JP2019035021A - Recording liquid set and image formation method - Google Patents

Abstract

To provide a recording liquid set that can form an image having high picture quality on a variety of non-water absorbing base materials at a high speed, has high adhesion to such a base material and is used for producing an image formed product having excellent laminate suitability in lamination processing, and to provide an image formation method using the recording liquid set.SOLUTION: A recording liquid set comprises: aqueous undercoat liquid containing a hydrophobic resin, a hydrophilic resin, a pigment coagulant and water; and aqueous inkjet ink containing a pigment, a resin for pigment dispersion, a surfactant having an HLB value of 5 to 15, a water-soluble organic solvent having an SP value of 25 MPato 32 MPaand water and having a mass ratio of the total amount of a resin component to the pigment included in the ink of 0.3 to 1.0. An image formation method using the recording ink set is also provided.SELECTED DRAWING: None

Description

  The present invention relates to a recording liquid set and an image forming method.

  The inkjet image forming method is a method of performing printing by ejecting small ink droplets from a fine nozzle head and attaching them to a recording medium. Since this method can print a high-resolution image at a high speed with a relatively inexpensive apparatus, it has been attracting attention in the field of packaging materials for printing a wide variety of products in a small lot. In particular, inkjet water-based inks (hereinafter sometimes abbreviated as “inks” or “inkjet inks”) containing water and a coloring material have attracted attention from the viewpoint of environmental safety, Problems such as adhesion to the substrate and poor adhesion between the image and the resin layer provided thereon are likely to occur particularly when a non-water-absorbing substrate such as a film is used. For example, in a laminate obtained by laminating by directly printing on the surface of a plastic film or the like, providing a printing layer, applying an adhesive thereon, and bonding a sealant film that can be heat-sealed, it is important to solve the above problems. . Not only the adhesion between the substrate and the printed layer (image), but also the adhesion between the printed layer and the film layer thereon is good, and the laminate can be used as a packaging material by using an aqueous ink excellent in lamination suitability. This is because it is possible to prevent delamination and burst from the heat seal portion of the package, which may occur when the package used is manufactured, or an article is filled into the package.

  As an attempt to solve the above-described problems of water-based inks, water-based adhesives with improved laminating properties that can enhance the adhesion between the ink and the non-absorbent substrate by adding a fixing resin to the inks. An ink-jet ink is described in Japanese Patent Application Laid-Open No. H10-228707. Further, in Patent Document 2, an ink receiving layer containing a water-based polyurethane resin or the like is provided on a non-absorbing substrate, and an image is formed on the ink receiving layer using a water-based inkjet ink containing a fixing resin. Thus, there is described an image forming method for suppressing bleeding of images and improving adhesion.

  An inkjet recording medium having a non-absorbing substrate, an inorganic particle, a cationic polymer as a fixing resin, and an ink receiving layer containing a polyvalent metal salt as a pigment flocculant; An ink jet recording method to be used is described in Patent Document 3. This recording medium is supposed to form an image with a water-based ink that does not contain a fixing resin, achieves high-speed printing while maintaining long-term ejection stability with a water-based ink that does not contain a fixing resin, and the image quality of the ink-receiving layer. The purpose is to improve.

JP2013-216878A JP 2012-250416 A JP 2009-107256 A

  Conventionally, as a method for improving laminating suitability of water-based ink, as described in Patent Document 1 and Patent Document 2, a method of including a fixing resin in the ink is generally used. However, since the ink containing the fixing resin tends to thicken the ink by drying, the ink jet head is easily clogged, and it is difficult to maintain the ejection stability in the high-speed and one-pass printing method.

  Moreover, since the ink receiving layer containing only a hydrophilic resin as a resin component as described in Patent Document 2 has low adhesion to a low polarity resin such as a polyethylene film, the substrate is a low polarity resin film. In some cases, there are concerns such as delamination.

  Further, as described in Patent Document 3, an image is formed with an ink not containing a fixing resin on an ink jet recording medium provided with an ink receiving layer containing a cationic polymer serving as a fixing resin and a pigment flocculant, and further adhered thereon. When the layer and the film layer were provided, the adhesive strength between the image and the layer above it and the strength of the image itself were insufficient, and it was difficult to obtain an excellent laminate.

  In the image forming method using the ink and ink receiving layer described in Patent Documents 1 to 3 described above, a film substrate having a relatively low polarity (for example, OPP) and a film substrate having a relatively high polarity (PET or nylon). ), That is, it was difficult to form images showing the same adhesion on various film substrates.

  The present invention has been made in view of the above problems, and its purpose is to form high-quality images at high speed on various non-water-absorbing substrates such as OPP, PET, and nylon. In addition, the adhesiveness to the non-water-absorbing substrate is high, and when laminated, it has excellent laminating properties (that is, the adhesion between the image and the substrate, and the image and other layers provided thereon) An object of the present invention is to provide a recording liquid set capable of obtaining an image formed product (both in good adhesion). A further object of the present invention is to provide an image forming method using the recording liquid set.

The first of the present invention is the following recording liquid set.
[1] A recording liquid set including an aqueous undercoat liquid and an aqueous inkjet ink,
The undercoat liquid contains a hydrophobic resin, a hydrophilic resin, a pigment flocculant, and water,
The inkjet ink contains a pigment, a pigment dispersing resin, a surfactant, a water-soluble organic solvent, and water,
In the inkjet ink,
The HLB value of the surfactant is 5 or more and 15 or less,
The SP value of the water-soluble organic solvent is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less,
A recording liquid set, wherein a mass ratio of the pigment dispersing resin to the pigment is 0.3 or more and 1.0 or less.
[2] The recording liquid set according to [1], wherein the content of the water-soluble organic solvent in the inkjet ink is 10% by mass or more and 40% by mass or less.
[3] In the undercoat liquid, the ratio of the hydrophilic resin to the total mass of the hydrophobic resin and the hydrophilic resin is 20% by mass or more and 70% by mass or less. Recording liquid set.
[4] The recording liquid set according to any one of [1] to [3], wherein the pigment flocculant is a polyvalent metal salt.

The second of the present invention is the following image forming method.
[5] An undercoat liquid containing a hydrophobic resin, a hydrophilic resin, a pigment flocculant, and water is applied on a non-absorbent substrate to form an undercoat layer.
An ink layer is formed by applying an ink jet ink containing a pigment, a pigment dispersing resin, a surfactant, a water-soluble organic solvent, and water by an ink jet method in contact with the surface of the undercoat layer. An image forming method comprising:
In the inkjet ink,
The HLB value of the surfactant is 5 or more and 15 or less,
The SP value of the water-soluble organic solvent is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less,
The image forming method, wherein a mass ratio of the pigment dispersing resin to the pigment is 0.3 or more and 1.0 or less.
[6] The image forming method according to [5], further comprising forming a resin layer in contact with the surface of the ink layer.
[7] The image forming method according to [5] or [6], wherein the content of the water-soluble organic solvent in the inkjet ink is 10% by mass or more and 40% by mass or less.
[8] In any one of [5] to [7], in the undercoat liquid, a ratio of the hydrophilic resin to a total mass of the hydrophobic resin and the hydrophilic resin is 20% by mass to 70% by mass. The image forming method according to claim 1.
[9] The image forming method according to any one of [5] to [8], wherein the pigment flocculant is a polyvalent metal salt.
[10] The image forming method according to any one of [5] to [9], wherein the inkjet ink is applied by a single pass method.

