JP2003313468A - Ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pigment ink for inkjet recording which is excellent in ink preservation stability, causes no nozzle clogging, and gives printed matter exhibiting good preservation stability and excellent print qualities. <P>SOLUTION: The ink for inkjet recording comprises a pigment, a polyester resin fine particle having a particle size of 30-300 nm and a water-soluble epoxy compound as essential ingredients, where the polyester resin has an elongation at break at 25°C of at least 10% and a glass transition temperature of lower than 40°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aqueous pigment-dispersed ink composition suitable for an inkjet recording system.

[0002]

2. Description of the Related Art As an ink jet recording ink,
Generally, a dye ink composed of a water-soluble dye and an aqueous medium is widely used. However, due to the fate of the water-soluble dyes, problems such as poor water resistance, insufficient light resistance, and high resolution due to bleeding have been pointed out. In order to solve this problem, inks using pigments such as carbon black and organic pigments instead of dyes as colorants have been proposed.

On the other hand, the ink jet recording ink does not change its physical properties during long-term storage, does not clog fine nozzles, has a high density of printed matter and is clear, and has good storage stability (water resistance). Properties, light resistance, etc.) are required. In particular, pigment-based inks are required to have storage stability (that is, to disperse the pigment stably for a long period of time) and to prevent nozzle clogging during printing or during restarting after printing is interrupted. At the same time, the fixing property to the recording paper is required.

As the pigment-based ink, an ink in which a pigment is finely dispersed in an aqueous medium with a so-called dispersant is used.
The dispersant is a low molecular weight, so-called surfactant-like dispersant,
Alternatively, polymer type dispersants are widely used.
In recent years, a pigment dispersion having high stability has been obtained by using a block copolymer having a hydrophilic part and a hydrophobic part as a polymer dispersant. Further, in the case of carbon black, a product in which the surface of the carbon black is treated by acid value treatment, graft treatment or the like to increase hydrophilicity and self-dispersed has been put on the market.

When such a pigment dispersion is used for an ink jet ink, fixing of pigment particles on a recording paper becomes a problem. It is considered that a water-soluble polymer component is usually used for fixing the water-based ink, but as is well known, the water-soluble polymer has a function of increasing the viscosity of the solution. Ink jet inks are required to have a very low viscosity as compared with ordinary inks, and therefore it is difficult to add a large amount of such a water-soluble fixing aid component. For this reason, a water-dispersible polymer component, which is not water-soluble, has been mainly studied as a fixing aid for the pigment.

The addition of a water-dispersible polymer component, that is, a fine particle component, to a pigment ink is widely performed without being limited to ink jet recording. For example, JP-A-55-157668 discloses that dispersion stability is maintained even at a relatively low viscosity by dispersing a pigment in a water-insoluble resin fine particle dispersion liquid. Further, Japanese Patent Laid-Open No. 1-217088 discloses that
The use of fine particles having a specific film-forming temperature is said to improve the storage stability and fluidity of the ink. However, these inks also had insufficient stability at low and high temperatures, and clogging still occurred. Similarly, an ink using resin fine particles is disclosed in Japanese Patent Laid-Open No. 3-1.
Although disclosed in JP-A-60068 and JP-A-4-18462, there is room for further improvement in ink stability even with these inks.

On the other hand, addition of a specific epoxy compound to the ink has been attempted in order to improve the durability after recording on a recording paper. For example, JP-A-9-27
2826 discloses an ink containing a colorant, an epoxy group-containing compound, an inorganic oxide colloid, an organic solvent, and water. Here, the epoxy compound is defined as a compound having two or more epoxy groups in the molecule. In the present invention, the epoxy group is reacted after recording to crosslink the resin and improve the fixability. Although it is certainly expected that the fixability of the recorded image will be improved, adding a multi-sensitive compound to the ink suggests that a crosslinking reaction will occur even in the ink, and the ink will gel during long-term storage. There is a concern about problems such as doing. JP-A-9-286940, JP-A-1
No. 1-10856 proposes an ink jet recording method using two liquids. The purpose is to improve the durability of the recorded image by adding epoxy to one side of the ink separated in the two liquids and adding a component that reacts with the epoxy to one side and reacting after the recording. Although the effect of the invention can be sufficiently expected, there are concerns that the device becomes large and complicated, and that the total amount of ejected ink increases and the drying is delayed.

[0008]

DISCLOSURE OF THE INVENTION In the present invention, in a pigment-based ink jet recording ink having improved fixing property,
It is an object to improve poor ink stability and poor ejection stability. The present inventors have found that the above problems can be achieved by blending fine particles of a polyester resin having specific physical properties and a specific epoxy compound in an ink, and have reached the present invention.

[0009]

Means for Solving the Problems That is, the present invention is an ink jet recording ink containing a pigment, fine particles of a polyester resin having a particle diameter of 30 to 300 nm, and a water-soluble epoxy compound as essential components. 2. The inkjet recording ink according to claim 1, wherein the breaking elongation at 25 ° C. is 10% or more, and the minimum film-forming temperature of the polyester resin fine particles is less than 40 ° C. The ink according to claim 1 or 2, wherein the polyester resin has a glass transition temperature of less than 40 ° C, wherein the water-soluble epoxy compound has one epoxy group in the molecule. The inkjet recording ink is characterized in that the water-soluble epoxy compound is An ink jet recording ink, characterized in that indicated in general formula.

