JP2003192965A - Ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition capable of effectively preventing deposition of a precipitate in the neighborhood of an ink discharge nozzle in a recording apparatus and having good permeability. <P>SOLUTION: The ink composition substantially consists only of a pigment, a dispersant for dispersing the pigment, 1,2-alkanediol, water as a main solvent, and a penetration accelerator as an optional component. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition having excellent head ejection stability. More specifically, a pigment as a colorant,
The present invention relates to an ink composition containing a dispersant for dispersing a pigment.

2. Background Art Ink jet recording is an ink from a fine nozzle and ejected as droplets, a method of recording characters or figures on a recording surface. The inkjet recording method uses an electrostrictive element to convert an electrical signal into a mechanical signal and intermittently ejects the ink stored in the nozzle head to record characters or symbols on the surface of a recording medium, or a nozzle. The ink stored in the head part is heated rapidly in a part very close to the ejection part to generate bubbles, which are intermittently ejected by the volume expansion due to the bubbles to record characters or symbols on the surface of the recording medium. Methods are being put to practical use.

The ink used for such ink jet recording has good dryness of printing, no bleeding of printing, uniform printing on various recording medium surfaces, and in the case of multiple colors Various performances such as immiscibility are required.

Therefore, conventionally, in order to prevent the ink composition from drying quickly on a recording paper or to prevent mixing between inks of different colors which are adjacent to each other, a component which promotes permeation into the recorded material is contained in the ink composition. It is considered to be added to.

For example, Japanese Patent Laid-Open No. 14260/1990 describes the use of lower alcohols as a component for promoting the permeability of ink. JP-A-57-5
Japanese Patent No. 5975 describes that a surfactant is added to an ink composition to reduce the surface tension of the ink and improve the permeability of the ink.

Japanese Patent Application Laid-Open No. 7-157698 describes 1,2-alkanediol as a penetrant.
However, all the inks specifically disclosed in this publication contain a dye as a colorant.

[0007]

SUMMARY OF THE INVENTION The present inventors have now printed using an ink composition prepared by dispersing a pigment with a dispersant, the ink composition having a specific composition containing a 1,2-alkanediol. As a result, it has been found that it is possible to effectively prevent deposits from adhering to the vicinity of the ink ejection nozzles in the recording apparatus, and to realize stable ink ejection. Further, the present inventors have also found that 1,2-alkanediol can impart excellent penetrability to an ink composition by adding a relatively small amount. The present invention is based on these findings.

Therefore, it is an object of the present invention to provide an ink composition which can effectively prevent deposits from adhering to the vicinity of the ink ejection nozzles of a recording apparatus and has excellent penetrability. And the ink composition according to the present invention, a pigment, a dispersant for dispersing the pigment,
It essentially consists of a 1,2-alkanediol, a nonionic surfactant, a humectant, water as a main solvent, and a penetration enhancer as an optional component. In the present invention, the dispersant has an acid value of 7 at this time.
0-200 and AB, ABA, or AB
A block copolymer having a C structure, wherein the A block is hydrophilic, the B block is hydrophobic, and (1) CH ₂ ═CH—R (where R is C _6- ). C ₂₀ is a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group or alkaryl _{group,), (2) CH 2} = CH-oR 1 ( wherein the substituent ^{R 1} is _C 3 _{-C 20} Or an unsubstituted alkyl group, an aryl group, an aralkyl group, or an alkaryl group), (3) CH ₂ ═CH—O—C (O) —R ¹ (wherein R ¹ is as defined in the above (2)). And (4) CH ₂ ═CH—NR ² R ³ (wherein R ² and R ³ are H, C, provided that neither R ² nor R ³ are both H). _3- C
₂₀ independently selected from the group consisting of a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group, and an alkaryl group), based on B block weight. As at least 30% by weight, and further C
The block is characterized by being arbitrarily selectable.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Ink Composition The ink composition according to the present invention is used in a recording system using the ink composition. Examples of the recording method using the ink composition include an inkjet recording method, a recording method using a writing instrument such as a pen, and various other printing methods. The ink composition according to the present invention is preferably used in an inkjet recording method. More preferably, the ink composition according to the present invention is used in an inkjet recording method using an inkjet head that forms ink droplets by mechanical deformation of an electrostrictive element.

In the present invention, "consisting essentially of" means that the ink composition according to the present invention contains a pigment, a dispersant for dispersing the pigment, a 1,2-alkanediol, a nonionic surfactant, and a humectant. , Water as the main solvent, and
Other conventional moisturizing components not meant to be included in the present invention, such as 2-pyrrolidone, are meant to consist essentially of the individual components of the penetration enhancer as an optional component, and other conventional moisturizing components are not included in the ink compositions of the present invention. Means that it is not included as a component of. However, in this case, auxiliary components commonly used in general ink compositions, such as preservatives and p
H regulators and antioxidants (details will be described later)
Does not exclude the use of. Therefore, 2-pyrrolidone is not included in the ink composition of the present invention, but an antiseptic agent that is supplementarily added for the purpose of preventing deterioration of the ink composition may be included.

In a preferred embodiment of the present invention,
The ink composition is substantially free of 2-pyrrolidone. The term "substantially free of" as used herein naturally includes the case where the 2-pyrrolidone is not contained at all, and the case where 2-pyrrolidone is contained in such an amount that the moisturizing action is not significantly shown in the ink composition. It also means to include.

According to the ink composition of the present invention, it is possible to prevent deposits from adhering to the vicinity of the discharge nozzle of the recording head, prevent clogging of the nozzle, and maintain stable print quality. That is, the ink composition according to the present invention has excellent head ejection stability and clogging stability.

