Inkjet ink

Abstract

The present invention provides an inkjet ink that contains a metal complex dye, a polyoxyethylene based compound with which a number average molecular weight Mn is not less than 200, a tackifier with which a hydroxyl value is 30 to 70 mgKOH/g, a first solvent of at least one type selected from a group consisting of ketones, ethers, and esters and with which an SP value is less than 11, and a second solvent being an alcohol including at least an alcohol with 1 to 3 carbon atoms and with which the SP value is not less than 11 and is solvent based and does not contain (excludes) water, is unlikely to cause cogation, is also excellent in intermittent printing performance, and yet enables a character of excellent fixing property and abrasion resistance to be printed on a surface of a printing object with a non-absorbing property.

Claims

1. An inkjet ink comprising: a metal complex dye; a polyoxyethylene based compound as a binder of at least one type selected from a group consisting of polyoxyalkylene glycols and polyoxyalkylene alkyl ethers and with which a number average molecular weight Mn is not less than 800 and not more than 4000; a tackifier of at least one type selected from a group consisting of terpene phenol resins and rosin esters and with which a hydroxyl value is not less than 30 mgKOH/g and not more than 70 mgKOH/g; a first solvent of at least one type selected from a group consisting of ketones, ethers, and esters and with which a solubility parameter (SP value) is less than 11; a second solvent being an alcohol including at least an alcohol with 1 to 3 carbon atoms and with which the solubility parameter (SP value) is not less than 11; wherein an amount of the polyoxyethylene based compound is not less than 3 mass % and not more than 55 mass % with respect to an amount of the metal complex dye, the inkjet ink excluding a binder resin.

2. The inkjet ink according to claim 1, wherein an amount of the tackifier is not less than 0.5 mass % and not more than 5 mass % in a total amount of the inkjet ink.

3. The inkjet ink according to claim 1, wherein an amount of the first solvent is not less than 4 mass % and not more than 42 mass % in a total amount of the first solvent and the second solvent.

4. The inkjet ink according to claim 1, wherein an amount of the metal complex dye is not less than 5 mass % and not more than 15 mass % in a total amount of the inkjet ink.

5. The inkjet ink according to claim 1, wherein an amount of the metal complex dye is not less than 7 mass % and not more than 12 mass % in a total amount of the inkjet ink, an amount of the polyoxyethylene based compound is not less than 3 mass % and not more than 55 mass % with respect to the amount of the metal complex dye, an amount of the tackifier is not less than 1 mass % and not more than 4 mass % in a total amount of the inkjet ink, and an amount of the first solvent is not less than 5 mass % and not more than 40 mass % in a total amount of the first solvent and the second solvent.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) An inkjet ink according to a preferred embodiment of the present invention is characterized in containing

(2) a metal complex dye,

(3) a polyoxyethylene based compound of at least one type selected from a group consisting of polyoxyalkylene glycols and polyoxyalkylene alkyl ethers and with which a number average molecular weight Mn is not less than 200,

(4) a tackifier of at least one type selected from a group consisting of terpene phenol resins and rosin esters and with which a hydroxyl value is not less than 30 mgKOH/g and not more than 70 mgKOH/g,

(5) a first solvent of at least one type selected from a group consisting of ketones, ethers, and esters and with which a solubility parameter (SP value) is less than 11, and

(6) a second solvent being an alcohol including at least an alcohol with 1 to 3 carbon atoms and with which the solubility parameter (SP value) is not less than 11.

(7) Thereby, an inkjet ink that, by the mechanisms described above, is solvent based and does not contain water, is unlikely to cause cogation, is also excellent in intermittent printing performance, and yet enables a character of excellent fixing property and abrasion resistance to be printed on a surface of a printing object with a non-absorbing property can be provided.

(8) <Metal Complex Dye>

(9) As the metal complex dye, various metal complex dyes that dissolve in both the first solvent and the second solvent can be used.

(10) Although not restricted thereto, for example, the following various dyes can be cited as specific examples of the metal complex dye.

(11) (Yellow)

(12) C. I. 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 Industries Co., Ltd.; Neo SuperColor Yellow C-131 manufactured by Chuo Synthetic Chemical 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 Technologies Corp.; and Savinyl Yellow 2GLS01, RLS, RLSN, and 2RLS manufactured by Clariant AG.

(13) (Orange)

(14) C. I. solvent orange 5, 6, 11, 20, 41, 54, 56, 58, 59, 62, and 99; VALIFAST ORANGE 2210, 3208, 3209, and 3210 manufactured by Orient Chemical Industries Co., Ltd.; Neo Super Color Orange C-232 manufactured by Chuo Synthetic Chemical Co., Ltd.; Orasol Orange 245, 247, 251, and 272 manufactured by BASF Japan Ltd.; Intraplast Orange G and RLN manufactured by Sensient Technologies Corp.; and Savinyl Orange RLS and RLSE manufactured by Clariant AG.

(15) (Red)

(16) C. I. solvent red 8, 91, 99, 100, 102, 109, 118, 119, 122, 124, 125, 127, 130, 132, 142, 160, 218, and 233; VALIFAST Red 2303, 2320, 3304, 3306, 3311, 3312, and 3320 and PINK 2310N manufactured by Orient Chemical Industries Co., Ltd.; Neo Super Color RED C-431 and PINK C-331 manufactured by Chuo Synthetic Chemical Co., Ltd.; Oleosol Fast RED BL and PINK FB manufactured by Taoka Chemical Co., Ltd.; Orasol Red 330, 335, 355, 363, 365, 385, 395, and 471 and Pink 478 manufactured by BASF Japan Ltd.; Intraplast Red GC and Scarlet 3GL manufactured by Sensient Technologies Corp.; and Savinyl Red 3BLS and 3GLS and Pink 6BLS manufactured by Clariant AG.

(17) (Brown)

(18) C. I. solvent brown 37, 42, 43, and 44; Orasol Brown 324 and 326 manufactured by BASF Japan Ltd.; and Intraplast Brown GC manufactured by Sensient Technologies Corp.

(19) (Blue)

(20) C. I. solvent blue 24, 25, 38, 44, 45, 55, 64, 67, and 70; VALIFAST Blue 2606, 2620, and 2670 manufactured by Orient Chemical Industries Co., Ltd.; Neo Super Color Blue C-555 manufactured by Chuo Synthetic Chemical Co., Ltd.; Orasol Blue 825 and 855 manufactured by BASF Japan Ltd.; Intraplast Blue GN manufactured by Sensient Technologies Corp.; and Savinyl Blue RS and GLS manufactured by Clariant AG.

(21) (Black)

(22) C. I. solvent black 22, 27, 28, 29, 34, 35, and 43; VALIFAST BLACK 3804, 3807, 3808, 3810, 3820, 3830, 3840, 3866, 3870, 3877, and 3878 manufactured by Orient Chemical Industries Co., Ltd.; Neo Super Color Black C-832 manufactured by Chuo Synthetic Chemical Co., Ltd.; Orasol Black X45, X51, and X55 manufactured by BASF Japan Ltd.; Intraplast Black CN and RLS manufactured by Sensient Technologies Corp.; and Savinyl Black RLSN01 manufactured by Clariant AG.

(23) One type or two or more types of the metal complex dye can be blended in appropriate amounts in accordance with a shade of color and color density of the inkjet ink.

