JP2003213183A - Radiation-curable ink for inkjet and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet technique whereby a high-quality image free of blur can be printed with a high sensitivity without causing curl, waves, or the like, on a substrate comprising an easily deformable thin film, such as a plastic film, usually difficult to be directly printed by an inkjet recording method. <P>SOLUTION: The radiation-curable ink for inkjet is used in an inkjet recording method wherein the ink is jetted on a heat-shrinkable substrate and an ink image formed thereon is exposed to a radiation to be cured. The cure shrinkage of the ink image formed from the radiation-curable ink on the substrate is -0.5 to +1.0%. <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 inkjet ink capable of reacting and curing by being irradiated with radiation such as ultraviolet rays and electron beams, and an inkjet recording method using this ink.

[0002]

2. Description of the Related Art In recent years, the inkjet recording method has been simple and easy.
Since an image can be produced at low cost, it has been applied to various printing fields such as photography, various types of printing, marking, and special printing such as color filters. Emit particularly fine dots
Using a recording device to control, ink with improved color reproduction range, durability, and ejection suitability, and special paper with dramatically improved ink absorbency, color material coloring, surface gloss, etc., for silver salt photography It is also possible to obtain comparable image quality. The improvement in image quality of today's inkjet recording system is achieved only when all the recording devices, inks, and special papers are prepared.

However, the ink jet system requiring special paper has 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 dedicated paper by an 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 a UV inkjet method in which crosslinking is performed by UV light after recording.

Among them, the UV ink jet system has been receiving 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. Specifically, for example, Japanese Patent Fairness 5
-54667, JP-A-6-200204, and Table 20
No. 00-504778 discloses UV curable inkjet inks.

[0005]

However, an image is formed by jetting droplets of these inks onto a heat-shrinkable support such as a thin plastic film, and after fixing the image on the plastic film, ultraviolet rays are applied. When the ink is irradiated, there is a problem that the ink itself is cured and shrunk, or the thin film plastic film is deformed due to heat generated during the reaction, so that curling or waviness occurs and the value of the printed matter is reduced. In particular, such a problem was conspicuous in a support having strong heat shrinkability such as a shrink film used for package printing.

Since it is difficult to obtain ink adhesion on a support such as a film and it is desired to increase the sensitivity of the ink composition, a polyfunctional monomer or polyfunctional oligomer having a relatively high viscosity as a polymerizable compound is desired. It is desirable to use a prepolymer, a resin, etc. in combination, but such a highly reactive ink has a high curing shrinkage ratio of the ink and is prominent in curling and waviness. Higher viscosity inks are typically 40-90
It is desirable to heat the ink to about ℃ and lower the viscosity to eject the ink from the viewpoints of stable ejection and landing accuracy, but there is also a problem that the heat of the ink causes curling and waviness.

As described above, the UV-curable ink jet system utilizing UV light has an excellent feature that it can be drawn on a support such as a plastic film that does not absorb ink, but it can be applied to a thin film or the like. Due to the problem of suitability, it has not been put into practical use for printing on flexible packaging materials, especially shrink films.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent curling or waviness on a support such as a plastic film, which is usually difficult to be directly recorded by an ink jet recording method. Another object of the present invention is to provide an inkjet technology capable of printing a high-quality image without image blurring with high sensitivity.

[0009]

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

1. A radiation-curable inkjet ink used in an inkjet recording method in which an ink is ejected onto a support that shrinks by heating, and an ink image formed on the support is irradiated with radiation to be cured, which is formed on the support. The curing shrinkage of the ink image is -0.5 to
A radiation-curable inkjet ink having a content of + 1.0%.

2. 2. The radiation-curable inkjet ink as described in 1 above, which contains a monofunctional monomer, a bifunctional monomer, and a trifunctional or higher functional monomer.

3. 3. The radiation curable inkjet printer according to 1 or 2 above, which contains a plurality of monomers and has a maximum difference in solubility parameter between the monomers arbitrarily selected from the plurality of monomers is 1 or more and 2.5 or less. ink.

4. In an inkjet recording method of injecting a radiation-curable inkjet ink onto a support that contracts by heating, and curing the ink image by irradiating the ink image formed on the support with radiation,
The curing shrinkage of the ink image formed on the support is −
The ink jet recording method is characterized by being 0.5 to + 1.0%.

5. 5. The ink jet recording method according to 4, wherein the curing of the ink image by irradiation with radiation is performed twice or more.

