Pigment dispersion and inkjet ink composition using the pigment dispersion

The present invention relates to a pigment dispersion liquid and an ink for inkjet, which are excellent in characteristics such as light resistance, color tone sharpness, liquid stability, and pigment particle size stability of printed matter.

Conventional Techniques Conventionally, inks used in an inkjet recording method are disclosed in JP-A-63-51485, JP-A-63-56575, JP-A-1-198671 and the like. As described above, the mainstream is that various water-soluble dyes are dissolved in water alone or in a solvent composed of water and a water-soluble solvent, and various additives are added as necessary.

[0003] However, when printing is performed using such a dye-based ink, the water resistance of the recorded image on the recording material is poor (dye bleeding in the recording portion easily occurs when water is spilled). There was a problem that the light resistance was poor (when the recording part was exposed to light, the color tone changed and the density decreased).

[0004] In order to improve these problems of dye-based inks, it is possible to apply so-called pigment-based inks using carbon black or various organic pigments instead of dyes as colorants to the inkjet recording method. It is disclosed in Japanese Patent Application Laid-Open No. 10660, Japanese Patent Application Laid-Open No. 57-10661, Japanese Patent Application Laid-Open No. 1-15542, Japanese Patent Application Laid-Open No. 2-255875, Japanese Patent Application Laid-Open No. 2-276876, and the like.

[0005] When printing is performed using a pigment-based ink, since the colorant of the ink dried on the recording material is a pigment, it may dissolve like a dye and cause bleeding even when it is exposed to water. It has good water resistance.

[0006] Further, since the pigment has a lower reactivity to light than the dye, the light resistance of the pigment-based ink is superior to that of the dye-based ink.

[0007] In such pigment-based inks, a mixture consisting of a pigment, a liquid medium, and a dispersant is generally dispersed by a disperser such as a ball mill or a sand mill, and various additives are added to the produced pigment dispersion as necessary. Although manufactured by adding, the pigment dispersion used for ink for inkjet recording is usually 200 nm or less, preferably 150 nm or less in order to prevent nozzle clogging, sharpness of printed images, secondary color reproducibility, and transparency. It is necessary to atomize and disperse the pigment particles in the pigment dispersion to the level. Furthermore, it is necessary to make fine particles in a short time in order to manufacture them industrially at low cost.

[0008] Further, in order to prevent nozzle clogging, the finely divided and dispersed pigment dispersion liquid must be able to maintain the initial particle size over time and / or in a storage environment such as high temperature and low temperature.

[0009] However, the pigment dispersants conventionally used in the present field can realize the above-mentioned fine particle dispersion in a short time, and can reduce the change in the pigment particle size during storage, and the dispersion. Until now, there has been no additive that can be suitably used in combination with an agent and improves its effect.

[0010] [Problem to be Solved by the Invention] The present invention can efficiently prepare a fine particle size pigment dispersion liquid that can be particularly preferably used for inkjet recording ink in a short time, and at the time of storing the pigment particle size. It is an object of the present invention to provide a pigment dispersion liquid using a dispersant capable of reducing changes and an ink jet ink using the dispersion liquid.

[Means for Solving the Problems] As a result of diligent studies to solve the above problems, the present inventors use a specific dispersant, more preferably a specific dispersant and a specific additive in combination. We have found that the above problems can be solved by doing so, and have arrived at the present invention.

That is, according to the present invention, firstly, at least<u style="single">The average particle size is 20 nm or more and 200 nm or less.</u>In a pigment dispersion liquid containing a pigment, a dispersant and water, a pigment dispersion liquid characterized by using a compound of the following general formula (I) as a dispersant is provided.

[0013] General formula (I) [Chemical formula 5]<img file="JP4100594B2_D0001.tif" />(In the equation, R₁Represents an alkyl group, an allyl group, or an aralkyl group having 1 to 20 carbon atoms, l represents an integer of 0 to 7, and m represents an integer of 30 to 60. ) [0015] According to the present invention, secondly, the pigment dispersion liquid according to the first description described above, which contains the compound of the following general formula (II), is provided.

