JP6677574B2 - Aqueous inkjet ink and inkjet printing method using the ink - Google Patents

Description

  The present invention relates to an aqueous inkjet ink used for printing on a substrate to be printed having low surface permeability of an ink not subjected to a surface treatment by an inkjet printing method, and an inkjet printing method using the ink.

  2. Description of the Related Art In recent years, various printings using an inkjet printing method have been performed not only for office use and home use but also for a wide range of uses. For example, for industrial applications, sign displays include outdoor advertisements, facility signs, displays, POP advertisements, traffic advertisements, etc., created by inkjet printing. Many of these sign displays are produced by printing on a large-sized substrate to be printed by an ink jet recording apparatus. However, most of the inks used at that time are solvent-based inks (Patent Document 1). In addition, the substrate to be used for image formation is often subjected to a surface treatment so as to be easily printed with the ink for inkjet, but the substrate to be subjected to the surface treatment is naturally expensive. . When a substrate to be printed having been subjected to a surface treatment suitable for an aqueous ink is used, an aqueous ink may be used. On the other hand, when a substrate to be printed that has not been subjected to a surface treatment is used, a solvent-based ink containing, as a main component, a solvent having a high dissolving power for the substrate to be printed is used as a solvent component in the ink. Ink jet printing is performed by making it easy for the ink to penetrate into an unprinted base material. For this reason, when inkjet printing is performed on a substrate to be printed that has not been subjected to a surface treatment, there are environmental and safety problems due to the solvent-based ink used. It is necessary to provide a duct or the like. For this reason, in this case, there is a problem that the provision of a device such as an exhaust duct increases the scale and also increases the cost.

  In order to solve the above-mentioned problems, there has been a long-awaited demand for an aqueous ink that can be printed on a substrate to be printed that has not been surface-treated by an inkjet printing method. In particular, when a printing substrate containing a plasticizer such as polyvinyl chloride is used, the plasticizer in the substrate is raised on the surface, so when printing with an aqueous ink, the ink repels on the substrate surface, It was difficult to obtain the desired image quality. Patent Literatures 2 and 3 propose water-based inks as means for solving these problems. However, the technique described in Patent Document 2 uses a special pigment derivative, and some of the pigments in the ink are effective and some are not, and are not general-purpose techniques. Further, in the technique described in Patent Document 3, two kinds of organic solvents having different boiling points are essential, so that the compatibility with the resin component in the ink is limited, and there is a possibility that the stability as an inkjet ink may be impaired. .

JP 2014-055263 A JP 2014-214160 A JP 2014-205770 A

  Accordingly, an object of the present invention is to provide a substrate to be printed having low ink permeability without surface treatment, in particular, a vinyl chloride substrate without surface treatment, or a polypropylene-based substrate without surface treatment. Alternatively, a water-based inkjet that can perform high-quality color printing by an inkjet printing method on a polyethylene-based substrate that has not been subjected to a surface treatment, and has good adhesion of a formed ink image to a substrate to be printed. It is to provide an ink for use. Another object of the present invention is to provide a high-quality color print image on a substrate to be printed, which has a low permeable property of the ink that has not been subjected to a surface treatment, by an inkjet printing method using an aqueous inkjet ink, An object of the present invention is to provide an ink jet printing method in which an obtained image has high adhesion to a substrate to be printed.

  The above object is achieved by the present invention described below. That is, the present invention relates to [1] an aqueous inkjet ink for a substrate to be printed, which has low permeability of an ink not subjected to a surface treatment, wherein at least a pigment, a pigment dispersant, and an alkylene group have at least one carbon atom. A water-soluble solvent containing 2 to 12 alkylene glycol alkyl ethers having an alkyl group having 1 to 12 carbon atoms, water and an alkali, and further containing a methacrylic resin as a binder resin, wherein the methacrylic resin Is a block copolymer comprising a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component, wherein the hydrophobic polymer block comprises at least benzyl methacrylate (BzMA ), Isobutyl methacrylate (IBMA), t-butylcyclohexane A monomer containing at least one selected from the group consisting of silmethacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), and dicyclopentanyl methacrylate (DCPMA); Provided is an aqueous inkjet ink, wherein the acid value of the polymer block is 50 to 250 mgKOH / g.

  Since the specific methacrylic resin constituting the present invention is an aggregate (mixture) of various polymer molecules having different molecular weights, it is impossible to directly specify the substance as a substance by its structure or properties or Since it is almost impractical, the monomer used as the raw material was specified by a limited process (production method).

The present invention also provides the following aqueous inkjet ink as a preferred embodiment of the aqueous inkjet ink of the present invention.
[2] The aqueous inkjet ink according to [1], wherein the alkylene glycol alkyl ether has a boiling point of 200 ° C. or more and 250 ° C. or less and a content of 3 to 30% by mass based on the total amount of the ink.
[3] The above-mentioned water-soluble solvent contains at least one selected from the group consisting of diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol dimethyl ether and tripropylene glycol monomethyl ether. The aqueous inkjet ink according to [1] or [2].
[4] The aqueous inkjet ink according to any one of [1] to [3], wherein the content of the methacrylic resin is in a range of 1 to 20% by mass as a solid content with respect to the total amount of the ink.
[5] The above-mentioned [1] to [4], wherein the pigment dispersant is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component. The aqueous inkjet ink according to any one of the above.
[6] The aqueous inkjet ink according to any one of [1] to [5], further comprising a surfactant.
[7] The aqueous inkjet ink according to the above [6], wherein the surfactant is a fluorine-based surfactant.
[8] The aqueous inkjet according to any one of [1] to [7], wherein the substrate to be printed is at least one selected from a polyvinyl chloride-based substrate, a polypropylene-based substrate, and a polyethylene-based substrate. For ink.

  The present invention also provides, as another embodiment, [9] the aqueous solution according to any one of the above [1] to [8], on a surface of a substrate to be printed having low permeability of the ink not subjected to the surface treatment. The present invention provides an ink jet printing method, wherein when printing is performed by an ink jet recording method using an ink for ink jet, the surface temperature of the substrate to be printed is heated to 40 to 80 ° C.

  In a preferred embodiment of the ink jet printing method of the present invention, [10] the substrate to be printed is at least one selected from a polyvinyl chloride-based substrate, a polypropylene-based substrate, and a polyethylene-based substrate. ] The inkjet printing method described in [1].

  According to the present invention, a substrate to be printed having low ink permeability without surface treatment, such as a vinyl chloride substrate without surface treatment, or a polypropylene-based substrate without surface treatment, or Aqueous printing that enables high-quality color printing to be performed on an untreated polyethylene-based substrate by the inkjet printing method, and that the formed ink image has good adhesion to the substrate to be printed. An inkjet ink is provided. Further, according to the present invention, a high-quality color print image can be produced on a substrate to be printed, which has a low permeable property of the ink that has not been subjected to a surface treatment, by an inkjet printing method using an aqueous inkjet ink, An ink jet printing method is provided in which the obtained image has high adhesion to a substrate to be printed.

