JP2017214469A - Aqueous ink-jet ink and ink-jet printing method using the ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous ink-jet ink that can perform a high-quality color printing by an ink-jet printing method to a substrate to be printed having low permeability of an ink that is not surface-treated and can obtain excellent adhesiveness to the substrate to be printed of a formed ink image.SOLUTION: An aqueous ink-jet ink for printing on a substrate to be printed having low permeability of an in k that is not surface-treated includes: an aqueous solvent containing a pigment, a pigment dispersant, and a specific alkylene glycol alkyl ether; water and alkali; and further, a methacrylic resin as a binder resin, in which the methacrylic resin is a block copolymer formed with specific hydrophobic polymer block and a hydrophilic polymer block that is formed with methacrylate-based monomer containing methacrylic acid as a forming component and has an acid value of 50 to 250 mgKOH/g, and an ink-jet printing method using the ink.SELECTED DRAWING: None

Description

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

  In recent years, various printing by the ink-jet printing method has been performed not only for office use and home use but also for a wide range of uses. For example, in industrial applications, there are outdoor advertisements, facility signs, displays, POP advertisements, traffic advertisements, and the like created by inkjet printing as sign displays. Many of these sign displays are created by printing on a large substrate to be printed with an inkjet recording apparatus. However, most of the ink used at that time is solvent-based (Patent Document 1). In addition, many of the substrates to be printed used for image formation are surface-treated so that printing with ink-jet ink is easy, but naturally the substrates to be printed with surface treatment are expensive. . In the case of using a substrate to be printed on which a surface treatment suitable for water-based ink is used, water-based ink may be used. On the other hand, when using a substrate to be printed that has not been surface-treated, a solvent-based ink mainly composed of a solvent having a high dissolving power with respect to the substrate to be printed is used as the solvent component in the ink. Inkjet printing is performed by making it easy for the ink to penetrate into an unprinted substrate. For this reason, when ink jet printing is performed on a substrate to be printed that has not been surface-treated, there are environmental and safety problems caused by the solvent-based ink used. It is necessary to provide a duct or the like. Therefore, in this case, when an apparatus such as an exhaust duct is provided, there is a problem that, in addition to being large, the cost becomes expensive.

  In order to solve the above problems, there has long been a long-awaited aqueous ink that can be printed on a substrate to be printed that has not been surface-treated by the inkjet printing method. In particular, when a substrate to be printed containing a plasticizer such as polyvinyl chloride is used, the plasticizer in the substrate is raised on the surface. It was difficult to obtain the desired image quality. Patent Documents 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 there are some which are effective depending on the pigment in the ink, and this is not a general-purpose technique. In addition, the technique described in Patent Document 3 requires two types of organic solvents having different boiling points, which limits the compatibility with the resin component in the ink and may impair the stability as an inkjet ink. .

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

  Accordingly, the object of the present invention is to provide a substrate to be printed with low permeability of the ink that has not been subjected to surface treatment, in particular, a vinyl chloride substrate that has not undergone surface treatment, or a polypropylene substrate that has not undergone 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 surface treatment, and has good adhesion of the formed ink image to the substrate to be printed It is to provide ink. In addition, an object of the present invention is an ink jet printing method using an aqueous ink jet ink, which can display a high-quality color print image on a substrate to be printed with low surface permeability of ink that has not been surface-treated. The obtained image is to provide an ink jet printing method having high adhesion to a substrate to be printed.

  The above object is achieved by the present invention described below. That is, the present invention provides [1] a water-based inkjet ink for a substrate to be printed with low permeability of an ink that has not been surface-treated, wherein at least the carbon number of the pigment, the pigment dispersant, and the alkylene group. A water-soluble solvent containing 2 to 12 and an alkylene glycol alkyl ether having 1 to 12 carbon atoms in the alkyl group, water and alkali, and further containing a methacrylic resin as a binder resin, the methacrylic resin Is a block copolymer comprising a hydrophobic polymer block and a hydrophilic polymer block comprising a methacrylate monomer containing methacrylic acid as a forming component, and the hydrophobic polymer block includes at least benzyl methacrylate (BzMA). ), Isobutyl methacrylate (IBMA), t-butylcyclohexane It comprises a monomer containing a monomer selected from the group consisting of syl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA) and dicyclopentanyl methacrylate (DCPMA), and the hydrophilic property. An aqueous inkjet ink characterized in that an acid value of a polymer block is 50 to 250 mgKOH / g.

  In addition, since the above-mentioned specific methacrylic resin constituting the present invention is an aggregate (mixture) of various polymer molecules having different molecular weights, it is impossible to directly identify the product by its structure or characteristics or Since it is almost impractical, the monomer used as the raw material was specified by a limited process (production method).

Moreover, this invention provides the water-based inkjet ink mentioned below as a preferable form of the water-based inkjet ink of the said invention.
[2] The water-based 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 with respect to the total amount of the ink.
[3] The above water-soluble solvent includes 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 the range of 1 to 20% by mass as a solid content with respect to the total amount of the ink.
[5] The above [1] to [4], wherein the pigment dispersant is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate monomer containing methacrylic acid as a forming component. The aqueous inkjet ink according to any one of the above.
[6] The water-based 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 water-based inkjet according to any one of [1] to [7], wherein the substrate to be printed is at least one selected from a polyvinyl chloride base, a polypropylene base, and a polyethylene base. For ink.