  High-quality images can be formed at high speed on various non-water-absorbing substrates such as OPP, PET, and nylon, and the adhesiveness to the non-water-absorbing substrate is high. An image-formed product having excellent laminating properties (that is, both the adhesion between the image and the substrate and the adhesion between the image and the other layer provided thereon) can be obtained. A liquid set is provided. Furthermore, an image forming method using the recording liquid set is provided.

As a result of intensive studies in view of the above problems, the present inventors have found that an undercoat liquid containing a hydrophobic resin, a hydrophilic resin, a pigment flocculant, water, a pigment, and a pigment dispersion resin , the HLB value of 5 to 15 surfactant, and the SP value of ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less of a water-soluble organic solvent, containing water, present in said ink When an image is formed on a non-water-absorbing substrate such as a film using a recording liquid set containing an ink having a mass ratio of the pigment-dispersing resin to the pigment of 0.3 to 1.0, non-water-absorbing Whether the base material is a high-polarity resin (PET, nylon, etc.) or a low-polarity resin (OPP, etc.), it has high adhesion to the base material and can form high-quality images at high speed. I found. In addition, the ink ejection stability is high, and the strength of the image (ink layer) is also high. When laminated, it has excellent laminating properties (that is, adhesion between the image and the substrate, and It was found that an image-formed product was obtained (both good adhesion to other layers provided thereon). The reason is not clear, but is estimated as follows.

  The surfactant in the ink is conventionally used in order to improve the light emission and wettability of the ink. However, in the image-formed product using the ink containing the surfactant having an HLB value exceeding 15. Was found to be prone to delamination. When ink droplets land on the recording medium, water contained in the landed ink is first evaporated, and the concentration of the water-soluble organic solvent in the ink gradually increases. At this time, when the HLB value of the surfactant contained in the ink exceeds 15, the surfactant precipitates and moves to the surface of the ink droplet, and a surfactant film tends to be formed on the surface of the ink layer. It is in. When a resin layer is provided on the ink layer, such a surfactant film hinders the adhesion between the resin layer and the ink layer, and the interlayer adhesion between the ink layer and the resin layer is considered to decrease. .

Meanwhile, the ink contained in the ink set of the present invention, the HLB value of 5 to 15 surfactant, SP value and less water-soluble organic solvent ^{25 MPa (1/2)} or ^{32 MPa (1/2)} Including. By combining such a specific surfactant and a specific water-soluble organic solvent, ink droplets land on the undercoat layer formed by the undercoat liquid, and the water-soluble organic in the ink is evaporated by moisture evaporation. Even when the concentration of the solvent is increased, the surfactant can maintain a state of being dissolved in the water-soluble organic solvent. Therefore, it is considered that film formation on the surface of the ink layer by the deposited surfactant is suppressed, and interlayer adhesion between the ink layer and the resin layer provided thereon is increased.

  Furthermore, since surfactants having an HLB value of 5 or more and 15 or less are not too soluble in water-soluble organic solvents in the ink, after the ink has landed on the substrate, a part of the surfactant is present on the surface of the ink. It is thought that it can be oriented. Therefore, it is possible to enlarge the dots even with a small amount of surfactant.

  Furthermore, the mass ratio of the pigment dispersing resin contained in the ink to the pigment is 0.3 or more and 1.0 or less. By suppressing the mass ratio of the pigment dispersing resin to 1.0 or less, it is possible to prevent ink thickening due to drying and to ensure ink ejection stability while dispersing the pigment in the ink. Become.

  The ink set of the present invention includes an undercoat liquid containing both a hydrophilic resin and a hydrophobic resin. It is considered that the hydrophilic resin contained in the undercoat liquid diffuses into the ink containing the specific surfactant and the specific water-soluble organic solvent that has landed on the undercoat layer, and interacts with the ink. By such interaction, the resin component in the ink can at least increase the strength of the ink layer, and further improve the interlayer adhesion between the ink layer and the undercoat layer.

  Furthermore, since the undercoat liquid contains a hydrophilic resin having good adhesion to a high polarity resin such as PET and nylon and a hydrophobic resin having good adhesion to a low polarity resin such as OPP, it has no water absorption. It is possible to form an undercoat layer having high adhesion even if the conductive substrate is a high-polar resin or a low-polar resin.

  Therefore, by using the recording set of the present invention in which the above-described specific undercoat liquid and specific ink are combined, it becomes possible to form a high-quality image on a non-absorbent substrate at high speed, and the ink. It is possible to obtain an image with high interlayer adhesion with little risk of peeling of the layer.

  Hereinafter, the present invention will be described with reference to exemplary embodiments, but the present invention is not limited to the following embodiments.

1. Recording liquid set The recording liquid set of the present invention is a recording liquid set including an aqueous undercoat liquid and an aqueous inkjet ink.

  First, the undercoat liquid will be described.

  The undercoat liquid contains a hydrophobic resin, a hydrophilic resin, a pigment flocculant, and water.

  In the present invention, the hydrophobic resin is a resin that is hydrophobic with respect to water, that is, is easily swelled with water or not easily mixed with water. A preferred hydrophobic resin is an olefin resin. The olefin-based resin may be modified or unmodified, but a modified olefin-based resin is more preferable from the viewpoint of affinity with the hydrophilic resin used in combination.

  Specific examples of the olefin resin include homopolymers of α-olefins such as ethylene, propylene, 1-butene, 1-hexene, 4-methyl-1-pentene, and 1-octene, or copolymers thereof, and the above-described examples. Examples thereof include modified polyolefins obtained by modifying an α-olefin homopolymer or copolymer with chlorine or the like. A preferred olefin-based resin is a water-based chlorinated polyolefin, and for example, Supercron E415 or Supercron E480 manufactured by Nippon Paper Industries Co., Ltd. can be used.

  In the present invention, the hydrophilic resin is a resin other than the hydrophobic resin, and has affinity for water, is easily wetted with water, or is easily mixed with water.

  Examples of the hydrophilic resin include silicone resin, polyester resin, epoxy acrylate resin, polyol acrylate resin, epoxy resin, urethane resin, polycarbonate, and acrylic urethane resin. The preferred hydrophilic resins are urethane resin and acrylic urethane resin since the composition with the adhesive that can be used for forming the laminate and the resin for pigment dispersion is close, and the adhesion between the layers is expected to be improved. For example, Superflex 650 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., which is a urethane resin, Passcall JK-870 manufactured by Meisei Chemical Co., Ltd., and WEM-505c manufactured by Taisei Fine Chemical Co., Ltd., which is an acrylic urethane resin, can be used. .

