JP2020105527A - Binder resin used in aqueous inkjet ink - Google Patents

Abstract

To provide a binder resin used in an aqueous inkjet ink, capable of forming a high-picture quality color printing image using the inkjet ink on a substrate to be printed which does not apply a surface treatment and has a low ink penetrability and capable of obtaining a favorable adhesion of the formed ink image to the substrate.SOLUTION: A binder resin includes a methacrylic resin which is a block copolymer including a hydrophobic polymer block and a hydrophilic polymer block comprising a methacrylate monomer including methacrylic acid. The hydrophobic polymer block is prepared using a monomer including as a formation component, at least one monomer A selected from the group consisting of benzyl methacrylate, isobutyl methacrylate, tert-butyl cyclohexyl methacrylate, dicyclopentenyloxyethyl methacrylate and dicyclopentanyl methacrylate and besides, the acid value of the hydrophilic polymer block is 50 to 250 mgKOH/g.SELECTED DRAWING: None

Description

The present invention relates to a water-based inkjet ink used when an inkjet printing method is used to print on a substrate to be printed, which has a low permeability of an ink that has not been surface-treated, and an inkjet printing method using the ink.

2. Description of the Related Art In recent years, various printings have been performed by an inkjet printing method for a wide range of applications, not only for office use and home use. For example, in industrial applications, as sign displays, there are outdoor advertisements, facility signs, displays, POP advertisements, traffic advertisements, etc. created by the inkjet printing method. Many of these sign displays are produced by printing on a large printed substrate with an inkjet recording device. However, most of the inks used at that time are solvent-based (Patent Document 1). In addition, many print substrates used for image formation have been surface-treated so that they can be printed easily with an inkjet ink, but the print-treated substrates subjected to the surface treatment are naturally expensive. .. When a substrate to be printed having a surface treatment suitable for water-based ink is used, the water-based ink may be used. On the other hand, when a substrate to be printed that has not been surface-treated is used, a solvent-based ink whose main component is a solvent having a high dissolving power for the substrate to be printed is used as the solvent component in the ink, and the surface treatment is performed. Inkjet printing is performed by making it easier for ink to permeate into a substrate to be printed that has not been printed. For this reason, when performing inkjet printing on a substrate to be printed that has not been surface-treated, there are environmental and safety issues that result from the solvent-based ink used. It is necessary to provide a duct or the like. Therefore, in this case, provision of a device such as an exhaust duct causes a large scale, and there is a problem that the cost becomes expensive.

In order to solve the above problems, there has been a long-felt demand for an aqueous ink capable of printing on a substrate to be printed which has not been surface-treated by an inkjet printing method. In particular, when a substrate to be printed containing a plasticizer such as polyvinyl chloride is used, since the plasticizer in the substrate is raised on the surface, the ink repels on the surface of the substrate when printed with an aqueous ink, 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 depending on the pigment in the ink, it may or may not be effective, and it is not a general-purpose technique. Further, in the technique described in Patent Document 3, two kinds of organic solvents having different boiling points are essential, the compatibility with the resin component in the ink is limited, and the stability as an inkjet ink may be impaired. ..

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

Therefore, the object of the present invention is a substrate to be printed having low penetrability of ink which has not been subjected to surface treatment, in particular, a vinyl chloride substrate which is not subjected to surface treatment, and a polypropylene-based substrate which is not subjected to 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 surface-treated and that has good adhesion of the formed ink image to the substrate to be printed. To provide the ink for use. Further, an object of the present invention is an inkjet printing method using a water-based inkjet ink, which allows a high-quality color printed image to appear on a substrate to be printed having low penetrability of an ink not subjected to surface treatment, and An object of the present invention is to provide an inkjet printing method in which an image obtained 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 is [1] a water-based inkjet ink for a substrate to be printed, which has low penetrability of an ink that is not surface-treated, and has at least a pigment, a pigment dispersant, and an alkylene group having carbon atoms. The methacrylic resin comprises 2 to 12 and a water-soluble solvent containing an alkylene glycol alkyl ether having an alkyl group having 1 to 12 carbon atoms, water and an alkali, and a methacrylic resin as a binder resin. Is a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block containing a methacrylate monomer containing methacrylic acid as a forming component, wherein the hydrophobic polymer block is at least benzyl methacrylate (BzMA). ), isobutylmethacrylate (IBMA), t-butylcyclohexylmethacrylate (TBCHMA), dicyclopentenyloxyethylmethacrylate (DCPOEMA) and dicyclopentanylmethacrylate (DCPMA) forming monomer. And an acid value of the hydrophilic polymer block is 50 to 250 mgKOH/g.

Since the above-mentioned peculiar methacrylic resin constituting the present invention is an assembly (mixture) of various polymer molecules having different molecular weights, it is impossible to directly specify the product as a product by its structure or characteristics. Since it is almost impractical, the monomer as a raw material was specified by a limited process (manufacturing method).

