JP2003192944A - Ink for inkjet recording, method for inkjet recording by using it, and inkjet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet recording, which makes it possible to record an image with a high sensitivity and a high adherence to a recording medium without blurring on various base materials and which has low irritativeness to the skin, is lowly sensitinogenic and has high safety, a method for inkjet recording by using the ink, and an inkjet recording device. <P>SOLUTION: The ink for inkjet recording is characterized in that it is curable by radiation, contains at least a coloring material and polymerizable compounds which comprise at least one compound selected from the group of specified acrylic compounds, and the content of the group of acrylic compounds is 20-95 mass% of the whole mass of the ink. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for ink jet recording (hereinafter also simply referred to as ink) capable of reacting and curing by irradiation with radiation such as ultraviolet rays and electron beams, an ink jet recording method and ink jet recording using this ink. Regarding the device, in detail, even for a substrate for which direct inkjet recording is difficult, a high-quality image with high image durability can be obtained by using an inkjet recording ink with low skin irritation and sensitization and high safety. , Relates to an inkjet recording technology capable of printing with high sensitivity.

[0002]

2. Description of the Related Art In recent years, the ink jet recording system has been applied to various printing fields such as photography, various printings, markings, special printings such as color filters, etc., since an image can be formed easily and inexpensively. In particular, a recording device that emits and controls fine dots, ink that has improved color reproduction range, durability, emission suitability, etc., and dramatically improved ink absorption, coloring material coloring, surface gloss, etc. It is also possible to obtain image quality comparable to silver halide photography by using special paper. The improvement in image quality of today's ink jet recording system has been achieved only when all the ink jet recording devices, inks, and special papers are provided.

However, in an ink jet system requiring special paper, there are problems that the recording medium is limited and the cost of the recording medium is increased. Therefore, many attempts have been made to record on a transfer medium different from the special paper by the inkjet method. Specifically, there are a phase change inkjet method using a solid wax ink at room temperature, a solvent inkjet method using an ink mainly composed of a quick-drying organic solvent, and an ultraviolet curable inkjet method in which crosslinking is performed with ultraviolet light after recording. Can be mentioned,
At present, all of them have various problems.

For example, in the phase change ink jet system, since wax is used as the ink, sufficient image strength and fixability cannot be obtained. In the solvent-based inkjet method, the ink is easily volatilized, and the odor (environment), head clogging due to ink drying, and ink permeability differ depending on the recording medium used, so bleeding and drying are not stable, and ink bleeding easily occurs. There's a problem.

On the other hand, the ultraviolet ray curable ink jet system has been attracting attention in recent years because it has a relatively low odor as compared with the solvent type ink jet system, and can perform recording on a recording medium which is quick-drying and does not absorb ink. For example, Japanese Patent Publication No. 5-54667, Japanese Patent Application Laid-Open No. 6-200204, and Japanese Patent Publication No. 2000-504778 disclose UV-curable inkjet inks. In either method, an acrylic monomer is used as the polymerizable compound. However, the polymerizable monomer used in the ink is one that has skin irritation and sensitization from the viewpoint of lowering the viscosity for obtaining stable ink ejection properties, increasing the curing sensitivity or adhering the recording medium. Has been selected,
It was very dangerous for users. Further, as disclosed in JP 2000-504778 A, there is a method of containing 80 to 95% by mass of relatively safe alkoxy acrylate or polyalkoxy acrylate, but 80% by mass of a monofunctional or polyfunctional monomer. %, It is difficult to obtain sufficient adhesiveness with the recording medium, and the ink bleeds over a wide range of recording media such as a highly penetrative recording medium or a polyethylene terephthalate film that is very wettable and easily bleeds. There was a problem that odor was generated due to unreacted monomer.

Further, even if a highly reactive ink having a high sensitivity is designed using the polymerizable compound disclosed in the related art, the uncured ink may be touched by the user in various situations. There is. That is, in the case of a recording medium with a very high permeability, the ink penetrates into the recording medium and the irradiation rays do not reach (for example, it occurs with Japanese paper or textiles), during ink refilling and maintenance, waste liquid treatment, radiation It is estimated that the user may come into contact with the irradiation unit due to an abnormality.

As a method for improving the safety against the above problems, a polymerizable monomer having a low reactivity or a polymerizable oligomer having a relatively large molecular weight should be mainly used, but in the conventional method, the former is low. In addition to ink bleeding and odor due to poor curing due to sensitivity, there is a problem of cost increase due to power up of the radiation irradiation device, and the latter has a problem that stable ink ejection cannot be achieved due to increased ink viscosity.

As described above, the irradiation-curing type ink jet system of ultraviolet rays and the like has excellent characteristics as compared with other ink jet systems, but at the present time, it is not as good as the aqueous ink jet system from the viewpoint of safety. , The urgent need to develop a solution.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to achieve high sensitivity and high adhesion to a recording medium without causing bleeding, even on a support which is usually difficult to record directly by an ink jet recording method. An object of the present invention is to provide an inkjet recording ink capable of recording a high image and having low skin irritation and sensitization and high safety, an inkjet recording method and an inkjet recording apparatus using the same.

[0010]

The above objects of the present invention have been achieved by the following constitutions.

1. In an inkjet recording ink curable by irradiation of radiation, the inkjet recording ink contains at least a coloring material and a polymerizable compound,
The polymerizable compound is at least one kind selected from the compound group A, and the compound group A is 20 to 9 of the total ink mass.
An ink for inkjet recording characterized by containing 5% by mass.

2. 40 ~ for inkjet recording ink
It is heated to a constant temperature in the range of 80 ° C., the viscosity of the inkjet recording ink is adjusted to 7 to 30 mPa · s, the inkjet recording ink is jetted, and 0 after the inkjet recording ink lands on the recording medium. .01-
In an inkjet recording ink curable by irradiation with radiation after 0.5 seconds, the inkjet recording ink contains at least a coloring material and a polymerizable compound, and the polymerizable compound is selected from the compound group A. At least one compound of which the compound group A is 20
Ink for ink jet recording, characterized in that it is contained in an amount of ˜95 mass%.

