JP2020094084A - Aqueous inkjet ink and inkjet recording method - Google Patents

Abstract

To provide an aqueous inkjet ink excellent in storage stability, image quality and drying property after printing with respect to a PVC base material, and maintenance property.SOLUTION: The aqueous inkjet ink comprises water, a coloring material, a water-soluble organic solvent component, a surfactant and resin fine particles, in which the water-soluble organic solvent component comprises a first monool represented by RO(CHO)H (where Ris a linear or branched alkyl group having 1 to 4 carbon atoms, and n is 2 or 3), a second monool that is 3-methoxy-1-butanol and/or 3-methoxy-3-methyl-1-butanol, and both terminal diols represented by HO-R-OH (where Ris a branched alkylene group having 5 to 7 carbon atoms); the content of the second monool in the ink is 8 to 27 mass%; the content of the first monool in the ink is 1 to 9 mass%; and the content of both terminal diols in the ink is 7 to 18 mass%.SELECTED DRAWING: None

Description

The present invention relates to aqueous inkjet inks. The present invention also relates to an inkjet recording method using the aqueous inkjet ink.

Inkjet printers that employ an inkjet recording method are widely used as output devices in homes and offices because they have advantages such as easy operation, low noise, and easy color printing. In recent years, inkjet printers have been used for industrial applications such as displays, posters, and bulletin boards.

The ink jet recording system is a recording system in which ink droplets are directly ejected from a very fine nozzle onto a medium and adhered to obtain a character or an image. In industrial applications, non-absorbent substrates are often used as media. One of the typical non-absorbent substrates is polyvinyl chloride (PVC) substrate.

For printing (image formation) on a PVC substrate, an eco-solvent ink jet ink containing a glycol ether solvent and a resin dissolving solvent (eg, lactones) is suitable. The eco-solvent ink jet ink dissolves the surface of the PVC substrate, and the pigment and the fixing resin coat the surface of the PVC substrate to form an image. Therefore, according to the eco-solvent type inkjet ink, good image quality such as less bleeding can be obtained and the fixability is also high.

However, the eco-solvent ink-jet ink is feared that the volatilized solvent adversely affects the environment and the human body. Therefore, a water-based inkjet ink suitable for printing on a PVC substrate is desired, and its development is being promoted. Such an aqueous inkjet ink typically contains water, a water-soluble organic solvent, a coloring material, and resin fine particles as a fixing component (see, for example, Patent Document 1).

In Patent Document 1, a monool having an ethylene glycol chain, a monool having a propylene glycol chain, and 3-methoxy-1-butanol or 3-methoxy-3-methyl-1-butanol are combined to form an aqueous solution. By adding it to an inkjet ink, the storage stability of an aqueous inkjet ink is improved, and when used for printing on a PVC substrate, it is possible to form an image with less blurring and high fixability with high optical density. It is stated that there is. Further, Patent Document 1 describes that the storage stability is further improved by further blending diols.

JP, 2018-123293, A

When an image is recorded using an aqueous inkjet ink by an inkjet recording device, the ink adheres to a part of the device such as an inkjet head and a print head cap. If the adhered ink is dried and solidified, it may cause a problem. Therefore, the inkjet recording apparatus is regularly maintained such as cleaned. However, as a result of diligent studies by the present inventor, it was found that the conventional technique described in Patent Document 1 has room for improvement in ease of maintenance (in other words, maintainability).

On the other hand, changing the ink composition can adversely affect the ink properties. Specifically, for example, changing the ink composition can adversely affect storage stability, image quality, and dryness after printing.

Therefore, an object of the present invention is to provide a water-based inkjet ink which is excellent in storage stability, image quality on a PVC substrate, drying property after printing, and maintainability.

The water-based inkjet ink of the present invention contains at least water (A), a coloring material (B), a water-soluble organic solvent component (C), a surfactant (D), and resin fine particles (E). The water-soluble organic solvent component (C) is R ¹ O(C ₃ H ₆ O) _n H (wherein, R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms, and n is A first monool solvent represented by 2 or 3) and at least one selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol. and there second monool solvent, (wherein, R ² is a is branched alkylene group having 5-7 carbon atoms) HO-R ² -OH containing the both terminal diol compound represented by. The content of the second monool-based solvent in the ink is 8% by mass or more and 27% by mass or less. The content of the first monool-based solvent in the ink is 1% by mass or more and 9% by mass or less. The content of the both-end diol compound in the ink is 7% by mass or more and 18% by mass or less.

