Inkjet ink

Abstract

To provide an inkjet ink capable of achieving both excellent continuous printability and excellent fixability.SOLUTION: There is provided an inkjet ink containing a dye, at least one polyoxyethylene-based compound having a number average molecular weight Mn of 200 or more selected from the group consisting of a polyoxyethylene polyalkylene glycol, a polyalkylene glycol and a polyoxyethylene alkyl ether, a phenol resin and an organic solvent. The organic solvent includes a first solvent having a solubility parameter (SP value) of less than 11 and a second solvent which is an alcohol having a solubility parameter (SP value) of 11 or more and the blending ratio of the first solvent to the total amount of the organic solvent may be 20 mass% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to ink-jet inks. [Background technology]

[0002] For example, when characters or the like are printed by inkjet printing on the surface of a non-absorbent printing medium such as plastic, the printed characters or the like are generally dried by heating.

[0003] In recent years, solvent-based inkjet inks such as HEATLESSINK (registered trademark) have been put into practical use. These inks are quick-drying inks that use only organic solvents or a combination of water and organic solvents, making it possible to omit the heat drying step.

[0004] Patent Document 1 discloses an inkjet ink containing a metal complex dye, a phenolic resin having a softening point of 70°C or higher and 125°C or lower, a tackifier which is a terpene phenolic resin having a hydroxyl value of 30 mgKOH / g, and an organic solvent which is an alcohol.

[0005] Patent Document 2 discloses an inkjet ink containing a metal complex dye, a polyoxyethylene compound that is a Pluronic (registered trademark) type surfactant having a number average molecular weight Mn of 1100, a tackifier that is a terpene phenol resin having a hydroxyl value of 60 mgKOH / g, a first solvent that is 3-methyl-2-butanone (SP value: 8.5), and a second solvent that is ethanol (SP value: 12.7). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6599972 [Patent Document 2] Patent No. 7311411 Summary of the Invention [Problem to be solved by the invention]

[0007] In Patent Document 1, a phenolic resin is blended into the ink to improve the ink's adhesion to the surface of a non-porous substrate such as aluminum. The phenolic resin in the ink adheres to the substrate, improving ink adhesion, but further improving continuous printing tends to be difficult. This is because the ink in Patent Document 1 contains a relatively high amount of phenolic resin, which tends to solidify inside the inkjet printer head. Solidification of the resin inside the head can cause kogation in the head nozzles.

[0008] The ink of Patent Document 2 does not contain a resin commonly used as a binder resin, such as a phenolic resin, but instead contains a polyoxyethylene compound. Because the polyoxyethylene compound behaves as a surfactant, continuous printing can be improved (comparison between Examples 1 to 33 and Comparative Example 9 of Patent Document 2), but fixation tends to decrease. This is because although the polyoxyethylene compound also functions as a fixing component of the ink, it is difficult for it to exhibit superior fixation compared to common binder resins.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an inkjet ink that can achieve both excellent continuous printing properties and excellent fixability.

[0010] Another object of the present invention is to provide an ink-jet ink that can maintain excellent quick-drying properties and improve decap properties even after long-term storage. [Means for solving the problem]

[0011] An inkjet ink according to one aspect of the present invention comprises a dye, at least one polyoxyethylene compound selected from the group consisting of polyoxyethylene polyalkylene glycol, polyalkylene glycol, and polyoxyethylene alkyl ether, the polyoxyethylene compound having a number average molecular weight Mn of 200 or more, a phenolic resin, and an organic solvent.

[0012] In an inkjet ink according to one aspect of the present invention, the organic solvent may include a first solvent having a solubility parameter (SP value) of less than 11 and a second solvent that is an alcohol having a solubility parameter (SP value) of 11 or more, and the blending ratio of the first solvent to the total amount of the organic solvents may be 20 mass % or less.

[0013] In an inkjet ink according to one aspect of the present invention, the first solvent may include solvent A having a relatively low flash point and solvent B having a relatively high flash point compared to solvent A, and the blending ratio of solvent A to the total amount of the first solvent may be greater than the blending ratio of solvent B.

[0014] In the ink-jet ink according to one aspect of the present invention, the solvent A may have a flash point of less than 0°C, and the solvent B may have a flash point of 0°C or higher.

[0015] In an inkjet ink according to one aspect of the present invention, the solvent A may be at least one selected from the group consisting of 2-butanone [methyl ethyl ketone (MEK)], acetone [dimethyl ketone], and 3-methyl-2-butanone [methyl isopropyl ketone (MIPK)], and the solvent B may be at least one selected from the group consisting of 1-methoxy-2-propanol [propylene glycol monomethyl ether (PM)], 2-ethoxyethanol [ethyl cellosolve (EGMEE)], and ethyl acetate [ethyl acetate].

[0016] The ink-jet ink according to one aspect of the present invention may further contain a tackifier that is at least one selected from the group consisting of terpene phenol resins and rosin esters.

[0017] The inkjet ink according to one aspect of the present invention may further contain a tackifier that is at least one selected from the group consisting of a terpene phenol resin having a hydroxyl value of 30 mgKOH / g or more and 70 mgKOH / g or less, and a rosin ester having an acid value of 0.1 or more and 20 or less.

[0018] In the inkjet ink according to one aspect of the present invention, the amount of the tackifier may be 1.5% by mass or more and 4.5% by mass or less with respect to the total amount of the inkjet ink.

[0019] In the ink-jet ink according to one aspect of the present invention, the polyoxyethylene compound may have a number average molecular weight Mn of 1,000 or more and 4,000 or less.

[0020] In the ink-jet ink according to one aspect of the present invention, the polyoxyethylene compound may be a polyoxyethylene polyalkylene glycol having a number average molecular weight Mn of 200 or more.

[0021] In the ink-jet ink according to one aspect of the present invention, the softening point of the phenol resin may be 65°C or higher and 125°C or lower.

[0022] In the inkjet ink according to one aspect of the present invention, the dye may be a metal complex dye, and the amount of the polyoxyethylene compound may be 5% by mass or more and 50% by mass or less relative to the metal complex dye.

[0023] In an inkjet ink according to one aspect of the present invention, the total amount of the polyoxyethylene compound and the phenol resin may be 2% by mass or more and 6% by mass or less relative to the total amount of the inkjet ink, and the amount of the polyoxyethylene compound may be 35% by mass or more and 75% by mass or less relative to the total amount of the polyoxyethylene compound and the phenol resin.

[0024] An inkjet ink according to another aspect of the present invention comprises a metal complex dye, a polyoxyethylene-based compound consisting of polyoxyethylene polyalkylene glycol having a number average molecular weight Mn of 1,000 or more and 4,000 or less, a phenol resin, and an organic solvent, wherein the amount of the polyoxyethylene-based compound is 5% by mass or more and 50% by mass or less relative to the metal complex dye and 35% by mass or more and 75% by mass or less relative to the total amount of the polyoxyethylene-based compound and the phenol resin, the organic solvent comprises a first solvent having a solubility parameter (SP value) of less than 11, and a second solvent which is an alcohol having a solubility parameter (SP value) of 11 or more, the first solvent comprising solvent A having a relatively low flash point and solvent B having a flash point of 0°C or more that is relatively higher than that of solvent A.

[0025] In the ink-jet ink according to another aspect of the present invention, the blending ratio of the first solvent to the total amount of the organic solvents may be 20 mass % or less.

[0026] An inkjet ink according to another aspect of the present invention may further contain a tackifier that is at least one selected from the group consisting of terpene phenol resins having a hydroxyl value of 30 mgKOH / g or more and 70 mgKOH / g or less and rosin esters having an acid value of 0.1 or more and 20 or less, and the amount of the tackifier may be 1.5% by mass or more and 4.5% by mass or less with respect to the total amount of the inkjet ink. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide an inkjet ink that can achieve both excellent continuous printing properties and excellent fixability. DETAILED DESCRIPTION OF THE INVENTION

[0028] In the following embodiments, "dissolution" is defined as the state in which a substance is placed in a liquid, mixed, and left for 24 hours, resulting in transparency without precipitation or turbidity. "Miscibility" is defined as a state in which dissolution is achieved between two or more substances. "Fixability" is defined as the ability of an ink to adhere to a substrate, and the superiority or inferiority of fixability can be evaluated by various fixability confirmation tests, such as a tape peeling test, a scratch resistance test (e.g., a finger rub test), and an oil resistance test.

[0029] The ink-jet ink of the present invention contains a dye, a polyoxyethylene compound, a phenolic resin, and an organic solvent.

[0030] [dye] As the dye, various dyes that dissolve in organic solvents can be used, more specifically, various oil-soluble dyes that dissolve well in both alcohols and ketones can be used.

[0031] Among oil-soluble dyes, metal complex dyes are preferably used, and more preferably metal complex dyes containing chromium as the main component are used. Metal complex dyes form a structure in which the polyoxyethylene compound, which is a fixing component, is coordinated, so the polyoxyethylene compound is likely to precipitate or aggregate. As a result, the polyoxyethylene compound can be firmly fixed to the surface of the printing substrate.

[0032] Specific examples of the oil-soluble dye include, but are not limited to, one or more of the following dyes.

[0033] (Yellow) Examples of yellow metal complex dyes include CI Solvent Yellow 19, 21, 25, 32, 41, 61, 62, 65, 79, 81, 82, 83, 83:1, 88, 89, 90, and 151; VALIFAST (registered trademark) YELLOW 3108, 3120, 3150, 3170, 3180, 4120, and 4121 manufactured by Orient Chemical Industry Co., Ltd.; Ne SuperColor Yellow C-131 manufactured by Chuo Synthetic Chemical Industry Co., Ltd.; Oleosol (registered trademark) Fast Yellow 2G and GCN manufactured by Taoka Chemical Co., Ltd.; Orasol (registered trademark) Yellow 141, 152, 157, and 190 manufactured by BASF Japan Ltd.; Intraplast Yellow 2GLN and 3R manufactured by Sensient; and Savinyl Yellow 2GLS01, RLS, RLSN, and 2RLS manufactured by CLARIANT K.K.

[0034] Other yellow oil-soluble dyes include, for example, CI Solvent Yellow 2, 14, 15, 16, 56, 76, 80, and 91; AIZEN (registered trademark) SBN Yellow 543, SPILON (registered trademark) Yellow C-GNH, and C-2GH manufactured by Hodogaya Chemical Co., Ltd.; Oplas (registered trademark) Yellow 140, VALIFAST (registered trademark) YELLOW 1101, 1109, 1151, and 1171 manufactured by Orient Chemical Industry Co., Ltd.; Alcohol Yellow Y-10 and Oil Yellow CH manufactured by Chuo Synthetic Chemical Industry Co., Ltd.; and DIARESIN (registered trademark) Yellow L3G manufactured by Mitsubishi Chemical Corporation.

[0035] (orange) Examples of orange metal complex dyes include CI Solvent Orange 5, 6, 11, 20, 41, 54, 56, 58, 59, 62, and 99; VALIFAST (registered trademark) ORANGE 2210, 3208, 3209, and 3210 manufactured by Orient Chemical Industry Co., Ltd.; Neo Super Color Orange C-232 manufactured by Chuo Synthetic Chemical Industry Co., Ltd.; Orasol Orange 245, 247, 251, and 272 manufactured by BASF Japan Ltd.; Intraplast Orange G and RLN manufactured by Sensient; and Savinyl Orange RLS and RLSE manufactured by CLARIANT K.K.