[0016] General formula (II) [Chemical formula 6]<img file="JP4100594B2_D0002.tif" />(Equation R₂Represents an alkyl group having 8 to 14 carbon atoms, OA represents an oxyethylene unit or a mixture of an oxyethylene unit and an oxypropylene unit, and n represents an integer of 3 to 16. ) [0018] According to the present invention, thirdly, the pigment dispersion according to the first or second description is provided, which comprises the compound of the following general formula (III).

[0019] General formula (III) [Chemical formula 7]<img file="JP4100594B2_D0003.tif" />(In the formula, M₁Represents Na or K or Li and R₃Represents an alkyl group having 1 to 20 carbon atoms. ) [0021] According to the present invention, fourthly, the pigment dispersion according to any one of the above 1 to 3 is provided, which comprises the compound of the following general formula (IV).

[0022] General formula (IV) [Chemical formula 8]<img file="JP4100594B2_D0004.tif" />[0023] (M in the formula₂Represents Na or K or Li and R₄Represents an alkyl group having 1 to 20 carbon atoms, and x represents an integer of 1 to 12. ) [0024] According to the present invention, fifthly, the pigment dispersion liquid according to any one of the above 1 to 4 is provided, which comprises using Pigment Yellow 138 as a pigment.

[0025] According to the present invention, sixthly, the pigment dispersion liquid according to any one of the above 1 to 4 is provided, which comprises using Pigment Red 122 as a pigment.

[0026] According to the present invention, seventhly, the pigment dispersion liquid according to any one of the above 1 to 4 is provided, which comprises using Pigment Blue 15 as a pigment.

[0027] According to the present invention, eighthly, the pigment dispersion liquid according to any one of the first to fourth above, which is characterized by using carbon black as a pigment, is provided.

[0028] According to the present invention, ninthly, the content ratio of the compound of the general formula (I) to the compound of the general formula (II) is 99.99 / 0.01 to 60/40 in terms of weight ratio. The pigment dispersion liquid according to any one of the second to eighth is provided.

[0029] According to the present invention, tenth, the content ratio of the compound of the general formula (I) to the compound of the general formula (III) is 99.99 / 0.01 to 60/40 in terms of weight ratio. The pigment dispersion liquid according to any one of the third to ninth is provided.

[0030] According to the present invention, eleventh, the content ratio of the compound of the general formula (I) to the compound of the general formula (IV) is 99.99 / 0.01 to 60/40 by weight. The pigment dispersion liquid according to any one of the fourth to tenth is provided.

[0031] According to the present invention, twelfth, the pigment dispersion liquid according to any one of the first to eleventh items described above, wherein the ratio of the dispersant to the pigment is 1/15 to 1/1 is provided. Will be done.

[0033] According to the present invention, the first<u style="single">13</u>In addition, the above-mentioned first to third pigment concentrations are 5% or more and 30% or less.<u style="single">12</u>The pigment dispersion liquid according to any one of the above is provided.

[0034] According to the present invention, the first<u style="single">14</u>In addition, the above 1st to 1st<u style="single">13</u>An ink jet ink is provided, which is prepared by adding an additive to the pigment dispersion liquid according to any one of the above.

[0035] According to the present invention, the first<u style="single">15</u>In addition, the above-mentioned item is characterized in that the average particle size of the pigment is 20 nm or more and 200 nm or less.<u style="single">15</u>The inkjet inks described are provided.

[0036] According to the present invention, the sixth aspect is that the pigment concentration is 1% or more and 8% or less.<u style="single">14</u>Or the first<u style="single">15</u>The inkjet inks described are provided.

[0037] According to the present invention, the first<u style="single">17</u>In addition to the above<u style="single">14</u>To the first<u style="single">16</u>An image forming method is provided, which comprises printing with an inkjet printer using the ink according to any one of the above.

[Embodiments of the Invention] Hereinafter, the present invention will be described in more detail. Specific examples of the compound represented by the general formula (I) used in the pigment dispersion of the present invention are described below, but the present invention is not limited to these specific examples.

