JP6736876B2 - Treatment liquid, recording liquid set, and inkjet recording method - Google Patents

Description

The present invention relates to a treatment liquid, a recording liquid set, and an inkjet recording method, and more specifically, a treatment liquid, a recording liquid set, and inkjet recording that can be suitably used for a low water-absorption recording medium, especially a non-water-absorptive film. Regarding the method.

Since the inkjet recording method can easily and inexpensively produce an image, it has been applied to various printing fields in recent years, such as photography, various printing, marking, and special printing such as color filters.

As the inkjet ink used in such an inkjet recording system, a water-based ink composed of water and a small amount of an organic solvent, a non-aqueous ink containing substantially no water using an organic solvent, and a solid ink at room temperature are melted by heating. There are a plurality of inkjet inks, such as hot-melt inks for printing and actinic ray curable inks that are cured by actinic rays such as light after printing.

Among them, the water-based ink is widely used in household printers and the like because it generally has a low odor and high safety, and good image quality can be obtained by using an ink-absorbing medium such as inkjet paper. On the other hand, water-based ink has a low viscosity. Therefore, when an image is formed with a water-based ink on a low-absorbent medium such as gravure or a coated paper for offset printing, and particularly on a non-absorptive medium such as a film, the ink stays on the recording medium for a long time, so that bleeding between the inks occurs. There are problems such as easy occurrence and low adhesion of the image to the recording medium.

To solve this problem, an ink set has been proposed which suppresses bleeding by printing an ink containing a cationic resin on a heated recording medium prior to a pigment ink (see Patent Document 1).

In addition, an ink set is proposed in which an ink containing a polyvalent metal salt for aggregating a pigment on a recording medium and a cationic polyurethane resin particle is printed prior to the pigment ink to enhance the adhesion of the image to the recording medium. (See Patent Document 2).

JP, 2014-1378, A JP, 2010-115854, A

However, in the method of Patent Document 1, it was found that the heat from the heated recording medium adversely affects the ink ejection property, the suppression of bleeding is insufficient, and the adhesion to the recording medium is low.

It was also found that the method of Patent Document 2 does not sufficiently suppress bleeding even when an ink containing a polyvalent metal salt and cationic polyurethane resin particles is applied.

These problems are particularly noticeable in a system that continuously prints for a long time, such as a roll-to-roll transport system that uses a film as a recording medium.

The present invention has been made in view of the above problems, and its object is to adhere to a low-absorption medium or a non-absorptive medium such as a film, in particular, with high-quality image quality with suppressed bleeding and adhesion. An object of the present invention is to provide a processing liquid, a recording liquid set, and an inkjet recording method that can obtain durability.

The above-mentioned object of the present invention is achieved by the following means.

[1] A treatment liquid for inkjet recording ink, which contains at least a cation or nonionic resin having a polyurethane structure, an organic acid, and water, and the organic acid has a first dissociation of 3.5 or less. A treatment liquid having a constant and a pH of the treatment liquid being less than a first dissociation constant of the organic acid.
[2] The treatment liquid according to [1], wherein the cationic resin contains resin fine particles having a quaternary ammonium group.
[3] An inkjet recording ink containing at least a pigment, an organic solvent and water, and the treatment liquid according to [1] or [2]. The organic acid contained in the treatment liquid is contained in the inkjet recording ink. A recording liquid set characterized by being an organic acid that aggregates the pigment.
[4] The pigment contained in the inkjet recording ink is an anionic dispersion pigment or a pigment dispersed with an anionic polymer dispersant, and the anionic dispersion pigment or the anionic polymer dispersant has an acryloyl group. The recording liquid set according to [3], which has.
[5] The mass ratio of the polyhydric alcohol to the total mass of the organic solvent contained in the inkjet recording ink is higher than the mass ratio of the components of the organic solvent other than the polyhydric alcohol [3] ] Or [4] the recording liquid set.
[6] The recording liquid set according to any one of [3] to [5], wherein the amount of resin fine particles contained in the inkjet recording ink is less than 2% by mass based on the total mass of the ink.
[7] The pigment contained in the ink jet recording ink is titanium oxide, and the titanium oxide is dispersed with a polymer dispersant having an acryloyl group, [3] to [6]. The recording liquid set described in any one.
[8] An inkjet recording method, which comprises using the treatment liquid or the recording liquid set according to any one of [1] to [7] to perform recording on a non-water-absorbent film which is a recording medium.
[9] The recording method according to [8], wherein the recording medium is a film that has been subjected to an antifogging process.
[10] After pre-coating at least a part of the surface of the recording medium with the treatment liquid by a roll coating method, the inkjet recording ink is ejected to land the treatment liquid on the surface of the pre-coated recording medium. The recording method according to [8] or [9], which is characterized.

INDUSTRIAL APPLICABILITY According to the present invention, a processing liquid, a recording liquid set, and an inkjet recording that can obtain high-quality image quality with suppressed bleeding and adhesion durability even when printed on a low-absorptive medium, particularly a non-absorbent medium such as a film A method can be provided.

Hereinafter, the present invention will be described with reference to embodiments, but the present invention is not limited to the following embodiments.

Hereinafter, one mode for carrying out the present invention will be described in detail.