(24) However, an amount of the metal complex dye in a total amount of the inkjet ink is preferably not less than 5 mass % and especially preferably not less than 7 mass % and preferably not more than 15 mass % and especially preferably not more than 12 mass %.

(25) Here, the amount mentioned above when just one type of metal complex dye is used is the amount of the just one type of metal complex dye and that when two or more types are used in combination is a total amount of the two or more types of metal complex dyes.

(26) According to examination by the inventor, even among oil-soluble dyes that are solvent-soluble, the effects of the present invention are expressed specifically just in the metal complex dyes.

(27) That is, other oil-soluble dyes besides the metal complex dyes cannot form the structure where the polyoxyethylene based compound is coordinated as mentioned above and therefore do not precipitate or aggregate together with the polyoxyethylene based compound and the tackifier and do not become fixed firmly on a surface of a printing object.

(28) Therefore, an effect of improving the fixing property, the abrasion resistance, etc., of a character formed on a surface of a printing object cannot be obtained with the other oil-soluble dyes besides the metal complex dyes.

(29) <Polyoxyethylene Based Compound>

(30) As the polyoxyethylene based compound, various compounds that are of at least one type selected from a group consisting of polyoxyalkylene glycols and polyoxyalkylene alkyl ethers, have a number average molecular weight Mn is not less than 200, and can be used as a binder can be cited.

(31) As the polyoxyethylene based compound, for example, one type or two or more types among polyethylene glycols, polyoxyethylene alkyl ethers having a structure in which a polyoxyethylene chain and an alkyl group are ether bonded hereinafter mentioned at times by the synonym, “alcohol ethoxylates”, and polyoxyethylene polyoxypropylene glycols each being a block or random copolymer of ethylene oxide (EO) and propylene oxide (PO) hereinafter abbreviated at times as “poloxamer” that is a synonym of a representative block copolymer, etc.

(32) can be cited.

(33) Although not restricted thereto, for example, one type or two or more types of the following various compounds can be cited as specific examples of the polyoxyethylene based compound.

(34) (Polyethylene Glycols)

(35) 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, PEG-6000 number average molecular weight Mn: 8300, and PEG-20000 number average molecular weight Mn: 20000 of the ADEKA (registered trademark) PEG series manufactured by ADEKA Corp.

(36) 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, and 6000 number average molecular weight Mn: 8300 of the Toho Polyethylene Glycol series manufactured by TOHO Chemical Industry Co., Ltd.

(37) (Alcohol Ethoxylates)

(38) Polyoxyethylene lauryl ether bridge 35 number average molecular weight Mn: 1200 manufactured by Junsei Chemical Co., Ltd.

(39) DKS-NL15 number average molecular weight Mn: 2900 manufactured by DKS Co., Ltd.

(40) (Poloxamers)

(41) 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) of the NEWPOL (registered trademark) PE series manufactured by Sanyo Chemical Industries, Ltd.

(42) 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)) of the ADEKA PLURONIC (registered trademark) L series, F-68 (POE (160) POP (30)), F-87 (POE (120) POP (40)), and F-127 (POE (196) POP (67)) of the ADEKA PLURONIC F series, and P-85 (POE (54) POP (39)) and P-123 (POE (42) POP (67)) of the ADEKA PLURONIC P series manufactured by ADEKA Corp.

(43) P188 POE (160) POP (30) and P407 POE (196) POP (67) of the Kolliphor series and F68 POE (160) POP (30) and F127 POE (196) POP (67) of the Lutrol series manufactured by BASF Japan Ltd.

(44) These polyoxyethylene based compounds are compounds that are ordinarily used as nonionic surfactants or raw materials, etc., thereof and are compounds of lower molecular weight than ordinary binder resins that easily cause cogation.

(45) Incidentally, as other binders that do not easily cause cogation, use, for example, of acetylene glycol and other low molecular compounds besides polyoxyethylene based compounds can be considered.

(46) However, these other compounds are low in film formability in comparison to polyoxyethylene based compounds and therefore in some cases do not enable printing of a character of excellent fixing property and abrasion resistance on a surface of a printing object and also cause stickiness such that a quick drying property after printing is decreased.

(47) On the other hand, the polyoxyethylene based compounds have a high film formability and are unlikely to cause stickiness.

(48) Therefore, by combining the polyoxyethylene based compound with both the first and second solvents it becomes possible, by the mechanisms described above, to print a character that is excellent in fixing property, abrasion resistance, and quick drying property on a surface of a printing object without causing cogation.

(49) Among the above, the polyoxyethylene based compound of a number average molecular weight Mn of not less than 400 is preferable, that of not less than 600 is more preferable, and that of not less than 800 is especially preferable.

(50) The polyoxyethylene based compound with a number average molecular weight Mn less than this range is still insufficient in film formability and in some cases does not enable printing of a character of excellent fixing property and abrasion resistance on a surface of a printing object or causes stickiness such that the quick drying property after printing is decreased.

(51) On the other hand, the polyoxyethylene based compound with a number average molecular weight Mn not less than the range mentioned above has an especially high film formability and is even more unlikely to cause stickiness and therefore enables a character that is more excellent in the characteristics mentioned above to be printed.

(52) However, even within the range mentioned above, the number average molecular weight Mn of the polyoxyethylene based compound is preferably not more than 5000 and is especially preferably not more than 4000.

(53) The polyoxyethylene based compound with a number average molecular weight Mn that exceeds this range is too large and is thus decreased in solubility inside the inkjet ink and, for example, tends to easily precipitate during storage of the inkjet ink or easily cause cogation during printing.

(54) On the other hand, the polyoxyethylene based compound with a number average molecular weight Mn that is not more than the range mentioned above is excellent insolubility inside the inkjet ink and can thus suppress the occurrence of precipitation and the causing of cogation more effectively.

(55) Although not restricted thereto, for example, the following various compounds can be cited as especially preferable polyoxyethylene based compounds with which, even in the range mentioned above, the number average molecular weight Mn is in a range of not less than 800 and not more than 4000.

(56) PEG-1000 number average molecular weight Mn: 1000, PEG-1540 number average molecular weight Mn: 1500, and PEG-4000 number average molecular weight Mn: 3000 of the ADEKA PEG series.

(57) 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 of the Toho Polyethylene Glycol series.

(58) Polyoxyethylene lauryl ether bridge 35 number average molecular weight Mn: 1200 manufactured by Junsei Chemical Co., Ltd.

(59) DKS-NL15 number average molecular weight Mn: 2900 manufactured by DKS Co., Ltd.

(60) 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% of the ADEKA PLURONIC L series.

(61) One type or two or more types of these polyoxyethylene based compounds can be used.

(62) An amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye is preferably not less than 2 mass % and especially preferably not less than 3 mass % and preferably not more than 60 mass % and especially preferably not more than 55 mass %.

(63) If the amount of the polyoxyethylene based compound is either less than this range or exceeds this range, the abrasion resistance of a character decreases in some cases.

(64) <Tackifier>

(65) As the tackifier, at least one type of compound selected from a group consisting of terpene phenol resins and rosin esters and with which a hydroxyl value is not less than 30 mgKOH/g and not more than 70 mgKOH/g is used.

(66) The hydroxyl values of both the terpene phenol resins and rosin esters each to be used as the tackifier are restricted to the above range due to the following reasons.

