JP2003305839A - Method of forming image, ink, and recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an image, an ink, and a recorder whereby a stable image can be reproduced without creating contraction of a recording material. <P>SOLUTION: In this method of forming an image, the ink curable by an active light beam is ejected on a recording material by a recording head having at least one nozzle which can selectively control ejection of ink drops. A value obtained by dividing an illuminance (mW/cm<SP>2</SP>) of an ink ejection section in a wavelength effective to curing of the ink by a sensitivity (mJ/cm<SP>2</SP>) of the ink is in the range of 1.0×10<SP>-5</SP>-1.0×10<SP>-1</SP>. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method by an ink jet recording method capable of stably reproducing a high-definition image on any recording material without the recording material shrinking.
The present invention relates to an ink and a recording device.

[0002]

2. Description of the Related Art In recent years, the inkjet recording method has been simple and easy.
Since it is possible to create images at low cost, it has been applied to various printing fields such as photography, various printing, marking, and special printing such as color filters. Discharges 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 development of color materials, surface gloss, etc. 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 which requires a special paper has a problem that the recording medium is limited or 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 method has been attracting attention in recent years because it has a relatively low odor as compared with the solvent ink jet method, and is capable of recording on a recording medium that is quick-drying and does not absorb ink. Japanese Patent Fair 5-546
No. 67, JP-A-6-200204, Special Table 2000-5.
No. 04778 discloses an ultraviolet curable inkjet ink.

However, even if these inks are used, there is a problem that the ejection is not stable depending on the working environment. Further, the ink used in the conventional UV inkjet system has a problem that the recording material is likely to shrink.
In particular, thin film plastic films and adhesive labels used in soft packaging such as food packaging tend to shrink, and the UV inkjet method has not been put to practical use in soft packaging printing and label printing due to the unstable discharge described above. Is the current situation.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is an image forming method and an ink by an ink jet recording method capable of reproducing a very stable image without contraction of a recording material. , Providing a recording device.

[0006]

The object of the present invention is achieved by the following constitutions.

1. Selective control of ink drop ejection
With a recording head that has at least one nozzle, the actinic ray
Image formation by ejecting ink that hardens by recording onto recording material
In the method, the ink at a wavelength effective for curing the ink is used.
Illuminance of discharge part (mW / cm ²) Is the ink sensitivity (mJ
/ Cm²) Divided by 1.0 × 10^-Five~ 1.0 x 10
^-1And an image forming method.

2. The sensitivity (mJ / cm ² ) of the ink at a wavelength effective for curing the ink is 0.01 to 50 mJ.
/ Cm ² The image forming method as described in 1 above, wherein

3. At a wavelength that is effective for curing the ink
Illuminance of the ink ejection unit (mW / cm ²) Is 0.001
1 mW / cm²In the above 1 or 2 characterized in that
The image forming method described.

4. 4. The image forming method described in any one of 1 to 3 above, wherein at least one color of the ink is white ink.

5. Oxetane compounds, epoxy compounds,
And at least one selected from vinyl ether compounds, The ink for use in the image forming method described in any one of 1 to 4 above.

6. 6. The ink according to the above 5, which contains at least one kind of acid multiplying agent.

7. 7. The ink according to 5 or 6 above, which contains at least one tertiary amine compound.

8. Any one of the above items 5 to 7, characterized in that it contains at least one photopolymerizable tertiary amine monomer.
Ink according to item.

9. Print head and ink 35-100
The above-mentioned 1 characterized in that the ink is discharged by heating to ℃
A recording device used in the image forming method according to any one of items 1 to 4.

10. 10. The recording apparatus according to 9, wherein the ink contains at least one selected from an oxetane compound, an epoxy compound, and a vinyl ether compound.

11. 9 or 1, wherein the ink contains at least one selected from an acid multiplying agent, a tertiary amine compound and a photopolymerizable tertiary amine monomer.
The recording device according to 0.

The present invention will be described in detail below. Of the present invention
The image forming method has a small amount of ink droplets that can be selectively controlled.
With a recording head that has at least one nozzle, the actinic ray
When ejecting ink that hardens due to
Illuminance of the ink ejection part at the wavelength effective for curing the ink
(MW / cm²) Is the sensitivity of the ink (mJ / cm²)
The value divided (divided) is 1.0 x 10 ^-Five~ 1.0 x 10^-1And
It is characterized by

When considering stable ejection, the illuminance of the ink ejection portion and the sensitivity of the ink are important factors, and as a result of intensive studies by the present inventors, the value obtained by dividing the illuminance of the ink ejection portion by the sensitivity of the ink is 1. The inventors of the present invention have found that the range of 0.0 × 10 ^{−5 to} 1.0 × 10 ⁻¹ is very effective for stable ejection, and have arrived at the present invention. The means for achieving this image forming method can be achieved by appropriately adopting the following inks and recording devices.

