JP5591611B2 - Active energy ray-curable ink composition and ink jet recording method - Google Patents

Description

  The present invention relates to an active energy ray-curable ink composition and an ink jet 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. Among these, the ink jet method can be implemented with an inexpensive apparatus, and the ink can be efficiently used because the image is directly formed on the recording medium by ejecting the ink only to the required image portion. Running cost is low.

According to the inkjet method, printing is possible not only on plain paper but also on non-water-absorbing recording media such as plastic sheets and metal plates, but speeding up and high image quality when printing are important issues. The time required for drying and curing the droplets after printing has a property that greatly affects the productivity of printed matter and the sharpness of printed images.
As one of the ink jet methods, there is a recording method using an ink for ink jet recording that can be cured by irradiation of radiation. According to this method, the productivity of printing can be improved and a sharp image can be formed by irradiating the ink immediately after ink ejection or after a certain time and curing the ink droplets.

Here, Patent Document 1 discloses a non-aqueous active energy ray-curable ink containing a curable ethylenically unsaturated oligomer, a photopolymerization initiator, and a pigment dispersion for the purpose of improving dischargeability and viscosity. Proposed.
Patent Document 2 proposes a photocurable ink composition containing a urethane-based oligomer compound and a vinyl ether compound for the purpose of improving curability.

Special table 2008-507598 JP 2009-108171 A

  However, Patent Document 1 does not discuss any blocking resistance. Japanese Patent Application Laid-Open No. H10-228867 does not discuss improving the adhesion of recorded images to a substrate. Furthermore, in each of the above technologies, there is still room for improvement in improving the dischargeability of the ink composition when forming an image using the ink composition.

  The present invention has been made in light of the above circumstances, has high curing sensitivity to irradiation with active energy rays, is excellent in dischargeability when an image is recorded by an inkjet method, and is a recording medium for a recorded image. Another object of the present invention is to provide an ink-jet ink composition suitable for ink-jet recording having excellent adhesion and blocking resistance.

Specific means for solving the above problems are as follows.
Item 1. Polymerizable compounds, polymerization initiators, and have a structure of the following general formula (1) in a side chain, a urethane oligomer or polymer having a repeating unit represented by the following general formula (3), At least one terminal has a group represented by —O (C _m H _2m ) —CH═CH ₂ (m represents 0 or 1), and has a weight average molecular weight of 1,000 to 10,000. An active energy ray-curable ink composition containing a urethane oligomer or polymer.

(In Formula (1), R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group. N represents 1. In Formula (3), R ³ represents cyclo A group containing an alkylene group.

Item 2. Item 2. The active energy ray-curable ink composition according to item 1, wherein the urethane oligomer or polymer has a repeating unit represented by the following general formula (2).

(In the formula (2), ^{R 1} and ^{R 2} are each independently a hydrogen atom, an alkyl group, .X representing the .n is 1 represents a cycloalkyl group, or aryl group of trivalent 3 to 10 carbon atoms Represents a linking group.)

Item 3 . A monool compound having at least two groups represented by —O (C _m H _2m ) —CH═CH ₂ (m represents 0 or 1) is introduced into at least one end of the urethane oligomer or polymer. Item 3. The active energy ray-curable ink composition according to Item 1 or 2 .

Item 4 . Item 4. The active energy ray-curable ink composition according to any one of Items 1 to 3 , wherein the polymerizable compound is a radically polymerizable compound.

Item 5 . Item 5. The active energy ray-curable type according to any one of Items 1 to 4 , wherein the content of the urethane oligomer or polymer is 0.5 to 5% by mass with respect to the total amount of the active energy ray-curable ink composition. Ink composition.

Item 6 . Item 6. The active energy ray-curable ink composition according to any one of Items 1 to 5 , wherein the content of water relative to the active energy ray-curable ink composition is 1% by mass or less.

Item 7 . Item 7. The active energy ray-curable ink composition according to any one of Items 1 to 6 , which is for inkjet recording.

Item 8 . A step of ejecting the active energy ray-curable ink composition according to any one of Items 1 to 7 on a recording medium with an inkjet recording apparatus,
And a step of irradiating the ejected ink composition with active energy rays to cure the ink composition.

  According to the present invention, the curing sensitivity is high with respect to the irradiation of active energy rays, the ejection property when recording an image by an ink jet method, and the adhesion of the recorded image to a recording medium and the blocking resistance are excellent. An ink composition suitable for ink jet recording and an ink jet recording method using the ink composition of the present invention can be provided.

[Active energy ray curable ink composition]
The active energy ray-curable ink composition of the present invention comprises a polymerizable compound, a polymerization initiator, and a urethane oligomer or polymer having a structure represented by the following general formula (1) in the side chain. It is.

(In formula (1), R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group. N represents an integer of 0 to 5.)

  The urethane oligomer or polymer of the present invention only needs to have two or more urethane structural units represented by [—CONH—R—NHCOO—R′—O—] (R is an isocyanate component, R ′. Is a divalent group constituting the alcohol component.) The urethane oligomer or urethane polymer of the present invention refers to a so-called urethane oligomer or urethane polymer (polyurethane). Hereinafter, these may be simply referred to as “urethane compound”.

  The urethane compound of the present invention is preferably a compound having a weight average molecular weight of 1,000 or more and 100,000 or less, more preferably 1,000 or more and 50,000 or less, and most preferably 1,000 or more and 10,000 or less.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). For GPC, HLC-8220GPC (manufactured by Tosoh Corporation) is used, and as columns, TSKgeL SuperHZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as eluents. Use THF (tetrahydrofuran). As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

  The oligomer represented by the urethane oligomer in the present invention is not limited, but refers to, for example, a polymer having a molecular weight of 1,000 to 5,000. The polymer represented by a urethane polymer (polyurethane) refers to, for example, a polymer having a molecular weight of 5,000 or more, preferably a compound having a molecular weight of 5,000 to 10,000.

  The urethane compound of the present invention is preferably a urethane oligomer.

  Here, the “active energy ray” as used in the present invention is not particularly limited as long as it can impart energy capable of generating an initiation species in the composition by irradiation, and widely used as α-ray, γ Including X-rays, X-rays, ultraviolet rays, visible rays, electron beams, and the like. Among these, ultraviolet rays and electron beams are preferable from the viewpoint of curing sensitivity and device availability, and ultraviolet rays are particularly preferable.