  The hydrophobic resin and the hydrophilic resin only need to be contained at least one each. The ratio of the hydrophilic resin to the total mass of the hydrophobic resin and the hydrophilic resin is preferably 20% by mass to 70% by mass, and more preferably 30% by mass to 50% by mass. If the ratio of the hydrophilic resin is within the above range, an undercoat layer having good adhesion to the substrate can be obtained regardless of the polarity of the non-absorbent substrate.

The range of the total amount of the hydrophobic resin and the hydrophilic resin in the undercoat liquid is not particularly limited, but the amount of the resin in the undercoat layer formed on the substrate using the undercoat liquid is 0.5 g / m ^2. The amount of 10 g / m ² or less is preferable, and the amount of 0.5 g / m ² or more and 3 g / m ² or less is more preferable. In order to use an image-formed product produced using a recording liquid set as a thin film material, the amount of resin in the undercoat layer formed with the undercoat liquid is preferably within the above range.

  In addition, content of the hydrophobic resin and the hydrophilic resin in the undercoat layer can be measured by a known method, for example, high performance liquid chromatography (HPLC).

  The undercoat liquid contains a pigment flocculant capable of aggregating the pigment contained in the ink contained in the recording liquid set.

  As the pigment aggregating agent, particularly when the pigment contained in the ink is an anionic dispersion pigment, at least one selected from the group consisting of an acid, a cationic compound, and a metal chelating agent can be preferably used.

  The acid can agglomerate the anionic dispersed pigment in the ink due to pH fluctuation. Examples of the acid include formic acid, acetic acid, propionic acid, isobutyric acid, oxalic acid, fumaric acid, malic acid, citric acid, malonic acid, succinic acid, maleic acid, benzoic acid, 2-pyrrolidone-5-carboxylic acid, and lactic acid. Acrylic acid or a derivative thereof, methacrylic acid or a derivative thereof, acrylamide or a derivative thereof, a sulfonic acid derivative, phosphoric acid or a derivative thereof can be preferably exemplified. As the acid, an organic acid can be preferably used rather than an inorganic acid. By using an organic acid, compatibility with other components such as a resin constituting the undercoat liquid can be improved, and further, even if the undercoat layer formed by the undercoat liquid is dried, it is difficult to become a salt. The effect which is excellent in transparency is also acquired.

  The cationic compound can agglomerate the anionic dispersed pigment in the ink by salting out. Examples of the cationic compound include polyvalent metal salts and cationic surfactants and polymers. Preferred examples of the polyvalent metal salt include water-soluble salts such as calcium salts, magnesium salts, aluminum salts, and zinc salts.

  As the cationic surfactant (also referred to as cationic surfactant), for example, aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salts and the like are preferable. Can be mentioned.

  Examples of the cationic polymer include polymers having 1 to quaternary amines such as polyallylamine, polyvinylamine, polyethyleneimine, polydiallyldimethylammonium chloride, and the like. Further, specific examples include the Cachio Master series manufactured by Daiichi Kogyo Seiyaku Co., Ltd., the Unisense series manufactured by Senka Co., Ltd., and the polyallylamine series manufactured by Nittobo Medical Co., Ltd.

  As the metal chelating agent, a complex (chelate complex) composed of a metal ion and a ligand (multidentate ligand) can be used. Here, as the metal ion, for example, a metal ion constituting the polyvalent metal salt described above can be used, and as the ligand, a compound having a plurality of coordination sites can be used. Examples of compounds having a plurality of coordination sites are ethylenediamine, ethylenediaminetetraacetic acid, 1,2-propylenediaminetetraacetic acid, 1-phenylethylenediaminetetraacetic acid, 3,3-dimethylbutane-1,2-diaminetetraacetic acid, 1 , 2,3-triaminopropanehexaacetic acid, trimethylenediaminetetraacetic acid, nitrilotriacetic acid, 1,2-cyclohexanediaminetetraacetic acid, diethylenetriaminepentaacetic acid, glycolethylenediaminetetraacetic acid, triethylenetetraminehexaacetic acid, triethylenetetramine, tetra Ethylenepentamine, propane-1,2-diamine, butane-1,2-diamine, 3,3-dimethylbutane-1,2-diamine, 1,2,3-triaminopropane, trimethylenediamine, tetralin-2 , 3-diaminetetraacetic acid, de -2,3-tetraacetic acid, cyclohexane-1,2-diamine tetraacetic acid, cyclohexane-1,3-diamine tetraacetic acid, cyclohexane-1,4-diaminetetraacetic acid, oxalic acid, Tiron, an acetylacetone.

  Specific examples of the metal chelating agent that can be used as the pigment flocculant include ZC-126 manufactured by Matsumoto Fine Chemical Co., Ltd.

  A preferred pigment flocculant is a polyvalent metal salt. When a polyvalent metal salt is used as a pigment flocculant, the diffusion of the pigment flocculant into the ink layer is performed at an appropriate speed, so that it is possible to form an image with good solid filling and suppressed bleeding.

  A pigment flocculant may be used individually by 1 type, and may use multiple types together.

The range of the content of the pigment flocculant in the undercoat liquid is not particularly limited, but the amount of the pigment flocculant in the undercoat layer formed on the substrate is preferably within the following range. For example, when using a polyvalent metal salt as a pigment flocculant, 0.1 g / m ² or more and 20 g / m ² or less are preferable. In order to effectively suppress bleeding, it is preferably contained in an amount of 0.1 g / m ² or more, and in order to effectively suppress cracks, it is preferably 20 g / m ² or less.

  The amount of the pigment flocculant in the undercoat layer can be measured by a known method. For example, when the pigment flocculant is a polyvalent metal salt, the content can be measured by ICP emission analysis, and when the pigment flocculant is an acid, the content can be measured by high performance liquid chromatography (HPLC). Further, when the pigment flocculant is a metal chelating agent, for example, the content of the metal element is determined by a known metal analysis method such as an atomic absorption analysis method or a plasma emission analysis method (for example, described in JP-A-2006-251179). Method).

  The undercoat liquid preferably contains water as a solvent, and may contain other known organic solvents.

  The undercoat liquid may contain a surfactant different from the surfactant used as the pigment flocculant. Thereby, the adaptability to various application methods can be improved. Preferred examples of the surfactant include amphoteric surfactants, nonionic surfactants, anionic surfactants and the like.

  Preferred examples of amphoteric surfactants include carboxybetaine type, sulfobetaine type, aminocarboxylate, imidazolinium betaine and the like.

  Examples of nonionic surfactants include polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene Preferred examples include castor oil, hydrogenated castor oil, fatty acid alkanolamide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetylene glycol, and acetylene alcohol.

  In the undercoat liquid, other components such as a crosslinking agent, an antifungal agent, and a bactericidal agent can be appropriately blended within a range not impairing the effects of the present invention.

