JP2008068516A - Inkjet recording method and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method superior in hardenability and a recorded matter with an image superior in flexibility and adhesiveness to a medium to be recorded. <P>SOLUTION: The inkjet recording method includes a step (a) to discharge an ink composition on the medium to be recorded and a step (b) to harden the ink composition under an ambient atmosphere with oxygen concentration lower than the air by irradiating the discharged ink composition with active nuclear radiation, the ink composition contains (A) at least one kind of composition selected from a group comprising an ester or an amide of an (metha)acrylic acid having 6-32C hydrocarbon groups which may have substitutional groups or a vinylether having 6-32C hydrocarbon groups which may have substitutional groups and (B) a polymerization initiator. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet recording method and a method for producing a lithographic printing plate, and relates to an inkjet recording method in which an ink composition is discharged and then cured by irradiation with actinic radiation, and a recorded matter obtained by the inkjet recording method.

As an image recording method for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic method, a sublimation type and a melt type thermal transfer method, an ink jet method and the like. The electrophotographic system requires a process of forming an electrostatic latent image on a photosensitive drum by charging and exposure, and there is a problem that the system becomes complicated and consequently the manufacturing cost becomes high. In addition, although the thermal transfer method is inexpensive, there are problems such as high running costs and waste materials due to the use of ink ribbons.
On the other hand, the ink jet method is an inexpensive device and ejects the ink composition only to the required image area to form an image directly on the recording medium. Is cheap. Furthermore, there is little noise and it is excellent as an image recording method.

  Ink compositions that can be cured by irradiation with actinic radiation such as ultraviolet rays (radiation curable ink compositions), such as ink compositions for ink jet recording, can be cured with high sensitivity and form high-quality images. It has been demanded. By achieving high sensitivity, high curability is imparted by irradiation with actinic radiation, so that sufficient curing is achieved in addition to reducing power consumption and extending life by reducing the load on the actinic radiation generator. As a result, there are various advantages such as suppression of volatilization of uncured low molecular weight substances and reduction in the strength of the formed image. Further, the improvement in the image strength by increasing the sensitivity results in high printing durability in the image area when this ink composition is used for forming the image area of a lithographic printing plate.

  As an ultraviolet curable ink composition, for example, an ink composition using a combination of a plurality of monomers having different degrees of functionality has been proposed (see, for example, Patent Document 1). However, in order to maintain the curing speed in such an ink composition, many polyfunctional monomers must be used, and in this case, there is a problem in the flexibility of the image after the ink composition is cured.

  In particular, when a radically polymerizable ink composition is used in an actinic radiation curable ink jet recording method, the ink composition is difficult to cure on the surface of the recording medium due to inhibition of curing by oxygen. It becomes a problem. Furthermore, in a device in which image recording is performed by a recording medium passing under the inkjet head only once, such as a single-pass system using a full line head, curing is performed only once. It is hoped that this factor will be suppressed.

Japanese Patent Laid-Open No. 5-214280

  An object of the present invention is to provide an ink jet recording method excellent in curability. Another object of the present invention is to provide a recorded matter having an image excellent in flexibility and adhesion to a recording medium.

As a result of intensive studies, the inventor uses a specific polymerizable compound in the ink composition, and further defines the oxygen concentration at the time of curing, so that the sensitivity is high and the flexibility after the ink composition is cured. The present inventors have found that an ink jet recording method that is excellent and has improved adhesion to a recording medium can be obtained, and has solved the above problems.
The problem to be solved by the present invention has been solved by means described in the following <1> or <5>. It is described below together with <2> to <4> which are preferred embodiments.
<1> (a) a step of ejecting an ink composition onto a recording medium; and (b) irradiating the ejected ink composition with actinic radiation so that the ink composition has an oxygen concentration lower than that in the atmosphere. The ink composition includes a step of curing under an atmosphere, and (A) an ester or amide of (meth) acrylic acid having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent, or a substitution Inkjet recording comprising at least one compound selected from the group consisting of vinyl ethers having a hydrocarbon group having 6 to 32 carbon atoms which may have a group, and (B) a polymerization initiator Method,
<2> The inkjet recording method according to <1>, wherein the hydrocarbon group having 6 to 32 carbon atoms which may have a substituent is an alkyl group or an alkylene group which may have a substituent,
<3> The inkjet recording method according to <1> or <2>, wherein the ink composition contains (C) a colorant.
<4> The inkjet recording method according to any one of <1> to <3>, wherein the ink composition contains N-vinyl lactams,
<5> A recorded matter obtained by the inkjet recording method according to any one of <1> to <4>.

  According to the present invention, an ink jet recording method having excellent curability can be provided. Further, it is possible to provide a recorded matter having an image excellent in flexibility and adhesion to a recording medium.

The inkjet recording method of the present invention comprises (a) a step of ejecting an ink composition onto a recording medium, and (b) irradiating the ejected ink composition with actinic radiation so that the ink composition is exposed to the atmosphere. A step of curing in an atmosphere having a lower oxygen concentration, and the ink composition is (A) an ester of (meth) acrylic acid having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent. Or at least one compound selected from the group consisting of an amide or a vinyl ether having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent, and (B) a polymerization initiator. Features.
So far, when the above-mentioned (A) is used as the polymerizable compound, the hardness sensitivity is low, and its use has been greatly limited. The present invention provides an ink jet recording method that can provide a recorded matter that has excellent curing sensitivity, adhesion to a recording medium, and excellent flexibility by regulating the oxygen concentration during curing.
The ink composition containing (A) and (B) is also referred to as the ink composition of the present invention.

<Ink composition>
The ink composition of the present invention is curable by irradiation with heat or actinic radiation, and (A) an ester of (meth) acrylic acid having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent. Or at least one compound selected from the group consisting of an amide or a vinyl ether having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent, and (B) a polymerization initiator. Features.
The ink composition of the present invention is used for inkjet recording.
“Actinic radiation” as used in the present invention is not particularly limited as long as it can impart energy capable of generating a starting species in the ink composition by irradiation, and widely includes α rays, γ rays, X Including rays, ultraviolet rays, visible rays, electron beams, and the like. Among these, from the viewpoints of curing sensitivity and device availability, ultraviolet rays and electron beams are preferable, and ultraviolet rays are particularly preferable. Therefore, the ink composition of the present invention is preferably an ink composition that can be cured by irradiating ultraviolet rays as actinic radiation.

[(A) An ester or amide of (meth) acrylic acid having an optionally substituted hydrocarbon group having 6 to 32 carbon atoms, or an optionally substituted group having 6 to 32 carbon atoms At least one compound selected from the group consisting of vinyl ethers having hydrocarbon groups]
In the present invention, the ink composition has (A) an ester or amide of (meth) acrylic acid having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent, or a substituent. Or at least one compound selected from the group consisting of vinyl ethers having a hydrocarbon group having 6 to 32 carbon atoms (hereinafter also referred to as “component (A)” as appropriate).
In the present invention, it is preferable that the ink composition contains the component (A) because adhesion to a recording medium is improved. By using the component (A), the hydrophobicity of the entire ink composition can be increased, a high-quality image can be obtained, and it can be suitably used for a lithographic printing plate. Further, by using the component (A), it is possible to improve the adhesion and flexibility with the recording medium.
In the present invention, “(meth) acrylic acid” is an abbreviation that indicates both acrylic acid and methacrylic acid.
The component (A) is represented by the following formula (A).

  Here, X represents an m-valent group having 6 to 32 carbon atoms which may have a substituent, and Y is selected from the following groups.

When Y is (a), component (A) is an ester of acrylic acid, and when (b) is an ester of methacrylic acid.
When Y is (c), the component (A) is an amide of acrylic acid, and when (d) is an amide of methacrylic acid.
Further, when Y is (e), the component (A) is vinyl ether.

  In the formula (A), m represents the number of functional groups Y, and m is an integer of 1 or more. m is preferably 1 to 6, more preferably 1 to 4, still more preferably 1 to 3, and particularly preferably 1 or 2.

In the formula (A), when Y is (a), (b) or (e), X represents an m-valent hydrocarbon group having 6 to 32 carbon atoms which may have a substituent. X is preferably a hydrophobic group, more preferably a linear or branched hydrocarbon group having 6 to 32 carbon atoms which may have a substituent.
Specific examples of X include an alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, and an m-valent group obtained by removing (m-1) hydrogen atoms from these groups. Among these, an m-valent group obtained by removing hydrogen from an alkyl group or an alkyl group is preferable, and the alkyl group may be linear or branched.
Among these, X is preferably a linear alkyl group having 6 to 32 carbon atoms or an m-valent group obtained by removing (m-1) hydrogen from this.
Although carbon number is 6-32, it is more preferable that it is 6-28, and it is especially preferable that it is C6-C24.
When the number of carbon atoms is less than 6, the glass transition temperature (Tg) of the cured product becomes high, and the flexibility and adhesion to the plastic substrate are not sufficiently exhibited, which causes a problem. Moreover, when carbon number exceeds 32, the compatibility in a composition will fall, and the deterioration of the stability of a composition and the softness | flexibility after hardening will be brought about.
Examples of the substituent include an alkoxy group, a polyalkoxy group, a halogen atom, a silyl group, a mono-, di-, or trialkylsilyl group, a hydroxyl group (—OH), an amino group (—NH ₂ ), a mono- or dialkylamino group, Examples thereof include alkylsulfanyl. These substituents are preferably hydrophobic groups. Among these, an alkyl group and a cycloalkyl group are preferable.

  In the formula (A), when Y is (c) or (d), X ′ represents a hydrogen atom or X. X has the same meaning as above. That is, when the component (A) is an amide of (meth) acrylic acid, the nitrogen atom may be monosubstituted or disubstituted.

  Here, the hydrocarbon group having 6 to 32 carbon atoms in the component (A) is a hydrocarbon directly bonded to an oxygen atom of an ester bond portion, a nitrogen atom of an amide bond portion, or an oxygen atom of a vinyl ether bond portion. The whole group is meant. That is, when having a plurality of such groups, the whole of the plurality of groups corresponds to a hydrocarbon group having 6 to 32 carbon atoms in the component (A), and the total number of carbon atoms contained in such groups is 6 to 32 is required. For example, when the component (A) is an amide in which two alkyl groups are directly bonded to the nitrogen atom of the amide bond portion, the total number of carbon atoms contained in the two alkyl groups is 6 to 32 It will be necessary.

In the present invention, the component (A) is an ester or amide of (meth) acrylic acid, or vinyl ether. If an ester of (meth) acrylic acid is taken as an example, the component (A) is mono (meth) acrylic acid. The polyfunctional compound such as di (meth) acrylic acid ester and tri (meth) acrylic acid ester may be used. That is, the component (A) is not limited to the monofunctional compound in which m is 1 in the above formula (I), and may be a polyfunctional compound in which m is 2 or more. As described above, the component (A) is preferably monofunctional or bifunctional (m is 1 or 2).
Accordingly, as the component (A) in the present invention, monoalcohol having an alkyl group having 6 to 32 carbon atoms or an ester of a diol having an alkylene group having 6 to 32 carbon atoms and (meth) acrylic acid, or 6 to 6 carbon atoms. A monoamine having 32 alkyl groups, an amide of (meth) acrylic acid with a diamine having an alkylene group having 6 to 32 carbon atoms, a monoalcohol having an alkyl group having 6 to 32 carbon atoms, or 6 to 32 carbon atoms A vinyl ether of a diol having an alkylene group can be preferably used.

  Further, the vinyl group in the vinyl ether having a group having 6 to 32 carbon atoms may be an unsubstituted vinyl group or a 1-3 substituted vinyl group. It is preferable that That is, the hydrogen atom in (e) above may be substituted, but is preferably a hydrogen atom.

