JP2005179506A - Active ray-curable inkjet ink - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an active ray-curable inkjet ink good in storage stability and jetting stability, and superior in color density reproducibility and image transparency. <P>SOLUTION: In the active ray-curable inkjet ink which contains a photopolymerizable compound, a photopolymerization initiator, a pigment and a dispersant, the secondary pigment particles of the pigment have a D<SB>50</SB>being an average particle size defined by the descriptions below obtained by a normal distribution conversion based on mass is 50 to 200 nm, and the difference width ΔD (D<SB>90</SB>-D<SB>10</SB>) of D<SB>90</SB>and D<SB>10</SB>defined by the descriptions below is 170 nm or smaller. The above D<SB>90</SB>, D<SB>50</SB>, and D<SB>10</SB>express respectively particle sizes which are equal to 0.9 (90 mass%), 0.5 (50 mass%), and 0.1 (10 mass%) of the total mass of the secondary pigment particles in the integrating curve of ditribution function dG=F(D)dD of the secondary pigment particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel cationic actinic ray curable inkjet ink.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, a recording device that emits and controls fine dots, ink that has improved color reproduction gamut, durability, and emission suitability, and ink absorbability, coloring material color development, surface gloss, etc. have been dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper. The image quality improvement of today's ink jet recording system is achieved only when all of the recording apparatus, ink, and special paper are available.

  However, in an inkjet system that requires dedicated paper, the recording medium is limited, and the cost of the recording medium increases. Therefore, many attempts have been made to record on a transfer medium different from dedicated paper by an ink jet method. Specifically, a phase change ink jet method using a wax ink solid at room temperature, a solvent ink jet method using an ink mainly composed of a fast-drying organic solvent, or cross-linking with active light such as ultraviolet (UV) light after recording. An actinic ray curable ink jet method.

  In particular, the actinic ray curable ink jet method has been attracting attention in recent years because it has a relatively low odor compared to the solvent-based ink jet method, and can be recorded on a recording medium that does not dry quickly and absorbs ink. In Japanese Laid-Open Patent Application No. 6-200204 and Japanese Translation of PCT International Publication No. 2000-504778, ultraviolet curable ink-jet inks are disclosed.

  In addition, actinic ray curable ink jet ink is generally classified into radical polymerization type and cationic polymerization type, but the cationic polymerization type is not subject to oxygen inhibition, and the cationic monomer used has a relatively low odor and cure shrinkage. It has been attracting attention because of its advantages such as low

  For example, there is a cationic ultraviolet curable ink jet ink in which a pigment component is contained in a liquid component composed of an oxirane group-containing compound, an oxetane ring-containing compound, and a vinyl ether compound, and a pigment having an average particle diameter D50 of 10 to 150 nm is dispersed. (For example, refer to Patent Document 1). However, since the pigment particles described in Patent Document 1 have a wide particle size distribution width and coarse particles, they have problems in ink storage stability and emission stability, and further, light scattering increases and image transparency is inferior. Has the disadvantages.

  Further, an actinic ray curable ink containing a photocationic polymerizable substance, a photocationic polymerization initiator, and a surfactant having a functional group and having an acid value of 150 mgKOH or less or an amine value of 23 mgKOH or less is disclosed ( For example, see Patent Document 2.) However, as a result of detailed studies by the present inventors on the actinic ray curable ink disclosed in Patent Document 2, the distribution range of pigment particles is wide and coarse particles are present, so that the storability and emission of the ink are increased. It has been found that there is a disadvantage that it is inferior in stability and image transparency.

  Further, as in Patent Document 2, the cationic actinic ray curable composition has an average particle size of 15 times or less after a predetermined time with respect to the average particle size at the time of production, and the surfactant has a high molecular weight. An ink that is a polymer or a high molecular weight polyester acid amide amine salt is disclosed (for example, see Patent Document 3). However, the actinic ray curable ink disclosed in Patent Document 2 has been studied in detail by the present inventor. As a result, the particle size distribution range is wide, and sedimentation of coarse particles causes ink storage stability, ejection stability, It was found that the color density reproducibility was inferior.

As described above, in the prior art, a cationic polymerization system capable of satisfying both ink performance such as storage stability and emission stability and image quality performance such as image density and image transparency formed on a recording medium after printing. At present, no actinic ray curable ink has been found yet. Therefore, development of a cationic actinic ray curable ink jet ink that is excellent in storage stability and emission stability, color density reproducibility, and image transparency is demanded.
JP 2002-188025 A JP 2002-348478 A JP 2003-55563 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object the actinic ray curable ink jet ink having excellent ink storage stability and emission stability, and excellent color density reproducibility and image transparency. Is to provide.

The above object of the present invention is achieved by the following configurations.
(Claim 1)
In the actinic radiation curable inkjet ink containing a photopolymerizable compound, a photopolymerization initiator, a pigment, and a dispersant, the secondary pigment particles of the pigment are average particles defined below, which are obtained in terms of mass-based normal distribution. is D ₅₀ is the diameter a 50 to 200 nm, and active ray curable width ΔD of the distribution of the D ₉₀ and D ₁₀ defined below (D ₉₀ -D ₁₀₎ is equal to or less than 170nm Ink for inkjet.

D ₅₀ : Secondary pigment particle distribution function dG = F (D) An integral curve of dD, which represents a particle size equal to 0.5 (50% by mass) of the total mass of the secondary pigment particles.

D ₉₀ : Secondary pigment particle distribution function dG = F (D) An integral curve of dD, which represents a particle size equal to 0.9 (90% by mass) of the total mass of the secondary pigment particles.

D ₁₀ : Secondary pigment particle distribution function dG = F (D) An integral curve of dD, which represents a particle size equal to 0.1 (10% by mass) of the total mass of the secondary pigment particles.

G represents the number of particles, D represents the particle size, and dG represents the mass of the secondary pigment particles in the particle size interval dD.
(Claim 2)
The actinic ray curable inkjet ink according to claim 1, wherein the pigment surface has a hydrophilicity δm of 22 or less.
(Claim 3)
The actinic ray curable inkjet ink according to claim 1, wherein the dispersant is a polymer dispersant.
(Claim 4)
The actinic ray curable inkjet ink according to claim 1, wherein at least one of the photopolymerizable compounds is a photopolymerizable compound having an oxetane ring.
(Claim 5)
The actinic ray curable inkjet ink according to any one of claims 1 to 4, wherein the photopolymerization initiator is a cationic photopolymerization initiator.
(Claim 6)
The average particle diameter defined above determined in terms of the mass-based normal distribution D ₅₀ is ₅₀ to 150 nm, and the distribution width ΔD (D ₉₀ −D) between D ₉₀ and D ₁₀ defined above. ₁₀ ) is 150 nm or less, The actinic-light curable inkjet ink of any one of Claims 1-5 characterized by the above-mentioned.

  According to the present invention, it is possible to provide an actinic ray curable ink jet ink that has excellent ink storage stability and emission stability, and excellent color density reproducibility and image transparency.