3. 1 characterized by containing a polymerizable monomer or a polymerizable oligomer having a molecular weight of 400 or more
Alternatively, the inkjet recording ink according to the item 2.

4. The above compound group A based on the total ink mass
1 to 50% to 90% by mass of the above
The ink for inkjet recording according to any one of 3 above.

5. The polymerizable compound is the compound group A.
5. The inkjet recording ink according to any one of items 1 to 4, which is a monoacrylate compound selected from the group consisting of a polyfunctional acrylate monomer and a polyfunctional acrylate oligomer.

6. The monoacrylate compound is at least one selected from stearyl acrylate, cetyl acrylate, isoamyl acrylate, isomystyl acrylate and isostearyl acrylate, and the total amount of the monoacrylate compound is 7 to 70% by mass based on the total mass of the ink. 6. The ink for inkjet recording according to the item 5, wherein the ink is present.

7. 6. The inkjet recording ink according to the above 5, wherein the polyfunctional acrylate monomer or the polyfunctional acrylate oligomer is a caprolactam-modified acrylic monomer or oligomer.

8. As the polymerizable compound, polyalkoxy acrylate is used in an amount of 0 to 75% by mass based on the total mass of the ink.
8. The ink for inkjet recording according to any one of items 1 to 7, which contains the ink.

9. 1 which can be cured by irradiation with radiation
In the inkjet recording method, the ink for inkjet recording according to any one of items 1 to 8 is jetted onto a recording medium by a drop-on-demand inkjet method, and then the ink landed by irradiation of radiation is reacted and cured. 40-80 recording ink
The ink composition is heated to a constant temperature in the range of ℃, the viscosity of the ink jet recording ink is adjusted to 7 to 30 mPa · s to eject the ink jet recording ink, and 0.01 after the ink jet recording ink lands on the recording medium. An inkjet recording method, which comprises irradiating with radiation after 0.5 seconds.

10. The inkjet recording ink according to any one of items 1 to 8 that is curable by irradiation with radiation is jetted onto a recording medium by a drop-on-demand inkjet method, and then the ink that has landed by irradiation with radiation reacts. In an ink jet recording apparatus for curing, the jet nozzle and the ink supply tank or the ink supply pipe system are heated to keep the ink for ink jet recording at a constant temperature in the range of 40 to 80 ° C. to increase the viscosity of the ink for ink jet recording. 7-30mP
An ink jet recording apparatus comprising: a viscosity adjusting means for adjusting to a.s and a means for irradiating radiation 0.01 to 0.5 seconds after the ink for ink jet recording has landed.

As a result of intensive studies in view of the above problems, the present invention uses at least one polymerizable compound selected from the above compound group A in an ink jet recording ink, and the compound group A is used in the total ink mass. By containing 20 to 95% by mass, it is possible to record an image with high resolution and high adhesion to a recording medium without causing bleeding even on various recording media. It has been found that the present invention has been achieved by finding that a small amount of highly safe inkjet recording ink can be obtained.

Further, the object and effect of the present invention are that the molecular weight is 40
It contains 0 or more polymerizable monomers or polymerizable oligomers, and the compound group A is 50 to 9 based on the total mass of the ink.
0% by mass, the polymerizable compound is a monoacrylate compound selected from the compound group A and a polyfunctional acrylate monomer or a polyfunctional acrylate oligomer, and the monoacrylate compound is stearyl acrylate, cetyl acrylate, isoamyl. It is at least one kind selected from acrylate, isomistyl acrylate, and isostearyl acrylate, and the total amount of the monoacrylate compound is 7 to 7 with respect to the total mass of the ink.
70% by mass, the polyfunctional acrylate monomer or the polyfunctional acrylate oligomer is a caprolactam-modified acrylic monomer or oligomer,
As a polymerizable compound, a polyalkoxy acrylate is contained in an amount of 0 to 75% by mass with respect to the total mass of the ink, or the above inkjet recording ink is used to eject onto a recording medium by a drop-on-demand inkjet method, and then irradiated with radiation. In the ink jet recording method of reacting and curing the ink landed by, the ink liquid for ink jet recording is heated to a constant temperature in the range of 40 to 80 ° C. to adjust the viscosity of the ink for ink jet recording to 7 to 30 mPa · s. By using the inkjet recording method of ejecting the inkjet recording ink and irradiating with radiation from 0.01 to 0.5 seconds after the inkjet recording ink lands on the recording medium,
It has been found that it can be further expressed.

The details of the present invention will be described below. In the invention according to claim 1, in an inkjet recording ink curable by irradiation of radiation, the inkjet recording ink contains at least a coloring material and a polymerizable compound, and the polymerizable compound is selected from the following compound group A. And the compound group A has a total ink mass of 2
It is characterized by containing 0 to 95% by mass.

First, compound group A which is a polymerizable compound
Will be described. The polymerizable compound belonging to the compound group A (hereinafter, also referred to as an acrylate compound) according to the present invention is
As described above, isomyristyl acrylate, isostearyl acrylate, cetyl acrylate, isoamyl acrylate, stearyl acrylate, methoxy-polyethylene glycol acrylate, methoxydipropylene glycol acrylate, 2 (2-ethoxyethoxy) ethyl acrylate, butoxyethyl acrylate, phenoxy-polyethylene. Glycol acrylate, 2-ethylhexyl-diglycol acrylate,
2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol ethylene oxide adduct acrylate, 2-acryloyloxyethyl Hexahydrophthalic acid, lactone-modified towable acrylate, hydroxypivalic acid neopentyl glycol diacrylate, dimethylol tricyclodecane diacrylate,
Dimethylol dicyclopentane diacrylate, propylene glycol diglycidyl ether acrylic acid adduct, bisphenol A diglycidyl ether (meth) acrylic acid adduct, bisphenol A propylene oxide adduct diacrylate, bisphenol A ethylene oxide adduct diacrylate Modified bisphenol A diacrylate, glycerin propoxytriacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxytetraacrylate, dipentaerythritol hexaacrylate, caprolactone modified dipentaerythritol hexaacrylate, caprolactone modified trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate Acrylate, amine modified poly Stell tetraacrylate,
Pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer and pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer.

