JP2015067676A - Nonaqueous pigment ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous pigment ink which is excellent in storage stability and prevents an odor of a printed matter.SOLUTION: The nonaqueous pigment ink is a block copolymer containing a pigment, a pigment dispersant, and a low polar solvent in which: the pigment dispersant has a lipophilic block having a lipophilic group and a pigment affinity-having block having a pigment affinity-having group; a molar ratio of the lipophilic block and the pigment affinity-having block is 10:90-90:10; a number average molecular weight of the lipophilic block is 7,000 or more; a content of a unit having a pigment affinity-having group in all units constituting the pigment affinity-having block is 20 mol%-60 mol%; and a content of a unit having a pigment affinity-having group in all units constituting the lipophilic group is 10 mol% or less.

Description

  The present invention relates to a non-aqueous pigment ink and a pigment dispersant.

  Ink used for inkjet is classified into a water-based ink in which the main component of the solvent is water and a non-aqueous ink in which the main component of the solvent is a non-aqueous solvent. Non-aqueous inks generally have better water resistance than aqueous inks and can prevent paper deformation due to paper swelling.

  Non-aqueous inks are classified into solvent-based inks mainly composed of volatile solvents and oil-based inks mainly composed of non-volatile solvents. The oil-based ink can reduce the volatilization amount of the solvent, so that nozzle clogging can be prevented and the number of cleanings can be reduced. When the solvent content in the ink volatilizes, the ink becomes highly viscous and nozzle clogging may occur. Thus, the oil-based ink is suitable as a high-speed ink jet printer ink.

  On the other hand, since the non-volatile solvent used in the ink is a solvent having a relatively high boiling point, in the printed matter on which the ink after printing is applied, the evaporation of the solvent is slow, and when plain paper or the like is used as the permeable recording medium. Has a problem that the ink penetrates to the back side of the printed matter, that is, so-called back-through occurs.

  In addition, when a solvent having a relatively low boiling point is used for the ink, the odor of the solvent evaporating from the printed matter after the ink application may become a problem. Usually, the lower the polarity of the solvent, the less the odor is felt.

Patent Document 1 proposes a recording liquid in which pigment fine particles are dispersed in a non-aqueous solvent body containing a specific dispersant. Examples of the non-aqueous solvent include alkyl alcohols, aliphatic or aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ether solvents, ketone solvents, ester solvents, polyhydric alcohols, and the like.
However, this dispersant cannot be said to have sufficient storage stability with respect to a low polarity solvent. In addition, selection of a non-aqueous solvent from the viewpoint of odor and strikethrough has not been studied.

Patent Document 2 proposes a stable inkjet ink composition comprising a nonpolar component, a pigment, and a dispersant and having a specific dewetting rate.
However, the storage stability of the ink composition has not been studied, and it cannot be said that this dispersant has sufficient dispersibility in a low-polar solvent. Moreover, selection of a nonpolar component from a viewpoint of an odor and a strike-through is not examined.

Patent Document 3 proposes a non-aqueous ink composition containing a pigment, a solvent containing a polar organic solvent, and a dispersant having an ester structure. This ink composition is excellent in storage stability.
However, this dispersant cannot be said to have sufficient dispersibility in a low polarity solvent. In addition, selection of a solvent from the viewpoint of odor has not been studied.

Patent Document 4 proposes an ink composition in which an isoparaffin is used as a dispersion medium and a colorant is dispersed using a polymer dispersant, and two specific types of dispersion aids are used in combination. . By using this isoparaffin, human harm is avoided, and dispersion stability is obtained by using a dispersion aid in combination with a known polymer dispersant.
However, it cannot be said that this known polymer dispersant has sufficient dispersibility in isoparaffin. Further, this dispersion aid is used in combination of two specific types, and its application is limited, and since it is a monomer, there is a problem that the ink composition is likely to be altered.

Patent Document 5 includes a pigment, a pigment dispersant, and a non-aqueous solvent, and the pigment dispersant includes a copolymer of vinyl pyrrolidone and an alkene having 10 to 40 carbon atoms, so that a sufficient image density can be obtained. Non-aqueous pigment inks have been proposed.
However, in a simple copolymer, units derived from vinylpyrrolidone and units derived from alkene are randomly polymerized. A pigment dispersant made of such a copolymer cannot be said to have sufficient dispersibility in a low polarity solvent. In addition, selection of a solvent from the viewpoint of odor has not been studied.

Japanese Patent Laid-Open No. 57-10661 JP-T 9-511780 JP 2003-261808 A JP 2008-1853 A JP 2009-270061 A

  An object of the present invention is to provide a non-aqueous pigment ink that has excellent storage stability and prevents the odor of printed matter.

  An aspect of the present invention includes a pigment, a pigment dispersant, and a low-polarity solvent, and the pigment dispersant includes a lipophilic block having a lipophilic group and a pigment affinity block having a pigment affinity group. A copolymer, the molar ratio of the lipophilic block to the pigment affinity block is 10:90 to 90:10, the number average molecular weight of the lipophilic block is 7000 or more, and the pigment affinity The unit having the pigment affinity group with respect to all units constituting the block is 20 mol% to 60 mol%, and the unit having the pigment affinity group with respect to all units constituting the lipophilic block is 10 mol% or less. It is a non-aqueous pigment ink which is a certain block copolymer.

  Another aspect of the present invention is a block copolymer having a lipophilic block having a lipophilic group and a pigment affinity block having a pigment affinity group, wherein the lipophilic block and the pigment affinity block are The number ratio molecular weight of the lipophilic block is 7000 or more, and the unit having the pigment affinity group with respect to all the units constituting the pigment affinity block is 20 mol. The pigment dispersant is a block copolymer in which the unit having the pigment affinity group with respect to all units constituting the lipophilic block is 10% by mole or less.

  ADVANTAGE OF THE INVENTION According to this invention, the non-aqueous pigment ink which is excellent in storage stability and prevents the odor of printed matter can be provided.

  Hereinafter, although the embodiment concerning the present invention is described, the illustration in this embodiment does not limit the present invention.