  Hereinafter, the best mode for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

As a result of intensive studies in view of the above problems, the present inventor has found that the secondary pigment particles of the pigment in the actinic ray curable inkjet ink containing a photopolymerizable compound, a photopolymerization initiator, a pigment, and a dispersant are: D ₅₀ is the average particle diameter determined by the normal distribution in terms of mass is a 50 to 200 nm, the width ΔD (D ₉₀ -D ₁₀₎ is less sharp particle size 170nm of the distribution of the D ₉₀ and D ₁₀ By using an actinic ray curable inkjet ink (hereinafter also referred to simply as ink) having a distribution, ink performance of storage stability, emission stability, and image quality performance after printing such as color density reproducibility and image transparency As a result, the present invention has been found to be remarkably improved.

That is, the average particle diameter D ₅₀ of the pigment particles 50 to 200 nm, by setting the width D ₉₀ -D ₁₀ of distribution than a sharp particle size distribution 170 nm, even when stored for a long period of time the ink, the particle size distribution The change in the ink is small, and the storage stability of the ink is ensured. The reason is that if the average particle diameter D ₅₀ of the pigment particles is less than ₅₀ nm, the energy required for dispersion becomes too large in the region where the primary particles of the pigment are crushed, and the energy cost per unit of dispersion is too high. This is because a surface-active new surface is generated by crushing primary particles, and coarse particles are generated by aggregation of pigment fine particles. Further, when the average particle diameter D ₅₀ of the pigment particles exceeds 200 nm or the distribution width D ₉₀ -D ₁₀ exceeds 170 nm, the pigment particles dispersed during the long storage period after the ink is formed. This is because there is a risk of sedimentation.

  Also, with respect to the emission stability, since there is no generation of coarse particles for the same reason as the storage stability of the ink described above, stable emission with reduced nozzle clogging and oblique emission during emission is ensured. .

  Conventionally, many of the actinic ray curable ink jet inks do not have sufficient long-term storage stability as inks, so that coarse particles are generated due to aggregation of pigment particles, etc., and settle. As a result, since the apparent pigment density decreases due to long-term storage, the printed image density is reduced. In contrast, an ink having an average particle size and a particle size distribution defined in the present invention can suppress the generation and aggregation of pigment fine particles during long-term storage and obtain a desired image density with little change in color density. And good color density reproducibility is ensured.

  In addition, when the distribution width of the pigment particles is wide, coarse particles having a large particle diameter are present in the ink. As a result, light scattering in the formed image increases, resulting in a decrease in transparency. On the other hand, by setting the average particle size and particle size distribution of the pigment particles specified in the present invention, light scattering is reduced and transparency is excellent with an ink having a small particle size and a narrow particle size distribution width. Images can be obtained.

In the present invention, the average particle diameter D ₅₀ of the secondary pigment particles of the pigment defined in the present invention is ₅₀ to 200 nm, or the distribution width ΔD (D ₉₀ -D ₁₀ ) between D ₉₀ and D ₁₀ is sharply 170 nm or less. There is no particular limitation as a means for realizing a fine particle size distribution, but a pigment having a surface hydrophilicity δm of 22 or less is selected as a pigment, a polymer dispersant is preferably used as a dispersant, preferably an amine value From a method of removing coarse particles by using a polymer dispersant having a basic functional group or a polymer dispersant having a basic functional group, by appropriately adjusting the dispersion conditions of the pigment, or by filtration through a filter or centrifugation. This can be achieved by selection or combination.

  Details of the present invention will be described below.

In the ink of the present invention, the secondary pigment particles of the contained pigment have an average particle diameter D50 as defined above determined in terms of a mass-based normal distribution, which is ₅₀ to 200 nm, and are defined above. the D ₉₀ and D ₁₀ and the distribution in the width ΔD (D ₉₀ -D ₁₀₎ is equal to or less than 170 nm.

In the present invention, D ₉₀ , D ₅₀ , and D ₁₀ are each an integral of the distribution function dG = F (D) dD (G is the number of particles, D is the particle size) of 0.9 (90% by mass) of the total particle mass. ), 0.5 (50 mass%) and 0.1 (10 mass%).

  The above relational expression will be further described with reference to the drawings.

FIG. 1 shows the distribution function of the ink particle size in a coordinate system in which the particle size (D) of the particles is plotted on the abscissa and the mass function (G) of each particle of a given size is plotted on the ordinate. This curve is shown as a solid line. Further, in the same coordinate system, the integral of the distribution function in which the points of the 10%, 50% and 90% particle mass functions and the related points D ₁₀ , D ₅₀ and D _{90 of the} particle size are represented by crosses is represented by a dashed curve. Show.

Here, D ₅₀ is the average particle diameter determined by the normal distribution in terms of mass, the present invention is one that is characterized by a 50 to 200 nm, preferably from 50 to 150 nm.

Further, the difference ΔD (D ₉₀ -D ₁₀ ) between D ₉₀ and D ₁₀ defined in the present invention is 170 nm or less. That is, ΔD (D ₉₀ -D ₁₀ ) indicated by 16 in FIG. 1 is 170 nm or less. Preferably 1 to 170 nm, and more preferably 1 to 150.

  Moreover, the particle size as used in the field of this invention means the particle size calculated | required by normal distribution conversion of a mass reference | standard, for example, can be calculated | required using Malvern company Zetasizer 1000.

  In the ink of the present invention, it is preferable to use a pigment having a surface hydrophilicity δm of 22 or less.

  The hydrophilicity δm of the pigment surface referred to in the present invention is the surface hydrophilicity δm determined by the titration method described in Coloring Materials, 73 [3], 136 (2000). The degree of hydrophilicity δm is preferably 22 or less, more preferably 21.5 or less, and still more preferably 10.0 to 21.5. If δm exceeds 22, the dispersibility is greatly deteriorated, which is not preferable.

  In the present invention, in order to set the hydrophilicity of the pigment surface to 22 or less as defined in the present invention, a known surface treatment method such as pigment derivative treatment, rosin treatment, polymer treatment, surface grafting treatment, plasma treatment or the like is used. This can be achieved by appropriate selection or combination.

  Next, specific examples of the pigment that can be used in the ink of the present invention are listed below, but the present invention is not limited thereto.

  As red or magenta pigments, Pigment Red; 3, 5, 19, 22, 31, 38, 43, 48: 1, 48: 2, 48: 3, 48: 4, 48: 5, 49: 1, 53: 1, 57: 1, 57: 2, 58: 4, 63: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 88, 104, 108, 112, 122, 123, 144, 146, 149, 166, 168, 169, 170, 177, 178, 179, 184, 185, 208, 216, 226, 257, Pigment Violet; 3, 19, 23, 29, 30, 37, 50, 88, Pigment Orange; 13, 16, 20, 36, blue or cyan pigments include pigment blue; 1, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 1 17-1, 22, 27, 28, 29, 36, 60, Pigment Green; 7, 26, 36, 50 as a green pigment; Pigment Yellow; 1, 3, 12, 13, 14 as a yellow pigment 17, 34, 35, 37, 55, 74, 81, 83, 93, 94, 95, 97, 108, 109, 110, 120, 128, 137, 138, 139, 151, 153, 154, 155, 157 166, 167, 168, 180, 185, 193, Pigment Black; 7, 26, 28 as the black pigment, and Pigment White; 6, 18, 21 as the white pigment can be used according to the purpose.

  In the present invention, a polymer dispersant is preferably used as the dispersant used for dispersing the pigment, and a polymer dispersant having an amine value or a polymer dispersant having a basic functional group is used. It is preferable.

