JP3207784U - Can body - Google Patents

Abstract

Provided is a can body in which an ink layer formed of an ultraviolet curable inkjet ink composition and having excellent adhesion to a coating layer made of a solvent-based paint is formed on an outer peripheral surface having a curvature. A can body 1 is provided on a can base 12 and an outer peripheral surface of curvature of the can base 12, and includes a monofunctional monomer, a polyfunctional monomer, a photopolymerization initiator, and a colorant, and is irradiated with ultraviolet rays. An ink layer 14 made of an ultraviolet curable ink-jet ink composition that is cured by the above, and a coating layer 16 made of a solvent-based paint and laminated on the ink layer 14 to cover the ink layer 14. [Selection] Figure 1

Description

  The present invention relates to a can body.

There is a can in which an image is formed by ink jet printing on the outer peripheral surface of a can made of a cylindrical metal material.
Patent Document 1 discloses a beverage can in which an image is formed by ejecting ink onto an outer peripheral surface of a can body with an inkjet head.

JP2013-169975A

By the way, when an ink layer is formed by inkjet printing using an ultraviolet curable inkjet ink composition that is cured by irradiation of ultraviolet rays with respect to a can body, a solvent system is formed on the ink layer for the purpose of protecting the ink layer. In some cases, a coating layer made of a paint is formed.
The present invention provides a can body in which an ink layer formed of an ultraviolet curable inkjet ink composition and having excellent adhesion to a coating layer made of a solvent-based paint is formed on an outer peripheral surface having a curvature. With the goal.

  A can body to which the present invention is applied is provided on a can base, a curved outer peripheral surface of the can base, a monofunctional monomer (A), a polyfunctional monomer (B), a photopolymerization initiator (C), And an ink layer comprising an ultraviolet curable ink-jet ink composition containing a colorant (D) and cured by irradiation with ultraviolet rays, and a solvent-based coating, which is laminated on the ink layer and covers the ink layer And a layer.

  According to the present invention, a can in which an ink layer formed of an ultraviolet curable ink jet ink composition and having excellent adhesion with a coating layer made of a solvent-based paint is formed on the outer peripheral surface having a curvature of the can body. The body can be provided.

(A)-(b) is the figure which showed the can which printed with the ultraviolet curable inkjet ink composition to which this Embodiment is applied.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Fig.1 (a)-(b) is the figure which showed the can 1 which printed with the ultraviolet curable inkjet ink composition to which this Embodiment is applied. Fig.1 (a) is the figure which showed the outline of the can 1 and FIG.1 (b) is the figure which expanded a part of cross section of Fig.1 (a).
As shown in FIGS. 1A to 1B, the can 1 includes a bottomed cylindrical container portion 10 and a lid member 20 that closes an opening formed in the upper portion of the container portion 10. The container part 10 and the cover member 20 are comprised by metal materials, such as aluminum, for example.

  The container part 10 is laminated on a can base 12 that can be filled with contents, and a curvature outer peripheral surface that is an outer peripheral surface having a curvature of the can base 12, and an ultraviolet curable ink-jet ink composition to be described later is printed by ink jet printing. And a coating layer 16 that is laminated on the ink layer 14 and covers the surface of the ink layer 14. An undercoat layer may be further provided between the outer peripheral surface of the can base 12 and the ink layer 14 for the purpose of improving the adhesion between the can base 12 and the ink layer 14, for example.

The ink layer 14 according to the present embodiment is formed by irradiating ultraviolet rays after an ultraviolet curable inkjet ink composition that is cured by irradiating ultraviolet rays is ejected onto the can base 12 by an inkjet printer. The In the present embodiment, the ultraviolet ray curable inkjet ink composition is used for forming the ink layer 14, and the ink composition is cured in a shorter time than when, for example, a solvent-based or water-based ink composition is used. It becomes possible to make it. Moreover, it becomes possible to reduce the usage-amount of the organic solvent in an ink composition, and can reduce the influence on an environment.
The ultraviolet curable inkjet ink composition forming the ink layer 14 will be described in detail later.

