JP2015085576A - Inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method which is excellent in color mixture preventing properties and scratch resistance when printing is performed on a recording medium having low water absorptivity, and to provide a processing liquid.SOLUTION: The inkjet recording method (1) comprises: a step A of imparting the processing liquid, which contains polyvinyl alcohol having 95% of lower saponification degree, to the recording medium; and a step B of forming an image on the processing liquid-imparted recording medium by an inkjet recording method using a water-based ink containing a pigment on condition that the recording medium and the processing liquid satisfy the following conditions 1 and 2. The condition 1 is that the amount of the water to be absorbed on the recording medium during 100 millisecond contact time of the recording medium with purified water is 0-10 g/m. The condition 2 is that the viscosity of the water-based ink is increased by 5-100 mPa-s when the polyvinyl alcohol in the processing solution is added to 100 pts. mass of the water-based ink by 2.0 pts. mass. The processing liquid (2) is used for processing the recording medium.

Description

  The present invention relates to an ink jet recording method and a processing liquid for processing a recording medium.

The ink jet recording method is a recording method in which characters and images are obtained by ejecting ink droplets directly from a very fine nozzle onto a recording medium and attaching them. This method is widely spread because it is easy to make full color and is inexpensive, and has many advantages such as the ability to use plain paper as a recording medium and non-contact with the substrate.
In recent years, inks using pigments as colorants have been widely used in order to impart weather resistance and water resistance to printed matter.
On the other hand, in addition to printing on the above-described conventional plain paper and high-absorbent recording medium called copy paper, low-absorbent coated paper such as offset coated paper, or polyvinyl chloride resin, polypropylene resin, There has been a demand for printing on a recording medium for commercial printing using a non-absorbing synthetic resin film such as a polyester resin.

When printing is performed on these low liquid-absorbing and non-liquid-absorbing recording media by the ink jet recording method, the liquid component is slowly absorbed or not absorbed, so it takes time to dry and the initial scratch resistance is poor. It has been known.
In order to solve these problems, a recording medium having an ink absorbing layer, a treatment liquid for the recording medium, a recording method using them, and the like have been proposed.
For example, in Patent Document 1, in order to improve that the dye ink diffuses on the surface of the paper or sinks into the inside of the paper and the sharpness or the like of the obtained image decreases, A recording method is disclosed in which a solution of carboxymethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone, or the like is jetted to deposit ink jet recording droplets on the formed film.
Patent Document 2 includes a water-soluble or water-dispersible resin (A) and a specific ester-based nonionic surfactant in a specific ratio as an inkjet recording sheet having good print quality and excellent ink absorption. A recording sheet provided with an ink absorbing layer is disclosed. As the resin (A), partially saponified polyvinyl alcohol and cation-modified polyvinyl alcohol having a cationic group are disclosed.

Patent Document 3 can provide a high-quality image having high image density, no density unevenness, and no color bleed by roller coating the reaction liquid on plain paper, and can provide an image excellent in scratch resistance. As a reaction solution, a reaction solution containing at least a polyvalent metal and a nonionic polymer and having a Ka value and a viscosity in a specific range is disclosed. Polyvinyl acetal and polyvinyl alcohol are disclosed as nonionic polymers.
Patent Document 4 discloses a flocculant for aggregating components in an ink composition and an agglomeration of the components as a recording method capable of suppressing ink bleeding and color mixing while suppressing curling due to ink jet recording. A method of recording with a water-based ink containing a colorant, resin particles, and a water-soluble organic solvent after applying a treatment liquid containing a water-soluble polymer that does not occur on a recording medium is disclosed. Polyvinyl alcohol, cellulose, and derivatives thereof are disclosed as water-soluble polymers.

JP-A-56-89595 Japanese Patent Laid-Open No. 9-226231 Japanese Patent Laid-Open No. 2004-130792 JP 2010-23339 A

However, the recording method of Patent Document 1 is intended for a highly liquid-absorbing recording medium using a dye as a colorant, and is intended for a low-absorbing recording medium using a pigment as a colorant. Is not disclosed.
The technique of Patent Document 2 improves the absorbability of a dye as a colorant. When a pigment is used, the ink solvent is rapidly absorbed and the pigment tends to aggregate on the recording medium.
In the recording methods of Patent Documents 3 and 4, the ink viscosity rapidly increases when the ink comes into contact with the pretreated liquid with low water absorption, so that the ink does not spread on the recording medium and the pigment is recorded on the recording medium. It tends to agglomerate and have poor scratch resistance.
The present invention relates to an inkjet recording method excellent in color mixing prevention, scratch resistance, and curl suppression when printing on a low water-absorbing recording medium using a water-based ink containing a pigment, and a method for processing the recording medium It is an object to provide a treatment liquid.

The inventors of the present invention previously applied a specific treatment liquid containing polyvinyl alcohol to a specific recording medium, so that even when printing on a low water-absorbing recording medium using a water-based ink containing a pigment, It has been found that an image excellent in color mixing prevention and scratch resistance can be obtained.
That is, the present invention relates to the following [1] and [2].
[1] Provided is an ink jet recording method comprising the following steps A and B, and the recording medium and the treatment liquid used in the step A satisfy the following conditions 1 and 2.
Step A: Step of applying a treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less to the recording medium Step B: Inkjet recording using a water-based ink containing a pigment on the recording medium to which the treatment liquid is applied Step of forming an image by the method Condition 1: The water absorption amount of the recording medium at a contact time of 100 msec between the recording medium and pure water is 0 g / m ² or more and 10 g / m ² or less.
Condition 2: Polyvinyl alcohol increases the viscosity of the water-based ink by 5 mPa · s or more and 100 mPa · s or less when 2.0 parts by mass of the polyvinyl alcohol in the treatment liquid is added to 100 parts by mass of the water-based ink. It is.
[2] A treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less, which is used for forming an image using a water-based ink containing a pigment after the treatment liquid is applied to a recording medium. When polyvinyl alcohol is added in an amount of 2.0 parts by mass with respect to 100 parts by mass of the water-based ink, the viscosity of the water-based ink is increased by 5 mPa · s to 100 mPa · s. liquid.
SHAPE \ * MERGEFORMAT

  According to the present invention, when printing is performed on a low-water-absorbing recording medium using a water-based ink containing a pigment, the inkjet recording method excellent in color mixing prevention, scratch resistance, and curl suppression, and the recording medium are processed. For the treatment liquid.

The inkjet recording method of the present invention includes the following steps A and B, and the recording medium and the treatment liquid used in step A satisfy the following conditions 1 and 2.
Step A: Step of applying a treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less to the recording medium Step B: Inkjet recording using a water-based ink containing a pigment on the recording medium to which the treatment liquid is applied Step of forming an image by the method Condition 1: The water absorption amount of the recording medium at a contact time of 100 msec between the recording medium and pure water is 0 g / m ² or more and 10 g / m ² or less.
Condition 2: Polyvinyl alcohol increases the viscosity of the water-based ink by 5 mPa · s or more and 100 mPa · s or less when 2.0 parts by mass of the polyvinyl alcohol in the treatment liquid is added to 100 parts by mass of the water-based ink. It is.

According to the recording method of the present invention, when printing is performed on a low-water-absorbing recording medium using a water-based ink containing a pigment, the effect of excellent color mixing prevention and scratch resistance is achieved. The reason is not clear, but it is thought as follows.
When a treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less is applied to a low water-absorbing recording medium, a thin film of polyvinyl alcohol is formed on the surface of the recording medium. When an aqueous ink containing a pigment is formed on this film by an ink jet recording method, ink droplets that have landed on the recording medium are quickly absorbed into the film by interaction with the hydroxyl groups in the film. Simultaneously thicken and fix. This thickening prevents color mixing with the ink droplets that land next, and the pigment is taken into the film containing polyvinyl alcohol, so it is considered that the scratch resistance is improved. On the other hand, when polyvinyl alcohol having a saponification degree higher than 95% is used, since the number of hydroxyl groups is large, a strong network of polyvinyl alcohols is formed through the hydroxyl groups, and ink droplets are absorbed into the film. In addition, it is considered that the speed of thickening is reduced and it becomes difficult to obtain the effect of preventing color mixing and scratch resistance.
In addition, when recording on a recording medium such as low water-absorbing paper by the ink jet recording method of the present invention, the ink stays in the film formed of polyvinyl alcohol, and the ink is delayed from penetrating into the paper. Subsequent curling of the recording medium can be effectively suppressed.
On the other hand, when a treatment liquid containing a flocculant such as a polyvalent metal or an acid known as a prior art is used, before the ink droplet is absorbed by the coating containing the flocculant, the pigment and the flocculant interact with each other. Aggregation occurs, and the solvent in the ink separates from the pigment. As a result, the pigment stays in the vicinity of the surface of the coating containing the flocculant, and the scratch resistance is considered to decrease.

[Inkjet recording method]
In the ink jet recording method of the present invention, after applying a treatment liquid containing polyvinyl alcohol to the recording medium in advance in Step A, an aqueous ink containing a pigment is used in the portion to which the treatment liquid is applied in Step B. Thus, an image is formed by an ink jet recording method.

