JP6020177B2 - Inkjet ink - Google Patents

Description

  One embodiment of the present invention relates to an inkjet ink, an ink cartridge, an inkjet recording apparatus, and an image recorded matter.

  In recent years, as an image forming apparatus, an ink jet recording apparatus has become widespread because the process is simple, full-colorization is easy, and a high-resolution image can be obtained even with a simple configuration.

  An ink jet recording apparatus is an apparatus that forms an image by causing ink to fly and adhere to a recording medium by pressure generated using bubbles, piezo, electrostatic, or the like generated by heat. Applications are expanding to printing.

  In recent years, research on pigment inks has been advanced in ink jet recording apparatuses.

  However, the pigment ink has a problem that the storage stability is insufficient.

  Patent Document 1 discloses an inkjet ink containing water, a water-soluble organic solvent, a pigment, and a polymer dispersant having a weight average molecular weight of 800 or more for dispersing the pigment. At this time, (ratio of the polymer dispersant to the pigment in the ink excluding the sediment after centrifugation (centrifugation condition: centrifugal acceleration 9000 g × 30 min)) / (polymer dispersion to the pigment in the ink before the centrifugation) The characteristic value indicated by the ratio of the agent is 1.0 to 1.5.

  However, there is a problem that the image density and storage stability of plain paper cannot be compatible.

  An object of one embodiment of the present invention is to provide an inkjet ink that is excellent in image density and storage stability in plain paper in view of the problems of the above-described conventional technology.

  One embodiment of the present invention includes, in an inkjet ink, water, a water-soluble organic solvent, a pigment, and a copolymer, wherein the copolymer has a general formula

（式中、Ｒ_１は、メチル基又は水素原子であり、Ｍ_１ ^＋は、プロトン、アルカリ金属イオン又は有機アンモニウムイオンであり、Ｍ_２ ^＋は、アルカリ金属イオン又は有機アンモニウムイオンである。）
で表される構成単位と、一般式

(In the formula, R ₁ is a methyl group or a hydrogen atom, M ₁ ⁺ is a proton, an alkali metal ion, or an organic ammonium ion, and M ₂ ⁺ is an alkali metal ion or an organic ammonium ion.)
And the general formula

（式中、Ｒ_２は、メチル基又は水素原子である。）
で表される構成単位を有する。

(In the formula, R ₂ is a methyl group or a hydrogen atom.)
It has the structural unit represented by these.

  According to one embodiment of the present invention, it is possible to provide an inkjet ink that is excellent in image density and storage stability on plain paper.

It is a perspective view which shows an example of an inkjet recording device. It is the schematic which shows the whole structure of the inkjet recording device of FIG. FIG. 2 is a partially enlarged view of the ink jet recording apparatus of FIG. 1. FIG. 2 is a schematic diagram illustrating the ink cartridge of FIG. 1.

  Next, an embodiment of the inkjet ink of the present invention will be described.

  The inkjet ink includes water, a water-soluble organic solvent, a pigment, and a copolymer.

  As water, pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water can be used.

  The copolymer has a structural unit represented by the general formula (1) and a structural unit represented by the general formula (2).

で表される化合物と、一般式

And a compound represented by the general formula

で表される化合物を含むモノマーを共重合した後、アルカリ金属塩基又は有機アミン塩基で中和することにより合成することができる。このとき、共重合体は、通常、水溶性樹脂又は水分散性樹脂である。

It can synthesize | combine by copolymerizing the monomer containing the compound represented by these, and neutralizing with an alkali metal base or an organic amine base. At this time, the copolymer is usually a water-soluble resin or a water-dispersible resin.

  The method for copolymerizing the monomer is not particularly limited, but in a flask equipped with a stirrer, a thermometer, and a nitrogen introduction tube, while flowing nitrogen gas in the presence of a solvent and a polymerization initiator, at 60 to 150 ° C. Examples thereof include a method of copolymerizing monomers.

  The compound represented by the general formula (3) is 2- (methacryloyloxy) ethyl phosphate or 2- (acryloyloxy) ethyl phosphate.

  As a commercial item of 2- (methacryloyloxy) ethyl phosphate, light ester P-1M (manufactured by Kyoeisha Chemical Co., Ltd.), Phosmer M (manufactured by Unichemical Co., Ltd.) and the like can be mentioned.

  As a commercial item of 2- (acryloyloxy) ethyl phosphate, light acrylate P-1A (manufactured by Kyoeisha Chemical Co., Ltd.) and the like can be mentioned.

  The neutralization rate when neutralizing with an alkali metal base or organic amine base is usually 50 to 100%.

  For this reason, the copolymer has the general formula

で表される構成単位をさらに有していてもよい。

It may further have a structural unit represented by

Although it does not specifically limit as an alkali metal ion in General formula (1), Li ^<+> , Na ^<+> , K ^<+> etc. are mentioned.

  Examples of the organic ammonium ion in the general formula (1) include mono-, di- or trimethylammonium ions, alkylammonium ions such as mono-, di- or triethylammonium ions, monoethanolammonium ions, diethanolammonium ions, triethanolammonium ions, methylethanolammonium ions. Ion, methyldiethanolammonium ion, dimethylethanolammonium ion, monopropanolammonium ion, dipropanolammonium ion, tripropanolammonium ion, isopropanolammonium ion, 1,1-bis (hydroxymethyl) -2-hydroxyethylammonium ion, 1, Alcohols such as 1-bis (hydroxymethyl) propylammonium ion Nmo ions, coli ions, morpholinium ion, N- methyl mono formate Li ions, N- methyl-2-pyrrolide ions, ammonium ions derived from cyclic amine such as 2-pyrrolide ion.

  The compound represented by the general formula (4) is oleyl methacrylate or oleyl acrylate.

  The compound represented by the general formula (4) can be obtained by dehydrating acrylic acid or methacrylic acid and oleyl alcohol.

  Content of the structural unit represented by General formula (1) of a copolymer is 10-90 mass% normally, and it is preferable that it is 20-60 mass%. Thereby, it is possible to achieve both the image density and the storage stability of the inkjet ink on plain paper.