  Next, the ink contained in the recording liquid set of the present invention will be described.

  The ink contained in the recording liquid set contains a pigment, a pigment dispersing resin, a surfactant, a water-soluble organic solvent, and water.

  As the pigment, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments and the like can be used. For example, organic pigments such as insoluble pigments and lake pigments, titanium oxide and carbon black Inorganic pigments such as can be preferably used. These pigments can be used, for example, in the state of being dispersed in the ink by a pigment dispersant.

  The insoluble pigment is not particularly limited. For example, azo pigment, azomethine pigment, methine pigment, diphenylmethane pigment, triphenylmethane pigment, quinacridone pigment, anthraquinone pigment, perylene pigment, indigo pigment, quinophthalone Pigments, isoindolinone pigments, isoindoline pigments, azine pigments, oxazine pigments, thiazine pigments, dioxazine pigments, thiazole pigments, phthalocyanine pigments, diketopyrrolopyrrole pigments and the like are preferable.

  Although a pigment is not specifically limited, For example, the following can be illustrated preferably.

  Examples of pigments used for yellow ink or orange ink include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. And CI Pigment Yellow 155.

  Examples of pigments used for magenta ink or red ink include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment violet 19 and the like.

  Examples of pigments used for cyan ink or green ink include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of pigments used for black ink include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. And CI pigment black 7 (carbon black).

  Moreover, titanium oxide is mentioned as a pigment used for white ink.

  The average particle diameter of the dispersed state of the pigment in the ink is preferably in the range of 50 nm to 200 nm. Thereby, the dispersion stability of the pigment can be improved, and the storage stability of the ink can be improved. The particle size of the pigment can be determined by a commercially available particle size measuring instrument using a dynamic light scattering method, an electrophoresis method, etc., but the measurement by the dynamic light scattering method is simple and the particle size region is Accurate measurement.

  The pigment can be used by being dispersed by a disperser together with, for example, a pigment dispersant and other desired additives.

  As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Among them, it is preferable to disperse the pigment by a sand mill because the particle size distribution becomes sharp. The material of the beads used for sand mill dispersion is not particularly limited, but zirconia or zircon is preferable from the viewpoint of preventing generation of bead fragments and contamination of ionic components. Further, the bead diameter is preferably 0.3 mm or more and 3.0 mm or less.

  The pigment content in the ink is not particularly limited. For example, the inorganic pigment is preferably in the range of 7% by mass to 18% by mass with respect to the total mass of the ink, and the organic pigment is in the total mass. On the other hand, the range is preferably 0.5% by mass or more and 7% by mass or less.

  It is particularly preferable to use an anionic dispersion pigment as the pigment. Examples of the anionic dispersed pigment include a pigment having an anionic group introduced on the surface, a pigment dispersed with a pigment dispersant having an anionic group, and the like.

  Preferred examples of the anionic group include a carboxyl group, a sulfonic acid group, and a phosphonic acid group.

  The anionic group is preferably alkali-neutralized. Examples of the alkali that neutralizes the anionic group include metal base compounds such as sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide, organic amines such as ammonia, triethylamine, pyridine, morpholine, and monoethanol. Preferable examples include alkanolamines such as amines.

  The ink according to the present invention contains a pigment dispersing resin. As the pigment dispersion resin, for example, an acrylic dispersant can be preferably used. As the acrylic dispersant, one or more selected from poly (meth) acrylic acid and (meth) acrylic acid copolymers can be suitably used.

  As an acrylic dispersant, a copolymer of (meth) acrylic acid (ie, poly (meth) acrylic acid) or a copolymer obtained by copolymerizing other monomer components such as styrene as needed (ie, (meth)) (Acrylic acid copolymer) can be preferably used.

  Examples of the acrylic dispersant include “Joncrill 819” manufactured by BASF (“Johncrill” is a registered trademark of the company) (acid value 75 mgKOH / g), “Johncrill 67” (acid value 213 mgKOH / g), and the like. Commercial products can be used.

  The pigment dispersion resin may be used alone or in combination of two or more.

  The mass ratio of the pigment-dispersing resin to the pigment contained in the ink is preferably 0.3 or more and 1.0 or less, and more preferably 0.3 or more and 0.6 or less. If the mass ratio of the pigment dispersing resin is 0.3 or more, the pigment can be uniformly dispersed without agglomerating. Moreover, if it is 1.0 or less, the fall of the ejection stability by the thickening of an ink can be suppressed.

  Note that the resin component contained in the ink is substantially only the pigment-dispersing resin, but other resins may be included. When the ink includes a plurality of resin components, the total amount of the pigment dispersing resin and the other resin is preferably 1.0 or less as a mass ratio with respect to the pigment. When the total amount of the resin is 1.0 or less as a mass ratio with respect to the pigment, an ink having excellent ejection stability can be obtained.

  The ink contains a surfactant having an HLB value of 5 or more and 15 or less in order to improve light emission and wettability.

  The HLB value is Hydrophile-Lipophile-Balance, hydrophilic-lipophilic-balance, and is a value indicating the hydrophilicity or lipophilicity of a compound. The smaller the HLB value, the higher the lipophilicity, and the higher the value, the higher the hydrophilicity.

The HLB value according to the present invention can be obtained by the following calculation formula.
HLB = 7 + 11.7Log (Mw / Mo)
In the formula, Mw represents the molecular weight of the hydrophilic group, Mo represents the molecular weight of the lipophilic group, and Mw + Mo = M (molecular weight of the compound).

  Alternatively, according to the Griffin method, HLB value = 20 × total formula weight of hydrophilic part / molecular weight (J. Soc. Cosmetic Chem., 5 (1954), 294).

  The HLB value of the surfactant contained in the ink is 5 or more and 15 or less, preferably 7 or more and 13 or less. When the HLB value of the surfactant is 5 or more, the surfactant is dissolved during the production of the ink, and a uniform aqueous ink can be obtained. Further, when the HLB value is 15 or less, even if the concentration of the water-soluble organic solvent in the ink is increased by drying, the surfactant is less likely to precipitate and form a film on the surface of the ink droplet. Interlayer adhesion between the layer and the resin layer thereon can be enhanced.

  Surfactants having an HLB value of 5 or more and 15 or less include polyoxyethylene alkylamine (HLB value: 5.1), polyethylene glycol monostearate (HLB value 6.5), self-emulsifying glyceryl monostearate ( HLB value 8.0), sorbitan monolaurate (HLB value: 8.6), polyoxyethylene stearyl ether (HLB value 9.0), polyoxyethylene cetyl ether (HLB value: 14.2), polyoxyethylene And sorbitan monostearate (HLB value 15.0).

  Commercially available products of such surfactants include Amito 302 (polyoxyethylene alkylamine), Rhedol SP-L10 (sorbitan monolaurate), Emulgen 220 (polyoxyethylene cetyl ether), Nissin, manufactured by Kao Corporation. Examples include Olphine E1010 (acetylene-based surfactant, HLB value: 13 to 14) manufactured by Chemical Industries.