6. 6. The ink jet recording method according to 4 or 5, wherein the temperature of the ink is adjusted to 25 to 70 ° C. and then the ink is ejected.

7. 7. The ink jet recording method according to any one of 4 to 6 above, wherein the support is held under a tension of 1.0 to 7.0 kg / m to eject the ink and irradiate with radiation.

8. The heat shrinkage of the support at 80 ° C is 5
-50%, any one of the above-mentioned 4-7
Inkjet recording method according to the item.

9. 9. The ink jet recording method according to any one of 4 to 8 above, wherein the support is any one of a PET film, an OPS film, an OPP film, an ONy film and a PVC film.

As a result of intensive studies aimed at addressing the above-mentioned problems, the present inventors have found that an image forming method of irradiating an ink image formed by ejecting an ink composition with radiation, of which radiation curing is particularly preferable. Focusing on the shrinkage rate due to the curing of the ink used in the inkjet recording method using a positive inkjet ink, when the curing shrinkage rate of the ink image formed on the support shows a specific value,
It was founded that a high-quality image with no image blurring can be printed with high sensitivity without causing curling or waviness even on various recording media such as a support having no ink absorbency .

The present invention will be described in more detail below. First, the radiation curable inkjet ink (hereinafter, also simply referred to as an ink or an ink composition) will be described. (Ink) The ink used in the present invention is used for an ink jet recording method of ejecting onto a support and irradiating the ink image formed on the support with radiation.
It is preferably composed of at least a polymerizable monomer and an initiator.

Various (meth) acrylate monomers can be used as the polymerizable monomer. For example, isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomystil acrylate, isostearyl acrylate, 2-ethylhexyl-diglycol acrylate, 2-hydroxybutyl acrylate, 2-acryloyloxyethyl hexahydrophthalic acid. , Butoxyethyl acrylate, ethoxydiethylene glycol acrylate, methoxydiethylene glycol acrylate,
Methoxy polyethylene glycol acrylate, methoxypropylene glycol acrylate, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
2-hydroxy-3-phenoxypropyl acrylate, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2
-Hydroxyethyl-phthalic acid, lactone-modified flexible acrylate, monofunctional monomers such as t-butylcyclohexyl acrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol Diacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,9
Nonanediol diacrylate, neopentyl glycol diacrylate, dimethylol-tricyclodecane diacrylate, EO adduct diacrylate of bisphenol A, PO adduct diacrylate of bisphenol A, neopentyl glycol diacrylate hydroxypivalate, polytetramethylene Bifunctional monomers such as glycol diacrylate, trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, pentaerythritol triacrylate,
Trifunctional or more than pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, ditrimethylolpropane tetraacrylate, glycerin propoxy triacrylate, cowprolactone modified trimethylolpropane triacrylate, pentaerythritol ethoxy tetraacrylate, caprolactam modified dipentaerythritol hexaacrylate, etc. The polyfunctional monomer of is mentioned.

Besides, polymerizable oligomers can be blended in the same manner as the monomers. As the polymerizable oligomer,
Epoxy acrylate, aliphatic urethane acrylate,
Aromatic urethane acrylates, polyester acrylates, linear acrylic oligomers and the like can be mentioned.

In the present invention, it is particularly preferable to use a monofunctional, difunctional, trifunctional or higher polyfunctional monomer in combination as the polymerizable monomer. The monofunctional monomer has a large effect of reducing the shrinkage rate at the time of curing, has a low viscosity, and can easily obtain injection stability at the time of inkjet recording. The bifunctional monomer is preferably added because it has suitable sensitivity and excellent adhesion to various substrates. A trifunctional or higher polyfunctional monomer provides sensitivity and film strength after curing. By using these three together, curling and waviness due to curing shrinkage can be prevented, adhesion to a support and high sensitivity can be achieved.

The monofunctional monomer is 5 to 5 parts of the total ink composition.
40% by mass, 5 to 40% by mass of the bifunctional monomer, and 5 to 30% by mass of the polyfunctional monomer are preferably contained.
The monomer used in combination has a solubility parameter (SP
A combination in which the difference between the maximum value and the minimum value of the values is 1 or more is preferable in terms of adhesion to various substrates and curling due to curing shrinkage. The SP value is more preferably 1.5 or more, and its upper limit is preferably about 2.5.