  Content of the structural unit represented by General formula (2) of a copolymer is 10-90 mass% normally, and it is preferable that it is 20-60 mass%. Thereby, it is possible to achieve both the image density and the storage stability of the inkjet ink on plain paper.

  The weight average molecular weight of the copolymer before neutralization with an alkali metal base or organic amine base is usually 3000 to 60000, preferably 5000 to 50000, and more preferably 6000 to 30000. Thereby, it is possible to achieve both the image density and the storage stability of the inkjet ink on plain paper.

  The content of the copolymer in the inkjet ink is usually 0.05 to 10% by mass, preferably 0.5 to 5% by mass, and more preferably 1 to 3% by mass. When the copolymer content in the inkjet ink is 0.05% by mass or more, the image density on plain paper can be improved, and when the content is 10% by mass or less, the ejection stability of the inkjet ink is improved. Can be improved.

  The mass ratio of the copolymer to the pigment is usually from 0.01 to 1, preferably from 0.05 to 0.8, and more preferably from 0.1 to 0.5. When the mass ratio of the copolymer to the pigment is 0.01 or more, the storage stability of the inkjet ink can be improved, and when it is 1 or less, the image density on plain paper can be improved.

  The water-soluble organic solvent is not particularly limited, but glycerin, ethylene glycol, diethylene glycol, isopropylideneglycerol, 1,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, propylene glycol, dipropylene Glycol, trimethylolpropane, trimethylolethane, ethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol Glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, petriol, etc. Polyhydric alcohols; polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene Polyhydric alcohol aryl ethers such as glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, Nitrogen-containing heterocyclic compounds such as ε-caprolactam and γ-butyrolactone; formamide, N-methylformamide Amides such as N, N-dimethylformamide, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropionamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, Amines such as triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, thiodiethanol; 3-ethyl-3-hydroxymethyloxetane, propylene carbonate, ethylene carbonate, and the like, polyols having 8 to 11 carbon atoms, and carbon numbers of 8 ˜11 glycol ethers, lower alcohols and the like may be mentioned, and two or more kinds may be used in combination.

  Among water-soluble organic solvents, glycerin, ethylene glycol, diethylene glycol, isopropylideneglycerol, 1,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, propylene are preferred in terms of the wettability of inkjet inks. Glycol, dipropylene glycol, trimethylolpropane, trimethylolethane, ethylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1, 6-hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol Polyhydric alcohols such as petriol; polyhydric alcohol alkyls such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether Ethers; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimid Nitrogen-containing heterocyclic compounds such as idazolidinone, ε-caprolactam, γ-butyrolactone; formamide, N-me Amides such as formamide, N, N-dimethylformamide, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropionamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine Amines such as diethylamine and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol; 3-ethyl-3-hydroxymethyloxetane, propylene carbonate, ethylene carbonate and the like are preferable, 1,3-butanediol, diethylene glycol 2,2,4-trimethyl-1,3-pentanediol, triethylene glycol and / or glycerin are more preferred.

  The wettability is a property that retains moisture in the ink-jet ink and prevents the ink-jet ink from drying, and a material having wettability is abbreviated as a wetting agent.

  The content of the wetting agent in the inkjet ink is usually 10 to 60% by mass, and preferably 20 to 50% by mass. When the content of the wetting agent in the inkjet ink is 10% by mass or more, the ejection stability of the inkjet ink can be improved, and when it is 60% by mass or less, the drying property of the inkjet ink is improved. Can do.

  Among water-soluble organic solvents, from the viewpoint of penetrability of inkjet ink, a polyol having 8 to 11 carbon atoms, a glycol ether having 8 to 11 carbon atoms, and a lower alcohol are preferable, and 2-ethyl-1,3-hexanediol is preferable. (Solubility of 4.2% by mass) and 2,2,4-trimethyl-1,3-pentanediol (solubility of 2.0% by mass) are more preferable.

  Examples of the polyol having 8 to 11 carbon atoms include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, and 2,2-diethyl-1,3-propane. Diol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1,2 -Diol etc. are mentioned.

  Examples of the glycol ether having 8 to 11 carbon atoms include diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether. Can be mentioned.

  Examples of the lower alcohol include ethanol.

  The penetrability is a property that promotes the penetration of the ink-jet ink into the recording medium, and the penetrable is abbreviated as a penetrant.

  The content of the penetrant in the inkjet ink is usually 0.1 to 4% by mass. When the content of the penetrant in the inkjet ink is 0.1% by mass or more, bleeding of the image can be suppressed, and when it is 4% by mass or less, the ejection stability of the inkjet ink can be improved. The image density can be improved.

  The inkjet ink may further contain a wetting agent other than the water-soluble organic solvent.

  The wetting agent other than the water-soluble organic solvent is not particularly limited, and examples thereof include saccharides and derivatives thereof, and two or more kinds may be used in combination.

  The saccharides are not particularly limited, but monosaccharides such as glucose, mannose, fructose, ribose, xylose, arabinose, galactose; disaccharides such as maltose, cellobiose, lactose, sucrose, trehalose; oligosaccharides such as maltotriose; α -Polysaccharides such as cyclodextrin and cellulose.

  Examples of saccharide derivatives include reducing sugars such as sugar alcohols such as D-sorbitol, sorbitan, maltitol, erythritol, lactitol, and xylitol; oxidized sugars of aldonic acid and uronic sugar; amino acids, thioic acids, and the like. Of these, sugar alcohols are preferred.

  Although it does not specifically limit as a pigment, Either an inorganic pigment and an organic pigment may be used and it may use 2 or more types together.

  Examples of inorganic pigments include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, metal powder, and carbon black. Among these, carbon black is preferable.

  Although it does not specifically limit as a manufacturing method of carbon black, A contact method, a furnace method, a thermal method etc. are mentioned.

  Examples of organic pigments include azo pigments, azomethine pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Of these, azo pigments and polycyclic pigments are preferred.

  Examples of the azo pigments include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments.

  Examples of the polycyclic pigment include a phthalocyanine pigment, a perylene pigment, a perinone pigment, an anthraquinone pigment, a quinacridone pigment, a dioxazine pigment, an indigo pigment, a thioindigo pigment, an isoindolinone pigment, a quinofullerone pigment, and a rhodamine B lake pigment.