  The active energy ray-curable ink composition of the present invention forms a cured ink image by irradiating active energy rays after applying the ink composition to a recording medium. In particular, the active energy ray-curable ink composition of the present invention can be suitably used as an ink composition for inkjet recording.

  Hereinafter, each component of the active energy ray-curable ink composition of the present invention will be described in detail. In the following description, the active energy ray-curable ink composition of the present invention is also referred to as “ink composition” as appropriate. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

<Urethane compound having a structure represented by the general formula (1) in the side chain>
The ink composition of the present invention contains a urethane compound having a structure represented by the following general formula (1) in the side chain. In the general formula, * represents a bonding part.

  By having the structure represented by the general formula (1) in the side chain, the polymerization of the ink composition can proceed. The urethane compound having a structure represented by the general formula (1) in the side chain preferably causes a polymerization reaction by irradiating light.

(In formula (1), R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group. N represents an integer of 0 to 5.)

In the general formula (1), R ¹ and R ² may have a substituent or may not have a substituent, but preferably have no substituent.

Although it does not limit as an alkyl group represented by R < ¹ > and R < ² >, it represents a C1-C4 alkyl group, A linear structure or a branched structure may be sufficient. Specifically, it represents a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group and the like. R ¹ and R ² may combine with each other to form a 4- to 6-membered ring. R ¹ and R ² are each independently preferably an alkyl group having 1 to 2 carbon atoms, and particularly preferably a methyl group.

Examples of the substituent that R ¹ and R ² may have include a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a hydroxyl group, a carboxyl group, a halogen atom, Preferred are an aryloxycarbonyl group having 7 to 11 carbon atoms, an arylcarbonyloxy group having 7 to 11 carbon atoms, an arylcarbamoyl group having 7 to 11 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, a carboxyl group, A halogen atom is more preferred.

The cycloalkyl group represented by R ¹ and R ² is not limited, but represents, for example, a cycloalkyl group having 3 to 10 carbon atoms. Specifically, a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, and the like. Represents. A cycloalkyl group having 3 to 8 carbon atoms is preferable, and a cycloalkyl group having 3 to 6 carbon atoms is more preferable.

The substituents that may be present when R ¹ and R ² are cycloalkyl groups include alkyl groups having 1 to 8 carbon atoms, alkoxy groups having 1 to 8 carbon atoms, hydroxyl groups, carboxyl groups, and halogen atoms. , An alkyloxycarbonyl group having 2 to 7 carbon atoms, an alkylcarbonyloxy group having 2 to 7 carbon atoms, an aryloxycarbonyl group having 7 to 11 carbon atoms, an arylcarbonyloxy group having 7 to 11 carbon atoms, and 1 to 7 carbon atoms Are preferably an alkyl carbamoyl group, an aryl carbamoyl group having 7 to 11 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, a carboxyl group, and a halogen atom.

The aryl group represented by R ¹ and R ² is not limited, but represents, for example, an aryl group having 6 to 20 carbon atoms, and specifically represents a phenyl group, a naphthyl group, or the like. An aryl group having 6 to 16 carbon atoms is preferable, and an aryl group having 6 to 10 carbon atoms is more preferable.

Examples of the substituent that R ¹ and R ² may have are an alkyl group having 1 to 8 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, and an alkoxy group having 1 to 8 carbon atoms. A hydroxyl group, a carboxyl group, a halogen atom, an alkyloxycarbonyl group having 2 to 7 carbon atoms, an alkylcarbonyloxy group having 2 to 7 carbon atoms, an alkylcarbamoyl group having 1 to 7 carbon atoms, and the like. And an alkyl group having 1 to 4 carbon atoms, a hydroxyl group, a carboxyl group, and a halogen atom are more preferable.

R ¹ and R ² represented by the general formula (1) are preferably a hydrogen atom or a methyl group, and most preferably a hydrogen atom.

  N represented by the general formula (1) represents an integer of 0 to 5. Most preferably n is 1. Curing sensitivity can be improved by making n into the range of 0-5.

  Examples of the structure represented by the general formula (1) include, but are not limited to, exemplary compounds (M-0) to (M-8) shown below, and (M-0) to (M-5). ) Is preferred, and (M-1) is most preferred. The effect of this invention can be exhibited more as it is the said compound. The urethane compound of the present invention may have a plurality of different substituents represented by the general formula (1).

  The urethane compound of the present invention may have the structure of the general formula (1) in either or both of the isocyanate component and the alcohol component, and is particularly represented by the following general formula (2) as the alcohol component (c). It is preferable to have a repeating unit.

(In Formula (2), R ¹ and R ² each independently represents a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group. N represents an integer of 0 to 5. X represents a carbon number of 3 to 10. Represents a trivalent linking group.)

^{R 1} and ^{R 2} in the general formula (2) are the same, including the preferred ranges of ^{R 1} and ^{R 2} in the general formula (1) above.

  X in the general formula (2) represents a trivalent linking group having 3 to 10 carbon atoms. Examples of the trivalent linking group having 3 to 10 carbon atoms include a residue obtained by removing three hydrogen atoms from at least one compound selected from the group consisting of an alkane or cycloalkane having 3 to 10 carbon atoms. The alkane residue represented by the trivalent linking group may be linear or branched. Specific examples include, but are not limited to, residues obtained by removing three hydrogen atoms from alkanes or cycloalkanes such as propane, 2-methylpropane, butane, pentane, and cyclohexane. X preferably has 3 to 7 carbon atoms, and most preferably 3 to 5 carbon atoms.

  Specific examples (Y-1) to (Y-15) of the repeating unit represented by the general formula (2) of the urethane compound of the present invention are listed below, but are not limited thereto.

  Specific examples (y-1) to (y-9) of the repeating unit of the alcohol component (b) which is an alcohol component other than the repeating unit represented by the general formula (2) of the urethane compound of the present invention are listed below. However, it is not limited to these.

  The urethane compound of the present invention preferably has a repeating unit represented by the following general formula (3) as the isocyanate component (a).

(In Formula (3), R ³ represents at least one group selected from the group consisting of an alkylene group, a cycloalkylene group, and an arylene group.)

The alkylene group represented by ^{R 3} in the general formula (3) is preferably an alkylene group having 1 to 20 carbon atoms, more preferably from 1 to 16, more preferably from 1 to 12. The alkylene group may be a straight chain structure or a branched structure.

