JP2011063778A - Active energy ray-curable ink composition, inkjet recording method, and printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active energy ray-curable ink composition which is easily curable within a short period of time even in high humidity, which is excellent in adhesive properties to a substrate and in flexibility, and with which a wrinkle and curl of the substrate are suppressed, and to provide an inkjet recording method, and printed matter. <P>SOLUTION: The active energy ray-curable ink composition contains oxetane compounds and an epoxy compound, wherein the content of the oxetane compounds is less than 50 mass% with respect to the total mass of polymerizable compounds and the content of the epoxy compound is more than 50 mass% with respect to the total mass of polymerizable compounds, and at least one of the oxetane compounds is a first oxetane compound represented by general formula (A1). (In formula (A1), R<SP>1</SP>-R<SP>5</SP>each independently represents a hydrogen atom, a halogen atom, a 1-6C alkyl group or a 1-6C alkoxy group; R<SP>6</SP>and R<SP>7</SP>each independently represents a hydrogen atom, a halogen atom, a 1-6C alkyl, allyl or aryl group). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an active energy ray-curable ink composition suitably used for ink jet recording, an ink jet recording method, and a printed matter using the same.

  Cyclic ether compounds such as three-membered rings and four-membered rings are known to exhibit high reactivity, and the polymerizability contained in curable compositions to which photocationic polymerization or thermal polymerization using acid anhydrides is applied. It is used as a compound (see, for example, Patent Documents 1 and 2).

  On the other hand, 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 melt type thermal transfer method, an ink jet method and the like. In particular, the ink jet method can be implemented with an inexpensive apparatus, and the ink can be used efficiently because the image is directly formed on the recording medium by ejecting the ink only to the required image portion. Cost is low. Furthermore, there is little noise and it is excellent as an image recording method. According to the inkjet 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 productivity of printed matter and the sharpness of the printed image.

As one of the ink jet methods, there is a recording method using an ink for ink jet recording that can be cured by irradiation of radiation. According to this method, the productivity of printing can be improved and a sharp image can be formed by irradiating the ink immediately after ink ejection or after a certain time and curing the ink droplets.
By achieving high sensitivity of ink for ink jet recording that can be cured by irradiation with radiation such as ultraviolet rays, high curability is imparted to radiation, improving productivity of ink jet recording, reducing power consumption, and applying to radiation generators. There are many benefits such as longer life by reducing the load and prevention of volatilization of low molecular weight materials due to insufficient curing.

  In recent years, the curable ink jet method using such radiation, for example, ultraviolet rays has been attracting attention because it has a relatively low odor and can be recorded on a recording medium having no quick drying and no ink absorption. As one of the forms, there has been proposed a cationic polymerization type ink composition that is excellent in adhesion to a recording medium and has a small shrinkage rate upon UV curing (for example, see Patent Document 3).

  In general, as the active energy ray curable ink, a radical polymerization type ink is well known, and there are many examples of practical use. On the other hand, the cationic polymerization type ink has no polymerization inhibition due to oxygen as seen in radical polymerization type inks, can use a light source with low illuminance, has no odor of acrylic monomers, and has low irritation. However, there are limited examples of practical use.

  One reason for this is the property that the sensitivity decreases significantly under high humidity and the property that the sensitivity depends on the temperature. Environment-dependent inks have the essential problem that their image quality depends on the environment.

  In response to such a problem, 2- (4-methoxyphenyl) -3,3-dimethyloxetane is an oxetane compound in which the hydrogen atom at the 2-position of the oxetane ring is substituted with an aryl group as a compound for improving the reaction rate. Is disclosed (for example, see Patent Document 4).

  Patent Document 5 describes a system mainly using an epoxy compound for the purpose of obtaining a high-definition image with excellent character quality, in which the hydrogen atom at the 2-position of the oxetane ring is substituted with an aryl group and an alkyl group. An example of a curable composition using a combined bifunctional oxetane compound is shown.

Japanese Patent Laid-Open No. 11-43540 Japanese Patent Laid-Open No. 11-60702 Japanese Patent Laid-Open No. 9-183928 JP 2001-181386 A JP 2006-37112 A

  However, the oxetane compound described in Patent Document 4 is intended to mainly use an oxetane compound instead of an epoxy compound in a ring-opening cationic polymerization system. In this case, although there is a certain degree of reactivity, the sensitivity level in a high-humidity environment is still not sufficient in the case of curing a fine droplet with a low illumination source. Further, even in the curable composition described in Patent Document 5, when microscopic droplets are cured with a low illuminance light source, the sensitivity level in a high humidity environment is not yet sufficient, and the flexibility of the cured film is not sufficient. In some cases, wrinkles and curls were generated.

The present invention has been made in view of the above problems in the prior art, and an object thereof is to achieve the following object.
That is, the object of the present invention is an active energy ray curable type that is easy to cure in a short time even under high humidity, has excellent adhesion to the base material and flexibility, and can suppress wrinkling and curling of the base material. An object is to provide an ink composition.
Another object of the present invention is to provide an ink jet recording method using the active energy ray-curable ink composition and a printed matter recorded by the ink jet recording method.

Means for solving the above problems are as follows.
<1> At least an oxetane compound and an epoxy compound, wherein the content of the oxetane compound is less than 50% by mass with respect to the total polymerizable compound mass, and the content of the epoxy compound is the total polymerizable compound mass The active energy ray-curable ink composition is a first oxetane compound represented by the following general formula (A1), wherein at least one of the oxetane compounds exceeds 50% by mass.

In General Formula (A1), R ^{1 to} R ⁵ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ⁶ and R ⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group.

  <2> A second oxetane compound other than the first oxetane compound is further contained, and the content of the first oxetane compound and the second oxetane compound is 5 with respect to the total polymerizable compound mass, respectively. The active energy ray-curable ink composition according to <1>, in which the content of the epoxy compound is 55% by mass to 90% by mass with respect to the total polymerizable compound mass. .

  <3> A second oxetane compound other than the first oxetane compound is further contained, and the content of the first oxetane compound and the second oxetane compound is 10 with respect to the total polymerizable compound mass, respectively. The active energy ray-curable ink composition according to <1>, in which the content of the epoxy compound is 60% by mass to 80% by mass with respect to the total polymerizable compound mass. .

  <4> The active energy ray-curable ink composition according to any one of <1> to <3>, wherein the monofunctional epoxy compound is 50% by mass or less based on the total mass of the epoxy compound. It is.

  <5> Any one of <1> to <4>, wherein the monofunctional oxetane compound is 50% by mass or less based on the total mass of the first oxetane compound and the second oxetane compound. The active energy ray-curable ink composition described in 1.

  <6> The active energy ray-curable ink composition according to any one of <1> to <5>, wherein the epoxy compound has a weight average molecular weight of 100 to 300.

  <7> The active energy ray-curable ink composition according to any one of <1> to <6>, further including a sulfonium salt represented by the following general formula (P).

〔一般式（Ｐ）中、Ｘ⁻は、陰イオンを表す。〕

[In the general formula (P), X ⁻ represents an anion. ]

  <8> The active energy ray-curable ink composition according to any one of <1> to <7>, which is for inkjet recording.

  <9> A step of ejecting the active energy ray-curable ink composition according to <8> onto a recording medium using an ink jet recording apparatus, and an active energy ray to the ejected active energy ray-curable ink composition Is an ink jet recording method including a step of curing the active energy ray-curable ink composition.

<10> The active energy ray is irradiated by a light emitting diode, has an emission peak wavelength in a range of 350 nm to 420 nm, and a maximum illuminance on the surface of the recording medium of 10 mW / cm ^{2 to} 2,000 mW / cm ^2. It is the inkjet recording method as described in said <9> which is an ultraviolet-ray which becomes.

  <11> A printed matter recorded by the inkjet recording method according to <9> or <10>.

According to the present invention, an active energy ray-curable ink composition that is easy to cure in a short time even under high humidity, has excellent adhesion to the substrate and flexibility, and can suppress wrinkling and curling of the substrate. Things can be provided.
In addition, an inkjet recording method using the active energy ray-curable ink composition and a printed matter recorded by the inkjet recording method can be provided.

<Active energy ray-curable ink composition>
The active energy ray-curable ink composition of the present invention (hereinafter also referred to as “ink composition”) contains at least an oxetane compound and an epoxy compound, and the content of the oxetane compound is based on the total polymerizable compound mass. On the other hand, the content of the epoxy compound is less than 50% by mass, the content of the epoxy compound exceeds 50% by mass with respect to the total polymerizable compound mass, and at least one of the oxetane compounds is represented by the following general formula (A1). The first oxetane compound.

