WO2017169762A1 - Photocurable ink, ink containing body and image forming method - Google Patents

Abstract

A photocurable ink which contains a polymerizable compound and a photopolymerization initiator, and which is characterized by containing a low-boiling-point solvent that has a boiling point of from 40°C to 120°C (inclusive) at 1 atmosphere and particles that have an unsaturated hydrocarbon group on the particle surfaces.

Description

Photocurable ink, ink container, and image forming method

The present invention relates to a photocurable ink, an ink container, an image forming method, and the like.

In recent years, in the commercial printing market, there is a strong demand for a method for forming an image on a recording medium (base material) other than white, such as a transparent or translucent film or colored paper. In order to form an image on these recording media other than white, it is necessary to form a white image.

A photo-curable ink containing a polymerizable compound and a low boiling point solvent has been proposed as an ink for forming a white image (Patent Document 1). In Patent Document 1, since the low boiling point solvent volatilizes when the photocurable ink is cured, the cured film obtained by curing the photocurable ink is a porous film having a large number of voids in the film. Become. The light is scattered by the large number of voids, so that the cured film has a white color.

JP 2005-298757 A

However, when a white film is formed on a base material by forming a porous film as in the technique described in Patent Document 1, the contact area between the film and the base material is reduced. There was a problem that the adhesion between the film and the substrate was lowered.

Therefore, in view of the above-described problems, the present invention provides a photocurable ink that forms a porous cured product and has excellent adhesion between the cured product and a substrate. Objective.

The photocurable ink as one aspect of the present invention is a photocurable ink containing a polymerizable compound and a photopolymerization initiator, and a low boiling point solvent having a boiling point of 40 ° C. or higher and 120 ° C. or lower at 1 atmosphere. And particles having an unsaturated hydrocarbon group on the particle surface.

According to the present invention, there is provided a photocurable ink that forms a porous cured product on a substrate, and that has excellent adhesion between the cured product and the substrate. it can.

It is a figure which shows an example of the ink container which accommodated the photocurable ink which concerns on this embodiment. It is a figure which shows typically the image forming method using the photocurable ink which concerns on this embodiment.

Hereinafter, embodiments of the present invention will be described in detail. It should be noted that the present invention is not limited to the following embodiments, and is appropriately modified with respect to the following embodiments based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Those with improvements and the like are also included in the scope of the present invention.

<Photocurable ink>
The photocurable ink 10 according to this embodiment (hereinafter referred to as “ink 10”) contains a polymerizable compound (A), a photopolymerization initiator (B), and a low boiling point solvent (C). It is a photocurable ink and contains particles (P) having an unsaturated hydrocarbon group on the particle surface. In the following description, “photocurable ink” may be simply referred to as “ink”.

The ink 10 is irradiated with light after being placed on the substrate. Thereby, the polymerization reaction of the polymerizable compound (A) is started by the photopolymerization initiator (B) in the ink 10. As the polymerization reaction of the polymerizable compound (A) proceeds, the ink 10 is cured and becomes a cured product. The ink 10 contains a low boiling point solvent (C), but the low boiling point solvent (C) volatilizes while the ink 10 is cured and / or after the ink 10 is cured. Thus, the portion where the low boiling point solvent (C) was present remains as voids, and the cured product becomes a porous cured product in which many voids are present in the cured product. Therefore, the cured product exhibits a white color due to irregular reflection of the light incident on the cured product due to these voids.

Note that paper, a polymer material such as vinyl chloride or PET, metal, wood, cloth, glass, ceramics, or the like can be used as a substrate on which the ink 10 is disposed on the surface thereof to form a cured product. In addition, the shape of a base material is not specifically limited, A film, a board may be sufficient, and another solid thing may be sufficient. Among these, in the present embodiment, it is particularly preferable to use a polymer material film, plate, or three-dimensional object as a base material.

In the present specification, the “cured product” means a product obtained by polymerizing the polymerizable compound (A) contained in the ink 10 and partially or completely curing it. In addition, when emphasizing that the thickness of the cured product is extremely thin compared to the area, it may be described as “cured film”.

Hereinafter, each component contained in the ink 10 will be described in detail.

[Polymerizable compound]
The polymerizable compound (A) contained in the ink 10 reacts with a polymerization factor (radical or the like) generated from the photopolymerization initiator (B) described later, and a polymer compound (heavy polymer) is generated by a chain reaction (polymerization reaction). It is a compound that becomes a cured product formed from the combination.

The polymerizable compound (A) has a polymerizable functional group. In the present specification, the polymerizable functional group refers to a polymerizable functional group. The polymerizable functional group that the polymerizable compound (A) has is preferably a polymerizable functional group capable of radical polymerization, and more preferably an ethylenically unsaturated group. Specifically, the polymerizable functional group of the polymerizable compound (A) is particularly preferably an acryloyl group, a methacryloyl group, a vinyl group, an allyl group, or a vinyl ether group.

The polymerizable compound (A) contained in the ink 10 may be one type of polymerizable compound or a plurality of types of polymerizable compounds. When a plurality of types of polymerizable compounds are contained, the blending ratio of the polymerizable compounds in the ink 10 is calculated based on the total mass of the plurality of types of polymerizable compounds.

The polymerizable compound (A) is not particularly limited as long as it is a compound having a polymerizable functional group, and monomers, oligomers, polymers, mixtures thereof, and the like can be used. When using a solid polymerizable compound, it is preferable to mix with a liquid polymerizable compound and dissolve the solid polymerizable compound in the liquid polymerizable compound.

In addition, it is preferable that the boiling point of a polymeric compound (A) is higher than 120 degreeC.

Examples of such polymerizable compounds include radical polymerizable compounds. The radically polymerizable compound is particularly preferably a compound having at least one acryloyl group or methacryloyl group which is a polymerizable functional group, that is, a (meth) acrylic compound.

Examples of monofunctional (meth) acrylic compounds having one acryloyl group or methacryloyl group include phenoxyethyl (meth) acrylate, phenoxy-2-methylethyl (meth) acrylate, phenoxyethoxyethyl (meth) acrylate, and 3-phenoxy. -2-hydroxypropyl (meth) acrylate, 2-phenylphenoxyethyl (meth) acrylate, 4-phenylphenoxyethyl (meth) acrylate, 3- (2-phenylphenyl) -2-hydroxypropyl (meth) acrylate, EO modified p-cumylphenol (meth) acrylate, 2-bromophenoxyethyl (meth) acrylate, 2,4-dibromophenoxyethyl (meth) acrylate, 2,4,6-tribromophenoxyethyl (meth) acrylate Rate, EO-modified phenoxy (meth) acrylate, PO-modified phenoxy (meth) acrylate, polyoxyethylene nonylphenyl ether (meth) acrylate, isobornyl (meth) acrylate, 1-adamantyl (meth) acrylate, 2-methyl-2-adamantyl (Meth) acrylate, 2-ethyl-2-adamantyl (meth) acrylate, bornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, cyclohexyl (Meth) acrylate, 4-butylcyclohexyl (meth) acrylate, acryloylmorpholine, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, -Hydroxybutyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, amyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) ) Acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, lauryl ( (Meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, benzyl (meth) acrylate, 1-naphthylmethyl (meth) acrylate, 2-naphthylmethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, butoxy Ethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxyethylene glycol (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) Acrylate, methoxypolypropylene glycol (meth) acrylate, diacetone (meth) acrylamide, isobutoxymeth (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, t-octyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 7-amino-3,7-dimethyloctyl (meta) ) Acrylate, N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide and the like, but are not limited thereto.

