JP2002167537A - Ultraviolet-curing ink-jet ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet-curing ink-jet ink composition excellent in curability with its cured film also excellent in solvent resistance and friction resistance. SOLUTION: This composition contains a polyurethane (meth)acrylate synthesized from a polyisocyanate and hydroxy (meth)acrylate or a polyurethane (meth)acrylate synthesized from a polyol with its molecular weight less than 800 and (meth)acryloyloxyisocyanate. The composition should preferably contain no non-reactive diluent for better curability and cured film resistance to solvents and friction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet curable ink composition for an ink jet recording system which provides a quick-drying property, excellent curability and a tough cured film.

[0002]

2. Description of the Related Art The jet ink recording system is quiet and easy to miniaturize, and at the same time, is a non-contact printing system, so that printing and image formation on a non-flat recording medium can be performed. Used in Particularly in industrial applications, oil-based or water-based inks containing a resin in the ink to enhance the adhesion to the recording medium are used, such as marking on beverage cans, electronic components such as printed wiring boards, and color for liquid crystal panels. There is no receiving layer for ink jet recording such as filters, metals and plastics, glass, etc.
Or, it is applied to a target that cannot be printed with a normal aqueous inkjet recording ink because a receiving layer cannot be formed.

In such applications, the cured film is required to have quick drying properties, water resistance, solvent resistance, abrasion resistance, etc., and ink jet printing which is excellent in these film properties and ejection stability during ink jet recording. As a system, an ultraviolet curable inkjet system using an ultraviolet curable ink composition is expected. Since the conventional ink cures the resin contained by drying the film, there is a limit in achieving a high level of both ejection stability and strength of the cured film. That is, the viscosity suitable for the ejection of the ink composition for inkjet is usually not more than ten CPs, and the viscosity stability over time is required so that the ejection characteristics do not change during printing. However, when a high-boiling solvent is used for stabilizing the viscosity, the drying property and curability of the printed film are reduced, and a cured film having excellent durability cannot be formed. On the other hand, when a low-boiling solvent is used to enhance the drying property and curability of the cured film, the solvent evaporates and the viscosity of the ink tends to increase,
Stable ink ejection cannot be obtained.

On the other hand, in a system using an ultraviolet-curable ink composition as an ink-jet ink (hereinafter referred to as a system using an ultraviolet-curable jet ink), curing of a film is performed not by evaporation of a solvent but by irradiation of ultraviolet rays. Therefore, the above-mentioned problems associated with the drying of the film can be eliminated, and both the ejection stability of the ink and the excellent curability of the cured film can be achieved at a high level. However, when considering various uses of printed matter by ink jet recording, the strength of the cured film of such an ultraviolet curable jet ink is not always sufficient, and particularly, the durability of the cured film formed on a non-absorbent recording medium is not sufficient. It was desired to further improve.

[0005]

For this reason, polyurethane (meth) acrylate has recently been included as an ultraviolet curing component for improving the curability. However, most of commercially available functional polyurethane (meth) acrylates, such as polyester urethane (meth) acrylate and polyether urethane (meth) acrylate, use a polyol for synthesis, and furthermore, they exhibit their functionality. The viscosity increases because the molecular weight of the polyol is as large as 800 or more. In addition, a polyol and a diisocyanate are reacted to synthesize a urethane prepolymer having an isocyanate group at a terminal, and then modified with hydroxy (meth) acrylate having a hydroxyl group, so that the number of urethane bonds increases and the viscosity increases. Get higher. Generally, in a jet ink recording method, the viscosity of the ink is about several tens mPa ·
It is preferably as low as about s or less. Therefore, when an attempt is made to add a commercially available functional polyurethane (meth) acrylate to the jet ink composition, the addition amount must be reduced, and a sufficient effect cannot be obtained. Also, if the addition amount is increased in order to obtain a sufficient effect, the viscosity becomes high and the ejection at the printer head becomes unstable.

As an ultraviolet curable jet ink, an aqueous ink mainly containing water as a non-reactive diluting solvent has been proposed, and an ink containing polyurethane (meth) acrylate as a curable component has been disclosed.
These inks were inferior in quick drying when printed on a non-absorbent medium, and often had a weak coating strength after curing, so that they did not realize characteristics sufficient for the above applications.

