JP7494727B2 - Pretreatment liquid, aqueous inkjet ink set using same, printed matter, and method for producing printed matter - Google Patents

Description

The present invention relates to a pretreatment liquid used when printing on non-permeable substrates using an inkjet printing method.

Digital printing, unlike traditional plate-based printing such as offset printing, does not require plate-making film or plates, making it possible to reduce costs and increase speed, and is expected to become more widespread in the future.

Inkjet printing, a type of digital printing, prints characters and images by ejecting ink droplets from extremely fine nozzles directly onto the print substrate and allowing them to adhere to the substrate. Inkjet printing has the advantages of low noise from the equipment used, good operability, and easy colorization, and is widely used as an output device in offices and homes. Furthermore, with improvements in inkjet technology, inkjet printing is beginning to be used as a digital printing output device for industrial purposes as well.

Traditionally, the inks used in inkjet printing for industrial applications have been solvent-based inks or UV inks. However, in recent years, there has been an increasing demand for water-based inks due to environmental considerations.

Water-based inks used in inkjet printing (hereafter simply referred to as "inkjet ink") have traditionally been intended for use on plain paper or specialty paper (e.g., glossy photographic paper). In other words, they are primarily made of water, and water-soluble organic solvents such as glycerin or glycol are added to control the wettability and drying properties of the ink on the substrate. When inkjet ink consisting of these liquid components is used to print a pattern of letters or images on the substrate, the liquid components penetrate the substrate, dry, and become fixed.

Meanwhile, in the market for flexible packaging materials, changes and diversification of consumer needs are driving a diversification of product varieties and shorter product life cycles. In addition, inkjet printing using water-based inks is desired due to considerations of environmental issues and occupational safety. However, when it comes to non-permeable substrates such as film substrates, ink droplets do not penetrate into the substrate at all after landing, so drying due to said penetration hardly occurs, and as a result, the droplets coalesce, causing bleeding and unevenness, compromising image quality.

As a solution to the above problem, a treatment of applying a pretreatment liquid to a non-permeable substrate is known. Generally, two types of pretreatment liquids are known for aqueous inkjet inks: one that forms a layer (ink-receiving layer) that absorbs the liquid components in the aqueous inkjet ink and improves drying properties (see Patent Documents 1 and 2), and one that forms a layer (ink aggregation layer) that prevents bleeding between aqueous inkjet ink droplets and color unevenness and improves image quality by intentionally inducing aggregation of solid components and thickening of the ink (see Patent Documents 3 and 4).

However, in the case of an ink-receiving layer, for example, when a large amount of ink is received at one time, there is a possibility that the ink-receiving layer will swell to cause image cracking, bleeding or uneven color due to exceeding the acceptable amount, and a decrease in density due to absorption of ink components into the receiving layer. In addition, when forming a receiving layer, it is necessary to make the coating thickness of the pretreatment liquid that forms the ink-receiving layer thicker than in the case of an ink aggregation layer, which will be described later. If the amount of coating is large, the drying properties of the pretreatment liquid itself will decrease, and there is a concern that problems such as poor drying will occur. As mentioned above, when used on a non-permeable substrate such as a film substrate, the pretreatment liquid will not penetrate at all, and it is thought that the above problems are likely to occur.

On the other hand, as an example of a pretreatment liquid that forms an ink aggregation layer, Patent Document 3 describes a pretreatment liquid that contains a polyvalent metal salt and (cationized) hydroxyethyl cellulose and has a specified surface tension. It is said that the use of this pretreatment liquid makes it possible to obtain high-quality printed matter with high image density, no bleeding, and excellent abrasion resistance.

Patent document 5 describes an example of a method for producing an inkjet recording medium in which an ink layer is provided on a support, in which a cationic resin obtained from an ethylenically unsaturated monomer is used, and describes an ink layer that has excellent ink bleeding resistance in images in a high humidity environment.

Patent document 6 describes a pretreatment liquid that can produce printed matter with excellent image quality without color bleeding or color unevenness, and that also has excellent adhesion to the non-permeable substrate.

In addition, when printing on non-permeable substrates such as the film substrates used for flexible packaging materials, the ink droplets do not penetrate or be absorbed by the substrate after landing, so sufficient adhesion to the film substrate is required. If the adhesion to the film substrate is insufficient, the ink film may peel off due to rubbing, or when the film is laminated with another film via an adhesive (lamination adhesive), the adhesive strength between the layers that make up the laminate may not be sufficient, resulting in delamination between the laminated layers.

In addition, flexible packaging materials often undergo a post-thermal sterilization process such as boiling or retorting after being formed into packaging materials. For this reason, a strong ink film that can withstand this thermal sterilization process is required, and water resistance is particularly required. This is because the water vapor generated during thermal sterilization and the moisture in the packaged contents when heated become water vapor, which permeates the plastic film and comes into direct contact with the ink film. Therefore, if the ink film does not have sufficient water resistance, the adhesive strength between the layers will decrease, as will the adhesion, resulting in peeling and poor appearance.

However, these documents use a flocculation-type pretreatment liquid, and because the flocculants, such as polyvalent metal salts, are highly water-soluble, the ink film has poor resistance to water, resulting in reduced adhesive strength and poor appearance during thermal sterilization of flexible packaging materials.

As described above, there has not been a water-based inkjet ink set that can produce printed matter with excellent image quality without color bleeding or uneven coloring, and that contains an aggregating pretreatment liquid that provides good adhesion and appearance when soft packaging materials are thermally sterilized.

JP 2000-238422 A JP 2000-335084 A JP 2005-074655 A JP 2006-281568 A JP 2006-334911 A JP 2020-075436 A

The present invention has been made to solve the above problems, and its purpose is to provide an aggregating pretreatment liquid, an aqueous inkjet ink set, and a printed matter that can produce printed matter with excellent image quality without color bleeding or color unevenness on non-permeable substrates such as film substrates, and that has good adhesive strength and appearance when thermally sterilizing soft packaging materials.

That is, the present invention provides a pretreatment liquid for a non-permeable substrate used in an inkjet printing system, comprising:
the pretreatment liquid contains resin fine particles (A), a flocculant (B), and water,
The flocculant (B) is a vinyl polymer and contains a structural unit (B1) containing a cationic group and a structural unit (B2) containing a hydroxyl group, and contains water and a water-soluble cationic resin (C);
The water-soluble cationic resin (C) has a weight average molecular weight of 10,000 to 100,000 and a hydroxyl value of 50 to 300 mgKOH/g.

The present invention also relates to the above pretreatment liquid, in which the glass transition temperature of the resin fine particles (A) in the pretreatment liquid is -50 to 50°C.

The present invention also relates to the above pretreatment liquid, characterized in that the content of the flocculant (B) is 60 to 200 parts by mass per 100 parts by mass of the resin fine particles (A).

The present invention also provides an aqueous inkjet ink set comprising the above pretreatment liquid and one or more types of aqueous inkjet ink,
The one or more types of aqueous inkjet inks contain a pigment (P), a pigment dispersion resin (D), and water,
The pigment dispersing resin (D) has an acid value of 30 to 375 mgKOH/g.

The present invention also relates to the above water-based inkjet ink set, in which one or more water-based jet inks include a white ink.

The present invention also relates to a printed matter obtained by sequentially printing the pretreatment liquid of the above-mentioned aqueous inkjet ink set and the aqueous inkjet ink on a non-permeable substrate.

The present invention also provides a method for producing a printed matter, comprising printing on a non-permeable substrate using the aqueous inkjet ink set, the method comprising the steps of:
printing a pretreatment liquid on the non-permeable substrate in an amount such that the film thickness after drying is 0.1 to 1.6 μm;
printing an aqueous inkjet ink on the portion of the non-permeable substrate on which the pretreatment liquid has been printed, by one-pass inkjet printing;
and drying the non-permeable substrate on which the aqueous inkjet ink has been printed.

The present invention makes it possible to obtain printed matter with excellent image quality without color bleeding or color unevenness on non-permeable substrates such as film substrates, and to provide a coagulation-type pretreatment liquid, aqueous inkjet ink set, and printed matter that have good adhesion and appearance when thermally sterilizing soft packaging materials.

The aqueous inkjet ink of the present invention will be described below with reference to preferred embodiments. Hereinafter, "aqueous inkjet ink" may be referred to as "aqueous ink" or "ink."

<Resin Fine Particles (A)>
The pretreatment liquid of the present invention contains resin fine particles (A), a flocculant (B), and water. In the present invention, the term "resin fine particles" refers to particles having a particle diameter of 5 to 1000 nm as measured by the method described below. In the present invention, particles having a particle diameter of more than 1000 nm are called "resin particles" and are distinguished from resin fine particles.

The type of resin fine particles (A) that can be used in the pretreatment liquid of the present invention is not particularly limited. For example, from the viewpoint of adhesion to non-permeable substrates, polyurethane resin, polyurea resin, polyurethane urea resin, poly(meth)acrylic resin, acrylic-modified polyurethane resin, styrene-(meth)acrylic resin, styrene-(anhydride)maleic acid resin, rosin-modified maleic acid resin, polyolefin resin, polyester resin, polyether resin, polycarbonate resin, etc. are preferred. More preferably, it is preferred to contain one or more types of resin fine particles selected from the group consisting of polyurethane resin, polyurethane polyurea resin, poly(meth)acrylic resin, acrylic-modified polyurethane resin, and polyolefin resin, and it is particularly preferred to contain a polyolefin resin. In the present invention, "(meth)acrylic" means acrylic and/or methacrylic, and "(anhydride)maleic acid" means maleic acid and/or maleic anhydride.

The pretreatment liquid of the present invention may contain only one type of resin fine particles (A) exemplified above, or two or more types may be used in combination. This is because the use of a combination of resin fine particles with different properties and types makes it possible to favorably achieve both the adhesion, blocking resistance, and drying properties of the printed matter, and the storage stability of the pretreatment liquid. In particular, from the viewpoint of achieving both of the above properties, it is particularly preferable for the resin fine particles (A) to contain two or more types selected from polyurethane resin, polyurethane polyurea resin, and poly(meth)acrylic resin.

The resin microparticles (A) may be synthesized by a known synthesis method, or may be commercially available products. When selected from commercially available products, for example, ADEKA BONTITOR HUX series (manufactured by ADEKA Corporation); IURIANO series (manufactured by Arakawa Chemical Industries Co., Ltd.); PARAZOLE series (manufactured by Ohara Palladium Chemical Co., Ltd.); U-COAT series, PERMALIN series (all manufactured by Sanyo Chemical Industries Co., Ltd.); SUPERFLEX series, SUPERFLEX E series (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.); WBR series (manufactured by Taisei Fine Chemical Co., Ltd.); HYDRAN series (manufactured by DIC Corporation); HI-TECH series (manufactured by Toho Chemical Co., Ltd.); Suitable examples include: Superchron series, Auroren series (manufactured by Nippon Paper Industries Co., Ltd.); Nichigo Polyester series (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.); AQUACER series, Hordamer series (all manufactured by BYK-Chemie Co., Ltd.); Takelac series (manufactured by Mitsui Chemicals, Inc.); Pascol series (manufactured by Meisei Chemical Industry Co., Ltd.); Arrowbase series (manufactured by Unitika Co., Ltd.); NeoCryl series, NeoRez series (manufactured by DSM Coating Resins Co., Ltd.), etc.

The amount of resin fine particles (A) contained in the pretreatment liquid of the present invention is preferably 1 to 40 mass % in terms of solid content, more preferably 1 to 30 mass %, and particularly preferably 3 to 20 mass %, based on the total amount of the pretreatment liquid. By setting the blending amount of resin fine particles (A) within the above range, the storage stability of the pretreatment liquid is improved, and printed matter having excellent adhesion to non-permeable substrates and excellent image quality can be obtained.

<Melting Point of Resin Fine Particles (A)>
The melting point of the resin fine particles (A) is preferably 0 to 130°C. More preferably, it is 15 to 105°C, and particularly preferably 30 to 90°C. If the melting point is 0°C or higher, the pretreatment liquid has good storage stability, and if it is 130°C or lower, it has excellent adhesion to non-permeable substrates. The melting point is a value measured using differential scanning calorimetry (DSC), and can be measured, for example, as follows. After weighing about 2 mg of a sample obtained by drying the resin on an aluminum sample container, the aluminum sample container is set in a holder in a DSC measurement device (for example, Shimadzu Corporation's "DSC-60Plus"). Then, measurement is performed under a temperature rise condition of 10°C/min, and the temperature of the endothermic peak read from the obtained DSC chart is taken as the melting point in the present invention. Indium is used for temperature calibration.

