TW201821555A - Inkjet ink composition - Google Patents

Abstract

Provided is an inkjet ink composition which contains an active energy ray-curable compound (A) and a photopolymerization initiator (B), wherein a monofunctional (meth)acrylate compound represented by formula (1) (in formula (1), R1 is a hydrogen atom or a methyl group, R2 groups are each independently a hydrogen atom, a fluorine atom, a chlorine atom or bromine atom, and n1 and n2 are each 1-4) is contained at a quantity of 60 mass% or more of the active energy ray-curable compound (A).

Description

   Inkjet printing ink composition   

The present invention relates to an inkjet printing ink composition used in an optical article, and a hardened material that hardens the composition.

In recent years, various attempts have been made to form optical components such as lenticular lenses and condenser lenses used in image display devices such as liquid crystal displays and organic EL displays by an inkjet method (for example, refer to Patent Document 1). .

As an inkjet printing ink composition for forming an optical member of an image display device by an inkjet method, for example, a low-viscosity photocurable spray containing a fluorene-based (meth) acrylate and a specific diluent is disclosed. Ink is printed by ink (for example, refer to Patent Document 2).

    [Prior technical literature]         [Patent Literature]    

[Patent Document 1] Japanese Patent Laid-Open No. 2010-224200

[Patent Document 2] Japanese Patent Laid-Open No. 2013-185040

The above-mentioned Patent Document 2 discloses that a low-viscosity photo-curable inkjet ink containing a fluorene-based (meth) acrylate, a specific diluent, and a polymerization initiator in combination can be specifically formulated to achieve a high viscosity. Refractive index and excellent adhesion.

However, since the image display device is used in various environments depending on the application, it is necessary to achieve high adhesion not only in a normal state but also in a hot and humid environment.

The subject of the present invention is to provide an inkjet printing ink composition which can be applied to inkjet, and has a high refractive index and excellent wet heat adhesion.

An inkjet printing ink composition comprising an active energy ray-curable compound (A) and a photopolymerization initiator (B), wherein the active energy ray-curable compound (A) contains the following A monofunctional (meth) acrylate compound represented by formula (1).

(In formula (1), R ₁ is a hydrogen atom or a methyl group; R ₂ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a bromine atom; and n ₁ and n _{2 each} represent 1 to 4).

The content of the monofunctional (meth) acrylate compound represented by formula (1) in the active energy ray-curable compound (A) contained in the inkjet printing ink composition is 60% by mass or more. The ink composition can solve the above problems.

The inkjet printing ink composition of the present invention contains the phenylbenzyl acrylate represented by the above formula (1) as an active energy ray hardening compound, thereby maintaining low viscosity and high refractive index that can be applied to inkjet , And can achieve excellent wet heat adhesion. Since this composition can arbitrarily form a member with a high refractive index by an inkjet method, it can be suitably applied to various optical articles, such as a cymbal, a stereo photograph, or a projection screen used in a display such as a liquid crystal display device Formation of various optical sheets such as a lenticular lens sheet used in a lens, a condenser lens of a transparent sheet projector, etc., a diffraction grating used in a color filter, and the like.

    [Form of Implementing Invention]    

(Active energy ray polymerizable compound)

The inkjet printing ink composition of the present invention is a printing ink composition that can be discharged by an inkjet device, and is a printing ink composition that is hardened by irradiation with active energy rays. This ink composition contains an active energy ray-curable compound (A) and a photopolymerization initiator (B), and the active energy ray-curable compound (A) contains a monofunctional (methyl group) represented by the following formula (1) ) Acrylate compound, which has a low viscosity that can be ejected by an inkjet device, and can achieve a high refractive index and good adhesion to the adherend.

(In formula (1), R ₁ is a hydrogen atom or a methyl group. R ₂ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a bromine atom; and n ₁ and n ₂ represent 1 to 4).