The non-aqueous pigment ink according to an embodiment of the present invention (hereinafter sometimes simply referred to as “ink”) includes a pigment, a pigment dispersant, and a low polarity solvent, and the pigment dispersant has a lipophilic group. A block copolymer having a lipophilic block and a pigment affinity block having a pigment affinity group, wherein the molar ratio of the lipophilic block to the pigment affinity block is 10:90 to 90:10, and is lipophilic. The number average molecular weight of the block is 7000 or more, the unit having a pigment affinity group with respect to all units constituting the pigment affinity block is 20 mol% to 60 mol%, and the pigment affinity for all units constituting the lipophilic block The unit having a functional group is a block copolymer of 10 mol% or less.
As a result, it is possible to provide a non-aqueous pigment ink that has excellent storage stability and prevents the odor of printed matter. Further, it is possible to prevent the back-through.

  By using a low-boiling solvent as the solvent for the ink, the ink in the printed matter can be easily evaporated from the recording medium, thereby preventing the ink from penetrating into the recording medium. Can be reduced.

  Further, by using a low polarity solvent as the solvent of the ink, odor can be reduced even with a low boiling point solvent. When a low-boiling and high-polarity solvent is used, odor becomes a problem because the solvent evaporates. In particular, when printing on a large number of sheets with a large amount of ink, a large amount of solvent evaporates and odor becomes more problematic.

  According to the pigment dispersant of the present embodiment, excellent storage stability can be obtained even when a low polarity solvent is used as the solvent of the ink. The pigment dispersant of this embodiment is a block copolymer of a lipophilic block and a pigment affinity block. As a result, the unit having the pigment affinity group is concentrated on the pigment affinity block part and easily adsorbed to the pigment, and the length of the lipophilic block part is increased, and the lipophilic block is easily oriented to the solvent side. This is considered to improve the dispersibility with respect to the low-polar solvent.

  The pigment dispersant according to this embodiment is a block copolymer having a lipophilic block having a lipophilic group and a pigment affinity block having a pigment affinity group.

  The lipophilic group is a group that becomes a solvent affinity site for a low polarity solvent. The lipophilic group is preferably a group having 6 to 40 carbon atoms.

  The lipophilic group is preferably a hydrocarbon group having 6 to 40 carbon atoms, more preferably a linear or branched alkyl group having 8 to 22 carbon atoms, and still more preferably 12 to 22 carbon atoms. A linear alkyl group, more preferably a linear alkyl group having 12 to 18 carbon atoms.

As such a hydrocarbon group, for example,
Linear alkyl group (decyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosanyl group, heicosanyl group, docosanyl group, etc.);
Examples include branched chain alkyl groups (isooctyl group, 2-ethylhexyl group, isostearyl group, tert-octyl group and the like).

Moreover, as a lipophilic group, for example,
A group represented by -C (= O) -O-R (wherein R is a hydrocarbon group having 6 to 40 carbon atoms, preferably an alkyl group having 12 to 22 carbon atoms);
A group represented by —O—C (═O) —R (wherein R is a hydrocarbon group having 6 to 40 carbon atoms, and preferably an alkyl group having 12 to 22 carbon atoms); Can be mentioned.

  These lipophilic groups may be included in the lipophilic block alone or in combination of two or more.

  The lipophilic block preferably contains substantially no pigment affinity group, and usually the unit constituting the pigment affinity group with respect to all units constituting the lipophilic block is 10 mol% or less, more preferably. Is 5 mol% or less, more preferably 1 mol% or less.

  The lipophilic block may have other groups in addition to the lipophilic group and the pigment affinity group, as long as the effects of the present invention are not impaired. Examples of other groups include hydrocarbon groups having 5 or less carbon atoms (methyl group, ethyl group, butyl group, etc.) and the like.

  The pigment affinity group is a group that becomes a pigment adsorption site for the pigment. Examples of the pigment affinity group include a nitrogen-containing heterocyclic group, a carboxy group, a urethane bond-containing group, an amino group, an amide bond-containing group, a sulfo group, a glycidyl group, and an aromatic group. A nitrogen-containing heterocyclic group, a carboxy group, a urethane bond-containing group, an amino group, and an amide bond-containing group are preferable. When using a colorant modified with a polycyclic aromatic such as carbon black, an aromatic group can be preferably used.

The nitrogen-containing heterocyclic group means a group having an aromatic heterocyclic ring and an alicyclic heterocyclic ring having a nitrogen atom as a ring constituent atom. For example,
A pyrrolyl group, an imidazolyl group, a pyrazolyl group, a triazolyl group, a pyridyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, etc. as a nitrogen-containing aromatic heterocyclic ring;
Examples of the nitrogen-containing alicyclic heterocycle include azetidinyl group, pyrrolidinyl group, piperidinyl group, morpholinyl group, thiomorpholinyl group, piperazinyl group, azepanyl group, caprolactam group and the like.
Examples of the aromatic group include a phenyl group, a naphthyl group, and an anthracene group.

  These nitrogen-containing heterocyclic group and aromatic group may each have a substituent, and examples of the substituent include oxygen, sulfur, hydroxy group, saturated or unsaturated hydrocarbon having 1 to 5 carbon atoms. Group, a carboxy group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, and the like.

  The nitrogen-containing heterocyclic group is preferably a pyrrolidinyl group, an oxopyrrolidinyl group, a morpholinyl group, or a pyridinyl group, and more preferably a pyrrolidinyl group or an oxopyrrolidinyl group.

The amide bond-containing group is a group represented by —C (═O) —N—R′R ″. Here, R ′ and R ″ are each independently preferably hydrogen, a saturated or unsaturated hydrocarbon having 1 to 5 carbon atoms. For example, dimethyl (meth) acrylamide bond, diethyl (meth) acrylamide bond, (meth) acrylamide bond and the like can be mentioned.
Here, (meth) acryl means acryl, methacryl or both (hereinafter the same).

  The amino group is a group represented by —N—R′R ″. Here, it is preferable that R ′ and R ″ each independently represent hydrogen, a saturated or unsaturated hydrocarbon having 1 to 5 carbon atoms. For example, a dimethylamino group, a diethylamino group, etc. can be mentioned.

  When the pigment is carbon black, since it has an acidic site, the pigment affinity group may be a basic nitrogen-containing heterocyclic group, a urethane bond-containing group, an amide bond-containing group, an amino group, a carboxy group, or the like. preferable.

