JP2009191118A - Ink composition, inkjet recording method, and printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink composition, which has excellent stability over time and a good hue, can cure with high sensitivity by irradiation of active radiation, and contains a white pigment, and to provide an inkjet recording method using this ink composition and a printed matter. <P>SOLUTION: The ink composition includes (A) a white pigment, (B) polymerizable compounds, (C) a polymerization initiator, and (D) a fluorescent brightener. As the polymerizable compounds for the component (B), an aromatic monofunctional ethylenically unsaturated compound and at least one compound selected from the group consisting of N-vinyllactams and monofunctional ethylenically unsaturated compounds having an aliphatic ring structure are contained in the ink composition. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  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 ink is ejected only to the required image portion to form an image directly on the recording medium, so that the ink can be used efficiently and the running cost is reduced. Is cheap. Furthermore, there is little noise and it is excellent as an image recording method.

According to the inkjet system, 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 sharpness of the 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 with actinic radiation. According to this method, a sharp image can be formed by irradiating with radiation immediately after printing and curing the ink droplets.
Such a curable ink composition is required to form a high-definition image having excellent color developability.

Attempts have been made to improve ultraviolet curable inks that are easily colored yellow by ultraviolet irradiation when transparent inks require colorless and transparent properties or when white inks require high whiteness.
For example, Patent Document 1 contains at least a polymerizable compound, a photopolymerization initiator, a polymerization accelerator, and a fluorescent brightening agent, and overlaps the absorption wavelength band of the photopolymerization initiator and the emission wavelength band of the fluorescent brightening agent. Disclosed is an ink composition characterized in that there is a portion.
Patent Document 2 discloses that in an ink set comprising a plurality of inks containing a colorant, a polymerizable compound, and a photopolymerization initiator, at least one of the inks is a white ink containing a white pigment, An ink set is disclosed wherein the ink contains a fluorescent brightener.

JP 2006-274025 A JP 2005-1265884 A

The ink composition described in Patent Document 1 uses an initiator having light absorption at a long wavelength in order to avoid a decrease in sensitivity due to the overlap of absorption of the optical brightener and absorption of the photopolymerization initiator. It is characterized by overlapping with the emission wavelength of the white agent. However, when high-concentration titanium oxide is used for the white ink, a decrease in sensitivity cannot be sufficiently suppressed.
In addition, Patent Document 2 proposes an improvement in the color of white ink by an ink set including a photopolymerizable white ink using a fluorescent whitening agent. I can't. In addition, the white ink described in Patent Document 2 cannot obtain sufficient temporal stability.

  The present invention aims to solve the above-described problems. That is, an ink composition containing a white pigment, which has excellent temporal stability, has a good hue, and can be cured with high sensitivity by irradiation with actinic radiation, an ink jet recording method using the same, and a printed matter are provided. For the purpose.

The above-described problems of the present invention have been solved by the means described in <1>, <10>, <11>. It describes below with <2>-<8> which is a preferable embodiment.
<1> Contains (A) a white pigment, (B) a polymerizable compound, (C) a polymerization initiator, and (D) a fluorescent brightener, and (B) an aromatic monofunctional ethylenic compound as the polymerizable compound. An ink composition comprising an unsaturated compound and further containing at least one compound selected from the group consisting of N-vinyllactams and monofunctional ethylenically unsaturated compounds having an aliphatic cyclic structure;
<2> The ink composition according to <1>, wherein the white pigment (A) is titanium oxide.
<3> The ink composition according to <1> or <2>, wherein the content of the white pigment (A) is 10% by weight or more based on the total amount of the ink composition,
<4> The ink composition according to any one of <1> to <3>, wherein the (C) polymerization initiator is a radical polymerization initiator,
<5> The above (1) to <4>, wherein the polymerization initiator (C) includes at least one compound selected from the group consisting of an acylphosphine oxide compound and an α-aminoacetophenone compound. An ink composition,
<6> The ink composition according to any one of <1> to <5>, wherein the aromatic monofunctional ethylenically unsaturated compound is a compound represented by the formula (B5).

式（Ｂ５）中、Ｒ¹は水素原子、ハロゲン原子、又は、炭素数１〜４のアルキル基を表し、Ｘ¹は二価の連結基を表し、Ｒ⁵は置換基を表し、ｕは０〜５の整数を表し、また、ｕ個存在するＲ⁵はそれぞれ同じであっても、異なっていてもよく、複数のＲ⁵がお互いに結合して環を形成してもよく、その環は芳香環であってもよい。

In Formula (B5), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, R ⁵ represents a substituent, and u is 0 Represents an integer of ˜5, and u ⁵ R ^{5 s} may be the same or different, and a plurality of R ⁵ may be bonded to each other to form a ring. An aromatic ring may be sufficient.

<7> The ink composition according to any one of <1> to <6>, wherein the monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure is a compound represented by the formula (B2):

式（Ｂ２）中、Ｒ¹は水素原子、ハロゲン原子、又は、炭素数１〜４のアルキル基を表し、Ｘ¹は二価の連結基を表し、Ｒ²は置換基を表し、ｒは０〜５の整数を表し、ｑは環状炭化水素構造を表し、前記環状炭化水素構造として炭化水素結合以外にカルボニル結合（−Ｃ（Ｏ）−）及び／又はエステル結合（−Ｃ（Ｏ）Ｏ−）を含んでいてもよく、ｒ個存在するＲ²はそれぞれ同じであっても、異なっていてもよく、また、ノルボルネン骨格中の一炭素原子をエーテル結合（−Ｏ−）及び／又はエステル結合（−Ｃ（Ｏ）Ｏ−）で置換してもよい。

In Formula (B2), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, R ² represents a substituent, and r is 0 Represents an integer of ˜5, q represents a cyclic hydrocarbon structure, and the cyclic hydrocarbon structure includes a carbonyl bond (—C (O) —) and / or an ester bond (—C (O) O—) in addition to the hydrocarbon bond. ), And r ² R ^{2 s} may be the same or different, and one carbon atom in the norbornene skeleton may be replaced with an ether bond (—O—) and / or an ester bond. You may substitute by (-C (O) O-).

<8> The ink composition according to <7>, wherein the compound represented by the formula (B2) is a compound represented by the formula (B3) or the formula (B4),

式（Ｂ３）及び式（Ｂ４）中、Ｒ¹は水素原子、ハロゲン原子、又は、炭素数１〜４のアルキル基を表し、Ｘ¹は二価の連結基を表し、Ｒ³及びＲ⁴はそれぞれ独立に置換基を表し、ｓ及びｔはそれぞれ独立に０〜５の整数を表し、また、ｓ個存在するＲ³及びｔ個存在するＲ⁴はそれぞれ同じであっても、異なっていてもよい。

In Formula (B3) and Formula (B4), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, and R ³ and R ⁴ represent Each independently represents a substituent, s and t each independently represent an integer of 0 to 5, and s R ³ and t R ⁴ may be the same or different. Good.

<9> The ink composition according to any one of <1> to <8> above, wherein the N-vinyllactam is N-vinylcaprolactam,
<10> (a ¹ ) A step of discharging the ink composition according to any one of <1> to <9> above on a recording medium, and (b ¹ ) the discharged ink composition Irradiating actinic radiation to cure the ink composition, and an ink jet recording method comprising:
<11> A printed matter recorded by the inkjet recording method according to <10>.

  According to the present invention, it is possible to provide an ink composition containing a white pigment that has excellent temporal stability, has a good hue, and can be cured with high sensitivity by irradiation with actinic radiation. Furthermore, according to this invention, the inkjet recording method and printed matter using the said ink composition could be provided.

(1) Ink composition The ink composition of the present invention contains (A) a white pigment, (B) a polymerizable compound, (C) a polymerization initiator, and (D) a fluorescent whitening agent, and (B) Contains an aromatic monofunctional ethylenically unsaturated compound as the polymerizable compound, and further contains at least one compound selected from the group consisting of N-vinyl lactams and monofunctional ethylenically unsaturated compounds having an aliphatic cyclic structure It is characterized by doing.
In addition to the above-described components, the ink composition of the present invention includes a sensitizer, a co-sensitizer, the above-mentioned aromatic monofunctional ethylenically unsaturated compound, and a monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure. A polymerizable compound other than the compound and N-vinyl lactams can be contained.

  In an ink composition using a white pigment as a colorant, particularly titanium oxide as a white pigment, the white pigment has absorption at a wavelength of 400 nm or less, particularly 380 nm or less. Therefore, since the initiator and the sensitizer need to have absorption at a wavelength exceeding 380 nm, yellow coloring has been a problem. On the other hand, when the hue is improved by using a fluorescent brightening agent, the fluorescent brightening agent also absorbs at a wavelength exceeding 380 nm as in the case of the initiator. There was a problem of causing a drop in In the present invention, by using a specific polymerizable monomer, high sensitivity is maintained while the hue is improved by the fluorescent brightening agent. Further, when a specific polymerization initiator is used, particularly high sensitivity can be maintained.

In the present invention, the ink composition can be cured by irradiation with actinic radiation.
The “active radiation” as used in the present invention is not particularly limited as long as it is an active radiation capable of imparting energy capable of generating a starting species in the ink composition by the irradiation, and is widely limited to α rays, γ rays, X-rays, ultraviolet rays (UV), visible rays, electron beams and the like are included, and among them, ultraviolet rays and electron beams are preferable from the viewpoint of curing sensitivity and device availability, and ultraviolet rays are particularly preferable. Therefore, in the present invention, the ink composition is preferably an ink composition that can be cured by irradiating ultraviolet rays as radiation.
Hereinafter, each component will be described.

(A) White pigment The ink composition of the present invention contains a white pigment.
The white pigment is not particularly limited. For example, 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), hollow polymer particles, and the like can be used.
In addition, you may surface-treat these white pigments as needed.

  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.

Titanium oxide is not particularly limited, and can be appropriately selected from known titanium oxides used as white pigments. Both rutile titanium dioxide and anatase titanium dioxide can be used, but rutile titanium dioxide is preferably used because of its low catalytic activity and excellent stability over time.
Titanium oxide is on the market, and examples include Tipaque CR60-2 and Tipaque A-220 (both manufactured by Ishihara Sangyo Co., Ltd.).

In the present invention, the amount of white pigment added to the ink composition is preferably 10% by weight or more based on the total amount of the ink composition.
In the conventional white ink composition, when the amount of the white pigment added is large, the sensitivity to actinic radiation is lowered. The ink composition of the present invention is active even when the amount of white pigment added to the ink composition is 10% by weight or more by using a specific polymerizable compound having excellent curability and an optical brightener. High sensitivity to radiation can be maintained.
The amount of white pigment added to the ink composition is preferably 10 to 30% by weight, more preferably 12 to 25% by weight, even more preferably 15 to 23% by weight, based on the total amount of the ink composition. It is. When the addition amount is 10% by weight or more, excellent concealability is obtained. Further, it is preferable that the addition amount be 30% by weight or less because curability, particularly curability inside the cured film is good.

For the dispersion of the white pigment, for example, a dispersion device such as a ball mill, sand mill, attritor, roll mill, jet mill, homogenizer, paint shaker, kneader, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, etc. Can be used.
In addition, when adding a white pigment to the ink composition, a synergist corresponding to various pigments can be used as a dispersion aid, if necessary. The dispersion aid is preferably added in an amount of 1 to 50 parts by weight with respect to 100 parts by weight of the white pigment.

  In the ink composition, as a dispersion medium for various components such as a white pigment, a solvent may be added, or a solvent-free low molecular weight component (B) polymerizable compound described later may be used as a dispersion medium. However, the ink composition of the present invention is a radiation curable ink, and is preferably solventless in order to cure the ink after it 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 such a viewpoint, as the dispersion medium, (B) a polymerizable compound is used, and among these, it is preferable to select a 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 white pigment is preferably 0.1 to 0.5 μm, more preferably 0.1 to 0.3 μm, and still more preferably 0.15 to 0.25 μm. The maximum particle size is preferably 1 μm or less, more preferably 0.5 μm or less. It is preferable to set the white pigment, the dispersant, the dispersion medium, the dispersion conditions, and the filtration conditions so that the maximum particle size is within the above range. It is also effective to remove large particles by post-treatment such as centrifugation. By controlling the particle size, clogging of the head nozzle can be suppressed, and ink storage stability (particularly, suppression of sedimentation), sufficient concealability and curing sensitivity can be maintained.
The particle size of the white pigment in the ink composition can be measured by a known measurement method. Specifically, it can be measured by a centrifugal sedimentation light transmission method, an X-ray transmission method, a laser diffraction / scattering method, and a dynamic light scattering method.