Further, the ink composition according to the present invention exhibits excellent penetrability into a recording medium. In order to improve the permeability of the ink composition, it is generally known to add a penetration enhancer such as triethylene glycol monobutyl ether (TEGmBE). According to the ink composition of the present invention, it is possible to achieve the same level of penetrability to media with a smaller amount of 1,2-alkanediol used as compared with the case of using a penetration enhancer such as TEGmBE. it can. Therefore, in the present invention, the amount of penetrant added to the ink composition can be relatively reduced. This is advantageous in improving the stability of the dispersed state of the pigment in the ink composition, and can improve the storage stability and reliability of the ink composition.
Further, in the ink composition, the allowable addition amount of a component other than the colorant or the ratio of the component in the ink composition can be increased, which is advantageous from the viewpoint of designing or improving the ink composition. Further, in the present invention, it is possible to suppress the increase in the viscosity of the ink composition to be lower than that of a conventional penetration enhancer such as TEGmBE, and thus it is possible to increase the amount of the moisturizing agent added. .

1,2-Alkanediol In the ink composition according to the present invention, 1,2-alkanediol is included as an essential component. In the present invention, 1,2-alkanediol has 4 carbon atoms.
Preference is given to using 1,2-alkanediols of 10 to 10.
Two or more kinds of 1,2-alkanediols may be mixed and added. In a preferred embodiment of the present invention, the 1,2-alkanediol is 1,2-butanediol, 1,2-alkanediol.
Pentanediol, 1,2-hexanediol, 1,2
-Selected from the group consisting of heptanediol, and mixtures thereof. These are more preferable because they have excellent penetrability into a recording medium. In a more preferred embodiment of the present invention, the 1,2-alkanediol is preferably 1,2-hexanediol or 1,2-pentanediol, and more preferably 1,2-hexanediol.

The ink composition according to the present invention comprises the above 1, 2
-Alkanediol was added in an amount of 0.
It is preferably contained in the range of 5 to 10% by weight, more preferably 1 to 5% by weight. 0.
If it is 5% by weight or more, sufficient permeability can be obtained,
Further, if it is 10% by weight or less, it becomes easy to adjust the viscosity of the printable ink together with other additives, which is advantageous.

According to a more preferred embodiment of the present invention,
When the 2-alkanediol is 1,2-butanediol, the ink composition according to the present invention preferably comprises 3 to 10% by weight of 1,2-butanediol,
More preferably, it comprises 5 to 10% by weight. Also, 1,
When the 2-alkanediol is 1,2-pentanediol, the ink composition according to the present invention comprises 1,2-pentanediol, preferably 3-10% by weight, more preferably 3-7% by weight. . Furthermore, when the 1,2-alkanediol is 1,2-hexanediol, the ink composition according to the present invention preferably contains 1 to 6% by weight of 1,2-hexanediol, more preferably 3 to 5%.
It comprises by weight. When the 1,2-alkanediol is 1,2-heptanediol, the ink composition according to the present invention preferably contains 1,2-heptanediol in an amount of 0.5 to 3% by weight, more preferably 1 to 3% by weight. It comprises 2% by weight.

According to a further preferred aspect of the present invention, the ink composition preferably has a 1,2-alkanediol of 1,2-hexanediol.
It is preferable to contain 1 to 6% by weight of 2-hexanediol.

Pigment The ink composition according to the present invention uses a pigment as a colorant. In the present invention, any pigment can be selected as the pigment as long as it can be dispersed in the ink composition with a dispersant. Therefore, such a pigment may be any pigment that emits any color when recorded on a recording medium, and may be either an inorganic pigment or an organic pigment. It may also be a mixture of these.

As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method or a thermal method can be used. As the organic pigment, azo pigment (including azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, etc.), polycyclic pigment (for example, phthalocyanine pigment, perylene pigment, perinone pigment, anthraquinone pigment, quinacridone pigment, dioxazine pigment, A thioindigo pigment, an isoindolinone pigment, a quinophthalone pigment, etc.), a dye chelate (for example, a basic dye type chelate, an acid dye type chelate, etc.), a nitro pigment, a nitroso pigment, aniline black and the like can be used.

The pigments usable in the present invention include:
Specifically, for example, as a color type, C.I. I.
Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 1
0, 11, 12, 13, 14, 14C, 16, 17, 2
4, 34, 35, 37, 42, 53, 55, 65, 7
3, 74, 75, 81, 83, 93, 95, 97, 9
8, 100, 101, 104, 108, 109, 11
0, 114, 117, 120, 128, 129, 13
8, 150, 151, 153, 154, 180 and the like.

In addition, C.I. I. Pigment Red 1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1
3, 14, 15, 16, 17, 18, 19, 21, 2
2, 23, 30, 31, 32, 37, 38, 39, 4
0, 48 (Ca), 48 (Mn), 48: 2, 48:
3, 48: 4, 49, 49: 1, 50, 51, 52,
52: 2, 53: 1, 53, 55, 57 (Ca), 5
7: 1, 60, 60: 1, 63: 1, 63: 2, 64,
64: 1, 81, 83, 87, 88, 89, 90, 10
1 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112, 114, 122 (Quinacridone Magenta), 123, 146, 149, 163, 1
66, 168, 170, 172, 177, 178, 17
9, 184, 185, 190, 193, 202, 20
9, 219 and the like are also included.

Further, C.I. I. Pigment Blue 1,
2, 3, 15, 15: 1, 15: 2, 15: 3, 15:
34, 16, 17: 1, 22, 25, 56, 60, C.I.
I. Bat Blue 4, 60, 63, C.I. I. Pigment Orange 5, 13, 16, 17, 36, 43, 51, C
． I. Pigment Green 1, 4, 7, 8, 10, 1
7, 18, 36, C.I. I. Pigment Violet 1
(Rhodamine lake), 3, 5: 1, 16, 19 (quinacridone red), 23, 38 and the like are also included.

