivative and pectin is disclosed (for example, refer patent document 5). This is to add pectin as a thickener to prevent bleeding. However, since pectin is nonionic with a hydroxyl group as a hydrophilic group, there is a problem of lack of ejection stability after printing is stopped. .

When surfactants such as those mentioned above are used for the purpose of increasing the permeability, there is a problem that the foaming property of the ink is increased, so a method for increasing the permeability with a material other than the surfactant has been proposed. ing. Examples of such materials include C _{4 to} C ₆ diol derivatives (see, for example, Patent Document 6), 2-methylpentane-2,4-diol (for example, see Patent Document 7), and water at 25 ° C. Ink using a diol derivative having 6 to 8 carbon atoms (for example, see Patent Document 8) and 1,3-propanediol derivative (for example, see Patent Document 9) having a solubility of 4.5% by weight. Is disclosed.

  However, since the diol derivative has a high solubility in water, the surface tension of the ink, which is one measure of the permeability, cannot be reduced, and the permeability for improving the drying property of the ink can be secured. Not done.

  For this reason, water-based inks containing 2-ethyl-1,3-hexanediol and a recording method using the same have been proposed for the purpose of increasing permeability (for example, Patent Document 10, Patent Document 11, Patent Document). 12). By containing 2-ethyl-1,3-hexanediol as an ink composition, ink permeability and drying properties are improved.

However, the output speed of inkjet printers is steadily increasing, and water-based recording liquid (ink) does not cause color bleeding even at higher speed printing, and dries immediately without rubbing fingers even after output. In addition, there is a need for an ink that is highly dry, has no bleeding, and is capable of double-sided printing with little show-through.
JP 55-29546 A Japanese Patent Publication No. 60-23793 Japanese Examined Patent Publication No. 58-6752 JP 56-57862 A JP-A-1-203483 Japanese Patent Laid-Open No. 62-169875 JP-A-3-2286 Japanese Patent No. 2714482 Japanese Patent Laid-Open No. 9-268266 Japanese Patent No. 3350117 JP 2001-172534 A JP 2001-254036 A

  The present invention has been made in view of such problems, the purpose of which is an inkjet printer capable of high-speed printing, has a practically sufficient drying property without using a special drying device, It is an object of the present invention to provide an aqueous recording liquid which does not cause image deterioration such as image back-through or bleeding and a recording method using the same.

  The present invention includes, as an ink composition, a colorant that is dissolved or dispersed in water, water, a diol derivative having 8 or more carbon atoms, a compound containing a sulfur atom in the molecule, and a water-soluble organic solvent. The above problems could be solved.

That is, the present inventors examined various diol derivatives as materials for improving the permeability to paper in order to improve the drying property, and as a diol derivative having 8 or more carbon atoms, 2-n-butyl-2-ethyl is used. A small amount of at least one compound selected from -1,3-propanediol, 2,4-diethyl-1,5-pentanediol and 2-ethyl-1,3-hexanediol is added to an aqueous recording liquid (ink) By reducing the surface tension to 35 mN / m or less, the wettability between the ink and the paper surface can be improved, and the penetration rate into the paper can be increased. As compared with the case where the penetrability was increased by using this, it was found that the image deterioration was extremely small, and the present invention could be achieved.
Hereinafter, the present invention will be specifically described.

  The invention of claim 1 contains, as an ink composition, a colorant that dissolves or disperses in water, water, a diol derivative having 8 or more carbon atoms, a compound containing a sulfur atom in the molecule, and a water-soluble organic solvent. It is an aqueous recording liquid characterized by the above.

  The invention according to claim 2 is that the diol derivative having 8 or more carbon atoms is 2-n-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl 2. The aqueous recording liquid according to claim 1, wherein the aqueous recording liquid is at least one compound selected from 1,3-hexanediol.

  The invention according to claim 3 is characterized in that the diol derivative having 8 or more carbon atoms is contained in the range of 0.1 to 5.0% by weight with respect to the total amount of the ink composition. The aqueous recording liquid described.

  The invention according to claim 4 is characterized in that the compound containing a sulfur atom in the molecule is at least one compound selected from dimethylsulfone, dipropylsulfone, and ethylpropylsulfone. It is a recording liquid.

  The invention according to claim 5 is characterized in that the compound containing a sulfur atom in the molecule is contained in the range of 1.0 to 20.0% by weight with respect to the total amount of the ink composition. The aqueous recording liquid described in 1.

  The invention according to claim 6 is the aqueous recording liquid according to any one of claims 1 to 5, wherein the aqueous recording liquid further contains 2-pyrrolidone.

According to a seventh aspect of the invention, the aqueous recording liquid further contains a surfactant represented by the following general formula (1) in a proportion of 0.01 to 5% by weight based on the total weight of the ink composition. The aqueous recording liquid according to any one of claims 1 to 6, wherein
_{R1-O- (CH 2 CH 2} O) m -CH 2 COOM ... (1)

  (In the formula, R1 is an alkyl group having 6 to 14 carbon atoms which may be branched, m is a natural number of 3 to 12, M represents an alkali metal ion, quaternary ammonium, quaternary phosphonium, or alkanolamine. )

  The invention according to claim 8 is the aqueous recording liquid according to any one of claims 1 to 7, wherein the colorant has an average particle diameter in the range of 10 nm to 200 nm.

  The invention according to claim 9 is the aqueous recording liquid according to any one of claims 1 to 8, wherein the colorant is a pigment dispersed in water by a dispersant having a carboxyl group bonded thereto. It is.

  The invention of claim 10 is characterized in that the colorant is a pigment whose surface is modified with a carboxyl group bonded to the surface and dispersed in water. It is a recording liquid.

  The invention according to claim 11 is the pigment according to any one of claims 1 to 8, wherein the colorant is a pigment whose surface is modified with a sulfonic acid group bonded to the surface and dispersed in water. It is an aqueous recording liquid.

  A twelfth aspect of the invention is a recording method characterized in that the aqueous recording liquid according to the first to eleventh aspects is ejected and ejected as droplets from a fine ejection port to form an image on a recording medium.

  2. The ink composition according to claim 1, wherein the colorant is dissolved or dispersed in water, water, a diol derivative having 8 or more carbon atoms, a compound containing a sulfur atom in the molecule, and a water-soluble organic solvent. As a result, it is possible to provide an aqueous recording liquid that is excellent in permeability and drying property and has little bleeding regardless of the colorant or paper type. In addition, by using a diol derivative having 8 or more carbon atoms as a penetrant and a compound containing a sulfur atom in the molecule as a dissolution stabilizer, the surface tension can be reduced to exhibit the above penetrability and dryness. In addition, it is possible to provide an aqueous recording liquid that has high penetrability characteristics and does not cause problems such as an increase in viscosity.

  The aqueous recording liquid according to claim 2, wherein among the diol derivatives having 8 or more carbon atoms, 2-n-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, By selecting at least one compound selected from 2-ethyl-1,3-hexanediol, a stable aqueous recording liquid having high penetrability and excellent image quality for the above purpose can be provided.