As a result of intensive studies in view of the above problems, the present inventors have contained at least a cation or nonionic resin having a polyurethane structure and an organic acid having a first dissociation constant of 3.5 or less, and having a pH of the above organic compound. It was found that by forming an image using an inkjet recording ink on a recording medium precoated with a treatment liquid that is less than the first dissociation constant of acid, high quality image quality with suppressed bleeding and adhesion durability can be obtained. It was In particular, the present inventors have found that the method of the present invention hardly causes bleeding even when printed at high speed for a long time. The present invention is preferably used when the recording medium is a non-water-absorbing film, and is particularly effective for a non-water-absorbing film that has been subjected to an antifogging process, which makes it difficult to secure adhesion.

In the present invention, the first dissociation constant means that the organic acid has only one dissociation constant (the organic acid has only one acidic group), and the organic acid has a plurality of dissociation constants ( When the organic acid has two or more acidic groups), it means the smallest dissociation constant of the organic acid.

Hereinafter, details of the treatment liquid, the recording liquid set, and the inkjet recording method of the present invention will be described.

First, the processing liquid of the present invention will be described.

The organic acid contained in the treatment liquid is capable of aggregating the pigment that may be contained in the inkjet recording ink, and is not particularly limited as long as the first dissociation constant is 3.5 or less, but malonic acid, malic acid, citric acid, etc. Acids such as acids, phosphoric acid, oxalic acid and phthalic acid can be used.

It is preferable to use an organic acid that has not been completely neutralized with a base. Neutralization with a base means that the acidic groups of these acids are ionically bonded to other positively charged elements or compounds (for example, inorganic compounds such as metals). Further, “not completely neutralized” means that among the acidic groups of the organic acid, there are acidic groups that do not form the ionic bond. By using an organic acid having an acidic group that does not form an ionic bond, compatibility with a cation or nonionic resin having a polyurethane structure contained in the treatment liquid is high, and a transparent treatment layer can be formed. It is considered that the color tone of the formed image becomes brighter than in the case of using a polyvalent metal salt or the like. Further, by using an organic acid, the storage stability of the treatment liquid is easily maintained, and blocking is less likely to occur after the treatment liquid is applied and dried. From the above viewpoint, preferred organic acids are polyvalent organic acids such as malonic acid and malic acid.

The content of the organic acid in the treatment liquid may be an amount that adjusts the pH of the treatment liquid to less than the first dissociation constant of the organic acid. By adding an organic acid in an amount such that the pH of the treatment liquid is less than the first dissociation constant of the organic acid, bleeding during high-speed printing can be effectively suppressed.

The cation or nonionic resin having a polyurethane structure which is further contained in the treatment liquid of the present invention makes it possible to achieve both suppression of bleeding of an ink jet recorded image and adhesion. The reason for this is not clear, but is speculated as follows.

In the present invention, by printing the inkjet recording ink on the coating layer formed by the treatment liquid, the organic acid is dissolved/diffused from the treatment liquid coating layer to the recording ink to aggregate and fix the pigment to prevent bleeding. I think it will be suppressed. Therefore, it is preferable to increase the dissolution/diffusion rate of the organic acid in the ink jet recording ink as the printing speed becomes higher. In order to increase the dissolution/diffusion rate of the organic acid, the resin of the treatment liquid layer may be swollen or dissolved by the recording ink. On the other hand, it is presumed that if the swelling property or the solubility is too high, a uniform film cannot be formed and the adhesion cannot be obtained. Resins with a polyurethane structure have a polyol component in their structure that swells moderately with the organic solvent contained in the recording ink to promote the diffusion of organic acids, and maintains a uniform film state due to the hard segment of the isocyanate component. We believe that by doing so, we can ensure close contact. Further, it is particularly preferable that the polyol component has a polycarbonate structure in terms of storage stability of the treatment liquid.

As the resin having a polyurethane structure in the treatment liquid, water-soluble resin and dispersible resin fine particles can be used.

The content of the resin having a polyurethane structure in the treatment liquid is 0.3 g/m ² or more as a coating amount of the resin when the treatment liquid is applied to the recording medium, and a more preferable range is 0.8 g/m ² or more. The effects of the present invention can be suitably obtained by adjusting the resin content and application amount. The upper limit of the coating amount of the resin is not particularly limited, but in consideration of the drying load and the cost, the preferable range is approximately 3.0 g/m ² or less.

The content of the resin having a polyurethane structure in the treatment liquid is preferably 5% by mass to 40% by weight, more preferably 10% by weight to 30% by weight, based on the total mass of the treatment liquid.

In the present invention, in order to obtain high-quality image quality and adhesion durability in which bleeding is suppressed even when printed on a low-absorptive medium, particularly a non-absorptive medium such as a film, the treatment liquid is In addition to the above, it is essential to contain a cationic or nonionic resin having the above-mentioned polyurethane structure. If the treatment liquid does not contain the above resin, the organic acid is deposited and a layer having a uniform thickness cannot be formed.

Particularly preferred resin having a polyurethane structure is cationic resin fine particles, which can suppress bleeding and enhance the adhesiveness more effectively. Among them, self-emulsifying cationic resin fine particles are more preferable. Although the cation component is not limited, a quaternary ammonium salt is particularly preferable.