The inkjet recording method of the present invention comprises a step of ejecting the above-mentioned aqueous inkjet ink onto a medium having a non-absorbent substrate, and a step of drying the aqueous inkjet ink ejected onto the medium to form an ink coating film. including.

ADVANTAGE OF THE INVENTION According to this invention, the water-based inkjet ink which is excellent in storage stability, the image quality with respect to a PVC substrate, the drying property after printing, and maintainability is provided.

The water-based inkjet ink of the present invention contains at least water (A), a coloring material (B), a water-soluble organic solvent component (C), a surfactant (D), and resin fine particles (E). Here, the water-soluble organic solvent component (C) is R ¹ O(C ₃ H ₆ O) _n H (in the formula, R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms, n represents an integer of 2 or 3 and a first monool solvent (hereinafter, also referred to as “monool solvent (1)”), 3-methoxy-1-butanol and 3-methoxy- A second monool-based solvent (hereinafter, also referred to as “monool-based solvent (2)”) that is at least one selected from the group consisting of 3-methyl-1-butanol, and HO—R ² —OH (formula). R ² contains a both-end diol compound represented by a branched alkylene group having 5 to 7 carbon atoms (hereinafter, also referred to as “C _5-7 both-end branched diol solvent”). The content of the monool solvent (2) in the ink is 8% by mass or more and 27% by mass or less. The content of the monool solvent (1) in the ink is 1% by mass or more and 9% by mass or less. The content of the C _5-7 both-end branched diol solvent in the ink is 7% by mass or more and 18% by mass or less.

[Water (A)]
The water-based inkjet ink of the present invention contains water (A). By containing water (A), the water-based inkjet ink of the present invention has an advantage that the environmental load is small. The water (A) used in the present invention is not particularly limited, but from the viewpoint of preventing contamination of impurities, ion-exchanged water, ultrafiltered water, reverse osmosis water, distilled water, or ultrapure water is preferable, Ion-exchanged water is more preferred.

The content of water (A) in the aqueous inkjet ink of the present invention is preferably 40% by mass or more, more preferably 45% by mass or more, and further preferably 50% by mass or more. On the other hand, 80 mass% or less is preferable, 75 mass% or less is more preferable, and 70 mass% or less is further preferable.

[Coloring material (B)]
Examples of the color material (B) include dyes and pigments. The coloring material (B) may be used alone or in combination of two or more kinds at any ratio.

As the dye, for example, various dyes known to be usable in an aqueous inkjet ink can be used, and examples thereof include a direct dye, an acid dye, an edible dye, a basic dye, and a reactive dye. , Disperse dyes, vat dyes and the like.

More specifically, examples of cyan dyes include C.I. I. Acid Blue 1,7,9,15,22,23,25,27,29,40,41,43,45,54,59,60,62,72,74,78,80,82,83,90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 199, 203, 204, 205, 229, 234, 236, 249, C.I. I. Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 120, 123, 158, 160, 163, 165. 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249, C.I. I. Reactive Blue 1,2,3,4,5,7,8,9,13,14,15,17,18,19,20,21,25,26,27,28,29,31,32,33, 34, 37, 38, 39, 40, 41, 43, 44, 46, C.I. I. Food Blue 1, 2, C.I. I. Basic Blue 9, 25, 28, 29, 44 and the like can be mentioned.

Examples of magenta dyes include C.I. I. Acid Red 1,6,8,9,13,14,18,26,27,32,35,37,42,51,52,57,75,77,80,82,85,87,88,89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184. 186, 194, 198, 209, 211, 215, 219, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, C.I. I. Direct Red 1,2,4,9,11,13,17,20,23,24,28,31,33,37,39,44,46,62,63,75,79,80,81,83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, C.I. I. Reactive Red 1,2,3,4,5,6,7,8,11,12,13,15,16,17,19,20,21,22,23,24,28,29,31,32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, C.I. I. Food Red 7,9,14 etc. are mentioned.