The cycloalkylene group represented by R ³ in the general formula (3) include, but are not limited to, represent a cycloalkylene group having 3 to 10 carbon atoms, cyclopropylene group, a cyclohexylene group and the like. A cycloalkylene group having 3 to 8 carbon atoms is preferable, and a cyclohexylene group is most preferable.

The arylene group represented by R ³ in the general formula (3) is not limited, but is preferably an arylene group having 6 to 15 carbon atoms, specifically, a phenylene group, a tolylene group, or a naphthalenylene group. And biphenylene group.

R ³ in the general formula (3) may be a combination of an alkylene group, a cycloalkylene group or an arylene group. Preferred group combinations are preferably a combination of an alkylene group having 1 to 12 carbon atoms and an arylene group having 6 to 15 carbon atoms, or a combination of a cycloalkylene group having 2 to 16 carbon atoms and an alkylene group having 1 to 12 carbon atoms. A combination of a cycloalkylene group having 2 to 16 carbon atoms and an alkylene group having 1 to 12 carbon atoms is most preferable. The combination of these groups is not limited. For example, a combination of one group and one group is preferable, such as a combination of one kind of cycloalkylene group and one kind of alkylene group.

R ³ in the general formula (3) may or may not have a substituent, but preferably has a substituent.

  When these groups have a substituent, examples of the substituent include an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 20 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a hydroxyl group, a carboxyl group, and a halogen atom. , An alkyloxycarbonyl group having 2 to 7 carbon atoms, an alkylcarbonyloxy group having 2 to 7 carbon atoms, an aryloxycarbonyl group having 7 to 11 carbon atoms, an arylcarbonyloxy group having 7 to 11 carbon atoms, and 1 to 7 carbon atoms Alkylcarbamoyl groups, aryl carbamoyl groups having 7 to 11 carbon atoms and the like are preferable, alkyl groups having 1 to 4 carbon atoms are more preferable, and alkyl groups having 1 carbon atom (methyl group) are most preferable.

R ³ in the general formula (3) preferably contains a cycloalkylene group.

  Specific examples (Z-1) to (Z-13) of the repeating unit represented by the general formula (3) of the urethane compound of the present invention are listed below, but are not limited thereto.

The terminal group of the urethane compound of the present invention is not limited, but is represented by an alkoxy group, a cycloalkyloxy group, an alkylamino group, a cycloalkylamino group, or —O— (C _m H _2m ) —CH═CH _2. that group (m is 0 or 1), and the like, preferably a _{-O- (C} m H 2m) a group represented by -CH = CH _2.

Although the alkoxy group represented by the terminal group of a urethane compound is not limited, it represents a C1-C8 alkoxy group, and may be a linear structure or a branched structure. Specifically, it represents a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, or the like.
Although the cycloalkoxy group represented by the terminal group of a urethane compound is not limited, it represents a C1-C10 cycloalkoxy, and examples thereof include a cyclohexyloxy group, a cyclopentyloxy group, and a cyclohexylmethoxy group.
The alkylamino group represented by the terminal group of the urethane compound is not limited, but represents an alkylamino group having 1 to 8 carbon atoms, and may be a linear structure or a branched structure. Specifically, it represents a methylamino group, dimethylamino group, ethylamino group, propylamino group, isopropylamino group, morpholino group, piperidino group or the like.
The cycloalkylamino group represented by the terminal group of the urethane compound is not limited, but represents a cycloalkylamino group having 1 to 10 carbon atoms, and examples thereof include a cyclohexylamino group, a cyclopentylamino group, and a cyclohexylmethylamino group.

The group represented by —O (C _m H _2m ) —CH═CH ₂ (m is 0 or 1), which is a preferable terminal group of the urethane compound of the present invention, is not limited, but specifically, O—CH═CH ₂ or —O—CH ₂ —CH═CH _{2 and the} like are mentioned, and m is most preferably 1. Groups represented by _{-O (C m H 2m) -CH} = CH 2 is preferred end groups, one terminal may but be present in any of both ends, it is preferably present at both ends .

The urethane compound of the present invention is an oligomer obtained by introducing a monool compound having at least two groups represented by —O (C _m H _2m ) —CH═CH ₂ at both ends. It is preferable from the viewpoint. The monool compound having at least two groups represented by _{-O (C m H 2m) -CH} = CH 2 to be introduced into both terminals, but are not limited _{to, -O (C m H 2m)} -CH = preferably has one to four groups represented by CH _2, more preferably to have two.

  The urethane compound of the present invention comprises a ternary urethane compound in which an isocyanate component (a), an alcohol component (b) and an alcohol component (c) having a structure of the general formula (2) are copolymerized, or an isocyanate component (a ) And an alcohol component (c) are copolymerized. As the urethane compound of the present invention, a ternary urethane compound is preferable.

  The copolymerization ratio of the isocyanate component (a) of the urethane compound of the present invention is a, the copolymerization ratio of the alcohol component (b) is b, and the copolymerization ratio of the alcohol component (c) is c. As for the copolymerization ratio of the urethane compound of the present invention, the sum of a, b and c is 100 in the case of a ternary system, and the sum of a and b or c is 100 in the case of a binary urethane compound.

  In the urethane compound of the present invention, the copolymerization ratio represented by b is preferably 0 ≦ b ≦ 45, and more preferably 10 ≦ b ≦ 40.

  In the urethane compound of the present invention, the copolymerization ratio represented by c is preferably 5 ≦ c ≦ 50, more preferably 10 ≦ c ≦ 40.

C Specific examples of the urethane compound (1-1) to (1-10). However listed below, the present invention is not limited thereto. In addition, the urethane compound which concerns on this invention is a specific example (1-1), (1-2), (1-4), (1-7), (1-8) among the following.

  The urethane compound in the present invention is produced by well-known and conventional means by using, as a precursor, a diol compound having an allyl ether group such as 3-allyloxy-1,2-propanediol (manufactured by Wako Pure Chemical Industries, Ltd.). be able to. For example, compounds represented by the formulas (1-1) to (1-10) can be obtained with reference to J. Polym. Sci., Vol 45, 49 (1960) and JP-A-2006-45362. be able to.

