JP2003105237A - Ink for ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink for an ink jet printer for high-speed printing which has a low viscosity and excellent redispersibility. SOLUTION: In the ink containing a pigment and a polymer compound, it is characterized in that the compound has a glass-transition temperature of 10 deg.C or less and is contained in the range of 0.1-3 wt.% based on the total weight of the ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-viscosity inkjet printer ink useful for inkjet printers for high-speed printing. For more details,
The present invention relates to a continuous circulation type ink jet printer ink.

[0002]

2. Description of the Related Art Conventionally, in inks for ink jet printers using pigments, the dispersed particle diameter of the pigments is made fine and various additives are used to improve ejection stability, storage stability, redispersibility and the like. For example, US Pat. No. 5,512,
In 089, the pH is adjusted to between 9 and 12,
Improves redispersibility of dried ink.

Further, Japanese Patent Laid-Open No. 2000-212486 discloses a water-based ink for an ink jet printer using a general acrylic acid copolymer as a dispersant.
JP-A-269418 discloses an aqueous ink for an inkjet printer using a block polymer.
No. 87768 discloses water-based inks for inkjet printers using a graft polymer.

[0004]

However, as described above, in the ink for an ink jet printer which adjusts the pH and uses a general dispersant or a block polymer or a graft polymer, a low viscosity which enables high speed printing is obtained. However, it was not possible to satisfy the requirements for good balance and fine dispersion, and redispersibility for improving the reliability of the device.

Therefore, an object of the present invention is to provide an ink for an ink jet printer having a low viscosity and excellent redispersibility, thereby enabling stable operation of the ink jet printer for high speed printing.

[0006]

Means for Solving the Problems As a result of intensive studies on the above-mentioned objects, the present inventors have found that in an ink for an ink jet printer containing a pigment and a polymer compound, the polymer compound has a low temperature of 10 ° C. or lower. By using a material having a glass transition temperature and using a small amount of 0.1 to 3% by weight with respect to the total amount of the ink, the viscosity of the ink can be reduced, and the polymer compound It was found that the rate of dissolution in the solvent is increased and the redispersibility of the dried ink can be improved, which enables stable operation of the inkjet printer for high-speed printing.

The present invention is based on these findings.
It has been completed. That is, the present invention provides an ink for an ink jet printer containing a pigment and a polymer compound, wherein the polymer compound has a glass transition temperature of 10 ° C. or lower, and the polymer compound is contained in an amount of 0.1 to 0.1% based on the total amount of the ink. The present invention relates to an ink for an inkjet printer, which is in the range of 3% by weight.

Particularly, in the present invention, the ink having the above-mentioned constitution in which the polymer compound is a polymer compound having an alkyl ester structure in which the alkyl group has 8 to 32 carbon atoms, and the acid value of the polymer compound is 130 to 400 mgKOH. / G of the above-mentioned composition, the polymer compound having a weight-average molecular weight of 1,000 to 20,000, and the viscosity of 1 to 2 mPa · s. An ink having the above-mentioned constitution, which contains a water-soluble organic solvent as a solvent, and the water-soluble organic solvent is in the range of 1 to 30% by weight based on the total amount of the ink, Each,
Can be provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that a polymer compound having a glass transition temperature of 10 ° C. or lower is used in an amount of 0.1 to 3% by weight based on the total amount of ink. As a result, it becomes possible to obtain an ink for an ink jet printer which has a reduced viscosity of the ink and a fine dispersion of the pigment and is excellent in redispersibility. The preferred glass transition temperature of the polymer compound is −40 ° C. to 0 ° C., and the preferred usage amount is 0.
It is in the range of 15 to 2% by weight.

Such polymer compounds include acrylic, vinyl-based, polyester-based, polyurethane-based, epoxy-based and amino-based polymer compounds, and one or more of them may be used. Synthesis and acquisition of monomers,
Acrylic and vinyl polymer compounds are particularly preferred because of the ease of introduction of polar groups.

