JP6758214B2 - Oil-based inkjet ink - Google Patents

Description

The present invention relates to oil-based inkjet inks.

In the inkjet recording method, highly fluid inkjet ink is ejected as droplets from a fine nozzle, and an image is recorded 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) whose main solvent is a volatile organic solvent and oil-based inks (oil-based inks) whose 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.

As an oil-based inkjet ink having a high pigment concentration and a low viscosity, there is a technique of using a capsule-type pigment surface-treated with a (meth) acrylic acid-based copolymer having an acid value of 30 to 60 (see Patent Document 1).
However, such ink has good wettability with respect to the nozzle plate surface of the head of the inkjet printing apparatus, and easily adheres to the nozzle plate surface. Therefore, there is a problem that the ink adhering to the surface of the nozzle plate drips on the paper and stains the image, and the ink adhering to the surface of the nozzle plate hinders the ejection of the ink.

In addition, the inkjet printing apparatus is designed so that the head cleaning operation is performed periodically. This head cleaning operation generally consists of a pressurized purge that ejects ink from the nozzle and wiping of the nozzle plate.
When ink that easily adheres to the nozzle plate surface is used, when the nozzle plate is wiped, the pigment in the ink becomes an abrasive and scrapes off the film such as fluororesin on the nozzle plate surface, reducing the ink repellency of the nozzle plate. May cause you to.

In response to the above problem, Patent Document 2 uses a capsule-type pigment in which a compound having an α value of 5 to 60 is added as a side chain and surface-treated with a comb-shaped polyurethane compound miscible with a solvent in an oil-based inkjet ink. It is disclosed that the nozzle plate is excellent in repellent property and deterioration of the nozzle plate can be suppressed.

JP-A-2007-314651 Japanese Unexamined Patent Publication No. 2011-57812

On the other hand, in oil-based inkjet ink, when the ink is ejected onto the paper, the solvent in the ink permeates the inside of the paper on the surface of the paper. At this time, when the pigment penetrates into the paper together with the solvent in the ink, a so-called strike-through phenomenon occurs in which the image strikes through on the back surface of the paper. When strike-through occurs, the image density on the paper surface also decreases.
In Patent Document 2, since a comb-shaped polyurethane compound miscible with a solvent is used for the capsule-type pigment, the capsule-type pigment permeates the inside of the paper together with the solvent in the ink, causing strike-through and lowering the image density. There's a problem.

Further, in the oil-based inkjet ink, after the ink lands on the paper, the solvent in the ink permeates the paper and the pigment remains on the paper surface, so that a high-density printed image can be obtained. At this time, the scratch resistance of the printed matter is important so that the image does not rub off even if the printed image surface is rubbed.

One object of the present invention is to reduce image strike-through of printed matter, increase image density, and improve scratch resistance of printed matter. A further object of the present invention is to improve wettability and wipe durability with respect to the nozzle plate.

The gist of the present invention is as follows.
(1) The urethane-modified epoxy resin contains an encapsulating pigment containing a pigment and a urethane-modified epoxy resin that coats the surface of the pigment, and a non-aqueous solvent. The urethane-modified epoxy resin has a urethane portion and an epoxy resin portion, and is said to be non-aqueous. It is a solvent-insoluble compound, and the urethane moiety is selected from the group consisting of an aromatic ring, a heterocycle, a carboxy group, an amide bond, a fluoroalkyl group having one or more fluorine atoms, an amino group, and a nitrile group. An oil-based inkjet ink containing one or more side chains.
(2) The oil-based inkjet ink according to (1), wherein the mass ratio of the urethane portion to the epoxy resin portion is 85: 15-40: 60.

(3) An encapsulating pigment containing a pigment and a urethane-modified (meth) acrylic resin that coats the surface of the pigment, and a non-aqueous solvent are contained, and the urethane-modified (meth) acrylic resin is a urethane portion and (meth) acrylic. It is a compound that has a resin moiety and is insoluble in the non-aqueous solvent, and the urethane moiety is an aromatic ring, a heterocycle, a carboxy group, an amide bond, a fluoroalkyl group having one or more fluorine atoms, an amino group, and An oil-based inkjet ink containing one or more side chains selected from the group consisting of nitrile groups.
(4) The (meth) acrylic resin moiety has a reactive functional group that is reactive with an isocyanate group, and a unit a to which the urethane moiety is bonded via the reactive functional group and a unit b having an aromatic ring. The oil-based inkjet ink according to (3), which comprises and / or a unit c having a carboxy group.
(5) The oil-based inkjet ink according to any one of (3) and (4), wherein the mass ratio of the urethane portion to the (meth) acrylic resin portion is 85: 15-40: 60.

(6) The oil-based inkjet ink according to any one of (3) to (5), wherein the urethane-modified (meth) acrylic resin has an acid value of 15 to 200 mgKOH / g.
(7) The side chain of the urethane portion is selected from the group consisting of an aromatic ring, a heterocycle, a carboxy group, an amide bond, a fluoroalkyl group having one or more fluorine atoms, an amino group, and a nitrile group1 The oil-based inkjet ink according to any one of (1) to (6), which has more than one species.
(8) The urethane portion has a structure in which units derived from polyhydric isocyanate and units derived from polyhydric alcohol are alternately arranged, and the units derived from polyhydric alcohol include units derived from alkanolamine. The oil-based inkjet ink according to any one of (1) to (7), wherein the side chain of the urethane portion is bonded to the urethane portion via a nitrogen atom of a unit derived from the alkanolamine.
(9) The unit derived from the alkanolamine is a unit derived from a dialkanolamine obtained by Michael-adding an acrylate having an aromatic ring, a unit derived from a dialkanolamine obtained by Michael-adding an acrylamide having a heterocycle, and a unit derived from N-alkylacrylamide by Michael addition. Selected from the group consisting of units derived from dialkanolamines derived from dialkanolamines, units derived from dialkanolamines to which N, N-dialkylacrylamide was Michael-added, acrylonitrile, and units derived from dialkanolamines to which acrylates having an amino group were Michael-added. The oil-based inkjet ink according to (8), which comprises one or more.
(10) The oil-based inkjet ink according to any one of (8) and (9), wherein the unit derived from the polyhydric alcohol further contains a unit derived from asymmetric glycol.

According to the present invention, it is possible to reduce image strike-through of printed matter, increase image density, and improve scratch resistance of printed matter. Further, according to the present invention, the wettability to the nozzle plate and the wipe durability can be improved.
The oil-based inkjet ink according to the present invention can improve scratch resistance to coated paper as well as plain paper.

Hereinafter, the present invention will be described using one embodiment. The illustrations in the following embodiments do not limit the invention.
(First Embodiment)
The oil-based inkjet ink according to the present embodiment (hereinafter, may be simply referred to as "ink") includes an encapsulating pigment containing a pigment and a urethane-modified epoxy resin that coats the surface of the pigment, and a non-aqueous solvent. The urethane-modified epoxy resin has a urethane portion and an epoxy resin portion, and is a compound insoluble in a non-aqueous solvent. The urethane portion has an aromatic ring, a heterocycle, a carboxy group, an amide bond, and one or more fluorine atoms. It is characterized by containing one or more side chains selected from the group consisting of fluoroalkyl groups, amino groups, and nitrile groups.
According to this embodiment, it is possible to reduce the image strike-through of the printed matter, increase the image density, and improve the scratch resistance of the printed matter. Further, according to the present embodiment, the wettability to the nozzle plate and the wipe durability can be improved.
The oil-based ink according to the present embodiment can improve the scratch resistance to coated paper as well as plain paper.

In oil-based inkjet inks, when a pigment that is not encapsulated in resin is used, the pigment becomes an abrasive and the surface of the nozzle plate of the printing apparatus may be scraped, which causes a problem of reducing the ink repellency of the nozzle plate. .. Then, ink droplets may adhere to the nozzle portion, and ink droplets may drip from the nozzle plate to stain the printed matter, and the nozzles may be clogged, leading to poor ejection.

In the present embodiment, the side chain of the urethane portion of the urethane-modified epoxy resin has the above-mentioned structure, so that the wettability to the nozzle plate and the wipe durability can be improved. Further, after specifying the side chain of the urethane portion, the urethane-modified epoxy resin has low solubility in the ink solvent, so that image strike-through can be reduced and the image density can be increased.
When the urethane-modified epoxy resin becomes less soluble in the ink solvent, the pigment encapsulated in the urethane-modified epoxy resin becomes more solvent-removable on the recording medium. Then, when the pigment is separated from the solvent on the surface of the recording medium and the solvent permeates into the recording medium, the pigment tends to remain on the surface of the recording medium. As a result, image strike-through can be reduced and the image density can be increased.

Further, since the urethane-modified epoxy resin has excellent adsorptivity to the pigment, the coating efficiency of the pigment can be improved. Then, it is possible to prevent the ink solvent from being caught in the urethane-modified epoxy resin of the coating film and penetrating into the pigment in the ink. As a result, the detachability between the pigment and the solvent can be improved.
Further, by improving the coating efficiency of the pigment by the urethane-modified epoxy resin, it is possible to prevent the pigment surface from directly contacting the nozzle plate and polishing, and the wipe durability can be further improved.

Further, since the urethane-modified epoxy resin has an epoxy resin portion, the effects of reducing strike-through and improving image density can be further enhanced. Further, this can improve the scratch resistance to the coated paper as well as the plain paper.
Since the urethane-modified epoxy resin contains the epoxy resin portion together with the urethane portion, a certain degree of hardness is imparted to the resin, and the ink coating film on the paper surface can be made stronger, so that the printed matter has scratch resistance. Can be improved.