In order to suppress the curing shrinkage rate upon irradiation with radiation, it is preferable to use a monomer having a curing shrinkage rate of 10% or less. Among them, a monofunctional monomer has a lower shrinkage rate than a bifunctional or higher functional monomer or oligomer, and is used for suppressing curling and obtaining adhesion to a support in order to impart flexibility to an ink image. Is preferred.

In addition, sensitization, skin irritation, eye irritation,
From the viewpoint of safety such as mutagenicity and toxicity, among the above monomers, particularly, isoamyl acrylate, stearyl acrylate, lauryl acrylate, octyl acrylate, decyl acrylate, isomyrstil acrylate, isostearyl acrylate, ethoxydiethylene glycol acrylate, methoxy polyethylene glycol acrylate. , Methoxypropylene glycol acrylate, isobornyl acrylate, lactone modified flexible acrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, EO modified trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ditrimethylol Propane tetraacrylate Glycerol propoxy triacrylate, caprolactone modified trimethylolpropane triacrylate, pentaerythritol tetraacrylate, caprolactam modified dipentaerythritol hexaacrylate preferred.

Further, among these, stearyl acrylate, lauryl acrylate, isostearyl acrylate, ethoxydiethylene glycol acrylate, isobornyl acrylate, tetraethylene glycol diacrylate, EO-modified trimethylolpropane triacrylate, glycerin propoxytriacrylate, cowprolactone-modified tri Methylolpropane triacrylate and caprolactam-modified dipentaerythritol hexaacrylate are particularly preferred.

As the initiator, conventionally known initiators such as arylalkyl ketone, oxime ketone, S-phenyl thiobenzoate, titanocene, aromatic ketone, thioxanthone, benzyl and quinone derivatives and ketocoumarins can be used. For more information on initiators, see "Applications and Markets of UV / EB Curing Technology" (CMC Publishing, edited by Yoneho Tabata / edited by Radtech Study Group). Among them, acyl phosphine oxide and acyl phosphonate have high sensitivity and their absorption is reduced by photocleavage of the initiator. Therefore, they are suitable for internal curing in an ink image having a thickness of 3 to 20 μm per color as in the inkjet method. Especially effective. In particular,
Bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide are preferable.

Further, like the above-mentioned monomers, 1-hydroxy-cyclohexyl-phenyl-ketone and 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropane-1 were selected in consideration of safety. -One, 2-hydroxy-2-methyl-1-phenyl-propane-1-
ON is preferably used.

The preferred amount of the initiator added is 1 to 6% by mass, preferably 2 to 5% by mass, based on the total weight of the ink composition.
In the present invention, it is preferable to irradiate the ink composition in two or more stages with different wavelengths or intensities, and it is particularly preferable to use two or more initiators in combination. Furthermore, by appropriately selecting the illuminance and time of irradiation, it is possible to suppress the curing shrinkage rate of the ink image within a preferable range.

In addition to this, when coloring the ink composition,
Add colorant. As the coloring material, a coloring material that can be dissolved or dispersed in the main component of the polymerizable compound can be used, but a pigment is preferable from the viewpoint of weather resistance. The following pigments can be used, but the pigments are not limited to these. C. I Pigment Yellow-1,3,1
2, 13, 14, 17, 42, 74, 81, 83, 8
7, 95, 109, 128, 185, C.I. I Pigm
ent Orange-16, 36, 38, C.I. I P
igment Red-5, 9, 22, 38, 48:
1,48: 2,48: 4,49: 1,53: 1,57:
1,63: 1, 101, 122, 144, 146, 18
4,185,188,212, C.I. I Pigment
Violet-19, 23, C.I. I Pigment
Blue-15: 1, 15: 3, 15: 4, 18,6
0, 27, 29, C.I. I Pigment Green
-7, 36, C.I. I Pigment White-
6,18,21, other organic white pigments, C.I. I Pig
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 for dispersing the ment Black-7 pigment. It is also possible to add a dispersant when dispersing the pigment. A polymer dispersant is preferably used as the dispersant. As a polymer dispersant, Sols by Avecia
Perse series can be mentioned. It is also possible to use synergists corresponding to various pigments as a 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 a polymerizable compound. The ink composition used in the present invention is preferably solvent-free because it reacts and cures immediately after landing on the support. If the solvent remains in the cured image, the solvent resistance deteriorates and the residual solvent V
OC (Volatile OrganicCompou
The problem of nd) arises. Therefore, it is preferable to select a polymerizable compound, not the solvent, as the dispersion medium, and a monomer having the lowest viscosity among them in view of dispersion suitability.