[Chemical 2] R: at least one group selected from a phenyl group which may have a substituent, a linear alkyl group and a branched alkyl group, n = 0 to an integer of 20

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the pigment in the present invention, an inorganic pigment or an organic pigment can be used without particular limitation. 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 furnest method or a thermal method, more specifically, furnace black, lamp black, acetylene black or channel black. Carbon black (C.I. Pigment Black 7) and the like can be used. The organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (for example, basic dye type chelates, acid dye type chelates, etc.), nitro pigments, nitroso pigments, aniline black and the like can be used.

More specifically, pigments that can be used mainly for yellow include C.I. l. Pigment Yellow 1 (Hansa Yellow G), 2, 3 (Hansa Yellow 10G), 4,5 (Hansa Yellow 5G), 6, 7,
10, 11, 12 (Disazo Yellow AAA), 13, 1
4, 16, 17, 24 (flavantron yellow), 55
(Disazo Yellow AAPT), 61, 61: 1, 65,
73,74 (Fast Yellow 5GX), 75,81,8
3 (Disazo Yellow HR), 93 (Condensed Azo Yellow 3
G), 94 (condensed azo yellow 6G), 95 (condensed azo yellow GR), 97 (fast yellow FGL), 98, 9
9 (anthraquinone), 100, 108 (anthrapyrimidine yellow), 109 (isoindolinone yellow 2G
LT), 110 (Isoindolinone Yellow 3RLT),
113, 117, 120 (Benzimidazolone Yellow H2G), 123 (Anthraquinone Yellow), 124,
128 (Condensed Azo Yellow 8G), 129, 133, 13
8 (quinophthalone yellow), 139 (isoindolinone yellow), 147, 151 (benzimidazolone yellow H4G), 153 (nickel nitroso yellow), 15
4 (Benz Imidazolone Yellow H3G), 155, 15
6 (Benz Imidazolone Yellow HLR), 167, 16
8,172,173 (Isoindolinone Yellow 6G
L), 180 (benzimidazolone yellow) and the like.

Further, examples of magenta pigments include C.I.
l. Pigment Red 1 (Para Red), 2, 3 (Toluidine Red), 4,5 (lTR Red), 6, 7, 8,
9,10,11,12,14,15,16,17,1
8, 19, 21, 22, 23, 30, 31, 32, 3
7,38 (Pyrazolone Red B), 40,41,42,8
8 (Thioindigo Bordeaux), 112 (Naphthol Red FGR), 114 (Brilliant Carmine BS), 122
(Dimethylquinacridone), 123 (Perylene Vermilion), 144, 146, 149 (Perylene Scarred), 150, 166, 168 (Antoanthrone Orange), 170 (Naphthol Red F3RK), 171 (Benzimidazolone Maroon HFM), 175 (Benzimidazolone Red HFT), 176 (Benzimidazolone Carmine HF3C), 177, 178 (Perylene Red), 1
79 (perylene maroon), 185 (benzimidazolone carmine HF4C), 187, 188, 189 (perylene red), 190 (perylene red), 194 (perinone red), 202 (quinacridone magenta), 209 (dichloroquinacridone red), 214 (Condensed azo red), 2
16, 219, 220 (condensed azo), 224 (perylene red), 242 (condensed azo scarlet), 245 (naphthol red), or C.I. I. Pigment Violet 19 (quinacridone), 23 (Dioxazine Violet), 31, 32, 33, 36, 38, 43, 50 and the like.

Further, as a pigment for cyan, C.I.
l. Pigment Blue 15, 15: 1, 15: 2, 1
5: 3,15: 4,15: 6 (all above phthalocyanine blue), 16 (metal-free phthalocyanine blue), 1
7: 1,18 (Alkaline blue toner), 19,21,2
2,25,56,60 (Thren blue), 64 (Dichloroindanthrone blue), 65 (Violanthrone), 66
(Indigo) and the like.

As an organic pigment for black, a black organic pigment such as aniline black (Cl Pigment Black 1) can be used. Furthermore, as an organic pigment other than yellow, cyan, or magenta, C.I. I. Pigment Orange 1, 2, 5, 7, 1
3,14,15,16 (Vulcan orange), 24,31
(Condensed azo orange 4R), 34, 36 (benzimidazolone orange HL), 38, 40 (pyrantron orange), 42 (isoindolinone orange RLT), 43,
51, 60 (benzimidazolone-based insoluble monoazo pigment), 62 (benzimidazolone-based insoluble monoazo pigment), 63; C.I. I. Pigment Green 7 (Phthalocyanine Green), 10 (Green Gold), 36 (Salt Brominated Phthalocyanine Green), 37, 47 (Violanthrone Green); C.I. I. Pigment Brown 1, 2,
3, 5, 23 (condensed azo brown 5R), 25 (benzimidazolone brown HFR), 26 (perylene bordeaux), 32 (benzimidazolone brown HFL) and the like can be mentioned.

The amount of such pigment added to the ink is
0.3-30% by weight, preferably 1-25% by weight, more preferably 2-20% by weight, even more preferably 3
~ 15% by weight. If the blending ratio of the pigment is less than this range, the recording density may be insufficient. Further, if the amount of the pigment compounded exceeds this range, the nozzle head portion is likely to be clogged.

The particle size of the pigment is preferably 3 μm or less, more preferably 1 μm or less, still more preferably 0.3.
μm or less, more preferably 0.1 μm or less, still more preferably 0.8 μm or less. If the pigment particle size is larger than a predetermined particle size, storage stability may be problematic.

