JP6871121B2 - Oil-based inkjet ink - Google Patents

Description

The present invention relates to an oil-based inkjet ink.

The inkjet recording method injects highly fluid inkjet ink as droplets from a fine nozzle and records an image on a recording medium placed facing the nozzle, enabling high-speed printing with low noise. Therefore, it has spread rapidly in recent years. As inks used in such an inkjet recording method, water-based inks containing water as a main solvent, ultraviolet curable inks (UV inks) containing a high content of polymerizable monomers as main components, and wax as main components are high. A so-called non-aqueous ink containing a non-aqueous solvent as a main solvent is known as well as a hot melt ink (solid ink) contained in a content. Non-aqueous inks can be classified into solvent inks (solvent-based inks) in which the main solvent is a volatile organic solvent and oil-based inks (oil-based inks) in which the main solvent is a low-volatile or non-volatile organic solvent. The solvent ink dries on the recording medium mainly by evaporation of the organic solvent, whereas the oil-based ink dries mainly by penetrating into the recording medium.

Some oil-based inkjet inks use carbon black as a coloring material.

In Patent Document 1, ink for an inkjet printer using a pigment, a resin, and an insulating solvent having a siloxane bond in the molecular skeleton enables clear printing at a high density, has scratch resistance, and is stable. It is proposed that ejection becomes possible, and inks using aniline black and carbon black as pigments are described.

In Patent Document 2, a non-aqueous inkjet ink composition containing a pigment, a non-aqueous solvent, and a surfactant, and containing a siloxane-based surfactant having an HLB value of 1.0 or more and 7.0 or less as the surfactant. It is proposed to improve the optical density, ejection stability and storage stability of an image depending on the object, and an ink using carbon black as a pigment is described.

In Patent Document 3, a non-aqueous pigment ink for inkjet, which contains a silicone-based solvent and a pigment and further contains a specific modified silicone oil as a dispersant, improves ink stability, nozzle clogging, and clear file deformation. It is proposed that the ink using carbon black as a pigment is described.

Japanese Unexamined Patent Publication No. 4-161467 Japanese Unexamined Patent Publication No. 2016-196564 Japanese Unexamined Patent Publication No. 2004-217703

For oil-based inks, high print density can usually be obtained by using carbon black having a small primary particle size and a large structure. Further, in the oil-based ink, usually, by using acidic carbon black, good storage stability can be obtained even if the primary particle size is small and the structure is large. However, as the pigment concentration in the ink increases, the storage stability of the ink tends to decrease.

On the other hand, an inkjet printer ejects ink droplets from a nozzle plate to form an image on a recording medium. Normally, a cured film made of fluororesin or the like is applied to the nozzle plate to prevent ink or the like from adhering to the nozzle plate, but it is not possible to completely prevent the adhesion of dust, foreign matter and the like. Therefore, the nozzle plate is usually cleaned regularly. The most commonly used cleaning method is to wipe the nozzle plate with a blade. However, when the winding is repeated, pigments such as carbon adhering to the nozzle plate wear the cured film of the nozzle plate, which lowers the durability against wiping (hereinafter referred to as "wiping resistance") and ejects ink. May cause problems.

An object of the present invention is to provide an oil-based inkjet ink having excellent storage stability and wiping resistance.

According to an embodiment of the present invention, the pigment, a pigment dispersant and a non-aqueous solvent are contained, the pigment contains acidic carbon black having a pH of 2 to 6, and the non-aqueous solvent has a surface tension of 27 mN / m or less. An oil-based inkjet ink containing a modified silicone oil and having a modified silicone oil of 15% by mass or more and 80% by mass or less with respect to the total amount of the ink is provided.

According to the embodiment of the present invention, it is possible to provide an oil-based inkjet ink having excellent storage stability and wiping resistance.

Hereinafter, embodiments of the present invention will be described, but the following embodiments do not limit the present invention.
Hereinafter, the oil-based inkjet ink may be simply referred to as "ink".

The oil-based inkjet ink according to one embodiment contains a pigment, a pigment dispersant and a non-aqueous solvent, the pigment contains acidic carbon black having a pH of 2 to 6, and the non-aqueous solvent has a surface tension of 27 mN / m or less. The modified silicone oil A is an oil-based inkjet ink containing 15% by mass or more and 80% by mass or less with respect to the total amount of the ink, which contains the modified silicone oil (hereinafter, may be referred to as modified silicone oil A).
This oil-based inkjet ink has excellent storage stability and makes it possible to improve wiping resistance.

In order to improve the optical density, it is one of the means to increase the pigment density in the ink. However, increasing the pigment concentration tends to reduce the storage stability of the ink.
In addition, acidic carbon black tends to improve the storage stability of ink, but when ink using acidic carbon black is used, cleaning the nozzle plate tends to damage the surface of the nozzle plate and has wiping resistance. Tends to decrease. It is presumed that this is because the affinity between the acidic carbon black and the nozzle plate is high, and the acidic carbon black easily adheres to the nozzle plate. Further, it is presumed that the strength of the affinity between the acidic carbon black and the nozzle plate depends on the amount of acidic functional groups on the surface of the carbon black.

Although not bound by theory, the use of modified silicone oil A, which has a low surface tension of 27 mN / m or less, makes it easier for the pigment to get wet and improves the dispersion efficiency, thereby stabilizing the storage of ink. It is presumed that the sex can be improved. In addition, the adsorption efficiency of the pigment dispersant is also improved, and the acidic functional groups on the surface of the acidic carbon black can be efficiently protected by the pigment dispersant, so that it is presumed that the wiping resistance can be improved.

The ink preferably contains a pigment as a coloring material.
Further, in the ink, the pigment preferably contains acidic carbon black having a pH of 2 to 6.
By using acidic carbon black having a pH of 2 to 6 as the carbon black, it is easy to improve the storage stability of the ink. It is presumed that this is because acidic carbon black has an acidic functional group on the pigment surface, so that it easily interacts with the pigment dispersant, and is superior in dispersibility as compared with, for example, neutral carbon black.
The acidic carbon black is not particularly limited as long as it is an acidic carbon black having a pH of 2 to 6, and any of furnace carbon black, lamp black, acetylene black, channel black and the like may be used.
The pH of the acidic carbon black is preferably 2 or more, and may be 2.5 or more. The pH of the acidic carbon black is preferably 6 or less, more preferably 5.5 or less, and may be 5.0 or less, from the viewpoint of obtaining good storage stability of the ink.
The pH of carbon black is a value obtained by measuring the pH of a mixed solution of carbon black and distilled water according to JIS K5101.

