JP7111519B2 - Ink set and printing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing method, and more particularly to a printing method capable of suppressing bleeding of a printed layer.

Various inks have been developed as inks used for printing by inkjet printers, but water-based inks are widely used from the viewpoint of reducing environmental impact. However, since water-based ink contains water as a solvent, it tends to cause bleeding during printing. As a method for improving blurring of a printed layer formed by printing, for example, a method of using a treatment liquid having an action of aggregating colored ink together is known. A water-based ink set in which such treatment liquid and colored ink are combined is also called a two-liquid reaction type water-based ink set.

Japanese Patent Laying-Open No. 6-57192 (Patent Document 1) describes an ink set comprising a plurality of colored inks, the ink set including a black ink containing an anionic dye and a yellow ink containing a cationic dye. describes that the use of these dyes reduces bleed between color and black, but further describes that bleed can be reduced by incorporating a polyvalent precipitant into the yellow ink. . In Patent Document 1, it is recognized that this yellow ink also acts as a processing liquid.

Japanese Patent Application Laid-Open No. 2009-190379 (Patent Document 2) discloses a colorless ink containing a pigment (water-dispersible pigment) coated with a crosslinked water-soluble polymer and an aggregation accelerator that promotes aggregation of the colored ink. It describes that the ink set containing the ink can improve liquid stability and ejection property, and can suppress curling and image deformation of the recording medium after the ink is applied.

JP-A-6-57192 JP 2009-190379 A

Under such circumstances, an object of the present invention is to provide a printing method capable of suppressing the bleeding of the printed layer by a method different from the conventional technique.

As a result of intensive studies in order to achieve the above object, the present inventors have found that in a printing method that uses a combination of a plurality of types of water-based colored inks and a water-based coating liquid, the water-based coating liquid that has landed on the substrate is first attached to the The inventors have found that by using an ink having the lowest surface tension among water-based colored inks, it is possible to effectively suppress the occurrence of bleeding in the printed layer, and have completed the present invention.

As a result of further studies, the present inventor found that when printing is performed by ejecting four types of water-based colored inks from the print head in order, after printing by ejecting two types of ink in order and the remaining two It has been found that a higher definition printed layer can be formed by performing primary drying and then printing with a water-based coating liquid before printing by sequentially ejecting the seed inks.

That is, a first printing method of the present invention is a printing method for forming a printed layer on a substrate by an inkjet printer equipped with an ink set containing a water-based colored ink and a water-based coating liquid,
The water-based colored inks include at least four types of inks, a first ink, a second ink, a third ink, and a fourth ink, and each ink independently contains water, a pigment, a water-soluble solvent, and containing a resin, the water-based coating liquid containing water, a water-soluble solvent and a resin, the resin contained in the water-based coating liquid containing a cationic polymer,
A step of ejecting the water-based coating liquid from a print head to land coating droplets on a substrate;
a step of ejecting a first ink, a second ink, a third ink and a fourth ink from a print head in this order to form a print layer by causing ink droplets to land on the coating liquid; including
The first ink is characterized by having the lowest surface tension at 25° C. among the water-based colored inks.

A preferred embodiment of the first printing method of the present invention further includes the step of drying after forming the printed layer.

In another preferred embodiment of the first printing method of the present invention, said drying is performed at 70-130°C.

A second printing method of the present invention is a printing method for forming a printed layer on a substrate by an inkjet printer equipped with an ink set containing a water-based colored ink and a water-based coating liquid,
The water-based colored inks include at least four types of inks, a first ink, a second ink, a third ink, and a fourth ink, and each ink independently contains water, a pigment, a water-soluble solvent, and containing a resin, the water-based coating liquid containing water, a water-soluble solvent and a resin, the resin contained in the water-based coating liquid containing a cationic polymer,
A step of ejecting the water-based coating liquid from a print head to land coating droplets on a substrate;
A step of ejecting the first ink and the second ink from the print head in this order and causing ink droplets to land on the coating liquid to form a first printing layer;
a step of performing primary drying after forming the first printed layer;
A step of ejecting the water-based coating liquid from the print head and causing the coating droplets to land on the first printing layer that has undergone primary drying;
a step of ejecting a third ink and a fourth ink from the print head in this order to form a second printing layer by causing ink droplets to land on the coating liquid on the first printing layer; including
The first ink is characterized by having the lowest surface tension at 25° C. among the water-based colored inks.

A preferred embodiment of the second printing method of the present invention further includes the step of performing secondary drying after forming the second printing layer.

In another preferred embodiment of the second printing method of the present invention, said primary drying is performed at 25-45°C.

In another preferred embodiment of the second printing method of the present invention, said secondary drying is performed at 70-130°C.

In another preferred embodiment of the first and second printing methods of the present invention, the temperature of the substrate is 30 to 45° C. in the step of landing the coating droplets on the substrate.

In another preferred embodiment of the first and second printing methods of the present invention, the first ink has the lowest mass ratio of pigment contained in the ink among the water-based colored inks.

In another preferred embodiment of the first and second printing methods of the present invention, the fourth ink has the highest oil absorption of the pigment contained in the ink among the water-based colored inks.

In another preferred embodiment of the first and second printing methods of the present invention, the first ink is magenta ink or cyan ink.

In another preferred embodiment of the first and second printing methods of the present invention, the third ink is magenta ink or cyan ink.

In another preferred embodiment of the first and second printing methods of the present invention, the first ink, second ink, third ink and fourth ink are cyan ink, yellow ink and magenta ink, respectively. and black ink.

In another preferred embodiment of the first and second printing methods of the present invention, the first ink, the second ink, the third ink and the fourth ink are magenta ink, yellow ink and cyan ink, respectively. and black ink.

In another preferred embodiment of the first and second printing methods of the present invention, the water-based colored ink has a surface tension of 20 to 50 mN/m at 25°C.

In another preferred embodiment of the first and second printing methods of the present invention, the surface tension of the water-based coating liquid at 25°C is lower than the surface tension of the first ink at 25°C.

In another preferred embodiment of the first and second printing methods of the present invention, the water-based coating liquid contains 50% to 90% by weight of water, 5% to 35% by weight of a water-soluble solvent, and 0% of resin. It is contained within the range of 0.005% by mass to 2% by mass.

In another preferred embodiment of the first and second printing methods of the present invention, the substrate is a non-absorbent substrate or a non-absorbent substrate.

ADVANTAGE OF THE INVENTION According to this invention, the printing method which can suppress generation|occurrence|production of the bleeding of a printing layer can be provided.

