JP2022191658A - Ink set, recorded material, recording method, and method for producing recorded material - Google Patents

Abstract

To provide an ink set that can effectively prevent blurred printing even though the ink set is composed of a plurality of ink compositions containing deep-color ink and pale-color ink.SOLUTION: An ink set contains a colorant and an organic solvent. The ink set contains a plurality of nonaqueous ink compositions to be discharged by the inkjet technique. The ink set contains a deep-color ink and a pale-color ink having a smaller colorant content than that of the deep-color ink. At least one of the plurality of nonaqueous ink compositions contained in the ink set contains an organic solvent A (at least one of predetermined alkylamide solvents and predetermined cyclic amide solvents).SELECTED DRAWING: None

Description

The present invention relates to an ink set, a recorded matter, a recording method, and a method for producing a recorded matter.

As ink compositions, non-aqueous ink compositions in which various coloring materials are dissolved or dispersed in a mixed liquid with an organic solvent are widely used. Characters and images can be obtained by applying the ink composition to a substrate such as paper directly or via another layer by an inkjet method, and drying the non-aqueous ink composition.

In recent years, an ink set has been developed that includes a plurality of dark and light inks of the same color but with different color densities. The ink set, which includes a plurality of dark and light inks, colors by changing the amount of the coloring agent that lands per unit area of the recording medium (high and low duty). Recording using such an ink set makes it possible to improve the expression of gradation and output a high-quality color image.

For example, in Patent Document 1, there are a plurality of light-colored inks and a plurality of dark-colored inks. An ink set for ink jet recording is described in which each of the system inks does not contain polymer fine particles or contains polymer fine particles in a smaller amount than the light color ink. Patent Document 1 describes that this ink set for inkjet recording can form characters and/or images excellent in both color developability and abrasion resistance in the same system.

Patent 3612704

Now, when a plurality of ink compositions are ejected onto a substrate (recording medium) by an inkjet method in order to form a desired image, the plurality of ink compositions containing dark-colored ink and light-colored ink are mixed with each other, resulting in poor printing. bleeding may occur.

In particular, the light-colored ink contains less coloring material than the dark-colored ink, so the content of the organic solvent is relatively large. As a result, the content of the organic solvent ejected onto the base material (recording medium) increases, making it more likely that bleeding of the print will occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ink set that can effectively suppress print bleeding even when the ink set is composed of a plurality of ink compositions containing a dark-colored ink and a light-colored ink.

As a result of intensive studies to solve the above problems, the inventors of the present invention have found that an ink set containing a non-aqueous ink composition containing a predetermined organic solvent can solve the above problems, and have completed the present invention. reached. Specifically, the present invention provides the following.

（式（１）中、Ｒ_１は、水素若しくは炭素数１以上４以下のアルキル基であり、Ｒ_２、Ｒ_３は、それぞれ独立して炭素数１以上４以下のアルキル基を表す。

（式（２）中、Ｒ_４は、炭素数３以上５以下のアルキレン基であり、Ｒ_５は、水素若しくは炭素数１以上４以下のアルキル基または不飽和炭化水素基を表す。） (1) An ink set containing a plurality of non-aqueous ink compositions that contain a coloring material and an organic solvent and are ejected by an inkjet method, the ink set comprising a dark-colored ink and a more coloring material than the dark-colored ink. and a light color ink having a low content, wherein at least one non-aqueous ink composition among a plurality of non-aqueous ink compositions contained in the ink set contains an organic solvent A.
Organic solvent A: at least one of an alkylamide solvent (a1) represented by the following formula (1) and a cyclic amide solvent (a2) represented by the following formula (2)

(In Formula (1), R ₁ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each independently represent an alkyl group having 1 to 4 carbon atoms.

(In formula (2), R ₄ is an alkylene group having 3 to 5 carbon atoms, and R ₅ represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an unsaturated hydrocarbon group.)

(2) The ink set according to (1), wherein the content of the organic solvent A is in the range of 1.0% by mass or more and 90% by mass or less in the total amount of the non-aqueous ink composition.

(3) The ink set according to (1) or (2), wherein the organic solvent A contains the alkylamide solvent (a1).

(4) The alkylamide solvent (a1) contains at least one selected from the group consisting of N,N-diethylformamide, N,N-diethylpropanamide, and N,N-diethylacetamide (3 ).

(5) The ink set according to (1) or (2), wherein the organic solvent A contains a cyclic amide solvent (a2).

(6) The ink set according to (5), wherein the cyclic amide solvent (a2) contains at least one selected from the group consisting of ε-caprolactam, N-methyl-ε-caprolactam, and N-vinylcaprolactam. .

(7) Any one of (1) to (6), wherein at least two non-aqueous ink compositions among the plurality of non-aqueous ink compositions contained in the ink set contain an organic solvent A. ink set.

(8) The ink according to any one of (1) to (7), wherein at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set further contains a glycol ether solvent. set.

(9) The ink set according to (8), wherein the glycol ether solvent contains a dialkyl ether.

(10) The ink set according to (8) or (9), wherein the glycol ether solvent contains a monoalkyl ether.

(11) The ink set according to any one of (8) to (10), wherein the glycol ether solvent contains at least two solvents having different flash points.

(12) The ink set according to any one of (1) to (11), wherein the dark-colored ink and the light-colored ink contained in the ink set further contain a resin.

(13) The ratio (B2/B1) of the resin content B1 with respect to 100 parts by mass of the coloring material contained in the dark ink and the resin content B2 with respect to 100 parts by weight of the coloring material contained in the light color ink is The ink set according to (12), which ranges from 2.5 to 8.0.

(14) The ink set according to (12) or (13), wherein the content of the resin is in the range of 1% by mass or more and 15% by mass or less based on the total amount of the non-aqueous ink composition.

(15) The resin contains at least one selected from the group consisting of acrylic resins, vinyl chloride resins, polyurethane resins, polyester resins and cellulose resins, from (12) to ( 14) The ink set described in 14).

(16) A recording method comprising ejecting the non-aqueous ink composition contained in the ink set according to any one of (1) to (15) onto the surface of a substrate by an inkjet method.

(17) The recording method according to (16), wherein the non-aqueous ink composition ejected onto the surface of the substrate is dried by a heating mechanism.

(18) A method for producing recorded matter, comprising ejecting the non-aqueous ink composition contained in the ink set according to any one of (1) to (15) onto the surface of a substrate by an inkjet method.

(19) A recorded matter in which a recording layer of the non-aqueous ink composition contained in the ink set according to any one of (1) to (15) is formed on the surface of a substrate.

The ink set of the present invention can effectively suppress print bleeding even when the ink set is composed of a plurality of ink compositions including a dark-colored ink and a light-colored ink.

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. can do. In addition, in this specification, the notation "to" means "more than" and "less than".

<<1-1. Ink set≫
The ink set according to the present embodiment is composed of a plurality of ink compositions containing a dark color ink and a light color ink. By including such dark-colored ink and light-colored ink, it is possible to improve the expression of gradation.

In this specification, the term “dark-colored ink” means an ink containing a coloring material that is higher than that of a light-colored ink, and the term “light-colored ink” refers to an ink that contains a coloring material that is lower than that of the dark-colored ink. means that

At least one non-aqueous ink composition of the plurality of non-aqueous ink compositions contained in the ink set contains the organic solvent A.

（式（１）中、Ｒ_１は、水素若しくは炭素数１以上４以下のアルキル基であり、Ｒ_２、Ｒ_３は、それぞれ独立して炭素数１以上４以下のアルキル基を表す。 Organic solvent A: at least one of an alkylamide solvent (a1) represented by the following formula (1) and a cyclic amide solvent (a2) represented by the following formula (2)

(In Formula (1), R ₁ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each independently represent an alkyl group having 1 to 4 carbon atoms.

（式（２）中、Ｒ_４は、炭素数３以上５以下のアルキレン基であり、Ｒ_５は、水素若しくは炭素数１以上４以下のアルキル基または不飽和炭化水素基を表す。）

(In formula (2), R ₄ is an alkylene group having 3 to 5 carbon atoms, and R ₅ represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an unsaturated hydrocarbon group.)

By containing the organic solvent A, it is possible to effectively suppress print bleeding in recorded matter obtained even with an ink set comprising a plurality of ink compositions containing a dark-colored ink and a light-colored ink.