Examples of yellow dyes include C.I. I. Acid Yellow 1,3,11,17,19,23,25,29,36,38,40,42,44,49,59,61,70,72,75,76,78,79,98,99, 110, 111, 127, 131, 135, 142, 162, 164, 165, C.I. I. Direct Yellow 1,8,11,12,24,26,27,33,39,44,50,58,85,86,87,88,89,98,110,132,142,144, Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42, C.I. I. Food Yellow 3, 4 and the like can be mentioned.

Examples of black dyes include C.I. I. Direct Black 1,7,19,32,51,71,108,146,154,166 etc. are mentioned.

Examples of dyes other than cyan, magenta, yellow, and black include C.I. I. Acid Green 7, 12, 25, 27, 35, 36, 40, 43, 44, 65, 79, C.I. I. Direct Green 1, 6, 8, 26, 28, 30, 31, 37, 59, 63, 64, C.I. I. Reactive Green 6,7, C.I. I. Direct Violet 2, 48, 63, 90, C.I. I. Reactive Violet 1, 5, 9, 10 etc. are mentioned.

As the pigment, both an inorganic pigment and an organic pigment can be used.

Examples of organic pigments include azo pigments (eg, azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, etc.), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments). , Dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofuraron pigments), dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc. .

Examples of inorganic pigments include titanium oxide, zinc oxide, zinc sulfide, lead white, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, black iron oxide, cadmium red, red iron oxide, molybdenum, molybdenum. Red, molybdate orange, chrome vermillion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine blue, navy blue, cobalt blue, cerulean. Blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, cobalt violet and the like can be mentioned.

More specifically, examples of black pigments include carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black; copper, iron (CI pigment black). 11) and other metals; metal oxides such as titanium oxide; organic pigments such as aniline black (CI Pigment Black 1).

Examples of cyan pigments include C.I. I. Pigment Blue 1, 2, 3, 15:1, 15:3, 15:4, 15:6, 16, 21, 22, 60, 64 and the like.

Examples of magenta pigments include C.I. I. Pigment Red 5,7,9,12,31,48,49,52,53,57,97,112,120,122,146,147,149,150,168,170,177,178,179,184, 188, 202, 206, 207, 209, 238, 242, 254, 255, 264, 269, 282; C.I. I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 40, 50 and the like.

Examples of yellow pigments include C.I. I. Pigment Yellow 1, 2, 3, 12, 13, 14, 14, 16, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185, 213 and the like.

Examples of pigments of other colors include C.I. I. Pigment Green 7, 10, 36; C.I. I. Pigment Brown 3, 5, 25, 26; C.I. I. Pigment Orange 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 62, 63, 64, 71 and the like.

Further, a pigment having a hydrophilic group such as a carboxyl group, a sulfonic acid group, a phosphonic acid group or a hydroxyl group on the surface (so-called “self-dispersion pigment”) can be used. Examples of the carbon black self-dispersion pigments include CAB-O-JET200, 300, 352K, 400 (above, manufactured by Cabot Corporation). Examples of the cyan self-dispersion pigments include CAB-O-JET250C, 450C, 554B (all manufactured by Cabot Corporation). Examples of magenta-based self-dispersion pigments include CAB-O-JET260M, 265M, 465M (above, manufactured by Cabot Corporation). Examples of yellow self-dispersion pigments include CAB-O-JET270Y, 470Y, 740Y (above, manufactured by Cabot Corporation). A self-dispersion pigment is preferable as the coloring material (B) because it can be dispersed in water (A) without using a dispersant.

The content of the coloring material (B) in the aqueous inkjet ink of the present invention is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and 1% by mass or more as a solid content (solid content concentration). Is more preferable. On the other hand, 20 mass% or less is preferable, 15 mass% or less is more preferable, and 12 mass% or less is further preferable.

[Water-soluble organic solvent component (C)]
In the present specification, the "water-soluble organic solvent" constituting the water-soluble organic solvent component (C) refers to an organic solvent having a solubility in water at 20°C of 500 g/L or more. The water-soluble organic solvent is preferably an organic solvent which is uniformly miscible with water at 20° C. at an arbitrary ratio.

The water-soluble organic solvent component (C) is at least R ¹ O(C ₃ H ₆ O) _n H (wherein, R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms, and n is A monool solvent (1) represented by 2 or 3) and at least one selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol. there second monool solvents (2), (wherein, ^{R 2} is a branched alkylene group having 5-7 carbon atoms) ^HO-R 2 -OH _{C 5-7} both ends which is represented by And a branched diol solvent.

