Ink composition for forming surface protective layer

Abstract

To provide an ink composition for forming surface-protecting layers which is capable of forming a film having excellent yellowing resistance and blocking resistance.SOLUTION: An ink composition for forming surface-protecting layers contains (A) a photopolymerizable compound, (B) a photopolymerization initiator and (C) an ultraviolet absorber. The ink composition does not contain a compound containing an ethylene oxide as a constitutional unit or contains such a compound in the range of 10 mass% or less. The proportion of cyclic structure-containing photopolymerizable compounds in the (A) photopolymerizable compound is 50 to 100 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an ink composition for forming a surface protective layer, and more particularly to an ink composition for forming a surface protective layer that can form a film that is excellent in yellowing resistance and blocking resistance. [Background technology]

[0002] In recent years, improvements in printing technology using inkjet printers and the like have led to the widespread use of printed materials with a variety of designs. In particular, photocurable inks, which are cured by actinic energy rays or the like, are used in a wide range of applications, as they are quick-drying and can provide images with little bleeding when decorating non-absorbent or poorly absorbent media, such as plastics and PVC sheets. However, when these printed materials are placed outdoors, there is a problem in that the ink-decorated areas are easily deteriorated by light, causing the printed materials to fade and deteriorate in appearance over time.

[0003] JP 2011-47152 A (Patent Document 1) describes an invention that makes it difficult to notice a decline in weather resistance for building boards patterned with yellow, magenta, and cyan pigments by making the color difference before and after discoloration approximately the same. This is an effective method when inorganic pigments, which have excellent weather resistance, are used, but it is insufficient for designs that are vivid and prone to fading, such as organic pigments and dyes.

[0004] Japanese Patent Application Laid-Open No. 2012-214603 (Patent Document 2) describes an invention relating to an actinic radiation-curable inkjet ink composition that uses a pigment ink containing a light stabilizer and has excellent weather resistance. However, there is a problem in that the effect of the light stabilizer is limited due to the coexistence of a pigment in the ink.

[0005] Japanese Patent Application Laid-Open Publication No. 2019-30998 (Patent Document 3) describes an invention of a decorative sheet in which a top coat layer covering a decorative portion contains an ultraviolet absorber and a light stabilizer. The decorative sheet described in Patent Document 3 is manufactured by dry lamination, extrusion lamination, or the like. As such, there are methods for protecting the decorative portion using techniques such as lamination, but the decorative layer must be separately protected using a laminating machine, etc. Furthermore, in order to melt and process an ultraviolet absorber and a light stabilizer into a transparent laminating material and further demonstrate the effect of maintaining weather resistance, there is a large degree of material selection, which poses difficult challenges.

[0006] To address these issues, Japanese Patent Application Laid-Open No. 2019-81867 (Patent Document 4) proposes improving weather resistance by preparing a separate clear ink, but there is still room for improvement in improving the weather resistance of the clear ink. Known methods for improving weather resistance include blending ultraviolet absorbers and radical scavengers, as described in, for example, Japanese Patent Application Laid-Open No. 6094771 (Patent Document 5) and Japanese Patent Application Laid-Open No. 2011-148918 (Patent Document 6). However, these tend to bleed from the printed film over time, making the sustainability of the effects of the ultraviolet absorbers and radical scavengers an issue. Patent Document 6 attempts to solve this issue by selecting the ultraviolet absorber and adjusting the molecular weight of the radical scavengers. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-47152 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-214603 [Patent Document 3] Japanese Patent Application Publication No. 2019-30998 [Patent Document 4] Japanese Patent Application Publication No. 2019-81867 [Patent Document 5] Patent No. 6094771 [Patent Document 6] Japanese Patent Application Laid-Open No. 2011-148918 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, various methods have been proposed for improving the weather resistance of films obtained using photocurable inks, but the yellowing resistance of the obtained films has not been fully investigated. Furthermore, although a film with good weather resistance and yellowing resistance is suitable as a surface protection layer that protects a decorative layer, when used as a surface protection layer, there is also the issue of blocking resistance.

[0009] Therefore, an object of the present invention is to provide an ink composition for forming a surface protective layer that can form a film that is excellent in yellowing resistance and blocking resistance. [Means for solving the problem]

[0010] As a result of extensive research to achieve the above object, the present inventors have found that, in an ink composition containing a photopolymerizable compound, a photopolymerization initiator, and an ultraviolet absorber, by reducing the amount of a compound containing ethylene oxide as a structural unit and increasing the proportion of a photopolymerizable compound containing a cyclic structure in the photopolymerizable compound, it is possible to form a film that is excellent in yellowing resistance and blocking resistance, and that such a film is suitable as a surface protection layer.

[0011] Therefore, a first aspect of the present invention is an ink composition for forming a surface protective layer, comprising (A) a photopolymerizable compound, (B) a photopolymerization initiator, and (C) an ultraviolet absorber, characterized in that the ink composition does not contain a compound containing ethylene oxide as a structural unit, or contains ethylene oxide in an amount of 10 mass % or less, and the proportion of the cyclic structure-containing photopolymerizable compound contained in (A) the photopolymerizable compound is in the range of 50 to 100 mass %.

[0012] In a preferred embodiment of the ink composition for forming a surface protective layer of the present invention, the (A) photopolymerizable compound contains 50 to 95 mass % of the (A1) monofunctional photopolymerizable compound and the (A2) polyfunctional photopolymerizable compound.

[0013] In another preferred embodiment of the ink composition for forming a surface protective layer of the present invention, the (A) photopolymerizable compound contains a monofunctional photopolymerizable compound having a heterocyclic structure in the range of 30 to 90% by mass.

[0014] In another preferred embodiment of the ink composition for forming a surface protective layer of the present invention, the polyfunctional photopolymerizable compound (A2) has a plurality of ester bonds and / or urethane bonds in addition to the ester bond derived from the (meth)acrylate group.

[0015] In another preferred embodiment of the ink composition for forming a surface protective layer of the present invention, the ultraviolet absorber (C) has a molar absorption coefficient of 1.5×10 at a wavelength of 385 nm. 3 (l·mol -1 ·cm -1 ) or less.

[0016] Another preferred embodiment of the ink composition for forming a surface protective layer of the present invention further contains (D) a radical scavenger.

[0017] In another preferred embodiment of the ink composition for forming a surface protective layer of the present invention, the ratio AM / DM of the total number of moles of photopolymerizable functional groups of the (A) photopolymerizable compound to the effective number of moles DM of the (D) radical scavenger is 10 or more.

[0018] In another preferred embodiment of the ink composition for forming a surface protective layer of the present invention, it further contains a resin.

[0019] In another preferred embodiment of the ink composition for forming a surface protective layer of the present invention, the ink composition further contains at least one of a cellulose derivative and a polyvinyl alcohol derivative. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide an ink composition for forming a surface protective layer that can form a film that is excellent in yellowing resistance and blocking resistance. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described in detail below.

[0022] One embodiment of the present invention is an ink composition comprising (A) a photopolymerizable compound, (B) a photopolymerization initiator, and (C) an ultraviolet absorber. The ink composition of the present invention is preferably a photocurable ink composition. In this specification, photocurable ink refers to an ink composition that can be cured by irradiation with actinic energy rays such as ultraviolet rays, visible light, or electron beams.

[0023] The (A) photopolymerizable compound is a compound that undergoes a polymerization reaction via a functional group that exhibits reactivity upon irradiation with actinic energy rays (for example, a photopolymerizable unsaturated group such as an acryloyl group, a methacryloyl group, a vinyl group, or a carbon-carbon double bond that constitutes an allyl group). The (A) photopolymerizable compound may be used alone or in combination of two or more. In the ink composition of the present invention, the amount of the (A) photopolymerizable compound is preferably 75 to 95% by mass.

[0024] (A) Photopolymerizable compounds are classified into monofunctional photopolymerizable compounds and polyfunctional photopolymerizable compounds. Examples of monofunctional photopolymerizable compounds include monofunctional photopolymerizable monomers having one functional group that exhibits reactivity upon irradiation with active energy rays (e.g., monofunctional photopolymerizable monomers having one photopolymerizable unsaturated group) and monofunctional photopolymerizable oligomers having one functional group that exhibits reactivity upon irradiation with active energy rays (e.g., monofunctional polymerizable oligomers having one photopolymerizable unsaturated group). Examples of polyfunctional photopolymerizable compounds include polyfunctional photopolymerizable monomers having two or more functional groups that exhibit reactivity upon irradiation with active energy rays (e.g., polyfunctional photopolymerizable monomers having two or more photopolymerizable unsaturated groups) and polyfunctional photopolymerizable oligomers having two or more functional groups that exhibit reactivity upon irradiation with active energy rays (e.g., polyfunctional photopolymerizable oligomers having two or more polymerizable unsaturated groups).