  4. The water-based recording liquid according to claim 3, wherein the penetrability is suitably maintained by containing the diol derivative having 8 or more carbon atoms in a range of 0.1 to 5.0% by weight with respect to the total amount of the ink composition. Further, the storage stability of the composition, the jet stability of the ink jet, and the like can be improved.

  5. The aqueous recording liquid according to claim 4, wherein at least one compound selected from dimethyl sulfone, dipropyl sulfone, and ethylpropyl sulfone is contained as an ink composition as the compound containing a sulfur atom in the molecule, thereby forming the diol. The solubility of the derivative in an aqueous solution is increased, the surface tension that can effectively exhibit the permeability and drying property of the diol derivative is lowered, and high penetration characteristics are obtained. As a result, an aqueous recording liquid capable of obtaining an excellent effect in increasing the image density is provided.

  6. The aqueous recording liquid according to claim 5, wherein the content of the compound containing a sulfur atom in the molecule is in the range of 1.0 to 20.0% by weight relative to the total amount of the ink composition, whereby the penetration of the diol derivative. Provided is an aqueous recording liquid capable of effectively exerting the property of drying and drying.

  7. The aqueous recording liquid according to claim 6, wherein 2-pyrrolidone is contained, so that the penetration of the ink into the paper layer more than necessary after penetrating the paper is suppressed without impairing the permeability of the ink into the paper. Thus, it is possible to provide a water-based recording liquid that can retain a coloring material in the vicinity of the paper surface and has an excellent effect of preventing further see-through as well as further improving the image density.

  The aqueous recording liquid according to claim 7, wherein the surfactant represented by the general formula (1) is added at a ratio of 0.01 to 5% by weight with respect to the total weight of the ink composition, whereby the ink and the paper surface It is possible to further improve the wettability and increase the penetration rate into the paper.

  9. The aqueous recording liquid according to claim 8, wherein the average particle size of the pigment is in the range of 10 nm to 200 nm, whereby the dispersion stability is improved, the particle is not aggregated during storage, and the ejection is performed in the ink jet recording method. Provided is an excellent aqueous recording liquid that is excellent in stability and prevents image back-through.

  10. The aqueous recording liquid according to claim 9, wherein a pigment dispersed in water by a dispersant having a carboxyl group is used as a colorant, whereby dispersion stability is increased, high-quality print quality is obtained, and printing is performed. An aqueous recording liquid in which the water resistance of the later recording medium is further improved is provided.

  12. The aqueous recording liquid according to claim 10, wherein a carboxyl group is bonded to the surface of the colorant to modify the surface, or a sulfonic acid group is bonded to the surface to be dispersed in water. According to the pigment structure, dispersion stability is improved, high-quality printing quality is obtained, and water resistance of the recording medium after printing is further improved. Further, an aqueous recording liquid excellent in redispersibility after the ink is dried is provided.

  According to the recording method of the twelfth aspect, since the aqueous recording liquid comprising the ink composition of the present invention does not cause aggregation or thickening, an image is formed on the recording medium by ejecting and flying as droplets from a fine ejection port. It is suitable for use in the recording method to be formed. Provided a recording method that can suspend printing for a long period of time and easily perform good printing with a simple cleaning operation without causing clogging even when water in the aqueous recording liquid (ink) that stays in the vicinity of the nozzles of the inkjet head evaporates. The

Embodiments of the present invention will be described below.
As described above, the present invention provides a colorant that dissolves or disperses in water, water, a diol derivative having 8 or more carbon atoms, a compound containing a sulfur atom in the molecule, and a water-soluble organic solvent. For the purpose of enhancing the permeability to paper, 2-n-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl as the diol derivative having 8 or more carbon atoms is used. By incorporating at least one compound selected from -1,5-pentanediol and 2-ethyl-1,3-hexanediol in the ink composition, a conventionally known diol derivative (for example, the above-mentioned Patent No. 2), the wettability between the aqueous recording liquid (ink) and the paper surface can be improved, and the surface tension value can be lowered to a value capable of exerting the permeation effect on the paper.

  However, these diol derivatives themselves have low solubility in water, and when used alone, their liquidity is unstable. It has been found that dimethylsulfone, dipropylsulfone, and ethylpropylsulfone as compounds containing atoms have a large dissolving action on these diol derivatives.

  By using both of these diol derivatives and a compound containing a sulfur atom in the molecule, stability over time as an aqueous recording liquid increases, and these diol derivatives have a large penetrating effect even if the addition amount is small, In addition, since the addition amount is small, changes such as an increase in viscosity are small, and the target aqueous recording liquid is realized by taking full advantage of the feature that the influence on the ink physical properties is small.

  That is, by using a diol derivative having 8 or more carbon atoms and a compound containing a sulfur atom in the molecule as the ink composition of the aqueous recording liquid of the present invention, the surface tension is lowered and the wettability between the ink and the paper surface is reduced. In addition to improving the penetration rate of paper, it is possible to increase the penetration rate into paper, and there is very little image degradation compared to the case where the penetration property is increased by using a surfactant as conventionally known. Regardless of the type of paper, it has excellent penetrability and dryness, and has little bleeding. This provides a highly dry aqueous recording liquid that does not show through and enables high-speed printing and double-sided printing.

  The diol derivative having 8 or more carbon atoms is preferably contained in the range of 0.1 to 5.0% by weight, more preferably 0.5 to 4.0% by weight, based on the total amount of the ink composition. If it is less than 0.1% by weight, the effect of increasing the permeability is small, and if it is added more than 5.0% by weight, it does not dissolve stably in the composition, and there is a problem in the storage stability of the composition and the jetting stability in the ink jet. Occur.

  The compound containing a sulfur atom in the molecule is preferably contained in the range of 1.0 to 20.0% by weight, more preferably 3.0 to 15.0% by weight, based on the total amount of the ink composition. preferable. If it is less than 1.0% by weight, the effect of improving the solubility of the diol derivative having 8 or more carbon atoms is small, and if it is added more than 20.0% by weight, there arises a problem that the ink viscosity becomes high.

  The aqueous recording liquid (ink) of the present invention uses water as a liquid medium. In order to make the ink have desired physical properties, to prevent clogging due to drying of the ink, or in each ink in the ink. For the purpose of improving the dissolution stability of the composition, the following water-soluble organic solvent is used as a wetting agent.

  For example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1 , 6-hexanediol, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, 3-methylpentane-1,3,5-triol, etc. A nitrogen-containing heterocyclic compound such as 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone Formamide, N-methylformamide, N, N-dimethyl Amides such as tilformamide; alcohol amines such as monoethanolamine, diethanolamine and triethanolamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol; propylene carbonate and ethylene carbonate. These water-soluble organic solvents are used alone or in combination with water.

  The content of these wetting agents in the ink composition is 5 to 50% by weight, preferably 10 to 40% by weight. If it is less than 5% by weight, the storage stability of the ink and the jetting stability in the ink jet are inferior, and if it is added more than 50% by weight, the jetting stability in the ink jet is inferior due to an increase in viscosity.