  As another embodiment of the present invention, [9] the water-based material according to any one of [1] to [8] described above on the surface of a substrate to be printed that has low surface permeability of ink that has not been surface-treated. Provided is an ink jet printing method wherein the surface temperature of the substrate to be printed is heated to 40 to 80 ° C. when printing with an ink jet recording method using ink jet ink.

  In a preferred embodiment of the inkjet printing method of the present invention, [10] the printed substrate is at least one selected from a polyvinyl chloride substrate, a polypropylene substrate and a polyethylene substrate [9] ] The inkjet printing method of description.

  According to the present invention, a substrate to be printed with low permeability of ink that has not been surface-treated, such as a vinyl chloride substrate that has not been surface-treated, a polypropylene-based substrate that has not been surface-treated, or a surface Aqueous solution that enables high-quality color printing by an inkjet printing method on an untreated polyethylene-based substrate and that the formed ink image has good adhesion to the substrate to be printed. Ink jet ink is provided. In addition, according to the present invention, a high-quality color print image can be produced on a substrate to be printed which has low surface permeability of ink that has not been subjected to surface treatment by an inkjet printing method using an aqueous inkjet ink. In addition, an inkjet printing method is provided in which the obtained image has high adhesion to a substrate to be printed.

  Specifically, in the configuration of an aqueous inkjet ink in which a pigment is dispersed by a pigment dispersant, the present invention has a block copolymer having a structure composed of a specific hydrophobic polymer block and a specific hydrophilic polymer block. By including a methacrylic resin as a binder resin, and further containing a water-soluble solvent that can function as a leveling agent or a film-forming aid when adhering to a moisturizing agent of an ink or a film, the above object is achieved. Achieve. Further, in the present invention, when ink-jet printing is performed, a substrate to be printed on which is not subjected to surface treatment is used and the surface temperature is heated to 40 to 80 ° C. By forming an inkjet print image on the surface of the material with the above-described aqueous inkjet ink, the image quality is extremely excellent in adhesion even to a substrate surface that is difficult to print with ordinary aqueous inkjet ink. Thus, a remarkable effect of the present invention that a color print image can be produced is obtained. In addition, since the ink-jet ink provided by the present invention is a water-based ink, it is excellent in terms of environment and safety, and has a large facility such as an exhaust duct as a countermeasure against solvent in the ink used for image formation. Since it does not need to be provided, there is a practical advantage that color printing can be performed by an 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 water-based inkjet ink of the present invention is applied to the surface of a substrate to be printed, such as a polyvinyl chloride-based substrate, a polypropylene-based substrate and a polyethylene-based substrate. It is also suitably used when performing ink jet printing. The aqueous inkjet ink of the present invention contains at least a pigment, a pigment dispersant, and 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. It is characterized by containing a characteristic solvent, water and alkali, and further a methacrylic resin peculiar as a binder resin. The methacrylic resin, which is an essential component of the water-based 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). A monomer containing one type selected from the group consisting of: and the acid value of the hydrophilic polymer block is 50 to 250 mgKOH / g, That. Hereinafter, the water-based inkjet ink of the present invention will be described in detail.

[Substrate for printing]
In general, when ink jet printing is performed on a film having low ink permeability, an ink jet exclusive film subjected to a treatment such as providing an image receiving layer on the printing surface of the film is used. Moreover, in the polypropylene film, for example, when performing gravure printing other than ink jet printing, there is a film in which the printing surface is subjected to corona treatment or the like so that ink can be easily applied. In the case of a polyvinyl chloride base material, the plasticizer floats on the surface, and when ink jet printing is performed with water-based ink, the ink is repelled on the surface of the base material, and a good image cannot be obtained. For this reason, solvent-based ink is usually used. On the other hand, the water-based inkjet ink of the present invention can be applied to a film that is not subjected to the above-described treatment and has a low ink permeability, a polyvinyl chloride base material, a polypropylene base material, a polyethylene base material, and the like. In contrast, good ink jet printing is possible.

[Components of water-based 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 ink-jet 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, diindole. Examples include chromatic pigments such as ketopyrrolopyrrole, quinophthalone, and induslen pigments, and carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. Any of these can be used. Examples of inorganic pigments include extender pigments, titanium oxide pigments, iron oxide pigments, and spinnel pigments.

  In the present invention, it is desirable to select and use the pigment type, particle size, and treatment type according to the purpose. In particular, organic fine-particle pigments are preferable unless the colorant needs a hiding power. Furthermore, when high clarity and transparency are desired, it is desirable to use a pigment that has been refined by wet grinding such as salt milling or dry grinding. In that case, in consideration of nozzle clogging at the time of printing, a pigment having a large particle diameter exceeding 1.0 μm is removed, the average particle diameter is 0.2 μm or less with an organic pigment, and the average particle diameter is 0.4 μm with an inorganic pigment. It is desirable to use the following.

  More specifically, the pigments as described above are exemplified by color index (CI) numbers. 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, C.I. 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 thereof. As a method of mixing, mixing with a powder pigment, mixing with a paste pigment, mixing in pigmentation is possible. There is a synthesis of solid solution by.

  Among the above, as a pigment suitable for the water-based inkjet ink of the present invention, yellow is C.I. I. Pigment Yellow 74, 83, 109, 128, 139, 151, 154, 155, 180, 181, 185, red is C.I. I. Pigment red 122, 170, 176, 177, 185, 269, C.I. I. Pigment Violet 19, 23, blue is C.I. I. Pigment Blue 15: 3, 15: 4, 15: 6 black is C.I. I. Pigment Black 7, white is C.I. I. And CI Pigment White 6.