Pigments usable in the present invention include:
Examples of black type include carbon black. Specific examples of such carbon black include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 4 manufactured by Mitsubishi Chemical.
5, No.52, MA7, MA8, MA100, No2200B etc., Raven5750, Raven5250, Raven5000, Raven3500, made by Colombia.
Raven1255, Raven700 etc.Regal 400 made by Cabot
R, Regal330R, Regal660R, Mogul L, Monarch700, Mona
rch 800, Monarch 880, Monarch 900, Monarch 1000, M
onarch 1100, Monarch 1300, Monarch 1400 etc., and Degussa Color Black FW1 and Color Black FW
2, Color Black FW2V, Color Black FW18, Color Black
FW200, ColorBlack S150, Color Black S160, Color B
lack S170, Printex 35, Printex U, Printex V, Print
ex 140U, Special Black 6, Special Black 5, Special
Black4A, Special Black 4 etc. are mentioned.

The above pigments may be used alone,
In addition, a plurality of types may be selected from within each group or between each group and used in combination.

The particle size of the pigment used in the present invention is
0.2 μm or less is preferable, and more preferably 0.05
Is about 0.15 μm.

The content of the pigment in the ink composition of the present invention is 0.5 to 15% by weight based on the total amount of the ink composition.
Is preferable, and more preferably 0.75 to 10% by weight.

Dispersant In the ink composition according to the present invention, a dispersant for dispersing the pigment is an essential component. In the present invention, the pigment is dispersed in the ink composition by the dispersant. As the dispersant in the present invention, in addition to a conventional surfactant, a dispersant commonly used for preparing a pigment dispersion liquid, for example, a polymer dispersant can be preferably used. It will be apparent to those skilled in the art that the dispersant contained in this pigment dispersion will also function as a dispersant and a surfactant for the ink composition. As a more preferable dispersant, a polymer dispersant, particularly a resin dispersant can be used. According to one preferred embodiment of the present invention, the above-mentioned pigment is preferably added to the ink composition as a pigment dispersion liquid obtained by dispersing the pigment in an aqueous medium.

Preferred examples of the polymer dispersant include natural polymers. Specific examples thereof include glue, gelatin, casein, proteins such as albumin, gum arabic, natural rubber such as gum tragacanth, glucosides such as savonine, alginic acid and propylene glycol alginate, triethanolamine alginate, and alginate derivatives such as ammonium alginate,
Examples thereof include cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose and ethyl hydroxycellulose.

Further, as a preferable example of the polymer dispersant, a synthetic polymer can be mentioned. Specific examples thereof include polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, acrylate-acrylonitrile copolymers, vinyl acetate-acrylic acid ester copolymers, acrylic acid- Acrylic resin such as acrylic ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer Styrene-acrylic resins such as polymers, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymers, styrene-maleic acid copolymers, styrene-maleic anhydride copolymers, isobutylene-maleic acid resins, rosins Modified maleic acid resin, vinylnaphthalene-acrylic Acid copolymer, vinyl naphthalene-maleic acid copolymer, and vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer Examples thereof include polymers, vinyl acetate-based copolymers such as vinyl acetate-acrylic acid copolymer, and salts thereof.

Of these, styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, acrylic acid-acrylic acid ester copolymers, and styrene-maleic anhydride copolymers are preferable as the dispersant.

According to a more preferred embodiment of the present invention, the dispersant is a block polymer resin produced by block copolymerization and has an acid value of 70 to 200, more preferably 100 to 200. is there. Here, the acid value refers to the number of milligrams of potassium hydroxide required to neutralize the free fatty acid contained in 1 g of the block polymer resin. This acid value can be adjusted by selecting the monomer species to be copolymerized. Selection of such a dispersant is advantageous in preventing bleeding during printing of the ink composition and improving quick-drying property of the ink.

According to a further preferred embodiment of the present invention, the dispersant is preferably the dispersant described in JP-A No. 11-269418. That is, such a suitable dispersant is a block copolymer having an AB, ABA, or ABC structure, wherein the A block is hydrophilic, the B block is hydrophobic, and
A non-acrylic monomer selected from the group consisting of the following (1) to (4) is contained in at least 30% by weight based on the weight of the B block, and the C block can be arbitrarily selected. . (1) CH ₂ ═CH—R (wherein R is a C _{6 to} C ₂₀ substituted or unsubstituted alkyl group, aryl group, aralkyl group, or alkaryl group; Alkyl, aryl, aralkyl groups containing one or more substituents which do not interfere with the polymerization process including, for example, hydroxy, amino, ester, acid, acyloxy, amide, nitrile, halogen, haloalkyl, alkoxy, or Alkaryl group, and specific examples thereof include styrene, alpha-methylstyrene, vinylnaphthalene, vinylcyclohexane, vinyltoluene, vinylanisole, vinylbiphenyl, vinyl2-norbornene, and the like, (2) CH ₂ = CH-oR ¹ (where, ^{R 1} is _C 3 _{-C 20} substituted or It is a substituted alkyl group, an aryl group, an aralkyl group, or an alkaryl group; the substitution is as described above, and specific examples thereof include vinyl n-propyl ether, vinyl t-butyl ether, vinyl decyl ether. , Vinyl iso-octyl ether, vinyl octadecyl ether, vinyl phenyl ether, etc.), (3) CH ₂ ═CH—O—C (O) —R ¹ (wherein R ¹ is as defined in the above (2)). Specific examples include vinyl propionate, vinyl butyrate, vinyl n-decanoate, vinyl stearate, vinyl laurate, vinyl benzoate, etc.), and (4) CH ₂ ═CH—NR ² R ³ (However, in R ² and R ³ , both R ² and R ³ are H
H and C ₃ to
C ₂₀ is independently selected from the group consisting of a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group, and an alkaryl group, wherein the substitution is as defined above, and Examples include N-vinylcarbazole, vinylphthalimide and the like).

In the block copolymer having the AB, ABA, or ABC structure described above, each of the letters indicates a block of the block copolymer. That is, different letters indicate blocks having different monomer compositions and the same letters indicate blocks having the same monomer composition. Thus, the AB block copolymer is a diblock where the two blocks are different, and the ABA block copolymer is three blocks and only two different blocks (ie, the two A blocks are the same). It includes. The ABC block copolymer also contains three blocks, meaning that all three blocks are different from each other.