  These pigment affinity groups may be contained alone or in combination of two or more in the pigment affinity block.

  The pigment affinity block preferably contains the above-described lipophilic group together with the pigment affinity group. In this case, the molar ratio of the units constituting the pigment affinity group of the pigment affinity block to the units constituting the lipophilic group is preferably 20:80 to 60:40.

  The pigment affinity block may have other groups other than the pigment affinity group and the lipophilic group as long as the effects of the present invention are not impaired. Examples of other groups include hydrocarbon groups having 5 or less carbon atoms (methyl group, ethyl group, butyl group, etc.) and the like.

  Here, the monomer peak change amount of the pigment affinity group will be described. The amount of change in monomer peak can be used as one evaluation criterion for the pigment affinity of the pigment affinity group. The method for measuring the amount of change in monomer peak is as described in detail in the Examples.

  According to the measurement method of the example, the change amount of the monomer peak is preferably 5% or more, more preferably 10% or more, and further preferably 20% or more.

  The pigment affinity group having such a monomer peak change amount preferably includes a nitrogen-containing heterocyclic group, a carboxy group, a urethane bond-containing group, and / or an amide bond-containing group, such as a pyrrolidinyl group, oxo A pyrrolidinyl group, a morpholinyl group, a pyridinyl group, a carboxy group, a urethane bond-containing group, an amide bond-containing group, and the like can be exemplified, and a pyrrolidinyl group and an oxopyrrolidinyl group are more preferable.

  Even if the group has a low pigment adsorption rate, pigment affinity can be obtained by increasing the number of pigment affinity groups contained in the pigment affinity block.

  The molar ratio of the lipophilic block to the pigment affinity block may be 10:90 to 90:10, preferably 90:10 to 40:60, more preferably 90:10 to 50:50. . This molar ratio can be determined from the total number of moles of monomers used for the pigment affinity block and the total number of moles of monomers used for the lipophilic block in the polymerization stage. Thereby, the adsorptivity to the pigment can be further increased by setting the ratio of the pigment affinity block to 10 mol% or more. Moreover, the dispersibility to a solvent can be improved more because the ratio of a lipophilic block shall be 10 mol% or more.

  The number average molecular weight (Mn) of the lipophilic block may be 7000 or more, more preferably 7300 or more, and further preferably 7500 or more. As a result, the lipophilic block can be easily oriented in the solvent, and the dispersibility can be further improved. The upper limit of the number average molecular weight (Mn) of the lipophilic block is not particularly limited, and is usually about 30000 or less, preferably 20000 or less, and more preferably 18000 or less.

  The number average molecular weight (Mn) of the lipophilic block can be determined by measuring the number average molecular weight at the stage where the monomers constituting the lipophilic block are polymerized to polymerize the lipophilic block. The number average molecular weight (Mn) can be measured in terms of polystyrene using GPC (gel permeation chromatography) (hereinafter the same).

  Although it does not restrict | limit especially as a number average molecular weight (Mn) of the whole block copolymer which comprises a pigment dispersant, It is preferable that it is 8000 or more, More preferably, it is 10,000 or more, More preferably, it is 13000 or more. The upper limit of the number average molecular weight (Mn) of the block copolymer is not particularly limited, and is usually about 100,000 or less.

  The unit having a pigment affinity group may be 20 mol% to 60 mol% with respect to all units constituting the pigment affinity block. Preferably it is 25 mol% or more, More preferably, it is 30 mol% or more. Moreover, it is preferably 55 mol% or less, more preferably 50 mol% or less.

  When the unit having a pigment affinity group is 60 mol% or less, it is possible to prevent the pigment dispersant from becoming excessively high in polarity and to improve the solubility in a low polarity solvent. When the ratio of units having pigment affinity groups in the pigment affinity block becomes excessive, the pigment dispersant becomes a form in which the pigment affinity block is the core part and the lipophilic block is the shell part. Pigment dispersibility may be reduced.

  When the unit having the pigment affinity group is 20 mol% or more, the ratio of the pigment affinity group becomes sufficient, and the adsorptivity to the pigment can be enhanced. Thereby, pigment dispersibility can be improved.

  The number of moles of all units constituting the pigment affinity block can be determined from the total number of moles of monomers used for polymerizing the pigment affinity block. The number of moles of the unit having a pigment affinity group can be determined from the number of moles of the monomer having a pigment affinity group used for polymerizing the pigment affinity block.

  The unit having a pigment affinity group may be 10 mol% or less, preferably 5 mol% or less, more preferably 1 mol% or less, substantially with respect to all units constituting the lipophilic block. More preferably, it is not included. By reducing the ratio of the pigment affinity group in the lipophilic block, the length of the lipophilic group in the lipophilic block can be increased, and the solvent affinity can be increased. When a pigment affinity group is contained between the lipophilic groups in the lipophilic block, the pigment affinity group is oriented to the pigment, and the length of the lipophilic group extending in the solvent direction may be shortened.

  The blending amount of the pigment dispersant in the ink can be appropriately set, but from the viewpoint of pigment dispersibility, the mass ratio is preferably about 0.05 to 2.0 parts with respect to 1 part of the pigment, 0.1 More preferably, it is -1.5 parts. The pigment dispersant is preferably contained in an amount of about 0.5 to 15% by mass, and more preferably 1 to 12% by mass with respect to the whole ink. All are solid content conversion.

  Next, the manufacturing method of a pigment dispersant is demonstrated.

  As an example, the pigment dispersant according to this embodiment includes a first block obtained by radical polymerization of one of a monomer mixture a containing a monomer A having a lipophilic group and a monomer mixture b containing a monomer B having a pigment affinity group. Can be produced by polymerizing the other monomer mixture together with the polymerized first block to obtain a second block.

  The monomer A having a lipophilic group is preferably a compound having a polymerizable unsaturated group together with the above-described lipophilic group, and more preferably a vinyl monomer having a lipophilic group. For example, fatty acid vinyl esters, fatty acid vinyl ethers, alkyl (meth) acrylates, alkenes and the like can be preferably used.