(B) Polymerizable compound The ink composition of the present invention contains a polymerizable compound, an aromatic monofunctional ethylenically unsaturated compound as the polymerizable compound, and further an N-vinyl lactam and an aliphatic cyclic structure. And at least one compound selected from the group consisting of monofunctional ethylenically unsaturated compounds having The ink composition of the present invention can be used in combination with other polymerizable compounds as the polymerizable compound. Each will be described in detail below.

<Aromatic monofunctional ethylenically unsaturated compound and monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure>
The monofunctional ethylenically unsaturated compound and the aromatic monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure are preferably monofunctional ethylenically unsaturated compounds represented by the following formula (B1). The monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure is a monofunctional ethylenically unsaturated compound having an alicyclic hydrocarbon group which may contain a hetero atom, and an aromatic monofunctional ethylenically unsaturated compound. The compound is a monofunctional ethylenically unsaturated compound having an aromatic group. The monofunctional ethylenically unsaturated compound is a radical polymerizable monomer and is a monomer having only one polymerizable ethylenically unsaturated bond. Preferred examples of the group having a polymerizable ethylenically unsaturated bond include acryloyloxy group, methacryloyloxy group, acrylamide group, methacrylamide group, vinyl group and vinyloxy group.
In the present invention, the radical polymerizable monomer having an aliphatic cyclic structure has an ethylenically unsaturated bond in addition to the aliphatic cyclic structure, and the ethylenic unsaturated bond in the aliphatic cyclic structure is: Not applicable to polymerizable ethylenically unsaturated bonds. The aromatic monofunctional ethylenically unsaturated compound is a compound having one ethylenically unsaturated bond in addition to the aromatic group.

In the above formula (B1), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, and X ¹ represents a single bond, an ether bond (—O—), an ester bond (—C ( O) O- or -OC (O)-), amide bond (-C (O) NH- or -NHC (O)-), carbonyl bond (-C (O)-), branched An alkylene group having 20 or less carbon atoms, or a second divalent linking group in combination of these may be bonded, and only the first divalent linking group or the second divalent linking group may be bonded. When it has, what has an ether bond, an ester bond, and a C20 or less alkylene group is preferable.
Y is an aromatic group or alicyclic hydrocarbon group containing a monocyclic aromatic group and a polycyclic aromatic group, and the aromatic group and alicyclic hydrocarbon group are a halogen atom, a hydroxyl group, an amino group, It may have a siloxane group and a substituent having 30 or less carbon atoms, and the aromatic structure or the alicyclic hydrocarbon group may contain a heteroatom such as O, N, or S.

In the above formula (B1), R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom.
X ¹ preferably has an ester bond (—C (O) O—).
That is, in the present invention, the monofunctional ethylenically unsaturated compound and the aromatic monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure are preferably acrylate (acrylic acid ester) or methacrylate (methacrylic acid ester).

[Aromatic monofunctional ethylenically unsaturated compounds]
The aromatic monofunctional ethylenically unsaturated compound is preferably a polymerizable monomer represented by the following formula (B5).

In Formula (B5), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, R ⁵ represents a substituent, and u is 0 Represents an integer of ˜5, and u ⁵ R ^{5 s} may be the same or different, and a plurality of R ⁵ may be bonded to each other to form a ring. An aromatic ring may be sufficient.

In formula (B5), R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and still more preferably a hydrogen atom.
X ¹ has the same meaning as X ¹ in the formula (B1). The end bonded to the vinyl group of X ¹ in the formula (B5) is preferably an ester group or an amide group in which the carbonyl carbon of X ¹ and the vinyl group are bonded, and more preferably an ester bond. In particular, it is preferable to have a structure of H ₂ C═C (R ¹ ) —C (O) O—. In that case, the other part of X ¹ bonded to the aromatic ring may be a single bond or may be arbitrarily selected from the aforementioned groups.
The vinyl moiety containing R ¹ and X ¹ (H ₂ C═C (R ¹ ) —X ¹ —) can be attached at any position of the aromatic ring. In addition, from the viewpoint of improving the affinity with (A) the white pigment, the end bonded to the aromatic ring of X ¹ in Formula (B5) is preferably an oxygen atom, and is an etheric oxygen atom. Is more preferable, and X ¹ in formula (B5) is more preferably —C (O) O (CH ₂ CH ₂ O) _p — (p represents 1 or 2).
u ⁵ R ^{5 s} may be each independently a monovalent or polyvalent substituent, and as a monovalent substituent, a hydrogen atom, a hydroxyl group, a substituted or unsubstituted amino group, a thiol group, a siloxane group Or a hydrocarbon group or heterocyclic group having a total carbon number of 30 or less which may further have a substituent.

In the formula (B5), when a plurality of R ⁵ are bonded to each other to form a ring, it is preferable to form an aromatic ring.
That is, in the formula (B5), preferred as the aromatic group is a group obtained by removing one or more hydrogen from monocyclic aromatic benzene (phenyl group, phenylene group, etc.), as well as 2 to 4 rings. It is the polycyclic aromatic group which has, and is not limited. Specifically, naphthalene, anthracene, 1H-indene, 9H-fluorene, 1H-phenalene, phenanthrene, triphenylene, pyrene, naphthacene, tetraphenylene, biphenylene, as-indacene, s-indacene, acenaphthylene, fluoranthene, acephenanthrylene , Groups obtained by removing one or more hydrogen atoms from, for example, aceanthrylene, chrysene, and preandene.

  These aromatic groups may be aromatic heterocyclic groups containing heteroatoms such as O, N, and S. Specifically, furan, thiophene, 1H-pyrrole, 2H-pyrrole, 1H-pyrazole, 1H-imidazole, isoxazole, isothiazole, 2H-pyran, 2H-thiopyran, pyridine, pyridazine, pyrimidine, pyrazine, 1,2 Group obtained by removing at least one hydrogen atom from a monocyclic aromatic heterocyclic compound such as 1,3-triazole or 1,2,4-triazole.

  Thianthrene, isobenzofuran, isochromene, 4H-chromene, xanthene, phenoxathiin, indolizine, isoindole, indole, indazole, purine, 4H-quinolidine, isoquinoline, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine , Carbazole, β-carboline, phenanthridine, acridine, perimidine, phenanthroline, phenazine, phenothiazine, phenoxazine, pyrrolidine, and the like, a group obtained by removing at least one hydrogen atom.

  The aromatic group may have one or more halogen atoms, hydroxyl groups, amino groups, thiol groups, siloxane groups, and substituents having 30 or less carbon atoms. For example, you may form the cyclic structure containing hetero atoms, such as O, N, and S, by two or more substituents which an aromatic group has like phthalic anhydride and phthalimide anhydride.

  In the present invention, the polycyclic aromatic group is more preferably a polycyclic aromatic group having 2 to 3 rings, and particularly preferably a naphthyl group.

  Specific examples of the aromatic monofunctional ethylenically unsaturated compound include [L-1] to [L-71], but are not limited to the following.

<Monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure>
The monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure is more preferably a compound having a norbornene skeleton represented by the following formula (B2).

In Formula (B2), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, an ether group (—O—), an ester group ( -C (O) O- or -OC (O)-), amide group (-C (O) NR'-), carbonyl group (-C (O)-), nitrogen atom (-NR'-), substitution It is preferable that it is a C1-C15 alkylene group which may have group, or a bivalent group which combined these 2 or more. R ′ represents a hydrogen atom, a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms. R ² represents a substituent, r represents an integer of 0 to 5, q represents a cyclic hydrocarbon structure, and the cyclic hydrocarbon structure includes a carbonyl bond (—C (O) —) and / or a hydrocarbon bond in addition to the hydrocarbon bond. Alternatively, an ester bond (—C (O) O—) may be contained, and r ² R ^{2 s} may be the same or different from each other, and one carbon atom in the norbornene skeleton is replaced with an ether. A bond (—O—) and / or an ester bond (—C (O) O—) may be substituted.
In formula (B2), R ¹ is preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group.

In the formula (B2), the end bonded to the vinyl group of X ¹ is preferably an ester group or an amide group in which the carbonyl carbon of X ¹ and the vinyl group are bonded, and more preferably an ester bond. In particular, it is preferable to have a structure of H ₂ C═C (R ¹ ) —C (O) O—. In that case, the other part of X ¹ bonded to the norbornene skeleton may be a single bond or may be arbitrarily selected from the aforementioned groups.
The vinyl moiety containing R ¹ and X ¹ (H ₂ C═C (R ¹ ) —X ¹ —) can be attached at any position on the alicyclic hydrocarbon structure. In addition, "on each alicyclic hydrocarbon structure" refers to the norbornene structure and the cyclic hydrocarbon structure containing q in the formula (B2).
In addition, from the viewpoint of improving the affinity with (A) the white pigment, the end bonded to the alicyclic hydrocarbon structure of X ¹ in Formula (B2) is preferably an oxygen atom, and etheric oxygen More preferably, it is an atom, and X ¹ in formula (B2) is more preferably —C (O) O (CH ₂ CH ₂ O) _p — (p represents 1 or 2).

R ² in formula (B2) independently represents a substituent, and can be bonded at any position on the alicyclic hydrocarbon structure. Further, r R ^{2 s} may be the same or different.
The r ² R ^{2 s} may be each independently a monovalent or polyvalent substituent, and as a monovalent substituent, a hydrogen atom, a hydroxyl group, a substituted or unsubstituted amino group, a thiol group, a siloxane group Furthermore, it is preferably a hydrocarbon group or heterocyclic group having a total carbon number of 30 or less which may have a substituent, or an oxy group (═O) as a divalent substituent.
The substitution number r of R ² represents an integer of 0 to 5.

  Q in the formula (B2) represents a cyclic hydrocarbon structure, and both ends thereof may be substituted at any position of the norbornene skeleton, and may be a monocyclic structure or a polycyclic structure; In addition to the hydrocarbon bond, the cyclic hydrocarbon structure may contain a carbonyl bond (—C (O) —) and / or an ester bond (—C (O) O—).

  The monomer represented by the formula (B2) is preferably a monomer represented by the formula (B3) or the formula (B4). Note that the unsaturated bond in the cyclic hydrocarbon structure in the formula (B4) has low radical polymerizability, and in the present invention, the compound represented by the formula (B4) is a monofunctional ethylenically unsaturated compound.

In Formula (B3) and Formula (B4), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, and R ³ and R ⁴ represent Each independently represents a substituent, s and t each independently represent an integer of 0 to 5, and s R ³ and t R ⁴ may be the same or different. Good.

R ¹ and X ¹ in Formula (B3) or Formula (B4) has the same meaning as R ¹ and X ¹ in Formula (B2), and preferred ranges are also the same.
The vinyl moiety containing R ¹ and X ¹ in formula (B3) or formula (B4) is bonded at any position on each alicyclic hydrocarbon structure shown below in formula (B3) or formula (B4). Can do.

R ³ and R ⁴ in Formula (B3) or Formula (B4) each independently represent a substituent, and are bonded at any position on each alicyclic hydrocarbon structure in Formula (B3) or Formula (B4). can do. Substituents in R ³ and R ⁴ has the same meaning as the substituent in R ² of formula (B2), and preferred ranges are also the same.
In formula (B3) or formula (B4), s and t each independently represent an integer of 0 to 5, and s R ³ and t R ⁴ are the same or different. May be.

As the monomer represented by the formula (B2), preferred specific examples of monofunctional acrylates are shown below.
In some of the following exemplary compounds, the hydrocarbon chain is described by a simplified structural formula in which the symbols of carbon (C) and hydrogen (H) are omitted.

  As the monomer represented by the formula (B2), preferred specific examples of monofunctional methacrylate are shown below.

  As the monomer represented by the formula (B2), preferred specific examples of monofunctional acrylamide are shown below.

<N-vinyl lactams>
In the present invention, it is preferable to use N-vinyl lactams as the polymerizable compound. Preferable examples of N-vinyl lactams that can be used in the present invention include compounds represented by the following formula (B6).

  In formula (B6), m represents an integer of 1 to 5, and m is 2 to 4 from the viewpoint of flexibility after the ink composition is cured, adhesion to the support, and availability of raw materials. It is preferably an integer, more preferably m is 2 or 4, and particularly preferably m is 4, that is, N-vinylcaprolactam. N-vinylcaprolactam is preferable because it is excellent in safety, is generally available and can be obtained at a relatively low price, and provides particularly good ink curability and adhesion of a cured film to a support.

  The N-vinyl lactams may have a substituent such as an alkyl group or an aryl group on the lactam ring, and may be linked with a saturated or unsaturated ring structure. The N-vinyl lactams may be included in the ink composition alone or in a plurality of types.