The covering layer 16 of the present embodiment is provided for the purpose of protecting the ink layer 14 or imparting gloss to the surface of the ink layer 14. In addition, by providing the coating layer 16, it is possible to prevent the unreacted photopolymerization initiator or monomer remaining in the ink layer 14 obtained by curing the ultraviolet curable ink jet ink composition from directly touching the human body. be able to.
The coating layer 16 of the present embodiment is formed by applying a solvent-based paint on the ink layer 14 and drying it. The solvent-based paint forming the coating layer 16 will be described in detail later.

  In the present embodiment, the can base 12 has, for example, a bottomed cylindrical shape whose upper portion is opened in the drawing in order to fill the contents. Although it does not specifically limit as a content, For example, it is a drink illustrated by soft drinks, such as alcohols, such as beer, and juice. Further, the can base 12 is not particularly limited as long as it can be filled with the contents. For example, metals such as an aluminum can, a steel can, a tin can and the like can be used. In addition, as the can base 12, a tubular substrate may be used as long as it is made of metal such as aluminum, steel, tin, etc. and has a cylindrical shape.

<Ultraviolet curable inkjet ink composition>
Next, an ultraviolet curable inkjet ink composition to which the present embodiment is applied will be described.
In the present embodiment, the ink composition used to form the ink layer 14 is an ultraviolet curable inkjet ink composition that is cured by ultraviolet irradiation. In the following description, the ultraviolet curable inkjet ink composition may be simply referred to as an ink composition.

  The ink composition of the present embodiment includes a monofunctional monomer (A) and a polyfunctional monomer (B) as a polymerizable compound. Furthermore, the ultraviolet curable inkjet ink composition of the present embodiment includes a photopolymerization initiator (C) and a colorant (D).

Here, in general, an ultraviolet curable ink composition has a larger volume shrinkage ratio upon curing than a solvent-based or water-based ink composition. Therefore, in order to improve the adhesion between the ink layer 14 and the can base 12 or the coating layer 16, the ink layer 14 formed from the ultraviolet curable ink composition is subjected to low crosslinking or low glass transition point (low Tg). It is preferable that
Hereinafter, each component contained in the ink composition will be described in detail.

[Polymerizable compound]
As described above, the ink composition of the present embodiment includes the monofunctional monomer (A) and the polyfunctional monomer (B) as the polymerizable compound. Here, the polymerizable compound means a compound having a radical polymerizable functional group that is reactive when irradiated with ultraviolet rays. Although details will be described later, the ink composition of the present embodiment may contain an acrylate oligomer in addition to the monofunctional monomer (A) and the polyfunctional monomer (B) as the polymerizable compound. In the description of the present embodiment, a radical polymerizable functional group that exhibits reactivity upon ultraviolet irradiation may be simply referred to as a functional group.

  In the ink composition of the present embodiment, the content of the polymerizable compound is preferably in the range of 20% by mass to 95% by mass with respect to the total mass of the ink composition.

(Monofunctional monomer)
As described above, the ink composition of the present embodiment contains the monofunctional monomer (A) as the polymerizable compound. Here, the monofunctional monomer (A) is a monomer having 1 functional group.

In the ink composition of the present embodiment, the content of the monofunctional monomer (A) is 40 in the total mass of the ink composition from the viewpoint of viscosity adjustment of the ink composition, curability or strength of the ink layer 14, and the like. The range is preferably in the range of mass% to 80 mass%, more preferably in the range of 50 mass% to 70 mass%.
When the content of the monofunctional monomer (A) in the ink composition is less than 40% by mass, it becomes difficult to adjust the viscosity of the ink composition to a desired range. On the other hand, when the content of the monofunctional monomer (A) in the ink composition exceeds 80% by mass, the curability or strength of the ink layer 14 may be insufficient.

