JPH09176533A - Ink composition for ink jet recording and ink jet recording method - Google Patents

Abstract

(57) [Abstract] [Object] There is little irregular bleeding on a recording medium, there is no change in physical properties or ejection characteristics during storage, and there is no precipitation of solids.
Also provided are an ink composition for inkjet recording and a recording method which are excellent in redispersibility. The composition contains a pigment, a resin dispersant, a thermoplastic resin emulsion, and water, and the weight ratio of the pigment to the resin dispersant is 20: 1 to 5: 2. In the recording method, a droplet of the composition is ejected from an inkjet recording head to be attached to a recording medium, and at the same time as the attachment, heat is applied to the ink composition droplet from the recording medium support through the recording medium. Fix it.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ink composition for inkjet recording and an inkjet recording method. That is, the present invention relates to an ink composition for an ink jet printer which obtains an ink image on a recording medium, for example, recording paper or a recording medium such as cotton or silk fiber by ejecting ink droplets from an inkjet recording head, and more specifically, a color inkjet. The present invention relates to an ink composition for a printer and an inkjet recording method using the ink composition.

[0002]

2. Description of the Related Art Ink jet recording ink compositions are generally required to have the following characteristics.

(1) Little irregular bleeding on the recording medium; and (2) No change in physical properties or ejection characteristics during storage and no precipitation of solids.

In particular, bleed-free printing is important in printing color images. In the case of color printing, a multicolor ink composition is printed on the same recording medium. In order to obtain color printing without color unevenness, it is necessary that the boundaries of colors in the image be clear. For that purpose, it is necessary to prevent the ink composition from mixing in this region.

Various proposals have been made so far in order to realize printing without bleeding. For example, JP-A-58-
No. 1,886,841 and JP-A No. 62-288042 disclose methods for printing while heating a recording medium. However, the use of ink compositions containing a thermoplastic resin is not disclosed in each of these publications.

Recently, pigment-based ink compositions have also been researched and developed for the purpose of realizing printing without blurring and improving light resistance and weather resistance. For example,
Japanese Unexamined Patent Publication No. 6-116522 discloses an ink composition containing a water-soluble resin, a water-soluble solvent, a pigment, and specific additives based on water. However, since the ink composition disclosed in the above publication has a problem that clogging occurs in the ink discharge head, a recording method of a type in which fixing is performed at the same time when the ink composition reaches a heated recording medium. Cannot be used for. Further, JP-B-62-1426 and JP-A-2-255875.
JP-A-4-18462 and JP-A-4-18462 contain water, a pigment and a resin emulsion as constituents of an ink composition, thereby solving the problems of water resistance and light resistance, and at the same time, using conventional dyes. Inks have been reported that solve problems such as character bleeding, which was a problem with system inks.

When an ink composition containing a thermoplastic resin is attached to a recording medium by an ink jet recording method and the recording medium is heated at a specific temperature or higher, bleeding of print can be suppressed well. As a matter of course, the ink composition used in this recording method is also desired to have no change in physical property value or change in ejection characteristic during storage and no precipitation of solid content. Further, since heat is used in this recording method, the ink composition may dry and solidify on the nozzle plate.

Further, when the ink composition used is a pigment-based ink composition and contains a large amount of solids, the following two problems are the main problems resulting from this.

The first problem is that the ink composition may solidify due to some accident in the ink flow path from the ink tank, which is usually a sealed system, to the ink ejection head, and the solidification causes clogging in the recording head. May cause

The second problem is that when the ink composition adheres and dries on the plate on which the nozzles of the recording head are arranged,
If the ink cannot be removed promptly by the cleaning operation of the recording apparatus, ejection failure (flight bending) of the ink composition may occur during printing.

[0011]

The present inventors have proposed a method in which an ink composition containing a pigment and a thermoplastic resin is attached to a recording medium by an inkjet recording method, and the recording medium is heated at a specific temperature or higher. As a result of further development of an ink composition that can be suitably used, by setting the ratio of the pigment and the dispersant for the pigment within a specific range, bleeding of the print is suppressed and the ink is stored for a long period of time. However, it has been found that an ink composition having excellent redispersibility can be obtained while maintaining the ink characteristics in which solid content does not precipitate without any change in physical property value or ejection characteristic.

Therefore, an object of the present invention is to provide an ink composition containing a pigment and a thermoplastic resin, which can be suitably used in a system in which a recording medium is heated at a specific temperature or higher, and in which bleeding of print is suppressed. To do.

A further object of the present invention is to provide an ink composition which does not undergo changes in physical properties or ejection characteristics even after storage for a long period of time, and in which solids do not precipitate.

Further, an object of the present invention is to dry the ink composition in the ink flow path or on the plate in which the nozzles of the recording head are arranged, until the ink composition is heated and fixed on the recording medium at a specific temperature or higher. It is an object of the present invention to provide an ink composition for inkjet recording, which can be rapidly redispersed by contacting a solid matter solidified by the above with a new ink composition.

[0015]

The present invention comprises a pigment, a resin dispersant, a thermoplastic resin emulsion, and water, and the weight ratio of the pigment to the resin dispersant is 20: 1 to.
The present invention relates to an ink composition for inkjet recording, which is 5: 2.

Further, according to the present invention, droplets of the above-mentioned ink composition are ejected from an ink jet recording head to be attached to a recording medium, and at the same time as the attachment, the recording medium is removed from a recording medium support (eg platen). The present invention also relates to an inkjet recording method, which includes applying heat to the ink composition droplets to fix the droplets.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The ink composition for ink jet recording of the present invention contains at least a pigment, a resin dispersant, a thermoplastic resin emulsion, and water as essential components.

In the ink composition of the present invention, as the pigment, an organic pigment or an inorganic pigment, for example, an organic pigment or an inorganic pigment conventionally used in an ink composition for ink jet recording can be used. As the inorganic pigment, titanium oxide and iron oxide, and carbon black manufactured by a known method such as a contact method, a furnest method, or a thermal method can be used.
The organic pigments include azo pigments (for example, azo lake, insoluble azo pigments, condensed azo pigments, or chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, verinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigment, thioindigo pigment,
An isoindolinone pigment or a quinophthalone pigment), a dye chelate (for example, a basic dye type chelate, or an acid dye type chelate), a nitro pigment, a nitroso pigment, or aniline black can be used. Of these pigments, it is preferable to use a pigment having a good affinity with water.

More specifically, examples of pigments for black ink include carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black.
Alternatively, copper oxide, iron oxide (CI Pigment Black 11), metals such as titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1) can be used.

Further, as a pigment for color ink, C.I.
I. Pigment Yellow 1 (Fast Yellow G),
3, 12 (Disazo Yellow AAA), 13, 14, 1
7, 23, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 81, 83 (disazo yellow H
R), 95, 97, 98, 100, 101, 104, 1
08, 109, 110, 117, 120, 138, 15
3; I. Pigment Red 1, 2, 3, 5, 17,
22 (Brilliant First Scarlet), 23,
31, 38, 48: 2 (Permanent Red 2B (B
a)), 48: 2 (Permanent Red 2B (C
a)), 48: 3 (Permanent Red 2B (S
r)), 48: 4 (Permanent Red 2B (M
n)), 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 6
3: 2, 64: 1, 81 (Rhodamine 6G rake), 8
3, 88, 92, 101 (bengara), 104, 10
5, 106, 108 (Cadmium Red), 112, 1
14, 122 (quinacridone magenta), 123, 14
6, 149, 166, 168, 170, 172, 17
7, 178, 179, 185, 190, 193, 20
9, 219; or C.I. I. Pigment Blue 1, 2, 1
5 (phthalocyanine blue R), 15: 1, 15: 2,
15: 3 (phthalocyanine blue G), 15: 4, 1
5: 6 (phthalocyanine blue E), 16, 17: 1,
56, 60, 63; etc. can be used. The above-mentioned pigments can be used alone or in an appropriate combination of two or more. In the ink composition of the present invention, since a pigment is used, deterioration of the physical properties of the ink composition due to decomposition of the dye during storage, which is observed in the ink composition using a dye, and the resulting change in ejection characteristics and the ejection nozzle. Will not be clogged.

The content of the above-mentioned pigment is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight, based on the whole ink composition. By setting the content to 0.1% by weight or more, a sufficient printing density can be secured, and by setting the content to 10% by weight or less, structural viscosity is not generated in the viscosity characteristic of the ink, Further sufficient ejection stability can be secured. Further, when the content is 0.5 to 5% by weight, durability of ejection stability can be particularly improved.

The particle size of the pigment is not particularly limited, but the particle size (average particle size) is preferably 2
It is 5 μm or less, more preferably 1 μm or less. By using a pigment having a particle size of 25 μm or less, the occurrence of clogging can be suppressed, and more satisfactory ejection stability can be realized.

