Ink set, inkjet recording method, printing media, and printing media set

Abstract

To provide an ink set, an inkjet printing method, a printing media, and a printing media set capable of providing a printed image that is extremely excellent in bleeding between colors, further does not deteriorate the bleeding between colors irrespective of a storage period.SOLUTION: An ink set containing a first ink composition containing water, a first coloring agent, a first silicone surfactant, and a first nonionic surfactant; and a second ink composition containing water, a second coloring agent, a second silicone surfactant and a second nonionic surfactant, and is applied onto a first image formed using the first ink composition to form a second image is provided.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an ink set, an inkjet printing method, a printing medium, and a printing medium set.

Background Art

[0002] Among various color printing methods, a printing method using an inkjet printer, which is one of the representative methods, generates small droplets of ink and attaches them to a printing medium such as paper to perform printing. In recent years, the demand for industrial use has been increasing, and inks that can print on various printing media have been demanded.

[0003] Among printing media, for ink non-absorbent media and ink poorly absorbent media (hereinafter sometimes referred to as "ink non- / poorly absorbent media"), inks with good wet spread on the media are desired. When the wet spread on the media is good, the area that can be colored increases when the same amount of ink droplets are used (in other words, the dot diameter of the ink becomes larger), so that the consumption of the ink can be suppressed. However, ink non- / poorly absorbent media are media with poor ink absorbency. For this reason, the ink is difficult to penetrate into the media, and compared with ink absorbent media, the wet spread of the ink is poor, so generally the dot diameter of the ink becomes smaller. For this reason, its improvement has been desired.

[0004] Furthermore, regarding the printed image quality, it is required that the graininess be as little as possible. Inks containing water-insoluble colorants are in a non-uniform state themselves (not in a solution state but in a dispersion state). When solid printing is performed on a printing medium using such non-uniform inks, the printed image may appear to have "grains" of shading scattered therein and may not look like a uniform image. Such a printed image is evaluated as "showing graininess" and is one of the factors that significantly deteriorate the printing quality. For this reason, there is a strong demand for inks that can obtain a printed image with as little graininess as possible. For example, Patent Documents 1 to 3 disclose ink compositions combined with specific organic solvents and surfactants, and inks with good spreading properties for non-ink-absorbing and non-difficult-to-absorb media are disclosed.

[0005] Also, when performing color printing, an ink set consisting of a plurality of colors is used. When performing color printing using such an ink set, it is known that bleeding may occur between the first color and the second color when the landing position of the ink of the first color and the landing position of the ink of the second color are adjacent to each other on the printing medium. This "bleeding between colors" is one of the factors that significantly deteriorate the printing quality. For this reason, elimination of this bleeding between colors is required, and ink sets for solving this have also been proposed.

[0006] According to Patent Document 4, in order to eliminate this bleeding between colors, inks containing polyalkoxylates of acetylene glycol-based surfactants are disclosed, and inks that can obtain high-quality images without color unevenness and bleeding between colors for non-ink-absorbing and non-difficult-to-absorb media are proposed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

[0008] However, it has been found that the problem of bleeding between colors involves more complex factors. That is, at the initial stage of printing, it is possible to perform printing by using both a first ink composition and a second ink composition, both of which have been newly manufactured (in other words, both are new). Therefore, by selecting and using an ink set that takes into account bleeding between colors, it is possible to perform high-quality printing without bleeding between colors.

[0009] However, as printing continues, depending on the type of color of the ink composition, the consumption amount of each ink composition will differ. For this reason, an ink composition with a large consumption amount will be replaced with a new ink composition when the ink composition runs out. On the other hand, an ink composition with a small consumption amount will continue to be used as it is until the initially used ink composition runs out. As a result, a new ink composition and an old ink composition will be used in combination. There may be a difference of several months to about one year in the storage period until use between an ink composition with a large consumption amount and an ink composition with a small consumption amount. When printing by using ink compositions with different storage periods in combination, although there is no significant change in the storage stability (various physical property values such as ejection property, average particle diameter, viscosity, pH, etc.) of each ink composition itself, the bleeding between colors may deteriorate and the print image quality may decrease, and a solution to this is desired.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide an ink set that enables a print image with extremely good bleeding between colors and that does not deteriorate bleeding between colors regardless of the storage period, an inkjet recording method using the ink set, a printing medium, and a printing medium set. [Means for Solving the Problems]

[0011] As a result of intensive studies to solve the above-described problems, the inventors of the present invention have found that the above problems can be solved by the inventions described in the following [1] to

[12] , and have completed the present invention.

[0012] That is, the present invention relates to the following [1] to

[12] . [1] A first ink composition containing water, a first colorant, a first silicone surfactant, and a first nonionic surfactant, and A second ink composition containing water, a second colorant, a second silicone surfactant, and a second nonionic surfactant, and applied onto a first image formed using the first ink composition to form a second image, the ink set comprising: wherein the first silicone surfactant and the second silicone surfactant are each independently represented by the following formula (1): [Chemical formula] (In the formula, a is an integer of 1 to 80, x and y are each independently an integer of 1 to 4, m and n are each independently an integer of 1 to 50, o and p are each independently an integer of 0 to 40, m + n is 2 to 100, o + p is 0 to 80, R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a (meth)acrylic group.) is a silicone surfactant represented by the formula, wherein the first nonionic surfactant and the second nonionic surfactant are nonionic surfactants having an HLB value of 6.0 or more and less than 12.0 other than silicone surfactants, When the content of the first silicone surfactant is A1, the content of the first nonionic surfactant is A2, the content of the second silicone surfactant is B1, and the content of the second nonionic surfactant is B2, 0.10 ≦ (B1 - A1) + (B2 - A2) ≦ 0.95 An ink set satisfying [2] The ink set according to [1], wherein in the formula (1), m and n are each independently an integer of 1 to 30. [3] The ink set according to [1] or [2], wherein one or both of the first ink composition and the second ink composition further contain a binder. [4] The ink set according to [3], wherein the binder contains at least one selected from wax and (meth)acrylic acid-based polymers. [5] The ink set according to [4], wherein the wax is one or more selected from polyalkylene wax, oxidized polyalkylene wax, and paraffin wax. [6] The ink set according to [4] or [5], wherein the wax is oxidized polyethylene wax. [7] The ink set according to any one of [1] to [6], wherein the first nonionic surfactant and the second nonionic surfactant have an HLB value of 6.0 or more. [8] An inkjet recording method using the ink set according to any one of [1] to [7], comprising: a step of discharging droplets of the first ink composition and attaching them to a printing medium to form a first image; a step of discharging droplets of the second ink composition and attaching them onto the printing medium on which the first image is formed to form a second image. [9] A printing medium on which a second image is formed by applying the second ink composition onto a first image formed by applying the first ink composition included in the ink set according to any one of [1] to [7].

[10] An ink medium set including the ink set according to any one of [1] to [7] and a printing medium.