  In the present invention, the N-vinyl lactam is preferably contained in an amount of 5 to 50% by weight of the total ink composition, more preferably 8 to 40% by weight, and still more preferably 10 to 30%. % By weight. Within the above range, an ink composition that exhibits good copolymerizability with other polymerizable compounds and is excellent in curability and blocking resistance is preferable.

In the present invention, an aromatic monofunctional ethylenically unsaturated compound is contained as the polymerizable compound, and a monofunctional ethylenically unsaturated compound having an N-vinyl lactam and / or an aliphatic cyclic structure is contained.
In this case, the content of the aromatic monofunctional ethylenically unsaturated compound is preferably 10 to 80% by weight, more preferably 15 to 70% by weight, and further preferably 20 to 60% by weight of the entire ink composition. % By weight.
When N-vinyl lactams are used in the ink composition, it is preferably contained in an amount of 5 to 50% by weight, more preferably 8 to 40% by weight, and more preferably 10 to 30% by weight. It is more preferable to contain.
Moreover, when using the monofunctional ethylenically unsaturated compound which has an aliphatic cyclic structure, it is preferable to contain 5 to 50 weight% of the whole ink composition, and it is more preferable to contain 8 to 40 weight%, It is more preferable to contain 10 to 35% by weight.

The total amount of the monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure, the N-vinyl lactams and the aromatic monofunctional ethylenically unsaturated compound with respect to the entire polymerizable compound is preferably 20% by weight or more, and 40% by weight. % Or more, more preferably 60% by weight or more.
It is preferable for the content in the ink composition to be in the above range since an ink composition having low viscosity and good curability can be obtained. Moreover, since the cured film which hardened | cured the ink composition did not have the surface stickiness, the cured film excellent in the softness | flexibility can be obtained, and it is preferable.

<Other polymerizable compounds>
As the polymerizable compound, the following acyclic monofunctional monomers can also be used. The acyclic monofunctional monomer has a relatively low viscosity, and can be preferably used, for example, for the purpose of reducing the viscosity of the ink composition. However, the ratio of the following acyclic monofunctional monomer to the entire ink composition is 20% by weight or less from the viewpoint of suppressing the stickiness of the cured film and giving a high film strength that does not cause scratches during molding. It is preferable. More preferably, it is 15 weight% or less.
Specifically, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate, 2 -Hydroxyethyl acrylate, butoxyethyl acrylate, carbitol acrylate, 2-ethylhexyl-diglycol acrylate, polyethylene glycol (meth) acrylate monomethyl ether, polypropylene glycol (meth) acrylate monomethyl ether, polytetraethylene glycol (meth) acrylate monomethyl ether, etc. Is mentioned.

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, ethylene Anhydrides having an unsaturated group, acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, unsaturated urethane (meth) acrylic monomers or prepolymers, epoxy monomers or prepolymers, urethanes A (meth) acrylic ester such as a monomer or a prepolymer is preferably used.
Specific examples include (poly) ethylene glycol mono (meth) acrylate, (poly) ethylene glycol (meth) acrylate methyl ester, (poly) ethylene glycol (meth) acrylate ethyl ester, (poly) ethylene glycol (meth) acrylate phenyl Ester, (poly) propylene glycol mono (meth) acrylate, (poly) propylene glycol mono (meth) acrylate phenyl ester, (poly) propylene glycol (meth) acrylate methyl ester, (poly) propylene glycol (meth) acrylate ethyl ester, Neopentyl glycol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) tetramethylene glycol di (meth) acrylate, (poly Tetramethylene glycol di (meth) acrylate, bisphenol A PO adduct di (meth) acrylate, ethoxylated neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, bisphenol A EO adduct di (meth) acrylate, EO Modified pentaerythritol triacrylate, PO modified pentaerythritol triacrylate, EO modified pentaerythritol tetraacrylate, PO modified pentaerythritol tetraacrylate, EO modified dipentaerythritol tetraacrylate, PO modified dipentaerythritol tetraacrylate, EO modified trimethylolpropane triacrylate , PO-modified trimethylolpropane triacrylate, EO-modified tetramethylolmethane Traacrylate, PO-modified tetramethylolmethane tetraacrylate, 2-ethylhexyl acrylate, n-octyl acrylate, n-nonyl acrylate, n-decyl acrylate, isooctyl acrylate, n-lauryl acrylate, n-tridecyl acrylate, n-cetyl acrylate , N-stearyl acrylate, 2-hydroxyethyl acrylate, butoxyethyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylolpropane triacrylate, tetramethylol methane tetra Acrylate, oligoester acrylate, N-methylo Acrylic acid derivatives such as ethyl acrylamide, diacetone acrylamide, epoxy acrylate, methyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, n-nonyl methacrylate, n-decyl methacrylate, isooctyl methacrylate, n- Lauryl methacrylate, n-tridecyl methacrylate, n-cetyl methacrylate, n-stearyl methacrylate, allyl methacrylate, glycidyl methacrylate, benzyl methacrylate, dimethylaminomethyl methacrylate, trimethylolethane trimethacrylate, trimethylolpropane trimethacrylate, 2,2-bis Methacryl derivatives such as (4-methacryloxypolyethoxyphenyl) propane, In addition, derivatives of allyl compounds such as allyl glycidyl ether, diallyl phthalate, triallyl trimellitate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, 2 -Ethylhexyl-diglycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, 2-hydroxybutyl acrylate, hydroxypivalic acid neopentyl glycol diacrylate, 2-acryloyloxyethylphthalic acid, tetramethylol methane triacrylate, 2-acrylic Leuoxyethyl-2-hydroxyethylphthalic acid, dimethylol tricyclodecane diacrylate, ethoxylated phenyl acrylate, 2-acryloyloxyethyl succinic acid, modified glycerin Phosphorus triacrylate, bisphenol A diglycidyl ether acrylic acid adduct, modified bisphenol A diacrylate, 2-acryloyloxyethyl hexahydrophthalic acid, dipentaerythritol hexaacrylate, pentaerythritol triacrylate tolylene diisocyanate urethane prepolymer, lactone modified Examples include flexible acrylate, butoxyethyl acrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, 2-hydroxyethyl acrylate, methoxydipropylene glycol acrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer. And more specifically , Yamashita Shinzo ed. “Cross-linking agent handbook” (1981, Taiseisha); Kato Kiyomi ed. “UV / EB curing handbook (raw material edition)” (1985, Polymer publication society); Application and Market of EB Curing Technology "page 79 (1989, CMC); commercial products described in" Polyester resin handbook "by Eiichiro Takiyama (1988, Nikkan Kogyo Shimbun), etc. Crosslinkable monomers, oligomers and polymers can be used.

Two or more ethylenically unsaturated double bond groups selected from the group consisting of an acrylate group, a methacrylate group, an acrylamide group, a methacrylamide group, a vinyloxy group, and an N-vinyl group as the radically polymerizable monomer. Polyfunctional monomers having them can also be used together. By containing a polyfunctional monomer, an ink composition having high cured film strength can be obtained. However, from the viewpoint of maintaining the adhesion of the base material (recording medium) of the cured film, the proportion of the following polyfunctional monomer in the entire ink composition is preferably 50% by weight or less. More preferably, it is 45% by weight or less. In particular, in order to obtain a flexible cured film, the content is preferably 20% by weight or less, and more preferably 10% by weight or less.
Specifically, bis (4-acryloxypolyethoxyphenyl) propane, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, Ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, penta Erythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, trimethylol propane triacrylate, tetramethylol methetate Acrylate, tetramethylol methane triacrylate, dimethylol tricyclodecane diacrylate, modified glycerin triacrylate, modified bisphenol A diacrylate, PO adduct diacrylate of bisphenol A, EO adduct diacrylate of bisphenol A, dipentaerythritol hexaacrylate And caprolactone-modified dipentaerythritol hexaacrylate.

Furthermore, it is also preferable to use a vinyl ether compound as the radical polymerizable compound. Suitable vinyl ether compounds include, for example, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, diethylene glycol divinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol. Di- or trivinyl ether compounds such as divinyl ether, 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 compounds such as ruvinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, isopropenyl vinyl ether, dodecyl vinyl ether, diethylene glycol monovinyl ether, octadecyl vinyl ether, etc. It is done.
Of these vinyl ether compounds, divinyl ether compounds and trivinyl ether compounds are preferable from the viewpoints of curability, adhesion, and surface hardness, and divinyl ether compounds are particularly preferable. A vinyl ether compound may be used individually by 1 type, and may be used in combination of 2 or more type as appropriate. In the present invention, the vinyl ether compound is particularly preferably used for the purpose of lowering the viscosity. However, when the addition amount is increased, the curability may be deteriorated or the surface of the cured film may be sticky. It is preferably 20% by weight or less, more preferably 10% by weight or less, based on the whole.

  In the present invention, the monomers listed as the polymerizable compound described above have high reactivity, low viscosity, and excellent adhesion to a recording medium.

  The total amount of the polymerizable compound with respect to the entire ink composition that can be used in the present invention is preferably 40 to 95% by weight, more preferably 50 to 90% by weight, and 60 to 85% by weight. Is more preferable. It is preferable for it to be in the above range since the curability is excellent and the viscosity is moderate.

(C) Polymerization initiator The ink composition of the present invention contains (C) a polymerization initiator. In the present invention, a known radical polymerization initiator is preferably used as the polymerization initiator (photopolymerization initiator). The polymerization initiator that can be used in the present invention may be used alone or in combination of two or more. Moreover, a radical polymerization initiator and a cationic polymerization initiator can also be used together, and when using a cationic polymerizable compound together as a polymerizable compound, it is preferable to use a cationic polymerization initiator.
The polymerization initiator that can be used in the present invention is a compound that generates a polymerization initiating species upon irradiation with actinic radiation. Examples of the actinic radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays. However, ultraviolet rays or visible rays are preferable from the viewpoint of device cost and operational safety.
Specific polymerization initiators known to those skilled in the art can be used without limitation, and specifically, for example, Bruce M. Monroe et al., Chemical Review, 93, 435 (1993), RS Davidson, Journal, of Photochemistry and Biology A: Chemistry, 73. 81 (1993), JP Faussier, Photoinitiated Polymerization-Theory and Applications: Rapra Review vol. 9, Report, Rapra Technology (1998), M. Tsunooka et al., Prog. Many are described in Polym. Sci., 21, 1 (1996). In addition, a large number of chemical amplification type photoresists and compounds used for photocationic polymerization are described in (Organic Electronics Materials Study Group, “Organic Materials for Imaging”, Bunshin Publishing (1993), pages 187 to 192). ing. Furthermore, FD Saeva, Topics in Current Chemistry, 156, 59 (1990), GG Maslak, Topics in Current Chemistry, 168, 1 (1993), HB Shuster et al, JACS, 112, 6329 (1990), IDF Eaton et A group of compounds that undergo bond oxidative or reductive cleavage through interaction with the electronically excited state of a sensitizer as described in al, JACS, 102, 3298 (1980) and the like is also known.

  In the present invention, the photopolymerization initiator preferably contains at least one compound selected from the group consisting of acylphosphine oxide compounds and α-aminoacetophenone compounds. It is preferable to use the above compound as a photopolymerization initiator because it can be cured with particularly high sensitivity. Acylphosphine oxide compounds and α-aminoacetophenone compounds that can be preferably used are as follows.

<Acylphosphine oxide compound>
The acylphosphine oxide compound is preferably a compound represented by the following formula (C1) or the following formula (C2).