The present invention also provides the following aqueous inkjet inks as a preferred form of the above-described aqueous inkjet ink of the present invention.
[2] The aqueous inkjet ink according to the above [1], wherein the boiling point of the alkylene glycol alkyl ether is 200° C. or higher and 250° C. or lower, and the content thereof is 3 to 30 mass% with respect to the total amount of the ink.
[3] The 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 water-based inkjet ink according to [1] or [2].
[4] The aqueous inkjet ink according to any one of the above [1] to [3], wherein the content of the methacrylic resin is within 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 containing a methacrylate monomer containing methacrylic acid as a forming component. 5. The aqueous inkjet ink according to any one of 1.
[6] The aqueous inkjet ink according to any one of the above [1] to [5], further containing 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 the above [1] to [7], wherein the substrate to be printed is at least one selected from a polyvinyl chloride substrate, a polypropylene substrate and a polyethylene substrate. Ink.

As another embodiment of the present invention, [9] the aqueous solution according to any one of the above [1] to [8] is formed on the surface of a base material to be printed, which has low permeability of ink that has not been surface-treated. Provided is an inkjet printing method, which comprises heating the surface temperature of the substrate to be printed to 40 to 80° C. when printing with an inkjet recording method using an inkjet ink.

As a preferable mode of the inkjet printing method of the present invention, [10] the printed substrate 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 the above is mentioned.

According to the present invention, a substrate to be printed having a low permeability of ink that has not been surface-treated, for example, a vinyl chloride substrate that has not been surface-treated, or a polypropylene-based substrate that has not been surface-treated, or a surface High-quality color printing can be performed by an inkjet printing method on a polyethylene-based substrate that has not been treated, and the adhesion of the formed ink image to the substrate to be printed is good. An inkjet ink is provided. Further, according to the present invention, an inkjet printing method using a water-based inkjet ink can produce a high-quality color printed image on a substrate to be printed, which has a low permeability of the ink which is not surface-treated, and An inkjet printing method is provided in which the obtained image has high adhesion to the substrate to be printed.

Specifically, in the constitution of an aqueous inkjet ink in which a pigment is dispersed 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. By containing a methacrylic resin as a binder resin, and further containing a water-soluble solvent that can also function as a moisturizing agent for ink and a leveling agent or a film-forming aid when attached to a film, the above-mentioned purpose can be achieved. To achieve. Further, in the present invention, during inkjet printing, a substrate to be printed, which is not surface-treated and has low penetrability of ink, 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 water-based inkjet ink having the above-described structure, it is possible to obtain a high image quality with excellent adhesion even to a substrate surface that is difficult to print with a normal water-based inkjet ink. The remarkable effect of the present invention is that a large color printed image can be displayed. Further, since the inkjet ink provided by the present invention is a water-based ink, it is excellent in terms of environment and safety. Furthermore, as a measure against the solvent in the ink used for image formation, large equipment such as an exhaust duct is required. Since it is not necessary to provide it, there is also a practical advantage that color printing can be performed by an inkjet recording method at 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 a substrate having a low permeability of an ink that has not been surface-treated, such as a polyvinyl chloride-based substrate, a polypropylene-based substrate and a polyethylene-based substrate. It is also preferably used when performing inkjet printing. The aqueous inkjet ink of the present invention is a water-soluble ink containing 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 in that it contains an organic solvent, water and an alkali, and a methacrylic resin peculiar 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 monomer containing methacrylic acid as a forming component. The hydrophobic polymer block is at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA) and dicyclopentanyl methacrylate (DCPMA). It is characterized in that it comprises a monomer containing one kind selected from the group consisting of as a forming component, and the hydrophilic polymer block has an acid value of 50 to 250 mgKOH/g. Hereinafter, the water-based inkjet ink of the present invention will be described in detail.

[Printed substrate]
Generally, when inkjet printing is performed on a film having low ink permeability, an inkjet-dedicated film that has been subjected to a treatment such as providing an image receiving layer on the printing surface of the film is used. In addition to the inkjet printing, there is a polypropylene film that is used when performing gravure printing, for example, such that corona treatment is performed on the printed surface so that the ink can easily spread. Further, in the case of a polyvinyl chloride base material, the plasticizer floats on the surface, and when ink jet printing is performed with an aqueous ink, the ink is repelled on the base material surface, and a good image cannot be obtained. Therefore, solvent-based ink is usually used. On the other hand, in the water-based inkjet ink of the present invention, a film having low ink permeability, which has not been subjected to the above-mentioned treatment, is used as a polyvinyl chloride base material, a polypropylene base material, a polyethylene base material, or the like. Also good inkjet printing is 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, as an organic pigment, a phthalocyanine-based, azo-based, azomethine azo-based, azomethine-based, anthraquinone-based, perinone-perylene-based, indigo-thioindigo-based, dioxazine-based, quinacridone-based, isoindoline-based, isoindolinone-based, di-based Examples include chromatic color pigments such as ketopyrrolopyrrole pigments, quinophthalone pigments and indanthrene pigments, carbon black pigments such as furnace black, lamp black, acetylene black and channel black, and any of them can be used. Examples of the inorganic pigment include extender pigments, titanium oxide pigments, iron oxide pigments, spinel pigments and the like.