<Process A>
Step A is a step of applying a treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less to the recording medium.
The processing liquid containing the recording medium and polyvinyl alcohol will be described later.
Regarding the method for applying the treatment liquid to the recording medium according to the present invention, the treatment liquid may be applied using an inkjet recording method in the same manner as the water-based ink, but the treatment liquid is recorded using a wire coater, a roller, or the like. It can also be applied by applying to a medium. Unlike the ink jet recording method, the coating method using a wire coater, a roller, or the like does not require consideration of the discharge property of the processing liquid, and the processing liquid according to the present invention is easily and uniformly applied to the recording medium. be able to.
The amount of treatment liquid applied to the recording medium can be adjusted as appropriate depending on the type of water-based ink, but from the viewpoint of improving color mixing prevention and scratch resistance, it is preferably 0.5 g / m ² or more, more preferably. 1.0 g / m ² or more, more preferably 1.3 g / m ² or more, still more preferably 1.5 g / m ² or more, and preferably 20 g / m ² or less, more preferably 15 g / m ^2. Hereinafter, it is more preferably 10 g / m ² or less, and still more preferably 8 g / m ² or less.

<Process B>
Step B is a step of forming an image by an inkjet recording method using a water-based ink containing a pigment on a recording medium to which a treatment liquid is applied.
The water-based ink containing the pigment will be described later.
There is no particular limitation on the time until the process B is started after the treatment liquid is applied to the recording medium in the process A. However, it is preferable that the process B is started after the amount of water (other than solid content) of the treatment liquid applied to the recording medium in Step A is 100 parts by mass and the dry amount of water is 5 parts by mass or more. . When the recording medium is particularly paper, from the viewpoint of preventing color mixing, the mass of water (other than solid content) of the treatment liquid applied to the recording medium is 100 parts by mass, preferably 5 parts by mass or more, more preferably water. Is preferably 10 parts by mass or more, more preferably 20 parts by mass or more after drying, and then step B is preferably started. Further, when the recording medium is particularly paper, from the viewpoint of curling of the recording medium, the amount of water (other than solid content) of the treatment liquid applied to the recording medium is preferably 100 parts by mass, and the dry amount of water is preferable. Is less than 98 parts by weight, more preferably not more than 95 parts by weight, still more preferably not more than 90 parts by weight, still more preferably not more than 70 parts by weight, and still more preferably not more than 40 parts by weight. It is preferable to start. The drying method is not particularly limited, and a known method such as natural drying or hot air drying can be employed.
Here, the solid content concentration of the treatment liquid applied to the recording medium can be obtained from the mass measurement of the treatment liquid applied to the recording medium.
The ink jet recording method of the present invention is a method for forming an image by recording the above water-based ink in an ink jet recording apparatus having ink flying means, and causing ink droplets to fly and land on a low water-absorbing recording medium. It is. You may have the process of drying printed matter after recording on a recording medium.
The ink flying means includes means for flying ink using a thermal or piezo type ink jet head, and is not particularly limited. In the present invention, the piezo type is preferable.

<Recording medium>
The recording medium used in the present invention is a low water-absorbing recording medium. Here, “low water absorption” is a concept including low liquid absorption and non-liquid absorption, and the water absorption amount at a contact time of 100 msec between the recording medium and pure water is 0 g / m ² or more and 10 g / m. It means ² or less (condition 1).
The water absorption amount of the recording medium is preferably 1.0 g / m ² or more, more preferably 2.0 g / m ² or more, from the viewpoint of increasing the drying property of the printed matter, improving the fixing strength, and preventing color mixing. More preferably, it is 3.0 g / m ² or more, and still more preferably 4.0 g / m ² or more. From the viewpoint of preventing color mixing of printed matter and improving printing density, preferably 8.0 g / m ² or less. More preferably, it is 7.0 g / m < ² > or less, More preferably, it is 6.0 g / m < ² > or less, More preferably, it is 5.5 g / m < ² > or less.
In addition, the said water absorption is measured by the method as described in an Example.

Examples of the recording medium used in the present invention include coated paper and synthetic resin film.
As the coated paper, for example, “OK Top Coat Plus” manufactured by Oji Paper Co., Ltd. (basis weight: 104.7 g / m ² , water absorption at a contact time of 100 msec between the recording medium and pure water (hereinafter the same). 9g / m ^2), Oji paper multi-colored foam gloss paper Co., Ltd. (104.7g / m ^2, the water absorption amount of 5.2g / m ^2), "Aurora coat" (104.7g / m ^2, the water absorption 4 .5g / m ^2), "U-LITE" (104.7g / m ^2, the water absorption amount 5.5g / m ^2), UPM manufactured by "UPM Finesse Gloss" (115g / m ^2, water absorption 3.1 g / m ² ), “UPM Finesse Matt” (115 g / m ² , water absorption 4.4 g / m ² ), “TerraPress Silk” (80 g / m ² , water absorption 4.1 g / m ² ) manufactured by Stora Enso, Examples include “LumiArt” (90 g / m ² ) manufactured by Stora Enso.

Examples of the synthetic resin film include a polyester film, a vinyl chloride film, a polypropylene film, a polyethylene film, and a nylon film. These films may be subjected to surface treatment such as corona treatment as necessary.
Commonly available synthetic resin films include, for example, “Lumirror T60” manufactured by Toray Industries, Inc. (polyethylene terephthalate, thickness 125 μm, water absorption 2.3 g / m ² ), “PVC80BP” (salt chloride) manufactured by Lintec Corporation. Vinyl, water absorption 1.4 g / m ² ), “Kinus KEE70CA” (polyethylene) manufactured by Lintec Corporation, “YUPO SG90 PAT1” (polypropylene) manufactured by Lintec Corporation, “Bonyl” manufactured by Kojin Film & Chemicals Co., Ltd. RX (nylon) etc. are mentioned.

<Treatment liquid containing polyvinyl alcohol>
The treatment liquid used in the present invention contains polyvinyl alcohol having a saponification degree of 95% or less (hereinafter also simply referred to as “polyvinyl alcohol”), and the polyvinyl alcohol uses the polyvinyl alcohol in the treatment liquid as a water-based ink. When 2.0 parts by mass is added to 100 parts by mass, the viscosity of the water-based ink is increased by 5 mPa · s or more and 100 mPa · s or less (Condition 2).
As the polyvinyl alcohol, partially saponified polyvinyl alcohol and its anion-modified product, cation-modified product, acid-modified product and the like can be used. Among these, partially saponified polyvinyl alcohol, cation-modified polyvinyl alcohol, and acid-modified polyvinyl alcohol are preferable from the viewpoints of film formability, color mixing prevention, and scratch resistance.
The average degree of polymerization of the polyvinyl alcohol is preferably 400 or more, more preferably 800 or more, still more preferably 1000 or more, still more preferably 1200 or more, and preferably 5000 or less, more preferably from the viewpoint of preventing color mixing. Is 4000 or less, more preferably 3000 or less, and still more preferably 2500 or less.
The degree of saponification of partially saponified polyvinyl alcohol is preferably 65% or more, more preferably 70% or more, still more preferably 75% or more, and preferably 90% or less, more preferably, from the viewpoint of color mixing prevention. Is 85% or less, more preferably 83% or less.
Moreover, the suitable range of the average degree of polymerization of partially saponified polyvinyl alcohol is as described above.
Partially saponified polyvinyl alcohol can be produced by a known method, and polyvinyl acetate can be adjusted to a desired saponification degree by an acid saponification method or an alkali saponification method. As the partially saponified polyvinyl alcohol, a commercially available one can be used. The saponification degree is a value depending on the hydrolysis degree of polyvinyl acetate.

The molecular weight of polyvinyl alcohol can be calculated from the degree of polymerization.
The degree of polymerization can be calculated from the relative viscosity between a completely saponified aqueous polyvinyl alcohol solution and water (see JIS K6726: 1994).
Polyvinyl alcohols having different degrees of polymerization and saponification of 95% or less, and those having different degrees of cation modification and acid modification may be used in combination.
Polyvinyl alcohol can be used alone or in admixture of two or more at any ratio.

When the polyvinyl alcohol used in the present invention is added in an amount of 2.0 parts by mass with respect to 100 parts by mass of the water-based ink, the viscosity of the water-based ink at 20 ° C. is 5 mPa · s or more and 100 mPa · s. The polyvinyl alcohol is preferably 8 mPa · s or more, more preferably from the viewpoint of color mixing prevention and scratch resistance when printed on a low water-absorbing recording medium. The viscosity is increased by 10 mPa · s or more, more preferably 12 mPa · s or more, and is preferably 150 mPa · s or less, more preferably 100 mPa · s or less, and even more preferably 80 mPa · s or less. is there.
The viscosity (20 ° C.) of the treatment liquid used in the present invention is preferably 10 mPa · s or more, more preferably 50 mPa · s or more, further preferably 100 mPa · s or more, from the viewpoint of operability when applied to a recording medium. And preferably 3000 mPa · s or less, more preferably 2000 mPa · s or less, and still more preferably 1000 mPa · s or less.

