Oil-based inkjet ink

Abstract

To provide an oil-based inkjet ink that prevents bleeding due to dyeing of dye lake pigments and is suitable for inkjet printing. The present invention provides an oil-based inkjet ink containing a dye lake pigment and a fatty acid ester solvent represented by the following general formula (1): 1 and R 2 are each independently a hydrocarbon group, and R 1 and R 2 at least one of R has a side chain bonded to at least one of the α-position carbon atom and the β-position carbon atom; 1 the α- and β-position carbon atoms of R 2 The total number of carbon atoms in the side chains bonded to the α- and β-carbon atoms is 4 or more. TIFF2022017300000008.tif35169

Description

Technical Field

[0001] The present invention relates to an oil-based inkjet ink.

Background Art

[0002] In the inkjet recording method, highly fluid inkjet ink is ejected as droplets from a fine nozzle, and an image is recorded on a recording medium placed opposite the nozzle. Since it can record at low noise and high speed, it has been rapidly spreading in recent years. As inks used in such an inkjet recording method, there are water-based inks containing water as a main solvent, ultraviolet curable inks (UV inks) containing a high content of polymerizable monomers as a main component, hot melt inks (solid inks) containing a high content of wax as a main component, and so-called non-aqueous inks containing a non-aqueous solvent as a main solvent. Non-aqueous inks can be classified into solvent inks (solvent-based inks) whose main solvent is a volatile organic solvent and oil-based inks (oil-based inks) whose main solvent is a low-volatile or non-volatile organic solvent. Solvent inks mainly dry on the recording medium by evaporation of the organic solvent, while oil-based inks mainly dry by penetration into the recording medium.

[0003] Since the colorants of inks used in the inkjet recording method are excellent in light resistance, weather resistance, and water resistance required for high-quality printing, inks using pigments as colorants tend to increase. Among the pigments used in oil-based inks, there are mordant lake pigments. A mordant lake pigment is a pigment obtained by insolubilizing a water-soluble dye and fixing it to a extender pigment. It can obtain various hues derived from the dye and is also excellent in light resistance, weather resistance, and water resistance.

[0004] In Patent Document 1 (Japanese Patent Application Laid-Open No. 2012-224781), a non-aqueous pigment ink using two or more lake pigments has been proposed in order to improve color reproducibility and storage stability. In Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-19766), in a non-aqueous inkjet ink, in order to obtain a printed matter with high density and high color saturation, a xanthene-based pigment, which is one of the mordant lake pigments, is used.

[0005] In Patent Document 3 (Japanese Patent Application Laid-Open No. 2007-154149), an inkjet non-aqueous ink composition having high ejection stability without swelling or greatly deforming a transparent film is proposed, which contains a pigment, a dispersant, and a non-aqueous solvent, and 50% or more of the total weight of the non-aqueous solvent is an ester-based solvent having 24 to 36 carbon atoms.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] In Patent Documents 1 and 2, a non-aqueous ink is prepared by blending a pigment into a non-aqueous solvent obtained by combining an ester-based solvent, an alcohol-based solvent, and a non-polar solvent. The mordant lake pigment may be dyed in a polar solvent such as an ester-based solvent or an alcohol-based solvent. Due to the dyed components, problems such as bleeding occurring at the boundary between the printed area and the unprinted area of the printed matter and a decrease in light resistance occur.

[0008] In Patent Document 3, although it is disclosed that an ester-based solvent is used to prevent deformation of a transparent film, the problem of bleeding of the printed matter has not been studied. In addition, an ester-based solvent having a high number of carbon atoms has a problem of a decrease in ejection performance because it has a relatively high viscosity.

[0009] Isocetyl 2-ethylhexanoate used in the examples of Patent Document 3 has 24 carbon atoms, but the side chain of the fatty acid side has 2 carbon atoms, and the carbon number of the side chain of the alcohol side is unknown. The inks of Comparative Examples 1 to 6 of Patent Document 1 use ester solvents having 18 to 23 carbon atoms, but the branched structure cannot be specified. Ester solvents with a low carbon number are relatively low in viscosity and are useful for improving ejection performance, but there is a problem that the bleeding lake pigment is dyed due to the branched structure.

[0010] One object of the present invention is to provide an oil-based inkjet ink suitable for inkjet printing while preventing bleeding and the like due to dyeing of the bleeding lake pigment contained in the ink.

Means for Solving the Problems

[0011] One embodiment of the present invention is an oil-based inkjet ink containing a bleeding lake pigment and a fatty acid ester solvent represented by the following general formula (1).

Chemical formula

Effects of the Invention

[0012] According to one embodiment of the present invention, it is possible to prevent bleeding and the like due to dyeing of the bleeding lake pigment contained in the ink and to provide an oil-based inkjet ink suitable for inkjet printing.

Mode for Carrying Out the Invention

[0013] Hereinafter, the present invention will be described using an embodiment. The exemplification in the following embodiments does not limit the present invention.

[0014] An oil-based inkjet ink according to an embodiment (hereinafter sometimes simply referred to as ink) is characterized by containing a mordant lake pigment and a fatty acid ester solvent represented by the following general formula (1). [Chemical formula] (In general formula (1), R 1 and R 2 are each independently a hydrocarbon group, and at least one of R 1 and R 2 has a side chain bonded to at least one of the carbon atom at the α-position and the carbon atom at the β-position, and the total number of carbon atoms of the side chain bonded to the carbon atom at the α-position and the carbon atom at the β-position of R 1 and the total number of carbon atoms of the side chain bonded to the carbon atom at the α-position and the carbon atom at the β-position of R 2 is 4 or more.)