  Examples of the dye chelates include basic dye chelates and acidic dye chelates.

  Black pigments include furnace black, lamp black, acetylene black, channel black and other carbon blacks (CI Pigment Black 7); copper, iron (CI Pigment Black 11), titanium oxide, etc. Metals: Organic pigments such as aniline black (CI Pigment Black 1) and the like.

Carbon black is manufactured by the furnace method or the channel method, the average primary particle size is 15 to 40 nm, the specific surface area by the BET method is 50 to 300 m ² / g, the DBP oil absorption is 40 to 150 mL / 100 g, the volatile content is It is preferable that it is 0.5-10 mass% and pH is 2-9.

  As a commercial product of carbon black, No. 2300, no. 900, MCF-88, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B (above, manufactured by Mitsubishi Chemical Corp.); Raven700, 5750, 5250, 5000, 3500, 1255 (above, made by Columbia); Regal400R, 330R, 660R, MoguL L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, Monarch 1400 (above, manufactured by Cabot); Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, 140V, Special Black 6, 5, 4A, 4 (Above, manufactured by Degussa).

  Examples of yellow pigments include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 2, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 73, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 75, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 95, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 98, C.I. I. Pigment yellow 114, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 174, C.I. I. And CI Pigment Yellow 180.

  Examples of the magenta pigment include C.I. I. Pigment red 5, C.I. I. Pigment red 7, C.I. I. Pigment red 12, C.I. I. Pigment red 48 (Ca), C.I. I. Pigment red 48 (Mn), C.I. I. Pigment red 57 (Ca), C.I. I. Pigment red 57: 1, C.I. I. Pigment red 112, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 146, C.I. I. Pigment red 168, C.I. I. Pigment red 176, C.I. I. Pigment red 184, C.I. I. Pigment red 185, C.I. I. Pigment Red 202, Pigment Violet 19 and the like.

  Examples of cyan pigments include C.I. I. Pigment blue 1, C.I. I. Pigment blue 2, C.I. I. Pigment blue 3, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15:34, C.I. I. Pigment blue 16, C.I. I. Pigment blue 22, C.I. I. Pigment blue 60, C.I. I. Pigment blue 63, C.I. I. Pigment blue 66; C.I. I. Bat Blue 4, C.I. I. Examples include Bat Blue 60.

  The content of the pigment in the inkjet ink is usually 1 to 20% by mass. When the pigment content in the inkjet ink is 1% by mass or more, the image density can be improved, and when it is 20% by mass or less, the ejection stability of the inkjet ink can be improved.

  The volume average particle diameter (D50%) of the pigment is usually 150 nm or less.

  The volume average particle diameter of the pigment can be measured by a dynamic light scattering method using Microtrac UPA (manufactured by Nikkiso Co., Ltd.) in an environment of 23 ° C. and 55% RH.

  Ink-jet ink further includes dispersants, penetrants, pH adjusters, water-dispersible resins, antiseptic / antifungal agents, chelating reagents, rust inhibitors, antioxidants, UV absorbers, oxygen absorbers, light stabilizers, etc. May be included.

  The dispersant is not particularly limited as long as it can promote the dispersion of the pigment in the inkjet ink, but anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, and the like And two or more of them may be used in combination.

  Examples of anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, N-acyl amino acids and salts thereof, N-acyl methyl taurates, polyoxyalkyl ether sulfates. , Polyoxyethylene alkyl ether phosphate, rosin acid soap, castor oil sulfate ester salt, lauryl alcohol sulfate ester salt, alkylphenol type phosphate ester, naphthalenesulfonate formalin condensate, alkyl type phosphate ester, alkylallylsulfone hydrochloride, diethyl Examples include sulfosuccinate, diethylhexyl sulfosuccinate, and dioctyl sulfosuccinate.

  Examples of the cationic surfactant include 2-vinylpyridine derivatives and poly (4-vinylpyridine) derivatives.

  Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine, imidazoline derivatives, etc. Is mentioned.

  Nonionic surfactants include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyoxyallyl Ether-based surfactants such as kill alkyl ethers; polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, poly Ester surfactants such as oxyethylene monooleate and polyoxyethylene stearate; 2,4,7,9-tetramethyl-5- Shin-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1-hexyne-3-acetylene glycol surface active agents such as all-like.

  The pH adjuster is not particularly limited as long as the pH of the inkjet ink can be adjusted. Examples of the pH adjuster include alcohol amine, alkali metal hydroxide, ammonium hydroxide, phosphonium hydroxide, and alkali metal carbonate. Can be mentioned.

  Examples of the alcohol amine include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol and the like.

  Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.

  Examples of ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.

  Examples of phosphonium hydroxide include quaternary phosphonium hydroxide.

  Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

  Although it does not specifically limit as water-dispersible resin, A condensation type synthetic resin, an addition type synthetic resin, a natural polymer compound, etc. are mentioned, You may use 2 or more types together.

  Examples of the condensed synthetic resin include polyester, polyurethane, polyepoxy resin, polyamide, polyether, poly (meth) acrylic resin, acrylic-silicone resin, and fluorine-based resin.

  Examples of the addition type synthetic resin include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, unsaturated carboxylic acid resins, and the like.

  Examples of the natural polymer compound include celluloses, rosins, natural rubber and the like.

  Of these, polyurethane, acrylic-silicone resin and fluorine-based resin are preferable.

  The antiseptic / antifungal agent is not particularly limited as long as it can suppress the growth of bacteria in the inkjet ink, but sodium dehydroacetate, sodium sorbate, 2-pyridinethiol-1-oxide sodium, sodium benzoate And sodium pentachlorophenol.

  Examples of the chelating reagent include, but are not limited to, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.

  The rust inhibitor is not particularly limited, and examples thereof include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

  Although it does not specifically limit as antioxidant, A phenolic antioxidant (a hindered phenolic antioxidant is included), an amine antioxidant, a sulfuric antioxidant, phosphorus antioxidant, etc. are mentioned.