The treatment liquid used in the present invention is preferably substantially free of a colorant. If the treatment liquid does not substantially contain a colorant, the ink hue is not affected when printing is performed with the water-based ink overlaid.
The content of water in the treatment liquid used in the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 85% by mass or more, and preferably 98% by mass or less, more Preferably it is 96 mass% or less, More preferably, it is 93 mass% or less.

The treatment liquid used in the present invention can contain a sizing agent used in papermaking from the viewpoint of preventing color mixing. Examples of the sizing agent include alkyl ketene dimer, rosin, gelatin, starch, latex and the like, but alkyl ketene dimer sizing agent is more preferable.
In addition, the treatment liquid used in the present invention is a water-soluble organic solvent, a dispersant, a surfactant, a viscosity modifier, an antifoaming agent, an antiseptic, an antifungal agent, ordinarily used in the treatment liquid used in the inkjet method. A rust preventive agent and the like can be contained.
Preferable examples of the water-soluble organic solvent include polyols such as ethylene glycol, diethylene glycol, polyethylene glycol, and glycerin, and polyethylene glycol and glycerin are more preferable.
The surfactant is preferably a nonionic surfactant, more preferably an acetylenic diol surfactant, from the viewpoint of ejection stability and print head material compatibility.

<Water-based ink containing pigment>
Examples of the aqueous ink containing a pigment include an aqueous ink containing a pigment and a dispersant, an aqueous ink containing a self-dispersing pigment, or an aqueous ink containing water-insoluble polymer particles containing a pigment.
The water-based ink containing a pigment is a water-based ink containing water-insoluble polymer particles containing a pigment (hereinafter also referred to as “pigment-containing polymer particles”) from the viewpoint of improving the fixing strength to a low water-absorbing recording medium. It is preferable.

(Pigment)
The water-based ink used in the present invention contains a pigment as a colorant from the viewpoint of improving the water resistance and weather resistance of the printed matter.
The pigment may be either an inorganic pigment or an organic pigment. If necessary, they can be used in combination with extender pigments.
Examples of the inorganic pigment include carbon black and metal oxide, and carbon black is particularly preferable for black ink. Examples of carbon black include furnace black, thermal lamp black, acetylene black, and channel black.
Specific examples of the organic pigment include azo pigments, diazo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, dioxazine pigments, perylene pigments, perinone pigments, thioindigo pigments, anthraquinone pigments, and quinophthalone pigments.
The hue is not particularly limited, and any chromatic pigment such as yellow, magenta, cyan, blue, red, orange, and green can be used.
Specific examples of preferred organic pigments include C.I. I. Pigment yellow, C.I. I. Pigment Red, C.I. I. Pigment orange, C.I. I. Pigment violet, C.I. I. Pigment blue, and C.I. I. One or more types of products selected from the group consisting of pigment green are listed.

In the present invention, a self-dispersing pigment can also be used. The self-dispersing pigment refers to one or more types of hydrophilic functional groups (anionic hydrophilic groups such as carboxy groups and sulfonic acid groups, or cationic hydrophilic groups such as quaternary ammonium groups) directly or 1 to 1 carbon atoms. By binding to the surface of the pigment through other atomic groups such as 12 alkanediyl groups, it means a pigment that can be dispersed in an aqueous medium without using a surfactant or resin. In order to make the pigment a self-dispersing pigment, for example, a necessary amount of the hydrophilic functional group may be chemically bonded to the pigment surface by a conventional method.
The above pigments can be used alone or in admixture of two or more at any ratio.

<Water-insoluble polymer particles containing pigment (pigment-containing polymer particles)>
(Water-insoluble polymer)
The water-insoluble polymer means a polymer that is dried at 105 ° C. for 2 hours and reaches a constant weight in 100 g of water at 25 ° C. and has a dissolution amount of 10 g or less. Is 5 g or less, more preferably 1 g or less. In the case of an anionic polymer, the dissolution amount is the dissolution amount when the anionic group of the polymer is neutralized 100% with sodium hydroxide.
Examples of polymers used include polyesters, polyurethanes, and vinyl polymers. From the viewpoint of improving the storage stability of water-based inks, they can be obtained by addition polymerization of vinyl monomers (vinyl compounds, vinylidene compounds, vinylene compounds). Vinyl-based polymers are preferred.

  Examples of vinyl polymers include (c-1) ionic monomer (hereinafter also referred to as “(c-1) component”) and (c-2) hydrophobic monomer (hereinafter also referred to as “(c-2) component”). A vinyl polymer obtained by copolymerization of a monomer mixture containing the following (hereinafter also simply referred to as “monomer mixture”) is preferable. This vinyl polymer has a structural unit derived from the component (c-1) and a structural unit derived from the component (c-2). Especially, what contains the structural unit derived from (c-3) macromonomer (henceforth "(c-3) component") is preferable.

[(C-1) ionic monomer]
(C-1) The ionic monomer is preferably used as a monomer component of the water-insoluble polymer from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink. Examples of the ionic monomer include an anionic monomer and a cationic monomer, and an anionic monomer is preferable.
Examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer.
Examples of the carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid.
Among the anionic monomers, carboxylic acid monomers are preferable and acrylic acid and methacrylic acid are more preferable from the viewpoint of improving dispersion stability of the pigment-containing polymer particles in the ink.

[(C-2) Hydrophobic monomer]
(C-2) The hydrophobic monomer is preferably used as a monomer component of the water-insoluble polymer from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink. Examples of the hydrophobic monomer include alkyl (meth) acrylates and aromatic group-containing monomers.
As the alkyl (meth) acrylate, those having an alkyl group having 1 to 22 carbon atoms, preferably 6 to 18 carbon atoms are preferable. For example, methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meta) ) Acrylate, (iso or tertiary) butyl (meth) acrylate, (iso) amyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) Examples include decyl (meth) acrylate, (iso) dodecyl (meth) acrylate, and (iso) stearyl (meth) acrylate.
In addition, “(iso or tertiary)” and “(iso)” mean both cases in which these groups are present and cases in which these groups are not present. “(Meth) acrylate” indicates acrylate and / or methacrylate.

As the aromatic group-containing monomer, a vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may have a substituent containing a hetero atom, is preferable, and a styrene monomer or an aromatic group-containing (meth) acrylate. Is more preferable.
As the styrenic monomer, styrene, 2-methylstyrene, and divinylbenzene are preferable, and styrene is more preferable.
Moreover, as an aromatic group containing (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, etc. are preferable, and benzyl (meth) acrylate is more preferable.
(C-2) As the hydrophobic monomer, two or more kinds of the aforementioned monomers may be used, or a styrene monomer and an aromatic group-containing (meth) acrylate may be used in combination.

[(C-3) Macromonomer]
(C-3) The macromonomer is a compound having a polymerizable functional group at one end and a number average molecular weight of 500 to 100,000, and from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink, It is preferably used as a monomer component of an insoluble polymer. The polymerizable functional group present at one end is preferably an acryloyloxy group or a methacryloyloxy group, and more preferably a methacryloyloxy group.
(C-3) The number average molecular weight of the macromonomer is preferably 1,000 or more and 10,000 or less. The number average molecular weight is measured using polystyrene as a standard substance by gel permeation chromatography using chloroform containing 1 mmol / L dodecyldimethylamine as a solvent.
(C-3) The macromonomer is preferably an aromatic group-containing monomer-based macromonomer or a silicone-based macromonomer from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink. Monomers are more preferred.
Examples of the aromatic group-containing monomer constituting the aromatic group-containing monomer-based macromonomer include the aromatic group-containing monomers described in the above (c-2) hydrophobic monomer, and styrene and benzyl (meth) acrylate are preferable, Styrene is more preferred.
Specific examples of the styrenic macromonomer include AS-6 (S), AN-6 (S), HS-6 (S) (trade name of Toagosei Co., Ltd.), and the like.
Examples of the silicone-based macromonomer include organopolysiloxane having a polymerizable functional group at one end.

[(C-4) Nonionic monomer]
From the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink, the water-insoluble polymer further includes (c-4) a nonionic monomer (hereinafter also referred to as “(c-4) component”) as a monomer component. It is preferable to use it.
(C-4) As a component, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, polypropylene glycol (n = 2-30, n shows the average addition mole number of an oxyalkylene group. Same) Polyalkylene glycol (meth) acrylate such as (meth) acrylate, polyethylene glycol (meth) acrylate (n = 2 to 30), and alkoxy polyalkylene glycol such as methoxypolyethylene glycol (n = 1 to 30) (meth) acrylate (Meth) acrylate, phenoxy (ethylene glycol / propylene glycol copolymer) (n = 1 to 30, ethylene glycol therein: n = 1 to 29) (meth) acrylate, and the like.