[0036] Other orange oil-soluble dyes include, for example, CI Solvent Orange 1, 2, 14, 36, 44, 45, and 57; and VALIFAST (registered trademark) ORANGE 1201 manufactured by Orient Chemical Industries, Ltd.

[0037] (Red) Examples of red metal complex dyes include CI Solvent Red 8, 91, 99, 100, 102, 109, 118, 119, 122, 124, 125, 127, 130, 132, 142, 160, 218, and 233; VALIFAST (registered trademark) Red 2303, 2320, 3304, 3306, 3311, 3312, 3320, and PINK 2310N manufactured by Orient Chemical Industry Co., Ltd.; Neo Super Color RED C-431 and PINK C-331 manufactured by Chuo Synthetic Chemical Industry Co., Ltd.; Oleosol Fast RED BL and PINK FB manufactured by Taoka Chemical Industry Co., Ltd.; and Orasol Red 330, 335, 355, 363, 365, 385, 395, 471, and Pink manufactured by BASF Japan Ltd. 478; Intraplast Red GC and Scarlet 3GL manufactured by Sensient; Savinyl Red 3BLS, 3GLS, and Pink 6BLS manufactured by CLARIANT.

[0038] Other red oil-soluble dyes include, for example, CI Solvent Red 1, 3, 23, 24, 25, 27, 35, 49, 78, 81, 82, 83, 84, 96, 121, 123, 128, 129, 131, 133, 134, and CI Disperse Red 9; Orient Oil Pink OP, SPIRIT Red 102, and VALIFAST (registered trademark) Red 1308, 1320, 1355, 1364, and 1388, all manufactured by Orient Chemical Industry Co., Ltd.; AIZEN SPILON Fiery Red BH, Red C-GH, C-BH, and Pink BH, all manufactured by Hodogaya Chemical Co., Ltd.; and AL Red 2308 and Alcohol Pink P-30, all manufactured by Chuo Synthetic Chemical Industry Co., Ltd.

[0039] (Brown) Examples of brown metal complex dyes include CI Solvent Brown 37, 42, 43, and 44; Orasol Brown 324 and 326 manufactured by BASF Japan Ltd.; and Intraplast Brown GC manufactured by Sensient.

[0040] Other brown oil-soluble dyes include, for example, CI Solvent Brown 3, 23, 24, 25, and 58.

[0041] (green) Examples of green oil-soluble dyes include CI Solvent Green 3, 16, 21, and 22; and VALIFAST (registered trademark) GREEN 1501 manufactured by Orient Chemical Industries, Ltd.

[0042] (blue) Examples of blue metal complex dyes include CI Solvent Blue 24, 25, 38, 44, 45, 55, 64, 67, and 70; VALIFAST (registered trademark) Blue 2606, 2620, and 2670 manufactured by Orient Chemical Industry Co., Ltd.; Neo Super Color Blue C-555 manufactured by Chuo Synthetic Chemical Industry Co., Ltd.; Orasol Blue 825 and 855 manufactured by BASF Japan Ltd.; Intraplast Blue GN manufactured by Sensient; and Savinyl Blue RS and GLS manufactured by CLARIANT K.K.

[0043] Other blue oil-soluble dyes include, for example, CI Solvent Blue 5, 11, 12, 46, 73, and 75; Orient Oil Blue 603, VALIFAST (registered trademark) Blue 1621, 1631, and 2604 manufactured by Orient Chemical Industry Co., Ltd.; AIZEN SPILON Blue C-RH, GNH, and SPT Blue 121 manufactured by Hodogaya Chemical Co., Ltd.; and Alcohol Blue B-10 manufactured by Chuo Synthetic Chemical Industry Co., Ltd.

[0044] (violet) Examples of violet oil-soluble dyes include CI Solvent Violet 1, 2, 19, and 21; VALIFAST (registered trademark) VIOLET 1701 and 1704 manufactured by Orient Chemical Industry Co., Ltd.; and AIZEN SPILON Violet C-RH and ECH manufactured by Hodogaya Chemical Co., Ltd.

[0045] (black) Examples of black metal complex dyes include CI Solvent Black 22, 27, 28, 29, 34, 35, and 43; VALIFAST (registered trademark) BLACK 3804, 3807, 3808, 3810, 3820, 3830, 3840, 3866, 3870, 3877, and 3878 manufactured by Orient Chemical Industry Co., Ltd.; Orasol (registered trademark) Black X45, X51, and X55 manufactured by BASF Japan Ltd.; Intraplast Black CN and RLS manufactured by Sensient; and Savinyl Black RLSN01 manufactured by CLARIANT K.K.

[0046] Other black oil-soluble dyes include, for example, CI Solvent Black 3, 5, 7, 23, 25, 30, 47, and 123; VALIFAST (registered trademark) BLACK 1807 and 1815 manufactured by Orient Chemical Industries, Ltd.; and RLS (Solvent Black 29) and CN (Solvent Black 28) manufactured by Instraplast.

[0047] One or more oil-soluble dyes can be blended in appropriate amounts depending on the color and color density of the inkjet ink. When a metal complex dye is used as the oil-soluble dye, the amount is, for example, 5% by mass or more, and preferably 7% by mass or more, of the total amount of the inkjet ink. The amount of the metal complex dye is, for example, 15% by mass or less, and preferably 12% by mass or less, of the total amount of the inkjet ink. The amount of the metal complex dye is, for example, preferably 5% by mass or more and 15% by mass or less, and more preferably 7% by mass or more and 12% by mass or less, of the total amount of the inkjet ink.

[0048] The amount of the dye mentioned above is the amount of only one metal complex dye when only one metal complex dye is used, and is the total amount of the two or more metal complex dyes when two or more metal complex dyes are used in combination.

[0049] [Polyoxyethylene compounds] The polyoxyethylene compound of the present invention contributes to the fixation of ink-jet ink to a substrate.

[0050] The polyoxyethylene compound can be at least one compound selected from the group consisting of polyoxyethylene alkylene glycol, polyalkylene glycol, and polyoxyethylene alkyl ether, having a number average molecular weight Mn of 200 or more. Specific examples of the polyoxyethylene compound include, but are not limited to, one or more of the following compounds:

[0051] (Polyoxyethylene alkylene glycol) The polyoxyethylene alkylene glycol may be, for example, polyoxyethylene polyoxypropylene glycol (hereinafter, sometimes abbreviated as "poloxamer," which is another name for a representative block copolymer), which is a block copolymer or random copolymer of ethylene oxide (EO) and propylene oxide (PO).

[0052] Examples of poloxamers include PE-61 [POE (5) POP (30)], PE-62 [POE (10) POP (30)], PE-71 [POE (5) POP (35)], PE-74 [POE (30) POP (35)], and PE-75 [POE (48) POP (35)] from the Newpol (registered trademark) PE series manufactured by Sanyo Chemical Industries, Ltd.; L-31 [POE (3) POP (17)], L-34 [POE (16) POP (17)], L-61 [POE (5) POP (30)], L-62 [POE (10) POP (30)], L-101 [POE (8) POP (55)], and L-121 [ POE (10) POP (65))], F-68 [POE (160) POP (30)], F-87 [POE (120) POP (40)], F-127 [POE (196) POP (67)] of the ADEKA (registered trademark) Pluronic F series, P-85 [POE (54) POP (39)], P-123 [POE (42) POP (67)] of the ADEKA (registered trademark) Pluronic P series; P188 [POE (160) POP (30)], P407 [POE (196) POP (67)] of the BASF Japan Co., Ltd. Corifol series, F68 [POE (160) POP (30)], F127 [POE (196) POP (67)] of the Lutrol series, and the like.

[0053] (Polyalkylene glycol) The polyalkylene glycol (PAG) may be, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), polybutylene glycol (PBG), or the like.

[0054] Examples of polyethylene glycol include ADEKA Corporation's ADEKA (registered trademark) PEG series, such as PEG-200 (number average molecular weight Mn: 200), PEG-300 (number average molecular weight Mn: 300), PEG-400 (number average molecular weight Mn: 400), PEG-600 (number average molecular weight Mn: 600), PEG-1000 (number average molecular weight Mn: 1000), PEG-1500 (number average molecular weight Mn: 570), PEG-1540 (number average molecular weight Mn: 1500), PEG-4000 (number average molecular weight Mn: 3000), and PEG-6000 (number average molecular weight Mn: 8300). PEG-20000 (number average molecular weight Mn: 20000); Toho Polyethylene Glycol series manufactured by Toho Chemical Industry Co., Ltd., including 200 (number average molecular weight Mn: 200), 300 (number average molecular weight Mn: 300), 400 (number average molecular weight Mn: 400), 600 (number average molecular weight Mn: 600), 1000 (number average molecular weight Mn: 1000), 1500 (number average molecular weight Mn: 570), 1540 (number average molecular weight Mn: 1500), 2000 (number average molecular weight Mn: 2000), 4000 (number average molecular weight Mn: 3000), 6000 (number average molecular weight Mn: 8300), etc.

[0055] Examples of polypropylene glycols include those in the Sannix (registered trademark) series manufactured by Sanyo Chemical Industries, Ltd., such as PP-200 (number average molecular weight Mn: 200), PP-400 (number average molecular weight Mn: 400), PP-600 (number average molecular weight Mn: 600), PP-950 (number average molecular weight Mn: 950), PP-1000 (number average molecular weight Mn: 1000), PP-1200 (number average molecular weight Mn: 1200), PP-2000 (number average molecular weight Mn: 2000), PP-3000 (number average molecular weight Mn: 3000), PP-4000 (number average molecular weight Mn: 4000), GP-250 (number average molecular weight Mn: 250), GP-400 (number average molecular weight Mn: 400), and GP-600. [number average molecular weight Mn: 600], GP-1000 [number average molecular weight Mn: 1000], GP-1500 [number average molecular weight Mn: 1500], GP-3000 [number average molecular weight Mn: 3000], GP-4000 [number average molecular weight Mn: 4000]; and from the Newpol (registered trademark) series manufactured by Sanyo Chemical Industries, Ltd., PP-200 [number average molecular weight Mn: 200], PP-400 [number average molecular weight Mn: 400], PP-600 [number average molecular weight Mn: 600], PP-1000 [number average molecular weight Mn: 1000], PP-2000 [number average molecular weight Mn: 2000], PP-3000 [number average molecular weight Mn: 3000], PP-4000 [number average molecular weight Mn: 4000], and the like.

[0056] (Polyoxyethylene alkylene ether) The polyoxyethylene alkylene ether may be, for example, a polyoxyethylene alkyl ether (hereinafter, also referred to as "alcohol ethoxylate") having a structure in which a polyoxyethylene chain and an alkyl group are ether-bonded.

[0057] Examples of alcohol ethoxylates include Polyoxyethylene Lauryl Ether Bridge 35 (number average molecular weight Mn: 1200) manufactured by Junsei Chemical Co., Ltd.; and DKS-NL15 (number average molecular weight Mn: 2900) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0058] Of the above, in consideration of fixability to the surface of the printing medium, it is preferable to use polyoxyethylene alkylene glycol, and it is more preferable to use polyoxyethylene propylene glycol.