[0025] In the ink composition of the present invention, the amount of the monofunctional photopolymerizable compound is preferably 70 to 90% by mass. In the ink composition of the present invention, the amount of the polyfunctional photopolymerizable compound is, for example, 30% by mass or less, and preferably 20% by mass or less. The (A) photopolymerizable compound preferably contains a polyfunctional photopolymerizable compound having multiple ester bonds and / or urethane bonds, and in this case, the amount of the polyfunctional photopolymerizable compound having multiple ester bonds and / or urethane bonds in the ink composition of the present invention is preferably 5 to 20% by mass or less.

[0026] In the ink composition of the present invention, the proportion of the monofunctional photopolymerizable compound contained in the (A) photopolymerizable compound is preferably within a range of 50 to 100% by mass, more preferably within a range of 50 to 95% by mass, and even more preferably within a range of 70 to 95% by mass. By increasing the proportion of the monofunctional photopolymerizable compound contained in the (A) photopolymerizable compound, a film with excellent flexibility can be obtained, and also the occurrence of cracks can be suppressed.

[0027] Specific examples of the monofunctional photopolymerizable compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, polyoxyethylene mono(meth)acrylate, polyoxypropylene mono(meth)acrylate, polyoxybutylene mono(meth)acrylate, stearyl (meth)acrylate, N-acryloylmorpholine, N-methacryloylmorpholine, γ-butyrolactone ( (meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, 4-t-butylcyclohexyl acrylate, dimethylacrylamide, hydroxyethyl acrylamide, hydroxyethyl methacrylamide, diethylacrylamide, isopropyl acrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, diacetone acrylamide, Nn-butoxymethyl acrylamide, N-isobutoxymethyl acrylamide, N-methoxymethyl acrylamide, N-methylol acrylamide Acrylamide, N-vinylcaprolactam, decyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, isodecyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, octyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, cyclohexyl (meth)acrylate ) acrylate, t-butylcyclohexyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, EO (ethylene oxide) modified 2-ethylhexyl (meth)acrylate, neopentyl glycol (meth)acrylic acid benzoate, N-acryloyloxyethyl hexahydrophthalimide, N-methacryloyloxyethyl hexahydrophthalimide, 1-acryloylpyrrolidin-2-one, 1-methacryloylpyrrolidin-2-one, 1-acryloylpiperidin-2-one,Examples of such acrylates include 1-methacryloylpiperidin-2-one, N-vinyl-2-pyrrolidone, N-vinylimidazole, tetrahydrofurfuryl (meth)acrylate, methoxydipropylene glycol (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, and ethoxydiethylene glycol (meth)acrylate.

[0028] Furthermore, when used in places where the material will be visible to the public, such as outdoor advertisements or plastic boards, it is preferable to use a monomer that does not leave an odor on the printed material, and preferred examples include tridecyl acrylate, ethoxydiethylene glycol acrylate, hydroxyethyl acrylamide, N-acryloylmorpholine, N-methacryloylmorpholine, 1-acryloylpyrrolidin-2-one, 1-methacryloylpyrrolidin-2-one, 1-acryloylpiperidin-2-one, 1-methacryloylpiperidin-2-one, 2-hydroxy-3-phenoxypropyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, hydroxyethyl methacrylamide, dimethylaminopropyl acrylamide, dimethylaminopropyl methacrylamide, and 4-t-butylcyclohexyl acrylate.

[0029] Among the polyfunctional photopolymerizable compounds, specific examples of polyfunctional photopolymerizable monomers (bifunctional photopolymerizable monomers) having two functional groups that show reactivity when irradiated with active energy rays include 1,12-dodecanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tert-butyl acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol diacrylate, cyclohexane dimethanol diacrylate, neopentyl glycol di(meth)acrylate, PO (propylene oxide)-modified neopentyl glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, and the like.

[0030] Furthermore, when used in places where the product will be visible to the public, such as outdoor advertisements or plastic boards, it is preferable to use a monomer that does not leave an odor on the printed matter, and preferred examples include 3-methyl-1,5-pentanediol diacrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

[0031] Specific examples of polyfunctional photopolymerizable monomers having three or more functional groups that exhibit reactivity upon irradiation with active energy rays (tri- or higher functional polyfunctional photopolymerizable monomers) include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, EO-modified diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and EO-modified dipentaerythritol hexa(meth)acrylate.

[0032] As used herein, the term "(meth)acrylate" refers to either methacrylate or acrylate. For example, 2-hydroxyethyl (meth)acrylate is 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate. When a prefix indicating plural is added to a (meth)acrylate, such as di(meth)acrylate or tri(meth)acrylate, each (meth)acrylate may be the same or different.

[0033] The polyfunctional photopolymerizable compound is preferably a polyester / polyurethane acrylate having a plurality of ester bonds and / or urethane bonds in the molecule, excluding ester bonds attached to (meth)acrylate groups.

[0034] The polyfunctional photopolymerizable compound is preferably a polyester acrylate. The number of functional groups of the polyester acrylate is preferably 2 to 12, more preferably 2 to 4, and the molecular weight is preferably 5000 or less. Here, the molecular weight of the polyester acrylate is the number average molecular weight in terms of polystyrene.

[0035] Further, the following polyester acrylates are known: CN2285, CN2203 NS, CN2254 NS, CN2271, CN2273, CN2279, CN2281, CN2283 NS, CN8201 NS, CN7001 NS, CN2259, CN2261, CN292, CN294, CN299, CN2282, CN2295, CN293, CN296, CN2267 (manufactured by Sartomer Corporation), U-200PA, UA-122P (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), EBECRYL 436, EBECRYL 438, EBECRYL 450, EBECRYL 524, EBECRYL 525, EBECRYL 800, EBECRYL 811, EBECRYL 812, EBECRYL 1830, EBECRYL 846, EBECRYL 851, EBECRYL 852, EBECRYL 853, EBECRYL 870, EBECRYL 884, EBECRYL 1885, EBECRYL 888, EBECRYL 893, EBECRYL 571, EBECRYL 809 (manufactured by Daicel-Allnex Co., Ltd.), Aronix M-6100, M-6250, M-6500, M-7100, M-7300K, M-8030, M-8060, M-8100, M-8530, M-8560, M-9050 (manufactured by Toagosei Co., Ltd.)

[0036] The ink composition of the present invention preferably contains, as the photopolymerizable compound (A), a photopolymerizable compound having a cyclic structure, more preferably a monofunctional photopolymerizable compound having a cyclic structure, and even more preferably a monofunctional photopolymerizable monomer having a cyclic structure. In this specification, a "photopolymerizable compound having a cyclic structure" is also referred to as a "photopolymerizable compound containing a cyclic structure."

[0037] The proportion of the photopolymerizable compound having a cyclic structure contained in the photopolymerizable compound (A) is preferably within the range of 40 to 100% by mass, more preferably within the range of 50 to 100% by mass. Photopolymerizable compounds having a cyclic structure are highly reactive, and the polymerization reaction proceeds well even when the intensity of the light source of the active energy rays is low. Furthermore, by including a large amount of the photopolymerizable compound having a cyclic structure, preferably by having the proportion of the photopolymerizable compound having a cyclic structure contained in the photopolymerizable compound (A) within the range of 50 to 100% by mass, the blocking resistance of the resulting film can be improved.

[0038] Monofunctional photopolymerizable compounds having a cyclic structure can be classified into monofunctional photopolymerizable compounds having a cyclic structure containing a heteroatom and monofunctional photopolymerizable compounds having a cyclic structure without a heteroatom. Here, it is preferable that the (A) photopolymerizable compound contains both a monofunctional photopolymerizable compound (preferably a monomer) having a cyclic structure containing a heteroatom and a monofunctional photopolymerizable compound (preferably a monomer) having a cyclic structure without a heteroatom. A heteroatom refers to an atom other than carbon or hydrogen.

[0039] Monofunctional photopolymerizable compounds having a cyclic structure containing a heteroatom (heterocyclic structure) are preferred from the viewpoint of the blocking resistance and stretchability of the resulting film. The stretchability of the cured film makes it less susceptible to cracking. In the photopolymerizable compound (A) in the ink composition of the present invention, the amount of the monofunctional photopolymerizable compound having a cyclic structure containing a heteroatom is preferably within a range of 30 to 90% by mass, more preferably within a range of 40 to 90% by mass, and particularly preferably within a range of 70 to 90% by mass.

[0040] A monofunctional photopolymerizable compound having a cyclic structure containing no heteroatoms is preferred from the viewpoint of the balance between adhesion and blocking resistance of the resulting film. In the ink composition of the present invention, the amount of the monofunctional photopolymerizable compound having a cyclic structure containing no heteroatoms is preferably 5% by mass or more, and more preferably 10% by mass or more.

