JP2003253170A - Ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition which has a good covering property of a transparent film and can realize good setting stability favorable for an inkjet recording process. <P>SOLUTION: The ink composition essentially consists of at least 5 wt.% titanium oxide as a colorant, a controlled-pH resin prepared by neutralizing a copolymer of an acid value of at most 40 obtained by polymerizing an ethylenically unsaturated carboxylic acid monomer with other monomers copolymerizable therewith in the presence of a water-soluble alcoholic-hydroxyl- containing polymer compound or a copolymerizable surfactant with an inorganic base, and water. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an ink composition, particularly to an ink composition used in an inkjet recording method.

[0002]

2. Description of the Related Art An ink jet recording method is a recording method in which droplets of ink are ejected and adhered to a recording medium such as paper for printing. This ink jet recording method has a feature that an image with high resolution and high quality can be printed at high speed. The ink composition used in the ink jet recording method generally contains a water-soluble solvent as a main component, and further contains a coloring material component and a wetting agent such as glycerin for the purpose of preventing clogging.

Glass using the ink jet recording method,
Various ink compositions for printing on recording media such as metals and plastics have been proposed so far. For example, in JP-A-6-57188, a colorant, an electrolyte complex of 2-hydroxycarboxylic acid and a resin should be contained. Discloses that adhesion to a recording medium can be improved.

Further, Japanese Patent Application Laid-Open No. 11-343443 discloses an ink composition containing titanium oxide having an isoelectric point higher than the pH of the ink, resin particles, a binder, and water. According to the formulation, the redispersibility of titanium oxide is improved, and it is possible to achieve both hiding power and redispersibility.
Further, JP-A-8-113746 discloses an ink composition containing titanium dioxide, a binder and an aqueous carrier, which is suitable for recording on foods by an inkjet recording method.

Various proposals have also been made for ink compositions and recording methods in which titanium dioxide can be used as a colorant. For example, in Japanese Patent Laid-Open No. 216379/1990, a component which is polymerized by application of ultraviolet rays is contained. Ink compositions are disclosed. Regarding the recording method, a recording method has been proposed in which printing is performed on a recording medium by using two liquids of an ink composition containing a colorant and a reaction liquid containing a polymerization initiator. (For example, JP-A-5-186725) However, in the conventional ink compositions using titanium oxide as a colorant, in order to obtain fixability on a recording medium, a resin as a binder is used with respect to titanium oxide. It was necessary to add a large amount and additional means (such as ultraviolet irradiation) after printing. If the amount of resin component in the ink increases, there are problems that the viscosity of the ink increases, the drying near the nozzle of the inkjet head progresses, and the ejection stability deteriorates.

[0006]

DISCLOSURE OF THE INVENTION The inventor of the present invention uses various kinds of water-based ink compositions containing titanium oxide as a colorant and a binder resin as described above, which are required for various ink compositions for ink jet recording methods. While maintaining the characteristics (for example, ejection stability, storage stability, color developability (hiding property)), there is no need for post-treatment such as UV irradiation or heat treatment after printing, and recording media (especially OHP sheet-like As a result of intensive studies on means for improving the abrasion resistance to a transparent recording medium), it was found that the above problem can be solved by containing a specific resin in the ink composition. The present invention is based on these findings.

[0007]

Accordingly, the ink composition of the present invention contains at least 5% by weight of titanium oxide as a colorant, and is capable of being copolymerized with an ethylenically unsaturated carboxylic acid monomer and the same. Prepared by neutralizing with an inorganic base a copolymer having an acid value of 40 or less obtained by polymerizing other monomer in the presence of a water-soluble polymer compound containing an alcoholic hydroxyl group or a copolymerizable surfactant. It is characterized by containing the pH adjusting resin and water.

Further, in the ink composition of the present invention, the weight ratio of the pH adjusting resin (a) and the titanium oxide (b) in the ink composition is a / b = 0.05 to solid basis.
It is preferably 0.3. The weight ratio a / b (solid content conversion) of the pH adjusting resin (a) and the titanium oxide (b) was 0.
When it is less than 05, sufficient fixability to the print medium may not be obtained, and when the weight ratio a / b is 0.3 or more, printing stability may be deteriorated.

Further, the ink composition of the present invention is characterized in that the inorganic base used for the preparation of the resin is an alkali metal hydroxide or an alkaline earth metal hydroxide.