Specific examples of commercially available acidic carbon black products include MA7, MA8, MA77, MA100, MA11, MA230, MA14, MA220, # 1000, # 970, # 2350, # 2650, Orion Engineer manufactured by Mitsubishi Chemical Co., Ltd. Special Black 350, Special Black 550, Special Black 4, Special Black 5, Special Black 6, Color Black S160, Color Black S160, Color Black S170, Black Black S170, Black, etc., manufactured by Docarbons.

Acidic carbon black having a pH of 2 to 6 may be used alone or in combination of two or more.

The amount of acidic carbon black having a pH of 2 to 6 in the ink is preferably 0.01% by mass or more, more preferably 1% by mass or more, still more preferably 3% by mass or more, based on the total amount of the ink, from the viewpoint of printing density. For example, it may be 5% by mass or more. The amount of acidic carbon black having a pH of 2 to 6 in the ink is preferably 20% by mass or less, more preferably 15% by mass or less, and for example, 10% by mass or less, based on the total amount of ink, from the viewpoint of ink viscosity. You can.

The ink can contain other pigments as a coloring material together with acidic carbon black having a pH of 2 to 6.
As other pigments, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments and dyed lake pigments; and inorganic pigments such as carbon blacks and metal oxides other than acidic carbon blacks having a pH of 2 to 6 should be used. Can be done. Examples of the azo pigment include soluble azo lake pigments, insoluble azo pigments and condensed azo pigments. Examples of the phthalocyanine pigment include metal phthalocyanine pigments and non-metal phthalocyanine pigments. Polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindolin pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthracinone pigments, quinophthalone pigments, and metal complex pigments. And diketopyrrolopyrrole (DPP) and the like. Examples of the metal oxide include titanium oxide and zinc oxide. These other pigments may be used alone or in combination of two or more.

The dispersion form of the pigment may be a so-called capsule pigment in which the pigment is coated with a non-oil-soluble resin or a dispersion in which colored resin particles are dispersed with a pigment dispersant, but the pigment dispersant is directly adsorbed on the pigment surface. It is preferably a dispersed dispersion.

The average particle size of the pigment is preferably 300 nm or less, more preferably 200 nm or less, still more preferably 150 nm or less, from the viewpoint of discharge stability and storage stability.
The pigment is usually 0.01 to 20% by mass with respect to the total amount of ink, and is preferably 1 to 15% by mass, more preferably 5 to 10% by mass, from the viewpoint of printing density and ink viscosity. ..

In order to stably disperse the pigment in the ink, a pigment dispersant can be used together with the pigment.
Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a salt of a long-chain polyaminoamide and a high-molecular-weight acid ester, a salt of a high-molecular-weight polycarboxylic acid, a salt of a long-chain polyaminoamide and a polar acid ester, and a high-molecular-weight unsaturated acid. Esters, copolymers of vinylpyrrolidone and long-chain alkene, modified polyurethanes, modified polyacrylates, polyether ester-type anionic activators, polyoxyethylene alkyl phosphates, polyester polyamines and the like are preferably used.

Examples of commercially available pigment dispersants include "Antalon V216 (vinylpyrrolidone / hexadecene copolymer)" and V220 (vinylpyrrolidone / eikosen copolymer) "manufactured by ISP Japan Co., Ltd. (both are commercial products. Name);
"Solsperse 13940 (polyester amine type), 16000, 17000, 18000 (fatty acid amine type), 11200, 24000, 28000" manufactured by Japan Lubrizol Co., Ltd. (all trade names);
BASF Japan Ltd. "Fuka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)" (all trade names);
Kusumoto Kasei Co., Ltd. "Disparon KS-860, KS-873N4 (polyester amine salt)" (both trade names);
"Discol 202, 206, OA-202, OA-600 (multi-chain polymer nonionic)" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (all trade names);
"DISPERBYK2155, 9077" manufactured by Big Chemie Japan Co., Ltd. (both product names);
Examples thereof include "Hypermer KD2, KD3, KD11, KD12" (all trade names) manufactured by Croda Japan Co., Ltd.

The pigment dispersant may be appropriately set as long as the amount of the pigment can be sufficiently dispersed in the ink. For example, in terms of mass ratio, the pigment dispersant can be blended in an amount of 0.1 to 5 with respect to the pigment 1, preferably 0.1 to 1. The pigment dispersant can be blended in an amount of 0.01 to 10% by mass, preferably 0.01 to 5% by mass, based on the total amount of the ink.
The resin component containing the pigment dispersant can be blended in the oil-based ink in an amount of 10% by mass or less, more preferably 7% by mass or less, still more preferably 5% by mass or less, based on the total amount of the ink. As a result, it is possible to prevent an increase in ink viscosity and further improve the ejection performance.

The ink can include a modified silicone oil (modified silicone oil A) having a surface tension of 27 mN / m or less.

The surface tension of the modified silicone oil A is preferably 27 mN / m or less, more preferably less than 27 mN / m, still more preferably 26 mN / m or less, from the viewpoint of improving storage stability and wiping resistance. The surface tension of the modified silicone oil A may be, for example, 15 mN / m or more, or 17 mN / m or more.
Here, the surface tension can be obtained according to the bubble pressure method (maximum bubble pressure method). For example, the surface tension can be measured using "SITA Mechanism GmbH Science line t60" manufactured by SITA Process Solutions.

The modified silicone oil A is preferably a liquid compound at 23 ° C.