<<1-2. Ink set containing non-aqueous ink composition>>
An ink set containing a non-aqueous ink composition will be described below as an example of the ink set according to the present embodiment.

Here, the term “non-aqueous ink composition” refers to an ink composition that does not intentionally contain water (oil-based ink composition It is different from an aqueous ink composition in which a coloring material is dissolved or dispersed in water or a mixture of water and an organic solvent.

The ink set of the present invention may contain, for example, an aqueous ink composition containing water as a main component. In this case, the problem of the occurrence of blurring occurs more remarkably. With the ink set according to the present embodiment containing the ink composition containing the organic solvent A, it is possible to effectively solve the problems of the present invention caused by containing the non-aqueous ink composition.

The ink set of the present invention may contain at least one or more non-aqueous ink compositions, but preferably contains at least three or more non-aqueous ink compositions, and at least seven or more non-aqueous ink compositions. It is more preferred to include an ink composition, and even more preferably all of the ink composition is a non-aqueous ink composition.

Further, in this specification, the phrase "at least one non-aqueous ink composition among the plurality of ink compositions contained in the ink set contains the organic solvent A" means and a light-colored ink, the ink set may be an ink set containing the organic solvent A in one or more of the ink compositions, or may be included in the ink set, and the dark-colored ink and the light-colored ink may be different ink compositions The ink set may contain the organic solvent A in any one or more ink compositions. Since the non-aqueous ink composition containing the organic solvent A dries easily on the substrate (recording medium), if at least one non-aqueous ink composition contained in the ink set contains the organic solvent A, other Even if the non-aqueous ink composition does not contain the organic solvent A, the ink set can achieve the object of the present invention, which is to suppress the bleeding of printing.

In this specification, the phrase "an ink set containing dark-colored ink and light-colored ink" means an ink set containing at least one or more dark-colored inks and light-colored inks. Among these, the dark-colored ink and the light-colored ink are preferably an ink set containing at least two colors of dark-colored ink and a light-colored ink, and an ink set containing at least three colors or more of dark-colored ink and light-colored ink. It is more preferable to have

An ink set containing one dark-colored ink and a light-colored ink means an ink set containing one dark-colored ink, such as yellow ink and light yellow ink, and a light-colored ink. An ink set containing dark ink and light color ink means an ink set containing two dark color inks, such as yellow ink, light yellow ink, cyan ink, and light cyan ink, and light color ink. An ink set including three dark color inks and light color inks is, for example, three dark color inks including yellow ink, light yellow ink, cyan ink, light cyan ink, magenta ink, and light magenta ink, It means an ink set containing light colored inks.

It is sufficient that at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set contains the organic solvent A. It is preferable that two or more non-aqueous ink compositions among the non-aqueous ink compositions contain the organic solvent A, and four or more non-aqueous ink compositions among the plurality of non-aqueous ink compositions contained in the ink set more preferably contains the organic solvent A, and more preferably seven or more of the plurality of non-aqueous ink compositions contained in the ink set contain the organic solvent A, and the ink set contains It is even more preferable that all the non-aqueous ink compositions among the plurality of non-aqueous ink compositions contain the organic solvent A.

In addition, the water content in the non-aqueous ink composition contained in the ink set according to the present embodiment is preferably 1.0% by mass or less, preferably 0.5% by mass or less, based on the total amount of the non-aqueous ink composition. It is more preferable to have When moisture derived from the raw material or moisture from the air during the manufacturing process is mixed, the storage stability of the non-aqueous ink composition may be deteriorated, and solid matter may be generated due to the components contained in the non-aqueous ink composition. . By reducing the water content in the non-aqueous ink composition so that it contains as little water as possible (intentionally avoiding water), the storage stability and the like are more effectively improved. becomes possible.

Hereinafter, among the ink compositions contained in the ink set according to the present embodiment, the non-aqueous ink composition containing the organic solvent A will be described. The ink set according to the present embodiment may contain an ink composition (including a non-aqueous ink composition and an aqueous ink composition) different from the non-aqueous ink composition containing the organic solvent A. .

[Organic solvent]
The organic solvent is capable of dispersing or dissolving each component contained in the non-aqueous ink composition according to this embodiment. The organic solvent contains organic solvent A (at least one selected from the group consisting of alkylamide solvents (a1) and cyclic amide solvents (a2)).

(1) Alkylamide-based solvent The alkylamide-based solvent (a1) is a compound having an alkyl group (C _n H _2n+1 -) and a -C(=O)-N- group (amide bond), Among organic solvents composed of a compound composed of an alkyl group and a —C(═O)—N— group, it is an alkylamide solvent represented by the following general formula (1).

（式（１）中、Ｒ_１は、水素若しくは炭素数１以上４以下のアルキル基であり、Ｒ_２、Ｒ_３は、それぞれ独立して水素若しくは炭素数１以上４以下のアルキル基を表す。

(In Formula (1), R ₁ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms.

R ₂ and R ₃ in formula (1) are preferably alkyl groups having 1 to 4 carbon atoms, and more preferably alkyl groups having 2 to 4 carbon atoms.

Although the alkylamide-based solvent (a1) has a low volatilization rate in a closed space inside a plastic tube, it has a high volatilization rate in an open space. Therefore, by using an alkylamide-based solvent as the organic solvent A, it is possible to effectively suppress print bleeding even with an ink set composed of a plurality of ink compositions containing a dark-colored ink and a light-colored ink. can. The same applies to cyclic amide solvents.

Specific examples of the alkylamide solvent (a1) include N,N-diethylformamide, N,N-diethylacetamide, N,N-dipropylformamide, N,N-dibutylformamide, and N,N-diethylpropane. amide, N,N-dipropylpropanamide, N-ethylformamide, N-ethylacetamide and the like. Among these, from the viewpoint of particularly exhibiting the effects of the present invention, it is preferable to contain at least one selected from the group consisting of N,N-diethylformamide, N,N-diethylpropanamide and N,N-diethylacetamide. preferable.

The content of the alkylamide solvent (a1) is not particularly limited, but the lower limit of the content of the alkylamide solvent (b1) is preferably in the range of 1% by mass or more based on the total amount of the non-aqueous ink composition. The range of 5% by mass or more is more preferable, and the range of 8% by mass or more is even more preferable.

The upper limit of the content of the alkylamide solvent (a1) is preferably 90% by mass or less, more preferably 80% by mass or less, and 75% by mass or less in the total amount of the non-aqueous ink composition. More preferred.

(2) Cyclic amide-based solvent The cyclic amide-based solvent (a2) is a solvent having a cyclic structure and a -C(=O)-N- group in the cyclic structure, and having the following structure: is.

（式（２）中、Ｒ_４は、炭素数３以上５以下のアルキレン基であり、Ｒ_５は、水素若しくは炭素数１以上４以下のアルキル基または不飽和炭化水素基を表す。）

(In formula (2), R ₄ is an alkylene group having 3 to 5 carbon atoms, and R ₅ represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an unsaturated hydrocarbon group.)

An unsaturated hydrocarbon group means a hydrocarbon group containing at least one or more multiple bonds such as a vinyl group.

R ₅ is preferably hydrogen, an alkyl group having 1 to 3 carbon atoms, or an unsaturated hydrocarbon group, and is preferably hydrogen, an alkyl group having 1 to 2 carbon atoms, or an unsaturated hydrocarbon group. preferable.

Specific examples of the cyclic amide solvent (a2) include N-methylcaprolactam, N-acetylcaprolactam, ε-caprolactam, N-vinylcaprolactam, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl- 2-pyrrolidone, N-propyl-2-pyrrolidone, N-ethyl-ε-caprolactam, N-propyl-ε-caprolactam, N-methyl-ε-caprolactam and the like. Among these, it is preferable to contain at least one selected from the group consisting of ε-caprolactam, N-methylcaprolactam, and N-vinylcaprolactam.

The content of the cyclic amide-based solvent (a2) is not particularly limited, but the lower limit of the content of the cyclic amide-based solvent (b2) is preferably in the range of 1% by mass or more based on the total amount of the non-aqueous ink composition. The range of 5% by mass or more is more preferable, and the range of 8% by mass or more is even more preferable.