  The fatty acid vinyl ester is preferably a vinyl ester of a fatty acid having 8 to 22 carbon atoms, such as vinyl octoate (C8), vinyl decanoate (C10), vinyl laurate (C12), vinyl myristate (C14). ), Vinyl palmitate (C16), vinyl stearate (C18), vinyl behenate (C22), and the like. The number in parentheses is the number of carbon atoms in the fatty acid group.

  Examples of the fatty acid vinyl ether include lauryl vinyl ether, octyl vinyl ether, 2-ethylhexyl vinyl ether, stearyl vinyl ether and the like.

  The alkyl (meth) acrylate is preferably an alkyl (meth) acrylate having an alkyl group having 8 to 22 carbon atoms, more preferably an alkyl group having 12 to 18 carbon atoms, such as lauryl (meth) acrylate or cetyl. (Meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate, behenyl (meth) acrylate, isolauryl (meth) acrylate, isostearyl (meth) acrylate, palmityl stearyl (meth) acrylate, etc. can be mentioned.

  Monomer A described above can be used alone or in combination of two or more.

  The monomer B having a pigment affinity group is preferably a compound having a polymerizable unsaturated group together with the above-described pigment affinity group, and more preferably a vinyl monomer having a pigment affinity group. For example, a vinyl monomer having one or more of a nitrogen-containing heterocyclic group, a carboxy group, a urethane bond-containing group, an amino group, and an amide bond-containing group can be used, and these are used alone or in combination of two or more. be able to. Moreover, when using coloring materials, such as carbon black modified by the polycyclic aromatic group, you may use an aromatic vinyl monomer.

  Examples of the vinyl monomer having a nitrogen-containing heterocyclic group include vinyl imidazole, vinyl imidazoline, vinyl pyridine, vinyl pyrrolidone, vinyl morpholine, vinyl caprolactam, and more preferably vinyl pyrrolidone.

  Examples of the vinyl monomer having a urethane bond-containing group include methacryloyloxyethyl isocyanate (MOI), acryloyloxyethyl isocyanate (AOI), 2- (0- [1′-methylpropylideneamino] carboxyamino) ethyl methacrylate, 2-[(3,5-dimethylpyrazolyl) carbonylamino] ethyl methacrylate, 1,1- (bisacryloyloxymethyl) ethyl isocyanate (BEI), vinyl isocyanate, allyl isocyanate, methacryloyl isocyanate (MAI), acryloyl isocyanate, isopropenyl Examples thereof include those obtained by reacting an isocyanate group such as -α, α-dimethylbenzyl isocyanate (TMI) with an alcohol such as methanol or ethanol.

  Examples of vinyl monomers having an amide bond include (meth) acrylamides such as acrylamide, methacrylamide, α-ethylacrylamide; dimethylacrylamide (DMAA), dimethylmethacrylamide, methylacrylamidemethylmethacrylamide, methylolacrylamide, and methylolmethacrylamide. And (meth) acrylamide dimers such as methylenebisacrylamide and methylenebismethacrylamide; and vinylpyrrolidone.

  Examples of the vinyl monomer having a carboxy group include 2-acryloyloxyethyl-hexahydrophthalic acid, 2-acryloyloxyethyl-succinic acid, ***, ***, and the like.

  As a vinyl monomer which has an amino group, acrylic acid 2 (dimethylamino) ethyl, acrylic acid 2 (diethylamino) ethyl, etc. can be mentioned, for example.

Examples of the aromatic vinyl monomer include styrene and vinyl naphthalene.
Monomers B described above can be used alone or in combination of two or more.

  Hereinafter, after polymerizing the monomer mixture a containing the monomer A having a lipophilic group as the first step and polymerizing the lipophilic block, the monomer mixture b containing the monomer B having the pigment affinity group is polymerized as the second step. A method for polymerizing the pigment affinity block at the end of the lipophilic block will be described.

  First, in the first stage, the monomer mixture a may contain any monomer C other than the monomer A and the monomer B within a range not impairing the effects of the present invention, together with the monomer A having a lipophilic group.

  As the monomer C, fatty acid vinyl esters having a fatty acid group having 5 or less carbon atoms (vinyl acetate, vinyl benzoate, etc.), alkyl (meth) acrylates having 5 or less carbon atoms (butyl acrylate, ethyl acrylate, etc.) ).

  The monomer A is preferably 50 mol% or more, more preferably 80 mol% or more, and still more preferably 90 mol% or more with respect to the entire monomer mixture a. The monomer B having a pigment affinity group may be 10 mol% or less, more preferably 5 mol% or less, still more preferably 1 mol% or less, and substantially contained in the monomer mixture a. More preferably not. Monomer C can be contained in the range of 5 to 0 mol% as the balance.

  These monomer mixtures a can be polymerized by known radical polymerization. The reaction system is preferably carried out by solution polymerization or dispersion polymerization. A polymerization reaction can be accelerated | stimulated by heating and performing a polymerization reaction as needed. As heating temperature, it can adjust suitably, for example within 50-130 degreeC.

  In this case, in order to narrow the molecular weight distribution of the lipophilic block after polymerization, a chain transfer agent may be used in combination during the polymerization. As the chain transfer agent, for example, thiols such as n-butyl mercaptan, lauryl mercaptan, stearyl mercaptan, and cyclohexyl mercaptan can be used.

  Examples of the polymerization initiator include azo compounds such as AIBN (azobisisobutyronitrile), t-butylperoxybenzoate, t-butylperoxy-2-ethylhexanoate (perbutyl O, manufactured by NOF Corporation), and the like. Known thermal polymerization initiators such as oxides can be used. In addition, a photopolymerization initiator that generates radicals upon irradiation with active energy rays can be used.

  As the polymerization solvent used for the solution polymerization, for example, an ester solvent such as ethyl acetate, a petroleum solvent such as a hydrocarbon solvent, or the like can be used. One or more polymerization solvents may be selected from solvents (described later) that can be used as ink solvents as they are. Further, by using ethyl acetate, the second stage monomer can be dissolved together with the first stage monomer. That is, both the monomer having a lipophilic group and the monomer having a pigment affinity group can be dissolved.

  In the polymerization reaction, other commonly used polymerization inhibitors, polymerization accelerators, dispersants and the like can also be added to the reaction system.