  Specific examples of the monofunctional monomer (A) used in the ink composition of the present embodiment include stearyl acrylate, acryloylmorpholine, tridecyl acrylate, lauryl acrylate, N, N-dimethylacrylamide, decyl acrylate, phenoxyethyl acrylate, Decyl acrylate, isobornyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, isooctyl acrylate, octyl acrylate, dicyclopentenyloxyethyl acrylate, cyclohexyl acrylate, N-vinylcaprolactam, isoamyl acrylate, 2-ethylhexyl-diglycol Acrylate, EO (ethylene oxide) modified 2-ethylhexyl acrylate, neopentyl glycol acrylic Acid benzoate ester, N-vinyl-2-pyrrolidone, N-vinylimidazole, tetrahydrofurfuryl acrylate, methoxydipropylene glycol acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl) methyl acrylate , Cyclic trimethylolpropane formal acrylate, ethoxy-diethylene glycol acrylate, 2- (2′-vinyloxyethoxy) ethyl acrylate, 2-hydroxyethoxyethyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl Acrylate, 4-hydroxybutyl acrylate, hydroxy (caprolactone modified) 2-ethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate 2-ethylhexyl-diglycol acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl-2-hydroxyethylphthalic acid, polypropylene glycol monoacrylate, 1,4 -Cyclohexane dimethanol monoacrylate etc. are mentioned. Among these, lauryl acrylate, phenoxyethyl acrylate, isobornyl acrylate, methoxydipropylene glycol acrylate, cyclic trimethylolpropane formal acrylate, ethoxy-diethylene glycol acrylate, 2-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxy Ethyl acrylate, 4-hydroxybutyl acrylate, hydroxy (caprolactone modified) 2-ethyl acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and 2- (2′-vinyloxyethoxy) ethyl acrylate are preferred. In addition, these monofunctional monomers (A) may be used individually by 1 type, and may be used in combination of 2 or more type.

In the ink composition of the present embodiment, the monofunctional monomer (A) is a monofunctional monomer having a glass transition point of less than 20 ° C. (Tg <20 ° C.) from the viewpoint of imparting flexibility to the ink layer 14. It is preferable to include.
Moreover, it is preferable that the monofunctional monomer whose glass transition point is less than 20 degreeC is the range of 50 to 100 mass% in the total mass of the said monofunctional monomer (A). When the content of the monofunctional monomer having a glass transition point of less than 20 ° C. is less than 50% by mass in the total mass of the monofunctional monomer (A), the flexibility of the ink layer 14 decreases, and the can base 12 or Adhesion with the coating layer 16 may be reduced.

  Specific examples of the monofunctional monomer having a glass transition point of less than 20 ° C. include stearyl acrylate, tridecyl acrylate, lauryl acrylate, phenoxyethyl acrylate, isodecyl acrylate, cyclohexyl acrylate, tetrahydrofurfuryl acrylate, methoxydipropylene glycol acrylate, Examples include ethoxy-diethylene glycol acrylate, 2-hydroxyethoxyethyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and hydroxy (caprolactone modified) 2-ethyl acrylate. . Among these, phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, methoxydipropylene glycol acrylate, ethoxy-diethylene glycol acrylate, 4-hydroxybutyl acrylate, and hydroxy (caprolactone modified) 2-ethyl acrylate are preferable. In addition, the monofunctional monomer whose glass transition point is less than 20 degreeC may be used individually by 1 type, and may be used in combination of 2 or more type.

(Polyfunctional monomer)
As described above, the ink composition of the present embodiment contains the polyfunctional monomer (B) as the polymerizable compound. Here, the polyfunctional monomer (B) is a monomer having 2 or more functional groups.

In the ink composition of the present embodiment, the content of the polyfunctional monomer (B) is in the total mass of the ink composition from the viewpoint of the strength of the ink layer 14 or the volume shrinkage when the ink composition is cured. The range is preferably 5% by mass or more and 50% by mass or less.
When the content of the polyfunctional monomer (B) in the ink composition is less than 5% by mass, the strength of the ink layer 14 may be insufficient. On the other hand, when the content of the polyfunctional monomer (B) in the ink composition exceeds 50% by mass, the volume shrinkage rate when the ink composition is cured increases, and the adhesion to the can base 12 or the coating layer 16 is improved. May decrease.