  The content of the pigment used in the aqueous inkjet ink of the present invention can be 0.1 to 25% by mass with respect to the total amount of the ink, but the preferable content range is 0.2 to the total amount of the ink. ˜20 mass%.

<Water-soluble solvent containing specific alkylene glycol alkyl ether>
In the case of water-based inkjet ink, if the solvent component is only water, 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. The water-based inkjet ink of the present invention contains a water-soluble solvent, but its use is for a substrate to be printed with low permeability of the ink that has not been surface-treated. The water-soluble solvent constituting the ink for ink not only functions as a moisturizing agent for the ink, but also has good wettability with respect to the substrate film, and preferably can also function as a leveling agent for the surface of the substrate to be printed. Is preferably capable of functioning as a film-forming aid that enhances the film-forming property of the binder resin contained in the ink.

  As a result of diligent studies under the above recognition, the present inventors have found that when an alkylene glycol alkyl ether such as diethylene glycol monobutyl ether is used in an aqueous inkjet ink, any of the above functions can be achieved. As found useful. That is, an alkylene glycol alkyl ether such as diethylene glycol monobutyl ether not only functions as a moisturizing agent for ink but also functions as a leveling agent because it has good wettability with respect to the film. Furthermore, since it has a certain level of dissolving power, it has been found that, for example, a polyvinyl chloride surface is slightly dissolved on a polyvinyl chloride-based printing substrate, thereby contributing to ink leveling and adhesion. Furthermore, as described below, it has been found that the film can also function as a film-forming aid for the 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 comprising 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. Since the hydrophobic polymer block is insoluble in water, it is a particle. In order to function as a good binder resin, it is necessary that this particle portion becomes a film, and for this purpose, it is possible to improve the film-forming property of the binder resin, that is, the water solution that can function as a film-forming auxiliary. It is preferable to include a functional solvent in the ink.

  The inventors of the present invention have made extensive studies in consideration of the above-described ink moisturizing properties, leveling properties with respect to the substrate to be printed, solubility in the substrate material, and 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 in which the alkylene group has 2 to 12 carbon atoms and the alkyl group has 1 to 12 carbon atoms as the water-soluble solvent constituting the ink. It 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 monopropylene 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 more and 250 ° C. or less, and examples include 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 specific water-soluble solvent as described above constituting the water-based inkjet ink of the present invention is preferably 3 to 30% by mass with respect to the total amount of the ink. Further, it is more preferably about 5 to 25% by mass with respect to the total amount of ink. If it is less than 3% by mass, the ink is liable to dry, and further, the effect of imparting leveling to the substrate film is also deteriorated, which is not preferable. On the other hand, when the amount is more than 30% by mass, the viscosity of the ink tends to increase, the ink dischargeability tends to deteriorate, and the stability as the ink also tends to deteriorate. In some cases, the binder resin in the ink may precipitate or the pigment may aggregate, which is not preferable. On the other hand, if the content is too large, the water-soluble solvent remains in the printed image film, which may cause blocking of the image film, and the physical properties of the image such as water resistance and abrasion resistance are inferior. This is not preferable from this point.

<Water>
The water-based inkjet ink of the present invention contains water as an essential component. Water is used to impart fluidity to the ink when other components are dissolved and dispersed and ink jet printing is performed. The water used is preferably ion-exchanged water, distilled water, purified water or the like from the viewpoint of not containing impurities such as ionic components. The water content is preferably about 30 to 90% by mass with respect to the total amount of 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 constituent component and a hydrophilic polymer block having a methacrylate monomer containing methacrylic acid as a constituent component. A methacrylic resin, which is a block copolymer, is contained as a binder component. Further, in the block copolymer, the hydrophobic polymer block has at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), dicyclopenta. A monomer containing one type selected from the group consisting of nyl methacrylate (DCPMA) is used as a forming component, and the hydrophilic polymer block has an acid value of 50 to 250 mgKOH / g.

  The inkjet ink of the present invention contains a methacrylic resin, which is a specific block copolymer, as a binder component, so that even when an image is formed on a substrate to be printed that has not been surface-treated, Good adhesion to the printing substrate. Furthermore, the methacrylic resin constituting the ink of the present invention is considered to be a block copolymer having a structure composed of a specific hydrophobic polymer block and a specific hydrophilic polymer block. For example, the inclusion of such a block copolymer as a binder component significantly improves the stability of various physical properties such as ink ejection properties, viscosity, and particle size compared to other binder resins. To do.

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

  In the present invention, a group consisting of water-insoluble benzyl methacrylate, isobutyl methacrylate, t-butylcyclohexyl methacrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentanyl methacrylate (these methacrylate groups) A monomer containing at least one selected from monomer A) as an essential component. As a result of investigations by the present inventors, by including such a monomer A in a methacrylic resin forming component to be contained as a binder component, a substrate to be printed that has not been subjected to surface treatment, for example, polyvinyl chloride It has been found that even when an ink image is formed on a polyolefin-based substrate such as a polypropylene-based substrate and a polypropylene-based substrate and a polyethylene-based substrate, it works to improve the adhesion of the formed ink image to the substrate. .

  In addition, the methacrylic resin used in the present invention uses a monomer containing monomer A selected from the group of the above-mentioned specific methacrylates as a component for forming the hydrophobic block. It may be copolymerized. As other methacrylates used in this case, conventionally known methacrylates are used and are not particularly limited as long as they are monomers as described below. That is, since the hydrophilic block constituting the specific block copolymer used in the present invention is formed from a methacrylate monomer containing at least methacrylic acid, there is a particular problem if it does not react with the carboxylic acid of methacrylic acid. Absent. The amount of the monomer A in the hydrophobic block forming component is not particularly limited, but is preferably 50% by mass or more.