In the present invention, the sensitivity of the ink is preferably 0.01 to 50 mJ / cm ² . The image forming method of the present invention is particularly effective for high-sensitivity inks having a sensitivity in this range. In addition, the ink sensitivity is 0.01 to
In the case of a high-sensitivity ink of 50 mJ / cm ² , the illuminance of the ink ejection portion is preferably 0.001 to 1 mW / cm ² . This does not apply to the case of a low-sensitivity ink whose ink sensitivity exceeds 50 mJ / cm ² .

In the present invention, the "wavelength effective for curing the ink" means the light absorption wavelength of the photoinitiator and the sensitizer contained in the ink, and irradiation with actinic rays within this wavelength is required. Then, the curing reaction of the ink occurs.

Further, the "illuminance of the ink ejecting portion" means the illuminance in the vicinity of the meniscus ejecting ink in the recording head, and the active light rays radiated on the recording head and / or from the side of the recording head are the recording materials. Or caused by reflection on the platen.

The term "ink sensitivity" means the exposure energy required for the ink to cure, and "curing".
As a criterion for judgment, it means a level at which the ink film does not break even if the ink surface is touched with a hand.

Next, the ink used in the present invention will be described. The ink jet recording ink used in the present invention is composed of at least a coloring material, a polymerizable monomer, and an initiator, and also contains other components depending on the use.

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.

In addition, 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.

Further, in the present invention, it is preferable that the ink contains a tertiary amine compound in addition to the above polymerizable monomer for the purpose of suppressing the curing shrinkage of the ink. The target tertiary amine compound may be any compound in which all three hydrogen atoms of ammonia are independently substituted with an alkyl group, a hydroxyalkyl group or an aralkyl group, and any publicly known compound is used. be able to. Specific examples thereof include triethylamine, tri-n-propylamine, tri-n-butylamine, dimethylethanolamine, diethylethanolamine, triethanolamine, N, N-dimethylbenzylamine, N, N-diethylbenzyl. Amine, N,
Examples thereof include, but are not limited to, N-dimethylphenethylamine.

Further, in the present invention, it is preferable to use a photopolymerizable tertiary amine monomer for the purpose of suppressing curing shrinkage of the ink. The photopolymerizable tertiary amine monomer is the above polymerizable monomer with a tertiary amino group attached,
For example, N-ethyl (meth) acrylamide, Nn-
Propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-cyclopropyl (meth)
Acrylamide, N-methyl-N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N
-Dimethylaminoethyl (meth) acrylate, N, N
-Dimethylaminopropyl (meth) acrylamide, N
-Methyl-N-isopropyl (meth) acrylamide,
N-methyl-N-n-propyl (meth) acrylamide, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidine, N- (meth) acryloylpiperidine, N-vinyl-2-pyrrolidone, N- Methylenebisacrylamide, N-methoxypropyl (meth) acrylamide, N-isopropoxypropyl (meth) acrylamide, N-ethoxypropyl (meth) acrylamide, N-1-methoxymethylpropyl (meth) acrylamide, N-methoxyethoxypropyl ( (Meth) acrylamide, N-1-methyl-2-methoxyethyl (meth) acrylamide, N-methyl-Nn
Examples thereof include, but are not limited to, amine monomers such as -propyl (meth) acrylamide and N- (1,3-dioxolan-2-yl) (meth) acrylamide.

As the cationic photopolymerizable monomer, various known cationically polymerizable monomers can be used. For example, JP-A-6-9714 and JP-A-2001-3189.
2, JP 2001-40068, JP 2001-555
07, JP 2001-310938 A, JP 2001-3 A
10937, epoxy compounds, vinyl ether compounds, oxetane compounds and the like exemplified in JP-A-2001-220526.

The epoxy compounds include the following aromatic epoxides, alicyclic epoxides and aliphatic epoxides.

Preferred aromatic epoxides are:
A di- or polyglycidyl ether produced by reacting a polyhydric phenol having at least one aromatic nucleus or its alkylene oxide adduct with epichlorohydrin, for example, bisphenol A or its di- or polyglycidyl ether of an alkylene oxide adduct. , Di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, and novolac type epoxy resin. Examples of the alkylene oxide include ethylene oxide and propylene oxide.

As the alicyclic epoxide, at least 1
Preferred is a cyclohexene oxide- or cyclopentene oxide-containing compound obtained by epoxidizing a compound having a cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid.