[0041] In the ink composition of the present invention, the total amount of the monofunctional photopolymerizable compound having a cyclic structure containing a heteroatom and the monofunctional photopolymerizable compound having a cyclic structure not containing a heteroatom is preferably within a range of 70 to 90% by mass.

[0042] Examples of monofunctional photopolymerizable compounds having a cyclic structure containing a heteroatom include N-acryloylmorpholine, N-methacryloylmorpholine, N-vinylcaprolactam, γ-butyrolactone (meth)acrylate, N-vinyl-2-pyrrolidone, cyclic trimethylolpropane formal (meth)acrylate, N-acryloyloxyethyl hexahydrophthalimide, N-methacryloyloxyethyl hexahydrophthalimide, 1-acryloylpyrrolidin-2-one, 1-methacryloylpyrrolidin-2-one, 1-acryloylpiperidin-2-one, 1-methacryloylpiperidin-2-one, N-vinylimidazole, tetrahydrofurfuryl (meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate.

[0043] Examples of monofunctional photopolymerizable compounds having a cyclic structure without a heteroatom include 4-t-butylcyclohexyl acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, and neopentyl glycol (meth)acrylic acid benzoate. The monofunctional photopolymerizable compound having a cyclic structure without a heteroatom preferably has a boiling point of 180°C or higher. 4-t-butylcyclohexyl acrylate is particularly preferred.

[0044] In the ink composition of the present invention, from the viewpoint of suppressing odor, it is preferable that the photopolymerizable compound (A) does not contain isobornyl (meth)acrylate, particularly isobornyl acrylate, as a monofunctional photopolymerizable compound having a cyclic structure containing no heteroatom. Furthermore, the use of such a monofunctional photopolymerizable compound may result in reduced adhesion to the substrate or reduced blocking resistance due to increased tackiness.

[0045] In the ink composition of the present invention, the photopolymerizable compound (A) preferably does not contain a compound having an aromatic ring. The use of a compound having an aromatic ring tends to cause yellowing of the resulting film, so from the viewpoint of improving yellowing resistance, it is preferable not to use a compound having an aromatic ring. Even when the photopolymerizable compound (A) contains a compound having an aromatic ring, the amount of the compound having an aromatic ring contained in the photopolymerizable compound (A) is preferably within the range of 40% by mass or less, more preferably within the range of 30% by mass or less, and even more preferably within the range of 25% by mass or less.

[0046] Examples of compounds having an aromatic ring include N-vinyl-2-pyrrolidone, N-acryloyloxyethyl hexahydrophthalimide, N-methacryloyloxyethyl hexahydrophthalimide, N-vinylimidazole, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, and neopentyl glycol (meth)acrylic acid benzoate.

[0047] In the ink composition of the present invention, the photopolymerizable compound (A) may include a polyfunctional photopolymerizable compound having a cyclic structure. Examples of the polyfunctional photopolymerizable compound having a cyclic structure include tricyclodecane dimethanol diacrylate and cyclohexane dimethanol diacrylate.

[0048] In the ink composition of the present invention, the photopolymerizable compound (A) preferably contains a photopolymerizable monomer having a glass transition temperature of 0°C or lower and a photopolymerizable monomer having a glass transition temperature of 85°C or higher. In the ink composition of the present invention, the amount of each of the photopolymerizable monomer having a glass transition temperature of 0°C or lower and the photopolymerizable monomer having a glass transition temperature of 85°C or higher is preferably 10% by mass or higher, and more preferably 15% by mass or higher. When the Tg of the entire coating film is near room temperature, a tough film with high hardness and high molecular weight is obtained. On the other hand, when the Tg of the entire coating film is lower than room temperature, a high molecular weight film is obtained, but the hardness is insufficient, and blocking resistance and abrasion resistance are often poor. Furthermore, when the Tg of the entire coating film is higher than room temperature, the film is hard, restricting molecular movement, preventing polymerization from proceeding sufficiently, and causing problems such as a sticky feel. These Tg, polymerization, and film properties are derived from the side chain structure, so adding a certain amount of monomer with a high Tg can ensure blocking resistance and scratch resistance, while adding a certain amount of monomer with a low Tg can ensure curability and film toughness. Furthermore, designing the total Tg to be between 15°C and 45°C, especially between 20°C and 40°C, allows for a more balanced design.

[0049] In this specification, the glass transition temperature (Tg) of a photopolymerizable monomer refers to the glass transition temperature of a homopolymer made from the photopolymerizable monomer. The glass transition temperature of the cured coating of the photopolymerizable ink obtained by combining these monomers can be theoretically determined using Fox's equation. The theoretical glass transition temperature [Tg(K)] of a cured coating film is calculated using the glass transition temperatures of the homopolymers of the polymer components (monomers and oligomers having ethylenically unsaturated groups) that form the cured coating film, and can be determined using the following Fox equation [Equation (1)]: 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+···+(Wn / Tgn)···Formula (1) (Wherein, Tgn is the glass transition temperature (K) of each homopolymer of n types of polymer components (monomers or oligomers having an ethylenically unsaturated group), and Wn is the mass fraction of each of the polymer components. W1 + W2 + + Wn = 1.)

[0050] Examples of photopolymerizable monomers having a glass transition temperature of 0°C or lower include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, polyoxyethylene mono(meth)acrylate, polyoxypropylene mono(meth)acrylate, polyoxybutylene mono(meth)acrylate, tridecyl (meth)acrylate, lauryl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, isodecyl (meth)acrylate, 2-ethylhexyl diglycol (meth)acrylate, EO (ethylene oxide)-modified 2-ethylhexyl (meth)acrylate, and ethoxydiethylene glycol (meth)acrylate.

[0051] Examples of photopolymerizable monomers having a glass transition temperature of 85°C or higher include N-acryloylmorpholine, N-methacryloylmorpholine, dimethylacrylamide, hydroxyethylacrylamide, hydroxyethylmethacrylamide, isopropylacrylamide, dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, diacetoneacrylamide, isobornyl(meth)acrylate, dicyclopentanyl(meth)acrylate, and dicyclopentenyl(meth)acrylate.

[0052] In the ink composition of the present invention, the photopolymerizable compound (A) is preferably a photopolymerizable compound having a low viscosity and a homopolymer glass transition temperature of room temperature (23°C) or lower. Such a photopolymerizable compound can maintain the viscosity of the ink at a low level, facilitating the design of an ink with excellent ejection stability, and also has excellent curing properties and the effect of improving the copolymerization of the ink. Examples of such photopolymerizable compounds (A) include phenoxyethyl (meth)acrylate, phenoxydiethylene glycol acrylate, phenoxy-polyethylene glycol acrylate, ethoxy-diethylene glycol acrylate, methoxy-triethylene glycol acrylate, 2-ethylhexyl-diglycol acrylate, methoxydipropylene glycol acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, and tetrahydrofurfuryl acrylate. Furthermore, from the viewpoint of further enhancing the curability, it is preferable that the compound contains a cyclic structure, and in the present invention, from the viewpoint of protecting the coating film from yellowing, it is most preferable that the compound contains tetrahydrofurfuryl acrylate that does not contain ethylene oxide as a structural unit.

[0053] The ink composition of the present invention preferably contains a polyfunctional photopolymerizable compound as the photopolymerizable compound (A), and more preferably contains at least one polyfunctional photopolymerizable compound having multiple ester bonds and / or urethane bonds in the molecule (wherein, "ester bonds" refers to ester bonds other than those derived from (meth)acrylate groups). Polyfunctional photopolymerizable compounds having multiple ester bonds in the molecule, in particular, produce less yellowing and coloration in coating films and have high curing properties, making it possible to obtain printed materials with excellent weather resistance and blocking resistance. Polyfunctional photopolymerizable compounds having multiple ester bonds and / or urethane bonds in the molecule contain pre-polymerized high-molecular-weight moieties and multiple functional groups, making it possible to obtain printed materials with high curing properties and excellent blocking resistance by incorporating a certain amount of such compounds.

[0054] The proportion of the polyfunctional photopolymerizable compound contained in the (A) photopolymerizable compound is preferably within the range of 3 to 20 mass %, more preferably 5 to 20 mass %, and even more preferably 5 to 15 mass %.

[0055] The ink composition of the present invention preferably does not contain a compound containing ethylene oxide as a structural unit. When a compound containing ethylene oxide as a structural unit is used, the resulting film tends to turn yellow. Therefore, from the viewpoint of improving yellowing resistance, it is preferable not to use a compound containing ethylene oxide as a structural unit. Even when the ink composition of the present invention contains a compound containing ethylene oxide as a structural unit, the amount of the compound containing ethylene oxide as a structural unit contained in the ink composition of the present invention is preferably within the range of 10% by mass or less, more preferably within the range of 5% by mass or less, and even more preferably within the range of 3% by mass or less.

[0056] Examples of compounds containing ethylene oxide as a structural unit include phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, ethoxyethyl acrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, glycidyl (meth)acrylate, allyl glycidyl ether, and various ethylene oxide-modified acrylates.