  Further, the molecular weight of the hydrophobic block constituting the methacrylic resin used in the present invention is not particularly limited, but the number average molecular weight is preferably 5000 to 70000. When the number average molecular weight is 5000 or more, adhesion to a substrate is improved as a performance as a film formed of a methacrylic resin having such a hydrophobic block chain. Further, by setting the number average molecular weight to 70000 or less, the viscosity of the ink is optimized, and the ink ejection property and the like are improved. The number average molecular weight of the hydrophobic block constituting the methacrylic resin used in the present invention is more preferably 7,000 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 having a methacrylate monomer containing methacrylic acid as a constituent 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, so that the hydrophilic block chain is dissolved in water. This hydrophilic polymer block may be composed entirely of methacrylic acid, but may be copolymerized with a methacrylate monomer as long as it falls within the above-described acid value 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 by 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 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 be precipitated or aggregated in the ink. Therefore, 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 1000 to 20000, and more preferably 3000 to 15000.

  The method for obtaining the methacrylic resin having the above-described structure used in the present invention is not particularly limited. However, since ordinary radical polymerization cannot easily obtain a polymer having a precisely designed block structure as described above, it is preferable to use living radical polymerization. Any method may be used for living radical polymerization, such as NMP method using nitroxide, ATRP method using oxidation reduction of metal complex, RAFT method using dithiocarboxylic acid ester, etc., method using cobalt catalyst, tellurium Examples include TERP method using a compound, iodine transfer polymerization using iodine, and 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.

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

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

<Pigment dispersant>
A conventionally well-known pigment dispersant can be used for the pigment dispersant which comprises the water-based inkjet ink of this invention. It may be a low molecular weight dispersant such as a surfactant, or a random copolymer, block copolymer, graft copolymer, gradient copolymer, star polymer, such as acrylic, styrene, methacrylic, ester, amide, or polyether. One or more polymer-type dispersants having a higher order structure such as dendrimer can be used. More preferably, it comprises a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate 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 inhibited, higher dispersibility and storage stability can be obtained. The amount of the dispersant relative to the pigment is not particularly limited. For example, 5 to 100 parts can be used with respect to 100 parts of pigment on a mass basis.

<Alkali>
The aqueous inkjet ink of the present invention contains an alkali so as to neutralize the acidic group of the methacrylic resin or the pigment dispersant and dissolve it in water, or to adjust the pH of the ink. As this alkali, the following can be used. For example, ammonia; aliphatic primary to 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, An alkali metal hydroxide such as potassium hydroxide can be used and is not particularly limited. The alkali content is preferably added in an amount that neutralizes part or all of the acidic groups of the methacrylic resin or the dispersant. The pH range of the aqueous inkjet ink of the present invention is preferably 7.0 to 10.0, more preferably 7.5 to 9.5, and the ink can be used in such an amount that the pH falls within such a range. There is no particular limitation. 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, it becomes a strong alkali, which is difficult to handle.

<Other components>
As described above, the water-based inkjet ink of the present invention contains, as essential components, a water-soluble solvent, water, alkali, and the like described above, which contain an alkylene glycol alkyl ether defined in the present invention such as a pigment, a pigment dispersant, and diethylene glycol monobutyl ether. A methacrylic resin having a specific structure is contained, but as described below, a surfactant can be further contained as an additional component as a preferred embodiment. Furthermore, other water-soluble organic solvents and other additives can be blended depending on the purpose.

(Surfactant)
The aqueous inkjet ink of the present invention may further contain a surfactant for the purpose of, for example, maintaining the surface tension at a predetermined value. In that case, the surface tension of a preferable ink is 15 to 45 mN / m, and the particularly preferable surface tension is 20 to 40 mN / m. Examples of the surfactant suitably used in the present invention include those based on silicone, acetylene glycol, fluorine, alkylene oxide, hydrocarbon and the like. Of these, fluorine-based surfactants are particularly preferably used. In general, the surfactant is preferably caused to suppress foaming as much as possible, because it causes foaming, causes repelling on the film surface when ink is printed, and further causes the pigment to aggregate. Compared with other types of surfactants, fluorine-based surfactants have the effect of lowering the surface tension with a slight addition, and have the advantage that the amount added to the ink can be reduced. Specific examples include perfluoroalkyl-based and perfluoroalkenyl-based fluorosurfactants such as hexafluoropropene-based and tetrafluoroethylene-based, among which perfluoroalkyl-based surfactants are preferable.

  The content of the fluorosurfactant used in the water-based inkjet ink of the present invention can be used in a range of 10 to 10,000 ppm based on the total mass of the ink. A more preferable content range is 20 to 5000 ppm. If it is less than 10 ppm, the surface tension of the ink is not sufficiently lowered, and if it exceeds 10000 ppm, the surface tension of the ink is excessively lowered and further causes foaming.

(Other additives)
Moreover, an antiseptic | preservative, a water-soluble organic solvent, etc. can be added to the aqueous inkjet ink of this 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, and siabendazole are effective. . The content of the preservative used in the aqueous inkjet ink of the present invention can be used in a range of 0.05 to 2.0% by mass with respect to the total amount of the ink on a mass basis, but a preferable content range is 0.1 to 1.0% by mass.