  Among the water-soluble organic solvents, diethylene glycol, triethylene glycol and / or glycerin are used in combination as a wetting agent in particular, resulting in clogging due to drying of the aqueous recording liquid (ink) of the present invention, that is, poor jetting characteristics due to water evaporation. An excellent effect is obtained in prevention and improvement in ink dissolution stability.

  Further, it has been found that when 2-pyrrolidone is added to the ink composition, an excellent effect can be obtained in improving the image density and preventing back-through without impairing the permeability of the ink to the paper. This is because the inclusion of 2-pyrrolidone makes it easier for the ink to wet and spread on the paper surface, and the permeation in the thickness direction of the paper is relatively suppressed, so that the colorant tends to stay near the paper surface. Presumed to be. The amount of 2-pyrrolidone added is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight.

  In the present invention, by further adding a surfactant to the ink composition, the wettability between the ink and the paper surface can be further improved, and the penetration rate into the paper can be increased. For that purpose, the addition amount of these surfactants in the ink composition is 0.01 to 5% by weight, preferably 0.5 to 3% by weight. If it is less than 0.01% by weight, there is no effect, and if it is more than 5% by weight, the permeability to the recording medium is unnecessarily high, and there is a problem in that the image density is lowered and show-through occurs.

  Examples of the surfactant used in the present invention include anionic surfactants such as sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether acetate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, Cationic surfactants such as quaternary ammonium salts, amphoteric surfactants such as imidazoline derivatives, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl Amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, ethylene oxide addition of acetylene alcohol Nonionic surfactants such things like.

In particular, an anionic surfactant is preferable, and polyoxyethylene alkyl ether acetate represented by the following general formula (1) is particularly preferable. Using this will improve the filling of the image, and will have an excellent effect in increasing the image density.
_{R1-O- (CH 2 CH 2} O) m -CH 2 COOM ... (1)

  (In the formula, R1 is an alkyl group having 6 to 14 carbon atoms which may be branched, m is a natural number of 3 to 12, M represents an alkali metal ion, quaternary ammonium, quaternary phosphonium, or alkanolamine. )

  Specific examples of the compound represented by the general formula (1) are shown in the following formulas (1-1) to (1-14) in a free acid form, but are not limited thereto.

  As a commercially available surfactant containing this compound as a main component, ECTD3NEX available from Nikko Chemicals (in general formula (1), R1: tridecyl group, m: 3, M: Na), Surfactants such as ECT3 (in general formula (1), R1: tridecyl group, m: 3, M: H), ECTD6NEX (in general formula (1), R1: tridecyl group, m: 6, M: Na) Can also be used.

  In addition to the above-mentioned compounds, penetrants added for the purpose of adjusting the surface tension and the like include 2,2,4-trimethyl-1,3-pentanediol, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, Alkyl and aryl of polyhydric alcohols such as ethylene glycol butyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, propylene glycol monobutyl ether, tetraethylene glycol chlorophenyl ether And lower alcohols such as ethers, fluorosurfactants, ethanol and 2-propanol. That.

  The colorant of the present invention may be a dye and / or a pigment. As the water-soluble dye used as the colorant, dyes classified into acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes in the color index are used. These dyes may be used as a mixture of a plurality of types, or may be used as a mixture with other pigments such as pigments as necessary. These colorants are added within a range that does not hinder the effects of the present invention. Specific examples of these dyes are listed below.

  Examples of acid dyes and food dyes include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142; C.I. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254 289; C.I. I. Acid Blue 9, 29, 45, 92, 249; I. Acid Black 1, 2, 7, 24, 26, 94; I. Food Yellow 2, 3, 4; C.I. I. Food Red 7, 9, 14; C.I. I. Food black 1, 2 etc. are mentioned.

  As a direct dye, C.I. I. Direct yellow 1, 12, 24, 26, 33, 44, 50, 86, 120, 132, 142, 144; I. Direct red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227; I. Direct orange 26, 29, 62, 102; I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202; C.I. I. Direct black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171 etc. are mentioned.

  As a basic dye, C.I. I. Basic Yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 65, 67 70, 73, 77, 87, 91; C.I. I. Basic Red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70 73, 78, 82, 102, 104, 109, 112; I. Basic Blue 1, 3, 5, 7, 9, 21, 22, 26, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93 105, 117, 120, 122, 124, 129, 137, 141, 147, 155; I. Basic black 2, 8 etc. are mentioned.

  As reactive dyes, C.I. I. Reactive Black 3, 4, 7, 11, 12, 17; C.I. I. Reactive Yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67; C.I. I. Reactive Red 1, 14, 17, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97; C.I. I. Reactive blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95 and the like.

  As the dye, acid dyes and direct dyes can be preferably used, and excellent effects can be obtained in terms of improvement in the dissolution stability of the recording liquid according to the present invention, color tone, water resistance and light resistance. The addition amount of the dye as the colorant in the recording liquid composition is preferably 0.5 to 25% by weight, more preferably 1 to 10% by weight.

The pigment as the colorant of the present invention is not particularly limited, and an inorganic pigment or an organic pigment can be used.
Inorganic pigments include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, as well as carbon produced by known methods such as the contact method, furnace method, and thermal method. Black 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, berylene pigments, verinone pigments, anthraquinone pigments, quinacridone pigments). , Dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (eg basic dye chelates, acid dye chelates), nitro pigments, nitroso pigments, aniline black, etc. be able to. Of these pigments, those having good affinity with water are preferably used. The amount of pigment added as a colorant in the ink composition is preferably about 0.5 to 25% by weight, more preferably about 1 to 10% by weight.

  Specific examples of pigments preferably used in the present invention include black for carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black, or copper, iron (C.I. And CI pigment black 11), metals such as titanium oxide, and organic pigments such as aniline black (CI pigment black 1).

  The black ink pigment used in these is preferably carbon black. Carbon black as a black ink has excellent color tone, water resistance, light resistance, excellent dispersion stability, and is inexpensive.

  Further, for color use, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 81, 83, 95, 97, 98, 100, 101, 104, 108 109, 110, 117, 120, 138, 150, 153; I. Pigment orange 5, 13, 16, 17, 36, 43, 51; C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 1, 48: 2 [Permanent Red 2B8 (Ca)], 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 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; I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38; I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3 (phthalocyanine blue), 16, 17: 1, 56, 60, 63; I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like.

  Other pigments (for example, carbon) are treated with resin, etc., and graft pigments that are dispersible in water, and functional groups such as sulfone groups and carboxyl groups are added to the surface of pigments (for example, carbon). Dispersible processed pigments can be used. Further, the pigment may be included in the microcapsule so that the pigment can be dispersed in water.

According to a preferred embodiment of the present invention, the pigment in the ink composition preferably has an average particle size in the range of 10 nm to 200 nm.
The average particle diameter here refers to the amount of change in the frequency (frequency of light) of light (backscattered light) returning from the particle when the Brownian motion particles in the recording liquid are irradiated with laser light. This refers to a value of 50% cumulative volume measured by using a dynamic light scattering method (Doppler scattering light analysis) for determining the particle diameter.