Specific examples of the commercially available (c-4) component include NK Esters M-20G, 40G, 90G, and TM-230G of Shin-Nakamura Chemical Co., Ltd., Bremer PE- 90, 200, 350, PME-100, 200, 400, PP-500, 800, 1000, AP-150, 400, 550, 50 PEP-300, 50POEP-800B, 43 PAPE -600B etc. are mentioned.
The components (c-1) to (c-4) can be used alone or in admixture of two or more.

(Content of each component or structural unit in the monomer mixture or polymer)
The content of the components (c-1) to (c-4) in the monomer mixture (content as an unneutralized amount; the same applies hereinafter) or the water-insoluble polymer (c-1) The content of the structural unit derived from the components (c) to (c-4) is as follows from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink.
The content of the component (c-1) is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, and preferably 40% by mass or less, more preferably 30% by mass. %, More preferably 20% by mass or less.
The content of the component (c-2) is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 20% by mass or more, and preferably 86% by mass or less, more preferably 70% by mass. % Or less, more preferably 50% by mass or less.
The content of the component (c-3) is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 7% by mass or more, and preferably 25% by mass or less, more preferably 20% by mass. % Or less, more preferably 18% by mass or less.
The content of the component (c-4) is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, and 60% by mass or less, more preferably 55% by mass or less. More preferably, it is 50 mass% or less.
The mass ratio of [(c-1) component / [(c-2) component + (c-3) component]] is preferably 0.01 or more, more preferably 0.05 or more, and still more preferably 0. .10 or more, and preferably 1 or less, more preferably 0.60 or less, and still more preferably 0.40 or less.

(Production of water-insoluble polymer)
The water-insoluble polymer is produced by copolymerizing a monomer mixture by a known polymerization method. As the polymerization method, a solution polymerization method is preferable.
Although there is no restriction | limiting in the solvent used by the solution polymerization method, Polar organic solvents, such as C1-C3 aliphatic alcohol, ketones, ethers, and esters, are preferable, specifically, methanol, ethanol, acetone, and methyl ethyl ketone. And methyl ethyl ketone is preferred.
In the polymerization, a polymerization initiator or a polymerization chain transfer agent can be used. As the polymerization initiator, an azo compound is preferable, and 2,2′-azobis (2,4-dimethylvaleronitrile) is more preferable. . As the polymerization chain transfer agent, mercaptans are preferable, and 2-mercaptoethanol is more preferable.

Although preferable polymerization conditions vary depending on the type of polymerization initiator and the like, from the viewpoint of reactivity, the polymerization temperature is preferably 50 ° C. or higher and 90 ° C. or lower, and the polymerization time is preferably 1 hour or longer and 20 hours or shorter. The polymerization atmosphere is preferably a nitrogen gas atmosphere or an inert gas atmosphere such as argon.
After completion of the polymerization reaction, the produced polymer can be isolated from the reaction solution by a known method such as reprecipitation or solvent distillation. In addition, unreacted monomers and the like can be removed from the obtained polymer by reprecipitation, membrane separation, chromatographic methods, extraction methods and the like.
The water-insoluble polymer is used as an organic solvent used in Step 1 to be described later without removing the solvent used in the polymerization reaction from the viewpoint of improving the productivity of the aqueous dispersion of pigment-containing polymer particles. In addition, it is preferably used as a polymer solution as it is.
From the viewpoint of improving the productivity of the aqueous dispersion of pigment-containing polymer particles, the solid content concentration of the water-insoluble polymer solution is preferably 30% by mass or more, more preferably 40% by mass or more, and preferably 60% by mass. % Or less, more preferably 50% by mass or less.
The weight average molecular weight of the water-insoluble polymer used in the present invention is from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink and from the viewpoint of improving the fixing strength of the water-based ink on the low water-absorbing recording medium. Preferably it is 5,000 or more, more preferably 10,000 or more, still more preferably 20,000 or more, and preferably 500,000 or less, more preferably 400,000 or less, still more preferably 300,000 or less, More preferably, it is 200,000 or less.
In addition, the measurement of a weight average molecular weight can be performed by the method as described in an Example.

<Production of pigment-containing polymer particles>
The pigment-containing polymer particles can be efficiently produced as an aqueous dispersion by a method having the following step I and step II.
Step I: A step of dispersing a mixture containing a water-insoluble polymer, an organic solvent, a pigment, and water (hereinafter also referred to as “pigment mixture”) to obtain a dispersion of pigment-containing polymer particles. Step II: In Step I The step of removing the organic solvent from the obtained dispersion to obtain an aqueous dispersion of pigment-containing polymer particles (hereinafter also referred to as “pigment aqueous dispersion”) is an optional step. You may go.
Step III: Step of mixing the water dispersion obtained in Step II and a crosslinking agent, and crosslinking treatment to obtain an aqueous dispersion

(Process I)
In Step I, first, the water-insoluble polymer is dissolved in an organic solvent, and then a pigment, water, and, if necessary, a neutralizing agent, a surfactant and the like are added to the obtained organic solvent solution and mixed. A method of obtaining an oil-type dispersion is preferred. Although there is no restriction | limiting in the order added to the organic solvent solution of a water-insoluble polymer, It is preferable to add in order of water, a neutralizing agent, and a pigment.
Although there is no restriction | limiting in the organic solvent in which a water-insoluble polymer is dissolved, C1-C3 aliphatic alcohol, ketones, ethers, esters, etc. are preferable, ketones are more preferable, and methyl ethyl ketone is still more preferable. When a water-insoluble polymer is synthesized by a solution polymerization method, the solvent used in the polymerization may be used as it is.

When the water-insoluble polymer is an anionic polymer, an anionic group in the water-insoluble polymer may be neutralized using a neutralizing agent. When a neutralizing agent is used, it is preferable to neutralize so that the pH is preferably 7.0 or higher, more preferably 7.5 or higher, and preferably 11.0 or lower, more preferably 9.5 or lower. Examples of the neutralizing agent include bases such as lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia, and various amines. Further, the water-insoluble polymer may be neutralized in advance.
The degree of neutralization of the anionic group of the water-insoluble polymer is preferably 30 mol% or more, more preferably 40 mol% or more, from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the ink and in the pigment water dispersion. More preferably, it is 50 mol% or more, and preferably 300 mol% or less, more preferably 200 mol% or less, still more preferably 150 mol% or less.
Here, the degree of neutralization is obtained by dividing the molar equivalent of the neutralizing agent by the molar amount of the anionic group of the water-insoluble polymer.

(Content of each component in the pigment mixture)
The content of the pigment in the pigment mixture is preferably 10% by mass or more, more preferably from the viewpoint of improving the dispersion stability of the pigment-containing polymer particles in the pigment water dispersion and the productivity of the pigment water dispersion. It is 12 mass% or more, More preferably, it is 14 mass% or more, Preferably it is 30 mass% or less, More preferably, it is 25 mass% or less, More preferably, it is 20 mass% or less.
The content of the water-insoluble polymer in the pigment mixture is preferably from the viewpoint of the dispersion stability of the pigment water dispersion and the storage stability of the water-based ink, and from the viewpoint of improving the fixing strength of the water-based ink on a low water-absorbing recording medium. Is 2.0% by mass or more, more preferably 4.0% by mass or more, further preferably 5.0% by mass or more, and preferably 15% by mass or less, more preferably 12% by mass or less, still more preferably. It is 10 mass% or less.
The content of the organic solvent in the pigment mixture is preferably 10% by mass or more, more preferably 12% by mass or more, and still more preferably from the viewpoint of improving the wettability to the pigment and the adsorptivity of the water-insoluble polymer to the pigment. It is 15% by mass or more, and preferably 35% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less.
The content of the water in the pigment mixture is preferably 40% by mass or more, more preferably 45% by mass or more, from the viewpoint of improving the dispersion stability of the pigment water dispersion and improving the productivity of the pigment water dispersion. More preferably, it is 50% by mass or more, and preferably 75% by mass or less, more preferably 70% by mass or less, and still more preferably 65% by mass or less.

  The mass ratio of the pigment to the water-insoluble polymer [pigment / water-insoluble polymer] is the viewpoint of improving the dispersion stability of the pigment water dispersion and the storage stability of the water-based ink, and the fixing strength of the water-based ink on a low water-absorbing recording medium. From the viewpoint of improving the ratio, it is preferably 30/70 to 90/10, more preferably 40/60 to 80/20, still more preferably 50/50 to 70/30.

In step I, the pigment mixture is further dispersed to obtain a dispersion-treated product. There is no particular limitation on the dispersion method for obtaining the dispersion treatment product. Although the average particle size of the pigment particles can be atomized only by the main dispersion until the desired particle size is reached, preferably the pigment mixture is pre-dispersed and further subjected to shear stress to perform the main dispersion. It is preferable to control the average particle size of the particles so as to have a desired particle size.
The temperature in the preliminary dispersion in step I is preferably 0 ° C. or higher, and preferably 40 ° C. or lower, more preferably 30 ° C. or lower, still more preferably 20 ° C. or lower, and the dispersion time is preferably 0.5 hours. More preferably, it is 1 hour or more, and preferably 30 hours or less, more preferably 10 hours or less, and further preferably 5 hours or less.
When the pigment mixture is predispersed, commonly used mixing and stirring devices such as anchor blades and disper blades can be used, and among them, a high-speed stirring and mixing device is preferable.