In the inkjet printing ink composition of the present invention, the content of the compound represented by formula (1) in the active energy ray-curable compound (A) contained in the composition is 60% by mass or more, and 70% by mass or more is It is preferably 80% by mass or more, and more preferably 90% by mass or more. By setting the content of the compound represented by the formula (1) in the above range, it has a low viscosity, and at the same time, it is easy to ensure a high refractive index and good adhesion to the adherend. In addition, since the compounding is easy, the content of the compound represented by the formula (1) may also be 95% by mass or more, and preferably 100% by mass.

The inkjet ink composition of the present invention may contain other active energy ray polymerizable compounds in addition to the compound represented by the formula (1). As for the other active energy ray polymerizable compounds, a monofunctional compound having one active energy ray polymerizable group and a polyfunctional compound having two or more such polymerizable groups can be suitably used.

In terms of monofunctional compounds, for example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, n-amyl (meth) acrylate, ( N-hexyl methacrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, (meth) acrylic acid Phenoxyethyl ester, phenoxy benzyl (meth) acrylate, phenoxy diethylene glycol (meth) acrylate, glycidyl (meth) acrylate, morpholinyl (meth) acrylate , 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol Mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, 2-methoxyethyl (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethyl Glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, 2-butoxyethyl (meth) acrylate, butoxytriethylene glycol (meth) acrylate, 2-ethoxyethyl (meth) acrylate 2- (2-ethoxyethoxy) ethyl (meth) acrylate, ethoxy polyethylene glycol (meth) acrylate, 4-nonylphenoxy ethylene glycol (meth) acrylate , Tetrahydrofurfuryl (meth) acrylate, caprolactone modified tetrahydrofurfuryl (meth) acrylate, cyclohexyl (meth) acrylate, isoamyl (meth) acrylate, (meth) acrylic acid -Hydroxy-3-phenoxypropyl, cyclohexyl methyl (meth) acrylate, cyclohexyl ethyl (meth) acrylate, dicyclopentyl (meth) acrylate, dicyclopentyl (meth) acrylate Monofunctional (meth) acrylates such as esters, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and ethylene oxide modified acrylates of phenylphenol. These monofunctional (meth) acrylates may be used either alone or in combination.

As for the monofunctional compound used in combination in the present invention, it is preferable to use a compound having a viscosity of 300 mPa · s or less at 25 ° C, and more preferably a compound of 200 mPa · s or less. In addition, the refractive index at 25 ° C and 589 nm is preferably 1.4 or more, more preferably 1.5 or more, and even more preferably 1.55 or more.

Among the above monofunctional compounds, phenoxybenzyl acrylate or ethylene oxide modified acrylate of o-phenylphenol is preferred because it maintains the viscosity of the composition and easily increases the refractive index of the obtained hardened product. .

When these monofunctional compounds are used in combination, the content of monofunctional compounds other than the compound represented by formula (1) in the active energy ray polymerizable compound (A) contained in the inkjet ink composition of the present invention is 50%. Mass% or less is preferable, 30 mass% or less is more preferable, and 10 mass% or less is particularly preferable because the refractive index can be maintained.

In the present invention, a polyfunctional compound may be further used in combination. Examples of the polyfunctional compound include fluorene di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) Acrylate, butanediol di (meth) acrylate, tetrabutylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di ( (Meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, bis (methyl) of ethylene oxide adduct of bisphenol A Acrylate, di (meth) acrylate of propylene oxide adduct of bisphenol A, di (meth) acrylate of ethylene oxide adduct of bisphenol F, propylene oxide addition of bisphenol F Di (meth) acrylate, dicyclopentyl di (meth) acrylate, glycerol di (meth) acrylate, neopentyl glycol hydroxytrimethylacetate di (meth) acrylate Caprolactone Modified Hydroxytrimethylacetic Acid Neopentyl glycol di (meth) acrylate, tetrabromobisphenol A di (meth) acrylate, hydroxytrimethylacetaldehyde modified trimethylolpropane di (meth) acrylate, 1,4- Cyclohexanedimethanol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tri (meth) acrylate of trimethylolpropane ethylene oxide adduct, trihydroxy Tri (meth) acrylates of propylene oxide adducts of methylpropane, neopentaerythritol tri (meth) acrylate, glycerol tri (meth) acrylate, alkyl modified dipentaerythritol Tris (meth) acrylate, di-trimethylolpropane tetra (meth) acrylate, tetra- (meth) acrylate di-trimethylolpropane ethylene oxide adduct, di- Multifunctional (meth) acrylates such as tetra (meth) acrylates of propylene oxide adducts of trimethylolpropane. In addition, the polyfunctional (meth) acrylate also includes acrylic resins such as urethane (meth) acrylate, polyester (meth) acrylate, and (meth) acrylate epoxy. Polyfunctional oligomer. These systems may use one kind or plural kinds.