  Preferred components (A) include hexyl acrylate, hexyl methacrylate, N-hexyl acrylamide, N, N-dihexyl acrylamide, hexyl vinyl ether, heptyl acrylate, heptyl methacrylate, N-heptyl acrylamide, octyl acrylate, nonyl acrylate, decyl acrylate , Undecyl acrylate, dodecyl acrylate (lauryl acrylate), tridecyl acrylate, tetradecyl acrylate (myristyl acrylate), pentadecyl acrylate, hexadecyl acrylate (palmityl acrylate), heptadecyl acrylate, octadecyl acrylate (stearyl acrylate), nonadecyl Acrylate, icosyl acrylate, docosyl acrylate (Behenyl acrylate), tricosyl acrylate, tetracosyl acrylate, hexacosyl acrylate, octacosyl acrylate, triacontyl acrylate, dotriacontyl acrylate, 1,6-hexane diacrylate, 1,7-heptane diacrylate 1,8-octane diacrylate, 1,9-nonane diacrylate, 1,10-decane diacrylate, 1,11-undecane diacrylate, 1,12-dodecane diacrylate, 1,6-hexane dimethacrylate, 1,7-heptane dimethacrylate, 1,8-octane dimethacrylate, 1,9-nonane dimethacrylate, 1,10-decane dimethacrylate, 1,11-undecane dimethacrylate, 1,12-dodecane Dimethacryl 1,6-hexane diacrylamide, 1,7-heptane diacrylamide, 1,8-octane diacrylamide, 1,9-nonane diacrylamide, 1,10-decane diacrylamide, 1,11-undecane diacrylamide, 1,12-dodecane diacrylamide, 1,6-hexane divinyl ether, 1,7-heptane divinyl ether, 1,8-octane divinyl ether, 1,9-nonane divinyl ether, 1,10-decane divinyl ether, 1, 11-undecane divinyl ether, 1,12-dodecane divinyl ether, 1,6- (2-ethylhexane) diacrylate, 1,6- (2-ethylhexane) dimethacrylate, 1,6- (2-ethylhexane) ) Diacrylamide, 1,6- (2-ethylhexane) dibi Nyl ether and the like can be exemplified, but the present invention is not limited thereto.

  Moreover, (A) component may be used by 1 type, and 2 or more types may be used, but the aspect which mixes and uses 2 or 3 types is also preferable, and a C6-C13 alkyl group A mode in which two or three types of (meth) acrylic acid ester having a carboxylic acid and / or a bifunctional (meth) acrylic acid ester having an alkylene group having 6 to 13 carbon atoms are used in combination is particularly preferable.

The content of the component (A) in the ink composition of the present invention is in the range of 1 to 90% by weight with respect to the total weight of the ink composition, from the viewpoints of adhesion improvement effect and ink jet suitability of the ink composition. Preferably, the range is 15 to 60% by weight, more preferably 20 to 50% by weight.
Moreover, it is preferable that it is 5-100 weight% of the whole polymeric compound, More preferably, it is 10-80 weight%, More preferably, it is 15-60 weight%.

[(B) polymerization initiator]
The ink composition of the present invention contains a polymerization initiator. As the polymerization initiator, a known polymerization initiator can be used. In the present invention, it is preferable to use a radical polymerization initiator.
The polymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy and generates a polymerization initiating species. External energy used for initiating polymerization is roughly divided into heat and radiation, and a thermal polymerization initiator and a photopolymerization initiator are used, respectively. Examples of radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.
Known compounds can be used as the thermal polymerization initiator and the photopolymerization initiator.

<Radical polymerization initiator>
The radical polymerization initiator that can be used in the present invention includes (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic peroxides, and (e) thio compounds. (F) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) carbon halogen bond And (m) an alkylamine compound. These radical polymerization initiators may use the above compounds (a) to (m) alone or in combination. The radical polymerization initiator in the present invention is preferably used alone or in combination of two or more.

  (A) As a preferable example of aromatic ketones, “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY” P. FOUASSIER J.M. F. RABEK (1993), pp. Examples thereof include a compound having a benzophenone skeleton described in 77 to 117 (benzophenone compound) or a compound having a thioxanthone skeleton (thioxanthone compound). Examples of preferable (a) aromatic ketones and (b) acylphosphine compounds include α-thiobenzophenone compounds described in JP-B-47-6416, benzoin ether compounds described in JP-B-47-3981, Α-substituted benzoin compounds described in JP-B-47-22326, benzoin derivatives described in JP-B-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, and JP-B-60-26483 Dialkoxybenzophenone, benzoin ethers described in JP-B-60-26403, JP-A-62-81345, JP-B-1-34242, US Pat. No. 4,318,791, European Patent 0284561A1 Α-Aminobenzophenones, JP-A-2-211452 P-di (dimethylaminobenzoyl) benzene described in JP-A-61-194062, thio-substituted aromatic ketone described in JP-A-61-194062, acylphosphine sulfide described in JP-B-2-9597, described in JP-B-2-9596 Acyl phosphines, thioxanthones described in JP-B-63-61950, and coumarins described in JP-B-59-42864.

  Examples of the benzophenone compound include benzophenone, 4-phenylbenzophenone, isophthalophenone, 4-benzoyl-4'-methylphenyl sulfide and the like. Examples of the thioxanthone compound include 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone and the like.

In the present invention, the (a) aromatic ketone is preferably an α-hydroxyketone, such as 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1 -One, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone and the like.
Among these, as the (a) aromatic ketone, a 1-hydroxycyclohexyl phenyl ketone compound is particularly preferable. In the present invention, the 1-hydroxycyclohexyl phenyl ketone compound means a compound in which 1-hydroxycyclohexyl phenyl ketone and 1-hydroxycyclohexyl phenyl ketone are substituted with an arbitrary substituent. The substituent can be arbitrarily selected as long as it can exhibit the ability as a radical polymerization initiator, and specific examples thereof include alkyl groups (eg, methyl group, ethyl group, propyl group, butyl group). it can.

In the present invention, the (b) acylphosphine compound is preferably an acylphosphine oxide compound.
As the acylphosphine oxide compound, a monoacylphosphine oxide compound, a bisacylphosphine oxide compound, or the like can be used. As the monoacylphosphine oxide compound, a known monoacylphosphine oxide compound can be used. Examples thereof include monoacylphosphine oxide compounds described in JP-B-60-8047 and JP-B-63-40799. Specific examples include isobutyryl-methylphosphinic acid methyl ester, isobutyryl-phenylphosphinic acid methyl ester, pivaloyl-phenylphosphinic acid methyl ester, 2-ethylhexanoyl-phenylphosphinic acid methyl ester, pivaloyl-phenylphosphinic acid isopropyl ester, p. -Toluyl-phenylphosphinic acid methyl ester, o-toluyl-phenylphosphinic acid methyl ester, 2,4-dimethylbenzoyl-phenylphosphinic acid methyl ester, p-tert-butylbenzoyl-phenylphosphinic acid isopropyl ester, acryloyl-phenylphosphinic acid Methyl ester, isobutyryl-diphenylphosphine oxide, 2-ethylhexanoyl-diphenylphosphine oxide, o-to Yl-diphenylphosphine oxide, p-tertiarybutylbenzoyl-diphenylphosphine oxide, 3-pyridylcarbonyl-diphenylphosphine oxide, acryloyl-diphenylphosphine oxide, benzoyl-diphenylphosphine oxide, pivaloyl-phenylphosphinic acid vinyl ester, adipoyl-bis- Diphenylphosphine oxide, pivaloyl-diphenylphosphine oxide, p-toluyl-diphenylphosphine oxide, 4- (tert-butyl) -benzoyl-diphenylphosphine oxide, terephthaloyl-bis-diphenylphosphine oxide, 2-methylbenzoyl-diphenylphosphine oxide, versatoyl -Diphenylphosphine oxide, 2-methyl-2-ethyl Examples include ruhexanoyl-diphenylphosphine oxide, 1-methyl-cyclohexanoyl-diphenylphosphine oxide, pivaloyl-phenylphosphinic acid methyl ester, and pivaloyl-phenylphosphinic acid isopropyl ester.

  A known bisacylphosphine oxide compound can be used as the bisacylphosphine oxide compound. Examples thereof include bisacylphosphine oxide compounds described in JP-A-3-101686, JP-A-5-345790, and JP-A-6-298818. Specific examples include bis (2,6-dichlorobenzoyl) -phenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6-dichlorobenzoyl). -4-ethoxyphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-propylphenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2-naphthylphosphine oxide, bis (2,6-di Chlorobenzoyl) -1-naphthylphosphine oxide, bis (2,6-dichlorobenzoyl) -4-chlorophenylphosphine oxide, bis (2,6-dichlorobenzoyl) -2,4-dimethoxyphenylphosphine oxide, bis ( 2,6-dichlorobenzoyl) -decylphosphine oxide, bis (2 , 6-Dichlorobenzoyl) -4-octylphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -2,5-dimethylphenylphosphine oxide Bis (2,6-dichloro-3,4,5-trimethoxybenzoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6-dichloro-3,4,5-trimethoxybenzoyl) -4- Ethoxyphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -2,5-dimethylphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -4-ethoxyphenylphosphine oxide, bis (2-methyl-1 -Naphthoyl) -2-naphthylphosphine oxide, bis (2-methyl- 1-naphthoyl) -4-propylphenylphosphine oxide, bis (2-methyl-1-naphthoyl) -2,5-dimethylphenylphosphine oxide, bis (2-methoxy-1-naphthoyl) -4-engineered phenylphenylphosphine oxide Bis (2-chloro-1-naphthoyl) -2,5-dimethylphenylphosphine oxide, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, and the like.

  Among these, in the present invention, as the acylphosphine oxide compound, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (Irgacure 819: manufactured by Ciba Specialty Chemicals), bis (2,6-dimethoxybenzoyl) -2,4,4-Trimethyl-pentylphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Darocur TPO: manufactured by Ciba Specialty Chemicals, Lucirin TPO: manufactured by BASF) and the like are preferable.

  (C) As aromatic onium salt compounds, elements of Groups 15, 16 and 17 of the periodic table, specifically N, P, As, Sb, Bi, O, S, Se, Te, or I fragrances Group onium salts are included. For example, iodonium salts described in European Patent No. 104143, US Pat. No. 4,837,124, Japanese Patent Laid-Open No. 2-150848, Japanese Patent Laid-Open No. 2-96514, European Patent Nos. 370693, 233567, and 297443 are disclosed. The diazonium salts described in the specifications of U.S. Pat. Nos. 2,974,279, 279210, and 422570, U.S. Pat. Nos. 3,902,144, 4,933,377, 4,760013, 4,734,344, and 2,833,827 Benzenediazonium which may have a substituent), diazonium salt resins (formaldehyde resin of diazodiphenylamine, etc.), N-alkoxypyridinium salts, etc. (for example, US Pat. No. 4,743,528, JP-A-63) -138345, JP-A-63 No. 142345, JP-A-63-142346, and JP-B-46-42363, specifically 1-methoxy-4-phenylpyridinium tetrafluoroborate, etc. The compounds described in JP-A 52-147277, 52-14278, and 52-14279 are preferably used. Generates radicals and acids as active species.

  (D) The organic peroxide includes almost all organic compounds having one or more oxygen-oxygen bonds in the molecule. Examples thereof include 3,3 ′, 4,4′-tetra- ( t-butylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra- (t-amylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra- (t-hexylperoxycarbonyl) ) Benzophenone, 3,3 ′, 4,4′-tetra- (t-octylperoxycarbonyl) benzophenone, 3,3 ′, 4,4′-tetra- (cumylperoxycarbonyl) benzophenone, 3,3 ′, Perester ester compounds such as 4,4′-tetra- (p-isopropylcumylperoxycarbonyl) benzophenone and di-t-butyldiperoxyisophthalate Thing is preferable.