Further, the ink composition of the present invention is characterized in that the alcoholic hydroxyl group-containing water-soluble polymer compound used in the preparation of the resin is a vinyl alcohol polymer.

In the ink composition of the present invention, the ethylenically unsaturated carboxylic acid monomer used for preparing the resin is
It is characterized by being acrylic acid or methacrylic acid.

In the ink composition of the present invention, the monomer copolymerizable with the ethylenically unsaturated carboxylic acid monomer used for preparing the resin is an ethylenically unsaturated carboxylic acid ester monomer. It is characterized by being.

The ink composition of the present invention is preferably for inkjet recording.

The present invention is also an inkjet recording method for printing on a recording medium by the inkjet recording method using the above-mentioned ink composition.

Further, the present invention is a recorded matter formed on a recording medium by an ink jet recording method using the above ink composition.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Titanium oxide contained in the ink composition used in the present invention includes TiO _{2 which} is generally used as a pigment. TiO ₂ can be classified into rutile type, anatase type, brookite type and the like depending on the difference in crystal structure. The TiO ₂ used in the ink composition of the present invention may be any of those belonging to any of the above categories, preferably rutile type and anatase type.

According to a preferred embodiment of the present invention, titanium oxide is preferably added to the ink composition as a titanium oxide dispersion obtained by dispersing it in an aqueous medium with a dispersant or a surfactant.

Examples of the dispersant which can be used in the ink composition used in the present invention include a dispersant which is commonly used for preparing a pigment dispersion, for example, a polymer dispersant, and a surfactant which is used as the dispersant. Examples include various anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants described below.

Preferred examples of the polymer dispersant include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein and albumin, natural gums such as gum arabic and tragacanth, and saponin. Glucosides, alginic acid and propylene glycol alginate, alginate triethanolamine, alginate derivatives such as ammonium alginate, methyl cellulose, carboxymethyl cellulose,
Examples thereof include cellulose derivatives such as hydroxyethyl cellulose and ethyl hydroxycellulose. Furthermore,
Synthetic polymers are mentioned as preferred examples of the polymer dispersant, and polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylic nitrile copolymers, potassium acrylate-acrylonitrile copolymers, vinyl acetate- Acrylic ester copolymer, acrylic resin such as acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, Styrene-acryl resin such as styrene-α-methylstyrene-acrylic ester copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid Copolymer, and vinyl acetate-ethylene copolymer Vinyl acetate-based copolymers such as polymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, vinyl acetate-acrylic acid copolymer and the like Examples include salt. Among these, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer composed of a monomer having both a hydrophobic group and a hydrophilic group in the molecular structure are preferable.

The particle size of titanium oxide used in the ink composition of the present invention is preferably 10 μm or less,
It is more preferably 1 μm or less, further preferably about 0.1 to 0.5 μm.

The addition amount of titanium oxide in the ink composition of the present invention is preferably 5% by weight or more, preferably in the range of 5 to 50% by weight, and more preferably in the range of 5 to 30% by weight. The amount of titanium oxide added is 5% by weight
In the following cases, sufficient hiding property may not be obtained when printed on a recording medium.

The ink composition used in the present invention is
An acid value obtained by polymerizing an ethylenically unsaturated carboxylic acid monomer and another monomer copolymerizable therewith in the presence of an alcoholic hydroxyl group-containing water-soluble polymer compound or a copolymerizable surfactant. It further contains a pH adjusting resin obtained by neutralizing a copolymer of 40 or less with an inorganic base.

The alcoholic hydroxyl group-containing water-soluble polymer compound used in the production of the above-mentioned pH-adjusting resin includes, for example, 5 to 25 alcoholic hydroxyl groups per 1,000 molecular weight among the water-soluble polymer compounds. A compound refers to a vinyl alcohol polymer such as polyvinyl alcohol and various modified products thereof; a saponification product of a copolymer of vinyl acetate and acrylic acid, methacrylic acid or maleic anhydride; alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxy Cellulose and other cellulose derivatives; alkyl starch, carboxymethyl starch, oxidized starch and other starch derivatives; gum arabic, tragacanth gum, polyalkylene glycol and the like. Among them, vinyl alcohol-based polymers are preferable from the viewpoint of easy availability of industrially stable products.