According to a preferred embodiment of the present invention, this pigment is preferably added to the ink composition as a pigment dispersion obtained by dispersing the pigment in a solvent with a dispersant. As a preferable dispersant, a known dispersant used for preparing a conventionally known pigment dispersion liquid, for example, a polymer dispersant or a surfactant can be used.

Preferred examples of the polymer dispersant include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein and albumin; natural gums such as gum arabic and tragacanth; savonin and the like. Glucosides; alginic acid and alginic acid derivatives such as propylene glycol alginate, triethanolamine alginate and ammonium alginate; methyl cellulose, carboxymethyl cellulose,
Examples thereof include cellulose derivatives such as hydroxyethyl cellulose and ethyl hydroxyethyl cellulose.

Further, synthetic polymers can be mentioned as preferred examples of the polymer dispersant. Polyvinyl alcohols; polyvinyl pyrrolidones; polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer, vinyl acetate. -Acrylic ester copolymers, acrylic resins such as acrylic acid-acrylic acid alkyl ester copolymers; styrene-acrylic acid copolymers, styrene-methacrylic acid copolymers, styrene-methacrylic acid-acrylic acid alkyl ester copolymers Styrene-acrylic acid resins such as polymers, styrene-α-methylstyrene-acrylic acid copolymers, styrene-α-methylstyrene-acrylic acid-acrylic acid alkyl ester copolymers; styrene-maleic acid; styrene-maleic anhydride Acid; vinyl naphthale Vinyl-naphthalene-maleic acid copolymer; vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate maleate ester copolymer, vinyl acetate crotonic acid copolymer Examples thereof include coalesce, vinyl acetate-based copolymers such as vinyl acetate acrylic acid copolymer, and salts thereof. Among these, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer composed of a monomer having both a hydrophobic group and a hydrophilic group are particularly preferable. Examples of the above salts include salts with diethylamine, ammonia, ethylamine, triethylamine, propylamine, isopropylamine, dipropylamine, butylamine, isobutylamine, triethanolamine, diethanolamine, aminomethylpropanol, morpholine and the like. The weight average molecular weight of these copolymers is preferably 3,000 to 30,000, more preferably 5,000 to 15,000.

Examples of surfactants preferable as the dispersant are fatty acid salts, higher alkyl dicarboxylic acid salts, higher alcohol sulfuric acid ester salts, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinic acid esters. Anionic surfactants such as salts, naphthenates, liquid fatty oil sulfuric acid ester salts and alkylallyl sulfonates; cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene Examples include nonionic surfactants such as alkyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, and polyoxyethylene sorbitan alkyl esters.

The amount of these dispersants added is preferably 0.06 to 50% by weight, more preferably 0.125 to 10% by weight, and further preferably 0.2 to 3 with respect to the pigment 1. It is in the range of% by weight.

As the polyester resin in the present invention, both saturated polyester resin and unsaturated polyester resin can be used. The polyester resin is obtained by condensation of polyvalent carboxylic acid and polyhydric alcohol. Examples of the polyvalent carboxylic acids used for the polyester resin include: terephthalic acid, isophthalic acid, orthophthalic acid,
Aromatic dicarboxylic acids such as 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 9,10-anthracene dicarboxylic acid, 9,10-anthracene dipropionic acid and diphenic acid, p-oxybenzoic acid Aromatic oxycarboxylic acids such as p- (hydroxyethoxy) benzoic acid, succinic acid, adipic acid, azelaic acid, sebacic acid,
Aliphatic dicarboxylic acids such as dodecanedicarboxylic acid, alicyclic polycarboxylic acids such as cyclohexanedicarboxylic acid, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, cyclohexenedicarboxylic acid, dimer acid, trimer acid, Aliphatic unsaturated polycarboxylic acid such as tetramer acid, etc.-Aromatic unsaturated polycarboxylic acid such as phenylene diacrylic acid-Alicyclic dicarboxylic acid such as hexahydrophthalic acid, tetrahydrophthalic acid, -Trimerit Examples thereof include trivalent or higher polycarboxylic acids such as acids, trimesic acid and pyromellitic acid. In the present invention, polycarboxylic acids may be partially used in combination with monocarboxylic acids. Aromatic monocarboxylic acids are preferred as the monocarboxylic acids.
Examples of the aromatic monocarboxylic acid include benzoic acid, chlorobenzoic acid, bromobenzoic acid, parahydroxybenzoic acid, naphthalenecarboxylic acid, 4-methylbenzoic acid, 3-methylbenzoic acid, salicylic acid, thiosalicylic acid, phenylacetic acid, and these. Lower alkyl ester of, cyclohexylaminocarbonylbenzoic acid, n-dodecylaminocarbonylbenzoic acid, t-butylbutylbenzoic acid, naphthalenecarboxylic acid, anthracenecarboxylic acid, t-butylbutylnaphthalenecarboxylic acid, etc. can be used,
Further, it is particularly preferable to use tertiary benzoic acid. The amount of the aromatic monocarboxylic acid used is preferably 2 to 25 mol%, more preferably 5 to 20 mol%, and further preferably 8 to 16 mol% based on the acid component.

