Pretreatment liquid, aqueous inkjet ink set using the same, and printed material

Abstract

To provide a printed material which, when printing on packaging or labeling materials, does not cause color mixing blur or uneven coloring, and exhibits superior water resistance, rub resistance, and wet rub resistance.SOLUTION: The present invention provides a pretreatment liquid for use in combination with an aqueous inkjet ink, the pretreatment liquid comprising a water-soluble cationic resin (A), cationic resin particles (B), and water. The water-soluble cationic resin (A) contains a structural unit represented by the formula (1) in an amount of 50 to 100 mass% relative to the total mass% of the water-soluble cationic resin (A). The cationic resin particles (B) contain the structural unit represented by the formula (1) in an amount of 1 to 40 mass% relative to the total mass% of the cationic resin particles (B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a pretreatment liquid, an aqueous inkjet ink set using the same, and a printed matter.

Background Art

[0002] An inkjet printing method, which is a type of digital printing method, forms an image or characters (hereinafter collectively referred to as "printed matter") on a printing medium by flying and landing minute droplets of ink from an inkjet head onto a substrate as the printing medium. Compared with other digital printing methods, it is excellent in terms of the size and cost of the printing apparatus, the running cost during printing, and the ease of full-colorization, and in recent years, it has been increasingly used also in industrial printing applications.

[0003] Inks used in the inkjet printing method cover a wide range, such as oil-based, solvent-based, active energy ray curable, and water-based. Heretofore, solvent-based and active energy ray curable inks have been used in industrial printing applications. However, in recent years, due to considerations and responses regarding environmental and human hazards, the demand for water-based inks (also referred to as aqueous inks) has been increasing.

[0004] By the way, substrates used for package packaging of daily necessities, label materials, etc. require the formation of printed matter having characteristics that can withstand actual use with respect to hardly permeable substrates such as art paper and coated paper, and non-permeable substrates such as polyolefin and polyethylene terephthalate (PET) films, from the viewpoints of their cosmetic properties, protection of the contents, and long-term information display. In particular, in recent years, as the use applications of the inkjet printing method have expanded, correspondence to such package applications has been demanded.

[0005] When printing on hardly permeable substrates and non-permeable substrates used for package packaging and label materials, since the ink droplets after landing are difficult to penetrate and absorb into the substrate, drying due to penetration does not occur, and problems such as color mixing bleeding and color unevenness occur, and the printed image quality is impaired.

[0006] Regarding the problem of impaired printing quality, pretreatment liquids are known. Generally, as pretreatment liquids for aqueous inkjet inks, there are those that form a layer (ink receiving layer) that absorbs the liquid components in the aqueous inkjet ink and improves the drying property (see Patent Documents 1 and 2), and those that form a layer (ink aggregation layer) that intentionally aggregates solid components contained in the aqueous inkjet ink, such as colorants and resins, to prevent bleeding between droplets and color unevenness and improve the printing quality (see Patent Documents 3 to 5). Two types are known.

[0007] However, printed matter using aqueous ink has problems such as low resistance of the coating film to liquids such as water and alcohol, rubbing off of the ink layer, and bleeding of the image. Therefore, regarding the problem of low resistance of the ink layer, for example, Patent Documents 6 to 7 disclose that using an emulsion in the inkjet ink can obtain a certain improvement effect in resistance. Patent Document 6 improves the adhesion between the PET substrate and the pretreatment layer. Also, Patent Document 7 reports an improvement in water resistance by immersing the pretreatment layer in water. However, in any of the patent documents, problems such as insufficient water friction resistance against friction during wetting and low printing quality occurred.

[0008] In addition, for printed matter used in package packaging, label materials, etc., the pretreatment layer, like the ink layer forming the image portion, is required to have strong water resistance, alcohol resistance, abrasion resistance, and water friction resistance. This is because even if the ink layer has good resistance, if the pretreatment layer existing between the substrate and the ink layer is fragile, the ink layer will also peel off together with the pretreatment layer.

[0009] For the above reasons, when forming the ink-receiving layer, since the receiving layer forms an image by absorbing water molecules in the ink, it is necessary to make the coating film thickness of the pretreatment liquid for forming the receiving layer thicker than in the case of the ink-aggregating layer. As a result, drying failure is likely to occur and water molecules are likely to remain in the receiving layer, so the water resistance after printing deteriorates. Also, when a large amount of ink is received at once, cracks in the image occur due to swelling of the receiving layer, water molecules easily enter during wetting, leading to a decrease in water resistance and water-rubbing resistance. Furthermore, problems such as bleeding and color unevenness due to exceeding the receivable amount also occur, resulting in a decrease in the print quality of the printed image.

[0010] As examples of the pretreatment liquid for forming the ink-aggregating layer, Patent Documents 3 to 5 describe polyvalent metal salts, organic acids, organic acid ammonium salts, and water-soluble cationic resins as aggregating agents. Polyvalent metal salts, organic acids, and organic acid ammonium salts have high water solubility and low molecular weight, so when an inkjet ink lands on the pretreatment layer, they can quickly aggregate the solid components contained in the inkjet ink, and excellent print quality can be obtained. However, due to their properties, the water resistance of the image area deteriorates. Also, in the pretreatment liquid, since the above aggregating agents are dissolved as ionic components, the dissolved low-molecular ions easily aggregate with other materials contained in the pretreatment liquid, such as resin components and additives that form a film after printing, and the storage stability of the pretreatment liquid is likely to decrease. On the other hand, water-soluble cationic resins have good water resistance in the image area due to their large molecular weight. However, due to their large molecular weight, the dissolution rate in water is slow. When performing high-speed printing or printing an image with a high printing rate, bleeding and color unevenness occur, resulting in poor print quality.

[0011] As described above, in printing on package packaging and label materials by the inkjet method, a pretreatment liquid that has water resistance and water-rubbing resistance suitable for packaging materials and provides excellent print quality without bleeding and color unevenness has not been found so far.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0013] The present invention has been made to solve the above problems, and its object is to provide water resistance, abrasion resistance, and water-abrasion resistance suitable for packaging materials even in printing on hardly permeable substrates and non-permeable substrates used for package packaging and label materials, and a pretreatment liquid, an aqueous inkjet ink set, and a printed matter that can obtain excellent print image quality without bleeding or color unevenness.

[0014] As a result of intensive studies by the present inventors, it has been found that the above problems can be solved by using a composition for a pretreatment liquid having a specific water-soluble cation resin and cation resin particles.

Means for Solving the Problems

[0015] That is, the present inventors A pretreatment liquid used together with a water-based inkjet ink, comprising a water-soluble cationic resin (A), cationic resin particles (B), and water, wherein the water-soluble cationic resin (A) contains a structural unit represented by formula (1) in an amount of 50 to 100% by mass based on the total mass of the water-soluble cationic resin (A), and the cationic resin particles (B) contain a structural unit represented by formula (1) in an amount of 1 to 40% by mass based on the total mass of the cationic resin particles (B). The present invention relates to a pretreatment liquid characterized by the above. Formula (1)

Chemical formula

[0016] The present invention also relates to a pretreatment liquid characterized in that the cationic resin particles (B) contain a block polymer having a hydrophilic unit (b-1) and a hydrophobic unit (b-2).

[0017] The present invention also relates to a pretreatment liquid characterized in that the cationic resin particles (B) have a number average molecular weight of 8,000 to 50,000.

[0018] The present invention also relates to a pretreatment liquid characterized by performing printing by an inkjet recording method.

[0019] The present invention also relates to an aqueous inkjet ink set comprising the pretreatment liquid and one or more aqueous inkjet inks containing white ink.

[0020] The present invention also relates to a printed matter obtained by printing the pretreatment liquid and one or more aqueous inkjet inks containing white ink.

Advantages of the Invention

[0021] The pretreatment liquid of the present invention enables the provision of a printed matter having water resistance and water rub resistance suitable for packaging materials, excellent printing image quality without bleeding or color unevenness.

Modes for Carrying Out the Invention

[0022] Hereinafter, preferred embodiments will be given to explain the pretreatment liquid and the aqueous inkjet ink set of the present invention. Hereinafter, the "aqueous inkjet ink" may be referred to as "aqueous ink" or "ink".

[0023] <Pretreatment Liquid> The pretreatment liquid of the present invention contains a water-soluble cationic resin and cationic resin particles. As described above, the water-soluble cationic resin is used in the pretreatment liquid as a flocculant for flocculating the inkjet ink that forms an image. Different from low-molecular-weight flocculants such as polyvalent metal salts and organic acids, the water-soluble cationic resin can impart good water resistance and rub resistance to the printed matter by forming a high-molecular-weight resin film on the substrate. However, compared with low-molecular-weight flocculants, since the volume per molecule is bulky, the solubility in water is slow, the flocculation rate of the ink is slow, and bleeding and the like are likely to occur.

[0024] On the other hand, the cationic resin particles are used as the main component of the coating film that forms the pretreatment layer. Since the resin particles do not dissolve in water, a coating film with excellent water resistance and water rub resistance is formed after printing. However, in order to obtain the dispersion stability of the resin particles in water, it is necessary to emulsify them using a surfactant, include hydrophilic functional groups in the resin particles, etc. As a result, the water resistance of the coating film decreases. Furthermore, problems such as a decrease in the dispersion stability of the resin particles due to the reaction with the flocculant and a deterioration in the storage stability of the pretreatment liquid occur.

[0025] As a result of the intensive studies by the present inventors, both the water-soluble cationic resin used as a flocculant and the cationic resin particles used as the main component of the coating film of the pretreatment layer contain a structural unit represented by the formula (1). The water-soluble cationic resin contains the structural unit represented by the formula (1) in an amount of 50 to 100% by mass based on the total mass of the water-soluble cationic resin, and the cationic resin particles contain the structural unit represented by the formula (1) in an amount of 1 to 40% by mass based on the total mass of the cationic resin particles. By doing so, a printed matter having excellent print quality, good water resistance, abrasion resistance, and water-abrasion resistance can be obtained, and furthermore, a pretreatment liquid having good storage stability can be obtained. Although the detailed mechanism is not clear, for example, the following is considered.