The weight average molecular weight of the alcoholic hydroxyl group-containing water-soluble polymer compound is not particularly limited, but is usually 1.
000 to 500,000, preferably 2,000 to 30
It is 000. If the molecular weight is less than 1,000, the dispersion stabilizing effect may be reduced, and conversely 500,000.
When it is larger, the viscosity becomes high when polymerizing in the presence of this polymer compound, and the polymerization may become difficult.

The amount of the alcoholic hydroxyl group-containing water-soluble polymer compound used in the production of the pH adjusting resin is the monomer 1
It is usually 0.05 to 20 parts by weight, preferably 1 to 10 parts by weight, relative to 00 parts by weight. If the amount is less than 0.05 parts by weight, the effect of stabilizing the dispersion becomes low, so that an aggregate is generated during the polymerization, and if it is more than 20 parts by weight, the viscosity becomes high during the polymerization, which may make the polymerization difficult. .

In the production of the pH adjusting resin, it is preferable not to use a surfactant which is usually used in emulsion polymerization, but when the surfactant is used in combination, the amount of the surfactant is not limited to the alkali-soluble co-polymerization. It is usually less than 0.05 parts by weight to 100 parts by weight of all the monomers used for the synthesis of the combined product. When the amount of the surfactant is large, the water resistance of the obtained image tends to be poor.

The ethylenically unsaturated carboxylic acid monomer used in the production of the pH adjusting resin is not particularly limited, and examples thereof include ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; itaconic acid, maleic acid and fumaric acid. Ethylenically unsaturated polycarboxylic acid monomer such as acid and butenetricarboxylic acid; Monoester partial ester of ethylenically unsaturated polycarboxylic acid such as monobutyl fumarate, monobutyl maleate and mono-2-hydroxypropyl maleate Body; polyvalent carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride and the like can be mentioned. These monomers can be used alone or in combination of two or more kinds. Among these ethylenically unsaturated monomers, ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid are preferable, and methacrylic acid is more preferable.

The amount of the ethylenically unsaturated carboxylic acid monomer used is such that the acid value of the pH adjusting resin is 40 or less, and preferably 10 to 10.
40, and more preferably an amount calculated to be 30-40. Converting this amount, if the acid value of the alkali-soluble copolymer exceeds 40 or becomes less than 10,
The quality of the obtained image may be inferior.

Other monomers copolymerizable with the ethylenically unsaturated carboxylic acid monomer that can be used for producing the pH adjusting resin are not particularly limited, and examples thereof include styrene, α-methylstyrene, Aromatic vinyl monomers such as vinyltoluene and chlorostyrene; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, ( (Meth) acrylic acid-n-amyl, (meth) acrylic acid isoamyl, (meth) acrylic acid-n-hexyl, (meth) acrylic acid-2-ethylhexyl, (meth) acrylic acid-n-octyl, (meth) acrylic Acid-2-
Ethylenically unsaturated carboxylic acid ester monomers such as hydroxyethyl, hydroxypropyl (meth) acrylate and glycidyl (meth) acrylate; Ethylenically unsaturated nitrile monomers such as (meth) acrylonitrile; Allyl glycidyl ether Ethylenically unsaturated glycidyl ether monomer of (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl, (meth) acrylamide and the like ethylenically unsaturated amide monomer; 1,3-butadiene, Isoprene, 2,3-dimethyl
Examples thereof include conjugated diene monomers such as -1,3-butadiene and 1,3-pentadiene; carboxylic acid vinyl esters such as vinyl acetate. Among them, the ethylenically unsaturated carboxylic acid ester monomer is preferable, and methyl methacrylate and ethyl acrylate are more preferable, from the viewpoint of excellent light resistance and glossiness of the obtained image.

The pH adjusting resin can be obtained by polymerizing the above-mentioned monomer mixture, preferably in an aqueous medium, in the presence of an alcoholic hydroxyl group-containing water-soluble polymer compound. At this time, the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer mixture are added to the reactor all at once before the start of the polymerization, or a part of the mixture is charged before the start of the polymerization and the remaining amount after the start of the polymerization. The portions can be added in portions in portions or the rest can be added continuously. In the case of divided addition or continuous addition, the addition amount may be uniform or constant, and may be changed according to the stage of progress of polymerization.

The alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer mixture can be obtained by mixing the alcoholic hydroxyl group-containing water-soluble polymer compound, the monomer mixture and water, even if they are added separately. It may be added in the form of a monomer dispersion. When the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer are added separately, it is desirable to start the addition of both at substantially the same time. Aggregates tend to occur when only a large amount of the monomer mixture is added first,
On the contrary, when only a large amount of the alcoholic hydroxyl group-containing water-soluble polymer compound is added, problems such as increase in viscosity of the polymerization system and easy occurrence of aggregates are likely to occur. After the addition of both is not necessarily simultaneous, it is desirable that they are almost simultaneous.

Among the methods for adding the alcoholic hydroxyl group-containing water-soluble polymer compound and the monomer mixture, the alcoholic hydroxyl group-containing water-soluble polymer compound is mixed with the monomer mixture and water to disperse, and after the initiation of polymerization, The method of adding to the reactor is preferable because the chain distribution of the ethylenically unsaturated acid monomer in the polymer chain of the pH adjusting resin becomes uniform.

The pH-adjusting resin is obtained by polymerizing (preferably emulsion polymerization) an ethylenically unsaturated carboxylic acid monomer and another monomer copolymerizable therewith in the presence of a copolymerizable surfactant. Can be manufactured.

The copolymerizable surfactant is a surfactant having at least one polymerizable vinyl group in its molecule.
Specific examples thereof include propenyl-2-ethylhexyl sulfosuccinate sodium salt, (meth) acrylic acid polyoxyethylene sulfate ester, polyoxyethylene alkylpropenyl ether sulfate ammonium salt, (meth) acrylic acid polyoxyethylene ester phosphate ester, and the like. Examples of the anionic polymerizable surfactants include nonionic polymerizable surfactants such as polyoxyethylene alkylbenzene ether (meth) acrylic acid ester and polyoxyethylene alkyl ether (meth) acrylic acid ester. Among these copolymerizable surfactants, polyoxyethylene alkylpropenyl ether ammonium sulfate is preferable because it has an excellent emulsion-dispersion performance of monomers and copolymerizability with monomers.

The amount of copolymerizable surfactant is usually 0.01 to 5.0 parts by weight, preferably 0.05 to 5.0 parts by weight, based on 100 parts by weight of all the monomers used for the synthesis of the pH adjusting resin.
The amount is 5.0 parts by weight, more preferably 0.1 to 3.0 parts by weight. If it is less than 0.01 part by weight, the emulsion stability will be low, and a large amount of aggregates may be generated during the polymerization. On the other hand, when it exceeds 5.0 parts by weight, the resin composition may easily foam. In addition, in the pH adjusting resin, it is preferable not to use the non-polymerizable surfactant together, but when the non-polymerizable surfactant is used in combination, the amount of the non-polymerizable surfactant is used for the synthesis of the pH adjusting resin. It is usually less than 0.05 parts by weight with respect to 100 parts by weight of all the monomers. When the amount of the non-polymerizable surfactant is large, the water resistance of the obtained image tends to be poor.

The polymerization initiator that can be used for producing the pH adjusting resin is not particularly limited. Specific examples thereof include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide;
Diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl peroxide, isobutyryl peroxide, benzoyl-peroxide Examples thereof include organic peroxides such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and azo compounds such as methyl azobisisobutyrate. These initiators can be used alone or in combination of two or more. Of these, persulfates such as potassium persulfate and ammonium persulfate are preferable.

The amount of the polymerization initiator used varies depending on the kind thereof, but is preferably 0.5 to 5 parts by weight, based on 100 parts by weight of all the monomers used in the production of the aqueous dispersion of the pH adjusting resin. It is more preferably 0.8 to 4 parts by weight.

Further, these polymerization initiators can be used as a redox polymerization initiator in combination with a reducing agent.

The reducing agent for the redox type initiator is not particularly limited, and specific examples thereof include compounds containing a metal ion in a reduced state such as ferrous sulfate and cuprous naphthenate;
Examples thereof include sulfonic acid compounds such as sodium methanesulfonate; amine compounds such as dimethylaniline.

These reducing agents can be used alone or in combination of two or more.

The amount of the reducing agent used varies depending on the reducing agent, but is preferably 0.03 to 10 parts by weight with respect to 1 part by weight of the polymerization initiator.