Commercially available products of the above monofunctional (meth) acrylic compounds are Aronix M101, M102, M110, M111, M113, M117, M5700, TO-1317, M120, M150, M156 (above, manufactured by Toagosei Co., Ltd., “Aronix” is registered. Trademarks), MEDOL10, MIBDOL10, CHDOL10, MMDOL30, MEDOL30, MIBDOL30, CHDOL30, LA, IBXA, 2-MTA, HPA, Viscoat # 150, # 155, # 158, # 190, # 192, # 193, # 220, # 2000, # 2100, # 2150 (manufactured by Osaka Organic Chemical Industry), light acrylate BO-A, EC-A, DMP-A, THF-A, HOP-A, HOA-MPE, HOA-MPL, PO-A , P-200A, NP-4E NP-8EA, epoxy ester M-600A (above, manufactured by Kyoeisha Chemical), KAYARAD TC110S, R-564, R-128H (above, manufactured by Nippon Kayaku), NK ester AMP-10G, AMP-20G (above, new) Nakamura Chemical Co., Ltd.), FA-511A, 512A, 513A (Hitachi Chemical Co., Ltd.), PHE, CEA, PHE-2, PHE-4, BR-31, BR-31M, BR-32 (above, Daiichi Kogyo) Pharmaceutical), VP (BASF), ACMO, DMAA, DMAPAA (above, manufactured by Kojin) and the like, but are not limited thereto.

Examples of the polyfunctional (meth) acrylic compound having two or more acryloyl groups or methacryloyl groups include trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and EO-modified trimethylolpropane tri (meth) acrylate. , PO-modified trimethylolpropane tri (meth) acrylate, EO, PO-modified trimethylolpropane tri (meth) acrylate, dimethyloltricyclodecane diacrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ethylene Glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-adamantane dimethanol diacrylate, o- Xylylene di (meth) acrylate, m-xylylene di (meth) acrylate, p-xylylene di (meth) acrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, tris (2-hydroxyethyl) isocyanurate tri (Meth) acrylate, tris (acryloyloxy) isocyanurate, bis (hydroxymethyl) tricyclodecane di (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (me ) Acrylate, EO modified 2,2-bis (4-((meth) acryloxy) phenyl) propane, PO modified 2,2-bis (4-((meth) acryloxy) phenyl) propane, EO, PO modified 2,2 -Bis (4-((meth) acryloxy) phenyl) propane and the like are exemplified, but not limited thereto.

Commercially available products of the above polyfunctional (meth) acrylic compounds include Iupimer UV SA1002 and SA2007 (Mitsubishi Chemical, “Iupimer” is a registered trademark), Biscote # 195, # 230, # 215, # 260, # 335HP, # 295, # 300, # 360, # 700, GPT, 3PA (above, manufactured by Osaka Organic Chemical Industry), Light Acrylate 4EG-A, 9EG-A, NP-A, DCP-A, BP-4EA, BP-4PA , TMP-A, PE-3A, PE-4A, DPE-6A (above, manufactured by Kyoeisha Chemical), A-DCP, A-HD-N, A-NOD-N, A-DOD-N (above, Shin-Nakamura) Chemical Industry), KAYARAD PET-30, TMPTA, R-604, DPHA, DPCA-20, -30, -60, -120, HX-620, D-310, -330 (above, Nippon Kayaku), Aronix M208, M210, M215, M220, M240, M305, M309, M310, M315, M325, M400 (above, Toagosei), Lipoxy VR-77, VR-60, VR-90 (manufactured by Showa Denko, “Lipoxy” is a registered trademark), and the like, are not limited thereto.

In the above compound group, (meth) acrylate means acrylate or methacrylate having an alcohol residue equivalent thereto. The (meth) acryloyl group means an acryloyl group or a methacryloyl group having an alcohol residue equivalent thereto. EO represents ethylene oxide, and EO-modified compound A refers to a compound in which the (meth) acrylic acid residue and alcohol residue of compound A are bonded via a block structure of an ethylene oxide group. PO represents propylene oxide, and PO-modified compound B refers to a compound in which the (meth) acrylic acid residue and alcohol residue of compound B are bonded via a block structure of a propylene oxide group.

The blending ratio of the polymerizable compound (A) in the ink 10 is preferably 30% by mass or more and 90% by mass or less when the total mass of the ink 10 is 100% by mass. Moreover, it is more preferable that it is 40 to 80 mass%. By setting the blending ratio of the polymerizable compound (A) in the ink 10 to 30% by mass or more with respect to the total mass of the ink, the mechanical strength of the formed cured product can be increased.

[Photopolymerization initiator]
The photopolymerization initiator (B) contained in the ink 10 is a compound that generates a polymerization factor (radical or the like) by sensing light of a predetermined wavelength (active energy ray). Specifically, the photopolymerization initiator is a polymerization initiator that generates a polymerization factor by active energy rays such as light (infrared rays, visible rays, ultraviolet rays, far ultraviolet rays, charged particle rays such as X rays, electron rays, radiation, etc.). It is an agent. More specifically, the photopolymerization initiator (B) preferably contains, for example, a polymerization initiator that generates a polymerization factor by light having a wavelength of 150 nm or more and 400 nm or less.

The photopolymerization initiator contained in the ink 10 may be one type of photopolymerization initiator or a plurality of types of photopolymerization initiators. When a plurality of types of photopolymerization initiators are contained, the blending ratio of the photopolymerization initiator in the ink 10 is calculated based on the total mass of the plurality of types of photopolymerization initiators.

Examples of such a photopolymerization initiator include a radical generator.