<Glass Transition Temperature of Resin Fine Particles (A)>
From the viewpoint of obtaining a printed matter having excellent adhesion to a non-permeable substrate, the glass transition temperature (Tg) of the resin fine particles (A) is preferably −50 to 50° C., more preferably −40 to 40° C. Like the melting point, the glass transition temperature can also be measured by differential scanning calorimetry (DSC). Specifically, from the DSC chart obtained by the above method, the intersection point between the low-temperature side baseline and the tangent at the inflection point of the baseline is obtained, and the temperature of the intersection point is taken as the glass transition temperature.

<Particle diameter of resin fine particles (A)>
The particle diameter (D50) of the resin fine particles (A) is preferably 30 to 500 nm, more preferably 40 to 400 nm, and particularly preferably 50 to 300 nm. If it is 30 nm or more, the storage stability of the pretreatment liquid is good, and if it is 500 nm or less, a printed matter having excellent adhesion to a non-permeable substrate is obtained. The particle diameter (D50) is a cumulative 50% diameter value (median diameter) on a volume basis measured by a dynamic light scattering method using a particle size distribution measuring device (e.g., Microtrac UPAEX-150 manufactured by Microtrac-Bell).

<Flocculant (B)>
The pretreatment liquid of the present invention contains a flocculant (B), water, and a water-soluble cationic resin (C), and the flocculant (B) is a vinyl polymer containing a structural unit (B1) containing a cationic group and a structural unit (B2) containing a hydroxyl group. The weight average molecular weight of the cationic resin (C) is 10,000 to 100,000, and the hydroxyl value is 50 to 300 mgKOH/g. As described above, the cationic component derived from the flocculant (B) flocculates solid components in the aqueous inkjet ink and/or causes thickening due to a component having an anionic group, and thus a printed matter with excellent image quality can be obtained.

The weight-average molecular weight of the water-soluble cationic resin (C) is 10,000 to 100,000, and preferably 30,000 to 80,000. If the weight-average molecular weight is 10,000 or more, the water resistance and abrasion resistance are good, and sufficient adhesive strength after lamination can be secured, which is preferable, and peeling phenomenon after thermal sterilization treatment can be suppressed. If it is 100,000 or less, it has excellent solubility and diffusibility in water, and when it comes into contact with droplets of the aqueous inkjet ink, it quickly mixes with the droplets, causing thickening and aggregation of the droplets, suppressing wetting and spreading on non-permeable substrates, and a printed matter with excellent image quality can be obtained.

The weight average molecular weight (Mw) of the water-soluble cationic resin (C) can be measured by a conventional method. In the present invention, it was measured using a TSKgel column (manufactured by Tosoh Corporation) and a GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with an RI detector, and THF was used as the developing solvent. All values are polystyrene equivalent.

The hydroxyl value of the water-soluble cationic resin (C) is 50 to 300 mgKOH/g. If the hydroxyl value is 50 mgKOH/g or more, it will chemically bond with the isocyanate component of the laminating adhesive, resulting in good water resistance and abrasion resistance, which is preferable as it ensures sufficient adhesive strength after lamination and can suppress peeling after thermal sterilization. If the hydroxyl value is 300 mgKOH/g or less, no excess hydroxyl groups will remain, resulting in good water resistance.

The water-soluble cationic resin (C) used in the present invention is a vinyl polymer that contains a structural unit (B1) containing a cationic group and a structural unit (B2) containing a hydroxyl group as essential components, provided that it contains the above-mentioned (B1) and (B2) as essential components and may further contain structural units other than (B1) and (B2).
Although the presence of a structural unit containing a cationic group and a hydroxyl group is not excluded, it is essential that there are at least a structural unit containing a cationic group but not a hydroxyl group, and a structural unit containing a hydroxyl group but not a cationic group.

In the water-soluble cationic resin (C), the mass ratio of the structural units derived from the ethylenically unsaturated monomer (b1) containing a cationic group to the structural units derived from the ethylenically unsaturated monomer (b2) containing a hydroxyl group is preferably 4/1 to 1/3, and more preferably 2/1 to 1/2.

The cationic group of the structural unit (B1) containing a cationic group may be, but is not limited to, a quaternary ammonium base.

The water-soluble cationic resin (C) used in the present invention can be obtained, for example, by vinyl polymerization of an ethylenically unsaturated monomer (b1) containing a cationic group, an ethylenically unsaturated monomer (b2) containing a hydroxyl group, and, if necessary, an ethylenically unsaturated monomer (b3) other than (b1) and (b2).

Examples of the ethylenically unsaturated monomer having a quaternary ammonium salt group, which is the ethylenically unsaturated monomer (b1) containing a cationic group, include alkyl (meth)acrylate-based quaternary ammonium salts such as (meth)acryloyloxyethyl trimethyl ammonium chloride, (meth)acryloyloxyethyl triethyl ammonium chloride, (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride, and (meth)acryloyloxyethyl methyl morpholino ammonium chloride;
Examples of the quaternary ammonium salts include alkyl (meth)acryloylamide-based quaternary ammonium salts such as (meth)acryloylaminopropyl trimethyl ammonium chloride, (meth)acryloylaminoethyl triethyl ammonium chloride, and (meth)acryloylaminoethyl dimethyl benzyl ammonium chloride; dimethyl diallyl ammonium methyl sulfate; and trimethyl vinyl phenyl ammonium chloride.

As the ethylenically unsaturated monomer (b2) containing a hydroxyl group, known substances can be used. Specific examples include hydroxyethyl methacrylate, hydroxyethyl acrylate, and 4-hydroxybutyl acrylate. Further examples include (poly)ethylene glycol mono(meth)acrylate, (poly)propylene glycol mono(meth)acrylate, (poly)butylene glycol mono(meth)acrylate, and (poly)(ethylene glycol-propylene glycol) mono(meth)acrylate.
These ethylenically unsaturated monomers (b2) containing a hydroxyl group can be used alone or in combination.

Examples of the ethylenically unsaturated monomer (b3) other than (b1) and (b2) include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-methoxystyrene, and p-phenylstyrene;
alkyl group-containing (meth)acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, tetratriacontanoyl (meth)acrylate, and hexatriacontanoyl (meth)acrylate;
Alkylene oxide chain-containing (meth)acrylic monomers such as (poly)ethylene glycol mono(meth)acrylate monomethyl ether, (poly)ethylene glycol mono(meth)acrylate monobutyl ether, (poly)ethylene glycol mono(meth)acrylate monooctyl ether, (poly)ethylene glycol mono(meth)acrylate monobenzyl ether, (poly)ethylene glycol mono(meth)acrylate monophenyl ether, (poly)ethylene glycol mono(meth)acrylate monohexadecyl ether, and (poly)ethylene glycol mono(meth)acrylate monooctadecyl ether;
Aromatic ring-containing (meth)acrylic monomers such as phenyl (meth)acrylate, benzyl (meth)acrylate, and phenoxyethyl (meth)acrylate;
Amino group-containing (meth)acrylic monomers such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate;
Polyfunctional (meth)acrylic monomers such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate are exemplified. Note that "(meth)acrylic" refers to at least one selected from "acrylic" and "methacrylic".

In another embodiment, a vinyl polymer having no cationic group or no hydroxyl group can be modified to give a vinyl polymer having structural units containing a cationic group and a hydroxyl group.
For example, a monomer containing glycidyl (meth)acrylate is vinyl polymerized, and the glycidyl group after polymerization is modified with a compound that reacts with the glycidyl group to give a vinyl polymer having a structural unit (B2) containing a hydroxyl group.

Alternatively, for example, an ethylenically unsaturated monomer having a functional group such as an amino group, an amide group, or a _-NHCONH2 group is vinyl polymerized, and after the polymerization, the functional group is modified into a cationic group with an onium chloride agent or the like, to give a vinyl polymer having a structural unit (B1) containing a cationic group.
Examples of the onium chloride agent include alkyl sulfates such as dimethyl sulfate, diethyl sulfate, and dipropyl sulfate; sulfonate esters such as methyl p-toluenesulfonate and methyl benzenesulfonate; alkyl chlorides such as methyl chloride, ethyl chloride, propyl chloride, and octyl chloride; alkyl bromides such as methyl bromide, ethyl bromide, propyl bromide, and octyl chloride bromide; benzyl chloride; and benzyl bromide.

Examples of the ethylenically unsaturated monomer having an amino group include (meth)acrylic acid esters or (meth)acrylamides having a dialkylamino group such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, diisopropylaminoethyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, diisobutylaminoethyl (meth)acrylate, di-t-butylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, dipropylaminopropyl (meth)acrylamide, diisopropylaminopropyl (meth)acrylamide, dibutylaminopropyl (meth)acrylamide, diisobutylaminopropyl (meth)acrylamide, and di-t-butylaminopropyl (meth)acrylamide; styrenes having a dialkylamino group such as dimethylaminostyrene and dimethylaminomethylstyrene; diallylamine compounds such as diallylmethylamine and diallylamine; and amino group-containing aromatic vinyl monomers such as N-vinylpyrrolidine, N-vinylpyrrolidone, and N-vinylcarbazole.
Other examples of polymers that can be modified into cationic groups using an onium chloride agent or the like include polymers of amine compounds such as vinylamine, allylamine, methyldiallylamine, and ethyleneimine; amide compounds such as acrylamide, vinylformamide, and vinylacetamide; cyanamide compounds such as dicyandiamide; epihalohydrin compounds such as epifluorohydrin, epichlorohydrin, methylepichlorohydrin, epibromohydrin, and epiiodohydrin; cyclic vinyl compounds such as vinylpyrrolidone, vinylcaprolactam, and vinylimidazole; amidine compounds; pyridinium salt compounds; and imidazolium salt compounds.

In the present invention, the term "hydroxyl value" refers to the number of milligrams of potassium hydroxide (mgKOH/g) required to neutralize the acetic acid required to acetylate 1 g of a sample. The hydroxyl value may be calculated from each structural unit (monomer) constituting the resin, as with the acid value, or may be measured experimentally. An example of an experimental measurement method is to add an acetylation reagent (a 25% by mass pyridine solution of acetic anhydride) to the sample, heat it to acetylate it, then allow it to cool, and add water to hydrolyze the acetic anhydride. Then, ethanol is added as a solvent, and the sample solution is titrated with an ethanol solution of potassium hydroxide (0.5 mol/L) using an automatic potentiometric titrator similar to that for the acid value. After the titration is completed, the hydroxyl value is calculated from the amount of the ethanol solution added until the end point is reached.

In the pretreatment solution of the present invention, a water-soluble cationic resin (C) and a metal salt may be used in combination.

The content of the flocculant (B) is preferably 60 to 200 parts by mass, and more preferably 80 to 160 parts by mass, per 100 parts by mass of the resin fine particles (A). By keeping the blending amount of the flocculant (B) within the above range, it is possible to obtain printed matter with excellent image quality by suppressing bleeding and color mixing, and it is also preferable because it becomes a pretreatment liquid with excellent storage stability.

In one embodiment, the flocculant (B) used in the pretreatment liquid of the present invention preferably has low hygroscopicity. When a flocculant (B') with low hygroscopicity is used, not only can a print with excellent adhesion and abrasion resistance be obtained, but the print will not absorb moisture from the air even when stored in a high humidity environment or for a long period of time, and excellent quality can be maintained for a long period of time.

In the present invention, the term "low hygroscopic flocculant" specifically refers to one whose hygroscopic weight increase rate measured by the following method is 80% by mass or less. First, the flocculant is stored for 24 hours in an environment with a temperature of 100°C and a relative humidity of 75% or less. If the flocculant is only available in the form of an aqueous solution, such as a commercially available product, the water is removed by evaporation beforehand, and then the flocculant is stored in an environment with a temperature of 100°C and a relative humidity of 75% or less. After storing in an environment with a temperature of 100°C and a relative humidity of 75% or less, the weight of the flocculant is measured (referred to as W1 (g)), and then the flocculant is stored for 24 hours in an environment with a temperature of 40°C and a relative humidity of 80% RH. After storing in an environment with a temperature of 40°C and a relative humidity of 80% RH, the weight is measured again (referred to as W2 (g)), and the hygroscopic weight increase rate is calculated by the following formula (1).

Formula (1): Moisture absorption weight increase rate (mass%) = 100 x {(W2 - W1) / W1}

From the viewpoint of obtaining a printed matter with excellent adhesion and image quality even when a substrate to which the pretreatment liquid of the present invention has been applied is stored for a long period of time in a high humidity environment, the moisture absorption weight increase rate of the flocculant (B') is preferably 80% by mass or less, and more preferably 40% by mass or less.