When resin fine particles are used as the resin having a polyurethane structure, the average particle diameter of the resin fine particles is not particularly limited, but is preferably in the range of 10 nm to 500 nm, more preferably in the range of 10 nm to 300 nm, and more preferably 10 nm to More preferably, it is in the range of 200 nm. The average particle size can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoretic method, etc., but the measurement by the dynamic light scattering method is simple, and Can measure accurately.

The resin having a polyurethane structure preferably contains fine resin particles having a quaternary ammonium group and a polyurethane structure.

Hereinafter, specific examples of the cation or nonionic resin having a polyurethane structure that can be used in the treatment liquid of the present invention will be given. Examples of the cationic resin include "Superflex 620" and "Superflex 650" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. ("Superflex" is a registered trademark of the same company), and "Permarin UC-20" manufactured by Sanyo Kasei Co., Ltd. (“Permarin” is a registered trademark of the same company), “Parasurf UP-22” manufactured by Ohara Palladium Chemical Co., Ltd., and nonionic resin fine particles include “Super Flex 500M” and “Super Super” manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Flex E-2000" and the like.

The treatment liquid may contain an organic solvent. For example, one kind or two or more kinds selected from the organic solvents described in the description of the recording ink described later can be contained in combination.

When the treatment liquid contains an organic solvent, it is preferably contained in an amount of less than 30% by mass, more preferably less than 25% by mass, and most preferably less than 20% by mass.

Further, the treatment liquid may contain a surfactant. The surfactant to be contained in the treatment liquid may be, for example, one or a combination of two or more selected from the surfactants described in the description of the recording ink described later.

When the treatment liquid contains a surfactant, its content is not particularly limited, but is preferably in the range of 0.1% by mass to 3.0% by mass.

Next, the inkjet recording ink of the present invention (hereinafter referred to as recording ink) will be described in detail.

As the pigment contained in the recording ink, an anionic dispersion pigment, for example, an anionic self-dispersible pigment, or a pigment dispersed with an anionic polymer dispersant can be used. It is preferable that the pigment is dispersed by the polymer dispersant.

As the pigment, conventionally known pigments can be used without particular limitation. For example, insoluble pigments, organic pigments such as lake pigments, and inorganic pigments such as titanium oxide can be preferably used.

In the case of titanium oxide, for which it is generally difficult to secure ink ejection stability and adhesiveness, the present invention makes it possible to prevent bleeding from occurring and to improve adhesiveness.

Titanium oxide has three crystal forms of anatase type, rutile type, and brookite type, but they can be roughly divided into anatase type and rutile type as general-purpose ones. Although not particularly limited, a rutile type having a large refractive index and a high hiding property is preferable. Specific examples include TR series manufactured by Fuji Titanium Industry, JR series manufactured by Teika Co., Ltd., and Taipaque manufactured by Ishihara Sangyo Co., Ltd.

The insoluble pigment is not particularly limited, for example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

Specific pigments that can be preferably used include the following pigments.

Examples of magenta or red pigments include C.I. I. Pigment Red 2, C.I. I. Pigment Red 3, C.I. I. Pigment Red 5, C.I. I. Pigment Red 6, C.I. I. Pigment Red 7, C.I. I. Pigment Red 15, C.I. I. Pigment Red 16, C.I. I. Pigment Red 48:1, C.I. I. Pigment Red 53:1, C.I. I. Pigment Red 57:1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 123, C.I. I. Pigment Red 139, C.I. I. Pigment Red 144, C.I. I. Pigment Red 149, C.I. I. Pigment Red 166, C.I. I. Pigment Red 177, C.I. I. Pigment Red 178, C.I. I. Pigment Red 202, C.I. I. Pigment Red 222, C.I. I. Pigment Violet 19 and the like.

Examples of orange or yellow pigments include C.I. I. Pigment Orange 31, C.I. I. Pigment Orange 43, C.I. I. Pigment Yellow 12, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 14, C.I. I. Pigment Yellow 15, C.I. I. Pigment Yellow 15:3, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 74, C.I. I. Pigment Yellow 93, C.I. I. Pigment Yellow 128, C.I. I. Pigment Yellow 94, C.I. I. Pigment Yellow 138, C.I. I. Pigment Yellow 155 and the like. Particularly in the balance of color tone and light resistance, C.I. I. Pigment Yellow 155 is preferable.

Examples of pigments for green or cyan include C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15:2, C.I. I. Pigment Blue 15:3, C.I. I. Pigment Blue 16, C.I. I. Pigment Blue 60, C.I. I. Pigment Green 7 and the like.

Examples of black pigments include C.I. I. Pigment Black 1, C.I. I. Pigment Black 6, C.I. I. Pigment Black 7 and the like.

The dispersant used to disperse the pigment is not particularly limited, but a polymer dispersant having an anionic group is preferable, and those having a molecular weight of 5,000 or more and 200,000 or less can be suitably used.

