US008507585B2
(12) United States Patent (10) Patent No.: US 8,507,585 B2 Hosoya et al. (45) Date of Patent: *Aug. 13, 2013
2010/0136236 A1* 6/2010 Hosoya et al...... 427,261 (54) NON-AQUEOUS PIGMENT INK 2012/0083567 A1* 4/2012 Hosoya et al...... 524,516 (75) Inventors: Tetsuo Hosoya, Ibaraki-ken (JP); 2012/0220702 A1* 8/2012 Hosoya et al...... 524.88 Hiroshi Hayashi, Ibaraki-ken (JP); FOREIGN PATENT DOCUMENTS Yoshifumi Watanabe, Ibaraki-ken (JP); CN 101001905. A 7/2007 Kazuyuki Ando, Ibaraki-ken (JP); CN 101OO7917 A 8, 2007 Marie Morinaga, Ibaraki-ken (JP) CN 101.154038 A 4/2008 EP 1205815 A1 5, 2002 Assignee: Riso Kagaku Corporation, Tokyo (JP) EP 15O2935 A1 2, 2005 (73) JP 10-060353 A 3, 1998 JP 2000-1193.61 A 4/2000 (*) Notice: Subject to any disclaimer, the term of this JP 2004-231870 A 8, 2004 patent is extended or adjusted under 35 JP 2005-239.947 A 9, 2005 U.S.C. 154(b) by 293 days. JP 2007-131753. A 5/2007 JP 2007-197500 A 8, 2007 This patent is Subject to a terminal dis JP 2007-277397 A 10/2007 claimer. JP 2008-019333 A 1, 2008 TW 200808918 A 2, 2008 (21) Appl. No.: 12/990,379 OTHER PUBLICATIONS PCT Fled: Apr. 8, 2009 (22) Form PCT/IB1338 (Notification of Transmittal of Translation of the PCT/UP2009/057.192 International Preliminary Reporton Patentability (Chapter I or Chap (86). PCT No.: ter II of the Patent Cooperation Treaty)) for International Application S371 (c)(1), No. PCT/JP2009/057192, with a mailing date of Jan. 20, 2011, one (2), (4) Date: Oct. 29, 2010 (1) page. English translation of the International Preliminary Report on Pat (87) PCT Pub. No.: WO2009/142075 entability (Chapter I of the Patent Cooperation Treaty), issued Jan. 11, 2011, for International Application No. PCT/JP2009/057192, PCT Pub. Date: Nov. 26, 2009 eight (8) pages. Search Report, issued on Sep. 4, 2012, in the counterpart European (65) Prior Publication Data Application, Application No. EP 0975 0437, four (4) pages. US 2011 FOO46298 A1 Feb. 24, 2011 Official Action, issued on Jan. 10, 2013, in the counterpart Chinese application, in Chinese, eight (8) pages. (30) Foreign Application Priority Data * cited by examiner May 23, 2008 (JP) ...... 2008-135274 Nov. 18, 2008 (JP) ...... 2008-294.829 Primary Examiner — Patrick Niland (51) Int. Cl. (74) Attorney, Agent, or Firm — Nath, Goldberg & Meyer; CSF 8/30 (2006.01) Jerald L. Meyer, Sanjana Mangalagiri CSF28.3/04 (2006.01) C08G 18/08 (2006.01) (57) ABSTRACT C08G 18/10 (2006.01) C08G 18/28 (2006.01) A non-aqueous pigment ink comprising a pigment, a non C83/00 (2006.01) aqueous solvent, and non-aqueous resin dispersion micropar CSK 3/20 (2006.01) ticles having a pigment dispersion capability, wherein the COSL 39/00 (2006.01) non-aqueous resin dispersion microparticles are an acrylic COSL 73/00 (2006.01) polymer comprising an alkyl (meth)acrylate unit having an (52) U.S. C. alkyl group of 12 or more carbon atoms and a (meth)acrylate USPC ...... 523/160; 523/161:524/555; 524/589; unit having aurethane group. The acrylic polymer is a copoly 524/590; 524/591; 524/839; 524/840; 525/123; mer of a monomer mixture comprising an alkyl (meth)acry 525/455; 525/920 late (A) having an alkyl group of 12 or more carbonatoms and (58) Field of Classification Search a reactive (meth)acrylate (B) having a functional group USPC ...... 523/160, 161; 524/589, 590,591, capable of reacting with an amino group, wherein the ure 524/839, 840, 555; 525/123,455, 920 thane group is introduced by a reaction between the func See application file for complete search history. tional group capable of reacting with an amino group, an amino alcohol and a polyvalent isocyanate compound, and (56) References Cited the mass ratio within the acrylic polymer between the copoly mer portion and the introduced urethane group portions is U.S. PATENT DOCUMENTS within a range from 60:40 to 99:1. 7,214,725 B2 5/2007 Narayan-Sarathy et al. 2007/0173560 A1* 7, 2007 UoZumi ...... 523,160 2009/00928O1 A1 4/2009 Sato et al. 8 Claims, No Drawings US 8,507,585 B2 1. 2 NON-AQUEOUS PIGMENT INK Solvent, and non-aqueous resin dispersion microparticles having a pigment dispersion capability, wherein This is a National Phase Application filed under 35 U.S.C. the non-aqueous resin dispersion microparticles are an S371 as a national stage of PCT/JP2009/057192, filed on Apr. acrylic polymer comprising an alkyl (meth)acrylate unit hav 8, 2009, claiming the benefit of Japanese Patent Application 5 ing an alkyl group of 12 or more carbon atoms and a (meth) 2008-135274, filedon May 23, 2008, and claiming the benefit acrylate unit having a urethane group, of Japanese Patent Application 2008-294829, filed on Nov. the acrylic polymer is a copolymer of a monomer mixture 18, 2008, the content of each of which is hereby incorporated comprising an alkyl (meth)acrylate (A) having an alkyl group by reference in its entirety. of 12 or more carbon atoms and a reactive (meth)acrylate (B) 10 having a functional group capable of reacting with an amino TECHNICAL FIELD group, wherein the urethane group is introduced by a reaction between the functional group capable of reacting with an The present invention relates to a non-aqueous pigment amino group, an amino alcohol and a polyvalent isocyanate ink, and relates particularly to a non-aqueous pigment ink that compound, and is suitable for use in an inkjet recording system. 15 the mass ratio within the acrylic polymer between the copolymer portion and the introduced urethane group por BACKGROUND ART tions is within a range from 60:40 to 99:1. Another aspect of the present invention provides a pigment The coloring materials for inks used in inkjet recording dispersant for a non-aqueous pigment ink, wherein systems can be broadly classified into materials that use pig the pigment dispersant is composed of an acrylic polymer ments and materials that use dyes, and there is a growing comprising an alkyl (meth)acrylate unit having an alkyl group tendency for the use of inks that use pigments as the coloring of 12 or more carbon atoms and a (meth)acrylate unit having materials, as such inks exhibit the excellent levels of light a urethane group, and is insoluble in solvents having a 50% resistance, weather resistance and water resistance that are distillation point of 150° C. or higher, required for high image quality printing. 