  Next, in the second stage, the monomer mixture b may contain the monomer A together with the monomer B having a pigment affinity group, and may further contain the monomer C as long as the effects of the present invention are not impaired. Monomer C is as described above.

  Although monomer B should just be 20 mol% or more with respect to the whole monomer mixture b, More preferably, it is 25 mol% or more, More preferably, it is 30 mol% or more. Although monomer A should just be less than 80 mol% with respect to the whole monomer mixture b, More preferably, it is less than 75 mol%, More preferably, it is less than 70 mol%. Monomer C can be contained in the range of 0 to 5 mol% as the balance.

  By polymerizing the monomer mixture b in the presence of the synthesized lipophilic block, the pigment affinity block is bonded to the terminal portion of the lipophilic block, and a block copolymer can be obtained. Polymerization conditions, additives, and the like are common to the above-described affinity block polymerization.

  In the present embodiment, the pigment dispersant is preferably polymerized by a living polymerization method which is a kind of precision polymerization. That is, the monomer mixture B containing the monomer b having a pigment affinity group together with the synthesized lipophilic block is subjected to living polymerization. After polymerizing the pigment affinity block first, the monomer mixture A containing the monomer a having a lipophilic group may be subjected to living polymerization.

  According to the living polymerization method, the lipophilic block and the pigment affinity block are sequentially polymerized, and can be synthesized by controlling the molecular weight of the lipophilic block and the molecular weight of the pigment affinity block, respectively. Thereby, the solvent affinity can be increased by reducing the variation in the length of the lipophilic block and ensuring the necessary chain length.

  Since living polymerization is susceptible to oxygen damage, the polymerization is preferably performed under vacuum or in an inert atmosphere.

  As the RAFT agent, thiocarbonylthio compounds such as dithioesters, dithiocarbamates, trithiocarbonates, and xanthates can be used. For example, cyanomethyl N-methyl-N-phenyldithiocarbamate (“723002” manufactured by Aldrich), 2-cyano-2-propyldodecyltrithiocarbonate (“723037” manufactured by Aldrich), 2-dodecylthiocarbonothioyl Thio) -2-methylpropionic acid (“723010” manufactured by Aldrich) and the like.

  Any number of pigments may be included in the ink according to the present embodiment. Examples of pigments for black ink include carbon blacks such as furnace black, lamp black, acetylene black, and channel black; copper, iron, titanium oxide, and the like. And organic pigments such as ortho-nitroaniline black. These can be used alone or in any desired mixture.

  Color ink pigments include toluidine red, permanent carmine FB, disazo orange PMP, lake red C, brilliant carmine 6B, quinacridone red, dioxane violet, orthonitroaniline orange, dinitroaniline orange, vulcan orange, toluidine red, chlorinated para red. , Brilliant First Scarlet, Naphthol Red 23, Virazolone Red, Barium Red 2B, Calcium Red 2B, Strontium Red 2B, Manganese Red 2B, Barium Resome Red, Pigment Scar Red 3B Lake, Lake Bordeaux 10B, Anthosine 3B Lake, Anthosine 5B Rake, Rhodamine 6G Rake, Eosin Rake, Bengala, Fattor Red FGR, Rhodamine B , Methyl bio red lake, dioxazine bio red, naphthol carmine FB, naphthol red M, fast yellow AAA, fast yellow 10G, disazo yellow AAMX, disazo yellow AAAT, disazo yellow AAOA, disazo yellow HR, isoindoline yellow, fast Yellow G, Disazo Yellow AAA, Phthalocyanine Blue, Pictoria Pure Blue, Basic Blue 5B Lake, Basic Blue 6G Lake, Fast Sky Blue, Alkaline Blue R Toner, Peacock Blue Lake, Bituminous Blue, Ultraviolet, Reflex Blue 2G, Reflex Blue R, alkali blue G toner, brilliant green lake, diamond green thioflavin lake, phthalocyanine green G Examples include green gold, phthalocyanine green Y, iron oxide powder, rust, zinc white, titanium oxide, calcium carbonate, clay, barium sulfate, alumina white, aluminum powder, bronze powder, daylight fluorescent pigment, pearl pigment, etc. May be used alone or in any mixture.

  The average particle diameter of the pigment is preferably 300 nm or less, more preferably 150 nm or less, and even more preferably 100 nm or less from the viewpoint of ejection stability and storage stability. Here, the average particle diameter of the pigment can be measured by a dynamic light scattering particle size distribution analyzer LB-500 manufactured by Horiba, Ltd.

  The content of the pigment in the ink is usually 0.01 to 20% by mass, and preferably 3 to 15% by mass from the viewpoint of printing density and ink viscosity.

  In the ink of the present embodiment, the dispersibility can be enhanced by using the above-described pigment dispersant, but other pigment dispersants can be added within a range not impairing the effects of the present invention, and the pigment in the ink can be added. Dispersibility can be adjusted. The other pigment dispersant is not particularly limited as long as the pigment is stably dispersed in the solvent.

  The amount of the other pigment dispersant in the ink can be added as a part of the pigment dispersant described above. The other pigment dispersant is preferably 50% by mass or less, more preferably 10% by mass or less, based on the entire dispersant including the pigment dispersant described above.

  The low polarity solvent of this embodiment is a low polarity solvent, and preferably a nonpolar solvent. By using a low-polarity solvent, even when the low-polarity solvent in the ink evaporates when printing the ink, the problem of odor can be prevented.

  The low polarity solvent used in the present embodiment is not particularly limited as long as it has a low polarity. For example, it is preferable that the relative dielectric constant is usually 3.5 or less at a measurement frequency of 1 kHz. More preferably, the relative dielectric constant is 3.0 or less. The lower limit of the relative dielectric constant is not particularly limited, but is usually 0 or more, preferably 1.5 or more.

  The boiling point of the low polarity solvent is preferably 150 ° C. or higher. Thereby, good on-machine stability can be obtained. For example, when ink is ejected, evaporation of the solvent in the ink can be prevented and nozzle clogging can be prevented. Moreover, as a boiling point of a low polarity solvent, it is preferable that it is 300 degrees C or less, More preferably, it is 270 degrees C or less, More preferably, it is 250 degrees C or less. Thereby, after ink printing, evaporation of the solvent in the ink applied to the printed matter can be promoted, and the back-through can be prevented.