Preferred aliphatic epoxides are aliphatic polyhydric alcohols or di- or polyglycidyl ethers of alkylene oxide adducts thereof, and the like.
As typical examples thereof, diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol, diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, di- or tri-glycerin or its alkylene oxide adduct. Examples thereof include polyglycidyl ethers of polyhydric alcohols such as glycidyl ether, diglycidyl ethers of polyethylene glycol or its alkylene oxide adducts, and diglycidyl ethers of polyalkylene glycols such as polypropylene glycol or its diglycidyl ether of alkylene oxide adducts. . Examples of the alkylene oxide include ethylene oxide and propylene oxide.

Of these epoxides, in consideration of the rapid curing property, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the above epoxides may be used alone,
You may use it in combination of 2 or more types as appropriate.

Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether,
Dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether,
Di- or trivinyl ether compounds such as trimethylolpropane trivinyl ether, ethyl vinyl ether, n
-Butyl vinyl ether, isobutyl vinyl ether,
Octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-
Examples thereof include monovinyl ether compounds such as O-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

Of these vinyl ether compounds, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable, in consideration of curability, adhesion and surface hardness. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in an appropriate combination.

The oxetane compound is a compound having an oxetane ring, and is disclosed in JP-A-2001-220526,
Any known oxetane compound as introduced in JP 2001-310937 A can be used.

When a compound having five or more oxetane rings is used, the viscosity of the composition becomes high, which makes the handling difficult, and the glass transition temperature of the composition becomes high. Will not be enough. The compound having an oxetane ring used in the present invention is
A compound having 1 to 4 oxetane rings is preferable.

Examples of the compound having one oxetane ring include compounds represented by the following general formula (1).

[0040]

[Chemical 1]

In the general formula (1), R ¹ is a hydrogen atom,
It is an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group or a thienyl group. R ² is an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, 1
-Propenyl group, 2-propenyl group, 2-methyl-1-
Propenyl group, 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group and other alkenyl groups having 2 to 6 carbon atoms, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group Groups or groups having an aromatic ring such as phenoxyethyl group, alkylcarbonyl groups having 2 to 6 carbon atoms such as ethylcarbonyl group, propylcarbonyl group or butylcarbonyl group, ethoxycarbonyl group, propoxycarbonyl group or butoxycarbonyl group It is an alkoxycarbonyl group having 2 to 6 carbon atoms, or an N-alkylcarbamoyl group having 2 to 6 carbon atoms such as an ethylcarbamoyl group, a propylcarbamoyl group, a butylcarbamoyl group or a pentylcarbamoyl group.

As the oxetane compound used in the present invention, it is particularly preferable to use a compound having one oxetane ring since the resulting composition has excellent tackiness, low viscosity and workability.

Next, examples of the compound having two oxetane rings include compounds represented by the following general formula (2).

[0044]

[Chemical 2]

[0045] In formula (2), R ¹ has the same meaning as R ¹ in the general formula (1). R ³ is, for example, a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, a linear or branched poly (alkyleneoxy) group such as a poly (ethyleneoxy) group or a poly (propyleneoxy) group. ) Group, propenylene group, linear or branched unsaturated hydrocarbon group such as methylpropenylene group or butenylene group, carbonyl group, alkylene group containing carbonyl group, alkylene group containing carboxyl group, or alkylene containing carbamoyl group Group etc.

R ³ is also a polyvalent group selected from the groups represented by the following general formulas (3), (4) and (5).

[0047]

[Chemical 3]

In the general formula (3), R ⁴ is a hydrogen atom,
An alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, a methoxy group, an ethoxy group,
It is an alkoxy group having 1 to 4 carbon atoms such as a propoxy group or a butoxy group, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkylcarboxyl group, a carboxyl group, or a carbamoyl group.

[0049]

[Chemical 4]

In the general formula (4), R ⁵ is an oxygen atom,
Sulfur atom, methylene group, NH, SO, SO ₂ , C (C
F ₃ ) ₂ or C (CH ₃ ) ₂ .

[0051]

[Chemical 5]

In the general formula (5), R ⁶ is a methyl group,
1 to 4 carbon atoms such as ethyl, propyl or butyl
Is an alkyl group or an aryl group. n is 0 to 20
00 is an integer. R ⁷ is an alkyl group having 1 to 4 carbon atoms such as methyl group, ethyl group, propyl group or butyl group,
Or, it is an aryl group. R ⁷ is also a group selected from the groups represented by the following general formula (6).

[0053]

[Chemical 6]

In the general formula (6), R ⁸ has a carbon number of 1 to 1 such as methyl group, ethyl group, propyl group and butyl group.
It is four alkyl groups or aryl groups. m is 0 to 1
00 is an integer.

Specific examples of the compound having two oxetane rings include the following compounds.