(67) That is, a tackifier with which the hydroxyl value is less than 30 mgKOH/g is too low in polarity and is thus insufficient in solubility with respect to both the first and second solvents and cannot be dissolved satisfactorily inside the inkjet ink in some cases.

(68) Therefore in some cases, discharge becomes unstable such that continuous printing performance is easily decreased or intermittent printing performance is insufficient and clogging of a nozzle is easily caused during a decap time.

(69) On the other hand, a tackifier with which the hydroxyl value exceeds 70 mgKOH/g is high in solubility not just with respect to the solvents but also with respect to water and therefore the effects of improving the intermittent printing performance by the mechanism described above cannot be obtained in some cases.

(70) That is, the tackifier with which the hydroxyl value exceeds 70 mgKOH/g is high in polarity and can thus be dissolved satisfactorily in the solvent mixture and the continuous printing performance is improved.

(71) However, such a tackifier is also high in solubility with respect to water and therefore, even when the inkjet ink is exposed to ambient air inside the nozzle and contacts moisture in the ambient air, cannot precipitate rapidly on the liquid surface and form a satisfactory film capable of suppressing volatilization of the solvents.

(72) A viscosity of the inkjet ink thus increases during the decap time such as to easily cause clogging of the nozzle and the intermittent printing performance decreases in some cases.

(73) Also, especially if a surface of a printing object is constituted of plastic, etc., that is nonporous and low in polarity, an adhesive property of a character tends to decrease easily.

(74) Moreover, there is also a problem in that tackifiers with a high hydroxyl value such as mentioned above are special, few in type, and restricted in choices of characteristics as described above.

(75) On the other hand, tackifiers with which the hydroxyl value is within the range mentioned above are numerous in type, are abundant in choices of characteristics, have appropriate solubilities that are neither too low nor too high with respect to the two types of the first and second solvents differing in SP value, and can be dissolved satisfactorily inside the inkjet ink.

(76) Therefore, the continuous printing performance of the inkjet ink can be improved, the intermittent printing performance can be improved as well, and clogging of the nozzle during the decap time can also be made unlikely to be caused.

(77) Further, the adhesive property of a character can be secured sufficiently even on a surface of a printing object constituted of plastic, etc., of low polarity.

(78) As the terpene phenol resins, various terpene phenol resins each being a copolymer of terpene and a phenol having a basic skeleton (C5H8)p (where p is an integer) with isoprenes bonded head-to-tail successively and with which the hydroxyl value is within the range mentioned above can be used.

(79) Although not restricted thereto, for example, the following various compounds can be cited as specific examples of the terpene phenol resins.

(80) U115 hydroxyl value: 30 mgKOH/g, T80 hydroxyl value: 60 mgKOH/g, T100 hydroxyl value: 60 mgKOH/g, T115 hydroxyl value: 60 mgKOH/g, T130 hydroxyl value: 60 mgKOH/g, and T145 hydroxyl value: 60 mgKOH/g of the YS Polyster series manufactured by Yasuhara Chemical Co., Ltd.

(81) TP95 hydroxyl value: 40 mgKOH/g, TP105 hydroxyl value: 40 mgKOH/g, and TP115 hydroxyl value: 50 mgKOH/g of the SYLVARES (registered trademark) series manufactured by Arizona Chemical Ltd.

(82) Also, as the rosin esters, various rosin esters each being an ester of a rosin mainly constituted of an abietene type or pimarene type resin acid that is a monobasic carboxylic acid with an alkylated hydrophenanthrene nucleus and an alcohol and with which the hydroxyl value is within the range mentioned above can be used.

(83) Here, as the rosin, for example, that constituted of abietic acid, dextropimaric acid, or other resin acid containing an unsaturated bond, a hydrogenated rosin mainly constituted of dihydroabietic acid or tetrahydroabietic acid, etc., that is hydrogenated, and so forth can be cited. Also, as the alcohol, for example, glycerol, pentaerythritol, or triethylene glycol, etc., can be cited.

(84) Although not restricted thereto, for example, the following various compounds can be cited as specific examples of the rosin esters.

(85) PENSEL (registered trademark) D-125 hydroxyl value: 30 mgKOH/g and PINECRYSTAL (registered trademark) KE-359 hydroxyl value: 43 mgKOH/g manufactured by Arakawa Chemical Industries, Ltd.

(86) At least one type of these tackifiers can be used.

(87) An amount of the tackifier in the total amount of the inkjet ink is preferably not less than 0.5 mass % and especially preferably not less than 1 mass % and preferably not more than 5 mass % and especially preferably not more than 4 mass %.

(88) If the amount of the tackifier is less than this range, a satisfactory film capable of sufficiently suppressing the volatilization of the solvents when the inkjet ink is exposed to the ambient air inside the nozzle during the decap time does not form and the viscosity of the inkjet ink increases and the intermittent printing performance decreases in some cases.

(89) On the other hand, if the amount of the tackifier exceeds the range mentioned above, the abrasion resistance and an alcohol resistance of a character decreases in some cases due to the tackifier hardly having any film formability as mentioned above.

(90) Also, due to the viscosity of the inkjet ink increasing and the discharge becoming unstable, the continuous printing performance decreases or cogation is easily caused in some cases.

(91) On the other hand, by setting the amount of the tackifier to be within the range mentioned above, the intermittent printing performance of the inkjet ink can be improved further while suppressing the decreases in abrasion resistance, alcohol resistance, and continuous printing performance and the occurrence of cogation.

(92) If two or more types of the tackifier are to be used in combination, a total amount thereof should be set within the range mentioned above.

(93) <First Solvent>

(94) As mentioned above, as the first solvent, various solvents that are of at least one type selected from the group consisting of ketones, ethers, and esters and with which the SP value is less than 11 are used.

(95) Although not restricted thereto, for example, one type or two or more types of the following various ketones can be cited as specific examples of a ketone.

(96) 2-butanone methyl ethyl ketone (MEK); number of carbon atoms: 4; SP value: 9.3, acetone dimethyl ketone; number of carbon atoms: 3; SP value: 10, 2-pentanone methyl propyl ketone (MPK); number of carbon atoms: 5; SP value: 8.7, 3-pentanone diethyl ketone (DEK); number of carbon atoms: 5; SP value: 8.8, 3-methyl-2-butanone methyl isopropyl ketone (MIPK); number of carbon atoms: 5; SP value: 8.5, 2-methyl-4-pentanone methyl isobutyl ketone (MIBK); number of carbon atoms: 6; SP value: 8.4, 2,6-dimethyl-4-heptanone diisobutyl ketone (DIBK); number of carbon atoms: 9; SP value: 7.8, cyclohexanone number of carbon atoms: 6; SP value: 9.3, and 4-hydroxy-4-methyl-pentan-2-one diacetone alcohol; number of carbon atoms: 6; SP value: 9.2.

(97) Although not restricted thereto, for example, one type or two or more types of the following various ethers can be cited as specific examples of an ether.

(98) 1,4-dioxane dioxane; SP value: 10, 1,1-dimethyldiethyl ether diisopropyl ether; SP value: 6.9, 2-ethoxyethanol ethyl cellosolve (EGMEE); SP value: 10.5, 2-butoxyethanol butyl cellosolve (EGMBE); SP value: 9.5, and methyl tert-butyl ether MTBE.

(99) Also, as the ether, a glycol ether can also be used.

