JP5344871B2 - Inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method excellent in an image drawing property, and an ink set. <P>SOLUTION: The inkjet recording method includes a processing liquid imparting step for imparting a processing liquid containing a flocculant which flocculates an ingredient in the ink composition on a recording medium before the ink composition for forming an ink image is discharged and an image recording step for sequentially discharging on the recording medium imparted with the processing liquid from the ink composition low in surface tension by an inkjet method to record an image using at least two types of ink compositions different in the surface tension. In the method, the surface tension A of the processing liquid and the surface tension B of the ink composition satisfy a relation of A&gt;B. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention relates to an ink jet recording how to record an image by ejecting ink by an inkjet method.

  Various recording media have been studied as recording media for inkjet recording, and a technique capable of forming high-quality images is required. Also, various ink materials have been studied for inks from the viewpoints of water resistance and light resistance.

  For example, a pigment is widely used for a colorant that is one of the components of the ink material, and the pigment is used by being dispersed in a medium such as water. When pigments are used in a dispersed manner, the dispersed particle size when dispersed, the stability after dispersion, size uniformity, etc., and ejection properties from the ejection head are important. It is done.

  On the other hand, when recording on plain paper or the like, sufficient performance may not be obtained in terms of fixability (for example, scratch resistance) and resolution in addition to the color density. In particular, there is a case where the speed of ink-jet recording is increased, and there is a demand for recording suitability in the case of performing high-speed recording by a single pass method capable of recording by one head operation instead of the shuttle scan method.

  As a technique related to the above, in an ink jet recording method in which a reaction liquid containing a reactive agent and an ink composition are attached to a recording medium for printing, the surface tension of the reaction liquid and the ink composition is both less than 40 mN / m. The technique to do is disclosed (for example, refer patent document 1).

  Also, each liquid is ejected while scanning a recording portion for ejecting a pigment ink and a reaction liquid having a higher surface tension than that of the pigment ink and containing a polyvalent metal salt with respect to the recording medium. An ink jet recording method for recording the image is disclosed (for example, see Patent Document 2).

  Further, an ink set having a reaction liquid containing a zirconium salt and an ammonium salt has been proposed, and the surface tension of the reaction liquid is made larger than the average value of the surface tension of the aqueous pigment ink used in combination with the reaction liquid, It is disclosed that the surface tension of the reaction liquid is 25 to 50 mN / m, the surface tension of the ink is 20 to 50 mN / m, and the difference between the average value of the surface tension of the reaction liquid and the ink is 5 to 25 mN / m. (For example, refer to Patent Document 3).

In addition to the above, there has been proposed an image forming method in which a plurality of types of ink are used, and after applying a reaction liquid containing a component that reacts with the ink, a plurality of types of ink are applied in order from the ink with the highest surface tension. (For example, see Patent Document 4).
Japanese Patent No. 3550637 Patent 4040584 JP 2005-74654 A JP 2007-331171 A

  However, as described above, in the ink jet recording method in which the surface tension of the reaction liquid and the ink are both less than 40 mN / m, when a single ink (single color) is applied, the dot diameter is greatly increased, which can be a preferable point quality. However, when a plurality of inks of different colors are overprinted, bleeding is increased and image quality is degraded. In addition, the above-described ink jet recording method using a pigment ink and a reaction liquid having a surface tension higher than that of the pigment ink is such that both liquids come into contact with each other in a liquid state on the recording medium, and the aggregate of the pigment aggregate is removed from the reaction liquid. Since it is generated on the surface, this method has a problem that the liquid moves or expands on the paper surface before drying and solidifying. The above ink set is a balance of surface tension established in a system limited to a reaction solution containing a zirconium compound and an ammonium salt, and cannot be established in a system that does not use these salts, and an image with high drawability can be obtained. Absent. Further, in the image forming method in which ink is applied in order from the one having the highest surface tension, bleeding easily occurs when the reaction liquid and the ink come into contact with each other on the recording medium, and an image with high drawing performance cannot always be obtained.

  Further, if the aggregation reaction between the treatment liquid that aggregates the components in the ink and the ink is insufficient, it tends to cause image unevenness, and in particular, attempts to record multicolor images by overlapping different color inks. In this case, image unevenness appears remarkably. At this time, if the application amount of the treatment liquid is increased, the aggregation reaction is promoted, but the original texture of the recording medium is impaired due to a decrease in the surface gloss of the non-image area.

The present invention has been made in view of the above, and aims to provide an excellent ink jet recording how the image printing properties (e.g. image reproducibility such as details and thin lines), to achieve the objective Let it be an issue.

Specific means for achieving the above object are as follows.
<1> A treatment liquid application step of applying a treatment liquid containing an aggregating agent that agglomerates components in the ink composition onto a recording medium before discharging an ink composition for forming an ink image, and at least different in surface tension. An image recording step of recording an image by sequentially ejecting an ink composition having a low surface tension from an ink composition having a low surface tension onto the recording medium using two types of ink compositions by an ink jet method. the surface tension a of the liquid and the surface tension B of the ink composition meets the relation of a> B, the surface tension of the largest ink composition surface tension of the at least two different kinds of ink compositions of the surface tension And the difference in surface tension of the treatment liquid is 3 mN / m or more .
<2> The inkjet recording method according to <1>, wherein at least one of the at least two ink compositions having different surface tensions is a yellow ink composition, and the surface tension of the yellow ink composition is the largest. .
< 3 > The inkjet recording method according to <1> or <2> , wherein the content of the flocculant is 10 to 40% by mass with respect to the total mass of the treatment liquid.
< 4 > The inkjet recording method according to any one of <1> to < 3 > , wherein the flocculant is an organic carboxylic acid.
< 5 > The inkjet recording method according to < 4 >, wherein the organic carboxylic acid is a divalent or higher polyvalent carboxylic acid.
< 6 > The inkjet recording method according to any one of <1> to < 5 >, wherein the treatment liquid has a pH (25 ° C.) of 3.5 or less.

< 7 > The inkjet recording method according to < 6 >, wherein the treatment liquid has a pH (25 ° C.) of 0.5 to 2.5.
< 8 > The inkjet recording method according to any one of <1> to < 7 >, wherein the discharge of the ink composition is started within 10 seconds from the end of application of the treatment liquid. .
< 9 > The ink jet recording medium method according to any one of <1> to < 8 >, wherein the treatment liquid has a surface tension of 40 to 60 mN / m.
< 10 > The ink composition includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition, and the surface tension B of the ink composition is magenta ink composition <cyan ink. The inkjet recording method according to any one of <1> to < 9 >, wherein the composition satisfies a relationship of <a yellow ink composition.
<1 1 > The inkjet according to any one of <1> to < 10 >, wherein a difference in surface tension between the at least two ink compositions is 1 to 5 mN / m. It is a recording method.

<1 2 > The treatment liquid further contains 1 to 40% by mass of an organic solvent with respect to the total mass. The inkjet according to any one of <1> to <1 1 >, It is a recording method.
<1 3 > The inkjet recording method according to <12>, wherein the content of the organic solvent is 5 to 20% by mass.
<1 4 > The treatment liquid further contains at least one selected from an anionic surfactant and a nonionic surfactant, and any one of the above <1> to <1 3 > Ru inkjet recording method der according to.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording method and ink set excellent in image drawing property (for example, reproducibility of the detail of an image, a thin line, etc.) can be provided.

  Hereinafter, the ink jet recording method of the present invention will be described in detail, and the ink set of the present invention will be described in detail through the description.

The inkjet recording method of the present invention includes a treatment liquid application step of applying a treatment liquid containing an aggregating agent that aggregates the components in the ink composition onto a recording medium before discharging the ink composition for forming an ink image; An image recording step of recording an image by sequentially ejecting the ink composition having a low surface tension from the ink composition having a low surface tension by an ink jet method on a recording medium coated with a treatment liquid using at least two types of ink compositions having different surface tensions; The surface tension A of the treatment liquid applied onto the recording medium and the surface tension B of the ink composition discharged onto the applied treatment liquid satisfy A> B, and at least two types of ink compositions having different surface tensions are used. and surface tension of the highest ink composition surface tension of the difference between the surface tension of the treatment liquid is Ru der than 3 mN / m.

When recording an ink image, a second color, a third color,..., An n-th color ink composition is overprinted to record a multicolor image composed of secondary colors, tertiary colors,. In this case, the diameter of the ink droplets of the second and subsequent inks tends to be larger than the diameter of the first color droplets, and the dot diameter tends to change in the same image during multicolor recording. In the present invention, a plurality of ink compositions are ejected in order from the one having the lowest surface tension onto a recording medium to which a treatment liquid has been applied in advance. It is possible to suppress the change, improve the reproducibility of details and fine lines in the recorded image, and record an image having excellent drawing performance.
That is, in the present invention, when the ink composition is ejected onto the recording surface to which the processing liquid having a certain surface tension is applied, the ink composition dots gradually deposited as the processing liquid is consumed. Since the surface tension of the processing liquid is relatively high, droplets of an ink composition having a low surface tension are deposited and the surface tension on the ink side increases as the surface tension of the processing liquid decreases. By ejecting multiple ink compositions in order, the final recorded image has less dot size variation (diameter change), high dot diameter uniformity, and excellent resolution. Is obtained.

  In the present invention, the surface tension A of the treatment liquid is in the range of 40 to 60 mN / m (preferably 42 to 50 mN / m) and the surface tension B of the ink composition is 20 to 45 mN / m (preferably 20 to 20 mN / m). 40 mN / m) is preferable, and in this case, A> B is preferably satisfied.

-Treatment liquid application process-
In the treatment liquid application step, a treatment liquid containing an aggregating agent for aggregating the components in the ink composition is applied onto the recording medium before discharging the ink composition forming the ink image. A treatment liquid for aggregating the components (for example, pigments and resin particles) in the ink composition is applied in advance to the recording medium before applying the ink composition described below, and then contacted with the applied treatment liquid. By performing the recording by discharging the ink composition as described above, the inkjet recording can be performed at a high speed, and an image having a high density and resolution can be obtained even at a high speed.

