JP4686692B2 - Active energy ray-curable white ink composition used for ink jet recording system - Google Patents

Description

  The present invention relates to an active energy ray-curable white ink composition. More specifically, the present invention relates to an active energy ray-curable white ink composition that is suitably used for an inkjet recording method.

  In a normal ink jet recording system, an image is formed using water-based ink on a special paper provided with an ink receiving layer.

  On the other hand, it contains a photocationic polymerization initiator and an epoxy compound, a vinyl ether compound or an oxetane compound as an ink that can form an image on a substrate such as a film or metal that does not absorb ink, and does not contain a solvent. An active energy ray-curable ink composition for an ink jet recording system has been proposed (Patent Document 1).

  However, most inks for ordinary inkjet recording are highly transparent inks for the purpose of image formation on a white recording medium. Therefore, for example, a transparent base material used in soft packaging or When an image is formed using a substrate with low brightness as a recording medium, contrast may not be obtained, and clear color development may not be obtained, or display with visibility may be difficult.

  When the image visibility is inferior, a technique for obtaining good color image visibility by performing background printing using a white ink with high concealment and forming a color image thereon is known. As the white ink composition for inkjet recording to be used, for example, a photocurable white ink composition comprising a white pigment and at least one compound selected from the group consisting of an oxetane compound, an epoxy compound and a vinyl ether compound has been proposed. (Patent Document 2).

  However, in the case of a cationic polymerization type ink composition containing a white pigment, there are problems such as a slow curing rate by ultraviolet irradiation and generation of wrinkles on the surface during ultraviolet irradiation.

  In order to solve these problems, it is known to use a cationic polymerization material and a radical polymerization material in combination (Patent Documents 1 and 2 also describe that a cationic polymerization material and a radical polymerization material are used in combination. Have been).

  In addition, as a cationic photopolymerization initiator, aromatic sulfonium salts are used because they have absorption up to a relatively long wavelength region, have good solubility and good storage stability when dissolved in monomers. Although widely used, this generally has poor compatibility with acrylic monomers, which are radical polymerization materials, causing problems such as poor curing and poor ink storage stability (Non-Patent Document 1). .

In addition, as a counter anion of the photocationic polymerization initiator, it is necessary to select one having a low nucleophilicity in order to avoid polymerization termination reaction. From this point, SbF ₆ ⁻ (hexafluoroantimonate) is preferable. (Non-patent Document 1).

JP 2001-220526 A JP 2004-59627 A “Hardening failure / inhibition factors in UV curing and countermeasures for them: Monomer / oligomer, initiator / resin selection / mixing technology”, Technical Information Association, issued December 11, 2003

In view of the problems of the prior art, the present invention uses a cationic polymerization material and a radical polymerization material (acrylic monomer) in combination to increase the curing rate during irradiation with active energy rays and to prevent wrinkles during curing. It is an object of the present invention to provide an active energy ray-curable white ink composition that is used in an ink jet recording system that prevents generation and has good compatibility between a cationic photopolymerization initiator and an acrylic monomer.

ラジカル重合性物質として、一般式：
The present invention provides an active energy ray-curable white ink composition for use in the following inkjet recording method .
(1) In the active energy ray-curable white ink composition used for an ink jet recording method including a cationic polymerizable substance and a radical polymerizable substance, and a white pigment, the cationic polymerizable substance has at least one aromatic ring. Diglycidyl ether or polyglycidyl ether of polyhydric phenol or its alkylene oxide adduct, diglycidyl ether or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, alicyclic ring represented by formulas (27) to (29) An epoxy compound which is a diglycidyl ether or polyglycidyl ether of a polyepoxy compound, an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof, and a diglycidyl ether of a polyalkylene glycol,

As a radically polymerizable substance, a general formula:

(Wherein f represents an integer of 3 to 15), and the content of the monomer of formula (1) is 10 to 30% with respect to the weight of the cationically polymerizable substance. An active energy ray-curable white ink composition for use in an ink jet recording system , comprising an aromatic sulfonium salt whose counter anion is SbF ₆ ^— as a photocationic polymerization initiator.
(2) The active energy ray-curable white ink composition for use in the ink jet recording method according to the item (1), wherein the cationically polymerizable substance further comprises at least one selected from the group consisting of oxetane compounds.