<Metal Salts>
When a metal salt is combined as the flocculant (B), any material can be used as long as it can flocculate and thicken the aqueous inkjet ink. It is also preferable to select a material that has excellent solubility in the pretreatment liquid and diffusibility in the liquid. Two or more types of metal salts may be used in combination.

In the pretreatment liquid of the present invention, the type of metal salt is not particularly limited as long as it is composed of a metal ion and an anion bonded to the metal ion. Among them, it is preferable that the metal salt contains a polyvalent metal salt, since it can instantly interact with the pigment to suppress bleeding and color mixing and obtain a clear image. Although the details are unclear, it is more preferable that the polyvalent metal ion constituting the polyvalent metal salt is a trivalent cation, particularly an aluminum ion, from the viewpoint of obtaining a pretreatment liquid having excellent storage stability.
Metal salts include inorganic metal salts and organic metal salts.

Specific examples of inorganic metal salts include, but are not limited to, aluminum chloride, polyaluminum chloride (PAC), calcium chloride, magnesium chloride, aluminum chloride, calcium bromide, magnesium bromide, aluminum nitrate, calcium nitrate, magnesium nitrate, aluminum sulfate, magnesium sulfate, calcium carbonate, magnesium carbonate, etc. Among these inorganic metal salts, it is preferable to select aluminum sulfate and/or aluminum nitrate in terms of hygroscopicity and the coagulation and thickening effect of aqueous inkjet inks.

Specific examples of organic metal salts include, but are not limited to, aluminum salts, calcium salts, magnesium salts, nickel salts, and zinc salts of organic acids such as pantothenic acid, propionic acid, ascorbic acid, acetic acid, and lactic acid. Among these metal salts of organic acids, it is preferable to select aluminum salts or calcium salts of lactic acid and/or acetic acid in terms of hygroscopicity and the coagulation and thickening effect of aqueous inkjet inks.

<Organic Solvent>
The pretreatment liquid of the present invention may further contain an organic solvent. By using an organic solvent in combination, the solubility of the flocculant (B) and the drying property and wettability of the pretreatment liquid can be adjusted to be suitable. In the pretreatment liquid of this embodiment, only one organic solvent may be used, or two or more organic solvents may be used in combination.

There are no particular limitations on the organic solvent that can be used in the pretreatment liquid of the present invention, but it is preferable that the pretreatment liquid contains a water-soluble organic solvent. In the present invention, a "water-soluble organic solvent" refers to a solvent that is liquid at 25°C and has a solubility of 1% by mass or more in water at 25°C.

Furthermore, the organic solvent used in the pretreatment liquid of the present invention has good affinity with the resin particles (A) and the coagulant (B), and from the viewpoint of improving the storage stability of the pretreatment liquid, it is more preferable to use a water-soluble organic solvent containing one or more hydroxyl groups in the molecular structure. From the viewpoint of realizing uniform application to non-absorbent substrates and particularly improving adhesion and image quality, it is particularly preferable to select a water-soluble organic solvent having a boiling point of 75 to 210°C at 1 atmosphere as the water-soluble organic solvent containing one or more hydroxyl groups in the molecular structure. In this specification, the boiling point at 1 atmosphere is a value measured by a known method, such as a differential thermal analysis (DTA) method or a differential scanning calorimetry (DSC) method.

Examples of water-soluble organic solvents having one or more hydroxyl groups in their molecular structure that are suitable for use in the pretreatment liquid of the present invention include monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol; 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,2-heptanediol, 2,2-dimethyl-1,3-propanediol, and 2-methyl-1,3-propanediol. dihydric aryl alcohols such as 1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methylpentane-2,4-diol, 2-ethyl-1,3-hexanediol, 1,2-octanediol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol #200, polyethylene glycol #400, dipropylene glycol, tripropylene glycol, and dibutylene glycol; Examples of the glycol monoalkyl ethers include alcohols (glycols); ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl 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 monobutyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, 1,2-butylene glycol monomethyl ether, and 1,3-butylene glycol monomethyl ether; and chain polyol compounds such as glycerin, trimethylolpropane, 1,2,4-butanetriol, 1,2,6-hexanetriol, diglycerin, and polyglycerin. As explained above, among the water-soluble organic solvents listed above, those with a boiling point of 75 to 210°C at 1 atmosphere are particularly suitable.

In addition, in one preferred embodiment, from the viewpoint of having excellent affinity with the resin fine particles (A) and the flocculant (B), improving the storage stability of the pretreatment liquid, and improving the wettability of the pretreatment liquid, it is preferable to select a water-soluble organic solvent containing one or two hydroxyl groups in the molecular structure from among the compounds exemplified above, and among them, it is preferable to use monohydric alcohols.

In addition to the above-listed compounds, the pretreatment liquid of the present invention may also contain glycol dialkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol butyl methyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, triethylene glycol methyl ethyl ether, triethylene glycol butyl methyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol methyl ethyl ether, tetraethylene glycol butyl methyl ether, and tetraethylene glycol diethyl ether; 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, ε-caprolactam, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, N,N-dimethyl-β-methanone, N,N-dimethyl-β-ethoxypropionamide, N,N-dimethyl-β-butoxypropionamide, N,N-dimethyl-β-pentoxypropionamide, N,N-dimethyl-β-hexoxypropionamide, N,N-dimethyl-β-heptoxypropionamide, N,N-dimethyl-β-2-ethylhexoxypropionamide, N,N-dimethyl-β-octoxypropionamide, N,N- Nitrogen-containing solvents such as diethyl-β-butoxypropionamide, N,N-diethyl-β-pentoxypropionamide, N,N-diethyl-β-hexoxypropionamide, N,N-diethyl-β-heptoxypropionamide, and N,N-diethyl-β-octoxypropionamide; heterocyclic compounds such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone, etc. can be used.

The total amount of organic solvents contained in the pretreatment liquid of the present invention is preferably 1 to 50% by mass, more preferably 2 to 40% by mass, and particularly preferably 3 to 30% by mass, based on the total amount of the pretreatment liquid. By keeping the amount of organic solvent within the above range, a pretreatment liquid can be obtained that has both the solubility of the resin fine particles (A) and the flocculant (B) and the wettability to the non-absorbent substrate, and stable printing without print defects can be achieved over a long period of time, regardless of the printing method of the pretreatment liquid.

When a water-soluble organic solvent containing one or more hydroxyl groups is used as the organic solvent, the blending amount is preferably 35 to 100% by mass, more preferably 50 to 100% by mass, and particularly preferably 65 to 100% by mass, based on the total amount of the organic solvent. By keeping the blending amount within the above range, the effect of the water-soluble organic solvent containing one or more hydroxyl groups can be optimally expressed.

In addition, in the pretreatment liquid of the present invention, the content of organic solvents having a boiling point of 240°C or higher at 1 atmosphere is preferably less than 10% by mass (0% by mass is also acceptable) relative to the total amount of the pretreatment liquid. By not including an organic solvent having a boiling point of 240°C or higher, or by keeping the amount of the organic solvent within the above range if it is included, printed matter with excellent image quality can be obtained and the drying properties of the pretreatment liquid can be sufficient.

Furthermore, for the same reasons as above, the content of organic solvents having a boiling point of 240°C or higher at 1 atmospheric pressure is less than 10% by mass relative to the total amount of the pretreatment liquid, and in addition, the content of organic solvents having a boiling point of 220°C or higher at 1 atmospheric pressure is preferably less than 15% by mass, more preferably less than 10% by mass, relative to the total amount of the pretreatment liquid.

<Surfactant>
The pretreatment liquid of the present invention may contain a surfactant. The surfactant may be of a siloxane type, an acrylic type, a fluorine type, an acetylene diol type, a polyoxyalkylene alkyl ether type, or the like. Any one of these may be selected, or two or more of them may be used in combination.

In a preferred embodiment, from the viewpoint of forming a uniform pretreatment liquid layer and obtaining a printed matter with excellent adhesion and image quality by imparting suitable wettability to a non-absorbent substrate, it is preferable to use acetylene diol surfactants and/or polyoxyalkylene alkyl ether surfactants among the above.

The surfactant used in the pretreatment liquid of the present invention can be synthesized by a known method or a commercially available product. When selecting a surfactant from commercially available products, for example, acetylene-based surfactants such as Surfynol 61, 104E, 104H, 104A, 104BC, 104DPM, 104PA, 104PG-50, 420, 440, 465, 485, SE, SE-F, Dynol 604, 607 (manufactured by Air Products), Olfine E1004, E1010, E1020, PD-001, PD-002W, PD-004, PD-005, EXP. 4001, EXP. 4200, EXP. 4123, EXP. 4300 (manufactured by Nissin Chemical Industry Co., Ltd.), and polyoxyalkylene alkyl ether surfactants include the Emulgen series (manufactured by Kao Corporation), Emulmin series, Sanonic series, Cedran series, Naroacty series (manufactured by Sanyo Chemical Industries Co., Ltd.), Pegnol series (manufactured by Toho Chemical Industry Co., Ltd.), Nonion series, Unilube series, and Unisafe series (manufactured by NOF Corporation). The above surfactants may be used alone or in combination of two or more.

When the pretreatment liquid of the present invention contains a surfactant, the amount of the surfactant is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass, based on the total amount of the pretreatment liquid, from the viewpoint of forming a uniform pretreatment liquid layer on the non-absorbent substrate. The amount is particularly preferably 0.1 to 3% by mass.

<Water>
As described above, the pretreatment liquid of the present invention contains water as a main component. In this specification, the phrase "containing water as a main component" means that the blending amount of water is the largest among all the constituent components.

The content of water in the pretreatment liquid of the present invention is preferably in the range of 30 to 95% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 85% by mass, based on the total amount of the pretreatment liquid. Water increases the mutual solubility of various materials such as the resin fine particles (A), the flocculant (B), and even the surfactant, and is therefore an essential material for improving the storage stability of the pretreatment liquid.

<pH Adjuster>
The pretreatment liquid of the present invention may contain a pH adjuster. By using the pH adjuster, damage to the members used in the coating device can be suppressed, and the performance of the pretreatment liquid can be maintained for a long period of time by suppressing pH fluctuation over time, and storage stability can be maintained and improved. There is no limitation on the material that can be used as the pH adjuster, and only one type may be used, or two or more types may be used in combination. Specifically, when the pretreatment liquid is made basic, alkanolamines such as dimethylethanolamine, diethanolamine, triethanolamine, and N-methyldiethanolamine; ammonia water; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate, and potassium carbonate can be used. In addition, when the pretreatment liquid is made acidic, hydrochloric acid, sulfuric acid, acetic acid, citric acid, maleic acid, maleic anhydride, succinic acid, tartaric acid, malic acid, phosphoric acid, boric acid, fumaric acid, malonic acid, ascorbic acid, glutamic acid, and the like can be used.

The amount of the pH adjuster is preferably 0.01 to 5% by mass, and more preferably 0.1 to 4.5% by mass, based on the total amount of the pretreatment liquid. By keeping the amount of the pH adjuster within the above range, pH changes due to external stimuli such as the dissolution of carbon dioxide in the air are less likely to occur, and the effect of the coagulant (B) is not inhibited.

<Coloring Agent>
In a preferred embodiment, the pretreatment liquid of the present invention does not substantially contain a colorant such as a pigment or a dye. By using a pretreatment liquid that does not contain a colorant and is substantially transparent, a printed matter that makes use of the color and transparency specific to the substrate can be obtained. In the present invention, "substantially does not contain" means that the material is not intentionally added to an extent that would prevent the effect of the present embodiment from being expressed, and does not exclude, for example, unintended mixing as an impurity or by-product. Specifically, the pretreatment liquid does not contain 2.0% by mass or more of the material, preferably 1.0% by mass or more, more preferably 0.5% by mass or more, and particularly preferably 0.1% by mass or more of the material, based on the total amount of the pretreatment liquid.

On the other hand, in another preferred embodiment, the pretreatment liquid of the present invention contains a white pigment as a colorant. By using a white pretreatment liquid on a colored and/or transparent substrate, a printed matter with excellent clarity and visibility can be obtained. When the pretreatment liquid of the present invention contains a white pigment, any conventionally known material can be used as the white pigment. Specifically, inorganic oxides such as titanium oxide, zinc oxide, and zirconium oxide; water-insoluble inorganic salts such as strontium titanate and barium sulfate; water-dispersible resin particles (emulsions) such as hollow resin particles and non-hollow resin particles; and the like can be used.