[0026] First, in the present invention, the water-soluble cationic resin (A) serves as a flocculant for aggregating the inkjet ink that forms an image, and the cationic resin particles (B) form a film after printing and play a role as the main component of the coating film. In the pretreatment liquid, the former exists in a dissolved state in water, and the latter exists in a particulate state. However, since both contain the structural unit represented by the formula (1), the interaction between polymer molecules hardly occurs, and the storage stability of the pretreatment liquid is excellent.

[0027] In addition, the cationic groups of the cationic resin particles (B) exert the ability as a flocculant and complement the aggregating power of the water-soluble cationic resin (A). Since the cationic groups are contained in the structural unit represented by the formula (1), it is considered that the ability to aggregate the inkjet ink is the same. Therefore, the aggregating power of the water-soluble cationic resin (A) is complemented, and a print quality without bleeding or color unevenness can be obtained. When the structure and properties of the cationic groups are completely different, the aggregating power is also different, so a difference in aggregating ability occurs, and it is considered that the complementary effect is not exhibited. Although the water resistance and abrasion resistance of the printed matter are good, the drawback that the aggregation rate of the water-soluble cationic resin (A) with respect to the ink is slow can be improved by using the cationic resin particles (B) containing the same structural unit, thereby enhancing the aggregating ability and obtaining excellent print quality. Also, since they are resins having the same cationicity, the interaction between polymer molecules is suppressed, and the storage stability of the pretreatment liquid is excellent. However, the above is based on scientific considerations, and the present invention is not limited to such actions.

[0028] <Water-soluble cationic resin (A)> In the present invention, the water-soluble cationic resin contains a structural unit represented by the formula (1) in an amount of 50 to 100% by mass based on the total mass of the water-soluble cationic resin. By setting it to 50% by mass or more, the action of aggregating the solid components in the aqueous inkjet ink and / or the action of causing thickening due to the interaction between the components having an anionic group via the water-soluble cationic resin can provide a printed matter with excellent print quality. More preferably, it is 60 to 80% by mass. Formula (1)

Chemical formula

[0029] From the viewpoint of solubility in the inkjet ink, Z is an oxygen atom or -NH-, and it is preferable that at least two of R 2 , R 3 , R 4 are methyl groups.

[0030] As a method for introducing a structural unit represented by the formula (1) into a water-soluble cationic resin, there are a method of copolymerizing using a vinyl monomer containing a cationic group, and a method of reacting an onium chloride agent after obtaining a polymer having a tertiary amino group by copolymerizing a vinyl monomer having a tertiary amino group as a monomer component to quaternary ammonium chloride. In the present invention, either polymerization method can be selected.

[0031] As the vinyl monomer containing a cationic group for introducing the structural unit represented by the formula (1) into the water-soluble cationic resin, a quaternary ammonium salt type monomer is preferable. For example, alkyl (meth)acrylate quaternary ammonium salts such as (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxyethyltriethylammonium chloride, (meth)acryloyloxyethyldimethylbenzylammonium chloride, (meth)acryloyloxyethylmethylmorpholinoammonium chloride, 2-hydroxy-3-(meth)acryloyloxypropyltrimethylammonium chloride; alkyl (meth)acryloylamide quaternary ammonium salts such as (meth)acryloylaminopropyltrimethylammonium chloride, (meth)acryloylaminoethyltriethylammonium chloride, (meth)acryloylaminoethyldimethylbenzylammonium chloride, etc. are mentioned, but it is not particularly limited to these. These can be used alone or in combination of two or more.

[0032] When introducing a structural unit represented by the formula (1) into a water-soluble cation resin from a vinyl monomer having a tertiary amino group, the vinyl monomer having a tertiary amino group used may be, for example, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dipropylaminoethyl (meth)acrylate, diisopropylaminoethyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, diisobutylaminoethyl (meth)acrylate, dit-butylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, dipropylaminopropyl (meth)acrylamide, diisopropylaminopropyl (meth)acrylamide, dibutylaminopropyl (meth)acrylamide, diisobutylaminopropyl (meth)acrylamide, dit-butylaminopropyl (meth)acrylamide, etc. Examples include (meth)acrylic acid esters or (meth)acrylamides having a dialkylamino group, but are not particularly limited thereto. These can be used alone or in combination of two or more.

[0033] When reacting an onium chlorinating agent with a tertiary amino group to ammonium chloride, examples of the onium chlorinating agent used include alkyl halides such as chloromethane, chloroethane, chloropropane, chlorobutane, bromomethane, bromoethane, bromopropane, bromobutane, iodomethane, iodoethane, iodopropane, iodobutane, benzyl chloride, benzyl bromide, etc., alkyl sulfates such as dimethyl sulfate, diethyl sulfate, or dipropyl sulfate, sulfonic acid esters such as methyl p-toluenesulfonate, methyl benzenesulfonate, etc., but are not particularly limited thereto. These can be used alone or in combination of two or more. A part or all of the tertiary amino group can be ammonium chlorinated.

[0034] The vinyl monomers constituting the water-soluble cationic resin (A) include, among others, linear or branched alkyl group-containing vinyl monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, etc., alicyclic alkyl group-containing vinyl monomers such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc., and aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, phenoxyhexaethylene glycol (meth)acrylate, phenyl (meth)acrylate, etc.

[0035] Furthermore, hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono(meth)acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, allyl alcohol, (meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, etc., amide group-containing vinyl monomers, (poly)ethylene glycol mono(meth)acrylate, (poly)propylene glycol mono(meth)acrylate, (poly)butylene glycol mono(meth)acrylate, ( poly)(ethylene glycol-propylene glycol) mono(meth)acrylate, (po ly)ethylene glycol mono(meth)acrylate monomethyl 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 other alkylene oxide chain-containing vinyl monomers can be mentioned.

[0036] The weight average molecular weight (Mw) of the water-soluble cationic resin (A) is preferably from 10,000 to 100,000, more preferably from 20,000 to 80,000. By setting the weight average molecular weight to 10,000 or more, the water resistance and water friction resistance of the coating film after printing are excellent. By setting it to 100,000 or less, good printing image quality can be obtained.

[0037] The weight average molecular weight of the water-soluble cationic resin (A) in the present invention can be measured by a conventional method. In the present invention, it was measured using GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with a TSKgel column (manufactured by Tosoh Corporation) and an RI detector, and using a calcium nitrate solution as the developing solvent. For both, PEG (polyethylene glycol) and PEO (polyethylene oxide), which are water-soluble molecular weight standard polymers, were used to prepare the calibration curve.

[0038] The water-soluble cationic resin (A) is preferably contained in an amount of 2 to 30% by mass, more preferably 3 to 20% by mass, based on the total mass% of the pretreatment liquid. By keeping the blending amount of the water-soluble cationic resin (A) within the above range, bleeding and color mixing can be suppressed, and a printed matter with excellent image quality can be obtained, and the water resistance and friction resistance of the printed matter are also improved.

[0039] <Cationic resin particles (B)> In the present invention, the cationic resin particles contain the structural unit represented by the formula (1) in an amount of 1 to 40% by mass based on the total mass% of the cationic resin particles (B). The cationic resin particles (B) have the same structural unit represented by the formula (1) as the water-soluble cationic resin (A), but differ in the form as a resin composition. The water-soluble cationic resin (A) has solubility in water and exists in a dissolved state in the pretreatment liquid. On the other hand, the cationic resin particles (B) are insoluble in water and exist in a dispersed state as particles in water. Thus, it becomes the main component of the coating film forming the pretreatment layer, and a coating film with excellent water resistance and friction resistance can be formed after printing. Formula (1)

Chemical formula

[0040] From the viewpoints of ease of synthesis and dispersion stability in water, Z is an oxygen atom or -NH-, and it is preferable that at least two of R 2 , R 3 , R 4 are methyl groups.

[0041] The structural unit represented by formula (1) is contained in an amount of 1 to 40% by mass, more preferably 5 to 30% by mass, based on the total mass% of the cationic resin particles (B). By setting it to 1% by mass or more, the storage stability and printing image quality of the pretreatment liquid become good. Also, by setting it to 40% by mass or less, the water resistance and abrasion resistance of the coating film after printing become good.

[0042] In addition, the determination of whether it has a water-soluble form that dissolves in water or a form dispersed in water as particles is carried out by measuring the 50% volume average particle diameter (D50) by the particle size distribution measurement method using dynamic light scattering with a NanoTrac UPA-EX150 manufactured by Microtrac Bell Corporation. A resin sample with a measurable particle diameter has a particle form, has a small average particle diameter, and a resin sample with an unmeasurable particle diameter is judged not to have a particulate state and is a water-soluble resin.

[0043] The average particle diameter of the cationic resin particles of the present invention is preferably 30 to 150 nm, more preferably 40 to 120 nm. If the water solubility is too strong and the particle state is not exhibited, the water resistance and rub resistance of the coating film after printing will deteriorate. By setting the average particle diameter to 30 nm or more, the water resistance and rub resistance of the coating film after printing will be improved. By setting it to 150 nm or less, the storage stability of the pretreatment liquid will be improved, and excellent print image quality can be obtained.

[0044] The cationic resin particles may be those polymerized by a known polymerization method or commercially available products as long as the resin particles are uniformly dispersed in water. Specifically, emulsion resin particles polymerized using an emulsifier or the like, amphiphilic block polymers, and the like can be mentioned. Although not particularly limited thereto, in the present invention, from the viewpoint of print image quality, it is preferably an amphiphilic block polymer.

[0045] A block polymer is a copolymer composed of two or more types of monomers, and is a polymer in which two or more polymer units having different copolymerization compositions are bonded in one polymer chain, and is also called a block copolymer or a block copolymer. There are two methods for a block polymer: a method of chemically bonding each polymer unit and a method of polymerizing another monomer at the end of one polymer unit. Different from a random copolymer (also called a random polymer), a block polymer has the properties of each polymer unit.