In the present invention, it is desirable to select and use the type of pigment, the particle size, and the type of treatment depending on the purpose. In particular, organic fine particle pigments are desirable, except when hiding power is required for colored products. Furthermore, when high definition and transparency are desired, it is desirable to use a pigment finely divided by wet milling or dry milling such as salt milling. In that case, in consideration of nozzle clogging at the time of printing, pigments having a large particle size of more than 1.0 μm are removed, the organic pigment has an average particle size of 0.2 μm or less, and the inorganic pigment has an average particle size of 0.4 μm. It is desirable to use the following.

More specifically, examples of the above-mentioned pigments by color index (C.I.) numbers include C.I. 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. Further, these pigments may be used alone or in combination of two or more, and as a mixing method, mixing with a powder pigment, mixing with a paste pigment, mixing with a pigmentation is performed. 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. because of its color developability, dispersibility, and weather resistance. 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 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 is mentioned.

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

<Water-soluble solvent containing specific alkylene glycol alkyl ether>
In the case of a water-based inkjet ink, if water is the only solvent component, the ink will dry and cause clogging of the nozzles of the head. For this reason, a water-soluble high-boiling point solvent is also added as a moisturizer. The water-based inkjet ink of the present invention contains a water-soluble solvent, but its use is for a substrate to be printed, which has low penetrability of an ink that is not surface-treated, and thus the inkjet ink of the present invention. The water-soluble solvent constituting the ink for use not only functions as a moisturizing agent for the ink, but also has good wettability with respect to the substrate film, and preferably, it can also function as a leveling agent for the surface of the substrate to be printed, and It is preferable that is also capable of functioning as a film-forming aid that enhances the film-forming property of the binder resin contained in the ink.

The present inventors, as a result of diligent studies under the above recognition, showed that an alkylene glycol alkyl ether such as diethylene glycol monobutyl ether can exhibit any of the above functions when used in an aqueous inkjet ink, and a water-soluble solvent. It was found to be useful as That is, the alkylene glycol alkyl ether such as diethylene glycol monobutyl ether not only functions as a moisturizing agent for the ink, but also functions as a leveling agent because it has good wettability with respect to the film. Furthermore, since it also has a certain degree of dissolving power, it was found that, for example, for a polyvinyl chloride-based substrate to be printed, a slight dissolution of the polyvinyl chloride surface contributes to ink leveling and adhesion. Furthermore, as described below, it has been found that it can also function as a film-forming aid for the binder resin that constitutes the aqueous inkjet ink of the present invention. The methacrylic resin used as the binder resin in the present invention has a block structure composed of a hydrophobic polymer block containing a methacrylate monomer as a forming component and a hydrophilic polymer block containing 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, this particle portion needs to form a film, and for this reason, it enhances the film forming property of the binder resin, that is, it is a water-soluble material that can exhibit the function as a film forming aid. It is preferable that the ink contains a protic solvent.

The inventors of the present invention have conducted intensive studies in consideration of the above-described moisturizing property of ink, leveling property for a substrate to be printed, solubility for a substrate material, and improvement in film-forming property of a 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. 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 monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol Examples include monomethyl ether. More preferably, the boiling point is 200° C. or higher and 250° C. or lower, and examples thereof include 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 content of the above specific water-soluble solvent that constitutes the aqueous 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 mass% with respect to the total amount of ink. If it is less than 3% by mass, the ink tends to be dried, and the effect of imparting leveling to the base film is deteriorated, which is not preferable. On the other hand, if it is more than 30% by mass, the viscosity of the ink tends to be high, the ejection property of the ink tends to deteriorate, and the stability as the ink tends to deteriorate. In addition, in some cases, the binder resin in the ink may precipitate or the pigment may agglomerate, which is not preferable. Further, if the content is too large, the water-soluble solvent remains in the film of the printed image, which may cause blocking of the image film, or deteriorate the physical properties of the image such as water resistance and abrasion resistance. This is also not preferable from this point of view.

<water>
The water-based inkjet ink of the present invention contains water as an essential component. Water is used to dissolve and disperse other constituent components and to impart fluidity to the ink during inkjet printing. It is preferable to use ion-exchanged water, distilled water, purified water, or the like as the water used, from the viewpoint of not containing impurities such as ionic components. The content of water is preferably about 30 to 90 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 containing a methacrylate monomer as a constituent and a hydrophilic polymer block containing a methacrylate monomer containing methacrylic acid as a constituent. Methacrylic resin, which is a block copolymer, is contained as a binder component. Furthermore, in the block copolymer, the hydrophobic polymer block has at least benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA), dicyclopentamethacrylate. A monomer containing at least one selected from the group consisting of nyl methacrylate (DCPMA) is used as a forming component, and the acid value of the hydrophilic polymer block is 50 to 250 mgKOH/g.

The ink-jet ink of the present invention contains the methacrylic resin, which is the above-mentioned specific block copolymer, as a binder component, so that even when an image is formed on a substrate to be printed which is not surface-treated, Adhesion to the printing substrate is good. 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 unique hydrophobic polymer block and a unique hydrophilic polymer block, but according to the study by the present inventors, For example, by containing such a block copolymer as a binder component, the stability of various physical properties such as ink ejection properties, viscosity, particle size, etc. is significantly improved compared to the case where other binder resins are included. To do.