  Similar to the preferred range of the boiling point described above, the distillation range of the low polarity solvent is preferably 150 ° C. or higher, more preferably 170 ° C. or higher. Moreover, as a distillation range of a low polarity solvent, it is preferable that it is 270 degrees C or less, More preferably, it is 250 degrees C or less. Here, the distillation range is the temperature from the first distillation to the end point.

  Examples of the low polarity solvent include hydrocarbon solvents. As the hydrocarbon solvent, a linear or branched saturated or unsaturated aliphatic hydrocarbon solvent, an alicyclic hydrocarbon solvent, an aromatic hydrocarbon solvent, a petroleum solvent such as petroleum naphtha is preferable. Can be mentioned.

Examples of the aliphatic hydrocarbon solvent and the alicyclic hydrocarbon solvent include n-decane, isodecane, decalin, nonane, dodecane, isododecane, tetradecane, hexadecane, paraffinic solvent, naphthenic solvent, and the like.
Commercially available products include “Teclean N-16, Teclean N-20, Teclean N-22”, “Nisseki Naphthezol L, Nissho Naphthezol M, Nissho Naftesol H”, “No. 0” manufactured by JX Nippon Oil & Energy Corporation. Solvent L, No. 0 Solvent M, No. 0 Solvent H (all are n-paraffin solvents), “Nisseki Isosol 300, Nisseki Isosol 400 (all are isoparaffin solvents)”, “AF-4, AF-5 , AF-6, AF-7 (both naphthenic solvents) ",
“IP Solvent 1016, 1620, 2028, 2835 (all are isoparaffinic solvents)”, “IP Clean LX (isoparaffinic solvent)” manufactured by Idemitsu Petrochemical Co., Ltd.,
“Isopar G, Isopar H, Isopar L, Isopar M (all are isoparaffinic solvents)” manufactured by Exxon, “ExxsolD40, ExxsolD80, ExxsolD100, ExxsolD130, ExxsolD140”,
“Normal paraffin H” manufactured by Japan Energy Co., Ltd. can be used.

  As the aromatic hydrocarbon solvent, “Nisseki Clean Sol G” (alkylbenzene) manufactured by JX Nippon Oil & Energy Corporation, “Solvesso 200” manufactured by Exxon, etc. can be used.

  These can be used alone or in combination of two or more.

  From the viewpoint of viscosity, boiling point and distillation range, the low polarity solvent preferably includes a hydrocarbon solvent, more preferably an aliphatic or alicyclic hydrocarbon solvent, and still more preferably an n-paraffin material. Isoparaffinic solvents and naphthenic solvents. Commercially available products include the above-mentioned No. 0 Solvent L, M, H, Isosol 300, 400, AF-4, IP Solvent 1620, 2028, IP Clean LX, Isopar G, H, L, M, etc. Can be mentioned.

  In this embodiment, it is preferable that the ink does not contain water or a high-polarity solvent, but may be contained within a range that does not impair the effects of the present invention.

  The non-aqueous pigment ink of the present embodiment includes, for example, a nozzle clogging preventive agent, an antioxidant, a conductivity adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen within a range that does not impair the effects of the present invention. Absorbers, fixing agents, preservatives, surfactants, and the like can be added as appropriate. These types are not particularly limited, and those used in the field can be used.

  The viscosity range of the non-aqueous pigment ink varies depending on the nozzle diameter of the ejection head, the ejection environment, and the like, but in general, it is preferably 5 to 30 mPa · s, preferably 5 to 15 mPa · s at 23 ° C. More preferably, the pressure is about 10 to 13 mPa · s. Here, the viscosity is a viscosity at 23 ° C., and can be measured by “Stress Control Rheometer RS75” (Cone Angle 1 °, Diameter 60 mm) manufactured by Harke.

  As an example of an ink production method, all components including pigment, pigment dispersant, and low polarity solvent are added to a disperser such as a bead mill at one time or divided and stirred and mixed. Obtained by filtration. For example, a pigment dispersion is prepared by preparing a mixed liquid in which a part of the low-polar solvent, the total amount of the pigment, and the pigment dispersant are uniformly mixed, and dispersing with a disperser. It can be prepared by mixing the remaining low polarity solvent and passing through a filter.

  The ink jet recording method using the non-aqueous pigment ink may be any method such as a piezo method or an electrostatic method. When an ink jet recording apparatus is used, it is preferable that the ink according to the present embodiment is ejected from the ink jet head based on the digital signal, and the ejected ink droplets are attached to the recording medium.

  The recording medium is not particularly limited, and the thickness of the ink absorbing layer is larger than that of plain paper, high-quality plain paper, inkjet (IJ) paper, IJ matte paper, coated paper in which an ink absorbing solution is coated on the recording medium, and coated paper. Can be used for thin coated paper, glossy paper (photo glossy paper), special paper, cloth, etc.

<Pigment dispersant>
A pigment dispersant according to an embodiment of the present invention is a block copolymer having a lipophilic block having a lipophilic group and a pigment affinity block having a pigment affinity group, the lipophilic block having a pigment affinity. The molar ratio with the block is 10:90 to 90:10, the number average molecular weight of the lipophilic block is 7000 or more, and the unit having a pigment affinity group with respect to all units constituting the pigment affinity block is 20 mol%. It is ˜60 mol%, and the unit having a pigment affinity group with respect to all units constituting the lipophilic block is a block copolymer having 10 mol% or less.

  By blending this pigment dispersant into an ink, particularly an ink of a low-polarity solvent, it is possible to provide excellent storage stability and dispersion stability while preventing odor, and to prevent back-through. The details are the same as those of the above-described ink pigment dispersant.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

<Preparation of pigment dispersant>
Tables 1 to 3 show the formulation and physical properties of the pigment dispersant. The components shown in each table are as follows. The unit of the blending amount is “g”.