(100) Although not restricted thereto, for example, one type or two or more types of the following various glycol ethers can be cited as specific examples of the glycol ether.

(101) 1-methoxy-2-propanol propylene glycol monomethyl ether (PM); SP value: 10.2, 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 hexyl diglycol, 1-methoxy-2-propyl propanoate methotate, and 1- or 2-(methoxymethylethoxy) propanol dipropylene glycol monomethyl ether (DPM), isomer mixture.

(102) Although not restricted thereto, for example, one type or two or more types of the following various esters can be cited as specific examples of an ester.

(103) Ethyl acetate SP value: 9.1, methyl acetate SP value: 9.6, n-butyl acetate SP value: 8.5, sec-butyl acetate SP value: 8.3, 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, (R)-ethyl-2-hydroxypropanoate ethyl lactate, methyl-2-hydroxypropanoate methyl lactate, and butyl-2-hydroxypropanoate butyl lactate.

(104) Also as the ester, a glycol ester can also be used.

(105) Although not restricted thereto, for example, one type or two or more types of the following various glycol esters can be cited as specific examples of the glycol ester.

(106) 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, and 2-(2-ethoxyethoxy)ethyl acetate ethyl carbitol acetate.

(107) The first solvent is excellent in dissolving ability with respect to the metal complex dye, the polyoxyethylene based compound, and the tackifier and can thus dissolve these components satisfactorily as mentioned above.

(108) Hence, the dissolved metal complex dye, etc., can be suppressed effectively from precipitating during storage of the inkjet ink or causing cogation.

(109) Among the above, as the ketone, a ketone with 3 to 5 carbon atoms and an SP value of not more than 9 is used favorably.

(110) The ketone that satisfies these ranges of number of carbon atoms and SP value is especially excellent in dissolving ability with respect to the metal complex dye, the polyoxyethylene based compound, and the tackifier and can thus further improve the effect of suppressing these components from precipitating or causing cogation.

(111) Among the various ketones given as examples above, for example, 2-pentanone MPK; number of carbon atoms: 5; SP value: 8.7, 3-pentanone DEK; number of carbon atoms: 5; SP value: 8.8, 3-methyl-2-butanone MIPK; number of carbon atoms: 5; SP value: 8.5, etc., can be cited as ketones that satisfy these conditions.

(112) Also, among the various ethers given as examples above, for example, 2-(2-ethoxyethoxy)ethanol ethyl carbitol; SP value: 10.2, 1-methoxy-2-propanol propylene glycol monomethyl ether (PM); SP value: 10.2, etc., can be cited as the ether.

(113) Further, among the various esters given as examples above, for example, ethyl acetate SP value: 9.1, etc., can be cited as the ester.

(114) One type or two or more types of these first solvents can be used.

(115) <Second Solvent>

(116) As the second solvent to be used in combination with the first solvent, an alcohol that includes at least an alcohol with 1 to 3 carbon atoms and with which a solubility parameter (SP value) is not less than 11 is used.

(117) Although not restricted thereto, for example, one type or two or more types of the following various alcohols can be cited as specific examples of such an alcohol.

(118) Methanol methyl alcohol; number of carbon atoms: 1; SP value: 14.5 to 14.8, ethanol ethyl alcohol; number of carbon atoms: 2; SP value: 12.7, 1-propanol propyl alcohol; number of carbon atoms: 3; SP value: 11.97, 2-propanol isopropyl alcohol (IPA); number of carbon atoms: 3; SP value: 11.5, 1-butanol butyl alcohol; number of carbon atoms: 4; SP value: 11.4, and 2-butanol sec-butyl alcohol; number of carbon atoms: 4; SP value: 11.

(119) These alcohols, especially when the inkjet ink is used in a thermal type inkjet printer and heated, volatilize and foam as a forming component of bubbles and function to form and discharge ink droplets of predetermined volume through a nozzle.

(120) Also, by using these alcohols as the second solvent in combination, a material adaptability, that is, a material compatibility of the inkjet ink with a member forming the head, etc., of the inkjet printer, etc., can be improved.

(121) Also, in particular, the alcohols with 1 to 3 carbon atoms are low in boiling point and high in volatility in comparison to other alcohols besides these with an SP value not less than 11 and can thus further improve the quick drying property of the inkjet ink after printing.

(122) Therefore, although it is preferable to use the alcohol with 1 to 3 carbon atoms solely (including a case where two or more types of the alcohols with 1 to 3 carbon atoms are used in combination; the same applies hereinafter) as the second solvent, the alcohol with 1 to 3 carbon atoms may be used in combination with another alcohol besides it.

(123) However, in a case of combined use, an amount of the alcohol with 1 to 3 carbon atoms is preferably not less than 70 mass % in a total amount of the second solvent such as not to compromise the quick drying property of the inkjet ink.

(124) Also, an upper limit of the alcohol with 1 to 3 carbon atoms is 100 mass % from a standpoint of the quick drying property.

(125) That is, as mentioned above, it is preferable for an entire amount of the second solvent to be the alcohol with 1 to 3 carbon atoms.

(126) <Regarding the Amount of Solvent>

(127) The amount of the first solvent in a total amount of the first solvent and the alcohol as the second solvent is preferably not less than 4 mass % and especially preferably not less than 5 mass % and preferably not more than 42 mass % and especially preferably not more than 40 mass %.

(128) If the amount of the first solvent is less than this range, satisfactory dissolving ability with respect to the metal complex dye, etc., cannot be maintained and precipitation occurs easily during storage of the inkjet ink or cogation is caused easily during printing in some cases.

(129) On the other hand, if the amount of the first solvent is greater than the range mentioned above, the amount of the second solvent becomes low relatively and therefore, the material compatibility of the inkjet ink becomes poor and various defects due to erosion and dissolution of a member constituting the head, etc., are caused in some cases.

(130) That is, if a member constituting the head, etc., becomes eroded or dissolved and becomes mixed into the inkjet ink and, for example, precipitates as an insoluble component inside the nozzle, the discharge of the inkjet ink becomes unstable and nozzle clogging is caused to decrease the continuous printing performance in some cases.

(131) Also, in some cases, the insoluble component obstructs the discharge of the ink droplets such that a trajectory of the discharged ink droplets changes or chipping or blurring of a character is caused thereby.

(132) Further, in some cases, the precipitated insoluble component impedes the film of the tackifier from forming on the liquid surface inside the nozzle during the decap time and becomes a cause of decreasing the intermittent printing performance.

(133) Also, in some cases, the amount of the alcohol as the second solvent that functions as the forming component of bubbles upon being heated in use in a thermal type inkjet printer becomes insufficient such that even if the inkjet ink is heated, bubbles cannot be formed satisfactory and appropriate ink droplets cannot be discharged.

(134) On the other hand, by setting the amount of the first solvent to be within the range mentioned above, the solubility of the metal complex dye, etc., inside the inkjet ink can be improved to satisfactorily suppress precipitation and cogation from occurring.

(135) Also, the material compatibility of the inkjet ink can be improved to satisfactorily suppress the occurrence of the various defects mentioned above due to erosion and dissolution of a member constituting the head, etc.

(136) Further, when the inkjet ink is used in a thermal type inkjet printer and heated, bubbles can be formed satisfactorily to discharge appropriate ink droplets.

(137) <Other Components>

(138) In addition to the respective components described above, a binder resin may further be blended in the inkjet ink.