In an acrylic or vinyl polymer compound, as a structure for keeping the glass transition temperature below 10 ° C., an alkyl ester structure in which the alkyl group has 8 to 32 carbon atoms, particularly lauryl ester or stearyl. It is desirable to have an alkyl ester structure such as ester. As such a polymer compound, usually, one or more monomers having an alkyl ester structure in which the alkyl group has 8 to 32 carbon atoms, and one or two monomers having an acidic group are used. More than seeds,
Further, if necessary, these can be obtained by copolymerizing one or two or more kinds of other monomers copolymerizable therewith.

Examples of the monomer having an alkyl ester structure in which the alkyl group has 8 to 32 carbon atoms include, for example, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate and acryl. Examples thereof include lauryl acid salt, lauryl methacrylate, cetyl acrylate, cetyl methacrylate, stearyl acrylate, stearyl methacrylate, behenyl acrylate and behenyl methacrylate. The amount of these monomers used is 3 to 5 in all the monomers.
The range is 0% by weight, preferably 5 to 40% by weight. If it is less than 3% by weight, the interaction with the pigment becomes weak, and if it is more than 50% by weight, the hydrophobicity as a dispersant becomes high and the redispersibility of the ink becomes poor.

The above-mentioned monomer having an acidic group is used for enhancing the water solubility of the polymer compound and improving the redispersibility. Specifically, carboxyl groups such as acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic acid, fumaric acid, acroyloxyethyl phthalate, and acroyloxy succinate. Having a monomer, 2-ethyl acrylate acrylate, methacrylic acid 2
A monomer having a sulfonic acid group such as ethyl sulfonate, ethylacrylamide sulfonic acid, methacrylic acid 2
-Examples include monomers having a phosphonic acid group such as ethyl phosphonate and ethyl 2-phosphonate acrylate.
Among these, a monomer having a carboxyl group is preferable.

Other copolymerizable monomers mentioned above include methyl acrylate, ethyl acrylate, isopropyl acrylate, -n-propyl acrylate, -n-acrylic acid.
Butyl, tert-butyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, -n-propyl methacrylate, methacrylic acid-n-Bunal, isobutyl methacrylate, tert-butyl methacrylate, (Meth) acrylic acid esters such as tridecyl methacrylate and benzyl methacrylate; styrene, α-methylstyrene, o-methylsterene, m-methylsterene, p-methylstyrene, pt
styrene-based monomers such as rt-butylstyrene; vinyl acetate; α-olefins such as ethylene; itaconic acid esters such as benzyl itaconate; maleic acid esters such as dimethyl maleate; fumaric acid esters such as dimethyl fumarate; acrylonitrile, Methacrylonitrile, vinyl acetate; 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
Monomers having a hydroxyl group such as glycerol monomethacrylate, polyethylene glycol monomethacrylate, propylene glycol monomethacrylate, polyethylene glycol monoacrylate and propylene glycol monoacrylate; monomers having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate;
Methoxy group-containing monomers such as methoxy polyethylene glycol acrylate and methoxy polyethylene glycol methacrylate, acrylamide, methacrylamide, acrylic acid amide, aminoethyl acrylate, aminopropyl acrylate, methacrylic acid amide, aminoethyl methacrylate, aminopropyl methacrylate, etc. A monomer having a primary amino group, methylaminoethyl acrylate, methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropyl acrylate, methylaminoethyl methacrylate, methylaminopropyl methacrylate, ethylaminomethacrylate Monomers having secondary amino groups such as ethyl, ethiaminopropyl methacrylate, 2-vinylpyridine, 4-vinylpyridine, Acrylic acid dimethylaminoethyl, diethylaminoethyl acrylate, dimethylaminopropyl, acrylate diethylaminopropyl, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl,
Tertiary amino group-containing monomers such as diethylaminopropyl methacrylate, dimethylaminoethyl methyl chloride acrylate, dimethylaminoethyl methyl chloride methacrylate, dimethylaminoethyl benzyl acrylate, dimethylaminoethyl benzyl methacrylate And amino group-containing monomers such as quaternary amino group-containing monomers, and silicone-based monomers.

The copolymerization of these monomers is carried out by a known general polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method and a redox polymerization method. Among them, the solution polymerization method is particularly preferably used because the reaction operation is simple. In this solution polymerization method,
For example, the above-mentioned monomer may be dissolved in a solvent, and a catalyst may be added thereto to carry out a polymerization reaction at a temperature of 180 ° C or lower, preferably 30 to 150 ° C for 30 minutes to 40 hours, preferably 2 to 30 hours.