Examples of the radical generator include 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di (methoxyphenyl) imidazole dimer, 2- May have a substituent such as (o-fluorophenyl) -4,5-diphenylimidazole dimer, 2- (o- or p-methoxyphenyl) -4,5-diphenylimidazole dimer, 4,5-triarylimidazole dimer; benzophenone, N, N′-tetramethyl-4,4′-diaminobenzophenone (Michler ketone), N, N′-tetraethyl-4,4′-diaminobenzophenone, 4-methoxy -4'-dimethylaminobenzophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diamy Benzophenone derivatives such as benzophenone; 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1,2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propane- Α-amino aromatic ketone derivatives such as 1-one; 2-ethylanthraquinone, phenanthrenequinone, 2-t-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenantharaquinone, 2-methyl-1,4-naphthoquinone, 2,3-dimethylanthraquinone, etc. Quinones; Benzoin methyl Benzoin ether derivatives such as ether, benzoin ethyl ether and benzoin phenyl ether; benzoin derivatives such as benzoin, methyl benzoin, ethyl benzoin and propyl benzoin; benzyl derivatives such as benzyldimethyl ketal; 9-phenylacridine, 1,7-bis (9 , 9′-acridinyl) heptane derivatives; N-phenylglycine derivatives such as N-phenylglycine; acetophenone, 3-methylacetophenone, acetophenone benzyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2- Acetophenone derivatives such as phenylacetophenone; thioxanthone such as thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, bis- (2,6-dimethoxybenzoyl) -2,4,4-trimethyl Acylphosphine oxide derivatives such as pentylphosphine oxide; 1,2-octanedione, 1- [4- (phenylthio)-, 2- (O-benzoyloxime)], ethanone, 1- [9-ethyl-6- Oxime ester derivatives such as (2-methylbenzoyl) -9H-carbazol-3-yl]-, 1- (O-acetyloxime); xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 1- ( 4-Isopropylphenyl) -2- Proxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1 but one, and the like, but are not limited to.

Commercially available Irgacure 184, 369, 651, 500, 819, 907, 784, 2959, CGI-1700, -1750, -1850, CG24-61, Darocur 1173, Lucirin TPO, LR 8893, LR 8970 (above, BASF) “Darocur” and “Lucirin” are registered trademarks), Ubekrill P36 (manufactured by UCB), and the like, but are not limited thereto.

The blending ratio of the photopolymerization initiator is preferably 0.01% by mass or more and 15% by mass or less, and 0.1% by mass or more and 10% by mass or less when the total mass of the ink is 100% by mass. It is more preferable.

By setting the blending ratio of the photopolymerization initiator to 0.01% by mass or more with respect to the total mass of the ink, the curing rate of the ink can be increased and the reaction efficiency can be increased. Moreover, the mechanical strength of the hardened | cured material formed can be raised by making this compounding ratio into 15 mass% or less with respect to the total mass of an ink.

[Low boiling solvent]
The low boiling point solvent (C) contained in the ink 10 is a component that volatilizes while the ink 10 is cured and / or after the ink 10 is cured. Thus, the portion where the low boiling point solvent (C) was present remains as voids, and the cured product becomes a porous cured product in which many voids are present in the cured product.

As described above, the low boiling point solvent (C) volatilizes during and / or after the ink 10 is cured. From the viewpoint of volatilization efficiency, the boiling point of the low boiling point solvent (C) is preferably 40 ° C. or higher and 120 ° C. or lower. In this embodiment, “boiling point” refers to a boiling point at 1 atm, and “low boiling point” refers to a boiling point of 120 ° C. or lower. In the present embodiment, the low boiling point solvent (C) is a compound having no polymerizable functional group such as acryloyl group, methacryloyl group, vinyl group, allyl group, or vinyl ether group.

Specific examples of the low boiling point solvent (C) include, for example, water; alcohols such as ethanol, 2-propanol and butanol; various aliphatic or fats such as n-hexane, n-octane, cyclohexane and cyclopentane. Cyclic hydrocarbons; various aromatic hydrocarbons such as toluene; various esters such as ethyl formate and ethyl acetate; various ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; dimethoxyethane and tetrahydrofuran And various ethers such as dioxane, diisopropyl ether; various chlorinated hydrocarbons such as chloroform, methylene chloride, and carbon tetrachloride, but are not limited thereto. These low boiling point solvents may be used alone or in combination of two or more.

The low boiling point solvent (C) may be a liquid that is compatible with the polymerizable compound (A) and the photopolymerization initiator (B), or may be a liquid that is not compatible, but is preferably a liquid that is not compatible. . Since the polymerizable compound (A) and the photopolymerization initiator (B) are oily liquids (O), the low boiling point solvent (C) is an aqueous liquid containing water that is incompatible with the oily liquid (O) ( W) is preferably used.

As described above, by using the aqueous liquid (W) as the low boiling point solvent (C), an interface is generated between the aqueous liquid (W) and the oil liquid (O), and the ink 10 is converted into the aqueous liquid (W). Can be formed by dispersing the droplets 101 in the oily liquid (O). That is, the ink 10 can have a form in which the droplets 101 formed by the liquid containing the low boiling point solvent (C) are dispersed in the ink 10 (in the photocurable ink). In this way, the liquid containing the low boiling point solvent (C) is dispersed by forming the droplets 101 with the ink 10, so that the low boiling point solvent (C) is volatilized and formed. The size of the gap can be increased. Moreover, the size of the voids in the cured product can be controlled by controlling the size (particle size) of the liquid droplet 101 containing the low boiling point solvent (C). Thereby, the degree of whiteness of the cured product obtained by curing the ink 10 can be improved.

The ink 10 is preferably an emulsion in which the aqueous liquid (W) is dispersed by forming droplets in the oil liquid (O) (so-called W / O emulsion). In other words, the ink 10 is preferably an emulsion in which the droplets 101 formed by the liquid containing the low boiling point solvent (C) are dispersed in the ink 10 (in the photocurable ink). It is preferable that the ink 10 is such an emulsion because the size and dispersibility of the droplets 101 formed by the liquid containing the low boiling point solvent (C) can be stably maintained. That is, it is preferable because the storage characteristics of the ink 10 are improved.

The blending ratio of the low boiling point solvent (C) in the ink 10 is preferably 10% by mass or more and 50% by mass or less, preferably 10% by mass or more and 40% by mass or less when the total mass of the ink 10 is 100% by mass. It is more preferable that Furthermore, the blending ratio of the low boiling point solvent (C) is more preferably 10% by mass or more and 30% by mass or less, and particularly preferably 15% by mass or more and 25% by mass or less. By setting the blending ratio of the low boiling point solvent (C) in the ink 10 to 10% by mass or more, the volume of voids formed in the cured product can be increased, and the degree of whiteness of the cured product can be increased. it can. In addition, when the blending ratio of the low boiling point solvent (C) in the ink 10 is larger than 50% by mass, the mechanical strength of the cured product may be lowered.

[particle]
The ink 10 contains particles (P) having an unsaturated hydrocarbon group on the particle surface in addition to the components described above.