Examples of the polyvalent alcohols used for the polyester resin include aliphatic polyvalent alcohols, alicyclic polyvalent alcohols, aromatic polyvalent alcohols and the like.
As the aliphatic polyhydric alcohols, ethylene glycol
, Propylene glycol, 1,3-propanedioe
2,3-butanediol, 1,4-butanediol
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol
, Dipropylene glycol, 2,2,4-trimethyl-1,3-pentanediol, polyethylene glycol
Examples include aliphatic diols such as propylene, polypropylene glycol and polytetramethylene glycol, triols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol and tetraols. it can. .As the alicyclic polyvalent alcohols, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol,
Spiroglycol, hydrogenated bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A and propylene oxide adduct, tricyclodecanediol,
Examples thereof include tricyclodecane dimethanol. .As the aromatic polyhydric alcohols, ethylene oxide addition of para-xylene glycol, meta-xylene glycol, ortho-xylene glycol, 1,4-phenylene glycol, and 1,4-phenylene glycol Examples thereof include bisphenol A, bisphenol A, ethylene oxide adduct of bisphenol A, and propylene oxide adduct. Further, as the polyester polyol, lactone type polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone can be exemplified. Further, like the carboxylic acids, monoalcohols such as aliphatic alcohols, aromatic alcohols and alicyclic alcohols can be used.

The number average molecular weight of the polyester resin of the present invention is preferably in the range of 1,000 to 20,000. Also, 20
The range of 00 or more and 5000 or less is preferable, and the range of 3000 or more and 4000 or less is more preferable. Glass transition point,
In addition, when the molecular weight is lower than this, there is a problem in printing durability.

In the present invention, it is essential that the elongation at break when such a resin is formed into a film is 10% or more. Here, the breaking elongation is based on JIS-C2318 in a resin film obtained by coating a resin on a polytetrafluoroethylene plate so as to have a laminated thickness of 10 μm, completely forming a film, and then peeling the resin film. It is the breaking elongation obtained by the measuring method. It is essential that the elongation at break is 10% or more, preferably 15% or more and 25%
The above is more preferable.

The minimum film forming temperature of the resin in the present invention is 4
The temperature is preferably lower than 0 ° C, preferably 35 ° C or lower, more preferably 30 ° C or lower, and further preferably 25 ° C or lower.

The glass transition temperature of the resin in the present invention is preferably lower than 40 ° C., preferably 5 ° C. or lower, more preferably 30 ° C. or lower, and further preferably 25 ° C. or lower. .

In the present invention, the polyester resin preferably has an ionic group. The ionic group content is preferably in the range of 20 to 2000 meq./kg. As the ionic group, a sulfonic acid group, a carboxyl group, a sulfuric acid group, a phosphoric acid group, a phosphonic acid group, an anionic group such as a phosphinic acid group or an ammonium salt or a metal salt thereof, or a primary to tertiary amine It is a cationic group such as a group, and preferably a sulfonic acid alkali metal salt group or a carboxylate ammonium base can be used. It is preferable that these ionic groups are contained in a form copolymerized with polyester or introduced into the polymer terminal. Examples of the polyvalent carboxylic acid containing a metal sulfonate copolymerizable with polyester include sulfoterephthalic acid,
Examples thereof include 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7dicarboxylic acid, 5 [4-sulfophenoxy] isophthalic acid, and salts thereof. Further, by using a metal salt of sulfobenzoic acid together, a metal sulfonate base can be introduced at the polymer terminal. As salts, ammonium-based ions, Li, Na, K, Mg, Ca, Cu, Fe, N
i. Salts such as Co and Al are mentioned, and particularly preferable are K salt or Na salt. The carboxyl group can be added to the polymer terminal by introducing a polyvalent carboxylic acid such as trimellitic acid into the system at the final stage of polymerization of polyester. Further, by neutralizing this with ammonia, sodium hydroxide or the like, the carboxylate group can be exchanged. The content of these ionic groups is essentially in the range of 20 to 2000 meq./kg, preferably 20 to 500 meq./kg, and more preferably 50 to 200 meq./kg with respect to the polyester resin.

The average particle size of the polyester resin particles in the present invention is essential to be in the range of 30 to 300 nm, preferably about 50 to 200 nm, and more preferably 50 to 150 nm. .

Since the ionic group-containing polyester resin of the present invention has a self-emulsifying property, the fine particles in the aqueous dispersion obtained by self-emulsification can be used. The aqueous fine dispersion of the ionic group-containing polyester resin of the present invention can be produced by any known method. That is, the ionic group-containing polyester resin and the water-soluble organic compound are premixed at 50 to 200 ° C. and water is added thereto, or the mixture of the ionic group-containing polyester resin and the water-soluble organic compound is added to water. In addition, 40 ~
It is produced by stirring at 120 ° C. Alternatively, it is also produced by a method in which an ionic group-containing polyester resin is added to a mixed solution of water and a water-soluble organic compound and dispersed by stirring at 40 to 100 ° C. Water-soluble organic compounds include ethanol, butanol, isopropanol
, Ethyl cellosolve, butyl cellosolve, dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, etc. can be used. It is not preferable to use a surfactant together, but the use is not particularly limited. In the present invention, in addition to the self-emulsification method, it is also possible to use fine particles contained in an emulsion obtained by forced emulsification with an emulsifier, a solvent and the like.