  When the colorant is used as a pigment, the water resistance and light resistance are improved, and further, it is possible to prevent the print medium from leaking through the recording medium layer and oozing out to the back surface.

  Since the pigment is not dissolved in the aqueous recording liquid (ink) but dispersed, it is less likely to enter the recording medium than water or a wetting agent in the ink in the recording medium when the ink is printed. Slightly slower, but can be prevented from falling through. When the average particle size is 10 nm or less, the effect of preventing the back-through is small. When the average particle size is 200 nm or more, the dispersion stability of the ink is poor, and the particle size increases due to aggregation during storage, resulting in poor discharge stability.

  The pigment is preferably dispersed in an aqueous medium in advance using a dispersant to obtain a pigment dispersion, and the ink composition is preferably added in this state. As a preferable dispersing agent, a known dispersion used for preparing a conventionally known pigment dispersion can be used. Examples of the dispersant include the following.

  Polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer Polymer, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene- Acrylic acid copolymer-acrylic acid-alkyl ester copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, Vinyl acetate-maleic acid ester copolymer, vinyl acetate Examples thereof include a ru-crotonic acid copolymer and a vinyl acetate-acrylic acid copolymer.

  The polymer or copolymer preferably has a weight average molecular weight of 3,000 to 50,000, more preferably 5,000 to 30,000, and still more preferably 7,000 to 15,000.

  The addition amount of the dispersant may be appropriately added as long as the pigment is stably dispersed and the other effects of the present invention are not lost. As a dispersing agent, the range of 1: 0.06 to 1: 3 is preferable with respect to a pigment, More preferably, it is the range of 1: 0.125 to 1: 3.

  It is also possible to use a water-soluble surfactant as a pigment dispersant. In this case, the increase in the ink viscosity with respect to the amount used is smaller than when the polymer dispersant is used, and it is easy to obtain a pigment ink having good ejection characteristics when used in the ink jet recording method.

  Specific examples of water-soluble surfactants used as pigment dispersants include, for example, anionic surfactants such as alkylallyl or alkylnaphthalene sulfonate, alkyl phosphate, alkyl sulfate, alkyl sulfonate, alkyl ether sulfate. Salt, alkyl sulfosuccinate, alkyl ester sulfate, alkyl benzene sulfonate, alkyl diphenyl ether disulfonate, alkyl aryl ether phosphate, alkyl aryl ether sulfate, alkyl aryl ether ester sulfate, olefin sulfonate, alkane olefin Sulfonate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether sulfate ester, ether carboxylate, sulfosuccinate, α-sulfo fatty acid ester , Fatty acid salts, condensates of higher fatty acid and an amino acid, a naphthenic acid salt or the like.

  Examples of the cationic surfactant include alkylamine salts, dialkylamine salts, aliphatic amine salts, benzalkonium salts, quaternary ammonium salts, alkylpyridinium salts, imidazolinium salts, sulfonium salts, phosphonium salts, and the like.

  Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene glycol ester, polyoxyethylene fatty acid amide, polyoxyethylene fatty acid ester, polyoxyethylene poly Oxypropylene glycol, glycerin ester, sorbitan ester, sucrose ester, polyoxyethylene ether of glycerin ester, polyoxyethylene ether of sorbitan ester, polyoxyethylene ether of sorbitol ester, fatty acid alkanolamide, amine oxide, polyoxyethylene alkylamine Glycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fat Esters, polyoxyethylene sorbitol fatty acid esters, alkyl (poly) Gurikokishido like.

  Examples of amphoteric surfactants include imidazoline derivatives such as imidazolinium betaine, dimethylalkyllauryl betaine, alkylglycine, and alkyldi (aminoethyl) glycine.

  The addition amount of the surfactant as the dispersant may be appropriately added within the range in which the pigment is stably dispersed and the other effects of the present invention are not lost.

  As a dispersant, it is preferable that a carboxyl group is bonded to the dispersant in the ink. When a carboxyl group is bonded to the dispersant, not only the dispersion stability is improved, but also high-quality print quality is obtained, and the water resistance of the recording medium after printing is further improved. Furthermore, the effect of preventing the above-described back-through can be obtained.

  As another form, a form in which the pigment in the ink is surface-modified and the carboxyl group or the sulfonic acid group is directly bonded to the pigment and dispersed in water is also preferable. In this case, since the surface of the pigment is modified and the carboxyl group is bonded, not only the dispersion stability is improved, but also high-quality printing quality is obtained and the water resistance of the recording medium after printing is further improved. Also, this form of ink has excellent redispersibility after drying, so printing is suspended for a long period of time, and clogging does not occur even when ink moisture near the nozzles of the inkjet head evaporates, making it easy with a simple cleaning operation. Good printing can be performed.

  In addition to the colorant, wetting agent and surfactant, conventionally known additives can be added to the aqueous recording liquid of the present invention. For example, a resin emulsion may be added as the ink composition of the present invention. The resin emulsion has the property of thickening and agglomerating, has the effect of suppressing the penetration of the coloring component, and further promoting the fixing to the recording material. Further, depending on the type of resin emulsion, a film is formed on the recording material, and the printed material has an effect of improving the abrasion resistance.

  The resin emulsion that can be used in the present invention means an emulsion in which the continuous phase is water and the dispersed phase is the following resin component. Examples of the resin component in the dispersed phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, and styrene resins. This resin is preferably a polymer having both a hydrophilic part and a hydrophobic part. The particle size of these resin components is not particularly limited as long as an emulsion is formed, but is preferably about 150 nm or less, more preferably about 5 to 100 nm. These resin emulsions can be obtained by mixing resin particles in water, optionally with a surfactant.

  Commercially available resin emulsions include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink and Chemicals, Inc.), Boncoat 5454 (styrene-acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), SAE-1014 (styrene-acrylic resin emulsion, manufactured by Nippon Zeon Co., Ltd.), Cybinol SK-200 (acrylic resin emulsion, Seiden Chemical Co., Ltd.) Company-made).

  When a resin emulsion is added as the ink composition of the present invention, the resin component is preferably contained in an amount of 0.1 to 40% by weight, more preferably 1 to 25% by weight, based on the total amount of the ink composition. Range.

Furthermore, antiseptic / antifungal agents, pH adjusters, chelating reagents and the like can be added to the ink composition of the aqueous recording liquid of the present invention.
As the antiseptic / antifungal agent, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol and the like can be used.

As the pH adjuster, any substance can be used as long as the pH can be adjusted to 7 or more without adversely affecting the ink to be prepared.
Examples thereof include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide, and quaternary phosphonium. Examples thereof include carbonates of alkali metals such as hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate.

  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. In addition, a water-soluble ultraviolet absorber and a water-soluble infrared absorber can be added depending on the purpose.

