JP2010001437A - Ink composition, inkjet recording method and printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: an ink composition capable of forming an image which has favorable curing sensitivity, is excellent in rubbing resistance and blocking properties, and has controlled surface stickiness and improved surface curing properties; an inkjet recording method using the ink composition; and a printed matter. <P>SOLUTION: The ink composition contains (A) a polymer containing a thiol group and at least one partial structure on the side chain that is selected from the group consisting of (i) a fluorine-substituted hydrocarbon group, (ii) a siloxane skeleton and (iii) a long-chain alkyl group, (B) a photoinitiator and (C) a polymerisable compound. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink composition suitably used for inkjet recording, an inkjet recording method, and a printed matter using the same.

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. In particular, the ink jet method can be implemented with an inexpensive apparatus, and the ink can be used efficiently because the image is directly formed on the recording medium by ejecting the ink only to the required image portion. Cost is low. Furthermore, there is little noise and it is excellent as an image recording method.
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. However, high speed and high image quality are important issues for printing. The time required for drying and curing the droplets after printing has a property of greatly affecting the productivity of printed matter and the sharpness of the printed image.

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 with radiation immediately after ink ejection or after a certain period of time to cure ink droplets.
By achieving high sensitivity of ink for ink jet recording that can be cured by irradiation with radiation such as ultraviolet rays, high curability is imparted to radiation, improving productivity of ink jet recording, reducing power consumption, and applying to radiation generators. There are many benefits such as longer life by reducing the load and prevention of volatilization of low molecular weight materials due to insufficient curing. In addition, high sensitivity improves the strength of the image formed by the ink for ink jet recording, particularly when applied to the formation of a lithographic printing plate. Will be obtained.

  Such a curable ink jet method using radiation, for example, ultraviolet rays, has been attracting attention in recent years because it has a relatively low odor, and can be recorded on a recording medium having no quick drying and no ink absorption. There has been proposed a cationic polymerization type ink composition that is excellent in adhesion to the ink and has a small shrinkage rate upon UV curing (for example, see Patent Document 1). However, these cationic polymerization type inks are not sufficiently stable at the time of storage due to a reaction based on an acid generated with the passage of time, which has been a major obstacle to practical use. For this reason, as an attempt to improve the storage stability, a technique of adding a basic compound or a thermal base generator has been proposed (for example, see Patent Documents 2 to 4). It has been found that a new problem arises that the curing sensitivity of the ink is lowered due to the inhibition of the function of the ink.

For the purpose of achieving both high sensitivity and storage stability of the ink composition, a photopolymerization initiator composition containing a thiol compound having a specific structure has been proposed (see, for example, Patent Document 5). However, in order to achieve high sensitivity, it is necessary to add a large amount of the thiol compound. However, if a large amount of the thiol compound is added, the flexibility of the film due to the photosensitive composition is lowered, and the sensitivity is increased. It was found that it was difficult to achieve both film flexibility.
Therefore, an ink composition that has good storage stability, is cured with high sensitivity, and can form a flexible film is desired.
Japanese Patent Laid-Open No. 9-183928 JP 2003-312121 A JP 2003-341217 A JP 2004-91558 A JP 2004-149755 A

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, an object of the present invention is to provide an ink composition capable of forming an image having good curing sensitivity, excellent scratch resistance and blocking properties, suppressed surface stickiness, and improved surface curability, and the ink composition. It is an object of the present invention to provide an ink jet recording method and a printed matter.

Specific means for achieving the object is as follows.
<1> (A) a thiol group and at least one partial structure selected from the group consisting of (i) a fluorine-substituted hydrocarbon group, (ii) a siloxane skeleton, and (iii) a long-chain alkyl group in the side chain; An ink composition comprising: (B) a photopolymerization initiator; and (C) a polymerizable compound.
<2> The ink composition according to <1>, wherein the thiol group is included in the main chain of the polymer (A).

<3> The ink composition according to <1>, wherein the thiol group is included in a side chain of the polymer (A).
<4> The ink composition according to any one of <1> to <3>, which is for inkjet recording.

<5> A step of ejecting the ink composition according to any one of <1> to <4> onto a recording medium by an ink jet recording apparatus, and irradiating the ejected ink composition with actinic radiation to form an ink And a step of curing the composition.
<6> Printed matter recorded by the inkjet recording method according to <5>.

  According to the present invention, an ink composition capable of forming an image having good curing sensitivity, excellent scratch resistance, blocking properties, suppressed surface stickiness, and improved surface curability, and the ink composition are used. An inkjet recording method and a printed matter can be provided.

Although the operation of the present invention is not clear, it is estimated as follows.
The ink composition of the present invention contains a polymer containing a thiol group and at least one partial structure selected from the group consisting of a fluorine-substituted hydrocarbon group, a siloxane skeleton, and a long-chain alkyl group.
The partial structure selected from the group consisting of a fluorine-substituted hydrocarbon group, a siloxane skeleton, and a long-chain alkyl group acts as a surface orientation group, whereby (A) the polymer segregates on the surface of the composition, and the surface energy Has the effect of lowering.

Further, (A) the polymer has a thiol group having a chain transfer mechanism. The presence of multiple thiol groups in the polymer (polyfunctional), (A) the polymer has a chain transfer action, and the polyfunctional thiol group serves as a crosslinkable group, thereby cross-linking the ink composition surface. The density can be increased, and the curability of the film surface is effectively improved even with a small amount of addition.
Therefore, since the surface of the film is sufficiently cured by the (A) polymer without adding a large amount, and the surface energy of the cured film surface is low, the polymer having such a partial structure is formed on the surface. The surface of the ink image using the ink composition of the present invention that segregates is excellent in scratch resistance and blocking resistance in combination, and compared with the case where a large amount of normal polyfunctional monomer is added. It is considered that the curability, flexibility and scratch resistance of the film are compatible.
When the ink composition of the present invention is used as an inkjet ink, (A) a partial structure selected from a fluorine-substituted hydrocarbon group, a siloxane skeleton, and a long-chain alkyl group present in the polymer is a surface orientation group. Thus, it is considered that these segregate on the surface of the composition, the surface tension of the ink droplets can be adjusted to an appropriate range for ejection, and the ink ejection properties are improved. For this reason, the ink composition of the present invention is particularly suitable for an inkjet ink.

[Ink composition]
The ink composition of the present invention comprises at least one selected from the group consisting of (A) a thiol group, (i) a fluorine-substituted hydrocarbon group, ii) a siloxane skeleton, and (iii) a long-chain alkyl group in the side chain. A polymer containing a partial structure (hereinafter sometimes referred to as specific sites (i), (ii), and (iii), respectively), and (B) photopolymerization. It contains an initiator and (C) a polymerizable compound.

The ink composition of the present invention is an ink composition that can be cured by irradiation with radiation. Here, the “radiation” referred to in the present invention is not particularly limited as long as it can impart energy capable of generating an initial species in the composition by irradiation, and widely used as α-ray, γ-ray, X-rays, ultraviolet rays, visible rays, electron beams and the like are included. Among these, from the viewpoint 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 radiation. In addition, since the ink composition of the present invention contains the specific polymer, it has high sensitivity, and can be sufficiently cured by a light source with a low exposure amount such as a light emitting diode as an exposure light source. When applied, it can be said that the effect of the present invention is remarkable.
The ink composition of the present invention preferably contains a colorant in order to form an image by being cured by the radiation.

Hereinafter, each component contained in the ink composition of the present invention will be described in detail.
First, the specific polymer (A) which is a characteristic component of the present invention will be described.

The specific polymer (A) according to the present invention has at least one selected from the group consisting of a thiol group and (i) a fluorine-substituted hydrocarbon group, ii) a siloxane skeleton, and (iii) a long-chain alkyl group in the side chain. A partial structure.
Hereinafter, each component will be described.

<(A) Specific polymer>
-Thiol group-
The specific polymer (A) according to the present invention has a thiol group.
(A) The specific polymer may have a thiol group in the main chain of the polymer, or may have a thiol group in the side chain of the polymer.

  (A) The case of having a thiol group in the main chain of the specific polymer is a compound having a thiol group at the end of the main chain, and more preferably a compound having a structure represented by the following formula.

In the formula, each L independently represents a divalent linking group which may have a substituent. R ₁ , R ₂ , R ₃ , and R ₄ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Note that R ₁ and R ₂ , R ₃ and R ₄ may be connected to each other to form a ring structure having 3 to 8 carbon atoms that may include a plurality of heteroatoms. Each X independently represents a straight chain directly linked to the polymer main chain or a linking group having 2 to 12 branched structures. m and n are integers of 1-12.

From the viewpoint of synthesis such as the substitution position of the thiol group and the amount of the thiol group, it is a preferable embodiment that the (A) specific polymer has a thiol group in the side chain.
(A) Although there is no restriction | limiting in particular as a thiol group in the case of having a thiol group in the side chain of a specific polymer, The secondary / tertiary couple | bonded with the primary thiol, the secondary thiol, the tertiary thiol, and the heterocyclic ring Examples include thiol. Among these, from the viewpoint of reactivity and stability, secondary thiol or tertiary thiol is preferable, and secondary thiol is more preferable.

The number of thiol groups may be either monofunctional or polyfunctional when in the main chain, but from the viewpoint of curing sensitivity, (A) 1 to 12 in one polymer molecule is preferable, and 2 to 12 It is more preferable that it is 4-12.
The number of thiol groups is preferably 20 mol% or more and 80 mol% or less, more preferably 30 mol% or more and 80 mol% or less, based on the number of repeating units of the monomer, when it is in the side chain, Most preferably, it is 60 mol% or more and 80 mol% or less.

  Moreover, when it has a thiol group in the side chain of (A) specific polymer, it is more preferable that it is a compound which has a thiol group containing group represented by following structural formula.

In the above structural formulas, R ¹ and R ² each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Note by R ¹ and R ² are linked, it may form a ring structure of a plurality of carbon atoms which may contain a hetero atom 3-8. L represents a divalent linking group bonded to the polymer main chain.

The alkyl group having 1 to 6 carbon atoms represented by R ¹ and R ² has more preferably 1 to 4 carbon atoms, and still more preferably 1 to 2 carbon atoms. These alkyl groups may further have a substituent if possible. Examples of the substituent that can be introduced into the alkyl group include a halogen atom, a hydroxyl group, an alkoxy group, and an alkylphenyl group.