  Surfactant may be used individually by 1 type and may use multiple types together.

  The content of the surfactant in the ink is not particularly limited, but is preferably in the range of 0.1% by mass to 2.0% by mass.

The ink according to the present invention, water and, SP value further comprises a water-soluble organic solvent is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less.

  The SP value is an abbreviation for solubility parameter, and is a numerical value obtained by the Fedor calculation method. The SP value calculation method by Fedor is described in R.D. F. Fedor; Polymer Engineering Science, 14 (2) 147-154 (1974).

SP value of the water-soluble organic ^{solvent, 25 MPa (1/2)} or ^{32 MPa (1/2)} or less. When the SP value of the water-soluble organic solvent is within the above range, the surfactant can be dissolved in the ink even when the organic solvent is concentrated in the drying process after printing. It is considered that film formation on the surface of the layer is suppressed and interlayer adhesion between the ink layer and the resin layer provided thereon is enhanced.

The water-soluble organic solvent SP value is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less, ethylene glycol (SP ^{value: 29.9MPa (1/2)),} propylene glycol (SP value: 30. 3MPa ^(1/2)), diethylene glycol (SP value: ^{28.4MPa (1/2))} can be exemplified preferably glycols such like.

  These solvents may be used alone or in combination of two or more.

  The content of the water-soluble organic solvent in the ink is 10% by mass or more and 40% by mass or less, and preferably 10% by mass or more and 40% by mass or less, and 15% by mass with respect to the total mass of the ink. More preferably, it is in the range of 30% by mass or less. When the content of the water-soluble organic solvent is 10% by mass or more, it is possible to form an image with high peel strength. When the content is 40% by mass or less, the ink droplets spread appropriately and solid white spots are generated. Since it hardly occurs, a high-quality image can be formed.

Further, in an amount of SP value is not compromised the effect of ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less of a water-soluble organic solvent, other water-soluble organic solvent (i.e., SP value ^{25 MPa (1/2 )} of less than or water-soluble organic solvent, SP value may include the ^{32 MPa (water-soluble} organic solvent of greater than ^1/2)). When such a water-soluble organic solvent is contained, the content of the water-soluble organic solvent is preferably in the range of more than 0% by mass and 15% by mass or less, and 0% by mass with respect to the total mass of the ink. More preferably, it is in the range of more than 10% by mass.

  Other components can be appropriately blended in the ink as long as the effects of the present invention are not impaired.

2. Image Forming Method The second embodiment of the present invention is an image forming method using the recording liquid set of the present invention. The image forming method of the present invention includes the following steps.
A first step of forming an undercoat layer by applying an undercoat liquid containing a hydrophobic resin, a hydrophilic resin, a pigment flocculant, and water on a non-absorbent substrate;
A second step of applying an ink jet ink containing a pigment, a pigment dispersing resin, a surfactant, an organic solvent, and water by an ink jet method in contact with the surface of the undercoat layer;

  In the first step, an undercoat liquid containing a hydrophilic resin, a pigment flocculant, and water is applied onto the substrate to form an undercoat layer. The undercoat liquid used here is an undercoat liquid contained in the recording liquid set of the present invention described in detail above.

  The non-water-absorbing substrate to which the undercoat liquid is applied is not particularly limited as long as it is a substrate that does not substantially absorb water, such as plastic, plastic film, glass, and metal. In particular, when a plastic film is used as the non-water-absorbing substrate, the effect of the present invention is remarkably exhibited.

  Further, the surface of the non-water-absorbing substrate may be subjected to a surface treatment such as corona discharge treatment or ozone treatment from the viewpoint of improving the adhesion with the undercoat layer formed thereon.

  Although the resin constituting the plastic film is not particularly limited, for example, plastics such as polyolefins such as polypropylene and polyethylene, polyesters such as polyethylene terephthalate, polyamides such as nylon, etc. can be preferably mentioned. A low polarity resin may be used. The plastic film may be either an unstretched film or a stretched film. The thickness of the non-absorbent substrate is not particularly limited, but is preferably 5 μm or more and 300 μm or less. In particular, when the obtained image formed product is used as a flexible packaging material, the thickness of the film is more preferably 50 μm or less.

  In the first step, an undercoat liquid is applied on the substrate. Although the coating method of the undercoat liquid on a base material is not specifically limited, For example, a roller coating method, a curtain coating method, a spray coating method, an inkjet method etc. can be mentioned preferably.

  Subsequently, the undercoat liquid applied on the substrate may be completely dried or semi-cured. Semi-curing is a state in which the undercoat liquid is thicker than before curing and has fluidity.

  For drying the undercoat liquid, for example, a non-contact heating type drying device such as a drying furnace or a hot air blower may be used, or a contact heating type drying device such as a hot plate or a heat roller is used. May be.

  The film thickness of the formed undercoat layer is not particularly limited, but the effect of the present invention is remarkably exhibited when the thickness is in the range of 0.2 μm to 10.0 μm. A preferable film thickness is 0.3 μm or more and 3.0 μm or less, and 1.0 μm or more and 3.0 μm or less. When the film thickness is 0.3 μm or more, it is possible to improve the adhesion while suppressing the occurrence of curling, and when the film thickness is 1.0 μm or more, the adhesion is further increased. Further, when the film thickness is 3.0 μm or less, it is possible to suppress curling and bleeding while maintaining adhesion. For example, when a film substrate is used, the film thickness of the recording layer is more preferably in the range of 0.3 μm or more and 2.0 μm or less in that the texture can be suitably prevented from changing.

  The film thickness of the undercoat layer can be measured by cross-sectional observation using an electron microscope (SEM, TEM, etc.) or by a light interference film thickness meter.

  In the second step, an inkjet ink containing a pigment, a pigment dispersing resin, a surfactant, an organic solvent, and water is applied in contact with the surface of the undercoat layer by an inkjet method. The ink used here is an ink contained in the recording liquid set of the present invention.

  When ink is applied in contact with the surface of the undercoat layer, a printer having an inkjet head can be used. Specifically, an image can be formed by ejecting ink as droplets from a nozzle of an ink jet head based on a digital signal and landing the ink on an undercoat layer provided on a substrate.

  The ink jet head may be either an on-demand system or a continuous system. As an inkjet head droplet discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method ( For example, any system such as a thermal ink jet type or a bubble jet (“Bubble Jet” is a registered trademark of Canon Inc.) may be used.

  In particular, an ink jet head (also referred to as a piezo ink jet head) using a piezoelectric element as the electro-mechanical conversion element used in the electro-mechanical conversion system is suitable.

  In view of the fact that high-speed printing is possible, it is preferable to use a single-pass inkjet image forming method. The effect of the present invention is particularly remarkable in the single-pass inkjet image forming method. Specifically, the ink on the undercoat layer spreads to an appropriate extent to fill the solid image, but aggregates at a speed sufficient to suppress bleeding in single-pass high-speed image formation. Is possible.