Examples of means for imparting the shear stress of this dispersion include a kneader such as a roll mill and a kneader, a high-pressure homogenizer such as a microfluidizer (manufactured by Microfluidics), a media-type disperser such as a paint shaker and a bead mill. Examples of commercially available media dispersers include Ultra Apex Mill (manufactured by Kotobuki Industries Co., Ltd.), Picomill (manufactured by Asada Tekko Co., Ltd.), and the like. A plurality of these devices can be combined. Among these, it is preferable to use a high-pressure homogenizer from the viewpoint of reducing the particle size of the pigment.
When this dispersion is performed using a high-pressure homogenizer, the pigment can be controlled to have a desired particle size by controlling the processing pressure and the number of passes.
From the viewpoint of productivity and economy, the treatment pressure is preferably 60 MPa or more, more preferably 100 MPa or more, further preferably 130 MPa or more, and preferably 220 MPa or less, more preferably 200 MPa or less, and even more preferably 190 MPa or less. It is.
The number of passes is preferably 3 passes or more, more preferably 10 passes or more, and preferably 30 passes or less, more preferably 25 passes or less.

(Process II)
In Step II, an aqueous dispersion of pigment-containing polymer particles can be obtained by removing the organic solvent from the obtained dispersion by a known method. It is preferable that substantially all of the organic solvent in the aqueous dispersion containing the obtained pigment-containing polymer particles is removed, but it may remain as long as the object of the present invention is not impaired. The amount of the residual organic solvent is preferably 0.1% by mass or less, more preferably 0.01% by mass or less.
If necessary, the dispersion can be heated and stirred before the organic solvent is distilled off.
The obtained aqueous dispersion of pigment-containing polymer particles is obtained by dispersing solid water-insoluble polymer particles containing a pigment in a medium containing water as a main medium. Here, the form of the water-insoluble polymer particles is not particularly limited as long as the particles are formed of at least a pigment and a water-insoluble polymer. For example, a particle form in which a pigment is included in the water-insoluble polymer, a particle form in which the pigment is uniformly dispersed in the water-insoluble polymer, a particle form in which the pigment is exposed on the surface of the water-insoluble polymer particle, and the like are included. Mixtures of these are also included.

(Process III)
Step III is an optional step, but is a step in which the aqueous dispersion obtained in Step II and a crosslinking agent are mixed and subjected to crosslinking treatment to obtain an aqueous dispersion. It is preferable to perform Step III from the viewpoint of storage stability of the aqueous dispersion and the ink.
Here, when the water-insoluble polymer is an anionic water-insoluble polymer having an anionic group, the crosslinking agent is preferably a compound having a functional group that reacts with the anionic group. , Preferably 2 to 6 are more preferable.
Preferred examples of the crosslinking agent include compounds having two or more epoxy groups in the molecule, compounds having two or more oxazoline groups in the molecule, and compounds having two or more isocyanate groups in the molecule. Then, a compound having two or more epoxy groups in the molecule is preferable, and trimethylolpropane polyglycidyl ether is more preferable.

The non-volatile component concentration (solid content concentration) of the obtained pigment aqueous dispersion is preferably 10% by mass or more from the viewpoint of improving the dispersion stability of the pigment aqueous dispersion and facilitating preparation of the water-based ink. Preferably it is 15 mass% or more, Preferably it is 30 mass% or less, More preferably, it is 25 mass% or less.
The average particle diameter of the pigment-containing polymer particles in the pigment aqueous dispersion is preferably 40 nm or more, more preferably 60 nm or more, and still more preferably 75 nm or more, from the viewpoint of reducing coarse particles and improving the discharge property of water-based ink. And preferably 150 nm or less, more preferably 120 nm or less, still more preferably 110 nm or less.
The average particle size of the pigment-containing polymer particles is measured by the method described in the examples.
The average particle diameter of the pigment-containing polymer particles in the water-based ink is the same as the average particle diameter in the pigment water dispersion.

<Manufacture of water-based ink>
The water-based ink can be obtained by mixing an aqueous dispersion of pigment-containing polymer particles, an organic solvent, water, and the like and stirring. Various additives such as known viscosity modifiers, antifoaming agents, antiseptics, antifungal agents, and rust inhibitors can be added to the water-based ink as optional components.
As the organic solvent, polyhydric alcohols such as glycerin, 1,2-hexanediol, diethylene glycol and ethylene glycol, pyrrolidones such as 2-pyrrolidone, glycol ethers such as triethylene glycol monobutyl ether and polyoxyethylene lauryl ether are preferable. It is more preferable to use two or more in combination.
In the present invention, the content of the organic solvent is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more in the aqueous ink from the viewpoint of improving the dischargeability of the aqueous ink. From the viewpoint of preventing color mixing when printing on a low water-absorbing recording medium and from the viewpoint of improving the storage stability of the water-based ink, it is preferably 50% by mass or less, more preferably 40% by mass or less.

(Content of each component in water-based ink)
The content of the pigment in the water-based ink is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and further preferably 2.5% by mass or more, from the viewpoint of improving the printing density of the water-based ink. is there. The pigment content is low in the ink viscosity when the solvent is volatilized, from the viewpoint of preventing color mixing when printed on a low water-absorbing recording medium, and from the viewpoint of improving the storage stability of the water-based ink. Preferably, it is 15 mass% or less, More preferably, it is 10 mass% or less, More preferably, it is 7 mass% or less.
The blending amount of the pigment aqueous dispersion in the aqueous ink is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more in the aqueous ink from the viewpoint of improving the printing density of the aqueous ink. It is. In addition, the amount of pigment aqueous dispersion blended in water-based ink reduces the ink viscosity when the solvent is volatilized, and prevents color mixing when printing on a low water-absorbing recording medium, storage stability and ejection of water-based ink. From the viewpoint of improving the properties, it is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less in the water-based ink.

The content of the pigment-containing polymer particles in the aqueous ink is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 4% by mass or more from the viewpoint of improving the printing density of the aqueous ink. In addition, the content of the pigment-containing polymer particles is from the viewpoint of lowering the ink viscosity at the time of solvent volatilization, preventing color mixing when printing on a low water-absorbing recording medium, and improving the storage stability of the water-based ink. In water-based ink, it is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less.
The content of the water-insoluble polymer in the water-based ink is preferably 0.5% by mass or more, more preferably from the viewpoint of improving the storage stability of the water-based ink and the fixing strength to a low water-absorbing recording medium. It is 8 mass% or more, More preferably, it is 1.0 mass% or more. In addition, the content of the water-insoluble polymer is low from the viewpoint of reducing ink viscosity when the solvent is volatilized, preventing color mixing when printing on a low water-absorbing recording medium, and from the viewpoint of improving the storage stability of the water-based ink. In the ink, it is preferably 6% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less.

(Physical properties of water-based ink)
The viscosity at 32 ° C. of the water-based ink is preferably 2.0 mPa · s or more, more preferably 3.0 mPa · s or more, and further preferably 4.0 mPa · s or more, from the viewpoint of improving the discharge property of the water-based ink. And, from the viewpoint of improving the storage stability and dischargeability of the water-based ink, it is preferably 12 mPa · s or less, more preferably 10.0 mPa · s or less, still more preferably 8.0 mPa · s or less, and even more preferably 7. 0 mPa · s or less.
The static surface tension of the water-based ink at 20 ° C. is preferably 25.0 mN / m or more, more preferably 26.0 mN / m or more, from the viewpoint of preventing color mixing when printing on a low water-absorbing recording medium. Preferably it is 26.5 mN / m or more, preferably 30.0 mN / m or less, more preferably 29.0 mN / m or less.
The pH of the water-based ink is preferably 7.0 or higher, more preferably 8.0 or higher, and still more preferably 8.5 or higher, from the viewpoint of improving the storage stability of the water-based ink. From the viewpoints of tolerance and skin irritation reduction, it is preferably 11.0 or less, more preferably 10.0 or less, and still more preferably 9.5 or less.
The pH can also be adjusted using a basic compound such as an alkali metal hydroxide, ammonia or an organic amine, and a pH adjuster such as an acid.
The viscosity, surface tension, and pH of the water-based ink are measured by the methods described in the examples.

[Treatment solution]
The treatment liquid of the present invention is a treatment liquid for treating the surface of a recording medium, contains polyvinyl alcohol having a saponification degree of 95% or less, and contains a pigment after the treatment liquid is applied to the recording medium. Used for forming an image using water-based ink. And when polyvinyl alcohol adds 2.0 parts by mass of the polyvinyl alcohol in the treatment liquid to 100 parts by mass of the water-based ink, the viscosity of the water-based ink is increased by 5 mPa · s or more and 100 mPa · s or less. is there.
The details of the treatment liquid are the same as those described in the ink jet recording method.