  In addition, the water-based inkjet ink of the present invention not only functions as an ink moisturizer, but also has good wettability with respect to the substrate film, and is preferably a leveling agent on the surface of the substrate to be printed. In addition to the specific alkylene glycol alkyl ethers defined in the present invention, which can also function as a film-forming aid that enhances the film-forming property of the binder resin contained in the ink, 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 include 1,4-dioxane, γ-butyrolactone, ethylene glycol allyl ether, polyethylene glycol, polypropylene glycol and the like.

[Method for producing aqueous inkjet ink]
The aqueous inkjet ink of the present invention contains a pigment and a pigment dispersant. For example, the aqueous inkjet ink is obtained by previously dispersing a pigment with a pigment dispersant using a conventionally known method to produce a pigment dispersion. It can be easily prepared using a pigment dispersion, and the production method is not particularly limited. For example, water or a water-soluble solvent may be added to prepare a mixture of a pigment, a pigment dispersant, etc., and a pigment is used using a paint shaker, ball mill, attritor, sand mill, horizontal media mill, colloid mill, roll mill, etc. A pigment dispersion is prepared by fine dispersion. Furthermore, water, a specific alkylene glycol alkyl ether specified in the present invention, a water-soluble organic solvent used as necessary, and a specific methacrylic resin specified in the present invention are added to the obtained pigment dispersion. , Each is adjusted to a desired concentration, and the pH is adjusted by adding alkali. Furthermore, it can manufacture by adding various additives, such as surfactant and antiseptic | preservative, as needed.

  When forming an image using the water-based 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 inks for the three primary color inks prepared as described above. Furthermore, if the substrate to be printed is colored with a color other than white or is transparent, after printing with white ink, color printing is performed on it, or conversely color printing is performed, then white ink is printed. Can be printed.

[Printing method using water-based inkjet ink]
Hereinafter, the ink jet 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 surface permeability of ink that has not been surface-treated, 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 inkjet recording method, the surface temperature of the substrate to be printed is heated to 40 to 80 ° C. That is, the surface treatment is not performed in order to stably form a higher quality color print by the ink jet printing method on the substrate to be printed which is not subjected to the surface treatment using the water-based ink-jet ink of the present invention. The substrate to be printed is heated in advance, and the ink jet ink of the present invention is applied to the surface to form an image. And in that case, it is necessary to make the temperature of a to-be-printed base material into 40-80 degreeC, and also it is preferable to make it become 50-70 degreeC. When the temperature is lower than 40 ° C., the water-based ink may be repelled on the surface of the base material, and it becomes difficult to stably obtain a print of a higher quality image of interest. On the other hand, when the substrate to be printed is preheated to a temperature higher than 80 ° C., the periphery of the head of the ink jet printer becomes hot, which may cause ink non-ejection. The design and pattern for color printing can be converted into electronic data as usual, and color printing can be performed by transmitting the electronic data to an inkjet printing apparatus. Examples of the substrate to be printed that is used in the ink jet printing method of the present invention and has low surface permeability of ink that has not been surface-treated include, for example, a polyvinyl chloride-based substrate or a polypropylene-based substrate that has not been surface-treated. Examples thereof include a material or a polyethylene-based substrate.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited at all by the polymerization method or these examples. In the text, “part” or “%” is based on mass unless otherwise specified.

(Synthesis example 1: Methacrylic resin-1)
The methacrylic resin (block copolymer) used as the binder resin in the examples of the present invention was prepared with reference to documents of International Publication Nos. 2008/139980, 2009/136510, and 2010/027093. . The outline of the production procedure is described below. A 1-liter separable flask is equipped with a stirring blade, a cooling tube, a thermometer, and a nitrogen introduction tube, 350.5 parts of diethylene glycol monobutyl ether (hereinafter abbreviated as BDG), 1.0 part of iodine, 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, 52.8 parts of benzyl methacrylate (hereinafter abbreviated as BzMA) and 99.4 parts of isobutyl methacrylate (hereinafter abbreviated as IBMA) were charged and stirred and heated to 45 ° C.

  After 2 hours, the brown color of iodine disappeared, and during this period, it was confirmed that V-70 as a polymerization initiator reacted with iodine to become a polymerization initiation compound as an iodine compound. Further, polymerization was carried out for 3 hours while maintaining the above temperature, and a part of the reaction solution was sampled at this point. When the solid content of this sample was measured, it was 30.1%, and the polymerization rate calculated based on this was almost 100%. Hereinafter, the polymerization rate was calculated by the same method as described above. Further, when the molecular weight was measured by GPC using tetrahydrofuran (hereinafter abbreviated as THF) as a developing solvent, the number average molecular weight (abbreviated as Mn) was 11200, 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 the temperature of the polymer block solution of A obtained above was lowered 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 acid value in the B chain is calculated to be 128.4 mgKOH / g. The acid value in the B chain was calculated as follows.

First, the amount of MAA per part of B chain composition is determined.
15.1 / (15.1 + 61.6) = 0.197 parts Next, when the molecular weight of MAA is 86.1 and the molecular weight of KOH is 56.1, the acid value of the B chain is calculated as follows: The Hereinafter, the acid value in the B chain was calculated by the same method.
(0.197 / 86.1) × 56.1 × 1000 = 12.8 mgKOH / g

  This polymer solution had a solid content of 50.0%, and it was confirmed that the polymerization rate was almost 100%. Moreover, Mn was 17500 and dispersion degree was 1.33. From the fact that 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 the 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 calculated as Mn = 6300. Furthermore, after the sample was diluted with toluene and ethanol, the acid of the entire AB block copolymer was measured by acid-base titration using a 0.1% ethanolic potassium hydroxide solution with a phenolphthalein solution as an indicator. The price was calculated. 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. Hereinafter, the above AB block copolymer is referred to as methacrylic resin-1.