In General Formula (A1), R ^{1 to} R ⁵ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ⁶ and R ⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group.

  The oxetane compound and the epoxy compound are cationically polymerizable compounds that can be polymerized by irradiation with active energy rays, and at least one of the oxetane compounds needs to be represented by the general formula (A1). Hereinafter, the oxetane compound represented by the general formula (A1) is also referred to as “specific polymerizable compound”. The ink composition of the present invention may contain a polymerizable compound other than the specific polymerizable compound and the epoxy compound. In order to accelerate curing, for example, a photoacid generator that generates an acid may be further contained by irradiation with active energy rays.

In the ink composition of the present invention, it is necessary that the total content of the epoxy compound is larger than the total content of the oxetane compound. Specifically, the content of the oxetane compound is the total polymerizable compound mass. On the other hand, the content is less than 50% by mass, and the content of the epoxy compound exceeds 50% by mass with respect to the total mass of the polymerizable compound.
Conventionally, when an active energy ray-curable ink composition is obtained by using an oxetane compound and an epoxy compound in combination, the total amount of oxetane compound is contained in the ink composition more than the total content of epoxy compound. There was a need. This is because when the total content of the epoxy compound is larger than the total content of the oxetane compound, the molecular weight of the polymer obtained by the polymerization of the oxetane compound and the epoxy compound is difficult to increase, and the film curability may decrease. Because there was.

However, when the first oxetane compound (specific polymerizable compound) represented by the general formula (A1) is used as at least one oxetane compound, the total content of the oxetane compound is not clear. Rather than increasing the total content of the epoxy compound, rather, the curability is improved, and a cured film can be formed in a short time even at a low exposure, particularly in a high humidity environment (for example, 80% RH). I understood.
In particular, the ink composition of the present invention contains a specific polymerizable compound, and the content of the first oxetane compound and the second oxetane compound is less than 50% by mass with respect to the total polymerizable compound mass, and By making the content of the total epoxy compound exceed 50% by mass with respect to the total polymerizable compound mass, it is easy to be cured in a short time even under high humidity, and has excellent adhesion to the substrate and flexibility. , Wrinkles and curling of the substrate can be suppressed.

The ink composition does not contain the first oxetane compound (specific polymerizable compound). Instead, the monofunctional compound has a substituent other than one aryl group represented by the general formula (A1) at the 2-position of the oxetane ring. When an oxetane compound or a polyfunctional oxetane compound in which an aryl group is substituted at the 2-position of the oxetane ring is used, sufficient curability and flexibility of a cured film cannot be obtained. This is presumed to be due to low molecular mobility.
In the present invention, an oxetane compound other than the specific polymerizable compound may be contained, and the oxetane compound other than the specific polymerizable compound is referred to as a “second oxetane compound”. Moreover, what combined both the 1st oxetane compound and the 2nd oxetane compound is called "all oxetane compound."

  Hereinafter, the first and second oxetane compounds, the epoxy compound, and optional components that can be contained as necessary in the active energy ray-curable ink composition of the present invention will be described.

[Oxetane compound]
-First oxetane compound (specific polymerizable compound)-
The active energy ray-curable ink composition of the present invention contains a first oxetane compound (specific polymerizable compound) represented by the following general formula (A1) as a polymerizable compound. More specifically, the specific polymerizable compound is a monofunctional compound having one aryl group having R ^{1 to} R ⁵ and three hydrogen atoms at the 2-position of the oxetane ring, as shown in the general formula (A1 ′). The oxetane compound.

In general formula (A1) and general formula (A1 ′), R ^{1 to} R ⁵ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Show. R ⁶ and R ⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group.

Examples of the halogen atom represented by R ^{1 to} R ⁵ in the general formula (A1) and the general formula (A1 ′) include a fluorine atom, a chlorine atom, a bromine atom, and the like. preferable.
In the general formula (A1) and general formula (A1 ′), the alkyl group having 1 to 6 carbon atoms represented by R ^{1 to} R ⁵ may be linear, branched, or cyclic. For example, a methyl group , Ethyl group, isopropyl group, tert-butyl group, cyclohexyl group and the like. Of these, linear or branched is preferable, and branched is more preferable. The number of carbon atoms is preferably 1 to 4.

In the general formula (A1) and the general formula (A1 ′), the alkoxy group having 1 to 6 carbon atoms represented as R ^{1 to} R ⁵ can be represented as R ⁸ O—, and the R ⁸ is represented by 1 to 1 carbon atoms. 6 alkyl groups. R ⁸ represented as an alkyl group having 1 to 6 carbon atoms may be linear, branched or cyclic, and examples thereof include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, and a cyclohexyl group. It is done. Accordingly, examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group and an ethoxy group.
R ⁸ is preferably linear or branched, and more preferably linear. It is preferable that carbon number is 1-2, and 1 is more preferable.

In General Formula (A1) and General Formula (A1 ′), R ^{1 to} R ⁵ may be bonded to each other via a divalent linking group. Examples of the divalent linking group include an alkylene group, an arylene group, an ester group, a carbonyl group, an amide group, an oxygen atom, and a sulfur atom, and two or more divalent linking groups may be used by linking them. Good.

From the viewpoint of curability of the ink composition, R ^{1 to} R ⁵ are preferably electron-donating substituents, and therefore R ^{1 to} R ⁵ are preferably an alkyl group or an alkoxy group. More preferably, it is a group.

Examples of the halogen atom represented by R ⁶ and R ⁷ in the general formula (A1) and the general formula (A1 ′) include a fluorine atom, a chlorine atom, a bromine atom, and the like. preferable.
In the general formula (A1) and general formula (A1 ′), the alkyl group having 1 to 6 carbon atoms represented by R ⁶ and R ⁷ may be linear, branched, or cyclic. For example, a methyl group , Ethyl group, isopropyl group, tert-butyl group, cyclohexyl group and the like. Of these, linear or branched is preferable, and linear is more preferable. The number of carbon atoms is preferably 1 to 3, and more preferably 1.

An alkoxy group having from 1 to 6 carbon atoms represented as ^{R 6} and ^{R 7} in the general formula (A1) and the general formula (A1 ^'), can be represented as ^R 9 O-, said ^{R 9} is 1 to carbon atoms 6 alkyl groups. R ⁸ represented as an alkyl group having 1 to 6 carbon atoms may be linear, branched or cyclic, and examples thereof include a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, and a cyclohexyl group. It is done. Accordingly, examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group and an ethoxy group.
R ⁹ is preferably linear or branched, and more preferably linear. It is preferable that carbon number is 1-2, and 1 is more preferable.

Examples of the aryl group represented by R ⁶ and R ⁷ in the general formula (A1) and the general formula (A1 ′) include a phenyl group, a naphthyl group, and a tolyl group. Among these, an aryl group having 6 to 12 carbon atoms is preferable.

R ⁶ and R ⁷ may be bonded via any divalent linking group. Examples of the divalent linking group include an alkylene group, an arylene group, an ester group, a carbonyl group, an amide group, an oxygen atom, and a sulfur atom, and two or more divalent linking groups may be used by linking them. Good.
In general formula (A1) and general formula (A1 ′), R ⁶ and R ⁷ are preferably alkyl groups.

R ^{1 to} R ⁷ may further have a substituent within the above range of carbon number.
Examples of the substituent include an alkyl group, alkenyl group, alkynyl group, allyl group, aryl group, aralkyl group, alkoxy group, alkoxycarbonyl group, hydroxyl group, carboxy group, amino group, and halogen atom.

  Moreover, it is preferable that the weight average molecular weight (Mw) of a specific polymeric compound is 100-800, It is more preferable that it is 120-500, It is further more preferable that it is 150-350.

  Specific examples of the specific polymerizable compound [first oxetane compound represented by formula (A1)] are shown below, but the present invention is not limited to these specific examples.

In (a-10), Ph represents a phenyl group.
Among (a-1) to (a-22), (a-1), (a-2), (a-3), (a-4), and (a-6) are preferable, and (a- 1), (a-2), and (a-3) are preferable.

  The specific polymerizable compound can be produced, for example, by the method described in Synthesis 1995, pages 533 to 538.

  The content of the specific polymerizable compound in the ink composition of the present invention is preferably less than 50% by mass, more preferably 5% by mass to 40% by mass with respect to the total polymerizable compound mass. More preferably, the content is from mass% to 30 mass%. When the content of the specific polymerizable compound with respect to the total polymerizable compound mass is in the above range, a cured product having sufficient hardness after curing, higher adhesion to the recording medium and higher flexibility is formed. Can do.