The present invention further discloses the following ink jet recording method and processing liquid with respect to the above-described embodiment.
<1> An ink jet recording method comprising the following steps A and B, wherein the recording medium and the treatment liquid used in step A satisfy the following conditions 1 and 2.
Step A: Step of applying a treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less to the recording medium Step B: Inkjet recording using a water-based ink containing a pigment on the recording medium coated with the treatment liquid Step of forming an image by the method Condition 1: The water absorption amount of the recording medium at a contact time of 100 msec between the recording medium and pure water is 0 g / m ² or more and 10 g / m ² or less.
Condition 2: Polyvinyl alcohol increases the viscosity of the water-based ink by 5 mPa · s or more and 100 mPa · s or less when 2.0 parts by mass of the polyvinyl alcohol in the treatment liquid is added to 100 parts by mass of the water-based ink. It is.

<2> The amount of treatment liquid applied to the recording medium in step A is preferably 0.5 g / m ² or more, more preferably 1.0 g / m ² or more, still more preferably 1.5 g / m ² or more, and even more. Preferably it is 2.0 g / m ² or more, and preferably 20 g / m ² or less, more preferably 15 g / m ² or less, still more preferably 10 g / m ² or less, and even more preferably 8 g / m ² or less. The inkjet recording method according to <1>.
<3> The amount of water (other than solid content) of the treatment liquid applied to the recording medium in Step A is 100 parts by mass, and water is preferably up to 95 parts by mass, more preferably up to 90 parts by mass, and even more preferably 80. The ink jet recording method according to <1> or <2>, wherein Step B is started after drying to part by mass.
<4> The water absorption amount of the recording medium at a contact time of 100 msec between the recording medium and pure water is preferably 1.0 g / m ² or more, more preferably 2.0 g / m ² or more, and further preferably 3.0 g / m. m ² or more, more preferably 4.0 g / m ² or more, and preferably 8.0 g / m ² or less, more preferably 7.0 g / m ² or less, still more preferably 6.0 g / m ^2. The inkjet recording method according to any one of <1> to <3>, further preferably 5.5 g / m ² or less.
<5> The inkjet recording method according to any one of <1> to <4>, wherein the recording medium is a coated paper or a synthetic resin film.
<6> The inkjet recording method according to any one of <1> to <5>, wherein the synthetic resin film is any one selected from a polyester film, a vinyl chloride film, a polypropylene film, a polyethylene film, and a nylon film.

<7> The polyvinyl alcohol is preferably one or more selected from completely or partially saponified polyvinyl alcohol and anion-modified, cation-modified, and acid-modified products thereof, more preferably partially saponified polyvinyl alcohol. The inkjet recording method according to any one of <1> to <6>, wherein the inkjet recording method is one or more selected from cation-modified polyvinyl alcohol and acid-modified polyvinyl alcohol.
<8> The average degree of polymerization of the polyvinyl alcohol is preferably 400 or more, more preferably 800 or more, still more preferably 1000 or more, still more preferably 1200 or more, and preferably 5000 or less, more preferably 4000 or less, More preferably, it is 3000 or less, More preferably, it is 2500 or less, The inkjet recording method in any one of said <1>-<7>.
<9> The saponification degree of the partially saponified polyvinyl alcohol is preferably 65% or more, more preferably 70% or more, still more preferably 75% or more, and preferably 90% or less, more preferably 85% or less. The ink jet recording method according to any one of <1> to <8>, more preferably 83% or less.
<10> The average degree of polymerization of the partially saponified polyvinyl alcohol is preferably 400 or more, more preferably 800 or more, still more preferably 1000 or more, still more preferably 1200 or more, and preferably 5000 or less, more preferably The inkjet recording method according to any one of <1> to <9>, which is 4000 or less, more preferably 3000 or less, and still more preferably 2500 or less.
<11> When the polyvinyl alcohol is added in an amount of 2.0 parts by mass with respect to 100 parts by mass of the water-based ink, the viscosity of the water-based ink is preferably 8 mPa · s or more, more preferably 10 mPa · s. s or higher, more preferably 12 mPa · s or higher, and preferably 150 mPa · s or lower, more preferably 100 mPa · s or lower, more preferably 80 mPa · s or lower. The inkjet recording method according to any one of <1> to <10>.

<12> The viscosity (20 ° C.) of the treatment liquid is preferably 10 mPa · s or more, more preferably 50 mPa · s or more, further preferably 100 mPa · s or more, and preferably 3000 mPa · s or less, more preferably The inkjet recording method according to any one of <1> to <11>, which is 2000 mPa · s or less, more preferably 1000 mPa · s or less.
<13> The water content in the treatment liquid is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 85% by mass or more, and preferably 98% by mass or less, more preferably The inkjet recording method according to any one of <1> to <12>, which is 96% by mass or less, more preferably 93% by mass or less.
<14> The treatment liquid preferably contains a sizing agent used in papermaking, more preferably one or more selected from alkyl ketene dimer, rosin, gelatin, starch, and latex sizing agent, More preferably, the inkjet recording method according to any one of <1> to <13>, further comprising an alkyl ketene dimer sizing agent.

<15> The inkjet recording method according to any one of <1> to <14>, wherein the aqueous ink containing a pigment is an aqueous ink containing water-insoluble polymer particles containing a pigment.
<16> The water-insoluble polymer is preferably a vinyl polymer containing (c-1) a structural unit derived from an ionic monomer and (c-2) a structural unit derived from a hydrophobic monomer, more preferably (c- 3) The inkjet recording method according to any one of <1> to <15>, which is a vinyl polymer containing a structural unit derived from a macromonomer or a structural unit derived from (c-4) a nonionic monomer.
<17> The inkjet recording method according to <16>, wherein the ionic monomer is preferably an anionic monomer, more preferably a carboxylic acid monomer, and still more preferably acrylic acid or methacrylic acid.
<18> The inkjet recording method according to <16> or <17>, wherein the hydrophobic monomer is preferably an alkyl (meth) acrylate or an aromatic group-containing monomer.
<19> A vinyl monomer having an aromatic group having 6 to 22 carbon atoms, which may preferably have a substituent containing a hetero atom, more preferably a styrenic monomer or an aromatic group-containing monomer. The inkjet recording method according to <18>, wherein the inkjet recording method is (meth) acrylate.
<20> The macromonomer is preferably an aromatic group-containing monomer-based macromonomer and a silicone-based macromonomer, more preferably an aromatic group-containing monomer-based macromonomer, according to any one of the above <16> to <19>. Inkjet recording method.

<21> The content of the pigment in the water-based ink is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, still more preferably 2.5% by mass or more, and preferably 15% by mass. % Or less, more preferably 10% by mass or less, and further preferably 7% by mass or less, according to any one of <1> to <20>.
<22> The content of the water-insoluble polymer particles containing the pigment in the water-based ink is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and preferably 20%. The inkjet recording method according to any one of <15> to <21>, wherein the inkjet recording method is 10% by mass or less, more preferably 10% by mass or less, and still more preferably 8% by mass or less.
<23> The content of the water-insoluble polymer in the water-based ink is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, still more preferably 1.0% by mass or more, and preferably The inkjet recording method according to any one of <15> to <22>, which is 6% by mass or less, more preferably 4% by mass or less, and still more preferably 3% by mass or less.

<24> The water-based ink has a viscosity at 32 ° C. of preferably 2.0 mPa · s or more, more preferably 3.0 mPa · s or more, still more preferably 4.0 mPa · s or more, and preferably 12 mPa · s. Inkjet recording according to any one of <1> to <23>, more preferably 10.0 mPa · s or less, still more preferably 8.0 mPa · s or less, and even more preferably 7.0 mPa · s or less. Method.
<25> The static surface tension of the water-based ink at 20 ° C. is preferably 25.0 mN / m or more, more preferably 26.0 mN / m or more, further preferably 26.5 mN / m or more, and preferably The inkjet recording method according to any one of <1> to <24>, which is 30.0 mN / m or less, more preferably 29.0 mN / m or less, and still more preferably 28.5 mN / m or less.
<26> The amount of water (other than solid content) of the treatment liquid applied to the recording medium in Step A is 100 parts by mass, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 20 parts by mass. The inkjet recording method according to any one of <1> to <25>, wherein Step B is started after drying by mass part or more.
<27> The mass of water (other than solid content) of the treatment liquid applied to the recording medium in Step A is 100 parts by mass, and water is preferably 98 parts by mass or less, more preferably 95 parts by mass or less, and still more preferably 90 After drying to be equal to or less than part by mass, more preferably equal to or less than 70 parts by mass, and even more preferably equal to or less than 40 parts by mass, the process B is started, according to any one of <1> to <26>. Inkjet recording method.
<28> A treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less, and after the treatment liquid is applied to a recording medium, it is used for an application for forming an image using a water-based ink containing a pigment. When polyvinyl alcohol is added in an amount of 2.0 parts by mass with respect to 100 parts by mass of the water-based ink, the viscosity of the water-based ink is increased by 5 mPa · s to 100 mPa · s. liquid.

  In the following production examples, examples and comparative examples, “parts” and “%” are “parts by mass” and “mass%” unless otherwise specified. In addition, each physical property value etc. were measured with the following method.