[0056]

[Chemical 7]

Exemplified compound 1 is a compound in which R ¹ is an ethyl group and R ³ is a carboxyl group in the general formula (2). Exemplified compound 2 is a compound of the general formula (2) in which R ¹ is an ethyl group, R ³ is the general formula (5), R ⁶ and R ⁷ are methyl groups, and n is 1.

In the compound having two oxetane rings,
As a preferable example other than the above compounds, there is a compound represented by the following general formula (7). In general formula (7), R ¹ has the same meaning as R ¹ in the general formula (1).

[0059]

[Chemical 8]

Examples of the compound having 3 to 4 oxetane rings include compounds represented by the following general formula (8).

[0061]

[Chemical 9]

[0062] In the general formula (8), R ¹ is the same meaning as R ¹ in the general formula (1). R ⁹ is, for example, a branched alkylene group having 1 to 12 carbon atoms such as the groups represented by the following A to C, a branched poly (alkyleneoxy) group such as the group represented by the following D, or the following E. Examples thereof include branched polysiloxy groups such as the groups shown. j is 3 or 4.

[0063]

[Chemical 10]

In the above A, R ¹⁰ is a lower alkyl group such as methyl group, ethyl group or propyl group. Further, in the above D, p is an integer of 1 to 10.

As an example of the compound having 3 to 4 oxetane rings, Exemplified Compound 3 can be mentioned.

[0066]

[Chemical 11]

Further, examples of compounds having 1 to 4 oxetane rings other than those described above include compounds represented by the following general formula (9).

[0068]

[Chemical 12]

[0069] In the general formula (9), R ⁸ has the same meaning as R ⁸ in the general formula (6). R ¹¹ is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, or a trialkylsilyl group, and r is 1 to 4.

The following compounds are preferred specific examples of the oxetane compound used in the present invention.

[0071]

[Chemical 13]

The method for producing the above-mentioned compound having an oxetane ring is not particularly limited, and a conventionally known method may be used.
For example, Pattyson (J.A.
m. Chem. Soc. , 3455, 79 (195
7)) discloses an oxetane ring synthesis method from a diol. In addition to these, the molecular weight of 1000-
A compound having 1 to 4 oxetane rings having a high molecular weight of about 5000 is also included. Examples of these include the following compounds.

[0073]

[Chemical 14]

In the present invention, it is preferable to contain at least one oxetane compound and / or epoxy compound and / or vinyl ether compound for the purpose of suppressing shrinkage of the recording material during ink curing. More preferably, in addition to at least one oxetane compound, it preferably contains at least one compound selected from an epoxy compound and a vinyl ether compound. This further reduces the shrinkage of the recording material during curing.

As the initiator (photoradical 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 the initiator, see "U
Application and Market of V / EB Curing Technology "(CMC Publishing,
Details by Yoneho Tabata / edited by the Radtech Study Group). Among them, acyl phosphine oxide and acyl phosphonate have high sensitivity, and absorption is reduced by photocleavage of the initiator.
It is particularly effective for internal curing in an ink image having a thickness of m. Specifically, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, bis (2,2
6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide and the like 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, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide, 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocur (R) 1173) Is preferably used.

As the photocation (acid) initiator, any known photoacid generator can be used.

As the photoacid generator, for example, a chemically amplified photoresist or a compound used for photocationic polymerization is used (Organic Electronics Materials Research Group, "Organic Materials for Imaging", Bushin Publishing (1993).
Year), pp. 187-192). Examples of compounds suitable for the present invention are given below. First, diazonium, ammonium, iodonium, sulfonium, aromatic onium compounds such as phosphonium _{B (C 6 F 5) 4} -, PF 6 -, A
Mention may be made of sF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt. Specific examples of onium compounds are shown below.

[0079]

[Chemical 15]

Secondly, a sulfonated product which generates a sulfonic acid can be mentioned. Specific compounds are exemplified below.

[0081]

[Chemical 16]

Thirdly, a halide capable of photogenerating hydrogen halide can also be used. Specific compounds are exemplified below.

[0083]

[Chemical 17]

Fourthly, an iron allene complex can be mentioned.

[0085]

[Chemical 18]

The ink of the present invention is disclosed in JP-A-8-24856.
No. 1, JP-A-9-34106 and the like, it is preferable to contain an already known acid-proliferating agent that newly generates an acid by the acid generated by irradiation with actinic rays. By using the acid multiplying agent, it is possible to further improve the ejection stability.