As the modified silicone oil, a silicone oil in which various organic groups are introduced into some silicon atoms of the chain or cyclic dimethyl silicone oil can be used. As the modified silicone oil, it is preferable that all silicon atoms are bonded only to either carbon atoms or siloxane-bonded oxygen atoms. The modified silicone oil is preferably a non-reactive silicone oil. The modified silicone oil preferably has only silicon atoms, carbon atoms, oxygen atoms, and hydrogen atoms as constituent atoms.
The modified silicone oil is, for example, a group in which at least one methyl group contained in a chain or cyclic dimethyl silicone oil is composed of an alkyl group, a carboxylic acid ester bond-containing group, an aromatic ring-containing group, and an ether bond-containing group. Compounds substituted by one or more selected from are available.
Further, as the modified silicone oil, for example, a silicon atom of another chain or cyclic dimethyl silicone oil is bonded to at least one silicon atom contained in the chain or cyclic dimethyl silicone oil via an alkylene group. Compounds can be used. In this case, at least one methyl group contained in the chain or cyclic dimethyl silicone oil bonded via an alkylene group is composed of an alkyl group, a carboxylic acid ester bond-containing group, an aromatic ring-containing group, and an ether bond-containing group. It may be replaced by one or more selected from the group.
Examples of the modified silicone oil include alkyl-modified silicone oil, aryl-modified silicone oil such as phenyl-modified silicone oil and aralkyl-modified silicone oil, carboxylic acid ester-modified silicone oil, alkylene-modified silicone oil, and polyether-modified silicone oil. ..
The modified silicone oil preferably has a silicon number of 2 to 20, more preferably 2 to 10, further preferably 2 to 6, and even more preferably 3 to 6.

Examples of the organic group that can be introduced into the modified silicone oil are those exemplified as a monovalent organic group having a total of 2 or more carbon atoms and oxygen numbers of R2 in the explanation of the general formula (X) described later. , And those exemplified as the divalent organic group of R1 are included.

Among them, examples of the phenyl-modified silicone oil include trimethylsiloxyphenyldimethicone, phenyltrimethicone, diphenylsiloxyphenyltrimethicone, 1,1,1,5,5,5-hexamethyl-3-phenyl-3- (trimethylsilyloxy). ) Methylphenyl silicone such as trisiloxane can be mentioned.

Examples of the modified silicone oil include silicone oil, which is a compound represented by the following general formula (X).

In the general formula (X), R ¹ is an oxygen atom or a divalent organic group, and R ² is independently a methyl group or a monovalent group having a total of 2 or more carbon atoms and oxygen numbers. It is an organic group, and m and n are independently integers of 0 or more (preferably 0 to 4), and p is independently an integer of 0 or more (preferably 0 to 2). The total number of silicon atoms in one molecule is 2 to 20 (preferably 2 to 10, more preferably 2 to 6, still more preferably 3 to 6).
When m + n = 0, R ¹ is an oxygen atom, and ^{at least one of R 2} is a monovalent organic group having a total of 2 or more carbon atoms and oxygen numbers.
When R ¹ is a divalent organic group, m + n ≧ 1.

Examples of monovalent organic groups having a total of 2 or more carbon atoms and oxygen numbers in the general formula (X) include, for example, an alkyl group having 2 or more carbon atoms, a carboxylic acid ester bond-containing group, an aromatic ring-containing group, and an aromatic ring-containing group. Examples include ether bond-containing groups. Examples of the divalent organic group in the general formula (X) include an alkylene group and the like.
The alkyl group having 2 or more carbon atoms may have a straight chain or a branched chain, and may be a chain or an alicyclic. The alkyl group having 1 or more carbon atoms preferably has 2 to 20 carbon atoms, and more preferably 4 to 20 carbon atoms. Examples of the alkyl group having 2 or more carbon atoms include an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group and a nonyl group. Examples thereof include a group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, an eikosyl group and the like.
Examples of the carboxylic acid ester bond-containing group include those listed as the carboxylic acid ester-containing group in the modified silicone oil S described later.
Examples of the aromatic ring-containing group include those listed as aromatic ring-containing groups in the modified silicone oil S described later.
The alkylene group may have a straight chain or a branched chain, and may be a chain or an alicyclic. The alkylene group preferably has 1 to 20 carbon atoms, and more preferably 4 to 20 carbon atoms. Examples of the alkylene group include methylene, ethylene, ethylene group, propylene group, trimethylene group, n-butylene group, isobutylene group, pentylene group, hexylene group, heptylene group, octylene group, isooctylene group, nonylene group, decylene group and dodecylene. Examples include a group, a hexadecylene group, an eicosilene group and the like.

Examples of the modified silicone oil include silicone oil, which is a compound represented by the following general formula (Y).

In the general formula (Y), R ¹ is an oxygen atom or a divalent organic group ^{independently, and R 2} is a methyl group or a total of 2 or more carbon atoms and oxygen numbers independently. a monovalent organic group, n is an integer of 5 or more, the sum of silicon atoms per molecule is 5 to 9, at least one of R ¹ is an oxygen atom,
When all of R ¹ are oxygen atoms, ^{at least one of R 2} is a monovalent organic group having a total of 2 or more carbon atoms and oxygen numbers.

As an example of a monovalent organic group having a total of 2 or more carbon atoms and oxygen numbers in the general formula (Y), an example of a monovalent organic group having a total carbon number and oxygen number of 2 or more in the general formula (X). The ones listed are listed. Examples of the divalent organic group in the general formula (Y) include those listed as examples of the divalent organic group in the general formula (X).

In each of the general formulas (X) and (Y), the total number of monovalent organic groups and divalent organic groups having a total of 2 or more carbon atoms and oxygen numbers is preferably 3 or less, preferably 2 or less. , For example, it may be 1.

An example of a modified silicone oil has an organic group in which the number of silicon in one molecule is 2 to 6, the carbon atom is directly bonded to the silicon atom, and the total number of carbon and oxygen is 4 or more. A silicone oil having a total carbon number and oxygen number of 4 to 20 contained in an organic group having a total carbon number and oxygen number of 4 or more in a molecule is included. Hereinafter, this silicone oil is also referred to as modified silicone oil S.

The modified silicone oil S can have one or more selected from the group consisting of the following (A) to (D) as an organic group having a total of 4 or more carbon atoms and oxygen numbers.
(A) An alkyl group having 4 or more carbon atoms.
(B) A carboxylic acid ester bond-containing group having a total of 4 or more carbon atoms and oxygen numbers.
(C) An aromatic ring-containing group having 6 or more carbon atoms.
(D) An alkylene group having 4 or more carbon atoms.