  Examples of the polymeric dispersant include Avecia's Solsperse series, Ajinomoto Fine Techno's Ajisper series, BYK Chemie's Disperbyk series, Enomoto Kasei's Disparon series and PLAAD series. Further, as the dispersion aid, synergists corresponding to various pigments can be used.

  Examples of the dispersing device used for dispersing the pigment include a ball mill, a sand mill, an attritor, a roll mill, an agitator, a paint shaker, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a Henschel mixer. .

  An example of preferable dispersion process conditions for pigment dispersion according to the present invention will be shown below, but the present invention is not limited to these exemplified conditions.

  1: The solid content concentration and the amount of the dispersant are appropriately selected by a bead mill using zirconia beads having a small particle size (particle size: 0.3 mm to 1.0 mm). The solid content concentration (ratio of pigment + dispersant) is preferably 10 to 40% by mass. Further, as the bead mill, for example, a paint shaker, a sand grinder, a circulating medium stirring bead mill, or the like can be used.

2: Use amount of polymer dispersant with respect to pigment When the BET specific surface area (m ² / g) of the pigment is A, the additive amount ratio B of the dispersant with respect to the pigment is B = (0.1 to 0.8) × A (%) is preferable, and B = (0.2 to 0.6) × A (%) is more preferable.

  One of the characteristics of the pigment dispersion is that the average particle diameter of the pigment particles is 200 nm or less, and more preferably 150 nm or less. Moreover, selection of a pigment, a dispersing agent, a dispersion medium, dispersion conditions, and filtration conditions are appropriately set so that the maximum particle diameter is 0.2 to 10 μm, preferably 0.2 to 3 μm. In the ink composition according to the present invention, the color material concentration is preferably 1% by mass to 10% by mass of the entire ink.

  Next, the photopolymerizable compound according to the present invention will be described.

  The actinic ray curable ink-jet ink of the present invention is characterized by containing a polymerizable compound, and particularly preferably contains a photopolymerizable compound having an oxetane ring.

  As the photopolymerizable compound having an oxetane ring according to the present invention (hereinafter also referred to as an oxetane compound), for example, any known oxetane compound as introduced in JP-A-2001-220526 and JP-A-2001-310937 can be used. .

  In the oxetane compound according to the present invention, when a compound having 5 or more oxetane rings is used, the viscosity of the ink composition becomes high, so that handling becomes difficult, and the glass transition temperature of the ink composition becomes high. The resulting cured product will not be sufficiently sticky. The compound having an oxetane ring used in the present invention is preferably a compound having 1 to 4 oxetane rings.

  Hereinafter, although the specific example of the photopolymerizable compound which has an oxetane ring based on this invention is demonstrated, this invention is not limited to these.

  An example of a compound having one oxetane ring is a compound represented by the following general formula (A).

In the general formula (A), R ¹ is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group or other alkyl group having 1 to 6 carbon atoms, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group , Furyl group or thienyl group. R ² is an alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl group, 2-methyl- C2-C6 alkenyl group such as 2-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group, phenoxyethyl group, etc. A group having an aromatic ring, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethylcarbonyl group, a propylcarbonyl group, and a butylcarbonyl group, an alkylcarbonyl group having 2 to 6 carbon atoms such as an ethoxycarbonyl group, a propoxycarbonyl group, and a butoxycarbonyl group; Alkoxycarbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylcarbamoyl Is N- alkylcarbamoyl group having a carbon number of 2-6 and the like.

  An example of a compound having two oxetane rings includes a compound represented by the following general formula (B).

In the general formula (B), R ¹ is the same group as that in the general formula (A). R ³ is, for example, a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, a linear or branched poly (alkyleneoxy) such as a poly (ethyleneoxy) group or a poly (propyleneoxy) group. ) Group, propenylene group, methylpropenylene group, butenylene group or other linear or branched unsaturated hydrocarbon group, alkylene group containing carbonyl group or carbonyl group, alkylene group containing carboxyl group, alkylene containing carbamoyl group Group.

Moreover, as R < ³ >, the polyvalent group selected from the group shown by the following general formula (C), (D) and (E) can also be mentioned.

In the general formula (C), R ⁴ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a methoxy group, an ethoxy group, a propoxy group, or a butoxy group. An alkoxy group having 1 to 4 carbon atoms, a halogen atom such as a chlorine atom or a bromine atom, a nitro group, a cyano group, a mercapto group, a lower alkyl carboxyl group, a carboxyl group, or a carbamoyl group.

In the general formula (D), R ⁵ represents an oxygen atom, a sulfur atom, a methylene group, NH, SO, SO ₂ , C (CF ₃ ) ₂ , or C (CH ₃ ) ₂ .

In general formula (E), R < ⁶ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. n is an integer of 0-2000. R ⁷ is a methyl group, an ethyl group, a propyl group, a butyl group having 1 to 4 carbon atoms, or an aryl group. R ⁷ may further include a group selected from the group represented by the following general formula (F).

In the general formula (F), R ⁸ 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 an aryl group. m is an integer of 0-100.

  Specific examples of the compound having two oxetane rings include the following compounds.

Exemplary compound 1 is a compound in which R ¹ is an ethyl group and R ³ is a carboxyl group in the general formula (B). Exemplary compound 2 is a compound in which, in the general formula (B), R ¹ is an ethyl group, R ³ is the general formula (E), R ⁶ and R ⁷ are methyl groups, and n is 1.

Among the compounds having two oxetane rings, preferred examples other than the above compounds include compounds represented by the following general formula (G). In the general formula (G), R ¹ has the same meaning as R ¹ in the general formula (A).

  An example of a compound having 3 to 4 oxetane rings includes a compound represented by the following general formula (H).

In formula (H), R ¹ has the same meaning as R ¹ in the general formula (A). As R ⁹ , 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 (alkyleneoxy) group such as a group represented by the following D, or the following E And branched polysiloxy groups such as those shown. j is 3 or 4.

In A above, R ¹⁰ is a lower alkyl group such as a methyl group, an ethyl group or a propyl group. Moreover, in said D, p is an integer of 1-10.

  Illustrative compound 3 is an example of a compound having 3 to 4 oxetane rings.

  Furthermore, examples of the compound having 1 to 4 oxetane rings other than those described above include compounds represented by the following general formula (I).

In general formula (I), R ⁸ has the same meaning as R ⁸ in the general formula (F). R ¹¹ 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 1 to 4.

  Preferable specific examples of the oxetane compound used in the present invention include the following compounds.

  The method for producing each compound having an oxetane ring described above is not particularly limited, and may be a conventionally known method, for example, Pattisson (DB Pattison, J. Am. Chem. Soc., 3455, 79). (1957)) discloses a method for synthesizing an oxetane ring from a diol. In addition to these, compounds having 1 to 4 oxetane rings having a high molecular weight of about 1000 to 5000 are also included. Examples of these specific compounds include the following compounds.

  In the actinic ray curable inkjet ink of the present invention, a 2-substituted oxetane compound can also be used.

  Examples of the 2-substituted oxetane compound that can be used in the present invention include a compound having one or more oxetane rings in a molecule represented by the following general formula (1).

(Wherein R _{1 to} R ₆ each represent a hydrogen atom, a monovalent or divalent organic group, and at least one of R _{3 to} R ₆ is not a hydrogen atom.)
Examples of the compound having one oxetane ring in the molecule include compounds represented by the following general formulas (2) to (5).