The ink composition according to the present invention contains a resin dispersant capable of dispersing and stabilizing the pigment in the form of fine particles in the ink composition. As the resin dispersant that can be used, for example, a copolymer resin having a hydrophilic portion and a hydrophobic portion in the molecule, specifically, an acrylic acid-based dispersant, for example, styrene-acrylic acid copolymer. Coal, styrene-acrylic acid-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, or styrene-methacrylic acid-acrylic acid ester copolymer, maleic acid-based dispersant, for example, styrene-maleic acid copolymer , Acrylic acid ester-maleic acid copolymer, or styrene-acrylic acid ester-maleic acid copolymer, sulfonic acid-based dispersant, for example, acrylic acid ester-styrene sulfonic acid copolymer, styrene-methacryl sulfonic acid copolymer Examples thereof include a polymer, an acrylic ester-allyl sulfonic acid copolymer, or a salt thereof. Weight average molecular weight (hereinafter, simply referred to as molecular weight) is 1600 to 25
It is preferable to use a copolymer resin having an acid value of 000 and an acid value of 100 to 250, particularly a styrene acrylic acid copolymer resin. When a copolymer resin having a molecular weight of 1600 to 25,000 and an acid value other than 100 to 250, particularly a styrene acrylic acid copolymer resin, is used, the ink composition may be left in the ink composition for a long period of time. There may be a problem that it is not possible to secure the leaving stability of the ink composition, such as the occurrence of pigment aggregates.

The above-mentioned resin dispersant can be prepared by a method known per se (for example, bulk polymerization or solution polymerization), or a commercially available resin dispersant can also be used.
As an example of the commercially available resin dispersant, John Kryl 68 (molecular weight = 10000; manufactured by Johnson Polymer Co., Ltd .;
Acid value = 195), Jonkryl 679 (molecular weight = 700)
0; acid value = 200), John Cryl 680 (molecular weight = 3)
900; acid value = 215), Jonkryl 682 (molecular weight = 1600; acid value = 235), Jonkryl 550 (molecular weight = 7500; acid value = 200), Jonkryl 555
(Molecular weight = 5000; Acid value = 200), John Kryl 5
86 (molecular weight = 3100; acid value = 105), Jonkryl 683 (molecular weight = 7300; acid value = 150), or B
-36 (molecular weight = 6800; acid value = 250) and the like can be mentioned.

In the ink composition of the present invention, the weight ratio of the pigment to the resin dispersant (pigment: resin dispersant) is in the range of 20: 1 to 5: 2.

If the content of the resin dispersant is lower than this ratio, the dispersion stability of the pigment when the ink composition is left standing deteriorates with time, aggregation occurs, and the viscosity characteristics deteriorate. When the content of the resin dispersant is higher than the above ratio, the redispersibility required for drying the ink composition cannot be obtained.

In order to dissolve the above resin dispersant in the aqueous ink composition of the present invention, it is preferable to form a salt with a counter ion in the acid group (eg acrylic acid group) contained in the resin dispersant. The compound that can be used for this purpose is not particularly limited as long as it is a base capable of forming a salt with a carboxyl group, and organic amines such as primary, secondary, tertiary amine or quaternized amine, Alternatively, amino alcohol compounds (eg, aminomethyl propanol, 2-aminoisopropanol, triethanolamine), cyclic amines such as morpholine, and inorganic bases such as aqueous ammonia can be used. The content of the base is preferably equal to or more than the neutralization equivalent of the resin dispersant, and more preferably about 1.3 times the neutralization equivalent from the viewpoint of fixability after printing.

Further, glycols such as propylene glycol and / or monohydric alcohols such as isopropanol may be used as a dissolution aid for the resin dispersant.

Further, in order to facilitate the ion dissociation of the salt in the dispersant obtained as described above, the ink composition of the present invention contains a pH buffer solution so that the ink composition has an optimum pH.
It is preferable to adjust the value to obtain the dissolution stability of the dispersant. The pH buffer solution is used for treating the ink composition at pH 7 to pH 10.
It is not particularly limited as long as it is a buffering agent that can be adjusted to, but specific examples include potassium hydrogen phthalate, potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium tetraborate, potassium hydrogen tartrate, sodium hydrogen carbonate. ,
Examples thereof include sodium carbonate, tris (hydroxymethyl) aminomethane, and / or tris (hydroxymethyl) aminomethane hydrochloride. From the viewpoint of the durability of the member of the head and the stability of the ink composition, the content thereof is preferably an amount such that the pH of the ink composition is approximately 7 to 10.

The ink composition of the present invention contains a thermoplastic resin emulsion. This thermoplastic resin emulsion is a dispersion of a thermoplastic resin in an aqueous medium.

As the thermoplastic resin component in the above-mentioned thermoplastic resin emulsion, the same thermoplastic resin component as that conventionally used in the ink composition for ink jet recording can be used. Specific examples of the thermoplastic resin include acrylic polymers, such as polyacrylic acid ester or its copolymer, polymethacrylic acid ester or its copolymer, polyacrylonitrile or its copolymer, polyacrylamide, and polyacrylamide. Acrylic acid or polymethacrylic acid; polyolefin polymers such as polyethylene, polystyrene or copolymers thereof; vinyl acetate polymers or vinyl acetate containing copolymers, for example,
Polyvinyl acetate or its copolymer, or polyvinyl acetal; polyvinyl chloride or its copolymer, polyvinylidene chloride, fluororesin, polychloroprene, or natural polymer resin can be used. In particular, styrene-acrylic acid ester copolymer, polyacrylic acid ester, polymethacrylic acid ester, polystyrene, polyethyl acrylic acid ester, styrene-butadiene copolymer, butadiene copolymer, acrylonitrile-butadiene copolymer, Chloroprene copolymer, crosslinked acrylic resin, crosslinked styrene resin, fluororesin, vinylidene fluoride, benzoguanamine resin, polyolefin resin, styrene-methacrylic acid ester copolymer, polystyrene, styrene-acrylamide copolymer, n-isobutyl acrylate, Acrylonitrile, vinyl acetate, acrylamide, polyvinyl acetal, rosin resin, polyethylene, vinylidene chloride resin, vinyl acetate resin, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic copolymer Or a vinyl chloride resin is preferred.

The thermoplastic resin component in the thermoplastic resin emulsion used in the ink composition of the present invention is
The "softening / melting temperature" is preferably 50 to 150 ° C, more preferably 60 to 100 ° C. In the present specification, the "softening / melting temperature" means a glass transition point, a melting point, a temperature at which the viscosity of the thermoplastic resin is 10 ¹¹ to 10 ¹² poise, a softening point, or a minimum film-forming temperature (MFT). It shall mean the lowest temperature of any of them.

It is generally said that the ink jet recording method is weaker in fixing strength (water resistance and / or scratch resistance) on a recording medium than an electrophotographic printer. However, when the ink jet recording method is carried out using the ink composition of the present invention containing the thermoplastic resin emulsion, the fixing strength is higher than that when the ink jet recording method is carried out using the conventional ink composition. Becomes higher. That is, the fixing of the printed matter of the ink jet recording method using the ink composition of the present invention is carried out in the recording apparatus at a temperature exceeding the "softening / melting temperature" of the resin component of the thermoplastic resin emulsion. The temperature of the platen at this time is a temperature at which a sufficient fixing strength with respect to the recording medium is given in consideration of clogging of the ink composition ejection head [at least the minimum film forming temperature (MFT) of the resin component of the thermoplastic resin emulsion). And sufficient temperature for drying the ink composition solvent]. Fixing by forming a film of the thermoplastic resin component shows sufficient fixing strength on a recording medium.
Therefore, the ink composition fixed on the recording medium by applying heat energy has sufficient water fastness and printing fastness such as scratch resistance.

The thermoplastic resin emulsion used in the ink composition of the present invention can be prepared by a method known per se (for example, emulsion polymerization), but a known or commercially available resin dispersant can also be used. For example, as a thermoplastic resin emulsion, resins described in JP-B-62-1426, JP-A-3-56573, JP-A-3-79678, JP-A-3-160068, JP-A-4-18462, etc. The emulsion can be used as is. In addition, as a commercially available resin emulsion,
For example, Microgel E-1002, E-2002,
E-5002 (styrene acrylic resin emulsion;
Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic emulsion; Dainippon Ink and Chemicals, Inc.), Boncoat 5454 (styrene acrylic resin emulsion; Dainippon Ink and Chemicals, Inc.), SA
E1014 (styrene acrylic resin emulsion; manufactured by Zeon Corporation), Cybinol SK-200 (acrylic resin emulsion; manufactured by Saiden Chemical Co., Ltd.), Nanocryl SBCX-2821 (silicon modified acrylic resin emulsion; manufactured by Toyo Ink Co., Ltd.), nanocryl SBCX-3689 (silicon modified acrylic resin emulsion; Toyo Ink Co., Ltd.), # 3070 (methyl methacrylate polymer resin emulsion; Mikuni dye company), S
G-60 (styrene-acrylic resin emulsion; manufactured by Gifu Ceramic Co., Ltd.), Grandol PP-
1000 (styrene-acrylic resin emulsion; manufactured by Dainippon Ink and Chemicals, Inc.) and the like.

The ratio of water to the resin component (dispersed phase) in the thermoplastic resin emulsion is 60 to 400 parts by weight of water, preferably 100 to 20 parts by weight relative to 100 parts by weight of the horizontal fat component.
A range of 0 parts by weight is suitable.

Also in these thermoplastic resin emulsions, the ink composition is adjusted to an optimum pH range (preferably 7 to 10, more preferably 7.5 to 9) in order to maintain the dispersion stability as well as the pigment. Preferably. Therefore, in order to maintain the dispersion stability of both the pigment and the thermoplastic resin emulsion, the pH value of the ink composition is in the optimum range for both (preferably 7-10, more preferably 7.5).
It is preferable to maintain at 9).