-Second oxetane compound-
The ink composition of the present invention may contain a second oxetane compound that is an oxetane compound other than the first oxetane compound (specific polymerizable compound).
The second oxetane compound is not particularly limited as long as it has an oxetane ring in the molecule and is not a specific polymerizable compound, and a known oxetane compound can be used. The second oxetane compound may be monofunctional or polyfunctional.

As the second oxetane compound, a known oxetane compound can be arbitrarily selected and used as described in JP-A Nos. 2001-220526, 2001-310937, and 2003-341217.
The second oxetane compound is preferably a compound having 1 to 4 oxetane rings. By using such a compound, it becomes easy to maintain the viscosity of the ink composition in a more favorable range for handling, and the cured film formed by curing the ink composition and the recording medium High adhesion can be obtained.

  Among the second oxetane compounds, examples of the oxetane compound having 1 to 2 oxetane rings in the molecule include compounds represented by the following general formulas (A2-1) to (A2-3).

In general formulas (A2-1) to (A2-3), R ^a1 is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group, a furyl group, Or represents a thienyl group. When two R ^a1 are present in the molecule as in the general formulas (A2-1) and (A2-2), they may be the same or different.
Examples of the alkyl group represented by R ^a1 include a methyl group, an ethyl group, a propyl group, and a butyl group.
Preferred examples of the fluoroalkyl group include those in which part or all of the hydrogen atoms in the alkyl group are substituted with fluorine atoms.
Examples of the aryl group represented by R ^a1 include a phenyl group, a naphthyl group, and a tolyl group.

In General Formula (A2-1), R ^a2 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 2 to 6 carbon atoms, a group having an aromatic ring, or an alkyl having 2 to 6 carbon atoms. A carbonyl group, an alkoxycarbonyl group having 2 to 6 carbon atoms, or an N-alkylcarbamoyl group having 2 to 6 carbon atoms is represented.
Examples of the alkyl group represented by R ^a2 include a methyl group, an ethyl group, a propyl group, and a butyl group.
^Examples of the alkenyl group represented by R ^a2 include 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group, 3 -Butenyl group etc. are mentioned.
^Examples of the group having an aromatic ring represented by R ^a2 include a phenyl group, a benzyl group, a fluorobenzyl group, a methoxybenzyl group, and a phenoxyethyl group.
Examples of the alkylcarbonyl group represented by R ^a2 include an ethylcarbonyl group, a propylcarbonyl group, and a butylcarbonyl group.
Examples of the alkoxycarbonyl group represented by R ^a2 include ethoxycarbonyl group, propoxycarbonyl group, butoxycarbonyl group and the like, and examples of N-alkylcarbamoyl group include ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl group. Groups and the like.
R ^a2 may have a substituent, and examples of the substituent include an alkyl group of 1 to 6 and a fluorine atom.

In general formula (A2-2), R ^a3 includes a chain or branched alkylene group, a poly (alkyleneoxy) group chain or branched divalent unsaturated hydrocarbon group, a carbonyl group, and a carboxyl group. An alkylene group, an alkylene group containing a carbamoyl group, or any one of the partial structures (R ^a3 -1) to (R ^a3 -3) shown below is represented.

Examples of the alkylene group represented by R ^a3 include an ethylene group, a propylene group, and a butylene group. Examples of the poly (alkyleneoxy) group include a poly (ethyleneoxy) group and a poly (propyleneoxy) group. It is done.
Examples of the divalent unsaturated hydrocarbon group represented by R ^a3 include a propenylene group, a methylpropenylene group, and a butenylene group.

When the partial structures (R ^a3 -1) to (R ^a3 -3) are divalent or higher polyvalent groups, R ^a4 in the partial structure (R ^a3 -1) is a hydrogen atom or 1 to 4 carbon atoms. An alkyl group, an alkoxy group having 1 to 4 carbon atoms, a halogen atom, a nitro group, a cyano group, a mercapto group, a lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group. R ^a5 in the partial structure (R ^a3 -2) is an oxygen atom, a sulfur atom, a methylene group,>NH,>SO,> SO ₂ , —C (CF ₃ ) ₂ —, or —C (CH ₃ ). _2- represents. R ^a6 in the partial structure (R ^a3 -3) represents an alkyl group having 1 to 4 carbon atoms or an aryl group, and n is an integer of 0 to 2,000. R ^a7 in the partial structure (R ^a3 -3) represents a monovalent group having an alkyl group having 1 to 4 carbon atoms, an aryl group, or the following partial structure (R ^a7 -1). In the following partial structure (R ^a7 -1), R ^a8 is an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms, and m is an integer of 0 to 100.

  As a compound represented by the general formula (A2-1), 3-ethyl-3-hydroxymethyloxetane (OXT-101: manufactured by Toagosei Co., Ltd.), 3-ethyl-3- (2-ethylhexyloxymethyl) Examples include oxetane [OXT-212: manufactured by Toagosei Co., Ltd.], 3-ethyl-3-phenoxymethyloxetane [OXT-211: manufactured by Toagosei Co., Ltd.] Examples of the compound represented by the formula (P) 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene [OXT-121: Toagosei Co., Ltd.], and the compound represented by the formula (A2-1) Bis (3-ethyl-3-oxetanylmethyl) ether [OXT-221: Toagosei Co., Ltd.].

  Examples of the compound having 3 to 4 oxetane rings include compounds represented by the following general formula (A2-4).

In formula ^{(A2-4), R a1} has the same meaning as ^{R a1} in Formula (A2-1). R ^a9 represents a polyvalent linking group, for example, a branched alkylene group having 1 to 12 carbon atoms such as groups represented by the following A to C, a branched poly ( An alkyleneoxy) group, or a branched polysiloxy group such as a group represented by E below. j is 3 or 4.

In the above A, R ^a10 represents a methyl group, an ethyl group, or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Another embodiment of the oxetane compound that can be suitably used in the present invention includes a compound represented by the following general formula (A2-5) having an oxetane ring in the side chain.

In formula ^{(A2-5), R a1} and ^{R a8} has the same meaning as ^{R a8} in the general formula (A2-1) in ^{R a1} and substructure ^(R a7 -1). R ^a11 is an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, or a trialkylsilyl group, and r is an integer of 1 to 4.

The compound having such an oxetane ring is described in detail in JP-A No. 2003-341217, paragraph numbers [0021] to [0084], and the compound described therein can be suitably used in the present invention.
Oxetane compounds described in JP-A-2004-91556 can also be used in the present invention. The compound is described in detail in paragraphs [0022] to [0058] of the publication.

  In the ink composition of the present invention, the content of the monofunctional oxetane compound is 50% by mass or less based on the total content of all oxetane compounds (the first oxetane compound and the second oxetane compound). Preferably, it is 30% by mass or less.

  The content of all oxetane compounds (first oxetane compound (specific polymerizable compound) and second oxetane compound) in the ink composition of the present invention is determined from the viewpoint of curing sensitivity and film physical properties of the ink composition. It is necessary to be less than 50% by mass with respect to the total mass of the polymerizable compound in the product, preferably 10 to 45% by mass, and more preferably 20 to 40% by mass.

[Epoxy compound]
The ink composition of the present invention contains at least one epoxy compound as a cationic polymerizable compound together with a specific polymerizable compound.

  By controlling the content of the epoxy compound, the sensitivity and film properties of the ink composition of the present invention can be further improved. Specifically, the content of the epoxy compound in the ink composition of the present invention needs to exceed 50% by mass with respect to the total mass of the polymerizable monomer, and is preferably 55 to 90% by mass, More preferably, it is 60-80 mass%.

  The epoxy compound may be a monofunctional epoxy compound having one epoxy ring or a polyfunctional epoxy compound having two or more epoxy rings, and may be a monofunctional epoxy compound and a polyfunctional epoxy compound. However, from the viewpoint of curability, the monofunctional epoxy compound in the total epoxy compound contained in the ink composition of the present invention is 50% by mass or less based on the total mass of the epoxy compound. Preferably, it is 30% by mass or less.

Examples of the epoxy compound include epoxy compounds such as aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.
Aromatic epoxides include di- or polyglycidyl ethers produced by the reaction of polyphenols having at least one aromatic nucleus or their alkylene oxide adducts with epichlorohydrin. Examples thereof include di- or polyglycidyl ether of bisphenol A or its alkylene oxide adduct, di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, and novolak-type epoxy resin. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

As the alicyclic epoxide, cyclohexene oxide obtained by epoxidizing a compound having at least one cycloalkane ring such as cyclohexene or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid. Or a cyclopentene oxide containing compound is mentioned preferably.
Examples of the aliphatic epoxide include dihydric polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol, or 1,6. -Diglycidyl ether of alkylene glycol such as diglycidyl ether of hexanediol, diglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, diglycidyl of polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols typified by diglycidyl ethers of ethers, polypropylene glycols or alkylene oxide adducts thereof And the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

Next, monofunctional and polyfunctional epoxy compounds suitable for the present invention will be exemplified in detail.
Examples of monofunctional epoxy compounds include, for example, phenyl glycidyl ether, p-tert-butylphenyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allyl glycidyl ether, 1,2-butylene oxide, 1,3-butadiene. Monooxide, 1,2-epoxydodecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide, cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide, 3-acryloyloxymethylcyclohexene oxide, 3-vinylcyclohexene oxide, etc. Is mentioned.