The total number of carbons and oxygens in one molecule of the modified silicone oil S is 4 or more, and the total number of carbons and oxygens contained in the organic group is preferably 4 or more, more preferably 8 or more. , More preferably 10 or more.
The modified silicone oil S preferably has a total carbon number and oxygen number of 20 or less, more preferably 16 or less, contained in an organic group having a total carbon number and oxygen number of 4 or more in one molecule. , More preferably 12 or less.
When one molecule of the modified silicone oil S contains two or more organic groups having a total of 4 or more carbon atoms and oxygen numbers, an organic group having a total of 4 or more carbon atoms and oxygen numbers in one molecule. The total number of carbon atoms and oxygen number of organic groups is the total number of carbon atoms and oxygen number of organic groups having a total number of carbon atoms and oxygen numbers of 2 or more and 4 or more.

The modified silicone oil S preferably has a total of 4 to 12 carbons and oxygens contained in an organic group having a total of 4 or more carbons and oxygens in one molecule.
Further, the modified silicone oil S preferably has a total of 8 to 20 carbon atoms and oxygen numbers contained in an organic group having a total carbon number and oxygen number of 4 or more in one molecule.

As an example of the modified silicone oil S, in the above general formula (X), R ¹ is a divalent compound in which a carbon bond is directly bonded to an oxygen atom or a silicon atom and the total number of carbon atoms and oxygen number is 4 or more. ^{R 2} is a monovalent organic group in which a carbon bond is directly bonded to a methyl group or a silicon atom and the total number of carbon atoms and oxygen number is 4 or more. m and n are independently integers of 0 to 4, and p is independently an integer of 0 to 2.
The number of silicon in one molecule is 2 to 6, and ^{at least one of R 1} and R ² is an organic group having a total of 4 or more carbon and oxygen, and the total number of carbon and oxygen in one molecule is 4 or more. The total number of oxygen and carbon contained in the organic group having a total number of 4 or more is 4 to 20.
When m + n = 0, R ¹ is an oxygen atom.
When R ¹ is a divalent organic group having a total of 4 or more carbon atoms and oxygen numbers, silicone oil, which is a compound having m + n ≧ 1, is included.

Preferably, in the general formula (X), R ¹ is an oxygen atom or an alkylene group having 4 or more carbon atoms, and R ² is independently a methyl group, an alkyl group having 4 or more carbon atoms, and a carbon number of carbons, respectively. And a carboxylic acid ester bond-containing group having a total oxygen number of 4 or more, or an aromatic ring-containing group having 6 or more carbon atoms, and ^{at least one of R 1} and R ² is an alkylene group having 4 or more carbon atoms. Selected from the group consisting of an alkyl group having 4 or more carbon atoms, a carboxylic acid ester bond-containing group having a total of 4 or more carbon atoms and an oxygen number, and an aromatic ring-containing group having 6 or more carbon atoms, the number of carbon atoms in one molecule. The number of oxygen and carbon contained in an alkylene group having 4 or more, an alkyl group having 4 or more carbon atoms, a carboxylic acid ester bond-containing group having a total of 4 or more carbon atoms and an oxygen number, and an aromatic ring-containing group having 6 or more carbon atoms. The total number is 4-20.

Other examples of the modified silicone oil S include silicone oil, which is a compound represented by the following general formula (X-1).

In the general formula (X-1), R ² is a monovalent organic group in which a carbon atom is directly bonded to a methyl group or a silicon atom and the total number of carbon atoms and oxygen number is 4 or more. N is an integer from 0 to 4, p is independently 0 or 1, the number of silicon in one molecule is 2 to 6, and at least one of ^{R 2 is.} An organic group having a total of 4 or more carbon atoms and an oxygen number, and an organic group having a total of 4 or more carbon atoms and oxygen numbers in one molecule has a total oxygen number and carbon number of 4 to 20. is there.
In the general formula (X-1), ^{at least one of R 2} is an alkyl group having 4 or more carbon atoms, a carboxylic acid ester bond-containing group having a total of 4 or more carbon atoms and oxygen number, and 6 or more carbon atoms. It is preferable to select from the group consisting of aromatic ring-containing groups.

In the modified silicone oil S, the alkyl group having 4 or more carbon atoms may have a straight chain or a branched chain, and may be a chain or an alicyclic. The alkyl group having 4 or more carbon atoms preferably has 4 to 20 carbon atoms.
The number of carbon atoms of the alkyl group is preferably 4 or more, more preferably 8 or more, and further preferably 10 or more.
The number of carbon atoms of the alkyl group is preferably 20 or less, more preferably 16 or less, still more preferably 12 or less.

The alkyl group having 4 or more carbon atoms is, for example, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, a decyl group, a dodecyl group, or a tetradecyl group. , Hexadecyl group, Eikosyl group and the like.
It is preferably an octyl group, a decyl group, a dodecyl group, a tetradecyl group or a hexadecyl group, and more preferably a decyl group or a dodecyl group.

In the modified silicone oil S, the carboxylic acid ester bond-containing group is represented by ^{-R Bb-} O- (CO) -R ^Ba in which the carboxylic acid ester bond is bonded to the silicon atom of the siloxane bond in the main chain via the alkylene group. Or ^{a group represented by −R Bb} − (CO) −OR ^Ba can be preferably used.
Here, R ^Ba may have a linear or branched chain having one or more carbon atoms, and is preferably a chain or alicyclic alkyl group. Further, R ^Bb may have a linear or branched chain having 1 or more carbon atoms, and is preferably a chain or alicyclic alkylene group. The alkylene group that connects the silicon atom of the siloxane bond in the main chain and the carboxylic acid ester bond is more preferably having 2 or more carbon atoms.

The total number of carbon atoms and oxygen number of the carboxylic acid ester bond-containing group is the number of carbon atoms of one carbon atom and two oxygen atoms of the ester bond (-O- (CO)-) and the number of carbon atoms of the alkyl group (R ^Ba ). And the number of carbon atoms of the alkylene group ( ^RBb).