The upper limit of the content of the cyclic amide solvent (a2) is preferably 90% by mass or less, more preferably 80% by mass or less, and 75% by mass or less in the total amount of the non-aqueous ink composition. More preferred.

Among the organic solvents A, "those containing an alkylamide solvent (a1)" are more preferable. If it "includes the alkylamide solvent (a1)", it becomes a non-aqueous ink composition that exhibits the above effects more effectively.

The organic solvent A sufficiently exhibits the effects of the present invention by containing at least one of the alkylamide solvent (a1) and the cyclic amide solvent (a2). You may mix two or more types. By mixing two or more types, the balance between the ejection stability and the surface dryness of the resulting recorded matter can be made arbitrarily. When two or more kinds of organic solvent A are mixed, the lower limit of the total content of organic solvent A is preferably in the range of 1% by mass or more, and in the range of 5% by mass or more in the total amount of the non-aqueous ink composition. More preferably, it is in the range of 10% by mass or more. The upper limit of the total content of the organic solvent A is preferably 90% by mass or less in the total amount of the non-aqueous ink composition.

(3) Other organic solvents The non-aqueous ink composition contained in the ink set according to the present embodiment may contain an organic solvent other than the organic solvent A described above. Specific examples include glycol ether dialkyl in which the OH groups at both ends of the glycol are alkyl-substituted, glycol ether monoalkyl in which one OH group of the glycol is alkyl-substituted, carbonate esters, and cyclic esters.

Glycol ether solvents include glycol ether dialkyl in which OH groups at both ends of glycol are alkyl-substituted, and glycol ether monoalkyl in which one OH group of glycol is alkyl-substituted. Glycol ether solvents include, for example, those containing at least one of glycol ether dialkyl and glycol ether monoalkyl represented by the following formula (5).

R ₈ —(—OR ₉ ) _n —OR ₁₀ (3)
(In formula (3), R ₈ and R ₁₀ are each independently hydrogen or an optionally branched alkyl group having 1 to 8 carbon atoms, and R ₉ is a branched group having 1 to 4 carbon atoms. (n represents an integer of 1 or more and 6 or less).

Examples of such glycol ether solvents include ethylene glycol mono-n-butyl ether, ethylene glycol mono-isobutyl ether, ethylene glycol mono-t-butyl ether, ethylene glycol mono-2-ethylhexyl ether, diethylene glycol monomethyl (or ethyl, Propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl ether, triethylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl) ether, tetraethylene glycol Monomethyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-isobutyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-2-ethylhexyl ether, dipropylene glycol monomethyl (or ethyl, propyl, isopropyl, n-butyl , isobutyl, t-butyl, 2-ethylhexyl) ether, tripropylene glycol monomethyl ether (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl) ether, tetrapropylene glycol monomethyl ether (or ethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl), alkylene glycol monoalkyl ethers; ethylene glycol dibutyl ether, ethylene glycol dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol dipropyl Ether, diethylene glycol propyl methyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol butyl ethyl ether, diethylene glycol methyl-2-ethylhexyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol ethyl methyl ether, tetraethylene glycol Dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol ethyl methyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, propylene glycol methyl ether pyrether, propylene glycol methyl butyl ether, propylene glycol methyl-2-ethylhexyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol ethyl methyl ether, dipropylene glycol methyl propyl ether, dipropylene glycol dipropyl ether, dipropylene glycol Examples include dialkyl ethers of polyhydric alcohols such as propylene glycol methyl butyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, and tripropylene glycol ethyl methyl ether.

Among these, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol ethyl methyl ether, diethylene glycol dipropyl ether, diethylene glycol propyl methyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, diethylene glycol butyl ethyl ether, diethylene glycol methyl-2-ethylhexyl ether. , triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol ethyl methyl ether, tetraethylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, propylene glycol methyl propyl ether, propylene glycol methyl butyl ether, propylene glycol methyl- 2-ethylhexyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol ethyl methyl ether, dipropylene glycol methyl propyl ether, dipropylene glycol dipropyl ether, tripropylene glycol dimethyl ether, tripropylene glycol ethyl methyl ether, etc. , are preferred.

Moreover, it is preferable to combine two or more types of glycol ether solvents having different flash points among these glycol ether solvents. By containing a glycol ether solvent with a high flash point (for example, a flash point of 70° C. or higher), a non-aqueous ink composition having high recovery from cleaning can be obtained. By containing a glycol ether solvent with a low flash point (for example, a flash point of less than 70° C.), a non-aqueous ink composition with high surface drying property on a substrate can be obtained. By containing a glycol ether-based solvent having a flash point of 70°C or higher and a glycol ether-based solvent having a flash point of lower than 70°C, both high recovery from cleaning and surface drying on the substrate can be achieved.

Moreover, other solvents than the glycol ether solvent may be contained. Specifically, γ-butyrolactone, δ-valerolactone, δ-hexanolactone, ε-caprolactone, γ-valerolactone, γ-hexalactone, γ-heptalactone, γ-octalactone, γ-nonalactone, γ- Cyclic esters such as decalactone, γ-undecalactone, δ-heptalactone, δ-octalactone, δ-nonalactone, δ-decalactone, δ-undecalactone; carbonate esters such as propylene carbonate and ethylene carbonate; 3-methyl- Oxazolidinone solvents such as 2-oxazolidinone, 3-ethyl-2-oxazolidinone, N-vinylmethyloxazolidinone; triethylene glycol butyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol methyl ether acetate, diethylene glycol butyl ether acetate, propylene glycol Acetate solvents such as methyl ether acetate, dipropylene glycol methyl ether acetate, 1-methoxy-2-propyl acetate, 2-methylbutyl acetate, 3-methoxybutyl ether acetate, cyclohexyl acetate; 3-methoxypropanamide, 3- butoxypropanamide, N,N-dimethyl-3-methoxypropanamide, N,N-dibutyl-3-methoxypropanamide, N,N-dibutyl-3-butoxypropanamide, N,N-dimethyl-3-butoxypropane Amide solvents different from alkylamide solvents (a1) such as amides and cyclic amide solvents (a2); methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert -C1-C5 alkyl alcohols such as butyl alcohol, isobutyl alcohol and n-pentanol; 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol , 3-methoxy-n-butanol and other monohydric alcohol solvents; acetone, diacetone alcohol, methyl ethyl ketone, methyl-n-propyl ketone, methyl isopropyl ketone, methyl-n-butyl ketone, methyl isobutyl ketone, methyl-n- amyl ketone, methylhexyl ketone, methyl isoamyl ketone, diethyl ketone, ethyl-n-propyl ketone , ethyl isopropyl ketone, ethyl-n-butyl ketone, ethyl isobutyl ketone, di-n-propyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, methylcyclohexanone, isophorone, acetyl ketone and other ketones or ketoalcohols; tetrahydrofuran, dioxane, etc. Ethers; polyethylene glycol, oxyethylene or oxypropylene copolymer such as polypropylene glycol; ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, Tetraethylene glycol, 1,3-propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4 -butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3 -Diols such as butanediol, 3-methyl-1,5-pentanediol and 2-methyl-2,4-pentanediol; Triols: tetrahydric alcohols such as mesoerythritol and pentaerythritol, monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, N- alkanolamines such as ethyldiethanolamine and N-butyldiethanolamine; acetic acid esters such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, hexyl acetate and octyl acetate; methyl lactate , ethyl lactate, butyl lactate, propyl lactate, ethylhexyl lactate, amyl lactate, and isoamyl lactate; saturated hydrocarbons such as n-hexane, isohexane, n-nonane, isononane, dodecane, and isododecane; Unsaturated hydrocarbons such as 1-heptene and 1-octene; Cyclic unsaturated hydrocarbons such as cyclohexene, cycloheptene, cyclooctene, 1,1,3,5,7-cyclooctatetraene and cyclododecene Hydrocarbons, aromatic hydrocarbons such as benzene, toluene and xylene, morpholines such as N-methylmorpholine, N-ethylmorpholine and N-formylmorpholine, terpene solvents; dimethyl oxalate, diethyl oxalate, malonic acid Dibasic acid esters such as dimethyl, diethyl malonate, dipropyl malonate, dimethyl succinate, diethyl succinate, dimethyl glutarate, and diethyl glutarate. It is preferable to select a solvent with an appropriate HLB value according to the resin, dispersant, etc. to be combined.