As the polymer dispersant, for example, 2 selected from styrene, styrene derivative, vinylnaphthalene derivative, acrylic acid, acrylic acid derivative, maleic acid, maleic acid derivative, itaconic acid, itaconic acid derivative, fumaric acid and fumaric acid derivative are used. Examples thereof include block copolymers having a structure derived from one or more kinds of monomers, random copolymers and salts thereof, polyoxyalkylenes, polyoxyalkylene alkyl ethers, and the like.

The polymer dispersant preferably has an acryloyl group and is preferably neutralized with a neutralizing base before addition. The neutralizing base is not particularly limited here, but is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, or morpholine. In particular, when the pigment is titanium oxide, it is preferable that the titanium oxide is dispersed with a polymer dispersant having an acryloyl group.

The amount of the polymer dispersant added is preferably 10 to 100% by mass, and more preferably 10 to 40% by mass, based on the pigment.

It is particularly preferable that the pigment has a so-called capsule pigment form in which the pigment is coated with the above-mentioned polymer dispersant. As a method for coating the pigment with the polymer dispersant, various known methods can be used, for example, a phase inversion emulsification method, an acid precipitation method, or a method in which the pigment is dispersed with a polymerizable surfactant, and A preferable example is a method of supplying a monomer to the composition and coating it while polymerizing.

As a particularly preferred method, a water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and the acidic groups in the resin are partially or completely neutralized with a base, and then a pigment and ion-exchanged water are added and dispersed. Then, a method of removing the organic solvent and, if necessary, adding water to prepare the solution can be mentioned.

The average particle size of the pigment dispersed in the recording ink is preferably 50 nm or more and less than 200 nm. Thereby, the dispersion stability of the pigment can be improved and the storage stability of the recording ink can be improved. The particle size of the pigment can be measured by a commercially available particle size measuring device using a dynamic light scattering method, an electrophoretic method, etc., but the measurement by the dynamic light scattering method is simple, and Can measure accurately.

The pigment can be used by dispersing it with a disperser together with a dispersant and other additives necessary for various desired purposes.

As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Above all, it is preferable to disperse the pigment by a sand mill because the particle size distribution becomes sharp. The material of the beads used for the sand mill dispersion is not particularly limited, but zirconia or zircon is preferable from the viewpoint of preventing the generation of bead fragments and the contamination of ionic components. Furthermore, the bead diameter is preferably 0.3 mm to 3 mm.

The content of the pigment in the recording ink is not particularly limited, but the range of 7% by mass to 18% by mass is preferable for titanium oxide, and the range of 0.5% by mass to 7% by mass is preferable for the organic pigment.

As the organic solvent contained in the recording ink, a water-soluble organic solvent can be preferably used. Preferable examples of the water-soluble organic solvent include alcohols, polyhydric alcohols, amines, amides, glycol ethers, and 1,2-alkanediols having 4 or more carbon atoms.

Preferable examples of the alcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol and the like.

Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol having 5 or more ethylene oxide groups, propylene glycol, dipropylene glycol, tripropylene glycol, and propylene oxide groups. Preferred examples include polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, and thiodiglycol having a ratio of 4 or more.

Examples of amines include ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, Pentamethyldiethylenetriamine and tetramethylpropylenediamine can be preferably exemplified.

Preferred examples of the amides include formamide, N,N-dimethylformamide, N,N-dimethylacetamide and the like.

Examples of the glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol. Preferable examples include monomethyl ether and the like.

Preferred examples of 1,2-alkanediols having 4 or more carbon atoms include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, and 1,2-heptanediol. it can.

Particularly preferably used organic solvents are polyhydric alcohols, which can favorably suppress bleeding during high-speed printing. Specifically, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol and tripropylene glycol are preferable.

The recording ink may contain one kind or a combination of two or more kinds selected from these organic solvents. Further, when the recording ink contains two or more kinds of organic solvents, the mass ratio of the polyhydric alcohol to the total mass of the whole organic solvent is made higher than the mass ratio of the components of the organic solvent of the polyhydric alcohol. As a result, the blur suppression effect, particularly the blur suppression effect at the time of high-speed printing, can be further enhanced. Preferably, the mass ratio of the polyhydric alcohols to the mass of the entire organic solvent is 50% or more. When two or more polyhydric alcohols are contained, the total mass ratio of all polyhydric alcohols is higher than the mass ratio of any other type of organic solvent, for example, with respect to the mass of the entire organic solvent. It is preferable if the mass ratio of the polyhydric alcohols is 50% or more.

The reason for this is that the polyol component contained in the structure of the resin having a polyurethane structure contained in the treatment liquid swells moderately with the polyhydric alcohol, and the effect of increasing the dissolution/diffusion rate of the organic acid is high. thinking.

The content of the organic solvent in the recording ink is not particularly limited, but is preferably in the range of 10% by mass to 60% by mass.

The recording ink preferably does not contain resin fine particles in an amount of 2% by mass or more, more preferably 0.1% by mass or more, based on the total mass of the recording ink. By setting the concentration of the resin fine particles within this range, stable ejection performance can be secured in continuous ejection or intermittent ejection of the recording ink.

When the recording ink contains less than 2% by mass of resin fine particles with respect to the total mass thereof, the resin fine particles are not particularly limited, but resin fine particles having a polyurethane structure, resin fine particles having a polyolefin structure such as polypropylene, styrene, Preferable examples are resin fine particles having an acrylic structure, and resin fine particles having a polyurethane structure are particularly preferable.