The dispersion has an average particle size of 0.08 to 0.5 μm.
And the maximum particle size is 0.3 to 10 μm,
A pigment, a dispersant, so that the thickness is preferably 0.3 to 3 μm,
Set the dispersion medium selection, dispersion conditions, and filtration conditions. 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 color material is preferably added in an amount of 1 to 10% by mass of the total ink. -Other components In order to improve the storage stability of the ink composition, 2 polymerization inhibitors have been added.
It is possible to add from 0 to 20000 ppm. Above all, the radiation curable ink is preferably heated and reduced in viscosity before being ejected. Therefore, it is preferable to add a polymerization inhibitor in order to prevent head clogging due to thermal polymerization.

In addition to these, a surfactant, a leveling additive, a matting agent, a polyester resin for adjusting the physical properties of the film, a polyurethane resin, a vinyl resin, if necessary,
Acrylic resins, rubber resins, and waxes can be added. In order to improve the adhesion to the recording medium, it is also effective to add an extremely small amount of organic solvent. in this case,
Addition is effective within the range where solvent resistance and VOC problems do not occur, and the amount is 0.1-5%, preferably 0.1-3.
%.

Further, due to the light shielding effect of the ink coloring material, as a means for preventing sensitivity, it is also possible to combine a cationically polymerizable monomer having a long initiator life with an initiator to form a radical / cation hybrid type cured ink. .

The composition ratio of the ink composition is determined so that the temperature at the time of ejection is preferably 7 to 30 mPa · s, more preferably 7 to 20 mPa · s, in consideration of ejectability. still,
The ink viscosity at 25 ° C. is preferably 35 mPa · s or more. By increasing the viscosity at room temperature, it is possible to prevent the ink composition from penetrating into the porous recording medium, reduce uncured monomer, reduce odor, and prevent dot bleeding when landing. Is improved. The surface tension is preferably 20 to 30 dyn / cm, more preferably 23 to 28 dyn / cm. (Inkjet recording method) In the inkjet recording method of the present invention, an ink composition as described above is injected onto a support,
The ink image is cured by drawing and irradiating the ink image formed on the support with radiation.

In the present invention, as the ejection conditions of the ink composition, it is necessary to adjust (heat) the temperature of the ink composition to 25 to 70 ° C. and lower the viscosity of the ink to eject the composition to prevent the ejection stability and the deformation of the support. Is particularly preferable in terms of. If the temperature is less than 25 ° C, sufficient stable ejection properties and landing accuracy cannot be obtained.
If the temperature is higher than 0 ° C., the support is likely to be thermally deformed, causing a curling problem. More preferably, it is 30 to 60 ° C. Since the radiation curable ink generally has a higher viscosity than the water-based ink, the fluctuation range of viscosity due to temperature fluctuation is large. The viscosity fluctuation directly affects the droplet size and droplet ejection speed,
Since the image quality deteriorates, it is necessary to keep the ink temperature as constant as possible. The control range of the ink temperature is set temperature ± 5 ° C, preferably set temperature ± 2 ° C, and more preferably set temperature ± 1 ° C.

Next, an important process is irradiation conditions. The basic irradiation method is disclosed in JP-A-60-132767. According to this, the light source is 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. US Pat. No. 6,145,979 discloses, as an irradiation method, a method using an optical fiber and a method of irradiating a recording section with UV light by applying a collimated light source to a mirror surface provided on the side surface of the head unit. These irradiation methods can be used in the inkjet recording method of the present invention.

It is preferable to heat the ink composition to a constant temperature and to irradiate it after 0.01 to 0.3 seconds, preferably 0.01 to 0.15 seconds, from the time of landing to irradiation. By controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before curing. In particular, the ink viscosity at 25 ° C is 35m.
A great effect can be obtained by using an ink of Pa · s or more. 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. In order to obtain a color image, it is preferable to superimpose the colors in the order of low lightness. When inks of low lightness are piled up, the radiation does not easily reach the lower inks, so that the curing sensitivity is impaired, the amount of residual monomer increases, the odor is generated, and the adhesiveness is easily deteriorated. In addition, it is possible to irradiate all colors and expose them collectively, but it is preferable to expose each color one by one from the viewpoint of curing acceleration.