In the active energy ray-curable white ink composition of the present invention, by using a cationically polymerizable substance and a radically polymerizable substance in combination, the curing rate during irradiation with active energy rays is increased and wrinkles are generated during curing. In addition, the hardness of the cured product is improved by further promoting the curing of the cationic polymerizable substance by heat. Further, in the present invention, as a cationic photopolymerization initiator, it has an absorption up to a relatively long wavelength region, has good solubility and good storage stability when dissolved in a monomer, and is aromatic. A sulfonium salt is used, and SbF ₆ ^- having a low nucleophilicity is used as a counter anion in the aromatic sulfonium salt in order to avoid the termination reaction of polymerization, but it has good compatibility with such a photocationic polymerization initiator. Since such an acrylic monomer is used, problems such as poor curing and ink storage stability are solved.

  The active energy ray-curable white ink composition of the present invention comprises a cationically polymerizable substance, a radically polymerizable substance, an aromatic sulfonium salt as a photocationic polymerization initiator, and a white pigment.

In the present invention, as a cationic photopolymerization initiator, aromatic sulfonium has absorption in a relatively long wavelength range, has good solubility, and has good storage stability when dissolved in a monomer. A salt is used, and SbF ₆ ⁻ having low nucleophilicity is used as a counter anion in the photocationic polymerization initiator in order to avoid a termination reaction of polymerization.

  As the aromatic sulfonium salt, the general formula (2):

(Wherein three Rs independently represent a hydrogen atom or a substituent), a compound represented by formula (3):

The compound etc. which are represented by these are mentioned. Examples of the substituent represented by R in the general formula (2) include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, t-butyl, and isobutyl, methoxy, ethoxy, and propoxy. Group, an alkoxy group such as a butoxy group, and a halogen atom. Typical examples of the compound represented by the general formula (2) include triphenylsulfonium hexafluoroantimonate. These photocationic polymerization initiators can be used alone or in admixture of two or more.

  The content of the cationic photopolymerization initiator is preferably 1 to 15% by weight, more preferably 2 to 10% by weight, based on the cationic photopolymerizable substance. If the content of the photocationic polymerization initiator is less than the above range, the curability at the time of irradiation with active energy rays tends to be insufficient. On the other hand, if the content exceeds the above range, the light transmittance becomes poor and uniform curing cannot be achieved. The smoothness of the film surface may be lost.

  In the present invention, ethylene glycol diacrylate represented by the general formula (1) is used as the radical polymerizable substance. This diacrylate has good compatibility with the photocationic polymerization initiator. In particular, f is more preferably from 3 to 10.

  The content of diacrylate is preferably 5 to 50% by weight, more preferably 10 to 30% by weight, based on the weight of the cationic polymerizable substance. If the content of diacrylate is less than the above range, the curability improving effect and the wrinkle prevention effect tend not to be sufficiently achieved, while if it exceeds the above range, the adhesion to metal or the like tends to be impaired.

  In the present invention, since diacrylate which is a radical polymerizable substance is used, a radical polymerization initiator is blended. Various radical polymerization initiators can be used, and preferable ones include benzophenone and its derivatives, benzoin alkyl ether, 2-methyl [4- (methylthio) phenyl] -2-morpholino-1-propanone, Benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, alkylphenyl glyoxylate, diethoxyacetophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, acylphosphine oxide, 2,4,6-trimethylbenzyl-diphenyl-phosphine oxide and the like. These radical polymerization initiators can be used alone or in combination of two or more. The radical polymerization initiator causes photocuring of the radical polymerizable substance when irradiated with active energy rays, and also causes thermal polymerization when heated in post-processing, thereby obtaining a cured product having high hardness. The content of the radical polymerization initiator is preferably 1 to 15% by weight, more preferably 2 to 10% by weight with respect to diacrylate.