  Examples of polyfunctional epoxy compounds include, for example, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, and brominated bisphenol. S diglycidyl ether, epoxy novolac resin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3 ′, 4′-epoxycyclohexanecarboxy 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane-meta-dioxane, bis (3,4-epoxysilane) Chloromethyl) adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, 3,4-epoxy-6-methylcyclohexyl-3 ′, 4′-epoxy -6'-methylcyclohexanecarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene diepoxide, ethylene glycol di (3,4-epoxycyclohexylmethyl) ether, ethylenebis (3,4-epoxycyclohexanecarboxy) Rate), dioctyl epoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl Ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ethers, 1,1,3-tetradecadiene dioxide, limonene dioxide, 1,2,7,8 -Diepoxyoctane, 1,2,5,6-diepoxycyclooctane and the like.

  Among these epoxy compounds, polyfunctional aromatic epoxides and alicyclic epoxides are preferable from the viewpoint of excellent curing speed, and polyfunctional alicyclic epoxides are particularly preferable.

  In addition, from the viewpoint of ink viscosity, ejection stability, and film physical properties, all epoxy compounds contained in the composition preferably have a weight average molecular weight (Mw) of 100 or more and 300 or less, and 120 or more and 250 or less. It is more preferable.

-Other polymerizable compounds-
(Vinyl ether compound)
In the present invention, a vinyl ether compound can also be used as a curing component. Examples of vinyl ether compounds applicable to the present invention include monofunctional vinyl ether compounds and polyfunctional vinyl ether compounds such as di- or trivinyl ether compounds.
As the monofunctional vinyl ether compound and the polyfunctional vinyl ether compound, compounds described in paragraph numbers [0121] and [0122] of JP-A-2008-257892 can be suitably used.

  As the vinyl ether compound, a di- or trivinyl ether compound is preferable from the viewpoints of curability, adhesion to a recording medium, surface hardness of the formed image, and the like, and a divinyl ether compound is particularly preferable.

  The content of vinyl ether is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total solid mass of the ink composition of the present invention.

(Other cationic polymerizable compounds)
The ink composition of the present invention may contain, in addition to the specific polymerizable compound and the epoxy compound, which are essential components, other cationic polymerizable compounds as necessary. The other cationic polymerizable compound is not particularly limited as long as it is a compound that initiates a polymerization reaction with an acid generated from a compound that generates an acid upon irradiation with radiation and cures, and various known compounds known as photocationic polymerizable compounds Cationic polymerizable monomers can be used. Examples of other cationic polymerizable compounds include JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, Among the cationic polymerizable compounds described in each publication such as 2001-220526, cationic polymerizable compounds that are not included in the categories of specific polymerizable compounds, epoxy compounds, and vinyl ether compounds can be given. For example, other oxetane compounds shown below are listed.

[Compounds that generate acid upon irradiation]
The ink composition of the present invention preferably contains a compound that generates an acid upon irradiation with radiation (hereinafter also referred to as a “photoacid generator”). In the present invention, the polymerization reaction of the polymerizable compound is accelerated by the acid generated by the irradiation of radiation, and it is easy to cure more rapidly.
Examples of the photoacid generator include photoinitiators for photocationic polymerization, photoinitiators for photoradical polymerization, photodecolorants for dyes, photochromic agents, and light (400 to 200 nm) used in microresists. A compound that generates an acid upon irradiation with ultraviolet rays, far ultraviolet rays, particularly preferably g-line, h-line, i-line, KrF excimer laser beam), ArF excimer laser beam, electron beam, X-ray, molecular beam or ion beam. Can be appropriately selected and used.

  Examples of such a photoacid generator include an onium salt compound such as diazonium salt, phosphonium salt, sulfonium salt, iodonium salt, imide sulfonate, oxime sulfonate, diazodisulfone, disulfone, which decomposes upon irradiation with radiation to generate an acid. Examples thereof include sulfonate compounds such as o-nitrobenzyl sulfonate. Examples of the photocationic polymerization initiator that can be used in the ink composition of the present invention, specific compounds, and preferred examples include the compounds described in paragraphs 0066 to 0122 of JP-A-2008-13646. .

  Particularly preferred examples of the photoacid generator that can be used in the ink composition of the present invention include sulfonium salts represented by the following general formula (P). Higher curability can be obtained by using the ink composition of the present invention in combination with the sulfonium salt represented by the general formula (P).

In the general formula (P), X ⁻ represents an anion.

X ^- is an anion (anion) represented by the view of stability, polymer type anion. For example, sulfonate anion (for example, alkyl sulfonate anion, aryl sulfonate anion), benzoyl formate anion, PF ⁶⁻ , SbF ⁶⁻ , BF ⁴⁻ , ClO ⁴⁻ , carboxylate anion (for example, alkyl carboxylate anion, Aryl carboxylate anion, aralkyl carboxylate anion), sulfinate anion, sulfate anion, borate anion, sulfonylimide anion, bis (alkylsulfonyl) imide anion, tris (alkylsulfonyl) methyl anion, halogen anion, polymer sulfonate anion , Polymer type carboxylate anion, and tetraarylborate anion.

Among these, non-nucleophilic anions are preferable. The non-nucleophilic anion is an anion having an extremely low ability to develop a nucleophilic reaction, and is an anion capable of suppressing degradation with time due to intramolecular nucleophilic reaction.
Preferred examples of the non-nucleophilic anion include PF ⁶⁻ , SbF ⁶⁻ , BF ⁴⁻ , sulfonylimide anion, bis (alkylsulfonyl) imide anion, tris (alkylsulfonyl) methyl anion, and tetraarylborate anion. Can be mentioned.

A photo-acid generator can be used individually by 1 type or in combination of 2 or more types.
The content of the photoacid generator in the ink composition of the present invention is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, with respect to the total solid content mass of the ink composition. -7 mass% is still more preferable.

[Colorant]
The ink composition of the present invention preferably contains a colorant in order to obtain a colored image.
The colorant that can be used in the present invention is not particularly limited, but pigments and oil-soluble dyes that are excellent in weather resistance and excellent in color reproducibility are preferable, and are selected from any known colorant such as a soluble dye. Can be used. The colorant that can be suitably used in the ink composition of the present invention preferably does not function as a polymerization inhibitor in a polymerization reaction that is a curing reaction. This is because the sensitivity of the curing reaction by active energy rays is not lowered.

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

  Specific examples of organic pigments and inorganic pigments that can be used in the present invention include compounds described in paragraphs 0126 to 0131 of JP-A-2008-13646.

For dispersing the pigment, for example, a dispersion device such as a ball mill, a sand mill, an attritor, a roll mill, a jet mill, a homogenizer, a paint shaker, a kneader, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, or a wet jet mill is used. be able to.
It is also possible to add a dispersant when dispersing the pigment. Examples of the dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high molecular weight acid ester, a salt of a high molecular weight polycarboxylic acid, a high molecular weight unsaturated acid ester, a high molecular weight copolymer, a modified polyacrylate, an aliphatic Examples thereof include polyvalent carboxylic acids, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate esters, and pigment derivatives. It is also preferable to use a commercially available polymer dispersant such as the Solsperse series from Zeneca.
Moreover, it is also possible to use a synergist according to various pigments as a dispersion aid. These dispersants and dispersion aids are preferably added in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the pigment.

  In the ink composition, as a dispersion medium for various components such as pigments, a solvent may be added, or a cationic polymerizable compound which is a low molecular weight component without a solvent may be used as a dispersion medium. The ink composition to which the invention is applied is a radiation curable ink, and is preferably solvent-free 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, a cationic polymerizable compound is used, and among them, it is preferable to select a cationic polymerizable compound having the lowest viscosity from the viewpoint of improving dispersibility and handling properties of the ink composition.