As the radiation, UV-A, UV-B, U
UV rays such as V-C, vacuum ultraviolet rays, visible light, γ rays,
Beta rays can be used. When γ rays or β rays are used, an ink initiator is not required.

As a source of ultraviolet rays, a high pressure mercury lamp,
Metal halide lamp, black light, cold cathode tube, L
ED, an ultraviolet laser, etc. can be used. It is particularly preferable to cut off heat rays such as infrared rays that do not contribute to the reaction by a known method from the viewpoint of curling in recording on a film or the like.

In the present invention, curl and waviness can be prevented while obtaining an image quality without blurring by appropriately adjusting the illuminance and the irradiation time without dividing the irradiation into two stages. Irradiate in two or more stages,
Further, it is more preferable to use the above ink composition. When the radiation of the ink of the present invention is applied in two steps, the shrinkage of the ink due to curing and the generated reaction heat are dispersed in two steps, which prevents abrupt ink shrinkage, heat generation and curl prevention. It becomes possible. When irradiating in two stages, the illuminance and wavelength can be changed.
It is preferable because not only curling and waving can be prevented, but also bleeding can be prevented and the curing rate in the vicinity of the support can be increased to obtain adhesiveness with the support. It is preferable that the irradiation immediately after landing weakens the light having many short wavelength components, and the post-irradiation strongly irradiates the light having many long wavelength components.

Further, in a series of image formation of ejecting ink and irradiating with radiation, the transport tension of the support is 1.0 to.
It is preferably 7.0 kg / m. 1.0 kg / m
If it is less than this, stable conveyance cannot be obtained, and problems such as curling may occur. If it is greater than 7.0 kg / m,
The support may be deformed when it receives a thermal history such as reaction heat at the time of ink ejection and radiation irradiation.

The ink ejection amount is 3 to 2 per color.
The coating amount is preferably 5 g / cm ² , and further 3 to
A coating amount of 20 g / cm ² is preferable. When it is less than 3, sufficient color developability and dot diameter cannot be obtained, and when it is more than 25, thermal deformation of the support due to heated ink or reaction heat occurs.

By optimizing the ink selection, the irradiation method, the ink ejection amount, and the transport conditions in this way, the shrinkage ratio due to the curing of the ink image can be set to -0.5 to + 1.0%. Therefore, even for a heat-shrinkable support,
It is possible to effectively prevent curling and waviness.
Further, since the ink is appropriately heated within a range that does not affect the support, good ejection stability and landing accuracy can be obtained, and a high-quality image without bleeding can be obtained.

Here, the curing shrinkage rate of the ink is defined as a value measured by reading a scale after the solid image is output under actual image forming conditions after the scale is attached to the support in advance and the scale is read. . By measuring in this way, a substantial cure shrinkage of the ink can be obtained.

As the heat-shrinkable support, the effect of the present invention can be obtained as long as it is a support which shrinks in the longitudinal direction or the lateral direction by heat, and various ordinary plastics and films thereof can be used. As the plastic film, PET film, OPS (stretched polystyrene) film, OPP (stretched polypropylene) film, ONy
(Stretched nylon) film, PVC (polyvinyl chloride)
Film, PE film, TAC film can be used. Other plastics include polycarbonate, acrylic resin, ABS, polyacetal, PVA,
Rubber, etc. can be used. Further, it is also applicable to metals and glasses.

Among these supports, the heat shrinkage in the longitudinal or transverse direction at 80 ° C. (immersion in warm water at 80 ° C. 10
A film whose second) is 5 to 50% is preferable. The constitution of the present invention is particularly effective when an image is formed on a PET film, an OPS film, an OPP film, an ONy film, or a PVC film, which can be shrunk by heat. On these supports, the film is likely to curl and deform due to the shrinkage of the ink when cured and the heat generated during the curing reaction.

[0049]

The present invention will be described in more detail with reference to the following examples. In addition, the following "part" represents a "mass part."