(1) Weight average molecular weight of water-insoluble polymer Gel permeation chromatography using a solution in which phosphoric acid and lithium bromide are dissolved in N, N-dimethylformamide at concentrations of 60 mmol / L and 50 mmol / L, respectively. It was measured using polystyrene as a standard substance by the method [GPC apparatus (HLC-8120GPC) manufactured by Tosoh Corporation, column (TSK-GEL, α-M × 2), manufactured by Tosoh Corporation, flow rate: 1 mL / min].

(2) Solid content concentration of aqueous dispersion Weigh out 10.0 g of sodium sulfate constant in a desiccator into a 30 mL ointment container, add about 1.0 g of sample to this, mix, and accurately weigh. The mixture was maintained at 105 ° C. for 2 hours to remove volatile components, and further left in a desiccator for 15 minutes to measure the mass. The mass of the sample after removal of the volatile matter was taken as the solid content and divided by the mass of the added sample to obtain the solid content concentration.

(3) Average particle diameter of water-insoluble polymer particles containing pigment The measurement was performed using a laser particle analysis system (Otsuka Electronics Co., Ltd., model number: ELS-8000, cumulant analysis). A dispersion diluted with water so that the concentration of particles to be measured was about 5 × 10 ⁻³ mass% was used. The measurement conditions were a temperature of 25 ° C., an angle between incident light and a detector of 90 °, and the number of integrations of 100. The refractive index of water (1.333) was input as the refractive index of the dispersion solvent.

(4) Viscosity of water-based ink Viscosity was measured at 32 ° C. using an E-type viscometer “TV-25” (manufactured by Toki Sangyo Co., Ltd., using standard cone rotor 1 ° 34 ′ × R24, rotation speed 50 rpm). did.
(5) Viscosity of processing liquid and viscosity of water-based ink added with agent in processing liquid Using MCR301 rheometer (manufactured by Anton Paar, CP50-1 cone plate), at 32 ° C., the shear rate was set to 0. The viscosity at a shear rate of 200 (1 / s) when increasing from 1 to 1000 (1 / s) over 200 seconds and decreasing from 1000 to 0.1 (1 / s) was employed.
(6) Static surface tension of water-based ink A platinum plate was immersed in a cylindrical polyethylene container (diameter 3.6 cm × depth 1.2 cm) containing 5 g of ink adjusted to 20 ° C., and the surface tension meter “CBVP-Z ”(Manufactured by Kyowa Interface Chemical Co., Ltd.) and measured by the Wilhelmi method.
(7) pH of water-based ink
The pH of the ink at 25 ° C. was measured using a desktop pH meter “F-71” (manufactured by Horiba, Ltd.) using a pH electrode “6337-10D” (manufactured by Horiba, Ltd.).

(8) Amount of water absorption at a contact time of 100 msec between the recording medium and pure water Using an automatic scanning absorption meter (Kumaya Riki Kogyo Co., Ltd., KM500win) under the conditions of 23 ° C. and relative humidity of 50%, The amount of transition at a pure water contact time of 100 ms was measured, and the amount of water absorbed was 100 ms. The measurement conditions are shown below.
"Spiral Method"
Contact Time: 0.010 to 1.0 (sec) Pitch (mm): 7
Length Per Sampling (degree): 86.29
Start Radius (mm): 20 End Radius (mm): 60
Min Contact Time (ms): 10 Max Contact Time (ms): 1000
Sampling Pattern (1-50): 50
Number of Sampling Points (> 0): 19
"Square Head"
Slit Span (mm): 1 Slit Width (mm): 5

Production Example 1 (Manufacture of treatment liquid A)
A treatment liquid A was prepared by dissolving polyvinyl alcohol (manufactured by Kuraray Co., Ltd., trade name: PVA417, polymerization degree 1700, saponification degree 78-81%) in ion-exchanged water so as to be a 10% by mass aqueous solution. The viscosity (20 degreeC) of the process liquid A was 480 mPa * s.

Production Example 2 (Preparation of water-based ink A)
(1) Synthesis of anionic water-insoluble polymer 46 parts of styrene, 14 parts of methacrylic acid, styrene macromer (manufactured by Toagosei Co., Ltd., trade name: AS-6 (S), solid content concentration 50%, number average molecular weight 6000) 30 Part and 50 parts of polypropylene glycol monomethacrylate (NOF Corporation, trade name: BLEMMER PP-1000, propylene oxide average added mole number: 5) were mixed to prepare a monomer mixture.
In a reaction vessel, 18 parts of methyl ethyl ketone, 0.03 part of 2-mercaptoethanol (chain transfer agent) and 10% of the monomer mixture were mixed and sufficiently substituted with nitrogen gas.
On the other hand, the remaining 90% of the monomer mixture, 0.27 part of the chain transfer agent, 42 parts of methyl ethyl ketone, and polymerization initiator 2,2′-azobis (2,4-dimethylvaleronitrile) (Wako Pure Chemical Industries, Ltd.) (Product name: V-65) 3 parts of the mixed liquid is added to the dropping funnel, and the mixture is heated to 75 ° C. while stirring the mixed solution in the reaction vessel in a nitrogen atmosphere. The solution was added dropwise over 3 hours. After 2 hours at 75 ° C. from the end of the dropwise addition, a solution prepared by dissolving 3 parts of the polymerization initiator in 5 parts of methyl ethyl ketone was added, and further aged at 75 ° C. for 2 hours and at 80 ° C. for 2 hours to obtain an anionic water-insoluble polymer solution ( Weight average molecular weight: 100,000, solid content concentration: 40% by mass). When the anionic water-insoluble polymer was dissolved in 100 g of water at 25 ° C., the amount dissolved was 0.3 g.
(2) Preparation of aqueous dispersion of anionic water-insoluble polymer particles containing pigment 66 parts of polymer obtained by drying the polymer solution obtained in (1) under reduced pressure was dissolved in 151 parts of methyl ethyl ketone, and As a neutralizing agent, 20.3 parts of 5N aqueous sodium hydroxide solution, 1.6 parts of 25% aqueous ammonia, and 379 parts of ion-exchanged water were added, and a cyan pigment (manufactured by Dainichi Seika Kogyo Co., Ltd., product number: CFB-6338JC) After adding 100 parts and mixing for 1 hour under the conditions of 7000 rpm and 20 ° C. using a disperse blade, the obtained dispersion was microfluidizer (trade name, model: M-140K, high pressure homogenizer manufactured by Microfluidics). Was further dispersed for 15 passes at a pressure of 180 MPa.
After adding 301.9 g of ion-exchanged water to the obtained dispersion, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, a part of the water was further removed, the mixture was centrifuged, and a filter (manufactured by Sartorius, mini-Salto syringe) was obtained. Filtering with a filter, pore size: 5 μm, material: cellulose acetate) to remove coarse particles, an aqueous dispersion 1 of anionic water-insoluble polymer particles containing a pigment (solid content concentration: 20% by mass, average particle size 100 nm) Obtained. The neutralization degree of the anionic group of the water-insoluble polymer was 100%, and the pH was 9.2. The mass ratio of pigment to water-insoluble polymer [pigment / water-insoluble polymer] was 60/40.
(3) Preparation of water-based ink Glycerin 10 was added to 25.3 parts (3.04 parts of pigment, 2.03 parts of resin) of pigment aqueous dispersion 1 (solid content concentration: 20%) obtained in the above (2). Parts, diethylene glycol 25 parts, Surfynol 104 (Nisshin Chemical Industry Co., Ltd., acetylenic diol) 1 part, Emulgen 120 (Kao Co., Ltd., ethylene glycol 12 mol adduct of lauryl alcohol), and residual ion Exchange water was added to make the total amount 100 parts, and the resulting mixture was filtered with a 1.2 μm filter (manufactured by Sartorius, Mini-Salto syringe filter) to obtain water-based ink A. The static surface tension of the water-based ink A at 20 ° C. was 28.9 mN / m, and the viscosity at 32 ° C. was 5 mPa · s.

Comparative production example 1 (Preparation of treatment liquid A′-1)
In Production Example 1, treatment liquid A′-1 was prepared in the same manner as in Production Example 1 except that trimethylolpropane was used instead of polyvinyl alcohol.

Comparative Production Example 2 (Preparation of treatment liquid A′-2)
In Production Example 1, treatment liquid A′-2 was prepared in the same manner as in Production Example 1 except that calcium nitrate was used instead of polyvinyl alcohol.