  Specifically, in the configuration of the aqueous inkjet ink obtained by dispersing a pigment with a pigment dispersant, the present invention has a block copolymer having a structure composed of a unique hydrophobic polymer block and a unique hydrophilic polymer block. Methacrylic resin is contained as a binder resin, and furthermore, a humectant for the ink, and a water-soluble solvent that can also function as a leveling agent and a film-forming aid when attached to a film, to achieve the above object. To achieve. Further, in the present invention, when performing ink-jet printing, a substrate to be printed having low permeability of the ink not subjected to surface treatment is used, and the surface temperature is heated to 40 to 80 ° C. By forming an inkjet printed image on the surface of the material with the aqueous inkjet ink having the above configuration, high image quality with extremely excellent adhesion even to a substrate surface that is difficult to print with a normal aqueous inkjet ink. The remarkable effect of the present invention is that the color print image can be displayed. In addition, since the inkjet ink provided in the present invention is a water-based ink, it is environmentally friendly and is excellent in safety.Furthermore, as a measure against a solvent in the ink used for image formation, large equipment such as an exhaust duct is required. Since there is no need to provide them, there is also a practical advantage that color printing can be performed by the inkjet recording method at a low cost.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention. The aqueous inkjet ink of the present invention has a low printability of the ink that has not been subjected to a surface treatment, such as a polyvinyl chloride-based substrate, a polypropylene-based substrate, and a polyethylene-based substrate. It is also suitably used when performing inkjet printing. The aqueous inkjet ink of the present invention is a water-based ink containing at least a pigment, a pigment dispersant, an alkylene glycol having an alkylene group having 2 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. Characterized by comprising a basic solvent, water and an alkali, and a specific methacrylic resin as a binder resin. The methacrylic resin as an essential component of the aqueous inkjet ink of the present invention is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component. And the hydrophobic polymer block is at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), and dicyclopentanyl methacrylate (DCPMA) And a monomer comprising at least one selected from the group consisting of: wherein the hydrophilic polymer block has an acid value of 50 to 250 mgKOH / g. That. Hereinafter, the aqueous inkjet ink of the present invention will be described in detail.

[Substrate to be printed]
Generally, when inkjet printing is performed on a film having low ink permeability, an inkjet-specific film that has been subjected to processing such as providing an image receiving layer on the printing surface of the film is used. Further, in the case of a polypropylene film other than ink jet printing, for example, when performing gravure printing, there is a film in which a corona treatment or the like is performed on a printing surface to make it easy for ink to be applied. Further, in the case of a polyvinyl chloride substrate, the plasticizer floats on the surface, and when performing inkjet printing with an aqueous ink, the ink is repelled on the surface of the substrate, and a good image cannot be obtained. For this reason, a solvent-based ink is usually used. On the other hand, in the aqueous inkjet ink of the present invention, the above-described treatment is not performed, the ink has low permeability, a polyvinyl chloride-based substrate, a polypropylene-based substrate, a polyethylene-based substrate, and the like. Good ink jet printing is also possible.

[Components of aqueous inkjet ink]
<Pigment>
As the pigment that can be used in the present invention, any of organic pigments and inorganic pigments used in conventionally known inkjet inks can be used, and there is no particular limitation. For example, organic pigments include phthalocyanine, azo, azomethine azo, azomethine, anthraquinone, perinone perylene, indigo / thioindigo, dioxazine, quinacridone, isoindoline, isoindolinone, Examples include chromatic color pigments such as ketopyrrolopyrrole-based, quinophthalone-based, and induslene-based pigments, and carbon black pigments such as furnace black, lamp black, acetylene black, and channel black, and any of them can be used. Inorganic pigments include extender pigments, titanium oxide pigments, iron oxide pigments, and spinel pigments.

  In the present invention, it is desirable to select and use the type of pigment, the particle diameter, and the type of treatment depending on the purpose. In particular, organic fine particle pigments are desirable unless the colored material requires hiding power. Further, when high definition and transparency are desired, it is desirable to use a pigment finely divided by wet pulverization such as salt milling or dry pulverization. In that case, taking into account nozzle clogging during printing, the pigment having a large particle size exceeding 1.0 μm is removed, and the average particle size of the organic pigment is 0.2 μm or less, and the average particle size of the inorganic pigment is 0.4 μm. It is desirable to use the following.

  More specifically, the above-mentioned pigments are exemplified by a color index (CI) number. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 97, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 175, 180, 181, 185, 191; I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, 71, 73, C.I. I. Pigment Red 4, 5, 9, 23, 48, 49, 52, 53, 57, 97, 112, 122, 123, 144, 146, 147, 149, 150, 166, 168, 170, 176, 177, 180, 184, 185, 192, 202, 207, 214, 215, 216, 217, 220, 221, 223, 224, 226, 227, 228, 238, 240, 242, 254, 255, 264, 269, 272, C.I. I. Pigment Violet 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64, C.I. I. Pigment Green 7, 36, C.I. I. Pigment Black 7, C.I. I. Pigment White 6 and the like. These pigments may be used alone or as a mixture of two or more. Mixing methods include mixing with powder pigment, mixing with paste pigment, and mixing with pigmentation. Synthesis of a solid solution.

  Among the above, as the pigment suitable for the aqueous inkjet ink of the present invention, yellow is preferably C.I. I. Pigment Yellow 74, 83, 109, 128, 139, 151, 154, 155, 180, 181, 185, and red are C.I. I. Pigment Red 122, 170, 176, 177, 185, 269, C.I. I. Pigment Violet 19, 23, blue color is C.I. I. Pigment Blue 15: 3, 15: 4, 15: 6 Black is C.I. I. Pigment Black 7 and white are C.I. I. Pigment White 6.

  The content of the pigment used in the aqueous inkjet ink of the present invention can be used in the range of 0.1 to 25% by mass based on the total amount of the ink. -20% by mass.

<Water-soluble solvent containing specific alkylene glycol alkyl ether>
In the case of an aqueous inkjet ink, if only water is used as the solvent component, the ink dries and causes nozzle clogging of the head. For this reason, addition of a water-soluble high boiling point solvent as a humectant has been performed. Although the aqueous inkjet ink of the present invention contains a water-soluble solvent, its use is for a substrate to be printed on which the ink not subjected to surface treatment has low permeability, so that the inkjet ink of the present invention is used. The water-soluble solvent constituting the ink for use not only functions as a humectant for the ink, but also has good wettability to the substrate film, and preferably can function as a leveling agent for the surface of the substrate to be printed. Is preferably one that can also function as a film-forming aid that enhances the film-forming properties of the binder resin contained in the ink.

  The present inventors have conducted intensive studies based on the above recognition, and as a result, when an alkylene glycol alkyl ether such as diethylene glycol monobutyl ether is used in an aqueous inkjet ink, the above functions can be all exhibited, and a water-soluble solvent Was found to be useful. That is, an alkylene glycol alkyl ether such as diethylene glycol monobutyl ether functions not only as a humectant for the ink but also as a leveling agent because of its good wettability to the film. Furthermore, since it has a certain degree of dissolving power, it has been found that, for example, by slightly dissolving the polyvinyl chloride surface with respect to a polyvinyl chloride-based printing substrate, it contributes to leveling and adhesion of the ink. Furthermore, as described below, it has been found that it can also function as a film-forming aid of a binder resin constituting the aqueous inkjet ink of the present invention. The methacrylic resin used as a binder resin in the present invention has a block structure consisting of a hydrophobic polymer block having a methacrylate monomer as a forming component and a hydrophilic polymer block having a methacrylate monomer containing methacrylic acid as a forming component. The hydrophobic polymer blocks are insoluble in water, and thus are particles. In order to function as a good binder resin, it is necessary that these particle portions become a film, and for this purpose, a film forming property of the binder resin is enhanced, that is, a water-soluble material capable of exhibiting a function as a film forming aid. It is preferred that a neutral solvent be contained in the ink.