[0046] The block polymer of the present invention is an amphiphilic block polymer having a hydrophilic unit (b-1) and a hydrophobic unit (b-2). The hydrophilic unit has a high affinity for water and is dissolved in water, while the hydrophobic unit is not dissolved in water. Therefore, in water, micelles with particulate properties are formed. This is because polymer units with significantly different solubilities, namely hydrophilicity and hydrophobicity, cause repulsion between the hydrophilic-hydrophobic units and phase separation occurs in the microscopic region. Thus, by having a hydrophobic unit, the hydrophobic units of multiple polymers aggregate and maintain a particulate state, resulting in good water resistance, abrasion resistance, and water-abrasion resistance of the ink coating film after printing. Furthermore, even for the pretreatment liquid, the ejection stability during printing on a recording medium by an inkjet printing method is improved. Also, by including a structural unit represented by formula (1) in the hydrophilic unit (b-1), the inkjet ink has a function of aggregating, and the printed image quality is improved.

[0047] The polymerization method of the block polymer can be carried out by polymerization using the living radical polymerization method, which is a known polymerization method. Living radical polymerization methods include nitroxide-mediated polymerization, atom transfer polymerization, reversible addition-fragmentation chain transfer polymerization, organotellurium-mediated polymerization, iodine transfer polymerization, and the like. It is preferable to use the reversible addition-fragmentation chain transfer polymerization method (also referred to as RAFT polymerization) for the block polymer of the present invention.

[0048] Reversible addition-fragmentation chain transfer polymerization is a type of reversible deactivation radical polymerization and is one of the methods that can impart living properties to radical polymerization. In living polymerization, the polymerization reaction starts in all polymer chains from the initial stage of the reaction, and the polymer chains grow and polymerize at the same reaction rate. Therefore, there are no irreversible chain transfer or termination reactions, and a polymer with a narrow molecular weight distribution (PDI = weight average molecular weight / number average molecular weight) can be obtained. Also, by adding more monomers to the polymerization reaction system, the polymer chains can be extended. Utilizing this, multiple blocks with different properties can be connected, and AB diblock polymers, ABA or ABC triblock polymers, etc. can be obtained.

[0049] The block polymer of the present invention preferably has a number average molecular weight (Mn) of 8,000 to 50,000. More preferably, it is 10,000 to 30,000, and even more preferably, it is 12,000 to 20,000. By setting the number average molecular weight to 8,000 or more, the water resistance, abrasion resistance, and water-abrasion resistance of the coating film after printing are excellent. By setting it to 50,000 or less, good storage stability of the pretreatment liquid and excellent printing image quality can be obtained. The number average molecular weight (Mn) of the block polymer can be measured in the same manner as the water-soluble cationic resin (A).

[0050] In addition, the block polymer obtained by living radical polymerization can obtain a polymer with a narrow molecular weight distribution compared to the random polymer obtained by conventional radical polymerization. The more uniform the molecular weight distribution of the block polymer, the stronger the phase separation in the micro region, and the stronger the characteristics of each polymer unit with different solubility can be expressed. The molecular weight distribution of the block polymer of the present invention is preferably 1.6 or less, more preferably 1.5 or less. By setting it to 1.6 or less, the characteristics of each polymer unit are expressed, and good dispersion stability and printing image quality can be obtained.

[0051] Regardless of whether the cationic resin particles (B) are emulsion resin particles polymerized using an emulsifier or the like, or amphiphilic block polymers, as a method for introducing the structural unit represented by the formula (1) into the cationic resin particles, similar to the case of introducing it into the water-soluble cationic resin described above, a method of copolymerizing using a vinyl monomer containing a cationic group, a method of obtaining a polymer having a tertiary amino group by copolymerizing a vinyl monomer having a tertiary amino group as a monomer component, and then reacting with an onium chloride agent to quaternary ammonium chloride can be mentioned.

[0052] In addition, for the vinyl monomer constituting other than the structural unit represented by the formula (1) contained in the cationic resin particles (B), the same vinyl monomer as the water-soluble cationic resin (A) can be used.

[0053] When the cationic resin particles (B) are an amphiphilic block polymer having a hydrophilic unit (b-1) and a hydrophobic unit (b-2), it is preferable that all of the structural units represented by the formula (1) are contained in the hydrophilic unit (b-1). As described above, polymer units with significantly different solubilities, namely hydrophilic and hydrophobic units, cause repulsion between the hydrophilic and hydrophobic units, phase-separate in microscopic regions, and the hydrophilic units are present at the interface with water as if covering the hydrophobic units. From this, it aggregates by contacting with the pigment dispersion or binder resin component in the ink for forming an image, which is mainly designed to be anionic, and although it is the main component of the coating film after printing, it has a high function as a flocculant. Also, the storage stability as a pretreatment liquid is improved.

[0054] Examples of the vinyl monomer constituting other than the structural unit represented by the formula (1) contained in the hydrophilic unit (b-1) include, as hydrophilic monomers, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol mono (meth)acrylate, 4-hydroxyvinylbenzene, 1-ethynyl-1-cyclohexanol, hydroxyl group-containing vinyl monomers such as allyl alcohol, (meth)acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl-N-methoxymethylmethacrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-dimethylaminopropylacrylamide, N,N-diethylaminopropylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide and other amide group-containing vinyl monomers.

[0055] Furthermore, examples of the hydrophobic monomer include vinyl monomers containing a linear or branched alkyl group such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, etc.; vinyl monomers containing an alicyclic alkyl group such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc.; aromatic vinyl monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, phenoxyhexaethylene glycol (meth)acrylate, phenyl (meth)acrylate, etc.

[0056] The hydrophilic unit (b-1) is not particularly limited as long as it is a unit exhibiting hydrophilicity, but the content of the structural unit derived from the hydrophilic monomer is preferably 60% by mass or more, more preferably 80% by mass or more.

[0057] Examples of the vinyl monomer constituting the hydrophobic unit (b-2) include the above-mentioned vinyl monomers containing a linear or branched alkyl group, vinyl monomers containing an alicyclic alkyl group, aromatic vinyl monomers, vinyl monomers containing a hydroxyl group, and vinyl monomers containing an amide group, but are not particularly limited thereto. These can be used alone or in combination of two or more. The hydrophobic unit (b-2) preferably has a content of the structural unit derived from the hydrophobic monomer of 60% by mass or more, more preferably 80% by mass or more.

[0058] More preferable vinyl monomers constituting the hydrophobic unit (b-2) are monomers having a cyclic structure, and preferably include alicyclic alkyl group-containing vinyl monomers and aromatic vinyl monomers. By having a cyclic structure, the water resistance and abrasion resistance of the coating film after printing are improved. Also, the repulsion with the hydrophilic unit in water is strengthened, phase separation in the micro-region is promoted, the particulate state is maintained, and the ejection stability is improved. The vinyl monomer having a cyclic structure constituting the hydrophobic unit is preferably contained in an amount of 5 to 50% based on the total mass% of the cationic resin particles (B).

[0059] The mass ratio of the hydrophilic unit (b-1) to the hydrophobic unit (b-2) is preferably 10:90 to 70:30. More preferably, it is 20:80 to 50:50. When the mass ratio of the hydrophilic unit is 10 or more, the storage stability is improved, and when it is 70 or less, the ejection stability and the water resistance and water abrasion resistance of the coating film after printing are improved.

[0060] Examples of the RAFT agent (chain transfer agent) used in the reversible addition-fragmentation chain transfer polymerization method include diester-based, trithiocarbonate-based, dithiocarbamate-based, and xanthate-based agents. Among these, trithiocarbonate-based and diester-based RAFT agents, which are highly active and have good reactivity with alkyl group-containing vinyl monomers such as (meth)acrylates, aromatic vinyl monomers, amide group-containing vinyl monomers, and aromatic vinyl monomers, are preferred. Specifically, examples include methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, S,S-dibenzyl trithiocarbonate, trithiocarbonic acid bis{4-[ethyl-(2-acetoxyethyl)carbamoyl]benzyl}, benzyl 4-methoxybenzodithioate, 2-cyanopropan-2-yl benzodithioate, and the like. The mass of the RAFT agent used in the polymerization can be calculated from the molecular weight of the RAFT agent, the molecular weights and composition ratios of the respective vinyl monomers to be polymerized, and the number average molecular weight of the desired block polymer.

[0061] In addition, as the polymerization initiator necessary for radical generation at the initial stage of polymerization, known ones can be used. From the viewpoints of polymerizability and molecular weight control, azo compounds are preferable, and it is preferable to use 0.2 to 0.8 mol with respect to 1 mol of the RAFT agent. Examples of the azo compound include, but are not particularly limited to, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(isobutyric acid)dimethyl, etc.

[0062] In addition, the total amount of the cationic resin particles of the present invention is preferably 3% by mass or more and 30% by mass or less with respect to the total amount of the pretreatment liquid. By setting it to 3% by mass or more, the print image quality, water resistance, and abrasion resistance after printing become good, and by setting it to 30% by mass or less, the storage stability becomes good. More preferably, it is 5% by mass or more and 20% by mass or less.

[0063] Subsequently, other constituent materials of the pretreatment liquid of the present invention will be described.

[0064] <Coagulant> For the purpose of aggregating and thickening the inkjet ink containing the colorant that forms the image portion to obtain an excellent image, the pretreatment liquid of the present invention contains a water-soluble cationic resin having a structural unit represented by the formula (1) and cationic resin particles, but other coagulants may be used as long as the effects of the present invention are not impaired. Specifically, metal salts and water-soluble cationic resins that do not contain the structural unit represented by the formula (1) can be mentioned.

[0065] 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. 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.

[0066] When selecting a water-soluble cationic resin, examples of cationic groups contained in the water-soluble cationic resin include, but are not limited to, amino groups, ammonium groups, amide groups, -NHCONH2 groups, etc.

[0067] Materials used to introduce the above cationic groups into the water-soluble cationic resin include, for example, 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; imidazolium salt compounds, etc.

