JP7569663B2 - Water-based inkjet inks and ink sets - Google Patents

Description

The present invention relates to aqueous inkjet inks and ink sets.

Inkjet recording systems are printing systems that spray highly fluid liquid ink from minute nozzles and deposit it onto a substrate to perform printing. This system has recently become increasingly popular due to its features of being able to print high-resolution, high-quality images at high speed and with little noise using relatively inexpensive equipment.
Water-based inks are widely used because they can produce high-quality prints at low cost. Water-based inks have an increased drying time due to their water content, and also have the advantage of being environmentally friendly.

In recent years, inkjet recording systems have been used not only on paper media such as plain paper and specialty paper, but also on textiles where the ink tends to spread along the fibers, nonwoven fabrics such as felt, wood materials, functional porous materials where the functionality is expressed by the pores in the substrate, and even on plastic substrates, synthetic paper, metal substrates, glass substrates, etc. where the ink does not easily penetrate. In order to perform high-quality printing on such a variety of substrates, in addition to high image quality, high durability is required, especially in the case of substrates used for various building materials, furniture, daily necessities, etc.

There is a method of forming a printed image and then coating it with an overcoat layer containing a highly durable resin to impart durability to the printed matter (Patent Document 1).
Furthermore, Patent Document 2 discloses a coated metal sheet in which a color coating film, a print layer, and a clear coating film are provided on a metal sheet, and the clear coating film contains a specific polyester resin.

Substrates used for building materials, furniture, daily necessities, etc. are more expensive than general paper and may have a very large surface area, so the occurrence of defective products due to poor ejection during inkjet printing has a significant impact on costs. Therefore, higher ejection reliability is required than in normal printing methods used for paper, etc.
In order to prevent ejection failures in inkjet printing, printers are usually equipped with a maintenance mechanism. In particular, ink may gradually adhere to the area around the nozzles of the inkjet head during continuous printing. If ink stains around the nozzles become noticeable, the ink may not be able to shoot straight from the nozzles, or foreign matter may adhere to the ink stains and enter the head through the nozzles, causing the nozzles to become clogged.

One method of maintenance is to wipe off the ink adhering to the nozzle surface, but since wiping with a dry member may damage the nozzle plate, another method is to wipe it off with a cleaning liquid. Patent Document 3 proposes an inkjet head cleaning liquid containing a solvent with a surface tension of less than 35 mN/m and a basic compound as a cleaning liquid for aqueous pigment inkjet printers.

JP 2013-163370 A JP 2008-149584 A JP 2009-233911 A

Although the method of coating an overcoat layer is effective, if the strength and durability of the ink coating film itself is low, the amount of resin in the overcoat layer becomes very large. As a result, a fairly thick resin film is formed on the substrate, which causes a problem of losing the texture that the substrate originally has. Furthermore, when a functional substrate is used, there is a problem that an excessive overcoat layer reduces the original function of the functional substrate.
In addition, it is desirable that the ink coating film on the substrate has flexibility. In the case of deformable substrates such as paper media, woven fabrics, and nonwoven fabrics, it is desirable that the ink coating film should deform in accordance with the deformation of the substrate, and that cracks should not occur in the ink coating film. In addition, there are applications in which the printed portion is subjected to processing such as bending, and it is also important to ensure the image quality of the processed portion. When the portion to which the overcoat layer is applied is bent, the resin film may crack due to the large amount of resin, and so-called whitening may be observed.

In addition, because water-based inks are environmentally friendly, they are expected to be applied to a variety of substrates. However, the technology of blending a resin component into water-based ink and then forming the resin component in the water-based ink into a coating on a substrate requires appropriate control of the dispersibility of the resin in water and the ease with which the resin spreads on the substrate, and further improvements are expected.

In the cleaning solution proposed in Reference 3, the basic compound may be effective in redissolving or redispersing the acid component-containing resin used in the ink, but depending on the combination with the resin and the amount used, it may actually make the ink less stable when mixed with the ink, causing the thickened mixture and foreign matter to contaminate the area around the nozzle, resulting in a loss of ejection reliability such as image uniformity and continuous ejection. It is also important to consider the combination of the maintenance liquid with the ink, and it is desirable for the cleaning efficiency to be good even when mixed with the ink, for example when it has dried and become concentrated.

One object of the present invention is to provide an aqueous inkjet ink capable of producing printed matter having excellent durability and processability of printed images.

One aspect of the present invention is an aqueous inkjet ink comprising a water-dispersible polyether-type aliphatic urethane resin (A), a water-dispersible (meth)acrylic resin (B), an acetylene glycol surfactant (C) having an HLB value of 10.0 or less, a colorant, and water.
Another aspect of the present invention is an ink set comprising the above-mentioned aqueous inkjet ink, and a maintenance liquid containing an acetylene glycol-based surfactant (C') having an HLB value of 10.0 or less, and glycerin in an amount of 30% by mass or more relative to the total amount of the maintenance liquid.

According to one embodiment of the present invention, it is possible to provide an aqueous inkjet ink capable of forming printed matter having excellent durability and processability of the printed image.

The present invention will be described below using one embodiment. The examples in the following embodiment do not limit the present invention.

"Water-based inkjet ink"
An aqueous inkjet ink according to one embodiment (hereinafter, may be simply referred to as ink or aqueous ink) is characterized by comprising a water-dispersible polyether-type aliphatic urethane resin (A), a water-dispersible (meth)acrylic resin (B), an acetylene glycol surfactant (C) having an HLB value of 10.0 or less, a colorant, and water.
According to one embodiment, it is possible to provide a printed matter having excellent durability and processability of a printed image. Also, according to one embodiment, it is possible to provide a printed matter having excellent image quality of a printed image.
Hereinafter, the water-dispersible polyether-type aliphatic urethane resin (A) will also be referred to as urethane resin (A), the water-dispersible (meth)acrylic resin will also be referred to as (meth)acrylic resin (B), and the acetylene glycol surfactant (C) having an HLB value of 10.0 or less will also be referred to as surfactant (C).

In one embodiment, the ink uses a combination of a polyether-type aliphatic urethane resin (A) having flexibility and a (meth)acrylic resin (B) having hardness, and further uses an acetylene glycol surfactant (C) having a low HLB value that has high wettability and easily swells the urethane resin (A) in the ink, so that the ink coating film uniformly covers the substrate after printing and drying, and an ink coating film having excellent durability and processability can be formed. Since the ink coating film has excellent durability and processability, even when processing such as bending is performed after the ink coating film is formed, the occurrence of cracks or whitening in the processed parts can be suppressed. In addition, the durability of the ink coating film after processing can be increased.
One of the reasons will be explained below, but the following reason is not restrictive.
According to one embodiment, the ink contains both the polyether-type aliphatic urethane resin (A), which has flexibility, and the (meth)acrylic resin (B), which has hardness, thereby making it possible to improve the durability and processability of the ink coating film.
By including the urethane resin (A) and the surfactant (C) having a low HLB value that swells the urethane resin (A) in the ink, when the ink coating is dried and formed after printing, the surfactant (C) is concentrated while the water evaporates on the substrate, and the swelling of the urethane resin (A) progresses, making it easier to form a film, forming a stronger ink coating film, and improving the durability of the ink coating film. In addition, since the urethane resin (A) has flexibility, the processability of the ink coating film can be improved. As a surfactant that easily swells the polyether-type aliphatic urethane resin (A), an acetylene glycol-based surfactant having an HLB value of 10.0 or less and showing a low HLB value can be preferably used.

In addition, the polyether-type aliphatic urethane resin (A) can impart a good balance of durability and processability to the ink coating. In addition, this urethane resin (A) can prevent yellowing and deterioration of the ink coating, allowing the formation of an ink coating with higher image quality.

The ink according to one embodiment may include a water-dispersible polyether-type aliphatic urethane resin (A).
Since the urethane resin (A) exhibits water dispersibility, it can be dispersed in water in particulate form without dissolving in water to form an oil-in-water (O/W) type resin emulsion. The urethane resin (A) is preferably contained in the ink in a dispersed state as resin particles.
The urethane resin (A) may be any of anionic resin, cationic resin, amphoteric resin, and nonionic resin. Since many coloring materials suitable for aqueous inks have anionic surface charges when dispersed in water, anionic resins, amphoteric resins, and nonionic resins can be preferably used in consideration of the stability of the coloring material in water.
The water-dispersible urethane-based resin (A) may be a resin in which functional groups are present on the surface of the resin particles, such as a self-emulsifying resin, or may be a resin that has been subjected to a surface treatment, such as by attaching a dispersant to the surface of the resin particles.

The urethane resin (A) has an aliphatic urethane skeleton and is preferably a polyether-type aliphatic urethane resin containing an ether bond in the main chain in addition to the aliphatic urethane skeleton.
As the urethane-based resin (A), a reaction product of an aliphatic polyisocyanate and a polyether polyol can be used.

As the aliphatic polyisocyanate, an aliphatic polyisocyanate compound having two or more isocyanate groups in one molecule can be used, and an aliphatic diisocyanate is preferred.
In the urethane-based resin (A), when the urethane skeleton portion is an aliphatic urethane skeleton, more preferably when the urethane skeleton portion is derived from an aliphatic diisocyanate and is chain-like, the strength of the ink coating film can be further increased, and the flexibility of the ink coating film can be further increased, and the durability of the ink coating film can be further increased, and the processability of the ink coating film can be further increased.
In addition, when a urethane-based resin (A) synthesized from an aliphatic polyisocyanate is used, yellowing of the urethane-based resin itself can be prevented, the resin film becomes more transparent, and the color development of the water-based ink can be further improved.

Specific examples of aliphatic polyisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, isophorone diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane.
These may be used alone or in combination of two or more.

