Manufacturing method of printed matter

Abstract

To provide a method for manufacturing a printed matter less prone to breakage while maintaining hardness even when a printed layer built up thick is subjected to heat treatment.SOLUTION: A method for manufacturing a printed matter with a clear layer includes: a first step including forming a clear layer by carrying out printing with an active energy ray-curable clear ink on a substrate or a layer formed on the substrate, followed by curing the clear layer, in which the clear ink includes a polymerizable compound and a photoinitiator, and an average function base number of the polymerizable compound in the clear ink is 1.05 to 1.60; and a second step of heating a printed matter including a cured clear layer.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for producing a printed matter, and more particularly to a method for producing a printed matter in which a thick, raised printed layer maintains its hardness and is resistant to cracking even when subjected to heat treatment. [Background technology]

[0002] In recent years, active energy ray curable inks have been used for decoration. Active energy ray curable inks are cured by irradiation with active energy rays, so they have the advantage of being less susceptible to nozzle clogging and other ejection problems caused by the evaporation and drying of water or organic solvents, as was the case with conventional organic solvent-based inks and water-based inks, and their quick drying properties improve productivity.

[0003] Also under study is a method for obtaining printed matter with excellent design by ink-jet printing using active energy ray-curable ink on a heat-resistant substrate.

[0004] JP 2018-79400 A (Patent Document 1) describes an invention relating to a method for producing a substrate with a printed layer, which comprises coating the surface of a heat-resistant substrate with an undercoat paint, baking and curing the resulting undercoat coating film, and then inkjet printing the surface of the formed undercoat coating film using an active energy ray-curable ink, followed by irradiating the ink with active energy rays to cure the ink and form a printed layer. The invention describes how an acrylic resin having a specific crosslinkable functional group is blended into the undercoat paint and baked to form an undercoat coating film, thereby enabling the formation of a printed layer that has good adhesion and excellent design properties even on non-absorbent substrates such as metals that do not absorb ink.

[0005] JP 2018-83343 A (Patent Document 2) describes an invention of a method for producing a printed matter, in which an active energy ray-curable ink is printed on an underlayer, a printed layer is formed, the printed layer is cured, and then heating is performed. Here, it describes that by using an active energy ray-curable ink containing a compound having a specific structure as a monomer having an ethylenically unsaturated group, and an underlayer containing a functional group capable of reacting with the compound, even in the case of a printed layer formed from an active energy ray-curable ink, a portion derived from the compound present in the printed layer can be reacted with the functional group contained in the underlayer, thereby improving the interlayer adhesion between the printed layer and the underlayer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-79400 A [Patent Document 2] JP 2018-83343 A Summary of the Invention [Problem to be solved by the invention]

[0007] The printing layers described in Patent Documents 1 and 2 are methods for obtaining a printing layer that has good adhesion to non-absorbent substrates such as metals that do not absorb ink, and has excellent design, but the surface protection layer that protects the decorative ink layer has not been fully studied. For example, Patent Document 2 describes that conventionally known paints and inks can be used to form a surface protection layer that protects the printing layer.

[0008] Here, in order to solve the problems of odor and stickiness of the ink layer, it is preferable to subject the printed matter to a heat treatment when printing is performed on a heat-resistant substrate, and this also improves the adhesion of the surface protective layer.

[0009] The present inventors have been studying a method of printing on a heat-resistant substrate such as metal, glass, ceramic, or artificial marble, curing the surface protective layer, and then further heating the substrate, but there is a problem that the surface protective layer cracks or peels off during the heat treatment after printing and curing. In recent years, it has been proposed to apply various designs such as glossy, matte, and lenticular to the surface by using a colorless and transparent clear ink layer using an active energy ray curable ink in addition to protecting the base layer, but when applying such designs, there is a significant problem of cracking and peeling off of the clear ink layer, especially in the thickly deposited portion.

[0010] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a method for producing printed matter in which a thick, raised printed layer maintains its hardness and is less likely to crack even when subjected to heat treatment. [Means for solving the problem]

[0011] As a result of intensive research into achieving the above object, the present inventors have found that by adjusting the average number of functional groups of the polymerizable compound contained in the active energy ray-curable clear ink to 1.05 to 1.60, it is possible to form a clear layer that is resistant to cracking while maintaining hardness against heat treatment after printing and curing, and have thus completed the present invention.

[0012] That is, the method for producing a printed matter of the present invention is a method for producing a printed matter having a clear layer, a first step of printing an active energy ray-curable clear ink on a substrate or on a layer formed on the substrate to form a clear layer, and then curing the clear layer, the clear ink containing a polymerizable compound and a photopolymerization initiator, and the average number of functional groups of the polymerizable compound in the clear ink is 1.05 to 1.60; A second step of heating the print having the cured clear layer; The present invention is characterized by comprising:

[0013] In a preferred embodiment of the method for producing a printed matter of the present invention, the clear layer has a thickness of 10 to 400 μm, and the difference between the minimum thickness and the maximum thickness is 30 μm or more.

[0014] In another preferable embodiment of the method for producing a printed matter of the present invention, the layer formed on the substrate includes a colored layer.

[0015] In another preferable embodiment of the method for producing a printed matter of the present invention, the layer formed on the substrate includes a base coat layer or a primer layer, and a colored layer.

[0016] In another preferable embodiment of the method for producing a printed matter of the present invention, the heating temperature is within a range of 70 to 300°C in the second step. Effect of the Invention

[0017] According to the present invention, it is possible to provide a method for producing a printed matter in which a thick, raised printed layer is resistant to cracking while maintaining hardness even when subjected to heat treatment. [Brief description of the drawings]

[0018] [Figure 1] Pattern A of the clear layer printed for crack resistance evaluation [Diagram 2] Pattern B of the clear layer printed for crack resistance evaluation [Diagram 3] Pattern C of the clear layer printed for crack resistance evaluation [Figure 4] Clear layer printed for crack resistance evaluation (clear layer printed with patterns A, B, and C in order) DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The method for producing a printed matter of the present invention will be described in detail below. The present invention is a method for producing a printed matter having a clear layer, which includes a step of forming a clear layer using an active energy ray-curable clear ink (first step: clear layer forming step) and a step of heating the printed matter having the clear layer (second step: heat treatment step).