[0059] The number average molecular weight Mn of the polyoxyethylene compound is preferably 600 or more, more preferably 1000 or more. The number average molecular weight Mn of the polyoxyethylene compound is preferably 5000 or less, more preferably 4000 or less. The number average molecular weight Mn of the polyoxyethylene compound is preferably 600 or more and 5000 or less, more preferably 1000 or more and 4000 or less.

[0060] If the number-average molecular weight Mn of the polyoxyethylene compound is less than 1,000, the film-forming ability may be insufficient, resulting in poor adhesion to the surface of the printed substrate. If the number-average molecular weight Mn of the polyoxyethylene compound is greater than 4,000, the solubility in the inkjet ink may be reduced. For example, the compound may precipitate in the inkjet ink during storage or may cause kogation during printing. As a result, the decap ability may be reduced after long-term storage. In addition, stickiness may occur after printing, resulting in poor quick-drying properties.

[0061] Particularly preferred polyoxyethylene compounds having a number average molecular weight Mn of 1000 or more and 4000 or less include, but are not limited to, the ADEKA (registered trademark) Pluronic L series manufactured by ADEKA CORPORATION, including L-31 [number average molecular weight Mn: 1100, POE content: 10%], L-61 [number average molecular weight Mn: 2000, POE content: 10%], L-62 [number average molecular weight Mn: 2500, POE content: 20%], and L-101 [number average molecular weight Mn: 3800, POE content: 10%]; and the ADEKA (registered trademark) PEG series manufactured by ADEKA CORPORATION, including PEG-100. PEG-0 (number average molecular weight Mn: 1000), PEG-1540 (number average molecular weight Mn: 1500), PEG-4000 (number average molecular weight Mn: 3000); Toho Polyethylene Glycol series manufactured by Toho Chemical Industry Co., Ltd., including 1000 (number average molecular weight Mn: 1000), 1540 (number average molecular weight Mn: 1500), 2000 (number average molecular weight Mn: 2000), and 4000 (number average molecular weight Mn: 3000); Polyoxyethylene Lauryl Ether Bridge 35 manufactured by Junsei Chemical Co., Ltd. (number average molecular weight Mn: 1200); and DKS-NL15 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (number average molecular weight Mn: 2900). One or more of these polyoxyethylene compounds can be used.

[0062] The amount of the polyoxyethylene compound is, for example, 3% by mass or more, preferably 5% by mass or more, relative to the amount of the dye. The amount of the polyoxyethylene compound is, for example, 60% by mass or less, preferably 55% by mass or less, relative to the amount of the dye. The amount of the polyoxyethylene compound is, for example, preferably 3% by mass or more and 60% by mass or less, more preferably 5% by mass or more and 50% by mass or less, relative to the amount of the metal complex dye.

[0063] If the amount of polyoxyethylene compound is less than 5% by mass relative to the amount of metal complex dye, it becomes difficult to form a complex with the metal complex dye, which may result in reduced fixation to the surface of the substrate. If the amount of polyoxyethylene compound is more than 55% by mass relative to the amount of metal complex dye, it becomes difficult for the compound to remain at the interface with the substrate, which may result in reduced fixation to the surface of the substrate. In addition, quick-drying properties may also be reduced.

[0064] When the total amount of the polyoxyethylene compound and the phenol resin (total amount of fixing components) is 2% by mass or more and 6% by mass or less relative to the total amount of the inkjet ink, the amount of the polyoxyethylene compound may be 35% by mass or more and 75% by mass or less relative to the total amount of the fixing components.

[0065] Under the above conditions, if the amount of polyoxyethylene compound is less than 35% by mass of the total amount of fixing components, the absolute amount of phenolic resin will be excessive, which may cause kogation and reduce continuous printing performance.Also, if the amount of polyoxyethylene compound is more than 75% by mass of the total amount of fixing components, the absolute amount of phenolic resin will be too small, resulting in insufficient fixing performance to the printed material.

[0066] [Phenol resin] Examples of phenolic resins include various phenolic resins having a softening point VT (°C) of 65°C or more and 130°C or less. Within the above range, the softening point VT (°C) of the phenolic resin is preferably 65°C or more and 125°C or less, and more preferably 80°C or more and 120°C or less.

[0067] The inclusion of a phenolic resin provides good adhesion to non-porous substrates (non-polar substrates), such as OPP (oriented polypropylene: biaxially oriented polypropylene), CPP (cast polypropylene: unoriented polypropylene), aluminum, and PE.

[0068] If the softening point VT (°C) of the phenolic resin exceeds 130°C, the solubility in organic solvents tends to decrease, so a lower softening point is preferable. The lower limit of the softening point VT (°C) of the phenolic resin may be 65°C as described above, or may be less than 65°C.

[0069] As the phenolic resin, novolac resin, which is a thermoplastic resin, is particularly preferred. As the phenolic resin, two types of phenolic resins with different softening points VT (°C), each of which has a softening point VT (°C) within the above range, may be used in combination.

[0070] The amount of phenol resin is the remainder obtained by subtracting the amount of polyoxyethylene compound from the total amount of inkjet ink. For example, the amount of phenol resin is 0.5% by mass or more to 4% by mass, preferably 0.75% by mass or more to 3% by mass, and more preferably 0.75% by mass or more to 1.5% by mass, relative to the total amount of inkjet ink.

[0071] The amount of phenolic resin refers to the amount of that phenolic resin when only one type of phenolic resin is blended, and refers to the total amount of the two phenolic resins when two types of phenolic resins with different softening points are used in combination.

[0072] [Organic solvents] The organic solvent preferably includes a first solvent and a second solvent having different solubility parameters (SP values). The "SP value" can be defined, for example, as either the Hildebrand solubility parameter or the Hansen solubility parameter. In this specification, the Hildebrand solubility parameter is defined as the "SP value," and the Hansen solubility parameter is defined as the "HSP value." When simply referring to the "SP value" in this specification, the SP value indicates the Hildebrand solubility parameter.

[0073] <First solvent> As the first solvent, various solvents having an SP value of less than 11 are used. As the first solvent, for example, various solvents having an SP value of less than 11, such as at least one selected from the group consisting of ketones, ethers, esters, and acetals, are used.

[0074] Specific examples of the ketone include, but are not limited to, one or more of the following ketones.

[0075] 2-Butanone [methyl ethyl ketone (MEK), carbon number: 4, SP value: 9.3, flash point: -5.6°C], acetone [dimethyl ketone, carbon number: 3, SP value: 10, flash point: -10°C], 2-pentanone [methyl propyl ketone (MPK), carbon number: 5, SP value: 8.7, flash point: 7.2°C], 3-pentanone [diethyl ketone (DEK), carbon number: 5, SP value: 8.8, flash point: 13°C], 3-methyl-2-butanone [methyl isopropyl ketone (MIPK), carbon number: 5, SP value : 8.5, flash point: -1.0°C), 2-methyl-4-pentanone [methyl isobutyl ketone (MIBK), carbon number: 6, SP value: 8.4, flash point: 3°C], 2,6-dimethyl-4-heptanone [diisobutyl ketone (DIBK), carbon number: 9, SP value: 7.8, flash point: 60°C], cyclohexanone [carbon number: 6, SP value: 9.3, flash point: 44°C], 4-hydroxy-4-methyl-pentan-2-one [diacetone alcohol, carbon number: 6, SP value: 9.2, flash point: 58°C].

[0076] Specific examples of the ether include, but are not limited to, one or more of the following ethers.

[0077] 1,4-dioxane [dioxane, SP value: 10, flash point: 15.6°C], diethyl ether [SP value: 7.4, flash point: -45°C], 1,1-dimethyldiethyl ether [diisopropyl ether, SP value: 6.9, flash point: -28°C], 2-ethoxyethanol [ethyl cellosolve (EGMEE), SP value: 10.5, flash point: 45°C], 2-butoxyethanol [butyl cellosolve (EGMBE), SP value: 9.5, flash point: 63°C], tert-butyl methyl ether [MTBE, flash point: -28°C].

[0078] As the ether, glycol ethers can also be used.

[0079] Specific examples of glycol ethers include, but are not limited to, one or more of the following glycol ethers.

[0080] 1-Methoxy-2-propanol [propylene glycol monomethyl ether (PM), SP value: 10.2, flash point: 32°C], 2-(2-methoxyethoxy)ethanol [methyl carbitol], 2-(2-ethoxyethoxy)ethanol [ethyl carbitol, SP value: 10.2], 2-(2-butoxyethoxy)ethanol [butyl carbitol, SP value: 10.2], 2-[2-(2-methoxyethoxy)ethoxy]ethanol [methyl triglycol], 1 -butoxy-2-propanol [propylene glycol-1-monobutyl ether (PNB)], 3-methoxy-3-methyl-1-butanol [methyl methoxybutanol (MMB)], 2-[2-(hexyloxy)ethoxy]ethanol [hexyldiglycol], 1-(methoxymethyl)ethyl propionate [methotate], 1 or 2-(methoxymethylethoxy)propanol [dipropylene glycol monomethyl ether (DPM), isomer mixture].

[0081] Specific examples of the ester include, but are not limited to, one or more of the following esters.

[0082] Ethyl acetate [ethyl acetate, SP value: 9.1, flash point: 7.2°C], methyl acetate [methyl acetate, SP value: 9.6], n-butyl acetate [n-butyl acetate, SP value: 8.5, flash point: 22°C], sec-butyl acetate [sec-butyl acetate, SP value: 8.3], 3-methoxybutyl acetate [3-methoxybutyl acetate], pentyl ethanoate [amyl acetate, SP value: 8.5], propyl acetate [n-propyl acetate, SP value: 8.8], isopropyl ethanoate [isopropyl acetate, SP value: 8.4], ethyl (R)-2-hydroxypropanoate [ethyl lactate], methyl 2-hydroxypropanoate [methyl lactate], butyl 2-hydroxypropanoate [butyl lactate].

[0083] As the ester, glycol esters can also be used.

[0084] Specific examples of glycol esters include, but are not limited to, one or more of the following glycol esters.

[0085] 1-Acetoxy-2-ethoxyethane [ethylene glycol monoethyl ether acetate], 1-methoxy-2-propanyl acetate [propylene glycol monomethyl ether acetate (PGMEA)], 2-(2-butoxyethoxy)ethyl acetate [butyl carbitol acetate, SP value: 8.5], 2-(2-ethoxyethoxy)ethyl acetate [ethyl carbitol acetate].

[0086] Carbonate esters can also be used as the esters.

[0087] Specific examples of the carbonate ester include, but are not limited to, one or more of the following carbonate esters.

[0088] Dimethyl carbonate [flash point: 17°C], diethyl carbonate [SP value: 8.8, flash point: 25°C], ethyl methyl carbonate [SP value: 9.4, flash point: 23°C].

[0089] Specific examples of acetals include, but are not limited to, one or more of various acetals such as dimethoxymethane (methylal, flash point: -17.8°C).

[0090] The first solvent has excellent solubility for the metal complex dye, the polyoxyethylene compound, and the tackifier, and can therefore dissolve these components well, effectively preventing the dissolved metal complex dye and other components from precipitating or causing kogation during storage of the inkjet ink.