  Specific examples of the polyfunctional monomer (B) used in the ink composition of the present embodiment include 1,10-decanediol diacrylate, 2-methyl-1,8-octanediol diacrylate, and 2-butyl-2- Ethyl-1,3-propanediol diacrylate, 1,9-nonanediol diacrylate, 1,7-heptanediol diacrylate, 1,6-hexanediol diacrylate, 1,4-butanediol diacrylate, polytetramethylene Glycol diacrylate, 3-methyl-1,5-pentanediol diacrylate, neopentyl glycol diacrylate, hydroxypivalic acid neopentyl glycol diacrylate, tetraethylene glycol diacrylate, tetrapropylene glycol diacrylate, triethyl Glycol diacrylate, tripropylene glycol diacrylate, diethylene glycol diacrylate, dipropylene glycol diacrylate, 2- (2′-vinyloxyethoxy) ethyl acrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, propoxylation Trimethylolpropane triacrylate, ethoxylated glycerin triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, ethoxylated diglycerin tetraacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol pentaacrylate, dipenta Erythritol hexaac Rate, 2-hydroxy-3-acryloyloxy propyl methacrylate. Among these, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, dipentaerythritol hexa Acrylate, 2- (2′-vinyloxyethoxy) ethyl acrylate, trimethylolpropane triacrylate, and pentaerythritol triacrylate are preferred. In addition, these polyfunctional monomers (B) may be used individually by 1 type, and may be used in combination of 2 or more type.

In the ink composition of the present embodiment, at least one of the monofunctional monomer (A) and the polyfunctional monomer (B) is a hydroxyl group-containing monomer from the viewpoint of imparting adhesion to the coating layer 16 to the ink layer 14. It is preferable to include. Specifically, at least one of the monofunctional monomer (A) or the polyfunctional monomer (B) is
_{CH 2 CR 1 COO (R 2} O) n H
[R ₁ is hydrogen or a methyl group, R ₂ is an alkylene group having 2 to 6 carbon atoms, and n is an integer of 1 to 4]
And / or a compound represented by
_{CH 2 CR 1 COOC 2 H 5} O (CO (CH 2) 5 O) n H
[R ₁ is hydrogen or a methyl group, and n is an integer of 1 to 3]
It is preferable that the compound represented by these is included. In addition, these hydroxyl-containing monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

The ink composition of the present embodiment is a combination of the monofunctional monomer (A) and the polyfunctional monomer (B) from the viewpoint of adhesion of the ink layer 14 to the coating layer 16 and flexibility of the ink layer 14. The quantity ratio (monofunctional monomer (A) / polyfunctional monomer (B)) preferably satisfies the relationship of 2 ≦ (monofunctional monomer (A) / polyfunctional monomer (B)) ≦ 20.
When the blending ratio of the monofunctional monomer (A) and the polyfunctional monomer (B) is less than 2, the crosslink density of the ink layer 14 increases and the adhesion of the ink layer 14 tends to decrease. On the other hand, when the blending ratio of the monofunctional monomer (A) and the polyfunctional monomer (B) exceeds 20, the strength of the ink layer 14 may be insufficient.

(Acrylate oligomer)
The ink composition of the present embodiment may contain an acrylate oligomer as the polymerizable compound from the viewpoint of improving the strength of the ink layer 14. Here, the acrylate oligomer is an oligomer having one or more acryloyloxy groups, and the number of functional groups is preferably 2-6.
When the ink composition includes an acrylate oligomer as the polymerizable compound, the content of the acrylate oligomer is, for example, in the range of 1% by mass to 10% by mass in the total mass of the polymerizable compound.

  Specific examples of the acrylate oligomer include amino acrylate oligomer, urethane acrylate oligomer, epoxy acrylate oligomer, silicone acrylate oligomer, ester acrylate oligomer, and butadiene acrylate oligomer, but are not particularly limited.

In the ink composition of the present embodiment, the average functional group number of the polymerizable compound is preferably in the range of 1.0 to 1.4. Here, the average number of functional groups of the polymerizable compound can be calculated by (total number of functional groups of polymerizable compound in the ink composition / total amount of polymerizable compound in the ink composition). This represents the number of functional groups per molecule.
When the average number of functional groups of the polymerizable compound in the ink composition exceeds 1.4, the crosslink density of the ink layer 14 increases, and the adhesion between the ink layer 14 and the can base 12 or the coating layer 16 may be reduced. .