[0020] In the method for producing a printed matter of the present invention, the clear layer forming step is a step of printing on a substrate or on a layer formed on the substrate with an active energy ray-curable clear ink to form a clear layer, and then curing the clear layer.

[0021] Here, when printing is performed on the substrate in the clear layer forming step, the clear layer is formed on a part or the whole of the substrate surface. When printing is performed on a layer formed on the substrate, the clear layer is formed on a part or the whole of the surface of the layer formed on the substrate. When printing is performed on a layer formed on a part of the substrate surface, the clear layer may be formed on a part or the whole of the substrate surface that is not covered by the layer. The clear layer may be one layer or two or more layers. When the clear layer is a multi-layer, a thick portion can be easily formed, which makes it possible to impart texture and three-dimensionality according to the design applied to the base.

[0022] The ink used in the clear layer forming process is an active energy ray curable clear ink, and contains a polymerizable compound and a photopolymerization initiator. In this specification, the ink used in the clear layer forming process is also referred to as a clear layer ink.

[0023] In this specification, the actinic radiation curable ink refers to an ink composition that can be cured by irradiation with actinic radiation such as ultraviolet rays, visible light, or electron beams.

[0024] In this specification, the clear ink refers to a clear ink that has a light transmittance of 80% or more in the wavelength range of 380 to 800 nm when a film having a thickness of 30 μm is formed, and the light transmittance is preferably 80% or more, and more preferably 90% 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".

[0025] The polymerizable compound is a compound that undergoes a polymerization reaction via a functional group that exhibits reactivity when irradiated with active energy rays (for example, a polymerizable 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 polymerizable compound may be used alone or in combination of two or more kinds. In the active energy ray-curable clear ink, the amount of the polymerizable compound is preferably 70 to 97% by mass.

[0026] The polymerizable compound is classified into a monofunctional polymerizable compound or a polyfunctional polymerizable compound. Here, the monofunctional polymerizable compound includes a monofunctional polymerizable monomer having one functional group that shows reactivity when irradiated with active energy rays (for example, a monofunctional polymerizable monomer having one polymerizable unsaturated group) and a monofunctional polymerizable oligomer having one functional group that shows reactivity when irradiated with active energy rays (for example, a monofunctional polymerizable oligomer having one polymerizable unsaturated group). The polyfunctional polymerizable compound includes a polyfunctional polymerizable monomer having two or more functional groups that show reactivity when irradiated with active energy rays (for example, a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups) and a polyfunctional polymerizable oligomer having two or more functional groups that show reactivity when irradiated with active energy rays (for example, a polyfunctional polymerizable oligomer having two or more polymerizable unsaturated groups).

[0027] Specific examples of monofunctional polymerizable monomers 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, acryloylmorpholine, tridecyl (meth)acrylate, and lauryl. (Meth)acrylate, dimethylacrylamide, hydroxyethylacrylamide, diethylacrylamide, isopropylacrylamide, dimethylaminopropylacrylamide, diacetone acrylamide, Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-methoxymethylacrylamide, N-methylol acrylamide, N-vinyl caprolactam, 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, t-butylcyclohexyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, E Examples of the methacrylate include O(ethylene oxide)-modified 2-ethylhexyl (meth)acrylate, neopentyl glycol (meth)acrylic acid benzoate, 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 ethoxy-diethylene glycol (meth)acrylate.

[0028] Among the polyfunctional polymerizable monomers, specific examples of polyfunctional polymerizable monomers having two functional groups that show reactivity upon irradiation with active energy rays (bifunctional polymerizable monomers) 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, and 1,4-butanediol di(meth)acrylate. , polytetramethylene glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, dimethylolcyclohexane di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, 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, and dipropylene glycol di(meth)acrylate.

[0029] Specific examples of polyfunctional polymerizable monomers having three or more functional groups that show reactivity when irradiated with active energy rays (polyfunctional polymerizable monomers having three or more functional groups) 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.

[0030] As used herein, the term (meth)acrylate means methacrylate or acrylate, and when a plural prefix is ​​added to the (meth)acrylate, such as di(meth)acrylate, tri(meth)acrylate, etc., each (meth)acrylate moiety may be the same or different.

[0031] In the active energy ray curable clear ink, the amount of the monofunctional polymerizable monomer is preferably 30 to 90% by mass. In the active energy ray curable clear ink, the amount of the polyfunctional polymerizable monomer is, for example, 1 to 50% by mass, preferably 5 to 40% by mass, and particularly preferably 5 to 30% by mass. If the amount of the polyfunctional polymerizable monomer is less than 1% by mass, the curability may decrease, and if it exceeds 50% by mass, the ink layer may be easily cracked when it is a thick film due to the volumetric shrinkage of the printed film during curing. Among the polyfunctional polymerizable monomers, it is preferable to combine a bifunctional polymerizable monomer having an alicyclic structure.

[0032] The active energy ray curable clear ink preferably contains a polyfunctional polymerizable compound having an alicyclic structure as a polymerizable compound. By using a polyfunctional polymerizable compound having an alicyclic structure, a printed film that is difficult to crack even when formed into a thick film can be formed. In this regard, the present inventors presume that a polyfunctional polymerizable compound having an alicyclic structure has the properties of both a cyclic compound and an aliphatic compound, and therefore can suppress the volumetric shrinkage of the printed film during curing, relieve the internal stress in the film, and provide a printed film that is difficult to crack even when formed into a thick film. In addition, it is possible to improve the curability.

[0033] The polyfunctional polymerizable compound having an alicyclic structure is preferably a bifunctional polymerizable monomer having an alicyclic structure, and among these, tricyclodecane dimethanol di(meth)acrylate or cyclohexane dimethanol di(meth)acrylate is particularly preferred.

[0034] In the active energy ray-curable clear ink, the amount of the polyfunctional polymerizable compound having an alicyclic structure is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass. The polyfunctional polymerizable compound having an alicyclic structure may be used alone or in combination of two or more. If the amount of the polyfunctional polymerizable compound having an alicyclic structure is less than 1% by mass, the curability may decrease, and if it exceeds 50% by mass, the ink layer may be easily cracked when it is a thick film due to the volumetric shrinkage of the printed film during curing.