[0091] As the first solvent, it is preferable to use a combination of solvent A having a relatively low flash point and solvent B having a flash point relatively higher than that of solvent A. More preferably, solvent A having a flash point lower than 0°C and solvent B having a flash point of 0°C or higher are used in combination.

[0092] Solvents with low flash points are highly volatile and can improve quick-drying properties, but solvents with an SP value of less than 11 also dissolve fixing components such as resins. Therefore, if the solvent balance changes drastically due to evaporation during the fixing process, the fixing components may not be able to be dissolved, resulting in insufficient fixing properties. On the other hand, solvents with high flash points alone may not be able to dry quickly enough. Therefore, it is preferable to use a combination of solvent A, which has a low flash point, and solvent B, which has a high flash point.

[0093] Specific examples of solvent A include, among the above-mentioned first solvents, ketones having 3 to 5 carbon atoms, such as 2-butanone [methyl ethyl ketone (MEK), carbon number: 4, SP value: 9.3, flash point: -5.6°C], acetone [dimethyl ketone, carbon number: 3, SP value: 10, flash point: -10°C], and 3-methyl-2-butanone [methyl isopropyl ketone (MIPK), carbon number: 5, SP value: 8.5, flash point: -1.0°C]. Ketones whose carbon number and SP value satisfy the above ranges are particularly excellent in solubility of metal complex dyes, polyoxyethylene compounds, and tackifiers, and can further improve the effect of suppressing precipitation of these components and kogation.

[0094] Specific examples of solvent B include ethers and esters of the above-mentioned first solvents, such as 1-methoxy-2-propanol [propylene glycol monomethyl ether (PM), SP value: 10.2, flash point: 32°C], 2-ethoxyethanol [ethyl cellosolve (EGMEE), SP value: 10.5, flash point: 45°C], and ethyl acetate [ethyl acetate, SP value: 9.1, flash point: 7.2°C].

[0095] With regard to the blending amounts of solvent A and solvent B, it is preferable that the blending ratio of solvent A to the total amount of the first solvent is greater than the blending ratio of solvent B. More specifically, the blending ratio of solvent A is preferably greater than 50% by mass, and more preferably 60% by mass or greater. The blending ratio of solvent A is preferably 95% by mass or less, and more preferably 90% by mass or less. The blending ratio of solvent A to the total amount of the first solvent is preferably greater than 50% by mass but not greater than 95% by mass, and more preferably 60% by mass or greater but not greater than 90% by mass.

[0096] Because the first solvent has an SP value of less than 11, it is prone to damage to components that make up the printer head, and if it is used in large quantities, there is a concern that continuous printing will be impaired. On the other hand, if the amount of first solvent used is small, the solubility of the dye, polyoxyethylene compound, phenolic resin, and tackifier will be insufficient, and there is a concern that the ink's dissolution stability will be impaired. Therefore, by setting the blending ratio of solvent A within the above range, the first solvent can be easily volatilized, reducing head damage, while the use of solvent B in combination can maintain the ink's dissolution stability.

[0097] <Second solvent> As the second solvent to be used in combination with the first solvent, various solvents having an SP value of not less than 11 are used. As the second solvent, for example, an alcohol having an SP value of not less than 11 is used. The number of carbon atoms in the alcohol is, for example, 1 to 4, and preferably 1 to 3.

[0098] Specific examples of the alcohol include, but are not limited to, one or more of the following alcohols.

[0099] Methanol [methyl alcohol, carbon number: 1, SP value: 14.5-14.8], ethanol [ethyl alcohol, carbon number: 2, SP value: 12.7], 1-propanol [propyl alcohol, carbon number: 3, SP value: 11.97], 2-propanol [isopropyl alcohol (IPA), carbon number: 3, SP value: 11.5], 1-butanol [butyl alcohol, carbon number: 4, SP value: 11.4], 2-butanol [sec-butyl alcohol, carbon number: 4, SP value: 11].

[0100] These alcohols function to volatilize and foam as bubble-generating components, particularly when the inkjet ink is used in a thermal inkjet printer and heated, thereby generating ink droplets of a predetermined volume and ejecting them through the nozzle.

[0101] Furthermore, by using these alcohols as a second solvent, it is possible to improve the material compatibility of the ink-jet ink with the components that form the head of the ink-jet printer.

[0102] Furthermore, alcohols having 1 to 3 carbon atoms in particular have a lower boiling point and higher volatility than other alcohols having an SP value of 11 or greater, and therefore can improve the quick-drying properties of the inkjet ink after printing.

[0103] As the second solvent, it is preferable to use a C1-3 alcohol alone (including the case where two or more C1-3 alcohols are used in combination; the same applies below), but the C1-3 alcohol may also be used in combination with other alcohols. However, when used in combination, the amount of the C1-3 alcohol is preferably 70% by mass or more of the total amount of the second solvent so as not to impair the quick-drying properties of the inkjet ink. From the viewpoint of quick-drying properties, the upper limit of the amount of the C1-3 alcohol is 100% by mass of the total amount of the second solvent. In other words, it is preferable that the entire amount of the second solvent is a C1-3 alcohol.

[0104] <About the amount of solvent> The blending ratio of the first solvent is preferably 20% by mass or less, more preferably 18% by mass or less, based on the total amount of the first solvent and the alcohol as the second solvent (total amount of organic solvents). The blending ratio of the first solvent is preferably 5% by mass or more, based on the total amount of organic solvents. The blending ratio of the first solvent is preferably 5% by mass or more and 20% by mass or less, more preferably 5% by mass or more and 18% by mass or less, based on the total amount of organic solvents.

[0105] If the blending ratio of the first solvent is less than 5% by mass, the tackifier in particular may not be dissolved sufficiently, resulting in poor dissolution stability, which may result in clogging of the nozzles during continuous printing and poor continuous printing performance.

[0106] If the blending ratio of the first solvent exceeds 20% by mass, the amount of the second solvent becomes relatively small, which can reduce the material compatibility of the inkjet ink and cause various defects due to erosion or dissolution of components constituting the head. That is, if components constituting the head are eroded or dissolved and mixed into the inkjet ink, for example, and precipitate as insoluble components in the nozzle, the ejection of the inkjet ink can become unstable, causing nozzle clogging and reducing continuous printing performance. Furthermore, the insoluble components can interfere with the ejection of ink droplets, changing the trajectory of the ejected ink droplets and resulting in missing or blurred characters, etc.

[0107] Furthermore, the precipitated insoluble matter may inhibit the formation of a tackifier film on the liquid surface inside the nozzle during decap time, resulting in a decrease in intermittent printing performance. Also, when the ink is used in a thermal inkjet printer and heated, the amount of alcohol as a second solvent, which functions as a bubble-generating component, may be insufficient, and bubbles may not be generated properly even when the inkjet ink is heated, making it impossible to eject appropriate ink droplets.

[0108] In contrast, by setting the amount of the first solvent within the above range, the solubility of the metal complex dye, etc. in the inkjet ink can be improved, and precipitation and kogation can be effectively suppressed. Furthermore, the material compatibility of the inkjet ink can be improved, and the above-mentioned various defects due to erosion or dissolution of the components constituting the head can be effectively suppressed. Furthermore, when the inkjet ink is used in a thermal inkjet printer and heated, bubbles can be effectively generated, allowing appropriate ink droplets to be ejected.

[0109] [Tackifier] The ink-jet ink of the present invention may further comprise a tackifier.

[0110] As the tackifier, at least one compound selected from the group consisting of terpene phenol resins and rosin esters is used.

[0111] The terpene phenol resin preferably has a hydroxyl value of 30 mgKOH / g or more and 70 mgKOH / g or less, and the rosin ester preferably has an acid value of 0.1 or more and 20 or less.

[0112] If the hydroxyl value of the terpene phenolic resin is less than 30 mgKOH / g or the acid value of the rosin ester is less than 0.1, the polarity is not high, resulting in insufficient solubility in both the first and second solvents and insufficient dissolution in the inkjet ink. This can result in reduced ink stability and, ultimately, continuous printability. This can lead to unstable ejection, reduced continuous printability, or insufficient intermittent printability, making nozzles more susceptible to clogging during decap time.

[0113] On the other hand, if the hydroxyl value of the terpene phenol resin exceeds 70 mgKOH / g or the acid value of the rosin ester exceeds 20, the solubility in organic solvents is poor and the solubility in water is high, which may prevent the effect of improving continuous printability and intermittent printability from being obtained.

[0114] That is, a tackifier with a hydroxyl value exceeding 70 mgKOH / g or an acid value exceeding 20 has high polarity, and therefore the resolubility of the tackifier in organic solvents (first solvent + second solvent) is insufficient, resulting in poor continuous printability. However, because the tackifier also has high solubility in water, even if the inkjet ink is exposed to the outside air within the nozzle and comes into contact with moisture in the outside air, it may quickly precipitate on the liquid surface, making it impossible to form a good film that can suppress the evaporation of the solvent.

[0115] As a result, the viscosity of the inkjet ink increases during the decap time, making the nozzles more susceptible to clogging and reducing intermittent printing performance. Furthermore, when the surface of the substrate is made of a non-porous, low-polarity plastic or similar material, the adhesion of characters and other images tends to decrease. Furthermore, as mentioned above, tackifiers with high hydroxyl and acid values ​​are specialized, and there are only a few types available, limiting the options for properties.

[0116] In contrast, tackifiers having a hydroxyl value or acid value within the above ranges are available in a wide variety of types, offering a wide range of properties to choose from, and also have an appropriate solubility that is neither too low nor too high in two solvents, the first solvent and the second solvent, which have different SP values, and can be dissolved well in inkjet ink.

[0117] This improves the continuous printing performance of the inkjet ink, as well as the intermittent printing performance, making it less likely for nozzle clogging to occur during decap time.Furthermore, sufficient adhesion of characters and the like can be ensured even on the surface of a printing substrate made of low-polarity plastics, etc.

[0118] Here, we will explain the relationship between the tackifier and the first solvent (SP value < 11). The tackifier (terpene phenol resin) that dissolves only in the second solvent (alcohol) has a high hydroxyl value of 70 mg KOH / g or more and is highly compatible with water. Therefore, unless the amount of tackifier is increased, the effect of adding the tackifier is difficult to achieve. On the other hand, if the amount of tackifier is excessive, continuous printability may decrease, as with an excessive amount of resin.

[0119] Therefore, by using a first solvent that is compatible with the second solvent and dissolves a tackifier with a low hydroxyl value, it becomes possible to use a tackifier with a hydroxyl value ranging from 30 mgKOH / g to 60 mgKOH / g. As a result, the amount of tackifier used can be reduced, improving continuous printability. Similarly, when the tackifier is a rosin ester, a tackifier with an acid value of 100 or more can be dissolved in only the second solvent (alcohol).

[0120] Terpene phenol resins, for example, have a basic skeleton (C5H8) in which isoprene is bonded sequentially from head to tail. p (where p is an integer) and a copolymer of a terpene and a phenol, and various terpene phenol resins having a hydroxyl value within the above range can be used.

[0121] Specific examples of the terpene phenol resin include, but are not limited to, the following compounds.