  In the present invention, as a result of intensive studies on an ink composition suitable for inkjet recording, by using a urethane compound having a structure represented by the general formula (1) in the side chain, a polymerizable compound, and a polymerization initiator, It has been found that ejection properties, curing sensitivity to irradiation with active energy rays, adhesion of formed images and blocking resistance are improved. Although this mechanism has not been clarified, the structure represented by the general formula (1) functions as a radical-reactive group having an appropriate reactivity, so that the urethane compound of the present invention can form a substrate with a substrate in a recording medium. It is presumed that this is because it is distributed at a relatively high concentration in the vicinity of the interface and can effectively exhibit adhesion. Since the adhesiveness can be efficiently exhibited, the content of the urethane compound with respect to the total amount of the ink composition can be reduced, so that the dischargeability or the curing sensitivity that becomes a problem when adding a urethane compound other than the present invention is problematic. It is speculated that it can also be improved. Note that the present invention is not limited to the above estimation mechanism.

  The urethane compound of the present invention is preferably 0.5 to 5% by mass, more preferably 0.5 to 3.0% by mass, and 1.0 to 3.0% with respect to the total amount of the ink composition. Most preferably, it is mass%. By setting it as 0.5 mass% or more, it is preferable from a viewpoint of adhesiveness, and setting it as 5 mass% or less is preferable from a discharge property viewpoint.

<Polymerizable compound (other polymerizable compounds)>
In addition to the urethane compound, the ink composition of the present invention includes a polymerizable compound other than the urethane compound having a structure represented by the general formula (1) (hereinafter also referred to as “other polymerizable compound” as appropriate). contains.
The polymerizable compound in the present invention may be either a radical polymerizable compound or a cationic polymerizable compound, but in the present invention, a radical polymerizable compound is preferable.

Hereinafter, other polymerizable compounds applicable to the present invention will be further described.
The radical polymerizable compound is a compound having an ethylenically unsaturated bond capable of radical polymerization, and may be any compound as long as it has at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. , Oligomers, polymers and the like having a chemical form. Only one kind of radically polymerizable compound may be used, or two or more kinds 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.

  Examples of polymerizable compounds having an ethylenically unsaturated bond include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, unsaturated carboxylic acid esters and salts thereof, ethylene And radically polymerizable compounds such as anhydrides having an unsaturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides.

Specifically, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol Diacrylate, 1,6-hexanediol diacrylate, phenoxyethyl acrylate, propoxylated neopentyl glycol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate , Polypropylene glycol diacrylate, pentae Thritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylolmethane tetraacrylate, oligoester acrylate, N-methylolacrylamide, diacetoneacrylamide, epoxy acrylate, cyclic trimethylpropane formal acrylate (CTFA), acrylic acid derivatives such as tetrahydrofurfuryl acrylate (THFA),
Methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, 1,6-hexanediol dimethacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, Methacryl derivatives such as polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis (4-methacryloxypolyethoxyphenyl) propane,
Other examples include derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, and triallyl trimellitate. More specifically, Yamashita Shinzo, “Cross-linking agent handbook” (1981 Taiseisha); Ed., "UV / EB Curing Handbook (raw material)" (1985, Polymer Press Society); Radtech Study Group, "Application and Market of UV / EB Curing Technology", 79 pages, (1989, CMC) Commercially available products described in Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun), etc., or radically polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used. Among these, cyclic trimethylpropane formal acrylate (CTFA) is particularly preferable.

  Examples of the radical polymerizable compound are described in JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011 and the like. And a photocurable polymerizable compound used in the photopolymerizable composition.

In order to further improve sensitivity, bleeding, and adhesion to a recording medium, a monoacrylate and a polyfunctional acrylate monomer or a polyfunctional acrylate oligomer having a molecular weight of 400 or more, preferably 500 or more are used in combination as a radical polymerizable compound. Is preferred. 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.
Furthermore, the mode in which at least two polymerizable compounds of monofunctional and bifunctional or higher polyfunctional monomers are used in combination further improves sensitivity, bleeding, and adhesion to the recording medium while maintaining safety. It is preferable from the viewpoint that it can be performed.

Monoacrylates include phenoxyethyl acrylate, stearyl acrylate, isoamyl acrylate, isomistyl acrylate, isostearyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, isobornyl acrylate, isooctyl acrylate, propoxyethyl acrylate, 2- (2- Ethoxyethoxy) ethyl acrylate is preferable in terms of high sensitivity, low shrinkage and prevention of curling, as well as prevention of bleeding, odor of printed matter, and cost reduction of irradiation apparatus.
As the oligomer that can be used in combination with the monoacrylate, an epoxy acrylate oligomer is particularly preferable.
In addition, methacrylate has better skin irritation than acrylate.

  In this invention, it is preferable to use from the above-mentioned acrylate compound as another polymeric compound, It is preferable that the said acrylate compound is 30 mass% or more with respect to the total mass of another polymeric compound, 40 masses % Or more, and more preferably 50% by mass or more. Moreover, all the other polymerizable compounds can also be made into the said acrylate compound.

  In the ink composition of the present invention, the total content of the polymerizable compounds (the urethane compound of the present invention and other polymerizable compounds) is the total content of the ink composition of the present invention from the viewpoint of the physical properties and curing sensitivity of the ink composition. It is preferable that it is 60 to 95 mass% with respect to mass, More preferably, it is 65 to 90 mass%.

  The content of the polymerizable compound that may be contained in addition to the urethane compound of the present invention is preferably 55% by mass or more and 90% by mass or less, and 60% by mass or more with respect to the total mass of the polymerizable compound of the present invention. It is preferable that it is 85 mass% or less.

  The molecular weight of the other polymerizable compound in the present invention is preferably 130 to 3000, more preferably 130 to 500, as a weight average molecular weight.

<Polymerization initiator>
The ink composition of the present invention needs to contain a polymerization initiator.

As a polymerization initiator in this invention, a photoinitiator is mentioned preferably. As the photopolymerization initiator, a known photopolymerization initiator can be appropriately selected and used according to the kind of the polymerizable compound and the purpose of use of the ink composition.
The photopolymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy (light) and generates radicals that are polymerization initiation species. Examples of light include active energy rays, that is, γ rays, β rays, electron beams, ultraviolet rays, visible rays, infrared rays, and the like.

  As the photopolymerization initiator, known compounds can be used. Preferred photopolymerization initiators that can be used in the present invention include (a) aromatic ketones, (b) acylphosphine oxide compounds, and (c) aromatics. Onium salt compound, (d) organic peroxide, (e) thio compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) Examples thereof include metallocene compounds, (k) active ester compounds, (l) compounds having a carbon halogen bond, and (m) alkylamine compounds.