[0039] [Chemical 9]<img file="JP4100594B2_D0005.tif" />[0040] [Chemical 10]<img file="JP4100594B2_D0006.tif" />[0041] When m is 29 or less or 61 or more in the compound represented by the general formula (I), it is difficult to disperse the pigment into fine particles at the time of pigment dispersion, and 30 or more and 60 or less are preferable.

[0042] The pigment used in the pigment dispersion liquid of the present invention is not particularly limited, and examples thereof include the following.

[0043] Examples of blacks include carbon blacks such as furnace black, lamp black, acetylene black and channel black, metals such as copper, iron and titanium oxide, and organic pigments such as altonitroaniline black. For colors, Truisin Red, Permanent Carmine FB, First Yellow AAA, Disazo Orange PMP, Lake Red C, Brilliant Carmin 6B, Phthalocyanine Blue, Quinacridone Red, Dioxan Violet, Victoria Pure Blue, Alkaline Blue Toner, First Yellow 10G, Disazo Yellow AAMX, Disazoero AAOT, Disazoero AAOA, Yellow Iron Oxide, Disazoero HR, Orthonitroaniline Orange, Dinitroaniline Orange, Balkan Orange, Truizin Red, Chlorinated Parared, Brilliant First Scarlet, Naftor Red 23, Pyrazolone Red, Barium Red 2B, Calcium Red 2B, Strontium Red 2B, Manganese Red 2B, Barium Lysome Red, Pigment Scar Red 3B Lake, Lake Bordeaux 10B, Anthocin 3B Lake, Ansocin 5B Lake, Rhodamine 6G Lake, Eosin Lake, Bengara, Faftor Red FGR, Rhodamine B Lake, Methyl Bio Red Lake, Dioxazine Bio Red, Basic Blue 5B Lake, Basic Blue 6G Lake, Fast Sky Blue, Alkaline Blue R Toner, Peacock Blue Lake, Navy Blue, Ultramarine, Reflex Blue 2G, Reflex Blue R, Brilliant Green Lake, Diamond Green Thioflavin Lake, Phthalocyanine Green G, Green Gold, Phthalocyanine Green Y, Iron Oxide Powder, Sabiko, Zinc Hua, Titanium Oxide, Calcium Carbonate, Clay, Barium Sulfate, Alumina, Alumina White, Aluminum Powder, Bronze Powder, daylight fluorescent pigment, pearl pigment, naphthol carmine FB, naphthol red M, permanent carmine FB, first Other processed pigments such as graft carbon whose pigment surface is treated with resin or the like can be used, such as yellow G, disazoero AAA, dioxane violet, alkaline blue G toner, etc. In some cases, these can be mixed in two or more types.

[0044] Among these, carbon black for black, pigment yellow 138 for yellow, pigment red 122 for magenta, and pigment for cyan are used in terms of dispersion stability, color reproducibility, and light resistance. Blue 15: 3 can be preferably used. Of these, Pigment Red 122, which has been surface-treated with a pigment derivative or the like, has good dispersion stability and can be used more preferably.

[0045] Examples of the water-soluble organic solvent that can be added to the pigment dispersion liquid and the ink for inkjet using the pigment dispersion liquid in the present invention include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, and n-butyl. Alcohols, sec-butyl alcohols, tert-butyl alcohols and other alkyl alcohols with 1 to 4 carbon atoms: dimethylformamides, dimethylacetamides and other amides: acetone, diacetone alcohols and other ketones or ketone alcohols: tetrahydrofuran, dioxane, etc. Ethers: [0046] Polyalkylene glycols such as polyethylene glycol and polypropylene glycol: ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol Alkylene glycols containing 2 to 6 carbon atoms such as alkylene groups: [0047] Glycerin, ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether, etc. Lower alkyl ethers of polyhydric alcohols: N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like.

[0048] Among many of these water-soluble organic solvents, a lower alkyl ether of a polyhydric alcohol such as diethylene glycol and a polyhydric alcohol such as triethylene glycol monomethyl (or ethyl) ether is preferable.