<Other materials>
In addition, in order to obtain the desired physical properties, the pretreatment liquid of the present invention may contain additives such as antifoaming agents, thickeners, and preservatives as necessary. When these additives are used, the amount of the additives is preferably 0.01 to 5 mass % relative to the total amount of the pretreatment liquid, and more preferably 0.01 to 3 mass %. If an excessive amount is added, the function of the flocculant in the pretreatment liquid may be inhibited, so the amount added is preferably within the above range.

It is also preferable that the pretreatment liquid of the present invention does not substantially contain polymerizable monomers.

<Properties of pretreatment liquid>
When the pretreatment liquid of the present invention contains water-insoluble particles having an average particle size (D50) of 1 μm or more, the content thereof is preferably 1 mass % or less based on the total amount of the pretreatment liquid. By limiting the blending amount of water-insoluble particles having an average particle size of 1 μm or more, the pretreatment liquid has good storage stability over a long period of time.

In the present invention, "water-insoluble" refers to a material having a solubility of less than 1% by mass in water at 25°C. Specific examples of water-insoluble particles having an average particle size of 1 μm or more include organic pigments, inorganic oxides, water-insoluble inorganic salts, and water-dispersible resin particles (emulsions) that satisfy the above particle size conditions. Note that even the materials described above, such as the flocculant (B) and colorant, that have an average particle size of 1 μm or more, are considered to fall under the above water-insoluble particles.

The pretreatment liquid of the present invention preferably has a viscosity at 25°C of 5 to 200 mPa·s, more preferably 5 to 180 mPa·s, even more preferably 10 to 160 mPa·s, and particularly preferably 15 to 140 mPa·s. A pretreatment liquid that satisfies the above viscosity range can be applied evenly to the substrate, resulting in a printed matter with excellent image quality and adhesion. The viscosity of the pretreatment liquid can be measured using, for example, an E-type viscometer (Toki Sangyo Co., Ltd. TVE25L viscometer) or a B-type viscometer (Toki Sangyo Co., Ltd. TVB10 viscometer), depending on the viscosity of the treatment liquid.

The static surface tension of the pretreatment liquid of the present invention is preferably 20 to 45 mN/m, more preferably 22 to 40 mN/m, and particularly preferably 25 to 35 mN/m, from the viewpoint of imparting suitable wettability to a non-absorbent substrate and forming a uniform pretreatment liquid layer to obtain a printed matter with excellent image quality. Note that the static surface tension in this specification is a value based on the Wilhelmy method (plate method, vertical plate method) in an environment of 25°C, and can be measured, for example, using an automatic surface tensiometer DY-300 (manufactured by Kyowa Interface Science Co., Ltd.) and a platinum plate.

<Method of producing pretreatment liquid>
The pretreatment liquid of the present invention, which is composed of the above components, is produced, for example, by adding resin fine particles (A), aggregating agent (B), and, if necessary, an organic solvent, a surfactant, a pH adjuster, or an additive component appropriately selected as listed above, stirring and mixing, and then filtering if necessary. However, the method for producing the pretreatment liquid is not limited to the above. For example, when a white pigment is used as a colorant, a white pigment dispersion containing the white pigment and water may be prepared in advance, and then mixed with the resin fine particles (A) and aggregating agent (B).

<Water-based inkjet ink set>
The pretreatment liquid of the present invention can be used in combination with one or more aqueous inkjet inks in the form of an aqueous inkjet ink set. The components of the aqueous inkjet inks constituting the aqueous inkjet ink set of the present invention will be described below.
At least one of the aqueous inkjet inks used in the present invention contains a pigment (P), a pigment dispersion resin (D), and water. It is more preferable that all of the aqueous inkjet inks in the aqueous inkjet ink set contain a pigment (P), a pigment dispersion resin (D), and water.

<Pigment (P)>
The aqueous inkjet ink used in the present invention contains a pigment (P) as a coloring material from the viewpoint of having blocking resistance, water resistance, light resistance, weather resistance, gas resistance, and the like. Any known organic pigment or inorganic pigment can be used as the pigment (P). Of these, the pigment other than the white ink is preferably contained in the range of 2 to 20 mass% relative to the total amount of the aqueous ink, more preferably in the range of 2.5 to 15 mass%, and particularly preferably in the range of 3 to 10 mass%. In the case of the white ink, the content of the pigment is preferably 3 to 40 mass% relative to the total amount of the white ink, more preferably in the range of 5 to 35 mass%, and particularly preferably in the range of 7 to 30 mass%. By making the content of the pigment 2 mass% or more (3 mass% or more in the case of the white ink), a printed matter having sufficient color development and clarity can be obtained. Furthermore, by keeping the pigment content to 20% by mass or less (40% by mass or less in the case of white ink), the viscosity of the water-based ink can be kept within a range suitable for inkjet printing and the storage stability of the water-based ink is also improved, resulting in long-term ejection stability.

Examples of cyan organic pigments that can be used in the aqueous ink used in the present invention include C.I. Pigment Blue 1, 2, 3, 15:3, 15:4, 15:6, 16, 22, 60, 64, and 66. Among them, one or more selected from the group consisting of C.I. Pigment Blue 15:3 and 15:4 are preferred because of their excellent color development and light resistance.

As magenta organic pigments, for example, C.I. Pigment Red 5, 7, 12, 22, 23, 31, 48 (Ca), 48 (Mn), 49, 52, 53, 57 (Ca), 57:1, 112, 122, 146, 147, 150, 185, 202, 209, 238, 242, 254, 255, 266, 269, 282, C.I. Pigment Violet 19, 23, 29, 30, 37, 40, 43, 50, etc. can be used. Among them, C.I. Pigment Red 122, 150, 166, 185, 202, 209, 266, 269, 282, and C.I. Pigment Violet 19 is preferred.

In addition, from the viewpoint of further enhancing color development, it is also preferable to use a solid solution pigment containing a quinacridone pigment as the magenta organic pigment. Specifically, a solid solution pigment containing C.I. Pigment Red 122 and C.I. Pigment Vio Red 19, a solid solution pigment containing C.I. Pigment Red 202 and C.I. Pigment Vio Red 19, a solid solution pigment containing C.I. Pigment Red 209 and C.I. Pigment Vio Red 19, a solid solution pigment containing C.I. Pigment Red 282 and C.I. Pigment Vio Red 19, a solid solution pigment containing C.I. Pigment Red 122 and C.I. Pigment Red 150, a solid solution pigment containing C.I. Pigment Red 122 and C.I. Pigment Red 185, a solid solution pigment containing C.I. Examples include solid solution pigments containing C.I. Pigment Red 122 and C.I. Pigment Red 269.

As the yellow organic pigment, for example, C.I. 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, 213, etc. can be used. Among them, one or more selected from the group consisting of C.I. Pigment Yellow 12, 13, 14, 74, 120, 180, 185, and 213 are preferred from the viewpoint of excellent color development.

As black organic pigments, for example, aniline black, lumogen black, azomethine azo black, etc. can be used. Note that it is also possible to mix multiple chromatic pigments such as the above-mentioned cyan pigments, magenta pigments, and yellow pigments, as well as the below-mentioned orange pigments, green pigments, and brown pigments, to produce black pigments.

Aqueous inkjet inks can also use special pigments such as orange pigments, green pigments, and brown pigments. Specific examples include C.I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 64, and 71, C.I. Pigment Green 7, 36, 43, and 58, and Pigment Brown 23, 25, and 26.

There are no particular limitations on the inorganic pigments that can be used in aqueous inkjet inks; for example, carbon black or iron oxide can be used as a black pigment, and titanium oxide can be used as a white pigment.

Examples of carbon black include furnace black, channel black, and acetylene black. Of these carbon blacks, those having a primary particle size of 11 to 50 nm, a specific surface area measured by the BET method of 50 to 400 m ² /g, a volatile content of 0.5 to 10 mass %, and a pH of 2 to 10 are preferred. Commercially available products having such properties include, for example, No. 25, 30, 33, 40, 44, 45, 52, 850, 900, 950, 960, 970, 980, 1000, 2200B, 2300, 2350, 2600; MA7, MA8, MA77, MA100, MA230 (manufactured by Mitsubishi Chemical Corporation), RAVEN760UP, 780UP, 860UP, 900P, 1000P, 1060UP, 1080UP, 1255 (manufactured by Birla Carbon Corporation), REGAL330R, Examples of suitable inks include 400R, 660R, MOGULL (manufactured by Cabot Corporation), Nipex 160IQ, 170IQ, 35, 75; PrinteX 30, 35, 40, 45, 55, 75, 80, 85, 90, 95, 300; Special Black 350, 550; Nerox 305, 500, 505, 600, 605 (manufactured by Orion Engineered Carbons), and any of these can be preferably used.

As titanium oxide, which is suitable for use as a white pigment, either anatase or rutile type can be used, but it is preferable to use rutile type in order to improve the hiding power of printed matter. Titanium oxide produced by either the chlorine method or the sulfuric acid method may be selected, but titanium oxide produced by the chlorine method is preferably used because of its high whiteness.

The titanium oxide is preferably surface-treated with an inorganic compound and/or an organic compound. Examples of inorganic compounds include compounds of silicon (Si), aluminum, zirconium, tin, antimony, and titanium, and hydrated oxides thereof. Examples of organic compounds include polyhydric alcohols, alkanolamines or derivatives thereof, higher fatty acids or metal salts thereof, and organometallic compounds. Among these, polyhydric alcohols or derivatives thereof are preferably used, as they can highly hydrophobize the titanium oxide surface and improve the storage stability of the ink.

In addition, in the aqueous inkjet ink used in the present invention, a mixture of the above pigments can be used in order to keep the hue and color development of the printed matter within a suitable range. For example, in order to improve the color tone at low printing rates in a black ink using a carbon black pigment, a small amount of one or more pigments selected from a cyan organic pigment, a violet red organic pigment, a magenta organic pigment, an orange organic pigment, and a brown organic pigment may be added.

<Pigment Dispersing Resin (D)>
Methods for stably dispersing and maintaining a pigment in an aqueous ink include (1) a method in which a water-soluble pigment dispersing resin is adsorbed onto the surface of the pigment and then dispersed; (2) a method in which a water-soluble and/or water-dispersible surfactant is adsorbed onto the surface of the pigment and then dispersed; (3) a method in which hydrophilic functional groups are chemically or physically introduced onto the pigment surface and then dispersed in the ink without a dispersing resin or surfactant (self-dispersing pigment); and (4) a method in which a pigment is coated with a water-insoluble resin and, if necessary, further dispersed in the ink using another water-soluble pigment dispersing resin or surfactant.

For the aqueous ink used in the present invention, it is preferable that the above-mentioned method (1) or (4), i.e., the method using a pigment dispersion resin, is selected, and the pigment dispersion resin contains 20 to 90 mass% of a monomer having an aromatic ring structure based on the total amount of monomers constituting the pigment dispersion resin. This is intended to improve adhesion and image quality by the π-cation interaction formed between the aromatic ring contained in the pigment dispersion resin and the coagulant (B) contained in the pretreatment liquid, and to ensure and improve storage stability in aqueous inkjet inks containing water-soluble organic solvents. In this specification, the term "pigment dispersion resin" is defined as a general term for the water-soluble pigment dispersion resin used in the above-mentioned method (1) or (4), and the water-insoluble resin used in the above-mentioned method (4). In addition, the term "water-insoluble resin" refers to a resin whose 25°C 1 mass% aqueous solution is not transparent to the naked eye.

For the aqueous ink used in the present invention, it is particularly preferable to select the method (1) using a water-soluble pigment dispersion resin among the above. This is because by selecting and examining the monomer composition and molecular weight that make up the resin, the resin's adsorption ability to the pigment and the charge of the pigment dispersion resin can be easily adjusted, resulting in improved storage stability of the ink and control of the pigment aggregation ability using the pretreatment liquid of this embodiment.

The type of the pigment dispersion resin is not particularly limited, and examples of the resin that can be used include (meth)acrylic resin, styrene (meth)acrylic resin, (anhydrous) maleic acid resin, styrene (anhydrous) maleic acid resin, olefin (anhydrous) maleic acid resin, polyurethane resin, and polyester resin (polycondensation product of polycarboxylic acid and polyhydric alcohol). Among these, it is particularly preferable to use acrylic resin, styrene acrylic resin, polyurethane resin, and polyester resin in terms of the large material selectivity including monomers having aromatic ring structures and the ease of synthesis. The pigment dispersion resin can be synthesized by a known method, or a commercially available product can be used.