[0068] When using a water-soluble cationic resin that does not contain the structural unit represented by formula (1) in combination, it is preferable that the water-soluble cationic resin is a compound containing one or more structural units selected from the group consisting of a mono(meth)acrylamine structural unit, a mono(meth)acrylammonium chloride structural unit, a diallylamine structural unit, a diallylammonium structural unit, and an epihalohydrin structural unit. As the above water-soluble cationic resin, those synthesized by known synthesis methods may be used, or commercially available products may be used.

[0069] <Organic solvent of the pretreatment liquid> The pretreatment liquid of the present invention preferably contains a water-soluble organic solvent. By using a water-soluble organic solvent, the solubility of the water-soluble cationic resin (A), the dispersion stability of the cationic resin particles (B), and the wettability of the pretreatment liquid to the substrate can be adjusted to suitable values. In the present invention, the "water-soluble organic solvent" refers to a liquid at 25 °C and having a solubility in water at 25 °C of 1 mass% or more.

[0070] The water-soluble organic solvent is not particularly limited, and known ones can be arbitrarily used. However, from the viewpoints of the solubility of the water-soluble cationic resin (A), the dispersion stability of the cationic resin particles (B), and the wettability of the pretreatment liquid to the substrate, it is preferable to contain a glycol ether solvent and / or an alkyl polyol solvent containing one or more hydroxyl groups in the molecular structure. In particular, the boiling point of the water-soluble organic solvent under 1 atm is preferably 70 °C or higher and lower than 210 °C. By setting it to 70 °C or higher, the storage stability of the pretreatment liquid becomes good, and by setting it to lower than 210 °C, the drying property of the pretreatment liquid, the water resistance of the printed matter, and the water rubbing resistance become good. The water-soluble organic solvent may be used alone or in combination of two or more.

[0071] The boiling point under 1 atm described above can be measured by using a thermal analyzer such as DSC (differential scanning calorimetry).

[0072] The total amount of the water-soluble organic solvent is preferably 1% by mass or more and 40% by mass or less based on the total amount of the pretreatment liquid. Further, from the viewpoints of wettability to the substrate and drying property of the pretreatment liquid, it is more preferably 3% by mass or more and 35% by mass, and particularly preferably 5% by mass or more and 30% by mass or less.

[0073] Examples of the alkyl polyol-based solvent suitably used as the water-soluble organic solvent include monohydric alcohols such as methanol, ethanol, 1-propanol, isopropyl alcohol, 1-butanol, and 2-butanol; dihydric alcohols (glycols) such as 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, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, 2-ethyl-2-methyl-1,3-propanediol, 3-methyl-1,3-butanediol, diethylene glycol, and dipropylene glycol.

[0074] Examples of the glycol ether-based solvent suitably used as the water-soluble organic solvent include glycol monoalkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, tetraethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monopropyl ether, and tripropylene glycol monomethyl ether; and glycol dialkyl ethers such as diethylene glycol diethyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether.

[0075] <Surfactant of the pretreatment liquid> For the pretreatment liquid of the present invention, in order to adjust its surface tension, ensure wettability on the substrate, and improve printing image quality, it is preferable to use a surfactant. On the other hand, when the pretreatment liquid is printed by an inkjet printing method, if the surface tension is too low, the nozzle surface of the inkjet head will be wetted by the aqueous ink, which will impair the ejection stability. Therefore, the selection of the type and amount of the surfactant is important. From the viewpoints of ensuring optimal wettability and realizing stable ejection, it is preferable to use surfactants such as siloxane-based, acetylene-based, acrylic-based, fluorine-based, polyoxyalkylene alkyl ether-based surfactants, etc., and it is particularly preferable to use siloxane-based and / or acetylene-based surfactants. As the addition amount of the surfactant, 0.05% by mass or more and 5.0% by mass or less is preferable with respect to the total amount of the pretreatment liquid, and 0.1% by mass or more and 3.0% by mass or less is more preferable. By setting it to 0.05% by mass or more, the function of the surfactant can be sufficiently exerted, and by setting it to 5.0% by mass or less, the storage stability and printing image quality of the pretreatment liquid can be maintained at a suitable level.

[0076] <Other components of the pretreatment liquid> In addition to the above components, additives such as a pH adjuster, an antifoaming agent, a preservative, an infrared absorber, an ultraviolet absorber, a thickener, a wax additive, a crosslinking agent, etc. can be appropriately added as necessary. As an example of the addition amount of these additives, 0.01% by mass or more and 10% by mass or less is suitable with respect to the total mass of the pretreatment agent.

[0077] <Preparation method of the pretreatment liquid> The pretreatment liquid of the present invention composed of the above components is adjusted, for example, by adding a water-soluble cationic resin (A), cationic resin particles (B), a surfactant, water, and, if necessary, a water-soluble organic solvent, a pH adjuster, and appropriately selected additive components as described above, stirring and mixing, and then filtering if necessary. However, the manufacturing method of the pretreatment liquid is not limited to the above.

[0078] <Printing method> When manufacturing a printed matter using the pretreatment liquid of the present invention, preferably, before printing aqueous inkjet ink, the pretreatment liquid is printed on a substrate. As the printing method, either a method of printing non - contact with respect to the substrate like inkjet printing or a method of printing by bringing the pretreatment liquid into contact with the substrate may be adopted. Further, as the printing method of the pretreatment liquid, when selecting a printing method of bringing the pretreatment liquid into contact, roller types such as a gravure coater, a doctor coater, a bar coater, a blade coater, a flexo coater, a roll coater, etc. can be preferably used.

[0079] <Inkjet ink set> The pretreatment liquid of the present invention can be used in the form of an aqueous inkjet ink set in combination with one or more types of aqueous inkjet inks. Hereinafter, the components of the aqueous ink constituting the aqueous inkjet ink set will be described. The aqueous ink used in combination with the pretreatment liquid of the present invention preferably contains at least one type of white ink.

[0080] <Pigment> As the pigment used in the aqueous ink, either an inorganic pigment or an organic pigment can be used, and it is not particularly limited. Examples of the organic pigment include pigments such as azo - based, phthalocyanine - based, anthraquinone - based, perylene - based, perinone - based, quinacridone - based, thioindigo - based, dioxazine - based, isoindoline - based, quinophthalone - based, azomethine azo - based, diketopyrrolopyrrole - based. Examples of the inorganic pigment include carbon black, titanium oxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, chromium oxide, silica, red iron oxide, aluminum, mica, etc. Titanium oxide is preferably titanium oxide surface - coated with at least silica or alumina. In addition, pigments described as C.I. Pigments in the Color Index can be used at any time. These pigments may be used alone or in combination of two or more.

[0081] In addition, it is also suitable to use hollow resin particles as the white pigment. Since the hollow resin particles have a smaller specific gravity (apparent density) compared to titanium oxide or the like and are less likely to settle over time, an ink with excellent storage stability can be obtained. Further, in order to obtain a white ink that achieves both storage stability and hiding power, hollow resin particles and titanium oxide may be used in combination as the pigment.

[0082] Also, in the case of aqueous ink, in order to keep the hue and color developability of the printed matter within a suitable range, the above pigments can be mixed and used in plural. For example, for black ink using carbon black, in order to improve the color tone at a low printing rate, one or more pigments selected from the group consisting of cyan pigment, magenta pigment, orange pigment, and brown pigment can be added in a small amount.

[0083] These pigments are preferably contained in the range of 2% by mass or more and 20% by mass or less, more preferably in the range of 2.5% by mass or more and 15% by mass or less, and particularly preferably in the range of 3% by mass or more and 10% by mass or less with respect to the total amount of the ink, except in the case of white ink. In the case of white ink, the content of the pigment is preferably 5% by mass or more and 40% by mass or less, and more preferably 8% by mass or more and 30% by mass or less with respect to the total amount of the white ink. By setting the content rate of the pigment to 2% by mass or more (5% by mass or more in the case of white ink), sufficient color developability (hiding power in the case of white ink) can be obtained. Also, by setting the content rate of the pigment to 20% by mass or less (40% by mass or less in the case of white ink), the viscosity of the ink can be kept within a range suitable for inkjet printing.

[0084] <Pigment dispersion resin> As methods for stably dispersing and retaining pigments in aqueous inks, there can be mentioned: (1) a method of coating at least a part of the pigment surface with a water-soluble or water-insoluble pigment dispersion resin; (2) a method of adsorbing and dispersing a water-soluble and / or water-dispersible surfactant on the pigment surface; (3) a method of chemically and physically introducing hydrophilic functional groups onto the pigment surface and dispersing it in the ink without a dispersion resin or surfactant (self-dispersing pigment); (4) a method of coating the pigment with a water-insoluble resin and dispersing it in the ink using, if necessary, another pigment dispersion resin and / or surfactant, etc.

[0085] The type of the pigment dispersion resin is not particularly limited, and examples thereof include (meth)acrylic-based, styrene (meth)acrylic-based, (anhydrous) maleic acid-based, styrene (anhydrous) maleic acid-based, α-olefin (anhydrous) maleic acid-based, urethane-based, and ester-based resins. Among them, from the viewpoint of strengthening the adsorption of the pigment and stabilizing the pigment dispersion, it is preferable to use one or more resins selected from the group consisting of α-olefin (anhydrous) maleic acid-based, (meth)acrylic-based, and styrene (meth)acrylic-based resins. In this specification, "(anhydrous) maleic acid" represents maleic acid or maleic anhydride.

[0086] Also, the weight average molecular weight of the pigment dispersion resin is preferably 5,000 or more and 100,000 or less. More preferably, it is in the range of 10,000 or more and 50,000 or less, and still more preferably, it is in the range of 15,000 or more and 30,000 or less. When the weight average molecular weight is within the above range, the pigment is stably dispersed in water, and it is easy to adjust the viscosity when applied to an aqueous ink. In particular, when the weight average molecular weight is 5,000 or more, the pigment dispersion resin is less likely to dissolve in the water-soluble organic solvent added to the aqueous ink, so the adsorption of the pigment dispersion resin to the pigment is strong and the dispersion stability is excellent. Also, when the weight average molecular weight is 100,000 or less, the viscosity during the dispersion of the aqueous ink can be kept low, and the ejection stability from the inkjet head is excellent, enabling stable printing over a long period.