The type of particle (P) is not particularly limited as long as it has an unsaturated hydrocarbon group on the particle surface. That is, the particles (P) may be organic particles having an unsaturated hydrocarbon group on the particle surface, or may be inorganic particles having an unsaturated hydrocarbon group on the particle surface. The particle (P) preferably has an unsaturated hydrocarbon group bonded to the particle surface directly or via another atomic group.

Examples of organic particles having an unsaturated hydrocarbon group on the particle surface include resin particles surface-modified with a surface modifier containing an unsaturated hydrocarbon group, resin particles containing a resin containing an unsaturated hydrocarbon group, and the like. Can be mentioned. The resin particles may be solid particles that do not have cavities inside, or may be hollow particles that have cavities inside. The type of resin is not particularly limited, and examples thereof include acrylic resins, styrene resins, and styrene-acrylic resins.

Examples of inorganic particles having an unsaturated hydrocarbon group on the particle surface include inorganic particles whose surface has been modified with a surface modifier containing an unsaturated hydrocarbon group. Examples of the inorganic particles include, but are not limited to, titanium oxide particles, silicon dioxide particles (silica particles), zirconium oxide particles, aluminum oxide particles, zinc oxide particles, and barium titanate particles. Moreover, these inorganic particles may be used independently and may use 2 or more types together.

The particles (P) are preferably inorganic particles having an unsaturated hydrocarbon group on the particle surface. This is because many inorganic particles have a high refractive index, and by using inorganic particles having a high refractive index, the degree of whiteness and concealment of the cured product can be improved. Among these, titanium oxide particles having an unsaturated hydrocarbon group on the particle surface are preferable.

As described above, the photocurable ink containing the polymerizable compound (A), the photopolymerization initiator (B), and the low boiling point solvent (C) is disposed on the substrate and irradiated with light. The polymerization reaction of (A) and the volatilization of the low boiling point solvent (C) occur, forming a porous cured product. At this time, the cured product is adsorbed to the base material by the interaction between the polymer formed by polymerization of the polymerizable compound (A) and the base material. However, in the porous cured product, since there are voids at the interface between the cured product and the substrate, the contact area with the substrate is reduced as compared with the cured product that is not porous. For this reason, the porous cured product tends to have lower adhesion with the substrate than the non-porous cured product. Therefore, in the photocurable ink containing the low boiling point solvent (C), the adhesion with the substrate is a particularly significant problem.

However, the ink 10 according to this embodiment includes particles (P) having an unsaturated hydrocarbon group on the particle surface in addition to the polymerizable compound (A), the photopolymerization initiator (B), and the low boiling point solvent (C). Containing.

The unsaturated hydrocarbon group contained in the particles (P) is not particularly limited, and examples thereof include a vinyl group, an acryloyl group, a methacryloyl group, and a styryl group. These unsaturated hydrocarbon groups interact with a base material made of a polymer material such as PET and develop adhesiveness. Further, the particles (P) are surrounded by a polymer formed by polymerization of the polymerizable compound (A) in the cured product and embedded in the cured product. Therefore, the particle (P) having an unsaturated hydrocarbon group on the particle surface acts as an anchor between the cured product and the substrate, and the anchor effect can improve the adhesion between the cured product and the substrate. It is guessed.

The present inventors speculate as follows about the mechanism by which the particles (P) having an unsaturated hydrocarbon group exhibit adhesiveness with the substrate. When the ink 10 is disposed on the substrate, each component of the ink 10, for example, the polymerizable compound (A) and the particles (P) penetrate into the substrate. In this state, when the ink 10 is cured by irradiating light to the ink 10, the ink 10 is cured in a state in which a part of the ink 10 penetrates into the substrate. Therefore, the contact area between the cured product and the substrate is increased, and as a result, the effect of the interaction between the unsaturated hydrocarbon group and the substrate is increased.

In addition, it is preferable that the unsaturated hydrocarbon group which particle | grains (P) have also has a polymeric compound (A). When the particles (P) and the polymerizable compound (A) have the same unsaturated hydrocarbon group, the unsaturated carbonization of the particles (P) when the polymerizable compound (A) is polymerized to form a polymer. A polymerization reaction occurs with the hydrogen group, and the anchor effect described above can be more effectively expressed. As a result, the adhesion between the cured product and the substrate can be further improved. As described above, since the polymerizable compound (A) preferably has an acryloyl group or a methacryloyl group, the unsaturated hydrocarbon group of the particles (P) is more preferably an acryloyl group or a methacryloyl group.

The average particle diameter of the particles (P) is preferably 5 nm or more and 100 nm or less. When the average particle diameter of the particles (P) is larger than 100 nm, inorganic particles having a large specific gravity may be precipitated in the ink 10. In addition, the average particle diameter of particle | grains (P) can be measured by the dynamic light scattering method, for example.

The content of the particles (P) in the ink 10 is preferably 1% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 15% by mass when the total mass of the ink 10 is 100% by mass. It is as follows. If the content of the particles (P) in the ink 10 exceeds 20% by mass, the storage stability of the ink is lowered. On the other hand, when the content of the particles (P) in the ink 10 is less than 1% by mass, the effect of improving the adhesion with the substrate cannot be obtained sufficiently.

The ink 10 contains a plurality of particles (P), and the plurality of particles (P) are adsorbed on the droplet 101 (on the droplet) formed by the liquid containing the low boiling point solvent (C). preferable. In other words, the plurality of particles (P) are arranged on the interface formed between the first liquid (oil liquid (O)) and the second liquid (aqueous liquid (W)). preferable. As described above, when a plurality of particles (P) are adsorbed on the droplet 101, even if two or more droplets 101 having the particle (P) adsorbed on the interface approach each other, the particles adsorbed on the interface (P) The solids repel each other, so that coalescence of the droplets 101 is suppressed. Therefore, the droplet 101 can be maintained in a desired size for a long period of time, and the storage characteristics of the ink 10 can be improved. The phenomenon in which the state in which droplets are dispersed in this way is stabilized by particles is known as Pickering emulsion, and can be realized by appropriately controlling the wettability and particle size of particles (P).

(Surface modifier)
The particles (P) can be obtained by modifying the particle surfaces of organic particles or inorganic particles with a surface modifier having an unsaturated hydrocarbon group. As the surface modifier having an unsaturated hydrocarbon group, for example, an alkoxysilane compound having an unsaturated hydrocarbon group and an alkoxyl group can be used. Alternatively, a silane compound having an unsaturated hydrocarbon group and a silanol group can be used. In the following description, these may be collectively referred to as a silane coupling agent.

The alkoxylane compound may be a trifunctional alkoxide having three alkoxyl groups in addition to a functional group containing an unsaturated hydrocarbon group, or may be a bifunctional alkoxide having two alkoxyl groups.