The content of the other organic solvent is not particularly limited, but the lower limit of the content of the other organic solvent is preferably in the range of 10% by mass or more, and more preferably in the range of 20% by mass or more. , 30% by mass or more. The upper limit of the content of other organic solvents is preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.

[Color material]
Of the ink compositions contained in the ink set according to the present embodiment, at least the dark-colored ink and the light-colored ink contain coloring materials. By containing the coloring material, the ink set can form a desired image.

The coloring material is not particularly limited, and may be a dye-based or a pigment-based coloring material. pigment-based coloring materials) are preferably used. The pigment that can be used in the ink composition included in the ink set according to the present embodiment is not particularly limited, and examples thereof include organic pigments and inorganic pigments that are used in conventional ink compositions. These may be used individually by 1 type, or may be used in combination of 2 or more type.

When a pigment is used in the non-aqueous ink composition contained in the ink set according to the present embodiment, the dispersion stability of the pigment is improved by using a dispersant or dispersion aid (pigment derivative) described later. be able to.

Specific organic pigments include, for example, insoluble azo pigments, soluble azo pigments, derivatives from dyes, phthalocyanine-based organic pigments, quinacridone-based organic pigments, perylene-based organic pigments, perinone-based organic pigments, azomethine-based organic pigments, and anthraquinone-based pigments. Organic pigments (anthrone-based organic pigments), xanthene-based organic pigments, diketopyrrolopyrrole-based organic pigments, dioxazine-based organic pigments, nickel azo-based pigments, isoindolinone-based organic pigments, pyranthrone-based organic pigments, thioindigo-based organic pigments, condensed azo organic solid solution pigments such as organic pigments, benzimidazolone organic pigments, quinophthalone organic pigments, isoindoline organic pigments, quinacridone solid solution pigments, perylene solid solution pigments, and other pigments such as lake pigments and carbon black. be done.

When organic pigments are exemplified by color index (C.I.) numbers, C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 20, 24, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 117, 120, 125, 128, 129, 130, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, 213, 214, C.I. I. Pigment Red 5, 7, 9, 12, 48, 49, 52, 53, 57: 1, 97, 112, 122, 123, 146, 149, 150, 168, 177, 180, 184, 192, 202, 206, 208, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 269, 291, C.I. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71, 73, C.I. I. pigment violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 16, 22, 60, 64, C.I. I. Pigment Green 7, 36, 58, 59, 62, 63, C.I. I. Pigment Brown 23, 25, 26, C.I. I. Pigment Black 7 and the like.

Specific examples of dyes that can be used in the non-aqueous ink composition included in the ink set according to the present embodiment include azo dyes, benzoquinone dyes, naphthoquinone dyes, anthraquinone dyes, cyanine dyes, and squarylium dyes. dyes, croconium dyes, merocyanine dyes, stilbene dyes, diarylmethane dyes, triarylmethane dyes, fluoran dyes, spiropyran dyes, phthalocyanine dyes, indigo dyes such as indigoids, fulgide dyes, nickel Examples include complex dyes and azulene dyes.

Specific examples of inorganic pigments that can be used in the non-aqueous ink composition contained in the ink set according to the present embodiment include titanium oxide, barium sulfate, calcium carbonate, zinc oxide, barium carbonate, silica, talc, and clay. , synthetic mica, alumina, zinc oxide, lead sulfate, yellow lead, zinc yellow, red iron oxide (III), cadmium red, ultramarine blue, Prussian blue, chromium oxide green, cobalt green, amber, titanium black, aluminum, titanium , indium, synthetic iron black, inorganic solid solution pigments, and the like.

In the non-aqueous ink composition contained in the ink set according to the present embodiment, the average dispersed particle size of the pigment that can be contained is not particularly limited as long as the desired color development is possible. Although it varies depending on the type of pigment used, the volume average particle diameter is preferably 5 nm or more, preferably 20 nm or more, from the viewpoint of good dispersibility and dispersion stability of the pigment and obtaining sufficient coloring power. is more preferable, and 30 nm or more is even more preferable. When the volume average particle size is at least the above lower limit, the light resistance of the non-aqueous ink composition can be improved. The volume average particle size is preferably 300 nm or less, more preferably 200 nm or less, and even more preferably 150 nm or less. When the non-aqueous ink composition is a non-aqueous inkjet ink composition that is ejected onto the surface of a substrate by an inkjet method, the ejection stability of inkjet is improved by adjusting the volume average particle diameter to be equal to or less than the above upper limit. can be made In the present embodiment, the volume average particle diameter of the pigment is the volume average particle diameter (D50 ).

Moreover, in the ink set according to the present embodiment, the volume average particle diameters of the pigments contained in the respective non-aqueous ink compositions may be the same, or may be different.

In the ink set according to the present embodiment, the content of the pigment contained in the non-aqueous ink composition is not particularly limited as long as a desired image can be formed, and is appropriately adjusted. Specifically, it is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on the total amount of the non-aqueous ink composition, although it varies depending on the type of pigment. It is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total amount of the non-aqueous ink composition. When the content of the pigment is in the range of 0.05% by mass or more and 20% by mass or less, the balance between the dispersion stability and the coloring power of the pigment can be excellent.

In addition, the non-aqueous ink composition according to the present embodiment is not particularly limited in the color to be recorded (printed), and coloring materials may be selected and used in combination depending on the intended color. Colors can also be used for each color ink such as yellow, magenta, cyan, black, light magenta, light cyan, light black, orange, green, red, white, and the like. At this time, coloring materials of the same color may be selected.

[Dispersant]
A dispersant may be used as necessary in the non-aqueous ink composition contained in the ink set according to the present embodiment. Any dispersant used in non-aqueous ink compositions can be used as the dispersant. As the dispersant, a polymer dispersant is preferably used. Such a dispersant has a main chain of polyester, polyacrylic, polyurethane, polyamine, polycaprolactone, etc., and has a polar group such as an amino group, a carboxyl group, a sulfone group, or a hydroxyl group as a side chain. is. For polyacrylic dispersants, for example, Disperbyk-2000, 2001, 2008, 2009, 2010, 2020, 2020N, 2022, 2025, 2050, 2070, 2095, 2150, 2151, 2155, 2163, 2164, BYKJET-9130, 9131 , 9132, 9133, 9151 (manufactured by Vic Chemie), Efka PX4310, PX4320, PX4330, PA4401, 4402, PA4403, 4570, 7411, 7477, PX4700, PX4701 (manufactured by BASF), TREPLUS D-1200, D-1410, D-1420, MD-1000 (manufactured by Otsuka Chemical Co., Ltd.), Floren DOPA-15BHFS, 17HF, 22, G-700, 900, NC-500, GW-1500 (manufactured by Kyoeisha Chemical Co., Ltd.), and the like are used. Polycaprolactone-based dispersants include, for example, Ajisper PB821, PB822, PB881 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), Hinoact KF-1000, T-6000, T-7000, T-8000, T-8000E, T-9050 ( Kawaken Fine Chemicals Co., Ltd.), Solsperse 20000, 24000, 32000, 32500, 32550, 32600, 33000, 33500, 34000, 35200, 36000, 37500, 39000, 71000, 76400, 76500, 86000, 88000, J10 TEGO Dispers 652, 655, 685, 688, 690 (manufactured by Evonik Japan) and the like are used.好ましい分散剤としては、ＢＹＫＪＥＴ－９１３０、９１３１，９１３２，９１３３，９１５１、ＥｆｋａＰＸ４３１０、ＰＸ４３２０、ＰＸ４３３０、ＰＸ４７００、ＰＸ４７０１、Ｓｏｌｓｐｅｒｓｅ２００００、２４０００、３２０００、３３０００、３３５００、３４０００、３５２００、３９０００、７１０００、７６５００、８６０００、 88000, J180, J200, TEGO Dispers 655, 685, 688, 690, etc. are used. These individual or mixtures thereof can be used.

[Dispersing aid]
A dispersing aid may be used as necessary in the non-aqueous ink composition contained in the ink set according to the present embodiment. The dispersing aid is adsorbed on the surface of the coloring material (pigment), and the functional group increases affinity with the organic solvent and dispersant in the non-aqueous ink composition, thereby improving dispersion stability. As the dispersing aid, a known pigment derivative having a functional group such as an acidic group, a basic group, or a neutral group in the organic pigment residue can be used.