Among the above, when a cured product having a high refractive index is obtained, a fluorene-containing di (meth) acrylate represented by the following formula (2) can be applied.

(In formula (2), R ₃ and R ₄ each independently represent a hydrogen atom or a methyl group; X ₁ and X ₂ each independently represent an alkylene group having 2 or 3 carbon atoms; m ₁ and m _{2 are} independent of each other Represents an integer from 0.)

In the compound represented by the formula (2) used in the present invention, the refractive index is preferably 1.50 or more, and more preferably 1.53 or more. Moreover, its viscosity is preferably 15,000 mPa‧s or less, and more preferably 3000 mPa · s or less. In addition, m ₁ + m ₂ in the formula (2) is preferably 2 to 30.

When using these polyfunctional (meth) acrylates, the polyfunctional compound in the active energy ray polymerizable compound (A) contained in the inkjet printing ink composition of the present invention, from the viewpoint of maintaining a low viscosity, The content is preferably 20% by mass or less, and more preferably 10% by mass or less.

Further, in the inkjet printing ink composition of the present invention, a compound having an active energy ray polymerizable group other than the (meth) acrylate may be used. When using a compound other than these (meth) acrylates, it is preferable to use 20% by mass or less of the active energy ray polymerizable compound, and it is more preferable to use 10% by mass or less. In addition, since it is easy to adjust the high refractive index and the wet heat adhesion, it is also preferable that it is not substantially contained.

(Photopolymerization initiator)

The photopolymerization initiator used in the present invention can use various initiators used in inkjet printing ink compositions, for example, the following are applicable: 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl 1-1-phenylpropane-1-one, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propane-1-one, thia anthrone (thioxanthone) and thiaxanthone derivatives, 2,2'-dimethoxy-1,2-diphenylethane-1-one, 2,4,6-trimethylbenzylidene diphenyl Phosphine oxide, bis (2,4,6-trimethylbenzylidene) phenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinyl -1-acetone, 2-benzyl-2-dimethylamino-1- (4-morpholinylphenyl) -butane-1-one, and the like. These initiators may be used singly or in combination of two or more.

The use amount of the photopolymerization initiator is not particularly limited, but from the viewpoints of obtaining good hardenability, good scratch resistance and self-healing properties of the obtained hardened material, etc., compared with the inkjet ink composition for optical articles The active energy ray polymerizable compound is preferably 100 parts by mass, preferably 0.05 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass.

(Inkjet ink composition)

The inkjet printing ink composition of the present invention contains the compound represented by the above formula (1), and is a composition having a viscosity of 100 mPa · s or less and a liquid refractive index of 1.57 or more. The ink composition of the present invention can be applied to inkjet by this structure, and can achieve a high refractive index and excellent wet heat adhesion.

The viscosity of the inkjet printing ink composition of the present invention at 25 ° C is preferably 100 mPa · s or less, and more preferably 50 mPa · s or less. Thereby, various optical articles made by ejection in an inkjet device are used. In addition, it is easy to apply / shape into a desired shape and thickness. In addition, it is preferably 30 mPa · s or less, and more preferably 20 mPa · s or less.

In the inkjet printing ink composition of the present invention, the liquid refractive index is preferably 1.57 or more, more preferably 1.575 or more, and more preferably 1.58 or more. The hardened | cured material obtained by setting the refractive index of this liquid can provide a high refractive index, and can be used suitably for various optical articles.

Moreover, the surface tension of the inkjet printing ink composition of the present invention is preferably 20 to 50 mN / m, and more preferably 30 to 50 mN / m. In the case of an inkjet printing ink composition having a surface tension within this range, it is easy to appropriately adjust to a good inkjet suitability by using a leveling agent or the like as necessary.