In the carboxylic acid ester bond-containing group, the alkyl group (R ^Ba ) is, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group and a heptyl group. Examples thereof include a group, an octyl group, an isooctyl group, a nonyl group, a decyl group, a dodecyl group, a hexadecyl group, a heptadecyl group and the like.
A pentyl group, a heptyl group, a nonyl group and a tridecylic group are preferable, and a heptyl group and a nonyl group are more preferable.

In the carboxylic acid ester bond-containing group, the alkylene group ( ^RBb ) is preferably a linear alkylene group having 1 to 8 carbon atoms, for example, a methylene group, an ethylene group, a propylene group, a trimethylene group, n-butylene, and the like. Examples thereof include an isobutylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group and the like. It is preferably an ethylene group.

In modified silicone oil S, the aromatic ring-containing group is a group the aromatic ring to the silicon atom of the siloxane bond in the main chain is represented by a direct bond to -R ^Ca, or an alkylene group to the silicon atom of the siloxane bond in the main chain ^{A group represented by -RCb-} R ^{Ca to} which an aromatic ring is bonded can be preferably used.
Here, ^RC is preferably an aromatic ring having 6 or more carbon atoms. Further, ^RCb may have a linear or branched chain having 1 or more carbon atoms, and is preferably a chain or alicyclic alkylene group.
Aromatic ring-containing group, if the aromatic ring to the silicon atom of the siloxane bond in the main chain is a group represented by direct binding to -R ^Ca, as branched side chain, such as trimethylsilyloxy group from the siloxane bond in the main chain It is preferable that it is branched. The aromatic ring-containing group is more preferably a group represented by ^-RCb- R ^{Ca in} which an aromatic ring is bonded to a silicon atom of a siloxane bond in the main chain via an alkylene group.

The carbon number of the aromatic ring-containing group is the sum of ^{the carbon number of the aromatic ring (RCa} ) and the carbon number of any alkylene group ( ^RCb).

In the aromatic ring-containing group, the aromatic ring moiety ( ^RCa ) contains, for example, a phenyl group, a tolyl group, a xsilyl group, a trimethylphenyl group, a biphenyl group, a naphthyl group, an anthracenyl group, or at least one hydrogen atom thereof. A functional group substituted with an alkyl group can be mentioned.
The aromatic ring-containing group may contain one or two or more aromatic rings, but it is preferable that the aromatic ring-containing group having 6 or more carbon atoms in one molecule has 6 to 20 carbon atoms. ..

In the aromatic ring-containing group, any alkylene group ( ^RCb ) is preferably an alkylene group which may have a linear or branched chain having 1 to 8 carbon atoms, for example, a methylene group, an ethylene group, or a propylene. Examples thereof include a group, a trimethylene group, an n-butylene group, an isobutylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group and the like.
Preferably, it is a propylene group, a methylethylene group, or an ethylene group.

In the modified silicone oil S, the alkylene group having 4 or more carbon atoms may have a straight chain or a branched chain, and may be a chain or an alicyclic. The alkylene group having 4 or more carbon atoms preferably has 4 to 20 carbon atoms.
The alkylene group preferably has 4 or more carbon atoms, and more preferably 8 or more carbon atoms.
The carbon number of the alkylene group is preferably 20 or less, more preferably 12 or less, still more preferably 10 or less.
In one embodiment of the modified silicone oil S, of the carbon atoms at both ends of an alkylene group having 4 or more carbon atoms, one carbon atom is bonded to a siloxane bond and the other carbon atom is bonded to a siloxane bond or a silyl group. Examples include compounds.

The alkylene group having 4 or more carbon atoms includes, for example, an n-butylene group, an isobutylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, an isooctylene group, a nonylene group, a decylene group, a dodecylene group, a hexadecylene group, an ecosilene group and the like. Can be mentioned. It is preferably an octylene group, a decylene group, or a dodecylene group, and more preferably an octylene group or a decylene group.

The modified silicone oil S described above is not limited to this, and can be produced by the following method.
For example, a modified silicone oil S can be obtained by reacting a siloxane raw material with a reactive compound having a reactive group together with an organic group having a total of 4 or more carbon atoms and oxygen numbers in an organic solvent. .. The siloxane raw material and the reactive compound are preferably reacted with the reactive group of the siloxane raw material and the reactive group of the reactive compound in a molar ratio of 1: 1 to 1: 1.5. Further, in the reaction, a catalyst such as a zero-valent platinum olefin complex, a zero-valent platinum vinyl siloxane complex, a divalent platinum olefin complex halide, or a platinum catalyst such as chloroplatinic acid can be preferably used.

Examples of the siloxane raw material include 1,1,3,3-tetramethyldisiloxane, 1,1,1,3,5,5,5-heptamethyltrisiloxane, 1,1,1,3,3,5. , 7,7,7-Nonamethyltetrasiloxane, 1,1,1,3,3,5,7,7,9,9,9-Undecamethylpentasiloxane, Pentamethyldisiloxane, 1,1,3 , 3,5,5,5-heptamethyltrisiloxane, 1,1,3,3-tetramethyldisiloxane, 1,1,3,3,5,5-hexamethyltrisiloxane, 1,1,3 3,5,5,7,7-octamethyltetrasiloxane, 1,1,3,3,5,5,7,7,9,9-decamethylpentasiloxane, 1,1,1,3,5 5,5-Heptamethyltrisiloxane, 1,1,1,5,5,5-hexamethyl-3- (trimethylsilyloxy) trisiloxane, 1,1,1,5,5,5-hexamethyltrisiloxane, 1 , 1,1,3,5,7,7,7-Octamethyltetrasiloxane, 1,1,3,5,5-pentamethyl-3- (dimethylsilyloxy) trisiloxane, 1,1,3,3 5,5,7,7,9,9,11,11-dodecamethylhexasiloxane, 1,1,1,5,5,5-hexamethyl-3- (trimethylsilyloxy) trisiloxane and the like can be used.