[0007] In addition, when the coloring component in the ink is increased in order to satisfy the hiding power and the color density, the irradiated ultraviolet light is absorbed and reflected by the coloring component, thereby deteriorating the curability or causing the ultraviolet curability to decrease. There is also a problem that the strength of the cured product such as the solvent resistance and abrasion resistance of the cured product is reduced by preventing the growth of the three-dimensional network structure of the compound. Therefore, there has been a demand for an ultraviolet-curable ink-jet composition that can improve the solvent resistance and abrasion resistance of a cured film without impairing good ejection characteristics as an ink-jet.

The present invention solves the above-mentioned drawbacks of the conventional jet ink, has good ejection properties, and is excellent in curability. An object of the present invention is to provide an ultraviolet curable ink composition for jet ink recording, which has good friction and quick drying properties.

[0009]

Means for Solving the Problems The present inventors have intensively studied the constitution of the polymerization component used in the jet ink composition in order to solve the above problems, and as a result, by incorporating a specific photopolymerization resin component, Have been found to be able to be effectively improved, and the present invention has been reached.

That is, the present invention is a non-aqueous ultraviolet curable jet ink composition containing at least a polyurethane (meth) acrylate, a photopolymerization initiator and a colorant component, wherein the polyurethane (meth) acrylate is a polyisocyanate. And a polyurethane (meth) acrylate synthesized from hydroxy (meth) acrylate or a polyurethane (meth) acrylate synthesized from a polyol having a molecular weight of less than 800 and (meth) acryloyloxyisocyanate. An object of the present invention is to provide an ultraviolet curable jet ink composition.

The reason that the jet ink composition of the present invention shows good curability is that the composition contains a polyurethane (meth) acrylate, which is compared with a general (meth) acrylate terminal double bond. It is considered that the terminal double bond of the polyurethane (meth) acrylate is easily cleaved due to the presence of a urethane bond in the vicinity. Further, the abrasion resistance is improved due to the characteristics of the polyurethane. For this reason, the ultraviolet curable jet ink composition of the present invention can form a cured film having both good curability and abrasion resistance.

Further, a polyurethane (meth) acrylate synthesized from a polyisocyanate and hydroxy (meth) acrylate, or a polyol having a molecular weight of 800 or less and (meth) acryloyloxyisocyanate used in the ultraviolet-curable jet ink composition of the present invention is used. Although the viscosity of the polyurethane (meth) acrylate itself is low due to its low viscosity or its crystallinity or the like, it can be easily reduced by dilution with (meth) acrylate or an organic solvent. Therefore, it can be added to the ink composition without increasing the viscosity of the ink composition, and the solvent resistance and abrasion resistance of the cured film can be improved. In the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate. The ultraviolet-curable jet ink composition of the present invention may contain an appropriate amount of a non-reactive diluting solvent in order to obtain appropriate viscosity, wettability, and adhesion. However, the quick drying of the coating,
In order to further improve curability and durability, it is preferable that the ink composition does not substantially contain a non-reactive diluting solvent. Further, a dispersant for increasing the dispersibility of the coloring component,
A photocryogen for increasing the curability may be contained.

[0013]

DETAILED DESCRIPTION OF THE INVENTION In order to achieve the object of the present invention, a polyisocyanate and a monohydroxy (meth) acrylate are used without using a polyol such as a long-chain polyether or polyester having a molecular weight of 800 or more. Reacted polyurethane (meth) acrylate or polyurethane (meth) obtained by reacting (meth) acryloyloxyisocyanate with a polyol having a molecular weight of less than 800
It is necessary to use acrylate.

The polyisocyanate used as a raw material of the polyurethane (meth) acrylate used in the present invention includes tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, norbornene diisocyanate, dicyclohexylmethane-4,4-
Diisocyanate, diphenylmethane-4,4-diisocyanate, dimer acid diisocyanate, and the like.

Examples of the hydroxy (meth) acrylate include hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, dipropylene glycol monoacrylate, 2-hydroxybutyl (meth) acrylate, and 1,4-cyclohexanedimethanol monoacrylate. (Meth) acrylate, caprolactone-modified hydroxyethyl (meth) acrylate, 2-hydroxy-
3-phenoxypropyl (meth) acrylate and the like.

The (meth) acryloyloxyisocyanate includes 2- (meth) acryloyloxyethyl isocyanate.