  The treatment liquid comprises at least an aggregating agent as an aggregating component capable of aggregating particles such as pigments and resin particles in the ink composition to form an aggregate when mixed with the ink composition described below. Accordingly, other components can be used.

(Flocculant)
The treatment liquid contains at least one flocculant capable of forming an aggregate upon contact with the ink composition. By mixing the flocculant with the ink composition ejected by the ink jet method, aggregation of pigments, resin particles and the like stably dispersed in the ink composition is promoted.

As an example of the treatment liquid, a liquid capable of generating an aggregate by changing the pH of the ink composition can be used. At this time, the pH (25 ° C.) of the treatment liquid is preferably 3.5 or less, more preferably 0.5 to 2.5, and further preferably from the viewpoint of the aggregation rate of the ink composition. More preferably, it is 5-1.5. In this case, the pH (25 ° C.) of the ink composition used in the image recording process described later is preferably 7.5 or more (more preferably 8 or more).
In particular, in the present invention, the pH (25 ° C.) of the ink composition is 8 or more and the pH (25 ° C.) of the treatment liquid is 3. The case of 5 or less (preferably 0.5 to 2.5) is preferable.

  The treatment liquid can be configured using at least one acidic compound as a flocculant. As the acidic compound, a compound having a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxyl group, or a salt thereof (for example, a polyvalent metal salt) may be used. it can. Among these, from the viewpoint of the aggregation rate of the aqueous ink composition, a compound having a phosphoric acid group or a carboxyl group is more preferable, a compound having a carboxyl group is more preferable, and an organic carboxylic acid is particularly preferable.

The compound having a carboxyl group includes polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid. , Pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof (for example, polyvalent metal salts), etc. It is preferable to be selected from among
Among these, organic carboxylic acids having a valence of 2 or more are preferable from the viewpoint of fixing the whole ink by reacting with the ink composition.

The flocculants can be used alone or in combination of two or more.
The content of the flocculant in the treatment liquid is preferably 5 to 95% by mass and more preferably 10 to 40% by mass with respect to the total mass of the treatment liquid from the viewpoint of the aggregation effect. In particular, when the content of the organic carboxylic acid is 10 to 40% by mass, a change in dot diameter when an image is recorded using a plurality of ink compositions in an image recording process described later is effectively suppressed, and the dot diameter The image drawing performance with high uniformity and excellent reproducibility of fine lines and minute portions can be expressed.

  Further, as a preferred example of the treatment liquid for improving the high-speed aggregation property, a treatment liquid to which a polyvalent metal salt or polyallylamine is added can be mentioned. Examples of the polyvalent metal salt include alkaline earth metals belonging to Group 2 of the periodic table (eg, magnesium, calcium), transition metals belonging to Group 3 of the periodic table (eg, lanthanum), and cations from Group 13 of the periodic table. (For example, aluminum), salts of lanthanides (for example, neodymium), polyallylamine, and polyallylamine derivatives. As the metal salt, carboxylate (formic acid, acetic acid, benzoate, etc.), nitrate, chloride, and thiocyanate are suitable. Among them, preferred are calcium salts or magnesium salts of carboxylic acids (formic acid, acetic acid, benzoates, etc.), calcium salts or magnesium salts of nitric acid, calcium chloride, magnesium chloride, and calcium salts or magnesium salts of thiocyanic acid.

  As content in the process liquid of a metal salt, 1-10 mass% is preferable, More preferably, it is 1.5-7 mass%, More preferably, it is the range of 2-6 mass%.

  The treatment liquid in the present invention can be configured to further contain an aqueous solvent (for example, water or an organic solvent) together with the flocculant. In the processing liquid of this invention, it is preferable to contain a water-soluble organic solvent in 1-40 mass% with respect to the total mass of a processing liquid. When the content of the organic solvent is within the above range, the effect of preventing dry precipitation at the liquid / air interface such as the processing liquid container wall of the flocculant or the container wall during coating, and the flocculant is applied to the recording medium, particularly the coating medium. This is advantageous in that the acid neutralization reaction with calcium carbonate added to the surface coat layer of the paper is suppressed by the presence of the organic solvent, and the acid acts effectively as a flocculant. The content of the organic solvent is more preferably in the range of 5 to 20% by mass with respect to the total mass of the treatment liquid.

  As the organic solvent contained in the treatment liquid, the same organic solvents that can be used in the ink composition described later can be used, and the preferred embodiments thereof are also the same.

  The treatment liquid preferably further contains an anionic surfactant and / or a nonionic surfactant. By containing these surfactants, the surface tension of the treatment liquid can be adjusted to an appropriate level.

  Examples of the anionic surfactant include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, and naphthalene sulfonate formalin condensation in hydrocarbons. Products, polyoxyethylene alkylsulfuric acid ester salts, oleoyl taurine salts and the like, among which N-methyl-N-oleoyl taurine sodium salt and oleic acid sodium salt are preferable.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylamine, and glycerin fatty acid ester. Oxyethyleneoxypropylene block copolymer, and the like. Among them, polyoxyethylene (7 to 20 repeating units) alkyl (carbon chain length 6 to 20) ether, polyoxyethylene sorbitan monostearate and the like are preferable. Commercial products may be used, for example, Emulgen 109P (manufactured by Kao Corporation), Olphine 1010 (manufactured by Nissin Chemical Industry Co., Ltd.), New Pole PE-62 (manufactured by Sanyo Chemical Industries Co., Ltd.) and the like. It is done.

  As content in the processing liquid of anionic surfactant and / or nonionic surfactant, 0.0001-1 mass% is preferable with respect to the total mass of a processing liquid, 0.001-0.5 mass % Is preferred. When the content of these surfactants is within the above range, it is advantageous in that separation in the treatment liquid and generation of precipitates are not caused, and the surface tension can be adjusted to an appropriate place.

  The viscosity of the treatment liquid is preferably in the range of 1 to 30 mPa · s, more preferably in the range of 1 to 20 mPa · s, still more preferably in the range of 2 to 15 mPa · s, from the viewpoint of the aggregation rate of the ink composition. The range of 10 mPa · s is particularly preferable. In addition, a viscosity is measured on 25 degreeC conditions using VISCOMETER TV-22 (made by TOKI SANGYO CO. LTD).

  Further, the surface tension of the treatment liquid is preferably 40 to 60 mN / m from the viewpoint of the aggregation rate of the ink composition. In addition, the coating property of the treatment liquid, specifically, for example, the color density in the recorded image Taking into consideration the prevention of the occurrence of unevenness, stripe-shaped shading unevenness, and repellency unevenness, the range of 42 to 50 mN / m is more preferable, and the range of 43 to 48 mN / m is more preferable. The surface tension is measured under conditions of 25 ° C. ± 1 ° C. using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

(Other ingredients)
The treatment liquid in the present invention can generally contain a water-soluble organic solvent in addition to the aggregating agent, and can be constituted using other various additives. The details of the water-soluble organic solvent and other various additives are the same as those in the aqueous ink described later.

  For applying the treatment liquid onto the paper, a known liquid application method can be used without any particular limitation, and any method such as spray application, application using an application roller, application by an ink jet method, and immersion can be selected.

  Specifically, for example, a size press method represented by a horizontal size press method, a roll coater method, a calendar size press method, etc .; a size press method represented by an air knife coater method, etc .; Knife coater method; transfer roll coater method such as gate roll coater method, direct roll coater method, reverse roll coater method, roll coater method represented by squeeze roll coater method; bill blade coater method, short duel coater method; Blade coater method typified by stream coater method, etc .; Bar coater method typified by rod bar coater method, etc .; Bar coater method typified by rod bar coater method, etc .; Cast coater method; Gravure coater method; Coater method; die coater method; brush coater method; and the like transfer method.

  Moreover, the method of apply | coating by controlling a coating amount by using the coating device provided with the liquid quantity limiting member like the coating device of Unexamined-Japanese-Patent No. 10-230201 may be used.

  The region to which the treatment liquid is applied may be the entire surface application to be applied to the entire recording medium or may be the partial application to be partially applied to the region where ink jet recording is performed in the subsequent image recording process. In the present invention, from the viewpoint of uniformly adjusting the application amount of the processing liquid, uniformly recording fine lines and fine image portions, and suppressing density unevenness such as image unevenness, a recording medium is applied by application using an application roller or the like. The entire surface is preferably applied to the entire surface.

The amount of treatment liquid applied is not particularly limited as long as it is an amount sufficient to stabilize the ink composition, but it is preferably 0.25 g / m ² or more, and the ink composition is easily fixed by aggregation. In this respect, it is more preferably 0.30 g / m ² or more and less than 3.0 g / m ² , and further preferably 0.5 g / m ² or more and less than 2.0 g / m ² .

~ Dry removal process ~
In the treatment liquid application process, it is preferable to provide a dry removal process for drying and removing the solvent contained in the treatment liquid after application of the treatment liquid (before an image recording process described later). In addition to being able to improve the scratch resistance of the image by suppressing the occurrence of curling, crackling and repellency by drying and removing the solvent in the processing solution after applying the processing solution, the ink deposited in the image recording process described later The movement of the composition can be suppressed, and dots with higher uniformity can be formed to improve the image drawability (reproducibility of fine lines and fine portions).

  The drying removal step is not particularly limited as long as at least a part of the solvent (for example, water, organic solvent) contained in the aqueous treatment liquid can be removed. For example, the drying and removal can be performed by a method of drying by heating, blowing air (applying dry air, etc.) and the like.

-Image recording process-
In the image recording process, at least two types of ink compositions having different surface tensions are used, and the ink composition having a low surface tension is sequentially applied onto the treatment liquid application surface of the recording medium to which the treatment liquid is applied in the treatment liquid application process. An image is recorded by discharging the ink jet method.