[0057] The (B) photopolymerization initiator has the effect of initiating polymerization of the above-mentioned photopolymerizable compound when irradiated with active energy rays. The amount of the (B) photopolymerization initiator in the ink composition is preferably 1 to 25 mass %, more preferably 3 to 20 mass %, and even more preferably 3 to 15 mass %. If the content of the (B) photopolymerization initiator is less than 1 mass %, the film may not cure properly, and if it exceeds 25 mass %, precipitates may form at low temperatures, making the ink discharge unstable. Furthermore, to promote the initiation reaction of the (B) photopolymerization initiator, an auxiliary agent such as a photosensitizer may be used in combination.

[0058] Examples of the (B) photopolymerization initiator include benzophenone-based compounds, acetophenone-based compounds, thioxanthone-based compounds, and phosphine oxide-based compounds. From the viewpoint of curability, however, it is preferable that the wavelength of the irradiated active energy ray overlaps as much as possible with the absorption wavelength of the photopolymerization initiator. In particular, from the viewpoint of LED curing and coloration during curing, it is preferable that the (B) photopolymerization initiator contains an acylphosphine oxide-based initiator. The (B) photopolymerization initiator may be used alone or in combination of two or more.

[0059] Specific examples of the (B) photopolymerization initiator include: 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methyl-propan-1-one, Phenylglyoxylic acid methyl ester, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)], Ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, etc.

[0060] Among these, from the viewpoint of ink curability, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, and 2,4-diethylthioxanthone are preferred, and from the viewpoint of LED curing and coloration during curing, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide are more preferred.

[0061] The (C) ultraviolet absorber has the effect of absorbing ultraviolet rays and preventing deterioration caused by ultraviolet rays. Examples of the (C) ultraviolet absorber include cyanoacrylate compounds, benzophenone compounds, benzoate compounds, benzotriazole compounds, hydroxyphenyltriazine compounds, benzylidene camphor compounds, and inorganic fine particles. The (C) ultraviolet absorber is preferably one having a triazine skeleton, and among these, hydroxyphenyltriazine compounds that absorb ultraviolet rays at shorter wavelengths are preferred from the perspective of ink curing properties. Furthermore, among hydroxyphenyltriazine compounds, solid ones are particularly preferred, as they tend to have lower fluidity and bleed out less easily than liquid ones.

[0062] From the viewpoint of curability, it is preferable that the wavelength of the irradiated actinic energy ray and the absorption wavelength of the ultraviolet absorber (C) do not overlap as much as possible. In the ink composition of the present invention, the ultraviolet absorber (C) has a molar absorption coefficient of 1.5×10 at a wavelength of 385 nm. 3 (l·mol -1 ·cm -1 ) or less, and more preferably 2.0 × 10 2 (l·mol -1 ·cm -1 ) or less.

[0063] In this specification, the molar extinction coefficient of a UV absorber is calculated using the Beer-Lambert law based on the absorbance obtained by UV-visible absorption spectroscopy. The UV-visible absorption spectrum is measured using acetonitrile or tetrahydrofuran as the solvent, at a concentration of 50-100 μM, using a 1 cm cell.

[0064] Specific examples of (C) ultraviolet absorbers include: 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone-2-hydroxy-4-benzyloxybenzophenone, bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole 2-[2'-hydroxy-3',5'-bis(α,α-(dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2,2'-methylene-bis[4-(1,1,3,3-tetramethylbutyl)-6-(2N-benzotriazol-2-yl)phenol], Condensation products of methyl-3-[3-t-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate and polyethylene glycol, 2-(2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2,6-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate, hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate and the like.

[0065] In the ink composition of the present invention, the amount of (C) ultraviolet absorber is preferably within the range of 0.1 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass. If the amount of ultraviolet absorber is too large, the film may not be sufficiently cured. (C) ultraviolet absorbers may be used alone or in combination of two or more, but it is preferable that (C) ultraviolet absorber contains at least two types of ultraviolet absorbers. By using multiple types of ultraviolet absorbers with different structures, the effect of the ultraviolet absorbers can be maintained longer.

[0066] In the ink composition of the present invention, the ultraviolet absorber (C), in relation to the photopolymerizable compound (A), has a value B calculated by the following formula (1) of preferably 100 or more, more preferably 120 or more, and even more preferably 200 or more. The upper limit of the value B is, for example, 20,000 or less. Molecular weight of UV absorber (g / mol) / |SP value of UV absorber - average SP value of photopolymerizable compound| = B ... Equation (1) The above formula (1) is derived from the compatibility (SP value) of the ultraviolet absorber (UVA) with the film and the molecular weight of the UVA. When the value B is 100 or more, the effect of suppressing UVA bleed-out is high. When the value B is less than 100, the difference (absolute value) in the SP value between the UVA and the photopolymerizable compound is large and / or the molecular weight of the UVA is low, which may result in a reduced effect of suppressing UV absorber bleed-out.

[0067] [How to calculate SP value] In this specification, the SP values ​​of the ultraviolet absorber and the photopolymerizable compound are values ​​of the Hansen solubility parameters, which are calculated using the Y-MB method.

[0068] [Calculation method for average SP value] (A) When the photopolymerizable compound is composed of n kinds of photopolymerizable compounds, the SP value of each photopolymerizable compound is expressed as SP 1 , SP 2 ,···,SP n The mass fraction of each photopolymerizable compound is W 1 , W 2 , , W n (W 1 +W 2 +···+W n =1) and can be calculated using the following formula: Average SP value = SP 1 ×W 1 +SP 2 ×W 2 +···+SP n ×W n

[0069] The ink composition of the present invention preferably contains (D) a radical scavenger. (D) A radical scavenger can scavenge free radicals and improve light stability. (D) Radical scavengers also include substances that react with free radicals and prevent polymerization reactions (so-called polymerization inhibitors). Use of (D) a radical scavenger is also preferred from the viewpoint of preventing cracking.

[0070] (D) Examples of the radical scavenger include hindered amine compounds, hydroquinone compounds, phenol compounds, phenothiazine compounds, nitroso compounds, and N-oxyl compounds, with hindered amine light stabilizers (HALS) being particularly preferred.

[0071] The (D) radical scavenger is preferably a radical scavenger other than methylhydroquinone (MEHQ) and butylhydroxytoluene (BHT), which are less effective in preventing cracking than other radical scavengers.

[0072] Specific examples of the (D) radical scavenger include hindered amine compounds such as bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 1-{2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl}-2,2,6,6-tetramethylpiperidine, and 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro{4.5}decane-2,4-dione; phenol; o-, m-, or p- Phenolic compounds such as cresol, 2-t-butyl-4-methylphenol, 6-t-butyl-2,4-dimethylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol, hydroquinone, hydroquinone monomethyl ether, methylhydroquinone, 2,5-di-t-butyl Hydroquinone compounds such as methylhydroquinone, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, 4-methylbenzcatechin, t-butylhydroquinone, 3-methylbenzcatechin, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, benzoquinone, t-butyl-p-benzoquinone, 2,5-diphenyl-p-benzoquinone, etc., phenotypic compounds azine and other phenothiazine compounds; nitroso compounds such as N-nitroso-N-phenylhydroxylamine ammonium and N-nitroso-N-phenylhydroxylamine aluminum salt; and N-oxyl compounds such as 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, and 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl.

[0073] In the ink composition of the present invention, the amount of (D) radical scavenger is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. If the amount of radical scavenger is too high, it may cause poor curing. The lower limit of the content of (D) radical scavenger is, for example, 0.01% by mass or more, preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more. (D) radical scavengers may be used alone or in combination of two or more.

[0074] In the ink composition of the present invention, the ratio AM / DM of the total number of moles of photopolymerizable functional groups in (A) the photopolymerizable compound to the effective number of moles DM of the radical scavenger in (D) is preferably 10 or greater. Radical scavengers have a polymerization inhibitory effect by capturing the radicals necessary for polymerization. Therefore, incorporating a large amount of radical scavenger will result in a lower curing rate. AM / DM represents the ratio of the polymerization components surrounding the generated radicals to the radical scavenger, and if AM / DM is 10 or greater, it is determined that the effect of the radical scavenger on polymerization is sufficiently small. The effective number of moles of a radical scavenger represents the number of functional groups capable of capturing radicals. For example, if a molecule has five radical-scavenging sites in one molecule, and the number of moles of the radical scavenger is 1 mole, the effective number of moles is 5 moles.

[0075] The ink composition of the present invention may contain a resin. By blending a resin in the ink composition, the flying properties and stability of the ink can be improved. The resin used in the ink composition of the present invention is preferably a resin that does not have a functional group that shows reactivity when irradiated with actinic energy rays. The resin may be used alone or in combination of two or more types. The amount of resin in the ink composition of the present invention is preferably 5% by mass or less.