The polyol for synthesizing the polyurethane (meth) acrylate used in the present invention includes ethylene glycol, polyethylene glycol having a molecular weight of less than 800, propylene glycol, and a molecular weight of 80.
Polypropylene glycol less than 0, 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, neopentyl glycol, methylpentanediol, 1,6-hexanediol, trimethylhexamethylenediol, 2-methyl Octanediol, 1,9-
Nonanediol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, polycaprolactone diol having a molecular weight of less than 800, polycarbonate diol having a molecular weight of less than 800, glycerin, trimethylolpropane, trimethyloloctane, pentaerythritol, molecular weight of less than 800 But the scope of the present invention is not limited thereto. In addition, any combination may be used as long as it is a combination of polyisocyanate and hydroxy (meth) acrylate, or a combination of polyol and (meth) acryloyloxyisocyanate, and is not limited to the synthesis examples described in this specification.

As the polyurethane (meth) acrylate, a polyurethane (meth) acrylate synthesized from polyisocyanate and hydroxy (meth) acrylate is more preferable from the viewpoint of reducing the viscosity of the ink composition for ink jet recording. Of these, polyurethane (meth) acrylate synthesized from polyisocyanate and caprolactone-modified hydroxy acrylate has a better balance between viscosity and curability, and is more preferable.

The polyurethane (meth) acrylate is desirably used in a range of 5 to 30% by mass based on the total amount of the ultraviolet curable compound, but exceeds the range when dilution with (meth) acrylate or an organic solvent is possible. Can be used.

As the coloring agent, dyes and pigments conventionally used in jet inks can be used.
For example, examples of the dye include an azo dye, a phthalosinine dye, and an anthraquinone dye. Further, as the pigment, azo pigments such as azo lake pigments, insoluble azo pigments, condensed azo pigments and chelated azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene pigments, quinacdrine pigments, isoindoline pigments, thioindigo pigments, dioxazine pigments, quinophthalone pigments and the like Polycyclic pigments, dye lakes such as basic dye lakes and acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, titanium oxides, iron oxides and carbon blacks And the like. These dyes and pigments may be used in combination, but it is preferable to use pigments in terms of light resistance.

The coloring component is used in the range of 0.1 to 15% by mass, preferably 2 to 6% by mass of the total solid content. Conventionally, the amount of the colorant component is adjusted so that the curability of the film is not impaired.However, by using the ultraviolet-curable ink jet recording composition of the present invention, the curability of the film is increased, so that the pigment Etc. can be increased.

It is preferable to add (meth) acrylate from the viewpoint of dilutability, in addition to the above urethane (meth) acrylate. (Meth) acrylates include monofunctional (meth) acrylates and polyfunctional (meth) acrylates, each of which can be used alone or in combination of two or more.

The monofunctional (meth) acrylate usable in the present invention includes, for example, methyl, ethyl, propyl, butyl, 3-methoxybutyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl (Meth) acrylates having substituents such as methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, glycidyl, dimethylaminoethyl, diethylaminoethyl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, etc. And the like.

Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl-acrylate.
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecanedimethanol, ethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol ,
Di (meth) acrylates such as tripropylene glycol and polypropylene glycol, di (meth) acrylates of tris (2-hydroxyethyl) isocyanurate,
Di (meth) acrylate of diol obtained by adding 4 moles or more of ethylene oxide or propylene oxide to 1 mole of neopentyl glycol, and di (meth) acrylate of diol obtained by adding 2 moles of ethylene oxide or propylene oxide to 1 mole of bisphenol A 4 moles or more of ethylene oxide or propylene oxide are added to 1 mole of (meth) acrylate or triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of trimethylolpropane. Di (meth) acrylate of diol obtained by addition, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, poly (meth) acrylate of dipentaerythritol ) Acrylate, ethylene oxide-modified phosphoric acid (meth) acrylate, ethylene oxide-modified alkylated phosphoric acid (meth) acrylate.

The photopolymerization initiator used in the present invention includes:
Any known and commonly used ultraviolet-curable compound that can be cured can be used. As the photopolymerization initiator, a molecular cleavage type or a hydrogen abstraction type is suitable for the present invention.