As described above, the pigment dispersion resin preferably contains 20 to 90% by mass, more preferably 20 to 80% by mass, and particularly preferably 20 to 70% by mass, of monomers having an aromatic ring structure out of all monomers used in its synthesis. By keeping the amount of aromatic ring structure within the above range, it is possible to obtain an advantageous effect of improving adhesion and image quality by utilizing π-cation interactions, and an advantageous effect of ensuring and improving storage stability in aqueous inks that contain water-soluble organic solvents with low boiling points.

In one embodiment, the pigment dispersion resin preferably contains an alkyl group having 10 to 36 carbon atoms in addition to the aromatic ring structure. By making the alkyl group have 10 to 36 carbon atoms, it is possible to reduce the viscosity of the pigment dispersion liquid and further improve image quality and storage stability. From the viewpoint of optimizing compatibility with the water-soluble organic solvent in the aqueous ink and improving the drying properties of the printed matter, the alkyl group preferably has 12 to 30 carbon atoms, and more preferably has 18 to 24 carbon atoms. Furthermore, as long as the alkyl group has 10 to 36 carbon atoms, it may be linear or branched, but linear alkyl groups are preferred. Examples of linear alkyl groups include lauryl (C12), myristyl (C14), cetyl (C16), stearyl (C18), arachyl (C20), behenyl (C22), lignoceryl (C24), cerotoyl (C26), montanyl (C28), melissyl (C30), dotriacontanoyl (C32), tetratriacontanoyl (C34), and hexatriacontanoyl (C36).

The content of the monomer containing an alkyl chain having 10 to 36 carbon atoms in the pigment dispersion resin is preferably 5 to 60% by mass, more preferably 15 to 55% by mass, and particularly preferably 25 to 50% by mass, from the viewpoint of achieving both low viscosity of the pigment dispersion and good abrasion resistance, drying properties, blocking resistance and gloss of the printed matter.

In one embodiment, it is also suitable that the pigment dispersion resin contains an alkylene oxide group in addition to the aromatic ring structure. By introducing an alkylene oxide group, the hydrophilicity/hydrophobicity of the pigment dispersion resin can be adjusted as desired, improving the storage stability of the aqueous ink, and the alkylene oxide group causes hydrogen bonding with the resin fine particles (A) in the pretreatment liquid layer and the non-absorbent substrate, thereby significantly improving the adhesion of the printed matter. In order to optimally express the above function, when a water-soluble pigment dispersion resin is used as the pigment dispersion resin, it is preferable to select an ethylene oxide group as the alkylene oxide group. Similarly, when a water-insoluble resin is used as the pigment dispersion resin, it is preferable to select a propylene oxide group as the alkylene oxide group.

The content of the monomer having an alkylene oxide group in the pigment dispersion resin is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and particularly preferably 15 to 30% by mass of the total monomers used in the resin synthesis, from the viewpoint of achieving both low viscosity of the pigment dispersion, storage stability of the water-based ink, and adhesion of the printed matter.

When the above method (1) is selected as a method for stably dispersing and retaining the pigment in the aqueous ink, that is, when a water-soluble pigment dispersion resin is used as the pigment dispersion resin, it is preferable to neutralize the acid groups in the pigment dispersion resin with a base in order to increase the solubility in the ink. However, if an excessive amount of base is added, if the pretreatment liquid contains cationic components, the cationic components will be neutralized and the effect will not be sufficient, so care must be taken with the amount added. Whether the amount of base added is excessive can be confirmed, for example, by preparing a 10% by mass aqueous solution of the pigment dispersion resin and measuring the pH of the aqueous solution. In particular, in order to fully express the function of the pretreatment liquid, the pH of the aqueous solution is preferably 7 to 11.5, and more preferably 7.5 to 11.

Examples of bases for neutralizing the pigment dispersion resin include alkanolamines such as diethanolamine, triethanolamine, and N-methyldiethanolamine; aqueous ammonia; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogen carbonate, and potassium carbonate.

When the above method (1) is selected as a method for stably dispersing and retaining the pigment in the ink, that is, when a water-soluble pigment dispersion resin is used as the pigment dispersion resin, it is preferable that the acid value is 30 to 375 mgKOH/g. By keeping the acid value within the above range, the solubility of the pigment dispersion resin in water can be ensured, and the interaction between the pigment dispersion resins becomes favorable, so that the viscosity of the pigment dispersion liquid can be suppressed. If the acid value is 30 mgKOH/g or more, the solubility in water is good and the viscosity of the pigment dispersion liquid can be suppressed, and if it is 400 mgKOH/g or less, the storage stability of the water-based ink is excellent. The acid value of the pigment dispersion resin is more preferably 65 to 340 mgKOH/g, even more preferably 100 to 300 mgKOH/g, and particularly preferably 135 to 270 mgKOH/g.

On the other hand, when the above method (4) is selected, that is, when a water-insoluble resin is used as the pigment dispersion resin, the acid value is preferably 0 to 100 mgKOH/g, more preferably 5 to 90 mgKOH/g, and even more preferably 10 to 80 mgKOH/g. By keeping the acid value within the above range, a printed matter with excellent blocking resistance and abrasion resistance can be obtained. The acid value of the pigment dispersion resin is the number of mg of potassium hydroxide (KOH) required to neutralize the acid contained in 1 g of the pigment dispersion resin, and is the value obtained by titrating with a KOH solution in an ethanol/toluene mixed solvent. The measurement can be performed, for example, using an "automatic potentiometric titrator AT-610" manufactured by Kyoto Electronics Manufacturing Co., Ltd.

The molecular weight of the pigment dispersion resin is preferably in the range of 1,000 to 300,000 in weight average molecular weight, and more preferably in the range of 5,000 to 200,000 in weight average molecular weight. When the weight average molecular weight is in the above range, the pigment is stably dispersed in water, improving the storage stability of the water-based ink, and it is also easy to adjust the viscosity when used in the water-based ink. When the weight average molecular weight is 1,000 or more, the pigment dispersion resin is less likely to dissolve in the water-soluble organic solvent added to the water-based ink, so that the adsorption of the dispersion resin to the pigment is stronger, improving the storage stability of the ink. When the weight average molecular weight is 300,000 or less, not only is the viscosity during dispersion kept low, but the ejection stability from the inkjet head is improved, enabling stable printing over a long period of time.

In the present invention, the amount of pigment dispersion resin is preferably 2 to 60% by mass relative to the pigment. By setting the amount of pigment dispersion resin to 2 to 60% by mass relative to the pigment, the viscosity of the pigment dispersion is suppressed, the storage stability and dispersion stability of the pigment dispersion and water-based ink are improved, and aggregation occurs quickly when mixed with the pretreatment liquid of this embodiment. The ratio of pigment to pigment dispersion resin is more preferably 4 to 55% by mass, and even more preferably 5 to 50% by mass.

<Water-soluble organic solvent>
The aqueous inkjet ink used in the present invention preferably contains a water-soluble organic solvent. In addition, the amount of the water-soluble organic solvent having a boiling point of 250° C. or higher at 1 atmospheric pressure is preferably 5% by mass or less (may be 0% by mass) based on the total amount of the aqueous inkjet ink. By making the amount of the high-boiling water-soluble organic solvent 5% by mass or less, the drying property and ejection stability of the aqueous inkjet ink are improved, and when combined with a pretreatment liquid, an aqueous ink having no image quality defects such as bleeding and good blocking resistance is obtained. In addition, from the viewpoint of further improving image quality and blocking resistance, the amount of the water-soluble organic solvent having a boiling point of 250° C. or higher at 1 atmospheric pressure is preferably 2% by mass or less, more preferably 1% by mass or less (both may be 0% by mass).

For the same reason, the amount of water-soluble organic solvent having a boiling point of 220°C or higher at 1 atmosphere is preferably 5% by mass or less (may be 0% by mass) relative to the total amount of the water-based ink, and particularly preferably 2% by mass or less (may be 0% by mass). Note that the amount of water-soluble organic solvent having a boiling point of 220°C or higher at 1 atmosphere is calculated including water-soluble organic solvent having a boiling point of 250°C or higher at 1 atmosphere.

In one embodiment, the weighted boiling point average value at 1 atmosphere of the water-soluble organic solvent contained in the aqueous inkjet ink is preferably 145 to 215°C, more preferably 150 to 200°C, and particularly preferably 155 to 190°C. By keeping the weighted boiling point average value of the water-soluble organic solvent within the above range, when combined with the pretreatment liquid of this embodiment, high quality images can be obtained even in high-speed printing, and the ejection stability is also excellent. Note that the calculation of the weighted boiling point average includes water-soluble organic solvents having a boiling point of 250°C or higher at 1 atmosphere and water-soluble organic solvents having a boiling point of 220°C or higher at 1 atmosphere. The weighted boiling point average value at 1 atmosphere is a value obtained by adding together the multiplication values of the boiling points at 1 atmosphere calculated for each water-soluble organic solvent and the mass ratio to the total water-soluble organic solvents.

The boiling point at 1 atmosphere can be measured using a thermal analysis device such as a DSC (differential scanning calorimetry).

The total amount of water-soluble organic solvents used in the aqueous inkjet ink is preferably 3 to 40% by mass relative to the total amount of the aqueous inkjet ink. Furthermore, from the viewpoints of ensuring ejection stability from the nozzle, sufficient wettability and drying properties when combined with the pretreatment liquid, and obtaining a printed matter with excellent adhesion and image quality, it is more preferable that it is 5 to 35% by mass, and particularly preferable that it is 8 to 30% by mass or less. By making the total amount of water-soluble organic solvents 3% by mass or more, the ink has good moisture retention and excellent ejection stability. Furthermore, by making the content of water-soluble organic solvents 40% by mass or less, an ink with good drying properties is obtained, and a printed matter with excellent image quality is obtained. Note that, from the viewpoints of compatibility and affinity with material components such as pigment dispersion resins, binder resins described later, and surfactants, it is preferable that the ink contains glycol ether-based solvents and/or alkyl polyol-based solvents.

Examples of glycol ether solvents having a boiling point of less than 250°C at 1 atmosphere that are preferably used include glycol monoalkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, 1,2-butylene glycol monomethyl ether, and 1,3-butylene glycol monomethyl ether; and glycol dialkyl ethers such as diethylene glycol diethyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, and triethylene glycol methyl ethyl ether.

In particular, from the viewpoint of achieving both excellent moisturizing and drying properties, it is preferable to select ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, 1,2-butylene glycol monomethyl ether, 1,3-butylene glycol monomethyl ether, diethylene glycol butyl methyl ether, and triethylene glycol methyl ethyl ether from among the above glycol ether solvents.

Alkyl polyol solvents with a boiling point of less than 250°C at 1 atmosphere include, for example, 1,2-ethanediol (ethylene glycol), 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 3-methyl-1,3-butanediol, 2-methylpentane-2,4-diol, 2-ethyl-1,3-hexanediol, diethylene glycol, and dipropylene glycol.

Among these, it is preferable to select 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,2-hexanediol, diethylene glycol, and dipropylene glycol from among the above alkyl polyol solvents, since these solvents can achieve both excellent moisture retention and drying properties.

<Binder resin>
The aqueous inkjet ink used in the present invention preferably contains a binder resin. The form of the binder resin may be any of a water-soluble resin, an emulsion, and a dispersion which is an intermediate form between the two, and two or more types may be used in combination depending on the properties required for the aqueous inkjet ink and the printed matter. For example, emulsions and dispersions can reduce the viscosity of the aqueous inkjet ink and can incorporate a larger amount of resin, and are therefore suitable for enhancing the resistance of the printed matter. In addition, aqueous inkjet inks using a water-soluble resin as the binder resin are excellent in ejection stability and in image quality of printed matter when combined with the pretreatment liquid of the present embodiment.

As for the type of binder resin, any of (meth)acrylic resin, styrene (meth)acrylic resin, (anhydride) maleic acid resin, styrene (anhydride) maleic acid resin, olefin (anhydride) maleic acid resin, polyurethane resin, polyester resin, polyolefin resin, etc. can be suitably used. Among them, (meth)acrylic resin, styrene (meth)acrylic resin, polyurethane resin, and polyolefin resin are preferably used from the viewpoint of storage stability of the aqueous inkjet ink and adhesion and abrasion resistance of the printed matter when combined with the pretreatment liquid of this embodiment.

When an emulsion is used as the binder resin, it is preferable to adjust the type and compounding ratio of the monomers constituting the emulsion to make the minimum film formation temperature (MFT) 50°C or higher in order to obtain favorable discharge stability.