  In general formulas (2) to (5), each Z is independently an oxygen or sulfur atom, or a divalent hydrocarbon group that may contain an oxygen or sulfur atom in the main chain.

R _{1 to} R ₆ are each independently a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group or a butyl group, such as 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 a thienyl group.

R ₇ and R ₈ are each independently an alkyl group having 1 to 6 carbon atoms such as methyl group, ethyl group, propyl group or butyl group, 1-propenyl group, 2-propenyl group, 2-methyl-1-propenyl. Group, 2-methyl-2-propenyl group, 1-butenyl group, 2-butenyl group or 3-butenyl group such as alkenyl group having 1 to 6 carbon atoms, phenyl group, benzyl group, fluorobenzyl group, methoxybenzyl group Or an aryl group such as a phenoxyethyl group, an alkylcarbonyl group having 1 to 6 carbon atoms such as a propylcarbonyl group, a butylcarbonyl group or a pentylcarbonyl group, an carbon number of 1 to 1 such as an ethoxycarbonyl group, a propoxycarbonyl group or a butoxycarbonyl group 6 alkoxycarbonyl groups, ethoxycarbamoyl group, propylcarbamoyl group or butylpentylca An alkoxycarbamoyl group having 1 to 6 carbon atoms such as a ruberamoyl group is represented.

In the general formulas (2) to (4), at least one of R _{3 to} R ₆ is not a hydrogen atom.

As the oxetane ring-containing compound used in the present invention, in the above general formulas (2) to (5), R ₁ is a lower alkyl group, particularly ethyl group, R ₇ and R ₈ are propyl group, butyl group, phenyl group or A benzyl group and Z are preferably hydrocarbon groups containing no oxygen or sulfur atom.

  In addition, as a compound which has a 2 or more oxetane ring in a molecule | numerator, the compound represented by the following general formula (6) or (7) can be mentioned.

  In the general formulas (6) and (7), m is 2, 3 or 4, and Z is each independently an oxygen or sulfur atom, or a divalent hydrocarbon group which may contain an oxygen or sulfur atom.

R _{1 to} R ₆ are each independently a hydrogen atom, a fluorine atom, a methyl group, an ethyl group, a propyl group or a butyl group, such as an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a fluoro having 1 to 6 carbon atoms. An alkyl group, an allyl group, an aryl group or a furyl group;

In the general formula (6), at least one of R _{3 to} R ₆ is not a hydrogen atom.

R ₉ is, for example, a linear or branched alkylene group having 1 to 12 carbon atoms represented by the following general formula (8), or a linear or branched poly (alkyleneoxy) group.

In the general formula (8), R ₁₀ represents a lower alkyl group such as a methyl group, an ethyl group, or a propyl group.

Alternatively, R ₉ is a polyvalent group selected from the group of the following general formulas (9), (11) and (12).

In general formula (9), n is 0 or an integer of 1 to 2000, R ₁₁ is an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, and the following general formula (10) Represents a group selected from the group consisting of R ₁₂ represents an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group.

In General Formula (10), j represents 0 or an integer of 1 to 100, and R ₁₃ represents an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group.

In the general formula (11), R ₁₄ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms such as a methyl group, an ethyl group, a propyl group or a butyl group, an alkoxy group having 1 to 10 carbon atoms, a halogen atom, A nitro group, a cyano group, a mercapto group, a lower alkyl carboxylate group or a carboxyl group is represented.

In the general formula (12), R ₁₅ represents an oxygen atom, a sulfur atom, NH, SO, SO ₂ , CH ₂ , C (CH ₃ ) ₂ or C (CF ₃ ) ₂ .

As the oxetane ring-containing compound used in the present invention, in the above general formulas (6) and (7), R ₁ is a lower alkyl group, particularly an ethyl group, R ₉ is R ₁₄ is a hydrogen atom in the general formula (11). In the general formula (8), R ₁₀ is an ethyl group, in the general formula (9), R ₁₂ is a methyl group, and in the general formula (10), R ₁₃ is a methyl group, and Z is oxygen or sulfur. Those which are hydrocarbon groups containing no atoms are preferred.

  Furthermore, examples of the compound having a plurality of oxetane rings in the molecule include compounds represented by the following general formula (13).

In the general formula (13), r is an integer of 25 to 200, R ₁₆ is an alkyl group or a trialkylsilyl group having 1 to 4 carbon atoms. R _{1 to} R ₆ are the same as those shown in the general formula (1), R ₁₃ is the same as that shown in the general formula (10), and at least one of R _{3 to} R ₆ is not a hydrogen atom.

  The compound having an oxetane ring substituted at least at the 2-position according to the present invention can be synthesized with reference to the following literature.

(1) Hu Xianming, Richard M. et al. Kellogg, Synthesis, 533-538, May (1995)
(2) A. O. Fitton, J .; Hill, D.C. Ejan, R.A. Miller, Synth. , 12, 1140 (1987)
(3) Toshiro Imai and Shinya Nishida, Can. J. et al. Chem. Vol. 59, 2503-2509 (1981)
(4) Nobujiro Shimizu, Shintaro Yamaoka, and Yuho Tsuno, Bull. Chem. Soc. Jpn. 56, 3853-3854 (1983)
(5) Walter Fisher and Cyril A.M. Grob, Helv. Chim. Acta. , 61, 2336 (1978)
(6) Chem. Ber. 101, 1850 (1968)
(7) “Heterocyclic Compounds with Three- and Four-membered Rings”, Part Two, Chapter IX, Interscience Publishers, John Wiley & Sons, New York, 1964.
(8) Bull. Chem. Soc. Jpn. 61, 1653 (1988)
(9) Pure Appl. Chem. , A29 (10), 915 (1992)
(10) Pure Appl. Chem. , A30 (2 &amp; 3), 189 (1993)
(11) Japanese Patent Laid-Open No. 6-16804 (12) DE1021858
Hereinafter, specific examples of the compound having an oxetane ring substituted at the 2-position according to the present invention are shown as exemplary compounds 1 to 15, but the compound according to the present invention is not limited thereto.

Exemplary Compound 1: trans-3-tert-Butyl-2-phenyloxetane Exemplary Compound 2: 3,3,4,4-Tetramethyl-2,2-diphenyloxetane Exemplary Compound 3: Di [3-ethyl (2-methoxy -3-oxetanyl)] methyl ether Exemplified compound 4: 1,4-bis (2,3,4,4-tetramethyl-3-ethyl-oxetanyl) butane Exemplified compound 5: 1,4-bis (3-methyl-) 3-ethyloxetanyl) butane Exemplified Compound 6: Di (3,4,4-trimethyl-3-ethyloxetanyl) methyl ether Exemplified Compound 7: 3- (2-ethyl-hexyloxymethyl) -2,2,3,4 -Tetramethyloxetane Exemplary Compound 8: 2- (2-Ethyl-hexyloxy) -2,3,3,4,4-pentamethyl-oxetane Exemplary Compound 9 4,4'-bis [(2,4-dimethyl-3-ethyl-3-oxetanyl) methoxy] biphenyl Exemplary compound 10: 1,7-bis (2,3,3,4,4-pentamethyl-oxetanyl) heptane Illustrative compound 11: Oxetanyl silsesquioxane Illustrative compound 12: 2-methoxy-3,3-dimethyloxetane Illustrative compound 13: 2,2,3,3-tetramethyloxetane Illustrative compound 14: 2- (4-methoxyphenyl) -3,3-dimethyloxetane Exemplified Compound 15: Di (2- (4-methoxyphenyl) -3-methyloxetane-3-yl) ether In the present invention, any known oxirane group is used as the photopolymerizable compound. A compound (hereinafter referred to as an epoxy compound) or a vinyl ether compound can be used.