  The present inventors have conducted intensive studies in consideration of the above-described moisturizing properties of the ink, the leveling property for the substrate to be printed, the solubility in the base material, and the improvement of the film forming property of the binder resin. It has been found that it is effective to use an alkylene glycol alkyl ether having an alkylene group having 2 to 12 carbon atoms and an alkyl group having 1 to 12 carbon atoms as a water-soluble solvent constituting the ink. Was. More specifically, for example, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol methyl ethyl ether, triethylene glycol Monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl Ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, and the like. More preferably, the boiling point is 200 ° C. or higher and 250 ° C. or lower, for example, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol dimethyl ether, tripropylene glycol monomethyl ether, and the like. .

  The content of the above-mentioned specific water-soluble solvent constituting the aqueous inkjet ink of the present invention is preferably 3 to 30% by mass based on the total amount of the ink. More preferably, it is about 5 to 25% by mass based on the total amount of the ink. If the amount is less than 3% by mass, the ink tends to dry, and the effect of imparting leveling to the base film also deteriorates. On the other hand, if the content is more than 30% by mass, the viscosity of the ink tends to be high, and the ejection property of the ink tends to deteriorate, and further, the stability as the ink tends to deteriorate. Further, in some cases, the binder resin in the ink may precipitate or the pigment may aggregate, which is not preferable. Further, if the content is too large, the water-soluble solvent will remain in the film of the printed image, and there is a risk of blocking of the image film, and the physical properties of the image such as water resistance and abrasion resistance are inferior. It is not preferable from this point, because there is a possibility of this.

<Water>
The aqueous inkjet ink of the present invention contains water as an essential component. Water is used for dissolving and dispersing other components and for imparting fluidity to the ink during inkjet printing. It is preferable to use ion-exchanged water, distilled water, purified water, or the like, from the viewpoint that water used does not contain impurities such as ionic components. The content of water is preferably about 30 to 90% by mass based on the total amount of the ink.

<Methacrylic resin as binder resin>
The aqueous inkjet ink of the present invention has, as essential components, a hydrophobic polymer block having a methacrylate monomer as a component and a hydrophilic polymer block having a methacrylate monomer containing methacrylic acid as a component. A methacrylic resin as a block copolymer is contained as a binder component. Further, in the above block copolymer, the hydrophobic polymer block has at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), dicyclopentane And a monomer containing at least one selected from the group consisting of nil methacrylate (DCPMA), and the acid value of the hydrophilic polymer block is 50 to 250 mgKOH / g.

  The inkjet ink of the present invention contains the methacrylic resin, which is the above-mentioned specific block copolymer, as a binder component. Good adhesion to the printing substrate. Further, it is considered that the methacrylic resin constituting the ink of the present invention is a block copolymer having a structure composed of a specific hydrophobic polymer block and a specific hydrophilic polymer block. For example, by including such a block copolymer as a binder component, the stability of various physical properties such as ink ejection property, viscosity, and particle diameter is remarkably improved as compared with a case where other binder resin is included. I do.

  The hydrophobic polymer block constituting the specific block copolymer is a portion of a water-insoluble hydrophobic block chain composed of a methacrylate monomer. Since the water-insoluble hydrophobic portion is present in the methacrylic resin contained as a binder component, the ink image formed by the ink containing the same has improved water resistance, abrasion resistance, and film forming property. And a strong film is formed, and as a result, the durability of the printed matter can be improved.

  In the present invention, as a component for forming the hydrophobic polymer block, a group consisting of water-insoluble benzyl methacrylate, isobutyl methacrylate, t-butylcyclohexyl methacrylate, dicyclopentenyloxyethyl methacrylate, and dicyclopentanyl methacrylate (these methacrylate groups) Is referred to as a monomer A). As a result of investigations by the present inventors, the formation of a methacrylic resin to be contained as a binder component, by including such a monomer A, is a substrate to be printed without surface treatment, for example, polyvinyl chloride When an ink image is formed on a polyolefin-based substrate such as a polypropylene-based substrate or a polyethylene-based substrate, it has been found that the formed ink image functions to enhance the adhesion to the substrate. .

  In the methacrylic resin used in the present invention, a monomer containing a monomer A selected from the above-described specific methacrylate group is used as a component for forming the hydrophobic block, and another methacrylate may be used if necessary. It may be copolymerized. As the other methacrylate used at this time, a conventionally known methacrylate is used, and is not particularly limited as long as it is the following monomer. That is, since the hydrophilic block constituting the unique block copolymer used in the present invention contains a methacrylate-based monomer containing at least methacrylic acid as a forming component, there is no particular problem if it does not react with the carboxylic acid of methacrylic acid. Absent. The amount of the monomer A in the component for forming the hydrophobic block is not particularly limited, but is preferably 50% by mass or more.

  The molecular weight of the hydrophobic block constituting the methacrylic resin used in the present invention is not particularly limited, but preferably the number average molecular weight is preferably 5,000 to 70,000. When the number average molecular weight is 5,000 or more, the performance as a film formed of such a methacrylic resin having a hydrophobic block chain, such as adhesion to a substrate, is improved. Further, by setting the number average molecular weight to 70,000 or less, the viscosity as the ink is optimized, and the ejection property of the ink is improved. The number average molecular weight of the hydrophobic block constituting the methacrylic resin used in the present invention is more preferably 7000 to 50,000.

  Next, the hydrophilic polymer block constituting the methacrylic resin used in the present invention will be described. The hydrophilic polymer block is a hydrophilic polymer block containing a methacrylate monomer containing methacrylic acid as a component, and has an acid value of 50 to 250 mgKOH / g. The carboxylic acid derived from methacrylic acid is neutralized and ionized by the alkali contained in the ink, and the hydrophilic block chain is dissolved in water. The hydrophilic polymer block may be formed entirely of methacrylic acid, but may be copolymerized with a methacrylate monomer as long as the acid value falls within the above-mentioned range. The methacrylate is not particularly limited, and it is preferable to use a methacrylate that does not react with a carboxylic acid derived from methacrylic acid used for forming a hydrophilic block chain.

  The molecular weight of the hydrophilic polymer block constituting the methacrylic resin used in the present invention is defined as a value obtained by subtracting the number average molecular weight of the hydrophobic polymer block from the number average molecular weight of the entire block copolymer. There is no limitation. Preferably, it is good to be 1000 or more. If the number average molecular weight calculated as described above is too small, the solubility in water tends to be insufficient, and the methacrylic resin added as a binder resin component may precipitate or aggregate in the ink. It is not preferable. On the other hand, if the molecular weight is too large, the viscosity of the ink becomes high, and the ejection properties deteriorate. Therefore, the number average molecular weight of the hydrophilic polymer block constituting the methacrylic resin used in the present invention is preferably from 1,000 to 20,000, more preferably from 3,000 to 15,000.

  The method for obtaining the methacrylic resin having the above-mentioned configuration used in the present invention is not particularly limited. However, it is preferable to use living radical polymerization since ordinary radical polymerization cannot easily obtain a polymer having a block structure that is precisely designed as described above. Any method may be used as long as it is a living radical polymerization, such as NMP method using nitroxide, ATRP method using redox of metal complex, RAFT method using dithiocarboxylic acid ester, method using cobalt catalyst, tellurium Examples include a TERP method using a compound, iodine transfer polymerization using iodine, and an RTCP method using an iodide as an initiator and an organic compound as a catalyst. Among these, it is preferable to synthesize by the RTCP method.