The content of the above-mentioned thermoplastic resin component is preferably 0.2 to 20% by weight, more preferably 7 to 20% by weight, based on the whole ink composition. By setting the content to 0.2% by weight or more, better printing quality can be secured, and by setting the content to 20% by weight or less, the viscosity of the ink composition can be appropriately suppressed. .

The ink composition of the present invention contains water as a main solvent. Conventionally, water is mainly used as a solvent for an ink composition because of its low viscosity, excellent safety, easy handling, low cost, and no odor. To be The water for the ink composition is preferably pure water or ultrapure water such as ion-exchanged water, ultrafiltered water, reverse osmosis water, or distilled water. Furthermore,
It is preferable to use water that has been sterilized by ultraviolet irradiation or the addition of hydrogen peroxide, because it is possible to prevent the generation of mold and bacteria during long-term storage.

The ink composition for ink jet recording of the present invention may further contain a saccharide. By containing the saccharide, the ink composition can be thickened and the ink composition can be provided with a moisturizing property. The content of the saccharide is a weight ratio (sugar / thermoplastic resin component) to the thermoplastic resin component in the thermoplastic resin emulsion, and is preferably 2/1 or less, more preferably 1/5 to 1 .

Examples of the saccharides include monosaccharides such as glucose, xylose or arabinose; disaccharides such as saccharose or maltose; polysaccharides such as maltotriitol or starch; and sugar derivatives such as maltitol or oligosaccharide alcohols. be able to.

The ink composition for ink jet recording of the present invention can contain a nonionic surfactant having a polyoxyethylene group in its molecular skeleton. By including this nonionic surfactant, excellent water resistance, abrasion resistance, marker resistance and water abrasion resistance can be imparted after printing. The content of this nonionic surfactant is
It is preferably 12% by weight or less, and more preferably 0.05 to 10% by weight, based on the entire ink composition. 12
If it is more than wt%, foaming may become severe,
If it is less than 0.05% by weight, the ink may not spread sufficiently on the recording medium.

The nonionic surfactant having a polyoxyethylene group in its molecular skeleton has an HLB value of 13
It is preferable to use the above nonionic surfactants.
As a nonionic surfactant having an HLB value of 13 or more,
For example, polyoxyethylene adduct to acetylene glycol, alcohol ethylene oxide, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene polystyryl phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyethylene-polyol propylene Alkyl ether, polyoxyethylene polyhydric alcohol fatty acid partial ester, polyoxyethylene fatty acid ester, polyglycerin fatty acid ester, polyoxyethylenated castor oil, polyoxyethylene alkylamine, or polyoxyethylene sorbitan fatty acid ester from the viewpoint of printing fastness preferable. These nonionic surfactants can be used alone or in combination of two or more.

The ink composition for ink jet recording of the present invention can contain an anionic surfactant having a polyoxyethylene group in its molecular skeleton. By including the nonionic surfactant, excellent ejection stability and abrasion resistance or water resistance of the printed matter can be imparted. The content of the nonionic surfactant is preferably 12% by weight or less, and more preferably 0.05 to 10% by weight, based on the entire ink composition. If it exceeds 12% by weight, foaming may become severe, and 0.05% by weight
If it is less than the range, the ink may not spread sufficiently on the recording medium.

Examples of the anionic surfactant containing a polyoxyethylene group in its molecular skeleton include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, and polyoxyethylene styrenated phenyl ether sulfate. Examples thereof include salts, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, and the like. Particularly preferred are polyoxyethylene alkyl ether sulfate and polyoxyethylene alkylphenyl ether sulfate. Preferable examples of the salt include potassium salt, sodium salt, ammonium salt, monoethanolamine salt, diethanolamine salt and the like, and ammonium salt is particularly preferable. These anionic surfactants may be used alone or in combination of two or more. Further, in each of the compounds listed for the anionic surfactant, the polyoxyethylene group preferably has a degree of polymerization of about 3 to 10, and the alkyl group preferably has about 1 to 17 carbon atoms.

Furthermore, the ink composition of the present invention contains a nonionic surfactant having a polyoxyethylene group in its molecular skeleton and an anionic surfactant having a polyoxyethylene group in its molecular skeleton at the same time. It can also be contained. In this case, the total content of both surfactants is preferably such that the weight ratio (nonion / anion) of both is 1/10 to 1, and by containing both surfactants, while suppressing foaming, It is possible to secure a sufficient spread of the ink on the recording medium.

The ink composition according to the present invention may contain a hydrophilic high-boiling point low-volatile solvent (water-soluble organic solvent). By containing a hydrophilic high boiling point low volatility solvent,
It is possible to improve the anti-clogging property, the moisture retention property, and / or the dispersion stability of the nozzle.

Specific examples include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, polyethylene glycol,
Or high boiling point and low volatility polyhydric alcohols such as polypropylene glycol, their mono-etherified products, di-etherified products or esterified products, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether. , Diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, etc., and further N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, monoethanolamine, N, N-dimethylethanolamine,
Contains a hydrophilic high-boiling point low-volatile solvent such as a nitrogen-containing organic solvent such as N, N-diethylethanolamine, diethanolamine, N-n-butyldiethanolamine, triisopropanolamine, or triethanolamine within a range that does not cause bleeding. can do.

Further, with respect to water as a main solvent, highly volatile monohydric alcohols such as ethanol, propanol, isopropanol or butanol may be contained in a small amount for the purpose of improving the drying property.

According to a preferred embodiment of the present invention, the ink composition droplets are ejected from the ink jet recording head to be attached to the recording medium, and at the same time as the attachment, the ink composition droplets are ejected from the platen through the recording medium. In an ink composition that can be suitably used in a heating type ink jet recording apparatus that applies heat to a toner to perform fixing, by adjusting the amount of dissolved air in the ink composition of the present invention to 14 ppm or less, it can be manufactured at low cost. The ink composition for inkjet recording can satisfy both the ejection stability and the long-term storage stability in the heating type inkjet recording device at the same time.

When air bubbles are present in the ink composition for ink jet recording, ejection failure may occur, or dissolved air in the ink composition may react with the ink composition components to cause problems in long-term storage. Therefore, various deaerating methods and bubble removing methods for removing dissolved air in the ink composition, which causes bubbles, have been proposed.

For example, Japanese Patent Application Laid-Open No. 05-320549 discloses a method of bringing a gas such as nitrogen or helium into contact with an ink composition under a low pressure, and provides an ink composition containing no dissolved oxygen. I am trying. Further, JP-A-53-61412 also proposes an ink composition containing no dissolved oxygen by adding an oxygen absorbent to the ink composition. Further, Japanese Patent Application Laid-Open No. 59-65664 describes a technique in which the ink composition is completely degassed by a pressure fluctuation generated by ejecting the ink composition into a low-pressure container. Also, JP-A-59-656.
Japanese Patent Laid-Open No. 65 describes a technique in which the ink composition is heated and then vacuum degassed to realize complete degassing of the ink composition.

By removing oxygen from the ink composition,
Regarding the ink composition that is intended to suppress the deterioration of the ink composition component due to the oxidation reaction and improve the long-term storage stability of the ink composition, the remaining dissolved nitrogen becomes bubbles due to changes in temperature and pressure, and ejection failure occurs. There is a drawback that causes. This drawback is remarkable in the heating type ink jet recording apparatus in which the print head is exposed to a high temperature. In addition, an ink composition that is completely deaerated and aims to prevent ejection defects and improve the long-term storage stability of the ink composition requires a high degree of vacuum and high-temperature conditions during the production of the ink composition, resulting in a low manufacturing cost. It has the drawback of being expensive.

The present inventor has found that the amount of dissolved air in the ink composition, that is, the sum of dissolved oxygen and dissolved nitrogen is 14 ppm.
It has been found that an ink composition for inkjet recording which can be manufactured at low cost and which can satisfy ejection stability in a heating type inkjet recording device and long-term storage stability can be obtained by adjusting the following. .

When air is dissolved in the dye-based ink composition, the air component reacts with the ink composition component,
It may cause deterioration of various ink compositions, such as changes in physical properties such as viscosity or surface tension, or generation of aggregates. In particular, oxygen dissolved in the ink composition often oxidizes the dye component of the ink composition, causing a change in color density and hue. Therefore, in the dye-based ink composition, it is essential to remove dissolved air, especially oxygen. Since the pigment is more stable than the dye, the use of the pigment as the colorant makes it possible to prepare an ink composition in which the concentration change and the hue change due to dissolved oxygen are small.
Therefore, it is said that it is not necessary to completely remove dissolved air in the pigment-based ink composition.

However, the ink composition for ink jet recording is ejected in the form of droplets under the mechanical pressure or the pressure at the time of vaporization thermal expansion of the ink composition components. At this time, if bubbles are present in the ink composition, the bubbles absorb the ejection pressure and cause ejection failure.

Therefore, attention must be paid to the following points so as not to generate bubbles even in the ink composition for ink jet recording.

Since the amount of saturated dissolved air in water decreases as the temperature rises as shown in FIG. 3, the air dissolved in the ink composition also becomes undissolved when the temperature of the ink composition rises, and becomes air bubbles. Become. Therefore, the amount of dissolved air in the ink composition must be kept low in consideration of the head temperature increase.