Vinyl stearate: Wako Pure Chemical Industries, Ltd.
Vinyl laurate: Wako Pure Chemical Industries, Ltd.
PSMA: Palmityl stearyl methacrylate, “Exepearl PS-MA” manufactured by Kao Corporation.
Vinylpyrrolidone Wako Pure Chemical Industries, Ltd.
723002: “723002” manufactured by Aldrich, RAFT agent.
723037: “723037” manufactured by Aldrich, RAFT agent.
AIBN: Azobisisobutyronitrile, manufactured by Wako Pure Chemical Industries, Ltd.
Perbutyl O: t-butyl peroxy 2-ethylhexanoate, manufactured by NOF Corporation.
Ethyl acetate: manufactured by Wako Pure Chemical Industries, Ltd.
DMAA: dimethylacrylamide, “DMAA” manufactured by Kojin Co., Ltd.
Karenz MOI: 2-isocyanatoethyl methacrylate, “Karenz MOI” manufactured by Showa Denko KK
LMA: Dodecyl methacrylate, manufactured by Wako Pure Chemical Industries, Ltd.

(Pigment dispersant 1)
“First stage: Preparation of lipophilic block”
In the flask, each component of the first stage among the components shown in Table 1 was prepared. After sufficiently degassing, the flask was filled with argon gas, and reacted for 24 hours while heating and stirring at 65 ° C. After completion of the reaction, the number average molecular weight (Mn) was measured by GPC (gel permeation chromatography, “10A system” manufactured by Shimadzu Corporation, the same shall apply hereinafter) to be 8700 in terms of polystyrene.

“Second stage: Preparation of pigment affinity block”
Next, each component of the second stage among the components shown in Table 1 was added to the polymerization solution prepared in the first stage. After sufficiently degassing, the flask was filled with argon gas and reacted for 24 hours while heating and stirring at 65 ° C. After completion of the reaction, methanol was added to the polymerization solution to precipitate a resin and dried. When the number average molecular weight (Mn) was measured by GPC, it was 13900 in terms of polystyrene.

(Pigment dispersant 2-17)
The pigment dispersants 2 to 8 and 10 to 16 were synthesized in the same manner as the pigment dispersant 1 described above according to the formulations shown in Tables 1 to 3.
The pigment dispersant 9 was synthesized in the same manner as the pigment dispersant 1 according to the formulation shown in Table 2, and then 2.4 g of ethanol and 0.05 g of dibutyltin dilaurate (catalyst) in the polymerization solution. And heated at 50 ° C. for 5 hours to react the isocyanate group derived from Karenz MOI with methanol to introduce a urethane-containing group.
The pigment dispersant 17 was synthesized by polymerizing all components in the first stage according to the formulation shown in Table 3.

(Physical properties)
In Tables 1 to 3, the ratio (mol%) of the lipophilic block is the number of moles of monomers used in the first stage relative to the total number of moles of monomers used through the first stage and the second stage.
The molar ratio of the monomers A and B in the pigment adsorbing block is the molar ratio of the lipophilic monomer (monomer A) and the pigment affinity monomer (monomer B) used in the second stage.
The ratio of the monomer B of the pigment affinity block is the number of moles of the pigment affinity monomer (monomer B) with respect to the total number of moles of the monomer used in the second stage.

<Ink adjustment>
Tables 4 and 5 show the formulations and evaluation results of the non-aqueous pigment inks of Examples and Comparative Examples. The components shown in each table are as follows. The unit of the blending amount is “mass%”.

S11200: “Solsperse 11200” manufactured by Nippon Lubrizol Co., Ltd., a comb-type polyamide-based dispersant having a plurality of side chains composed of polyester chains, solid content 50.0% by mass.
V216: “ANTARONV216” manufactured by IPS Japan Ltd., vinylpyrrolidone-hexadecene copolymer.
Carbon black: “MA11” manufactured by Mitsubishi Chemical Corporation.
AF4: “AF Solvent No. 4” manufactured by JX Nippon Oil & Energy Corporation, naphthenic solvent (low polarity solvent, distillation range of 240 to 265 ° C.).
Isopar G: “Isopar G” manufactured by Exxon, an isoparaffin-based solvent (low polarity solvent, distillation range: 167 to 176 ° C.).
IOP: Isooctyl palmitate, “Nikkor IOP” manufactured by Nikko Chemicals Co., Ltd., ester solvent (high polarity solvent).

Example 1
According to each table | surface, each component was mixed in each ratio. Next, 200 g of the mixture was taken out and dispersed with a bead mill using zirconia beads having a diameter of 0.5 mm. Next, the mixture was treated with a centrifugal separator at 20000 G for 7 minutes, passed through a 0.8 micron filter to remove coarse particles, and ink was prepared.

  In the other Examples and Comparative Examples, the ink was prepared in the same manner. In Comparative Examples 7 and 8, S11200, which is a commercially available dispersant, was used instead of the synthesized pigment dispersant. In Comparative Example 10, commercially available V216 was used instead of the synthesized pigment dispersant.

<Evaluation>
The following evaluation was performed on the inks of the above-described Examples and Comparative Examples.

"Storage stability"
After measuring the initial viscosity of each ink described above, each ink was put in a sealed container and allowed to stand in an environment of 70 ° C. After 1 week (70 ° C., 1 w) and 4 weeks (70 ° C., 4 w) The viscosity of each ink was measured, and the rate of change in viscosity ((viscosity after standing-initial viscosity) / (initial viscosity) × 100 (%)) was determined and evaluated according to the following criteria. In addition, all the initial viscosities of the ink of each Example were the appropriate ranges as an inkjet ink.

  The viscosity is a viscosity at 23 ° C., and was measured by “Stress Control Rheometer RS75” (Cone Angle 1 °, Diameter 60 mm) manufactured by Harke.

A: Viscosity change rate is 3% or less.
B: Viscosity change is more than 3% and not more than 5%.
C: Viscosity change is more than 5% and 10% or less.
D: The viscosity change exceeds 10%.

"Odor"
Each ink described above was used as an inkjet ink. Each ink was introduced into “Inkjet Head CB2” manufactured by TOSHIBA TEC CO., LTD. On plain paper (“Ideal Paper Thin Edge” manufactured by RISO Kagaku Kogyo Co., Ltd.) under the conditions of a pixel density of 300 dpi × 300 dpi and a droplet of 30 pL per pixel. The solid image was printed out. Immediately after printing, the smell of the solid image of the printed material was smelled by a panel of * people, and sensory evaluation was performed according to the following criteria. The evaluation result is an average of the evaluation results of the panel of five people.
A: Level at which almost no odor is felt.
B: Level at which odor is felt.