The ink of the present embodiment contains an encapsulating pigment, and the encapsulating pigment contains a pigment and a urethane-modified epoxy resin that coats the surface of the pigment.

As the pigment, organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments and dyed lake pigments, and inorganic pigments such as carbon black and metal oxides can be used.
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 carbon black include furnace carbon black, lamp black, acetylene black, and channel black. Examples of the metal oxide include titanium oxide and zinc oxide. These pigments may be used alone or in combination of two or more.

The average particle size of the pigment is preferably 300 nm or less, more preferably 200 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 from the viewpoint of print density and ink viscosity.

In the encapsulated pigment, a partial or total area of the pigment surface is coated with a urethane-modified epoxy resin.
The urethane-modified epoxy resin is preferably insoluble in the non-aqueous solvent used for the ink.
Specifically, the urethane-modified epoxy resin is preferably dissolved in 100 g of the non-aqueous solvent used for the ink at 23 ° C. at 3 g or less, more preferably 1 g or less, and further preferably 0. It is 5 g or less. More preferably, the urethane-modified epoxy resin is substantially insoluble in the non-aqueous solvent used for the ink at 23 ° C.
When two or more kinds of solvents are mixed in the ink, the solubility in the non-aqueous solvent used in the ink is the solubility in a mixture of two or more kinds of solvents mixed in the same mixing ratio as the ink.

The urethane-modified epoxy resin has a urethane portion having a side chain and an epoxy resin portion.
As the urethane portion, for example, a compound containing a main chain composed of a urethane skeleton and a side chain graft-polymerized on the main chain can be used.
The side chain of the urethane moiety contains at least one selected from the group consisting of aromatic rings, heterocycles, carboxy groups, amide bonds, fluoroalkyl groups having one or more fluorine atoms, amino groups, and nitrile groups. Is preferable.
When the urethane portion contains one or more of a heterocycle, an amide bond, an amino group and a nitrile group as a side chain, the adsorptivity of the urethane-modified epoxy resin to the pigment can be further enhanced.
Since the side chain of the urethane portion branches from the urethane skeleton, it has a comb-shaped polyurethane structure.

In the urethane-modified epoxy resin, for example, by reacting a polyhydric alcohol, a polyhydric isocyanate, and an epoxy resin, a urethane skeleton is formed by the polyhydric alcohol and the polyhydric isocyanate, and this urethane skeleton is bonded to the epoxy resin. And can be synthesized.
For example, by using a hydroxyl group-containing epoxy resin or an epoxy resin in which the epoxy group of the epoxy resin is modified with alkanolamine to introduce a hydroxyl group, the isocyanate group of the urethane skeleton is bonded to the hydroxyl group of the epoxy resin. Can be made to.

The urethane moiety has, for example, a structure in which units derived from polyisocyanate and units derived from alkanolamine are alternately arranged, and the side chains of the urethane moiety are bonded via a nitrogen atom of the unit derived from alkanolamine. Can be used.
Such a urethane moiety can be obtained by reacting a multivalent isocyanate with an alkanolamine or a derivative thereof.

As the alkanolamine, monoalkanolamine, dialkanolamine, or a combination thereof can be used.
Examples of monoalkanol amines include monomethanol amine, monoethanolamine, mono (n-propanol) amine, monoisopropanol amine, monobutanol amine, monopentanol amine, monohexanol amine, monoheptanol amine, monooctanol amine, and the like. Monononanolamine, monodecanolamine, monoundecanolamine, monododecanolamine, monotridecanolamine, monotetradecanolamine, monopentadecanolamine, monohexadecanolamine and the like can be used.
As the dialkanolamine, for example, diethanolamine, diethanolamine, di (n-propanol) amine, diisopropanolamine, dibutanolamine, dipentanolamine, dihexanolamine, diheptanolamine and the like can be used.
Further, the monoalkanolamine and the dialkanolamine may each have a branched chain or may have a substituent.

Preferably, a dialkanolamine can be used in the urethane moiety.
The isocyanate group of the polyhydric isocyanate and the hydroxy group of the dialkanolamine, which is a dihydric alcohol, form a urethane bond "-NH-CO-O-", and further, "-(CH ₂ ) _m " derived from the dialkanolamine. A bond represented by −NR− (CH ₂ ) _n− ”is formed. Here, m and n are positive integers and R is a side chain.

Specifically, a urethane portion having a repeating unit represented by the following formula (1) can be used. In the formula (1), R is a side chain, and the unit "-O- (CH ₂ ) _m- NR- (CH ₂ ) _n- O-" derived from dialkanolamine having the side chain R and the unit derived from diisocyanate. "-CONH-Y-NHCO-" are arranged alternately.

In the formula (1), m and n are independently positive integers, and are preferably integers of 1 to 18. p is a positive integer, which varies depending on the degree of polymerization of the urethane portion, and may be an integer of 5 to 100.
Y is an arbitrary divalent group.
R is -A-R ¹ , A is a single bond or any divalent group, R ¹ is an aromatic ring-containing group, a heterocyclic group, a hydrogen atom, a carboxy group, an amide bond-containing group, 1 It is selected from a fluoroalkyl group having more than one fluorine atom, an amino group, and a nitrile group, which may have a substituent.

In the formula (1), R is ^{-A-R 1,} A is, - _{(CH 2) 2} - it will be preferable to include. In this case, the dialkanolamine "OH- (CH ₂ ) _m- NH- (CH ₂ ) _n- OH" is subjected to a Michael addition reaction with a vinyl monomer having a group represented by R ¹ to carry out a Michael addition reaction to the nitrogen of the dialkanolamine. The target urethane moiety can be produced by using a dialkanolamine derivative having a group represented by R ¹ introduced from the atom "N" as a base point.
The general formula of the dialkanolamine derivative is shown below.
OH- (CH ₂ ) _m- NR- (CH ₂ ) _n- OH
Here, m and n are independently positive integers, and are preferably integers of 1 to 18. R is a side chain.

In addition, monoalkanolamines or derivatives thereof may be used in place of or in combination with dialkanolamines or derivatives thereof.
The monoalkanolamine derivative can be produced, for example, by subjecting monoalkanolamine to a Michael addition reaction of a vinyl monomer having a group represented by R ¹ in the same manner as the above-mentioned dialkanolamine.

The introduction of the side chain by this Michael addition reaction is usually performed on the dialkanolamine monomer before the urethanization reaction, but it is performed on the unit derived from the dialkanolamine contained in the urethane moiety after the polymerization. May be good.
As the vinyl monomer, a monomer having an acryloyloxy group such as acrylate, a monomer having an acryloyl group, acrylamides, a monomer having a vinyl group and the like can be used.
For example, when a Michael addition reaction is carried out between an acrylate having a group represented by R ¹ and a dialkanolamine, the reaction proceeds as shown in the following formula, and a dialkanolamine derivative can be obtained.

(1) Side chain derived from acrylate As an example of the urethane portion, in the formula (1), the side chain R is − (CH ₂ ) _2- COO-R ^1a , and R ^1a contains a hydrogen atom and an aromatic ring. A group, a heterocyclic group, or a fluoroalkyl group having one or more fluorine atoms, which may have a substituent.
According to the urethane-modified epoxy resin containing such a urethane portion, it is possible to improve the image strike-through and the image density as well as the wettability to the nozzle plate and the wipe durability.
When the side chain of the urethane portion has a carboxy group, an aromatic ring or a heterocycle, the storage stability of the ink can be further maintained well.
Further, when the side chain of the urethane portion has a fluoroalkyl group having one or more fluorine atoms, the scratch resistance of the printed matter can be further improved.

When R ^1a is a hydrogen atom, a carboxy group is introduced into the side chain of the urethane portion.
As an example of the aromatic ring-containing group in R ^1a , the following functional groups can be mentioned.

Examples of the heterocyclic ring-containing group in R ^1a include the following functional groups.

As the fluoroalkyl group having one or more fluorine atoms in R ^1a , 50% or more, preferably 80% or more of the hydrogen atoms (number) of the alkyl group having 1 to 10 carbon atoms in the linear or branched chain is fluorine. Those substituted with atoms are preferable. Examples of fluoroalkyl groups include the following functional groups.

When producing the urethane moiety described above, the following monomer was introduced from the nitrogen atom "N" of the dialkanolamine "OH- (CH ₂ ) _m- NH- (CH ₂ ) _n- OH". Alkanolamine derivatives can be used. An acrylate having an aromatic ring such as benzyl acrylate or phenoxyethyl acrylate is preferable.

Further, as an example of the urethane portion, in the formula (1), the side chain R is − (CH ₂ ) _2- COO-R ^1a , and R ^1a is a nitrogen atom-containing group such as an amino group. May have a substituent.
When producing the urethane portion described above, dimethylaminomethyl acrylate and dimethylamino are used as the starting point of the nitrogen atom "N" of the dialkanolamine "OH- (CH ₂ ) _m- NH- (CH ₂ ) _n- OH". A dialkanolamine derivative introduced with ethyl acrylate, diethylaminoethyl acrylate or the like can be used.

(2) As an example of the urethane portion of the side chain derived from acrylamide, in the formula (1), the side chain R is − (CH ₂ ) _2- R ^1b , and R ^1b is represented by the following formula (2). It is an amide bond-containing group.
―CO-NR'R''
In formula (2), R'and R'' are groups that independently form a heterocycle with a hydrogen atom, an alkyl group, or N, R'and R'', respectively, and these have substituents. You may.
According to the urethane-modified epoxy resin containing such a urethane portion, it is possible to improve the image strike-through and the image density as well as the wettability to the nozzle plate and the wipe durability.
Since the side chain of the urethane portion has an amide bond-containing group, it is possible to further maintain good storage stability of the ink.