The reactive compound preferably has a carbon double bond as a reactive group.
In order to introduce an alkyl group into the modified silicone oil S, the reactive compounds include 1-butene, 2-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 2-octene and 1-. Alkenes having 4 or more carbon atoms such as nonene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene can be used. In addition to the alkene, an alicyclic hydrocarbon group having an ethylenically unsaturated double bond such as vinylcyclohexane can be used.

In order to introduce a carboxylic acid ester-containing group into the modified silicone oil S, the reactive compounds include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutate, vinyl pentanate, vinyl pivalate, vinyl hexanoate, and heptane. Vinyl acid, vinyl 2-ethylhexanoate, vinyl octanate, vinyl isooctate, vinyl nonanoate, vinyl decanoate, vinyl laurate, vinyl myristate, vinyl palmitate, vinyl eicoate, allyl hexanoate, etc. A fatty acid vinyl or a fatty acid allyl compound having a total oxygen number of 6 or more can be used.

In order to introduce an aromatic ring-containing group into the modified silicone oil S, the reactive compounds include styrene, 4-methylstyrene, 2-methylstyrene, 4-tert-butylstyrene, allylbenzene, 1-allylnaphthalene, 4 −Phenyl-1-butene, 2,4-diphenyl-4-methyl-1-pentene, 1-vinylnaphthalene, α-methylstyrene, 2-methyl-1-phenylpropene, 1,1-diphenylethylene, triphenylethylene , 2,4,6-trimethylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 3-phenyl-1-propene and other allyl compounds having a vinyl bond and an aromatic ring having 6 or more carbon atoms. Can be used.

In order to introduce an alkylene group into the modified silicone oil S, the reactive compounds include 1,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, 1,5-hexadiene, and 1,6-heptadiene. 1,7-Octadiene, 1,8-Nonadiene, 1,9-Decadiene, 1,11-Dodecadiene, 1,10-Undecadiene, 1,13-Tetradecadiene, Hexadecadiene, Eikosaziene, etc. have 4 or more carbon atoms. Diene compounds and the like can be used.

Commercially available products of modified silicone oil A include "KF-56A" (diphenylsiloxyphenyltrimethicone) manufactured by Shin-Etsu Chemical Co., Ltd., "SS-3408" (caprylyl methicone) manufactured by Toray Dow Corning, and Momentive Performance Materials. "TSF410" and "TSF411" manufactured by Japan GK, "Phenyltiltris (trimethylsiloxy) silane" manufactured by Gelest, "3-phenylheptamethyltrisiloxane" and the like may be used.

As the modified silicone oil A, one type may be used alone, or a plurality of types may be used in combination.
The amount of the modified silicone oil A in the ink is preferably 15% by mass, more preferably 20% by mass or more, further preferably 25% by mass or more, based on the total mass of the ink, from the viewpoint of improving the wiping resistance. preferable. This makes it possible to sufficiently wet the pigment, promote the dispersion of the pigment, and improve the wiping resistance.
The amount of the modified silicone oil A in the ink is preferably 80% by mass or less, and less than 80% by mass, based on the total mass of the ink, from the viewpoint of controlling the wettability of the nozzle plate and improving the wiping resistance. More preferably, 75% by mass or less is further preferable, and 70% by mass or less is further preferable.

The ink may contain other non-aqueous solvents.
As the other non-aqueous solvent, either a non-polar organic solvent or a polar organic solvent can be used. In the present embodiment, it is preferable to use a water-insoluble organic solvent that does not uniformly mix with the same volume of water at 1 atm and 20 ° C. as the non-aqueous solvent.

As the non-polar organic solvent, for example, petroleum-based hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents can be preferably mentioned.
Examples of the aliphatic hydrocarbon solvent and the alicyclic hydrocarbon solvent include non-aqueous solvents such as paraffin-based, isoparaffin-based, and naphthenic-based solvents. Commercially available products include No. 0 Solvent L, No. 0 Solvent M, No. 0 Solvent H, Cactus Normal Paraffin N-10, Cactus Normal Paraffin N-11, Cactus Normal Paraffin N-12, Cactus Normal Paraffin N-13, Cactus Normal. Paraffin N-14, Cactus Normal Paraffin N-15H, Cactus Normal Paraffin YHNP, Cactus Normal Paraffin SHNP, Isosol 300, Isosol 400, Teclean N-16, Teclean N-20, Teclean N-22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No. 7, Naftesol 160, Naftesol 200, Naftesol 220 (all manufactured by JXTG Energy Co., Ltd.); Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exol D60, Exol D80, Exol D95, Exol D110, Exol D130 (all manufactured by Exxon Mobile); Moresco White P-40, Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White P-100, Moresco White P-120, Moresco White P-150, Moresco White P-200, Moresco White P-260, Moresco White P-350P (all manufactured by MORESCO Co., Ltd.) and the like are preferably mentioned. be able to.
Preferred examples of the aromatic hydrocarbon solvent include Grade Alken L, Grade Alken 200P (all manufactured by JXTG Energy Co., Ltd.), Solbesso 100, Solbesso 150, Solbesso 200, and Solbesso 200ND (all manufactured by ExxonMobil). it can.
The distillation initial distillation point of the petroleum-based hydrocarbon solvent is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, and even more preferably 200 ° C. or higher. The distillation initial distillation point can be measured according to JIS K0066 "Distillation test method for chemical products".

As the polar organic solvent, a fatty acid ester solvent, a higher alcohol solvent, a higher fatty acid solvent and the like can be preferably mentioned.
For example, isononyl isononanoate, isodecyl isononanoate, isotridecyl isononanoate, methyl laurate, isopropyl laurate, hexyl laurate, isopropyl myristate, isopropyl palmitate, hexyl palmitate, isooctyl palmitate, isostearyl palmitate, methyl oleate. , Ethyl oleate, isopropyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, isobutyl linoleate, butyl stearate, hexyl stearate, isooctyl stearate, isopropyl isostearate, 2-octyl pivalate A fatty acid ester-based solvent having 13 or more carbon atoms in one molecule, such as decyl, methyl soybean oil, isobutyl soybean oil, methyl tall oil, and isobutyl tall oil;
A higher alcohol-based solvent having 6 or more carbon atoms in one molecule, preferably 12 to 20 carbon atoms, such as isomiristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, and decyltetradecanol;
Higher fatty acid-based solvents such as lauric acid, isomyristic acid, palmitic acid, isoparmitic acid, α-linolenic acid, linoleic acid, oleic acid, isostearic acid, etc., which have 12 or more carbon atoms in one molecule, preferably 14 to 20 carbon atoms. Can be mentioned.
The boiling point of a polar organic solvent such as a fatty acid ester solvent, a higher alcohol solvent, or a higher fatty acid solvent is preferably 150 ° C. or higher, more preferably 200 ° C. or higher, and further preferably 250 ° C. or higher. preferable. The non-aqueous solvent having a boiling point of 250 ° C. or higher also includes a non-aqueous solvent having a boiling point.