In addition to the above-mentioned alkoxysilane compound, the surface modifier may be a hydrolysis product or a condensation polymerization product of an alkoxysilane compound. The hydrolysis product or polycondensation product of an alkoxysilane compound refers to a product in which part or all of the alkoxyl group of alkoxysilane is hydrolyzed or polycondensed. Silanol groups produced by hydrolysis of alkoxyl groups are bonded to hydroxyl groups, etc. present on the surface of organic particles and inorganic particles by intermolecular interactions such as covalent bonds or hydrogen bonds. Alternatively, the surface of the inorganic particles can be modified. The aforementioned silanol group also includes a silanol group in a polycondensation product formed by hydrolysis of a part of the alkoxyl group of alkoxysilane or condensation of silanol groups.

The alkoxysilane compound is preferably a trifunctional alkoxide capable of generating more silanol groups that serve as reaction points for the reaction that occurs with the functional groups present on the surface of the organic or inorganic particles. Thereby, the surface of an organic particle or an inorganic particle can be modified efficiently.

Specific examples of the trifunctional alkoxysilane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, vinylsilane such as triethoxyvinylsilane, 3-methacryloxypropyltriethoxysilane, and 3-methacryloxy. Examples thereof include methacrylic silane such as propyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, acrylic silane such as 3- (trimethoxysilyl) propyl acrylate, and styrylsilane such as p-styryltrimethoxysilane. Moreover, the compound which hydrolyzed or polycondensed one part or all part of the alkoxyl group which these trifunctional alkoxysilane compounds have can also be used. These silane coupling agents may be used alone or in combination of two or more.

(Particle surface modification method)
First, a silane coupling agent is dissolved in an organic solvent to prepare a silane coupling agent solution. The amount of the organic solvent added to the silane coupling agent is preferably about 2 to 1000 in terms of molar ratio with respect to the silane coupling agent. In the present specification, “the amount of A added is X in terms of a molar ratio with respect to B” means that the molar amount of A to be added is X times the molar amount of B.

Examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, butanol, and ethylene glycol; various aliphatic or alicyclic such as n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane. Aromatic hydrocarbons; various aromatic hydrocarbons such as toluene, xylene, ethylbenzene; ethyl formate, ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether Various esters such as acetate; various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; dimethoxyethane, tetrahydrofuran, dioxane, diisopropyl Various ethers such as pill ether; various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, tetrachloroethane; N-methylpyrrolidone, dimethylformamide, dimethylacetamide, ethylene carbonate, etc. And aprotic polar solvents. In this embodiment, it is preferable to use alcohols among the various organic solvents described above from the viewpoint of the stability of the silane coupling agent solution.

The solution used for surface modification of particles is generally prepared by adding acidic catalytic water to an alcohol solution of a silane coupling agent. Hydrochloric acid can be illustrated as an acidic catalyst. The pH of the acidic catalyst water is preferably 1 or more and 4 or less. When the acidic catalyst water is added, the particles are preferably added to the alcohol solution of the silane coupling agent as a mixed solution of the acidic catalyst water and the alcohol. The addition amount of the acidic catalyst water is preferably 2 or more and 10 or less in molar ratio with respect to the alkoxysilane compound.

Next, organic particles or inorganic particles are dispersed in the solution of the silane coupling agent thus prepared, and surface modification treatment is performed. Thereafter, the particles are settled using a centrifuge, washed with alcohol several times, and then recovered to obtain surface-modified organic particles or inorganic particles.

Furthermore, the surface-modified particles obtained in the above step may be re-dispersed in alcohol to obtain an alcohol solution in which the surface-modified particles are dispersed.

[Other additive components]
The ink 10 may contain additional additives according to various purposes as long as the effects of the present invention are not impaired. Such an additive component includes a surfactant. When the ink 10 contains a surfactant, the dispersion stability of the droplets 101 dispersed in the ink 10 can be improved, and the size of the droplets 101 can be controlled. That is, since the ink 10 contains a surfactant, coalescence of the droplets 101 can be suppressed, and the droplets 101 can be maintained in a desired size for a long period of time.

The surfactant may be composed of one type of surfactant or a plurality of types of surfactant.

The surfactant is preferably a nonionic surfactant. When the surfactant is a nonionic surfactant, it is easy to form a W / O emulsion in which droplets of the aqueous liquid (W) are dispersed in the oil liquid (O). Examples of the nonionic surfactant include hydrocarbon surfactants.

Examples of hydrocarbon surfactants include polyoxyalkylene alkyl ethers obtained by adding alkylene oxides having 2 to 4 carbon atoms to alkyl alcohols having 1 to 50 carbon atoms.

Polyoxyalkylene alkyl ether includes methyl alcohol ethylene oxide adduct, decyl alcohol ethylene oxide adduct, lauryl alcohol ethylene oxide adduct, cetyl alcohol ethylene oxide adduct, oleyl alcohol ethylene oxide adduct, stearyl alcohol ethylene oxide adduct And stearyl alcohol ethylene oxide / propylene oxide adduct. In addition, the terminal group of the alkyl alcohol polyalkylene oxide adduct is not limited to a hydroxyl group that can be produced by simply adding a polyalkylene oxide to an alkyl alcohol. This hydroxyl group may be converted to other substituents, for example, a polar functional group such as a carboxyl group, an amino group, a pyridyl group, a thiol group, or a silanol group, or a hydrophobic functional group such as an alkyl group or an alkoxy group.

As the polyoxyalkylene alkyl ether, a commercially available product may be used. Commercially available products include, for example, NOF made by NOF (“NONION” is a registered trademark), BLAUNON series, FINESURF series, BASF made Pluriol series (“Pluriol” is a registered trademark), Kao The EMULGEN series (“EMULGEN” is a registered trademark) and the like are exemplified, but not limited thereto.

When the ink 10 contains a surfactant, the content of the surfactant is preferably 0.001% by mass to 20% by mass with respect to the total amount of the ink 10, for example. More preferably, it is 0.01 mass% or more and 10 mass% or less, More preferably, it is 0.1 mass% or more and 10 mass% or less. By setting the content of the surfactant within the above range, the dispersion stability of the droplet 101 can be improved.

[Physical properties of photocurable ink]
The viscosity of the ink 10 at 25 ° C. is preferably 1 mPa · s or more and 75 mPa · s or less. The viscosity of the ink 10 is more preferably 1 mPa · s or more and 30 mPa · s or less. By setting the viscosity of the ink 10 to 1 mPa · s or more and 75 mPa · s or less, it is possible to improve the ejection stability when the ink 10 is ejected by the inkjet method.

[Method for preparing photocurable ink]
A method for preparing the ink 10 is not particularly limited, but an example of a method for preparing the ink 10 will be described below. First, the polymerizable compound (A) and the photopolymerization initiator (B) are mixed to prepare an oily liquid (O). There, a low boiling point solvent (C) is added and mixed with stirring. Then, the dispersion liquid of particle | grains (P) is further added, and it stirs and mixes, and the ink 10 is prepared.