In addition, 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 thereto. C. I Pigment Yellow-1,3,1
2, 13, 14, 17, 81, 83, 87, 95, 10
9, 42, C.I. I Pigment Orange-16, 36,
38, C.I. I Pigment Red-5, 22, 38, 4
8: 1, 48: 2, 48: 4, 49: 1, 53: 1, 5
7: 1, 63: 1, 144, 146, 185, 101, C.I. I Pigment Violet-19, 23, C.I. I Pigment Blue-15: 1, 15:
3,15: 4,18,60,27,29, C.I. I Pigment Green-7, 36, C.I. I Pigment White-6, 18, 2
1, C.I. I Pigment Black-7 In the present invention, it is preferable to use a white ink in order to improve the color hiding property on a transparent substrate such as a plastic film. White ink is indispensable especially in flexible packaging printing and label printing, but since the discharge amount is large,
The above-mentioned problems of ejection stability and occurrence of curling and wrinkling of the recording material become remarkable.

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 to disperse the pigment. It is also possible to add a dispersant when dispersing the pigment. A polymer dispersant is preferably used as the dispersant. Aveci as a polymer dispersant
The Solsperse series of a company is mentioned.

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 mass% with respect to 100 mass% of the pigment.

The dispersion medium is a solvent or a polymerizable compound. The actinic ray-curable ink used in the present invention is preferably solvent-free because it reacts and cures immediately after landing of the ink. If the solvent remains in the cured image, the solvent resistance deteriorates and the residual solvent VOC (Volatile Or
The problem of "ganic 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 dispersion has an average particle diameter 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 amount of color material added is 1 to 10 of the total ink.
Mass% is preferred. (Other components) In order to improve the storage stability of the ink composition, a polymerization inhibitor can be added in an amount of 200 to 20000 ppm. Since the actinic ray curable ink is preferably heated and reduced in viscosity before being ejected, 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 a range that does not cause problems of solvent resistance and VOC, and its amount is 0.1 to 5%, preferably 0.1 to 5%.
3%.

Further, in the present invention, a radical / cation hybrid type curing ink may be used. (Image formation) In the image forming method of the present invention, the ink composition is ejected onto a recording material by an ink jet recording method to draw an image, and then the ink is cured by irradiating with actinic rays such as ultraviolet rays.

As the ink ejection conditions, heating the head and the ink to 35 to 100 ° C. and ejecting are preferable from the viewpoint of ejection stability. The actinic radiation curable ink has a large fluctuation range of viscosity due to temperature fluctuation. Since the viscosity variation directly affects the droplet size and the droplet ejection speed and deteriorates the image quality, 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, regarding the irradiation method, the basic irradiation method is disclosed in JP-A-60-132767. According to this, a light source which is an irradiation means is provided on both sides of the head unit, and the head and the light source are scanned by a 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. In US6145979, as an irradiation method,
Apply UV light to the recording unit by applying an optical fiber or applying a collimated light source to the mirror surface provided on the side of the head unit.
A method of irradiating with light is disclosed. In the image forming method of the present invention, any of these irradiation methods can be used.

The recording apparatus of the present invention will be described below with reference to the drawings. The recording device in the drawings is only one example, and the present invention is not limited to this.

FIG. 1 is a front view showing the structure of the main part of the recording apparatus of the present invention. The recording device 1 includes a head carriage 2,
The recording head 3, the irradiation unit 4, the platen unit 5, and the like are provided. In this recording apparatus 1, a platen section 5 is installed below the recording material P. The platen portion 5 has a function of absorbing ultraviolet rays, and absorbs extra ultraviolet rays that have passed through the recording material P. As a result, a high definition image can be reproduced very stably.

The recording material P is guided by the guide member 6,
By the operation of the conveying means (not shown), it moves from the front side to the back side in FIG. Head scanning means (not shown)
Scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

The head carriage 2 is installed on the upper side of the recording material P, and accommodates a plurality of recording heads 3 to be described later and their ejection openings on the lower side according to the number of colors used for image printing on the recording material P. To do. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 so as to be reciprocable in the Y direction in FIG. 1, and is reciprocally moved in the Y direction in FIG. 1 by driving the head scanning unit.

In FIG. 1, the head carriage 2 has white (W), yellow (Y), magenta (M), cyan (C), black (K), light yellow (Ly), light magenta (Lm), and light cyan. (Lc), light black (Lk), and white (W) recording heads 3 are illustrated as being accommodated, but the number of colors of the recording heads 3 accommodated in the head carriage 2 at the time of implementation is It can be decided as appropriate.

The recording head 3 has an actinic ray curable ink (U, for example) supplied by an ink supply means (not shown).
The V-curing ink) is ejected toward the recording material P from the ejection port by the operation of a plurality of ejection means (not shown) provided inside. The UV ink ejected from the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator and the like, and the crosslinking of the monomer due to the initiator acting as a catalyst when irradiated with ultraviolet rays. , Has the property of being cured by a polymerization reaction.