  Manufacturing conditions such as these polymerization steps and post-treatment of the obtained polymer solution are not particularly limited. Solution polymerization performed in any conventional organic solvent is preferred. In particular, considering the subsequent preparation of the ink, which is an essential component in the aqueous inkjet ink of the present invention, it also functions as the above-described film-forming auxiliary, the specific alkylene glycol alkyl defined in the present invention. Preferably, ether is used as the polymerization solvent. In this case, the resin may be taken out of the obtained resin solution or may be used as it is.

  The content of the methacrylic resin as a binder component constituting the aqueous inkjet ink of the present invention can be used at a solid content of 1 to 20% by mass based on the total amount of the ink. A more preferable content range is 2 to 15% by mass based on the total amount of the ink. When the amount is less than 1% by mass, the function as a binder resin is not sufficiently exhibited, and the adhesion of the ink to the substrate to be printed tends to be insufficient. When the amount is more than 20% by mass, the viscosity of the ink becomes high. This is not preferable because the ink ejection property may be impaired.

<Pigment dispersant>
As the pigment dispersant constituting the aqueous inkjet ink of the invention, conventionally known pigment dispersants can be used. A low molecular weight dispersant such as a surfactant may be used, or a random copolymer, a block copolymer, a graft copolymer, a gradient copolymer, or a star polymer such as an acrylic, styrene, methacryl, ester, amide, or polyether. And at least one polymer-type dispersant having a higher-order structure such as dendrimer. More preferably, it comprises a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component, and further a block copolymer having a structure defined in the present invention. Since the compatibility between the dispersant and the binder resin is not hindered, higher dispersibility and storage stability can be obtained. The amount of the dispersant with respect to the pigment is not particularly limited. For example, 5 to 100 parts can be used for 100 parts of the pigment on a mass basis.

<Alkali>
The aqueous inkjet ink of the present invention contains an alkali to neutralize the acidic group of the methacrylic resin or the pigment dispersant and dissolve in water, or to adjust the pH of the ink. As the alkali, the followings can be used. For example, ammonia; aliphatic tertiary amines such as mono-, di-, or tri-methylamine, mono-, di-, or tri-ethylamine; mono-, di-, or tri-ethanolamine, mono- Alcohol amines such as-, di- or tri-propanolamine, methylethanolamine, dimethylethanolamine, methylisopropylamine; heterocyclic amines such as piperidine, morpholine and N-methylmorpholine; lithium hydroxide, sodium hydroxide, Alkali metal hydroxides such as potassium hydroxide can be used and are not particularly limited. The content of the alkali is preferably added in such an amount as to neutralize a part or all of the acidic groups of the methacrylic resin or the dispersant. The preferred pH range of the aqueous inkjet ink of the present invention is from 7.0 to 10.0, more preferably from 7.5 to 9.5, and it can be used in such an amount that the pH of the ink falls within such a range. Is not particularly limited. If the pH of the ink is lower than 7.0, the methacrylic resin contained in the aqueous inkjet ink of the present invention may be precipitated, and further, the pigment may be aggregated. On the other hand, if the pH of the ink is higher than 10.0, the ink becomes strongly alkaline and is difficult to handle and dangerous.

<Other components>
As described above, the aqueous inkjet ink of the present invention contains, as essential components, a pigment, a pigment dispersant, a water-soluble solvent containing an alkylene glycol alkyl ether defined in the present invention such as diethylene glycol monobutyl ether, water, an alkali, and the above. Although it contains a methacrylic resin having a specific structure, as described below, a preferred embodiment may further contain a surfactant as an additional component. Furthermore, other water-soluble organic solvents and other additives can be blended according to the purpose.

(Surfactant)
The aqueous inkjet ink of the invention may further contain a surfactant for the purpose of, for example, maintaining the surface tension at a predetermined value. At that time, the surface tension of the preferred ink is 15 to 45 mN / m, and the particularly preferred surface tension is 20 to 40 mN / m. Examples of the surfactant suitably used in the present invention include silicone-based, acetylene glycol-based, fluorine-based, alkylene oxide-based, and hydrocarbon-based surfactants. Among these, fluorine surfactants are particularly preferably used. In general, surfactants cause foaming, cause repelling on the film surface when ink is printed, and further cause agglomeration of pigments. Therefore, it is preferable to suppress the addition amount of the surfactant as much as possible. Compared to other types of surfactants, fluorine-based surfactants have the effect of lowering the surface tension with a small amount of addition, and have the advantage of requiring less addition to the ink. Specific examples include perfluoroalkyl-based and perfluoroalkenyl-based fluorine-based surfactants such as hexafluoropropene-based and tetrafluoroethylene-based ones, and among them, perfluoroalkyl-based surfactants are preferred.

  The content of the fluorinated surfactant used in the aqueous inkjet ink of the present invention can be used in a range of 10 to 10000 ppm based on the total amount of the ink on a mass basis. A more preferable content range is 20 to 5000 ppm. If it is less than 10 ppm, the surface tension of the ink will not sufficiently decrease, and if it is more than 10,000 ppm, the surface tension of the ink will be too low, and this will cause foaming, which is not preferable.

(Other additives)
Further, a preservative, a water-soluble organic solvent, and the like can be added to the aqueous inkjet ink of the present invention as needed. As the preservative used in this case, for example, sodium benzoate, benzimidazole, thiabendazole, potassium sorbitanate, sodium sorbitanate, sodium dehydroacetate, thiazosulfamide, pyridinethiol oxide, thiabendazole and the like are effective. . The content of the preservative used in the aqueous inkjet ink of the present invention can be used in the range of 0.05 to 2.0% by mass, based on the mass of the ink, but the preferable range of the content is 0.1 to 1.0% by mass.

  Further, the aqueous inkjet ink of the present invention, as described above, not only functions as a humectant for the ink, but also has good wettability to the substrate film, preferably a leveling agent for the surface of the substrate to be printed In addition to the specific alkylene glycol alkyl ether defined in the present invention, it can also function as a film-forming aid that enhances the film-forming property of the binder resin contained in the ink, and optionally, Then, a water-soluble organic solvent compatible with the alkylene glycol alkyl ether or the like can be added. Specifically, for example, 1,2-hexanediol, 2-ethyl-1,3-hexanediol, 1,2,6-hexanetriol, 2-methyl-1,3-propanediol, thiodiglycol, glycerin N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone and 3-methyl-3-methoxybutanol, phenoxyethanol, 1,3-dioxolane, Examples thereof include 1,4-dioxane, γ-butyrolactone, ethylene glycol allyl ether, polyethylene glycol, and polypropylene glycol.

[Production method of aqueous inkjet ink]
The aqueous inkjet ink of the present invention contains a pigment and a pigment dispersant.For example, a pigment dispersion is prepared by previously dispersing the pigment with the pigment dispersant using a conventionally known method. It can be easily prepared using a pigment dispersion, and the production method is not particularly limited. For example, water, optionally a water-soluble solvent is also added, a pigment, a mixture of a pigment dispersant, etc. is prepared, and a pigment is prepared using a paint shaker, a ball mill, an attritor, a sand mill, a horizontal media mill, a colloid mill, a roll mill, etc. Finely disperse to prepare a pigment dispersion. Furthermore, to the obtained pigment dispersion, water, a specific alkylene glycol alkyl ether defined in the present invention, and other water-soluble organic solvents used as needed, a specific methacrylic resin defined in the present invention are added. Each is adjusted to a desired concentration, and the pH is adjusted by adding an alkali. Further, if necessary, it can be produced by adding various additives such as a surfactant and a preservative.