[0015] According to this, bleeding due to dyeing of the mordant lake pigment contained in the ink can be prevented, and an oil-based inkjet ink suitable for inkjet printing can be provided. This ink can prevent the phenomenon that the printed image bleeds from the printed area to the unprinted area by preventing the dyeing of the mordant lake pigment. When the mordant lake pigment is dyed, when the ink is applied to the recording medium, the dyed component may penetrate into the recording medium together with the solvent and bleed from the printed area to the unprinted area. Further, the dyed component may enter the fibers of the recording medium and dye with a color more vivid than the pigment itself, coloring the boundary between the printed area and the unprinted area.

[0016] A lake pigment is a pigment obtained by insolubilizing a water-soluble dye and fixing it to an extender pigment. The dye component is likely to dissolve and dye due to polar components such as alcohol. The bleeding phenomenon of printed matter resulting from this dyeing is also manifested by trace amounts of lower alcohols and lower fatty acids generated by the hydrolysis of fatty acid ester solvents in the ink. Fatty acid ester solvents in the ink may absorb moisture from the atmosphere and, particularly in a high-temperature environment, may undergo hydrolysis and decomposition. The fatty acid ester solvent represented by the general formula (1) has a side chain bonded to a carbon atom close to the ester bond, resulting in a bulky molecular structure near the ester bond, making it difficult for water molecules to approach. This can suppress the hydrolysis of the fatty acid ester solvent. And it can suppress the generation of alcohols and fatty acids that cause dyeing, and prevent the deterioration of the printed image quality due to the bleeding phenomenon.

[0017] The ink contains a lake pigment. As the lake pigment, basic lake pigments, acidic lake pigments, etc. can be used. Since the lake pigment is a pigment obtained by insolubilizing a highly coloring dye, a printed matter with high color saturation can be obtained. Also, because of the good dispersibility of the pigment, a printed matter with even higher color saturation can be obtained, and the storage stability can be improved. Basic lake pigments have better dispersibility and can be preferably used.

[0018] A basic lake pigment is a pigment obtained by insolubilizing a dye having a basic group such as an amino group using a precipitating agent and fixing it to an extender pigment. As the precipitating agent, phosphotungstic acid, phosphomolybdic acid, phosphotungstomolybdic acid, silicomolybdic acid, silicotungstomolybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide and ferrocyanide, synthetic mordants (katanol, tamol), etc. can be used. As basic lake pigments, for example, pigments obtained by lake-forming xanthene dyes (such as rhodamine 6G, rhodamine, etc.), triphenylmethane dyes (such as methyl violet, malachite green, etc.), triphenylmethane thiazole dyes, thiazole dyes, diphenylmethane dyes, azomethine dyes, etc. and fixing them to extender pigments can be used.

[0019] Acid dyed lake pigments are pigments obtained by insolubilizing dyes having acidic groups such as sulfo groups and carboxy groups using a precipitating agent and fixing them to extender pigments. As the precipitating agent, metal salts such as calcium, barium, aluminum, sodium, etc. can be used. As acid dyed lake pigments, for example, pigments obtained by lake-forming Persian orange dyes, nitroso dyes, monoazo dyes, quinoline dyes, acid type xanthene dyes, anthraquinone dyes (such as alizarin, madder, etc.), indigoid dyes, etc. and fixing them to extender pigments can be used.

[0020] The lake pigments include, for example, C.I. Pigment Yellow 18, C.I. Pigment Yellow 100, C.I. Pigment Yellow 104, C.I. Pigment Yellow 115, C.I. Pigment Yellow 117; C.I. Pigment Orange 17:1 (Persian Orange Lake), C.I. Pigment Orange 39; C.I. Pigment Red 63 (Indigo Carmine Lake), C.I. Pigment Red 81, C.I. Pigment Red 81:1, C.I. Pigment Red 81:2, C.I. Pigment Red 81:3, C.I. Pigment Red 81:4, C.I. Pigment Red 82, C.I. Pigment Red 83, C.I. Pigment Red 84, C.I. Pigment Red 90, C.I. Pigment Red 90:1, C.I. Pigment Red 151, C.I. Pigment Red 169, C.I. Pigment Red 172, C.I. Pigment Red 173, C.I. Pigment Red 174, C.I. Pigment Red 191, C.I. Pigment Red 193; C.I. Pigment Violet 1, C.I. Pigment Violet 2, C.I. Pigment Violet 2:2, C.I. Pigment Violet 3, C.I. Pigment Violet 3:1, C.I. Pigment Violet 3:3, C.I. Pigment Violet 4, C.I. Pigment Violet 5, C.I. Pigment Violet 5:1, C.I. Pigment Violet 6:1, C.I. Pigment Violet 7:1, C.I. Pigment Violet 9, C.I. Pigment Violet 12, C.I. Pigment Violet 20, C.I. Pigment Violet 26, C.I. Pigment Violet 27, C.I. Pigment Violet 39; C.I. Pigment Blue 1, C.I. Pigment Blue 1:2, C.I. Pigment Blue 2, C.I.Pigment Blue 3, C.I. Pigment Blue 8, C.I. Pigment Blue 9, C.I. Pigment Blue 10, C.I. Pigment Blue 11, C.I. Pigment Blue 12, C.I. Pigment Blue 14, C.I. Pigment Blue 53 (Brilliant Blue Lake), C.I. Pigment Blue 62, C.I. Pigment Blue 63; C.I. Pigment Green 1, C.I. Pigment Green 2, C.I. Pigment Green 3, C.I. Pigment Green 4, C.I. Pigment Green 8, C.I. Pigment Green 9, C.I. Pigment Green 10, C.I. Pigment Green 12, C.I. Pigment Green 45; C.I. Pigment Brown 3 and the like can be mentioned. These can be used alone or in combination of two or more.

[0021] Among them, xanthene-based basic dyeing lake pigments obtained by lake-forming xanthene-based dyes and triphenylmethane-based basic dyeing lake pigments obtained by lake-forming triphenylmethane-based dyes can be preferably used, and xanthene-based basic dyeing lake pigments are more preferable.