[Photopolymerization initiator]
Examples of the photopolymerization initiator (C) used in the ink composition of the present embodiment include α-aminoketone compounds, benzophenone compounds, acetophenone compounds, thioxanthone compounds, acylphosphine oxide compounds, and the like. . Among these, from the viewpoint of curability of the ink composition, it is preferable to use a photopolymerization initiator (C) in which the wavelength of the ultraviolet ray irradiated when the ink composition is cured and the absorption wavelength overlap as much as possible. For example, when using ultraviolet light having a dominant wavelength of 360 nm to 425 nm, it is preferable to use an acylphosphine oxide compound as the photopolymerization initiator (C).

  Specific examples of the photopolymerization initiator (C) include 2,2-dimethoxy-1,2-diphenylethane-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- Methylamino-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)], 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone and the like. Among these, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide and bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide are preferable from the viewpoint of curability of the ink composition. In addition, these photoinitiators (C) may be used individually by 1 type, and may be used in combination of 2 or more type.

[Colorant]
Examples of the colorant (D) used in the ink composition of the present embodiment include dyes and pigments. From the viewpoint of the weather resistance of the ink layer 14, it is preferable to use a pigment.
In the ink composition, the content of the colorant (D) can be, for example, 1% by mass or more and 10% by mass or less in the total mass of the ink composition. In addition, a coloring agent (D) may be used individually by 1 type, and may be used in combination of 2 or more type.

Specific examples of the colorant (D) include
C. I. Pigment 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, 91,193,194,199,205,206,209,212,213,214,215,219,
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, 20 208, 209, 210, 211, 213, 214, 216, 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, 282,
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, 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, and hollow particles.

Among these, from the viewpoint of weather resistance and color reproducibility in the ink layer 14, C.I. I. Pigment Black 7,
C. I. Pigment Blue 15: 3, 15: 4, 28,
C. I. Pigment Red 101, 122, 202, 254, 282,
C. I. Pigment Violet 19,
C. I. Pigment White 6,
C. I. It is preferable to use Pigment Yellow 42, 120, 138, 139, 150, 151, 155, 180, 213.

  When a pigment is used as the colorant (D), the volume average particle diameter of the pigment particles present in the ink composition is 0.05 μm or more and 0.4 μm or less from the viewpoint of ejection stability of the ink composition portion in the ink jet head. It is preferable that the volume maximum particle diameter is in the range of 0.2 μm to 1 μm. When the volume average particle diameter of the pigment particles is larger than 0.4 μm or the maximum volume particle diameter is larger than 1 μm, it tends to be difficult to stably eject the ink composition. In addition, the volume average particle diameter and the volume maximum particle diameter of the pigment particles can be measured by a measuring instrument using a dynamic light scattering method.

  In the ink composition of the present embodiment, the blending ratio of the photopolymerization initiator (C) and the colorant (D) in the total mass of the ink composition is 0.5 ≦ (photopolymerization initiator / colorant. ) ≦ 5.0 is preferably satisfied. When the blending ratio of the photopolymerization initiator (C) and the colorant (D) in the total mass of the ink composition is less than 0.5, ultraviolet rays are easily absorbed by the pigment, and the ink composition is sufficiently cured. Sexuality may not be obtained. On the other hand, if the blending ratio of the photopolymerization initiator (C) and the colorant (D) in the total mass of the ink composition exceeds 5.0, the number of radicals generated by ultraviolet irradiation becomes excessive, resulting in a reaction product. In some cases, the molecular weight of the product decreases and the strength of the ink layer 14 decreases.

[Other additives]
In the ink composition of the present embodiment, as other components, a light stabilizer, a polymerization inhibitor, a dispersant, an antioxidant, a surface conditioner, an adhesion promoter, a plasticizer, a rust inhibitor, a solvent, Use additives such as reactive polymers, fillers, pH adjusters, antifoaming agents, charge control agents, stress relaxation agents, penetrating agents, light guide materials, glittering materials, magnetic materials, and phosphors as necessary. Also good.

[Characteristics of ink composition]
The ink composition of the present embodiment has a viscosity at 40 ° C. of preferably 5 mPa · s or more and 30 mPa · s or less, and more preferably 5 mPa · s or more and 20 mPa · s or less. By setting the viscosity of the ink composition at 40 ° C. in such a range, good ejection stability can be achieved when the ink composition is ejected by the inkjet head. The viscosity of the ink composition can be measured using a cone plate viscometer.