When the recording ink contains resin fine particles, the resin fine particles preferably contain anionic resin fine particles.

When the recording ink contains resin fine particles, the average particle diameter of the resin fine particles is not particularly limited, but is preferably in the range of 10 nm to 200 nm. The average particle size can be easily measured using a commercially available measuring device using a light scattering method or a laser Doppler method. It is also possible to freeze-dry a dispersion of resin fine particles and convert the average particle size from the particles observed with a transmission microscope.

Further, the recording ink may contain a surfactant. As a result, it is possible to improve the stability of ink ejection and to control the spread (dot diameter) of the droplet that has landed on the recording medium.

The surface tension of the recording ink is preferably 35 mN/m or less, more preferably 30 mN/m or less.

The surfactant that can be used in the recording ink of the present invention can be used without particular limitation. However, when the other components of the ink contain an anionic compound, the ionicity of the surfactant is an anion, Nonionic or betaine type is preferred.

In the present invention, preferably a fluorine-based or silicon-based surfactant having a high static surface tension lowering ability, and a high dynamic surface tension lowering ability, an anionic surfactant such as dioctylsulfosuccinate, relatively. Nonionic surfactants such as low molecular weight polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, acetylene glycols, pluronic type surfactants and sorbitan derivatives are preferably used. It is also preferable to use a fluorine-based or silicon-based surfactant in combination with a surfactant having a high ability to lower the dynamic surface tension.

The content of the surfactant in the recording ink is not particularly limited, but is preferably in the range of 0.1% by mass to 5.0% by mass.

In addition to the above description, the recording ink of the present invention is known in accordance with the need for emission stability, print head or ink cartridge compatibility, storage stability, image storability, and other various performance improvement objectives. Various additives such as polysaccharides, viscosity modifiers, resistivity modifiers, film-forming agents, UV absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust-preventive agents, etc. should be appropriately selected and used. For example, liquid paraffin, dioctyl phthalate, tricresyl phosphate, fine particles of oil droplets such as silicone oil, and ultraviolet rays described in JP-A-57-74193, 57-87988 and 62-261476. Absorbent, described in JP-A-57-74192, JP-A-57-87989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091 and JP-A-3-13376. Anti-fading agents described in JP-A-59-421993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871 and JP-A-4-219266. Fluorescent brighteners and the like can be mentioned.

The viscosity of the ink of the present invention having the above-mentioned constitution is preferably 1 to 40 mPa·s at 25° C., and more preferably 2 to 10 mPa·s.

The recording medium that can be used in the present invention is not particularly limited, but a low water-absorbing recording medium such as gravure or offset printing coated paper that is difficult to obtain image formation and adhesion by inkjet, and a non-water-absorbing medium. Some films, plastic boards (soft vinyl chloride, hard vinyl chloride, acrylic plates, polyolefin-based, etc.), glass, tiles, rubbers, etc. exhibit their effects and can be suitably used.

A known plastic film can be used as the non-water-absorbent film. Specific examples include polyester films such as polyethylene terephthalate, polyethylene films, polypropylene films, polyamide films such as nylon, polystyrene films, polyvinyl chloride films, polycarbonate films, polyacrylonitrile films, biodegradable films such as polylactic acid films, etc. Are listed. Further, in order to impart gas barrier property, moistureproof property, aroma retaining property, etc., a film in which polyvinylidene chloride is coated on one side or both sides, or a film in which a metal oxide is vapor-deposited can be preferably used.

The non-water-absorbent film can be preferably used as an unstretched film or a stretched film.

In addition, the effect of the present invention becomes remarkable when recording is performed on a non-water-absorptive film that has been subjected to an antifogging process, which is generally difficult to obtain the adhesion of the recording ink.

A film containing a surfactant is generally used as the anti-fogging film, but it is known that this surfactant adversely affects the adhesion of the recording ink. .. When such a film is pre-coated with the treatment liquid of the present invention, the surfactant is dissolved and diffused in the treatment liquid to prevent the surfactant from being oriented at a high concentration at the interface with the recording ink layer. It is estimated that it does not impede sex.

Further, the effect of the present invention that the transparency is not easily impaired when recording is performed on a recording medium having high transparency is remarkable.

Specific examples of the highly transparent recording medium include a film, a plastic board and glass.

Further, it is preferable that the surface of the non-water-absorbent film is surface-treated by corona discharge, ozone treatment, or the like.

In the ink jet recording method of the present invention using the recording liquid set consisting of the processing liquid and the recording ink described above, it is preferable to pre-coat the surface of the recording medium with the processing liquid and then perform recording on the surface with the recording ink. ..

The method of precoating the treatment liquid is not particularly limited, but in order to obtain good adhesion of the recording ink, the amount of the cationic or nonionic resin having a polyurethane structure contained in the treatment liquid is 0.3 g with respect to the recording medium. /M ² or more, more preferably 0.8 g/m ² or more.

Performing a resin amount in this range by precoating with an inkjet is accompanied by problems in terms of injection stability.

As a preferable precoating method of the treatment liquid, a roller coating method such as gravure roll or flexo can be mentioned.