The printing method of the present invention will be described in detail below. One embodiment of the printing method of the present invention is a printing method for forming a print layer on a substrate by an inkjet printer equipped with an ink set containing a water-based colored ink and a water-based coating liquid, wherein the water-based colored ink is At least four inks of a first ink, a second ink, a third ink, and a fourth ink are included, each ink independently including water, a pigment, a water-soluble solvent, and a resin, and the water-based The coating liquid contains water, a water-soluble solvent and a resin, the resin contained in the water-based coating liquid contains a cationic polymer, and the water-based coating liquid is ejected from the print head to form coating droplets on the substrate. A step of landing, and ejecting the first ink, the second ink, the third ink and the fourth ink from the print head in this order, and making the ink droplets land on the coating liquid to form a printing layer The first ink is characterized by having the lowest surface tension at 25° C. among the water-based colored inks. A printing method having such features is also referred to as a "first printing method of the present invention".

Further, another embodiment of the printing method of the present invention is a printing method for forming a print layer on a substrate by an inkjet printer equipped with an ink set containing a water-based colored ink and a water-based coating liquid, wherein the water-based coloring The inks include at least four types of inks of a first ink, a second ink, a third ink, and a fourth ink, and each ink independently includes water, a pigment, a water-soluble solvent, and a resin. , the water-based coating liquid contains water, a water-soluble solvent and a resin, the resin contained in the water-based coating liquid contains a cationic polymer, the water-based coating liquid is ejected from the print head, and the coating droplets are formed as a base. A step of landing on the material, and a step of ejecting the first ink and the second ink from the print head in this order and making the ink droplets land on the coating liquid to form a first printing layer. , a step of performing primary drying after forming the first printing layer, and a step of ejecting the water-based coating liquid from the print head and making the coating droplets land on the first printing layer that has undergone the primary drying. , ejecting the third ink and the fourth ink from the print head in this order to form a second printing layer by causing ink droplets to land on the coating liquid on the first printing layer; wherein the first ink has the lowest surface tension at 25° C. among the water-based colored inks. A printing method having such features is also referred to as a "second printing method of the present invention". By using this "second printing method of the present invention", it is possible to produce a clearer image than "the first printing method of the present invention".

The ink set used in the printing method of the present invention is an ink set containing a water-based colored ink and a water-based coating liquid. Here, the water-based colored inks are composed of four or more types of water-based colored inks emitting different colors, and include at least a first ink, a second ink, a third ink, and a fourth ink.

In the ink set used in the printing method of the present invention, each of the water-based colored inks independently contains water, a pigment, a water-soluble solvent and a resin, and is preferably an inkjet ink. The inkjet ink is an ink composition for inkjet printers. In the ink set used in the printing method of the present invention, the water-based coating liquid is a liquid for coating the base material and aggregating the colored ink, and contains water, a water-soluble solvent and a resin. It is preferably a coating liquid that can be used for In the present invention, a composition containing more than 0.1% by mass of a coloring agent is referred to as "ink", and a composition containing no coloring agent or containing 0.1% by mass or less of coloring agent is simply referred to as "liquid ink". ” is expressed as.

In the ink set used in the printing method of the present invention, the aqueous coating liquid preferably has a pH within the range of 7.1 to 10.0. Water-based coating liquids containing cationic polymers are generally acidic, which may cause corrosion. Addition of corrosion inhibitors and other neutralizing agents can make the coating liquid neutral or basic. However, in this case, the expected aggregation effect of the coating liquid may not be sufficiently exhibited, and bleeding may occur. By setting the pH of the water-based coating liquid in such a basic range, it is possible to suppress the occurrence of corrosion in metal parts (especially print heads) of printing equipment such as printers. When a cationic polymer, preferably a water-soluble polymer having a quaternary ammonium cation, is used as the resin of the water-based coating liquid, the desired flocculation effect can be exhibited even if the pH of the water-based coating liquid is in the basic range. .
On the other hand, although the pH of the water-based colored ink varies depending on the type of pigment selected, etc., for the same reason, it is preferably basic and has a pH within the range of 7.01 to 10.0. is preferred.
A pH adjuster can be used for pH adjustment, but an amine compound is preferably used, and an amine compound having a boiling point of 70 to 270° C. is more preferably used. The amine compound has the effect of appropriately adjusting the pH in the water-based coating liquid and the water-based colored ink, and also preventing aggregation of the resin. Further, by adding an amine compound to the ink or coating liquid, it is possible to make corrosion more difficult to occur. Furthermore, if the boiling point of the amine compound is in the range of 70 to 270° C., it is difficult to evaporate, and the amine compound remains in the water-based colored ink or water-based coating liquid for a long period of time, resulting in stable discharge of the water-based colored ink or water-based coating liquid. The properties are excellent over a long period of time, and there is also a tendency for the glossiness of the printed layer to be high. Specific examples of amine compounds having a boiling point of 70 to 270° C. include N-methyldiethanolamine, N-ethyldiethanolamine, N,N-dimethylethanolamine, N,N-diethylethanolamine and the like. These amine compounds may be used individually by 1 type, and may be used in combination of 2 or more types. The content of the amine compound in the water-based colored ink and the water-based coating liquid is preferably 0.1 to 2.0% by mass independently.

The resin used in the water-based coating liquid contains a cationic polymer, preferably a water-soluble polymer having a cation, particularly preferably a water-soluble polymer having a quaternary ammonium cation. The water-soluble polymer having the quaternary ammonium cation (cationized nitrogen atom) can exhibit the ability to coagulate the colored ink even when present in an aqueous coating liquid whose pH is in the basic range. can. However, since the water-soluble polymer has a high ability to aggregate the colored ink, the occurrence of aggregation of the colored ink occurs remarkably quickly, and there is a problem that the glossiness of the printed layer decreases. becomes important. As a result, it is possible to suppress the occurrence of bleeding of the printed layer, suppress the occurrence of corrosion of printing equipment, and form a printed layer with good adhesion without lowering the gloss.
In the present invention, a water-soluble polymer means a polymer that dissolves in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

The water-soluble polymer having the cation preferably has a weight average molecular weight of 1,000 to 50,000, more preferably 2,500 to 45,000, and 5,000 to 40,000. is more preferred. When the weight-average molecular weight of the cation-containing polymer is 1,000 or more, the ability to agglomerate the colored ink increases, and bleeding is less likely to occur. On the other hand, when the weight-average molecular weight of the cation-containing water-soluble polymer is 50,000 or less, the speed of aggregation of the colored ink is suppressed, and a highly glossy printed matter can be obtained.
In this specification, the weight average molecular weight is a value measured by gel permeation chromatography (GPC), polystyrene is used as a standard substance, and tetrahydrofuran is used as a mobile phase.