In the above structure, the B block is hydrophobic and can bind to the colorant regardless of which block copolymer is used.
The A block is hydrophilic and soluble in an aqueous vehicle. Third block (A block or C
Any of the blocks) can be chosen arbitrarily and can be used to fine-tune the balance of polymer hydrophobicity and hydrophilicity. Thus, this third block may have the same composition as the hydrophilic block, such as ABA, or it may have a different composition than either A or B, such as ABC. The aqueous vehicle here usually means water and a water-soluble organic solvent.

The size of the hydrophobic block must be large enough so that effective binding occurs on the pigment surface. The number average molecular weight is at least 300, preferably at least 500. The hydrophilic block also needs to be large enough to provide a steric and electrostatic stabilizing mechanism for stable dispersion, and so that the entire polymer is soluble in the aqueous vehicle,
It is desirable to be balanced with the size of the hydrophobic block.

The hydrophobic block may also contain other ethylenically unsaturated monomers, ie acrylic monomers. Specific examples of such a monomer include C ₁ to
C _{2 0} a is acrylic acid or may be included esters of methacrylic acid, such as methyl acrylate, ethyl acrylate, n- butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n- butyl methacrylate, t- Butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate and the like can be mentioned.

The hydrophilic block can be prepared from ethylenically unsaturated monomers. This hydrophilic block needs to be soluble in the aqueous vehicle chosen and contains up to 100% by weight, preferably at least 50% by weight, of ionizable monomers, based on the total weight of the hydrophilic block. Good. The choice of ionic monomer depends on the desired ionic properties of the ink for the selected application. In the case of anionic block copolymer dispersants, the ionic monomer is primarily a monomer containing acid groups, or acid precursor groups. Specific examples of useful monomers include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, and the like.

In the case of cationic block copolymer dispersants, the preferred ionic monomers for the hydrophilic portion are amine containing monomers. The amine group may be a primary, secondary or tertiary amine group, or a mixture thereof. Specific examples of the amine-containing monomer include N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, t-butylaminoethyl methacrylate, 2-N-morpholinoethyl acrylate, 2-N-
Morpholinoethyl methacrylate, 4-aminostyrene, 2-vinyl pyridine, 4-vinyl pyridine, vinyl imidazole and the like are included.

A nonionic hydrophilic monomer or a water-soluble monomer may be appropriately used to finely adjust the hydrophobic / hydrophilic balance and adjust the solubility property of the block copolymer. These can be readily copolymerized to either a hydrophobic block or a hydrophilic block, or to a third separate block such as the C block of an ABC block copolymer to achieve the desired effect. Useful specific examples include alkyl acrylates and alkyl methacrylates having alkyl groups of 1 to 12 carbon atoms, such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, etc.
And acrylamide and methacrylamide.

The block copolymer as a dispersant usable in the present invention can be efficiently produced by simultaneously making a plurality of blocks continuously by using a macromonomer as an intermediate. The macromonomer with terminal polymerizable double bonds becomes one of the blocks of the block copolymer and is first prepared. It is then copolymerized with the monomer selected for the second block. In the case of ABA and ABC triblock copolymers, it is preferred to start with the synthesis of hydrophilic macromonomers as the first block. For AB block copolymers, either hydrophobic or hydrophilic macromonomers are the effective first step in the synthesis. The macromonomer is preferably prepared by a free radical polymerization method, and at this time, as a catalytic chain transfer agent or an organic chain transfer agent which enables chain transfer,
Cobalt (II) and cobalt (III) complexes are used.
Organic chain transfer agents include allyl sulfide, allyl bromide, methacrylate end-group-containing methacrylate oligomers including dimers, alpha-methylstyrene dimers, and related compounds.

Further, the block copolymer has the international publication W.
It can be synthesized via a macromonomer as taught in O96 / 15157 (June 1996). The block copolymers useful in the present invention have a weight average molecular weight of about 1,000 to 50,000, preferably 2,0.
It is from 00 to 20,000. The AB block copolymer prepared by the above method is terminated at its end by a polymerizable double bond and is further polymerized with other groups of the monomer to give ABA or ABA via conventional free radical polymerization in the above method. Form an ABC block copolymer.

Many conventional organic solvents can be used as the polymerization medium to prepare both macromonomers and block copolymers. These include alcohols such as methanol, ethanol, n-propanol and isopropanol, ketones such as acetone, butanone, pentanone and hexanone, tetrahydrofuran, diethyl ether, and ethylene glycol monoalkyls such as commonly available cellosolve and carbitol. Ethers, ethers such as ethylene glycol dialkyl ethers, polyethylene glycol monoalkyl ethers, and polyethylene glycol dialkyl ethers, alkyl esters of acetic acid, propionic acid, and butyric acid, glycols such as ethylene glycol, and mixtures thereof are included. It is not limited.

In order for the block copolymer to be soluble in the aqueous vehicle, it is necessary to produce a salt of ionic groups in the hydrophilic part. Acid group salts are prepared by neutralizing them with a neutralizing agent. Specific examples of useful bases include alkali metal hydroxides (lithium hydroxide,
Sodium hydroxide and potassium hydroxide), alkali metal carbonates and bicarbonates (sodium carbonate, potassium carbonate, sodium bicarbonate, and potassium bicarbonate),
Organic amines (monomethylamine, dimethylamine, trimethylamine, morpholine, N-methylmorpholine),
Examples thereof include organic alcohol amines (N, N-dimethylethanolamine, N-methyldiethanolamine, monoethanolamine, diethanolamine, triethanolamine), ammonium salts (ammonium hydroxide, tetraalkylammonium hydroxide), and pyridine. In the case of cationic block copolymer dispersants, the amine groups are neutralized with acids including organic and inorganic acids. Specific examples of useful acids include organic acids (acetic acid, propionic acid, formic acid, oxalic acid), hydroxylated acids ((hydroxyla
ted acids) glycolic acid, lactic acid), halogenated acids (hydrochloric acid, hydrobromic acid), and inorganic acids (sulfuric acid, phosphoric acid,
Nitric acid).