The above-mentioned acrylate compound is compared with the polymerizable compound which has been used in the conventional UV-curable ink,
It has low skin irritation and sensitization (rash) and a relatively low viscosity, resulting in stable ink ejection properties, curing sensitivity, and good adhesion to recording media. have.

The invention according to claim 1 is characterized in that the compound group A is contained in an amount of 20 to 95% by mass with respect to the total mass of the ink.
It is a feature that the content is ˜95 mass%, more preferably 70 to 95 mass%.

Each of the monomers listed in the above-mentioned compound group A according to the present invention has a low sensitizing property even with a low molecular weight, has a high reactivity, has a low viscosity, and has a close adhesion to a recording medium. It was found that it has excellent properties.

In the present invention, in order to further improve the curing sensitivity, the bleeding characteristics, and the adhesion to the recording medium, the third aspect of the present invention is provided.
In the invention according to, among the acrylate compounds according to the present invention, a monoacrylate compound and a polyfunctional acrylate monomer having a molecular weight of 400 or more or a polyfunctional acrylate oligomer are used in combination, and preferably a polyfunctional acrylate having a molecular weight of 500 or more. That is, a monomer or a polyfunctional acrylate oligomer is used in combination. By using the above configuration, while maintaining safety, curing sensitivity,
Bleeding and adhesion to a recording medium can be further improved.

A molecular weight of 400 that can be used in the present invention
The above-mentioned polyfunctional acrylate monomer or polyfunctional acrylate oligomer is not particularly limited, and known compounds can be used, but in the present invention, epoxy acrylate oligomer, urethane acrylate oligomer, and polyester acrylate oligomer are particularly preferable.

In the present invention, when recording on a flexible recording medium such as a polyethylene terephthalate (hereinafter abbreviated as PET) film or a polypropylene film,
A monoacrylate selected from the above compound group A,
By using the polyfunctional acrylate monomer or the polyfunctional acrylate oligomer in combination, the formed coating film can have flexibility, and as a result, high film strength can be obtained while enhancing the adhesiveness, which is preferable.

The invention according to claim 6 is characterized in that, as the monoacrylate, at least one selected from stearyl acrylate, isoamyl acrylate, isomystyl acrylate and isostearyl acrylate is used, and the curing sensitivity is high due to this constitution. It is preferable in that it has low shrinkage, can prevent curling, prevents bleeding, reduces odor of printed matter, and reduces the cost of the irradiation device.

The invention according to claim 7 is characterized in that the polyfunctional acrylate monomer or the polyfunctional acrylate oligomer is a caprolactam-modified acrylic monomer or oligomer. With this constitution, compatibility with other monomers is enhanced. The sensitivity can be effectively improved.

Methacrylate is better than acrylate in skin irritation, but is not suitable because sensitization is generally not different from acrylate and curing sensitivity is lower than that of acrylate, but it is highly reactive and sensitizing. If it is good, it can be preferably used.

Among the above compounds, alkoxy acrylate has low curing sensitivity and causes problems such as bleeding, odor and restriction of irradiation light source. Therefore, its content is limited to less than 75% by mass, and other acrylates are used in combination. It is preferable.

Next, the coloring material that can be used in the present invention will be described. The coloring material that can be used in the present invention is not particularly limited, but a pigment having excellent weather resistance is preferable, but any known coloring material such as a soluble dye and an oil dye can be used.

The pigment preferably used in the present invention will be described. The color developability (color density per added concentration) is not always high, and in addition, since it is difficult to produce a uniform fine particle dispersion, there is a phenomenon in which the melt viscosity increases excessively when the concentration is high. Those that have not been put to practical use can be used. Although not particularly limited, for example, the following organic or inorganic pigments described in the color index can be used in the present invention.

As the red or magenta pigment, Pig
ment Red 3, 5, 19, 22, 31, 38,
43, 48: 1, 48: 2, 48: 3, 48: 4, 4
8: 5, 49: 1, 53: 1, 57: 1, 57: 2, 5
8: 4, 63: 1, 81, 81: 1, 81: 2, 81:
3, 81: 4, 88, 104, 108, 112, 12
2, 123, 144, 146, 149, 166, 16
8, 169, 170, 177, 178, 179, 18
4, 185, 208, 216, 226, 257, Pig
ment Violet 3, 19, 23, 29, 3
0, 37, 50, 88, Pigment Orange
13, 16, 20, 36, as a blue or cyan pigment, Pigment Blue 1, 15, 15: 1,
15: 2, 15: 3, 15: 4, 15: 6, 16, 17
-1, 22, 27, 28, 29, 36, 60, and as the green pigment, Pigment Green 7, 26, 3
6, 50, as a yellow pigment, Pigment Yell
ow 1, 3, 12, 13, 14, 17, 34, 35,
37, 55, 74, 81, 83, 93, 94, 95, 9
7, 108, 109, 110, 137, 138, 13
9,153,154,155,157,166,16
7, 168, 180, 185, 193, as black pigments, Pigment Black 7, 28, 26, and as white pigments, Pigment White 6, 1
8, 21, etc. can be used according to the purpose.

To disperse the pigment, for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker or the like can be used. . It is also possible to add a dispersant when dispersing the pigment. The type of dispersant is not particularly limited, but a polymer dispersant is preferably used, and examples of the polymer dispersant include Solsperse series manufactured by Zeneca. It is also possible to use synergists corresponding to various pigments as the dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment. The dispersion medium is a solvent or the polymerizable compound according to the present invention, but in the radiation curable ink used in the present invention, it is preferable to be solvent-free since it reacts and cures immediately after landing of the ink. When the solvent remains on the cured image, the solvent resistance is deteriorated, and the residual solvent VOC (Volatile Org)
The problem of an anic compound) arises. Therefore, it is preferable in view of dispersion suitability that the dispersion medium is selected from a polymerizable compound, not a solvent, and a monomer having the lowest viscosity among them.