[0035] The active energy ray curable clear ink preferably contains a nitrogen-containing polymerizable compound as a polymerizable compound. By using a nitrogen-containing polymerizable compound, the adhesion of the printed film can be improved. Furthermore, since it is thermosetting, it can react by heating and increase the surface hardness. Although the nitrogen-containing polymerizable compound can cause yellowing of the printed film, by using a silicon-containing compound (II) described later, the heat yellowing resistance can be improved, so that excellent transparency can be provided even when a thick film is formed.

[0036] The nitrogen-containing polymerizable compound is preferably a nitrogen-containing polymerizable monomer. The nitrogen-containing polymerizable compound has a nitrogen-containing group such as an amino group, an amide group, an imide group, a urea group, or a urethane group. In the active energy ray-curable clear ink, the amount of the nitrogen-containing polymerizable compound is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and particularly preferably 3 to 10% by mass. The nitrogen-containing polymerizable compound may be used alone or in combination of two or more kinds.

[0037] The nitrogen-containing polymerizable compound is represented by the structural formula (I) [ka] (In the formula, R 1 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 2is a hydrogen atom or a methyl group). The compound represented by structural formula (I) is highly effective in improving adhesion. Furthermore, since it is thermosetting, it undergoes a reaction by heat treatment and is highly effective in increasing surface hardness.

[0038] In structural formula (I), R 1 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Here, the alkyl group may be a straight chain or a branched chain, and is preferably an alkyl group having 1 to 4 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, and the like. The alkyl group may be unsubstituted or substituted, but is preferably an unsubstituted alkyl group. Examples of the substituent of the alkyl group include halogens. In addition, in structural formula (I), R 2 is a hydrogen atom or a methyl group, and is preferably a hydrogen atom.

[0039] Suitable specific examples of the compound represented by structural formula (I) include Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-methoxymethylacrylamide, and N-methylolacrylamide.

[0040] In the active energy ray-curable clear ink, the amount of the compound represented by structural formula (I) is preferably 1 to 30 mass%, more preferably 2 to 20 mass%, and particularly preferably 3 to 10 mass%. The compound represented by structural formula (I) may be used alone or in combination of two or more kinds.

[0041] From the viewpoint of decreasing the viscosity and improving the ejection properties, the active energy ray-curable clear ink preferably contains phenoxyethyl acrylate as a polymerizable compound.

[0042] From the viewpoint of improving adhesion, the active energy ray curable clear ink preferably contains a hydroxyl group-containing polymerizable monomer as a polymerizable compound, and more preferably contains a hydroxyl group-containing monofunctional polymerizable monomer. Specific examples of the hydroxyl group-containing polymerizable monomer are preferably 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, hydroxyethyl acrylamide, and the like. In the active energy ray curable clear ink, the amount of the hydroxyl group-containing polymerizable monomer is preferably 1 to 15% by mass. The hydroxyl group-containing polymerizable monomer may be used alone or in combination of two or more kinds.

[0043] The active energy ray-curable clear ink preferably contains a polymerizable oligomer as a polymerizable compound. The polymerizable oligomer has little volume shrinkage, and even when formed into a thick film, it is possible to provide a printed film that is not easily cracked when heated. The polymerizable oligomer is preferably an acrylate oligomer. The number of functional groups of the polymerizable oligomer is preferably 2 to 6, and the molecular weight of the polymerizable oligomer is preferably 500 to 30,000, and more preferably 1,000 to 20,000. Here, the molecular weight of the polymerizable oligomer is a weight average molecular weight calculated based on polystyrene.

[0044] Specific examples of acrylate oligomers include urethane acrylate oligomers [acrylate oligomers with multiple urethane bonds (-NHCOO-)], amino acrylate oligomers [amino groups (-NH 2acrylate oligomer having a plurality of -SiO- bonds], epoxy acrylate oligomer [acrylate oligomer having a plurality of epoxy groups], silicone acrylate oligomer [acrylate oligomer having a plurality of siloxane bonds (-SiO-)], ester acrylate oligomer [acrylate oligomer having a plurality of ester bonds (-COO-)], and butadiene acrylate oligomer [acrylate oligomer having a plurality of butadiene units]. Among these, urethane acrylate oligomers are preferred.

[0045] Furthermore, the following acrylate oligomers are known: Beam Set 502H, Beam Set 505A-6, Beam Set 550B, Beam Set 575, Beam Set AQ-17 (manufactured by Arakawa Chemical Industries, Ltd.), AH-600, UA-306H, UA-306T, UA-306I, UA-510H, UF-8001G (Kyoeisha Chemical Co., Ltd.), CN910, CN959, CN963, CN964, CN965NS, CN966NS, CN969NS, CN980NS, CN981NS, CN982, CN983NS, CN985, CN991NS, CN996NS, CN 2920, CN2921, CN8881NS, CN8883NS, CN9001NS, CN9004, CN9005, CN9009, CN9011, CN9021NS, CN9023, CN9028, CN9030, CN917 8NS, CN9290, CN9893NS, CN929, CN989NS, CN968NS, CN9006NS, CN9010NS, CN9025, CN9026, CN9039, CN9062, CN9110NS, CN9029, CN8885NS, CN9013NS, CN973, CN978NS, CN992, CN9167, CN9782, CN9783, CN970, CN971, CN972, CN975NS, CN9165 (manufactured by Sartomer Corporation), U-2PPA, U-6LPA, U-10HA, U-10PA, UA-1100H, U-15HA, UA-53H, UA-33H, U-200PA, UA-200PA, UA-160TM, UA-290TM, UA-4200, UA-4400, UA-122P (manufactured by Shin-Nakamura Chemical Co., Ltd.), New Frontier R-1235, R-1220, RST-201, RST-402, R-1301, R-1304, R-1214, R-1302XT, GX-8801A, R-1603, R-1150D (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), EBECRYL204, EBECRYL205, EBECRYL210, EBECRYL215, EBECRYL220, EBECRYL230, EBECRYL244, EBECRYL245, EBECRYL264, EBECRYL265, EBECRYL270, EBECRY L280 / 15IB, EBECRYL284, EBECRYL285, EBECRYL294 / 25HD, EBECRYL1259, EBECRYL1290, KRM8200, EBECRYL4265, EBECRYL4820, EBECRYL4858, EBECRYL5129, EBECRYL8210, EBECRYL8254, EBECRYL8301R, EBECRYL8307, EBECRYL8402, EBECRYL8405, EBECRYL8411, EBECRYL8465, EBECRYL8800, EBECRYL8804, EBECRYL8807, EBECRYL9260, EBECRYL9270, EBECRYL7735, EBECRYL8296, EBECRYL8452, EBECRYL8904, EBECRYL8311, EBECRYL8701, EBECRYL8667 (manufactured by Daicel-Allnex), UV-1700B, UV-6300B, UV-7550B, UV-7600B, UV-7605B, UV-7610B, UV-7630B, UV-7640B, UV-7650B, UV-6630B, UV-7000B, UV-7510B, UV-7461TE, UV-2000B, UV-2750B, UV-3000B, UV-3200B, UV-3300B, UV-3310B, UV-3700B, UV6640B (manufactured by Nippon Gosei Kagaku Co., Ltd.), Art resin UN-333, UN-350, UN-1255, UN-2600, UN-2700, UN-5590, UN-6060PTM, UN-6200, UN-6202, UN-6300 , UN-6301, UN-7600, UN-7700, UN-9000PEP, UN-9200A, UN-3320HA, UN-3320HC, UN-904, UN-906S (manufactured by Negami Kogyo)