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

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, dicyclopentanyl methacrylate (these methacrylate groups). Is referred to as a monomer A), and a monomer containing at least one selected from the group A) is an essential component. As a result of studies by the present inventors, by including such a monomer A in a component for forming a methacrylic resin to be contained as a binder component, a substrate to be printed which is not surface-treated, for example, polyvinyl chloride. It was found that even when an ink image is formed on a base material or a polyolefin base material such as a polypropylene base material and a polyethylene base material, the adhesion of the formed ink image to the base material is enhanced. ..

In the methacrylic resin used in the present invention, a monomer containing a monomer A selected from the above-mentioned group of unique methacrylates is used as a component for forming the hydrophobic block, but other methacrylates may be added as necessary. It may be copolymerized. As the other methacrylate used at this time, a conventionally known methacrylate is used, and it 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 comprises a methacrylate-based monomer containing at least methacrylic acid as a forming component, there is no particular problem as long as 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.

The molecular weight of this hydrophobic block constituting the methacrylic resin used in the present invention is not particularly limited, but preferably the number average molecular weight is 5,000 to 70,000. When the number average molecular weight is 5,000 or more, the adhesiveness to the substrate is improved as the performance of the film formed by the methacrylic resin having such a hydrophobic block chain. Further, by setting the above-mentioned number average molecular weight to 70,000 or less, the viscosity of 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 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 containing a methacrylate-based 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, and the hydrophilic block chain is dissolved in water. The hydrophilic polymer block may be one in which methacrylic acid is used as a forming component, but a methacrylate-based monomer may be copolymerized within the range of the acid value described above. 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 above-mentioned hydrophobic polymer block from the number average molecular weight of the entire block copolymer, There is no limitation. It is preferably 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 the binder resin component may precipitate in the ink or aggregate. 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 property becomes poor. Therefore, the number average molecular weight of the hydrophilic polymer block constituting the methacrylic resin used in the present invention is preferably 1,000 to 20,000, more preferably 3,000 to 15,000.

The method for obtaining the methacrylic resin having the above-mentioned constitution used in the present invention is not particularly limited. However, since it is not possible to easily obtain a polymer having a finely designed block structure as described above by ordinary radical polymerization, it is preferable to use living radical polymerization. Any method may be used as long as it is living radical polymerization, such as NMP method using nitroxide, ATRP method utilizing redox of metal complex, RAFT method utilizing dithiocarboxylic acid ester, etc., method using cobalt catalyst, tellurium. Examples thereof include a TERP method using a compound, an 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.

There are no particular restrictions on these polymerization steps and manufacturing conditions such as post-treatment of the obtained polymer solution. Solution polymerization performed in any conventional organic solvent is preferred. In particular, considering the preparation of the ink to be performed thereafter, it is an essential constituent component of the water-based inkjet ink of the present invention, which also functions as the above-mentioned film-forming aid, and a specific alkylene glycol alkyl defined in the present invention. It is preferable to use ether as the 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 a binder component, which constitutes the aqueous inkjet ink of the present invention, can be 1 to 20% by mass as a solid content based on the total amount of the ink. A more preferable content range is 2 to 15 mass% with respect to the total amount of the ink. If it is less than 1% by mass, the function as a binder resin may not be sufficiently exhibited and the adhesion of the ink to the substrate to be printed tends to be insufficient, and if it exceeds 20% by mass, the viscosity of the ink will be high. However, this is not preferable because the ejection property of the ink may be impaired.

<Pigment dispersant>
A conventionally known pigment dispersant can be used as the pigment dispersant constituting the aqueous inkjet ink of the present invention. It may be a low molecular weight dispersant such as a surfactant, or an acrylic, styrene, methacrylic, ester, amide or polyether random copolymer, block copolymer, graft copolymer, gradient copolymer, star polymer. One or more polymer-type dispersants having a higher-order structure such as dendrimer and dendrimer can be used. More preferably, it comprises a block copolymer having a hydrophobic polymer block and a hydrophilic polymer block containing 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 impaired, 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 by weight can be used based on 100 parts by weight of the pigment.

<Alkali>
The aqueous inkjet ink of the present invention contains an alkali so as to neutralize the acidic groups of the methacrylic resin and the pigment dispersant and dissolve in water, or to adjust the pH of the ink. The following can be used as the alkali. 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 alcohols such as -, di- or tri-propanolamine, methylethanolamine, dimethylethanolamine and 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 content of the alkali is preferably such that the acid groups of the methacrylic resin or dispersant are partially or wholly neutralized. 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 pH of the ink can be used in such an amount range. It is not particularly limited. If the pH of the ink is lower than 7.0, the methacrylic resin contained in the water-based 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 and is difficult to handle.

<Other components>
As described above, the water-based inkjet ink of the present invention, as an essential component, 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, alkali, the above-mentioned. Although it contains a methacrylic resin having a specific constitution, as described below, in a preferred embodiment, a surfactant can be further contained as an additional constituent component. Furthermore, other water-soluble organic solvents and other additives can be blended according to the purpose.