The average particle size of the pigment particles is 0.08 to 0.5.
Preferably, the maximum particle size is 0.3 to 10 μm.
m, preferably 0.3 to 3 μm, the selection of pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set.
By controlling the particle size, clogging of the head nozzle can be suppressed, and the ink storage stability, ink transparency, and curing sensitivity can be maintained. The addition amount of the coloring material is preferably 1 to 10% by mass with respect to the total mass of the ink.

The ink jet recording ink of the present invention includes
In addition to the above description, other components can be added if necessary.

When an electron beam, an X-ray or the like is used as the irradiation light, a polymerization initiator is not necessary, but when an ultraviolet light (UV light), visible light or infrared light is used as the radiation source,
A radical polymerization initiator, a polymerization initiation auxiliary agent, a sensitizing dye, etc. are added according to each wavelength. The addition amount of these compounds needs to be approximately 1 to 10% by mass of the entire ink. As the polymerization initiator, various known compounds can be used, but it is preferable to select from those that are soluble in the polymerizable compound according to the present invention, and specific polymerization initiators include, for example, xanthone or Examples thereof include thiooxanthone-based polymerization initiators, benzophenone-based polymerization initiators, quinone-based polymerization initiators and phosphine oxide-based polymerization initiators.

From the viewpoint of improving the storage stability, it is preferable to add a polymerization inhibitor in an amount of 200 to 20000 ppm. The ink jet recording ink of the present invention is 40 to 80
It is preferable to heat the composition in the range of 0 ° C. to lower the viscosity and then to inject it, and it is preferable to add a polymerization inhibitor in order to prevent head clogging due to thermal polymerization.

In addition to these, known compounds can be used as required. For example, surfactants, leveling additives, matting agents, polyester resins, polyurethane resins, vinyl resins for adjusting the physical properties of the film. Resins, acrylic resins, rubber resins, waxes and the like can be appropriately selected and used. Further, in order to improve adhesion to a recording medium such as polyolefin or PET, it is also preferable to include a tackifier that does not inhibit polymerization. Specifically, a high-molecular-weight adhesive polymer described in JP-A 2001-49200, 5-6p (for example, an ester of (meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms, ( (Meth) acrylic acid and 3 to 14 carbon atoms
With an alicyclic alcohol, a copolymer of an ester of (meth) acrylic acid and an aromatic alcohol having 6 to 14 carbon atoms), or a low molecular weight tackifying resin having a polymerizable unsaturated bond. is there.

It is also effective to add an extremely small amount of organic solvent in order to improve the adhesion to the recording medium. In this case, it is effective to add it within a range that does not cause problems of solvent resistance and VOC, and its amount is 0.1% with respect to the total ink mass.
Is preferably 5 to 5% by mass, more preferably 0.1 to 3% by mass.

Further, as a means for preventing the sensitivity from being lowered due to the light shielding effect of the ink coloring material, a combination of a cationic polymerizable monomer having a long life of a polymerization initiator and a polymerization initiator is used to produce a radical
It is also one of the preferable embodiments to use a cationic hybrid type curing ink.

The ink jet recording ink of the present invention has an ink viscosity of 7 at the temperature at the time of ejection in consideration of ejection property.
It is preferably ˜30 mPa · s, more preferably 7 to 20 mPa · s, and it is preferable to appropriately determine the composition ratio so as to be in the above range. 25
The ink viscosity at -30 ° C is 35 to 500 mPa · s,
It is preferably 35 to 200 mPa · s. By setting the viscosity at room temperature to a high level, even when using a porous recording medium, it is possible to prevent ink from penetrating into the recording medium, reduce uncured monomer, and reduce odor. It is possible to suppress dot bleeding at the time, and as a result, the image quality is improved. When the ink viscosity at 25 to 30 ° C. is less than 35 mPa · s, the bleeding prevention effect is small, and when it is more than 500 mPa · s, there is a problem in the delivery of the ink liquid.

The surface tension of the ink jet recording ink of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. Polyolefin, PE
When recording on various recording media such as T, coated paper, and uncoated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

Next, the ink jet recording method and ink jet recording apparatus of the present invention will be described below.

In the ink jet recording method according to the ninth aspect, one of the features is that the ink is heated to 40 to 80 ° C. to reduce the viscosity of the ink to 7 to 30 mPa · s and then ejected. High injection stability can be realized by using this method. In general, the radiation curable ink generally has a higher viscosity than the water-based ink, so that the fluctuation range of the viscosity due to the temperature fluctuation during printing is large. This variation in ink viscosity has a great effect on the droplet size and droplet ejection speed as it is, causing image quality deterioration. Therefore, it is necessary to keep the ink temperature during printing as constant as possible. The ink temperature control range is preferably set temperature ± 5 ° C, more preferably set temperature ± 2 ° C, and further preferably set temperature ± 1 ° C.

One feature of the ink jet recording apparatus according to the tenth aspect is that it is provided with means for stabilizing the ink temperature, and the portion for keeping the temperature constant is from the ink tank (the intermediate tank if there is an intermediate tank) to the nozzle. All piping systems and members up to the exit surface are covered.

The method for controlling the temperature is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping portion and control the heating according to the ink flow rate and the environmental temperature. Further, the head unit to be heated is preferably thermally shielded or insulated so that the apparatus body is not affected by the temperature from the outside air. In order to shorten the printer startup time required for heating or to reduce the loss of thermal energy, it is preferable to perform heat insulation from other parts and reduce the heat capacity of the entire heating unit.

Another important process in the present invention is the irradiation condition of radiation. The basic irradiation method is disclosed in JP-A-60-132767. Specifically, light sources are provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain time has elapsed after the ink has landed. Further, curing is completed by another light source that is not driven. WO 9,95
No. 4,415 discloses, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording section with UV light. These irradiation methods can be used in the inkjet recording method of the present invention.