25 the acrylic polymer is a copolymer of a monomer mixture In terms of the solvent, inks can be broadly classified into comprising an alkyl (meth)acrylate (A) having an alkyl group aqueous inks and non-aqueous inks. Non-aqueous inks that of 12 or more carbon atoms and a reactive (meth)acrylate (B) do not use water as the ink solvent, including solvent-based having a functional group capable of reacting with an amino inks that use a volatile solvent as the main constituent and group, wherein the urethane group is introduced by a reaction oil-based inks that use a non-volatile solvent as the main 30 between the functional group capable of reacting with an constituent, exhibit good drying properties to aqueous inks, amino group, an amino alcohol and a polyvalent isocyanate and also display excellent printability. compound, and In non-aqueous inks, a pigment dispersant that dissolves in the mass ratio within the acrylic polymer between the the solvent is generally used, but because this pigment dis copolymer portion and the introduced urethane group por persant improves the affinity between the solvent and the 35 tions is within a range from 60:40 to 99:1. pigment, when the solvent penetrates into the recording paper, the pigment tends to be also drawn into the interior of Effects of Invention the recording paper. As a result, the print density tends to fall, and show-through becomes more prevalent. The non-aqueous ink according to the present invention Accordingly, a non-aqueous pigment ink has been pro 40 (hereafter also referred to as simply “the ink”) uses, as a posed that uses as a dispersant non-aqueous resin dispersion pigment dispersant, non-aqueous resin dispersion micropar microparticles (NAD=Non Aqua Dispersion) having a pig ticles composed of an acrylic polymer comprising an alkyl ment dispersion capability. (meth)acrylate unit having an alkyl group of 12 or more Prior Art Documents carbon atoms and a (meth)acrylate unit having a urethane Patent Documents 45 group. These non-aqueous resin dispersion microparticles Patent Document 1: Japanese Patent Laid-OpenNo. 2007 undergo a powerful interaction (adsorption) with the pig 197500 ment, and therefore image show-through on the printed item can be reduced, and the storage stability of the ink can be DISCLOSURE OF INVENTION improved. Moreover, because even a small amount of the 50 non-aqueous resin dispersion microparticles is capable of Problems Invention Aims to Solve generating a satisfactory pigment dispersion effect, the vis cosity of the ink can be suppressed to a low level, thereby By using a pigment dispersant that does not dissolve in the enabling the discharge stability to be improved when the ink Solvent, the above non-aqueous ink is able to provide is used as an inkjet ink. improved print density for printed items on plain paper. How 55 ever, according to investigations conducted by the inventors BEST MODE FOR CARRYING OUT THE of the present invention, further improvements are still INVENTION required in terms of the pigment dispersion stability. Accordingly, the present invention has an object of provid The ink according to the present invention comprises, as ing a non-aqueous pigment ink which suppresses show 60 essential components, a pigment, a non-aqueous solvent through and improves the print density in printed items, and (hereafter also referred to as simply “the solvent'), and non also exhibits excellent storage stability. aqueous resin dispersion microparticles (NAD, hereafter also referred to as “NAD microparticles') having a pigment dis Means for Solution of the Problems persion capability as a pigment dispersant. 65 The NAD microparticles are composed of an acrylic poly A first aspect of the present invention provides a non mer (or more specifically a urethane-modified acrylic poly aqueous pigment ink comprising a pigment, a non-aqueous mer) comprising an alkyl (meth)acrylate unit having an alkyl US 8,507,585 B2 3 4 group of 12 or more carbon atoms and a (meth)acrylate unit backbone polymer) of a monomer mixture comprising an having a urethane group, and this polymer does not dissolve alkyl (meth)acrylate (A) having an alkyl group of 12 or more in the non-aqueous solvent used in the ink, but rather forms carbon atoms (hereafter also referred to as “the monomer microparticles within the ink. Here, the term “(meth)acry (A)'), and a reactive (meth)acrylate (B) having a functional late includes both acrylate and methacrylate. group capable of reacting with an amino group (hereafter also The NAD microparticles form a core/shell structure com referred to as “the monomer (B)), by introducing urethane posed of a core portion (a polar portion) that does not dissolve groups into the copolymer via a reaction between the func in the non-aqueous solvent of the ink, and a shell portion (a tional group capable of reacting with an amino group, an low-polarity portion) that is positioned at the solvent side of amino alcohol and a polyvalent isocyanate compound. each microparticle and is solvated. It is thought that the core 10 Specific examples of the alkyl (meth)acrylate (A) having a portion that is insoluble in the solvent has a role of improving long-chain alkyl group of 12 or more carbon atoms, and the separation of the solvent and the pigment following print preferably 12 to 25 carbon atoms, include lauryl (meth)acry ing, thereby preventing the pigment from penetrating into the late, cetyl (meth)acrylate, Stearyl (meth)acrylate, behenyl interior of the paper together with the solvent, which enables (meth)acrylate, isolauryl (meth)acrylate and isostearyl the pigment to be retained at the paper Surface, thus improv 15 (meth)acrylate. A plurality of these (meth)acrylates may also ing the print density. In contrast, it is thought that the shell be included. portion (steric repulsion layer) has a role of enhancing the Preferred examples of the functional group capable of dispersion stability within the solvent, enabling the formation reacting with an amino group within the reactive (meth)acry of the particle dispersion system. late (B) include a glycidyl group, vinyl group and (meth) Due to the inclusion of a long-chain alkyl group of 12 or acryloyl group. more carbon atoms, the aforementioned alkyl (meth)acrylate A preferable example of the monomer (B) having a gly unit exhibits excellent affinity with the non-aqueous solvent, cidyl group is glycidyl (meth)acrylate, whereas preferable thereby enhancing the dispersion stability within the non examples of the monomer (B) having a vinyl group include aqueous solvent and performing the role of the shell portion. vinyl (meth)acrylate and 2-(2-vinyloxyethoxy)ethyl (meth) The alkyl chain of the ester portion may be either a linear or 25 acrylate. Examples of the monomer (B) having a (meth)acry branched chain. Although there are no particular restrictions loyl group include dipropylene glycol di(meth)acrylate and on the upper limit for the number of carbonatoms within this 1,6-hexanediol di(meth)acrylate. A plurality of these reactive alkyl group, for reasons including availability of the raw (meth)acrylates (B) may also be included. material, the number of carbon atoms is preferably not more Besides the aforementioned monomers (A) and (B), the than 25. 30 monomer mixture may also include another monomer (C) Examples of the alkyl group of 12 or more carbon atoms capable of undergoing copolymerization with the monomers include a dodecyl group, tridecyl group, tetradecyl group, (A) and (B), provided inclusion of the monomer (C) does not pentadecyl group, hexadecyl group, heptadecyl group, octa impair the effects of the present invention. decyl group, nonadecyl group, eicosanyl group, heneicosanyl Examples of this monomer (C) include styrene-based group, docosanyl group, isododecyl group or isooctadecyl 35 monomers such as styrene and C.-methylstyrene, vinyl group. A plurality of these groups may also be included. acetate, vinyl benzoate, vinyl ether-based monomers such as As a result of containing a urethane group (urethane bond) butyl vinyl ether, maleate esters, fumarate esters, acryloni that has a high polarity and adsorbs the pigment, namely a trile, methacrylonitrile and C-olefins. Further, alkyl (meth) carbamate ester portion (HNCOOR or RNHCOOR), the acrylates in which the alkyl chain length is less than 12 carbon aforementioned (meth)acrylate unit having a urethane group 40 atoms may also be used, including 2-ethylhexyl (meth)acry encapsulates the pigment to form the core portion (the Sol late, isooctyl (meth)acrylate and tert-octyl (meth)acrylate. vent-insoluble portion) of the NAD microparticles. These monomers may be used individually, or in combina The urethane groups form side chains (branches) off the tions of two or more compounds. main chain (backbone) of the acrylic polymer together with The amount of the alkyl (meth)acrylate (A) in the above the above long-chain alkyl groups. These urethane group 45 monomer mixture is preferably not less than 30% by mass, containing branches may be polyurethanes formed from more preferably within a range from 40 to 95% by mass, and repeating urethane bonds, thereby forming branch polymers. most preferably from 50 to 90% by mass. There are no particular restrictions on the molecular weight The amount of the reactive (meth)acrylate (B) is preferably (mass average molecular weight) of the acrylic polymer, within a range from 1 to 30% by mass, and more preferably although if the ink is to be used as an inkjet ink, then from the 50 from 3 to 25% by mass. viewpoint of achieving favorable ink dischargeability, the The amount of the monomer (C) other than the monomers molecular weight is preferably within a range from approxi (A) and (B) is preferably not more than 60% by mass, and mately 10,000 to 100,000, and is more preferably from more preferably within a range from 10 to 40% by mass. approximately 20,000 to 80,000. For the monomer (C), the use of a monomer (C1) having a The glass transition temperature (Tg) of the acrylic poly 55 3-diketone group or (B-keto ester group is preferred. Includ mer is preferably not higher than room temperature, and is ing such a monomer (C1) enables the viscosity of the ink to be more preferably 0°C. or lower. This ensures that when the ink reduced. This means that when selecting a solvent for the ink, is fixed on the recording medium, film formation can be there are fewer restrictions on the viscosity of the solvent promoted at room temperature. itself, thereby expanding the range of non-aqueous solvents There are also no particular restrictions on the particle size 60 that may be selected. Further, in those cases where fixing of the NAD microparticles, but when used within an inkjet resins or additives are added to the ink according to need, the ink, the particle size of the NAD microparticles must be permissible increase in the ink viscosity caused by adding Sufficiently Small compared with the nozzle diameter, and is Such components is expanded, resulting in a greater degree of typically not more than 0.3 um, and preferably not more than freedom when determining the ink formulation. 