  Examples of the epoxy compound include the following aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  A preferable aromatic epoxide is a di- or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic nucleus or an alkylene oxide adduct thereof and epichlorohydrin, such as bisphenol A or an alkylene oxide thereof. Examples thereof include di- or polyglycidyl ethers of adducts, di- or polyglycidyl ethers of hydrogenated bisphenol A or its alkylene oxide adducts, and novolak-type epoxy resins. 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 preferable.

  Preferred aliphatic epoxides include di- or polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof, and typical examples thereof include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or Diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, polyglycidyl ether of polyhydric alcohol such as di- or triglycidyl ether of glycerin or its alkylene oxide adduct, polyethylene glycol or its alkylene oxide adduct Diglycidyl ethers of polyalkylene glycols such as diglycidyl ethers, polypropylene glycols or diglycidyl ethers of adducts thereof Tel and the like. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among these epoxides, in view of fast curability, aromatic epoxides and alicyclic epoxides are preferable, and alicyclic epoxides are particularly preferable. In the present invention, one of the epoxides may be used alone, or two or more may be used in appropriate combination.

  Examples of the vinyl ether compound include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, Di- or trivinyl ether compounds such as trimethylolpropane trivinyl ether, ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexane dimethanol monovinyl ether, n Propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether -o- propylene carbonate, dodecyl vinyl ether, diethylene glycol monovinyl ether, and octadecyl vinyl ether.

  Among these vinyl ether compounds, in consideration of curability, adhesion, and surface hardness, di- or trivinyl ether compounds are preferable, and divinyl ether compounds are particularly preferable. In the present invention, one of the above vinyl ether compounds may be used alone, or two or more thereof may be used in appropriate combination.

  The actinic ray curable inkjet ink of the present invention contains a photopolymerization initiator, preferably a cationic photopolymerization initiator.

  Examples of the photopolymerization initiator include aromatic onium salts. Examples of the aromatic onium salt include salts of group Va elements in the periodic table such as phosphonium salts (for example, triphenylphenacylphosphonium hexafluorophosphate), salts of group VIa elements such as sulfonium salts (for example, tetrafluoroborates). Triphenylsulfonium acid, triphenylsulfonium hexafluorophosphate, tris (4-thiomethoxyphenyl) hexafluorophosphate, sulfonium and triphenylsulfonium hexafluoroantimonate), and salts of Group VIIa elements, such as iodonium A salt (for example, diphenyliodonium chloride etc.) can be mentioned. The use of such an aromatic onium salt as a cationic polymerization initiator in the polymerization of an epoxy compound is disclosed in U.S. Pat. Nos. 4,058,401, 4,069,055, and 4,101,513. And No. 4,161,478.

  Preferred photopolymerization initiators include sulfonium salts of Group VIa elements. Among these, from the viewpoint of storage stability of ultraviolet curable and ultraviolet curable compositions, triarylsulfonium hexafluoroantimonate is preferable. In addition, the photopolymerization initiators described in pages 39 to 56 of the photopolymer handbook (published by Photographic Society Committee, 1989), JP-A 64-13142, JP-A-2-4804 Any compound can be used.

  Moreover, it is preferable to use the sulfonium salt which does not generate | occur | produce benzene by actinic ray irradiation as a photoinitiator.

In the present invention, “does not generate benzene by irradiation with actinic rays” means that benzene is not substantially generated. Specifically, 5 mass of an onium salt (photoacid generator) is contained in the ink composition. Occurs when an image containing approximately 100 m ² is printed with a thickness of 15 μm using an ink containing 100%, and the photoacid generator is sufficiently decomposed with an actinic ray that is sufficiently decomposed with the ink film surface kept at 30 ° C. It means that the amount of benzene to be produced is extremely small or less than 5 μg. The onium salt is preferably a sulfonium salt or an iodonium salt, and satisfies the above condition as long as it has a substituent on the benzene ring bonded to S ⁺ or I ⁺ .

The sulfonium salt is preferably a sulfonium salt compound represented by the following general formulas [1] to [4], and satisfies the above conditions as long as it has a substituent on the benzene ring bonded to S ⁺ .

In the above general formulas [1] to [4], R _{1 to} R ₁₇ each represent a hydrogen atom or a substituent, R _{1 to} R ₃ do not simultaneously represent a hydrogen atom, and R _{4 to} R ₇ represent simultaneously. It does not represent a hydrogen atom, R _{8 to} R ₁₁ do not represent a hydrogen atom at the same time, and R _{12 to} R ₁₇ do not represent a hydrogen atom at the same time.

The substituent represented by R _{1 to} R ₁₇ is preferably an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a t-butyl group, a pentyl group, or a hexyl group, Alkoxy groups such as methoxy group, ethoxy group, propyl group, butoxy group, hexyloxy group, decyloxy group, dodecyloxy group, acetoxy group, propionyloxy group, decylcarbonyloxy group, dodecylcarbonyloxy group, methoxycarbonyl group, ethoxycarbonyl Group, carbonyl group such as benzoyloxy group, phenylthio group, halogen atom such as fluorine, chlorine, bromine and iodine, cyano group, nitro group and hydroxy group.

X represents a non-nucleophilic anion residue, for example, a halogen atom such as F, Cl, Br, or I, B (C ₆ F ₅ ) ₄ , R ₁₈ COO, R ₁₉ SO ₃ , SbF ₆ , AsF ₆ , PF ₆ , BF _{4 and the} like. However, R ₁₈ and R ₁₉ are each an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a halogen atom such as fluorine, chlorine, bromine or iodine, a nitro group, a cyano group, a methoxy group or an ethoxy group. Represents an alkyl group or a phenyl group which may be substituted with an alkoxy group or the like. Among these, B (C ₆ F ₅ ) ₄ and PF ₆ are preferable from the viewpoint of safety.

  The above compounds can be obtained from THE CHEMICAL SOCIETY OF JAPAN Voi. 71 no. 11, 1998, as well as the photoacid generator described in “Organic Materials for Imaging”, edited by Organic Electronics Materials Research Group, Bunshin Publishing (1993), can be easily synthesized by a known method.

  In the present invention, it is particularly preferable that the sulfonium salt represented by the general formulas [1] to [4] is at least one sulfonium salt selected from the following general formulas [5] to [13]. X represents a non-nucleophilic anion residue and is the same as described above.

  Various additives other than those described above can be used in the actinic ray curable inkjet ink of the present invention. For example, surfactants, leveling additives, matting agents, polyester resins for adjusting film properties, polyurethane resins, vinyl resins, acrylic resins, rubber resins, and waxes can be added. In addition, for the purpose of improving storage stability, any known basic compound can be used, but representative examples include basic organic compounds such as basic alkali metal compounds, basic alkaline earth metal compounds, and amines. Compounds and the like. It is also possible to combine a radically polymerizable monomer and an initiator into a radical / cation hybrid type curable ink.