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

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

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

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

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

As the magenta dye, compounds having a structure represented by the general formulas (A2-1) and (4) described in JP-A No. 2002-114930 are preferable, and specific examples thereof include JP-A No. 2002-114930. And the compounds described in paragraphs [0054] to [0073].
Particularly preferred dyes are azo dyes represented by the general formulas (M-1) to (M-2) described in paragraph numbers [0084] to [0122] of JP-A No. 2002-121414, and specific examples Examples thereof include compounds described in paragraph numbers [0123] to [0132] of JP-A No. 2002-121414. The oil-soluble dyes represented by the general formulas (3), (4) and (M-1) to (M-2) described in the publication are used not only for magenta but also for any color ink such as black ink and red ink. May be.

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

  These colorants are preferably added in an amount of 1 to 20% by mass in terms of solid content in the ink composition, and more preferably 2 to 10% by mass.

  Hereinafter, various additives that can be used in the ink composition of the present invention as needed are described.

[Ultraviolet absorber]
In the ink composition of the present invention, an ultraviolet absorber can be used from the viewpoint of improving the weather resistance of the resulting image (cured product) and preventing discoloration.
Examples of the ultraviolet absorber are described in JP-A-58-185679, JP-A-61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Benzotriazole compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194843, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492 and 56-21141 Cinnamic acid compounds described in JP-A-10-88106, JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP No. 8-502911, etc., triazine compounds, Research Disclosure No. 1 Examples thereof include compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays, such as stilbene and benzoxazole compounds, so-called fluorescent brighteners, and the like.
The content of the ultraviolet absorber in the ink composition of the present invention is appropriately selected according to the purpose, but is generally 0.5 to 15% by mass with respect to the total solid mass of the ink composition. Preferably there is.

[Sensitizer]
A sensitizer may be added to the ink composition of the present invention as necessary for the purpose of improving the acid generation efficiency of the photoacid generator and increasing the photosensitive wavelength.
Any sensitizer may be used as long as the photoacid generator is sensitized by an electron transfer mechanism or an energy transfer mechanism. Preferably, aromatic polycondensed compounds such as anthracene, 9,10-dialkoxyanthracene, pyrene and perylene, aromatic ketone compounds such as acetophenone, benzophenone, thioxanthone and Michlerketone, heterocyclic compounds such as phenothiazine and N-aryloxazolidinone Is mentioned.
The content of the sensitizer in the ink composition of the present invention is appropriately selected according to the purpose, but is preferably 0.1 to 5 mol% based on the total solid content mass of the photoacid generator, 0.3-1.5 mol% is more preferable.

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

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

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

〔solvent〕
In order to improve the adhesion to the recording medium, it is also effective to add a very small amount of an organic solvent to the ink composition of the present invention.
Examples of the solvent include ketone solvents such as acetone, methyl ethyl ketone, and diethyl ketone, alcohol solvents such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol, and chlorine such as chloroform and methylene chloride. Solvents, aromatic solvents such as benzene and toluene, ester solvents such as ethyl acetate, butyl acetate and isopropyl acetate, ether solvents such as diethyl ether, tetrahydrofuran and dioxane, glycols such as ethylene glycol monomethyl ether and ethylene glycol dimethyl ether And ether solvents.
In this case, it is effective to add the solvent within a range that does not cause the problem of solvent resistance and VOC, and the amount thereof is preferably 0.1 to 5% by mass, more preferably 0%, based on the total solid content of the ink composition. 0.1 to 3% by mass.

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

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

  In addition to the above, the ink composition of the present invention includes, for example, leveling additives, matting agents, waxes for adjusting film physical properties, and adhesion to recording media such as polyolefin and PET. In order to improve this, a tackifier or the like that does not inhibit the polymerization 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). Copolymers composed of esters with alcohols having an ester, esters of (meth) acrylic acid with alicyclic alcohols having 3 to 14 carbon atoms, and esters of (meth) acrylic acid with aromatic alcohols having 6 to 14 carbon atoms And low molecular weight tackifying resin having a polymerizable unsaturated bond.

<Preferred physical properties of ink composition>
When the ink composition of the present invention is applied to inkjet recording, the ink viscosity at the temperature during ejection is preferably 5 mPa · s to 30 mPa · s, and preferably 7 mPa · s to 20 mPa · s in consideration of ejection properties. Is more preferable. For this reason, it is preferable to adjust and determine a composition ratio suitably so that it may become the said range.
The viscosity of the ink composition at room temperature (25 to 30 ° C.) is preferably 7 to 120 mPa · s, and more preferably 10 to 80 mPa · s. By setting the viscosity at room temperature high, even when a porous recording medium is used, ink penetration into the recording medium can be prevented, uncured monomer can be reduced, and odor can be reduced. Dot bleeding at the time of landing can be suppressed, and as a result, image quality can be improved.

  The surface tension of the ink composition of the present invention is preferably 20 mN / m to 40 mN / m, and more preferably 20 mN / m to 30 mN / m. In addition, when recording the ink composition of the present invention on various recording media such as polyolefin, PET, coated paper, and uncoated paper, the surface tension is preferably 20 mN / m or more from the viewpoint of bleeding and penetration, and is wet. From the viewpoint of properties, it is preferably 30 mN / m or less.

The ink composition of the present invention can be suitably used as an ink for inkjet recording.
There are no particular restrictions on the ink jet recording method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses the vibration pressure of a piezo element, and an electrical signal that is acoustic Either an acoustic ink jet system that irradiates ink by irradiating it with ink instead of using a beam, or a thermal ink jet system that uses ink to form bubbles by heating the ink and use the generated pressure. Also good. The inkjet recording method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent. A method using ink is included.
Among these, the ink is suitable as a drop-on-demand type (pressure pulse type) ink jet recording ink using a piezo element.

<Inkjet recording method and printed matter>
The ink jet recording method of the present invention comprises a step of ejecting the active energy ray-curable ink composition of the present invention onto a recording medium using an ink jet recording apparatus (image recording step), and the discharged active energy ray-curable ink composition. A step of irradiating an active energy ray on the product to cure the active energy ray-curable ink composition (image curing step).
That is, the ink jet recording method of the present invention is a method including an image recording step of forming an image by ink jet recording and an image curing step.
The printed matter of the present invention is a recorded matter recorded by the inkjet recording method of the present invention.

In the image curing step, active energy rays are used in the image curing step, and after recording an image on a recording medium in the image recording step, the recorded image is irradiated with active energy rays, thereby contributing to imaging. Polymerization and curing of the polymerizable compound proceeds, and it is possible to form an image that is cured well and has high fastness.
In the image curing step, an exposure process for accelerating polymerization and curing can be performed using a light source that emits active energy rays in a wavelength region corresponding to the sensitive wavelength of the ink composition. The light source, the exposure time, and the light amount may be appropriately selected according to the degree of polymerization and curing of the polymerizable compound such as the cationic polymerizable compound according to the present invention.

  The thickness of the image cured in the image curing step is preferably 2 μm to 30 μm. Here, “image thickness” refers to the thickness of a cured product obtained by curing an image formed by the ink composition. When the thickness of the image is 2 μm to 30 μm, an image having a low density to a high density can be expressed.

  In the image curing step, an exposure process for accelerating polymerization and curing can be performed using a light source that emits active energy rays in a wavelength region corresponding to the sensitive wavelength of the ink composition. The light source will be described later.

  The printed matter recorded by inkjet recording using the ink composition of the present invention has an image portion that is cured by irradiation with radiation such as ultraviolet rays and is excellent in strength of the image portion. For example, an ink receiving layer (image portion of a lithographic printing plate) ).

  In the image recording step, it is preferable to apply an ink jet recording method using an ink jet recording apparatus such as an ink jet printer. Specifically, it is preferable that the image recording step records an image using an ink jet recording apparatus that discharges the ink composition of the present invention.

  Next, specific embodiments of the inkjet recording method of the present invention will be described below, including details of an inkjet recording apparatus that can be suitably employed in the method.

System As an ink jet recording system for ejecting ink, a form as shown in Japanese Patent Application Laid-Open No. 2002-11860 is given as an example, but the invention is not limited to this, and other forms may be used.

Ink holding means As a means for holding ink, it is preferable to fill a known ink cartridge, and it can be stored in a deformable container and used as a tank as disclosed in JP-A-5-16377. It is. Further, as disclosed in Japanese Patent Laid-Open No. 5-16382, when the sub tank is provided, the supply of ink to the head is further stabilized. Further, as disclosed in JP-A-8-174860, it is also possible to use a cartridge that supplies ink by moving a valve when the pressure in the ink supply chamber decreases. As a method of applying a negative pressure for appropriately holding the meniscus in the head with these ink holding means, a method based on the height of the ink holding means, that is, water head pressure, or a method based on the capillary force of the filter provided in the ink flow path In addition, a method of controlling the pressure with a pump or the like, and a method of holding the ink on the ink absorber and applying a negative pressure by this capillary force as disclosed in Japanese Patent Application Laid-Open No. 50-74341 are suitable. It is.