  Examples of the divalent linking group represented by L include an alkylene group having 1 to 12 carbon atoms, an alkyleneoxy group, an alkylphenylene group, a thioether group, an ester group, a thioester group, a phenylene group, and the like. Examples thereof include a linking group formed by bonding. Of these, an alkylene group having an ester bond is preferred.

In the above structural formula, a preferable combination of the substituents is that R ¹ is a hydrogen atom, R ² is a methyl group or an ethyl group, and L is an alkylene group having 6 or less carbon atoms including an ester group or an alkylphenylene group. is there. When R ¹ and R ² have a ring structure, cyclopentane, cyclohexane, benzene, pyridine, benzimidazole, thiazole, thiadiazole, quinoxaline, triazine, naphthalene, imidazole, oxazole, benzoxazole, and the like are preferable.

(A) As a method for introducing a thiol group into the main chain of the specific polymer, a method in which a polymer having a halogen atom at the terminal is reacted with a polyfunctional thiol compound can be mentioned.
(A) As a method for introducing a thiol group into a side chain of a specific polymer, a method in which a reactive functional group is introduced into a polymer having a side chain by a polymer reaction or a monomer in which a thiol group is protected by a protective group are used. A method of deprotecting after polymerization is mentioned.

(A) As for content of the thiol group in a specific polymer, 5 mol%-80 mol% are preferable, More preferably, they are 20 mol%-80 mol%, More preferably, they are 30 mol%-80 mol%. By setting it as the above range, the curability of the ink composition and the flexibility of the film are improved.
The content of thiol groups in the polymer can be measured by a method such as titration with a standard sodium thiosulfate solution after excess oxidation with iodine.

  The preferred molecular weight of the specific polymer is 3000 to 100,000 from the viewpoint of viscosity and curability, and the more preferred molecular weight is 10,000 to 80,000, most preferably 15,000 to 80,000.

-(I) Fluorine-substituted hydrocarbon group-
The fluorine-substituted hydrocarbon group as a specific site in the specific polymer according to the present invention may be a hydrocarbon group containing at least one fluorine in a side chain, for example, at least one hydrogen atom in an alkyl group or an alkylene group A fluoroalkyl group and a fluoroalkylene group substituted with a fluorine atom, a perfluoroalkyl group and a perfluoroalkylene group in which all hydrogens of the alkyl group and alkylene group are substituted with fluorine are more preferred, and a perfluoroalkyl group is further preferable.

As an alkyl group, C3-C12 is preferable, 4-10 are more preferable, and 6-8 are still more preferable.
As an alkylene group, C2-C12 is preferable, 4-10 are more preferable, and 6-8 are still more preferable.

Specific embodiments of the fluorine-substituted hydrocarbon group in the present invention will be described.
(A) Preferred fluorine-substituted hydrocarbon groups possessed by the specific polymer include those shown in the following (a) or (b).

(A) Substituents derived from fluoroaliphatic compounds produced by telomerization or oligomerization (also referred to as fluoroaliphatic groups)
(B) Substituents having a structure represented by the following (General Formula I)

In general formula I, R ² and R ³ are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, X is a covalent bond or a divalent linking group (organic group), and m is an integer of 0 or more. N represents an integer of 1 or more. When m is 2 or more, functional groups on adjacent carbons (that is, R ² and R ³ bonded to adjacent carbons) may be bonded to form an aliphatic ring. .
The substituent represented by (general formula I) is connected to the main chain of the polymer at the portion *.

(A) Substituents derived from fluoroaliphatic compounds produced by telomerization or oligomerization methods Such (i) substituents in the present invention are telomerization methods (also referred to as telomer methods) or A group derived from a fluoroaliphatic compound produced by an oligomerization method (also referred to as an oligomer method) is preferable. Regarding the method for producing the above fluoroaliphatic compound, for example, “Synthesis and Function of Fluorine Compound” (Supervision: Nobuo Ishikawa, Issue: CMC Co., 1987), “Chemistry of Organic Fluorine Compounds II” (Monograph 187, Ed by Milos Hudlicky and Attila E. Pavlath, American Chemical Society 1995), pages 747-752.

  The telomerization method is a method of synthesizing a telomer by radical polymerization of a fluorine-containing vinyl compound such as tetrafluoroethylene using an alkyl halide having a large chain transfer constant such as iodide as a telogen. As a specific example, Synthesis Example 1 below is shown.

  The obtained terminal iodinated telomer is usually subjected to appropriate terminal chemical modification as in, for example, Synthesis Example 2 below, and led to a fluoroaliphatic compound. These compounds are further converted into a desired monomer structure as necessary, and used for the production of a fluoroaliphatic group-containing polymer.

  As a monomer synthesize | combined by the said telomer method, the monomer represented by the following general formula [TM-1] is preferable, and such a monomer can be introduce | transduced into the specific polymer of this invention.

  In the above general formula [TM-1], T is one group selected from the following (Group T), Z is one group selected from the following (Group Z), and n is an integer of 0 to 20. And can be copolymerized with the specific polymer of the present invention by a double bond in Z.

  In the above general formula [TM-1], the compound represented by Z is a group selected from the following (Z ′ group) has an acryloyl group or a methacryloyl group at the molecular end. In particular, a polymer having a group derived from the above-described fluoroaliphatic compound in the side chain (that is, the fluorine-based polymer in the present invention) can be easily obtained by vinyl polymerization.

  Specific examples of the compound produced by the telomer method suitable as a compound led to the side chain of the specific polymer in the present invention (compound mainly composed of the monomer represented by the above general formula [TM-1]) For example, fluorine chemical products A-1110, A-1210, A-1310, A-1420, A-1620, A-1820, A-2020, A-1260 sold by Daikin Chemicals Sales Co., Ltd. , A-1460, A-1660, A-1860, A-1435, A-1635, A-1835, A-1473, A-1637, A-1837, A-1514, A-3420, A-3620, A -3820, A-4020, A-3260, A-3460, A-3660, A-3860, A-3737, A-3737, A-5210, A-5410 A-5610, A-5810, A-7110, A-7210, A-7310, A-9221, C-1100, C-1200, C-1300, C-1400, C-1500, C-1600, C- 1700, C-1800, C-1900, C-2000, C-5200, C-5400, C-5600, C-5800, C-5208, C-5408, C-5608, C-6008, C-8200, C-8300, C-8500, C-9221, C-8208, C-8308, C-8508, C-9216, E-1430, E-1630, E-1830, E-2030, E-3430, E- 3630, E-3830, E-4030, E-5244, E-5444, E-5644, E-5844, F-1420, F-1620, F-1820, F-2 20, I-1200, I-1300, I-1400, I-1600, I-1700, I-1800, I-2000, I-1420, I-1620, I-1820, I-2020, I-3200, I-3400, I-3600, I-3800, I-4000, I-3620, I-3820, I-4020, I-5200, I-5400, I-5600, I-8208, I-8207, I- 8407, I-8607, M-1110, M-1210, M-1420, M-1620, M-1820, M-2020, M-3420, M-3620, M-3820, M-4020, M-3433 M-3633, M-3833, M-4033, M-5210, M-5410, M-5610, M-5810, M-6010, M-7210, M-7310, R -1110, R-1210, R-1420, R-1620, R-1820, R-2020, R-1433, R-1633, R-1833, R-3420, R-3620, R-3820, R-4020 , R-3433, R-5210, R-5410, R-5610, R-5810, 6010, R-7210, R-7310, U-1310, U-1710, and also manufactured by Nippon Mektron Co., Ltd. CHEMINOX FA, FA-M, FAAC, FAAC-M, FAMAC, FAMAC-M and the like.

  The compound produced by the telomer method can be easily led to a polymer having a fluoroaliphatic group in the side chain by a method known to those skilled in the art.

  In the present invention, a fluoroaliphatic compound produced by an oligomerization method (oligomer method) is also preferred. The oligomerization method is a method for producing an oligomer by cationic polymerization of tetrafluoroethylene in a polar solvent such as diglyme using potassium fluoride or cesium fluoride as a catalyst. As a specific example, Synthesis Example 3 below is shown. The fluoroaliphatic compound obtained by the oligomer method, like the compound by the telomer method described above, uses a reactive group (unsaturated bond) in the oligomer obtained by polymerization and undergoes appropriate chemical modification, and then the fluoroaliphatic compound. A polymer derived from a compound can be led to a polymer having a side chain (that is, a fluorine-based polymer in the present invention).

(B) Substituent having the structure represented by (General Formula I) In the present invention, it is preferable to have a polymerizable group having the following structure (General Formula I) from the viewpoint of uneven distribution on the ink surface. .

In the general formula I, R ² and R ³ are each a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, * is a linking site to a polymer chain, X is a covalent bond or a divalent linking group ( Organic group), m represents an integer of 0 or more, and n represents an integer of 1 or more. When m is 2 or more, functional groups on adjacent carbons (that is, R ² and R ³ bonded to adjacent carbons) may be bonded to form an aliphatic ring. .

  Among the fluorine-based specific substituents i-1 in the present invention having the structure represented by the above (General Formula I), those in which “n” in (General Formula I) is 1 to 10 are preferable. More preferably, it is -4, and it is especially preferable that it is 2,3.

  That is, as the fluoropolymer in the present invention, the structure of the side chain portion bonded to the polymer chain is a structure represented by the following (general formula IB), and particularly, n = 2, 3 is extremely good. We found that both performance and safety are compatible.

((Formula IB) in, ^{R 2} and ^R 3, X, m, n have the same meanings as ^{R 2} and ^R 3, X, m, n in either (formula I))

Examples of the alkyl group having 1 to 4 carbon atoms represented by R ² and R ³ in (General Formula I) and (General Formula IB) include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, isobutyl, tert- butyl group and the like, preferably a hydrogen atom R ² and R ^3, a methyl group, more preferably a hydrogen atom.

In (General Formula I) and (General Formula IB), the covalent bond represented by X represents a case where it is directly bonded to the polymer main chain. As the divalent linking group (organic group), -O -, - S - , - N (R 4) -, - CO- , and the like. Among these, -O- is more preferable.