Example 1
(1) Inkjet recording (Process A)
Using the wire coater, the amount of the treatment liquid A obtained in Production Example 1 is 1.6 g / m ² (the film thickness calculated from the weight of the paper is 16 μm). A general glossy paper (Oji Paper Co., Ltd., “OK Top Coat Plus”, water absorption of 4.9 g / m ^{2 with a} contact time of 100 msec) was coated on a paper surface to obtain a recording medium.
(Process B)
120 minutes after the completion of step A, an image was formed on the recording medium using water-based ink A by the following inkjet recording method on the recording medium coated with treatment liquid A.
In addition, as a result of calculating | requiring the solid content concentration of the processing liquid provided to the recording medium at the time of the start of the process B from the mass measurement of the processing liquid provided to the recording medium, it dried to 80 mass%.
(Inkjet recording method)
In an environment with a temperature of 25 ± 1 ° C and a relative humidity of 30 ± 5%, an aqueous printing system (manufactured by Tritech Co., Ltd.) equipped with an inkjet head (Kyocera Corporation, “KJ4B-HD06MHG-STDV”, Piezo type) Ink A was filled.
A head voltage of 26 V, a head temperature of 32 ° C., a resolution of 600 dpi, a pre-discharge flushing count of 200 shots, a negative pressure of −4.0 kPa are set, and the recording medium is placed on the transport base in the same direction as the longitudinal direction of the recording medium. Fixed under reduced pressure.

(2) Evaluation of water-based ink Water-based ink was evaluated by the following method. The results are shown in Table 1.
(1) Viscosity evaluation when mixing treatment liquid and water-based ink In order to confirm the degree of increase in viscosity when the treatment liquid and water-based ink are in contact, the viscosity when the agent contained in the treatment liquid is mixed with the water-based ink is determined. It was measured. With respect to 100 parts by mass of the water-based ink A, the polyvinyl alcohol in the treatment liquid was added while changing the solid content from 0.1 parts by mass to 4.0 parts by mass. When there is no increase in viscosity, the color mixing prevention property is inferior, and when the increase in viscosity is too large, the scratch resistance tends to decrease.

(2) Evaluation of color mixing prevention A print command is transferred to the print evaluation apparatus, and a high-definition color digital standard image ISO / JIS-SCID N1A (portrait under the conditions of a frequency of 5 kHz, a discharge liquid amount of 7 pl, and 600 * 600 dpi. ) Printed the image. The printed matter was visually evaluated according to the following criteria.
[Evaluation criteria]
A +: The outline of the hair and neck of a woman is clear.
A: There is no bleeding of the hair part of the woman and the contour of the neck is clear.
B: The hair of a woman bleeds slightly and the neck contour is slightly unclear.
C: Women's hair bleeds and the outline is unclear overall.

(3) Evaluation of scratch resistance A print command is transferred to the print evaluation apparatus, and a water-based ink A is driven into a recording medium to which a treatment liquid is applied 100% (frequency 30 kHz, discharge liquid appropriate amount 12 pl, 600 × 600 dpi). A solid image was printed. After printing on the recording medium coated with the treatment liquid and drying at 25 ° C. for 1 minute, the following scratch resistance was evaluated.
A print sample is set in a scratch evaluation apparatus having a mechanism for reciprocating a metal weight (mass 450 g, bottom shape 2.5 cm × 2.5 cm) so as to scratch the long side direction of the printed matter. The OK top coat plus paper was cut into 2.5 cm × 7 cm and wrapped so that no slack was produced on the weight. A weight was set in the apparatus so that the paper surface and the printing surface were in contact.
After the weight was reciprocated 10 times in the long side direction of the printed matter at a speed of about 30 cm / sec, the OK topcoat plus paper for rubbing wound around the weight was removed, and the surface of the printed matter was visually observed. The scratch resistance was evaluated according to the following criteria.
[Evaluation criteria]
A: The image is not disturbed or hardly seen.
B: The rubbing trace can be clearly seen, but the image can be recognized.
C: The image cannot be recognized.

Comparative Examples 1 and 2
An image was printed and evaluated in the same manner as in Example 1 except that the treatment liquid A was replaced with the treatment liquid A′-1 or the treatment liquid A′-2. The results are shown in Table 1.

Comparative Example 3
An image was printed and evaluated in the same manner as in Example 1 except that general-purpose glossy paper not coated with the treatment liquid was used as the recording medium without performing Step A. The results are shown in Table 1.

  From Table 1, the treatment liquid of Example 1 using polyvinyl alcohol is less water-absorbing using a water-based ink containing a pigment than the treatment liquids of Comparative Examples 1 and 2 using trimethylolpropane and calcium nitrate. When printing on a recording medium, it can be seen that there is no color mixing, the image quality is excellent, and the scratch resistance is also excellent.

Example 2 and Comparative Example 4
Example 1 and Comparative Example 3 except that the general-purpose glossy paper as the recording medium was replaced with a PET film (Toray Industries, Inc., “Lumirror T60”, water absorption of 2.3 g / m ^{2 with a} contact time of 100 msec). Was evaluated. The results are shown in Table 2.

  From Table 2, it can be seen that the treatment liquid of Example 2 using polyvinyl alcohol has no color mixing even when a PET film is used as a recording medium, has excellent image quality, and excellent scratch resistance.

Examples 3 to 5 and Comparative Example 5
A treatment solution was prepared in the same manner as in Example 1 except that polyvinyl alcohol having a different saponification degree and polymerization degree was used, and the color mixing prevention property was evaluated. The results are shown in Table 3.
The details of the used polyvinyl alcohol (PVA) are as follows.
PVA424H: manufactured by Kuraray Co., Ltd., trade name, polymerization degree 2400, saponification degree 78-81%
PVA217: manufactured by Kuraray Co., Ltd., trade name, polymerization degree 1700, saponification degree 87-89%
PVA224: manufactured by Kuraray Co., Ltd., trade name, polymerization degree 2400, saponification degree 87-89%
PVA117: manufactured by Kuraray Co., Ltd., trade name, polymerization degree 1700, saponification degree 98-99%

Example 6
The same as Example 1 except that the total amount was 10.1 parts of 100 parts of the treatment liquid, 10 parts of polyvinyl alcohol and 0.1 part of a sizing agent (manufactured by Kao Corporation, “Syrene S91” alkyl ketene dimer sizing agent). A treatment solution was prepared and the color mixing prevention property was evaluated. The results are shown in Table 3.

  From Table 3, it can be seen that Comparative Example 5 using polyvinyl alcohol having a saponification degree exceeding 98% is inferior in color mixing prevention.

Examples 7-13
After performing Step A using the treatment liquid of Example 1, it was dried at 90 ° C. and normal pressure. The dryness before the process B was calculated from the mass after drying. In addition, the absolute dry mass when the paper subjected to Step A using the treatment liquid of Example 1 was dried for 48 hours under the conditions of 23 ° C. and 50% humidity (100% drying) was 106.3 g / m ² .
Further, the paper was adjusted to a 10 cm square, the coating liquid was applied and dried, and then a piece of paper was fixed, and the height at which the facing pieces were lifted was measured to evaluate the curl height. Furthermore, using the paper after drying, the process B was performed continuously and the color mixing prevention property was evaluated. The results are shown in Table 4.
For example, in Example 7, the dryness is [100.0− [mass after drying (119.9 g / m ² ) −absolute dry mass (106.3 g / m ² )] / [mass immediately after application of the treatment liquid] (120.7 g / m ² ) -absolute dry mass (106.3 g / m ² )]]. Examples 8 to 13 were also calculated in the same manner as in Example 7 using the mass after each drying.

  From Table 4, curl tends to be suppressed as the dryness is small, and color mixing prevention property tends to be excellent as the dryness is large. In Example 9, it can be seen that the curl suppression effect and the color mixing prevention effect are compatible at a dryness of about 21% (21 parts by mass with respect to 100 parts by mass of water (other than solid content) of the treatment liquid).

Claims (5)

An ink jet recording method comprising the following steps A and B, wherein the recording medium and the treatment liquid used in step A satisfy the following conditions 1 and 2.
Step A: Step of applying a treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less to the recording medium Step B: Inkjet recording using a water-based ink containing a pigment on the recording medium to which the treatment liquid is applied Step of forming an image by the method Condition 1: The water absorption amount of the recording medium at a contact time of 100 msec between the recording medium and pure water is 0 g / m ² or more and 10 g / m ² or less.
Condition 2: Polyvinyl alcohol increases the viscosity of the water-based ink by 5 mPa · s or more and 100 mPa · s or less when 2.0 parts by mass of the polyvinyl alcohol in the treatment liquid is added to 100 parts by mass of the water-based ink. It is.   The inkjet recording method according to claim 1, wherein the aqueous ink containing a pigment is an aqueous ink containing water-insoluble polymer particles containing a pigment.   The inkjet recording method according to claim 1 or 2, wherein the average degree of polymerization of polyvinyl alcohol is 400 or more and 5000 or less.   The mass of water (other than solid content) of the treatment liquid applied to the recording medium in Step A is 100 parts by mass, and after drying the water so that the amount of water is 98 parts by mass or less, Step B is started. The ink jet recording method according to claim 1.   A treatment liquid containing polyvinyl alcohol having a saponification degree of 95% or less, which is used for forming an image using a water-based ink containing a pigment after the treatment liquid is applied to a recording medium. A treatment liquid that increases the viscosity of the water-based ink by 5 mPa · s or more and 100 mPa · s or less when 2.0 parts by mass of the polyvinyl alcohol in the treatment liquid is added to 100 parts by mass of the water-based ink.