The inkjet ink composition of the present invention may contain components other than the above-mentioned active energy ray polymerizable compound, and for example, a resin may be used in combination for the purpose of improving viscosity and improving adhesion to a transparent substrate. Examples of the resin include acrylic resins such as methyl methacrylate resin and methyl methacrylate copolymer; polystyrene, methyl methacrylate-styrene copolymer; polyester resin; polyamine Urethane resin; polybutadiene resin such as polybutadiene or butadiene-acrylonitrile copolymer; epoxy resin such as bisphenol epoxy resin, phenoxy resin or phenolic epoxy resin Wait. When using components other than these active energy ray polymerizable compounds, it is preferable to use 20 parts by mass or less, and more preferably 10 parts by mass or less, with respect to 100 parts by mass of the active energy ray polymerizable compound.

(Inorganic filler)

In the present invention, an inorganic material (nano particles) can be blended as necessary. Examples of the inorganic nano particles having a high refractive index include alumina, zirconia, titanium oxide, a compound thereof, a mixed oxide thereof, or a metal oxide thereof. Since the refractive index of these inorganic nano particles (fillers) is higher than that of ordinary organic materials, it is effective in improving the refractive index of the hardened product, but it must take into account the balance with the strength of the molded product or the adhesion of the substrate In terms of the blending amount, it is practical to make the range of the inorganic nanoparticle 1-20% by mass relative to the total amount of the active energy ray polymerizable compound (A) and the inorganic nanoparticle. Among them, in order to further combine high refractive index and low viscosity, it is more preferably 1 to 10% by mass.

(Additive)

In addition, various additives may be used in the inkjet printing ink composition of the present invention. Examples of the additives include ultraviolet absorbers, antioxidants, silicon-based additives, fluorine-based additives, rheology control agents, defoamers, release agents, silane coupling agents, antistatic agents, antifog agents, and colorants. Wait. These additives are preferably 0.05 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the active energy ray polymerizable compound in the inkjet ink composition for optical articles.

The inkjet printing ink composition of the present invention may contain a solvent according to necessity, but the smaller the solvent content is, the better the inkjet printing ink composition which is less likely to pollute the operating environment is obtained. Specifically, the solvent content in the inkjet printing ink composition of the present invention is preferably 100 ppm or less, and more preferably it is substantially free of the solvent content.

(Hardened)

The inkjet printing ink composition of the present invention can be formed into a cured product by coating the substrate and the like with an inkjet device and irradiating active energy rays after molding according to the intended use. In terms of active energy rays, examples include electron beams, ultraviolet rays, and visible rays. As the active energy ray, when using an electron beam, a Kirklauf-Wolton-type accelerator, a Van der Graf type electron accelerator, a resonance transformer type accelerator, an insulated core transformer type, a ground-nano (Dynamitron) type, Electron beam generating devices such as a linear filament type and a high-frequency type harden the curable composition of the present invention. Moreover, when using ultraviolet rays as active energy rays, ultra-high-pressure mercury lamps, high-pressure mercury lamps, low-pressure mercury lamps, and other mercury lamps, metal halogen lamps, fusion lamps, xenon lamps, carbon arc lamps, and high-output LEDs can be used. A UV lamp or the like is irradiated to harden it.

The cured product of the inkjet printing ink composition of the present invention preferably has a refractive index of 1.60 or more, more preferably 1.61 or more, and more preferably 1.62 or more. Since this hardened material has a high refractive index and good toughness, it can be applied to various optical articles.

The hardness of the hardened product of the present invention can be appropriately designed according to various applications. For example, when used in a cymbal, the elastic modulus at 25 ° C is preferably 200 to 800 MPa, and more preferably 300 to 500 MPa. By setting the elastic modulus to this range, the balance between mechanical strength and toughness (elongation) is improved, and the occurrence of cracks is also easily suppressed.