In the image recording step of the present invention, an ink image is recorded using a plurality of types of ink compositions, for example, at least two types of ink compositions having different hues. The plural types of ink compositions are used for forming a multicolor image (for example, a full color image), and an image can be recorded by selecting two or more desired colors. When forming a full-color image, magenta ink, cyan ink, and yellow ink can be used as the ink composition. Further, in order to adjust the color tone, a black ink may be further used.
In addition, ink compositions having red (R), green (G), blue (B), and white (W) tones other than yellow (Y), magenta (M), and cyan (C), and so-called printing fields. Ink-colored ink compositions and the like can be used.
The ink composition of each color tone can be prepared by changing the hue of a colorant (for example, a pigment) as desired.

  In the present invention, as an ink set including a plurality of types of ink compositions together with the processing liquid, an ink image is formed using an ink set including at least two types of ink compositions including a yellow ink composition and the processing liquid. A mode of recording is preferable, and a mode of recording an ink image using an ink set including a yellow ink composition, a magenta ink composition, a cyan ink composition, and the treatment liquid is more preferable.

  In the image recording step, a plurality of ink compositions are ejected in order from the one having the lowest surface tension onto the recording medium to which the treatment liquid has been applied to record an ink image. For example, when recording using an ink set including a yellow ink composition (surface tension p), a magenta ink composition (surface tension q), and a cyan ink composition (surface tension r) together with the treatment liquid, When the surface tension is p <q <r, the ink compositions of the respective colors are ejected in the order of pqr. A low surface tension ink composition that tends to cause dot spreading after landing by ejecting a yellow ink composition having a surface tension p having the lowest surface tension while the surface tension of the treatment liquid applied in advance is high. Can be formed as dots having a shape close to the desired diameter, so that the dot diameter between the ink composition and the dots of the ink composition having higher surface tension can be made uniform. Thereby, the drawability of the image finally obtained (that is, the reproducibility of fine lines and minute parts in the image) can be improved.

  In the present invention, in consideration of color reproducibility, the processing liquid has at least two kinds of ink compositions containing a yellow ink composition, and the surface tension A of the processing liquid and the surface tension B of the ink composition Is preferable to satisfy the relationship of A> B and form an ink image using an ink set having the highest surface tension of the yellow ink composition. When the surface tension is in the above relationship, it is possible to further improve the drawability of the image that is finally recorded (the fineness of the appearance of the image, the reproducibility of fine lines and minute parts). For the same reason, in particular, at least a yellow ink composition, a magenta ink composition, and a cyan ink composition are included together with the treatment liquid, and the relationship between the surface tensions of these inks is magenta ink composition <cyan ink composition. <The form which forms an ink image using the ink set which is a yellow-type ink composition is preferable.

  The difference in surface tension between the plurality of ink compositions used in combination during image recording is preferably 1 to 5 mN / m, more preferably 2 to 4 mN / m from the viewpoint of image drawing properties.

Further, among the plurality of ink compositions in combination at the time of image recording, and the surface tension of the largest ink composition of the surface tension, the difference between the surface tension of the treatment liquid, Ru Ah or 3 mN / m. As the plurality of ink compositions are sequentially ejected onto the treatment liquid as described above, the treatment liquid is consumed, and the dot diameter of the secondary color and the tertiary color is likely to increase. If the tension is set high and the difference between the last ejected ink composition (the ink composition having the largest surface tension) and the surface tension is 3 mN / m or more, the last deposited ink The dot diameter of the composition can be maintained at a diameter that does not greatly differ from the dot diameter of the ink composition that has first deposited droplets.
The difference between the surface tension of the ink composition having the largest surface tension and the surface tension of the treatment liquid is preferably 1 mN / m or more, and more preferably 3 mN / m or more.

  In image recording by the ink jet method, an ink composition is ejected onto a recording medium by applying energy to form a colored image. As a preferable ink jet recording method for the present invention, the method described in paragraph Nos. 0093 to 0105 of JP-A No. 2003-306623 can be applied.

The inkjet method is not particularly limited, and is a known method, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that uses vibration pressure of a piezoelectric element, An acoustic ink jet system that converts an electrical signal into an acoustic beam, irradiates the ink with ink, and ejects the ink using radiation pressure, and a thermal ink jet that forms bubbles by heating the ink and uses the generated pressure (bubble jet (registered) Trademark)) method or the like. As an ink-jet method, in particular, the method described in Japanese Patent Application Laid-Open No. 54-59936 causes a sudden volume change of the ink subjected to the action of thermal energy, and the ink is ejected from the nozzle by the action force caused by this state change. Ink jet method can be used effectively.
The ink jet method includes a method of ejecting many low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent inks. The method using is included.

In addition, an ink jet head used in the ink jet method may be an on-demand method or a continuous method. In addition, 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 electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.) and a discharge type (for example, a spark jet type). However, any discharge method may be used.
There are no particular restrictions on the ink nozzles used when recording by the ink jet method, and they can be appropriately selected according to the purpose.

The ejection of the ink composition is preferably started within 10 seconds from the end of application of the treatment liquid. Within 10 seconds from the end of the application of the treatment liquid, the treatment liquid can be appropriately dried before ink discharge, and the ink does not mix with each other when ink is ejected, so that bleeding due to liquid movement during mixing is suppressed, In addition, it is advantageous in that it can proceed smoothly to ink ejection, which is the next process online. The ink composition is more preferably discharged within 5 seconds from the end of application of the treatment liquid, and more preferably within 1 second.
Here, the end of the application of the treatment liquid refers to a time point at which application by application or the like has been completed in advance on the recording area of the ink image on the recording medium before the discharge of the ink composition, and the start of the discharge of the ink composition The ink droplets ejected from the nozzles of the ink jet head first land on the treatment liquid application surface of the recording medium.

<Ink composition>
A visible image can be recorded by ejecting an ink composition (hereinafter also simply referred to as “ink”) onto a recording medium in an image-like manner. The ink composition can include, for example, at least one coloring material, at least one polymer particle, at least one water-soluble organic solvent, and water. In addition, the ink composition can be constituted using a pigment dispersion material, a surfactant, and other components as required.

(Polymer particles)
The ink composition in the invention contains at least one polymer particle. By including the polymer particles, the fixability of the ink composition to the recording medium and the scratch resistance of the image can be further improved. The polymer particles have a function of fixing the ink, that is, the image by increasing the viscosity of the ink by destabilizing the aggregation or dispersibility when contacting the treatment liquid described above or a dried region thereof. . Such polymer particles are preferably dispersed in water and an organic solvent.

  Examples of polymer particles include thermoplastic, thermosetting or modified acrylic, epoxy, polyurethane, polyether, polyamide, unsaturated polyester, phenol, silicone, or fluorine resins, chlorides, and the like. Amino resins such as polyvinyl resins such as vinyl, vinyl acetate, polyvinyl alcohol, or polyvinyl butyral, polyester resins such as alkyd resins and phthalic resins, melamine resins, melamine formaldehyde resins, aminoalkyd co-condensation resins, urea resins, urea resins, etc. Examples thereof include particles of a resin having an anionic group such as a system material, a copolymer or a mixture thereof. Among these, anionic acrylic resins include, for example, an acrylic monomer having an anionic group (anionic group-containing acrylic monomer) and, if necessary, other monomers copolymerizable with the anionic group-containing acrylic monomer. Obtained by polymerization in a solvent. Examples of the anionic group-containing acrylic monomer include an acrylic monomer having one or more selected from the group consisting of a carboxyl group, a sulfonic acid group, and a phosphonic group. Among them, an acrylic monomer having a carboxyl group (for example, acrylic acid) Methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, fumaric acid and the like), and acrylic acid or methacrylic acid is particularly preferred.

  The polymer particles in the present invention are preferably self-dispersing polymer particles having a carboxyl group from the viewpoint of ejection stability and liquid stability (particularly dispersion stability) when a colorant (particularly pigment) described later is used. Self-dispersing polymer particles are more preferred. Self-dispersing polymer particles are water-insoluble polymers that can be dispersed in an aqueous medium by the functional groups (particularly acidic groups or salts thereof) of the polymer itself in the absence of other surfactants, By means of water-insoluble polymer particles containing no free emulsifier.

Here, the dispersed state refers to both an emulsified state (emulsion) in which a water-insoluble polymer is dispersed in an aqueous medium and a dispersed state (suspension) in which a water-insoluble polymer is dispersed in an aqueous medium in a solid state. It includes the state of.
The water-insoluble polymer in the present invention is preferably a water-insoluble polymer that can be in a dispersed state in which the water-insoluble polymer is dispersed in a solid state from the viewpoint of aggregation speed and fixing property when an ink composition is used.

  The dispersion state of the self-dispersing polymer particles in the present invention refers to a solution obtained by dissolving 30 g of a water-insoluble polymer in 70 g of an organic solvent (for example, methyl ethyl ketone), and a neutralizing agent capable of neutralizing 100% of the salt-forming group of the water-insoluble polymer. After mixing and stirring (apparatus: stirring apparatus with stirring blade, rotation speed 200 rpm, 30 minutes, 25 ° C.) (sodium hydroxide if the salt-forming group is anionic, acetic acid if cationic) and 200 g of water The state in which even after removing the organic solvent from the mixed solution, it can be visually confirmed that the dispersed state exists stably at 25 ° C. for at least one week.

  The water-insoluble polymer means a polymer having a dissolution amount of 10 g or less when the polymer is dried at 105 ° C. for 2 hours and then dissolved in 100 g of water at 25 ° C., and the dissolution amount is preferable. Is 5 g or less, more preferably 1 g or less. The dissolution amount is the dissolution amount when neutralized with sodium hydroxide or acetic acid according to the kind of the salt-forming group of the water-insoluble polymer.

  The aqueous medium is configured to contain water, and may contain a hydrophilic organic solvent as necessary. In the present invention, it is preferably composed of water and 0.2% by mass or less of a hydrophilic organic solvent with respect to water, and more preferably composed of water.

  The main chain skeleton of the water-insoluble polymer is not particularly limited. For example, a vinyl polymer or a condensation polymer (epoxy resin, polyester, polyurethane, polyamide, cellulose, polyether, polyurea, polyimide, polycarbonate, etc.) is used. it can. Of these, vinyl polymers are particularly preferred.