The recording head 3 moves from one end of the recording material P to the other end of the recording material P in the Y direction in FIG. 1 by the driving of the head scanning means.
The UV ink is ejected as an ink droplet to a certain area (a landable area) of the ink droplet, and the ink droplet is landed on the landable area.

After the above-mentioned scanning is performed a proper number of times to eject the UV ink toward one landable area, the recording material P is appropriately moved from the front side to the back side in FIG. 1 by the conveying means, and the head scanning is performed again. While the scanning is performed by the means, the recording head 3 is applied to the landable area in FIG.
U for the next possible landing area adjacent to the back in
V ink is ejected.

By repeating the above-mentioned operation and ejecting the UV ink from the recording head 3 in association with the head scanning means and the conveying means, an image composed of an aggregate of UV ink droplets is formed on the recording material P.

The irradiation means 4 comprises an ultraviolet lamp that emits ultraviolet rays in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet rays of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a cold cathode tube, a black light, an LED (light
Mitting diode) or the like is applicable, and a strip-shaped metal halide lamp tube, a cold cathode tube, a mercury lamp tube or a black light is preferable. Especially wavelength 365n
It is preferable that the cold cathode tube and the black light that emit ultraviolet rays of m can prevent bleeding, efficiently control the dot diameter, and reduce wrinkles during curing. By using the black light as the radiation source of the irradiation unit 4, the irradiation unit 4 for curing the UV ink can be manufactured at low cost.

The irradiation unit 4 is almost the largest landable region in which the recording head 3 ejects UV ink by one-time scanning by driving the head scanning unit, which can be set in the recording apparatus (UV ink jet printer) 1. It has the same shape or a shape larger than the landable area.

The irradiation means 4 is fixedly installed on both sides of the head carriage 2 substantially parallel to the recording material P.

As described above, as a means for adjusting the illuminance of the ink ejecting portion, it is needless to say that the recording head 3 is entirely shielded from light, and in addition, the recording head 3 is determined by the distance h1 between the irradiation means 4 and the recording material P. It is effective to increase the distance h2 between the ink ejection unit 31 and the recording material P (h1 <h2) or increase the distance d between the recording head 3 and the irradiation unit 4 (increase d). Further, it is more preferable to form a bellows structure 7 between the recording head 3 and the irradiation means 4.

Here, the wavelength of the ultraviolet rays irradiated by the irradiation means 4 can be appropriately changed by replacing the ultraviolet lamp or the filter provided in the irradiation means 4.

As the recording material, in addition to ordinary non-coated paper, coated paper and the like, various non-absorbent plastics and films thereof used for so-called soft packaging can be used. Examples of various plastic films include PE
T (polyethylene terephthalate) film, OPS
(Stretched polystyrene) film, OPP (stretched polypropylene) film, ONy (stretched nylon) film,
There are PVC (polyvinyl chloride) film, PE film, and TAC film. As other plastics, polycarbonate, acrylic resin, ABS, polyacetal, PVA, rubbers and the like can be used. Further, it is also applicable to metals and glasses.

Among these recording materials, PET film, OPS film, OP which can be shrunk by heat
The effect of the present invention becomes more effective when an image is formed on a P film, an ONy film, or a PVC film. In these base materials, not only the film is easily curled and deformed due to the curing shrinkage of the ink and the heat generated during the curing reaction, but also the ink film is difficult to follow the shrinkage of the base material.

In the present invention, a long material (web) is used in terms of recording material costs such as packaging costs and production costs, print creation efficiency, and compatibility with prints of various sizes.
It is advantageous to use different recording materials.

[0113]

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

Example 1 << Preparation of Ink Composition (Radical Polymerization System) >> Tables 1 to 3
To obtain the ink compositions 1 to 3. The added compounds are as follows, and the numerical values of the added compounds shown in Tables 1 to 3 are% by mass.・ Ink composition 1

[0115]

[Table 1]

Ink composition 2

[0117]

[Table 2]

Ink composition 3

[0119]

[Table 3]

-Photopolymerizable compound 1: Lauryl acrylate (monofunctional) -Photopolymerizable compound 2: Bisphenol A glycidyl ether methacrylic acid adduct (bifunctional) -Photopolymerizable compound 3: Tetraethylene glycol diacrylate (bifunctional) ) -Photopolymerizable compound 4: trimethylolpropane triacrylate (trifunctional) -Photopolymerizable compound 5: Caprolactam-modified dipentaerythritol hexaacrylate (hexafunctional) -Photopolymerizable compound 6: 2- (diethylamino) ethyl methacrylate ( DMAEMA) Contains a tertiary amino group:
Structural formula ・ Initiator 1: Irgacure 651 Ciba Specialty Chemicals ・ Initiator 2: Irgacure 369 Ciba Specialty Chemicals ・ Initiator Auxiliary: Diethylthioxanthone ・ Titanium oxide: Anatase type: Particle size 0.2 μm ・ 3rd grade Amine compound a: the following structural formula