The cationic polymer is preferably two or more cationic polymers having different cationic degrees. By using a plurality of cationic polymers with different cationic degrees, it becomes easy to adjust the size of the dot diameter and bleeding.
Specifically, the cationic polymer includes a cationic polymer having a cationic degree of 5.5 to 7.5 meq/g at pH 7.1 and a cationic polymer having a cationic degree of 2.0 to 5.0 meq/g at pH 7.1. a water-soluble polymer having a cationic degree at pH 7.1 of 6.0 to 7.0 meq/g and a cationic degree at pH 7.1 of 2.5 to 4 and a water-soluble polymer that is 0.5 meq/g. The ratio of the two types of cationic resins is preferably in the range of 1:1 to 20:1, preferably in the range of 7:3 to 10:1, where the mass ratio of polymer with high cationic degree:polymer with low cationic degree is in the range of 1:1 to 20:1. is more preferable.
In this specification, the degree of cation can be determined by colloidal titration using a polyvinyl potassium sulfate reagent. The detailed procedure is as follows.
90 mL of deionized water is placed in a conical beaker, 10 mL of a 500 ppm aqueous solution of the sample (on a dry basis) is added, adjusted to pH 7.1 with an aqueous amine solution, and stirred for about 1 minute. Then add 2-3 drops of toluidine blue indicator and titrate with N/400 polyvinyl potassium sulfate reagent (N/400 PVSK). The titration rate is 2 mL/min, and the end point is when the color of the test water changes from blue to reddish purple and is maintained for 10 seconds or longer. The formula for calculating the degree of cation (meq/g) is as follows.
Cationic degree = (N/400 PVSK titer) x (N/400 PVSK titer)/2

The water-soluble polymer having a cation preferably has a cation in its main chain. When a water-soluble polymer having such a structure is used, when the water-based colored ink lands on the water-based coating liquid, only the interface of the water-based colored ink instantly aggregates, and the position where the water-based colored ink lands without mixing with each other. , it is possible to form a highly glossy print layer without bleeding.

A commercially available product can be used as the water-soluble polymer having the above cation. Among them, a water-soluble polymer having a quaternary ammonium cation is preferable, but from the viewpoint of stably existing even in basic conditions, for example, DK6810, DK6851, DK6864, WS4030, WS4027, WS4052, CA6018 (manufactured by Seiko PMC), Hersize CP-300, CP-800 (manufactured by Harima Chemicals), PAS-H-1L, PAS-H-5L, PAS-2401, PAS-A-1 (manufactured by Nitbo Medical), Catiomaster PDT -2, PD-7, PD-30 (manufactured by Yokkaichi Gosei Co., Ltd.). The water-soluble polymer having the cation may be used singly or in combination of two or more.

The ratio of the water-soluble polymer having the cation to the resin contained in the aqueous coating liquid is preferably 50% by mass or more, but in particular, from the viewpoint of appropriately controlling the aggregation action, the water-based coating liquid The proportion of the water-soluble polymer having the quaternary ammonium cation in the resin contained in is preferably 50% by mass or more.

As other resins that can be used in the water-based coating liquid, resins commonly used in the ink industry other than the cationic polymer can be used. Examples include acrylic resins, silicone resins, acrylic silicone resins, styrene-acrylic copolymer resins, polyester resins, rosin resins, phenolic resins, urethane resins, melamine resins, urea resins, epoxy resins, cellulose resins, butyral resins, maleic acid resins, and fumaric resins. acid resins, vinyl resins, and the like. These resins may be used individually by 1 type, and may be used in combination of 2 or more types.

The resin used for the water-based colored ink is not particularly limited, and resins commonly used in the ink industry can be used. Examples include acrylic resins, silicone resins, acrylic silicone resins, styrene-acrylic copolymer resins, Polyester resin, rosin resin, petroleum resin, coumarone resin, phenolic resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin, fumaric resin acid resins, vinyl resins, and the like. These resins may be used individually by 1 type, and may be used in combination of 2 or more types.

The resin used in the water-based colored ink may contain a self-dispersing resin. A self-dispersing resin is a resin that can maintain a dispersed state in an ink without using a surfactant or an emulsifier. A polymer having a group at its terminal or side chain, a polymer having a hydrophilic group such as a polycarbonate group, a polyester group, or a polyether group in its main chain, and the like are preferably used. The hydrophilic groups of the self-dispersing resin and the hydrophilic groups of the self-dispersing pigment repel each other, so that the dispersed state is maintained, and as a result, an ink having excellent storage stability can be prepared. These self-dispersible resins may be used singly or in combination of two or more. In addition, self-dispersing resin may use a commercial item.

The self-dispersing resin preferably contains a self-dispersing urethane resin from the viewpoint of improving the performance of the printed layer such as scratch resistance and water resistance, and from the viewpoint of imparting high adhesion to various substrates. , a polyester group- or polyether group-containing self-dispersible urethane resin. The proportion of the self-dispersing urethane resin in the self-dispersing resin is preferably 30 to 100% by mass.

The self-dispersible urethane resin preferably has a weight average molecular weight of 100,000 to 1,000,000, more preferably 150,000 to 750,000, and more preferably 200,000 to 500,000. is more preferred. If the weight-average molecular weight of the self-dispersible urethane resin is within the specified range, the abrasion resistance can be further improved, and a strong printed layer can be formed.
In this specification, the weight average molecular weight is a value measured by gel permeation chromatography (GPC), polystyrene is used as a standard substance, and tetrahydrofuran is used as a mobile phase.

The self-dispersible urethane resin can be obtained by reacting a polyol component such as polyester polyol, polyether polyol, polycarbonate polyol, etc., a polyisocyanate component, and optionally a chain extender.

The polyester polyol is not particularly limited, and examples thereof include polyethylene adipate, polyethylene propylene adipate, polybutylene adipate, polyhexamethylene adipate, polydiethylene adipate, polyethylene terephthalate, polyethylene isophthalate, polyhexamethylene isophthalate, polyethylene succinate, poly Butylene sac 2-cyanate, polyethylene sebacate, polybutylene sebacate, poly-ε-caprolactamdiol, poly(3-methyl-1,5-pentylene adipate) and the like can be mentioned. A polyester group-containing self-dispersible urethane resin can be obtained by using a polyester polyol as the polyol component.
The polyether polyol is not particularly limited, and examples thereof include polyoxytetramethylene glycol, polyoxypropylene glycol, polyoxyethylene glycol and polyoxyethylene/propylene glycol. A polyether group-containing self-dispersible urethane resin can be obtained by using a polyether polyol as the polyol component.
Polycarbonate polyols are not particularly limited, and examples thereof include 1,6-hexanediol polycarbonate polyol, 1,4-butanediol polycarbonate polyol and poly-1,4-cyclohexanedimethylene carbonate diol. By using a polycarbonate polyol as the polyol component, a polycarbonate group-containing self-dispersible urethane resin can be obtained.
Acrylic polyol or the like may be used as the polyol component.
These polyol components can be used singly or in combination of two or more.

Examples of polyisocyanate components include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, naphthylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate and Examples include polyisocyanate compounds such as norbornane diisocyanate. Among these polyisocyanate components, xylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate) and norbornane diisocyanate are preferred. These polyisocyanate components can be used singly or in combination of two or more.