Example 1 << Preparation of Ink >> A pigment dispersion was prepared with the following composition. The average particle size was dispersed so as to be 0.2 to 0.3 μm. (Magenta Pigment Dispersion) Pigment Red 122 15 parts Polymer Dispersant 5 parts Tetraethylene glycol diacrylate 80 parts (Cyan Pigment Dispersion) Pigment Blue 15: 3 15 parts Polymer Dispersant 5 parts Tetraethylene glycol diacrylate 80 parts An ink having the following formulation was prepared using the above dispersion. (1) Magenta ink 1 Magenta pigment dispersion 20 parts Lauryl acrylate (monofunctional) 15 parts Stearyl acrylate (monofunctional) 10 parts Tetraethylene glycol diacrylate (difunctional) 25 parts Ethylene oxide modified trimethylolpropane triacrylate (trifunctional) ) (Kyoeisha Chemical Co., Ltd., TMP-3EO-A) 24.5 parts Initiator 1 (Ciba, Irgacure 907 = 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropane-1 -ON) 5 parts Initiator 2 (diethylthioxanthone) 0.5 part (2) Cyan ink 1 Cyan pigment dispersion 20 parts Lauryl acrylate (monofunctional) 15 parts Stearyl acrylate (monofunctional) 10 parts Tetraethylene glycol diacrylate ( Bifunctional) 25 parts ethylene oxide Modified trimethylolpropane triacrylate (trifunctional) (manufactured by Kyoeisha Chemical Co., Ltd., TMP-3EO-A) 24.5 parts Initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl-1 [4- (methylthio) phenyl] -2-Moliphorinopropan-1-one) 5 parts Initiator 2 (diethylthioxanthone) 0.5 parts or more of ink was filtered with a filter having an absolute filtration accuracy of 2 μm to obtain an ink. The maximum calculated SP value of the monomer used in the above ink is 9.02 for ethylene oxide-modified trimethylolpropane triacrylate, and the minimum value is 6.85 for stearyl acrylate. SP value is calculated by "Adhesion", Vol. 40, No. 8 (1996), p7
It calculated by referring to -14. << Inkjet recording >> Inkjet recording was performed on a recording medium by an inkjet recording apparatus using a piezo type inkjet nozzle. The ink supply system was composed of an ink tank, a supply pipe, an anterior chamber ink tank immediately before the head, a pipe with a filter, and a piezo head, and heat insulation and heating were performed from the anterior chamber ink tank to the head portion. The temperature sensors were provided in the vicinity of the nozzles of the front chamber ink tank and the piezo head, respectively, and the temperature was controlled so that the nozzle portions were always at 60 ° C ± 2 ° C. The piezo head uses 720x7 multi-size dots of 7 to 14 pl.
It was driven so that it could be ejected at a resolution of 20 dpi. Incidentally, d
Pi represents the number of dots per inch, that is, 2.54 cm.

As a recording medium for recording, a PET film for shrink having a thickness of 50 μm was used. The PET film is
It is HISHIPET (Mitsubishi resin, LX-60S, polyester shrink film), and the heat shrinkage rate (TD) when immersed in warm water at 80 ° C. for 10 seconds is 70%.

After landing on the recording medium, a high pressure mercury lamp (UV-
C) was set to an exposure surface illuminance of 50 mW / cm ² , an exposure system was arranged so that the irradiation started 0.1 seconds after the ink landed, and the irradiation was performed so that the exposure energy was 10 mJ / cm ² . Then, after irradiation with the UV-C light source is completed, a high pressure mercury lamp (UV-
Secondary exposure was performed according to A). Exposure surface illuminance is 200mW
/ Cm ² , and the exposure energy was 100 mJ / cm ² . By this secondary exposure, the inside of the ink can be cured, and the durability of the image and the adhesiveness with the recording medium can be obtained.
In this inkjet recording, the conveyance tension of the recording medium was 5 kg / m.