  The aqueous recording liquid (ink) of the present invention is particularly preferably used in an ink jet recording method for forming a color image on a recording medium by ejecting and flying ink as droplets from a fine ejection port. Needless to say, it can be used as a recording liquid for general writing instruments such as water-based ballpoint pens, recorders, and pen plotters. Further, the aqueous recording liquid of the present invention is not limited to the above uses.

  When the aqueous recording liquid of the present invention is used in an ink jet recording method, it is necessary to adjust the recording liquid viscosity to a desired value. In general, the viscosity of the recording liquid is preferably 10 mPa · s or less, depending on the ejection force of the head. When the pressure is higher than 10 mPa · s, sufficient ejection cannot be performed with an ink jet, and a problem of image failure often occurs.

  The recording medium suitable for the aqueous recording liquid (ink) of the present invention preferably comprises pulp fibers as a main component and a sizing degree of 10 s or more and an air permeability of 5 s to 50 s. The degree of sizing mentioned here is carried out in accordance with the JIS P8122-76 test method for paper sizing and sizing, and the air permeability is measured in accordance with JIS P8117-80. If the sizing degree is less than 10 s, the ink penetrates to the back surface, resulting in a back-through, and if the air permeability is less than 5 s, the ink penetrates to the back surface and causes a back-through, and if it exceeds 50 s, printing occurs. There is no problem in quality and drying properties, but the cost is increased because the filler is added more than necessary.

  In addition, when this recording medium is used in an electrophotographic copying machine or printer, the filling amount is transferred to a photoconductor or a fixing roller, which causes deterioration of image quality or failure. It must be used, and it will be a burden because consumers will be asked to use it properly. By using the above sizing and air permeability, it is handled in the same way as various non-coated plain paper such as electrophotographic transfer paper, printing paper, tie writer paper, wire dot printer paper, word processor paper, letter paper, report paper, etc. Accordingly, there is no need for the user to separate from other plain paper. In addition, the paper can be basically produced with an existing paper machine, and the capital investment can be minimized. It can also be used in common for these other recording methods.

  The pulp fiber material used in the present invention can be appropriately used regardless of the type of pulp and the treatment method as long as it does not affect the inkjet process. Further, non-wood pulp (kenaf, flax, bamboo, seaweed, etc.) or waste paper pulp may be used, or these may be mainly used. Preferably, it is a chemical pulp represented by LBKP and NBKP. Paper making of these pulps is carried out in the usual manner using known sizing agents, fillers, and other paper making aids as required, as with ordinary plain paper.

  Examples of the sizing agent include rosin size, AKD, sodium chloride, potassium chloride, styrene monomaleic acid copolymer, quaternary ammonium salt, alkenyl succinic anhydride, petroleum resin-based size, epichlorohydrin, cationic starch, acrylamide and the like. Examples of the filler include clay, calcium carbonate, talc, titanium dioxide, and synthetic silica. Further, a paper strength enhancer, a yield improver, a fixing agent, a dye, and other paper making aids are added.

  Next, the aqueous recording liquid of the present invention is stored in a recording liquid cartridge (ink cartridge), and the ink cartridge is mounted on an ink jet printer, and ejected and ejected as droplets from a fine ejection port to form an image on a recording medium. Although the method to do is demonstrated with reference to an accompanying drawing, the following is only one of the structural examples, Comprising: This invention is not limited at all.

FIG. 1 is a schematic front view of a mechanism part of a serial type ink jet recording apparatus equipped with an ink cartridge equipped with a recording liquid storage part storing an aqueous recording liquid of the present invention.
The mechanism of this ink jet recording apparatus has a main support guide rod 3 and a sub support guide rod 4 mounted between the side plates 1 and 2 on both sides in a substantially horizontal positional relationship, and the main support guide rod 3 and the sub support guide. The carriage 4 is supported by the rod 4 so as to be slidable in the main scanning direction.

  The carriage unit 5 has four heads 6 for ejecting yellow (Y) ink, magenta (M) ink, cyan (C) ink, and black (Bk) ink, respectively, and an ejection surface (nozzle surface) 6a. The four ink cartridges 7y, 7m, 7c, and 7k, which are ink supply bodies for each color, are mounted downward and are provided on the upper side of the head 6 of the carriage unit 5 to supply ink to the four heads 6, respectively. Is installed in a replaceable manner.

  The carriage unit 5 is connected to a timing belt 11 stretched between a driving pulley (drive timing pulley) 9 and a driven pulley (idler pulley) 10 that are rotated by the main scanning motor 8, and the main scanning motor 8 is connected to the carriage unit 5. By controlling the driving, the carriage 5, that is, the four heads 6 are moved in the main scanning direction.

  Further, sub-frames 13 and 14 are erected on the bottom plate 12 connecting the side plates 1 and 2, and a conveying roller 15 for feeding the paper 16 in the sub-scanning direction orthogonal to the main scanning direction is provided between the sub-frames 13 and 14. Holds freely. A sub-scanning motor 17 is disposed on the side of the sub-frame 14, and a gear 18 fixed to the rotation shaft of the sub-scanning motor 17 and the transporting roller 15 in order to transmit the rotation of the sub-scanning motor 17 to the transporting roller 15. And a gear 19 fixed to the shaft.

  Further, a reliability maintenance / recovery mechanism (hereinafter referred to as “subsystem”) 21 of the head 6 is disposed between the side plate 1 and the subframe 13. The sub-system 21 holds four cap means 22 for capping the ejection surface of each head 6 by a holder 23, and this holder 23 is held by a link member 24 so as to be swingable so that the carriage unit 5 can move in the main scanning direction. When the carriage unit 5 comes into contact with the engaging portion 25 provided on the holder 23 by the movement of the holder 23, the holder 23 is lifted up according to the movement of the carriage unit 5 and the ejection surface 6a of the inkjet head 6 is capped by the cap means 22, As the carriage unit 5 moves to the printing region side, the holder 23 is lifted down as the carriage unit 5 moves, so that the cap means 22 moves away from the ejection surface 6 a of the inkjet head 6.

  The cap means 22 is connected to the suction pump 27 via the suction tube 26, forms an atmosphere opening port, and communicates with the atmosphere via the atmosphere opening tube and the atmosphere opening valve. The suction pump 27 discharges the sucked waste liquid to a waste liquid storage tank (not shown) through a drain tube or the like.

  Further, on the side of the holder 23, a wiper blade 28, which is a wiping means made of an elastic member such as a fiber member, a foam member, or rubber, for wiping the discharge surface 6a of the inkjet head 6 is attached to a blade arm 29. Reference numeral 29 is pivotally supported so that it can be swung by rotation of a cam that is rotated by a driving means (not shown).

  Next, the ink cartridge 7 will be described with reference to FIGS. Here, FIG. 2 shows an external perspective view of the ink cartridge before loading into the recording apparatus of FIG. 1, and FIG. 3 shows a front sectional view of the ink cartridge.