Examples of chain extenders include low molecular weight polyhydric alcohols and low molecular weight polyamines. Examples of low molecular weight polyhydric alcohols include ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, trimethylolpropane, penta erythritol, 1,4-cyclohexanedimethanol, dimethylolalkanoic acids such as dimethylolbutanoic acid and dimethylolpropionic acid, and the like. Examples of low-molecular-weight polyamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, hydrazine, piperazine, isophoronediamine, norbornanediamine, diaminodiphenylmethane, diaminocyclohexylmethane, tolylenediamine, xylenediamine, diethylenetriamine, triamine. ethylenetetramine, tetraethylenepentamine, iminobispropylamine and the like. These chain extenders can be used singly or in combination of two or more.

The self-dispersing resin is dispersed in the ink and is in the form of particles. Here, the self-dispersing resin preferably has a 50 volume % particle diameter (D50) of 10 nm to 90 nm, more preferably 20 nm to 70 nm, even more preferably 30 nm to 60 nm. If the particle size is 50% by volume within the specified range, an ink can be prepared in which the self-dispersing resin is well dispersed and the storage stability is excellent. In the present invention, the 50% particle size (D50) refers to the 50% particle size (D ₅₀ ) of the volume-based particle size distribution, and a laser diffraction/scattering particle size distribution analyzer (eg, SALD-7000: Shimadzu Corporation). (manufactured) can be obtained from the particle size distribution measured using. The particle diameter in the present invention is represented by the equivalent sphere diameter according to the laser diffraction/scattering method.

The self-dispersible resin preferably has an acid value of 5.0 to 60.0. If the acid value is within the range specified above, the dispersibility can be improved. As used herein, the acid value of a resin means mg of potassium hydroxide required to neutralize 1 g of resin.

In the ink set used in the printing method of the present invention, by adjusting the acid value of the self-dispersible resin contained in the water-based colored ink and the cation degree of the cationic polymer contained in the water-based coating liquid, dots of the water-based colored ink It is possible to form a printed layer having a large diameter and excellent gloss without bleeding. Here, the ratio (A:B) of the acid value (A) of the self-dispersing resin and the cationic degree (meq/g) (B) of the cationic polymer at pH 7.1 is 10:1 to 1:1. is preferably within the range of , more preferably within the range of 6:1 to 1.5:1, and even more preferably within the range of 3:1 to 2:1.

The proportion of the self-dispersible resin in the resin contained in the water-based colored ink is preferably 50% by mass or more.

The resin content in the water-based colored ink is preferably 1 to 10% by mass. In addition, the content of the resin in the water-based coating liquid is preferably 0.005 to 2% by mass, more preferably 0.01 to 1.5% by mass. If the content of the resin in the water-based coating liquid is too small, the reaction with the water-based colored ink will be insufficient. , it becomes possible to reduce the resin content. In addition, in the second printing method of the present invention, since the water-based coating liquid is discharged in two batches, it is possible to further reduce the resin content. When the resin content in the water-based coating liquid is high, printing streaks tend to occur during printing.

The water-based colored ink is not particularly limited, and pigments such as organic pigments and inorganic pigments that are commonly used as colorants in the ink industry can be used, but it preferably contains a self-dispersing pigment. A self-dispersing pigment is a pigment that can maintain a dispersed state in ink without using a pigment dispersant, and is usually obtained by imparting a highly hydrophilic functional group to the surface. The present inventor believes that if the cationic polymer described above, particularly a water-soluble polymer having a quaternary ammonium cation, and a self-dispersing pigment are combined, aggregation will occur too quickly to form unevenness on the surface of the printed layer. It has been found that it is possible to prevent the glossiness of the printed layer from deteriorating.

In the present invention, the self-dispersible pigment is preferably a pigment having anions such as carboxyl ions, sulfate ions, nitrate ions, phosphate ions, and hydroxide ions directly bonded to the surface. By using such an anionic self-dispersing pigment, the pigment can be stably dispersed in the ink without adding a dispersant, and a clearer image can be printed. Commercially available products can be suitably used as these anionic self-dispersing pigments.

Pigment yellow 12, 13, 14, 17, 20, 24, 31, 42, 53, 55, 74, 83, 86, 93, 109, 110, 117, 120, 122, 125, 128 , 129, 137, 138, 139, 147, 148, 150, 151, 152, 153, 154, 155, 166, 168, 180, 181, 184, 185, 213; Pigment Orange 16, 36, 38, 43, 51 Pigment Red 9, 48, 49, 52, 53, 57, 97, 101, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215 , 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 244, 254; Pigment Violet 19, 23, 29, 30, 32, 37, 40, 50; Pigment Blue 15, 15:1 , 15:3, 15:4, 15:6, 22, 27, 28, 29, 30, 60, 64, 80; Pigment Green 7, 36; Pigment Brown 23, 25, 26; 26, 27, 28, Pigment White 6 and the like. In addition, these pigments may be used individually by 1 type, and may be used in combination of 2 or more types.
Examples of pigments that can be used in cyan ink include Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 27, 28, 29, 30, 60, 64, 80, and the like. ,
Pigments that can be used in magenta ink include, for example, Pigment Red 9, 48, 49, 52, 53, 57, 97, 101, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216 , 217, 220, 223, 224, 226, 227, 228, 238, 240, 244, 254, etc.
Examples of pigments that can be used in yellow ink include Pigment Yellow 12, 13, 14, 17, 20, 24, 31, 42, 53, 55, 74, 83, 86, 93, 109, 110, 117, 120, 122. , 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 152, 153, 154, 155, 166, 168, 180, 181, 184, 185, 213, etc.
Examples of pigments that can be used in black ink include Pigment Black 1, 7, 26, 27, and 28.
Pigment Orange 16, 36, 38, 43, 51, 55, 59, 61, 64, 65, 71; Pigment Violet 19, 23, 29, 30, 32, 37, 40, 50; Pigment Green 7, 36; Pigments such as Pigment Brown 23, 25, 26; and Pigment White 6 can be used for the basic color inks, and can also be used for special color inks such as orange ink, violet ink, green ink, and red ink.

The content of the pigment in the water-based colored ink can be arbitrarily determined depending on the type of pigment used, but is preferably 0.5 to 10% by mass in the water-based colored ink.

The water-soluble solvent used for the water-based colored ink and the water-based coating liquid is not particularly limited, and water-soluble solvents commonly used in the ink industry can be used. In addition, in the water-based colored ink and the water-based coating liquid, the content of the water-soluble solvent is preferably 60% by mass or less, more preferably 35% by mass or less, independently. Although the lower limit of the content of the water-soluble solvent is not particularly limited, it is usually preferably 5% by mass or more.

The water-soluble solvent is selected from the group consisting of glycol ethers, three- to five-membered ring lactone compounds, amide compounds, and alkanediols, from the viewpoint of improving ejection stability, wettability, and storage stability of inks and coating liquids. It is preferable to include at least one selected type.