For example, even in an ordinary ink jet printer having no heating system, it is fully conceivable that the head temperature rises to around 35 ° C. due to changes in environmental temperature. At that time, in order to prevent generation of bubbles, it is necessary to suppress the dissolved air amount of the ink composition to a saturated dissolved air amount (18 ppm) or less at 35 ° C. Further, in order to improve the fixability of the ink composition and suppress bleeding, in the case of a recording method in which a recording medium is heated for printing, the head temperature becomes higher, so the amount of dissolved air must be kept lower. . For example, if the head temperature rises to 80 ° C. or 100 ° C., the dissolved air amount of the ink composition needs to be suppressed to 14 ppm or less. In other words, the dissolved air volume is 14pp
By adjusting to m or less, it is possible to obtain an ink composition in which bubbles are not generated even in a heating type inkjet.

The method for suppressing the dissolved air amount of the ink composition to 14 ppm or less is not particularly limited, but, for example, the ink composition prepared by a usual method is brought into contact with diluted air in a closed container. The amount of dissolved air can be controlled by. The pressure of the lean air, that is, the degree of pressure reduction is preferably 200 mmHg or less, more preferably 5 to 100 mmHg. The pressure of lean air is 200
If it exceeds mmHg, the dissolved air may be poorly removed. The lower limit is not particularly limited, but if it is less than 5 mmHg, the cost becomes too high, which is not preferable. When the ink composition is heated to 20 to 60 ° C., more preferably 30 to 50 ° C., the dissolved air can be efficiently removed when the ink composition is brought into contact with diluted air. The contact time between the ink composition and the dilute air is not particularly limited, but the fact that the predetermined dissolved air amount has been reached can be determined by measuring the dissolved air amount by gas chromatography.

According to another preferred embodiment, the invention provides
(A) The non-evaporated component at the heating temperature of the heated recording medium is contained in an amount of 23% by weight or more based on the total weight of the ink composition, and (b) the alcoholic hydroxyl group 2
Ink composition having a total of two or more hydroxy compounds having one or more and a ratio (N / M) of the number (N) of alcoholic hydroxyl groups and the molecular weight (M) in one molecule is 0.01 or more Provided is an ink composition for inkjet recording, which is contained in an amount of 10% by weight or more based on the total weight.

As a conventional ink composition containing a water-soluble resin and a resin emulsion in the ink composition, for example, JP-A-4-18462 and JP-A-5-148 are known.
Each of Japanese Patent No. 441 discloses an ink composition aiming to secure fixing property to a recording medium while securing ejection stability. However, when printing is performed on a heated recording medium using these conventional ink compositions,
When the thermoplastic resin in the ink composition is heated above its softening temperature, the viscosity is rapidly increased due to the evaporation of the solvent and the phase change of the resin, while there is an effect that a high-quality image can be obtained. A large amount of the water-soluble moisturizing component is required to prevent ejection failure due to thickening inside.
If the moisturizing effect is excessive, or if the surrounding environment such as humidity or temperature changes, uneven drying of the image occurs immediately after printing. Further, this defective phenomenon appears in a mode such as stickiness of the image surface or cloudiness, which causes deterioration of image quality.

The present inventor has proposed an ink jet recording method in which ink is ejected from an ink jet recording head and adhered to a recording medium, and at the same time as the adhesion, heat is applied to droplets of the ink composition from the platen through the recording medium to fix. In the ink composition to be used, (a) the non-evaporated component at the heating temperature of the heated recording medium is 2 based on the total weight of the ink composition.
3% by weight or more, and (b) the above two or more hydroxy compounds are added in a total amount of 10% by weight or more based on the total weight of the ink composition.
An ink composition for ink jet recording capable of preventing defective drying immediately after printing without causing defective ejection and capable of obtaining a high quality image without being affected by the surrounding environment [hereinafter, a hydroxy compound-containing ink composition It may be referred to as a thing].

In the hydroxy compound-containing ink composition, the non-evaporated component at the heating temperature of the heated recording medium is preferably 23% by weight or more, more preferably 25 to 35% by weight, based on the total weight of the ink composition. By doing so, when the ink composition adheres to the heated recording medium, a rapid thickening phenomenon due to heating can be obtained, and as a result, a high quality image can be obtained. In addition,
The heating temperature of the recording medium is generally 80 to 120, and the specific heating temperature used in each recording method and the non-evaporated component content of the hydroxy compound-containing ink composition used in the recording method are It can be determined as an amount that gives a sufficient thickening rate.

Further, as the water-insoluble component among the above-mentioned non-evaporable components, the pigment dispersed in water and the resin component of the thermoplastic resin emulsion are added in total with respect to the amount of the non-evaporable component,
Preferably 10% by weight or more, more preferably 20 to 50
By setting the content to the weight%, the viscosity of the ink can be increased more quickly. In addition to the pigment and the resin component of the thermoplastic resin emulsion, the non-evaporable component may be, for example,
A pigment dispersant and the like are included.

However, when the ratio of the non-evaporated component or the solid content is increased in this way, ejection failure is likely to occur due to the thickening phenomenon accompanying the temperature rise in the head. In order to prevent this, it is effective to contain a moisturizing water-soluble component, but if the type and content of these components are inappropriate, drying unevenness occurs in the printed image after printing. There is a possibility to let.

Therefore, in order to prevent this problem, the ink composition containing water as the main solvent has two or more alcoholic hydroxyl groups (—OH) in the molecule, and the content of the alcoholic hydroxyl group is The ratio (N / M) of the number (N) of alcoholic hydroxyl groups in one molecule to the molecular weight (M) is 0.01.
It is effective to contain two or more kinds of the above-mentioned (preferably 0.1 or more) hydroxy compounds, and the hydroxy compounds may be water-soluble polymer compounds such as sugars and polyhydric alcohols. preferable. That is, by containing an appropriate amount of a compound having a large hydroxyl value as each of the water-soluble components and having a strong interaction with each other, while maintaining an appropriate moisturizing property in the head, when attached to the heated recording medium, It is possible to prevent drying unevenness caused by the mutual compatibility of the two and the specific component being separated and floating.

Further, the effect is enhanced by adding the optimum ratio of the water-soluble component to the optimum amount of the thermoplastic resin. That is, the pigment (A) and the thermoplastic resin emulsion (B) dispersed in the hydroxy compound-containing ink composition, the water-soluble polymer compound (C) and the polyhydric alcohol (D) dissolved in water, The total amount of the components (A + B + C + D) is 20 to 50% by weight based on the total weight of the ink composition, and the thermoplastic resin emulsion (B), the water-soluble polymer compound (C), and the polyhydric alcohol (D). ) And the weight ratio (B: C: D) is 1: 0.3.
It is effective that the range is from 1 to 0.1 to 1.

The two types of hydroxy compounds that can be used in the hydroxy compound-containing ink composition include
A combination of a water-soluble polymer compound and a polyhydric alcohol is preferable.

As the water-soluble polymer compound, at least one compound selected from the group consisting of saccharose, maltitol, maltose, gluconic acid, sorbitol, mannitol, glucose, polyvinyl alcohol, sodium alginate, and polyethylene oxide is used. You can The polyhydric alcohol is a compound selected from the group consisting of glycerin, diglycerin, polyglycerin, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, hexylene glycol, and 1,2,6-hexanetriol. At least one kind can be used.

Further, the hydroxy compound-containing ink composition may contain a surfactant. Examples of the surfactant that can be used include anionic surfactants such as higher fatty acid salts, higher alkyl dicarboxylic acid salts, higher alcohol sulfate ester salts, higher alkyl sulfonates, alkylbenzene sulfonates, and alkylnaphthalene sulfones. Acid salts, salts of naphthalene sulfonic acid (Na, K, Li, Ca), formalin polycondensates, condensates of higher fatty acids and amino acids, dialkyl sulfosuccinic acid ester salts, alkyl sulfosuccinic acid salts, naphthenic acid salts, etc., alkyl ethers Carboxylate, acylated peptide, α-olefin sulfonate, N-acylmethyl taurine, alkyl ether sulfate, secondary higher alcohol ethoxy sulfate, monoglyculfate, alkyl ether phosphate salt, alkyl phosphate ester salt, poly Ammonium xyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene alkyl sulfate monoethanolamine, polyoxyethylene alkyl ether phosphate Ammonium salt, potassium salt of polyoxyethylene alkyl ether phosphate, diethanolamine of polyoxyethylene alkyl ether phosphate, sodium alkylnaphthalene sulfonate, sodium lauryl sulfate, etc .; cationic surfactant, for example, aliphatic amine salt, quaternary ammonium salt, sulfonium Salts, phosphonium salts, etc .; amphoteric surfactants such as carboxybetaine type, aminocal Bonates, lecithin, etc .; or nonionic surfactants such as fluorine-based surfactants, silicone-based surfactants, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monostearate, polyoxyethylene alkylphenyl ethers , Sorbitan monostearate, acetylene glycol, ethylene oxide adduct of acetylene glycol (acetylene glycol alcohol ethylene oxide), propylethanolamide, polyoxyethylene alkyl ether, or polyoxyethylene alkylphenyl ether. By using one or more of the above-mentioned surfactants, the drying property immediately after printing can be further homogenized, and it is effective in preventing uneven drying.