  The cationically polymerizable substance in the present invention is not particularly limited and any ordinary one can be used. For example, one or more selected from the group consisting of oxetane compounds, epoxy compounds, vinyl ether compounds, etc. are used. it can. In particular, the combined use of an oxetane compound and an epoxy compound is preferable from the viewpoint of good ink curability, curing speed, and flexibility of a cured film.

  The oxetane compound used in the present invention means a compound having an oxetane ring. For example, oxetane compounds described in JP-A Nos. 2001-220526 and 2001-310937 can be used. .

  If a compound with too many oxetane rings is used, the viscosity of the prepared ink will be high and handling will be difficult, and the glass transition temperature of the ink will be high, and the resulting cured product will not be sufficiently sticky. There is a tendency for problems to occur. From this point, in the present invention, a compound having 1 to 4 oxetane rings is preferable.

  Hereinafter, although the specific example of the oxetane compound which can be used by this invention is demonstrated, this invention is not limited to these.

  Examples of the compound having one oxetane ring include compounds represented by the following general formula (4).

In the general formula (4), R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a fluoroalkyl group having 1 to 6 carbon atoms, an allyl group, an aryl group. Group, furyl group or thienyl group. R ² represents an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, a propyl group, or a butyl group, a 1-propenyl group, a 2-propenyl group, a 2-methyl-1-propenyl group, or 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 or a butylcarbonyl group, an ethoxycarbonyl group, a propoxycarbonyl group or a butoxycarbonyl group having 2 to 6 carbon atoms. Alkoxycarbonyl group, ethylcarbamoyl group, propylcarbamoyl group, butylcarbamoyl group, pentylca And the like N- alkylcarbamoyl group having a carbon number 2-6 such as Bamoiru group. As the oxetane compound used in the present invention, it is particularly preferable to use a compound having one oxetane ring because the resulting composition has excellent tackiness, low viscosity and excellent workability.

  Examples of the compound having two oxetane rings include a compound represented by the following general formula (5).

In general formula (5), R ¹ has the same meaning as R ¹ in the general formula (4). R ³ is, for example, a linear or branched poly (alkyleneoxy) group such as a linear or branched alkylene group such as an ethylene group, a propylene group or a butylene group, 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 (6), (7) and (8) can also be mentioned.

In the general formula (6), 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 (7), 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 (8), 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 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. Examples of R ^{7 also} include a group selected from the group represented by the following general formula (9).

In General formula (9), R < ⁸ > is a C1-C4 alkyl group, such as a methyl group, an ethyl group, a propyl group, a butyl group, or an aryl group. m is an integer of 0-100.

  Specific examples of the compound having two oxetane rings include compounds represented by formula (10) and formula (11).

The compound represented by the formula (10) is a compound in which R ¹ is an ethyl group and R ³ is a carbonyl group in the general formula (5). The compound represented by the formula (11) is a compound represented by the general formula (5), wherein R ¹ is an ethyl group, R ³ is a group represented by the general formula (8), and R ⁶ and R ⁷ are A compound in which a methyl group 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 (12). In the general formula (12), R ¹ has the same meaning as R ¹ in the general formula (4).

  Examples of the compound having 3 to 4 oxetane rings include a compound represented by the following general formula (13).

In the general formula (13), R ¹ has the same meaning as R ¹ in the general formula (4). Examples of R ⁹ include branched alkylene groups having 5 to 12 carbon atoms such as groups represented by the following formulas (14) to (16), and branched poly groups such as groups represented by the following formula (17). (Alkyleneoxy) group or branched polysiloxy group such as a group represented by the following formula (18). j is 3 or 4.

In the above formula (14), R ¹⁰ is a lower alkyl group such as a methyl group, an ethyl group, or a propyl group. Moreover, in said formula (17), p is an integer of 1-10.