In the case of stirring and mixing, a homogenizer, an ultrasonic disperser, a stirrer, or the like can be used. Among these, it is preferable to use a homogenizer or an ultrasonic disperser from the viewpoint of preparing a homogeneous ink.

<Ink container>
The ink 10 is stored in an ink container. In other words, the ink container according to this embodiment contains the ink 10. Hereinafter, the ink container according to the present embodiment will be described in more detail.

The ink container according to the present embodiment is an ink container that contains a photocurable ink. In this specification, the “container” is a concept including a container and a package, and refers to one that contains a photocurable ink directly or indirectly. That is, the container is one in which a container is filled with photocurable ink, or at least a container filled with photocurable ink is sealed with a package. That is, it can be said that the ink container according to the present embodiment has a container, and the ink 10 is stored in the container.

The ink container is used for storing and transporting the photocurable ink before using the photocurable ink in the image forming apparatus. When using the ink container, the photocurable ink contained in the ink container is used. This is supplied to the image forming apparatus.

Examples of the ink container include, but are not limited to, an ink cartridge, a bag (pack), a bottle, a tank, a bottle, and a can. Among these, an ink cartridge, a bag, a bottle, and a tank are preferable, and a bag is more preferable from the viewpoint of being widely used and easily controlling moisture permeability and oxygen permeability to desired values.

The usage mode of the ink container is not particularly limited. For example, the ink container, which is a separate body from the image forming apparatus, is attached to the image forming apparatus, and the ink container is photocured from the ink container. There is a mode (1) like a cartridge for supplying ink to the image forming apparatus. Further, there is an aspect (2) like a bottle that supplies an ink composition to an ink tank or the like of the image forming apparatus from an ink container that is a separate body from the image forming apparatus. Furthermore, there is an aspect (3) in which the ink container is provided in advance as a part of the image forming apparatus. In the case of the mode (1) and the mode (3), the photocurable resin is applied to the head of the image forming apparatus from the mounted ink container or the provided ink container through a connecting portion such as an ink tube. Ink can be supplied to form an image. In the aspect (2), after the photocurable ink is transferred from the ink container to the ink tank or the like of the image forming apparatus, it is photocured from the ink tank to the head of the image forming apparatus through a connection portion such as an ink tube. An image can be formed by supplying an ink.

FIG. 1 is a diagram illustrating an example of an ink container according to the present embodiment. FIG. 1A illustrates an ink container as an ink bag, and FIG. 1B illustrates an ink cartridge as an ink container. Examples of cases are shown respectively.

As shown in FIG. 1A, the ink bag 20 according to the present embodiment includes a bag 21 that stores the ink 10 and an ink supply port 22 that communicates with the inside of the bag 21. The ink 10 stored in the ink bag 20 is supplied to the image forming apparatus via the ink supply port 22. In the state where the ink bag 20 is not attached to the image forming apparatus, the opening of the ink supply port 22 is preferably closed by a valve provided inside.

The shape, size, structure, material, etc. of the bag 21 are not particularly limited, but it is preferably a bag formed of a film having low air permeability. Examples of the film include an aluminum laminate film, a polyamide film, a polyethylene terephthalate (PET) film, a polyethylene film, a polypropylene film, a polystyrene film, an ethylene vinyl acetate polymer film, an ethylene vinyl alcohol copolymer film, and a polybutadiene film. The resin film can be preferably used.

As shown in FIG. 1B, the ink cartridge 30 according to this embodiment includes the above-described ink bag 20 and a case 31 that houses the ink bag 20 and protects the ink bag 20. Here, the ink supply port 22 of the ink bag 20 is exposed to the outside of the case 31 from a notch provided in the side surface of the case 31. The ink 10 is supplied to the image forming apparatus via the ink supply port 22 in a state where the ink cartridge 30 is mounted in the cartridge holder of the image forming apparatus. As described above, by adopting a configuration in which the ink supply body is detachably mounted on the image forming apparatus as an ink cartridge, it is possible to further improve work efficiency such as replenishment or replacement of the photocurable ink. The ink cartridge 30 may further include a recording head having an ejection port that communicates with the ink supply port 22.

<Image forming method>
The image forming method according to the present embodiment is a method for forming an image by disposing the ink 10 according to the present embodiment described above on a substrate. More specifically, in the image forming method according to the present embodiment, the step of placing the ink 10 on the base material 102 that is a recording medium (placement step), and the ink 10 placed on the base material 102 is irradiated with light. Irradiating step (light irradiation step). The “image” in this specification includes a solid pattern filled with a single color within a certain range.

Hereinafter, the image forming method according to the present embodiment will be described with reference to FIG. FIG. 2 is a diagram schematically illustrating the image forming method according to the present embodiment. In the present embodiment, the ink 10 is a photocurable ink in which droplets 101 formed by a liquid containing a low boiling point solvent (C) are dispersed in the ink 10 (in the photocurable ink).

[1] Step of placing the ink 10 on the recording medium 102 (placement step)
In this step, the ink 10 is disposed on the base material 102. Preferably, the ink 10 is ejected from an ink jet recording head and disposed on the substrate 102. By disposing the ink jet recording head and disposing it, the resolution of the image to be formed can be increased. The method of ejecting ink by the ink jet method is not particularly limited, but since the ink 10 contains the polymerizable compound (A), a method of ejecting droplets by applying mechanical energy to the ink (piezo jet method) is preferable. .

Note that the type of the substrate 102 that is a recording medium is not particularly limited, and paper, a polymer material such as vinyl chloride and PET, metal, wood, cloth, glass, ceramics, and the like can be used. In addition, the shape of a base material is not specifically limited, A film, a board may be sufficient, and another solid thing may be sufficient.

[2] A step of irradiating the ink 10 disposed on the substrate 102 with light (light irradiation step)
After the ink 10 is placed on the base material 102 (FIG. 2 (a)), as shown in FIG. 2 (b), light 103 such as ultraviolet light is irradiated. As a result, the ink 10 is cured.

The type of light 103 irradiated in this step is not particularly limited, and can be selected according to the sensitivity wavelength of the ink 10. Specifically, it is preferable to appropriately select and use ultraviolet light having a wavelength of 150 nm to 400 nm, X-rays, electron beams, and the like.

Among these, the light irradiated onto the ink 10 is particularly preferably ultraviolet light. This is because many commercially available photopolymerization initiators are sensitive to ultraviolet light. Examples of light sources that emit ultraviolet light include high-pressure mercury lamps, ultra-high pressure mercury lamps, low-pressure mercury lamps, deep-UV lamps, carbon arc lamps, chemical lamps, metal halide lamps, xenon lamps, light-emitting diode (LED) lamps, and KrF excimer lasers. , ArF excimer laser, F ₂ excimer laser, and the like, and an ultra-high pressure mercury lamp or LED lamp is particularly preferable. Further, the number of light sources used may be one or plural.