[0087] When a water-soluble resin is used as the pigment-dispersing resin, its acid value is preferably 60 to 400 mgKOH / g. By setting the acid value within the above range, the dispersion stability of the pigment and the storage stability of the ink can be made suitable. Furthermore, the cohesiveness with the cationic group of the pretreatment liquid becomes suitable, excellent printing quality can be obtained, and the abrasion resistance of the printed matter also becomes good. Further, as the acid value, it is more preferably 120 to 350 mgKOH / g. On the other hand, when a water-insoluble resin is used as the pigment-dispersing resin, its acid value is preferably 0 to 100 mgKOH / g, and more preferably 5 to 90 mgKOH / g.

[0088] The blending amount of the pigment-dispersing resin is preferably 1 to 50% by mass based on the pigment. By setting the blending amount of the pigment-dispersing resin to 1 to 50% by mass based on the pigment, the viscosity of the pigment dispersion can be suppressed, and the viscosity stability and dispersion stability of the pigment dispersion and the aqueous ink can be made good. As the blending amount of the pigment-dispersing resin with respect to the pigment, it is more preferably 2 to 45% by mass, and still more preferably 4 to 35% by mass.

[0089] <Binder resin> The aqueous inkjet ink used in combination with the pretreatment liquid of the present invention preferably contains a binder resin. The form of the binder resin may be either a water-soluble resin or resin particles, and two or more kinds may be used in combination according to the properties required for the aqueous ink and the printed matter. For example, resin particles can lower the viscosity of the aqueous ink and can incorporate a larger amount of resin, so they are suitable for enhancing the water resistance and abrasion resistance of the printed matter. In addition, an aqueous ink using a water-soluble resin as the binder resin has excellent ejection stability and printing quality when combined with the pretreatment liquid of the present embodiment.

[0090] Regarding the type of binder resin, (meth)acrylic resin, styrene (meth)acrylic resin, (anhydrous) maleic acid resin, styrene (anhydrous) maleic acid resin, olefin (anhydrous) maleic acid resin, polyurethane resin, polyester resin, polyolefin resin, etc. can all be suitably used. Among them, from the viewpoints of the storage stability of the aqueous ink and the adhesion and abrasion resistance between the ink surface and the substrate in the printed matter when combined with the pretreatment liquid of the present embodiment, (meth)acrylic resin, styrene (meth)acrylic resin, polyurethane resin, and polyolefin resin are preferably used.

[0091] When resin particles are used as the binder resin, from the viewpoint of making the ejection stability suitable, it is preferable to adjust the type and blending ratio of the monomers constituting the resin particles so that the minimum film-forming temperature (MFT) is 50°C or higher. MFT can be measured, for example, by an MFT tester manufactured by Tester Sangyo Co., Ltd. Specifically, after printing a 25% by mass aqueous solution of the binder resin on a film so that the WET film thickness becomes 300 μm, it is left standing on the above tester with a temperature gradient applied, and the temperature at the boundary between the region where a white precipitate occurs and the region where a transparent resin film is formed after drying is taken as MFT.

[0092] When a water-soluble resin is used as the binder resin, from the viewpoint of achieving both the ejection stability of the aqueous ink and the abrasion resistance of the printed matter, its weight average molecular weight is preferably 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. Also, for the same reason, the acid value of the water-soluble resin is preferably 5 to 80 mgKOH / g, and more preferably 10 to 50 mgKOH / g.

[0093] The content of the binder resin in the total amount of the aqueous ink is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and particularly preferably 3 to 10% by mass in terms of solid content.

[0094] <Organic solvent of aqueous ink> The water-based inkjet ink used in combination with the pretreatment liquid of the present invention preferably contains a water-soluble organic solvent. The water-soluble organic solvent is not particularly limited, and known ones can be arbitrarily used. However, from the viewpoint of compatibility and affinity with material components such as pigment dispersion resins and surfactants, it preferably contains a glycol ether-based solvent and / or an alkyl polyol-based solvent. In particular, the boiling point of the water-soluble organic solvent under 1 atm is preferably 120°C or higher and less than 240°C. By setting it to 120°C or higher, the dispersion stability, ejection stability, and moisture retention of the water-based ink become good. By setting it to less than 240°C, the drying property of the water-based ink, the water resistance, and the water rubbing resistance of the printed matter become good. The water-soluble organic solvent may be used alone or in combination of two or more.

[0095] The total amount of the water-soluble organic solvent is preferably 3% by mass or more and 40% by mass or less based on the total amount of the water-based ink. Further, from the viewpoint of ensuring ejection stability, water resistance, and water rubbing resistance from the inkjet head, it is more preferably 5% by mass or more and 35% by mass, and particularly preferably 8% by mass or more and 30% by mass or less. By setting the total amount of the water-soluble organic solvent to 3% by mass or more, a water-based ink excellent in moisture retention and ejection stability is obtained. By setting it to 40% by mass or less, the drying property of the water-based ink becomes good, and a printed matter with good water resistance and water rubbing resistance can be obtained.

[0096] Solvents preferably used as the water-soluble organic solvent for inkjet ink include alkyl polyol-based solvents and glycol ether-based solvents, etc. Specifically, they are the same as the water-soluble organic solvents for the pretreatment liquid described above.

[0097] <Surfactant of water-based ink> For water-based inks, similar to the pretreatment liquid, it is preferable to use a surfactant to adjust its surface tension, ensure wettability on the substrate, and improve the printing quality. On the other hand, if the surface tension is too low, the nozzle surface of the inkjet head will be wetted by the water-based ink, impairing the ejection stability. Therefore, the selection of the type and amount of the surfactant is important. From the viewpoints of ensuring optimal wettability and achieving stable ejection, it is preferable to use surfactants such as siloxane-based, acetylene-based, acrylic-based, fluorine-based, polyoxyalkylene alkyl ether-based surfactants, etc. It is particularly preferable to use siloxane-based and / or acetylene-based surfactants. As for the addition amount of the surfactant, it is preferably 0.05% by mass or more and 5.0% by mass or less, more preferably 0.1% by mass or more and 3.0% by mass or less, based on the total amount of the water-based ink. By setting it at 0.05% by mass or more, the function of the surfactant can be fully exerted, and by setting it at 5.0% by mass or less, the storage stability and ejection stability of the water-based ink can be maintained at a suitable level.

[0098] <Other components of water-based ink> In addition to the above components, additives such as a pH adjuster, an antifoaming agent, a preservative, an infrared absorber, an ultraviolet absorber, a thickener, a wax additive, a crosslinking agent, etc. can be appropriately added as necessary. As an example of the addition amount of these additives, it is preferably 0.01% by mass or more and 10% by mass or less based on the total mass of the pretreatment agent.

[0099] <Method for preparing inkjet ink> Examples of the method for preparing water-based ink include, but are not limited to, the following method. First, a pigment is added to an aqueous solution in which at least a pigment dispersion resin and water are mixed, and after mixing and stirring (premixing), a dispersion treatment is performed using the dispersion means described below, and a centrifugation treatment is performed as necessary to obtain a pigment dispersion. Next, a binder resin, a water-soluble organic solvent, water, and, if necessary, optional components as described above are appropriately added to the pigment dispersion, stirred and mixed well, and then filtered to obtain a water-based ink.

[0100] <Inkjet printing> A water-based inkjet ink is printed on a substrate by an inkjet printing method. At this time, it is preferably printed by a one-pass printing method (also referred to as a line printing method). The one-pass printing method has fewer scanning times than the multi-pass method that scans the inkjet head multiple times, and can increase the printing speed. Therefore, it is suitable for industrial applications that require a high printing speed. Also, it is suitable because a printed matter with high print quality can be obtained at a high recording resolution of 600 dpi or more. Note that the "recording resolution" is expressed in units of dpi (Dots Per Inch) and represents the number of inkjet ink droplets printed per inch. Also, the "recording resolution" in this specification refers to both the recording resolution in the conveyance direction of the substrate and the recording resolution in the direction perpendicular to the conveyance direction within the substrate surface (hereinafter referred to as the recording width direction).

[0101] When printing the inkjet ink by the one-pass printing method, the drop volume of the ink depends largely on the performance of the inkjet head. However, in order to obtain a printed matter with excellent various resistances and print quality, it is preferably in the range of 0.6 to 60 pL. More preferably, it is 1 to 50 pL, and particularly preferably, it is 1.4 to 40 pL. Also, in order to obtain a high-quality image, it is particularly preferable to use a gradation-specification inkjet head capable of changing the drop volume.

[0102] The water-based ink may be used alone, or it can also be used as an ink set combining multiple colors according to the application. The combination is not particularly limited, but a full-color image can be obtained by using three colors of cyan, yellow, and magenta. Additionally, by adding black ink, the black color perception can be improved, and the visibility of characters, etc. can be enhanced. Furthermore, it is also possible to improve color reproducibility by adding colors such as orange, green, and violet. Also, when using white ink in combination, when printing on a substrate other than white, a clear printed image quality can be obtained, and a packaging material with high concealability for the contents can be obtained. Even for a white substrate, by using white ink in combination, the color ink can be made into a higher-quality and clearer printed image quality. To achieve these, high cohesiveness between the pretreatment liquid and the water-based ink is required, but it can be achieved by using the pretreatment liquid of the present invention. Note that it may include an ink (clear ink) that is substantially free of a colorant component excluding pigments.

[0103] <Substrate> The substrate on which the ink of the present invention is printed is not particularly limited, and known ones can be arbitrarily used. Among them, from the viewpoints of package packaging and label materials, non-permeable substrates or hardly permeable substrates are suitable, and they can be particularly preferably used for non-permeable substrates.

[0104] Examples of non-permeable substrates or hardly permeable substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, and polyvinyl alcohol, coated paper substrates such as coated paper, art paper, and cast paper, metal substrates such as aluminum, iron, stainless steel, and titanium, and glass substrates.