(Surfactant)
The aqueous inkjet ink of the present invention may further contain a surfactant for the purpose of keeping the surface tension at a predetermined value. At that time, the preferable surface tension of the ink is 15 to 45 mN/m, and the particularly preferable surface tension is 20 to 40 mN/m. Examples of the surfactant preferably used in the present invention include silicone-based, acetylene glycol-based, fluorine-based, alkylene oxide-based, and hydrocarbon-based surfactants. Among these, fluorine-based surfactants are particularly preferably used. In general, the surfactant causes foaming, causes repellency on the film surface when ink is printed, and further causes the pigment to agglomerate. Therefore, it is preferable to suppress the addition amount as much as possible. Fluorine-based surfactants have the effect of lowering the surface tension with a small amount of addition as compared with other types of surfactants, and have the advantage that the amount added to the ink can be small. Specific examples thereof include hexafluoropropene-based and tetrafluoroethylene-based perfluoroalkyl-based and perfluoroalkenyl-based fluorine-based surfactants, with perfluoroalkyl-based surfactants being preferred.

The content of the fluorine-based surfactant used in the aqueous inkjet ink of the present invention can be within the 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 is more than 10,000 ppm, the surface tension of the ink is excessively lowered, and further it causes foaming, which is not preferable.

(Other additives)
In addition, a preservative, a water-soluble organic solvent, or the like can be added to the aqueous inkjet ink of the present invention, if necessary. As the preservative used in this case, for example, sodium benzoate, benzimidazole, thiabendazole, potassium sorbitate, sodium sorbitate, sodium dehydroacetate, thiazosulfamide, pyridinethiol oxide and siabendazole are effective. .. The content of the preservative used in the water-based inkjet ink of the present invention can be used in the range of 0.05 to 2.0% by mass based on the total mass of the ink, but the preferred range of the content is It is 0.1 to 1.0 mass %.

Further, the water-based inkjet ink of the present invention not only functions as a moisturizing agent for the above-mentioned ink, but also has good wettability with respect to the base film, and is preferably a leveling agent for the surface of the base material to be printed. In addition to the specific alkylene glycol alkyl ether defined in the present invention, which may also function as a film-forming aid that enhances the film-forming property of the binder resin contained in the ink, if necessary. 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, 1,4-dioxane, γ-butyrolactone, ethylene glycol allyl ether, polyethylene glycol, polypropylene glycol and the like can be mentioned.

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

When an image is formed 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. In the case of printing using a plurality of color inks, for example, full color printing can be performed by simultaneously using a black ink with the color inks of the three primary colors prepared as described above using different pigments. Further, when 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 vice versa, white ink is used. 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, which has low penetrability of ink that has not been subjected to surface treatment, and uses the aqueous inkjet ink of the present invention having the above-mentioned 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, in order to stably form a higher quality color print by the inkjet printing method on the substrate to be printed which has not been surface-treated, the surface treatment is not applied using the aqueous inkjet ink of the present invention. 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. And in that case, it is necessary to set the temperature of the substrate to be printed to 40 to 80°C, and it is preferable to set the temperature to 50 to 70°C. When the temperature is lower than 40° C., the water-based ink may be repelled on the surface of the substrate, and it becomes difficult to stably obtain a desired printed image of higher quality. On the other hand, when the base material 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. Designs, patterns, and the like for color printing can be converted into electronic data, and color printing can be performed by transmitting the electronic data to an inkjet printing apparatus, as is commonly done. Examples of the substrate to be used in the inkjet printing method of the present invention, which has a low permeation property of ink that has not been surface-treated, include, for example, a polyvinyl chloride-based substrate or a polypropylene-based substrate that is not surface-treated. Examples of the material include polyethylene base materials.

Next, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the polymerization method and 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 the documents of International Publication No. 2008/139980, International Publication No. 2009/136510, and International Publication No. 2010/027093. .. The outline of the manufacturing procedure is described below. A 1-liter separable flask was equipped with a stirring blade, a cooling pipe, a thermometer, and a nitrogen introducing pipe, and 350.5 parts of diethylene glycol monobutyl ether (hereinafter, abbreviated as BDG), 1.0 part of iodine, 2, 2' -Azobis(4-methoxy-2,4-dimethylvaleronitrile) (hereinafter, abbreviated as V-70) 3.7 parts, 0.1 parts 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 and stirred, and heated to 45°C.

After 2 hours, the brown color of iodine disappeared, and during this period, it was confirmed that the polymerization initiator V-70 reacted with iodine to become a polymerization initiation compound which was 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 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 11,200, and the dispersity was 1.19. Hereinafter, the molecular weight is a value measured by a GPC differential refractive index detector using a THF solvent as a developing solvent. In this way, a block copolymer of A (hereinafter sometimes abbreviated as A chain) was obtained.