  When an image is formed using the aqueous inkjet ink of the present invention, it may be used in a single color or may be printed using a plurality of color inks. When printing using a plurality of color inks, for example, full-color printing can be performed by using different pigments and simultaneously using black ink for the three primary color inks prepared as described above. Further, when the substrate to be printed is colored with a color other than white or transparent, after printing with white ink, color printing is performed thereon, or after performing color printing, Can be printed.

[Printing method using aqueous inkjet ink]
Hereinafter, the inkjet printing method of the present invention will be described. The inkjet printing method of the present invention uses a substrate to be printed that has low permeability of the ink that has not been subjected to a surface treatment, and uses the aqueous inkjet ink of the present invention having the above-described configuration on the surface of the substrate to be printed. When printing by the ink jet recording method, the surface temperature of the substrate to be printed is heated to 40 to 80 ° C. In other words, using the aqueous inkjet ink of the present invention, in order to stably form a higher quality color print by an inkjet printing method on a substrate to be printed that has not been subjected to a surface treatment, the surface treatment is not performed. The substrate to be printed is heated in advance, and the inkjet ink of the present invention is applied to the surface of the substrate to form an image. In this case, the temperature of the substrate to be printed needs to be 40 to 80 ° C, and more preferably 50 to 70 ° C. If the temperature is lower than 40 ° C., the aqueous ink may be repelled on the surface of the base material, and it is difficult to stably obtain a desired higher quality print of an image. On the other hand, when the substrate to be printed is heated in advance to a temperature higher than 80 ° C., the temperature around the head of the inkjet printer becomes high, which may cause non-ejection of ink. A color print can be performed by converting the design, pattern, and the like at the time of color printing into electronic data and transmitting the electronic data to an inkjet printing apparatus, as is usually performed. Examples of the substrate to be used in the inkjet printing method of the present invention, which has a low permeability of the ink not subjected to surface treatment, include, for example, a polyvinyl chloride-based substrate or a polypropylene-based substrate without surface treatment. Or a polyethylene-based substrate.

  Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited by the polymerization method or these examples. In the following description, “parts” or “%” is based on mass unless otherwise specified.

(Synthesis example 1: methacrylic resin-1)
The methacrylic resin (block copolymer) used as a binder resin in the examples of the present invention was prepared with reference to WO 2008/139980, WO 2009/136510, and WO 2010/027093. . The outline of the manufacturing procedure is described below. A 1-liter separable flask was equipped with a stirring blade, a cooling tube, a thermometer, and a nitrogen inlet tube, 350.5 parts of diethylene glycol monobutyl ether (hereinafter abbreviated as BDG), 1.0 part of iodine, and 2,2 ′. 3.7 parts of -azobis (4-methoxy-2,4-dimethylvaleronitrile) (hereinafter abbreviated as V-70), 0.1 part of iodosuccinimide (hereinafter abbreviated as NIS) as a catalyst, and 52.8 parts of benzyl methacrylate (hereinafter abbreviated as BzMA) and 99.4 parts of isobutyl methacrylate (hereinafter abbreviated as IBMA) were charged, stirred, and heated to 45 ° C.

  Two hours later, the brown color of iodine disappeared, and during this time, it was confirmed that V-70 as a polymerization initiator reacted with iodine to become a polymerization initiator compound as an iodine compound. Further, polymerization was carried out for 3 hours while maintaining the above temperature, and at this time, a part of the reaction solution was sampled. The solid content of this sample was measured to be 30.1%, and the polymerization rate calculated based on the solid content was almost 100%. Hereinafter, the polymerization rate was calculated by the same method as described above. The molecular weight was measured by GPC using tetrahydrofuran (hereinafter abbreviated as THF) as a developing solvent. As a result, the number average molecular weight (abbreviated as Mn) was 11,200, and the degree of dispersion was 1.19. Hereinafter, the molecular weight is a value measured by a differential refractive index detector of GPC using a THF solvent as a developing solvent. As described above, a block copolymer of A (hereinafter sometimes abbreviated as A chain) was obtained.

  Next, after cooling the polymer block solution of A obtained above to 40 ° C., 15.1 parts of methacrylic acid (hereinafter abbreviated as MAA) and 61.6 parts of benzyl methacrylate (hereinafter abbreviated as BzMA) were added. Further, polymerization was carried out at 40 ° C. for 4 hours to form a polymer block of B (hereinafter, sometimes abbreviated as B chain). The calculated acid value in the B chain is 128.4 mgKOH / g. The acid value in the B chain was calculated as follows.

First, the amount of MAA per part of the B chain composition is determined.
15.1 / (15.1 + 61.6) = 0.197 parts Then, using the molecular weight of MAA as 86.1 and the molecular weight of KOH as 56.1, the acid value of the B chain is calculated as follows. You. Hereinafter, the acid value in the B chain was calculated by the same method.
(0.197 / 86.1) x 56.1 x 1000 = 128.4 mgKOH / g

  The solid content of this polymer solution was 50.0%, and it was confirmed that the polymerization rate was almost 100%. Mn was 17,500 and the degree of dispersion was 1.33. Since it was confirmed that the molecular weight was shifted to the higher molecular weight side than when the A chain was formed, it is considered that an AB block copolymer was formed. The molecular weight of the B chain can be calculated as a value obtained by subtracting the molecular weight of the A chain from the molecular weight of the AB block copolymer, and Mn was calculated to be 6300. Further, after diluting the sampled product with toluene and ethanol, the measured acid value of the entire AB block copolymer was determined by acid-base titration using a phenolphthalein solution as an indicator using a 0.1% ethanolic potassium hydroxide solution. The price was determined. As a result, the actually measured acid value was 43.0 mgKOH / g. Hereinafter, the actually measured acid value is a value calculated by performing the same operation as described above. The above AB block copolymer is hereinafter referred to as methacrylic resin-1.

(Synthesis examples 2 to 4: methacrylic resins -2 to -4)
Methacrylic resins-2 to -4 were synthesized in the same manner except that the monomer mixture of IBMA and BzMA used in Synthesis Example 1 was changed to the following monomers, respectively. In Synthesis Example 2, t-butylcyclohexyl methacrylate (TBCHMA), in Synthesis Example 3, dicyclopentenyloxyethyl methacrylate (DCPOEMA), and in Synthesis Example 4, dicyclopentanyl methacrylate (DCPMA). Each resin was synthesized in the same manner as in Synthesis Example 1. Those obtained by synthesis were referred to as methacrylic resins-2 to -4, respectively. The details of the obtained methacrylic resins-1 to -4 are shown in Table 1.

(Synthesis Example-5: Methacrylic resin-5)
In Synthesis Example 4, a resin was synthesized in the same manner as in Synthesis Example 1 except that half of the amount of DCPMA was changed to lauryl methacrylate (hereinafter abbreviated as LMA). The obtained resin was designated as methacrylic resin-5.

