JP2001311020A - Ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink having weather resistance, excellent in water resistance and fixability and further discharge stability, preservation stability and safety of the ink when an ink absorbent medium is used and especially suitable for ink jets. SOLUTION: This ink comprises at least either one of a colorant and an energy curing emulsion type monomer or oligomer dispersed in an aqueous medium. The emulsion type monomer or oligomer is prepared by encapsulating the periphery of at least either one of an energy polymerizable monomer or oligomer with en energy decomposable or an energy degradable resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[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. Further, the resins used here are often water-soluble or hydrophilic, and have a problem in the water resistance of the 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 ink-absorbing media, there is a problem in that the ink penetrates into the media, resulting in insufficient curing, or a smell of the monomer, which cannot be said to be environmentally safe.

As still another embodiment, for example, Japanese Patent Application Laid-Open
As described in JP-A-48922, there is known an ink in which a radiation-curable macromer is contained in an emulsion state in an ink.

According to this embodiment, the water resistance, the smell of the ink and the like are considerably improved, but there is a problem in the stability during storage of the ink due to the coalescence of the emulsion.

[0010]

DISCLOSURE OF THE INVENTION The present invention provides a water-resistant, ink-absorbing medium which is excellent in water resistance and fixability, discharge stability, ink storage stability, and the like.
An object of the present invention is to provide an inkjet ink having excellent safety.

[0011]

Means for Solving the Problems The present invention has been made to achieve the above-mentioned object, and the invention according to claim 1 comprises at least a colorant and an energy-curable emulsion in an aqueous medium. An ink in which at least one of the monomer or oligomer of the emulsion type is dispersed, wherein the monomer or oligomer of the emulsion type has energy decomposability or energy decay around at least one of the energy polymerizable monomer or oligomer. The ink is characterized by being encapsulated with a resin having a property.

The invention according to claim 2 is the ink according to claim 1, wherein at least one of the emulsion type monomer and the oligomer has an average particle diameter of 500 nm or less.

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

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 pigment has an average particle diameter of 10 nm to 200 nm.

According to the invention described in claim 5, the energy is:
The ink according to any one of claims 1 to 4, wherein the ink is an ultraviolet ray or an electron beam.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In this specification, “monomer / oligomer” in the text means at least one of a monomer and an oligomer. Further, each of the monomer and the oligomer follows the general definition (differentiated by the weight average molecular weight).

The pigment used in the present invention may be any pigment that can be dispersed in water or an aqueous solvent.
Alternatively, inorganic pigments can be used. For example, azo lakes, insoluble azo pigments, condensed azo pigments, azo pigments such as chelate azo pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, perylene pigments,
Thioindigo pigments, isoindolinone pigments, quinophthalone pigments, dioxazine pigments, metal complex pigments,
Organic pigments such as fluorescent pigments, and inorganic pigments such as barium sulfate, barium carbonate, alumina white, titanium oxide, iron oxide pigments, and carbon black can be used, but are not limited thereto.

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 energy-curable emulsion-type monomer / oligomer, those generally known as an ultraviolet-curable monomer / oligomer and an electron beam-curable monomer / oligomer can be used. For example,
Monofunctional monomers which are photopolymerizable monomers: hydroxyethyl acrylate, polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, nonylphenyl carbitol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-
Ethylhexyl carbitol acrylate, glycidyl methacrylate, bifunctional monomers such as ethylene glycol diacrylate, diethylene glycol methacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, and the like trifunctional monomer trimethylolpropane triacrylate,
In addition to dipentaerythritol pentaacrylate and dipentaerythritol hexamethacrylate which are polyfunctional monomers such as pentaerythritol triacrylate, polyester acrylate, urethane acrylate and the like can be mentioned. These may be used alone or in various mixtures.

The photo-degradable or photo-decomposable resins include generally known methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, methyl isopropyl ketone, α-chloromethyl acrylate, α- Polymers such as chloroethyl acrylate, α-cyanomethyl acrylate and α-nitromethyl acrylate are used.