(139) By blending the binder resin together with the polyoxyethylene based compound and the tackifier, the fixing property and the abrasion resistance, especially of a character formed on a surface of the corona-treated OPP mentioned above, etc., can be improved even further.

(140) However, the binder resin becomes a cause of cogation as mentioned above and is preferably restricted to a small amount even when it is blended.

(141) Even by blending at such a small amount, the fixing property and the abrasion resistance of a character can be improved by combined use with the polyoxyethylene based compound and the tackifier.

(142) Specifically, an amount of the binder resin in the total amount of the inkjet ink is preferably not more than 5 mass % and more preferably not more than 2 mass %.

(143) Especially in consideration of occurrence of cogation, etc., the amount of the binder resin is preferably 0 mass % even within the range mentioned above, that is, it is after all preferable for the binder resin not to be contained (excluded).

(144) The inkjet ink of the present invention that contains the respective components described above can be used in the drop-on-demand type inkjet printer mentioned above. It can be used especially favorably in a drop-on-demand type inkjet printer that is of a thermal type.

EXAMPLES

(145) Although the present invention shall now be described based on examples and comparative examples, the arrangement of the present invention is not necessarily restricted to these examples.

Example 1

(146) The respective components indicated below were blended and thereafter filtered using a 5 μm membrane filter to prepare an inkjet ink.

(147) TABLE-US-00001 TABLE 1 Component Mass % Colorant 9 Polyoxyethylene based compound 2 Tackifier 2 First solvent (ketone) 20 Second solvent (alcohol) 67 Total amount 100

(148) The respective components in the table are as follows.

(149) Colorant: Metal complex dye VALIFAST BLACK 3810 manufactured by Orient Chemical Industries Co., Ltd.

(150) Polyoxyethylene based compound: ADEKA PEG-1000 polyethylene glycol; number average molecular weight Mn: 1000 manufactured by ADEKA Corp.

(151) Tackifier: Terpene phenol resin YS Polyster T80 manufactured by Yasuhara Chemical Co., Ltd.; hydroxyl value: 60 mgKOH/g

(152) First solvent (ketone): 3-methyl-2-butanone methyl isopropyl ketone (MIPK); number of carbon atoms: 5; SP value: 8.5

(153) Second solvent: Ethanol ethyl alcohol; number of carbon atoms: 2; SP value: 12.7

(154) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 2

(155) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of polyoxyethylene lauryl ether bridge 35alcohol ethoxylate; number average molecular weight Mn: 1200 manufactured by Junsei Chemical Co., Ltd. as the polyoxyethylene based compound.

(156) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 3

(157) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of ADEKA PLURONIC L-31 poloxamer; POE (3) POP (17); number average molecular weight Mn: 1100, POE content: 10% manufactured by ADEKA Corp. as the polyoxyethylene based compound.

(158) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 4

(159) An inkjet ink was prepared in the same manner as in Example 1 with the exception of using 60 mass % of ethanol and 7 mass % of 2-propanol isopropyl alcohol (IPA); number of carbon atoms: 3; SP value: 11.5 in combination as the second solvent.

(160) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 5

(161) An inkjet ink was prepared in the same manner as in Example 1 with the exception of using 60 mass % of ethanol and 7 mass % of 1-butanol butyl alcohol; number of carbon atoms: 4; SP value: 11.4 in combination as the second solvent.

(162) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 6

(163) An inkjet ink was prepared in the same manner as in Example 1 with the exception of using 2 mass % of MIPK and 18 mass % of 2-(2-ethoxyethoxy)ethanol ethyl carbitol; SP value: 10.2 in combination as the first solvent.

(164) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 7

(165) An inkjet ink was prepared in the same manner as in Example 1 with the exception of using 2 mass % of MIPK and 18 mass % of 1-methoxy-2-propanol propylene glycol monomethyl ether (PM); SP value: 10.2 in combination as the first solvent.

(166) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 8

(167) An inkjet ink was prepared in the same manner as in Example 1 with the exception of using 2 mass % of MIPK and 18 mass % of ethyl acetate SP value: 9.1 in combination as the first solvent.

(168) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 9

(169) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of MIPK, the same amount of 2-butanone methyl ethyl ketone (MEK); number of carbon atoms: 4; SP value: 9.3 as the first solvent.

(170) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 10

(171) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of MIPK, the same amount of 2-(2-ethoxyethoxy)ethanol as the first solvent.

(172) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 11

(173) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of MIPK, the same amount of 1-methoxy-2-propanol as the first solvent.

(174) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 12

(175) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of MIPK, the same amount of ethyl acetate as the first solvent.

(176) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 13

(177) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of Toho Polyethylene Glycol 2000 number average molecular weight Mn: 2000 manufactured by TOHO Chemical Industry Co., Ltd. as the polyoxyethylene based compound.

(178) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 14

(179) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of DKS-NL15 number average molecular weight Mn: 2900 manufactured by DKS Co., Ltd. as the polyoxyethylene based compound.

(180) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 15

(181) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of ADEKA PLURONIC L-61 POE (5) POP (30); number average molecular weight Mn: 2000, POE content: 10% manufactured by ADEKA Corp. as the polyoxyethylene based compound.

(182) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 16

(183) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of ADEKA PEG-600 number average molecular weight Mn: 600 manufactured by ADEKA Corp. as the polyoxyethylene based compound.

(184) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 17

(185) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of ADEKA PEG-400 number average molecular weight Mn: 400 manufactured by ADEKA Corp. as the polyoxyethylene based compound.

(186) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 18

(187) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of ADEKA PLURONIC L 101 (POE (8) POP (55)); number average molecular weight Mn: 3800, POE content: 10) manufactured by ADEKA Corp. as the polyoxyethylene based compound.

(188) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 19

(189) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000, the same amount of ADEKA PLURONIC L-121 POE (10) POP (65); number average molecular weight Mn: 4500, POE content: 10% manufactured by ADEKA Corp. as the polyoxyethylene based compound.

(190) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 20

(191) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of ADEKA PEG-1000 as the polyoxyethylene based compound to 0.2 mass % and setting the amount of ethanol as the second solvent to 68.8 mass %.

(192) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 2.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 22.5 mass %.

Example 21

(193) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of ADEKA PEG-1000 as the polyoxyethylene based compound to 0.3 mass % and setting the amount of ethanol as the second solvent to 68.7 mass %.

(194) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 3.3 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 22.5 mass %.

Example 22

(195) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of ADEKA PEG-1000 as the polyoxyethylene based compound to 4.5 mass % and setting the amount of ethanol as the second solvent to 64.5 mass %.

(196) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 50.0 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.7 mass %.

Example 23

(197) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of ADEKA PEG-1000 as the polyoxyethylene based compound to 5 mass % and setting the amount of ethanol as the second solvent to 64 mass %.

(198) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 55.6 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.8 mass %.

Comparative Example 1

(199) Although, in place of YS Polyster T80, the same amount of YS Polyster U130 terpene phenol resin; hydroxyl value: 25 mgKOH/g manufactured by Yasuhara Chemical Co., Ltd. was blended as the tackifier, an entire amount thereof could not be dissolved.

(200) The preparation of an inkjet ink and subsequent tests were therefore abandoned.