[0076] The number average molecular weight of the resin is preferably not more than 500,000, and more preferably not more than 20,000. In this specification, the number average molecular weight is a value measured by gel permeation chromatography, and polystyrene is used as the standard substance.

[0077] Specific examples of resins include polyvinyl acetate, vinyl chloride-vinyl acetate copolymers, vinyl chloride resins, chlorinated rubber, chlorinated polyethylene resins, chlorinated polypropylene resins, chlorinated ethylene-vinyl acetate resins, acrylic resins, polystyrene resins, polyamide resins, polyurethane resins, polyolefin resins, silicone resins, fluororesins, epoxy resins, polyester resins, ketone resins, phenolic resins, polyvinyl alcohol, polyvinyl alcohol derivatives (anion-modified polyvinyl alcohol, etc.), cellulose, cellulose derivatives (hydroxymethyl cellulose, hydroxyethyl cellulose, cellulose acetate, etc.), rosin resins, oil-based resins, petroleum resins, alkyd resins, alginic acid, alginic acid derivatives (propylene glycol alginate, etc.), and the like. Modified versions of these resins are also included. For example, for resins having hydroxyl groups, modifications such as hydroxyalkyl etherification and carboxylic acid modification are examples.

[0078] The ink composition of the present invention preferably contains at least one of a cellulose derivative and a polyvinyl alcohol derivative as a resin, and more preferably contains a cellulose derivative. These resins are highly effective in improving the jet properties and stability of the ink, and cellulose derivatives are particularly suitable.

[0079] Examples of cellulose derivatives include cellulose ether, cellulose ester, nitrocellulose, cellulose sulfate, cellulose phosphate, and cellulose acetate nitrate. Examples of cellulose ethers include methyl cellulose, ethyl cellulose, benzyl cellulose, trityl cellulose, cyanoethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, aminoethyl cellulose, and oxyethyl cellulose (also known as hydroxyethyl cellulose). Examples of cellulose esters include cellulose acetate, cellulose acetate propionate, cellulose acetate butyrate, cellulose propionate, and cellulose butyrate.

[0080] Other examples of cellulose derivatives include acrylic-modified cellulose derivatives, polyester-modified cellulose derivatives, and polyurethane-modified cellulose derivatives. Acrylic-modified cellulose derivatives are compounds obtained by graft polymerizing cellulose derivatives such as cellulose ethers and cellulose esters with acrylic components such as (meth)acrylates. Polyester-modified cellulose derivatives are compounds obtained by bonding cellulose derivatives such as cellulose ethers and cellulose esters with polyester components (i.e., components having multiple ester bonds in the main chain) such as polytrimethylene terephthalate, polyethylene terephthalate, and polybutylene terephthalate. Polyurethane-modified cellulose derivatives are compounds obtained by reacting hydroxyl groups of cellulose derivatives such as cellulose ethers and cellulose esters with, for example, an isocyanate prepolymer.

[0081] As the cellulose derivative, cellulose acetate alkylate is preferred, cellulose acetate alkylate substituted with an acyl group having about 1 to 6 carbon atoms is more preferred, and cellulose acetate propionate and cellulose acetate butyrate are even more preferred.

[0082] The ink composition of the present invention may contain a colorant such as a dye or pigment, and in this case, it is preferable to contain a pigment from the viewpoint of weather resistance. For example, a metallic ink can be made by using a metal pigment. The content of the colorant in the ink composition is, for example, 0.1 to 15% by mass. The colorant may be used alone or in combination of two or more types.

[0083] Specific examples of colorants include: CIPigment Yellow 1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 14, 15, 16, 17, 24, 32, 34, 35, 36, 37, 41, 42, 43, 49, 53, 55, 60, 61, 62, 63, 65, 73, 74, 75, 77, 81, 83, 87, 93, 94, 95, 97, 98, 99, 100, 101, 104, 105, 106, 108, 109, 110, 111, 113, 114, 116, 117, 119, 120, 123, 124, 126, 127, 128, 129, 130, 133, 138, 139, 150, 151, 152, 153, 154, 155, 165, 167, 168, 169, 170, 172, 173, 174, 175, 176, 179, 180, 181, 182, 183, 184, 185, 191, 193, 194, 199, 205, 206, 209, 212, 213, 214, 215, 219, CIPigment Orange 1, 2, 3, 4, 5, 13, 15, 16, 17, 19, 20, 21, 24, 31, 34, 36, 38, 40, 43, 46, 48, 49, 51, 60, 61, 62, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 81, C.I.Pigment Red 1、2、3、4、5、6、7、8、9、10、11、12、14、15、16、17、18、21、22、23、31、32、38、41、48、48:1、48:2、48:3、48:4、48:5、49、52、52:1、52:2、53:1、54、57:1、58、60:1、63、64:1、68、81:1、83、88、89、95、101、104、105、108、112、114、119、122、123、136、144、146、147、149、150、164、166、168、169、170、171、172、175、176、177、178、179、180、181、182、183、184、185、187、188、190、193、194、200、202、206、207、208、209、210、211、213、214、216、220、220、221、224、226、237、238、239、242、245、247、248、251、253、254、255、256、257、258、260、262、263、264、266、268、269、270、271、272、279、 C.I.Pigment Violet 1、2、3、3:1、3:3、5:1、13、15、16、17、19、23、25、27、29、31、32、36、37、38、42、50、 C.I.Pigment Blue 1、15、15:1、15:2、15:3、15:4、15:5、15:6、16、17:1、24、24:1、25、26、27、28、29、36、56、60、61、62、63、75、79、80、 C.I.Pigment Green 1、4、7、8、10、15、17、26、36、50、 C.I.Pigment Brown 5、6、23、24、25、32、41、42、 C.I.Pigment Black 1、6、7、9、10、11、20、26、28、31、32、34、 C.I.Pigment White 1、2、4、5、6、7、11、12、18、19、21、22、23、26、27、28、 Examples include aluminum flakes, glass flakes, pearl pigments, and hollow particles.

[0084] Among these, from the viewpoint of weather resistance and color reproducibility of the obtained film, CIPigment Black 7, CIPigment Blue 15:3, CIPigment Blue 15:4, CIPigment Blue 28, CIPigment Red 101, CIPigment Red 122, CIPigment Red 202, CIPigment Red 254, CIPigment Red 282, CIPigment Violet 19, CIPigment White 6, CIPigment Yellow 42, CIPigment Yellow 120, CIPigment Yellow 138, CIPigment Yellow 139, CIPigment Yellow 150, CIPigment Yellow 151, CIPigment Yellow 155, CIPigment Yellow 213 are preferred.

[0085] The ink composition of the present invention may contain various compounds for the purpose of imparting functionality. For example, it may contain calcium carbonate, barium sulfate, etc. in order to increase the hardness of the resulting film, it may contain indium tin composite oxide, antimony tin composite oxide, etc. in order to impart a heat ray absorption function to the resulting film, and it may contain fine particle titanium oxide, fine particle zirconium oxide, etc. in order to increase the refractive index of the resulting film.

[0086] From the viewpoint of ejection stability, the pigment particles dispersed in the ink composition preferably have a volume average particle diameter of 0.05 to 0.4 μm and a volume maximum particle diameter of 0.2 to 1 μm. If the volume average particle diameter is greater than 0.4 μm and the volume maximum particle diameter is greater than 1 μm, it tends to be difficult to eject the ink composition stably. The volume average particle diameter and volume maximum particle diameter can be measured using a measuring device that uses dynamic light scattering.

[0087] The ink composition of the present invention may further contain a pigment dispersant as needed to disperse the pigment. The content of the pigment dispersant in the ink composition is, for example, 0.1 to 5% by mass. The pigment dispersants may be used alone or in combination of two or more.