Examples of the above-mentioned solvent include aliphatic hydrocarbon solvents such as hexane and mineral spirit; aromatic hydrocarbon solvents such as benzene, toluene and xylene; ester solvents such as butyl acetate; alcohols such as methanol and butanol. Solvents; ketone solvents such as methyl ethyl ketone and isobutyl methyl ketone; dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone,
Examples include aprotic polar solvents such as pyridine, water and the like. Among these, it is preferable to use a water-soluble solvent because it can be used as it is as a solvent for ink. If necessary, two or more kinds of these solvents may be used in combination.

Examples of the above catalyst include organic peroxides such as t-butylperoxybenzoate, di-t-butylperoxide, cumene perhydroxide, acetylperoxide, benzoylperoxide and lauroylperoxide; azo. Bisisobutyl nitrile, azobis-2,4
-A known polymerization initiator such as an azo compound such as dimethylvaleronitrile or azobiscyclohexanecarbonitrile is used.

The thus obtained polymer compound having a glass transition temperature of 10 ° C. or lower has an acid value of 13
It is preferably in the range of 0 to 400 mg KOH / g, 1
More preferably, it is in the range of 50 to 350 mg KOH / g. If the acid value is less than 130 mgKOH / g, the solubility of the polymer compound in water will be weak and the redispersibility will be poor, and if it is more than 400 mgKOH / g, the interaction with the pigment will be weak and the dispersion stability will be poor. It becomes difficult to print at high speed due to deterioration of viscosity.

Further, such a polymer compound having a glass transition temperature of 10 ° C. or lower has a weight average molecular weight of 1,0.
It is preferably in the range of 00 to 20,000, and 1,5
It is more preferably in the range of 00 to 15,000, and most preferably in the range of 2,000 to 10,000. If the weight average molecular weight is less than 1,000, the ink film becomes sticky and color transfer occurs when the printed matter is overlaid, resulting in poor water resistance. If the weight average molecular weight is more than 20,000, the viscosity of the ink is high and high-speed printing property is high. Becomes worse.

The ink for an ink jet printer of the present invention usually uses water such as ion-exchanged water or pure water as a solvent, and the pigment is used in the solvent at 10 ° C. as a dispersant.
A polymer compound having the following glass transition temperature is used in the above proportion and is finely dispersed uniformly. An inorganic pigment, an organic pigment, a disperse dye or the like is used as the pigment. The content of the pigment is preferably in the range of 1 to 20% by weight, more preferably 2 to 10% by weight, based on the total amount of the ink. If the pigment is less than 1% by weight,
Ink is not practical because the color density is too low,
On the other hand, if it is more than 20% by weight, the viscosity becomes too high and printing cannot be performed.

Among the pigments, examples of the inorganic pigments include carbon black, titanium oxide, zinc white, zinc oxide, tribonite, iron oxide, aluminum oxide, silicon dioxide, kaolinite, montmorillonite, talc, barium sulfate and calcium carbonate. Silica, alumina, cadmium red, red iron oxide, molybdenum red, chrome vermillion, molybdate orange, yellow lead, chrome yellow, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, pyridian, cobalt green, titanium cobalt green, cobalt Chrome green, ultramarine,
Ultramarine blue, navy blue, cobalt blue, cerulean blue, manganese violet, cobalt violet, mica, etc. are used.

The organic pigments include azo type, azomethine type, polyazo type, phthalocyanine type, quinacridone type, anthraquinone type, indigo type, thioindigo type,
A quinophthalone-based pigment, a benzimidazolone-based pigment, an isoindoline-based pigment, an isoindolinone-based pigment, or the like is used. Furthermore, as disperse dyes, azo type, anthraquinone type,
Indigo type, phthalocyanine type, calponyl type, quinone imine type, methine type, quinoline type, nitro type dyes are used.

In addition to the polymer compound having a glass transition temperature of 10 ° C. or lower, another polymer compound may be used as the dispersant. These include polymer compounds for dispersing pigments and polymer compounds for improving print quality. The types of these polymer compounds include styrene-acrylic acid resin, stellene-maleic acid resin, acrylic resin, vinyl resin,
Examples thereof include acrylic emulsion and acrylic urethane resin.