[0022] Xanthene-based basic dyeing lake pigments are pigments in which xanthene-based dyes are lake-formed and fixed to extender pigments. Xanthene-based dyes are dyes having a xanthene skeleton represented by the following structural formula, and examples thereof include rhodamine-based dyes, fluorescein-based dyes, eosin-based dyes and the like. From the viewpoint of color tone, rhodamine-based dyes such as rhodamine, rhodamine B, and rhodamine 6G are preferably used.

[0023]

Chemical formula

[0024] As the xanthene-based basic mordant lake pigments, from among those described above, C.I. Pigment RED 81 (Rhodamine 6G (PTMA)), C.I. Pigment RED 81:1 (Rhodamine 6G (STMA)), C.I. Pigment RED 81:2 (Rhodamine (SMA)), C.I. Pigment RED 81:3 (Rhodamine (PMA)), C.I. Pigment RED 81:4 (Rhodamine (PTMA) and Rhodamine 6G (tannic acid)), C.I. Pigment RED 169 (Rhodamine 6G (CFA)), etc. can be preferably used. Among them, C.I. Pigment RED 81, C.I. Pigment RED 81:4, and C.I. Pigment RED 169 can be preferably used. These may be used alone or in combination of two or more.

[0025] From the viewpoints of ejection stability and storage stability, the average particle diameter of the mordant lake pigment is preferably 300 nm or less, more preferably 200 nm or less, and still more preferably 150 nm or less. The mordant lake pigment is usually 0.01 to 20% by mass based on the total amount of the ink. From the viewpoint of printing density, the mordant lake pigment based on the total amount of the ink is preferably 1% by mass or more, and more preferably 5% by mass or more. Also, from the viewpoint of ink viscosity, the mordant lake pigment based on the total amount of the ink is preferably 15% by mass or less, and more preferably 10% by mass or less.

[0026] The ink may contain other pigments as long as the effects of the present invention are not inhibited. Examples of other pigments include organic pigments such as azo pigments, phthalocyanine pigments, and polycyclic pigments; and inorganic pigments such as carbon black and metal oxides. For example, from the viewpoints of the density and chroma of the printed image, an azo lake pigment can be used together with the xanthene-based mordant lake pigment. The azo lake pigments that can be used in combination are preferably soluble azo pigments. For example, C.I.Pigment RED 48:1, C.I.Pigment RED 48:2, C.I.Pigment RED 48:3, C.I.Pigment RED 48:4, C.I.Pigment RED 48:5, C.I.Pigment RED 49, C.I.Pigment RED 49:1, C.I.Pigment RED 49:2, C.I.Pigment RED 49:3, C.I.Pigment RED 52:1, C.I.Pigment RED 52:2, C.I.Pigment RED 53:1, C.I.Pigment RED 54, C.I.Pigment RED 57:1, C.I.Pigment RED 58, C.I.Pigment RED 58:1, C.I.Pigment RED 58:2, C.I.Pigment RED 58:3, C.I.Pigment RED 58:4, C.I.Pigment RED 60:1, C.I.Pigment RED 63, C.I.Pigment RED 63:1, C.I.Pigment RED 63:2, C.I.Pigment RED 63:3, C.I.Pigment RED 64:1, C.I.Pigment RED 68, C.I.Pigment RED 200, C.I.Pigment RED 237, C.I.Pigment RED 239, and C.I.Pigment RED 247, etc. can be mentioned. The mass ratio of the xanthene-based lake pigment to the azo lake pigment is preferably 10:0 to 3:7, more preferably 10:0 to 5:5.

[0027] In order to stably disperse the pigment in the ink, a pigment dispersant can be used together with the pigment. Examples of the pigment dispersant include, for example, hydroxyl group-containing carboxylic acid esters, salts of long-chain polyaminoamides and high molecular weight acid esters, salts of high molecular weight polycarboxylic acids, salts of long-chain polyaminoamides and polar acid esters, high molecular weight unsaturated acid esters, copolymers of vinylpyrrolidone and long-chain alkenes, modified polyurethanes, modified polyacrylates, polyether ester type anionic surfactants, polyoxyethylene alkyl phosphoric acid esters, polyester polyamines, etc., which are preferably used.

[0028] Examples of commercially available products of the pigment dispersant include, for example, "Antaron V216 (vinylpyrrolidone-hexadecene copolymer), V220 (vinylpyrrolidone-eicosene copolymer)" (both are trade names) manufactured by ISP Japan Co., Ltd.; "Solsperse 13940 (polyesteramine type), 16000, 17000, 18000 (fatty acid amine type), 19000, 11200, 24000, 28000" (both are trade names) manufactured by Lubrizol Japan Co., Ltd.; "Efka 400, 401, 402, 403, 450, 451, 453 (modified polyacrylate), 46, 47, 48, 49, 4010, 4055 (modified polyurethane)" (both are trade names) manufactured by BASF Japan Ltd.; "Disparon KS-860, KS-873N4 (amine salts of polyester)" (both are trade names) manufactured by Namboku Kasei Co., Ltd.; "Discol 202, 206, OA-202, OA-600 (multi-chain type high molecular nonionic type)" (both are trade names) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; "DISPERBYK 2155, 9077" (both are trade names) manufactured by BYK-Chemie Japan Co., Ltd.; "Hypermer KD2, KD3, KD11, KD12" (both are trade names) manufactured by Croda Japan Co., Ltd., etc.

[0029] The pigment dispersant is sufficient as long as it can disperse the above pigments in the ink in a sufficient amount and can be appropriately set. For example, in terms of mass ratio, the pigment dispersant can be blended at 0.1 to 5 with respect to 1 of the pigment, preferably 0.1 to 1. Further, the pigment dispersant can be blended at 15% by mass or less with respect to the total amount of the ink, preferably 0.01 to 10% by mass.