Next, after the polymer block solution of A obtained above was cooled 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, the mixture was polymerized 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, 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. It 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 mg KOH/g

It was confirmed that this polymer solution had a solid content of 50.0% and a polymerization rate of almost 100%. The Mn was 17500 and the dispersity 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 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 was calculated as Mn=6300. Furthermore, after diluting the sampled product with toluene and ethanol, acid-base titration using a 0.1% ethanolic potassium hydroxide solution with a phenolphthalein solution as an indicator was carried out to measure the actual acid content of the AB block copolymer. I asked for a price. As a result, the actually measured acid value was 43.0 mgKOH/g. In addition, hereinafter, the actually measured acid value is a value calculated by performing the same operation as above. Hereinafter, the AB block copolymer will be referred to as methacrylic resin-1.

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

(Synthesis example-5: Methacrylic resin-5)
A resin was synthesized in the same manner as in Synthesis Example 1 except that half of DCPMA was replaced with lauryl methacrylate (hereinafter, abbreviated as LMA). The resin thus obtained was designated as methacrylic resin-5.

(Synthesis example-6: Methacrylic resin-6)
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 resin thus obtained was designated as methacrylic resin-6.

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

The 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)
A resin was synthesized in the same manner as in Synthesis Example 1 except that the IBMA of Synthesis Example 1 was changed to BzMA, that is, the A chain was composed of BzMA only. The obtained resin was designated as methacrylic resin-9, and its 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, 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 another 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 Mn was 12600 and PDI was 2.15. The acid value was also 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)
Ion-exchanged water (675 parts by mass), diethylene glycol monobutyl ether (50 parts by mass), and as a pigment dispersant, styrene/methyl methacrylate/lauryl methacrylate/2-hydroxyethyl methacrylate/methacrylic acid (30/20/20/15/15 parts by 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, and C.I. I. Pigment Red 122 (manufactured by Dainichiseika 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.

A zirconia bead having a diameter of 1 mm was used as a dispersion medium, and this mixture was 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 liquid. Furthermore, this pigment dispersion liquid is subjected to a centrifugal separation treatment (7500 rotations, 20 minutes), then filtered through a 10 μm membrane filter to remove coarse particles, and adjusted with ion-exchanged water to give a red pigment having a pigment concentration of 14%. A water-based pigment dispersion of was obtained.

Next, 520.8 parts of ion-exchanged water and 1.4 parts of ammonia water were mixed in another container to homogenize, and 76.8 parts of methacrylic resin-1 obtained in Synthesis Example 1 was added while stirring with a disper. Then, 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 ammonia water, 30 parts by mass of a 1% aqueous solution of Surflon S-211 (trade name, manufactured by Asahi Glass Co., Ltd.), which is a fluorosurfactant, of the red color previously prepared 250 parts of the aqueous pigment dispersion was added to make a total of 1000 parts by mass. Then, after stirring for 10 minutes, coarse particles were removed by filtration with a 5 μm membrane filter to obtain a red inkjet ink-1. The viscosity of the obtained red inkjet ink-1 was 3.53 mPa·s at 25°C. Other physical property values of the red inkjet ink-1 are shown in Table 4.

(Production Examples 2 to 4: Inkjet inks 2 to 4 of Examples 2 to 4)
C. used in Production Example 1 I. Pigment Red 122 (manufactured by Dainichiseika Kogyo Co., Ltd.) was added to C.I. I. Pigment Blue 15:3 (manufactured by Dainichiseika Kogyo KK), C.I. I. Pigment Yellow 155 (manufactured by Clariant Japan), C.I. I. Pigment Black 7 (Degussa), except that blue inkjet ink (viscosity is 3.22 mPa·s at 25° C.) and yellow inkjet ink (viscosity at 25° C.) were the same as in Production Example 1. 3.90 mPa·s) and a black inkjet ink (viscosity at 25° C. was 3.10 mPa·s) were obtained. Other physical property values of the inkjet inks of each of these colors are shown in Table 4.

(Production Example 5: White inkjet ink of Example 5)
To 271 parts by mass of ion-exchanged water and 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 parts by mass) 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, and C.I. 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.

A zirconia bead having a diameter of 1 mm was used as a dispersion medium, and this mixture was 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 liquid. Then, the mixture was filtered through a 10 μm membrane filter to remove coarse particles to obtain a white aqueous pigment dispersion liquid having a pigment concentration of 50%.

Next, 577 parts of ion-exchanged water and 3 parts of ammonia water were mixed in another container to homogenize, and 90 parts of methacrylic resin-1 obtained in Synthesis Example 1 was added while stirring with a disper to prepare a methacrylic resin of 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, and 180 parts of the white aqueous pigment dispersion liquid previously prepared were added, and the total amount was 1000 parts by mass. And Then, after stirring for 10 minutes, coarse particles were removed by filtering with 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. Other physical property values of the obtained white inkjet ink are shown in Table 4.

(Production Example 6: Red inkjet ink-2 of Example 6)
A styrene/methyl methacrylate/lauryl methacrylate/2-hydroxyethyl methacrylate/methacrylic acid (30/20/20/15/15 mass ratio) copolymer that is a pigment dispersant used in Production Example 1 (number average). An inkjet ink was prepared 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 15000). It was This is 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 collectively shows the physical properties of the inkjet inks of each color of Examples 1 to 6.