  Although it does not specifically limit as a ultraviolet absorber, A benzophenone type ultraviolet absorber, a benzotriazole type ultraviolet absorber, a salicylate type ultraviolet absorber, a cyanoacrylate type ultraviolet absorber, a nickel complex salt type ultraviolet absorber, etc. are mentioned.

  The ink-jet ink can be produced by dispersing or dissolving a composition containing water, a water-soluble organic solvent, a pigment and a copolymer using a disperser and then stirring the composition using a stirrer.

  In addition, it is preferable to prepare a pigment dispersion in advance by dispersing a composition containing water, a pigment, and a copolymer using a disperser.

  The content of the pigment in the pigment dispersion is usually 0.1 to 50% by mass, and preferably 0.1 to 30% by mass.

  Although it does not specifically limit as a disperser, A sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser etc. are mentioned.

  The stirrer is not particularly limited, and examples thereof include a stirrer having a stirring blade, a magnetic stirrer, and a high-speed disperser.

  When producing a pigment dispersion and an inkjet ink, it is preferable to filter coarse particles using a filter, a centrifugal separator or the like.

  The viscosity of the inkjet ink at 25 ° C. is usually 3 to 20 mPa · s. When the viscosity of the ink-jet ink at 25 ° C. is 3 mPa · s or more, the image density can be improved or the bleeding of the image can be suppressed. Can be improved.

  The viscosity of the inkjet ink at 25 ° C. can be measured using a viscometer RL-550 (manufactured by Toki Sangyo Co., Ltd.).

  The pH of the inkjet ink is usually 8.5 to 11, and preferably 9 to 11. When the pH of the inkjet ink is 8.5 or more, the storage stability of the inkjet ink can be improved, and when it is 11 or less, corrosion of the inkjet head and the ink supply unit can be suppressed.

  The pH of the inkjet ink can be measured using a pH meter HM-30R (manufactured by TOA-DKK).

  The surface tension of inkjet ink at 25 ° C. is usually 40 mN / m or less. Thereby, the leveling property of inkjet ink can be improved.

  Next, an embodiment of the ink jet recording apparatus of the present invention will be described.

  The ink jet recording apparatus has means for ejecting the ink jet ink of the above embodiment, and further has control means as necessary.

  The means for ejecting the ink-jet ink is not particularly limited, and examples thereof include an ink-jet head that applies a stimulus (energy) to the ink-jet ink.

  Although it does not specifically limit as irritation | stimulation (energy), A heat | fever (temperature), a pressure, a vibration, light, etc. are mentioned, You may use 2 or more types together. Of these, heat and pressure are preferred.

  For example, when the stimulus is heat, the thermal energy corresponding to the recording signal is applied to the inkjet ink in the inkjet head using a heating resistor to generate bubbles in the inkjet ink. Inkjet ink is discharged from the nozzle.

  In addition, when the stimulus is pressure, by applying a voltage to the piezoelectric element bonded to the pressure chamber in the ink flow path in the ink jet head, the piezoelectric element is bent, and the volume of the pressure chamber is reduced. Inkjet ink is ejected from the nozzles.

  Examples of the control means include a sequencer and a computer.

  Examples of the ink jet recording apparatus include an ink jet printer, a facsimile apparatus, a copying apparatus, and a printer / fax / copier multifunction machine.

  The recording medium on which an image is recorded using an inkjet recording apparatus is not particularly limited, and examples thereof include plain paper, coated paper for printing, glossy paper, special paper, cloth, film, and OHP sheet.

  FIG. 1 shows an ink jet printer as an example of the ink jet recording apparatus.

  The ink jet printer 100 includes a paper feed tray 101 for loading plain paper, a paper discharge tray 102 for stocking plain paper on which an image is recorded, and an ink cartridge loading unit 103. On the upper surface of the ink cartridge loading unit 103, an operation unit 104 on which operation keys, a display, and the like are installed is disposed. The ink cartridge loading unit 103 is provided with an openable and closable cover 103 a for attaching and detaching the ink cartridge 200.

  In the inkjet printer 100, as shown in FIGS. 2 and 3, a carriage 107 is slidably held in the main scanning direction A by a guide rod 105 and a stay 106 that are horizontally mounted on left and right side plates (not shown). It is moved and scanned in the main scanning direction A by a main scanning motor (not shown).

  The carriage 107 includes four inkjet heads 108 that eject ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). And are mounted so that the direction in which the ink droplets are ejected is downward.

  The inkjet head 108 is not particularly limited, but a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by film boiling of a liquid using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator to be used, an electrostatic actuator using an electrostatic force, or the like can be used.

  Also, the carriage 107 is equipped with a sub tank 109 for each color for supplying each color ink to the inkjet head 108. The sub tank 109 is supplied with ink-jet ink from an ink cartridge 200 loaded in the ink cartridge loading unit 103 via an ink supply tube (not shown) and is replenished.

  On the other hand, the plain paper P is separated and fed from the plain paper stacking unit 102a one by one as a paper feeding unit for feeding the plain paper P stacked on the plain paper stacking unit (pressure plate) 102a of the paper feed tray 102. A sheet feeding roller 110 to be fed and a separation pad 111 made of a material having a large friction coefficient are disposed to face the sheet feeding roller 110. At this time, the separation pad 111 is biased toward the paper feed roller 110 side.

  A transport belt 113 for electrostatically attracting and transporting the plain paper P as a transport section for transporting the plain paper P fed from the paper feed section via the guide 112 on the lower side of the inkjet head 108; The counter roller 114 for transporting the plain paper P sandwiched between the transport belt 113 and the plain paper P transported substantially vertically upward is changed by approximately 90 ° to follow the transport belt 113. A conveying guide 115 and a tip pressurizing roller 117 urged toward the conveying belt 113 by a pressing member 116 are installed. A charging roller 118 for charging the surface of the conveyor belt 113 is provided.

  The conveyance belt 113 is an endless belt, is stretched between the conveyance roller 119 and the tension roller 120, and can circulate in the direction B in which the plain paper P is conveyed. Further, a guide member 121 is disposed on the back side of the conveyance belt 113 so as to correspond to an image recording area by the inkjet head 108.