A feature of the ink jet recording method according to a ninth aspect is that the above ink is used to heat the ink to a constant temperature, and the time from landing to irradiation is 0.01 to 0.
It is 5 seconds, and preferably 0.01 to 0.3.
The irradiation is performed after a second, more preferably 0.01 to 0.15 seconds. By controlling the time from landing to irradiation to an extremely short time in this way, it becomes possible to prevent the landing ink from bleeding before curing. Further, even when the recording medium is porous, the exposure can be performed before the ink penetrates to a deep portion where the light source does not reach, so that the unreacted monomer can be suppressed from remaining and as a result, the odor can be reduced. The combined use of the ink jet recording method described above and the ink of the present invention brings about a great synergistic effect. In particular, when an ink having an ink viscosity at 25 ° C. of 35 to 500 MP · s is used, a great effect can be obtained. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. Note that in order to obtain a color image, it is preferable to superimpose the colors in order of low lightness.
When inks of low lightness are piled up, it is difficult for the irradiation line to reach the lower ink, and the curing sensitivity is impaired, the residual monomer increases, odor is generated, and the adhesiveness is apt to deteriorate. Also,
Irradiation can be carried out by exposing all colors and exposing them in a lump, but it is preferable to expose each color in order from the viewpoint of accelerating curing.

An example of the ink jet recording apparatus of the present invention will be shown below. FIG. 1 is a schematic bottom view showing an example of a print head unit having a radiation irradiation section that can be used in the present invention.

In FIG. 1, the carriage 5 has an ink jet head 4Y for yellow ink, an ink jet head 4M for magenta ink, an ink jet head 4C for cyan ink and an ink jet head 4K for black ink. A radiation irradiator (UV light irradiator) 3 connected to the ultraviolet light source 1 and the optical fiber 2 is provided adjacent to each other. While moving the carriage 5 in the main scanning direction, ink is ejected onto the recording medium from each of the head jet heads 4Y to 4K having a plurality of nozzles, and immediately after that, the radiation irradiating section 3 provided in the downstream section thereof causes ultraviolet rays to be emitted. Is applied to cure the landed ink droplets.

FIG. 2 is a schematic side view showing an example of a print head unit having a viscosity adjusting means by heating which can be used in the present invention.

In FIG. 2, an ink supply tank 6, a filter 7 and ink heads 4Y-4 which are connected to a carriage 5 via a supply pipe 8 are connected to a carriage 5.
It has each color inkjet unit composed of K,
These are kept at a predetermined temperature by the heating unit 9. Further, a radiation irradiation unit (UV light irradiation unit) 3 connected to the ultraviolet light source 1 by an optical fiber 2 is provided adjacent to the heating unit 9. Further, the inkjet heads 4Y to 4K for each color are provided with a pair of shielding plates 12 so as not to be directly exposed to ultraviolet rays. Similar to FIG. 1, while moving the carriage 5 in the main scanning direction, the ink droplets 1 from the inkjet heads 4Y to 4K of each color having a plurality of nozzles maintained at a constant temperature.
Immediately after landing 1 on the recording medium 10, ultraviolet rays are radiated by each radiation irradiating section 3 provided on the downstream side to cure the landed ink droplet 11.

FIG. 3 is an overall schematic view showing an example of the ink jet recording apparatus of the present invention. In FIG. 3, the recording medium 10 conveyed from the original roll 12 is conveyed to the printing unit via the support roll 14, and the ink liquid is ejected from each inkjet head in the carriage 5 having the configuration shown in FIGS. 1 and 2. A droplet 11 is ejected and landed on the recording medium 10,
After curing and then cooling the recording medium 10 with the chiller roll 15, in order to completely cure the unreacted polymerizable compound, the post-treatment exposure device 16 provided downstream thereof radiates ultraviolet rays again to carry out the curing reaction. To complete. Then
The recording medium 10 on which the image printing and fixing are completed is wound up by a winding roll.

[0059]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to the forms in these examples.

Example 1 Preparation of Pigment Dispersion Pigment Dispersion 1 of yellow, magenta, cyan and black according to the method described below.
Was prepared. The dispersion conditions are adjusted appropriately by using a known dispersing device so that the average particle size of each pigment particle is in the range of 0.2 to 0.3 μm, and then the filter is heated under heating. It was prepared by filtration.

(Yellow Pigment Dispersion 1) C.I. I. Pigment Yellow 12 10 parts by mass Polymer dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Stearyl acrylate 85 parts by mass (Magenta Pigment Dispersion 1) C.I. I. Pigment Red 57: 1 15 parts by mass Polymeric dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Stearyl acrylate 80 parts by mass (Cyan pigment dispersion 1) C.I. I. Pigment Blue 15: 3 20 parts by mass Polymeric dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Stearyl acrylate 75 parts by mass (Black pigment dispersion 1) C.I. I. Pigment Black 7 20 parts by mass Polymeric dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Stearyl acrylate 75 parts by mass << Preparation of Ink >> Using each dispersion 1 prepared above, each color ink is prepared according to the method described below. Prepared.

(Yellow Ink 1) Yellow Pigment Dispersion 1 20 parts by mass Stearyl acrylate 60 parts by mass Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts by mass 6 functional aliphatic urethane acrylate (molecular weight 1000) 5 parts by mass Polymerization initiator (Manufactured by Ciba, Irgacure 184) 5 parts by mass (Magenta ink 1) Magenta pigment dispersion 1 20 parts by mass Stearyl acrylate 60 parts by mass Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts by mass 6 functional aliphatic urethane acrylate (molecular weight) 1000) 5 parts by mass Polymerization initiator (manufactured by Ciba, Irgacure 184) 5 parts by mass (Cyan ink 1) Cyan pigment dispersion 1 15 parts by mass Stearyl acrylate 65 parts by mass Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts by weight 6-functional aliphatic urethane acrylate (molecular weight 1000) 5 parts by weight Polymerization initiator (manufactured by Ciba, Irgacure 184) 5 parts by weight (Black ink 1) Black pigment dispersion 1 15 parts by weight Stearyl acrylate 65 parts by weight Bifunctional Aromatic urethane acrylate (Molecular weight 1500) 10 parts by mass Hexafunctional aliphatic urethane acrylate (Molecular weight 1000) 5 parts by mass Polymerization initiator (Ciba, Irgacure 184) 5 parts by mass Absolutely each color ink 1 prepared as described above Filtration accuracy 2
Ink 1 of each color was obtained by filtering with a μm filter.