  (F) Examples of hexaarylbiimidazole compounds include lophine dimers described in JP-B Nos. 45-37377 and 44-86516, such as 2,2′-bis (o-chlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-bromophenyl) -4,4 ′, 5,5′tetraphenylbiimidazole, 2,2′-bis (o, p-dichlorophenyl) -4,4 ', 5,5'-tetraphenylbiimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetra (m-methoxyphenyl) biimidazole, 2, 2′-bis (o, o′-dichlorophenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-nitrophenyl) -4,4 ′, 5,5 ′ − Traphenylbiimidazole, 2,2′-bis (o-methylphenyl) -4,4 ′, 5,5′-tetraphenylbiimidazole, 2,2′-bis (o-trifluorophenyl) -4,4 Examples include ', 5,5'-tetraphenylbiimidazole.

  (G) Examples of the ketoxime ester compound include 3-benzoyloxyiminobutane-2-one, 3-acetoxyiminobutane-2-one, 3-propionyloxyiminobutane-2-one, and 2-acetoxyiminopentane-3. -One, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminotan-2-one, 2-ethoxy And carbonyloxyimino-1-phenylpropan-1-one.

  (H) Examples of the borate compound include compounds described in US Pat. Nos. 3,567,453, 4,343,891, European Patents 109,772, and 109,773. Can be mentioned.

  (I) Examples of azinium salt compounds include JP-A-63-138345, JP-A-63-142345, JP-A-63-142346, JP-A-63-143537, and JP-B-46-42363. The compound group which has NO bond of each gazette description can be mentioned.

  (J) Examples of metallocene compounds include titanocenes described in JP-A-59-152396, JP-A-61-151197, JP-A-63-41484, JP-A-2-249, and JP-A-2-4705. Examples thereof include iron-arene complexes described in JP-A-1-304453 and JP-A-1-152109.

  Specific examples of the titanocene compound include di-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl, and di-cyclopentadienyl-Ti-bis-2,3. 4,5,6-pentafluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluorophen-1-yl, di-cyclopentadienyl-Ti- Bis-2,4,6-trifluorophen-1-yl, di-cyclopentadienyl-Ti-2,6-difluorophen-1-yl, di-cyclopentadienyl-Ti-bis-2,4 -Difluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluorophen-1-yl, di-methylcyclopentadienyl-Ti- -2,3,5,6-tetrafluorophen-1-yl, di-methylcyclopentadienyl-Ti-bis-2,4-difluorophen-1-yl, bis (cyclopentadienyl) -bis (2,6-difluoro-3- (pyridin-1-yl) phenyl) titanium, bis (cyclopentadienyl) bis [2,6-difluoro-3- (methylsulfonamido) phenyl] titanium, bis (cyclopenta And dienyl) bis [2,6-difluoro-3- (N-butylbialoyl-amino) phenyl] titanium.

  (K) Examples of the active ester compound include the specifications of European Patent Nos. 0290750, 046083, 156153, 271851, and 0388343, U.S. Pat. Nos. 3,901,710, and 4,181,531. Nitrobenzol ester compounds described in JP-A-60-198538 and JP-A-53-133022, European Patents 0199672, 84515, 199672, 0441115, and 0101122. No. 4,618,564, U.S. Pat. No. 4,371,605, and U.S. Pat. No. 4,431,774, JP-A 64-18143, JP-A 2-245756, and JP-A-4-365048. Iminosulfonate compound, Japanese Examined Patent Publication No. 62-6223, Japanese Examined Publication No. 63 No. 14340, and compounds, and the like described in the JP-A No. 59-174831.

  (L) Preferable examples of the compound having a carbon halogen bond include, for example, compounds described in Wakabayashi et al., Bull. Chem. Soc. Japan, 42, 2924 (1969), compounds described in British Patent No. 1388492, Examples thereof include compounds described in Japanese Utility Model Publication No. 53-133428, compounds described in German Patent No. 3337024, and the like.

  Further, compounds described in J. Org. Chem., 29, 1527 (1964) by FC Schaefer et al., Compounds described in JP-A-62-258241, compounds described in JP-A-5-281728, and the like can be mentioned. it can. A compound as described in German Patent No. 2641100, a compound described in German Patent No. 3333450, a compound group described in German Patent No. 3021590, or a compound group described in German Patent No. 3021599, etc. Can be mentioned.

In the present invention, the polymerization initiator (B) is polymerized with respect to the total amount of the component (A) or when the component (A) and (D) another polymerizable compound as an optional component are used in combination. Preferably, it is contained in the range of 0.01 to 35% by weight, more preferably 0.1 to 30% by weight, and still more preferably 0.5 to 30% by weight, based on the total amount of the active compound. .
Further, (B) the polymerization initiator is 200: 1 to 1: 200 in a weight ratio of polymerization initiator: sensitizer with respect to (E) sensitizer, which can be used as necessary, which will be described later. It is preferable that it is contained in the range, More preferably, it is 50: 1 to 1:50, More preferably, it is 20: 1 to 1: 5.

[(C) Colorant]
The ink composition of the present invention preferably contains (C) a colorant.
The colorant that can be used in the present invention is not particularly limited, but (C-1) pigments and (C-2) oil-soluble dyes that are excellent in weather resistance and rich in color reproducibility are preferable, and are soluble. Any known colorant such as a dye can be selected and used. The colorant that can be suitably used in the ink composition of the present invention is a compound that does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction, from the viewpoint of not reducing the sensitivity of the curing reaction by actinic radiation. preferable.

(C-1) Pigment The pigment that can be used in the present invention is not particularly limited. For example, organic or inorganic pigments having the following numbers described in the color index can be used.
Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53: 1 as red or magenta pigment 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange 13 16, 20, 36,
As the 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 ,
Examples of green pigments include Pigment Green 7, 26, 36, 50,
As yellow pigments, Pigment Yellow 1, 3, 12, 13, 14, 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120, 137 138, 139, 153, 154, 155, 157, 166, 167, 168, 180, 185, 193,
As the black pigment, Pigment Black 7, 28, 26,
As the white pigment, Pigment White 6, 18, 21
Etc. can be used according to the purpose.

(C-2) Oil-soluble dye The oil-soluble dye that can be used in the present invention is described below.
The oil-soluble dye that can be used in the present invention means a dye that is substantially insoluble in water. Specifically, the solubility in water at 25 ° C. (the mass of the dye that can be dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Accordingly, the oil-soluble dye means a so-called water-insoluble pigment or oil-soluble dye, and among these, an oil-soluble dye is preferable.

  Among the oil-soluble dyes that can be used in the present invention, any yellow dye can be used. For example, phenols, naphthols, anilines, pyrazolones, pyridones, aryl or heteryl azo dyes having open-chain active methylene compounds as coupling components; for example, azomethine dyes having open-chain active methylene compounds as coupling components; Examples include methine dyes such as benzylidene dyes and monomethine oxonol dyes; quinone dyes such as naphthoquinone dyes and anthraquinone dyes; and other dye species such as quinophthalone dyes, nitro / nitroso dyes, acridine And dyes and acridinone dyes.

  Of the oil-soluble dyes usable in the present invention, any magenta dye can be used. For example, aryl or heteryl azo dyes having phenols, naphthols, anilines as coupling components; for example, azomethine dyes having pyrazolones, pyrazolotriazoles as coupling components; for example arylidene dyes, styryl dyes, merocyanine dyes, oxonol dyes Methine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone, anthrapyridone; condensed polycyclic dyes such as dioxazine dyes, etc. Can be mentioned.

  Among the oil-soluble dyes applicable to the present invention, any cyan dye can be used. For example, indoaniline dyes, indophenol dyes or azomethine dyes having pyrrolotriazoles as coupling components; polymethine dyes such as cyanine dyes, oxonol dyes, merocyanine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes Phthalocyanine dyes; anthraquinone dyes; for example, aryl or heteryl azo dyes having phenols, naphthols and anilines as coupling components; indigo / thioindigo dyes;

  Each of the above dyes may exhibit yellow, magenta, and cyan colors only after a part of a chromophore (color-forming atomic group) is dissociated. In this case, the counter cation may be an alkali metal or ammonium. Such inorganic cations may be used, and organic cations such as pyridinium and quaternary ammonium salts may be used, and furthermore, polymer cations having such a partial structure may be used.

Although not limited to the following, preferred specific examples include C.I. I. Solvent Black 3, 7, 27, 29 and 34; C.I. I. Solvent Yellow 14, 16, 19, 29, 30, 56, 82, 93 and 162; C.I. I. Solvent Red 1, 3, 8, 18, 24, 27, 43, 49, 51, 72, 73, 109, 122, 132 and 218; C.I. I. Solvent Violet 3; C.I. I. Solvent Blue 2, 11, 25, 35, 38, 67 and 70; C.I. I. Solvent Green 3 and 7; I. Solvent orange 2; and the like.
Particularly preferred among these are: Nubian Black PC-0850, Oil Black HBB, Oil Yellow 129, Oil Yellow 105, Oil Pink 312, Oil Red 5B, Oil Scallet 308, Vali Fast Blue chemistry 2606e B2 (Manufactured by Co., Ltd.), Aizen Spiron Blue GNH (manufactured by Hodogaya Chemical Co., Ltd.), Neopen Yellow 075, Neopen Magenta SE1378, Neopen Blue 808, Neopen Blue FF4012, and Neo42 Cy FF4012.
In the present invention, the oil-soluble dye may be used alone or in combination of several kinds.

Moreover, when using an oil-soluble dye as a colorant, other water-soluble dyes, disperse dyes, pigments, and other colorants can be used in combination as long as the effects of the present invention are not impaired.
In the present invention, a disperse dye can be used as long as it is soluble in a water-immiscible organic solvent. The disperse dye generally includes a water-soluble dye, but in the present invention, the disperse dye is preferably used as long as it is soluble in a water-immiscible organic solvent. Preferable specific examples of the disperse dye include C.I. I. Disperse Yellow 5, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 184: 1, 186, 198, 199, 201, 204, 224 and 237 C. I. Disperse Orange 13, 29, 31: 1, 33, 49, 54, 55, 66, 73, 118, 119 and 163; C.I. I. Disperse Red 54, 60, 72, 73, 86, 88, 91, 92, 93, 111, 126, 127, 134, 135, 143, 145, 152, 153, 154, 159, 164, 167: 1, 177 , 181, 204, 206, 207, 221, 239, 240, 258, 277, 278, 283, 311, 323, 343, 348, 356 and 362; I. Disperse Violet 33; C.I. I. Disperse Blue 56, 60, 73, 87, 113, 128, 143, 148, 154, 158, 165, 165: 1, 165: 2, 176, 183, 185, 197, 198, 201, 214, 224, 225 257, 266, 267, 287, 354, 358, 365 and 368; I. Disperse Green 6: 1 and 9;

  It is preferable that the colorant that can be used in the present invention is appropriately dispersed in the ink composition after being added to the ink composition of the present invention. For dispersing the colorant, for example, a dispersion device such as 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, or a paint shaker can be used.

  It is also possible to add a dispersant when dispersing the colorant. The type of the dispersant is not particularly limited, but a polymer dispersant is preferably used, and examples of the polymer dispersant include Solsperse series manufactured by Zeneca. Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. In the present invention, these dispersant and dispersion aid are preferably added in an amount of 1 to 200 parts by weight, more preferably 30 to 150 parts by weight, based on 100 parts by weight of the colorant.

  In preparing the ink composition of the present invention, the colorant may be blended by adding directly with each component. However, in order to improve dispersibility, the solvent or the component (A) used in the present invention in advance or in combination as desired (D) It can also be added to a dispersion medium such as other polymerizable compounds and uniformly dispersed or dissolved before blending.