  In the single-pass inkjet image forming method, when a recording medium passes under one inkjet head unit, ink droplets are applied to all pixels where dots should be formed in one pass.

  As a means for achieving the single-pass inkjet image forming method, it is preferable to use a line head type inkjet head.

  The line head type ink jet head refers to an ink jet head having a length longer than the width of the printing range. As the line head type ink jet head, a single head having a width larger than the print range may be used, or a plurality of heads may be combined so as to be larger than the width of the print range.

  It is also preferable to arrange a plurality of heads side by side so that the nozzles are arranged in a staggered arrangement, thereby increasing the resolution of the heads as a whole.

  Then, the inkjet ink provided on the undercoat layer is dried. For drying the ink, for example, a non-contact heating type drying device such as a drying furnace or a hot air blower may be used, or a contact heating type drying device such as a hot plate or a heat roller may be used. Good.

  In addition to the first and second steps described above, the image forming method may include a third step of forming a resin layer in contact with the surface of the ink layer.

  The resin layer formed in the third step is a layer made of a resin bonded to the ink layer directly on the ink layer or via an adhesive layer containing an adhesive. By providing the resin layer, the strength and water resistance of the image can be increased, and the ink layer can be protected. In addition, when a resin layer is provided on an image formed using the recording liquid set of the present invention, since there is no surfactant film on the ink layer, the interlayer adhesion between the ink layer and the resin layer is improved. it is conceivable that. In addition, it is considered that hydrophilic resin contained in the undercoat layer diffuses into the ink layer and interacts with the resin layer, so that not only the strength of each layer of the image is high, but also an image with high interlayer adhesion can be obtained. It is done.

  The resin constituting the resin layer is not particularly limited as long as it can be bonded to the ink layer. Polyester film such as polyethylene terephthalate or polyethylene naphthalate, polyolefin film such as polyethylene or polypropylene, polyamide film such as nylon, polystyrene film , Polyvinyl alcohol film, ethylene vinyl acetate copolymer film, polyvinyl chloride film, polycarbonate film, polyacrylonitrile film and the like. These resins may contain additives as long as they do not affect other layers of the image.

  The method for forming the resin layer on the ink layer in the third step is not particularly limited. For example, a method of applying a resin solution or a molten resin directly on the ink layer by a method such as coating or a film-like resin (resin And a method of adhering the film) onto the ink layer via an adhesive layer composed of an adhesive.

  The thickness of the resin layer is not particularly limited because it varies depending on the application, etc., but is preferably 5 μm or more and 300 μm or less. Especially when the obtained image formed product is used as a flexible packaging material, the thickness of the film is 50 μm or less. More preferred.

  The adhesive that constitutes the adhesive layer between the ink layer and the resin layer is not particularly limited as long as both the ink layer and the resin layer can be bonded. Acrylic resin, urethane resin, urethane-modified polyester resin, polyester resin , Epoxy resin, ethylene-vinyl acetate copolymer resin (EVA), vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, natural rubber, SBR, NBR, synthetic rubber such as silicone rubber, and the like. Among them, urethane resin is preferable for increasing the interlayer strength between the adhesive layer and the ink layer because it can interact with the hydrophilic resin diffused from the undercoat layer to the ink layer. A particularly preferable adhesive is a two-component adhesive using a urethane resin.

  Specific examples of such adhesives include Takelac / Takenate series manufactured by Mitsui Chemicals, Dick Dry series manufactured by DIC Corporation, and TM series adhesives manufactured by Toyo Morton Corporation.

  Examples of the method for forming the resin layer via the adhesive layer include a dry lamination method, a non-solvent lamination method, an extrusion lamination method, a hot melt lamination method, and the like.

  In the dry lamination method, an adhesive is coated on the ink layer by a gravure roll method to provide an adhesive layer, and then a resin film is stacked thereon and bonded by dry lamination (dry lamination method).

  In the non-solvent lamination method, an adhesive layer that was previously heated on the ink layer to about room temperature to 120 ° C. was applied by a roll such as a roll coater that was heated to about room temperature to 120 ° C. to provide an adhesive layer. Immediately thereafter, a resin film is bonded to the surface.

  In the case of the extrusion laminating method, an organic solvent solution of an adhesive is applied onto the ink layer as a bonding aid (anchor coating agent) with a roll such as a gravure roll, and the solvent is dried and cured at room temperature to 140 ° C. And provide an adhesive layer. Thereafter, an image having a resin layer can be obtained by laminating a resin melted by an extruder. The resin to be melted is preferably a polyolefin resin such as a low density polyethylene resin, a linear low density polyethylene resin, or an ethylene-vinyl acetate copolymer resin.

  In the case of the hot melt lamination method, the surface of the ink layer of the image and the resin film are passed through a hot melt adhesive composed of a heat-melted ethylene-vinyl acetate copolymer (EVA), wax, tackifier, and the like. Laminate immediately.

  The thickness of the adhesive layer is not particularly limited as long as the thickness is sufficient to adhere the resin layer, but is preferably 1 μm or more and 10 μm or less, and more preferably 5 μm or less from the viewpoint of thinning the image formed product.

  The resin layer may be a single layer or a plurality of layers. When a plurality of resin layers are present, they may be the same or different.

  The thickness of each layer included in the image can be measured by cross-sectional observation with an electron microscope (SEM, TEM, etc.) or an optical interference film thickness meter.

  The recording liquid set and the inkjet image forming method of the present invention can be suitably used for various applications in which an image is formed on a substrate by an inkjet method. The application of the present invention is not particularly limited. A specific example of the application is preferably a packaging film.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

1. Undercoat liquid material <Hydrophobic resin>
E415: Chlorinated polyolefin (Super Clone E415, manufactured by Nippon Paper Industries Co., Ltd.)
E480: Chlorinated polyolefin (Supercron E480, manufactured by Nippon Paper Industries Co., Ltd.)

<Hydrophilic resin>
SF650: Urethane resin (Superflex 650, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
JK870: Urethane resin (Perthcol JK-870, manufactured by Meisei Chemical Co., Ltd.)
WEM: Acrylic urethane resin (WEM-505c, manufactured by Taisei Fine Chemical Co., Ltd.)