Preferable examples of the vinyl polymer and the monomer constituting the vinyl polymer include those described in JP-A Nos. 2001-181549 and 2002-88294. In addition, radical transfer of vinyl monomers using dissociable groups (or substituents that can be induced to dissociable groups), polymerization initiators, and iniferters, or dissociable groups on either initiators or terminators A vinyl polymer in which a dissociable group is introduced at the end of a polymer chain by ionic polymerization using a compound having (or a substituent that can be derived from a dissociable group) can also be used.
Moreover, as a suitable example of the monomer which comprises a condensation type polymer and a condensation type polymer, what is described in Unexamined-Japanese-Patent No. 2001-247787 can be mentioned.

  The self-dispersing polymer particles in the present invention preferably contain a water-insoluble polymer containing a hydrophilic constituent unit and a constituent unit derived from an aromatic group-containing monomer from the viewpoint of self-dispersibility.

The hydrophilic structural unit is not particularly limited as long as it is derived from a hydrophilic group-containing monomer, and even if it is derived from one kind of hydrophilic group-containing monomer, it contains two or more hydrophilic groups. It may be derived from a monomer. The hydrophilic group is not particularly limited, and may be a dissociable group or a nonionic hydrophilic group.
In the present invention, the hydrophilic group is preferably a dissociable group and more preferably an anionic dissociable group from the viewpoint of promoting self-dispersion and the stability of the formed emulsified or dispersed state. Examples of the dissociable group include a carboxyl group, a phosphoric acid group, and a sulfonic acid group. Among them, a carboxyl group is preferable from the viewpoint of fixability when an ink composition is configured.

The hydrophilic group-containing monomer in the present invention is preferably a dissociable group-containing monomer from the viewpoints of self-dispersibility and aggregation, and is a dissociable group-containing monomer having a dissociable group and an ethylenically unsaturated bond. It is preferable.
Examples of the dissociable group-containing monomer include an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer, and an unsaturated phosphoric acid monomer.

Specific examples of the unsaturated carboxylic acid monomer include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and 2-methacryloyloxymethyl succinic acid. Specific examples of the unsaturated sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acrylate, and bis- (3-sulfopropyl) -itaconate. It is done. Specific examples of unsaturated phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, bis (methacryloxyethyl) phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, dibutyl-2- Examples include acryloyloxyethyl phosphate.
Among the dissociable group-containing monomers, unsaturated carboxylic acid monomers are preferable and acrylic acid and methacrylic acid are more preferable from the viewpoints of dispersion stability and ejection stability.

The self-dispersing polymer particles in the present invention preferably contain a polymer having a carboxyl group from the viewpoint of self-dispersibility and agglomeration speed when contacted with the treatment liquid, and have a carboxyl group and an acid value (mgKOH / g It is more preferable that the polymer contains 25-100. Furthermore, the acid value is more preferably from 25 to 80, and particularly preferably from 30 to 65, from the viewpoints of self-dispersibility and the aggregation rate when contacted with the treatment liquid.
In particular, when the acid value is 25 or more, the stability of self-dispersibility is good, and when it is 100 or less, the cohesiveness is improved.

The aromatic group-containing monomer is not particularly limited as long as it is a compound containing an aromatic group and a polymerizable group. The aromatic group may be a group derived from an aromatic hydrocarbon or a group derived from an aromatic heterocycle. In the present invention, an aromatic group derived from an aromatic hydrocarbon is preferable from the viewpoint of particle shape stability in an aqueous medium.
The polymerizable group may be a condensation polymerizable polymerizable group or an addition polymerizable polymerizable group. In the present invention, from the viewpoint of particle shape stability in an aqueous medium, an addition polymerizable group is preferable, and a group containing an ethylenically unsaturated bond is more preferable.

  The aromatic group-containing monomer in the present invention is preferably a monomer having an aromatic group derived from an aromatic hydrocarbon and an ethylenically unsaturated bond. The aromatic group-containing monomer may be used alone or in combination of two or more.

Examples of the aromatic group-containing monomer include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, and a styrene monomer. Of these, aromatic group-containing (meth) acrylate monomers are preferred from the viewpoint of the balance between the hydrophilicity and hydrophobicity of the polymer chain and the ink fixability, and include phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and phenyl (meth). At least one selected from acrylates is more preferable, and phenoxyethyl (meth) acrylate and benzyl (meth) acrylate are more preferable.
“(Meth) acrylate” means acrylate or methacrylate.

The self-dispersing polymer particles in the present invention include a structural unit derived from an aromatic group-containing (meth) acrylate monomer, and the content is preferably 10% by mass to 95% by mass. When the content of the aromatic group-containing (meth) acrylate monomer is 10% by mass to 95% by mass, the stability of the self-emulsification or dispersion state can be improved, and further the increase in ink viscosity can be suppressed.
In the present invention, from the viewpoints of stability in a self-dispersed state, stabilization of particle shape in an aqueous medium due to hydrophobic interaction between aromatic rings, and reduction in the amount of water-soluble components due to appropriate hydrophobicization of particles. More preferably, the content is from mass% to 90 mass%, more preferably from 15 mass% to 80 mass%, and particularly preferably from 25 mass% to 70 mass%.

  The self-dispersing polymer particles in the present invention can be constituted using, for example, a structural unit derived from an aromatic group-containing monomer and a structural unit derived from a dissociable group-containing monomer. Furthermore, other structural units may be further included as necessary.

The monomer that forms the other structural unit is not particularly limited as long as it is a monomer copolymerizable with the aromatic group-containing monomer and the dissociable group-containing monomer. Among these, an alkyl group-containing monomer is preferable from the viewpoint of flexibility of the polymer skeleton and ease of control of the glass transition temperature (Tg).
Examples of the alkyl group-containing monomer include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, alkyl (meth) acrylates such as t-butyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate; hydroxymethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Ethylenically unsaturated monomers having a hydroxyl group such as acrylate, 4-hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate; Dialkylaminoalkyl (meth) acrylates such as ru (meth) acrylate; N-hydroxyalkyl (meth) such as N-hydroxymethyl (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide Acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meta And (meth) acrylamides such as N-alkoxyalkyl (meth) acrylamides such as acrylamide and N- (n-, iso) butoxyethyl (meth) acrylamide.

  The molecular weight range of the water-insoluble polymer constituting the self-dispersing polymer particles in the present invention is preferably 3000 to 200,000, more preferably 5000 to 150,000, and more preferably 10,000 to 100,000 in terms of weight average molecular weight. More preferably it is. By setting the weight average molecular weight to 3000 or more, the amount of water-soluble components can be effectively suppressed. Moreover, self-dispersion stability can be improved by making a weight average molecular weight into 200,000 or less.

  The weight average molecular weight is measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns, and THF (tetrahydrofuran) as an eluent. ) Is used. The conditions are as follows: the sample concentration is 0.35 / min, the flow rate is 0.35 ml / min, the sample injection amount is 10 μl, the measurement temperature is 40 ° C., and an IR detector is used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It is prepared from 8 samples of “A-2500”, “A-1000”, “n-propylbenzene”.

The water-insoluble polymer constituting the self-dispersing polymer particle in the present invention is a structural unit derived from an aromatic group-containing (meth) acrylate monomer (preferably phenoxyethyl (meth) acrylate) from the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer. It is preferable that 15-80 mass% of the total mass of a self-dispersing polymer particle is included as a copolymerization ratio for the structural unit derived from and / or the structural unit derived from benzyl (meth) acrylate.
In addition, the water-insoluble polymer has a constitution derived from a carboxyl group-containing monomer having a copolymerization ratio of 15 to 80% by mass of a constitutional unit derived from an aromatic group-containing (meth) acrylate monomer from the viewpoint of controlling the hydrophilicity / hydrophobicity of the polymer. And a structural unit derived from an alkyl group-containing monomer (preferably a structural unit derived from an alkyl ester of (meth) acrylic acid), and a structural unit derived from phenoxyethyl (meth) acrylate and / or Alternatively, a structural unit derived from benzyl (meth) acrylate as a copolymerization ratio of 15 to 80% by mass, a structural unit derived from a carboxyl group-containing monomer, and a structural unit derived from an alkyl group-containing monomer (preferably (meth) Structural unit derived from an alkyl ester having 1 to 4 carbon atoms of acrylic acid) More preferably, the acid value is 25 to 100 and the weight average molecular weight is preferably 3000 to 200,000, the acid value is 25 to 95, and the weight average molecular weight is 5000 to 150,000. It is more preferable that

  Specific examples of the water-insoluble polymer constituting the self-dispersing polymer particles are listed below as exemplary compounds B-01 to B-19, but the present invention is not limited thereto. In addition, the parenthesis represents the mass ratio of the copolymerization component.

B-01: Phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (50/45/5)
B-02: Phenoxyethyl acrylate / benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (30/35/29/6)
B-03: Phenoxyethyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (50/44/6)
B-04: Phenoxyethyl acrylate / methyl methacrylate / ethyl acrylate / acrylic acid copolymer (30/55/10/5)
B-05: benzyl methacrylate / isobutyl methacrylate / methacrylic acid copolymer (35/59/6)
B-06: Styrene / phenoxyethyl acrylate / methyl methacrylate / acrylic acid copolymer (10/50/35/5)
B-07: benzyl acrylate / methyl methacrylate / acrylic acid copolymer (55/40/5)
B-08: Phenoxyethyl methacrylate / benzyl acrylate / methacrylic acid copolymer (45/47/8)
B-09: Styrene / phenoxyethyl acrylate / butyl methacrylate / acrylic acid copolymer (5/48/40/7)
B-10: benzyl methacrylate / isobutyl methacrylate / cyclohexyl methacrylate / methacrylic acid copolymer (35/30/30/5)
B-11: Phenoxyethyl acrylate / methyl methacrylate / butyl acrylate / methacrylic acid copolymer (12/50/30/8)
B-12: benzyl acrylate / isobutyl methacrylate / acrylic acid copolymer (93/2/5)
B-13: Styrene / phenoxyethyl methacrylate / butyl acrylate / acrylic acid copolymer (50/5/20/25)
B-14: Styrene / butyl acrylate / acrylic acid copolymer (62/35/3)
B-15: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/51/4)
B-16: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/49/6)
B-17: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/48/7)
B-18: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/47/8)
B-19: Methyl methacrylate / phenoxyethyl acrylate / acrylic acid copolymer (45/45/10)

  The method for producing the water-insoluble polymer constituting the self-dispersing polymer particles in the present invention is not particularly limited. For example, emulsion polymerization is carried out in the presence of a polymerizable surfactant to obtain a surfactant and a water-insoluble polymer. Examples include a method of covalent bonding, and a method of copolymerizing a monomer mixture containing the hydrophilic group-containing monomer and the aromatic group-containing monomer by a known polymerization method such as a solution polymerization method or a bulk polymerization method. Among the polymerization methods, a solution polymerization method is preferable and a solution polymerization method using an organic solvent is more preferable from the viewpoint of aggregation rate and droplet ejection stability when an ink composition is used.