[0122] From the YS Polyster series manufactured by Yasuhara Chemical Co., Ltd., U115 (hydroxyl value: 30 mg KOH / g), T80 (hydroxyl value: 60 mg KOH / g), T100 (hydroxyl value: 60 mg KOH / g), T115 (hydroxyl value: 60 mg KOH / g), T130 (hydroxyl value: 60 mg KOH / g), T145 (hydroxyl value: 60 mg KOH / g).

[0123] From the SylVares (registered trademark) series manufactured by KRATON, TP95 (hydroxyl value: 40 mg KOH / g), TP105 (hydroxyl value: 40 mg KOH / g), TP115 (hydroxyl value: 50 mg KOH / g), TP2040, TP2019, TP2040HM, 1095, 1105, and 1115.

[0124] As the rosin ester, various rosin esters can be used, which are esters of rosin, mainly consisting of an abietic or pymarinic resin acid having a monobasic carboxylic acid and an alkylated hydrophenanthrene nucleus, with alcohols, and have an acid value within the above range.

[0125] Examples of rosins include those made of resin acids containing unsaturated bonds, such as abietic acid and dextropimaric acid, and hydrogenated rosins mainly composed of hydrogenated dihydroabietic acid, tetrahydroabietic acid, etc. Examples of alcohols include glycerin, pentaerythritol, and triethylene glycol.

[0126] Specific examples of rosin esters include, but are not limited to, the following compounds:

[0127] Harima Chemical Co., Ltd.'s Haritack (registered trademark) series includes SE-10 (hydrogenated rosin ester, acid value: 2-10), FK100 (disproportionated rosin ester, acid value: 5 or less), FK125 (disproportionated rosin ester, acid value: 14-20), F85 (hydrogenated rosin ester, acid value: 4-12), PH (hydrogenated rosin ester, acid value: 7-16), AQ-90A (special rosin resin, acid value: 100-110), and Hariestar (registered trademark) series includes MSR-4 (acid value: 120-150). DS-70L (acid value: 8 or less), R-80 of the Halimacs series (acid value: 20 or less); Ester Gum (registered trademark) AA-G (rosin ester, acid value: 0.1 to 7.0), Ester Gum (registered trademark) 105 (rosin ester, acid value: 20 or less), Pencel (registered trademark) AZ (rosin ester, acid value: 35 to 50) manufactured by Arakawa Chemical Industries, Ltd.; RE80HP, RE85GB, and RE100L of the SylValite (registered trademark) series manufactured by Kraton.

[0128] One or more of these tackifiers can be used.

[0129] The amount of tackifier is, for example, 0.5% by mass or more, and preferably 1.5% by mass or more, relative to the total amount of the inkjet ink. The amount of tackifier is, for example, 5% by mass or less, and preferably 4.5% by mass or less. The amount of tackifier is, for example, preferably 0.5% by mass or more and 5% by mass or less, and more preferably 1.5% by mass or more and 4.5% by mass or less, relative to the total amount of the inkjet ink.

[0130] If the amount of tackifier is less than this range, when the inkjet ink is exposed to the outside air in the nozzle during the decap time, a satisfactory film capable of sufficiently suppressing solvent evaporation may not be formed, resulting in an increase in the viscosity of the inkjet ink and a decrease in intermittent printability. On the other hand, if the amount of tackifier exceeds the above range, the tackifier has almost no film-forming properties, which may result in a decrease in the fixation of characters and continuous printability. For example, an excessive amount of tackifier may cause a tacky feeling, which may lead to increased peeling due to the adhesiveness of the tape in a tape peel resistance test, which is an example of an indicator of fixation. Furthermore, an increase in the viscosity of the inkjet ink may cause unstable ejection, resulting in a decrease in continuous printability and increased susceptibility to kogation.

[0131] In contrast, by setting the amount of tackifier within the above range, it is possible to further improve the intermittent printability of the inkjet ink while suppressing deterioration in fixability, alcohol resistance, and continuous printability and the occurrence of kogation.

[0132] When two or more tackifiers are used in combination, the total amount should be within the above range. For example, a terpene phenol resin and a rosin ester can be used in combination. In this case, the compounding ratio of the terpene phenol resin and the rosin ester can be appropriately changed according to the specifications.

[0133] <Other ingredients> In addition to the above components, the inkjet ink may further contain a binder resin.

[0134] By blending a binder resin with a polyoxyethylene compound and a tackifier, the fixation of letters and other marks formed on the surface of corona-treated OPP and the like can be further improved. However, because binder resins can cause kogation, it is preferable to limit the amount of binder resin used, even when blended in small amounts. Even with such a small amount, the fixation of letters and other marks can be improved by combining the polyoxyethylene compound and the tackifier.

[0135] Specifically, the amount of binder resin is preferably 5% by mass or less, and particularly 2% by mass or less, of the total amount of inkjet ink. In order to prevent kogation, it is preferable that the amount of binder resin be 0% by mass even within the above range, i.e., no binder resin is added (excluded).

[0136] The ink-jet ink of the present invention containing the above components can be used in on-demand ink-jet printers, and is particularly suitable for on-demand thermal ink-jet printers. [Example]

[0137] The present invention will be described below based on examples and comparative examples, but the configuration of the present invention is not limited to these examples.

[0138] Example 1 The following components were mixed and then filtered using a 5 μm membrane filter to prepare an inkjet ink.

[0139] [Table 1]

[0140] The components in the table are as follows:

[0141] Colorant: Metal complex dye (VALIFAST (registered trademark) BLACK 3810 manufactured by Orient Chemical Industries Co., Ltd.) Polyoxyethylene compound: ADEKA Corporation's ADEKA (registered trademark) Pluronic L-31 [poloxamer, POE(3)POP(17), number average molecular weight Mn: 1100, POE content: 10%] Phenolic resin: Phenolite (registered trademark) TD-2131 manufactured by DIC Corporation (novolac resin, softening point VT (°C) = 80°C) First solvent (solvent A): 2-butanone [methyl ethyl ketone (MEK), carbon number: 4, SP value: 9.3, flash point: -5.6°C] First solvent (solvent B): 1-methoxy-2-propanol [propylene glycol monomethyl ether (PM), SP value: 10.2, flash point: 32°C] Second solvent: Ethanol (ethyl alcohol, carbon number: 2, SP value: 12.7) Tackifier: Terpene phenol resin (YS Polystar T80 manufactured by Yasuhara Chemical Co., Ltd., hydroxyl value: 60 mg KOH / g) Surfactant: Silicone surfactant The amount of the polyoxyethylene compound was 22.2% by mass relative to the amount of the metal complex dye. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 11.9% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 90% by mass.

[0142] Example 2 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with ADEKA (registered trademark) Pluronic L-61 (poloxamer, POE(5)POP(30), number average molecular weight Mn: 2000, POE content: 10%) manufactured by ADEKA CORPORATION in the same amount as in Example 1.

[0143] Example 3 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of ADEKA (registered trademark) Pluronic L-101 (poloxamer, POE(8)POP(55), number average molecular weight Mn: 3800, POE content: 10%) manufactured by ADEKA CORPORATION was used instead of ADEKA (registered trademark) Pluronic L-31 as the polyoxyethylene compound.

[0144] Example 4 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with ADEKA (registered trademark) Pluronic L-121 (poloxamer, POE(10)POP(65), number average molecular weight Mn: 4500, POE content: 10%) manufactured by ADEKA Corporation.

[0145] Example 5 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with the same amount of Toho Polyethylene Glycol 2000 (polyethylene glycol, number average molecular weight Mn: 2000) manufactured by Toho Chemical Industry Co., Ltd., instead of ADEKA (registered trademark) Pluronic L-31.

[0146] Example 6 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with ADEKA (registered trademark) Pluronic L-31 and the same amount of ADEKA (registered trademark) PEG-1000 (polyethylene glycol, number average molecular weight Mn: 1000) manufactured by ADEKA Corporation was used.

[0147] Example 7 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with ADEKA (registered trademark) Pluronic L-31 and the same amount of ADEKA (registered trademark) PEG-600 (polyethylene glycol, number average molecular weight Mn: 600) manufactured by ADEKA Corporation was used.

[0148] Example 8 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with ADEKA (registered trademark) PEG-400 (polyethylene glycol, number average molecular weight Mn: 400) manufactured by ADEKA Corporation in the same amount as in Example 1.

[0149] Example 9 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with Adeka (registered trademark) Pluronic L-31 by blending the same amount of Polyoxyethylene Lauryl Ether Bridge 35 (alcohol ethoxylate, number average molecular weight Mn: 1200) manufactured by Junsei Chemical Co., Ltd.

[0150] Example 10 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound was replaced with DKS-NL15 (alcohol ethoxylate, number average molecular weight Mn: 2900) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. in the same amount as in Example 1, instead of ADEKA (registered trademark) Pluronic L-31.

[0151] Comparative Example 1 An inkjet ink was prepared in the same manner as in Example 1, except that the polyoxyethylene compound ADEKA (registered trademark) Pluronic L-31 was replaced with the same amount of sorbitan lauryl ester (ADEKA (registered trademark) Estol S-20, manufactured by ADEKA Corporation).

[0152] Example 11 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Phenolite (registered trademark) TD-2090 (novolac resin, softening point VT (°C) = 120°C) manufactured by DIC Corporation was used instead of Phenolite (registered trademark) TD-2131 as the phenolic resin.

[0153] Example 12 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Shownol (registered trademark) BRG-564G (novolak resin, softening point VT (°C) = 65°C) manufactured by Showa Denko K.K. was used as the phenolic resin instead of Phenolite (registered trademark) TD-2131.

[0154] Example 13 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Shownol (registered trademark) CKM-2432 (novolak resin, softening point VT (°C) = 130°C) manufactured by Showa Denko K.K. was used as the phenolic resin instead of Phenolite (registered trademark) TD-2131.

[0155] Comparative Example 2 An inkjet ink was prepared in the same manner as in Example 1, except that the phenolic resin, Phenolite (registered trademark) TD-2131, was replaced with the same amount of acrylic resin (JONCRYL682 manufactured by BASF Japan Ltd.).

[0156] Example 14 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of 2-propanol [isopropyl alcohol (IPA), carbon number: 3, SP value: 11.5] was used as the second solvent instead of ethanol.

[0157] Example 15 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of 1-butanol (butyl alcohol, carbon number: 4, SP value: 11.4) was used as the second solvent instead of ethanol.

[0158] Example 16 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of 3-methyl-2-butanone [methyl isopropyl ketone (MIPK), carbon number: 5, SP value: 8.5, flash point: -1°C] was used as the first solvent (solvent A) instead of methyl ethyl ketone (MEK).

[0159] Example 17 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of ethyl acetate (ethyl acetate, carbon number: 4, SP value: 9.1, flash point: 7.2°C) was used as the first solvent (solvent B) instead of methyl ethyl ketone (MEK).

[0160] Example 18 An inkjet ink was prepared in the same manner as in Example 1, except that 9% by mass of solvent A, 3-methyl-2-butanone [methyl isopropyl ketone (MIPK), carbon number: 5, SP value: 8.5, flash point: -1°C], and 1% by mass of solvent B, 2-ethoxyethanol [ethyl cellosolve (EGMEE), carbon number: 4, SP value: 10.5, flash point: 45°C], were used in combination as the first solvent.