<Pigment flocculant>
Calcium acetate malonic acid

2. Ink material <Pigment>
PB15: 3: Pigment Blue 15: 3 (Fastogen Blue FGF, manufactured by DIC Corporation)

<Resin for pigment dispersion>
J819: Styrene acrylic copolymer (Johncrill 819, manufactured by BASF)

<Surfactant>
Surfactant A: Sorbitan monooleate (Rheodor SP-O10V, manufactured by Kao Corporation, HLB value: 4.3)
Surfactant B: Polyoxyethylene alkylamine (Amit 302, manufactured by Kao Corporation, HLB value: 5.1)
Surfactant C: Sorbitan monolaurate (Rheidol SP-L10, manufactured by Kao Corporation, HLB value: 8.6)
Surfactant D: Polyoxyethylene cetyl ether (Emulgen 220, manufactured by Kao Corporation, HLB value: 14.2)
Surfactant E: Polyoxyethylene sorbitan monolaurate (Rheodor TW-L120, manufactured by Kao Corporation, HLB value: 15.6)

<Water-soluble organic solvent>
EG: Ethylene glycol (SP value: 29.9 MPa ^(1/2) )
PG: Propylene glycol (SP value: 30.3 MPa ^(1/2) )
Gly: Glycerin (SP value: 33 MPa ^(1/2) )
dEGMBE: Diethylene glycol monobutyl ether (SP value: 20.5 MPa ^(1/2) )

3. Production of recording liquid set <Example 1>
(1) Preparation of undercoat liquid The components shown below were sequentially added with stirring, and then filtered through a 5.0 μm filter to obtain an undercoat liquid.
-E415 7.0 mass%
・ SF650 7.0 mass%
・ Calcium acetate 4.7% by mass
・ Ion-exchanged water The total amount is 100% by mass

(2) Preparation of ink Premixed mixture of joncrill 819 as pigment dispersing resin, 5.4% by mass of PB15: 3 as pigment, 20 parts by mass of ethylene glycol, and ion-exchanged water as the balance Then, it was dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads, the pigment content was 20% by mass, and the mass ratio of the pigment dispersing resin to the pigment was 0.3. A cyan pigment dispersion was obtained.

  Using the above cyan pigment dispersion, the pigment content in the ink is 5% by mass (pigment dispersing resin amount 1.5% by mass), the surfactant C is 1% by mass, and the ethylene glycol as the water-soluble organic solvent is 20%. It adjusted so that the mass% and the remainder might become ion-exchange water, and it mixed and stirred. After sufficiently stirring, the mixture was filtered through a 5.0 μm filter to obtain an ink.

<Examples 2 to 16>
As shown in Table 1 and Table 2, undercoat liquids were prepared in the same manner as in Example 1 except that the type and amount of each additive were changed. Further, inks were respectively prepared in the same manner as in Example 1 except that the types and addition amounts of the respective additives were changed as shown in Tables 1 and 2.

<Comparative Examples 1-9>
As shown in Table 3, undercoat liquids were prepared in the same manner as in Example 1 except that the types and addition amounts of the respective additives were changed. Furthermore, as shown in Table 3, inks were prepared in the same manner as in Example 1 except that the type and amount of each additive were changed.

4). Image formation 4-1. Formation of undercoat layer The following films were prepared as non-absorbent substrates, and each was used for image formation.
PET: Biaxially stretched polyester film (25 μm thick, E-5200 manufactured by Toyobo Co., Ltd.)
Ny: Nylon film (thickness 15 μm, emblem ON manufactured by Unitika Ltd.)
OPP: Biaxially stretched polypropylene film (FOS # 60 manufactured by Futamura Chemical Co., Ltd.)

On the prepared non-absorbent substrate, the undercoat liquid prepared in Examples and Comparative Examples was applied using a bar coater # 5 so that the solid content was 1.6 g / m ² . Subsequently, the applied undercoat solution was dried at 70 ° C. for 5 minutes to form an undercoat layer.

4-2. Formation of Ink Layer High-speed image formation was performed by a single-pass method (one-pass printing) using the non-absorbent substrate on which the undercoat layer was formed as a recording medium and using the inks prepared in Examples and Comparative Examples.

  A stage-moving inkjet printer equipped with a drop-on-demand piezo inkjet head (nozzle number 1024 (512 × 2 rows), nozzle spacing 70.5 μm (141 μm × 2 rows)) was used. On the recording medium, the character (3 point, 4 point, 5 point character) formed by not discharging the ink in the solid image under the condition of the ink droplet volume of 32 pl and the recording density of 360 × 360 dpi, Printing was performed by one scan at a scanning speed of either 100 m / min or 50 m / min. Similarly, a solid image was printed by one scan at a linear velocity of 50 m / min under the condition of a recording density of 360 × 360 dpi. In this specification, dpi represents the number of dots per 2.54 cm. The ink droplet volume was controlled by adjusting the ejection voltage for each recording ink. In addition, the environment during ink jet printing was room temperature of 25 ° C., and the temperature of the recording medium was similarly 25 ° C.

4-3. Formation of Resin Layer An adhesive (Takelac A-969V / Takenate A-5 = 3/1) was applied onto the recording medium on which an image was formed so that the applied film thickness was 1.6 g / m ² . An unstretched propylene (CPP) film was bonded onto the applied adhesive to form a resin layer, whereby an image formed product was obtained.

5. Evaluation method <Peel strength>
The image formed product obtained above was allowed to stand in a constant temperature bath at 40 ° C. for 72 hours for aging. After the image-formed product was air-cooled to room temperature, it was cut into a tape having a width of 15 mm, a T-type peel test was performed, and the peel strength was measured (tensile speed: 300 mm / s, apparatus: Tensilon universal material testing machine). Based on the peel strength, the peel strength was evaluated according to the following evaluation criteria.
◎: Peel strength is over 1.5N ○: Peel strength is over 1N, 1.5N or less △: Peel strength is 0.5 or more, 1N or less ×: Peel strength is less than 0.5

<Image quality>
Using the OPP on which the undercoat layer was formed as a recording medium, the character size recognizable at a distance of 30 cm was visually confirmed for the extracted characters formed in the above method. Furthermore, the presence or absence of white spots on the solid surface was visually observed, and the image quality was evaluated according to the following evaluation criteria.
◎: All 3-5 point characters are recognizable, and there is no omission on the solid surface. ○: All 3-5 point characters are recognizable, but there are omissions on the solid surface. △: 4-5 points. Characters are recognizable, but there are gaps on the solid surface. X: All 3 to 5 point characters cannot be recognized.

<Discharge stability>
The ink discharge stability was evaluated using the same printer as described above using the OPP with the undercoat layer formed as a recording medium.
A solid image of 35 × 35 mm was formed in one scan on a recording medium under the condition of a stage scanning speed of 100 m / min. After the inkjet head was stopped for 3 minutes at a position 5 mm apart from the above image, solid images were similarly formed adjacent to each other, and two solid images adjacent to each other at intervals of 5 mm were formed.
Using the square image formed as described above, the presence or absence of disturbance in the edge of the image due to abnormal ejection of ink was confirmed, and ejection stability was evaluated according to the following criteria.
○: At the head stop time of 3 minutes, no disturbance was observed at the edge of the image, and a good print image was obtained. ×: At the head stop time of 3 minutes, disturbance was observed at the edge of the image.

  All the evaluation results are shown in Tables 4 and 5.