The MFT can be measured, for example, by using an MFT tester manufactured by Tester Sangyo Co., Ltd. Specifically, a 25% by weight aqueous solution of resin fine particles is applied to a film so that the wet film thickness is 300 μm, and then the film is left to stand on the tester under a temperature gradient. After drying, the temperature at the boundary between the area where white precipitates have formed and the area where a transparent resin film has been formed is taken as the MFT.

When a water-soluble resin and dispersion are used as the binder resin, from the viewpoint of achieving both the ejection stability of the aqueous inkjet ink and the abrasion resistance of the printed matter, it is preferable that the weight average molecular weight is in the range of 5,000 to 80,000, more preferably in the range of 8,000 to 60,000, and particularly preferably in the range of 10,000 to 50,000. For the same reasons, it is preferable that the acid value of the water-soluble resin and dispersion is in the range of 5 to 80 mgKOH/g, and more preferably in the range of 10 to 50 mgKOH/g.

The content of the binder resin in the total amount of the aqueous inkjet ink is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and particularly preferably 3 to 10% by mass, calculated as solid content.

<Surfactant>
The aqueous ink used in the present invention preferably contains a surfactant for the purpose of adjusting the surface tension and improving image quality. On the other hand, if the surface tension is too low, the nozzle surface of the inkjet head is wetted with the aqueous ink, impairing the ejection stability, so the selection of the type and amount of the surfactant is very important. From the viewpoint of ensuring wettability to the substrate and optimizing the ejection stability from the nozzle, it is preferable to use a siloxane-based, acetylene diol-based, fluorine-based, or polyoxyalkylene alkyl ether-based surfactant, and it is particularly preferable to use a siloxane-based or acetylene diol-based surfactant. The amount of the surfactant added is preferably 0.01 to 5.0% by mass, more preferably 0.05 to 3.0% by mass, based on the total amount of the aqueous ink.

The surfactant can be synthesized by a known method, or a commercially available product can be used. When selecting a surfactant from commercially available products, for example, acetylene diol surfactants and polyoxyalkylene alkyl ether surfactants can be suitably selected from those listed above as surfactants that can be used in the pretreatment liquid. In addition, examples of siloxane surfactants include BY16-201, FZ-77, FZ-2104, FZ-2110, FZ-2162, F-2123, L-7001, L-7002, SF8427, SF8428, SH3749, SH8400, 8032 ADDITIVE, SH3773M (manufactured by Dow Corning Toray Co., Ltd.), and Tegoglide 4. 10, Tegoglide 432, Tegoglide 435, Tegoglide 440, Tegoglide 450, Tegotwin 4000, Tegotwin 4100, Tegowet 250, Tegowet 260, Tegowet 270, Tegowet 280 (manufactured by Evonik Degussa), SAG-002, SAG-503 A (manufactured by Nissin Chemical Industry Co., Ltd.), BYK-331, BYK-333, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-UV3500, BYK-UV3510 (manufactured by BYK-Chemie Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF355A, KF-615A, KF-64 0, KF-642, KF-643 (manufactured by Shin-Etsu Chemical Co., Ltd.), and fluorosurfactants such as Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, Capstone FS-30, FS-31 (manufactured by DuPont), PF-151N, PF-154N (manufactured by Omnova), can be used. The above surfactants can be used alone or in combination of two or more.

The surfactant used in the water-based ink and the surfactant used in the pretreatment liquid may be the same or different. When using different surfactants, it is preferable to determine the blending amounts while taking into consideration the surface tension of both.

<Water>
The water contained in the aqueous ink used in the present invention is preferably ion-exchanged water (deionized water) rather than ordinary water containing various ions.

The water content that can be used in water-based inks is preferably in the range of 20 to 90% by weight of the total weight of the ink.

<Other ingredients>
In addition to the above components, the aqueous ink used in the present invention may contain a pH adjuster as necessary to obtain an ink having desired physical properties, and any material having pH adjustability may be selected. In the case of basifying the ink, alkanolamines such as dimethylethanolamine, diethanolamine, triethanolamine, and N-methyldiethanolamine; aqueous ammonia; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium hydrogencarbonate, and potassium carbonate may be used. In the case of acidifying the ink, hydrochloric acid, sulfuric acid, acetic acid, citric acid, maleic acid, maleic anhydride, succinic acid, tartaric acid, malic acid, phosphoric acid, boric acid, fumaric acid, malonic acid, ascorbic acid, and glutamic acid may be used. The above pH adjusters may be used alone or in combination of two or more.

The amount of the pH adjuster is preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass, and most preferably 0.2 to 1.5% by mass, based on the total amount of the aqueous inkjet ink. Keeping the amount within the above range is preferable because it prevents pH changes due to dissolution of carbon dioxide in the air, and also prevents the aggregation effect of the aggregating agent (B) from being inhibited when the pretreatment liquid comes into contact with the aqueous ink, allowing the effects of the present invention to be optimally achieved.

In addition to the above components, additives such as antifoaming agents, preservatives, infrared absorbers, and ultraviolet absorbers can be added to the water-based ink as needed to obtain ink with the desired physical properties. For example, the amount of these additives added is preferably 0.01 to 5% by weight based on the total weight of the ink.

As with the pretreatment liquid, it is preferable that the water-based ink contains substantially no polymerizable monomers.

<Water-based inkjet ink set>
The aqueous inkjet ink used in the present invention may be used in a single color, but may also be used as a set of aqueous inkjet inks in which multiple colors are combined according to the purpose. Although the combination is not particularly limited, a full-color image can be obtained by using three colors, cyan, yellow, and magenta. In addition, the blackness can be improved by adding black ink, and the visibility of characters, etc. can be increased. Furthermore, color reproducibility can be improved by adding colors such as orange and green. In the case of a film substrate, which is an example of a non-absorbent substrate, a clear image can be obtained by printing white ink on a transparent film, and the clarity and visibility of characters, etc. printed with black ink can be increased, so that it is preferably combined.

<Method of manufacturing water-based inkjet ink>
The aqueous inkjet ink containing the above-mentioned components is produced, for example, through the following process. However, the production method of the aqueous inkjet ink is not limited to the following.

(1) Production of Pigment Dispersion Liquid When a water-soluble pigment dispersion resin is used as the pigment dispersion resin, the water-soluble pigment dispersion resin is mixed and stirred with water, and if necessary, with a water-soluble organic solvent, to prepare a water-soluble pigment dispersion resin mixture. A pigment is added to the water-soluble pigment dispersion resin mixture, and the mixture is mixed and stirred (premixed), and then a dispersion treatment is performed using a dispersing machine. Thereafter, centrifugal separation, filtration, and adjustment of the solid content concentration are performed as necessary to obtain a pigment dispersion liquid.

When producing a dispersion of a pigment coated with a water-insoluble resin, the water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone beforehand, and the water-insoluble resin is neutralized as necessary to prepare a water-insoluble resin solution. The pigment and water are added to the water-insoluble resin solution, and the mixture is mixed and stirred (premixed), and then a dispersion process is performed using a disperser. The organic solvent is then removed by vacuum distillation, and centrifugal separation, filtration, and adjustment of the solids concentration are performed as necessary to obtain a pigment dispersion.

The dispersing machine used in dispersing the pigment may be any commonly used dispersing machine, such as a ball mill, roll mill, sand mill, bead mill, and nanomizer. Among the above, bead mills are preferably used, and are commercially available under the trade names of Super Mill, Sand Grinder, Agitator Mill, Grain Mill, Dyno Mill, Pearl Mill, and Cobol Mill.

Methods for controlling the particle size distribution of pigment dispersions include reducing the size of the grinding media of the disperser mentioned above, changing the material of the grinding media, increasing the packing rate of the grinding media, changing the shape of the stirring member (agitator), lengthening the dispersion processing time, classifying the pigment after dispersion processing using a filter or centrifuge, and combinations of these methods. In order to keep the pigment within a suitable particle size range, it is preferable that the diameter of the grinding media of the disperser mentioned above is 0.1 to 3 mm. Furthermore, glass, zircon, zirconia, and titania are preferably used as materials for the grinding media.

(2) Preparation of Water-Based Inkjet Ink Next, a water-soluble organic solvent, water, and, if necessary, the binder resin, surfactant, and other additives listed above are added to the pigment dispersion liquid, and the mixture is stirred and mixed. If necessary, the mixture may be stirred and mixed while being heated in the range of 40 to 100°C.

(3) Removal of Coarse Particles Coarse particles contained in the mixture are removed by a method such as filtration separation or centrifugation to obtain an aqueous inkjet ink. As a method for filtration separation, a known method can be appropriately used. The filter pore size is not particularly limited as long as it can remove coarse particles and dust, but is preferably 0.3 to 5 μm, more preferably 0.5 to 3 μm. When performing filtration, a single type of filter may be used, or multiple types may be used in combination.

<Characteristics of water-based inkjet ink>
The viscosity of the aqueous inkjet ink is preferably adjusted to 3 to 20 mPa·s at 25° C. This viscosity range exhibits stable ejection characteristics, particularly from inkjet heads having a normal frequency of 4 to 10 KHz to inkjet heads having a high frequency of 10 to 70 KHz. In particular, by adjusting the viscosity at 25° C. to 4 to 10 mPa·s, stable ejection can be achieved even when used with an inkjet head having a design resolution of 600 dpi or more.

The viscosity can be measured by a conventional method. Specifically, it can be measured using an E-type viscometer (TVE25L type viscometer manufactured by Toki Sangyo Co., Ltd.) and 1 mL of ink.

In order to obtain a water-based inkjet ink that can be stably discharged and to obtain a printed matter having excellent adhesion and image quality when combined with the pretreatment liquid of the present invention, the water-based inkjet ink of this embodiment preferably has a static surface tension at 25°C of 18 to 35 mN/m, more preferably 19 to 32 mN/m, and particularly preferably 20 to 28 mN/m. In order to prevent bleeding and color mixing of the printed matter and to obtain a printed matter having particularly excellent image quality, it is preferable to adjust the type and amount of the water-soluble organic solvent and surfactant so that the surface tension of the water-based ink of this embodiment is equal to or lower than the surface tension of the pretreatment liquid. The static surface tension in this embodiment can be measured by a platinum plate method in a 25°C environment using, for example, a surface tensiometer (CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.).

For the same reasons as above, the aqueous inkjet ink preferably has a dynamic surface tension at 25°C and 10 msec of 25 to 40 mN/m, more preferably 28 to 38 mN/m, and particularly preferably 30 to 36 mN/m. The dynamic surface tension in this embodiment can be measured by the maximum bubble pressure method in a 25°C environment using a Kruss Bubble Pressure Dynamic Surface Tensiometer BP100.

In order to obtain printed matter with excellent color development, the average secondary particle diameter (D50) of the pigment in the aqueous inkjet ink is preferably 40 nm to 500 nm, more preferably 50 nm to 400 nm, and particularly preferably 60 nm to 300 nm. In order to keep the average secondary particle diameter within the above preferred range, the pigment dispersion process can be controlled as described above.

<Method of manufacturing printed matter>
As a method for producing a printed matter using an aqueous inkjet ink set that combines the pretreatment liquid of the present invention with the aqueous inkjet ink, a method including the steps of printing the pretreatment liquid on a non-absorbent substrate, printing the aqueous inkjet ink by one-pass inkjet printing on the portion of the non-absorbent substrate on which the pretreatment liquid has been printed, and drying the non-absorbent substrate on which the aqueous inkjet ink has been printed. Note that the above steps are preferably performed in this order.

In the present invention, "one-pass inkjet printing" refers to a method of printing in which an inkjet head is scanned over a stationary substrate only once, or the substrate is passed under a fixed inkjet head only once, and ink is not printed on top of the printed ink again. However, when scanning the inkjet head, it is necessary to adjust the ejection timing taking into account the movement of the inkjet head, and deviations in the landing position are likely to occur. Therefore, when printing the water-based ink of this embodiment, a method of passing the substrate under a fixed inkjet head is preferably used.

The following describes a method for producing printed matter using the aqueous inkjet ink set of the present invention.

<Pretreatment liquid printing method>
When producing a printed matter using the pretreatment liquid of the present invention, the pretreatment liquid is preferably printed on a non-absorbent substrate before printing with an aqueous inkjet ink. As the printing method, either a method of printing without contacting the substrate, such as inkjet printing, or a method of printing by contacting the substrate with the pretreatment liquid may be adopted. In addition, when a printing method of contacting the pretreatment liquid is selected as the printing method of the pretreatment liquid, a roller type such as an offset gravure coater, gravure coater, doctor coater, bar coater, blade coater, flexo coater, or roll coater can be preferably used.