  As shown in FIG. 3, the ink cartridge 7 includes an ink absorber 42 that absorbs ink of a required color in a cartridge main body 41. The cartridge body 41 is formed by adhering or welding an upper lid member 44 to an upper opening of a case 43 having a wide opening at the upper portion, and is made of, for example, a resin molded product. The ink absorber 42 is made of a porous material such as a urethane foam, and after being compressed and inserted into the cartridge body 41, the ink is absorbed.

  An ink supply port 45 for supplying ink to the recording head 6 is formed at the bottom of the case 43 of the cartridge body 41, and a seal ring 46 is fitted on the inner peripheral surface of the ink supply port 45. The upper lid member 44 has an air opening 47 formed therein. In the cartridge main body 41, the case 43 is compressed and deformed by the pressure applied to the wide side wall when the ink supply port 45 is closed and the cartridge is handled during loading and transportation, or during vacuum packaging. In order to prevent the internal ink from leaking, a cap member 50 is attached.

Further, as shown in FIG. 2, the air opening 47 is sealed by sticking a film-like seal member 55 having an oxygen permeability of 100 ml / m ² or more to the upper lid member 44. In this way, the air opening 47 is sealed with the sealing member 55 having an oxygen permeability of 100 ml / m ² or more, so that the ink cartridge 7 is packaged in a reduced pressure state using a packaging member such as a non-permeable aluminum laminate film. Thus, even when the gas is dissolved in the ink due to the atmosphere in the space A (see FIG. 3) generated between the ink absorber 42 and the cartridge main body 41 when the ink is filled, the ink passes through the seal member 55. The air inside is discharged into a space between the packaging body outside the cartridge main body 41 having a high degree of vacuum, and the degree of deaeration of the ink is improved.

  FIG. 4 shows an example of the configuration of a recording cartridge (recording unit) provided with a recording liquid storage unit storing the recording liquid of the present invention and a head unit for discharging recording droplets. The recording unit will be described below.

  The recording unit 30 is of a serial type, and includes a head 6, an ink tank 33 that stores an aqueous recording liquid (ink) supplied to the head 6, and a lid member 34 that seals the inside of the ink tank 33. The main part is composed.

  The head 6 of the recording unit 30 has a large number of nozzles 32 for discharging an aqueous recording liquid. The recording liquid is guided from the ink tank 33 to a common liquid chamber (not shown) through an ink supply pipe (not shown), and is discharged from the nozzle 32 in accordance with an electric signal from the recording apparatus main body input from the electrode 31. The Such a type of recording unit 30 has a structure suitable for a head of a type that can be manufactured at low cost, a so-called thermal type or bubble type head that uses thermal energy as a driving power source. The recording liquid of the present invention improves the wettability to a thermal element in a recording method such as bubble or thermal method, so that even when added in a small amount, ejection stability and frequency stability can be obtained, and safety is also high. Is very suitable.

  Here, the serial type ink jet recording apparatus as described above has been described, but the aqueous recording liquid of the present invention has a density equal to or about a fraction of the target image resolution in an arbitrary arrangement such as a staggered nozzle. It is also possible to apply the present invention to a recording apparatus having a so-called line head, which is integrated in an array and arranged more than the width of the recording medium. In addition, the recording apparatus here may be an apparatus having a complex function in combination with a fax machine, a scanner, a telephone, or the like as well as a PC or a digital camera output printer.

  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.

Example 1
Each component of the following ink composition formulation (1) was uniformly mixed, and then adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8-9. Then, it filtered with the membrane filter with an average hole diameter of 0.2 micrometer, and obtained the aqueous recording liquid 1.

<Ink composition formulation (1)>
Direct Blue 199 3.0% by weight
Glycerol 7.0% by weight
Diethylene glycol 20.0% by weight
Dimethylsulfone 5.0% by weight
2-n-butyl-2-ethyl-1,3-propanediol 1.5% by weight
Ion exchange water

Example 2
Each component of the following ink composition formulation (2) was uniformly mixed, and then adjusted with a 10% aqueous solution of sodium hydroxide so that the pH was 8-9. Thereafter, filtration with a membrane filter having an average pore diameter of 0.2 μm was performed to obtain an aqueous recording liquid 2.

<Ink composition prescription (2)>
Direct Yellow 132 2.5% by weight
Glycerol 7.0% by weight
Triethylene glycol 20.0% by weight
Dipropylsulfone 10.0% by weight
2,4-diethyl-1,5-pentanediol 4.0% by weight
Ion exchange water

Example 3
Each component of the following ink composition formulation (3) was uniformly mixed, and then adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8-9. Thereafter, filtration with a membrane filter having an average pore diameter of 0.2 μm was performed to obtain an aqueous recording liquid 3.

<Ink composition prescription (3)>
Acid Red 249 3.0% by weight
Glycerol 7.0% by weight
1,3-propanediol 15.0% by weight
Ethylpropylsulfone 10.0% by weight
2-n-butyl-2-ethyl-1,3-propanediol 1.0% by weight
Nikko Chemicals Corporation ECTD3NEX (* 1) 0.5% by weight
Ion exchange water
(* 1): R1 = tridecyl group of the general formula (1), m = 3, M = Na

Example 4
Each component of the following ink composition formulation (4) was uniformly mixed, and then adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8-9. Thereafter, filtration with a membrane filter having an average pore diameter of 0.2 μm was performed to obtain an aqueous recording liquid 4.

<Ink composition prescription (4)>
Direct Black 168 5.0% by weight
Glycerol 7.0% by weight
Ethylene glycol 25.0% by weight
Dimethylsulfone 5.0% by weight
2-ethyl-1.3-hexanediol 2.5% by weight
Ion exchange water

Example 5
Each component of the following ink composition formulation (5) was uniformly mixed, and then adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8-9. Thereafter, filtration with a membrane filter having an average pore diameter of 0.2 μm was performed to obtain an aqueous recording liquid 5.

<Ink composition formulation (5)>
Direct Black 168 4.0% by weight
Glycerol 7.0% by weight
Diethylene glycol 15.0% by weight
Dipropylsulfone 15.0% by weight
2,4-diethyl-1,5-pentanediol 4.0% by weight
2-pyrrolidone 2.0% by weight
Ion exchange water

Example 6
A pigment dispersion was prepared according to the following pigment dispersion formulation (1). After premixing the mixture having the following formulation, it was put into a 1 liter vessel, 900 g of zirconia beads having a diameter of 0.3 mm was added, and the mixture was dispersed for 48 hours with a Campe batch type tabletop sand mill to obtain pigment dispersion 1. The average particle diameter of the pigment in the obtained pigment dispersion 1 was 102 nm (measured using Microtrac UPA150).

<Pigment dispersion formulation (1)>
C. I. Pigment Blue 15: 3 15.0% by weight
Styrene-acrylate-methacrylic acid-
Diethanolamine salt copolymer 3.0% by weight
Ion exchange water

  Using the obtained pigment dispersion 1, the components were uniformly mixed and stirred according to the following ink composition prescription (6), and then a 10% aqueous solution of sodium hydroxide was used so that the pH was 8-9. It was adjusted. Thereafter, filtration with a membrane filter having an average pore diameter of 0.8 μm was performed to obtain an aqueous recording liquid 6.