[0030] The non-aqueous solvent contains a fatty acid ester solvent represented by the above general formula (1). This fatty acid ester solvent has a side chain at at least one of the α-position carbon atom and the β-position carbon atom of at least one of R 1 and R 2 , which prevents it from being decomposed by a hydrolysis reaction and can prevent the dyeing of the lake pigment by the decomposition product.

[0031] In the general formula (1), R 1 and R 2 are each independently a hydrocarbon group, and at least one of R 1 and R 2 has a side chain bonded to at least one of the α-position carbon atom and the β-position carbon atom, and the total number of carbon atoms of the side chain bonded to the α-position carbon atom and the β-position carbon atom of R 1 , and the total number of carbon atoms of the side chain bonded to the α-position carbon atom and the β-position carbon atom of R 2 is 4 or more.

[0032] The α-position carbon atom of R 1 is the carbon atom bonded to the carbonyl group of the ester bond, and the β-position carbon atom of R 1 is the second carbon atom counted from the carbon atom bonded to the carbonyl group of the ester bond. The α-position carbon atom of R 2 is the carbon atom bonded to the oxygen atom of the ester bond, and the β-position carbon atom of R 2 is the second carbon atom counted from the carbon atom bonded to the oxygen atom of the ester bond.

[0033] A side chain may be bonded to at least one of the α-position and the β-position of at least one of R 1 and R 2 . Also, a side chain may be bonded to at least one of the α-position and the β-position of both R 1 and R 2 . R 1 and R 2 may each independently have a side chain bonded to one of the α-position carbon atom and the β-position carbon atom. Also, R 1and R 2 may each independently have a side chain bonded to both the α-carbon atom and the β-carbon atom. R 1 and R 2 may each independently have one or two side chains bonded to the α-carbon atom and one or two side chains bonded to the β-carbon atom.

[0034] Here, the main chain of R 1 and R 2 is the carbon chain with the most carbon atoms when counted from the carbon atom bonded to the ester bond moiety “-COO-”. The carbon chains branched from this main chain of R 1 and R 2 are used as side chains. When R 1 and / or R 2 has a side chain, each side chain may be linear or branched. Also, in R 1 and R 2 , when there are multiple carbon chains with the most carbon atoms when counted from the carbon atom bonded to the ester bond moiety, the one with the most carbon atoms in the side chain is taken as the main chain. Also, in R 1 and R 2 , when there are multiple carbon chains with the most carbon atoms when counted from the carbon atom bonded to the ester bond moiety and the number of carbon atoms in the side chains included in the multiple carbon chains is the same, the one with the fewest number of side chains is taken as the main chain.

[0035] R 1 and R 2 may be a saturated or unsaturated, linear or cyclic hydrocarbon group, preferably a linear or branched alkyl group. R 1 When it is a linear alkyl group, the number of carbon atoms may be 1 or more, preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more. In this case, the number of carbon atoms of R 1 is preferably 25 or less, and more preferably 20 or less. R 2When it is a linear alkyl group, the number of carbon atoms may be 1 or more, preferably 4 or more, more preferably 6 or more, and even more preferably 8 or more. In this case, R 2 preferably has 25 or fewer carbon atoms, and more preferably 20 or fewer carbon atoms. For the R of the fatty acid ester solvent 1 or R 2 When it is a linear alkyl group, by having a certain length of the linear alkyl group, the fatty acid ester solvent becomes bulky and hydrolysis can be further prevented.

[0036] R 1 When it is a branched alkyl group, the number of carbon atoms is preferably 4 or more, more preferably 8 or more, and even more preferably 10 or more. In this case, R 1 preferably has 28 or fewer carbon atoms, and more preferably 20 or fewer carbon atoms. R 2 When it is a branched alkyl group, the number of carbon atoms is preferably 4 or more, more preferably 8 or more, and even more preferably 10 or more. In this case, R 2 preferably has 28 or fewer carbon atoms, and more preferably 20 or fewer carbon atoms. For the R of the fatty acid ester solvent 1 and / or R 2 When it is a branched alkyl group, by having a certain length of the carbon chain of the main chain and the side chain, the fatty acid ester solvent becomes bulky and hydrolysis can be further prevented. R 1 and R 2 The total number of carbon atoms of is adjusted according to the length of the main chain of each other, the number of carbon atoms of the side chain, and the total number of carbon atoms of the fatty acid ester solvent.

[0037] R 1 and R 2 are each preferably an alkyl group having 6 or more carbon atoms independently. R 1 and R 2By both being alkyl groups having 6 or more carbon atoms, while improving the bleeding and ejection performance of printed matter, the solubility of the oil-based inkjet ink with respect to the toner image formed by the toner ink can be lowered. Specifically, when a toner printed matter on which an image is formed by the toner ink and a printed matter by the oil-based inkjet ink are overlaid, the printed matter by the oil-based inkjet ink can be prevented from sticking to the toner printed matter.

[0038] R 1 and R 2 At least one of them is preferably a branched alkyl group having a side chain at at least one of the α-position carbon atom and the β-position carbon atom. R 1 The α-position carbon atom and the β-position carbon atom of R, and the total number of carbon atoms of the side chain bonded to the α-position carbon atom and the β-position carbon atom of R 2 is preferably 4 or more, more preferably 6 or more. Thereby, due to the steric hindrance of the fatty acid ester-based solvent, hydrolysis of the fatty acid ester-based solvent can be prevented, and dyeing of the lake pigment by the decomposition product can be prevented. The total number of these carbon atoms is preferably 20 or less, more preferably 15 or less, further preferably 10 or less, and still more preferably 8 or less. R 1 and / or R 2 The number of carbon atoms of the side chain bonded to the α-position and / or β-position carbon atom of is independently 1 or 2 or more, preferably 4 or more, and more preferably 6 or more. Thereby, hydrolysis of the fatty acid ester-based solvent can be further prevented. The number of carbon atoms of this side chain is not particularly limited, preferably 12 or less, more preferably 10 or less, and still more preferably 8 or less.