According to one preferred embodiment of the invention, it is preferred to use the dispersants mentioned above in an amount of from 0.1 to 2.0% by weight, based on the pigment, more preferably from 0.2 to.
The amount is 1.0% by weight.

Nonionic Surfactant According to the present invention, the ink composition comprises a nonionic surfactant. Examples of such nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide. , And acetylene glycol-based surfactants described later. Two or more kinds of nonionic surfactants may be mixed and used.

According to a preferred embodiment of the present invention, the ink composition preferably contains an acetylene glycol-based surfactant as the nonionic surfactant. In the present invention, preferred specific examples of the acetylene glycol-based surfactant include compounds represented by the following formula (a).

[0047]

[Chemical 1] [Wherein, 0 ≦ m + n ≦ 50, R ^{1 *} , R ^{2 *} , R
^{3 *} and R ^{4 *} independently represent an alkyl group (preferably an alkyl group having 1 to 6 carbon atoms).

Among the compounds represented by the above formula (a), 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 3,6-dimethyl-4-octyne are particularly preferable. -3,6-diol, 3,5-dimethyl-1-hexyne-3-ol and the like can be mentioned. It is also possible to use a commercially available product as the acetylene glycol-based surfactant represented by the above formula (a), and specific examples thereof include Surfynol 82, 104, 440, 465, 485, or TG. (Available from Air Products and Chemicals. Inc.), Olfine STG, Olfine E101
0 (trade name) (above, manufactured by Nisshin Chemical Co., Ltd.) can be mentioned. Two or more kinds of these acetylene glycol-based surfactants may be mixed and used.

The amount of the nonionic surfactant added is preferably in the range of about 0.1 to 5% by weight, more preferably in the range of about 0.5 to 2% by weight, based on the ink composition.

Humectant In the present invention, the humectant is preferably a chain or alicyclic monohydric alcohol having 1 to 7 carbon atoms or polyhydric alcohol, more preferably 1 to 5 carbon atoms. It is a dihydric to trihydric alcohol. In the present invention, the humectant is mainly used for suppressing the drying of the ink and preventing the solidification of the ink at the ejection nozzle of the inkjet recording apparatus.

Specific examples of the moisturizer include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol and tert.
-Butanol, iso-ptanol, monohydric alcohol such as n-pentanol, glycerin, ethylene glycol, diethylene glycol, triethylene glycol,
Polyethylene glycol, propylene glycol, butylene glycol, dipropylene glycol, polypropylene glycol, thiodiglycol, hexylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexane Examples include polyhydric alcohols such as diols, 1,2,6-hexanetriol, and pentaerythritol. Two or more kinds of moisturizers may be mixed and added.

In a further preferred embodiment of the present invention, the humectant is one selected from glycerin, ethylene glycol, diethylene glycol, triethylene glycol, 1,4-pentanediol and 1,5-pentanediol.

These humectants, together with other ink composition components, have an ink viscosity of 25 mPas at 25 ° C.
-It can be added in an addition amount of s or less.

Water as Main Solvent In the ink composition according to the present invention, the main solvent is water. Here, as water, ion-exchanged water, ultrafiltered water,
Pure water such as reverse osmosis water and distilled water, or ultrapure water can be preferably used. In addition, it is preferable to use water sterilized by irradiation with ultraviolet rays and addition of hydrogen peroxide because it is possible to prevent the generation of mold, bacteria and the like during long-term storage.

Penetration Promoter The ink composition according to the present invention may contain a penetration promoter as an optional component. be able to. In a preferred aspect of the invention, the penetration enhancer is a glycol monoether. Here, glycol monoether is
The compounds are selected from monoether compounds of glycols such as mono and polyethylene glycols and mono and polypropylene glycols, and are selected from compounds represented by the following formula (α). _{R a -O- [C x H 2x} -O] y -H (α) [ In the formula, _{R a} is an alkyl group, a phenyl group having 1 to 6 carbon atoms or a benzyl group, preferably a methyl group, ethyl Group, propyl group, or butyl group, more preferably n
A butyl group, x is 1-3, preferably 2 or 3.
And y is 1 to 4, preferably 1 to 3].

Specific examples of the penetration enhancer in the present invention include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, Ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether,
Ethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol mono-n-butyl ether, diethylene glycol mono-t
-Butyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene Examples include glycol mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether. To be

Of these, ethylene glycol mono-n-
Butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n-butyl ether, propylene glycol monobutyl ether,
Or dipropylene glycol monobutyl ether,
It is preferable because it has high compatibility with 1,2-alkanediol.

As described above, in the ink composition,
By combining the 2-alkanediol and the glycol monoether, it is possible to impart the same permeability to the ink composition with a smaller addition amount as compared with the case of using the 1,2-alkanediol alone. In addition, it is possible to reduce the wetting of the ink to the ejection nozzles of the inkjet printing apparatus. Furthermore, ink adhesion to the ejection nozzle, which may occur due to the addition of 1,2-alkanediol, can be effectively prevented by further adding glycol monoether. Therefore, the ink composition, combined with the effect of reducing the addition amount described above,
It is possible to effectively prevent ink from adhering to the ejection nozzles of the inkjet recording apparatus, and it is possible to ensure high printing stability.

In the present invention, when a glycol monoether is added as a penetration enhancer, the glycol monoether is preferably added in an amount of 0.25 to 10% by weight based on the ink composition, More preferably, the amount is in the range of 3 to 10% by weight. Within the above range, the ink composition can obtain sufficient penetrability, and the viscosity of the ink composition can be adjusted to a printable ink viscosity in combination with other additives.

In the present invention, the ratio (weight ratio) of glycol monoether to 1,2-alkanediol in the ink composition is preferably in the range of 1: 5 to 5: 1, more preferably The weight ratio is in the range of 1: 2 to 2: 1. Within such a range, 1,
This is advantageous from the viewpoint of reducing the amount of 2-alkanediol added.