(201) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 24

(202) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of YS Polyster T80, the same amount of YS Polyster U115 terpene phenol resin; hydroxyl value: 30 mgKOH/g manufactured by Yasuhara Chemical Co., Ltd. as the tackifier.

(203) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 25

(204) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of YS Polyster T80, the same amount of SYLVARES TP115 terpene phenol resin; hydroxyl value: 50 mgKOH/g manufactured by Arizona Chemical Ltd. as the tackifier.

(205) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Comparative Example 2

(206) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of YS Polyster T80, the same amount of YS Polyster 5145 terpene phenol resin; hydroxyl value: 100 mgKOH/g manufactured by Yasuhara Chemical Co., Ltd. as the tackifier.

(207) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Example 26

(208) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of MIPK as the first solvent to 4 mass % and setting the amount of ethanol as the second solvent to 83 mass %.

(209) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 4.6 mass %.

Example 27

(210) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of MIPK as the first solvent to 5 mass % and setting the amount of ethanol as the second solvent to 82 mass %.

(211) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 5.7 mass %.

Example 28

(212) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of MIPK as the first solvent to 32 mass % and setting the amount of ethanol as the second solvent to 55 mass %.

(213) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 36.8 mass %.

Example 29

(214) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of MIPK as the first solvent to 36 mass % and setting the amount of ethanol as the second solvent to 51 mass %.

(215) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 41.4 mass %.

Example 30

(216) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of YS Polyster T80 as the tackifier to 0.5 mass % and setting the amount of ethanol as the second solvent to 68.5 mass %.

(217) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 22.6 mass %.

Example 31

(218) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of YS Polyster T80 as the tackifier to 1 mass % and setting the amount of ethanol as the second solvent to 68 mass %.

(219) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 22.7 mass %.

Example 32

(220) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of YS Polyster T80 as the tackifier to 4 mass % and setting the amount of ethanol as the second solvent to 65 mass %.

(221) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.5 mass %.

Example 33

(222) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of YS Polyster T80 as the tackifier to 5 mass % and setting the amount of ethanol as the second solvent to 64 mass %.

(223) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.8 mass %.

Comparative Example 3

(224) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, as the colorant, the same amount of an oil-soluble dye OIL BLACK 860 manufactured by Orient Chemical Industries Co., Ltd. that is not a metal complex dye.

(225) The amount of the polyoxyethylene based compound with respect to the amount of the oil-soluble dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Comparative Example 4

(226) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of MIPK as the first solvent to 87 mass % and not blending ethanol as the second solvent.

(227) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 100.0 mass %.

Comparative Example 5

(228) An inkjet ink was prepared in the same manner as in Example 1 with the exception of setting the amount of ethanol as the second solvent to 87 mass % and not blending MIPK as the first solvent.

(229) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 0 mass %.

Comparative Example 6

(230) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of YS Polyster T80, 10 mass % of YS Polyster 5145 terpene phenol resin; hydroxyl value: 100 mgKOH/g manufactured by Yasuhara Chemical Co., Ltd. as the tackifier, setting the amount of ethanol as the second solvent to 79%, and not blending MIPK as the first solvent.

(231) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 22.2 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 0 mass %.

Comparative Example 7

(232) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000 as the polyoxyethylene based compound, the same amount of sorbitan lauryl ester ADEKA ESTOL S-20 manufactured by ADEKA Corp..

(233) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 0 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Comparative Example 8

(234) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000 as the polyoxyethylene based compound, the same amount of an acetylene glycol OLFINE (registered trademark) E1020 manufactured by Nissin Chemical Industry Co., Ltd..

(235) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 0 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Comparative Example 9

(236) An inkjet ink was prepared in the same manner as in Example 1 with the exception of blending, in place of ADEKA PEG-1000 as the polyoxyethylene based compound, the same amount of an acrylic resin JONCRYL 682 manufactured by BASF Japan Ltd. as a binder resin.

(237) The amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye was 0 mass % and the amount of the first solvent in the total amount of the first solvent and the second solvent was 23.0 mass %.

Comparative Example 10

(238) An inkjet ink was prepared in the same manner as in Example 1 with the exception of not blending YS Polyster T80 as the tackifier, setting the amount of MIPK as the first solvent to 18 mass %, and using 69 mass % of ethanol and 2 mass % of 1-butanol in combination as the second solvent.

(239) <Continuous Printing Performance Test>

(240) Using a drop-on-demand type inkjet printer of a thermal type, solid images each of 0.5 inches×0.5 inches were printed continuously at a resolution of 300×300 dpi on a surface of a corona-treated OPP with each of the inkjet inks prepared in the Examples and Comparative Examples.

(241) The printed solid images were then observed, the number of times of printing for which chipping or omission due to a discharge defect of the inkjet ink caused mainly by cogation, etc., did not occur was recorded and the continuous printing performance was evaluated by the following standards.

(242) ∘: Not less than 30,000 times.

(243) Δ: Not less than 10,000 times but less than 30,000 times.

(244) x: Less than 10,000 times.

(245) <Abrasion Resistance Test>

(246) Using the same inkjet printer as that used in the continuous printing performance test, a barcode of 0.2 pt line width: 0.07 mm was printed on a surface of a corona-treated OPP with each of the inkjet inks prepared in the Examples and Comparative Examples.

(247) Next, changes when the printed barcode was rubbed for 10 reciprocations with a cotton swab were observed and the abrasion resistance was evaluated by the following standards.

(248) ∘: No changes were seen in the barcode even when rubbed.

(249) Δ: Although when rubbed, elongation was seen in a portion of the barcode, chipping was not seen.

(250) x: Elongation and chipping were seen at least in a portion of the barcode when rubbed.

(251) <Quick Drying Property Test>

(252) Using the same inkjet printer as that used in the continuous printing performance test, a character of approximately 8.5 pt was printed at a resolution of 300×300 dpi on a surface of a corona-treated OPP with each of the inkjet inks prepared in the Examples and Comparative Examples.

(253) Next, the printed character was dried for a certain time until the character does not become removed even when rubbed with a cotton swab and the time required for this was recorded and the quick drying property was evaluated by the following standards.

(254) ∘: Less than 10 seconds.

(255) Δ: Not less than 10 seconds but less than 15 seconds.

(256) x: Not less than 15 seconds.

(257) <Intermittent Printing Performance Test>

(258) Using the same inkjet printer as that used in the continuous printing performance test, a character of approximately 8.5 pt was printed at a resolution of 300×300 dpi on a surface of a corona-treated OPP with each of the inkjet inks prepared in the Examples and Comparative Examples.

(259) Next, the inkjet printer was left to stand in a decapped state for a certain time under an environment of ordinary temperature and low humidity (25° C., 30%) and then printed again to record the standing time during which clear character without blur, etc., could be printed and the intermittent printing performance was evaluated by the following standards.

(260) ∘: Not less than 10 minutes.

(261) Δ: Not less than 5 minutes but less than 10 minutes.

(262) x: Less than 5 minutes.

(263) <Storage Stability Test>

(264) Changes in state after 1 day and after 2 days when each of the inkjet inks prepared in the Examples and Comparative Examples was placed and sealed in a screw cap bottle and thereupon contained inside a freezer and stored at −20° C. were observed. Storage stability was then evaluated by the following standards.

(265) ∘: No changes were seen at all even after 1 day and even after 2 days.

(266) Δ: Although no changes were seen after 1 day, precipitation was seen after 2 days.