  Further, the ink composition of the present embodiment preferably has a surface tension at 25 ° C. in the range of 22 mN / m to 36 mN / m. By setting the surface tension of the ink composition at 25 ° C. in such a range, when the ink composition is ejected by the ink jet head, good ejection stability can be realized. The surface tension of the ink composition can be measured by a platinum plate method.

  In order to produce the ink composition of the present embodiment, a monofunctional monomer (A), a polyfunctional monomer (B), a photopolymerization initiator (C), and a colorant (D) are appropriately selected as necessary. Mix various ingredients. Thereafter, the obtained mixture is filtered using a filter having a pore diameter of about 1/10 or less of the nozzle diameter of the ink jet print head used for forming the ink layer 14 as necessary. Thereby, the ink composition of this Embodiment is obtained.

  In this embodiment, the viscosity and surface of the ink composition are adjusted by adjusting the blending ratio of the monofunctional monomer (A), the polyfunctional monomer (B), and the photopolymerization initiator (C) in the ink composition. The tension can be in a desired range.

<Solvent paint>
Subsequently, in the present embodiment, a solvent-based paint that is applied on the ink layer 14 formed of the ultraviolet curable inkjet ink composition to form the coating layer 16 will be described. In the present embodiment, a solvent-based paint is used to form the coating layer 16.
Examples of the solvent-based paint used in the present embodiment include a room temperature drying solvent-based paint, a bake curable solvent-based paint, and an ultraviolet curable solvent-based paint. Among these, it is preferable to use a bake curable solvent-based paint from the viewpoint of the stability, safety, and productivity of the paint.

  Examples of the bake curable solvent-based paint used for forming the coating layer 16 include alkyl resin-based, acrylic resin-based, vinyl resin-based, polyester resin-based, amino resin-based, polyurethane resin-based, and epoxy resin-based paints. Among these, it is most preferable to use an amino resin-based paint from the viewpoints of coating film hardness and water resistance.

<Method for forming ink layer and coating layer on container substrate>
Next, a method for obtaining the can body 1 by forming the ink layer 14 and the coating layer 16 on the can base 12 will be described.
In the present embodiment, the ink layer 14 is formed on the can base 12 of the can body 1 by ink jet printing using an ink jet printer. Ink-jet printing does not require a plate for forming the ink layer 14, and therefore the cost can be reduced as compared with the case where the ink layer 14 is formed by offset printing. In addition, the design of the ink layer 14 can be changed in a short time compared to the case where the ink layer 14 is formed by offset printing.

Hereinafter, a method for forming the ink layer 14 and the covering layer 16 on the can base 12 will be specifically described.
In the present embodiment, first, an undercoat layer is formed on the outer peripheral surface of the can base 12 made of a cylindrical metal material as necessary. The coating material used for forming the undercoat layer is not particularly limited, and for example, water-based, solvent-based, and ultraviolet curable coating materials can be used.

Subsequently, the ultraviolet curable ink-jet ink composition described above is ejected directly onto the undercoat layer formed on the outer peripheral surface of the can base 12 or directly onto the outer peripheral surface of the can base 12 using an ink-jet head of an ink-jet printer. Etc. are printed. Specifically, an undercoat layer formed on the outer peripheral surface of the can base 12 by rotating the can base 12 in the circumferential direction around the can axis under the ink jet head while discharging the ultraviolet curable ink jet ink composition. Printing is performed on the outer surface of the can base 12.
As the inkjet printer, for example, an inkjet printer that ejects an ink composition by a charge control method or a piezo method can be used.

Next, the ink composition is cured by irradiating the ink composition laminated on the undercoat layer or the outer peripheral surface of the can base 12 with ultraviolet rays, thereby forming the ink layer 14. It is preferable that the wavelength of the ultraviolet ray used for curing the ink composition overlaps with the absorption wavelength of the photopolymerization initiator (C) contained in the ink composition. Moreover, it is preferable that the wavelength of the ultraviolet light used for forming the ink layer 14 has little overlap with the absorption wavelength of the colorant (D) contained in the ink composition.
For the ultraviolet curable inkjet ink composition of the present embodiment, it is preferable to use ultraviolet light having a dominant wavelength of 360 nm to 425 nm. Further, for irradiation with ultraviolet rays, an LED or a metal halide lamp that emits ultraviolet rays can be used.