R ¹ and R ² in the formula (C1) each independently represent an aliphatic group, an aromatic group, an aliphatic oxy group, an aromatic oxy group, or a heterocyclic group, and R ³ represents an aliphatic group or an aromatic group. Represents a group or heterocyclic group. R ¹ and R ² may combine to form a 5-membered to 9-membered ring. The ring structure may be a heterocyclic ring having an oxygen atom, a nitrogen atom, a sulfur atom or the like in the ring structure.
Examples of the aliphatic group represented by R ¹ , R ² or R ³ include an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, a substituted alkynyl group, an aralkyl group, and a substituted aralkyl group. Among them, an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an aralkyl group, or a substituted aralkyl group is preferable, and an alkyl group and a substituted alkyl group are more preferable. The aliphatic group may be a cyclic aliphatic group or a chain aliphatic group. The chain aliphatic group may have a branch.
Examples of the alkyl group include linear, branched, and cyclic alkyl groups. The number of carbon atoms of the alkyl group is preferably 1 or more and 30 or less, and more preferably 1 or more and 20 or less. The preferred range of the number of carbon atoms in the alkyl part of the substituted alkyl group is the same as in the case of the alkyl group. Examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group, decyl group, dodecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, neopentyl group, An isopropyl group, an isobutyl group, etc. are mentioned.
Examples of the substituent of the substituted alkyl group include —COOH (carboxyl group), —SO ₃ H (sulfo group), —CN (cyano group), halogen atom (for example, fluorine atom, chlorine atom, bromine atom), —OH. (Hydroxy group), C30 or less alkoxycarbonyl group (for example, methoxycarbonyl group, ethoxycarbonyl group, benzyloxycarbonyl group), C30 or less alkylsulfonylaminocarbonyl group, arylsulfonylaminocarbonyl group, alkylsulfonyl group An arylsulfonyl group, an acylaminosulfonyl group having 30 or less carbon atoms, an alkoxy group having 30 or less carbon atoms (for example, a methoxy group, an ethoxy group, a benzyloxy group, a phenoxyethoxy group, a phenethyloxy group, etc.), Alkylthio groups (eg methylthio , Ethylthio group, methylthioethylthioethyl group, etc.), aryloxy groups having 30 or less carbon atoms (for example, phenoxy group, p-tolyloxy group, 1-naphthoxy group, 2-naphthoxy group, etc.), nitro group, alkoxycarbonyloxy group , Aryloxycarbonyloxy group, acyloxy group having 30 or less carbon atoms (for example, acetyloxy group, propionyloxy group, etc.), acyl group having 30 or less carbon atoms (for example, acetyl group, propionyl group, benzoyl group, etc.), carbamoyl group (For example, carbamoyl group, N, N-dimethylcarbamoyl group, morpholinocarbonyl group, piperidinocarbonyl group, etc.), sulfamoyl group (for example, sulfamoyl group, N, N-dimethylsulfamoyl group, morpholinosulfonyl group, piperidinyl) Nosulfonyl group), carbon number 0 or less aryl group (for example, phenyl group, 4-chlorophenyl group, 4-methylphenyl group, α-naphthyl group, etc.), substituted amino group (for example, amino group, alkylamino group, dialkylamino group, arylamino group, Diarylamino group, acylamino group, etc.), substituted ureido group, substituted phosphono group, heterocyclic group and the like. Here, the carboxyl group, the sulfo group, the hydroxy group, and the phosphono group may be in a salt state. In this case, the cation that forms a salt is a group that can form a cation, and is an organic cationic compound, a transition metal coordination complex cation (such as the compound described in Japanese Patent No. 2791143) or a metal cation (for example, Na ⁺ , K ⁺ , Li ⁺ , Ag ⁺ , Fe ²⁺ , Fe ³⁺ , Cu ⁺ , Cu ²⁺ , Zn ²⁺ , Al ^3+, etc.) are preferred.

Examples of the alkenyl group include linear, branched, and cyclic alkenyl groups. The number of carbon atoms of the alkenyl group is preferably 2 or more and 30 or less, and more preferably 2 or more and 20 or less. The alkenyl group may be a substituted alkenyl group having a substituent or an unsubstituted alkenyl group, and the preferred range of the number of carbon atoms in the alkenyl part of the substituted alkenyl group is the same as that of the alkenyl group. . Examples of the substituent for the substituted alkenyl group include the same substituents as those for the substituted alkyl group.
Examples of the alkynyl group include linear, branched, and cyclic alkynyl groups, and the number of carbon atoms of the alkynyl group is preferably 2 to 30, and more preferably 2 to 20. The alkynyl group may be a substituted alkynyl group having a substituent or an unsubstituted alkynyl group, and the preferred range of the number of carbon atoms in the alkynyl part of the substituted alkynyl group is the same as in the case of the alkynyl group. . Examples of the substituent for the substituted alkynyl group include the same substituents as those for the substituted alkyl group.
Examples of the aralkyl group include aralkyl groups having a linear, branched, or cyclic alkyl side chain, and the number of carbon atoms of the aralkyl group is preferably 7 or more and 35 or less, and more preferably 7 or more and 25 or less. . The aralkyl group may be a substituted aralkyl group having a substituent or an unsubstituted aralkyl group, and the preferred range of the number of carbon atoms in the aralkyl part of the substituted aralkyl group is the same as in the case of the aralkyl group. . Examples of the substituent for the substituted aralkyl group include the same substituents as those for the substituted alkyl group. In addition, the aryl part of the aralkyl group may have a substituent, and the substituent is the same as that of the alkyl group and a linear, branched or cyclic alkyl group having 30 or less carbon atoms. Can be illustrated.

Examples of the aromatic group represented by R ¹ , R ² or R ³ include an aryl group and a substituted aryl group. The number of carbon atoms of the aryl group is preferably 6 or more and 30 or less, and more preferably 6 or more and 20 or less. The preferable range of the number of carbon atoms in the aryl part of the substituted aryl group is the same as that of the aryl group. Examples of the aryl group include a phenyl group, an α-naphthyl group, a β-naphthyl group, and the like. Examples of the substituent of the substituted aryl group include the same substituents as those in the case of the substituted alkyl group and linear, branched or cyclic alkyl groups having 30 or less carbon atoms.
The aliphatic oxy group represented by R ¹ or R ² is preferably an alkoxy group having 1 to 30 carbon atoms, and examples thereof include a methoxy group, an ethoxy group, a butoxy group, an octyloxy group, and a phenoxyethoxy group. It is done. However, it is not limited to these.
The aromatic oxy group represented by R ¹ or R ² is preferably an aryloxy group having 6 to 30 carbon atoms, for example, phenoxy group, methylphenyloxy group, chlorophenyloxy group, methoxyphenyloxy group, octyl An oxyphenyloxy group etc. are mentioned. However, it is not limited to these.
The heterocyclic group represented by R ¹ , R ² or R ³ is preferably a heterocyclic group containing an N, O or S atom, for example, a pyridyl group, a furyl group, a thienyl group, an imidazolyl group, a pyrrolyl group or the like. Is mentioned.

R ⁴ and R ⁶ in the formula (C2) each independently represent an alkyl group, an aryl group, or a heterocyclic group, and R ⁵ represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, or a heterocyclic group. To express.
The alkyl group, aryl group, heterocyclic group, alkoxy group, and aryloxy group represented by R ⁴ , R ^5, or R ⁶ may have a substituent. The same substituents as in (B1) can be mentioned.
The alkyl group, aryl group, heterocyclic group, alkoxy group and aryloxy group in the formula (C2) have the same meaning as in the formula (C1).

  The compound represented by the formula (C1) is more preferably a compound represented by the following formula (C3).

In the formula (C3), R ⁷ and R ⁸ each independently represent a phenyl group, a methoxy group, or an isopropoxy group, and R ⁹ represents a 2,4,6-trimethylphenyl group or a 2,4-dimethylphenyl group. , 2-methylphenyl group (o-toluyl group), isobutyl group, or t-butyl group.

  The compound represented by the formula (C2) is more preferably a compound represented by the following formula (C4).

In formula (C4), R ¹⁰ and R ¹² each independently represents a 2,4,6-trimethylphenyl group, a 2,6-dimethylphenyl group, or a 2,6-dimethoxyphenyl group, and R ¹¹ represents phenyl. Represents a group or a 2,4,4-trimethylpentyl group.

Examples of the acylphosphine oxide compound represented by the formula (C1) or (C2) include, for example, JP-B 63-40799, JP-B 5-29234, JP-A-10-95788, JP-A-10- Examples include compounds described in Japanese Patent No. 29997.
Specific examples of the acylphosphine oxide compound include the following compounds (Exemplary Compounds (P-1) to (P-26)), but the present invention is not limited to these.

  As the acylphosphine oxide compound, a monoacylphosphine oxide compound, a bisacylphosphine oxide compound, or the like can be used. As the monoacylphosphine oxide compound, a known monoacylphosphine oxide compound can be used. Examples thereof include monoacylphosphine oxide compounds described in Japanese Patent Publication No. 60-8047 and Japanese Patent Publication No. 63-40799. Specific examples include isobutyryl-methylphosphinic acid methyl ester, isobutyryl-phenylphosphinic acid methyl ester, pivaloyl-phenylphosphinic acid methyl ester, 2-ethylhexanoyl-phenylphosphinic acid methyl ester, pivaloyl-phenylphosphinic acid isopropyl ester, p. -Toluyl-phenylphosphinic acid methyl ester, o-toluyl-phenylphosphinic acid methyl ester, 2,4-dimethylbenzoyl-phenylphosphinic acid methyl ester, p-tert-butylbenzoyl-phenylphosphinic acid isopropyl ester, acryloyl-phenylphosphinic acid Methyl ester, isobutyryl-diphenylphosphine oxide, 2-ethylhexanoyl-diphenylphosphine oxide, o-to Yl-diphenylphosphine oxide, p-tertiarybutylbenzoyl-diphenylphosphine oxide, 3-pyridylcarbonyl-diphenylphosphine oxide, acryloyl-diphenylphosphine oxide, benzoyl-diphenylphosphine oxide, pivaloyl-phenylphosphinic acid vinyl ester, adipoyl-bis- Diphenylphosphine oxide, pivaloyl-diphenylphosphine oxide, p-toluyl-diphenylphosphine oxide, 4- (tertiarybutyl) -benzoyl-diphenylphosphine oxide, 2-methylbenzoyl-diphenylphosphine oxide, 2-methyl-2-ethylhexanoyl -Diphenylphosphine oxide, 1-methyl-cyclohexanoyl-diphenylphosphine Examples thereof include oxide, pivaloyl-phenylphosphinic acid methyl ester, and pivaloyl-phenylphosphinic acid isopropyl ester.

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

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

[Α-aminoacetophenone compound]
The α-aminoacetophenone compound may be used alone or in combination of two or more.
As the α-aminoacetophenone compound, a compound represented by the following formula (C5) can be preferably used.

In the formula, X ¹ represents a group represented by the following (a), (b) or (c).

式中ｐは０又は１である。

In the formula, p is 0 or 1.

式中ｑは０乃至３の整数であり、ｒは０又は１である。

In the formula, q is an integer of 0 to 3, and r is 0 or 1.

In the formula, Y represents a hydrogen atom, a halogen atom, an OH group, or an alkyl group having 1 to 12 carbon atoms (note that unless otherwise specified, an alkyl group means a linear or branched alkyl group. In the invention, the same applies hereinafter.), An alkoxy group having 1 to 12 carbon atoms, an aromatic ring group, or a heterocyclic group. A preferable example of the aromatic ring group is a phenyl group or a naphthyl group. Moreover, as said heterocyclic group, a furyl group, a thienyl group, or a pyridyl group can be illustrated preferably.
The alkyl group, alkoxy group, aromatic ring group, and heterocyclic group in Y may have a substituent.
Examples of the substituent that the alkyl group in Y may have include an OH group, a halogen atom, -N (X ¹⁰ ) ₂ (X ¹⁰ is a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, and 3 or more carbon atoms. Represents an alkenyl group having 5 or less, a phenylalkyl group having 7 to 9 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, or a phenyl group.), An alkoxy group having 1 to 12 carbon atoms, -COOR (R Represents an alkyl group having 1 to 18 carbon atoms.), —CO (OCH ₂ OCH ₂ ) _n OCH ₃ (n represents an integer of 1 to 20), or —OCOR (R represents 1 carbon atom). Represents an alkyl group of 4 or less.).
As the substituent that the alkoxy group in Y may have, —COOR (R represents an alkyl group having 1 to 18 carbon atoms) or —CO (OCH ₂ CH ₂ ) _n OCH ₃ (n Represents an integer of 1 or more and 20 or less.
As the substituent that the aromatic ring group or heterocyclic group in Y may have, — (OCH ₂ CH ₂ ) _n OH (n represents an integer of 1 or more and 20 or less), — (OCH ₂ CH ₂ ) _N OCH ₃ (n represents an integer of 1 to 20), an alkylthio group having 1 to 8 carbon atoms, a phenoxy group, and —COOR (R represents an alkyl group having 1 to 18 carbon atoms), _{-CO (OCH 2 CH 2) n} OCH 3 (n represents an integer of 1 to 20.), a phenyl group, or, benzyl groups.
If possible, these substituents may have two or more, and if possible, the substituents may be further substituted.
In the formula, X ¹² represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a phenyl group. X ¹³ , X ¹⁴ and X ¹⁵ each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. X ¹³ and X ¹⁴ may be cross-linked to form an alkylene group having 3 to 7 carbon atoms.