[0161] Example 19 An inkjet ink was prepared in the same manner as in Example 1, except that 9% by mass of solvent A, 2-butanone [methyl ethyl ketone (MEK), carbon number: 4, SP value: 9.3, flash point: -5.6°C], and 1% by mass of solvent A, 3-methyl-2-butanone [methyl isopropyl ketone (MIPK), carbon number: 5, SP value: 8.5, flash point: -1°C], were used in combination as the first solvent.

[0162] Example 20 An inkjet ink was prepared in the same manner as in Example 1, except that 9% by mass of ethyl acetate (ethyl acetate, carbon number: 4, SP value: 9.1, flash point: 7.2°C) and 1% by mass of 2-ethoxyethanol (ethyl cellosolve (EGMEE), carbon number: 4, SP value: 10.5, flash point: 45°C) were used in combination as the first solvent. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 0% by mass.

[0163] Example 21 An inkjet ink was prepared in the same manner as in Example 1, except that, instead of using a combination of methyl ethyl ketone (MEK) and propylene glycol monomethyl ether (PM) as the first solvent, 10% by mass of solvent A, 3-methyl-2-butanone [methyl isopropyl ketone (MIPK), carbon number: 5, SP value: 8.5, flash point: -1°C] was blended alone.

[0164] Example 22 An inkjet ink was prepared in the same manner as in Example 1, except that instead of using the first solvent and the second solvent in combination, 84 mass% of the second solvent, ethanol (ethyl alcohol, carbon number: 2, SP value: 12.7) was used alone as the organic solvent, and the same amount of Hariestar (registered trademark) MSR-4 (rosin ester, acid value: 120-150) manufactured by Harima Chemicals Co., Ltd. was used as the tackifier instead of YS Polystar T80. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 0 mass%.

[0165] Example 23 An inkjet ink was prepared in the same manner as in Example 1, except that instead of using a combination of the first and second solvents, 84% by mass of ethyl acetate (ethyl acetate, carbon number: 4, SP value: 9.1, flash point: 7.2°C) as the first solvent (solvent B) was used alone. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 100.0% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 0% by mass.

[0166] Example 24 An inkjet ink was prepared in the same manner as in Example 1, except that the metal complex dye was replaced with an acid dye (VALIFAST BLACK 1807 manufactured by Orient Chemical Industries Co., Ltd.) in the same amount as the colorant.

[0167] Comparative Example 3 An inkjet ink was prepared in the same manner as in Example 1, except that a polyoxyethylene compound was not blended as a fixing component. The amount of the polyoxyethylene compound was 0% by mass relative to the amount of the metal complex dye.

[0168] Example 25 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the polyoxyethylene compound was 0.3% by mass. The amount of the polyoxyethylene compound was 3.3% by mass relative to the amount of the metal complex dye.

[0169] Example 26 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the polyoxyethylene compound was 0.5% by mass. The amount of the polyoxyethylene compound was 5.6% by mass relative to the amount of the metal complex dye.

[0170] Example 27 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the polyoxyethylene compound was 4.5% by mass. The amount of the polyoxyethylene compound was 50.0% by mass relative to the amount of the metal complex salt dye.

[0171] Example 28 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the polyoxyethylene compound was 5% by mass. The amount of the polyoxyethylene compound was 55.6% by mass relative to the amount of the metal complex dye.

[0172] Comparative Example 4 An inkjet ink was prepared in the same manner as in Example 1, except that the phenol resin was not blended as a fixing component.

[0173] Example 29 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the phenol resin was set to 0.5% by mass.

[0174] Example 30 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the phenolic resin was set to 0.75% by mass.

[0175] Example 31 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the phenolic resin was 3% by mass.

[0176] Example 32 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amount of the phenolic resin was 4% by mass.

[0177] Example 33 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amounts of the organic solvents were changed so that the first solvent (solvent A) was 4.5% by mass of methyl ethyl ketone (MEK), the first solvent (solvent B) was 0.5% by mass of propylene glycol monomethyl ether (PM), and the second solvent was 79% by mass of ethanol. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 6.0% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 90% by mass.

[0178] Example 34 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amounts of the organic solvents were changed so that the first solvent (solvent A) was 13.5% by mass of methyl ethyl ketone (MEK), the first solvent (solvent B) was 1.5% by mass of propylene glycol monomethyl ether (PM), and the second solvent was 69% by mass of ethanol. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 17.9% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 90% by mass.

[0179] Example 35 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amounts of the organic solvents were changed so that the first solvent (solvent A) was 18% by mass of methyl ethyl ketone (MEK), the first solvent (solvent B) was 2% by mass of propylene glycol monomethyl ether (PM), and the second solvent was 64% by mass of ethanol. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 23.8% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 90% by mass.

[0180] Example 36 An inkjet ink was prepared in the same manner as in Example 1, except that the amounts of the organic solvents were changed so that the first solvent (solvent A) was 1% by mass of methyl ethyl ketone (MEK), the first solvent (solvent B) was 9% by mass of propylene glycol monomethyl ether (PM), and the second solvent was 74% by mass of ethanol. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 11.9% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 10% by mass.

[0181] Example 37 An inkjet ink was prepared in the same manner as in Example 1, except that the blending amounts of the organic solvents were changed so that the first solvent (solvent A) was 5% by mass of methyl ethyl ketone (MEK), the first solvent (solvent B) was 5% by mass of propylene glycol monomethyl ether (PM), and the second solvent was 74% by mass of ethanol. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 11.9% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 50% by mass.

[0182] Example 38 An inkjet ink was prepared in the same manner as in Example 1, except that the amounts of the organic solvents were changed so that the first solvent (solvent A) was 6% by mass of methyl ethyl ketone (MEK), the first solvent (solvent B) was 4% by mass of propylene glycol monomethyl ether (PM), and the second solvent was 74% by mass of ethanol. The blending ratio of the first solvent to the total amount of organic solvents (first solvent / first solvent + second solvent) was 11.9% by mass. The blending ratio of solvent A (flash point <0°C) to the total amount of the first solvent (solvent A / solvent A + solvent B) was 60% by mass.

[0183] Example 39 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of YS Polystar U115 (terpene phenol resin, hydroxyl value: 30 mgKOH / g) manufactured by Yasuhara Chemical Co., Ltd. was used as the tackifier instead of YS Polystar T80.

[0184] Example 40 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of SylVares TP115 (terpene phenol resin, hydroxyl value: 50 mgKOH / g) manufactured by Kraton was used as the tackifier instead of YS Polystar T80.

[0185] Example 41 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of YS Polystar S145 (terpene phenol resin, hydroxyl value: 100 mgKOH / g) manufactured by Yasuhara Chemical Co., Ltd. was used as the tackifier instead of YS Polystar T80.

[0186] Example 42 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Haritack (registered trademark) SE-10 (rosin ester (hydrogenated), acid value: 2 to 10) manufactured by Harima Chemicals Co., Ltd. was used as the tackifier instead of YS Polystar T80.

[0187] Example 43 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Ester Gum (registered trademark) AA-G (rosin ester, acid value: 0.1 to 7.0) manufactured by Arakawa Chemical Industries, Ltd. was used as the tackifier instead of YS Polystar T80.

[0188] Example 44 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Ester Gum (registered trademark) 105 (rosin ester, acid value: 20 or less) manufactured by Arakawa Chemical Industries, Ltd. was used as a tackifier instead of YS Polystar T80.

[0189] Example 45 An inkjet ink was prepared in the same manner as in Example 1, except that the same amount of Pencel (registered trademark) AZ (rosin ester, acid value: 35 to 50) manufactured by Arakawa Chemical Industries, Ltd. was blended as the tackifier instead of YS Polystar T80.

[0190] Example 46 An inkjet ink was prepared in the same manner as in Example 1, except that 0.6% by mass of a terpene phenol resin (YS Polystar T80 manufactured by Yasuhara Chemical Co., Ltd., hydroxyl value: 60 mgKOH / g) and 2.4% by mass of a rosin ester (Haritac (registered trademark) SE-10 manufactured by Harima Chemical Co., Ltd., acid value: 2 to 10) were used in combination as tackifiers.

[0191] Example 47 An inkjet ink was prepared in the same manner as in Example 1, except that 1.5% by mass of a terpene phenol resin (YS Polystar T80 manufactured by Yasuhara Chemical Co., Ltd., hydroxyl value: 60 mgKOH / g) and 1.5% by mass of a rosin ester (Haritac (registered trademark) SE-10 manufactured by Harima Chemical Co., Ltd., acid value: 2 to 10) were used in combination as tackifiers.

[0192] Example 48 An inkjet ink was prepared in the same manner as in Example 1, except that 2.4% by mass of a terpene phenol resin (YS Polystar T80 manufactured by Yasuhara Chemical Co., Ltd., hydroxyl value: 60 mgKOH / g) and 0.6% by mass of a rosin ester (Haritac (registered trademark) SE-10 manufactured by Harima Chemical Co., Ltd., acid value: 2 to 10) were used in combination as tackifiers.

[0193] Example 49 An inkjet ink was prepared in the same manner as in Example 1, except that no tackifier was added.

[0194] Example 50 An inkjet ink was prepared in the same manner as in Example 1, except that the amount of tackifier added was 1% by mass.

[0195] Example 51 An inkjet ink was prepared in the same manner as in Example 1, except that the amount of tackifier added was 2% by mass.

[0196] Example 52 An inkjet ink was prepared in the same manner as in Example 1, except that the amount of tackifier added was 4% by mass.

[0197] Example 53 An inkjet ink was prepared in the same manner as in Example 1, except that the amount of tackifier added was 5% by mass.

[0198] [Evaluation method] <Continuous printing test> Using an on-demand thermal inkjet printer, the alphabets A to F were continuously printed in 8.5 pt at a resolution of 300 x 300 dpi on the surface of corona-treated OPP using the inkjet inks prepared in the Examples and Comparative Examples.

[0199] Next, the printed alphabet images were observed, and the number of prints without chipping or missing due to poor inkjet ink ejection, mainly caused by kogation, was recorded, and continuous printability was evaluated according to the following criteria.

[0200] ○: More than 40,000 times.

[0201] △: More than 20,000 times but less than 40,000 times.

[0202] ×: Less than 20,000 times.

[0203] <Tape peeling test> Using the same inkjet printer as in the continuous printability test, a 0.2 pt (line width 0.07 mm) bar code was printed on the surface of the corona-treated OPP using the inkjet inks prepared in the Examples and Comparative Examples.

[0204] Next, SCOTCH's "BK-24 Ultra-Transparent Tape S" and Sekisui Chemical Co., Ltd.'s "Sekisui Cellotape (registered trademark) No. 252" were separately applied to the printed barcode, and a 2 kg load was applied to each, after which a 90° peel test was performed. The fixation was evaluated based on the print residue after peeling the tape, using the following criteria.

[0205] ○: No change in the print was observed even after the tape manufactured by Sekisui Chemical Co., Ltd. was peeled off.

[0206] △: The print becomes lighter after peeling off the tape manufactured by Sekisui Chemical Co., Ltd., but no change in the print is observed after peeling off the tape manufactured by SCOTCH.

[0207] △△: The print became faint after peeling off the SCOTCH tape.

[0208] ×: Part of the print was chipped off after the SCOTCH tape was peeled off.

[0209] <Quick-drying test> Using the same inkjet printer as in the continuous printability test, characters of about 8.5 pt were printed at a resolution of 300 x 300 dpi on the surface of the corona-treated OPP using the inkjet inks prepared in the Examples and Comparative Examples.