After the pretreatment of the treatment liquid on the recording medium, the recording ink is deposited on the surface of the recording medium on which the treatment liquid has been precoated by inkjet continuously without the step of drying the precoated treatment liquid. Then, a method of forming an image by drying the treatment liquid and the recording ink, and a method of pre-coating the treatment liquid on the recording medium and then drying the pre-coat liquid, the same treatment of the recording medium pre-coated with the treatment liquid by inkjet. An image can be formed by a method of landing the recording ink on the surface and drying the recording ink to form an image. The more preferred method is the latter.

The inkjet head that can be used in the present invention may be an on-demand type or a continuous type. Further, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electric-heat conversion method (for example, a thermal inkjet) Type, bubble jet (registered trademark) type, etc.) may be used.

The conveying speed of the recording medium can be set, for example, between 1 m/min and 120 m/min. The faster the transport speed, the faster the image forming speed. According to the present invention, an image which can be applied by a single-pass inkjet image forming method and which further suppresses the occurrence of bleeding and has high adhesion even at a very high linear velocity of 50 m/min to 120 m/min Can be obtained.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In the examples, "parts" or "%" are used, but unless otherwise specified, "parts by mass" or "% by mass" is shown.

[Preparation of treatment liquid 1]
The additives shown below were sequentially added with stirring, and then filtered through a 5.0 μm filter to obtain a treatment liquid. The composition did not change substantially before and after filtration.

Emulsion-1: Emulsion containing a cationic resin having a polyurethane structure (self-emulsifying carbonate-based polyurethane resin fine particles, containing quaternary ammonium group, solid content concentration 26 mass%, "Superflex 650" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. ) 76.9 parts by mass-malonic acid 30% by mass aqueous solution 13.3 parts by mass-ion-exchanged water 100 parts by mass

The treatment liquid 1 contained 20.0 parts by mass of Resin-1 and 4.0 parts by mass of malonic acid.

[Preparation of treatment liquids 2 to 14]
Treatment liquids 2 to 14 were prepared in the same manner except that the type and addition amount of each additive were changed as shown in Table 1. The details of the resin used to prepare the treatment liquid are as follows. Table 1 also shows the pH of each treatment solution measured at 25° C. using a digital pH meter HM-30S manufactured by Toa Denpa Kogyo Co., Ltd., and the first dissociation constant of the organic acid.

Emulsion-2: Emulsion containing a cationic resin having a polyurethane structure (self-emulsifying ester polyurethane resin fine particles, containing quaternary ammonium group, solid content concentration 30%, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., “Superflex 620” ,)
Emulsion-3: Emulsion containing a nonionic resin having a polyurethane structure (self-emulsifying type ester polyurethane resin fine particles, no quaternary ammonium group, solid content concentration 45%, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "Superflex 500M" ))
-Emulsion-4: Emulsion containing a cationic resin having no polyurethane structure (self-emulsifying acrylic resin fine particles, solid content concentration 30%, Nisshin Chemical Co., Ltd. "Vini Blanc 2687"("ViniBlanc" And registered trademark of Shin-Etsu Chemical Co., Ltd.)
Emulsion-5: Emulsion containing nonionic resin having no polyurethane structure (surfactant emulsifying type polyolefin resin fine particles, solid content concentration 30%, Nippon Paper Industries "Auroraen AE-202"("Viny Blanc Is a registered trademark of the company)
Emulsion-6: Emulsion containing a cationic resin having a polyurethane structure (forced emulsification type ether-based polyurethane resin fine particles, solid content concentration 23%, "Permarin UC-20" manufactured by Sanyo Kasei Co., Ltd.)

[Preparation of Pigment Dispersion-1]
Polymer dispersant having an acryloyl group as a polymer dispersant (TEGO Dispers 715W, acid value 120, active ingredient 40% by mass, Evonik Tego Chemie Co., Ltd.) 30.0% by mass, rutile titanium oxide as a pigment (CR-50) -2, manufactured by Ishihara Sangyo Co., Ltd.) 40% by mass, premixed with a mixed solution containing ion-exchanged water as the balance, and then dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads. A pigment dispersion liquid-1 having a pigment content of 40 mass% was prepared. The average particle diameter of the pigment particles contained in this pigment dispersion liquid-1 was 128 nm. The particle size was measured with a Zetasizer 1000HS manufactured by Malvern Instruments.

[Preparation of Pigment Dispersion Liquid-2]
Styrene-acrylic acid copolymer as a polymer dispersant (John Kryl 678, molecular weight 8500, acid value 215, manufactured by BASF, "John Kryl" is a registered trademark of the same company) 3.0% by mass, pigment (Pigment Yellow 155) After premixing a mixed solution containing 15% by mass and ion-exchanged water as the balance, 0.5 mm zirconia beads were dispersed using a sand grinder filled with 50% by volume, and the pigment content was 15% by mass. Pigment Dispersion Liquid-2 was prepared. The average particle diameter of the pigment particles contained in this pigment dispersion liquid-2 was 122 nm. The particle size was measured in the same manner as Pigment Dispersion-1.