[11] An ink composition used together with an ink composition for forming a second image on a first image, the ink composition for forming the first image, The ink composition for forming the first image contains water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant The ink composition for forming the second image contains water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant, the first silicone-based surfactant and the second silicone-based surfactant are each independently represented by the following formula (1):

Chemical formula

[12] An ink composition for forming a second image, which is used together with an ink composition for forming a first image on which the second image is formed, the ink composition for forming the first image contains water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant The ink composition for forming the second image contains water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant. The first silicone-based surfactant and the second silicone-based surfactant are each independently represented by the following formula (1): [Chemical formula] (In the formula, a is an integer from 1 to 80, x and y are each independently an integer from 1 to 4, m and n are each independently an integer from 1 to 50, o and p are each independently an integer from 0 to 40, m + n is from 2 to 100, o + p is from 0 to 80, and R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a (meth)acrylic group.) and are silicone-based surfactants represented by The first nonionic surfactant and the second nonionic surfactant are nonionic surfactants other than silicone-based surfactants and having an HLB value of 6.0 or more and less than 12.0. When the content of the first silicone-based surfactant is A1, the content of the first nonionic surfactant is A2, the content of the second silicone-based surfactant is B1, and the content of the second nonionic surfactant is B2, 0.10 ≦ (B1 - A1) + (B2 - A2) ≦ 0.95 An ink composition that satisfies the above. [Advantages of the Invention]

[0013] According to the present invention, it is possible to provide an ink set, an inkjet printing method, a printing medium, and a printing medium set that can provide a printed image with extremely good bleeding between colors and that does not deteriorate bleeding between colors regardless of the storage period. [Embodiments for Carrying Out the Invention]

[0014] <Ink set> The ink set according to the present invention includes a first ink composition containing water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant, and a second ink composition containing water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant, which is applied onto a first image formed using the first ink composition to form a second image.

[0015] [First ink composition] The first ink composition contains water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant, and optionally further contains other components. Examples of the other components include a dispersant and an ink preparation agent.

[0016] (First colorant) The first colorant is not particularly limited as long as it is a water-insoluble colorant. In the specification and claims of the present application, the water-insoluble colorant means a colorant having a solubility of usually 5 g or less, preferably 3 g or less, more preferably 1 g or less, and even more preferably 0.5 g or less in 1 liter of water at 25°C. The lower limit of the solubility includes 0 g. Hereinafter, unless otherwise specified, the "water-insoluble colorant" is also simply referred to as "colorant". As the colorant, for example, known pigments, disperse dyes, solvent dyes, and water-insoluble resins colored with colorants such as dyes and pigments can be used. The colorant is preferably a pigment. Examples of the pigment include inorganic pigments, organic pigments, and extender pigments.

[0017] Examples of inorganic pigments include carbon black, titanium oxide, metal oxides, hydroxides, sulfides, ferrocyanides, and metal chlorides. As the carbon black to be contained in the black ink, thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black are preferable. Specific examples of carbon black include, for example, Raven series manufactured by Columbian Carbon; Monarch series, Regal series, and Mogul series manufactured by Cabot; ColorBlack series, Printex series, SPECIALBLACK series, and Nerox series manufactured by Orion Engineered Carbons; MA series, MCF series, No.25, No.33, No.40, No.47, No.52, No.900, and No.2300 manufactured by Mitsubishi Chemical Corporation, and the like.

[0018] Examples of organic pigments include various pigments such as azo, diazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, anthraquinone, and quinophthalone. Specific examples of organic pigments include, for example, yellows such as C.I.Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 180, 185, 193, 199, 202, 213; reds such as C.I.Pigment Red 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 272; blues such as C.I.Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80; violets such as C.I.Pigment Violet 19, 23, 29, 37, 38, 50; oranges such as C.I.Pigment Orange 13, 16, 68, 69, 71, 73; greens such as C.I.Pigment Green7, 36, 54; and blacks such as C.I.Pigment Black 1.

[0019] Examples of extender pigments include, for example, silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. Extender pigments are often used in combination with other colorants.

[0020] Examples of the disperse dyes include known disperse dyes. Among them, dyes selected from C.I. Disperse are preferred. Specific examples thereof include, for example, C.I. Disperse Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237, etc. of yellow; C.I. Disperse Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283, etc. of red; C.I. Disperse Orange 9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97, etc. of orange; C.I. Disperse Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1, etc. of violet; C.I. Disperse Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, 368, etc. of blue disperse dyes of various colors.

[0021] The content of the colorant based on the total mass of the ink composition is usually 1 to 30%, preferably 1 to 10%, more preferably 2 to 7%. Here, in the specification and claims of the present application, unless otherwise specified, “%” and “parts” are described on a mass basis. In addition, the average particle size of the colorant is usually 50 nm to 250 nm, preferably 60 nm to 200 nm. In the specification and claims of the present application, the average particle size refers to the particle size at the integrated value of 50% in the particle size distribution determined by the laser diffraction / scattering method.

[0022] In order to disperse a water-insoluble colorant in the ink composition, it is preferable to use a dispersant. The dispersant is not particularly limited, and known dispersants can be used. As the dispersant, generally, a polymer dispersant such as a resin is used. Examples of such resins include polyvinyl alcohol, cellulose derivatives, polyethylene oxide, polypropylene oxide, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, fumaric acid monoester, vinyl sulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, ionic monomers such as α,β-unsaturated monomers of sulfonated vinyl naphthalene, styrene, styrene derivatives, vinyl naphthalene, vinyl naphthalene derivatives, aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids, acrylonitrile, vinylidene chloride, vinyl acetate, vinyl chloride, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, N-butoxymethylacrylamide, and polymers derived therefrom.

[0023] Examples of the resin as the dispersant include copolymers composed of at least two monomers (preferably at least one of which is a hydrophilic monomer) selected from the group of monomers consisting of styrene and its derivatives; vinyl naphthalene and its derivatives; aliphatic alcohol esters of α,β-ethylenically unsaturated carboxylic acids; acrylic acid and its derivatives; maleic acid and its derivatives; itaconic acid and its derivatives; fumaric acid and its derivatives; vinyl acetate, vinyl alcohol, vinyl pyrrolidone, acrylamide, and their derivatives. Examples of such copolymers include styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylate copolymer, (meth)acrylate-(meth)acrylic acid copolymer, polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer, styrene-maleic acid copolymer, and the like. Among these, styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylate copolymer, (meth)acrylate-(meth)acrylic acid copolymer, and polyethylene glycol (meth)acrylate-(meth)acrylic acid copolymer are preferable; styrene-(meth)acrylic acid copolymer, styrene-(meth)acrylic acid-(meth)acrylate copolymer, and (meth)acrylate-(meth)acrylic acid copolymer are more preferable; (meth)acrylate-(meth)acrylic acid copolymer is even more preferable; and methacrylate-methacrylic acid copolymer is particularly preferable. In the description and claims of the present application, the term “(meth)acrylic acid” is used to mean both “acrylic acid” and “methacrylic acid”. Similarly, “(meth)acrylate” means both methacrylate and acrylate. Examples of the type of copolymer include block copolymer, random copolymer, graft copolymer, and / or salts thereof.