As the polyether polyol, a polyether compound having two or more hydroxyl groups in one molecule can be used, preferably a chain-like polyether compound having two or more hydroxyl groups, and more preferably a polyether diol.
In the urethane-based resin (A), when the ether bond is a chain-like ether bond, more preferably when the ether bond is a chain-like ether bond derived from a polyether diol, the strength of the ink coating film can be further increased, and the flexibility of the ink coating film can be further increased, and the durability of the ink coating film can be further increased, and the processability of the ink coating film can be further increased.
Furthermore, when a urethane-based resin (A) synthesized from a polyether polyol is used, the ether portion is not affected by hydrolysis, and therefore the water resistance of the ink coating can be further improved.
On the other hand, when a urethane resin synthesized from a polyester polyol is used, the ester moiety is hydrolyzed, which may result in deterioration of the image quality, durability, and processability of the ink coating film, whereas when a urethane resin synthesized from a polycarbonate polyol is used, it may be possible to form an ink coating film with high durability, but sufficient processability may not be obtained.

Specific examples of polyether polyols include polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether polyol; and polyether polyols obtained by addition polymerization of ethylene oxide, propylene oxide, or the like to low molecular weight polyols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, and tripropylene glycol.
These may be used alone or in combination of two or more.

When a test piece of the urethane resin (A) made of a dried film of the water-dispersible polyether-type aliphatic urethane resin (A) is immersed in the surfactant to be blended in the ink and removed after 12 hours, it is preferable that the swelling rate based on mass from before immersion is 10% or more and 100% or less.

The swelling ratio of the urethane resin (A) is a value determined by measurement according to the following procedure.
In the combination of the urethane resin (A) and the surfactant blended in the ink to be measured, the mass ratio of the urethane resin (A) swelling is obtained when the urethane resin (A) is immersed in the surfactant. When the ink to be measured contains two or more urethane resins, the mass ratio of the two or more urethane resins (A) is mixed with the blending ratio in the ink and used in the measurement of the swelling ratio. Similarly, when the ink to be measured contains two or more surfactants, the mass ratio of the two or more surfactants is mixed with the blending ratio in the ink and used in the measurement of the swelling ratio. When the ink to be measured contains other surfactants other than the acetylene glycol surfactant (C) having an HLB value of 10.0 or less, the surfactant (C) is mixed with the other surfactants and used in the measurement of the swelling ratio.
The urethane resin (A) has a plurality of ether bonds in its structure. In addition, the surfactant enters the gaps in the resin's network structure, causing the resin to swell. Therefore, the swelling ratio can be controlled by adjusting the crystallinity of the urethane resin (A), the molecular weight and amount of ether bonds in the surfactant, the difference in solubility parameters between the urethane resin (A) and the surfactant, and the like.

Specifically, the urethane resin (A) used in the ink to be measured or its resin emulsion is dried at 100°C to thoroughly evaporate the water, thereby obtaining a dry film of the urethane resin (A). After measuring the mass of the test piece that has become a dry film, the test piece is immersed in the surfactant used in the ink to be measured, and after being held for 12 hours, it is removed, the surfactant on the surface of the test piece is wiped off, and the mass of the test piece is measured. The swelling ratio can be calculated from the following formula:
Swelling ratio [%]={((mass of test piece after immersion)−(mass of test piece before immersion))/(mass of test piece before immersion)}×100

The swelling ratio of the urethane resin (A) may be from 0 to 150%, preferably from 10 to 100%, more preferably from 20 to 80%, and further preferably from 30 to 60%.
The swelling ratio of the urethane resin (A) is preferably 10% or more, more preferably 20% or more, and even more preferably 30% or more, so that in the ink coating, the urethane resin (A) is appropriately softened by the action of the surfactant, and the ink coating can be imparted with greater flexibility and the processability of the ink coating can be further improved.
The swelling ratio of the urethane resin (A) is preferably 100% or less, more preferably 80% or less, and even more preferably 60% or less, which prevents the urethane resin (A) from becoming too soft due to the action of the surfactant in the ink coating film, thereby further increasing the strength of the ink coating film and further increasing the durability of the ink coating film.

The urethane resin (A) is preferably a resin that forms a transparent coating film on the substrate. This reduces the effect on the color development of the water-based ink. By using a polyether-based aliphatic urethane resin as the urethane resin (A), yellowing and deterioration of the resin during the heat treatment in the ink coating film formation can be prevented, and the color development of the water-based ink can be further improved.

The weight average molecular weight (Mw) of the urethane resin (A) is not particularly limited, but is preferably 10,000 to 100,000, and more preferably 15,000 to 80,000. Here, the weight average molecular weight of the resin is a value calculated using the gel permeation chromatography (GPC) method in terms of polystyrene. The same applies hereinafter unless otherwise specified.

The urethane resin (A) can be blended in the ink as an oil-in-water (O/W) type resin emulsion that becomes particulate in the ink, and it is preferable that the urethane resin (A) becomes particulate in the ink.
The average particle size of the resin particles in the ink of the urethane resin (A) may be any size suitable for inkjet printing, and is generally preferably 300 nm or less. From the viewpoints of the ejection properties and storage stability of the ink, this average particle size is more preferably 250 nm or less, even more preferably 200 nm or less, and even more preferably 150 nm or less. Furthermore, when a pigment is used as the coloring material, from the viewpoint of further increasing the binding strength between the pigment particles, it is preferable that the average particle size of the resin particles is smaller than the average particle size of the pigment (generally about 80 to 200 nm).
The lower limit of the average particle size of the resin particles of the urethane resin (A) in the ink is not particularly limited, but from the viewpoint of the storage stability of the ink, it is preferably 5 nm or more, and more preferably 10 nm or more.

In this specification, unless otherwise specified, the average particle size is the volume-based particle size value (median size) in the particle size distribution measured by dynamic light scattering. A nanoparticle analyzer nanoPartica SZ-100 (Horiba, Ltd.) or the like can be used as a dynamic light scattering type particle size distribution measuring device.

Commercially available resin emulsions of urethane resin (A) include, for example, "Takelac W-5661, W-6020" manufactured by Mitsui Chemicals, Inc., "Permarin UA-200" manufactured by Sanyo Chemical Industries, Ltd., "Superflex 130", "Superflex 870", and "Superflex E-4800" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "Adeka Bontitor HUX-350" and "Adeka Bontitor HUX-550" manufactured by Adeka Corporation, and "WBR-016U" manufactured by Taisei Fine Chemical Co., Ltd. (all trade names).

The urethane resin (A) may have a solid content of 0.1 to 15% by mass, or 1 to 10% by mass, based on the total amount of the ink. The urethane resin (A) has a solid content of preferably 3 to 8% by mass, or more preferably 3 to 5% by mass, based on the total amount of the ink.
The solid content of the urethane resin (A) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 3% by mass or more, based on the total amount of the ink. The urethane resin (A) alone tends to have a lower film strength than the (meth)acrylic resin (B), but the strength of the ink coating can be increased by the interaction between the urethane resin (A) and the (meth)acrylic resin (B), and the durability of the ink coating can be improved. In addition, by including a larger amount of the urethane resin (A), the flexibility of the ink coating can be increased. As a result, when the ink coating part of the printed matter is bent or processed, the ink coating can be flexibly deformed along the processed shape, and cracking and whitening at the processed part can be prevented.
The solid content of the urethane resin (A) is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and even more preferably 5% by mass or less, based on the total amount of the ink. By having the amount of the urethane resin (A) in this range, the amount of the resin content in the ink can be appropriately limited while maintaining an appropriate blending balance with the (meth)acrylic resin (B), and an increase in the viscosity of the ink can be further prevented, and the ejection properties of the ink can be further improved.

The solid content mass ratio of the urethane resin (A) to the colorant is preferably 0.5 to 10, more preferably 1 to 8, and even more preferably 1.5 to 2.

The ink according to one embodiment may include a water-dispersible (meth)acrylic resin (B).
Here, the (meth)acrylic resin means a polymer containing at least a methacrylic unit, an acrylic unit, or a combination thereof.

Since the (meth)acrylic resin (B) exhibits water dispersibility, it can be dispersed in water in particulate form without dissolving in water to form an oil-in-water (O/W) type resin emulsion. The (meth)acrylic resin (B) is preferably contained in the ink in a dispersed state as resin particles.
The (meth)acrylic resin (B) may be any of anionic resin, cationic resin, amphoteric resin, and nonionic resin. Since many coloring materials suitable for aqueous inks have anionic surface charges, particularly when dispersed in water, anionic resins, amphoteric resins, and nonionic resins can be preferably used in consideration of the stability of the coloring material in water.
The water-dispersible (meth)acrylic resin (B) may be a resin in which a functional group is present on the surface of the resin particles, such as a self-emulsifying resin, or may be a resin that has been subjected to a surface treatment, such as by attaching a dispersant to the surface of the resin particles.

The (meth)acrylic resin (B) is preferably a polymer containing a unit derived from a (meth)acrylic monomer. The (meth)acrylic resin (B) may contain a unit derived from another monomer together with the unit derived from the (meth)acrylic monomer.
Examples of (meth)acrylic monomers include acrylic acid, methacrylic acid, acrylate, methacrylate, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, and derivatives thereof, etc. These may be used alone or in combination of two or more.
Examples of other units include a styrene unit, a vinyl acetate unit, a vinyl chloride unit, etc. These may be used alone or in combination of two or more.
Examples of the (meth)acrylic resin (B) include a (meth)acrylic polymer, a styrene-(meth)acrylic copolymer, a vinyl acetate-(meth)acrylic copolymer, a vinyl chloride-(meth)acrylic copolymer, or a combination thereof, etc. Preferred are a (meth)acrylic polymer, a styrene-(meth)acrylic copolymer, or a combination thereof.

It is preferable that the (meth)acrylic resin (B) is a resin that forms a transparent coating film on the substrate. This reduces the effect on the color development of the water-based ink.

The weight average molecular weight (Mw) of the (meth)acrylic resin (B) is not particularly limited, but is preferably 1,000 to 100,000, and more preferably 5,000 to 80,000.