<Ink composition formulation (6)>
Pigment dispersion 1 20.0% by weight
Glycerol 7.0% by weight
1,3-propanediol 23.0% by weight
Dimethylsulfone 5.0% by weight
2-n-butyl-2-ethyl-1,3-propanediol 1.5% by weight
Ion exchange water

Example 7
A pigment dispersion was prepared according to the following pigment dispersion formulation (2). After premixing the mixture of the following formulation, it was put into a 1 liter vessel, 900 g of zirconia beads having a diameter of 0.3 mm was added, and the mixture was dispersed for 48 hours with a Campe batch type tabletop sand mill to obtain pigment dispersion 2. The average particle diameter of the pigment in the obtained pigment dispersion 2 was 114 nm (measured using Microtrac UPA150).

<Pigment dispersion formulation (2)>
Carbon black 15.0% by weight
Styrene-acrylate-methacrylic acid-
Diethanolamine salt copolymer 3.0% by weight
Ion exchange water

  Using the obtained pigment dispersion 2, the components were uniformly mixed and stirred according to the following ink composition prescription (7), and then a 10% aqueous solution of sodium hydroxide was used so that the pH was 8-9. It was adjusted. Thereafter, filtration with a membrane filter having an average pore diameter of 0.8 μm was performed to obtain an aqueous recording liquid 7.

<Ink composition formulation (7)>
Pigment dispersion 2 33.33% by weight
Glycerol 7.0% by weight
1,3-butanediol 23.0% by weight
Dipropylsulfone 10.0% by weight
2-ethyl-1.3-hexanediol 2.5% by weight
Nikko Chemicals Corporation ECTD6NEX (* 2) 0.5% by weight
2-pyrrolidone 2.0% by weight
Residual amount of ion-exchanged water (* 2): R1 = tridecyl group of general formula (1), m = 6, M = Na

Example 8
In the same manner as in Example 1 except that each composition of the following ink composition formulation (8) is used, the pH is adjusted to 8 with a 10% aqueous solution of lithium hydroxide, and then the average pore size is 0.2 μm. An aqueous recording liquid 8 was obtained by filtration through a membrane filter.

<Ink composition formulation (8)>
Carboxylate-bonded carbon black
Dispersion (* 3) 33.33% by weight
Glycerol 7.0% by weight
Diethylene glycol 23.0% by weight
Dipropylsulfone 5.0% by weight
2-n-butyl-2-ethyl-1,3-propanediol 1.5% by weight
Ion-exchanged water remaining amount (* 3): CAB-O-JET 300 (Cabot Corporation)

Example 9
In the same manner as in Example 1 except that each component of the following ink composition formulation (9) was used, the pH was adjusted to 8 with a 10% aqueous solution of lithium hydroxide, and then the average pore size was 0.2 μm. An aqueous recording liquid 9 was obtained by filtration through a membrane filter.

<Ink composition formulation (9)>
Sulfonate-bonded carbon black dispersion (* 4) 25.0% by weight
Glycerol 7.0% by weight
1,3-butanediol 25.0% by weight
Dimethylsulfone 5.0% by weight
2-ethyl-1.3-hexanediol 2.5% by weight
Ion-exchanged water remaining amount (* 4): CAB-O-JET 200 (Cabot Corporation)

Comparative Example 1
In the same manner as in Example 1 except that each component of the following ink composition formulation (10) was used, the pH was adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8 to 9, and then the average pore size was adjusted to 0.00. The aqueous recording liquid 10 was obtained by filtration through a 2 μm membrane filter.

<Ink composition formulation (10)>
Direct Black 168 4.0% by weight
Glycerol 7.0% by weight
Triethylene glycol 23.0% by weight
Ion exchange water

Comparative Example 2
In the same manner as in Example 1 except that each component of the following ink composition formulation (11) was used, the pH was adjusted with a 10% aqueous solution of sodium hydroxide so as to be 8 to 9, and then the average pore size was adjusted to 0.00. The aqueous recording liquid 11 was obtained by filtration through a 2 μm membrane filter.

<Ink composition formulation (11)>
Direct Black 168 4.0% by weight
Glycerol 7.0% by weight
Diethylene glycol 23.0% by weight
2-methyl-2-propyl-1,3-propanediol 2.0% by weight
Ion exchange water

Comparative Example 3
In the same manner as in Example 1 except that each composition of the following ink composition formulation (12) was used, the pH was adjusted with a 10% aqueous solution of sodium hydroxide so that the pH was 8 to 9, and then the average pore size was adjusted to 0.00. The aqueous recording liquid 12 was obtained by filtration through a 2 μm membrane filter.

<Ink composition formulation (12)>
Direct Black 168 4.0% by weight
Glycerol 7.0% by weight
Diethylene glycol 23.0% by weight
2-methyl-2-propyl-1,3-propanediol 4.0% by weight
Ion exchange water

Comparative Example 4
Except for using each component of the following ink composition formulation (13), the mixture was adjusted with a 10% aqueous solution of lithium hydroxide so that the pH was 8-9, and then the average pore size was adjusted to 0.00. An aqueous recording liquid 13 was obtained by filtration through a 2 μm membrane filter.

<Ink composition formulation (13)>
Pigment dispersion 2 of Example 7 33.33% by weight
Glycerol 7.0% by weight
Triethylene glycol 23.0% by weight
Triethylene glycol monobutyl ether 4.0% by weight
Ion exchange water

  Next, for the aqueous recording liquids 1 to 13 obtained in Examples 1 to 9 and Comparative Examples 1 to 4, the surface tension of the ink, the sharpness of the image, the drying property of the image, the breakthrough, the scratching property, the image The embedding and storage properties were evaluated under the following evaluation conditions. The evaluation results for each evaluation item are shown in Table 1 below.

The evaluation conditions and evaluation judgments for image sharpness, image dryness, back-through, scratching, image embedding, and storage stability were as follows.
(1) Ink surface tension:
The surface tension of the ink was measured using an automatic surface tension meter K10ST made by KRUSS. The measurement temperature was 25 ° C.
(2) Image clarity:
As a recording medium, My Paper (size: 12 s, air permeability: 16 s) manufactured by NBS Ricoh Co., Ltd. was used. This recording medium is printed with a piezo ink jet printer (IPSIO JET 300 manufactured by Ricoh Co., Ltd.). The colorimetric densitometer (manufactured by X-Rite) was used for comprehensive judgment. Good was judged as ○, and bad was judged as ×.
(3) Image dryness:
The filter paper was pressed against the image after printing the solid image on the recording medium at a pressure of 0.1 kg / cm @ 2, and the time until the ink was not transferred to the filter paper was measured. When any paper was dried within 3 seconds, it was judged as ◯. The case of exceeding 3 seconds was judged as x.
(4) Betrayal:
A solid image was formed on the recording medium so that the density of each ink color measured with a reflective color spectrocolorimetric densitometer (manufactured by X-Rite) was 1.0. When this image is visually observed from the back side and the boundary between the solid image and the white background is clear and there is a problem in using it for double-sided printing, ×, the boundary between the solid image and the white background is almost unclear and double-sided printing In the case of a level where there is no problem even if it is used for, the boundary between the solid image and the white background is completely unclear, and in the case where there is no problem even if it is used for double-sided printing, it is judged as ◎.
(5) Abrasion:
If the image formed with each ink on the recording medium is scraped with a finger, cloth, eraser, or marking pen 30 seconds after printing, and the image after the rubbing is visually observed and an image change due to rubbing occurs. If there was no occurrence, it was rated as ○.
(6) Image filling:
After drying, the solid image was visually observed. When the recording medium was uniformly colored with ink, it was marked as ◯, and when it was unevenly colored so that the background could be seen, it was marked as x.
(7) Storage stability:
With the ink set in the inkjet printer, it was left at 60 ° C. for 7 days. After that, it could be returned by a cleaning operation of the inkjet printer.