[0105] The above-mentioned substrate may have a smooth or uneven surface, and may be transparent, translucent, or opaque. Further, two or more of these recording media may be laminated together. Additionally, a release adhesive layer or the like may be provided on the side opposite to the printing surface, or an adhesive layer or the like may be provided on the printing surface after printing. Also, the shape of the recording medium used in the inkjet recording method of the present invention may be in the form of a roll or a sheet.

[0106] In addition, in order to improve the wettability of the pretreatment liquid and the aqueous ink of the present invention, improve the printing image quality and drying property, and also improve the abrasion resistance and adhesion so that the surface of the printed matter becomes uniform, it is also preferable to perform a surface modification method such as corona treatment or plasma treatment on the non-permeable substrate or the hardly permeable substrate exemplified above.

[0107] On the substrate, the pretreatment liquid of the present invention and one or more aqueous inkjet inks containing white ink can be sequentially printed to obtain a printed matter.

Examples

[0108] Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following description, "parts" and "%" represent "parts by mass" and "mass%" respectively unless otherwise specified.

[0109] <Synthesis Example of Water-Soluble Cationic Resin CP1> 85 parts of isopropyl alcohol was charged into a reaction vessel equipped with a thermometer, a reflux condenser, a stirring device, two dropping funnels, and a gas inlet tube. While stirring and introducing nitrogen gas, the temperature was raised to 80 °C. Next, two dropping funnels were prepared. In one of them, 96.2 parts of methacrylate DMC-80, 15 parts of methyl methacrylate, and 10 parts of benzyl methacrylate were dissolved in 150 parts of isopropyl alcohol and charged, and then added dropwise over 2 hours. In the other, 1.2 parts of 2,2'-azobis(isobutyric acid)dimethyl was dissolved in 7.5 parts of isopropyl alcohol and charged, and then added dropwise over 2 hours. After the dropping was completed, the reaction was carried out at 80 °C for 1 hour. Then, 0.4 part of 2,2'-azobis(isobutyric acid)dimethyl was dissolved in 2 parts of isopropyl alcohol, charged into the reaction vessel, and the reaction was continued for another 1 hour and then terminated. Subsequently, 180 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 95 °C, and the total amount of isopropyl alcohol was distilled off. After cooling to room temperature, more ion-exchanged water was added to obtain an aqueous solution containing 30% of the water-soluble cationic resin CP1.

[0110] The weight-average molecular weight (Mw) of the obtained water-soluble cationic resin CP1 was 38,000, and the molecular weight distribution (PDI) was 1.97.

[0111] <Synthesis Examples of Water-Soluble Cationic Resins CP2 to CP8 and CP31> Except for using the materials described in Table 1, 30% aqueous solutions of water-soluble cationic resins CP2 to CP8 and CP31 were obtained by the same operations as those for water-soluble cationic resin CP1.

[0112] <Synthesis Example of Water-Soluble Cationic Resin CP9> Except for using the materials described in Table 1, the polymerization reaction was carried out in the same manner as for the water-soluble cationic resin CP1 to obtain an isopropyl alcohol solution of a polymer containing a tertiary amino group. Subsequently, 47 parts of bromobutane was added to the obtained isopropyl alcohol solution, the temperature was raised to 80 °C again, and after stirring for 6 hours, 60% of the tertiary amino groups contained in the polymer were quaternized with ammonium chloride. Subsequently, 165 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 95 °C, and the total amount of isopropyl alcohol was distilled off. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content fraction became 30%, and an aqueous solution containing the water-soluble cationic resin CP9 was obtained.

[0113]

Table 1

[0114] <Synthesis Example of Cationic Resin Particles DP1> Into a reaction vessel equipped with a thermometer, a reflux condenser, a stirrer, a dropping funnel, and a gas inlet tube, while introducing nitrogen gas, 32 parts of methacrylate DMC-80, 5 parts of methyl methacrylate, 2.8 parts of methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, and 33 parts of ethanol were charged, and the temperature was raised to 80 °C with stirring. After stirring for 15 minutes, 10 parts of ethanol and 0.2 part of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. Further, after continuing the reaction at 80 °C for 1 hour, it was cooled to room temperature to obtain an ethanol solution containing the hydrophilic unit part of the block polymer type cationic resin particles.

[0115] To the obtained ethanol solution, 40 parts of benzyl methacrylate, 30 parts of methyl methacrylate, and 96 parts of ethanol were further added, and the temperature was raised to 80 °C again with stirring. After stirring for 15 minutes, 10 parts of ethanol and 0.5 part of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. Further, the reaction was continued at 80 °C for 1 hour to obtain an ethanol solution containing block polymer-type cation resin particles in which a hydrophobic unit part was bonded to a hydrophilic unit part. Subsequently, 165 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 90 °C, and the total amount of ethanol was distilled off. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content fraction became 30%, and an aqueous dispersion containing cation resin particles DP1 was obtained.

[0116] The number average molecular weight (Mn) of the obtained cation resin particles DP1 was 15,400, and the molecular weight distribution (PDI) was 1.27. Also, the average particle diameter was 67 nm.

[0117] <Synthesis Examples of Cation Resin Particles DP2 to 8, DP31 to 32> Except for using the materials described in Table 2, 30% aqueous dispersions of cation resin particles DP2 to 8 and DP31 to 32 were obtained by the same operations as those for cation resin particles DP1.

[0118]

Table 2

[0119] <Synthesis Example of Cation Resin Particles DP21> While introducing nitrogen gas into a reaction vessel equipped with a thermometer, a reflux condenser, a stirring device, a dropping funnel, and a gas introduction tube, 40 parts of methacrylate DMA, 5 parts of methyl methacrylate, 2.8 parts of methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, and 63 parts of methyl ethyl ketone were charged, and the temperature was raised to 80 °C with stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.3 part of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. Further, after continuing the reaction at 80 °C for 1 hour, it was cooled to room temperature to obtain a methyl ethyl ketone solution containing a polymer having a tertiary amino group.

[0120] To the obtained methyl ethyl ketone solution, 30 parts of benzyl methacrylate, 25 parts of methyl methacrylate, and 74 parts of methyl ethyl ketone were further added, and the temperature was raised to 80 °C again with stirring. After stirring for 15 minutes, 10 parts of methyl ethyl ketone and 0.4 part of 2,2'-azobisisobutyronitrile were mixed and added dropwise to the reaction solution over 6 hours. Further, after continuing the reaction at 80 °C for 1 hour, it was cooled to room temperature to obtain a methyl ethyl ketone solution of block polymer type cation resin particles containing a unit part having a tertiary amino group and a hydrophobic unit part.

[0121] Subsequently, 19.3 parts of benzyl chloride was further added to the obtained methyl ethyl solution, the temperature was raised to 80 °C again, and after stirring for 6 hours, the tertiary amino group was quaternized to ammonium chloride to form a hydrophilic unit. Subsequently, 165 parts of ion-exchanged water was added dropwise over 1 hour, the temperature was raised to 90 °C, and the total amount of methyl ethyl ketone was distilled off. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content ratio became 30% to obtain an aqueous dispersion containing cation resin particles DP21. The mass of benzyl chloride used was calculated from the molar amount required to quaternize 60% of the tertiary amino groups contained in one molecule of the polymer to ammonium chloride.

[0122] <Synthesis Examples of Block Polymers DP22 to 25> Except for using the materials described in Table 3, 30% aqueous dispersions of cation resin particles DP22 to 25 were obtained by the same operations as those for cation resin particles DP21.

[0123]

Table 3

[0124] <Synthesis Example of Cationic Resin Particles DP26> 85 parts of isopropyl alcohol was charged into a reaction vessel equipped with a thermometer, a reflux condenser, a stirrer, two dropping funnels, and a gas inlet tube. The mixture was stirred and heated to 80 °C while introducing nitrogen gas. Next, two dropping funnels were prepared. In one funnel, 32 parts of methacrylate DMC-80, 20 parts of methacrylate DMA, 35 parts of methyl methacrylate, and 20 parts of styrene were dissolved in 150 parts of isopropyl alcohol and charged, and then dropped over 2 hours. In the other funnel, 0.5 part of 2,2'-azobis(isobutyric acid) dimethyl was dissolved in 7.5 parts of isopropyl alcohol and charged, and then dropped over 2 hours. After the dropping was completed, the reaction was carried out at 80 °C for 1 hour. Then, 0.4 part of 2,2'-azobis(2-methylpropionate) was dissolved in 2 parts of isopropyl alcohol and charged into the reaction vessel, and the reaction was continued for 1 hour and then terminated. Subsequently, 165 parts of ion-exchanged water was dropped over 1 hour, the temperature was raised to 95 °C, and the total amount of isopropyl alcohol was distilled off. After cooling to room temperature, more ion-exchanged water was added so that the resin solid content fraction became 30%, and an aqueous dispersion containing cationic resin particles DP26, which is a random polymer, was obtained.

[0125] <Synthesis Example of Cationic Resin Particles DP27> 85 parts of isopropyl alcohol were charged into a reaction vessel equipped with a thermometer, a reflux condenser, a stirring device, two dropping funnels, and a gas inlet tube, and the temperature was raised to 80 °C while stirring and introducing nitrogen gas. Next, two dropping funnels were prepared. In one of them, 77 parts of methacrylate DMC-80, 10 parts of methacrylate DMA, 10 parts of methyl methacrylate, and 20 parts of styrene were dissolved in 150 parts of isopropyl alcohol and charged, and then dropped over 2 hours. In the other, 1.5 parts of 2,2'-azobis(isobutyric acid) dimethyl was dissolved in 7.5 parts of isopropyl alcohol and charged, and then dropped over 2 hours. After completion of the dropping, the reaction was carried out at 80 °C for 1 hour, then 0.4 part of 2,2'-azobis(2-methylpropionate) was dissolved in 2 parts of isopropyl alcohol, charged into the reaction vessel, and the reaction was continued for another 1 hour and then terminated. Subsequently, 165 parts of ion-exchanged water was dropped over 1 hour, the temperature was raised to 95 °C, and the total amount of isopropyl alcohol was distilled off. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content fraction became 30%, and an aqueous solution containing a water-soluble cationic resin that would become the shell part of the cationic resin particles DP27 was obtained.