[0024] The resin as the dispersant can be synthesized or obtained as a commercial product. Specific examples of commercial products include, for example, styrene-acrylic copolymers such as Joncryl 62, 67, 68, 678, and 687 (manufactured by BASF); Mowinyl S-100A (a modified vinyl acetate copolymer manufactured by Japan Coating Resin); and Julimer AT-210 (a polyacrylate copolymer manufactured by Toagosei Co., Ltd.). As the copolymer obtained by synthesis, the A-B block polymer disclosed in International Publication No. 2013 / 115071 is preferably mentioned.

[0025] The acid value of the dispersant is usually 90 to 200 mgKOH / g, preferably 100 to 150 mgKOH / g, more preferably 100 to 120 mgKOH / g. The mass average molecular weight of the dispersant is usually 10,000 to 60,000, preferably 10,000 to 40,000, more preferably 15,000 to 30,000, and even more preferably 20,000 to 25,000. The PDI (weight average molecular weight / number average molecular weight) of the dispersant is about 1.29 to 1.49. By setting it within the above range, the dispersibility and storage stability of the ink composition can be improved.

[0026] Examples of the neutralizing agent used to dissolve the dispersion of the colorant prepared using the block copolymer in water include ammonia, alkali metal hydroxides, alkaline earth metal hydroxides, aliphatic amine compounds, and alkanolamine compounds. Ammonia and alkali metal hydroxides are preferred, and ammonia is particularly preferred. The amount of the neutralizing agent used is not particularly limited. As a guideline, when neutralized to the theoretical equivalent of the acid value of the dispersant, 100% neutralization degree is taken as the standard, and it is usually 30 to 300% neutralization degree, more preferably 50 to 200% neutralization degree.

[0027] The resin as the above dispersant can be used either in a state of being mixed with the colorant or in a state where a part or all of the surface of the colorant is coated with the resin as the dispersant. Also, both of these states can be used in combination. It is preferable to prepare the ink composition by mixing with other components after preparing a dispersion liquid containing a water-insoluble colorant and a resin as a dispersant. As a method for preparing the dispersion liquid, a known method can be used. As an example, the phase inversion emulsification method can be mentioned. That is, the resin as the dispersant is dissolved in an organic solvent such as 2-butanone, and an aqueous solution of the neutralizing agent is added to prepare an emulsion. The colorant is added to the obtained emulsion and dispersion treatment is performed. By distilling off the organic solvent and a part of the water from the liquid thus obtained under reduced pressure, the target dispersion liquid can be obtained. The dispersion treatment can be performed using, for example, a sand mill (bead mill), a roll mill, a ball mill, a paint shaker, an ultrasonic disperser, a microfluidizer, etc. As an example, when using a sand mill, beads with a particle size of about 0.01 mm to 1 mm are used, and the filling rate of the beads is appropriately set to perform the dispersion treatment. Operations such as filtration and / or centrifugation can be performed on the dispersion obtained as described above. By this operation, the particle sizes of the particles contained in the dispersion can be made uniform. When foaming occurs during the preparation of the dispersion, a very small amount of a known antifoaming agent such as a silicone-based or acetylene glycol-based antifoaming agent can be added. Examples of the preparation methods of the dispersion other than the above include the acid precipitation method, the interfacial polymerization method, the in-situ polymerization method, the in-liquid curing film method, the coacervation (phase separation) method, the in-liquid drying method, the melt dispersion cooling method, the air suspension coating method, and the spray drying method. Among these, the acid precipitation method and the interfacial polymerization method are preferred.

[0028] The average particle size (D50) of the colorant dispersion in the dispersion is usually 300 nm or less, preferably 30 to 280 nm, more preferably 40 to 270 nm, and still more preferably 50 to 250 nm. Also, D90 is usually 400 nm or less, preferably 350 nm or less, and more preferably 300 nm or less. The lower limit is preferably 100 nm. D10 is usually 10 nm or more, preferably 20 nm or more, and more preferably 30 nm or more, and the upper limit is 100 nm. When the particle size of the colorant in the dispersion is in the above range, there is an effect of stably discharging the ink without clogging the inkjet head nozzles while ensuring the storage stability of the ink. Here, the average particle size (D50) is the particle size at which the cumulative particle size distribution from the small particle size side in the particle size distribution determined by the laser diffraction / scattering method is 50%, D10 is the particle size at which the cumulative particle size distribution from the small particle size side is 10%, and D90 is the particle size at which the cumulative particle size distribution from the small particle size side is 90%.

[0029] (First silicone-based surfactant) It is important for ink compositions to have sufficient wettability on non-ink-absorbent or poorly ink-absorbent media. To achieve this, surfactants are commonly used. Various surfactants, including silicone-based, fluorine-based, and acetylene-based surfactants, are widely known for their wettability, depending on the application. Among these, silicone-based surfactants excel in their ability to provide wettability. However, the present inventors have observed that when printing inks with different storage periods, intercolor bleeding worsens depending on the structure of each silicone-based surfactant, even though the storage stability of the inks themselves (various physical properties such as ejection performance, average particle size, viscosity, and pH) remains unchanged. According to the Journal of the Japan Society of Color Materials, Vol. 74, No. 1, pp. 34-38 (by Koji Sakuta), it has been confirmed that silicone-based surfactants generally decompose over time during long-term storage. From this, it is inferred that silicone-based surfactants with specific structures lose their ability to control intercolor bleeding due to structural decomposition.

[0030] The present inventors have investigated the relationship between the structure of a silicone surfactant and changes in inter-color bleeding over time, and have found that by using a silicone surfactant represented by the following formula (1) as the first surfactant, it is possible to provide a set of ink compositions that can produce printed images that do not deteriorate in inter-color bleeding, regardless of whether the storage periods of the two ink compositions are the same or different. The reason why changes in inter-color bleeding over time can be suppressed is not clear, but it is thought that this is because by using a silicone surfactant represented by formula (1), even if the structure decomposes over time, most of the structural portion consisting of the hydrophobic part of the siloxane structure (-Si-O-) and the hydrophilic part consisting of an ethyleneoxy group and a propyleneoxy group is maintained, so that the function as a surfactant is not impaired. [ka]

[0031] In formula (1), a is an integer of 1 to 80, preferably 2 to 40. x and y each independently represent an integer of 1 to 4, preferably 1 to 3. m and n are each independently an integer from 1 to 50, preferably from 2 to 40, more preferably from 4 to 20. o and p are each independently an integer from 0 to 40, preferably from 0 to 20, more preferably from 0 to 10. m + n is from 2 to 100, preferably from 4 to 80, more preferably from 8 to 40. o + p is from 0 to 80, preferably from 0 to 40, more preferably from 0 to 20. R 1 and R 2 are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a (meth)acrylic group, and are preferably a hydrogen atom.