(Synthesis Example-6: Methacrylic resin-6)
In Synthesis Example 1, a resin was synthesized in the same manner as in Synthesis Example 1 except that TBCHMA was used instead of IBMA and DCPOEMA was used instead of BzMA. The obtained resin was designated as methacrylic resin-6.

(Synthesis examples -7 and -8: methacrylic resins -7 and -8)
A resin was synthesized in the same manner as in Synthesis Example 6 except that the amount of iodine in Synthesis Example 6 was 1.2 times and 1.4 times. These were designated as methacrylic resin-7 and methacrylic resin-8, respectively.

Table 2 summarizes the details of the methacrylic resins-5 to -8 obtained in Synthesis Examples 5 to 8.

(Synthesis example 9: methacrylic resin-9)
A resin was synthesized in the same manner as in Synthesis Example 1 except that the IBMA in Synthesis Example 1 was changed to BzMA, that is, except that the A chain was composed of only BzMA. The obtained resin was referred to as methacrylic resin-9, and the properties are summarized in Table 3.

(Comparative Synthesis Example 1: Comparative methacrylic resin-1)
Using the same apparatus as in Synthesis Example 1, 350.5 parts of BDG was charged, stirred, and heated to 45 ° C. Next, in a separate container, 114.4 parts of BzMA, 99.4 parts of IBMA, 15.1 parts of methacrylic acid, and 7.0 parts of V-70 were mixed and homogenized. When the system reached 45 ° C, 1/3 of the monomer mixture was added and added dropwise for another 2 hours. The mixture was stirred at 45 ° C for 2 hours, and then heated to 50 ° C and polymerized for 2 hours. The polymerization rate was almost 100%, and Mn was 12,600 and PDI was 2.15. The acid value also showed 43.2 mgKOH / g. This is designated as comparative methacrylic resin-1. This is a random type methacrylic resin.

(Production Example 1: Red inkjet ink-1 of Example 1)
In 675 parts by mass of ion-exchanged water and 50 parts by mass of diethylene glycol monobutyl ether, styrene / methyl methacrylate / lauryl methacrylate / 2-hydroxyethyl methacrylate / methacrylic acid (30/20/20/15/15 mass) Ratio) 125 parts by mass of an aqueous solution (solid content 28.0%) of an ammonia neutralized product of a copolymer (number average molecular weight 15000) was dissolved therein. I. 150 parts by mass of CI Pigment Red 122 (manufactured by Dainichi Seika Kogyo) were added, and the mixture was sufficiently stirred and mixed with a dissolver to obtain a mixture containing a pigment and a pigment dispersant.

  This mixture was used as a dispersion medium with zirconia beads having a diameter of 1 mm, placed in a paint shaker having a volume ratio of the dispersion medium of 40% by volume, and dispersed for 120 minutes to obtain a pigment dispersion. Further, this pigment dispersion was centrifuged (7,500 rotations, 20 minutes), and then filtered with a 10 μm membrane filter to remove coarse particles, and adjusted with ion-exchanged water to obtain a red pigment having a pigment concentration of 14%. Was obtained.

  Next, 520.8 parts of ion-exchanged water and 1.4 parts of ammonia water are mixed in a separate container to homogenize, and 76.8 parts of the methacrylic resin-1 obtained in Synthesis Example 1 is added while stirring with a disper. Thus, an aqueous solution of a methacrylic resin was prepared. As a result, a translucent whitish emulsion was obtained. To this, 120 parts by mass of diethylene glycol monobutyl ether, 1 part by mass of aqueous ammonia, 30 parts by mass of a 1% aqueous solution of Surflon S-211 (trade name, manufactured by Asahi Glass Co., Ltd.) which is a fluorine-based surfactant, 250 parts of an aqueous pigment dispersion were added to make a total of 1000 parts by mass. After stirring for 10 minutes, the mixture was filtered through a 5 μm membrane filter to remove coarse particles, and a red inkjet ink-1 was obtained. The viscosity of the obtained red inkjet ink-1 was 3.53 mPa · s at 25 ° C. Table 4 shows other physical property values of the red inkjet ink-1.

(Production Examples 2 to 4: Ink jet inks of Examples 2 to 4 -2 to -4)
C. used in Production Example 1 I. Pigment Red 122 (manufactured by Dainichi Seika Kogyo) in an amount of 150 parts by mass. I. Pigment Blue 15: 3 (manufactured by Dainichi Seika Kogyo), C.I. I. Pigment Yellow 155 (manufactured by Clariant Japan), C.I. I. Pigment Black 7 (Degussa), and a blue inkjet ink (viscosity: 3.22 mPa · s at 25 ° C.) and a yellow inkjet ink (viscosity at 25 ° C.) in the same manner as in Production Example 1. 3.90 mPa · s) and a black inkjet ink (viscosity: 3.10 mPa · s at 25 ° C.). Table 4 shows other physical property values of these ink-jet inks.

(Production Example 5: White inkjet ink of Example 5)
271 parts by mass of ion-exchanged water, 50 parts by mass of diethylene glycol monobutyl ether, and styrene / methyl methacrylate / lauryl methacrylate / 2-hydroxyethyl methacrylate / methacrylic acid (30/20/20/15/15 parts by mass) as a pigment dispersant 179 parts by mass of an aqueous solution (solid content: 28.0%) of an ammonia neutralized product of a copolymer (number average molecular weight = 15000) was dissolved therein. I. Pigment White 6 (manufactured by Ishihara Sangyo Co., Ltd.) (500 parts by mass) was added, and the mixture was sufficiently stirred and mixed with a dissolver to obtain a mixture containing a pigment and a pigment dispersant.

  This mixture was used as a dispersion medium with zirconia beads having a diameter of 1 mm, placed in a paint shaker having a volume ratio of the dispersion medium of 40% by volume, and dispersed for 120 minutes to obtain a pigment dispersion. Thereafter, the mixture was filtered through a 10 μm membrane filter to remove coarse particles, and a white aqueous pigment dispersion having a pigment concentration of 50% was obtained.

  Next, 577 parts of ion-exchanged water and 3 parts of ammonia water are mixed and homogenized in another container, and 90 parts of the methacrylic resin-1 obtained in Synthesis Example 1 is added while stirring with a disper, and 90 parts of the methacrylic resin is added. An aqueous solution was prepared. As a result, a translucent whitish emulsion was obtained. To this, 120 parts by mass of diethylene glycol monobutyl ether, 30 parts by mass of a 1% aqueous solution of Surflon S-211 as a fluorine-based surfactant, and 180 parts of the previously prepared white aqueous pigment dispersion were added, and the total was 1000 parts by mass. And After stirring for 10 minutes, coarse particles were removed by filtration through a 5 μm membrane filter to obtain a white inkjet ink. The viscosity of the obtained white ink was 5.12 mPa · s at 25 ° C. Table 4 shows other physical property values of the obtained white inkjet ink.

(Production Example 6: Red inkjet ink-2 of Example 6)
Styrene / methyl methacrylate / lauryl methacrylate / 2-hydroxyethyl methacrylate / methacrylic acid (30/20/20/15/15 mass ratio) copolymer (number average) used in Production Example 1 Ink-jet ink was produced in the same manner except that the methacrylic resin-8 obtained in Synthesis Example 8 was used in place of the aqueous solution (solid content: 28.0%) of the ammonia neutralized product having a molecular weight of 15,000. Was. This is designated as red inkjet ink-2. That is, in this example, the block copolymer specified in the present invention is used as the pigment dispersant.