  In the actinic ray curable ink-jet ink of the present invention, the viscosity at 25 ° C. is 7 to 50 mPa · s in order to obtain stable curability and good curability regardless of the curing environment (temperature / humidity). Is preferable.

  Next, an image forming method that can be used in the present invention will be described.

  In the image forming method according to the present invention, the above ink is ejected and drawn on a substrate by an ink jet recording method, and then the ink is cured by irradiation with an actinic ray such as ultraviolet rays.

  In the present invention, the total ink film thickness after the ink has landed on the substrate and cured by irradiation with actinic rays is preferably 2 to 20 μm. In the actinic ray curable ink jet recording in the screen printing field, the total ink film thickness currently exceeds 20 μm, but in the flexible packaging printing field where the base material is often a thin plastic material, the above-mentioned base material is used. In addition to the problem of curling and wrinkles, there is a problem in that the entire printed material is changed in its strain and texture.

  Here, the “total ink film thickness” means the maximum value of the film thickness of the ink drawn on the base material, and even for a single color, other two-color superposition (secondary color), three-color superposition, four colors Even when recording is performed by the overlapping (white ink base) inkjet recording method, the meaning of the total ink film thickness is the same.

  As the ink discharge conditions, it is preferable from the viewpoint of discharge stability that the ink jet recording head and the ink are heated to 35 to 100 ° C. and discharged. Actinic ray curable ink has a large viscosity fluctuation range due to temperature fluctuation, and the viscosity fluctuation directly affects the droplet size and droplet ejection speed, causing image quality degradation. It is necessary to keep on. The control range of the ink temperature is set temperature ± 5 ° C., preferably set temperature ± 2 ° C., more preferably set temperature ± 1 ° C.

  In the present invention, it is preferable that the minimum amount of droplets discharged from each nozzle is 2 to 15 pl. Originally, in order to form a high-definition image, it is necessary for the amount of droplets to be within this range, but when discharging with this amount of droplets, the above-described discharge stability becomes particularly severe.

  A basic method of actinic ray irradiation is disclosed in JP-A-60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the 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 US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method according to the present invention.

  Next, an ink jet recording apparatus (hereinafter simply referred to as a recording apparatus) that can be used in the present invention will be described.

  Hereinafter, a recording apparatus according to the present invention will be described with reference to the drawings as appropriate. Note that the recording apparatus in the drawings is only one aspect of the recording apparatus that can be preferably used in the present invention, and the present invention is not limited to the drawing of the recording apparatus exemplified here.

  FIG. 2 is a front view showing an example of the configuration of the main part used in the serial printing method in the ink jet recording apparatus that can be used in the present invention. The recording apparatus 1 includes a head carriage 2, a recording head 3, an irradiation unit 4, a platen unit 5, and the like. In the recording apparatus 1, the platen unit 5 is installed under the base material P. The platen unit 5 has a function of absorbing ultraviolet rays, and absorbs excess ultraviolet rays that have passed through the substrate P. As a result, a high-definition image can be reproduced very stably.

  The base material P is guided by the guide member 6 and moves from the near side to the far side in FIG. 2 by the operation of the conveying means (not shown). Head scanning means (not shown) scans the recording head 3 held by the head carriage 2 by reciprocating the head carriage 2 in the Y direction in FIG.

  The head carriage 2 is installed on the upper side of the substrate P, and stores a plurality of recording heads 3 to be described later according to the number of colors used for image printing on the substrate P, with the discharge ports arranged on the lower side. The head carriage 2 is installed with respect to the main body of the recording apparatus 1 in such a manner that it can reciprocate in the Y direction in FIG. 2, and reciprocates in the Y direction in FIG. 2 by driving the head scanning means.

  In FIG. 2, the head carriage 2 is illustrated as accommodating the recording heads 3 of yellow (Y), magenta (M), cyan (C), and black (K). The number of colors of the recording head 3 housed in the head carriage 2 can be determined as appropriate.

  The recording head 3 is operated by a discharge means (not shown) provided with a plurality of actinic ray curable inks (for example, UV curable ink) supplied by an ink supply means (not shown). It discharges toward the base material P from a discharge outlet. The UV ink ejected by the recording head 3 is composed of a coloring material, a polymerizable monomer, an initiator, and the like, and the monomer crosslinks when the initiator acts as a catalyst when irradiated with ultraviolet rays. It has the property of being cured by a polymerization reaction.

  The recording head 3 is a fixed region (landing possible region) on the substrate P during the scanning in which the recording head 3 is moved from one end of the substrate P to the other end of the substrate P in the Y direction in FIG. ), UV ink is ejected as ink droplets, and ink droplets are landed on the landable area.

  The above scanning is performed as many times as necessary, and after UV ink is ejected toward one landable area, the substrate P is appropriately moved from the front to the back in FIG. 2 by the conveying means, and scanning by the head scanning means is performed again. 2, the recording head 3 discharges UV ink to the next landable area adjacent in the rear direction in FIG. 2 to the landable area.

  By repeating the above-described operation and discharging the UV ink from the recording head 3 in conjunction with the head scanning unit and the conveying unit, an image composed of an aggregate of UV ink droplets is formed on the substrate P.

  The irradiation unit 4 includes an ultraviolet lamp that emits ultraviolet light in a specific wavelength region with stable exposure energy and a filter that transmits ultraviolet light of a specific wavelength. Here, as the ultraviolet lamp, a mercury lamp, a metal halide lamp, an excimer laser, an ultraviolet laser, a hot cathode tube, a cold cathode tube, a black light, an LED (light emitting diode), etc. can be applied. Cathode tubes, mercury lamps or black lights are preferred.

  The irradiating means 4 has substantially the same shape as the maximum one that can be set by the recording apparatus (UV inkjet printer) 1 among the landable areas in which the recording head 3 ejects UV ink by one scan driven by the head scanning means. , Having a shape larger than the landable area.

  The irradiating means 4 is fixed on both sides of the head carriage 2 so as to be substantially parallel to the substrate P.

  As described above, as means for adjusting the illuminance of the ink discharge portion, not only the entire recording head 3 is shielded, but in addition, the ink discharge of the recording head 3 is determined from the distance h1 between the irradiation means 4 and the substrate P. It is effective to increase the distance h2 between the portion 31 and the substrate P (h1 <h2), or to increase the distance d between the recording head 3 and the irradiation means 4 (d is increased). Further, it is more preferable to provide a bellows structure 7 between the recording head 3 and the irradiation means 4.

  Here, the wavelength of the ultraviolet rays irradiated by the irradiation means 4 can be changed as appropriate by replacing the ultraviolet lamp or filter provided in the irradiation means 4.

  As described above, in FIG. 2, the serial printing method has been described as an example, but in addition, an ink jet recording apparatus of each ink jet printing method as shown in FIG. 3 can be used.