[0088] Specific examples of pigment dispersants include: ANTI-TERRA-U, ANTI-TERRA-U100, ANTI-TERRA-204, ANTI-TERRA-205, DISPERBYK-101, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-108, DISPERBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-112, DISPERBYK-116, DISPERBYK-130, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-180, DISPERBYK-182, DISPERBYK-183, DISPERBYK-184, DISPERBYK-185, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2008, DISPERBYK-2009, DISPERBYK-2020, DISPERBYK-2025, DISPERBYK-2050, DISPERBYK-2070, DISPERBYK-2096, DISPERBYK-2150, DISPERBYK-2155, DISPERBYK-2163, DISPERBYK-2164, BYK-P104, BYK-P104S, BYK-P105, BYK-9076, BYK-9077, BYK-220S, BYKJET-9150, BYKJET-9151 (all manufactured by BYK Japan), Solsperse3000, Solsperse5000, Solsperse9000, Solsperse11200, Solsperse13240, Solsperse13650, Solsperse13940, Solsperse16000, Solsperse17000, Solsperse18000, Solsperse20000, Solsperse21000, Solsperse24000SC, Solsperse24000GR, Solsperse26000, Solsperse27000, Solsperse28000, Solsperse32000, Solsperse32500, Solsperse32550, Solsperse32600, Solsperse33000, Solsperse34750, Solsperse35100, Solsperse35200, Solsperse36000, Solsperse36600, Solsperse37500, Solsperse38500, Solsperse39000, Solsperse41000, Solsperse54000, Solsperse55000, Solsperse56000, Solsperse71000, Solsperse76500, SolsperseX300 (all manufactured by Lubrizol), Disparlon DA-7301, Disparlon DA-325, Disparlon DA-375, Disparlon DA-234 (all manufactured by Kusumoto Chemicals Co., Ltd.), FLORENE AF-1000, FLORENE DOPA-15B, FLORENE DOPA-15BHFS, FLORENE DOPA-17HF, FLORENE DOPA-22, FLORENE DOPA-33, FLORENE G-600, FLORENE G-700, FLORENE G-700AMP, FLORENE G-700DMEA, FLORENE G-820, FLORENE G-900, FLORENE GW-1500, FLORENE KDG-2400, FLORENE NC-500, FLORENE WK-13E (all manufactured by Kyoeisha Chemical Co., Ltd.), TEGO Dispers610, TEGO Dispers610S, TEGO Dispers630, TEGO Dispers650, TEGO Dispers652, TEGO Dispers655, TEGO Dispers662C, TEGO Dispers670, TEGO Dispers685, TEGO Dispers700, TEGO Dispers710, TEGO Dispers740W, LIPOTIN A, LIPOTIN BL, LIPOTIN DB, LIPOTIN SB (both manufactured by Evonik Degussa), PB821, PB822, PN411, PA111 (all manufactured by Ajinomoto Fine-Techno Co., Ltd.), Texahall 963, Texahall 964, Texahall 987, Texahall P60, Texahall P61, Texahall P63, Texahall 3250, Texahall SF71, Texahall UV20, Texahall UV21 (all manufactured by Cognis), Examples include BorchiGenSN88 and BorchiGen0451 (both manufactured by Borchias).

[0089] The ink composition of the present invention may further contain a surface conditioner from the viewpoint of improving wettability, etc. In this specification, a surface conditioner means a substance that has a hydrophilic moiety and a hydrophobic moiety in its molecular structure and that can adjust the surface tension of the ink composition by adding it.

[0090] Specific examples of surface conditioners that can be used in the ink composition of the present invention include anionic surface conditioners such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surface conditioners such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surface conditioners such as alkylamine salts and quaternary ammonium salts; acrylic surface conditioners, silicone surface conditioners, and fluorine-based surface conditioners. Silicon-based and acrylic surface conditioners are particularly preferred, and commercially available products from BYK, Evonik, Dow Corning Toray, and other companies can be used. Furthermore, in the case of silicone-based surface conditioners, polyether-modified silicone oils with an HLB value of 7.6 to 12 are preferred.

[0091] The amount of the surface conditioner can be appropriately selected depending on the purpose of use, but is preferably 0.01 to 1 mass % in the ink composition. The surface conditioner may be used alone or in combination of two or more types.

[0092] Specific examples of the surface conditioner include BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315N, BYK-320, BYK-322, BYK-323, BYK-325, BYK-326, BYK-330, BYK-331, BYK-333, BYK-342, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-350, BYK-354, BYK-355, BYK-356, BYK-358N, BYK-361N, BYK-370, BYK-375, BYK-377, BYK-378, BYK-381, BYK-392, BYK-394, BYK-399, BYK-3440, BYK-3441, BYK-3455, BYK-3550, BYK-3560, BYK-3565, BYK-3760, BYK-DYNWET 800N, BYK-SILCLEAN 3700, BYK-SILCLEAN 3701, BYK-SILCLEAN 3720, BYK-UV3500, BYK-UV3505, BYK-UV3510, BYK-UV3530, BYK-UV3535, BYK-UV3570, BYK-UV3575, BYK-UV3576 (manufactured by BYK Chemie Japan Co., Ltd. as above), TEGO Flow 300, TEGO Flow 370, TEGO Flow 425, TEGO Flow ATF 2, TEGO Flow ZFS 460, TEGO Glide 100, TEGO Glide 110, TEGO Glide 130, TEGO Glide 406, TEGO Glide 410, TEGO Glide 411, TEGO Glide 415, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Glide 482, TEGO GlideA 115, TEGO GlideB 1484, TEGO GlideZG 400 (manufactured by Evonik Japan Co., Ltd. as above), 501W ADDITIVE, FZ-2104, FZ-2110, FZ-2123, FZ-2164, FZ-2191, FZ-2203, FZ-2215, FZ-2222, FZ-5609, L-7001, L-7002, L-7604, OFX-0193, OFX-0309 FLUID, OFX-5211 FLUID, SF 8410 FLUID, SH3771, SH 3746 FLUID, SH 8400 FLUID, SH 8700 FLUID, Y-7006 (all manufactured by Dow Corning Toray Co., Ltd.), Examples of such polysiloxanes include KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6004, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, X-22-2516, and X-22-4515 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0093] Among these, 501W ADDITIVE, FZ-2104, FZ-2123, FZ-2215, L-7002, OFX-0309 FLUID, OFX-5211 FLUID, SH 8400 FLUID, KF-351A, KF-353, KF-355A, KF-615A, KF-642, KF-644, KF-6004, KF-6011, and KF-6204 are preferred from the viewpoints of structure and HLB.

[0094] The ink composition of the present invention may contain, as other components, additives such as antioxidants, plasticizers, rust inhibitors, solvents, fillers, defoamers, charge control agents, stress relaxation agents, penetrating agents, light-guiding materials, glittering materials, magnetic materials, fluorescent materials, antibacterial agents, antiviral agents, and anti-algae agents, as needed.

[0095] The ink composition of the present invention can be prepared by mixing various components appropriately selected as needed, and, if necessary, filtering the resulting mixture using a filter having a pore size of not more than about 1 / 10 of the nozzle diameter of the inkjet printhead to be used.

[0096] The ink composition of the present invention preferably has a viscosity at 40°C of 5 to 25 mPa·s, more preferably 5 to 15 mPa·s. When the ink viscosity at 40°C is within the above-specified range, good ejection stability can be obtained. The ink viscosity can be measured using a cone-plate viscometer.

[0097] The ink composition of the present invention preferably has a static surface tension of 20 to 35 mN / m, more preferably 23 to 28 mN / m, at 25°C. When the ink surface tension at 25°C is within the above-specified range, good ejection stability can be obtained. The ink surface tension can be measured by a plate method.

[0098] The ink composition of the present invention is preferably a clear ink. In this specification, "clear ink" refers to a clear ink that, when formed into a 30 μm-thick film, has a light transmittance of 80% or more in the wavelength range of 380 to 800 nm, and the light transmittance is preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more. In this specification, the light transmittance is measured in accordance with JIS K7361-1:1997 "Plastics - Test method for total light transmittance of transparent materials - Part 1: Single beam method."

[0099] The ink composition of the present invention is preferably used for surface protection and is suitable as an ink composition for forming a surface protector. Specifically, the ink composition of the present invention is preferably a clear ink for protecting the surface of a decorative layer, particularly a decorative layer containing a dye or an organic pigment. The decorative layer is, for example, a decorative layer formed from at least one of paint, ink (e.g., printing ink, inkjet ink), and powder toner.

[0100] The glass transition temperature of the film formed from the ink composition of the present invention is preferably 15 to 50°C. By setting the glass transition temperature to 15°C or higher, it becomes easier to ensure the blocking resistance required of an ink for forming a surface protective layer. Furthermore, by setting the glass transition temperature to 50°C or lower, it becomes easier to ensure sufficient polymerizability even when the ink is ejected and cured at room temperature without heating, which contributes to improving the weather resistance and abrasion resistance of the resulting coating film. Note that the glass transition temperature when the ink is heated for printing and curing is preferably 60°C or lower.

[0101] In this specification, the glass transition temperature (Tg) of a film formed from an ink composition is calculated using the FOX equation.

[0102] Another aspect of the present invention is a printing method using the ink composition of the present invention. The printing method of the present invention is characterized in that printing (preferably inkjet printing) is performed on the surface of a decorative layer using the ink composition of the present invention described above. The contents described in the description of the ink composition of the present invention also apply to the printing method of the present invention.

[0103] In one embodiment of the printing method of the present invention, the decorative layer is a layer that contains a colorant such as a dye or a pigment and is colored by this, and is decorated by this. The decorative layer is, for example, a decorative layer formed by at least one of paint, ink (e.g., printing ink, inkjet ink), and powder toner.