Auxiliary component The ink composition of the present invention comprises a pigment, a dispersant for dispersing the pigment, a 1,2-alkanediol, a nonionic surfactant, a humectant, water as a main solvent, and an optional component. Although it is basically composed of only the above-mentioned respective components of the penetration enhancer, even in such a case, as described above, it is supplementarily used in a general ink composition. Auxiliary components can also be included.
Such auxiliary components include, for example, nozzle clogging preventive agents, preservatives, antioxidants, ultraviolet absorbers, conductivity adjusters, pH adjusters, dissolution aids, viscosity adjusters, surface tension adjusters, Examples include oxygen absorbers.

Examples of preservatives include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzothiazolin-3-one (ICI company). Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-
2, Proxel TN) and the like.

Examples of pH adjusters, solubilizers, or antioxidants include amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, Inorganic salts such as lithium hydroxide, ammonium hydroxide, quaternary ammonium hydroxide (tetramethylammonium, etc.), potassium carbonate, sodium carbonate,
Examples thereof include L-ascorbic acid and salts thereof, such as carbonates such as lithium carbonate and other phosphates, alohanates such as alohanate and methylallohanate, biurets such as biuret, dimethylbiuret, and tetramethylbiuret.

In the present invention, a plurality of these auxiliary components may be selected in each group and between each group, and mixed and added.

The surface tension of the ink composition according to the present invention is about 20 to 50 mN / m, preferably about 25 to 40 mN / m.

The ink composition according to the present invention can be produced by dispersing and mixing the above-mentioned components by a conventional and appropriate method. A suitable disperser is preferably used for the mixture excluding the organic solvent and volatile components (eg, ball mill, roll mill, sand mill, attritor, agitator mill, Henschel mixer, colloid mill, jet mill, ong mill, ultrasonic homogenizer, etc.). It is preferable that the organic solvent and the volatile component are added after the above-mentioned mixing is carried out to obtain a homogeneous composition. Then, in order to remove coarse particles and foreign substances, it is preferable to carry out pressure reduction and pressure filtration using a metal filter, a membrane filter or the like, or centrifugation.

Recording Method According to the present invention, there is provided a recording method in which the ink composition is attached to a recording medium to perform printing. Examples of the recording method using the ink composition include an inkjet recording method, screen printing, a recording method with a writing instrument such as a pen, and various other printing methods.

According to a preferred embodiment of the present invention, there is provided an ink jet recording method in which droplets of the ink composition according to the present invention are ejected and the droplets are attached to a recording medium for printing. In the present invention, any method can be used for the ink jet recording method as long as it is a method of ejecting the ink composition as droplets from a fine nozzle and adhering the droplets to the recording medium. As a method like this,
For example, a method using an inkjet head having a mechanism based on the response of an electrostrictive element, that is, a method in which pressure and a print information signal are simultaneously applied to an ink liquid by an electrostrictive element and an ink droplet is ejected by mechanical deformation to form ink By a method of rapidly expanding the ink liquid by the action, a method of an electrostatic suction method, and applying a pressure to the ink liquid with a small pump, and mechanically vibrating the nozzle with a crystal oscillator or the like,
For example, a method of forcibly ejecting ink droplets may be used. According to a more preferable aspect of the present invention, the inkjet recording method according to the present invention is a method using an inkjet head that forms ink droplets by mechanical deformation of an electrostrictive element.

Further, according to the present invention, a recorded matter recorded by the above-mentioned recording method is also provided.

[0070]

The present invention will be described in detail below with reference to examples, but these do not limit the scope of the present invention.

Preparation of Dispersant Dispersants α and β for dispersing the pigment were prepared as follows. The preparation of these dispersants is described in JP-A-11-
This is according to the procedure described in Japanese Patent No. 269418.

Dispersant α: t-butylstyrene / styrene
// Methacrylic acid (27/18 // 55% by weight) block
Copolymer First, the following components were prepared, and macromonomer a was prepared as follows. Ingredient Weight (grams) Part 1: Methanol 233.4 Isopropanol 120.3 Part 2: Methacrylic acid monomer 238.1 Methanol 39.3 Part 3: Isopropropyl-bis (boronyl chloromethyl glyoxymat) cobalt (III) salt 0 .143 2,2'-Azovice (2,2-Dimethylvaleronitrile) (Vazo (trademark, manufactured by DuPont)) 6.52 Acetone 87.2

Mix the mixture of Part 1 with a thermometer, stirrer,
A 2 liter flask equipped with an additional funnel, reflux condenser, and means to maintain a nitrogen blanket over the reaction was charged. The mixture was heated to reflux temperature and refluxed for about 20 minutes. Portions 2 and 3 were added simultaneously while maintaining the reaction mixture at reflux temperature. The addition of Part 2 was completed in 4 hours and the addition of Part 3 was completed in 4 and a half hours. 2 more reflux
Continued for a time, and the solution was cooled to room temperature to obtain macromonomer solution a.

Next, in addition to the obtained macromonomer a, the following components were further prepared, and the dispersant α was prepared by the following procedure. Component Weight (gram) Part 1a: Macromonomer a 152.4 2-Pyrrolidone 40.0 Part 2a: Lupersol 11 (t-butyl peroxypropylate) (manufactured by Elf Arochem North America) 0.67 Acetone 10.0 Part 3a: 1-butylstyrene 27.0 styrene 18.0 Part 4a: Lupersol 11 2.67 Acetone 20.0 Part 5a: Lupersol 11 0.67 Acetone 10.0

The mixture of Part 1a was charged to a 500 mL flask equipped with a thermometer, stirrer, additional funnel, reflux condenser, and means for maintaining a nitrogen blanket over the reaction mixture. The mixture was heated to reflux temperature and refluxed for about 10 minutes. The solution of part 2a was added. Subsequently, portions 3a and 4a were added simultaneously while maintaining the reaction mixture at reflux temperature. The addition of Portions 3a and 4a was completed over 3 hours. The reaction mixture was refluxed for 1 hour and then the solution of part 5a was added. The reaction mixture was then refluxed for another hour. The mixture was distilled until about 117 g of volatiles were collected and 75.0 g of 2-pyrrolidone was added to give 239.0 g of 41.8% polymer solution (dispersant α).