(267) x: Precipitation was seen after 1 day.

(268) <Material Compatibility Test>

(269) Each of the inkjet inks prepared in the Examples and Comparative Examples was filled into an ink cartridge, stored at 45° C., and every other week, a character was printed upon installing the stored ink cartridge in an inkjet printer. Presence/non-presence of chipping or blurring of the character caused by the material compatibility being poor was then observed and the material compatibility was evaluated by the following standards.

(270) ∘: No chipping or blurring was seen even in observations on the 6th week and onward.

(271) Δ: Although chipping or blurring was seen in observation on the 5th week, no chipping or blurring was seen up to the 4th week.

(272) x: Chipping or blurring was seen by the 4th week or earlier.

(273) The results of the above are shown in Table 2 to Table 10. Here, in each table, the symbols in the column of the polyoxyethylene based compound are as follows.

(274) PEG: polyethylene glycol

(275) AE: alcohol ethoxylate

(276) PLX: poloxamer

(277) TABLE-US-00002 TABLE 2 Example Example Example Example Example 1 2 3 4 5 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG AE PLX PEG PEG based compound Number average 1000 1200 1100 1000 1000 molecular weight Mn Mass % 2 2 2 2 2 Mass % 22.2 22.2 22.2 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 60 60 Mass % 2 2 2 2 2 Solvent First solvent: Ketone MIPK: 8.5 20 20 20 20 20 SP value MEK: 9.3 — — — — — Ethyl carbitol: — — — — — 10.2 PM: 10.2 — — — — — Ethyl acetate: — — — — — 9.1 Second solvent: Ethanol: 12.7 67 67 67 60 60 SP value 2-propanol: 11.5 — — — 7 — 1-butanol: 11.4 — — — — 7 Amount of first solvent (mass %) 23.0 23.0 23.0 23.0 23.0 Evaluation Continuous printing property ○ ○ ○ ○ ○ Abrasion resistance ○ ○ ○ ○ ○ Quick drying property ○ ○ ○ ○ ○ Intermittent printing performance ○ ○ ○ ○ ○ Storage stability ○ ○ ○ ○ ○ Material compatibility ○ ○ ○ ○ ○

(278) TABLE-US-00003 TABLE 3 Example Example Example Example Example 6 7 8 9 10 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG PEG PEG PEG PEG based compound Number average 1000 1000 1000 1000 1000 molecular weight Mn Mass % 2 2 2 2 2 Mass % 22.2 22.2 22.2 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 60 60 Mass % 2 2 2 2 2 Solvent First solvent: Ketone MIPK: 8.5 2 2 2 — — SP value MEK: 9.3 — — — 20 — Ethyl carbitol: 18 — — — 20 10.2 PM: 10.2 — 18 — — — Ethyl acetate: — — 18 — — 9.1 Second solvent: Ethanol: 12.7 67 67 67 67 67 SP value 2-propanol: 11.5 — — — — — 1-butanol: 11.4 — — — — — Amount of first solvent (mass %) 23.0 23.0 23.0 23.0 23.0 Evaluation Continuous printing property ○ ○ ○ ○ ○ Abrasion resistance ○ ○ ○ ○ ○ Quick drying property ○ ○ ○ ○ ○ Intermittent printing performance ○ ○ ○ ○ ○ Storage stability ○ ○ ○ ○ ○ Material compatibility ○ ○ ○ ○ ○

(279) TABLE-US-00004 TABLE 4 Example Example Example Example Example 11 12 13 14 15 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG PEG PEG AE PLX based compound Number average 1000 1000 2000 2900 2000 molecular weight Mn Mass % 2 2 2 2 2 Mass % 22.2 22.2 22.2 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 60 60 Mass % 2 2 2 2 2 Solvent First solvent: Ketone MIPK: 8.5 — — 20 20 20 SP value MEK: 9.3 — — — — — Ethyl carbitol: — — — — — 10.2 PM: 10.2 20 — — — — Ethyl acetate: — 20 — — — 9.1 Second solvent: Ethanol: 12.7 67 67 67 67 67 SP value 2-propanol: 11.5 — — — — — 1-butanol: 11.4 — — — — — Amount of first solvent (mass %) 23.0 23.0 23.0 23.0 23.0 Evaluation Continuous printing property ○ ○ ○ ○ ○ Abrasion resistance ○ ○ ○ ○ ○ Quick drying property ○ ○ ○ ○ ○ Intermittent printing performance ○ ○ ○ ○ ○ Storage stability ○ ○ ○ ○ ○ Material compatibility ○ ○ ○ ○ ○

(280) TABLE-US-00005 TABLE 5 Example Example Example Example Example 16 17 18 19 20 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG PEG PLX PLX PEG based compound Number average 600 400 3800 4500 1000 molecular weight Mn Mass % 2 2 2 2 0.2 Mass % 22.2 22.2 22.2 22.2 2.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 60 60 Mass % 2 2 2 2 2 Solvent First solvent: Ketone MIPK: 8.5 20 20 20 20 20 SP value MEK: 9.3 — — — — — Ethyl carbitol: — — — — — 10.2 PM: 10.2 — — — — — Ethyl acetate: — — — — — 9.1 Second solvent: Ethanol: 12.7 67 67 67 67 68.8 SP value 2-propanol: 11.5 — — — — — 1-butanol: 11.4 — — — — — Amount of first solvent (mass %) 23.0 23.0 23.0 23.0 22.5 Evaluation Continuous printing property ○ ○ ○ ○ ○ Abrasion resistance ○ ○ ○ ○ Δ Quick drying property Δ Δ ○ ○ ○ Intermittent printing performance ○ ○ ○ ○ ○ Storage stability ○ ○ ○ Δ ○ Material compatibility ○ ○ ○ ○ ○

(281) TABLE-US-00006 TABLE 6 Comparative Example Example Example Example Example 21 22 23 1 24 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG PEG PEG PEG PEG based compound Number average 1000 1000 1000 1000 1000 molecular weight Mn Mass % 0.3 4.5 5 2 2 Mass % 3.3 50.0 55.6 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 25 30 Mass % 2 2 2 2 2 Solvent First solvent: Ketone MIPK: 8.5 20 20 20 20 20 SP value MEK: 9.3 — — — — — Ethyl carbitol: — — — — — 10.2 PM: 10.2 — — — — — Ethyl acetate: — — — — — 9.1 Second solvent: Ethanol: 12.7 68.7 64.5 64 67 67 SP value 2-propanol: 11.5 — — — — — 1-butanol: 11.4 — — — — Amount of first solvent (mass %) 22.5 23.7 23.8 23.0 23.0 Evaluation Continuous printing property ○ ○ ○ — ○ Abrasion resistance ○ ○ Δ — ○ Quick drying property ○ ○ ○ — ○ Intermittent printing performance ○ ○ ○ — ○ Storage stability ○ ○ ○ — ○ Material compatibility ○ ○ ○ — ○