[resin]
The non-aqueous ink composition contained in the ink set according to the present embodiment may not contain a resin, but may contain a resin. At least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set contains a resin, thereby improving the fixability, water resistance, and stretchability of the recording layer formed from the non-aqueous ink composition. can be improved. Furthermore, the glossiness of the obtained recorded matter can be improved.

In this specification, the phrase “at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set contains a resin” refers to the dark ink contained in the ink set. , light-colored inks, and ink compositions containing a resin in at least one of the ink compositions, or the ink set includes ink compositions of dark-colored inks and light-colored inks that are different from each other. It may be an ink set containing a resin in any one or more ink compositions.

Among these, the dark color ink and the light color ink contain a resin, the resin content B1 with respect to 100 parts by mass of the coloring material contained in the dark ink, and the resin content B1 with respect to 100 parts by mass of the coloring material contained in the light color ink It is preferable that the ratio (B2/B1) of B2 is in the range of 2.5 or more and 8.0 or less. Within this range, the content of the coloring material contained in the light-colored ink is relatively small, so that it is possible to effectively improve the expression of gradation. In addition, B2/B1 is more preferably 3.0 or more, and further preferably 3.2 or more. B2/B1 is more preferably 7.0 or less, even more preferably 6.5 or less.

Examples of resins include, but are not limited to, acrylic resins, polystyrene resins, polyester resins, vinyl chloride resins, vinyl acetate resins, vinyl chloride vinyl acetate copolymer resins, polyethylene resins, polyurethane resins, and rosin-modified resins. Resin, phenolic resin, terpene resin, polyamide resin, vinyltoluene-α-methylstyrene copolymer, ethylene-vinyl acetate copolymer, cellulose acetate butyrate, cellulose acetate propionate, silicone (silicon) Resins, acrylamide-based resins, epoxy-based resins, or copolymer resins or mixtures thereof can be used. Among these, those containing acrylic resins, vinyl chloride resins, cellulose resins, polyester resins, and polyurethane resins are preferable.

The acrylic resin is not particularly limited as long as it is contained as a main component of the monomer constituting the (meth)acrylic acid ester monomer. The acrylic resin may be a homopolymer of one kind of radically polymerizable monomer, or may be a copolymer of two or more kinds of selected radically polymerizable monomers. A preferred acrylic resin for the non-aqueous ink composition according to the embodiment is a polymer of methyl methacrylate, or selected from the group consisting of methyl methacrylate, butyl methacrylate, ethoxyethyl methacrylate, and benzyl methacrylate. It is a copolymer with at least one or more compounds that are Examples of commercially available (meth)acrylic resins include "Paraloid B99N", "Paraloid B60", "Paraloid B66" and "Paraloid B82" manufactured by Rohm and Haas.

The vinyl chloride resin may be either a homopolymer composed of a vinyl chloride monomer or a copolymer using two or more selected polymerizable monomers. Examples of copolymers of vinyl chloride resins include vinyl chloride-vinyl acetate copolymer resins. A vinyl chloride-vinyl acetate copolymer resin is a polymer of vinyl chloride monomer and vinyl acetate monomer. Vinyl chloride-vinyl acetate copolymer resins include, for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride/vinyl acetate/maleic acid copolymer, vinyl chloride/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinyl acetate / hydroxyalkyl acrylate copolymers, etc., and mixtures thereof. Examples of the vinyl chloride-vinyl acetate copolymer resins include "SOLBIN C", "SOLBIN CL", "SOLBIN CNL", "SOLBIN CLL", "SOLBIN CLL2", and "SOLBIN C5R" from Nissin Chemical Industry Co., Ltd. ”, “SOLBIN TA2”, “SOLBIN TA3”, “SOLBIN A”, “SOLBIN AL”, “SOLBIN TA5R”, “SOLBIN M5” and the like.

A vinyl chloride-vinyl acetate copolymer resin can be obtained by polymerizing a vinyl chloride monomer and a vinyl acetate monomer. A conventionally known polymerization method may be used as the polymerization method. The polymerization method is preferably emulsion polymerization or suspension polymerization, more preferably suspension polymerization.

A cellulose-based resin is a resin having a cellulose skeleton obtained by biologically or chemically introducing a functional group using cellulose as a raw material. For example, cellulose-based resins include cellulose acetate butyrate resins, cellulose acetate propionate resins, cellulose acetate alkylate resins such as cellulose acetate propionate butyrate resins, cellulose acetate resins, nitrocellulose resins, and mixtures thereof. mentioned. Examples of the cellulose resins include "CAB551-0.01", "CAB551-0.2", "CAB553-0.4", "CAB531-1", "CAB381-0.1" and "CAB381-0.1" available from EASTMAN. 5”, “CAB381-2”, “CAB381-20”, “CAP504”, “CAP482-0.5” and the like.

A polyester resin contains at least a structural unit obtained by polycondensation of an alcohol component and a carboxylic acid component. The polyester-based resin may include a modified polyester-based resin. Examples of polyester resins include "VYLON226", "VYLON270", "VYLON560", "VYLON600", "VYLON630", "VYLON660", "VYLON885", "VYLONGK250", "VYLONGK810", "VYLON GK890" manufactured by Toyobo Co., Ltd. It can be obtained and used under trade names such as "elitleUE-3200", "elitleUE-3285", "elitleUE-3320", "elitleUE-9800" and "elitleUE-9885" manufactured by Unitika.

A polyurethane resin contains at least a structural unit obtained by copolymerizing an alcohol component and an isocyanate component. Polyurethane-based resins may include polyurethane-based resins modified with polyester, polyether, or caprolactone. Examples of the polyurethane-based resins include "Uriano KL-424", "Uriano KL-564", "Uriano KL-593", and "Uriano 3262" available from Arakawa Chemical Industries, Ltd., and "Pandex 372E" and "Uriano 372E" available from DIC. Pandex 390E”, “Pandex 394E”, “Pandex 304”, “Pandex 305E”, “Pandex P-870”, “Pandex P-910”, “Pandex P-895”, “Pandex 4030", "Pandex 4110", and the like.

Further, these acrylic resins, vinyl chloride resins, cellulose resins, polyester resins, and polyurethane resins may be used alone, but it is preferable to use two of them in combination. It is more preferable to use a resin in which a resin and a vinyl chloride resin are mixed. The content ratio of the acrylic resin and the vinyl chloride resin can be controlled so as to meet the requirements for the non-aqueous ink composition, such as color development, drying property, coating properties, printability, and the like. When an acrylic resin and a vinyl chloride resin are mixed, the mixing ratio is not particularly limited and can be changed as appropriate.

The resin contained in the non-aqueous ink composition is not particularly limited, but it is preferably contained in the range of 0.05% by mass or more, and contained in the range of 0.1% by mass or more, based on the total amount of the non-aqueous ink composition. is more preferable, and it is even more preferable to contain in the range of 0.5% by mass or more. As a result, the surface drying property of the resulting recorded matter can be improved. The resin contained in the non-aqueous ink composition is preferably contained in the range of 15.0% by mass or less, more preferably 12.0% by mass or less, based on the total amount of the non-aqueous ink composition. It is more preferable to contain in the range of 10.0% by mass or less. This makes it possible to more effectively eliminate clogging in the nozzles of the inkjet head, improve the ejection stability and recovery from cleaning, and improve the storage stability of the non-aqueous ink composition.