  Although it does not specifically limit as the conveyance belt 113, The surface layer which electrostatically adsorbs the plain paper P comprised from resin, such as a tetrafluoroethylene and ethylene copolymer (ETFE) about 40 micrometers thick, and carbon Except for the resistance being controlled, one having a back layer (medium resistance layer, earth layer) made of the same material as the surface layer can be used.

  As a paper discharge unit for discharging the plain paper P on which an image is recorded by the inkjet head 108, a separation claw 122 for separating the plain paper P from the transport belt 113, a discharge roller 123, and a discharge roller. 124 is installed, and a paper discharge tray 103 is disposed below the paper discharge roller 123.

  A double-sided paper feeding unit 125 is detachably attached to the back surface of the inkjet recording apparatus 100. The double-sided paper feeding unit 125 takes in and reverses the plain paper P returned by rotating the transport belt 113 in the reverse direction to the direction B in which the plain paper P is transported. Paper is fed between. A manual paper feed unit 126 is installed on the upper surface of the double-sided paper feed unit 125.

  In the ink jet printer 100, the plain paper P is separated and fed one by one from the paper feed unit, and the plain paper P fed substantially vertically upward is guided by the guide 112, and the conveyance belt 113 and the counter roller 114 are in contact with each other. It is sandwiched and conveyed. Further, the front end is guided by the transport guide 115 and pressed against the transport belt 113 by the front end pressure roller 117, and the transport direction is changed by about 90 °.

  At this time, since the conveying belt 113 is charged by the charging roller 118, the plain paper P is conveyed by being electrostatically attracted to the conveying belt 113. Therefore, by driving the inkjet head 108 according to the image signal while moving the carriage 107, the inkjet ink is ejected onto the stopped plain paper P to record an image for one line. After transporting a predetermined amount, the image for the next line is recorded. Upon receipt of a signal indicating the end of image recording or a signal indicating that the trailing edge of the plain paper P has reached the image recording area, the image recording operation is terminated and the plain paper P is discharged onto the discharge tray 103.

  When the near end of the remaining amount of ink in the sub tank 109 is detected, a required amount of inkjet ink is supplied to the sub tank 109 from an ink cartridge (not shown).

  In the inkjet printer 100, when the inkjet ink in the ink cartridge 200 is used up, the casing of the ink cartridge 200 can be disassembled and the ink bag inside can be replaced. Further, the ink cartridge 200 can supply ink stably even when the ink cartridge 200 is vertically placed and has a front loading configuration. Therefore, even when the upper part of the ink jet printer 100 is closed and installed, for example, when it is stored in a rack or when an object is placed on the upper surface of the ink jet printer 100, The ink cartridge 200 can be easily replaced.

  FIG. 4 shows the ink cartridge 200.

  The ink cartridge 200 is used by mounting an ink bag 201 filled with inkjet ink in a plastic casing 202 detachably attached to the inkjet printer 100.

  The ink bag 201 is composed of a packaging member such as a non-permeable aluminum laminate film or resin film, and after filling and discharging the ink jet ink from the ink injection port 201a, the ink injection port 201a is fused. It is sealed by. Further, the ink bag 201 is formed with an ink discharge port 201b made of a rubber member. When supplying ink jet ink to the sub tank 109, the ink bag 201 is installed at the tip of the ink supply tube at the ink discharge port 201b. Stab the needle.

  The example in which the inkjet ink of the above embodiment is applied to a serial (shuttle type) inkjet recording apparatus in which a carriage scans has been described above, but the present invention can be similarly applied to a line inkjet recording apparatus having a line type head. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, this invention is not limited to an Example. In addition, a part means a mass part.

<Synthesis of oleyl methacrylate>
In a 2 L eggplant-shaped flask equipped with a stirrer, an air bubbling tube, a dehydration tube, and a cooling tube, 600 g of oleyl alcohol UNJECOL-90N (manufactured by Nippon Nippon Chemical Co., Ltd.), 392 g of methacrylic acid, 400 g of n-heptane, p-toluenesulfonic acid 1.0 g and 4.96 g of hydroquinone monomethyl ether were added, and a dehydration reaction was performed at 120 ° C. for 9 hours. Next, after washing with alkaline water, it was washed twice. In addition, using an evaporator, de-boiling while bubbling air, the chemical formula

で表されるメタクリル酸オレイル７４９ｇを得た。

As a result, 749 g of oleyl methacrylate was obtained.

The ¹ H NMR δ value of the product is shown below.

δ = 0.8 to 1.0 (3.0H): proton of methyl group in oleyl group δ = 1.2 to 1.7 (26H): bonded to carbonyloxy group or methine group in oleyl group Proton of methylene group which is not bonded δ = 1.95 to 2.1 (6.2H): Proton of methyl group in methacryl group and proton of methylene group bonded to methine group in oleyl group δ = 4.1-4.2 vicinity (2.0H): Proton of methylene group bonded to carbonyloxy group in oleyl group δ = 5.3-5.5 vicinity (1.7H): In oleyl group Proton of methine group δ = 5.5 to 5.6 (1.0H): one proton of methylene group in methacryloyl group δ = 6.1 to 6.2 (1.0H): in methacryloyl group The other proton of the methylene group (copolymer having an acid group The synthesis of the body 1)
In a flask equipped with a stirrer, thermometer, and nitrogen introduction tube, 500 parts of solvent 1-methoxy-2-propanol, chemical formula

で表されるホスマーＭ（リン酸２−（メタクリロイルオキシ）エチル）６０部、メタクリル酸オレイル４０部、重合開始剤アゾビスイソブチロニトリル４部を入れた後、１１０℃に昇温し、窒素気流下、４時間重合した。次に、溶媒の半量程度を留去した後、大量のメタノール中に注入して、酸基を有する共重合体１を析出させた。さらに、析出した酸基を有する共重合体１を乾燥させた。酸基を有する共重合体１は、重量平均分子量が１３０００であった。

After adding 60 parts of phosmer M (2- (methacryloyloxy) ethyl phosphate), 40 parts of oleyl methacrylate, and 4 parts of a polymerization initiator azobisisobutyronitrile, the temperature was raised to 110 ° C. and nitrogen was added. Polymerization was conducted for 4 hours under an air stream. Next, after distilling off about half of the solvent, it was poured into a large amount of methanol to precipitate the copolymer 1 having an acid group. Furthermore, the copolymer 1 having precipitated acid groups was dried. The copolymer 1 having an acid group had a weight average molecular weight of 13,000.