  In the present invention, in order to avoid the deterioration of the solvent resistance when the solvent remains in the cured image and the problem of the VOC (Volatile Organic Compound) of the remaining solvent, the colorant contains the component (A). And / or (D) It is preferable to add and mix | blend with any one of those other polymerizable compounds or those mixtures previously. In consideration of only dispersibility, it is preferable to select a monomer having the lowest viscosity as the polymerizable compound used for the addition of the colorant.

  These colorants may be used by appropriately selecting one type or two or more types according to the purpose of use of the ink composition.

  When using a colorant such as a pigment that remains solid in the ink composition of the present invention, the average particle diameter of the colorant particles is preferably 0.005 to 0.5 μm, more preferably 0. It is preferable to set the colorant, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so as to be 0.01 to 0.45 μm, more preferably 0.015 to 0.4 μm. This particle size control is preferable because clogging of the head nozzle can be suppressed and the storage stability of the ink composition, the transparency of the ink composition, and the curing sensitivity can be maintained.

  The content of the colorant in the ink composition of the present invention is appropriately selected depending on the purpose of use. However, considering the physical properties and colorability of the ink composition, generally, the content of the colorant is 1 with respect to the total weight of the ink composition. It is preferable that it is 10 to 10 weight%, and it is more preferable to contain 1 to 8 weight%.

In the present invention, an ink composition that does not contain the colorant described above can also be used. In this case, clear ink can be used. If such an ink is used, a clear film can be obtained because it does not contain a colorant. Clear inks that do not contain color materials can be used for undercoats to give recording materials suitable for image printing, or for surface protection of images formed with ordinary inks, further decoration and gloss For example, it may be used for an overcoat for the purpose of application. In the clear ink, colorless pigments or fine particles that are not intended for coloring can be dispersed and contained according to these applications. By adding these, it is possible to improve various characteristics such as image quality, fastness and workability (handling property) of the recorded matter in both the undercoat and the overcoat.
Moreover, it can be used for various purposes where coloring is not required, and application to, for example, a Braille block is also expected.

  In the ink composition of the present invention, in addition to the essential components described above, other components can be used in combination for the purpose of improving physical properties as long as the effects of the present invention are not impaired. Hereinafter, these other components will be described.

[(D) Other polymerizable compound]
The ink composition of the present invention preferably contains (D) another polymerizable compound in addition to the component (A). Examples of other polymerizable compounds that can be used in combination with the present invention include radically polymerizable compounds and cationically polymerizable compounds.
(D) Other polymerizable compounds may be appropriately selected and used in relation to the objective properties or the relationship with the (B) polymerization initiator.

  In the present invention, the radically polymerizable compound that can be used in combination with the component (A) is a compound having a radically polymerizable ethylenically unsaturated bond, and at least one radically polymerizable ethylenically unsaturated bond in the molecule. Any compound may be used as long as it has a chemical form such as a monomer, oligomer, or polymer. Only one type of radically polymerizable compound may be used, or two or more types thereof may be used in combination at an arbitrary ratio in order to improve desired properties. It is preferable to use two or more kinds in combination for controlling performance such as reactivity and physical properties.

  In the ink composition of the present invention, N-vinyl lactams are preferably used in combination as the polymerizable compound. Preferable examples of N-vinyl lactams include compounds represented by the following formula (I).

  In the formula (I), n represents an integer of 1 to 5, and n is 2 to 4 from the viewpoints of flexibility after the ink composition is cured, adhesion to a recording medium, and availability of raw materials. It is preferable that n is an integer of 2 or 4, and n is 4, that is, N-vinylcaprolactam is particularly preferable. N-vinylcaprolactam is preferable because it is excellent in safety, is generally available and can be obtained at a relatively low price, and provides particularly good ink curability and adhesion of a cured film to a recording medium.

  The N-vinyl lactams may have a substituent such as an alkyl group or an aryl group on the lactam ring, and may be linked with a saturated or unsaturated ring structure.

  The ink composition of the present invention preferably contains 10% by weight or more of the total ink when (D) N-vinyl lactam is used as the other polymerizable compound. It is preferable to contain N-vinyl lactams in an amount of 10% by weight or more based on the whole ink because an ink composition excellent in curability, cured film flexibility, and cured film substrate adhesion can be provided. A more preferable content of the N-vinyl lactam in the ink composition is in the range of 10% by weight to 40% by weight. N-vinyl lactams are compounds having a relatively high melting point. A content of 40% by weight or less is preferable because it exhibits good solubility even at a low temperature of 0 ° C. or less, and the temperature range in which the ink composition can be handled becomes wide. More preferably, it is in the range of 12 wt% or more and 40 wt% or less, and particularly preferably in the range of 15 wt% or more and 35 wt% or less.

  The N-vinyl lactams may be contained in the ink composition alone or in a plurality of kinds.

  Examples of other polymerizable compounds having an ethylenically unsaturated bond capable of radical polymerization include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, and salts thereof. , Radically polymerizable compounds such as anhydrides having an ethylenically unsaturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

  Specifically, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, tetrahydrofurfuryl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate , Triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate , Oligoes Acrylic acid derivatives such as polyacrylate, N-methylolacrylamide, diacetoneacrylamide, epoxy acrylate, methyl methacrylate, n-butyl methacrylate, allyl methacrylate, glycidyl methacrylate, dimethylaminomethyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, Polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, methacryl derivatives such as 2,2-bis (4-methacryloxypolyethoxyphenyl) propane, other allyl glycidyl ether, diallyl phthalate , Allyl compounds such as triallyl trimellitate Derivatives, and more specifically, Shinzo Yamashita, “Crosslinker Handbook”, (1981 Taiseisha); Kato Kiyomi, “UV / EB Curing Handbook (Raw Materials)” (1985, Polymer) Radtech Study Group, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) ) And the like, or radically polymerizable or crosslinkable monomers, oligomers, and polymers known in the industry can be used.

  Examples of the radical polymerizable compound include those disclosed in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011, and the like. Photo-curable polymerizable compound materials used for the described photopolymerizable compositions are known, and these can also be applied to the ink composition of the present invention.

Furthermore, it is also preferable to use a vinyl ether compound as the radical polymerizable compound. Suitable vinyl ether compounds include, for example, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol. Di- or trivinyl ether compounds such as divinyl ether, hydroxyethyl monovinyl ether, trimethylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, hydroxybutyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O— Propi Emissions carbonate, monovinyl ether compounds, and the like, such as diethylene glycol monovinyl ether.
Of these vinyl ether compounds, divinyl ether compounds and trivinyl ether compounds are preferable from the viewpoints of curability, adhesion, and surface hardness, and divinyl ether compounds are particularly preferable. A vinyl ether compound may be used individually by 1 type, and may be used in combination of 2 or more type as appropriate.

  Other polymerizable compounds in the present invention include N-vinyl lactams, (meth) acrylic monomers or prepolymers, epoxy monomers or prepolymers, urethane monomers or prepolymers, excluding the component (A). A (meth) acrylic acid ester (hereinafter referred to as an acrylate compound as appropriate) is preferably used. More preferred are the above-mentioned N-vinyl lactams and the following compounds.

  That is, 2-ethylhexyl-diglycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxypivalate neopentyl glycol diacrylate, 2-acryloyloxyethyl phthalate, methoxy-polyethylene glycol acrylate, Tetramethylol methane triacrylate, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, dimethylol tricyclodecane diacrylate, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, nonylphenol EO adduct acrylate, modified glycerin Triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, phenoxy-polyethylene glycol acrylate, 2- Acryloyloxyethyl hexahydrophthalic acid, bisphenol A PO adduct diacrylate, bisphenol A EO adduct diacrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer, lactone modified flexibility Acrylate, butoxyethyl acrylate, propylene glycol diglycidyl ether acrylic acid adduct, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, 2-hydroxyethyl acrylate, methoxydipropylene glycol acrylate, ditrimethylolpropane tetraacrylate, pentaerythritol tri Acrylate hexamethylene diisocyanate urethane prepoly Chromatography, isoamyl acrylate, lactone-modified acrylate.

These acrylate compounds can have a relatively lower viscosity than the polymerizable compounds conventionally used in UV curable ink compositions, provide stable ink composition ejection properties, polymerization sensitivity, and recording medium. Adhesion with is also good.
The monomers listed here are preferable because they have a low molecular weight, high reactivity, low viscosity, and excellent adhesion to a recording medium.

In order to further improve the sensitivity, bleeding, and adhesion to the recording medium, it is preferable to use a monoacrylate and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer having a molecular weight of 400 or more, preferably 500 or more.
In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, a combination of a monoacrylate selected from the above compound group and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer is used. It is preferable because the film strength can be increased while the film is flexible to improve adhesion.
In addition, the embodiment in which at least three polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination further improves sensitivity, bleeding, and adhesion to the recording medium while maintaining safety. From the viewpoint that it can be further improved, it is mentioned as a preferred embodiment.

As the monoacrylate, isoamyl acrylate is preferable in terms of high sensitivity, low shrinkage and prevention of curling, prevention of bleeding, and cost reduction of the irradiation apparatus.
As the oligomer that can be used in combination with the monoacrylate, an epoxy acrylate oligomer and a urethane acrylate oligomer are particularly preferable.
Among the above compounds, when alkoxy acrylate is used in an amount of 70% by weight or less and the remainder is acrylate, it is preferable because of having good sensitivity and bleeding characteristics.

  In the present invention, when the acrylate compound is used as (D) the other polymerizable compound, the acrylate compound is 30% by weight with respect to the total weight of the other polymerizable compound (that is, the total amount of the component (D)). Preferably, it is 40% by weight or more, and more preferably 50% by weight or more. Moreover, (D) all the other polymerizable compounds used together can also be made into the said acrylate compound.

  In the present invention, regarding the selection of the polymerization initiator and the polymerizable compound, radical polymerization may be performed according to various purposes (for example, as a means for preventing a decrease in sensitivity due to the light-shielding effect of the colorant used in the ink composition). In addition to the combination of a reactive compound and a radical polymerization initiator, a radical / cation hybrid curable ink composition may be used in combination with a cationic polymerization compound and a cationic polymerization initiator as shown below.

  The cationically polymerizable compound that can be used in the present invention is not particularly limited as long as it is a compound that initiates a polymerization reaction with an acid generated from a photoacid generator and cures, and various known cations known as photocationically polymerizable monomers. Polymerizable monomers can be used. Examples of the cationic polymerizable monomer include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, and 2001-2001. Examples thereof include epoxy compounds, vinyl ether compounds, oxetane compounds and the like described in each publication such as No. 220526.

  In addition, as the cationic polymerizable compound, for example, a polymerizable compound applied to a cationic polymerization type photocurable resin is known, and recently, a photo cationic polymerization type sensitized in a visible light wavelength region of 400 nm or more. Examples of the polymerizable compound applied to the photocurable resin are disclosed in JP-A-6-43633 and JP-A-8-324137. These can also be applied to the ink composition of the present invention.

In the present invention, as the cationic polymerization initiator (photoacid generator) used in combination with the above cationic polymerizable compound, for example, a chemical amplification type photoresist or a compound used for photocationic polymerization is used (Organic Electronics Materials Research) Edited by “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187-192).
Examples of the cationic polymerization initiator suitable for the present invention are listed below.

That is, first, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , CF ₃ SO ₃ ⁻ salt of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium and phosphonium. Can be mentioned. Secondly, sulfonated products that generate sulfonic acid can be mentioned. Thirdly, a halide that generates hydrogen halide can also be used. Fourthly, an iron allene complex can be mentioned.
Such cationic polymerization initiators may be used alone or in combination of two or more.

[(E) Sensitizer]
To the ink composition of the present invention, (E) a sensitizer can be added in order to accelerate the decomposition of the (B) polymerization initiator by irradiation with actinic rays. The sensitizer absorbs specific actinic radiation and enters an electronically excited state. A sensitizer in an electronically excited state is brought into contact with a polymerization initiator to cause actions such as electron transfer, energy transfer, and heat generation, thereby causing a chemical change of the polymerization initiator, that is, decomposition, radical, acid or base. It promotes the generation of. A sensitizing dye is preferable as the sensitizer.