  Specific examples of the compound having 3 to 4 oxetane rings include a compound represented by the formula (19).

  Furthermore, specific examples of the compound having 1 to 4 oxetane rings other than those described above include compounds represented by the following general formula (20).

In the general formula (20), R ¹ has the same meaning as R ¹ in the general formula (4), R ⁸ has the same meaning as R ⁸ in the general formula (9). 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 an integer of 1 to 4.

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

  Production of each compound having an oxetane ring described above can be carried out according to a conventionally known method, for example, Pattisson (DB Pattison, J. Am. Chem. Soc., 3455, 79 (1957). There is a method for synthesizing an oxetane ring from a diol. In addition to the oxetane compounds described above, compounds having 1 to 4 oxetane rings having a high molecular weight of about 1000 to 5000 are also included. Specific examples thereof include the following compounds.

  Next, the epoxy compound used in the present invention will be described.

  The epoxy compound used in the present invention is not particularly limited, and is shown in, for example, JP-A-2001-55507, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-310938. The epoxy compound currently used can be used.

  Preferred as the aromatic epoxy compound is diglycidyl ether or polyglycidyl ether produced by the reaction of a polyhydric phenol having at least one aromatic ring or an alkylene oxide adduct thereof and epichlorohydrin, for example, bisphenol A Alternatively, diglycidyl ether or polyglycidyl ether of an alkylene oxide adduct thereof, hydrogenated bisphenol A or diglycidyl ether or polyglycidyl ether of an alkylene oxide adduct thereof, and a novolak type epoxy resin can be used. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  The alicyclic epoxy compound can be 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 peroxide. Cyclohexene oxide or cyclopentene oxide-containing compounds are preferred. Preferred alicyclic epoxy compounds include those represented by formulas (27) to (29).

  Preferred examples of the aliphatic epoxy compound include diglycidyl ether or polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof, and typical examples thereof include diglycidyl ether of ethylene glycol and propylene glycol. Polyglycidyl ethers of polyhydric alcohols such as diglycidyl ether or diglycidyl ether of alkylene glycol such as diglycidyl ether of 1,6-hexanediol, diglycerin or its adduct of alkylene oxide, polyethylene glycol or the like Diglycidyl ether of alkylene oxide adduct, polypropylene glycol or diglycidyl ether of alkylene oxide adduct Like diglycidyl ethers of polyalkylene glycols such as. Here, examples of the alkylene oxide include ethylene oxide and propylene oxide.

  Among the above epoxy compounds, in view of fast curability, aromatic epoxy compounds and alicyclic epoxy compounds are preferable, and alicyclic epoxy compounds are particularly preferable.

  In the active energy ray-curable white ink composition of the present invention, the content of the cationic polymerizable material is preferably 40 to 80% by weight, more preferably 50 to 70% by weight, based on the total amount of the ink composition. If the content of the cationic polymerizable substance is less than the above range, the photocurability is not sufficient. On the other hand, if it exceeds the above range, there is a tendency that the curing rate is reduced by light irradiation and wrinkles are generated on the coated surface.

  In the active energy ray-curable white ink composition of the present invention, the ratio of the oxetane compound and the epoxy compound in the cationic polymerizable material is such that the content of the oxetane compound is 5 to 95% by weight with respect to the total amount of the oxetane compound and the epoxy compound. It is preferable that it is 10 to 90% by weight. If the content of the oxetane compound is less than the above range, the effect of improving the curing rate of the epoxy resin tends to be poor. On the other hand, if it exceeds the above range, the flexibility of the ink cured film tends to decrease.

  The white pigment used in the present invention is not particularly limited as long as it makes the ink composition white, and white pigments usually used in this field can be used. As such a white pigment, for example, an inorganic white pigment, an organic white pigment, white hollow polymer fine particles, or the like can be used.