  The self-dispersing polymer particles in the present invention include a polymer synthesized in an organic solvent from the viewpoint of aggregation rate, and the polymer has a carboxyl group (preferably having an acid value of 20 to 100). Part or all of the carboxyl groups of the polymer are preferably neutralized and prepared as a polymer dispersion having water as a continuous phase. That is, the production of the self-dispersing polymer particles in the present invention includes a step of synthesizing a polymer in an organic solvent and a dispersion step of making an aqueous dispersion in which at least a part of the carboxyl groups of the polymer is neutralized. It is preferable to do so.

The dispersion step preferably includes the following step (1) and step (2).
Step (1): Step of stirring a mixture containing a polymer (water-insoluble polymer), an organic solvent, a neutralizing agent, and an aqueous medium Step (2): Step of removing the organic solvent from the mixture

The step (1) is preferably a treatment in which a polymer (water-insoluble polymer) is first dissolved in an organic solvent, then a neutralizing agent and an aqueous medium are gradually added, mixed and stirred to obtain a dispersion. In this way, by adding a neutralizing agent and an aqueous medium to a water-insoluble polymer solution dissolved in an organic solvent, a self-dispersing polymer having a particle size with higher storage stability without requiring strong shearing force. Particles can be obtained.
There is no restriction | limiting in particular in the stirring method of this mixture, Dispersing machines, such as a generally used mixing stirring apparatus and an ultrasonic disperser, a high-pressure homogenizer, can be used as needed.

Preferred examples of the organic solvent include alcohol solvents, ketone solvents, and ether solvents.
Examples of the alcohol solvent include isopropyl alcohol, n-butanol, t-butanol, ethanol and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone. Examples of ether solvents include dibutyl ether and dioxane. Among these solvents, ketone solvents such as methyl ethyl ketone and alcohol solvents such as isopropyl alcohol are preferable. It is also preferable to use isopropyl alcohol and methyl ethyl ketone in combination for the purpose of moderating the polarity change during the phase inversion from oil to water. By using this solvent in combination, it is possible to obtain self-dispersing polymer particles having a fine particle size with high dispersion stability without aggregation and sedimentation and fusion between particles.

  The neutralizing agent is used so that a part or all of the dissociable group is neutralized and the self-dispersing polymer forms a stable emulsified or dispersed state in water. When the self-dispersing polymer of the present invention has an anionic dissociative group (for example, a carboxyl group) as a dissociable group, the neutralizing agent used is basic such as an organic amine compound, ammonia, or an alkali metal hydroxide. Compounds. Examples of organic amine compounds include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monopropylamine, dipropylamine, monoethanolamine, diethanolamine, triethanolamine, N, N-dimethyl-ethanolamine, N, N-diethyl-ethanolamine, 2-dimethylamino-2-methyl-1-propanol, 2-amino-2-methyl-1-propanol, N-methyldiethanolamine, N-ethyldiethanolanine, monoisopropanolamine, di Examples include isopropanolamine and triisopropanolamine. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Among these, sodium hydroxide, potassium hydroxide, triethylamine, and triethanolamine are preferable from the viewpoint of stabilizing the dispersion of the self-dispersing polymer particles of the present invention in water.

  These basic compounds are preferably used in an amount of 5 to 120 mol%, more preferably 10 to 110 mol%, still more preferably 15 to 100 mol%, based on 100 mol% of the dissociable group. . By setting it as 15 mol% or more, the effect which stabilizes dispersion | distribution of the particle | grains in water expresses, and there exists an effect which reduces a water-soluble component by setting it as 100 mol% or less.

  In the step (2), the aqueous dispersion of the self-dispersing polymer particles is obtained by distilling off the organic solvent from the dispersion obtained in the step (1) by a conventional method such as distillation under reduced pressure and phase-inversion into an aqueous system. A dispersion can be obtained. The organic solvent in the obtained aqueous dispersion has been substantially removed, and the amount of the organic solvent is preferably 0.2% by mass or less, more preferably 0.1% by mass or less.

The average particle size of the polymer particles (particularly self-dispersing polymer particles) is preferably in the range of 10 to 400 nm, more preferably in the range of 10 to 200 nm, still more preferably in the range of 10 to 100 nm, and particularly preferably in terms of volume average particle size. It is the range of 10-50 nm. Manufacturability is improved by having an average particle diameter of 10 nm or more. Moreover, storage stability improves by setting it as an average particle diameter of 400 nm or less. Moreover, there is no restriction | limiting in particular regarding the particle size distribution of a polymer particle, Any of what has a wide particle size distribution or a monodispersed particle size distribution may be sufficient. Further, two or more water-insoluble particles may be mixed and used.
The average particle size and particle size distribution of the polymer particles are determined by measuring the volume average particle size by a dynamic light scattering method using a nanotrack particle size distribution measuring device UPA-EX150 (manufactured by Nikkiso Co., Ltd.). It is what

The content of the polymer particles (particularly self-dispersing polymer particles) in the ink composition is preferably 1 to 30% by mass with respect to the ink composition from the viewpoint of glossiness of the image, More preferably, it is 15 mass%.
The polymer particles (particularly self-dispersing polymer particles) can be used singly or in combination of two or more.

(Organic solvent)
The ink composition in the present invention contains water as a solvent, but further contains at least one organic solvent. By containing an organic solvent, drying prevention and penetration can be promoted. When an organic solvent is used as an anti-drying agent, it is possible to effectively prevent nozzle clogging that may occur due to drying of the ink at the ink discharge port when the ink composition is discharged by an inkjet method to record an image. it can.

In order to prevent drying, an organic solvent having a vapor pressure lower than that of water is preferable. Specific examples of the organic solvent suitable for preventing drying include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6. -Hexatriol, acetylene glycol derivatives, polyhydric alcohols represented by glycerol, trimethylolpropane, etc., ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether Lower alkyl ethers of polyhydric alcohols such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfora , Dimethyl sulfoxide, sulfur-containing compounds such as sulfolane, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives.
Of these, polyhydric alcohols such as glycerin and diethylene glycol are preferred. Moreover, these may be used individually by 1 type, or may use 2 or more types together. These organic solvents are preferably contained in the ink composition in an amount of 10 to 50% by mass.

  In order to promote penetration, an organic solvent is preferably used from the viewpoint of allowing the ink composition to penetrate better into the recording medium. Specific examples of organic solvents suitable for promoting penetration include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, sodium oleate, and nonion. Surfactants and the like. A good effect is acquired by containing these 5-30 mass% in an ink composition. These organic solvents are preferably used within a range of addition amounts that do not cause printing / image bleeding and paper loss (print-through).

In addition to the above, the organic solvent can be used for adjusting the viscosity. Specific examples of organic solvents that can be used to adjust the viscosity include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, cyclohexanol). Benzyl alcohol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodi) Glycol), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, triethylene Glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amine (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethyl) Diamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone, N -Methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone).
In addition, you may use an organic solvent individually by 1 type or in mixture of 2 or more types.

(Color material)
The ink composition in the present invention contains at least one coloring material. By containing a color material, a visible image can be recorded. As the coloring material, known dyes, pigments and the like can be used without particular limitation. Among these, from the viewpoint of ink colorability, a color material that is almost insoluble or hardly soluble in water is preferable. Specific examples include various pigments, disperse dyes, oil-soluble dyes, dyes forming J aggregates, and the like, and pigments are more preferable.
In the present invention, the water-insoluble pigment itself or the pigment surface-treated with a dispersant can be used as the color material.

There are no particular restrictions on the type of the pigment, and conventionally known organic and inorganic pigments can be used. For example, polycyclic pigments such as azo lakes, azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, diketopyrrolopyrrole pigments, thioindigo pigments, isoindolinone pigments, quinophthaloni pigments, basic Examples include dye lakes such as dye-type lakes and acid dye-type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as titanium oxide, iron oxide, and carbon black. Further, any pigment that is not described in the color index can be used as long as it is dispersible in the aqueous phase. Further, pigments whose surface is treated with a surfactant, a polymer dispersant, or the like, or graft carbon can also be used.
Of these pigments, azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, and carbon black pigments are particularly preferable.

Specific examples of organic pigments are shown below.
Examples of organic pigments for orange or yellow 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 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of organic pigments for magenta or red 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 222C. I. Pigment violet 19 and the like.

  Examples of organic 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 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and siloxane-crosslinked aluminum phthalocyanine described in US Pat. No. 4,311,775.

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

(Dispersant)
When a pigment is contained as a coloring material, it is preferably dispersed in an aqueous solvent by a dispersant. The dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. Further, the polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  The low molecular surfactant type dispersant (hereinafter sometimes referred to as “low molecular dispersant”) can stably disperse an organic pigment in an aqueous solvent while maintaining a low viscosity of the ink. The low molecular dispersant herein is a low molecular dispersant having a molecular weight of 2000 or less. Moreover, 100-2000 are preferable and, as for the molecular weight of a low molecular dispersing agent, 200-2000 are more preferable.