As the sensitizer, a compound corresponding to the wavelength of actinic radiation that generates an initiation species in the polymerization initiator (B) used in the ink composition may be used.
Examples of preferred sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region.
Polynuclear aromatics (eg, pyrene, perylene, triphenylene), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, thiacarbocyanine, oxacarbocyanine), merocyanines ( For example, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (eg, anthraquinone), squalium (eg, squalium) ), Coumarins (for example, 7-diethylamino-4-methylcoumarin), and the like.

  More preferable examples of the sensitizing dye include compounds represented by the following formulas (II) to (VI).

In the formula (II), A ¹ represents a sulfur atom or NR ⁵⁰ , R ⁵⁰ represents an alkyl group or an aryl group, and L ² forms a basic nucleus of the dye together with the adjacent A ¹ and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² may be bonded to each other to form an acidic nucleus of the dye. Good. W represents an oxygen atom or a sulfur atom.

In formula (III), Ar ¹ and Ar ² each independently represent an aryl group, and are linked via a bond with —L ³ —. Here, L ³ represents —O— or —S—. W is synonymous with that shown in Formula (II).

In the formula (IV), A ² represents a sulfur atom or NR ⁵⁹ , L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of a dye together with adjacent A ² and a carbon atom, R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.

In formula (V), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, wherein R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, substituted or represents an unsubstituted aryl group, L to ^5, L ⁶ are each independently, together with the adjacent a ^3, a ⁴ and adjacent carbon atoms represents a nonmetallic atom group necessary for forming a basic nucleus of a dye, R ⁶⁰ , R ⁶¹ each independently represents a hydrogen atom or a monovalent non-metallic atomic group, or may be bonded to each other to form an aliphatic or aromatic ring.

In the formula (VI), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent, and A ⁵ represents an oxygen atom, a sulfur atom or ═NR ⁶⁷ . R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent non-metallic atomic group; R ⁶⁷ and R ⁶⁴ , and R ⁶⁵ and R ⁶⁷ each represent an aliphatic or aromatic ring. Can be combined to form.

(E) The amount of the sensitizer is preferably 0.1 to 20% by weight, more preferably 0.2 to 15% by weight, based on the weight of the entire ink composition of the present invention.
Preferable specific examples of the compounds represented by formulas (II) to (VI) include those shown below.

[(F) Co-sensitizer]
The ink composition of the present invention can also contain a co-sensitizer. In the present invention, the co-sensitizer has functions such as further improving the sensitivity of the sensitizing dye to actinic radiation or suppressing polymerization inhibition of the polymerizable compound by oxygen.
Examples of such cosensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60-84305, JP-A 62-18537, JP-A 64-33104, Research Disclosure 33825, and the like. Specific examples include triethanolamine. P-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

  Other examples of co-sensitizers include thiols and sulfides, for example, thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142773, and JP-A-56. And the like. Specific examples include 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzoimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercaptonaphthalene. Etc.

Other examples include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), and hydrogen described in Japanese Patent Publication No. 55-34414. Donors, sulfur compounds described in JP-A-6-308727 (eg, trithiane), phosphorus compounds described in JP-A-6-250387 (diethylphosphite, etc.), Si-H described in JP-A-8-65779 , Ge—H compounds and the like.
(F) The amount of the co-sensitizer is preferably 0.1 to 20% by weight, more preferably 0.2 to 15% by weight, based on the weight of the entire ink composition of the present invention. .

[(G) Other ingredients]
If necessary, other components can be added to the ink composition of the present invention. Examples of other components include a polymerization inhibitor and a solvent.
A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. Further, when the ink composition of the present invention is used as an ink composition for ink jet recording, it is preferably discharged at a temperature in the range of 40 to 80 ° C. with a reduced viscosity, and also for preventing head clogging due to thermal polymerization. It is preferable to add a polymerization inhibitor. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, Cuperon Al, Fisture ST-1 (manufactured by Chem First) and the like.

In view of the fact that the ink composition of the present invention is a radiation curable ink composition, it is preferable that no solvent is contained so that the ink composition can react quickly and cure immediately after landing of the ink composition. However, a predetermined solvent can be included as long as the curing rate of the ink composition is not affected. In the present invention, an organic solvent or water can be used as the solvent. In particular, the organic solvent can be added in order to improve the adhesion to the recording medium (support such as paper). The addition of an organic solvent is effective because the VOC problem can be avoided.
The amount of the organic solvent is preferably from 0.1 to 5% by weight, more preferably from 0.1 to 3% by weight, based on the weight of the entire ink composition of the present invention.

  In addition, a known compound can be added to the ink composition of the present invention as necessary. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes and the like are appropriately selected and added. be able to. In order to improve the adhesion to a recording medium such as polyolefin or PET, it is also preferable to contain a tackifier that does not inhibit the polymerization. Specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, pages 5 to 6 (for example, (meth) acrylic acid and an alcohol having an alkyl group having 1 to 20 carbon atoms). An ester, a copolymer of (meth) acrylic acid and an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer of an ester of (meth) acrylic acid and an aromatic alcohol having 6 to 14 carbon atoms), and polymerizability. Examples thereof include a low molecular weight tackifying resin having an unsaturated bond.

[Properties of ink composition]
The ink composition of the present invention can be suitably used as an ink composition for ink jet recording. The preferable physical property in such a use aspect is demonstrated.
When the ink composition is used as an ink composition for inkjet recording, the viscosity is preferably at a temperature at the time of ejection (preferably 25 to 80 ° C., more preferably 25 to 50 ° C.) in consideration of ejectability. 7 to 30 mPa · s, more preferably 7 to 25 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 to 30 ° C.) is preferably 35 to 500 mPa · s, more preferably 35 to 200 mPa · s.
It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium is used, it is possible to avoid penetration of the ink composition into the recording medium and to reduce uncured monomers. Furthermore, it is possible to suppress bleeding of the ink composition upon landing of the ink composition droplet, and as a result, the image quality is improved.

  The surface tension of the ink composition of the present invention is preferably 20 to 30 mN / m, more preferably 23 to 28 mN / m. When recording on various recording media such as polyolefin, PET, coated paper, and non-coated 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.

<Inkjet recording method>
The ink jet recording method of the present invention and the ink jet recording apparatus applicable to the ink jet recording method will be described below.
In the inkjet recording method of the present invention, the ink composition of the present invention is ejected onto a recording medium (support, recording material, etc.) for inkjet recording, and actinic radiation is applied to the ink composition ejected onto the recording medium. This is a method of forming an image by irradiating and curing the ink composition, and is characterized by curing in an atmosphere having a lower oxygen concentration than in the atmosphere.

That is, the inkjet recording method of the present invention comprises (a) a step of ejecting an ink composition onto a recording medium, and (b) irradiating the ejected ink composition with actinic radiation to apply the ink composition. The method includes a step of curing in an atmosphere having an oxygen concentration lower than that in the atmosphere.
By including the steps (a) and (b), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.
In the present invention, by curing the ink composition in an atmosphere having an oxygen concentration lower than that in the air, the polymerization inhibition action by oxygen can be suppressed, and excellent curability can be obtained.

The ink composition is cured in an atmosphere having an oxygen concentration lower than that in the atmosphere. The oxygen concentration is preferably 0.1 to 10% by volume, more preferably 0.1 to 8% by volume. Preferably it is 0.1-6 vol%.
In order to make the oxygen concentration lower than in the atmosphere, it is preferable to supply a gas other than oxygen. The gas to be used is not particularly limited, but a gas that does not suppress the curing of the ink composition is selected. Specifically, nitrogen, helium, argon, neon, xenon, carbon dioxide and the like can be exemplified, and these can be used alone or in combination of two or more.
Among these, it is preferable to use a gas heavier than oxygen, for example, carbon dioxide, neon, argon, xenon and the like, and a gas lighter than oxygen, for example, helium, nitrogen and the like. By using such a mixed gas, the atmosphere of the mixed gas can be quickly formed in the irradiation range of the active radiation, and oxygen does not remain in a layer shape due to the difference in specific gravity, so that the ink on the recording medium can be surely obtained. Oxygen is excluded from the composition range, and when the ink composition is cured by actinic radiation, inhibition of curing by oxygen can be suppressed, which is preferable. This is also preferable because it inhibits the inhibition of curing caused by oxygen and enables high-speed and high-quality image formation.

[Inkjet recording device]
The ink jet recording apparatus used in the ink jet recording method of the present invention is not particularly limited, and a known ink jet recording apparatus capable of achieving an oxygen concentration lower than that in the atmosphere and a desired resolution is arbitrarily selected and used. be able to. That is, any known inkjet recording apparatus including a commercially available product can discharge the ink composition onto the recording medium in step (a) of the inkjet recording method of the present invention.
Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink composition supply system, a temperature sensor, and an actinic radiation source.
The ink composition supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink composition supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head has a multi-size dot of 1 to 100 pl, preferably 8 to 30 pl, for example, 320 × 320 to 4000 × 4000 dpi, preferably 400 × 400 to 1600 × 1600 dpi, and more preferably 720 × 720 dpi. It can drive so that it can discharge with the resolution of. In the present invention, dpi represents the number of dots per 2.54 cm.

  As described above, since it is desirable that the radiation curable ink composition, like the ink composition of the present invention, has a constant temperature in the ejected ink composition, from the ink composition supply tank to the inkjet head portion. Insulation and heating can be performed. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. The temperature sensor can be provided near the ink composition supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

Using the above inkjet recording apparatus, the ink composition of the present invention is ejected by heating the ink composition to 40 to 80 ° C., more preferably 25 to 50 ° C. Preferably it is performed after lowering to 7-30 mPa · s, more preferably 7-25 mPa · s. In particular, it is preferable to use an ink composition having an ink composition viscosity of 25 to 500 mPa · s at 25 ° C. because a great effect can be obtained. By using this method, high ejection stability can be realized.
A radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than a water-based ink composition usually used in an ink composition for ink jet recording, and therefore has a large viscosity fluctuation due to temperature fluctuations during ejection. Viscosity fluctuation of the ink composition has a great influence on the change of the droplet size and the change of the droplet discharge speed, and thus causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink composition during ejection as constant as possible. Therefore, in the present invention, the temperature control range of the ink composition is appropriately set to ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, and more preferably set temperature ± 1 ° C.

Next, (b) the step of irradiating the discharged ink composition with active radiation and curing the ink composition in an atmosphere having an oxygen concentration lower than that in the air will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the (B) polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate initiating species such as radicals, acids, bases, and the like (A This is because the polymerization reaction of the component (D) and other polymerizable compound (D) used in combination as desired occurs and is accelerated. At this time, when (E) sensitizer is present together with (B) polymerization initiator in the ink composition, (E) sensitizer in the system absorbs actinic radiation and becomes excited, and (B) polymerization initiator. (B) can accelerate | stimulate decomposition | disassembly of a polymerization initiator and can achieve a more highly sensitive hardening reaction.

  Here, α rays, γ rays, electron beams, X rays, ultraviolet rays, visible light, infrared rays, or the like can be used as the active radiation used. Although the peak wavelength of actinic radiation is based also on the absorption characteristic of a sensitizer, it is preferable that it is 200-600 nm, for example, it is more preferable that it is 300-450 nm, and it is still more preferable that it is 350-420 nm.

In addition, the polymerization initiation system of the ink composition of the present invention has sufficient sensitivity even with a low output actinic radiation. Thus, the output of the active radiation is preferably 2,000 mJ / cm ² or less, more preferably 10 to 2,000 mJ / cm ^2, more preferably from 20 to 1,000 mJ / cm ^2, especially Preferably it is 50-800 mJ / cm < ² >.
Furthermore, the actinic radiation is, the exposure surface illuminance, and preferably be 10 to 2,000 mW / cm ^2, more preferably irradiated with 20 to 1,000 mW / cm ^2.