R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. R ⁴ is preferably a hydrogen atom or a methyl group.

  m represents an integer of 0 or more, an integer of 2 to 8 is preferable, and m = 2 is particularly preferable. When m is 2 or more, functional groups on adjacent carbons may be bonded to form an aliphatic ring.

  n represents an integer of 1 or more, and an integer of 1 to 10 is preferable. Here, n is particularly preferably 1 to 4, and n is preferably 2 or 3 in the fluoropolymer in the present invention.

In (General Formula I), * represents a linking site with a polymer chain, and examples of the polymer chain include the following.
Specific forms include acrylic resin, methacrylic resin, styryl resin, polyester resin, polyurethane resin, polycarbonate resin, polyamide resin, polyacetal resin, phenol / formaldehyde condensation resin, polyvinylphenol resin, maleic anhydride / α-olefin resin. , Α-hetero-substituted methacrylic resin and the like can be used. Among these, acrylic resins, methacrylic resins, styryl resins, polyester resins, and polyurethane resins are useful, and acrylic resins, methacrylic resins, and polyurethane resins are particularly useful.

  The specific polymer having (i) a fluorine-substituted hydrocarbon group in the present invention includes, for example, (a) a monomer having a fluoroaliphatic group, and (b) a substituent having a configuration represented by (General Formula I). It can be easily obtained by a method known to those skilled in the art, such as condensation polymerization, addition polymerization, and ring-opening polymerization. Moreover, it can manufacture by further mixing these monomers as needed, or mixing the polymer after superposition | polymerization.

(Fluorine group-containing monomer having a polymerizable group)
In this invention, it can copolymerize with the specific polymer of this invention using the monomer which has a substituent and a polymeric group as described in said (a) or (b).
Preferred examples of the monomer having a substituent and a polymerizable group described in (a) or (b) include monomers represented by the following (General Formula II).

In (General Formula II), R ¹ represents a hydrogen atom, a halogen atom, a methyl group which may have a substituent, or an ethyl group which may have a substituent. Also, ^{R 2} and ^R 3, X, m, n have the same meanings as ^{R 2} and ^R 3, X, m, n in either (Formula IB).

In addition, examples of the halogen atom represented by R ¹ in (General Formula II) include a fluorine atom, a chlorine atom, and a bromine atom.

  Next, specific examples of the monomer represented by (General Formula II) used in the present invention are shown below.

  As the monomer used for the production of the specific polymer (fluorinated polymer) in the present invention, among the monomers represented by the above (General Formula II), “n” in (General Formula II) is preferably 1 to 10 1 to 4 is more preferable, and 2, 3 is particularly preferable.

-(Ii) Siloxane skeleton-
The (ii) siloxane skeleton that is a specific site in the specific polymer contained in the ink composition of the present invention can be used without particular limitation as long as it has a siloxane skeleton in the molecule.
The siloxane skeleton is a compound represented by the following structural formula (A) (hereinafter referred to as “specific”) from the viewpoint of increasing the ejection stability of the ink composition and increasing the surface segregation when the ink composition is used as a coating film. It is preferably a polysiloxane obtained by polymerizing a “siloxane compound”. In the structural formula (A), R ¹ is introduced as a linking group with a Si atom of a siloxane bond.

In the structural formula (A), R ¹ represents a linear or branched alkylene group having 2 to 6 carbon atoms or a divalent linking group represented by the following structural formula (B).

In the structural formula (B), R ² represents a hydrogen atom or a methyl group, and n represents an integer of 1 to 50.

In the structural formula (A), x ¹ , x ² and x ³ are integers in which the sum of x ¹ , x ² and x ³ is 1 to 100, respectively. y ¹ is an integer of 1 to 10.
In the structural formula (A), X may not be present. In some cases, it is a divalent group represented by the following structural formula C.

In the structural formula (C), Z ¹ represents an oxygen atom, a sulfur atom or NR ⁴ , and R ⁴ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.
In the structural formula (C), Z ¹ is bonded to R ¹ in the structural formula (A).
In the structural formula (C), R ³ represents a divalent group having 6 to 10 carbon atoms including an aliphatic or alicyclic diisocyanate structure.

  In the structural formula (A), Y represents a monovalent group represented by the following structural formula (D) to the following structural formula (F).

In the structural formulas (D) to (F), R ⁵ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms, and R ⁶ represents a linear or branched chain. Represents an alkylene group having 2 to 10 carbon atoms, and R ⁷ represents a linear or branched alkylene group having 1 to 6 carbon atoms.

  In the structural formula (A), Z represents a monovalent group represented by the following structure.

The above structures, ^{z 1} represents an integer of 3 to 100, preferably 5 to 50, more preferably an integer of 7-20.

-(Iii) Long chain alkyl group-
The (iii) long-chain alkyl group, which is a specific site in the specific polymer contained in the ink composition of the present invention, is a substituent represented by -C _n H _{2n + 1} in the following general formula (1). It is preferably introduced into the polymer in the form shown in (I).

In formula (1), n represents an integer of 6 to 40, preferably 10 to 30, and more preferably 12 to 20 from the viewpoint of surface segregation.
Y represents a trivalent linking group, and a long-chain alkyl group can be bonded to the polymer side chain via this linking group.
What is preferable as such a structural unit represented by the general formula (1) is shown in the following general formula (1-2), but the present invention is not limited thereto.

In general formula (1-2), n represents an integer of 6 to 40. W represents a divalent linking group, and Z ¹ , Z ² , and Z ³ each independently represent a hydrogen atom or a monovalent organic group.
In addition, a plurality of such long-chain alkyl groups may be included in the structural unit. In that case, an aspect in which the long-chain alkyl group is bonded to the position of Z ¹ or Z ³ via the linking group W, The connecting group W has a branched structure, and another long chain alkyl group is connected to the tip of the connecting group W.
As the above W, linear or branched alkylene having 1 to 20 carbon atoms, chain or cyclic alkylene, linear or branched chain having 2 to 20 carbon atoms, chain or cyclic alkenylene, alkynyl group having 2 to 20 carbon atoms, Arylene (monocyclic, heterocyclic) having 6 to 20 carbon atoms, -OC (= O)-, -OC (= O) Ar-, -OC (= O) O-, -OC (= O) OAr-, -C (= O) NR -, - C (= O) NAr -, - SO 2 NR -, - SO 2 NAr -, - O- ( alkyleneoxy, polyalkyleneoxy), - OAr- aryleneoxy, polyarylene Oxy), —C (═O) O—, —C (═O) O—Ar—, —C (═O) Ar—, —C (═O) —, —SO ₂ O—, —SO ₂ OAr _{-, - OSO 2 -, -} OSO 2 Ar -, - NRSO 2 -, - NArSO 2 -, - NR C (= O)-, -NArC (= O)-, -NRC (= O) O-, -NArC (= O) O-, -OC (= O) NR-, -OC (= O) NAr- , -NAr-, -NR-, -N + RR'-, -N + RAr-, -N + ArAr'-, -S-, -SAr-, -ArS-, a heterocyclic group (including heteroatoms such as nitrogen, oxygen and sulfur) At least one or the like, a 3- to 12-membered monocyclic or condensed ring), —OC (═S) —, —OC (═S) Ar—, —C (═S) O—, —C ( = S) OAr-, -C (= S) OAr-, -C (= O) S-, -C (= O) SAr-, -ArC (= O)-, -ArC (= O) NR-, -ArC (= O) NAr-, -ArC (= O) O-, -ArC (= O) O-, -ArC (= O) S-, -ArC (= S) O-, -ArO-, ArNR-, and the like.
R and R ′ are a hydrogen atom, a linear or branched alkyl group, a chain or cyclic alkyl group, a linear or branched alkenyl group, a chain or cyclic alkenyl group, a linear or branched alkynyl. Represents a group, a chain or cyclic alkynyl group, and Ar and Ar ′ represent an aryl group.

  Among these linking groups, arylene having 6 to 20 carbon atoms (monocyclic, heterocyclic), -C (= O) NR-, -C (= O) NAr-, -O- (alkyleneoxy, polyalkyleneoxy) ), -OAr- (aryleneoxy, polyaryleneoxy), -C (= O) O-, -C (= O) O-Ar-, -C (= O)-, -C (= O) Ar- , -S-, -SAr-, -ArS-, -ArC (= O)-, -ArC (= O) O-, -ArC (= O) O-, -ArO-, -ArNR- and the like are preferable. Arylene (monocyclic, heterocyclic) having 6 to 20 carbon atoms, —C (═O) NR—, —C (═O) NAr—, —O— (alkyleneoxy, polyalkyleneoxy), —OAr— (arylene) Oxy, polyaryleneoxy), -C (= O) O-, -C (= O) O-Ar-, -SAr , -ArS -, - ArC (= O) -, - ArC (= O) O -, - ArC (= O) O -, - ArO -, - ArNR- are more preferable.

  In the present invention, the linking group represented by W may be a combination of two or more of the linking groups listed here.