[0032] The content of the silicone surfactant represented by formula (1) in the ink composition is usually 0.01 to 3%, preferably 0.05 to 2%, more preferably 0.1 to 1%. Specific examples of commercially available products of the silicone surfactant represented by formula (1) include Silwet CoatOSil 2812, Silwet CoatOSil 2816, Silwet CoatOSil 3500, and Silwet CoatOSil 3505 manufactured by Momentive Performance Materials, BYK-331, BYK-333, BYK-UV3500 manufactured by BYK Chemie, BYK-New Product 1 general grade and BYK-New Product 2 cyclic siloxane reduction grade described in the published material on June 22, 2020 (URL:https: / / www.byk.com / ja / company-news / media / news / detail / japanese-news-20200622-new-silicone-surface-modifier-for-aqueous-systems), Tegoglide410, Tegoglide432, Tegoglide435, Tegoglide440, and Tegoglide450 manufactured by Evonik Degussa, and Silface SWP-001, Silface SAG003, and Silface SAG005 manufactured by Nissin Chemical Industry Co., Ltd. The silicone surfactant represented by formula (1) can be synthesized by a hydrosilylation reaction using polyethylene glycol having an allyl group at one end and polydimethylsiloxane containing hydrogen groups at both ends as materials and a platinum catalyst.

[0033] (First nonionic surfactant) The first nonionic surfactant is a nonionic surfactant other than the silicone surfactant and having an HLB value of 6.0 or more and less than 12.0. The HLB value of the nonionic surfactant is preferably 6.5 to 11.0, more preferably 7.0 to 10.0. By setting the partition coefficient within this range, there is an effect of further improving the color bleeding that is insufficient with the silicone surfactant alone. In the specification and claims of the present application, the "HLB value" is a value obtained by the method for calculating the HLB value shown on page 324 et seq. of "Surfactant Handbook" (edited by Ichiro Nishi et al., Industrial Publishing Co., Ltd., 1960) (see "Surfactant Handbook" (edited by Ichiro Nishi et al., Industrial Publishing Co., Ltd., 1960, p. 324)).

[0034] [Method for calculating HLB value] Dissolve 0.5 g of the nonionic surfactant in 5 mL of ethanol to obtain a solution. Stir the obtained solution at 25°C, and dropwise add a 2 mass% aqueous phenol solution to this solution. The end point is when the solution becomes turbid. When the amount of the 2 mass% aqueous phenol solution required to reach the end point is Q (mL), the HLB value is calculated by the following formula, and by rounding the second digit after the decimal point, the first digit after the decimal point is described as the HLB value. HLB value = 0.89 × Q + 1.11

[0035] The first nonionic surfactant is preferably a nonionic surfactant represented by the following formula (2). [Chemical formula] In formula (2), R 3represents a linear or branched hydrocarbon group having 6 to 20 carbon atoms. The linear or branched hydrocarbon group is preferably a linear alkyl group or a branched alkyl group. The branched alkyl group is preferably a branched alkyl group in which an alkyl group is substituted at the 1st or 2nd carbon. The linear alkyl group may have a substituent at the terminal, and the substituent is, for example, a benzyl group or a naphthyl group. When the linear alkyl group and the branched alkyl group have a substituent, the total number of carbon atoms is 6 to 20. s represents the number of propyleneoxy groups, and t represents the number of ethyleneoxy groups, where s is 1 to 20 and t is 0 to 5.

[0036] Examples of the nonionic surfactant having an HLB value within the above numerical range include Newcol 2303 (7.9), Newcol NT-3 (6.3) manufactured by Nippon Emulsifier Co., Ltd., GENAPOL EP2564 (7.4), GENAPOL EP2584 (8.2) manufactured by Clariant, Lutensol XL40 (8.1), Lutensol FT XL70 (11.1) manufactured by BASF, BYK DYNWET 800N (8.1), BYK-LP X 7113 (9.9) manufactured by BYK Chemie, TEGO Wet500 (6.5), TEGO Wet505 (8.2), TEGO Wet510 (9.1) manufactured by EVONIC, etc.

[0037] The content of the first nonionic surfactant in the first ink composition is 0.01 to 2%, preferably 0.05 to 1.5%, more preferably 0.1 to 1% by mass.

[0038] (Ink preparation agent) Examples of the ink preparation agent include a binder, a penetrant, a viscosity modifier, a surfactant other than a silicone-based surfactant, a preservative, a fungicide, a pH adjuster, a chelating agent, a rust inhibitor, a water-soluble ultraviolet absorber, an antioxidant, etc. With respect to the total mass of the ink composition, the total content of the ink preparation agent excluding the binder, the penetrant, and the viscosity modifier is usually 0 to 30%, preferably 0.1 to 20%, more preferably about 0.5 to 10%.

[0039] (a) Binder The binder is preferably at least one selected from wax and (meth)acrylic acid polymers. By including the binder in the ink composition, the rubbing resistance of the printed image can be improved. The binder is preferably contained in the form of an emulsion, and among them, an aqueous emulsion is more preferable. The average particle size of the binder is preferably 50 nm to 5 μm, more preferably 100 nm to 1 μm, in order to prevent clogging of the inkjet head. When the ink composition contains a binder, the content of the binder in terms of solid content in the total mass of the ink composition is usually 0.1 to 14%, preferably 0.5 to 12%, more preferably 2 to 10%, and even more preferably 3 to 8%. At such a content, the rubbing resistance of the printed image can be made better.

[0040] As the wax, natural wax and synthetic wax can be used. Examples of natural waxes include paraffin wax, microcrystalline wax, etc., which are petroleum waxes; montan wax, etc., which are lignite waxes; carnauba wax, candelilla wax, etc., which are plant waxes; and emulsions in which waxes such as beeswax and lanolin, which are animal and plant waxes, are dispersed in an aqueous medium. Examples of synthetic waxes include polyalkylene waxes (preferably poly C2-C4 alkylene waxes), oxidized polyalkylene waxes (preferably oxidized poly C2-C4 alkylene waxes), and paraffin waxes. Among the above, one or more waxes selected from polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax, and paraffin wax are preferable, and oxidized polyethylene wax is more preferable. Examples of commercially available wax emulsions include CERAFLOUR 925, 929, 950, 991; AQUACER 498, 515, 526, 531, 537, 539, 552, 1547; AQUAMAT 208, 263, 272; MINERPOL 221, etc. manufactured by BYK Chemie GmbH; Mitsui High Wax NL100, NL200, NL500, 4202E, 1105A, 2203A, NP550, NP055, NP505, etc. manufactured by Mitsui Chemicals, Inc.; KUE-100, 11, etc. manufactured by Sanyo Chemical Industries, Ltd. Among these, AQUACER 515, 531, 537, 539, 1547 are preferred, and AQUACER 515, 531, 537, 1547 are more preferred.