The (meth)acrylic resin (B) can be blended in the ink as an oil-in-water (O/W) type resin emulsion that becomes particulate in the ink, and it is preferable that the (meth)acrylic resin (B) becomes particulate in the ink.
The average particle size of the resin particles of the (meth)acrylic resin (B) in the ink may be any size suitable for inkjet printing, and is preferably in the same numerical range as that of the urethane resin (A) described above.

Commercially available resin emulsions of (meth)acrylic resin (B) include, for example, "Mowinyl 9780, 727, 745" and "Mowinyl 966A, 940" manufactured by Nippon Synthetic Chemical Industry Co., Ltd.; "Joncryl 7100, PDX-7370, PDX-7341" manufactured by BASF; "Boncoat EC-905EF, 5400EF, CG-8400" manufactured by DIC Corporation; "NeoCryl A-1125", "NeoCryl A-1127", "NeoCryl A-6069", "NeoCryl A-1092", and "NeoCryl A-2092" manufactured by DSM (all trade names).

The (meth)acrylic resin (B) may have a solid content of 0.1 to 15% by mass, or 1 to 10% by mass, based on the total amount of the ink. The (meth)acrylic resin (B) has a solid content of preferably 1 to 8% by mass, or more preferably 2 to 5% by mass, based on the total amount of the ink.
The (meth)acrylic resin (B) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, in terms of solid content, relative to the total amount of the ink. By including the (meth)acrylic resin (B) in this range, the strength of the ink coating film can be further increased, and the durability of the ink coating film can be further improved. Although the flexibility of the ink coating film tends to be insufficient when the (meth)acrylic resin (B) is used alone, the interaction between the urethane resin (A) and the (meth)acrylic resin (B) can improve both the strength and flexibility of the ink coating film, and can further increase the durability and processability of the ink coating film.
The solid content of the (meth)acrylic resin (B) is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and even more preferably 5% by mass or less, based on the total amount of the ink. By having the amount of the (meth)acrylic resin (B) in this range, it is possible to appropriately limit the amount of resin in the ink while appropriately maintaining the blending balance with the urethane resin (A), thereby more effectively preventing an increase in the viscosity of the ink and more effectively improving the ejection properties of the ink.

The mass ratio of the solid content of the (meth)acrylic resin (B) to the colorant is preferably 0.1 to 8, more preferably 0.5 to 5, and even more preferably 1 to 3.

The total amount of the urethane resin (A) and the (meth)acrylic resin (B) is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 5% by mass or more, in terms of solid content, based on the total amount of the ink.
The total amount of the urethane resin (A) and the (meth)acrylic resin (B) is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less, in terms of solid content, based on the total amount of the ink.
For example, the total amount of the urethane resin (A) and the (meth)acrylic resin (B) is preferably 1 to 20 mass %, more preferably 3 to 10 mass %, and even more preferably 5 to 8 mass %, in terms of solid content, relative to the total amount of the ink.

In terms of the mass ratio blended into the ink, the mass of the urethane-based resin (A) is preferably greater than the mass of the (meth)acrylic resin (B).
The mass proportion of the urethane resin (A) relative to the total amount of the urethane resin (A) and the (meth)acrylic resin (B) is preferably 10 to 90 mass%, more preferably 20 to 80 mass%, and still more preferably 40 to 70 mass%.

The ink according to one embodiment may contain other resins in addition to the above-mentioned urethane resin (A) and (meth)acrylic resin (B). For example, a binder resin may be blended as the other resin.
Examples of the other resins include other water-dispersible resins, water-soluble resins, and combinations thereof.

Other water-dispersible resins include, for example, ethylene-vinyl chloride copolymer resins, styrene-maleic anhydride copolymer resins, vinyl acetate-ethylene copolymer resins, etc. These water-dispersible resins can be blended in the ink as oil-in-water (O/W) type resin emulsions.
Examples of the water-soluble resin include polyvinyl alcohol, polyacrylic acid, neutralized polyacrylic acid, acrylic acid/maleic acid copolymer, acrylic acid/sulfonic acid copolymer, styrene/maleic acid copolymer, etc. In addition, anionic water-soluble resins obtained by introducing an anionic functional group into these resins can be used.
The above-mentioned other resins may be used alone or in combination of two or more.
The other resins (active ingredients) are preferably 1 to 20% by mass with respect to the total amount of the ink. When other resins are blended into the ink, the total amount of the urethane-based resin (A) and the (meth)acrylic resin (B) with respect to the total amount of all the resins blended into the ink is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

In one embodiment, the ink may contain an acetylene glycol-based surfactant (C) having an HLB value of 10.0 or less.

The acetylene glycol surfactant (C) is a glycol having an acetylene group, preferably a glycol having a symmetrical structure with the acetylene group located in the center, and may have a structure in which ethylene oxide is added to acetylene glycol.
When acetylene glycol having ethylene oxide added thereto is used as the acetylene glycol surfactant (C), the number of moles of ethylene oxide added is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less.

The acetylene glycol surfactant (C) preferably has an HLB value of 10.0 or less, more preferably 9.0 or less, still more preferably 8.0 or less, and may be 5.0 or less. This can further improve the coatability of the resin components contained in the ink, particularly the urethane resin (A), further improve the strength of the ink coating film, and further increase the durability of the ink coating film. In addition, since the urethane resin (A) is applied more uniformly, the flexibility of the ink coating film can be further improved, and the processability of the ink coating film can be further increased.
The lower limit of the HLB value of the acetylene glycol surfactant (C) is not particularly limited, but from the viewpoint of the storage stability of the ink, it is preferably 1.0 or more, more preferably 2.0 or more, and may be 3.0 or more.
For example, the acetylene glycol surfactant (C) preferably has an HLB value of 1.0 or more and 10.0 or less, more preferably 2.0 or more and 8.0 or less, and even more preferably 3.0 or more and 5.0 or less.

Here, the HLB value is one of the scales that indicate the properties of a surfactant, and is a numerical representation of the balance between hydrophilic groups and lipophilic groups in the molecule. The HLB value is proposed by several calculation methods, but in this specification, it is a value calculated by the Griffin method, and is calculated by the following formula (1).
HLB value = 20 x (formula weight of hydrophilic part) / (molecular weight of surfactant) ... formula (1)

Here, the "hydrophilic portion" refers to a hydrophilic portion contained in the molecular structure of the surfactant, and is preferably a polyoxyalkylene group, an alcohol group having 3 or less carbon atoms in the main chain relative to the hydroxyl group, or a combination thereof. When the surfactant contains multiple hydrophilic portions, the formula weight of the hydrophilic portion in the above formula (1) is the total amount of these.
Examples of the polyoxyalkylene group include a polyoxyethylene group (polyethylene oxide; EO: --(CH ₂ CH ₂ O) _n --), a polyoxypropylene group (polypropylene oxide; PO: --(CH ₂ CH ₂ CH ₂ O) _n --), and the like.
Examples of the alcohol group include groups derived from methanol, ethanol, propanol, isopropanol, glycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, sorbitan, sucrose (cane sugar), mannite, glycols, and the like (for example _{, --CH.sub.2CH.sub.2OH} for ethanol).

The "hydrophobic portion" refers to the hydrophobic portion contained in the molecular structure of the surfactant, and is, for example, an aliphatic alcohol having 4 or more carbon atoms in the main chain relative to the hydroxyl group, an alkylphenol, an aliphatic hydrocarbon group derived from a fatty acid, an aromatic hydrocarbon group, an organic siloxane, an alkyl halide, or a combination of these.

Commercially available acetylene surfactants (C) having an HLB value of 10.0 or less include, for example, "Olfine E1004" and "Surfinol 420, 440, 104" (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.).
The above-mentioned acetylene glycol surfactants (C) may be used alone or in combination of two or more kinds.

The active ingredient amount of the surfactant (C) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the ink. This can further improve the affinity with the substrate to which the ink is applied in the coating film formation by the urethane-based resin (A) and the (meth)acrylic resin (B), and can form a stronger ink coating film, thereby further increasing the durability of the ink coating film. In addition, the urethane-based resin (A) swells due to the action of the surfactant, which gives it further flexibility, and can further improve the processability of the ink coating film.
The amount of the surfactant (C) in terms of the active ingredient is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on the total amount of the ink, which can prevent a decrease in the storage stability of the ink.
For example, the amount of the active ingredient of the surfactant (C) is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 3% by mass, based on the total amount of the ink.

The surfactant (C) preferably has an active ingredient mass ratio of 0.1 to 1, more preferably 0.2 to 0.5, relative to the solid content of the urethane resin (A).
The surfactant (C) preferably has an active ingredient amount of 0.1 to 2, more preferably 0.5 to 1, by mass ratio relative to the solid content of the (meth)acrylic resin (B).

The ink according to one embodiment may contain other surfactants in addition to the above-mentioned surfactant (C). As the other surfactants, nonionic surfactants, anionic surfactants, or combinations thereof can be preferably used, and nonionic surfactants are more preferable.
As the other surfactant, an acetylene glycol surfactant having an HLB value of more than 10.0 may be used.
Commercially available acetylene surfactants having an HLB value of greater than 10.0 include, for example, Olfine E1010, E1006, E1020, and Surfynol 465, 485 (all trade names, manufactured by Nissin Chemical Industry Co., Ltd.).

Other surfactants include, for example, ester-type surfactants such as glycerin fatty acid esters and fatty acid sorbitan esters; ether-type surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers and polyoxypropylene alkyl ethers; ether ester-type surfactants such as polyoxyethylene sorbitan fatty acid esters; acetylene alcohol-based surfactants; surfactants having an acetylene group; silicone-based surfactants; fluorine-based surfactants, etc. Among these, acetylene alcohol-based surfactants, surfactants having an acetylene group, and silicone-based surfactants can be preferably used.

When other surfactants are blended into the ink, the surfactant (C) is preferably present in an amount of 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of surfactants, in terms of the mass ratio of active ingredients.

The ink may contain a coloring material. The coloring material may include a pigment, a dye, or a combination of these. In terms of the weather resistance and color development of the image, a pigment is preferably used.