Subsequently, the above-described solvent-based paint is applied on the ink layer 14. Examples of the method for applying the paint include, but are not limited to, methods using an air spray, an airless spray, a roll coater, a curtain flow coater, and the like.
Thereafter, the coating is dried and cured according to the type of coating to form the coating layer 16. For example, when a baking curable solvent-based paint is used as the paint, the coating layer 16 is formed by baking the paint in an oven or the like. The baking conditions in the case of using the baking curable solvent-based paint are preferably a baking temperature of 100 ° C. to 250 ° C. and a baking time of 10 seconds to 30 minutes.

As described above, the can body 1 including the ink layer 14 laminated on the outer peripheral surface of the can base 12 directly or through the undercoat layer and the coating layer 16 laminated on the ink layer 14 is obtained.
Here, sufficient wettability is obtained by applying a solvent-based paint on the ink layer 14 formed from the ultraviolet curable inkjet ink composition of the present embodiment. As a result, compared with the case where the ultraviolet curable inkjet ink composition of the present embodiment is not used for forming the ink layer 14, the solvent-based paint can be applied without repelling, and the ink layer 14 and the coating layer 16 can be applied. Adhesion is improved.

Then, this invention is demonstrated in detail using an Example. In addition, this invention is not limited to a following example.
(1) Adjustment of ink composition Each raw material was mixed with the compounding ratio shown in Table 1 and Table 2, and the resulting mixture was kneaded with a bead mill to prepare ink composition 1 to ink composition 15, respectively.

1) Ethoxyethoxyethyl acrylate (Kyoeisha Chemical Co., Ltd.)
2) Dipropylene glycol monomethyl acrylate (Kyoeisha Chemical Co., Ltd.)
3) Phenoxyethyl acrylate (Kyoeisha Chemical Co., Ltd.)
4) 2-hydroxyethyl acrylate (Osaka Organic Chemical Co., Ltd.)
5) 4-hydroxybutyl acrylate (Osaka Organic Chemical Co., Ltd.)
6) Isobornyl acrylate (Nippon Shokubai Co., Ltd.)
7) Tetraethylene glycol diacrylate (Kyoeisha Chemical Co., Ltd.)
8) 1,9-nonanediol diacrylate (Kyoeisha Chemical Co., Ltd.)
9) Dipentaerythritol hexaacrylate (Shin Nakamura Chemical Co., Ltd.)
10) Trimethylolpropane triacrylate (Kyoeisha Chemical Co., Ltd.)
11) Photopolymerization initiator (BASF Japan Ltd.)
12) Raven 450 (Colombian Carbon Japan)
13) Sico Yellow FR1252HD (BASF)
14) Heliogen Blue L7080 (BASF)
15) SicoFast Red 3855 (BASF)
16) Pigment dispersant (Bic Chemie Japan Co., Ltd.)

(2) Formation of Ink Layer 14 and Cover Layer 16 on Can Base 12 Each ink composition was applied to the outer peripheral surface of a cylindrical aluminum can having a diameter of 66 mm by an inkjet printer at a coating amount of 5.6 g / m ^2. Printed. Subsequently, the ink composition laminated on the outer peripheral surface of the aluminum can was irradiated with ultraviolet rays using an LED (main wavelength: 385 mm) to cure the ink composition, whereby the ink layer 14 was formed.
Next, a solvent-based melamine coating was applied on each ink layer 14 formed from the ink composition 1 to the ink composition 15 using a roll coater so as to form a film of 5.9 g / m ² after drying. Then, it hardened | cured by heat drying, the coating layer 16 was formed, and the aluminum can of Example 1- Example 15 was obtained.
Similarly, a water-based melamine paint was applied on each ink layer 14 formed from ink composition 1 to ink composition 4 using a roll coater so as to form a film of 5.9 g / m ² after drying. Then, it hardened | cured by heat drying, the coating layer 16 was formed, and Reference Example 1-Reference Example 4 were obtained.