In order to manufacture the ink jet printer ink of the present invention, it is necessary to disperse the pigment finely, and therefore the pigment is dispersed by a disperser. The disperser may be any commonly used disperser. Examples thereof include a container drive medium mill such as a roll mill, a ball mill, a centrifugal mill and a planetary ball mill, a high speed rotation mill such as a sand mill, or a medium stirring mill such as a stirring tank type mill.

As the dispersion medium used in the disperser, glass beads, steel beads, ceramic beads, etc. are used. Among these, it is preferable to use ceramic beads having a particle diameter of 0.01 to 1.0 mm. The dispersion conditions are not particularly limited, but it is preferable that the acceleration is 5 to 50 G in the planetary ball mill, the ceramic bead filling rate is 50 to 90% in the sand mill, and the peripheral speed is 5 to 20 m / sec.

In dispersing the pigment, the polymer compound having a glass transition temperature of 10 ° C. or lower as a dispersant is
It is preferable to neutralize this with a neutralizing agent in advance.
This neutralizer includes lithium hydroxide, sodium hydroxide,
Monovalent alkali metal ions such as potassium hydroxide, ammonia, triethylamine, triethanolamine,
Organic amines such as diethanolamine, ethanolamine and dimethylaminoethanol are used. In particular, a neutralizing agent that is less likely to volatilize is preferable because it can prevent clogging of the head when used in an inkjet ink.

In the ink jet printer ink of the present invention, a pigment is added to water as a solvent, a neutralized polymer compound having a glass transition temperature of 10 ° C. or lower as a dispersant, or a pigment dispersant and a general pigment dispersant. In that order,
In addition, water-soluble organic solvents, pH adjusters, surfactants, anti-clogging agents for print heads, ink defoamers, bactericides, anti-mold agents, water resistance imparting agents for printing, charge control agents, etc. Various additives that have been conventionally used in inks for inkjet printers are appropriately mixed and dispersed by a disperser until a desired particle size is obtained. In order to stabilize the dispersion liquid, the dispersion liquid may be further subjected to heat treatment at 40 to 100 ° C.

The water-soluble organic solvent is preferably used in order to suppress drying of the ink and to impart redispersibility in which the pigment is redispersed in the solvent after drying. The water-soluble organic solvent is
In the range of 1 to 30% by weight, preferably 2 to 20% by weight, more preferably 4 to 10% by weight, based on the total amount of the ink.
It should be in the range of. If the amount of the water-soluble organic solvent is too small, the effect of preventing clogging of the print head becomes insufficient, and if it is too large, the organic property of the solution becomes high, and problems such as impairing the dispersibility of the pigment are likely to occur.

As the water-soluble organic solvent, water-soluble polyhydric alcohol is preferable, and particularly ethylene glycol, diethylene glycol or glycerin is preferably used. As other water-soluble polyhydric alcohol, for example, triethylene glycol, tripropylene glycol, dimethylsulfoxide, diacetone alcohol, glycerin monoallyl ether, propylene glycol,
Polyethylene glycol, thiodiglycol, N-methyl-2-pyrrolidone, 2-pyrrolidone, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, sulfolane, trimethylolpropane, neopentyl glycol, ethylene glycol monomethyl Ether, ethylene glycol monoethyl ether, ethylene glycol
Monoisopropyl ether, ethylene glycol monoallyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, β-dihydroxy Ethyl urea, urea,
Acetonyl acetone, pentaerythritol, hexylene glycol, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monophenyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether. , Triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono Propi Ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, glycerin monoacetate, glycerin diacetate, glycerin triacetate, ethene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate, cyclohexanol, 1-butanol, 2,5- Hexanediol, ethanol, n-propanol, 2-propanol, 1-methoxy-2-propanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, 1,2-
Butanediol, 1,4-butanediol, 1,3-butanediol, 2,4-pentanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,2-cyclohexanediol, 1, 4-cyclohexanediol, trimethylolethane, trimethylolpropane, 1,2,4-butanetriol, 1,
2,6-hexanetriol, 1,2,5-pentanetriol, 3-methyl-1,5-pentanediol, 3
-Hexene-2,5-diol, polyethylene glycol, polypropylene glycol and the like.