R ¹ O(C ₃ H ₆ O) _n OH (wherein, R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms, and n represents an integer of 2 or 3) The monool solvent (1) is a component that improves the wettability and spreadability of the water-based inkjet ink of the present invention and improves the image quality. As the monool-based solvent (1), a monool-based solvent satisfying the above formula can be used alone or in combination of two or more kinds. In the above formula, R ¹ is preferably a methyl group or an ethyl group, more preferably a methyl group. As the monool solvent (1), dipropylene glycol monomethyl ether and tripropylene glycol monomethyl ether are preferable, and tripropylene glycol monomethyl ether is more preferable. The propylene group (C ₃ H ₆ ) may be either an n-propylene group or an isopropylene group, and is preferably an isopropylene group. The content of the monool solvent (1) in the aqueous inkjet ink of the present invention is 1% by mass or more and 9% by mass or less. If the content is less than 1% by mass, coalescence between ink dots ejected from the inkjet head occurs, resulting in non-uniform image density and poor image quality. Therefore, the content is preferably 2% by mass or more, more preferably 2.5% by mass or more, and further preferably 3% by mass or more. On the other hand, if the content exceeds 9% by mass, the storage stability of the ink decreases. Therefore, the content is preferably 8.5% by mass or less, more preferably 8% by mass or less, and further preferably 7.5% by mass or less.

The monool solvent (2), which is at least one selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol, improves the initial drying property of the aqueous inkjet ink of the present invention. It is an ingredient to enhance. As the monool-based solvent (2), 3-methoxy-1-butanol is preferable because it improves image quality. The content of the monool-based solvent (3) in the aqueous inkjet ink of the present invention is 8% by mass or more and 27% by mass or less. If the content is less than 8% by mass, the initial drying speed of the ink becomes slow, coalescence between the ink dots ejected from the inkjet head occurs, the image density becomes uneven, and the image quality deteriorates. Therefore, the content is preferably 10% by mass or more, and more preferably 12.5% by mass or more. On the other hand, if the content exceeds 27% by mass, the storage stability of the ink decreases. Therefore, the content is preferably 25 mass% or less, more preferably 20 mass% or less.

(Wherein, ^{R 2} is a branched alkylene group having 5-7 carbon atoms) ^HO-R 2 -OH _{C 5-7} both terminally branched diol solvent represented by the storage of the aqueous inkjet ink of the present invention It is a component that not only improves stability but also greatly improves maintainability. In the C _5-7 both-end branched diol solvent, the position of the hydroxyl group is at both ends of the compound, so that the hydroxyl group stabilizes the mixed state of the monool-based solvent and water, and thereby the monool-based solvent. It is considered that the side reaction between the solvent and the resin dispersion is suppressed, and as a result, the storage stability becomes high. Further, since R ² is a branched alkylene group having 5 to 7 carbon atoms, maintainability is improved. This is because the diol solvent at both terminal ends volatilizes last regardless of the boiling point in the solvent component of the water-based inkjet ink, but the linear diol solvent at both terminals is completely dried even at room temperature, so the water-based inkjet ink is dried and solidified. On the other hand, when R ² is a branched alkylene group having an appropriate carbon number, entanglement between diol molecules increases during the ink drying process, which makes the diol molecules difficult to move, and This is considered to be because the drying is suppressed, and as a result, the drying and solidification of the aqueous inkjet ink is suppressed. In order to effectively cause this entanglement between the diol molecules, the branched alkylene group represented by R ² has 5 or more carbon atoms, and is represented by R ² from the viewpoint of the drying property after printing. The branched alkylene group has 7 or less carbon atoms. The branched alkylene group represented by R ² preferably has 6 carbon atoms. The alkylene group represented by R ² may have one branch or two or more branches, and preferably one branch.

Examples of the C _5-7 both-end branched diol solvent include 2,2-dimethyl-1,3-propanediol (boiling point: about 208° C.), 2-methyl-1,4-butanediol, 2,3-dimethyl. -1,4-butanediol, 2-ethyl-1,4-butanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,5 -Pentanediol, 2,3-dimethyl-1,5-pentanediol, 3,3-dimethyl-1,5-pentanediol, 2,4-dimethyl-1,5-pentanediol, 2-ethyl-1,5 -Pentanediol, 3-ethyl-1,5-pentanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol and the like. Of these, 3-methyl-1,5-pentanediol is preferable.