(3) Evaluation test <Evaluation of paintability>
For each of Examples 1 to 15 and Reference Examples 1 to 4, the appearance of the paint when a solvent-based paint and a water-based paint were applied on the ink layer 14 to form the coating layer 16 was observed. The paintability of the paint in the ink layer 14 was evaluated. The evaluation was performed according to the following criteria.
A: No repelling occurs on the ink layer 14 when the paint is applied.
B: When the paint is applied, the ink layer 14 is repelled.

<Pencil hardness evaluation>
The aluminum cans of Examples 1 to 15 having the ink layer 14 and the coating layer 16 formed thereon were subjected to a scratch hardness test described in JIS K 5600-5-4 to evaluate the pencil hardness. The evaluation was performed according to the following criteria.
A: Pencil hardness is H or more.
B: Pencil hardness is F.
C: Pencil hardness is HB or less.

<Adhesion evaluation>
Tests by the cross-cut method described in JIS K 5600-5-6 were performed on the aluminum cans of Examples 1 to 15 in which the ink layer 14 and the coating layer 16 were formed, and the adhesion was evaluated. The evaluation was performed according to the following criteria.
A: It corresponds to the classification 0 in JIS K 5600-5-6.
B: Corresponds to classifications 1 and 2 in JIS K 5600-5-6.
C: Corresponds to classifications 3, 4, and 5 in JIS K 5600-5-6.

(4) Evaluation results Tables 3 to 5 show the configurations of the ink layers 14 and the coating layers 16 of Examples 1 to 15 and Reference Examples 1 to 4, and the results of each evaluation test.

  As shown in Tables 3 to 5, in the aluminum cans of Examples 1 to 15 in which the coating layer 16 formed from the solvent-based paint was laminated on the ink layer 14 formed from the ultraviolet curable inkjet ink composition. It was confirmed that good results were obtained in evaluation tests of paintability, pencil hardness, and adhesion.

  Further, when Examples 1 to 15 are compared with each other, the blending ratio of the monofunctional monomer (A) and the polyfunctional monomer (B) is (monofunctional monomer (A) / polyfunctional monomer (B). In Example 5, it was confirmed that the adhesion ratio was inferior to Example 1 in which the blending ratio of the monofunctional monomer (A) to the polyfunctional monomer (B) was in the range of 2 to 20. In Example 6, where the blending ratio of the monofunctional monomer (A) and the polyfunctional monomer (B) exceeds 20, it was confirmed that the result of the pencil hardness test was inferior to that of Example 1.

Furthermore, in Example 7 in which the average number of functional groups exceeds 1.4, it was confirmed that the adhesiveness was inferior compared to Example 1 in which the average number of functional groups was in the range of 1.0 to 1.4.
Furthermore, in Example 8 and Example 10 in which the content of the monofunctional monomer whose glass transition point is less than 20 ° C. with respect to the total mass of the monofunctional monomer (A) is less than 50% by mass, the glass transition point is 20 ° C. It is confirmed that the adhesion of the ink layer 14 to the can base 12 or the coating layer 16 is inferior to that of Example 1 in which the content of the monofunctional monomer is less than 50% by mass and less than 100% by mass. It was.

  In Reference Examples 1 to 4, in which a coating layer 16 formed from a water-based paint is laminated on an ink layer 14 formed from an ultraviolet curable ink-jet ink composition, the ink layer 14 is applied when the paint is applied. As a result, the paint repelled and a good appearance could not be obtained.

DESCRIPTION OF SYMBOLS 1 ... Can body, 10 ... Container part, 20 ... Lid member, 12 ... Can base | substrate, 14 ... Ink layer, 16 ... Covering layer

Claims (1)

A can base;
It is provided on the outer peripheral surface of curvature of the can base and contains a monofunctional monomer (A), a polyfunctional monomer (B), a photopolymerization initiator (C), and a colorant (D), and is cured by irradiation with ultraviolet rays. An ink layer comprising an ultraviolet curable inkjet ink composition,
A can body comprising a solvent-based paint, and a coating layer laminated on the ink layer and covering the ink layer.

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