In order to adjust the weight average molecular weight of the pH adjusting resin, a chain transfer agent can be used at the time of polymerization, if necessary. Examples of chain transfer agents include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan; α-methylstyrene dimer; sulfides such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide; 2-methyl-3-butynenitrile, 3-pentenenitrile Nitrile compounds such as; thioglycolic acid esters such as methyl thioglycolate, propyl thioglycolate and octyl thioglycolate; β-mercaptopropionic acid esters such as methyl β-mercaptopropionate and octyl β-mercaptopropionate These can be used alone or in combination of two or more. Among these chain transfer agents, thioglycolic acid ester is preferable, and octyl thioglycolic acid is more preferable.

When a chain transfer agent is used, its addition amount is usually 0.1 to 5 parts by weight, preferably 0.5 to 100 parts by weight of the monomer used for producing the pH adjusting resin.
~ 4 parts by weight. If the amount of the chain transfer agent used is too small, the viscosity after neutralization may be high and handling may be difficult, and if it is too large, the molecular weight may be significantly reduced. The method of adding the chain transfer agent is not particularly limited,
The whole amount may be added all at once, or may be added to the polymerization system in small portions intermittently or continuously.

The polymerization temperature for producing the pH adjusting resin is
Usually, it is 0 to 100 ° C, preferably 30 to 90 ° C.
The polymerization conversion rate is usually 90% by weight or more, preferably 95% by weight or more.

The neutralization degree in the neutralized product of the pH adjusting resin used in the present invention (the molar equivalent of the inorganic base to the molar equivalent of the ethylenically unsaturated carboxylic acid monomer) is not particularly limited, but the neutralization degree is 70. % Or more, preferably 95% or more.

The inorganic base used for neutralizing the pH adjusting resin is not particularly limited, but examples thereof include hydroxides of alkaline earth metals such as sodium hydroxide and potassium hydroxide; calcium hydroxide, Examples thereof include hydroxides of alkaline earth metals such as magnesium hydroxide, and these can be used alone or in combination of two or more kinds. Of these inorganic bases, sodium hydroxide is preferred. Ammonia can also be used as the inorganic base, but this may cause deterioration in the temporal stability (for example, pH decrease) and the ejection stability of the ink.

As the pH adjusting resin used in the present invention, among the above-mentioned ones, those obtained by polymerization in the presence of the alcoholic hydroxyl group-containing water-soluble polymer compound are viscosity-changeable during long-term storage of the resin composition. It is preferable in that it is difficult to do.

The weight average molecular weight of the resin used in the present invention is
Although not particularly limited, if it is too large (for example, if it exceeds 50,000), the viscosity of the aqueous resin solution becomes high, and its handling may be difficult. on the other hand,
If it is too low (for example, less than 8,000), the abrasion resistance may deteriorate. The weight average molecular weight of the resin is preferably 8,000 or more, more preferably 9,000 to 10
10,000, more preferably 10,000 to 50,000
It is 0.

The glass transition temperature of the resin used in the present invention is
Although it can be set arbitrarily, it is preferably 5 to 50 ° C, more preferably 20 to 40 ° C. When the glass transition temperature of the resin is within this range, an image excellent in bending resistance and blocking resistance can be obtained. In addition, even if the glass transition temperature of the resin used in the present invention is somewhat high, the film forming temperature of the ink composition of the present invention is generally kept low.

In the ink composition of the present invention, the resin is
Usually, it is used in the state of an aqueous solution. In this case, the solid content concentration is usually 1 to 40% by weight, preferably 20 to 30% by weight. This aqueous solution may contain a water-soluble organic solvent described later.

In the resin used in the present invention, the amount of the pH adjusting resin used is, in terms of solid content, preferably 0.02 to 2, more preferably 0.05 to 2 by weight ratio with respect to the solid content of the colorant. 1, particularly preferably 0.05 to 0.3.

The pH adjusting resin which can be used in the present invention can be added to the ink in the form of any of water-soluble resin, resin emulsion and polymer fine particles.

According to a preferred embodiment of the ink composition usable in the present invention, it is desirable that the ink composition contains a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, n-propyl alcohol, is
o-propyl alcohol, n-butanol, sec-butanol, tert-butanol, iso-butanol, n-pentanol, ethylene glycol, propylene glycol, diethylene glycol, pentamethylene glycol, trimethylene glycol, 2-butyne-
1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, 2- Pyrrolidone, glycerin, tripropylene glycol monomethyl ether, dipropylene glycol monoethyl glycol, dipropylene glycol monomethyl ether, dipropylene glycol, triethylene glycol monomethyl ether, tetraethylene glycol, triethylene glycol, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, Diethylene glycol monomethyl ether and the like can be mentioned.