[0039] R 1 and / or R 2The side chain bonded to the carbon atom at the α-position and / or β-position of can be either a straight-chain alkyl group or a branched alkyl group. The side chain preferably contains a carbon chain in which 4 or more, more preferably 6 or more carbon atoms are linearly bonded. For example, the side chain is preferably a straight-chain alkyl group having 4 or more, more preferably 6 or more carbon atoms.

[0040] R 1 and / or R 2 The side chain bonded to the carbon atom at the α-position and / or β-position of can include, for example, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, an isooctyl group, a nonyl group, a decyl group, a dodecyl group, etc. Preferably, they are an ethyl group, an n-butyl group, a hexyl group, an octyl group, and more preferably an n-butyl group and a hexyl group.

[0041] The number of carbon atoms in one molecule of the fatty acid ester-based solvent is preferably 9 or more, more preferably 16 or more, still more preferably 18 or more, and even more preferably 20 or more. When the number of carbon atoms of the fatty acid ester-based solvent is within this range, the total number of carbon atoms of the alkyl group and the number of carbon atoms of the side chain can be sufficiently ensured, the fatty acid ester-based solvent can be made bulky, and the hydrolysis of the fatty acid ester-based solvent can be more suppressed. Also, the number of carbon atoms in one molecule of the fatty acid ester-based solvent is preferably 30 or less, more preferably 25 or less, and still more preferably 24 or less. Since the viscosity may increase when the number of carbon atoms is high, when the number of carbon atoms of the fatty acid ester-based solvent is within this range, the viscosity of the ink can be reduced and the ejection performance can be improved.

[0042] Examples of the fatty acid ester solvent represented by the general formula (1) include esterified products of acetic acid, butanoic acid, pentanoic acid, neopentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, or octadecanoic acid with 1-butyl-1-pentanol; esterified products of acetic acid, butanoic acid, pentanoic acid, neopentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, or hexadecanoic acid with 2-hexyl-1-octanol or 2-hexyldecanol; esterified products of acetic acid, butanoic acid, pentanoic acid, neopentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, 2-ethylhexanoic acid, nonanoic acid, or decanoic acid with 2-octyl-1-dodecanol; esterified products of 2-ethylhexanoic acid with butan-2-ol, tert-butyl alcohol, pentan-2-ol, 2-methylpentan-2-ol, or 2-ethylhexanol; esterified products of 2-butyloctanoic acid with methanol, ethanol, propanol, propan-2-ol, butanol, butan-2-ol, tert-butyl alcohol, pentanol, pentan-2-ol, hexanol, 2-methylpentan-2-ol, heptanol, octanol, 2-ethylhexanol, nonanol, decanol, undecanol, dodecanol, tridecanol, tetradecanol, hexadecanol, heptadecanol, or octadecanol; esterified products of 1-butyl-1-pentanol, 2-hexyl-1-octanol, 2-hexyldecanol, or 2-octyl-1-dodecanol with 2-ethylhexanoic acid or 2-butyloctanoic acid, and the like.

[0043] Specific examples of the fatty acid ester solvent represented by the general formula (1) include 1-butylpentyl acetate, 2-ethylhexyl 2-ethylhexanoate, decyl 2-butyloctanoate, 1-hexyloctyl nonanoate, 2-hexyldecyl octanoate, 2-octyldodecyl neopentanoate, 2-hexyldecyl hexanoate, 2-hexyldecyl heptanoate, 2-butyloctyl octanoate, hexyl 2-butyloctanoate, nonyl 2-butyloctanoate, 1-butylhexyl 2-butyloctanoate, and the like. The fatty acid ester solvent may be used alone or in combination of two or more.

[0044] The fatty acid ester solvent represented by the general formula (1) is not particularly limited with respect to the total amount of the non-aqueous solvent, but is preferably contained in an amount of 10% by mass or more. From the viewpoint of preventing bleeding and eliminating the influence of other solvents, the fatty acid ester solvent represented by the general formula (1) is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 80% by mass or more, for example, 90% by mass or more, and even 100% by mass, based on the total amount of the non-aqueous solvent.

[0045] The blending amount of the fatty acid ester solvent represented by the general formula (1) with respect to the total amount of the ink varies depending on the amount of the non-aqueous solvent used as a whole, but may be contained in an amount of 10 to 98% by mass, or may be contained in an amount of 15 to 90% by mass. The fatty acid ester solvent represented by the general formula (1) is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 50% by mass or more, and even more preferably 55% by mass or more, based on the total amount of the ink. Thereby, bleeding can be more effectively prevented.

[0046] The fatty acid ester solvent represented by the above general formula (1) can be produced by the following method, although not limited thereto. The fatty acid ester solvent can be obtained by reacting a fatty acid with an alcohol. For example, in order to introduce a branched alkyl group, a fatty acid in which a side chain is bonded to at least one of the α-position and β-position carbon atoms relative to the carboxy group, or an alcohol in which a side chain is bonded to at least one of the α-position and β-position carbon atoms relative to the hydroxy group can be used. Also, for R 2 in order to introduce a side chain, a secondary alcohol having 3 or more carbon atoms or a tertiary alcohol having 4 or more carbon atoms can be used. Examples of the secondary alcohol having 3 or more carbon atoms include propan-2-ol, butan-2-ol, pentan-2-ol, and the like. Examples of the tertiary alcohol having 4 or more carbon atoms include tert-butyl alcohol, 2-methylbutan-2-ol, 2-methylpentan-2-ol, and the like. As the fatty acid and alcohol that are raw materials for the fatty acid ester-based solvent, the exemplified combinations of the above-described fatty acid ester-based solvents can be mentioned.