In general formula (1-2), each of Z ¹ , Z ² and Z ³ is independently a hydrogen atom, a linear or branched, linear or cyclic alkyl group having 1 to 20 carbon atoms (for example, methyl, ethyl Propyl, heptafluoropropyl, isopropyl, butyl, t-butyl, t-pentyl, cyclopentyl, cyclohexyl, octyl, 2-ethylhexyl, dodecyl, etc.), linear or branched, linear or cyclic alkenyl having 2 to 20 carbon atoms A group (eg, vinyl, 1-methylvinyl, cyclohexen-1-yl, etc.), an alkynyl group having 2-20 carbon atoms (eg, ethynyl, 1-propynyl, etc.), an aryl group having 6-20 carbon atoms (eg, phenyl, Naphthyl, anthryl, etc.), C1-C20 acyloxy groups (for example, acetoxy, tetradecanoyloxy, benzoyl) ), C2-C20 alkoxycarbonyloxy groups (e.g., methoxycarbonyloxy group, 2-methoxyethoxycarbonyloxy group, etc.), C7-C20 aryloxycarbonyloxy groups (e.g., phenoxycarbonyloxy group, etc.) ), A carbamoyloxy group having 1 to 20 carbon atoms (for example, N, N-dimethylcarbamoyloxy and the like), a carbonamido group having 1 to 20 carbon atoms (for example, formamide, N-methylacetamide, acetamide, N-methylformamide, Benzamide, etc.), C1-C20 sulfonamido groups (for example, methanesulfonamide, dodecanesulfonamide, benzenesulfonamide, p-toluenesulfonamide, etc.), C1-C20 carbamoyl groups (for example, N- Methylcarbamoyl, N, N -Diethylcarbamoyl, N-mesylcarbamoyl, etc.), C0-20 sulfamoyl group (for example, N-butylsulfamoyl, N, N-diethylsulfamoyl, N-methyl-N- (4-methoxyphenyl) Sulfamoyl etc.), C1-C20 alkoxy groups (for example, methoxy, propoxy, isopropoxy, octyloxy, t-octyloxy, dodecyloxy, 2- (2,4-di-t-pentylphenoxy) ethoxy, poly Alkyleneoxy, etc.), aryloxy groups having 6 to 20 carbon atoms (for example, phenoxy, 4-methoxyphenoxy, naphthoxy, etc.), aryloxycarbonyl groups having 7 to 20 carbon atoms (for example, phenoxycarbonyl, naphthoxycarbonyl, etc.),

C2-C20 alkoxycarbonyl group (for example, methoxycarbonyl, t-butoxycarbonyl, etc.), C1-C20 N-acylsulfamoyl group (for example, N-tetradecanoylsulfamoyl, N-benzoyl) Sulfamoyl and the like), an N-sulfamoylcarbamoyl group having 1 to 20 carbon atoms (eg, N-methanesulfonylcarbamoyl group), an alkylsulfonyl group having 1 to 20 carbon atoms (eg, methanesulfonyl, octylsulfonyl, 2- Methoxyethylsulfonyl, 2-hexyldecylsulfonyl, etc.), C6-C20 arylsulfonyl groups (e.g., benzenesulfonyl, p-toluenesulfonyl, 4-phenylsulfonylphenylsulfonyl, etc.), C2-C20 alkoxycarbonylamino Groups (eg ethoxycal Nylamino, etc.), C7-20 aryloxycarbonylamino groups (eg, phenoxycarbonylamino, naphthoxycarbonylamino, etc.), C0-20 amino groups (eg, amino, methylamino, diethylamino, diisopropylamino, anilino) , Morpholino, etc.), an ammonio group having 3 to 20 carbon atoms (for example, trimethylammonio group, dimethylbenzylammonio group, etc.), cyano group, nitro group, carboxyl group, hydroxy group, sulfo group, mercapto group, carbon number 1 -20 alkylsulfinyl groups (for example, methanesulfinyl, octanesulphinyl, etc.), arylsulfinyl groups having 6-20 carbon atoms (for example, benzenesulfinyl, 4-chlorophenylsulfinyl, p-toluenesulfinyl, etc.), C1-20 An alkylthio group (for example, methylthio, octylthio, cyclohexylthio, etc.), an arylthio group having 6-20 carbon atoms (for example, phenylthio, naphthylthio, etc.), a ureido group having 1-20 carbon atoms (for example, 3-methylureido, 3, 3 -Dimethylureido, 1,3-diphenylureido, etc.), a C2-C20 heterocyclic group (the hetero atom includes, for example, at least one nitrogen, oxygen, sulfur and the like, a 3- to 12-membered monocyclic ring) A condensed ring such as 2-furyl, 2-pyranyl, 2-pyridyl, 2-thienyl, 2-imidazolyl, morpholino, 2-quinolyl, 2-benzimidazolyl, 2-benzothiazolyl, 2-benzoxazolyl, etc.) , C1-20 acyl group (for example, acetyl, benzoyl, trifluoroacetyl, etc.), carbon number 0-20 sulfamoylamino groups (for example, N-butylsulfamoylamino, N-phenylsulfamoylamino, etc.), silyl groups having 3-50 carbon atoms (for example, trimethylsilyl, dimethyl-t-butylsilyl, trimethyl) Phenylsilyl, etc.), azo groups, and halogen atoms (for example, fluorine atom, chlorine atom, bromine atom, etc.).
In addition, when Z ^{1 to} Z ³ are other than a hydrogen atom or a halogen atom, these may further have a substituent, and examples of the substituent include the substituents mentioned in the above specific examples. It is done.

As the ^Z 1 to Z ^3, a hydrogen atom, a linear or branched, chain or cyclic alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an acyloxy group having 1 to 20 carbon atoms, carbon Carbon number group having 1 to 20 carbon atoms, alkoxy group having 1 to 20 carbon atoms, aryloxy group having 6 to 20 carbon atoms, aryloxycarbonyl group having 7 to 20 carbon atoms, alkoxycarbonyl group having 2 to 20 carbon atoms, carbon An amino group having 0 to 20 amino acids, a cyano group, a hydroxy group, or a halogen atom is preferable, a hydrogen atom, a linear or branched alkyl group having 1 to 20 carbon atoms, a chain or cyclic alkyl group, an aryl group having 6 to 20 carbon atoms, C1-C20 acyloxy group, C1-C20 alkoxy group, C6-C20 aryloxy group, C7-C20 aryloxycarbonyl group, C2-C20 Alkoxycarbonyl group, an amino group having 0 to 20 carbon atoms, a cyano group, a halogen atom is more preferable.

  The structural unit represented by the general formula (1-2) is preferably a structural unit represented by the following general formula (1-3) from the viewpoint of segregation on the ink surface.

In General Formula (1-3), n represents an integer of 6 to 40, and R represents a hydrogen atom or a methyl group.
W is synonymous with what was quoted by the said general formula (1-2). Specific examples of such a divalent substituent represented by W are shown below in particular from the viewpoint of segregation on the ink surface, but the present invention is not limited thereto.

Z ¹ has the same meaning as those described by the general formula (1-2). Specific examples of such monovalent organic groups represented by Z ¹ are shown below from the viewpoint of stable solubility in the ink composition, but the present invention is not limited thereto.

  Here, although the specific example of the structural unit which has a long-chain alkyl group in this invention is given below, this invention is not limited to these.

  In the present invention, the content in the specific polymer of at least one partial structure (specific site) selected from the group consisting of (i) a fluorine-substituted hydrocarbon group, (ii) a siloxane skeleton, and (iii) a long-chain alkyl group is 3 mass% to 50 mass%, respectively, more preferably 3 mass% to 40 mass%, still more preferably 5 mass% to 30 mass%. By setting it as the said range, this polymer which has a specific part can be surface-segregated efficiently in an ink composition.

-Polymerizable group-
The (A) specific polymer may further contain a polymerizable group. By containing a polymerizable group, the curability of the ink composition is further improved, the surface stickiness is further suppressed, and the blocking property is further improved.

The polymerizable group contained in the (A) specific polymer is preferably a radical polymerizable group.
The number of polymerizable groups introduced at the end of the (A) specific polymer is preferably 2 or more, more preferably 4 or more, and still more preferably 8 or more.

  Examples of the radical polymerizable group include a polymerizable group having an ethylenically unsaturated bond capable of radical polymerization, and any substituent having at least one ethylenically unsaturated bond capable of radical polymerization in the polymer side chain may be used. It may be anything. Examples of polymerizable groups having an ethylenically unsaturated bond capable of radical polymerization include acrylic acid ester groups, methacrylic acid ester groups, itaconic acid ester groups, crotonic acid ester groups, isocrotonic acid ester groups, and maleic acid ester groups. Examples thereof include radically polymerizable groups such as unsaturated carboxylic acid ester groups and styrene groups. Among these, a methacrylic acid ester group and an acrylic acid ester group are preferable.

  As a method for introducing a radically polymerizable group into a specific polymer, a method in which a double bond of a radically polymerizable group is sealed with a protecting group, copolymerized, and the protecting group is removed to form a double bond. And a method of introducing a low molecular compound having a radical polymerizable group into a specific polymer by a polymer reaction.

  In the specific polymer (A), the content of the structural unit having a polymerizable group is preferably 5 mol% to 90 mol%, more preferably 10 mol% to 60 mol%, from the viewpoint of blocking suppression performance and flexibility maintenance. Yes, more preferably 15 mol% to 60 mol%.

  A preferred embodiment as the main chain structure of the (A) specific polymer contained in the ink composition of the present invention is a methacrylic resin or an acrylic resin.

  Hereinafter, specific examples of the (A) specific polymer of the present invention having a thiol group and at least one partial structure selected from a fluorine-substituted hydrocarbon group, a siloxane skeleton, and a long-chain alkyl group in the side chain will be given. . The present invention is not limited to these specific examples.

  The weight average molecular weight of the specific polymer (A) in the present invention is 3000 to 100,000, preferably 5,000 to 80,000, more preferably 10,000, from the viewpoints of dischargeability, sensitivity, and viscosity. ~ 70,000.

The ink composition of the present invention may contain only one type of the specific polymer (A) or two or more types.
The content of the (A) specific polymer contained in the ink composition of the present invention is preferably 0.2 to 5% by mass, more preferably 0.2 to 3% by mass, based on the total solid content of the ink composition. More preferably, it is 2 to 1.5% by mass.
By setting it as the said range, it is excellent in surface curability and blocking suppression, and the surface tension (22 mN / m-28 mN / m) and moderate viscosity which can be discharged are obtained.

<(B) Photopolymerization initiator>
The ink composition of the present invention contains (B) a photopolymerization initiator.
(B) As a photoinitiator, a well-known polymerization initiator can be suitably selected and used according to the kind of polymerizable compound used together, and the intended purpose of the ink composition.
The (B) photopolymerization initiator used in the ink composition of the present invention is a compound that absorbs external energy (light) and generates a polymerization initiating species. Examples of light include actinic radiation, that is, γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.

(B) Although a well-known compound can be used for a photoinitiator, as a preferable (B) photoinitiator which can be used by this invention, (a) aromatic ketones, (b) acyl phosphine oxide compound, (c) Aromatic onium salt compound, (d) organic peroxide, (e) thio compound, (f) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, ( j) metallocene compounds, (k) active ester compounds, (l) compounds having a carbon halogen bond, and (m) alkylamine compounds.
In the present invention, the (B) photopolymerization initiator may be used alone or in combination. From the viewpoint of the effect, it is preferable to use two or more kinds of (B) photoinitiators in combination.