  From the results shown in Table 1, when using the aqueous recording liquid comprising the ink composition of the present invention, the surface tension of the ink is lower than that of the comparative example, and the sharpness of the image, the drying property of the image, It has been confirmed that it has excellent show-through, scratching, image embedding, and storage stability, is highly dry for high-speed printing, and can be printed without show-through.

In the aqueous recording liquid of the present invention, 2-n-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl as a diol derivative having 8 or more carbon atoms. By using at least one compound selected from 1,3-hexanediol and using dimethyl sulfone, dipropyl sulfone, and ethylpropyl sulfone as compounds containing sulfur atoms in the molecule, high permeation characteristics and high image quality Is obtained.
Further, when a surfactant is used in combination, a synergistic effect is exhibited, and further, image density reduction and back-through are prevented. Furthermore, by adding polyoxyethylene alkyl ether acetate, the filling of the image is further improved and the image density is increased. Furthermore, when 2-pyrrolidone is added, the penetration into paper is not impaired, and further image density is improved, and back-through is prevented. Further, by adjusting the average particle diameter of the pigment (in the range of 10 nm to 200 nm), the dispersion stability is improved, the ejection stability is further improved, and the image see-through is prevented.
Further, when a dispersant having a carboxyl group bonded thereto is used, the dispersion stability is increased, high printing quality is obtained, and the water resistance of the recording medium after printing is further improved. When the pigment is surface-modified with a carboxyl group or a sulfonic acid group, the dispersion stability is improved and high print quality is obtained, the water resistance of the recording medium after printing is further improved, and the ink is dried after the ink is dried. Dispersibility is improved.
Since the aqueous recording liquid comprising the ink composition of the present invention is stable without causing aggregation or thickening as described above, a recording method for forming an image on a recording medium by ejecting and flying as droplets from a fine ejection port It is suitable for use in. In particular, even when printing is suspended for a long time and the water content of the aqueous recording liquid (ink) evaporates, clogging does not occur, and good printing can be easily performed with a simple cleaning operation.

FIG. 2 is a schematic front view showing an example of the structure of a mechanical part of a serial type ink jet recording apparatus equipped with an ink cartridge containing the aqueous recording liquid of the present invention. FIG. 2 is an external perspective view of an ink cartridge before being loaded into the recording apparatus illustrated in FIG. 1. FIG. 3 is a front sectional view of the ink cartridge shown in FIG. 2. FIG. 2 is an external perspective view of a recording unit (an ink cartridge integrated with a head) before being loaded into the recording apparatus illustrated in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Side plate 2 Side plate 3 Main support guide rod 4 Sub support guide rod 5 Carriage unit 6 Head 6a Discharge surface (nozzle surface)
7 Ink Cartridge 7y Ink Cartridge 7m Ink Cartridge 7c Ink Cartridge 7k Ink Cartridge 8 Main Scanning Motor 9 Drive Pulley (Drive Timing Pulley)
10 Driven pulley (idler pulley)
11 Timing belt 12 Bottom plate 13 Sub frame 14 Sub frame 15 Transport roller 16 Paper 17 Sub scanning motor 18 Gear 19 Gear 21 Sub system 22 Cap means 23 Holder 24 Link member 25 Engaging portion 26 Suction tube 27 Suction pump 28 Wiper blade 29 Blade Arm 30 Recording unit 31 Electrode 32 Nozzle 32
33 Ink tank 34 Lid member 41 Cartridge body 42 Ink absorber 43 Case 44 Upper lid member 45 Ink supply port 46 Seal ring 47 Air release port 50 Cap member 55 Seal member A Space

Claims (12)

  An aqueous composition comprising a colorant that dissolves or disperses in water, water, a diol derivative having 8 or more carbon atoms, a compound containing a sulfur atom in the molecule, and a water-soluble organic solvent as an ink composition. Recording liquid.   The diol derivative having 8 or more carbon atoms is 2-n-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol. The aqueous recording liquid according to claim 1, wherein the aqueous recording liquid is at least one compound selected from the group consisting of:   3. The aqueous recording liquid according to claim 1, wherein the diol derivative having 8 or more carbon atoms is contained in the range of 0.1 to 5.0% by weight with respect to the total amount of the ink composition.   2. The aqueous recording liquid according to claim 1, wherein the compound containing a sulfur atom in the molecule is at least one compound selected from dimethylsulfone, dipropylsulfone, and ethylpropylsulfone.   5. The aqueous recording liquid according to claim 1, wherein a compound containing a sulfur atom in the molecule is contained in the range of 1.0 to 20.0 wt% with respect to the total amount of the ink composition.   6. The aqueous recording liquid according to claim 1, wherein the aqueous recording liquid further contains 2-pyrrolidone. The aqueous recording liquid further contains a surfactant represented by the following general formula (1) in a proportion of 0.01 to 5% by weight based on the total weight of the ink composition. 7. The aqueous recording liquid according to any one of 6.
_{R1-O- (CH 2 CH 2} O) m -CH 2 COOM ... (1)
(In the formula, R1 is an alkyl group having 6 to 14 carbon atoms which may be branched, m is a natural number of 3 to 12, M represents an alkali metal ion, quaternary ammonium, quaternary phosphonium, or alkanolamine. )   The aqueous recording liquid according to claim 1, wherein the colorant has an average particle diameter in a range of 10 nm to 200 nm.   The aqueous recording liquid according to any one of claims 1 to 8, wherein the colorant is a pigment dispersed in water by a dispersant having a carboxyl group bonded thereto.   The aqueous recording liquid according to any one of claims 1 to 8, wherein the colorant is a pigment having a surface modified with a carboxyl group bonded thereto and dispersed in water.   9. The aqueous recording liquid according to claim 1, wherein the colorant is a pigment having a sulfonic acid group bonded to the surface thereof and surface-modified and dispersed in water. 12. A recording method, wherein the aqueous recording liquid according to claim 1 is ejected and ejected as droplets from a fine ejection port to form an image on a recording medium.

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