Specific examples of glycol ethers include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol pentyl ether, ethylene glycol hexyl ether, ethylene glycol cyclohexyl ether, ethylene glycol phenyl ether, and ethylene glycol benzyl. Ether, ethylene glycol isobutyl ether, ethylene glycol tertiary butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol propyl ether, diethylene glycol butyl ether, diethylene glycol pentyl ether, diethylene glycol hexyl ether, diethylene glycol cyclohexyl ether, diethylene glycol phenyl ether, diethylene glycol benzyl ether, diethylene glycol mono Butyl ether, diethylene glycol isobutyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol propyl ether, triethylene glycol butyl ether, triethylene glycol pentyl ether, triethylene glycol hexyl ether, triethylene glycol cyclohexyl ether, triethylene glycol Ethylene glycol ethers such as phenyl ether, triethylene glycol benzyl ether and triethylene glycol monobutyl ether, and propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol propyl ether, propylene glycol butyl ether, propylene glycol pentyl ether, propylene glycol hexyl ether , propylene glycol cyclohexyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol pentyl ether, dipropylene glycol hexyl ether, dipropylene glycol cyclohexyl ether, tripropylene glycol Methyl ether, tripropylene glycol ethyl ether, tripropylene glycol propyl ether, tripropylene glycol and propylene glycol ethers such as ethyl ether, tripropylene glycol pentyl ether, tripropylene glycol hexyl ether and tripropylene glycol cyclohexyl ether. Among these, ethylene glycol monobutyl ether, ethylene glycol isobutyl ether, ethylene glycol tertiary butyl ether, diethylene glycol monobutyl ether, diethylene glycol isobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether and triethylene Glycol monobutyl ether is preferred.

A three- to five-membered ring lactone compound is a three-membered ring having 3 atoms constituting the ring, among compounds having a lactone ring containing -C(=O)-O- as a part, and having 4 atoms. is a compound of a four-membered ring or a five-membered ring having five atoms. Specific examples include α-acetolactone, β-propionlactone, γ-butyrolactone, δ-valerolactone and the like. Among these, γ-butyrolactone is preferred.

Amide compounds are preferably non-cyclic amide compounds such as dimethylacetamide, dimethylformamide, sulfanilamide, toluenesulfonamide, benzenesulfonamide, N-dimethyl-β-methoxypropionamide, N,N-dimethyl-β-butoxy Propionamide, N,N-dimethyl-β-pentoxypropionamide, N,N-dimethyl-β-hexoxypropionamide, N,N-dimethyl-β-heptoxypropionamide, N,N-dimethyl-β- 2-ethylhexoxypropionamide, N,N-dimethyl-β-octoxypropionamide, N,N-diethyl-β-methoxypropionamide, N,N-diethyl-β-butoxypropionamide, N,N-diethyl -β-pentoxypropionamide, N,N-diethyl-β-hexoxypropionamide, N,N-diethyl-β-heptoxypropionamide, N,N-diethyl-β-octoxypropionamide and the like. . Among these, dimethylacetamide, dimethylformamide, N,N-dimethyl-β-methoxypropionamide, N,N-dimethyl-β-butoxypropionamide, N,N-diethyl-β-methoxypropionamide, N,N- Diethyl-β-butoxypropionamide is preferred.

Alkanediols are alkane compounds in which two hydrogen atoms are replaced by two hydroxyl groups, such as ethylene glycol, propylene glycol, 2-methyl-1,3-propanediol, 1,2-butanediol, 1, 3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,2-heptanediol, 1,2-octanediol, 1,9 -nonanediol, 1,10-decanediol, and the like. Among these, propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol and 1,2-hexanediol are preferred.

The water-based colored ink and the water-based coating liquid naturally contain water, and examples of the water used include pure water such as ion-exchanged water and distilled water, ultrapure water, and the like. Further, when the ink or coating liquid is to be stored for a long period of time, water sterilized by ultraviolet irradiation or the like may be used in order to prevent the generation of mold or bacteria. Furthermore, it is also possible to dilute the ink or coating liquid with water according to the printing conditions of the inkjet printer. The content of water in the water-based colored ink is preferably, for example, in the range of 20 to 80% by mass. In addition, the content of water in the water-based coating liquid can be exemplified in the range of 20 to 90% by mass, preferably in the range of 50 to 90% by mass.

The water-based colored ink and water-based coating liquid may further contain surface conditioners, antifoaming agents, moisturizing agents, wetting and dispersing agents, preservatives/antifungal agents, dissolution aids, antioxidants, and metal trapping agents, if necessary. etc. may be appropriately selected and blended within a range that does not impair the object of the present invention.

In the ink set used in the printing method of the present invention, the water-based colored ink and the water-based coating liquid can be prepared by mixing various components appropriately selected as necessary.

In the ink set used in the printing method of the present invention, the water-based colored ink has a surface tension of 20.0 at 25° C. from the viewpoint of forming a good printed layer without causing bleeding when in contact with the water-based coating liquid. It is preferably from 0 to 50.0 mN/m, more preferably from 23.0 to 45.0 mN/m, even more preferably from 26.0 to 40.0 mN/m. On the other hand, the water-based coating liquid preferably has a surface tension of 18.0 to 30.0 mN/m at 25° C. from the viewpoint of improving the wettability to the substrate, and 20.0 to 30.0 mN/m. It is more preferably 19.0 to 27.5 mN/m, particularly preferably 20.0 to 25.0 mN/m. The surface tension of the coating liquid or ink can be measured by the plate method.

In the ink set used in the printing method of the present invention, the water-based coating liquid and the water-based colored ink preferably have a viscosity at 25° C. of 3.0 to 10.0 mPa·s, more preferably 4.0 to 8.5 mPa. · s, more preferably 5.0 to 7.0 mPa·s. Good ejection stability can be obtained if the viscosity at 25° C. is within the specified range. The viscosity of the coating liquid or ink can be measured using a Brookfield viscometer.

The ink set used in the printing method of the present invention can be used in various inkjet printers. Such an inkjet printer is equipped with a print head, and droplets of the ink and coating liquid forming the ink set are ejected from the nozzles of the print head.

In the printing method of the present invention, first, the water-based coating liquid is discharged from the print head so that the coating droplets land on the substrate (first step). Since the coating liquid contains a cationic polymer, it has the effect of aggregating the colored ink, and can suppress bleeding of the printed layer.

In the printing method of the present invention, the temperature of the substrate is preferably 30 to 45° C. in the step of causing the coating droplets to land on the substrate. This can prevent the water-based coating liquid from drying too quickly. The temperature of the base material is the temperature of the surface of the base material on which the coating droplets land. Subsequent steps are generally performed while maintaining the temperature of the substrate here.