The pigment may be preferably incorporated into the ink as a pigment dispersion.
The pigment dispersion may be any one in which the pigment can be dispersed in a solvent and in which the pigment is in a dispersed state in the ink. For example, a pigment dispersed in water using a pigment dispersant, a self-dispersing pigment dispersed in water, or a microencapsulated pigment in which the pigment is coated with a resin dispersed in water may be used.

Examples of pigments that can be used include organic pigments such as azo pigments, phthalocyanine pigments, polycyclic pigments, and dye lake pigments; and inorganic pigments such as carbon black and metal oxides. Examples of azo pigments include soluble azo lake pigments, insoluble azo pigments, and condensed azo pigments. Examples of phthalocyanine pigments include metal phthalocyanine pigments such as copper phthalocyanine pigments, and metal-free phthalocyanine pigments. Examples of polycyclic pigments include quinacridone pigments, perylene pigments, perinone pigments, isoindoline pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, metal complex pigments, and diketopyrrolopyrrole (DPP). Examples of carbon black include furnace carbon black, lamp black, acetylene black, and channel black.

Further, examples of organic pigments include brilliant carmine 6B, lake red C, watching red, disazo yellow, Hansa yellow, phthalocyanine blue, phthalocyanine green, alkali blue, and aniline black.
Examples of inorganic pigments include metals such as cobalt, iron, chromium, copper, zinc, lead, titanium, vanadium, manganese, and nickel, oxides and sulfides of these metals, as well as yellow ochre, ultramarine, and Prussian blue.
Furthermore, a white pigment may be used as the pigment, and examples of the white pigment include inorganic pigments such as titanium oxide, zinc white, zinc sulfide, antimony oxide, and zirconium oxide.

Specific examples of pigments include Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 154, 155, 166, 168, 180, 185; Pigment Orange 16, 36, 38, 43, 51, 55, 59, 61, 64, 65, 71; Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 149, 168 , 177, 178, 179, 206, 207, 209, 242, 254, 255; Pigment Violet 19, 23, 29, 30, 37, 40, 50; Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 30, 64, 80; Pigment Green 7 (chlorinated phthalocyanine green), 36 (brominated phthalocyanine green); Pigment Brown 23, 25, 26; Pigment Black 7 (carbon black), 26, 27, 28, etc.

Commercially available examples of carbon black include Monarch 1000 and ELFTEX 415 (all carbon blacks manufactured by Cabot Corporation), #960, #970, MA8, and MA77 (all carbon blacks manufactured by Mitsubishi Chemical Corporation).
Commercially available examples of color pigments include LIONOL BLUE FG-7400G (phthalocyanine pigment manufactured by Toyo Ink Mfg. Co., Ltd.); YELLOW PIGMENT E4GN (nickel complex azo pigment manufactured by Bayer AG); Cromophtal Pink PT (quinacridone pigment manufactured by BASF Corporation); Fastogen Super Magenta RG (quinacridone pigment manufactured by DIC Corporation); Fastogen Super Magenta RGT (quinacridone pigment manufactured by DIC Corporation); YELLOW PIGMENT E4GN (nickel complex azo pigment manufactured by LANXESS AG); Irgalite Blue 8700 (phthalocyanine pigment manufactured by BASF Corporation); E4GN-GT (quinacridone pigment manufactured by LANXESS AG) Nickel complex azo pigment); Fastogen Blue TGR (cyan pigment manufactured by DIC Corporation); Cinquasia Magenta D4550J (magenta pigment manufactured by BASF); Inkjet Yellow 4GP (yellow pigment manufactured by Clariant).

The average particle size of these pigments is preferably 50 to 500 nm, and more preferably 50 to 200 nm. From the viewpoint of color development, the average particle size of these pigments is preferably 50 nm or more, and from the viewpoint of ejection stability, the average particle size is preferably 500 nm or less.

In order to stably disperse the pigment in the ink, a pigment dispersant such as a polymer dispersant or a surfactant can be preferably used.
Examples of commercially available polymer dispersants include the TEGO Disperse series "TEGO Disperse 740W, 750W, 755W, 757W, 760W" manufactured by EVONIK Corporation, the Solsperse series "Solsperse 20000, 27000, 41000, 41090, 43000, 44000, 46000" manufactured by Lubrizol Japan Co., Ltd., the Joncryl series "Joncryl 57, 60, 62, 63, 71, 501" manufactured by Johnson Polymer Co., Ltd., "DISPERBYK-102, 185, 190, 193, 199" manufactured by BYK Corporation, and polyvinylpyrrolidone "K-30, K-90" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. (all trade names).

As the surfactant-type dispersant, a non-ionic surfactant can be preferably used, taking into consideration the dispersion stability of the pigment in the ink and the influence of ionic properties from the pretreatment agent.
Commercially available surfactant-type dispersants include, for example, nonionic surfactants such as the Emulgen series manufactured by Kao Corporation, such as "Emulgen A-60, A-90, A-500, B-40, L-40, and 420" (all trade names).

These pigment dispersants may be used alone or in combination of two or more.
When a pigment dispersant is used, the amount of the pigment dispersant added varies depending on the type of the pigment dispersant and is not particularly limited. For example, the pigment dispersant can be added in an amount of 0.005 to 0.5 parts by mass of the active ingredient per 1 part of the pigment.

A self-dispersing pigment may be blended as a coloring material. A self-dispersing pigment is a pigment in which a hydrophilic functional group has been introduced to the surface of the pigment by chemical or physical treatment. The hydrophilic functional group introduced to the self-dispersing pigment is preferably ionic, and by charging the pigment surface anionically or cationic, the pigment particles can be stably dispersed in water by electrostatic repulsion. Preferred anionic functional groups are sulfonic acid groups, carboxy groups, carbonyl groups, hydroxy groups, phosphonic acid groups, etc. Preferred cationic functional groups are quaternary ammonium groups, quaternary phosphonium groups, etc.

These hydrophilic functional groups may be bonded directly to the pigment surface or through other atomic groups. Examples of other atomic groups include, but are not limited to, alkylene groups, phenylene groups, naphthylene groups, etc. Methods for treating the pigment surface include diazotization treatment, sulfonation treatment, hypochlorous acid treatment, humic acid treatment, vacuum plasma treatment, etc.

As self-dispersing pigments, for example, CAB-O-JET series "CAB-O-JET 200, 300, 250C, 260M, 270" manufactured by Cabot Corporation, and "BONJET BLACK CW-1, CW-2, CW-4" manufactured by Orient Chemical Industries Co., Ltd. can be preferably used (all are product names).

A pigment dispersion in which the pigment is pre-dispersed with a pigment dispersant may be used. Commercially available pigment dispersions dispersed with a pigment dispersant include, for example, the HOSTAJET series manufactured by Clariant and the FUJI SP series manufactured by Fuji Pigment Co., Ltd. (both are trade names). A pigment dispersion dispersed with the above-mentioned pigment dispersant may be used. Also, a microencapsulated pigment in which the pigment is coated with a resin may be used.

Dyes may be blended as coloring materials. Dyes that are generally used in the technical field of printing can be used, and are not particularly limited. Specific examples include basic dyes, acid dyes, direct dyes, soluble vat dyes, acid mordant dyes, mordant dyes, reactive dyes, vat dyes, and sulfur dyes. Of these, those that are water-soluble and those that become water-soluble by reduction or the like can be preferably used. More specific examples include azo dyes, rhodamine dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, triphenylmethane dyes, diphenylmethane dyes, and methylene blue.

The above coloring materials can be used alone or in combination of two or more.
The coloring material preferably has an active ingredient content of 0.1 to 20% by mass, more preferably 1 to 10% by mass, and even more preferably 2 to 5% by mass, based on the total amount of the ink.

The ink preferably contains water as an aqueous solvent, and may be a main solvent. When the above-mentioned resin emulsion, pigment dispersion, etc. contain water as a solvent, the water in each component is calculated as a part of the water in the ink when preparing the ink.
The water is not particularly limited, but is preferably one that contains as few ionic components as possible. In particular, from the viewpoint of the storage stability of the ink, it is preferable that the content of polyvalent metal ions such as calcium is small. As the water, for example, ion-exchanged water, distilled water, ultrapure water, etc. may be used.
From the viewpoint of adjusting the ink viscosity, the water content is preferably from 20 to 90% by mass, and more preferably from 30 to 80% by mass, based on the total amount of the ink.

The ink may contain a water-soluble organic solvent. The water-soluble organic solvent is preferably compatible with water. As the water-soluble organic solvent, an organic compound that is liquid at room temperature and can be dissolved or mixed in water may be used, and it is preferable to use a water-soluble organic solvent that is uniformly mixed with the same volume of water at 20°C under 1 atmosphere.

Examples of the water-soluble organic solvent include lower alcohols such as methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, isobutanol, and 2-methyl-2-propanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and 1,3-propanediol; glycerins such as glycerin, diglycerin, triglycerin, and polyglycerin; acetins such as monoacetin and diacetin; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether. Examples of the glycol ethers that can be used include glycol ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol dimethyl ether, and tetraethylene glycol diethyl ether; triethanolamine, 1-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, β-thiodiglycol, and sulfolane.
These may be used alone or in combination of two or more kinds as long as they form a single phase.

Among the water-soluble organic solvents, glycols, glycol ethers, and combinations thereof are preferably used, and glycol ethers are more preferable. These water-soluble organic solvents have better compatibility with water. In the mixed solvent of these water-soluble organic solvents and water, the dispersion stability of the urethane resin (A) and the (meth)acrylic resin (B) can be further improved.
Furthermore, it is preferable to use a low-polarity solvent among water-soluble organic solvents. Surfactants with low HLB values are difficult to dissolve in aqueous solvents and may float in the ink. In this case, the solubility of the surfactant with low HLB value can be increased by adding a low-polarity solvent to the ink. As low-polarity solvents, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, triacetin, 3,5,5-trimethyl-2-cyclohexene-1-one, 2-pyrrolidone, etc. can be preferably used.