Ink supply path As a method of supplying ink from these ink holding means to the head, a method of directly connecting the holding means to the head unit or a method of connecting by a flow path such as a tube may be used. The ink holding means and the flow path are preferably made of a material having good wettability with respect to the ink or subjected to a surface treatment.

-As a method of ejecting head ink, as disclosed in Japanese Patent Application Laid-Open No. 5-104725, ink droplets are continuously ejected, and the droplets are deflected according to the image to land on the recording medium. Alternatively, a method of selectively controlling whether or not to perform the operation may be used, or a so-called on-demand method, in which ink droplets are ejected only to a portion necessary as an image, may be used. As disclosed in JP-A-5-16349, the on-demand system may be a system that generates and discharges ink pressure by deformation of a structure using a piezoelectric element or the like. As disclosed, it may be a method of discharging at a pressure generated by expansion accompanying vaporization by thermal energy. Further, as disclosed in Japanese Patent Laid-Open No. 2001-277466, a method of controlling ejection to a recording medium by an electric field may be used.

  In the ink jet recording method, image recording is performed on a recording medium using the ink composition of the present invention. There are no particular restrictions on the ink discharge nozzles used at that time, and they can be appropriately selected according to the purpose. it can. As the nozzle, for example, a form as described in JP-A-5-31908 can be applied. At this time, in order to eject ink of a plurality of colors, the nozzles are configured in a plurality of rows as described in JP-A-2002-316420, so that a color image can be formed at high speed. Furthermore, it is possible to further increase the speed by arranging a plurality of head units having a plurality of nozzle rows.

Further, as described in Japanese Patent Application Laid-Open No. Sho 63-160849, nozzles are arranged by a width equal to or larger than the width of the image to form a so-called line head, and the recording medium is moved simultaneously with droplet ejection from these nozzles. As a result, an image can be formed at high speed.
Further, the surface of the nozzle is subjected to a surface treatment as disclosed in Japanese Patent Laid-Open No. 5-116327, whereby it is possible to prevent ink droplets from adhering to the nozzle surface and ink droplets from adhering.

Even if such treatment is performed, dirt may still adhere, and therefore it is preferable to perform cleaning with a blade as disclosed in JP-A-6-71904.
In addition, the inks of the respective colors are not necessarily ejected from the nozzles uniformly, and specific inks may not be ejected for a long time. In such a case, in order to keep the meniscus stable, as disclosed in Japanese Patent Application Laid-Open No. 11-157102, ink is appropriately ejected outside the image area, and new ink is supplied to the head, thereby providing ink physical properties. Is preferably maintained at a suitable value.

Further, even if such treatment is performed, bubbles may enter the head or be generated in the head. In such a case, as described in JP-A-11-334092, by forcibly sucking ink from outside the head, the ink whose physical properties have changed is discarded, and bubbles are also discharged outside the head. be able to. In the case where the droplets are not ejected for a long time, the nozzle surface can be protected by covering the nozzle surface with a cap as disclosed in JP-A-11-138830. Even if these measures are taken, there is a case where the liquid is still not discharged.
If an image is printed in a state where some of the nozzles do not discharge, problems such as unevenness in the image occur. In order to avoid such a situation, it is effective to take a measure by detecting that no discharge has occurred, as disclosed in Japanese Unexamined Patent Publication No. 2000-343686.

  When the head unit is mechanically moved as described in Japanese Patent Laid-Open No. 6-115099 and the recording medium is intermittently moved in the orthogonal direction in synchronization with the head unit, This has the effect of making it difficult to see the unevenness caused by the accuracy of intermittent movement of the medium, and can achieve high image quality. At this time, the relationship between the image quality and the recording speed can be set to a preferable relationship by appropriately setting the relationship between the moving speed of the head, the moving amount of the recording medium, and the number of nozzles.

  Conversely, the same effect can be obtained by fixing the head and mechanically reciprocating the recording medium in a predetermined direction and intermittently moving the recording medium in a direction orthogonal thereto.

-Temperature control The ink jet recording apparatus is preferably provided with a means for stabilizing the ink composition temperature, and the part to be kept at a constant temperature is a piping system from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface, All of the members are targeted.

  In the ink jet recording method, the ink composition is heated to 40 to 80 ° C., and the viscosity of the ink composition is reduced to 30 mPa · s or less, preferably 20 mPa · s or less, and then ejected. By using this, high injection stability can be realized. In general, radiation curable ink compositions generally have a higher viscosity than aqueous inks, so that the viscosity fluctuation range due to temperature fluctuations during printing is large. This viscosity variation of the ink composition directly affects the droplet size and droplet ejection speed as it is, which causes image quality deterioration. Therefore, it is necessary to keep the ink composition temperature as constant as possible during printing. is there. For this purpose, it is preferable to have an ink temperature detecting means, an ink heating means, and a control means for controlling heating according to the detected ink temperature.

The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors in each piping portion and perform heating control according to the ink composition flow rate and the environmental temperature. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time required for heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.
Alternatively, it is also preferable to have means for controlling energy applied to the means for ejecting ink according to the ink temperature.

  The control range of the ink composition temperature is preferably set temperature ± 5 ° C., more preferably set temperature ± 2 ° C., and further preferably set temperature ± 1 ° C.

-Exposure As a light source, alpha rays, gamma rays, X rays, ultraviolet rays, visible rays, infrared rays, electron rays, etc. are mentioned. Specifically, a commonly used mercury lamp, metal halide lamp, or the like may be used, and a light emitting diode, a semiconductor laser, a fluorescent lamp, or the like may be used. In addition, a light source, an electromagnetic wave, or the like in which a polymerization reaction of ink proceeds, such as a hot cathode tube, a cold cathode tube, an electron beam, or an X-ray, can be used.

The peak wavelength of the active energy ray is preferably 200 nm to 600 nm, more preferably 300 nm to 450 nm, and further preferably 350 nm to 420 nm. The output of the active energy rays, is preferably 2,000 mJ / cm ² or less, more ^preferably from ^{10mJ / cm 2 ~2,000mJ / cm 2} , more preferably, 20 mJ / ^cm 2 to 1 a 000mJ / cm ^2, particularly ^{preferably 50mJ / cm 2 ~800mJ / cm 2} .

Irradiation of active energy rays, the emission peak wavelength of 350Nm～420nm, and emission maximum illuminance of the surface of the recording medium is exposed surfaces generates ultraviolet rays becomes 10mW ^/ cm ² ~1,000mW ^/ cm 2 Irradiation from a diode is preferred.

If a metal halide lamp is used for exposure, the lamp is preferably 10 to 1000 W / cm, and the exposure surface illuminance is preferably 1 mW / cm ^{2 to} 100 W / cm ² .

  Further, since high pressure mercury lamps, metal halide lamps and the like generate ozone with discharge, it is preferable to have an exhaust means. The exhaust means is preferably arranged so as to also collect ink mist generated during ink ejection.

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

  When active energy rays for curing are applied to the ink discharge nozzles, ink mist attached to the surface of the nozzle surface may solidify and hinder ink discharge. In order to keep it, it is preferable to take measures such as shading. Specifically, it is preferable to provide a partition for preventing the nozzle plate from being irradiated, or to provide means for limiting the incident angle to the recording medium so as to reduce stray light.

  In the present invention, the time from landing to irradiation is desirably 0.01 seconds to 0.5 seconds, preferably 0.01 seconds to 0.3 seconds, and more preferably 0.01 seconds to 0.00 seconds. It is to irradiate radiation after 15 seconds. Thus, by controlling the time from landing to irradiation to an extremely short time, it is possible to prevent the landing ink from bleeding before being cured. Also, since the ink composition can be exposed to a porous recording medium before it penetrates deeper than the light source reaches, unreacted monomer remains, and as a result, odor can be reduced. Can do. By using the inkjet recording method described above and the ink composition of the present invention in combination, a great synergistic effect is brought about. By adopting such a recording method, the dot diameter of the landed ink can be kept constant even on various recording media having different surface wettability, and the image quality is improved.

System parameters In forming an image, it is preferable that the ink landing diameter on the recording medium is between 10 μm and 500 μm, and for this purpose, the diameter of the ink droplets during ejection is 5 μm to 250 μm. The nozzle diameter at this time is preferably 15 μm to 100 μm.
In order to form an image, the number of pixels per inch is preferably 50 dpi to 2400 dpi, and for that purpose, the nozzle density of the head is preferably 10 dpi to 2400 dpi. Here, even if the nozzle density of the head is low, it is inclined with respect to the conveyance direction of the recording medium, or a plurality of head units are arranged relatively offset to achieve high-density landing with a head with a large nozzle interval. Is possible. In addition, as described above, by reciprocating the head or the recording medium, each time the head moves at a low nozzle pitch, the recording medium is conveyed by a predetermined amount, and ink droplets are landed at different positions, thereby recording high-density images. Can be realized.