[Surfactant]
In the non-aqueous ink composition according to the present embodiment, for the purpose of suppressing volatilization of the non-aqueous ink composition in devices such as nozzles and tubes, preventing solidification, and resolubility when solidified, In addition, for the purpose of reducing the surface tension and improving the wettability with the recording medium (substrate), for the purpose of suppressing bleeding of the ink composition on the substrate, and for improving the abrasion resistance of the coating film. For purposes, a surfactant may be added. For example, polyoxyalkylene alkyl ethers nonionic P-208, P-210, P-213, E-202S, E-205S, E-215, K-204, K-220, S-207, S-215 , A-10R, A-13P, NC-203, NC-207 (manufactured by NOF Corporation), Emulgen 106, 108, 707, 709, A-90, A-60 (manufactured by Kao Corporation), Floren G-70, D-90, TG-740W (manufactured by Kyoeisha Chemical Co., Ltd.), Poem J-0081HV (manufactured by Riken Vitamin Co., Ltd.), Adekatol NP-620, NP-650, NP-660, NP-675, NP-683, NP-686, Adekacol CS-141E, TS-230E (manufactured by Adeka Co., Ltd.), Sorgen 30V, 40, TW-20, TW-80, Neugen CX-100 (Daiichi Kogyo Seiyaku Co., Ltd.) It is preferable to use a fluorine-modified polymer as a fluorine-based surfactant, such as BYK-340 (manufactured by BYK-Chemie Japan), and as a silicon-based surfactant, polyester-modified silicone or Polyether-modified silicone is preferably used, and specific examples include BYK-313, 315N, 322, 326, 331, 347, 348, BYK-UV3500, 3510, 3530, 3570 (all manufactured by BYK-Chemie Japan), etc. , Specific examples of acetylene glycol-based surfactants include Surfynol (registered trademark) 82, 104, 465, 485, TG (all manufactured by Air Products Japan), Olfine (registered trademark) STG, E1010 (all manufactured by Nissin Chemical Co., Ltd.) and the like are exemplified.

Surfactants are not limited to those described above, and anionic, cationic, amphoteric or nonionic surfactants may be used, and may be appropriately selected according to the purpose of addition. Silicon-based surfactants are particularly desirable from the viewpoint of suppressing bleeding and improving abrasion resistance.

[Other ingredients]
The non-aqueous ink composition according to the present embodiment contains light stabilizers such as antioxidants and ultraviolet absorbers, epoxides and the like, polyvalent carboxylic acids, surface modifiers, slip agents, leveling agents (acrylic and silicone etc.), defoamers, pH adjusters, bactericides, preservatives, deodorants, charge control agents, wetting agents, and other known additives as optional components. Specific examples of antioxidants include hindered phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, hydrazine-based antioxidants, and the like. Specific examples include BHA (2,3-butyl-4-oxyanisole) and BHT (2,6-di-t-butyl-p-cresol). Moreover, a benzophenone-based compound or a benzotriazole-based compound can be used as the ultraviolet absorber. Specific examples of the epoxidized product include epoxy glyceride, epoxy fatty acid monoester, and epoxy hexahydrophthalate, and specific examples include ADEKA CIZER O-130P and ADEKA CIZER O-180A (manufactured by ADEKA). exemplified. Specific examples of polycarboxylic acids include citric acid and maleic acid.

<<1-3. Method for producing non-aqueous ink composition>>
The method for producing a non-aqueous ink composition constituting the ink set according to the present embodiment includes at least one organic solvent A (alkylamide solvent (a1) and cyclic amide solvent (a2) selected from the group consisting of ), a coloring material, and, if necessary, other components (for example, a resin, etc.) using a paint shaker. At this time, each component may be dispersed with zirconia beads. In addition, the obtained non-aqueous ink composition may be adjusted to a desired dissolved oxygen content and dissolved nitrogen content by, for example, deaeration treatment, if necessary.

At this time, it is preferable to dry the organic solvent in advance. By drying the organic solvent in advance, the amount of water contained in the non-aqueous ink composition can be reduced. As a method for drying the organic solvent, for example, a method of spraying an inert gas (e.g., nitrogen gas) dried in an inert gas atmosphere such as nitrogen for a predetermined time, a method of distilling and refining the organic solvent, and water are selected. Examples include a method of allowing the organic solvent to permeate through a semi-permeable membrane that selectively permeates the organic solvent, and a method of selectively adsorbing water mixed in the organic solvent with a water adsorbent that adsorbs water.

(Viscosity and Surface Tension of Ink Composition)
The viscosity of the non-aqueous ink composition contained in the ink set according to the present embodiment is preferably 30 mPa s or less at 25° C. from the viewpoint of inkjet ejection property and ejection stability, and more preferably 20 mPa s. It is more preferably 15 mPa·s or less, more preferably 15 mPa·s or less. Further, the viscosity of the non-aqueous ink composition contained in the ink set according to the present embodiment is preferably 2.0 mPa·s or more, more preferably 3.0 mPa·s or more, and more preferably 3.5 mPa. · It is more preferably s or more.

In addition, the surface tension of the non-aqueous ink composition contained in the ink set according to the present embodiment is 20 mN at 25° C. from the viewpoint of inkjet ejection property, ejection stability, and leveling property to the substrate. /m or more, more preferably 22 mN/m or more, and even more preferably 24 mN/m or more. Also, the surface tension of the ink composition according to the present embodiment is preferably 40 mN/m or less, more preferably 37 mN/m or less, and even more preferably 35 mN/m or less.

≪2. Recording method using ink set>>
The recording method according to the present embodiment is a recording method in which the ink composition constituting the above ink set is ejected onto the surface of a substrate by an inkjet method. The ink set described above can effectively suppress bleeding of printing even if the ink set is composed of a plurality of ink compositions including a dark color ink and a light color ink. Also in this method, a recorded matter in which bleeding is suppressed can be obtained. Furthermore, by using dark-colored ink and light-colored ink, it is possible to improve the expressiveness of gradation, and it is possible to output a high-quality color image.

A conventionally known inkjet recording apparatus for ejecting the ink composition constituting the above ink set by an inkjet method can be used. For example, an inkjet printer such as VersaArt RE-640 manufactured by Roland DG Co., etc. can be used.

As an example of the configuration of the inkjet recording apparatus, an on-carriage type and serial printer type inkjet recording apparatus will be described. It may be an off-carriage type inkjet recording device fixed to the head, or a line printer type inkjet recording device in which the ink composition is ejected onto the recording medium (substrate) without moving the inkjet head. good.

Also, the inkjet recording apparatus preferably includes a heating mechanism and a fixing mechanism for fixing the substrate. In the recording method according to the present embodiment, the use of such a mechanism is not essential. ), the organic solvent contained in the non-aqueous ink composition can be volatilized by drying the non-aqueous ink composition. This makes it possible to volatilize the organic solvent contained in the non-aqueous ink composition before it spreads, so that it is possible to more effectively suppress bleeding of the print.

Furthermore, the fixing mechanism for fixing the base material makes it possible to dry the non-aqueous ink composition while the base material (recording medium) is fixed. Uniformity can be suppressed. As a result, it is possible to effectively dry the non-aqueous ink composition that has landed on the substrate (recording medium), so that the bleeding of the print that can occur by ejecting a plurality of ink compositions can be more effectively prevented. can be suppressed to

The heating mechanism provided in the inkjet recording apparatus may be a pre-heater, a platen heater, an after-heater, or the like, or may be a mechanism for blowing warm air onto the recorded matter. Also, a plurality of these heating mechanisms may be combined.

The surface temperature of the substrate heated by the heating mechanism is not particularly limited as long as the organic solvent contained in the non-aqueous ink composition can be volatilized, and the lower limit of the surface temperature of the substrate is 20° C. or higher. , more preferably 30° C. or higher, and even more preferably 40° C. or higher. The upper limit of the surface temperature of the substrate is preferably 70° C. or lower, more preferably 60° C. or lower, and even more preferably 50° C. or lower.

A method of ejecting ink by an inkjet method may be a piezo method using a piezoelectric element or a thermal method using a heating element, and is not particularly limited.

≪3. Method for Producing Recorded Matter Using Ink Set>>
A recording method using the above ink set can also be defined as a method of manufacturing a recorded matter. The ink set described above can effectively suppress bleeding of printing even if the ink set is composed of a plurality of ink compositions including a dark color ink and a light color ink. It is also possible to produce recorded matter in which blurring is suppressed in the article production method. Furthermore, by using dark-colored ink and light-colored ink, it is possible to improve the expressiveness of gradation, and it is possible to output a high-quality color image.

≪4. Records≫
Each layer constituting the recorded matter manufactured by the method for manufacturing the recorded matter of the above-described embodiment will be described. Note that the recorded matter in this embodiment is a recorded matter in which a recording layer is formed on the surface of a substrate using the ink composition that constitutes the above ink set. For example, the ink composition constituting the above ink set may be used for forming an underlayer or an overcoat layer, and is not particularly limited.

[Medium (recording medium)]
The base material (recording medium) that can be used in the recording method according to the present embodiment is not particularly limited. It may be an absorbent substrate such as , or a substrate having a surface coating such as a substrate having a receiving layer, and various substrates can be used.