  Specific examples of the (B) photopolymerization initiator used in the present invention include, for example, benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, bis (2,4,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, 1 , 2-octanedione, 1- (4- (phenylthio) -2,2- (O-benzoyloxime)) and the like. Further, other molecular cleavage initiators include 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1- (4-isopropyl Phenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, and the like may be used in combination. Further, hydrogen abstraction type photoinitiators such as benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4′-methyl-diphenyl sulfide and the like can be used in combination.

  The content of the (B) photopolymerization initiator in the present invention is preferably in the range of 1% by mass to 50% by mass with respect to the total solid content of the ink composition of the present invention, and in the range of 2% by mass to 40% by mass. Is more preferable, and the range of 5% by mass to 35% by mass is still more preferable.

<(C) Polymerizable compound>
The ink composition of the present invention contains (C) a polymerizable compound. (C) The polymerizable compound is a radical polymerizable compound.

  The radical polymerizable compound applicable to the present invention is a compound having an ethylenically unsaturated bond capable of radical polymerization and any compound having at least one ethylenically unsaturated bond capable of radical polymerization in the molecule. Such a thing may be sufficient, and what has chemical forms, such as a monomer, an oligomer, and a polymer, is contained. 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 the polymerizable compound 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, Examples thereof include radically polymerizable compounds such as anhydrides having a saturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes.

  Specifically, 2-hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, tridecyl acrylate, 2-phenoxyethyl acrylate, bis (4-acryloxypolyethoxyphenyl) Propane, polyethylene glycol diacrylate, polypropylene glycol diacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, oligoester acrylate, N-methylolacrylamide, diacetone acrylamide, epoxy acrylate, isobornyl acrylate, dicyclopentenyl acrylate, Dicyclopentenyloxyethyl acrylate, Acrylic acid derivatives such as cyclopentanyl acrylate; methyl methacrylate, n-butyl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2-bis (4- Methacryl derivatives such as methacryloxypolyethoxyphenyl) propane; and other derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, and triallyl trimellitate. More specifically, Shinzo Yamashita, “Crosslinker Handbook”, (1981 Taiseisha); Kato Kiyosumi, “UV / EB Curing Handbook (Materials)” (1985, Polymer Publications); Radtech Study Group, “Application and Market of UV / EB Curing Technology”, p. 79, (1989, CMC); Eiichiro Takiyama, “Polyester Resin Handbook”, (1988, Nikkan Kogyo Shimbun) Commercially available products or radically polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used.

  Among these acrylates and methacrylates, alcohol acrylates having an ether oxygen atom such as tetrahydrofurfuryl acrylate and 2-phenoxyethyl acrylate are preferable from the viewpoints of curability and film properties after curing. For the same reason, an acrylate of an alcohol having an alicyclic structure is also preferable, and a bicyclo ring structure or a tricyclo ring structure such as isobornyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, dicyclopentanyl acrylate, etc. Specific examples of preferable acrylates include dicyclopentenyl acrylate and dicyclopentenyloxyethyl acrylate having a double bond in the alicyclic structure.

  Examples of the radically polymerizable compound include JP-A-7-159983, JP-B-7-31399, JP-A-8-224982, JP-A-10-863, JP-A-9-134011, and JP-T-2004. Photo-curable polymerizable compounds used in the photopolymerizable compositions described in each publication such as JP-A-514014 are known, and these can also be applied to the ink composition of the present invention.

Furthermore, it is 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, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, hydroxyethyl monovinyl ether, hydroxynonyl monovinyl ether, trimethylolpropane trivinyl ether; ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octade Monovinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O-propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, etc. Examples include vinyl ether compounds.
Commercially available products such as Rapi-Cure DVE-3 and Rapi-Cure DVE-2 (both manufactured by ISP Europe) can be used as the vinyl ether compound.

  Of these vinyl ether compounds, divinyl ether compounds and trivinyl ether compounds are preferable from the viewpoints of curability, adhesiveness, 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 include (meth) acrylic monomers or prepolymers, (meth) acrylic acid esters such as epoxy monomers or prepolymers, urethane monomers or prepolymers (hereinafter referred to as acrylate compounds as appropriate). .) May be used, and the compounds shown below are listed as compound examples.

  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, modified bisphenol A diacrylate, phenoxy-poly Tylene glycol acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, PO adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer Lactone-modified flexible 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 triacrylate hexamethyl Nji diisocyanate urethane prepolymer, stearyl acrylate, isoamyl acrylate, isomyristyl acrylate, isostearyl acrylate, lactone-modified acrylate, and the like.

These acrylate compounds are polymerizable compounds that have been used in UV curable inks, have low skin irritation and sensitization (ease of rashes), and have relatively low viscosity and stable ink ejection properties. It is preferable because the sensitivity and adhesiveness with the recording medium are good.
The monomers listed here as other polymerizable compounds are low in sensitization even with a low molecular weight, have 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, as other polymerizable compound components, monoacrylate and a polyfunctional acrylate monomer or polyfunctional acrylate oligomer having a molecular weight of 400 or more, preferably 500 or more are used. It is a preferable aspect to use together.

  In particular, in an ink composition used for recording on a flexible recording medium such as a PET film or a PP film, a monoacrylate selected from the above compound group, and one kind selected from the above-mentioned specific heterocyclic compound, The combined use with a polyfunctional acrylate monomer or polyfunctional acrylate oligomer selected from other polymerizable compounds is preferable because the film strength can be increased while the film is made flexible to enhance the adhesion.

  In addition, the embodiment in which at least three kinds of polymerizable compounds of monofunctional, bifunctional, and trifunctional or higher polyfunctional monomers are used in combination improves sensitivity, bleeding, and adhesiveness to the recording medium while maintaining safety. From the viewpoint that it can be further improved, it is mentioned as a preferred embodiment.

  As monoacrylate, stearyl acrylate, isoamyl acrylate, isomystil acrylate, and isostearyl acrylate have high sensitivity and low shrinkage and can prevent curling, and are preferable in terms of prevention of bleeding, odor of printed matter, and cost reduction of irradiation device. .

As the oligomer that can be used in combination with the monoacrylate, an epoxy acrylate oligomer and a urethane acrylate oligomer are particularly preferable.
In addition, methacrylate has better skin irritation than acrylate.
Among the above compounds, when alkoxy acrylate is used in an amount of 70% by mass or less and the balance is acrylate, it is preferable because it has good sensitivity, bleeding characteristics, and odor characteristics.

  The radically polymerizable compound used in the present invention is preferably a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule from the viewpoint of curing speed, flexibility after curing, and adhesion to a recording medium. It is preferably at least one selected from (meth) acrylates containing atoms or N-vinyl lactams.

  The compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule that can be used in the present invention includes "an amide group or lactam ring in the molecule, and the nitrogen atom of the amide group or lactam ring is a vinyl group. And compounds selected from “N-vinylamides having a structure substituted by”, “compounds having an amide group in the molecule”, and “(meth) acrylates having a tertiary amine structure in the molecule”.

  As the compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule, from the viewpoint of physical properties of the cured film after curing and adhesion between the cured film and the recording medium, the nitrogen atom of the amide group or lactam ring is vinyl. N-vinylamides having a structure substituted with a group are preferred. Among N-vinylamides, N-vinyllactams having a structure in which a nitrogen atom of a lactam ring is substituted with a vinyl group are more preferable from the viewpoint of safety and availability.

  When the compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule is an N-vinyl lactam, the N-vinyl lactam has a number of lactam rings which is determined by the stability of the compound and the ink composition. From the viewpoint of solubility, availability, etc., it is preferably 5-7. Specifically, such N-vinyl lactams are preferably N-vinyl pyrrolidone having a 5-membered ring structure or N-vinyl caprolactam having a 7-membered ring structure, and particularly preferably N-vinyl caprolactam.

  Other examples of N-vinylamides that can be used as compounds having a nitrogen atom and a polymerizable unsaturated bond in the molecule include N-vinylacetamide, N-vinylformamide, N-methyl-N-vinylacetamide, N -Methyl-N-vinylformamide and the like.

  On the other hand, as a (meth) acrylate having a tertiary amine structure in the molecule that can be used as a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule, for example, 1,2,2,6,6-pentamethyl- Preferred examples include 4-methacryloxypiperidine (FA-711MM manufactured by Hitachi Chemical Co., Ltd.) and amine-modified acrylates (for example, CN2100, CN501, CN550, CN551 manufactured by Sartomer).

  Examples of the compound having an amide group in the molecule that can be used as a compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule include 4-acryloylmorpholine, diacetone acrylamide, and diisopropyl acrylamide.

  In the ink composition of the present invention, the content of the compound having a nitrogen atom and a polymerizable unsaturated bond in the molecule depends on the curing speed, the adhesion between the cured film and the recording medium, and the film of the cured film after curing. From the viewpoint of physical properties, the range is preferably 1% by mass to 35% by mass, more preferably 3% by mass to 30% by mass, and more preferably 5% by mass to 26% by mass with respect to the mass of the entire ink composition. The range of is more preferable.

  The radically polymerizable compound in the ink composition of the present invention is 60% by mass to 60% by mass in the total solid content of the ink composition from the viewpoints of curing speed, adhesion of the cured film to the recording medium, and film physical properties after curing. The range is preferably 90% by mass, more preferably 65% by mass to 90% by mass, and still more preferably 70% by mass to 85% by mass. In order to maintain the flexibility of the coating film, the addition amount of the polyfunctional monomer is 0 to 20% by mass, more preferably 0 to 10% by mass, and most preferably 0 to 5% by mass in the total solid content of the ink composition. is there.

<Colorant>
The ink composition of the present invention can form a visible image by adding a colorant. For example, when forming an image area of a lithographic printing plate, it is not always necessary to add it, but it is also preferable to use a colorant from the viewpoint of plate inspection of the obtained lithographic printing plate.
There is no restriction | limiting in particular in the coloring agent which can be used here, According to a use, well-known various color materials and (pigment, dye) can be selected suitably, and can be used. For example, when forming an image excellent in weather resistance, a pigment is preferable. As the dye, both water-soluble dyes and oil-soluble dyes can be used, but oil-soluble dyes are preferred.