In the formula, X ² represents the same group as X ¹ , a cycloalkyl group having 5 or 6 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or a phenyl group.
The alkyl group and phenyl group in X ² may have a substituent.
Examples of the substituent that the alkyl group in X ² may have include an alkoxy group having 1 to 4 carbon atoms, a phenoxy group, a halogen atom, and a phenyl group.
Examples of the substituent that the phenyl group in X ² may have include a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.
If possible, these substituents may have two or more, and if possible, the substituents may be further substituted.
In the formula, X ¹ and X ² may be cross-linked to form a group represented by the following formula.

In the formula, X ³ is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 3 to 5 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, or a phenylalkyl having 7 to 9 carbon atoms. Represents a group.
The alkyl group, alkenyl group, cycloalkyl group, and phenylalkyl group in X ³ may have a substituent, such as an OH group, an alkoxy group having 1 to 4 carbon atoms,- CN or -COOR (R represents an alkyl group having 1 to 4 carbon atoms).
In the formula, X ⁴ is an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 3 to 5 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, a phenylalkyl group having 7 to 9 carbon atoms, or phenyl Represents a group.
The alkyl group, alkenyl group, cycloalkyl group, phenylalkyl group, and phenyl group in X ⁴ may have a substituent.
Examples of the substituent that the alkyl group, alkenyl group, cycloalkyl group, and phenylalkyl group in X ⁴ may have include an OH group, an alkoxyl group having 1 to 4 carbon atoms, —CN, or —COOR. (R represents an alkyl group having 1 to 4 carbon atoms). When the alkyl group denoted by X ⁴ has a substituent, the number of carbon atoms in the alkyl group that is substituted is preferably 2 to 4.
As the substituent that the phenyl group in X ⁴ may have, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or —COOR (where R is 1 carbon atom) Represents an alkyl group of 4 or less.).
Here, X ² and X ⁴ are cross-linked to form an alkylene group having 1 to 7 carbon atoms, a phenyl alkylene group having 7 to 10 carbon atoms, an o-xylylene group, a 2-butenylene group, or 2 or 3 oxa- or aza-alkylene groups may be formed.
X ³ and X ⁴ may be cross-linked to form an alkylene group having 3 to 7 carbon atoms.
The alkylene group formed by crosslinking X ³ and X ⁴ is, as a substituent, an OH group, an alkoxy group having 1 to 4 carbon atoms, or —COOR (R represents an alkyl having 1 to 4 carbon atoms). .), And —O—, —S—, —CO—, or —N (X ¹⁶ ) — (X ¹⁶ is a hydrogen atom, having 1 to 12 carbon atoms) in the bond. An alkyl group, or 1 or 2 or more -O- in a bonding chain, an alkenyl group having 3 to 5 carbon atoms, a phenylalkyl group having 7 to 9 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, —CH ₂ CH ₂ CN, —CH ₂ CH ₂ COOR (where R represents an alkyl group having 1 to 4 carbon atoms), an alkanoyl group having 2 to 8 carbon atoms or a benzoyl group intervening 1 or more carbon atoms Represents an alkyl group of 12 or less.) .
In the formula, X ⁵ , X ⁶ , X ⁷ , X ⁸ and X ⁹ are each independently a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, a cycloalkyl group having 5 or 6 carbon atoms, a phenyl group, benzyl group, a benzoyl group, -OX ¹⁷ group, -SX ¹⁸ group, -SO-X ¹⁸ group, -SO ₂ -X ^{18 group, -N (X 19) (X} 20) group, -NH-SO ₂ -X ²¹ groups or a group represented by the following formula is represented.

Wherein, Z is -O -, - S -, - N (X 10) -X 11 -N (X 10) - or a group represented by the following formula. X ¹ , X ² , X ³ and X ⁴ are as defined in the above formula (C5).

In the formula, X ¹⁰ is the same as described above, X ¹¹ is a linear or branched alkylene group having 2 to 16 carbon atoms, or one or more —O—, —S—, or —N in these chains. (X ¹⁰ ) — represents a linear or branched alkylene group having 2 to 16 carbon atoms (X ¹⁰ is the same as described above).
X ¹⁷ is a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, — (CH ₂ CH ₂ O) _n H (n is an integer of 2 to 20), an alkanoyl group having 2 to 8 carbon atoms, and 3 carbon atoms. Alkenyl group having 12 or less, cyclohexyl group, hydrocyclohexyl group, phenyl group, phenylalkyl group having 7 to 9 carbon atoms, or —Si (R ⁴ ) _r (R ⁵ ) _3-r (R ⁴ is carbon number) 1 to 8 alkyl groups, R ⁵ represents a phenyl group, and r represents 1, 2 or 3).
The alkyl group and phenyl group in X ¹⁷ may have a substituent.
As the substituent that the alkyl group for X ¹⁷ may have, —CN, —OH, an alkoxy group having 1 to 4 carbon atoms, an alkenyloxy group having 3 to 6 carbon atoms, —OCH ₂ CH ₂ CN , —CH ₂ CH ₂ COOR (R represents an alkyl group having 1 to 4 carbon atoms), —COOH, or —COOR (R represents an alkyl group having 1 to 4 carbon atoms). . When the alkyl group denoted by X ¹⁷ has a substituent, the carbon number of the alkyl group is substituted is preferably 1 or more and 6 or less.
Examples of the substituent that the phenyl group in X ¹⁷ may have include a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.
X ¹⁸ represents a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 3 to 12 carbon atoms, a cyclohexyl group, a phenyl group, or a phenylalkyl group having 7 to 9 carbon atoms.
The alkyl group and phenyl group in X ¹⁸ may have a substituent.
The substituent which the alkyl group in X ¹⁸ may have is —SH, —OH, —CN, —COOR (R represents an alkyl group having 1 to 4 carbon atoms), 1 to 4 carbon atoms. Or an —OCH ₂ CH ₂ CN or —OCH ₂ CH ₂ COOR (wherein R represents an alkyl having 1 to 4 carbon atoms).
Examples of the substituent that the phenyl group in X ¹⁸ may have include a halogen atom, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.
X ¹⁹ and X ²⁰ are each independently a hydrogen atom; an alkyl group having 1 to 12 carbon atoms; a hydroxyalkyl group having 2 to 4 carbon atoms; an alkoxyalkyl group having 2 to 10 carbon atoms; The following alkenyl groups; a cycloalkyl group having 5 to 12 carbon atoms; a phenylalkyl group having 7 to 9 carbon atoms; a phenyl group; a halogen atom; an alkyl group having 1 to 12 carbon atoms; A phenyl group substituted by an alkoxy group; or an alkanoyl group having 2 or 3 carbon atoms; or a benzoyl group. X ¹⁹ and X ²⁰ are cross-linked to form an alkylene group having 2 to 8 carbon atoms, or an OH group, an alkoxy group having 1 to 4 carbon atoms, or —COOR (R is an alkyl group having 1 to 4 carbon atoms. ) An alkylene group having 2 to 8 carbon atoms substituted by a group; an alkylene group having 2 to 8 carbon atoms in which —O—, —S— or —N (X ¹⁶ ) — is interposed in the bond chain (X ¹⁶ may be the same as described above.
X ²¹ represents an alkyl group having 1 to 18 carbon atoms; phenyl group; naphthyl group; or a phenyl group substituted by a halogen atom, an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 8 carbon atoms; Represents a naphthyl group.

  The formula (C5) is more preferably represented by the formula (d).

In formula (d), X ¹ and X ² each independently represent a methyl group, an ethyl group, or a benzyl group, —NX ³ X ⁴ represents a dimethylamino group, a diethylamino group, or a morpholino group, and X ⁵ Represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, an alkylthio group having 1 to 8 carbon atoms, a dimethylamino group, or a morpholino group. -NX ³ X ⁴ is a dimethylamino group Among these, or, more preferably morpholino group.

Furthermore, as the α-aminoacetophenone compound, an acid adduct salt of the compound represented by the above formula (C5) can also be used.
As commercially available α-aminoacetophenone compounds, polymerization initiators available from Ciba Specialty Chemicals under the trade names Irgacure 907 (IRGACURE 907), Irgacure 369 (IRGACURE 369), and Irgacure 379 (IRGACURE 379) are available. It can be illustrated.

Specific examples of the α-aminoacetophenone compound include the following compounds.
For example, 2-dimethylamino-2-methyl-1-phenylpropan-1-one, 2-diethylamino-2-methyl-1-phenylpropan-1-one, 2-methyl-2-morpholino-1-phenylpropane- 1-one, 2-dimethylamino-2-methyl-1- (4-methylphenyl) propan-1-one, 2-dimethylamino-1- (4-ethylphenyl) -2-methylpropan-1-one, 2-dimethylamino-1- (4-isopropylphenyl) -2-methylpropan-1-one, 1- (4-butylphenyl) -2-dimethylamino-2-methylpropan-1-one, 2-dimethylamino -1- (4-methoxyphenyl) -2-methylpropan-1-one, 2-dimethylamino-2-methyl-1- (4-methylthiophenyl) propane- -One, 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (IRGACURE 907), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane -1-one (IRGACURE 369), 2-benzyl-2-dimethylamino-1- (4-dimethylaminophenyl) -butan-1-one, 2-dimethylamino-2-[(4-methylphenyl) methyl] And -1- [4- (4-morpholinyl) phenyl] -1-butanone (IRGACURE 379).

<Other radical polymerization initiators>
In the present invention, other radical polymerization initiators can be contained as the radical polymerization initiator. Examples of other radical polymerization initiators include α-hydroxyacetophenone compounds and oxime ester compounds.

[Α-hydroxyacetophenone compound]
The α-hydroxyacetophenone compound is preferably a compound represented by the following formula (C6).

In Formula (C6), R ¹ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms. R ² and R ³ each independently represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. R ² and R ³ may be bonded to form a ring having 4 to 8 carbon atoms.
The alkyl group, alkoxy group, alkyl group, and ring having 4 to 8 carbon atoms may have a substituent, and examples of the substituent include the substituents exemplified in Formula (C1).

Examples of α-hydroxyacetophenones include 2-hydroxy-2-methyl-1-phenylpropan-1-one (DAROCURE 1173), 2-hydroxy-2-methyl-1-phenylbutan-1-one, 1- (4-methylphenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-isopropylphenyl) -2-methylpropan-1-one, 1- (4-butylphenyl) -2-hydroxy 2-methylpropan-1-one, 2-hydroxy-2-methyl-1- (4-octylphenyl) propan-1-one, 1- (4-dodecylphenyl) -2-methylpropan-1-one, 1- (4-methoxyphenyl) -2-methylpropan-1-one, 1- (4-methylthiophenyl) -2-methylpropan-1-one, 1 (4-Chlorophenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-bromophenyl) -2-hydroxy-2-methylpropan-1-one, 2-hydroxy-1- (4- Hydroxyphenyl) -2-methylpropan-1-one, 1- (4-dimethylaminophenyl) -2-hydroxy-2-methylpropan-1-one, 1- (4-carboethoxyphenyl) -2-hydroxy- 2-methylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone (IRGACURE 184), 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one (IRGACURE 2959).
Further, as commercially available α-hydroxyacetophenone compounds, trade names of Irgacure 184 (IRGACURE 184), Darocur 1173 (DARUCUR 1173), Irgacure 127 (IRGACURE 127), and Irgacure 2959 (IRGACURE 2959) manufactured by Ciba Specialty Chemicals, Inc. Available polymerization initiators can also be used.

[Oxime ester compound]
The oxime ester compound is preferably a compound represented by the following formula (C7).

In the formula, Ar ¹ represents a structure selected from the group consisting of naphthalene structure, anthracene structure, anthraquinone structure, benzophenone structure, thianthrene structure, phenoxathian structure, diphenylthioether structure, thioxanthone structure, and morpholinobenzene structure. Among these, naphthalene structure, anthraquinone structure, benzophenone structure, diphenylthioether structure, thioxanthone structure, and morpholinobenzene structure are preferable, and thioxanthone structure is particularly preferable. Ar ² represents a phenyl group. These structures or groups may have a substituent such as an alkyl group such as a methyl group or an ethyl group, a halogen atom, or —CN (cyano group).
n represents an integer of 1 or 2. When n is 1, M is an alkyl group having 1 to 20 carbon atoms such as methyl group or ethyl group, a cycloalkyl group having 5 to 8 carbon atoms such as cyclopropane group or cyclohexane group, acetyloxy group, propylene. A divalent group in which an alkanoyl group having 2 to 20 carbon atoms such as noyloxy, an alkoxycarbonyl group having 2 to 12 carbon atoms such as propyloxycarbonyl group and butyloxycarbonyl, and a plurality of polymethylene groups are connected by an ether bond. A monovalent group in which an alkoxy group is linked to one of the bonds, phenyl group, benzoyl group, benzoyloxy group, phenoxycarbonyl group, aralkylcarbonyloxy group having 7 to 13 carbon atoms, 7 to 13 carbon atoms An aralkyloxycarbonyl group or an alkylthio group having 1 to 6 carbon atoms is represented. Among these, M is preferably an alkyl group having 1 to 20 carbon atoms or a phenyl group.