As described above, the ink 10 according to the present embodiment contains the low boiling point solvent (C). When the ink 10 is irradiated with light, components (oil-based liquid (O)) other than the low boiling point solvent (C) are cured to form a cured product 104 (FIG. 2C).

At this time, the low boiling point solvent (C) is not cured, and the low boiling point solvent (C) evaporates during and / or after curing of the oily liquid (O). As a result, a gap 105 is formed in the portion where the low boiling point solvent (C) was present (FIG. 2 (d)). When the low boiling point solvent (C) forms droplets in the ink 10, a gap 105 having a size corresponding to the particle size of the droplet is formed. As a result, a cured film 106 having a large number of voids 105 therein is formed, and incident light is scattered by the numerous voids 105, whereby the cured film 106 exhibits a white color.

In addition, you may provide the heating process by a heater etc. in the middle of the said light irradiation process, and / or after a process, and the drying process by ventilation. Thereby, evaporation of the low boiling point solvent (C) is promoted, and the cured product can be quickly dried.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples, and Reference Examples. However, the present invention is not limited to the following examples.

(Preparation example 1-1) Preparation of particle (P-1) dispersion 3-Methacryloxypropyltrimethoxysilane (3-mpTMS) was added to 2-propanol (isopropyl alcohol, IPA). Thereafter, a mixed solution of IPA and 0.01 M hydrochloric acid (HClaq.) Was added to the solution and stirred for about 1 day to obtain a solution (surface modifying solution) for surface modification of particles. The molar ratio of each component in the above solution was 3-mpTMS: IPA: HClaq. = 1: 6: 6.

To the solution, a dispersion liquid (TKD-701, manufactured by Teika) in which titanium oxide particles were dispersed in commercially available IPA was added and stirred for about 3 hours to modify the surface of the titanium oxide particles. The surface-modified titanium oxide particles were precipitated using a centrifuge and washed with IPA to obtain surface-modified titanium oxide particles (particles (P-1)). The particle (P-1) is considered to have a methacryloyl group which is an unsaturated hydrocarbon group on the particle surface.

The obtained titanium oxide particles (particles (P-1)) were redispersed in IPA to prepare a dispersion of about 20 wt%.

Preparation Example 1-2 Preparation of Particle (P-2) Dispersion Vinyltrimethoxysilane (VTMS) was added to 2-propanol (isopropyl alcohol, IPA). Thereafter, a mixed solution of IPA and 0.01 M hydrochloric acid (HClaq.) Was added to the solution and stirred for about 1 day to obtain a solution (surface modifying solution) for surface modification of particles. The molar ratio of each component in the solution was VTMS: IPA: HClaq. = 1: 6: 6.

To the solution, a dispersion liquid (TKD-701, manufactured by Teika) in which titanium oxide particles were dispersed in commercially available IPA was added and stirred for about 3 hours to modify the surface of the titanium oxide particles. The surface-modified titanium oxide particles were precipitated using a centrifuge and washed with IPA to obtain surface-modified titanium oxide particles (particles (P-2)). The particle (P-2) is considered to have a vinyl group which is an unsaturated hydrocarbon group on the particle surface.

The obtained titanium oxide particles (particles (P-2)) were redispersed in IPA to prepare a dispersion of about 20 wt%.

(Preparation Example 1-3) Preparation of Particle (P-3) Dispersion Triethoxyvinylsilane (VTES) was added to 2-propanol (isopropyl alcohol, IPA). Thereafter, a mixed solution of IPA and 0.01 M hydrochloric acid (HClaq.) Was added to the solution and stirred for about 1 day to obtain a solution (surface modifying solution) for surface modification of particles. The molar ratio of each component in the solution was VTES: IPA: HClaq. = 1: 6: 6.

To the solution, a dispersion liquid (TKD-701, manufactured by Teika) in which titanium oxide particles were dispersed in commercially available IPA was added and stirred for about 3 hours to modify the surface of the titanium oxide particles. The surface-modified titanium oxide particles were precipitated using a centrifuge and washed with IPA to obtain surface-modified titanium oxide particles (particles (P-3)). The particle (P-3) is considered to have a vinyl group which is an unsaturated hydrocarbon group on the particle surface.

The obtained titanium oxide particles (particles (P-3)) were redispersed in IPA to prepare a dispersion of about 20 wt%.

(Preparation Example 1-4) Preparation of Particle (P-4) Dispersion Solution 3- (Trimethoxysilyl) propyl acrylate (3-apTMS) was added to 2-propanol (isopropyl alcohol, IPA). Thereafter, a mixed solution of IPA and 0.01 M hydrochloric acid (HClaq.) Was added to the solution and stirred for about 1 day to obtain a solution (surface modifying solution) for surface modification of particles. The molar ratio of each component in the above solution was 3-apTMS: IPA: HClaq. = 1: 6: 6.

To the solution, a dispersion liquid (TKD-701, manufactured by Teika) in which titanium oxide particles were dispersed in commercially available IPA was added and stirred for about 3 hours to modify the surface of the titanium oxide particles. The surface-modified titanium oxide particles were precipitated using a centrifuge and washed with IPA to obtain surface-modified titanium oxide particles (particles (P-4)). The particle (P-2) is considered to have an acryloyl group which is an unsaturated hydrocarbon group on the particle surface.

The obtained titanium oxide particles (particles (P-4)) were redispersed in IPA to prepare a dispersion of about 20 wt%.

(Preparation Example 1-5) Preparation of Particle (P-5) Dispersion Liquid Titanium oxide particles in a dispersion liquid (TKD-701, manufactured by Teika) in which titanium oxide particles are dispersed in commercially available IPA are centrifuged. The resulting mixture was precipitated and washed with IPA to obtain titanium oxide particles (particles (P-5)) not subjected to surface modification.

The obtained titanium oxide particles (particles (P-5)) were redispersed in IPA to prepare a dispersion of about 20 wt%.

(Preparation example 2) Preparation of photocurable ink The following polymerizable compound (A), photopolymerization initiator (B), and low-boiling solvent (C) were blended in the blending amounts shown in Table 1, and mixed and stirred. Thus, inks of Examples and Comparative Examples were respectively prepared.

In the blending amounts shown in Table 1, the polymerizable compound (A), the photopolymerization initiator (B), the low boiling point solvent (C), the titanium oxide particle dispersion prepared in Preparation Example 1 and Preparation Example 2 were mixed and stirred, The inks of Examples 1 to 4, Comparative Examples 1 to 3, and Reference Example 1 were obtained. In Comparative Example 2, the surface modification liquid used in preparing the titanium oxide particles (P-1) was used instead of the titanium oxide particle dispersion. In addition, the unit of the numerical value described in the Example of Table 1 and a comparative example is all the mass%.