From the viewpoint of viscosity adjustment and moisturizing effect, the water-soluble organic solvent may be contained in an amount of 1 to 80% by mass, more preferably 10 to 60% by mass, and even more preferably 20 to 50% by mass, based on the total amount of the ink.
The content of the low polarity water-soluble organic solvent is preferably from 1 to 20% by mass, more preferably from 1 to 10% by mass, and even more preferably from 2 to 3% by mass.

In addition to the above components, the ink may optionally contain a wetting agent (moisturizing agent), a surface tension adjuster (penetrating agent), an antifoaming agent, a fixing agent, a pH adjuster, an antioxidant, a preservative, etc.

To adjust the pH of the ink, known pH adjusters can be added. Sulfuric acid, nitric acid, acetic acid, sodium hydroxide, potassium hydroxide, ammonium hydroxide, triethanolamine, etc. can be used as pH adjusters or as ink thickening aids.

By adding an antioxidant, it is possible to prevent the oxidation of the ink components and improve the storage stability of the ink. Examples of antioxidants that can be used include L-ascorbic acid, sodium L-ascorbate, sodium isoascorbate, potassium sulfite, sodium sulfite, sodium thiosulfate, sodium dithionite, and sodium pyrosulfite.

By incorporating a preservative, it is possible to prevent the ink from spoiling and improve storage stability. Examples of preservatives include isothiazolone preservatives such as 5-chloro-2-methyl-4-isothiazolin-3-one, 2-methyl-4-isothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, and 1,2-benzisothiazolin-3-one; triazine preservatives such as hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine; pyridine/quinoline preservatives such as 2-pyridinethiol sodium-1-oxide and 8-oxyquinoline; Preservatives that can be used include dithiocarbamate preservatives such as sodium dimethyldithiocarbamate; organic bromine preservatives such as 2,2-dibromo-3-nitrilopropionamide, 2-bromo-2-nitro-1,3-propanediol, 2,2-dibromo-2-nitroethanol, and 1,2-dibromo-2,4-dicyanobutane; methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, potassium sorbate, sodium dehydroacetate, and salicylic acid.

The suitable range of ink viscosity varies depending on the nozzle diameter of the ejection head and the ejection environment, but generally, it is preferable for the ink to have a viscosity of 1 to 30 mPa·s at 23°C, and more preferably 5 to 15 mPa·s, which is suitable for use with inkjet printing devices.

The method for preparing the ink is not particularly limited, but the desired ink can be obtained by appropriately mixing each component. For example, when a pigment dispersion is used as the colorant, a mixture of the pigment, pigment dispersant, and water is dispersed using a dispersing machine such as a bead mill to obtain a pigment dispersion, and then the pigment dispersion, a resin emulsion of a urethane resin (A), a resin emulsion of a (meth)acrylic resin (B), a surfactant (C), water, and a water-soluble organic solvent are mixed together or in portions to obtain an ink. The obtained composition may also be filtered using a filter or the like.

The resin emulsion of the urethane resin (A) incorporated in the ink preferably has a solid content of 10 to 50% by mass, and more preferably 30 to 40% by mass.
The resin emulsion of the urethane resin (A) blended in the ink preferably has a viscosity in the emulsion state of 1 to 300 mPa·s, and more preferably 1 to 100 mPa·s.
The resin emulsion of the (meth)acrylic resin (B) incorporated in the ink preferably has a solid content of 10 to 50 mass %.
The resin emulsion of the (meth)acrylic resin (B) blended in the ink preferably has a viscosity in an emulsion state at 23° C. of 1 to 300 mPa·s, and more preferably 1 to 100 mPa·s.
In order to achieve high-quality printing on a variety of substrates with different surface energies, it is important that the ink wets and spreads easily, so it is preferable for the viscosity of the resin emulsion in the ink to be low.

The aqueous inkjet ink according to an embodiment may be printed on an untreated substrate, or may be printed on a substrate treated with a pretreatment agent. In particular, when a substrate having low permeability is used as the substrate, it is preferable to treat the substrate with a pretreatment agent, since the aqueous inkjet ink is unlikely to permeate the substrate.
The pretreatment agent preferably contains, for example, an aqueous medium, a surfactant, a flocculant, inorganic particles, or a combination thereof. More preferably, the pretreatment agent contains an aqueous medium, and a surfactant and/or a flocculant. The pretreatment agent may also contain a binder resin to fix the flocculant to the substrate.
The surfactant is preferably contained in an amount of 0.1 to 10 mass %, more preferably 0.5 to 5 mass %, and even more preferably 0.7 to 2 mass %, in terms of the amount of active ingredient relative to the total amount of the pretreatment agent.
The binder resin is preferably present in an amount of 0.5 to 20.0% by mass in terms of the amount of the active ingredient relative to the total amount of the pretreatment agent.

By treating the substrate with an aggregating agent, the coloring material components in the ink are agglomerated on the substrate when the aqueous inkjet ink is applied to the substrate, thereby further enhancing the color development of the printed matter.
The flocculant may be a cationic resin, a polyvalent metal salt, an organic acid, an inorganic acid, a salt of an inorganic acid, or a combination thereof. The cationic resin may be a cationic water-soluble resin, a cationic water-dispersible resin, or a combination thereof.
The total amount of the flocculant containing the cationic resin, polyvalent metal salt, organic acid, and inorganic acid is preferably from 1 to 50 mass %, and more preferably from 3 to 20 mass %, based on the total amount of the pretreatment agent.

The pretreatment agent preferably contains water as an aqueous solvent, and the main solvent may be water.
The pretreatment agent may contain a water-soluble organic solvent from the standpoint of viscosity adjustment and moisturizing effect.
As for the water and the water-soluble organic solvent, those explained above regarding the ink can be used.
Furthermore, in addition to the above-mentioned components, the pretreatment agent may optionally contain a wetting agent (moisturizing agent), a surface tension adjuster (penetrating agent), an antifoaming agent, a fixing agent, an antioxidant, a preservative, a pH adjuster, and the like.

"Method of manufacturing printed matter"
An example of a method for producing a printed matter will be described below.
The method for producing a printed matter can include, for example, forming an image on a substrate using an aqueous inkjet ink. The aqueous inkjet ink can be any of the aqueous inkjet inks described above.
It may also include treating the substrate with a pretreatment prior to aqueous ink jet imaging.
Furthermore, before forming an image on the substrate using the aqueous inkjet ink, the substrate may be coated with a white ink. This can further enhance the color development of the ink coating film formed by the aqueous inkjet ink. The white ink is not particularly limited, and may be an ink having a normal formulation that contains a white pigment as a coloring material, or an aqueous inkjet ink according to an embodiment that contains a white pigment as a coloring material.

An image can be formed on a substrate using an aqueous inkjet ink by inkjet printing, which allows easy and flexible image formation on demand without contacting the substrate.
The inkjet printing device may be of any type, such as a piezoelectric type, an electrostatic type, or a thermal type, and ejects ink from an inkjet head based on a digital signal, causing the ejected ink droplets to adhere to a substrate.

The resulting printed matter is preferably subjected to a heat treatment to remove volatile matter. The heat treatment temperature is preferably 25°C to 150°C, and more preferably 50°C to 120°C.
In one embodiment, since the ink contains the urethane-based resin (A) and the (meth)acrylic-based resin (B), by heat-treating the obtained printed matter, the resin components in the ink melt or soften to form a uniform coating film, and the strength and flexibility of the ink coating film can be further increased, and the durability and processability of the ink coating film can be further increased.
In addition, when the (meth)acrylic resin (B) is used, the durability of the ink coating film can be further improved by using it in combination with a crosslinking agent that has the property of crosslinking by an external stimulus such as heat. As such a (meth)acrylic resin (B), a resin having a carboxy group, a glycidyl group, a ketone group, or the like as a functional group in its structure is preferable. Examples of crosslinking agents that can be preferably used in combination with the (meth)acrylic resin (B) include (poly)carbodiimide compounds, (poly)isocyanate compounds, epoxy compounds, silyl compounds, oxazoline compounds, and hydrazine compounds.

After the ink is applied to the substrate, a step of post-treating the substrate to form an overcoat layer may be further provided. The method of post-treating the substrate may involve applying a post-treatment agent to the substrate. Since the ink according to one embodiment contains a resin component, the ink itself can form a resin film, which provides sufficient strength and flexibility to the ink coating film, and the durability and processability of the ink coating film can be further improved. However, depending on the application, an overcoat layer may be further formed.
As the post-treatment agent, for example, a post-treatment liquid containing a resin capable of forming a film and an aqueous medium or an oil-based medium can be used.

According to one embodiment, an ink set can be provided that includes an aqueous inkjet ink and a pretreatment agent. The aqueous inkjet ink and the pretreatment agent can be the same as those described above. The ink set may further include other inks and/or a posttreatment agent.

The aqueous inkjet ink according to one embodiment can be applied to both permeable and low-permeable substrates. In particular, for low-permeable substrates, the strength and flexibility of the ink coating can be further improved, and the durability and processability of the ink coating can be further increased.

A low-permeability substrate is one in which liquid does not penetrate into the substrate, specifically, one in which most of the liquid in the ink remains on the surface of the substrate.
Examples of low permeability substrates include metal substrates such as metal plates of aluminum, iron, copper, titanium, tin, chromium, cadmium, alloys (e.g., stainless steel, steel, etc.); glass substrates such as plate glass such as borosilicate glass, quartz glass, soda lime glass, etc.; resin substrates such as resin sheets such as PET films, OHT sheets, polyester sheets, polypropylene sheets, etc., and acrylic plates; and ceramic substrates such as molded bodies of alumina, zirconia, steatite, silicon nitride, etc.
These substrates may have a plating layer, a metal oxide layer, a resin layer, etc. formed thereon, or may have been surface-treated using a surfactant, a corona treatment, etc. The aqueous inkjet ink according to an embodiment can exert its effect even when applied to an untreated substrate.

Examples of permeable substrates include printing paper such as plain paper, coated paper, and specialty paper; fabrics such as woven fabrics and nonwoven fabrics; porous building materials for humidity control, sound absorption, and heat insulation; wood, concrete, and porous materials.