When n is 2, M is an alkylene group having 1 to 12 carbon atoms such as an ethylene group or a propylene group, a polymethylene group having 3 to 12 carbon atoms such as a tetramethylene group, an oxypropyleneoxy group, or an oxybutyloxy group. An oxyalkyleneoxy group having 1 to 12 carbon atoms, such as cyclohexylene group, phenylene group, —CO—O—A—O—CO—, —CO—O— (CH ₂ CH ₂ O) m—CO—, Or represents -CO-A-CO-, A represents an alkylene group having 2 to 12 carbon atoms, and m represents an integer of 1 to 20. Among these, M is preferably an alkylene group having 1 to 6 carbon atoms, a polymethylene group having 1 to 6 carbon atoms, or a cyclohexylene group.

Specific examples of the oxime ester compound include 3-benzoyloxyiminobutan-2-one, 3-acetoxyiminobutan-2-one, 3-propionyloxyiminobutane-2-one, and 2-acetoxyiminopentane-3. -One, 2-acetoxyimino-1-phenylpropan-1-one, 2-benzoyloxyimino-1-phenylpropan-1-one, 3-p-toluenesulfonyloxyiminotan-2-one, 2-ethoxy And carbonyloxyimino-1-phenylpropan-1-one.
Further, as commercially available oxime ester compounds, Irgacure OXE-01 (1- (4-phenylthiophenyl) -1,2-octanedione-2- (O-benzoyloxime)), Irgacure manufactured by Ciba Specialty Chemicals, Inc. Polymerization initiator available under the trade name OXE-02 (1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl] -ethanone-1- (O-acetyloxime)) Can also be used.

In the ink composition of the present invention, the total amount of the polymerization initiator is preferably 0.01 to 35% by weight, more preferably 0.5 to 20% by weight, and still more preferably 1. It is in the range of 0 to 15% by weight. When the content is 0.01% by weight or more, the composition can be sufficiently cured, and when it is 35% by weight or less, a cured film having a uniform degree of curing can be obtained.
In the present invention, an acylphosphine oxide compound is preferably used as a polymerization initiator, and the acylphosphine oxide compound is preferably used in an amount of 0.01 to 35% by weight, more preferably based on the total amount of the ink composition. It is 1 to 25% by weight, and more preferably 3 to 20% by weight.

  Moreover, when using the sensitizer mentioned later for the ink composition of this invention, the total usage-amount of a polymerization initiator is a weight ratio of a polymerization initiator: sensitizer with respect to a sensitizer, Preferably it is 200: It is 1-1: 200, More preferably, it is the range of 50: 1 to 1:50, More preferably, it is the range of 20: 1 to 1: 5.

(D) Optical brightener The ink composition of the present invention contains a fluorescent brightener.
Here, the fluorescent whitening agent in the present invention is a colorless or pale yellow dye that absorbs in the near ultraviolet region and emits purple-blue to blue fluorescence.
In the present invention, the fluorescent brightening agent can be appropriately selected from various fluorescent brightening agents conventionally known by those skilled in the art. Fluorescent brighteners include diaminobenzene sulfonic acid, benzoxazole, coumarin, pyrazoline, pyrene, oxazole, thiazole, imidazole, benzimidazole, imidazolone, benzidine and stilbene. Whitening agents can be exemplified. Among these, benzoxazole, coumason, pyrazoline, and the like are preferable, and benzoxazolinaphthalene and benzoxazolyl stilbene are particularly preferable.

  Specific examples include fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771, JP-A-4-219266, and the like. However, it is preferably at least one selected from compounds represented by the following formula (F) or compounds represented by the following formulas (W1) to (W5).

A ⁿ⁻ · n (B ⁺ ) (F)
In formula (F), A represents a group having an anionic group, B represents an organic cation having a total carbon number of 15 or more, and n represents an integer of 1 to 9.

In the formula (F), the fluorescent brightener component having an anionic group represented by A includes a stilbene fluorescent brightener having an anionic group, a coumarin fluorescent brightener having an anionic group, an anion A thiophene fluorescent brightening agent having a functional group is preferred. Examples of the anionic group in the fluorescent brightener component having an anionic group include a sulfonic acid group and a carboxyl group, and a sulfonic acid group is particularly preferable.
Examples of the fluorescent brightener component having a sulfonic acid group include a stilbene fluorescent whitening agent having a sulfonic acid group, a coumarin fluorescent whitening agent having a sulfonic acid group, and a thiophene fluorescent whitening agent having a sulfonic acid group. preferable.

  Examples of the fluorescent brightener component having an anionic group represented by A include, for example, “Fluorescent brightener” edited by Kasei Kogyo Kogyo Kyokai, British Patent No. 920,988, German Patent No. 1,065,838. It can be easily synthesized with reference to the specification, US Pat. No. 2,610,152 and the like.

The organic cation represented by B is preferably an ammonium cation or pyridinium cation having a total carbon number of 15 or more, and particularly preferably an ammonium cation having a total carbon number of 15 or more.
The ammonium cation having a total carbon number of 15 or more is preferably an ammonium cation represented by the following formula (F-1).

  The pyridinium cation having 15 or more carbon atoms is preferably a pyridinium cation represented by the following formula (F-2).

In the formula (F-2), R ₅ represents an alkyl group or phenyl group having a total carbon number of 10 or more, and the total carbon number of R ₅ is more preferably 15 or more.
In the present invention, the organic salt compound having a fluorescent whitening effect represented by the formula (F) is a mixture of a fluorescent whitening agent component having an anionic group corresponding to A and a compound having an organic cation of B. Therefore, it can be easily synthesized.

  Next, although the specific example of the organic salt compound which has the fluorescent whitening effect represented by Formula (F) used for this invention is given, this invention is not limited by these description.

  In the present invention, the fluorescent brightening agent is preferably at least one selected from the group consisting of compounds represented by the following formulas (W1) to (W5).

In formulas (W1) to (W5), R _{1 to} R ₁₇ each represent a hydrogen atom or an organic group.

The fluorescent brightener represented by the formula (W1) is a bis (benzoxazolyl) stilbene fluorescent brightener.
In the formula (W1), R ₁ , R ₂ , R ₃ and R ₄ each represent a hydrogen atom or an organic group which may be the same or different. As the organic group, an alkyl group having 1 to 15 carbon atoms, an alkoxy group, an aryl group, or the like is preferable. Moreover, these organic groups may be further substituted.
Preferable examples of R ₁ , R ₂ , R ₃ , and R ₄ include a hydrogen atom, a methyl group, an ethyl group, a tert-butyl group, and a tert-octyl group.

The fluorescent brightener represented by the formula (W2) is a bis (benzoxazolyl) naphthalene fluorescent brightener.
In the formula (W2), R ₅ , R ₆ , R ₇ and R ₈ each represent a hydrogen atom or an organic group which may be the same or different. As the organic group, an alkyl group having 1 to 15 carbon atoms, an alkoxy group, an aryl group, or the like is preferable. Moreover, these organic groups may be further substituted.
Preferable examples of R ₅ , R ₆ , R ₇ and R ₈ include a hydrogen atom, a methyl group, an ethyl group, a tert-butyl group and a tert-octyl group.

The fluorescent brightener represented by the formula (W3) is a bis (benzoxazolyl) thiophene fluorescent brightener.
In the formula (W3), R ₉ , R ₁₀ , R ₁₁ and R ₁₂ each represent a hydrogen atom or an organic group which may be the same or different. As the organic group, an alkyl group having 1 to 15 carbon atoms, an alkoxy group, an aryl group, or the like is preferable. Moreover, these organic groups may be further substituted.
Preferable examples of R ₉ , R ₁₀ , R ₁₁ , and R ₁₂ include a hydrogen atom, a methyl group, an ethyl group, a tert-butyl group, and a tert-octyl group.

The fluorescent brightener represented by the formula (W4) is a pyrazoline-based fluorescent brightener. Pyrazoline-based optical brighteners include pyrazoline derivatives and pyrazolone derivatives.
In the formula (W4), R ₁₃ , R ₁₄ , and R ₁₅ each represent a hydrogen atom or an organic group that may be the same or different. As the organic group, an alkyl group having 1 to 15 carbon atoms, an alkoxy group, an aryl group, a sulfonamide group and the like are preferable. Moreover, these organic groups may be further substituted.
Preferable examples of R ₁₃ , R ₁₄ and R ₁₅ include a hydrogen atom, a methyl group, an ethyl group, a tert-butyl group, a tert-octyl group and a phenyl group.

The fluorescent brightener represented by the formula (W5) is a coumarin fluorescent brightener.
In the formula (W5), R ₁₆ and R ₁₇ each represents a hydrogen atom or an organic group which may be the same or different. R ₁₆ is preferably an organic group containing a triazine or triazole ring, and R ₁₇ is preferably an organic group such as an alkyl group, an alkoxy group or an aryl group.

  Specific examples of the fluorescent brightener represented by the formulas (W1) to (W5) are described below, but the fluorescent brightener that can be used in the present invention is not limited by these descriptions.

A fluorescent brightening agent may be used alone or in combination of two or more.
The content of the fluorescent brightening agent in the ink composition of the present invention is preferably 0.01% by weight or more and 10% by weight or less based on the total mass of the ink composition from the viewpoint of ejection stability. It is more preferably 0.02% by weight or more and 7% by weight or less, and further preferably 0.03% by weight or more and 5% by weight or less.
It is preferable for the content of the optical brightener to be in the above range because high curing sensitivity can be obtained and coloring of the ink composition can be suppressed.

(E) Other components <sensitizing dye>
In the present invention, a sensitizing dye may be added for the purpose of improving the sensitivity of the photopolymerization initiator. As the sensitizing dye, those belonging to the following compounds and having an absorption wavelength in the range of 350 nm to 450 nm are preferable.
Examples of the sensitizing dye include polynuclear aromatics (for example, pyrene, perylene, triphenylene), xanthenes (for example, fluorescein, eosin, erythrosine, rhodamine B, rose bengal), cyanines (for example, thiacarbocyanine, Oxacarbocyanine), merocyanines (eg, merocyanine, carbomerocyanine), thiazines (eg, thionine, methylene blue, toluidine blue), acridines (eg, acridine orange, chloroflavin, acriflavine), anthraquinones (eg, anthraquinone) ), Squalium (eg, squalium), and coumarins (eg, 7-diethylamino-4-methylcoumarin).

  Further, as the sensitizing dye, compounds represented by the following formulas (IX) to (XIII) are more preferable.

In formula (IX), A ¹ represents a sulfur atom or —NR ⁵⁰ —, R ⁵⁰ represents an alkyl group or an aryl group, and L ² represents a basic nucleus of the dye in combination with the adjacent A ² and the adjacent carbon atom. R ⁵¹ and R ⁵² each independently represents a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁵¹ and R ⁵² are bonded to each other to form an acidic nucleus of the dye. May be. W represents an oxygen atom or a sulfur atom.
In formula (X), Ar ¹ and Ar ² each independently represent an aryl group and are linked via a bond with —L ³ —. Here, L ³ represents —O— or —S—. W is synonymous with that shown in Formula (IX).
In the formula (XI), A ² represents a sulfur atom or NR ⁵⁹ , L ⁴ represents a nonmetallic atomic group that forms a basic nucleus of the dye together with adjacent A ² and a carbon atom, R ⁵³ , R ⁵⁴ , R ⁵⁵ , R ⁵⁶ , R ⁵⁷ and R ⁵⁸ each independently represent a monovalent nonmetallic atomic group, and R ⁵⁹ represents an alkyl group or an aryl group.

In formula (XII), A ³ and A ⁴ each independently represent —S— or —NR ⁶² — or —NR ⁶³ —, wherein R ⁶² and R ⁶³ each independently represent a substituted or unsubstituted alkyl group, or Represents a substituted or unsubstituted aryl group, and L ⁵ and L ⁶ each independently represent a nonmetallic atomic group that forms a basic nucleus of a dye in cooperation with adjacent A ³ , A ^4, and adjacent carbon atoms. , R ⁶⁰ and R ⁶¹ are each independently a hydrogen atom or a monovalent non-metallic atomic group, or may be bonded to each other to form an aliphatic or aromatic ring.
In formula (XIII), R ⁶⁶ represents an aromatic ring or a hetero ring which may have a substituent, and A ⁵ represents an oxygen atom, a sulfur atom or —NR ⁶⁷ —. R ⁶⁴ , R ⁶⁵ and R ⁶⁷ each independently represent a hydrogen atom or a monovalent nonmetallic atomic group, and R ⁶⁷ and R ⁶⁴ and R ⁶⁵ and R ⁶⁷ are each aliphatic or aromatic with respect to each other. They can be joined to form a ring.