0.1 um. 65 Moreover, including the monomer (C1) enables functional The acrylic polymer is preferably produced from a copoly groups having an ionic group to be introduced into the back mer (hereafter, this copolymer is also referred to as “the bone polymer. Generally, introducing ionic groups into a US 8,507,585 B2 5 6 low-polarity non-aqueous solvent causes an increase in the amino group within the monomer (B). The isocyanate ester ink viscosity, but the existence of the monomer (C1) is able to group (R'N=C=O) of the polyvalentisocyanate compound Suppress this viscosity increase. The inclusion of the mono then undergoes an addition reaction with the hydroxyl group mer (C1) also contributes to electrostatic aggregation and of the amino alcohol in the manner illustrated below, thus fixation of the ink upon contact with the recording medium, 5 yielding a urethane group (urethane bond) (a carbamate ester: resulting in improved print density and Suppression of show R'NHCOOR): through. RN=C=O+R OH->ROCONHR'. Moreover, by overprinting a black ink containing the wherein R— represents the amino alcohol portion bonded to monomer (C1) on top of a cyan ink, a printed item with a the functional group of the backbone polymer. higher print density can be obtained with good Suppression of 10 In this manner, urethane groups that function as pigment image show-through. The inventors of the present invention adsorption groups are introduced into the backbone polymer, found that this effect was more marked when the backbone which has no pigment adsorption capability. polymer included the monomer (C1) than when the backbone Examples of the amino alcohol include monomethyletha polymer did not include the monomer (C1). nolamine, diethanolamine and diisopropanolamine. Of these, In the monomer (C1), preferred examples of the B-diketone 15 dialkanolamines (secondary alkanolamines) represented by a group include an acetoacetyl group and a propionylacetyl general formula (HOR), NH (wherein R is a divalent hydro group, whereas preferred examples of the B-keto ester group carbon group) are preferred, as they provide two hydroxyl include an acetoacetoxy group and a proionylacetoxy group, groups, enabling the number of urethane groups formed to be although these are not exhaustive lists. increased. A combination of a plurality of these amino alco Preferred examples of the monomer (C1) include (meth) hols may also be used. acrylates and (meth)acrylamides comprising a B-diketone From the viewpoint of introducing an appropriate amount group or B-keto ester group in the ester chain. Specific ofurethane groups, this aminoalcohol is preferably reacted in examples include acetoacetoxyalkyl (meth)acrylates Such as an amount within a range from 0.05 to 1 molar equivalents, acetoacetoxyethyl (meth)acrylate, hexadione (meth)acrylate, and more preferably 0.1 to 1 molar equivalents, relative to the and acetoacetoxyalkyl (meth)acrylamides such as acetoac 25 amount of the functional group capable of reacting with an etoxyethyl (meth)acrylamide. These monomers may be used amino group within the monomer (B). When the amount of individually, or in combinations of two or more compounds. the amino alcohol is less than 1 molar equivalent, unreacted When included, the amount of the monomer (C1) within functional groups will remain in Some of the monomer (B) the monomer mixture is preferably within a range from 3 to units, but it is thought that these residual functional groups act 30% by mass, and more preferably from 5 to 20% by mass in 30 as pigment adsorption groups. view of the effects obtained by adding the monomer (C1) and Examples of the polyvalent isocyanate compound include the storage stability of the resulting ink. aliphatic, alicyclic and aromatic compounds, such as 1.6- The monomers described above can be polymerized easily diisocyanatohexane, 1,3-bis(isocyanatomethyl)benzene, 1.3- by conventional radical copolymerization. The reaction is bis(isocyanatomethyl)cyclohexane, and 1.5-naphthalene preferably conducted as either a solution polymerization or a 35 diisocyanate. A plurality of these compounds may also be dispersion polymerization. used in combination. In Such cases, in order to ensure that the molecular weight In order to ensure that no unreacted raw materials or the of the acrylic polymer following polymerization satisfies the like remain following introduction of the urethane groups via preferred range mentioned above, the use of a chain transfer reaction of the polyvalent isocyanate compound with the agent during polymerization is effective. Examples of com 40 hydroxyl groups, the polyvalent isocyanate compound is pounds that can be used as this chain transfer agent include preferably reacted in an amount that is substantially equimo thiols such as n-butyl mercaptan, lauryl mercaptan, Stearyl lar (0.98 to 1.02 molar equivalents) with the amount of mercaptain and cyclohexyl mercaptan. hydroxyl groups contained with the Supplied raw material. Examples of polymerization initiators that may be used In this manner, urethane side chains (grafts) that are include conventional thermal polymerization initiators, 45 insoluble in the solvent are formed at the amino alcohol sites including azo compounds such as AIBN (aZobisisobutyroni bonded to the monomer (B) units within the copolymer por trile) and peroxides such as t-butyl peroxybenzoate and t-bu tion (backbone polymer) that is soluble in the solvent, and tylperoxy-2-ethylhexanoate (Perbutyl O. manufactured by these urethane side chains form dispersion particle nuclei. NOF Corporation). Alternatively, a photopolymerization ini The final result of this process is the formation of polymer tiator may be used in which irradiation with an active energy 50 particles (NAD microparticles) enveloped within a shell beam is used to generate radicals. structure (the backbone polymer) that can undergo Solvation Petroleum-based solvents (such as aroma-free (AF) sol within the solvent. vents) and the like can be used as the polymerization solvent In the above reaction, a polyhydric alcohol is preferably used in a solution polymerization. This polymerization sol also added, so that the polyhydric alcohol and the polyvalent vent is preferably one or more solvents selected from among 55 isocyanate