In the ink composition of the present invention, when the water-soluble organic solvent is used, the content thereof is preferably about 10 to 40% by weight, more preferably 10 to 20% by weight based on the total weight of the ink composition. % By weight.

The ink composition of the preferred embodiment of the present invention is
Further, a surfactant can be contained. The surfactant used in the present invention is one or more surfactants selected from the group consisting of anionic surfactants, nonionic surfactants, and amphoteric surfactants.

Examples of the surfactant include anionic surfactants (for example, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, ammonium salt of polyoxyethylene alkyl ether sulfate, etc.), nonionic surfactants (for example, polyoxy). Ethylene alkyl ether, polyoxyethylene alkyl ester,
Polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, etc.) and acetylene glycol. These may be used alone or in combination of two or more.

Further, the ink composition according to the preferred embodiment of the present invention contains a tertiary amine as a pH adjusting agent.

Examples of the tertiary amine that can be added to the ink composition according to the present invention include trimethylamine, triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, triisopropanolamine, butyldiethanolamine and the like.
These may be used alone or in combination. The amount of these tertiary amines added to the ink composition of the present invention is
It is 0.1 to 10% by weight, and more preferably 0.5 to 5% by weight.

Further, the ink composition according to the present invention may contain a penetration enhancer, a sugar, and / or an alginic acid derivative.

Examples of the penetration enhancer include alkyl ether derivatives of polyhydric alcohols having 3 or more carbon atoms, such as diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and the like. And one or more of these can be used.

Examples of sugars include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose. , Aldonic acid, glucitol, (Sorbit),
Maltose, cellobiose, lactose, sucrose,
Examples thereof include trehalose and maltotriose. Here, the term "polysaccharide" means a sugar in a broad sense, and is meant to include substances widely existing in nature such as alginic acid, α-cyclodextrin, and cellulose. Examples of derivatives of these saccharides include reducing sugars [(for example, sugar alcohol (general formula HOCH ₂ (C
HOH) _n CH ₂ OH (where n represents an integer of 2 to 5)], oxidized sugar (eg, aldonic acid, uronic acid, etc.), amino acid, thiosugar and the like. Sugar alcohols are particularly preferable, and specific examples thereof include maltitol and sorbit. The addition amount of these sugars is preferably about 0.1 to 40% by weight,
More preferably, it is about 1 to 30% by weight. Preferable examples of the alginic acid derivative include alkali metal alginate salts (for example, sodium salt and potassium salt), organic alginate salts (for example, triethanolamine salt), ammonium alginate salt and the like. The amount of the alginic acid derivative added to the ink composition is preferably about 0.01 to 1% by weight, more preferably 0.0 to 1% by weight.
It is about 5 to 0.5% by weight.

In addition, an antiseptic, a fungicide, and / or a phosphoric acid-based antioxidant may be added to the ink composition of the present invention, if necessary.

The ink composition of the present invention can be prepared by a conventional method, for example, by dispersing and mixing the above-mentioned components by an appropriate method. Preferably, first, a pigment (titanium oxide), a polymer dispersant, and ion-exchanged water are dispersed in a suitable disperser (for example, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, Jet mill, ong mill, etc.) to prepare a uniform pigment dispersion. Then, p
An H-adjusted resin solution, ion-exchanged water, a water-soluble organic solvent, a preservative, and / or a fungicide are sufficiently stirred at room temperature to prepare an ink solvent. While the ink solvent is being stirred by a suitable disperser, the pigment dispersion is gradually added and sufficiently stirred. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove coarse particles and foreign matters that cause clogging.

(Examples) The present invention will be described in more detail with reference to the following examples, but these do not limit the scope of the present invention. In the examples, "%" and "parts" are based on weight unless otherwise specified. Further, the acid value of the copolymer obtained in the following preparation example is JIS K 0070.
It was measured according to.

<Preparation of Resin><Preparation Example 1> 60 parts of ethyl methacrylate, 36 parts of methyl methacrylate, 4 parts of methacrylic acid, 3 parts of octyl thioglycolate as a molecular weight modifier, 1 part of polyvinyl alcohol and 280 ion-exchanged water. The parts were mixed by stirring to prepare a dispersion of the monomer mixture.