[0041] The (meth)acrylic acid-based polymer used as a binder is a polymer different from the above dispersant. The (meth)acrylic acid-based polymer is preferably a (meth)acrylic acid-based polymer composed of four types of monomers: C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate. As the C1-C4 alkyl methacrylate, the alkyl part is preferably linear or branched, and more preferably linear. The C1-C4 alkyl methacrylate is preferably a C1-C3 alkyl methacrylate, more preferably a C1-C2 alkyl methacrylate, and even more preferably methyl methacrylate. As the C6-C10 alkyl acrylate, the alkyl part is preferably linear or branched, and more preferably branched. The C6-C10 alkyl acrylate is preferably a C7-C9 alkyl acrylate, more preferably a C8 alkyl acrylate, and even more preferably 2-ethylhexyl acrylate. In the (meth)acrylic acid polymer, the contents of four types of monomers, namely C1-C4 alkyl methacrylate, C6-C10 alkyl acrylate, methacrylic acid, and allyl methacrylate, are usually 40-60%, 38-58%, 1-10%, and 1-5% by mass, respectively, preferably 45-55%, 52-42%, 2-4%, and 1-3%. In the range of these monomer contents, it is preferably 100% in total. The acid value (unit: mgKOH / g) of the (meth)acrylic acid polymer is usually -10 to 35, preferably -5 to 30, more preferably 0 to 25. The glass transition temperature (Tg) of the (meth)acrylic acid polymer is usually -20 to 30 °C, preferably -15 to 25 °C, more preferably -10 to 20 °C.

[0042] (b) Penetrant The ink composition can further contain at least one organic solvent selected from glycol ethers and C4-C9 alkanediols having a water-octanol partition coefficient of 0.00 or more and less than 2.00 as a penetrant. Thereby, on the ink non- or hardly absorbent medium, the wet spreading of the ink and the drying of the ink tend to be improved. Examples of the penetrant having a Clog P within the above numerical range include 1,2-pentanediol (-0.00), ethylene glycol monoallyl ether (0.03), isopropyl alcohol (0.07), isopropyl glycol (0.09), diethylene glycol ethyl methyl ether (0.13), dipropylene glycol dimethyl ether (0.36), 3-methoxy-3-methyl-1-butanol (0.42), butyl triglycol (0.49), diethylene glycol diethyl ether (0.52), 1,2-hexanediol (0.53), diethylene glycol monoisobutyl ether (0.54), propyl propylene glycol (0.62), butyl diglycol (0.67), dipropylene glycol n-propyl ether (0.75), 2,2-diethyl-1,3-propanediol (0.82), 2,2,4-trimethyl-1,3-pentanediol (1.00), 2-ethyl-1,3-hexanediol (1.26), 1,2-octanediol (1.58), and hexyl diglycol (1.72), etc. In the total mass of the ink composition, the total content of these is usually 0.1 to 30%, preferably 0.2 to 20%, more preferably 0.5 to 10%, still more preferably 2 to 8%, and particularly preferably 4 to 6%.

[0043] (c) Viscosity modifier The ink composition can further contain a viscosity modifier. An industrial inkjet printer usually has a determined viscosity range of the ink that can be ejected based on the specifications of the printer head (the head that ejects the ink) it is equipped with. Therefore, a viscosity modifier can be added to the ink to adjust its viscosity to an appropriate range. The viscosity modifier is not particularly limited as long as it can adjust the viscosity of the ink, and known substances can be used. Specific examples thereof include, for example, water-soluble organic solvents (the "organic solvents" listed as the above penetrants are not included therein), saccharides, and the like. Among these, water-soluble organic solvents having a ClogP value usually less than 0.00, preferably -0.05 or less, more preferably -0.08 or less, can be mentioned. The lower limit of the ClogP value of the water-soluble organic solvent is not particularly limited, but is usually -4.00 or more, preferably -3.00 or more, more preferably -2.00 or more, and still more preferably -1.50 or more. Examples of such water-soluble organic solvents include 2-methyl-2,4-pentanediol (-0.02), tripropylene glycol monomethyl ether (-0.03), isopropyl diglycol (-0.08), dipropylene glycol monomethyl ether (-0.16), ethanol (-0.24), 3-methyl-1,5-pentanediol (-0.24), diethylene glycol dimethyl ether (-0.26), propylene glycol monomethyl ether (-0.30), 3-methyl-1,3-butanediol (-0.33), trimethylolpropane (-0.39), N-methyl-2-pyrrolidone (-0.40), 1,2-butanediol (-0.53), 3-ethyl-3-hydroxymethyloxetane (-0.58), 1,5-pentanediol (-0.64), 2-methyl-1,3-propanediol (-0.64), dipropylene glycol (-0.69), 1,3-butanediol (-0.73), methyldiglycol (-0.78), methyltriglycol (-0.96), 2-pyrrolidone (-0.97), propylene glycol (-1.06), 1,4-butanediol (-1.16), diethylene glycol (-1.30), ethylene glycol (-1.37), triethylene glycol (-1.48), glycerin (-1.54), diglycerin (-2.96), Glyceress-3 (-3.49) manufactured by Aoki Yushi Kogyo, and Glyceress-20 (-5.42), etc. The total content of the water-soluble organic solvent is usually 0% to 55%, preferably 5% to 40%, and more preferably about 10% to 30%.

[0044] (d) Preservative Examples of the preservative include compounds such as organic sulfur-based, organic nitrogen-sulfur-based, organic halogen-based, haloaryl sulfone-based, iodopropargyl-based, haloalkylthio-based, nitrile-based, pyridine-based, 8-hydroxyquinoline-based, benzothiazole-based, isothiazoline-based, dithiol-based, pyridine oxide-based, nitropropane-based, organotin-based, phenol-based, quaternary ammonium salt-based, triazine-based, thiazine-based, anilide-based, adamantane-based, dithiocarbamate-based, brominated indanone-based, benzyl bromoacetate-based, and inorganic salt-based. Specific examples of commercially available preservatives include Proxel GXL(S) and XL-2(S) manufactured by Arch Chemicals, Inc.

[0045] (e) Antimildew agent Examples of the antimildew agent include sodium dehydroacetate, sodium benzoate, sodium pyridine thione-1-oxide, ethyl p-hydroxybenzoate, 1,2-benzisothiazolin-3-one, and salts thereof.

[0046] (f) pH adjuster As the pH adjuster, any substance can be used as long as it can adjust the pH of the prepared ink composition to 5 to 11 without adversely affecting it. Specific examples thereof include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; hydroxides of alkali metals such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; ammonium hydroxide (aqueous ammonia); or carbonates of alkali metals such as lithium carbonate, sodium carbonate, sodium hydrogen carbonate, and potassium carbonate; alkali metal salts of organic acids such as sodium silicate and potassium acetate; and inorganic bases such as disodium phosphate.

[0047] (g) Chelating agent Examples of the chelating agent include disodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, and sodium uracildiacetate.

[0048] (h) Rust inhibitor Examples of the rust inhibitor include acid sulfite, sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[0049] (i) Water-soluble ultraviolet absorber Examples of the water-soluble ultraviolet absorber include sulfonated benzophenone compounds, benzotriazole compounds, salicylic acid compounds, cinnamic acid compounds, and triazine compounds.

[0050] (j) Antioxidant Examples of the antioxidant include various organic and metal complex-based fading inhibitors. Examples of the organic-based fading inhibitors include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, and heterocycles.