A printed matter according to one embodiment has a substrate and an ink image layer formed on the substrate, and the ink image layer contains a water-dispersible polyether-type aliphatic urethane resin (A), a water-dispersible acrylic resin (B), an acetylene glycol-based surfactant (C) having an HLB value of 10.0 or less, and a colorant.
According to this, it is possible to provide a printed matter having excellent durability and processability of a printed image. Also, according to one embodiment, it is possible to provide a printed matter having excellent image quality of a printed image.
In particular, when a decorative article is produced using a rigid substrate such as a metal substrate as the substrate, the ink coating has flexibility when bending or processing the printed area, so that cracking and whitening of the printed image can be prevented in the processed area.
In the printed matter, details of the substrate, the urethane-based resin (A), the (meth)acrylic resin (B), the surfactant (C), and the coloring material are as described above.

"Ink set"
An ink set according to one embodiment will be described below. In the following description, unless otherwise specified, the same as described in the above-mentioned aqueous inkjet ink and method for producing a printed matter, and description of parts common to the above-mentioned aqueous inkjet ink and method for producing a printed matter may be omitted.

An ink set according to one embodiment includes an aqueous inkjet ink and a maintenance liquid, the aqueous inkjet ink including a water-dispersible polyether-type aliphatic urethane resin (A), a water-dispersible (meth)acrylic resin (B), an acetylene glycol-based surfactant (C) having an HLB value of 10.0 or less, a colorant, and water, and the maintenance liquid including an acetylene glycol-based surfactant (C') having an HLB value of 10.0 or less, and glycerin that is 30% by mass or more relative to the total amount of the maintenance liquid.
According to an embodiment of the ink set, a printed matter having excellent durability and processability of a printed image can be provided, and the continuous ejection property of the aqueous inkjet ink can be improved. Furthermore, according to an embodiment of the ink set, a printed matter having excellent uniformity of a printed image can be provided.

Maintenance liquid is a liquid used in inkjet printing devices to clean components such as the nozzle surface of a nozzle head and the inside of a nozzle head. Ink tends to adhere to the nozzle surface near the nozzle outlet and the inside of the head, so maintenance liquid can be used to remove this ink stain by cleaning. With normal water-based ink, even if water is used as the maintenance liquid, the ink is removed by the miscibility of the water and ink, making cleaning possible. Since acetylene glycol surfactants with low HLB values are less soluble in water than surfactants with high HLB values, if the nozzle surface, inside of the head, etc. are washed with water alone after printing with water-based ink containing an acetylene glycol surfactant with a low HLB value, the surfactant in the ink may not be washed away and may remain adsorbed on the walls of the nozzle surface, inside of the head, etc. If this adsorbed material increases, it may clog the nozzle outlet, reducing the ejection reliability such as uniformity of the image and continuous ejection.

When cleaning the nozzle surface, if the ink and maintenance liquid are not sufficiently miscible, the nozzle surface cannot be sufficiently cleaned, and the nozzle ejection ports may become clogged and ejection defects may occur. By forming a stable mixture of ink and maintenance liquid on the nozzle surface, the removal of ink is promoted and the nozzle surface can be properly cleaned.
By using a maintenance liquid that is miscible with the aqueous ink according to an embodiment at any ratio, cleaning efficiency can be further improved. Furthermore, even when a mixture containing the ink and the maintenance liquid is concentrated on the nozzle surface, the miscibility is maintained, and thus occurrence of foreign matter in the concentrated mixture can be suppressed. For example, even when the maintenance liquid is applied to the nozzle surface in a state where the ink adhering to the nozzle surface is concentrated, or when the maintenance liquid is concentrated due to volatilization of a volatile component of the maintenance liquid after the maintenance liquid is applied to the nozzle surface, occurrence of aggregation of the ink pigment, resin emulsion, and the like can be suppressed in the concentrated mixture.

The maintenance liquid contains an acetylene glycol surfactant with a low HLB value as a component common to the ink, and this surfactant is preferably contained in a dissolved state in the maintenance liquid. This maintenance liquid maintains the stability of the mixture even when mixed with the ink at any ratio on the nozzle surface, and can prevent aggregation of the pigment, resin emulsion, etc. derived from the ink, thereby improving the uniformity of the image and the continuous ejection property.
Furthermore, by containing 30% by mass or more of glycerin in the maintenance liquid, the moisturizing properties of the maintenance liquid are increased, and even if the maintenance liquid alone or a mixture of the maintenance liquid and ink is exposed to the atmosphere, the generation of aggregates due to rapid evaporation of water can be suppressed. Furthermore, when the maintenance liquid contains glycerin, the proportion of water is relatively small, and therefore the proportion of water in the mixture of the ink and the maintenance liquid is also small, and the acetylene glycol-based surfactant with a low HLB value can be maintained in a dissolved state in the mixture, thereby improving the uniformity of images and continuous ejection properties.

The aqueous inkjet inks included in the ink set can be the aqueous inkjet inks described above. The details are as described above.
The maintenance liquid provided in the ink set can contain an acetylene glycol surfactant (C') having an HLB value of 10.0 or less, and glycerin. Hereinafter, the acetylene glycol surfactant (C') having an HLB value of 10.0 or less will also be referred to as surfactant (C').

The acetylene glycol surfactant (C') contained in the maintenance liquid may be a component common to the acetylene glycol surfactant (C) contained in the above-mentioned aqueous ink-jet ink. The types of acetylene glycol surfactants may be the same or different between the maintenance liquid and the aqueous ink-jet ink. The maintenance liquid and the aqueous ink-jet ink may each contain one or more types of acetylene glycol surfactants. When at least one of the maintenance liquid and the aqueous ink-jet ink contains two or more types of acetylene glycol surfactants, the acetylene glycol surfactants may be partly or entirely the same between the maintenance liquid and the aqueous ink-jet ink, or may be entirely different.
It is preferable that the acetylene glycol surfactant (C) contained in the aqueous inkjet ink and the acetylene glycol surfactant (C') contained in the maintenance liquid contain the same components. This makes it possible to further increase the stability of the mixed liquid when the maintenance liquid and the ink are mixed on the nozzle surface during maintenance, thereby improving continuous ejection properties.

The amount of the active ingredient of the surfactant (C') is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, based on the total amount of the maintenance liquid. This makes it possible to provide a maintenance liquid that is miscible with an aqueous ink containing an acetylene glycol surfactant with a low HLB value and that suppresses the generation of foreign matter. This maintenance liquid can more efficiently remove ink stains adhering to the nozzle surface, including the surfactant in the ink, and can improve the uniformity and continuous ejection of images.
The amount of the surfactant (C') in terms of the active ingredient is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, relative to the total amount of the maintenance liquid.
For example, the amount of the active ingredient of the surfactant (C') is preferably 0.1 to 10 mass %, more preferably 0.5 to 5 mass %, and even more preferably 1 to 3 mass %, relative to the total amount of the maintenance liquid.

The maintenance liquid may contain other surfactants in addition to the above-mentioned surfactant (C'). As the other surfactants, nonionic surfactants, anionic surfactants, or combinations thereof can be preferably used, and nonionic surfactants are more preferred. As the other surfactants, for example, the other surfactants described in the above-mentioned aqueous inkjet ink can be mentioned.
When other surfactants are blended in the ink, the surfactant (C') is preferably present in an amount of 50 mass % or more, more preferably 80 mass % or more, and even more preferably 90 mass % or more, in terms of the mass ratio of the active ingredient, relative to the total amount of surfactants.

The maintenance liquid may contain an aqueous medium, which may be a water-soluble organic solvent, water, or a combination thereof.
Examples of the water-soluble organic solvent contained in the maintenance liquid include the water-soluble organic solvents described above in relation to the aqueous inkjet ink.

Among the water-soluble organic solvents, it is preferable to use glycerins, glycols, glycol ethers, and combinations thereof, and more preferably glycerins, specifically glycerin. These water-soluble organic solvents have good compatibility with water and also good affinity with the acetylene alcohol surfactant (C').

The maintenance liquid preferably contains glycerin.
The content of glycerin is preferably 20% by mass or more, more preferably 30% by mass or more, based on the total amount of the maintenance liquid. This can increase the moisturizing property of the maintenance liquid and reduce the evaporation of water from the cleaning surface. For example, even if the maintenance liquid alone or a mixture of the maintenance liquid and ink is exposed to the atmosphere on the cleaning surface, it is possible to suppress the generation of aggregates due to the rapid evaporation of water, and it is possible to improve the uniformity and continuous dischargeability of images.
The amount of glycerin in the maintenance liquid is preferably 50% by mass or less, more preferably 40% by mass or less, and may be 35% by mass or less, based on the total amount of the maintenance liquid, which makes it possible to suppress a sudden increase in viscosity of the maintenance liquid when water evaporates.
For example, the amount of glycerin is preferably 20 to 50% by mass, more preferably 30 to 40% by mass, and even more preferably 30 to 35% by mass, based on the total amount of the maintenance liquid.

Furthermore, it is preferable to use a low-polarity solvent from among the water-soluble organic solvents. Surfactants with a low HLB value are difficult to dissolve in aqueous solvents and may float in the maintenance liquid. In this case, the solubility of the surfactant with a low HLB value can be increased by adding a low-polarity solvent to the maintenance liquid. As low-polarity solvents, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, triacetin, 3,5,5-trimethyl-2-cyclohexene-1-one, 2-pyrrolidone, etc. can be preferably used.

From the viewpoint of viscosity adjustment and moisturizing effect, the water-soluble organic solvent may be contained in an amount of 20 to 80% by mass, more preferably 30 to 60% by mass, and even more preferably 30 to 50% by mass, based on the total amount of the maintenance liquid.
The content of the low polarity water-soluble organic solvent is preferably 1 to 20 mass %, more preferably 1 to 10 mass %, and even more preferably 2 to 3 mass %, based on the total amount of the maintenance liquid.