The viscosity of each color ink 1 at 30 ° C. is 8
0-150 mPa · s, viscosity at 70 ° C is 10-2
Surface tension at 0 mPa · s, 30 ° C is 24-28 m
It was N / m.

<Inkjet image recording> Next, recording was carried out on a recording medium using an inkjet recording apparatus having a structure of FIGS. 1 to 3 having a piezo type inkjet nozzle. The ink supply system was composed of a main tank, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo type inkjet head. The ink supply tank and the inkjet head were thermally insulated and heated. The temperature sensor was provided in the vicinity of each of the nozzles of the ink supply tank and the inkjet head, and the temperature was controlled so that the nozzle portion was always 70 ° C ± 2 ° C. The piezo type inkjet head is 8 ~
Multi-size dots of 30 pl at 720 x 720 dpi
It was driven so that it could be ejected at a resolution of. UV-A after landing
The exposure system, the main scanning speed and the emission frequency were adjusted so that the light was condensed at an exposure surface illuminance of 100 mW / cm ² and the irradiation was started 0.1 seconds after the ink landed on the recording medium. Also, the exposure time was variable and the exposure energy was applied. In addition,
The term "dpi" in the present invention means the number of dots per 2.54 cm.

Each of the color inks prepared above was ejected in the order of black → cyan → magenta → yellow at an ambient temperature of 25 ° C., and UV light was irradiated for each color. The total exposure energy per color is uniformly 300 mJ / cm as the energy to completely cure so that the tackiness disappears by palpation.
Exposed at ² . As a recording medium, each color image was recorded on PET film, surface-treated transparent biaxially oriented polypropylene film with printability, soft vinyl chloride sheet, cast coated paper, and high quality paper. A high-resolution image with no image was obtained. Further, even on high-quality paper, the ink did not spread around the back surface, the ink was sufficiently cured, and the odor due to the unreacted monomer was hardly generated. Further, the ink recorded on the film had sufficient flexibility, the ink did not crack even when bent, and there was no problem in the adhesion test by peeling the cellophane tape (R). As described above, it was possible to record a high quality inkjet image on various recording media by using the polymerizable compound having low skin irritation and sensitization.
However, under the above printing conditions, if the ink temperature during ejection was set to 25 ° C., stable ejection could not be achieved.

Example 2 << Preparation of Ink >> Magenta inks 2 to 5 were prepared according to the method described below.

(Magenta Ink 2) Magenta Pigment Dispersion 1 20 parts by mass Stearyl acrylate 50 parts by mass Lactone-modified acrylate (molecular weight 458) 20 parts by mass 6-functional aliphatic urethane acrylate (molecular weight 1000) 5 parts by mass Polymerization initiator (manufactured by Ciba) , Irgacure 184) 5 parts by mass The magenta ink 2 prepared above had an ink viscosity at 25 ° C. of 150 mPa · s and an ink viscosity at 70 ° C. of 20 mPa · s.

(Magenta Ink 3) Magenta Pigment Dispersion 1 20 parts by mass Stearyl acrylate 75 parts by mass Polymerization initiator (Ciba, Irgacure 184) 5 parts by mass The above prepared magenta ink 3 has an ink viscosity of 15 mPa · s, ink viscosity at 70 ° C is 8
It was mPa · s.

(Magenta Ink 4: Comparative Example) Magenta Pigment Dispersion 2 20 parts by mass Isobornyl acrylate 60 parts by mass Tetramethylolmethane triacrylate 15 parts by mass Polymerization initiator (Ciba, Irgacure 184) 5 parts by mass <Magenta Preparation of Pigment Dispersion Liquid 2> Magenta Pigment Dispersion Liquid 2 was prepared in the same manner as in Preparation of Magenta Pigment Dispersion Liquid 1 described in Example 1 except that isobornyl acrylate was used instead of stearyl acrylate.

The magenta ink 4 prepared above had an ink viscosity at 25 ° C. of 16 mPa · s.

(Magenta Ink 5: Comparative Example) Magenta Pigment Dispersion 3 20 parts by mass Triethylene glycol diacrylate 45 parts by mass 1-4 butanediol diacrylate 30 parts by mass Polymerization initiator (manufactured by Ciba, Irgacure 184) 5 parts by mass Part <Preparation of Magenta Pigment Dispersion Liquid 3> Magenta Pigment Dispersion Liquid 3 was prepared in the same manner as in Magenta Pigment Dispersion Liquid 1 described in Example 1 except that triethylene glycol diacrylate was used instead of stearyl acrylate. Prepared.

The magenta ink 5 prepared above had an ink viscosity at 25 ° C. of 19 mPa · s.

<Inkjet image recording> Using the magenta inks 2 to 5 prepared as described above and the magenta ink 1 prepared in Example 1, a magenta image is printed in the same manner as in Example 1. went.

<< Evaluation of Inkjet Image >> Next, for each formed image, according to the method described below, sensitivity required for curing, penetrability in high-quality paper, ink bleeding in PET film, adhesion, and bending The flexibility, skin irritation, and sensitization were evaluated.

(Measurement of Curing Sensitivity) The amount of exposure energy (mJ /
cm ² ) was defined as the cure sensitivity.

(Evaluation of Penetration to Fine Paper) The images printed on the fine paper were evaluated for their permeability according to the following criteria.

◯: Almost no penetration, no residual monomer odor Δ: Permeation slightly, residual monomer odor slightly recognized X: Clearly ink penetrates to the back side and strong residual monomer odor (PET film) Ink bleeding evaluation in) The ink printed on the PET film was evaluated for ink bleeding according to the following criteria.

◯: No bleeding between adjacent dots Δ: Slightly bleeding of dots X: Blurring of dots and clear blurring of image (evaluation of adhesion in PET film) The printed image prepared above was completely printed surface A sample that does not scratch the
In accordance with JISK 5400, make 11 cuts vertically and horizontally at 1 mm intervals on the printed surface to make 100 1 mm square grid samples, and attach cellophane tape on each printed surface. Then, the printed image was peeled off rapidly at an angle of 90 degrees, and the condition of the printed image or the state of the cross-cut which was not peeled off was evaluated according to the following criteria.