(1) Polymerizable compound (A)
<A-1> Biscote # 230 (1,6-hexanediol diacrylate, manufactured by Osaka Organic Chemicals)
(2) Photopolymerization initiator (B)
<B-1> Lucirin TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF)
(3) Low boiling point solvent (C)
<C-1> IPA (2-propanol, manufactured by Kishida Chemical)
<C-2> Ion exchange water

(Evaluation methods)
17 μL of each ink of Examples, Comparative Examples, and Reference Examples was dropped on a slide glass (S111 manufactured by Matsunami Glass Industry Co., Ltd.) using a micropipette. Further, a 100 μm thick PET film (manufactured by Teijin DuPont Films, Tetron HL92W) was placed thereon, and an area of 26 mm × 26 mm was filled with ink.

Next, light emitted from a UV light source equipped with an ultrahigh pressure mercury lamp was irradiated for 20 seconds through a PET film after passing through a diffusion plate. As a result, the ink sandwiched between the PET film and the slide glass was cured. The irradiation light used was UV light having a wavelength of 365 nm and an illuminance of 15 mW / cm ² .

After light irradiation, the PET film was peeled off from the slide glass. Thereafter, the low boiling point solvent (C) contained in the cured film formed on the PET film was evaporated by allowing it to stand at room temperature, thereby forming a film having a thickness of about 25 μm on the PET film.

Evaluation of the degree of whiteness of the film formed on the PET film was evaluated using visual observation and brightness L *. The lightness L * was measured using a spectrocolorimeter (Konica Minolta Co., Ltd., CM-2600d) to measure the lightness (SCI including regular reflection light).

In the evaluation of the adhesion of the film formed on the PET film to the PET film, peeling of the formed 26 mm × 26 mm film was visually evaluated. The case where the peeling of the film in the region was 30% or less was marked as ◯, and the case where the peeling of the film in the region was above 70% was marked as x.

(Summary of results)
In any of the examples and comparative examples, the film formed on the PET film was visually a white film. The films formed in Examples 1 to 4 and Comparative Example 1 were sufficiently white visually, and the brightness L * was 60 or more. In addition, since the film | membrane formed in the reference example 1 became transparent visually, the brightness L * was not measured.

On the other hand, in the evaluation of adhesion with the PET film as the substrate, Examples 1 to 4 and Reference Example 1 showed good adhesion, while Comparative Examples 1 to 3 had low adhesion. That is, the results showed that the adhesion was improved when titanium oxide particles (particles P-1 to P-3) whose surfaces were modified with a functional group containing an unsaturated hydrocarbon group were added (Examples 1 to 4). Moreover, the result that adhesiveness did not improve only by adding the titanium oxide particle which is not surface-modified by the functional group containing an unsaturated hydrocarbon group was obtained (comparative example 1). Furthermore, the result that the effect which improves adhesiveness is not acquired only by adding the surface modification liquid for surface modification by the functional group containing an unsaturated hydrocarbon group was obtained (comparative example 2).

In each of the inks of Examples 1 to 4, droplets formed by a liquid containing water (ion-exchanged water (C-2)), which is a low boiling point solvent (C), are formed from the polymerizable compound (A) and photopolymerization. It is considered that an emulsion dispersed in the initiator (B) is formed. In these inks, it is presumed that the particles (P) are adsorbed on the droplets, thereby stabilizing the emulsion. In these inks, the IPA contained in each ink is compatible with both the droplet formed by the liquid containing water and the phase other than the droplet in the ink. Conceivable.

Based on the above results, a cured product (cured film) and a substrate obtained by curing the composition by adding titanium oxide particles surface-modified with a functional group containing an unsaturated hydrocarbon group to the photocurable ink. It was found that the adhesion with the (PET film) can be improved.

The present invention is not limited to the above embodiment, and various changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, in order to make the scope of the present invention public, the following claims are attached.

This application claims priority based on Japanese Patent Application Patent Application 2016-072980 filed on March 31, 2016 and Japanese Patent Application Patent Application 2017-006980 filed on January 18, 2017, All the descriptions are incorporated herein.

Claims (18)

1. A photocurable ink containing a polymerizable compound and a photopolymerization initiator,
   A low boiling point solvent having a boiling point of 40 ° C. or more and 120 ° C. or less at 1 atm,
   A photocurable ink comprising: particles having an unsaturated hydrocarbon group on a particle surface.
2. The photocurable ink according to claim 1, wherein the low boiling point solvent is water.
3. 3. The photocurable ink according to claim 1 or 2, wherein droplets formed by the liquid containing the low boiling point solvent are dispersed in the photocurable ink.
4. Containing a plurality of the particles,
   The photocurable ink according to claim 3, wherein a plurality of the particles are adsorbed on the droplet.
5. The photocurable ink according to any one of claims 1 to 4, wherein the particles are particles having an average particle diameter of 5 nm or more and 100 nm or less.
6. The photocurable ink according to any one of claims 1 to 5, wherein the particles are inorganic particles.
7. 7. The particle according to claim 6, wherein the particles include at least one selected from the group consisting of titanium oxide particles, silicon dioxide particles, zirconium oxide particles, aluminum oxide particles, zinc oxide particles, and barium titanate particles. The photocurable ink as described.
8. The content of the particles is 1% by mass or more and 20% by mass or less when the total mass of the photocurable ink is 100% by mass. The photocurable ink described in 1.
9. The content of the low boiling point solvent is 10% by mass or more and 50% by mass or less when the total mass of the photocurable ink is 100% by mass. The photocurable ink according to one item.
10. The unsaturated hydrocarbon group is at least one selected from the group consisting of a vinyl group, an acryloyl group, a methacryloyl group, and a styryl group. The photocurable ink described in 1.
11. The photocurable ink according to any one of claims 1 to 9, wherein the unsaturated hydrocarbon group is an acryloyl group or a methacryloyl group.
12. The photocurable ink according to claim 1, wherein the polymerizable compound has a polymerizable functional group.
13. The photocurable ink according to any one of claims 1 to 12, wherein the polymerizable compound has an acryloyl group or a methacryloyl group.
14. A photocurable ink containing a (meth) acrylic compound, a photopolymerization initiator, water, and particles having an unsaturated hydrocarbon group on the particle surface.
15. An ink container in which the photocurable ink according to any one of claims 1 to 14 is contained.
16. Arranging the photocurable ink according to any one of claims 1 to 14 on a substrate;
    Irradiating the photocurable ink disposed on the substrate with light.
17. The image forming method according to claim 16, wherein the base material includes a polymer material.
18. The step of disposing the photocurable ink on the substrate is a step of discharging the photocurable ink from an ink jet recording head and disposing the photocurable ink on the substrate. Item 18. The image forming method according to Item 17.

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