When using a non-aqueous ink composition that does not contain water, it is preferable that the surface is mainly composed of a resin. In particular, since at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set contains an organic solvent A that exhibits permeability to the resin base material, the dark ink and Even with an ink set containing a light-colored ink, blurring of printing on a medium (recording medium) whose surface is made of resin is reduced, and the printing becomes clear. Examples of resins include polyvinyl chloride-based polymers, acryl, PET, polycarbonate, PE, and PP. It may also be used as a resin base material (so-called resin base material for lamination) that assumes that a film is laminated to the recording surface of a recorded matter. In particular, a base material (recording medium) whose surface is made of a hard or soft polyvinyl chloride polymer is preferred. Examples of the substrate (recording medium) whose surface is made of a polyvinyl chloride polymer include polyvinyl chloride substrates (films or sheets).

When a water-based ink composition containing water as a main component is used, it is preferable to use an absorbent substrate such as paper or fabric, or a surface-coated substrate such as a substrate having a receiving layer.

[Recording layer]
The recording layer is a layer formed by volatilization of the solvent contained in the ink composition, and forms a desired image. The above ink set contains dark color ink and light color ink, and can reproduce various color tones while suppressing a decrease in saturation. Furthermore, at least one non-aqueous ink composition among the plurality of ink compositions contained in the ink set contains an organic solvent A, and the ink is composed of a plurality of ink compositions containing a dark-colored ink and a light-colored ink. Even in a set, the recording layer suppresses bleeding of printing.

[Other layers]
The recorded matter according to this embodiment may further include a layer having a desired function on the upper surface of the recording layer. For example, an overcoat layer containing at least one of resin and wax may be formed for the purpose of further imparting abrasion resistance and glossiness to the recorded matter. Further, a layer having an uneven surface (a matte surface) may be formed by adding a filler or changing the film thickness for each pixel. Moreover, in order to impart weather resistance to the recorded matter, a weather resistant layer containing an ultraviolet absorber, a light stabilizer, etc., a glittering layer containing a glittering pigment, or the like may be formed.

The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these descriptions.

1. Preparation of resin (1) Acrylic resin In 300 g of diethylene glycol diethyl ether kept at 100 ° C, 150 g of methyl methacrylate and 50 g of butyl methacrylate and a predetermined amount of t-butyl peroxy-2-ethylhexanoate (polymerization initiation agent) (1.20 g) was added dropwise over 1.5 hours. After completion of the dropwise addition, the mixture was allowed to react at 100° C. for 2 hours and then cooled to obtain a colorless and transparent polymer solution of methyl methacrylate. Thereafter, the solvent was sufficiently distilled off from this polymer solution to obtain a polymer of methyl methacrylate having a polymerization average molecular weight of 30,000.

(2) Vinyl chloride-vinyl acetate copolymer resin In an autoclave equipped with a stirrer, after purging with nitrogen, 100 parts by mass of deionized water, 40 parts by mass of methanol, 32 parts by mass of vinyl chloride, 5 parts by mass of vinyl acetate, glycidyl methacrylate. 0.2 parts by mass, 3.55 parts by mass of hydroxypropyl acrylate, 0.1 parts by mass of hydroxypropyl methylcellulose (suspending agent), and 0.026 parts by mass of di-2-ethylhexylperoxydicarbonate (polymerization initiator) , Di-3,5,5-trimethylhexanol peroxide (polymerization initiator) 0.58 g was charged in a predetermined amount, heated to 63 ° C. while stirring in a nitrogen gas atmosphere, and immediately after reaching 63 ° C., vinyl chloride 48 A mixture of 0.6 parts by mass of glycidyl methacrylate and 10.65 parts by mass of hydroxypropyl acrylate was continuously injected for 5.4 hours to carry out a copolymerization reaction. When the internal pressure of the autoclave reached 0.3 MPa, the residual pressure was released, the slurry was cooled, the resin slurry was taken out, filtered and dried to obtain a vinyl chloride copolymer resin having a polymer average molecular weight of 30,000.

(3) Polyester-based resin 104 parts by mass of terephthalic acid, 104 parts by mass of isophthalic acid, 79 parts by mass of ethylene glycol, 89 parts by mass of neopentyl glycol, and 0.1 part by mass of tetrabutyl titanate were placed in a round-bottomed flask and allowed to cool for 4 hours. The temperature was gradually raised to 240° C., and the esterification reaction was carried out while removing the distillate out of the system. After completion of the esterification reaction, the pressure was reduced to 10 mmHg over 30 minutes, and the temperature was raised to 250° C. for initial polymerization. After that, post-polymerization was carried out at 1 mmHg or less for 1 hour to obtain a polyester resin.

(4) Polyurethane resin 192.5 parts by mass of polycarbonate diol (PLAXEL CD-220: manufactured by Daicel), 41.6 parts by mass of isophorone diisocyanate (IPDI: manufactured by Evonik), and 100 parts by mass of N,N-diethylformamide (DEF). After being uniformly mixed in a round-bottomed flask, a mixture of 0.01 parts by mass of T100BHJ (catalyst) and 0.09 parts by mass of N,N-diethylformamide (DEF) was added, reacted at 75 ° C. for 3 hours, and isocyanate was added to the end. A prepolymer with groups was obtained. 250 parts by mass of N,N-diethylformamide (DEF) was added thereto and dissolved uniformly. A chain extender solution dissolved in 100 parts by mass of DEF) was added, and the mixture was further stirred at 60°C for 40 minutes. After that, 3.8 parts by mass of monoisopropanolamine (MIPA: manufactured by Daicel) dissolved in 50 parts by mass of N,N-diethylformamide was added as a reaction terminator, and finally 250 parts by mass of N,N-diethylformamide (DEF) was added. addition to give a 25.0% solids polyurethane solution.

1. Production of Ink Sets Ink sets of Examples and Comparative Examples were produced. Specifically, first, each component (resin, dispersant, additive, pigment) described in Table 2 is dispersed in the organic solvent described as "balance" in Table 1 with zirconia beads using a paint shaker. rice field. Then, the ink sets of the non-aqueous ink compositions of Test Examples A to F were prepared by adding organic solvents other than the base materials shown in Table 1. At this time, in the ink sets of Test Examples A to F, the content of the organic solvent contained in each non-aqueous ink composition was in the ratio shown in Table 1, and the non-aqueous ink compositions of Test Examples A to F The content of each component (resin, dispersant, additive, pigment) contained in was adjusted to the ratio shown in Table 2. In Table 2, "Y" means yellow, "YL" means light yellow, "M" means magenta, "LM" means light magenta, and "C" means cyan. "LC" means light cyan, "K" means black, and "LK" means light black. Next, the non-aqueous ink compositions of Test Examples A to F were combined as shown in Table 3 to obtain ink sets of Examples and Comparative Examples. Here, the notations a to z in "1: solvent" in Table 3 correspond to the mixed solvents a to z in Table 1, and the notations A to F in "2: other than solvent" in Table 3 are It corresponds to A to F in Table 2. The unit is % by mass.

(Bleeding)
The bleeding property was evaluated for the ink sets of Examples and Comparative Examples. Specifically, each of the non-aqueous ink compositions of the ink sets of Examples and Comparative Examples was applied by an inkjet method using an inkjet printer (trade name: VersaArt RE-640, manufactured by Roland DG Co., Ltd.). A recording medium (polyvinyl chloride film with adhesive (IMAGin JT5829R: manufactured by MACtac)) was printed in high quality printing mode (1440x720dpi) at a substrate surface temperature of 40°C, and a 6pt character in a color different from that of the solid portion was printed in the solid portion of each color. A certain image was printed, and the printed matter obtained was dried in an oven at 60° C. for 5 minutes, and the bleeding of the printed matter was visually observed with a magnifying glass (×10) (denoted as “bleeding property” in the table). Also, Y printing rate was 100% for yellow, M100%+LM100% for magenta, C100%+LC100% for cyan, and K100%+LK100% for black, and solid images and 6pt character images were printed in different colors.
Evaluation Criteria Evaluation 5: No bleeding of the ink was observed by observation with a magnifying glass.
Evaluation 4: No bleeding of the ink was visually observed, and 6 pt characters were clear.
Evaluation 3: Slight bleeding of the ink was visually observed, but the design was not impaired.
Evaluation 2: Bleeding of the ink was visually observed, but the 6pt characters were recognizable.
Evaluation 1: Remarkable bleeding of the ink was visually observed, and 6 pt characters were not visually recognized.