[0046] In the active energy ray-curable clear ink, the amount of the polymerizable oligomer is preferably 1 to 20% by mass, more preferably 5 to 15% by mass. The polymerizable oligomer may be used alone or in combination of two or more. By including 1% by mass or more of the polymerizable oligomer, it is possible to effectively prevent thick film formation and cracking during heating, and to improve the weather resistance of the ink film, and by including 20% ​​by mass or less, it is easy to adjust the ink to a viscosity suitable for a head.

[0047] In the method for producing a printed matter of the present invention, the average number of functional groups of the polymerizable compound in the active energy ray-curable clear ink is 1.05 to 1.60, preferably 1.10 to 1.50, and more preferably 1.20 to 1.40. If the average number of functional groups of the polymerizable compound is within the above-specified range, even if the clear layer has a thick portion, it is possible to prevent cracking of the clear layer that may occur during heat treatment. On the other hand, if the average number of functional groups of the polymerizable compound is too high, the stress in the clear layer cannot be completely released during heat treatment, and the clear layer, especially the thick portion, is likely to crack. In addition, if the average number of functional groups of the polymerizable compound is too low, the hardness of the clear layer is insufficient, making it easy to be scratched and easy to adhere to contaminants.

[0048] [Calculation method for average number of functional groups] In this specification, the term "functional group" in "average number of functional groups" refers to a functional group that exhibits reactivity when irradiated with active energy rays. The average number of functional groups is a value that represents the average number of functional groups per molecule of the polymerizable compound contained in the ink composition.

[0049] The photopolymerization initiator has the effect of initiating polymerization of the above-mentioned polymerizable compound by irradiation with active energy rays. The amount of the photopolymerization initiator in the ink is preferably 1 to 25% by mass, more preferably 3 to 20% by mass, and even more preferably 3 to 15% by mass. If the content of the photopolymerization initiator is less than 1% by mass, the printing layer may not be cured properly, and if it exceeds 25% by mass, precipitation may occur at low temperatures, making the ejection of the ink unstable. Furthermore, in order to promote the initiation reaction of the photopolymerization initiator, it is also possible to use an auxiliary such as a photosensitizer in combination.

[0050] Examples of photopolymerization initiators include benzophenone-based compounds, acetophenone-based compounds, thioxanthone-based compounds, and phosphine oxide-based compounds. From the viewpoint of curability, it is preferable that the wavelength of the irradiated active energy ray overlaps with the absorption wavelength of the photopolymerization initiator as much as possible. In particular, it is preferable that the photopolymerization initiator contains an acylphosphine oxide-based initiator from the viewpoint of improving the yellowing resistance during heating. Although the acylphosphine oxide-based initiator is more likely to cause yellowing of the printed film when cured by irradiation with active energy rays than other initiators, the transparency is improved by subsequent heat treatment. Note that the photopolymerization initiator may be used alone or in combination of two or more types.

[0051] Specific examples of the 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.

[0052] Among these, from the viewpoint of ink curing properties, 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 further from the viewpoint of improving yellowing resistance during heating, 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 preferred, with 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide being particularly preferred.

[0053] The active energy ray-curable clear ink may contain a silicon-containing compound, and may be represented by the following structural formula (II): [ka] (wherein x is 0 or 1; R 1 , R 2 and R 3 are each independently a hydrogen atom or an alkyl group, R 4 is an organic group having 1 to 10 carbon atoms). The compound represented by structural formula (II) is a substance used for the purpose of improving adhesion, but surprisingly, by using the compound represented by structural formula (II), it is possible to improve heat yellowing resistance and provide excellent transparency even when a thick film is formed. In this regard, the present inventor presumes that when the compound represented by structural formula (II) is blended into the ink composition, the compound represented by structural formula (II) bonds with the polymerizable compound in the ink, increasing the crystallinity of the film itself and improving the transparency after heat treatment. In this specification, the compound represented by structural formula (II) is also referred to as (II) silicon-containing compound.

[0054] In structural formula (II), R 1 , R 2 and R 3 are each independently a hydrogen atom or an alkyl group. Here, the alkyl group may be a straight chain or a branched chain, and is preferably an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms. Specific examples include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, and a t-butyl group. The alkyl group may be unsubstituted or substituted, but is preferably an unsubstituted alkyl group. In addition, examples of the substituent of the alkyl group include halogen and the like.