compound are reacted. By adding a polyhydric those solvents (listed below) that can be used, as is, for the alcohol, the urethane group formation can be repeated, non-aqueous solvent within the ink. enabling polyurethane side chains (namely, branch polymers) During the polymerization reaction, other typically that function as higher polarity side chains to be obtained. employed polymerization inhibitors, polymerization accel Examples of the polyhydric alcohol include ethylene gly erators and dispersants and the like may also be added to the 60 col, propylene glycol, dipropylene glycol, 1,3-propanediol. reaction system. polyethylene glycol and polypropylene glycol. A plurality of Subsequently, urethane groups are introduced into the these polyhydric alcohols may also be used. obtained copolymer (the backbone polymer) by reacting the The polyhydric alcohol is important for controlling the size functional group capable of reacting with an amino group of the NAD particles, and as the amount of the polyhydric with an amino alcohol and a polyvalent isocyanate com 65 alcohol is increased, the NAD particles increase in size. How pound. The amino group of the aminoalcohol reacts with, and ever, if the particle size increases excessively, then the dis bonds to, the functional group capable of reacting with an charge stability and pigment dispersibility of the ink tend to US 8,507,585 B2 7 8 deteriorate, and therefore the amount of the polyhydric alco and most preferably 100 nm or less. In this description, the hol relative to the amino alcohol is preferably within a range average particle size of the pigment refers to the value mea from 0 to 20 molar equivalents, and more preferably from 1 to Sured using a dynamic light-scattering particle size distribu 10 molar equivalents. tion measurement apparatus LB-500 manufactured by The mass ratio between the copolymer portion (backbone Horiba, Ltd. polymer) and the introduced urethane group portions The term “non-aqueous solvent” refers to non-polar (branches or branch polymers) within the acrylic polymer is organic solvents and polar organic solvents for which the 50% preferably within a range from 60:40 to 99:1, and is more distillation point is at least 150° C. The “50% distillation preferably from 70:30 to 99:1. The mass of the copolymer point” is measured in accordance with JIS KO066 “Test Meth 10 ods for Distillation of Chemical Products” and refers to the portion within the acrylic polymer represents the combined temperature at which 50% by mass of the solvent is evapo mass of the monomers used in the copolymerization, whereas rated. From the viewpoint of safety, the use of a solvent for the mass of the introducedurethane group portions represents which this 50% distillation point is at least 160° C., and the combined mass of the amino alcohol and the polyvalent particularly 230° C. or higher, is preferred. isocyanate compound used in the grafting reaction, or in those 15 For example, examples of preferred non-polar organic Sol cases where a polyhydric alcohol is also used, represents the vents includealiphatic hydrocarbon solvents, alicyclic hydro combined mass of the amino alcohol, the polyvalent isocy carbon Solvents and aromatic hydrocarbon solvents. Specific anate compound and the polyhydric alcohol. examples of the aliphatic hydrocarbon Solvents and alicyclic The obtained NAD microparticles themselves exhibit an hydrocarbon solvents include Teclean N-16, Teclean N-20, excellent pigment dispersion capability, and therefore the Teclean N-22, Nisseki Naphtesol L. Nisseki Naphtesol M, amount of the NAD microparticles may be less than that of Nisseki Naphtesol H, No. 0 Solvent L, No. 0 Solvent M, No. conventional pigment dispersants, and no other separate pig O Solvent H, Nisseki Isosol 300, Nisseki Isosol 400, AF-4, ment dispersant needs to be added. As a result, the types of AF-5, AF-6 and AF-7, all manufactured by Nippon Oil Cor problems typically associated with the addition of a polymer poration; and Isopar G, Isopar H. Isopar L. Isopar M, EXXSol based pigment dispersant, namely an increase in the Viscosity 25 D40, Exxsol D80, Exxsol D100, Exxsol D130 and Exxsol of the ink and a deterioration in the storage stability, can be D140, all manufactured by ExxonMobil Corporation. Spe Suppressed, and the discharge stability within an inkjet cific examples of the aromatic hydrocarbon Solvents include recording system can be improved. Moreover, favorable stor Nisseki Cleansol G (alkylbenzene) manufactured by Nippon age stability can be achieved not only under normal operating Oil Corporation and Solvesso 200 manufactured by Exxon conditions, but also under high-temperature conditions. 30 Mobil Corporation. Examples of pigments that may be used for a black ink Examples of solvents that can be used as the polar organic solvent include esters solvent (or ester-based solvents), alco include carbon blacks Such as furnace black, lamp black, hols solvent (or alcohol-based solvents), higher fatty acids acetylene black and channel black, metals or metal oxides solvent (or higher fatty acid-based solvents), ethers solvent Such as copper, iron and titanium oxide, and organic pigments 35 (or ether-based solvents), and mixtures thereof. Specific Such as orthonitroaniline black. These pigments may be used examples include: either individually, or in combinations of two or more differ esters solvent containing 14 or more carbon atoms within ent pigments. each molecule, such as methyl laurate, isopropyl laurate, Examples of pigments that may be used for color inks isopropyl myristate, isopropyl palmitate, isostearyl palmi include toluidine red, permanent carmine FB, disazo orange 40 tate, methyl oleate, ethyl oleate, isopropyl oleate, butyl ole PMP, lake red C, brilliant carmine 6B, quinacridone red, ate, methyl linoleate, isobutyl linoleate, ethyl linoleate, iso dioxane violet, orthonitroaniline orange, dinitroaniline propyl