  The low molecular weight dispersant has a structure including a hydrophilic group and a hydrophobic group. In addition, the hydrophilic group and the hydrophobic group may be independently contained in one molecule or more, and may have a plurality of types of hydrophilic groups and hydrophobic groups. In addition, a linking group for linking a hydrophilic group and a hydrophobic group can be appropriately included.

Examples of the hydrophilic group include an anionic group, a cationic group, a nonionic group, and a betaine type combining these.
The anionic group is not particularly limited as long as it has a negative charge, but may be a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, or a carboxylic acid group. Preferably, it is a phosphoric acid group or a carboxylic acid group, and more preferably a carboxylic acid group.
The cationic group is not particularly limited as long as it has a positive charge, but is preferably an organic cationic substituent, more preferably a cationic group containing nitrogen or phosphorus, and nitrogen. More preferably, it is a cationic group. Among these, a pyridinium cation or an ammonium cation is particularly preferable.
The nonionic group is not particularly limited as long as it has no negative or positive charge, and examples thereof include polyalkylene oxide, polyglycerin, and a part of sugar unit.

In the present invention, the hydrophilic group is preferably an anionic group from the viewpoint of dispersion stability and aggregation of the pigment.
Moreover, when a low molecular weight dispersing agent has an anionic hydrophilic group, it is preferable that the pKa is 3 or more from a viewpoint of making it contact with an acidic process liquid and promoting aggregation reaction. The pKa of the low molecular dispersant in the present invention is determined experimentally from a titration curve by titrating a solution of 1 mol / L of the low molecular dispersant in a tetrahydrofuran-water = 3: 2 (V / V) solution with an acid or alkaline aqueous solution. It is the value obtained in
Theoretically, if the pKa of the low molecular dispersant is 3 or more, 50% or more of the anionic groups are in a non-dissociated state when in contact with a treatment solution having a pH of about 3. Accordingly, the water solubility of the low molecular weight dispersant is remarkably lowered, and an agglomeration reaction occurs. That is, the aggregation reactivity is improved. From this viewpoint, it is preferable that the low molecular dispersant has a carboxylic acid group as an anionic group.

On the other hand, the hydrophobic group may have any structure such as hydrocarbon, fluorocarbon, and silicone, but is preferably hydrocarbon. Further, these hydrophobic groups may have a linear structure or a branched structure. The hydrophobic group may have a single-chain structure or two or more chain structures, and may have a plurality of types of hydrophobic groups in the case of a structure having two or more chains.
The hydrophobic group is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 4 to 24 carbon atoms, and still more preferably a hydrocarbon group having 6 to 20 carbon atoms.

  Among the polymer dispersants, hydrophilic polymer compounds can be used as the water-soluble dispersant. For example, natural hydrophilic polymer compounds include plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, seaweeds such as alginic acid, carrageenan and agar. Examples include molecules, animal polymers such as gelatin, casein, albumin and collagen, and microorganism polymers such as xanthene gum and dextran.

  Examples of hydrophilic polymer compounds chemically modified from natural products include fibrin polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylcellulose, sodium starch glycolate, sodium starch phosphate, etc. And seaweed polymers such as alginic acid propylene glycol ester.

  Synthetic water-soluble polymer compounds include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, acrylic polymers such as polyacrylamide, polyacrylic acid or alkali metal salts thereof, and water-soluble styrene acrylic resins. Resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salt of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium, amino group, etc. And a polymer compound having a cationic functional group salt in the side chain.

  Among these, from the viewpoint of pigment dispersion stability and aggregation, a polymer compound containing a carboxyl group is preferable. For example, an acrylic resin such as a water-soluble styrene acrylic resin, a water-soluble styrene maleic resin, and a water-soluble vinyl naphthalene. High molecular compounds containing a carboxyl group such as an acrylic resin and a water-soluble vinyl naphthalene maleic resin are particularly preferred.

  As the water-insoluble dispersant among the polymer dispersants, a polymer having both a hydrophobic part and a hydrophilic part can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol ( Examples thereof include a meth) acrylate- (meth) acrylic acid copolymer and a styrene-maleic acid copolymer.

  The weight average molecular weight of the polymer dispersant is preferably 3,000 to 200,000, more preferably 5,000 to 100,000, still more preferably 5,000 to 80,000, and particularly preferably 10,000 to 60. , 000.

  Further, the mixing mass ratio of the pigment and the dispersant (pigment: dispersant) is preferably in the range of 1: 0.06 to 1: 3, more preferably in the range of 1: 0.125 to 1: 2. Preferably it is 1: 0.125 to 1: 1.5.

In the case where a dye is used as the coloring material, a material in which the dye is held on a water-insoluble carrier can be used as the water-insoluble colored particles. As the dye, known dyes can be used without particular limitation. For example, the dyes described in JP-A-2001-115066, JP-A-2001-335714, JP-A-2002-249677 and the like can be used in the present invention. It can be used suitably. The carrier is not particularly limited as long as it is insoluble in water or hardly soluble in water, and inorganic materials, organic materials, and composite materials thereof can be used. Specifically, the carriers described in JP-A-2001-181549, JP-A-2007-169418, etc. can be suitably used in the present invention.
The carrier holding the dye (water-insoluble colored particles) can be used as an aqueous dispersion using a dispersant. As the dispersant, the above-described dispersants can be suitably used.

The colorant preferably includes a pigment and a dispersant, more preferably includes an organic pigment and a polymer dispersant, and includes a polymer dispersant including an organic pigment and a carboxyl group, from the viewpoint of image light resistance and quality. It is particularly preferred that In addition, it is also preferable that the coloring material is coated with a polymer dispersant having a carboxyl group and is insoluble in water from the viewpoint of aggregation.
Furthermore, from the viewpoint of cohesiveness, it is preferable that the acid value of the polymer dispersant is larger than the acid value of the above-described polymer particles (preferably self-dispersing polymer particles).

The average particle diameter of the color material is preferably 10 to 200 nm, more preferably 10 to 150 nm, and still more preferably 10 to 100 nm. When the average particle size is 200 nm or less, the color reproducibility is good, the droplet ejection characteristics when droplets are ejected by the ink jet method are good, and when it is 10 nm or more, the light resistance is good. Further, the particle size distribution of the color material is not particularly limited, and may be either a wide particle size distribution or a monodisperse particle size distribution. Two or more color materials having a monodisperse particle size distribution may be mixed and used.
In addition, the average particle diameter and particle size distribution of a color material can be measured using a light scattering method, for example.

The content of the color material in the ink composition is preferably 1 to 25 mass%, more preferably 2 to 20 mass%, and more preferably 5 to 20 mass% with respect to the ink composition from the viewpoint of image density. % Is more preferable, and 5 to 15% by mass is particularly preferable.
You may use a color material individually by 1 type or in combination of 2 or more types.

  The content ratio of the colorant and polymer particles (preferably self-dispersing polymer particles) in the ink composition (water-insoluble colored particles / polymer particles) is 1 / 0.5 from the viewpoint of image scratch resistance and the like. It is preferably ˜1 / 10, more preferably 1/1 to ¼.

(Surfactant)
The ink composition in the present invention contains at least one surfactant. The surfactant is used as a surface tension adjusting agent. Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants and betaine surfactants.

The surfactant preferably contains an amount capable of adjusting the surface tension of the ink composition to 20 to 45 mN / m in order to eject droplets well by the ink jet method. Among them, the content of the surfactant is preferably an amount capable of adjusting the surface tension to 20 to 40 mN / m, and more preferably an amount capable of adjusting to 25 to 35 mN / m.
The surface tension of the ink composition is measured under conditions of 25 ° C. by the plate method using an Automatic Surface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

  Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

Furthermore, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used.
In addition, fluorine (fluorinated alkyl-based) surfactants, silicone-based surfactants and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are also included. Scratch resistance can also be improved.

  These surface tension modifiers can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

(water)
The ink composition contains water, but the amount of water is not particularly limited. Especially, the preferable content of water is 10 to 99% by mass, more preferably 30 to 80% by mass, and still more preferably 50 to 70% by mass.

(Other ingredients)
The ink composition can contain other additives as other components in addition to the above components. Examples of other additives include antifading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, antiseptics, antifungal agents, pH adjusters, antifoaming agents, viscosity modifiers, dispersants, and dispersion stabilizers. And known additives such as rust preventives and chelating agents. These various additives may be added directly after the ink composition is prepared, or may be added when the ink composition is prepared.

  By containing the ultraviolet absorber, image storability can be improved. Examples of the ultraviolet absorber include benzotriazoles described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492, 56-21114, Cinnamic acid compounds described in JP-A-10-88106, etc., JP-A-4-298503, JP-A-8-53427, JP-A-8-239368, JP-A-10-182621, JP-A-8-501291 Triazine compounds described in Japanese Patent Publication No. The compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene and benzoxazole compounds, so-called fluorescent brighteners can also be used.

  By containing the anti-fading agent, image storability can be improved. As the antifading agent, various organic and metal complex antifading agents can be used. Examples of organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. There are nickel complexes and zinc complexes. More specifically, Research Disclosure No. No. 17643, Nos. VII to I, J; 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in Japanese Patent No. 15162 and the compounds represented by the general formulas and compound examples of the representative compounds described on pages 127 to 137 of JP-A-62-215272 can be used.

  Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof. These are preferably used in the water-based ink composition in an amount of 0.02 to 1.00% by mass.

  As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used. From the viewpoint of improving the storage stability of the ink composition, the pH adjuster is preferably added so that the pH of the ink composition is 6 to 10, and more preferably added so that the pH is 7 to 10. .

  The surface tension (25 ° C.) of the ink composition in the present invention is preferably 20 mN / m or more and 45 mN / m or less. More preferably, it is 20 mN or more and 40 mN / m or less, More preferably, it is 25 mN / m or more and 35 mN / m or less.

In addition, the viscosity of the ink composition is preferably in the range of 1 to 30 mPa · s, preferably from 1 to 30 mPa · s, from the viewpoint of ejection stability when ejected by the ink jet method and the aggregation rate when using the treatment liquid described below. The range of s is more preferable, the range of 2 to 15 mPa · s is more preferable, and the range of 2 to 10 mPa · s is particularly preferable.
The viscosity is measured by using an ink composition at 20 ° C. using VISCOMETER TV-22 (manufactured by TOKI SANGYO CO. LTD).