The content of the surfactant is 0.1 to 1
% By weight is preferred. This is because if the content exceeds 1% by weight, the foaming property becomes large and there is a risk of impairing the ejection stability.

According to yet another preferred embodiment, the present invention provides a compound of formula (I):

[0073]

Embedded image

It relates to an ink composition containing a compound represented by (ie, 1,2-benzisothiazolin-3-one).

The ink composition comprising the pigment and the resin emulsion has excellent properties. However, on the other hand, when the amount of solids dispersed in water is large, the solids are likely to be affected by the environment during storage, and there is a high possibility that the solids will agglomerate or settle. Further, since the pigment, resin emulsion, resin dispersant, etc., which are the main components of the ink composition, are organic compounds, it is difficult to avoid generation of mold, microorganisms, etc. In particular, when the ink composition is brought into contact with air, the risk of generation of foreign matter becomes higher. Aggregation of such solids,
Furthermore, the generation of foreign matter such as mold and microorganisms causes adverse effects such as deterioration in ejection characteristics of the ink composition. However, the addition of an antifungal agent, an antiseptic agent, or the like for the purpose of suppressing the generation of these foreign substances tends to cause the dispersion system of the ink composition to become unstable.

The present inventor has found that the above problems can be solved by incorporating the compound represented by the formula (I). The compound represented by the above formula (I) is a known compound and can be prepared by a method known per se, but a commercially available compound can also be used. Examples of commercially available compounds include Proxel BDN (a form in which the above compound is dispersed in water), Proxel CRL, Proxel manufactured by Zeneca Corporation.
XL-2 and the like (the above compound dissolved in water) can be used. The content of the compound represented by the formula (I) is preferably 0.0001% by weight to 0.5% by weight, more preferably 0.005% by weight to 0.1% by weight based on the total weight of the ink composition. % By weight. If the content is less than 0.0001% by weight, the desired effect cannot be obtained, and if it exceeds 0.5% by weight, harmful effects may occur.

The ink composition containing the compound represented by the formula (I) can contain a surfactant which can be contained in the hydroxy compound-containing ink composition.

The compound represented by the above formula (I) may be contained in a solution state, but is preferably contained in a dispersed state.

According to another preferred embodiment, the present invention provides an ink composition in which the pigment particles have an average particle diameter of 200 nm or less, and the dispersed phase component of the thermoplastic resin emulsion has an average particle diameter of 200 nm or less. Regarding

In the pigment-based ink composition, it is necessary to stably finely disperse the pigment in the medium. In the ink composition used in the inkjet recording method, since it is necessary to eject ink droplets from fine nozzles, the generation of deposits causes mess of the nozzles. Therefore, the ink composition needs to have the property of suppressing the generation of deposits and easily removing them even if they occur.

As a pigment-based ink composition, for example, the particle size distribution of pigment is described in JP-A-1-204979.
An ink composition is described in which a value of 0.6 μm or less and 0.2 μm or less is used as an index. According to this ink composition, nozzles are not clogged, and ink droplets can be stably ejected. Further, JP-A-4-18462 describes an ink composition in which a pigment and a microemulsion are combined. In this publication, it is required that the average particle size of the microemulsion in the ink composition be 50 nm or less for an inkjet recording method without clogging.

However, there is still a need for better ink compositions. In particular, in order for the pigment particles to be stably present in the ink composition, the pigment particles must be dispersed to an extremely fine particle size.
It can be said that if the pigment can be stably dispersed with a certain particle size, its production will be easy. Further, when printed on an OHP sheet, a dark image results if the light transmittance of the image is low. Therefore, an ink composition capable of obtaining an image having higher light transmittance is desired. Further, an ink composition capable of realizing a glossy image is desired in order to give a high quality image.

As described above, the present inventors set the average particle diameter of the pigment particles to 200 nm or less and the average particle diameter of the disperse phase component of the thermoplastic resin emulsion to 200 nm or less, whereby the ink of the present invention is obtained. OH
The image on the P sheet has an extremely high light transmittance and is bright, and the image on the ordinary recording paper has a glossy ink composition (hereinafter, sometimes referred to as an ink composition containing fine particles). And found that you can.

The pigment which can be used in the ink composition containing fine particles has an average particle diameter of 200 n.
m or less, preferably 150 nm or less, more preferably 1
00 nm or less. In the ink composition containing fine particles of the present invention, it is desirable that the pigment particles are small, but in order to make them small, more energy is required to prepare the pigment particles. The fine particle-containing ink composition of the present invention has the above-mentioned 200 nm
Even a pigment having the following slightly larger average particle diameter can be stably present.

In the ink composition containing fine particles of the present invention, the pigments listed above can be used except that the average particle diameter is 200 nm or less. As described above, the content of the pigment is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight.

In the ink composition containing fine particles of the present invention, the average particle size of the resin component (disperse phase component) of the thermoplastic resin emulsion is also 200 nm or less, preferably 150.
nm or less, more preferably 100 nm or less. As such a thermoplastic resin emulsion, the thermoplastic resin emulsions listed above can be used as they are.

In the ink composition containing fine particles of the present invention, the content of the resin emulsion is as described above.
0.2 to 20% by weight is preferable, and more preferably 7 to 2
0% by weight.

The thermoplastic resin emulsion used in the ink composition containing fine particles according to the present invention, when dried in a room temperature environment, does not form a film but forms a solid or brittle solid, and is softened or melted. If heated above temperature,
Those that form a strong and water-resistant film when cooled are preferable. Furthermore, the minimum film forming temperature, which is the minimum necessary temperature for forming such a strong and water resistant film, is 6
The temperature is preferably 0 ° C or higher, more preferably 70 ° C or higher.

Although various physical properties of the ink composition according to the present invention can be controlled appropriately, in a preferred embodiment of the present invention, the viscosity of the ink composition is preferably 25 mPa · sec or less, more preferably 10 mPa · s.・ Seconds or less (25
° C). When the viscosity is within this range, the ink composition is stably ejected from the ink ejection head. The surface tension of the ink composition can be controlled as appropriate, but
It is preferably ˜50 mN / m (25 ° C.).

The ink composition for ink jet recording of the present invention is prepared by appropriately mixing the above-mentioned respective components in an arbitrary order, dissolving and / or dispersing them, and then removing impurities and the like by filtration. be able to. In particular, it is preferable to prepare an aqueous pigment dispersion with a pigment, a resin dispersant and water, and mix the aqueous pigment dispersion with other compounding ingredients such as a thermoplastic resin emulsion.

Further, a pigment is appropriately selected, and if necessary, other compounding ingredients are appropriately selected in combination with the selected pigment, and the yellow ink composition and the magenta ink composition according to the present invention for color ink jet recording are selected. A cyan ink composition, a black ink composition, a blue ink composition, a green ink composition, or a red ink composition can be prepared.

The ink composition according to the present invention can be put into a conventional ink cartridge and inserted into a conventional ink jet recording apparatus to carry out the ink jet recording method. Further, a yellow ink composition, a magenta ink composition, a cyan ink composition, a black ink composition, a blue ink composition, a green ink composition,
Alternatively, the ink cartridge containing a magenta ink composition and an ink containing a yellow ink composition using at least one of the red ink compositions (preferably all the ink compositions of the respective colors) as the ink composition according to the present invention. A cartridge, an ink cartridge containing a cyan ink composition, and optionally an ink cartridge containing a black ink composition, which is inserted in combination or a magenta ink composition, a yellow ink composition, and a cyan ink composition In some cases, the color ink jet recording method can be performed using a color ink jet recording apparatus in which an ink cartridge for accommodating the black ink composition and the black ink composition separately in the separated fractions is inserted.

The ink composition according to the present invention can be advantageously used in any ink jet recording method, but is preferably used in an ink jet recording method in which a recording medium is heated to fix the ink composition on the recording medium. be able to. That is, when the ink droplets of the ink composition according to the present invention are used in an inkjet recording method in which an ink image is formed by ejecting ink droplets from a print head onto a heated recording medium, the ink is not formed on the heated recording medium. When attached,
By heating, the ink composition rapidly thickens, and a high quality image can be obtained.

Therefore, according to the present invention, the ink is ejected from the ink jet recording head to be attached to the recording medium, and at the same time as the attachment, heat is applied from the recording medium support (eg, platen) to the ink composition droplets through the recording medium. In addition, the present invention also relates to an inkjet recording method including fixing. The heating temperature of the platen is preferably about 80 to 120 ° C. 8
If the temperature is lower than 0 ° C, insufficient drying and fixing may occur, and if the temperature is higher than 120 ° C, excessive energy may be required.

The ink jet recording method according to the present invention comprises:
There is no particular limitation as long as one or more ink compositions according to the present invention are used. In particular, in a color ink jet recording method carried out using an ink composition of at least two colors, the method according to the present invention of two or more colors is used. It is preferable to use an ink composition. That is, a red image, a green image, and a blue image are formed using an ink set obtained by combining the above-described yellow ink composition, magenta ink composition, and cyan ink composition, and in some cases, a black ink composition. A color ink jet recording method is preferred in which a black image is formed with a black ink composition that is overlaid on or separately used. In addition, the present invention also includes a color inkjet recording method for forming various images using a blue ink composition, a green ink composition, and / or a red ink composition in addition to the above-described ink compositions of each color.