Example 2 The ink of Example 1 was changed to the following, and an ink image was formed in the same manner as in Example 1. (1) Magenta ink 2 Magenta pigment dispersion 20 parts Tetraethylene glycol diacrylate (difunctional) 74.5 parts Initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl-1 [4- (methylthio) phenyl] 2-Moliphorinopropan-1-one) 5 parts Initiator 2 (diethylthioxanthone) 0.5 part (2) Cyan ink 2 Cyan pigment dispersion 20 parts Tetraethylene glycol diacrylate (difunctional) 74.5 parts Initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one) 5 parts Initiator 2 (diethylthioxanthone) 0.5 parts Example 3 The ink of Example 1 was changed to the following, and an ink image was formed in the same manner as in Example 1. (1) Magenta ink 3 Magenta pigment dispersion 20 parts Stearyl acrylate (monofunctional) 40 parts Tetraethylene glycol diacrylate (difunctional) 10 parts Initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl-1 [4- (Methylthio) phenyl] -2-morpholinopropan-1-one) 5 parts Initiator 2 (diethylthioxanthone) 0.5 part (2) Cyan ink 3 Cyan pigment dispersion 20 parts Stearyl acrylate (monofunctional) 40 Parts tetraethylene glycol diacrylate (difunctional) 10 parts initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one) 5 Part Initiator 2 (diethylthioxanthone) 0.5 part Example 4 The ink of Example 1 was changed to the following. And, similarly form an ink image as in Example 1 and evaluated. (1) Magenta ink 4 Magenta pigment dispersion 20 parts Tetraethylene glycol diacrylate (difunctional) 50 parts Trimethylolpropane triacrylate (trifunctional) 24.5 parts Initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl) -1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one) 5 parts Initiator 2 (diethylthioxanthone) 0.5 part (2) Cyan ink 4 Cyan pigment dispersion 20 parts Tetraethylene Glycol diacrylate (difunctional) 50 parts Trimethylolpropane triacrylate (trifunctional) 24.5 parts Initiator 1 (manufactured by Ciba, Irgacure 907 = 2-methyl-1 [4- (methylthio) phenyl] -2- Morifolinopropan-1-one) 5 parts Initiator 2 (diethylthioxanthone) 0. 5 parts The ink images obtained in Examples 1 to 4 were evaluated as follows. The results are shown in Table 1. (Evaluation) -Measurement of Ink Shrinkage Ratio The ink shrinkage ratio of the ink image after irradiation is measured from the length measured after preparing a solid image as 14 pl / dot by calibrating the recording medium in advance during the inkjet recording. It was calculated. Curl (waviness) The curl and waviness of the recording medium after irradiation were evaluated as follows.

O: The step between the solid image portion and the non-image portion is less than 0.2 mm. The difference between the solid image portion and the non-image portion is less than 0.5 mm. The step difference from the image area is 0.5 mm or more. The bleeding of the ink image after the bleeding irradiation was evaluated as follows.

B: There is no blur at the boundary of the cyan image arranged on magenta solid. Δ: A slight blur is seen between the cyan images arranged on magenta solid. × ... Arranged on magenta solid. The boundary of the cyan image is blurred. Adhesiveness The adhesiveness between the recording medium and the ink image was evaluated as follows.

[0056] ◯: Solid image cannot be removed even if the tape is peeled off △: A slightly solid image can be obtained by peeling the tape ×: A solid image can be obtained by peeling the tape

[0057]

[Table 1]

As is clear from Table 1, the total exposure energy is 110 mJ / cm ^{2 under the} condition that the ink can be stably ejected.
Even if the PET film was irradiated, the PET film had almost no curl or waviness, no bleeding, and an image having good adhesion between the PET film and the ink could be obtained.