As the photopolymerization initiator used in the present invention, benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2 -Dimethylamino-1- (4-morpholinophenyl) -butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,
4-trimethylpentylphosphine oxide and the like are preferably used. Further, as other molecular cleavage types, 1-hydroxycyclohexyl phenyl ketone,
Benzoin ethyl ether, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropylphenyl) -2
-Hydroxy-2-methylpropan-1-one and 2
-Methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one and the like may be used in combination, and benzophenone, 4-phenylbenzophenone, and isophthalphenone, which are hydrogen abstraction type photopolymerization initiators. , 4-benzoyl-4'-methyl-diphenyl sulfide and the like can also be used in combination.

Further, sensitizers such as trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, p-dimethylaminoethyl benzoate, and
Amines that do not cause an addition reaction with the polymerizable component, such as isoamyl dimethylaminobenzoate, N, N-dimethylbenzylamine, and 4,4′-bis (diethylamino) benzophenone, can also be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that have excellent solubility in the ultraviolet curable compound and do not inhibit the ultraviolet transmittance.

The photopolymerization initiator and the sensitizer are used in an amount of 0.1 to 20% by mass, preferably 7% by mass, based on the total amount of the ultraviolet curable compound.
Used in the range of １４14% by mass.

Further, a dispersant can be used as needed to enhance the dispersibility of the coloring component. In this case, it is desirable to use the coloring compound and the optimum compounding value determined according to the type of the dispersant.

In the composition of the present invention, a non-reactive diluting solvent may be used for the purpose of adjusting the viscosity and the like.
In the present invention, the polyurethane (meth) acrylate used is water-insoluble or hardly water-soluble, and the solution contains an organic solvent. Examples of the organic solvent include ketones, esters, ethers, alcohols, and organic solvents such as aliphatic and aromatic hydrocarbons. These organic solvents may be used alone or in combination of two or more.

The organic solvent can be used up to 70% by mass of the total amount of the jet ink, but a more preferable amount is 5%.
0 mass% or less. When the ink composition of the present invention has no problem in properties such as viscosity, it can be used without a solvent, and it is preferable that the ink composition does not substantially contain a solvent for dilution. That is, by not including a diluting solvent, first, a solvent drying step is not required. Furthermore, the remaining diluent solvent does not lower the density of the three-dimensional network structure of the cured film or prevent deterioration of the solvent resistance and abrasion resistance caused by preventing high molecular weight. In addition, it is possible to exhibit excellent characteristics such that there is no fear that the residual solvent is gradually evaporated and the human body is adversely affected. However, in the ink composition, additives such as a dispersant are added as an organic solvent solution, which may be several mass% in terms of the content of the solvent. Since the composition is not a diluting solvent but has a small content, the above problem does not occur.

The production of the ultraviolet curable jet ink of the present invention is carried out by mixing and kneading polyurethane (meth) acrylate, (meth) acrylate, coloring components and the like in an appropriate ratio, excluding the photopolymerization initiator, followed by photopolymerization initiator. Can be prepared by adding, stirring, and dissolving.

The kneading can be carried out using a dispersing machine such as a paint shaker, a ball mill, a disper mat (open type vertical bead mill).

[0034]

The present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to these examples. In addition, in the following Examples, a part represents a mass part.

(Synthesis Example of Polyurethane (meth) acrylate) (Synthesis Example 1) 394 g of 2-hydroxypropyl acrylate was placed in a 1 L four-necked flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel, and the reaction solution was stirred. Carefully so that the temperature does not exceed 70 ° C., 315.5 g of trimethylhexamethylene diisocyanate is added dropwise from the dropping funnel. After completion of the dropwise addition, stirring is continued while maintaining the temperature of the reaction solution at about 70 ° C., and after 30 minutes, 0.1 g of dibutyltin dilaurate is added, and stirring is further continued. After about 15 hours, it is confirmed that there is no unreacted isocyanate group, and is taken out.

(Synthesis Example 2) 526 g of hydroxyethyl methacrylate was placed in a 1-L four-necked flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel, and the temperature of the reaction solution was kept below 70 ° C. while stirring. 412 g of norbornene diisocyanate is dropped from the dropping funnel. After completion of the dropwise addition, stirring was continued while maintaining the reaction solution temperature at about 70 ° C., and 1 hour later, 0.1 g of dibutyltin dilaurate was added.
And continue stirring further. After about 10 hours, it is confirmed that there is no unreacted isocyanate group, and is taken out.