  These photopolymerization initiators may use the above compounds (a) to (m) alone or in combination. The photopolymerization initiator in the present invention is preferably used alone or in combination of two or more.

  Preferable examples of (a) aromatic ketones, (b) acylphosphine oxide compounds, and (e) thio compounds include “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY”, J. MoI. P. FOUASSIER, J.A. F. RABEK (1993), pp. Examples include compounds having a benzophenone skeleton or a thioxanthone skeleton described in 77-117. More preferable examples 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, dialkoxybenzophenones described in JP-B-60-26483, JP-B-60-26403, JP-A Benzoin ethers described in JP-A-62-81345, JP-B-1-34242, US Pat. No. 4,318,791, α-aminobenzophenones described in European Patent 0284561A1, JP-A-2-21152 P-Di (dimethylaminobenzoyl) benze Thio-substituted aromatic ketones described in JP-A-61-194062, acylphosphine sulfides described in JP-B-2-9597, acylphosphines described in JP-B-2-9596, and JP-B-63-61950 Thioxanthones, and coumarins described in JP-B-59-42864. Moreover, the polymerization initiators described in JP 2008-105379 A and JP 2009-114290 A are also preferable.

  Among these, in the present invention, it is preferable to use an aromatic ketone or an acylphosphine oxide compound as a photopolymerization initiator, and p-phenylbenzophenone (manufactured by Wako Pure Chemical Industries, Ltd.), bis (2,4,6- Trimethylbenzoyl) -phenylphosphine oxide (Irgacure 819: manufactured by Ciba Japan), bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphenylphosphine oxide, 2,4,6-trimethylbenzoyl- Diphenyl-phosphine oxide (Darocur TPO: manufactured by Ciba Japan, Lucirin TPO: manufactured by BASF) and the like are preferable.

A polymerization initiator can be used individually by 1 type or in combination of 2 or more types.
The preferable content of the polymerization initiator in the ink composition is preferably in the range of 0.1 to 15% by mass.

  In addition, the radical polymerization initiator is in a mass ratio of polymerization initiator: sensitizing dye to the sensitizing dye that can be used as necessary, which will be described later, and is 200: 1 to 1: 200, preferably 50: It is appropriate that it is included in the range of 1: 1 to 50, more preferably 20: 1 to 1: 5.

<Colorant>
The ink composition of the present invention is not particularly required to form a colored image, but can contain a colorant when a colored image is to be formed.

  There is no restriction | limiting in particular as a coloring agent which can be used for this invention, It can select and use from arbitrary well-known coloring agents, such as a pigment, an oil-soluble dye, a water-soluble dye, a disperse dye. Among these, as the colorant, pigments and oil-soluble dyes that are excellent in weather resistance and rich in color reproducibility are preferable, and pigments are more preferable.

  A colorant that can be suitably used in the ink composition of the present invention is selected from compounds that do 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 active energy rays. Is preferred.

-Pigment-
Although it does not necessarily limit as a pigment which can be used for this invention, For example, the organic or inorganic pigment of the following number described in a color index can be used.

Examples of the red or magenta pigment include Pigment Red 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53. : 1, 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, and the like.
Examples of the blue or cyan pigment include Pigment Blue 1,15,15: 1,15: 2,15: 3, 15: 4,15: 6,16,17-1,22,27,28,29,36. , 60, and the like.

Examples of the green pigment include Pigment Green 7, 26, 36, 50, and the like.
Examples of the yellow pigment include 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, and the like, and Pigment Yellow 120, 155, 180 are preferable.
Examples of the black pigment include Pigment Black 7, 28, 26, and the like.
Examples of the white pigment include Pigment White 6, 18, 21, and the like.
These pigments can be appropriately selected and used according to the purpose.

-Oil-soluble dye-
Below, the oil-soluble dye which can be used by this invention is demonstrated.
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 For example, methine dyes such as benzylidene dyes and monomethine oxonol dyes; for example, quinone dyes such as naphthoquinone dyes and anthraquinone dyes; and other dye species such as quinophthalone dyes, nitro Examples thereof include nitroso dyes, acridine dyes, acridinone dyes and the like.

  Among the oil-soluble dyes that can be used 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, Methine dyes such as oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes and xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone and anthrapyridone; A ring dye; and the like.

  Of 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; carboniums such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes Examples include dyes; phthalocyanine dyes; anthraquinone dyes; 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 chromophore (chromogenic 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. Furthermore, polymer cations having such a 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; I. Solvent Violet 3; C.I. I. Solvent Blue 2,11,25,35,38,67 and 70; 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 2600e, Orient Chemical Co., Ltd.), Aizen Spillon Blue GNH (Hodogaya Chemical Co., Ltd.), Neopen Yellow 075, Neopen Mazena SE1378, Neopen Blue 808, Neopen FF4012, Neopen FF4012 .

-Disperse dye-
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; 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;

  The colorant that can be used in the present invention is preferably subjected to a dispersion treatment so as to be 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. Examples of the polymer dispersant include the Solsperse series of Noveon. 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 50 parts by mass with respect to 100 parts by mass 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 colorant is added in advance to a dispersion medium such as a solvent or a polymerizable compound, and uniform. It can also be blended after being dispersed or dissolved.

  One or more colorants may be appropriately selected according to the intended use of the ink composition.

  In the ink composition of the present invention, when using a colorant such as a pigment that remains in a solid state, the average particle diameter of the colorant particles is preferably 0.005 to 0.5 μm, more preferably. 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, and more preferably 0.015 to 0.4 μm. This particle size control is preferable because clogging of the head nozzle can be suppressed and ink storage stability, ink transparency, and 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 of the ink composition, but generally considering the ink physical properties and colorability, the content of the colorant is generally based on the total mass of the ink composition. The content is preferably 0.5 to 10% by mass.
In the case where the ink composition of the present invention is a white ink composition having a white pigment such as titanium oxide as a colorant, the content of the colorant is the mass of the entire ink composition in order to ensure concealment. It is preferable that it is 5-30 mass% with respect to it, and it is more preferable that it is 10-25 mass%.

<Water>
The ink composition of the present invention is preferably a non-aqueous ink composition containing substantially no water. Specifically, it is preferably 5% by mass or less, more preferably 1% by mass or less, based on the total amount of the ink composition.