isostearate, methyl soybean oil, isobutyl Soybean oil, orange, Vulcan orange, chlorinated para red, brilliant fast methyl tallate, isobutyl tallate, diisopropyl adipate, diisopro scarlet, naphthol red 23, pyrazolone red, barium red 2B, cal pyl sebacate, diethyl sebacate, propylene glycol monoca cium red 2B, strontium red 2B, manganese red 2B, barium 45 prate, trimethylolpropane tri-2-ethylhexanoate and glyceryl lithol red, pigment scarlet 3Blake, lake bordeaux 10B, antho tri-2-ethylhexanoate: cyn 3B lake, anthocyn 5B lake, rhodamine 6G lake, eosine alcohols solvent containing 12 or more carbon atoms lake, iron oxide red, naphthol red FGR, rhodamine Blake, within each molecule. Such as isomyristyl alcohol, isopalmi methyl violet lake, dioxazine violet, naphthol carmine FB, tyl alcohol, isostearyl alcohol and oleyl alcohol; naphthol red M, fast yellow AAA, fast yellow 10G. disazo 50 higher fatty acids solvent such as isononanoic acid, yellow AAMX, disazo yellow AAOT, disazo yellow AAOA, isomyristic acid, hexadecanoic acid, isopalmitic acid, oleic acid and isostearic acid; and disazo yellow HR, isoindoline yellow, fast yellow G, disazo ethers solvent such as diethylene glycol monobutyl ether, yellow AAA, phthalocyanine blue, Victoria pure blue, basic ethylene glycol monobutyl ether, propylene glycol monobu blue 5B lake, basic blue 6G lake, fast sky blue, alkali blue R 55 tyl ether and propylene glycol dibutyl ether. toner, peacock blue lake, Prussian blue, ultramarine, reflex These non-aqueous solvents may be used either individu blue2G, reflex blue R, alkali blue G toner, brilliant greenlake, ally, or in mixtures of two or more different solvents. diamond green thioflavine lake, phthalocyanine green G, The ink may also include other arbitrary components in green gold, phthalocyanine green Y, iron oxide powder, rust amounts that do not impair the effects of the present inven powder, Zinc white, titanium oxide, calcium carbonate, clay, 60 tion. barium sulfate, alumina white, aluminum powder, bronze For example, resins that may be added besides the above powder, daylight fluorescent pigments, and pearl pigments. NAD microparticles include acrylic resins, styrene-acrylic These pigments may be used either individually, or in arbi resins, styrene-maleic acid resins, rosin-based resins, rosin trary mixtures. ester-based resins, ethylene-vinyl acetate resins, petroleum From the viewpoints of discharge stability and storage 65 resins, coumarone-indene resins, terpenephenol resins, phe stability, the average particle size of the pigment is preferably nolic resins, urethane resins, melamine resins, urea resins, not more than 300 nm, more preferably not more than 150 nm, epoxy resins, cellulose-based resins, vinyl chloride acetate US 8,507,585 B2 10 resins, Xylene resins, alkyd resins, aliphatic hydrocarbon res ratio between the copolymer portion and the introducedure ins, butyral resins, maleic acid resins, fumaric acid resins, thane group portions is preferably within a range from 60:40 hydroxyl group-containing carboxylate esters, salts of long to 99:1. chain polyaminoamides and high-molecular weight acid When added to a non-aqueous pigment ink, this pigment esters, salts of high-molecular weight polycarboxylic acids, dispersant forms NAD microparticles that exhibit the type of salts of long-chain polyaminoamides and polar acid esters, pigment dispersion effect described above. As a result, a high-molecular weight unsaturated acid esters, high-molecu non-aqueous pigment ink can be provided which yields lar weight copolymers, modified polyurethanes, modified increased print density for printed items, and also offers polyacrylates, polyether ester anionic Surfactants, naphthale excellent storage stability. nesulfonic acid-formalin condensate salts, aromatic Sulfonic 10 acid-formalin condensate salts, polyoxyethylene alkyl phos Although there are no particular restrictions on the printing phate esters, polyoxyethylene nonylphenyl ethers, polyester method used with the ink according to the present invention, polyamines, and Stearylamine acetate. printing is preferably conducted using an inkjet recording Appropriate amounts of nozzle blockage prevention apparatus. The inkjet printer may employ any of various agents, antioxidants, conductivity modifiers, Viscosity modi 15 printing systems, including a piezo system, electrostatic sys fiers, Surface tension modifiers and oxygen absorbers and the tem or thermal system. In those cases where an inkjet record like may also be added. There are no particular restrictions on ing apparatus is used, the ink according to the present inven the specific variety of these additives, and the types of mate tion is discharged from the inkjet head based on a digital rials typically used within this technical field may be used. signal, and the discharged ink droplets are adhered to a The amount of the pigment within the ink is typically recording medium. within a range from 0.01 to 20% by mass, and from the The ink according to the present invention can be used viewpoints of print density and ink viscosity, is preferably favorably even under low-temperature conditions, and exhib within a range from 1 to 15% by mass, and more preferably its excellent discharge stability when used within an inkjet from 5 to 10% by mass. recording system. In terms of ensuring favorable pigment dispersibility, the 25 In the obtained printed item, the pigment within the ink is amount of the NAD microparticles within the ink is prefer inhibited from penetrating into the interior of the printing ably not less than 0.1% by mass, and is more preferably 2% by paper, and is rather retained at the Surface of the paper, result mass or greater. However, if the amount of the NAD micro ing in a high print density. particles is too high, then not only does the ink viscosity become overly high, but the storage stability under high 30 temperature conditions also