  Preferable specific examples of the compounds represented by formulas (IX) to (XIII) include the exemplified compounds (A-1) to (A-20) shown below.

<Co-sensitizer>
Furthermore, the ink composition of the present invention may contain a known compound having a function of further improving sensitivity or suppressing inhibition of polymerization by oxygen as a cosensitizer.
Such co-sensitizers include amines such as M.I. R. Sander et al., “Journal of Polymer Society”, Vol. 10, 3173 (1972), Japanese Patent Publication No. 44-20189, Japanese Patent Publication No. 51-82102, Japanese Patent Publication No. 52-134692, Japanese Patent Publication No. 59-138205. No. 60, 84305, JP 62-18537, JP 64-33104, Research Disclosure 33825, and the like. Examples include ethanolamine, p-dimethylaminobenzoic acid ethyl ester, p-formyldimethylaniline, p-methylthiodimethylaniline and the like.

Other co-sensitizers include thiols and sulfides, for example, thiol compounds described in JP-A-53-702, JP-B-55-500806, JP-A-5-142772, and JP-A-56- No. 75643, and more specifically, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2-mercaptobenzimidazole, 2-mercapto-4 (3H) -quinazoline, β-mercaptonaphthalene. Etc.
Other co-sensitizers include, for example, amino acid compounds (eg, N-phenylglycine), organometallic compounds described in Japanese Patent Publication No. 48-42965 (eg, tributyltin acetate), Japanese Patent Publication No. 55-34414. The hydrogen donor described in JP-A-6-308727, the sulfur compound described in JP-A-6-308727 (eg, trithiane, etc.), the phosphorus compound described in JP-A-6-250387 (diethylphosphite, etc.), Japanese Patent Application No. 6-191605 Si-H and Ge-H compounds described in the above No.

In the ink composition of the present invention, (A) the white pigment, (B) the polymerizable compound, (C) the polymerization initiator, and (D) the sensitizing dye and co-sensitizer used together with the fluorescent whitening agent. In addition, various additives can be used in combination depending on the purpose. For example, an antioxidant and a polymerization inhibitor can be added to improve the stability of the ink composition.
The ink composition of the present invention further includes various organic and metal complex anti-fading agents, potassium thiocyanate, lithium nitrate, ammonium thiocyanate, dimethylamine hydrochloride, etc. for the purpose of controlling ejection properties. In order to improve the adhesion between the conductive salt and the recording medium, a trace amount of organic solvent can be added.

In addition, various polymer compounds can be added to the ink composition of the present invention in order to adjust film physical properties.
In addition, a nonionic surfactant, a cationic surfactant, an organic fluoro compound, or the like can be added to the ink composition of the present invention in order to adjust liquid properties.
In addition to the above, the ink composition of the present invention can be applied to recording media such as leveling additives, matting agents, waxes for adjusting film physical properties, polyolefins, PET, etc., if necessary. In order to improve adhesion, a tackifier or the like that does not inhibit polymerization can be contained.
Below, each additive is described.

<Surfactant>
A surfactant may be added to the ink composition of the present invention in order to impart stable ejection properties for a long time.
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.

  A polymerization inhibitor may be added from the viewpoint of enhancing the storage stability. Further, when the ink composition of the present invention is used as an ink composition for ink jet recording, it is preferably discharged at a temperature in the range of 40 to 80 ° C. with a reduced viscosity, and also for preventing head clogging due to thermal polymerization. It is preferable to add a polymerization inhibitor. The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition of the present invention. Examples of the radical polymerization inhibitor include hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, cuperon Al, tris (N-nitroso-N-phenylhydroxylamine) aluminum salt, and the like.

<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.
Although the addition amount is appropriately selected according to the purpose, it is preferably 0.1 to 8% by weight 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-based antifading agent include nickel complexes and zinc complexes. No. 17643, Nos. VII to I, J. 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. .
Although the addition amount is appropriately selected according to the purpose, it is preferably 0.1 to 8% by weight 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 Examples include ether solvents.
In this case, it is effective to add the solvent within the range that does not cause the problem of solvent resistance and VOC, and the amount is preferably 0.1 to 5% by weight, more preferably 0.1 to 3% by weight based on the whole ink composition. % Range.

<Polymer compound>
Various polymer compounds can be added to the ink composition of the present invention in order to adjust film physical properties. 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, as a copolymer composition of the polymer compound, a copolymer containing “carboxyl group-containing monomer”, “alkyl methacrylate ester” or “alkyl acrylate ester” as a structural unit is also preferably used.

<Basic compound>
The basic compound is preferably added from the viewpoint of improving the storage stability of the ink composition. As the basic compound that can be used in the present invention, known basic compounds can be used. For example, basic inorganic compounds such as inorganic salts, and basic organic compounds such as amines can be preferably used. .

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 tackifier resin having a polymerizable unsaturated bond.

(Ink properties)
In the present invention, it is preferable to use an ink composition having a viscosity at 25 ° C. of 40 mPa · s or less in consideration of ejection properties. More preferably, it is 5-40 mPa * s, More preferably, it is 7-30 mPa * s. Moreover, it is preferable that the viscosity in discharge temperature (Preferably 25-80 degreeC, More preferably, 25-50 degreeC) is 3-15 mPa * s, and it is more preferable that it is 3-13 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 monomer can be reduced. Furthermore, it is preferable that 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 at 25 ° C. is preferably 20 to 35 mN / m. More preferably, it is 23-33 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 35 mN / m or less.

(2) Inkjet recording method, inkjet recording apparatus, and printed material The ink composition of the present invention is suitably used for inkjet recording.
In the inkjet recording method of the present invention, the ink composition of the present invention is ejected onto a recording medium (support, recording material, etc.) for inkjet recording, and actinic radiation is applied to the ink composition ejected onto the recording medium. It is a method of forming an image by irradiating and curing the ink.

More specifically, the inkjet recording method of the present invention comprises (a ¹ ) a step of ejecting the ink composition of the present invention onto a recording medium, and (b ¹ ) actinic radiation on the ejected ink composition. And a step of curing the ink composition.
By including the steps (a ¹ ) and (b ¹ ), the ink jet recording method of the present invention forms an image with the ink composition cured on the recording medium.
The printed matter of the present invention is a printed matter recorded by the inkjet recording method of the present invention.

In the step (a ¹ ) in the ink jet recording method of the present invention, an ink jet recording apparatus described in detail below can be used.

[Inkjet recording device]
There is no restriction | limiting in particular as an inkjet recording device used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can eject ink onto a recording medium in the step (a ¹ ) of the inkjet recording method of the present invention.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an actinic radiation source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head preferably has a multi-size dot of 1 to 100 pl, more preferably 8 to 30 pl, preferably 320 × 320 to 4,000 × 4,000 dpi, more preferably 400 × 400 to 1,600 ×. It can be driven so that it can discharge at a resolution of 1,600 dpi, more preferably 720 × 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

As described above, since it is desirable that the radiation curable ink, like the ink composition of the present invention, has a constant temperature for the ejected ink, the ink jet recording apparatus has a means for stabilizing the ink composition temperature. It is preferable to provide. The parts to be kept at a constant temperature are all the piping systems and members from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface. That is, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

Using the above inkjet recording apparatus, the ink composition of the present invention is ejected by heating the ink composition to preferably 25 to 80 ° C., more preferably 25 to 50 ° C. Preferably it is performed after lowering to 3 to 15 mPa · s, more preferably 3 to 13 mPa · s. In particular, it is preferable to use an ink composition having an ink viscosity at 25 ° C. of 50 mPa · s or less as the ink composition of the present invention, since it can be discharged satisfactorily. By using this method, high ejection stability can be realized.
A radiation curable ink composition such as the ink composition of the present invention generally has a higher viscosity than a water-based ink usually used in ink jet recording inks, and therefore has a large viscosity fluctuation due to temperature fluctuations during ejection. The ink viscosity fluctuation has a great influence on the change of the droplet size and the change of the droplet discharge speed, and causes the image quality deterioration. Therefore, it is necessary to keep the temperature of the ink at the time of ejection as constant as possible. Therefore, in the present invention, the control range of the ink temperature is preferably set to ± 5 ° C. of the set temperature, more preferably ± 2 ° C. of the set temperature, and further preferably set to ± 1 ° C.

Next, the step (b ¹ ) of curing the ink composition by irradiating the discharged ink composition with actinic radiation will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with actinic radiation to generate radicals, acids, bases, and other starting species, and the function of the starting species is polymerization of a radical polymerizable compound. This is because the reaction occurs and is accelerated. At this time, if a sensitizer is present together with the polymerization initiator in the ink composition, the sensitizer in the system absorbs actinic radiation and enters an excited state, and the polymerization initiator is decomposed by contact with the polymerization initiator. It can be accelerated and a more sensitive curing reaction can be achieved.

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

In addition, the polymerization initiation system of the ink composition of the present invention has sufficient sensitivity even with a low output actinic radiation. Therefore, it is appropriate to cure the exposed surface with an illuminance of 10 to 4,000 mW / cm ² , more preferably 20 to 2,500 mW / cm ² .

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

The ink composition of the present invention is appropriately irradiated with such actinic radiation, preferably for 0.01 to 120 seconds, more preferably for 0.1 to 90 seconds.
Actinic radiation irradiation conditions and a basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink ejection device, and the head unit and the light source are scanned by a so-called shuttle method. Irradiation with actinic radiation takes a certain period of time (preferably 0.01 to 0.5 seconds, more preferably 0.01 to 0.3 seconds, still more preferably 0.01 to 0.15 seconds) after ink landing. Will be done. In this way, by controlling the time from ink landing to irradiation to an extremely short time, it is possible to prevent the ink that has landed on the recording medium from spreading before curing. Further, it is preferable that the porous recording medium can be exposed before the ink penetrates to a deep portion where the light source does not reach, so that the remaining unreacted monomer can be suppressed.
Further, the curing may be completed by another light source that is not driven. International Publication No. 99/54415 pamphlet discloses a method using an optical fiber or a method of irradiating a recording unit with UV light by applying a collimated light source to a mirror surface provided on the side of the head unit as an irradiation method. Such a curing method can also be applied to the ink jet recording method of the present invention.

By adopting the ink jet recording method as described above, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved.
The ink composition of the present invention can also be used as an ink set in combination with ink compositions of other colors. For example, the ink composition can be used together with a cyan ink composition, a magenta ink composition, and a yellow ink composition. Further, it can be used as an ink set together with a black ink composition, or can be used as an ink set together with an ink composition such as light magenta and light cyan. In order to obtain a color image, it is preferable to superimpose in order from the lightest color. By superimposing the inks in the order of low lightness, it becomes easier for the irradiation line to reach the lower ink, and good curing sensitivity, reduction of residual monomers, and improvement in adhesion can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.
Thus, the ink composition of the present invention can form an image on the surface of a recording medium by being cured with high sensitivity by irradiation with actinic radiation.

  In the ink jet recording method of the present invention, an ink set containing the ink composition of the present invention can be suitably used. The order of each colored ink composition to be ejected is not particularly limited, but it is preferably applied to the recording medium from a colored ink composition having low brightness, and the ink composition of the present invention (white ink composition) When yellow, cyan, magenta, and black are used, the ink composition of the present invention is preferably applied onto the recording medium in the order of yellow → cyan → magenta → black. Furthermore, the present invention is not limited to this, and an ink set including at least a total of seven colors of light cyan and light magenta ink compositions and cyan, magenta, gray, black, white and yellow dark ink compositions is used. In this case, it is preferable that the toner is applied on the recording medium in the order of white → light cyan → light magenta → yellow → cyan → magenta → black.

  In the present invention, the recording medium is not particularly limited, and a known recording medium can be used as a support or a recording material. For example, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, cellulose propionate) Cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic film on which the above-mentioned metal is laminated or deposited. In addition, as the recording medium in the present invention, a non-absorbable recording medium can be preferably used.