[0051] [Water] The first ink composition contains the above components and, if necessary, an ink preparation agent, and the balance is water. The water used for the ink is preferably one with a low content of impurities such as metal ions, such as ion-exchanged water and distilled water.

[0052] The pH of the first ink composition is usually 7 to 11, preferably 8 to 10. The surface tension of the ink composition is usually 10 to 50 mN / m, preferably 20 to 40 mN / m. The viscosity of the ink composition is usually 2 to 30 mPa·s, preferably 3 to 20 mPa·s. The pH and surface tension of the ink composition can be adjusted by using a pH adjuster, a surfactant, a water-soluble organic solvent, and the like.

[0053] The first ink composition can be used in various types of printing. For example, it is suitable for writing instruments, various types of printing, information printing, dyeing, etc., and is particularly preferably used for inkjet printing.

[0054] [Second Ink Composition] The second ink composition contains water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant, and optionally further contains other components. Examples of other components include a dispersant, a water-soluble organic solvent, and an ink preparation agent. As the water, the second colorant, the second silicone-based surfactant, the second nonionic surfactant, and other components, those similar to the first ink composition can be used. The content of each component in the second ink composition can also be an amount within the preferred range described for the first ink composition. The preferred ranges of the pH, surface tension, and viscosity of the second ink composition are the same as those of the first ink composition. The second colorant is preferably a different color from the first colorant. This is because color bleeding is likely to be observed when the first colorant and the second colorant are visually distinguishable.

[0055] The content of the first silicone-based surfactant and the first nonionic surfactant in the first ink composition and the content of the second silicone-based surfactant and the second nonionic surfactant in the second ink composition are determined to have a specific relationship. That is, when the content of the first silicone-based surfactant is A1, the content of the first nonionic surfactant is A2, the content of the second silicone-based surfactant is B1, and the content of the second nonionic surfactant is B2, 0.10 ≦ (B1 - A1) + (B2 - A2) ≦ 0.95 is satisfied. In the above relational expression, the coefficient was determined according to the degree of influence on color bleeding. By satisfying this formula, an effect of suppressing color bleeding and achieving good print quality is achieved. When the value of this formula is outside the range, it has been confirmed that the balance of the hydrophilicity and hydrophobicity of the ink interface between the first ink composition and the second ink composition is disrupted, resulting in deterioration of color bleeding. When the numerical value of this formula is less than 0.10, a phenomenon occurs in which the ink of the first ink composition bleeds out with respect to the second ink composition. On the other hand, when the numerical value of this formula is greater than 0.95, it has been confirmed that a phenomenon occurs in which the ink of the second ink composition bleeds out with respect to the first ink composition. Although the reason for this is not clear, it is presumed that when two different colors of ink are continuously printed, if the balance of the ink interface tension between the two colors is disrupted, the color will bleed out to the other side. It is presumed that this is because surfactants and hydrophobic organic solvents are oriented at the ink interface and are greatly affected by them. In addition, the inventors have also found that the phenomenon of reduced color bleeding when the above relational expression is satisfied occurs only when the silicon-based surfactant represented by formula (1) is used in the first and second ink compositions.

[0056] According to the ink set of the present invention, it is possible to realize a printed image with extremely good color bleeding and no deterioration of color bleeding regardless of the storage period. Furthermore, the ink set according to the present invention can obtain a printed image with good wet spreading on an ink non- or hardly absorbent medium and extremely little graininess. The ink set of the present invention is extremely useful for various printing applications, particularly inkjet printing.

[0057] <Inkjet recording method> An inkjet recording method is an inkjet recording method using the above ink set, and includes a step of ejecting droplets of a first ink composition and attaching them to a printing medium to form a first image, and a step of ejecting droplets of a second ink composition and attaching them to the printing medium on which the first image is formed to form a second image. The step of forming the first image and the step of forming the second image can be performed using an inkjet method.

[0058] As the inkjet method, a known method can be used. Specific examples of the inkjet method include, for example, a charge control method, a drop-on-demand (pressure pulse) method, an acoustic inkjet method, a thermal inkjet method, and the like. In addition, the inkjet method includes a method of improving image quality by ejecting a large number of inks with a small volume in which the content of the colorant in the ink is small, a method of improving image quality by using a plurality of inks having substantially the same hue and different concentrations of the colorant in the ink, and a method of improving the fixing property of the colorant by using a colorless and transparent ink.

[0059] <Printing medium> The printing medium means a substance to which the ink composition of the above ink set can adhere. Examples of the printing medium include, for example, paper, film, etc., fibers and cloth (cellulose, nylon, wool, etc.), leather, a substrate for a color filter, and the like. The printing medium can be roughly classified into those having an ink receiving layer and those not having an ink receiving layer. The above ink set can be applied to any printing medium, but can be preferably used for a printing medium not having an ink receiving layer. Printing media having an ink receiving layer are usually called inkjet special paper, inkjet special film, glossy paper, etc. Examples of typical commercially available products include Canon's Professional Photo Paper, Super Photo Paper, Glossy Gold and Matte Photo Paper; Seiko Epson Corporation's Photo Paper Crispia (high gloss), Photo Paper (glossy), and Photo Matte Paper; Hewlett-Packard Japan, Ltd.'s Advance Photo Paper (glossy); and Fujifilm Corporation's Kasei Photo Finish Pro, etc. Examples of printing media without an ink receiving layer include various papers such as coated paper and art paper used for applications such as gravure printing and offset printing; and cast coated paper used for label printing applications. When using a printing media without an ink receiving layer, it is also preferably performed to perform a surface modification treatment on the printing media for the purpose of improving the fixing property of the colorant and the like. Examples of the surface modification treatment include known methods such as corona discharge treatment, plasma treatment, and flame treatment.

[0060] <Ink Media Set> An ink media set is a set including the ink set of the present invention and a printing media.

[0061] Regarding all the matters described above, combinations of preferable ones are more preferable, and combinations of more preferable ones are even more preferable. The same applies to combinations of a preferable one and a more preferable one, combinations of a more preferable one and an even more preferable one, and the like. In addition, unless otherwise specified, all the components and the like described above can be used alone or in combination of two or more.

Examples

[0062] Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited by the following examples. In the examples, when it is necessary to measure the content (solid content) of the colorant contained in various liquids, it was calculated as a converted value of only the colorant by the dry weight method using MS-70 manufactured by A&D Company, Limited.

[0063] [Preparation Example 1 of Dispersion Liquid (Dp1) of Colorant] By repeating Synthesis Example 3 of International Publication No. 2013 / 115071, a block copolymer (Block Copolymer A) was obtained. The obtained block copolymer (4.8 parts) was dissolved in 20 parts of 2-butanone to form a uniform solution. To this solution, a solution prepared by dissolving sodium hydroxide (0.35 parts) in water (58.8 parts) was added, and the mixture was stirred for 1 hour to obtain a solution. To this solution, C.I. Pigment Blue 15:4 (hereinafter referred to as "PB15:4"; 16 parts) was added, and dispersion treatment was carried out in a sand grinder at 1500 rpm for 15 hours to obtain a solution. After adding water (100 parts) dropwise to the obtained solution, the solution was filtered to obtain a filtrate. From the obtained filtrate, a part of 2-butanone and water was distilled off under reduced pressure using an evaporator to obtain a cyan dispersion having a coloring agent content of 12.0%. The obtained dispersion is designated as "Dp1".