Table 4 shows the physical properties of the inkjet inks of each color of Examples 1 to 6 collectively.

(Production Examples 7 to 14, Comparative Production Example 1: Red inks -3 to -10 of Examples 7 to 14, Comparative red ink -1 of Comparative example 1)
Production Example 1 except that methacrylic resin-1 used in Production Example 1 was replaced with methacrylic resin-2 to 9 and comparative methacrylic resin-1, respectively obtained in Synthesis Examples 2 to 9 and Comparative Synthesis Example 1. In the same manner as in Example 1, a red inkjet ink was prepared. The obtained inks were referred to as red ink-3 to -10 and comparative red ink-1, and the physical properties thereof are shown in Table 5.

(Production Examples 15 to 17: Red Inks 11 to -13 of Examples 15 to 17)
A red inkjet ink was prepared in the same manner as in Production Example 1 except that diethylene glycol monobutyl ether used in the prescription of the ink in Production Example 1 was changed to diethylene glycol monoisobutyl ether, and the obtained ink was referred to as Red Ink-11. did. Also, the red inkjet ink obtained in the same manner as in Production Example 1 was replaced with triethylene glycol dimethyl ether, and was designated as Red Ink-12, and was manufactured in the same manner as in Production Example 1 except that tripropylene glycol monomethyl ether was used. The obtained red inkjet ink was designated as red ink-13. Physical properties of the obtained red inks 11 to 13. The results are summarized in Table 6. The same pigment dispersant as that used in Production Example 1 was used.

(Comparative Production Examples 2 and 3: Red Comparative Inks-2 and -3 of Comparative Examples 2 and 3)
A red inkjet ink was prepared in the same manner as in Production Example 1 except that diethylene glycol monobutyl ether (boiling point: 230 ° C.) used at the time of formulating the ink in Production Example 1 was changed to ethylene glycol monobutyl ether (boiling point: 171 ° C.) The obtained ink was designated as comparative red ink 2. The red inkjet ink obtained in the same manner as in Production Example 1 except that ethylene glycol was used was used as comparative red ink 3. Table 6 summarizes the physical properties of Comparative Red Inks 2 and 3.

(Examples 18 to 27: inkjet printing method)
Using each of the red inks -1 to -10 of the examples shown in Table 7 and an ink jet printer equipped with a plate heater [MMP825H (trade name) manufactured by Master Mind Co., Ltd.], as follows. The image was printed by the ink jet recording method. Specifically, a polyvinyl chloride film (Control Tack 180-10 (trade name), manufactured by 3M, abbreviated as “PVC”) that has not been subjected to a surface treatment is previously heated with a plate heater so that the surface temperature becomes 50 ° C. And then printed. As a result, in the printing methods of Examples 18 to 27, good images could be printed without any problem in the leveling property.

Next, the images obtained by the printing methods of Examples 18 to 27 were each checked for adhesion by a cellophane tape peeling test. As a method, after printing, the printed matter was sufficiently dried with a drier, a solid tape (registered trademark) was sufficiently pressed against a solid portion, and the state of peeling of the printed matter when the cellotape (registered trademark) was peeled was visually observed. And it evaluated based on the following criteria.
◎: not peeled at all ○: peeled slightly △: peeled area is smaller ×: peeled area is larger

  As a result, the images obtained by the printing methods of Examples 18 to 27 were good with almost no peeling. In particular, the ink of Example 19 was not peeled off at all. This is probably because the methacrylic resin of the present invention was used as a dispersant.

(Comparative Example 4: inkjet printing method)
In the same manner as in Examples 18 to 27, except that Comparative Red Ink-1 was used, a non-surface-treated PVC was used as a substrate to be printed, and heated so that the surface temperature became 50 ° C., and then inkjet printing was performed. Printed. As a result, in the printing method of Comparative Example 4, streaks were formed and a good printed matter could not be obtained. The reason is that the comparative red ink-1 of the aqueous inkjet ink of Comparative Example 1 used in the printing method of the present comparative example uses a random type polymer for the methacrylic resin added as a binder. This is considered to be because the droplets were splashed and the ejection property was poor. The obtained images were subjected to a cellophane tape peeling test in the same manner as in Examples 18 to 27. As a result, in the image obtained by the printing method of Comparative Example 4, the image was peeled off with Cellotape (registered trademark), and the adhesion was poor.

(Comparative Example 5: inkjet printing method)
In Example 19 using red ink-2, printing was performed in the same manner as in Example 19 except that the polyvinyl chloride film used as the substrate to be printed was not heated and the surface temperature was 25 ° C. As a result, the ink repelled on the surface of the polyvinyl chloride film, did not sufficiently level, and the adhesion of the cellophane tape peeling test was poor, and a good image could not be printed. As shown in Table 7, from the evaluation results of Example 19 and Comparative Example 5, it was confirmed that it is effective to heat the substrate to be printed in advance.

(Examples 28 to 30: inkjet printing method)
Inkjet printing was performed in the same manner as in Example 18 except that the red ink-1 used in Example 18 was changed to each of the red inks 11 to -13. As a result, in each case of Examples 28 to 30, the ejection property, the leveling property, and the adhesion of the obtained image were good.

(Comparative Examples 6 and 7: inkjet printing method)
Printing was performed in the same manner as in Example 18, except that the red ink-1 used in Example 18 was changed to Red Comparative Ink-2 and -3, respectively. As a result, as shown in Table 7, in the case of the printing method of Comparative Example 6, since the drying property of ethylene glycol monobutyl ether, which is a water-soluble solvent in the ink, was high, the drying of the ink also became faster, causing nozzle clogging. And the ejection property was poor. The leveling property and the adhesion of the obtained image were also poor. In Comparative Example 7, although the ejection property was good, the ink was repelled on the surface of PVC due to the low solubility of ethylene glycol, which is a water-soluble solvent, and the leveling property was poor.

(Example 31: inkjet printing method)
When full-color printing was performed using the five color inks of Examples 1 to 5, printing was performed in the same manner as in Example 18, and evaluation was performed. It was good.

(Examples 32 to 41: inkjet printing method)
Using each of the red inkjet inks -1 to -10 of the examples, an inkjet printing machine equipped with a plate heater [MMP825H (trade name) manufactured by Master Mind Co., Ltd.] was used for inkjet recording as follows. The image was printed by the method. Specifically, a polypropylene film not subjected to a surface treatment (Yupo 80 (UV) KV11 (trade name), manufactured by Lintec Corporation, abbreviated as “PP”) was previously heated with a plate heater so that the surface temperature became 50 ° C. Printed after heating. As a result, in the printing methods of Examples 32 to 41, good printing was achieved in both the ejection property and the leveling property.

  Next, the images obtained by the printing methods of Examples 32 to 41 were subjected to the same cellophane tape peeling test as previously performed. As a result, the images obtained by the printing method of the examples using the respective inkjet inks of the examples were hardly peeled off. In particular, as shown in Table 8, images obtained by the printing methods of Examples 34 and 38 to 40 using each ink using a methacrylic resin having TBCHMA as a forming component as a binder resin were completely peeled off from images. I didn't.