The content of the C _5-7 both-end branched diol solvent in the aqueous inkjet ink of the present invention is 7% by mass or more and 18% by mass or less. If the content is less than 7% by mass, the storage stability tends to decrease, and particularly the maintainability becomes insufficient. Therefore, the content is preferably 7.5% by mass or more, and more preferably 8% by mass or more. On the other hand, when the content exceeds 18% by mass, the drying property after printing is deteriorated and the image quality is deteriorated. Therefore, the content is preferably 15% by mass or less, more preferably 12.5% by mass or less.

The water-soluble organic solvent component (C) is another water-soluble organic solvent within the range that does not significantly impair the effects of the present invention, that is, a monool-based solvent (1), a monool-based solvent (2), and C _{5 −.} A water-soluble organic solvent other than the _7- terminal branched diol solvent may be contained. As the other water-soluble organic solvent, those known as water-soluble organic solvents for water-based inkjet inks can be used without particular limitation. Examples thereof include propylene glycol-n-butyl ether, propylene glycol-t-butyl ether, ethylene glycol-n-propyl ether, ethylene glycol-n-butyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, 1-ethoxy-2-. Other monools such as propanol; ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol, 1,3- Butanediol, 2-methyl-1,3-propanediol, 1,2-pentanediol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 1,5-pentanediol, 1,2- Other diols such as hexanediol, 1,6-hexanediol and 2-ethyl-1,3-hexanediol; nitrogen-containing water-soluble organic solvents and the like. These may be used alone or in combination of two or more at any ratio.

The content of the water-soluble organic solvent component (C) in the aqueous inkjet ink of the present invention (that is, the total content of the water-soluble organic solvent) is not particularly limited, but by adding the water-soluble organic solvent described above, Since the effect to be exhibited is higher, it is preferably 17.5% by mass or more, more preferably 20% by mass or more, further preferably 25% by mass or more, and most preferably 27.5% by mass. % Or more. On the other hand, the content is preferably 42.5% by mass or less, more preferably 40% by mass or less, further preferably 36% by mass or less, and most preferably 33% by mass or less.

[Surfactant (D)]
The surfactant (D) is a component that optimizes surface tension and interfacial tension. As the surfactant (D), known ones that can be used in an aqueous inkjet ink can be used without particular limitation, and examples thereof include anionic surfactants, nonionic surfactants, and cationic surfactants. , Amphoteric surfactants and the like. Among them, anionic surfactants or nonionic surfactants are preferable, and nonionic surfactants are more preferable.

Examples of the nonionic surfactants include sorbit surfactants, acetylene glycol surfactants, sorbitan surfactants, silicone surfactants, polyoxyethylene alkyl ether surfactants, and fluorine surfactants. Etc. Among them, the silicone-based surfactant is preferable because the static surface tension can be adjusted with a small amount, and thereby the wettability to a non-absorbent substrate such as a PVC substrate can be greatly improved.

As the silicone-based surfactant, a known silicone-based surfactant can be used without particular limitation, and it is also available as a commercial product. Examples of commercially available products include BYK-306, BYK-307, BYK-333, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349 (above, manufactured by Big Chemie Japan), KF-. 351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-. 6011, KF-6012, (all manufactured by Shin-Etsu Chemical Co., Ltd.), Silface SAG002, SAG005, SAG503A, SAG008 (all manufactured by Nissin Chemical Industry Co., Ltd.) and the like. As the silicone-based surfactant, a polyether-modified silicone-based surfactant is preferable.

The content of the surfactant (D) in the inkjet ink of the present invention may be appropriately determined depending on the type of the surfactant used so that the surface tension and the interfacial tension of the ink are optimized. The content of the surfactant (D) is preferably 0.05% by mass or more, more preferably 0.2% by mass or more. On the other hand, the content is preferably 5% by mass or less, more preferably 3% by mass or less, and further preferably 2.5% by mass or less.

[Resin particles (E)]
The resin fine particles (E) are a binder component that enhances the fixability to the non-absorbent substrate and the coating film resistance.