[0064] [Preparation Example 2 of Dispersion of Colorant (Dp2)] A yellow dispersion having a coloring agent content of 12.0% was obtained in the same manner as in Preparation Example 1, except that C.I. Pigment Yellow 74 (hereinafter referred to as "PY74"; 16 parts) was used instead of PB15:4. The obtained dispersion is designated as "Dp2".

[0065] [Synthesis Example of Silicon-Based Surfactant B] To a 20 mL solution of 7.0 g of hexaethylene glycol allyl methyl ether in tetrahydrofuran, 5.8 g of hexadecamethyloctasiloxane and 0.1 mL of chloroplatinic acid were added, and the mixture was reacted by holding at 65 °C for 24 hours while stirring. After completion of the reaction, the solvent was distilled off by rotary evaporation to obtain a silicon-based surfactant. The obtained silicon-based surfactant has a = 6, x = 2, y = 2, m = 7, n = 7, o = 0, p = 0, R 1 and R 2 in the formula (1) are hydroxyl groups.

[0066] [Method for Calculating HLB Value] The HLB value of the compound was calculated as follows. As an example, the calculation example of Lutensol X L 40 is described. As the compound represented by the formula (1), 500 mg of "Lutensol XL 40" was dissolved in 10 mL of ethanol with stirring to obtain a visually transparent solution. To this solution, 25 mL of a 2% aqueous phenol solution was added dropwise using a burette. As the 2% aqueous phenol solution was added dropwise, the liquid in the beaker became turbid and did not return to transparency. The amount of the 2% aqueous phenol solution added dropwise at this time, Q, was 7.8 mL. Taking "Q = 7.8", the HLB value was calculated using the above formula (2) (HLB value = 0.89×7.8 + 1.11 = 8.052), and by rounding off the second digit after the decimal point, the HLB value of the compound represented by the formula (1) was calculated to be 8.1. In the same manner as Lutensol XL 40, the HLB values of the compounds described in Table 1 were calculated.

[0067] [Preparation Example of Ink Composition] Dispersions Dp1 and Dp2 were mixed with each of the components described in Tables 1 and 2 below, and then filtered through a 3 μm membrane filter (cellulose mixed ester type membrane filter manufactured by Advantec) to obtain ink compositions C1 to 16 and Y1 to 15 for evaluation tests. The content of the colorant with respect to the total mass of the ink composition was adjusted to 4.5% for all inks. The ink compositions C1 to 16 described in Table 1 are all cyan inks. Also, the ink compositions Y1 to 15 described in Table 2 are all yellow inks.

[0068]

Table 1

Table 2

[0069] Details of the components in Tables 1 and 2 are as follows. · Dp1: Dispersant 1 obtained in Preparation Example 1 · Dp2: Dispersant 2 obtained in Preparation Example 1 · PG: Propylene glycol · 1,2-HD: 1,2-Hexanediol ·TEA: Triethanolamine ·TG450: TEGO Glide 450 ·SAG005: Silface SAG005 ·Surfactant A: BYK - New Product 1 General Grade described in the published document on June 22, 2020 ·Surfactant B: Surfactant B obtained in the synthesis example ·XL40: Lutensol XL40 (HLB = 8.1) ·EP2564: GENAPOL EP2564 (HLB = 7.4) ·TW510: TEGO Wet510 (HLB = 9.1) ·NT - 3: Newcol NT - 3 (HLB = 6.3) ·EP12030: SOFTANOL EP12030 (HLB = 4.5) ·XL70: Lutensol XL70 (HLB = 11.1) ·XL100: Lutensol XL100 (HLB = 14.3)

[0070] [Examples 1 - 11 and Comparative Examples 1 - 11] After storing the ink compositions C1 - C18 and Y1 - 18 adjusted as described above at room temperature for 4 weeks each, they were combined as the first ink composition and the second ink composition as shown in Tables 3 and 4 to prepare the ink sets of Examples 1 - 11 and Comparative Examples 1 - 11.

[0071] [(A) Evaluation of bleeding between colors - Initial] (1) Preparation of Test Piece 1 Using the ink sets of Examples 1 to 11 and Comparative Examples 1 to 11, one solid image (second image) of 100% of the second ink composition with a line width of 1.0 mm was printed so as to overlap on the solid image (first image) of 100% of the first ink composition to obtain a printed image. The printing was performed using a printing jig equipped with two KJ4B inkjet heads manufactured by Kyocera Corporation, and under the conditions of a frequency of 10 kHz and binary (medium droplet), in the order of the first ink composition and the second ink composition, using "OK Top Coat +" manufactured by Oji Paper Co., Ltd. as a printing medium. The two inkjet heads are provided in a printing evaluation apparatus in the order of the first ink composition and the second ink composition from the upstream side in the feeding direction of the printing medium. At this time, the interval between the respective inkjet heads filled with the first ink composition and the second ink composition was set to 90 mm. The obtained printed image was dried for 3 seconds under an IR heater set at 100°C to obtain Test Specimen 1. The line width of the second image formed on the first image of the test specimen was measured. For the measurement of the line width, a printing image evaluation apparatus PIAS-II manufactured by QEA was used. (2) Preparation of Test Specimen 2 Using the ink sets of Examples 1 to 11 and Comparative Examples 1 to 11, one solid image (second image) of 100% of the second ink composition was printed so as to overlap on a linear image (first image) of 100% of the first ink composition with a line width of 1.0 mm to obtain a printed image. The apparatus, conditions, and printing medium used for printing were the same as in (1). The obtained printed image was dried in the same manner as in (1) to obtain Test Specimen 2. The line width of the first image observed through the second image of Test Specimen 2 was measured. (3) Evaluation The measured value of the line width was divided by 1.0 mm which is the line width to calculate the ratio of the line width, and the evaluation was performed according to the following four-level evaluation criteria. The smaller the ratio of the line width, the better the bleeding performance between colors. The evaluation results are shown in Tables 3 and 4 below. [Evaluation Criteria] D: Ratio 101% or more C: Ratio 51 - 100% B: Ratio 26 - 50% A: Ratio 25% or less

[0072] [Table 3] [Table 4]

[0073] [Examples 12 to 22 and Comparative Examples 12 to 22] An accelerated test was conducted by storing the first ink compositions in Tables 5 and 6 in a thermostat at 60°C for 4 weeks. The second ink composition was stored at room temperature for 4 weeks without conducting an accelerated test. The accelerated test of storing at 60°C for 4 weeks is equivalent to storing at 25°C for 1 year. The first ink composition subjected to the accelerated test and the second ink composition stored at room temperature were combined as shown in Tables 5 and 6 to prepare ink sets of Examples 9 to 16 and Comparative Examples 12 to 22.