◯: No peeling of the printed image was observed even in the cross-cut test. Δ: Some ink peeling was found in the cross-cut test, but almost no peeling was found unless the ink surface was scratched. Under both conditions, peeling with Cellotape (R) was easily recognized (evaluation of flexibility in PET film) The image printed on the PET film was evaluated for flexibility according to the following criteria.

◯: The printed image is in close contact even when the PET film is repeatedly bent, and no cracks are generated. Δ: The printed image is in close contact even after repeated bending, but
Cracks appear slightly ×: Cracks occur in the printed image area when bent, and film peeling occurs repeatedly (evaluation of skin irritation and sensitization) Evaluation of each magenta ink for irritation and sensitization to the skin did.

Table 1 shows each evaluation result obtained as described above.

[0082]

[Table 1]

As is clear from Table 1, when the magenta inks 1, 2 and 3 are compared, the curing sensitivity, bleeding and adhesion are improved by blending not only monoacrylate but also a high molecular weight polyfunctional monomer. I understand. On the other hand, the magenta ink 4 containing less than 20% by mass of the polymerizable compound according to the present invention could not obtain sufficient adhesion and flexibility. Further, although the magenta ink 5 containing no polymerizable compound according to the present invention can obtain a certain degree of curing sensitivity, adhesiveness and flexibility,
Triethylene glycol diacrylate used, 1
-4 Butanediol diacrylate was found to have skin irritation and sensitization.

Example 3 Using the magenta ink 1 prepared in Example 1 and the magenta ink 3 prepared in Example 2, ink droplets were landed on the recording medium by the ink jet image recording method described in Example 1. From the start to UV irradiation is 0.1
Seconds, 0.2 seconds, 0.4 seconds, 0.6 seconds, PE
An image was recorded on a T film, bleeding was evaluated by the method described in Example 1, and the obtained results are shown in Table 2.

[0085]

[Table 2]

As is clear from Table 2, in the magenta ink 1 of the present invention, the ink bleeding as a color image was gradually deteriorated as the time from landing to irradiation with ultraviolet rays was lengthened. Even in the magenta ink 3 in which the total amount of stearyl acrylate was a low-viscosity ink, clear image bleeding occurred when the time from landing to irradiation was 0.4 seconds or more. That is, printing is performed by heating ink of 35 mPa · s or more at room temperature, and after the ink droplets land on the recording medium, ultraviolet rays are radiated within 0.3 seconds to effectively suppress image bleeding. I was able to confirm that I could.

Example 4 Preparation of Magenta Pigment Dispersion 4 Magenta Pigment Dispersion 4 was prepared according to the method described below. The dispersion conditions are adjusted appropriately by using a known dispersing device so that the average particle size of each pigment particle is in the range of 0.2 to 0.3 μm, and then the filter is heated under heating. It was prepared by filtration.

C. I. Pigment Red 57: 1 15 parts by mass Polymeric dispersant (Solsperse series manufactured by Zeneca) 5 parts by mass Tetraethylene glycol diacrylate (purity 99% or more) 80 parts by mass << Preparation of magenta inks 11 to 28 >> Each described below. After adding the additives, in the same manner as described in Example 1,
Magenta inks 11 to 28 were prepared.

Magenta Pigment Dispersion Liquid 4 20 parts by mass Polymerizable compound mixture (combination shown in Table 3) 75 parts by mass Polymerization initiator (manufactured by Ciba, Irgacure 369) 4 parts by mass Polymerization initiator (manufactured by Ciba, Irgacure) 184) 1 part by mass Table 3 shows the details of the polymerizable compound mixed liquid used in the preparation of each magenta ink. The numerical value in the parentheses in the table is the mass ratio of each polymerizable compound.

The abbreviations of the polymerizable compounds shown in Table 3 are listed below. M1: phenoxy-polyethylene glycol acrylate M2: hydroxypivalic acid neopentyl glycol diacrylate M3: glycerine propoxytriacrylate M4: isomyristyl acrylate M5: isostearyl acrylate M6: ethoxylated phenyl acrylate M7: butoxyethyl acrylate M8: pentaerythritol tetraacrylate M9: cetyl acrylate M10: dimethylol tricyclodecane diacrylate M11: pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer M12: 2-ethylhexyl-diglycol acrylate M13: lactone-modified towable acrylate M14: caprolactone-modified dipentaerythritol hexa Acrylate M15: (2-Ethoxyethoxy) ethyl acrylate M16: Methoxy-polyethylene glycol acrylate M17: Caprolactone-modified trimethylolpropane triacrylate M18: 2-Acryloyloxyethylsuccinic acid M19: Dimethyloldicyclopentanediacrylate M20: Pentaerythritol ethoxytetraacrylate M21: propylene glycol diglycidyl ether acrylic acid adduct M22: ditrimethylolpropane tetraacrylate M23: 6-functional urethane acrylate M24: 2-acryloyloxyethyl phthalic acid M25: bisphenol A diglycidyl ether (meth) acrylic acid adduct M26: Dipentaerythritol hexaacrylate M27: 2-acryloyloxyethyl hexahydrophthalic acid 28: methoxydipropylene glycol acrylate M29: ethylene oxide-modified trimethylolpropane triacrylate M30: propylene oxide adduct of bisphenol A diacrylate M31: amine-modified polyester tetraacrylate M32: 2-acryloyloxyethyl-2-hydroxyethylphthalic acid M33: bisphenol A ethylene oxide adduct diacrylate M34: nonylphenol ethylene oxide adduct acrylate M35: stearyl acrylate M36: tetraethylene glycol diacrylate << inkjet image recording >> Magenta inks 11 to 28 prepared as described above are used. A magenta image was printed in the same manner as in Example 1.

<< Evaluation of Inkjet Image >> Then, for each formed image, according to the method described in Example 2, the sensitivity required for curing, the penetrability in high-quality paper, and PET.
The film was evaluated for ink bleeding, adhesion, flexibility at bending, skin irritation / sensitization, and the results are shown in Table 3.