(Comparative Example 8: inkjet printing method)
Except for using Comparative Red Ink-1, in the same manner as in the printing method of Examples 32 to 41, PP without surface treatment was used as a substrate to be printed, and heated so that the surface temperature became 50 ° C. And then inkjet printing. As a result, in the printing method of Comparative Example 8, streaks were formed and a good printed matter could not be obtained. The reason is that, in the aqueous inkjet ink of Comparative Red Ink-1, a random type polymer is used for the methacrylic resin added as a binder, droplets are splashed at the time of ejection, and the ejection property is poor. it is conceivable that. The obtained image was subjected to a cellophane tape peeling test in the same manner as described above. As a result, in the image obtained by the printing method of Comparative Example 8, slight peeling was observed, and the adhesion was slightly inferior to that of the example.

(Comparative Example 9: inkjet printing method)
In Example 34 using red ink-3, inkjet printing was carried out in the same manner as in Example 34 except that the polypropylene film used as the substrate to be printed was not heated and the surface temperature was 25 ° C. As a result, the ink repelled on the surface of the polypropylene film, did not sufficiently level, and a good image could not be printed. Further, the results of the cellophane tape peeling test of the obtained images were also poor in adhesion. From a comparison of the evaluation results of the printing methods of Example 34 and Comparative Example 9, it was confirmed that it is effective to heat the printing substrate in advance.

(Example 42: inkjet printing method)
When full-color printing was performed using the five color inks of Examples 1 to 5, printing was performed in the same manner as in Example 32, and evaluation was performed. It was good.

(Examples 43 to 52: inkjet printing method)
Using the red aqueous inkjet inks -1 to -10, an image was printed by an inkjet recording method as follows using an inkjet printer with a plate heater similar to that described above. Specifically, a polyethylene film without surface treatment (LDPE film, 30μ, manufactured by Takigawa, abbreviated as “PE”) was printed after being heated by a plate heater in advance so that the surface temperature became 50 ° C. . As a result, with the printing methods of Examples 43 to 52, good images could be printed.

  Next, the images obtained by the printing methods of Examples 43 to 52 were subjected to the same cellophane tape peeling test as previously performed, and the images obtained by the printing methods of Examples using the respective inkjet inks of Examples were obtained. All of the images obtained had little peeling. Particularly, as shown in Table 9, images obtained by the printing methods of Examples 45 and 49 to 51 using each ink using a methacrylic resin containing TBCHMA as a binder resin were completely peeled off from images. I didn't.

(Comparative Example 10: inkjet printing method)
Using the red comparative ink-1, in the same manner as in the printing method of Examples 43 to 52, PE without surface treatment was used as a substrate to be printed, and heated so that the surface temperature became 50 ° C. Inkjet printing. As a result, in the method using the aqueous inkjet ink of Comparative Example 1, streaks were formed, and a good printed matter could not be obtained. It is considered that the reason is that a random type polymer is used for the methacrylic resin, and there is a splash and the ejection property is poor. When the obtained image was subjected to a cellophane tape peeling test in the same manner as described above, slight peeling was observed in the image, and the adhesion was slightly inferior to that of the example.

(Comparative Example 11: inkjet printing method)
In Example 45 using Red Ink-3, inkjet printing was performed in the same manner as in Example 45 except that the polyethylene film as the substrate to be printed was not heated and the surface temperature was 25 ° C. As a result, the ink repelled on the surface of the polyethylene film, did not sufficiently level, and a good image could not be printed. Further, the results of the cellophane tape peeling test of the obtained images were also poor in adhesion. From a comparison of the evaluation results of the printing methods of Example 45 and Comparative Example 11, it was confirmed that it is effective to heat the substrate to be printed in advance.

(Example 53)
Full-color printing was performed using the five color inks of Examples 1 to 5, printing was performed in the same manner as in Example 43, and evaluation was made. As a result, the ink ejection properties, leveling properties, and image adhesion were good. Was.

  According to the present invention, an excellent color tone is exhibited on a polyvinyl chloride base material not subjected to a surface treatment, or a polypropylene base material not subjected to a surface treatment, or a polyethylene base material not subjected to a surface treatment. On the other hand, it is possible to provide a water-based inkjet ink capable of producing a clear, well-adhered color print image having a desired color, and thus widespread use is expected.

Claims (8)

The surface temperature of the substrate to be printed is reduced to 40 to 80 ° C. when printing is performed by an inkjet recording method using an aqueous inkjet ink on the surface of the substrate to be printed, which has low permeability of the ink that has not been subjected to the surface treatment. An inkjet printing method of heating,
The substrate to be printed is at least one selected from a polyvinyl chloride-based substrate, a polypropylene-based substrate, and a polyethylene-based substrate,
A water-soluble solvent, wherein the aqueous inkjet ink contains at least a pigment, a pigment dispersant, an alkylene group having 2 to 12 carbon atoms, and an alkyl group having 1 to 12 carbon atoms. , Water and alkali, and further contains a methacrylic resin as a binder resin, the content of the methacrylic resin as a binder component is 1 to 20% by mass as a solid content with respect to the total amount of the ink,
The methacrylic resin is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component,
The hydrophobic polymer block comprises at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), and dicyclopentanyl methacrylate (DCPMA). A monomer containing one selected from the group as a forming component, and the acid value of the hydrophilic polymer block is 50 to 250 mgKOH / g;
The alkylene glycol alkyl ether is diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol methyl ethyl ether, triethylene glycol monomethyl Ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Recall monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, an inkjet printing method, which comprises at least one selected from the group consisting of tripropylene glycol monomethyl ether. Any of a polyvinyl chloride-based substrate, a polypropylene-based substrate, or a polyethylene-based substrate, which has a low permeation property of the ink not subjected to the surface treatment, in a state where the surface temperature is heated to 40 to 80 ° C. An aqueous inkjet ink used when forming an inkjet printed image on a substrate,
At least, a pigment, a pigment dispersant, a water-soluble solvent containing an alkylene glycol alkyl ether having 2 to 12 carbon atoms in the alkylene group and 1 to 12 carbon atoms in the alkyl group, water and an alkali, and A methacrylic resin is contained as a binder resin, and the content of the methacrylic resin as a binder component is 1 to 20% by mass as a solid content with respect to the total amount of the ink,
The methacrylic resin is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component,
The hydrophobic polymer block comprises at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), and dicyclopentanyl methacrylate (DCPMA). A monomer containing at least one selected from the group as a forming component, and
The hydrophilic polymer block has an acid value of 50 to 250 mgKOH / g,
The alkylene glycol alkyl ether is diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol methyl ethyl ether, triethylene glycol monomethyl Ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene Recall monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, aqueous inkjet inks, which comprises at least one selected from the group consisting of tripropylene glycol monomethyl ether. Before boiling Kia Ruki glycol alkyl ether is at 200 ° C. or higher 250 ° C. or less, the content thereof, the aqueous inkjet ink according to claim 2 which is 3 to 30 mass% relative to the total amount of the ink. 3. The alkylene glycol alkyl ether contains at least one selected from the group consisting of diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, triethylene glycol dimethyl ether and tripropylene glycol monomethyl ether. Or the aqueous inkjet ink according to 3. The aqueous inkjet ink according to any one of claims 2 to 4, wherein the content of the methacrylic resin is in a range of 2 to 15 % by mass as a solid content with respect to the total amount of the ink.   The pigment dispersant is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate-based monomer containing methacrylic acid as a forming component. The aqueous inkjet ink according to the above.   The aqueous inkjet ink according to any one of claims 2 to 6, further comprising a surfactant.   The aqueous inkjet ink according to claim 7, wherein the surfactant is a fluorine-based surfactant.