(Synthesis of copolymer 2 having acid group)
Instead of Phosmer M, the chemical formula

で表されるライトアクリレートＰ−１Ａ（リン酸２−（アクリロイルオキシ）エチル）を用いた以外は、酸基を有する共重合体１と同様にして、重量平均分子量が１２０００の酸基を有する共重合体２を得た。

The copolymer having an acid group having a weight average molecular weight of 12,000 is the same as the copolymer 1 having an acid group, except that light acrylate P-1A (2- (acryloyloxy) ethyl phosphate) represented by A polymer 2 was obtained.

(Synthesis of copolymer 3 having acid group)
Copolymer 3 having an acid group having a weight average molecular weight of 16000, similar to copolymer 1 having an acid group, except that the addition amounts of Phosmer M and oleyl methacrylate were changed to 10 parts and 90 parts, respectively. Got.

(Synthesis of copolymer 4 having acid group)
Copolymer 4 having an acid group with a weight average molecular weight of 15000, similar to copolymer 1 having an acid group, except that the addition amounts of Phosmer M and oleyl methacrylate were changed to 20 parts and 80 parts, respectively. Got.

(Synthesis of copolymer 5 having acid group)
Copolymer 5 having an acid group having a weight average molecular weight of 15000, similar to copolymer 1 having an acid group, except that the addition amounts of Phosmer M and oleyl methacrylate were changed to 90 parts and 10 parts, respectively. Got.

(Synthesis of homopolymer having acid group)
Polymerization was carried out in the same manner as copolymer 1 having an acid group except that the addition amounts of Phosmer M and oleyl methacrylate were changed to 100 parts and 0 parts, respectively, but gelled.

(Synthesis of copolymer 6 having acid group)
A copolymer 6 having an acid group having a weight average molecular weight of 10,000 was obtained in the same manner as the copolymer 4 having an acid group, except that styrene was used instead of oleyl methacrylate.

(Synthesis of copolymer 7 having acid group)
A copolymer 7 having an acid group having a weight average molecular weight of 11,000 was obtained in the same manner as the copolymer 4 having an acid group, except that cetyl methacrylate was used instead of oleyl methacrylate.

(Synthesis of copolymer 8 having acid group)
A copolymer 8 having an acid group having a weight average molecular weight of 11,000 was obtained in the same manner as the copolymer 4 having an acid group, except that methacrylic acid was used instead of the phosmer M.

  Table 1 shows the characteristics of the copolymers 1 to 8 having an acid group.

＜重量平均分子量＞
カラム恒温槽ＣＴＯ−２０Ａ（島津製作所社製）、検出器ＲＩＤ−１０Ａ（島津製作所社製）、溶離液流路ポンプＬＣ−２０ＡＤ（島津製作所社製）、デガッサＤＧＵ−２０Ａ（島津製作所社製）及びオートサンプラーＳＩＬ−２０Ａ（島津製作所社製）を用いて、ＧＰＣ法により、重量平均分子量を測定した。カラムとしては、排除限界分子量が２×１０^５の水系ＳＥＣカラムＴＳＫｇｅｌＧ３０００ＰＷＸＬと、排除限界分子量が２．５×１０^６のＴＳＫｇｅｌＧ５０００ＰＷＸＬと、排除限界分子量が５×１０^７のＴＳＫｇｅｌＧ６０００ＰＷＸＬ（東ソー社製）を接続したものを用いた。サンプルとしては、溶離液で２ｇ／１００ｍｌに調製したものを用いた。溶離液としては、酢酸及び酢酸ナトリウムの含有量をそれぞれ０．５ｍｏｌ／Ｌに調整した水溶液を用いた。カラム温度を４０℃とし、流速を１．０ｍｌ／ｍｉｎとした。較正曲線は、分子量が１０６５、５０５０、２４０００、５００００、１０７０００、１４００００、２５００００、５４００００、９２００００の９種のポリエチレングリコールの標準サンプルを用いて作成した。

<Weight average molecular weight>
Column thermostat CTO-20A (manufactured by Shimadzu Corp.), detector RID-10A (manufactured by Shimadzu Corp.), eluent channel pump LC-20AD (manufactured by Shimadzu Corp.), degasser DGU-20A (manufactured by Shimadzu Corp.) And the weight average molecular weight was measured by GPC method using autosampler SIL-20A (manufactured by Shimadzu Corporation). As a column, an aqueous SEC column TSKgelG3000PWXL with an exclusion limit molecular weight of 2 × 10 ^5, a TSKgelG5000PWXL with an exclusion limit molecular weight of 2.5 × 10 ⁶ , and a TSKgelG6000PWXL (made by Tosoh Corporation) with an exclusion limit molecular weight of 5 × 10 ⁷ are connected. What was done was used. As the sample, an eluent prepared to 2 g / 100 ml was used. As an eluent, an aqueous solution in which the contents of acetic acid and sodium acetate were adjusted to 0.5 mol / L was used. The column temperature was 40 ° C. and the flow rate was 1.0 ml / min. Calibration curves were generated using nine polyethylene glycol standard samples with molecular weights of 1065, 5050, 24000, 50000, 107000, 140000, 250,000, 540000, and 920000.

<Example 1>
After 10 g of copolymer 1 having an acid group and 80 g of water were mixed, a 10% by mass aqueous potassium hydroxide solution was added dropwise to neutralize the neutralization rate to 100%. Next, it diluted with water and obtained the aqueous solution of the potassium salt of the copolymer 1 containing a 10 mass% acid group.

  Carbon black NIPEX150 (manufactured by Degussa) 20 parts, 10 parts by mass of an aqueous solution of potassium salt of copolymer 1 having an acid group of 50 parts and 30 parts of pure water were mixed, and then a disk-type bead mill KDL type (Shinmaru Enterprise) The product was circulated and dispersed for 10 minutes at a peripheral speed of 10 m / s. At this time, zirconia balls having a diameter of 0.1 mm were used as media. Next, after filtration using a membrane filter having a pore size of 1.2 μm, the membrane was diluted with water to obtain a 20% by mass pigment dispersion.