In the printing method of the present invention (especially the first printing method of the present invention), next, the first ink, the second ink, the third ink and the fourth ink are ejected from the print head in this order. The printing layer is formed by causing ink droplets to land on the water-based coating liquid that has landed on the substrate in the first step (second step). In the second step, since the first ink is the first ink to be ejected onto the coating liquid, the first ink is most strongly affected by the aggregation of the colored inks by the coating liquid.

According to the printing method of the present invention, by using the ink having the lowest surface tension at 25° C. among the water-based colored inks as the first ink, the aggregating action of the colored ink by the coating liquid can be effectively exhibited. can be done. In addition, when the mass ratio of the pigment contained in the ink is low, the surface tension tends to be low. It can be an ink with the lowest weight percentage of pigment that is included. In the printing method of the present invention, the first ink has the lowest surface tension at 25°C among the water-based colored inks. It is preferably lower than the third ink and the fourth ink, and the third ink preferably has a lower surface tension at 25° C. than the fourth ink.

In the second step, among the first ink, the second ink, the third ink, and the fourth ink, the fourth ink that is finally ejected onto the coating liquid is the aggregation of the colored ink by the coating liquid. Inks with high pigment oil absorption are preferred because they have the weakest effect. Therefore, in the printing method of the present invention, the fourth ink preferably has the highest oil absorption of the pigment contained in the ink among the water-based colored inks. In the present invention, the oil absorption is measured according to the "refined linseed oil method" specified in JIS K 5101-13-1:2004.

The second printing method of the present invention also includes ejecting the first ink, the second ink, the third ink and the fourth ink from the print head in this order to form a print layer. However, in the second printing method of the present invention, after the first ink and the second ink are ejected in this order to form a print layer, primary drying and then printing with the coating liquid are performed again. As a result, the third ink and the fourth ink to be ejected afterward can also effectively exhibit the aggregating action, and a higher-definition printed layer can be formed.

Specifically, in the second printing method of the present invention, the first ink and the second ink are ejected from the print head in this order, and the coating liquid that has landed on the substrate in the first step A first printed layer is formed by landing ink droplets thereon (third step). The embodiment of the second printing method of the present invention is as described in the description of the printing method of the present invention. To give a specific example, in the second printing method of the present invention, the first ink has the lowest surface tension at 25° C. among water-based colored inks, and the first ink is Among the water-based colored inks, the ink may have the lowest mass ratio of the pigment contained in the ink. In the second printing method of the present invention, the fourth ink preferably has the highest oil absorption of the pigment contained in the ink among the water-based colored inks.

In the second printing method of the present invention, primary drying is performed after forming the first printed layer in the third step (fourth step). By performing the primary drying, the surface of the first printed layer is strengthened, and the dot shape of the water-based coating liquid or water-based colored ink to be landed thereafter can be maintained. In the fourth step, since it is not necessary to completely dry the first printed layer, the primary drying is preferably performed at 25 to 45°C, more preferably 30 to 40°C. Also, the drying time is preferably 10 seconds or less, more preferably 1 second or more and 6 seconds or less. Drying means used for the primary drying is not particularly limited, but a dryer equipped with an air blowing function is preferable. When drying the first printed layer by blowing air (usually using air) (that is, when drying the first printed layer by blowing air), the air volume is 1.0 m ³ /min or more. It is preferably 1.5 to 5.0 m ³ /min, more preferably 1.5 to 5.0 m 3 /min.

In the second printing method of the present invention, the water-based coating liquid is discharged from the print head, and coating droplets are made to land on the first printing layer that has undergone primary drying in the fourth step (fifth process). As a result, the third ink and the fourth ink to be ejected afterward can also effectively exhibit the aggregating action, and a higher-definition printed layer can be formed. In addition, in the fifth step, the water-based coating liquid can be discharged for the second time after rewinding the base material provided with the first printed layer to the inkjet printer.

In the second printing method of the present invention, the third ink and the fourth ink are ejected from the print head in this order, and on the coating liquid that has landed on the first printing layer in the fifth step A second printed layer is formed by landing ink droplets on the surface (sixth step).

In the second printing method of the present invention, it is preferable to further perform secondary drying after forming the second printed layer in the sixth step (seventh step). By performing secondary drying, the resin contained in the printed layer can be fused onto the base material to form a strong film, and as a result, it is possible to provide a printed matter with excellent robustness. In the seventh step, the secondary drying is preferably carried out at 70 to 130°C, more preferably at 80 to 110°C, from the viewpoint of fusing the resin contained in the printed layer onto the substrate. . Also, the drying time is preferably 2 seconds or more and 180 seconds or less, more preferably 5 seconds or more and 120 seconds or less. Drying means used for secondary drying is not particularly limited, but a dryer having a blower function is preferable. When the second printed layer is dried by blowing air such as hot air (usually using air) (that is, when drying the second printed layer by blowing air), the air volume is 1.0 m ³ / min or more, and more preferably 1.5 to 5.0 m ³ /min.

In addition, such a secondary drying step is preferably applied to the first printing method of the present invention. In this case, after forming the printed layer in the second step, the same secondary drying as the above secondary drying drying is performed. Specifically, in the first printing method of the present invention, it is preferable to further dry after forming the printed layer in the second step (eighth step). It is preferably carried out at 130°C, more preferably at 80-110°C.

In the printing method of the present invention, the first ink is preferably magenta ink or cyan ink. Among water-based colored inks, magenta ink and cyan ink tend to have relatively low surface tension at 25° C., and therefore are preferably used as the first ink. Further, in the printing method of the present invention, the third ink may be magenta ink or cyan ink. In the second printing method of the present invention, the third ink is the ink that is first ejected onto the coating liquid that has landed on the first printing layer in the fifth step. Strongly affected by ink aggregation. Therefore, in the second printing method of the present invention, the third ink is preferably magenta ink or cyan ink.

In the printing method of the present invention, when the first ink, the second ink, the third ink, and the fourth ink are cyan ink, magenta ink, yellow ink, and black ink, respectively, cyan ink, yellow ink , magenta ink and black ink, and magenta ink, yellow ink, cyan ink and black ink. The second ink, the third ink, and the fourth ink are preferably cyan ink, magenta ink, yellow ink, and black ink, respectively. , the second ink, the third ink, and the fourth ink are preferably cyan ink, yellow ink, magenta ink, and black ink, or magenta ink, yellow ink, cyan ink, and black ink, respectively. Cyan ink is relatively easy to prepare as an ink with the lowest surface tension at 25°C among water-based colored inks, and black ink is prepared using a pigment with the highest oil absorption among water-based colored inks. It is relatively easy to

In the printing method of the present invention, the water-based coating liquid preferably has better wettability than the water-based colored ink. Therefore, in the printing method of the present invention, the surface tension of the water-based coating liquid at 25°C is preferably lower than the surface tension of the first ink at 25°C.