(Pigment)
The pigment preferably used in the present invention will be described.
The pigment is not particularly limited, and all commercially available organic and inorganic pigments or pigments dispersed in an insoluble resin or the like as a dispersion medium, or the resin is grafted onto the pigment surface Can be used. Moreover, what dye | stained the resin particle with dye can be used.
Examples of these pigments include, for example, “Pigment Dictionary” (2000), edited by Seijiro Ito. Herbst, K.M. Hunger “Industrial Organic Pigments”, JP 2002-12607 A, JP 2002-188025 A, JP 2003-26978 A, and JP 2003-342503 A3.

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as C.I. Pigment Yellow 17; I. Non-benzidine type azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. And metal complex salt azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow, etc.).

  C. As a thing which exhibits red or magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G 'lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).

  As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Phthalocyanine pigments such as C.I. Pigment Blue 15 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

As a pigment exhibiting green, C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. And azo metal complex pigments such as CI Pigment Green 8 (Nitroso Green).
As a pigment exhibiting an orange color, C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. And anthraquinone pigments such as CI Pigment Orange 51 (dichloropyrantron orange).

Examples of the black pigment include carbon black, titanium black, and aniline black.
Specific examples of the white pigment include basic lead carbonate (2PbCO ₃ Pb (OH) ₂ , so-called silver white), zinc oxide (ZnO, so-called zinc white), titanium oxide (TiO ₂ , so-called titanium white), Strontium titanate (SrTiO ₃ , so-called titanium strontium white) or the like can be used.

  Here, titanium oxide has a smaller specific gravity than other white pigments, a large refractive index, and is chemically and physically stable, so that it has a large hiding power and coloring power as a pigment. Excellent durability against other environments. Therefore, it is preferable to use titanium oxide as the white pigment. Of course, other white pigments (may be other than the listed white pigments) may be used as necessary.

For dispersing the pigment, for example, a dispersing device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. be able to.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic Examples thereof include polyvalent carboxylic acids, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate esters, and pigment derivatives. It is also preferable to use a commercially available polymer dispersant such as the Solsperse series from Zeneca.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.
In the ink composition, as a dispersion medium for various components such as pigments, a solvent may be added, and the polymerizable compound which is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition of the invention is a radiation curable ink, and is preferably solvent-free in order to be cured after the ink is applied to a recording medium. This is because if the solvent remains in the cured ink image, the solvent resistance is deteriorated or a VOC (Volatile Organic Compound) problem of the remaining solvent occurs. From this point of view, it is preferable to use a polymerizable compound as the dispersion medium, and in particular, to select a radically polymerizable compound having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

The average particle diameter of the pigment is preferably 0.02 to 0.4 μm, more preferably 0.02 to 0.1 μm, and more preferably 0.02 to 0.07 μm.
The selection of pigment, dispersant, dispersion medium, dispersion conditions, and filtration conditions are set so that the average particle diameter of the pigment particles is within the above-mentioned preferable range. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability, ink transparency, and curing sensitivity can be maintained.

(dye)
The dye used in the present invention is preferably oil-soluble. Specifically, it means that the solubility in water at 25 ° C. (the mass of the dye dissolved in 100 g of water) is 1 g or less, preferably 0.5 g or less, more preferably 0.1 g or less. Therefore, a so-called water-insoluble oil-soluble dye is preferably used.

The dye used in the present invention preferably has an oil-solubilizing group introduced into the above-described dye mother core in order to dissolve the necessary amount in the ink composition.
As the oil-solubilizing group, long chain, branched alkyl group, long chain, branched alkoxy group, long chain, branched alkylthio group, long chain, branched alkylsulfonyl group, long chain, branched acyloxy group, long chain, branched alkoxycarbonyl group, Long chain, branched acyl group, long chain, branched acylamino group long chain, branched alkylsulfonylamino group, long chain, branched alkylaminosulfonyl group and these long chains, aryl groups containing branched substituents, aryloxy groups, aryloxycarbonyl Group, arylcarbonyloxy group, arylaminocarbonyl group, arylaminosulfonyl group, arylsulfonylamino group and the like.
In addition, for water-soluble dyes having carboxylic acid and sulfonic acid, long chain, branched alcohol, amine, phenol, aniline derivatives are used as oil-solubilizing alkoxycarbonyl groups, aryloxycarbonyl groups, alkylaminosulfonyl groups, A dye may be obtained by conversion to an arylaminosulfonyl group.

The oil-soluble dye preferably has a melting point of 200 ° C. or lower, more preferably has a melting point of 150 ° C. or lower, and still more preferably has a melting point of 100 ° C. or lower. By using an oil-soluble dye having a low melting point, the precipitation of dye crystals in the ink composition is suppressed, and the storage stability of the ink composition is improved.
Further, it is desirable that the oxidation potential is noble (high) in order to improve fading, particularly resistance to oxidizing substances such as ozone and curing characteristics. For this reason, as the oil-soluble dye used in the present invention, those having an oxidation potential of 1.0 V (vs SCE) or more are preferably used. The oxidation potential is preferably higher, the oxidation potential is more preferably 1.1 V (vs SCE) or more, and particularly preferably 1.15 V (vs SCE) or more.

As the yellow dye, a compound having a structure represented by the general formula (Y-I) described in JP-A No. 2004-250483 is preferable.
Particularly preferred dyes are dyes represented by general formulas (Y-II) to (Y-IV) described in paragraph [0034] of JP-A No. 2004-250483. And the compounds described in paragraph numbers [0060] to [0071] of JP-A-250483. The oil-soluble dye of the general formula (Y-I) described in the publication may be used not only for yellow but also for inks of any color such as black ink and red ink.

The magenta dye is preferably a compound having a structure represented by the general formulas (3) and (4) described in JP-A No. 2002-114930. Specific examples include paragraphs of JP-A No. 2002-114930. Examples include the compounds described in [0054] to [0073].
Particularly preferred dyes are azo dyes represented by the general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414, and specific examples Examples thereof include compounds described in paragraph numbers [0123] to [0132] of JP-A No. 2002-121414. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.

Examples of the cyan dye include dyes represented by formulas (I) to (IV) described in JP-A No. 2001-181547, and paragraphs [0063] to [0078] of JP-A No. 2002-121414. The dyes represented by the general formulas (IV-1) to (IV-4) described above are preferred, and specific examples include paragraph numbers [0052] to [0066] of JP-A No. 2001-181547. Examples thereof include the compounds described in paragraph Nos. [0079] to [0081] of Kai 2002-121414.
Particularly preferred dyes are phthalocyanine dyes represented by general formulas (CI) and (C-II) described in paragraphs [0133] to [0196] of JP-A No. 2002-121414, A phthalocyanine dye represented by formula (C-II) is preferred. Specific examples thereof include the compounds described in JP-A No. 2002-121414, paragraph numbers [0198] to [0201]. The oil-soluble dyes of the formulas (I) to (IV), (IV-1) to (IV-4), (CI) and (C-II) are not only cyan but also black ink or green ink. The ink may be used for any color ink.

(Oxidation potential)
The oxidation potential value (Eox) of the dye in the present invention can be easily measured by those skilled in the art. Regarding this method, for example Delahay, “New Instrumental Methods in Electrochemistry” (1954, published by Interscience Publishers), A.C. J. et al. "Electrochemical Methods" by Bard et al. (1980, published by John Wiley & Sons), Akira Fujishima et al., "Electrochemical Measurement Method" (published by Gihodo Publishing Co., Ltd., 1984).
Specifically, the oxidation potential is measured by placing a test sample in a solvent such as dimethylformamide or acetonitrile containing a supporting electrolyte such as sodium perchlorate or tetrapropylammonium perchlorate in the range of 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / Approximate the oxidization wave in a straight line by dissolving 1 liter and sweeping to the oxidation side (noble side) using carbon (GC) as the working electrode and rotating platinum electrode as the counter electrode by cyclic voltammetry and DC polarography equipment Then, the intermediate potential of the line segment formed by the intersection of this straight line and the residual current / potential line and the intersection of the straight line and the saturation current line (or the intersection of the straight line parallel to the vertical axis passing through the peak potential value) Values are measured as values for SCE (saturated calomel electrode). Although this value may be deviated by several tens of mil volts due to the influence of the liquid potential difference or the liquid resistance of the sample solution, the reproducibility of the potential can be ensured by inserting a standard sample (for example, hydroquinone). The supporting electrolyte and solvent to be used can be selected appropriately depending on the oxidation potential and solubility of the test sample. The supporting electrolytes and solvents that can be used are described in Akira Fujishima et al., “Electrochemical Measurement Method” (published by Gihodo Publishing Co., Ltd., 1984), pages 101-118.

The colorant is preferably added in an amount of 1% by mass to 20% by mass in terms of solid content in the ink composition, and more preferably 2% by mass to 10% by mass.
When the content of the colorant is 1% by mass or more, the color density is not insufficient, and when the content is 20% by mass or less, the curability tends not to decrease.

<Ultraviolet absorber>
In the present invention, an ultraviolet absorber can be used from the viewpoint of improving the weather resistance of the obtained image and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194843, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492 and 56-21141 Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP The triazine compounds described in JP-A-8-501291, Research Disclosure No. Examples thereof include compounds described in No. 24239, compounds that emit ultraviolet light by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.5% by mass to 15% by mass in terms of solid content.

<Sensitizer>
If necessary, a sensitizer may be added to the ink composition of the present invention for the purpose of increasing the photosensitive wavelength. Any sensitizer may be used as long as the photoacid generator is sensitized by an electron transfer mechanism or an energy transfer mechanism.

<Antioxidant>
An antioxidant can be added to improve the stability of the ink composition. Examples of the antioxidant include European published patents, 223739, 309401, 309402, 310551, 310552, 359416, and 3435443. JP, 54-85535, 62-262417, 63-113536, 63-163351, JP-A-2-262654, JP-A-2-71262, Examples thereof include those described in Kaihei 3-121449, JP-A-5-61166, JP-A-5-119449, US Pat. No. 4,814,262, US Pat. No. 4,980,275, and the like.
The addition amount is appropriately selected according to the purpose, but is generally about 0.1% by mass to 8% by mass in terms of solid content.

<Anti-fading agent>
In the ink composition of the present invention, various organic and metal complex anti-fading agents can be used. Examples of the organic anti-fading agent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles. Examples of the metal complex anti-fading agent include nickel complexes and zinc complexes. No. 17643, No. VII, I to J, i. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in No. 15162 and the compounds included in the general formulas and compound examples of representative compounds described in JP-A-62-215272, pages 127 to 137 can be used. .
The addition amount is appropriately selected according to the purpose, but is generally about 0.1% by mass to 8% by mass in terms of solid content.