  Inorganic white pigments include alkaline earth metal sulfates such as barium sulfate, alkaline earth metal carbonates such as calcium carbonate, silicates such as fine silicate and synthetic silicate, calcium silicate, silica, and alumina. , Alumina hydrate, titanium oxide, zinc oxide, talc, clay and the like. In particular, titanium oxide is a white pigment with preferable hiding properties, coloring properties, and dispersed particle sizes. Examples of the organic white pigment include organic compound salts disclosed in JP-A No. 11-129613 and alkylene bismelamine derivatives disclosed in JP-A Nos. 11-14365 and 2001-234093. Examples of the white hollow polymer fine particles include thermoplastic fine particles made of a substantially organic polymer and disclosed in US Pat. No. 4,089,800. These white pigments may be used alone or in combination.

  For dispersing the pigment, a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, a paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the pigment. As the dispersant, a polymer dispersant is preferably used.

  Examples of the polymeric dispersant include Solsperse series manufactured by 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 weight with respect to 100 parts by weight of the white pigment. The curable ink by active energy ray irradiation of the present invention is preferably substantially solvent-free because it reacts and cures immediately after ink landing. If the solvent remains in the cured image, the solvent resistance deteriorates and the VOC of the remaining solvent arises. Therefore, it is preferable to use a polymerizable compound instead of a solvent as the dispersion medium. Among them, it is preferable in view of dispersibility to select a monomer having a low viscosity.

  The content of the white pigment is preferably 5 to 30% by weight, and more preferably 10 to 20% by weight, based on the entire ink composition. If the content of the white pigment is less than the above range, sufficient concealing property cannot be obtained. On the other hand, if the content exceeds the above range, the ejection property from the ink jet recording head is deteriorated, which causes clogging.

  In addition to the photo cationic polymerization initiator and the photo radical polymerization initiator, a photosensitizer may be added to the ink composition of the present invention to adjust the wavelength in the ultraviolet region. Typical sensitizers that can be used in the present invention include those disclosed by Krivello [JV Crivello, Adv. In Polymer Sci., 62, 1 (1984)]. Examples include pyrene, perylene, acridine orange, thioxanthone, 2-chlorothioxanthone, benzoflavine, and 9,10-dibutoxyanthracene.

  In the white ink composition of the present invention, in addition to the above components, a polymerization inhibitor, a surfactant, a leveling additive, a matting agent, and film physical properties are adjusted as necessary within the range not impairing the effects of the present invention. Polyester resins, polyurethane resins, vinyl resins, acrylic resins, rubber resins, waxes, fillers, antifoaming agents, antioxidants, and the like can be added.

  When the white ink composition of the present invention is used in an inkjet recording system, it is preferable to determine the composition so that the viscosity is 50 mPa · s or less, preferably 25 mPa · s or less at the ink discharge temperature (for example, 40 ° C.). .

  The white ink composition of the present invention is printed by an ink jet recording method using paper, a film or sheet, metal or the like as a base material. After printing, it is cured by irradiation with active energy rays. Examples of active energy rays include ultraviolet rays, X-rays, and electron beams. As a light source that can be used for curing with ultraviolet rays, various light sources can be used, and examples thereof include a pressurized or high-pressure mercury lamp, a metal halide lamp, a xenon lamp, an electrodeless discharge lamp, and a carbon arc lamp. In the case of curing with an electron beam, various irradiation devices can be used, such as a cockloftwaldsin type, a bandegraph type, or a resonance transformer type. An electron beam having an energy of 50 to 1000 eV is preferable. More preferably, it is 100-300 eV. In the present invention, since an inexpensive apparatus can be used, it is preferable to use ultraviolet rays for curing the composition. After curing by irradiating active energy rays, it may be further cured by heat treatment. The heat treatment can be performed, for example, at 100 to 150 ° C. for about 10 minutes to 1 hour. When the white ink composition of the present invention is cured after printing and an image is formed thereon with a normal color ink for inkjet recording, a color image with good visibility can be obtained.

  The ink composition of the present invention can be used as an ink composition such as lithographic printing such as offset printing, letterpress printing, silk screen printing or gravure printing by adjusting the composition.