Dispersant β: Styrene / methyl methacrylate
Methacrylic acid (25.0 / 29.2 // 45.
8 wt%) Block Copolymer The following components were prepared and the dispersant β was prepared by the following procedure. Component Weight (grams) Part 1b: Macromonomer a 152.4 2-Pyrrolidone 40.0 Part 2b: Lupersol 11 0.67 Acetone 10.0 Part 3b: Styrene 30.0 Styrene methacrylate 35.0 Part 4b: Lupersol 11 2.67 Acetone 20.0 Portion 5b: Lupersol 11 0.67 Acetone 10.0

Using the above parts 1b to 5b, the same procedure as in the case of the dispersant α was carried out to obtain 270 g of a 44.0% polymer solution (dispersant β).

Preparation of Ink Compositions Using the dispersants α and β obtained as described above, the following ink compositions 1 to 9 were prepared. Ink Composition 1 As a yellow pigment, C.I. I. Pigment Yellow 74 100 g, dispersant α 150 g, potassium hydroxide 6
g and 250 g of water were mixed, and a dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. The resulting dispersion stock solution is filtered through a membrane filter (manufactured by Nippon Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and the filtrate is diluted with water to a pigment concentration of 10% by weight to obtain a yellow pigment dispersion liquid 1. Prepared. 30 g of the obtained yellow pigment dispersion liquid 1, 15 g of glycerin, 1,
10 g of 2-pentanediol and Olfine E1
1g of 010 was mixed, and then ultrapure water was added to bring the total amount to 1
It was set to 00 g. Furthermore, this mixed solution was adjusted to pH 9.5 by using triethanolamine as a pH adjuster, stirred for 2 hours, and then filtered with a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm. Ink Composition 1 was prepared.

Ink composition 2 C.I. I. Pigment Blue 15: 3 100 g, dispersant α 100 g, and potassium hydroxide 4.
5 g and 250 g of water were mixed, and dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. The resulting dispersion stock solution is filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and the filtrate is diluted with water until the pigment concentration becomes 10% by weight to obtain a cyan pigment dispersion liquid 2. Prepared. 30 g of the obtained cyan pigment dispersion 2, 10 g of glycerin, 5 g of diethylene glycol, 1 g of 1,2-hexanediol,
Further, 1 g of Olfine STG was mixed, and ultrapure water was further added to bring the total amount to 100 g. Further, using triethanolamine as a pH adjuster, the mixed solution was adjusted to pH 9.
After adjusting to 5, the mixture was stirred for 2 hours, and then filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm to prepare ink composition 2.

Ink Composition 3 As a cyan pigment, C.I. I. Pigment Blue 15: 3 100 g, dispersant α 100 g, and potassium hydroxide 4.
5 g and 250 g of water were mixed, and dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. The resulting dispersion stock solution was filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and the filtrate was diluted with water to a pigment concentration of 10% by weight to obtain a cyan pigment dispersion liquid 3. Prepared. 30 g of the obtained cyan pigment dispersion 3, 10 g of glycerin, 5 g of diethylene glycol, 6 g of 1,2-hexanediol,
1 g of Olfine E1010 was mixed, and ultrapure water was further added to make the total amount 100 g. Furthermore, using triethanolamine as a pH adjuster,
After adjusting to 9.5 and stirring for 2 hours, the pore size is about 1.2 μm
Membrane Filter (Millipore Japan Limited)
And filtered to prepare Ink Composition 3.

Ink Composition 4 As a yellow pigment, C.I. I. Pigment Yellow 128
100 g, dispersant β 150 g, potassium hydroxide 6
g and 250 g of water were mixed, and a dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. The resulting dispersion stock solution was filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and the filtrate was diluted with water to a pigment concentration of 10% by weight to obtain a yellow pigment dispersion liquid 4. Prepared. 30 g of the obtained yellow pigment dispersion liquid 4 and 15 g of glycerin 1,
3 g of 2-hexanediol and Olfine E10
1g of 10 was mixed and ultrapure water was added to bring the total amount to 10
It was set to 0 g. Furthermore, this mixed solution was adjusted to pH 9.5 by using triethanolamine as a pH adjuster, stirred for 2 hours, and then filtered with a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm. Ink Composition 4 was thus prepared.

Ink Composition 5 As a pigment, C.I. I. Pigment Red 122 100
g, 150 g of dispersant β, 6 g of potassium hydroxide, and 250 g of water were mixed, and a dispersion treatment was performed for 10 hours by a ball mill using zirconia beads. The resulting dispersion stock solution is filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and the filtrate is diluted with water until the pigment concentration becomes 10% by weight, to obtain a magenta pigment dispersion liquid 5. Prepared. 30 g of the obtained magenta pigment dispersion 5, 15 g of glycerin, 0.5 g of 1,2-heptanediol and 1 g of Olfine E1010 were mixed, and ultrapure water was added to make the total amount 100 g. Furthermore, the pH of this mixed solution was adjusted to 9.5 using triethanolamine as a pH adjuster, stirred for 2 hours, and then filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm to prepare an ink composition. Item 5 was prepared.

Ink Composition 6 In the same manner as in Ink Composition 4, Yellow Pigment Dispersion Liquid 6 was prepared. The obtained Yellow Pigment Dispersion Liquid 6 was added to 30
g, 15 g of glycerin, 3 g of 1,2-hexanediol, 0.5 g of Olfine E1010 and 0.8 g of Olfine STG, and ultrapure water was added to make the total amount 100 g. Furthermore, this mixed solution was adjusted to pH 9.5 by using triethanolamine as a pH adjuster, stirred for 2 hours, and then filtered with a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm. Ink Composition 6 was prepared.