(Synthesis Examples 2-4: Methacrylic resin-2-4)
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 replaced with the following monomers, respectively. In Synthesis Example 2, t-butylcyclohexyl methacrylate (TBCHMA) was replaced, in Synthesis Example 3, dicyclopentenyloxyethyl methacrylate (DCPOEMA) was replaced, and in Synthesis Example 4, dicyclopentanyl methacrylate (DCPMA) was replaced. Each resin was synthesized in the same manner as in Synthesis Example 1. Those obtained by synthesis were designated as methacrylic resins-2 to -4. Details of the obtained methacrylic resins-1 to -4 are summarized in Table 1.

(Synthesis Example-5: Methacrylic resin-5)
In Synthesis Example 4, the 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)
Resin was synthesized in the same manner as in Synthesis Example 1 except that in Synthesis Example 1, TBCHMA was substituted for IBMA and DCPOEMA was substituted for BzMA. The obtained resin was designated as methacrylic resin-6.

(Synthesis Example-7, -8 :: Methacrylic resin-7, -8)
Resins were 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.

Details of the methacrylic resins-5 to -8 obtained in these synthesis examples 5 to 8 are summarized in Table 2.

(Synthesis Example 9: Methacrylic resin-9)
The resin was synthesized in the same manner as in Synthesis Example 1 except that IBMA in Synthesis Example 1 was replaced with BzMA, that is, the A chain was composed of only BzMA. The resulting resin was methacrylic resin-9 and the properties thereof 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, 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 in a separate container 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, then heated to 50 ° C. and polymerized for 2 hours. The polymerization rate was almost 100%, and Mn12600 and PDI2.15. The acid value was 43.2 mgKOH / g. This is designated as comparative methacrylic resin-1. This is a random methacrylic resin.

(Production Example 1: Red inkjet ink-1 of Example 1)
To 675 parts by mass of ion-exchanged water, 50 parts by mass of diethylene glycol monobutyl ether, as a pigment dispersant, 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. I. 150 parts by mass of Pigment Red 122 (manufactured by Dainichi Seika Kogyo Co., Ltd.) 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 placed in a paint shaker with a volume ratio of 40% by volume of zirconia beads having a diameter of 1 mm as a dispersion medium, and dispersed for 120 minutes to obtain a pigment dispersion. Further, this pigment dispersion is centrifuged (7500 rpm, 20 minutes), then filtered through a 10 μm membrane filter to remove coarse particles, adjusted with ion-exchanged water, and the pigment concentration is 14% red. An aqueous pigment dispersion was obtained.

  Next, 520.8 parts of ion-exchanged water and 1.4 parts of ammonia water were mixed in a separate container, homogenized, and 76.8 parts of methacrylic resin-1 obtained in Synthesis Example 1 was added while stirring with a disper. Thus, an aqueous solution of 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 was added to make a total of 1000 parts by mass. And after stirring for 10 minutes, it filtered with a 5-micrometer membrane filter, the coarse particle was removed, and the 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: Inkjet inks 2 to 4 of Examples 2 to 4)
C. used in Production Example 1 I. 150 parts by mass of CI Pigment Red 122 (manufactured by Dainichi Seika Kogyo Co., Ltd.) I. Pigment Blue 15: 3 (manufactured by Dainichi Seika Kogyo), C.I. I. Pigment Yellow 155 (manufactured by Clariant Japan), C.I. I. A blue inkjet ink (viscosity is 3.22 mPa · s at 25 ° C.) and a yellow inkjet ink (viscosity is 25 ° C.) except that Pigment Black 7 (Degussa) is used. 3.90 mPa · s), a black inkjet ink (viscosity 3.10 mPa · s at 25 ° C.) was obtained. Table 4 shows other physical property values of the ink jet inks of these colors.

(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, styrene / methyl methacrylate / lauryl methacrylate / 2-hydroxyethyl methacrylate / methacrylic acid (30/20/20/15/15 mass) as a pigment dispersant Ratio) 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. 500 parts by weight of CI Pigment White 6 (manufactured by Ishihara Sangyo Co., Ltd.) was added and sufficiently stirred and mixed with a dissolver to obtain a mixture containing a pigment and a pigment dispersant.

  This mixture was placed in a paint shaker with a volume ratio of 40% by volume of zirconia beads having a diameter of 1 mm as a dispersion medium, 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, thereby obtaining a white aqueous pigment dispersion having a pigment concentration of 50%.

  Next, 577 parts of ion-exchanged water and 3 parts of ammonia water were mixed and homogenized in a separate container, and 90 parts of the methacrylic resin-1 obtained in Synthesis Example 1 was added while stirring with a disper. 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 which is a fluorosurfactant, 180 parts of the previously prepared white aqueous pigment dispersion are added, and the total is 1000 parts by mass. It was. And after stirring for 10 minutes, it filtered with a 5-micrometer membrane filter, the coarse particle was removed, and the white inkjet ink was obtained. 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 ink-jet 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 as a pigment dispersant Ink jet ink was prepared in the same manner except that the methacrylic resin-8 obtained in Synthesis Example 8 was used instead of the aqueous solution (solid content 28.0%) of the neutralized ammonia having a molecular weight of 15000). It was. This is designated as red inkjet ink-2. That is, in this example, the block copolymer defined in the present invention is used as the pigment dispersant.