<Sensitizing dye>
A sensitizing dye can be added to the ink composition of the present invention in order to accelerate the decomposition of the polymerization initiator by irradiation with actinic rays. A sensitizing dye absorbs specific active energy rays and enters an electronically excited state. Sensitizing dyes in an electronically excited state come into contact with the polymerization initiator and cause actions such as electron transfer, energy transfer, and heat generation, thereby promoting chemical changes of the polymerization initiator, that is, decomposition and generation of radicals. It is something to be made.

  As the sensitizing dye, a compound corresponding to the wavelength of the active energy ray that generates an initiation species in the radical polymerization initiator used in the ink composition may be used. Considering that it is used for a curing reaction of a general ink composition, examples of preferable sensitizing dyes include those belonging to the following compounds and having an absorption wavelength in the 350 nm to 450 nm region. Can be mentioned.

  Polynuclear aromatics (eg, anthracene, pyrene, perylene, triphenylene), thioxanthones (eg, isopropylthioxanthone), xanthenes (eg, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (eg, Thiacarbocyanine, oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (For example, anthraquinone), squalium (for example, squalium), coumarins (for example, 7-diethylamino-4-methylcoumarin), and the like. Xanthones may be mentioned as preferred class.

<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 the active energy ray or suppressing inhibition of polymerization of the polymerizable compound by oxygen.

  Examples of co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Science”, Vol. 10, page 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 such as thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142772, No. 56-75643, such as 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercapto. And naphthalene.

  Other examples of co-sensitizers include amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), Japanese Patent Publication No. 55-34414. Hydrogen donors described in JP-A-6-308727, sulfur compounds (e.g., trithiane) described in JP-A-6-308727, phosphorus compounds (such as diethyl phosphite) described in JP-A-6-250387, JP-A-8-65779 Examples include Si—H and Ge—H compounds.

<Other ingredients>
The active energy ray-curable ink composition of the present invention may further contain other components as necessary. 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, the active energy ray-curable ink composition of the present invention is preferably discharged in the range of 40 to 80 ° C. by heating and reducing the viscosity, and a polymerization inhibitor is added to prevent clogging of the head due to thermal polymerization. It is preferable. 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 and the like.

In view of the fact that the ink composition of the present invention is an active energy ray-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, an organic solvent can be added to improve the adhesion with a recording medium (a support such as paper). Suitable solvents include propylene carbonate, dimethyl succinate, dimethyl glutarate, dimethyl adipate, and mixtures thereof.
The amount of the organic solvent is, for example, in the range of 0 to 5% by mass, preferably 0.1 to 3% by mass, with respect to the total mass of the ink composition of the present invention.

  In addition, a known compound can be added to the active energy ray-curable ink composition of the present invention as necessary. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film physical properties, rubber resins, waxes and the like can be appropriately selected and added. In order to improve the adhesion to a recording medium such as polyolefin or PET, it is also preferable to include 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]
As described above, the ink composition of the present invention has active energy ray curability, and there are no particular limitations on the means for image formation using this ink composition, and general coating methods, transfer methods, ink jet recording, and the like. In a preferred embodiment of the present invention, since the ratio of the polymerizable compound in the ink composition is 60% by mass or more and contains a large amount of low molecular weight compounds, from the viewpoint of viscosity, ink jet recording is possible. It has the characteristic that it can be used conveniently for use.
Hereinafter, preferable physical properties when the ink composition of the present invention is used for inkjet recording will be described.
The ink composition of the present invention has a viscosity of preferably 5 to 30 mPa · s, more preferably at a temperature at the time of ejection (for example, 25 to 60 ° C., preferably 25 to 50 ° C.) in consideration of ejectability. Is 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 10 to 50 mPa · s, more preferably 12 to 40 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, ink permeation into the recording medium can be avoided, and uncured monomers can be reduced and odors can be reduced. Furthermore, ink bleeding at the time of ink droplet landing can be suppressed, 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 uncoated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and the wettability is preferably 30 mN / m or less.

[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.

The ink jet recording method of the present invention includes a step of ejecting an active energy ray-curable ink composition onto a recording medium by an ink jet recording apparatus, and irradiating the ejected ink composition with active energy rays to thereby produce the ink composition. A step of curing the product.
The ink jet recording method of the present invention includes the above steps, whereby an image is formed from the ink composition cured on the recording medium.

  In the step of discharging the active energy ray-curable ink composition by the inkjet recording apparatus in the inkjet recording method of the present invention, an inkjet recording apparatus described in detail below can be used.

-Inkjet recording device-
There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can eject ink onto a recording medium in the process of ejecting the active energy ray-curable ink composition of the inkjet recording method of the present invention by the inkjet recording apparatus. Can be implemented.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an active energy ray source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink 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 ×. It can drive so that it can discharge with a resolution of 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

  In the active energy ray-curable ink composition such as the ink composition of the present invention, it is desirable to set the ejected ink to a constant temperature, so that the ink supply tank to the ink jet head portion are insulated and heated. be able to. The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink 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.

  For discharging the active energy ray-curable ink composition of the present invention using the ink jet recording apparatus, the ink composition is preferably heated to 25 to 60 ° C., more preferably 25 to 50 ° C. It is preferably performed after the viscosity of the product is lowered to 5 to 30 mPa · s, more preferably 7 to 25 mPa · s. In particular, it is preferable to use an ink composition having an ink viscosity of 25 to 500 mPa · s at 25 ° C. as the ink composition for ink jet recording of the present invention, because a large effect can be obtained. By using this method, high dischargeability can be realized.

  Since the active energy ray-curable ink composition such as the ink composition of the present invention generally has a higher viscosity than the water-based ink that is usually used in ink for inkjet recording, the viscosity fluctuation due to temperature fluctuation during ejection is large. The ink viscosity fluctuation has a great influence on the change of the droplet size and the change of the droplet discharge speed, and causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink at the time of ejection as constant as possible. Therefore, in the present invention, it is appropriate that the control range of the ink temperature is ± 5 ° C. of the set temperature, preferably ± 2 ° C. of the set temperature, more preferably ± 1 ° C. of the set temperature.