As the pH adjuster, at least one selected from organic amines, water-soluble inorganic salts and hydroxides is used, and when the pH of the ink is adjusted within the range of 7 to 11, nozzle clogging is prevented. Is effective in. Organic amines include ammonia, monoethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, monomethylaminoethanol, dimethylaminoethanol, monoethylaminoethanol, diethylaminoethanol and the like. Water-soluble inorganic salts include sodium carbonate, calcium carbonate and the like. Examples of the water-soluble inorganic hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and the like.

The surfactant gives a good result in improving the printing stability. In particular, it is preferably used in a thermal type inkjet printer because it stably generates bubbles when heated by a heater. From the viewpoint of printing stability, it is preferable that the addition amount is in the range of 0.5 to 5% by weight based on the total amount of the ink.

Considering the above printing stability, as the surfactant, a water-soluble ionic surfactant or HLB is used.
It is preferable to use a nonionic surfactant having a valency of 12 or more. Such surfactants include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, etc., and particularly preferred are anionic surfactants or nonionic surfactants. Is.

Examples of the anionic surfactant include fatty acid salts such as sodium stearate soap, potassium oleate potassium soap, and semi-cured tallow fatty acid soda soap, sodium lauryl sulfate, triethanolamine lauryl sulfate, and higher alkyl alcohol sulfates such as sodium sulfate. Salts, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, alkylnaphthalenesulfonates such as sodium alkylnaphthalenesulfonate, alkylsulfosuccinates such as sodium dialkylsulfosuccinate, alkyldiphenyl ethers, etc. Alkyldiphenyl ethers Disulfonates, alkyl phosphates such as potassium alkyl phosphate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene acetate Polyoxyethylene alkyl sulfate ester salts such as kill sulfate triethanolamine, alkyl aryl sulfates such as polyoxyethylene alkyl phenyl ether sodium sulfate, polyoxyethylene alkyl phosphate esters, naphthalene sulfonic acid formalin condensates.

Examples of the cationic surfactant include alkylamine salts such as coconut amine acetate and stearyl amine acetate, lauryl trimethyl ammonium chloride, quaternary ammonium salts such as stearyl trimethyl ammonium chloride and alkylbenzyl dimethyl ammonium chloride, and lauryl betaine. And alkyl betaines such as stearyl betaine and amine oxides such as lauryl dimethyl amine oxide.

Nonionic surfactants having an HLB value of 12 or more include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether and polyoxyethylene higher alcohol ether. Polyoxyethylene alkyl ethers, polyoxyethylene octyl phenyl ethers, polyoxyethylene nonyl phenyl ethers and other polyoxyethylene alkyl allyl ethers, polyoxyethylene derivatives, oxyethylene / oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan Monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxye Ren sorbitan tristearate,
Polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate and other polyoxyethylene sorbitan fatty acid esters, tetraoleic acid polyoxyethylene sorbit and other polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, acetylene glycol and the like are used.

Examples of the defoaming agent include cationic surfactants such as alkylbenzene sulfonic acid type, alkyl sulfate ester type, fatty acid salt type and quaternary ammonium salt type, amphoteric surfactants such as alkyl betaine and amine oxide, and sorbitan. A fatty acid ester such as an acid ester type, a nonionic surfactant such as polyoxyethylene alkyl ether, an organic silicone type nonionic surfactant such as a methyl polysiloxane copolymer, and a silicone oil are used. In addition, sterilizing cracks and antifungal agents include benzoate,
Alkylamine salts, quaternary ammonium salts and the like are used.

The charge control agent is used to adjust the conductivity of the ink to an appropriate value in an ink jet printer of the type that applies a charge to the ink, but the required conductivity varies depending on the printer model, and The conductivity of the ink differs depending on the other components in the ink, and thus it is appropriately used as necessary. The electrolyte used for such a purpose includes, for example, inorganic salts such as ammonium chloride, sodium chloride, lithium nitrate, ammonium nitrate, ammonium thiocyanate, potassium thiocyanate, sodium thiocyanate, ammonium nitrite, lithium acetate, potassium acetate and ammonium acetate. , Triethanolamine hydrochloride, triethanolamine nitrate, triethanolamine sulfate, and the like.