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

(Production Examples 15 to 17: Red inks of Examples 15 to 17 -11 to -13)
A red inkjet ink was prepared in the same manner as in Production Example 1 except that the diethylene glycol monobutyl ether used in the ink formulation of Production Example 1 was changed to diethylene glycol monoisobutyl ether, and the obtained ink was designated as Red Ink-11. did. In addition, a red ink jet ink obtained in the same manner as in Production Example 1 except that triethylene glycol dimethyl ether was used was Red Ink-12 and the same 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. They are collectively shown in Table 6. The pigment dispersants used were all the same as those used in Production Example 1.

(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 the ethylene glycol monobutyl ether (boiling point 171° C.) was used instead of the diethylene glycol monobutyl ether (boiling point 230° C.) used in the ink formulation of Production Example 1. The obtained ink was used as a comparative red ink 2. Further, a red inkjet ink obtained in the same manner as in Production Example 1 except that ethylene glycol was used was set as Comparative Red Ink 3. The physical properties of comparative red inks 2 and 3 are summarized in Table 6.

(Examples 18 to 27: inkjet printing method)
Using each of the red inks -1 to -10 of the examples shown in Table 7 and using an inkjet printer equipped with a plate heater [MMP825H (trade name) manufactured by MasterMind Co., Ltd.] as follows: The image was printed by an inkjet recording method. Specifically, a surface-treated polyvinyl chloride film [Control Tuck 180-10 (trade name), manufactured by 3M, abbreviated as "PVC"] is preliminarily heated with a plate heater to a surface temperature of 50°C. Printed after heating to. 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, with respect to the images obtained by the printing methods of Examples 18 to 27, the adhesion was confirmed by a cellophane tape peeling test. As a method, after printing, the printed matter was sufficiently dried with a dryer, Cellotape (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 the following criteria evaluated.
◎: No peeling at all ○: Slight peeling at Δ: Smaller peeling area ×: Larger peeling area

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. It is considered that this is because the methacrylic resin of the present invention was used as the 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, vinyl chloride that had not been surface-treated was used as the substrate to be printed, and the surface temperature was heated to 50° C. before inkjet. Printed. As a result, with the printing method of Comparative Example 4, streaks were formed and a good printed matter could not be obtained. The reason is that in the comparative red ink-1 of the water-based inkjet ink of Comparative Example 1 used in the printing method of this Comparative Example, a random type polymer is used for the methacrylic resin added as a binder, and when discharging, It is considered that this is because the droplets splash and the dischargeability is poor. Further, 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)
Printing was performed in the same manner as in Example 19 using Red Ink-2, 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 was repelled on the surface of the polyvinyl chloride film, the leveling was not sufficiently performed, and the result of the cellophane tape peeling test was also inferior in adhesiveness, 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 was effective to preheat the substrate to be printed.

(Examples 28 to 30: inkjet printing method)
Inkjet printing was performed in the same manner as in Example 18 except that Red Ink-1 used in Example 18 was changed to Red Inks -11 to -13, respectively. As a result, in each 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, was fast, and the ink was dried quickly, causing nozzle clogging. The dischargeability was poor. The leveling property and the adhesion of the obtained image were also poor. Further, in Comparative Example 7, although the ejection property was good, the ink was repelled on the vinyl chloride surface due to the weak dissolving power of ethylene glycol, which is a water-soluble solvent, and the leveling property was poor.

(Example 31: inkjet printing method)
Full-color printing was performed using the five color inks of Examples 1 to 5, and printing was performed in the same manner as in Example 18 and evaluated. As a result, the ink dischargeability, leveling property, and adhesion of the obtained image were evaluated. It was good.

(Examples 32 to 41: inkjet printing method)
Inkjet recording was carried out as follows using the inkjet printers with plate heaters [MMP825H (trade name) manufactured by Mastermind Co., Ltd.] using the red inkjet inks -1 to -10 of the examples. The image was printed by the method. Specifically, a polypropylene film (Yupo 80 (UV) KV11 (trade name), manufactured by Lintec Co., abbreviated as “PP”) that has not been surface-treated is preliminarily heated to a surface temperature of 50° C. by a plate heater. Printed after heating. As a result, with the printing methods of Examples 32 to 41, good ejection properties and leveling properties were achieved.

Next, the same cellophane tape peeling test as that performed previously was performed on the images obtained by the printing methods of Examples 32 to 41, respectively. As a result, the images obtained by the printing method of the examples using the inkjet inks of the examples 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 the respective inks in which the methacrylic resin containing TBCHMA as a forming component was used as the binder resin were completely peeled off in the image. I didn't.

(Comparative Example 8: inkjet printing method)
Except for using Comparative Red Ink-1, the same printing method as in Examples 32 to 41 was performed using PP that was not surface-treated as a printing substrate, and the surface temperature was heated to 50°C. Then, inkjet printing was performed. As a result, with the printing method of Comparative Example 8, streaks were generated and a good printed matter could not be obtained. The reason is that in the comparative red ink-1, the water-based inkjet ink uses a random polymer in the methacrylic resin added as a binder, and droplets splash during ejection, resulting in poor ejection properties. it is conceivable that. Further, 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, some peeling was observed, and the adhesiveness was slightly inferior to that of the example.