The maintenance liquid may contain water together with a water-soluble organic solvent.
The water content is preferably 60% by mass or less, and more preferably 50% by mass or less, based on the total amount of the maintenance liquid. Since a surfactant with a low HLB value is more likely to precipitate when the water content is high, a smaller water content can suppress precipitation of the surfactant with a low HLB value.
The amount of water is preferably 30% by mass or more, and more preferably 40% by mass or more, based on the total amount of the maintenance liquid, so that the aqueous components contained in the aqueous ink can be dissolved or dispersed and removed.
For example, the content of water is preferably 30 to 60% by mass, more preferably 40 to 60% by mass, and even more preferably 40 to 50% by mass, based on the total amount of the maintenance liquid.

In addition to the above components, the maintenance liquid may optionally contain a wetting agent (moisturizing agent), a surface tension adjuster (penetrating agent), a defoaming agent, a pH adjuster, an antioxidant, a preservative, etc. Examples of these optional components include the components described above for the aqueous inkjet ink.

The viscosity of the maintenance liquid at 23° C. is preferably from 1 to 200 mPa·s, and more preferably from 3 to 100 mPa·s.
The pH of the maintenance liquid is preferably 5.5 to 9.0, in which case the occurrence of aggregates during cleaning of the head surface can be suppressed, nozzle clogging can be prevented, and continuous ejection can be improved.
The surface tension of the maintenance liquid is preferably from 20 to 50 mN/m, and more preferably from 25 to 40 mN/m.
The method for preparing the maintenance liquid is not particularly limited, but a desired maintenance liquid can be obtained by appropriately mixing each component. The obtained composition may be filtered using a filter or the like.

An example of a method for performing a maintenance operation using an ink set according to an embodiment will now be described.
In an inkjet printing apparatus, a maintenance operation can be performed on the inkjet head in order to reduce ink ejection defects from the inkjet head.
Examples of maintenance operations include a method of applying maintenance liquid to the nozzle surface, a method of applying maintenance liquid to the nozzle surface and wiping the nozzle surface with a wiper, a method of wiping the nozzle surface with the wiper while maintenance liquid is applied to the wiper, etc. In any of these methods, according to one embodiment, it is possible to increase the stability of the mixture of ink and maintenance liquid on the nozzle surface, and to efficiently remove ink stains from the nozzle surface.
The wiper is made of a material that is more elastic than a hard material, such as silicone rubber or fluororubber, in order to avoid damaging the nozzles, since it comes into contact with the head. The wiper is also preferably durable enough to withstand the effects of maintenance liquid and ink, as it frequently comes into contact with these liquids.

The timing for executing the maintenance operation may be immediately before or after printing, or both. Furthermore, the timing for executing the maintenance operation may be the timing after printing has been performed a predetermined number of times, the timing when dirt on the nozzle surface is detected by a sensor or the like, etc.
The maintenance operation may be performed by providing a maintenance mechanism, such as a maintenance liquid container, a wiper, etc., inside the inkjet printing device. As another method, when the nozzle surface becomes dirty, the dirt on the nozzle surface may be manually wiped off using the maintenance liquid, or the nozzle surface may be immersed in the maintenance liquid to dissolve and remove the ink.
The maintenance liquid is suitable for cleaning the nozzle surface, but can also be applied to other members such as the inside of the nozzle head, the transport path of the substrate, the ink tank, and the housing.

The present invention will be described in detail below with reference to examples. The present invention is not limited to the following examples. In the following description, unless otherwise specified, "%" indicates "mass %" and "-" in the tables indicates that no additive is added.

[Production Example A]
<Preparation of Pigment Dispersion>
Table 1 shows the pigment dispersion formulation.
Each component was premixed according to the recipe shown in the table. Then, 300 g of the mixture was placed in a 500 mL PP (polypropylene) container, and zirconia beads with a diameter of Φ0.5 mm were added so that the total amount in the PP container was about 90% of the container. This PP container was set in a rocking mill (manufactured by Seiwa Giken Co., Ltd.) and dispersed for 2 hours, after which the zirconia beads were separated from the dispersion liquid to obtain a pigment dispersion.

The components used are as follows:
Magenta pigment: "FASTOGEN SUPER MAGENTA RGT" manufactured by DIC Corporation.
Acrylic dispersant: BYK "DISPERBYK-190", active ingredient 40%.
pH adjuster: "TEA (triethanolamine)" manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.
Preservative: "PROXEL XL2(S)" manufactured by Lonza Japan Co., Ltd.

<Preparation of ink>
Tables 2 to 5 show the ink formulations of the examples and comparative examples. In each table, the blending amount of the magenta pigment dispersion is shown as the total amount of the pigment dispersion. Also, the blending amount of each resin emulsion is shown as the total amount of the resin emulsion. The units of the pigment content of the pigment dispersion and the solid content of the resin emulsion shown in the tables are mass %. The solvent contained in the pigment dispersions and resin emulsions in the tables is mainly water.
According to the ink formulation shown in each table, each component was mixed and then filtered through a membrane filter having a pore size of 3 μm to obtain an ink.

The components used are as follows:
(Component 1: Pigment Dispersion)
Magenta Dispersion: Prepared by procedure above; 20% pigment.

(Component 2: Urethane resin emulsion)
Polyether-type aliphatic urethane resin (1): "Takelac W-6020" manufactured by Mitsui Chemicals, Inc., solid content 30.0%.
Polyether-type aliphatic urethane resin (2): "Permarine UA-200" manufactured by Sanyo Chemical Industries, Ltd., solid content 30.0%.
Polyether-type aliphatic urethane resin (3): "Takelac W-5661" manufactured by Mitsui Chemicals, Inc., solid content 35.0%.
Polyether type aromatic urethane resin: "NeoRez R-9404" manufactured by DSM, solid content 31.0%.
Polyester-type aliphatic urethane resin: "ADEKA BONTITOR HUX-370" manufactured by ADEKA Corporation, solid content 33.0%.
Polycarbonate-type aliphatic urethane resin: "U-coat UX-485" manufactured by Sanyo Chemical Industries, Ltd., solid content 40.0%.
The above urethane resin emulsions are all anionic. In the table, component (2a) indicates a polyether-type aliphatic urethane resin emulsion, and component (2b) indicates a comparative urethane resin emulsion.

(Component 3: Acrylic resin emulsion)
Styrene acrylic resin: "Movinyl 966A" manufactured by Japan Coating Resins, solid content 45.0%.
Acrylic resin: "Movinyl 9760" manufactured by Japan Coating Resins, solid content 19.5%.
The above acrylic resin emulsions are all anionic.

(Component 4: Water-soluble organic solvent)
Glycerin, 1,3-propanediol, diethylene glycol, propylene glycol, and diethylene glycol monoethyl ether in the table are available from FUJIFILM Wako Pure Chemical Industries, Ltd.

(Component 5: Surfactant)
Acetylene glycol (HLB: 4.0): "Surfynol 420" manufactured by Nissin Chemical Industry Co., Ltd.
Acetylene glycol (HLB: 8.1): "Surfynol 440" manufactured by Nissin Chemical Industry Co., Ltd.
Acetylene glycol (HLB: 13.2): "Olfine E1010" manufactured by Nissin Chemical Industry Co., Ltd.
Acetylene glycol (HLB: 17.1): "Surfynol 485" manufactured by Nissin Chemical Industry Co., Ltd.
The above surfactants are all acetylene glycol-based surfactants, nonionic, and contain 100% by mass of active ingredient. In the table, component (5a) indicates a surfactant with an HLB value of 10.0 or less, and component (5b) indicates a surfactant with an HLB value of more than 10.0.

The HLB value of a surfactant is a value calculated from the molecular structure of the surfactant using the following formula (1) according to the Griffin method.
HLB value = 20 x (formula weight of hydrophilic part) / (molecular weight of surfactant) ... formula (1)

The swelling ratio of the urethane resin emulsion was measured according to the following procedure.
In the combination of the urethane resin emulsion and the surfactant blended in the ink to be measured, the swelling ratio of the urethane resin emulsion was determined when the urethane resin emulsion was immersed in the surfactant. When the ink to be measured contained two types of surfactants, the mass ratio of the two types of surfactants was adjusted to the blending ratio in the ink and used.
The urethane resin emulsion contained in the ink to be measured was placed in a glass petri dish with a diameter of 5 cm, in an amount equivalent to 1.5 g of solid content, and placed in a thermal dryer at 100°C to evaporate the water and dry the resin to obtain a dry film. The test piece made into the dry film was cut into a size of 1 cm x 1 cm, its mass was measured, and then placed in a glass bottle, to which 1.0 g of the surfactant contained in the ink to be measured was added, and the dry film was immersed. After 12 hours, it was taken out, the surfactant on the surface of the dry film was wiped off, and the mass was measured. The swelling ratio was calculated from the following formula.
Swelling ratio [%]={((mass of dry film after immersion)−(mass of dry film before immersion))/(mass of dry film before immersion)}×100

<Evaluation method>
Using the resulting ink, decorated articles were produced according to the following procedure and evaluated as follows. The results are shown in Tables 2 to 5.
The substrate used was a white-painted aluminum plate (Nikkaru Shoko Co., Ltd., aluminum flat plate).
A white-painted aluminum plate cut to 10 cm x 10 cm was heated in an oven at 70°C for 10 minutes.
Each ink was introduced into the inkjet head of an inkjet printer (Anajet mPower-10 manufactured by Anajet Corporation), and a photographic image was printed in a single color of magenta on a heated white-painted aluminum plate with the surface temperature at 40°C.
After printing, the printed matter was dried in an oven at 150° C. for 10 minutes, and the resulting printed matter was used as a decorative article.

(Durability of printed images)
The image portion of the obtained decorative article was reciprocated with a steel wool having a bottom area of 9 cm x 9 cm under a load of 60 kg/ ^m2, and the change in the substrate surface was observed. The durability of the printed image was evaluated according to the following criteria.
AA: The image does not change significantly even after 30 reciprocal rubs.
A: After rubbing back and forth 30 times, the image becomes slightly whitish.
B: The image peels off after 30 strokes or less.
C: The image peels off after 10 strokes or less.
D: The image peels off after one round trip.