These non-aqueous solvents may be used alone or in combination of two or more as long as they form a single phase.

The amount of the modified silicone oil A in the ink is preferably 20% by mass or more, more preferably 25% by mass or more, based on the total amount of the non-aqueous solvent in the ink. The amount of the modified silicone oil A in the ink may be, for example, 90% by mass or less, or 80% by mass or less, based on the total amount of the non-aqueous solvent in the ink.

In addition to the above components, the oil-based ink may contain various additives as long as the effects of the present invention are not impaired. As the additive, a nozzle clogging inhibitor, an antioxidant, a conductivity adjuster, a viscosity adjuster, a surface tension adjuster, an oxygen absorber and the like can be appropriately added. These types are not particularly limited, and those used in the art can be used.

The ink can be produced by mixing each component including a coloring material and a non-aqueous solvent.
Preferably, each component can be collectively or divided, mixed and stirred to prepare an ink. Specifically, all the components can be collectively or divided and dispersed in a disperser such as a bead mill, and if desired, prepared by passing through a filter such as a membrane filter.

The appropriate range of the viscosity of the oil-based inkjet ink varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, etc., but in general, it is preferably 5 to 30 mPa · s at 23 ° C., and 5 to 15 mPa · s. It is more preferable that it is about 10 mPa · s, and it is more preferable that it is about 10 mPa · s.

The printing method using the inkjet ink is not particularly limited, and any method such as a piezo method, an electrostatic method, or a thermal method may be used, but the piezo method is preferable. When an inkjet recording device is used, it is preferable to eject the ink according to the present embodiment from the inkjet head based on a digital signal so that the ejected ink droplets adhere to the recording medium.

In the present embodiment, the recording medium is not particularly limited, and a printing paper such as plain paper, coated paper, or special paper, a cloth, an inorganic sheet, a film, an OHP sheet, or the like is used as a base material and an adhesive layer is formed on the back surface. An adhesive sheet or the like provided with the above can be used. Among these, printing paper such as plain paper and coated paper can be preferably used from the viewpoint of ink permeability.

Here, the plain paper is a paper in which an ink receiving layer, a film layer, or the like is not formed on the ordinary paper. Examples of plain paper include high-quality paper, medium-quality paper, PPC paper, stencil paper, recycled paper, and the like. Plain paper is a paper in which ink easily permeates because paper fibers having a thickness of several μm to several tens of μm form voids of several tens to several hundreds of μm.

Further, as the coated paper, an inkjet coated paper such as matte paper, glossy paper, or semi-glossy paper, or so-called coated printing paper can be preferably used. Here, the coating printing paper is a printing paper that has been conventionally used for letterpress printing, offset printing, gravure printing, etc., and has an inorganic pigment such as clay or calcium carbonate on the surface of high-quality paper or medium-quality paper. , A printing paper provided with a coating layer using a paint containing a binder such as starch. Coated printing paper can be used for finely coated paper, high-quality lightweight coated paper, medium-quality lightweight coated paper, high-quality coated paper, medium-quality coated paper, art paper, cast-coated paper, etc., depending on the amount of paint applied and the coating method. being classified.

Hereinafter, the present invention will be described in detail with reference to Examples. The present invention is not limited to the following examples.

<Synthesis of modified silicone oil>
Hexane was charged in 50 parts by mass, 1,1,1,3,5,5,5-heptamethyltrisiloxane in 10 parts by mass, and 1-tetradecene in 9.6 parts by mass in a four-necked flask. 0.02 parts by mass of a platinum catalyst (“1,3-divinyl-1,1,3,3-tetramethyldisiloxane platinum complex” manufactured by Sigma-Aldrich) was added dropwise thereto, and the mixture was stirred at room temperature for 2 to 3 hours. did. Then, the reaction solvent (hexane) and the unreacted raw material were distilled off by distillation under reduced pressure to obtain "solvent A (tetradecylmethicone)". Solvent A (tetradecylmethicone) is a compound modified with a tetradecyl group.
"Solvent B (dioctyldisiloxane)" was synthesized in the same manner as above except that the siloxane raw material and the reactive compound were blended according to the formulations shown in Table 1. Solvent B (dioctyldisiloxane) is a compound modified with two octyl groups.
In the synthesis of solvent A (tetradecylmethicone), the siloxane compound was blended so that the molar ratio of the reactive compound was 1: 1.1. In the synthesis of solvent B (dioctyldisiloxane), the siloxane compound was blended so that the molar ratio of the reactive compound was 1: 2.2.
The 1,1,1,3,5,5,5-heptamethyltrisiloxane, 1,1,3,3-tetramethyldisiloxane and reactive compounds shown in Table 1 shall be obtained from Tokyo Chemical Industry Co., Ltd. Can be done.

<Making ink>
The ink formulations are shown in Tables 2, 3 and 4. Pigments, pigment dispersants, and various solvents shown in each table are mixed according to the blending amount shown in each table, and the residence time is 15 minutes with the bead mill "Dynomill KDL-A" (manufactured by Simmal Enterprises Co., Ltd.). , The pigment was sufficiently dispersed. Subsequently, coarse particles were removed with a membrane filter to obtain ink.

The materials used are as follows.