Mercury lamps and gas / solid lasers are mainly used as actinic radiation sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing UV photocurable ink jet recording ink compositions. It has been. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long life, have high efficiency, and are low in cost, and are expected as light sources for photo-curable ink jets.
Further, a light emitting diode (LED) and a laser diode (LD) can be used as the active radiation source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit actinic radiation centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. The actinic radiation source particularly preferred in the present invention is a UV-LED, particularly preferably a UV-LED having a peak wavelength at 350 to 420 nm.
Incidentally, it is preferable that maximum illumination intensity of the LED on a recording medium is 10 to 2,000 mW / cm ^2, more preferably 20 to 1,000 mW / cm ^2, particularly preferably 50 to 800 mW / cm ² .

The ink composition of the present invention is appropriately irradiated with such actinic radiation, preferably for 0.01 to 120 seconds, more preferably for 0.1 to 90 seconds.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink composition discharge device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation is performed for a certain period of time after the ink composition has landed (preferably 0.01 to 0.5 seconds, more preferably 0.02 to 0.3 seconds, still more preferably 0.03 to 0.15 seconds). It will be done after. In this way, by controlling the time from ink composition landing to irradiation to an extremely short time, it is possible to prevent the ink composition that has landed on the recording medium from spreading before curing. In addition, since the ink composition can be exposed to a porous recording medium before the ink composition penetrates to a deep portion where the light source does not reach, it is preferable that residual unreacted monomer can be suppressed.
Further, the curing may be completed by another light source that is not driven. WO99 / 54415 pamphlet discloses a method using an optical fiber and a method of applying a collimated light source to a mirror surface provided on the side surface of the head unit and irradiating the recording unit with UV light as an irradiation method. The curing method can also be applied to the ink jet recording method of the present invention.

By adopting the ink jet recording method as described above, the dot diameter of the landed ink composition can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. By superimposing the ink compositions in order of low lightness, it becomes easy for the irradiation rays to reach the lower ink composition, and good curing sensitivity, reduction of residual monomers, and improvement in adhesion can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.
Thus, the ink composition of the present invention can form an image on the surface of a recording medium by being cured with high sensitivity by irradiation with actinic radiation.

In the present invention, the oxygen concentration is set to an atmosphere lower than that in the atmosphere at the time of irradiation with actinic radiation. The oxygen concentration is preferably 0.1 to 10 vol%. The means for setting the oxygen concentration in the above range can be arbitrarily selected. Preferably, the curing atmosphere after ink landing is replaced with an inert gas.
As a means for controlling the oxygen concentration in the curing atmosphere to be lower than that in the atmosphere, for example, there is a method in which the image forming apparatus is closed and a nitrogen atmosphere or a carbon dioxide atmosphere is used. Other usable gases include helium, argon, neon, and xenon. Nitrogen supply means includes, for example, a method using a nitrogen cylinder or a device that separates only nitrogen gas from the air using the difference in permeability between oxygen and nitrogen through the hollow fiber membrane. As a means for supplying carbon dioxide, there is a supply method using a cylinder.

Next, an ink jet recording apparatus that can be suitably used in the present invention will be described in detail.
FIG. 1 is a schematic view of an actinic radiation curable ink jet recording apparatus that can be suitably used in the present invention.
In FIG. 1, in a housing 12 of the actinic radiation curable ink jet recording apparatus 10, a recording medium storage unit 20 that stores a plurality of sheets of recording medium S of the same size in a stacked manner, and from the storage unit 20. A conveyance unit 30 that takes out the recording medium S, a scanning conveyance unit 40 that performs scanning while holding the recording medium S carried in by the conveyance unit 30 in a recording position range, and held and transferred and scanned by the scanning conveyance unit 40. An image recording unit 50 that performs inkjet image recording, actinic radiation (ultraviolet light in the present recording apparatus) irradiation and fixing, and a recording medium S that has been recorded by the image recording unit 50 are sent out And a tray 90. An ink cartridge mounting unit 70 is connected to the image recording unit 50 for supplying ink through an ink supply path 72. An ink cartridge is detachably provided in the ink cartridge mounting portion 70. Further, a gas supply / suction mechanism 60 which is a gas supply unit for supplying and exhausting a mixed gas is disposed at least in the active radiation irradiation fixing range of the image recording unit 50.

  A separation claw 92 is disposed downstream of the position where the recording medium S is separated from the conveyance belt 48 (downstream belt roller 46 in the present recording apparatus), and promotes the separation of the recording medium S from the conveyance belt 48. The tray 90 accommodates the recording medium S peeled from the transport belt 48.

In the recording medium storage unit 20, a storage cassette 22 for storing the recording medium S is detachably disposed below the casing 12 of the actinic radiation curable inkjet recording apparatus 10, and the recording medium S of different sizes is supplied by replacement. can do.
The recording medium storage unit 20 may be configured to mount a plurality of cassettes. As another configuration of the recording medium storage unit 20, a cassette for supplying a recording medium wound on a roll may be used. In this case, a cutter that cuts the recording medium into a desired length is disposed instead of the feed roller 32 of the transport unit 30.

  The transport unit 30 is provided with a feed roller 32 that comes into contact with the leading end of the recording medium S in the storage cassette 22 set in the housing 12 in the insertion direction. Further, the recording medium S fed out by the feed roller 32 is supplied to the transport unit 30. Conveying roller pairs 34 and 36 for conveying to the scanning conveying unit 40 are provided.

  The scanning conveyance unit 40 includes a conveyance belt 48 that is stretched and driven by three belt rollers 42, 44, and 46. The conveyance belt 48 is driven in the X direction from the upstream belt roller 44 to the downstream belt roller 46, and the recording medium S is placed on the conveyance belt 48 between the upstream belt roller 44 and the downstream belt roller 46. Be transported.

  In the image recording section 50, a head unit 52 to which the ink cartridge mounting section 70 is connected for supplying ink is provided with the tip of the ink discharge nozzle facing the conveyance belt 48 at an image recording position 48P. A head driver 54 is connected to the head unit 52 to control the ejection amount of each ink color. In addition, an actinic radiation irradiating unit 56 is disposed immediately after the image recording position 48P and downstream of the head unit 52, and gives strong active energy sufficient for the ink to get on the recording medium S and be cured immediately afterward. Since the actinic radiation (ultraviolet) irradiation unit 56 uses strong light for curing the ink as described above, the exhaust cooling unit 80 is provided in the upper part of the housing 12 in order to suppress the temperature rise in the housing 12. Is arranged. The head unit 52 employs a full-line type head in which the length in the width direction of the recording medium S is an array.

  Further, the image recording unit 50 includes a housing 62 that covers the head unit 52, the active radiation irradiation unit 56, and the conveyance belt 48 near the image recording position 48 </ b> P. A gas supply nozzle 64 having an opening directed on the recording medium S at the active radiation irradiation position is provided. A gas recovery nozzle 66 having an opening toward the recording medium S is provided between the actinic radiation irradiation unit 56 and the head unit 52. Further, an oxygen-containing gas supply nozzle 68 for supplying a gas containing oxygen toward the tip of the ink discharge nozzle of the head unit 52 is provided on the upstream side surface of the head unit 52 in the transport direction. The gas supply nozzle 64, the gas recovery nozzle 66, and the oxygen-containing gas supply nozzle 68 constitute a gas supply / suction mechanism 60.

Next, regarding the present recording apparatus, the image recording unit 50 and the gas supply / suction mechanism 60 will be described in detail with reference to the drawings.
FIG. 2 is an external perspective view showing the arrangement of the gas supply / suction mechanism 60 in the image recording unit 50 of the recording apparatus shown in FIG.

  As shown in FIG. 2, the gas supply nozzle 64 disposed downstream of the actinic radiation (ultraviolet) irradiation unit 56 has a width direction of the recording medium S (longitudinal direction of the head unit 52) at the tip of the gas supply pipe 65. ), And is opened toward the irradiation position of the actinic radiation irradiation unit 56. The gas supply pipe 65 is connected in communication with a gas storage tank (not shown) and a pump for pressure feeding. A gas storage tank (not shown) stores a gas heavier than oxygen such as carbon dioxide, neon, argon, and xenon, and a gas lighter than oxygen such as helium and nitrogen. A gas heavier and lighter than oxygen is mixed, and the mixed gas is supplied from the gas supply nozzle 64 around the irradiation position of the active radiation irradiation unit 56 on the recording medium S by a pump for pressure feeding. The ratio of the volume of gas heavier than oxygen / volume of the mixed gas is preferably 30 to 90%, more preferably 40 to 80%.

  As an image forming operation, when the recording medium S is unloaded from the recording medium storage unit 20 by the conveyance unit 30 and image formation is started by the image forming unit 50 by the scanning conveyance unit 40, the mixed gas is formed on the recording medium S. Thus, the light is supplied around the irradiation position of the active radiation irradiation unit 56. As a result, the oxygen molecules existing on the recording medium S are pushed out without rising or lowering due to mixing of a gas mixture heavier and lighter than oxygen, and remain in the atmosphere of the gas mixture. I can't. Therefore, at least in the vicinity of the irradiation position of the actinic radiation irradiation unit 56, it is quickly eliminated from the recording medium S, and inhibition of ink curing due to oxygen in the air can be suppressed.

  Next, the gas recovery nozzle 66 disposed between the actinic radiation irradiating unit 56 and the head unit 52 is formed in a long-expanded shape in the width direction of the recording medium S at the tip of the gas recovery tube 67. The opening is directed toward the image forming surface of the recording medium S. The gas recovery pipe 67 is connected to a gas recovery tank (not shown) through a suction pump. By driving the suction pump, the mixed gas and the air in the housing 62 are sucked from the gas recovery nozzle 66 and recovered in the gas recovery tank. With such a configuration, the atmosphere in the vicinity of the ink discharge nozzle tip of the head unit 52 can be left in a state where normal air remains, and ink sticking occurs when the ink curing inhibition effect at the ink discharge nozzle tip is lost. Ink ejection failure due to the ink can be suppressed.

Regarding the mixed gas recovery operation by the gas recovery pipe 67, it is preferable to form the mixed gas atmosphere before the image formation is started. In this case, the housing 62 is filled with the mixed gas to some extent. It is preferable to start the operation of the gas recovery pipe 67 after the state.
When speed is required for starting up the recording apparatus of the present embodiment, the gas supply pipe 65 and the gas recovery pipe 67 are simultaneously operated to reduce the suction amount, thereby reducing the atmosphere of the mixed gas in the housing 62. Can be formed.
In any case, when the mixed gas in the housing 62 is stabilized, the supply and suction are made approximately the same, and the leakage of the mixed gas to the outside of the housing 62 is suppressed.

  In addition, since the dust in the housing 62 can be sucked together by sucking the gas in the housing 62 from the gas recovery nozzle 66, the inside of the housing 62 can be kept clean. In addition, these recovered gases include active gases such as oxygen in the housing 62, but these active gases can be removed and reused. Apart from this, it is preferred to recover these gases, but they can also be released into the air if they are environmentally harmless.

Next, during operation of the gas supply nozzle 64 and the gas recovery nozzle 66, a gas containing oxygen is supplied from the oxygen-containing gas supply nozzle 68 disposed on the upstream side surface of the head unit 52 toward the tip of the ink discharge nozzle. can do. With this configuration, it is possible to supply oxygen to the atmosphere at the tip of the ink discharge nozzle of the head unit 52, and it is possible to inhibit ink curing only at the tip edge of the ink discharge nozzle and suppress the occurrence of discharge failure. .
The oxygen-containing gas supplied in this way is supplied from the oxygen-containing gas supply nozzle 68 during image formation and passes through the ink discharge nozzle tip of the head unit 52. Then, the suction force of the gas recovery nozzle 66 can be adjusted so as to be sucked by the gas recovery nozzle 66. With this setting, it is possible to form a state in which a gas heavier than oxygen supplied from the gas supply nozzle 64 comes into contact with the ink landing position on the recording medium S, and use of ink curing inhibition due to oxygen at the tip of the ink discharge nozzle. Inhibition of ink curing on the recording medium S can be suppressed.

