JP2001311023A - Ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink having weather, water and solvent resistances, excellent in fixability, discharge stability and preservation stability of the ink and especially suitable for ink jets. SOLUTION: This ink is characterized as comprising at least a colorant (especially suitably a pigment), a dispersing agent and resin particles in a nonaqueous medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink-jet ink, and more particularly to an ink-jet ink excellent in fixability, weather resistance, water resistance, solvent resistance, storage stability of the ink, and discharge suitability.

[0002]

2. Description of the Related Art Conventionally, as an ink-jet ink, there has been known an ink in which various water-soluble dyes are dissolved in an aqueous liquid as described in Japanese Patent Application Laid-Open No. 55-65269. .

However, the ink using the water-soluble dye as described above has a problem in weather resistance of a recorded image because the dye has poor weather resistance. That is, when the image is exposed to sunlight, fluorescent light, light from a projector, or the like, the image has a defect that the image becomes unreadable, disappears, or fades.

As a form for solving the drawback of poor weather resistance, for example, as described in JP-B-56-18623 and JP-A-4-18463, those using water-dispersible pigments are known. Are known.

[0005] However, inks using pigments are improved in weather resistance, but generally have the disadvantages of poor fixability and poor storage stability of the ink due to sedimentation of the pigment.

[0006] In order to solve this drawback, an ink to which a resin is added is known as an ink having fixability. However, when a resin is contained in the ink, there is a problem in that the head is clogged with the resin when the solvent in the ink evaporates or the viscosity of the ink is increased, so that ejection is difficult. Furthermore, the resin used here is water-soluble,
Alternatively, many of them are hydrophilic and have a problem in water resistance of a recorded image.

As a method for solving these problems, for example, as described in JP-A-8-218016, a method using a monomer which is cured by an electron beam is known. However, the monomer used here is dissolved in the ink, and although water resistance increases after curing,
For an ink-absorbing medium, there is a problem that the ink penetrates to the inside of the medium and is thus insufficiently cured.

As still another embodiment, for example, Japanese Patent Application Laid-Open
As described in JP-A-60353 or JP-A-8-48922, those using an emulsion resin or those containing a radiation-curable macromer in an ink in an emulsion state are known. . According to this embodiment, the penetration into the inside of the recording medium can be suppressed, but there is a problem that the solvent is a little slow in terms of dryness because the solvent mainly composed of water is used.

Further, as an example in which quick drying of ink is emphasized, there is known an ink jet printer using a volatile solvent and a resin soluble in the solvent, as described in, for example, JP-A-5-214279. Have been. However, since the drying on the recording medium is fast and the drying on the tip of the ink jet head is fast, clogging of the head due to deposition of the resin becomes a problem, and stable ejection cannot be performed.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink-jet ink having weather resistance, water resistance, solvent resistance, and excellent fixability, ejection stability, and storage stability of the ink. Aim.

[0011]

Means for Solving the Problems The present invention has been made to achieve the above object, and the invention according to claim 1 contains at least a coloring agent and resin particles in a non-aqueous medium. This is an ink characterized in that: If the dispersibility of the colorant or the resin particles is poor, the colorant,
It is preferable to add a dispersant in addition to the resin particles.

According to a second aspect of the present invention, there is provided the ink according to the first aspect, wherein the average particle diameter of the resin particles is 500 nm or less.

The invention according to claim 3 is the ink according to any one of claims 1 and 2, wherein the resin particles have a crosslinked structure.

According to a fourth aspect of the present invention, there is provided the ink according to any one of the first to third aspects, wherein the colorant is a pigment.

According to a fifth aspect of the present invention, the pigment has an average particle size of 10 nm to 200 nm.
The ink described in 1. above.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The colorant used in the present invention is not particularly limited as long as it is dispersible in a non-aqueous solvent, and is preferably a pigment, and known organic or inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelated azo pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, perylene pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments Organic pigments such as dioxazine pigments, metal complex pigments, and fluorescent pigments, and inorganic pigments such as barium sulfate, barium carbonate, alumina white, titanium oxide, iron oxide pigments, and carbon black can be used. It is not limited.

The particle size of these pigments is determined in consideration of prevention of nozzle clogging, coloring, transparency, and dispersion stability of the ink over time because the produced ink is used in an ink jet system. Then, a smaller one is preferable, and the average particle size is 10 nm to 200 nm and the maximum particle size is 50 nm.
Those having a thickness of 0 nm or less are used.