(282) TABLE-US-00007 TABLE 7 Comparative Example Example Example Example Example 25 2 26 27 28 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG PEG PEG PEG PEG based compound Number average 1000 1000 1000 1000 1000 molecular weight Mn Mass % 2 2 2 2 2 Mass % 22.2 22.2 22.2 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 50 100 60 60 60 Mass % 2 2 2 2 2 Solvent First solvent: Ketone MIPK: 8.5 20 20 4 5 32 SP value MEK: 9.3 — — — — — Ethyl carbitol: — — — — — 10.2 PM: 10.2 — — — — — Ethyl acetate: — — — — — 9.1 Second solvent: Ethanol: 12.7 67 67 83 82 55 SP value 2-propanol: 11.5 — — — — — 1-butanol: 11.4 — — — — — Amount of first solvent (mass %) 23.0 23.0 4.6 5.7 36.8 Evaluation Continuous printing property ○ ○ Δ ○ ○ Abrasion resistance ○ ○ ○ ○ ○ Quick drying property ○ ○ ○ ○ ○ Intermittent printing performance ○ x ○ ○ ○ Storage stability ○ ○ Δ ○ ○ Material compatibility ○ ○ ○ ○ ○

(283) TABLE-US-00008 TABLE 8 Example Example Example Example Example 29 30 31 32 33 Colorant Metal complex dye (mass %) 9 9 9 9 9 Oil-soluble dye (mass %) — — — — — Binder Polyoxyethylene Type PEG PEG PEG PEG PEG based compound Number average 1000 1000 1000 1000 1000 molecular weight Mn Mass % 2 2 2 2 2 Mass % 22.2 22.2 22.2 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — — Acetylene glycol (mass %) — — — — — Acrylic resin (mass %) — — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 60 60 Mass % 2 0.5 1 4 5 Solvent First solvent: Ketone MIPK: 8.5 36 20 20 20 20 SP value MEK: 9.3 — — — — — Ethyl carbitol: — — — — — 10.2 PM: 10.2 — — — — — Ethyl acetate: — — — — — 9.1 Second solvent: Ethanol: 12.7 51 68.5 68 65 64 SP value 2-propanol: 11.5 — — — — — 1-butanol: 11.4 — — — — — Amount of first solvent (mass %) 41.4 22.6 22.7 23.5 23.8 Evaluation Continuous printing property Δ ○ ○ ○ Δ Abrasion resistance ○ ○ ○ ○ ○ Quick drying property ○ ○ ○ ○ Δ Intermittent printing performance ○ Δ ○ ○ ○ Storage stability ○ ○ ○ ○ ○ Material compatibility Δ ○ ○ ○ ○

(284) TABLE-US-00009 TABLE 9 Comparative Comparative Comparative Comparative Example Example Example Example 3 4 5 6 Colorant Metal complex dye (mass %) — 9 9 9 Oil-soluble dye (mass %) 9 — — — Binder Polyoxyethylene Type PEG PEG PEG PEG based compound Number average 1000 1000 1000 1000 molecular weight Mn Mass % 2 2 2 2 Mass % 22.2 22.2 22.2 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) — — — — Acetylene glycol (mass %) — — — — Acrylic resin (mass %) — — — — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 100 Mass % 2 2 2 10 Solvent First solvent: Ketone MIPK: 8.5 20 87 — — SP value MEK: 9.3 — — — — Ethyl carbitol: — — — — 10.2 PM: 10.2 — — — — Ethyl acetate: — — — — 9.1 Second solvent: Ethanol: 12.7 67 — 87 79 SP value 2-propanol: 11.5 — — — — 1-butanol: 11.4 — — — — Amount of first solvent (mass %) 23.0 100.0 — — Evaluation Continuous printing property ○ x x x Abrasion resistance x ○ ○ x Quick drying property ○ ○ ○ x Intermittent printing performance ○ x x ○ Storage stability ○ ○ x ○ Material compatibility ○ x ○ ○

(285) TABLE-US-00010 TABLE 10 Comparative Comparative Comparative Comparative Example Example Example Example 7 8 9 10 Colorant Metal complex dye (mass %) 9 9 9 9 Oil-soluble dye (mass %) — — — — Binder Polyoxyethylene Type — — — PEG based compound Number average — — — 1000 molecular weight Mn Mass % — — — 2 Mass % — — — 22.2 (vs Colorant) Sorbitan lauryl ester (mass %) 2 — — — Acetylene glycol (mass %) — 2 — — Acrylic resin (mass %) — — 2 — Tackifier Hydroxyl value (mgKOH/g) 60 60 60 — Mass % 2 2 2 — Solvent First solvent: Ketone MIPK: 8.5 20 20 20 18 SP value MEK: 9.3 — — — — Ethyl carbitol: — — — — 10.2 PM: 10.2 — — — — Ethyl acetate: — — — — 9.1 Second solvent: Ethanol: 12.7 67 67 67 69 SP value 2-propanol: 11.5 — — — — 1-butanol: 11.4 — — — 2 Amount of first solvent (mass %) 23.0 23.0 23.0 20.2 Evaluation Continuous printing property ○ ○ x ○ Abrasion resistance x x ○ ○ Quick drying property ○ ○ ○ ○ Intermittent printing performance ○ ○ x x Storage stability ○ ○ ○ ○ Material compatibility ○ ○ ○ ○

(286) From the results of Examples 1 to 33 and Comparative Examples 1 to 3 and 6 to 10 in Table 2 to Table 10, it was found that the colorant must contain a metal complex dye, a polyoxyethylene based compound must be used as a binder, a tackifier must further be contained, and a terpene phenol resin and/or a rosin ester with which the hydroxyl value is 30 to 70 mgKOH/g must be used as the tackifier.

(287) From the results of Examples 1 to 33 and Comparative Examples 4 to 6, it was found that a first solvent of at least one type selected from a group consisting of ketones, ethers, and esters and with which the SP value is less than 11 and a second solvent being an alcohol including at least an alcohol with 1 to 3 carbon atoms and with which the SP value is not less than 11 must be used in combination as a solvent.

(288) From the results of Examples 1 to 3 and 13 to 19, it was found that a polyethylene glycol, an alcohol ethoxylate, or a poloxamer can be used as the polyoxyethylene based compound, the number average molecular weight Mn of the polyoxyethylene based compound must be not less than 200 and even then, is preferably not less than 400, more preferably not less than 600, and especially preferably not less than 800, and yet even in the range mentioned above, the number average molecular weight Mn is preferably not more than 5000 and especially preferably not more than 4000.

(289) From the results of Examples 1 and 20 to 23, it was found that the amount of the polyoxyethylene based compound with respect to the amount of the metal complex dye is preferably not less than 2 mass % and especially preferably not less than 3 mass % and preferably not more than 60 mass % and especially preferably not more than 55 mass %.

(290) From the results of Examples 1 and 26 to 29, it was found that the amount of the first solvent in the total amount of the first solvent and the second solvent is preferably not less than 4 mass % and especially preferably not less than 5 mass % and preferably not more than 42 mass % and especially preferably not more than 40 mass %.

(291) Further, from the results of Examples 1 and 30 to 33, it was found that the amount of the tackifier in the total amount of the inkjet ink is preferably not less than 0.5 mass % and especially preferably not less than 1 mass % and preferably not more than 5 mass % and especially preferably not more than 4 mass %.

(292) The present application corresponds to Japanese Patent Application No. 2019-227263 filed on Dec. 17, 2019 in the Japan Patent Office, and the entire disclosure of this application is individually incorporated herein by reference.

(293) While preferred embodiments of the present invention were described in detail above, these are merely specific examples used to clarify the technical contents of the present invention and the present invention should not be interpreted as being limited to these specific examples and the scope of the present invention is limited only by the appended claims.