[0210] Next, the printed letters were allowed to dry for a certain period of time, and the drying time required for the letters to become indelible when rubbed with a cotton swab was recorded, and the quick-drying property was evaluated according to the following criteria.

[0211] ○: Less than 10 seconds.

[0212] △: More than 10 seconds but less than 15 seconds.

[0213] ×: More than 15 seconds.

[0214] <Intermittent printing test> Using the same inkjet printer as in the continuous printability test, characters of about 8.5 pt were printed at a resolution of 300 x 300 dpi on the surface of the corona-treated OPP using the inkjet inks prepared in the Examples and Comparative Examples.

[0215] Next, the inkjet printer was left to stand for a certain period of time in a decapped state in a room temperature, low humidity environment (25°C, 30%), and then printing was performed again. The time required for the printer to be left to stand until clear characters could be printed without blurring was recorded. Intermittent printing performance was evaluated based on this record according to the following criteria.

[0216] ○: Clear printing was possible even with a decap time of 10 minutes or more.

[0217] △: Clear printing was possible even with a decap time of 5 minutes or more.

[0218] △△: Clear printing was possible with a decap time of 1 minute or more and less than 5 minutes.

[0219] ×: Clear printing was not possible unless the decap time was less than 1 minute.

[0220] Long-term storage and intermittent printing The inkjet inks prepared in the Examples and Comparative Examples were placed in ink cartridges for an on-demand thermal inkjet printer and stored in a warming cabinet (approximately 45°C) for a certain period of time. After storage, the ink cartridges were removed and subjected to the intermittent printability test described above, and the long-term storage intermittent printability was evaluated according to the following criteria.

[0221] ○: The same decap time was maintained for more than 6 weeks.

[0222] △: The same decap time was maintained until the 5th week.

[0223] △△: The same decap time was maintained until the fourth week, but deterioration was observed by the fifth week.

[0224] ×: Deterioration of decap time was observed within 3 weeks.

[0225] The results are shown in Tables 2 to 12. In each table, the symbols in the column for the type of polyoxyethylene (POE) compound are as follows:

[0226] PLX: Poloxamer (polyoxyethylene polyalkylene glycol) PEG: Polyethylene glycol (polyalkylene glycol) AE: Alcohol ethoxylate (polyoxyethylene alkyl ether) In each table, the symbols in the column for the type of organic solvent are as follows:

[0227] MEK: 2-butanone (methyl ethyl ketone) MIPK: 3-methyl-2-butanone (methyl isopropyl ketone) PM: 1-methoxy-2-propanol (propylene glycol monomethyl ether) In each table, the symbols in the column for the type of tackifier are as follows:

[0228] Tp: Terpene phenolic resin Ro: Rosin ester resin

[0229] [Table 2]

[0230] [Table 3]

[0231] [Table 4]

[0232] [Table 5]

[0233] [Table 6]

[0234] [Table 7]

[0235] [Table 8]

[0236] [Table 9]

[0237] [Table 10]

[0238] [Table 11]

[0239] [Table 12]

[0240] <Evaluation Results> From a comparison of Examples 1 to 5 in Table 2, Examples 6 to 10 in Table 3, Examples 11 to 13 in Table 4, Examples 25 to 28 in Table 7, Examples 29 to 32 in Table 8, Comparative Example 1 in Table 3, Comparative Example 2 in Table 4, Comparative Example 3 in Table 7, and Comparative Example 4 in Table 8, it was found that excellent fixability can be achieved by using, as the fixing component in the ink, at least one polyoxyethylene-based compound selected from the group consisting of polyoxyethylene polyalkylene glycol, polyalkylene glycol, and polyoxyethylene alkyl ether, and having a number average molecular weight Mn of 200 or more, in combination with a phenolic resin.

[0241] For example, in Comparative Example 3 in Table 7, no polyoxyethylene compound was contained and only a phenolic resin was used, and in Comparative Example 4 in Table 8, no phenolic resin was contained and only a polyoxyethylene compound was used, so the tape peel resistance was rated as "X".

[0242] Polyoxyethylene compounds are compounds that are usually used as nonionic surfactants (ether type) or as raw materials for such surfactants, etc. Comparative Example 1 in Table 3 uses sorbitan lauryl ester, which is generally used as a nonionic surfactant (ester type) like polyoxyethylene compounds, as a component to be used in combination with a phenolic resin.

[0243] In Comparative Example 1, the tape peel resistance was improved to a rating of "Good", but the continuous printability was rated "Poor". This is thought to be because the solubility of sorbitan lauryl ester in organic solvents is lower than that of polyoxyethylene compounds. One of the reasons for this is thought to be that sorbitan lauryl ester precipitated, making the ejection of the inkjet ink unstable and causing nozzle clogging, which reduced the continuous printability.

[0244] On the other hand, Comparative Example 2 in Table 4 shows an example in which an acrylic resin was used as a resin component in place of a phenolic resin as a component used in combination with a polyoxyethylene compound. In Comparative Example 2, the tape peel resistance remained unimproved and was rated "x", and further, the continuous printability was also rated "x". This is thought to be because resins other than phenolic resins do not function well as fixing components for inkjet inks and have low solubility in organic solvents.

[0245] A comparison of Examples 1 to 5 in Table 2 and Examples 6 to 10 in Table 3 revealed that, among polyoxyethylene compounds to be used in combination with phenolic resins, polyoxyethylene compounds having a number average molecular weight Mn of 1000 or more and 4000 or less are preferred.

[0246] When the number average molecular weight Mn of the polyoxyethylene compound exceeded 4000 as in Example 4 (Table 2), the solubility in organic solvents was low, and the continuous printing properties were inferior to those of Examples 1 to 3 and Examples 5 to 10, and the quick-drying properties were also inferior.

[0247] On the other hand, when the number average molecular weight Mn of the polyoxyethylene compound was less than 1000 as in Examples 7 and 8 (both in Table 3), the tape peel resistance was inferior to that of Examples 1 to 6 and Examples 9 to 10.

[0248] A comparison of Examples 1 to 5 in Table 2 and Examples 6 to 10 in Table 3 reveals that, among the polyoxyethylene compounds used in combination with phenolic resins, polyoxyethylene polyalkylene glycols, polyalkylene glycols, and polyoxyethylene alkyl ethers are the most preferable for achieving sufficient adhesion. The tape peel resistance of polyalkylene glycols (Examples 5 to 8) and polyoxyethylene alkyl ethers (Examples 9 and 10) was rated "Fair" or "Fair Fair." In contrast, the tape peel resistance of Examples 1 to 4, which used polyoxyethylene polyalkylene glycols, was rated "Good."

[0249] From the viewpoint of improving fixability, a preferable range of the amount of the polyoxyethylene compound was found from a comparison of Examples 25 to 28 in Table 7. The preferable range may be 5% by mass or more and 50% by mass or less of the amount of the polyoxyethylene compound relative to the metal complex salt dye.

[0250] For example, as in Example 25, if the amount of polyoxyethylene compound is small relative to the amount of metal complex dye, it may be difficult to form a complex with the metal complex dye, which may reduce adhesion to the surface of the printed substrate. As a result, it is believed that the tape peel resistance was rated "△". As in Example 28, if the amount of polyoxyethylene compound is excessive relative to the amount of metal complex dye, it may be difficult for the compound to remain at the interface with the printed substrate, which may reduce adhesion to the surface of the printed substrate. In addition, quick-drying properties may be reduced. As a result, it is believed that both tape peel resistance and quick-drying properties were rated "△".

[0251] Furthermore, a comparison of Examples 27 to 28 in Table 7 and Examples 29 to 32 in Table 8 revealed that when the total amount of polyoxyethylene-based compounds and phenolic resins (total amount of fixing components) is 2% by mass or more and 6% by mass or less relative to the total amount of inkjet ink, it is preferable that the amount of polyoxyethylene-based compounds is 35% by mass or more and 75% by mass or less relative to the total amount of fixing components.

[0252] A comparison of Example 1 in Table 2 and Examples 11 to 13 in Table 4 reveals that the softening point of the phenolic resin is preferably 65° C. or higher and 125° C. or lower. Example 13, in which the phenolic resin has a softening point of 130° C., had low solubility in organic solvents, and the long-term storage intermittent printability was evaluated as “Fair.”

[0253] A comparison of Example 1 in Table 2 and Examples 22 and 23 in Table 6 revealed that a combination of a first solvent (SP value <11) and a second solvent (alcohol with an SP value ≥ 11) is preferable as the organic solvent. When only the first solvent was used, as in Example 23, all tests except for quick-drying were rated as "Fair" or "Fair Fair." Furthermore, when only the second solvent was used in Example 22, all tests except for quick-drying and long-term storage intermittency were rated as "Fair" or "Fair Fair."

[0254] Even when the first solvent and the second solvent are used in combination, it is particularly preferable that the blending ratio of the first solvent to the total amount of organic solvents is 20 mass % or less. This is derived from a comparison of Examples 33 to 35 in Table 9. In Example 35, in which the blending ratio of the first solvent to the total amount of organic solvents was 23.8 mass %, the intermittent printability was rated "Fair" and the long-term storage intermittent printability was rated "Fair". It is thought that when the first solvent is used in large amounts, material compatibility (compatibility of the inkjet ink with components that form the inkjet printer head, etc.) decreases, resulting in decreased intermittent printability and long-term storage intermittent printability.

[0255] The first solvent (SP value <11) preferably contains solvent A, which has a relatively low flash point, and solvent B, which has a relatively high flash point compared to solvent A. In particular, it is preferable that the blending ratio of solvent A to the total amount of the first solvent is greater than the blending ratio of solvent B. A comparison of Example 1 in Table 2 and Examples 36 to 38 in Table 9 reveals that the blending ratio of solvent A to the first solvent is preferably at least more than 50 mass% and not more than 95 mass%.

[0256] In Example 1 (compounding ratio of solvent A = 90 mass%) and Example 38 (compounding ratio of solvent A = 60 mass%), both of which used MEK as solvent A and PM as solvent B, the quick-drying performance was rated as "Good." On the other hand, in Example 36 (compounding ratio of solvent A = 10 mass%) and Example 37 (compounding ratio of solvent A = 50 mass%), the quick-drying performance was rated as "Fair." This is thought to be due to the fact that solvent B, which has a relatively low flash point, is less volatile than solvent A.

[0257] Considering the improvement of quick-drying properties, the use of a solvent with a flash point below 0°C alone is considered. However, as is clear from Example 21 in Table 6, when an organic solvent with a flash point below 0°C was used alone, the long-term storage intermittent printability was rated "Fair." This is thought to be because if the solvent used alone has strong solubility and a low flash point, it will volatilize near the nozzle or from the ink pack during long-term storage, causing a change in the solvent balance inside the ink pack. This change in the solvent balance is thought to change the solubility state of the components, resulting in ejection problems when reprinting.

[0258] Furthermore, a comparison of Example 1 in Table 2, Examples 16 to 18 in Table 5, and Examples 19 to 20 in Table 6 revealed that it is preferable that the flash point of solvent A is less than 0°C and that the flash point of solvent B is 0°C or higher.