When both R'and R'are hydrogen atoms, an amide group is introduced into the side chain of the urethane portion.
When either one of R'and R'is an alkyl group and the other is a hydrogen atom, a monoalkylamide group is introduced into the side chain of the urethane portion.
When both R'and R'are alkyl groups, a dialkylamide group will be introduced into the side chain of the urethane moiety.
The alkyl group of the monoalkylamide group and the dialkylamide group may independently have a substituent such as an amino group or a hydroxy group.
When the side chain of the urethane portion has a monoalkylamide group or a dialkylamide group, the wipe durability can be further improved.
R'and R'' may form a heterocycle with the nitrogen atom "N" of "-CO-NR'R'".

Examples of "-NR" R "" include the following functional groups.

When producing the urethane portion described above, a dialkanolamine derivative into which the following monomers are introduced from the nitrogen atom of the dialkanolamine can be used. Preferred is N-alkylacrylamide; N, N-dialkylacrylamide such as dimethylacrylamide and diethylacrylamide; acrylamide having a heterocycle such as acryloylmorpholine.

(3) Side chain derived from acrylonitrile As an example of the urethane portion, in the formula (1), the side chain R is − (CH ₂ ) _2- R ^1c , and R ^1c is a nitrile group.
When producing such a urethane moiety, a dialkanolamine derivative introduced with the following acrylonitrile from the nitrogen atom of the dialkanolamine can be used.

According to the urethane-modified epoxy resin containing such a urethane portion, it is possible to improve the image strike-through and the image density as well as the wettability to the nozzle plate and the wipe durability.
Since the side chain of the urethane portion has a nitrile group, the wipe durability can be further improved, and the storage stability of the ink can be maintained well.

The urethane portion may contain one or more of the above-mentioned side chain structures. A urethane moiety having two or more types of side chains can be obtained by reacting a polyisocyanate compound with two or more types of dialkanolamine derivatives having different functional groups.
Preferably, the urethane moiety has a first side chain having an aromatic ring and a second side chain having a heterocycle, a carboxy group, an amide bond, a fluoroalkyl group having one or more fluorine atoms, an amino group, or a nitrile group. It is preferable to have a side chain. Since the urethane portion has the second side chain, each effect is exhibited, while the first side chain has the aromatic ring, so that the wettability to the nozzle plate can be surely improved. The first side chain and the second side chain are preferably in a molar ratio of 25:75 to 75:25.

In the urethane portion, as the unit derived from the multivalent isocyanate, it is preferable that Y has the following structure in the above formula (1).
Examples thereof include a linear or branched alkylene group having 1 to 8 carbon atoms; a divalent group having an aromatic ring such as benzene and naphthalene; and a divalent group having a cycloalkane such as cyclohexane and norbornene.

The polyisocyanate used in producing such a urethane portion is a compound having two or more isocyanate groups, and may be any of an aliphatic polyisocyanate, an alicyclic polyisocyanate, an aromatic polyisocyanate and the like. Good.

Specific examples of the polyisocyanate include 1,6-diisocyanate hexane, 1,3-bis (isocyanatomethyl) benzene, 1,3-bis (isocyanatomethyl) cyclohexane, 1,5-naphthalenediocyanate, and diphenylmethane. Diisocyanates such as -4,4-diisocyanate, hexamethylene diisocyanate, metaxylene diisocyanate; triisocyanates such as 1-methylbenzene-2,4,6-triyl triisocyanate, 1,6,11-triisocyanatoundecane ; Polyisocyanate such as polymethylene polyphenyl polyisocyanate and the like can be mentioned.
Examples of the polyisocyanate compound include those having three or more isocyanate groups, such as a polyisocyanate compound containing an isocyanurate ring, a polyisocyanate compound containing an adduct structure, a polyvalent isocyanate compound containing a bullet structure, and unddione. Polyvalent isocyanate compounds containing a structure can be used.
Examples of the polyisocyanate compound containing an isocyanurate ring include hexamethylene diisocyanate isocyanurate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate isocyanate isocyanurate, and the like. Moreover, as a polyvalent isocyanate compound containing an adduct structure, hexamethylene diisocyanate containing an adduct structure and the like can be mentioned.
Particularly preferably, divalent isocyanate can be used.

The urethane moiety may further contain units derived from polyhydric isocyanates and units derived from alkanolamines, as well as units derived from other polyhydric alcohols other than alkanolamines. By using a polyhydric alcohol having no side chain as another polyhydric alcohol, it is possible to prevent the urethane-modified epoxy resin containing the urethane portion from crystallizing in the ink solvent and to obtain miscibility with the ink solvent. Can be done.
Examples of other polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, polyethylene glycol, polypropylene glycol and the like. The unit derived from this may be contained in the urethane portion by one type or a combination of two or more types.
Above all, the urethane moiety preferably contains a unit derived from asymmetric glycol. The asymmetric glycol is preferably propylene glycol or polypropylene glycol having 3 to 600 carbon atoms.

The urethane moiety preferably contains units derived from alkanolamines and units derived from other polyhydric alcohols in a molar ratio of 25:75 to 75:25 (alkanolamines: other dihydric alcohols).

Hereinafter, the epoxy resin portion of the urethane-modified epoxy resin will be described.
As the epoxy resin constituting the epoxy resin portion, for example, a resin having epoxy groups at both ends of the epoxy resin, a resin having a repeating unit having an epoxy group, or the like can be used.

Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin and other bisphenol type epoxy resin; phenol novolac type epoxy resin, cresol novolac type epoxy resin and other novolac type epoxy resin; glycidyl. Examples thereof include an ester type epoxy resin, a glycidylamine type epoxy resin, an alicyclic type epoxy resin, a heterocyclic type epoxy resin, and an epoxy polyol.
These can be used alone or in combination of two or more.

The epoxy resin moiety is derived from an epoxy resin having a reactive functional group that is reactive with the isocyanate group, and it is preferable that the urethane moiety is bonded via the reactive functional group. Examples of the reactive functional group include a hydroxyl group and an amino group.
Among them, as the epoxy resin, an epoxy resin obtained from epichlorohydrin and an active hydrogen compound can be preferably used. Specifically, a glycidyl ether type epoxy resin is preferable, and a bisphenol type epoxy resin produced by a condensation reaction of epichlorohydrin and bisphenol (A, F, AD) can be preferably used.

The urethane-modified epoxy resin is, for example, added by adding an epoxy resin containing a reactive functional group having reactivity with the isocyanate group of the polyhydric isocyanate in the process of reacting the polyhydric alcohol with the polyhydric isocyanate to synthesize a urethane portion. Obtainable.
The bisphenol type epoxy resin can bond urethane portions with a hydroxyl group as a reaction point. Further, since the bisphenol type epoxy resin has a hydroxyl group in the repeating structure, it has excellent compatibility with an organic solvent.

Further, the epoxy resin moiety is derived from an epoxy resin having an amine-modified moiety in which an epoxy group is modified with an amine, and it is preferable that the urethane moiety is bonded via the amine-modified moiety.
In this case, the reactivity of the epoxy group is used to react the epoxy group of the epoxy resin with the 1st and 2nd grade amines to introduce an amino group, or to react the epoxy group with an alkanolamine to introduce a hydroxyl group. Therefore, a reaction point with an isocyanate group can be introduced into the epoxy resin.
In such an amine-modified epoxy resin, the urethane-modified epoxy resin becomes more basic, and the adsorptivity to the pigment can be enhanced.

As the amine-modified epoxy resin, for example, the above-mentioned various epoxy resins may be amine-modified.
Specifically, the amine-modified epoxy resin can be obtained by reacting an epoxy resin with an alkanolamine in a solvent. As the alkanolamine, for example, monoalkanolamine, dialkanolamine, or a combination thereof can be used. As these alkanolamines, the same alkanolamines described when introducing the side chain into the urethane portion can be used.
It is preferable to react so that the amino group of the alkanolamine is 0.1 to 1.02 equivalent with respect to 1 equivalent of the epoxy group of the epoxy resin.

Examples of commercially available bisphenol A type epoxy resins include jER epoxy resins manufactured by Mitsubishi Chemical Corporation: 834, 1001, 1002, 1003, 1055, 1004AF, 1004, 1007, 1009, 1010 and the like.
Examples of commercially available bisphenol F type epoxy resins include jER epoxy resins manufactured by Mitsubishi Chemical Corporation: 806, 806H, 807, 4004P, 4005P, 4007P, 4010P and the like.
Phenolic novolac type epoxy resin Examples of commercially available products of the epoxy resin include jER epoxy resin manufactured by Mitsubishi Chemical Corporation: 152, 154 and the like.

The weight average molecular weight of the epoxy resin is preferably 300 to 7000, more preferably 450 to 3000.
When the weight average molecular weight of the epoxy resin is 300 or more, the scratch resistance to plain paper and coated paper can be further improved.
When the weight average molecular weight of the epoxy resin is 7,000 or less, the wettability to the nozzle plate and the wipe durability can be further improved.
Here, the weight average molecular weight (Mw) is a value obtained in terms of standard polystyrene by the GPC method (the same applies hereinafter).

The epoxy equivalent of the epoxy resin is preferably 150 to 6000, more preferably 200 to 3000, and even more preferably 250 to 2500.
When the epoxy equivalent is 150 or more, the scratch resistance to plain paper and coated paper can be further improved.
When the epoxy equivalent is 6000 or less, the wettability to the nozzle plate and the wipe durability can be further improved.
Here, the epoxy equivalent is the number of grams of the epoxy resin containing 1 gram equivalent of the epoxy group (the same applies hereinafter).