In the present invention, the monomer / oligomer of the energy-curable emulsion type is used in a configuration in which the energy-polymerizable monomer / oligomer is encapsulated with an energy-decomposable or energy-degradable resin.

As a method for preparing an energy-curable emulsion-type monomer / oligomer, various generally known encapsulation methods can be used.
After emulsifying a monomer obtained by mixing an energy-polymerizable monomer / oligomer and an energy-decomposable or energy-disintegrating monomer together with an emulsifier in an aqueous medium, the in situ
Particularly preferred is a method in which an energy-decomposable or energy-disintegrable monomer is polymerized and deposited around an energy-polymerizable monomer / oligomer by a polymerization method, and then encapsulated.

The energy-curable emulsion-type monomer / oligomer obtained here takes into account the dispersion stability in the ink, the ejection stability from the ink jet head, and the ability to form a film on the recording medium after ejection. Then
The average particle size is preferably 500 nm or less. Particularly preferably, it is in the range of 20 nm to 200 nm. Qualitatively,
It is preferable that the average particle diameter of the pigment as the colorant is approximately equal to or slightly larger than the average particle diameter in order to solve the above-mentioned problem.

Since the energy-curable emulsion-type monomer / oligomer has a configuration in which the energy-polymerizable monomer / oligomer is encapsulated with an energy-decomposable or energy-degradable resin, the odor of the monomer is reduced to the outside. It does not extend. Further, since the emulsion particles are covered with the resin layer, the emulsion particles do not unite with each other. For this reason, the storage stability of the ink and the ejection stability of the ink are excellent. Further, the encapsulated energy-curable emulsion-type monomer / oligomer remains together with the pigment on the recording medium when the aqueous medium of the ink evaporates, absorbs and dries on the recording medium, and penetrates into the recording medium. Because there is no
There is no fear of insufficient curing at the time of energy application, and good fixability can be exhibited.

The fixing of the ink of the present invention is performed as follows. That is, the ink ejected from the ink jet head is applied with energy by ultraviolet rays or electron beams after the aqueous medium of the ink absorbs on the recording medium or is dried by evaporation. With this energy, the energy-decomposable or energy-degradable resin, which is the resin layer of the capsule, is decomposed or decomposed, and the energy-polymerizable monomer / oligomer contained in the capsule leaks out of the resin layer and is hardened at the same time. By this curing, the pigment as the colorant is effectively fixed on the recording medium.

When an energy polymerizable monomer / oligomer having a high functional number is used, higher water resistance and solvent resistance can be obtained after curing.

When the energy-polymerizable monomer / oligomer is cured by applying energy, particularly when it is irradiated with ultraviolet rays, a photoinitiator or a sensitizer is appropriately used.

As photoinitiators, acetophenone, benzophenone, benzoin ethyl ether, 2-chlorobenzophenone, 2,4-diethylthioxanthone, 1-
Hydroxycyclohexylphenyl ketone, benzyl dimethiketal, 2-chlorothioxanthone, 2,4,
6-tris (trichloromethyl) -s-triazine, 2
-(P-methoxystyryl) -4,6-bis (trichloromethyl) -s-triazine and the like can be used, and these may be used alone or in combination of two or more.

As a sensitizer, diethylaminobenzophenone, Michler's ketone, o-toluthiourea, sodium diethyldithiophosphate and the like can be used, and it is effective when used in combination with a photoinitiator.

The amounts of the photoinitiator and the sensitizer are not particularly limited, but generally 0.1 to 20 parts by mass of the polymerizable monomer.

The preparation of the ink is carried out by mixing a pigment dispersion in which a pigment is dispersed together with a dispersant in an aqueous medium, and an energy-curable monomer / oligomer emulsion.

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.

The amount of the dispersant added is not particularly limited, but is generally 0.1 to 50.0 parts by mass of the pigment.

The dispersion of the pigment is performed using a disperser such as a homogenizer, a paint shaker, a ball mill, and a sand mill.