[0055] In structural formula (II), R 4 is an organic group having 1 to 10 carbon atoms. Here, the organic group preferably has at least one functional group showing reactivity to a polymerizable compound, more preferably has one or more polymerizable unsaturated groups such as an acryloyl group, a methacryloyl group, a vinyl group, or a carbon-carbon double bond constituting an allyl group, and further preferably has one or more functional groups such as an acryloyl group or a methacryloyl group. In this specification, the term (meth)acryloyl group means an acryloyl group or a methacryloyl group. Examples of the organic group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a hexyl group, an octyl group, a decyl group, a cyclohexyl group, a phenyl group, a vinyl group, an allyl group, a 2-(3,4-epoxycyclohexyl)ethyl group, a 3-glycidoxypropyl group, a p-styryl group, a 3-methacryloxypropyl group, a 3-acryloxypropyl group, an N-2-(aminoethyl)-3-aminopropyl group, a 3-aminopropyl group, and an N-(1,3-dimethyl-butylidene)propylamino group.

[0056] In structural formula (II), x is 0 or 1.

[0057] (II) Specific examples of silicon-containing compounds include methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, n-propyltrimethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, cyclohexylmethyldimethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyl p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, and N-phenyl-3-aminopropyltrimethoxysilane.Among these, methyltrimethoxysilane, n-propyltrimethoxysilane, phenyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane are preferred.

[0058] The amount of the silicon-containing compound (II) in the active energy ray-curable clear ink is preferably 0.1 to 20 mass%, more preferably 0.5 to 10 mass%, particularly preferably 1 to 5 mass%, and most preferably 2 to 5 mass%. The silicon-containing compound (II) may be used alone or in combination of two or more kinds.

[0059] The active energy ray-curable clear ink preferably contains either an ultraviolet absorbing agent or a radical scavenger, or both an ultraviolet absorbing agent and a radical scavenger.

[0060] The ultraviolet absorbent has the effect of absorbing ultraviolet rays and preventing deterioration caused by ultraviolet rays. Examples of the ultraviolet absorbent include cyanoacrylate compounds, benzophenone compounds, benzoate compounds, benzotriazole compounds, hydroxyphenyltriazine compounds, benzylidene camphor compounds, inorganic fine particles, etc., and among them, hydroxyphenyltriazine compounds that absorb ultraviolet rays at shorter wavelengths are preferred from the viewpoint of curability of the ink. From the viewpoint of curability, it is preferred that the wavelength of the irradiated active energy rays and the absorption wavelength of the ultraviolet absorbent do not overlap as much as possible.

[0061] Specific examples of ultraviolet absorbents 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 with polyethylene glycol, 2-(2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2,6-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate, Examples thereof include hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate.

[0062] In the active energy ray curable clear ink, the amount of the ultraviolet absorbent is preferably within the range of 0.1 to 15% by mass, more preferably 0.1 to 10% by mass, and even more preferably 0.2 to 5% by mass, from the viewpoint of weather resistance. If the amount of the ultraviolet absorbent is too large, the printed layer may not be cured sufficiently. The ultraviolet absorbent may be used alone or in combination of two or more kinds, but it is preferable that the ultraviolet absorbent contains at least two kinds of ultraviolet absorbents. By using multiple kinds of ultraviolet absorbents with different structures, the effect of the ultraviolet absorbent can be further sustained.

[0063] The radical scavenger can capture free radicals and improve light stability. In addition, substances that react with free radicals and have the function of preventing polymerization reactions (so-called polymerization inhibitors) are also included in the radical scavenger. Examples of the radical scavenger include hindered amine compounds, hydroquinone compounds, phenol compounds, phenothiazine compounds, nitroso compounds, and N-oxyl compounds, and particularly preferred are hindered amine light stabilizers (HALS).

[0064] Specific examples of the 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-cresol. phenolic compounds such as 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 4-methylbenzcatechin, t-butylhydroquinone, 3-methylbenzcatechin, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, benzoquinone, t-butyl-p-benzoquinone, and 2,5-diphenyl-p-benzoquinone; phenothiazine compounds; nitroso-based compounds such as N-nitroso-N-phenylhydroxylamine ammonium and N-nitroso-N-phenylhydroxylamine aluminum salt; and N-oxyl-based 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.

[0065] In the active energy ray curable clear ink, the amount of the radical scavenger is preferably within a range of 0.1 to 15 mass%, more preferably 0.1 to 10 mass%, and particularly preferably 0.2 to 5 mass%, from the viewpoint of weather resistance. If the amount of the radical scavenger is too large, it may cause poor curing. The radical scavenger may be used alone or in combination of two or more kinds.

[0066] The active energy ray curable clear ink may contain a colorant such as a dye or pigment as long as it is a clear ink. In this case, it is preferable to contain a pigment from the viewpoint of weather resistance. For example, it is possible to make a metallic ink by using a metal pigment or a pearl pigment. The content of the colorant in the ink is preferably, for example, 0.1 to 5% by mass, and more preferably 0.1 to 1% by mass. The colorant may be used alone or in combination of two or more kinds.

[0067] 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, C.I.Pigment 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、 CIPigment Black 1, 6, 7, 9, 10, 11, 20, 26, 28, 31, 32, 34, CIPigment 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.

[0068] Among these, from the viewpoint of weather resistance and color reproducibility of the printed layer, 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, CI Pigment Violet 19, CI Pigment 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.

[0069] From the viewpoint of ejection stability, the pigment particles dispersed in the ink 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 stably. The volume average particle diameter and the volume maximum particle diameter can be measured by a measuring device using a dynamic light scattering method.

[0070] The active energy ray curable clear ink may further contain a pigment dispersant as necessary to disperse the pigment. The content of the pigment dispersant in the ink is, for example, 0.1 to 5% by mass. The pigment dispersant may be used alone or in combination of two or more kinds.

[0071] Specific examples of the pigment dispersant 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 Chemical Industries, Ltd.), FLOHREN AF-1000, FLOHREN DOPA-15B, FLOHREN DOPA-15BHFS, FLOHREN DOPA-17HF, FLOHREN DOPA-22, FLOHREN DOPA-33, FLOHREN G-600, FLOHREN G-700, FLOHREN G-700AMP, FLOHREN G-700DMEA, FLOHREN G-820, FLOHREN G-900, FLOHREN GW-1500, FLOHREN KDG-2400, FLOHREN NC-500, FLOHREN 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.), Texahol 963, Texahol 964, Texahol 987, Texahol P60, Texahol P61, Texahol P63, Texahol 3250, Texahol SF71, Texahol UV20, Texahol UV21 (all manufactured by Cognis), Examples include BorchiGenSN88 and BorchiGen0451 (both manufactured by Borchias).