Table 4 summarizes the physical properties of the inkjet inks of the respective colors of Examples 1 to 6.

(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 the methacrylic resin-1 used in Production Example 1 was obtained in Synthesis Examples 2-9 and Comparative Synthesis Example 1, respectively, and was replaced with methacrylic resin-2-9 and comparative methacrylic resin-1. In the same manner as in Example 1, a red inkjet ink was prepared. The obtained inks were designated as red inks -3 to -10 and comparative red ink-1, and their physical properties are summarized 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 ink formulation of Production Example 1 was replaced with diethylene glycol monoisobutyl ether, and the resulting ink was designated as Red Ink-11. did. Further, the red ink jet ink obtained in the same manner as in Production Example 1 except that triethylene glycol dimethyl ether was used was changed to Red Ink-12, and the same procedure as in Production Example 1 was conducted except that tripropylene glycol monomethyl ether was used. The obtained red ink-jet ink was named red ink-13. Physical properties of the obtained red inks 11-13. Table 6 summarizes the results. In addition, 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 in 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 in the ink formulation of Production Example 1 was replaced with ethylene glycol monobutyl ether (boiling point 171 ° C.). The obtained ink was designated as comparative red ink 2. A red ink-jet 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 the 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, using an inkjet printer with a plate heater [MMP825H (trade name) manufactured by Mastermind Co., Ltd.], as follows: An image was printed by an inkjet recording method. Specifically, a surface-treated polyvinyl chloride film (control tack 180-10 (trade name), manufactured by 3M, abbreviated as “PVC”) is previously heated to a surface temperature of 50 ° C. with a plate heater. And then printed. As a result, in the printing methods of Examples 18 to 27, a good image could be printed without any problem in leveling properties.

Next, adhesion of each of the images obtained by the printing methods of Examples 18 to 27 was confirmed by a cellophane tape peeling test. As a method, after printing, the printed material was sufficiently dried with a drier, and the cellophane (registered trademark) was sufficiently pressed against the solid portion, and the degree of peeling of the printed material when the cellotape (registered trademark) was peeled off was visually observed. And it evaluated on the following references | standards.
◎: Not peeled off ○: Slightly peeled △: Peeled area is smaller ×: Peeled area is larger

  As a result, the images obtained by the printing methods of Examples 18 to 27 were satisfactory 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, polyvinyl chloride not subjected to surface treatment was used as a substrate to be printed, and the ink was heated so that the surface temperature became 50 ° C. Printed. As a result, in the printing method of Comparative Example 4, a streak occurred and a good print could not be obtained. The reason for this is that in the comparative red ink-1 of the aqueous inkjet ink of Comparative Example 1 used in the printing method of this Comparative Example, a random polymer is used for the methacrylic resin added as a binder. It is thought that this is because the droplets are splashed and the ejection properties are poor. Moreover, the cellophane tape peeling test was done about the obtained image similarly to the case of Examples 18-27. As a result, in the image obtained by the printing method of Comparative Example 4, the image peeled off with cello tape (registered trademark), and the adhesion was poor.

(Comparative Example 5: Inkjet printing method)
In Example 19 using the red ink-2, printing was performed in the same manner as in Example 19 except that the polyvinyl chloride film used for the substrate to be printed was not heated and the surface temperature was 25 ° C. As a result, the ink bounced on the surface of the polyvinyl chloride film, and the leveling was not sufficient, and the result of the cellophane tape peeling test was inferior, and a good image could not be printed. As shown in Table 7, it was confirmed from the evaluation results of Example 19 and Comparative Example 5 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 red ink-11 to -13, respectively. As a result, in any 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 inks-2 and -3, respectively. As a result, as shown in Table 7, in the case of the printing method of Comparative Example 6, the drying property of ethylene glycol monobutyl ether, which is a water-soluble solvent in the ink, is fast, so that the drying of the ink is fast, and nozzle clogging occurs. The ejection property was poor. It was inferior also in leveling property and the adhesiveness of the obtained image. In Comparative Example 7, although the ejection property was good, the solubility of ethylene glycol, which is a water-soluble solvent, was weak, so the ink repelled on the surface of vinyl chloride and the leveling property was poor.

(Example 31: Inkjet printing method)
When full-color printing was performed using the five colors of inks of Examples 1 to 5 and printing was performed in the same manner as in Example 18, the ink ejection properties, leveling properties, and adhesion of the obtained images were also evaluated. It was good.

(Examples 32-41: Inkjet printing method)
Each of the red ink jet inks -1 to -10 of the examples was used, and ink jet recording was performed as follows using an ink jet printer with a plate heater [MMP825H (trade name) manufactured by Mastermind Co., Ltd.]. The image was printed by the method. Specifically, a surface-treated polypropylene film (Yupo 80 (UV) KV11 (trade name), manufactured by Lintec Corporation, abbreviated as “PP”) is preliminarily set to a surface temperature of 50 ° C. with a plate heater. Printed after heating. As a result, in the printing methods of Examples 32-41, good printing was achieved for both the ejection properties and the leveling properties.

  Subsequently, the same cellophane tape peeling test as previously performed was performed about the image obtained by the printing method of each of Examples 32-41. As a result, the images obtained by the printing methods of the examples using the respective ink jet inks of the examples were hardly peeled off. In particular, as shown in Table 8, the 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 in the image. I did not.