[Preparation of recording ink 1]
While stirring 29.8 parts by mass of the above-prepared pigment dispersion liquid-1, the following additives were sequentially added to prepare an ink composition, which was then filtered through a 0.8 μm filter to obtain a recording ink. Got 1.

Pigment Dispersion-1 29.8 parts by mass Ethylene glycol 15.0 parts by mass Propylene glycol 10.0 parts by mass Silicone-based surfactant (KF-351A manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2 parts by mass Ion-exchanged water total amount is 100 Amount to be part by mass

[Preparation of recording inks 2 to 14]
Recording Inks 2 to 14 were prepared in the same manner as in the preparation of the above recording ink 1 except that the types and addition amounts of the additives were changed as shown in Tables 2 and 3. The resin fine particles used in the recording inks 10 and 11 are anionic styrene acrylic emulsion (John Kryl 537, average particle diameter 70 nm, acid value 40, solid content concentration 46 mass%, manufactured by BASF).

[Example 1]
Using the treatment liquids 1 to 14 and the recording ink 1 prepared above, each evaluation was performed according to the following methods.

(Preparation of print sample)
Treatment liquids 1 to 14 were applied to the following recording media by the roller coating method at the wet film thickness shown in Table 4, and then dried with hot air at 70° C. for 5 minutes to prepare recording media. Details of the recording media shown in Table 5 are shown below.

OPP-1... Biaxially oriented polypropylene film (AF-642, 20 μm thickness, double-sided corona treatment, double-sided anti-fog property, manufactured by Futamura Chemical Co., Ltd., with anti-fog processing)
OPP-2... Biaxially oriented polypropylene film (FOS-BT, 30 μm thickness, double-sided corona treatment, manufactured by Futamura Chemical Co., Ltd., without anti-fog processing)
PET: Biaxially stretched polyester film (E-5200, thickness of 25 μm, double-sided corona treatment, Toyobo Co., Ltd., no anti-fog finish)
Printing coated paper: Cast coated paper (mirror coated platinum, basis weight 157 g/m ² , manufactured by Oji Paper Co., Ltd.)

Next, a treatment liquid was applied by a stage moving type inkjet printer equipped with a drop-on-demand piezo system inkjet head (nozzle number 1024 (512×2 rows), nozzle interval 70.5 μm (141 μm×2 rows)). The scanning speed of the stage is set to the blank character (3 point, 4 point, 5 point character) formed by not ejecting the ink in the solid image under the condition of the ink droplet volume of 32 pl and the recording density of 360×360 dpi on the medium. Was printed by one scan at a linear velocity of 100 m/min or a linear velocity of 50 m/min. Similarly, a solid image was printed by one scan at a linear velocity of 50 m/min under the condition of recording density of 360×360 dpi. The term "dpi" as used herein means the number of dots per 2.54 cm. The ink droplet volume was controlled by adjusting the ejection voltage for each recording ink. Further, the environment during inkjet printing was room temperature of 25° C., and the temperature of the recording medium was similarly set at 25° C.

Images 1-2 to 1-16 were printed in the same manner except that the combination of the treatment liquid and the recording ink and the coating conditions of the treatment liquid were changed as shown in Table 4.

The images formed as described above were evaluated for bleeding and adhesion of recorded images. As for images 1-14 using the treatment liquid 12, in films other than the print-coated paper, only the print-coated paper was evaluated because a uniform coating layer could not be formed due to acid precipitation.

(Evaluation of bleeding)
The extracted characters of the created image were evaluated according to the following criteria from the size of characters that can be recognized at a distance of 30 cm without blurring due to bleeding.
◯: All 3 to 5 point characters can be recognized. △: 4 to 5 point characters can be recognized and there is no practical problem. ×: All 3 to 5 point characters cannot be recognized and are practically unacceptable.

(Adhesion evaluation)
A tape peeling test was performed on the solid image of the created image by a cross cut method in which the image was cut with a cutter in a 5×5 grid pattern at 1 mm intervals, and evaluated according to the following criteria.
◯: Good without peeling off with tape Δ: Level of not less than 1 to 3 squares in a grid pattern, but practically acceptable level ×: Peeling in a grid of notches of 4 or more is not practically acceptable

Table 5 shows the evaluation results of the bleeding and the adhesion.

Treatment liquids 1 to 3 containing a cation or nonionic resin having a polyurethane structure, an organic acid having a first dissociation constant of 3.5 or less, and water, and having a pH of less than the first dissociation constant of the organic acid. When the recording ink 1 was printed on the recording medium precoated with Nos. 6, 6 to 8, 13 and 14, bleeding was difficult to occur in both low speed printing and high speed printing, and the image adhesion was high.

[Example 2]
Using the treatment liquid 1 and the recording inks 1 to 14 prepared above, blank characters and solid images (images 2-1 to 2-14) were printed in the same manner as in Example 1. The printed characters and solid images were evaluated for bleeding and adhesion in the same manner as in Example 1. Bleeding was evaluated by printing blank characters only on OPP-1, and adhesion was evaluated by printing a solid image only on OPP-1 and OPP-2.

Table 6 shows the results obtained as described above.