The urethane-modified epoxy resin can be produced by reacting a polyhydric alcohol, a polyhydric isocyanate, and an epoxy resin in an aprotic solvent having a low boiling point such as methyl ethyl ketone. As the polyhydric alcohol, one or more selected from alkanolamines and derivatives thereof, and selectively other polyhydric alcohols can be used.

At this time, as a catalyst, tin-based catalysts such as dibutyltin dilaurate and dioctyltin dilaurate; organic titanium compounds such as tetranormal butyl titanate, tetraoctyl titanate, titanium acetylacetonate, titanium ethyl acetate and titanium ethyl acetoacetate; zirconium tetraacetyl Organic zirconium compounds such as acetonate and zirconium ethyl acetoacetate; zinc-based catalysts, bismuth-based catalysts and the like may be added to the solvent.

Examples of commercially available tin-based catalysts include "L-101, OL-1" manufactured by Tokyo Fine Chemicals Co., Ltd.
Examples of commercially available organic titanium compounds include "Organics: TA-21, TA-30, TC-100, TC-710, TC-750" manufactured by Matsumoto Fine Chemicals Co., Ltd.
Examples of commercially available organic zirconium compounds include "Organics: ZC-21, ZC-700, ZC-580" manufactured by Matsumoto Fine Chemicals Co., Ltd.
Examples of commercially available zinc-based catalysts include "BiCAT: Z (M), 3228 (M)" manufactured by Shepherd Chemical.
Examples of commercially available bismuth-based catalysts include "BiCAT: 8118 (M), 8108 (M), 8124 (M), 8106 (M), 8210 (M)" manufactured by Shepherd Chemical.

It is preferable to mix and react the polyhydric alcohol and the polyhydric isocyanate so that the isocyanate group of the polyhydric isocyanate is 0.60 to 1.02 mol with respect to 1.0 mol of the hydroxy group of the polyhydric alcohol. ..

In the urethane-modified epoxy resin, the mass ratio (U: E) of the urethane portion (U) and the epoxy resin portion (E) may be in the range of 90:10 to 30:70, and is 85: 15 to 35:65. It is preferably 85: 15-40: 60, and more preferably 85: 15-40: 60.
More preferably, U: E is 80:20 to 40:60, and even more preferably 70:30 to 40:60.
As a result, the wettability to the nozzle plate and the wipe durability can be improved, and the scratch resistance to plain paper and coated paper can be improved.
Here, the mass of the urethane portion can be obtained from the total amount of the polyhydric alcohol and the polyisocyanate used in the reaction, and the mass of the epoxy resin portion can be obtained from the total amount of the epoxy resin used in the reaction.

The weight average molecular weight of the urethane-modified epoxy resin is preferably 2000 to 50,000. If the weight average molecular weight is lower than 2000, the urethane-modified epoxy resin may float in the ink solvent and the morphology of the encapsulated pigment may not be maintained. When the weight average molecular weight of the urethane-modified epoxy resin is higher than 40,000, coarse capsule particles may be generated, which may lead to deterioration of stability and ejection property. More preferably, the urethane-modified epoxy resin has a weight average molecular weight of 2000 to 40,000, more preferably 2000 to 30000, and even more preferably 4000 to 20000.

The urethane-modified epoxy resin described above can be preferably used as an encapsulating pigment in oil-based inks.
The urethane-modified epoxy resin is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and further preferably 0.15 part by mass or more with respect to 1 part by mass of the pigment. Thereby, the coating property of the pigment surface can be improved.
On the other hand, the urethane-modified epoxy resin is preferably 5.0 parts by mass or less, more preferably 1.0 part by mass or less, and further preferably 0.5 parts by mass or less with respect to 1 part by mass of the pigment. .. As a result, it is possible to prevent the surface of the pigment from being coated with the excess resin, and to prevent the excess resin from being mixed in the solvent.
The urethane-modified epoxy resin is preferably 0.01 to 30% by mass, more preferably 1 to 20% by mass, based on the total amount of the ink.

The encapsulating pigment is the total amount of the urethane-modified epoxy resin and the pigment, and is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, based on the total amount of the ink.

The oil-based ink may contain a pigment dispersant in order to stabilize the dispersibility of the encapsulating pigment.
Examples of the pigment dispersant include a hydroxyl group-containing carboxylic acid ester, a long-chain polyaminoamide and a high-molecular-weight acid ester salt, a high-molecular-weight polycarboxylic acid salt, a long-chain polyaminoamide and a polar acid ester salt, 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)" (trade name) manufactured by ISP Japan Co., Ltd. and "Solsperse 13940 (polyester amine) manufactured by Nippon Lubrizol Co., Ltd." System), 17,000, 18,000 (fatty acid amine system), 11200, 24,000, 28,000 "(all trade names)," Fuka 400, 401, 402, 403, 450, 451 and 453 (modified polyacrylate) manufactured by BASF Japan Co., Ltd.) , 46, 47, 48, 49, 4010, 4055 (modified polyurethane) "(all trade names), Kusumoto Kasei Co., Ltd." Disparon KS-860, KS-873N4 (polyester amine salt) "(all trade names) ), Dai-ichi Kogyo Seiyaku Co., Ltd. "Discol 202, 206, OA-202, OA-600 (multi-chain polymer non-ionic)" (all trade names), Big Chemie Japan Co., Ltd. "DISPERBYK2155, 9077 ”(all product names),“ Hypermer KD2, KD3, KD11, KD12 ”(all product names) manufactured by Crowder Japan Co., Ltd. can be mentioned.
The content of the dispersant is sufficient as long as the pigment can be sufficiently dispersed in the ink, and can be appropriately set. For example, the pigment dispersant can be blended in a mass ratio of 0.1 to 5 with respect to the pigment 1.

As the non-aqueous solvent, either a non-polar organic solvent or a polar organic solvent can be used. These may be used alone or in combination. 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, 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 naphthen-based solvents, and commercially available products include No. 0 solvent L and No. 0 solven M, 0. No. 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 4, AF Solvent 5, AF Solvent 6, AF Solvent 7, Naftesol 160, Naftesol 200, Naftesol 220 (all manufactured by JX Energy Co., Ltd.); Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exol D60, Exol D80, Exol D95, Exol D110, Exol D130 (all are Tonen General Oil Co., Ltd.) (Manufactured by Co., Ltd.) and the like can be preferably mentioned.
Preferred examples of the aromatic hydrocarbon solvent include Grade Alken L, Grade Alken 200P (all manufactured by JX Energy Co., Ltd.), Solbesso 100, Solbesso 150, Solbesso 200, and Solbesso 200ND (all manufactured by TonenGeneral Sekiyu Co., Ltd.). be able to.
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, 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-octyldecyl pivalate, soybean oil Fatty acid ester-based solvent having 13 or more carbon atoms in one molecule such as methyl, soybean oil isobutyl, linoleic acid methyl, and linoleic acid isobutyl; preferably 16 to 30; isomiristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl. Higher alcoholic solvents such as alcohols, isoeicosyl alcohols, decyltetradecanols, etc., which have 6 or more carbon atoms in one molecule, preferably 12 to 20; lauric acid, isomilystinic acid, palmitic acid, isopalmitic acid, α- Examples thereof include higher fatty acid-based solvents having 12 or more carbon atoms in one molecule, such as linolenic acid, linoleic acid, oleic acid, and isostearic acid, preferably 14 to 20.
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.

In the method for producing an encapsulated pigment according to the present embodiment, it is preferable to use a urethane-modified epoxy resin solution in which the above-mentioned urethane-modified epoxy resin is dissolved in an aprotic solvent having a low boiling point.
Examples of low-boiling aprotic solvents include amide-based solvents such as dimethylformamide, diethylformamide, dimethylacetamide, and N-methylpyrrolidone; sulfoxide-based solvents such as dimethyl sulfoxide; and ketone-based solvents such as methylethylketone, cyclohexanone, and methylisobutylketone; Ether-based solvents such as tetrahydrofuran and dioxane; ester-based solvents such as methyl acetate, ethyl acetate and butyl acetate, aromatic hydrocarbon solvents such as toluene and xylene, and the like can be mentioned.

This urethane-modified epoxy resin solution is obtained by reacting a polyhydric alcohol containing the above-mentioned alkanolamine or the like, a polyhydric isocyanate, and an epoxy resin in an aprotic solvent having a low boiling point, and if necessary, a diluting solvent. Etc. may be added and used as it is.
Then, the encapsulating pigment is prepared by mixing a urethane-modified epoxy resin solution with an optional component such as a high-boiling solvent for ink, a pigment, and a pigment dispersant, dispersing the mixture with a disperser such as a bead mill, and then using the pigment dispersion. It can be produced by removing the low boiling point solvent. Pressurization, heating, distillation or the like can be used to remove the low boiling point solvent. If desired, it may be produced through a filter such as a membrane filter.
The obtained encapsulated pigment dispersion can be used as it is as an oil-based ink by adding a diluting solvent or the like if necessary.

The oil-based ink preferably has a non-volatile content of 1 to 40% by mass. It is advisable to adjust the blending amount of the ink solvent so as to obtain this non-volatile content.
Further, in the manufacturing process of the encapsulating pigment, it is preferable to add a low boiling point aprotic solvent in a sufficient amount so that aggregation does not occur when the urethane-modified epoxy resin is mixed with the ink solvent. .. The amount of the aprotic solvent having a preferable low boiling point is 1 to 15 in terms of mass ratio with respect to 1 urethane-modified epoxy resin.