(Comparative Example 8: Inkjet printing method)
Except for using Comparative Red Ink-1, the same printing method as in Examples 32 to 41 was used, and PP that had not been surface-treated was used as a printing substrate, and heated so that the surface temperature was 50 ° C. Then, inkjet printing was performed. As a result, in the printing method of Comparative Example 8, a streak occurred and a good print could not be obtained. The reason is that the water-based inkjet ink of comparative red ink-1 uses a random type polymer for the methacrylic resin added as a binder, and droplets are splashed during ejection, resulting in poor ejection properties. it is conceivable that. In addition, the obtained image was subjected to a cellophane tape peeling test in the same manner as described above. As a result, some peeling was seen in the image obtained by the printing method of Comparative Example 8, and the adhesion was slightly inferior to that of the example.

(Comparative Example 9: Inkjet printing method)
In Example 34 using the red ink-3, inkjet printing was performed in the same manner as in Example 34 except that the polypropylene film used for the substrate to be printed was not heated and the surface temperature was 25 ° C. As a result, the ink bounced on the surface of the polypropylene film, and the image was not sufficiently leveled and a good image could not be printed. Moreover, the result of the cellophane tape peeling test of the obtained image was also inferior in adhesion. From comparison of the evaluation results of the printing methods of Example 34 and Comparative Example 9, it was confirmed that it was effective to heat the substrate to be printed in advance.

(Example 42: Inkjet printing method)
When full-color printing was performed using the inks of the five colors of Examples 1 to 5 and printing was performed in the same manner as in Example 32, the ink ejection properties, leveling properties, and adhesion of the obtained images were also evaluated. It was good.

(Examples 43 to 52: Inkjet printing method)
An image was printed by the inkjet recording method as described below using the same red-water-based inkjet inks -1 to -10 and the same inkjet printer with a plate heater as described above. Specifically, a surface-treated polyethylene film (LDPE film, 30μ, manufactured by Takigawa Co., Ltd., abbreviated as “PE”) was printed with a plate heater heated to a surface temperature of 50 ° C. in advance. . As a result, in the printing methods of Examples 43 to 52, good images could be printed.

  Next, the same cellophane tape peeling test as previously performed was performed on the images obtained by the printing methods of Examples 43 to 52, and the images were obtained by the printing methods of the examples using the respective inkjet inks of the examples. All the obtained images hardly peeled off. In particular, as shown in Table 9, the images obtained by the printing methods of Examples 45 and 49 to 51 using each ink using a methacrylic resin having TBCHMA as a forming component as a binder resin are completely peeled off in the image. I did not.

(Comparative Example 10: inkjet printing method)
After using the red comparison ink-1 and the same printing method as in Examples 43 to 52, PE that has not been surface-treated is used as a substrate to be printed, and the surface temperature is heated to 50 ° C. Inkjet printing was performed. As a result, the method using the water-based inkjet ink of Comparative Example 1 caused streaks and failed to obtain a good print. The reason is considered to be that a random type polymer is used for the methacrylic resin, there is a splash, and dischargeability is poor. Further, when the obtained image was subjected to a cellophane tape peeling test in the same manner as described above, the image was slightly peeled off, and the adhesion was slightly inferior to that of the example.

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

(Example 53)
When full-color printing was performed using the inks of the five colors of Examples 1 to 5 and printing was performed in the same manner as in Example 43, the ink ejection property, leveling property, and image adhesion were good. It was.

  According to the present invention, an excellent color tone is exhibited on a polyvinyl chloride base material that has not been surface-treated, a polypropylene base material that has not been surface-treated, or a polyethylene base material that has not been surface-treated. On the other hand, since it is possible to provide a water-based inkjet ink that can produce a clear color print image having a desired color and good adhesion, it is expected to be widely used.

Claims (10)

A water-based inkjet ink for a substrate to be printed with low permeability of ink that has not been surface-treated,
At least a pigment, a pigment dispersant, a water-soluble solvent containing 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, water and an alkali; and Containing methacrylic resin as binder resin,
The methacrylic resin is a block copolymer comprising a hydrophobic polymer block and a hydrophilic polymer block having a methacrylate 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 type selected from the group is used as a forming component, and
An aqueous inkjet ink, wherein the hydrophilic polymer block has an acid value of 50 to 250 mgKOH / g.   2. The water-based inkjet ink according to claim 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 with respect to the total amount of the ink.   The water-soluble solvent includes 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. 2. A water-based inkjet ink as described in 2.   The water-based inkjet ink according to any one of claims 1 to 3, wherein a content of the methacrylic resin is in a range of 1 to 20% by mass as a solid content with respect to a total amount of the ink.   5. The block copolymer according to claim 1, 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 water-based inkjet ink described.   The aqueous inkjet ink according to any one of claims 1 to 5, further comprising a surfactant.   The aqueous inkjet ink according to claim 6, wherein the surfactant is a fluorine-based surfactant.   The aqueous inkjet ink according to any one of claims 1 to 7, wherein the substrate to be printed is at least one selected from a polyvinyl chloride base, a polypropylene base, and a polyethylene base.   When using the water-based inkjet ink according to any one of claims 1 to 8 on the surface of a substrate to be printed that has low surface permeability of ink that has not been subjected to surface treatment, An inkjet printing method, wherein the surface temperature of a substrate to be printed is heated to 40 to 80 ° C.   The inkjet printing method according to claim 9, wherein the substrate to be printed is at least one selected from a polyvinyl chloride substrate, a polypropylene substrate, and a polyethylene substrate.