  Since the gas supplied from the oxygen-containing gas supply nozzle 68 may be normal air, for example, the outside of the housing 62 is communicated with the oxygen-containing gas supply nozzle 68 and the outside air is drawn using the suction pressure of the gas recovery nozzle 66. It can also be introduced.

FIG. 3 is a schematic view showing another example of an actinic radiation curable ink jet recording apparatus that can be suitably used in the present invention.
As shown in FIG. 3, in the casing 112 of the actinic radiation curable inkjet recording apparatus 110, the recording medium S wound around the delivery-side roll 121 is extended by the conveyance roller 130, and the flexible light shielding door 114 is provided. It passes through and is conveyed into the housing 112. The conveyed recording medium S is sent out from a flexible light shielding door 116 disposed on the opposite side of the casing 112 and is taken up by a take-up roll 123. The recording medium S carried into the housing 112 is held by the conveyance holding roller 142 and sent out onto the platen 140. Further, the recording medium S is held by the conveyance holding roller 144 arranged on the opposite side across the platen 140, scanned and conveyed on the platen 140, and sent out from the light shielding door 116. In the platen 140, the image recording unit 150 is disposed at an opposite position across the recording medium S. The image recording unit 150 performs inkjet image recording and actinic radiation (ultraviolet light in this recording apparatus) irradiation fixing on the recording medium S being scanned and conveyed on the platen 140. An ink storage unit that supplies and stores ink to the image recording unit 150 through a supply path (not shown) is provided in the housing 112.

In the image recording unit 150, a head unit 152 that is an inkjet head is provided with the tip of the ink discharge unit facing the platen 140 at the image recording position. The head unit 152 ejects ink curable by actinic radiation toward the recording medium S. The head unit 152 is connected to a head driver 154 that is an ink-jet head driving device, and controls the ejection amount of each ink color. An actinic radiation irradiation unit 156 is disposed downstream of the head unit 152. A gas supply nozzle 164 extends from the upper cover 112a toward the downstream position of the active radiation irradiation unit 156 and opens. Further, a gas recovery nozzle 166 extends from the upper cover 112a to the position downstream of the head unit 152 and the actinic radiation irradiation unit 156 and opens.
An oxygen-containing gas supply nozzle 168 that supplies a gas containing oxygen toward the tip of the ink discharge nozzle of the head unit 152 is provided on the upstream side surface of the head unit 152 in the transport direction. These gas supply nozzle 164, gas recovery nozzle 166, and oxygen-containing gas supply nozzle 168 constitute a gas supply mechanism.

Next, the operation of the actinic radiation curable ink jet recording apparatus 110 will be described.
Before the image recording operation is started, the supply of the mixed gas from the gas supply nozzle 164 starts around the irradiation position of the active radiation irradiation unit 156 on the recording medium S in the housing 112, and the output side roll is used for image recording. 121 and the winding roll 123 start scanning and rotating. Then, the head unit 152 starts ink ejection for image recording. The gas recovery nozzle 166 starts gas recovery, and oxygen is excluded from the recording medium S immediately below the active radiation irradiation unit 156 between the gas supply nozzle 164 and the gas recovery nozzle 166 by the mixed gas. Therefore, the ink that has been image-formed on the recording medium is cured well, and a good image without bleeding is obtained and wound on the winding-side roll 123.

  Here, similarly to the image recording apparatus shown in FIG. 1, the distribution of the mixed gas in the housing 112 can be adjusted by adjusting the supply speed of the gas supply nozzle 164 and the recovery speed of the gas recovery nozzle 166. . By filling the mixed gas to some extent, oxygen at the ink landing position directly below the head unit 152 can be eliminated, and the factor of ink curing inhibition can be further reduced. At this time, it is necessary to prevent sticking of ink at the tip of the ink discharge nozzle, and a gas that is heavier than oxygen rides on the recording medium S, and air (oxygen) remains at the tip of the ink discharge nozzle of the head unit 152. It is necessary to adjust the supply speed of the supply nozzle 164 and the recovery speed of the gas recovery nozzle 166.

  When the oxygen-containing gas supply nozzle 168 is provided on the upstream side surface in the transport direction of the head unit 152, the gas supply nozzle 164 is supplied by supplying an oxygen-containing gas (for example, air) to the vicinity of the tip of the ink discharge nozzle. There is no need to pay attention to the adjustment of the speed and the recovery speed of the gas recovery nozzle 166.

  As another effect, a gas mixture heavier and lighter than oxygen is supplied from the gas supply nozzle 164 into the housing 112, and the gas and other air are recovered from the gas recovery nozzle 166. The interior of the housing 112 can always be kept clean. Furthermore, the actinic radiation irradiation unit 156 can be cooled by supplying the gas supply nozzle 164. Furthermore, since the gas recovery nozzle 166 is disposed in the vicinity of the head unit 152, it can give kinetic energy to the gas, so that the gas can be moved positively, and the movement of the gas causes the head unit 152 to move. Indirect cooling can be performed. By these, the inhibition of curing caused by oxygen can be suppressed, and high-speed and high-quality image formation can be performed.

  In the head unit of each of the above embodiments, the oxygen-containing gas supply nozzle can be installed for each color head. Also, the active radiation irradiation unit can be arranged immediately downstream of each color head.

  1 to 3, the head unit is a full-line head in which inkjet nozzles are arranged in the width direction of the recording medium S. However, a scanning head or a multi-channel type that performs vertical scanning in the conveyance direction of the recording medium S can be used. It is also possible to adopt a configuration that does this. When the scanning head is used, the actinic radiation irradiation unit is provided so as to move together with the scanning head. In this embodiment, the ink jet recording position is transported by the transport belt. As another configuration, the recording medium is sandwiched between transport rollers and transported on the platen at the ink jet recording position. You can also. The platen can be a fixed type or a movable type.

[Recording medium]
The recording medium to which the ink composition of the present invention can be applied is not particularly limited, and various kinds of non-absorbing resin materials used for ordinary non-coated paper, coated paper, so-called soft packaging, or the like. A resin film formed into a film can be used, and examples of the various plastic films include PET film, OPS film, OPP film, ONy film, PVC film, PE film, and TAC film. In addition, examples of the plastic that can be used as a recording medium material include polycarbonate, acrylic resin, ABS, polyacetal, PVA, and rubbers. Metals and glasses can also be used as the recording medium.
In the ink composition of the present invention, when a material with low thermal shrinkage at the time of curing is selected, the adhesive property between the cured ink composition and the recording medium is excellent. Films that tend to curl and deform, such as heat-shrinkable PET film, OPS film, OPP film, ONy film, PVC film, etc., have the advantage that a high-definition image can be formed.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the embodiments in these examples.
In the following description, “parts” means “parts by weight” unless otherwise specified.

The materials used in the present invention are as shown below.
・ IRGALITE BLUE GLVO (Cyan Pigment (Pigment Blue 15: 4), manufactured by Ciba Specialty Chemicals)
・ CINQUASIA MAGENTA RT-335 D (Magenta pigment, manufactured by Ciba Specialty Chemicals)
NOVOPERM YELLOW H2G (yellow pigment (Pigment Yellow 120), manufactured by Clariant)
SPECIAL BLACK 250 (black pigment (Pigment Black 7), manufactured by Ciba Specialty Chemicals)
・ KRONOS2300 (white pigment, manufactured by KRONOS)
N-vinyl-ε-caprolactam (Aldrich)
Actilane 421 (propoxylated neopentyl glycol diacrylate, manufactured by Akcros)
-Actilane 422 (dipropylene glycol diacrylate, manufactured by Akcros)
・ Rapi-Cure DVE-3 (triethylene glycol divinyl ether, ISP
(Europe)
・ Ebecryl 657 (acrylate oligomer, manufactured by Daicel Cytec)
・ ODA-N (octyldecyl acrylate, manufactured by Daicel Cytec)
・ Blemmer LA (Lauryl acrylate, manufactured by NOF Corporation)
・ Light acrylate SA (stearyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.)
Sartomer 395 (isodecyl acrylate, manufactured by SARTOMER)
N-hexyl acrylate (Aldrich)
・ NK ester A-BH (behenyl acrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.)
-Firstcure ST-1 (polymerization inhibitor, manufactured by Chem First)
・ Lucirin TPO (photopolymerization initiator (2,4,6-trimethylbenzoyldiphenylphosphine oxide), manufactured by BASF)
・ Benzophenone (photopolymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd.)
・ Irgacure 184 (Photopolymerization initiator (1-hydroxycyclohexylphenylketone), manufactured by Ciba Specialty Chemicals)
・ Byk 307 (surfactant, manufactured by BYK Chemie)
-Solsperse 32000 (dispersant, manufactured by Noveon)

(Preparation of cyan mill base A)
IRGALITE BLUE GLVO 300 parts by weight Actilane 421 (acrylate monomer manufactured by Akcros) 500 parts by weight Solsperse 32000 200 parts by weight The above components were stirred and mixed to obtain a pigment ink. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 4 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Preparation of magenta mill base B)
CINQUASIA MAGENTA RT-335 D 300 parts by weight Actilane 421 (acrylate monomer manufactured by Akcros) 300 parts by weight Solsperse 32000 400 parts by weight The above components were stirred and mixed to obtain a pigment ink. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 10 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Preparation of yellow mill base C)
NOVOPERM YELLOW H2G 300 parts by weight Actilane 421 (acrylate monomer manufactured by Akcros) 300 parts by weight Solsperse 32000 400 parts by weight The above components were mixed by stirring to obtain a pigment ink. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 10 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Preparation of black mill base D)
SPECIAL BLACK 250 300 parts by weight Actylene 421 (Akcros acrylate monomer) 300 parts by weight Solsperse 32000 400 parts by weight The above components were stirred and mixed to obtain a pigment ink. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 7 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Preparation of white mill base E)
KRONOS2300 500 parts by weight Actilane 421 (Acrycros acrylate monomer) 400 parts by weight Solsperse 32000 100 parts by weight The above components were stirred and mixed to obtain a pigment ink. The pigment mill base was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 4 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

[Example 1]
The following components were stirred with a high-speed water-cooled stirrer to obtain a cyan UV inkjet ink. The viscosity was 21 mPa · s.
(Cyan ink composition)
(C) (D) Cyan mill base A 6.0 parts (A) ODA-N 25.0 parts (D) Actilane 422 36.9 parts (D) Rapi-Cure DVE-3 9.5 parts (D) Ebecryl 657 9.0 parts, First cure ST-1 0.05 part, (B) Lucirin TPO 8.5 parts, (B) Benzophenone 3.0 parts, (B) Irgacure 184 2.0 parts, Byk 307 0.05 parts

<Inkjet image recording method>
Next, recording was performed on a recording medium using an inkjet recording experimental apparatus having a piezoelectric inkjet nozzle capable of supplying an inert gas from the inert gas supply apparatus shown in FIGS. The ink supply system was composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and heat insulation and heating were performed from the ink supply tank to the inkjet head portion. Temperature sensors were provided near the ink supply tank and the nozzles of the ink jet head, respectively, and temperature control was performed so that the nozzle portions were always 45 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that 8 to 30 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi. After landing, UV light is condensed to an exposure surface illuminance of 1,630 mW / cm ² , and the exposure system, main scanning speed, and emission frequency are adjusted so that irradiation starts 0.1 seconds after ink landing on the recording medium. The ink was cured by changing the exposure conditions in an atmosphere having an oxygen concentration of 10%. A HAN250NL high-cure mercury lamp (manufactured by GS Yuasa Corporation) was used as the ultraviolet lamp. In the present invention, dpi represents the number of dots per 2.54 cm. As a recording medium, an ester film E5000 (film thickness 125 μm, manufactured by Toyobo Co., Ltd.) was used.