[0104] In addition to colorants, the decorative layer may contain resins, ultraviolet absorbers, radical scavengers, antioxidants, plasticizers, rust inhibitors, anti-algae agents, antibacterial agents, antiviral agents, fillers, charge control agents, light-guiding materials, lustrous materials, magnetic materials, phosphors, waxes, and the like, as needed.

[0105] In one embodiment of the printing method of the present invention, the decorative layer is formed on at least a part of the surface of a substrate or an undercoat layer formed on the substrate.

[0106] The substrate is not particularly limited, but suitable examples include substrates used in industrial lines. The substrate may be in the form of, for example, a film, a sheet, or a plate. Examples of the substrate material include plastics such as epoxy resin, ABS resin, polycarbonate, polyvinyl chloride, polystyrene, and acrylic resin, particularly polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polypropylene (PP); metals such as iron, stainless steel, and aluminum; wood; cement; concrete; gypsum; calcium silicate; calcium carbonate; and glass. Specific examples of substrates include vinyl chloride sheets, tarpaulin, plastic cardboard, acrylic boards, flexible boards, calcium silicate boards, gypsum slag barite boards, calcium carbonate boards, wood chip cement boards, precast concrete boards, lightweight foamed concrete (ALC) boards, gypsum boards, tiles, and glass plates.

[0107] In order to improve the adhesion and color development of the decorative layer, the substrate may be subjected to a surface treatment, for example, the substrate may have an undercoat layer on its surface.

[0108] In the printing method of the present invention, printing is preferably performed by an inkjet printing method, but is not limited to this, and various printing methods such as gravure printing method, offset printing method, flexographic printing method, screen printing method, coater method, and spray method can also be used.

[0109] Various inkjet printers can be used for inkjet printing. Examples of inkjet printers include inkjet printers that eject ink compositions using a charge control system or a piezoelectric system. Large-format inkjet printers, specifically inkjet printers designed for printing on products produced on industrial lines, can also be used.

[0110] In one embodiment of the printing method of the present invention, a layer covering a decorative layer is formed by printing using the ink composition of the present invention. This layer is preferably a clear layer. In this specification, the clear layer is a film having a thickness of 30 μm and a light transmittance of 80% or more, preferably 90% or more, more preferably 95% or more, and even more preferably 97% or more in a wavelength range of 380 to 800 nm, and can be formed from the above-mentioned clear ink.

[0111] In one embodiment of the printing method of the present invention, when there is a portion of the surface of the substrate or the undercoat layer formed on the substrate where a decorative layer is not present, a layer formed from the ink composition of the present invention may be formed on the surface of the substrate or the undercoat layer formed on the substrate.

[0112] The layer formed by printing using the ink composition of the present invention is cured by irradiation with active energy rays such as ultraviolet rays. Examples of light sources for active energy rays include high-pressure mercury lamps, metal halide lamps, and LED lamps. The wavelength of the active energy rays irradiated to cure this layer preferably overlaps with the absorption wavelength of the photopolymerization initiator, and the dominant wavelength of the active energy rays is preferably 350 to 400 nm. The cumulative light intensity of the active energy rays is 100 to 2000 mJ / cm. 2 It is preferable that the temperature is in the range of

[0113] The ink composition of the present invention can be used to achieve a surface finish such as a glossy finish, a matte finish, etc. by appropriately selecting the ejection conditions for inkjet printing and the subsequent curing conditions. For example, if the ink composition spreads and then hardens over time, it will have a glossy finish, and if the ink droplets harden while remaining in a lens shape, it will have a matte finish.

[0114] Another aspect of the present invention is a printed matter using the ink composition of the present invention. The printed matter of the present invention comprises a decorative layer and a layer located on the decorative layer, and the layer located on the decorative layer is a layer formed by the ink composition of the present invention described above, and is preferably a clear layer. The contents described in the description of the ink composition of the present invention and the printing method of the present invention also apply to the printed matter of the present invention.

[0115] In one embodiment of the printed matter of the present invention, the decorative layer is disposed on at least a portion of the surface of a substrate, an undercoat layer located on the substrate, etc. That is, the printed matter of the present invention can be a printed matter comprising a substrate, a decorative layer located on the substrate, and a layer located on the decorative layer and formed from the ink composition of the present invention, or a printed matter comprising a substrate, an undercoat layer located on the substrate, a decorative layer located on the undercoat layer, and a layer located on the decorative layer and formed from the ink composition of the present invention.

[0116] In one embodiment of the printed matter of the present invention, the layer formed using the ink composition of the present invention is a layer that covers at least a portion of the decorative layer, but it is preferable that the layer formed using the ink composition of the present invention is a layer that covers the entire surface of the decorative layer.

[0117] In one embodiment of the printed matter of the present invention, when there is a portion on the surface of the substrate, undercoat layer, or the like where a decorative layer is not present, a layer formed from the ink composition of the present invention may be disposed on the surface of the substrate, undercoat layer, or the like. [Example]

[0118] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0119] <Ink preparation method> Mixtures containing the components shown in Tables 1 to 6 in the amounts (parts by mass) shown in Tables 1 to 6 were stirred and dissolved to homogenize, and then filtered to prepare the actinic ray-curable inkjet inks shown in Examples 1 to 51 and Comparative Examples 1 to 10.

[0120] The details of the ingredients shown in the table are given below. <Photopolymerizable compound> Compound name / product name (manufacturer), molecular weight (g / mol), Tg (K) 1) Hydroxyethyl acrylate (Kyoeisha Chemical Co., Ltd.), 116, 258 2) Lauryl acrylate (Kyoeisha Chemical Co., Ltd.), 240, 270 3) Acryloylmorpholine (KJ Chemicals Co., Ltd.), 141,418 4) N-vinylcaprolactam (BASF), 139,363 5) (3-Ethyloxetan-3-yl)methyl acrylate (Osaka Organic Chemical Industry Co., Ltd.), 170, 275 6) (2-Methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (Osaka Organic Chemical Industry Co., Ltd.), 200, 266 7) Cyclic trimethylolpropane formal acrylate (Osaka Organic Chemical Industry Ltd.), 200, 300 8) Tetrahydrofurfuryl acrylate (Kyoeisha Chemical Co., Ltd.), 156, 261 9) Isobornyl acrylate (Kyoeisha Chemical Co., Ltd.), 208, 361 10) 4-tertBu cyclohexyl acrylate (Sartomer), 210, 307 11) Benzyl acrylate (Kyoeisha Chemical Co., Ltd.), 162, 279 12) Phenoxyethyl acrylate (Kyoeisha Chemical Co., Ltd.), 192, 278 13) Phenoxydiethylene glycol acrylate (Kyoeisha Chemical Co., Ltd.), 236, 260 14) Ethoxydiethylene glycol acrylate (Kyoeisha Chemical Co., Ltd.) 188, 203 15) Triethylene glycol diacrylate (Kyoeisha Chemical Co., Ltd.), 258, 319 16) 1,6-Hexanediol diacrylate (Kyoeisha Chemical Co., Ltd.), 226, 336 17) Tricyclodecane dimethanol diacrylate (Kyoeisha Chemical Co., Ltd.), 304, 383 18) Pentaerythritol triacrylate (Kyoeisha Chemical Co., Ltd.), 298, 305 19) Dipentaerythritol hexaacrylate (Kyoeisha Chemical Co., Ltd.), 578, 383 20) EBECRYL8402 (Daicel-Allnex Co., Ltd.), <5000, 287 21) Aronix M-6250 (Toagosei Co., Ltd.), <5000, 318 22) Aronix M-8100 (Toagosei Co., Ltd.), <5000, 436 23) Aronix M-7100 (Toagosei Co., Ltd.), <5000, 378 <Photopolymerization initiator> Compound name (manufacturer), molecular weight (g / mol) 24) 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (BASF), 348 25) Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (BASF), 419 <UV absorber> Product name (manufacturer), molecular weight (g / mol) 26) Tinuvin 400 (BASF), 647 27) Tinuvin 405 (BASF), 584 28) Tinuvin 479 (BASF), undisclosed 29) Tinuvin 900 (BASF), 448 30) Tinuvin PS (BASF), 267 <Radical scavenger> Compound name / product name (manufacturer), molecular weight (g / mol), number of functional groups 31) EVERSORB 90(Everlight Chemical), 481, 2 32) Tinuvin 123(BASF), 737, 2 33) Methylhydroquinone (Seiko Chemical Co., Ltd.), 124, 1 34) Dibutylhydroxytoluene (Tokyo Chemical Industry Co., Ltd.), 220, 2 <Resin> Product name (manufacturer), resin type 35) CAB551-00.1 (Eastman), Cellulose acetate butyrate 36) S-LEC BL-2 (Sekisui Chemical Co., Ltd.), polyvinyl acetal 37) AddBond LTH (Evonik), modified polyester

[0121] <Discharge stability> An image was printed on a substrate using an inkjet printer with an actinic radiation-curable inkjet ink composition, and the ejection stability was evaluated visually according to the following criteria. The printing was performed with the distance from the inkjet printer's print head to the substrate set to 1.5 mm. The results are shown in Tables 1 to 6. [Evaluation criteria] ⊚: Printing can be easily performed at a predetermined position without causing nozzle clogging, and any desired printed surface can be obtained by adjusting the discharge amount and curing timing. ◯: Printing can be performed at the specified position without causing nozzle clogging, but adjustment of the ejection amount and curing timing is required. △: No nozzle clogging occurs, but slight deflection occurs. ×: Nozzle clogging occurs, resulting in missing ink droplets, and furthermore, the ink cannot be deposited in the desired position, making it impossible to obtain a clean printed surface.