(Processability of printed images)
The resulting decorated article was folded at 90 degrees with a bender, and the change in the image at the folded portion was observed. The processability of the printed image was evaluated according to the following criteria.
A: No whitening due to minute cracks in the image caused by bending was observed.
B: No whitening was observed, but minute cracks were observed under a magnifying glass.
C: Whitening was observed.
D: Whitening was observed, and peeling occurred at cracked portions of the image.

(Image quality of printed image)
The image portion of the resulting decorated article was observed under a zoom microscope to check for yellowing of the photographic image. The image quality of the printed image was evaluated according to the following criteria.
A: No yellowing is observed in the color of the photographic image.
B: The color of the photographic image is slightly yellowish.
C: The photographic image has a strong yellowish tinge.

As shown in each table, the prints of each Example were excellent in durability and processability of the printed images, and further, the image quality of the printed images was also good.
Throughout each example, even if the types of urethane resin (A), (meth)acrylic resin (B), surfactant (C), and pigment were different, by using the components of one embodiment, each evaluation was good.
Throughout each of the examples, it can be seen that when the blending amount of the urethane resin (A) is 3% by mass or more, the durability and processability of the printed image, especially the durability, are further improved.
Throughout each of the examples, it can be seen that the durability and processability of printed images are further improved when the swelling ratio of the urethane resin used in the ink being measured with respect to the surfactant is 10 to 100%.
Through Examples 3, 5 and 7, it is understood that two types of surfactant (C) may be combined, or surfactant (C) may be combined with another surfactant.

Throughout each of the comparative examples, it can be seen that when at least one of the urethane resin (A), the (meth)acrylic resin (B), and the surfactant (C) is not included, sufficient results cannot be obtained.
In Comparative Example 1, a polyester-type aliphatic urethane resin was used, and the durability and processability of the printed image were deteriorated. Furthermore, in Comparative Example 1, the image quality of the printed image was deteriorated due to the ester bond of the urethane resin.
In Comparative Example 2, a polycarbonate-type aliphatic urethane resin was used, and the processability of the printed image was reduced. This is thought to be because the resin itself is hard but has insufficient flexibility due to the carbonate bond of the urethane resin.
In Comparative Example 3, a polyether-type aromatic urethane resin was used, and the durability and processability of the printed image were deteriorated. In addition, in Comparative Example 3, yellowing of the ink coating occurred due to the aromatic urethane bond of the urethane resin, and the image quality of the printed image was deteriorated.
Comparative Example 4 is an example in which a (meth)acrylic resin was not used, and no deterioration in image quality due to the ink coating film occurred, but the durability and processability of the printed image deteriorated.

Comparative Examples 5 to 7 are examples in which the (meth)acrylic resin (B) was not used, unlike Comparative Examples 1 to 3, and the durability of the printed image was further reduced.
Comparative Example 8 is an example in which no urethane resin was used, and the durability and processability of the printed image, especially the processability, were deteriorated.
Comparative Examples 9 and 10 are examples using a surfactant with an HLB value of more than 10.0, and the durability and processability of the printed image were deteriorated. This is considered to be due in part to the fact that no interaction was obtained between the urethane resin (A) and the surfactant (C) with an HLB value of 10.0 or less, resulting in a deterioration in the uniformity of the ink coating.
In all the comparative examples, when the swelling ratio of the urethane resin used in the ink being measured with respect to the surfactant was less than 10%, it is believed that the durability and processability of the printed image was reduced for this reason as well.

[Production Example B]
<Preparation of Pigment Dispersion>
A magenta pigment dispersion was prepared in the same manner as in Production Example A above.

<Preparation of ink>
Table 6 shows the ink formulation. In each table, the blending amount of the magenta pigment dispersion is shown as the total amount of the pigment dispersion. Also, the blending amount of each resin emulsion is shown as the total amount of the resin emulsion. The units of the pigment content of the pigment dispersion and the solid content of the resin emulsion shown in the table are mass %. The solvent contained in the pigment dispersion and the resin emulsion in the table is mainly water.
According to the ink formulation shown in the table, each component was mixed and then filtered through a membrane filter having a pore size of 3 μm to obtain an ink.
The components used are the same as those in the ink of Production Example A. The HLB value of the surfactant and the swelling ratio of the urethane resin emulsion were determined in the same manner as in Production Example A.

<Preparation of maintenance liquid>
The formulation of the maintenance liquid is shown in Table 7. The components were mixed according to the formulation of the maintenance liquid shown in the table, and then filtered through a membrane filter with a pore size of 3 μm to obtain a maintenance liquid. The pH of the obtained maintenance liquid was measured and is shown in the table.
The water-soluble organic solvents used were all available from Fujifilm Wako Pure Chemical Industries, Ltd. The surfactants and preservatives used were the same as those used in the ink of Production Example A described above.

<Evaluation method>
Using the obtained ink, a decorated article was produced according to the same procedure as in Production Example A, and the following evaluations were carried out. In the evaluation of the uniformity and continuous ejection property of the printed image described below, a decorated article with a solid image was produced by repeating the same operations as in Production Example A, except that a solid image was printed in a single color of magenta instead of a photographic image.
The durability of the printed image, the processability of the printed image, and the image quality of the printed image were evaluated in the same manner and according to the same criteria as in Production Example A described above.

The uniformity of the printed image and the continuous ejection property were evaluated by combining the ink and the maintenance liquid as shown in Table 8.
(Uniformity of printed image)
After printing three borderless solid images on a 10 cm x 10 cm aluminum plate, the nozzle surface of the inkjet head was wiped with a rubber blade immersed in each maintenance liquid. In this state, a borderless solid image was printed again on a 10 cm x 10 cm aluminum plate. After wiping the nozzle surface, the image portion of the decorative article obtained by printing was observed with a zoom microscope to observe the uniformity of the solid image. The uniformity of the printed image was evaluated according to the following criteria.
A: A uniform solid image is formed.
B: There are unevenness in parts of the solid image.
C: Unevenness is present in about half of the solid image.

(Continuous ejection ability)
After printing 10 sheets of borderless solid images on a 10 cm x 10 cm aluminum plate, the nozzle surface of the inkjet head was wiped with a rubber blade soaked in each maintenance liquid. In this state, after printing 10 sheets of borderless solid images on a 10 cm x 10 cm aluminum plate again, a nozzle check pattern was printed to check how many nozzles were not ejecting. The continuous ejection property was evaluated according to the following criteria.
AA: The number of missing fibers is 0.
A: The number of missing fibers is 1 or more and 2 or less.
B: The number of missing fibers is 3 or more and 4 or less.
C: The number of missing fibers is 5 or more.

As shown in each table, the decorative articles of each example had excellent durability and processability of the printed images, and the image quality of the printed images was also good. Furthermore, when the maintenance liquid of each example was used for the treatment, the uniformity and continuous ejection of the printed images were good in the subsequent printing.

Examples B1 to B6 used inks B1 to B3, and the durability, processability, and image quality of the printed images were good.

In Examples B1 to B3, the HLB value of the surfactant contained in the maintenance liquid was 8.1, and the uniformity of the printed image and the continuous ejection property were good. In Examples B1 to B3, the ink and the maintenance liquid contained the same surfactant, and therefore the continuous ejection property was even better.
In Example B4, the HLB value of the surfactant contained in the maintenance liquid was 4.0, and the uniformity of the printed image and the continuous ejection property were good.
In Example B5, the HLB value of the surfactant contained in the maintenance liquid was 13.2, and the uniformity and continuous ejection property of the printed image were reduced.
In Example B6, the HLB value of the surfactant contained in the maintenance liquid was 17.1, and the uniformity and continuous ejection property of the printed image were reduced.
Throughout Examples B1 to B6, it is believed that when the HLB value of the surfactant contained in the maintenance liquid is in the range of 10.0 or less, ink adhering to the nozzle surface of the nozzle head is appropriately removed, improving the uniformity and continuous ejection properties of the printed image.

Claims (8)

1. An aqueous inkjet ink comprising: a water-dispersible polyether-type aliphatic urethane resin (A); a water- dispersible (meth)acrylic resin (B); an acetylene glycol-based surfactant (C) having an HLB value of 10.0 or less; a colorant; and water, wherein the water-dispersible polyether-type aliphatic urethane resin (A) and the water-dispersible (meth)acrylic resin (B) are each contained in the ink in a dispersed state as resin particles . The aqueous ink-jet ink according to claim 1 , wherein the water-dispersible polyether-type aliphatic urethane resin (A) and the water-dispersible (meth)acrylic resin (B) are not formed into composite resin particles. The aqueous inkjet ink according to claim 1 or 2, wherein a test piece of the water-dispersible polyether-type aliphatic urethane resin (A) in the form of a dried film is immersed in a surfactant to be blended in the ink and removed after 12 hours, and the mass-based swelling rate from before immersion is 10% or more and 100% or less. 4. The aqueous ink-jet ink according to claim 1, wherein the water-dispersible polyether-type aliphatic urethane resin (A) is present in an amount of 3.0% by mass or more based on the total amount of the ink. 4. The aqueous ink-jet ink according to claim 1, wherein the content of the water-dispersible (meth)acrylic resin (B) is 2.0% by mass or more based on the total amount of the ink. The aqueous inkjet ink according to claim 1 ,
An ink set comprising a maintenance liquid containing an acetylene glycol surfactant (C') having an HLB value of 10.0 or less, and glycerin in an amount of 30% by mass or more relative to the total amount of the maintenance liquid. 7. The ink set according to claim 6 , wherein the maintenance liquid has a water content of 40 to 60% by mass relative to the total amount of the maintenance liquid. an acetylene glycol-based surfactant (C) contained in the aqueous inkjet ink;
8. The ink set according to claim 6 , wherein the acetylene glycol surfactant (C') contained in the maintenance liquid contains the same components as the acetylene glycol surfactant (C').