  3, a) in FIG. 3 is a method (line head method) in which the recording head 19 is arranged in the width direction of the substrate 20 and actinic rays are irradiated from the printing and irradiation means 24 while conveying the recording medium. 3b) is a method (flat head method) in which the recording head 19 performs printing while moving in the sub-scanning direction, and further irradiates actinic rays from the irradiating means 24 (c) in FIG. This is a method (serial printing method) in which the recording head 24 described performs printing while scanning in the width direction on the base material, and further irradiates actinic rays from the irradiation means 24 provided at both ends. it can.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

<Preparation of ink>
[Preparation of Ink 1: Present Invention]
(Preparation of pigment dispersion 1)
Pigment: Cyanine Blue 4044 (Sanyo dye phthalocyanine blue)
14.3g
Dispersant: Azisper PB822 (Ajinomoto Fine Techno Polymer Dispersant Amine 13) 5.7 g
Photopolymerizable compound: Aron oxetane OXT-221 (Oxetane compound manufactured by Toa Gosei)
80.0g
Pigment Dispersion 1 was prepared by putting each of the above additives into a glass bottle together with 360 g of zirconia beads having a diameter of 0.5 mm (apparent volume of 100 ml) and performing a dispersion treatment for 2 hours using a paint shaker.

(Preparation of ink 1)
Pigment Dispersion 1 28.0 parts by mass Photopolymerizable compound: Aron oxetane OXT-221 (supra) 40.2 parts by mass Photopolymerizable compound: Celoxide 2021P (Daicel Chemical Industries alicyclic epoxy compound) 26.8 parts by mass Part Photopolymerization initiator: Adeka optomer SP-152 (cationic polymerization initiator, manufactured by Asahi Denka Kogyo Co., Ltd.) 5.0 parts by mass After the pigment dispersion 1 prepared above and each of the above additives were mixed with a stirrer, 1 Filtration through a 0.0 micron membrane filter prepared Ink 1 which is an actinic ray curable inkjet ink.

[Preparation of ink 2: the present invention]
In the preparation of Pigment Dispersion 1, Pigment Dispersion 2 was prepared in the same manner except that Dispersbyk-161 (manufactured by Big Chemie, polymer dispersant, amine value: 11) was used instead of Azisper PB822 as a dispersant. Prepared. However, with Disperbyk-161, the active ingredient was 30% by mass, and the addition amount was appropriately adjusted so that the substantial addition amount was 5.7 g. Next, ink 2 was prepared in the same manner as in the preparation of the ink 1, except that the pigment dispersion 2 prepared above was used instead of the pigment dispersion 1.

[Preparation of Ink 3: Present Invention]
In the preparation of Pigment Dispersion 1, Pigment Dispersion 3 was similarly used except that Disparon ED-214 (manufactured by Enomoto Kasei Co., Ltd., polymer dispersant, amine value: 17) was used as a dispersant instead of Azisper PB822. Was prepared. Next, ink 3 was prepared in the same manner as in the preparation of the ink 1, except that the pigment dispersion 3 prepared above was used instead of the pigment dispersion 1.

[Preparation of ink 4: the present invention]
In the preparation of Pigment Dispersion 1, Pigment Dispersion 4 was similarly used except that Disparon ED-251 (manufactured by Enomoto Kasei Co., Ltd., polymer dispersant, amine value: 20) was used as a dispersant instead of Azisper PB822. Was prepared. Next, ink 4 was prepared in the same manner as in the preparation of the ink 1 except that the pigment dispersion 4 prepared above was used instead of the pigment dispersion 1.

[Preparation of ink 5: the present invention]
In the preparation of Pigment Dispersion 1, Pigment Dispersion 5 was similarly prepared except that Dispersbyk-2150 (manufactured by BYK Chemie, polymer dispersant, amine value: 57) was used instead of Azisper PB822 as a dispersant. did. However, the amount of Disperbyk-2150 was appropriately adjusted so that the active ingredient was 52% by mass and the substantial addition amount was 5.7 g. Next, ink 5 was prepared in the same manner as in the preparation of the ink 1 except that the pigment dispersion 5 prepared above was used instead of the pigment dispersion 1.

[Preparation of Ink 6: Comparative Example]
In the preparation of Pigment Dispersion 1, Pigment Dispersion 6 was prepared in the same manner except that Dispersbyk-116 (manufactured by Big Chemie, amine value: 0) was used instead of Azisper PB822 as a dispersant. Next, ink 6 was prepared in the same manner as in the preparation of the ink 1 except that the pigment dispersion 6 prepared above was used instead of the pigment dispersion 1.

[Preparation of Ink 7: Comparative Example]
Pigment dispersion 7 was prepared in the same manner as in the preparation of pigment dispersion 1, except that Cyanine Blue B120 (Sanyo Dye Phthalocyanine Blue) was used instead of Cyanine 4044. Next, ink 7 was prepared in the same manner as in the preparation of the ink 1 except that the pigment dispersion 7 prepared above was used instead of the pigment dispersion 1.

[Preparation of Ink 8: Comparative Example]
In the preparation of Pigment Dispersion 1, Pigment Dispersion 8 was prepared in the same manner except that Dispersbyk-109 (manufactured by BYK Chemie, amine value: 0) was used instead of Azisper PB822 as a dispersant. Next, an ink 8 was prepared in the same manner as in the preparation of the ink 1 except that the pigment dispersion 8 prepared above was used instead of the pigment dispersion 1.

[Preparation of Ink 9: Comparative Example]
In the preparation of the pigment dispersion 1, instead of Cyanine 4044, the pigment was Cyanine 4920 (Phthalocyanine Blue, manufactured by Dainichi Seika Kogyo Co., Ltd.), and Dispersone ED213 (Tsumoto Kasei) A pigment dispersion 9 was prepared in the same manner except that the amine value: 32) was used. Next, ink 9 was prepared in the same manner as in the preparation of the ink 1 except that the pigment dispersion 9 prepared above was used instead of the pigment dispersion 1.

[Preparation of Ink 10: Comparative Example]
A pigment dispersion 10 was prepared in the same manner as in the preparation of the pigment dispersion 8, except that Cyanine Blue 4927 (phthalocyanine blue manufactured by Dainichi Seika Kogyo Co., Ltd.) was used instead of the cyan blue 4044. Next, ink 10 was prepared in the same manner as in the preparation of the ink 8 except that the pigment dispersion 10 prepared above was used instead of the pigment dispersion 8.

[Measurement of hydrophilicity δm of pigment surface]
The hydrophilicity δm of the pigment particle surface in each prepared pigment dispersion was determined by a titration method described in Coloring Materials, 73 [3], 136 (2000).

[Measurement of Average Particle Size D ₅₀ and ΔD (D ₉₀ -D ₁₀ ) of Pigment Particles in Ink]
The pigment particles in each ink prepared above were measured using a Zetasizer 1000 manufactured by Malvern, and the abscissa was the particle size (D) and the ordinate was based on the mass particle size measurement data obtained on a mass basis. A particle size distribution curve composed of a particle mass function (G) and an integral curve of the distribution function are prepared, and from the integral curve, the particle size point D ₁₀ corresponding to 10% by mass, 50% by mass, 90% by mass, After obtaining D ₅₀ and D ₉₀ , ΔD (D ₉₀ -D ₁₀ ) was calculated.

  Table 1 shows the measurement results obtained as described above.

From the results of Table 1, the ink of the present invention using the polymer dispersant having a pigment surface δm value of 22 or less and having an amine value has an average particle size of 200 nm or less and a particle size distribution width ΔD (D _90- D ₁₀ ) is 170 nm or less, which indicates that the particle size distribution is narrower and the average particle size is smaller than that of the comparative ink.

<< Inkjet image formation >>
[Inkjet recording device]
A serial type ink jet recording apparatus having the configuration shown in FIG. 2 was used, and each of the inks 1 to 10 prepared above was loaded therein.