tends to worsen, and therefore the amount of the NAD microparticles is preferably not more than 20% by mass, and is more preferably 10% by mass or EXAMPLES less. The amount of the NAD microparticles within the ink is most preferably within a range from 3 to 8% by mass. 35 A more detailed description of the present invention is The mass of the NAD microparticles (or the total mass of provided below based on a series of examples, although the resin in those cases where the ink includes other resins present invention is in no way limited by these examples. In besides the NAD microparticles) relative to a value of 1 for the following description, the units “96 by mass” are abbre the mass of the pigment is preferably at least 0.5 from the viated as simply "96. viewpoint of ensuring a favorable pigment dispersibility 40 effect, and is preferably not more than 1 from the viewpoints of improving the ink viscosity and avoiding discharge faults caused by changes in the ink over time. When used within an inkjet recording system, the ideal Example 1 range for the Viscosity of the ink varies depending on factors 45 Such as the diameter of the discharge head nozzles and the (1) Synthesis of Copolymers (Backbone Polymers a to f) discharge environment, but at 23°C., is preferably within a A300 ml four-neck flask was charged with 75 g of AF-4 (a range from 5 to 30 mPas, and more preferably from 5 to 15 naphthene-based solvent, manufactured by Nippon Oil Cor mPas. An ink viscosity of approximately 10 mPa is is the most poration), and the temperature was raised to 110° C. under a desirable for use within an inkjet recording apparatus. Here, 50 stream of nitrogen gas and with constant stirring. Subse the viscosity is measured at 23°C. by raising the shear stress quently, with the temperature held at 110° C., a mixture from OPaatarate of 0.1 Pa?s, and refers to the measured value containing 16.7 g of AF-4 and 2 g of Perbutyl O (t-butylper at 10 Pa. oxy-2-ethylhexanoate, manufactured by NOF Corporation) A pigment dispersant for a non-aqueous pigment ink was added dropwise to a monomer mixture with the compo according to the present invention is composed of an acrylic 55 polymer comprising an alkyl (meth)acrylate unit having an sition shown in Table 1 over a period of 3 hours. Subse alkyl group of 12 or more carbon atoms and a (meth)acrylate quently, with the temperature maintained at 110° C., addi unit having a urethane group, and is insoluble in solvents tional 0.2 g samples of Perbutyl O were added after stirring having a 50% distillation point of 150° C. or higher. for an additional one hour and two hours respectively. The The acrylic polymer is preferably a copolymer of a mono 60 reaction mixture was aged for a further one hour at 110°C., mer mixture comprising an alkyl (meth)acrylate (A) having and was then diluted with 10.6 g of AF-4, yielding a colorless an alkyl group of 12 or more carbon atoms and a reactive and transparent solution of a backbone polymera to f with a (meth)acrylate (B) having a functional group capable of non-volatile fraction of 50%. reacting with an amino group, wherein urethane groups have The mass average molecular weight (determined by a GPC been introduced therein by a reaction between the functional 65 method and referenced against polystyrene standards) of each group capable of reacting with an amino group, an amino of the obtained backbone polymers was within a range from alcohol and a polyvalent isocyanate compound, and the mass 20,000 to 23,000. US 8,507,585 B2 11 12 TABLE 1 Backbone polymer composition Backbone Backbone Backbone Backbone Backbone Backbone polymer polymer polymer polymer polymer polymer Monomer (g) 8. b C d e f VMA Behenyl methacrylate 50 50 50 O O 50 (monomer A) (Mw: 339) LMA Dodecyl methacrylate O O O 50 O O (monomer A) (Mw: 254) EHMA 2-ethylhexyl methacrylate 35 45 25 35 85 15 (monomer C) (Mw: 198) AAEM 2-acetoacetoxyethyl methacrylate O O O O O 2O (monomer C1) (Mw:214) GMA Glycidyl methacrylate 15 5 25 15 15 15 (monomer B) (Mw: 142)
Details of the monomers used are as listed below. perature was raised to 110°C. under a stream of nitrogen gas Monomer (A): VMA (number of carbon atoms within the and with constant stirring. The temperature was held at 110° alkyl group: 22): behenyl methacrylate (manufactured by C. for one hour to enable the reaction between the glycidyl NOF Corporation) groups of the backbone polymera and the diethanolamine to Monomer (A): LMA (number of carbon atoms within the proceed to completion. Subsequently, 0.2 g of dibutyltin alkyl group: 12): dodecyl methacrylate dilaurate was added, and a mixture containing 10.2 g of Monomer (C): EHMA: (number of carbon atoms within Takenate 600 (1,3-bis(isocyanatomethyl)cyclohexane, the alkyl group: 8): 2-ethylhexyl methacrylate 25 manufactured by Mitsui Chemicals, Inc.) and 91.8g of IOP Monomer (B): GMA:glycidyl methacrylate was then added dropwise to the flask over a period of one Monomer (C1): AAEM: 2-acetoacetoxyethyl methacry hour. Following completion of the dropwise addition, the late (manufactured by Nippon Synthetic Chemistry Industry temperature was raised to 120°C., the reaction was allowed to Co., Ltd.) proceed for 6 hours, and the reaction mixture was then cooled, Unless stated otherwise, all reagents were manufactured by 30 yielding a non-aqueous dispersion D1 having a solid fraction Wako Pure Chemical Industries, Ltd. (this also applies in the (NAD microparticles) of 30%. following description). Using the same method, non-aqueous dispersions D2 to D9 (2) Production of Non-Aqueous Dispersions Containing were produced with the formulations shown in Table 2. The NAD Microparticles amounts listed for the backbone polymers in Table 2 represent A500 mL four-neck flask was charged with 81 g of isooctyl 35 Solid fraction amounts. palmitate (IOP, manufactured by Nikko Chemicals Co., Ltd.), The mass average molecular weight (determined by a GPC 200 g of the solution of the backbone polymera obtained in method and referenced against polystyrene standards) for (1) above (solid fraction within AF-4 solvent: 50%). 4.0 g of each of the obtained acrylic polymers (including the branch propylene glycol and 2.8 g of diethanolamine, and the tem polymers) was within a range from 22,000 to 26,000. TABLE 2