As the resin fine particles (E), known ones that can be used in an aqueous inkjet ink can be used without particular limitation. Examples of the resin constituting the resin fine particles (E) include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, polyethylene resin, polypropylene resin, fluoroolefin resin, butadiene resin, styrene resin, styrene-butadiene resin, styrene- Acrylic resins, ethylene-acrylic resins, vinyl chloride resins, acrylic-silicone resins and the like can be mentioned.

The resin fine particles (E) do not have to be composed of one kind of resin, and may be composed of two or more kinds of resins. For example, different kinds of monomers are further emulsified with respect to core-shell type resin fine particles in which the resin composition is different between the core portion and the shell portion, or acrylic fine particles (seed particles) previously prepared to control the particle diameter. Fine particles obtained by polymerization can be used. Furthermore, hybrid type resin fine particles in which fine resin particles made of different resins such as fine particles made of acrylic resin and fine particles made of urethane resin are chemically bonded can be used.

The resin fine particles (E) preferably contain an acrylic resin or a urethane resin at least in the surface layer portion, and more preferably include a urethane resin in at least the surface layer portion, because the fixing property and the ink stability are particularly excellent.

The volume average particle diameter of the resin fine particles (E) is not particularly limited, but is preferably 10 to 1000 nm, more preferably 10 to 200 nm, and further preferably 10 to 50 nm. The volume average particle diameter can be obtained using, for example, a particle size distribution measuring device.

The content of the resin fine particles (E) in the inkjet ink of the present invention is preferably 3% by mass or more, more preferably 5% by mass or more, as a solid content (solid content concentration). On the other hand, it is preferably 15% by mass or less, more preferably 12% by mass or less.

The water-based inkjet ink of the present invention includes, in addition to the above components, an antiseptic agent, an antifungal agent, a thickener, an antifoaming agent, a pH adjusting agent, an anticorrosive agent, etc. within a range that does not significantly impair the effects of the present invention. You may contain the additive.

The aqueous inkjet ink of the present invention can be prepared by mixing the components according to a known method. For example, water (A), an emulsion containing a coloring material (B), a water-soluble organic solvent (C), a surfactant (D), an emulsion containing resin fine particles (E), and other components are mixed with a known mixing device. Alternatively, it can be prepared by uniformly mixing with a stirring device.

The above-described water-based inkjet ink of the present invention has an advantageous effect of being excellent in all of storage stability, image quality on a PVC substrate, drying property after printing, and maintainability.

The aqueous inkjet ink of the present invention can be particularly preferably used for printing on a PVC substrate. In addition, non-absorptive substrates other than PVC substrates such as PET substrates, surface-treated (corona-treated) polyethylene (PE) substrates, surface-treated (corona-treated) polypropylene (PP) substrates, polystyrene substrates, etc. , And can be used for printing (image formation) on paper base materials such as art paper, coated paper, cast paper, high-quality paper, synthetic paper, inkjet paper, etc., and is preferably used for printing on non-absorbent base materials. You can

Therefore, from another aspect, the present invention is a step of ejecting the above-described aqueous inkjet ink (the ink described as the aqueous inkjet ink of the present invention) onto a medium having a non-absorbent substrate (hereinafter, also referred to as “ejection step”). ), and a step of drying the aqueous inkjet ink ejected onto the medium to form an ink coating film (hereinafter, also referred to as “coating film forming step”).

Examples of the non-absorbent base material include PVC base material, PET base material, surface-treated (corona-treated) PE base material, surface-treated (corona-treated) PP base material, polystyrene base material, and the like. Wood is preferred.

The medium may have a single-layer structure or a multilayer structure of a non-absorbent substrate. When the medium has a multilayer structure, for example, the medium may have a non-absorbing substrate that is a substrate to be printed, an adhesive layer, and the like.

In the discharging step, the inkjet ink is discharged onto the non-absorbent substrate of the medium by the inkjet method. The discharging step can be performed according to a known method. The inkjet recording method of the present invention may further include a step of heating the medium before the discharging step. At this time, the surface temperature of the medium is, for example, 30° C. or higher and lower than the softening point of the medium (preferably 30 to 80° C.).

The coating film forming step can be performed according to a known method, and the medium may be heated to accelerate the drying in the coating film forming step. At this time, the surface temperature of the medium is, for example, 30° C. or higher and lower than the softening point of the medium (preferably 30 to 80° C.).