-Other processes-
The ink jet recording method of the present invention can be constituted by providing other processes as necessary in addition to the treatment liquid applying process and the image recording process.

  There are no particular restrictions on the other steps, for example, an ink drying step for drying and removing the organic solvent in the ink composition applied to the recording medium, and polymer particles and polymer latex contained in the ink composition are melt-fixed. The heating and fixing step can be appropriately selected according to the purpose.

  The ink drying step can be configured in the same manner as the drying and removal step that may be provided in the treatment liquid application step described above, and is particularly limited as long as it is a method that can dry and remove at least part of the solvent in the ink composition. There is no. Specifically, a commonly used method such as heating or blowing (supplying dry air) can be applied to the image portion. This ink drying step is more preferably provided after the image recording step of discharging the ink composition from the viewpoints of curling and cockle generation suppression and image scratch resistance.

  The heat fixing step is not particularly limited as long as it is a method capable of melting and fixing the resin particles contained in the water-based ink, and can be appropriately selected according to the purpose.

<Recording medium>
The inkjet recording method of the present invention records an image on a recording medium.
The recording medium is not particularly limited, and general printing paper mainly composed of cellulose, such as so-called high-quality paper, coated paper, and art paper, used for general offset printing and the like can be used. General printing paper mainly composed of cellulose is relatively slow in ink absorption and drying in image recording by a general ink jet method using water-based ink, and color material movement is likely to occur after droplet ejection, and image quality is likely to deteriorate. However, according to the ink jet recording method of the present invention, it is possible to record a high-quality image excellent in color density and drawing performance by suppressing color material movement.

  As the recording medium, commercially available media can be used. For example, “OK Prince fine quality” manufactured by Oji Paper Co., Ltd., “Shiorai” manufactured by Nippon Paper Industries Co., Ltd., and Nippon Paper Industries ( Fine coated paper such as “New NPI fine quality” manufactured by Co., Ltd., “OK Everlight Coat” manufactured by Oji Paper Co., Ltd., and “Aurora S” manufactured by Nippon Paper Industries Co., Ltd., Oji Lightweight coated paper (A3) such as “OK Coat L” manufactured by Paper Industries Co., Ltd. and “Aurora L” manufactured by Nippon Paper Industries Co., Ltd. “OK Top Coat +” manufactured by Oji Paper Co., Ltd. and Nippon Paper Industries Co., Ltd. ) Coated paper (A2, B2) such as “Aurora Coat” manufactured by Oji Paper Co., Ltd. Art paper (A1) such as “OK Kanfuji +” manufactured by Oji Paper Co., Ltd. and “Tokuhishi Art” manufactured by Mitsubishi Paper Industries Co., Ltd. Is mentioned. It is also possible to use various photographic papers for ink jet recording.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” is based on mass.

  The weight average molecular weight was measured by gel permeation chromatography (GPC). GPC uses HLC-8020GPC (manufactured by Tosoh Corporation), TSKgel, Super Multipore HZ-H (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) as columns, and THF (tetrahydrofuran) as an eluent. ) Was used. The conditions were as follows: the sample concentration was 0.35 / min, the flow rate was 0.35 ml / min, the sample injection amount was 10 μl, the measurement temperature was 40 ° C., and an IR detector was used. In addition, the calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, It produced from eight samples of "A-2500", "A-1000", and "n-propylbenzene".

<Preparation of water-based ink>
(Synthesis of polymer dispersant P-1)
According to the following scheme, a polymer dispersant P-1 was synthesized as shown below.

To a 1000 ml three-necked flask equipped with a stirrer and a condenser tube, 88 g of methyl ethyl ketone was added and heated to 72 ° C. in a nitrogen atmosphere. Here, 50 g of methyl ethyl ketone was mixed with 0.85 g of dimethyl 2,2′-azobisisobutyrate and 60 g of benzyl methacrylate. Then, a solution in which 10 g of methacrylic acid and 30 g of methyl methacrylate were dissolved was dropped over 3 hours. After completion of the dropwise addition, the reaction was further continued for 1 hour, and then a solution of 0.42 g of dimethyl 2,2′-azobisisobutyrate in 2 g of methyl ethyl ketone was added, heated to 78 ° C. and heated for 4 hours. The obtained reaction solution was reprecipitated twice in a large excess amount of hexane, and the precipitated resin was dried to obtain 96 g of a polymer dispersant P-1.
The composition of the obtained resin was confirmed by ¹ H-NMR, and the weight average molecular weight (Mw) determined by GPC was 44,600. Furthermore, when the acid value was calculated | required by the method as described in JIS specification (JIS K0070: 1992), it was 65.2 mgKOH / g.

(Preparation of dispersion C of resin-coated pigment particles)
Pigment Blue 15: 3 (phthalocyanine blu-A220, manufactured by Dainichi Seika Co., Ltd .; cyan pigment), 5 parts of the polymer dispersant P-1, 42 parts of methyl ethyl ketone, and 1N aqueous NaOH solution 5.5 Part and 87.2 parts of ion-exchanged water were mixed and dispersed with a bead mill using 0.1 mmφ zirconia beads for 2 to 6 hours.
After removing methyl ethyl ketone at 55 ° C. under reduced pressure and removing a part of water in the obtained dispersion, using a high-speed centrifugal cooler 7550 (manufactured by Kubota Seisakusho), using a 50 mL centrifuge, Centrifugation was performed at 8000 rpm for 30 minutes, and the supernatant liquid other than the precipitate was collected. Thereafter, the pigment concentration was determined from the absorbance spectrum, and a dispersion C of resin-coated pigment particles (pigment coated with a polymer dispersant) having a pigment concentration of 10.2% by mass was obtained.

(Preparation of dispersion M of resin-coated pigment particles)
In the preparation of the dispersion C of the resin-coated pigment particles, instead of Pigment Blue 15: 3 (cyan pigment), C.I. I. Except for using Pigment Red 122 (manufactured by Clariant Japan), a dispersion M of resin-coated pigment particles (pigment coated with a polymer dispersant) was prepared in the same manner as in the preparation of dispersion C of resin-coated pigment particles. Prepared.

(Preparation of dispersion Y of resin-coated pigment particles)
In the preparation of the dispersion C of the resin-coated pigment particles, instead of Pigment Blue 15: 3 (cyan pigment), C.I. I. Except for using Pigment Yellow 74 (manufactured by Clariant Japan), dispersion Y of resin-coated pigment particles (pigment coated with a polymer dispersant) was prepared in the same manner as in the preparation of dispersion C of resin-coated pigment particles. Prepared.

(Preparation of dispersion K of resin-coated pigment particles)
Resin-coated pigment particles except that carbon black (NIPEX 160-IQ manufactured by Degussa) was used in place of Pigment Blue 15: 3 (cyan pigment) in preparing dispersion C of resin-coated pigment particles A dispersion K of resin-coated pigment particles (pigment coated with a polymer dispersant) was prepared in the same manner as in the preparation of Dispersion C.

(Preparation of self-dispersing polymer fine particles)
-Synthesis Example 1
360.0 g of methyl ethyl ketone was charged into a 2-liter three-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube, and the temperature was raised to 75 ° C. While maintaining the temperature in the reaction vessel at 75 ° C., 180.0 g of phenoxyethyl acrylate, 162.0 g of methyl methacrylate, 18.0 g of acrylic acid, 72 g of methyl ethyl ketone, and “V-601” (manufactured by Wako Pure Chemical Industries, Ltd.) A mixed solution consisting of 44 g was added dropwise at a constant speed so that the addition was completed in 2 hours. After completion of the dropwise addition, a solution composed of 0.72 g of “V-601” and 36.0 g of methyl ethyl ketone was added thereto, stirred at 75 ° C. for 2 hours, and further a solution composed of 0.72 g of “V-601” and 36.0 g of isopropanol. And stirred at 75 ° C. for 2 hours. Thereafter, the temperature was raised to 85 ° C., and stirring was further continued for 2 hours to obtain a resin solution of a phenoxyethyl acrylate / methyl methacrylate / acrylic acid (= 50/45/5 [mass ratio]) copolymer.
The weight average molecular weight (Mw) of the obtained copolymer was 64000 (calculated in terms of polystyrene by gel permeation chromatography (GPC)), and the acid value was 38.9 (mgKOH / g).

Next, 668.3 g of the obtained resin solution was weighed, 388.3 g of isopropanol and 145.7 ml of 1 mol / L NaOH aqueous solution were added thereto, and the temperature in the reaction vessel was raised to 80 ° C. Next, 720.1 g of distilled water was added dropwise at a rate of 20 ml / min to disperse in water. Thereafter, the temperature in the reaction vessel was maintained at 80 ° C. for 2 hours, 85 ° C. for 2 hours, and 90 ° C. for 2 hours under atmospheric pressure, and then the reaction vessel was depressurized, and isopropanol, methyl ethyl ketone, and distilled water totaled 913. 7 g was distilled off to obtain an aqueous dispersion (emulsion) of self-dispersing polymer fine particles B-01 having a solid content concentration of 28.0%.
In addition, the structure of the self-dispersing polymer fine particle B-01 is as follows, and the number on the lower right of each structural unit in the structure below represents “mass ratio”.

(Preparation of water-based ink)
Using the dispersion of resin-coated pigment particles of each color obtained above and the self-dispersing polymer fine particles B-01, each component was mixed to prepare a water-based ink so as to have the composition shown in Table 1 below. The prepared aqueous ink was packed in a plastic disposable syringe and filtered through a PVDF (polyvinylidene fluoride) 5 μm filter (diameter 25 mm, Millex-SV, manufactured by Millipore) to obtain a finished ink.