In the printing method of the present invention, the substrate is not particularly limited. Absorption of inks and coating liquids such as metal substrates such as aluminum alloys, inorganic substrates such as glass and ceramics, and plastic substrates such as acrylic resin, polyvinyl chloride, polycarbonate, ABS resin, polyethylene terephthalate, and polyolefin. non-absorbent substrates, coated paper, art paper, cast paper, lightly coated paper, etc. It is also suitable for printing on In particular, the second printing method of the present invention is a printing method in which the coating liquid is discharged in two steps and the primary drying is performed. When a non-absorbent base material is used, the contact between the coating liquid and the first to fourth inks is facilitated, making it possible to obtain a printed matter with better image fixability and print quality. Examples of other base materials include paper base materials such as fine paper, synthetic paper, and inkjet paper, and inorganic base materials such as wood, gypsum, calcium silicate, concrete, cement, mortar, and slate. In addition, the base material may be subjected to a general surface treatment such as primer treatment or corona treatment in order to improve adhesion to the printed layer.

In the printing method of the present invention, ink droplets of water-based colored ink can be made to land in the coating liquid without waiting for drying of the coating liquid (that is, without drying the coating liquid). Therefore, in the printing method of the present invention, it is not necessary to perform a drying step for each layer. However, in the second printing method of the present invention, primary drying is performed after forming the first printing layer in the third step. In the above printing method, the total thickness of the ejected coating liquid and the colored ink immediately after printing (that is, before the water and the water-soluble solvent evaporate) may be in the range of 1 to 20 μm. preferable. The printing layer that is finally formed in the printing method of the present invention means a printing layer that is formed through curing and drying after the ink droplets have landed on the coating droplets.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

<Water-based coating liquid>
According to the formulation shown in Table 1, a resin, an amine compound, a water-soluble solvent, a surface conditioner and ion-exchanged water were mixed by a known method to prepare a water-based coating liquid. The pH, surface tension (25° C.) and viscosity (25° C.) of each water-based coating liquid were measured, and Table 1 shows the obtained results.

The formulations listed in Table 1 above are as follows.
*1 The following was used as the aqueous solution A of the water-soluble polymer having a quaternary ammonium cation.
Catiomaster PE-30 (manufactured by Yokkaichi Synthesis, dimethylamine/ethylenediamine/epichlorohydrin polymer resin, resin content 50% by mass, weight average molecular weight (Mw): 9000, cation degree at pH 7.1 6.5 meq/ g)
*2 The following was used as the aqueous solution B of the water-soluble polymer having a quaternary ammonium cation.
DK6851 (manufactured by Seiko PMC Co., Ltd., polyamine resin, resin content 70.0% by mass, cation degree 6.8 meq/g at pH 7.1)
*3 TSF4446 (manufactured by Momentive, polyether-modified silicone oil, silicone oil content 100% by mass, surface conditioner)

<Water-based colored ink containing self-dispersing pigment>
According to the formulation shown in Tables 2 and 3, the self-dispersing pigment, resin, water-soluble solvent, surface conditioner and ion-exchanged water were mixed by a known method to prepare a water-based colored ink containing the self-dispersing pigment. The surface tension (25° C.) and viscosity (25° C.) of each water-based colored ink were measured, and the obtained results are shown in Tables 2 and 3.

The formulations described in Tables 2 and 3 above are as follows.
*4 The following was used as the self-dispersible pigment dispersion.
・CAB-O-JET 250C
(manufactured by Cabot Corporation, cyan self-dispersing pigment aqueous dispersion, pigment content 10% by mass)
・CAB-O-JET-465M
(manufactured by Cabot Corporation, magenta self-dispersible pigment aqueous dispersion, pigment content 15% by mass)
・CAB-O-JET 270Y
(manufactured by Cabot Corporation, yellow self-dispersing pigment aqueous dispersion, pigment content 10% by mass)
・CAB-O-JET 300K
(manufactured by Cabot Corporation, black self-dispersing pigment aqueous dispersion, pigment content 15% by mass)
*5 As the resin dispersion liquid C, the following was used.
NEOREZ R-9621 (manufactured by DSM Coating Resins, polyester group-containing self-dispersing urethane resin, particle size 50 nm, acid value 18, resin content 38% by mass)

<Water-based colored ink containing non-self-dispersing pigment>
According to the formulation shown in Tables 4 and 5, a non-self-dispersing pigment, an antifoaming agent, a water-soluble solvent, a wetting dispersant, and an ion-exchanged water are dispersed by a known method in an aqueous coloring dispersion, and a resin and a surface control agent are added. In addition, water-based colored inks containing non-self-dispersed pigments were prepared. The surface tension (25° C.) and viscosity (25° C.) of each water-based colored ink were measured, and the obtained results are shown in Tables 4 and 5.

The formulations described in Tables 4 and 5 above are as follows.
*6 The following non-self-dispersing pigments were used.
・FASTOGEN Blue FA5380 (phthalocyanine blue, cyan pigment manufactured by DIC)
・Shinkasha Magenta RT (dichloroquinacridone, magenta pigment manufactured by BASF)
・Hostaperm Yellow H5G (Quinoxaline dione, yellow pigment manufactured by Clariant)
・ Nerox-1000 (carbon black, manufactured by Orion Engineered Carbon Co., Ltd., black pigment)
* 7 Defoamer (SN Deformer 1312, manufactured by San Nopco)
* 8 Wetting and dispersing agent (Noigen EA-157, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

<Bleeding between first and second colors>
Using Ramirez PJ-1304NX manufactured by Muto Kogyo Co., Ltd., first, the coating droplets are ejected, the coating droplets are allowed to land on the surface of the vinyl chloride sheet that is the base material, and then the coating liquid is dried without drying. Ink droplets of the first color ink, the second color ink, the third color ink, and the fourth color ink were landed in this order to print an image. In addition, the printed image is obtained by printing a plurality of lines with each ink, and the lines printed with the first color ink are partially printed with the second, third, and fourth color inks. , intersects with the printed lines of to form overlapping portions. After that, under a microscope, VHX-5000, manufactured by Keyence Corporation, overlapping portions of the first color ink and the second and subsequent color inks were observed and evaluated according to the following evaluation criteria. Tables 6 to 10 show the composition of the ink set used, the substrate temperature, and the evaluation results.
A: Bleeding is less than 150 μm in all three overlapping portions of the overlapping portions of the first color ink and the second and subsequent color inks ○: portions overlapping the first and second and subsequent color inks Bleeding of 150 μm or more and less than 200 μm in one or more overlapping parts among them △: 200 μm or more and less than 300 μm Bleeding ×: Bleeding of 300 μm or more in at least one of the overlapped portions of the first color ink and the second and subsequent color inks

<Definition of printed image (1)>
Using Ramirez PJ-1304NX manufactured by Muto Kogyo Co., Ltd., first, the coating droplets are ejected, the coating droplets are allowed to land on the surface of the vinyl chloride sheet that is the base material, and then the coating liquid is dried without drying. Ink droplets of the first color ink, the second color ink, the third color ink, and the fourth color ink are landed on the top in this order, and an image specified by JIS X9201 2001 N3A is printed, and the air volume is 2.5 m ³ The printed layer was dried for 2 minutes by applying hot air at 90° C. using a drier of /min (the printing method here corresponds to the first printing method of the present invention). The degree of blurring of the printed layer obtained after drying was visually evaluated. Evaluation criteria are as follows. Tables 6 to 10 show the composition of the ink set used, the substrate temperature, and the evaluation results.
○+: Bleeding is not observed in the image, and dots of four colors are present independently ○: Bleeding is not observed in the image △: Bleeding between colors is small, but the entire image is slightly blurred ×: Clearly bleeding - : Bleeding is not observed in the image, but print streaks are conspicuous.