Non-aqueous dispersion formulations
D1 D2 D3 D4 D5 D6 D7 D8 D9 D10
Backbone Backbone polymer a 100.0 O.O O.O OO 100.0 1 OOO 100.0 O.O OO 100.0 polymer Backbone polymer b OO 100.0 O.O O.O O.O O.O O.O O.O O.O O.O (g) Backbone polymer c O.O O.O 1OOO O.O O.O O.O O.O O.O O.O O.O Backbone polymer d O.O O.O OO 10O.O O.O O.O O.O O.O O.O O.O Backbone polymere O.O O.O O.O O.O O.O O.O O.O OO 100.O O.O Backbone polymer f O.O O.O O.O O.O O.O O.O OO 10O.O O.O O.O Branch Propylene glycol 4.0 5.4 2.7 4.0 10.3 16.0 O.O 4.0 4.0 O.O polymer Diethanolamine 2.8 3.7 1.9 2.8 2.8 2.8 2.8 2.8 2.8 O.O (g) Diisocyanate 10.2 24.4 10.1 10.2 30.7 45.5 S.1 10.2 10.2 O.O Solvent AF-4 1OOO 100.0 1OOO 100.O 1OOO 100.O 1OOO 10O.O 1 OOO 100.0 (g) IOP 172.8 211.6 167.6 172.8 251.8 283.4 251.8 172.8 172.8 168.3 Mass ratio of backbone polymer? 85/15 75.25 77/23 85/15 70.3O 61/39 93.7 85.15 85/15 1000 branch polymers (note) Mass ratio (%) of monomer B 15 5 25 15 15 15 15 15 15 15 within backbone polymer Molar ratio (equivalents) of amino O.25 1.O O.10 O.25 0.25 O.25 0.25 O.25 0.25 O alcohol relative to monomer B
(Note): Polyurethane side chains US 8,507 585 B2 13 14 In a separate preparation, an acrylic-modified polymer D9: solid fraction 30%, AF-4: 25.5%, IOP 44.5% (NAD microparticles) in which the branch polymers were D10: solid fraction 30% AF-4: 25.5%, IOP 445.9% also acrylic polymers was synthesized in the manner (3) Preparation of Inks described below for the purpose of comparison. A 500 mL four-neck flask was charged with 100 g of IOP 5 Example 1 and 200 g of the solution of the backbone polymera obtained in (1) above (solid fraction within AF-4 solvent: 50%), and 12.5g of the prepared dispersion D1, 5.0 g of a pigment the temperature was raised to 110° C. under a stream of (carbon black MA11, manufactured by Mitsui Chemicals, nitrogen gas and with constant stirring. Subsequently, with Inc.), 7.9 g of AF-4 and 7.9 g of IOP were mixed, zirconia the temperature held at 110°C., a mixture containing 7.6 g of 10 beads (diameter: 0.5 mm) were added, and the mixture was acrylic acid, 5.0 g of methyl methacrylate, 5.0 g of butyl dispersed for 120 minutes using a rocking mill (manufactured acrylate and 0.5g of Perbutyl O (t-butylperoxy-2-ethylhex by Seiwa Technical Lab Co., Ltd.). Following dispersion, the anoate, manufactured by NOF Corporation) was added drop zirconia beads were removed, the dispersion was filtered wise to the flask over a period of 15 minutes. Following sequentially through 3.0 um and 0.8 um membrane filters to completion of the dropwise addition, the reaction was 15 remove any contaminants and coarse particles, and the mix allowed to proceed for 4 hours with the temperature held at ture was diluted with 8.4 g of AF-4 and 8.4 g of IOP, thus 110° C. The reaction mixture was then cooled and diluted completing preparation of an ink (pigment content: 10%) in with 74.4 g of IOP, yielding a non-aqueous dispersion D10 which the pigment was dispersed by the NAD microparticles. having a solid fraction of 30%. The solid fraction and solvent composition for each of the 20 Examples 2 to 8, Comparative examples 1 to 4 non-aqueous dispersions D1 to D10 were as follows. D1: solid fraction 30%, AF-4: 25.7%, IOP 44.3% Using the blend amounts shown in Table 3, inks of each of D2: solid fraction 30%, AF-4: 22.5%, IOP 47.5% the examples and comparative examples were prepared in the D3: solid fraction 30%, AF-4: 25.7%, IOP 44.3% same manner as example 1. D4: solid fraction 30%, AF-4: 26.2%, IOP 43.8% 25 In comparative examples 2 and 3, a solution of the back D5: solid fraction 30%, AF-4: 19.9%, IOP 50.1% bone polymer a (solid fraction: 50%) and Solsperse 28000 D6: solid fraction 30%, AF-4: 18.4%, IOP 51.6% (manufactured by The Lubrizol Corporation, solid fraction: D7: solid fraction 30%, AF-4: 21.8%, IOP 54.8% 100%) respectively were used instead of the non-aqueous D8: solid fraction 30%, AF-4: 25.7%, IOP 44.3% dispersion. TABLE 3
Inks and evaluations thereof Blend amount/g Compara- Compara- Compara- Compara Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- tive ex- tive ex- tive ex- tive ex ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ample 1 ample 2 ample 3 ample 4 Pigment 5 5 5 5 5 5 5 5 5 5 5 5 Non- D1 12.5 aqueous D2 12.5 disper- D3 12.5 sion D4 12.5 D5 12.5 D6 12.5 D7 12.5 D8 12.5 D9 12.5 D10 12.5 Backbone polymera 7.5 Solution Solsperse 28000 3.75 Diluent AF-4 7.9 7.9 7.9 7.9 7.9 7.9 7.9 7.9 7.9 7.9 12.3 7.9 during dis- IOP 7.9 7.9 7.9 7.9 7.9 7.9 7.9 7.9 7.9 12.9 12.3 7.9 persion Viscosity AF-4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.3 8.4 modifying IOP 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.4 8.3 8.4 solvent Physical Average 86 96 86 89 94 92 90 82 107 168 88 123 properties particle size (nm) Viscosity 12.4 12.3 12.9 12.7 12.8 14.1 12.7 10.3 12.9 13.9 12.4 15.1 (mPa is) Evaluation Print density A. A. A. A. A. A. A. A. B C C B (surface OD) Print density A. A. A. A. A. A. A. A. A. C C B (rear Surface OD) C composite B B B B B B B A. B C C B image print density (surface OD) US 8,507,585 B2 15 16 TABLE 3-continued
Inks and evaluations thereof Blend amount/g Compara- Compara- Compara- Compara Exam- Exam- Exam- Exam- Exam Exam- Exam- Exam- tive ex- tive ex- tive ex- tive ex ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 ple 7 ple 8 ample 1 ample 2 ample 3 ample 4 C composite A. A. A. B B B B A. B C D B image print density (rear surface OD) Storage A. A. A. A. A. A. B A. C C A. B stability Discharge A. A. A. A. A. B A. A. B C A. B stability
All of the prepared inks exhibited Viscosity and pigment