(Synthesis Example 3) 606.7 g of caprolactone-modified hydroxyethyl acrylate (Placcel FA-1; manufactured by Daicel Chemical) was placed in a 1 L four-necked flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel, and stirred. While keeping the reaction solution temperature below 70 ° C., 227.7 g of tolylene diisocyanate was added dropwise from the dropping funnel. After completion of the dropwise addition, stirring is continued while maintaining the temperature of the reaction solution at about 70 ° C., and one hour later, 0.1 g of dibutyltin dilaurate is added, and stirring is further continued. After about 10 hours, it is confirmed that there is no unreacted isocyanate group, and is taken out.

(Synthesis Example 4) 578.2 g of 2-hydroxypropyl acrylate was placed in a 1 L four-necked flask equipped with a stirrer, a thermometer, a condenser and a dropping funnel, and the temperature of the reaction solution did not exceed 70 ° C. while stirring. Carefully, 383.2 g of tolylene diisocyanate is dropped from the dropping funnel. After completion of the dropwise addition, stirring is continued while maintaining the temperature of the reaction solution at about 70 ° C., and one hour later, 0.1 g of dibutyltin dilaurate is added, and stirring is further continued. After about 15 hours, it is confirmed that there is no unreacted isocyanate group, and is taken out.

(Comparative Synthesis Example 1) (Polyurethane acrylic oligomer) Tolylene diisocyanate 20 was placed in a 1 L four-necked flask equipped with a stirrer, a thermometer, a condenser, and a dropping funnel.
9.4 g is added, and while stirring, 600.0 g of tetramethylene glycol having an average molecular weight of 1000 is dropped from the dropping funnel while paying attention so that the reaction solution temperature does not exceed 70 ° C. One hour after the completion of dropping, 2-hydroxyethyl acrylate 1
40.7 g are added dropwise. Stirring is continued while the temperature of the reaction solution is kept at about 70 ° C., and after 1 hour, 0.1 g of dibutyltin dilaurate is added and stirring is further continued. After about 5 hours,
Confirm that there is no unreacted isocyanate group and take it out.

(Example 1) Carbon black: 2.3 parts Polymer dispersant (manufactured by Zeneca, trade name “Sorespers 24000GR”): 0.7 parts Propylene glycol monomethoxy acetate: 42 parts Obtained in Synthesis Example 3 Polyurethane acrylate: 11 parts Ethylene oxide-added trimethylolpropane triacrylate: 22 parts Dipropylene glycol diacrylate: 20 parts Hydroxyethyl methacrylate: 2 parts The above is put in a poly bottle together with 200 g of zirconia beads having a diameter of 1 mm, and sealed tightly with a paint shaker. After the dispersion treatment for 2 hours, the zirconia beads were removed, the following photopolymerization initiator component was added, and the mixture was stirred and mixed. "Irgacure 369" (manufactured by Ciba Specialty Chemicals): 3 parts Diethylthioxanthone: 0.5 parts Ethyl 4-dimethylaminobenzoate: 2 parts This was filtered through a 1.2 μm membrane filter to prevent clogging of the printer. The resulting composition was designated as jet ink A.

(Example 2) Carbon black: 2.3 parts “Sorespers 24000GR”: 0.7 parts Propylene glycol monomethoxy acetate: 35 parts Polyurethane acrylate obtained in Synthesis Example 4: 12 parts Ethylene oxide-added trimethylolpropane Triacrylate: 25 parts Dipropylene glycol diacrylate: 20 parts Hydroxyethyl methacrylate: 5 parts A composition obtained by subjecting the above to dispersion treatment, addition of a photopolymerization initiator component, and filtration using the same formulation as in Example 1 is jetted. Ink B
And

(Example 3) Carbon black: 2.3 parts “Sorespers 24000GR”: 0.7 parts Polyurethane acrylate obtained in Synthesis Example 1: 7 parts Pentaerythritol tetraacrylate: 14 parts Neopentyl glycol diacrylate: 35 Part 3-methoxybutyl acrylate: 35 parts The composition obtained by the above-mentioned dispersion formulation, addition of a photopolymerization initiator component, and filtration was performed using the same formulation as in Example 1.
And