As the ultraviolet irradiation means, Vzero manufactured by Integration was used, the output voltage was appropriately adjusted so that the illuminance was 75 mW / cm ^2, and the time from the ink landing on the substrate to the ultraviolet irradiation was 0.00. Control was performed within 8 seconds.

  The recording head was equipped with piezo-type ink jet nozzles capable of emitting different ink droplet sizes in a range of 4 to 24 pl with 128 nozzles for each color and a nozzle pitch of 360 dpi. Further, the ink supply unit, the ink flow path, and the ink jet nozzle can be heated up to 55 ° C. by a heater. In addition, dpi as used in the field of this invention represents the number of dots per 2.54 cm.

(Image printing)
Using the above inkjet recording apparatus, a solid image with an output density of 100% is obtained in 4 passes, with a maximum ink liquid appropriate amount of 12 pl per pixel, a maximum solid ink adhesion amount of 8.9 g / m ^2, and 4 passes. Output images 1 to 10 were formed. A transparent polyethylene terephthalate film was used as the substrate. The wind speed of the outside air on the substrate surface was controlled to be less than 1 m / s.

<Evaluation of ink>
[Evaluation of storage stability]
For each of the inks prepared above, using a Zetasizer 1000 manufactured by Malvern Instruments Ltd., were measured an average particle diameter D ₁ of the pigment particles. Next, 100 ml of each ink was put in a sample bottle so as not to evaporate and sealed, and stored in a constant temperature bath at 60 ° C. for 1 week, and then the average particle diameter D ₂ after storage was determined in the same manner as above. The average particle size change rate was determined according to the following equation, and the storage stability was evaluated according to the following evaluation criteria.

Change rate of average particle size = {(D ₂ −D ₁ ) / D ₁ } × 100 (%)
5: Change rate of average particle size of ink is less than 5% 4: Change rate of average particle size of ink is less than 5 to 10% 3: Change rate of average particle size of ink is less than 10 to 25% 2: The change rate of the average particle size of the ink is less than 25 to 50% 1: The change rate of the average particle size of the ink is 50% or more [Evaluation of emission stability]
Each ink was continuously ejected by the ink jet recording apparatus shown in FIG. 2, the emission state was visually observed, and the ejection stability of the ink was evaluated according to the following criteria.

5: Even after performing continuous emission for 1 hour, the nozzles were normally emitted from all nozzles. 4: When continuous emission was performed for 1 hour, the nozzles that did not normally emit were 1 to 2. 3: Continuous emission The nozzles that did not emit normally were 3 to 5 at the time of performing 1 hour. 2: The nozzles that did not emit normally were 6 to 10 when continuous emission was performed for 1 hour 1: At the time of continuous emission for 1 hour, there were 11 or more nozzles that did not emit normally. << Evaluation of formed image >>
[Evaluation of color density reproducibility]
A solid image at an output density of 100% was printed on each of the ink before storage used in the storage stability evaluation and the ink stored at 60 ° C. for 1 week, and a reflection densitometer (X-Rite 938 manufactured by X-Rite) was printed. ) To measure the maximum reflection density value (Dmax1) of the image created with the ink before storage and the maximum reflection density value (Dmax2) of the image created with the ink stored at 60 ° C. for one week. A density change rate ΔDmax was determined, and color density reproducibility was evaluated according to the following criteria.

Maximum density change rate ΔDmax = (Dmax2 / Dmax1) × 100 (%)
5: Maximum density change rate ΔDmax is 95% or more 4: Maximum density change rate ΔDmax is 90% or more and less than 95% 3: Maximum density change rate ΔDmax is 80% or more and less than 90% 2 : Maximum density change rate ΔDmax is 70% or more and less than 80% 2: Maximum density change rate ΔDmax is less than 70% [Evaluation of image transparency]
The solid image created on the transparent polyethylene terephthalate film was subjected to visual observation of transparency by 20 general evaluators over an indoor fluorescent lamp, and image transparency was evaluated according to the following criteria.

5: 18 or more people who have determined that the image has transparency 4: 15-17 people who have determined that the image has transparency 3: 11-14 people who have determined that the image has transparency 2: 8 to 10 people who judged that the image has transparency 1: 7 or less people who judged that the image had transparency Table 2 shows the evaluation results of the ink and the formed image obtained as described above. Show.

As is apparent from the results shown in Table 2, the ink of the present invention in which the average particle diameter of the pigment particles is 50 to 200 nm and the width ΔD (D ₉₀ -D ₁₀ ) of the particle diameter distribution is 170 nm or less. It can be seen that the storage stability and the emission stability are good with respect to the comparative ink, and the color density reproducibility and image transparency of the formed image are excellent.

3 is a particle size distribution function curve representing D ₁₀ , D ₅₀ , and D _{90 according} to the present invention. It is a front view which shows an example of a structure of the principal part used with a serial printing system with the inkjet recording device which can be used by this invention. It is the schematic which shows an example of the inkjet printing system which can be used by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Recording device 2 Head carriage 3, 19 Recording head 4, 24 Irradiation means 5 Platen part 6 Guide member 7 Bellows structure P, 20 Base material 11 Particle size distribution function of pigment dispersion 12 Integral curve of particle size distribution function 13 D ₉₀ display 14 D ₅₀ display 15 D ₁₀ display 16 D ₉₀ -D ₁₀

Claims (6)

In the actinic radiation curable inkjet ink containing a photopolymerizable compound, a photopolymerization initiator, a pigment, and a dispersant, the secondary pigment particles of the pigment are average particles defined below, which are obtained in terms of mass-based normal distribution. is D ₅₀ is the diameter a 50 to 200 nm, and active ray curable width ΔD of the distribution of the D ₉₀ and D ₁₀ defined below (D ₉₀ -D ₁₀₎ is equal to or less than 170nm Ink for inkjet.
D ₅₀ : Secondary pigment particle distribution function dG = F (D) An integral curve of dD, which represents a particle size equal to 0.5 (50% by mass) of the total mass of the secondary pigment particles.
D ₉₀ : Secondary pigment particle distribution function dG = F (D) An integral curve of dD, which represents a particle size equal to 0.9 (90% by mass) of the total mass of the secondary pigment particles.
D ₁₀ : Secondary pigment particle distribution function dG = F (D) An integral curve of dD, which represents a particle size equal to 0.1 (10% by mass) of the total mass of the secondary pigment particles.
G represents the number of particles, D represents the particle size, and dG represents the mass of the secondary pigment particles in the particle size interval dD. The actinic ray curable inkjet ink according to claim 1, wherein the pigment surface has a hydrophilicity δm of 22 or less. The actinic ray curable inkjet ink according to claim 1, wherein the dispersant is a polymer dispersant. The actinic ray curable inkjet ink according to claim 1, wherein at least one of the photopolymerizable compounds is a photopolymerizable compound having an oxetane ring. The actinic ray curable inkjet ink according to claim 1, wherein the photopolymerization initiator is a cationic photopolymerization initiator. The average particle diameter defined above determined in terms of the mass-based normal distribution D ₅₀ is ₅₀ to 150 nm, and the distribution width ΔD (D ₉₀ −D) between D ₉₀ and D ₁₀ defined above. ₁₀ ) is 150 nm or less, The actinic-light curable inkjet ink of any one of Claims 1-5 characterized by the above-mentioned.

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