(Comparative Example 9: inkjet printing method)
In Example 34 using Red Ink-3, inkjet printing was performed in the same manner as in Example 34 except that the polypropylene film used as the printing substrate was not heated and the surface temperature was 25°C. As a result, the ink was repelled on the surface of the polypropylene film, the leveling was not sufficiently performed, and a good image could not be printed. Further, the result of the cellophane tape peeling test of the obtained image was also inferior in adhesiveness. From the 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)
Full-color printing was performed using the five color inks of Examples 1 to 5, and printing was performed in the same manner as in Example 32, and evaluation was made that ink discharge properties, leveling properties, and adhesion of the obtained images 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 inkjet printer with a plate heater as described above, using the red aqueous inkjet inks -1 to -10. Specifically, a polyethylene film (LDPE film, 30 μm, manufactured by Takigawa, abbreviated as “PE”) which has not been surface-treated is preliminarily heated with a plate heater to a surface temperature of 50° C., and then printed. .. As a result, good images could be printed by the printing methods of Examples 43 to 52.

Then, with respect to the images obtained by the printing methods of Examples 43 to 52, the same cellophane tape peeling test as that performed previously was performed, and it was obtained by the printing method of Examples using the inkjet inks of Examples. All the obtained images showed almost no peeling. In particular, as shown in Table 9, the images obtained by the printing methods of Examples 45 and 49 to 51 using the respective inks using the methacrylic resin containing TBCHMA as the forming component as the binder resin were completely peeled off in the image. I didn't.

(Comparative Example 10: inkjet printing method)
Using Red Comparative Ink-1, in the same manner as in the printing method of Examples 43 to 52, PE not surface-treated was used as a substrate to be printed, and the surface temperature was heated to 50° C. Inkjet printed. As a result, with the method using the water-based inkjet ink of Comparative Example 1, streaks occurred and a good printed matter could not be obtained. It is considered that the reason is that a random polymer is used for the methacrylic resin, there is a splash, and the dischargeability is poor. Further, when the obtained image was subjected to a cellophane tape peeling test in the same manner as described above, some peeling was observed in the image, and the adhesiveness was slightly inferior to that of the example.

(Comparative Example 11: inkjet printing method)
Inkjet printing was carried out 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 in Example 45 using Red Ink-3. As a result, the ink was repelled on the surface of the polyethylene film, the leveling was not sufficiently performed, and a good image could not be printed. Further, the result of the cellophane tape peeling test of the obtained image was also inferior in adhesiveness. 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 preheat the substrate to be printed.

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

According to the present invention, an excellent color tone is exhibited on a polyvinyl chloride-based substrate that has not been surface-treated, or a polypropylene-based substrate that has not been surface-treated, or a polyethylene-based substrate that has not been surface-treated. At the same time, it is possible to provide a water-based inkjet ink capable of developing a clear color printed image having a desired color and having good adhesion, and thus it is expected to be widely used.

Claims (8)

A binder resin used in a water-based inkjet ink for forming a color print image on a substrate to be printed, which has low permeability of ink that has not been surface-treated,
Contains methacrylic resin,
The methacrylic resin is a block copolymer comprising a hydrophobic polymer block and a hydrophilic polymer block containing a methacrylate monomer containing methacrylic acid as a forming component,
The hydrophobic polymer block is selected from the group consisting of benzyl methacrylate (BzMA), isobutyl methacrylate (IBMA), t-butylcyclohexyl methacrylate (TBCHMA), dicyclopentenyloxyethyl methacrylate (DCPOEMA) and dicyclopentanyl methacrylate (DCPMA). A monomer containing at least one selected monomer A as a forming component, and
The binder resin, wherein the hydrophilic polymer block has an acid value of 50 to 250 mgKOH/g. The binder resin according to claim 1, wherein the amount of the monomer A in the component for forming the hydrophobic polymer block is 50% by mass or more. The number average molecular weight of the said hydrophobic polymer block is 5,000-70000, The binder resin of Claim 1 or 2. The number average molecular weight of the said hydrophilic polymer block is 1000-20000, The binder resin of any one of Claims 1-3. The binder resin according to any one of claims 1 to 4, wherein a content of the methacrylic resin is within a range of 1 to 20% by mass as a solid content with respect to a total amount of the aqueous inkjet ink. The binder resin according to any one of claims 1 to 5, wherein the base material to be printed is a polyvinyl chloride base material, a polypropylene base material, or a polyethylene base material. The said water-based inkjet ink is for forming a color printing image on the said to-be-printed base material in the state which surface temperature was heated to 40-80 degreeC, The any one of Claims 1-6. Binder resin. The binder resin according to any one of claims 1 to 7, wherein the aqueous inkjet ink contains a water-soluble solvent containing an alkylene glycol alkyl ether in which an alkyl group has 1 to 12 carbon atoms.