(Comparative Example 1) Carbon black: 2.3 parts “Solespers 24000GR”: 0.7 parts Propylene glycol monomethoxy acetate: 42 parts Polyurethane acrylic oligomer obtained in Comparative Synthesis Example 1: 2 parts Ethylene oxide-added tri Methylolpropane triacrylate: 25 parts Dipropylene glycol diacrylate: 25 parts Hydroxyethyl methacrylate: 3 parts Composition obtained by dispersing the above, adding a photopolymerization initiator component, and filtering using the same formulation as in Example 1. To Jet Ink D
And

(Comparative Example 2) Carbon black: 3 parts “Sorespers 24000GR”: 0.9 parts Propylene glycol monomethoxy acetate: 26 parts Ethylene oxide-added trimethylolpropane triacrylate: 35 parts Dipropylene glycol diacrylate: 32 parts Hydroxy Ethyl methacrylate: 3 parts or more together with 150 g of zirconia beads having a diameter of 1 mm were placed in a poly bottle and sealed, and dispersed for 2 hours with a paint shaker, followed by addition of a photopolymerization initiator component and filtration with the same formulation as in Example 1. The resulting composition was used as a jet ink E.

Evaluation Method Viscosity: Each ink was measured at 25 ° C. with an E-type viscometer. UV irradiation conditions: Select blue plate glass as recording medium,
After a solid image is formed, the ink containing the diluting solvent is sufficiently evaporated, and then a metal halide lamp and a cold mirror are used by a conveyor type UV irradiation device.
Under the conditions of 0 W / cm and 0.5 J / cm ² , the number of passes until the tackiness disappeared was measured. Methanol rubbing: A cotton swab impregnated with methanol was pressed against the cured product and rubbed left and right to measure the number of times the swab passed before destruction such as peeling or thinning of the cured product occurred. Table 1 below shows the evaluation results of the jet inks manufactured in the examples and the comparative examples.

[0046]

[Table 1]

From Table 1, it can be seen that the ultraviolet-curable jet ink compositions obtained in Examples 1 to 3 to which polyurethane (meth) acrylate was added were satisfactory in dischargeability, curability and strength of the cured product. The UV-curable jet ink composition obtained in Comparative Example 1, in which a polyurethane (meth) acrylic oligomer synthesized from a polyol having a large molecular weight was added instead of (meth) acrylate, increased in viscosity with a small amount of addition. Since the added amount cannot be increased as described above, almost no effect is observed. Further, the ultraviolet-curable jet ink composition obtained in Comparative Example 2 to which no polyurethane (meth) acrylate was added had significantly poor curability, solvent resistance of the cured product, and friction resistance.

Since both Examples 1 and 2 contain a diluting solvent, in order to obtain a cured film having good abrasion resistance, it is necessary to sufficiently evaporate and dry the solvent before irradiating with ultraviolet rays. If drying before irradiation with ultraviolet rays is neglected, the abrasion resistance will be lower than in Example 3 because the solvent inhibits curing. On the other hand, the ink using the caprolactone-modified hydroxyethyl acrylate of Example 3 can be controlled to a viscosity that allows ejection without using a diluting solvent. Such an ink does not require drying of the diluting solvent before irradiation with ultraviolet light, and thus can be suitably used as an ink composition for an on-demand inkjet recording system.

[0049]

The ultraviolet-curable jet ink composition of the present invention has excellent curability, and has good solvent resistance and friction resistance of the cured product. It is suitable for printing on the like.

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Claims (4)

[Claims] 1. A non-aqueous ultraviolet curable jet ink composition containing at least a polyurethane (meth) acrylate, a photopolymerization initiator, and a colorant component, wherein the polyurethane (meth) acrylate is a polyisocyanate and a hydroxy (meth) A) polyurethane (meth) acrylate synthesized from acrylate, or a molecular weight of 8
An ultraviolet-curable jet ink composition comprising a polyurethane (meth) acrylate synthesized from a polyol of less than 00 and (meth) acryloyloxyisocyanate. 2. The ultraviolet curable jet ink composition according to claim 1, wherein the polyurethane acrylate is a polyurethane (meth) acrylate synthesized from a polyisocyanate and a caprolactone-modified hydroxy acrylate. 3. The ultraviolet curable jet ink composition according to claim 1, wherein the colorant is a pigment. 4. The ultraviolet-curable jet ink composition according to claim 1, which does not substantially contain a non-reactive diluting solvent.