Example 5 The same ink as in Example 1 was used, and the evaluation was carried out by changing the recording medium, the ink ejection temperature, the transport tension of the recording medium (hereinafter referred to as the recording medium tension), and the irradiation conditions. The obtained results are shown in Table 2. -Sample 5-1 Recording medium OPS film ink ejection temperature Magenta ink (60 ° C) Cyan ink (60 ° C) Irradiation conditions (primary) High pressure mercury lamp (UV-C) Exposure surface illuminance 50 mW / cm ² , 0.2 after ink landing Second irradiation condition (secondary) High pressure mercury lamp (UV-A) Exposure surface illuminance 200 mW / cm ² , after irradiation with UV-C light source,
0.5 sec Recording medium tension 5 kg / m ・ Sample 5-2 Recording medium PVC film ink ejection temperature Magenta ink (60 ° C) Cyan ink (60 ° C) Irradiation condition (primary) High pressure mercury lamp (UV-C) Exposure surface illuminance 50 mW / Cm ² , 0.2 second irradiation condition after ink landing (secondary) High-pressure mercury lamp (UV-A) Exposure surface illuminance 200 mW / cm ² , after irradiation with UV-C light source,
0.5 second Recording medium tension 5 kg / m Sample 5-3 Recording medium PVC film Ink ejection temperature Magenta ink (80 ° C) Cyan ink (80 ° C) Irradiation condition (primary) High pressure mercury lamp (UV-C) Exposure surface illuminance 50 mW / Cm ² , 0.2 second irradiation condition after ink landing (secondary) High-pressure mercury lamp (UV-A) Exposure surface illuminance 200 mW / cm ² , after irradiation with UV-C light source,
0.5 sec Recording medium tension 5 kg / m Sample 5-4 Recording medium PVC film Ink ejection temperature Magenta ink (60 ° C) Cyan ink (60 ° C) Irradiation condition (primary) High pressure mercury lamp (UV-C) Exposure surface illuminance 50 mW / Cm ² , 0.2 second irradiation condition after ink landing (secondary) High-pressure mercury lamp (UV-A) Exposure surface illuminance 200 mW / cm ² , after irradiation with UV-C light source,
0.5 sec Recording medium tension 10 kg / m Sample 5-5 Recording medium PVC film Ink ejection temperature Magenta ink (60 ° C) Cyan ink (60 ° C) Irradiation conditions (primary) High pressure mercury lamp (UV-A) Exposure surface illuminance 200 mW / Cm ² , 2 seconds after ink landing Recording medium tension 5 kg / m Sample 5-6 Recording medium PVC film ink ejection temperature Magenta ink (60 ° C) Cyan ink (60 ° C) Irradiation condition (primary) High pressure mercury lamp (UV-A ) Exposure surface illuminance 200 mW / cm ² , 3 seconds after ink landing Recording medium tension 5 kg / m ・ Sample 5-7 Recording medium PVC film Ink ejection temperature Magenta ink (60 ° C) Cyan ink (60 ° C) Irradiation condition (primary) High pressure mercury lamp (UV-A) exposure surface illuminance 50mW / cm ^{2, 2} seconds recording medium tension 5 kg / m (recording medium) after ink deposition OP Films; DXL film 219V-01 manufactured by Mitsubishi Plastics, 80 ° C. thermal shrinkage rate 25% (TD) PVC film; water chestnut Rex 302-S manufactured by Mitsubishi Plastics, thickness 50 [mu] m, 80 ° C. thermal shrinkage rate 36% (TD)

[0060]

[Table 2]

As is clear from Table 2, when the ink is irradiated under the condition that the ink can be stably ejected, the recording medium has almost no curl or waviness, no bleeding, and the adhesiveness between the recording medium and the ink is good. A good image could be obtained. In Sample 5-4, the PVC film did not curl, but the film itself deformed slightly. It is estimated that this is because the transport tension of the film was unnecessarily high.

[0062]

EFFECTS OF THE INVENTION Curling is caused by employing the ink jet recording method of the present invention even for a support which is usually difficult to directly record by the ink jet recording method, especially for a thin plastic film which is easily deformed. In addition, it is possible to form a high-quality image with high sensitivity, which has no image bleeding and good adhesiveness.

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Claims (9)

[Claims] 1. A radiation-curable inkjet ink used in an inkjet recording method, wherein an ink is ejected onto a support that contracts by heating, and an ink image formed on the support is irradiated with radiation to cure the ink image. The curing shrinkage of the ink image formed on the body is -0.5 to +
A radiation-curable inkjet ink, which is 1.0%. 2. The radiation curable inkjet ink according to claim 1, further comprising a monofunctional monomer, a bifunctional monomer, and a trifunctional or higher functional monomer. 3. The method according to claim 1 or 2, wherein a plurality of monomers are contained and the maximum difference in solubility parameter between the monomers arbitrarily selected from the plurality of monomers is 1 or more and 2.5 or less. Radiation curable inkjet ink. 4. An inkjet recording method for curing an ink image by injecting a radiation-curable inkjet ink onto a support that shrinks by heating and irradiating the ink image formed on the support with radiation. The curing shrinkage of the ink image formed on the support is −
The ink jet recording method is characterized by being 0.5 to + 1.0%. 5. The inkjet recording method according to claim 4, wherein the curing of the ink image by irradiation with radiation is performed twice or more. 6. The ink jet recording method according to claim 4, wherein the temperature of the ink is adjusted to 25 to 70 ° C., and then the ink is ejected. 7. The ink according to claim 4, wherein the support is held with a tension of 1.0 to 7.0 kg / m to eject the ink and irradiate with radiation. Inkjet recording method. 8. The heat shrinkage ratio of the support at 80 ° C. is 5 to 5.
It is 50%, Any one of Claims 4-7 characterized by the above-mentioned.
Inkjet recording method according to the item. 9. The inkjet recording method according to claim 4, wherein the support is a PET film, an OPS film, an OPP film, an ONy film, or a PVC film.