In the present invention, it is essential to add a water-soluble epoxy compound. The water-soluble epoxy compound in the present invention has at least one epoxy group (glycidyl group) in the molecule, and has a hydroxyl group, an ionic group, a hydrophilic group such as polyalkylene glycol chain, the water solubility Is 40% or more, preferably 70% or more, and more preferably 98% or more. The water solubility here means that the epoxy compound is added to 900 parts by weight of water at 25 ° C.
It is the dissolution rate when part by weight is dissolved. More specifically, sorbitol (mono-poly) glycidyl ether,
Polyglycerol (mono-poly) glycidyl ether,
Diglycerol (mono-poly) glycidyl ether, trimethylolpropane (mono-poly) glycidyl ether, ethylene glycol monoglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol monoglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol monoglycidyl ether, polyethylene Glycol diglycidyl ether, propylene glycol monoglycidyl ether, propylene glycol diglycidyl ether, dipropylene glycol monoglycidyl ether, dipropylene glycol diglycidyl ether, polypropylene glycol monoglycidyl ether, polypropylene glycol diglycidyl ether, phenyl (mono-poly) ethylene Green Over mono glycidyl ethers, alkyl alcohols (mono- to poly) ethylene glycol monoglycidyl ether can be exemplified

In the present invention, among the water-soluble epoxy compounds, it is particularly preferable to use a monoglycidyl ether compound having one epoxy group in the molecule.

Further, in the present invention, it is preferable to use a monoglycidyl compound represented by the general formula [Chemical Formula 1].

[Chemical 3] R: at least one group selected from a phenyl group which may have a substituent, a linear alkyl group, and a branched alkyl group, n = 0 to 20, an integer of 0 to 20. Or is preferably a lauryl group.

In the ink of the present invention, the ratio of the pigment particles to the polyester resin fine particles is pigment / polyester = 100/150 to 100/1.
0 is preferable, and pigment / polyester = 100/110 to 100/2
The range of 0 is more preferable, and pigment / polyester = 100/80 to 100/3
A range of 0 is still preferred. If the ratio of the resin fine particles is less than the above range, the effect of the addition is not obtained, and if it exceeds the above range, the printing density may be lowered and the viscosity of the ink may be too high, which is not preferable.

In the ink of the present invention, the ratio of the polyester resin fine particles to the epoxy compound is polyester / epoxy = 100/1 to 100/5.
0 is preferable, and polyester / epoxy = 100/3 to 100/3
The range of 0 is more preferable, and polyester / epoxy = 100 / 5-100 / 2
A range of 0 is still preferred. If the proportion of the epoxy compound is less than the above range, the effect of the addition cannot be obtained, and if it exceeds the above range, the printing density may be lowered and the viscosity of the ink may be too high, which is not preferable.

Further, according to a preferred embodiment of the present invention, the ink according to the present invention preferably further contains a wetting agent. Preferred examples of the wetting agent include diethylene glycol, polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,
6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylolpropane, urea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. In particular, those having an ethylene oxide group are preferable, and diethylene glycol is most preferable. Further, in addition to these wetting agents, it is preferable to further add a low boiling point organic solvent. Preferred examples of the low boiling point organic solvent include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol, iso-butanol, n-pentanol, ethylene glycol monomethyl ether, ethylene glycol. Examples thereof include monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether and triethylene glycol monoethyl ether. A monohydric alcohol is particularly preferable.

The amount of these wetting agents added is 0.5 in the ink.
A range of -40% by weight, preferably 2-20% by weight is suitable. Further, the addition amount of the low boiling point organic solvent is appropriately in the range of 0.5 to 10% by weight of the ink, preferably 1.5 to 6% by weight.

Further, in order to improve various physical properties of the ink, an appropriate additive may be added to the ink according to the present invention. Specific examples of the additive include a viscosity adjusting agent, a surface tension adjusting agent, a pH adjusting agent, an antifungal agent and an antiseptic agent. It is preferable to use amino acid or triethanolamine for pH adjustment.

The ink according to the present invention can be produced by dispersing and mixing the above components by an appropriate method. Preferably, the mixture obtained by removing the organic solvent and volatile components is treated with a suitable disperser (for example, ball mill, sand mill, attritor, roll mill, agitator mill,
(Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ong mill, etc.) to obtain a homogeneous composition, and then the organic solvent and the volatile component are preferably added. Thereafter, filtration (preferably vacuum or pressure filtration using a metal filter, a membrane filter or the like) or centrifugation is performed in order to remove coarse particles and foreign matter that cause clogging.

[0040]

In the ink according to the present invention, the ink composition forms a very thin and brittle film at the tip of the nozzle. This coating prevents further evaporation of components such as water from the ink composition and prevents clogging of the nozzle due to precipitation of solid components. On the other hand, since this coating is thin and brittle, it can be easily torn by a cleaning operation (return operation) that is usually performed, and the next printing can be immediately performed. Further, according to the ink of the present invention, it is possible to obtain a print having a high print density and good water rub resistance. Without being bound by theory, because the pigment particles and the resin particles form a film in a well-balanced manner so as to fill the gaps between them,
It is considered that a dense film is formed. Such a dense film is fragile and fragile on the surface that is smooth like the head surface and does not absorb water, and on the contrary has a large specific surface area like on recording paper and forms a firm film on the surface with high hygroscopicity. To do. An interesting point is that the ink according to the present invention has excellent storage stability. By blending resin fine particles in such a pigment-type ink, the resin fine particles are adsorbed on the pigment particles, and as a result, the repulsion between the particles is strengthened, and there is a tendency to argue that the characteristics are improved. Do not dictate the idea. Rather, the present inventors consider that the resin fine particles enter the space between the pigment particles and assist the repulsion between the particles, leading to storage stability. This is because when the resin fine particles are adsorbed on the pigment particles, the particle size of the dispersoid increases as a result, and the particles settle according to Stokes' theorem. As in the present invention, the addition of resin particles having a high elongation, preferably a low Tg, which is relatively soft, has an effect, so that the resin particles and the pigment particles are not fused in the ink. Is self-evident.