Next, a process of irradiating the discharged ink composition with active energy rays and curing the ink composition will be described.
The ink composition ejected onto the recording medium is cured by irradiating with active energy rays. This is because the radical polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with active energy rays to generate radicals and other starting species, and depending on the function of the starting species, a specific heterocyclic compound or desired This is because the polymerization reaction of other polymerizable compound used in combination occurs and is accelerated. At this time, if the sensitizing dye is present together with the radical polymerization initiator in the ink composition, the sensitizing dye in the system absorbs the active energy ray to be in an excited state and promotes its decomposition by contact with the radical polymerization initiator. And a more sensitive curing reaction can be achieved.

Further, the polymerization initiation system applied to the ink composition of the present invention has sufficient sensitivity even with a low output active energy ray. Therefore, the output of the active energy ray is preferably 2,000 mJ / cm ² or less, more preferably 10 to 2,000 mJ / cm ² , and still more preferably 20 to 1,000 mJ / cm ² . Yes, and particularly preferably 50 to 800 mJ / cm ² .
Further, the active energy rays, the exposure surface illuminance of, for example, 10 to 2,000 mW / cm ^2, preferably, it is suitable to be irradiated at 20 to 1,000 mW / cm ^2.

  Mercury lamps and gas / solid lasers are mainly used as active energy ray sources, and mercury lamps and metal halide lamps are widely known as light sources used for curing active energy ray-curable ink compositions. ing. 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.

  In addition, a light emitting diode (LED) and a laser diode (LD) can be used as an active energy ray 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. If even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit active energy rays centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. A particularly preferable active energy ray source in the present invention is a UV-LED, and a UV-LED having a peak wavelength of 350 to 420 nm is particularly preferable.

Incidentally, it is preferable that the maximum illumination intensity on the LED 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 It is.

The ink composition of the present invention is suitably irradiated with such active energy rays, for example, for 0.01 to 120 seconds, preferably for 0.1 to 90 seconds.
The irradiation conditions of active energy rays and the 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 ejection device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with active energy rays is performed for a certain period of time after ink landing (for example, 0.01 to 0.5 seconds, preferably 0.01 to 0.3 seconds, more preferably 0.01 to 0.15 seconds). It will be done after. Thus, by controlling the time from ink landing to irradiation to an extremely short time, it is possible to prevent the ink that has landed on the recording medium from spreading before being cured. Further, since the ink can be exposed to a porous recording medium before the ink penetrates to a deep part where the light source does not reach, residual unreacted monomer can be suppressed, and as a result, odor can be reduced.

  Further, curing may be performed 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 can be kept constant for 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 inks in the order of low lightness, it becomes easy for the irradiation line to reach the lower ink, and good curing sensitivity, reduction of residual monomers, reduction of odor, and improvement of adhesiveness 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.

In this way, the ink composition of the present invention can be cured with high sensitivity by irradiation with active energy rays, whereby a high-definition and high-strength image can be formed on the surface of the recording medium. In addition, an image excellent in adhesiveness with a recording medium can be formed.
Furthermore, when the ink composition of the present invention is applied to an ink jet apparatus, it does not cause precipitation of components in the vicinity of the ink jet head and the like, and is an ink composition having excellent ejection properties. Image formation can be performed.
Further, the ink composition of the present invention is cured with high sensitivity by irradiation with active energy rays as described above, and the formed ink image is flexible and has excellent adhesion to a recording medium. wide.

  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. Further, in the following description, unless otherwise specified, “parts” means “parts by mass”.

  Of the compounds used in Examples and Comparative Examples, compounds not described by the manufacturer were synthesized by applying known methods or known methods.

[Preparation of pigment dispersion (mill base)]
NOVOPERM YELLLOW H2G (CI Pigment Yellow 120, manufactured by Clariant) 30 parts by mass, DISPERBYK-168 (pigment dispersant, solid content 30%, manufactured by BYK Chemie) 30 parts by mass, RAPICURE DVE-3 (triethylene glycol) 40 masses of divinyl ether (made by ISP) was mixed, and it stirred for 10 minutes at 3,000 rpm using the mixer (Silverson L4R). After that, it is put into a bead mill disperser DISPERMAT SL (manufactured by VMA-GETZMANN GmbH), and zirconia beads having a diameter of 0.65 mm (YTZ balls, manufactured by Nikkato Co., Ltd.) are used. A yellow mill base was prepared by dispersing for 6 hours in minutes.

(Ink composition 1)
The lower component was stirred for 15 minutes at 2,500 rpm with a mixer (Silverson L4R) to obtain a yellow ink composition 1 used in Example 1.

・ Milbase 13.0 parts ・ N-vinyl-ε-caprolactam (monofunctional polymerizable compound, NVC, manufactured by BASF) 14.5 parts ・ Phenoxyethyl acrylate (monofunctional polymerizable compound, manufactured by SARTOMER) 37.7 Parts ・ Isobornyl acrylate (monofunctional polymerizable compound, manufactured by Wako Pure Chemical Industries, Ltd.) 15.0 parts ・ SR508 (polyfunctional polymerizable compound, dipropylene glycol diacrylate, manufactured by SARTOMER) 4.3 parts ・ p- Methoxyphenol (polymerization inhibitor, manufactured by Wako Pure Chemical Industries, Ltd.) 1.0 part ・ Lucirin TPO (polymerization initiator, manufactured by BASF) 9.5 parts ・ IRGACURE 184 (polymerization initiator, manufactured by Ciba Japan); 1-hydroxycyclohexyl phenyl ketone) 3.0 parts Urethane compound (1-1) (weight average molecular weight 3200, structure below) 2.0

The chemical structure of the urethane compound (1-1) is shown below.

<Synthesis of 1-1>
Isophorone diisocyanate 67.7 g (0.305 mol, manufactured by Wako Pure Chemical Industries, Ltd.), 3-allyloxy-1,2-propanediol 14.5 g (0.110 mol, manufactured by Wako Pure Chemical Industries, Ltd.), diethylene glycol 17.7 g (0 167 mol, manufactured by Wako Pure Chemical Industries, Ltd.) in a solution of 290 mL of methyl ethyl ketone, 60 mg of Neostan U-600 (bismuth catalyst, manufactured by Nitto Kasei Co., Ltd.) was added and stirred at 60 ° C. for 6 hours, and then trimethylolpropane diallyl ether was added. 7 g (0.05 mol, manufactured by ALDRICH) was added and stirred at 60 ° C. for 2 hours. The obtained reaction solution was diluted with 500 mL of acetone, poured into hexane with stirring, reprecipitated, washed with methanol and dried at room temperature to obtain 73 g of white solid (1-1). The molecular weight measured by GPC (GPC HLC-8220 GPC manufactured by Tosoh Corporation) was 3,200 in weight average molecular weight and 2,200 in number average molecular weight.