[0096]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. In the following examples, parts and percentages are by weight unless otherwise specified.

Example 1 (1) Preparation of Pigment Dispersion Styrene-acrylic acid copolymer resin (weight average molecular weight =
25000; acid value = 200) 4 parts, triethanolamine 2.7 parts, isopropyl alcohol 0.4 parts, and ion-exchanged water 72.9 parts were completely dissolved under heating at 70 ° C. Next, after adding 20 parts of carbon black MA-100 (manufactured by Mitsubishi Kasei Co., Ltd.) and performing premixing,
The pigment was dispersed with an Eiger mill (manufactured by Eiger Japan Co., Ltd.) until the average particle diameter of the pigment reached 100 nm (bead filling rate 70%, media diameter 0.7 mm). Thus, a pigment dispersion was obtained.

(2) Preparation of Ink Composition Next, an ink composition having the following composition was prepared using the above pigment dispersion.

The above pigment dispersion 10 parts Styrene acrylic ester emulsion 15 parts (as solid content) Diethylene glycol 3 parts Maltitol 10 parts (as solid content) Acetylene glycol surfactant 0.1 part Anion surfactant 0.3 Part disodium hydrogen phosphate 0.1 part ion-exchanged water 36.5 parts The styrene acrylic ester emulsion is an aqueous dispersion having a solid content of 50%, and maltitol has a solid content of 8%.
Since it is a 0% aqueous solution, the above values are shown in terms of solid content. As the acetylene glycol-based surfactant, Surfynol 465 (Nisshin Chemical Industry;
2,4,7,9-tetramethyl-5-decyne-4,7-
Polyethylene oxide adduct of diol) was used.
Further, as the anionic surfactant, Hitenol N.I.
07 (polyoxyethylene alkyl nonyl phenyl ether) was used.

An ink composition was prepared by mixing the above components. The ink composition thus obtained was passed through a metal mesh filter (manabe industry Co., Ltd .; twill weave 2300 mesh) to obtain an ink composition of Example 1 of the present invention.

<Examples 2 to 20> The preparation described in Example 1 except that the compounding ingredients shown in Tables 1 and 2 below were used in the compounding amounts shown in Tables 1 and 2 below. By repeating the method, an ink composition for inkjet recording according to the present invention was obtained. In addition, the value in the table indicates the addition amount in% by weight.

Comparative Example 1 (1) Preparation of Pigment Dispersion Styrene-maleic acid-maleic acid half ester copolymer 4 parts (acid value = 70; weight average molecular weight = 12000) 2-amino-2-methyl- 1-aminopropanol 2 parts Ion-exchanged water 74 parts Diethylene glycol 5 parts The above-mentioned respective components were mixed and completely dissolved under heating at 60 ° C. Carbon black (MCF88
After adding 15 parts of Mitsubishi Kasei Co., Ltd. and performing premixing (stirring the mixture in the container), dispersion was carried out with an Eiger mill (Eiger Japan Co., Ltd.) (bead filling rate 70%, media diameter 0.7 mm). A pigment dispersion was obtained.

(2) Preparation of Ink Composition Next, the above-mentioned pigment dispersion was used to prepare an ink composition having the following composition.

Pigment dispersion 30 parts Glycerin 9 parts Diethylene glycol 4 parts Propanol 4 parts Acetylene glycol-based surfactant 0.3 part Ion-exchanged water 52.7 parts As the acetylene glycol-based surfactant, Surfynol 465 is used. (Nissin Chemical Industry; 2, 4, 7, 9-
Tetramethyl-5-decyne-4,7-diol) was used.

Each of the above-mentioned components is mixed to obtain a pH of 8-10.
2-amino-2-methyl-1-propanol was added. The ink composition thus obtained was applied to a metal mesh filter (manabe industry Co., Ltd. twill weave 2
(300 mesh) to obtain an ink composition of Comparative Example 1. In addition, the ink composition of Comparative Example 1 was prepared as described in JP-A-6-11.
It has almost the same ink composition as the composition described in Japanese Patent No. 6522.

Comparative Example 2 In Comparative Example 2, an ink composition having substantially the same composition as the ink composition of a commercially available dye-based inkjet printer was prepared.

C. I. Direct Black 19 4.0 parts by weight Diethylene glycol 15.0 parts by weight Ion-exchanged water 81.0 parts by weight After ion-exchanged water and diethylene glycol are mixed and stirred, a direct dye (CI Direct Black 19) is added and completely. After being dissolved, the dye-based ink composition was prepared by filtering with a membrane filter.

<Examples 21 and 22> Using the compounding ingredients shown in Table 3 below in the compounding amounts shown in Table 3 below,
And the ink composition for ink jet recording according to the present invention, by repeating the production method described in Example 1 above, except that the obtained composition is left for 15 minutes in a dilute air environment of 70 mmHg at 45 ° C. Got In addition, the value in the table indicates the addition amount in% by weight.

<Examples 23 to 28> Using the compounding ingredients shown in the following Table 4 in the compounding amounts shown in the following Table 4, and 1,2-benzisothiazoline represented by the above formula (I). The inkjet recording ink composition according to the present invention was obtained by repeating the production method described in Example 1 except that 3-one was added. In addition, the value in the table indicates the addition amount in% by weight.

<Examples 29 to 32> The average particle diameter of the pigment is shown in Table 5 by using the compounding ingredients shown in Table 5 below in the compounding amounts shown in Table 5 below and controlling the dispersion time. The ink composition for ink jet recording according to the present invention was obtained by repeating the production method described in Example 1 except that the value was set to. In addition, the value in the table indicates the addition amount in% by weight.

<Evaluation of Physical Properties> Next, Example 1 according to the present invention.
The physical properties of the ink compositions of ~ 32 and the ink compositions of Comparative Examples 1 and 2 were evaluated.

(1) Inkjet recording device Regarding the inkjet recording device used in the following evaluation,
This will be described with reference to the drawings.

FIG. 1 shows an ink jet recording apparatus used for evaluation of an ink composition for ink jet recording.

As shown in FIG. 1, the platen 71 of the above-described recording apparatus also serves as a means for heating the recording medium 75 and a means for conveying the recording medium. This platen 7
Reference numeral 1 denotes a cylinder made of a metal (for example, aluminum) having high heat conductivity, which is rotated in the direction of the arrow in the drawing by a driving device not shown. The surface of the platen 71 may be formed by laminating silicone rubber or the like. Further, a heater 72 is arranged inside the platen 71 so that the platen 71 can be heated. Furthermore,
Paper pressing rollers 73 and 74 are pressed against the platen 71, and the platen 71 and the paper pressing roller 7 are in contact with each other.
The recording medium 75 can be inserted between the recording medium 3 and the recording medium 74, and the recording medium 75 can be conveyed as the recording medium 75 rotates. The paper pressing roller 73 can be configured, for example, by bonding an elastic member (for example, acrylonitrile rubber) to the surface of a metal core material.

In addition, the recording medium 7 is attached to the platen 71.
An inkjet recording head 76 is arranged at a position facing each other with 5 interposed therebetween. The recording head 76 may be one that forms a droplet by a piezoelectric element, or one that forms a droplet by thermal energy. The recording head 76 can have 48 nozzles arranged in an arbitrary matrix. The nozzles of the recording head 76 eject ink droplets based on print data given by a processing unit (not shown). The recording head 76 is supplied with an ink composition from an ink tank 77, and can move in a direction orthogonal to the direction in which a recording medium is fed by a recording head driving device 78.

Ink jet recording is carried out as follows. First, the recording medium 75 is nipped and conveyed between the platen 71 and the paper pressing rollers 73 and 74. While being conveyed, the recording medium 75 contacts the platen 71 heated by the heater 72 and is heated. Therefore, in the apparatus of this aspect, the platen 7 is set so that the temperature of the recording medium 75 becomes equal to or higher than the softening temperature of the thermoplastic resin described above.
The surface temperature of 1 is controlled. Next, the recording head 76 selectively ejects droplets of the ink composition onto the conveyed recording medium 75 in accordance with the print pattern. The droplets of the ink composition attached to the recording medium 75 are heated and formed into a film to form an ink dot. Next, the platen 71 and the paper pressing rollers 73 and 74 convey the recording medium by a predetermined amount, and the recording head 76 records again. Here, when the ink dots are formed adjacent to each other or in an overlapping manner, it is preferable that the printing be performed with a constant printing interval. After necessary recording is performed on the recording medium 75, the recording medium 75 is discharged from the apparatus.

In this apparatus, the distance between the ink jet recording head and the platen is about 1.5 mm, the temperature of the ink jet recording head is approximately 40 ° C. to 50 ° C., and the surface temperature of the platen 71 is approximately 120 ° C. The surface temperature of the recording medium was 80 ° C to 110 ° C.

FIG. 2 shows another recording apparatus in which the ink composition was evaluated. In this apparatus, the same elements as those of the apparatus of FIG. 1 are denoted by the same reference numerals as those of FIG. In this apparatus, a recording head is provided for each color of the ink composition. That is, the recording heads 81, 82, 83, and 84 are recording heads that eject the black ink composition, the magenta ink composition, the cyan ink composition, and the yellow ink composition, respectively. The ink composition is supplied to the recording heads from the ink tank 77.