The inkjet recording method of the present invention may further include a step of cutting the medium (hereinafter, also referred to as “cutting step”) after the coating film forming step.

The inkjet recording method of the present invention can be performed using a known inkjet recording apparatus, and it is particularly advantageous to use an inkjet recording apparatus having a cleaning mechanism.

According to the inkjet recording method of the present invention, it is possible to form an image with excellent image quality with good drying property after printing. Further, since the aqueous inkjet ink having excellent storage stability and maintainability is used, it is possible to stably form an image for a long period of time.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[Preparation of inkjet ink]
The components described in Tables 1 to 4 were uniformly mixed in the mass proportions shown in the tables to obtain inkjet inks of Examples and Comparative Examples. The storage stability of the obtained inkjet ink was evaluated by the following method. Further, the obtained inkjet ink was printed on a PVC film using an inkjet printer, and the image quality and the drying property after printing were evaluated by the following methods. Further, the maintainability of the obtained inkjet ink was evaluated by the following method.

[Storage stability]
The inkjet ink was placed in an environment of 45° C. and stored for 3 months. At this time, the ink viscosity before and after storage was measured using a viscometer to determine the rate of change in viscosity, and the storage stability was evaluated according to the following criteria. "○" and "△" were passed. The results are shown in each table.
◯: Viscosity change rate is within ±10% Δ: Viscosity change rate exceeds ±10% but within ±15% ×: Viscosity change rate exceeds ±15%

[Image quality (solid image quality)]
Using the inkjet inks of Examples and Comparative Examples and a commercially available inkjet printer, a full solid image was formed under the conditions of 22 pl per drop and a resolution of 600 dpi×600 dpi. At this time, as preheating, the surface temperature of the PVC film was heated to 30 to 45° C. before printing, and as the drying operation, the surface temperature of the PVC film was heated to 80° C. after the ink application. For the formed solid image, the degree of dot coalescence (beading) was observed. From the observation results, the solid image quality was evaluated according to the following criteria. "○" and "△" were passed. The results are shown in each table.
◯: Solid image is uniform Δ: Coalescence is seen in some dots, but density distribution is not seen in the whole solid image ×: Dot is coalesced and density distribution is seen in solid image

[Evaluation of dryness after printing]
A solid image was formed by the same method as the image quality evaluation method described above, using the inkjet inks of Examples and Comparative Examples and a commercially available inkjet printer. However, the heating time at 80° C. in the drying operation was 1 minute. A cotton swab was rubbed against the formed solid image, and the state of the solid image and the cotton swab was observed. From the observation results, the dryness after printing was evaluated according to the following criteria. "○" and "△" were passed. The results are shown in each table.
○: No color fading on the image and no color transfer on the cotton swab △: No color fading on the image, but color transfer is seen on the cotton swab ×: Peeling occurs on the image and the color fading occurs

[Maintenance]
The inkjet inks of Examples and Comparative Examples were left for 2 weeks while being filled in a commercially available inkjet printer. At this time, the cleaning mechanism of a commercially available inkjet printer was operated to perform cleaning every 8 hours. Then, the state of the print head cap was observed. From the observation results, the maintainability was evaluated according to the following criteria. "○" was passed. The results are shown in each table.
○: Dry matter does not remain around the print head cap ×: Dry matter remains around the print head cap

(The numerical value about each component in each table shows a mass ratio.)
CAB-O-JET300 (manufactured by Cabot): Black self-dispersion pigment (aqueous emulsion having a solid content of 15% by mass).
CAB-O-JET260M (manufactured by Cabot): Magenta self-dispersing pigment (aqueous emulsion having a solid content of 10% by mass).
SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.): Silicone-based surfactant "Silface SAG503A"
VINYBRAN 715S (manufactured by Nissin Chemical Industry Co., Ltd.): aqueous emulsion of polyvinyl chloride-polyurethane core-shell particles (solid content 25 mass%)
PE1126 (manufactured by SEIKO PMC): acrylic resin aqueous emulsion (solid content 41.5% by mass)

As shown in Table 1 and Table 2, the aqueous inkjet inks of Examples 1 to 10 within the scope of the present invention were excellent in all of storage stability, image quality, dryness after printing, and maintainability. ..