The pigment dispersion liquid is obtained by dispersing a mixture of the above pigment, dispersant, water or water-soluble organic solvent with a known disperser such as a sand mill, a pearl mill, a dyno mill, a ball mill, a roll mill, a nanomizer, or a homogenizer. .. Inkjet ink is obtained by stirring and mixing the pigment dispersion, water, a water-soluble organic solvent, a surfactant, and the like, filtering coarse particles with a filter, a centrifuge, and the like, and degassing.

[0050] In the present invention, the compounds of the general formula (II) and / or the general formula (III) and / or the general formula (IV) may be mixed with a dispersant at the time of pigment dispersion, or may be used at the time of producing an ink jet ink. It may be added.

[0051] In the present invention, R of the compound of the general formula (II).₂Is preferably an alkyl group having 8 to 14 carbon atoms. When the number of carbon atoms is 7 or less or 15 or more, the effect of stabilizing the particle size of the pigment fine particles in the pigment dispersion is small. Further, n is preferably an integer of 3 to 16. When n is 2 or less or 17 or more, the effect of particle size stabilization is small.

[0052] In the present invention, R of the compound of the general formula (III)₃Is preferably an alkyl group having 1 to 20 carbon atoms. R₃However, when a hydrogen atom or an alkyl group having 21 or more carbon atoms is used, the effect of stabilizing the particle size of the pigment fine particles in the pigment dispersion is small.

[0053] In the present invention, R of the compound of the general formula (IV)₄Is preferably an alkyl group having 1 to 20 carbon atoms. R₄However, when a hydrogen atom or an alkyl group having 21 or more carbon atoms is used, the effect of stabilizing the particle size of the pigment fine particles in the pigment dispersion is small. Further, x is preferably an integer of 1 to 12. When x is 0 or 13 or more, the effect of particle size stabilization is small.

[0054] In the present invention, the content ratio of the compound of the general formula (I) to the compound of the general formula (II) is preferably 99.99 / 0.01 to 60/40 in terms of weight ratio. If it is larger than 99.99 / 0.01, there is almost no effect of adding the general formula (II), so the degree of improvement in the particle size stabilizing effect of the pigment fine particles in the pigment dispersion is small, and even if it is smaller than 60/40, the particle size is stable. The degree of improvement in the chemical effect is small.

[0055] For the same reason, the content ratio of the compound of the general formula (I) to the compound of the general formula (II) is preferably 99.99 / 0.01 to 60/40.

[0056] The content ratio of the compound of the general formula (I) to the compound of the general formula (IV) is also preferably 99.99 / 0.01 to 60/40 for the same reason.

[0057] In the present invention, the ratio of the dispersant to the pigment is preferably 1/15 to 1/1. If it is smaller than 1/15, it is difficult to disperse the particles into fine particles, and the effect of stabilizing the particle size of the pigment fine particles in the pigment dispersant is small. If it is larger than 1/1, the viscosity of the pigment dispersion liquid and the ink for inkjet using the pigment dispersion liquid becomes too high, and as a result, printing with an inkjet printer tends to be difficult.

[0058] The average particle size of the pigment in the dispersion liquid and the ink is preferably 20 nm or more and 200 nm or less. If the average particle size of the pigment is larger than 200 nm, not only the nozzle is likely to be clogged, but also the color tone is inferior. Tends to be inferior. The average particle size in the present invention is a value measured by Microtrack UPA manufactured by Nikkiso Co., Ltd.

[0059] The pigment concentration of the dispersion is preferably 5% or more and 30% or less. If it is less than 5%, the productivity is poor, and if it is more than 30%, the viscosity of the dispersion tends to be too high and it tends to be difficult to disperse.

[0060] Examples of the additive to the dispersion include alcohols such as methanol, ethanol, 1-propanol and 2-propanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, glycerin and the like as water-soluble organic media in addition to water. polyhydric alcohol, N- methylpyrrolidone, pyrrolidone derivatives of 2-pyrrolidone, etc., acetone, ketones such as methyl ethyl ketone, monoethanolamine, diethanolamine, alkanolamines such as triethanolamine and the like, also Bruno anion, anionic, cationic, amphoteric Examples include various surfactants and preservatives.