In addition, this elastic modulus is a value obtained by performing dynamic viscoelasticity measurement using "RSA II" manufactured by Rheometric Scientific Corporation as a viscoelasticity measuring device, and using conditions of a temperature rise rate of 3 ° C / minute and a frequency of 3.5 Hz as measurement conditions.

In the present invention, the glass transition temperature Tg of the hardened material is preferably 30 ° C or higher, and more preferably 35 ° C or higher. By setting the glass transition temperature, it is easy to have both a high refractive index and good wet heat adhesion. The upper limit of Tg is not particularly limited, but if the Tg is high, in the wet heat treatment (accelerated test) at high temperature, it will humidify in the elastic region, which can reduce water absorption compared to the exposure below Tg (rubber-like region). Rate and therefore better. In addition, in the present invention, it is possible to easily adjust the range of the Tg by using the compound represented by the formula (1) or (2) and formulating the compound in an appropriate range.

In addition, the glass transition temperature is a value obtained by reading the temperature at the peak position of tan δ shown by the ratio of the storage elastic modulus E 'and the complex elastic modulus E "obtained from the viscoelasticity measurement as the value of Tg.

(Optical component)

The inkjet printing ink composition of the present invention uses an inkjet device on a transparent resin film, a conductive film, or the like, and can form an optical member by forming a ridge or a lens. Specifically, exemplified is a cymbal member used in a display such as a liquid crystal display device, a lenticular lens used in a stereo photograph or a projection screen, a condenser lens of a transparent sheet projector, a color filter, and the like. Optical gratings and other optical components.

According to the inkjet printing ink composition of the present invention, optical components of various shapes can be arbitrarily manufactured, and therefore, low-volume, multi-item optical components can be manufactured at low cost.

When forming the optical member, a film-like, sheet-like, or plate-like transparent substrate can be used as a substrate for ejecting the inkjet printing ink composition. The material of the substrate may be appropriately selected depending on the application and the like, and examples thereof include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); triethylamidine Acrylic resins such as cellulose, polycarbonate resin, methyl methacrylate copolymer; styrene resin; polyfluorene resin; polyether resin; polycarbonate resin; vinyl chloride resin; polymethacrylic acid Amine resins, etc. In addition, an inorganic substrate such as a glass substrate or a conductive film provided with a conductive layer such as a metal vapor-deposited film can be used in the same manner.

The inkjet ink composition for an optical article of the present invention can be suitably used in various optical components, in addition to a lenticular lens or a lenticular lens used in various displays, as well as having a plurality of refractions. Anti-reflection applications of laminated materials made of high-quality materials. This lens has a plurality of fine 成形 -shaped portions on one side of the sheet-shaped molded body, and is usually arranged on the back surface (light source side) of the liquid crystal display element with the 稜鏡 side facing the element side.

These lenses are lenses having a halide layer containing a hardened material of the inkjet printing ink composition for an optical article on a transparent film. The shape of the haze layer is excellent in light condensing property and brightness. The angle θ of the apex angle is preferably 70 to 110 °, more preferably 75 to 100 °, and particularly preferably 80 to 95 °.

In addition, the distance between ridges is preferably 100 μm or less, and particularly preferably 70 μm or less. It is more preferable to prevent the occurrence of moiré patterns on the screen and further improve the fineness of the screen, and more preferably 10 to 30 μm. Moreover, the height of the concavity and convexity of 稜鏡 is determined according to the distance between the angle θ of 稜鏡 vertex angle and 稜鏡, but it is preferably 50 μm or less. In addition, the thickness of the 稜鏡 lens is preferably the thicker from the viewpoint of the intensity side, but the optically thinner is the better to suppress the absorption of light. From the viewpoint of balance, the thickness is 50 μm to 150 μm. good.

    [Example]    

Hereinafter, the present invention will be described more specifically with reference to examples. Unless otherwise noted, the parts and% in the examples are based on quality. The measurement and evaluation of characteristics and the like in the examples and comparative examples were performed as follows.

<Measurement of refractive index>

The refractive index of the resin composition prepared in Examples and Comparative Examples was measured at a reference wavelength (589 nm) using a multi-wavelength Abbe refractometer (DR-M2) manufactured by ATAGO. The numerical values in the table indicate the refractive index of the formulation composition.