  EXAMPLES Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Examples 1-2 and Comparative Examples 1-3
A white ink composition for inkjet recording was prepared using the materials shown in Table 1. The amount of each material used in Table 1 is parts by weight.

  The obtained ink composition was examined for viscosity, ejection stability, curability, wrinkles on the cured product surface, and pencil hardness. The results are shown in Table 1.

The materials shown in Table 1 are as follows.
Epoxy compound: aliphatic cation polymerizable epoxy resin (Adekaoptomer KRM2720, manufactured by Asahi Denka Co., Ltd.)
Oxetane compound: bis [1-ethyl (3-oxetanyl)] methyl ether acrylic monomer 1: triethylene glycol diacrylate acrylic monomer 2: PEG200 # diacrylate (addition number of polyethylene glycol diacrylate, ethylene oxide manufactured by Kyoeisha Chemical Co., Ltd.) : 4 on average)
Acrylic monomer 3: Neopentyl glycol diacrylate photocationic polymerization initiator 1: Adekaoptomer SP-170 (Asahi Denka Co., Ltd., one of the compounds represented by general formula (2))
Photocationic polymerization initiator 2: Compound represented by formula (3) Photocationic polymerization initiator 3: (4-methylphenyl) [4- (2-methylpropyl) phenyl] iodonium hexafluorophosphate (1-)
Sensitizer: 9,10-dibutoxyanthracene radical polymerization initiator: 2,4,6-trimethylbenzyl-diphenyl-phosphine oxide

(1) Viscosity The viscosity was measured at 40 ° C. using a rotary viscometer (TV-20L manufactured by Tokimec Co., Ltd.).

(2) Discharge stability Printing was performed using an ink jet recording system printer having a piezo-type print head, and the discharge stability was examined according to the following evaluation criteria.
○: The ink can be discharged satisfactorily and there is no uneven printing
Δ: Ejected, but printing unevenness occurred.
X: Cannot be discharged.

(3) Curability A white ink composition was coated on a resist substrate to a thickness of 20 μm with a bar coater, and irradiated with a 120 W / cm metal halide A lamp with an integrated light amount of 250 mJ / cm ² per pass. Evaluation was made by the number of passes until the surface was cured (not sticky when touched). The smaller the number of passes, the better the curability.

(4) Wrinkles on the surface of the cured product In the evaluation of curability, the generation of wrinkles when the surface was cured was visually evaluated.

(5) Pencil hardness A white ink composition was coated on a resist substrate to a thickness of 20 μm with a bar coater, irradiated with a 120 W / cm metal halide A lamp with an accumulated light amount of 1250 mJ / cm ² , and then 150 ° C. Heat treatment was performed under the conditions of × 30 minutes, and the pencil hardness was measured according to JIS K 5400.

Claims (2)

In the active energy ray-curable white ink composition used for the ink jet recording method, which includes a cationic polymerizable substance and a radical polymerizable substance, and a white pigment, the cationic polymerizable substance is a polyhydric phenol having at least one aromatic ring. Or diglycidyl ether or polyglycidyl ether of an alkylene oxide adduct thereof, hydrogenated bisphenol A or diglycidyl ether or polyglycidyl ether of an alkylene oxide adduct thereof, or an alicyclic epoxy compound represented by formulas (27) to (29) An epoxy compound that is a diglycidyl ether or polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof, and a diglycidyl ether of a polyalkylene glycol,

As a radically polymerizable substance, a general formula:

(Wherein f represents an integer of 3 to 15), and the content of the monomer of formula (1) is 10 to 30% with respect to the weight of the cationically polymerizable substance. An active energy ray-curable white ink composition for use in an ink jet recording system , comprising an aromatic sulfonium salt whose counter anion is SbF ₆ ^— as a photocationic polymerization initiator. The active energy ray-curable white ink composition for use in an ink jet recording system according to claim 1, wherein the cationic polymerizable substance further contains at least one selected from the group consisting of oxetane compounds.