[0072] The active energy ray-curable clear ink may further contain a surface conditioner from the viewpoint of improving wettability, etc. In this specification, the 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 by adding it.

[0073] Specific examples of surface conditioners that can be used in active energy ray-curable clear inks 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 surface conditioners. In particular, silicone surface conditioners and acrylic surface conditioners are preferred, and commercially available products from BYK, Evonik, Toray Dow Corning, and the like can be used. Furthermore, in the case of silicone surface conditioners, it is preferred that they are polyether-modified silicone oils with an HLB value of 7.6 to 12.

[0074] The amount of the surface conditioner in the active energy ray-curable clear ink can be appropriately selected depending on the purpose of use, but is preferably, for example, 0.01 to 1 mass % in the ink. The surface conditioner may be used alone or in combination of two or more kinds.

[0075] 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 (The above are manufactured by BYK Chemie Japan Co., Ltd.), 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 (The above are manufactured by Evonik Japan Co., Ltd.), 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 compounds 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.).

[0076] Among these, from the viewpoints of structure and HLB, 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.

[0077] The active energy ray-curable clear ink may contain, as other components, additives such as antioxidants, plasticizers, rust inhibitors, solvents, non-reactive polymers, fillers, defoamers, charge control agents, stress relaxation agents, penetrating agents, light-guiding materials, glittering materials, magnetic materials, and phosphors, as necessary.

[0078] The active energy ray-curable clear ink can be prepared by mixing various components appropriately selected as necessary, and, if necessary, filtering the resulting mixture using a filter having a pore size of approximately 1 / 10 or less of the nozzle diameter of the inkjet printhead to be used.

[0079] The viscosity of the active energy ray-curable clear ink at 40° C. is preferably 5 to 25 mPa·s, and more preferably 5 to 20 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 type viscometer.

[0080] The active energy ray-curable clear ink preferably has a surface tension of 20 to 35 mN / m, more preferably 23 to 33 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.

[0081] In the clear layer formation process, 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, and coater method can also be used.

[0082] In this specification, printing means applying ink onto an object by a printing means, and is not limited to the purpose of coloring the object or drawing characters, images, etc. on the object, but also includes the purpose of covering the surface of the object or performing surface treatment on the object. In this specification, ink for use in inkjet printing methods is also referred to as inkjet ink.

[0083] For inkjet printing, various inkjet printers can be used. Examples of inkjet printers include inkjet printers that eject ink compositions using a charge control method or a piezoelectric method. Large-size inkjet printers, specifically inkjet printers designed for printing on products produced on industrial lines, can also be used.

[0084] In the clear layer forming step, the clear layer is cured by irradiation with light having a peak wavelength preferably in the range of 350 nm to 400 nm. Here, a high pressure mercury lamp, a metal halide lamp, an LED lamp, etc. can be used as the light source. In addition, it is preferable that the wavelength of the active energy ray irradiated to cure the ink layer overlaps with the absorption wavelength of the photopolymerization initiator. Although not particularly limited, for example, the integrated light amount of the active energy ray is 100 to 5,000 mJ / cm. 2 It is preferable that the range is .

[0085] In the clear layer forming process, the active energy ray curable clear ink can be used to perform surface finishing such as glossy or matte by appropriately selecting the ejection conditions of the inkjet printing and the subsequent curing conditions. For example, if the ink is ejected and cured after a certain time (after the ink has spread wet), the surface of the printed matter can be finished in a glossy tone, and if the ink ejected remains lenticular (the ink does not spread wet and the dots remain independent) and hardens, the surface of the printed matter can be finished in a matte tone. Furthermore, the gloss difference can be changed by adjusting the printed image, changing the ink distribution, changing the ink head to change the amount of ink droplets ejected, or changing the number of printing passes. In addition, by forming a thick portion in the clear layer, it is possible to impart texture and three-dimensional effect according to the design applied to the base. There are methods of drawing an image with color ink, forming unevenness with clear ink on it, and imparting texture and three-dimensional effect, and methods of forming unevenness with clear ink and drawing an image with color ink. Complex color shades can be expressed by combining and laminating color ink layers and clear ink layers. When forming a thick film portion with clear ink, a building-shaped convex portion can be formed by stacking the same image. By gradually decreasing the area of ​​the image and stacking it, a sharp-angled mountain-shaped convex portion can be formed. On the other hand, by gradually increasing the area of ​​the image and stacking it, a gentle mountain-shaped convex portion can be formed. When forming a thick portion with a clear layer, a method of increasing the amount of clear ink ejected by changing the ink head, etc., can be mentioned in order to increase the printing efficiency. Furthermore, lenticular printing can also be performed. For example, by ejecting clear ink on a colored layer consisting of two or more colors and forming a clear layer so as to be dome-shaped, a printed matter in which the image changes depending on the viewing angle can be provided. In addition, by combining a clear ink layer or a color ink layer with a clear ink layer, a wide variety of designs can be expressed, such as wood grain, stone grain, brick, leather, sand, concrete, fur, carbon, fabric, tile, glass, metal, ceramic, pearl, paper, Japanese paper, hairline, and etching.

[0086] The substrate can be used without any particular limitation as long as it has heat resistance that can withstand the heating of the printed matter described later. Examples of such materials include metals such as iron, stainless steel, aluminum, copper, titanium, and alloys thereof, cement, concrete, gypsum, calcium silicate, calcium carbonate, marble, artificial marble, glass, ceramics, and the like, and may be a combination of two or more of these materials. In addition, the substrate may have a surface that has been subjected to pretreatment such as degreasing treatment, chemical conversion treatment, and polishing, or may be coated with a sealer or primer. The substrate surface may be smooth, uneven, or three-dimensional. In the present invention, by using a substrate having such materials and properties, the substrate can be suitably used in applications such as furniture, building materials, and small metal items.