  20 parts by weight of pigment dispersion 40 parts, wetting agent 1,3-butanediol 20 parts, wetting agent glycerin 10 parts, penetrating agent 2-ethyl-1,3-hexanediol 1 part, penetrating agent 2,2,4- After mixing 1 part of trimethyl-1,3-pentadiol, 2 parts of 40% by mass of fluorosurfactant Zonyl FS-300 (manufactured by DuPont) and 26 parts of distilled water, the mixture was stirred for 1.5 hours. Next, it filtered using the membrane filter whose pore diameter is 1.2 micrometers, and obtained the inkjet ink.

<Example 2>
An inkjet ink was obtained in the same manner as in Example 1 except that the copolymer 2 having an acid group was used instead of the copolymer 1 having an acid group.

<Example 3>
An inkjet ink was obtained in the same manner as in Example 1 except that the copolymer 3 having an acid group was used instead of the copolymer 1 having an acid group.

<Example 4>
An inkjet ink was obtained in the same manner as in Example 1 except that the copolymer 4 having an acid group was used instead of the copolymer 1 having an acid group.

<Example 5>
An inkjet ink was obtained in the same manner as in Example 1, except that the copolymer 5 having an acid group was used instead of the copolymer 1 having an acid group.

<Example 6>
After 10 g of copolymer 1 having an acid group and 80 g of water were mixed, 10% by mass of a lithium hydroxide aqueous solution was added dropwise to neutralize the neutralization rate to 100%. Next, it diluted with water and obtained the aqueous solution of the lithium salt of the copolymer 1 containing a 10 mass% acid group.

  Example 1 except that an aqueous solution of a lithium salt of copolymer 1 containing 10% by mass of acid groups was used instead of an aqueous solution of a potassium salt of copolymer 1 containing 10% by mass of acid groups. In the same manner, an inkjet ink was obtained.

<Example 7>
After 10 g of copolymer 1 having an acid group and 80 g of water were mixed, 10% by mass of 2-amino-2-ethyl-1,3-propanediol (AEPD) aqueous solution was added dropwise to give a neutralization rate of 100. % To neutralize. Next, it diluted with water and obtained the aqueous solution of the 1, 1-bis (hydroxymethyl) propyl ammonium salt of the copolymer 1 containing a 10 mass% acid group.

  An aqueous solution of 1,1-bis (hydroxymethyl) propylammonium salt of copolymer 1 containing 10% by mass of acid groups instead of an aqueous solution of potassium salt of copolymer 1 containing 10% by mass of acid groups An inkjet ink was obtained in the same manner as in Example 1 except that was used.

<Example 8>
In the same manner as in Example 1, a 20% by mass pigment dispersion was obtained.

  40 parts by weight pigment dispersion 40 parts, 7.5 parts wetting agent 1,3-butanediol, 2.5 parts wetting agent glycerin, 1 part penetrating agent 2-ethyl-1,3-hexanediol, 2 penetrants After mixing 1 part of 2,4-trimethyl-1,3-pentadiol, 2 parts of 40% by mass of fluorosurfactant Zonyl FS-300 (manufactured by DuPont) and 46 parts of distilled water, the mixture was stirred for 1.5 hours. did. Next, it filtered using the membrane filter whose pore diameter is 1.2 micrometers, and obtained the inkjet ink.

<Example 9>
In the same manner as in Example 1, a 20% by mass pigment dispersion was obtained.

  20 parts by weight of pigment dispersion 40 parts, wetting agent, 15 parts of 3-butanediol, 5 parts of wetting agent glycerin, 1 part of penetrating agent 2-ethyl-1,3-hexanediol, penetrating agent 2,2,4-trimethyl After mixing 1 part of -1,3-pentadiol, 2 parts of 40% by mass of fluorosurfactant Zonyl FS-300 (manufactured by DuPont) and 36 parts of distilled water, the mixture was stirred for 1.5 hours. Next, it filtered using the membrane filter whose pore diameter is 1.2 micrometers, and obtained the inkjet ink.

<Example 10>
In the same manner as in Example 1, a 20% by mass pigment dispersion was obtained.

  20 parts by weight of pigment dispersion 40 parts, wetting agent 1,3-butanediol 35 parts, wetting agent glycerin 15 parts, penetrating agent 2-ethyl-1,3-hexanediol 1 part, penetrating agent 2,2,4- After mixing 1 part of trimethyl-1,3-pentadiol, 2 parts of 40% by mass of fluorosurfactant Zonyl FS-300 (manufactured by DuPont) and 6 parts of distilled water, the mixture was stirred for 1.5 hours. Next, it filtered using the membrane filter whose pore diameter is 1.2 micrometers, and obtained the inkjet ink.

<Example 11>
After 10 g of copolymer 1 having an acid group and 80 g of water were mixed, a 10% by mass lithium hydroxide aqueous solution was added dropwise to neutralize the neutralization rate to 50%. Next, it diluted with water and obtained the aqueous solution of the lithium salt of the copolymer 1 containing a 10 mass% acid group.

  Example 1 except that an aqueous solution of a lithium salt of copolymer 1 containing 10% by mass of acid groups was used instead of an aqueous solution of a potassium salt of copolymer 1 containing 10% by mass of acid groups. In the same manner, an inkjet ink was obtained.

<Example 12>
An inkjet ink was obtained in the same manner as in Example 1 except that Pigment Blue 15: 3 Chromofine Blue (manufactured by Dainichi Seika Co., Ltd.) was used instead of carbon black NIPEX150 (manufactured by Degussa).

<Example 13>
An inkjet ink was obtained in the same manner as in Example 1 except that Pigment Red 122 Toner Magenta EO02 (Clariant) was used instead of Carbon Black NIPEX150 (Degussa).

<Example 14>
An inkjet ink was obtained in the same manner as in Example 1 except that Pigment Yellow First Yellow 531 (manufactured by Dainichi Seika Co., Ltd.) was used instead of carbon black NIPEX150 (manufactured by Degussa).