Further, in the present invention, since polyester fine particles are used as the resin fine particles, a high degree of durability and a clear image can be obtained. It is well known that a polyester resin is preferably used as a binder resin of a toner used in a color type in a dry electrophotographic printer, which indicates that the polyester resin is excellent in recording a color image. Is. However, since the polyester resin has an ester bond, it cannot prevent hydrolysis when used in an aqueous medium. The decrease in molecular weight due to hydrolysis is likely to reduce durability, but such concern can be avoided by giving a sufficiently high molecular weight at the beginning. On the other hand, the hydrolysis is caused by the carboxyl group generated by the cleavage of the ester bond, so that the p
Another problem is that H is lowered. In the present invention, the carboxyl group thus generated is reacted with the epoxy group in the ink to prevent the pH from decreasing.

[0042]

The present invention will be explained in more detail by the following examples, but the present invention is not limited to these. In the examples, MFT represents the minimum film forming temperature.

[Polymerization of Polyester Resin] In an autoclave equipped with a thermometer and a stirrer, 60 parts by weight of dimethyl terephthalate, 120 parts by weight of dimethyl ester of isophthalic acid, and 5 parts of dimethyl ester of 5-sodiumsulfoisophthalic acid 9 By weight, ethylene glycol 93 parts by weight, neopentyl glycol 69 parts by weight, and tetrabutoxy titanate 0.1 parts by weight were charged, and the transesterification reaction was carried out by heating at 120 to 220 ° C. for 120 minutes. After that, the temperature of the reaction system is set to 220 to
Raise the temperature to 240 ° C and set the system pressure to 1 to 10 mmHg, 60
As a result of continuing the reaction for a minute, the copolyester resin (A
1) was obtained. Obtained copolymer polyester resin (A1)
Was analyzed by the NMR method and the copolymerization ratio was determined. As a result, terephthalic acid 32 mol%, isophthalic acid 65 mol%, 5-sodium sulfoisophthalic acid 3 mol%, acid component ethylene glycol 35 mol%, neopentyl glycol 65 mol% , Was an alcohol component. Glass transition temperature determined by DSC method is 61
° C, acid value 0.08 [mg / KOHg], number average molecular weight 12,000 determined by GPC, sodium sulfonate group equivalent (ionic group) determined by fluorescent X-ray analysis of S element is 1
It was 35 meq / kg. Also, the thickness of the resin is 50μ, which is made by melt shaping the resin into a polytetrafluoroethylene plate.
A strip-shaped sample having a width of 15 mm and a length of 100 mm was prepared using the m-thick film, and JIS-
The breaking elongation obtained by the method according to C-2318 is 15%.
Met.

Here, the NMR method: using a Bruker NMR apparatus, samples 10 to 10 were used.
15 mg was dissolved in 0.7 ml of deuterated chloroform containing 0 to 15 vol% of trifluoroacetic acid, and a proton was added at 23 to 25 ° C.
(1H) NMR (resonance frequency 500 MHz) was measured. The detection pulse is 45 pulses, and the repetition time is 5 seconds. DSC method Using Shimadzu's differential scanning calorimeter, heating rate 10 ° C /
Measurement in minutes Note that 5 mg of the sample was placed in an aluminum pressing lid type container and crimped. Acid value (carboxyl group content) 0.2 g of the sample was dissolved in 20 ml of chloroform,
Titration was performed with a 1N KOH ethanol solution, and the meq. [Meq. / Kg] to [mg / KOHg] was determined. Ionic groups: Determination of sodium sulfonate groups Melted copolyester in aluminum foil mold
(A1) was poured to prepare a disk having a diameter of 4 cm and a thickness of 5 mm. The obtained disk was subjected to fluorescent X-ray analysis to quantify the S element.

The following polyester resins were prepared by changing the raw materials in the same manner. Polyester resin (A2) composition Isophthalic acid 95 mol%, 5-sodium sulfoisophthalic acid 5 mol%, acid component diethylene glycol 100 mol% alcohol component glass transition temperature 20 ° C. acid value 0.15 mg / KOHg number average molecular weight 12000 sodium sulfonate group equivalent 210 m equivalent / kg, breaking elongation 800%

Polyester resin (A3) synthesis In an autoclave equipped with a thermometer and a stirrer, 80 parts by weight of dimethyl terephthalate, 56 parts by weight of dimethyl isophthalate, 48 parts by weight of sebacic acid. Ethylene glycol (159 parts by weight), tricyclodecane dimethanol (30 parts by weight) and tetrabutoxy titanate (0.1 parts by weight) were charged and heated at 180 to 230 ° C. for 120 minutes to carry out a transesterification reaction. Then, the reaction system is heated to 240 ° C., and the system pressure is gradually reduced to 1 to 10 mmHg,
The reaction was continued for 60 minutes, 8 parts by weight of trimellitic anhydride was added, and the reaction was carried out for 30 minutes to obtain a copolyester resin (A3) having a carboxyl group at the molecular end. Polyester resin (A3) composition Terephthalic acid 51 mol% Isophthalic acid 24 mol% Isophthalic acid 21 mol% Trimellitic acid 4 mol% Ethylene glycol 84 mol% Tricyclodecane dimethanol 16 mol% Glass transition temperature 28 ° C Acid value 5.9 mg / KOHg (330meq./kg) Number average molecular weight 11000 Break elongation 40%