[0087] The substrate may have a layer (e.g., a coating film or a printed film) formed on a part or the entire surface thereof, which allows various designs to be applied. For example, a coating film formed from paint, a printed film formed from ink, a printed film formed from powder toner, etc. may be formed on the substrate. The layer formed on the substrate may contain a resin, a colorant such as a dye or pigment, an ultraviolet absorber, a radical scavenger, an antioxidant, a plasticizer, an anti-rust agent, a filler, a charge control agent, a light-guiding material, a glittering material, a magnetic material, a phosphor, wax, etc.

[0088] Examples of paints and inks used when forming a layer on a substrate include organic solvent-based paints and inks that use an organic solvent as the main solvent, water-based paints and inks that use water as the main solvent, active energy ray-curable paints and inks that use a polymerizable compound, powder paints, and various other paints and inks, etc. Here, examples of components that can be used in the active energy ray-curable ink include the components that can be used in the clear layer ink described above.

[0089] In the clear layer forming process, the means for forming a layer on the substrate is not particularly limited. For example, in the case of paint, various coating means such as air spray, airless spray, roll coater, flow coater, electrostatic coating, etc. can be used. In addition, in the case of ink, various printing means such as gravure printing, offset printing, flexographic printing, screen printing, coater printing, inkjet printing, etc. can be used. In the case of powder toner, printing means of electrophotographic development type (specifically, image forming devices such as copiers and laser printers) can usually be used.

[0090] In the clear layer forming step, before printing for forming the clear layer, the layer formed on the substrate may be one or more layers, and in the case of multiple layers, it may be composed of different layers. The configuration of the layer formed on the substrate may include a configuration having a colored layer on the substrate, a configuration having a base coat layer or a primer layer on the substrate, a configuration having a primer layer and a base coat layer in order, a configuration having a base coat layer or a primer layer and a colored layer on the substrate in order, and a configuration having a primer layer, a base coat layer, and a colored layer on the substrate in order. In this specification, the colored layer is a layer mainly intended to color the substrate or to draw characters, images, etc., and the base coat layer or primer layer is a layer mainly intended to cover the surface of the substrate, such as from the viewpoint of improving the adhesion of the colored layer or clear layer and the color development of the colored layer, or the role as a colored layer. As the base coat layer or primer layer, known ones can be applied, for example, the coating layer described in JP-A-2019-77090 or JP-A-2019-162732, the undercoat layer described in JP-A-2018-83343, and the like.

[0091] In the method for producing a printed matter of the present invention, the heat treatment step is a step of heating the printed matter having the clear layer obtained in the clear layer forming step. This can solve the problems of odor and stickiness of the clear layer, etc., and can also improve the adhesion of the clear layer, etc. Here, the heat treatment is carried out, for example, within a range of 70°C to 300°C, and from the viewpoint of yellowing resistance, it is preferably carried out within a range of 70°C to 200°C, and more preferably within a range of 70°C to 180°C.

[0092] The printed matter obtained by the method for producing a printed matter of the present invention has a clear layer on a substrate, and may further have other layers such as a base coat layer, a primer layer, or a colored layer.

[0093] The printed matter obtained by the method for producing a printed matter of the present invention preferably has a clear layer thickness in the range of 10 to 400 μm, and the difference between the minimum thickness and the maximum thickness in the clear layer is preferably 30 μm or more. EXAMPLES

[0094] 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.

[0095] <Ink preparation method> Mixtures were obtained according to the formulations shown in Tables 1 to 3, and actinic ray-curable inkjet inks were prepared.

[0096] The details of the ingredients shown in the formulation are given below. 1) Light Acrylate PO-A, Kyoeisha Chemical Co., Ltd., Phenoxyethyl acrylate 2) Light Acrylate IB-XA, manufactured by Kyoeisha Chemical Co., Ltd., isobornyl acrylate 3) Light Acrylate EC-A, Kyoeisha Chemical Co., Ltd., ethoxy-diethylene glycol acrylate 4) Light Acrylate DPM-A, Kyoeisha Chemical Co., Ltd., methoxydipropylene glycol acrylate 5) Light Acrylate THF-A, Kyoeisha Chemical Co., Ltd., tetrahydrofurfuryl acrylate 6) Light Ester HOA(N), Kyoeisha Chemical Co., Ltd., 2-hydroxyethyl acrylate 7) 4-HBA, Osaka Organic Chemical Industry Co., Ltd., 4-hydroxyethyl acrylate 8) Plaxel FA2D, manufactured by Daicel Chemical Industries, Ltd., an adduct of 2-hydroxyethyl acrylate and ε-caprolactone 9) NBMA, MCC Unitech, Nn-butoxymethylacrylamide 10) Light Acrylate 1.6HX-A, Kyoeisha Chemical Co., Ltd., 1,6-Hexanediol diacrylate 11) Light Acrylate 1.9ND-A, Kyoeisha Chemical Co., Ltd., 1,9-nonanediol diacrylate 12) Light Acrylate DCP-A, Kyoeisha Chemical Co., Ltd., tricyclodecane dimethanol diacrylate 13) Light Acrylate TMP-A, Kyoeisha Chemical Co., Ltd., trimethylolpropane triacrylate 14) EBECRYL230, Daicel-Allnex, urethane acrylate oligomer, molecular weight 5,000 15) EBECRYL4265, Daicel-Allnex, urethane acrylate oligomer, molecular weight 650 16) EBECRYL1290, Daicel-Allnex Corporation, urethane acrylate oligomer, molecular weight 1,000 17) KBM-502, Shin-Etsu Chemical Co., Ltd., 3-methacryloxypropylmethyldimethoxysilane 18) SPEEDCURE TPO, Lambson, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide 19) Omnirad 651, BASF, 2,2-dimethoxy-2-phenylacetophenone

[0097] <Printing process> Inks prepared according to the formulations shown in Tables 1 to 3 are loaded into an inkjet printer, and the surface of an aluminum substrate measuring 0.8 mm x 100 mm x 50 mm is painted with a white acrylic resin paint manufactured by Dai Nippon Toryo Co., Ltd. to prepare a base layer, and a 100 mm x 50 mm image (printed layer) is prepared on the base layer.