The ink droplet ejection volume of the recording medium, to express a good tone is suitable can be controlled arbitrarily amount between ^{0.05g / m 2 ~25g / m 2} , to achieve this Therefore, it is preferable to control the size and / or quantity of the ejected ink droplets from the head.

  If the distance between the head and the recording medium is too wide, the flying of the ink droplets is disturbed by the air flow accompanying the movement of the head or the recording medium, and the landing position accuracy decreases. On the other hand, if the interval is narrow, there is a risk of contact between the head and the recording medium due to unevenness of the recording medium, vibration due to the transport mechanism, and the like, and it is preferable to maintain the recording medium at about 0.5 mm to 2 mm.

-Ink set The ink may be a single color, cyan, magenta, yellow, or four colors including black, or a specific color other than these called special color. Also good. The coloring material may be a dye or a pigment. These inks may be ejected in order of landing in order of increasing lightness, may be landed in order of increasing lightness, or are preferably ejected in an order suitable for image recording quality.

When the colors are stacked in order from the lightest color, the active energy ray easily reaches the lower ink, and it is difficult for inhibition of curing sensitivity, increase of residual monomers, generation of odor, and deterioration of adhesion. Irradiation can be performed by injecting all colors and exposing them together, but exposure for each color is preferable from the viewpoint of curing acceleration.
The image signal to be recorded is preferably subjected to signal processing to obtain good color reproduction, as described in, for example, Japanese Patent Laid-Open No. 6-210905.

  The ink composition of the present invention can be used not only for inkjet recording but also for three-dimensional modeling, and can also be used for can printing and food. For these uses, it is possible to form an image using a known method. For example, the description in Japanese Patent No. 2679586 can be referred to.

Recording medium As a recording medium to be recorded using the ink composition of the present invention, both an ink-permeable recording medium and an ink-impermeable recording medium can be used. Examples of the ink-permeable recording medium include plain paper, inkjet exclusive paper, coated paper, electrophotographic co-paper, cloth, non-woven fabric, porous film, and polymer absorber. These are described as “recording materials” in Japanese Patent Application Laid-Open No. 2001-181549.

  Examples of the ink-impermeable recording medium include art paper, synthetic resin, rubber, resin-coated paper, glass, metal, earthenware, and wood. In addition, in order to add each function, a base material obtained by combining a plurality of these materials can be used.

  Although any synthetic resin can be used as the synthetic resin, for example, polyethylene terephthalate and polyester such as polybutadiene terephthalate; polyolefin such as polyvinyl chloride, polystyrene, polyethylene, polyurethane, and polypropylene; and acrylic resin, Examples include polycarbonate, acrylonitrile-butadiene-styrene copolymer, diacetate, triacetate, polyimide, cellophane, and celluloid.

  The shape (thickness) of the base material using the synthetic resin may be a film shape, a card shape or a block shape, and can be appropriately selected according to a desired purpose without particular limitation. These synthetic resins may be transparent or opaque. As the usage form of the synthetic resin, it is one of the preferred forms used in the form of a film used for so-called soft packaging, and various non-absorbable plastics and films thereof can be used. Examples of plastic films include polyethylene terephthalate (PET) film, biaxially oriented polystyrene (OPS) film, biaxially oriented polypropylene (OPP) film, biaxially oriented nylon (ONy) film, and polyvinyl chloride (PVC). A film, a polyethylene (PE) film, and a triacetyl cellulose (TAC) film can be mentioned.

  Examples of the resin-coated paper include a transparent polyester film, an opaque polyester film, an opaque polyolefin resin film, and a paper support in which both sides of the paper are laminated with a polyolefin resin, and both sides of the paper are laminated with a polyolefin resin. A paper support is particularly preferred.

  As described above, according to the present invention, it is possible to obtain an ink composition that combines and highly satisfies various characteristics such as curability, adhesion, and flexibility, and according to image recording using this, the adhesion and flexibility are excellent. A printed material on which the recorded image is recorded can be obtained.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples. In this example, an example of producing ink for inkjet recording is shown as an example of the ink composition.

<Preparation of pigment dispersion>
Prior to ink preparation, a pigment dispersion was prepared by adding the pigment to the polymerizable compound together with a dispersant in the following formulation.

・ Pigment (Irgalite Blue GLVO (PB-15: 4))
: Ciba Specialty Chemicals) 20% by mass
-Polymerizable compound (OXT-221: manufactured by Toagosei Co., Ltd.) 72% by mass
・ Dispersant (Solsperse 28000: manufactured by Lubrizol) 8% by mass
A mixed liquid obtained by mixing the above-described components was placed in a ball mill and dispersed for 16 hours using zircon beads having a diameter of 0.6 mm to obtain a pigment dispersion.

[Example 1]
The prepared pigment dispersion, polymerizable compound (cationic polymerizable compound), photoacid generator, sensitizer, and surfactant are mixed and stirred with a high-speed water-cooled stirrer so that the composition shown below is obtained. A cyan ink composition for UV inkjet was obtained.

・ Pigment (Irgalite Blue GLVO (PB-15: 4))
: Ciba Specialty Chemicals) 2 parts by weight Dispersant (Solsperse 28000: manufactured by Lubrizol) 0.8 parts by weight Photoacid generator (Irgacure 250: manufactured by Ciba Specialty Chemicals)
6 parts by mass / sensitizer (9,10-dibutoxyanthracene) 3 parts by mass / surfactant (BYK307: manufactured by BYK Chemie) 0.2 part by mass / specific polymerizable compound (a-1) 2.5 parts by mass Part / bifunctional oxetane compound (OXT-221: manufactured by Toagosei Co., Ltd.) 27.5 parts by mass / bifunctional epoxy compound (C3000: manufactured by Daicel Chemical Industries) 70 parts by mass

[Examples 2 to 15 and Comparative Examples 1 to 6]
Inks of Examples 2 to 15 and Comparative Examples 1 to 6 were prepared in the same manner as in the preparation of the cyan ink composition for UV inkjet of Example 1, except that the composition was changed to the compositions shown in Tables 1 and 2. A composition was prepared. In the preparation of the ink composition of Example 2, as a polymerizable compound for preparing a pigment dispersion, C3000: manufactured by Daicel Chemical Industries, Ltd. instead of OXT-221: manufactured by Toagosei Co. (72% by mass) (72% by mass) was used.

In Tables 1 and 2, “second oxetane” means the second oxetane compound, that is, OXT-221, OXT-211 and comparative compounds c-1 to c- which are oxetane compounds other than the specific polymerizable compound. 3 is represented.
“Pigment”, “dispersant”, “photoacid generator”, “sensitizer”, “surfactant”, “specific polymerizable compound”, “bifunctional oxetane”, “tablet” shown in Tables 1 and 2 The numerical values in each column of “monofunctional oxetane”, “bifunctional epoxy”, “monofunctional epoxy”, and “comparative compound” indicate the compounding ratio (part by mass) of each component in the ink composition preparation. The unit of the numerical values of “polymerizable compound amount ratio”, “monofunctional compound ratio in all epoxy compounds”, and “monofunctional compound ratio in all oxetane compounds” is [% by mass]. The detail of each compound shown in the inside is shown below.

  “(P-1)” used as a photoacid generator is as shown in the following chemical formula.

The structures of “C3000” and “(b-1)” used as the bifunctional epoxy compound and “phenylglycidyl ether” used as the monofunctional epoxy compound are as shown in the following chemical formula.
“C3000” is an epoxy compound manufactured by Daicel Chemical Industries, Ltd., and “phenylglycidyl ether” is an epoxy compound manufactured by ALDRICH.

Specific polymerizable compounds (a-1), (a-2), and (a-3), and “OXT-211”, “OXT-221”, “c-1”, “c-1”, “other oxetane compounds” The structures of “c-2” and “c-3” are as shown in the following chemical formulas.
"C-1", "c-2", and "c-3" are bifunctional oxetane compounds in which an aryl group is substituted at the 2-position of the oxetane ring, and were used as comparative compounds for specific polymerizable compounds. .

  The specific polymerizable compounds (a-1), (a-2), and (a-3) were synthesized with reference to the method described in Synthesis 1995, pages 533 to 538. “OXT-221” and “OXT-211” are oxetane compounds manufactured by Toagosei Co., Ltd.