As the aqueous medium, in addition to water, those which can be mixed with water can be appropriately added. For example, alkyl alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, ethylene glycol, propylene glycol, butylene glycol, 1, 2, 6,
-Hexanetriol, alkylene glycols such as diethylene glycol, polyethylene glycol, polyalkylene glycols such as polypropylene glycol,
Ethers such as tetrahydrofuran and dioxane, amides such as dimethylformamide and dimethylacetamide, and lower alkyl ethers of polyhydric alcohols such as glycerin, ethylene glycol monomethyl ether, diethylene glycol methyl ether and triethylene glycol methyl ether can be used.

In addition, if necessary, a pH adjuster, an antioxidant, a fungicide, an antifoaming agent and the like can be added.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to specific embodiments. <Example 1> 10 parts by mass of a phthalocyanine blue pigment, 20 parts by mass of ethylene glycol, 5 parts by mass of glycerin, 1 part by mass of a nonionic activator (manufactured by Kao: Emulgen 109P), and a polymer dispersant (manufactured by Zeneca: Solsperse 2000)
0) 10 parts by mass of water and 59 parts by mass of water were mixed and dispersed in a sand mill for 3 hours to obtain a pigment dispersion (A).

Next, 30 parts by mass of a monomer (trimethylolpropane triacrylate, polyethylene glycol monoacrylate, α-cyanomethyl acrylate) was added to an aqueous solution obtained by dissolving 5 parts by mass of a polyoxyethylene alkyl ether salt in 55 parts by mass of water. After emulsifying a solution in which 10 parts by mass of benzophenone as an initiator was mixed, the mixture was heated to 60 ° C. to obtain an energy-curable monomer / oligomer emulsion (B) having an average particle size of 150 nm.

Pigment dispersion (A) 50 parts by mass, energy-curable monomer / oligomer emulsion (B) 1
2.5 parts by mass and 37.5 parts by mass of water were mixed, and the mixture was filtered through a membrane filter of 1 micron followed by 0.4 micron to obtain an inkjet ink.

The ink was recorded on plain paper using an ink jet printer (HG5130, manufactured by Seiko Epson Corporation), and then irradiated with ultraviolet rays having an irradiation intensity of 5 J / cm ² . The recorded image was excellent in water resistance and solvent resistance, and there was no change in the image density even after exposure to a fluorescent lamp for three months, and an image excellent in weather resistance was obtained.

[0041]

The ink-jet ink of the present invention uses an energy-curable emulsion-type monomer / oligomer as a fixing material for a pigment as a colorant. Is a structure in which the monomer / oligomer is encapsulated with an energy-decomposable or energy-degradable resin.

Therefore, it can be said that the ink is environmentally safe because the odor of the monomer does not reach the outside. Further, since the emulsion particles are covered with the resin layer, the emulsion particles do not unite with each other. For this reason, the storage stability of the ink and the ejection stability of the ink are excellent.

Further, the encapsulated energy-curable emulsion-type monomer / oligomer remains together with the pigment on the recording medium when the aqueous medium of the ink is evaporated and absorbed and dried on the recording medium. Since it does not penetrate, there is no fear of insufficient curing at the time of energy application, and good fixability can be exhibited.

Claims (5)

[Claims] 1. An ink in which at least a colorant and at least one of an energy-curable emulsion-type monomer or oligomer are dispersed in an aqueous medium, wherein the emulsion-type monomer or oligomer has an energy An ink characterized in that at least one of a polymerizable monomer and an oligomer is encapsulated with an energy-decomposable or energy-degradable resin. 2. The emulsion type monomer or oligomer has an average particle size of 500 or more.
2. The ink according to claim 1, wherein the diameter is equal to or less than nm. 3. The ink according to claim 1, wherein the colorant is a pigment. 4. The pigment has an average particle size of 10 nm to 200 n.
4. The ink according to claim 1, wherein m is m. 5. The ink according to claim 1, wherein the energy is ultraviolet light or an electron beam.