In addition to the above-mentioned components, the ink for an ink jet printer of the present invention has the following properties:
It is preferable to add a resin as a component for improving the abrasion resistance. As the type of resin, there are water-soluble resin and dispersion type resin having an average particle diameter of 10 to 300 nm. Examples of the chemical structure of the resin include acrylic type, vinyl type, polyester type, amide type, and copolymers thereof. The addition amount of these resins is preferably in the range of 1 to 15% by weight, and more preferably in the range of 2 to 10% by weight, based on the viscosity and other characteristics, with respect to the total amount of the ink.

The ink composition for an ink jet printer of the present invention thus constructed preferably has a viscosity in the range of 1 to 2 mPa · s, particularly preferably 1.2 to 1.
It should be in the range of 8 mPa · s. Viscosity of 1 mPa
If it is smaller than s, it is necessary to use a large amount of volatile solvent inevitably, which is not preferable for the human body and the environment. If it exceeds 2 mPa · s, it becomes unsuitable for high-speed printing.

The ink for an ink jet printer of the present invention is not limited to the model as long as it is a commercially available ink jet system such as a piezo type, a thermal type, and a continuous type.
It can be applied to all printers. Among them, the effects of the present invention can be particularly exerted on a continuous circulation type printer. For example, JP-A-8-1
09343 and U.S. Pat. No. 4,255,754.
Even if it is applied to a printer such as described in the specification,
Good printing is possible.

[0041]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples. In the following, "part"
The terms "%" and "%" mean "parts by weight" and "% by weight" unless otherwise specified. In addition, in the following, all reagents that are not particularly described in terms of trade names and the like are reagents of the first grade manufactured by Wako Pure Chemical Industries.
Further, the polymer compounds A to D used in the examples were synthesized by the following synthesis examples.

Synthesis Example 1 The following components were mixed to prepare a monomer solution.     n-Butyl acrylate 57.9 parts     Lauryl methacrylate 20.0 parts     Acrylic acid 22.1 parts     Peroxy ester (“Perhexyl O” manufactured by NOF Corporation) 8.0 parts

Separately from this, 100 parts of isopropyl alcohol was weighed into a reaction vessel equipped with a nitrogen introducing tube, and the temperature was raised to 78 ° C. while sealing with nitrogen. The above-mentioned monomer solution was added dropwise thereto over 2 hours, and after completion of the addition, reaction was carried out at 78 ° C. for 14 hours. The solution after the reaction has an acid value of 170 mgKOH / g and a weight average molecular weight of 8,70.
It was a solution containing a polymer compound A having a glass transition temperature of −35 ° C. of 0 and a nonvolatile content of 51.1%. This was neutralized with ammonia by 115% and ion-exchanged water was replaced with isopropyl alcohol to prepare a 25% aqueous solution of polymer compound A.

Synthesis Example 2 The following components were mixed to prepare a monomer solution.     26.8 parts of n-butyl acrylate     Lauryl methacrylate 40.0 parts     Acrylic acid 33.2 parts     Azobisisobutyl nitrile 8.0 parts     Isopropyl alcohol 100.0 parts

Separately from this, 100 parts of isopropyl alcohol was weighed into a reaction vessel equipped with a nitrogen introducing tube, and the temperature was raised to the reflux temperature while sealing with nitrogen. The above-mentioned monomer solution was added dropwise to this over 2 hours, and after completion of the addition, reaction was carried out at reflux temperature for 14 hours. The solution after the reaction has an acid value of 256 mgKOH / g and a weight average molecular weight of 6,10.
It was a solution containing a polymer compound B having a glass transition temperature of −37 ° C. of 0 and a nonvolatile content of 33.1%. This was neutralized 115% with ammonia, and ion-exchanged water was replaced with isopropyl alcohol to prepare a 25% aqueous solution of polymer compound B.