(Ink set)
When the ink of the present invention is prepared in a plurality of colors and used as an ink set, the ink set includes at least one white ink composition of the present invention and two or more ink compositions in combination with an ink composition other than the present invention. If there is no particular limitation, it is preferable to include at least one color ink composition selected from the group consisting of cyan, magenta, yellow, black, light magenta and light cyan, and the ink composition of the present invention. .
The above ink set can be suitably used for the ink jet recording method of the present invention.
In order to obtain a full-color image using the ink composition of the present invention, yellow, cyan, which is a combination of the ink composition of the present invention and four dark ink compositions comprising yellow, cyan, magenta, and black. , Magenta, black and white are preferable. More preferably, the ink set is a combination of a dark ink composition of five colors consisting of yellow, cyan, magenta, black and white and an ink composition of light cyan and light magenta.
The “dark ink composition” in the present invention means an ink composition in which the content of the colorant exceeds 1% by weight of the entire ink composition. There is no restriction | limiting in particular as said coloring agent, A well-known coloring agent can be used, A pigment and oil-soluble dye can be illustrated.
Needless to say, the ink set of the present invention may contain an ink composition containing 1% by weight or less of a colorant other than the pigment.

  The printed matter of the present invention can be obtained by printing the ink composition of the present invention on a recording medium using an ink jet printer, and then preferably irradiating the cured ink composition with actinic radiation and curing. The printed matter of the present invention can be applied to a wide range of fields because the ink used for image formation is excellent in hue and sensitivity, and thus has a high-quality image with excellent color development and sharpness.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to the form in these Examples.

The materials used in the present invention are as shown below.
Tipaque CR60-2 (white pigment (rutile titanium dioxide), average particle size 0.21 μm, manufactured by Ishihara Sangyo Co., Ltd.)
Tipaque A-220 (white pigment (anatase type titanium dioxide), average particle size 0.16 μm, manufactured by Ishihara Sangyo Co., Ltd.)
・ Solsperse 36000 (Dispersant manufactured by Nihon Lubrizol)
・ Fancryl 512A (dicyclopentenyloxyethyl acrylate, equivalent to Exemplified Compound M-11, manufactured by Hitachi Chemical Co., Ltd.)
・ Fancryl 513A (dicyclopentanyloxyethyl acrylate, equivalent to Exemplified Compound M-12, manufactured by Hitachi Chemical Co., Ltd.)
・ Fancryl 512M (dicyclopentenyloxyethyl methacrylate, equivalent to Exemplified Compound M-16, manufactured by Hitachi Chemical Co., Ltd.)
N-vinylcaprolactam (NVC, manufactured by Aldrich)
・ N-vinylpyrrolidone (NVP, manufactured by Nippon Shokubai Co., Ltd.)
Beam set 770 (NVF, N-vinylformamide, manufactured by Arakawa Chemical Industries, Ltd.)
Actilane 421 (propoxylated neopentyl glycol diacrylate, manufactured by Akcros)
・ KAYARAD DPCA-60 (DPCA, caprolactone-modified dipentaerythritol hexaacrylate, manufactured by Nippon Kayaku Co., Ltd.)
・ NK ester AMP-10G (PEA, phenoxyethyl acrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.)
・ NK ester A-TMPT (trimethylolpropane triacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.)
NK ester A-Gly-3E (glycerin EO-modified triacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd.)
・ DPGDA (dipropylene glycol diacrylate, manufactured by Daicel UCB)
・ TPGDA (Tripropylene glycol diacrylate, manufactured by Daicel UCB)
・ THFA (tetrahydrofurfuryl acrylate, manufactured by Aldrich)
・ Benzophenone (Photoinitiator, Wako Pure Chemical Industries, Ltd.)
-Firstcure ST-1 (polymerization inhibitor, manufactured by Chem First)
・ Darocur TPO (acylphosphine oxide photoinitiator, manufactured by Ciba Specialty Chemicals)
・ Irgacure 819 (acylphosphine oxide photoinitiator, manufactured by Ciba Specialty Chemicals)
・ Irgacure 184 (Photoinitiator, manufactured by Ciba Specialty Chemicals)
・ Irgacure 369 (α-aminoacetoacetophenone photoinitiator, manufactured by Ciba Specialty Chemicals)
・ Irgacure 907 (α-aminoacetophenone photoinitiator, manufactured by Ciba Specialty Chemicals)
・ Darocur EHA (polymerization accelerator, manufactured by Ciba Specialty Chemicals)
・ TINUVIN 770DF (Hindertoamine, Ciba Specialty Chemicals)
・ KF-353 (silicone surfactant, manufactured by Shin-Etsu Chemical Co., Ltd.)
・ Kayalight OS (fluorescent brightener, manufactured by Nippon Kayaku Co., Ltd.)
Bis (benzoxazolyl) stilbene fluorescent whitening agent (corresponding to Exemplified Compound W1-1)
Hostalux KCB (Naphthalene benzoxazoyl derivative (1,4-Bis (benzoxolyl-2-yl) naphthalene), optical brightener, manufactured by Clariant)

(Preparation of white mill base A)
Tipaque CR60-2 (rutile titanium oxide) 50 parts by weight NK ester AMP-10G 46.5 parts by weight Solsperse 36000 3.5 parts by weight The above ingredients were mixed with stirring to obtain White Mill Base A. The white mill base A was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 4 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

(Preparation of comparative white mill base B)
Tipaque A-220 50 parts by weight Actylene 421 45 parts by weight Solsperse 36000 5.0 parts by weight The above ingredients were mixed with stirring to obtain White Mill Base B. The white mill base B was prepared in a disperser motor mill M50 (manufactured by Eiger) and dispersed for 4 hours at a peripheral speed of 9 m / s using zirconia beads having a diameter of 0.65 mm.

  The components listed in Table 1 were stirred with a high-speed water-cooled stirrer to prepare inks of Examples 1 to 10 and Comparative Examples 1 to 4.

<< Inkjet recording method >>
Next, recording on a recording medium was performed using an inkjet recording experimental apparatus having a piezoelectric inkjet nozzle. The ink supply system was composed of an original tank, supply piping, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head, and heat insulation and heating were performed from the ink supply tank to the inkjet head portion. Temperature sensors were provided near the ink supply tank and the nozzle of the ink jet head, respectively, and temperature control was performed so that the nozzle portion was always 45 ° C. ± 2 ° C. The piezo-type inkjet head was driven so that 8 to 30 pl multi-size dots could be ejected at a resolution of 720 × 720 dpi. After landing, UV light was condensed to an exposure surface illuminance of 1,630 mW / cm ² , and the exposure system, main scanning speed, and ejection frequency were adjusted so that irradiation started 0.1 seconds after ink landed on the recording medium. . Further, the integrated light amount irradiated to the image was set to 1,500 mJ / cm ² . As an ultraviolet lamp, a HAN250NL high-cure mercury lamp (manufactured by GS Yuasa Corporation) was used. In the present invention, dpi represents the number of dots per 2.54 cm. As a recording medium, an ester film E5000 (thickness 125 μm, manufactured by Toyobo Co., Ltd.) was used.

(Viscosity stability over time)
The temporal stability in this example was evaluated by measuring the viscosity. Viscosity was measured using a B-type viscometer: Brookfield LVDV-I (manufactured by Brookfield) at 25 ° C. and a rotor rotation speed of 20 rpm. The viscosity change after storage for 2 weeks in an environment of 60 ° C. was evaluated as follows according to the ratio of the viscosity before and after storage (viscosity after storage ÷ viscosity before storage).
3: The viscosity ratio is 1.05 or less.
2: Ratio of viscosity is larger than 1.05 and 1.15 or less.
1: Ratio of viscosity is greater than 1.15 or aggregates are observed.

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

(Bending test)
Three solid images having an average film thickness of 12 μm, 24 μm, and 36 μm were drawn. In the bending test, the recording material on which the image was formed was bent once at 25 ° C. and evaluated by the presence or absence of cracks in the image area. In general, when the average film thickness is increased, distortion applied to the image portion when the image portion is bent increases, and cracks are likely to occur. That is, by testing whether the image portion is cracked with a thicker film thickness, a measure of flexibility can be obtained.
The evaluation criteria are as follows.
4: Cracks do not occur in all samples having an average film thickness of 12 μm, 24 μm, and 36 μm.
3: Cracks do not occur in samples having an average film thickness of 12 μm and 24 μm, but cracks occur in a bent portion of the image portion in a sample having an average film thickness of 36 μm.
2: Cracks do not occur in samples having an average film thickness of 12 μm, but cracks occur in the bent portions of the image portion in samples having an average film thickness of 24 μm and 36 μm.
1: In all samples having an average film thickness of 12 μm, 24 μm, and 36 μm, cracks occur in the bent portion of the image portion.

(Continuous discharge evaluation method)
Print a line with a line width of 0.5 points continuously for 30 minutes, and observe whether the printed line is interrupted, faint, or mist is generated around the line. did.
3: Line breaks, fading, and mist were not seen at all. Continuous discharge is very good.
2: Although the line was not interrupted, a slightly faint spot was observed, or a slight mist was observed. Good continuous discharge.
1: A part where the line was interrupted was seen, or a part where a severe mist was generated. Continuous discharge failure.

(Hue)
In accordance with the ink jet recording method, a solid image having an average film thickness of 12 μm was drawn, the image surface after ultraviolet irradiation was visually observed, and the hue of the white background portion was evaluated according to the following criteria.
3: Observed as a very good white background.
2: A white background with a slight yellowishness.
1: A white background with a strong yellowish tint.

(Concealment)
In accordance with the ink jet recording method, a solid image having an average film thickness of 12 μm was drawn, and on the image surface after ultraviolet irradiation, visual observation was performed in a state where a white background image was superimposed on black paper, and evaluation was performed based on the standard.
3: The black paper on the white background is sufficiently concealed and is observed to be sufficiently concealed.
2: Although the black paper on the white background is slightly transparent, it is observed that it has a concealing property that is not problematic in practice.
1: The black paper on the white background can be seen through, and the concealability is insufficient.

  Ink jet recording was performed using the obtained ink composition. The evaluation results are shown in Table 2.

Claims (11)

(A) a white pigment,
(B) a polymerizable compound,
(C) a polymerization initiator, and
(D) contains a fluorescent brightening agent,
(B) As the polymerizable compound, at least one selected from the group consisting of a monofunctional ethylenically unsaturated compound containing an aromatic monofunctional ethylenically unsaturated compound and further having an N-vinyllactam and an aliphatic cyclic structure. An ink composition comprising two compounds.   The ink composition according to claim 1, wherein the white pigment (A) is titanium oxide.   The ink composition according to claim 1 or 2, wherein the content of the (A) white pigment is 10% by weight or more based on the total amount of the ink composition.   The ink composition according to claim 1, wherein the polymerization initiator (C) is a radical polymerization initiator.   The ink composition according to claim 1, wherein the polymerization initiator (C) includes at least one compound selected from the group consisting of an acylphosphine oxide compound and an α-aminoacetophenone compound. The ink composition according to any one of claims 1 to 5, wherein the aromatic monofunctional ethylenically unsaturated compound is a compound represented by the formula (B5).

In Formula (B5), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, R ⁵ represents a substituent, and u is 0 Represents an integer of ˜5, and u ⁵ R ^{5 s} may be the same or different, and a plurality of R ⁵ may be bonded to each other to form a ring. An aromatic ring may be sufficient. The ink composition according to claim 1, wherein the monofunctional ethylenically unsaturated compound having an aliphatic cyclic structure is a compound represented by the formula (B2).

In Formula (B2), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, R ² represents a substituent, and r is 0 Represents an integer of ˜5, q represents a cyclic hydrocarbon structure, and the cyclic hydrocarbon structure includes a carbonyl bond (—C (O) —) and / or an ester bond (—C (O) O—) in addition to the hydrocarbon bond. ), And r ² R ^{2 s} may be the same or different, and one carbon atom in the norbornene skeleton may be replaced with an ether bond (—O—) and / or an ester bond. You may substitute by (-C (O) O-). The ink composition according to claim 7, wherein the compound represented by the formula (B2) is a compound represented by the formula (B3) or the formula (B4).

In Formula (B3) and Formula (B4), R ¹ represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms, X ¹ represents a divalent linking group, and R ³ and R ⁴ represent Each independently represents a substituent, s and t each independently represent an integer of 0 to 5, and s R ³ and t R ⁴ may be the same or different. Good.   The ink composition according to any one of claims 1 to 8, wherein the N-vinyllactam is N-vinylcaprolactam. (A ¹⁾ onto a recording medium, a step of discharging the ink composition according to any one claims 1 to 9 and,
(B ¹ ) An inkjet recording method comprising a step of irradiating the ejected ink composition with active radiation to cure the ink composition.   A printed matter recorded by the ink jet recording method according to claim 10.