<Conductive salts>
Conductive salts such as potassium thiocyanate, lithium nitrate, ammonium thiocyanate, and dimethylamine hydrochloride can be added to the ink composition of the present invention for the purpose of controlling ejection properties.

<Solvent>
In order to improve the adhesion to the recording medium, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add the solvent within a range that does not cause the problem of solvent resistance and VOC, and the amount thereof is preferably 0.1% by mass to 5% by mass, more preferably 0.1% by mass with respect to the entire ink composition. % To 3% by mass.

<Polymer compound>
In order to adjust film physical properties, various polymer compounds different from the specific polymer can be added to the ink composition of the present invention. High molecular compounds include acrylic polymers, polyvinyl butyral resins, polyurethane resins, polyamide resins, polyester resins, epoxy resins, phenol resins, polycarbonate resins, polyvinyl butyral resins, polyvinyl formal resins, shellacs, vinyl resins, acrylic resins. Rubber resins, waxes and other natural resins can be used. Two or more of these may be used in combination. Of these, vinyl copolymer obtained by copolymerization of acrylic monomers is preferred. Furthermore, a copolymer containing “carboxyl group-containing monomer”, “methacrylic acid alkyl ester”, or “acrylic acid alkyl ester” as a structural unit is also preferably used as the copolymer composition of the polymer binder.

<Surfactant>
A surfactant may be added to the ink composition of the present invention.
Examples of the surfactant include those described in JP-A Nos. 62-173463 and 62-183457. For example, anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, fatty acid salts, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene blocks Nonionic surfactants such as copolymers, and cationic surfactants such as alkylamine salts and quaternary ammonium salts. An organic fluoro compound may be used in place of the surfactant. The organic fluoro compound is preferably hydrophobic. Examples of the organic fluoro compounds include fluorine surfactants, oily fluorine compounds (eg, fluorine oil) and solid fluorine compound resins (eg, tetrafluoroethylene resin). No. (columns 8 to 17) and those described in JP-A Nos. 62-135826.

In addition to this, if necessary, for example, leveling additives, matting agents, waxes for adjusting film physical properties, polymerization to inhibit the adhesion to recording media such as polyolefin and PET, and the like, The tackifier which does not do can be contained.
As the tackifier, specifically, a high molecular weight adhesive polymer described in JP-A-2001-49200, 5-6p (for example, (meth) acrylic acid and an alkyl group having 1 to 20 carbon atoms). An ester with an alcohol having, an ester of (meth) acrylic acid with an alicyclic alcohol having 3 to 14 carbon atoms, a copolymer comprising an ester of (meth) acrylic acid with an aromatic alcohol having 6 to 14 carbon atoms) And a low molecular weight tackifying resin having a polymerizable unsaturated bond.

  The ink composition of the present invention preferably has an ink viscosity of 7 to 30 mPa · s, more preferably 7 to 20 mPa · s at the temperature at the time of ejection in consideration of ejection properties, and is in the above range. It is preferable to adjust the composition ratio appropriately. The ink viscosity at 25 to 30 ° C. is 35 to 500 mPa · s, preferably 35 to 200 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, the image quality is improved. If the ink viscosity at 25 to 30 ° C. is less than 35 mPa · s, the effect of preventing bleeding is small, and conversely if it is greater than 500 mPa · s, there is a problem in the delivery of the ink liquid.

  A preferable combination as a component of the ink composition of the present invention is more preferably a combination of preferable examples of each component.

  The surface tension of the ink composition of the present invention is preferably 20 mN / m to 30 mN / m, more preferably 23 mN / m 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.

The ink composition of the present invention thus prepared is used as an ink for inkjet recording. When used as an ink for ink jet recording, the ink composition is ejected onto a recording medium by an ink jet printer, and then the ejected ink composition is irradiated with radiation and cured to perform recording.
In the printed matter obtained with this ink, the image portion is cured by irradiation with radiation such as ultraviolet rays, and the strength of the image portion is excellent. Therefore, in addition to image formation with ink, for example, an ink receiving layer (image image of a lithographic printing plate) Part), and can be used for various purposes.

(Preferred embodiment of ink composition)
When the ink composition of the present invention is used as an ink for inkjet recording, the viscosity is determined at a temperature at the time of ejection (for example, 40 ° C. to 80 ° C., preferably 25 ° C. to 30 ° C.) in consideration of ejectability. Preferably, it is 7 mPa · s to 30 mPa · s, and more preferably 7 mPa · s to 20 mPa · s. For example, the viscosity of the ink composition of the present invention at room temperature (25 ° C. to 30 ° C.) is preferably 35 to 500 mPa · s, more preferably 35 mPa · s 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, ink penetration into the recording medium can be avoided, and uncured monomers and odors can be reduced. Further, it is preferable because 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 mN / m to 30 mN / m, more preferably 23 mN / m 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.

  The ink composition of the present invention is suitably used as an inkjet recording ink. When used as an ink for ink jet recording, the ink composition is ejected onto a recording medium by an ink jet printer, and then the ejected ink composition is irradiated with radiation and cured to perform recording.

  In the printed matter obtained with this ink, the image portion is cured by irradiation with radiation such as ultraviolet rays, and the strength of the image portion is excellent. Part), and can be used for various purposes.

[Inkjet recording method]
Next, an ink jet recording method and an ink jet recording apparatus that can be suitably employed in the present invention will be described below.
The inkjet recording method of the present invention comprises a step of ejecting the above-described ink composition of the present invention onto a recording medium by an inkjet recording apparatus, and irradiating the ejected ink composition with actinic radiation to form the ink composition. And a step of curing.

  In the ink jet recording method, the ink composition is preferably heated to 40 ° C. to 80 ° C. to lower the viscosity of the ink composition to 7 mPa · s to 30 mPa · s, and then ejected, and this method is used. High injection stability can be realized. In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, and thus have a large viscosity fluctuation range due to temperature fluctuations during ink ejection. Viscosity fluctuations of this ink composition directly affect the droplet size and droplet ejection speed, thereby causing image quality degradation. Therefore, it is necessary to keep the ink composition temperature as constant as possible when ejecting ink. It is. The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C.

  One feature of the ink jet recording apparatus is that it includes a means for stabilizing the temperature of the ink composition, and the portion to be kept at a constant temperature is a piping system from an ink tank (an intermediate tank if there is an intermediate tank) to the nozzle ejection surface. All of the members are targeted.

  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. 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 thermal energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

  Next, radiation irradiation conditions will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, a light source is provided on both sides of the head unit, and the head and the light source are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed. In the present invention, these irradiation methods can be used.

  In the present invention, the ink composition is heated to a constant temperature, and the time from landing to irradiation is desirably 0.01 seconds to 0.5 seconds, preferably 0.01 seconds to 0.3 seconds. More preferably, the irradiation is performed after 0.01 seconds to 0.15 seconds. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before being cured. Also, since the ink composition can be exposed to a porous recording medium before it penetrates deeper than the light source reaches, unreacted monomer remains, and as a result, odor can be reduced. Can do. By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. In particular, when an ink composition having an ink viscosity of 35 MP · s to 500 MP · s at 25 ° C. is used, a great effect can be obtained. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from the color with the lowest brightness. When inks with low lightness are stacked, it is difficult for the irradiation rays to reach the lower ink, and inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion tend to occur. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of promoting curing.

  There is no restriction | limiting in particular as an inkjet recording device used for this invention, A commercially available inkjet recording device can be used. That is, in the present invention, recording can be performed on a recording medium using a commercially available inkjet recording apparatus.

(Recording medium)
The recording medium to which the ink composition of the present invention can be applied is not particularly limited, and various non-absorbing resin materials used for ordinary non-coated paper, coated paper, and so on, 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.
The ink composition of the present invention has little heat shrinkage at the time of curing and excellent adhesion to the substrate (recording medium), so that the film curls and deforms due to the ink shrinkage and heat generation during the curing reaction. Films that tend to occur, such as PET film, OPS film, OPP film, ONy film, PVC film, and the like that can be shrunk by heat, have an advantage that a high-definition image can be formed.

[Printed matter]
The printed matter of the present invention has an image formed by the ink composition of the present invention by the above-described ink jet recording method (the ink jet recording method of the present invention).
Therefore, the printed matter has an image excellent in scratch resistance and having reduced surface stickiness.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples.

<< (A) Method for synthesizing specific polymer a-1 >>
・ 2-butanone 202g
・ 46.9g of 2-hydroxyethyl methacrylate
・ FM-0711 40.0g
(Shin-Etsu Chemical Co., silicone methacrylate)
・ V-601 (Wako Pure Chemical Industries, photoinitiator) 1.38g
The above compound was charged into a 500 ml three-necked flask equipped with a Dean-stark apparatus and reacted at 80 ° C. for 4 hours. Thereafter, 1.38 g of V-601 was added, and the mixture was further reacted for 4 hours. The solution was poured into a large amount of water, dissolved in acetone, and reprecipitated and purified in water twice. After drying under reduced pressure, 150 g of toluene, 1.2 equivalents of 2-mercaptoisobutanoic acid (52 g) and 0.02 equivalents of p-toluenesulfonic acid monohydrate (1.7 g) are added to the hydroxyl group in the polymer. The mixture was reacted at 140 ° C. for 2 hours, p-toluenesulfonic acid monohydrate (1.7 g) was added, and the mixture was further reacted for 6 hours. Thereafter, p-toluenesulfonic acid monohydrate (1.7 g) was added, and the mixture was further reacted for 2 hours, allowed to cool, and poured into a large amount of water for reprecipitation. Furthermore, it melt | dissolved in acetone, reprecipitation refinement | purification was performed twice, and 118 g of (A) specific polymer (compound a-1) was obtained by drying under reduced pressure at room temperature.

(A) Method for synthesizing specific polymer (a-2) to (a-7) << (A) Method for synthesizing specific polymer (a-2) >>
FM-0711 (40.0 g) in the synthesis method of the specific polymer (a-1) was replaced with TM-0701 (16.9 g) and polymerized, and the specific polymer (a-2 ) 92 g was obtained.