In another reactor equipped with a stirrer, 1 ion-exchanged water was added.
30 parts and 2 parts of potassium persulfate were charged, the temperature was raised to 80 ° C., and the dispersion of the monomer mixture was continuously added over 4 hours to polymerize. After the continuous addition, at 80 ℃,
The reaction was carried out for 30 minutes. The polymerization conversion rate was 99% or more. Next, 10% sodium hydroxide aqueous solution in an amount corresponding to the charged methacrylic acid and an equimolar amount of sodium hydroxide was added to the reactor, and after further heat treatment at 80 ° C. for 1 hour, an appropriate amount of ion-exchanged water was added. In addition, solid content concentration 1
A 5% resin solution A was obtained. The acid value of this resin solution A is 30
Met.

Preparation Example 2 56 parts of ethyl acrylate, 36 parts of methyl methacrylate, 8 parts of methacrylic acid, 3 parts of octyl thioglycolate as a molecular weight modifier, 2.5 parts of sodium lauryl sulfate and 80 parts of ion-exchanged water. Stir-mixed to prepare a dispersion of the monomer mixture.

Into another reactor equipped with a stirrer, 90 parts of ion-exchanged water in which 0.05 part of ethylenediaminetetraacetic acid was dissolved was heated, and the temperature was raised to 80 ° C.
After adding 1 part, the dispersion of the monomer mixture was continuously added and polymerized for 2 hours. 80 ° C after continuous addition
The reaction was carried out for 30 minutes. The polymerization conversion rate was 99% or more.

Then, 2 parts of 28% aqueous ammonia solution and 5% aqueous 5% sodium persulfate solution in an amount corresponding to the charged methacrylic acid and an equimolar amount of ammonia were added to the reactor and further treated at 80 ° C. for 1 hour. After that, an appropriate amount of ion-exchanged water was added to obtain a resin solution B having a solid content of 25%. The acid value of this resin solution B was 50.

<Preparation of Ink> A pigment (titanium dioxide), a dispersant, and water are mixed, and glass beads (diameter 1.7 mm, 1.5 times amount (weight) of the mixture) in a sand mill (Yasukawa Seisakusho) are mixed. After dispersing for 2 hours together, the glass beads were removed to prepare a pigment dispersion.

Next, titanium dioxide and a solvent excluding a dispersant are mixed to make an ink solvent, and the above ink solvent is mixed with the titanium dioxide dispersion and the resin solution A or B prepared in the above Preparation Example while stirring. Gradually drop it at room temperature for 2
Stir for 0 minutes. It was filtered with a membrane filter of 5 μm to obtain an ink for inkjet recording.

[0072] <Example 1> Titanium dioxide 5% by weight Styrene-acrylic acid copolymer (dispersant) 1% by weight Resin solution A (solid content 15%) 10% by weight Triethylene glycol monobutyl ether 5% by weight Olfine E-1010 3% by weight Glycerin 10% by weight Deionized water remaining Weight ratio: a / b = 0.3 (Solid content conversion: a: pH adjusting resin, b: titanium dioxide)

[0073] <Example 2> Titanium dioxide 20% by weight Styrene-acrylic acid copolymer (dispersant) 1% by weight Resin solution A 6.67% by weight Triethylene glycol monobutyl ether 5% by weight Olfine E-1010 3% by weight Glycerin 10% by weight Deionized water remaining Weight ratio: a / b = 0.05

[0074] <Example 3> Titanium dioxide 15% by weight Styrene-acrylic acid copolymer (dispersant) 1% by weight Resin solution A 40% by weight Triethylene glycol monobutyl ether 5% by weight Olfine E-1010 3% by weight Glycerin 10% by weight Deionized water remaining Weight ratio: a / b = 0.4

[0075] <Example 4> Titanium dioxide 5% by weight Styrene-acrylic acid copolymer (dispersant) 1% by weight Resin solution A 1.34% by weight Triethylene glycol monobutyl ether 5% by weight Olfine E-1010 3% by weight Glycerin 10% by weight Deionized water remaining Weight ratio: a / b = 0.04

[0076] <Comparative Example 1> Titanium dioxide 5% by weight Styrene-acrylic acid copolymer (dispersant) 1% by weight Resin solution B (solid content 25%) 6 weight % Triethylene glycol monobutyl ether 5% by weight Olfine E-1010 3% by weight Glycerin 10% by weight Deionized water remaining Weight ratio: a / b = 0.3

[0077] <Comparative example 2> Titanium dioxide 4% by weight Styrene-acrylic acid copolymer (dispersant) 1% by weight Resin solution B 2% by weight Triethylene glycol monobutyl ether 5% by weight Olfine E-1010 3% by weight Glycerin 10% by weight Deionized water remaining Weight ratio: a / b = 0.125

<Print Evaluation> Print evaluation was performed using each of the ink compositions prepared in the above Examples and Comparative Examples. Inkjet printer (EM-930C
(Seiko Epson Corp.) was used to print on a transparent OHP sheet.