[0259] For example, Example 17 in Table 5 (combined use of solvents with flash points of 7.2°C and 32°C) and Example 20 in Table 6 (combined use of solvents with flash points of 7.2°C and 45°C) were rated as "Fair" for quick-drying. This is thought to be due to the fact that the flash points of the solvents used in combination were both 0°C or higher and therefore low volatility.

[0260] On the other hand, in Example 19 in Table 6 (using a combination of solvents with flash points of -5.6°C and -1°C), quick-drying properties were improved, but tape peel resistance, intermittent printability, and long-term storage intermittent printability were all rated "Fair." This is thought to be because, as with Example 21 in Table 6 (using a solvent with a flash point of -1°C alone), the amount of solvent capable of dissolving the fixing components in the ink changes significantly over time due to evaporation, making it impossible to maintain stable dissolution of the fixing components. In particular, in Example 19, the blending ratio of MEK, which has a flash point of -5.6°C, to the total amount of the first solvent was as high as 90% by mass, which is thought to have caused the solvent to dry too quickly during the fixing process after printing, resulting in insufficient fixability and reduced tape peel resistance.

[0261] A comparison of Example 1 in Table 2 and Example 24 in Table 6 shows that metal complex dyes are preferred for the dyes contained in the ink. Example 24, which used an acid dye even though it was an oil-soluble dye, was rated "Fair" in all tests except for quick-drying.

[0262] A comparison of Example 1 in Table 2, Examples 39 to 43 in Table 10, Examples 44 to 48 in Table 11, and Examples 49 to 53 in Table 12 shows that it is preferable for the ink to further contain a tackifier which is at least one selected from the group consisting of terpene phenol resins and rosin esters.

[0263] For example, Example 49 in Table 12, which did not contain any tackifier, was rated as "Fair Fair" for intermittent printability. In contrast, Example 1 in Table 1, Examples 39 to 43 in Table 10, Examples 44 to 48 in Table 11, and Examples 50 to 53 in Table 12, which contained even small amounts of tackifier, were rated as "Good" or "Fair" for intermittent printability.

[0264] In particular, a comparison of Example 1 in Table 2 and Examples 50 to 53 in Table 12 reveals that the amount of tackifier is preferably 1.5% by mass or more and 4.5% by mass or less relative to the total amount of inkjet ink. When the amount of tackifier is less than 1.5% by mass, as in Example 50, intermittent printability was rated as "Fair." On the other hand, when the amount of tackifier exceeds 4.5% by mass, as in Example 53, tape peel resistance decreases (tape peel resistance was rated as "Fair"), which, like resins, causes kogation and reduces continuous printability.

[0265] Furthermore, a comparison of Example 1 in Table 2, Examples 39 to 43 in Table 10, and Examples 44 to 45 in Table 11 revealed that when the tackifier is a terpene phenol resin, the hydroxyl value is preferably 30 mgKOH / g or more and 70 mgKOH / g or less, and when the tackifier is a rosin ester, the acid value is preferably 0.1 or more and 20 or less.

[0266] In Example 41, which used a terpene phenolic resin with a hydroxyl value exceeding 70 mgKOH / g, the intermittent printability was rated "Fair." This is thought to be because the rosin ester's solubility in not only solvents but also water increased, filling the gap between the solubility in solvents and water, and no longer contributed to intermittent printability. On the other hand, when a terpene phenolic resin with a hydroxyl value of less than 30 mgKOH / g or a rosin ester with an acid value exceeding 20 (Example 45) was used, the continuous printability and intermittent printability were rated "Fair." This is thought to be because the polarity of the tackifier was too high, resulting in insufficient resolubility of the tackifier in both the first and second solvents, resulting in reduced continuous printability. Furthermore, as with the use of a terpene phenolic resin with a hydroxyl value exceeding 70 mgKOH / g, the intermittent printability was likely reduced due to its high solubility in water and the inability to form a good film.

[0267] Furthermore, a comparison of Example 1 in Table 2, Example 42 in Table 10, and Examples 46 to 48 in Table 11 revealed that a terpene phenolic resin and a rosin ester can also be used in combination. When comparing these Examples, which have the same total amount of tackifier, all test results were evaluated as "Good" in all cases, including the use of terpene phenolic resin alone (Example 1), rosin ester alone (Example 42), and the use of terpene phenolic resin and rosin ester in combination (Examples 46 to 48).

[0268] Moreover, as is clear from the results of Examples 46 to 48, the blending ratio of terpene phenolic resin (rosin ester) to the total amount of tackifier does not need to be set particularly precisely, and there is a relatively high degree of freedom. In Examples 46 to 48, the blending ratio of terpene phenolic resin (rosin ester) to the total amount of tackifier was in a wide range of 20% by mass or more and 80% by mass or less, and all test results were evaluated as "Good" throughout this range. From these results, it can be seen that when terpene phenolic resin and rosin ester are used in combination, the blending ratio of terpene phenolic resin (rosin ester) to the total amount of tackifier can be set in a wide range of more than 0% by mass and less than 100% by mass.

[0269] The features of the present invention have been explained above based on the examples and comparative examples, but a general summary will now be provided.

[0270] As described above, it was found that by combining a polyoxyethylene compound, which is generally used as a nonionic surfactant, with a phenolic resin as a fixing component of the ink, fixing properties that can withstand the tape peeling test can be achieved.

[0271] Phenolic resins have relatively good adhesion to non-absorbent substrates such as OPP and aluminum, but if sufficient adhesion is required, the amount of resin blended increases, resulting in a decrease in continuous printability. On the other hand, if the amount of resin blended is sufficient to maintain good continuous printability, adhesion decreases. In other words, when phenolic resin is used alone, improving continuous printability and improving adhesion are in a trade-off relationship, and it is difficult to achieve both by simply increasing or decreasing the blending amount.

[0272] Therefore, by using a polyoxyethylene compound and a phenolic resin in combination as materials that contribute to the fixation of ink, it has become possible to maintain fixation while reducing the amount of resin that causes kogation and affects continuous printing.

[0273] Regarding the combined use of solvent A and solvent B in the first solvent, solvents with an SP value of less than 11 dissolve phenolic resins and polyoxyethylene compounds well, but it is preferable to limit their amount because they can cause poor material compatibility with the inkjet ink. Therefore, solvents A and B with SP values ​​of less than 11 are used in combination, and more solvent A, which has a low flash point, is blended than solvent B, which has a high flash point. This has been found to maintain quick-drying properties and improve long-term storage stability (stability) while reducing the total amount of first solvents with an SP value of less than 11.

[0274] It was also found that the use of a tackifier in combination improves intermittent printing by forming a very thin film of the tackifier during the decap time.Furthermore, it was found that the combination of a first solvent with an SP value of less than 11, an alcohol-based second solvent, and a tackifier achieves both long-term storage stability and decap ability, and that decap ability is maintained even after long-term storage.

Claims

1. Dyes and at least one polyoxyethylene compound selected from the group consisting of polyoxyethylene polyalkylene glycols, polyalkylene glycols, and polyoxyethylene alkyl ethers, having a number average molecular weight Mn of 200 or more; A phenolic resin, and an organic solvent.

2. the organic solvent includes a first solvent having a solubility parameter (SP value) of less than 11 and a second solvent which is an alcohol having a solubility parameter (SP value) of 11 or more; The ink-jet ink according to claim 1 , wherein the blending ratio of the first solvent to the total amount of the organic solvents is 20% by mass or less.

3. The first solvent includes a solvent A having a relatively low flash point and a solvent B having a relatively high flash point compared to the solvent A, The ink-jet ink according to claim 2 , wherein a blending ratio of the solvent A to the total amount of the first solvent is greater than a blending ratio of the solvent B.

4. The ink-jet ink according to claim 3 , wherein the flash point of said solvent A is less than 0° C. and the flash point of said solvent B is 0° C. or higher.

5. the solvent A is at least one selected from the group consisting of 2-butanone [methyl ethyl ketone (MEK)], acetone [dimethyl ketone], and 3-methyl-2-butanone [methyl isopropyl ketone (MIPK)]; 4. The ink-jet ink according to claim 3, wherein the solvent B is at least one selected from the group consisting of 1-methoxy-2-propanol [propylene glycol monomethyl ether (PM)], 2-ethoxyethanol [ethyl cellosolve (EGMEE)], and ethyl acetate [ethyl acetate].

6. The ink-jet ink according to any one of claims 1 to 5, further comprising a tackifier which is at least one selected from the group consisting of terpene phenol resins and rosin esters.

7. 7. The ink-jet ink according to claim 6, further comprising a tackifier that is at least one selected from the group consisting of a terpene phenol resin having a hydroxyl value of 30 mgKOH / g or more and 70 mgKOH / g or less, and a rosin ester having an acid value of 0.1 or more and 20 or less.

8. The ink-jet ink according to claim 7 , wherein the amount of the tackifier is 1.5% by mass or more and 4.5% by mass or less with respect to the total amount of the ink-jet ink.

9. The ink-jet ink according to any one of claims 1 to 5, wherein the number average molecular weight Mn of the polyoxyethylene compound is 1,000 or more and 4,000 or less.

10. The ink-jet ink according to any one of claims 1 to 5, wherein the polyoxyethylene compound is a polyoxyethylene polyalkylene glycol having a number average molecular weight Mn of 200 or more.

11. The ink-jet ink according to any one of claims 1 to 5, wherein the softening point of the phenolic resin is 65°C or higher and 125°C or lower.

12. the dye is a metal complex dye, The ink-jet ink according to any one of claims 1 to 5, wherein the amount of the polyoxyethylene compound is 5% by mass or more and 50% by mass or less relative to the metal complex dye.

13. the total amount of the polyoxyethylene compound and the phenol resin is 2% by mass or more and 6% by mass or less with respect to the total amount of the inkjet ink, The ink-jet ink according to claim 12, wherein the amount of the polyoxyethylene compound is 35% by mass or more and 75% by mass or less based on the total amount of the polyoxyethylene compound and the phenol resin.

14. a metal complex dye; a polyoxyethylene-based compound comprising polyoxyethylene polyalkylene glycol having a number average molecular weight Mn of 1,000 or more and 4,000 or less; A phenolic resin, an organic solvent, the amount of the polyoxyethylene compound is 5% by mass or more and 50% by mass or less with respect to the metal complex dye, and is 35% by mass or more and 75% by mass or less with respect to the total amount of the polyoxyethylene compound and the phenol resin; the organic solvent includes a first solvent having a solubility parameter (SP value) of less than 11 and a second solvent which is an alcohol having a solubility parameter (SP value) of 11 or more; The ink-jet ink comprises a first solvent including a solvent A having a relatively low flash point and a solvent B having a flash point of 0° C. or higher that is relatively higher than that of the solvent A.

15. The ink-jet ink according to claim 14, wherein the blending ratio of the first solvent to the total amount of the organic solvents is 20% by mass or less.

16. The composition further comprises a tackifier which is at least one selected from the group consisting of a terpene phenol resin having a hydroxyl value of 30 mgKOH / g or more and 70 mgKOH / g or less and a rosin ester having an acid value of 0.1 or more and 20 or less, The ink-jet ink according to claim 14 or 15, wherein the amount of the tackifier is 1.5% by mass or more and 4.5% by mass or less with respect to the total amount of the ink-jet ink.

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