<< (A) Synthesis Method of Specific Polymer (a-3) >>
The specific polymer is the same as the above synthetic method except that FM-0711 (40.0 g) in the synthesis method of the specific polymer (a-1) is replaced with M-1620 (manufactured by Daikin Industries, Ltd.) (17.3 g). (A-3) 90 g was obtained.

<< (A) Synthesis Method of Specific Polymer (a-4) >>
Except for performing polymerization using M-1620 (manufactured by Daikin Industries) (17.3 g), 2-hydroxyethyl methacrylate (17.3 g), FA-513M (manufactured by Hitachi Chemical Co., Ltd.) (31.4 g), In the same manner as the synthesis method of the specific polymer (a-1), 94 g of the specific polymer (a-4) was obtained.

<< (A) Method for synthesizing specific polymer (a-5) >>
The specific polymer (a-5) is the same as the method for synthesizing the specific polymer (a-1) except that the polymerization is performed using stearyl methacrylate (27.1 g) and 2-hydroxyethyl methacrylate (41.6 g). 91 g was obtained.

<< (A) Method for synthesizing specific polymer (a-6) >>
Except that polymerization was performed using dodecyl methacrylate (20.4 g), 2-hydroxyethyl methacrylate (26.0 g), and isobornyl methacrylate (26.7 g), the same synthesis method as the specific polymer (a-1) Thus, 84.1 g of the specific polymer (a-6) was obtained.

<< (A) Synthesis Method of Specific Polymer (a-7) >>
Polymerization was performed using FM-0711 (40.0 g) and chloromethylstyrene (54.9 g), and 1,3,4-, instead of 2-mercaptoisobutanoic acid and p-toluenesulfonic acid monohydrate. Except for using 54 g of thiadiazole-2,5-dithiol and 54 g of DBU (1,8-diazabicyclo [5,4,0] -7-undecene), in the same manner as the synthesis method of the specific polymer (a-1), 91 g of specific polymer (a-7) was obtained.

<< (A) Synthesis Method of Specific Polymer (a-8) >>
・ MEK (Methyl ethyl ketone) 23g
・ FM-0711 10.0g
・ MMA (methyl methacrylate) 90.0g
・ Cu (I) Br 0.29g
・ Α, α'-Dibromo-p-xylene 0.26g
・ 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA)
0.35g
Was reacted for 16 hours under a nitrogen stream to obtain a polymer having a Br group at the end. The solution was poured into a large amount of water / methanol = 5/5, dissolved in acetone, re-precipitated twice with water / methanol = 5/5, and then dried under reduced pressure at room temperature overnight. After dissolving 15 g of the polymer in THF (tetrahydrofuran) to 5 wt%, 0.23 g of pentaerythritol tetrakis (3-mercaptopropionate) and 0.5 g of DBU were added and reacted at room temperature for 24 hours. After reprecipitation and purification in water, it was dried under reduced pressure to obtain 70 g of the specific polymer (a-8).

Example 1
<Preparation of ink composition>
An ink composition of Example 1 was obtained by filtering a mixture of the following components with a filter having an opening of 2 μm. The viscosity of the ink composition at an ink discharge temperature (45 ° C.) was 10 mPa · s.
-Phenoxyethyl acrylate 36 parts by mass-Actilane 421
(Akcros acrylate monomer) 2.0 parts by mass n-vinylcaprolactam 32 parts by mass Solsperse 32000 (Noveon, dispersant) 0.4 parts by mass Cinquasia Magenta RT-355D 3.6 parts by mass (Ciba (Specialty Chemicals, pigment)
・ Genorad 16 (manufactured by Rahn, Stabilizer) 0.05 part by mass ・ Rapi-Cure DVE-3
(ISP Europe, vinyl ether) 8.0 parts by mass Lucirin TPO (BASF, photopolymerization initiator) 8.5 parts by mass, benzophenone (photopolymerization initiator) 4.0 parts by mass, Irgacure 184 4.0 Part by mass (Ciba Specialty Chemicals, photopolymerization initiator)
・ Byk 307 (manufactured by BYK Chemie, defoaming agent) 0.05 part by mass ・ Specific polymer a-1 (compound obtained in the above synthesis example) 0.9 part by mass

<< Preparation of Ink Compositions of Examples 2 to 8 and Comparative Example 1 >>
In the preparation process of the ink composition of Example 1, (A) The specific polymer (a-1) was replaced with the polymer shown in Table 1 below, or the polymer was not used. Ink compositions of Examples 2 to 8 and Comparative Example 1 were prepared.

<Inkjet image recording>
Next, recording on a recording medium was performed using a commercially available inkjet recording apparatus having a piezoelectric inkjet nozzle. The ink supply system was composed of an original tank, a supply pipe, 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 70 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that multi-size dots of 8 pl to 30 pl could be ejected with a resolution of 720 × 720 dpi. After landing, UV light was condensed to an exposure surface illuminance of 100 mW / cm ² , and the exposure system, main scanning speed and ejection frequency were adjusted so that irradiation started 0.1 seconds after ink landing on the recording medium. Further, the exposure time was variable, and exposure energy was irradiated. In the present invention, dpi represents the number of dots per 2.54 cm.

  Next, radiation conditions will be described. A basic irradiation method is disclosed in JP-A-60-132767. Specifically, light sources are provided on both sides of the head unit, and the head and the light sources are scanned by a shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In WO99 / 54415, as an irradiation method, a method using an optical fiber or a method in which a collimated light source is applied to a mirror surface provided on the side surface of the head unit to irradiate the recording unit with UV light is disclosed. In the present invention, these irradiation methods can be used.

The radiation to be irradiated is not particularly limited and is active radiation including X-rays, ultraviolet rays, visible rays, electron beams, and the like, and particularly ultraviolet rays having a wavelength of 230 nm to 420 nm are preferable. As the light source, in addition to a polar or non-polar mercury lamp, metal halide lamp, and xenon lamp, a light emitting diode (UV-LED) in the same wavelength region can be used. When UV-LEDs are used, a plurality of LEDs are arranged in a linear or three-dimensional manner according to the energy power of the light emitting chip, and used as a multi-array.
Depending on the setting of the distance from the medium and the transport speed can be adjusted exposure energy on the medium between ^{0.01J / cm 2 ~15J / cm 2} . The irradiation time was set until the tackiness disappeared on the image surface after ultraviolet irradiation. A soft vinyl chloride sheet was used as the recording medium.
Under these conditions, ink transfer sensitivity, ejection stability, stretching ratio, and blocking sensitivity and scratch resistance of images formed using the ink were evaluated. The results are shown in Table 1. In addition, the measurement / evaluation method of each evaluation item in Table 1 is as follows.

(Measurement of transfer sensitivity)
The amount of exposure energy (mJ / cm ² ) at which the sticky feeling disappears on the image surface after UV irradiation was defined as sensitivity. The smaller the value, the higher the sensitivity.
Allowable range of the transfer sensitivity is ink of radical system and at 750 mJ / cm ² or less and preferably 350 mJ / cm ² or less.

(Blocking sensitivity evaluation)
Overlay 500 images of PET (size: same size as soft vinyl chloride sheet imaged both vertically and horizontally, weight: 2 g / sheet) on the image formed after UV irradiation and leave it for a day to transfer to PET. Visual evaluation was made. The case where there is no transfer is evaluated as ○, and the case where there is a transfer is evaluated as ×.
The permissible range of the blocking sensitivity is 12000 mJ / cm ² or less, preferably 6000 mJ / cm ² or less for radical inks.

(Abrasion resistance evaluation)
The soft vinyl chloride sheet was rubbed with an eraser (K-50 Plastic Eraser Keep manufactured by Hoshiya) to evaluate the transfer to the eraser. The evaluation criteria are as follows.
-Evaluation criteria-
○ No transfer × Transfer

(Elongation rate evaluation)
A cured film was prepared in the same manner as the tack-free sensitivity except that the integrated exposure was 12000 mJ / cm ² , the illuminance was 2140 mW / cm ^2, and Fasson PE (Fason's polyethylene film: film thickness 100 um) was used. The obtained cured film was cut into an axial length of 5 cm and a width of 2.5 cm, and stretched at a speed of 30 cm / min using a tensile tester (manufactured by Shimadzu Corporation), and the elongation at which the cured film was broken was measured. The state of elongation from the initial length to twice the length was defined as 100% elongation. The allowable range of the stretching ratio in the radical ink is 200% or more, and preferably 300% or more.

(Evaluation of ejection stability)
In order to evaluate the ejection stability of the ink head nozzles, the number of nozzle losses in continuous ejection for 60 minutes was evaluated using a commercially available inkjet recording apparatus having a piezo-type inkjet nozzle under the following conditions.
In the experiment, the number of nozzle losses (the number of clogged nozzles) when the ink composition was discharged onto the PET substrate and exposed (exposure amount: 1000 mW / cm ² ) was counted. When the nozzle loss was 0-5, ◯, when the nozzle loss was 5-10, Δ, and when 10 or more, x.
Number of channels: 318 / head drive frequency: 4.8 kHz / dot
Ink drops: 7 drops, 42 pl
Temperature: 45 ° C

From Table 1, it can be seen that all of the ink compositions containing the specific polymer (A) of Examples 1 to 8 are cured with high sensitivity and excellent in blocking properties and scratch resistance.
On the other hand, it can be seen that (A) Comparative Example 1 containing no specific polymer has extremely poor sensitivity and is inferior in blocking sensitivity and scratch resistance.

Claims (6)

  (A) a polymer comprising a thiol group and at least one partial structure selected from the group consisting of (i) a fluorine-substituted hydrocarbon group, (ii) a siloxane skeleton, and (iii) a long-chain alkyl group in the side chain An ink composition comprising: (B) a photopolymerization initiator; and (C) a polymerizable compound.   The ink composition according to claim 1, wherein the thiol group is included in a main chain of the polymer (A).   The ink composition according to claim 1, wherein the thiol group is present in a side chain of the polymer (A).   The ink composition according to any one of claims 1 to 3, which is for inkjet recording. A step of ejecting the ink composition according to any one of claims 1 to 4 on a recording medium using an ink jet recording apparatus;
Irradiating the ejected ink composition with actinic radiation to cure the ink composition;
An ink jet recording method comprising:   A printed matter recorded by the ink jet recording method according to claim 5.