(Ejection stability)
The ejection stability was evaluated for the ink sets of Examples and Comparative Examples. Specifically, in the same manner as in the bleeding evaluation, a recording medium (polyvinyl chloride film with glue (IMAGin JT5829R: manufactured by MACtac)) was continuously printed in a high-quality print mode (1440 x 720 dpi) at a substrate surface temperature of 40 ° C. Solids and fine lines were printed, and the presence or absence of missing dots, flight deflection, and ink scattering was visually observed, and the number of occurrences was counted (referred to as "discharge stability" in the table).
Evaluation Criteria Evaluation 5: Fine lines are correctly reproduced.
Evaluation 4: Fine lines are generally correctly reproduced.
Evaluation 3: A slight bend is observed in the thin wire.
Evaluation 2: The landing position is displaced and bending is observed.
Evaluation 1: The displacement of the landing position is severe, and fine lines cannot be reproduced.

(Surface drying property)
Surface drying properties were evaluated for the ink sets of Examples and Comparative Examples. Specifically, a solid image was printed on a recording medium (polyvinyl chloride film with glue (IMAGin JT5829R: manufactured by MACtac)) in a high-quality print mode (1440 x 720 dpi) in the same manner as in the bleeding evaluation above, and the image was printed at 40°C. The time until drying was measured (indicated as "surface dryness" in the table).
Rating Criteria Rating 5: Dries in less than 2 minutes.
Evaluation 4: Dry in 2 minutes or more and less than 4 minutes.
Evaluation 3: Dry in 4 minutes or more and less than 6 minutes.
Evaluation 2: Dry in 6 minutes or more and less than 8 minutes.
Evaluation 1: It dries in 8 minutes or more.

(process + light color dot shape evaluation)
Using an inkjet printer (trade name: VersaArt RE-640, manufactured by Roland DG Co., Ltd.), high-quality print mode (1440 x 720 dpi) on recording medium (polyvinyl chloride film with glue (IMAGin JT5829R: manufactured by MACtac)), substrate surface The image was printed at a temperature of 50° C. so that the printing rate of the dark color and the single color would be 100% in total. The image was printed by combining a dark color and a single color of the same color. After drying the resulting printed matter in an oven at 50° C. for 2 minutes, the dot shape of the printed matter was observed visually (×300) using a microscope. (Indicated as "dot shape evaluation" in the table.)
Evaluation Criteria Evaluation 5: When visually observed using a microscope, the process color dots were clear circles, and no bleeding with the light color was observed.
Evaluation 4: Visual observation using a microscope found that the process color dots were somewhat circular, and bleeding with the light color was not observed.
Evaluation 3: The process color dots did not become circular when visually observed using a microscope, but no bleeding of multiple colors was observed.
Evaluation 2: When visually observed using a microscope, the process color dots were not circular, and multi-color bleeding was slightly observed.
Evaluation 1: When visually observed using a microscope, the process color dots were not circular, and a large number of multi-color blurs were observed.

As can be seen from the above table, the ink set of the example in which at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contains the organic solvent A contains the dark color ink and the light color ink. It can be seen that the bleeding of the print can also be effectively suppressed. Further, in the dot shape evaluation, no bleeding of multiple colors was observed, which also confirmed that the bleeding of printing could be effectively suppressed.

In particular, in the ink sets of Examples 1, 9 to 11, 16 to 18 in which the type of organic solvent A was changed, the ink sets of Examples 1, 9 to 10 containing an alkylamide solvent It can be seen that even when compared with the No. 18 ink set, print bleeding can be suppressed more effectively.

Further, in the ink sets of Examples 1, 12, 13, and 14 in which the content of the organic solvent A was changed, the content of the organic solvent A was in the range of 1% by mass or more and 90% by mass or less. In comparison with Example 12, it can be seen that the bleeding of printing can be suppressed more effectively.

Further, the ratio (B2/B1) of the resin content B1 with respect to 100 parts by mass of the coloring material contained in the dark ink and the resin content B2 with respect to 100 parts by weight of the coloring material contained in the light color ink is 2.5. In the ink sets of Examples 25, 27, and 29, which are in the range of 8.0 or less, compared to Examples 26 and 28, the dots are more beautiful circular, and bleeding with light colors is not observed. The effect of the present invention was exhibited particularly effectively.

On the other hand, the ink sets of Comparative Examples 1 to 4, which did not contain the organic solvent A, could not effectively suppress print bleeding. In addition, bleeding of multiple colors was also observed in dot shape evaluation, and it was confirmed from this also that bleeding of printing could not be suppressed.

Claims (19)

An ink set containing a plurality of non-aqueous ink compositions containing a coloring material and an organic solvent and ejected by an inkjet method,
Containing a dark ink and a light color ink containing less coloring material than the dark ink,
At least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set contains an organic solvent A.
ink set.
Organic solvent A: at least one of an alkylamide solvent (a1) represented by the following formula (1) and a cyclic amide solvent (a2) represented by the following formula (2)

(In Formula (1), R ₁ is hydrogen or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ each independently represent an alkyl group having 1 to 4 carbon atoms.

(In formula (2), R ₄ is an alkylene group having 3 to 5 carbon atoms, and R ₅ represents hydrogen, an alkyl group having 1 to 4 carbon atoms, or an unsaturated hydrocarbon group.) 2. The ink set according to claim 1, wherein the content of the organic solvent A is in the range of 1.0% by mass or more and 90% by mass or less in the total amount of the non-aqueous ink composition. 3. The ink set according to claim 1, wherein the organic solvent A contains the alkylamide solvent (a1). 4. The alkylamide solvent (a1) contains at least one selected from the group consisting of N,N-diethylformamide, N,N-diethylpropanamide, and N,N-diethylacetamide. ink set. The organic solvent A contains a cyclic amide solvent (a2),
The ink set according to claim 1 or 2. The cyclic amide solvent (a2) contains at least one selected from the group consisting of ε-caprolactam, N-methyl-ε-caprolactam, and N-vinylcaprolactam.
The ink set according to claim 5. At least two non-aqueous ink compositions among the plurality of non-aqueous ink compositions contained in the ink set contain an organic solvent A.
The ink set according to any one of claims 1 to 6. The ink set according to any one of Claims 1 to 7, wherein at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set further contains a glycol ether solvent. 9. The ink set according to claim 8, wherein the glycol ether solvent contains dialkyl ether. 10. The ink set according to claim 8, wherein the glycol ether-based solvent contains monoalkyl ether. The ink set according to any one of claims 8 to 10, wherein the glycol ether solvent contains at least two solvents having different flash points. The ink set according to any one of Claims 1 to 11, wherein at least one non-aqueous ink composition among the plurality of non-aqueous ink compositions contained in the ink set further contains a resin. The dark-colored ink and light-colored ink contained in the ink set further contain a resin,
The ratio (B2/B1) of the resin content B1 with respect to 100 parts by mass of the coloring material contained in the dark ink and the resin content B2 with respect to 100 parts by weight of the coloring material contained in the light color ink is 2.5. 13. The ink set according to claim 12, wherein the range is 8.0 or less. 14. The ink set according to claim 12 or 13, wherein the content of the resin is in the range of 1% by mass or more and 15% by mass or less in the total amount of the non-aqueous ink composition. The resin contains at least one selected from the group consisting of acrylic resins, vinyl chloride resins, polyurethane resins, polyester resins, and cellulose resins.
The ink set according to Claims 12 to 14. A recording method, comprising ejecting the non-aqueous ink composition contained in the ink set according to any one of claims 1 to 15 onto the surface of a substrate by an inkjet method. The recording method according to Claim 16, wherein the non-aqueous ink composition ejected onto the surface of the substrate is dried by a heating mechanism. 16. A method for producing recorded matter, comprising ejecting the non-aqueous ink composition contained in the ink set according to any one of claims 1 to 15 onto the surface of a substrate by an inkjet method. A recorded matter, wherein a recording layer of the non-aqueous ink composition contained in the ink set according to any one of claims 1 to 15 is formed on the surface of a substrate.