<Printing and exposure>
The ink compositions of Examples and Comparative Examples obtained above were ejected using a piezo ink jet head. The head has a nozzle density of 150 per 25.4 mm and has 318 nozzles. By fixing these two nozzles in the nozzle row direction with a shift of 1/2 of the nozzle interval, 25 heads are arranged on the medium in the nozzle array direction. . 300 drops per 4 mm.

The head and ink are controlled so that the vicinity of the ejection portion is 50 ± 0.5 ° C. by circulating hot water in the head. Ink ejection from the head is controlled by a piezo drive signal applied to the head, and ejection of 6 to 42 pl per drop is possible. In this embodiment, the head is transported while the medium is conveyed at a position 1 mm below the head. More drops. The conveyance speed can be set in the range of 50 to 200 mm / s. The piezo drive frequency can be up to 4.6 kHz, and the droplet ejection amount can be controlled by these settings.
In this evaluation, by setting the transport speed to 90 mm / s and the drive frequency to 1.9 kHz, the ink discharge amount was controlled to 24 pl and droplets were ejected at 10 g / m ² to obtain a solid print image.

After the droplets are ejected, they are transported to an exposure unit and exposed by an ultraviolet light emitting diode (UV-LED). In this example, NCCU033 (trade name) manufactured by Nichia Corporation was used as the UV-LED. This LED outputs ultraviolet light having a wavelength of 365 nm from one chip. When a current of about 500 mA is applied, light of about 100 mW is emitted from the chip. A plurality of these are arranged at intervals of 7 mm, and a power of 0.3 W / cm ² can be obtained on the media surface. The exposure time after the droplet ejection and the exposure time can be changed according to the transport speed of the medium and the distance between the head and the LED in the transport direction.

In this example, exposure was performed about 0.5 seconds after landing. The exposure energy on the medium was adjusted between 0.01 and 15 J / cm ² according to the setting of the distance to the medium and the conveyance speed. In this embodiment, the exposure energy is adjusted according to the conveyance speed. For the measurement of exposure power and exposure energy, a spectroradiometer URS-40D (trade name) manufactured by USHIO ELECTRIC CO., LTD. Was used, and a value obtained by integrating between wavelengths 220 to 400 nm was used. In this evaluation, a PET film having a thickness or a sheet made of polyvinyl chloride was used as a medium, printing and exposure tests were performed in an environment of 25 ° C. and 50% RH, and the exposure amount was 500 mJ / cm ² . The thickness of the cured image was 19 μm.

<Evaluation>
The following methods were used to evaluate the flexibility of the cured products of the ink compositions of Examples and Comparative Examples, and the adhesion to the recording medium, wrinkles, and curling.

1. Flexibility Flexibility was also evaluated by the degree of cracks that occurred in the cured film after bending the PVC sheet 10 times. This bending test was performed in a five-step evaluation with 5 points indicating a state in which no cracks occurred, and 3 or more points were evaluated as having no practical problems.

2. Substrate adhesion As described below, adhesion to a polystyrene substrate was evaluated.
That is, cello tape (registered trademark) was applied in the range of 2 cm × 1 cm square of the cured product and strongly pressed, peeled off perpendicularly to the surface of the cured product, and the state of the cured product was visually observed. This adhesion test was performed in a five-step evaluation with 5 points indicating a state where the cured product was not peeled off from the substrate at all, and 3 points or more were evaluated as having no problem in practice.

3. Wrinkles and curls After irradiation and curing, the printed matter was visually observed for wrinkles and curls. This wrinkle and curl test was performed in a five-step evaluation with 5 points indicating a state in which no wrinkles or curls were generated, and 3 or more points were evaluated as having no practical problems.

  In addition, the curability of the ink was evaluated under the following conditions.

4). Curability Under an environment of 25 ° C. and 70% RH, each ink composition was ejected with 6 pL of dots so as not to overlap the PVC sheet using the above apparatus, and exposure of 50 mJ / cm ² was performed. The ink was cured to obtain a printed matter. Curability was judged by the presence or absence of surface stickiness of the printed matter, and evaluated according to the following criteria.
5: The image is not tacky when touched immediately after the exposure is finished 4: The image is tacky when touched immediately after the exposure is finished, but the tackiness disappears after 30 seconds 3: The image is tacky when touched immediately after the exposure is finished The tackiness disappears after 60 seconds 2: The image is tacky when touched immediately after the exposure ends, but the tackiness disappears after 90 seconds 1: The image is tacky when touched immediately after the exposure ends, and the tackiness remains after 90 seconds Will not disappear

From the results described in Table 1 and Table 2, the ink compositions of Examples 1 to 15 have higher sensitivity than the ink compositions of Comparative Examples 1 to 6, and have a good balance of flexibility and adhesion. It can be seen that there is no wrinkle or curling.
When the component compositions and evaluation items of the ink compositions of Examples 1 to 3, Examples 4 to 6, and Examples 7 to 9 are compared, the content of the specific polymerizable compound is 10 to 30% by mass, and the second oxetane It turns out that sclerosis | hardenability and film | membrane physical property become more favorable as a compound approaches 10-30 mass% and an epoxy compound approaches 60-80 mass%. Moreover, it is understood from the comparison between Examples 9 and 10 that the ink composition is sufficiently cured by using a specific sulfonium salt as the photoacid generator. Furthermore, the comparison between Example 9 and Examples 13 and 14 shows that the second oxetane compound and the epoxy compound have better curability when the main component is a bifunctional monomer. Moreover, it can be seen from a comparison between Example 9 and Example 15 that the epoxy compound has better film properties when the molecular weight is 300 or less.

  From the comparison between Example 9 and Comparative Examples 1 to 3, in the composition of the present invention, the oxetane compound having an aryl group substituted at the 2-position of the oxetane ring is a monofunctional compound and substituted at the 2-position other than the aryl group. It turns out that sclerosis | hardenability and film | membrane physical property improve large by not having a group. Further, from the comparison between Examples 1 to 9 and Comparative Examples 4 to 5, even when OXT having an aryl group substituted at the 2-position of the monofunctional oxetane ring is used, only in the composition of the present invention, high curing is achieved. It can be seen that the film properties and film properties are achieved.

Claims (11)

It contains at least an oxetane compound and an epoxy compound, the content of the oxetane compound is less than 50% by mass with respect to the total polymerizable compound mass, and the content of the epoxy compound is the total polymerizable compound mass. The active energy ray-curable ink composition is more than 50% by mass, and at least one of the oxetane compounds is a first oxetane compound represented by the following general formula (A1).

[In General Formula (A1), R ^{1 to} R ⁵ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. R ⁶ and R ⁷ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an allyl group, or an aryl group. ] It further contains a second oxetane compound other than the first oxetane compound, and the contents of the first oxetane compound and the second oxetane compound are 5 to 40 masses per mass of the total polymerizable compound, respectively. The active energy ray-curable ink composition according to claim 1, wherein the content of the epoxy compound is 55% by mass to 90% by mass with respect to the total mass of the polymerizable compound. It further contains a second oxetane compound other than the first oxetane compound, and the content of the first oxetane compound and the second oxetane compound is 10 to 30 masses per mass of the total polymerizable compound, respectively. The active energy ray-curable ink composition according to claim 1, wherein the content of the epoxy compound is 60% by mass to 80% by mass with respect to the total mass of the polymerizable compound.   4. The active energy ray-curable ink composition according to claim 1, wherein the monofunctional epoxy compound is 50% by mass or less based on the total mass of the epoxy compound.   The active energy according to any one of claims 2 to 4, wherein the monofunctional oxetane compound is 50% by mass or less based on the total mass of the first oxetane compound and the second oxetane compound. Line curable ink composition.   The active energy ray-curable ink composition according to any one of claims 1 to 5, wherein the epoxy compound has a weight average molecular weight of 100 or more and 300 or less. The active energy ray-curable ink composition according to any one of claims 1 to 6, further comprising a sulfonium salt represented by the following general formula (P).

[In the general formula (P), X ⁻ represents an anion. ]   The active energy ray-curable ink composition according to claim 1, which is for inkjet recording.   A step of ejecting the active energy ray-curable ink composition according to claim 8 onto the recording medium by an ink jet recording apparatus, and irradiating the discharged active energy ray-curable ink composition with active energy rays. An inkjet recording method comprising a step of curing the active energy ray-curable ink composition. UV the active energy ray is irradiated by the light emitting diodes, there emission peak wavelength in the range of 350Nm～420nm, and, the maximum illuminance of the surface of the recording medium becomes 10mW ^/ cm ² ~2,000mW ^/ cm 2 The inkjet recording method according to claim 9.   A printed matter recorded by the ink jet recording method according to claim 9 or 10.