[0047] The reaction temperature can be adjusted in the range of 80 to 230°C according to the types of the fatty acid and alcohol. The reaction time can be adjusted in the range of 1 to 48 hours according to the types of the fatty acid and alcohol and the amount of the raw materials used. It is preferable to remove the water generated during the esterification reaction. The fatty acid and the alcohol are preferably reacted in a molar ratio of 1:1. During the reaction, an appropriate amount of a catalyst such as concentrated sulfuric acid, p-toluenesulfonic acid, or methanesulfonic acid may be used.

[0048] The ink may contain other non-aqueous solvents. As the other non-aqueous solvents, either non-polar organic solvents or polar organic solvents can be used. In one embodiment, it is preferable to use a water-insoluble organic solvent that does not uniformly mix with the same volume of water at 1 atm and 20°C as the non-aqueous solvent.

[0049] Examples of the non-polar organic solvents preferably include petroleum hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents. Examples of aliphatic hydrocarbon solvents and alicyclic hydrocarbon solvents include non-aqueous solvents such as paraffinic, isoparaffinic, and naphthenic solvents. Commercially available products include Solvent L No. 0, Solvent M No. 0, Solvent H No. 0, Cactus Normal Paraffin N-10, Cactus Normal Paraffin N-11, Cactus Normal Paraffin N-12, Cactus Normal Paraffin N-13, Cactus Normal Paraffin N-14, Cactus Normal Paraffin N-15H, Cactus Normal Paraffin YHNP, Cactus Normal Paraffin SHNP, Isosol 300, Isosol 400, Tecleen N-16, Tecleen N-20, Tecleen N-22, AF Solvent No. 4, AF Solvent No. 5, AF Solvent No. 6, AF Solvent No. 7, Naphthosol 160, Naphthosol 200, Naphthosol 220 (all manufactured by JXTG Energy Corporation); Isopar G, Isopar H, Isopar L, Isopar M, Exxon D40, Exxon D60, Exxon D80, Exxon D95, Exxon D110, Exxon D130 (all manufactured by ExxonMobil); Moresco White P-40, Moresco White P-60, Moresco White P-70, Moresco White P-80, Moresco White P-100, Moresco White P-120, Moresco White P-150, Moresco White P-200, Moresco White P-260, Moresco White P-350P (all manufactured by MORESCO Corporation), etc. can be preferably mentioned. Examples of aromatic hydrocarbon solvents include Grade Alkene L, Grade Alkene 200P (both manufactured by JXTG Energy Corporation), Solvesso 100, Solvesso 150, Solvesso 200, Solvesso 200ND (all manufactured by ExxonMobil), etc. can be preferably mentioned. The initial boiling point of the petroleum-based hydrocarbon solvent is preferably 100 °C or higher, more preferably 150 °C or higher, and even more preferably 200 °C or higher. The initial boiling point can be measured according to JIS K0066 "Test Method for Distillation of Chemical Products".

[0050] Examples of the polar organic solvent include preferably fatty acid ester solvents, higher alcohol solvents, higher fatty acid solvents and the like. Examples of the fatty acid ester solvents include solvents having a linear alkyl group such as methyl laurate, hexyl laurate, hexyl palmitate, methyl oleate, ethyl oleate, butyl oleate, hexyl oleate, methyl linoleate, ethyl linoleate, butyl stearate, hexyl stearate, methyl soyate, methyl tallate, etc., with the total number of carbon atoms being 12 or more, preferably 16 to 30; and solvents such as isodecyl isononanoate, isotridecyl isononanoate, isopropyl isostearate, isononyl isononanoate, isopropyl laurate, isopropyl myristate, isopropyl palmitate, isooctyl palmitate, isopropyl oleate, isobutyl linoleate, isooctyl stearate, isobutyl soyate, isobutyl tallate, isostearyl palmitate (with 34 carbon atoms), etc., having no side chain bonded to the α-position and β-position or having a total number of carbon atoms in the side chain of 3 or less. Among the commercially available fatty acid ester solvents, isodecyl isononanoate (with 19 carbon atoms), isotridecyl isononanoate (with 22 carbon atoms), isopropyl isostearate (with 21 carbon atoms), etc., are fatty acid ester solvents having a total number of carbon atoms in the side chain bonded to the α-position and β-position of 3 or less.

[0051] Examples of the higher alcohol solvents include higher alcohol solvents having 6 or more, preferably 12 to 20 carbon atoms in one molecule, such as isomyristyl alcohol, isopalmityl alcohol, isostearyl alcohol, oleyl alcohol, isoeicosyl alcohol, decyltetradecanol and the like. Examples of the higher fatty acid solvents include higher fatty acid solvents having 12 or more, preferably 14 to 20 carbon atoms in one molecule, such as lauric acid, isomyristic acid, palmitic acid, isopalmitic acid, α-linolenic acid, linoleic acid, oleic acid, isostearic acid and the like. The boiling points of polar organic solvents such as fatty acid ester solvents, higher alcohol solvents, and higher fatty acid solvents are preferably 150 °C or higher, more preferably 200 °C or higher, and even more preferably 250 °C or higher. In addition, non-aqueous solvents with a boiling point of 250 °C or higher include non-aqueous solvents that do not exhibit a boiling point.

[0052] These non-aqueous solvents may be used alone or in combination of two or more as long as they form a single phase. When using other non-aqueous solvents in addition to the fatty acid ester solvent represented by the general formula (1), it is preferable to use a high-boiling solvent. As the high-boiling solvent, it is preferable to use a non-polar solvent with an initial distillation point of 200 °C or higher, a polar solvent with a boiling point of 250 °C or higher, or a combination thereof. From the perspective of the chroma of the printed matter, the content of non-polar solvents such as petroleum-based hydrocarbon solvents is preferably 50% by mass or less, more preferably 20% by mass or less, based on the total amount of the ink. Furthermore, it is not necessary to incorporate a non-polar solvent into the ink.