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. Further, from the viewpoint of color development, a dye may be used in combination with the encapsulating pigment. These types are not particularly limited, and those used in the art can be used.

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. Is more preferable, and about 10 mPa · s is more preferable.

The printing method using the oil-based inkjet ink is not particularly limited, and any method such as a piezo method, an electrostatic method, or a thermal method may be used. 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 the 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 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 and method of coating the paint. being classified.

(Second Embodiment)
Hereinafter, the second embodiment will be described. In the second embodiment, the parts not particularly described are the same as those in the first embodiment.
The oil-based inkjet ink according to the present embodiment (hereinafter, may be simply referred to as ink) includes an encapsulating pigment containing a pigment and a urethane-modified (meth) acrylic resin that coats the surface of the pigment, and a non-aqueous solvent. The urethane-modified (meth) acrylic resin has a urethane portion and a (meth) acrylic resin portion and is an insoluble compound in a non-aqueous solvent, and the urethane portion has an aromatic ring, a heterocycle, a carboxy group, an amide bond, 1 It is characterized by containing one or more side chains selected from the group consisting of fluoroalkyl groups, amino groups, and nitrile groups having one or more fluorine atoms.

According to the present embodiment, similarly to the urethane-modified epoxy resin described above, it is possible to reduce the image strike-through of the printed matter, increase the image density, and improve the scratch resistance of the printed matter. Further, according to the present embodiment, the wettability to the nozzle plate and the wipe durability can be improved.
The oil-based ink according to the present embodiment can improve the scratch resistance to coated paper as well as plain paper.

Further, since the urethane-modified (meth) acrylic resin has the (meth) acrylic resin portion, the effect of reducing strike-through and improving the image density can be further enhanced. Further, this can improve the scratch resistance to the coated paper as well as the plain paper.
Since the urethane-modified (meth) acrylic resin contains the (meth) acrylic resin portion together with the urethane portion, a certain degree of hardness is imparted to the resin, and the ink coating film on the paper surface can be made stronger. , The scratch resistance of printed matter can be improved.
Here, (meth) acrylic means methacrylic, acrylic, or a combination thereof, and (meth) acrylic resin includes a resin having a methacrylic unit, a resin having an acrylic unit, or both of these units. It means that it is a copolymer.

The ink of the present embodiment contains an encapsulating pigment, and the encapsulating pigment contains a pigment and a urethane-modified (meth) acrylic resin that coats the surface of the pigment. The details of the pigment are as described in the urethane-modified epoxy resin.

In the encapsulated pigment, a partial or total area of the pigment surface is coated with a urethane modified (meth) acrylic resin.
The urethane-modified (meth) acrylic resin is preferably insoluble in the non-aqueous solvent used in the ink. The details of the solubility of the urethane-modified (meth) acrylic resin are the same as those of the urethane-modified epoxy resin.

The urethane-modified (meth) acrylic resin has a urethane portion having a side chain and a (meth) acrylic resin portion.
The side chain of the urethane moiety contains at least one selected from the group consisting of aromatic rings, heterocycles, carboxy groups, amide bonds, fluoroalkyl groups having one or more fluorine atoms, amino groups, and nitrile groups. Is preferable.
When the urethane portion contains one or more of a heterocycle, an amide bond, an amino group and a nitrile group as a side chain, the adsorptivity of the urethane-modified (meth) acrylic resin to the pigment can be further enhanced.
The details of the urethane portion and the side chain are as described in the above-mentioned urethane-modified epoxy resin.

Preferably, the urethane moiety has a first side chain having an aromatic ring and a second side chain having a heterocycle, a carboxy group, an amide bond, a fluoroalkyl group having one or more fluorine atoms, an amino group, or a nitrile group. It is preferable to have a side chain. Since the urethane portion has the second side chain, each effect is exhibited, while the first side chain has the aromatic ring, so that the wettability to the nozzle plate can be surely improved. The first side chain and the second side chain are preferably in a molar ratio of 25:75 to 75:25.

In the urethane-modified (meth) acrylic resin, for example, by reacting a polyhydric alcohol, a polyhydric isocyanate, and a (meth) acrylic resin, a urethane skeleton is formed by the polyhydric alcohol and the polyhydric isocyanate, and this urethane The skeleton can be combined with (meth) acrylic resin and synthesized.
For example, by using a (meth) acrylic resin containing a reactive functional group reactive with an isocyanate group such as a hydroxyl group or an amino group as the (meth) acrylic resin, the reactive functional group of the (meth) acrylic resin can be treated. Therefore, the isocyanate group of the urethane skeleton can be bonded.

Hereinafter, the (meth) acrylic resin portion of the urethane-modified (meth) acrylic resin will be described.
The (meth) acrylic resin constituting the (meth) acrylic resin portion is preferably, for example, a (meth) acrylic resin having a reactive functional group reactive with an isocyanate group.
This makes it possible to react the reactive functional group of the (meth) acrylic resin portion with the isocyanate group of the urethane portion to more easily synthesize the urethane-modified (meth) acrylic resin.
As the reactive functional group having reactivity with the isocyanate group, one or more selected from the group consisting of a hydroxyl group, an amino group and the like can be used.

As a preferable example of the (meth) acrylic resin, for example, it is preferable to include a unit a having a reactive functional group having reactivity with an isocyanate group. Further, a preferred example of the (meth) acrylic resin is, for example, a polymer further containing the unit a, the unit b having an aromatic ring, and / or the unit c having a carboxy group.

The (meth) acrylic resin preferably has a unit a having a reactive functional group that is reactive with an isocyanate group. This unit a is a unit a to which the urethane portion is bonded via a reactive functional group, and in the urethane-modified (meth) acrylic resin, the urethane portion is bonded.
An example of the unit a is a unit in which a functional group represented by −COOR ^a is bonded to the carbon chain of the main chain. ^Ra is a group having a reactive functional group. In this case, it is preferable that the reactive functional group has an alkyl group having 1 to 8 carbon atoms bonded to the oxygen atom, and one or more hydrogen atoms of the alkyl group are substituted with the reactive functional group. Preferred examples of ^Ra include a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group and the like.

Further, the (meth) acrylic resin preferably has a unit b having an aromatic ring.
As a result, the aromatic ring is easily oriented to the pigment, and the pigment can be coated more uniformly.
As the aromatic ring, for example, a benzene ring, a naphthalene ring, an anthracene ring or the like, or a substitute thereof can be used, and a benzene ring is preferable.
An example of the unit b is a unit in which a functional group represented by −COOR ^b is bonded to the carbon chain of the main chain. R ^b is a group having an aromatic ring.
Further, R ^b is a group represented as −R ^b1 −R ^b2 , in which R ^b1 is an arbitrary divalent or higher functional group and has an aromatic ring at the terminal represented by R ^b2. It may be there. In the unit b, there may be two or more terminal aromatic rings.
Examples of the group having an aromatic ring include a benzyl group and a phenyl group.

Further, the (meth) acrylic resin preferably has a unit c having a carboxy group (-COOH).
The carboxy group of the unit c may be a (meth) acrylic resin in which −COOH is bonded to the carbon chain of the main chain. In this case, the unit c is a unit derived from acrylic acid and / or methacrylic acid.
In another form, it is a unit in which a group represented by -COOR ^c is bonded to the carbon chain of the main chain, R ^c is a group represented by -R ^c1- COOH, and R ^c1 is arbitrary. It is a divalent or higher valent group and has a carboxy group at the end. In the unit c, it may have two or more terminal carboxy groups.

The (meth) acrylic resin may further contain a unit d having an alkyl group having 1 to 8 carbon atoms. This unit d is a unit in which a group represented by −COOR ^d is bonded to a carbon atom of the main chain of the (meth) acrylic resin, and R ^d has 1 to 8 carbon atoms, particularly 1 to 4 carbon atoms. It is preferably an alkyl group.
As a result, it is possible to impart flexibility to the (meth) acrylic resin, increase the flexibility of the entire urethane-modified (meth) acrylic resin, and further improve the coating property of the pigment. Further, by having the unit d, the solvent affinity of the (meth) acrylic resin is increased, and the reaction with the urethane portion can be promoted.
In the unit d, as the alkyl group having 1 to 8 carbon atoms, for example, a methyl group, an ethyl group, a butyl group, a 2-ethylhexyl group and the like can be used.

The (meth) acrylic resin may have the unit a, the unit b, the unit c, and the unit d individually or in combination of two or more. Preferably, the (meth) acrylic resin further contains the unit b and / or the unit c together with the unit a.

In the (meth) acrylic resin, the unit a is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 5% by mass or more, based on the whole polymer. On the other hand, the unit a is preferably 20% by mass or less, more preferably 17% by mass or less, and further preferably 15% by mass or less.
In the (meth) acrylic resin, the unit b is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, based on the whole polymer. On the other hand, the unit b is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less.
In the (meth) acrylic resin, the unit c is preferably 5% by mass or more, more preferably 8% by mass or more, still more preferably 10% by mass or more, based on the whole polymer. On the other hand, the unit c is preferably 45% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less.
In the (meth) acrylic resin, the unit d is preferably 5% by weight or more with respect to the entire polymer. On the other hand, the unit d is preferably 90% by mass or less.
Here, the entire polymer is based on all the units constituting the (meth) acrylic resin.