  In Table 1 above, the pH of each color of water-based ink was measured at 25 ± 1 ° C. using a pH meter WM-50EG (manufactured by Toa DKK). The surface tension was measured under the condition of 25 ° C. using FASE Automatic Surface Tensionmeter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

  Next, the surface tension aqueous inks C2, M2, and Y2 shown in Table 2 below are adjusted by adjusting the amount of the orphine 1010 (surfactant) in each of the four water-based inks C1, M1, Y1, and K1. , K2 was prepared. pH and surface tension were measured as described above.

<Preparation of reaction solution>
(Processing liquid 1)
The component of the following composition was mixed and the processing liquid 1 was prepared. The pH and surface tension of the treatment liquid 1 measured by the same method as described above were 0.96 and 37.4 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
・ Anionic surfactant A (10% aqueous solution) of the following structural formula: 1.0 g
<Structural formula>
_{C 7 H 15 -CH = CH-} C 7 H 14 -C (O) -N (CH 3) -CH 2 CH 2 -SO 3 Na
・ Diethylene glycol monoethyl ether ... 20.0g
・ Ion exchange water: 56.5 g

(Processing liquid 2)
The component of the following composition was mixed and the processing liquid 2 was prepared. The pH and surface tension of the treatment liquid 2 measured by the same method as described above were 0.96 and 43.3 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
-Anionic surfactant A (10% aqueous solution) ... 0.24 g
・ Diethylene glycol monoethyl ether ... 20.0g
・ Ion exchange water: 57.26g

(Processing liquid 3)
The component of the following composition was mixed and the processing liquid 3 was prepared. The pH and surface tension of the treatment liquid 3 measured by the same method as described above were 1.04 and 42.8 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
・ 10% aqueous solution of Emulgen 109P (manufactured by Kao Corporation; polyoxyethylene lauryl ether (nonionic surfactant)) 0.24 g
・ Diethylene glycol monoethyl ether ... 20.0g
・ Ion exchange water: 57.26g

(Processing liquid 4)
The component of the following composition was mixed and the processing liquid 4 was prepared. The pH and surface tension of the treatment liquid 4 measured by the same method as described above were 1.00 and 44.5 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
-10% aqueous solution of Olfine 1010 (Nissin Chemical Industry Co., Ltd .; surfactant) 0.1 g
・ Diethylene glycol monoethyl ether ... 20.0g
・ Ion exchange water: 57.4g

(Processing liquid 5)
The component of the following composition was mixed and the processing liquid 5 was prepared. The pH and surface tension of the treatment liquid 5 measured by the same method as described above were 1.02 and 47.8 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
・ Emulgen 109P (manufactured by Kao Corporation; 10% aqueous solution of polyoxyethylene lauryl ether (nonionic surfactant)) 0.04 g
・ Dipropylene glycol: 10.0 g
・ Ion exchange water: 67.46g

(Processing liquid 6)
The component of the following composition was mixed and the processing liquid 6 was prepared. The pH and surface tension of the treatment liquid 6 measured by the same method as described above were 0.97 and 56.5 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
・ Diethylenecricol monoethyl ether ... 10.0g
・ Ion exchange water: 67.5g

(Processing liquid 7)
The component of the following composition was mixed and the processing liquid 7 was prepared. The pH and surface tension of the treatment liquid 7 measured by the same method as described above were 0.97 and 30.1 mN / m, respectively.
<Composition>
・ Malonic acid: 22.5g
-10% aqueous solution of Emulgen 109P (manufactured by Kao Corporation; polyoxyethylene lauryl ether (nonionic surfactant)) 2.0 g
・ Diethylene glycol monoethyl ether ... 20.0g
・ Ion exchange water: 57.26g

<Image recording>
An A4 size Tokuhishi art (Mitsubishi Paper Co., Ltd.) was used as the recording medium, and an image was recorded under the following image recording conditions by combining the treatment liquid and water-based ink as shown in Table 3 below.

[Drip ejection method]
As the water-based ink, the water-based inks C1, M1, Y1, K1, C2, M2, Y2, and K2 obtained above were used, and images were recorded by four-color single-pass recording under the following conditions.

[Recording]
(1) Treatment liquid application process First, it apply | coated to the whole surface of a recording medium so that it might become 1.7 g / m < ² > with the application | coating bar using the said treatment liquids 1-6 before drawing with aqueous ink.

(2) Drying and removing step Next, the recording medium coated with the treatment liquid was dried under the following conditions.
・ Wind speed: 15m / s
-Temperature: Heated from the opposite side (back side) of the recording surface of the recording medium with a contact type flat heater so that the surface temperature on the recording surface side of the recording medium becomes 60 ° C.-Air blowing area: 450 mm (drying time 0.7) Seconds)

(3) Image recording process After that, within 10 seconds after finishing the application of the treatment liquid, ejection of the first color water-based ink by the inkjet method is started under the following conditions on the application surface of the recording medium coated with the treatment liquid. The image was recorded. At this time, each water-based ink was ejected with dots in the order shown in Table 3 in a single color or in two colors.
・ Head: 1200 dpi / 20 inch wide piezo full line heads are arranged for 4 colors ・ Discharge droplet volume: Recording at 2.4 pL ・ Drive frequency: 30 kHz (recording medium conveyance speed 635 mm / sec)

(4) Ink Drying and Removing Step Next, the recording medium to which the aqueous ink was applied was dried under the following conditions.
・ Drying method: blow drying ・ wind speed: 15m / s
-Temperature: Heated from the opposite side (back side) of the recording surface of the recording medium with a contact type flat heater so that the surface temperature on the recording surface side of the recording medium becomes 60 ° C.-Air blowing area: 640 mm (drying time: 1 second) )

(5) Fixing Step Next, a heat fixing process was performed by passing a roller pair under the following conditions.
・ Silicon rubber roller (hardness 50 °, nip width 5mm)
・ Roller temperature: 70 ℃
・ Pressure: 0.8MPa

<Evaluation>
-1. Treatment liquid application surface-
1 g of the magenta-colored water-based ink M1 is added to each of the treatment liquids described above and colored, and each of the treatment liquids is applied onto a recording medium (the application conditions are the application of the treatment liquid described above). The same as the process), and the coated surface was visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 3 below.
<Evaluation criteria>
A: The color density was uniform throughout and was uniform.
B: Although there are slight streaks, the whole was homogeneous and practically acceptable.
C: Striped shading unevenness and partial repellency unevenness were generated, which were in an unacceptable range for practical use.

-2. Image drawability (dot diameter)
Halftone dots drawn as single-color dots, and halftone dots that are overprinted with water-based inks of different colors (hereinafter, dots overlaid with two colors are secondary colors, dots overlaid with three colors are tertiary For each of 50 color dots, the equivalent circle diameter was measured using a dot analyzer DA-6000 manufactured by Oji Scientific Instruments, and the average value was taken as the dot diameter.
Here, the difference (Δ dot diameter) between the dot diameter of the obtained single-color dot and the dot diameter of the two-color overstrike dot was obtained, and this value was used as an index for evaluating the image drawing performance. The image drawability indicates that the smaller the Δ dot diameter, the more uniform the dot diameter of each color, and the more uniform image can be drawn.

  As shown in Table 3 above, in the samples of the present invention, the difference between the single color dot diameter and the multicolored secondary color dot diameter and tertiary color dot diameter dot diameter is small, and good image drawing is possible. there were. On the other hand, in the comparative sample, even if the single-color dot diameter was small, the secondary color dot diameter and the tertiary color dot diameter, which were multiple colors, were large, and the image drawing performance was poor. In Sample No. 9, the single color was thick and the dot diameter of the multi-colored color was large, which was an undesirable result.

Claims (14)

A treatment liquid application step of applying a treatment liquid containing an aggregating agent for aggregating the components in the ink composition onto the recording medium before discharging the ink composition forming the ink image;
An image recording step of recording an image by sequentially ejecting from the ink composition having a low surface tension by an ink jet method onto the recording medium to which the treatment liquid is applied, using at least two types of ink compositions having different surface tensions; ,
Wherein the surface tension B of the processing liquid wherein the ink composition and the surface tension A of meet the relation of A> B, the largest ink surface tension of the at least two different kinds of ink compositions of the surface tension An ink jet recording method , wherein a difference between a surface tension of the composition and a surface tension of the treatment liquid is 3 mN / m or more . The inkjet recording method according to claim 1, wherein at least one of the at least two ink compositions having different surface tensions is a yellow ink composition, and the yellow ink composition has the highest surface tension. 3. The ink jet recording method according to claim 1, wherein the content of the flocculant is 10 to 40% by mass with respect to the total mass of the treatment liquid. The coagulant, an ink jet recording method according to any one of claims 1 to 3, characterized in that the organic carboxylic acid. The inkjet recording method according to claim 4 , wherein the organic carboxylic acid is a divalent or higher polyvalent carboxylic acid. The ink jet recording method according to any one of claims 1 to 5, wherein the pH of the treatment liquid (25 ° C.) is 3.5 or less. The inkjet recording method according to claim 6 , wherein a pH (25 ° C.) of the treatment liquid is 0.5 to 2.5. The ink jet recording method according to any one of claims 1 to 7, characterized in that to start the ejection of the ink composition within 10 seconds of applying the end of the treatment liquid. The ink jet recording medium method according to any one of claims 1 to 8 , wherein a surface tension of the treatment liquid is 40 to 60 mN / m. The ink composition includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition, and the surface tension B of the ink composition is magenta ink composition <cyan ink composition <. the ink jet recording method according to any one of claims 1 to 9, characterized in that to satisfy the relationship of the yellow-based ink composition. The ink jet recording method according to any one of claims 1 to 10 in which the difference in surface tension, characterized in that a 1~5mN / m between said at least two ink compositions. The processing solution further, the ink jet recording method according to any one of claims 1 to claim 1 1, characterized in that it contains 1 to 40 wt% of organic solvent relative to the total weight. The inkjet recording method according to claim 1 2 in which the content of said organic solvent, characterized in that from 5 to 20 wt%. Said processing liquid is an inkjet recording method according to any one of claims 1 to 1 3, characterized in that it contains at least one further selected from anionic surfactants and nonionic surfactants .