[0098] <Pencil hardness> As described above in the <Printing step>, an aluminum plate was painted with an acrylic resin white paint manufactured by Dai Nippon Toryo Co., Ltd. to prepare a base layer. Next, a solid image (thickness: 100 μm) was printed on the base layer by an inkjet printer using active energy ray-curable inkjet ink, and then an active energy ray having a dominant wavelength of 360 to 425 nm was irradiated at 2000 mJ / cm using a metal halide lamp. 2 The image (clear layer) was cured by irradiating the light. Next, the surface temperature of the substrate was raised to 180°C, and the substrate was heated for 20 minutes at that temperature to produce a printed matter. Next, the clear layer of the printed matter was evaluated for pencil hardness by scratch hardness (pencil method) according to JIS K-5600-5-4. The results are shown in Tables 1 to 3.

[0099] <Crack resistance> As described above in the <Printing step>, an aluminum plate was painted with an acrylic resin white paint manufactured by Dai Nippon Toryo Co., Ltd. to prepare a base layer. Next, a solid image was printed in stages on the base layer by an inkjet printer using active energy ray-curable inkjet ink, and then an active energy ray with a dominant wavelength of 360 to 425 nm was irradiated at 2000 mJ / cm using a metal halide lamp. 2 The image (clear layer) was cured by irradiation. Next, the surface temperature of the substrate was raised to 180° C., and heated at that temperature for 20 minutes to produce a printed matter. Specifically, the clear layer printed in stages was prepared by printing and laminating three patterns shown in Figures 1, 2, and 3 with the thicknesses shown in the following evaluation criteria. The results are shown in Tables 1 to 3. ◎: When a clear layer was created with a thickness of 100 μm for pattern A, 150 μm for pattern B, and 150 μm for pattern C, no cracks were observed in the pattern C area of ​​the print. The maximum thickness of the clear layer was 400 μm, and the difference between the minimum thickness (100 μm) and the maximum thickness (400 μm) was 300 μm. ○: When a clear layer was created with a thickness of 80 μm for pattern A, 100 μm for pattern B, and 120 μm for pattern C, no cracks were observed in the pattern C area of ​​the print. The maximum thickness of the clear layer was 300 μm, and the difference between the minimum thickness (80 μm) and the maximum thickness (300 μm) was 220 μm. △: When a clear layer was created with a thickness of 50 μm for pattern A, 100 μm for pattern B, and 100 μm for pattern C, no cracks were observed in the pattern C area of ​​the print. The maximum thickness of the clear layer was 250 μm, and the difference between the minimum thickness (50 μm) and the maximum thickness (250 μm) was 200 μm. ×: When a clear layer was prepared with a thickness of 50 μm for pattern A, 100 μm for pattern B, and 100 μm for pattern C, cracks were observed in the pattern C area of ​​the printed matter. The maximum thickness of the clear layer was 250 μm, and the difference between the minimum thickness (50 μm) and the maximum thickness (250 μm) of the outermost layer was 200 μm.

[0100] [Table 1]

[0101] [Table 2]

[0102] [Table 3]

[0103] <Heat yellowing resistance> A mixture was obtained according to the formulation of Example 1 in Table 1, and an active energy ray-curable inkjet ink was prepared. Printing, curing, and heating were performed in the same manner as described in the above <Pencil hardness>, except that the baking temperature was changed, to produce a printed matter. Next, the clear layer of the printed matter was subjected to color measurement using a spectrophotometer (SpectroEye, manufactured by X-Rite). In the L*a*b* color system, the b value is an index of yellowness. The b values ​​of the printed and non-printed parts were measured, and the difference between these b values ​​was calculated. The heat yellowing resistance was evaluated according to the following evaluation criteria, and the results are shown in Table 4. ◎: Less than 2.0. ○: 2.0 or more and less than 3.0. △: 3.0 or more but less than 4.0. ×:4.0 or higher.

[0104] <Adhesion> Printing, curing and heating were carried out in the same manner as described in the above <Heat yellowing resistance> to produce a printed matter. In addition, a printed matter was produced in the same manner when an acrylic plate was painted with an acrylic urethane resin white paint manufactured by Dai Nippon Toryo Co., Ltd. Regarding the baking temperature, a baking temperature of 100°C or higher was not carried out in consideration of the heat resistance temperature of acrylic. 100 cross cuts of 1 mm width were made on the clear layer of the printed matter, and cellophane tape was sufficiently adhered and then peeled off. Adhesion was evaluated according to the following evaluation criteria. The results are shown in Table 4. ⊚: No peeling was observed at the cut area. ○: Peeling of less than 5% was observed at the cut portion. △: Peeling of 5% or more and less than 20% was observed in the cut area. ×: Peeling of 20% or more was observed at the cut portion.

[0105] [Table 4]

Claims

1. A method for producing a printed matter having a clear layer, comprising: The minimum thickness of the clear layer is 10 μm or more and the maximum thickness is 400 μm or less, and the difference between the minimum thickness and the maximum thickness is 30 μm or more; a first step of printing an active energy ray-curable clear ink on a substrate or on a layer formed on the substrate to form a clear layer, and then curing the clear layer by irradiating the active energy ray, the clear ink containing a polymerizable compound and a photopolymerization initiator, and the average number of functional groups of the polymerizable compound in the clear ink is 1.05 to 1.60; and a second step of heating the printed matter having the cured clear layer.

2. The active energy ray-curable clear ink comprises, as a polymerizable compound, The method for producing a printed matter according to claim 1 , comprising the nitrogen-containing polymerizable compound represented by the following formula (I): 【Chemistry 1】 ... (I) (wherein R 1 is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 2 is a hydrogen atom or a methyl group).

3. The method for producing a printed matter described in claim 1 or 2, wherein the active energy ray-curable clear ink contains a silicon-containing compound represented by the following formula (II): 【Chemistry 2】 ... (II) (In the formula, x is 0 or 1; R 1 , R 2 and R 3 each independently represent a hydrogen atom or an alkyl group; and R 4 represents a polymerizable organic group having 1 to 10 carbon atoms.)

4. The method for producing a printed matter according to any one of claims 1 to 3, wherein the layer formed on the substrate includes a colored layer.

5. The method for producing a printed matter according to any one of claims 1 to 4, wherein the layer formed on the substrate includes a base coat layer or a primer layer, and a colored layer.

6. The method for producing a printed matter according to any one of claims 1 to 5, wherein the heating temperature in the second step is within a range of 70 to 300°C.

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