The (meth) acrylic resin can be produced by copolymerizing a monomer mixture containing at least the following monomer a. Further, the (meth) acrylic resin can be produced by copolymerizing a monomer mixture containing monomer a and one or more selected from the following monomer b and monomer c, which may optionally contain monomer d. it can.
The blending amount of the monomers a to d in the monomer mixture may be adjusted so as to be the ratio of the units a to d of the (meth) acrylic resin described above.
Monomer a containing a reactive functional group reactive with an isocyanate group;
Monomer b having an aromatic ring;
Monomer c having a carboxy group;
Monomer d having an alkyl group having 1 to 8 carbon atoms.

As the monomer a, for example, hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and the like can be used.
Examples of the monomer b include benzyl (meth) acrylate, phenoxyethyl methacrylate, phenoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol-polypropylene glycol (meth) acrylate, nonylphenoxypolypropylene glycol acrylate, and nonylphenoxypolyethylene glycol polypropylene glycol acrylate. Can be mentioned.

Examples of the monomer c include methacrylic acid, acrylic acid, β-carboxyethyl (meth) acrylate, 2-methacryloyloxyethyl hexahydrophthalic acid (CAS No. 51252-88-1), 4- [2- (methacryloyloxy). ) Ethoxy] -4-oxo-2-butenoic acid (CAS No. 51978-15-5) and the like can be mentioned.

Examples of the monomer d include methyl (meth) acrylate (C1), ethyl (meth) acrylate (C2), butyl (meth) acrylate (C4), 2-ethylhexyl (meth) acrylate (C8) and the like. .. The number in parentheses is the number of carbon atoms in the alkyl group.
The above-mentioned monomers a to d can be used independently or in combination of two or more.

In addition to the above-mentioned monomers a to d, other monomers may be used as long as the effects of the present invention are not impaired. Examples of other monomers include styrene-based monomers such as styrene and α-methylstyrene; vinyl ether-based polymers such as vinyl acetate, vinyl benzoate, and butyl vinyl ether; maleic acid esters; fumaric acid esters; acrylonitrile; methacrylonitrile; α. -Olefin; Examples thereof include alkyl (meth) acrylates having an alkyl group having 9 or more carbon atoms.

The above-mentioned monomer mixture can be polymerized by a known radical copolymerization. The reaction system is preferably solution polymerization or dispersion polymerization.
In order to adjust the reaction rate during the polymerization reaction, a polymerization initiator, a chain transfer agent, a polymerization inhibitor, a polymerization accelerator, a dispersant and the like can be appropriately added to the reaction system.
As the polymerization initiator, AIBN (azobisisobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) ) And other azo compounds; thermal polymerization initiators such as peroxides such as t-butylperoxybenzoate and t-butylperoxy-2-ethylhexanoate (Perbutyl O, manufactured by Nippon Oil & Fats Co., Ltd.) can be used. .. In addition, a photopolymerization type initiator that generates radicals by irradiation with active energy rays can be used.
Further, by using a chain transfer agent in combination with the reaction system, the molecular weight of the obtained (meth) acrylic resin can be adjusted. As the chain transfer agent, for example, thiols such as n-butyl mercaptan, lauryl mercaptan, stearyl mercaptan, cyclohexyl mercaptan and the like can be preferably used.
The polymerization solvent (reaction solvent) used for solution polymerization is not particularly limited, but one capable of dispersing or dissolving the resin obtained by polymerization is preferable.

The (meth) acrylic resin of the present embodiment is not limited to the (meth) acrylic resin having the above-mentioned structure.
Examples of commercially available products that can be used as the (meth) acrylic resin of the present embodiment include "ARUFON: UH-2000, UH-2041, UH-2170, UH-2190, UHE-2012" manufactured by Toagosei Co., Ltd. Can be mentioned.

The weight average molecular weight of the (meth) acrylic resin portion is preferably 5,000 to 100,000, more preferably 7,000 to 80,000, and even more preferably 1,000 to 50,000. Within this range, the scratch resistance to plain paper and coated paper can be improved.
The (meth) acrylic resin constituting the (meth) acrylic resin portion preferably has an acid value of 0 to 300 mgKOH / g, more preferably 15 to 200 mgKOH / g. Within this range, the image density and strike-through on plain paper can be improved.
Here, the acid value is the number of milligrams of potassium hydroxide required to neutralize the total acidic component in 1 g of the non-volatile content.

The urethane-modified (meth) acrylic resin can be produced by reacting a polyhydric alcohol, a polyhydric isocyanate, and a (meth) acrylic resin in a low-boiling aprotic solvent such as methyl ethyl ketone. As the polyhydric alcohol, one or more selected from alkanolamines and derivatives thereof, and selectively other polyhydric alcohols can be used.
At this time, a catalyst may be used. The details of the catalyst are as described in the urethane-modified epoxy resin described above.
It is preferable to mix and react the polyhydric alcohol and the polyhydric isocyanate so that the isocyanate group of the polyhydric isocyanate is 0.60 to 1.02 mol with respect to 1.0 mol of the hydroxy group of the polyhydric alcohol. ..

In the urethane-modified (meth) acrylic resin, the mass ratio (U: A) of the urethane portion (U) and the (meth) acrylic resin portion (A) may be in the range of 90:10 to 10:90, 85: It is preferably 15 to 40:60. More preferably, U: A is 85: 15-60: 40.
As a result, the wettability to the nozzle plate and the wipe durability can be improved, and the scratch resistance to plain paper and coated paper can be improved.
Here, the mass of the urethane portion is obtained from the total amount of the polyhydric alcohol and the polyhydric isocyanate used in the reaction, and the mass of the (meth) acrylic resin portion is obtained from the total amount of the (meth) acrylic resin used in the reaction. be able to.

The weight average molecular weight of the urethane-modified (meth) acrylic resin is preferably 5000 to 100,000. If the weight average molecular weight is lower than 5000, the urethane-modified (meth) acrylic resin may float in the ink solvent and the morphology of the encapsulated pigment may not be maintained. If the weight average molecular weight of the urethane-modified (meth) acrylic resin is higher than 100,000, coarse capsule particles are generated, and if it is higher than the risk of causing deterioration of stability and ejection property, coarse capsule particles are generated. It may occur, resulting in a decrease in stability and a deterioration in dischargeability. More preferably, the urethane-modified (meth) acrylic resin has a weight average molecular weight of 1000 to 80,000, and even more preferably 2000 to 60,000.

The urethane-modified (meth) acrylic resin preferably has an acid value of 5 to 300 mgKOH / g, more preferably 15 to 200 mgKOH / g. Within this range, the image density and strike-through on plain paper can be improved.

The urethane-modified (meth) acrylic resin described above can be preferably used as an encapsulating pigment in oil-based inks.
The urethane-modified (meth) acrylic resin is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and further preferably 0.15 part by mass or more with respect to 1 part by mass of the pigment. is there. Thereby, the coating property of the pigment surface can be improved.
On the other hand, the urethane-modified (meth) acrylic resin is preferably 5.0 parts by mass or less, more preferably 1.0 part by mass or less, and further preferably 0.5 parts by mass with respect to 1 part by mass of the pigment. It is as follows. As a result, it is possible to prevent the surface of the pigment from being coated with the excess resin, and to prevent the excess resin from being mixed in the solvent.
The urethane-modified (meth) acrylic resin is preferably 0.01 to 30% by mass, more preferably 1 to 20% by mass, based on the total amount of the ink.

The total amount of the urethane-modified (meth) acrylic resin and the pigment is preferably 1 to 40% by mass, more preferably 5 to 30% by mass, based on the total amount of the ink.
Details of the ink containing the urethane-modified (meth) acrylic resin and the manufacturing method thereof are as described in the above-mentioned urethane-modified epoxy resin.

Hereinafter, the present invention will be described in detail with reference to Examples. The present invention is not limited to the following examples.
Through the following examples and comparative examples, the common components are the same unless otherwise specified.

"Manufacturing Example A: Example of Urethane Modified Epoxy Resin"
Hereinafter, as Production Example A, an encapsulated pigment was produced using a urethane-modified epoxy resin.
<Type of epoxy resin>
Table 1 shows the types of epoxy resins. All of the epoxy resins shown in Table 1 were obtained from Mitsubishi Chemical Corporation.

<Amine modification of epoxy resin>
Table 2 shows the formulation of amine modification of epoxy resin.
Alkanolamine, epoxy resin, and aprotic solvent were charged at the ratios shown in the table, and the temperature was raised to 60 ° C. with stirring to react to obtain an amine-modified epoxy resin.

<Synthesis of diol>
Table 3 shows the formulation of the diethanolamine derivative (diol) that constitutes the side chain of the urethane portion.
Diethanolamine was charged at the ratio shown in the table, and the temperature was raised to 110 ° C. The monomers shown in the table were added dropwise to this in the respective blending amounts to complete the Michael addition reaction to obtain a diol.

The components shown in each table are as follows.
Diethanolamine: NH (C ₂ H ₄ OH) ₂ , MW105.1, "DEA" manufactured by Nippon Shokubai Co., Ltd.
Ethanolamine: NH ₂ C ₂ H ₂ OH, MW 61.08, "MEA" manufactured by Nippon Shokubai Co., Ltd.
MEK: Methyl ethyl ketone, manufactured by Wako Pure Chemical Industries, Ltd.
Benzyl acrylate: "Viscoat # 160" manufactured by Osaka Organic Chemical Industry Co., Ltd., MW 162.2.
Acryloyl Morpholine: "ACMO" manufactured by KJ Chemicals Co., Ltd., MW 141.2.
Dimethylacrylamide: "DMAA" manufactured by KJ Chemicals Co., Ltd., MW99.1.
Diethyl acrylamide: "DEAA" manufactured by KJ Chemicals Co., Ltd., MW 127.2.
Acrylonitrile: Wako Pure Chemical Industries, Ltd., MW53.1.
Dimethylaminoethyl acrylate: "Aron DA" manufactured by Toagosei Co., Ltd., MW 143.2.
Methoxypolyethylene glycol (PEG9) acrylate: Comparative monomer, CH ₂ = CH-CO- (OCH _2- CH ₂ ) _9- OCH ₃ , NOF CORPORATION "AME-400", MW482.0.
The MW is a molecular weight.