[Production of Polyester Resin Fine Particle Aqueous Micro Dispersion] A four-necked flask equipped with a thermometer, a stirrer, and a reflux tube was charged with 300 parts by weight of polyester resin (A1), 150 parts by weight of methyl ethyl ketone, and 100 parts by weight of tetrahydrofuran. , Dissolve at reflux with boiling point (about 80 ° C), cool the system to 70 ° C, and add 680 ° C water 680
After adding 1 part to disperse in water, the mixture is placed in a distillation flask, distilled until the distillate temperature reaches 100 ° C., and after cooling, water is added to adjust the concentration. Polyester water-based finely dispersed particles (B1) were obtained. The dispersed particle size of the polyester water-based finely dispersed particles (B1) measured with a particle size distribution analyzer LB-500 manufactured by HORIBA, Ltd. is 78 nm.
Met. The aluminum foil coated with the obtained water dispersion was placed on a hot plate heated to a predetermined temperature, the state of film formation was observed, and the minimum film formation temperature MFT was determined. The MFT of the polyester water-based finely dispersed particles (B1) was 58 ° C.

Thereafter, the same operation is carried out, and from the polyester resin (A2) to the polyester aqueous dispersion (B2) shown below.
Got Polyester resin fine particle water dispersion (B2) Solid content 30% by weight Particle size 65 nm MFT 15 ° C

Preparation of Polyester Resin Aqueous Dispersion (B3) A four-necked flask equipped with a thermometer, a stirrer and a reflux tube was charged with 340 parts by weight of the polyester resin (A3), 150 parts by weight of methyl ethyl ketone and 140 parts by weight of tetrahydrofuran, While refluxing at about 80 ° C., the mixture was stirred and mixed for 120 minutes to be dissolved. Then, 16 parts by weight of triethanolamine was added and stirring was continued for 3 minutes, then at 80 ° C.
680 parts of deionized water were slowly added. The resulting aqueous dispersion was transferred to a distillation flask and distilled until the distillation temperature reached 103 ° C. to remove methyl ethyl ketone and tetrahydrofuran, and after cooling, water was added to adjust the solid content concentration to 30% polyester. Water dispersion (B3)
Got Polyester resin fine particle water dispersion (B3) Solid content 30% by weight Particle size 110 nm MFT 33 ° C

[Production of Pigment Water Dispersion] 5 parts by weight of carbon black MA7 (manufactured by Mitsubishi Kasei Co., Ltd.) 5 parts by weight of styrene-maleic anhydride copolymer (dispersant) deionized in a sand mill (Yasukawa Seisakusho). 76 parts by weight of water was charged, and glass beads (diameter 1.7 mm, 1.
It was dispersed together with 5 times amount (weight) for 2 hours. Then, the glass beads were removed to obtain an aqueous dispersion of carbon black (K1). Similarly, from 5 parts by weight of carbon black MA100 (manufactured by Mitsubishi Kasei Co., Ltd.), an aqueous dispersion of carbon black (K2), 5 parts by weight of KETYELLOW403 pigment (manufactured by Dainippon Ink and Chemicals Co., Ltd.), and a yellow pigment water dispersion were prepared. Body (Y1) from pigment KET Red 309 5% by weight (manufactured by Dainippon Ink and Chemicals, Inc.), magenta pigment water dispersion (M1) from pigment KETBLUEEX-1 5% by weight (Dainippon Ink and Chemicals, Inc.) Cyan pigment dispersion (C1) was obtained from

Examples 1 to 20, the polyester resin fine particle water dispersion (B1) and the carbon black water dispersion (K1) obtained in the above Production Example were placed in a four-necked flask equipped with a thermometer, a stirrer and a reflux tube. Was blended in the following compositional ratio using carbon black aqueous dispersion (K1) 81 parts by weight resin fine particle aqueous dispersion (B1) 10 parts by weight glycerin 4 parts by weight Denacol EX-145 2 parts by weight arginine 0.5 parts by weight Sodium hydrogen carbonate 0.5 part by weight triethanolamine 1 part by weight At room temperature, after stirring and holding for 1 hour, the mixture was cooled to room temperature,
The ink was filtered through a 0.8 μm membrane filter to obtain an inkjet recording ink (IJP1). In the same manner, the carbon black aqueous dispersion, the pigment aqueous dispersion, the polyester resin fine particle aqueous dispersion, and the water-soluble epoxy compound were changed in the same manner, and the same operation was performed to obtain the inkjet recording inks shown in Table 1. Here, Denacol EX-145 is a water-soluble epoxy compound, phenyl (EO) 5 glycidyl ether manufactured by Nagase Chemtex Co., Ltd. EX-1
The water solubility of 45 is 100%. Denacol EX-17
Reference numeral 1 is a water-soluble epoxy compound manufactured by Nagase Chemtech Co., Ltd., lauryl alcohol (EO) 15 glycidyl ether (water-soluble rate 100%). Denacol EX-614 is sorbitol polyglycidyl ether (water solubility 78%), a water-soluble epoxy compound manufactured by Nagase Chemtech.