The printing by the apparatus of FIG. 2 is basically the same as the printing by the apparatus of FIG. That is, the recording medium 75 is moved by the recording medium winding device 85 to the platen 71.
Wrapped around. Next, the recording heads 81 to 84 perform printing in one line or a plurality of lines. Next, the recording head 78 is moved by a predetermined amount to perform printing in one line or a plurality of lines. By repeating this, an image is recorded on the recording medium 75.

FIG. 4 shows still another recording apparatus in which the ink composition was evaluated. In this apparatus, the platen 1 heats and conveys the recording medium 5. The platen 1 is a cylinder made of aluminum, and is rotated in the direction of the arrow in the drawing by a driving device (not shown). Silicone rubber is laminated on the surface of the platen 1. A heater 2 is arranged inside the platen 1,
The platen 1 is heated. Further, the paper pressing rollers 3 and 4 are pressed against the platen 1, and the recording medium 5 is interposed between the platen 1 and the paper pressing rollers 3 and 4.
Is placed, and the recording medium 5 is conveyed with the rotation thereof. The paper pressing roller 3 is configured by adhering acrylonitrile rubber to a surface of a metal core material, for example. Further, the inkjet recording head 6 is arranged at a position facing the platen 1 with the recording medium 5 interposed therebetween. The recording head 6 forms droplets by a piezoelectric element. The head 6 has 48 nozzles arranged in an arbitrary matrix. The nozzles of the recording head 6 eject ink composition droplets based on print data provided by an arithmetic unit (not shown). The recording head 6 is supplied with an ink composition from an ink tank 7, and can be moved on a guide shaft 8 by a recording head driving device (not shown) in a direction orthogonal to the direction in which the recording medium is fed.

Ink jet recording is performed as follows. First, the recording medium 5 is the platen 1 and the paper pressing roller 3.
It is sandwiched between and and 4 and conveyed. While being conveyed, the recording medium 5 contacts the platen 1 heated by the heater 2 and is heated. Next, the ink droplets of the ink composition are selectively ejected onto the conveyed recording medium 5 by the recording head 6 according to the print pattern. The ink composition droplets attached to the recording medium form an ink dot. Next, a predetermined amount of the recording medium is conveyed by the platen 1 and the paper pressing rollers 3 and 4, and recording is performed again by the recording head 6. After the necessary recording is performed on the recording medium 5, the recording medium 5
Is discharged from the device. In this apparatus, the distance between the inkjet recording head 6 and the platen 1 is separated by about 1 mm. The surface temperature of the platen 1 is adjusted to about 60 to 120 ° C, and the temperature of the inkjet recording head 6 is about 30 to 80 ° C.

(2) Evaluation of stability of ink composition left standing The stability of left standing was evaluated by the change with time when each ink composition was left in a sealed state at 50 ° C. for 1 month. There are three types of evaluation items: (a) pH change, (b) viscosity change, and (c) foreign matter generation state, and each is evaluated in three stages according to the following criteria.

(A) pH change ⊚ (suitable): No change from the initial value. ∘ (appropriate): Change is within 5% of the initial value, which is an acceptable level. X (unsuitable): Change exceeds 5% of initial value.

(B) Change in viscosity The viscosity was measured with a double cylindrical viscometer manufactured by Rheometrics. ⊚ (suitable): No change from the initial value. ∘ (appropriate): Change is within 5% of the initial value, which is an acceptable level. X (unsuitable): Change exceeds 5% of initial value.

(C) Situation of foreign matter A small amount of the ink composition was placed on a slide glass and observed under a microscope (400 times) to compare with the initial situation. ⊚ (suitable): No foreign matter is generated. ∘ (appropriate): Some foreign matter is present, but not large enough to cause clogging in the ink composition discharge nozzle. Poor (unsuitable): A size that causes clogging due to generation of foreign matter.

(D) Evaluation results Tables 6 to 9 show the evaluation results of Examples 1 to 28 and Comparative Examples 1 and 2 based on the above evaluation method.

As shown in Tables 6-9, Examples 1-2
The ink composition for inkjet recording according to the present invention No. 8 maintained the initial pH and viscosity even after being left for a long time, did not generate foreign matters, and was excellent in storage stability. On the other hand, in the ink composition of Comparative Example 1, generation of some foreign matter was recognized (at a level where there is no problem in actual use). In the ink composition of Comparative Example 1, it was confirmed that the change rate of pH and the change in viscosity were 5% or more as the initial values. In the ink composition of Comparative Example 2, the change in pH and the change in viscosity were within 5% of the initial values. Since the ink composition of Comparative Example 2 was a dye-based ink composition, no evaluation was made regarding the generation of foreign matter.

(3) Evaluation of Printing Quality of Ink Composition (a) Blurring Length of Single Color Ink Composition XEROX-R paper (manufactured by XEROX Co., Ltd.) which had relatively large ink bleeding among typical commercially available papers. :recycled paper)
Printing was performed using the inkjet printer having the configuration shown in FIG.

The printing condition is a resolution of 300 dpi (dot).
per inch), an ink ejection frequency of 6 kHz, and a carriage moving speed of 510 mm / sec. The heating temperature of the recording medium was about 100 ° C. (the platen temperature of the printer was 120 ° C.). The ink bleeding length of dots on the printed matter was evaluated according to the following criteria.

A (favorable): A good image can be obtained on recycled paper even at a high resolution exceeding 3 μm (= 600 dpi). ∘ (appropriate): good image quality can be obtained on recycled paper at a resolution of 3 to 5 μm (= 360 to 600 dpi). Δ (Fair): A good image can be obtained on recycled paper at a resolution of 5 to 10 μm (= 360 dpi). Poor (unsuitable): At a resolution of 10 μm (= 360 dpi) or higher, the image quality is clearly deteriorated due to ink bleeding.

(B) Length of ink bleeding in multicolor printing Recording paper XEROX 4024 (manufactured by XEROX: plain paper)
2 was solid-printed (100% duty) with the yellow ink composition of Example 7 using the inkjet printer having the configuration shown in FIG. 2, and the black ink composition of Example 1 was printed thereon. Printing conditions are resolution 600d
Pi, the ink ejection frequency was 14 kHz, the carriage moving speed was 590 mm / sec, and the distance between the nozzle for ejecting the yellow ink composition and the nozzle for ejecting the black ink composition was 10 mm. The temperature of the platen was 120 ° C.

Similarly, the ink compositions of Examples 2 to 20 were evaluated in combination with other color ink compositions.
The evaluation was made according to the following criteria.

A (favorable): A good image can be obtained with 4024 paper even at a high resolution exceeding 3 μm (= 600 dpi). ∘ (appropriate): good image quality can be obtained with 4024 paper at a resolution of 3 to 5 μm (= 360 to 600 dpi). Δ (Fair): A good image can be obtained with 4024 paper at a resolution of 5 to 10 μm (= 360 dpi). Poor (unsuitable): At a resolution of 10 μm (= 360 dpi), the image quality obviously deteriorates due to ink bleeding.

(C) Results Tables 6 and 7 show the evaluation results of Examples 1 to 20 and Comparative Examples 1 and 2 based on the above evaluation method.

As shown in Tables 6 and 7, Examples 1 to 1
No. 20, the ink composition for inkjet recording according to the present invention has an ink bleeding length of 3 μm or less in both tests of the bleeding length of a single color ink and the ink bleeding length of a multicolor printing. Can be suitably used as the ink.

On the other hand, in the ink composition of Comparative Example 1, since the platen was heated, clogging occurred in the recording head, and proper evaluation could not be performed.

The ink composition of Comparative Example 2 was 10 μm or more in the ink bleeding length test for single-color and multicolor printing, and was judged to be unsuitable as an ink composition for color printers.

(4) Evaluation of Redispersibility of Ink Compositions The ink compositions of Examples 1 to 20 and Comparative Examples 1 and 2 were dropped on the preparations in an amount of 10 μg each,
After being left to dry in a dryer at 40 ° C. for 1 week, 10 μg of an ink composition having the same composition was dropped, a cover glass was put on the surface, and the glass was pressed with a finger pad 2 to 3 times to obtain a microscope (400 times).
Was observed. The following judgment was made according to the redispersion state of the dried ink.

A (favorable): No aggregate of the ink composition is confirmed. ∘ (appropriate): all the ink aggregates that can be confirmed are 10 μm or less (even if there are aggregates of 10 μm or less,
It can be discharged from the nozzle of the recording head). X (unsuitable): Aggregates of 10 μm or more are confirmed.

The results of the redispersion evaluation of the ink composition are shown in Tables 6 and 7.

As shown in Tables 6 and 7, Examples 1-2
The ink composition for inkjet recording of the present invention of No. 0 showed good results in the redispersibility test, and was sufficiently practically usable as an ink composition of a color printer.

On the other hand, the ink composition of Comparative Example 1 was confirmed to have poor redispersibility. In addition, the ink composition of Comparative Example 2 is
The redispersibility was good.

(5) Evaluation of Effect of Preventing Drying Unevenness Solid printing was carried out on recycled paper and copy paper using the ink compositions of Examples 1 to 20 and Comparative Examples 1 and 2, depending on the standing time immediately after printing. The occurrence of uneven drying was evaluated. In addition, the evaluation was performed using the single color of the ink compositions of Examples 1 to 20, and 4 of Examples 1 to 4 and Examples 9 to 12.
Two types of full-color printing patterns, in which the color ink compositions were overlaid and printed, were used. The evaluation was performed in three stages according to the following criteria.