<Synthesis of urethane-modified epoxy resin>
Tables 4 and 5 show the formulations of urethane-modified epoxy resins.
According to the blending amount shown in each table, the diol solution obtained above, propylene glycol and MEK (methyl ethyl ketone) as other diol components were charged, dibutyltin dilaurate was added as a tin catalyst, and the temperature was raised to 78 ° C. did. Then, diisocyanate was added dropwise to obtain a resin solution having a solid content of 50.0% by mass. The weight average molecular weight (Mw; GPC method, standard polystyrene conversion, the same applies hereinafter) is shown in each table.

The components shown in each table are as follows.
Hexamethylene diisocyanate: OCN- (CH ₂ ) _6- NCO, MW168.2, manufactured by Wako Pure Chemical Industries, Ltd.
_{Diisocyanate: OCN-CH 2 -C 6 H} 4 -CH 2 -NCO, MW188.18, manufactured by Mitsui Chemicals, Inc. "Takenate 500".
Propylene glycol: manufactured by Wako Pure Chemical Industries, Ltd.
Tin-based catalyst: dibutyltin dilaurate, "L-101" manufactured by Tokyo Fine Chemicals Co., Ltd.

<Ink production>
Tables 6 and 7 show the ink formulations.
According to the blending amount shown in each table, the resin solution obtained above, the pigment "MOGUL L", the pigment dispersant "Hypermer KD12", methyl oleate, and AF-5 were mixed and locked mill (manufactured by Seiwa Giken Co., Ltd.). ) Dispersed. After the dispersion, the low boiling point solvent (methyl ethyl ketone) of the dispersion was desolved using an evaporator. In this way, the pigment was encapsulated with a urethane-modified epoxy resin to obtain an ink containing the encapsulated pigment.

Inks of each Example and Comparative Example were prepared according to the above method except for the following points.
In Example A11, urethane-modified epoxy resin A11 having a different diisocyanate was used, and the pigment, pigment dispersant, and solvent were changed.
In Comparative Example A1, urethane resin A12 was used.
In Comparative Example A2, urethane resin A13 having a comparative monomer as a side chain was used.

The components shown in each table are as follows.
Pigment "MOGUL L": Carbon black, "MOGUL L" manufactured by Cabot Specialty Chemicals, Inc.
Pigment "MA8": Carbon black, "MA8" manufactured by Mitsubishi Chemical Corporation.
Pigment dispersant "HYPERMER KD11": "Hypermer KD11" manufactured by Croda Japan Co., Ltd.
Pigment dispersant "S13940": "Solspers 13940" manufactured by Japan Lubrizol Co., Ltd.
Methyl oleate: fatty acid ester solvent, CH ₃ (CH ₂ ) ₇ CH = CH (CH ₂ ) ₇ COOCH ₃ , Tokyo Chemical Industry Co., Ltd.
Isopropyl myristate: fatty acid ester solvent, CH ₃ (CH ₂ ) ₁₂ COOCH (CH ₃ ) ₂ , manufactured by Wako Pure Chemical Industries, Ltd.
AF-5: Petroleum-based hydrocarbon solvent, "AF Solvent No. 5" manufactured by JX Energy Co., Ltd.

The urethane-modified epoxy resin used in each Example and Comparative Example is completely dissolved in 100 g of the non-aqueous solvent (mixture when two or more kinds of non-aqueous solvents are used) used in each Example and Comparative Example. The mass (g / 100 g) was measured to determine the solubility of the urethane-modified epoxy resins (resins A1 to A11) and the urethane resins (resins A12 and A13).
As a result, in each Example and Comparative Example A1, the solubility of each resin was less than 1 g / 100 g with respect to 100 g of the non-aqueous solvent.
In Comparative Example A2, the solubility of the resin A13 was more than 5 g / 100 g with respect to 100 g of the non-aqueous solvent. Resin A13 was miscible with non-aqueous solvents.

<Evaluation>
The inks of the above Examples and Comparative Examples were evaluated by the following methods. The evaluation results are shown in Tables 6 and 7.

(1) Wetness to Nozzle Plate Put each ink in a 30 ml glass container and use the nozzle plate (length 5 mm, width 5 mm) used in the inkjet printer "Orphis EX9050" (trade name: Riso Kagaku Corporation). One side was pinched with tweezers, and 2 cm from the other side was immersed in ink for 5 seconds. Then, the nozzle plate was quickly pulled up, and the time t until the ink film remaining on the nozzle plate became ink droplets was measured. The same operation was repeated 10 times using the same nozzle plate, and the time t was measured for each. The average value was calculated and used as the ink repellent time, which was evaluated according to the following criteria.
AA: The ink repellent time is less than 1 second.
A: The ink repellent time is 1 second or more and less than 3 seconds.
B: The ink repellent time is 3 seconds or more and less than 4 seconds.
C: The ink repellent time is 4 seconds or more.

(2) Wipe durability Using an inkjet printer "Orphis EX9050" (trade name: manufactured by Riso Kagaku Corporation), head cleaning was performed 1000 times by normal cleaning of head maintenance. After 1000 head cleanings, the ink repellency of the nozzle plate portion in contact with the wipe blade was visually evaluated.
AA: The ink repellency of all the parts in contact with the wipe blade is maintained. Immediately after the test, the ink is completely repelled.
A: The ink repellency of all parts in contact with the wipe blade is maintained. After the test, it takes a few seconds for the ink to completely repel.
B: The ink repellency of a part in contact with the wipe blade is reduced.
C: The ink repellency of all the parts in contact with the wipe blade is reduced.

(3) Storage stability (70 ° C, 1 month)
First, the viscosity of the ink immediately after the ink was produced was measured.
The ink was then placed in a 10 ml screw vial and left at 70 ° C. for 1 month. Then, the ink was sampled and the ink viscosity was measured.
The viscosity was measured using a rheometer ARG2 (manufactured by TA Instruments) at a cone angle of 2 °, a diameter of 40 mm, and room temperature (23 ° C.).
From the ink viscosity before and after leaving for 1 month, the viscosity change rate was calculated by the following formula, and the storage stability was evaluated according to the following criteria.
Viscosity change rate (%) = 100- (ink viscosity after standing (mPa · s) / ink viscosity immediately after production (mPa · s)) × 100
A: The viscosity change rate is within ± 5%.
B: The viscosity change rate is less than ± 10%.
C: The viscosity change rate is ± 10% or more.

(4) Image density and image strike-through Using the inkjet head mounted on the inkjet printer "Orphis EX9050", plain paper (Ideal Paper Multi, manufactured by Riso Kagaku Corporation) with a resolution of 600 dpi x 600 dpi per pixel. , 12pl solid image was printed. One day after printing, the OD value on the front surface of the printed matter (front OD value) and the OD value on the back surface of the printed matter (back OD value) were measured using an optical densitometer (RD920, manufactured by Macbeth). The image density was evaluated from the table OD value according to the following criteria. Image strike-through was evaluated from the back OD value according to the following criteria.

(Image density)
AA: The table OD value is 1.18 or more.
A: The table OD value is 1.12 or more and less than 1.18.
B: The table OD value is 1.00 or more and less than 1.12.
C: The table OD value is less than 1.00.
(Image strike through)
AA: The back OD value is less than 0.08.
A: The back OD value is 0.08 or more and less than 0.15.
B: Back OD value is 0.15 or more and less than 0.25 C: Back OD value is 0.25 or more.

(5) Scratch resistance (plain paper)
A printed matter was produced in the same manner as in the above method for evaluating image density and image strike through. One day after printing, the solid image portion of the printed matter was visually observed when rubbed with a clock meter (cloth) five times, and the scratch resistance was evaluated according to the following criteria.
A: Almost no contamination around the image is confirmed.
B: Some contamination around the image is confirmed.
C: Contamination around the image is remarkable.

(6) Scratch resistance (coated paper)
A printed matter was produced in the same manner as the above-mentioned image density and image strike-through evaluation method except that the high-quality coated paper "Aurora Coat" (manufactured by Nippon Paper Industries, Ltd.) was used. After printing and drying at 100 ° C. for 3 minutes, the state when the solid image portion of the printed matter was rubbed with a finger was visually observed, and the scratch resistance was evaluated according to the following criteria.
A: There is no ink on the fingers and no tack on the printed matter.
B: The finger does not get ink, but the printed matter has tack.
C: Ink gets on my finger.

As shown in each table, the inks of each example had good wettability to the nozzle plate and wipe durability, and prevented image strike-through of the printed matter, so that high image density could be obtained. In addition, the inks of each example had good storage stability and excellent scratch resistance of printed matter.
Compared with the ink using the urethane resin A12 of Comparative Example A1, the ink of each example improved the image density and the image strike-through of the printed matter, and was excellent in the scratch resistance of the printed matter.
In Comparative Example A2, an ink was produced using urethane resin A13 having a comparative monomer as a side chain, and the image density, image strike-through, and storage stability were insufficient.

In Examples A1 to A8, the pigment was encapsulated using the resins A1 to A8 having various side chains, and good results were obtained.
In Example A2, the resin A2 was synthesized using an amine-modified epoxy resin, and the wipe durability was further improved.
In Examples A3, A7, and A8, the resin A3 was synthesized using a higher molecular weight epoxy resin, and the wipe durability was further improved.