[0126] Next, 100 parts of an aqueous solution with a solid content fraction of 30% of the water-soluble cationic resin that would become the shell part of the cationic resin particles DP27 and 40 parts of ion-exchanged water were charged into a reaction vessel equipped with a thermometer, a reflux condenser, a stirring device, two dropping funnels, and a gas inlet tube, and the temperature was raised to 88 °C while stirring and introducing nitrogen gas. Next, two dropping funnels were prepared. In one of them, 45 parts of methyl methacrylate and 25 parts of styrene were charged and dropped over 2 hours. In the other, 12 parts of an aqueous solution of 3% 2,2'-azobis(2-methyl-N-(2-hydroxyethyl)propionamide) was charged and dropped over 2 hours. After completion of the dropping, the reaction was continued at 88 °C for 2 hours, then cooled to room temperature, and the reaction was terminated. Next, ion-exchanged water was added so that the resin solid content fraction became 30%, and an aqueous dispersion of core-shell type cationic resin particles DP27 was obtained.

[0127] The abbreviations described in Tables 1 to 3 are as follows. DMC-80: Methacrylate DMC-80 manufactured by Sanyo Chemical Industries; Methacryloyloxyethyltrimethylammonium chloride (78% by mass aqueous solution) DMAEA-BQ: 2-(Dimethylamino)ethyl acrylate - benzyl chloride quaternary salt (75% by mass aqueous solution) manufactured by KJ Chemicals DMAPAA-Q: N-[3-(Dimethylamino)propyl]acrylamide - methyl chloride quaternary salt (75% by mass aqueous solution) manufactured by KJ Chemicals DMA: Methacrylate DMA manufactured by Sanyo Chemical Industries; 2-(Dimethylamino)ethyl methacrylate BM1448: Methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate manufactured by BORON MOLECULAR AIBN: 2,2’-Azobisisobutyronitrile V601: 2,2’-Azobis(isobutyric acid)dimethyl manufactured by Fujifilm Wako Pure Chemical Corporation

[0128] The physical properties of each resin obtained in the above synthesis examples and the detailed structural units represented by formula (1) are as shown in Table 4.

[0129]

Table 4

[0130] <Production Example of Pretreatment Liquid PR1> 15 parts of an aqueous solution of water-soluble cationic resin CP1 (resin solid content rate 30%), 40 parts of cationic resin particles BP1 (resin solid content rate 30%), 3 parts of isopropyl alcohol, 0.5 part of TegoWet280, 0.5 part of Surfynol 440, and 0.1 part of adipic acid dihydrazide were sequentially added to a mixing container. Then, ion-exchanged water was added to adjust the total amount of the pretreatment liquid to 100 parts, and the mixture was stirred with a disper until it became sufficiently uniform. Thereafter, filtration was performed with a membrane filter having a pore size of 1.0 μm to prepare the pretreatment liquid PR1.

[0131] <Production Examples of Pretreatment Liquids PR-2 to 19, 21 to 28, 31 to 37> Except for using the materials described in Table 5, pretreatment liquids PR2 to 19, 21 to 28, and 31 to 37 were obtained by the same operations as the pretreatment liquid PR1.

[0132]

Table 5

[0133] The abbreviations described in Table 5 are as follows. PAS-H-1L: Diallyldimethylammonium chloride polymer manufactured by Nitto Boehringer Medical Co., Ltd. (Mw 8,500, resin concentration 28% aqueous solution) TegoWet280: Siloxane-based surfactant manufactured by Evonik Surfynol 440: Acetylenediol-based surfactant manufactured by Shin-Etsu Chemical Co., Ltd.

[0134] <Synthesis Example of Pigment-Dispersing Resin> 95 parts of butanol was charged into a reaction vessel equipped with a thermometer, a reflux condenser, a stirrer, a dropping funnel, and a gas inlet tube. While introducing nitrogen gas, the inside of the reaction vessel was heated to 110°C with stirring. After stirring for 15 minutes, 35 parts of styrene, 35 parts of acrylic acid, 30 parts of behenyl acrylate, and 6 parts of 2,2'-azobis(isobutyric acid)dimethyl, which is a polymerization initiator, were mixed as polymerizable monomers and dropped into the reaction solution over 2 hours. Further, after continuing the reaction at 110°C for 3 hours, 0.6 part of 2,2'-azobis(isobutyric acid)dimethyl was added, and the reaction was further continued at 110°C for 1 hour to obtain a pigment-dispersing resin solution. Subsequently, after cooling to room temperature, dimethylaminoethanol was added to completely neutralize it, and then 100 parts of ion-exchanged water was added to make it aqueous. Thereafter, the temperature was raised to 100°C or higher, and butanol was azeotroped with water to distill off the entire amount of butanol. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content fraction became 30% to obtain an aqueous solution of the pigment-dispersing resin. The weight average molecular weight of the pigment-dispersing resin was 28,000, and the acid value was 273 mgKOH / g.

[0135] <Production Example of Pigment Dispersion Cyan> 20 parts of Lionol Blue 7358G (C.I. Pigment Blue 15:3) manufactured by Toyo Color Co., 15 parts of an aqueous solution of a pigment-dispersing resin (resin solid content ratio: 30%), and 65 parts of water were mixed, and after preliminary dispersion with a disper, this dispersion was carried out using a Dyno-Mill with a volume of 0.6 L filled with 1,800 g of zirconia beads with a diameter of 0.5 mm to obtain a pigment dispersion liquid (cyan).

[0136] <Production Example of Pigment Dispersion Liquid Magenta> A pigment dispersion liquid (magenta) was obtained in the same manner as the above cyan, except that C.I. Pigment Red 122 (FASTGEN SUPER MAGENTA RGT manufactured by DIC Corporation) was used as the pigment.

[0137] <Production Example of Pigment Dispersion Liquid Yellow> A pigment dispersion liquid (yellow) was obtained in the same manner as the above cyan, except that C.I. Pigment Yellow 14 (Lionol Yellow TT-1405G manufactured by Toyo Color Co.) was used as the pigment.

[0138] <Production Example of Pigment Dispersion Liquid Black> A pigment dispersion liquid (black) was obtained in the same manner as the above cyan, except that C.I. Pigment Black 7 (Printex 85 manufactured by Orion Engineered Carbons Co., Ltd.) was used as the pigment.

[0139] <Production Example of Pigment Dispersion Liquid White> 40 parts of CR-90-2 (titanium oxide) manufactured by Ishihara Sangyo Co., 30 parts of an aqueous solution of a pigment-dispersing resin (resin solid content ratio: 30%), and 30 parts of water were mixed, and dispersion was carried out in the same manner as the pigment dispersion liquid cyan to obtain a pigment dispersion liquid (white).

[0140] <Synthesis Example of Binder Resin 1> 93.4 parts of butanol was charged into a reaction vessel equipped with a thermometer, a reflux condenser, a stirring device, a dropping funnel, and a gas inlet tube. While introducing nitrogen gas, the temperature inside the reaction vessel was raised to 110 °C with stirring. After stirring for 15 minutes, 30 parts of styrene, 5 parts of methacrylic acid, 50 parts of methyl methacrylate, 15 parts of lauryl methacrylate, and 6 parts of 2,2’-azobis(isobutyric acid) dimethyl, which is a polymerization initiator, were mixed as polymerizable monomers and added dropwise to the reaction solution over 2 hours. Further, after continuing the reaction at 110 °C for 3 hours, 0.6 part of 2,2’-azobis(isobutyric acid) dimethyl was added, and the reaction was continued at 110 °C for 1 hour to obtain a binder resin solution. Subsequently, after cooling to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization, and 100 parts of ion-exchanged water was added for water dilution. Then, the temperature was raised to 100 °C or higher, and butanol was azeotroped with water to distill off the entire amount of butanol. After cooling to room temperature, further ion-exchanged water was added so that the resin solid content fraction became 30%, and an aqueous solution of binder resin 1 was obtained. The weight average molecular weight of binder resin 1 was 18,000, and the acid value was 32 mgKOH / g.

[0141] <Production Example of Inkjet Ink> 25 parts of cyan pigment dispersion, 30 parts of a 30% aqueous solution of binder resin 1, 20 parts of 1,2-propanediol, 1 part of TegoWet280, 1 part of Surfynol 465 (an acetylene diol-based surfactant manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.05 part of Proxel GXL (a preservative) were sequentially charged into a mixing container. Then, ion-exchanged water was added to adjust the total amount of the ink to 100 parts, and the mixture was stirred with a disperser until it became sufficiently uniform. Thereafter, filtration was performed with a membrane filter having a pore size of 0.5 μm to prepare Ink C.

[0142] Except for using the materials described in Table 6, inkjet ink was prepared in the same manner as Ink C.

[0143]

Table 6

[0144] <Preparation of Printed Substrate with Pretreatment Liquid> The pretreatment liquid prepared above was applied at an application amount of 4 g / m 2 To apply it, using the K control coater K202 manufactured by Matsuo Sangyo Co., Ltd. and wire bar No. 0, the pretreatment liquid was applied to a biaxially stretched polypropylene film "U-1" (thickness 20 μm) manufactured by Mitsui Chemicals Toagosei Co., Ltd. After that, the film coated with the pretreatment liquid was dried in an air oven at 70°C for 3 minutes to prepare a printed substrate with the pretreatment liquid applied.

[0145] Also, as a method of applying the pretreatment liquid to the substrate, it was also prepared by an inkjet printing method separately from the above coater method. An inkjet head KJ4B-YH (manufactured by Kyocera Corporation, resolution 600 dpi, maximum drive frequency 40 kHz) was installed above the conveyor capable of transporting the printed substrate, and the pretreatment liquid prepared above was filled. Next, after fixing the same film substrate "U-1" as above on the conveyor, the conveyor was driven at 50 m / min, and when passing through the installation part of the inkjet head, the pretreatment liquid was discharged to print an image with a printing rate of 100% (also called a solid image). The drop volume during printing was 12 pL, and the printed matter was put into an air oven at 70°C and dried for 3 minutes.