Synthesis Example 3 The following components were mixed to prepare a monomer solution.     Ethyl acrylate 26.8 parts     2-ethylhexyl acrylate 40.0 parts     Acrylic acid 33.2 parts     Azobisisobutyl nitrile 8.0 parts     Isopropyl alcohol 100.0 parts

Separately from this, 100 parts of isopropyl alcohol was weighed into a reaction vessel equipped with a nitrogen introduction tube, and the temperature was raised to the reflux temperature while sealing with nitrogen. The above-mentioned monomer solution was added dropwise to this over 2 hours, and after completion of the addition, reaction was carried out at reflux temperature for 14 hours. The solution after the reaction has an acid value of 257 mgKOH / g and a weight average molecular weight of 5,80.
It was a solution containing a polymer compound C having a glass transition temperature of −20 ° C. of 0 and a nonvolatile content of 32.3%. This was neutralized 115% with ammonia, and ion-exchanged water was replaced with isopropyl alcohol to prepare a 25% aqueous solution of polymer compound C.

Synthesis Example 4 The following components were mixed to prepare a monomer solution.     n-Butyl acrylate 15.8 parts     Lauryl methacrylate 40.0 parts     Acrylic acid 44.2 parts     Azobisisobutyl nitrile 8.0 parts     Isopropyl alcohol 100.0 parts

Separately from this, 100 parts of isopropyl alcohol was weighed into a reaction vessel equipped with a nitrogen introducing tube, and the temperature was raised to the reflux temperature while sealing with nitrogen. The above-mentioned monomer solution was added dropwise to this over 2 hours, and after completion of the addition, reaction was carried out at reflux temperature for 14 hours. The solution after the reaction has an acid value of 342 mgKOH / g and a weight average molecular weight of 6,70.
It was a solution containing a polymer compound D having a glass transition temperature of -8 ° C and a nonvolatile content of 32.7%. This was neutralized with ammonia by 115% and ion-exchanged water was replaced with isopropyl alcohol to prepare a 25% aqueous solution of polymer compound D.

Example 1 Black pigment (“Printex 8 manufactured by Degussa”)
5 ") 20 parts, a commercially available dispersant (" John Kryl 62 "manufactured by Johnson Polymer Co., Ltd.) 14.3 parts, ion-exchanged water 6
With 5.7 parts and 2.5 parts of a wetting agent ("Surfinol 104" manufactured by Nissin Chemical Co., Ltd.) as a disperser, a particle size of 0.3 mm was obtained by "Dyno Mill KDL Special" manufactured by Shinmaru Enterprises. The zirconia beads of were dispersed for 2 hours to obtain a pigment dispersion. In this pigment dispersion liquid, the dispersed particle diameter of the pigment was 87 nm.

Next, 22.5 parts of this pigment dispersion was added with 4.5 parts of glycerin and the polymer compound A prepared in Synthesis Example 1.
Of 25% aqueous solution of 3.6 parts, 0.8 parts of sodium benzoate and 68.6 parts of ion-exchanged water were added. This was again mixed and dispersed by the above-mentioned disperser, and finally filtered by a membrane filter to prepare a black ink for an inkjet printer.

Comparative Example 1 25% aqueous solution of polymer compound A prepared in Synthesis Example 1.
Instead of 6 parts, a commercially available dispersant (“John Krill 62”)
Was used in the same manner as in Example 1 except that 3 parts was used and the ion-exchanged water when mixing the same was changed to 69.2 parts.
A black ink for inkjet printer was prepared.

Example 2 Black pigment (“Printex 8 manufactured by Degussa”)
5 ") instead of 20 parts, a copper phthalocyanine pigment (" Fastogen Blue manufactured by Dainippon Ink and Chemicals, Inc. "
TGR ") was used in the same amount, and instead of 3.6 parts of a 25% aqueous solution of the polymer compound A prepared in Synthesis Example 1, Synthesis Example 2 was used.
A cyan ink for an ink jet printer was prepared in the same manner as in Example 1 except that the same amount of the 25% aqueous solution of the polymer compound B prepared in 3) was used.

Example 3 Black pigment (“Printex 8 manufactured by Degussa”)
5 ”) instead of 20 parts, quinacridone pigment (“ Fastogen SuperMg ”manufactured by Dainippon Ink and Chemicals, Inc.)
enta RTS ") in the same amount, and instead of 3.6 parts of the 25% aqueous solution of the polymer compound A prepared in Synthesis Example 1, the same amount of the 25% aqueous solution of the polymer compound C prepared in Synthesis Example 3 is used. A magenta ink for an inkjet printer was prepared in the same manner as in Example 1 except that it was used.