(A) Drying unevenness due to elapsed time after printing ⊚ (suitable): There is no drying unevenness immediately after printing. ○ (Appropriate): Stickiness and cloudiness disappear after standing for 1 minute after printing. X (unsuitable): Stickiness remains and a cloudy part remains even after 5 minutes from printing.

(B) Drying unevenness due to humidity environment ⊚ (suitable): There is no drying unevenness under the environment of relative humidity 90% (30 ° C.). ◯ (appropriate): There is no drying unevenness in an environment of relative humidity of 60% (30 ° C.) or less. Poor (unsuitable): Drying unevenness occurs in the environment at a relative humidity of 60% (30 ° C.) or less.

(C) Results Tables 6 and 7 show the evaluation results of Examples 1 to 20 and Comparative Examples 1 and 2 based on the above evaluation method.

As shown in Tables 6 and 7, Examples 1 to 1
The 20 ink compositions according to the present invention can prevent poor drying immediately after printing, and can obtain high-quality images without being affected by the surrounding environment.

(6) Evaluation of ejection stability Using the apparatus shown in FIG. 4, various head temperatures (25 ° C.,
At 30 ° C., 40 ° C., 60 ° C., and 80 ° C.), the ejection states of the ink compositions prepared in Examples 21 and 22 were observed, and evaluated according to the following criteria in four levels.

⊚: Discharge amount and discharge speed from 48 nozzles are all within 10%. ◯: The difference in discharge amount and discharge speed from the 48 nozzles exceeds 10%, but is within 20%. Δ: The difference in discharge amount and discharge speed from 48 nozzles exceeds 20%, but there is discharge from 48 nozzles. X: There is a nozzle that does not fly.

The results are shown in Table 8.

(7) Evaluation of light transmittance (turbidity) (a) Preparation of OHP sheet 1 Polyvinylpyrrolidone (trade name: PVPK-90; GA
F) and styrene acrylic acid copolymer (trade name: AS
T-17022, manufactured by Nippon Shokubai Co., Ltd.) 10: 4.5
Were mixed at a weight ratio of 1 to prepare a coating liquid. This coating solution was applied to a 100 μm thick translucent polyethylene terephthalate (PE
T) The film has a thickness of 5 after being dried by bar coating.
The coating was applied so that the thickness became μm, and the coating was dried at 100 to 120 ° C. for about 20 minutes to obtain an OHP sheet (hereinafter referred to as OHP sheet 1).

(B) Preparation of OHP Sheet 2 Polyvinyl alcohol (trade name: PVA-1220, manufactured by Kuraray Co., Ltd.) and sili force were mixed at a weight ratio of 99.5: 0.5 to prepare a coating liquid. This coating solution is applied to a translucent polyethylene terephthalate (PET) film having a thickness of 100 μm by a bar coater so that the film thickness after drying is 10 μm, and dried at 100 to 120 ° C. for about 20 minutes. To obtain an OHP sheet (hereinafter referred to as OHP sheet 2).

(C) Print Evaluation Test (Unheated) The ink compositions of Examples 29 to 32 were used to print on the OHP sheets 1 and 2 obtained above. The inkjet recording printer used for printing was MJ-15000C (manufactured by Seiko Epson Corporation). The recording medium was not heated after printing and left at room temperature after printing.

(D) Printing evaluation test (heating) After printing on the OHP sheet 1 using the ink composition of Example 31, the recording medium was heated at the temperature shown in Table 10 except that the recording medium was heated (c). Print evaluation test (non-heated)
The same operation as described above was repeated.

(E) Results The light transmittance (turbidity: Haze) of the printed matter is the total transmitted light (H
Turbidity (Haze), which is defined as the ratio of scattered light (Hd) in t), is measured by a turbidimeter (Nippon Denshoku Industries Co., Ltd., ND)
H-100 IDP). Table 10 shows the results.

(8) Evaluation of Glossiness After printing on a commercially available recording paper (Xero × -4024) using the ink compositions of Examples 29 to 32, the glossiness of the printed portion recorded was measured according to JIS Z8741. 3 (θ = 6
0 °). Table 10 shows the results.

[0157]

[Table 1]

[0158]

[Table 2]

[0159]

[Table 3]

[0160]

[Table 4]

[0161]

[Table 5]

[0162]

[Table 6]

[0163]

[Table 7]

[0164]

[Table 8]

[0165]

[Table 9]

[0166]

[Table 10]

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing an inkjet recording apparatus used for evaluation of an inkjet recording ink composition of the present invention.

FIG. 2 is a perspective view schematically showing another inkjet recording device used for evaluation of the inkjet recording ink composition of the present invention.

FIG. 3 is a graph showing a saturated dissolved air amount of water at each temperature.

FIG. 4 is a perspective view schematically showing still another inkjet recording device used for evaluation of the inkjet recording ink composition of the present invention.

[Explanation of symbols]

 1,71 ··· Platen 2, 72 · · Heater 3, 4, 73, 74 · · Paper pressing roller 5, 75 · · Recording medium 6, 76 · · Inkjet recording head 7, 77 · · Ink tank 8 · · Guide Axis 78 ··· Recording head drive device 81, 82, 83, 84 ·· Recording head 85 · · Recording medium winding device

 ─────────────────────────────────────────────────── ─── Continuation of front page (31) Priority claim number Japanese Patent Application No. 7-278158 (32) Priority date Hei 7 (1995) October 25 (33) Priority claim country Japan (JP) (72) Inventor Yoshiyuki Ozawa 3-5 Yamato, Suwa, Nagano Seiko Epson Corporation (72) Inventor Hidehiko Komatsu 3-3-5 Yamato, Suwa, Nagano Prefecture Seiko Epson Corporation (72) Inventor Kazutoshi Fujisawa Nagano Seiko Epson Co., Ltd., 3-3-5 Yamato, Suwa Prefecture, Japan (72) Inventor Kenichi Kanbayashi 3-3-5, Yamato, Suwa City, Suwa City, Nagano Prefecture Seiko Epson Corporation

Claims (17)

[Claims] 1. Ink jet recording, comprising a pigment, a resin dispersant, a thermoplastic resin emulsion, and water, wherein the weight ratio of the pigment to the resin dispersant is 20: 1 to 5: 2. Ink composition. 2. The ink composition according to claim 1, further comprising a sugar. 3. The ink composition according to claim 1, further comprising a nonionic surfactant having a polyoxyethylene group. 4. The ink composition according to claim 1, further comprising an anionic surfactant having a polyoxyethylene group. 5. The ink composition according to claim 1, further comprising a nonionic surfactant having a polyoxyethylene group and an anionic surfactant having a polyoxyethylene group. 6. The ink composition according to claim 1, wherein the amount of dissolved air is 14 ppm or less. 7. The ink composition according to claim 6, further comprising sugar. 8. The non-evaporated component at the heating temperature of the heated recording medium is 23% by weight based on the total weight of the ink composition.
It is contained in the above amount and further has two or more alcoholic hydroxyl groups in the molecule, and the ratio (N / M) of the number (N) of alcoholic hydroxyl groups in one molecule to the molecular weight (M) is 0. The ink composition according to claim 1, comprising two or more hydroxy compounds of 01 or more in a total amount of 10% by weight or more based on the total weight of the ink composition. 9. The two types of the hydroxy compounds,
The ink composition according to claim 8, containing a water-soluble polymer compound and a polyhydric alcohol. 10. The water-soluble polymer compound contains at least one compound selected from the group consisting of saccharose, maltitol, maltose, gluconic acid, sorbitol, mannitol, glucose, polyvinyl alcohol, sodium alginate, and polyethylene oxide. The ink composition according to claim 9, which comprises: 11. The polyhydric alcohol is glycerin, diglycerin, polyglycerin, ethylene glycol, diethylene glycol, triethylene glycol,
The ink composition according to claim 9, containing at least one compound selected from the group consisting of dipropylene glycol, hexylene glycol, and 1,2,6-hexanetriol. 12. The ink composition according to claim 8, wherein the total amount of the pigment and the thermoplastic resin component of the thermoplastic resin emulsion is 10% by weight or more based on the total weight of the ink composition. . 13. The pigment, a thermoplastic resin component of the thermoplastic resin emulsion, and a water-soluble polymer compound,
The polyhydric alcohol is contained in a total amount of 20 to 50% by weight or more based on the total weight of the ink composition, and the thermoplastic resin component of the thermoplastic resin emulsion, the water-soluble polymer compound, and the polyhydric alcohol are contained. The weight ratio of the content with alcohol is 1
The ink composition according to claim 8, which is in the range of 0: 7.5: 12. 14. The ink composition according to claim 8, further comprising 0.1 to 1% by weight of a surfactant. 15. 1,2-Benzisothiazoline-3-
The ink composition according to claim 1, which contains on. 16. 1,2-Benzisothiazoline-3-
16. On% 0.005 to 0.1% by weight is contained.
3. The ink composition according to claim 1. 17. A droplet of the ink composition according to claim 1 is ejected from an ink jet recording head to be attached to a recording medium, and at the same time as the attachment, the ink composition is passed from the recording medium support through the recording medium. An inkjet recording method comprising applying heat to a droplet to perform fixing.