[0146] <Preparation of Inkjet Ink Printed Matter> Five inkjet heads KJ4B-1200 (manufactured by Kyocera Corporation, resolution 1200 dpi, maximum drive frequency 64 kHz) were installed side by side in the horizontal direction of the conveyance of the printed substrate above the conveyor capable of transporting the printed substrate, and the inkjet ink prepared above was filled. Next, after fixing the printed substrate with the above pretreatment liquid applied on the conveyor, the conveyor was driven at 50 m / min, and when passing through the installation part of the inkjet head, aqueous inkjet ink was discharged to perform the printing shown below. The drop volume during printing was 2.5 pL, and the printed matter was put into an air oven at 70°C and dried for 3 minutes.

[0147] As printed images, two types of printed matter were prepared: a 5-color (WKCMY) image with the total printing rate (the sum of the printing rates of each color) continuously varying from 50% to 250%, and a color 4-color (KCMY) image with a white ink printing rate of 100% and then continuously varying from 40% to 240%. Printed matter of each type was produced. Note that for each total printing rate, the printing rate of each color is the same, and all printed matter was printed in the order of white, black, cyan, magenta, and yellow inks.

[0148] For the produced printed matter, the following evaluations 1 to 6 were conducted. The results are shown in Table 7.

[0149] <Evaluation 1: Evaluation of color bleeding> On a printed substrate to which a pretreatment liquid was applied based on the above method, a printed matter of a 5-color (WKCMY) image with the total printing rate continuously varying from 50% to 250% was produced. Then, the dot shape in the portion of the obtained printed matter with a 5-color (WKCMY) printing rate of 150% to 250% was magnified and observed at 200 times using an optical microscope to evaluate color bleeding. The evaluation criteria are as follows, and ◎ and 〇 evaluations are in the practical usable range. ◎: In the portion where the total printing rate is 250%, no merging of dots or non-uniformity of dot shape was observed. 〇: In the portion where the total printing rate is 250%, merging of dots or non-uniformity of dot shape was observed, but in the portion where the total printing rate is 200%, no merging of dots or non-uniformity of dot shape was observed. △: In the portion where the total printing rate is 200%, merging of dots or non-uniformity of dot shape was observed, but in the portion where the total printing rate is 150%, no merging of dots or non-uniformity of dot shape was observed. ×: In the portion where the total printing rate is 150%, merging of dots or non-uniformity of dot shape was observed.

[0150] <Evaluation 2: Evaluation of color unevenness> Based on the above method, a printed matter was produced on a printed substrate to which a pretreatment liquid was applied based on the above method, with a solid image of 100% white, and then a four-color (KCMY) color image continuously changing from 40% to 240%. Then, the degree of color unevenness in the 40% to 160% area of the four-color (CMYK) printing rate of the obtained printed matter was visually observed, and an evaluation of color unevenness was performed. The evaluation criteria are as follows, and ◎ and 〇 evaluations are in the practical applicable range. ◎: No color unevenness was observed in the printed area even when the total printing rate of the four colors was 240%. 〇: Color unevenness was observed in the printed area where the total printing rate of the four colors was 240%, but no color unevenness was observed in the printed area where the total printing rate of the four colors was 160%. △: Color unevenness was observed in the printed area where the total printing rate of the four colors was 200%, but no color unevenness was observed at a printing rate of 160% of the total printing rate of the four colors. ×: Color unevenness was observed in the printed area where the total printing rate of the four colors was 160%.

[0151] <Evaluation 3: Storage stability> For each pretreatment liquid, the volume average particle size (D50) was measured using a NanoTrack UPA-EX150 manufactured by Microtrac Bell. This pretreatment liquid was placed in a sealed container, stored in a constant temperature machine at 70°C, and aged for 2 weeks. Then, the volume average particle size was measured again using the above device, and the change in the volume average particle size of the ink before and after aging was calculated to evaluate the storage stability of the pretreatment liquid. The criteria are as follows, and ◎ and 〇 evaluations are in the practical applicable range. ◎: The change rate of the volume average particle size was less than ±15%. 〇: The change rate of the volume average particle size was ±15% or more and less than ±30%. △: The change rate of the volume average particle size was ±30% or more and less than ±45%. ×: The change rate of the volume average particle size after 2 weeks of storage was ±45% or more.

[0152] <Evaluation 4: Rub resistance> A printed matter with the same image as in Evaluation 1 was produced. For the obtained printed matter, a Kagaku Shinkou type friction fastness tester was used, and with a cotton cloth (Kanakin No. 3), a load of 200 g / cm 2, Under the condition of 50 reciprocations, the printed surface was rubbed, and the abrasion resistance was evaluated from the ratio of the peeled area of the printed surface. The evaluation criteria are as follows, and the ◎ and 〇 evaluations are in the practical useable range. ◎: There is no peeling of the printed surface 〇: The peeling of the printed surface is less than 20% △: The peeling of the printed surface is 20% or more and less than 50% ×: The peeling of the printed surface is 50% or more

[0153] <Evaluation 5: Water resistance> A printed matter with the same image as in Evaluation 1 was produced, and for the obtained printed matter, the state when rubbed with a cotton swab dipped in water was visually observed to evaluate the water resistance. The evaluation criteria are as follows, and the ◎ and 〇 evaluations are in the practical useable range. ◎: Even when rubbed 20 times with a cotton swab dipped in water, there was no peeling of the printed matter or adhesion of ink to the cotton swab. 〇: Even when rubbed 10 times with a cotton swab dipped in water, there was no peeling of the printed matter or adhesion of ink to the cotton swab, but when rubbed 20 times, peeling of the printed matter and adhesion of ink to the cotton swab were observed. △: Even when rubbed 5 times with a cotton swab dipped in water, there was no peeling of the printed matter or adhesion of ink to the cotton swab, but when rubbed 10 times, peeling of the printed matter and adhesion of ink to the cotton swab were observed. ×: When strongly rubbed 5 times with a cotton swab dipped in water, peeling of the printed matter and adhesion of ink to the cotton swab were observed.

[0154] <Evaluation 6: Water abrasion resistance> A printed matter with the same image as in Evaluation 2 was produced, and for the obtained printed matter, using a Kagaku Shinkou type friction fastness tester, with a cotton cloth (Kanakin No. 3) dipped in water, under a load of 200 g / cm 2 , Under the condition of 20 reciprocations, the printed surface was rubbed, and the water abrasion resistance was evaluated from the ratio of the peeled area of the printed surface. The evaluation criteria are the same as those for the abrasion resistance in Evaluation 4.

[0155]

Table 7

[0156] Examples 1 to 19 and 21 to 28 contain a water-soluble cationic resin, cationic resin particles, and water in the pretreatment liquid. The water-soluble cationic resin contains the structural unit represented by formula (1) in an amount of 50 to 100% by mass based on the total mass of the water-soluble cationic resin. The cationic resin particles contain the structural unit represented by formula (1) in an amount of 1 to 40% by mass based on the total mass of the cationic resin particles. Therefore, the storage stability of the pretreatment liquid is good, and the resulting printed matter has excellent water resistance, rub resistance, and water rub resistance, with no color bleeding or color unevenness.

[0157] In Comparative Example 1, the structural unit represented by formula (1) contained in the water-soluble cationic resin is less than 50% by mass. In Comparative Example 2, the flocculant does not contain the structural unit represented by formula (1). As a result, color bleeding and color unevenness occurred in the printed matter. Furthermore, in Comparative Example 4, the pretreatment liquid does not contain a water-soluble cationic resin, resulting in color bleeding and color unevenness. In Comparative Example 3, although good print quality was obtained because the pretreatment liquid contains an inorganic metal salt, the water resistance and water rub resistance of the printed matter were poor.

[0158] In Comparative Example 5, the cationic resin particles do not contain the structural unit represented by formula (1), resulting in poor storage stability of the pretreatment liquid and color bleeding and color unevenness in the printed matter. In Comparative Example 6, the structural unit represented by formula (1) contained in the cationic resin particles exceeds 40% by mass, resulting in poor rub resistance, water resistance, and water rub resistance. In Comparative Example 7, the pretreatment liquid does not contain cationic resin particles, resulting in poor rub resistance, water resistance, and water rub resistance.

Claims

1. A pretreatment liquid used together with an aqueous inkjet ink, comprising a water-soluble cationic resin (A), cationic resin particles (B), and water, wherein the water-soluble cationic resin (A) contains a structural unit represented by the formula (1) in an amount of 50 to 100% by mass based on the total mass of the water-soluble cationic resin (A), and the cationic resin particles (B) contain a structural unit represented by the formula (1) in an amount of 1 to 40% by mass based on the total mass of the cationic resin particles (B). The pretreatment liquid is characterized by this. Formula (1) 【Chemical 1】 (In formula (1), R １ represents a hydrogen atom or a methyl group, Z represents an oxygen atom, -NH-, or -OCH ２ CH(OH)-, R ２ , R ３ , R ４ each independently represents an alkyl group having 1 to 8 carbon atoms, X － represents a monovalent anion, and n represents an integer of 1 to 6.)

2. The pretreatment liquid according to claim 1, characterized in that the cationic resin particles (B) contain a block polymer having a hydrophilic unit (b-1) and a hydrophobic unit (b-2).

3. The pretreatment liquid according to claim 1, characterized in that the cationic resin particles (B) have a number average molecular weight of 8,000 to 50,000.

4. The pretreatment liquid according to claim 1, characterized in that printing is performed by an inkjet recording method.

5. An aqueous inkjet ink set comprising the pretreatment liquid according to any one of claims 1 to 4 and one or more aqueous inkjet inks containing white ink.

6. A printed matter obtained by printing the pretreatment liquid according to any one of claims 1 to 4 and one or more aqueous inkjet inks containing white ink on a substrate.

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