Example 4 Black pigment (“Printex 8 manufactured by Degussa”)
5 ") in place of 20 parts, a monoazo yellow pigment (" Symuler FastYe "manufactured by Dainippon Ink and Chemicals, Inc.
flow 4190 ") in the same amount, and instead of 3.6 parts of the 25% aqueous solution of the polymer compound A prepared in Synthesis Example 1, the same amount of the 25% aqueous solution of the polymer compound D prepared in Synthesis Example 4 was used. A yellow ink for inkjet printer was prepared in the same manner as in Example 1 except that the yellow ink was used.

With respect to the inks for ink jet printers of Examples 1 to 4 and Comparative Example 1 described above, the particle size and viscosity of the pigment were measured by the following methods, and the redispersibility test and continuous operation test were performed. The results are as shown in Table 1.

<Measurement of Particle Size and Viscosity of Pigment> The particle size of the pigment was measured by "Laser Doppler type particle size distribution meter N4PLUS" manufactured by Coulter. Also, the viscosity is measured by "R type viscometer" manufactured by Toki Sangyo Co., Ltd. (rotation speed 100 rp
m)

<Redispersibility Test> The redispersibility was evaluated by dropping the ink on a slide glass, drying it in an oven at 60 ° C. for 30 minutes, and immersing it in ion-exchanged water. It was confirmed. The case where the particles were redispersed slowly was evaluated as ◯, and the case where the lumps were confirmed without redispersion was evaluated as ×.

<Continuous operation test> Continuous operation was carried out for 12 hours by using an inkjet printer manufactured by Domino.
One cycle of 2 hours rest was performed for 20 cycles, and when the operation did not start up smoothly or an error was displayed during the operation, the operation stop time was defined.

[0060]

As is clear from Table 1 above, the inks for ink jet printers of Examples 1 to 4 of the present invention were
Both have low viscosity and excellent redispersibility,
It is most suitable for high-speed type ink jet printers, and was continuously operated for 240 hours using a printer manufactured by Domino, but there was no problem. On the other hand, the ink for inkjet printers of Comparative Example 1 was inferior in redispersibility, and continuous operation was performed using a printer manufactured by Domino, but after 100 hours, the operation stopped and the continuous operation was stable. I was sexually charged.

[0062]

As described above, in the present invention, by using a specific amount of a polymer compound having a glass transition temperature of 10 ° C. or less as a dispersant for a pigment, a low viscosity and excellent redispersibility are exhibited. It is possible to provide an ink for an inkjet printer that enables stable operation of the inkjet printer for high-speed printing.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miyuki Nishimura             Hitachima, 1-88, Torora, Ibaraki City, Osaka Prefecture             Within Kucsel Co., Ltd. F-term (reference) 2C056 FC02                 2H086 BA53 BA59 BA60 BA61                 4J039 AD01 AD03 AD08 AD09 AD10                       AD11 AD12 AD20 AE04 AE05                       AE06 BA04 BA12 BC39 BC60                       BE01 BE12 CA06 DA02 EA44                       GA24

Claims (7)

[Claims] 1. An ink for an ink jet printer containing a pigment and a polymer compound, wherein the polymer compound has a glass transition temperature of 10 ° C. or lower, and the polymer compound is 0.1 to 3 with respect to the total amount of the ink. Ink for an ink jet printer characterized by being in the range of wt%. 2. The ink for an ink jet printer according to claim 1, wherein the polymer compound is a polymer compound having an alkyl ester structure in which an alkyl group has 8 to 32 carbon atoms. 3. The polymer compound has an acid value of 130 to 400.
The ink for an inkjet printer according to claim 1, which is in a range of mgKOH / g. 4. The polymer compound has a weight average molecular weight of 1,
The ink for an inkjet printer according to any one of claims 1 to 3, which is in a range of 000 to 20,000. 5. The ink for an ink jet printer according to claim 1, which has a viscosity in the range of 1 to 2 mPa · s. 6. The ink for an inkjet printer according to claim 1, which contains a water-soluble organic solvent as a solvent, and the water-soluble organic solvent is in the range of 1 to 30% by weight based on the total amount of the ink. 7. The ink for an ink jet printer according to claim 1, wherein the ink jet printer is of a continuous circulation type.