(Measurement method of curing sensitivity)
In accordance with the inkjet recording method, a solid image having an average film thickness of 12 μm was drawn, and the degree of stickiness of the image was evaluated by palpation on the image surface after ultraviolet irradiation. The curing sensitivity was evaluated according to the following criteria.
3: No stickiness in the image.
2: The image is slightly sticky.
1: Uncured ink is not hard enough to transfer to hand.

(Evaluation of ink curability)
Using the obtained ink composition, ink jet recording and photocuring were performed in an atmosphere in which the oxygen concentration was changed, and an image having a film thickness of 12 μm was obtained. Table 1 shows the results of evaluating the curability of this image.

(Evaluation of ink composition)
The obtained cyan ink composition was printed on a polyvinyl chloride sheet and irradiated by passing it through an iron-doped ultraviolet lamp (power 120 W / cm) at a speed of 40 m / min. The ink composition was cured to obtain a recorded matter.
At this time, the following evaluation was performed.
The adhesion to the recording medium was evaluated by a cross hatch test. As a result, high adhesion of ISO Class: 0 was shown.
The cross-hatch test is based on ISO 2409 (ASTM D 3359), and the cured film is cross-cut at 25 stitches at intervals of 2.0 mm (6 cuts in length and width). : Scotch tape (3M600), manufactured by Sumitomo 3M Co., Ltd.) was strongly attached, and then the adhesive tape was rapidly peeled off to examine the presence or absence of peeling of the cured film. An evaluation result is represented by ISO Class: 0-5.
ISO Class: 0 No peeling
ISO Class: 15% peeling
ISO Class: 2 20% peeling
ISO Class: 3 50% peeling
ISO Class: 4 80% peeling
ISO Class: 5 100% peeling The results are shown in Table 1 below.

(Flexibility evaluation method: Bending test)
In this example, a bending test was performed as a method for evaluating the flexibility of the cured film.
According to the inkjet ink jet image recording method, an ester film E5000 (film thickness 125 μm, manufactured by Toyobo Co., Ltd.) was used as a recording medium, and three solid images having an average film thickness of 12 μm, 24 μm, and 36 μm were drawn. In the bending test, the recording material on which an image was formed was bent once at 25 ° C. and evaluated by the presence or absence of cracks in the image area. In general, when the average film thickness is increased, distortion applied to the image portion when the image portion is bent increases, and cracks are likely to occur. In other words, by testing whether the image portion is cracked with a thicker film thickness, it can be a measure of flexibility.
The evaluation criteria are as follows.
4... Cracks do not occur in samples having an average film thickness of 12 μm, 24 μm, and 36 μm.
3 ... Cracks do not occur in samples having an average film thickness of 12 μm and 24 μm, but cracks occur in the bent portion of the image portion in the sample having an average film thickness of 36 μm.
2 ... Although cracks do not occur in samples having an average film thickness of 12 μm, cracks occur in the bent portions of the image area in samples having an average film thickness of 24 μm and 36 μm.
1... Samples having average film thicknesses of 12 [mu] m, 24 [mu] m, and 36 [mu] m are cracked in the bent portion of the image portion.

[Examples 2 to 10]
Examination and evaluation were performed in the same manner as in Example 1 except that the oxygen concentration during exposure in the inkjet image recording method used in Example 1 was 11%.

[Comparative Example 1]
Examination and evaluation were performed in the same manner as in Example 1 except that the oxygen concentration during exposure in the inkjet image recording method used in Example 1 was 11%.

[Comparative Example 2]
Examination and evaluation were performed in the same manner as in Example 1 except that all monomers (ODA-N) having a functional group having 6 to 32 carbon atoms used in Example 1 were replaced with Actilane 422.

As shown in Examples 1 to 10, by performing the curing in the oxygen concentration range of the present invention, the curability is improved as compared with Comparative Example 1 having a high oxygen concentration.
From this result, if the oxygen concentration is controlled to be lower than that in the atmosphere by the method of the present invention, it is sufficient even when a monomer having a functional group having 6 to 32 carbon atoms with high dissolved oxygen content and oxygen permeability is used. It can be said that curability is obtained.

[Examples 11-15, Comparative Examples 3-5]
A cyan ink composition was prepared in the same manner as in Example 1 except that the monomer “ODA-N” having a functional group having 6 to 32 carbon atoms used in Example 1 was replaced with the monomer of the present invention shown in the table below. And examined and evaluated. The results are shown in Table 2.

Example 16
The following components were stirred with a high-speed water-cooled stirrer to obtain a magenta UV inkjet ink. The viscosity was 22 mPa · s.
(Magenta ink composition)
(C) (D) Magenta mill base B 12.0 parts (A) ODA-N 25.0 parts (D) Actilane 422 30.9 parts (D) Rapi-Cure DVE-3 8.5 parts (D) Ebecryl 657 9.0 parts, First cure ST-1 0.05 part, (B) Lucirin TPO 8.5 parts, (B) Benzophenone 3.0 parts, (B) Irgacure 184 3.0 parts, Byk 307 0.05 parts

Example 17
The following components were stirred with a high-speed water-cooled stirrer to obtain a yellow UV inkjet ink. The viscosity was 23 mPa · s.
(Yellow color ink composition)
(C) (D) Yellow mill base C 12.0 parts (A) ODA-N 25.0 parts (D) Actilane 422 30.9 parts (D) Rapi-Cure DVE-3 8.5 parts (D) Ebecryl 657 9.0 parts, First cure ST-1 0.05 part, (B) Lucirin TPO 8.5 parts, (B) Benzophenone 3.0 parts, (B) Irgacure 184 3.0 parts, Byk 307 0.05 parts

Example 18
The following components were stirred with a high-speed water-cooled stirrer to obtain a black UV inkjet ink. The viscosity was 20 mPa · s.
(Black ink composition)
(C) (D) Black mill base D 6.0 parts (A) ODA-N 25.0 parts (D) Actilane 422 35.9 parts (D) Rapi-Cure DVE-3 9.5 parts (D) Ebecryl 657 9.0 parts, First cure ST-1 0.05 part, (B) Lucirin TPO 8.5 parts, (B) Benzophenone 3.0 parts, (B) Irgacure 184 2.0 parts, Byk 307 0.05 parts

Example 19
The following components were stirred with a high-speed water-cooled stirrer to obtain a white UV inkjet ink. The viscosity was 24 mPa · s.
(White ink composition)
(C) (D) White mill base E 31.0 parts (A) ODA-N 25.0 parts (D) Actilane 422 12.9 parts (D) Rapi-Cure DVE-3 9.5 parts (D) Ebecryl 657 9.0 parts, First cure ST-1 0.05 part, (B) Lucirin TPO 8.5 parts, (B) Benzophenone 3.0 parts, (B) Irgacure 184 2.0 parts, Byk 307 0.05 parts

Example 20
The following components were stirred with a high-speed water-cooled stirrer to obtain a clear UV inkjet ink. The viscosity was 16 mPa · s.
(Clear color ink composition)
-(A) ODA-N 25.0 parts-(D) Actilane 422 37.9 parts-(D) Rapi-Cure DVE-3 9.5 parts-(D) Ebecryl 657 9.0 parts-First cure ST-1 0.05 parts-(B) Lucirin TPO 8.5 parts-(B) Benzophenone 3.0 parts-(B) Irgacure 184 2.0 parts-(F) Byk 307 0.05 parts

Example 21
The following components were stirred with a high-speed water-cooled stirrer to obtain an NVC magenta UV inkjet ink. The viscosity was 20 mPa · s.
(NVC magenta ink composition)
(C) (D) Magenta mill base B 12.0 parts (A) ODA-N 20.0 parts (D) N-vinylcaprolactam 20.0 parts (D) Actilane 422 20.9 parts (D ) Rapi-Cure DVE-3 8.5 parts-(D) Ebecryl 657 4.0 parts-First cure ST-1 0.05 parts-(B) Lucirin TPO 8.5 parts-(B) Benzophenone 3.0 parts- (B) Irgacure 184 3.0 parts, Byk 307 0.05 parts

(Examples 16 to 21: Evaluation of ink curability)
Using the ink compositions obtained in Examples 16 to 21, inkjet recording was performed in the same manner as in Example 1, images having a film thickness of 12 μm were drawn, and curability and adhesion were evaluated in the same manner as in Example 1. The results are shown in Table 3.
As a result, it was confirmed that the produced color inks and clear inks had good curability in all Examples as in Example 1.

[Example 22]
The same ink composition as in Example 1 was used, the UV light after landing was condensed to an exposure surface illuminance of 400 mW / cm ² , the integrated light amount irradiated to the image was 3,000 mJ / cm ² , and the lamp UV-LED lamp: Inkjet recording was performed by the same method as the above inkjet recording except that NCCU033 (manufactured by Nichia Corporation) was used. There was no missing dot in the obtained image, and a bright image with a thickness of 12 μm could be drawn. Evaluation of curability, flexibility of the cured film, and adhesion was performed in the same manner as in Example 1.
As a result, it was confirmed that the curability, the flexibility of the cured film, and the adhesion were good as in Example 1. The results are shown in Table 3.

1 is a schematic configuration diagram of an example of an ink jet recording apparatus that can be suitably used in the present invention. It is an external appearance perspective view which shows arrangement | positioning of the gas supply mechanism in the image recording part of the inkjet recording device shown in FIG. It is the schematic which shows an example of other embodiment of the inkjet recording device which can be used conveniently for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Actinic radiation curable inkjet recording device 12 Housing | casing 20 Recording medium accommodating part 22 Storage cassette 30 Conveying part 32 Feed roller 34,36 Conveying roller pair 40 Scanning conveying part 42,44,46 Belt roller 48 Conveying belt 48P Image recording position 50 Image recording unit 52 Head unit 54 Head driver 56 Ultraviolet irradiation unit 60 Gas supply / suction mechanism 62 Housing 64 Gas supply nozzle 65 Gas supply tube 66 Gas recovery nozzle 67 Gas recovery tube 68 Oxygen-containing gas supply nozzle 70 Ink cartridge attachment Unit 80 exhaust cooling unit 90 tray 92 peeling claw 110 active curable ink jet recording apparatus 112 case 112a upper cover 114, 116 light shielding door 121 sending side roll 123 winding side roll 130 conveying roller 140 platen 142, 144 conveying Lifting roller 150 image recording unit 152 head unit 154 a head driver 156 active radiation irradiation section 164 gas supply nozzle 166 gas recovery nozzles 168 oxygen-containing gas supply nozzle S recording medium

Claims (5)

(A) a step of ejecting an ink composition onto a recording medium; and (b) irradiating the ejected ink composition with actinic radiation so that the ink composition is under an atmosphere having an oxygen concentration lower than that in the atmosphere. Including a curing step,
The ink composition comprises
(A) An ester or amide of (meth) acrylic acid having a hydrocarbon group having 6 to 32 carbon atoms which may have a substituent, or carbonization having 6 to 32 carbon atoms which may have a substituent An ink jet recording method comprising: at least one compound selected from the group consisting of vinyl ethers having a hydrogen group, and (B) a polymerization initiator.   The inkjet recording method according to claim 1, wherein the hydrocarbon group having 6 to 32 carbon atoms which may have a substituent is an alkyl group or an alkylene group which may have a substituent.   The inkjet recording method according to claim 1, wherein the ink composition contains (C) a colorant.   The inkjet recording method according to claim 1, wherein the ink composition contains N-vinyl lactams.   A recorded matter obtained by the ink jet recording method according to claim 1.

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