When the recording inks of recording inks 1 to 14 were printed on the recording medium precoated with the treatment liquid 1, bleeding was less likely to occur and the image adhesion was high. The recording inks 1 to 6 and 10 to 12, which contained the most polyhydric alcohol as the organic solvent, were more difficult to cause bleeding.

[Example 3]
The storage stability of the treatment liquids 1 to 14 was evaluated as follows.

(Evaluation of storage stability of treatment liquid)
The treated liquids 1 to 14 prepared above were stored for 1 week at 60° C., and evaluated according to the following criteria based on the change rate of viscosity and the change in appearance before and after storage. The viscosity was measured using a stress control rheometer using a cone plate, Physica MCR series, manufactured by Anton Paar.
◯: Viscosity ratio before and after storage is within 5% and no change in appearance is good. Δ: Viscosity ratio before and after storage is greater than 5% and within 10%, there is no change in appearance and is practically acceptable. ×: Viscosity ratio before and after storage. It is larger than 10%, or there is a change in appearance such as turbidity and agglomerates, which is unacceptable for practical use.

The evaluation results are shown in Table 7.

[Example 4]
The ejection stability of the recording inks 1 to 14 was evaluated as follows.
(Evaluation of ejection stability)
Using the same printer as used in the evaluation of Example 1, the treatment liquid 1 was applied to OPP-1 under the conditions of a stage scanning speed of 100 m/min, and a 35 x 35 mm solid image was formed with the recording inks 1 to 14 on the dried recording medium. The image was recorded in one scan. After the inkjet head was stopped for 20 seconds at a position 5 mm apart from the above image, a solid image was similarly recorded adjacently. Similarly, the stop time of the head was changed to 1 minute and 3 minutes, and two solid images adjacent to each other were recorded at 5 mm intervals.

Using the square image formed as described above, the head stop time at which the disturbance of the edge portion of the image due to the abnormal ejection of the ink starts to occur was determined, and the ejection stability was evaluated according to the following criteria.
◯: Disturbance is not observed at the edge of the image even after 3 minutes from the head stop time, and a good printed image is obtained. Δ: Disturbance is not observed at the edge of the image after 1 minute from the head stop time, but after 3 minutes. In the above-mentioned evaluation rank, Δ: good, in which a slight disturbance is observed is within the practically allowable range. ×: Disturbance is observed at the edge of the image after 20 seconds from the head stop time, which is outside the practical allowable range. Is a practically preferable range.

Table 8 shows each result obtained as described above.

The recording inks 1 to 14 could be stably ejected from the inkjet head. The recording inks 1 to 6 and 10 to 14 containing the most polyhydric alcohol as the organic solvent tended to have higher ejection stability. The recording inks 1 to 10 and 12 to 14 in which the content of the resin fine particles is less than 2% by mass based on the total mass of the recording ink, the content of the resin fine particles is 2% by mass or more based on the total mass of the recording ink. The ejection stability tended to be higher than that of a certain recording ink 11.

According to the treatment liquid and the ink set of the present invention, it is possible to form an image with low bleeding and high adhesiveness on a low-absorption medium or a non-absorption medium with an aqueous ink. Therefore, the present invention is expected to broaden the range of applications of the water-based ink by the inkjet method and contribute to the progress and spread of the technology in the same field.

Claims (10)

A treatment liquid for an inkjet recording ink containing an organic pigment or titanium oxide ,
A cationic or nonionic resin having a polyurethane structure,
A polyvalent organic acid,
water and,
Containing at least,
The organic acid has a first dissociation constant of 3.5 or less,
The treatment liquid has a pH of less than a first dissociation constant of the organic acid. The treatment liquid according to claim 1, wherein the cationic resin contains fine resin particles having a quaternary ammonium group. An inkjet recording ink containing at least an organic pigment or a pigment which is titanium oxide , an organic solvent and water, and the treatment liquid according to claim 1 or 2, wherein the organic acid contained in the treatment liquid is the inkjet recording ink. The recording liquid set is an organic acid that aggregates the pigment contained in. The pigment contained in the inkjet recording ink is a pigment dispersed with an anionic dispersion pigment or an anionic polymer dispersant,
The recording liquid set according to claim 3, wherein the anionic polymer dispersant has a structure derived from acrylic acid. The mass ratio of the polyhydric alcohol to the total mass of the organic solvent contained in the inkjet recording ink is higher than the mass ratio of the components of the organic solvent other than the polyhydric alcohol. Recording liquid set described in. The recording liquid set according to any one of claims 3 to 5, wherein the inkjet recording ink contains less than 2% by mass of resin fine particles with respect to the total mass of the ink. The pigment contained in the inkjet recording ink is titanium oxide,
The recording liquid set according to any one of claims 3 to 6, wherein the titanium oxide is dispersed with a polymer dispersant having a structure derived from acrylic acid . An ink jet recording method, wherein the treatment liquid or the recording liquid set according to any one of claims 1 to 7 is used to perform recording on a non-water-absorbent film which is a recording medium. The recording method according to claim 8, wherein the recording medium is an anti-fog processed film. The treatment liquid is pre-coated on at least a part of the surface of the recording medium by a roll coating method, and then the inkjet recording ink is ejected to land the treatment liquid on the pre-coated surface of the recording medium. The recording method according to claim 8.