Comparative Examples 1 to 5 Similarly, using a carbon black water dispersion, a pigment water dispersion, and a polyester resin fine particle water dispersion, the carbon black water dispersion (K1) 81 parts by weight resin was prepared in the following composition ratio. Particulate water dispersion (B2) 10 parts by weight Glycerin 6 parts by weight Arginine 0.5 parts by weight Sodium bicarbonate 0.5 parts by weight Triethanolamine 1 part by weight Comparative Example An inkjet recording ink was obtained.

Comparative Examples 6 to 10 Similarly, using a carbon black aqueous dispersion and a pigment aqueous dispersion, the carbon black aqueous dispersion (K1) 81 parts by weight deionized water 10 parts by weight arginine 0 were prepared in the following composition ratios. 0.5 parts by weight sodium hydrogencarbonate 0.5 parts by weight triethanolamine 1 part by weight Comparative Example An inkjet recording ink was obtained.

The characteristics of the ink jet recording inks obtained in Examples and Comparative Examples were evaluated by the following methods.
The results are shown in the table. (A) The clogging ink was filled in an inkjet printer MJ700V2C (manufactured by Seiko Epson Corporation), and after continuous printing for 10 minutes, printing was stopped. The printer was left for 2 weeks in an environment of 40 ° C. and 25% RH for the inks of Examples 1 to 8 and Comparative Examples 1 and 2 without capping the head, and for the inks of Examples 9 to 21 and Comparative Example 3. The ink was left for one day at room temperature. After standing, the nozzle was cleaned, and then printing was performed. The clogging characteristic of the ink was evaluated by the number of cleaning operations until the printing equivalent to the initial printing was possible without causing defective printing such as scraping and omission. The results are shown in the table. In the table, 0 to 2 times of cleaning operation can obtain the same print as the initial print- ○ 3 to 5 cleaning operations can obtain the same print as the initial print- △ Initial of 6 or more cleaning operations Cannot be printed equivalent to-

(B) Storage stability 1 50 cc of ink was placed in a laboratory bottle screw bottle and
It was left for 1 month at 0 ° C. and examined for the presence of sediment. The results are shown in the table. No sediment- ○ Sediment-No

(C) Storage stability 2 Put 50 cc of ink into a labran screw tube bottle and
The sample was allowed to stand for 1 month at ℃, and the change in pH was examined. The results are shown in the table. pH change within 0.3 ○ pH change 0.3 to 1.0 △ pH change 1.0 or more ×

(D) A solid image was printed on A4 size XeroxR paper (manufactured by Xerox Co., Ltd.) with a water-resistant inkjet printer MJ700V2C, and naturally dried for 24 hours. Next, the printed matter was cut into a square having a side of 6 cm, and the recording density was measured with an optical densitometer DM-800 (manufactured by Dainippon Screen Mfg. Co., Ltd.). Then, the printed matter was gently stirred at room temperature with a magnetic stirrer for 3000.
After immersing in cc deionized water for 1 minute, pulling it up, and naturally drying it, the optical density was measured again, and the density retention rate was calculated by the following formula. Density retention rate = (density after treatment / density before treatment) × 100 [%] The optical density was measured on a standard white plate.

(E) Eraser-resistant ink jet printer MJ700V2C was used to print a solid image on A4 size XeroxR paper (manufactured by Xerox Co., Ltd.) and naturally dried for 24 hours. Then, cut the printed matter into a square with a side of 6 cm, and use an optical densitometer D
The recording density was measured with M-800 (manufactured by Dainippon Screen Mfg. Co., Ltd.). Then, rub the printed matter 10 times with a plastic eraser, Poppy-51N (made by KOKUYO),
After that, the optical density was measured again, and the density retention rate was calculated by the following formula. Density retention rate = (density after treatment / density before treatment) × 100 [%]

(F) Print quality (bleeding) With an inkjet printer MJ700V2C, Xero
It was printed on xR paper (manufactured by Xerox Co., Ltd.) and examined for the occurrence of print bleeding. The results are shown in the table. In the table, clear printing with no bleeding- ○ Whisker-like bleeding- △ Bleeding to the extent that the outline of the character is not clear-x

(G) Show-through The solid image was printed on A4 size Xerox R paper (manufactured by Xerox Co., Ltd.) with an inkjet printer MJ700V2C, and the density on the back side of the paper was measured. The optical density value of the unrecorded paper was 0.05.

[0061]

[Table 1]

[0062]

As described above, the ink jet recording ink of the present invention has no nozzle clogging, excellent print quality, no show-through, and excellent storage stability. It is a very useful product because it has excellent water resistance and eraser resistance.

Claims (6)

[Claims] 1. A pigment and a particle size of 30 to 300 nm
Ink for inkjet recording, characterized in that the polyester resin particles and the water-soluble epoxy compound are essential components. 2. The inkjet recording ink according to claim 1, wherein the polyester resin has a breaking elongation at 25 ° C. of 10% or more. 3. The ink for inkjet recording according to claim 1, wherein the minimum film forming temperature of the fine particles of the polyester resin is lower than 40 ° C. 4. The ink jet recording ink according to claim 1, wherein the glass transition temperature of the polyester resin is lower than 40 ° C. 5. The inkjet recording ink according to claim 1, wherein the water-soluble epoxy compound has one epoxy group in the molecule. 6. The inkjet recording ink according to claim 1, wherein the water-soluble epoxy compound is represented by the following general formula. [Chemical 1] R: at least one group selected from a phenyl group which may have a substituent, a linear alkyl group, and a branched alkyl group, n = 0 to an integer of 20