<Drying method after printing pretreatment liquid>
The pretreatment liquid of the present invention may be printed on a non-absorbent substrate, the non-absorbent substrate may be dried, the pretreatment liquid on the substrate may be dried, and then the aqueous inkjet ink may be printed, or the aqueous inkjet ink may be printed before the pretreatment liquid on the substrate is completely dried. In one embodiment, it is preferable to completely dry the pretreatment liquid before printing the aqueous inkjet ink, that is, to bring the liquid component of the pretreatment liquid into a state where it has been completely removed. This is because printing the aqueous inkjet ink after the pretreatment liquid has completely dried prevents the aqueous inkjet ink that lands later from drying poorly, and a printed matter with excellent abrasion resistance can be obtained.

There are no particular limitations on the drying method used in printing the pretreatment liquid of the present invention, and examples include conventionally known methods such as heat drying, hot air drying, infrared drying, microwave drying, and drum drying. The above drying methods may be used alone or in combination, but hot air drying is preferred to reduce damage to non-absorbent substrates and dry efficiently. In addition, from the viewpoint of preventing damage to the substrate and bumping of the liquid components in the pretreatment liquid, when using heat drying, the drying temperature is preferably 35 to 100°C, and when using hot air drying, the hot air temperature is preferably 50 to 150°C.

<Printing method using water-based inkjet ink>
The aqueous inkjet ink is preferably applied by one-pass inkjet printing to the portion of the non-absorbent substrate on which the pretreatment liquid has been printed. The design resolution of the inkjet head used in the one-pass inkjet printing is preferably 600 dpi (Dots Per Inch) or more, more preferably 720 dpi or more, in order to obtain an image with excellent image quality.

<Drying method after printing with water-based inkjet ink>
After printing the aqueous inkjet ink, the method preferably includes a step of drying the non-absorbent substrate to which the aqueous inkjet ink has been applied in order to dry the aqueous ink and the undried pretreatment liquid. The drying method preferably used is the same as that for the pretreatment liquid.

<Printing amount of pretreatment liquid and water-based inkjet ink>
The thickness of the layer formed by printing the pretreatment liquid after drying is preferably 0.1 to 1.6 μm.
Alternatively, when printing the aqueous inkjet ink set of the present invention, the printing amount (after drying) of the pretreatment liquid of this embodiment on a non-absorbent substrate is preferably 1 to 25 g/m ^2. By keeping the film thickness and coating amount within the above ranges, it is possible to suppress color bleeding, improve the drying properties of the pretreatment liquid layer after coating, prevent adhesion to the inside of a coating device and blocking when printed materials are stacked, and obtain printed materials that are free of tack (stickiness) and have excellent abrasion resistance.

When printing the aqueous inkjet ink set of the present invention, it is preferable that the ratio of the printing amount of the aqueous inkjet ink to the printing amount of the pretreatment liquid is 0.1 or more and 10 or less. The ratio of the printing amounts is more preferably 0.5 or more and 9 or less, and particularly preferably 1 or more and 8 or less. By keeping the ratio of the printing amounts within the above range, it is possible to prevent a change in the texture of the substrate caused by an excessive amount of pretreatment liquid, and a deterioration in image quality caused by an excessive amount of aqueous inkjet ink that makes the effect of the pretreatment liquid insufficient.

<Non-absorbent substrate>
When printing with the aqueous inkjet ink set of the present invention, any of the conventionally known non-absorbent substrates can be used. For example, thermoplastic resin substrates such as polyvinyl chloride sheets, polyethylene terephthalate (PET) films, polypropylene films, polyethylene films, nylon films, polystyrene films, and polyvinyl alcohol films, and metal substrates such as aluminum foil can be used. The above substrates may have a smooth or uneven surface, and may be transparent, semi-transparent, or opaque. In addition, two or more of these substrates may be laminated together. Furthermore, a peelable adhesive layer or the like may be provided on the opposite side of the printing surface, and an adhesive layer or the like may be provided on the printing surface after printing. The shape of the substrate used in printing with the ink set of the present invention may be in the form of a roll or a sheet.

Among these, in order to fully exert the functions of the pretreatment liquid of the present invention, it is preferable that the non-absorbent substrate is a thermoplastic resin substrate, and it is particularly preferable that the substrate is a PET film, a polypropylene film, a polyethylene film, or a nylon film.

In addition, in order to improve image quality by uniformly printing the pretreatment liquid of the present invention and to particularly improve adhesion, it is also preferable to subject the non-absorbent substrates exemplified above to a surface modification method such as corona treatment or plasma treatment.

<Coating Treatment>
The printed surface of a printed matter produced using the aqueous inkjet ink set of the present invention may be subjected to a coating treatment, if necessary. Specific examples of the coating treatment include coating/printing of a coating composition, and lamination processing such as dry lamination, solventless lamination, and extrusion lamination, and any of these may be selected or a combination of two or more may be used.

When a coating treatment is performed on a printed matter by applying/printing a coating composition, the coating/printing method may be either a method of printing without contacting the substrate, such as inkjet printing, or a method of printing by contacting the substrate with the coating composition. When selecting a method of printing without contacting the substrate with the coating composition, it is preferable to use an ink (clear ink) that does not substantially contain colorant components, excluding pigments from the aqueous inkjet ink of this embodiment, as the coating composition.

The pretreatment liquid and aqueous inkjet ink set including the aqueous inkjet ink, which are embodiments of the present invention, will be described in more detail below with reference to examples and comparative examples. In the following description, "parts" and "%" refer to "parts by mass" and "% by mass", respectively, unless otherwise specified.

<Preparation of pretreatment liquid>
<Production Example of Water-Soluble Cation Resin 1>
In a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, 100 parts of ion-exchanged water and 100 parts of isopropyl alcohol (IPA) were charged and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and a mixture of 50 parts of acrylic ester DMC (manufactured by Mitsubishi Chemical) and 50 parts of 2-hydroxyethyl methacrylate and 50 parts of a 15% aqueous solution of ammonium persulfate were dropped over 3 hours, respectively, to carry out a polymerization reaction. After the dropwise addition was completed, the mixture was reacted at 110 ° C. for 1 hour and aged. Furthermore, the isopropyl alcohol and water in the liquid were distilled off, and water was added and adjusted so that the solid content was 30%, thereby obtaining a water-soluble cationic resin 1 (solid content 30%). The hydroxyl value of the water-soluble cationic resin 1 measured by the method shown above was 166 mg KOH / g, and the weight average molecular weight was 10,000.

<Production Examples of Water-Soluble Cation Resins 2 to 17>
Water-soluble cationic resins 2 to 17 were produced in the same manner as for water-soluble cationic resin 1, except that the materials shown in Table 1 were used.

DMC: Acrylic ester DMC (manufactured by Mitsubishi Chemical) Methacrylic acid dimethylaminoethyl methyl chloride salt 2HE-DMC: Methacrylic acid (2-hydroxyethyl) methylaminoethyl methyl chloride salt 2HEMA: 2-hydroxyethyl methacrylate 2HEA: 2-hydroxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate St: Styrene

<Production Example of Pretreatment Solution 1>
The following materials were placed in a mixing vessel equipped with a stirrer and mixed at room temperature (25° C.) for 1 hour, then heated to 50° C. and mixed for another 1 hour. The mixture was then cooled to room temperature and filtered through a membrane filter with a pore size of 1 μm to obtain pretreatment liquid 1.
NeoCrylXK-190 (40% solids) 18.75 parts Water-soluble cationic resin 1 (30% solids) 20.0 parts Adekanol UH-526 (30% solids) 5.0 parts Surfynol 465 1.0 parts IPA 5.0 parts Proxel GXL 0.10 parts Ion-exchanged water 50.15 parts

<(1-4) Production Examples of Pretreatment Solutions 2 to 25>
Pretreatment solutions 2 to 25 were produced in the same manner as pretreatment solution 1, except that the materials listed in Table 2 were used.

In the above production examples, the raw materials used are detailed below.
<Resin fine particles>
NeoCrylXK-190: styrene-acrylic resin fine particles manufactured by DSM Coating Resins (glass transition temperature 32°C, solid content 40%)
NeoRezR-9621: polyurethane resin particles manufactured by DSM Coating Resins (glass transition temperature -31°C, solid content 38%)
<Flocculant>
PAS-H-1L: Polydimethyldiallylammonium hydrochloride (weight average molecular weight 8,500, solid content 28%) manufactured by Nittobo Medical Co., Ltd.
Catiomaster PD-7: Polyepichlorohydrin manufactured by Yokkaichi Chemical Co., Ltd. (hydroxyl value 410 mg KOH/g, weight average molecular weight 5,000, solid content 50%)
Catiomaster PD-30: Polyepichlorohydrin manufactured by Yokkaichi Chemical Co., Ltd. (hydroxyl value 405 mg KOH/g, weight average molecular weight 9,000, solid content 50%)
Catiomaster PE-30: Polyepichlorohydrin manufactured by Yokkaichi Chemical Co., Ltd. (hydroxyl value 340 mg KOH/g, weight average molecular weight 9,000, solid content 50%)
<Thickener>
ADEKA NOL UH-526: Water-soluble urethane resin (solid content 30%) manufactured by ADEKA Corporation
<Surfactant>
Surfynol 465: Acetylene diol surfactant (solid content 100%) manufactured by Air Products
<Preservatives>
Proxel GXL: 1,2-benzisothiazol-3-one (solid content 100%) manufactured by Arch Chemicals

<Production of Water-Based Inkjet Inks>
<Production Example of Pigment Dispersion Resin 1>
A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 95 parts of butanol and substituted with nitrogen gas. The reaction vessel was heated to 110°C, and a mixture of 35 parts of styrene as a polymerizable monomer, 35 parts of acrylic acid, 30 parts of lauryl methacrylate, and 6 parts of V-601 (manufactured by Wako Pure Chemical Industries) as a polymerization initiator was dropped over 2 hours to carry out a polymerization reaction. After the dropwise addition, the mixture was reacted at 110°C for 3 hours, and then 0.6 parts of V-601 (manufactured by Wako Pure Chemical Industries) was added, and the reaction was continued for another 1 hour at 110°C to obtain a solution of pigment dispersion resin 1. Furthermore, after cooling to room temperature, dimethylaminoethanol was added to completely neutralize the mixture, and then 100 parts of water was added to make it aqueous. Thereafter, the mixture was heated to 100°C or higher, and butanol was distilled off by azeotroping with water, and the solid content was adjusted to 30%, thereby obtaining an aqueous solution of pigment dispersion resin 1 (solid content 30%). The acid value of pigment dispersion resin 1, measured by the method described above, was 272 mgKOH/g, and the weight average molecular weight was 28,000.

<Production Examples of Water-Based Solutions of Pigment Dispersion Resins 2 to 6>
As shown in Table 3 below, aqueous solutions (solid content 30%) of pigment dispersion resins 2 to 6 were obtained in the same manner as for pigment dispersion resin 1, except that the type and amount of the polymerizable monomer were changed.

<Production Examples of Pigment Dispersions 1C, 1M, 1Y, and 1K>
20 parts of LIONOL BLUE 7358G (C.I. Pigment Blue 15:3) manufactured by Toyo Color Co., Ltd., 20 parts of an aqueous solution of pigment dispersion resin 1 (solid content 30%), and 60 parts of water were mixed and premixed with a stirrer, and then main dispersion was carried out using a 0.6 L Dyno Mill filled with 1800 g of zirconia beads with a diameter of 0.5 mm to obtain pigment dispersion liquid 1C. Pigment dispersion liquids 1M, 1Y, and 1K were obtained in the same manner as pigment dispersion liquid 1C, except that the above C.I. Pigment Blue 15:3 was replaced with the pigments shown below.
Magenta: FASTGENSUPERMAGENTARG (C.I. Pigment Red 122) manufactured by DIC Corporation
Yellow: LIONOLYELLOWTT1405G (C.I. Pigment Yellow 14) manufactured by Toyo Color Co., Ltd.
Black: PrinteX85 (carbon black) manufactured by Orion Engineered Carbons

<Production Examples of Pigment Dispersions 2 to 6 (C, M, Y, K)>
Pigment dispersions 2 to 6 (C, M, Y, and K, respectively) were obtained in the same manner as in the preparation of pigment dispersions 1C, 1M, 1Y, and 1K, except that the aqueous solution of pigment dispersion resin 1 was used instead of the aqueous solutions of pigment dispersion resins 2 to 6 (solid content 30%) as the pigment dispersion resin.