[0092]

[Table 3]

As is clear from Table 3, similar to the result of Example 2, the ink containing 20 to 95% by mass of the polymerizable compound described in the compound group A according to the present invention, in the total mass of the ink, is the ink bleeding. Good results were obtained with respect to adhesiveness, flexibility during bending, skin irritation and sensitization.

[0094]

According to the present invention, even for a support which is usually difficult to directly record by an ink jet recording method,
Highly safe inkjet recording ink capable of recording an image without bleeding, having high sensitivity and high adhesion to a recording medium, and having low skin irritation and sensitization and an inkjet recording method and inkjet recording using the same Equipment could be provided.

[Brief description of drawings]

FIG. 1 is a schematic bottom view showing an example of a print head unit having a radiation irradiation unit that can be used in the present invention.

FIG. 2 is a schematic side view showing an example of a print head unit having a heating viscosity adjusting means that can be used in the present invention.

FIG. 3 is an overall schematic diagram showing an example of an inkjet recording apparatus of the present invention.

[Explanation of symbols]

1 UV light source 2 optical fiber 3 Radiation irradiation part (UV light irradiation part) 4Y, 4M, 4C, 4K inkjet head 5 carriage 6 Ink supply tank 7 filters 8 supply piping 9 heating unit 10 recording media 11 ink droplets 15 Chiller roll 16 Post-processing exposure equipment

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI Theme Coat (Reference) B41J 3/04 102Z

Claims (10)

[Claims] 1. An inkjet recording ink curable by irradiation of radiation, wherein the inkjet recording ink contains at least a coloring material and a polymerizable compound, and the polymerizable compound is at least 1 selected from the following compound group A. And the compound group A is 20 to 95% of the total ink mass.
An ink for inkjet recording, characterized in that the content of the ink is in the range of mass%. Compound group A: isomyristyl acrylate, isostearyl acrylate, cetyl acrylate, isoamyl acrylate, stearyl acrylate, methoxy-polyethylene glycol acrylate, methoxydipropylene glycol acrylate, 2 (2-ethoxyethoxy) ethyl acrylate, butoxyethyl acrylate, phenoxy-polyethylene Glycol acrylate, 2-ethylhexyl-diglycol acrylate,
2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethyl phthalic acid, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol ethylene oxide adduct acrylate, 2-acryloyloxyethyl Hexahydrophthalic acid, lactone-modified towable acrylate, hydroxypivalic acid neopentyl glycol diacrylate, dimethylol tricyclodecane diacrylate,
Dimethylol dicyclopentane diacrylate, propylene glycol diglycidyl ether acrylic acid adduct, bisphenol A diglycidyl ether (meth) acrylic acid adduct, bisphenol A propylene oxide adduct diacrylate, bisphenol A ethylene oxide adduct diacrylate Modified bisphenol A diacrylate, glycerin propoxytriacrylate, pentaerythritol tetraacrylate, pentaerythritol ethoxytetraacrylate, dipentaerythritol hexaacrylate, caprolactone modified dipentaerythritol hexaacrylate, caprolactone modified trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate Acrylate, amine modified poly Stell tetraacrylate,
Pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer. 2. An ink jet recording ink of 40 to 8 is used.
After the ink jet recording ink is heated to a constant temperature in the range of 0 ° C. to adjust the viscosity of the ink jet recording ink to 7 to 30 mPa · s, the ink jet recording ink is jetted, and after the ink jet recording ink lands on the recording medium, 0 .01-0.
An inkjet recording ink curable by irradiation with radiation after 5 seconds, wherein the inkjet recording ink contains at least a coloring material and a polymerizable compound,
The polymerizable compound is at least one kind selected from the compound group A, and the compound group A is 20 to 9 of the total ink mass.
An ink for inkjet recording characterized by containing 5% by mass. 3. A polymerizable monomer or a polymerizable oligomer having a molecular weight of 400 or more is contained.
Or the ink jet recording ink according to item 2. 4. The compound group A is contained in an amount of 50 to 90% by mass with respect to the total mass of the ink.
4. The inkjet recording ink according to any one of 3 above. 5. The polymerizable compound is a monoacrylate compound selected from the compound group A and a polyfunctional acrylate monomer or a polyfunctional acrylate oligomer, according to any one of claims 1 to 4. The ink jet recording ink according to item 1. 6. The monoacrylate compound is at least one selected from stearyl acrylate, cetyl acrylate, isoamyl acrylate, isomystyl acrylate and isostearyl acrylate,
The inkjet recording ink according to claim 5, wherein the total amount of the monoacrylate compound is 7 to 70% by mass based on the total mass of the ink. 7. The ink for ink jet recording according to claim 5, wherein the polyfunctional acrylate monomer or the polyfunctional acrylate oligomer is a caprolactam-modified acrylic monomer or oligomer. 8. The ink for ink jet recording according to claim 1, wherein the polymerizable compound contains polyalkoxy acrylate in an amount of 0 to 75% by mass based on the total mass of the ink. 9. The method according to claim 1, which is curable by irradiation with radiation.
In the inkjet recording method, the ink for inkjet recording according to any one of items 1 to 8 is jetted onto a recording medium by a drop-on-demand inkjet method, and then the ink landed by irradiation of radiation is reacted and cured. Ink for 40 ~ 80 ℃
In the range of 0.01 to 0.01% after the inkjet recording ink is ejected onto the recording medium by heating the inkjet recording ink to a constant temperature and adjusting the viscosity of the inkjet recording ink to 7 to 30 mPa · s. An inkjet recording method, which comprises irradiating with radiation after 0.5 seconds. 10. The ink for inkjet recording according to claim 1, which is curable by irradiation with radiation, is jetted onto a recording medium by a drop-on-demand inkjet system, and then landed by irradiation with radiation. In an ink jet recording apparatus for reacting and curing the ink, the ink for ink jet recording is kept at a constant temperature in the range of 40 to 80 ° C. by heating the jet nozzle and the ink supply tank or the ink supply pipe system,
The viscosity of the inkjet recording ink is 7 to 30 mPa.
An ink jet recording apparatus comprising: a viscosity adjusting unit for adjusting to s, and a unit for irradiating radiation 0.01 to 0.5 seconds after the ink for ink jet recording has landed.