[0122] <Weather resistance test 1. Yellowing resistance> Accelerated weather resistance (compliant with JIS K 5600-7-7:2008) A polyvinyl chloride sheet was attached to an aluminum substrate, and the actinic radiation-curable inkjet inks shown in Examples 1 to 51 and Comparative Examples 1 to 10 were applied thereto using a bar coater #10. The inks were then irradiated with actinic radiation (dominant wavelength 385 nm) to sufficiently cure the cured film. The color difference ΔE between the L*a*b* colorimetric values ​​and the colorimetric values ​​after 1500 hours of accelerated weather resistance testing was determined and evaluated according to the following criteria. The results are shown in Tables 1 to 6. [Evaluation criteria] ◎: Color difference ΔE from the color measurement value before the test is less than 2 ○: Color difference ΔE from the color measurement value before the test is 2 or more and less than 3 △: Color difference ΔE from the color measurement value before the test is 3 or more and less than 5 ×: Color difference ΔE from the color measurement value before the test is 5 or more

[0123] <Weather resistance test 2. Crack resistance> Accelerated weather resistance (compliant with JIS K 5600-7-7:2008) A cured film was prepared in the same manner as in <Weathering Resistance Test 1. Yellowing Resistance> and subjected to an accelerated weathering test. After the test was continued for 1500 hours, the appearance of the coating film was visually evaluated based on the following criteria. The results are shown in Tables 1 to 6. [Evaluation criteria] ◎: No cracks were observed even after 1500 hours of testing. 〇: Cracks occurred between 1200 and 1500 hours of testing. △: Cracks occurred after 1000-1200 hours of testing. ×: Cracks occurred before 1000 hours of testing.

[0124] <Blocking resistance> For the inks of Examples 1 to 51 and Comparative Examples 1 to 10, each ink was applied to an ester film E5000 (manufactured by Toyobo Co., Ltd.) using a bar coater #10, and then irradiated with active energy rays (dominant wavelength 385 nm) to sufficiently cure the ink, producing a printed product. An unprinted ester film E5000 was placed on top of the cured film so that the entire cured film of the printed product was covered. Furthermore, 0.200 g / cm was applied from above. 2The sample was left for 1 day in an atmosphere at 25° C. under a load of 1000 kJ / cm2, and the blocking resistance was evaluated according to the following criteria. The results are shown in Tables 1 to 6. [Evaluation criteria] ◎: The films peel off completely smoothly, and there are no abnormalities in appearance such as crushing of the film. ○: The films peel off with some noise, but there are no abnormalities in appearance such as film crushing △: When the films were peeled apart, there was slight damage to the film. ×: When the films were peeled off, the coating peeled off.

[0125] <Adhesion> For a printed material obtained in the same manner as in Weather Resistance Test 1 above, 100 crosscuts of 1 mm width were made in the printed layer. The material was then folded at a 90° angle around the crosscut surface, and cellophane tape was thoroughly adhered to the surface. The cellophane tape was then peeled off, and the adhesion was evaluated according to the following criteria. The results are shown in Tables 1 to 6. [Evaluation criteria] ◎: No peeling was observed at the cut area. ○: Peeling of less than 5% was observed at the cut portion. △: Peeling of 5% or more but less than 20% was observed at the cut portion. ×: Peeling of 20% or more was observed at the cut portion.

[0126] [Table 1] TIFF0007756497000002.tif216158

[0127] [Table 2] TIFF0007756497000004.tif215153

[0128] [Table 3] TIFF0007756497000006.tif213155

[0129] [Table 4] TIFF0007756497000008.tif213156

[0130] [Table 5] TIFF0007756497000010.tif228136

[0131] [Table 6] TIFF0007756497000012.tif218162

[0132] In the table, "Proportion of ethylene oxide-containing compound" indicates the proportion (mass %) of compounds containing ethylene oxide as a constituent unit in the ink composition. In the table, "Ratio of cyclic structure-containing compound / photopolymerizable compound" indicates the ratio (mass %) of the cyclic structure-containing photopolymerizable compound in the photopolymerizable compound. In the table, "heterocyclic structure-containing polymerizable compound / photopolymerizable compound" indicates the proportion (mass %) of photopolymerizable compounds having a heterocyclic structure in the photopolymerizable compounds. In the table, "monofunctional polymerizable compound / photopolymerizable compound" indicates the ratio (mass %) of the monofunctional photopolymerizable compound in the photopolymerizable compound. In the table, "AM / DM" indicates the ratio AM / DM of the total number of moles of photopolymerizable functional groups in the photopolymerizable compound AM to the effective number of moles of the radical scavenger DM.

Claims

1. 1. An ink composition for forming a surface protective layer, comprising: (A) a photopolymerizable compound; (B) a photopolymerization initiator; (C) an ultraviolet absorber; and (D) a radical scavenger, wherein the ink composition does not contain a compound containing ethylene oxide as a structural unit, or contains ethylene oxide in an amount of 10% by mass or less; the ratio of the cyclic structure-containing photopolymerizable compound contained in the (A) photopolymerizable compound is within the range of 50 to 100% by mass; the ratio AM / DM of the total number of moles of photopolymerizable functional groups in the (A) photopolymerizable compound to the effective number of moles DM of the (D) radical scavenger is 10 or greater; and the (A) photopolymerizable compound contains 50 to 95% by mass of an (A1) monofunctional photopolymerizable compound and an (A2) polyfunctional photopolymerizable compound.

2. An ink composition for forming a surface protective layer, comprising (A) a photopolymerizable compound, (B) a photopolymerization initiator, (C) an ultraviolet absorber, and (D) a radical scavenger, wherein the ink composition does not contain a compound containing ethylene oxide as a structural unit, or contains ethylene oxide in an amount of 10% by mass or less, the proportion of photopolymerizable compounds having a cyclic structure contained in the (A) photopolymerizable compound is in the range of 50 to 100% by mass, the ratio AM / DM of the total number of moles of photopolymerizable functional groups in the (A) photopolymerizable compound to the effective number of moles DM of the (D) radical scavenger is 10 or more, and the (A) photopolymerizable compound contains a monofunctional photopolymerizable compound having a heterocyclic structure in an amount of 30 to 90% by mass.

3. An ink composition for forming a surface protective layer, comprising: (A) a photopolymerizable compound; (B) a photopolymerization initiator; (C) an ultraviolet absorber; and (D) a radical scavenger, wherein the ink composition does not contain a compound containing ethylene oxide as a structural unit, or contains ethylene oxide in an amount of 10% by mass or less; the proportion of photopolymerizable compounds having a cyclic structure contained in the (A) photopolymerizable compound is in the range of 50 to 100% by mass; the ratio AM / DM of the total number of moles of photopolymerizable functional groups in the (A) photopolymerizable compound to the effective number of moles DM of the (D) radical scavenger is 10 or greater; the (A) photopolymerizable compound comprises 50 to 95% by mass of an (A1) monofunctional photopolymerizable compound and an (A2) polyfunctional photopolymerizable compound; and the (A2) polyfunctional photopolymerizable compound has a plurality of ester bonds and / or urethane bonds in addition to ester bonds derived from (meth)acrylate groups.

4. 3. The ink composition for forming a surface protective layer according to claim 2, wherein the photopolymerizable compound (A) contains 50 to 95 mass% of a monofunctional photopolymerizable compound (A1) and a polyfunctional photopolymerizable compound (A2).

5. The ink composition for forming a surface protective layer according to claim 3, wherein the photopolymerizable compound (A) contains a monofunctional photopolymerizable compound having a heterocyclic structure in an amount within a range of 30 to 90 mass %.

6. (C) The ultraviolet absorber has a molar absorption coefficient of 1.5 × 10 at a wavelength of 385 nm. 3 (l mol -1 ・cm -1 6. The ink composition for forming a surface protective layer according to claim 1, comprising at least an ultraviolet absorber having a molecular weight of 100 or less.

7. The ink composition for forming a surface protective layer according to any one of claims 1 to 6, further comprising a resin.

8. 8. The ink composition for forming a surface protective layer according to claim 1, further comprising at least one of a cellulose derivative and a polyvinyl alcohol derivative.

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