[0053] The blending amount of other polar solvents such as higher alcohol solvents, higher fatty acid solvents, and other fatty acid ester solvents other than the fatty acid ester solvent represented by the general formula (1) is preferably limited to suppress the dyeing of the lake pigment. For example, the blending amount of other polar solvents is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and still more preferably 15% by mass or less, based on the total amount of the ink.

[0054] In addition to the above components, the oily ink may contain various additives as long as the effects of the present invention are not impaired. As additives, a nozzle clogging preventive agent, an antioxidant, a conductivity adjuster, a viscosity adjuster, a surface tension adjuster, an oxygen absorber, etc. can be appropriately added. The types of these are not particularly limited, and those used in the art can be used.

[0055] The ink can be prepared by mixing each component including a coloring material and a non-aqueous solvent. Preferably, the ink can be prepared by mixing and stirring each component all at once or in portions. Specifically, all components can be put into a disperser such as a bead mill all at once or in portions for dispersion, and if desired, it can be prepared by passing through a filter such as a membrane filter.

[0056] The viscosity of the oil-based inkjet ink varies depending on the nozzle diameter of the ejection head of the inkjet recording system, the ejection environment, etc., but generally, it is preferably 5 to 30 mPa·s at 23°C, and more preferably 5 to 15 mPa·s.

[0057] The printing method using the inkjet ink is not particularly limited, and it may be any method such as a piezo method, an electrostatic method, a thermal method, etc. When using an inkjet recording apparatus, it is preferable to eject the ink according to one embodiment from the inkjet head based on a digital signal and attach the ejected ink droplets to a recording medium. The ink according to one embodiment can be ejected appropriately near room temperature (23°C) because it has a low viscosity and is suitable for ejection from an inkjet nozzle while preventing the dyeing of the mordant lake pigment.

[0058] In one embodiment, the recording medium is not particularly limited, and printing papers such as plain paper, coated paper, and special paper, cloth, inorganic sheets, films, OHP sheets, etc., and adhesive sheets provided with an adhesive layer on the back surface using these as a base material can be used. Among these, from the viewpoint of the ink permeability, printing papers such as plain paper and coated paper can be preferably used.

[0059] Here, plain paper is paper on which an ink receiving layer, a film layer, etc. are not formed on ordinary paper. Examples of plain paper include high-quality paper, medium-quality paper, PPC paper, blotting paper, recycled paper, etc. Plain paper is paper in which paper fibers with a thickness of several μm to several tens of μm form voids of several tens to several hundreds of μm, so it is paper that allows ink to penetrate easily.

[0060] Also, as the coated paper, inkjet coated papers such as matte paper, glossy paper, and semi-glossy paper, and so-called coated printing papers can be preferably used. Here, the coated printing paper is a printing paper that has been conventionally used in letterpress printing, offset printing, gravure printing, etc., and is a printing paper provided with a coating layer by a coating material containing an inorganic pigment such as clay or calcium carbonate and a binder such as starch on the surface of high-quality paper or medium-quality paper. Coated printing papers are classified into micro-coated papers, high-quality lightweight coated papers, medium-quality lightweight coated papers, high-quality coated papers, medium-quality coated papers, art papers, cast coated papers, etc. according to the coating amount and coating method of the coating material.

Examples

[0061] Hereinafter, the present invention will be described in detail by way of examples. The present invention is not limited to the following examples.

[0062] "Synthesis of Fatty Acid Esters" The formulation of the fatty acid ester is shown in Table 1. According to the formulation shown in Table 1, fatty acid and alcohol were put into a four-necked flask, mixed and stirred to obtain a uniform solution. A Dean-Stark apparatus was attached to the four-necked flask so that water generated by the reaction of the charged raw materials could be removed. An appropriate amount of sulfuric acid was further added to the four-necked flask containing the uniform solution as a catalyst, and the whole system was heated. The heating temperature was set to 80°C to 230°C according to the types of fatty acid and alcohol. The heating reaction time was set to 1 to 48 hours. After the reaction, the obtained solution was distilled under reduced pressure to remove unreacted raw materials and impurities, and a fatty acid ester was obtained. The fatty acid and alcohol were mixed so that the molar ratio was 1:1. The fatty acid and alcohol can be obtained from Tokyo Chemical Industry Co., Ltd., Sasol, and KH NeoChem Co., Ltd.

[0063]

Table 1

[0064] "Preparation of Ink" The formulations of the inks are shown in Tables 2 and 3. The number of carbon atoms in one molecule of the fatty acid ester, R 1 The number of carbon atoms in the side chains bonded to the α-position and β-position carbon atoms on the R 2 side are shown in each table. The number of carbon atoms in the side chains bonded to the α-position and β-position carbon atoms on the R 1 and R 2 When no side chain is bonded to the α-position and β-position carbon atoms, "-" is attached. According to the blending amounts shown in each table, a pigment, a pigment dispersant, and a solvent were mixed, and the pigment was sufficiently dispersed by a bead mill "Dyno-Mill KDL-A" (manufactured by Shinmaru Enterprises Corporation) under the condition of a residence time of 15 minutes. Subsequently, coarse particles were removed with a membrane filter to obtain an ink.

[0065] The components used are as follows. (Pigment) Dyeing lake pigment "P.R.81:1": "Fanal Pink D4830" manufactured by BASF Japan Ltd. Dyeing lake pigment "P.R.169": "Fanal Pink D4810" manufactured by BASF Japan Ltd. Quinacridone pigment "P.R.122": "FASTOGEN SUPER MAGENTA RG" manufactured by DIC Corporation. Dyeing lake pigment "P.B.1": "Fanal Blue D6390" manufactured by BASF Japan Ltd. (Pigment dispersant) Solsperse 19000: "Solsperse 19000" manufactured by Lubrizol Japan Ltd., active ingredient 100% by mass. Solsperse 13940: "Solsperse 13940" manufactured by Lubrizol Japan Ltd., active ingredient 40% by mass. The amount of the active ingredient is shown in parentheses in the table. (Hydrocarbon solvent) Non-polar solvent "petroleum-based hydrocarbon solvent": "Product name Moresco White P-60" manufactured by Moresco Corporation.