[0061] The pigment concentration of the ink is preferably 1% or more and 8% or less. If it is less than 1%, the image density is low and the print is lacking in sharpness. If it is more than 8%, not only the viscosity of the ink tends to be high, but also the nozzles are likely to be clogged.

[0062] Examples of the additive to the ink include the same materials as those described in the additive to the dispersion liquid. The content of the water-soluble organic solvent is preferably 0% or more and 50% or less with respect to the total amount of the recording liquid.

[0063] Examples of the method for printing the above ink include a continuous injection type and an on-demand type. Examples of the on-demand type include a piezo method, a thermal inkjet method, and an electrostatic method.

[Examples] Hereinafter, the present invention will be described in more detail based on Examples. In addition, "part" and "%" shown below both represent a weight standard.

Example 1 Mixture (A) Pigment Red 122 24 parts (Clariant, Toner Magenta EO2) POE (<u style="single">m</u>= 40) 120 parts of 10% aqueous solution of β-naphthyl ether (dispersant of compound No. 1) 16 parts of ion-exchanged water Put the mixture (A) having the above composition in a 500 ml beaker and use Teflon (<u style="single">Registered trademark</u>) A coated stirrer was added, and the mixture was stirred for 3 hours.

Next, the mixture (A) treated by this stirring was dispersed for 8 hours using a 0.3 mmφ zirconia ball with a sand mill (a batch type tabletop sand mill manufactured by Campe Hapio Co., Ltd.), and the average particle size was averaged. A pigment dispersion (A) of 120.5 nm (using Microtrac UPA150 manufactured by Nikkiso Co., Ltd.) was obtained.

[0067] Using the pigment dispersion (A) obtained by the above method, the ink for inkjet is prepared according to the following ink formulation (a), and after stirring for 30 minutes, filtration is performed with a membrane filter having a pore size of 0.8 μm, and vacuum removal is performed. Inkjet ink (a) was obtained with care.

Ink formulation (a) Pigment dispersion (A) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-Pyrrolidone 3.0 parts Polyoxyethylene (3) Alkyl (C13) Ether Sodium acetate 1.45 parts (Compound of general formula (IV) Of which, M₂Is Na, R₄Is a linear alkyl group with 13 carbon atoms and a compound with x of 3) Ion-exchanged water 75.55 parts [0069] This inkjet ink (a) is sealed in a plastic container and left in an environment of 70 ° C for 1 week. , The particle size after being left to stand was measured. The particle size after standing was 121.1 nm.

[0070] Example 2 Mixture (B) Pigment Red 122 24 parts (manufactured by Dainippon Ink Co., Ltd., FATOGEN SUPER MAGENTA RG) POE (<u style="single">m</u>= 40) 120 parts of 10% aqueous solution of β-naphthyl ether (dispersant of compound No. 1) 0.2 parts of heptaethylene glycol mono (5-decyl) ether (Of the compounds of general formula (II), R₂Is a linear alkyl group having 10 carbon atoms, OA is an oxyethylene unit, and n is a compound) 15.8 parts of ion-exchanged water [0071] A mixture (B) having the above composition is dispersed in the same manner as in Example 1. A pigment dispersion (B) having an average particle size of 118.7 nm was obtained. Using this pigment dispersion (B), adjust the inkjet ink with the following ink formulation (b), stir for 30 minutes, filter with a membrane filter with a pore size of 0.8 μm, vacuum degas, and then ink jet ink (b). ) Was obtained.

Ink formulation (b) Pigment dispersion (B) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-Pyrrolidone 3.0 parts Ion-exchanged water 77.0 parts [0073] This inkjet ink (b) is sealed in a plastic container, and 70 It was left for 1 week in an environment of ° C, and the particle size after leaving was measured. The particle size after standing was 119.1 nm.

[0074] Example 3 Using the pigment dispersion (A) of Example 1, adjust the ink for inkjet with the following ink formulation (c), stir for 30 minutes, filter with a membrane filter having a pore size of 0.8 μm, and remove the vacuum. Inkjet ink (c) was obtained.