In Examples A4 to A6, the pigment was encapsulated using the resins A4 to A6 having various side chains together with the benzyl group, and good results were obtained.
In Examples A4 and A6, resins A4 and A6 were synthesized using an amine-modified epoxy resin, and the wipe durability was further improved.
In Example A5, the resin A5 was synthesized using a higher molecular weight epoxy resin, and the wipe durability was further improved.

In Examples A9 and A10, the mass ratio of the urethane portion / epoxy portion was changed, which was a good result.
In Example A11, an ink was prepared by using a resin A13 having a different diisocyanate and changing a pigment, a pigment dispersant, and a solvent, and good results were obtained.

"Manufacturing Example B: Example of Urethane Modified (Meta) Acrylic Resin"
Hereinafter, as Production Example B, an encapsulated pigment was produced using a urethane-modified (meth) acrylic resin. The same components as those in Production Example A are used.
<Synthesis of (meth) acrylic resin>
Table 8 shows the monomer formulation of the (meth) acrylic resin.
Each monomer was mixed at the ratio shown in the table to obtain a monomer mixture. V-65 (azobis, 2-4-dimethylisovaleronitrile, manufactured by Wako Pure Chemical Industries, Ltd.) was added to the same amount of methyl ethyl ketone (MEK) as the monomer mixture at a ratio of 5% by mass with respect to the monomer mixture. The monomer mixture was added dropwise to this solution. After the dropping of the monomer mixture was completed, V-65 in a proportion of 0.3% by mass was further added to the monomer mixture to obtain a resin solution having a non-volatile content of 50%.

The weight average molecular weight of the obtained resin is shown in the table.
The acid value of the obtained resin was measured according to JIS K 2501 (hereinafter the same). The results are shown in the table.

The monomers used are as follows.
Methacrylic acid: Made by Wako Pure Chemical Industries, Ltd.
Acrylic acid: Made by Wako Pure Chemical Industries, Ltd.
Hydroxyethyl methacrylate: manufactured by Wako Pure Chemical Industries, Ltd.
Benzyl methacrylate: manufactured by Wako Pure Chemical Industries, Ltd.
Benzyl acrylate: Made by Osaka Organic Chemical Industry Co., Ltd.
Methyl methacrylate: manufactured by Wako Pure Chemical Industries, Ltd.

<Synthesis of diol>
Table 9 shows the formulation of the diethanolamine derivative (diol) that constitutes the side chain of the urethane portion.
Diethanolamine was charged at the ratio shown in the table, and the temperature was raised to 110 ° C. The monomers shown in the table were added dropwise to this in the respective blending amounts to complete the Michael addition reaction to obtain a diol.

<Synthesis of urethane-modified (meth) acrylic resin>
Tables 10 and 11 show the formulations of urethane-modified (meth) acrylic resins.
According to the blending amount shown in each table, the acrylic resin obtained above, the diol solution obtained above, propylene glycol and MEK (methyl ethyl ketone) as other diol components were charged, and dibutyltin dilaurate as a tin catalyst. Was added, and the temperature was raised to 78 ° C. Then, diisocyanate was added dropwise to obtain a resin solution having a solid content of 50.0% by mass. The weight average molecular weight and acid value of the obtained urethane-modified (meth) acrylic resin are shown in each table.

<Ink production>
Tables 12 and 13 show the ink formulations.
The resin solution, pigment "MA8", pigment dispersant "S13940", methyl oleate, and AF-5 obtained above were mixed according to the blending amounts shown in each table, and locked mill (manufactured by Seiwa Giken Co., Ltd.). Dispersed by After the dispersion, the low boiling point solvent (methyl ethyl ketone) of the dispersion was desolved using an evaporator. In this way, the pigment was encapsulated with a urethane-modified (meth) acrylic resin to obtain an ink containing the encapsulated pigment.

Inks of each Example and Comparative Example were prepared according to the above method except for the following points.
In Example B11, resin B12 having a different diisocyanate was used, and the pigment, pigment dispersant, and solvent were changed.
In Comparative Example B1, urethane resin B13 was used.
In Comparative Example B2, urethane resin B14 having a comparative monomer as a side chain was used.

The urethane-modified (meth) acrylic resin used in each Example and Comparative Example is completely applied to 100 g of the non-aqueous solvent (mixture when two or more non-aqueous solvents are used) used in each Example and Comparative Example. The mass (g / 100 g) dissolved in was measured, and the solubility of urethane-modified (meth) acrylic resins (resins B1 to B12) and urethane resins (resins B13 and B14) was determined.
As a result, in each Example and Comparative Example B1, the solubility of each resin was less than 1 g / 100 g with respect to 100 g of the non-aqueous solvent.
In Comparative Example B2, the solubility of the resin B14 exceeded 5 g / 100 g with respect to 100 g of the non-aqueous solvent. Resin B14 was miscible with non-aqueous solvents.

<Evaluation>
The inks of the above Examples and Comparative Examples were evaluated according to the same method and evaluation criteria as in Production Example A. The evaluation results are shown in Tables 12 and 13.

As shown in each table, the inks of each example had good wettability to the nozzle plate and wipe durability, and prevented image strike-through of the printed matter, so that high image density could be obtained. In addition, the inks of each example had good storage stability and excellent scratch resistance of printed matter.
Compared with the ink using the urethane resin B13 of Comparative Example B1, the ink of each example improved the image density and the image strike-through of the printed matter, and was excellent in the scratch resistance of the printed matter.
In Comparative Example B2, an ink was produced using resin B14 in which a comparative monomer was introduced into a urethane resin as a side chain, and the image density, image strike-through, and scratch resistance were insufficient.

In Examples B1 to B6, the pigment was encapsulated using the resins B1 to B6 having various side chains, and good results were obtained.
In Examples B4 to B6, the pigment was encapsulated using the resins B4 to B6 having various side chains together with the benzyl group, and good results were obtained.

In Examples B7 and B8, the mass ratio of the urethane portion / acrylic portion was changed, and good results were obtained.
In Examples B9 and B10, the type of side chain of the urethane portion was changed, and good results were obtained.
In Example B11, an ink was prepared by using a resin B11 having a different diisocyanate and changing a pigment, a pigment dispersant, and a solvent, and good results were obtained.
In Example B12, resin B12 having a different acrylic resin was used, and good results were obtained.

Claims (10)

It contains an encapsulating pigment containing a pigment and a urethane-modified epoxy resin that coats the surface of the pigment, and a non-aqueous solvent.
The urethane-modified epoxy resin is a compound that has a urethane portion and an epoxy resin portion and is insoluble in the non-aqueous solvent.
The urethane moiety contains one or more side chains selected from the group consisting of aromatic rings, heterocycles, carboxy groups, amide bonds, fluoroalkyl groups having one or more fluorine atoms, amino groups, and nitrile groups. , Oil-based inkjet ink. The oil-based inkjet ink according to claim 1, wherein the mass ratio of the urethane portion to the epoxy resin portion is 85: 15-40: 60. It contains an encapsulating pigment containing a pigment and a urethane-modified (meth) acrylic resin that coats the surface of the pigment, and a non-aqueous solvent.
The urethane-modified (meth) acrylic resin is a compound that has a urethane portion and a (meth) acrylic resin portion and is insoluble in the non-aqueous solvent.
The urethane moiety contains one or more side chains selected from the group consisting of aromatic rings, heterocycles, carboxy groups, amide bonds, fluoroalkyl groups having one or more fluorine atoms, amino groups, and nitrile groups. , Oil-based inkjet ink. The (meth) acrylic resin portion is
A unit a having a reactive functional group reactive with an isocyanate group and to which a urethane moiety is bonded via the reactive functional group,
The oil-based inkjet ink according to claim 3, which comprises a unit b having an aromatic ring and / or a unit c having a carboxy group. The oil-based inkjet ink according to any one of claims 3 or 4, wherein the mass ratio of the urethane portion to the (meth) acrylic resin portion is 85: 15-40: 60. The oil-based inkjet ink according to any one of claims 3 to 5, wherein the urethane-modified (meth) acrylic resin has an acid value of 15 to 200 mgKOH / g. The side chain of the urethane portion is one or more selected from the group consisting of an aromatic ring, a heterocycle, a carboxy group, an amide bond, a fluoroalkyl group having one or more fluorine atoms, an amino group, and a nitrile group. The oil-based inkjet ink according to any one of claims 1 to 6, which has the above. The urethane portion has a structure in which units derived from multivalent isocyanate and units derived from polyhydric alcohol are alternately arranged.
The unit derived from the polyhydric alcohol includes a unit derived from an alkanolamine.
The oil-based inkjet ink according to any one of claims 1 to 7, wherein the side chain of the urethane portion is bonded to the urethane portion via a nitrogen atom of a unit derived from the alkanolamine. The unit derived from the alkanolamine is
A unit derived from a dialkanolamine to which an acrylate having an aromatic ring is Michael-added,
A unit derived from a dialkanolamine in which acrylamide having a heterocycle is Michael-added,
A unit derived from dialkanolamine with Michael addition of N-alkylacrylamide.
A unit derived from dialkanolamine with Michael addition of N, N-dialkylacrylamide.
The oil-based inkjet ink according to claim 8, which comprises one or more selected from the group consisting of units derived from acrylonitrile and dialkanolamines to which an acrylate having an amino group is added by Michael. The oil-based inkjet ink according to any one of claims 8 or 9, wherein the unit derived from the polyhydric alcohol further includes a unit derived from an asymmetric glycol.