[0121]

[Chemical 19]

The abbreviations in the table are as follows. K: black ink, C: cyan ink, M: magenta ink, Y: yellow ink, Lk: light black ink, L
c: light cyan ink, Lm: light magenta ink, L
y: light yellow ink, W: white ink << inkjet recording >> By using an inkjet recording apparatus having a function shown in FIG. 1 using a piezo type inkjet nozzle, the recording material shown in Table 4 (width 600 mm,
Multiple images were recorded on a long recording material (1000 m long). The ink supply system consisted of an ink tank, a supply pipe, a front chamber ink tank immediately before the head, piping with a filter, and a piezo head. The front chamber tank and the head portion were thermally insulated and heated to 50 ° C. The piezo head is 2
Multi-size dots of 15 pl with 720 x 720 dpi
It was driven and ejected so that it could be ejected at a resolution of (dpi represents the number of dots per inch, that is, 2.54 cm). The irradiation conditions after landing were as shown in Table 4. The illuminance of the ink ejection unit was adjusted by adjusting the distance (d) between the light source, which is the irradiation unit shown in FIG. 1, and the head. After recording, the total ink film thickness was measured to be 2.3-1.
It was 3 μm. (Irradiation conditions) (1) Irradiation light source-Metal halide lamp; 120 W / cm (MAL 400NL manufactured by Nihon Battery Co., Ltd.)-High pressure mercury lamp; 80 W / cm (HN manufactured by Nihon Battery Co., Ltd.)
-64NL) ・ Electrodeless UV lamp (F450 series manufactured by Fusion UV Systems Japan Co., Ltd.) (2) Irradiation timing After landing, 0.2 seconds, 0.3 seconds, 0.4 seconds after using the irradiation light source. Then, irradiation was performed 0.5 seconds later. (3) Irradiation Method A linear light source was irradiated from both sides of the recording head. (4) The illuminance A of the ink ejection portion and the illuminance of 0.5 mW / cm ² at the peak wavelength of 365 nm.
Irradiation was carried out by changing to 5 mW / cm ² , 10 mW / cm ² , and 25 mW / cm ² . (5) Exposure energy and its peak wavelength 150 mJ at the peak wavelength of 365 nm
/ Cm ² , 200 J / cm ² , and 230 mJ / cm ² were changed to irradiation. In Table 4, this exposure energy is represented by "sensitivity B" of the ink.

[0123]

[Table 4]

<< Evaluation >> After recording the recording material for 10 m, 100
After m recording and 500 m recording, the evaluation was performed as follows, and the results are shown in Table 5. (Character quality) An 8-point character was printed at a target K density, and the character was rough and the shape of 1 dot for each color was magnified and evaluated with a loupe.

⊚: No shading, dot shape is perfect circle ∘: Slight shading is visible The dot shape is a perfect circle △: Roughness is visible and the dot shape is slightly disturbed (a level that can be used at the last minute) × ... Roughness is visible and the dot shape is also poor (color mixing (bleeding)) M target density 8 on solid image Output an image pattern with point characters and 1 dot for each color,
The quality after 10 minutes was magnified with a magnifying glass and visually evaluated.

⊚: No shading, dot shape is perfect circle ∘: Slight shading is visible Dot shape is a perfect circle △: Roughness is visible and the dot shape is slightly disturbed (a level that can be used at the last minute) ×: Roughness is visible and the dot shape is also bad (wrinkles and curls on the print) Pick up the print immediately after printing ,
It was visually evaluated whether wrinkles and curls were generated by irradiation and curing.

[0127]   ○: good   △ ・ ・ ・ Somewhat good (somehow practically manageable)   ×: Bad, wrinkles and curls are seen on the printed matter

[0128]

[Table 5]

As is clear from Table 5, the image forming method of the present invention can stably reproduce a high-definition image on any recording material without causing wrinkles on the recording material.