As the resin particles mainly used as a fixing material for the pigment, generally known natural resins or synthetic resins are used. Rosin is typical as a natural resin, and rosin derivatives, cellulose derivatives, rubber derivatives, protein derivatives and oligomers thereof are mentioned as modified natural resins. Synthetic resins include epoxy resin, acrylic resin, maleic acid resin, butyral resin,
Polyester resin, melamine resin, phenol resin, urea resin, styrene-maleic acid copolymer, chlorinated polyethylene, chlorinated polypropylene, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, alkyd resin, styrene resin, Examples include polyamide resin, rubber-based resin, cyclized rubber, celluloses, polybutadiene, polyimide resin, and polyurethane resin. Examples of the synthetic resin modified with a natural resin include a rosin-modified maleic resin, a rosin-modified phenol resin, and the like. These can be used alone or as a mixture.

The particle diameter of the resin particles is determined in consideration of the dispersion stability over time in ink, the stability of ejection from an ink jet head, the fixability on a recording medium after ejection, and the ability to form a film. , The smaller the better, the average particle size is 5
Those having a thickness of 00 nm or less are preferred.

The resin particles may be prepared by adding and dispersing resin particles prepared in advance in an ink solvent, or may be prepared in an ink solvent.

The preparation of the resin particles is carried out by polymerizing a monomer together with an initiator using a generally known emulsion polymerization method, soap-free polymerization method, dispersion polymerization method or the like, but is not limited thereto. Absent. In the present invention,
Since the ink is a non-aqueous solvent, it is preferably crosslinked so as not to be dissolved in the non-aqueous solvent. When the resin particles are prepared in an aqueous solvent such as emulsion polymerization or soap-free polymerization, they may be dried once and then dispersed in a non-aqueous solvent. Is preferable because aggregation can be prevented. In this case, the use of a polymer dispersant works effectively.
In general, resin particles are stabilized by ionic repulsion in an aqueous solvent, but in non-aqueous solvents, stabilization of particles by this ionic repulsion is not so expected, so consider stabilization by steric repulsion. It is necessary and a polymer dispersant is effective. In particular, a dispersant having both a component that is easily adsorbed by the resin particles and a component that is compatible with the solvent is effective.

Examples of the polymer dispersant include partial alkyl esters of polyacrylic acid, polyalkylene polyamine, polyacrylate, styrene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, polyphosphoric acid, polyvinyl alcohol, carboxylate Alkyl cellulose, polyvinylpyrrolidone, polyalkylene glycol, ethylene oxide-propylene glycol-propylene oxide condensate, polyethylene glycol derivative having a naphthalene ring, methacrylic acid derivative and the like are used.

Examples of the non-aqueous solvent include cyclohexanone, ethyl cellosolve acetate, butyl cellosolve acetate, 1-methoxy-2-propyl acetate,
Diethylene glycol dimethyl ether, ethylbenzene, ethylene glycol diethyl ether, diphenyl ether, xylene, ethyl cellosolve, methyl-n amyl ketone, propylene glycol monomethyl ether toluene, methyl ethyl ketone, ethyl acetate, butyl acetate, methyl cyclohexane, methanol, ethanol,
Examples thereof include isopropyl alcohol, butanol, isobutyl ketone, and a petroleum-based solvent, which may be used alone or as a mixture.

The ink-jet ink of the present invention can be obtained by mixing a dispersion in which a pigment is dispersed and a dispersion in which resin particles are dispersed.

The pigment is dispersed by dispersing the pigment together with a dispersant and a non-aqueous solvent, or by mechanically kneading the pigment in advance with the dispersant and then adding a solvent or dispersant solution to disperse the pigment. The pigment and the dispersant are mixed in a solid content ratio of 1: 4.
２０20: 1.

As the dispersant, anionic, nonionic, cationic, amphoteric activators, polymer dispersants and the like are used. Examples of anionic surfactants include alkyl sulfate salts, fatty acid salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, polyoxyethylene alkyl ether salts, and formalin naphthalene sulfonic acid. Condensates and the like. Examples of the nonionic activator include polyoxyethylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene fatty acid ester, glycerin fatty acid ester, silicone type, fluorine type and the like. Examples of the cationic activator include a quaternary ammonium salt and an alkylamine salt. Examples of amphoteric surfactants include dimethylalkyl lauryl betaine, alkyl glycine, imidazolinium betaine and the like. In practice, these dispersants are used alone or as a mixture.

For dispersing the pigment, various dispersing means such as a three-roll mill, a two-roll mill, a sand mill, a ball mill, and a kneader can be used.

The fixing of the ink of the present invention is performed as follows. That is, when the ink discharged from the inkjet head is absorbed by the non-aqueous solvent of the ink on the recording medium or dried by evaporation, the ink is formed into a film so that the resin particles wrap around the pigment. Effectively fixed on top. By heating during fixing, it becomes possible to fix more firmly.