[0066] "Evaluation" The inks of the above Examples and Comparative Examples were evaluated by the following method. The evaluation results are shown in Tables 2 and 3.

[0067] (Colorfulness of the printed matter) Each ink was loaded into a line inkjet printer "Office EX9050" (manufactured by Ideal Scientific Industry Co., Ltd.), and a solid image of approximately 51 mm in the main scanning direction × 260 mm in the sub-scanning direction was printed on plain paper "Ideal Paper Thin" (manufactured by Ideal Scientific Industry Co., Ltd.) to obtain a printed matter. One day after printing, the colorfulness of the printed surface of the printed matter was measured using a spectrophotometer "exact Advance" (manufactured by X-rite), and evaluated according to the following criteria. The inks shown in Table 2 were evaluated according to the evaluation criteria for the following magenta ink, and the inks shown in Table 3 were evaluated according to the evaluation criteria for the following cyan ink.

[0068] Evaluation criteria for magenta ink: A: The colorfulness of the printed matter is 60 or more. B: The colorfulness of the printed matter is less than 60. Evaluation criteria for cyan ink: A: The colorfulness of the printed matter is 65 or more. B: The colorfulness of the printed matter is less than 65.

[0069] (Bleeding of the printed matter) A printed matter was obtained in the same manner as the colorfulness of the printed matter. The boundary between the printed area and the unprinted area of the printed surface of the printed matter was observed with a microscope, and the bleeding at the boundary was evaluated according to the following criteria. When the pigment contained in the ink is dyed, bleeding is observed at the boundary of the printed surface. S: No bleeding was observed at the boundary of the printed surface. A: Bleeding was observed at the boundary of the printed surface. B: The boundary of the printed surface was significantly bleeding.

[0070] (Discharge performance) Each ink was loaded into a line-type inkjet printer "Office EX9050" (manufactured by Risoh Kagaku Kogyo Co., Ltd.), and a solid image was printed on one side of 100 sheets of plain paper "Risoh Paper Thin" (manufactured by Risoh Kagaku Kogyo Co., Ltd.) in succession to obtain a printed matter. The printing conditions were the same as those for the evaluation of the color density of the above-mentioned printed matter. The non-ejection of ink from the inkjet nozzles can be confirmed by the occurrence of white streaks and non-printed portions on the printed matter. Whether or not such white streaks occurred in the 100 sheets of printed matter, or the number of sheets in which they occurred, was observed. The ejection performance was evaluated from the total number of white streaks observed in the 100 sheets of printed matter. The evaluation criteria are shown below. S: There are 0 white spots due to non-ejection. A: There are 1 to 5 white spots due to non-ejection. B: There are 6 to 10 white spots due to non-ejection. C: There are 10 or more white spots due to non-ejection.

[0071] Although not described in detail, in the printing using the inks of the respective examples, printed matters with sufficient image density could be obtained. Also, the viscosities of the inks of the respective examples were appropriate.

[0072]

Table 2

[0073]

Table 3

[0074] As shown in the table, with the inks of the respective examples, the printed matters had excellent color density, bleeding was prevented, and ejection performance was improved. Throughout each example, the R of the fatty acid ester-based solvent 1 and / or R 2 It can be seen that bleeding is more effectively prevented by the bonding of side chains having 4 or more carbon atoms to the carbon atoms at the α-position and / or β-position. Also, it can be seen that the ejection performance is further improved by the fact that the number of carbon atoms in one molecule of the fatty acid ester-based solvent is 24 or less.

[0075] In Comparative Example 1, both R of the fatty acid ester-based solvent 1 and R 2 were linear alkyl groups, and bleeding occurred. In Comparative Examples 2 and 5, the total number of carbon atoms in the side chains at the α-position and β-position of R 1 and R 2 of the fatty acid ester-based solvent was 2 and 1, respectively, and bleeding occurred. Comparative Example 3 is an example in which a fatty acid ester-based solvent is not used, and the chroma of the printed matter decreased. Comparative Example 4 is an example in which a lake pigment is not used, and the chroma of the printed matter decreased. Examples 8 and Comparative Example 5 are examples using cyan ink, and good results were obtained in Example 8.

Claims

1. An oil-based inkjet ink containing a mordant lake pigment and a fatty acid ester solvent represented by the following general formula (1). 【Chemical 1】 (In general formula (1), R １ and R ２ are each independently an alkyl group, and at least one of R １ and R ２ has a side chain bonded to at least one of the carbon atoms at the α-position and the carbon atoms at the β-position, and the total number of carbon atoms of the side chain bonded to the carbon atoms at the α-position and the carbon atoms at the β-position of R １ , as well as the total number of carbon atoms of the side chain bonded to the carbon atoms at the α-position and the carbon atoms at the β-position of R ２ is 4 or more, and the number of carbon atoms in one molecule is 25 or less.)

2. In the general formula (1), R １ and R ２ At least one of them is bonded to at least one of the carbon atoms at the α-position and the carbon atoms at the β-position and has a side chain having 4 or more carbon atoms. The oil-based inkjet ink according to claim 1.

3. The oil-based inkjet ink according to claim 1 or 2, wherein the number of carbon atoms in one molecule of the fatty acid ester solvent represented by the general formula (1) is 24 or less.

4. In the general formula (1), R １ and R ２ are each independently an alkyl group having 6 or more carbon atoms. The oil-based inkjet ink according to claim 1 or 2.

5. The oil-based inkjet ink according to any one of claims 1 to 4, wherein the fatty acid ester solvent represented by the general formula (1) is 20% by mass or more based on the total amount of the ink.

6. The oil-based inkjet ink according to any one of claims 1 to 5, wherein in the general formula (1), R1 and R2 are each independently a linear alkyl group or a branched alkyl group.

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