<Evaluation 1><Evaluation of rubbing resistance (evaluation by rubbing with a finger)> At 1 hour after printing, the surface of the printed recording medium was rubbed with a finger to remove rubbing resistance by peeling the coloring material. It was judged visually. The evaluation criteria are as follows. A: There is no peeling of the coloring material. B: There is slight peeling of the coloring material (less than 20% of the entire coloring material). C: There is peeling of the coloring material (20% or more and less than 80% of the entire coloring material). D: Most of the coloring material is peeled off (80% or more of the entire coloring material is peeled off).

<Evaluation 2><Evaluation of concealment property> After the solid pattern was printed on the transparent OHP sheet with 100% duty, the concealment property was visually evaluated according to the following criteria. A: The concealing property for the transparent film is very excellent. B: The hiding property for the transparent film is at an acceptable level. C: The hiding property for the transparent film is poor. D: The hiding power for the transparent film is very poor.

<Evaluation 3><Evaluation of ejection stability> Inkjet printer EM-93
The 0C head was filled with ink, and alphanumeric characters were continuously printed on A4 size paper for 8 hours at room temperature. After printing for 8 hours, it was left without printing for 1 hour, and then alphanumeric characters were printed again. The ejection stability was evaluated based on the following criteria, and the printing stability was judged based on nozzle omission, bending, etc. during printing and after printing was restarted. A: No nozzle missing or curling during printing and after restarting printing B: No problem during printing, but several nozzles missing after restarting printing
Bending is confirmed C: Several nozzles are missing during printing, bending is confirmed D: Nozzles are missing during printing, and bending is noticeably confirmed. The evaluation results are as follows.

[0082]

[Table 1]

[0083]

According to the ink composition of the present invention, an ink composition containing titanium oxide as a colorant has good hiding properties, printing stability suitable for an ink jet recording method, and good abrasion resistance on a recording medium. realizable.

Continued front page    F-term (reference) 2C056 EA13 FC01                 2H086 BA55 BA59 BA60 BA62                 4J039 AD06 AD09 BA13 BA14 BE01                       BE22 CA06 GA24

Claims (9)

[Claims] 1. Titanium oxide is used as at least a coloring agent.
In the presence of an alcoholic hydroxyl group-containing water-soluble polymer compound or a copolymerizable surfactant, the ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable with the same are contained in an amount of at least 10% by weight. An ink composition comprising a pH adjusting resin prepared by neutralizing a copolymer having an acid value of 40 or less obtained by polymerization with an inorganic base, and water. 2. The weight ratio of the pH adjusting resin (a) to the titanium oxide (b) is a / b = 0.05 to solid content.
The ink composition according to claim 1, which is 0.3. 3. The ink composition according to claim 1, wherein the inorganic salt used for pH adjustment of the pH adjustment resin is an alkali metal hydroxide or an alkaline earth metal oxide. 4. The ink composition according to claim 1, wherein the alcoholic hydroxyl group-containing water-soluble polymer compound used for the preparation of the pH adjusting resin is a vinyl alcohol polymer. 5. The ink composition according to claim 1, wherein the ethylenically unsaturated carboxylic acid monomer used for the preparation of the pH adjusting resin is acrylic acid or methacrylic acid. 6. The ethylenically unsaturated carboxylic acid ester monomer is a monomer copolymerizable with the ethylenically unsaturated carboxylic acid monomer used for the preparation of the pH adjusting resin. 5. The ink composition according to any one of 5 above. 7. The ink composition according to claim 1, which is an ink composition for inkjet recording. 8. An inkjet recording method for recording on a recording medium using the ink composition according to any one of claims 1 to 7. 9. A recorded matter formed on a recording medium by the recording method according to claim 8.