<Measurement of film refractive index>

The resin composition was coated on a glass plate, sandwiched by a release PET film, and UV irradiated (1000 mJ / cm ² : metal halide lamp) from the release PET film side to harden the resin composition. Then, the resin cured film (100 μm thick) obtained by peeling the release PET film and the glass plate was measured at a reference wavelength (589 nm) using a multi-wavelength Abbe refractometer (DR-M2) manufactured by ATAGO.

<Viscosity measurement>

The viscosity at 25 ° C. of the resin compositions prepared in the examples and comparative examples was measured using an E-type viscometer (DV-II + VISCOMETER) manufactured by BROOKFIELD.

<Surface tension>

The surface tension of the resin compositions prepared in the examples and comparative examples at 25 ° C was measured using "CBVP-A3" manufactured by Kyowa Interface Science Co., Ltd.

<Storage elastic modulus>

Using "RSA II" manufactured by Rheometric Scientific as a viscoelasticity measuring device, dynamic viscoelasticity measurement was performed under measurement conditions at a temperature rising rate of 3 ° C / minute and a frequency of 3.5Hz, and the elastic modulus at 25 ° C was measured.

<Damp heat adhesion>

The resin composition was coated on a glass plate, sandwiched by a PET film, and UV irradiated (1000 mJ / cm ² : metal halide lamp) from the PET film side to harden the resin composition. Then, the glass plate was peeled to obtain a test piece having a thickness of a resin cured film of 100 μm. The obtained test piece was left to stand for one week under the conditions of a temperature of 40 ° C and a thickness of 90% RH, and then a 10 × 10 cross-cut was performed with a cutter, and the cross-cut portion was peeled with a tape to perform a cross-cut test. For 100 cells, the number of cells remaining after the tape was peeled off was measured.

(Examples 1 to 3, Comparative Examples 1 to 2)

The compound shown in Table 1 below was melt-mixed to prepare a resin composition. The obtained resin composition was subjected to the above evaluation. In addition, the numerical value of the composition formulation amount in a table | surface is a mass part.

The compounds described in the above table are as follows.

Phenylbenzyl acrylate: an acrylate represented by the following formula (i) (o-phenylbenzyl acrylate: p-phenylbenzyl acrylate = 8: 2 mixture)

EO modified acrylate of o-phenylphenol: o-phenylphenol modified (n ≒ 1) acrylate

It is clear from the above table that the resin composition of the present invention has a high refractive index, can be applied to inkjet, and has more excellent wet heat adhesion.

    [Industrial availability]    

Since the inkjet printing ink composition of the present invention is a composition having a high refractive index and excellent wet heat adhesion, it can be suitably applied to optical articles. Examples of suitable articles include display materials such as liquid crystal displays and organic EL displays; lighting members such as fluorescent lamps, LED lamps, and organic EL lamps; measuring / sensing devices such as cameras, sensors, and microscopes; glasses, etc. Lenses, etc. Specifically, among these articles, lenses, antireflection materials, filters, protective films, sealing materials, and the like are suitable.

Claims (4)

An inkjet printing ink composition comprising an active energy ray-curable compound (A) and a photopolymerization initiator (B), wherein the active energy ray-curable compound (A) contains the following The monofunctional (meth) acrylate compound represented by formula (1) and the monofunctional (methyl group) represented by formula (1) in the active energy ray-curable compound (A) contained in the inkjet printing ink composition ) The content of the acrylate compound is 60% by mass or more, (In formula (1), R ₁ is a hydrogen atom or a methyl group; R ₂ each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, or a bromine atom; and n ₁ and n _{2 each} represent 1 to 4).     For example, the inkjet printing ink composition of claim 1, wherein the viscosity is 100 mPa · s or less, and the liquid refractive index is 1.57 or more.         The inkjet printing ink composition of claim 1 or 2, wherein the surface tension is 20 ~ 50mN / m.         The inkjet printing ink composition according to any one of claims 1 to 3, wherein the glass transition temperature of the hardened material is 30 ° C or higher.