-Ink compositions 2-13-
Examples 2, 4, 8, 9, 11 to 13 and Comparative Examples 1 and 3 were the same as the ink composition 1 except that the types and addition amounts of the pigment dispersion, the polymerizable compound, and the urethane compound are shown in Table 1. Ink compositions 2 to 13 used in Nos . 5 to 7 and 10 were prepared.

The urethane compound (1-2) to urethane compound (1-10) used in the ink composition represented by Table 1 have the following structure and weight average molecular weight.

  Urethane compounds (1-2) to (1-10) can be synthesized by the same method as urethane compound (1-1) using the corresponding raw materials.

The abbreviations and product names in Table 1 are as follows.
・ N-vinyl-ε-caprolactam (NVC, manufactured by BASF)
CTFA (cyclic trimethyl formal acrylate, manufactured by Sartomer)
・ Lucirin TPO (manufactured by BASF)
・ P-methoxyphenol (polymerization inhibitor, manufactured by Wako Pure Chemical Industries, Ltd.)
・ IRGACURE184 (Ciba Japan)

(Evaluation of ink composition)
<Adhesion>
The ink composition was applied to the surface of a polyvinyl chloride sheet (thickness 220 μm) as a recording medium using a K hand coater (bar No. 2) so as to have a wet film thickness of 12 μm. Next, inside the UV conveyor device CSOT (manufactured by GS Yuasa Lighting) equipped with an ozone-less metal halide lamp MAN125L and set at a conveyor speed of 6 m / min and an exposure intensity of 1,800 W / cm ² until the adhesiveness of the coating surface disappears It was repeatedly passed and cured with active energy rays.
The adhesion to the recording medium is evaluated by a cross hatch test (EN ISO 2409), and expressed by notations 5B to 1B according to the ASTM method. It is evaluated that 5B is most excellent in adhesion and 3B, 4B, and 5B are at a level having no practical problem. The results are shown in Table 2.

<Tack-free sensitivity (curing sensitivity)>
An image was formed on the recording medium by the same method as the image forming method described in the adhesion evaluation. Curing sensitivity was evaluated according to the following criteria. The results are shown in Table 2. Note that “being tack-free” means that the adhesive on the coated surface does not stick.

-Standard-
5: Tack-free after one pass. The curing rate is extremely fast.
4: Tack-free after 2-3 passes. Cure speed is fast.
3: Tack-free after 4-5 passes. Curing time is somewhat slow.
2: It became tack-free when the number of passages was 6 to 10 or more. Curing time is slow.
1: It was not tack-free after 10 passes. Curing time is very slow.

<Blocking resistance>
An image was formed on the recording medium by the same method as the image forming method described in the adhesion evaluation. An uncoated recording medium was superimposed on the coated surface of the recording medium, a uniform load of 25 g / cm ² was applied to the entire recording medium, and the recording medium was stored at 25 ° C. for 24 hours. For blocking, the degree of transfer to an uncoated recording medium when the uncoated recording medium was peeled off from the coated recording medium was evaluated according to the following criteria. The results are shown in Table 2.

-Standard-
5: There is no transfer to an uncoated recording medium, and the blocking resistance is very good.
4: Slight transfer to an uncoated recording medium was observed (less than 10% of the coated area).
3: Transfer to an uncoated recording medium was observed (at least 10% but less than 30% of the coated area).
2: Large transfer to an uncoated recording medium was observed (30% or more of the coated area).
1: Large transfer to an uncoated recording medium was observed (50% or more of the coated area).

<Dischargeability>
JetLyzer (manufactured by Mimaki Engineering Co., Ltd.) equipped with inkjet print head CA3 (manufactured by TOSHIBA TEC CO., LTD.) Is set to discharge voltage 22V, the number of discharge drops is 7 drops, and the ink composition is continuously discharged at 45 ° C. for 60 minutes. The percentage of missing print was evaluated.
In Examples 1 , 2, 4 , 9 , and 13 , no missing print was observed. Regarding Example 12, omission occurred in 0 to 2% of the entire printing. Regarding Comparative Example 6 and Example 11, missing portions occurred in 2 to 5% of the entire printing. Regarding Example 8, missing occurred in 5 to 20% of the entire printing.

Claims (8)

Polymerizable compounds,
A polymerization initiator, and
The structure represented by the following general formula (1) possess a side chain, a urethane oligomer or polymer having a repeating unit represented by the following general formula (3), at least one terminal -O (C _m H _2m) having a group represented by -CH = CH ₂ (m is 0 or 1), the weight average molecular weight, the active energy ray curable containing urethane oligomer or polymer is 1,000 to 10,000 Type ink composition.

(In Formula (1), R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, a cycloalkyl group, or an aryl group. N represents 1. In Formula (3), R ³ represents cyclo A group containing an alkylene group. The active energy ray-curable ink composition according to claim 1, wherein the urethane oligomer or polymer has a repeating unit represented by the following general formula (2).


(In the formula (2), ^{R 1} and ^{R 2} are each independently a hydrogen atom, an alkyl group, .X representing the .n is 1 represents a cycloalkyl group, or aryl group of trivalent 3 to 10 carbon atoms Represents a linking group.) A monool compound having at least two groups represented by —O (C _m H _2m ) —CH═CH ₂ (m represents 0 or 1) is introduced into at least one end of the urethane oligomer or polymer. The active energy ray-curable ink composition according to claim 1 or 2 , wherein The polymerizable compound is an active energy ray-curable ink composition according to any one of claims 1 to 3 is a radical polymerizable compound. The active energy according to any one of claims 1 to 4 , wherein the content of the urethane oligomer or polymer is 0.5 to 5% by mass relative to the total amount of the active energy ray-curable ink composition. Line curable ink composition. The active energy ray-curable ink composition according to any one of claims 1 to 5 , wherein a content of water with respect to the active energy ray-curable ink composition is 1% by mass or less. The active energy ray-curable ink composition according to any one of claims 1 to 6 , which is for inkjet recording. A step of ejecting the active energy ray-curable ink composition according to any one of claims 1 to 7 on a recording medium by an inkjet recording apparatus;
And a step of irradiating the ejected ink composition with active energy rays to cure the ink composition.