Ink formulation (c) Pigment dispersion (A) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-Pyrrolidone 3.0 parts Dioctyl sulfosuccinate Na 0.5 parts (Of the compounds of the general formula (III), M₁Is Na, R₃Is a compound with a linear alkyl group having 8 carbon atoms) Ion-exchanged water 76.5 parts [0076] This inkjet ink (c) is sealed in a plastic container and left for 1 week in an environment of 70 ° C. The diameter was measured. The particle size after standing was 120.7 nm.

Example 4 Mixture (C) Pigment Yellow 138 24 parts (manufactured by Toyo Ink Co., Ltd., LIONOGEN YELLOW 1010) POE (<u style="single">m</u>= 40) 120 parts of 10% aqueous solution of α-naphthyl ether (dispersant of compound No. 2) 16 parts of ion-exchanged water [0078] Disperse the mixture (C) having the above composition in the same manner as in Example 1. A pigment dispersion (C) having an average particle size of 70.2 nm was obtained.

[0079] Inkjet ink is adjusted with the following ink formulation (d) using this pigment dispersion (C), stirred for 30 minutes, filtered with a membrane filter having a pore size of 0.8 μm, vacuum degassed, and inkjet ink. Obtained (d).

[0080] Ink formulation (d) Pigment dispersion (C) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-Pyrrolidone 3.0 parts Ion-exchanged water 77.0 parts [0081] This inkjet ink (d) is sealed in a plastic container, and 70 It was left for 1 week in an environment of ° C, and the particle size after leaving was measured. The particle size after standing was 71.6 nm.

[0082] Example 5 Using the pigment dispersion (A) of Example 1, adjust the ink for inkjet with the following ink formulation (e), stir for 30 minutes, filter with a membrane filter having a pore size of 0.8 μm, and evacuate. I was careful to obtain the ink for inkjet (e).

[0083] Ink formulation (e) Pigment dispersion (A) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-Pyrrolidone 3.0 parts Ion-exchanged water 77.0 parts [0084] This inkjet ink (e) is sealed in a plastic container, and 70 It was left for 1 week in an environment of ° C, and the particle size after leaving was measured. The particle size after standing was 145.6 nm.

Example 6 Mixture (D) Pigment Blue 15:3 24 parts (LIONOL BLUE FG-7351 manufactured by Toyo Ink Co., Ltd.) POE (<u style="single">m</u>= 40) 120 parts of 10% aqueous solution of β-naphthyl ether (dispersant of compound No. 1) 16 parts of ion-exchanged water [0086] Disperse the mixture (D) having the above composition in the same manner as in Example 1. A pigment dispersion (D) having an average particle size of 97.1 nm was obtained. Inkjet ink is adjusted with the following ink formulation (f) using this pigment dispersion (D), stirred for 30 minutes, filtered with a membrane filter with a pore size of 0.8 μm, vacuum degassed, and inkjet ink (f). Got

[0087] Ink formulation (f) Pigment dispersion (D) 40.0 parts Glycerin 7.5 parts Diethylene glycol 22.5 parts 2-Pyrrolidone 3.0 parts Ion-exchanged water 77.0 parts [0088] This inkjet ink (f) is sealed in a plastic container, and 70 It was left for 1 week in an environment of ° C, and the particle size after leaving was measured. The particle size after standing was 96.7 nm.

Comparative Example 1 Mixture (E) Pigment Red 122 24 parts (Clariant, Toner Magenta EO2) 120 parts of 10% aqueous solution of styrene-acrylic acid copolymer (Johnson Polymer, John Krill HPD71 aqueous solution) Ion 16 parts of exchanged water [0090] When the mixture (E) having the above composition was dispersed in the same manner as in Example 1, a pigment dispersion (E) having an average particle size of 210.8 nm was obtained.

[Effect of the Invention] In the pigment dispersion liquid of the present invention and the ink for inkjet using the dispersion liquid, the particle size of the dispersed pigment particles is fine, there is no concern about clogging of the inkjet head, and the pigment particle size with time. It has high stability and can be suitably used as a highly reliable ink.