Ink Composition 7 In the same manner as in Ink Composition 4, Yellow Pigment Dispersion Liquid 7 was prepared. 30% of the obtained yellow pigment dispersion liquid 7
g, 15 g of glycerin, 3 g of 1,2-hexanediol, 0.5 g of Olfine E1010, and 2 g of triethylene glycol monobutyl ether,
Furthermore, ultrapure water was added to make the total amount 100 g. Furthermore p
This mixed solution was adjusted to pH 9.5 by using triethanolamine as an H-adjusting agent, stirred for 2 hours, and then filtered with a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm. Ink Composition 7 was prepared.

Ink Composition 8 As a yellow pigment, C.I. I. Pigment Yellow 74 100 g, water-soluble resin dispersant John Cryl J-62
150 g (manufactured by Johnson Polymer Co., Ltd.), 6 g potassium hydroxide, and 250 g water were mixed and subjected to dispersion treatment for 10 hours by a ball mill using zirconia beads.
The obtained dispersion stock solution is filtered through a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and the filtrate is diluted with water to a pigment concentration of 10% to prepare a yellow pigment dispersion liquid 8. did. 30 g of the obtained yellow pigment dispersion liquid 8 and 15 g of glycerin 1,
10 g of 2-pentanediol and Olfine E1
1g of 010 was mixed, and then ultrapure water was added to bring the total amount to 1
It was set to 00 g. Further, the mixed solution was adjusted to pH 9.5 by using triethanolamine as a pH adjuster, stirred for 2 hours, and then filtered with a membrane filter (manufactured by Japan Millipore Limited) having a pore size of about 1.2 μm. Ink Composition 8 was prepared.

Ink Composition 9 (Comparative Example) A yellow pigment dispersion 9 was prepared in the same manner as in Ink Composition 4. The obtained yellow pigment dispersion liquid 9 is added to 30
g, glycerin 15 g, 1,2-hexanediol 3 g, Olfine E1010 1 g, 2-pyrrolidone 5 g, and ultrapure water were added to make the total amount 100 g. The mixture was adjusted to pH 9.5 by using triethanolamine as a pH adjuster, stirred for 2 hours, and then a membrane filter (Japan Millipore.
This mixed solution was filtered by (Limited) to prepare an ink composition 9.

Evaluation Test Evaluation Test 1: Ejection Stability Regarding the ink compositions 1 to 9 described above, a piezoelectric element type on-demand type ink jet printer MJ-930C was used.
(Manufactured by Seiko Epson Corporation) was used to continuously print patterns in which graphic texts were mixed.
At this time, the number of printed sheets before the first occurrence of the printing curve was counted. The obtained results were evaluated based on the following evaluation criteria. The printing paper used in the test was plain paper Xerox-P (manufactured by Fuji Xerox Co., Ltd.). Evaluation AA: Average continuous print number is 300 or more Evaluation A: Average continuous print number is 100 or more 300
Less than sheet evaluation B: Average continuous printing number is 50 or more and less than 100 sheets C: Average continuous printing number is less than 50 sheets

Evaluation test 2: Clogging recovery property The ink compositions 1 to 9 were applied to the printer MJ-930C.
After confirming that the ink was ejected from the nozzle, it was left in an environment of 25 ° C. for 1 year without a cap. After leaving, the cleaning operation required until ejection of all nozzles was possible was performed. The number of times was evaluated based on the following criteria. Evaluation A: cleaning less than 2 times evaluation B: cleaning 3 to 4 times evaluation C: cleaning 5 times or more

The results are shown in Table 1.

[0090]

[Table 1]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tsuyoshi Sano             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation (72) Inventor Bunji Ishimoto             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation (72) Inventor Kiyohiko Takemoto             Seiko, 3-3 Yamato 3-chome, Suwa City, Nagano Prefecture             -In Epson Corporation F-term (reference) 2C056 EA14 FC02                 2C057 AF72 AH07 BA03 BA14                 2H086 BA52 BA53 BA55 BA59 BA62                 4J039 AD01 AD06 BE01 BE22

Claims (6)

[Claims] 1. A pigment and a dispersant for dispersing the pigment;
An ink composition consisting essentially of a 2-alkanediol, a nonionic surfactant, a humectant, water as a main solvent, and a penetration enhancer as an optional component, wherein the dispersant comprises: A block copolymer having an acid value of 70 to 200 and having an AB, ABA, or ABC structure, wherein the A block is hydrophilic, the B block is hydrophobic, and (1) CH ₂ ═CH—R (wherein R is a C _{6 to} C ₂₀ substituted or unsubstituted alkyl group, aryl group, aralkyl group, or alkaryl group), (2) CH ₂ = CH-OR ¹ (provided that R ¹ is a C _{3 to} C ₂₀ substituted or unsubstituted alkyl group, aryl group, aralkyl group, or alkaryl group), (3) CH ₂ ═CH—O— C (O) -R ¹ (provided that, ^{R 1} is as defined above (2)), and _{(4) CH 2 = CH-} NR 2 R 3 ( provided that, ^{R 2} and ^{R 3, R 2} and R H and C _{3 to} C, provided that both ³ are not H at the same time.
₂₀ independently selected from the group consisting of a substituted or unsubstituted alkyl group, an aryl group, an aralkyl group, and an alkaryl group), based on B block weight. As at least 30% by weight, and further C
The ink composition, wherein the block is arbitrarily selectable. 2. The content of the 1,2-alkanediol is 0.5 to 10% by weight based on the total amount of the ink composition.
The ink composition according to claim 1. 3. The ink composition according to claim 1, which is substantially free of 2-pyrrolidone. 4. The ink composition according to claim 1, which is used in an inkjet recording method using an inkjet head that forms ink droplets by mechanically deforming an electrostrictive element. 5. An ink jet recording method for ejecting droplets of an ink composition, adhering the droplets to a recording medium to perform printing, wherein the ink composition is any one of claims 1 to 4. An inkjet recording method using the described ink composition. 6. A recorded matter recorded by the recording method according to claim 5.