On the other hand, the results of Comparative Example 1 in Table 3 show that the storage stability and the maintainability are poor when the C _5-7 both-end branched diol solvent is not added to the aqueous inkjet ink. From the results of Comparative Examples 2 to 4, it is understood that the storage stability is improved by blending the diol solvent at both ends. However, from the results of Comparative Example 2, it is understood that the maintainability is poor when the linear diol solvent having both ends and having 3 carbon atoms is used. From the results of Comparative Example 3, it can be seen that the maintainability is poor when the number of carbon atoms is less than 5, even when the branched diol solvent with both ends is used. From the results of Comparative Example 4, it can be seen that the maintenance property is poor in the case where the diol solvent of which both ends have a carbon number of 5 is used and is linear. Therefore, it can be seen that the use of the C _5-7 both-end branched diol solvent is effective for improving the maintainability.

From the results of Comparative Example 5 in Table 3, it can be seen that when the aqueous inkjet ink is not blended with the monool solvent (1), the image quality is low. From the results of Comparative Example 6, it is understood that when the blending amount of the monool solvent (1) is too large, the storage stability deteriorates. From the results of Comparative Example 7 in Table 4, it is understood that when the blending amount of the monool solvent (2) is too small, the image quality becomes low. From the results of Comparative Example 8, it is understood that if the blending amount of the monool solvent (2) is too large, the storage stability becomes poor. From the results of Comparative Example 9, it can be seen that when the blending amount of the C _5-7 both-end branched diol solvent is too small, the storage stability is slightly lowered and the maintainability is deteriorated. From the results of Comparative Example 10, it can be seen that when the blending amount of the C _5-7 both-end branched diol solvent is too large, the image quality and the drying property after printing are deteriorated. Therefore, from the results of Examples 1 to 6 and Comparative Examples 5 to 10, the content of the monool-based solvent (1), the monool-based solvent (2), and the C _5-7 both-end branched diol solvent was appropriate. It can be seen that there is a balance of various contents.

The aqueous inkjet ink of the present invention can be particularly preferably used for printing on a PVC substrate. In addition, non-absorptive substrates other than PVC substrates such as PET substrates, surface-treated (corona-treated) polyethylene (PE) substrates, surface-treated (corona-treated) polypropylene (PP) substrates, polystyrene substrates, etc. , And can be used for printing (image formation) on paper base materials such as art paper, coated paper, cast paper, high-quality paper, synthetic paper, inkjet paper, etc., and is preferably used for printing on non-absorbent base materials. You can

Claims (7)

An aqueous inkjet ink containing at least water (A), a coloring material (B), a water-soluble organic solvent component (C), a surfactant (D), and resin fine particles (E),
The water-soluble organic solvent component (C) is R ¹ O(C ₃ H ₆ O) _n H (in the formula, R ¹ represents a linear or branched alkyl group having 1 to 4 carbon atoms, and n is A first monool solvent represented by 2 or 3) and at least one selected from the group consisting of 3-methoxy-1-butanol and 3-methoxy-3-methyl-1-butanol. and there second monool solvent, (wherein, R ² is a is branched alkylene group having 5-7 carbon atoms) HO-R ² -OH contain and both terminal diol compound represented by,
The content of the second monool-based solvent in the ink is 8% by mass or more and 27% by mass or less,
The content of the first monool solvent in the ink is 1% by mass or more and 9% by mass or less,
The content of the diol compound at both ends in the ink is 7% by mass or more and 18% by mass or less, and an aqueous inkjet ink. The aqueous inkjet ink according to claim 1, wherein the diol compound having both terminals is 3-methyl-1,5-pentanediol. The water-based inkjet ink according to claim 1, wherein the resin fine particles (E) contain an acrylic resin or a urethane resin at least in a surface layer portion. The aqueous inkjet ink according to any one of claims 1 to 3, wherein the surfactant (D) is a silicone-based surfactant. The aqueous inkjet ink according to any one of claims 1 to 4, wherein the content of the diol compound at both ends in the ink is 7.5% by mass or more and 12.5% by mass or less. A step of ejecting the aqueous inkjet ink according to any one of claims 1 to 5 onto a medium having a non-absorbent substrate, and drying the aqueous inkjet ink ejected onto the medium to form an ink coating film. An inkjet recording method including a step of forming. The inkjet recording method according to claim 6, wherein the non-absorbent substrate is a polyvinyl chloride substrate.