"Betrayal"
A printed matter was produced in the same manner as the evaluation of the odor. The back surface density (OD value) of the solid image portion of the printed material 24 hours after printing was measured with an optical densitometer (“RD920” manufactured by Macbeth). Based on the back surface concentration, the back through was evaluated according to the following criteria. In the evaluation of the strikethrough, the breakthrough is prevented as the back surface density is lower.
A: Back surface density is less than 0.27.
B: The back surface density is 0.27 or more and less than 0.30.
C: Back surface density is 0.30 or more.

As shown in Table 1,
The pigment dispersant of each example was excellent in storage stability, and could prevent odor and show-through.

In Comparative Examples 1, 3 and 4, the Mn of the lipophilic block of the pigment dispersant was small, and the storage stability, particularly the long-term storage stability for 4 weeks, was lowered.
In Comparative Example 2, the ratio of the monomer B in the pigment affinity block of the pigment dispersant was high, the dispersibility was lowered, and the storage stability, odor, and back-through could not be evaluated.
In Comparative Example 5, the ratio of the lipophilic block was high, the dispersibility was lowered, and the storage stability, odor, and strikethrough could not be evaluated. Moreover, in the comparative example 6, the ratio of the lipophilic block was high and the storage stability fell.
In Comparative Example 7, a commercially available dispersant was used together with a low polarity solvent, and the storage stability was lowered.
In Comparative Example 8, a commercially available dispersant was used together with a polar solvent, and the storage stability was improved, but the breakthrough was reduced.
In Comparative Example 9, a pigment dispersant obtained by randomly polymerizing all moles in the same composition as in Example 10 was used, and the storage stability was lowered because it was not a block copolymer.
In Comparative Example 10, a commercially available dispersant which is a copolymer of polyvinyl pyrrolidone and alkene is used, but since it is not a block copolymer, the storage stability is lowered.

<Evaluation of pigment affinity>
Hereinafter, the pigment affinity of various monomers was evaluated. Table 6 shows various monomers and their pigment affinity.

  Carbon black “MA11” (manufactured by Mitsubishi Chemical Corporation) was used as a pigment. Using various monomers, an ethyl acetate solution of 1% by mass monomer (hereinafter referred to as 1% monomer solution) was prepared.

  4 g of the pigment was immersed in 40 g of a 1% monomer solution and left for 1 day. After standing, the supernatant solution was taken out. The supernatant solution and the 1% monomer solution before the pigment immersion were each subjected to high performance liquid chromatography. The monomer peak areas of the respective solutions were measured, and the monomer peak areas before and after the pigment immersion were compared to determine the monomer peak change rate (%) before and after the pigment immersion. Further, assuming that the monomer corresponding to the decrease in the monomer peak before and after the pigment immersion was adsorbed to the pigment, the amount of change in the monomer peak was determined as (100− (monomer peak change rate before and after pigment immersion (%))).

  In the table, “octyl isocyanate + methanol” is a monomer in which an urethane group is introduced by reacting an isocyanate group with methanol.

The pigment affinity was evaluated from the monomer peak change amount according to the following criteria.
AA: The monomer peak change amount is 20% or more.
A: The amount of monomer peak change is 10% or more and less than 20%.
B: The monomer peak change amount is 5% or more and less than 10%.
C: Monomer peak change amount is less than 5%.

  If the monomer peak change amount is 5% or more, it can be said that it has pigment affinity. Among various monomers, it has been found that a monomer having a nitrogen-containing heterocyclic group, a urethane bond group, an amide bond group or a carboxy group as a pigment affinity group is excellent in pigment affinity. Among the monomers considered to have pigment affinity, vinyl pyrrolidone was found to have very high pigment affinity.

Claims (6)

A pigment, a pigment dispersant, and a low polarity solvent,
The pigment dispersant is
A block copolymer having a lipophilic block having a lipophilic group and a pigment affinity block having a pigment affinity group,
The molar ratio of the lipophilic block to the pigment affinity block is 10:90 to 90:10,
The lipophilic block has a number average molecular weight of 7000 or more;
The unit having the pigment affinity group with respect to all the units constituting the pigment affinity block is 20 mol% to 60 mol%,
The unit having the pigment affinity group with respect to all units constituting the lipophilic block is a block copolymer of 10 mol% or less.
Non-aqueous pigment ink.   The pigment affinity group includes one or more of a nitrogen-containing heterocyclic group, a carboxy group, a urethane bond-containing group, an amino group, and an amide bond-containing group, and the lipophilic group is an alkyl group having 8 to 22 carbon atoms. The non-aqueous pigment ink according to claim 1, comprising:   The pigment affinity block further has a lipophilic group, and a molar ratio of a unit constituting the pigment affinity group of the pigment affinity block to a unit having the lipophilic group is from 20:80 to 60:40. The non-aqueous pigment ink according to claim 1 or 2.   The pigment dispersant is obtained by radical polymerization of one of a monomer mixture a containing a monomer A having a lipophilic group and a monomer mixture b containing a monomer B having a pigment affinity group to obtain a first block, and the polymerization The non-aqueous pigment ink according to any one of claims 1 to 3, which is a block copolymer produced by polymerizing the other monomer mixture together with the first block obtained to obtain a second block.   The non-aqueous pigment ink according to any one of claims 1 to 4, wherein a distillation range of the low polarity solvent is 150 ° C to 270 ° C. A block copolymer having a lipophilic block having a lipophilic group and a pigment affinity block having a pigment affinity group,
The molar ratio of the lipophilic block to the pigment affinity block is 10:90 to 90:10,
The lipophilic block has a number average molecular weight of 7000 or more;
The unit having the pigment affinity group with respect to all the units constituting the pigment affinity block is 20 mol% to 60 mol%,
The unit having the pigment affinity group with respect to all units constituting the lipophilic block is a block copolymer of 10 mol% or less.
Pigment dispersant.