(1) Carbon black MA77: "MA77" manufactured by Mitsubishi Chemical Corporation (pH 2.5)
FW18: Orion Engineered Carbons "Color Black FW18" (pH 2.5)
MA230: "MA230" (pH 3.0) manufactured by Mitsubishi Chemical Corporation
S160: "Color Black S160" manufactured by Orion Engineered Carbons (pH 3.0)
S170: "Color Black S170" manufactured by Orion Engineered Carbons (pH 4.5)
# 2600: "# 2600" manufactured by Mitsubishi Chemical Corporation (pH 6.5)
(2) Pigment dispersant S13940: "Solsperse 13940" manufactured by Japan Lubrizol Co., Ltd., polyesteramine-based, 40% by mass of active ingredient
S16000: "Solsperse 16000" manufactured by Japan Lubrizol K.K., fatty acid amine type, 100% by mass of active ingredient

(3) Non-aqueous solvent (3-1) Silicone oil KF-96L-5cs: "KF-96L-5cs" manufactured by Shin-Etsu Chemical Co., Ltd. (dimethylpolysiloxane, chain silicone oil, surface tension 19.7 mN / m)
DC246 fluid: "DC246 fluid" manufactured by Toray Dow Corning (dodecamethylcyclohexanesiloxane, cyclic silicone oil, surface tension 18.8 mN / m)
(3-2) Modified Silicone Oil HIVAC f-4: "HIVAC f-4" manufactured by Shin-Etsu Chemical Co., Ltd. (1,3,3,5-tetramethyl-1,1,5,5-tetraphenyltrisiloxane, Phenyl-modified silicone oil, surface tension 33.9 mN / m)
KF-56A: "KF-56A" manufactured by Shin-Etsu Chemical Co., Ltd. (diphenylsiloxyphenyl trimeticone, phenyl-modified silicone oil, surface tension 24.4 mN / m)
SS-3408: "SS-3408" manufactured by Toray Dow Corning Co., Ltd. (caprilyl methicone, alkyl-modified silicone oil, surface tension 20.3 mN / m)
Solvent A: Synthesized above (tetradecylmethicone, alkyl-modified silicone oil, surface tension 22.9 mN / m)
Solvent B: Synthesized above (dioctyldisiloxane, alkyl-modified silicone oil, surface tension 24.0 mN / m)
TSF410: "TSF410" manufactured by Momentive Performance Materials Japan GK (carboxylic acid ester-modified silicone oil, surface tension 23.0 mN / m)
TSF411: Momentive Performance Materials Japan GK "TSF410" (carboxylic acid ester-modified silicone oil, surface tension 26.0 mN / m)
(3-3) Non-aqueous solvent
KAK139: "KAK139" manufactured by Higher Alcohol Industry Co., Ltd. (isotridecyl isononanoate, surface tension 29.3 mN / m)

The pH of carbon black was determined according to JIS K5101.

The surface tension of the solvent was determined using "SITA Messtechnic GmbH science line t60" manufactured by SITA Process Solutions under the measurement conditions of 23 ° C. and 0.05 Hz.

<Evaluation>
The inks of the above Examples and Comparative Examples were evaluated by the following methods. The evaluation results are shown in Tables 2-4.

(1) Ink storage stability (70 ° C)
Each ink is placed in a closed container and left in an environment of 70 ° C. for 4 weeks, and the ink viscosity "initial value" before leaving and the ink viscosity "viscosity after 4 weeks" after leaving are measured. The viscosity change rate was calculated from the following formula. From the viscosity change rate, the storage stability was evaluated according to the following evaluation criteria.
The ink viscosity was the viscosity at 23 ° C., and was measured using "Rheometer MCR302" (cone angle 1 °, diameter 50 mm) manufactured by Anton Pearl Japan Co., Ltd.
Viscosity change rate = [(viscosity after 4 weeks x 100) / (initial value of viscosity)] -100 (%)
(Evaluation criteria)
A: Viscosity change rate is less than ± 1% B: Viscosity change rate is ± 1% or more and less than 2% C: Viscosity change rate is ± 2% or more

(2) Evaluation of wiping resistance Drop each ink onto the cured film of the nozzle plate, and rub the nozzle plate at a speed of 200 reciprocations / minute with a fluororubber (Viton MV454 53 ° DuPontau Elastomer Co., Ltd.) blade. The surface of the nozzle plate was visually observed every 1000 round trips, and the number of round trips on the blank nozzle plate until the nozzle plate surface was wetted with ink was counted. The amount of contact force between the fluororubber and the nozzle plate was about 6 × 10 ^-2 N. The fact that the surface is wet with the ink means that the cured film is damaged, and the more the number of reciprocations of the plate until the nozzle plate surface is wet with the ink, the higher the wiping resistance. Wiping resistance was evaluated according to the following evaluation criteria.
(Evaluation criteria)
S: The number of reciprocations of the blade is 2000 or more A: The number of reciprocations of the blade is 1000 or more and less than 2000 B: The number of reciprocations of the blade is less than 1000

As shown in Tables 2 and 3, in Examples 1 to 13 using an ink containing 15% by mass or more and 80% by mass or less of the modified silicone oil having a surface tension of 27 mN / m or less with respect to the total amount of the ink, storage stability and storage stability and storage stability and Excellent results were shown in all of the wiping resistance.

On the other hand, as shown in Table 4, in Comparative Example 1, the amount of the modified silicone oil having a surface tension of 27 mN / m or less was small, and the wiping resistance was poor.
In Comparative Example 2, the amount of the modified silicone oil having a surface tension of 27 mN / m or less was 90% by mass, and the wiping resistance was poor.
Comparative Example 3 used neutral carbon black and had poor storage stability.
In Comparative Examples 4 and 5, chain silicone oil or cyclic silicone oil, which was not modified silicone oil, was used, and the storage stability was poor.
Comparative Example 6 used a modified silicone oil having a high surface tension, and had poor storage stability and wiping resistance.

Claims (2)

Contains pigments, pigment dispersants and non-aqueous solvents
The pigment comprises acidic carbon black having a pH of 2-6.
The non-aqueous solvent contains a modified silicone oil having a surface tension of 27 mN / m or less.
The modified silicone oil is 15% by mass or more and 80% by mass or less with respect to the total amount of ink.
Oil-based inkjet ink. The oil-based inkjet ink according to claim 1, wherein the modified silicone oil is 15% by mass or more and 70% by mass or less with respect to the total amount of the oil-based inkjet ink.