Example 2 Preparation of Ink Composition (Cationic Polymerization System) Tables 6 to 8
To obtain ink compositions 4 to 6. The added compounds are as follows.・ Ink composition 4

[0131]

[Table 6]

Ink composition 5

[0133]

[Table 7]

Ink composition 6

[0135]

[Table 8]

Pigment (* 1 to * 5): as defined in Tables 1 to 3 Photopolymerizable compound 7 (oxetane compound): OXT-2
21 (Toa Gosei) -Photopolymerizable compound 8 (epoxy compound): Celoxide 2081 (Daicel Chemical Industries) -Photopolymerizable compound 9 (oxetane compound): OXT-2
12 (Toagosei) -Photopolymerizable compound 10 (epoxy compound): Celoxide 2021 (Daicel Chemical Industry) -Photopolymerizable compound 11 (epoxy compound): Celoxide 2081 (Daicel Chemical Industry) -Initiator 3: BBI102 (Midori Chemical) ) ・ Initiator 4: The following structural formula ・ Initiator 5: The following structural formula ・ Acid multiplying agent 1: The following structural formula ・ Acid multiplying agent 2: The following structural formula ・ Acid multiplying agent 3: The following structural formula

[0137]

[Chemical 20]

Subsequently, as shown in Table 9, a plurality of images were recorded on the recording material with the ink compositions 4 to 6. The irradiation conditions after landing were as shown in Table 9. Example 1 except that the heating from the antechamber tank to the head portion was changed to 60 ° C
Image recording and evaluation were performed in the same manner as in. Incidentally, the film thickness became thicker because the white ink was used and became 2.3 to 19.6 μm. The results obtained are shown in Table 10. (Irradiation conditions) (1) Irradiation light source insect trap (Harrison Toshiba Lighting FL20S ・
BL type) Cold cathode fluorescent lamp (manufactured by Hibeck Co., Ltd.) Black light (custom-made by Nippon Electric Co., Ltd.) (2) Irradiation timing After landing, 0.1 seconds, 0.3 seconds, 0.5 after using the irradiation light source. Irradiation was performed after 2 seconds. (3) Method of Irradiation Irradiation was performed from both sides of the recording head with three linear light sources or eight linear light sources. (4) Illuminance A of the ink ejection portion and its illuminance of 0.1 mW / cm ² at a peak wavelength of 365 nm.
0.5mW / cm ^2, it was irradiated by changing to 1mW / cm ^2. (5) Exposure energy and its peak wavelength 5 mJ / c at the peak wavelength of 365 nm
m ^2, 10mJ / cm ^2, was irradiated to change a 15 mJ / cm ^2. In Table 9, this exposure energy is represented by "sensitivity B" of the ink.

[0139]

[Table 9]

[0140]

[Table 10]

As is clear from Table 10, the image forming method of the present invention can stably reproduce a high-definition image on any recording material.

[0142]

According to the present invention, it is possible to provide an image forming method, an ink and a recording apparatus by an ink jet recording method capable of reproducing a very stable image without the recording material shrinking. Play.

[Brief description of drawings]

FIG. 1 is a front view showing a configuration of a main part of a recording apparatus of the present invention.

[Explanation of symbols]

1 recording device 2 head carriage 3 recording head 4 irradiation means 5 Platen part 6 Guide member 7 Bellows structure P recording material

Claims (11)

[Claims] 1. A wavelength effective for curing an ink in an image forming method in which an ink curable by actinic rays is ejected onto a recording material in a recording head having at least one nozzle capable of selectively controlling ejection of ink droplets. The illuminance (mW / cm ² ) of the ink ejection portion in
The value divided by cm ² ) is 1.0 × 10 ^{−5 to} 1.0 × 10 ^−1.
And an image forming method. 2. The sensitivity (mJ / cm ² ) of the ink at a wavelength effective for curing the ink is 0.01 to 50 mJ /
The image forming method according to claim 1, wherein the image forming method is cm ² . 3. The illuminance (mW / cm ² ) of the ink ejection portion at a wavelength effective for curing the ink is 0.001 to 1
The image forming method according to claim 1, wherein the image forming method is mW / cm ² . 4. The image forming method according to claim 1, wherein at least one color of the ink is white ink. 5. The ink for use in the image forming method according to claim 1, which contains at least one selected from an oxetane compound, an epoxy compound, and a vinyl ether compound. 6. The ink according to claim 5, which contains at least one acid multiplying agent. 7. The ink according to claim 5, which contains at least one tertiary amine compound. 8. The method according to claim 5, further comprising at least one photopolymerizable tertiary amine monomer.
Ink according to item. 9. A recording head and ink are heated at 35 to 100 ° C.
The ink is ejected by heating the ink to the above.
A recording device used in the image forming method according to any one of items 1 to 4. 10. The recording apparatus according to claim 9, wherein the ink contains at least one selected from an oxetane compound, an epoxy compound, and a vinyl ether compound. 11. The ink according to claim 9, wherein the ink contains at least one selected from an acid multiplying agent, a tertiary amine compound and a photopolymerizable tertiary amine monomer.
The recording device according to 0.