<Production Example of Pigment Dispersion Liquid 1W>
40 parts of Ishihara Sangyo Kaisha's Typeque CR-90-2 (titanium oxide), 20 parts of an aqueous solution of pigment dispersion resin 1 (solid content 30%), and 40 parts of water were mixed and premixed with a stirrer, and then main dispersion was carried out using a 0.6 L Dyno Mill filled with 1,800 g of zirconia beads with a diameter of 0.5 mm, to obtain pigment dispersion liquid 1W (pigment concentration 40%).

<Production Examples of Pigment Dispersions 2W to 6W>
Pigment dispersions 2W to 6W were obtained in the same manner as in the case of pigment dispersion 1W, except that pigment dispersion resin 1 was used instead of the aqueous solutions (solid content 30%) of pigment dispersion resins 2 to 6 as the pigment dispersion resin.

<Production example of water-based inkjet ink set 1 (CMYKW)>
The following materials were sequentially charged into a mixing vessel equipped with a stirrer and stirred until sufficiently uniform. The mixture was then filtered through a membrane filter with a pore size of 1 μm to remove coarse particles that may cause clogging of the inkjet head, yielding aqueous inkjet cyan ink 1. Furthermore, by using pigment dispersions 1M, 1Y, 1K, and 1W instead of pigment dispersion 1C, aqueous inkjet ink set 1 consisting of five colors, cyan (C), magenta (M), yellow (Y), black (K), and white (W):
Pigment dispersion 1C 25 parts Joncryl 8211 (solid content 44%) 15 parts 1,2-propanediol (1,2-PD) 20 parts Surfynol 465 1 part Proxel GXL 0.05 parts Ion-exchanged water 38.95 parts

In the above manufacturing example, Joncryl 8211 is an acrylic resin emulsion (MFT 57°C, solids content 44%) manufactured by BASF.

<Production example of inkjet ink sets 2 to 6 (CMYKW)>
Inkjet ink sets 2 to 6 consisting of five colors, cyan (C), magenta (M), yellow (Y), black (K), and white (W), were obtained in the same manner as in inkjet ink set 1, except that the materials listed in Table 4 below were used.

[Examples 1 to 18, Comparative Examples 1 to 12]
<Example of preparation of film substrate with pretreatment liquid applied>
Using a K Control Coater K202 and wire bar No. 0 manufactured by Matsuo Sangyo Co., Ltd., the pretreatment liquid prepared above was applied (printed) to the following film substrate in a wet film thickness of 4.0±0.2 μm, and then the film substrate coated with the pretreatment liquid was placed in an air oven at 70° C. and dried for 3 minutes to prepare a film substrate coated with the pretreatment liquid.

<Film substrates used in evaluation>
・Unitika nylon film "Emblem ON"
(Thickness: 15 μm, hereafter referred to as “NY”)

<Examples of printed matter>
An inkjet head KJ4B-QA (manufactured by Kyocera Corporation, design resolution 600 dpi) was installed on the top of a conveyor capable of transporting a substrate, and the set of aqueous inkjet inks produced above was filled in the order of K, C, M, Y, and W from the upstream side. Next, the film substrate to which the pretreatment liquid produced above was applied was fixed on the conveyor, and the conveyor was driven at a constant speed, and when passing through the installation section of the inkjet head, the inkjet inks were each ejected at a drop volume of 10 pL, thereby printing the following image. After printing, the printed matter was promptly placed in a 70° C. air oven and dried for 5 minutes to produce a printed matter.

The conveyor drive speed was set to two conditions, 30 m/min or 50 m/min, and printing was performed under each condition. Two types of printed images were prepared: an image in which 5 cm x 5 cm solid patches with a printing rate of 100% are adjacent to each other in the order of CMYK (hereafter referred to as a "solid patch image"), and a four-color (CMYK) image in which the total printing rate (the sum of the printing rates of each color) changes continuously from 40 to 320% (hereafter referred to as a "gradation image." Note that the printing rate of each color is the same for each total printing rate), and printed materials of each were produced.

The above printed matter was produced using the combination of the pretreatment liquid and aqueous inkjet ink set shown in Table 5. The following evaluations 1 to 5 were carried out using this printed matter or the pretreatment liquid itself. The evaluation results were as shown in Table 5.

<Evaluation 1: Evaluation of color mixing and bleeding>
Printing was performed under the above conditions, and 4C (CMYK) prints were produced on the film substrate coated with the pretreatment liquid, with the printing rate varying from 40% to 320%. The dot shapes of the printed areas were observed at 200x magnification using an optical microscope, and color mixing and bleeding were evaluated. The evaluation criteria were as follows, with ◎ and ◯ being practically usable.
⊚: At any printing rate, the dots in the 4C printed parts were independent and no color bleeding was observed. ○: The dots in the 4C printed parts with a printing rate of 40 to 280% were independent and no color bleeding was observed, but color bleeding was observed in printed parts with a printing rate of over 280%. △: The dots in the 4C printed parts with a printing rate of 40 to 240% were independent and no color bleeding was observed, but color bleeding was observed in printed parts with a printing rate of over 240%.
×: Clear color bleeding was observed in 4C printed areas with a print rate of 40 to 240%.

<Evaluation 2: Evaluation of color unevenness>
Printing was performed under the same conditions as in Evaluation 1 above, and 4C (CMYK) prints were produced on the film substrate coated with the pretreatment liquid, with the printing rate varied from 40% to 320%, and the degree of color unevenness in the 4C (CMYK) prints was visually observed to evaluate the color unevenness. The evaluation criteria were as follows, with ◎ and ◯ being ranges that are practically usable.
◎: No color unevenness was observed in the 4C printed part at any printing rate. ○: No color unevenness was observed in the 4C printed part with a printing rate of 40 to 280%, but color unevenness was observed in the printed part with a printing rate of over 280%. △: No color unevenness was observed in the 4C printed part with a printing rate of 40 to 240%, but color unevenness was observed in the printed part with a printing rate of over 240%. ×: Clear color unevenness was observed in the 4C printed part with a printing rate of 40 to 240%.

<Evaluation 3: Lamination strength (adhesive strength)>
Using a test coater, the following laminating adhesive was applied to the printed surface of a printed matter that had been solid printed with a printing rate of 100% for one color and solid printed with a total printing rate of 200% for two colors on the following film substrate that had been coated with a pretreatment liquid, at a temperature of 60°C and a coating speed of 50 m/min (coating amount: 2 g/ ^m2 ). For laminating adhesives that contained a solvent component, the solvent component was dried after coating, and the adhesive was applied so that the coating amount after drying was 2 g/ ^m2 . Furthermore, the following sealant film was superimposed on the coated surface of the laminating adhesive, and the laminate was aged for one day in an environment of 40°C and 80% RH to harden the laminating adhesive composition, thereby producing a laminated laminate.
<Film substrate>
- Unitika nylon film "EMBLEM ON" (thickness 15 μm)
<Sealant film>
- Mitsui Chemicals Tocello linear low-density polyethylene film "TUX-FC-D" (thickness 40 μm)
<Laminating adhesive>
・Toyo Morton TM-265L/CAT-RT37 (solvent-based lamination adhesive)

The laminated laminate thus produced was cut into a length of 300 mm and a width of 15 mm to prepare a test piece. Using an Instron tensile tester, the laminate was pulled at a peeling speed of 300 mm/min in an environment of 25°C, and the T-type peel strength (N) between the transparent substrate 1 and the substrate 4 was measured. This test was carried out five times, and the average value was calculated to evaluate the adhesive strength. The evaluation criteria were as follows, with ⊚ and ◯ being practically usable.
◎: Adhesive strength of 1.5 N or more ◯: Adhesive strength of 0.6 N or more, but less than 1.5 N △: Adhesive strength of 0.3 N or more, but less than 0.6 N ×: Adhesive strength of less than 0.3 N

<Evaluation 4: Adhesion strength after heat sterilization treatment>
Two laminated sheets were stacked with the sealant film on the inside and sealed using a heat sealer at 150°C, 2 kg/ ^cm2 , and 1 second to create a tare. This was then sterilized in hot water at 95°C for 30 minutes using a Hisaka Seisakusho "RCS-40RTGN" high-temperature, high-pressure cooking sterilization tester. After the test, the laminate strength was evaluated in the same manner as above.

<Evaluation 5: Appearance Evaluation>
The laminate test pieces used in the adhesive strength evaluation after the heat sterilization treatment were visually observed from the film substrate side to evaluate the appearance. The evaluation criteria were as follows, with ◎ and ◯ being practically usable.
⊚: There is no delamination or foaming in the laminate, or delamination and foaming are present over an area of less than 3%. ◯: There is delamination and foaming over an area of 3% or more and less than 20% of the laminate. △: There is delamination and foaming over an area of 20% or more and less than 50% of the laminate.
x: Delamination and bubbling are observed over 50% or more of the area of the laminate.

In Examples 1 to 18, the pretreatment liquid was a system using the water-soluble cationic resin defined in the present invention, and the inkjet ink set was a system using the pigment dispersion resin defined in the present invention. It was possible to obtain printed matter with excellent image quality without color bleeding or color unevenness, and the adhesive strength after lamination processing and the condition were maintained good even after hot water bacterial treatment, and all were within the range of practical use.

In Comparative Example 1, the weight average molecular weight of the water-soluble cationic resin was less than 10,000, resulting in poor appearance after heat sterilization treatment. In Comparative Example 2, the weight average molecular weight of the water-soluble cationic resin exceeded 100,000, resulting in poor image quality. In Comparative Example 3, the hydroxyl value of the water-soluble cationic resin was less than 50 mg KOH/g, resulting in poor crosslinking reaction with the lamination adhesive, poor adhesion after hot water bacterial treatment and lamination processing, and poor appearance after hot water bacterial treatment. In Comparative Example 4, the hydroxyl value of the water-soluble cationic resin exceeded 300 mg KOH/g, resulting in poor water resistance due to excess hydroxyl groups remaining, resulting in poor appearance after hot water bacterial treatment. Comparative Examples 5 and 6 are water-soluble cationic resins that do not have a hydroxyl value, Comparative Examples 8 to 10 are water-soluble cationic resins whose weight average molecular weight and hydroxyl value are not within the ranges specified by the present invention, Comparative Examples 11 and 12 are cationic substances with high water solubility that are not resins specified by the present invention, and therefore the adhesive strength after lamination processing and the appearance after the hot water bacterial treatment are poor. Comparative Example 7 is a water-soluble cationic resin that is not a resin specified by the present invention, and has a structure that contains hydroxyl groups in a structural unit containing a cationic group, and therefore has poor solubility in water, so the viscosity of the pigment dispersion cannot be suppressed, and it spreads wet on the non-permeable substrate, resulting in poor image quality.

Claims (7)

A pretreatment liquid for a non-permeable substrate used in an inkjet printing system, comprising:
the pretreatment liquid contains resin fine particles (A), a flocculant (B), and water,
The flocculant (B) is a vinyl polymer and contains a water-soluble cationic resin (C) that contains a structural unit (B1) containing a cationic group and a structural unit (B2) containing a hydroxyl group;
The water-soluble cationic resin (C) has a weight average molecular weight of 10,000 to 100,000 and a hydroxyl value of 50 to 300 mgKOH/g. The pretreatment liquid according to claim 1, wherein the glass transition temperature of the resin fine particles (A) in the pretreatment liquid is -50 to 50°C. The pretreatment liquid according to claim 1 or 2, characterized in that the content of the flocculant (B) is 60 to 200 parts by mass per 100 parts by mass of the resin fine particles (A). An aqueous inkjet ink set comprising the pretreatment liquid according to any one of claims 1 to 3 and one or more aqueous inkjet inks,
The one or more types of aqueous inkjet inks contain a pigment (P), a pigment dispersion resin (D), and water,
The aqueous inkjet ink set, wherein the acid value of the pigment dispersing resin (D) is 30 to 375 mgKOH/g. The aqueous inkjet ink set according to claim 4, wherein one or more aqueous jet inks include a white ink. A printed matter obtained by sequentially printing the pretreatment liquid of the aqueous inkjet ink set according to claim 4 or 5 and the aqueous inkjet ink on a non-permeable substrate. A method for producing a printed matter, comprising printing on a non-permeable substrate using the aqueous inkjet ink set according to claim 4 or 5,
printing a pretreatment liquid on the non-permeable substrate in an amount such that the film thickness after drying is 0.1 to 1.6 μm;
printing an aqueous inkjet ink by single-pass inkjet printing on the portion of the non-permeable substrate on which the pretreatment liquid has been printed;
and drying the non-permeable substrate on which the aqueous inkjet ink has been printed.