From the results of Examples 1 to 16 in Table 4 above, an undercoat liquid containing a hydrophobic resin, a hydrophilic resin, a pigment flocculant, water, a pigment, a pigment dispersing resin, and an HLB value are a surfactant 5 or more and 15 or less, SP value and a water-soluble organic solvent is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less, and containing a water resin components present in the ink When image formation was performed using a recording liquid set containing an ink having a total amount of 0.3 to 1.0 by mass ratio to the pigment, the non-absorbing substrate was a highly polar resin (PET, Ny). Even with a low polarity resin (OPP), it was possible to form a high-quality image with high peel strength by a high-speed printing method. Further, it can be seen that the ink ejection stability is also high. Particularly in Examples 1 to 4, in which the pigment flocculant contained in the undercoat liquid is a polyvalent metal salt, the image quality was very high. Similar excellent results were also obtained in Example 5 in which the water-soluble organic solvent was changed from ethylene glycol to propylene glycol.

  In Examples 1 to 8, in which the ratio of the hydrophilic resin to the total mass of the hydrophobic resin and the hydrophilic resin in the undercoat liquid is in the range of 20% by mass or more and 70% by mass or less, the non-absorbent substrate is highly polar. It can be seen that an image-formed product with high peel strength (that is, high interlayer adhesion) can be obtained with PET or nylon as a resin, or OPP as a low-polarity resin. In particular, in Examples 1 to 6 and 8 in which the ratio of the hydrophilic resin is in the range of 20% by mass or more and 50% by mass or less, the peel strength was very high for all of PET, nylon and OPP. On the other hand, in Example 9 in which the ratio of the hydrophilic resin exceeds 70% by mass, since the ratio of the hydrophilic resin is large, the adhesion with the OPP which is a low polarity resin is slightly decreased, and the peel strength is slightly decreased. In Example 10 in which the ratio of the hydrophilic resin was less than 20% by mass, the peel strength was slightly reduced when the non-absorbent substrate was PET or nylon, which is a highly polar resin.

  In Examples 11 and 12 in which the content of the water-soluble organic solvent is in the range of 10% by mass or more and 40% by mass or less, peeling is performed as compared with Example 13 in which the content of the water-soluble organic solvent is less than 10% by mass. The image quality was high as compared with Example 14, which had high strength and the content of the water-soluble organic solvent exceeded 40% by mass.

  In Examples 15 and 16 in which the HLB value of the surfactant contained in the ink was in the range of 5 to 15, the peel strength, image quality, and ejection stability were high regardless of the type of surfactant. On the other hand, in the image of Comparative Example 1 in which the HLB value of the surfactant exceeded 15, bleeding and solid loss occurred during high-speed printing, and the image quality was poor. Further, in Comparative Example 2 where the HLB value of the surfactant was less than 5, the surfactant did not dissolve in the ink, and a uniform ink could not be obtained.

In Comparative Example 3 in which the SP value of the water-soluble organic solvent contained in the ink is less than 25 MPa ^(1/2) , the peel strength is slightly reduced and the image quality is poor compared to Example 14 except for the other points. It was. On the other hand, in Comparative Example 4 in which the SP value of the water-soluble organic solvent is more than 32 MPa ^(1/2) , the image quality was better than that of Example 14 in other respects. Declined.

  Furthermore, in Comparative Example 5 in which the hydrophobic resin is not included in the undercoat liquid, the peel strength is low when the non-absorbent substrate is OPP which is a low-polarity resin, and the hydrophilic resin is not included in the undercoat liquid. In Comparative Example 6, the peel strength was low when the non-absorbent substrate was PET or nylon, which is a highly polar resin.

  In Comparative Example 7 in which the amount of the pigment dispersing resin contained in the ink exceeds 1% by mass with respect to the pigment, the ejection stability was poor. This is presumably because the ink was thickened by an excessive amount of pigment dispersing resin. On the other hand, in Comparative Example 8 in which the amount of the pigment dispersing resin contained in the ink was less than 0.3 by mass ratio to the pigment, the dispersion stability of the pigment was low, and a uniform ink could not be obtained.

  Further, in Comparative Example 9 in which the undercoat liquid did not contain the pigment flocculant, the image quality was deteriorated because the pigment cohesiveness in the ink layer was low.

  According to the present invention, high-quality images can be formed at high speed on various non-water-absorbing substrates such as OPP, PET, and nylon, and the adhesiveness to the non-water-absorbing substrate is high. When processed, an image formed article having excellent laminating properties (that is, both the adhesion between the image and the substrate and the adhesion between the image and the other layer provided thereon) are excellent. A recording liquid set that can be obtained can be provided. For this reason, the present invention is expected to contribute to the widespread use of the inkjet method in this field by expanding the compatible range of image formation using water-based ink by the inkjet method.

Claims (10)

A recording liquid set including an aqueous undercoat liquid and an aqueous inkjet ink,
The undercoat liquid contains a hydrophobic resin, a hydrophilic resin, a pigment flocculant, and water,
The inkjet ink contains a pigment, a pigment dispersing resin, a surfactant, a water-soluble organic solvent, and water,
In the inkjet ink,
The HLB value of the surfactant is 5 or more and 15 or less,
The SP value of the water-soluble organic solvent is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less,
A recording liquid set, wherein a mass ratio of the pigment dispersing resin to the pigment is 0.3 or more and 1.0 or less.   The recording liquid set according to claim 1, wherein a content of the water-soluble organic solvent in the inkjet ink is 10% by mass or more and 40% by mass or less.   The recording liquid set according to claim 1, wherein in the undercoat liquid, a ratio of the hydrophilic resin to a total mass of the hydrophobic resin and the hydrophilic resin is 20% by mass or more and 70% by mass or less.   The recording liquid set according to claim 1, wherein the pigment flocculant is a polyvalent metal salt. An undercoat liquid containing a hydrophobic resin, a hydrophilic resin, a pigment flocculant, and water is applied on a non-absorbent substrate to form an undercoat layer.
An ink layer is formed by applying an ink jet ink containing a pigment, a pigment dispersing resin, a surfactant, a water-soluble organic solvent, and water by an ink jet method in contact with the surface of the undercoat layer. An image forming method comprising:
In the inkjet ink,
The HLB value of the surfactant is 5 or more and 15 or less,
The SP value of the water-soluble organic solvent is ^{25 MPa (1/2)} or ^{32 MPa (1/2)} or less,
The image forming method, wherein a mass ratio of the pigment dispersing resin to the pigment is 0.3 or more and 1.0 or less.   The image forming method according to claim 5, further comprising forming a resin layer in contact with a surface of the ink layer.   The image forming method according to claim 5 or 6, wherein a content of the water-soluble organic solvent in the inkjet ink is 10% by mass or more and 40% by mass or less.   The said undercoat liquid WHEREIN: The ratio of the said hydrophilic resin with respect to the total mass of the said hydrophobic resin and the said hydrophilic resin is 20 to 70 mass%, It is any one of Claims 5-7. Image forming method.   The image forming method according to claim 5, wherein the pigment flocculant is a polyvalent metal salt.   The image forming method according to claim 5, wherein the inkjet ink is applied by a single pass method.