[0074] [(B) Evaluation of color bleeding after accelerated test] (1) Preparation of Test Piece 3 Using the ink sets of Examples 12 to 22 and Comparative Examples 12 to 22, one linear image (second image) with a line width of 1.0 mm and 100% of the second ink composition was printed so as to overlap on the solid image (first image) of 100% of each first ink composition to obtain a printed image. The apparatus, conditions, and printing medium used for printing were the same as those in (1) of (A) above. The obtained printed image was dried under an IR heater set at 100°C for 3 seconds to obtain Test Piece 3.

[0075] (2) Evaluation The line width of the second image formed on the first image of Test Piece 3 was measured. The ratio of the line width was calculated by dividing the measured value of the obtained line width by the line width of the second image of Test Piece 1 obtained in (1) of (A), and evaluated according to the following four-level evaluation criteria. A smaller ratio of the line width indicates that the color bleeding does not deteriorate regardless of the storage period, and thus the performance of color bleeding is excellent. The evaluation results are shown in Tables 5 and 6 below. [Evaluation Criteria] D: Ratio 101% or more C: Ratio 51 to 100% B: Ratio 26 - 50% A: Ratio 25% or less

[0076]

Table 5

Table 6

[0077] As is clear from Table 5 and Table 6 above, in the ink sets of Examples 1 to 11, bleeding between colors was suppressed to 25% or less. Therefore, it was shown that the ink sets of Examples 1 to 11 have excellent performance in suppressing bleeding between colors in a new state with a short storage period after the ink composition was prepared. Also, in the results shown in Table 5, bleeding between colors of the ink sets of Examples 12 to 22 was suppressed to 25%. From this, it was confirmed that in the ink sets of Examples 12 to 22, deterioration of bleeding between colors is reduced even when the storage periods of the ink compositions included in the ink sets are different. From the results of Tables 3 to 6, the ink sets of Examples 1 to 22 had excellent performance in that bleeding between colors was low whether the storage periods of the ink compositions were the same or different, while it was confirmed that the ink sets of Comparative Examples 1 to 22 were inferior in the evaluation of bleeding between colors in at least one of the cases where the storage periods were the same and where the storage periods were different.

Industrial Applicability

[0078] According to the present invention, it is possible to provide an ink set having two ink compositions with extremely good bleeding between colors and further having no deterioration of bleeding between colors regardless of the storage period, an inkjet printing method using the same, a printing medium, and a printing medium set. The ink set of the present invention is extremely useful for various printing applications, particularly inkjet printing.

Claims

1. A first ink composition containing water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant, and A second ink composition containing water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant, and applied onto a first image formed using the first ink composition to form a second image, an ink set having: The first silicone-based surfactant and the second silicone-based surfactant are each independently represented by the following formula (1): 【Chemical 1】 (In the formula, a is an integer of 1 to 80, x and y are each independently an integer of 1 to 4, m and n are each independently an integer of 1 to 50, o and p are each independently an integer of 0 to 40, m + n is 2 to 100, o + p is 0 to 80, R １ and R ２ are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a (meth)acrylic group.) A silicone-based surfactant represented by The first nonionic surfactant and the second nonionic surfactant are nonionic surfactants having an HLB value of 6.0 or more and less than 12.0, other than silicone-based surfactants, When the content of the first silicone-based surfactant is A1, the content of the first nonionic surfactant is A2, the content of the second silicone-based surfactant is B1, and the content of the second nonionic surfactant is B2, 0.10 ≦ (B1 - A1) + (B2 - A2) ≦ 0.95 An ink set satisfying the above.

2. The ink set according to claim 1, wherein in the formula (1), m and n are each independently an integer of 1 to 30.

3. The ink set according to claim 1 or 2, wherein one or both of the first ink composition and the second ink composition further contain a binder.

4. The ink set according to claim 3, wherein the binder contains at least one selected from wax and (meth)acrylic acid-based polymers.

5. The ink set according to claim 4, wherein the wax is one or more selected from polyalkylene wax, oxidized polyalkylene wax, and paraffin wax.

6. The ink set according to claim 4 or 5, wherein the wax is oxidized polyethylene wax.

7. The ink set according to any one of claims 1 to 6, wherein the first nonionic surfactant and the second nonionic surfactant have an HLB value of 6.0 or more.

8. An inkjet recording method using the ink set according to any one of claims 1 to 7, comprising: A step of ejecting droplets of the first ink composition and attaching them to a printing medium to form a first image; and A step of ejecting droplets of the second ink composition and attaching them onto the printing medium on which the first image is formed to form a second image. An inkjet recording method including

9. A printing medium on which a second image is formed by applying the second ink composition onto a first image formed by applying the first ink composition included in the ink set according to any one of Claims 1 to 7.

10. An ink-media set including the ink set according to any one of Claims 1 to 7 and a printing medium.

11. Used together with an ink composition that is applied onto a first image to form a second image, the ink composition for forming the first image, wherein the ink composition for forming the first image contains water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant the ink composition for forming the second image contains water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant, wherein the first silicone-based surfactant and the second silicone-based surfactant are each independently a silicone-based surfactant represented by the following formula (1): [Chemical 2] (wherein a is an integer of 1 to 80, x and y are each independently an integer of 1 to 4, m and n are each independently an integer of 1 to 50, o and p are each independently an integer of 0 to 40, m + n is 2 to 100, o + p is 0 to 80, R １ and R ２ are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a (meth)acrylic group.) and the first nonionic surfactant and the second nonionic surfactant are nonionic surfactants having an HLB value of 6.0 or more and less than 12.0, other than silicone-based surfactants, when the content of the first silicone-based surfactant is A1, the content of the first nonionic surfactant is A2, the content of the second silicone-based surfactant is B1, and the content of the second nonionic surfactant is B2, 0.10 ≦ (B1 - A1) + (B2 - A2) ≦ 0.95 An ink composition satisfying the above.

12. Used together with an ink composition for forming a first image on which a second image is formed, the ink composition for forming the second image, wherein the ink composition for forming the first image contains water, a first colorant, a first silicone-based surfactant, and a first nonionic surfactant the ink composition for forming the second image contains water, a second colorant, a second silicone-based surfactant, and a second nonionic surfactant, wherein the first silicone-based surfactant and the second silicone-based surfactant are each independently a silicone-based surfactant represented by the following formula (1): [Chemical Formula 3] (In the formula, a is an integer of 1 to 80, x and y are each independently an integer of 1 to 4, m and n are each independently an integer of 1 to 50, o and p are each independently an integer of 0 to 40, m + n is 2 to 100, o + p is 0 to 80, R １ and R ２ are each independently selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, and a (meth)acrylic group.) and the first nonionic surfactant and the second nonionic surfactant are nonionic surfactants having an HLB value of 6.0 or more and less than 12.0, other than silicone-based surfactants, When the content of the first silicon-based surfactant is A1, the content of the first nonionic surfactant is A2, the content of the second silicon-based surfactant is B1, and the content of the second nonionic surfactant is B2, 0.10 ≦ (B1 - A1) + (B2 - A2) ≦ 0.95 An ink composition satisfying the above condition.

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