<Definition of printed image (2)>
An image specified by JIS X9201 2001 N3A was printed using Ramirez PJ-1304NX manufactured by MUTOH INDUSTRIES CO., LTD. First, a coating droplet is ejected, and the coating droplet is allowed to land on the surface of the vinyl chloride sheet that is the base material. ink droplets were landed in this order to form the first printed layer. Next, primary drying was performed by blowing air at temperatures shown in Tables 6 to 10 to the first printed layer for 3 seconds using a dryer with an air volume of 1.5 m ³ /min. Next, the vinyl chloride sheet is rewound, the coating droplets are discharged again, and are deposited on the first printed layer that has undergone primary drying, and then the coating liquid that has landed on the first printed layer is not dried. Then, ink droplets of the third color ink and the fourth color ink were deposited in this order on the coating liquid to form a second printed layer. After printing, the printed layer was subjected to secondary drying for 2 minutes by blowing air at temperatures shown in Tables 6 to 10 using a dryer with an air volume of 2.5 m ³ /min. ). The degree of blurring of the finally obtained printed layer was visually evaluated. Evaluation criteria are as follows. Tables 6 to 10 show the composition of the ink set used, the substrate temperature, and the evaluation results.
○+: Bleeding is not observed in the image, and four color dots are present independently ○: Bleeding is not observed in the image △: Bleeding between colors is small, but the entire image is slightly blurred ×: Clearly bleeding - : No bleeding is observed in the image, but print streaks are conspicuous.

<Scratch resistance to vinyl chloride substrate>
Using Ramirez PJ-1304NX manufactured by Muto Kogyo Co., Ltd., first, coating droplets were made to land on each surface of a vinyl chloride sheet as a base material, and solid printing was performed. Next, without drying the coating liquid, cyan ink droplets, magenta ink droplets, and yellow ink droplets were made to land on the coating liquid, and solid printing was performed with a print density of 80% for each ink and a total print density of 240%. After that, using a dryer with an air volume of 2.5 m ³ /min, the printed layer was dried for 2 minutes by blowing air at a temperature shown in the column of secondary drying temperature in Tables 6 to 10. After drying, the printed portion was rubbed back and forth with a cotton swab (registered trademark, manufactured by Hakujuji Co., Ltd.) five times, and then visually evaluated according to the following evaluation criteria. Tables 6 to 10 show the composition of the ink set used, the substrate temperature, and the evaluation results.
○: Ink is not peeled off from the base material ×: Ink is peeled off from the base material -: The base material is deformed and cannot be evaluated.

Claims (15)

A printing method for forming a print layer on a substrate by an inkjet printer equipped with an ink set containing a water-based colored ink and a water-based coating liquid,
The water-based colored inks include at least four types of inks, a first ink, a second ink, a third ink, and a fourth ink, and each ink independently contains water, a pigment, a water-soluble solvent, and containing a resin, the water-based coating liquid containing water, a water-soluble solvent and a resin, the resin contained in the water-based coating liquid containing a cationic polymer,
A step of ejecting the water-based coating liquid from a print head to land coating droplets on a substrate;
A step of ejecting the first ink, the second ink, the third ink and the fourth ink in this order from the print head and making the ink droplets land on the coating liquid to form a printing layer. including
The first ink is a cyan ink and has the lowest surface tension at 25° C. among the water-based colored inks,
The printing method , wherein the surface tension of the water-based coating liquid at 25°C is lower than the surface tension of the first ink at 25°C . 2. The printing method according to claim 1, further comprising the step of drying after forming the printing layer. A printing method according to claim 2, wherein said drying is performed at 70 to 130°C. A printing method for forming a print layer on a substrate by an inkjet printer equipped with an ink set containing a water-based colored ink and a water-based coating liquid,
The water-based colored inks include at least four types of inks, a first ink, a second ink, a third ink, and a fourth ink, and each ink independently contains water, a pigment, a water-soluble solvent, and containing a resin, the water-based coating liquid containing water, a water-soluble solvent and a resin, the resin contained in the water-based coating liquid containing a cationic polymer,
A step of ejecting the water-based coating liquid from a print head to land coating droplets on a substrate;
A step of ejecting the first ink and the second ink from the print head in this order and causing ink droplets to land on the coating liquid to form a first printing layer;
a step of performing primary drying after forming the first printed layer;
A step of ejecting the water-based coating liquid from the print head and causing the coating droplets to land on the first printing layer that has undergone primary drying;
a step of ejecting a third ink and a fourth ink from the print head in this order to form a second printing layer by causing ink droplets to land on the coating liquid on the first printing layer; including
The first ink is a cyan ink and has the lowest surface tension at 25° C. among the water-based colored inks,
The printing method , wherein the surface tension of the water-based coating liquid at 25°C is lower than the surface tension of the first ink at 25°C . 5. The printing method according to claim 4, further comprising performing secondary drying after forming the second printing layer. 6. The printing method according to claim 4, wherein the primary drying is performed at 25-45.degree. The printing method according to claim 5, wherein the secondary drying is performed at 70 to 130°C. The printing method according to any one of claims 1 to 7, wherein the temperature of the substrate is 30 to 45°C in the step of landing the coating droplets on the substrate. The printing method according to any one of claims 1 to 8, wherein the first ink has the lowest mass ratio of pigment contained in the ink among the water-based colored inks. The printing method according to any one of claims 1 to 9, wherein the fourth ink has the highest oil absorption of a pigment contained in the ink among the water-based colored inks. The printing method according to any one of claims 1 to 10 , wherein the third ink is magenta ink . 12. The method according to any one of claims 1 to 11 , wherein said first ink, second ink, third ink and fourth ink are cyan ink, yellow ink, magenta ink and black ink, respectively. The printing method described in . The printing method according to any one of claims 1 to 12 , wherein the water-based colored ink has a surface tension of 20 to 50 mN/m at 25°C. The water-based coating liquid contains 50% to 90% by mass of water, 5% to 35% by mass of a water-soluble solvent, and 0.005% to 2% by mass of a resin, The printing method according to any one of claims 1-13 . A printing method according to any one of claims 1 to 14 , characterized in that said substrate is a non-absorbent substrate or a non-absorbent substrate.