In the ink-jet ink of the present invention, since the resin particles are crosslinked, the recorded image is very excellent in water resistance and solvent resistance, and the resin particles may unite during storage of the ink. Therefore, the storage stability of the ink and the ejection stability of the ink are excellent. In addition, since a non-aqueous solvent is used, it has excellent drying properties and can increase the recording speed.

Incidentally, in order to obtain a final ink, a pH adjuster, an antioxidant, a fungicide, an antifoaming agent and the like can be added as required.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to specific embodiments. <Example 1> 30 parts by mass of a phthalocyanine-based blue pigment, 10 parts by mass of a polymer dispersant (manufactured by Zeneca: Solsperse 20000), and 60 parts by mass of cyclohexanone were mixed, and dispersed by a sand mill for 3 hours to obtain a pigment dispersion (A). Obtained.

Crosslinked acrylic resin particles (average particle size,
200 nm) 20 parts by mass of polymer dispersant (styrene-acrylic acid copolymer) 5 parts by mass of cyclohexanone 75
It was mixed and dispersed in a solution dissolved in parts by mass to obtain a resin particle dispersion liquid (B).

10 parts by mass of the pigment dispersion (A), 25 parts by mass of the resin particle dispersion (B), and 65 parts by mass of cyclohexanone were sufficiently mixed, and filtered through a 1-micron and then a 0.4-micron membrane filter. Ink was obtained.

This ink was recorded on coated paper using an ink jet printer (HG5130, manufactured by Seiko Epson Corporation) and dried at 120 ° C. The recorded image was excellent in water resistance, solvent resistance, and adhesion. Even after exposure to a fluorescent lamp for three months, the density of the image did not change, and an image excellent in weather resistance was obtained.

Example 2 30 parts by mass of a carbon black pigment, a polymer dispersant (manufactured by Zeneca: Solsperse 2000)
0) 10 parts by mass and 60 parts by mass of cyclohexanone were mixed and dispersed in a sand mill for 3 hours to obtain a pigment dispersion (A).

Crosslinked acrylic resin particles (average particle size,
20 parts by mass (200 nm) were mixed and dispersed in a solution of 5 parts by mass of a polymer dispersant (vinylnaphthalene-maleic acid copolymer) in 75 parts by mass of cyclohexanone to obtain a resin particle dispersion (B).

10 parts by mass of the pigment dispersion (A), 25 parts by mass of the resin particle dispersion (B), and 65 parts by mass of cyclohexanone were thoroughly mixed, and filtered through a 1-micron, 0.4-micron membrane filter, followed by inkjet printing. Ink was obtained.

The ink was recorded on coated paper using an ink jet printer (HG5130, manufactured by Seiko Epson Corporation) and dried at 120 ° C. The recorded image was excellent in water resistance, solvent resistance, and adhesion. Even after exposure to a fluorescent lamp for three months, the density of the image did not change, and an image excellent in weather resistance was obtained.

[0040]

The ink-jet ink of the present invention contains a pigment as a colorant, a dispersant, and resin particles in a non-aqueous medium, and the non-aqueous solvent in the ink absorbs on the recording medium. Alternatively, when dried by evaporation, the resin particles form a film so as to enclose the pigment, so that the pigment as a colorant is effectively fixed on the recording medium, and an image having good adhesion is obtained. The obtained recorded image has excellent weather resistance.

In the ink-jet ink of the present invention, since the resin particles are crosslinked, the recorded image is very excellent in water resistance and solvent resistance.

Furthermore, since the crosslinked resin particles do not coalesce during storage of the ink, the storage stability of the ink and the ejection stability of the ink are excellent. In addition, since a non-aqueous solvent is used, it has excellent drying properties and can increase the recording speed.

Continued on the front page F-term (reference) 2C056 EA13 FC01 FC02 2H086 BA55 BA59 BA60 4J039 AB02 AB07 AB08 AB11 AD01 AD02 AD03 AD05 AD07 AD08 AD09 AD14 AE02 AE03 AE04 AE05 AE06 AE08 AE09 AF01 AF02 BC02 BC03 BC07 BC12 BC23 BD02 BE01 CA07 EA34 EA38 EA39 EA43 EA44 EA46 GA24

Claims (5)

[Claims] 1. An ink characterized in that a non-aqueous medium contains at least a colorant and resin particles. 2. The ink according to claim 1, wherein the average particle size of the resin particles is 500 nm or less. 3. The ink according to claim 1, wherein the resin particles have a crosslinked structure. 4. The ink according to claim 1, wherein the colorant is a pigment. 5. The pigment has an average particle size of 10 nm to 200 n.
The ink according to claim 4, wherein m is m.