<Comparative Example 1>
An inkjet ink was obtained in the same manner as in Example 1 except that the copolymer 6 having an acid group was used instead of the copolymer 1 having an acid group.

<Comparative example 2>
An inkjet ink was obtained in the same manner as in Example 1 except that the copolymer 7 having an acid group was used instead of the copolymer 1 having an acid group.

<Comparative Example 3>
An inkjet ink was obtained in the same manner as in Example 1, except that the copolymer 8 having an acid group was used instead of the copolymer 1 having an acid group.

<Comparative example 4>
In the same manner as in Comparative Example 1, a 20% by mass pigment dispersion was obtained.

  40 parts by weight pigment dispersion 40 parts, 7.5 parts wetting agent 1,3-butanediol, 2.5 parts wetting agent glycerin, 1 part penetrating agent 2-ethyl-1,3-hexanediol, 2 penetrants After mixing 1 part of 2,4-trimethyl-1,3-pentadiol, 2 parts of 40% by mass of fluorosurfactant Zonyl FS-300 (manufactured by DuPont) and 46 parts of distilled water, the mixture was stirred for 1.5 hours. did. Next, it filtered using the membrane filter whose pore diameter is 1.2 micrometers, and obtained the inkjet ink.

  Table 2 shows the characteristics of the inkjet inks of Examples 1 to 13 and Comparative Examples 1 to 4.

次に、実施例１〜１３及び比較例１〜４のインクジェットインクの画像濃度及び保存安定性を評価した。

Next, the image density and storage stability of the inkjet inks of Examples 1 to 13 and Comparative Examples 1 to 4 were evaluated.

<Image density on plain paper>
Inkjet printer IPSiO GX5000 (manufactured by Ricoh Co., Ltd.) was filled with inkjet ink in an environment of 23 ° C. and 50% RH. Next, after printing a chart with 64 point characters “■” created using Microsoft Word 2000 (manufactured by Microsoft) on plain paper MyPaper (manufactured by Ricoh Co., Ltd.), X-Rite 938 (manufactured by Romics Co., Ltd.) Was used to measure the image density of “■”. At this time, as the print mode, a mode in which the “plain paper—standard fast” mode was changed to “no color correction” from the user setting of plain paper with a driver attached to the inkjet printer.

  In the case of black ink, A when the image density is 1.30 or more, B when it is 1.25 or more and less than 1.30, C when it is 1.20 or more and less than 1.25, or 1.10 or more. The case of less than 1.20 was determined as D, the case of less than 1.10, or the case where the black ink was gelled and could not be evaluated as E.

  In the case of yellow ink, B when the image density is 0.75 or more, C if it is 0.70 or more and less than 0.75, D if 0.65 or more and less than 0.70, and 0.65. The case where it was less than or when the yellow ink was gelled and could not be evaluated was determined as E.

  In the case of magenta ink, B when the image density is 0.90 or more, C when the image density is 0.80 or more and less than 0.90, D when 0.70 or more and less than 0.80, and less than 0.70. Or when the magenta ink was gelled and could not be evaluated.

  In the case of cyan ink, B when the image density is 1.00 or more, C when it is 0.90 or more and less than 1.00, D when it is 0.70 or more and less than 0.80, and less than 0.80. Or when the cyan ink gelled and could not be evaluated.

<Storage stability>
Ink jet ink was filled into an ink cartridge and stored at 60 ° C. for 2 weeks, and the rate of change in viscosity before and after storage was determined. A when the absolute value of the rate of change in viscosity before and after storage is less than 5%, B when it is 5% or more and less than 8%, C when it is 8% or more and less than 10%, 10% or more but less than 30% In the case of D, 30% or more, or the case where the inkjet ink was gelled and could not be evaluated was determined as E.

  Table 3 shows the evaluation results of image density and storage stability of the inkjet inks of Examples 1 to 14 and Comparative Examples 1 to 4.

表３から、実施例１〜１４のインクジェットインクは、普通紙における画像濃度及び保存安定性に優れることがわかる。

From Table 3, it can be seen that the inkjet inks of Examples 1 to 14 are excellent in image density and storage stability in plain paper.

  On the other hand, since the inkjet inks of Comparative Examples 1 and 4 contain the potassium salt of the copolymer 6 having an acid group having a structural unit derived from styrene, the storage stability is lowered.

  Since the inkjet ink of Comparative Example 2 contains the potassium salt of the copolymer 7 having an acid group having a structural unit derived from cetyl methacrylate, the storage stability is lowered.

  Since the inkjet ink of Comparative Example 3 contains the potassium salt of the copolymer 8 having an acid group having a structural unit derived from methacrylic acid, the image density on plain paper is lowered.

100 Inkjet printer 108 Inkjet head 200 Ink cartridge

JP 2006-342201 A

Claims (7)

Including water, water-soluble organic solvents, pigments and copolymers,
The copolymer has the general formula

(In the formula, R ₁ is a methyl group or a hydrogen atom, M ₁ ⁺ is a proton, an alkali metal ion, or an organic ammonium ion, and M ₂ ⁺ is an alkali metal ion or an organic ammonium ion.)
And the general formula

(In the formula, R ₂ is a methyl group or a hydrogen atom.)
An inkjet ink comprising a structural unit represented by: The copolymer has the general formula

Compounds represented by general formula

2. The inkjet ink according to claim 1, which is synthesized by copolymerizing a monomer containing a compound represented by the formula (II) and then neutralizing with an alkali metal base or an organic amine base.   3. The inkjet ink according to claim 1, wherein the copolymer has a content of the structural unit represented by the general formula (1) of 20% by mass or more and 60% by mass or less. The water-soluble organic solvent includes a wetting agent,
The ink-jet ink according to any one of claims 1 to 3, wherein the content of the wetting agent is 20% by mass or more and 50% by mass or less.   An ink cartridge containing the ink-jet ink according to any one of claims 1 to 4.   An ink jet recording apparatus comprising: means for discharging the ink jet ink according to claim 1.   An image recorded matter, wherein an image is recorded by the inkjet ink according to claim 1.

Images